JPH10334457A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium, especially a disk type magnetic recording medium which is improved in electromagnetic conversion characteristics, especially significantly improved in high-density recording characteristics with excellent durability, and which is especially improves in the error rate in a high-density recording region. SOLUTION: This magnetic recording medium has a magnetic layer having a ferromagnetic metal powder dispersed in a binder on a support. The magnetic recording medium can record signals of 0.17 to 2 Gbit/inch<2> surface recording density. The coercive force of the magnetic layer is >1,800 Oe. The ferromagnetic metal powder consists of at least Fe and Co and has such features that (1) the atomic ratio A=Al/(Fe+Co) is 3.0 to 15.4%, and (2) the atomic ratio B = whole rare earth elements/(Fe+Co) is 0.5 to 9.0%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic recording medium having a large capacity and a high recording density. In particular, the present invention relates to a magnetic recording medium for high-capacity, high-density recording, which has a magnetic layer and a substantially nonmagnetic lower layer, and contains a ferromagnetic metal powder in the uppermost layer.

[0002]

2. Description of the Related Art In the field of magnetic disks, 2 MB MF-2HD floppy disks using Co-modified iron oxide have been standardly mounted on personal computers. However, in today's rapidly increasing data capacity, the capacity cannot be said to be sufficient, and it has been desired to increase the capacity of floppy disks.

In the field of magnetic tapes, in recent years, with the spread of office computers such as minicomputers, personal computers, and workstations, magnetic tapes for recording computer data as external storage media (so-called backup tapes).
Research is being actively conducted. In practical use of magnetic tapes for such applications, especially with the downsizing of computers and the increase in information processing capacity, the increase in recording capacity,
In order to achieve miniaturization, improvement in recording capacity is strongly required.

Conventionally, a magnetic recording medium has a magnetic layer obtained by dispersing iron oxide, Co-modified iron oxide, CrO ₂ , ferromagnetic metal powder, and hexagonal ferrite powder in a binder on a non-magnetic support. Is widely used. Among them, ferromagnetic metal powders and hexagonal ferrite powders are known to be excellent in high density recording characteristics. In the case of a disk, a 10 MB MF-2TD and a 21 MB MF-2S are used as a large-capacity disk using a ferromagnetic metal powder excellent in high-density recording characteristics.
Large-capacity disks using D or hexagonal ferrite include 4 MB MF-2ED, 21 MB floptical, and the like, but were not sufficient in capacity and performance. Under such circumstances, many attempts have been made to improve the high-density recording characteristics. An example is shown below.

In order to improve the characteristics of a disk-shaped magnetic recording medium, Japanese Patent Application Laid-Open No. 64-84418 proposes to use a vinyl chloride resin having an acidic group, an epoxy group and a hydroxyl group. It has been proposed to use a metal powder having a Hc of 1000 Oe or more and a specific surface area of 25 to 70 m ² / g. Japanese Patent Publication No. Hei 6-28106 proposes to determine the specific surface area and the amount of magnetization of a magnetic substance and to include an abrasive. I have.

In order to improve the durability of a disk-shaped magnetic recording medium, Japanese Patent Publication No. 7-85304 proposes to use a fatty acid ester having an unsaturated bond with an unsaturated fatty acid ester. It has been proposed to use a fatty acid ester having a fatty acid ester and an ether bond, and JP-A-54-124716 proposes to include a non-magnetic powder having a Mohs hardness of 6 or more and a higher fatty acid ester. Has a volume of pores containing lubricant and a center plane average surface roughness of 0.005 to
It has been proposed that the thickness be 0.025 μm.
No. 94637 proposes the use of low melting point and high melting point fatty acid esters, and Japanese Patent Publication No. 7-36216 discloses an abrasive having a particle size of ４ to ／ of the magnetic layer thickness and a low melting point fatty acid ester. It has been proposed to use
No. 018 proposes to use a metal magnetic material containing Al and chromium oxide.

As a configuration of a disk-shaped magnetic recording medium having a nonmagnetic lower layer and an intermediate layer, JP-A-3-120613 proposes a configuration having a conductive layer and a magnetic layer containing metal powder, and JP-A-6-290446. Has proposed a structure having a magnetic layer and a non-magnetic layer of 1 μm or less.
337 proposes a configuration including a carbon intermediate layer and a magnetic layer containing a lubricant, and JP-A-5-290358 proposes a configuration having a nonmagnetic layer having a defined carbon size.

On the other hand, a disk-shaped magnetic recording medium comprising a thin magnetic layer and a functional non-magnetic layer has recently been developed.
0MB class floppy disks have appeared. Japanese Patent Application Laid-Open No. 5-109061 shows these features.
Has an Hc of 1400 Oe or more and a thickness of 0.5 μm
A configuration having the following magnetic layer and a non-magnetic layer containing conductive particles has been proposed. Japanese Patent Application Laid-Open No. 5-197946 has proposed a configuration containing an abrasive larger than the magnetic layer thickness.
Japanese Patent Application Laid-Open No. Hei 6-68453 discloses a configuration in which the thickness of the magnetic layer is 0.5 μm or less, the thickness variation of the magnetic layer is within ± 15%, and the surface electric resistance is specified. There has been proposed a configuration in which an abrasive is included and the amount of abrasive on the surface is regulated.

[0009] In recent years, with the spread of office computers such as minicomputers and personal computers, magnetic tapes (so-called backup tapes) for recording computer data as external storage media have been developed for tape-shaped magnetic recording media. Research is being actively conducted. When a magnetic tape for such a purpose is put to practical use, especially in connection with the miniaturization of computers and the increase in information processing capacity, an increase in recording capacity is strongly demanded in order to achieve large-capacity recording and miniaturization. In addition, the use environment of magnetic tapes is widespread, so it can be used under a wide range of environmental conditions (especially in the circumstance where temperature and humidity fluctuates rapidly). Reliability for performance such as recording and reading is required more than before.

Conventionally, a magnetic tape used in a digital signal recording system is determined for each system, and a so-called DLT type, 3480, 3490, 3590,
Magnetic tapes compatible with QIC, D8 type, or DDS type are known. In any system, the magnetic tape used is composed of a relatively thick single-layer ferromagnetic powder having a thickness of 2.0 to 3.0 μm, a binder, and a polishing agent on one side of the nonmagnetic support. A magnetic layer containing an agent is provided, and a back coat layer is provided on the other side to prevent winding disturbance and maintain good running durability.
However, in the magnetic layer having a relatively thick single-layer structure as described above, there is a problem of a loss in thickness that the output is reduced.

It is known that the magnetic layer is made thinner in order to improve the reduction of the reproduction output due to the thickness loss of the magnetic layer. For example, Japanese Patent Application Laid-Open No. 5-182178 discloses that A lower nonmagnetic layer containing an inorganic powder and dispersed in a binder, and an upper magnetic layer having a thickness of 1.0 μm or less formed by dispersing a ferromagnetic powder in the binder while the nonmagnetic layer is in a wet state. Disclosed a magnetic recording medium.

However, with the rapid increase in capacity and density of magnetic recording media in the form of disks or tapes, it has become difficult to obtain satisfactory characteristics even with such techniques. Also, it is becoming difficult to achieve both durability and durability. Conventionally, JP-A-63-1034
In No. 23, the ferromagnetic metal powder has a metal equivalent weight of 1 to
A magnetic recording medium containing 6% by weight of aluminum and a binder of a magnetic layer containing a resin having a polar group is disclosed, and when the ferromagnetic metal powder contains an aluminum component in an amount in a specific range, a magnetic property is improved. Without lowering, it becomes a ferromagnetic metal powder having a higher hardness than the conventional ferromagnetic metal powder of the same type, and furthermore, the ferromagnetic metal powder together with a normal abrasive,
The present applicant has proposed that a magnetic layer obtained by dispersing in a binder containing a resin having a polar group becomes an excellent magnetic layer having both improved running durability and improved electromagnetic conversion characteristics. Indeed, it showed excellent durability, but when it was applied to a high-speed, high-capacity, high-density magnetic disk of 1800 rpm or more, there was room for further improvement in durability and electromagnetic conversion characteristics.

[0013]

SUMMARY OF THE INVENTION According to the present invention, there is provided a magnetic recording medium in which electromagnetic characteristics, particularly high-density recording characteristics, are remarkably improved and excellent durability is provided, and an error rate in a high-density recording region is remarkably improved. It is intended to provide a recording medium. Especially, the recording capacity is 0.17 to 2 Gbit / inch.
^2, preferably it is aimed at 0.2~2Gbit / inch ^2, which is particularly preferred to provide a magnetic recording medium, particularly a disc-like magnetic recording medium having a large capacity of 0.35~2Gbit / inch ^2.

[0014]

Means for Solving the Problems The present inventors have studied diligently to obtain a large-capacity magnetic recording medium which has good electromagnetic conversion characteristics and durability, and in particular has a significantly improved error rate in a high-density recording area. As a result, by using the following media,
It has been found that a magnetic recording medium having a large capacity and excellent high-density recording characteristics and excellent durability, which is the object of the present invention, can be obtained, and the present invention has been accomplished.

That is, according to the present invention, there is provided a magnetic recording medium having a magnetic layer formed by dispersing a ferromagnetic metal powder in a binder on a support, wherein the magnetic recording medium has an areal recording density of 0.1.
A magnetic recording medium for recording a signal of 7 to ² Gbit / inch ² , wherein the magnetic layer has a coercive force of 1800 Oe or more, and the ferromagnetic metal powder is composed of at least Fe and Co, and is composed of Al / (Fe + Co). Atomic ratio A is 3.0-1
5.4% of the magnetic recording medium, and a magnetic recording medium provided with a magnetic layer formed by dispersing a ferromagnetic metal powder in a binder on a support, wherein the magnetic recording medium is a surface recording medium. A magnetic recording medium for recording a signal having a density of 0.17 to ² Gbit / inch ² , wherein the magnetic layer has a coercive force of 1800
Oe or more, and the ferromagnetic metal powder is at least Fe
And Co, and the sum of the rare earth elements / (Fe +
The above object can be achieved by a magnetic recording medium characterized in that the atomic ratio B of Co) is 0.5 to 9.0%.

Preferred embodiments of the present invention are as follows. (1) A magnetic recording medium, wherein a lower layer, which is a substantially nonmagnetic layer, is provided between the support and the magnetic layer. (2) The magnetic recording medium, wherein the magnetic recording medium is a disk-shaped magnetic recording medium. (3) The dry thickness of the magnetic layer is 0.05 to 0.30 μm
And Φm is 10.0 × 10 ^{−3 to} 1.0 × 10 ⁻³ emu /
cm ² , a magnetic recording medium. (4) The magnetic recording medium, wherein the ferromagnetic metal powder is composed of at least Fe and Co, and the total ratio of rare earth elements / the atomic ratio B / A of Al is 0.05 to 1.2. (5) The ferromagnetic metal powder is composed of Fe and Co,
And the total ratio of rare earth elements / the atomic ratio B / A of Al is 0.1 to
A magnetic recording medium characterized by being 0.60. (6) The ferromagnetic metal powder is composed of at least Fe and Co, and the total ratio of rare earth elements / the atomic ratio of (Fe + Co) B
Is 1.0 to 6.0%, and the sum of the rare earth elements /
A magnetic recording medium, wherein the atomic ratio B / A of Al is 0.1 to 0.6. (7) The atomic ratio B is 1.0 to 8.0%, and the atomic ratio C of Mg / (Fe + Co) is 0.05 to 3.0%.
A magnetic recording medium characterized by the following. (8) The magnetic recording medium, wherein the ferromagnetic metal powder has an acicular ratio of 3.0 to 9.0. (9) The ferromagnetic metal powder has an average major axis length of from 0.04 to 0.04.
0.12 μm, and the crystallite size is 80 ° to 180 °
A magnetic recording medium characterized by the following. (10) The magnetic recording medium, wherein the rare earth element is Y or Nd.

The object of the present invention can be achieved by the above.
Preferably, the dry thickness of the magnetic layer is 0.05 to 0.25
μm and φm is 8.0 × 10 ^{−3 to} 1.0 × 10
^-3 emu / cm ² , and the magnetic recording medium has an areal recording density of 0.20 to 2 Gbi.
The magnetic recording medium, which records t / inch ² signals, is characterized by a large capacity, excellent high-density characteristics, and excellent durability that could not be obtained by conventional technologies. It has been found that it is possible to obtain a magnetic recording medium which has both characteristics and a significantly improved error rate in a high-density recording area. Further, in the present invention, the ferromagnetic metal powder is composed of at least Fe and Co, and the Hc fluctuation ΔHc of the magnetic layer after storage is preferably −5.
0% to + 10.0%, more preferably -3.0% to +
The decrease in Φm after storage of the magnetic recording medium or the magnetic layer, which is 8.0%, particularly preferably ± 0.0% to + 6.0%, is preferably within 10%, particularly preferably. It can be achieved by a magnetic recording medium characterized by being within 6%.

Here, the substantially non-magnetic lower layer means that it may have a magnetic property to the extent that it does not participate in recording, and is hereinafter simply referred to as the lower layer or the non-magnetic layer. When the lower layer contains magnetic powder, it is preferable to contain less than half of the inorganic powder. In the present invention, when a lower layer is provided, the magnetic layer is also referred to as an upper layer or an upper magnetic layer. The surface recording density is
It is obtained by multiplying the linear recording density and the track density.

Φm is defined by using a vibration sample type magnetometer (VSM: manufactured by Toei Kogyo Co., Ltd.) from the magnetic layer per unit area on one side,
The amount of magnetic moment (e
mu / cm ² ) and the magnetic flux density B determined by the VSM
It is equal to m (unit G = 4πemu / cm ³ ) multiplied by thickness (cm). Therefore, the unit of Φm is emu / cm ²
Or it is represented by G · cm.

The linear recording density is the number of bits of a signal recorded per inch in the recording direction. These linear recording density, track density, and areal recording density are values determined by the system. That is, in the present invention, in order to improve the areal recording density, the magnetic layer thickness, the magnetic layer Hc, and the center plane average surface roughness were improved in terms of the linear recording density, and Φm was optimized in terms of the track density. Things.

Further preferred embodiments of the present invention are as follows. As for the entire magnetic recording medium, (1)
The magnetic layer has a surface roughness of 5.0 nm or less, preferably 4.0 n, as a center plane average surface roughness by a 3D-MIRAU method.
m or less, more preferably 3.0 nm or less,
(2) The coercive force of the magnetic layer is preferably 2100 Oe or more, and the average long axis length of the ferromagnetic metal powder is preferably 0.04 to 0.12 μm, more preferably 0.10 μm or less; (3) The magnetic recording medium is a magnetic recording medium for recording a signal having a surface recording density of preferably 0.20 to ² Gbit / inch ² , more preferably a signal of 0.35 to ² Gbit / inch ^2. The magnetic recording medium is preferably a magnetic recording medium for a system having a high transfer rate of 1.0 MB / sec or more, more preferably 2.0 MB / sec or more. (5) The magnetic recording medium is preferably Has a disk rotation speed of 2000 rpm
More preferably, the disk rotation speed is 3000r.
It is preferable that the magnetic recording medium is a magnetic recording medium for a large-capacity floppy disk system of pm or more. (6) The magnetic recording medium is a magnetic recording medium for a large-capacity floppy-disk system that realizes backward compatibility capable of recording / reproducing with a current 3.5-inch floppy-disk.
(7) The magnetic recording medium is a large-capacity floppy disk employing a dual-disc gap head having both a narrow gap for high-density recording and a wide gap for the current 3.5-inch floppy disk. (8) The magnetic recording medium is a magnetic recording medium for a large-capacity floppy disk system in which a head floats by rotation of a disk. (9) The magnetic recording medium is a magnetic recording medium. It is preferable to use a magnetic recording medium for a large-capacity floppy disk system using a linear type voice coil motor for driving the head by rotating the disk. In addition, the present invention relates to the improvement of a magnetic material.
The acicular ratio is 4.0 to 9.0, (2) the ferromagnetic metal powder is mainly composed of Fe, and has an average major axis length of 0.10 μm.
Hereinafter, the crystallite size is preferably from 80 ° to 180 °. As for the improvement of the support, (1) the center surface average surface roughness of the support is 4.0 nm or less, and (2) 100 ° C. in each in-plane direction of the support.
Both the heat shrinkage in 30 minutes and the heat shrinkage in 80 ° C. for 30 minutes are 0.5% or less, and (3) the coefficient of thermal expansion in each in-plane direction of the support is 10 ^-4 . It is preferably 10 ^-8 / ° C. As regards the improvement of the lubricant, (1) the lower layer and / or the magnetic layer contain at least three kinds of fatty acids and / or fatty acid esters in total; (3) the fatty acid contains at least a saturated fatty acid, the fatty acid ester contains at least a saturated fatty acid ester or an unsaturated fatty acid ester, (4) the fatty acid ester contains a monoester and a diester, (5) the fatty acid ester contains a saturated fatty acid ester and an unsaturated fatty acid ester; and (6) a C / Fe peak ratio of 5 to 100 when the surface of the magnetic layer is measured by Auger electron spectroscopy. It is preferred that (1) The lower layer preferably has an average particle diameter of 5 nm to 8 nm.
0 nm carbon black, and the magnetic layer contains carbon black having a particle size of 5 nm to 300 nm.
(2) The lower layer has a mean particle size of 5 nm to 80 nm.
(3) Both the lower layer and the magnetic layer include carbon black having an average particle diameter of 5 nm to 80 nm, and (4) a carbon black having an average particle diameter of more than 80 nm. ) The lower layer has an average major axis length of preferably 0.20 µm or less, more preferably 0.10 µm.
m or less, and preferably contains a needle-like inorganic powder having a needle-like ratio of preferably 3.0 to 9.0, more preferably 4.0 to 9.0, and (5) the lower layer contains a needle-like inorganic powder. The magnetic layer includes a needle-shaped ferromagnetic metal powder, and the average long-axis length of the needle-shaped inorganic powder is 1.1 times the average long-axis length of the needle-shaped ferromagnetic metal powder.
(6) Preferably, the lower layer and / or the magnetic layer contains a phosphorus compound, and the lower layer contains an acicular or spherical inorganic powder. (1) The magnetic layer contains at least an abrasive having an average particle diameter of 0.01 to 0.30 μm, and (2) the magnetic layer has an average particle diameter of at least 2.0.
μm or less, preferably 0.01 to 1.0 μm, (3) the magnetic layer contains two types of abrasives having a Mohs hardness of 9 or more, and (4) the magnetic layer contains α.
Preferably, it contains alumina and diamond. (1) The lower layer and / or the magnetic layer preferably has a glass transition temperature of at least 0 ° C.
(2) The lower layer and / or the magnetic layer has a breaking stress of at least 0.05 to 10 kg / mm.
Preferably, it comprises ^two polyurethanes.

According to the present invention, the surface recording density, which cannot be obtained by the conventional technique, is 0.17 to less.
A magnetic recording medium of ² Gbit / inch ² having excellent high-density characteristics and excellent durability, and particularly having a remarkably improved error rate in a high-density region, particularly a disk-shaped magnetic recording medium Are found to be able to be obtained.

According to the present invention, the excellent areal recording density is 0.1
7 to ² Gbit / inch ² , preferably 0.2 to ² Gbit / inch
² Further, the magnetic recording medium having both high density characteristics and excellent durability, which has not been achieved by a coating type magnetic recording medium known in the world as a surface recording density of 0.35 to ² Gbit / inch ² In particular, the disk-shaped magnetic recording medium was obtained by organically combining the following points,
This is a comprehensive result.

The points of the present invention are high Hc, super smoothness,
Improvement of composite lubricants, high-durability binders, and ferromagnetic powders, ensuring durability by using high-hardness abrasives, ultra-thin magnetic layers and reduced fluctuations at the interface with the lower layer, powders (ferromagnetic powders, Higher filling of magnetic powder), powder (ferromagnetic powder, non-magnetic powder)
Of ultra fine particles, stabilization of head touch, dimensional stability and servo, improvement of heat shrinkage of magnetic layer and support, high temperature,
The effect of the lubricant at a low temperature can be mentioned, and these are combined, and as a result, the present invention has been accomplished.

First, the high Hc and ultra-smoothing will be described. By using a high Hc ferromagnetic powder, the Hc of the magnetic layer can be increased to 1800 Oe or more, preferably 210
0 Oe or more, and a large capacity and high density can be achieved. For ultra-smoothing, the center plane average surface roughness of the support is usually 5.0 nm or less, preferably 4.0 n.
m or less, and a smooth magnetic layer can be obtained by the ATOMM configuration.
High capacity and high density can be achieved. Next, the improvement of the composite lubricant, the highly durable binder, the ferromagnetic powder, and the securing of durability by using a high hardness abrasive will be described. First, the basic concept for enhancing the lubricating ability of the composite lubricant is as follows.

(1) A plurality of lubricants having different functions and performances are used in combination. (2) A plurality of lubricants having similar functions and performances are used in combination. According to the above (1), a wide range of functions and performances can be achieved under a wide range of conditions. Further, the affinity and compatibility between the lubricants are secured by the above (2), and a good lubrication function can be exhibited.

The following are examples of combinations of a plurality of lubricants having different functions and performances in the above (1). 1) A lubricant having a fluid lubrication function and a lubricant having a boundary lubrication function are used in combination. 2) A polar lubricant and a non-polar lubricant are used in combination.

3) A liquid lubricant and a solid lubricant are used in combination. 4) Lubricants having different polarities, particularly fatty acids and / or fatty acid esters are used in combination. For example, a monoester and a diester of a fatty acid ester are used in combination. 5) Lubricants having different melting points and boiling points, particularly fatty acids and / or fatty acid esters are used in combination.

6) A lubricant having a different number of carbon atoms, particularly a combination of fatty acids and / or fatty acid esters is used. 7) Linear and branched lubricants, especially fatty acids and / or fatty acid esters are used in combination. For example, a linear fatty acid ester and a branched fatty acid ester are used in combination.

8) Saturated and unsaturated carbon chain lubricants, especially fatty acids and / or fatty acid esters are used in combination. For example, a saturated fatty acid ester and an unsaturated fatty acid ester are used in combination. 9) Use a combination of lubricants having different affinities with the binder. 10) A lubricant having a different affinity for the inorganic powder is used in combination.

The combination of the lubricants of the above (1) allows a wide range of functions and functions under a wide range of conditions.
Performance can be achieved. An example of a combination of a plurality of lubricants having similar functions and performances in the above (2) is as follows. 1) The fatty acid residues of the fatty acid and the fatty acid ester are made identical.

2) The fatty acid residues of the fatty acid ester and / or the alcohol residue are used in combination with the same fatty acid ester. 3) Two or more kinds of saturated fatty acids are used in combination. 4) Saturated fatty acids are used in the fatty acid residue portion of the fatty acid and the fatty acid ester. 5) Unsaturated fatty acids are used in the fatty acid residue portion of the fatty acid and the fatty acid ester.

6) Only three or more fatty acid esters are used in combination. 7) Make the fatty acid portions of the fatty acid and the fatty acid amide identical. By the combination of the lubricant (2), affinity and compatibility between the lubricants are ensured, and a good lubrication function can be exhibited. By using the lubricant of the above (1) and the lubricant of the above (2) in various combinations, a wide range of functions and performances can be achieved under a wide range of conditions, and the affinity and compatibility between the lubricants are ensured. And a good lubrication function can be exhibited.

Next, the highly durable binder will be described. By having a polar group, the dispersing performance is high, the glass transition temperature is high, and since the breaking stress is high, the durability can be improved by using a binder, particularly a polyurethane resin, which has high durability. Further, it is preferable that the polyurethane has two or more OH groups at the molecular terminals, and it is particularly preferable that the polyurethane has three or more, particularly four or more OH groups at the molecular terminals. It is preferable because it has high reactivity and can be cured to form a three-dimensional network coating film. Next, regarding the improvement of the ferromagnetic metal powder, the hardness of the ferromagnetic metal powder can be increased, and the durability can be improved by increasing the Al component. Further, how to ensure durability by using a high hardness abrasive will be described. Durability can be further secured by using not only conventional abrasives such as α-alumina but also abrasives having a Mohs hardness of about 9, as well as diamonds of fine particles having a Mohs hardness of 10. Next, the ultra-thin layer of the magnetic layer and the reduction in fluctuation of the interface with the lower layer will be described. By making the magnetic layer ultra-thin, preferably 0.05-0.30 μm, more preferably 0.05-0.25 μm, and reducing the fluctuation of the interface with the lower layer, a uniform, smooth, thin layer And a large capacity and high density are achieved. A description will be given of further filling of powder (ferromagnetic metal powder, non-magnetic powder). The ferromagnetic metal powder is preferably filled with fine ferromagnetic metal powder having an average major axis length of preferably 0.15 μm or less, more preferably 0.12 μm or less, and particularly preferably 0.10 μm or less. As a result, large capacity and high density can be achieved. The durability can be improved by increasing the filling of the non-magnetic powder. Next, ultra-fine powder (ferromagnetic metal powder, non-magnetic powder) will be described. The average major axis length of the ferromagnetic metal powder is preferably 0.15 μm or less, and more preferably 0.1 μm or less.
Fine particles having a diameter of 2 μm or less, particularly preferably 0.10 μm or less, are used. In particular, the average major axis length is 0.10 μm or less, the acicular ratio is 4.0 to 9.0, and the crystallite size is 80 ° to 180 °.
Å, when the inorganic powder in the lower layer is acicular, the average major axis length is preferably 0.20 μm or less, more preferably 0.10 μm or less, so that high filling and ultra-smoothness of the magnetic layer are achieved. Is achieved, and large capacity and high density can be achieved. Next, stabilization of head touch will be described. The appropriate strength, flexibility, and smoothness of the entire magnetic recording medium can stabilize the head touch, and high-speed running and high-speed rotation can stably increase the capacity and density. Next, dimensional stability and servo will be described. For example, the heat shrinkage at 100 ° C. for 30 minutes and the 80
The heat shrinkage rate at 30 ° C. for 30 minutes is 0.5% or less,
The coefficient of thermal expansion in each direction in the plane of the support is 10 ^-4 to 1
By being 0 ^-8 / ° C, dimensional stability can be achieved, and high capacity and high density can be stably achieved even at high speed running and high speed rotation. Similarly, the heat shrinkage of the magnetic layer and the support can be improved. Regarding the action of the lubricant at high and low temperatures, good lubrication performance can be obtained at both high and low temperatures by selecting and combining the various lubricants described above based on a certain concept.

In the field of personal computers, which are becoming more and more multi-media, large-capacity recording media replacing floppy disks have begun to attract attention, and have been sold as ZIP disks by IOMEGA (Iomega), USA. This is an ATOMM (Advanced S) developed by the present applicant.
upper Thin Layer & High Ou
input Metal Media Technology
gy), a recording medium having a lower layer and a thin magnetic layer, and a product having a recording capacity of 3.7 inches and a recording capacity of 100 MB or more is sold. 100-120MB capacity is MO
(3.5 inches), and one newspaper article can fit in July or August. The transfer rate indicating the write / read time of data (information) is 2 MB or more per second, which is comparable to that of a hard disk.
20 times faster than MO and more than twice as fast as MO. Further, this recording medium having a lower layer and a thin magnetic layer can be mass-produced with the same coating type medium as that of the current FD, and has an advantage that it is lower in price than an MO or a hard disk.

