JPS6070528A - 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 hydrazide 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, and the running properties of the magnetic layer are reduced with less wear. There is a demand for something that is rich in energy and has 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 at high temperatures for a long period of time, lubricant seeps onto its surface and is absorbed by the non-woven fabric glued inside the jacket, causing damage to the magnetic head.

The friction with the guide part becomes too strong, causing unstable running and scratches on the magnetic layer, resulting in a reduction in the reproduction output.

SUMMARY OF THE INVENTION An object of the present invention is 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, a higher fatty acid and a polysiloxane-polyoxyalkylene copolymer represented by the general formula % where b is 5 to 20 and a/b (0, 2, R is an alkyl group having 1 to 4 carbon atoms) are used. A magnetic paint using a Σ first lubricant is coated and dried, and further on the obtained magnetic layer.

Higher fatty acid hydrazide and the month shown by the general formula above? A second layer made of lysiloxane-polyoxyalgylene copolymer
This method of manufacturing a magnetic recording medium is characterized by applying a solution of a lubricant mixed and dispersed in a volatile solvent.

The ratio of higher fatty acid and polysiloxane-polyoxyalkylene copolymer as the first lubricant used in the present invention is 2
Weight ratio of 20/80 to 50150°, preferably 30/7
0 to 40/60%, and the total amount of these is 0.5 to 2.0 parts by weight based on the magnetic powder.

Preferably it is contained in an amount of 1.0 to 15 parts by weight.

If the ratio of these higher fatty acids and polysiloxane-polyokine alkylene 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 placed inside the jacket,
The friction between the magnetic head and the guide section increases, 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 higher fatty acid hydrazide and polysiloxane-polyoxyalkylene copolymer as the second lubricant used in the present invention is 0.5799.5 to 30/70 as a 2 weight ratio. Preferably, it is in the range of 1/99 to 15/85, and further,
The total amount is 0.2 to 3.0 parts by weight based on the magnetic powder,
Preferably it is contained in an amount of 0.4 to 20 parts by weight.

If the ratio of the higher fatty acid amide and the polysiloxane-polyoxyalkylene copolymer is biased to 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.

The first 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 seepage phenomenon will occur, contaminating the magnetic head.

This effect will be insufficient.

Specific examples of the higher fatty acid hydrazide used as the second lubricant of the present invention include palmitic acid hydrazide, stearic acid hydrazide, and the like.

As described above, one aspect of the present invention is that the lubricant does not seep out not only at room temperature but also at high temperatures and high humidity 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.

That is, the polysiloxane-polyoxyalkylene copolymer used as the first lubricant has a polyoxyalkylene chain in the polysiloxane side chain, which is different from conventional silicone oils, so it has good compatibility with the binder. improved and uniformly dispersed 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, resulting in a magnetic layer with a small coefficient of friction and excellent running properties.

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

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 eight examples.

<Example 1> Magnetic powder γ-F820372 parts Antistatic agent Carbon black 5 parts Paint film reinforcement agent α-At203 (average particle size 0.5 μm)
2-part solvent MEK/) Luene/Anone 60/60/
60 parts of this composition were mixed with stearic acid as a first lubricant and a polysiloxane-polyoxyalkylene copolymer hereinafter represented by C3H6(OC3H6)2oOC2H5 in a weight ratio of 35:65 to the magnetic powder. 1.2 parts by weight was added and mixed and dispersed in a ball mill for 72 hours to obtain a magnetic paint. This magnetic paint was applied onto a 75 μm thick polyethylene terephthalate support and dried to form a 3 μm thick magnetic layer. Next, a solution of stearic acid hydrazide and the polysiloxane-polyoxyalkylene copolymer as a second lubricant dissolved in toluene at a weight ratio of 5:95 was added to the magnetic layer to improve the magnetic properties of the magnetic layer. The second lubricant was applied to the powder in an amount of 1.2 parts by weight, and after drying, it was punched out into a disk shape with an outer diameter of 130 TWn to prepare a sample.

<Example 2> The first example of Example 1. A sample was prepared in exactly the same manner as in Example 1, except that the I-lysiloxane-ponooxyalkylene copolymer represented by was used as the second lubricant.

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 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 125 kHz signal was recorded using a magnetic recording and reproducing tester, and a magnetic head was used at a circumferential speed of 17 m/s in an atmosphere of 40°C and 80% RH. While making contact, the temporal change in the reproduced output signal was read, 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 covered with non-woven fabric and heated at 40°C and 80% RH at a peripheral speed of 1.7fn/2.
Measurements were made while sliding contact with a magnetic head for seconds.

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, 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.

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