JPH0528465A - Production of protective film for magnetic disk - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a method for producing a magnetic disk having a hard carbon film as a protective film, which has a high hardness and is excellent in wear resistance and solid lubricity. [Structure] On the surface of a magnetic disk used in an information recording device such as a computer, as a scratch-resistant protective film,
A hard carbon film is formed using a hydrocarbon ion beam. The thickness of the protective film is 1 (nm) or more and 100 (nm) or less. When the magnetic disk of the present invention is used, the magnetic head can be moved closer to 50 to 60 (nm) for writing and reading operations, and the magnetic recording density can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a magnetic disk having a hard carbon film having a high hardness, excellent wear resistance and solid lubricity as a protective film.

[0002]

2. Description of the Related Art Magnetic disks are used as information recording devices for computers and the like. Magnetic disks are made of iron, oxygen, magnesium, chromium, manganese, cobalt, nickel, copper, zinc, cadmium, tantalum, neodymium, on a substrate of aluminum, plastic, glass, etc.
A substance containing an element such as samarium, gadolinium, and terbium is used as a magnetic recording medium after being formed into a film by a coating method or a sputtering method. Since a magnetic head for writing and reading a magnetic signal on such a recording medium is used as close to the magnetic disk surface as possible, the magnetic head may come into contact with the magnetic disk due to vibration or shock. In order to protect the surface of the recording medium of the magnetic disk from scratches caused at that time, it is widely practiced to coat the magnetic disk with a non-magnetic protective film.

As the protective film, there is used a film formed of silicon dioxide, alumina, a carbon film or an organic monomolecular film by a coating method, a sputtering method or a vapor deposition method. Further, the use of a hard carbon film or a diamond-like carbon film as a protective film is disclosed in JP-A-62-116749.
JP-A-62-116750 and JP-A-62-139.
No. 872, etc.

However, the hard carbon film formed on the magnetic disk by the parallel plate type triode glow discharge plasma vapor phase synthesizer disclosed in these publications is easily peeled off and is not sufficient as a protective film. .. Therefore, as disclosed in Japanese Unexamined Patent Publication No. 3-83224, an attempt was made to use a metal carbide film as an intermediate layer, but the film quality is uneven and this process is adopted in the current magnetic disk production line. It didn't reach.

In addition to the above-mentioned manufacturing method, JP-A-53-143
Japanese Patent Laid-Open No. 206-206 discloses that a carbon-based coating film formed by graphite electrode discharge sputtering in an inert gas atmosphere is used as a protective film for a magnetic disk. Although the film prepared by this method has high hardness, carbon atoms are clustered. Since it is deposited on the surface of the magnetic head, surface irregularities of about 10 nm to 20 nm are present, and there is a problem that the magnetic head is easily damaged.

[0006]

The silicon dioxide and alumina described in the preceding paragraph are not sufficient in terms of hardness and solid lubricity, and the carbon film has a weak adhesion and a rough surface, so these materials will be further integrated in the future. It was not sufficient as a protective film for magnetic disks that require high speed rotation. In addition, the hard carbon film by the conventional method is not sufficient in mass production because the film quality and adhesion are not sufficient and impurities such as soot due to the manufacturing process are easily mixed in the protective film, and stable film formation cannot be performed. Had. An object of the present invention is to provide a manufacturing method for coating a magnetic disk with a hard carbon film which eliminates the above drawbacks.

[0007]

The present invention is characterized in that a hard carbon film having a thickness of 1 nm or more and 100 nm or less is formed as an outer protective film on the surface of a magnetic disk by using a hydrocarbon ion beam. The present invention relates to a method for manufacturing a magnetic disk protective film.

What is referred to as hard carbon or diamond-like carbon in the present invention is as follows. The main constituent of the element is carbon, which has a hardness similar to that of natural diamond, is amorphous, and the electron beam diffraction pattern shows a halo pattern. Raman spectrum is 1100 cm ^-1 to 1
A wide peak peculiar to amorphous is shown up to 700 cm ^-1 . It is a uniform film in which no grain boundary is observed even when the hard carbon film is observed under a scanning electron microscope at a magnification of about 10,000 times.

