JPS61214125A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability and corrosion resistance of the titled medium by providing a nonmagnetic inorg. protective layer contg. sulfur on the surface of a ferromagnetic metallic thin film layer formed on a substrate and further forming a lubricant layer thereon. CONSTITUTION:A nonmagnetic inorg. protective layer 19 contg. sulfur is formed on a ferromagnetic metallic thin film layer 18 by coating an inorg. material such as titanium along with a sulfur compd. on the ferromagnetic metallic thin film layer 18 by vacuum deposition, etc. A sulfurized fatty acid, etc., as well as elementary sulfur are preferably used as the sulfur compd. The nonmagnetic inorg. protective layer 19 is excellently adhered to the ferromagnetic metallic thin film layer 18, the leaking property of the lubricant layer 20 further formed thereon is excellent since the layer contains sulfur, the adsorptive force is also high and the layer 19 is excellently adhered to the lubricant layer 20.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a magnetic recording medium having a ferromagnetic metal thin film layer as a magnetic recording layer, and more particularly relates to the above-mentioned magnetic recording medium having excellent durability and corrosion resistance. .

[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, sputtering, etc., and has characteristics suitable for high-density recording, but on the other hand, the coefficient of friction with the magnetic head is high, causing wear and damage. It also has disadvantages such as gradual oxidation in the air and deterioration of magnetic properties such as maximum magnetic flux density.

For this reason, various protective layers have been conventionally provided on the ferromagnetic metal thin film layer to improve durability and corrosion resistance. It has been proposed to provide a protective layer on the ferromagnetic metal thin film layer and further provide a lubricant layer on the nonmagnetic inorganic protective layer. (Unexamined Japanese Patent Publication No. 57-164433)
[Problems to be Solved by the Invention] However, this kind of non-magnetic inorganic protective layer such as metal oxide or metal nitride has poor adhesion to the lubricant layer formed thereon, and has difficulty in bonding with the magnetic head. The lubricant layer may be peeled off or destroyed in a relatively short period of time due to sliding contact.
Durability and corrosion resistance have not yet been sufficiently improved.

[Means for solving problems]

This invention was made as a result of various studies in view of the current situation, and includes providing a non-magnetic inorganic protective layer containing sulfur on the surface of a ferromagnetic metal thin film layer, and further forming a lubricant layer on the surface of the ferromagnetic metal thin film layer. By the action of sulfur contained in the non-magnetic inorganic protective layer, the wettability and adsorption of the lubricant layer to the non-magnetic inorganic protective layer are improved, and the adhesion of the lubricant layer to the non-magnetic inorganic protective layer is improved. A nonmagnetic inorganic protective layer and a lubricant layer are firmly adhered to the ferromagnetic metal thin film layer, thereby sufficiently improving durability and corrosion resistance.

In this invention, the formation of a non-magnetic inorganic protective layer containing sulfur on a ferromagnetic metal thin film layer includes titanium, tantalum,
Inorganic substances such as carbon, silicon, germanium, tin, lead, zirconium, hafnium, antimony, bismuth, vanadium, niobium, selenium, tellurium, boronium, ascutin, etc., are combined with sulfur compounds by methods such as vacuum evaporation, sputtering, and ion blating. This is done by depositing on a thin ferromagnetic metal layer. The non-magnetic inorganic protective layer thus formed may be made of oxides or nitrides of these inorganic substances as well as the above-mentioned inorganic substances, or a mixture thereof. In addition to simple sulfur, sulfurized fatty acids and the like are preferably used as the sulfur compound contained in this nonmagnetic inorganic protective layer. These sulfur compounds need to be contained in a small amount on the surface of the non-magnetic inorganic protective layer, but if they are contained in the surface, they do not necessarily need to be contained in the entire non-magnetic inorganic protective layer. The sulfur-containing non-magnetic inorganic protective layer formed in this manner is obtained by depositing a ferromagnetic material on a substrate by a method such as vacuum evaporation, sputtering, or ion blasting, and then immediately and subsequently reinforcing it by the same method. It is extremely easy to form because it can be deposited on a magnetic metal thin film layer.Furthermore, this type of nonmagnetic inorganic protective layer containing sulfur has extremely good adhesion with the ferromagnetic metal thin film layer. Also, since it contains sulfur, the lubricant layer formed on top of it has good wettability and strong adsorption power (
, has extremely good adhesion with the lubricant layer, so it is firmly adhered to the ferromagnetic metal thin film layer, and when the lubricant layer is formed on the sulfur-containing non-magnetic inorganic protective layer, the lubricant layer is strongly adhered to, and corrosion resistance and durability are sufficiently improved. The layer thickness is between the ferromagnetic metal thin film layer and the lubricant layer and is preferably within the range of 50 to 500 layers in order to ensure sufficiently good adhesion between the two. As a result, the spacing loss may increase (and the electromagnetic conversion characteristics may deteriorate).

