JPH01106313A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve lubrication durability, traveling property and wear resistance and to maintain these properties for a long period of time by providing at least one high-polymer layer of polymerizable LB film on the surface of a metal oxide layer formed on a thin ferromagnetic metallic film provided on a nonmagnetic substrate. CONSTITUTION:The thin ferromagnetic metallic film 2 consisting of a ferromagnetic material such as iron is formed on the nonmagnetic substrate 1 consisting of a film, sheet, etc., of a ceramics material, etc. A vacuum deposition method, sputtering method, etc., are used for the formation of said film. The metal oxide layer 3 consisting of SiO2, TiO2, etc., is formed by the vacuum deposition method, sputtering method, etc., on the thin ferromagnetic metallic film 2. The film thickness in the case of forming the metal oxide layer 3 on the thin ferromagnetic metallic film 2 is adequately 5-40nm. At least one high-polymer layer 4 of the polymerizable LB film is provided by, for example, a Langmuir- Blodgett's (LB) film contains at least one of long chain fatty acid having an unsatd. bond and the vinyl ester of the long-chain fatty acid. The LB film of the recording medium is ground off and lost by friction with a magnetic head, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high recording density magnetic recording medium used in the information industry and the like.

Conventional technology Conventional 7-Fe2O3, Co-containing 7-Fe2O3, C
Instead of coating-type magnetic recording media in which ferromagnetic powder such as rO2 is dispersed in an organic binder and coated on a non-magnetic substrate, ferromagnetic metal can be produced by methods such as plating, sputtering, vacuum evaporation, and ion plating. Magnetic recording media in which a thin film is provided on a nonmagnetic substrate are being researched as magnetic recording media for high recording density.

However, magnetic recording media using ferromagnetic metal thin films produced by the method described above have problems with lubricity, running properties, and wear resistance.

To begin with, magnetic recording media are placed under high-speed relative motion with a magnetic head during the process of recording and reproducing magnetic signals. At this time, the magnetic recording medium must run smoothly and stably.

Furthermore, wear and damage due to contact with the magnetic head must not occur.

However, the ferromagnetic metal thin film made by the method described above cannot withstand the harsh conditions of the magnetic recording and reproducing process, causing unstable running due to friction with the magnetic head, etc., and the formation of wear particles. Occasionally, the output would drop significantly due to this occurrence. Therefore, it has been proposed to form a monomolecular layer of saturated fatty acid or its metal salt directly on a ferromagnetic metal thin film (Japanese Unexamined Patent Publication No. 75001/1982).
Problems to be Solved by the Invention However, in this case, although there is a slight improvement in the initial lubricity, there is no lubricity durability, and running stability and wear resistance are still not sufficient. This is because the membrane strength of the molecular layer made of saturated fatty acids is weak, and the saturated fatty acids are broken off by the magnetic head or the like that slides while the vehicle is running.

The present invention has been made in view of the above, and an object of the present invention is to provide a magnetic recording medium with excellent lubricity, durability, runnability, and abrasion resistance.

Means for solving the problem A metal oxide layer is formed on a ferromagnetic metal thin film provided on a non-magnetic substrate, and at least one polymer layer of a polymerizable LB film is formed on the surface of the metal oxide layer. establish.

Since the LB film of long-chain fatty acids and the like having active unsaturated bonds is polymerized to form a polymer, the film strength of the LB film itself is higher than that of LBfi made of low molecules. In addition, since the bond between the metal oxide and the polymer layer of the polymerizable LB film is strong, the LB film is not scraped off by friction with a magnetic head, etc., and the lubrication durability, runnability, and wear resistance are improved. An excellent magnetic recording medium can be obtained.

The embodiment diagram is a cross-sectional view of the magnetic recording medium of the present invention. In the figure, 1 is a nonmagnetic substrate, 2 is a ferromagnetic metal thin film, 3 is a metal oxide layer, and 4 is a polymer layer of a polymerizable LB film.

Examples of the non-magnetic substrate 1 that can be used in the magnetic recording medium of the present invention include polymer materials such as polyvinyl chloride, cellulose acetate, polyethylene terephthalate, polyimide, and polyamide, non-magnetic metal materials, and ceramic materials such as glass and porcelain. There are films, plates, etc. made of well-known materials.

Further, as the ferromagnetic material forming the ferromagnetic metal thin film 2 that can be used in the magnetic recording medium of the present invention, any known material can be used, such as an alloy of one or more of iron, cobalt, and nickel, or an alloy of these. There are alloys that are a combination of and other metals such as manganese, chromium, titanium, phosphorus, yttrium, samarium, bismuth, etc., and there are also oxides of the above metals.

The ferromagnetic metal thin film 2 can be formed on the non-magnetic substrate 1 by any known method such as a vacuum evaporation method, a sputtering method, an ion blasting method, or a plating method.

According to the present invention, a metal oxide layer such as SiO2, TiO2, A12O3, etc. is formed on the ferromagnetic metal thin II5 and 2 described above.

The metal oxide layer 3 can be formed by a sputtering method, a vacuum evaporation method, or the like.

According to the present invention, a metal oxide layer 3 is formed on the ferromagnetic metal thin film 2.
When forming a film, the film thickness is preferably 5 to 40 nm.

When the film thickness was made larger than 40 nm, the output decreased due to spacing loss during signal reproduction.

Furthermore, when the layer thickness was less than 5 m, pinholes were likely to occur, and the lubricity and durability expected from the combined effect of the polymerizable LB film with the polymer film could not be observed.

