JPH11316948A - Manufacturing method of magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a magnetic recording medium which maintains sufficient strength even when the thickness of a non-magnetic support is reduced, prevents curling, and has excellent electromagnetic conversion characteristics. I do. SOLUTION: A non-magnetic support producing step for producing a non-magnetic support composed of polyethylene naphthalate, and a ferromagnetic metal thin film which becomes a magnetic layer on the non-magnetic support produced in the non-magnetic support producing step Forming a ferromagnetic metal thin film by vacuum evaporation, etching the surface of the ferromagnetic metal thin film formed in the ferromagnetic metal thin film forming step, and forming the ferromagnetic metal on the nonmagnetic support. A back coat layer forming step of forming a back coat layer containing at least a binder and an acicular nonmagnetic pigment on a surface opposite to a surface on which the thin film is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a magnetic recording medium in which a ferromagnetic metal thin film is formed as a magnetic layer on a non-magnetic support.

[0002]

2. Description of the Related Art A so-called ferromagnetic metal thin film type magnetic recording medium having a continuous layer of a magnetic metal or a magnetic alloy as a magnetic layer is excellent in coercive force, squareness ratio, etc. and excellent in electromagnetic conversion characteristics in a short wavelength region. However, since the magnetic layer can be made thinner, the thickness loss during recording demagnetization and reproduction is extremely small, and it is not necessary to mix a binder, which is a nonmagnetic material, in the magnetic layer. There are a number of advantages such as that the packing density of the magnetic material can be increased.

[0003] Such a metal thin film type magnetic recording medium is
Generally, it is manufactured by a vacuum evaporation method, and among the vacuum evaporation methods, a so-called continuous winding oblique evaporation method is employed. In the continuous winding oblique deposition method, for example, a non-magnetic support is moved and moved in a predetermined direction along the outer peripheral surface of a cooling can, and the strong magnetic material is evaporated on the non-magnetic support by a predetermined heating means. A magnetic layer made of a ferromagnetic metal thin film is formed by applying a magnetic metal material obliquely. At this time, in order to regulate the incident angle of the ferromagnetic metal material with respect to the non-magnetic support, a mask is provided near the cooling can along the outer peripheral surface of the cooling can. Oxygen gas is introduced from the low incident angle side with respect to the surface of the non-magnetic support from the vicinity of the position. By introducing oxygen gas when depositing the magnetic material, durability is given to the obtained ferromagnetic metal thin film and magnetic properties are improved.

As described above, in the method in which oxygen gas is introduced into the surface of the nonmagnetic support during vapor deposition, the amount of the oxygen gas introduced is appropriately set in order to obtain appropriate magnetic characteristics. For this reason, a surface oxide layer having a certain thickness is inevitably formed on the surface of the obtained magnetic layer composed of the ferromagnetic metal thin film according to the introduction amount of the oxygen gas. However, although such a surface oxide layer is useful for improving durability, the surface oxide layer itself is a non-magnetic layer, and therefore, the shorter the wavelength is recorded, the more the space oxide layer is used. The loss increases, making it difficult to ensure good electromagnetic conversion characteristics.

By the way, in order to ensure the durability of the magnetic layer,
It has been proposed and put to practical use to form a protective film made of carbon on a magnetic layer of a ferromagnetic metal thin film type magnetic recording medium. In a magnetic recording medium used in the DV format, the DV-CAM format, or the AIT format, sufficient durability has been obtained despite the use of a thin carbon protective film due to the practical use of a carbon protective film. And, in the magnetic recording medium of the ferromagnetic metal thin film type, the electromagnetic conversion characteristics, in particular,
Improvement of the electromagnetic conversion characteristics in the high frequency short wavelength region is the most important issue in the future.

In order to improve the electromagnetic conversion characteristics, attempts have been made to remove the surface oxide layer of the ferromagnetic metal thin film. For example, JP-A-5-159287 proposes to improve the electromagnetic conversion characteristics by irradiating the magnetic layer with ions, and JP-A-5-166165 discloses a reverse sputtering method and an ion etching method. It has been proposed to remove the surface oxide layer by an ECR plasma etching method or the like to improve the electromagnetic conversion characteristics.

[0007] A polyethylene terephthalate film is mainly used for the non-magnetic support of the metal thin film type magnetic recording medium as described above. Specifically, for example, a polyethylene terephthalate film having a thickness of about 7 μm to 10 μm is used for a nonmagnetic support of an 8 mm tape of a home video tape recorder. Further, a polyethylene terephthalate film having a thickness of about 5 μm to 7 μm is used for a non-magnetic support of a tape streamer for data backup of a computer.

In a tape-shaped magnetic recording medium (hereinafter, referred to as a magnetic tape) used for a video tape recorder, the size and length of a video cassette accommodating a magnetic tape are further reduced and the length is further reduced. Time recording is desired. Also, with the increase in the amount of information in recent years,
Larger capacities are also desired for magnetic tapes for tape streamers. Therefore, in order to meet these demands, studies have been made to reduce the thickness of the magnetic tape.

[0009]

In order to reduce the thickness of the magnetic tape, it is easy to reduce the thickness of the non-magnetic support. However, when a polyethylene terephthalate film is used as the non-magnetic support, if the thickness is reduced, the strength in the length direction or the width direction is reduced. When the strength of the magnetic tape in the longitudinal direction decreases, the magnetic tape tends to be deformed when running on a video tape recorder or a drive. In addition, magnetic tape
When the strength in the width direction is reduced, wrinkles and breaks are liable to occur, and further, there is a problem that a contact failure with the magnetic head is likely to occur.

Therefore, the use of a polyethylene naphthalate film as a nonmagnetic support has been studied and put to practical use. The polyethylene naphthalate film has a higher Young's modulus and is more excellent in heat resistance than the polyethylene terephthalate film. Therefore, a magnetic recording medium using this polyethylene naphthalate film as a support can be reduced in thickness, and can be used for a long time recording of a video cassette film and a large capacity of a tape streamer. It is attracting attention. In particular, in tape streamers, the capacity has doubled in two to three years, and in order to cope with the increase in capacity, it is desired to further reduce the thickness of the magnetic recording medium.

In order to obtain a thin, high-density, large-capacity magnetic recording medium, the present inventors have formed a ferromagnetic metal thin film on a non-magnetic support having a thickness of about 6.0 μm or less by vacuum evaporation. An attempt was made to form a magnetic layer and to etch a surface oxide layer formed on the magnetic layer.

However, since the thickness of the non-magnetic support is small, the mechanical strength is not sufficient, and the curl of the obtained magnetic recording medium is increased. If the curl of the magnetic recording medium is large, it is difficult to hit the magnetic head, causing a significant decrease in the electromagnetic conversion characteristics.Also, the edges that are likely to contact the magnetic head are liable to wear, resulting in dropouts and error rates. As a result, the magnetic recording medium for practical use could not be obtained.

The rigidity of the non-magnetic support is expressed by E × t ³ when the Young's modulus of the non-magnetic support is E and the thickness is t. To halve the thickness of the support, the Young's modulus of the material of the support must be increased by a factor of eight. Therefore, simply reducing the thickness of the nonmagnetic support is insufficient in mechanical strength.

The present invention has been proposed in view of the above-mentioned conventional circumstances. Even when the thickness of the nonmagnetic support is reduced, sufficient strength is maintained and curling is prevented. An object of the present invention is to provide a method for manufacturing a magnetic recording medium having excellent electromagnetic conversion characteristics.

[0015]

According to the present invention, there is provided a method for manufacturing a magnetic recording medium, comprising the steps of preparing a non-magnetic support for preparing a non-magnetic support made of polyethylene naphthalate, and the above-described non-magnetic support preparing step. A ferromagnetic metal thin film forming step of forming a ferromagnetic metal thin film serving as a magnetic layer on the non-magnetic support by a vacuum evaporation method, and a surface of the ferromagnetic metal thin film formed in the ferromagnetic metal thin film forming step. An etching step of etching, and forming a back coat layer containing at least a binder and a needle-shaped non-magnetic pigment on a surface of the non-magnetic support opposite to a surface on which the ferromagnetic metal thin film is formed. And a back coat layer forming step.

In the method for manufacturing a magnetic recording medium according to the present invention as described above, the non-magnetic support made of polyethylene naphthalate containing a reinforcing agent is formed in the step of preparing the non-magnetic support. A nonmagnetic support having excellent properties can be obtained. In the ferromagnetic metal thin film forming step, a ferromagnetic metal thin film serving as a magnetic layer is formed on the non-magnetic support by a vacuum evaporation method, so that a magnetic layer having excellent electromagnetic conversion characteristics is formed. In the etching step, since the surface of the ferromagnetic metal thin film is etched, the surface oxide layer of the ferromagnetic metal thin film is removed, and the electromagnetic conversion characteristics of the magnetic layer are further improved. In the back coat layer forming step, a back coat layer containing at least a binder and a needle-like non-magnetic pigment is provided on a surface of the non-magnetic support opposite to a surface on which the ferromagnetic metal thin film is formed. Forming the back coat layer, the rigidity of the magnetic recording medium is increased,
The deformation during running is suppressed as much as possible, and the durability is improved.

