JPH0954936A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability by forming a protective layer contg. carbon and a specified at.% of silicon by ECR plasma CVD using a silane coupling agent as starting material on a magnetic layer formed on one side of a substrate. SOLUTION: Two magnetic layers each having 90Å thickness are formed in a superposed state on a PET film having 6μm thickness by vapor-depositing Co and the film is set in an ECR plasma CVD device. A silane coupling agent is introduced into the plasma excitation chamber of the device and a protective layer contg. carbon and 0.1-45at.% silicon is formed in 100Å thickness on the upper magnetic layer. The top of the protective layer is coated with a soln. prepd. by diluting perfluoro-polyether as a lubricant with a fluorine-contg. inert solvent to form a top coating layer having 0.002μm thickness. An 8mm videotape using the resultant film has further improved durability of the magnetic layer of the vapor-deposited tape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium and a method for manufacturing the same, and more particularly to a method for manufacturing a magnetic recording medium having excellent durability.

[0002]

2. Description of the Related Art A so-called metal thin film type magnetic recording medium in which a metal is deposited on a support by vacuum evaporation or the like can increase the density of the magnetic material because the magnetic layer contains no binder. It is said to be promising for high density recording.

However, in the magnetic layer of the metal thin film type magnetic recording medium, since the metal is simply attached to the support, the corrosion resistance and durability are poor as they are, and for the purpose of improving this, a carboxylic acid-based or phosphorus-based material is used. It has been practiced to apply an acid-based lubricant or to provide a protective layer of a nonmagnetic metal on the magnetic layer.

Further, today, as a protective layer on the magnetic layer,
A technique for forming a thin film made of diamond-like carbon has attracted attention. The diamond-like carbon thin film is an amorphous carbon film, and is considered to have a structure in which graphite bonds and diamond bonds are mixed. As a method for forming a diamond-like carbon thin film on a magnetic layer, RF (Radio Frequency) plasma CVD (Chemi
cal Vapor Deposition: chemical vapor deposition method or ECR (E
lectron Cycrotoron Resonance (electron cyclotron resonance) plasma CVD method, sputtering method and the like. Of these, ECR plasma CVD is a method in which microwave is applied to the source gas in a high vacuum to turn the gas into plasma and form a thin film on the target (on the magnetic layer).

Usually, a diamond-like carbon thin film is
When forming by ECR plasma CVD, a mixed gas of argon or hydrogen and a lower hydrocarbon gas such as methane or ethane, which is a carbon source, is used. The reason for mixing argon and hydrogen is that both graphite and diamond components are generated in ECR plasma CVD, but it is desirable to increase the amount of diamond component as much as possible in terms of hardness. This is because the growth of the diamond component is promoted, so that a film having a larger diamond component can be obtained.

[0006]

However, even the diamond-like carbon thin film does not sufficiently improve the durability of the magnetic recording medium, and in particular, it is expected that the metal forming the magnetic layer will be diversified in the future. It is desired to obtain a protective layer having sufficient durability regardless of the kind.

[0007]

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that an ECR plasma is formed on the magnetic layer.
The inventors have found that a magnetic recording medium with significantly improved durability can be obtained by forming a thin film containing carbon and silicon as a protective layer by the CVD method, and completed the present invention.

That is, the present invention provides a support, a magnetic layer formed on the support, and ECR plasma CVD on the magnetic layer.
A magnetic recording medium having a protective layer formed by a method, wherein the protective layer contains carbon and silicon, and the protective layer of the magnetic recording medium of the present invention is provided. Can be formed by an ECR plasma CVD method using a silicon-containing organic compound as a raw material.

In the magnetic recording medium of the present invention, the protective layer formed on the magnetic layer by the ECR plasma CVD method contains carbon and silicon, and the proportion of silicon in the protective layer is 0.1-.
It is preferably 45 atom% (several percentages), and more preferably 10 to 40 atom% (several percentages). The proportion of silicon in the protective layer can be measured by Auger electron spectroscopy, X-ray photoelectron spectroscopy, electron microanalyzer, or the like.

The thin film forming the protective layer of the magnetic recording medium of the present invention may be one in which carbon-silicon bonds are mixed in a part of the carbon thin film mainly composed of carbon-carbon bonds,
It may be in a state in which silicon carbide is dispersed in a carbon thin film such as diamond-like carbon or graphite, and the existing states of carbon and silicon are not limited.

The protective layer is formed by ECR plasma CVD method on the magnetic layer formed on the support by a method such as vapor deposition. At that time, a silicon-containing organic compound is used as a raw material compound. For example, organic silanes such as organoalkoxysilanes and various silicon-containing organic compounds known as silane coupling agents are preferably used. Since these contain silicon and carbon in one molecule, they are advantageous in terms of production efficiency and handling. The ECR plasma CVD method may be performed according to a known method. The microwave wavelength is 2.45 GHz, the output is about 500 W, and the degree of vacuum is 10 ^-1 ~
It is preferable that the silicon-containing organic compound is gasified so as to be 10 ⁻⁴ and introduced into the plasma excitation chamber.