The present inventors have conducted intensive studies based on the knowledge of such media, and as a result, have found that the ZIP disk and MO
(3.5 inches), the areal recording density which is much larger than the recording capacity is 0.17 to ² Gbit / inch ² , preferably 0.2 to ² Gbit / inch ² .
Gbit / inch ^{2 and} surface recording density of 0.35 to ² Gbit / in
A ch ^2, preferably Φm is 10.0 × 10 ^-3 ~
1.0 × 10 ⁻³ emu / cm ² , especially φm is 8.0 × 1
It has high capacity, high density characteristics and excellent durability, which has never been achieved in products known in the world as 0 ^{-3 to} 1.0 × 10 ^-3 emu / cm ² , especially in high density recording areas. A magnetic recording medium having a significantly improved error rate, particularly a disk-shaped magnetic recording medium, has been obtained, and is an invention applicable to a magnetic tape such as a computer tape.

The magnetic recording medium of the present invention contains an ultra-thin magnetic layer containing an ultrafine ferromagnetic metal powder having high output and high dispersibility, and a lower layer containing a spherical or acicular inorganic powder. By reducing the thickness of the layer, the canceling of the magnetic force in the magnetic layer is reduced, the output in the high-frequency region is greatly increased, and the overwriting characteristics are further improved. By improving the magnetic head, the effect of the ultra-thin magnetic layer can be further exhibited in combination with the narrow gap head, and the digital recording characteristics can be improved.

The thickness of the magnetic layer is preferably from 0.05 to 0.30 μm, more preferably from 0.05 to 0.25 μm, so as to match the magnetic recording system for high density recording and the performance required from the magnetic head. Is selected as a thin layer. Such an ultrathin magnetic layer having a uniform and thin layer preferably has a multilayer structure of a lower layer and an upper layer. Highly dispersed by combination to achieve high filling. The ferromagnetic metal powder used is a ferromagnetic metal powder excellent in high output, high dispersibility, and high randomization in order to maximize the suitability of a large capacity FD or computer tape. That is, ferromagnetic metal powders having very fine particles and having an average major axis length of preferably at most 0.15 μm, more preferably at most 0.12 μm, which can achieve a high output, and especially having an average major axis length of at most 0.10 μm, Size is 80Å-180
By using a ferromagnetic metal powder that is Å, Co
And a high output and high durability can be achieved by further containing components such as Al, Si, Y, and Nd. In order to achieve a high transfer rate, a three-dimensional network binder system suitable for an ultra-thin magnetic layer is used to ensure running stability and durability during high-speed rotation. In addition, a composite lubricant that can maintain its effectiveness even when used under a wide range of temperature and humidity conditions or when used at high speeds is arranged in the upper and lower layers. An appropriate amount of lubricant can always be supplied to the layer, the durability of the upper magnetic layer is increased, and the reliability is improved. Further, the cushion effect of the lower layer can provide good head touch and stable running performance.

In a large-capacity recording system, a high transfer rate is required. For example, the transfer speed of Zip is 1.4 MB / sec, and the transfer speed of HiFD is 3.6 MB / sec at maximum. For this purpose, it is necessary to increase the number of rotations of the magnetic disk by one digit or more compared to the conventional FD system. Specifically, the rotational speed of the magnetic disk is preferably 1800 rpm or more,
0 rpm or more is more preferable. For example, in Zip, the magnetic disk rotation speed is 2968 rpm, and in HiFD, the magnetic disk rotation speed is 3600 rpm. In another system, when the recording capacity is 650 MB (0.65 GB), the magnetic disk rotation speed is 5400 rpm, and the transfer speed is 7.
It is predicted to be 5 MB / sec. As the capacity and density of magnetic recording increase, the recording track density increases. In general, a servo recording area is provided on a medium to ensure traceability of a magnetic head with respect to a recording track. In the magnetic recording medium of the present invention, it is preferable to use a support having improved isotropic dimensional stability as a support, and further stabilization of traceability can be achieved. By using an ultra-smooth support, the smoothness of the magnetic layer can be further improved.

In order to increase the density of disk-shaped magnetic recording,
It is necessary to improve the linear recording density and the track density. Of these, the characteristics of the support are important for improving the track density. In the medium of the present invention, the dimensional stability of the support, particularly the isotropy, is considered. Servo recording is an indispensable technique in recording and reproduction at a high track density, but this improvement can be achieved from the medium side by making the support as isotropic as possible.

The advantages of the present invention in which the magnetic layer is changed from a single layer to an ATOMM structure are considered as follows. (1) Improvement of electromagnetic conversion characteristics by forming a thin magnetic layer structure (2) Improvement of durability by stable supply of lubricant (3) High output by smoothing upper magnetic layer (4) Separation of functions of magnetic layer Easy provision of required functions These functions cannot be achieved simply by stacking the magnetic layers. In order to configure a multilayer structure, a “sequential multilayer system” in which layers are sequentially configured is generally used. In this method, first, a lower layer is applied, cured or dried, and then an upper magnetic layer is similarly applied, cured, and surface-treated. The FD differs from the magnetic tape in that the same processing is performed on both sides. After the coating process, it is completed as a final product through a slitting process, a punching process, a shell assembling process, and a certifying process. From the viewpoint of production yield, simultaneous or sequential wet application of applying the upper magnetic layer while the lower layer is still wet is preferred.

By forming the magnetic layer into a thin layer structure, the following electromagnetic conversion characteristics can be greatly improved. (1) Improvement of output in high frequency region by improvement of recording demagnetization characteristics (2) Improvement of overwriting (overwrite) characteristics (3) Ensuring window margin Durability is an important factor for magnetic disks. Particularly, in order to realize a high transfer rate, it is necessary to increase the number of rotations of the magnetic disk by one digit or more compared with the conventional FD system, and the medium durability when the medium in the magnetic head / cartridge slides at high speed with the medium. Is an important issue.
As means for improving the durability of the medium, there are a binder formulation for increasing the film strength of the disk itself, and a lubricant formulation for maintaining the slipperiness with the magnetic head. The media of the present invention improves upon the 3D network binder system proven in current FD systems for binder formulations.

The lubricant is used in combination with a plurality of lubricants which exhibit excellent effects under various temperature and humidity environments to be used, and has a wide range of temperature (low temperature, room temperature, high temperature) and humidity (low humidity, high humidity). Even under a wet environment, each lubricant exerts its function and can maintain a totally stable lubricating effect. In addition, by utilizing the structure of the upper and lower two layers, the lower layer has a lubricant tank effect so that an appropriate amount of lubricant is always supplied to the upper magnetic layer, and the durability of the upper magnetic layer can be improved. Things. There is a limit to the amount of lubricant that can be included in the ultra-thin magnetic layer, and simply thinning the magnetic layer reduces the absolute amount of lubricant, leading to deterioration in running durability. In this case, it was difficult to obtain a balance between the two. The upper and lower layers are provided with different functions and complement each other to achieve both improved electromagnetic conversion characteristics and improved durability. This functional differentiation was particularly effective in a system in which a magnetic head and a medium slide at high speed.

The lower layer can have a function of controlling surface electric resistance in addition to the function of holding the lubricant. Generally, for controlling the electric resistance, a solid conductive material such as carbon black is often added to the magnetic layer. These not only limit the packing density of the ferromagnetic metal powder but also affect the center plane average surface roughness as the magnetic layer becomes thinner. These disadvantages can be eliminated by adding a conductive material to the lower layer.

With the multi-media society, the need for image recording is increasing not only in the industrial world but also in homes. It has the ability to sufficiently meet the demands for function / cost as a medium. The large-capacity medium of the present invention is based on a coated magnetic recording medium with a proven track record, and has excellent long-term reliability and excellent cost performance.

The present invention is achieved for the first time by accumulating various factors as described above, acting synergistically and organically, and at the same time, selecting, combining and integrating all the above-mentioned technologies. The obtained magnetic recording medium has a capability of being applied to, for example, HiFD jointly developed by Sony Corporation and Fuji Film Corporation. HiF
In recent years, with the rapid development of the processing capability of personal computers and the large increase in the amount of information to be handled, D is a new high-performance data with a large capacity and a high data transfer rate.
The demand for a data recording system and the current 3.5-inch floppy disk are widely spread as easy-to-use recording media all over the world, and these disks will continue to be used and the vast amount of data accumulated. Has been developed as a new system that can read out and reuse. The 3.5-inch floppy disk "HiFD" has a large capacity of 200 MB and a high-speed transfer rate of 3.6 MB / sec, and is backward compatible with the current 3.5-inch floppy disk. Next generation large capacity floppy
It is a disk system. Newly developed ultra thin layer coated metal disk and dual disk gap head with both narrow gap for high density recording and wide gap for current 3.5 inch floppy disk A large capacity of 200 MB can be realized, and a large capacity data file such as an image or a sound can be easily handled. In addition, high linear recording density and 3600
By rotating the disk at a high speed of rpm, the transfer speed of a conventional 3.5-inch floppy disk (2HD) is reduced to about 0.0.
It realizes a high-speed transfer rate of 3.6 MB / sec at maximum for 6 MB / sec. This is about 6
This enables 0 times high-speed processing. In addition, since the dual disk gap head floats due to the rotation of the disk similar to the hard disk, recording and
Since the head does not contact during reproduction, a floating type with a long life and high reliability is used, and at the same time, a high-speed random access is realized by using a linear type voice coil motor for driving the head to realize a conventional 3.5-inch floppy disk. Compared to a disk drive, the speed can be increased by about 3 to 4 times. Further, the dual disk gap head realizes backward compatibility enabling recording and reproduction with the current 3.5-inch floppy disk. Furthermore, by incorporating a new mechanism that performs soft head loading, disc wear can be reduced, and further errors can be eliminated.
High reliability is ensured by installing a correction function. Such a large capacity of 200 MB, 3.6 MB / se
The current 3.5-inch floppy with high transfer speed
Achieved backward compatibility that allows recording and playback with disks.
The magnetic recording medium of the present invention has been developed so as to be applicable to a next-generation large-capacity floppy disk system.

[0047]

BEST MODE FOR CARRYING OUT THE INVENTION

[Magnetic Layer] In the magnetic recording medium of the present invention, an ultrathin magnetic layer may be provided on only one side or both sides of the support. When the lower layer is provided, the upper and lower layers are applied after the lower layer is applied, and the lower layer is in a wet state (W
/ W), the upper magnetic layer can be provided on the lower layer even after the lower layer is dried (W / D). From the viewpoint of production yield, simultaneous or sequential wet coating is preferable, but in the case of a disc, coating after drying can be used sufficiently. The upper layer / lower layer can be formed simultaneously by simultaneous or sequential wet coating (W / W) in the multilayer structure of the present invention, so that surface treatment steps such as a calendering step can be effectively utilized, and even in the case of an ultrathin layer, the surface roughness of the upper magnetic layer can be improved. Can be improved. The coercive force Hc of the magnetic layer needs to be 1800 Oe or more, and Bm is 2000 to 50.
00G (Gauss) is preferable.

[Ferromagnetic Metal Powder] The ferromagnetic metal powder used in the magnetic layer of the present invention is preferably a ferromagnetic alloy powder containing α-Fe as a main component. The ferromagnetic metal powder (hereinafter referred to as “ferromagnetic metal powder a”) used in the invention of claim 1 is composed of at least Fe and Co,
The atomic ratio A of (Fe + Co) is 3.0 to 15.4%, preferably 4.5 to 15.0%, and more preferably 6.
0 to 12.0%. .

The ferromagnetic metal powder (hereinafter referred to as “ferromagnetic metal powder b”) used in the second aspect of the present invention is composed of at least Fe and Co, and has a total sum of rare earth elements /
The atomic ratio B of (Fe + Co) is 0.5 to 9.0%,
Preferably it is 1.0 to 8.0%, more preferably 1.0 to 6.0%. The ferromagnetic metal powder a used for the magnetic layer of the present invention preferably contains a rare earth element and Mg, and the ferromagnetic metal powder b preferably contains Al.

The ferromagnetic metal powders a and b may further contain Mg, and the atomic ratio C of Mg / (Fe + Co) is preferably 0.05 to 3.0%, more preferably 0.1 to 3.0%.
It is 2.5%, particularly preferably 0.1 to 2.0%. In the present invention, the atomic ratio A, the atomic ratio B and the atomic ratio C
% Means atomic%.

In the present invention, as the ferromagnetic metal powder,
When referring to at least one of the ferromagnetic metal powders a and b, it is simply referred to as “ferromagnetic metal powder” hereinafter. In the ferromagnetic metal powder of the present invention, Co is 3 to 5 with respect to Fe.
0 atomic% is preferable, and 5 to 45 atomic% is more preferable.
Particularly preferred is 10 to 45 at%, most preferably 20 to 45 at%.
In the range of ３５35 at%. The ferromagnetic metal powder preferably has an atomic ratio B / A of total of rare earth elements / Al of 0.1.
05 to 1.20, more preferably 0.10 to 1.0, particularly preferably 0.1 to 0.6.

The ferromagnetic metal powder used in the magnetic layer of the present invention preferably contains Fe, Co, Al, Mg and a rare earth element within the above range, so that excellent high-density recording characteristics and excellent running durability can be obtained. And weather resistance can be obtained. Since the ferromagnetic metal powder contains the above essential components within the above range, it is a fine particle, but has a sharp particle size distribution, excellent uniformity, and appropriate hardness.
In addition, because of its excellent dispersibility, excellent high-density recording characteristics and excellent running durability and weather resistance can be obtained.

That is, in the ferromagnetic metal powder a, A
If the atomic ratio A of l / (Fe + Co) is less than 3.0%,
The running durability is poor, and if it is more than 15.4%, the high-density recording characteristics are poor. If the atomic ratio B of the ferromagnetic metal powder b is less than 0.5%, it is difficult to obtain excellent high-density recording characteristics. If it is more than 9.0%, it is difficult to obtain excellent running durability.

In the ferromagnetic metal powder, Mg / (Fe +
If the atomic ratio C of Co) is less than 0.05%, it tends to be difficult to achieve both excellent high-density recording characteristics and excellent running durability. If the atomic ratio C is more than 3.0%,
It tends to be difficult to obtain excellent high-density recording characteristics and excellent running durability and weather resistance. The rare earth elements used in the ferromagnetic metal powder of the present invention include Sc, Y, La, and C.
e, Pr, Nd, Pm, Sm, Eu, Gd, Tb, D
It means each element of y, Ho, Er, Tm, Yb, and Lu. In the present invention, Y is particularly preferable.

The content of Y is based on the total of the rare earth elements.
Preferably 40 to 100 atomic%, more preferably 55 to
The range is 100 atomic%.

The method for producing the ferromagnetic metal powder used in the present invention is not particularly limited, and examples thereof include a method described in JP-A-8-279137.
Specifically, goethite is formed from an aqueous solution of an Fe salt or an Fe salt and a Co salt, and a Co-containing compound, A
l-containing compound, a compound of a rare earth element, and further an aqueous solution of a Mg-containing compound or a compound of an element described below is added and mixed to prepare a goethite suspension containing these,
The suspension is granulated, dried, reduced, and then gradually oxidized to obtain a ferromagnetic metal powder of the present invention. Monodisperse hematite particles or, if necessary, goethite,
Containing compounds, Al-containing compounds, compounds of rare earth elements,
Further, a method of treating with an Mg-containing compound or the like and then reducing the same may be mentioned. Note that some Al compounds may be added in the process of forming goethite.

The ferromagnetic metal powder of the present invention can be manufactured by other known methods, including the following methods. Reduction with complex organic acid salt (mainly oxalate) and reducing gas such as hydrogen, thermal decomposition of metal carbonyl compound, sodium borohydride, hypophosphite or hydrazine in aqueous solution of ferromagnetic metal And a method of evaporating a metal in a low-pressure inert gas to obtain a fine powder.

Here, in order to satisfy at least the composition of the ferromagnetic metal powder of the present invention or to obtain desired characteristics, the type and amount of the salt or compound, dehydration conditions, reduction conditions, gradual oxidation conditions, etc. What is necessary is just to set suitably. It is also effective to reduce the ferromagnetic metal powder again to improve the properties. As the slow oxidation treatment, a method of drying after immersion in an organic solvent, a method of drying after immersing in an organic solvent, forming an oxide film on the surface by feeding an oxygen-containing gas,
A method of forming an oxide film on the surface by adjusting the partial pressure of an oxygen gas and an inert gas without using an organic solvent is exemplified.

In the present invention, a method of forming an oxide film on the surface by adjusting the partial pressure of oxygen gas and inert gas without using an organic solvent is suitable. These ferromagnetic metal powders include Si, S, Ca, Ti, V, Cr, C
u, Mo, Rh, Pd, Ag, Sn, Sb, Te, B
a, Ta, W, Re, Au, Hg, Pb, Bi, P, M
It may contain atoms such as n, Zn, Ni, Sr, and B. These elements are usually 5 × 10 ⁻⁴ to 1 with respect to Fe.
It is used at × 10 ^-1 atomic%. F as ferromagnetic metal powder
Specific examples in which Co, Al and rare earth elements are added to e are described in JP-A-6-215360 and JP-A-7-210.
No. 856, JP-A-8-185624, JP-A-8-27
No. 9142 and the like. These ferromagnetic metal powders may be preliminarily treated with a dispersant, a lubricant, a surfactant, an antistatic agent or the like before dispersion before the dispersion. Specifically, Japanese Patent Publication No. 44-14090 and Japanese Patent Publication No. 4
5-18372, JP-B-47-22062, JP-B-47-22513, JP-B-46-28466, JP-B-46-38755, JP-B-47-4286, JP-B-47-12422, and JP-B-47-12422 -17284, JP-B-47-18509, JP-B-47-18573,
JP-B-39-10307, JP-B-46-39639
No. 3,026,215, US Pat.
Nos. 3,100,194, 3,242,005, and 33
No. 89014 and the like. Specific examples of addition of Mg include Japanese Patent Publication No. 1-51042 and Japanese Patent Publication No. 8-313.
No. 66, JP-A-63-222404, JP-A-5-54
No. 371 and the like. In addition, Fe, Co, Al, Mg
Specific examples of the ferromagnetic metal powder containing a rare earth element and a rare earth element include JP-A-9-27117 and JP-A-9-35247.

The ferromagnetic metal powder of the magnetic layer of the present invention was
When expressed in terms of specific surface area by the method, it is usually 40 to 80 m ² / g, preferably 45 to 70 m ² / g. 40m ² /
If it is less than g, noise increases, and if it is more than 80 m ² / g, surface properties tend to be difficult to obtain, which is not preferable. The crystallite size of the ferromagnetic metal powder of the magnetic layer of the present invention is preferably 80 to 180 °, more preferably 100 to 180 °.
{, Particularly preferably 110-175}. The average major axis length of the ferromagnetic metal powder is usually 0.01 μm or more and 0.25
μm or less, preferably 0.03 μm or more and 0.15 μm
m or less, more preferably 0.04 μm or more and 0.1
It is 2 μm or less. The needle ratio of the ferromagnetic metal powder is usually
It is preferably from 3.0 to 15.0, more preferably from 3.0 to 12.0, particularly preferably from 3.0 to 9.0. The saturation magnetization s of the ferromagnetic metal powder is usually 1
100 to 180 emu / g, preferably 110 emu / g to
It is 170 emu / g, more preferably 125 to 160 emu / g. The coercive force Hc of the ferromagnetic metal powder is preferably from 1700 Oe to 3500 Oe, and more preferably from 1,800 Oe to 3000 Oe. The surface of the ferromagnetic metal powder is preferably covered with a dense oxide film. Further, it is preferable that a large amount of Al and rare earth elements be present in the surface layer of each particle of the ferromagnetic metal powder.

The water content of the ferromagnetic metal powder is 0.01 to 2%.
It is preferred that Ferromagnetic metal depending on the type of binder
Preferably, the moisture content of the powder is optimized. Ferromagnetic metal powder
The pH of the powder is optimized by the combination with the binder used.
Is preferred. The range is pH 4 to 12, but it is preferable.
The pH is preferably 6 to 10. Ferromagnetic metal powder needed
Depending on the surface, such as Al, Si, P or their oxides
Processing may be performed. The amount is ferromagnetic metal powder
0.1 to 20% by weight, preferably 0.1 to 10% by weight
%, And surface treatment will result in the absorption of lubricants such as fatty acids.
100mg / m ^TwoThe following is preferred. Ferromagnetic metal powder
Contains inorganics such as soluble Na, Ca, Fe, Ni, Sr
May contain ions. These are essentially not
Although it is preferable, if it is 200 ppm or less, the characteristics are particularly affected.
Little to give. Also, the ferromagnetic used in the present invention
It is preferable that the metal powder has few pores, and the value is 20 volumes.
%, More preferably 5% by volume or less. Also
The shape can be needle-shaped, rice-grained, or spindle-shaped.
I don't know. The smaller the SFD of the ferromagnetic metal powder itself, the better.
And 0.8 or less is preferable. Hc of ferromagnetic metal powder
The distribution needs to be small. SFD is 0.8 or less
, The electromagnetic conversion characteristics are good, the output is high, and
High density with sharp magnetization reversal, reduced peak shift
It is suitable for digital magnetic recording. Decrease Hc distribution
In order to achieve this, in ferromagnetic metal powder,
There are methods such as improving the particle size distribution and preventing sintering.
You.

[Non-magnetic layer] Next, the detailed contents of the lower layer
Will be described. Inorganic powder used for the lower layer of the present invention
Is a non-magnetic powder, for example, metal oxide, metal carbonate
Salt, metal sulfate, metal nitride, metal carbide, metal sulfide
And other inorganic compounds. Mineralization
As the compound, for example, α-alumina having an α conversion of 90% or more,
β-alumina, γ-alumina, θ-alumina, silicon carbide
Element, chromium oxide, cerium oxide, α-iron oxide, hematite
, Goethite, corundum, silicon nitride, titanium cover
, Titanium oxide, silicon dioxide, tin oxide, magnesia
Cium, tungsten oxide, zirconium oxide,
Iodine, zinc oxide, calcium carbonate, calcium sulfate, sulfuric acid
Barium acid, molybdenum disulfide, etc., alone or in combination
Used in. Particularly preferred are small particle size distribution,
Titanium dioxide, oxidation
Zinc, iron oxide and barium sulfate are more preferred.
Titanium dioxide and α-iron oxide. Average of these inorganic powders
Although the particle diameter is preferably 0.005 to 2 μm, if necessary,
Combine inorganic powders with different average particle diameters
The same effect can be achieved by widening the particle size distribution even with inorganic powders
You can also. Particularly preferred are inorganic powder particles
The diameter is between 0.01 μm and 0.2 μm. In particular, inorganic powder
Is a granular metal oxide, the average particle diameter is 0.08 μm.
m or less, and in the case of a needle-shaped metal oxide, an average
The major axis length is preferably 0.3 μm or less, and preferably 0.2 μm or less.
More preferably, it is particularly preferably 0.10 μm or less. needle
The state ratio is preferably 3 to 12, and more preferably 4 to 9. Ta
The tip density is usually 0.05-2 g / ml, preferably 0.2
１．５1.5 g / ml. The water content of the inorganic powder is usually 0.1
-5% by weight, preferably 0.2-3% by weight, more preferably
Or 0.3 to 1.5% by weight. PH of inorganic powder
Usually, it is 2 to 11, but the pH is particularly preferably between 5.5 and 10.
preferable. The specific surface area of the inorganic powder is usually 1 to 100 m^Two/
g, preferably 5 to 80 m^Two/ g, more preferably 10-7
0m^Two/ g. The crystallite size of the inorganic powder is 0.004
μm to 1 μm is preferable, and 0.04 μm to 0.1 μm is preferable.
More preferred. Using DBP (dibutyl phthalate)
Oil absorption is usually 5 to 100 ml / 100 g, preferably 10 to 100 ml / 100 g.
80 ml / 100 g, more preferably 20 to 60 ml / 100 g.
You. The specific gravity is usually 1 to 12, preferably 3 to 6.
The shape may be any of a needle shape, a spherical shape, a polyhedral shape, and a plate shape.
The Mohs' hardness is preferably 4 or more and 10 or less. inorganic
The SA (stearic acid) adsorption amount of the powder is usually 1 to 20 μ
mol / m^Two, Preferably 2 to 15 μmol / m ^Two, Even more preferred
Or 3-8 μmol / m^TwoIt is. pH between 3 and 6
Preferably. The surface treatment of these inorganic powders
Al_TwoO_Three, SiO_Two , TiO_Two, Zr
O_Two, SnO_Two, Sb_TwoO_Three, ZnO, Y_TwoO_ThreeExists
Preferably. Particularly preferred for dispersibility is Al_TwoO
_Three, SiO_Two, TiO_Two, ZrO_TwoBut more preferred
What's new is Al_TwoO_Three, SiO_Two, ZrO_TwoIt is. this
May be used in combination or used alone
Can also. Also, depending on the purpose, the co-precipitated surface treatment layer
May be used, or after the presence of alumina,
Use silica in the layer or vice versa.
You can also. Also, the surface treatment layer is porous depending on the purpose.
Although it may be a quality layer, it is generally better to be homogeneous and dense
preferable.

Specific examples of the inorganic powder used in the lower layer of the present invention include HIT-1 manufactured by Sumitomo Chemical as alumina.
00 (average particle diameter 0.11 μm), ZA-G1, nanotite (average particle diameter 0.06 μm) manufactured by Showa Denko as iron oxide,
Α hematite DPN-25 manufactured by Toda Kogyo KK as iron oxide
0, DPN-250BX (average major axis length 0.16 μm, average minor axis length 0.02 μm, needle ratio 7.45), DPN-2
45, DPN-270BX, DPN-550BX, DP
N-550RX (average major axis length 0.15 μm, average minor axis length 0.02 μm, needle ratio 7.5), DPN-650RX,
Α-hematite α-40 manufactured by Titanium Industry, α-hematite E270, E271, E300, E303 manufactured by Ishihara Sangyo, titanium oxide TTO-51B manufactured by Ishihara Sangyo as titanium oxide (average particle diameter: 0.01 to 0.03 μm), TTO-55A
(Average particle size 0.03-0.05 μm), TTO-55
B (average particle diameter 0.03-0.05 μm), TTO-5
5C (average particle size 0.03-0.05 μm), TTO-
55S (average particle size 0.03-0.05 μm), TTO
-55D (average particle diameter 0.03 to 0.05 μm), SN
-100, titanium oxide manufactured by Titanium Kogyo STT-4D (average particle diameter 0.013 μm), STT-30D (average particle diameter 0.09 μm), STT-30 (average particle diameter 0.12 μm)
m), STT-65C (average particle size 0.12 μm), Tyca-based titanium oxide MT-100S (average particle size 0.01
5 μm), MT-100T (average particle size 0.015 μm)
m), MT-150W (average particle size 0.015 μm),
MT-500B (average particle diameter 0.035 μm), MT-
600B (average particle size 0.050 μm), MT-100
F, MT-500HD, FIN as zinc oxide manufactured by Sakai Chemical
EX-25 (average particle size 0.5 μm), BF-1 (average particle size 0.05 μm) as barium sulfate manufactured by Sakai Chemical, B
F-10 (average particle diameter 0.06 μm), BF-20 (average particle diameter 0.03 μm), ST-M, DEF manufactured by Dowa Mining
IC-Y, DEFIC-R, AS2B made by Nippon Aerosil
M, TiO2P25, Ube Industries 100A, 500A,
And baked products thereof. Particularly preferred inorganic powders are titanium dioxide and α-iron oxide.

