JPH0465446B2 - - 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 So-called coated magnetic recording media in which conventional ferromagnetic powders such as γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , CrO ₂ , etc. are dispersed in an organic binder and coated on a non-magnetic support. Instead, magnetic recording media in which a ferromagnetic metal thin film is formed on a non-magnetic support by methods such as plating, sputtering, vacuum evaporation, and ion plating are used as magnetic recording media for high-density recording. being researched. However, the magnetic recording medium using the ferromagnetic metal thin film produced by the method described above has problems with its wear resistance and running properties. 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 method described above 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. When running, the output could be significantly reduced due to wear, damage, and generation of abrasion powder.
Therefore, it has been proposed to provide a lubricant layer on a ferromagnetic metal thin film, such as SiO ₂ , Al ₂ O ₃ ,
It has been proposed to form a metal oxide layer such as SiO, and to form a deposited film of a fatty acid lubricant on the surface of the metal oxide layer (Japanese Patent Laid-Open No. 154642/1983). Problems to be Solved by the Invention However, although there has been an improvement in lubricity in this case, running stability and wear resistance are still not sufficient. This is because the bond between the fatty acid lubricant and metal oxides such as SiO ₂ , Al ₂ O ₃ , and SiO is weak, so the fatty acid lubricant is scraped off by the sliding magnetic head while the vehicle is running. It is. 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, runnability, and wear resistance. Means for Solving the Problems A ferrite-containing layer is formed on a ferromagnetic metal thin film provided on a non-magnetic substrate, and a fatty acid-based lubricant-containing layer is provided on the surface of the ferrite-containing layer. Function The fatty acid lubricant can be strongly chemically bonded to the ferrite layer, and the fatty acid lubricant will not be scraped off by friction with the magnetic head, etc., resulting in improved lubricity, running performance, and wear resistance. An excellent magnetic recording medium can be obtained. The reason why higher fatty acids or their salts strongly bind to ferrite is presumed to be because they form coordinate bonds with iron ions in ferrite. 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 fatty acid-based lubricant-containing layer. Examples of the nonmagnetic substrate 1 that can be used in the magnetic recording medium of the present invention include polymeric materials such as polynyl 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. and other metals such as manganese, chromium, titanium,
There are alloys that combine phosphorus, yttrium, samarium, bismuth, etc., as well as oxides of the above metals. The ferromagnetic metal thin film 2 can be formed on the nonmagnetic substrate 1 by any known method such as vacuum evaporation, sputtering, ion plating, or plating. In the present invention, the key point is to provide the ferrite-containing layer 3 on the ferromagnetic metal thin film 2 as described above. 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⁺ , Fe ²⁺ , Co ²⁺ , Ni ²⁺ ,
Examples include Cu ²⁺ and Zn ²⁺ . Furthermore, M is not a single metal, but may be a composite such as Fe ²⁺ and Zn ²⁺ . According to the present invention, the ferrite-containing layer 3 can be formed on the ferromagnetic metal thin film 2 by a method such as a sputtering method or a coating method. From the viewpoint of controlling the film thickness and adhesion to the ferromagnetic metal thin film 2, the sputtering method is excellent. In the coating method, a liquid (magnetic fluid) in which 50 to 200 Å of ferrite is dispersed in a hydrocarbon solvent is applied by spin coating, etc., so the film formation method is simple, and in the case of tape-shaped products, long objects can be easily produced. . 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. In general, if the film thickness is greater than 400 Å, the output will decrease due to spacing loss during signal reproduction, which is undesirable, and if it is less than 50 Å, pinholes will easily occur and the combined effect with fatty acid lubricants will be reduced. I can't expect anything anymore. According to the present invention, a fatty acid-based lubricant-containing layer 4 is provided on the ferrite-containing layer 3 as described above. The fatty acid-based lubricant that can be used in the present invention is a fatty acid or a fatty acid salt. The fatty acid-based lubricant that can be used in the present invention is preferably a compound having a hydrocarbon chain having 12 to 26 carbon atoms or a fluorine carbide chain having 6 to 18 carbon atoms. In the case of a hydrocarbon chain, a fatty acid compound having 11 carbon atoms or less, and in the case of a fluorocarbon chain, a fatty acid compound having a carbon number of 5 or less cannot provide sufficient lubrication and durability. Also,
Fatty acid compounds that have a hydrocarbon chain with 27 or more carbon atoms or a fluorine carbide chain with 19 or more carbon atoms do not show any further improvement in lubricity, and their durability deteriorates. Hydrocarbon-based fatty acid lubricants that can be used in the present invention include lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid,
Lignoceric acid, cerotic acid, oleic acid, linoleic acid, linolenic acid, erucic acid and their Li
There are salts, Na salts, Ka salts, etc. Among the fluorine carbide types, perfluorocaproic acid, perfluorocaprylic acid, perfluorocapric acid, perfluorolauric acid, perfluoromyristic acid, perfluoropalmitic acid, and perfluorostearic acid. and their Li salts, Na salts, Ka salts, etc. The fatty acid-based lubricant-containing layer can be formed on the ferrite-containing layer by a vacuum deposition method, a coating method, a Langmiur-Blodget method, or the like. When forming a fatty acid-based lubricant-containing layer on a ferrite-containing layer according to the present invention, the film thickness is 50 to 500 mm.
Å is suitable, preferably 100-300 Å. However, the combined thickness of the ferrite-containing layer must 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. Furthermore, if the thickness of the fatty acid-based lubricant-containing layer is less than 50 Å, the lubricity will be significantly reduced, which is not preferable. The present invention will be explained below by giving specific examples. Example 1 Cobalt (90%) - chromium (10%) was deposited on a polyimide film substrate with a thickness of 20 μm using a vacuum evaporation method.
A ferromagnetic metal thin film with a thickness of 1500 Å was fabricated.
75mm in diameter from the substrate on which this ferromagnetic metal thin film was formed.
A piece of the size was cut out, and a Zn ferrite thin film with a thickness of 100 Å was provided on the ferromagnetic metal thin film by sputtering. Next, using a spinner,
100ppm stearic acid isopropanol (IPA)
The solution was coated on top of the Zn ferrite layer. 2 c.c. of the above IPA solution was applied at a rotation speed of 500 rpm, and then the rotation speed was increased to 1000 rpm.
The solvent was dried. After vacuum drying the sample, the stearic acid layer formed on the Zn ferrite layer was measured with an ellipsometer and found to have a thickness of 150 Å. Thereafter, the kinetic friction coefficient of the above sample was measured using a kinetic friction coefficient meter (model DFPM, manufactured by Kyowa Kagaku). The head used was a steel ball with a diameter of 3 mm, and the head load was 20
g, and the head running speed was 1.0 mm/s. Example 2 100 ppm of stearic acid in Example 1
A sample was prepared by replacing the IPA solution with an IPA solution of 100 ppm Na stearate, and the coefficient of dynamic friction was measured under the same conditions. Example 3 A sample was prepared by replacing the Zn ferrite in Example 1 with Mn/Zn ferrite, and the dynamic friction coefficient was measured under the same conditions. Example 4 The Zn ferrite in Example 1 was replaced with Mn/Zn ferrite, and an IPA solution of 100 ppm stearic acid was added.
A sample was prepared in place of the IPA solution of 100 ppm Na stearate, and the coefficient of dynamic friction was measured under the same conditions. Example 5 100 ppm of stearic acid in Example 1
A sample was prepared by replacing the IPA solution with an IPA solution of 100 ppm lignoceric acid, and the coefficient of dynamic friction was measured under the same conditions. Example 6 100 ppm of stearic acid in Example 1
A sample was prepared by replacing the IPA solution with an IPA solution of 100 ppm sodium lignocerate, and the coefficient of dynamic friction was measured under the same conditions. Example 7 100 ppm of stearic acid in Example 1
IPA solution of 100ppm perfluorolauric acid
A sample was made in place of the IPA solution and the friction coefficient was measured under the same conditions. Comparative Example 1 A sample was prepared in the same manner as in Example 1, in which a Co--Cr film was formed but without a ferrite-containing layer and a fatty acid-based lubricant-containing layer, and the dynamic friction coefficient was measured under the same conditions as in Example 1. Comparative Example 2 A sample was prepared in which a Co--Cr film and a Zn ferrite-containing layer were formed in the same manner as in Example 1, but without a fatty acid-based lubricant-containing layer, and the dynamic friction coefficient was measured under the same conditions as in Example 1. Comparative Example 3 A Co--Cr film was prepared in the same manner as in Example 1, and a sample was prepared in which only a stearic acid-containing layer was provided thereon, and the coefficient of dynamic friction was measured under the same conditions as in Example 1. Comparative Example 4 Co--Cr was made in the same manner as in Example 1, and a sample was prepared on which only a layer containing perfluorolauric acid was provided, and the coefficient of dynamic friction was measured under the same conditions as in Example 1. Comparative Example 5 A Co--Cr film was produced in the same manner as in Example 1, and a 100 Å thick SiO ₂ thin film was provided thereon by sputtering. Next, a stearic acid-containing layer was formed under the same conditions as in Example 1. After vacuum drying the sample, Example 1
The coefficient of dynamic friction was measured under the same conditions. The results of Examples 1 to 7 and Comparative Examples 1 to 5 are shown in the table.

