JPH056531A - Magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a protective film having high hardness and excellent wear resistance and lubricity even at <=500Angstrom by providing a hard amorphous carbon film contg. fluorine on the surface of a hard amorphous carbon film. CONSTITUTION:A silicon film 14 is provided mearly over the entire surface of a magnetic recording medium layer 13 provided on the surface of a substrate 12 and the hard amorphous carbon film 15 is formed thereon. The hard amorphous carbon film 16 contg. the fluorine is formed on the surface of the hard amorphous carbon film 15. A plasma chemical deposition method by DC glow discharge of a gaseous mixture composed of methane and hydrogen can synthesize the good film at a low temp. in the formation of the hard amorphous carbon film 15. Consequently, the excellent wear resistance by the hard amorphous carbon film 15 and the excellent lubricity by the hard amorphous carbon film 16 contg. the fluorine are obtd. The protective film having <=500Angstrom film thickness required for the high-density recording medium is thus obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk having high hardness and excellent wear resistance, and more specifically, high hardness,
The present invention relates to a magnetic disk having a surface protective film structure having both wear resistance and lubricity.

[0002]

2. Description of the Related Art Magnetic disks and magnetic heads are widely used in computer terminal information storage devices as magnetic disk devices. Magnetic disks are made of ferrite, iron, or
Cobalt, nickel, or a compound thereof, or a rare earth metal such as neodymium, samarium, gadolinium, or terbium, or a compound formed of these is used as a magnetic recording medium by being attached to a thin film by a coating method or a sputtering method. Although there are various types of magnetic heads, the magnetic head extracts magnetic flux from the magnetism written in the recording medium as a signal and is used as close to the magnetic disk surface as possible. As described above, the magnetic head and the magnetic disk are likely to collide with each other and rub against each other. Therefore, a protective film is required to protect the recording medium from scratches and the like generated on the magnetic recording medium. The requirements that the protective film should have are that it has excellent wear resistance and that it has excellent adhesion to the substrate.
It has excellent surface lubricity. The hardness of the film can be used for evaluation of wear resistance, and the higher the hardness, the better the wear resistance. Adhesion is important because the protective film does not peel off when the magnetic head comes into contact or rubs. The lubricity can be evaluated by the coefficient of friction between the magnetic disk and the magnetic head. The smaller the coefficient of friction, the better the protective film.

Conventionally, as a protective film for this purpose, silicon dioxide (Si) having a thickness of about 800 angstroms is used.
O _2), silicon nitride (Si ₃ N _4), alumina (Al ₂ O ₃₎
Oxides and nitrides such as, or carbon films are used. Si ₃ N ₄ , SiO ₂ and Al ₂ O ₃ are usually prepared by coating a solution of an organometallic compound of silicon or aluminum in a solvent and drying it, followed by heat treatment, in nitrogen or in a mixed gas of argon and oxygen. It is manufactured by a sputtering method or a vapor deposition method. For the carbon film, vapor deposition, sputtering and chemical vapor deposition using hydrocarbon gas are known. These protective films are 50
It was used with a film thickness of about 0 to 1000 angstroms. Regarding the lubricity, a conventional lubricant having a thickness of several tens of angstroms is applied on the surface of the conventional protective film so that the friction coefficient is 0.5 or less. The highly developed information processing technology in recent years requires an information processing technology with a larger capacity and accordingly, the high density magnetic recording medium technology occupies an important position. Therefore, the protective film on the surface of the magnetic disk is required to be further thinned, and a protective film having a thickness of about 100 to 50 angstroms is being demanded.

[0004]

However, various conventional protective film materials do not have sufficient hardness, adhesion, abrasion resistance and corrosion resistance, and for example, Vickers hardness is S.
iO ₂ In 2000 kg / mm ^2, the alumina or silicon nitride was about 3000 kg / mm ^2. Further, the protective film has a minimum thickness of about 500 Å, and if the film thickness is less than 500 Å, the hardness, wear resistance and corrosion resistance of the film have a fundamental defect. Needless to say, these protective films are used after being coated with a lubricant in order to improve lubricity.