For example, α-iron oxide (hematite) is produced under the following conditions. That is, α-Fe ₂ O
The production of _three- particle powder uses acicular goethite particles as precursor particles. Acicular goethite particles can be produced, for example, by the following method. An aqueous solution of an alkali hydroxide in an equal amount or more is added to the aqueous ferrous solution to prepare a suspension having a pH of 11 or more containing a ferrous hydroxide colloid, and an oxygen-containing gas is passed through the suspension at a temperature of 80 ° C. or less to form a suspension. A method in which ferrous ions are subjected to an oxidation reaction to generate acicular goethite particles.

An aqueous ferrous salt solution and an aqueous alkali carbonate solution are allowed to react with each other, and an oxygen-containing gas is passed through the resulting suspension containing FeCO ₃ to cause an oxidation reaction of iron ions. A method for producing goethite particles. An aqueous solution of alkali hydroxide or alkali carbonate, which is less than an equal amount, is added to the aqueous ferrous salt solution, and an oxygen-containing gas is passed through the resulting aqueous ferrous salt solution containing ferrous hydroxide colloid to oxidize iron ions. To produce acicular goethite core particles. Next, to the ferrous salt aqueous solution containing the acicular goethite core particles, an aqueous solution of an alkali hydroxide having an equivalent amount or more with respect to Fe ²⁺ in the ferrous salt aqueous solution is added,
A method of growing the needle-like goethite core particles by passing an oxygen-containing gas.

An aqueous ferrous salt solution containing a colloid of ferrous hydroxide is prepared by adding less than an equal amount of an aqueous alkali hydroxide or alkali carbonate solution to an aqueous ferrous solution, and an oxygen-containing gas is passed through the obtained aqueous solution. To cause the iron ions to undergo an oxidation reaction, thereby generating acicular goethite core particles,
Next, a method of growing the acicular goethite core particles in an acidic to neutral region.

It should be noted that Ni, Zn, and Ni which are usually added during the formation reaction of the goethite particles to improve the characteristics of the particle powder, etc.
There is no problem even if different elements such as P and Si are added.
Needle-like goethite particles, which are precursor particles, are prepared at 200-500.
Dehydrate in the temperature range of ℃, or if necessary, add
Annealing is performed by heat treatment in a temperature range of -800 ° C to obtain acicular α-Fe ₂ O ₃ particles. Note that P, Si, B, Z are added to the surface of the acicular goethite particles to be dehydrated or annealed.
There is no problem even if sintering inhibitors such as r and Sb are attached.
Annealing by heat treatment in a temperature range of 350 to 800 ° C. is performed by annealing pores formed on the particle surface of the acicular α-Fe ₂ O ₃ particles obtained by dehydration, so that the extreme surface of the particles is formed. This is because it is preferable that the pores are closed by melting to form a smooth surface.

The α-Fe ₂ O ₃ used in the present invention
The particle powder can be produced from the acicular α-Fe ₂ O ₃ particles obtained by the dehydration or annealing as follows. Acicular α-Fe ₂ O ₃ particles are dispersed in an aqueous solution to obtain a suspension. An Al compound is added to the obtained suspension, the pH of the suspension is adjusted, and the surface of the α-Fe ₂ O ₃ particles is coated with the Al compound. Then, filtration, washing with water, drying, and pulverization are performed. For further degassing and consolidation. As the Al compound to be used, aluminum salts such as aluminum acetate, aluminum sulfate, aluminum chloride and aluminum nitrate and alkali aluminates such as sodium aluminate can be used. In this case, the addition amount of the Al compound is 0.01 to 50% by weight in terms of Al with respect to the α-Fe ₂ O ₃ particle powder. When the amount is less than 0.01% by weight, the dispersion in the binder resin is insufficient.
These compounds are not preferable because they interact with each other. In the lower layer inorganic powder in the present invention, P, Ti, Mn, Ni,
The coating may be performed using one or more compounds selected from Zn, Zr, Sn, and Sb. The amount of these compounds used together with the Al compound is α-
In the range of 0.01 to 50 wt% with respect to Fe ₂ O ₃ particles. If it is less than 0.01% by weight, there is almost no effect of improving dispersibility by addition, and if it is more than 50% by weight, compounds floating on the surfaces other than the particle surface interact with each other, which is not preferable.

The method for producing titanium dioxide can be exemplified as follows. The methods for producing these titanium oxides are mainly a sulfuric acid method and a chlorine method. In the sulfuric acid method, a source ore of illuminite is digested with sulfuric acid, and Ti, Fe, and the like are extracted as sulfates. Iron sulfate is removed by crystallization separation, and the remaining titanyl sulfate solution is filtered and purified, and then thermally hydrolyzed to precipitate hydrous titanium oxide. After filtration and washing, impurities are washed and removed,
After addition of a particle size regulator and the like, firing at 80 to 1000 ° C. results in crude titanium oxide. Rutile type and anatase type are classified according to the type of nucleating agent added at the time of hydrolysis. The crude titanium oxide is prepared by pulverizing, sizing and surface treatment. Natural or synthetic rutile is used as the raw ore in the chlorine method. The ore is chlorinated in high-temperature reduced state,
i is TiCl ₄ and Fe is FeCl ₂ , and iron oxide which has been solidified by cooling is separated from liquid TiCl ₄ .
The obtained crude TiCl ₄ is purified by rectification, then a nucleating agent is added, and the mixture is instantaneously reacted with oxygen at a temperature of 1000 ° C. or more to obtain crude titanium oxide. The finishing method for imparting pigmentary properties to the crude titanium oxide produced in this oxidative decomposition step is the same as the sulfuric acid method.

In the surface treatment, after the above-mentioned titanium oxide material is dry-pulverized, water and a dispersant are added thereto, and wet-pulverization and centrifugal separation are performed to classify coarse particles. Thereafter, the fine slurry is transferred to a surface treatment tank, where the metal hydroxide is coated on the surface. First, a predetermined amount of Al, Si, Ti, Zr, Sb, S
an aqueous solution of a salt such as n or Zn, and an acid for neutralizing the solution;
Alternatively, the surface of the titanium oxide particles is coated with a hydrated oxide by adding an alkali. Water-soluble salts produced as by-products are removed by decantation, filtration and washing, and finally the slurry is adjusted in pH and filtered, and washed with pure water. The washed cake is dried with a spray drier or a band drier. Finally, the dried product is pulverized by a jet mill into a product.

Further, it is also possible to apply Al and Si surface treatment by passing steam of AlCl ₃ and SiCl ₄ into the titanium oxide powder and then flowing steam into the titanium oxide powder.

By mixing carbon black in the lower layer, it is possible to lower the surface electric resistance Rs and the light transmittance, which are known effects, and to obtain a desired micro-Vickers hardness. In addition, it is possible to bring about the effect of storing the lubricant by including carbon black in the lower layer. Examples of carbon black include furnace black for rubber, thermal black for rubber, black for color, acetylene black, and the like. The following characteristics of the carbon black in the lower layer should be optimized depending on the desired effect, and the combined effect may provide more effects.

The specific surface area of the lower carbon black is 10
0 to 500 m ² / g, preferably 150 to 400 m ² / g,
DBP oil absorption is 20-400ml / 100g, preferably 30
４００400 ml / 100 g. The average particle size of the carbon black is 5 nm to 80 nm, preferably 10 to 50 nm, and more preferably 10 to 40 nm. Average particle size is 8
A small amount of carbon black larger than 0 nm may be contained. The carbon black preferably has a pH of 2 to 10, a water content of 0.1 to 10% by weight, and a tap density of 0.1 to 1 g / ml. A specific example of carbon black used in the present invention is BLACKPEARL manufactured by Cabot Corporation.
S 2000 (average particle diameter 15 nm), 1400 (average particle diameter 13 nm), 1300 (average particle diameter 13 nm), 1100 (average particle diameter 14 nm), 1000, 900 (average particle diameter 15n)
m), 800, 880, 700, L (average particle size 24n
m), VULCAN XC-72 (average particle size 30 nm),
P (average particle diameter 19 nm), manufactured by Mitsubishi Kasei Industries Co., Ltd. # 3050
B, # 3150B, # 3250B (average particle size 30 nm),
# 3750B, # 3950B (average particle diameter 16 nm), # 9
50 (average particle diameter 16 nm), # 650B, # 970B, #
850B (average particle diameter 18 nm), MA-600 (average particle diameter 18 nm), MA-230, # 4000, # 4010, CONDUCTEX SC manufactured by Columbian Carbon Co., Ltd.
(Average particle diameter 17 nm), SC-U (average particle diameter 20 nm), 9
75 (average particle diameter 20 nm), RAVEN 8800 (average particle diameter 13 nm), 8000 (average particle diameter 13 nm), 7000
(Average particle diameter 14 nm), 5750 (average particle diameter 17 nm), 5
250 (average particle diameter 19 nm), 5000 (average particle diameter 12 n
m), 3500 (average particle diameter 16 nm), 2100 (average particle diameter 17 nm), 2000 (average particle diameter 18 nm), 1800
(Average particle diameter 18 nm), 1500 (average particle diameter 18 nm), 1
255 (average particle diameter 23 nm), 1250 (average particle diameter 21 n
m), 1035 (average particle diameter 27 nm), Ketjen Black EC (average particle diameter 30 nm) manufactured by Akzo, # 80 (average particle diameter 20 nm), # 70 (average particle diameter 27 nm) manufactured by Asahi Carbon Black Co., Ltd., # 60 (average particle diameter 49 nm), # 55 (average particle diameter 68 nm), Asahi thermal (average particle diameter 72 nm) and the like. The average particle size used for the lower layer is 80n
Examples of carbon blacks larger than m include # 50 (average particle diameter 94 nm) and # 35 (average particle diameter 82 nm) manufactured by Asahi Carbon Black. Carbon black may be used after being surface-treated with a dispersant or the like or grafted with a resin, or may be used after a part of the surface is graphitized. The carbon black may be dispersed with a binder before adding the carbon black to the paint. These carbon blacks can be used in an amount not exceeding 50% by weight and not exceeding 40% of the total weight of the nonmagnetic layer based on the inorganic powder. These carbon blacks are used alone,
Or they can be used in combination. The carbon black that can be used in the present invention can be referred to, for example, "Carbon Black Handbook" (edited by Carbon Black Association).

In the lower layer, an organic powder is used according to the purpose.
It can also be added. For example, acrylic styrene-based resin powder, benzoguanamine resin powder, melamine-based resin powder, phthalocyanine-based pigments, but also polyolefin-based resin powder, polyester-based resin powder, polyamide-based resin powder, polyimide-based resin powder, and polyfluoroethylene resin Can be used. The manufacturing method is disclosed in
No. 18,564, and those described in JP-A-60-255827 can be used.

The lower binder, lubricant, dispersant, additive,
The solvent, dispersion method, and the like can be applied to those of the magnetic layer described below. In particular, with respect to the amount and type of the binder, the amount of the additive and the type of the dispersant, and the like, the known technology for the magnetic layer can be applied. [Binder] In the present invention, the binder, lubricant, dispersant, additive, solvent, dispersion method, etc. of the magnetic layer, non-magnetic layer and back layer can be applied to the magnetic layer, non-magnetic layer and back layer. . In particular, for the non-magnetic layer and the back layer, known techniques relating to the magnetic layer can be applied with respect to the amount and type of the binder and the amount and type of the additive and dispersant.

As the binder used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins and mixtures thereof are used. As a thermoplastic resin, the glass transition temperature is −100 to 150 ° C., and the number average molecular weight is 1.0.
00 to 200,000, preferably 10,000 to 10
000 and a degree of polymerization of about 50 to 1,000.

Such examples include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid,
Acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene,
There are polymers or copolymers containing butadiene, ethylene, vinyl butyral, vinyl acetal, vinyl ether, and the like as constituent units, polyurethane resins, and various rubber resins. Examples of the thermosetting resin or the reactive resin include a phenol resin, an epoxy resin, a polyurethane curable resin, a urea resin, a melamine resin, an alkyd resin, an acrylic reaction resin, a formaldehyde resin, a silicone resin,
Epoxy-polyamide resin, mixture of polyester resin and isocyanate prepolymer, polyester polyol
And mixtures of polyurethane and polyisocyanate, and mixtures of polyurethane and polyisocyanate. These resins are described in detail in "Plastic Handbook" published by Asakura Shoten. In addition, a known electron beam-curable resin can be used for each layer. These examples and the production method thereof are described in detail in JP-A-62-256219. The above resins can be used alone or in combination, but preferred are vinyl chloride resins,
A combination of at least one selected from vinyl chloride vinyl acetate copolymer, vinyl chloride vinyl acetate vinyl alcohol copolymer, vinyl chloride vinyl acetate maleic anhydride copolymer and a polyurethane resin, or polyisocyanate to these. The combination is given.

As the structure of the polyurethane resin, known structures such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. For all of the binders shown here, -COO is required to obtain better dispersibility and durability.
_{M, -SO 3 M, -OSO 3} M, -P = O (OM) 2,
-OP = O (OM) ₂ , where M is a hydrogen atom,
Or an alkali metal ^{_{salt), - NR 2, -N +}} R 3 (R
Is preferably a group obtained by introducing at least one or more polar groups selected from a hydrocarbon group), an epoxy group, -SH, and -CN by copolymerization or addition reaction. The amount of such a polar group is 10 ^-1 to 10 ^-8 mol / g, preferably 10 ^-2 to 10 ^-6 mol / g. In addition to these polar groups, it is preferable to have at least one OH group at each terminal of the polyurethane molecule, that is, a total of two or more OH groups. Since the OH group forms a three-dimensional network structure by crosslinking with polyisocyanate as a curing agent, it is preferable that the OH group be contained in a large number in the molecule.
In particular, it is preferable that the OH group be located at the molecular terminal because the reactivity with the curing agent is high. It preferably has three or more OH groups at the molecular terminal, and particularly preferably four or more OH groups. In the present invention, when polyurethane is used, the glass transition temperature is -50 to 150C, preferably 0C to 100C,
Breaking elongation 100-2000%, breaking stress 0.05-
10 kg / mm ^2, yield point is preferably 0.05 to 10 kg / mm ^2. By having such physical properties, a coating film having good mechanical properties can be obtained even at a high rotational speed of preferably 1800 rpm or more, more preferably 3000 rpm or more.

Specific examples of these binders used in the present invention include VACH, VYHH, VMCH and VAG manufactured by Union Carbide as vinyl chloride copolymers.
F, VAGD, VROH, VYES, VYNC, VMC
C, XYHL, XYSG, PKHH, PKHJ, PKH
C, PKFE, manufactured by Nissin Chemical Industries, MPR-TA, MP
R-TA5, MPR-TAL, MPR-TSN, MPR
-TMF, MPR-TS, MPR-TM, MPR-TA
O, 1000W, DX80, DX81, D manufactured by Denki Kagaku
X82, DX83, 100FD, MR-
104, MR-105, MR110, MR100, MR
555, 400X-110A, Nipporan N2301, N230 manufactured by Nippon Polyurethane Co., Ltd. as polyurethane resin
2, N2304, Pandex T-5 manufactured by Dainippon Ink and Chemicals, Inc.
105, T-R3080, T-5201, Burnock D
-400, D-210-80, Crisbon 6109,7
209, Toyobo Byron UR8200, UR830
0, UR-8700, RV530, RV280, polycarbonate polyurethane manufactured by Dainichi Seika Co., Ltd., Diferamine 4020, 5020, 5100, 5300, 9020,
9022, 7020, Mitsubishi Kasei polyurethane, MX
5004, Sanyo Kasei's polyurethane, Samprene SP
-150, Asahi Kasei's polyurethane, Saran F310,
F210 and the like.

The binder used in the non-magnetic layer and the magnetic layer of the present invention may be 5 to 5 times
It is used in the range of 0% by weight, preferably in the range of 10 to 30% by weight. Here, the non-magnetic powder refers to an inorganic powder excluding carbon black. 5 to 30% by weight when using a vinyl chloride resin, 2 when using a polyurethane resin.
-20% by weight and polyisocyanate in a range of 2-20% by weight are preferably used in combination.
For example, when head corrosion occurs due to a small amount of dechlorination, it is also possible to use only polyurethane or only polyurethane and isocyanate.

The magnetic recording medium of the present invention can be composed of two or more layers. Accordingly, the amount of the binder, the amount of the vinyl chloride resin, the polyurethane resin, the polyisocyanate, or the other resin in the binder, the molecular weight of each resin forming the magnetic layer, the amount of the polar group, or the amount described above. It is of course possible to change the physical properties of the resin between the non-magnetic layer and the magnetic layer, if necessary. Rather, it should be optimized for each layer, and a known technique for a multilayer magnetic layer can be applied.
For example, when the amount of the binder is changed in each layer, it is effective to increase the amount of the binder in the magnetic layer in order to reduce the abrasion on the surface of the magnetic layer. The flexibility can be increased by increasing the amount of the binder in the magnetic layer.

The polyisocyanates used in the present invention include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, and naphthylene-1. ,
5-diisocyanate, o-toluidine diisocyanate
, Isophorone diisocyanate, triphenylmethane triisocyanate and other isocyanates; products of these isocyanates and polyalcohols; and polyisocyanates formed by condensation of isocyanates. -And the like can be used. Commercially available trade names of these isocyanates include Nippon Polyurethane Co., Ltd., Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate M
R, Millionate MTL, Takeda Pharmaceutical Co., Ltd., Takenate D
-102, Takenet D-110N, Takenet D-2
00, Takenate D-202, manufactured by Sumitomo Bayer, Desmodur L, Desmodur IL, Desmodur N, Desmodur HL, etc. These can be used alone or by utilizing the difference in curing reactivity. Each layer can be used in a combination of two or more.

[Carbon Black, Abrasive] As carbon black used in the magnetic layer of the present invention, furnace black for rubber, thermal black for rubber, black for color, acetylene black, and the like can be used. . Specific surface area is 5-50
0 m ² / g, DBP oil absorption 10-400 ml / 100
g, average particle size is 5 nm to 300 nm, pH is 2-1.
0, water content is 0.1-10% by weight, tap density is 0.1
-1 g / cc is preferred. Car used in the present invention
Specific examples of Bon Black include B
LACKPEARLS 2000 (average particle size 15 nm),
1300 (average particle diameter 13 nm), 1000 (average particle diameter 16
nm), 900 (average particle diameter 15 nm), 905, 800 (average particle diameter 17 nm), 700 (average particle diameter 18 nm), VULC
AN XC-72 (average particle size 30 nm), STERLIN
GFT (average particle diameter 180 nm), manufactured by Asahi Carbon Co., Ltd., # 8
0 (average particle diameter 20 nm), # 60 (average particle diameter 49 nm), #
55 (average particle diameter 68 nm), # 50 (average particle diameter 94 nm),
# 35 (average particle diameter 94 nm), manufactured by Mitsubishi Kasei Kogyo Co., Ltd., # 24
00B (average particle diameter 15 nm), # 2300 (average particle diameter 15 nm)
nm), # 900 (average particle diameter 16 nm), # 1000 (average particle diameter 18 nm), # 30 (average particle diameter 30 nm), # 40 (average particle diameter 20 nm), # 10B (average particle diameter 84 nm), Columbianca -CONDUCTEX SC (average particle diameter 17 nm), RAVEN 150 (average particle diameter 18 n)
m), 50 (average particle diameter 21 nm), 40 (average particle diameter 24n)
m), 15 (average particle diameter 27 nm), RAVEN MTP
(Average particle diameter 275 nm), RAVEN-MT-P
(Average particle size: 330 nm), manufactured by Japan EC Co., Ketjen Black EC40 (average particle size: 30 nm), manufactured by Kahncarb, thermal black (average particle size: 270 nm), and the like. Carbon black may be used after being surface-treated with a dispersant or the like or grafted with a resin, or may be used after a part of the surface is graphitized.
Before adding the carbon black to the magnetic paint, the carbon black may be dispersed in a binder in advance. These carbon blacks can be used alone or in combination. When carbon black is used, it is preferably used in an amount of 0.1 to 30% by weight based on the ferromagnetic metal powder. Carbon black has functions such as preventing the magnetic layer from being charged, reducing the coefficient of friction, imparting light-shielding properties, and improving the film strength. These functions differ depending on the carbon black used. Therefore, these carbon blacks used in the present invention are composed of an upper magnetic layer,
Change the type, amount and combination in the lower non-magnetic layer,
It is, of course, possible to use differently according to the purpose based on the above-mentioned properties such as oil absorption, conductivity, pH, etc. Rather, it should be optimized in each layer. The carbon black that can be used in the magnetic layer of the present invention can be referred to, for example, "Carbon Black Handbook" edited by Carbon Black Association.

The abrasive used in the magnetic layer of the present invention includes α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, artificial diamond, and nitride having an α conversion of 90% or more. Silicon, silicon carbide titanium carbide, titanium oxide, silicon dioxide, boron nitride,
For example, known materials having a Mohs hardness of 6 or more are used alone or in combination. In addition, a composite of these abrasives (abrasive whose surface has been treated with another abrasive) may be used. These abrasives may contain compounds or elements other than the main component, but the effect remains unchanged if the main component is 90% or more. The average particle diameter of these abrasives is usually 0.01 to 2 μm, preferably 0.01 to 1 μm, more preferably 0.01 to 0.5 μm, and 0.01 to 0.5 μm.
To 0.3 μm is particularly preferable, and in order to particularly enhance the electromagnetic conversion characteristics, it is preferable that the particle size distribution is narrow. Further, in order to improve the durability, it is possible to combine abrasives having different average particle diameters as needed, or to use a single abrasive to broaden the particle diameter distribution to have the same effect. Tap density is 0.3-2g / cc, water content is 0.1-5% by weight,
The pH is preferably ^{2 to} 11, and the specific surface area is preferably 1 to 30 m ² / g. The shape of the abrasive used in the present invention may be any of a needle shape, a spherical shape, and a dice shape, but a shape having a part of a corner is preferable because of high abrasiveness. Specifically, as an example of α-alumina, AKP-12 manufactured by Sumitomo Chemical Co., Ltd.
50 μm), AKP-15 (average particle size 0.45 μm), AK
P-20 (average particle diameter 0.39 μm), AKP-30 (average particle diameter 0.23 μm), AKP-50 (average particle diameter 0.16 μm)
m), HIT-20, HIT-30, HIT-55 (average particle diameter 0.20 μm), HIT-60, HIT-70 (average particle diameter 0.15 μm), HIT-80, HIT-100
(Average particle diameter: 0.11 μm), manufactured by Reynolds, ERC-D
BM (average particle diameter 0.22 μm), HP-DBM (average particle diameter 0.22 μm), HPS-DBM (average particle diameter 0.19 μm)
m), manufactured by Fujimi Abrasives, WA10000 (average particle diameter)
0.29 µm), UB20 (average particle size 0.13
μm), as an example of chromium oxide, G-
5 (average particle diameter 0.32 μm), Chromex U2 (average particle diameter 0.18 μm), Chromex U1 (average particle diameter 0.17 μm)
m), TF100 manufactured by Toda Kogyo KK as an example of α-iron oxide
(Average particle size 0.14 μm), TF140 (average particle size 0.17
μm), an example of silicon carbide, Beta Random Ultra Fine (average particle size 0.16 μm), manufactured by Showa Mining Co., Ltd., and an example of silicon dioxide, B-3 (average particle size: 0.16 μm).
17 μm). These abrasives can be added to the nonmagnetic layer as needed. By adding to the non-magnetic layer, the surface shape can be controlled, and the projected state of the abrasive can be controlled. The particle size and amount of the abrasive added to the magnetic layer and the non-magnetic layer should of course be set to optimal values.

The rotation speed is 1800 rpm or more, especially 30 rpm.
In the case of a large-capacity FD of 00 rpm or more, it is preferable to use fine-particle diamond as an abrasive. Diamond fine particles that can be used in the present invention, the average particle diameter is preferably 2.0 μm or less, more preferably 0.01 to 1.0 μm, particularly preferably 0.05 to 0.8 μm,
Most preferably, it is 0.05 to 0.3 μm. If the average particle diameter is less than 0.01 μm, the effect of improving the durability with respect to the added amount tends to be low. When it is larger than 2.0 μm, the durability tends to be high, but the noise tends to be high, and the object of the present invention is not achieved.

In the present invention, the maximum diameter of each diamond fine particle is defined as the particle diameter, and the average particle diameter indicates the average value of the measured values of 500 particles randomly extracted from an electron microscope. The addition amount of the diamond fine particles is usually in the range of 0.01 to 5% by weight, preferably 0.03 to 3.00% by weight based on the ferromagnetic metal powder. If it is less than 0.01% by weight, it is difficult to ensure durability, and if it exceeds 5% by weight, the noise reduction effect due to the addition of diamond decreases.

From the viewpoint of noise and durability, it is preferable that the addition amount and the average particle diameter of the diamond fine particles are defined in the above ranges. From the viewpoint of noise, the addition amount of the diamond is preferably as small as possible. In the magnetic recording medium of the present invention, it is preferable to appropriately select the amount of diamond added and the average particle diameter of the diamond suitable for the magnetic recording / reproducing apparatus from the above ranges.

The particle size distribution of the diamond fine particles is such that the number of particles having a particle diameter of 200% or more of the average particle diameter is 5% or less of the total number of diamonds, and the particle diameter is 50% or less of the average particle diameter. The number is preferably not more than 20% of the total number of diamonds. The maximum value of the diameter of the diamond fine particles used in the present invention is usually 3.
It is about 00 μm, preferably about 2.00 μm, and its minimum diameter is usually about 0.01 μm, preferably about 0.02 μm.

The particle size distribution is determined by counting the number of particles based on the average particle diameter when measuring the particle diameter. The particle size distribution of diamond particles also affects durability and noise. If the particle size distribution is wider than the above range, the effect corresponding to the average particle size set as described above is shifted. That is,
If the particle size is too large, noise may be increased or the head may be damaged. If there are many fine particles, the polishing effect becomes insufficient. Further, those having an extremely narrow particle size distribution increase the price of the diamond fine particles, and it is advantageous in terms of cost to keep the above range.

Further, in the present invention, the diamond fine particles can be used in combination with a conventionally used abrasive, for example, an alumina abrasive. The effect on durability and S / N ratio is better when only a small amount of diamond fine particles are used. %
Can be added. Also in this case, since alumina alone is used, alumina alone can considerably reduce the amount added for durability, which is preferable from the viewpoint of securing durability and reducing noise.

