JPS6070529A - 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 voids in a magnetic layer contg. the 1st lubricant with the 2nd 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 salt 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 acid amides, higher fatty acid alcohols, higher fatty acid esters, 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, when using a flexible magnetic disk that has been stored in high temperature and high humidity for a long period of time, lubricant seeps onto the surface of the disk and is absorbed by the nonwoven fabric glued inside the jacket, causing damage to the magnetic head.

Friction with the guide portion increases, causing unstable running and scratches on the magnetic layer, causing problems such as a reduction in reproduction output.

It is an object of the present invention to solve two or more problems and 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. Higher fatty acid as a lubricant and general formula % b is 5 to 20 and a/b (0,2, R is carbon number 1 to 71
A magnetic paint using a first lubricant made from a polysiloxane-polyoxyalgylene copolymer represented by (an alkyl group) is coated and dried, and further on the magnetic layer obtained.

A method for manufacturing a magnetic recording medium, comprising applying a solution in which a second lubricant consisting of a higher fatty acid salt and a polysiligiane-polyoxyalkylene copolymer represented by the above general formula is mixed and dispersed in a volatile solvent. It is.

The ratio of higher fatty acid and polysiloxane-polyoxyalkylene copolymer as the first lubricant used in the present invention is 2
Weight ratio: 20/80 to 50150. Good luck is 30/7
0 to 1.0/60, and furthermore, the total of these is 5 to 2.0 parts by weight, preferably 1.0 to 2.0 parts by weight, based on the magnetic powder.
The content is 0 to 1.5 parts by weight.

The ratio of these higher fatty acids and polysiloxane-polyoxyalkylene copolymer may be biased toward one side, or
Furthermore, if the amount of the lubricant contained in the magnetic powder is too large, the effect of using it in combination with the second lubricant will be impaired, and the phenomenon of seepage onto the surface of the magnetic layer will occur even at room temperature.

Inside the jacket, there is a layer of moisture that has been absorbed by a thick non-woven fabric.
The friction between the magnetic head and the guide section is large, causing unstable running, and the magnetic layer is scratched by the magnetic head and guide section, causing a reduction in reproduction output.

If it 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 higher fatty acid salt and the polysiloxane-polyoxyalkylene copolymer as the second lubricant used in the present invention is 05/995 to 30/70 in a 2 weight ratio. Ideally 1/
The range is 99 to 15/85, and the total is 0.2 to 30 parts by weight based on the magnetic powder, and the preferred weight is 04.
The content is 20 parts by weight.

If the ratio of the higher fatty acid salt and the polysiloxane-polyoxyalkylene copolymer is biased toward one side, or if the amount is too small relative to the magnetic powder, the effect of the combination with the first lubricant will be impaired, and the first The lubricant cannot be retained inside the magnetic layer for a long period of time, making it difficult to ensure sufficient durability. Also, if the amount is too large, a oozing phenomenon may occur, which may stain the magnetic head.

I think this effect is insufficient.

Specific examples of higher fatty acid salts used as the second lubricant of the present invention include sodium laurate, sodium myristate, and sodium palmitate.

Examples include saturated fatty acid salts such as sodium stearate.

As described above, in the present invention, the lubricant oozes out easily not only at room temperature but also at high temperature and high humidity only due to the combined effect of the first lubricant and the second lubricant.

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, but I think it is as follows.

Unlike conventional silicone oils, the polysiloxane-polyoxyalkylene copolymer used as the first lubricant has a polysiloxane side chain dipolyoxyalkylene chain, so the compatibility of the binder surface is This makes it possible to improve and uniformly disperse the particles in the magnetic layer. However, because the side chain polyoxyalkylene chain is lower,
Although sufficient lubricity cannot be obtained when used alone, it is effective when used in combination with higher fatty acids, and the coefficient of friction of the magnetic layer is small.

A product with excellent running properties can be obtained.

However, although these combinations alone are sufficient at room temperature, they are difficult to maintain over a long period of time in high temperature and high humidity environments.

The solution to this problem is to use the second lubricant in combination.

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 nine examples.

<Example 1> Magnetic powder r-Fe203 72 parts Hardening agent Polyisocyanate compound 5 parts (Coronate manufactured by Nippon Polyurethane) Antistatic agent Carbon black 5 parts Paint film reinforcement agent (X-A/1.203 (average particle Diameter 0.5μ
m) '2 part solvent MEK/) Rue//7/n 6
0/60/60 parts To this composition, a polysiloxane-polyoxyalkylene copolymer represented by stearic acid was added as a first lubricant in a weight ratio of 35:65 to 1.2 weight to magnetic powder. Add a section? The magnetic paint was mixed and dispersed for 72 hours using Lumil, and this magnetic paint was applied onto a 75 μm thick polyethylene terephthalem support and dried to form a 3 μm thick magnetic layer.Next, this magnetic layer Then, as a second lubricant, sodium stearate and the above polysiloxane-polyoxyalkylene copolymer were added in a weight ratio of 5.
A solution prepared by dissolving 95 parts in toluene is applied to the magnetic powder in the magnetic layer so that the second lubricant becomes 1.2 parts by weight, and after drying, it is shaped into a disc with an outer diameter of 13 off. A sample was prepared by punching.

<Example 2> First example of Example 1. A sample was prepared in exactly the same manner as in Example 1, except that the polysiloxane-polyoxyalkylene copolymer represented by was used as the second lubricant.

<Comparative Example 1> A sample was prepared by repeatedly adding the first lubricant of Example 1.

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

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

<Comparative Example 4> A sample was prepared by simultaneously applying the first lubricant and the 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, a 1.25 kHz signal was recorded using a magnetic recording/reproducing tester, and a magnetic head was inserted at a circumferential speed of 7 m/sec in an atmosphere of 40°C and 80% RH. The temporal change in the reproduced output signal was read while in contact with the original reproduced output signal, and the time at which the reproduced output signal reached 80% of the initial reproduced output signal was measured.

<Friction coefficient test> The prepared sample was inserted into a jacket to which a nonwoven fabric was attached and measured while sliding it against a magnetic head at a circumferential speed of 1.7 trV/sec in an atmosphere of 40° C. and 80° RH.

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

The results obtained are shown in Table 1.

Table 1 below shows that the samples prepared according to the present invention have a small coefficient of friction, excellent long-term running performance even at high temperatures and high humidity, and excellent durability.

Claims (1)

[Claims] 1. At least magnetic powder and lubricant in volatile solvent
In the method of manufacturing a magnetic recording medium by coating a magnetic paint mixed and dispersed on a non-magnetic support and drying, a lubricant mixed and dispersed in the magnetic paint is a higher fatty acid and the general formula % b is 5. ~20, a/b < 0.2, R is 1 carbon number
A magnetic paint using a first lubricant consisting of a polysiloxane-polyoxyalkylene copolymer represented by (-4 alkyl group) is coated and dried, and further on the obtained magnetic layer. Manufacture of a magnetic recording medium characterized by applying a solution in which a higher fatty acid salt and a second lubricant consisting of an I-lysiloxane-polyoxyalkylene copolymer represented by the above general formula are mixed and dispersed in a volatile solvent. Method 0