JPS6070527A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium causing no bleeding of a lubricant even at high temp. and humidity and having high traveling performance and superior durability by filling the 2nd lubricant into the voids in a magnetic layer contg. the 1st lubricant. CONSTITUTION:A magnetic coating material prepd. by dispersing magnetic powder and a lubricant in a volatile solvent is coated on a nonmagnetic support and dried to manufacture a magnetic recording medium. At this time, the 1st lubricant consisting of higher fatty acid and a polysiloxane-polyoxyalkylene copolymer represented by the general formula (where m is 5-40, n is 1-5, a is 0-4, b is 5-20, a/b<0.2, and R is 1-4C alkyl) is used as the lubricant. A soln. of the 2nd lubricant in a volatile solvent is then coated on a magnetic layer formed by coating the magnetic coating material contg. the 1st lubricant. The 2nd lubricant consists of higher fatty acid anhydride and a copolymer represented by the general formula. Thus, the desired magnetic recording medium can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium that has excellent running properties and excellent durability.

In general, magnetic recording media such as magnetic tapes and flexible magnetic disks come into contact with magnetic heads and guide parts during recording and reproduction, so the coefficient of friction of the magnetic layer is small.
Also, there is less wear on the magnetic layer.

There is a demand for something with excellent running properties and excellent durability.

For this reason, conventionally, higher aliphatic compounds such as higher fatty acids, higher fatty acids, higher fatty acid alcohols, higher fatty acid esters, and/or silicone oils have been used.

Fluorine oil and the like were contained singly or in combination.

However, sufficient durability was not yet achieved. For example, if you use a flexible magnetic disk that has been stored in high temperature and high humidity for a long period of time, the lubricant will seep onto its surface and be absorbed by the nonwoven fabric attached to the jacket, causing the magnetic head to become damaged.

The friction with the guide part increases, causing unstable running and scratches on the magnetic layer, resulting in a reduction in reproduction output, which has become a problem.

It is an object of the present invention to solve one or more problems and to provide a magnetic recording medium that has excellent running properties over a long period of time not only at room temperature but also at high temperatures and high humidity, and has excellent durability.

The present invention provides a method for manufacturing a magnetic recording medium by coating a magnetic paint in which at least a magnetic powder and a lubricant are mixed and dispersed in a volatile solvent on a non-magnetic support, and drying the magnetic paint. As a lubricant, higher fatty acids and the general formula %) b is 5 to 20, a/b < 0.2, R is carbon number 1
~4 alkyl group) ? A magnetic paint using a first lubricant consisting of lysilogysan-polyoxyalgylene copolymer is coated and dried, and then on the resulting magnetic layer.

Manufacture of a magnetic recording medium characterized by applying a solution in which a second lubricant consisting of anhydrous higher fatty acid and a siloxane-polyoxyalkylene copolymer represented by the above general formula is mixed and dispersed in a volatile solvent. It's a method.

Higher fatty acid and polysiloxane as the first lubricant used in the present invention 71? The ratio of the lyoxyalkylene copolymer is 1 polymerization ratio of 20/80 to 50150, preferably 3
0/70 to 40/60, and the total amount is 0.5 to 2.0 parts by weight based on the magnetic powder.

Preferably it is contained in an amount of 10 to 15 parts by weight.

If the ratio of these higher fatty acids and polysiloxane-polyoxyalkylene copolymer is biased toward one side, or if the amount contained in the magnetic powder is too large, the effect of combined use with the second lubricant will be impaired. Therefore, even at room temperature, seepage phenomenon occurs to the surface of the magnetic layer.

It is absorbed by the non-woven fabric attached inside the jacket,
The friction between the magnetic head and the guide section becomes too strong, causing unstable running, and the magnetic layer is scratched by the magnetic head and guide section, causing a reduction in reproduction output.

If the amount is too small, the seepage phenomenon will not occur, but running stability will be lacking, sufficient durability will not be obtained, and the reproduction output will similarly decrease, making the effects of the present invention insufficient.

Specific examples of higher fatty acids used as the first lubricant of the present invention include lauric acid and myristic acid.

Examples include saturated fatty acids such as stearic acid.

The ratio of the anhydrous higher fatty acid to the polyrinloxane/alkylene copolymer as the second lubricant used in the present invention is 0.57'99.5 to 30/70 in a weight ratio of 9.
.

It is preferably in the range of 1/99 to 15/85, and furthermore, the total is 0.2 to 30 parts by weight based on the magnetic powder.
Preferably it is contained in an amount of 0.4 to 20 parts by weight.

These anhydrous higher fatty acids and polysiloxanes, l? If the ratio of the lyoxyalkylene copolymer is biased to one side or the amount is too small relative to the magnetic powder, the effect of the combination with the first lubricant will be impaired.

It is difficult to retain the first lubricant inside the magnetic layer for a long period of time, making it difficult to ensure sufficient durability.Furthermore, if the amount is too large, a oozing phenomenon occurs, causing the magnetic head to or make it dirty.

This effect will be insufficient.

Examples include acid anhydrides such as higher fatty acid anhydrides used as the second lubricant of the present invention.