According to the present invention, a polymer layer 4 of a polymerizable LB film is provided on the metal oxide layer 3 described above.

The polymerizable LB film that can be used in the present invention contains at least one of a long chain fatty acid having an unsaturated bond, a vinyl ester of a long chain fatty acid, or a long chain alkyl ester of acrylic (methacrylic) acid.

Examples of long-chain fatty acids having unsaturated bonds include α-octadecyl acrylic acid, ω-tricosenic acid, 16-hebutadenoic acid, and octadecadienoic acid.

Examples of vinyl esters of long chain fatty acids include vinyl stearate, vinyl palmitate, vinyl oleate, and the like.

Examples of long chain alkyl esters of acrylic (methacrylic) acids include stearyl acrylic (methacrylic) acid,
Examples include palmityl acrylic (methacrylic) acid, araquinyl acrylic (methacrylic) acid, and the like.

A method for forming the polymer film layer 4 of the polymerizable LB film on the metal oxide layer 3 is the Langmuir-Blodgett (LB) method (Phys, Rev, 5H1937).
)964. ).

According to the present invention, on the metal oxide layer 3, the polymerizable LBJl
When forming the polymer layer 4 of i, 1 to 21 layers were suitable, and 3 to 15 layers were preferable from the viewpoint of slipperiness. However, the film thickness must be 50 m or less. If the thickness exceeds 50 m, the output will decrease due to spacing loss during signal reproduction, which is not preferable.

To polymerize LBrtA, after forming an LB film, it is irradiated with gamma rays, ultraviolet rays, or electron beams to polymerize.

The present invention will be explained below by giving specific examples.

Example 1 A 150 nm thick ferromagnetic metal thin film made of cobalt (90%)-chromium (10%) was formed on a 10 μm thick polyimide film substrate by vacuum deposition. Next, S i 02 is deposited on this ferromagnetic metal thin film by sputtering.
A film of 10 m was formed. From this board 10100X10
Cut out a piece of size 0 and place it on top of the metal thin film.
Three monomolecular layers of α-octadecyl acrylic acid were formed using a film accumulation device (manufactured by Kyowa Interface Science). Next, ultraviolet rays with an energy amount of 200 m J/cm 2 were irradiated using a high-pressure mercury lamp to polymerize the cumulative film.

Examples 2 to 6 Samples were prepared by replacing α-octadecyl acrylic acid in Example 1 with a compound having the composition shown below, and polymerizing cumulative films under the same conditions.

Example 2 ω-Trichosenic acid Example 3 Vinyl stearate Example 4 Vinyl palmitate Example 5 Stearyl acrylate Example 6 Palmityl acrylate Examples 7 to 8 5i02 in Example 1 was replaced with an oxide having the following composition , a sample was prepared by polymerizing the cumulative film under the same conditions.

Example 7 TiO□ Example 8 Al□03 Comparative Example A monomolecular film was formed by replacing α-octadecyl acrylic acid in Example 1 with the following compound.

Comparative Example 1 Stearic Acid Comparative Example 2 Palmitic Acid When the polymerized films of the samples prepared in Examples 1 to 8 were measured with an ellipsometer, the film thickness was 7 to 8 nm.

The dynamic friction coefficients of the samples of Examples 1 to 8 and Comparative Examples 1 to 2 were measured using a friction body count meter (DFPM meter, manufactured by Kyowa Interface Science). The head used was a steel ball with a diameter of 3 mm, and the head load was 100 g.
The measurement was performed at a head running speed of 1.0 mm/s. The results are shown in the table below.

(Margins below) Table (Continued) From the data in the table, the magnetic recording media of Examples 1 to 8 according to the present invention have a low coefficient of dynamic friction not only at the initial stage but also after 200 reciprocations, and in terms of lubricity and durability, compared It turns out that this is better than the example.

Furthermore, when these magnetic recording media were cut into pieces with a diameter of 75 mm and run on a test machine having the same function as a commercially available floppy disk, all of the magnetic recording media of Examples 1 to 8 were able to last for 100 hours. Even after that, the running is stable,
No wear scratches were observed. On the other hand, the magnetic recording medium of the comparative example ran unstable, and wear scratches were observed on the magnetic surface. In the above embodiments, magnetic disks have been described, but it is clear that the magnetic recording medium of the present invention can also be applied to magnetic tapes, magnetic cards, and the like.

Effects of the Invention The magnetic recording medium of the present invention has excellent lubricity durability, runnability, and abrasion resistance, and can maintain these properties for a long time.

[Brief explanation of the drawing]

The figure is a sectional view of a magnetic recording medium in an embodiment of the present invention. 1...Nonmagnetic substrate, 2...Ferromagnetic metal thin film, 3
...metal oxide layer, 4...polymerizable LBII polymer film layer.

Claims (3)

[Claims] (1) A magnetic recording medium in which a metal oxide layer is formed on a ferromagnetic metal thin film provided on a nonmagnetic substrate, and at least one polymer layer of a polymerizable LB film is provided on the surface of the metal oxide layer. . (2) Claim 1, wherein the polymerizable LB film contains at least one of a long chain fatty acid having an unsaturated bond, a vinyl ester of a long chain fatty acid, or a long chain alkyl ester of acrylic (methacrylic) acid. The magnetic recording medium described. (3) The magnetic recording medium according to claim 1, wherein the metal oxide layer has a thickness of 5 to 40 nm.