JPS62102418A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the durability of a thin ferromagnetic metallic film layer by forming a protective layer consisting of an org. high-polymer compd. contg. at least one kind of the lubricating agents expressed by the formula Rf-CH2-(R) m-X on the thin ferromagnetic metallic film layer. CONSTITUTION:The lubricating agent expressed by the formula (where Rf is fluoropolyoxyalkyl group of 8-152C, R is an oxyalkylene group of 2-3C, X is a polar group of any selected from -OH, -OCH3, -COOH, and -OCH2COOH and m is >=1 integer) is incorporated into the protective layer. Since said agent has the fluoropolyoxyalkylene group contg. carbon atoms at a high rate and having particularly excellent lubricity, said agent has the excellent lubricating function. The lubricating effect is thus obtd. substantially and continuously for a long period of time. The durability of the thin ferromagnetic metallic film is thereby substantially improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium having a single thin layer of ferromagnetic metal as a recording layer, and more particularly to the above-mentioned magnetic recording medium having excellent durability.

[Conventional technology]

In general, magnetic recording media made by depositing ferromagnetic metals or their alloys on a substrate by vacuum deposition, etc., have excellent high-density recording characteristics, but have a high coefficient of friction with the magnetic head and are susceptible to wear and damage. The problem is that magnetic disks are easily damaged and have poor durability, and in particular, magnetic disks have more severe sliding conditions with magnetic heads, so their durability tends to deteriorate.

For this reason, attempts have been made to improve the durability of the ferromagnetic metal thin film layer by depositing various lubricants on the ferromagnetic metal thin film layer. Inside, X is -3O3K, -5O3Na, 302
F, C00NI(4, COOH850311, -
A fluorine thread surfactant represented by OL (represents a polar group such as a group, n is an integer from 4 to 13) is applied to the surface of the ferromagnetic metal thin film layer (Japanese Patent Application Laid-Open No. 58-29147, Japanese Unexamined Patent Publication 1983
-1.6982, JP-A-5L-116931), or by coating the surface of the ferromagnetic metal thin film layer with a perfluoropolyether-based fluorine-based lubricant having a fluorine-containing carbon number of about 21 to 65 (U.S. Patent No. 3778308), and furthermore, perfluoropolyether carboxylic acid having a molecular skeleton of a fluorine-containing polyoxyalkyl group having about 21 to 65 carbon atoms and -C00H at the end is coated on the surface of a ferromagnetic metal thin film layer. Attempts have been made to improve the durability of the ferromagnetic metal thin film layer by, for example, (Japanese Unexamined Patent Publication No. 5L-85929).

[Problem that the invention seeks to solve]

However, in the method of applying a fluorine-based surfactant represented by the above general formula to the surface of a ferromagnetic metal thin film layer, the carbon number of the fluorine-containing alkyl group is too small and the effect as a lubricant is not very good. The durability of the magnetic metal thin film layer is not sufficiently improved.
In the method of applying a perfluoropolyether-based fluorine-based lubricant to the surface of a ferromagnetic metal thin film layer, a good hot-water effect is exhibited because the fluorine-containing alkyl group has a large number of carbon atoms. The durability of the ferromagnetic metal thin film layer cannot be sufficiently improved because the adhesion to the surface of the layer is not very good and the coating is only applied to the surface of the ferromagnetic metal thin film layer. Furthermore, the molecular skeleton is a fluorine-containing polyoxyalkyl group with about 21 to 65 carbon atoms, and -COOH
In the method of coating the surface of the magnetic layer with perfluoropolyether carboxylic acid having If used for a long time, the lubricant will disappear and good durability will not be obtained. In this way, simply fixing the fluorine-based lubricant and fluorine-based interfacial lubricant to the surface of the ferromagnetic metal thin film layer using interfacial energy will not allow the fluorine-based lubricant and fluorine-based interfacial lubricant to quickly spread to the surface of the ferromagnetic metal thin film layer. Durability is not very good because it is easy to fall off from the surface, and in particular, the sliding conditions with magnetic disks are more severe, so conventional fluorine-based lubricants and fluorine-based interface lubricants are Even if it adheres to the surface of the magnetic metal thin film layer, sufficient effects cannot be obtained.