As described above, the present invention has the advantage of the combined effect of the first lubricant and the second lubricant, which eliminates the lubricant seepage force not only at room temperature but also at high temperatures and high humidity.

It is possible to obtain a magnetic recording medium with excellent running properties and excellent durability without a decrease in reproduction output over a long period of time.

I don't know the reason for this in detail; I think it's as follows.

That is, the polysiloxane-polyoxyalkylene copolymer used as the first lubricant is a polysiloxane (because it has a polyoxyalkylene chain in the chain), unlike conventional silicone oil. The compatibility with the inder is improved, and it becomes possible to uniformly disperse the magnetic layer in the magnetic layer. However, since the side chain polyoxyalkylene chain is low, sufficient lubricity cannot be obtained when used alone, but it becomes effective when used in combination with a higher fatty acid, and the coefficient of friction of the magnetic layer is reduced by E/J%.

A product with excellent running properties can be obtained.

However, although these combinations alone are sufficient at room temperature, they cannot be used for long periods at high temperatures and high humidity.

The solution to this problem is to use it in combination with a second lubricant.

That is, by infiltrating the second lubricant into the gaps in the magnetic layer containing the first lubricant, the second lubricant forms a crystalline structure in the gaps, and the magnetic layer of the first lubricant is migration to the layer surface over a long period of time.

Moreover, it can be suppressed even under conditions of high temperature and high humidity.

The present invention will be explained below using examples.

<Example 1> Magnetic powder γ-Fe203 72 parts Vinyl chloride-vinyl acetate copolymer hardening agent Polyisocyanate compound 5 parts (Coronate manufactured by Nippon Polyurethane) Antistatic agent Carden black 5 parts Paint film reinforcement agent α-At203 (Average particle size 0.51 part m
) 2-part solvent MEK/) Nokyoshishifunon 60/6
0/60 part A polysiloxane-polyoxyalkylene copolymer represented by stearic acid was added as a first lubricant to this composition in a weight ratio of 35:65 to the magnetic powder in an amount of 1.2 parts by weight. were mixed and dispersed for 72 hours in a Lumil to form a magnetic paint, and this magnetic paint was applied onto a polyethylene terephthalate support with a thickness of 75 μm and dried to a thickness of 3.
A magnetic layer with a thickness of μm was formed. Next, a second layer is applied to this magnetic layer.
A solution of stearic anhydride and the polysiloxane-polyoxyalkylene copolymer dissolved in toluene at a weight ratio of 5:95 is used as a second lubricant for the magnetic powder in the magnetic layer. Apply to 12 parts by weight,
After drying, a sample was prepared by punching out a disk shape with an outer diameter of 130'+++m.

<Example 2> First example of Example 1. The polysiloxane-polyoxyalkylene copolymer used as the second lubricant is C3H6 (OC
A sample was prepared in exactly the same manner as in Example 1 except that 2H4)2(OC3H6)150C2F■5 was used.

<Comparative Example 1> A sample was prepared without adding the first lubricant of Example 1.

Comparative Example 2> A sample was prepared without applying the second lubricant of Example 1.

Comparative Example 3> A sample was prepared by adding the first lubricant and second lubricant of Example 1 simultaneously in the mixing and dispersion stage.

Comparative Example 4> A sample was prepared by simultaneously applying the first lubricant and second lubricant of Example 1 to the dried magnetic layer.

The following tests were conducted on the samples prepared in the above Examples and Comparative Examples.

<Durability test> The prepared sample was inserted into a jacket covered with non-woven fabric, and a 125 KHz signal was recorded using a magnetic recording/reproducing tester, and the peripheral speed was 1.7 r+v in an atmosphere of 4-0°C and 80% RH.
While making contact with the magnetic head at 'tJ', the temporal change in the reproduction output signal was read, and the time required for the reproduction output signal to reach 80% of the initial reproduction output signal was measured.

<Friction coefficient test> The prepared sample was inserted into a jacket covered with many non-woven fabrics and heated at 40°C and 80% RH at a circumferential speed of 1. Measurements were made while making sliding contact with the magnetic head at full ◇.

Bleeding test> The prepared sample was left in an atmosphere of 40° C. and 80% RH for 7 days, then taken out to room temperature and visually observed.

The results obtained are shown in Table 1.

From Table 1 below, it can be seen that the samples prepared according to the present invention have a small coefficient of friction, excellent running performance over a long period of time even under high temperature and high humidity, and excellent durability.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a magnetic recording medium by coating a non-magnetic support with a magnetic paint in which at least a magnetic powder and a lubricant are mixed and dispersed in a volatile solvent, and drying the magnetic paint. Higher fatty acids as a lubricant to be mixed and dispersed in the general formula % b is 5 to 20, a/b < 0.2, R is carbon number 1
A magnetic paint using a first lubricant consisting of a polysiloxane-polyoxyalkylene copolymer represented by (-4 alkyl group) is coated and dried, and on the obtained magnetic layer, anhydrous higher fatty acid and the above-mentioned 1. A method for producing a magnetic recording medium, comprising applying a solution of a second lubricant made of a polysiloxane-polyoxyalkylene copolymer represented by the general formula mixed and dispersed in a volatile solvent.