JPH0465449B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a high recording density magnetic recording medium used in the information industry and the like. Conventional technology This technology replaces the conventional coated magnetic recording media in which ferromagnetic powders such as γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , CrO ₂ are dispersed in an organic binder and coated on a non-magnetic substrate. ,
Magnetic recording media in which a ferromagnetic metal thin film is provided on a nonmagnetic substrate by methods such as plating, sputtering, vacuum evaporation, and ion plating are being studied as magnetic recording media for high-density recording. However, magnetic recording media using ferromagnetic metal thin films made by the method described above have poor slipperiness, running properties,
There are problems with wear resistance. In the first place, a magnetic recording medium is subjected to 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.
Also, wear and damage due to contact with the magnetic head must not occur. However, the ferromagnetic metal thin film made by the above method cannot withstand the harsh conditions of the magnetic recording and reproducing process, and the running becomes unstable due to the friction of the magnetic head, etc., and wear particles are generated. In some cases, the output decreased significantly. 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. 50-75001) Problems to be Solved by the Invention However, in this case, although the initial lubricity is slightly improved, there is no lubricity durability, and running stability and wear resistance are also affected. I cannot say that it is still sufficient. This is because the bond between the monomolecular layer of saturated fatty acids and the ferromagnetic metal thin film is weak at the level of physical adsorption, and the saturated fatty acids are scraped off by the sliding magnetic head or the like during running. The present invention has been made in view of these points, 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 ferrite-containing layer is formed on a ferromagnetic metal thin film provided on a non-magnetic substrate, and at least one layer of monolayer consisting of saturated fatty acids or metal salts thereof is coated on the surface of the ferrite-containing layer. Provide a molecular layer. Effect: A monomolecular layer of saturated fatty acids or their metal salts strongly binds polar groups toward ferrite. Therefore, the compound is not scraped off by friction with a magnetic head, etc., so that a magnetic recording medium with excellent lubrication durability, runnability, and wear resistance can be obtained. The reason why the above compound strongly binds to ferrite is presumed to be because it forms bonds such as coordinate bonds with metal ions in ferrite and is chemically adsorbed. Embodiment The figure is a sectional view of a 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 ferrite-containing layer, and 4 is a monomolecular layer made of a saturated fatty acid or a metal salt thereof. Examples of the nonmagnetic substrate 1 that can be used in the magnetic recording medium of the present invention include polymeric materials such as polyvinyl chloride, cellulose acetate, polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyimide, and polyamide, nonmagnetic metal materials, glass, and porcelain. There are films, plates, etc. made of well-known materials such as ceramic materials such as . 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 in combination with other metals such as manganese, chromium, titanium, phosphorus, yttrium, samarium, bismuth, etc., and oxides of the above metals. In forming the ferromagnetic metal thin film 2 on the non-magnetic substrate 1, vacuum evaporation method, sputtering method,
It can be formed by any known method such as ion plating method or plating method. In the present invention, the above-mentioned ferromagnetic metal thin film 2
The key point is to provide the ferrite-containing layer 3 on top of the ferrite-containing layer 3. The ferrite that can be used in the present invention has the general formula
It has the composition MO・Fe ₂ O ₃ (M: divalent metal), such as Mn ²⁺ , Zn ²⁺ , Fe ²⁺ , Co ²⁺ ,
Examples include Mi ²⁺ , Cu ^{2+ ,} etc. Furthermore, M is not a single metal, but may be a composite such as Fe ²⁺ and Zn ²⁺ . (Example: FexZn _1-x O.Fe ₂ O ₃ , O<x<1) In forming the ferrite-containing layer 3 on the ferromagnetic metal thin film 2 according to the present invention, sputtering method, wet plating method, It can be formed by a method such as a vacuum evaporation method, an arc evaporation method, a melt spray method, a deposition method, or an electrophoretic electrodeposition method. When the ferrite-containing layer 3 is formed on the ferromagnetic metal thin film 2 according to the present invention, the film thickness is 50 to 400 mm.
