JPH0242626A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To allow the use as a recording medium having a large capacity and high density by specifying the residual magnetic flux density and coercive force of a magnetic layer, the thickness of the magnetic layer and the center line average height and max. height of the surface of the magnetic layer in such a manner as to exhibit respectively specific values. CONSTITUTION:For example, acicular cobalt-contg. magnetic iron oxide powder having the major axis ranging 0.1-1.0mum is used as the magnetic powder to constitute the magnetic layer. The residual magnetic flux density of the magnetic layer is so specified as to be >=800 gauss, the coercive force thereof to be 800-1,100Oe the thickness of the magnetic layer to be 0.4-1.0mum, the center line average height of the surface of the magnetic layer to be <=0.03mum, and the max. height thereof to be <=0.15mum. Since the recording at the shorter wavelength than with the conventional magnetic recording medium is executed in this way, the recording density is increased and the recording capacity of the recording medium is decreased.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium comprising a magnetic layer containing magnetic powder and a binder provided on a non-magnetic support, particularly for high-density recording. The present invention relates to a magnetic recording medium capable of

[Conventional technology and its problems]

In recent years, as the capabilities of small computers have improved, programs and demi-files that are used on a daily basis require extremely large storage capacities, and magnetic recording media such as magnetic disks are also required to have large capacities. Further, there is a demand for smaller recording media due to ease of handling and space for installation or storage. Therefore, in order to meet these demands, it becomes necessary to record a large amount of information on a recording medium of the same size. To this end, the wavelength of signals recorded on recording media is becoming shorter and the so-called recording density is increasing. However, for example, in flexible disks, media (coercive force 100-7θ00e1 coating thickness/2-2.0μm) that can record / megabyte of information on a disk with a diameter tOW are widely used. The shortest recording wavelength is 2.2 .mu.m (J', 7 kbpi), and if recording is performed at a shorter wavelength to increase the recording appearance, the output will decrease and the S/N will deteriorate.

In addition, in the case of digital recording, if there is a large difference between the output for long wavelengths and the output for short wavelengths, the output waveform will be distorted and the peak will be distorted when the long wavelength record and short wavelength record are adjacent. A problem arises in that the position deviates significantly from the desired position. For this reason, it was not suitable for use as a recording medium with even larger capacity and higher density.

[Means to solve the problem]

In view of the above circumstances, the present inventors conducted various studies and as a result arrived at the present invention.

That is, the gist of the present invention is a magnetic recording medium comprising a magnetic layer containing magnetic powder and a binder on a non-magnetic support, wherein the magnetic layer has a residual magnetic flux density of 800 Gauss or more and a coercive force of 100 Gauss or more. ~/1000e, the thickness of the magnetic layer is 0. <1
~/, 0 μm1, and the center line average roughness (Ra) of the surface of the magnetic layer is 0.03 fim or less, the maximum height (Rmax
) is O1/! The present invention relates to a magnetic recording medium characterized in that the particle size is less than μm.

The present invention will be described in detail below. In the present invention, the magnetic material used as the magnetic powder constituting the magnetic layer is acicular cobalt having a major axis diameter in the range of θ, / to i, o μm. Containing magnetic iron oxide powder is preferred. Furthermore, it is more preferable that the long axis diameter is in the range of 0.2 to θ, l=l1m.

If the long axis diameter of the magnetic material is as small as 0.78 m, it is difficult to uniformly disperse the magnetic material in the binder, and the strength of the magnetic layer becomes insufficient, resulting in poor durability. i,
If it is larger than 0 μm, the distribution of magnetization in the magnetic layer becomes non-uniform and noise increases, resulting in a deterioration of S/N.

α-Fe, Fe-Co alloy, Fe-Co-Ni are used as magnetic materials that can provide large coercive force and residual magnetization.
Metal magnetic powders such as alloys are known, but compared to cobalt-containing magnetic iron oxide powders, they have poor environmental resistance due to problems with oxidative deterioration, and the strength of the magnetic layer is insufficient due to the low hardness of the magnetic material itself. Therefore, there is a problem with durability. Therefore, the magnetic material is preferably cobalt-containing magnetic iron oxide powder.

Furthermore, the coercive force is 800~/10θ Oe.

Preferably, the magnetization is in the range of 00 to 10,000 e, the maximum magnetization is 706 mu/9 or more, and the specific surface area by the BET method is 3 o -4 to rr? It is particularly preferable to use cobalt-containing magnetic iron oxide in the range of /f.0 Also, what is the residual magnetic flux density of the magnetic layer? θθ Gauss or more, the thickness of the magnetic layer is o, ty-~/, θ μm1, the center line average roughness (Ra) of the surface of the magnetic layer is 0.03 μm or less, the maximum height (
Rmax) is 0. /μm or less is preferable.

If the residual magnetic flux density of the magnetic layer is less than 800 Gauss, the output voltage will be small, making it impossible to read out the recorded information accurately. Furthermore, if the coercive force of the magnetic layer is smaller than 8000e, the output when recording short wavelength signals is small, and /10o
If the Oe is larger than Oe, the erasing characteristics will be poor, and if overwriting is performed, the already recorded signal will remain, and when the signal is read out again, there will be a problem that the subsequently recorded signal cannot be read correctly.

When the thickness of the magnetic layer is as thin as 0.4 tμm, the strength of the magnetic layer is insufficient and the durability deteriorates.