The method for producing a magnetic recording medium of the present invention comprises the steps of producing a non-magnetic support made of polyethylene naphthalate, and the above-mentioned non-magnetic support produced by the above-mentioned non-magnetic support production step. A ferromagnetic metal thin film forming step of forming a ferromagnetic metal thin film to be a magnetic layer thereon by a vacuum deposition method, and an etching step of etching the surface of the ferromagnetic metal thin film formed in the ferromagnetic metal thin film forming step, Forming a metal thin film on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film is formed.

In the method for manufacturing a magnetic recording medium according to the present invention as described above, the non-magnetic support made of polyethylene naphthalate containing a reinforcing agent is formed in the non-magnetic support preparation step, so that the Young's modulus is large and heat resistance is high. A nonmagnetic support having excellent properties can be obtained. In the ferromagnetic metal thin film forming step, a ferromagnetic metal thin film serving as a magnetic layer is formed on the non-magnetic support by a vacuum evaporation method, so that a magnetic layer having excellent electromagnetic conversion characteristics is formed. In the etching step, since the surface of the ferromagnetic metal thin film is etched, the surface oxide layer of the ferromagnetic metal thin film is removed, and the electromagnetic conversion characteristics of the magnetic layer are further improved. In the metal thin film forming step, the metal thin film is formed on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film is formed. Deformation is minimized and durability is improved.

The method for producing a magnetic recording medium of the present invention comprises the steps of producing a non-magnetic support made of polyethylene naphthalate, and the above-described non-magnetic support produced by the above-mentioned non-magnetic support production step. A ferromagnetic metal thin film forming step of forming a ferromagnetic metal thin film to be a magnetic layer thereon by a vacuum deposition method, and an etching step of etching the surface of the ferromagnetic metal thin film formed in the ferromagnetic metal thin film forming step, A plasma polymer layer on the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film is formed, by polymerizing a compound polymerizable by plasma by a plasma polymerization method to form a plasma polymer layer And a forming step.

In the method for manufacturing a magnetic recording medium according to the present invention as described above, the non-magnetic support made of polyethylene naphthalate containing a reinforcing agent is formed in the step of preparing the non-magnetic support. A nonmagnetic support having excellent properties can be obtained. In the ferromagnetic metal thin film forming step, a ferromagnetic metal thin film serving as a magnetic layer is formed on the non-magnetic support by a vacuum evaporation method, so that a magnetic layer having excellent electromagnetic conversion characteristics is formed. In the etching step, since the surface of the ferromagnetic metal thin film is etched, the surface oxide layer of the ferromagnetic metal thin film is removed, and the electromagnetic conversion characteristics of the magnetic layer are further improved. In the plasma polymer layer forming step, a compound polymerizable by plasma is polymerized by a plasma polymerization method on a surface of the nonmagnetic support opposite to a surface on which the ferromagnetic metal thin film is formed. Since the polymer layer is formed, the rigidity of the magnetic recording medium is increased, deformation during running is suppressed as much as possible, and durability is improved.

The method for producing a magnetic recording medium of the present invention comprises the steps of producing a non-magnetic support made of polyethylene naphthalate, and the above-described non-magnetic support produced by the above-mentioned non-magnetic support production step. A ferromagnetic metal thin film forming step of forming a ferromagnetic metal thin film to be a magnetic layer thereon by a vacuum deposition method, and an etching step of etching the surface of the ferromagnetic metal thin film formed in the ferromagnetic metal thin film forming step, An electron beam polymer layer forming step of forming an electron beam polymer layer by polymerizing a compound with an electron beam on a surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed. It is characterized by.

In the method for manufacturing a magnetic recording medium according to the present invention as described above, the non-magnetic support made of polyethylene naphthalate containing a reinforcing agent is formed in the step of preparing the non-magnetic support. A nonmagnetic support having excellent properties can be obtained. In the ferromagnetic metal thin film forming step, a ferromagnetic metal thin film serving as a magnetic layer is formed on the non-magnetic support by a vacuum evaporation method, so that a magnetic layer having excellent electromagnetic conversion characteristics is formed. In the etching step, since the surface of the ferromagnetic metal thin film is etched, the surface oxide layer of the ferromagnetic metal thin film is removed, and the electromagnetic conversion characteristics of the magnetic layer are further improved. In the electron beam polymer layer forming step, the electron beam polymer layer is formed by polymerizing a compound with an electron beam on the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film is formed. Since the magnetic recording medium is formed, the rigidity of the magnetic recording medium is increased, deformation during running is suppressed as much as possible, and durability is improved.

[0023]

Embodiments of the present invention will be described below.

FIG. 1 is a sectional view showing an example of the configuration of the magnetic recording medium according to the present embodiment. This magnetic recording medium 1
The ferromagnetic metal thin film 3 is formed on one main surface 2a of the long non-magnetic support 2, and the non-magnetic support 2 has a surface opposite to the surface on which the ferromagnetic metal thin film 3 is formed. One main surface 2
b, a back coat layer 4 is formed.

The non-magnetic support 2 is made of a polyethylene naphthalate film (PEN film). As a polymer material forming the polyethylene naphthalate film, polyethylene-2,6 naphthalenedicarboxylate may be mentioned. In the polyethylene-2,6 naphthalenedicarboxylate, other components may be copolymerized at a small ratio, or another polymer may be mixed at a small ratio. The polyethylene naphthalate film can be produced by a conventionally known method.

In particular, the polyethylene naphthalate film is superior in Young's modulus and heat resistance as compared with the polyethylene terephthalate film (PET film) generally used for the magnetic recording medium 1. On the other hand, this polyethylene naphthalate film has a high manufacturing cost, but since the manufacturing method and the manufacturing technique used for it are the same as the polyethylene terephthalate film, the polyethylene naphthalate film can be manufactured using the polyethylene terephthalate film manufacturing equipment as it is. . In addition, since an aromatic polyamide film having excellent mechanical strength requires a high production cost, a nonmagnetic support excellent in Young's modulus and heat resistance can be obtained at low cost by using a polyethylene naphthalate film.

The non-magnetic support 2 has a surface roughness 2a on the side on which the ferromagnetic metal thin film 3 is formed.
The center line average roughness Ra is preferably in the range of 2.0 nm to 6.0 nm. Here, if the center line average roughness Ra is larger than 6.0 nm, the spacing loss with the magnetic head becomes large, and a sufficient reproduction output cannot be obtained. When the center line average roughness Ra is less than 2.0 nm, friction between the magnetic head and the magnetic recording medium 1 becomes excessively large, and sticking between the magnetic head and the magnetic recording medium 1 becomes remarkable. As a result, runnability and durability are degraded.

In the magnetic recording medium 1, the magnetic layer is made of a ferromagnetic metal thin film 3 and has a small thickness, as described later, so that the magnetic layer is easily affected by the surface properties of the nonmagnetic support 2. The surface shape of the nonmagnetic support 2 is directly reflected on the surface shape of the magnetic layer. Therefore, in the magnetic recording medium 1, it is preferable that the surface shape of the nonmagnetic support 2 is controlled. That is, it is preferable that fine projections are formed on the surface of the nonmagnetic support 2. Since the fine protrusions are formed on the surface of the non-magnetic support 2, the magnetic recording medium 1
Driving performance is improved.

As described above, fine projections can be formed on the surface of the nonmagnetic support 2 by, for example, adding inert solid fine particles to polyethylene-2,6 naphthalenedicarboxylate.

As the inert solid fine particles, for example,
In addition to microgel particles composed of crosslinkable polymers, Ti, S
Examples include oxides of i, Ca, Mg, Al, Zn, Ba, and the like, carbonates, phosphates, sulfates, and particles made of complex salts thereof. Specific examples of the inert solid fine particles include inert inorganic particles such as calcium carbonate, SiO ₂ , Al ₂ O ₃ , natural clay, kaolinite, and carbon;
a, Si, Mn, Mg, Sb, Ge, P, Li, K, N
Particles of a polymer-insoluble composition containing a catalyst residue such as a. In addition, these particles may be used alone or in combination of two or more.

Instead of containing the inert fixed fine particles in polyethylene-2,6-naphthalenedicarboxylate, a colloidal solution in which these inert solid fine particles are dispersed in a water-soluble polymer is used as the surface of the polyethylene naphthalate film. , A surface roughness in the above range may be formed. At this time, these inert fixed fine particles have an average particle size of 0.05 μm to 0.1 μm.
m is preferable.

In consideration of handling when depositing the ferromagnetic metal thin film 3, the surface 2 b of the nonmagnetic support 2 opposite to the surface on which the ferromagnetic metal thin film 3 is formed, ie, the back coat layer 4. The surface of the surface 2b on which the surface is formed is preferably rough.

For this reason, as shown in FIG. 2, the nonmagnetic support may have a laminated structure of at least two layers so that the center line average roughness Ra on both surfaces of the nonmagnetic support can be controlled.