On the other hand, as a protective film material having high hardness and excellent lubricity, a hard carbon film formed by a sputtering method or a chemical vapor deposition method has been receiving attention in recent years. However, even with this hard carbon film, this lubricity is insufficient. Specifically, there is a problem that the coefficient of friction increases as the contact friction between the magnetic head and the protective film is repeated, that is, the lubricity deteriorates. This is, for example, the Proceedings of the International Tribology Confer published in 1990.
ence) on page 1881.
That is, press the magnetic head against the magnetic disk surface,
Next, the magnetic disk is rotated at high speed until the magnetic head floats, and after flying, the rotation is stopped and the magnetic head is brought into contact with the disk surface again.
The friction coefficient is measured after a start / stop (CSS) test, but even for hard carbon with a film thickness of 500 angstroms that does not use a lubricant, the friction coefficient is about 0.2 while the number of CSS times is small. And good,
The friction coefficients after 20,000 times are all 0.5 or more, and the lubricity is deteriorated. As described above, the conventional technique has not realized a protective film having a film thickness of 500 angstroms or less and having high hardness and excellent wear resistance, adhesion and lubricity. An object of the present invention is to solve such conventional problems.

[0006]

According to the present invention, in a magnetic disk having a hard amorphous carbon film on its surface, a layer containing fluorine is provided on the outermost surface of the hard amorphous carbon film. It is a magnetic disk.

The present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing the structure of a magnetic disk according to the present invention. 1A is a plan view of the magnetic disk 11, and FIG. 1B is a view showing a cross section taken along line XX ′ of FIG. In FIG. 1B, a silicon film 14 is provided on almost the entire surface of the magnetic recording medium layer 13 provided on the surface of the substrate 12, and a hard amorphous carbon film 15 is provided thereon. Here, it is desirable that the silicon film 14 is provided in order to improve the adhesion between the hard amorphous carbon film 15 and the magnetic recording medium 13 (Japanese Patent Application No. 62-234328).
issue). Further, a hard amorphous carbon film 16 containing fluorine is formed on the surface of the hard amorphous carbon film. Board 12
As the material, an organic film, a metal such as aluminum, or an alloy can be used, and there is no particular problem with the material 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, and is a thickness necessary for holding recorded information. The method for forming the silicon film 14 is not particularly limited as long as it is a method for forming a uniform film. That is, the vapor deposition method, the sputtering method and the plasma chemical vapor deposition method can be used, but the sputtering method gives particularly good results. As a method of forming the hard amorphous carbon film 15, a direct current glow discharge plasma chemical deposition method of a mixed gas of methane (CH ₄ ) and hydrogen (H ₂ ) is effective as a method of synthesizing a good film at a low temperature.

[0008]

According to the present invention, both excellent wear resistance due to the hard amorphous carbon film and excellent lubricity due to the hard amorphous carbon containing fluorine are simultaneously provided, and even at a thickness of 500 angstroms or less. It is possible to form a surface protective film of a magnetic disk having good wear resistance and lubricity.

[0009]

EXAMPLES Examples of the present invention will be described below. As the magnetic disk substrate, an aluminum alloy with a diameter of 5.25 inches and a thickness of 1.27 mm is used, on which a cobalt-chromium-tantalum compound is deposited by a sputtering method to a thickness of about 20 μm. I was there. The silicon film was formed by using an ordinary RF magnetron sputtering device. Vacuum degree is 10 ^-3 to 10 ^-2 Torr
Argon spatter is used as the range of the
The film was formed at room temperature with 0 to 150 W. The thickness of the silicon film was 50 Å. The apparatus shown in FIG. 2 was used to form the hard amorphous carbon film and the hard amorphous carbon film containing fluorine. In FIG. 2, a substrate 25 on which a hard amorphous carbon film serving as a cathode is to be formed is placed in a vacuum chamber 21, and flat plate-type electrodes 22 are arranged parallel to both surfaces of the substrate. A direct current power supply 23 is connected to the anode electrode 22 to generate a glow discharge between the electrodes. Specifically, the magnetic disk substrate 25 provided with a silicon film is placed in the vacuum chamber 21, and then a mixed gas from the methane cylinder 28 and the hydrogen cylinder 29 is introduced to form a hard amorphous carbon film. The quality of the obtained film greatly changes depending on the degree of vacuum, the gas mixing ratio, and the voltage applied to the electrodes, so that it is necessary to select an optimum value. The degree of vacuum is 0.1 with the exhaust pump 26 and the valve 27.
Adjust to a vacuum of ~ 20 Torr. Further, the mixing ratio of methane 28 and hydrogen 29 is CH ₄ / H ₂ = 0.01 to 0.10.
In the range of, give good results. On the other hand, the voltage value is
The condition of normal glow discharge and immediately before the occurrence of abnormal glow discharge gave relatively good results. Further, the hard amorphous carbon film containing fluorine is formed by the same method as the hard amorphous carbon film, instead of methane 28, tetrafluoromethane (CF ₄ ) 3
0 was used to form the film.

