JPS61267930A - Pretreatment of substrate for magnetic disk - Google Patents

Abstract

PURPOSE:To obtain a high-quality magnetic disk with less defects by sputtering a hard carbon film having 1,800-4,000 Hv hardness and <=10mum thickness on the base metal as the pretreatment when magnetic sputtering is applied to a substrate for a magnetic disk. CONSTITUTION:When a contact-start-stop system magnetic disk is formed, a hard carbon-sputtered film 2 is formed onn the surface of a substrate 1 made of Al as the backing coated magnetic film without using an ordinary anodized coated film. Then a magnetic sputtered film 3 and a protective sputtered film 4 are laminated and deposited on the film 2. At this time, the surface hardness Hv is regulated to 1,800-4,000, the thickness is controlled to <=10mum and the film is formed with a diamond or a similar composition. When the film 2 is coated, the surface of the substrate 1 is polished and then high-frequency sputtering is carried out in an H2 atmosphere by using pure carbon or high- purity graphite or vapor deposition is carried out by using the plasma of methane, etc.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a pretreatment method for a magnetic disk substrate.

(Prior art and its problems) Magnetic disks occupy an important position as high-density recording means, and are becoming widely used in various fields. Generally, this magnetic disk is made by coating a metal base such as an aluminum alloy substrate with a non-magnetic film, applying Co sputtering or the like as a magnetic film on the non-magnetic film, and then sputtering soft carbon onto the non-magnetic film for the purpose of lubrication. It is made by applying a protective film such as

The non-magnetic film is an important pre-treatment for hardening the metal base and forming a precise base for the magnetic film. Conventionally, the following method has been used to form the non-magnetic film as a pre-treatment for the magnetic film. method was adopted.

■A method in which the surface of the base metal is polished and then subjected to non-magnetic plating, such as N1-P electroless plating.

■A method in which the surface of the base metal is polished and then subjected to anodic oxide film treatment (alumite processing).

However, in such a pretreatment method, control of the quality of the work 1 becomes complicated because the work is different and separate from the step of forming layers such as the magnetic film and the protective film.

Furthermore, in the case of a plating film or an anodized film, in order to strengthen the underlying hardness, it is necessary to increase the film thickness to 20 μm or more, resulting in a rough surface. Therefore.

Before carrying out magnetic sputtering, it is necessary to polish the rough surface, which is a troublesome operation that requires a high level of skill, resulting in problems such as poor workability and efficiency, and being uneconomical.

Moreover, method (2) is fraught with unstable factors such as non-magnetic plating bath conditions and mixed chemical products, which affect the magnetic film in a complex manner. It is difficult to obtain a stable film that can withstand As a result, the electrical properties of the obtained magnetic disks vary, and when used as, for example, a Westchester-type contact-start-stop type magnetic recording medium, there is a problem in that various defects are likely to occur frequently.

(Means for Solving the Problems) The present invention was developed through research in order to solve the above-mentioned conventional problems, and produces high-quality magnetic disks with few defects in a small number of processes with good workability. The present invention aims to provide a method for pre-processing a magnetic disk substrate, which allows for the pretreatment of a magnetic disk substrate.

In order to achieve this object, one aspect of the present invention is to sputter a hard carbon film having a hardness of Hv 1800 to 4000° and a thickness of 10 μm or less on a base metal as a pretreatment for magnetic sputtering on a magnetic disk substrate.

(Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

This is an enlarged view of a contact start/stop type magnetic disk. 1 is an aluminum substrate (substrate), 2 is a hard carbon sputtered film coated on the aluminum substrate 1 as a pretreatment, 3
4 is a magnetic sputtered film formed on the hard carbon sputtered film, and 4 is a protective sputtered film formed on the magnetic sputtered film.

A feature of the present invention is that a hard carbon sputtered film 2 is applied as the base nonmagnetic film for the aluminum substrate 1, instead of conventional plating or anodic oxidation film.

This hard carbon sputtered film 2 has a surface hardness of Hv180.
It is a thin film with a diamond-like composition or properties similar to diamond-like or similar composition or properties. If the film thickness is 10 μm or more, the adhesion with the substrate will decrease and polishing will be required, which is not preferable.
m or less, the desired thermally stable high hardness cannot be achieved.

Specific methods for obtaining this hard carbon sputtered film 2 include a solid method and a gas method. In the one-body method, after polishing the surface of the aluminum substrate 1, high-frequency sputtering is performed using pure carbon or high-purity graphite as a target in a hydrogen atmosphere or a vaporized atmosphere of an aromatic compound such as benzene. .

As a gas method, there is a method of vapor depositing hard carbon using hydrocarbon plasma such as methane.

Note that there are no special conditions for the magnetic sputtered film and the protective sputtered film that are coated on the hard carbon sputtered film 2, and conventional methods may be applied.

In the conventional process, defects in the base metal that is the substrate of the magnetic disk, or defects due to the purity of chemicals, filtration methods, processing conditions, etc. in the plating method or oxide film method in the next step, remain as they are and are removed from the polishing process in the next step. Then, magnetic sputtering and protective film sputtering were layered on top of the sputtering, and production was carried out with many defects.In the present invention, a thin diamond-like hard carbon film is sputtered as a pretreatment for magnetic sputtering. Therefore, the surface polishing process that was conventionally considered indispensable can be omitted, and since the hard carbon film 2 is created by sputtering, the entire process is unified into a series of sputtering processes, which reduces the frequency of defects. significantly reduced.

Further, the hard carbon film 2 has good adhesion to the next layer, the magnetic sputtered film 3, and is very thermally stable, so that the magnetic film can have excellent characteristics as a recording medium.

Next, specific examples of the present invention will be shown.

Example 1 In manufacturing a contact start/stop type magnetic disk, a 5 inch diameter aluminum substrate was surface polished to a thickness of 1.905 mm, and then a hard carbon film was sputtered under the following conditions as a pretreatment.

In this process, the substrate is mounted on a jig, and the residual gas pressure is 10 Pa.
Then, hydrocarbon plasma deposition was performed at 1.5×10 Torr, mff 200° C., and a deposition rate of 5 nn+/see.

After cooling, the jig was removed.

The hard carbon sputtered film obtained had a hardness of Hv2000,
The film thickness was 1 μm and uniform.

Without polishing this hard carbon sputtered film, Co was sputtered to a thickness of 0.17 μm using a conventional method as a magnetic film.
0A soft carbon was sputtered.

The electrical properties of the obtained magnetic disks showed the following good values, and there was almost no variation among the disks.

Coercive force 700 0s Squareness ratio 0.9 Residual magnetic flux density 8000G (Effects of the invention) According to the invention described above, as a pretreatment of the magnetic film,
Since the hard carbon film is generated by sputtering, it can be made into a thin and thermally stable base, resulting in a high-quality magnetic disk with fewer defects than when using conventional plating or oxide film treatment. In terms of manufacturing, it is possible to omit the complicated polishing process after forming the non-magnetic film, and since the entire process can be performed by sputtering, process control, workability, and work efficiency can be improved. Excellent effects can be obtained.

[Brief explanation of drawings]

The drawing is an enlarged sectional view of a magnetic disk according to the present invention.

Claims (1)

[Claims] A pretreatment method for a magnetic disk substrate, which comprises sputtering a hard carbon film having a hardness of Hv 1800 to 4000 and a thickness of 10 μm or less onto a base metal as a pretreatment for magnetic sputtering of the magnetic disk substrate.