JPH0383224A - Magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a protective film having excellent abrasion resistance and adhesion property by providing a carbide film of one of Si, Ta, Co, W, Nb, Zr, Ti, and V, Mo, under a hard amorphous carbon film. CONSTITUTION:A magnetic recording medium layer 13 provided on a substrate 12 is almost wholly covered with a carbide film 14, on which a hard amorphous carbon film 15 containing H is formed. The film 14 consists of a carbide of one of Si, Ta, Co, W, Nb, Zr, Ti, V, and Mo. Particularly, when SiC is formed, plasma vapor phase precipitation method is preferable, and other carbides are preferably formed by sputtering. The hard amorphous carbon film 15 is preferably formed by plasma chemical precipitation method with using DC glow discharge on CH4 + H2. The obtd. magnetic disk 11 has extremely high hardness with excellent abrasion resistance and has a protective film of <=500Angstrom thickness, which can be practically used.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a material that can be attached to the surface of a magnetic disk, magnetic head, etc., and has high hardness, excellent adhesion, wear resistance, and lubricity. The present invention relates to a hard amorphous carbon film suitable for use as a surface protective film.

(Prior Art) Magnetic disks and magnetic heads are widely used as magnetic disk drives and computer terminal information storage devices. A magnetic disk is a magnetic recording medium made of ferrite, iron, cobalt, nickel, or a compound thereof, or an earth metal such as neodymium, samari cum, gadolinium, or terbium, or a compound made of these on a substrate such as an aluminum metal substrate or a plastic substrate. It is used as a thin film by coating or sputtering.

There are various types of magnetic heads, but they extract magnetic flux from magnetism written on a recording medium as a signal, and are used as close to the magnetic disk surface as possible. Therefore, the magnetic head and the magnetic disk are likely to collide and rub against each other, and a protective film is required to protect the recording medium from scratches and the like that occur on the recording medium of the magnetic disk.

Important points that the protective film should have include excellent wear resistance, excellent adhesion to the substrate, and excellent surface lubricity. The hardness of the film can be used to evaluate wear resistance, and the higher the hardness, the better the wear resistance. Adhesion is important so that the protective film does not peel off when the magnetic head contacts or rubs. Since surface properties of adhesion vary depending on the manufacturing method of the magnetic disk medium, a protective film material that matches the properties of the medium is required.

Conventionally, for this purpose, silicon dioxide (Si02), silicon nitride (Si3N4), alumina (
oxides such as Al2O2), nitrides, or carbon films are used. Si3N4.5i02yaA, 1203
It is usually made by coating an organometallic compound of silicon or aluminum dissolved in a solvent, drying it and then heat-treating it, sputtering it in nitrogen or a mixed gas of argon and oxygen, or by vapor deposition.

The carbon film can be produced using a carbon ion beam evaporation method made by discharging a carbon electrode as described in Japanese Patent Application Laid-open No. 52-90281, or by the method described in the Journal of Non-Blistering Solutions published in 1980.
NonCrystalline 5olids) No. 35
It was made by a method such as carbon evaporation deposition as described in &36, page 435.

As an example of providing a film mainly composed of carbon on the surface of a magnetic disk, for example, as seen in Japanese Patent Application No. 52-58140, a film mainly composed of carbon is provided on the part where there is no magnetic recording medium, and a film mainly composed of carbon is provided on the magnetic head. There is also a structure in which the film is thicker in areas where collision friction is likely to occur, and the film is thinner in the recording area. At this time, the thickness of the film is 500-100
0 persons were provided in the storage area, and 1000 to 1000 persons were provided in the area where the magnetic head stopped.

BACKGROUND ART The highly developed information processing technology of recent years requires increasingly large-capacity information recording technology, and high-density magnetic recording medium technology is occupying an important position along with this. The protective film technology for this purpose is to increase the thickness of the film from 100A to 50A.
People are starting to demand something similar to that of a husband.

(Problems to be Solved by the Invention) Various conventional protective film materials, however, do not have sufficient hardness or
It does not have adhesion, wear resistance, or corrosion resistance; for example, the Vickers hardness is 2000 Kg/mm2 for 5i02, 3000 Kg/mm2 for alumina, and 3000 K for hard carbon films made with silicon nitride or conventional sputtering methods.
It was about g/mm2. Furthermore, the minimum thickness of the protective film is about 500A, and a film with a thickness less than this has a fundamental defect in that its hardness, wear resistance, and corrosion resistance are significantly reduced.

In addition, because it is such a special protective film, it is
As seen in 58140, a special configuration is required, and there is also the problem of high manufacturing costs due to processing technology, and a protective film with good characteristics has not been realized even at 500A or less.

The present inventors have conducted various studies on the performance of the protective film, and have found that the apparent hardness and abrasion resistance vary greatly depending on the type of base material to which the protective film is attached, and have arrived at the present invention. .

That is, the object of the present invention is to provide a magnetic disk surface protective film that has high hardness, excellent wear resistance and adhesion to a substrate, and has good lubricity, which improves the various drawbacks mentioned above. .