That is, as shown in FIG. 2, the non-magnetic support 5 includes a first non-magnetic support 6 forming a surface 6a on the side on which the ferromagnetic metal thin film 3 is formed, and a back coat layer 4. And a second non-magnetic support member 7 forming a surface 7a on the side on which it is formed. At this time, the center line average roughness Ra of the surface 7a of the nonmagnetic support 5 on the side on which the back coat layer 4 is formed is 2
It is preferably at least 5 nm. For this purpose, the material of the second non-magnetic support 7 is polyethylene-
The inert solid fine particles contained in 2,6 naphthalenedicarboxylate have an average particle size of 0.15 μm to 0.30 μm.
m is preferable.

In order to produce such a non-magnetic support 5 having a laminated structure, liquid polyethylene-2,6-naphthalenedicarboxylate in which inert solid fine particles having different particle diameters are respectively dispersed is prepared by adding It is co-extruded from the die slit, pulled out by being overlapped by a roller means, and then cooled to obtain a long non-magnetic support in which two layers of non-magnetic supports 6 and 7 are laminated.

Then, the long non-magnetic support on which the two non-magnetic supports 6 and 7 are laminated is sequentially stretched in the longitudinal and width directions by a biaxial stretching method. Then, the heat shrinkage is set to a desired value by sequentially performing relaxation treatment in the longitudinal direction and the width direction, respectively. The non-magnetic support thus produced is wound into a roll and used as a raw material.

In order to control the center line average roughness Ra of both surfaces of the non-magnetic support 2, respectively, the non-magnetic support is not formed in a laminated structure as shown in FIG. Alternatively, surface treatment layers may be formed on both surfaces of the non-magnetic support 2.

That is, on both surfaces of the nonmagnetic support 2,
For example, a surface treatment layer may be formed by applying and drying an aqueous solution of a thermoplastic polyester. And
After forming the surface treatment layer, the non-magnetic support 2 is stretched in the longitudinal direction and the width direction, and thereafter, the non-magnetic support 2 is subjected to a heat treatment. At this time, the coating thickness of the surface treatment layer,
By controlling the heat treatment temperature after stretching, the surface properties of both surfaces of the non-magnetic support 2 can be controlled within the above-described ranges.

The ferromagnetic metal thin film 3 is made of Co, Ni, Fe,
Or a ferromagnetic metal material such as an alloy thereof, oblique deposition method,
It is formed as a continuous film on the non-magnetic support 2 by a technique such as a vertical evaporation method or a sputtering method. Ferromagnetic metal thin film 3
Is preferably 0.01 μm to 0.4 μm, and more preferably 0.1 μm to 0.2 μm.

The back coat layer 4 comprises at least a binder and a needle-like non-magnetic pigment, and is formed on a surface 2 b of the non-magnetic support 2 opposite to the surface on which the ferromagnetic metal thin film 3 is formed. Is done.

Examples of the binder include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-vinylidene chloride copolymer. Polymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride , Vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, polycarbonate resin, heat Of polyurethane resins, urea resins, melamine resins, alkyd resins, urea - formaldehyde resins or mixtures thereof. These resins may be those having improved durability by using an isocyanate compound as a cross-linking agent, or those having an appropriate polar group introduced.

As the acicular non-magnetic pigment contained in the back coat layer 4 in the present invention, it is preferable to use an acicular non-magnetic pigment having a ratio between the major axis and the minor axis, that is, an aspect ratio of 10 or more. . By using an acicular nonmagnetic pigment having an aspect ratio of 10 or more, not only the thickness direction of the magnetic recording medium 1 but also mechanical strength such as tensile strength and bending strength in a plane direction such as a longitudinal direction and a width direction can be reduced. Can also be improved. The material of the acicular nonmagnetic pigment is not particularly limited, and for example, hematite, goethite, titanium oxide, aluminum oxide, or the like can be used.

Assuming that the amount of the binder contained in the back coat layer 4 is B and the amount of the acicular nonmagnetic pigment is P, the ratio P / B between these binders and the acicular nonmagnetic pigment is as follows: 0.5
It is preferably from 5.0 to 5.0. This P / B ratio is 0.5
If smaller, the content of the acicular nonmagnetic pigment is small,
The effect of reinforcing the mechanical strength in the plane direction of the magnetic recording medium 1 is not exhibited. When the P / B ratio is larger than 5,
Since the content of the binder is small, the strength of the back coat layer 4 itself is weak, so that powder phenomena occur or the back coat layer 4
The durability of itself deteriorates.

Further, the thickness of the back coat layer 4 is preferably 0.1 μm to 0.6 μm.
If the thickness of the back coat layer 4 is too small, the magnetic recording medium 1
The effect of reinforcing the mechanical strength of the magnetic recording medium 1 does not appear, and if the thickness of the back coat layer 4 is too large, cracks are likely to occur in the magnetic recording medium 1. Further, the back coat layer 4 can contain an antistatic agent, a lubricant, and the like as necessary.

In this magnetic recording medium 1, it is preferable to form a protective film 8 on the ferromagnetic metal thin film 3, as shown in FIG. By forming the protective film 8 on the ferromagnetic metal thin film 3, the durability of the ferromagnetic metal thin film 3 is improved. The protective film 8 is formed by depositing, for example, carbon on the ferromagnetic metal thin film 3 by sputtering or the like. The thickness of the protective film 8 is preferably 3 nm to 15 nm, and more preferably 5 nm to 10 nm. If the thickness of the protective film 8 is too small, the durability of the protective film 8 is reduced, and the ferromagnetic metal thin film 3 cannot be protected. On the other hand, if the thickness of the protective film 8 is too large, spacing loss increases, and sufficient output cannot be obtained when performing short-wavelength recording. By setting the thickness of the protective film 8 to 3 nm to 15 nm, the ferromagnetic metal thin film 3 can be sufficiently protected without increasing a spacing loss.

In the magnetic recording medium 1, it is preferable that a lubricant is present on the surface of the protective film 8. The presence of the lubricant can further enhance the running performance improving effect based on the shape of the fine projections on the surface of the non-magnetic support 2.

Further, the surface of the magnetic recording medium 1, the protective film 8, the gap of the ferromagnetic metal thin film 3, the interface between the protective film 8 and the ferromagnetic metal thin film 3, the ferromagnetic metal thin film 3 and the non-magnetic support Various additives such as a rust inhibitor, an antistatic agent, and a fungicide can be added to the interface with the nonmagnetic support 2 and the nonmagnetic support 2 by known means, if necessary.

Hereinafter, a method for manufacturing the magnetic recording medium 1 as described above will be described.

First, liquid polyethylene-2,6-naphthalenedicarboxylate in which inert solid fine particles having different particle diameters are respectively dispersed is co-extruded from a die slit, and is drawn out by being overlapped by a roller means. , Then by cooling
A long non-magnetic support 5 in which two layers of non-magnetic supports 6 and 7 are laminated is obtained.

Then, the long non-magnetic support 5 on which the two non-magnetic supports 6 and 7 are laminated is sequentially stretched in the longitudinal direction and the width direction by the successive biaxial stretching method. Further, by performing a relaxation treatment in the longitudinal direction or the width direction, the heat shrinkage of the nonmagnetic support 5 is set to a desired value. At this time, the surface roughness of both surfaces 6a and 7a of the nonmagnetic support 5 is set to a desired value.

Next, the non-magnetic support 2 is set in a continuous winding type vacuum evaporation apparatus as shown in FIG. To form FIG. 4 is a schematic configuration diagram of a continuous winding vacuum evaporation apparatus.

This vacuum vapor deposition apparatus 10 is used for oblique vapor deposition, and is cooled to, for example, about −20 ° C. in a vacuum chamber 11 in which the inside is in a vacuum state of, for example, about 10 ⁻³ Pa. The cooling can 12 includes a cooling can 12 that rotates in the direction of the middle arrow A, and a metal thin film deposition source 13 disposed at a position facing the cooling can 12. The evaporation source 13 is a container in which a ferromagnetic metal material is accommodated in a container such as a crucible.

As shown in FIG. 4, the non-magnetic support 2 roll 16 is mounted on a rotatable supply shaft 22, and the vacuum evaporation apparatus 10 is driven to rotate by a driving source (not shown). The magnetic tape roll 17 is mounted on the winding shaft 23, and the nonmagnetic support 2 is caused to run continuously through the cooling can 12.

When the ferromagnetic metal thin film 3 is formed using the vacuum evaporation apparatus 10 having such a configuration, first, the ferromagnetic metal material in the evaporation source 13 is accelerated from the electron beam generation source 14. The emitted electron beam 15 is irradiated to heat and evaporate the ferromagnetic metal material.

Then, the heated and evaporated ferromagnetic metal material is applied to the non-magnetic support 2 roll 1 mounted on the supply shaft 22.
6 is drawn out in the direction of arrow B in FIG.
The ferromagnetic metal thin film 3 is formed by being vapor-deposited on the non-magnetic support 2 running along the peripheral surface of. Finally, the nonmagnetic support 2 on which the ferromagnetic metal thin film 3 is formed
It is wound on a magnetic tape roll 17 mounted on a winding shaft 23.

