JPS59148131A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having improved wear resistance and superior durability, especially a magnetic disk not contaminating a pad by impregnating an unsatd. fatty acid ester and a hydrocarbon lubricant into a magnetic layer. CONSTITUTION:A magnetic layer contg. essentially magnetic powder and a binder resin is formed on a substrate such as a polyester film, and a soln. of a lubricant mixture prepd. by mixing a hydrocarbon lubricant with an unsatd. fatty acid ester in 99:1-1:99 weight ratio is applied to the magnetic layer to impregnate the lubricant by 0.1-40wt% of the amount of the magnetic powder. The resulting magnetic recording medium may be dipped in the soln. The contamination of a magnetic head due to the bleeding-out of the lubricant is prevented, and a magnetic recording medium having superior wear resistance is obtd. When a magnetic disk is obtd. by punching out of the film, the disk does not contaminate a pad and has a prolonged life.

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 a magnetic layer that is less abraded and has excellent durability is required.

For this reason, various lubricants are mixed into the magnetic layer as a way to improve the wear resistance of the magnetic layer.
For example, a magnetic layer in which a hydrocarbon lubricant such as squalane or liquid paraffin is mixed has been proposed.

However, although the abrasion resistance is certainly improved by incorporating this hydrocarbon lubricant, it is not sufficient, and in particular, when this hydrocarbon lubricant is used in the magnetic layer of a magnetic disk, etc., the pad becomes dirty, etc. There is a drawback.

The inventors conducted various studies in view of the above circumstances and found that if an unsaturated fatty acid ester is contained in the magnetic layer in combination with a hydrocarbon lubricant, the pad will not become dirty and the magnetic layer will be It was discovered that a magnetic recording medium with sufficiently improved abrasion resistance and excellent durability could be obtained, and the present invention was completed.

The unsaturated fatty acid ester used in this invention has low volatility because it has an unsaturated double bond, and also has excellent lubrication ability, and when used in combination with a hydrocarbon-based lubricant, it is compatible and the lubrication function of both is synergistic. As a result, the wear resistance of the magnetic layer is further improved, and this effect is maintained for a long time. In addition, by incorporating these into the magnetic layer of the magnetic disk due to the synergistic effect of the two, the disadvantages of containing a hydrocarbon lubricant alone are eliminated, and the pad does not get dirty, and the unsaturated fatty acid ester When used alone, there is a tendency for variations in durability to occur when the head pressure changes or the temperature environment changes, but such variations are eliminated and durability is improved. Such unsaturated fatty acid esters include oleic acid ester,
Elaidic acid ester, linoleic acid ester, linoleic acid ester, etc. are preferably used, and specific examples include oleyl oleate, oleyl oleate, etc.
Examples include n-butyl.

As the hydrocarbon lubricant used in combination, liquid hydrocarbons that are liquid at room temperature, such as liquid paraffin, squalane, squalene, synthetic squalane, synthetic squalene, and olefin polymerized oil, are preferably used. This type of hydrocarbon lubricant has excellent lubricating ability, and when used in combination with an unsaturated fatty acid ester, the two act synergistically to further improve the wear resistance of the magnetic layer.

The blending ratio of the unsaturated fatty acid ester to such a hydrocarbon lubricant is preferably such that the weight ratio (hydrocarbon lubricant to unsaturated fatty acid ester) is in the range of 99:1 to 1:99. If the blending ratio of unsaturated fatty acid ester is too low, the wear resistance of the magnetic layer against the pad will not be sufficiently improved, and if the blending ratio of hydrocarbon lubricant is too low, the magnetic layer against the head will not improve sufficiently, especially when the head pressure is high. wear resistance is not sufficiently improved. In addition, the amount of unsaturated fatty acid ester and hydrocarbon lubricant blended in such a blending ratio is 0.1 in total based on the magnetic powder.
The amount is preferably in the range of ~40% by weight; if it is too small, the desired effect may not be obtained, and if it 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 the unsaturated fatty acid ester and hydrocarbon lubricant into the magnetic layer, these are dissolved in a suitable solvent such as n-hexane, and the solution obtained by dissolution is applied or sprayed onto the previously 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 a magnetic powder and a binder resin to form a magnetic layer.

Next, embodiments of the invention will be described.

Example I CO-containing rFe2O3 magnetic 270 parts by weight Powder VAGH (manufactured by U.C., USA, salt 80 vinylide-vinyl acetate-vinyl alcohol copolymer) N1432J (manufactured by Nippon Zeon Co., Ltd., 15 acrylonitrile-butadiene) Copolymer) Coronate L (Nippon Boliureta 10〃manufactured by Kogyo Co., Ltd., trifunctional low molecular weight isocyanate compound) H3-500 (manufactured by Asahi Carbon Co., Ltd. 34〃Carbon Black) Oleyl oleate 19〃α-Fe20
3 Powder 11 Methyl isobutyl ketone
420〃Toluene 420〃
A magnetic paint was prepared by mixing and dispersing this composition in a ball mill, and this magnetic paint was applied to both sides of a 75 μm thick polyester film to a dry thickness of 3 μm, and dried to form a magnetic layer. Next, this was immersed for a short time in an impregnating solution consisting of 60 parts by weight of squalane and 1000 parts by weight of n-hexane, dried, and punched out into a disk shape to produce a magnetic disk.

Example 2 Example 1 except that the same amount of liquid paraffin was used in place of squalane in the composition of the impregnating solution in Example 1.
I made a magnetic disk in the same way.

Example 3 A magnetic disk was produced in the same manner as in Example 1 except that the same amount of n-butyl oleate was used in place of oleyl oleate in the composition of the magnetic paint in Example 1.

Example 4 In the composition of the magnetic paint in Example 1, oleyl oleate was omitted, and in the composition of the impregnating solution, the amount of squalane used was changed from 60 parts by weight to 20 parts by weight, and 40 parts by weight of oleyl oleate was added. Example 1 except that
I made a magnetic disk in the same way.

Comparative Example 1 A magnetic disk was produced in the same manner as in Example 1 except that oleyl oleate was omitted from the composition of the magnetic paint in Example 1.

Comparative Example 2 A magnetic disk was produced in the same manner as in Example 1 except that squalane was omitted from the composition of the impregnating solution in Example 1.

In order to examine the durability of the magnetic disks obtained in each example and each comparative example, each obtained magnetic disk was
Prepare one sheet at a time, insert them into a dirt prevention jacket, load them into 10 recording/reproducing devices, and bring them into contact with a magnetic head at a pad pressure of 25 g/c+It at a circumferential speed of 10 m/s.
We measured the running time for each recording/playback device until the playback output reached 50% of the initial output while in sliding contact with the EC, and determined the shortest running time and the running time of 50 hours or more among the 10 recording/playback devices. The obtained ratio was investigated. In addition, pad staining was observed when the reproduction output reached 50% of the initial output.

The table below shows the results.

As is clear from the above table, the magnetic disks obtained by the present invention (Examples 1 to 4) all have a longer minimum running time than the conventional magnetic disks (Comparative Examples 1 and 2). Also, the percentage of driving for more than 50 hours was 10.
There was no variation at 0%, and no band stains were observed, indicating that the magnetic recording medium obtained by the present invention has excellent durability and improved reliability.

Patent applicant: Hitachi Maxell, Ltd. Agent Takaoka-Haru

Claims (1)

[Claims] 1. Magnetic recording medium having a magnetic layer containing an unsaturated fatty acid ester and a hydrocarbon lubricant