JPS60212823A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To increase the breaking strength and adsorptive powder of an org. lubricating layer and to obtain a long-life magnetic recording medium having excellent resistance to wear and sliding abrasion by forming an adsorptive layer of methacrylic acid or the metallic salt thereof on a magnetic recording surface and providing the org. lubricating layer on the adsorptive layer. CONSTITUTION:A soln. of methacrylic acid or the metallic salt of Na, Li or of Ba, Ca, etc. is coated within 40-500Angstrom thickness range on the magnetic recording surface of the magnetic recording medium formed by providing a thin magnetic metallic film consisting of a Co-Cr alloy, etc. on a non-magnetic substrate, by which the adsorptive layer is formed. The lubricating layer consisting of higher fatty acid, the ester thereof, etc. is coated as an org. lubricating agent to 50-300Angstrom film thickness on said adsorptive layer. The lubricating agent which has previously weak adsorptive strength to the magnetic layer and has easy tendency to removal of the lubricating film is strongly adsorbed by the adsorptive layer particularly when the fluorocarbon lubricating agent is coated thereon. The lubricity is thus maintained for a long period of time and the recording medium having excellent durability and running property is obtd.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to improving the mechanical durability of a magnetic recording medium.
In particular, the object is to provide a magnetic recording medium with excellent friction characteristics and abrasion resistance.

[Background of the invention]

As a method of improving the durability of magnetic recording media, various protective lubricant films, including those based on higher fatty acids or fluorocarbons, have been studied.

The characteristics required for the protective lubricant layer of magnetic recording media are as follows:
The first is that it exhibits good frictional properties, the second is that it strongly adheres to the surface to be lubricated, and the third is that it has a film rupture strength that is high enough to prevent direct contact between the magnetic head and the recording medium. It will be done.

The present inventors have so far investigated the effects of improving the durability of various lubricating materials, but in any case, it has not been possible to satisfy the above three requirements with one lubricant alone. For example, fluorocarbon-based liquid lubricants have a weak adsorption force to the lubricated object, and the lubricant film is easily removed when the magnetic head slides. Further, in the case of using only a lubricating layer of higher fatty acids, the film did not have sufficient breaking strength, and the magnetic head and the medium came into direct contact with each other in some areas, causing sliding scratches on the surface of the recording medium.

[Purpose of the invention]

An object of the present invention is to provide a novel magnetic recording medium that solves the above-mentioned problems of conventional protective lubricant layers.

[Summary of the invention]

In order to achieve the above object, the present inventors provided a two-layer structure in which a polymer layer that strongly adsorbs to a magnetic recording surface is used as a protective layer, and a lubricating layer is provided on the protective layer. As the protective layer in the present invention, methacrylic acid or a metal salt thereof, particularly alkali metal salts such as lithium and sodium, or alkaline earth metal salts such as barium and calcium, which are strongly adsorbed to the magnetic recording surface, was used.

The effective thickness range of the protective layer is 40 to 500 layers, and if the thickness does not reach 40 layers, the protective effect is insufficient. Moreover, when the film thickness exceeds 500 layers, a problem arises in that the void loss increases and the reproduction output decreases, although it depends on the film thickness of the lubricating layer on the protective layer.

The material for the lubricating film on the protective layer may be any organic substance exhibiting lubricity, and fluorocarbon-based lubricants, paraffin-based lubricants, and fatty acid-based lubricants represented by higher fatty acids and fatty acid esters are particularly effective. Ta. The preferred thickness range of the lubricating film is 50 to 300, and the film thickness is 50 to 300.
If it does not reach the person, there will be parts that are not covered with a lubricating film.
There are now areas with a locally high coefficient of friction, and no significant improvement is seen in running performance. Also, the thickness of the lubricating film is 3
If the number exceeds 0.00, stickiness of the magnetic head occurs with most lubricating materials, resulting in extremely poor running performance.

As mentioned above, a protective layer is formed on the magnetic recording surface of methacrylic acid or its metal salt, which has a high film breaking strength and strongly adsorbs to the magnetic recording medium surface, and a thin lubricating layer of organic material is further formed on the protective layer. By providing this, it was possible to obtain a magnetic recording medium with a low coefficient of friction and excellent durability.

[Embodiments of the invention]

The present invention will be explained below with reference to Examples.

The magnetic recording medium used as a sample had a diameter of 75 m.

Cog sputtered onto a Pyrex glass substrate with a thickness of 3++o. Crz. It is an alloy thin film medium. Film thickness is 0.2
It is μm. A sodium methacrylate solution was applied to the magnetic recording surface of the magnetic recording medium using a spin code method. According to ellipsometry measurements, the thickness of the protective layer was approximately 200 mm. Then, a fluorocarbon lubricant Kr1tox (trade name of Dupon Inc.) was applied onto the protective layer, or stearic acid was deposited on the surface of the protective layer.

The durability evaluation of the recording medium is based on the recording density IKBP of the recording medium.
A signal of 'I (Kilo-bit per 1 nch) was recorded, and evaluation was made by the number of passes of the magnetic head until the signal output decreased to 80% of the initial output. The magnetic head used in the experiment was a Winchester-type Mn--Zn ferrite ring head, and the evaluation was performed at a circumferential speed of 2 m/sec and a pushing load of 6 g.

The durability evaluation results are shown in Table 1. Kr1tox according to the table
When a lubricating layer of stearic acid or stearic acid is provided on a magnetic recording surface, the life of the magnetic recording medium is improved by 2 to 8 times compared to a non-lubricated case. However, if a thin layer of sodium methacrylate is provided as a protective layer on the magnetic recording surface, and the lubricating layer is provided on the protective layer, the service life can be further improved by nearly two orders of magnitude.

〔Effect of the invention〕

Claims (1)

[Claims] A magnetic recording medium characterized in that an adsorption layer of methacrylic acid or its metal salt is provided on a magnetic recording surface of the recording medium, and an organic lubricant layer is provided on the adsorption layer.