At this time, a deposition-preventing plate 18 is provided between the vapor deposition source 13 and the cooling can 12, and a shutter 19 is provided on the deposition-preventing plate 18 so as to be adjustable in position. Only vapor particles incident at an angle of. The ferromagnetic metal thin film 3 is formed by such an oblique deposition method.

Further, the ferromagnetic metal thin film 3
It is preferable that oxygen gas be introduced into the vicinity of the surface of the non-magnetic support 2 via an oxygen gas inlet (not shown). By introducing oxygen gas, the magnetic properties, durability and weather resistance of the metal magnetic thin film 3 can be improved.

Guide rollers 20 and 21 are disposed between the non-magnetic support 2 roll 16 and the cooling can 12 and between the cooling can 12 and the magnetic tape roll 17, respectively. 2 is applied with a predetermined tension so that the non-magnetic support 2 runs smoothly.

Further, in order to heat the evaporation source 13, in addition to the above-described heating means using an electron beam, for example,
Known means such as resistance heating means, high-frequency heating means, and laser heating means may be used.

In the above, the example of forming the ferromagnetic metal thin film 3 by the oblique deposition method has been described.
In addition to this example, a known thin film forming method such as a vertical vapor deposition method or a sputtering method can be applied as a method for forming a thin film.

Here, an oxide film exists near the surface of the ferromagnetic metal thin film 3 due to the oxygen gas introduced during the formation of the ferromagnetic metal thin film 3. Since this oxide film is non-magnetic, it causes spacing loss. Therefore, next, the oxide film existing on the surface of the ferromagnetic metal thin film 3 is removed by etching.

When etching is performed after the ferromagnetic metal thin film 3 is formed, the surface oxide layer present on the surface of the ferromagnetic metal thin film 3 is removed by etching, and the ferromagnetic metal thin film 3 has a desired thickness. Until it becomes thin. Therefore, the spacing loss can be suppressed by removing the nonmagnetic oxide film.

The etching method is not particularly limited, and for example, any of a reverse sputtering method, an ion etching method, an ECR plasma etching method and the like is effective. In any case of using any of these methods, the etching condition is that the pressure is 3 × 1 in an Ar gas atmosphere.
It is preferable to set to about 0 ^-3 Torr.

Next, a protective film 8 is formed on the ferromagnetic metal thin film 3. By forming the protective film 8 on the ferromagnetic metal thin film 3, abrasion of the ferromagnetic metal thin film 3 can be prevented.
To form the protective film 8, carbon is deposited on the ferromagnetic metal thin film 3 using a magnetron sputtering device 30 as shown in FIG.

In this magnetron sputtering apparatus 30, the inside of the chamber 31 is, for example, about 10 ⁻⁴ Pa
After the pressure has been reduced to the extent, the angle of the valve 33 for exhausting to the vacuum pump 32 side is reduced, thereby reducing the exhaust speed and introducing Ar gas from the gas introduction pipe 34 to reduce the degree of vacuum to about 0.8 Pa, for example. It is said. Further, the magnetron sputtering apparatus 30 includes, for example,-
A cooling can 35 cooled to 40 ° C. and rotating in the direction of arrow C in FIG. 5 and a target 36 disposed opposite to the cooling can 35 are provided. Target 36
Is a material of the protective film 8, and carbon is used. Further, the target 36 is supported by a backing plate 37 constituting a cathode electrode. On the back side of the backing plate 37, a magnet 38 for forming a magnetic field is provided.

The magnetron sputtering apparatus 30
The magnetic tape roll 17 on which the ferromagnetic metal thin film 3 is formed is mounted on a rotatable supply shaft 39, and the magnetic tape roll 17 is rotatably driven by a driving source (not shown). The non-magnetic support 2 on which the ferromagnetic metal thin film 3 is formed is mounted on the cooling can 35.
The vehicle is continuously driven in the direction D in FIG.

When the protective film 8 is formed by this magnetron sputtering apparatus 30, first, the gas introduction pipe 34
r gas was introduced, and the cooling can 35 was used as an anode, and the backing plate 37 was used as a cathode.
A voltage of 0 V is applied so that a current of about 1.4 A flows.

When the voltage is applied, the Ar gas is turned into plasma, and the ionized ions collide with the target 36, whereby the atoms of the target 36 are repelled. At this time, a magnet 38 is provided on the back side of the backing plate 37, and a magnetic field is formed near the target 36, so that the ionized ions are concentrated near the target 26. The atoms ejected from the target 36 are fed out from the magnetic tape roll 17 in the direction of arrow D in FIG. 5 and run on the outer peripheral surface of the cooling can 35 on the ferromagnetic metal thin film 3 of the nonmagnetic support 2. To form a protective film 8.
Finally, the nonmagnetic support 2 on which the protective film 8 is formed is wound by a magnetic tape roll 42 mounted on a winding shaft 41.

At this time, the protective film 8 has a thickness of about 3 nm to 15 nm so that the spacing loss can be suppressed as much as possible and the effect of preventing the abrasion of the ferromagnetic metal thin film 3 can be obtained. More preferably, the film thickness is 5
nm to about 10 nm.

Although the method using magnetron sputtering has been described above as a method for forming the protective film 8, in addition to this method, a known thin film forming method such as ion beam sputtering, ion beam plating, or CVD is used. Can be used.

Next, a coating material for a back coat layer containing a needle-shaped non-magnetic pigment and a binder was prepared, and the non-magnetic support member 5 on which the ferromagnetic metal thin film 3 and the protective film 8 were formed was strongly applied. The backcoat layer 4 is formed by applying the backcoat layer paint on the surface 7b on which the magnetic metal thin film 3 is not formed.

Finally, the raw material of the magnetic recording medium 1 on which the ferromagnetic metal thin film 3, the protective film 8 and the back coat layer 4 are formed is cut into a predetermined width along the length direction to cut the magnetic tape. Make it. Through the steps described above, the magnetic recording medium 1 can be obtained.

It is preferable that the magnetic recording medium 1 has a lubricant on the surface of the protective film 8. The presence of the lubricant can further enhance the running performance improving effect based on the shape of the fine projections on the surface of the non-magnetic support 2.

Further, the surface of the magnetic recording medium 1, the protective film 8, the gap of the ferromagnetic metal thin film 3, the interface between the protective film 8 and the ferromagnetic metal thin film 3, the ferromagnetic metal thin film 3 and the non-magnetic support Various additives such as a rust inhibitor, an antistatic agent, and a fungicide can be added to the interface with the nonmagnetic support 2 and the nonmagnetic support 2 by known means, if necessary.

<Second Embodiment> FIG. 6 is a sectional view showing a configuration example of a magnetic recording medium according to the present embodiment.
As shown in FIG. 6, the magnetic recording medium 50 includes a ferromagnetic metal thin film 5 on one main surface 51a of a long non-magnetic support member 51.
2 and one main surface 51 of the nonmagnetic support 51 on the side opposite to the surface on which the ferromagnetic metal thin film 52 is formed.
The metal thin film 53 and the back coat layer 54 are formed on the substrate b. Here, the non-magnetic support 51 and the ferromagnetic metal thin film 52 are the same as the non-magnetic support 2 described in the first embodiment.
And the same configuration as the ferromagnetic metal thin film 3,
Here, description of the nonmagnetic support 51 and the ferromagnetic metal thin film 52 will be omitted.

The metal used for the metal thin film 53 includes, for example, Cu, Al, Ni, Cr and alloys thereof. The thickness of the metal thin film 53 is preferably 0.1 μm to 0.5 μm.
Here, if the thickness of the metal thin film 53 is smaller than 0.1 μm, the effect of reinforcing the mechanical strength of the magnetic recording medium 50 is not exhibited. If the thickness of the metal thin film 53 is larger than 0.5 μm, cracks in the magnetic recording medium 50 tend to occur. By setting the thickness of the metal thin film 53 to 0.1 μm to 0.5 μm, the mechanical strength of the magnetic recording medium 50 can be reinforced without causing cracks.

The surface of the non-magnetic support 51 opposite to the surface 51a on which the ferromagnetic metal thin film 52 is formed is formed by a continuous winding vacuum evaporation apparatus as shown in FIG. It is formed by depositing the above-described metal material on the surface 51b.

The back coat layer 54 is formed by dispersing a non-magnetic pigment such as carbon or calcium carbonate in a binder such as polyurethane or a vinyl chloride-vinyl acetate copolymer. Providing the back coat layer 54 ensures good running properties of the magnetic recording medium 50.

The magnetic recording medium 50 according to the present embodiment
Since the metal thin film 53 is formed on the surface 51b of the nonmagnetic support 51 opposite to the surface 51a on which the ferromagnetic metal thin film 52 is formed, sufficient mechanical strength is ensured and durability is improved. . As a result, in the magnetic recording medium 50 to which the present invention is applied, the deformation of the shape is suppressed, the contact with the magnetic head can be sufficiently obtained, and the better electromagnetic conversion characteristics, recording / reproducing characteristics, and running properties are improved. Is achieved.

In the magnetic recording medium 50, a protective film made of, for example, carbon or the like may be formed on the ferromagnetic metal thin film 52. By forming a protective film on the ferromagnetic metal thin film 52, the durability of the ferromagnetic metal thin film 52 is improved.

