JPH04313812A - Magnetic disk - Google Patents

Abstract

PURPOSE:To obtain the magnetic disk having good adhesion and wear resistance by incorporating Si, C and H into the disk and changing the atomic ratios of the H, C/Si+C continuously in the thickness direction of the magnetic recording medium. CONSTITUTION:Protective films 14 contg. the Si, C and H are formed over the entire surface on the recording medium layers 13 formed on the surfaces of a substrate 12. The atomic ratio value of the C/Si+C is specified to <=0.4 right on the layers 13 and 1.0 on the surfaces of the films 14. The substrate 12 is an org. film or Al, etc. The thickness of the layers 13 is confined to <=10mum. The protective films 14 are synthesized by a DC glow discharge plasma chemical deposition method of a gaseous mixture composed of CH4, SiH4 and H2.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a magnetic disk with high hardness and excellent wear resistance, and more specifically, to a magnetic disk with high hardness and excellent wear resistance.
The present invention relates to a magnetic disk having a surface protective film structure on its surface that has excellent adhesion, wear resistance, and lubricity.

0002

2. Description of the Related Art Magnetic disks and magnetic heads are widely used as magnetic disk devices in computer terminal information storage devices. Magnetic disks are made of ferrite, iron,
Nickel, cobalt or neodymium, samarium,
Rare earth metals such as gadolinium and terbium, and compounds made of these metals are used as magnetic recording media by being deposited in a thin film form by coating or sputtering. There are various types of magnetic heads, but they extract magnetic flux from magnetization written on a recording medium as a signal, and are 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 therefore 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. Requirements for the protective film 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. Adhesion requires a protective film material that matches the properties of the magnetic disk medium.

Conventionally, for this purpose, an oxide or nitride film such as silicon dioxide (SiO2), alumina (Al2O3), silicon nitride (Si3N4), or carbon film with a thickness of about 800 angstroms has been used. ing. SiO
2. Al2O3 and Si3N4 are usually produced by applying a solution of an organometallic compound of silicon or aluminum in a solvent, drying it, and then heat treating it, sputtering it in nitrogen or a mixed gas of argon and oxygen, or vapor deposition. It is made with. Furthermore, the carbon film can be formed by a carbon ion beam evaporation method made by discharging a carbon electrode as described in Japanese Patent Application Laid-Open No. 52-90281.
Or Journal of Non-Crystalline Solids published in 1980.
-Crystalline Solids) Vol. 35 and 36, page 435, carbon evaporation deposition or other methods are used. As an example of providing a film mainly composed of carbon on the surface of a magnetic disk, for example, as shown in Japanese Patent Application No. 52-58140, a film mainly composed of carbon is provided on the inner part of a magnetic recording medium. There is also a structure in which the coating is thick in areas where collision friction with the magnetic head is likely to occur, and the coating is thin in the recording area. At this time, the thickness of the coating was 500 to 1000 angstroms in the recording area and 1000 to 10000 angstroms in the area where the magnetic head stopped. The highly developed information processing technologies of recent years require increasingly large-capacity information processing technologies, and high-density magnetic recording media technologies are occupying an important position along with this. For this reason, the protective film on the surface of the magnetic disk is required to be even thinner, and a thickness of about 100 angstroms to 50 angstroms is also required.

0004

[Problems to be Solved by the Invention] However, various conventional protective film materials do not have sufficient hardness, adhesion, wear resistance, or corrosion resistance. It was 2000 kg/mm2 for SiO2, 3000 kg/mm2 for Al2O3, and about 3000 kg/mm2 for silicon nitride or carbon produced by conventional sputtering method. Furthermore, the minimum thickness of the protective film is about 500 angstroms, and if the thickness is less than this, the hardness, abrasion resistance, and corrosion resistance of the protective film will be significantly reduced. Further, a film containing carbon as a main component has a problem in terms of adhesion to the recording medium film. In addition, since the protective film has such characteristics, it is necessary to have a special structure as seen in Japanese Patent Application No. 52-58140, and there is also the problem of high manufacturing costs due to processing technology. A protective film with good properties even below 100 nm has not been realized. An object of the present invention is to provide a magnetic disk having a surface protective film structure with high hardness, excellent wear resistance and adhesion, and good lubricity, which improves the various drawbacks described above. .

