JPH01104632A - Production of support for magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled support capable of improving running durability of a magnetic recording medium, by subjecting a polymer layer containing inorganic fine particles on a nonmagnetic support to plasma etching, partially removing the polymer and exposing the fine particles. CONSTITUTION:The aimed support obtained by providing (B) a polymer layer containing inorganic fine particles on (A) a nonmagnetic support, subjecting the above-mentioned surface to plasma etching to partially remove the organic polymer and exposing the fine particles so as to provide 50-200Angstrom height thereof.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing a support for a magnetic recording medium, and in particular to a method for manufacturing a support for a magnetic recording medium that is suitable for high-density recording and has improved running durability. Regarding the manufacturing method.

[Conventional technology]

In magnetic recording media for high-density recording, which has been developed in recent years, it is required that the surface of the magnetic layer be made smoother in order to reduce the so-called gap loss between the magnetic head and the magnetic tape. be done. For this purpose, the manufacturing technology of the magnetic layer, i.e. dispersion of magnetic particles, coating,
While it is necessary to improve the surface properties of the magnetic layer by improving surface molding techniques, it is also necessary to improve the surface properties of the support. In particular, since the recording wavelength becomes smaller as the recording density increases, attempts have been made to make the magnetic layer thinner in order to avoid thickness loss. As a result, the influence of the surface properties of the support on the surface properties of the magnetic layer is becoming increasingly large.

Recently, in order to realize even higher density recording, Co--Ni has been developed by vapor deposition, sputtering, etc.

Magnetic recording media with ferromagnetic metal thin films such as Co-Cr and Fe-Ni are being developed, but the above problems are further exacerbated because the magnetic layer is much thinner than a coated magnetic layer. .

However, there are limits to improving the surface properties of supports used in magnetic recording media for the following reasons. That is, in the process of forming and winding a film, if the surface of the film is good, the frictional resistance against the conveyance roller will be large, often causing meandering or wrinkles. Furthermore, the frictional resistance between the films increases and the shape of the take-up roll may become distorted.

Various attempts have been made to solve the above-mentioned contradictory problems. For example, JP-A-53-10
Publication No. 9605 describes a method in which fine particles of thermoplastic resin are made to protrude on a support, and then the fine particles are dissolved in a solvent to give an appropriate surface roughness and form a magnetic layer on the surface. .

Furthermore, Japanese Patent Publication No. 46-14555 describes a method of coating a support with a solution of a polymer such as polyamide or polyester, drying it to form minute wrinkles, and forming a magnetic layer on the surface. .

Japanese Patent Publication No. 47-6117 discloses that polyester or the like is used as the polymer to be coated on the support, Japanese Patent Publication No. 50-38001 discloses that thermoplastic polyester or the like is used, and Japanese Patent Publication No. 46-14555 discloses the use of thermoplastic polyester or the like. As in the publication, a method is described in which minute wrinkles are formed on the surface and a magnetic layer is formed on the surface.

Further, US Pat. No. 4,568,598 discloses a method of plasma etching the surface of the hair hair itself.

However, in all of the above five methods, projections or minute wrinkles are formed in the resin itself, and it is not possible to stably impart characteristics such as running durability that are satisfactory as a magnetic recording medium for high-density recording. It hasn't arrived yet.

In order to solve the above problem, the present applicant previously provided a non-magnetic layer containing a radiation-polymerizable compound and inorganic fine particles on a support, and provided a magnetic layer on the undercoat layer that was irradiated with ultraviolet rays. proposed a magnetic recording medium (Japanese Patent Application Laid-Open No. 60-2515
10).

[Problem that the invention seeks to solve]

However, although this proposal has resulted in considerable improvements in the surface properties and durability of the magnetic layer, there is a problem in that its running durability is not sufficient. Therefore, an object of the present invention is to provide a method for manufacturing a support for a magnetic recording medium that improves running durability.

[Means and effects for solving the problem] In order to achieve the above object, the present inventors provided a polymer layer containing inorganic fine particles on a non-magnetic support, and then subjected the polymer to plasma etching. It has been discovered that a support can be obtained which improves the running durability of a magnetic recording medium by partially removing the fine particles to expose the fine particles and controlling their height.
The present invention has been achieved.

That is, in the present invention, after a polymer layer containing fine particles is provided on a nonmagnetic support, a part of the organic polymer is removed by plasma etching the surface, and the height of the fine particles is 50 to 20 mm.
This is a method for manufacturing a support for a magnetic recording medium, which is characterized in that the support is exposed so that the number of particles is zero.

In the present invention, more preferable results can be obtained by using inorganic fine particles as the fine particles.

The present invention will be explained in detail below.

The present invention is particularly preferably applied to magnetic recording media of ferromagnetic metal thin film type formed by vapor deposition, sputtering, or the like.

