JPS6033357A - Aluminum alloy substrate for magnetic disc and preparation thereof - Google Patents

Abstract

PURPOSE:To prepare an aluminum alloy substrate for a magnetic disc capable of realizing good medium characteristics, by a method wherein a NiP layer is formed to the surface of an aluminum alloy plate and a thin Co-film is formed thereon so as to be converted to a non-magnetic oxide film in the next step. CONSTITUTION:After the surface of an aluminum alloy plate (a) is subjected to high accuracy processing (b), a non-magnetic NiP layer (c) is applied to the processed surface of said aluminum alloy plate and the surface thereof is subjected to mirror surface finish (d) by polishing processing. Subsequently, a thin film of Co or an alloy based on Co such as CoP is formed (e). In the next step, the thin film comprising Co or the like is subjected to chemical forming treatment and heat treatment succeeding thereto (f) to be converted to a non-magnetic oxide film to obtain an aluminium alloy substrate for a magnetic disc. An Fe3O4 film is formed at once on said substrate and oxidized to make it possible to easily form a gamma-Fe2O3 film medium (j).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum alloy substrate for a magnetic disk used in an external storage device of a converter, and a method for manufacturing the same.

Continuous thin film magnetic recording media, especially oxide magnetic thin film magnetic recording media, are attracting attention as high-density recording media superior to the γ-Fe and Q3 particle coating films (newly developed coating films) that have been widely used so far. As the oxide material, γ-Fe20 doped with other metal elements has been mainly studied.

The method for manufacturing this γ-Fe203 film medium is to first
e 304 film and oxidize it to 7-Fe2O3
Membrane is essential.

On the other hand, for the substrate, which is another component of the magnetic disk along with the magnetic recording medium, materials such as glass and ceramic were initially used to withstand the above-mentioned temperature conditions. There have been problems due to the fact that it has a single valence and is vulnerable to damage.

Therefore, conventional coating film discs have been used.
As a result of inspection of the possibility of aluminum alloy substrates, a substrate has been proposed in which an anodic oxide film (several microns thick) is formed on the surface of an aluminum alloy substrate by anodizing treatment as a recording medium underlayer. Since the anodic oxide film is aluminum oxide, it has high hardness and excellent workability.It is easy to obtain good surface properties by polishing, which is essential for high-density magnetic disk substrates.
Fe, O, and films have the advantage of having good magnetostatic properties.

However, in the anode one-year-old film substrate actually manufactured, pin hole defects are likely to occur due to impurities such as Si and Fe contained in the substrate material. For this reason, the H
Although progress is being made in the development of AIn, it is extremely difficult to remove the pin hole defects mentioned above.

On the other hand, there are continuous membranes and plated metal membranes.

As a substrate for a plated magnetic disk using this, a hard non-magnetic NiP film (several tens of microns thick) is formed on the surface of an aluminum alloy plate, and this is polished to a high quality disk substrate without pin-hole defects. is obtained. However, when an attempt was made to use the NiP substrate as an oxide magnetic thin film medium, there was a problem in that the NiP film became magnetized during the heat treatment step for conversion to γ-Fe2O3. Recently, however, studies have been conducted to demonstrate that NiP magnetism can be suppressed by not supporting some magnetization or by increasing the P ratio.

However, when a Fe,04 film is directly formed on the NiP film and converted to γ-Fe,O, the magnetic properties of the medium are similar to those of conventional lji+ bullets! A problem arose in that it was significantly inferior or worse than that obtained with the 'e9 film substrate.

An object of the present invention is to provide a new magnetic disk substrate and a method for manufacturing the same, which can eliminate these drawbacks of conventional NiP substrates for oxide magnetic thin film media and realize good media characteristics.