The hard carbon film is generally formed by a vapor phase synthesis method using a hydrocarbon compound as a raw material, and it is recognized by Rutherford scattering analysis using argon ions that it contains 40 atomic% or less of hydrogen. It is believed that hydrogen enters the dangling bond part of the carbon atom to stabilize the amorphous state. Also, about 6
Hard carbon transforms into graphite at 00 ° C or higher.

It is presumed that the hard carbon film has a high hardness and a low friction coefficient similar to those of natural diamond due to the presence of an appropriate amount of hydrogen, and if the hard carbon film contains too much hydrogen, it becomes a soft organic film. Therefore, the proportion of hydrogen is 35 atomic% or less, preferably 20 to 30 atomic% in the film as measured by Rutherford scattering analysis using argon ions.

It is sufficient that the hard carbon film as a magnetic disk protective film has a film thickness of 1 nm or more, but a film thickness suitable for mass production is preferably 9 nm or more and 30 nm or less. If it is less than 1 nm, the film thickness is too thin and pinholes are likely to occur in the protective film, which is unsuitable. On the other hand, if it exceeds 100 nm, the film thickness is too large to increase the recording density of the magnetic disk, which is also inappropriate.

The hard carbon film itself peeled off from the substrate is a soft film having elasticity, and when peeled off, it shrinks, rounds, or in some cases tears in order to eliminate internal stress. Therefore, it is considered that the following three conditions are necessary to bring out the high hardness physical properties of the hard carbon film as the coating film.

Internal stress is accumulated by the wedge effect due to high-velocity ions being implanted during film formation. The adhesion of the film to the base material is so strong that the film does not peel off despite the large internal stress. The base material surface is hard enough to support the stress received from the film. The above conditions depend on the film forming conditions, and it has been found that a film forming method using a hydrocarbon ion beam satisfies this condition.

Further, in the ion beam method using hydrocarbon as a raw material, each ion species is an ion of one hydrocarbon molecule (C _n H _m ^{M +} ) or a decomposed version of the same molecule (C _nx
H _{m- y} ^{M +} ), solid particles that interfere with the recording medium are not mixed. In addition, since a hard carbon film is formed only at the portion irradiated with the ion beam, which is an obstacle to other film forming methods, there is no generation of soot-like deposits on the side surface of the substrate table due to glow discharge. It can be used as a stable mass production process.

As a coating method of the hard carbon film used in the present invention, a method of irradiating an ion beam of hydrocarbon molecules generated by various ion sources such as a Kauffman type ion source, a bucket type ion source, a Hall type ion source, etc. Can be applied. Here, a method of coating with the Kauffman type ion source shown in FIG. 1 will be described as an example.

A hydrocarbon gas, which is a raw material for the hard carbon film, is introduced under reduced pressure, and is ionized by glow discharge in the ion source and the red hot filament 3, and the ions are extracted by the spreading magnetic field of the electromagnet 4. This part covered with an electromagnet is called an ion source. The extracted ions are accelerated toward the base material 1 to which a negative bias voltage is applied, and collide with the base material to form a film.

As the raw material gas, hydrocarbons such as methane, ethane, acetylene and benzene which can be easily introduced as a gas may be used, but methane is preferable. Hydrogen gas may be used as a diluent gas for the above-mentioned raw material gas, or other gas such as argon, carbon dioxide, carbon fluoride or silane may be added. Since the pressure in the container is required to generate plasma and accelerate ions,
1 × 10 ⁻⁶ Torr to 1 Torr may be used, but 1 × 10 ⁻⁴ Torr to 1 × 10 ⁻¹ Torr is preferable in terms of film quality and film formation rate.

