JPS6116030A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain excellent durability by exposing a thin ferromagnetic metallic film layer formed on a base body into the gaseous monomer of an org. compd. mixed with a photopolymn. initiator thereby forming a protective film on the thin ferromagnetic metallic film. CONSTITUTION:The thin ferromagnetic metallic film layer 9 is formed on the base body 1 then the layer 9 is exposed into the gaseous monomer of the org. compd. mixed with the photopolymn. initiator by which the plasma polymn. is executed and the plasma-polymerized protective layer 10 consisting of the org. compd. is formed on the film 9. The polymn. reaction of the org. compd. monomer, for example, ethylene, etc. is accelerated by such plasma polymn., by which the crosslinking density of the layer 10 is increased. The hard protective layer 10 is thus securely deposited and formed on the layer 9, by which the coefft. of friction is decreased and the durability is improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a magnetic recording medium having a ferromagnetic metal thin film layer as a magnetic recording layer. Regarding recording media.

[Conventional technology]

A magnetic recording medium whose magnetic recording layer is a ferromagnetic metal thin film layer is
It is usually made by depositing metals or their alloys on a base film by vacuum deposition, etc., and has characteristics suitable for high-density recording, but on the other hand, it has a high coefficient of friction with the magnetic head, making it susceptible to wear and damage. The problem is that it is easy to break and has poor durability.

For this reason, attempts have been made to improve durability and corrosion resistance by forming various protective film layers on the ferromagnetic metal thin film layer. By polymerizing, a plasma polymerized protective film layer of a fluorine-based organic compound is provided on a ferromagnetic metal thin film layer (Japanese Patent Application Laid-Open No. 58-88828°C, Japanese Patent Application Laid-Open No. 58-102).
No. 330), or a plasma polymerized protective film layer of a silicon-based organic compound is provided on a ferromagnetic metal thin film layer by plasma polymerizing a silicon-based organic compound chloride gas (JP-A No. 57-82229, JP-A No. 82229/1989). No. 58-60427) Koki has been proposed.

[Problem that the invention seeks to solve]

However, the plasma-polymerized protective film layer of an organic compound obtained by this conventional method does not yet have sufficient crosslinking density, so the film strength is weak and the coefficient of friction is large, resulting in insufficient improvement in durability, especially during plasma polymerization. If the deposition speed is increased by increasing the gas pressure, plasma polymerization occurs at a relatively low molecular weight, and the density of the 4F5 film decreases, making it impossible to obtain a hard protective film layer and not achieving good wear resistance. There was a problem.

[Means for solving problems]

This invention was made as a result of various studies in light of the current situation, and when forming a plasma polymerized protective film layer of an organic compound on the surface of a ferromagnetic metal thin film layer, an organic compound mixed with a photopolymerization initiator is used. By performing plasma polymerization using 70% gas, the crosslinking density of the plasma polymerized protective film layer is improved, a relatively hard plasma polymerized protective film layer is formed, and the abrasion resistance is improved to ensure sufficient durability. This has been improved.

In this invention, the plasma polymerized protective film layer is formed on the ferromagnetic metal thin film layer in a treatment tank using a hydrocarbon compound,
A photopolymerization initiator is mixed into a monomer gas such as a fluorine-based organic compound and a silicon-based organic compound, and this mixed gas is plasma-polymerized using high frequency waves to be deposited on a ferromagnetic metal thin film layer. When a photopolymerization initiator is mixed into the organic compound gas, a large amount of radicals are generated by the photopolymerization initiator during plasma polymerization, promoting plasma polymerization and forming a plasma polymerization protective film layer. Crosslink density is improved. As a result, a relatively hard plasma-polymerized protective film layer is firmly deposited and formed on the ferromagnetic metal thin film layer, the coefficient of friction is reduced, and the durability is sufficiently improved.

Examples of the monomer gas used to form this plasma-polymerized protective film layer include monomer gases of hydrocarbon compounds such as propane, ethylene, propylene, acetonitrile, and flopionitrile, C2F4, C3F6, etc.
Monomer gas of fluorine-based organic compounds such as tetramethylsilane, octamethylcyclotetrasiloxane,
Monomer gases of silicon-based organic compounds such as hexamethyldisilazane are preferably used.
The generated radicals react and polymerize to form a film.

The more double bonds or double bonds these organic compounds have, the more easily this radical is generated, so those having these unsaturated bonds are more preferably used. Also,
When plasma polymerizing these 7-mer gases, if a carrier gas such as argon gas, helium gas, or oxygen gas is present, the deposition rate is 3 to 5 times faster than when plasma polymerizing 7-mer gases alone. It is preferable to use these carrier gases together. When coexisting with these carrier gases, the composition ratio is 1:1 in terms of the ratio of the carrier gas to the 7-mer gas of the organic compound.
It is preferable to coexist within a range of ~20:1; if the carrier gas is too small, the deposition rate will decrease, and if it is too large, the monomer gas will be too small (which will interfere with the plasma polymerization reaction. When using a monomer gas of a compound, it is not preferable to use oxygen gas as a carrier gas because an oxidation reaction will occur if oxygen gas is used as a carrier gas.

