JPS62159331A - Magnetic recording medium and its production - Google Patents

Abstract

PURPOSE:To extremely improve lubricating performance by further providing a carbon film having a lower coefft. of friction on two-layered protective films consisting of a carbon film and carbide film. CONSTITUTION:An underlying film 2 is formed by Ni-P electroless plating to, for example, 20mum film thickness on a substrate 1 for a disk. This recording medium is made into, for example, the constitution consisting in adjusting the surface roughness of the substrate to 0.5-5nm Ra, forming a magnetic metallic film 3 consisting of Co-Ni or Co-Cr having chromium base thereon, and coating the metallic carbide film 4 consisting of chromium carbide, etc. thereon and further the carbon film (middle layer) 5 and carbon film (upper layer) 6 thereon. The carbon film having the lower coefft. of friction is further formed on the two-layered protective films consisting of the carbon film and the carbide film to form the protective films having 3-layered structure, then the lower layer of the protective films is the metallic carbide having high hardness and the surface exhibits the low coefft. of friction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording device, such as a magnetic recording medium used in a magnetic disk device.

2. Description of the Related Art Most of the magnetic disks currently used as magnetic recording media are oxide-coated media, and metal thin film media formed by plating or sputtering are attracting attention as a means of further improving recording density.

However, since metal thin film media are metal, they have insufficient lubricity, wear resistance, and corrosion resistance. therefore,
In general, metal thin film media require a protective film on the metal magnetic thin film to provide lubricity, wear resistance, and corrosion resistance.

Further, in order to increase the recording density, it is necessary that the magnetic head can be brought closer to the surface of the metal magnetic film, and the thinner this protective film is, the more preferable it is.

Conventionally, this type of protective film includes metal thin films (Ri, Au, Cr, Ni-P, etc.) formed by wet plating, oxide films (
Surface oxidation of metal magnetic film, 5i02゜AQ203, etc.),
Nitride film (Si3N4, etc.), carbide film (SiC, etc.)
Hard protective films such as those have been proposed.

Among these protective films, there is a carbon protective film that has excellent lubricity and abrasion resistance, for example, a carbon protective film that has excellent lubricity and does not require the application of lubricant (Japanese Patent Laid-Open No. 1983-1993).
41524 etc.).

A particularly excellent protective film among carbon protective films is a two-layer structure consisting of an upper layer, a carbon film, a lower layer, and a carbide film, which was previously invented by the present inventors and allows the thickness of the protective film to be made considerably thinner. There is a protective film.

Problems to be Solved by the Invention This two-layer protective film exhibits excellent lubricity with a coefficient of static friction of 0.5 or less. However, in order to reduce the size and power consumption of spindle motors, a lower coefficient of static friction has been required.

Therefore, an object of the present invention is to provide a magnetic recording medium having a protective film exhibiting a lower coefficient of friction.

Means for Solving the Problems In order to solve the above problems, the present invention provides a three-layer structure in which a carbon film having a lower coefficient of friction is provided on a two-layer protective film consisting of a carbon film and a carbide film. If the surface retention F(Ill) is.

For production The effect of this technical means 1 is as follows.

The lower the argon gas pressure during sputtering carbon film deposition, the lower the static friction coefficient. In particular, an argon gas pressure of 20 mtorr or less shows the lowest friction coefficient.

Therefore, as conditions for forming a carbon film in order to obtain a low coefficient of static friction, an argon gas pressure of 20 m torr or less is preferable, but on the other hand, a higher argon gas pressure is suitable for forming the lower layer and chromium carbide.
Argon gas pressure below orr is not preferred.

Therefore, in the present invention, a carbon film having a lower coefficient of friction is formed on a two-layer protective film consisting of a carbon film and a carbide film,
By forming a three-layer protective film, the lower layer of the protective film is made of a highly hard metal carbide, and the surface exhibits a low coefficient of friction.

Example FIG. 1 shows an example of a magnetic disk medium according to the present invention.

For example, a N1-P electroless plating base film 2 with a film thickness of 20 μm is deposited on a disk substrate 1 made of aluminum alloy or the like.
is formed, which has a surface roughness Ra of 0.5 to 5 nm, for example.
For example, Co-coat with a chrome undercoat is adjusted to
Ni alloy, C.