[0005]

[Means for Solving the Problems] The present invention has silicon (Si), carbon (C) and hydrogen (H) as constituent elements on a magnetic recording medium layer, and the hydrogen (H) content is low. 20
A magnetic disk on which a protective film with a concentration of ~30 at. This is a magnetic disk characterized by a continuous change in direction.

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 FIG.
(b) is a diagram showing a cross section taken along line XX' in FIG. 1(a). In FIG. 1B, a protective film 14 containing Si, C, and H as constituent elements is provided over almost the entire surface of the magnetic recording medium layer 13 provided on the surface of the substrate 12. In FIG. Here, the value of C/Si+C (atomic ratio) is 0.4 or less directly above the magnetic recording medium layer 13, 1.0 on the surface of the protective film layer, and in the thickness direction of the recording medium layer. Its value changes continuously. As the substrate 12, an organic film, a metal such as aluminum, or an alloy can be used, and 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 necessary to retain recorded information. It goes without saying that it is desirable that the thickness of the protective film 14 be as thin as possible. The method for forming the protective film layer 14 made of a mixture of Si, C and H is to use methane (C
Direct current glow discharge plasma chemical deposition using a mixed gas of H4), silane (SiH4), and hydrogen (H2) is effective as a method for synthesizing a protective film with high hardness and excellent wear resistance.

[0007]

[Operation] In the conventional protective film mainly composed of carbon,
As seen in Japanese Patent Application No. 52-58140, it is used by directly attaching it to a recording medium, but as mentioned earlier, this formation method has poor adhesion and the uniformity of the deposited carbon film is also poor. I couldn't say yes. 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. In the present invention, it is thought that some kind of chemical bonding force acts between the magnetic recording medium and the silicon contained in the protective film, increasing the adhesion strength of the thin film. In order to obtain sufficient adhesion with the recording medium, C/Si on the recording medium contact surface of the protective film must be
The value of +C needs to be 0.4 or less. Furthermore, the protective film according to the present invention contains 20 to 30 atomic percent of hydrogen, and by including hydrogen in this range, there is a mechanism that compensates for unsaturated bonds in the film and increases the hardness of the film itself. It also works effectively. Owing to the various features of the present invention described above, it is possible to form a good surface protective film for a magnetic disk even with a thin film, that is, a thickness of 500 angstroms or less, which was previously impossible.

[0008]

[Examples] Examples of the present invention will be described below. Example 1 An aluminum alloy with a diameter of 5.25 inches and a thickness of 2 mm was used as the substrate of a magnetic disk, and as a recording medium, a cobalt-chromium-tantalum compound was deposited to a thickness of about 20 μm by sputtering. there was. The protective film was formed using the apparatus shown in FIG. In Figure 2,
A substrate 25 on which a protective film is to be formed, which becomes a cathode in the vacuum chamber 21
The flat electrodes 22 are arranged parallel to both sides of the substrate 25. A DC power source 23 is connected to the anode electrode 22 to generate glow discharge between the electrodes. The quality of the obtained film varies greatly depending on the degree of vacuum and the voltage applied to the electrodes, so it is necessary to select the optimal value. The degree of vacuum is from 0.1 Torr to 20To with the exhaust pump 26 and valve 27.
Adjust the vacuum level to rr. On the other hand, the voltage value is
Conditions during discharge and immediately before abnormal glow discharge occurred gave relatively good results. For DC glow discharge, the substrate 25 side is grounded, and the electrode 22 facing it is connected to a DC power supply 23.
It was generated by applying a current of up to several hundred volts at a positive voltage. The discharge current density is 0.1 to 1 mA/
It was set as mm2. Methane, silane and hydrogen were used as reaction gases. The concentration difference of hard amorphous carbon and silicon in the thickness direction of the protective film is determined by the mass flow controller 31,
This was controlled by adjusting 32. Specifically, at the start of film formation, the mass flow controller 32 on the silane side and the mass flow controller 31 on the methane side are opened so that the silane flow rate/methane flow rate is 0.8/0.2. I'll keep it. Next, the mass flow controller 32 on the silane side is closed at a constant speed, and the mass flow controller 31 on the methane side is opened at the same speed. The controller 31 was set to be fully open. Since the thickness of the protective film was controlled by the film formation time, the opening/closing speed of the mass flow controller was set by the film formation time. In this example, (methane flow rate + silane flow rate)/(hydrogen flow rate) = 0.01 to 0.1
The reaction gas was introduced so that The pressure during film formation was 0.
The temperature was 1 to 20 Torr, and the substrate temperature was approximately room temperature.

