JPS60242520A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium having excellent running property and durability by coating a magnetic layer into which a polysiloxane/polyoxyalkylene copolymer and high fatty acid are incorporated on a substrate and a lubricating agent contg. said copolymer and sodium alkyl sulfonate on the magnetic layer. CONSTITUTION:The lubricating agent mixture contg. the polysiloxane/polyoxyalkylene copolymer A expressed by the formula (R is an alkyl or 1-4C, m is 5-40, n is 1-5, (a) is 0-4, (b) is 5-20 and a/b <0.2) and the higher fatty acid such as aluric acid or stearic acid in a 20/80-50/50 range by weight in incorporated into magnetic powder at 0.2-20wt% by the in weight of said powder to prepare a magnetic paint. Such paint is coated on the substrate and is dried to form the magnetic layer. A volatile org. solvent soln. of the lubricating agent mixture contg. the sodium alkylsulfonate/copolymer A at 0.5/99.5-30/70 by weight is coated on such magnetic layer and is dried to penetrate the lubricating agent to the voids of the magnetic layer so that the lubricating agent is migrated gradually toward the surface for a long period. The magnetic recording medium which obviates bleeding of the lubricating agent even at and under a high temp. and high humidity and has the excellent running property and durability is obtd.

Description

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

[Prior art]

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, the friction of the magnetic layer is low.

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.

[Technical issues to be solved]

However, sufficient durability was not yet achieved. For example, when using a flexible magnetic disk that has been stored at high temperature and high humidity for a long period of time, lubricant oozes out onto the surface of the disk and is absorbed into the nonwoven fabric inside the jacket, causing the magnetic spatula r.

The friction with the guide portion is large, causing unstable running and scratches on the magnetic layer, resulting in a reduction in reproduction output.

[Purpose of the invention]

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.

[Structure of the invention]

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. A magnetic paint using a first lubricant consisting of a higher fatty acid and a polysiloxane-polyoxyalkylene copolymer represented by the general formula (%) as a lubricant was applied and dried. Further on the magnetic layer.

A magnetic method characterized by applying a solution in which a second lubricant consisting of 11 um alkylsulfonate and a polysiloxane-polyoxyalkylene copolymer represented by the above general formula is mixed and dispersed in a volatile solvent. This is a method for manufacturing a recording medium.

The ratio of the higher fatty acid topolysiloxane-polyoxyalkylene copolymer used as the first lubricant used in the present invention is 2
Weight ratio of 20/80 to 50150°, preferably 3C1/
70 to 40/60, and the total of these is 0.5 to 20 parts by weight, preferably 1.0 to 1 part by weight based on the magnetic powder.
．． The content is 5 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.

The inside of the jacket has been absorbed by the non-woven fabric.
If the friction between the magnetic head and the guide part is not strong enough, running becomes unstable, and the magnetic layer is scratched by the magnetic head and the guide part, 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 sodium alkyl sulfonate and polysiloxane-polyoxyalkylene copolymer as the second lubricant used in the present invention is 2 weight ratio Q, 5/99.5 to 30/
70. Preferably in the range of 1/99 to 15/85,
Furthermore, the total of these is 0.2 to 3.0 relative to the magnetic powder.
It is contained in an amount of 0.4 to 2.0 parts by weight, preferably 0.4 to 2.0 parts by weight.

If the ratio of sodium alkyl sulfonate and 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. However, the first lubricant cannot be retained inside the magnetic layer for a long period of time, making it difficult to ensure sufficient durability. On the other hand, if the amount is too large, a seepage phenomenon will occur, contaminating the magnetic head and making the two-wire effect insufficient.

Specific examples of the sodium alkylsulfonate used as the second lubricant of the present invention include sodium 1-octadecanesulfonate, sodium 1-hexadecanesulfonate, and sodium 1-tetradecanesulfonate.

As described above, in the present invention, the lubricant does not ooze out not only at room temperature but also at high temperature 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 is the conventional linear-7,t
Since it has a polyoxyalkylene chain in the polysiloxane side chain, which is different from that of 'F', its compatibility with the binder is improved and it becomes possible to be uniformly dispersed in the magnetic layer. However, since the side chain polyoxyalkylene chain is low, sufficient lubricity cannot be obtained when used alone, but 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 in high temperature, high humidity environments for long periods of time.

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

That is, by impregnating the second lubricant into the voids in the magnetic layer containing the first lubricant, the second lubricant forms a crystalline structure in the voids, and the second lubricant forms a crystalline structure in the voids. Migration to the magnetic 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 two examples.

<Example 1> Magnetic powder γ-F820372 parts Antistatic agent Carbon black 5 parts Paint film reinforcement agent α-At203 (average particle size 05 μm) 2
Partial solvent MEK/Toluene/Anone 60/60/
60 parts To this composition, 1.2 parts by weight of a polysiloxane-polyoxyalkylene copolymer represented by stearic acid as a first lubricant was added to the magnetic powder at a weight ratio of 35:65, and the mixture was milled in a ball mill. Mix and disperse for 72 hours to obtain a magnetic paint, apply this magnetic paint onto a 75 μm thick polyethylene terephthalate support, and dry it to a thickness of 3 μm.
A magnetic layer was formed. Next, a solution prepared by dissolving sodium 1-octadecanesulfonate as a second lubricant and the above polysiloxane-polyoxyalkylene copolymer in toluene at a weight ratio of 5:95 is then applied to the magnetic layer. A second lubricant was applied to the magnetic powder in an amount of 1.2 parts by weight, and after drying, a sample was prepared by punching out a disk shape with an outer diameter of 130 cm.

<Example 2> 2IJ-7 used as the first and second lubricants in Example 1
A sample was prepared in exactly the same manner as in Example 1, except that a 0xane-polyoxyalkylene copolymer was used.

Comparative Example 1> A sample was prepared without 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 125 kHz signal was recorded using a magnetic recording and reproducing tester, and the sample was heated at a circumferential speed of 1.7 in 7 in an atmosphere of 40°C and 80% RH.
The temporal change in the reproduced output signal was read while the magnetic head was brought into contact with the magnetic head, and the time required for the reproduced output signal to reach 80% of the initial reproduced output signal was measured.

Friction coefficient test> The prepared sample was inserted into a jacket covered with a nonwoven fabric and measured in an atmosphere of 40° C. and 80% RH while sliding against a magnetic head at a wind speed of 1.7 m/sec.

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

The results obtained are shown in Table 1.

Table 1 [Effects of the Invention] Table 2 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. As a lubricant to be mixed and dispersed in the polysiloxane-polyoxyalkylene with a higher fatty acid and the general formula % (b is 5 to 20, a/b<o, z, R is an alkyl group having 1 to 4 carbon atoms). A magnetic paint using a first lubricant consisting of a copolymer 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 second lubricant consisting of sodium alkyl sulfonate and a polysiloxane-polyoxyalkylene copolymer represented by the above general formula is mixed and dispersed in a volatile solvent. Method.