(Means for Solving the Problems) The present invention provides a protective film material having high hardness, excellent wear resistance, and adhesion that is suitable for surface protection applications. An object of the present invention is to provide a magnetic disk characterized in that it is provided with a film of a carbide selected from cobalt carbide, tungsten carbide, niobium carbide, zirconium carbide, titanium carbide, vanadium carbide, and molybdenum carbide.

The present invention will be explained below based on the drawings. FIG. 1 is a diagram showing the structure of a magnetic disk according to the present invention.

FIG. 1(a) shows a plan view of the magnetic disk 11, and the first
Figure (b) is a diagram showing a cross section of the magnetic disk Xx'.

A carbide film 14 is provided over almost the entire surface of the magnetic medium layer 13 provided on the surface of the substrate 12 in FIG. 1(b),
A hard amorphous carbon film 15 containing hydrogen is further provided thereon. As the substrate 12, it is possible to use an organic film, a metal such as aluminum, or an alloy. In short, the material does not matter as long as it holds the magnetic recording medium layer 13. The thickness of the magnetic recording medium layer 13 is usually 10 μm or less, which is the thickness necessary to retain recorded information. The carbide film 14 and the hard amorphous carbon film together constitute a protective film. Needless to say, it is desirable that the thickness of the protective film be as thin as possible.

The method for forming the carbide film 14 is not particularly limited as long as it can form a homogeneous film. That is, vapor deposition or sputtering methods can be used, and in particular, for silicon carbide, thermal decomposition of a silicon compound such as silane (SiH4) or plasma vapor phase chemical deposition method can be used. As a method for achieving good adhesion between the magnetic recording medium layer and the silicon carbide film, the plasma vapor deposition method gave particularly good results. For other carbide films, particularly good results were obtained using the sputtering method.

The hard amorphous carbon film 15 is formed using methane (CH4).
Direct current glow discharge plasma chemical deposition using a mixed gas of hydrogen (H2) and hydrogen (H2) was effective as a method for synthesizing good films at low temperatures. FIG. 2 shows an example of the device. Here, a silane cylinder for forming silicon carbide is added.

In FIG. 2, a substrate on which hard amorphous carbon is to be formed as a cathode is placed in a vacuum chamber 21, and flat electrodes 22 are placed parallel to both sides of the substrate. A DC power source 23 is connected to the anode electrode 22 to generate glow discharge between the electrodes.

When forming a silicon carbide film, a mixed gas of methane 28, silane 30, and hydrogen 29 is first introduced into the vacuum chamber 21 through the gas inlet 24 to form a silicon carbide film. At this time, the degree of vacuum is adjusted from 0.1 Torr to 10 Torr using the exhaust pump 26 and valve 27. Also, the mixing ratio of methane 28 and silane 30 is CH4/
SiH4 = 0.8-1.5, and methane 28 and hydrogen 2
9 gives good results when the mixing ratio of CH47H2 is in the range of 0.01 to 0.10. Further, tantalum carbide, cobalt carbide, tungsten carbide, niobium carbide, zirconium carbide, titanium carbide, vanadium carbide, and molybdenum carbide can be formed using a common RF magnetron sputtering device.

Next, with the degree of vacuum and the mixing ratio of methane 28 and hydrogen 29 maintained as described above, the supply of silane 30 is stopped, and a hard amorphous carbon film is formed. The quality of the obtained film varies greatly depending on the degree of vacuum, gas mixture ratio, and voltage applied to the electrodes, so it is necessary to select optimal values. Regarding the voltage value, conditions for normal glow discharge and just before abnormal glow discharge occurred gave relatively good results.

(Function) Regarding the conventional protective film mainly composed of carbon,
As seen in No. 2-58140, the carbon film is directly attached to the recording medium, but as mentioned earlier, this formation method has poor adhesion and the uniformity of the deposited carbon film is not good. I got angry. Although the details of this cause are unclear, it is thought to be related to the bonding force between the carbon film and the recording medium. A similar situation occurs even if a film of silicon dioxide, alumina, or the like is used instead of the silicon film.

That is, it seems that some kind of chemical bonding force moves between the magnetic recording medium and the carbide film, and between the hard amorphous carbon film and the carbide film, increasing the adhesion strength of the thin film.

Furthermore, since the hard amorphous carbon film of the present invention uses a mixed gas of hydrocarbon and hydrogen as a raw material, as can be seen from the manufacturing method, the resulting film contains 20 to 30 atoms of hydrogen. %, and the mechanism in which hydrogen in this range compensates for unsaturated bonds in the carbon film and increases the hardness of the film itself also works effectively.

Owing to the various features of the present invention described above, it is possible to obtain a method of forming a good surface protective film for a magnetic disk even with a thin film, that is, a thickness of 500 Å or less, which was previously impossible.

Examples will be described below.