When carrying out such plasma polymerization, the photopolymerization initiator used by mixing with the organic compound gas is as follows:
Preferred examples include henzine ethers, hensifenones, xanthones, acetophenone derivatives, hensyl, 2-ethylanthraquinone, methylbenzoylformate, 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexylphenyl ketone, and the like. used as. The blending ratio of such a photopolymerization initiator to the monomer gas of the organic compound is 0.5 to 100 in terms of gas pressure ratio of the photopolymerization initiator to the monomer gas of the organic compound.
The ratio is preferably in the range of 10:100; if the amount of photopolymerization initiator is too small, the desired effect cannot be obtained, and if it is too large, the plasma polymerization protective film layer becomes brittle and easily damaged.

When performing plasma polymerization using a monomer gas of an organic compound mixed with a photopolymerization initiator, the higher the gas pressure, the faster the deposition speed, while the monomer gas is relatively low. It is difficult to obtain a hard protective film layer due to plasma polymerization due to low molecular weight, and if the gas pressure is lowered and the radio frequency power is increased, the deposition speed becomes slower, but on the other hand, a relatively hard protective film layer made of polymers can be obtained. If the gas pressure is too low and the high frequency power is too high, the monomer gas will turn into powder and a plasma polymerized protective film layer will not be formed.
The high frequency power per square senna is 0.1 to 5 W/
The gas pressure is preferably within the range of cnl, and the gas pressure is 0.0
More preferably, the high frequency power per square centimeter is within the range of 0.5 to 3 W/cJ. In this way, the plasma polymerized protective film layer of an organic compound that is formed by plasma polymerization using a monomer gas of an organic compound mixed with a photoinitiator has a large amount of radicals generated by the photoinitiator. As a result of the plasma polymerization being promoted and the crosslinking density of the plasma polymerized protective film layer being improved, the plasma polymerized protective film layer is dense and has a small friction coefficient, and therefore, when a plasma polymerized protective film layer of this organic compound is formed, the durability is further improved. The thickness of such a plasma-polymerized protective film layer of an organic compound is preferably within the range of 20 to 10 OO. If the film thickness is too thin, the durability effect of this protective film layer will not be sufficiently exhibited. If it is too thick, the spacing loss will be too large, which will adversely affect the electromagnetic conversion characteristics.

The material for forming the ferromagnetic metal thin film layer is C01Fe, N
i, Co-Ni alloy, Co-Cr alloy, Co-P alloy,
A ferromagnetic material such as a Co-N1-P alloy is used, and a ferromagnetic metal thin film layer made of these ferromagnetic materials is deposited on a substrate by means such as vacuum evaporation, ion blasting, sputtering, or plating. Ru.

In addition, as magnetic recording media, polyester film,
Magnetic tapes based on synthetic resin films such as polyimide films, magnetic disks and magnetic drums based on disks and drums made of synthetic resin films, aluminum plates, glass plates, etc., have a structure that makes sliding contact with magnetism. It includes various forms.

〔Example〕

Next, embodiments of the invention will be described.

Examples 1 to 6 A polyester film with a thickness of 10μ was loaded into a vacuum binding device, and cobalt was added to it under an atmosphere of lXl0-5 torr.
Polyester film with a thickness of 1000%
A ferromagnetic metal thin film layer made of cobalt was formed. Next, using the plasma processing apparatus shown in FIG. 1, the polyester film 1 on which the ferromagnetic metal thin film layer was formed was placed on the lower surface of the substrate 3 disposed at the upper part of the processing tank 2, and then attached to the processing tank 2. Tetramethylsilane monomer gas was introduced from the gas introduction tube 4, and hesiphenone was introduced from the gas introduction tube 5 at various flow rates as shown in Table 1 below. Plasma polymerization was performed while adjusting the time so that the thickness of the protective film layer was 0.05 μm to form a plasma polymerized protective film layer. Thereafter, it was cut to a predetermined size I+, and a magnetic tape A was prepared by sequentially laminating a ferromagnetic metal thin film layer 9 and a plasma polymerized protective film layer 10 on a polyester film 1'' as shown in FIG. In the figure, 7 is an exhaust system for reducing the pressure inside the processing tank 2, and 8 is a high-frequency power source for applying high-frequency waves to the electrodes 6.