In the aluminum alloy substrate for a magnetic disk according to the present invention, the surface of the aluminum alloy plate is coated with a nonmagnetic NiP layer, which is further coated with a nonmagnetic oxide film of cobalt or an alloy containing cobalt as a main component. Features. Furthermore, the method for manufacturing an aluminum alloy substrate for magnetic disks according to the present invention includes:
After forming a non-magnetic NiP layer on the surface of a highly precisely machined aluminum alloy plate and polishing the surface to a mirror finish,
It is characterized by forming a thin film of cobalt or an alloy containing cobalt as a main component thereon, and converting it into a non-magnetic oxide film by chemical conversion treatment.

The present invention will be described in detail below with reference to Examples and Comparative Examples.

Example 1 As shown in Figure 1, a non-magnetic hard NiP layer was formed on the surface of an aluminum alloy disk plate, and the surface was polished to a high degree of hardness. The thickness was formed by electroless plating.

Next, after chemical conversion treatment, further heat treatment (250℃
x 1 hour in air) to convert the CoP film into a nonmagnetic oxide film. The substrate AK produced in this way is made of γ-Fe2O by normal sputtering method (Fe3O4 film formation → thermal oxidation).
3) A K and Co-added γ-Fe10B film was formed. On the other hand, for comparison, a Co-added -Fe, 03 film was formed in the same process on a substrate B having a NiP layer finished with 01M. b) The magnetostatic properties of the γ-Fe, 03 film were measured and were as shown in the following table.

As shown in the table, substrate A having a non-magnetic Co alloy oxide film as an underlayer had better medium magnetic properties than substrate B having a NiP layer as an underlayer.

Example 2 Co
A N i P film was formed to a thickness of 200 OA by electroless arc plating. Next, in the same manner as in Example 1, the CoNiP film was converted into a nonmagnetic oxide film. After polishing the surface of the substrate thus created, the same procedure as in Example 1 was carried out.
A γ-Fe20B film was formed. The magnetostatic properties of the obtained film were clearly improved compared to a film formed directly on the NiP layer base.

The chemical conversion treatment agent used in the above examples is nitric acid.

Hydrogen peroxide, potassium chlorate, sodium dichromate, etc. are used, and EDTA and tartaric acid are used as pH buffers.

Organic chelating agents such as gluconic acid, succinic acid, citric acid, and thiourea are used.

As mentioned above, non-magnetic N on the surface of the aluminum alloy plate
An aluminum alloy substrate for a magnetic disk according to the present invention, which is coated with an iP film and further coated with a non-magnetic oxide film of cobalt or an alloy containing cobalt as a main component, and an aluminum alloy substrate processed with high precision. After forming a non-magnetic NiP layer on the surface of an aluminum alloy plate and polishing the surface to a sharp surface, a thin film of cobalt or an alloy containing cobalt as a main component is formed on top of it, and it is chemically converted. According to the manufacturing method of the aluminum alloy substrate according to the present invention, which is characterized in that it is converted into a non-magnetic oxide film by treatment and heat treatment, a single contact (AGS integrally formed) is formed on the base surface of the NiP layer, [1f]
It becomes possible to fabricate a ferrite film magnetic disk that has both the quality (defect-free) of the NiP layer lower layer and the high quality (long life) of the anodic oxide film substrate.

[Brief explanation of drawings]

The figure shows the manufacturing process of a puluminum alloy substrate for magnetic disks according to the present invention and a conventional substrate for metal disks.

Claims (1)

[Claims] 1. A nonmagnetic NiP layer is coated on the surface of an aluminum alloy substrate, and a nonmagnetic oxide film of cobalt or an alloy containing cobalt as a main component is further coated thereon. Aluminum alloy substrate for magnetic disks. After forming a non-magnetic NiP layer on the surface of a medically processed aluminum alloy plate and polishing the surface to a sharp surface,
Manufacture of an aluminum alloy substrate for a magnetic disk, which is characterized by forming a thin film of cobalt or an alloy containing cobalt as a main component thereon, and converting it into a non-magnetic oxide film by chemical conversion treatment and subsequent heat treatment. Method.