JPS61273732A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To reduce the coefficient of kinetic friction and to improve the traveling stability of the titled medium by providing a magnetic layer on one surface of a carrier and furnishing a layer contg. fatty acid-modified silicone and a stearic ester on the other surface. CONSTITUTION:A magnetic layer is provided on one surface of a carrier and a layer contg. a lubricant is furnished on the other surface as the back-coat layer. A fatty acid-modified silicone, especially the fatty acid-modified silicone shown by formula (A) and a stearic ester, especially the stearic ester expressed by formula (B), are used as the material to be incorporated into the back-coat layer. About 0.5-6.0pts.wt. fatty acid-modified silicone and about 0.5-6.5pts.wt. stearic ester are preferably incorporated into 100pts.wt. binder. Consequently, a magnetic recording medium having a small coefficient of kinetic friction and an excellent traveling property, whose reproduction output is not significantly decreased after repeated use and having excellent durability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks.

[Prior art and its problems]

Magnetic recording media for audio, video, and computers are becoming increasingly dense. That is, recording signals are becoming increasingly high-frequency, and for this reason, the spacing loss between the magnetic head and the magnetic recording medium has come to have a large effect on the output.

Therefore, as a countermeasure against such spacing loss, it has been proposed to make the magnetic layer of a magnetic recording medium as flat as possible.

However, if the surface of the magnetic layer is made too flat, the coefficient of friction will increase, making the magnetic tape more likely to become unevenly wound, and tend to cause stick-slip due to tension fluctuations.
Not only will the recording/reproducing operation deteriorate, but the magnetic tape will be damaged by the guide member or flange of the recording/reproducing device.

In order to overcome these drawbacks, it has been considered to specially configure the surface of the nonmagnetic support of the magnetic recording medium opposite to the surface on which the magnetic layer is formed, that is, the back layer.

In other words, one idea was to make the surface of the pack layer rough and thereby reduce the coefficient of friction.
For example, when a magnetic tape with a roughened surface is wound, the unevenness of the roughened surface is transferred to the magnetic layer, which means that unevenness is formed on the surface of the magnetic layer, resulting in the above-mentioned spacing loss. Therefore, attempts have been made to provide a so-called back coat layer and use a tool to reduce the coefficient of friction.

It has been proposed to include lubricants such as fatty acids, fatty acid esters, and silicone oils in this backcoat layer, but these lubricants are not enough to be included in the backcoat layer. No solution has been reached.

[Disclosure of the invention]

As a result of research on a magnetic recording medium in which a magnetic layer is provided on one side of a support and a lubricant-containing layer, so-called back coat layer, on the other side of a support, that is, research on substances to be included in the back coat layer. , these substances include fatty acid-modified silicones, especially fatty acid-modified silicones represented by the general formula CA), and stearic acid esters, especially the general formula C
When using the stearic acid ester represented by B),
It has been found that the friction coefficient can be reduced without reducing the S/N ratio, and a magnetic recording medium with excellent running stability can be obtained.

(However, R is a saturated or unsaturated hydrocarbon having 11 to 21 carbon atoms, X is an integer of 10 to 50, and y is an integer of O to 100.) C+t Ho Coo + CHt←CH (CHs h
(B') (However, n is an integer of 1 to 5) In general formula [A], R has 11 to 21 carbon atoms because if it is 10 or less, the lubricating effect is insufficient, especially Under high temperature conditions, the lubricity becomes insufficient and durability decreases, and when the number is 22 or more, the compatibility with the binder decreases, and furthermore, the lubricity tends to become insufficient under low temperature conditions. This is because X is an integer of 10 to 50, and y is O to 1
The reason why it is set as an integer of 00 is because if x and y become too large, the compatibility with the binder component decreases and the slipping effect tends not to be effectively exhibited.

Further, in the general formula CB), n is set to 1 to 5 because when n is 6 or more, it is compatible with the binder.

It should be noted that if the content of the fatty acid-modified silicone and stearic acid ester is too high, drum and head stains become severe and there is a tendency to cause head clock, whereas if the content is too low, the effect of addition is small. Since there is a tendency to
Preferably, the stearate ester is in the range of about 0.5 to 6.5 parts by weight.