[Means for solving problems]

This invention was made as a result of various studies in view of the above circumstances, and has the general formula % (%) (wherein, Rf is a fluorine-containing polyoxyalkyl group having 8 to 152 carbon atoms, and R is a fluorine-containing polyoxyalkyl group having 2 to 152 carbon atoms. ~3 oxyalkylene group, X is 1OH, -0CHa, ~C00II, -0C
Represents any polar group selected from T12COOH,
m is an integer of 1 or more. ) By forming a protective layer made of an organic polymer compound containing at least one of the lubricants represented by The durability of the ferromagnetic metal thin film layer is improved by firmly fixing it in the protective layer made of a polymer compound, and fully and sustainably exhibiting the excellent hot water effect of the fluorine-containing polyoxyalkyl group with a large number of carbon atoms. This is a fully developed approach.

In this invention, the lubricant contained in the protective layer has the general formula % (%) (wherein, Rf is a fluorine-containing polyoxyalkyl group having 8 to 152 carbon atoms, and R is oxyalkylene having 2 to 3 carbon atoms. group, X is -01(, OC+13, -COOI(, -0
Represents any polar group selected from CH2COOH,
m is an integer of 1 or more. ) is generally a viscous oily lubricant at room temperature and pressure, and has fluidity and is composed of a long-chain fluorine-containing polyoxyalkyl group, a fluorine-free oxyalkylene group, and a polar group. It has molecular chains with three different properties, and has a fluorine-containing polyoxyalkyl group with a large number of carbon atoms that has excellent lubricity, so it has an excellent lubrication function. In addition, since it has a polar group at the end, it is well adsorbed to the strong metal thin film layer via this polar group, and the fluorine-free oxyalkylene group is used as a binder resin in the protective layer made of organic polymer compound. The above-mentioned fluorine-containing polyoxyalkyl group, which has a particularly excellent lubricating effect, is oriented on the surface of the protective layer and is firmly fixed in the protective layer made of an organic polymer compound because of its good compatibility with the protective layer. This type of lubricant is firmly fixed in the protective layer on the thin ferromagnetic metal lI*1, and its excellent lubricating effect is maintained for a long time. It is sustained over a long period of time, and the durability of the ferromagnetic metal thin film layer is sufficiently improved.

Such lubricants of this type include, for example, the following general formula % (wherein, X is 1OH, -0CII3, -QCH2
It is any polar group selected from COOHl-COOII, and n and m are integers of 1 or more. ) is preferably used.

The use of this type of lubricant is within the range of 0.1 to 20% by weight, and more preferably within the range of 0.5 to 5% by weight based on the total solid content of the protective layer. is more preferable,
If it is too small, the desired effect will not be obtained, and if it is too large, the surface condition of the protective layer will deteriorate, which may cause dropouts or noise.

A protective layer containing this type of lubricant is usually prepared by mixing and dispersing this type of lubricant together with a binder resin, an organic solvent, and other necessary components to prepare a protective layer solution, and then preparing the protective layer solution in advance. It is formed by coating or spraying on a ferromagnetic metal thin film layer formed on the surface of a substrate such as a polyester film, and drying it, or by dipping the ferromagnetic metal thin film layer in the above-mentioned protective layer solution. . The thickness of the protective layer formed in this way is preferably within the range of 100 to 500 people, and if it is too thin, the desired effect will be reduced.
If it is too thick, it may cause a decrease in output or dropouts.

Here, the binder resin used for the protective layer includes polyimide resin, vinyl chloride-vinyl acetate copolymer, cellulose resin, polyurethane resin, polyester resin,
Polyvinyl butyral + A111! , isocyanate compounds, etc., which are generally used for magnetic recording media, are all suitable.

Further, as the organic solvent, trifluorotrichloroethane and a mixed solvent of trifluorotrichloroethane and an organic solvent such as N-methyl-2-pyrrolidone, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, toluene, etc. are used.