[0009] The resulting film has a molecular weight of 100 to 1000
With a film thickness of angstroms, all exhibited uniform interference colors. Surface irregularities are ±1 of the Talystep measurement limit.
It was less than 0 angstrom. This film was amorphous, and the hydrogen content in the film was 20 to 30 at.%. Further, FIG. 3 shows an example of the results of measuring the carbon and silicon compositions of this film in the film thickness direction using a secondary ion mass spectrometer. As shown in the figure, it can be seen that the compositions of carbon and silicon change linearly in the film thickness direction. Further, the hardness of this film is 8,000 to 10,000 kg/cm 2 in terms of Vickers hardness, and the surface of the protective film is a so-called hard amorphous carbon film. The wear resistance of the film was evaluated by the contact friction test method of a magnetic head and magnetic disk described below. That is, the magnetic head is made of aluminum and titanium carbide and has a Vickers hardness of 4000 kg.
/cm2 using a sintered body, a load of approximately 6 is applied to the magnetic disk surface.
The so-called contact start involves pressing the magnetic disk onto the protective film at 0 g/cm2, then rotating the magnetic disk at high speed until the magnetic head floats, stopping the rotation after floating, and repeating the process of bringing the head into contact with the disk surface again. ·stop(
CSS) test was conducted. As a result, it was confirmed that when the protective film according to the present invention was used, no wear occurred even after 100,000 cycles.

Comparative Example 1 In the same manner as in Example 1, C was heated directly above the magnetic recording medium.
The film formation conditions were set so that /Si+C=0.5, and film formation was performed. In this case, on the surface of the protective film, C/Si+C=
It was set to 1. When this magnetic disk was subjected to a CSS test in the same manner as in Example 1, peeling of the protective film was observed after 1000 cycles or less.

Comparative Example 2 A film was formed in the same manner as in Example 1, with conditions set so that C/Si+C=0.5 at all locations without any change in composition in the film thickness direction. . When a CSS test was conducted on this magnetic disk in the same manner as in Example 1, it was found that 10
Scratches were observed in the protective film after 00 cycles or less.

0012

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

[Brief explanation of the drawing]

FIG. 1 is a plan view and a cross-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 protective film on a magnetic disk according to the present invention.

FIG. 3: In the magnetic disk protective film according to the present invention,
FIG. 3 is a diagram showing an example of the results of measuring the distribution state of carbon and silicon from directly above the magnetic recording medium to the surface of the protective film using a secondary ion mass spectrometer.

[Explanation of symbols]

11 Magnetic disk
12, 25 Substrate 13 Magnetic recording medium layer
14 Protective film 21 Vacuum chamber
22 Counter electrode 23
DC power supply
24 Gas inlet 26 Exhaust pump
27 Valve 28 Methane cylinder
29 Hydrogen cylinder 30 Silane cylinder

Claims (1)

[Claims] Claim 1: Silicon (Si) is provided on the magnetic recording medium layer.
), carbon (C) and hydrogen (H) as constituent elements, and has a protective film formed with a hydrogen (H) content of 20 to 30 atomic %, the protective film having C/ Si
The atomic ratio of +C is 0.4 or less on the surface in contact with the magnetic recording medium,
1.0 on the surface of the protective film and continuously changing in the thickness direction.