JPS59191137A - Board for magnetic disk and its manufacture - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a bit error due to the exfoliation of a recording medium and to improve the quality of a signal by forming the oxide film on an anode, performing sealing treatment to extinguish pores on the oxide film, then, performing heat treatment on the film. CONSTITUTION:An oxide film 3 of an anode made of aluminium or aluminium alloy is formed on the surface of an aluminium or aluminium alloy base body after applying pre-treatment to said base body then, sealing treatment is performed on the film 3 so as to extinguish pores existing in the film 3. Thereafter, heat treatment at a 300 deg.-350 deg. temperature is performed to improve the strength of the oxide film 3 and the film 3 is finished by precise grinding. Thus a substrate for magnetic disk 4 is manufactured. The board 4 for magnetic disk manufactured by this manufacturing method has an anode oxide film 3 which is made of aluminium or aluminium alloy having pores because of the sealing treatment and formed on the base body made of aluminium or aluminium alloy, and a magnetic recording medium 2 formed on the surface of the anode oxide film 3. Therefore, no exfoliation of the magnetic recording medium 2 occurs.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an improvement in a sputter disk using an iron oxide magnetic thin film as a recording layer, and more particularly to a high-quality disk substrate with fewer errors and defects and a method for manufacturing the same.

[Background of the invention]

Conventionally, as a substrate for a sputtered magnetic disk, there is a method in which the surface of an M alloy substrate is anodized, heat treated, and then finished, as described in, for example, Japanese Patent Laid-Open No. 55-85694.

When iron oxide magnetic recording media are formed using these substrates by sputtering in a vacuum, etc., defects occur due to local peeling of the recording medium and pit errors are moved, resulting in undesirable results in terms of performance and quality as a magnetic disk. That was a problem.

In order to solve the above-mentioned conventional drawbacks, the inventors investigated the cause and found the following.

In other words, in conventional substrates, the anodic oxide film, so-called alumite film, has many microscopic pores (current through holes) that are generated as the alumite film is formed, and finishing fluid and Cleaning liquids and their residues remain, and these alter the substrate surface during vacuum, heating in vacuum, or sputtering, reducing the adhesion between the recording medium and the substrate, causing film peeling and causing defects. It became clear that it would happen.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-performance magnetic disk substrate with excellent signal quality and a method for manufacturing the same, which prevents the above-mentioned errors caused by recording medium peeling.

[Summary of the invention]

That is, the present invention does not form an aluminum or aluminum alloy anodic oxide film on the surface of an aluminum or aluminum alloy substrate and heat-treat it as it is, as in the conventional method, but instead performs a sealing treatment after forming an anodic oxide film. The pores existing in the anodic oxide film are removed by performing a heat treatment, and the aluminum or aluminum alloy substrate is first pretreated.
An aluminum or aluminum alloy anodic oxide film is formed on the surface, followed by sealing treatment to eliminate pores existing in the anodic oxide film, and then heat treatment at a temperature of 600°C to 350°C to anodize It is characterized by improving the strength of the film and then finishing it with precision polishing to produce a magnetic disk substrate.

In addition, in a single magnetic tape substrate manufactured by this manufacturing method, a pore-free aluminum or aluminum alloy anodic oxide film is formed on the surface of an aluminum or aluminum alloy base by a sealing process, and the surface of this anodic oxide film is A feature of the magnetic disk substrate is that it has a structure in which a magnetic recording medium is formed, and the magnetic recording medium does not peel off.

[Embodiments of the invention]

An embodiment of the present invention will be described in detail below.

Example 1 As the M alloy substrate, highly purified M-
The diameter is made by turning using M alloy material.

210φ - inner diameter iooφ, plate thickness 2. Ot, surface roughness 0.
It was processed into a shape of 0.010 μm Ra. Next, as alumite pretreatment, solvent degreasing, alkaline degreasing, and acid cleaning were performed, and then anodization was performed under the following conditions.

The above specifications indicate typical conditions).

Next, the disk on which the anodic oxide film was formed was thoroughly washed with water and then subjected to a 98°b sealing treatment. Other methods using high-temperature steam can also be used for this sealing treatment. Further, the processing time shall be changed as appropriate depending on the film thickness and film quality.

Next, the disks subjected to the sealing treatment were subjected to a preliminary heating treatment. The suitable heating temperature range is 300 to 350°C, and in this example, the heating temperature was 320°C for 3 hours.

This heating is performed to generate compressive stress in the film to increase the mechanical strength of the film and to prevent surface roughness from deteriorating during thermal oxidation treatment at 300° C. during formation of the magnetic thin film. If the heat treatment temperature is 350°C or less, there will be a problem of thermal cracking of the film, and if it is 300°C or less, surface roughness will deteriorate, so the temperature was set at 30 [7 to 350°C].

Next, the disc is finished polished to a surface roughness of 001
A high-performance substrate with an Ra of 0 μm or less was obtained.

Furthermore, 0.000.
After forming a 2 μm Fe 3 C) 4 thin film, γ-Fg 2. O, was converted into a film to form a recording medium.

Next, a fluorocarbon-based lubricant film was formed on the medium to complete the disk shown in the figure. In the figure, 1 is a lubricating film, 2 is a magnetic recording medium, 5 is a sealed aluminum or aluminum alloy anodic oxide film, and 4 is an aluminum or aluminum alloy substrate.

The recording characteristics of this disc were measured and compared with those of discs manufactured by conventional methods, and the results were as shown in the table. This table confirms that we have achieved a high-performance magnetic disk with approximately one digit lower number of sibit errors.

As a characteristic measuring means, 10. On the magnetic recording medium surface of d,
After making a 1-0 cut, tape is pasted on top of the cut, and then the tape is peeled off at a 45° angle. Judgment is made based on the number of pieces that stick to the tape and peel off (parameter: 1000 pieces). The results are summarized in the table below.

Table [Effects of the Invention] According to the present invention, the pores in the anodic oxide film of the magnetic disk substrate can be sealed, and a substrate can be formed in which the presence of processing fluid, cleaning fluid residue, etc. is minimized. The adhesion between the recording medium formed on the substrate and the substrate is improved, and as a result, pit errors due to medium peeling can be significantly reduced as shown in the table.

Therefore, it is possible to form a high-performance, high-quality magnetic disk with fewer bit errors than ever before.

Furthermore, by using the substrate of the present invention, when the gap between the head and the disk surface, the so-called flying spacing, is reduced, the number of protrusions that collide with the head can be reduced compared to conventional substrates. A magnetic disk with excellent flying properties can be formed.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional view of a magnetic disk substrate according to the present invention. 1......Lubricating film 2...Magnetic recording medium 3...
・・・・・・Aluminum or aluminum alloy anodic oxide film 4・・・・・・・・・Aluminum or aluminum alloy substrate subjected to pore sealing treatment

Claims (1)

[Claims] 1. A base plate for a magnetic disk, characterized in that the surface of the base body made of aluminum or aluminum alloy is sealed to eliminate pores and an anodic oxide film of aluminum or aluminum alloy is provided thereon. . 2. After pre-treating the aluminum or aluminum alloy substrate, an aluminum or aluminum anodic oxide film is formed thereon, followed by a sealing process to eliminate pores in the anodic oxide film, and then heated at 300°C to A method of manufacturing a magnetic disk substrate, which comprises performing heat treatment at a temperature of 650° C. to improve the strength of the anodic oxide film, and finally finishing with precision polishing.