JPS5894130A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce a frictional strength and improve the corrosion resistance of a titled medium, by applying a mixture of fluoro polymer and polytetrafluoroethylene of a low polymerization degree on a magnetic thin metallic film. CONSTITUTION:A dilute solution is prepared in which tetrafluoroethylene, polyvinylidene fluoride, tetrafluroethylene-ethylene coplymer, tetrafluoroethylene- hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer resin or other fluoropolymer resin is disolved in a solvent of fluorochemicals such as freon. Amrphous polytetrafluoroethylene having <=5,000mol.wt., preferably about 3,500 is dispersed in ''Freon '' to prepare a dispersion. A mixture of said solution with said dispersion is applied on a magnetic thin metallic film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium having a magnetic layer made of a ferromagnetic metal thin film, and an object of the present invention is to provide a magnetic recording medium with reduced frictional force and improved corrosion resistance.

Thin-film metal magnetic recording media formed on nonmagnetic substrates by vacuum deposition or plating are suitable for high-density recording. Therefore, in recent years, it has been expected to be used as magnetic recording media for audio and video, and thin films of cobalt-based alloys formed by vacuum deposition on plastic substrates have been put into practical use for small magnetic tapes. Entering the realm of
It has become commercially available. Metal thin film magnetic recording media differ from conventional powder-coated media in that the metal surface is directly exposed, so friction tends to be weaker due to the lack of binder resin. Possible methods for reducing the frictional force include roughening the surface or applying a lubricant to the surface.

Although the method of roughening the surface is a simple method, it creates unevenness on the surface, which increases plowing loss during recording and reproducing of magnetic recording, which is not desirable or convenient.

Although the method of applying a lubricant to the surface is an effective method, if the thickness of the lubricant layer becomes too thick, the same problem as the former method occurs, so it is not preferable. Therefore, the thickness of the lubricating layer is sufficiently small. , it is necessary to keep it to a level that does not cause any loss. For this purpose, a very thin and inexpensive lubricating layer must be formed, and the surface energy of the lubricating layer itself must be sufficiently low.

Various materials can be considered for the lubricating layer.

General-purpose products include higher fatty acids, their esters, and metal salts, but since these are hydrocarbons, they cannot necessarily be said to have excellent durability such as oxidation resistance, and they are also susceptible to microorganisms. There are also disadvantages such as breeding.

The present invention solves these problems by coating a metal thin-film magnetic recording medium with a fluorocarbon polymer film that is more durable than hydrocarbons and has a much lower surface energy. , thereby realizing a magnetic recording medium that reduces frictional force without deteriorating electromagnetic conversion characteristics.

Examples of fluorine-based polymers include polytetrafluoroethylene,
Polyvinylidene fluoride, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer resin.

And, as side chains or substituents on these resins, alkyl groups, acrylic groups, carboxyl groups, water groups, ether groups, nitro groups, carbonyl groups, amino groups,
There are also those with active groups such as sulfonic acid groups and halogens introduced. In the present invention, high adhesive strength is also required, so a material having active groups introduced therein is required. Commercially available products include the product names "Sumiflunon" (Sumitomo Chemical Industries, Ltd.) and "FC-721J (Sumitomo 3M Ltd.).
) "Scotchgard" (Sumitomo 3M Ltd.), "Zepel" (Dubo/Sha), "Asahigard J (Asahi Glass Ltd.)
)and so on.

The coating material used in the present invention is a dilute solution of a fluorine-containing polymer resin dissolved in a fluorine-containing solvent such as Freon, and a molecular weight of 6,000 or less, typically 3,500.
This is a mixture of amorphous polytetrafluoroethylene dispersed in Freon. This processing material consists of resin and polymer.

Since both the solvent and the fluorine-containing material are fluorine-containing materials, the low surface energy characteristic of fluorine compounds can be fully utilized, and it can be applied to the very KMi concavities on the electron microscopic scale of the magnetic medium surface and the gaps between micro Mi crystal grains. It is possible to create a magnetic recording medium that is stable, durable, and has low frictional force.

Furthermore, since the fluorine-containing polymer resin film is very strong and dense, it has the characteristic of keeping water out, and is also effective in improving the corrosion resistance of metal magnetic thin films.

Examples of the present invention will be shown below, and the effects thereof will also be described.

Example 1 A cobalt thin film with a thickness of 1000 A was formed on a polyethylene terephthalate barley plate with a thickness of 12 μm.

The coercive force of this thin film is 7500e, and the residual magnetic flux density is 850e.
It is 0G. The following treatment solution was applied to the cobalt thin film by immersion.

Treatment liquid composition 1 [Sumiflunon FP-s1J manufactured by Sumitomo Chemical Co., Ltd. concentration 500 ppm 2 [AG-LUBJ manufactured by Asahi Glass Co., Ltd. polytetrafluoroethylene telomer (molecular weight approximately 3500) concentration 300 ppm 3 Solvent r Daiflon turben) S3J Daikin The evaluation results made by Kogyo Co., Ltd. are shown in Table 1. The evaluation results for untreated products are also shown. Note that the environmental test was conducted by leaving the product in an atmosphere at a temperature of 60° C. and a relative humidity of 90%.

The contact angle with respect to water in Table 1 is used to determine the magnitude of surface energy, and a clear decrease in surface energy is seen in this example. It can be understood from the environmental test results that the effects of the present invention are sufficient. Friction coefficients are for stainless steel (sUs3oa).

Example 2 Cobalt (80%)-ester (20%) with a thickness of 100oA on a polyethylene terephthalate substrate with a thickness of 12μm
) Alloy thin film (coercive force 8090e, residual magnetic flux density 80o
oG) was formed, and a treatment solution having the following composition was applied by dipping.

Composition of treatment liquid 1 [Fc-721J manufactured by Sumitomo 3M Ltd. (fluorine-containing resin for surface treatment) concentration 300 ppm 2 rAG-LUBJ manufactured by Asahi Glass Ltd. concentration 200 ppm
m 3 solvent r Daiflon solvent, (33:52=1
:1) J manufactured by Daikin Industries, Ltd. The evaluation results are shown in Table 2.

Table 2 The above table also shows that the products of the present invention are superior.

As described above, it can be seen that the metal thin film magnetic recording medium of the present invention has reduced frictional force and improved corrosion resistance, and is of great industrial value.

Claims (1)

[Scope of Claims] A mixture of a fluorine-containing surface treatment resin and a dispersion of low-grade polytetrafluoroethylene having a molecular weight of 6,000 or less is coated on the surface of the metal magnetic thin film constituting the magnetic layer. magnetic recording media.