There are three methods for producing micron-sized diamond powder: a static high-pressure method, an explosion method, and a gas-phase method. Static high pressure process first produces crystals larger than a few tens of micrometers and then crushes the crystals to produce submicron diamond fines. The explosion method is a method of converting black smoke into diamond by generating an ultra-high pressure by a shock wave generated by exploding a gunpowder. The diamond produced by this method is a polycrystalline diamond whose primary particles are said to be 20 ° or 50 °. In the gas phase method, a gaseous compound containing carbon such as hydrocarbons is sent together with hydrogen gas to a closed container at normal pressure or lower, a high-temperature zone is formed by plasma or the like, and the raw material compounds are decomposed.
This is a method of depositing diamond on a substrate such as i or Mo. Specific examples of the diamond fine particles include LS600F, LS600T, LS600F coated products (30% nickel or 56% coated products), LS-NPM, and LS600F manufactured by Lands Superabrasives, Co.
BN2600, and the like. These are preferable because diamond fine particles of any size of 0 to 100 μm are obtained. In addition, IRM 0-1 of Tomei Diamond Industry Co., Ltd.
/ 4 (average particle diameter 0.12 μm), IRM 0-1 (average particle diameter 0.60 μm) and the like can be used.

[Additives] As the additives used in the magnetic layer and the nonmagnetic layer of the present invention, those having a lubricating effect, an antistatic effect, a dispersing effect, a plasticizing effect and the like are used. Performance can be improved. As a material exhibiting a lubricating effect, a lubricant is used which has an effect of remarkably reducing the adhesion that occurs when friction occurs between the surfaces of the substances. There are two types of lubricants. Although it is not possible to determine whether a lubricant used in a magnetic recording medium is completely fluid lubrication or boundary lubrication, if it is classified according to the general concept, higher fatty acid esters, liquid paraffin, silicon derivatives, etc. that indicate fluid lubrication and boundary lubrication. It is classified into lubricating long-chain fatty acids, fluorinated surfactants, fluorinated polymers and the like. In the application type medium, the lubricant is dissolved in the binder or partially exists in a state of being adsorbed on the surface of the ferromagnetic metal powder, and the lubricant migrates to the surface of the magnetic layer. It depends on the compatibility between the binder and the lubricant.
When the compatibility between the binder and the lubricant is high, the migration speed is low, and when the compatibility is low, the migration speed is high. One way of thinking about the compatibility is to compare the solubility parameters of the two. A non-polar lubricant is effective for fluid lubrication, and a polar lubricant is effective for boundary lubrication. In the present invention, high capacity, high density, and high durability are preferably exhibited by combining at least three types of higher fatty acid esters exhibiting fluid lubrication with different characteristics and long-chain fatty acids exhibiting boundary lubrication. You can do it. Solid lubricants can also be used in combination with these. As the solid lubricant, for example, molybdenum disulfide, tungsten graphite disulfide, boron nitride, fluorinated graphite and the like are used. As long-chain fatty acids exhibiting boundary lubrication, monobasic fatty acids having 10 to 24 carbon atoms (which may contain unsaturated bonds or may be branched), and metal salts thereof (Li, Na, K) , Cu, etc.).
Examples of the fluorine-containing surfactant and fluorine-containing polymer include fluorine-containing silicone, fluorine-containing alcohol, fluorine-containing ester, fluorine-containing alkyl sulfate and alkali metal salts thereof. As higher fatty acid esters showing fluid lubrication, monobasic fatty acids having 10 to 24 carbon atoms (which may contain unsaturated bonds or may be branched) and monovalent or divalent carbon atoms having 2 to 12 carbon atoms, Trivalent, tetravalent,
A mono- or di-fatty acid ester or a tri-fatty acid ester comprising any one of pentavalent and hexavalent alcohols (which may contain an unsaturated bond or may be branched), or an alkylene oxide polymer Fatty acid esters of monoalkyl ethers and the like can be mentioned. Liquid paraffin, and dialkyl polysiloxane (alkyl is 1 to 5 carbon atoms) and dialkoxy polysiloxane (alkoxy is 1 to 4 carbon atoms) as silicon derivatives.
), Monoalkyl monoalkoxypolysiloxane (alkyl has 1 to 5 carbon atoms, alkoxy has 1 to 4 carbon atoms)
), Phenylpolysiloxane, fluoroalkylpolysiloxane (alkyl has 1 to 5 carbon atoms)
Oil, polar group-containing silicone, fatty acid-modified silicone, fluorine-containing silicone and the like. As other lubricants, monovalent, divalent, trivalent, having 12 to 22 carbon atoms,
Tetravalent, pentavalent, hexavalent alcohols (including unsaturated bonds,
It may be branched), alkoxy alcohols having 12 to 22 carbon atoms (which may contain an unsaturated bond or may be branched), alcohols such as fluorine-containing alcohols, and polyethylene. Waxes, polyolefins such as polypropylene, polyglycols such as ethylene glycol and polyethylene oxide wax, alkyl phosphates and their alkali metal salts, alkyl sulfates and their alkali metal salts, polyphenyl ether
Ter, fatty acid amide having 8 to 22 carbon atoms, 8 to 22 carbon atoms
And the like.

Phenylphosphonic acid such as α-naphthylphosphoric acid, phenylphosphoric acid, diphenylphosphoric acid, p-ethylbenzene and the like exhibiting an antistatic effect, a dispersing effect, a plasticizing effect, etc. Phosphonic acid, phenylphosphinic acid, aminoquinones, various silane coupling agents, titanium coupling agents, fluorine-containing alkyl sulfates and alkali metal salts thereof can be used.

The lubricant used in the present invention is particularly
Fatty acids and fatty acid esters are preferred, and in addition to these
Different lubricants and additives can be used in combination.
Wear. Specific examples of these are given below. First with fatty acids
Is caprylic acid (C₇H_FifteenCOOH,
Melting point 16 ° C), Pelargonic acid (C₈H₁₇COOH, melting point
15 ° C), capric acid (C₉H₁₉COOH, melting point 31.
5 ° C), undecylic acid (C_{1 0}H_{twenty one}COOH, melting point 28.
6 ° C), lauric acid (C₁₁H_{twenty three}COOH, melting point 44 ° C)
Specifically, “NAA-122” by Nippon Yushi Co., Ltd.
And tridecylic acid (C ₁₂H_{twenty five}COOH, melting point 45.5
C), myristic acid (C₁₃H₂₇COOH, melting point 58 ° C)
Specifically, “NAA-142” by Nippon Yushi Co., Ltd.
Pentadecylic acid (C₁₄H₂₉COOH, melting point 53-5
4 ° C), palmitic acid (C_FifteenH₃₁COOH, melting point 63 ~
64 ° C.) Specifically, “NAA-16” manufactured by NOF Corporation
Heptadecylic acid (C₁₆H₃₃COOH, melting point 6
0-61 ° C), stearic acid (C₁₇H ₃₅COOH, melting point
71.5-72 ° C.) Specifically, “N
AA-173K ”and other nonadecanoic acids (C₁₈H₃₇COO
H, melting point 68.7 ° C), arachidic acid (C₁₉H₃₉COO
H, melting point 77 ° C), behenic acid (C_{twenty one}H₄₃COOH, melting point
81-82 ° C.). As unsaturated fatty acids
Oleic acid (C₁₇H₃₃COOH (cis), melting point 16 ° C)
Specifically, such as “Oleic acid” from Kanto Chemical Co., Ltd.
Lidic acid (C₁₇H₃₃COOH (trans), melting point 44-4
5 ℃) Specifically, "Elaidic acid" of Wako Pure Chemical Industries, Ltd.
Cetreic acid (C_{twenty one}H₄₁COOH, melting point 33.7
℃), erucic acid (C_{twenty one}H₄₁COOH, melting point 33.4-3
4 ℃） Specifically, “erucic acid” of Nippon Yushi Co., Ltd.
Throat, brassic acid (C_{twenty one}H₄₁COOH (trans), melting point 6
1.5 ° C), linoleic acid (C₁₇H₃₁COOH, boiling point 22
8 ° C (14 mm)), linolenic acid (C₁₇H₂₉COOH,
Boiling point: 197 ° C. (4 mm)). Branch saturation
Fatty acids include isostearic acid (CH_ThreeCH (CH_Three)
(CH_Two)₁₄COOH, melting point 67.6-68.1 ° C)
And so on.

As esters, isocetyl laurate (C ₁₁ H ₂₃ COOCH ₂ CH (C ₆
H ₁₃ ) C ₈ H ₁₇ ), oleyl laurate (C ₁₁ H ₂₃ CO
OC _{1 8} H _35), stearate Rirura urate (C ₁₁ H ₂₃ COO
C ₁₈ H _37), and isopropyl myristate as myristic acid ester _{(C 13 H 27 COOCH (CH} 3) 2) specifically by New Japan Chemical Co.'s "Enujerubu IPM", butyl myristate (C ₁₃ H ₂₇ COOC ₄ H ₉₎ such as, isobutyl myristate _{(C 13 H 27 COOiso-C} 4
H ₉ ) Specifically, heptyl myristate (C ₁₃ H ₂₇ COO) such as “Engelb IBM” of Nippon Rika Co., Ltd.
C ₇ H _15), octyl myristate (C ₁₃ H _{2 7} COOC ₈
H ₁₇ ), isooctyl myristate (C ₁₃ H ₂₇ COOC)
_{H 2 CH (C 2 H 5} ) C 4 H 9), isocetyl myristate _{(C 13 H 27 COOCH 2 CH} (C 6 H 13) C 8 H 17) , and the like.

Octyl palmitate (C ₁₅ H ₃₁ COOC ₈ H ₁₇ ), decyl palmitate (C ₁₅ H ₃₁ COOC ₁₀ H ₂₁ ), and isooctyl palmitate (C ₁₅ H ₃₁ COOCH ₂ CH (C ₂ H ₅₎ C
₄ H ₉ ), isocetyl palmitate (C ₁₅ H ₃₁ COOCH)
₂ CH (C ₆ H ₁₃ ) C ₈ H ₁₇ ), 2-octyldodecyl palmitate (C ₁₅ H ₃₁ COOCH ₂ CH (C ₈ H ₁₇ ) C ₁₂
H ₂₅ ), 2-hexyl decyl palmitate (C ₁₅ H ₃₁
COOCH ₂ CH (C ₆ H ₁₃ ) C ₁₂ H ₂₅ ) and oleyl palmitate (C ₁₅ H ₃₁ COOC ₁₈ H ₃₅ ).

As a stearic acid ester,
Allate (C₁₇H₃₅COOC_ThreeH₇), Isopropyl
Allate (C₁₇H₃₅COOCH (CH_Three)_Two), Butils
Tearate (C₁₇H₃₅COOC_FourH₉) Specifically, Nippon Oil
Such as "Butyl stearate" of Yasu Co., Ltd.
Rustearate (C₁₇H₃₅COOCH (CH_Three) C
_TwoH_Five), Tert-butyl stearate (C₁₇H₃₅COOC
(CH_Three)_Three), Amyl stearate (C₁₇H₃₅COOC
_FiveH₁₁), Isoamyl stearate (C₁₇H₃₅COOC
H_TwoCH_TwoCH (CH_Three)_Two), Such as hexyl stearate
(C₁₇H₃₅COOC₆H₁₃), Heptyl stearate
(C₁₇H₃₅COOC₇H_Fifteen) Specifically, Matsumoto Yushi Co., Ltd.
Octyl stearate such as "MYB-185"
(C₁₇H₃₅COOC ₈H₁₇) Specifically, Nippon Oil & Fats Co., Ltd.
Isooctyl such as "N-octyl stearate"
Stearate (C₁₇H₃₅COOisoC₈H₁₇)In particular
Decils such as "FAL-123" by Takemoto Yushi Co., Ltd.
Tearate (C₁₇H₃₅COOC_TenH_{twenty one}), Isodecyls
Tearate (C₁₇H₃₅COOiso-C_TenH_{twenty one}), Dodeci
Rustearate (C₁₇H₃₅COOC₁₂H_{twenty five}), Isotori
Decyl stearate (C₁₇H₃₅COOiso-C
₁₃H₂₇), 2-ethylhexyl stearate (C₁₇H₃₅
COOCH_TwoCH (C_TwoH_Five) C_FourH₉), Isohexadeshi
Rustearate (C₁₇H₃₅COOCH_TwoCH (C_TwoH_Five)
C_FourH₉), Isocetyl stearate (C₁₇H₃₅COOC
H_TwoCH (C₆H₁₃) C₈H₁₇) Specifically, New Japan Rika
Isosteari, Inc., Inc. “Engelbud HDS”
Rustearate (C₁₇H₃₅COOisoC₁₈H₃₇),me
Ilstelate (C₁₇H₃₅COOC₁₈H₃₇)
I can do it.

As a behenate ester, isotetracosylbehenate (C ₂₁ H ₄₃ COOCH ₂ CH (C ₆ H ₁₃ ) C ₁₂
H _25), etc. More specifically, New Japan Chemical Co., of "Enujerubu DTB"), and the like. Butoxyethyl stearate (C ₁₇ H ₃₅ CO
OCH ₂ CH ₂ OC ₄ H ₉ ), butoxyethyl oleate (C ₁₇ H ₃₃ COOCH ₂ CH ₂ OC ₄ H ₉ ), diethylene glycol monobutyl ether terstearate or butoxyethoxyethyl stearate (C ₁₇ H ₃₅ COO) (CH
₂ CH ₂ O) ₂ C ₄ H ₉ ), tetraethylene glycol monobutyl ether stearate (C ₁₇ H ₃₅ COO (CH ₂
CH ₂ O) ₄ C ₄ H ₉ ), diethylene glycol monophenyl ether terstearate (C ₁₇ H ₃₅ COO (CH ₂ CH ₂₎
O) ₂ C ₆ H ₆ ), diethylene glycol mono-2-ethylhexyl ether terstearate (C ₁₇ H ₃₅ COO (CH
_{2 CH 2 O) 2 CH 2} CH (C 2 H 5) C 4 H 9), such as JP 59-227030, the esters described in JP-A-59-65931 can be used.

As the isostearic acid ester, isocetyl isostearate (isoC ₁₇ H ₃₅ COOCH ₂ CH
(C ₆ H ₁₃ ) C ₈ H ₁₇ ) More specifically, oleyl isostearate (isoC ₁₇ H ₃₅ COOC ₁₈ H ₃₇ ), stearyl, etc. isostearate _{(isoC 17 H 35 COOC 18 H} 37), isostearyl isostearate _{(isoC 17 H 35 COOiso-C} 18 H
₃₇ ), eicosenyl isostearate (isoC ₁₇ H ₃₅ C
OOC ₂₂ H ₄₃ ).

Butyl oleate as oleic acid ester
To (C₁₇H₃₃COOC_FourH₉), Shin Nippon Rika Co., Ltd.
Oleyl oleate (C₁₇
H₃₃COOC₁₈H₃₅), Ethylene glycol dioleyl
(C₁₇H₃₃COOCH_TwoCH_TwoOCOC₁₇H₃₃)
I can do it. Oleyl erucate as erucate
(C_{twenty one}H₄₁COOC₁₈H₃₅). Diester
Georail Maleate (C₁₈H₃₅OCOCH = C
HCOOC₁₈H₃₅), Neopentyl glycol didecano
Eat (C₉H₁₉COOCH_TwoC (CH_Three)_TwoCH_TwoOCO
C₉H₁₉), Ethylene glycol dilaurate (C₁₁H
_{twenty three}COOCH_TwoCH_TwoOCOC₁₁H_{twenty three}), Ethylene glyco
-Rugio Rail (C₁₇H ₃₃COOCH_TwoCH_TwoOCOC₁₇
H₃₃) 1,4-butanediol-distearate (C₁₇
H₃₅COO (CH_Two)_FourOCOC₁₇H₃₅) 1,4-pig
Ngio-rujibehenate (C_{twenty one}H₄₃COO (CH_Two)_FourO
COC_{twenty one}H₄₃) 1,10-decandio-legioleil
(C₁₇H₃₃COO (CH_Two)_TenOCOC₁₇H₃₃), 2-
Butene-1,4-diol-setrail (C_{twenty one}H₄₁COOC
H_TwoCH = CHCH_TwoOCOC_{twenty one}H₄₁)
You.

Caprylic acid triglyceride as triester
Ride (C₇H_FifteenCOOCH_TwoCH (OCOC₇H_Fifteen) C
H_TwoOCOC₇H_Fifteen). These fatty acid esthetics
Oleyl alcohol for alcohols in addition to alcohol and fatty acids
(C ₁₈H₃₅OH), stearyl alcohol (C₁₈H₃₇O
H), lauryl alcohol (C₁₂H_{twenty five}OH)
Can be

As the fatty acid amide, lauric amide (C
₁₁ H ₂₃ CONH ₂ ) Specifically, myristic acid amide (C ₁₃ H ₂₇ ) such as “lauric amide” of Tokyo Chemical Industry Co., Ltd.
CONH ₂ ), palmitic amide (C ₁₅ H ₃₁ CON
H ₂ ), oleic acid amide (cis-C ₈ H ₁₇ CHＣＨCH
(CH ₂ ) ₇ CONH ₂ ) Specifically, erucamide (cis-C ₈ H ₁₇ CH = CH (CH ₂ ) ₁₁ CON, such as “Amoslip CP-P” of Lion Akzo Co.
H ₂ ) Concretely, stearamide (C ₁₇ H ₃₅ CON) such as “Amoslip E” of Lion Akzo Co., Ltd.
H ₂ ) Specific examples include “Amide HT” manufactured by Lion Akzo Co., Ltd.

As silicon compounds, “TAV-3630”, “TA-3” and “KF-69” manufactured by Shin-Etsu Chemical Co., Ltd.
Is mentioned. Also, nonionic surfactants such as alkylene oxides, glycerin, glycidols, alkylphenol ethylene oxide adducts, cyclic amines, ester amides, quaternary ammonium salts, hydantoin derivatives, heterocycles, phosphoniums Or cationic surfactants such as sulfoniums, anionic surfactants containing acidic groups such as carboxylic acid, sulfonic acid, phosphoric acid, sulfate group, and phosphate group, amino acids, aminosulfonic acids, and amino alcohols. Ampholytic surfactants such as sulfuric acid or phosphoric acid esters and alkylbedine type can also be used. These surfactants are described in detail in "Surfactant Handbook" (published by Sangyo Tosho Co., Ltd.). These lubricants, antistatic agents, etc.
Not pure, but isomers, unreacted materials,
Impurities such as by-products, decomposition products, and oxides may be included. These impurities are preferably 30% or less, more preferably 10% or less.

These lubricants and surfactants used in the present invention have different physical actions.
The type, amount, and combination ratio of the lubricant that produces a synergistic effect should be optimally determined according to the purpose.
To control leaching to the surface by using fatty acids with different melting points in the non-magnetic layer and magnetic layer, to control leaching to the surface by using esters with different boiling points, melting points and polarities, and to adjust the amount of surfactant It is conceivable to improve the stability of the coating and to improve the lubricating effect by increasing the amount of the lubricant added in the lower layer. In general, the total amount of the lubricant is selected in the range of 0.1% by weight to 50% by weight, preferably 2% by weight to 25% by weight based on the ferromagnetic metal powder or the nonmagnetic powder.

Further, all or a part of the additives used in the present invention may be added at any step in the production of magnetic and non-magnetic paints. For example, when the additives are mixed with the ferromagnetic metal powder before the kneading step. There is a case where it is added in a kneading step using a ferromagnetic metal powder, a binder and a solvent, a case where it is added in a dispersion step, a case where it is added after dispersion, and a case where it is added just before coating. Also, after applying the magnetic layer according to the purpose,
The purpose may be achieved by applying a part or all of the additive by simultaneous or sequential application. Depending on the purpose, a lubricant may be applied to the surface of the magnetic layer after calendering or after slitting.

[Layer Structure] The thickness structure of the magnetic recording medium of the present invention is such that the support is usually 2 to 100 μm, preferably 2 to 8 μm.
0 μm. The support of the computer tape is usually 3.0 to 6.5 μm (preferably 3.0 to 6.0 μm).
μm, and more preferably, a thickness in the range of 4.0 to 5.5 μm).

An undercoat layer for improving adhesion may be provided between the support and the nonmagnetic layer or the magnetic layer. The thickness of the undercoat layer is generally 0.01 to 0.5 μm, preferably 0.1 to 0.5 μm.
02 to 0.5 μm. The present invention may be a double-sided magnetic layer disk-shaped medium in which a nonmagnetic layer and a magnetic layer are provided on both sides of a support, or may be provided on only one side. In this case, a back coat layer may be provided on the side opposite to the non-magnetic layer and the magnetic layer in order to obtain effects such as antistatic and curl correction. This thickness is 0.1 to 4 μm, preferably 0.1 to 4 μm.
3 to 2.0 μm. Known undercoat layers and backcoat layers can be used.

The thickness of the magnetic layer of the magnetic recording medium of the present invention is optimized by the saturation magnetization of the head to be used, the head gap length, and the band of the recording signal.
It is not less than 05 μm and not more than 0.30 μm, preferably 0.1 μm.
It is at least 0.05 μm and at most 0.25 μm, more preferably at least 0.05 μm and at most 0.20 μm. The magnetic layer may be separated into two or more layers having different magnetic properties,
A known configuration relating to a multilayer magnetic layer can be applied. In this case, the thickness of the magnetic layer indicates the total sum.

In the present invention, the thickness of the nonmagnetic layer is usually
0.2 μm or more and 5.0 μm or less, preferably 0.3 μm
Not less than 3.0 μm, more preferably not less than 1.0 μm and not more than 2.5 μm. The lower layer that can be used in the present invention exerts its effect if it is substantially non-magnetic. For example, the lower layer may contain a small amount of a magnetic substance as an impurity or intentionally. Indicates that the residual magnetic flux density is 100 G or less or the coercive force is 100 Oersted or less, and preferably indicates that there is no residual magnetic flux density and no coercive force. When the lower layer contains a magnetic powder, it may contain less than 1/2 of all the inorganic powders in the lower layer.

[Backcoat Layer] Generally, magnetic tapes for recording computer data are required to have a higher repetitive running property than video tapes and audio tapes. In order to maintain such high running durability, the back coat layer preferably contains carbon black and inorganic powder.

The carbon black is preferably used in combination of two kinds having different average particle diameters.
In this case, it is preferable to use a combination of fine-particle carbon black having an average particle diameter of 10 to 20 nm and coarse-particle carbon black having an average particle diameter of 230 to 300 nm. In general, the surface electric resistance of the back coat layer can be set low and the light transmittance can be set low by the addition of the fine carbon black as described above. Some magnetic recording devices use the light transmittance of the tape and use it as an operation signal. In such a case, the addition of fine carbon black is particularly effective. In addition, fine carbon black is generally excellent in holding power of a liquid lubricant, and contributes to reduction of a friction coefficient when used in combination with a lubricant. On the other hand, coarse-grained carbon black having an average particle diameter of 230 to 300 nm has a function as a solid lubricant, and also forms fine projections on the surface of the back layer to reduce the contact area, thereby reducing the friction coefficient. Contributes to the reduction of However, coarse-grained carbon black is used in severe driving systems.
The sliding of the tape easily causes the tape to fall off from the back coat layer, which has a drawback of increasing the error ratio.

Specific examples of commercial products of the particulate carbon black include the following. RAVE
N2000B (average particle diameter 18 nm), RAVEN15
00B (average particle diameter 17 nm) (above, manufactured by Columbia Carbon Co.), BP800 (average particle diameter 17 nm) (manufactured by Cabot), PRINTENT 90 (average particle diameter 14)
nm), PRINTEX95 (average particle diameter 15 nm),
PRINTEX85 (average particle diameter 16nm), PRIN
TEX75 (average particle diameter 17 nm) (above, manufactured by Degussa), # 3950 (average particle diameter 16 nm) (manufactured by Mitsubishi Kasei Kogyo Co., Ltd.).

Specific examples of commercial products of coarse carbon black include thermal black (average particle size of 270).
nm) (manufactured by Khancarb) and RAVEN MTP (average particle size: 275 nm) (manufactured by Columbia Carbon Co., Ltd.).

In the case of using two types having different average particle diameters in the back coat layer, the content ratio (weight ratio) of the fine carbon black of 10 to 20 nm and the coarse carbon black of 230 to 300 nm is the former. : The latter is preferably in the range of 98: 2 to 75:25, more preferably in the range of 95: 5 to 85:15.

The content of carbon black in the back coat layer (when two types are used, the total amount thereof) is usually in the range of 30 to 80 parts by weight with respect to 100 parts by weight of the binder. Preferably, it is in the range of 45 to 65 parts by weight.

It is preferable to use two kinds of inorganic powders having different hardnesses in combination. Specifically, Mohs hardness 3 ~
It is preferable to use a 4.5 soft inorganic powder and a 5 to 9 Mohs hardness hard inorganic powder. Mohs hardness is 3-4.
By adding the soft inorganic powder of No. 5, the friction coefficient can be stabilized by repeated running. Further, with the hardness in this range, the sliding guide pole is not cut off. The average particle diameter of the inorganic powder is 30 to 50 nm.
Is preferably within the range.

Examples of the soft inorganic powder having a Mohs' hardness of 3 to 4.5 include calcium sulfate, calcium carbonate, calcium silicate, barium sulfate, magnesium carbonate, zinc carbonate, and zinc oxide. They are,
They can be used alone or in combination of two or more. Among these, calcium carbonate is particularly preferred.

The content of the soft inorganic powder in the back coat layer is from 10 to 14 with respect to 100 parts by weight of carbon black.
It is preferably in the range of 0 parts by weight, more preferably 35 to 100 parts by weight.

By adding a hard inorganic powder having a Mohs hardness of 5 to 9, the strength of the back coat layer is enhanced, and the running durability is improved. When these inorganic powders are used together with carbon black or the above-mentioned soft inorganic powders, they are less deteriorated even in repeated sliding and form a strong backcoat layer. In addition, the addition of the inorganic powder provides an appropriate polishing force, and reduces the adhesion of shavings to the tape guide pole and the like. In particular, when used in combination with a soft inorganic powder (among others, calcium carbonate), the sliding characteristics with respect to a guide pole having a rough surface are improved, and the friction coefficient of the back coat layer can be stabilized.

The hard inorganic powder has an average particle size of 80 to
It is preferably in the range of 250 nm (more preferably, 100 to 210 nm).

Examples of the hard inorganic powder having a Mohs hardness of 5 to 9 include α-iron oxide, α-alumina, and chromium oxide (Cr ₂ O ₃ ). These powders may be used alone or in combination. Of these, α-iron oxide or α-alumina is preferred. The content of the hard inorganic powder is usually 3 to 30 parts by weight based on 100 parts by weight of carbon black,
Preferably, it is 3 to 20 parts by weight.

When the soft inorganic powder and the hard inorganic powder are used in combination in the back coat layer, the difference in hardness between the soft inorganic powder and the hard inorganic powder is 2 or more (more preferably 2.5 or more, particularly preferably 2.5 or more). It is preferable to select and use a soft inorganic powder and a hard inorganic powder as in (3).