The magnetic material forming the magnetic layer of the magnetic recording medium of the present invention includes ferromagnetic metal materials used in the production of ordinary metal thin film type magnetic recording media, such as Co, Ni and Fe. Ferromagnetic metals, Fe-Co, Fe-Ni, Co
-Ni, Fe-Co-Ni, Fe-Cu, Co-Cu, Co-Au, Co-Y,
Co-La, Co-Pr, Co-Gd, Co-Sm, Co-Pt, Ni-Cu, Mn
-Bi, Mn-Sb, Mn-Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-
Ferromagnetic alloys such as Co-Cr and Ni-Co-Cr are exemplified. As the magnetic layer, a thin film of iron or a thin film of a ferromagnetic alloy containing iron as a main component is preferable, and at least one selected from a ferromagnetic alloy containing iron, cobalt, nickel as a main component and nitrides or carbides thereof is preferable.

For high-density recording, the magnetic layer of the magnetic recording medium is preferably formed on a substrate by oblique evaporation. The method of oblique vapor deposition is not particularly limited and is based on a conventionally known method. The degree of vacuum during vapor deposition is about 10 ⁻⁴ to 10 ⁻⁷ Torr. The magnetic layer formed by vapor deposition may have either a single-layer structure or a multi-layer structure, and in particular, the durability can be improved by introducing an oxidizing gas to form an oxide on the surface of the magnetic layer. In the present invention, the magnetic layer may be a single layer or a multi-layer. However, when forming a multi-layer magnetic layer by vapor deposition, the thickness of the magnetic layer is two, in the case of two layers, the thickness of the lower magnetic layer. Is 100-2000Å, the thickness of the upper magnetic layer is 50-1000Å
In the case of three layers, the thickness of the lower magnetic layer is 100 ~
It is preferable that the thickness of the magnetic layer in the middle is 2000Å, the thickness of the intermediate magnetic layer is 100 to 1000Å, and the thickness of the upper magnetic layer is 50 to 1000Å. Further, the number of magnetic layers is preferably as large as possible for high frequency recording, but it is considered that two to five layers are suitable as a practical range.

The support used in the magnetic recording medium of the present invention includes polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cellulose derivatives such as cellulose triacetate and cellulose diacetate; polycarbonates; Polyvinyl chloride; polyimide; plastics such as aromatic polyamide are used. The thickness of these supports is about 3 to 50 μm.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The magnetic recording medium of the present invention
A magnetic metal such as cobalt is deposited on the support by vapor deposition to form a magnetic layer, and a silicon-containing organic compound is gasified and introduced into the plasma excitation chamber of the ECR plasma CVD device to generate active species of carbon and silicon. Then, these are attached to the magnetic layer to form the protective layer of the present invention. ECR plasma
As a raw material in the CVD method, it is preferable to use a silane coupling agent represented by the following formula. YR-Si- (X) ₃ where Y is a functional group such as vinyl group, methacrylic acid residue, glycidyl ether residue, amino group, halogen group, thiol group, R is an alkylene group, and X is a silicon atom. Means a hydrolyzable group such as Cl, OR ', OCOR' (R 'is an alkyl group). Such silane coupling agents are exemplified by SILANES series A-150, A-1 of Nippon Unicar Co., Ltd.
It is available as 51 mag. Further, as the organic silane, it is preferable to use organoalkoxysilane such as CH ₃ Si (OC ₂ H ₅ ) ₃ and CH ₃ Si (OCH ₃ ) _{3 in particular} , and they are, for example, those of the SILANES series of Nippon Unicar Co., Ltd. It is available as A-162, A-163, etc. The thickness of the protective layer of the present invention formed as described above is preferably 10 to 300 Å.

In the magnetic recording medium of the present invention,
A back coat layer can be further formed on the surface of the support opposite to the surface on which the magnetic layer is formed. The back coat layer may be formed by applying an appropriate back coat paint containing carbon black or the like, or a metal such as Al, Cu, Zn, Sn, Ni, Ag or Si, Ge, As, Sc, It may be formed by depositing a semimetal such as Sb or an alloy thereof by vapor deposition or the like.