(Example) A magnetic disk substrate with a diameter of 5.25 inches and a thickness of 2
The recording medium was made of an aluminum alloy having a thickness of about 20 pm, on which a cobalt-tantalum-chromium compound was deposited to a thickness of about 20 pm by sputtering.

To form the protective film, first, for tantalum carbide, cobalt carbide, tungsten carbide, niobium carbide, zirconium carbide, titanium carbide, vanadium carbide, and molybdenum carbide films, a normal light magnetron sputtering device is used, and the degree of vacuum is set to 10-3 to 1 O. -2) Using argon sputtering in the range of -2) and using the carbide sintered body as a target, the film was formed at room temperature at a power of 100 to 150 W. The thickness of the carbide film was controlled by changing the sputtering time in the range of 100 to 100 OA.

The silicon carbide and hard amorphous carbon films were formed using the apparatus shown in FIG. The DC glow discharge was generated by grounding the substrate 25 side and applying a positive voltage of up to several hundred volts to the electrode 22 facing the substrate 25 from the DC power supply 23. The discharge current density was 0.1 to 1 mA/mm2. First, a mixed gas of methane, silane, and hydrogen was introduced as a reaction gas to form a silicon carbide film.

At this time, the flow rate ratio of methane and silane is CH4/SiH4=
Flow rate ratio of methane and hydrogen of 0.8 to 1.5 CH4/H
2=0.01 to 0.1. The pressure during film formation was 0.1 Torr to 20 Torr, and the substrate temperature was approximately room temperature. Next, the hard amorphous carbon film was made under the same conditions as above,
The silane supply was stopped and formation was completed.

The thickness of the resulting films was controlled by the reaction time, but all films exhibited uniform interference colors from 100A to tooA. The surface unevenness was less than ±10 Å, which was the measurement limit of Talystep. The silicon carbide film consisted of carbon, silicon, and a small amount of hydrogen, and the film was amorphous.

In addition, the carbon film is similarly amorphous and has a hydrogen content of 20~
It was 30 at%.

Furthermore, the hardness of this film is 8000 in terms of Vickers hardness.
~10000Kg/mm2.

The wear resistance of the film was evaluated by the contact friction test method between a magnetic head and a magnetic disk described below. That is, the magnetic head is made of aluminum and titanium carbide and has a Vickers hardness of 40.
Using a sintered body of 00 kg/am2, press it onto the protective film on the surface of the magnetic disk at a weight of about 60 g/cm2, then rotate the magnetic disk at high speed until the magnetic head floats.
In a so-called contact start-stop (C8S) test, in which the head is repeatedly brought into contact with the disk surface after it has floated, rotation is stopped and the head is brought into contact with the disk surface again, it was confirmed that no wear occurred even after 100,000 cycles.

(Effects of the Invention) As explained above, the magnetic disk of the present invention has extremely high hardness, excellent wear resistance, and has a protective film of 500A or less required for high-density magnetic recording technology, and is highly practical. It is.

It goes without saying that the type of magnetic recording medium is not particularly important.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are diagrams showing an example of the structure of a magnetic disk according to the present invention. 11...Magnetic disk, 12...Substrate, 13...
Magnetic recording medium layer, 14...Carbide film, 15...Hard amorphous carbon film FIG. 2 is a diagram schematically showing an apparatus for forming a silicon carbide film and a hard amorphous carbon film. 21... Vacuum chamber, 22... Counter electrode, 23... DC power supply, 24... Gas inlet, 25... Substrate, 26
...exhaust pump, 27...valve, 28...metal cylinder, 29...hydrogen cylinder, 29...silane cylinder

Claims (9)

[Claims] (1) A magnetic disk having a hard amorphous carbon film on its surface, characterized in that a silicon carbide film is formed on the lower surface of the hard amorphous carbon film. (2) A magnetic disk having a hard amorphous carbon film on its surface, characterized in that a tantalum carbide film is formed on the lower surface of the hard amorphous carbon film. (3) A magnetic disk having a hard amorphous carbon film on its surface, characterized in that a cobalt carbide film is formed on the lower surface of the hard amorphous carbon film. (4) A magnetic disk having a hard amorphous carbon film on its surface, characterized in that a tungsten carbide film is formed on the lower surface of the hard amorphous carbon film. (5) A magnetic disk having a hard amorphous carbon film on its surface, characterized in that a niobium carbide film is formed on the lower surface of the hard amorphous carbon film. (6) A magnetic disk having a hard amorphous carbon film on its surface, characterized in that a zirconium carbide film is formed on the lower surface of the hard amorphous carbon film. (7) A magnetic disk having a hard amorphous carbon film on its surface, characterized in that a titanium carbide film is formed on the lower surface of the hard amorphous carbon film. (8) A magnetic disk having a hard amorphous carbon film on its surface, characterized in that a vanadium carbide film is formed on the lower surface of the hard amorphous carbon film. (9) A magnetic disk having a hard amorphous carbon film on its surface, characterized in that a molybdenum carbide film is formed on the lower surface of the hard amorphous carbon film.