JPH0619834B2 - Method of manufacturing magnetic recording medium - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing a magnetic recording medium having a surface overcoated with a lubricant in order to improve wear resistance.

[Prior art]

In a device such as a magnetic tape device or a floppy disc device which uses a magnetic recording medium having a magnetic film formed on a flexible substrate, the magnetic head and the magnetic recording medium are in contact with each other when recording and reproducing a signal.

On the other hand, in a magnetic disk device using a magnetic recording medium having a magnetic film formed on a rigid substrate such as aluminum,
When a floating head slider, which is a dynamic pressure gas bearing, is used to float a magnetic head on a recording medium that rotates at high speed up to a minute clearance, and recording / reproducing signals in a non-contact state, the surface of the recording medium is rough. When the floating clearance of the magnetic head is reduced due to disturbance such as dust or dust, the magnetic head and the recording medium come into contact with each other.

In recent years, a contact start stop (CSS) type magnetic disk device that starts and stops a drive motor that rotates the recording medium with the magnetic head stationary on the recording medium has become mainstream. In this case, when the levitation clearance of the magnetic head does not reach the desired value and the rotation speed is lower than a certain value, contact travel between the head and the medium occurs.

As described above, the contact traveling between the magnetic head and the magnetic recording medium occurs in various states, but in general, the magnetic film itself of the magnetic recording medium does not have lubricity, or even if it does, it has extremely low lubricity and thus has a long life. When contact traveling for a long time occurs, the magnetic head or the magnetic film of the magnetic recording medium is abraded and so-called head crash occurs.

Therefore, it is generally widely practiced to over coat the surface of the magnetic recording medium with a lubricant to enhance its lubricating performance. If a large amount of lubricant is used here, the circulation performance is improved, but the coefficient of friction between the magnetic head and the recording medium is increased.As a result, the magnetic head is adsorbed on the recording medium surface at the time of rotation start, and both are damaged. It is necessary to use an appropriate amount so as not to increase the coefficient.

As a surface lubricant conventionally used, a fluorocarbon liquid lubricant containing fluorine and carbon as main components is generally used. Among them, liquid lubricants called perfluoroalkyl polyethers have the property that they are chemically stable, have a small surface tension and are difficult to evaporate, and have excellent lubricating performance under normal use conditions. Widely used as a lubricant.

However, perfluoroalkyl polyether is a liquid lubricant in the state where the head and the medium come into contact with each other at a high speed, and therefore the lubricating film is easily broken, and the head and the medium are easily worn and damaged. I got it.

In order to prevent the lubrication film from breaking, it is sufficient to use perfluoroalkyl ether having a large molecular weight, that is, a high viscosity, but when the viscosity is increased, the magnetic head easily adheres to the recording medium surface and the friction coefficient Forced to increase.

Particularly, in a continuous thin film medium having a magnetic film formed by a sputtering method or a plating method, its surface is smoother than that of a coating medium coated with conventional iron oxide particles. However, there is a drawback in that the head and the medium surface are firmly adhered to each other, resulting in a very large friction coefficient.

In order to eliminate such drawbacks, a surface lubricant in which an organic fixed lubricant powder having a cleavable lamella structure is dispersed in perfluoroalkyl polyether base oil has already been proposed, which is a perfluoroalkyl polyether simple substance. It has been reported that, with the same viscosity, the lubricating film is less likely to break and has excellent wear resistance.

However, since the perfluoroalkyl polyether base oil does not have a polar group in its molecule, the dispersed state of the organic solid lubricant having a cleavable lamella structure and the base oil is not always sufficiently desirable, It is difficult to stably maintain a friction coefficient of 0.2 or less when overcoating on the surface of the recording medium. Under severe conditions such as extreme pressure, the adhesion of the base oil itself to the surface of the recording medium is It was not sufficient, and there was a problem that the lubricating film was easily broken.

[Outline of Invention]

The present invention has been made in view of such problems, and an object thereof is to secure high wear resistance by making a lubricating film difficult to break in a magnetic recording medium having a surface overcoated with a lubricant. In addition, it is possible to reduce the friction coefficient between the magnetic head and the recording medium, further reduce the variations in the wear resistance and the friction coefficient, and to stably obtain the high wear resistance and the low friction coefficient. To provide a method.

In order to achieve such an object, the method for producing a magnetic recording medium of the present invention comprises a cleavable lamella in a solvent in which a fluorocarbon lubricating base oil containing carbon as a main component and fluorine having two or more active polar groups is dissolved. A first step in which a powder of an organic solid lubricant having a structure is added and stirred, and the surface of the magnetic recording medium is overcoated with the solution prepared in the first step and then heated and baked at a temperature of 80 ° C. or higher. The second step is to perform.

Hereinafter, the present invention will be described in detail with reference to examples.

〔Example〕

As an organic solid lubricant powder having a cleavable lamella structure, 1 gr of a molecular adduct of melamine and cyanuric acid was subjected to a dispersion treatment with a surfactant, and then this was mixed with CH ₃ —OOC—CF ₃ O (C
F ₂ ) m- (C ₂ F ₄ O) n-CF-COO-CF ₃ (where m and n are integers) is a perfluoroalkyl polyether having two polar groups at the ends of its molecular chain. A surface lubricant is prepared by stirring in a Freon solution dissolved at a concentration of 0.005%.

