JPS5933621A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a superior magnetic disc having lubricity lasting for a long term, and no fear of soiling and magnetic head, by incorporating oleic acid and oleate in a magnetic layer. CONSTITUTION:A magnetic layer is formed on a support by coating the support with a magnetic coating material contg. 100pts.wt. magnetic powder and 0.1- 20pts.wt. lubricants consisting of oleic acid and its ester in 99:1-50:50 weight ratio, or by coating the magnetic layer contg. no lubricant with a soln. contg. said lubricant mixture or doing the like. The synergistic effect of said two lubricants added in proper amt. and ratio prevents the lubricants from bleeding out, soiling the magnetic head, and resulting in deterioration of output, and hence, a magnetic disc, etc. superior in durability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and an object thereof is to provide a magnetic recording medium with excellent durability.

In general, magnetic recording media, which are made by coating a magnetic paint consisting of magnetic powder, binder resin, organic solvent, and other necessary components on a substrate such as a polyester film, are subject to intense rubbing against magnetic heads and pads during recording and playback. Since the magnetic layer is in contact with the magnetic layer, it is easily abraded, and the magnetic layer is required to have less abrasion and excellent durability.

For this reason, various lubricants are mixed into the magnetic layer as a way to improve the wear resistance of the magnetic layer.
The present inventors have already proposed mixing oleic acid or an unsaturated fatty acid ester such as oleic acid ester into the magnetic layer to improve the wear resistance.

However, although the abrasion resistance of the magnetic layer is certainly improved by mixing oleic acid or unsaturated fatty acid ester, it is not completely satisfactory, and oleic acid may wear out the magnetic head if used sparingly in q′η. Therefore, the wear resistance cannot be sufficiently improved.

The inventors conducted various studies in view of the current situation, and found that by incorporating oleic acid and oleic acid ester together in the magnetic layer, the amount of oleic acid used can be reduced without causing wear on the magnetic head. It has been found that the wear resistance of the magnetic layer can be sufficiently improved by increasing the wear resistance of the magnetic layer, leading to the present invention.

Olein 1!19 used in this invention is an oily unsaturated fatty acid with 18 carbon atoms and has excellent lubrication ability, especially when the magnetic layer is in sliding contact with the magnetic head. is fully exhibited, and the wear resistance of the magnetic layer is sufficiently improved. In addition, when used in combination with oleic acid ester, the lubrication functions of the two act synergistically to further improve the wear resistance of the magnetic layer. Although the magnetic head tends to wear out, the wear of the magnetic head is alleviated, the amount of oleic acid used can be increased, and the wear resistance is sufficiently improved.

In addition, the oleic acid ester used in combination is an unsaturated fatty acid ester with excellent lubricating ability, and has low volatility, so when it is contained in the magnetic layer together with oleic acid, it exhibits a long-term lubrication effect and makes the magnetic layer durable. Abrasion resistance is improved. Specific examples of such oleic acid esters include 0-butyl oleate, 1/yl oleate, and the like.

The blending ratio of oleic acid to such oleic acid ester is preferably within the range of 99:1 to 50:50 in terms of weight ratio (oleic acid ester to olein #), and the blending ratio of oleic acid is low. If it is too much, the wear resistance of the magnetic layer will not be sufficiently improved, and if it is too much, there is a risk that the magnetic head etc. will be worn out. In addition, it is preferable that the amount of oleic acid ester and oleic acid used in such a blending ratio be within the range of 0.1 to 20% by weight based on the magnetic powder. If the amount is too large, it may bleed out onto the surface of the magnetic layer, contaminating the magnetic head, and reducing the output.

In order to incorporate oleic acid and oleic acid ester into the magnetic layer, either dissolve them in a suitable solvent such as n-hemisane, and apply or spray the hydrated solution onto the pre-formed magnetic layer. Alternatively, the magnetic layer may be immersed in the above solution, or the magnetic layer may be incorporated by kneading these together with magnetic powder and binder resin to form a magnetic layer.

Next, embodiments of the invention will be described.

Example I Co-containing r-Fe203 magnetic powder 270 parts by weight VA
GH (manufactured by T1.C., USA, 80 parts by weight vinyl-vinyl acetate-vinyl alcohol copolymer) N1432J (11 parts by Zeon Co., Ltd., 15 Acrylonitrile-butadiene copolymer) Coronate 1. (EI polyurethane 10 〃manufactured by Nibu 1st Co., Ltd., trifunctional low-molecular isocyanate compound) MS-500 (manufactured by Asahi Carbon Co., Ltd., 34 / carbon black) σ-Fe203 powder 11'' Methyl isobutyl ketone 420 〃Toluene
420 This composition was mixed and dispersed in a ball mill to prepare a magnetic paint, and the magnetic paint was coated with a thickness of 75 mm.
A magnetic layer was formed by coating both sides of a μ polyester film to a dry thickness of 3 μ and drying. Next, this was immersed for a short time in an impregnating solution consisting of 2.5 parts by weight of oleic acid, 47.5 parts by weight of oleyl oleate, and 1000 parts by weight of n-hexane, and after drying, it was punched out into a disk shape to produce a magnetic disk.

Comparative Example 1 In the composition of the impregnation solution in Example 1, oleic acid was omitted and the amount of oleyl oleate used was changed to 47.5jli.
A magnetic disk was produced in the same manner as in Example 1 except that the amount was changed to 50 parts by weight.

Comparative Example 2 A magnetic disk was prepared in the same manner as in Example 1, except that the composition of the impregnating solution in Example 1 was omitted from oleyl oleate, and the mass-produced 2.5 electric part using oleic acid was changed to a 50 electric part. I made it.

In order to examine the durability of the magnetic disks obtained in Examples and Comparative Examples, each magnetic disk was inserted into a dirt-proof city jacket, loaded into a recording/reproducing device, and the magnetic head was heated at a pad pressure of 25 f/cm2. Contact and circumferential speed IQ
The running time from sliding contact to f1 raw output reaching 50% of the initial output was measured at frL/sec.

The table below shows the results.

As is clear from the above table, the magnetic disk obtained by this invention (Example 1) has a longer running time than the magnetic disks obtained in Comparative Examples and 2. It can be seen that the obtained magnetic recording medium has excellent durability.

Patent applicant: Hitachi Maxell, Ltd. 971

Claims (1)

[Claims] 1. Magnetic recording medium having a magnetic layer containing oleic acid and oleic acid ester