As the polymer for the polymer layer containing fine particles used in the present invention, conventionally known thermoplastic resins, thermosetting resins, reactive resins, and mixtures thereof are used.

The thermoplastic resin has a softening temperature of 150°C or less, an average molecular weight of 10,000 to 200,000, and a degree of polymerization of about 2.
00 to 2000, such as vinyl chloride vinyl acetate copolymer, vinyl chloride vinylidene chloride copolymer, vinyl chloride acrylonitrile copolymer, acrylic acid ester acrylonitrile copolymer, acrylic acid ester vinylidene chloride copolymer, acrylic Acid ester styrene copolymer, methacrylic acid ester acrylonitrile copolymer, methacrylic acid ester vinylidene chloride copolymer, methacrylic acid ester styrene copolymer, urethane elastomer, polyvinyl fluoride, vinylidene chloride acrylonitrile copolymer, butadiene acrylonitrile Copolymers, polyamide resins, polyvinyl butyral, cellulose derivatives (cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose probionate, nitrocellulose, etc.), styrene-butadiene copolymers, polyester resins, chlorovinyl ether Acrylic ester copolymers, amino resins, various synthetic rubber-based thermoplastic resins, and mixtures thereof are used.

The thermosetting resin or reactive resin has a molecular weight of 200,000 or less in the state of a coating liquid, and when heated after coating and drying, the molecular weight becomes infinite due to reactions such as condensation and addition. Also, among these resins, those that do not soften or melt before the resin is thermally decomposed are preferred. Specifically, for example, phenol resin, epoxy resin,
Polyurethane curable resin, urea resin, melamine resin, alkyd resin, silicone resin, acrylic reaction resin, epoxy-polyamide resin, mixture of high molecular weight polyester resin and isocyanate prepolymer, mixture of methacrylate copolymer and diisocyanate prepolymer , a mixture of polyester polyol and polyisocyanate,
These include urea formaldehyde resin, a mixture of low molecular weight glycol/high molecular weight diol/triphenylmethane triisocyanate, polyamine resin, and mixtures thereof.

Furthermore, compounds that can be polymerized by radiation are preferably used and are selected from the following. In other words, compounds that can be polymerized by radiation have one carbon-carbon unsaturated bond in the molecule.
Acrylic esters, acrylamides, methacrylic esters, methacrylamides, allyl compounds, vinyl ethers, vinyl esters, vinyl heterocyclic compounds, N-vinyl compounds, styrenes, crotonic acids , itaconic acids, and olefins. Among these, preferred are the following compounds containing two or more acryloyl groups or methacryloyl groups.

Acrylates such as diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, diethylene glycol dimethacrylate, triethylene glycol trimethacrylate, tetraethine glycol dimethacrylate, trimethylolpropane triacrylate, etc. Methacrylates such as methacrylate, pentaerythritol tetraacrylate, and esters of other bifunctional or higher functional polyols with acrylic acid and methacrylic acid.

Moreover, these compounds may be of high molecular weight. Preferably, it is a compound having an ester bond with acrylic acid or methacrylic acid at the end of the main chain or in the side chain of the polymer;
pec Congress”lL 19 (1972
) is quoted. For example, the polyester skeleton of the exemplified compound may be a polyurethane skeleton, an epoxy resin skeleton, a polyether skeleton, a polycarbonate skeleton, or a mixture of these skeletons.The molecular weight is 1.000 to 20. ,000 is preferred, but is not particularly limited.

The above-mentioned compounds that can be polymerized by radiation irradiation can be used alone or in combination in any proportion.

In particular, when heat resistance is required, use a (meth), 7-acrylate compound having a triazine ring, such as tris(2-acryloyloxyethyl) isocyanurate.

(n-1 to 5)0 The radiation used in the present invention is an electron beam and an ultraviolet ray. When using ultraviolet light, it is necessary to add a photopolymerization initiator to the above-mentioned compound. The thickness of the polymer layer is 0.1-1 μm, preferably 0.1 μm. 2-0.8μm
It is.

In the present invention, as the material of the fine particles, the inorganic particles are those called inorganic powders or abrasives, and α
-Alumina, T-alumina, silicon carbide, titanium oxide,
Magnesium oxide, iron phosphide, titanium carbide, titanium nitride, alpha and beta silicon oxides, aluminum, calcium oxalate, iron, alpha ferrous oxide, zinc, zinc dioxide, ferric oxide
These include nickel, nickel, copper, chromia, magnesium hydroxide, zirconia, ittria, ceria, zircon, and antimony oxide. The amount of inorganic particles used is 0.03 to 20 wt%, preferably 0.05 to 15 wt% based on the binder.
It is wt%.

In order to uniformly disperse fine particles in a polymer, silica fine particles introduced from silica sol (here, silica sol refers to a silica sol in which amorphous silicic anhydride (silica) fine particles are dispersed in an organic solvent), , organosols of the above abrasives are preferred.