This surface lubricant solution is overcoated on a magnetic disk medium having a γ-Fe ₂ O ₃ continuous thin film as a magnetic film, and then heated and baked at a temperature of 80 ° C. or higher.

FIG. 1 shows that the above-mentioned molecular adduct having a cleavable lamella structure was dispersed in a perfluoroalkyl polyether solution having two or more polar groups at the ends, and this was overcoated on the surface of the magnetic disk medium. In addition, about 20 ℃ ~ 160 ℃
3 shows the results of measurement of the heating and firing temperature and the coefficient of friction between the magnetic head and the magnetic disc medium when the heating and firing were performed while changing the temperature over the range. Here, the conditions such as the concentration of the perfluoroalkyl polyether in the Freon solution other than the firing temperature are the same.

As is clear from this figure, a low friction coefficient of 2.0 or less was stably obtained at a heating and firing temperature of 20 ° C., and a friction coefficient of 2.0 or less at a heating and firing temperature of 80 ° C. or higher. It is presumed that this is because the polar groups are activated more by heating and baking than at room temperature, and the lubricating film thereof is uniformly diffused on the surface of the magnetic disk medium to have a good lubricating surface.

Figure 2 shows the amount of surface lubricant overcoat and magnetic head
It is a characteristic view showing a result of measuring a friction coefficient between magnetic disk media. The overcoat amount here is a superposition of the lubricant when one surface of the disk having a diameter of 210 mm is overcoated.

In the figure, the characteristic curve A is the case where the surface lubricant used in this example, that is, the perfluoroalkyl polyether having two polar groups as the base oil, and the molecular adduct having the lamella structure is dispersed therein. The characteristic curve B shows the case where a conventional perfluoroalkyl polyether is used as a base oil and a molecular adduct having a lamella structure is dispersed therein.

As is clear from the figure, when a perfluoroalkyl polyether having two polar groups was used as a base oil (characteristic curve A), a conventional perfluoroalkyl polyether was used as a base oil (characteristic curve B). ) Compared to
The coefficient of friction was 1/4 or less, and the coefficient of friction tended to gradually decrease with an increase in the amount of lubricant overcoat, and a coefficient of friction of 0.2 or less was stably obtained in the region where the amount of overcoat was 1 mg or more.

Therefore, in the actual manufacturing process, a stable low friction coefficient can be always obtained without strictly controlling the lubricant overcoat amount.

FIG. 3 is a characteristic diagram showing the results of measuring the wear depth of the magnetic disk with respect to the pressing load of the ferrite pin. Specifically, the wear depth of the magnetic film was measured when a ferrite pole pin having a diameter of 2.3 mm was pressed and slid at a speed of 1 m / s.

In the figure, characteristic curve A shows the case of this embodiment, and characteristic curve B shows the one in which a molecular adduct having a lamella structure is dispersed in perfluoroalkyl polyether having no polar group as a surface lubricant. When used, the characteristic curve C,
D shows the case where the perfluoroalkyl polyether having two polar groups was used and the case where only the conventional perfluoroalkyl polyether having no polar group was used as the surface lubricant. The firing temperature is 80
C. and all other conditions are the same.

As is apparent from the figure, at a pressing load of 10 gr, the wear depth indicated by the characteristic curve A is 1/5 or less of the wear depth indicated by the characteristic curve B, 1/25 compared to the characteristic curve C, and further the characteristic curve. Compared with D, it is 1/40 or less, and it can be seen that good wear resistance characteristics are obtained.

In this example, a carboxyl group (CH ₃ COO) is used as the active polar group, but other polar groups such as a sulfone group and an amino group may be used.

Also, as the powder of the organic solid lubricant having a cleavable lamella structure, a molecular adduct of melamine and cyanuric acid is used. I do not care.

Further, in this embodiment, a magnetic disk medium having a magnetic film of γ-Fe ₂ O ₃ continuous thin film, which is strongly required to have high wear resistance and low friction coefficient, is used, but a magnetic tape, a floppy disk or the like is used. It goes without saying that another magnetic recording medium may be used.

〔The invention's effect〕

As described above, according to the method for producing a magnetic recording medium of the present invention, the cleavability in a solvent in which fluorocarbon lubricating base oil containing carbon as a main component and fluorine having two or more active polar groups is dissolved. The above-mentioned excellent magnetic recording is carried out by a simple process of adding powder of an organic solid lubricant having a lamella structure, stirring, overcoating the surface of the magnetic recording medium with this solution, and then heating and burning at a temperature of 80 ° C. or higher. A medium can be manufactured.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing the relationship between the heating and firing temperature and the friction coefficient between the magnetic head and the magnetic disk in one embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between the surface lubricant overcoat amount and the friction coefficient. FIG. 3 is a characteristic diagram showing the pressing load of the ferrite ball and the wear depth of the magnetic film of the magnetic disk.

Claims (1)

[Claims] 1. A powder of an organic solid lubricant having a cleavable lamella structure is added to a solvent in which a fluorocarbon lubricating base oil containing fluorine and carbon as main components having two or more active polar groups is dissolved. Magnetic recording comprising a first step of stirring, and a second step of overcoating the surface of the magnetic recording medium with the solution prepared in the first step and then heating and burning at a temperature of 80 ° C. or higher. Medium manufacturing method.