<Third Embodiment> FIG. 7 is a sectional view showing a configuration example of a magnetic recording medium according to the present embodiment.
As shown in FIG. 7, the magnetic recording medium 60 has a ferromagnetic metal thin film 6 on one main surface 61 a of a long non-magnetic support 61.
2 and one main surface 61 of the nonmagnetic support 61 opposite to the surface on which the ferromagnetic metal thin film 62 is formed.
The plasma polymer layer 63 is formed on b. Here, the nonmagnetic support 61 and the ferromagnetic metal thin film 62
Since the configuration is the same as that of the non-magnetic support 2 and the ferromagnetic metal thin film 3 described in the above embodiment, the description of the non-magnetic support 61 and the ferromagnetic metal thin film 62 is omitted here.

The plasma polymer layer 63 is formed by coating a compound polymerizable by plasma on the nonmagnetic support 61 by a plasma polymerization method.

In the plasma polymerization method, Ar, Ne, H ₂ , N ₂
By mixing a discharge plasma of a carrier gas such as described above and a monomer gas and bringing the mixed gas into contact with the surface of the substrate to be treated, a plasma polymerized film is formed on the surface of the substrate to be treated.

According to the principle of plasma polymerization, when an electric field is applied while the carrier gas is kept at a low pressure, the free electrons present in the carrier gas in a small amount have a very large intermolecular distance as compared with the normal pressure. Energy of 5 eV to 10 eV (electron temperature). When an atom that has obtained this energy collides with another atom or molecule, it breaks their atomic orbital or molecular orbital and dissociates into normally unstable chemical species such as electrons, ions, or neutral radicals. The dissociated electrons, ions or neutral radicals are again subjected to electrolytic acceleration to dissociate another atom or molecule. In this way, the dissociation of atoms and molecules occurs in a chain, and the carrier gas immediately becomes highly ionized. The gas in the highly ionized state is called a plasma gas. On the other hand, monomer gas molecules do not absorb much energy because they have less chance of collision with electrons, and are kept at a temperature close to room temperature.

A system in which the energy of electrons (electron temperature) and the thermal motion of molecules (gas temperature) are separated is called a low-temperature plasma. Here, a chemical species is used for polymerization or the like while keeping its relatively original form. A situation where an additive chemical reaction can be promoted has been created, and the plasma polymerization method utilizes this situation to form a plasma polymerized film on the surface of a substrate to be treated. Since low-temperature plasma is used, there is almost no thermal effect on the substrate to be processed.

As the monomer gas used for forming the plasma polymer layer 63, a carbon-hydrogen system, a carbon-hydrogen-oxygen system, a carbon-halogen system, a carbon-oxygen-halogen system, Any organic compound such as carbon-hydrogen-halogen or organic metal can be used, and among them, organic compounds having an unsaturated bond such as ethylene, acetylene, styrene, acrylonitrile, methyl methacrylate, butadiene, benzene, and pyridine are particularly preferable. Compounds are preferred. In addition, organic silicon compounds such as various silanes having a siloxane bond, and various organic compounds containing sulfur or nitrogen can also be used.

As the plasma generating source, those commonly used as plasma generating sources, such as high-frequency discharge, microwave discharge, DC discharge and AC discharge, can be used. Further, the degree of vacuum during plasma polymerization is preferably set to 1 Pa to 1000 Pa.

The plasma polymer layer 63 formed in this manner is formed very thinly and uniformly on the nonmagnetic support 61, and is densely and strongly adhered to the nonmagnetic support 61 and developed three-dimensionally. Organization. By forming the plasma polymer layer 63 on the surface of the non-magnetic support 61 opposite to the surface on which the ferromagnetic metal thin film 62 is formed, the mechanical strength of the magnetic recording medium 60 is increased, and the occurrence of curl is reduced. Can be prevented. Therefore, in the magnetic recording medium 60, the deformation of the shape is suppressed, the contact with the magnetic head can be sufficiently obtained, and more excellent electromagnetic conversion characteristics, recording / reproducing characteristics, and running properties can be realized.

The thickness of such a plasma polymer layer is
It is preferably from 0.1 μm to 1.0 μm. If the thickness of the plasma polymer layer is less than 0.1 μm, curling cannot be reduced. On the other hand, if the thickness of the plasma polymer layer is larger than 1.0 μm, the reverse curl becomes large. Further, when the thickness of the plasma polymer layer is 1.0
If it is larger than μm, the thickness of the magnetic recording medium 60 itself becomes large. Therefore, by setting the thickness of the plasma polymer layer to 0.1 μm to 1.0 μm, the magnetic recording medium 60
Can be prevented from being curled.

Incidentally, in the magnetic recording medium 60, a protective film made of, for example, carbon or the like may be formed on the ferromagnetic metal thin film 62. Further, in the magnetic recording medium 60, it is preferable to make a lubricant exist on the surface of the protective film. By allowing the lubricant to be present on the surface of the protective film, the effect of improving the running property based on the shape of the fine projections on the surface of the nonmagnetic support 61 can be further enhanced.

The surface of the magnetic recording medium 60, the protective film, the gap of the ferromagnetic metal thin film 62, the interface between the protective film and the ferromagnetic metal thin film 62, the ferromagnetic metal thin film 62 and the nonmagnetic support 61 If necessary, various additives such as a rust inhibitor, an antistatic agent, and a fungicide can be present at the interface of the substrate, in the nonmagnetic support 61, or the like by known means.

<Fourth Embodiment> FIG. 8 is a sectional view showing an example of the configuration of a magnetic recording medium according to the present embodiment.
As shown in FIG. 8, the magnetic recording medium 70 has a ferromagnetic metal thin film 7 on one main surface 71a of a long non-magnetic support 71.
2 and one main surface 71 of the nonmagnetic support 71 opposite to the surface on which the ferromagnetic metal thin film 72 is formed.
An electron beam polymer layer 73 is formed on b. here,
The nonmagnetic support 71 and the ferromagnetic metal thin film 72 have the same configuration as the nonmagnetic support 2 and the ferromagnetic metal thin film 3 described in the first embodiment. The description of the ferromagnetic metal film 71 and the ferromagnetic metal thin film 72 will be omitted.

The electron beam polymer layer 73 contains a compound polymerized by irradiation with an electron beam. The compound polymerizable by an electron beam is a compound having an unsaturated bond polymerizable by an electron beam, for example, a compound having a carbon-carbon double bond of a vinyl group or a carbon-carbon double bond of a vinylidene group. Among them, compounds having a plurality of carbon-carbon double bonds as described above are preferable. Specific examples of the compound having such an unsaturated bond include, for example, an acryloyl group, an acrylamide group, an allyl group,
Examples include compounds containing a vinyl ether group, a vinyl thioether group, and the like, and unsaturated polyesters.

The compound having an unsaturated bond is particularly preferably a polymer having a skeleton of polyester, polyurethane, epoxy resin, polyether or polycarbonate and having an acryloyl group or a methacryloyl group at both ends of a straight chain. . The molecular weight of such a polymer is preferably about 500 to 20,000.

Further, the above-mentioned polymer is added with carbon-
A monomer having a carbon unsaturated bond in the molecule can be added. As the monomer having a carbon-carbon unsaturated bond in the molecule, for example, acrylic acid, methacrylic acid, itaconic acid, methyl acrylate and its homologous alkyl acrylate, methyl methacrylate and its homologous methacryl Acid alkyl esters, styrene and its homologs α-methylstyrene, β-chlorostyrene and the like, acrylonitrile, methacrylonitrile,
Acrylamide, methacrylamide, vinyl acetate, vinyl propionate and the like can be mentioned. Of these, unsaturated esters of polyols, such as ethylene diacrylate, diethylene glycol diacrylate, glycerol trimethacrylate, ethylene dimethacrylate, pentaerythritol tetramethacrylate, and glycidyl methacrylate having an epoxy ring are particularly preferable.

Such a monomer may have two or more unsaturated bonds in the molecule. Further, such a monomer may be used as a mixture of a monomer having only one unsaturated bond in a molecule and a monomer having two or more unsaturated bonds. The amount of the monomer is preferably と す る or more of the polymer. If the amount of the monomer is less than 1/4 of the polymer, a large amount of energy is required for curing.

When forming the electron beam polymer layer 73, first, the coating for the electron beam polymer layer containing the compound polymerizable by the electron beam as described above is applied to the ferromagnetic metal of the nonmagnetic support 71. The coating is applied to the surface opposite to the surface on which the thin film 72 is formed. Next, the coating material for the electron beam polymer layer 73 applied on the non-magnetic support 71 is irradiated with an electron beam to polymerize a compound polymerizable by the electron beam.

Examples of electron beam accelerators for irradiating the electron beam polymer layer coating material with an electron beam include, for example, an electron beam accelerator of a bande-graf type, an electron beam accelerator of a double scanning type, and an electron beam accelerator of a curtain beam type. However, it is preferable to use a curtain beam type electron beam accelerator which is relatively inexpensive and can obtain a large output.