It is preferable that the back coat layer contains the two types of inorganic powders having different specific Mohs hardnesses, each having the specific average particle size, and the two types of carbon black having different average particle sizes. In particular, in this combination, it is preferable that calcium carbonate is contained as the soft inorganic powder.

The backcoat layer may contain a lubricant. The lubricant can be appropriately selected from the above-mentioned lubricants that can be used for the nonmagnetic layer or the magnetic layer. In the back coat layer, the lubricant is usually added in a range of 1 to 5 parts by weight based on 100 parts by weight of the binder. [Support] The support used in the present invention has a heat shrinkage of 0.5% or less at 100 ° C. for 30 minutes and a heat shrinkage at 80 ° C. for 30 minutes in each in-plane direction of the support. It is preferably at most 0.5%, more preferably at most 0.2%. Further, it is preferable that the heat shrinkage of the support at 100 ° C. for 30 minutes and the heat shrinkage at 80 ° C. for 30 minutes are equal to each other in the in-plane direction of the support with a difference within 10%. The support is preferably non-magnetic. These supports include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins,
Known films such as cellulose triacetate, polycarbonate, polyamide, polyimide, polyamide imide, polysulfone, polyaramid, aromatic polyamide and polybenzoxazole can be used. It is preferable to use a high-strength support such as polyethylene naphthalate or polyamide. If necessary, a laminated type support as disclosed in JP-A-3-224127 can be used to change the surface roughness of the magnetic surface and the base surface. These supports may be subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, or the like in advance. In addition, an aluminum or glass substrate can be used as the support of the present invention.

In order to achieve the object of the present invention, as a support, Mira of a surface roughness meter TOPO-3D manufactured by WYKO is used.
The center plane average surface roughness SRa measured by the u method is preferably 4.0 nm or less, more preferably 2.0 nm or less. It is preferable that these supports not only have a small center plane average surface roughness but also have no coarse protrusions of 0.5 μm or more. The surface roughness can be freely controlled by the size and amount of the filler added to the support as required. Examples of these fillers include oxides and carbonates such as Ca, Si and Ti, and organic powders such as acryl. The maximum height SRmax of the support is 1 μm or less, the ten-point average roughness SRz is 0.5 μm or less, and the height of the center plane peak SRp is 0.
5 μm or less, center plane valley depth SRv is 0.5 μm or less, center plane area ratio SSr is 10% or more and 90% or less, average wavelength S
λa is preferably 5 μm or more and 300 μm or less. In order to obtain the desired electromagnetic conversion characteristics and durability, the surface projection distribution of these supports can be arbitrarily controlled by a filler. Each of the particles having a size of 0.01 μm to 1 μm is reduced in number from 0 to 0.1 mm ^2. Control can be performed in a range of 2000 pieces.

The F-5 value of the support used in the present invention is preferably 5 to 50 kg / mm ² . Breaking strength is 5-100
Kg / mm ^2, the elastic modulus is preferably from 100 to 2,000 kg / mm ^2. The coefficient of thermal expansion is from 10 ^-4 to 10 ^-8 / ° C, preferably from 10 ^-5 to 10 ^-6 / ° C. Humidity expansion coefficient is 10 ^-4
/ RH% or less, preferably 10 ⁻⁵ / RH% or less.
These thermal characteristics, dimensional characteristics and mechanical strength characteristics are preferably substantially equal to each other in the in-plane direction of the support with a difference of 10% or less.

[Production Method] The step of producing the magnetic paint and the lower layer paint of the magnetic recording medium of the present invention comprises at least a kneading step,
It comprises a dispersion step and a mixing step provided before and after these steps as required. Each step may be divided into two or more steps. Ferromagnetic metal powder, non-magnetic powder, binder, carbon black used in the present invention,
All raw materials such as an abrasive, an antistatic agent, a lubricant, and a solvent may be added at the beginning or during any step. Further, individual raw materials may be added in two or more steps in a divided manner. For example, polyurethane may be divided and supplied in a kneading step, a dispersing step, and a mixing step for adjusting the viscosity after dispersion. In order to manufacture the magnetic recording medium of the present invention,
Conventionally known manufacturing techniques can be used as some of the steps. In the kneading step, it is preferable to use one having a strong kneading force, such as an open kneader, a continuous kneader, a pressure kneader, or an extruder. When a kneader is used, the ferromagnetic metal powder or the non-magnetic powder and all or a part of the binder (preferably at least 30% by weight of the total binder) and 15 to 500 parts per 100 parts of the ferromagnetic metal powder Is kneaded within the range. The details of these kneading processes are described in JP-A-1-106338 and JP-A-1-79274. Glass beads can be used to disperse the magnetic layer solution and the non-magnetic layer solution, but zirconia beads, titania beads, and steel beads, which are high-density dispersion media, are preferable. The particle size and the filling rate of these dispersion media are optimized and used. A well-known disperser can be used.

When applying a magnetic recording medium having a multilayer structure in the present invention, it is preferable to use the following method. First, a lower layer is first applied by a gravure coating, a roll coating, a blade coating, an extrusion coating device, etc., which are generally used in the application of a magnetic paint. Showa 60-238
179, Japanese Patent Application Laid-Open No. 2-265672, a method of applying an upper layer by a support pressure type extrusion coating apparatus.
No. 17971, Japanese Patent Application Laid-Open No. 2-265672, a method of applying upper and lower layers almost simultaneously by one coating head having two built-in slits, and a third method disclosed in Japanese Patent Application Laid-Open No. 2-174965. This is a method in which the upper and lower layers are applied almost simultaneously by an extrusion coating device with a backup roll. Incidentally, in order to prevent the electromagnetic conversion characteristics and the like of the magnetic recording medium from deteriorating due to the aggregation of the magnetic particles, JP-A-62-95174 and JP-A-1-236968 have been proposed.
It is desirable to apply shear to the coating liquid inside the coating head by a method as disclosed in US Pat. Further, the viscosity of the coating liquid must satisfy the numerical range disclosed in JP-A-3-8471. In order to realize the structure of the present invention, it is of course possible to use a sequential multi-layer coating in which a lower layer is applied and dried, and then a magnetic layer is provided thereon, and the effect of the present invention is not lost. However, in order to reduce coating defects and improve quality such as dropout, it is preferable to use the above-described simultaneous multilayer coating.

In the case of a disk, a sufficient isotropic orientation can be obtained even without orientation, without using an orientation device. However, a cobalt magnet is alternately arranged diagonally, and an alternating magnetic field is applied by a solenoid. It is preferable to use a known random alignment device. In the case of ferromagnetic metal powder, isotropic orientation is generally preferably in-plane two-dimensional random, but may be three-dimensional random with a vertical component.
In addition, isotropic magnetic characteristics can be imparted in the circumferential direction by using a known method such as a different polarity opposed magnet and making the magnets vertically oriented. In particular, when performing high-density recording, vertical alignment is preferable. In addition, circumferential orientation may be performed using spin coating.

In the case of a magnetic tape, it is oriented in the longitudinal direction using a cobalt magnet or a solenoid. It is preferable that the drying position of the coating film can be controlled by controlling the temperature of the drying air, the amount of air, and the coating speed.
The temperature of the drying air is preferably 60 ° C. or more at 000 m / min, and an appropriate preliminary drying can be carried out before entering the magnet zone.

A calendering roll is treated with a heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimideamide or a metal roll.
In particular, in the case of forming a double-sided magnetic layer, it is preferable to perform the treatment with metal rolls. The processing temperature is preferably 50 ° C. or higher,
More preferably, the temperature is 100 ° C. or higher. The linear pressure is preferably at least 200 kg / cm, more preferably at least 300 kg / cm.

[Physical Characteristics] The saturation magnetic flux density of the magnetic layer of the magnetic recording medium according to the present invention is usually from 2000 G to 500 G.
0 G or less. The coercive forces Hc and Hr are usually 180
0 Oe or more, preferably 5000 Oe or less, preferably 1800 Oe or more,
3000 Oersted or less. The distribution of coercive force is preferably narrow, and SFD and SFDr are preferably 0.6 or less. The squareness ratio is usually 0.5 for two-dimensional randomness.
5 or more and 0.67 or less, preferably 0.58 or more;
In the case of 64 or less, three-dimensional random, usually 0.45 or more, preferably 0.55 or less, and in the case of vertical orientation, the demagnetizing field was corrected in the vertical direction, usually 0.6 or more, preferably 0.7 or more. In this case, it is usually 0.7 or more, preferably 0.8 or more. The orientation ratio is preferably 0.8 or more for both two-dimensional random and three-dimensional random. In the case of two-dimensional randomness, it is preferable that the squareness ratio in the vertical direction, Br, Hc, and Hr be within 0.1 to 0.5 times the in-plane direction.

For a magnetic tape, the squareness ratio is usually 0.7
Or more, preferably 0.8 or more. Magnetic recording of the present invention
The coefficient of friction of the medium with respect to the head is from -10 ° C to 40
0.5 ° C or less in the range of 0 ° C to 95% humidity
Below, preferably below 0.3, the surface resistivity is preferably
Magnetic surface 10^Four-10¹²Ohm / sq, charge potential is -500V
+ 500V or less is preferable. 0.5% elongation of the magnetic layer
Is preferably 100 to 2000 kg in each direction in the plane.
/ mm^Two, Breaking strength is preferably 10 to 70 kg / mm ^Two, Magnetic
The elastic modulus of the recording medium is preferably 100 to 1 in each in-plane direction.
500Kg / mm^Two, The residual growth is preferably 0.5% or less,
The heat shrinkage at any temperature below 100 ° C. is preferably
1% or less, more preferably 0.5% or less, most preferably
Preferably it is 0.1% or less. Glass transition temperature of magnetic layer
(Pole of loss modulus of dynamic viscoelasticity measured at 110 Hz
(Large point) is preferably 50 ° C or higher and 120 ° C or lower, and the lower nonmagnetic layer
The temperature of the functional layer is preferably from 0 ° C to 100 ° C. The loss modulus is
1 × 10⁶~ 8 × 10⁹dyne / cm^TwoPreferably in the range
More preferably, the loss tangent is 0.2 or less.
If the loss tangent is too large, adhesion failure is likely to occur. this
Their thermal and mechanical properties are within 10% in each direction in the plane of the medium
Are preferably substantially equal. Residues contained in the magnetic layer
The solvent is preferably 100 mg / m^TwoThe following is more preferable
Is 10mg / m^TwoIt is as follows. The porosity of the coating layer is non-magnetic
Both the conductive layer and the magnetic layer are preferably 30% by volume or less, more preferably
It is preferably at most 20% by volume. High porosity output
Smaller is preferable for the purpose, but it depends on the purpose.
Sometimes it is better to secure the value. For example, for repetition
In the case of disk media, where
Row durability is often preferred.

The center surface average surface roughness Ra of the surface of the magnetic layer measured by the Mirau method using a surface roughness meter TOPO-3D manufactured by WYCO is preferably 5.0 nm or less, more preferably 4.0 nm or less, and particularly preferably. Is 3.5 nm or less, most preferably 3.3 nm or less. Maximum height SRmax of magnetic layer
Is 0.5 μm or less, the ten-point average roughness SRz is 0.3 μm or less, the center plane peak height SRp is 0.3 μm or less, the center plane trough depth SRv is 0.3 μm or less, and the center plane area ratio SSr is 20% or more. , 80% or less, average wavelength Sλa is 5 μm or more, 300 μm
m or less is preferable. The surface protrusions of the magnetic layer can be arbitrarily set in a range of 0 to 2000 with a size of 0.01 μm to 1 μm, and it is preferable to optimize the electromagnetic conversion characteristics and the friction coefficient. . These can be easily controlled by controlling the surface properties by the filler of the support, the particle size and amount of the powder to be added to the magnetic layer, and the roll surface shape of the calendar treatment. The curl is preferably within ± 3 mm.

When the magnetic recording medium of the present invention has a nonmagnetic layer and a magnetic layer, it is easily presumed that the physical properties of the nonmagnetic layer and the magnetic layer can be changed according to the purpose. For example, the elastic modulus of the magnetic layer is increased to improve running durability, and at the same time, the elastic modulus of the non-magnetic layer is made lower than that of the magnetic layer to improve the contact of the magnetic recording medium with the head.

[0136]

Example 1 <Preparation of paint> Magnetic paint 1ML-1 Ferromagnetic metal powder: 1M-1 100 parts Composition: 100% Fe, 30% Co (atomic ratio) Hc 2550 Oersted, specific surface area 55 m ² / g, σs 140 emu / g Crystallite size 120 °, average major axis length 0.048 μm, needle ratio 4 Al (Al / Fe atomic ratio 8.8%, atomic ratio A = Al / (Fe + Co) = 6.8 atomic% Y (Y / Fe Atomic ratio 4.6%) Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo) 3 parts α-alumina HIT55 (manufactured by Sumitomo Chemical) 10 parts Carbon black # 50 (Asahi Carbon Co.) 5 parts Phenylphosphonic acid 3 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 3 parts Stearic acid Parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint 1 ML-2 ferromagnetic metal powder: 1M-2 100 parts of composition: Fe100%, Co30% (atomic ratio) Hc2360 oersteds, a specific surface area of 49m ² / g, σs146emu / g Crystallite size 170Å , Average major axis length 0.100 μm, needle ratio 6, SFD 0.950 Al (Al / Fe atomic ratio 11.1%) atomic ratio A = Al / (Fe + Co) = 8.5 atomic% Y (Y / Fe Atomic ratio 6.7%) pH 9.4 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 10 parts Polyurethane resin UR5500 (manufactured by Toyobo) 4 parts α-alumina HIT70 (manufactured by Sumitomo Chemical) 10 parts Carbon black # 50 (made by Asahi Carbon Co., Ltd.) 1 part Phenylphosphonic acid 3 parts Oleic acid 1 part Stearic acid 0.6 part Ethylene glycol - Rujioreiru 12 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint 1 ML-3 (acicular magnetic powder used: Comparative Example) ferromagnetic metal powder: 1M-3 Composition / Fe: Ni = 96: 4 100 parts Hc1600Oe, specific surface area 45 m ² / g Crystallite size 220A, σs135 emu / g Average major axis length 0.20 μm, needle ratio 9 Vinyl chloride copolymer MR110 (Nippon Zeon) 12 parts Polyurethane resin UR-8600 (Toyobo) 5 parts α-alumina (Average particle diameter: 0.65 μm) 2 parts Chromium oxide (average particle diameter: 0.35 μm) 15 parts Carbon black (average particle diameter: 0.03 μm) 2 parts Carbon black (average particle diameter: 0.3 μm) 9 parts isohexadecyl stearate 4 parts n-butyl stearate 4 parts butoxyethyl stearate 4 parts olein 1 part of stearic acid 1 part Methyl ethyl ketone 300 parts nonmagnetic coating 1 nu-1 (spherical inorganic powder used) inorganic powder TiO ₂ crystal system rutile 80 parts Mean particle diameter 0.035 .mu.m, specific surface area by the BET method: 40m ² / g pH 7, TiO ₂ content 90% or more, DBP oil absorption 27-38 g / 100 g, 8% by weight of all particles as Al ₂ O _{3 on the} surface Carbon black Conductex SC-U (manufactured by Columbian Carbon Co.) 20 parts Vinyl chloride Copolymer MR110 (Nippon Zeon) 12 parts Polyurethane resin UR8200 (Toyobo) 5 parts Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / Cyclohexanone (8/2 mixed solvent) 250 parts Non-magnetic Fee 1 nu-2 (spherical inorganic powder used) inorganic powder TiO ₂ crystal system rutile 100 parts average particle diameter 0.035 .mu.m, specific surface area by the BET method: ^{40m 2 / g pH 7, TiO} 2 content of 90% or more, DBP oil absorption of 27 ３８38 g / 100 g, surface treatment agent Al ₂ O ₃ , SiO ₂ Ketjen Black EC (manufactured by AKUZO NOBEL) 13 parts Average particle diameter: 30 nm DBP oil absorption: 350 ml / 100 g pH: 9.5 Specific surface area by BET method: 950 m ² / g Volatile content: 1.0% Vinyl chloride copolymer MR110 (manufactured by Nippon Zeon) 16 parts Polyurethane resin UR8200 (manufactured by Toyobo) 6 parts Phenylphosphonic acid 4 parts Ethylene glycol dioleyl 16 parts Oleic acid 1 part Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Non-magnetic Paint 1 nu-3 (needle-like inorganic powder used) inorganic powder α-Fe ₂ O ₃ hematite 80 parts Average major axis length 0.15 [mu] m, specific surface area by the BET method: ^{50m 2 / g pH 9, Al} 2 acicular ratio 6 surface 8% by weight of all particles as O ₃ Carbon black Conductex SC-U (manufactured by Columbian Carbon Co., Ltd.) 20 parts Vinyl chloride copolymer MR110 (vinyl chloride copolymer) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) 5 parts Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Nonmagnetic paint 1NU-4 (needle) Jo inorganic powder used) inorganic powder α-Fe ₂ O ₃ hematite 100 parts average major axis length 0.15 m, BET method by a specific surface area of 50m ² / g pH 9, acicular ratio 6, 8 wt% presence mosquitoes of all particles as Al ₂ O ₃ on the surface - carbon black # 3250B (manufactured by Mitsubishi Chemical Industries, Ltd.) 18 parts Vinyl chloride copolymer Polymer MR104 (manufactured by Zeon Corporation) 15 parts Polyurethane resin UR5500 (manufactured by Toyobo) 7 parts Phenylphosphonic acid 4 parts Ethylene glycol-dioldioleyl 16 parts Oleic acid 1.3 parts Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8 / (2 mixed solvents) 250 parts Production method 1-1 (W / W) Each of the above-mentioned paints was kneaded with a kneader, and then dispersed using a sand mill. In the obtained dispersion, polyisocyanate was added to the coating liquid for the non-magnetic layer.
0 parts, 10 parts of the coating solution for the magnetic layer, and 40 parts of cyclohexanone were added to each, and the mixture was filtered using a filter having an average pore size of 1 μm. Was prepared respectively.

The obtained non-magnetic layer coating solution was applied to a thickness of 62 μm so that the thickness after drying was 1.5 μm, and immediately thereafter, the thickness of the magnetic layer was 0.15 μm thereon. At the same time, a multi-layer coating is performed simultaneously on a polyethylene terephthalate support having a center plane average surface roughness of 3 nm. After passing through two AC magnetic field generators and performing random orientation treatment and drying, the temperature is 90 ° C. and the linear pressure is 300 with a 7-stage calendar.
Kg / cm, 3.7-inch punching, surface polishing, and then 3.7-inch cartridge with a liner installed inside (zip-disk manufactured by Iomega, USA)
Cartridge) and add predetermined mechanical parts.
A 7-inch floppy disk was obtained. Further, some of the samples were subjected to longitudinal orientation using a 4000 G same-polarity opposed Co magnet before randomizing orientation treatment.

In this case, it is preferable to increase the frequency and the magnetic field strength of the AC magnetic field generator so that sufficient randomization is finally performed.
The above can be obtained. Production method 1-2 (W / D) For each of the above coating materials, each component was kneaded with a kneader, and then dispersed using a sand mill. In the obtained dispersion, polyisocyanate was added to the coating liquid for the non-magnetic layer.
0 parts, 10 parts of the coating solution for the magnetic layer, and 40 parts of cyclohexanone were added to each, and the mixture was filtered using a filter having an average pore size of 1 μm. Was prepared respectively.

The obtained coating solution for the nonmagnetic layer was applied onto a polyethylene terephthalate support having a thickness of 62 μm and a center plane average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm. Once dried and calendered, a magnetic layer is applied thereon by a blade method so that the thickness of the magnetic layer is 0.15 μm, and the frequency is 50 Hz, the magnetic field strength is 250 Gauss, and the frequency is 50 Hz and 120 Gauss. Two magnetic field strengths were passed through an AC magnetic field generator to perform a random orientation treatment, and thereafter, the same procedure as Production Method 1-1 was performed. Further, a method in which the calendering of the non-magnetic layer is not performed may be adopted. Production method 1-3 (spin coating) For each of the above coating materials, each component was kneaded with a kneader, and then dispersed using a sand mill. Polyisocyanate was added to the resulting dispersion, and 10% to the coating solution for the non-magnetic layer.
Parts and 10 parts of the coating solution for the magnetic layer, 40 parts of cyclohexanone was added to each, and the mixture was filtered using a filter having an average pore diameter of 1 μm to obtain a coating solution for forming the nonmagnetic layer and the magnetic layer. Each was prepared.

The obtained coating solution of the non-magnetic layer was spin-coated on a polyethylene terephthalate support having a thickness of 62 μm and a center plane average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm. After coating and drying once, a magnetic layer was further applied thereon by spin coating so that the thickness of the magnetic layer became 0.15 μm, and orientation treatment was performed in the circumferential direction by a 6000 G same-coop opposed Co magnet. . This is manufacturing method 1.
The surface was smoothed by performing a batch-type rolling treatment in which a pressure similar to -1 was obtained. Subsequent steps were performed in the same manner as in production method 1-1. Alternatively, a method of spin-coating the non-magnetic layer and spin-coating the magnetic layer on the non-magnetic layer while the non-magnetic layer is not dried may be used. By using the spin coating method, not only the amount of residual magnetization in the recording direction is increased, but also the perpendicular magnetization component of the ferromagnetic metal powder having a short needle ratio can be reduced, and the symmetry of the reproduced waveform can be improved. Production Method 1-4 (Single Layer) The magnetic layer coating solution of Production Method 1-1 is applied on a polyethylene terephthalate support so that the magnetic layer has a thickness of 0.15 m, and thereafter, in the same manner as in Production Method 1-1 Done. Support 1B-1 Polyethylene terephthalate Thickness: 62 μm, F-5 value: MD 114 MPa, TD 107 MPa Breaking strength: MD 276 MPa, TD 281 MPa Breaking elongation: MD 174 MPa, TD 139 MPa Heat shrinkage (80 ° C., 30 Min): MD 0.04%, TD 0.05% Heat shrinkage (100 ° C., 30 minutes): MD 0.2%, TD 0.3% Thermal expansion coefficient: major axis 15 × 10 ⁻⁵ / ° C. Minor axis 18 × 10 ⁻⁵ / ° C. Center plane average surface roughness 3 nm Support 1B-2 Polyethylene naphthalate Thickness: 55 μm, center plane average surface roughness 1.8 nm Thermal shrinkage (80 ° C., 30 minutes): MD 0.007%, TD 0.007% Heat shrinkage (100 ° C., 30 minutes): MD 0.02%, TD 0.02% Thermal expansion coefficient: major axis 10 × 10 ⁻⁵ / ° C., minor axis 11 × 10 ^-5 ℃ perform the orientation 1O-1 randomized orientation.

After the orientation in the longitudinal direction with a 10-2 Co magnet, randomized orientation is performed. Circumferential orientation is performed with a 10-3 Co magnet. Examples 1-1 to 1-16 and Comparative Example 1-1 Various samples were prepared by appropriately combining the above methods as shown in Table 1. Table 2 shows the evaluation results.

Examples 1-17 to 1-32, Comparative Example 1-2
~ Comparative Example 1-4,

In Example 1-11, the magnetic coating material 1ML-
Various magnetic disks were obtained in the same manner as in Example 1-11 except that the components (ferromagnetic metal powder and α-alumina (abrasive)) of Component 2 were changed (Tables 3 and 4). Table 5 and Table 6 show the evaluation results.
Shown in The method for evaluating the characteristics of each sample will be described below. (1) Magnetic properties (Hc): Measured using a vibration sample type magnetometer (manufactured by Toei Kogyo Co., Ltd.) with Hm10KOe (kilo Oersted). (2) Center plane average surface roughness (Ra): 3D-MIRAU
Surface roughness (Ra): Ra value of an area of about 250 μm × 250 μm was measured by MIRAU method using TOPO3D manufactured by WYKO. Spherical correction and cylindrical correction are added at a measurement wavelength of about 650 nm. This method is a non-contact surface roughness meter that measures by light interference. (3) The areal recording density is obtained by multiplying the linear recording density by the track density. (4) The linear recording density is the number of bits of a signal recorded per inch in the recording direction. (5) Track density is the number of tracks per inch. (6) Φm is the amount of magnetization per unit area of the magnetic recording medium. Bm (Gauss) multiplied by the thickness, using a vibrating sample magnetometer (Toei Kogyo Co., Ltd.)
It is a value measured with Hm10kOe and can be directly measured. (7) The error rate is obtained by converting the signal of the linear recording density into (2,
7) RLL modulation was recorded on a disk and measured. (8) Thickness of magnetic layer A magnetic recording medium was cut out to a thickness of about 0.1 μm with a diamond cutter over a longitudinal direction, and the transmission electron microscope was used to magnify 10,000 to 10,000 times.
Observation was performed at a magnification of 0, preferably 20,000 to 50,000, and the photograph was taken. Photo print size is A
4-A5. Thereafter, the interface was visually judged by paying attention to the shape difference between the ferromagnetic metal powder and the non-magnetic powder of the magnetic layer and the lower non-magnetic layer, and the surface of the magnetic layer similarly became black. After that, Zeiss image processing device IBAS2
The length of the edged line was measured at. When the length of the sample photograph was 21 cm, the measurement was performed 85 to 300 times. The average of the measured values at that time was defined as the magnetic layer thickness. (9) Running durability: floppy disk drive (US I
Omega ZIP100: 2968 rpm
m), the head is fixed at a position with a radius of 38 mm, recording is performed at a recording density of 34 kfci, and the signal is reproduced.
00%. Thereafter, the vehicle was run for 25 days (600 hours) in a thermocycle environment in which the following flow was defined as one cycle. The output was monitored every 24 hours of running, and the point where the output became 70% or less of the initial value was regarded as NG. (Thermocycle flow) 25 ° C, 50% RH 1 hour → (Temperature rise 2 hours) → 60 ° C, 20% RH 7 hours →
(Temperature drop 2 hours) → 25 ° C., 50% RH 1 hour → (Temperature drop 2 hours) → 5 ° C., 50% RH 7 hours → (Temperature rise 2
(Time) → <Repeat this> (10) Evaluation of liner wear In the same environment as the running durability with the head off, the sample was run for 600 hours, and after running the completed sample, the cartridge case was opened and the magnetic layer surface of the magnetic disk was exposed. It was visually observed and evaluated. ○: No defect on the surface of the magnetic layer △: Fine scratches on a part of the surface of the magnetic layer ×: Fine scratches on the entire surface of the magnetic layer (11) Composition of ferromagnetic metal powder The method for evaluating each of the magnetic properties and the particle size is based on the method described in JP-A-8-279137. (12) The weather resistance of the magnetic layer is as follows.
After being stored in an RH environment for 7 days, it is determined by the following measurement method. Hc fluctuation after storage of magnetic layer ΔHc (%) = 100 ×
It is calculated by the formula (Hc after storage−Hc before storage) / Hc before storage. The Hc variation ΔHc after storage is preferably −5.0%
+ 10.0%, more preferably -3.0% to +8.0.
%, Particularly preferably -1.0% to + 6.0%. Further, a decrease in Φm after storage of the magnetic layer ΔΦm (%) = 100
× (Φm before storage−Φm after storage) / Φm before storage The measurement was performed using a vibrating sample magnetometer VSM-5 (Toei Kogyo Co., Ltd.) at a time constant of 0.1 second, a sweep speed of 3 minutes / 10 KOe, and a measurement magnetic field of 10 KOe. Δ
Φm is preferably within 10%, particularly preferably within 6%.

