JPS59101031A - Method for treating surface of magnetic recording body - Google Patents

Abstract

PURPOSE:To obtain a good lubricant small in kinetic friction coefft. and stick slip and superior in durability by coating the surface of a thin continuous film of magnetic iron oxide formed on a base with an org. solvent soln. of an alkali metal or alkaline earth metal salt of a fatty acid in the limited range of wt% concn. CONSTITUTION:A flexible base, such as polyester or polyimide, is generally used for the base of a magnetic recording body. Its surface is treated as follows: An alkali metal salt, such as lithium, sodium, or potassium, of a fatty acid, such as caproic, caprylic, or capric acid, or an alkaline earth metal, such as magnesium, calcium, or barium, of said acid is dissolved in an org. solvent, such as benzene, toluene, ethylbenzene, or hexane, to 0.001-1wt% soln., and the surface of a continuous thin film of magnetic iron oxide is uniformly coated with said soln. by the coating method using a reverse roll coater in the case of a magnetic recording tape, and a spin coater or the like in the case of a magnetic recording disc, and it is dried to form a lubricant layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface treatment of magnetic recording bodies used for magnetic tapes, magnetic disks, and the like.

Improving the recording density in magnetic recording devices is a constant trend in this industry, and in order to achieve this, it is essential to make the magnetic recording medium thinner and thinner.

Conventionally, so-called coating media, in which a mixture of iron oxide fine particles and a polymeric resin binder is coated on a substrate, have been widely used as magnetic recording media.

These magnetic recording media include magnetic tape for audio, magnetic tape for VTRs, magnetic tape for computers, flexible magnetic disks, and rigid magnetic disks. We are trying to achieve higher density by increasing the coercive force of .

However, in coated media, it is extremely difficult to reduce the thickness of the magnetic layer to several thousand or less and to achieve uniform recording and reproducing characteristics. Therefore, as a high-density magnetic recording medium to replace coating media, a magnetic recording medium in which a continuous thin film is formed on a substrate is being developed. Among them, those using magnetic iron oxide continuous thin film have mechanical strength (abrasion resistance),
It is superior to those using coating media in terms of chemical stability (corrosion resistance), and is attracting attention in various fields.

However, in order to actually use a magnetic iron oxide continuous thin film as a magnetic recording medium of a magnetic storage device, it is necessary to reduce the friction. Generally, in a magnetic tape device, when the device is in use, a magnetic recording body, a magnetic head, a head cylinder, etc. are in a state of frictional contact. Even in a flexible disk device, when the device is in use, the magnetic recording body, the magnetic head, and the head slider are in a state of frictional contact. Furthermore, in a rigid magnetic disk drive, the head slider is in the air when it is in use, but it is in a contact friction state when the magnetic disk starts and stops rotating. Therefore, if the continuous magnetic iron oxide thin film is used as it is, it may wear out due to friction, and smooth contact with the head may not be achieved, resulting in large output fluctuations. Traditional coating media solve these problems by dispersing lubricants in binders, but in the case of magnetic iron oxide continuous thin films that do not use any binders, other methods are needed to reduce friction. There is. Conventionally, a method for reducing the friction of such a continuous thin film has been to apply a solid or liquid lubricant to the surface of the continuous thin film to form a thin lubricant layer on the continuous thin film. However, in this case, even if the same lubricant is applied, the frictional properties and the adhesion force between the lubricant and the continuous thin film will vary greatly depending on the type of continuous thin film on the base. The frictional properties change greatly depending on the concentration. Therefore, it is necessary to find the optimal lubricant and its application conditions depending on the type of continuous thin film.

For magnetic iron oxide continuous thin films, the selection of a lubricant and the conditions for applying the lubricant that exhibit frictional properties comparable to those of the coating medium have not been sufficiently established.

An object of the present invention is to provide a surface treatment method for forming a lubricant suitable for a magnetic recording medium using a magnetic iron oxide continuous thin film on the surface of the magnetic recording medium.

For the above purpose, the present inventor attempted surface treatment of a magnetic iron oxide continuous thin film with various fatty acids and their metal salts. That is, an attempt was made to form a lubricating layer by applying solutions of various fatty acids and their metal salts in different solvents and concentrations on the surface of a continuous magnetic iron oxide thin film. As a result, it was found that a good lubricating layer could be obtained by selecting the type of fatty acid metal salt, the type of solvent, and the concentration of the solution.

The present invention was made in view of these points, and the surface treatment method of the present invention involves applying an alkali metal salt or an alkaline earth metal salt of a fatty acid to the surface of a continuous magnetic oxide thin film formed on a substrate in an organic solvent. It is characterized in that a lubricating layer is formed on the surface of the magnetic recording material by applying a solution by melting it to a concentration range of 0.001 to 1 by weight and drying it.

Generally, the substrates of magnetic recording bodies include flexible substrates made of polyester, polyimide, etc., as well as rigid substrates made of aluminum alloy, glass, etc. whose surfaces are treated with alumite. The magnetic recording medium is produced by forming a continuous thin film of magnetic iron oxide on this substrate by sputtering, reactive vapor deposition, or the like.

In the present invention, the surface of this magnetic recording medium is treated as follows. namely, lithium of fatty acids such as caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, behelic acid, melisic acid, etc.
An alkali metal salt such as sodium, potassium, etc. or an alkaline earth metal salt such as magnesium, calcium, barium, etc. is dissolved in an organic solvent such as benzene, toluene, ethylbenzene, hexane, ethyl alcohol, isopropyl alcohol, acetone, etc., and the weight ratio is 0. 0011~is
After forming a solution, a continuous thin film of magnetic iron oxide is applied using a coating method such as a reverse roll coater, clavier coater, rod coater, or spray coater for tape-shaped magnetic recording media, or a spin coater for disc-shaped magnetic recording media. After being applied uniformly to the surface, it dries to form a lubricating layer.