Table 1 Example 7 In the formation of the plasma polymerized protective film layer in Example 1, the same amount of acetonitrile monomer gas was used instead of tetramethylsilane monomer gas, and the flow rate of hensifenone was 2 m ft / min. Other than that, Example 1
A plasma polymerized protective film layer was formed in the same manner as described above, and a magnetic tape was manufactured.

Example 8 In the formation of the plasma polymerized protective film layer in Example 1, c2
A plasma polymerized protective film layer was formed and a magnetic tape was produced in the same manner as in Example 1, except that the same amount of F4 monomer gas was used and the flow rate of hensifenone was 2 ml/min.

Example 9 Plasma polymerization was carried out in the same manner as in Example 1, except that in the formation of the plasma-polymerized protective film layer in Example 1, methyl-enduylformate was used at a flow rate of 1 ml/min in place of hensifenone. (〉A protective film layer was formed and a magnetic tape was made.

Example 10 Example 7 except that methyl benzoyl formate was used at a flow rate of 1 mR/min in place of benzophenone in forming the plasma polymerized protective film layer in Example 7.
A plasma polymerized protective film layer was formed in the same manner as described above, and a magnetic tape was manufactured.

Example 11 Example 8 except that in the formation of the plasma polymerized protective film layer in Example 8, methyl benzoyl formate was used at a flow rate of 1 mρ/min in place of hensifhenone.
A plasma polymerized protective film layer was formed in the same manner as described above, and a magnetic tape was manufactured.

Example 12 A polyimide film with a thickness of 50 μm was loaded into a vacuum evaporation apparatus, and the polyimide film L was heated to 300° C.
A ferromagnetic metal thin film layer consisting of a cobalt-chromium alloy (molar ratio 82:18) with a thickness of 3500 mm was formed on a polyimide film by heating and evaporating the cobalt-chromium alloy under a vacuum of 10-61 mm. . Next, Example 3 was added to this.
A plasma polymerized protective film layer was formed in the same manner as described above, and a magnetic tape was manufactured.

Comparative Example 1 A magnetic tape was produced by plasma polymerization in the same manner as in Example 1 except that the introduction of hensifenone was omitted in the formation of the plasma polymerized protective film layer in Example 1.

Comparative Example 2 A magnetic tape was produced by plasma polymerization in the same manner as in Example 7, except that in the formation of the plasma polymerized protective film layer in Example 7, the introduction of hensifenone was omitted.

Comparative Example 3 A magnetic tape was produced in the same manner as in Example 1 except that the formation of the plasma polymerized protective film layer was omitted.

Comparative IS-4 In Example 12, a magnetic tape was produced in the same manner as in Example 1 except that the formation of the plasma polymerized protective film layer was omitted.

The magnetic tape obtained in each Example and Comparative Example was cut into 5 mm width, and the elastic modulus was measured using a tensile tester. Comparative Example 3 The elastic modulus of the plasma polymerized protective film layer was determined by subtracting the elastic modulus obtained in . Further, as shown in FIG. 3, a load 11 is applied to one end of the magnetic tape A, and the pin 13 hangs down from the circumferential side of the cylindrical SOS pin 12, and the other end of the magnetic tape A is placed parallel to the SUS pin 12. The magnetic tape A was attached to the strain gauge 14 via the magnetic tape A, and the magnetic tape A was pulled horizontally at a speed of 1 m/min, and the coefficient of friction with the SUS pin 13 at this time was measured. Furthermore, when the magnetic tapes obtained in each Example and each Comparative Example were left for 7 days at 60°C and 190% RH, and their surfaces were observed with the naked eye, the magnetic tapes obtained in Comparative Examples 3 and 4 were Although many black pits were observed, no abnormality was observed in the surface gloss of the magnetic tapes obtained in each Example and Comparative Example 1.2.

Table 2 below shows the results.

Table 2 [Effects of the Invention] As is clear from the above table, the magnetic tapes obtained by the present invention (Examples 1 to 12) were all compared to the magnetic tapes obtained in Comparative Examples 1 to 4. The magnetic recording medium has a high elastic modulus and a low friction coefficient, and therefore, according to the manufacturing method of the present invention, the plasma polymerized protective film layer is cured by the action of a photopolymerization initiator, and the durability is further improved. It can be seen that the following can be obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an example of a plasma processing apparatus used in forming a plasma polymerized protective film layer, and FIG. 2 is a partially enlarged sectional view of a magnetic tape obtained by the manufacturing method of the present invention. FIG. 3 is an explanatory diagram of the friction coefficient measuring method.

Claims (1)

[Claims] 1. A ferromagnetic metal thin film layer is formed on a substrate, and then this ferromagnetic metal thin film layer is exposed to a monomer gas of an organic compound mixed with a photopolymerization initiator to perform plasma polymerization. A method for producing a magnetic recording medium, comprising forming a polymerized protective film layer on a ferromagnetic metal thin film layer.