In addition, if the thickness is thicker than 7.0 μm, the difference between the two becomes large because the output voltage does not increase in the case of short wavelength recording while the output voltage increases in the case of long wavelength recording, and the above-mentioned peak shift increases. Problems Occur When the centerline average roughness (Ra) of the surface of the magnetic layer is greater than 0.03 μm, fine fluctuations occur in the magnetization of the portion of the magnetic layer near the head, resulting in louder noise. Furthermore, if the maximum height of the surface of the magnetic layer is greater than 0.7 μm, the distance from the head becomes substantial, which deteriorates the recording/reproducing efficiency. The higher the density of recording, the greater the effect; the output voltage becomes smaller when a short wavelength signal is recorded, and the erasing characteristics become worse.

Binder components used in the present invention include polyurethane resins, vinyl chloride-vinyl acetate copolymers, epoxy resins, cellulose resins, polyester resins, acrylic resins, rubber resins, and isocyanates. Any compound that is normally used as a binder component of magnetic powder can be used.

As non-magnetic supports, polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, plastics such as polycarbonate, polyphenylene sulfide, and polyimide are usually used, and depending on the purpose, non-magnetic metals, ceramics, paper, etc. It's okay.

Further, additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and the like may be added to the magnetic layer in the present invention, if necessary.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to examples.
The present invention is not limited to the embodiments unless it goes beyond the gist thereof.

Example/Magnetic powder -00 parts by weight Acicular Co -r
Fezos Coercive force 00e Major axis diameter 0.6 μm Binder? 0 parts by weight Phosphate ester dispersant 1 part by weight α-alumina 3 parts by weight Stearate ester
70 parts by weight Conductive carbon black 20 parts by weight Organic solvent (mixture of cyclohexanone, 7! parts by weight methyl ethyl ketone, etc.) The above compositions were mixed and dispersed, and 7! The thickness of the magnetic layer is 0.6 μm on a μm thick polyethylene terephthalate film.
After drying, it was calendered and punched out into a donut shape to obtain a magnetic disk.

The coercive force and residual magnetic flux density of this sample were measured using a vibrating sample type magnetometer, and the thickness of the magnetic layer was measured using a stylus type surface roughness meter.

The surface roughness was measured using a stylus type surface roughness tester using a probe with a diamond tip and a diameter of /μmR.
tf, cutoff o, ortrrm, scanning speed 0
．． 03 rtvn/sec, reference length 0. JIS in Zsaku
It was measured according to B Otθ/.

Examples C and 3 The thickness of the magnetic layer is 0. A magnetic disk was obtained in the same manner as in Example except that the wolfberry μm and o and the txt were 9 μm.

Comparative Example / The magnetic powder is acicular Co-γFeze3 with a coercive force of &700e and a major axis diameter of 0.7 μm, and the thickness of the magnetic layer is 7.6 μm.
A magnetic disk was obtained in the same manner as in Example except that.

Comparative Example 2 A magnetic disk was obtained in the same manner as in Example except that the magnetic powder was acicular Co-γ Feze 3 with a coercive cuff 300e and a major axis diameter o 3 μm.

Comparative Example 3 The thickness of the magnetic layer was set to 0. ! A magnetic disk was obtained in the same manner as in Comparative Example G except that the diameter was set to μm.

Comparative Example A magnetic disk was obtained in the same manner as in Example except that the calendering treatment was omitted.

Comparative example! Example/Except that the thickness of the magnetic layer was 7.2θ μm.
A magnetic disk was obtained in the same manner.

The magnetic disks obtained in Examples/~3 and Comparative Examples/~J were rotated at 31!70 rpm using a ferrite head with a head gap of 0.9 μm, and the radius was 24t, 7m.
Table 1 shows Dso and output voltage when recording/reproducing is performed at the position yn.

Furthermore, D! 0 represents the recording density at which the reproduction output is 50 lines when a long wavelength signal is recorded, and is a guideline for the maximum recording density that can be realized by the device. Therefore, Dt
If θ is 23 kbpi or more, it can be said that it is suitable for performing higher density recording than in the past. Also, the output voltage must be sufficiently large compared to the amplifier noise, and the
The above is desirable.

Comparative Examples/, C and 3, the coercive force of the magnetic layer is 0θ
If it is lower than Oe, the output voltage when recording a short wavelength signal is small. In addition, even if the coercive force and Ra are the same as in the example as in Comparative Example G, if Rmax is large, the output voltage will be small, and the output voltage will drop particularly sharply when short wavelength signals are recorded. DjO gets worse. moreover,
Even if the coercive force, Ra, and Rmax are the same as in the example as in the comparative example, when the thickness of the magnetic layer becomes thicker than 0 μm, the output voltage is sufficient, but the DjO deteriorates.

〔Effect of the invention〕

According to the magnetic recording medium of the present invention, since recording can be performed at a much shorter wavelength than conventional magnetic recording media, the recording density can be increased and the recording capacity of the recording medium can be increased.

Claims (1)

[Claims] (1) In a magnetic recording medium comprising a magnetic layer containing magnetic powder and a binder on a non-magnetic support, the magnetic layer has a residual magnetic flux density of 800 Gauss or more and a coercive force of 800 to 1/1.
100 Oe, the thickness of the magnetic layer is 0.4 to 1.0 μm, and the center line average roughness (Ra) of the surface of the magnetic layer is 0.0.
A magnetic recording medium having a maximum height (Rmax) of 3 μm or less and a maximum height (Rmax) of 0.15 μm or less.