The DC glow discharge uses the substrate 25 as the ground,
It was generated by applying a positive voltage of several hundred volts to the electrode 22 facing it by a DC power supply 23. The discharge current density was 0.1 to 1 mA / mm ² . As a reaction gas, a mixed gas of methane and hydrogen was used as a flow rate ratio CH ₄ / H ₂ = 0.
It was introduced in the range of 01 to 0.1 to form a hard amorphous carbon film. The pressure during film formation was 0.1 to 20 Torr, and the substrate temperature was approximately room temperature. The film thickness of the hard amorphous carbon film was controlled to 100-200 angstroms by controlling the reaction time. Next, the exhaust chamber 26 is used for the vacuum chamber 2
After evacuating the inside of 1, the mixed gas of tetrafluoromethane and hydrogen was introduced at a flow rate ratio CF ₄ / H ₂ = 0.01 to 0.1,
A hard amorphous carbon film containing fluorine was formed. The film thickness was 50 to 100 Å. Other conditions were the same as those for forming the hard amorphous carbon film.

The wear resistance and the coefficient of friction of the film were determined by the so-called CSS-μ test method in which the CSS test and the coefficient of friction μ were simultaneously measured. In this embodiment,
The contact load of the magnetic head applied to the magnetic disk is 20 g /
cm ² , and the number of rotations of the magnetic disk was 3600 rotations per minute. FIG. 3 shows changes in the number of CSSs and changes in friction coefficient when the film thickness of the hard amorphous carbon film is 100 angstroms and the film thickness of the hard amorphous carbon film containing fluorine is 50 angstroms. .. In this example, even without using a lubricant, the coefficient of friction after 20,000 CSS times was 0.2 or less, and excellent lubricity was exhibited. The hardness of this film is 8000 to 10000k when converted to Vickers hardness.
It is g / mm ² , and it goes without saying that the CSS test does not cause wear on the magnetic disk surface and that the protective film is not peeled off. Further, as a comparative example, the result when only a hard amorphous carbon film having a film thickness of 100 angstrom is shown is also shown in FIG. In this case, although wear was not recognized by the CSS test of 20,000 times,
The coefficient of friction increased to a maximum of 0.6 as the number of CSSs increased.

[0012]

As described above, the magnetic disk according to the present invention has extremely high hardness, excellent wear resistance and lubricity, and a film thickness of 500, which is required for high density magnetic recording technology.
It has a protective film of less than angstrom and is highly practical.

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view of an example of a magnetic disk according to the present invention.

FIG. 2 is a schematic configuration diagram of an example of an apparatus used for forming a hard amorphous carbon film in the magnetic disk of the present invention.

FIG. 3 is a characteristic diagram showing a relationship between the number of CSS times and a change in friction coefficient.

[Explanation of symbols]

 11 magnetic disk 12, 25 substrate 13 magnetic recording medium layer 14 silicon film 15 hard amorphous carbon film 16 fluorine-containing hard amorphous carbon film 21 vacuum chamber 22 counter electrode 23 direct current power supply 24 gas inlet port 26 exhaust pump 27 valve 28 Methane 29 Hydrogen 30 Tetrafluoromethane

Claims (1)

Claim: What is claimed is: 1. A magnetic disk having a hard amorphous carbon film on its surface, wherein a magnetic layer is provided on the outermost surface of the hard amorphous carbon film. disk.