A lubricant layer that is further deposited on the surface of the sulfur-containing nonmagnetic inorganic protective layer thus formed includes lubricants such as toluene, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, ethyl acetate, tetrahydrofuran, The sulfur-containing non-magnetic inorganic protective layer is dissolved in a suitable solvent such as dimethylformamide or dioxane, and the sulfur-containing non-magnetic inorganic protective layer is immersed in the resulting solution, or the sulfur-containing non-magnetic inorganic protective layer is coated with the sulfur-containing non-magnetic inorganic protective layer. This can be done by coating or spraying, or by vacuum depositing a lubricant on the sulfur-containing non-magnetic inorganic protective layer.

The lubricant used is not particularly limited, but includes, for example, fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid, fatty acid metal salts such as zinc stearate, fatty acid amides such as stearic acid amide, and stearic acid. Fatty acid esters such as n-butyl and octyl myristate, aliphatic alcohols such as stearyl alcohol and myristyl alcohol, fluorinated fatty acids such as perfluoroalkylcarboxylic acids, CF3 (CF2)s (
Fluorinated fatty acid esters such as CH2)20H and phosphate esters such as trialkyl phosphate esters are preferably used, and these lubricants may be used alone or in combination of two or more. used.

The thickness of the lubricant layer formed using such a lubricant is preferably within the range of 20 to 500 layers, and if it is thinner than 20 layers, its excellent lubrication effect cannot be fully exhibited. Therefore, the coefficient of friction could not be sufficiently reduced, and the
thicker than 0 (then the spacing loss will be too large and have a negative effect on the electromagnetic conversion characteristics).

The material for forming the ferromagnetic metal thin film layer is C01F e
%NilCoNi alloy, (, o-Cr alloy,
Ferromagnetic materials such as Co-P alloy and Co-N1-P alloy are used, and ferromagnetic metal thin film layers made of these ferromagnetic materials can be formed by vacuum evaporation, ion blasting, sputtering,
It is deposited on the substrate by means such as plating.

In addition, as the substrate, any conventionally used materials such as synthetic resin films such as polyester films and polyimide films, aluminum plates and glass plates are suitably used, and as the magnetic recording medium,
Magnetic tapes using synthetic resin films such as polyester films and polyimide films as base materials,
It includes various forms of structure that come into sliding contact with a magnetic head, such as magnetic disks and magnetic drums that use a disk made of synthetic resin film, aluminum plate, glass plate, etc. as a base.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 Using the vacuum evaporation apparatus shown in FIG. 1, a polyimide film 1 with a thickness of 50 μm was moved from a raw roll 3 in a vacuum chamber 2 to a circumferential side of a cylindrical can 5 via a guide roll 4. Further, it was moved along the circumferential surface of the cylindrical can 8 via guide rollers 6 and 7, and set so as to be wound onto a winding roll 10 via a guide roll 9.

Next, the vacuum chamber 2 is evacuated to 1×10 4 Torr using an exhaust system 11 attached to its side wall, and a ferromagnetic material evaporation source 12 disposed below the cylindrical can 5 is used to evacuate cobalt.
A chromium alloy (weight ratio 80:20) 13 is heated and evaporated, and a polyimide film 1 is vacuum-deposited while being heated to a temperature of 250°C in a cylindrical can 5 to form a ferromagnetic film made of a cobalt-chromium alloy with a thickness of 0.2μ. A metal thin film layer was formed. Next, while the polyimide film 1 on which the ferromagnetic metal thin film layer made of cobalt-chromium alloy is moved along the circumferential side of the cylindrical can 8, an inorganic evaporation source disposed below the cylindrical can 8 is moved. At the same time, titanium 15 is heated and evaporated in step 14, and sulfur 17 is heated and evaporated in sulfur compound evaporation source 16, which is also placed below the cylindrical can 8, for vacuum deposition. A non-magnetic inorganic protective layer made of titanium containing 200 μm of sulfur was formed on the film layer.Next, Talitefuchs (manufactured by DuPont, with terminal ends A 0.1% by weight Freon solution of (carboxylated perfluoropolyether) was applied and dried to form a lubricant layer made of Krytox. After that, it is punched out into a disk shape, and on the polyimide film 1 as shown in FIG.
A magnetic disk A was prepared by sequentially laminating the following layers. In addition, 21 and 22 in the figure are adhesion prevention plates.