[0144]

[Table 1]

[0145]

[Table 2]

In Examples 1-14 to 1-16, the disk of Example 1-11 was used, and the error rate was measured in the same manner while changing the linear recording density and the track density.

From the results shown in the above table, the magnetic disk of the present invention has an error rate of 1 × 10 ⁻⁵ especially in a high-density recording area.
The following shows that it is much better.

[0148]

[Table 3]

[0149]

[Table 4]

[0150]

[Table 5]

[0151]

[Table 6]

In the running durability in the above table, 600 is 60
0 hours or more

From the results shown in the above table, it is understood that the magnetic disk of the present invention is excellent in high density characteristics and also has durability.

In the present invention, a ferromagnetic metal powder is bonded on a support.
Disk with a magnetic layer dispersed in an agent
The magnetic disk has an areal recording density of 0.17 to 2 Gbi.
t / inch ^TwoA magnetic disk for recording signals of
The coercive force of the conductive layer is 1800 Oe or more;
The powder of the genus consists mainly of Fe and Co, and Al / (Fe + C
o) The atomic ratio is 3.0 to 15.0%.
The dry thickness of the magnetic recording medium, especially the magnetic layer, is preferred.
Φ of the magnetic layer.
m is preferably 8.0 × 10^-3~ 1.0 × 10^-3emu / cm
^TwoWith conventional magnetic disks,
High capacity, excellent high density properties and durability
And especially that the running durability is remarkably improved.
Recognize. Example 2 <Preparation of paint> Magnetic paint 2ML-1 Ferromagnetic metal powder: 100 parts of 2M-1 Composition: 100% Fe, 30% Co (atomic ratio) Hc 2550 Oersted, specific surface area 55 m^Two/ g, σs140 emu / g Crystallite size 120 °, average major axis length 0.048 μm, needle ratio 4 Al (Al / Fe atomic ratio 8.8%) Y (Y / Fe atomic ratio 4.6%) Atomic ratio A : 6.8% Atomic ratio B: 3.5% Atomic ratio B / A: 0.52 Vinyl chloride copolymer MR110 (manufactured by Nippon Zeon) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) 3 parts α-alumina HIT55 ( Sumitomo Chemical Co., Ltd. 10 parts Carbon black # 50 (Asahi Carbon Co., Ltd.) 5 parts Phenylphosphonic acid 3 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 3 parts Stearic acid 2 parts Methyl ethyl ketone 180 Part Cyclohexanone 180 parts Magnetic paint 2ML-2 Ferromagnetic metal powder: 100 parts 2M-2 Composition: 100% Fe, 30% Co (atomic ratio) Hc2 360 Oersted, specific surface area 49m^Two/ g, σs 146 emu / g Crystallite size 170 °, average major axis length 0.100 μm, needle ratio 6, SFD 0.950 Al (Al / Fe atomic ratio 11.4%) Y (Y / Fe atomic ratio 6.7) %) Atomic ratio A: 8.98% Atomic ratio B: 5.2% Atomic ratio B / A: 0.59 pH 9.4 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 10 parts Polyurethane resin UR5500 (Toyobo) 4 parts α-alumina HIT70 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 1 part Phenylphosphonic acid 3 parts Oleic acid 1 part Stearic acid 0.6 part Ethylene glycol-diolioyl 12 Part: methyl ethyl ketone: 180 parts: cyclohexanone: 180 parts Magnetic paint: 2ML-3 (using acicular magnetic powder: comparative example) Ferromagnetic metal powder: 2M-3 Composition / Fe: Ni = 96: 4 10 Part Hc1600Oe, a specific surface area of 45m^Two/ g Crystallite size 220 °, σs135 emu / g Average major axis length 0.20 μm, Needle ratio 9 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR-8600 (manufactured by Toyobo Co., Ltd.) 5 parts α-alumina (Average particle diameter: 0.65 μm) 2 parts Chromium oxide (average particle diameter: 0.35 μm) 15 parts Carbon black (average particle diameter: 0.03 μm) 2 parts Carbon black (average particle diameter: 0.3 μm) 9 parts isohexadecyl stearate 4 parts n-butyl stearate 4 parts butoxyethyl stearate 4 parts oleic acid 1 part stearic acid 1 part methyl ethyl ketone 300 parts Nonmagnetic paint 2NU-1 (using spherical inorganic powder) inorganic powder TiO_Two Crystalline rutile 80 parts Average particle diameter 0.035 μm, BET specific surface area 40 m^Two/ g pH 7, TiO_TwoContent 90% or more, DBP oil absorption 27-38ml / 100g, Al on the surface_TwoO_Three5% by weight Carbon black Conductex SC-U (manufactured by Columbian Carbon Co., Ltd.) 20 parts Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Nonmagnetic paint 2NU-2 (using spherical inorganic powder) ) Inorganic powder TiO_Two Crystalline rutile 100 parts Average particle diameter 0.035 μm, specific surface area by BET method 40 m^Two/ g pH 7, TiO_TwoContent of 90% or more, DBP oil absorption 27-38ml / 100g, present as Al on the surface_TwoO_Three, SiO_TwoKetjen Black EC (manufactured by AKUZO NOBEL) 13 parts Average particle diameter: 30 nm DBP oil absorption: 350 ml / 100 g pH: 9.5 Specific surface area by BET method: 950 m^Two/ G Volatile content: 1.0% Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 16 parts Polyurethane resin UR8200 (manufactured by Toyobo) 6 parts Ethylene glycol-dioldiole 16 parts Oleic acid 1 part Stearic acid 0.8 part Methyl ethyl ketone / Cyclohexanone (8/2 mixed solvent) 250 parts Nonmagnetic paint 2NU-3 (using needle-like inorganic powder) Inorganic powder α-Fe_TwoO_Three Hematite 80 parts Average major axis length 0.15μm, BET specific surface area 50m^Two/ g pH 9, needle ratio 6 Al on the surface_TwoO_ThreeCarbon black Conductex SC-U (manufactured by Columbian Carbon Co., Ltd.) 20 parts Vinyl chloride copolymer MR110 (vinyl chloride copolymer) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) 5 Part Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Nonmagnetic paint 2NU-4 (needle inorganic) Powder) Inorganic powder α-Fe_TwoO_Three Hematite 100 parts Average long axis length 0.15μm, BET specific surface area 50m^Two/ g pH 9, needle ratio 6, Al on the surface_TwoO_ThreeCarbon black # 3250B (manufactured by Mitsubishi Kasei) 18 parts Vinyl chloride copolymer MR104 (manufactured by Zeon Corporation) 15 parts Polyurethane resin UR5500 (manufactured by Toyobo) 7 parts Phenylphosphonic acid 4 Parts ethylene glycol-dioleoleil 16 parts oleic acid 1.3 parts stearic acid 0.8 parts methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Production method 2-1 (W / W) For each of the above paints, Kneading by kneading
After that, it was dispersed using a sand mill. Minutes obtained
The polyisocyanate is used for the dispersion and the coating solution for the non-magnetic layer is used for the coating.
Parts and 10 parts of the coating solution for the magnetic layer,
And 40 parts of cyclohexanone to make an average pore size of 1 μm
The filter is used to form a non-magnetic layer.
And a coating solution for forming a magnetic layer were prepared.

The obtained non-magnetic layer coating solution was applied to a thickness of 62 μm so that the thickness after drying was 1.5 μm, and immediately thereafter, the thickness of the magnetic layer was 0.15 μm thereon. At the same time, a two-layer coating is performed simultaneously on a polyethylene terephthalate support having a center plane average surface roughness of 3 nm, and while both layers are still in a wet state, a frequency of 50 Hz, a magnetic field strength of 250 Gauss and a frequency of 50 Hz and 120 Gauss are applied. After passing through two AC magnetic field generators and performing random orientation treatment and drying, the temperature is 90 ° C and the linear pressure is 300 with a 7-stage calendar.
Kg / cm, 3.7-inch punching, surface polishing, and then 3.7-inch cartridge with a liner installed inside (zip-disk manufactured by Iomega, USA)
Cartridge) and add predetermined mechanical parts.
A 7-inch floppy disk was obtained. Further, some of the samples were subjected to longitudinal orientation using a 4000 G same-polarity opposed Co magnet before randomizing orientation treatment.

In this case, it is preferable to increase the frequency and the magnetic field strength of the AC magnetic field generator so that sufficient randomization is finally performed.
The above can be obtained. Production Method 2-2 (W / D) Each of the above-mentioned paints was kneaded with a kneader, and then dispersed using a sand mill. In the obtained dispersion, polyisocyanate was added to the coating liquid for the non-magnetic layer.
0 parts, 10 parts of the coating solution for the magnetic layer, and 40 parts of cyclohexanone were added to each, and the mixture was filtered using a filter having an average pore size of 1 μm. Was prepared respectively.

The obtained coating solution for the nonmagnetic layer was applied on a polyethylene terephthalate support having a thickness of 62 μm and an average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm. Once dried and calendered, a magnetic layer is applied thereon by a blade method so that the thickness of the magnetic layer is 0.15 μm, and the frequency is 50 Hz, the magnetic field strength is 250 Gauss, and the frequency is 50 Hz and 120 Gauss. Two magnetic field strengths were passed through an AC magnetic field generator to perform random orientation processing, and thereafter, the same procedure as in Production Method 2-1 was performed. Further, a method in which the calendering of the non-magnetic layer is not performed may be adopted. Production Method 2-3 (Spin Coating) Each of the above-mentioned paints was kneaded with a kneader, and then dispersed using a sand mill. Polyisocyanate was added to the resulting dispersion, and 10% to the coating solution for the non-magnetic layer.
Parts and 10 parts of the coating solution for the magnetic layer, 40 parts of cyclohexanone was added to each, and the mixture was filtered using a filter having an average pore diameter of 1 μm to obtain a coating solution for forming the nonmagnetic layer and the magnetic layer. Each was prepared.

The obtained coating solution for the non-magnetic layer was spin-coated on a polyethylene terephthalate support having a thickness of 62 μm and a center plane average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm. After being applied and dried once, a magnetic layer was further applied thereon by spin coating so that the thickness of the magnetic layer became 0.15 μm, and orientation treatment was performed in the circumferential direction with a 6000 G same-polarity opposed Co magnet. . This is manufacturing method 2.
The surface was smoothed by performing a batch-type rolling treatment in which a pressure similar to -1 was obtained. The subsequent steps were performed in the same manner as in Production Method 2-1. Alternatively, a method of spin-coating the non-magnetic layer and spin-coating the magnetic layer on the non-magnetic layer while the non-magnetic layer is not dried may be used. By using the spin coating method, not only the amount of residual magnetization in the recording direction is increased, but also the perpendicular magnetization component of the ferromagnetic metal powder having a short needle ratio can be reduced, and the symmetry of the reproduced waveform can be improved. Production method 2-4 (single layer) The magnetic layer coating solution of production method 2-1 was applied on a polyethylene terephthalate support so that the thickness of the magnetic layer was 0.15 m, and thereafter, the same as production method 2-1 Done. Support 2B-1 Polyethylene terephthalate Thickness: 62 μm, F-5 value: MD 114 MPa, TD 107 MPa Breaking strength: MD 276 MPa, TD 281 MPa Elongation at break: MD 174 MPa, TD 139 MPa Heat shrinkage (80 ° C., 30 Min): MD 0.04%, TD 0.05% Heat shrinkage (100 ° C., 30 minutes): MD 0.2%, TD 0.3% Thermal expansion coefficient: major axis 15 × 10 ⁻⁵ / ° C. Minor axis 18 × 10 ⁻⁵ / ° C. Center plane average surface roughness 3 nm Support 2B-2 polyethylene naphthalate Thickness: 55 μm, center plane average surface roughness 1.8 nm Thermal shrinkage (80 ° C., 30 minutes): MD 0.007%, TD 0.007% Heat shrinkage (100 ° C., 30 minutes): MD 0.02%, TD 0.02% Thermal expansion coefficient: major axis 10 × 10 ⁻⁵ / ° C., minor axis 11 × 10 ^-5 / ° C Orientation 2O-1 Randomized orientation is performed.

After orientation in the longitudinal direction with a 2O-2 Co magnet, random orientation is performed. Circumferential orientation is performed with a 2O-3 Co magnet. Examples 2-1 to 2-16 and Comparative Example 2-1 Various samples were prepared by appropriately combining the above methods as shown in Table 7. Table 8 shows the evaluation results.

Examples 2-17 to 2-22, Comparative Examples 2-2 to 2-4

The magnetic paint 2ML-2 in Example 2-11
Various magnetic disks were obtained in the same manner as in Example 2-11, except that the component (ferromagnetic metal powder) was changed (Table 9), and the added amount of α-alumina was changed to 8 parts. In Table 9, the atomic ratio A of the ferromagnetic metal powder 2M-9 indicates the atomic ratio of each component of Nd and Y to (Fe + Co).
The atomic ratio A of M-9 is 3.3%, and the sum of the rare earth elements for calculating the atomic ratio A of the other ferromagnetic metal powder is substantially regarded as one component of Y or Nd. The evaluation results are shown in Tables 10 and 11.

The method of evaluating the characteristics of each sample is the same as described above.

[0163]

[Table 7]

[0164]

[Table 8]

In Examples 2-14 to 2-16, the error rate was measured in the same manner by using the disk of Example 2-11 while changing the linear recording density and the track density.

From the results shown in the above table, the magnetic disk of the present invention has an error rate of 1 × 10 ⁻⁵ especially in a high-density recording area.
The following shows that it is much better.

[0167]

[Table 9]

[0168]

[Table 10]

[0169]

[Table 11]

In the running durability in the above table, 600 is 60
0 hours or more

From the results in the above table, it can be seen that the magnetic disk of the present invention has excellent high density characteristics and also has durability.

In the present invention, a ferromagnetic metal powder is bonded on a support.
Disk with a magnetic layer dispersed in an agent
The magnetic disk has an areal recording density of 0.17 to 2 Gbi.
t / inch ^TwoPreferably 0.2 to 2 Gbit / inch^TwoOf the signal
A magnetic disk on which the magnetic layer has a dry thickness.
Preferably, the thickness is 0.05 to 0.25 μm,
Φm is preferably 8.0 × 10^-3~ 1.0 × 10^-3emu /
cm^TwoWhen the coercive force of the magnetic layer is 1800 Oe or more,
The ferromagnetic metal powder is mainly composed of Fe and Co;
Atomic ratio B of {sum of rare earth elements / (Fe + Co)}
Is preferably 1.0 to 6.0%, and {Rare earth element
Elemental sum / Al 原子 atomic ratio B / A is 0.10 to 0.6
0
Excellent high density characteristics that could not be obtained with the technology of
Combined with durability, especially the running durability has been significantly improved
A magnetic recording medium can be obtained. Example 3 <Preparation of paint> Magnetic paint 3ML-1 Ferromagnetic metal powder: 100 parts of 3M-1 Composition: 100% Fe, 36% Co (atomic ratio) Hc 2550 Oersted, specific surface area 55 m^Two/ g, σs140 emu / g Crystallite size 110 °, average major axis length 0.048 μm, needle ratio 4 Atomic ratio A {Al / (Fe + Co)}: 6.2% Atomic ratio B {Y / (Fe + Co)}: 3 .2% Atomic ratio B / A: 0.516 Atomic ratio C {Mg / (Fe + Co)}: 1.2% Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) 3 Part α-alumina HIT55 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 5 parts phenylphosphonic acid 3 parts butyl stearate 10 parts butoxyethyl stearate 5 parts isohexadecyl stearate 3 parts stearin Acid 2 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts

Magnetic coating material 3ML-2 Ferromagnetic metal powder: 100 parts of 3M-2 Composition: 100% Fe, 30% Co (atomic ratio) Hc2380 Oersted, specific surface area 49 m ² / g, σs 144 emu / g crystallite size 140 °, average major axis 0.085 μm long, needle ratio 5.6, SFD 0.920, pH 9.4 Atomic ratio A: 8.8% Atomic ratio B {Y / (Fe + Co)}: 5.2% Atomic ratio B / A: 0.591 atomic ratio C: 0.8% pH 9.4 vinyl chloride copolymer MR110 (manufactured by Nippon Zeon) 10 parts Polyurethane resin UR5500 (manufactured by Toyobo) 4 parts α-alumina HIT70 (manufactured by Sumitomo Chemical) 10 parts Carbon black # 50 (made by Asahi Carbon Co., Ltd.) 1 part Phenylphosphonic acid 3 parts Oleic acid 1 part Stearic acid 0.6 part Ethylene glycoldioleyl 12 parts Methyl ethyl ke Down 180 parts Cyclohexanone 180 parts

Magnetic paint 3ML-3 (Comparative example) Ferromagnetic metal powder: 3M-3 Composition / Fe: Ni = 96: 4 100 parts Hc1600Oe, specific surface area 45 m ² / g Crystallite size 220 °, σs135 emu / g Average major axis 0.20 μm long, needle ratio 9 Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR-8600 (manufactured by Toyobo) 5 parts α-alumina (average particle diameter 0.65 μm) 2 parts chromium oxide ( Average particle diameter: 0.35 μm) 15 parts Carbon black (average particle diameter: 0.03 μm) 2 parts Carbon black (average particle diameter: 0.3 μm) 9 parts Isohexadecyl stearate 4 parts n-butyl Stearate 4 parts Butoxyethyl stearate 4 parts Oleic acid 1 part Stearic acid 1 part Methyl ethyl ketone 300 parts

Non-magnetic paint 3NU-1 (using spherical inorganic powder) Inorganic powder TiO ₂ crystalline rutile 80 parts Average particle diameter 0.035 μm, specific surface area by BET method 40 m ² / g pH 7, TiO ₂ content 90% or more DBP oil absorption: 27 to 38 ml / 100 g, Al ₂ O _{3 on the} surface: 8% by weight based on the whole particles Carbon black Conductex SC-U (manufactured by Columbian Carbon Co., Ltd.) 20 parts Vinyl chloride copolymer MR110 ( Zeon Corporation) 12 parts Polyurethane resin UR8200 (Toyobo) 5 parts Phenylphosphonic acid 4 parts Butyl ethyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8 / 2 mixed solvents) 250 parts

Non-magnetic paint 3NU-2 (using spherical inorganic powder) Inorganic powder TiO ₂ crystalline rutile 100 parts Average particle diameter 0.035 μm, specific surface area by BET method 40 m ² / g pH 7, TiO ₂ content 90% or more DBP oil absorption 27 to 38 ml / 100 g, Al ₂ O ₃ and SiO ₂ present on the surface Ketjen Black EC (manufactured by AKUZO NOBEL) 13 parts Average particle diameter: 30 nm DBP oil absorption: 350 ml / 100 g pH: 9.5 Specific surface area by BET method: 950 m ² / g Volatile content: 1.0% Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 16 parts Polyurethane resin UR8200 (manufactured by Toyobo) 6 parts Phenylphosphonic acid 4 parts Ethylene glycol-dioldioleyl 16 parts Oleic acid 1 part Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8/2 mixture Solvent) 250 parts

Nonmagnetic paint 3NU-3 (using acicular inorganic powder) Inorganic powder α-Fe ₂ O ₃ hematite 80 parts Average major axis length 0.15 μm, Specific surface area by BET method 50 m ² / g pH 9, Needle ratio 6 Al ₂ O _{3 on the} surface 8% by weight based on the whole particles Carbon black Conductex SC-U (manufactured by Columbian Carbon Co.) 20 parts Vinyl chloride copolymer MR110 (vinyl chloride copolymer) 12 parts Polyurethane Resin UR8200 (Toyobo) 5 parts Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts

Non-magnetic paint 3NU-4 (using acicular inorganic powder) Inorganic powder α-Fe ₂ O ₃ hematite 100 parts Average major axis length 0.15 μm, BET specific surface area 50 m ² / g pH 9, Needle ratio 6, Al ₂ O _{3 on the} surface is present in an amount of 8% by weight with respect to the whole particles Carbon black # 3250B (manufactured by Mitsubishi Kasei) 18 parts Vinyl chloride copolymer MR104 (manufactured by Zeon Corporation) 15 parts Polyurethane resin UR5500 (Toyobo) 7 parts Phenylphosphonic acid 4 parts Ethylene glycol-dioleoleil 16 parts Oleic acid 1.3 parts Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts

Production Method 3-1 (W / W) For each of the above coating materials, each component was kneaded with a kneader and then dispersed using a sand mill. 10 parts of polyisocyanate was added to the resulting dispersion,
To the coating liquid for the magnetic layer, 10 parts were added, and 40 parts of cyclohexanone was further added to each, followed by filtration using a filter having an average pore diameter of 1 μm to prepare coating liquids for forming the lower layer and for forming the magnetic layer, respectively.

The obtained lower layer coating liquid was applied to a thickness of 62 μm so that the thickness after drying was 1.5 μm and immediately thereafter the magnetic layer was 0.15 μm on the center. Polyethylene terephthalate having a surface average surface roughness of 3 nm
At the same time, two layers are applied simultaneously on the support, and while both layers are still in a wet state, they are passed through an AC magnetic field generator with a frequency of 50 Hz and a magnetic field strength of 250 gauss or a frequency of 50 Hz and 120 gauss and are randomly oriented. After processing and drying, the temperature is 90 ° C and the linear pressure is 300Kg with a 7-stage calendar.
/ cm, and punched into a 3.7-inch surface and polished, then placed in a 3.7-inch cartridge (Zip-disk cartridge manufactured by Iomega, USA) with a liner installed inside, and 3.7 additional mechanical parts
An inch floppy disk was obtained. Further, some of the samples were subjected to longitudinal orientation using a 4000 G same-polarity opposed Co magnet before randomizing orientation treatment.

In this case, it is preferable to increase the frequency and the magnetic field strength of the AC magnetic field generator so that sufficient randomization is finally performed.
The above can be obtained.

Production Method 3-2 (W / D) For each of the above coating materials, each component was kneaded with a kneader and then dispersed using a sand mill. 10 parts of polyisocyanate was added to the resulting dispersion,
To the coating liquid for the magnetic layer, 10 parts were added, and 40 parts of cyclohexanone was further added to each, followed by filtration using a filter having an average pore diameter of 1 μm to prepare coating liquids for forming the lower layer and for forming the magnetic layer, respectively.

The obtained lower layer coating solution was applied on a polyethylene terephthalate support having a thickness of 62 μm and a center plane average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm, and dried once. After performing a calendering process, a magnetic layer is further applied thereon by a blade method so that the magnetic layer has a thickness of 0.15 μm. The magnetic field intensity was passed through an AC magnetic field generator to perform a random orientation treatment. Alternatively, a method in which the lower layer is not calendered may be used.

Production Method 3-3 (Spin Coating) Each of the above-mentioned paints was kneaded with a kneader, and then dispersed using a sand mill. To the resulting dispersion, add 10 parts of polyisocyanate to the lower layer coating solution and 10 parts to the magnetic layer coating solution, and further add 40 parts of cyclohexanone to each, and use a filter having an average pore diameter of 1 μm. The mixture was filtered to prepare a coating solution for forming a lower layer and a coating solution for forming a magnetic layer.

The obtained lower layer coating solution was spin-coated on a polyethylene terephthalate support having a thickness of 62 μm and an average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm. After drying once, a magnetic layer was further applied thereon by spin coating so that the thickness of the magnetic layer became 0.15 μm, and an orientation treatment was performed in the circumferential direction with a 6000 G same-pole opposed Co magnet. This is the production method 3-
The surface was smoothed by performing a batch-type rolling treatment capable of obtaining the same pressure as in Example 1. The subsequent steps were performed in the same manner as in Production Method 3-1. Alternatively, a method of spin-coating the lower layer and spin-coating the magnetic layer thereon while the lower layer is not dried may be used. By using the spin coating method, not only the amount of residual magnetization in the recording direction is increased, but also the perpendicular magnetization component of the ferromagnetic metal powder having a short needle ratio can be reduced, and the symmetry of the reproduced waveform can be improved.

Production Method 3-4 (Single Layer) The magnetic layer coating solution of Production Method 3-1 was coated on a polyethylene terephthalate support so that the magnetic layer had a thickness of 0.15 m. Was performed in the same manner as described above. Support 3B-1 Polyethylene terephthalate Thickness: 62 μm, F-5 value: MD 114 MPa, TD 107 MPa Breaking strength: MD 276 MPa, TD 281 MPa Elongation at break: MD 174 MPa, TD 139 MPa Heat shrinkage (80 ° C., 30 Min): MD 0.04%, TD 0.05% Heat shrinkage (100 ° C., 30 minutes): MD 0.2%, TD 0.3% Thermal expansion coefficient: major axis 15 × 10 ⁻⁵ / ° C. Minor axis 18 × 10 ⁻⁵ / ° C. Center plane average surface roughness 3 nm Support 3B-2 polyethylene naphthalate Thickness: 55 μm, center plane average surface roughness 1.8 nm Thermal shrinkage (80 ° C., 30 minutes): MD 0.007%, TD 0.007% Heat shrinkage (100 ° C., 30 minutes): MD 0.02%, TD 0.02% Thermal expansion coefficient: major axis 10 × 10 ⁻⁵ / ° C., minor axis 11 × 10 ^-5 / ° C

Orientation 3O-1 Randomized orientation is performed. After orientation in the longitudinal direction with a 3O-2 Co magnet, randomized orientation is performed. Circumferential orientation is performed with a 3O-3 Co magnet.

Examples 3-1 to 3-16 and Comparative Example 3-1 Various samples were prepared by appropriately combining the above methods as shown in Table 12. Table 13 shows the evaluation results. Example 3-17 to Example 3-23, Comparative Example 3-2

In Examples 3 to 11, the magnetic paint 3ML-2 was used.
Were changed (Table 14) and the amount of α-alumina added was changed to 8 parts in the same manner as in Example 3-11 to obtain various magnetic recording media. In Table 14, the atomic ratio B of the ferromagnetic metal powder 3M-10 indicates the atomic ratio of each component of Nd and Y to (Fe + Co). Therefore, the atomic ratio B of 3M-10 is 6.3. %, And the total sum of the rare earth elements for calculating the atomic ratio B of the other ferromagnetic metal powders is substantially regarded as one component of Y or Sm. Tables 15 and 16 show the evaluation results.