Further, in the magnetic recording medium of the present invention,
A top coat layer made of a suitable lubricant may be further formed on the protective layer made of a carbon-silicon thin film. The lubricant may be formed by coating, or may be formed by spraying the lubricant on the protective layer in a vacuum using a sprayer equipped with an ultrasonic oscillator. As the lubricant for forming the top coat layer, a fluorine-based lubricant is preferable, and particularly a perfluoropolyether, for example, “FOMBLINZ DIAC” [carboxyl group-modified,
A commercially available product under the trade name of "FOMBLIN Z DOL" (alcohol-modified, manufactured by Montecatini Co.) can be used. These fluorine-based lubricants are suitable for fluorine-based inert solvents (for example, perfluorocarbons such as "Fluorinert" manufactured by Sumitomo 3M Ltd., perfluoropolyethers such as "Galden" manufactured by Montecatini Co., Ltd.), and alcohol solvents. It is preferable to use it after dissolving it in another solvent. The thickness of the top coat layer is 10 to 200
It is about Å.

[0018]

Embodiments of the present invention will be described below. However, the invention is not limited to these examples.

Example 1 First, Co was vapor-deposited on a PET film having a thickness of 6 μm to form two magnetic layers each having a thickness of 900 Å. next,
This film was set in an ECR plasma CVD device, and a silane coupling agent (A-151, manufactured by Nippon Unicar Co., Ltd.) was introduced into the plasma excitation chamber of the device to contain carbon and silicon on the magnetic layer of the film. A protective layer was formed. The thickness of the protective layer was 100Å. Then, on this protective layer, perfluoropolyether (FOMBLINZ DIAC, manufactured by Montecatini Co., Ltd.), which is a lubricant, was added with a fluorine-based inert solvent (Fluorinert FC-77, manufactured by Sumitomo 3M Co., Ltd.) to a concentration of 0.05% by weight. Apply a diluted solution to achieve a thickness of 0.002 μm
Was formed.

The film having the magnetic layer, the diamond-like carbon protective layer and the fluorine-based lubricating layer obtained above was cut to a width of 8 mm and loaded into a cassette case to obtain an 8 mm video tape. The 8 mm video tape was set in a commercially available 8 mm VTR, and the still mode time until the output decreased by 3 dB at 20 ° C. and 50% RH was measured. For the protective layer of the obtained tape, a scratch tester CSR-02 made by Resca Co., Ltd. was used to apply an indenter with a tip of 5.0 μm to a load of 61.6 mN / mm and a speed of 10.0 μm / sec. The load until the film was broken when the film was swept was measured, and the average value of 5 measurements was obtained. Table 1 shows the results.

Example 2 An 8 mm video tape was prepared in the same manner as in Example 1 except that A-151 manufactured by Nippon Unicar Co., Ltd. was used as the silane coupling agent, and the same test as in Example 1 was conducted. . Table 1 shows the results.

Example 3 An 8 mm video tape was prepared in the same manner as in Example 1 except that the organic silane monomer A-162 manufactured by Nippon Unicar Co., Ltd. was used in place of the silane coupling agent. Was tested. Table 1 shows the results.

Comparative Example 1 An 8 mm video tape was prepared in the same manner as in Example 1 except that methane gas was used instead of the silane coupling agent and a protective layer of diamond-like carbon having a thickness of 100 Å was formed. The same test was performed. Table 1 shows the results.

Comparative Example 2 An 8 mm video tape was produced in the same manner as in Comparative Example 1 except that benzene was gasified and used in place of methane gas to form a protective layer of diamond-like carbon having a thickness of 100 Å. The same test as in Example 1 was performed. Table 1 shows the results.

Comparative Example 3 Example 3 was repeated except that a 100 Å-thick protective layer made of diamond-like carbon was formed by a sputtering method using graphite as a target instead of the ECR plasma CVD method using a silane coupling agent. An 8 mm video tape was prepared in the same manner as in Example 1, and the same test as in Example 1 was performed. Table 1 shows the results.

[0026]

[Table 1]

[0027]

As described above, according to the present invention, a magnetic recording medium having a protective layer with higher durability can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Sasaki 2606 Akabane, Kai-cho, Haga-gun, Tochigi Kao Institute of Stock Research

Claims (5)

[Claims] 1. A magnetic recording medium having a support, a magnetic layer formed on the support, and a protective layer formed on the magnetic layer by an ECR plasma CVD method, wherein the protective layer is carbon. A magnetic recording medium containing silicon. 2. The magnetic recording medium according to claim 1, wherein the ratio of silicon in the protective layer is 0.1 to 45 atom% (several percentages). 3. A step of forming a protective layer containing carbon and silicon on the magnetic layer formed on a support by an ECR plasma CVD method using a silicon-containing organic compound as a raw material. Manufacturing method of magnetic recording medium. 4. The method for manufacturing a magnetic recording medium according to claim 3, wherein the silicon-containing organic compound is an organic silane. 5. The method for producing a magnetic recording medium according to claim 3, wherein the silicon-containing organic compound is a silane coupling agent.