The materials for forming the ferromagnetic metal thin film layer include C01Ni,
Fe, Co-N1 alloy, Co-Cr alloy, Co-P, G
All commonly used ferromagnetic materials such as o-Ni-P are preferably used, and the ferromagnetic metal thin film layer made of these ferromagnetic materials can be formed by means such as vacuum evaporation, ion blasting, sputtering, plating, etc. It is formed by a method such as adhering to a substrate.

Further, the magnetic recording medium includes various types of structures that come into sliding contact with a magnetic head, such as a magnetic tape having a synthetic resin film such as a polyester film as a base, a magnetic disk or a magnetic drum having a disk or drum as a base.

〔Example〕

Next, embodiments of the invention will be described.

Examples 1 to 8 An alumite-treated aluminum base material was used as a 5-inch nonmagnetic support disk, and this disk was loaded into a vacuum evaporation apparatus and coated with cobalt under a vacuum of 5xto-5 Torr.
The chromium alloy is heated and evaporated to form a disk with a thickness of 0.2 mm.
A ferromagnetic metal thin film layer made of a cobalt-chromium alloy with a thickness of μm was formed.

- Polyimide resin (product name: PIQ manufactured by Hitachi Chemical Co., Ltd.)
), 100 parts by weight of N-methyl-2-pyrrolidone, 0.04 parts by weight of various lubricants shown in Table 1 below, and 10 parts by weight of trichlorotrifluoroethane were mixed and dispersed. A mixed solution was prepared. Next, this mixed solution was applied to a disk on which a ferromagnetic metal thin film layer was formed, which was rotated by a spinner at 300 rpm. After coating, the disk was dried at 250°C for 30 minutes to form a protective layer on the ferromagnetic metal thin film layer. was formed to create a magnetic disk. The thickness of the protective layer at this time was 400 μm.

Comparative Example 1 Example 1: The same procedure was carried out except that in the formation of the protective layer, Krytosox 143AC (perfluoroalkyl polyether manufactured by DuPont) was used in place of the lubricant shown in Table 1. Thickness: 40077m as in Example 1
A protective layer was formed to create a magnetic disk.

The durability of the magnetic disks obtained in each example and comparative example was tested. The durability test was carried out by placing the IMed magnetic disk in a spherical sliding tester, applying a load of 10 g to the Zapphire spherical slider, and sliding the magnetic disk at a circumferential speed of 10 m/sec. Rated by the total number of revolutions until destruction! I did it.

Table 2 below shows the results.

Table 2 [Effects of the Invention] As is clear from the above Table 2, all of the magnetic disks obtained by the present invention (Example Works to 8) have lower performance compared to the conventional magnetic disk (Comparative Example 1). The total number of rotations is high, which indicates that the magnetic recording medium obtained by the present invention has excellent durability.

Claims (1)

[Claims] 1. A ferromagnetic metal thin film layer made of a ferromagnetic metal, an alloy thereof, or a compound containing these ferromagnetic metals is formed on a substrate, and on this ferromagnetic metal thin film layer, a compound having the general formula Rf -CH_2-(R)m-X (wherein, Rf is a fluorine-containing polyoxyalkyl group,
R represents an oxyalkylene group, X represents a polar group, and m is an integer of 1 or more. ) A magnetic recording medium 2 characterized in that it is provided with a protective layer made of an organic polymer compound containing at least one type of lubricant represented by: -OH, - O.C.
The magnetic recording medium 3 according to claim 1, wherein the oxyalkylene group represented by R in the general formula is one selected from H_3, -COOH, and -OCH_2COOH, and the oxyalkylene group represented by R in the general formula is an oxyalkylene group having 2 to 3 carbon atoms. In the magnetic recording medium 4 according to claims 1 and 2, the fluorine-containing polyoxyalkyl group represented by Rf in the general formula is a fluorine-containing polyoxyalkyl group having 8 to 152 carbon atoms. A magnetic recording medium according to claims 1 to 3, which is