The diameter of these fine particles is 0.01 to 0.5 μm, preferably 0.03 to 0.3 μm.

In the present invention, the plasma etching method is a method of exposing the support to plasma under reduced pressure. The plasma species include an inert gas such as argon, a gas that reacts with the support such as oxygen, or a mixture thereof.

When forming plasma, the gas pressure is reduced to 10
-'torr to 10-'torr, preferably lo-
A plasma is formed by introducing 02 or A'' so that the temperature is 2 to 10-''Lorr.Of course, other gases (N2°C
1...) may be mixed.

Although high-frequency plasma and DC plasma can be used as plasma, high-frequency plasma can process more efficiently.

The support is preferably left in an electrically floating state or held at a negative potential so that the plasma can effectively act on the support.

The temperature of the support during plasma treatment is preferably within a range where the support does not deform, generally 350'C or less, and preferably 100'C or less for materials with a low softening point such as PET.

Due to plasma etching, part of the organic polymer layer becomes volatile molecules and is carried away, but since the fine particles with a high degree of heat resistance do not become volatile molecules, the fine particles remain and only the part of the organic polymer layer is etched away. This creates uneven areas. The weight of the unevenness is preferably 50 to 200 people; if it is less than 50 Å, the effect on running durability will be reduced, and if it is more than 200 Å, the output will decrease, which is not preferable.

In the present invention, a polymer layer containing fine particles is provided on a non-magnetic support, and then a part of the organic polymer is removed by plasma etching the surface, so that the height of the fine particles is 50 to 50 mm.
By exposing the magnetic recording medium to 200 particles, the direct contact area between the magnetic recording medium surface and the head is reduced, and the inorganic fine particles are appropriately exposed to the surface, thereby increasing the running durability.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A coating film having the following formulation was applied to both sides of a polyimide base having a thickness of 50 IIm and was cured by irradiating it with a high pressure mercury lamp of 80 W/cm for 3 seconds so that the dry film thickness was 0.7 μm.

(Prescription) (a) Tris(2-acryloyloxyethyl) isocyanurate solution in methyl ethyl ketone 10% by weight...
......75 parts by weight (b) Urethane acrylate (molecular weight 8000) Methyl ethyl ketone 10
Weight% liquid...25 parts by weight (c) Silica sol (solid content 1
0 weight, isopropyl alcohol/methyl ethyl ketone VoJ ratio 1/1. Average particle size 80 mμ)...8 parts by weight (d) Benzyl ethyl ketal...4ffiit
This was then treated under the following conditions to expose the silica particles.

The support with the thin film formed thereon was introduced into a vacuum space of 10-'torr or less, and oxygen gas was introduced at l x 10-3 torr and argon gas was introduced at l x 10-'' torr for 13.5
Plasma is generated using a 6 MHz RF (Radio Frequency) voltage. The power at that time was 500 W, and the support was exposed to the power for 2 minutes. The substrate temperature on the opposite side of the plasma was set at 25°C.

On the surface of the resulting support, the result of observation with α-step is 80
A spike of ~120 people (average 100 people) was seen.

Co--Cr films were formed on these supports by DC magnetron sputtering at a power density of 3 w/c+A.

After forming the magnetic film, the Co-Cr film is dip-coated with a perfluoropolyether lubricant to a thickness of 50 to 100 coats,
After drying, a 3.5-inch floppy disk was punched and tested for running durability.

Recording and reproduction were performed under the following conditions: a head pressure of 20 g, an atmosphere of 23° C., 50% RH, a disk rotation of eoorpn, and a recording frequency of 500 Hz. As a result, the running durability was 6.8 million passes. The normalized output was -2.0.

Comparative Example = 1 A sample was prepared in the same manner as in Example 1 without performing the plasma treatment, and was used as a comparative sample.

When running durability was measured under the same conditions, it was 1.2 million passes. The normalized output was 0.

Example-2 Samples were made by changing the plasma treatment time and the exposure method of silica particles in Example-1, and the running durability and output at 100KBPi were measured.The running durability was determined from Example-2. It can be seen that the average height of the spike at which the output is balanced is between 50 and 200.

Comparative Example 2 Only a 50 μmW polyimide hair was subjected to plasma treatment in the same manner as in Example 1 to give an average height of 120 people. As a result, the running durability was 700,000 times, and the normalized output was -2.2
It was dB.

〔Effect of the invention〕

Claims (1)

[Claims] (1) After providing a polymer layer containing inorganic fine particles on a non-magnetic support, a part of the organic polymer is removed by plasma etching the surface so that the height of the fine particles is 50 to 200.
1. A method for producing a support for a magnetic recording medium, the method comprising: exposing the support so that the angle of .ANG.