As the electron beam characteristics, the acceleration voltage is 100 k
V to 1000 kV, preferably 150 kV to 700 kV
It is. If the accelerating voltage is less than 100 kV, the amount of transmitted energy is insufficient. If the accelerating voltage exceeds 1000 kV, the energy efficiency used for the polymerization is lowered, which is not economical. The absorbed dose is 0.5 to 20 Mrad, preferably 2 to 10 Mrad. If the absorbed dose is less than 0.5 Mrad, the curing reaction is insufficient and the coating film strength cannot be obtained.If the absorbed dose exceeds 20 Mrad, the energy efficiency used for curing decreases or the irradiated object generates heat,
In particular, the nonmagnetic support 71 is undesirably deformed.

The electron beam polymer layer 73 may contain a binder and a nonmagnetic inorganic pigment powder. As the binder, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-
Vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, Polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, polycarbonate resin, thermosetting Examples include polyurethane resins, urea resins, melamine resins, alkyd resins, urea-formaldehyde resins, or mixtures thereof.

Examples of the nonmagnetic inorganic pigment powder include carbon black, graphite, zinc oxide, titanium oxide, barium sulfate, talc, kaolin, chromium oxide, cadmium sulfide, goethite, silica aerosol, and the like.
Anhydrous alumina fine powder, calcium carbonate, molybdenum disulfide, carbon fluoride and the like are used.

The thickness of the electron beam polymer layer 73 is preferably from 0.1 μm to 0.6 μm.
If the thickness of the electron beam polymer layer 73 is too small, the effect of reinforcing the mechanical strength of the magnetic recording medium 70 will not be exhibited, and if the thickness of the electron beam polymer layer 73 is too large, cracks will occur in the magnetic recording medium 70. Tends to occur. The thickness of the electron beam polymer layer 73 is set to 0.1 μm.
When the thickness is from m to 0.6 μm, the mechanical strength of the magnetic recording medium 70 can be reinforced without causing cracks. As described above, by forming the electron beam polymer layer 73 on the surface of the nonmagnetic support 71 opposite to the surface on which the ferromagnetic metal thin film 72 is formed, the mechanical strength of the magnetic recording medium 70 is increased. , Curling can be prevented.

Accordingly, in the magnetic recording medium 70, the deformation of the shape is suppressed, the contact with the magnetic head can be sufficiently obtained, and better electromagnetic conversion characteristics, recording / reproducing characteristics and running properties can be realized. .

The magnetic recording medium 70 may contain an antistatic agent, a lubricant and the like in the electron beam polymer layer 73 as necessary.

Further, in the magnetic recording medium 70, a protective film made of, for example, carbon or the like may be formed on the ferromagnetic metal thin film 72. Further, in the magnetic recording medium 70, it is preferable that a lubricant is present on the surface of the protective film. By making the lubricant exist on the surface of the protective film, it is possible to further enhance the running improvement effect based on the shape of the fine projections on the surface of the nonmagnetic support 71.

Further, the surface of the magnetic recording medium 70, the protective film, the gap of the ferromagnetic metal thin film 72, the interface between the protective film and the ferromagnetic metal thin film 72, the ferromagnetic metal thin film 72 and the nonmagnetic support 71 If necessary, various additives such as a rust inhibitor, an antistatic agent, and a fungicide can be made to exist at the interface, the inside of the nonmagnetic support 71, and the like.

[0107]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

For a magnetic recording medium having a back coat layer formed thereon,
In the following Examples 1 to 6, in the non-magnetic support, the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film was formed was coated with a backcoat having different contents of acicular non-magnetic pigments. A sample tape was prepared by forming a layer, and each property was evaluated together with the sample tape of Comparative Example 1 in which the backcoat layer did not contain the acicular nonmagnetic pigment.

Example 1 First, a first material composed of liquid polyethylene-2,6 naphthalenedicarboxylate to which fine particles composed of microgel particles having a particle diameter of 60 nm were added, and microgel particles having a particle diameter of 300 nm A liquid polyethylene-2,6 naphthalenedicarboxylate-containing second material having fine particles added thereto is prepared, and the first material and the second material are co-extruded from a die slit, respectively. Thereafter, the mixture was rapidly cooled to produce a nonmagnetic support having a two-layer structure.

Then, the non-magnetic support is stretched in the longitudinal direction and the width direction by a sequential biaxial stretching method to have a thickness of about 4.
A 0 μm film was obtained, which was wound into a roll to obtain a raw material of a non-magnetic support. At this time, the non-magnetic support has a center line average roughness Ra of 2.0 nm on the surface on which the ferromagnetic metal thin film 3 is formed, and a center line average roughness on the surface on which the back coat layer is formed. Ra was 35 nm.

Next, the continuous winding type vapor deposition apparatus as shown in FIG. 4 was evacuated so that the inside thereof was brought into a vacuum state of about 10 ⁻³ Pa, and the non-polymerized film was formed as described above. The magnetic support was set on this vapor deposition device. Then, a ferromagnetic metal thin film made of Co was formed on the surface of the nonmagnetic support in the presence of a small amount of oxygen by a continuous oblique vapor deposition method. At this time, the incident angle of the vapor deposition is 90 to 45 degrees in the normal direction of the nonmagnetic support, the traveling speed of the nonmagnetic support is 50 m / min, and the thickness of the ferromagnetic metal thin film is 0. 18
It was manufactured by adjusting the intensity of the electron beam so as to be μm.

Next, the surface oxide layer formed on the ferromagnetic metal thin film was subjected to ECR plasma etching in an Ar gas atmosphere to reduce the thickness of the surface oxide layer to about 5 nm. At this time, the pressure was about 0.4 Pa, and the input power was 300 k.
W.

Next, the pressure of the magnetron sputtering apparatus as shown in FIG. 5 was reduced to about 10 ⁻⁴ Pa, and then Ar gas was introduced to about ^0.8 Pa. Then, the non-magnetic support on which the ferromagnetic metal thin film is formed is set in the magnetron sputtering apparatus, and is run at a speed of 5 m / min on a cooling can cooled to about -40 ° C. Was formed.

Next, 50 parts by weight of the acicular nonmagnetic pigment and 100 parts by weight of the polyurethane resin were mixed and dispersed in 300 parts by weight of a mixed solvent obtained by mixing methyl ethyl ketone and toluene at a ratio of 4: 1. Thus, a paint for a back coat layer was prepared. Here, goethite having a major axis length of 0.2 μm and an aspect ratio of 20 was used as the acicular nonmagnetic pigment. Then, on the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film was formed, the above-mentioned backcoat layer paint was applied and dried to form a 0.5 μm thick backcoat layer. .

Next, perfluoropolyether was applied as a lubricant on the protective film to form a top coat layer, thereby producing a magnetic recording medium. Finally, this magnetic recording medium is
The tape was cut into a tape having a width of mm to obtain a magnetic tape. The magnetic tape was housed in a cassette body to obtain a sample tape.

Example 2 When the amount of the acicular nonmagnetic pigment was 100
A sample tape was produced in the same manner as in Example 1 except that the amount was changed to parts by weight.

Example 3 When the amount of the acicular nonmagnetic pigment was 200
A sample tape was produced in the same manner as in Example 1 except that the amount was changed to parts by weight.

Example 4 The amount of the acicular nonmagnetic pigment was set to 300
A sample tape was produced in the same manner as in Example 1 except that the amount was changed to parts by weight.

Example 5 The amount of the acicular nonmagnetic pigment was 500
A sample tape was produced in the same manner as in Example 1 except that the amount was changed to parts by weight.

Example 6 The amount of the acicular nonmagnetic pigment was 800
A sample tape was produced in the same manner as in Example 1 except that the amount was changed to parts by weight.

Comparative Example 1 A sample tape was prepared in the same manner as in Example 1 except that no needle-shaped nonmagnetic pigment was added.

The sample tape produced as described above was evaluated for characteristics such as error rate, dropout, head contact characteristics, curl degree, and back surface adhesive strength. The evaluation of these characteristics was performed using a modified AIT drive SDX-S300C (trade name) manufactured by Sony. The record shows that the relative speed is 1
The measurement was performed under the conditions of 0.04 m / sec and the shortest recording wavelength of 0.35 μm.

The error rate is 170 as running durability.
The m length was run for 100 passes, and the block error rate after running for one pass and the block error rate after running for 100 passes were measured.

The number of dropouts of 1 μsec or more was measured for 10 minutes.

The hitting characteristics with the head were measured by measuring the ratio of the minimum value to the maximum value and the minimum value / maximum value in% when the output signal (hitting waveform) during tape reproduction was viewed for one track. .

The degree of curl is measured by measuring the width L of the sample tape and the maximum height H of the sample tape from the surface of the flat plate when the sample tape is placed on the flat plate.
L was used to measure the degree of curl. The case where the surface on which the ferromagnetic metal thin film is formed curls concavely is indicated by plus, and the case where the surface on which the ferromagnetic metal thin film is formed curls convex is indicated by minus. Here, in general, as the curl becomes negative, the contact with the head tends to be worse.