Example 2 In Example 1, a polyimide film with a thickness of 12 μm was used instead of the polyimide film with a thickness of 50 μm, and a cobalt-nickel alloy (weight ratio: 80: 20) was used to perform oblique incidence evaporation, carbon was evaporated instead of titanium using the inorganic evaporation source 14, and 0.1% by weight benzene solution of stearic acid was used instead of the 0.1% Freon solution of Talitox. A ferromagnetic metal thin film layer made of a cobalt-nickel alloy with a thickness of 0.1 μm was used on a polyimide film, and a non-magnetic inorganic protection layer made of carbon containing sulfur with a thickness of 200 μm was used on the polyimide film. and a lubricant layer consisting of 100 g stearic acid. Thereafter, a ferromagnetic metal thin film layer 18, a non-magnetic inorganic protective layer 19 mixed with sulfur, and a lubricant layer 20 are sequentially laminated on the polyimide film 1 cut to a predetermined width as shown in FIG. I made magnetic tape B.

Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1 except that the formation of the sulfur-containing nonmagnetic inorganic protective layer was omitted.

Comparative Example 2 A magnetic tape was produced in the same manner as in Example 2, except that the formation of the sulfur-containing nonmagnetic inorganic protective layer was omitted.

Comparative Example 3 Example 1 except that the formation of the sulfur-containing nonmagnetic inorganic protective layer and the lubricant layer were omitted.
I made a magnetic disk in the same way.

Comparative Example 4 Example 2 except that the formation of the sulfur-containing nonmagnetic inorganic protective layer and the lubricant layer were omitted.
I made magnetic tape in the same way.

The magnetic disks and magnetic tapes obtained in each Example and Comparative Example were tested for durability and corrosion resistance. To test the durability of a magnetic disk, a floppy drive was used to perform recording and playback on the resulting magnetic disk at a recording density of 10 KBPI, and the number of times the magnetic head slid until the output decreased to 80% of the initial output was measured. I went. The durability of the magnetic tape was also tested by performing a still test on the obtained magnetic tape and measuring the still playback life. Furthermore, a corrosion resistance test was conducted on the obtained magnetic disks and magnetic tapes at 60°C and 90°C.
The maximum magnetic flux density was measured after being left under the condition of 0% RH for 7 days, and the deterioration rate was compared with the maximum magnetic flux density of the magnetic tape before being left as 100%.

The table below shows the results.

〔Effect of the invention〕

As is clear from the above table, the magnetic disks and magnetic tapes obtained in Examples 1 and 2 had a greater number of sliding movements than the magnetic disks and magnetic tapes obtained in Comparative Examples 1 to 4. The still playback life is long and the deterioration rate is small, which indicates that the magnetic recording medium obtained by the present invention has further improved durability and corrosion resistance.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of a vacuum evaporation apparatus used in manufacturing the magnetic recording medium of the present invention, and FIG. 2 is a partially enlarged sectional view of a magnetic disk obtained by the present invention.
FIG. 3 is a partially enlarged sectional view of a magnetic tape obtained by the present invention. DESCRIPTION OF SYMBOLS 1... Polyimide film (substrate), 18... Ferromagnetic metal thin film layer, 19... Non-magnetic inorganic protective layer containing sulfur, 20... Lubricant layer, A... Magnetic disk (
magnetic recording medium), B...magnetic tape (magnetic recording medium Fig. 1, Fig. 2, Fig. 3)

Claims (1)

[Claims] 1. A ferromagnetic metal thin film layer made of metal or an alloy thereof is formed on a substrate, a nonmagnetic inorganic protective layer containing sulfur is provided on the surface of this ferromagnetic metal thin film layer, and a lubricant layer is further provided on this. A magnetic recording medium characterized by forming