Å is preferred. When the film thickness was greater than 500 Å, the output decreased due to spacing loss during signal reproduction.
Further, when the thickness was smaller than 50 Å, pinholes were likely to occur, and the lubricity durability expected from the combined effect with a monomolecular film made of a saturated fatty acid or its metal salt could not be observed. According to the present invention, the above-mentioned ferrite-containing layer 3
A monomolecular layer 4 made of saturated fatty acids or metal salts thereof is provided thereon. Examples of the saturated fatty acids or metal salts thereof that can be used in the present invention include linear saturated fatty acids having 12 to 28 carbon atoms and metal salts thereof such as Ba, Cd, Pb, and Ca. Saturated fatty acids having 16 to 22 carbon atoms and salts thereof are preferred because they have a well-balanced amphipathic property and are easy to prepare as a monolayer. Examples are palmitic acid, stearic acid, arachidic acid, behenic acid and their metal salts. As a method for forming the monomolecular layer 4 made of the saturated fatty acid or a metal salt thereof on the ferrite-containing layer 3, the Langmuir-Blodget (LB) method [Phys.Rev, 51 , 964 (1937)] is used. be. According to the present invention, a monomolecular layer 4 made of the saturated fatty acid or a metal salt thereof is formed on the ferrite-containing layer 3.
1 to 21 layers are suitable, and 3 to 15 layers are preferable from the viewpoint of slipperiness. However, the combined thickness of the ferrite-containing layer 3 needs to be 500 Å or less. If it is larger than 500 Å, the output will decrease due to spacing loss during signal reproduction, which is not preferable. The present invention will be explained below by giving specific examples. Examples 1 to 3 Cobalt (90%) - chromium (10%) was deposited on a 20 μm thick polyimide film substrate by vacuum evaporation method.
A ferromagnetic metal thin film with a thickness of 1500 Å was fabricated.
100×100 from the substrate on which this ferromagnetic metal thin film was formed.
A piece with a size of mm was cut out, and the following ferrite thin film having a thickness of 100 Å was provided on the metal thin film by sputtering. Example 1 Zn ferrite Example 2 Mn ferrite Example 3 Magnetite Example 4 Mn/Zn ferrite (Mn:
Zn=1:1) Next, three monomolecular layers of stearic acid were formed using an LB film accumulation device (manufactured by Kyowa Kaimen Kagaku). Example 5 In Example 1, three monomolecular layers of Ba stearate were formed instead of stearic acid. Comparative Example In Example 1, three monomolecular layers of stearic acid were formed directly on the Co-Cr ferromagnetic metal thin film without forming the Zn ferrite layer. After drying the samples prepared in Examples 1 to 4 at room temperature, the film of three monomolecular layers of stearic acid was measured using an ellipsometer, and the film thickness was 75 to 80 Å. The dynamic friction coefficients of the samples of Examples 1 to 5 and Comparative Example were measured using a friction coefficient meter (DFPM type, manufactured by Kyowa Interface Science). The head used was a steel ball with a diameter of 3 mm, the head load was 100 g, and the head traveling speed was 1.0 mm/s. The results are shown in the table below.

【table】

[Table] From the data in the table, it can be seen that the magnetic recording media of Examples 1 to 5 according to the present invention have low coefficients of dynamic friction not only at the initial stage but also after 200 reciprocations, and are superior to the comparative example in terms of sliding durability. I understand. In the comparative example, the bond between the stearic acid monolayer and the magnetic layer was weak, so it was scraped off by the head.
The coefficient of dynamic friction increased as the number of reciprocations of the head increased, and no durability of lubricity was observed. 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 5 had a diameter of 100 mm. The vehicle continued to run stably even after several hours, and 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 smooth durability, runnability,
It has excellent wear resistance and can be maintained 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
...Ferrite-containing layer, 4... Monomolecular layer consisting of saturated fatty acids or metal salts thereof.

Claims (1)

[Claims] 1. On a ferromagnetic metal thin film provided on a non-magnetic substrate,
A magnetic recording medium comprising a ferrite-containing layer and at least one monomolecular layer of a saturated fatty acid or a metal salt thereof provided on the surface of the ferrite-containing layer. 2. The magnetic recording medium according to claim 1, wherein the ferrite-containing layer has a thickness of 50 to 400 Å.