The adhesive strength of the back surface is determined by using a predetermined pressure-sensitive adhesive tape and peeling the layer formed on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film is formed from the non-magnetic support. The adhesive strength and the strength of the layer itself were measured.

Table 1 shows the characteristic evaluation results of the sample tapes of Examples 1 to 6 and Comparative Example 1.

[0129]

[Table 1]

Table 1 shows that the sample tape of Comparative Example 1 in which the backcoat layer did not contain the acicular non-magnetic pigment,
The back surface adhesive strength is weak, the curl degree is positively large,
Bad head contact. Also, the block error rate and dropout are bad. On the other hand, in Examples 1 to 6 in which the backcoat layer contained the acicular nonmagnetic pigment, the back surface adhesive strength was large, the curl degree was small, and the head contact was good. Also, the block error rate,
Good characteristics were obtained with few dropouts.

Therefore, by forming a back coat layer containing a needle-shaped non-magnetic pigment on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film is formed, the thickness of the magnetic recording medium can be reduced. Even if it is thin, necessary and sufficient strength is secured,
It has been found that the long-term storage property of the magnetic recording medium, that is, the durability can be improved.

Magnetic Recording Medium with Metal Thin Film Formed
In Examples 7 to 12 shown below, sample tapes were prepared by forming metal thin films having different thicknesses on the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film was formed. Each characteristic was evaluated together with the sample tape of Comparative Example 2 in which no metal thin film was formed.

<Example 7> First, a non-magnetic support was prepared, a ferromagnetic metal thin film was formed on the non-magnetic support, and a protective film was formed on the ferromagnetic metal thin film. Here, the nonmagnetic support, the ferromagnetic metal thin film, and the protective film were formed in the same manner as in Example 1 described above.

Next, Al is vapor-deposited on the surface of the nonmagnetic support 5 opposite to the surface on which the ferromagnetic metal thin film is formed by a continuous winding vacuum vapor deposition device as shown in FIG. Thus, a metal thin film having a thickness of 0.05 μm was formed. As the film forming conditions at this time, the internal pressure in the vacuum vapor deposition apparatus was evacuated to about 10 ⁻² Pa, and the incident angle of vapor deposition was 0 degree to
25 degrees.

Next, a lubricant composed of perfluoropolyether was applied on the protective film to form a top coat layer.
A 0.4 μm-thick back coat layer made of carbon and polyurethane resin was formed on the metal thin film to produce a magnetic recording medium. Finally, the magnetic recording medium was cut into an 8 mm width to form a magnetic tape, and the magnetic tape was stored in a cassette body to obtain a sample tape.

Example 8 The thickness of the metal thin film was 0.1 μm
A sample tape was produced in the same manner as in Example 7, except that

<Embodiment 9> The thickness of the metal thin film was 0.2 μm
A sample tape was produced in the same manner as in Example 7, except that

Example 10 The thickness of the metal thin film was 0.3 μm.
A sample tape was produced in the same manner as in Example 7, except that m was used.

Example 11 The thickness of a metal thin film was 0.5 μm.
A sample tape was produced in the same manner as in Example 7, except that m was used.

Example 12 The thickness of a metal thin film was 0.7 μm.
A sample tape was produced in the same manner as in Example 7, except that m was used.

Comparative Example 2 No metal thin film was formed on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film was formed. A sample tape was prepared in the same manner as in Example 7, except that a 4 μm backcoat layer was formed.

With respect to the sample tapes of Examples 7 to 12 and Comparative Example 2 produced as described above, the error rate, dropout, head contact characteristics, curl degree, and back surface adhesive strength were measured. Characteristic evaluation was performed. Table 2 shows the characteristic evaluation results.

[0143]

[Table 2]

From Table 2, it was found that the sample tape of Comparative Example 2 in which no metal thin film was formed had low back surface adhesive strength,
The degree of curl is positively large, and the head contact is poor. Also, the block error rate and dropout are bad. On the other hand, in Examples 7 to 12 in which a metal thin film was formed, the back surface bonding strength was large, the curl degree was small, and the head contact was good. In addition, good characteristics were obtained with less block error rate and dropout.

Therefore, by forming the metal thin film on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film is formed, necessary and sufficient strength can be obtained even if the thickness of the magnetic recording medium is small. It has been found that the long-term storage property of the magnetic recording medium, that is, the durability can be improved.
Among them, the thickness of the metal thin film is 0.1 μm to 0.5 μm
, It was found that particularly good characteristics were obtained.

Magnetic Recording Medium with Plasma Polymer Layer Formed
In Examples 13 to 18 shown below, a plasma polymer layer having a different thickness was formed on the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film was formed. A tape was prepared, and each characteristic was evaluated together with the sample tape of Comparative Example 3 in which a plasma polymer layer was not formed.

Example 13 First, a nonmagnetic support was prepared, a ferromagnetic metal thin film was formed on the nonmagnetic support, and a protective film was formed on the ferromagnetic metal thin film. Here, the nonmagnetic support, the ferromagnetic metal thin film, and the protective film were formed in the same manner as in Example 1 described above.

Next, the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film is formed has a thickness of 0.1 under the following conditions.
A μm plasma polymer layer was formed.

<Plasma polymer layer forming conditions> Monomer gas: ethylene Monomer gas flow rate: 30 ml / min Carrier gas: argon Carrier gas flow rate: 70 ml / min Vacuum degree: 70 Pa High frequency power supply: 13.56 MHz, 300 W A lubricant composed of perfluoropolyether was applied thereon to form a top coat layer, thereby producing a magnetic recording medium. Finally, the magnetic recording medium was cut into an 8 mm width to form a magnetic tape, and the magnetic tape was stored in a cassette body to obtain a sample tape.

Example 14 A sample tape was prepared in the same manner as in Example 13 except that the thickness of the plasma polymer layer was changed to 0.2 μm.

Example 15 A sample tape was produced in the same manner as in Example 13 except that the thickness of the plasma polymer layer was changed to 0.4 μm.

Example 16 A sample tape was produced in the same manner as in Example 13 except that the thickness of the plasma polymer layer was changed to 0.8 μm.

Example 17 A sample tape was prepared in the same manner as in Example 13, except that the thickness of the plasma polymer layer was changed to 1.0 μm.

Example 18 A sample tape was produced in the same manner as in Example 13 except that the thickness of the plasma polymer layer was changed to 1.2 μm.

Comparative Example 3 A plasma polymer layer was not formed on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film was formed. Instead, a thickness composed of carbon and a urethane binder was used. A sample tape was prepared in the same manner as in Example 13 except that a 0.5 μm backcoat layer was formed.

Examples 13 to 13 produced as described above
For the sample tapes of Example 18 and Comparative Example 3, the error rate, dropout, head
Characteristics of curl and back surface adhesive strength were evaluated. Table 3 shows the characteristic evaluation results.

[0157]

[Table 3]

From Table 3, it can be seen that the sample tape of Comparative Example 3 in which the plasma polymer layer was not formed had low back surface adhesive strength, a positively large curl degree, and poor head contact. Also, the block error rate and dropout are bad. On the other hand, in Examples 13 to 18 in which the plasma polymer layer was formed, the back surface adhesive strength was large, the curl degree was small, and the head contact was good. In addition, good characteristics were obtained with less block error rate and dropout.

Therefore, by forming the plasma polymer layer on the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film is formed, it is necessary and sufficient even if the thickness of the magnetic recording medium is small. It was found that the strength was secured and the long-term storage property of the magnetic recording medium, that is, the durability, could be improved. Among them, the thickness of the plasma polymer layer is 0.1
It has been found that particularly good characteristics can be obtained by setting the thickness to μm to 1.0 μm.

The magnetic recording medium having the electron beam polymer layer formed thereon
In Examples 19 to 24 shown below, the absorption dose of the electron beam was changed on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film was formed to change the electron beam weight. A sample tape was prepared by forming a united layer, and each characteristic was evaluated together with the sample tape of Comparative Example 4 in which an electron beam polymer layer was not formed.

Example 19 First, a nonmagnetic support was prepared, a ferromagnetic metal thin film was formed on the nonmagnetic support, and a protective film was formed on the ferromagnetic metal thin film. Here, the nonmagnetic support, the ferromagnetic metal thin film, and the protective film were formed in the same manner as in Example 1 described above.

Next, 100 parts by weight of carbon black, 50 parts by weight of a polyurethane resin, 20 parts by weight of an ester acrylate oligomer, 20 parts by weight of diethylene glycol diacrylate, and 20 parts by weight of butoxyethyl acrylate, Mixed solvent 300 in which methyl ethyl ketone and toluene are mixed at a ratio of 4: 1
The mixture was mixed and dispersed in parts by weight to prepare an electron beam polymer layer coating material.

The above-mentioned electron beam polymer layer coating material is applied to the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film is formed, and irradiated with an electron beam so that the absorbed dose becomes 1 Mrad. An electron beam polymer layer having a thickness of 0.5 μm was formed.

Next, a lubricant composed of perfluoropolyether was applied on the protective film to form a top coat layer, thereby producing a magnetic recording medium. Finally, the magnetic recording medium was cut into an 8 mm width to form a magnetic tape, and the magnetic tape was stored in a cassette body to obtain a sample tape.