[Table] From the data in the table above, Examples 1 to 1 according to the present invention
7 magnetic recording medium has an initial kinetic friction coefficient of 200
It can be seen that the coefficient of dynamic friction is low even after repeated reciprocation, and that the lubricity and wear resistance are superior to the others (comparative example). Furthermore, when these magnetic recording media were 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 6 showed
Although the running was stable even after 100 hours, the running of the magnetic recording media of Comparative Examples 1 to 4 in which no ferrite-containing layer or fatty acid lubricant-containing layer was not provided became unstable, and the ferromagnetic metal thin film surface wear was observed. In addition, in the magnetic recording medium of Comparative Example 5, which is a conventional example, the ferromagnetic metal thin film was exposed in 1 hour, and 100
After some time, the scratches appeared. Although the above embodiments have been described with respect to magnetic disks, the magnetic recording medium of the present invention can also be applied to magnetic tapes, magnetic disks, etc.
It is clear that the present invention can also be applied to magnetic cards and the like. Effects of the Invention The magnetic recording medium of the present invention has excellent lubricity, running stability, and wear resistance, and can maintain these properties for a long time.

[Brief explanation of drawings]

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... Fatty acid-based lubricant-containing layer.

Claims (1)

[Scope of Claims] 1. A magnetic recording medium in which a ferrite-containing layer is formed on a ferromagnetic metal thin film surface provided on a non-magnetic substrate, and a fatty acid-based lubricant-containing layer is formed 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 Å to 400 Å. 3. The magnetic recording medium according to claim 1, wherein the fatty acid-based lubricant contains a fatty acid or a fatty acid salt. 4. The magnetic recording medium according to claim 1, wherein the fatty acid-based lubricant contains a hydrocarbon chain having 12 to 26 carbon atoms or a fluorine carbide chain having 6 to 18 carbon atoms.