Next, the present invention will be explained in detail with reference to Examples.

It is a drum whose surface has been polished and then anodized, and 2 is a tape. 3 is a tension detection section, and 4 is a weight for applying a load to the tape corresponding to the pack tension in an actual tape device. Diameter 75 when measured
Using the WIIE drum, set the relative speed to tape 2 to 2c.
It was rotated so that it became IIL/S. Moreover, the weight 4 for pack tension was 50 g. These conditions, such as drum diameter, relative speed, back tension, etc., are commercially available β
The method was selected to match the friction conditions between the head cylinder drum and tape of a VTR. If the tension caused by the weight 4 is T1, and the tension measured by the tension detection unit 3 is T2, then
The coefficient of dynamic friction μ between the drum 1 and the tape 2 is determined by Euler's friction formula and by measuring the time until the friction increases when the drum is rotated continuously for a long time under the above conditions. The durability was measured.

Furthermore, the thickness of stick slip caused by friction was also evaluated from the fluctuation of the tension measured by the tension detection unit 3.

Example 1 A polyimide film was used as a substrate, and γ-Fe20. A continuous thin film was formed and cut out into a tape shape with a width of 100% and was used as a sample. Each lubricant listed in Table 1 was dissolved in toluene to a concentration of 0.01% by weight and applied to the surface. Evaluations were made using the kinetic friction coefficient measuring device shown above, and the results are summarized in Table 1.In addition, the untreated sample and the use of commercially available metal salts or alkaline earth metal salts showed improvement over the untreated sample. It is possible to obtain friction characteristics that are superior to, or even better than, a coated media pot.

Example 2 A continuous thin film of magnetic iron oxide was formed on a polyimide film by the spacing method, and cut out into a tape shape with a width of 30%. This was used as a sample. Chemical solvents with varying concentrations were applied to the surface. After that, the excess solvent was evaporated and the result was evaluated using a kinetic friction coefficient measuring device shown in Table 1.
We summarized the results.

As can be seen from Table 2, when an organic solvent is used, the weight%
Good frictional properties were obtained at concentrations ranging from 0.001% to 1%. When it reaches about 0.001%, the friction coefficient starts to increase and the durability time becomes shorter. On the other hand, when it reaches the 1st position, excess fatty acid metal salts can be seen on the surface, and the coefficient of kinetic friction μ
, durability time did not change much, but stick slip started to increase.

The solubility of fatty acids and fatty acid metal salts at room temperature is limited to about 1%, and even if a thick solution is made by raising the temperature, excess fatty acid metal salts will simply adhere to the tape surface.

When the tape was actually used in a tape device, such excess fatty acid metal salts clogged the gear pump, causing trouble.

Furthermore, when water was used as a solvent, a phenomenon in which the tape stuck to the drum occurred, and the frictional properties were rather worse than those without treatment.

Table 2 As shown above, according to the present invention, the metal salt of the fatty acid used must be an alkali metal salt or an alkaline earth metal salt;
A sufficient effect cannot be obtained with metal salts such as aluminum. In addition, the solvent must be an organic solvent, and although alkali metal salts of fatty acids are soluble in water, an aqueous solution not only does not provide a sufficient effect, but also degrades in some cases compared to an untreated solution. The concentration of the solution is 0.0% by weight.
A range of 0.001% to 1.0% is suitable; if it is thinner than this, no effect will be obtained, and if it is thicker, excess metal salts of fatty acids will remain on the surface of the medium and adhere to the head, causing adverse effects.

The lubricating effect of fatty acids or their metal salts is due to the carbonal ion (-COO"-), which is a hydrophilic group, being adsorbed to the surface of the material, and the hydrophobic hydrocarbon chains are arranged at a certain angle to the surface of the material, resulting in dense lubrication. It is thought that this is because a film is formed, or when multiple films are formed, a layered structure is created, and sliding lubrication works between the layers.As shown in the present invention, in the case of a continuous magnetic iron oxide thin film, the alkali metal of fatty acid It is believed that the reason why salts or alkaline earth metal salts are particularly effective is that these metal salts have strong polarity and good adhesion to the surface of the iron oxide thin film.

Although the measurement results for tape-shaped samples are shown in the examples, the same fatty acid metal salts were used for disk-shaped samples as well.
A good lubricating layer can be formed using a similar coating method.

Therefore, according to the method of the present invention, a lubricating layer can be provided on the surface of a magnetic tape, floppy magnetic disk, rigid magnetic disk, etc. using a magnetic iron oxide continuous thin film, and high frictional characteristics can be obtained.

As explained above, in the present invention, an alkali metal salt or an alkaline earth metal salt of a fatty acid is dissolved in an organic solvent on the surface of a magnetic iron oxide continuous thin film formed on a substrate.
By applying a solution with a concentration of 1.0% by weight, it is possible to form a good lubricating layer with low dynamic friction coefficient and stick slip, and excellent durability.

Figure shown. The numbers in the figure are 1 Nidrum, 2: Tape, and a diagram showing the values. The vertical axis shows the value of the dynamic friction coefficient μ, and the horizontal axis shows the number of carbon atoms in the fatty acid. If an element symbol is written next to a white circle, it is a metal salt of that metal.

Claims (1)

[Claims] A solution prepared by dissolving an alkali metal salt or an alkaline earth metal salt of a fatty acid in an organic solvent and forming a concentration of [1001 to 1% by weight] is coated on the surface of a magnetic recording medium in which a continuous magnetic iron oxide thin film is formed on a substrate. Characteristic surface treatment method for magnetic recording media.