- A structure in which a metal magnetic film 3 such as a Cr alloy is formed, and further a carbon film (middle layer) 5 and a carbon film (upper layer) 6 are coated thereon. It has become.

Next, an example of a method for manufacturing a three-layer protective film consisting of an upper layer carbon film, a middle layer carbon film, and a lower layer chromium carbide film will be described. However, those skilled in the art will clearly understand that the present invention is not limited to chromium carbide as the metal carbide, and that similar effects can be expected with other highly hard metal carbides.

An argon gas pressure of 1 to 40 mt is placed on the magnetic film 3.

Sputtering using a metal chromium plate as a target at a substrate temperature of 5 to 250°C to a film thickness of 5 to 30 nm.
Forms a metallic chromium film. Furthermore, argon gas pressure is 20 to 60 mtorr.

A film with a thickness of 40 nm was deposited on the chromium film by sputtering using a carbon plate as a target at a substrate temperature of 5 to 250°C.
At the same time as the following carbon film is formed, carbon diffuses into the chromium film and a lower layer chromium carbide is formed. Furthermore, on top of that, the argon gas pressure is 1 to 20 mtorr, and the substrate temperature is 5 to 2 mtorr.
By forming a carbon film with a thickness of 40 nm or less by sputtering using a carbon plate as a target at 50° C., a three-layer protective film consisting of an upper carbon film, a middle carbon film, and a lower chromium carbide film is formed.

In one embodiment of the present invention described above, the upper layer has a film thickness of 5n.
m carbon film (argon gas pressure 10 mt.

rr), the middle layer is a carbon film with a thickness of 10 nm (
The lower layer is a chromium carbide film with a thickness of 10 nm (containing about 30% chromium oxide due to inevitable oxidation during sputtering formation of a chromium film), with a total film thickness of 25 nm. Magnetic recording media with thin 1, t3 layer structure protective film (
A Mn-Zn ferrite head loaded with a load of Log was placed on top of this magnetic recording medium for 24 hours. The average coefficient of static friction when left alone is 0.
．． It showed a low value of 23.

On the other hand, the two-layer protective film of the magnetic recording medium according to the embodiment of the present invention excluding the upper carbon film, that is, the one corresponding to the conventional example, has a static friction coefficient of 0°36 (average).
As shown in Table 1, the embodiment of the present invention has 36
% low coefficient of friction, indicating excellent lubricity.

Further, as shown in Table 1, the scratch hardness load of the embodiment of the present invention and the conventional example is 2 g.

The stylus radius (R25 μm) is almost the same, and it can be seen that it has excellent abrasion resistance that can withstand more than 30,000 cycles in the CSS test (start-stop repeated test), similar to the conventional two-layer protective film.

Furthermore, the corrosion resistance is also excellent, with no corrosion observed even after being left in an atmosphere at a temperature of 60° C. and a relative humidity of 90% for 40 days.

Table 1 Effects of the Invention The magnetic recording medium of the present invention has an extremely good lubrication performance because it has a three-layer protective film consisting of a thin upper carbon film, a middle carbon film, and a lower carbide film. . Therefore, if a magnetic recording device is made using the magnetic recording medium of the present invention, the spindle motor can be made smaller and the power consumption can be reduced, and the magnetic recording device can be made smaller and more portable.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the magnetic disk of the present invention, and FIG. 2 is a graph showing the relationship between the coefficient of static friction and the argon gas pressure during sputtering of the carbon film (upper layer).

Claims (3)

[Claims] (1) A magnetic film, a carbide film provided on the magnetic film, a first carbon film provided on the carbide film, and a first carbon film provided on the first carbon film. A magnetic recording medium comprising a second carbon film having a smaller coefficient of friction. (2) The magnetic recording medium according to claim 1, wherein the carbide film is a chromium carbide film. (3) providing a carbide layer on the magnetic film, forming a first carbon film on the carbide layer by sputtering in an atmosphere of argon gas pressure of 20 to 60 mtorr;
A method for manufacturing a magnetic recording medium, characterized in that a second carbon film is formed on the carbon film by sputtering in an atmosphere with an argon gas pressure of 20 mtorr or less.