JPS6055518A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve running characteristics and durability for a long period of time by coating a soln. prepd. by mixing and dispersing the 2nd lubricating agent consisting of higher fatty acid amide and a specific polysiloxane-polyoxyalkylene copolymer with and into a volatile solvent on the magneticlayer obtd. by coating a magnetic material using the 1st lubricating consisting of the above- described copolymer on a base and drying the same. CONSTITUTION:The ratio of the higher fatty acid as the 1st lubricating agent and the polysiloxane-polyoxyalkylene copolymer expressed by the general formula I is 20/80-50/50 by weight and further the total thereof is incorporated at 0.5-2.0pts.wt. into the magnetic powder. The ratio of the fatty acid amide and polysiloxane-polyoxyalkylene copolymer as the 2nd lubricating agent is 0.5/99.5- 30/70 by weight and the total thereof is incorporated at 0.2-3.0pts.wt. into the magnetic powder. The oozing of the lubricating agent not only at an ordinary temp. but at high temp. and high humidity as well is obviated with this invention only by the combined effect of the 1st lubricating agent and the 2nd lubricating agent, by which the decrease in the reproduced output is obviated for a long period of time.

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.

Generally, magnetic recording media such as magnetic tapes and flexible magnetic disks come into contact with magnetic heads and guide parts during recording and reproduction.

There is a demand for a magnetic layer with a low coefficient of friction, less wear, 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, silicones, -2- oils, fluorine oils, etc. have been contained in the form of Lli alone or in combination.

However, it has not been possible to achieve 1, which ensures sufficient durability. 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 seeps onto its surface and is absorbed by the nonwoven fabric glued inside the jacket, causing friction with the magnetic head and guide section. It becomes larger, causing unstable running and scratching the magnetic layer.

This caused a problem in that the playback output decreased.

SUMMARY OF THE INVENTION An object of the present invention is to solve one 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. The lubricant is 1 to 1 and the higher fatty acid has a general formula (% formula %) of 5 to 20, a/b<o, 2. A magnetic paint using a first lubricant consisting of a polysiloxane-polyoxyalkylene copolymer represented by (R is an alkyl group having 1 to 4 carbon atoms) is coated and dried on the resulting magnetic layer.

Furthermore, a second compound comprising a higher fatty acid amide and a polysiloxane-polyoxyalkylene copolymer represented by the above general formula
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 9
The weight ratio is 20/80 to 50150°3- preferably 30/70 to 40/60, and the total 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 1.5 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 combined effect with the second lubricant will be impaired. Even at room temperature, the magnetic layer seeps out onto the surface and is absorbed by the non-woven fabric attached to the inside of the jacket, increasing friction between the magnetic head and the guide section, resulting in unstable running. Scratch the magnetic layer with the guide part.

This causes a decrease in playback output.

On the other hand, 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 saturated fatty acids such as lauric acid, myristic 4-acid, and stearic acid.

The ratio of higher fatty acid amide and polysiloxane-polyoxyalkylene copolymer as the second lubricant used in the present invention is 0.5/99.5 to 30/70 in a 9 weight ratio. It is preferably in the range of 1/99 to 15/85, and furthermore, the total content is 0.2 to 3.0 parts by weight, preferably 0.4 to 2.0 parts by weight based on the magnetic powder. .

If the ratio of higher fatty acid amide and 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 The lubricant No. 1 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 and the magnetic head will be contaminated, resulting in an insufficient single-stick effect.

A specific example of the higher fatty acid amide used as the second lubricant of the present invention is lauric acid amide.

Examples include saturated fatty acid amides such as myristic acid amide and stearic acid amide.

As described above, the present invention is achieved by the combined effect of the first lubricant and the second lubricant, which prevents the lubricant from seeping out not only at room temperature but also at high temperatures and high humidity, and allows the reproduction output to be maintained for a long period of time. It is possible to obtain a magnetic recording medium that has excellent running properties without deterioration and excellent durability.

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 improved compatibility with the binder because it has a polyoxyalkylene chain in the polysiloxane side chain, unlike conventional silicone oil. and can be uniformly dispersed in the magnetic layer. However, because the side chain polyoxyalkylene chain is lower,
However, sufficient lubricity cannot be obtained when used alone.

It becomes effective when used in combination with higher fatty acids, resulting in a magnetic layer with a low 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, and the solution to this problem is to use them 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 This makes it possible to suppress migration to the layer surface over a long period of time, even under conditions of high temperature and high humidity.

The present invention will be explained below using nine examples.

<Example 1> Magnetic powder γ-F020372 parts Hardening agent Polyincyanate compound 5 parts (Coronate manufactured by Nippon Polyurethane) Antistatic agent Carbon black 5 parts Paint film reinforcement agent α-A7.203 (average particle size 0.5 μm) )
2-part solvent MEK/Toluene/Anone 60/60/
60 parts Stearic acid and a polysiloxane-polyoxyalkylene copolymer represented by C3l(6(OC3H6)2oOC2H5) were added to this composition as a first lubricant in a weight ratio of 35:65 to magnetic powder. .2 parts by weight were 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.Then, this magnetic paint A solution prepared by dissolving stearic acid amide and the above-mentioned polysiloxane-polyoxyalkylene copolymer in toluene at a weight ratio of 5:95 as a second lubricant was applied to the magnetic powder in the magnetic layer. 2
After applying 1.2 parts by weight of lubricant and drying.

A sample was prepared by punching out a disk shape with an outer diameter of 133 fins.

<Example 2> The polysiloxane-polyoxyalkylene copolymer used as the 11th second lubricant of Example 1 was C3H6(OC2H4)2(OC3H6)150C2H
A sample was prepared in exactly the same manner as in Example 1, except that the sample represented by No. 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 6> The first lubricant and the second lubricant of Example 1 were added simultaneously in the mixing and dispersion stage to prepare a sample in 1-.

<Comparative Example 4> Sample 1 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 test t1 prepared in the above Examples and Comparative Examples.

[Durability test] Test sample 1 was inserted into a jacket with a non-woven fabric and a signal of 125 KITz was recorded using a magnetic recording/reproducing tester, and the peripheral speed was 1. 7m
The time change in the reproduced output signal was measured while contacting the magnetic head at a rate of 1/2 seconds, and the time at which the reproduction output signal reached 80% of the initial reproduced output signal was measured.

Friction coefficient test> Created test f! -1 was inserted into a jacket covered with non-woven fabric, and the circumferential speed was 1.7 rn in an atmosphere of 40°C and 801RH.
The measurement was made while slidingly contacting the magnetic head at a speed of 1/sec.

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 the table 2, the samples prepared according to the present invention have a small coefficient of friction, excellent running performance over a long period of time even at high temperatures and high humidity, and
It can be seen that it has excellent durability.

Claims (1)

[Claims] 1. Volatile solvent "In a method for manufacturing a magnetic recording medium by applying a magnetic paint mixed and dispersed with at least a magnetic powder and a lubricant to a non-magnetic support -1- and drying it. , as a lubricant to be mixed and dispersed in the above-mentioned magnetic paint, a polysiloxane represented by a higher fatty acid and the general formula (% formula %) 5 to 20 and a/b < 0.2 (R is an alkyl group having 1 to 4 carbon atoms). A magnetic coating using a first lubricant consisting of a polyogistial 1-cut/copolymer is coated and dried on the resulting magnetic layer.Furthermore, a higher fatty acid amide and a polysiloxane represented by the above general formula are coated and dried. - a second comprising a polyoxyalkylene copolymer;
A method for manufacturing a magnetic recording medium, comprising applying a solution of a lubricant mixed and dispersed in a volatile solvent.