The method of evaluating the characteristics of each sample is the same as described above, except for the following. -Starting torque evaluation The starting torque at the time of the head ON in a 3.5-inch floppy disk drive was measured using the torque gauge model 300ATG of Tohnichi Seisakusho. The sample was directly measured at 23 ° C. and 50% RH (before storage).
After storage at 0 ° C. and 90% RH for 10 days, it was left at RT for 24 hours, measured at 23 ° C. and 50% RH (after storage), and the starting torque before and after storage was compared. ○: little difference in starting torque between before and after storage △: slight increase in starting torque after storage ×: large increase in startup torque after storage

[0191]

[Table 12]

[0192]

[Table 13]

In Examples 3-14 to 3-16, the disk of Example 3-11 was used, and the error rate was measured in the same manner while changing the linear recording density and the track density.

From the results in the above table, it can be seen that the magnetic recording medium of the present invention has an error rate of 1 × 10 ⁻⁵ especially in a high-density recording area.
The following shows that it is much better.

[0195]

[Table 14]

[0196]

[Table 15]

[0197]

[Table 16]

In the running durability shown in the above table, 600 is 60
0 hours or more

From the results in the above table, it can be seen that the magnetic recording medium of the present invention is excellent in high density characteristics and also has durability.

The present invention relates to a magnetic recording medium provided with a magnetic layer comprising a support and a ferromagnetic metal powder dispersed in a binder, wherein the magnetic recording medium has an areal recording density of 0.17 to 2 Gbi.
A magnetic recording medium for recording a signal of t / inch ² , wherein the ferromagnetic metal powder is mainly composed of Fe and Co, and Al / (F
e + Co) has an atomic ratio A of 3.0 to 15.0% or an atomic ratio BGA of 0.5 to 9.0%, preferably the magnetic layer has a dry thickness of 0.05 to 0.25 μm. The Φm of the magnetic layer is preferably 1.0 × 10 ^{−3 to} 8.0 × 1.
0 ^-3 emu / cm ² , and the atomic ratio B is preferably 1 to 8%.
And a magnetic recording medium characterized in that the atomic ratio C of Mg / (Fe + Co) is preferably 0.05% to 3.0%, which makes it possible to obtain excellent high It is possible to obtain a magnetic recording medium which has both density characteristics and durability, and in particular, has significantly improved running durability. Example 4 <Preparation of paint> Magnetic paint 4ML-1 (using acicular magnetic powder) Ferromagnetic metal powder: 100 parts of 4M-1 Composition: Co / Fe (atomic ratio) 30%, Hc2550 Oersted, specific surface area 55 m ² / g, σs 140 emu / g Crystallite size 120 °, average major axis length 0.048 μm, needle ratio 4 Al compound (Al / Fe atomic ratio 8%) Y compound (Y / Fe atomic ratio 6%) Atomic ratio A: 6% Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) 3 parts α-alumina HIT55 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Average particle diameter: 0.20 μm, specific surface area: 8.0 to 8.0 9.0 m ² / g Mohs hardness: 9, pH: 7.7 to 9.0 Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 5 parts Average particle diameter: 94 nm, specific surface area: 28 m ² / g DBP Oil absorption: 1 ml / 100 g, pH: 7.5 Volatile content: 1.0% by weight Phenylphosphonic acid 3 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 3 parts Stearic acid 2 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint 4ML-2 (using needle-shaped magnetic powder) Ferromagnetic metal powder: 4M-2 100 parts Composition: Co / Fe (atomic ratio) 30%, Hc2360 Oersted, specific surface area 49 m ² / g, σs 146 emu / g crystallite size 170 °, average major axis length 0.100 μm, needle ratio 6, SFD 0.51 Al compound (Al / Fe atomic ratio 5%) Y compound (Y / Fe atomic ratio 5%) Atomic ratio A: 3.8% pH 9.4 Vinyl chloride copolymer MR110 (manufactured by Nippon Zeon) 10 parts Polyurethane resin UR5500 (manufactured by Toyobo) 4 parts α aluminum HIT70 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Average particle diameter: 0.15 [mu] m, a specific surface area: 17m ² / g mode - scan Hardness: 9, pH: 7.7~9.0 Ca - Carbon black # 50 (Asahi Carbon Co. 1 part) Average particle diameter: 94 nm, specific surface area: 28 m ² / g DBP oil absorption: 61 ml / 100 g, pH: 7.5 Volatile content: 1.0% by weight Phenylphosphonic acid 3 parts Oleic acid 1 part Stearic acid 0 6.6 parts Ethylene glycoldioleyl 12 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint 4ML-3 (using needle-shaped magnetic powder: Comparative example) Ferromagnetic metal powder: 4M-3 Composition / Fe: Ni = 96: 4 100 parts Hc1600 Oe, a specific surface area of 45 m ² / g crystallite size 220Å, σs135emu / g average major axis length 0.20 [mu] m, the acicular ratio of 9-vinyl copolymer MR 110 (Japan chloride Zeon) 12 parts Polyurethane resin UR-8600 (Toyobo) 5 parts α-alumina (average particle diameter 0.65 μm) 2 parts Chromium oxide (average particle diameter: 0.35 μm) 15 parts Carbon black (average particle Diameter: 0.03 μm) 2 parts Carbon black (average particle diameter: 0.3 μm) 9 parts Isohexadecyl stearate 4 parts n-butyl stearate 4 parts Butoxyethyl stearate 4 parts Oleic acid 1 part Stearic acid 1 Part: methyl ethyl ketone: 300 parts Magnetic paint: 4ML-4 (using needle-shaped magnetic powder) Ferromagnetic metal powder: 4M-2: 100 parts Composition: Co / Fe (atomic ratio) 30%, Hc2360 Oersted, specific surface area 49 m ² / g, σs 146 emu / g Crystallite size 170 °, average major axis length 0.100 μm, needle ratio 6, SFD 0.51 Al compound (Al / Fe atomic ratio 5%) Y compound (Y / Fe atomic ratio 5%) Atomic ratio A: 3.8% pH 9.4 Vinyl chloride copolymer MR110 (Nippon Zeon) 10 parts Polyurethane resin UR5500 (Toyobo) 4 parts α-alumina HIT70 (Sumitomo Chemical Co., Ltd.) 10 parts Average particle diameter: 0.15 μm, specific surface area: 17 m ² / g Mohs hardness: 9, pH: 7.7 to 9.0 Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 1) Average particle diameter: 94 nm, specific surface area: 28 m ² / g DBP oil absorption: 61 ml / 100 g, pH: 7.5 Volatile content: 1.0% by weight Phenylphosphonic acid 3 parts Myristic acid 1 part Stearic acid 0. 6 parts Butyl stearate 4 parts Cetyl palmitate 4 parts Oleyl oleate 4 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint 4ML-5 (using needle-shaped magnetic powder) Metal powder: 4M-2 100 parts Composition: Co / Fe (atomic ratio) 30%, Hc2360 Oersted, specific surface area 49 m ² / g, σs 146 emu / g Crystallite size 170 °, average major axis length 0.100 μm, needle ratio 6, SFD 0.51 Al compound (Al / Fe atomic ratio 5%) Y compound (Y / Fe atomic ratio 5%) Atomic ratio A: 3.8% pH 9.4 Vinyl chloride copolymer MR110 (Nihon Zeon Co., Ltd.) 10 parts Polyurethane resin UR5500 (manufactured by Toyobo Co., Ltd.) 4 parts α-alumina HIT70 (manufactured by Sumitomo Chemical Co., Ltd.) 10 parts Average particle diameter: 0.15 μm, specific surface area: 17 m ² / g Mohs hardness: 9, pH: 7 0.7 to 9.0 Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 1 part Average particle diameter: 94 nm, specific surface area: 28 m ² / g DBP oil absorption: 61 ml / 100 g, pH: 7.5 Volatile content: 1 0.0 weight Phenylphosphonic acid 3 parts Amyl stearate 4 parts Butoxyethyl stearate 6 parts Oleyl oleate 4 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic paint 4ML-6 (using needle-like magnetic powder) Ferromagnetic metal powder: 4M-3 100 Part Composition: Co / Fe (atomic ratio) 30%, Hc2360 Oersted, specific surface area 46 m ² / g, σs 153 emu / g crystallite size 160 °, average major axis length 0.100 μm, needle ratio 6, SFD 0.51, pH 9.4 Al compound (Al / Fe atomic ratio 11%) Y compound (Y / Fe atomic ratio 7%) Mg compound (Mg / Fe atomic ratio 1%) Atomic ratio A: 8.5% Atomic ratio C: 0. 77% vinyl chloride copolymer 10 parts MR110 (manufactured by Zeon Corporation) polyurethane resin 4 parts UR5500 (manufactured by Toyobo) α-alumina 10 parts ( Lumina terms) HIT55 (manufactured by Sumitomo Chemical Co., Ltd.) (HIT55 / MR110 / MEK 5 parts / 1 part / 4 parts of another dispersion product) Average particle diameter: 0.20 [mu] m, a specific surface area: 8.0~9.0m ² / g Mohs hardness: 9, pH: 7.7 to 9.0 1 part of Diamond LS600F (manufactured by Lands Super Abrasive) Average particle size: 0.27 μm, Carbon black # 50 (manufactured by Asahi Carbon Co.) Average particle size: 94 nm, specific surface area: 28 m ² / g DBP oil absorption: 61 ml / 100 g, pH: 7.5 Volatile content: 1.0% by weight Phenylphosphonic acid 3 parts Stearic acid 1 part Oleic acid 1 part Butyl stearate 4 parts butoxyethyl stearate 4 parts neopentyl glycol didecanoate 2 parts ethylene glycol dioleyl 2 parts methyl ethyl ketone 180 parts cyclohexano 180 parts Non-magnetic paint 4NU-1 (using spherical inorganic powder) Inorganic powder TiO ₂ crystalline rutile 80 parts Average particle diameter 0.035 μm, BET specific surface area 40 m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27~38ml / 100g, Al ₂ O ₃ is with respect to the entire particles to the surface 8 wt% presence mosquito - (manufactured by Columbian carbon Co., Ltd.) carbon black CONDUCTEX Tex SC-U 20 parts average particle size: 20 nm DBP oil absorption : 115 ml / 100 g pH: 7.0 Specific surface area by BET method: 220 m ² / g Volatile content: 1.5% Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) 5 parts Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Phosphoric acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts nonmagnetic coating 4NU-2 (spherical inorganic powder used) inorganic powder TiO ₂ crystal system rutile 100 parts average particle diameter 0.035 .mu.m, specific surface area by the BET method: 40m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27-38 ml / 100 g, Al ₂ O ₃ and SiO ₂ present on the surface Ketjen Black EC (manufactured by AKUZO NOBEL) 13 parts Average particle diameter: 30 nm DBP oil absorption: 350 ml / 100 g pH: 9.5 Specific surface area by BET method: 950 m ² / g Volatile content: 1.0% Vinyl chloride copolymer MR110 (manufactured by Zeon Corporation) 16 parts Polyurethane resin UR8200 (manufactured by Toyobo Co., Ltd.) 6 parts phenylphosphonic acid 4 parts ethylene glycol dioleyl 16 parts oleic acid 1 part Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts nonmagnetic coating 4NU-3 (spherical inorganic powder used) inorganic powder TiO ₂ crystal system rutile 75 parts Mean particle diameter 0.035 .mu.m, specific surface area 40 m ² / g pH 7 TiO ₂ content of 90% or more, DBP oil absorption of 27~38ml / 100g, there mosquitoes as Al ₂ O _3, SiO ₂ on the surface - carbon black Ketjen black EC 10 parts average particle size: 30 nm DBP oil absorption amount : 350 ml / 100 g pH: 9.5 Specific surface area by BET method: 950 m ² / g Volatile content: 1.0% α-alumina AKP-15 (manufactured by Sumitomo Chemical Co., Ltd.) Average particle diameter: 0.65 μm 15 parts Vinyl chloride Polymer MR110 (Nippon Zeon) 12 parts Polyurethane resin UR8600 (Toyobo) 5 parts Isohexadecyl stearate 4 parts n-butyl stearate 4 parts butoxyethyl stearate 4 parts oleic acid 1 part stearic acid 1 part methyl ethyl ketone 300 parts nonmagnetic paint 4NU-4 (using needle-like inorganic powder) inorganic powder α-Fe ₂ O ₃ hematite 80 parts Average long axis length 0.15 μm, specific surface area by BET method 50 m ² / g pH 9, needle ratio 6 Al ₂ O ₃ is present on the surface at 8% by weight of the whole particles Carbon black Conductex SC-U (Colombia 20 parts Average particle diameter: 20 nm DBP oil absorption: 115 ml / 100 g pH: 7.0 Specific surface area by BET method: 220 m ² / g Volatile content: 1.5% Vinyl chloride copolymer MR110 (Nihon Zeon) 12 parts Polyurethane resin UR8200 (Toyobo) 5 parts Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Nonmagnetic paint 4NU-5 (using needle-like inorganic powder) Inorganic powder α-Fe ₂ O ₃ Hematite 100 parts Average major axis length 0.15 μm, Specific surface area by BET method 50 m ² / g pH 9, Needle ratio 6 Al ₂ O ₃ is present on the surface at 8% by weight with respect to the whole particles Carbon black # 3250B (Mitsubishi 18 parts 5.0 Average particle diameter: 30 nm, Specific surface area: 245 m ² / g DBP oil absorption: 155 ml / 100 g, pH: 6.0 Volatile content: 1.5% by weight Vinyl chloride copolymer MR104 ( Nippon Zeon Co., Ltd. 15 parts Polyurethane resin UR5500 (Toyobo Co., Ltd.) 7 parts Phenylphosphonic acid 4 parts Ethylene glycoldioleyl 16 parts Maleic acid 1.3 parts Stearic acid 0.8 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts nonmagnetic coating 4NU-6 (needle-like inorganic powder used) the non-magnetic powder α-Fe ₂ O ₃ hematite 100 parts Average Long axis length 0.15 μm, specific surface area by BET method 50 m ² / g pH 9, needle ratio 6 Al ₂ O _{3 on the} surface 8% by weight of the whole particles Carbon black # 3250B (manufactured by Mitsubishi Chemical Corporation) 18 parts 5.0 Average particle diameter: 30 nm, Specific surface area: 245 m ² / g DBP oil absorption: 155 ml / 100 g, pH: 6.0 Volatile content: 1.5% by weight Vinyl chloride copolymer MR104 (manufactured by Zeon Corporation) 15 parts Polyurethane resin UR5500 (manufactured by Toyobo Co., Ltd.) 7 parts Phenylphosphonic acid 4 parts Myristic acid 1 part Stearic acid 0.6 parts Butyl stearate 4 parts Palmitate Le 4 parts oleyl oleate 4 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts nonmagnetic coating 4NU-7 (needle-like inorganic powder used) the non-magnetic powder α-Fe ₂ O ₃ hematite 100 parts Average major axis length 0 .15 μm, specific surface area by BET method 50 m ² / g pH 9, needle ratio 6 Al ₂ O ₃ is present on the surface at 8% by weight of the whole particles Carbon black Conductex SC-U (manufactured by Columbian Carbon Co., Ltd.) 10 parts Average particle diameter: 20 nm DBP oil absorption: 115 ml / 100 g pH: 7.0 Specific surface area by BET method: 220 m ² / g Volatile content: 1.5% Carbon black # 50 (manufactured by Asahi Carbon Co., Ltd.) 10 parts average particle diameter: 94 nm, specific surface area: 28 m ² / g DBP oil absorption amount: 61ml / 100g, pH: 7.5 volatiles: 1.0% by weight vinyl chloride copolymer MR 04 (manufactured by Zeon Corporation) 15 parts Polyurethane resin UR5500 (manufactured by Toyobo) 7 parts Phenylphosphonic acid 4 parts Amyl stearate 4 parts Butoxyethyl stearate 6 parts Oleyl oleate 4 parts Methyl ethyl ketone / cyclohexanone (8/2 mixture) Solvent) 250 parts Non-magnetic paint 4NU-8 (using needle-like inorganic powder) Non-magnetic powder α-Fe ₂ O ₃ hematite 100 parts Average major axis length 0.08 μm, BET specific surface area 50 m ² / g pH 9, needle Shape ratio 6.5 Al ₂ O _{3 present on the} surface in an amount of 8% by weight based on the whole particles Carbon black Conductex SC-U (manufactured by Columbian Carbon Co., Ltd.) 25 parts Average particle diameter: 20 nm DBP oil absorption: 115 ml / 100 g pH: 7.0 BET specific surface area: 220 m ² / g volatile content: 1.5% vinyl chloride copolymer MR 04 (manufactured by Zeon Corporation) 16 parts Polyurethane resin UR5500 (manufactured by Toyobo Co., Ltd.) 7 parts Phenylphosphonic acid 4 parts Stearic acid 1 part Oleic acid 1 part Butyl stearate 4 parts Butoxyethyl stearate 4 parts Neopentyl glycol-dioldioleyl 2 parts Ethylene glycoldioleyl 2 parts Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Production method 4-1 (disk: W / W) For each of the above coating materials, each component is kneaded with a kneader, and then sand milled. And dispersed using Polyisocyanate was added to the resulting dispersion, and 10% to the coating solution for the non-magnetic layer.
Parts and 10 parts of the coating solution for the magnetic layer, 40 parts of cyclohexanone was added to each, and the mixture was filtered using a filter having an average pore diameter of 1 μm to obtain a coating solution for forming the nonmagnetic layer and the magnetic layer. Each was prepared.

The obtained non-magnetic layer coating solution was applied to a thickness of 62 μm so that the thickness after drying was 1.5 μm, and immediately thereafter, the thickness of the magnetic layer was 0.15 μm thereon. At the same time, a multi-layer coating is performed simultaneously on a polyethylene terephthalate support having a center plane average surface roughness of 3 nm. After passing through two AC magnetic field generators and performing random orientation treatment and drying, the temperature is 90 ° C and the linear pressure is 300 with a 7-stage calendar.
Kg / cm, 3.7-inch punching, surface polishing, and then 3.7-inch cartridge with a liner installed inside (zip-disk manufactured by Iomega, USA)
Cartridge) and add predetermined mechanical parts.
A 7-inch floppy disk was obtained. Further, some of the samples were subjected to longitudinal orientation using a 4000 G same-polarity opposed Co magnet before randomizing orientation treatment.

In this case, it is preferable to increase the frequency and the magnetic field strength of the AC magnetic field generator so that sufficient randomization is finally performed.
The above can be obtained. When a barium ferrite magnetic material is used, vertical alignment can be performed in addition to the above-described alignment method. Also, if necessary, after punching into a disk shape, a high-temperature thermotreatment (usually 50 ° C to 90 ° C)
C.) to accelerate the curing treatment of the coating layer, perform a burnishing treatment with a polishing tape, and perform a post-treatment such as shaving projections on the surface. Production method 4-2 (Computer tape: W / W) After kneading each component of the above-mentioned paint with a kneader,
It was dispersed using a sand mill. To the obtained dispersion, 2.5 parts of polyisocyanate is added to the coating solution for the non-magnetic layer, 3 parts to the coating solution for the magnetic layer, and 40 parts of cyclohexanone is added to each, to have an average pore diameter of 1 μm. The mixture was filtered using a filter to prepare a coating solution for forming a nonmagnetic layer and a coating solution for forming a magnetic layer.

The obtained non-magnetic layer coating solution was applied to a thickness of 4 μm so that the thickness after drying became 1.7 μm and immediately thereafter the thickness of the magnetic layer became 0.15 μm. .4μ
m and an aramid support (trade name: MICRON) having a center plane average surface roughness of 2 nm. Orientation was carried out by the holding solenoid. After drying, 200 m / min. Speed / 85 ° C./min.
Then, a backing layer having a thickness of 0.5 μm (carbon black average particle diameter: 17 nm 100 parts, calcium carbonate average particle diameter: 40 nm 80 parts, α-alumina average particle diameter: 0.2 μm 5 parts) was nitrocellulose-treated. Resin, polyurethane resin and polyisocyanate). Slit to a width of 3.8 mm, attach the non-woven fabric and razor blade to a device having a slit product feeding and winding device so that the non-woven fabric and razor blade are pressed against the magnetic surface.
The surface of the magnetic layer was cleaned with a precleaning apparatus, and the obtained magnetic tape was incorporated into a DDS cartridge. Production Method 4-3 (Disk: W / D) For each of the above paints, each component was kneaded with a kneader, and then dispersed using a sand mill. Polyisocyanate was added to the resulting dispersion, and 10% to the coating solution for the non-magnetic layer.
Parts and 10 parts of the coating solution for the magnetic layer, 40 parts of cyclohexanone was added to each, and the mixture was filtered using a filter having an average pore diameter of 1 μm to obtain a coating solution for forming the nonmagnetic layer and the magnetic layer. Each was prepared.

The obtained coating solution for the nonmagnetic layer was applied on a polyethylene terephthalate support having a thickness of 62 μm and a center plane average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm. Once dried and calendered, a magnetic layer is further applied thereon by a blade method so that the thickness of the magnetic layer becomes 0.15 μm, frequency 50 Hz, magnetic field strength 250 gauss, frequency 50 Hz, 120 gauss. After passing through two magnetic field strength alternating magnetic field generators, random orientation treatment was performed, and after that, the same procedure as Production Method 4-1 was performed. Further, a method in which the calendering of the non-magnetic layer is not performed may be adopted. Production method 4-4 (computer tape: W / D) Each of the above-mentioned coating materials was kneaded with a kneader, and then dispersed using a sand mill. To the obtained dispersion, 2.5 parts of polyisocyanate is added to the coating solution for the non-magnetic layer, 3 parts to the coating solution for the magnetic layer, and 40 parts of cyclohexanone is added to each, to have an average pore diameter of 1 μm. The mixture was filtered using a filter to prepare a coating solution for forming a nonmagnetic layer and a coating solution for forming a magnetic layer.

The obtained non-magnetic layer coating solution was coated with an aramid support having a thickness of 4.4 μm and an average surface roughness of 2 nm (trade name: MICRON) so that the thickness after drying would be 1.7 μm. After coating and drying once, and performing a calendar process, a magnetic layer is further coated thereon by a blade method so that the thickness of the magnetic layer becomes 0.15 μm, and a cobalt magnet having a magnetic force of 6000 G and a 6000 G magnetic layer. It was oriented by a solenoid having magnetic force. After this, the production method 4-
Performed similarly to 2. Further, a method in which the calendering of the non-magnetic layer is not performed may be adopted. Production Method 4-5 (Disk: spin coating) Each of the above-mentioned paints was kneaded with a kneader, and then dispersed using a sand mill. Polyisocyanate was added to the resulting dispersion, and 10% to the coating solution for the non-magnetic layer.
Parts and 10 parts of the coating solution for the magnetic layer, 40 parts of cyclohexanone was added to each, and the mixture was filtered using a filter having an average pore diameter of 1 μm to obtain a coating solution for forming the nonmagnetic layer and the magnetic layer. Each was prepared.

The obtained coating solution for the nonmagnetic layer was spin-coated on a polyethylene terephthalate support having a thickness of 62 μm and an average surface roughness of 3 nm so that the thickness after drying would be 1.5 μm. After coating and drying once, a magnetic layer was further applied thereon by spin coating so that the thickness of the magnetic layer became 0.15 μm, and orientation treatment was performed in the circumferential direction with a 6000 G same-opposing Co magnet. . This is the manufacturing method
The surface was smoothed by performing a batch-type rolling treatment to obtain the same pressure as in 4-1. The subsequent steps were performed in the same manner as in Production Method 4-1. Alternatively, a method of spin-coating the non-magnetic layer and spin-coating the magnetic layer on the non-magnetic layer while the non-magnetic layer is not dried may be used. By using the spin coating method, not only the amount of residual magnetization in the recording direction is increased, but also the perpendicular magnetization component of the ferromagnetic metal powder having a short needle ratio can be reduced, and the symmetry of the reproduced waveform can be improved. Support 4B-1 Polyethylene terephthalate Thickness: 62 μm, F-5 value: MD 114 MPa, TD 107 MPa Breaking strength: MD 276 MPa, TD 281 MPa Breaking elongation: MD 174 MPa, TD 139 MPa Heat shrinkage (80 ° C., 30 Min): MD 0.04%, TD 0.05% Heat shrinkage (100 ° C., 30 minutes): MD 0.2%, TD 0.3% Thermal expansion coefficient: major axis 15 × 10 ⁻⁵ / ° C. Minor axis 18 × 10 ⁻⁵ / ° C. Center plane average surface roughness 3 nm Support 4B-2 Polyethylene naphthalate Thickness: 55 μm, center plane average surface roughness 1.8 nm Thermal shrinkage (80 ° C., 30 minutes): MD 0.007%, TD 0.007% Heat shrinkage (100 ° C., 30 minutes): MD 0.02%, TD 0.02% Thermal expansion coefficient: major axis 10 × 10 ⁻⁵ / ° C., minor axis 11 × 10 ^-5 / ° C Support 4B-3 Polyethylene terephthalate Thickness: 62 μm, center plane average surface roughness 9 nm Support 4B-4 Aramid Thickness 4.4 μm Center plane average surface roughness 2 nm Orientation 4O-1 Randomize orientation is performed.

