JPH02101616A - Thin-film magnetic recording medium - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thin film magnetic recording medium such as a magnetic disk,
In particular, it relates to reducing the coefficient of friction of the carbon protective film.

[Summary of the invention]

The present invention provides a thin film magnetic recording medium having a carbon protective film on a magnetic layer, in which the carbon protective film has a density of 2.0 g.
By forming the carbon protective film by sputtering using a carbon material of /cm' or more as a target, it is possible to reduce the coefficient of friction of the resulting carbon protective film.

[Conventional technology]

Currently, disk-shaped magnetic disks that can be randomly accessed are widely used as recording media for computers and the like. Among them, A
I! So-called hard disks are now being used as internal disks or external disks, which are made of hard materials such as alloy plates, glass plates, and plastic plates, on which a magnetic layer of Co--Ni alloy or the like is formed.

Recording and reproducing information on such magnetic disks is
This is done on concentric tracks within the magnetic layer while rotating the magnetic disk at high speed.

By the way, when performing recording and reproduction on the above-mentioned magnetic disk, the magnetic layer surface of the stationary magnetic disk and the magnetic head are held in contact with each other before scratching starts, but when the operation starts, the magnetic layer surface of the magnetic disk is held in contact with the magnetic head. As the disk rotates at high speed, the magnetic layer surface and the magnetic head face each other with a small gap between them.
A method is generally adopted in which the two come into contact again at the end of the operation. This method is called the C3S (contact start-stop) method.

In this manner, in the C3S system, the magnetic layer surface and the magnetic head come into contact repeatedly at the start and end of operation, and the frictional force generated between the two causes wear on the magnetic head and the magnetic disk. Alternatively, if dust or powder that has fallen off from the magnetic layer adheres to the magnetic head, a head crash (falling of the magnetic head) may occur, or a sudden shock to the magnetic layer surface may occur due to the magnetic head jumping. This is undesirable from the viewpoint of reliability of recording/reproduction and durability of the device. In particular, in recent years, there has been a tendency for magnetic layers to be made thinner by means of vacuum thin film forming technology, electroless plating, etc., and such thin film magnetic recording media are increasingly subject to problems due to the above-mentioned phenomena.

Therefore, it has been conventionally considered to form a carbon protective film on the surface of a thin film magnetic recording medium to improve its durability.

This carbon protective film is formed, for example, by sputtering using a carbon sintered body as a target. The carbon sintered body used here is generally 1.7 to 1.
It has a density of about 9 g/cm3.

[Problem to be solved by the invention]

However, even with the carbon protective film described above, it is currently difficult to simultaneously satisfy various requirements such as durability, runnability, and impact resistance.

Therefore, an object of the present invention is to provide a thin film magnetic recording medium having a carbon protective film having excellent various properties (so-called C8S properties).

[Means for Solving the Problem] As a result of extensive studies to achieve the above-mentioned object, the present inventors have developed a carbon material with higher density as a target for sputtering in place of the conventional carbon sintered body. The inventors have discovered that by using this method, the friction coefficient of the carbon protective film formed can be reduced and a thin film magnetic recording medium with good C3S characteristics can be obtained, leading to the present invention.

That is, the thin film magnetic recording medium according to the present invention has a density of 2
．． It is characterized by having a carbon protective film formed by sputtering using a carbon material of 0 g/cm' or more as a target.

The present invention is mainly applied to a magnetic disk in which a metal magnetic layer is formed on a substrate, and a carbon protective film is formed on the metal magnetic layer by sputtering using the above-mentioned carbon material as a target. be done.

In the present invention, as a target for sputtering, the density is 2.
．． 0 g/cm' or more, more preferably 2.1 g/cm3
The above carbon materials are used. The true density of graphite is known to be 2.25 g/cm3 by χ-ray diffraction etc., and the carbon material used in the present invention has a value closer to the above true density than conventional carbon materials. It can be said that As such carbon material, for example, CVD
Pyrolytifuku graphite is produced by this method and is commercially available in various densities. With conventional sintering methods, it is difficult to create a carbon material with a density of 2.0 g/cm or more, but by making some improvements or ingenuity, a carbon sintered body with a density of 2.0 g/cm or more can be obtained. If possible, you can also use this.

In addition, commercially available Pyroritifuku graphite has two sides that can be distinguished with the naked eye.

This is because graphite nodules grow upwards in a conical shape on the substrate during the CVD process. The nodule diameter appears small from the contact surface). During sputtering, it is preferable to use the back surface of the target with a smaller nodule diameter as the sputtering surface from the viewpoint of suppressing abnormal discharge (arcing).

Direct 1JL2 sputtering is performed by gas discharge method.
Polar sputtering, DC three-pole sputtering.

There are various types of sputtering, such as high frequency sputtering and magnetron sputtering, which may be selected as appropriate. Normal general conditions are applied as conditions, argon gas pressure 10-' to 10-'' Torr substrate temperature 5
High frequency sputtering with input power of 1 to 10 kW or DC sputtering with input power of 0.5 to 10 kW is performed at 0 to 250°C. The thickness of the carbon protective film to be formed is preferably 10 to 800.