Example 20 A sample tape was produced in the same manner as in Example 19 except that the absorbed dose was 2 Mrad.

Example 21 A sample tape was produced in the same manner as in Example 19 except that the absorbed dose was 5 Mrad.

Example 22 A sample tape was produced in the same manner as in Example 19 except that the absorbed dose was 10 Mrad.

Example 23 A sample tape was prepared in the same manner as in Example 19 except that the absorbed dose was set to 15 Mrad.

Example 24 A sample tape was prepared in the same manner as in Example 19 except that the absorbed dose was set to 20 Mrad.

Comparative Example 4 An electron beam polymer layer was not formed on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film was formed. Instead, the thickness was made of carbon and urethane binder. A sample tape was produced in the same manner as in Example 19 except that a backcoat layer having a thickness of 0.5 μm was formed.

Examples 19 to 19 produced as described above
For the sample tapes of Example 24 and Comparative Example 4, the error rate, dropout, and the hitting characteristics with the head
Characteristics of curl and back surface adhesive strength were evaluated. Table 4 shows the characteristic evaluation results.

[0172]

[Table 4]

As shown in Table 4, the sample tape of Comparative Example 4 in which the electron beam polymer layer was not formed had a low back surface adhesive strength, a large positive curl degree, and a poor head contact. Also, the block error rate and dropout are bad. On the other hand, in Examples 19 to 24 in which the electron beam polymer layer was formed, the back surface adhesive strength was large, the curl degree was small, and the head contact was good. In addition, good characteristics were obtained with less block error rate and dropout.

Therefore, by forming the electron beam polymer layer on the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film is formed, even if the thickness of the magnetic recording medium is small, it is necessary and sufficient. It has been found that high strength can be secured and the long-term storage property of the magnetic recording medium, that is, the durability can be improved.

[0175]

According to the method for manufacturing a magnetic recording medium of the present invention, the surface oxide layer of the ferromagnetic metal thin film is removed by etching, so that the spacing loss is reduced and the magnetic recording medium is excellent in electromagnetic conversion characteristics. Can be obtained.

Further, in the method for manufacturing a magnetic recording medium according to the present invention, the backcoat layer containing the acicular nonmagnetic pigment is provided on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed. As a result, the mechanical strength is enhanced, deformation during running is suppressed, and a magnetic recording medium with improved durability can be obtained.

In the method of manufacturing a magnetic recording medium according to the present invention, the metal thin film is formed on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is formed, so that the mechanical strength is enhanced. Thus, deformation of the magnetic recording medium during running can be prevented, and the durability is improved.

In the method for manufacturing a magnetic recording medium according to the present invention, since the plasma polymer layer is formed on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is formed, the mechanical strength is increased. , The deformation of the magnetic recording medium during running is suppressed, and a magnetic recording medium with improved durability can be obtained.

In the method of manufacturing a magnetic recording medium according to the present invention, since the electron beam polymer layer is formed on the surface of the non-magnetic support opposite to the surface on which the magnetic layer is formed, mechanical The strength is enhanced, the deformation of the magnetic recording medium during running is suppressed, and a magnetic recording medium with improved durability can be obtained.

Therefore, according to the present invention, since it has a sufficient mechanical strength, its shape does not change even during long-time running, and the contact with the magnetic head can be kept in a good state. A magnetic recording medium having both electromagnetic conversion characteristics, recording / reproducing characteristics, and running characteristics can be obtained. further,
According to the present invention, a sufficient strength is ensured even if the thickness is reduced, and a magnetic recording medium corresponding to a further increase in capacity can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration example of a magnetic recording medium according to the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration example of a magnetic recording medium according to the present invention.

FIG. 3 is a sectional view showing a configuration example of a magnetic recording medium according to the present invention.

FIG. 4 is a schematic configuration diagram illustrating an example of a vacuum evaporation apparatus for forming a ferromagnetic metal thin film.

FIG. 5 is a schematic configuration diagram illustrating an example of a magnetron sputtering apparatus for forming a protective film.

FIG. 6 is a sectional view showing a configuration example of a magnetic recording medium according to the present invention.

FIG. 7 is a sectional view showing a configuration example of a magnetic recording medium according to the present invention.

FIG. 8 is a sectional view showing a configuration example of a magnetic recording medium according to the present invention.

[Explanation of symbols]

1,50,60,70 magnetic recording medium, 2,5,5
1,61,71 Non-magnetic support, 3,52,62,7
2 Ferromagnetic metal thin film, 4 Back coat layer 53 Metal thin film, 63 Plasma polymer layer, 73 Electron beam polymer layer

Claims (14)

[Claims] 1. A non-magnetic support producing step for producing a non-magnetic support composed of polyethylene naphthalate, and a ferromagnetic metal to be a magnetic layer on the non-magnetic support produced in the non-magnetic support producing step A ferromagnetic metal thin film forming step of forming a thin film by a vacuum deposition method; an etching step of etching the surface of the ferromagnetic metal thin film formed in the ferromagnetic metal thin film forming step; and the magnetic layer of the nonmagnetic support A magnetic recording medium characterized by comprising a back coat layer forming step of forming a back coat layer containing at least a binder and an acicular nonmagnetic pigment on a surface opposite to a surface on which is formed. Production method. 2. The method of manufacturing a magnetic recording medium according to claim 1, wherein the thickness of the non-magnetic support is 3.0 μm to 6.0 μm in the non-magnetic support production step. 3. The method of forming a back coat layer according to claim 1, wherein
2. The method according to claim 1, wherein the thickness of the back coat layer is 0.1 [mu] m to 0.6 [mu] m. 4. In the back coat layer forming step,
2. The method according to claim 1, wherein the ratio between the major axis and the minor axis of the acicular nonmagnetic pigment is 10 or more. 5. A non-magnetic support producing step for producing a non-magnetic support composed of polyethylene naphthalate, and a ferromagnetic metal to be a magnetic layer on the non-magnetic support produced in the non-magnetic support producing step A ferromagnetic metal thin film forming step of forming a thin film by a vacuum deposition method; an etching step of etching the surface of the ferromagnetic metal thin film formed in the ferromagnetic metal thin film forming step; and the magnetic layer of the nonmagnetic support Forming a metal thin film on a surface opposite to the surface on which the metal recording medium is formed. 6. The method for manufacturing a magnetic recording medium according to claim 5, wherein the thickness of the non-magnetic support is 3.0 μm to 6.0 μm in the non-magnetic support production step. 7. The method for manufacturing a magnetic recording medium according to claim 5, wherein in the metal thin film forming step, the thickness of the metal thin film is set to 0.1 μm to 0.5 μm. 8. The magnetic recording medium according to claim 5, wherein in the metal thin film forming step, the metal thin film is made of a metal selected from the group consisting of Cu, Al, Ni, Cr, and alloys thereof. Manufacturing method. 9. A non-magnetic support producing step for producing a non-magnetic support composed of polyethylene naphthalate, and a ferromagnetic metal to be a magnetic layer on the non-magnetic support produced in the non-magnetic support producing step A ferromagnetic metal thin film forming step of forming a thin film by a vacuum deposition method; an etching step of etching the surface of the ferromagnetic metal thin film formed in the ferromagnetic metal thin film forming step; and the magnetic layer of the nonmagnetic support A plasma polymer layer forming step of forming a plasma polymer layer by polymerizing a compound polymerizable by plasma by a plasma polymerization method on a surface opposite to the surface on which the magnetic layer is formed. Manufacturing method of recording medium. 10. The method of manufacturing a non-magnetic support according to claim 1, wherein
10. The method for manufacturing a magnetic recording medium according to claim 9, wherein the thickness of the non-magnetic support is 3.0 μm to 6.0 μm. 11. In the plasma polymer layer forming step, the plasma polymer layer has a thickness of 0.1 μm to 1.0 μm.
The method for manufacturing a magnetic recording medium according to claim 9, wherein the thickness is set to μm. 12. A non-magnetic support producing step for producing a non-magnetic support composed of polyethylene naphthalate, and a ferromagnetic metal serving as a magnetic layer on the non-magnetic support produced in the non-magnetic support producing step A ferromagnetic metal thin film forming step of forming a thin film by a vacuum deposition method; an etching step of etching the surface of the ferromagnetic metal thin film formed in the ferromagnetic metal thin film forming step; and the magnetic layer of the nonmagnetic support An electron beam polymer layer forming step of forming an electron beam polymer layer by polymerizing a compound polymerizable by an electron beam with an electron beam on the surface opposite to the surface on which is formed Of manufacturing a magnetic recording medium. 13. The method of manufacturing a non-magnetic support according to claim 1, wherein
13. The method for manufacturing a magnetic recording medium according to claim 12, wherein the thickness of the non-magnetic support is 3.0 μm to 6.0 μm. 14. In the electron beam polymer layer forming step, the electron beam polymer layer has a thickness of 0.1 μm to 0.6 μm.
The method for manufacturing a magnetic recording medium according to claim 12, wherein m is set to m.