[Example 1] 5 parts by weight of nitrocellulose, 35 parts by weight of polyurethane resin, 20 parts by weight of polyisocyanate, 100 parts by weight of carbon black, fatty acid (oleic acid) modified silicone (R =CHs (CH
-)t CH=CH(CHt)y, x = 23, y
=45) 4.5 parts by weight, 2 parts by weight of methyl isobutyl stearate represented by the above general formula CB), and 450 parts by weight of a mixed solvent of equal amounts of toluene, methyl ethyl ketone, and methyl isobutyl ketone were thoroughly mixed and dispersed in a sand mill to make a paint. This paint containing oleic acid-modified silicone and methyl isobutyl stearate is applied to the base film surface of the magnetic tape on which the magnetic coating layer is formed, on the side opposite to the side on which the magnetic coating layer is formed, and then dried and surface treated. Approximately 0.3
A layer containing oleic acid-modified silicone and methyl isobutyl stearate having a thickness of ~1.5 μm is formed to obtain a magnetic tape of a magnetic recording medium according to the present invention.

[Examples 2 to 5] In Example 1, isoamyl stearate (Example υ, isohexyl stearate (Example 3), isohexyl stearate (Example 4), Isooctyl stearate (Example 5
) to obtain a magnetic tape of a magnetic recording medium according to the present invention.

[Examples 6 to 10] In Example 1, the fatty acid-modified silicone represented by the general formula (A) was treated with x=10. Oleic acid modified silicone with y=o (Example 6), x=10. Oleic acid modified silicone with y=30 (Example 7), x=10. y=100
of oleic acid-modified silicone (Example 8), x=23,
y=1oo oleic acid modified silicone (Example 9),
x=50. y=100 oleic acid modified silicone and t
Similarly, a magnetic tape of a magnetic recording medium according to the present invention is obtained.

[Examples 11 to 13] In Example 1, the fatty acid-modified silicone represented by the general formula (A) was replaced with myristic acid-modified silicone (Example 11) where x = 23 and y = 45, and x = 23 and y = 45. of palmitic acid-modified silicone (Example 12x=23, y
The same procedure is carried out using the stearic acid-modified silicone of 45 to obtain a magnetic tape of a magnetic recording medium according to the present invention.

[Comparative Example 1] A magnetic tape is obtained by carrying out the same procedure as in Example 1 except using no oleic acid-modified silicone and using 71% X.

[Comparative Example 2] A magnetic tape is obtained by carrying out the same procedure as in Example 1 without using any methyl isobutyl stearator.

[Comparative Example 3] A magnetic tape is obtained in the same manner as in Example 5 without using any oleic acid-modified silicone.

[Comparative Examples 4 to 6] The same procedures as in Examples 11 to 13 were carried out without using any isobutyl stearate to obtain magnetic tapes.

〔Characteristic〕

The dynamic friction coefficient, running properties, and jitter of the magnetic tapes on each side were examined and the results are shown in the table.

According to this, a so-called back coat layer containing both fatty acid-modified silicone, silicone, and stearate has a small coefficient of dynamic friction, excellent running properties, and almost no screen shake. On the other hand, those containing only stearic acid ester have a large coefficient of dynamic friction, poor running performance, and are relatively prone to jitter, while those containing only fatty acid-modified silicone have a small coefficient of dynamic friction, but It can be seen that the running performance is poor and jitter is likely to occur.

〔effect〕

Since the magnetic recording medium according to the present invention contains fatty acid-modified silicone and stearic acid ester in the so-called back coat layer, it has a small coefficient of dynamic friction and good running properties, and the reproduction output remains constant even after repeated use. Since the deterioration is small, it is highly durable, and furthermore, there is an effect that the screen shake is extremely small.

Patent applicant: Japan Victor Co., Ltd.-17 and Pa.

Claims (1)

[Claims] 1. A magnetic recording medium comprising a magnetic layer on one side of a support and a layer containing fatty acid-modified silicone and stearate on the other side.