When the temperature of the substrate is from room temperature (about 25 ° C.) to 350 ° C., a good thin film is formed. Even in that range, room temperature (about 25 ° C.) to 300 ° C. is particularly preferable. When the base material temperature is higher than 400 ° C., the formed film tends to become graphitic, and even if a hard carbon film is formed, if it is left to cool to room temperature, the residual thermal stress between the base material and the film will be reduced. It becomes large and the film easily peels off during the subsequent use.

The bias voltage between the substrate and the ion source is −
From 50V to -1500V, especially from -500V-
1200V is a preferable range. When a hydrocarbon ion is accelerated by a bias voltage and collides with a substrate, the collision energy breaks the C—H bond of the colliding ion,
The hydrogen atom will be ejected.

The amount by which the hydrogen atoms are ejected depends on the kinetic energy of the colliding ions, that is, the bias voltage. If the bias voltage is too low, an organic soft film containing a large amount of hydrogen tends to be formed. Film, and film self-sputtering occurs and the film formation rate decreases.

The magnetic flux density in the ion source is 100 G to 10
A range of 00G is suitable, and a range of 300G to 500G is a more preferable range. Detailed manufacturing conditions vary depending on the arrangement of the gas inlet in the apparatus, the size of the ion source, the position of the base material, etc., so it is desirable to set the optimum conditions appropriately.

[0022]

EXAMPLE A Kauffman type ion source shown in FIG. 1 was used for forming a hard carbon film. 5 vol.% Hydrogen gas to methane gas
The added material was irradiated for 1 minute under the conditions of atmospheric pressure of 1 × 10 ^-2 Torr, magnetic disk base material bias voltage of -800 V, magnetic disk base material temperature of 300 ° C., and ion current of 1 mA / cm ² , resulting in 20 nm thick The hard carbon film could be uniformly formed on the magnetic disk substrate.

The hydrogen content of the produced hard carbon film was 26 atomic%, and the electron diffraction pattern showed a halo pattern.
Raman spectrum is from 1100 cm ^-1 to 1700 cm
^A broad peak was shown around ^-1 . Diameter 1.6 at the tip
The adhesion of the film in the scratch test method with a needle having mm diamond spheres was 5 × 10 ⁷ N / m ² .

Similarly, the coefficient of friction of the hard carbon film by the scratch test method was 0.10. Surface roughness is R _MAX = 0.5
It was less than nm. The operation of irradiating the ion beam with the magnetic disk substrate for 1 minute was repeated 1000 times, and the magnetic disk protective film formed 1000 times was analyzed. As a result, the same result as that of the first film formation was shown. No inclusion of impurities or deterioration of physical properties of the film was observed.

The abrasion resistance of the film was evaluated as follows. A manganese-zinc-ferrite magnetic head is pressed onto the magnetic disk protective film with a load of 50 gf / cm ² . Next, the magnetic disk is rotated to float the magnetic head, and then the rotation is stopped and the magnetic head is brought into contact with the surface of the protective film again. This contact,
When the start and stop tests were performed on the magnetic disk of this example 250,000 times, no wear occurred on any of the magnetic disks.

[0026]

According to the present invention, a manufacturing method suitable for mass production of coating a hard carbon film on a magnetic disk is provided, and a magnetic disk resistant to collision wear with a magnetic head can be manufactured.

[Brief description of drawings]

FIG. 1 is a principle diagram of an ionization vapor deposition apparatus.

[Explanation of symbols] 1 base material 2 grid 3 filament 4 electromagnet 5 gas introduction tube 6 shutter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takumi Kono 1618 Ida, Nakahara-ku, Kanagawa Shin-Nippon Steel Corporation Advanced Technology Research Institute (72) Inventor Maki Sato 1618 Ida, Nakahara-ku, Kanagawa New Nippon Steel Shares Company Advanced Technology Research Center

Claims (1)

Claim: What is claimed is: 1. A magnetic disk comprising a hard carbon film having a thickness of 1 nm or more and 100 nm or less as an outer protective film formed on the surface of the magnetic disk by using a hydrocarbon ion beam. Method for manufacturing protective film.