After orientation in the longitudinal direction with a 4O-2 Co magnet, random orientation is performed. After orienting in the longitudinal direction with a 4O-3 Co magnet, it is oriented in the longitudinal direction with a solenoid. Perform vertical orientation with a 4O-4Co magnet. Circumferential orientation is performed with a 4O-5 Co magnet. Back layer paint BL-1 Fine carbon black powder 100 parts [(Cabot, BP-800, average particle diameter: 17 nm)] Coarse particle carbon black powder 10 parts [(Kahncarb, thermal black, average particle diameter) : 270 nm)] Calcium carbonate (soft inorganic powder) 80 parts [(Shiraishi Kogyo Co., Ltd., white luster O, average particle diameter: 40 nm, Mohs hardness: 3)] α-alumina (hard inorganic powder) 5 parts [(average Particle size: 200 nm, Mohs hardness: 9)] Nitrocellulose resin 140 parts Polyurethane resin 15 parts Polyisocyanate 40 parts Polyester resin 5 parts Dispersant: Copper oleate 5 parts Copper phthalocyanine 5 parts Barium sulfate 5 parts Methyl ethyl ketone 2200 parts Butyl acetate 300 Parts toluene 600 parts

The components forming the back coat layer were kneaded with a continuous kneader, and then dispersed using a sand mill. The obtained dispersion was filtered using a filter having an average pore diameter of 1 μm to prepare a coating liquid for forming a backcoat layer. The magnetic properties and the magnetic properties of the samples obtained by appropriately combining each of the above methods as shown in Tables 17 to 20,
The center surface average roughness, surface recording density, and the like were measured. (1) Magnetic properties (Hc): Measured using a vibration sample type magnetometer (manufactured by Toei Kogyo Co., Ltd.) with Hm10KOe (kilo Oersted). (2) Center plane average surface roughness (Ra): 3D-MIRAU
Surface roughness (Ra): Ra value of an area of about 250 μm × 250 μm was measured by MIRAU method using TOPO3D manufactured by WYKO. Spherical correction and cylindrical correction are added at a measurement wavelength of about 650 nm. This method is a non-contact surface roughness meter that measures by light interference. (3) The areal recording density is obtained by multiplying the linear recording density by the track density. (4) The linear recording density is the number of bits of a signal recorded per inch in the recording direction. (5) Track density is the number of tracks per inch. (6) Φm is the amount of magnetization per unit area of the magnetic recording medium. Bm (Gauss) multiplied by the thickness, using a vibrating sample magnetometer (Toei Kogyo Co., Ltd.)
It is a value measured with Hm10kOe and can be directly measured. (7) The error rate of the tape is obtained by recording the signal of the above linear recording density on the tape by the 8-10 conversion PR1 equalization method, and
It measured using the S drive. (8) The error rate of the disk was measured by recording the signal of the above linear recording density on the disk by the (2,7) RLL modulation method. (9) Thickness of the magnetic layer A magnetic recording medium was cut out to a thickness of about 0.1 μm with a diamond cutter over a longitudinal direction, and the transmission electron microscope was used to magnify 10,000 to 10,000 times.
Observation was performed at a magnification of 0, preferably 20,000 to 50,000, and the photograph was taken. Photo print size is A
4-A5. Thereafter, the interface was visually judged by paying attention to the shape difference between the ferromagnetic metal powder and the non-magnetic powder of the magnetic layer and the lower non-magnetic layer, and the surface of the magnetic layer similarly became black. After that, Zeiss image processing device IBAS2
The length of the edged line was measured at. When the length of the sample photograph was 21 cm, the measurement was performed 85 to 300 times. The average of the measured values at that time was defined as the magnetic layer thickness. (10) Running durability: floppy disk drive (US
Iomega ZIP100: 2968 rpm
m), the head is fixed at a position with a radius of 38 mm, recording is performed at a recording density of 34 kfci, and the signal is reproduced.
00%. Thereafter, the vehicle was run for 1500 hours in a thermocycle environment in which the following flow was defined as one cycle. The output was monitored every 24 hours of running, and the point where the output became 70% or less of the initial value was regarded as NG. (Thermocycle flow) 25 ° C, 50% RH 1 hour → (Temperature rise 2 hours) → 60 ° C, 20% RH 7 hours →
(Temperature drop 2 hours) → 25 ° C., 50% RH 1 hour → (Temperature drop 2 hours) → 5 ° C. 50% RH 7 hours → (Temperature rise 2 hours) → <Repeat this> (11) Liner wear evaluation Head off In this state, the sample was run for 1000 hours in the same environment as the running durability. After running the completed sample, the cartridge case was opened and the magnetic layer surface of the magnetic disk was visually observed and evaluated. ：: No defect on the magnetic layer surface △: Fine scratches on a part of the magnetic layer surface ×: Fine scratches on the entire magnetic layer surface (12) Evaluation of liner adhesion Head-off state In the same environment as the running durability, the sample was run for 1000 hours. After running the completed sample, the cartridge case was opened and the magnetic layer surface of the magnetic disk was visually observed and evaluated. ○: No liner adhered to the magnetic layer surface △: Liner adhered to a part of the magnetic layer surface ×: Liner adhered to the entire magnetic layer surface (13) Starting torque evaluation Using a torque gauge Model 300ATG, a start-up torque at the time of head-on in an LS-120 drive manufactured by Imation was measured (unit: g · c).
m). (14) Measurement of C / Fe The C / Fe value was measured using a PHI-660 type Auger electron spectrometer made by Φ. The measurement conditions were as follows.

The acceleration voltage of the primary electron beam was 3 kV and the sample current was 1
30 nA, magnification 250 times, inclination angle 30 degrees. The kinetic energy (Kinetic Energy) range of 130 eV to 730 eV was integrated three times, the intensity of the KLL peak of carbon and the intensity of the LMM peak of iron were obtained in a differential form, and the C / Fe ratio was obtained. (15) The weather resistance of the magnetic layer is as follows.
After being stored in an RH environment for 7 days, it is determined by the following measurement method. Hc fluctuation after storage of magnetic layer ΔHc (%) = 100 ×
It is calculated by the formula (Hc after storage−Hc before storage) / Hc before storage. The Hc variation ΔHc after storage is preferably −5.0%
+ 10.0%, more preferably -3.0% to +8.0.
%, Particularly preferably -1.0% to + 6.0%. Further, a decrease in Φm after storage of the magnetic layer ΔΦm (%) = 100
× (Φm before storage−Φm after storage) / Φm before storage The measurement was performed using a vibrating sample magnetometer VSM-5 (Toei Kogyo Co., Ltd.) at a time constant of 0.1 second, a sweep speed of 3 minutes / 10 KOe, and a measurement magnetic field of 10 KOe. Δ
Φm is preferably within 10%, particularly preferably within 6%.

[0210]

[Table 17]

[0211]

[Table 18]

Examples 4-18 to 4-20 and Reference Example 4-
In Example 1, the disk of Example 4-13 was used, and the error rate was measured similarly while changing the linear recording density and the track density.

[0213]

[Table 19]

[0214]

[Table 20]

As described above, the error rate was measured using a DDS drive by recording the above-mentioned linear recording density signal on a tape by the 8-10 conversion PR1 equalization method. Example 4-3
For the tapes Nos. 3, 4-34 and Reference Example 4-2, the tapes of Example 4-24 were used, and the error rates were similarly measured while changing the linear recording density and the track density.

From the results in the above table, it can be seen that the magnetic recording medium of the present invention is much better than the conventional disk-shaped medium, especially when the error rate in a high-density recording area is 10 ^-5 or less. It can also be seen that the error rate of the computer tape is remarkably good at an error rate of 10 ^-5 or less.

The present invention relates to a magnetic recording medium having a substantially non-magnetic lower layer and a magnetic layer obtained by dispersing a ferromagnetic metal powder in a binder in this order on a support, wherein the magnetic recording medium is A magnetic recording medium for recording a signal having a recording density of 0.17 to ² Gbit / inch ² , wherein the magnetic layer has a coercive force of 1
800 oersted or more, and the atomic ratio A is 3.0 to 1
At 5.4%, the ferromagnetic metal powder has an average major axis length of preferably 0.12 μm or less, or the dry thickness of the magnetic layer is 0.05 to 0.30 μm, and Φm is 10.0 × 10
Good results can be obtained by using a magnetic recording medium characterized by being in the range of ^{−3 to} 1.0 × 10 ⁻³ emu / cm ² . The present invention
Preferably, the dry thickness of the magnetic layer is preferably 0.05
0.25 μm, and φm is preferably 8.0 ×
A magnetic recording medium characterized by a density of 10 ^{−3 to} 1.0 × 10 ⁻³ emu / cm ² , and further, the magnetic recording medium records a signal having an areal recording density of 0.20 to ² Gbit / inch ^2. By using a magnetic recording medium characterized by being a magnetic recording medium, it has both high capacity and excellent high density characteristics and excellent durability that could not be obtained with the conventional coating type magnetic recording medium technology. It is possible to obtain a magneto-optical recording medium having a significantly improved error rate in a high-density recording area.

Example 5 Table 21 shows the characteristics of the ferromagnetic metal powder used in Example 5.

[0219]

[Table 21]

Using the ferromagnetic metal powders shown in Table 21, magnetic disks and magnetic tapes were prepared as follows. <Preparation of paint> Magnetic paint A (ferromagnetic metal: disk) Ferromagnetic metal powder: MP to MP 100 parts Vinyl chloride copolymer MR110 (Nippon Zeon) 12 parts Polyurethane resin UR8200 (Toyobo) 3 parts -Bon Black # 50 (made by Asahi Carbon Co., Ltd.) 5 parts Phenylphosphonic acid 3 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 3 parts Stearic acid 2 parts Methyl ethyl ketone 180 parts Cyclohexanone 180 parts Magnetic layer paint B (Ferromagnetic metal: tape) Ferromagnetic metal powder: MP, MP 100 parts Vinyl chloride copolymer MR110 (manufactured by Nippon Zeon) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo) 3 parts Carbon black # 55 (Asahi) Carbon Co.) 1 part Butyl stearate 1 part Steer Phosphoric acid 5 parts Methyl ethyl ketone 100 parts Cyclohexanone 20 parts Toluene 60 parts Nonmagnetic paint a (lower layer: disk) Inorganic powder TiO ₂ crystalline rutile 80 parts Average particle diameter 0.035 μm, specific surface area by BET method 40 m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27-38 ml / 100 g, Al ₂ O _{3 on the} surface 8% by weight of the whole particle Carbon black Conductex SC-U (manufactured by Columbian Carbon Co.) 20 parts Vinyl copolymer MR110 (manufactured by Zeon Corporation) 12 parts Polyurethane resin UR8200 (manufactured by Toyobo) 5 parts Phenylphosphonic acid 4 parts Butyl stearate 10 parts Butoxyethyl stearate 5 parts Isohexadecyl stearate 2 parts Stearic acid 3 parts Methyl ethyl ketone / cyclohexanone (8/2 mixture Solvent) 250 parts Nonmagnetic paint b (for lower layer: tape) Inorganic powder TiO ₂ crystalline rutile 80 parts Average particle diameter 0.035 μm, BET specific surface area 40 m ² / g pH 7 TiO ₂ content 90% or more, DBP oil absorption 27-38 ml / 100 g, Al ₂ O _{3 on the} surface 8% by weight of the whole particles Carbon black Conductex SC-U (Colombian Carbon Co.) 20 parts Vinyl chloride copolymer MR110 (Japan Zeon) 12 parts Polyurethane resin UR8200 (Toyobo) 5 parts Phenylphosphonic acid 4 parts Butyl stearate 1 part Methyl ethyl ketone / cyclohexanone (8/2 mixed solvent) 250 parts Production method 5-1a disk After kneading with kneader,
As shown in Table 22, predetermined diamond fine particles were added (or not added), and dispersed using a sand mill. Α-Alumina HIT55 (SLH55 manufactured by Sumitomo Chemical Co., Ltd.) was dispersed in the obtained dispersion with a medium as shown in Table 22.
With or without the addition of a predetermined amount of polyisocyanate, 10 parts of the polyisocyanate is added to the lower layer coating solution, 10 parts of the magnetic layer coating solution is added, and 40 parts of cyclohexanone is further added to each, to have an average pore diameter of 1 μm. The mixture was filtered using a filter to prepare a coating solution for forming a lower layer and a coating solution for forming a magnetic layer.

The obtained lower layer coating solution was applied to a thickness of 62 μm so that the thickness after drying was 1.5 μm, and immediately thereafter, the thickness of the magnetic layer was 0.2 μm thereon. Polyethylene terephthalate having a surface average surface roughness of 3 nm
At the same time, while the two layers are still in a wet state, they are passed through an AC magnetic field generator with a frequency of 50 Hz and a magnetic field strength of 250 Gauss or a frequency of 50 Hz and 120 Gauss, and are randomly oriented. Do the processing,
After drying, with a 7-stage calendar, the temperature is 90 ° C, and the linear pressure is 300 kg / c.
m and punched out 3.5 inches to give a disk medium. Production method 5-1b (disk) The medium No. 5-6 shown in Table 22 was prepared in the same manner as in the production method 5-1a except that the polyethylene terephthalate support having a center plane average surface roughness of 7 nm was used. Similarly, a disk medium was obtained. Production method 5-2 Computer tape For the above paint, after kneading each component with a kneader,
As shown in Table 24, predetermined diamond fine particles were added (or not added), and α-alumina HIT55 (SLH5 manufactured by Sumitomo Chemical Co., Ltd.) dispersed as shown in Table 24 with a medium was used.
A predetermined amount of 5) was added or not added, and dispersed using a sand mill. To the resulting dispersion, 2.5 parts of polyisocyanate was added to the lower layer coating solution, 3 parts to the magnetic layer coating solution, and 40 parts of cyclohexanone to each.
Filtering through a filter having an average pore size of 1 μm,
Coating solutions for forming the lower layer and for forming the magnetic layer were respectively prepared.

The obtained lower layer coating solution was applied to a thickness of 4 μm so that the thickness of the lower layer after drying was 1.7 μm, and immediately thereafter, the thickness of the magnetic layer was 0.15 μm thereon. .4
Coating is performed simultaneously on an aramid support (trade name: MICRON) having a center plane average surface roughness of 2 nm and a thickness of 2 μm,
While both layers were still wet, they were oriented by a cobalt magnet having a magnetic force of 6000 G and a solenoid having a magnetic force of 6000 G. After drying, 200 m / m / min at a temperature of 85 ° C. using a 7-stage calender consisting of only metal rolls.
in. And then a back layer having a thickness of 0.5 μm (carbon black average particle diameter: 17 nm 100
Part, calcium carbonate average particle diameter: 40 nm 80 parts,
α alumina Average particle diameter: 200 nm 5 parts were dispersed in a nitrocellulose resin, a polyurethane resin, and polyisocyanate). It is slit to a width of 3.8 mm, and the nonwoven fabric and razor blade are attached to a device having a slitting device for feeding and winding the product so that the nonwoven fabric and the razor blade are pressed against the magnetic surface. Clear
Was performed to obtain a tape sample.

The performance of each of the ferromagnetic metal powder, magnetic disk and computer tape prepared above was evaluated by the following measuring methods. Measurement method (1) Magnetic properties (Hc, σs): Measured using a vibration sample type magnetometer (manufactured by Toei Kogyo Co., Ltd.) with Hm10KOe. (2) Diamond fine particles (particle size distribution): An appropriate amount of diamond powder was taken, and 500 particles randomly extracted from an electron micrograph thereof were measured by the above method, and the average particle diameter φ and the average particle diameter were determined. Of the total number of diamonds (ΔN ₂₀₀ ) (%), and the ratio of the number of particles having a particle size of 50% or less of the average particle diameter φ to the total number of diamonds (ΔN ₅₀ ) (%). %). (3) Center plane average surface roughness Ra: TOPO manufactured by WYKO
Approximately 250 μm × 2 by 3D-MIRAU method using 3D
The Ra value of an area of 50 μm was measured. Measurement wavelength about 650
In nm, spherical correction and cylindrical correction are added. This method is a non-contact surface roughness meter that measures by light interference. (4) Disk electromagnetic conversion characteristics Output: The reproduction output was measured using a disk tester manufactured by Kokusai Denshi Kogyo Co., Ltd. (former Tokyo Engineering) and a SK606B.
After recording with a recording wavelength of 90 KFCI at a radius of 24.6 mm using a metal in-gap head having a gap length of 0.3 μm using a mold evaluation device, the reproduction output of the head amplifier was measured with an oscilloscope type 7633 manufactured by Tektronix.

SN ratio: The disk for which the reproduction output was measured
After C erasure, the reproduction output (noise) was measured with a TR4171 type spectroanalyzer manufactured by Advantest.
The S / N ratio was -20 log (noise / reproduction output), and the S / N ratio of the medium No. 5-1 was 0 dB and indicated as a relative value. (5) Tape electromagnetic conversion characteristics CN ratio (tape): recording head (MIG, gap 0.15μ)
m, 1.8 T) was attached to a drum tester to record and reproduce digital signals. Head-media relative speed 3m /
sec, the recording wavelength was 0.35 μm, and the modulation noise was measured. (6) Durability: Magnetic disk durability: Floppy disk drive (ZIP100 manufactured by Iomega, USA: 2968 revolutions)
rpm), the head was fixed at a position of a radius of 38 mm.
Thereafter, the vehicle was run in a thermocycle environment in which the following flow was defined as one cycle. The time when the surface of the sample was visually scratched was regarded as NG. 100% durability time of medium No5-1
And (Thermocycle flow) 25 ° C, 50% RH for 1 hour → (heating 2 hours) → 60 ° C, 20% RH for 7 hours →
(Temperature drop 2 hours) → 25 ° C., 50% RH 1 hour → (Temperature drop 2 hours) → 5 ° C., 10% RH 7 hours → (Temperature rise 2
Time) → <Repeat this> Computer tape durability: After recording a predetermined signal using a DDS drive, the tape was run at 50 ° C. and 10% RH while monitoring a reproduced signal. 7 of the initial playback output
When it became 0%, it was regarded as NG. The durability of the medium No. 5-13 was shown as 100%. (7) The weather resistance of the magnetic layer is measured at 60 ° C. and 90% R
After storage in the environment of H for 7 days, it is determined by the following measurement method. Hc fluctuation after storage of magnetic layer ΔHc (%) = 100 ×
It is calculated by the formula (Hc after storage−Hc before storage) / Hc before storage. The Hc variation ΔHc after storage is preferably −5.0%
+ 10.0%, more preferably -3.0% to +8.0.
%, Particularly preferably -1.0% to + 6.0%. Further, a decrease in Φm after storage of the magnetic layer ΔΦm (%) = 100
× (Φm before storage−Φm after storage) / Φm before storage The measurement was performed using a vibrating sample magnetometer VSM-5 (Toei Kogyo Co., Ltd.) at a time constant of 0.1 second, a sweep speed of 3 minutes / 10 KOe, and a measurement magnetic field of 10 KOe. Δ
Φm is preferably within 10%, particularly preferably within 6%. Table 23 shows the evaluation results of the magnetic disk, and Table 25 shows the evaluation results of the magnetic tape.

[0225]

[Table 22]

[0226]

[Table 23]

[0227]

[Table 24]

[0228]

[Table 25]

As is apparent from the results of Example 5, the average particle diameter in the magnetic layer is preferably 0.01 to 1.0.
By adding 0.01 μm to 10% by weight of the fine diamond particles to the ferromagnetic metal powder, it is possible to improve the noise in its electromagnetic conversion characteristics while ensuring the durability.

[0230]

According to the present invention, there is provided a magnetic recording medium comprising a support and a magnetic layer formed by dispersing a ferromagnetic metal powder in a binder, wherein the magnetic recording medium has an areal recording density of 0.17 to 2G.
A magnetic recording medium for recording a bit / inch ² signal, wherein the coercive force of the magnetic layer is 1800 Oe or more, the ferromagnetic metal powder is composed of at least Fe and Co, and
A magnetic layer comprising a ferromagnetic metal powder dispersed in a binder is provided on a magnetic recording medium or a support, wherein the atomic ratio of 1 / (Fe + Co) is 3.0 to 15.4%. The magnetic recording medium is a magnetic recording medium for recording a signal having an areal recording density of 0.17 to ² Gbit / inch ² , the coercive force of the magnetic layer is 1800 Oe or more, and the ferromagnetic metal The powder can be achieved by a magnetic recording medium comprising at least Fe and Co, and having an atomic ratio of (sum of rare earth elements) / (Fe + Co) of 0.5 to 9.0%. Preferably, the magnetic recording medium has a dry thickness of the magnetic layer of 0.05 to 0.30 μm, and the magnetic recording medium records a signal having an areal recording density of 0.20 to ² Gbit / inch ^2. The magnetic recording medium is characterized by being a magnetic recording medium that has a large capacity and excellent high-density characteristics and excellent durability that cannot be obtained by the conventional coating type magnetic recording medium technology. It is possible to obtain a magneto-optical recording medium having a significantly improved error rate in the high-density recording area.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Nobuo Yamazaki 2-12-1, Ogimachi, Odawara-shi, Kanagawa Inside Fuji Photo Film Co., Ltd.

Claims (36)

[Claims] 1. A magnetic recording medium having a magnetic layer formed by dispersing a ferromagnetic metal powder in a binder on a support, wherein the magnetic recording medium has an areal recording density of 0.17 to 2 Gbit / inch.
² wherein the coercive force of the magnetic layer is 1800 Oe or more, the ferromagnetic metal powder is composed of at least Fe and Co, and Al / (F
A magnetic recording medium, wherein the atomic ratio A of (e + Co) is 3.0 to 15.4%. 2. A magnetic recording medium provided with a magnetic layer comprising a support and a ferromagnetic metal powder dispersed in a binder, wherein the magnetic recording medium has an areal recording density of 0.17 to 2 Gbit / inch.
^2. A magnetic recording medium for recording signal No. ² , wherein the coercive force of the magnetic layer is 1800 Oe or more, the ferromagnetic metal powder is composed of at least Fe and Co, and the total ratio of rare earth elements / (Fe + Co) atomic ratio B is 0.5 to 9.0%
A magnetic recording medium characterized by the following. 3. The magnetic recording medium according to claim 1, wherein a lower layer, which is a substantially non-magnetic layer, is provided between the support and the magnetic layer. 4. The magnetic recording medium according to claim 1, wherein said magnetic recording medium is a disk-shaped magnetic recording medium.
Item 7. The magnetic recording medium according to Item 1. 5. The dry thickness of the magnetic layer is 0.05 to 0.5.
30 μm, and Φm is 10.0 × 10 ^{−3 to} 1.0 × 1
The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a density of 0 ⁻³ emu / cm ² . 6. The magnetic layer having a dry thickness of 0.05 to 0.5.
25 μm and φm is 8.0 × 10 ^{−3 to} 1.0 ×
6. The magnetic recording medium according to claim 5, wherein the magnetic recording medium has a density of 10 ^-3 emu / cm ² . 7. The ferromagnetic metal powder is composed of at least Fe and Co, and has an atomic ratio B / A of total of rare earth elements / Al of 0.05 to 1.20. The magnetic recording medium according to any one of claims 1 to 6, wherein 8. The method according to claim 1, wherein the atomic ratio B is 1.0 to 6.0%, and the atomic ratio B / A is 0.1 to 0.6. The magnetic recording medium according to claim 1. 9. The atomic ratio B is 1 to 8%, and the atomic ratio C of Mg / (Fe + Co) is 0.05 to 3.0%.
The magnetic recording medium according to claim 1, wherein: 10. The ferromagnetic metal powder has an acicular ratio of 3.0.
The magnetic recording medium according to any one of claims 1 to 9, wherein 11. The ferromagnetic metal powder has an average major axis length of 0.04 to 0.12 μm and a crystallite size of 80 °.
The magnetic recording medium according to any one of claims 1 to 10, wherein the angle is 180 to 180 °. 12. The magnetic recording medium according to claim 1, wherein the rare earth element is Y or Nd. 13. The magnetic layer according to claim 1, wherein the magnetic layer contains an abrasive having a Mohs hardness of 6 or more, and the abrasive is 15.0% by weight or less based on the ferromagnetic metal powder. 1 to
13. The magnetic recording medium according to any one of 12 above. 14. The magnetic layer having a Mohs hardness of 9 or more.
14. The magnetic recording medium according to claim 13, comprising a kind of abrasive. 15. The magnetic recording medium according to claim 1, wherein the magnetic layer contains diamond having at least an average particle diameter of 2.0 μm or less. 16. The magnetic recording medium according to claim 1, wherein the magnetic layer contains α-alumina and diamond. 17. The magnetic layer according to claim 1, wherein the magnetic layer contains at least a saturated fatty acid, and further contains at least a saturated fatty acid ester or an unsaturated fatty acid ester.
The magnetic recording medium according to any one of the preceding claims. 18. The magnetic recording medium according to claim 17, wherein said saturated fatty acid ester or unsaturated fatty acid ester includes monoester and diester fatty acid esters. 19. The magnetic layer having a surface roughness of 3D-MIR
The magnetic recording medium according to any one of claims 1 to 18, wherein a center plane average surface roughness according to an AU method is 4.0 nm or less. 20. The dry thickness of the magnetic layer is 0.05 to
20. The magnetic recording medium according to claim 1, wherein the magnetic layer contains an abrasive having a particle size of 0.20 [mu] m and an average particle size of 0.02 to 0.3 [mu] m. 21. The magnetic recording medium according to claim 1, wherein the coercive force of the magnetic layer is 2000 Oe or more. 22. The magnetic recording medium has a capacity of 1.0 MB / s.
22. The magnetic recording medium according to claim 1, which is a magnetic recording medium for a system having a high transfer rate of ec or higher. 23. The magnetic recording medium has a capacity of 2.0 MB / s.
23. The magnetic recording medium according to claim 22, which is a magnetic recording medium for a system having a high transfer rate of ec or higher. 24. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a magnetic recording medium for a large-capacity floppy-disk system having a disk rotation speed of 1800 rpm or more.
24. The magnetic recording medium according to any one of claims 23 to 23. 25. The magnetic recording medium according to claim 2, wherein the magnetic recording medium is a magnetic recording medium for a large-capacity floppy-disk system having a disk rotation speed of 3000 rpm or more.
5. The magnetic recording medium according to 4. 26. The magnetic recording medium according to claim 1, wherein a center plane average surface roughness of the support according to the 3D-MIRAU method is 5.0 nm or less. 27. In each of in-plane directions of the support, 10
Heat shrinkage at 0 ° C for 30 minutes is 0.5% or less and 80 ° C
The magnetic recording medium according to any one of claims 1 to 26, wherein a heat shrinkage per minute is 0.2% or less. 28. The lower layer has an average particle diameter of 5 nm to 80.
28. The magnetic recording medium according to claim 3, wherein the magnetic recording medium contains carbon black having a particle diameter of 5 nm and the magnetic layer contains carbon black having an average particle diameter of 5 nm to 300 nm. 29. The lower layer has an average major axis length of 0.20 μm.
The magnetic recording medium according to any one of claims 3 to 28, wherein the magnetic recording medium comprises a needle-like inorganic powder having a needle ratio of 4.0 to 9.0. 30. The lower layer contains acicular inorganic powder, the magnetic layer contains acicular ferromagnetic metal powder, and the average major axis length of the acicular inorganic powder is the average major axis of the acicular ferromagnetic metal powder. The length is 1.1 times to 3.0 times the length.
30. The magnetic recording medium according to any one of 29. 31. A magnetic recording medium for a large-capacity floppy disk system, which realizes backward compatibility capable of recording / reproducing with a current 3.5-inch floppy disk. Claims 1 to 30
The magnetic recording medium according to any one of the preceding claims. 32. A large-capacity magnetic recording medium employing a dual disc gap head having both a narrow gap for high-density recording and a wide gap for a current 3.5-inch floppy disk. The magnetic recording medium according to any one of claims 1 to 31, wherein the magnetic recording medium is a magnetic recording medium for a floppy disk system. 33. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a magnetic recording medium for a large-capacity floppy disk system in which a head floats by rotation of a disk.
33. The magnetic recording medium according to any one of items 32 to 32. 34. A large-capacity floppy disk having a magnetic recording medium in which a head floats by rotation of a disk, and a linear type voice coil motor is used for driving the head.
The magnetic recording medium according to any one of claims 1 to 33, wherein the magnetic recording medium is a magnetic recording medium for a disk system. 35. A magnetic recording medium provided with a magnetic layer formed by dispersing a ferromagnetic metal powder in a binder on a support,
The magnetic recording medium has an areal recording density of 0.17 to 2 Gbit / in.
a magnetic recording medium for recording ch ² signal, the ferromagnetic metal powder is composed of at least Fe and Co, and Hc variation ΔHc after storage of the magnetic layer is -5.0% +
A magnetic recording medium characterized by 10.0%. 36. A magnetic recording medium provided with a magnetic layer formed by dispersing a ferromagnetic metal powder in a binder on a support,
The magnetic recording medium has an areal recording density of 0.17 to 2 Gbit / in.
a magnetic recording medium for recording ch ² signal, the ferromagnetic metal powder is composed of at least Fe and Co, and Φm reduction ΔΦm after storage of the magnetic layer, characterized in that it is within 10% Magnetic recording medium.