The substrate used in the thin film magnetic recording medium of the present invention includes:
Examples include light alloys such as aluminum alloys and titanium alloys, plastics such as polystyrene, polyethersulfone, polyimide, and ABS resin, ceramics such as alumina glass, glass, and single crystal silicon. Here, when using a relatively soft material as the above board,
It is preferable to form a nonmagnetic metal base film to harden the surface. The material for this non-magnetic metal base film is N1
-P alloy, Cu, Cr, Zn, stainless steel, etc. These are covered and sputtered.

The film is formed to a thickness of about 4 to 20 μm on the surface of the substrate by a method such as vapor deposition. For example, A/! -N on the surface of the Mg alloy substrate
When a magnetic layer is formed by applying 1-P plating, its hardness is approximately 400. Alternatively, when an Al substrate is used, the hardness of its surface may be increased by alumite treatment or the like.

The magnetic layer may be made of Fe or Co.

In addition to metals such as Ni, Co-Ni alloy, Co-pt gold alloy, Co-Ni-Pt alloy, and Fe-Co alloy.

Fe-Ni alloy, Fe-Co-Ni alloy, Fe-Co-
B alloy, Co-N1-Fe-B alloy, C.

Examples include -Cr alloys or those to which metals such as Cr and A1 are added. In particular, when a Co--Cr alloy is used, a perpendicularly magnetized film is formed. The thickness of this magnetic layer is selected to be approximately 0.04 to 1 μm.

[Effect]

In the thin film magnetic recording medium of the present invention, the carbon protective film formed on the metal magnetic layer is made of a carbon material having a higher density than the carbon sintered body commonly used as a conventional sputtering target. It is formed. By using such a target, the coefficient of friction of the resulting carbon protective film is reduced.

A carbon protective film with a thickness of 300 mm was formed by direct current sputtering at an argon gas pressure of 1.5 x 10-'' Torr and an input power of 450 mm to create each thin-film magnetic recording medium. At this time, the sputtered surface was made of pyrolytic graphite. The nodule diameter was determined to be smaller on the back side, that is, to the naked eye.

(Example) Hereinafter, preferred embodiments of the present invention will be described.

Example 1 This example is an example of a thin film magnetic recording medium in which a carbon protective film was formed using pyrolytic graphite with a density of 2.03 g/cm3 as a target.

First, a magnetic disk with a diameter of 5.25 inches, on which a Co-Ni alloy was previously formed as a magnetic layer by sputtering,
Example 2 A target made of pyrolytic graphite with a density of 2.03 g/Cm" was placed facing each other in the chamber of a sputtering device, and the density of the pyrolytic graphite was 2.15 g/Cm".
A thin film magnetic recording medium was produced in the same manner as in the first example except that the thickness was set to cm'.

Example 3 The density of pyrolytic graphite is 2.22g/
A thin film magnetic recording medium was produced in the same manner as in the first example except that the thickness was changed to cm3.

Comparative Example 1 The density of the target carbon material is 1.82g/
A thin film magnetic recording medium was prepared in the same manner as in the first example except that a carbon sintered body having a lower value of cm' than the one defined by the present invention was used.

Comparative Example 2 The density of the target carbon material is 1.92g/
A thin-film magnetic recording medium was produced in the same manner as in the first example except that a carbon sintered body having a lower carbon sintered body than the cm3 limit according to the present invention was used.

C3S characteristics were measured for each thin film magnetic recording medium produced in each of the above examples and comparative examples. That is, after using an Mn-Zn mini-monolithic head as the magnetic head and repeating contact start and stop 3000 times with a head load of 9.5 g, the coefficient of static friction between each thin film magnetic recording medium and the magnetic head was calculated. It was measured.

The results are shown in FIG.

In the figure, the vertical axis represents the coefficient of static friction μ, and the horizontal axis represents the density ρ (g/cm') of the target carbon material. From this figure, density 2. In comparison examples using a target with a density of less than Qg/cm', that is, a carbon sintered body, the coefficient of static friction is as high as about 1.7 or more -E, whereas with a density of 2. Qg/
Cm" or higher target, i.e. pyrolytic
It is clear that in all of the Examples using graphite, the coefficient of static friction is reduced to about 0.7 or less.

Further, for a target with a density of 2.22 g/cm', sputtering was performed using the surface with a large nodule diameter as the sputtering surface, and a thin film magnetic recording medium was similarly produced. As a result, when the back side was used as the sputtering surface, the number of abnormal discharges during sputtering was 2, but when the front surface of the target was used as the sputtering surface, the number of abnormal discharges increased to 11 times within the same time. . Therefore, it was found that it is preferable to use the back surface of the target as the sputtering surface.

[Effect of the invention] As is clear from the above explanation, the present invention
In the il-film magnetic recording medium, the carbon protective film is formed by sputtering using a carbon material with a higher density than before using a target, so it has excellent C8S characteristics and enables highly reliable magnetic recording and reproducing. Furthermore, depending on how the target is used, it is possible to suppress abnormal discharge during manufacturing, thereby improving productivity and yield.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the change in the static friction coefficient μ of a thin film magnetic recording medium depending on the density ρ of the carbon material that is the sputtering target/nod.

Claims (1)

[Claims] A thin film magnetic recording medium having a carbon protective film formed by sputtering using a carbon material with a density of 2.0 g/cm^3 or more as a target.