JPS59110796A - Manufacture of magnetic disk substrate - Google Patents

Abstract

PURPOSE:To obtain the titled substrate whose surface roughness would not be deteriorated after it has been subjected to a step of forming an oxide magnetic thin film medium, by forming an anodized film on the surface of an Al alloy plate, and performing heat treatment under specified conditions prior to the planishing of the anodized film. CONSTITUTION:The process of manufacturing a substrate includes a heat treatment step between an anodizing step as in the conventional process and a planishing step. In this heat treatment step, the anodized Al alloy plate is heat- treated at higher temperature or longer period in comparison to the heat treatment that will be carried out in the subsequent medium forming step. The thus heat-treated Al alloy plate is planished to obtain a disk substrate. After an iron oxide magnetic thin film mainly consisting of Fe3O4 is formed on the disk substrate, it is heat-treated to obtain an iron oxide film mainly consisting of gamma- Fe2O3. The surface roughness of the thus produced magnetic disk is the same as the surface roughness of the substrate, and deterioration of the surface roughness would not be observed at all.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an aluminum alloy magnetic disk substrate used for magnetic disks for external storage devices of electronic computing materials.

(1) Continuous thin film magnetic storage media, especially oxide magnetic thin film magnetic storage media, have attracted attention as high-density magnetic recording media that are superior to the γ-Fe, 03 fine particle coating films (so-called coating films) that have been widely used. ing. Initially, the oxide magnetic thin film material was Fe, O, or Fe, 04-γ-Fe, 0
．． Intermediate phase was proposed, but problems related to reliability such as pressure demagnetization phenomenon due to contact with the head and instability of magnetic properties (particularly Hc) arose.Recently, γ-re,
03 is being considered exclusively.

γ-Fe, 0. As a method for manufacturing the membrane medium, first Fe,
0. A common method is to prepare a film and oxidize it to form a 1-Fe, Q, film. This γ-Fe, 0. Heat treatment at a temperature of at least 250°C, preferably 275°C or higher is essential for conversion into a film.

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, but from a practical standpoint, it was difficult to withstand shock. There were problems due to the fact that it is weak against the enemy, has a habit of being damaged, and has a high (2) value.

Therefore, the possibility of using aluminum alloy substrates, which have been conventionally used for coated film disks, was investigated. As a result, a substrate was proposed in which an anodized film was formed on the surface of an aluminum alloy base by anodizing treatment as a recording medium underlayer. ing.

Since the anodic oxide film is an oxide of aluminum, it has high hardness, excellent workability, and can be easily polished to obtain good surface properties, which are essential for high-density recording magnetic disk substrates.

However, if the aluminum alloy substrate used in current coated film disks is used for the above purpose, many defects will occur in the anodic oxide film, making it completely unsuitable for use as a disk substrate for high-density recording. . The reason for this is that impurities such as 8i and Fe contained in the aluminum alloy material create intermetallic compounds, and when these are on or near the substrate surface, the anodic oxide film does not grow in that area and pinhole defects occur. .

Therefore, high purity is achieved by minimizing the contamination of the above impurities (3) Development of aluminum alloy substrates is progressing.

This is made of high-purity aluminum with a purity of 99.9% or higher as a base material, and is alloyed with the required additional metals. However, according to experiments conducted by the present inventors, a substrate manufactured using such a highly purified aluminum alloy using the conventional manufacturing process for continuous thin film magnetic disk substrates shown in FIG. When a -Fe, O, film media magnetic disk was fabricated, it was found that the surface roughness of the disk deteriorated significantly, and in extreme cases, stable floating of the magnetic head became impossible. It has become clear that the reason for this is that alloy crystal grains in the substrate grow during the medium forming process, which causes an increase in the substrate surface roughness.

The purpose of the present invention is to eliminate such drawbacks found in conventional methods of manufacturing magnetic disk substrates for oxide magnetic thin film media, and to
It is an object of the present invention to provide a method for manufacturing a magnetic disk substrate that does not cause deterioration in surface roughness even after the process of forming the thin film medium.

The method for manufacturing a magnetic disk substrate according to the present invention includes (4) forming an anodized film on the surface of the aluminum alloy substrate, and then mirror-finishing the surface. After forming and prior to mirror finishing, the above anodized aluminum alloy plate is treated in advance under conditions where either the temperature or the time, or both, are the same or higher (or longer) than the heat treatment conditions performed in the subsequent medium forming step. % indicates that the process includes heat treatment.

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

Example 1 Using a highly purified aluminum alloy plate, the same alloy plate was subjected to anodization and heat treatment for 05 hours at 300°C prior to surface mirror polishing according to the process shown in Figure 2. ,
The surface is polished to Rmax O, 02 by grinding and polishing.
Finished with a surface roughness of μm.

[FIG. 3(a)] The thus obtained disk substrate is coated with Fe, 0. After forming an iron oxide magnetic thin film (~1.70OA thick) mainly composed of
) After oxidation treatment at 275°C for 1 hour, γ-re, 0
An iron oxide magnetic thin film containing 3 as the main component was obtained. The surface roughness of the thus produced magnetic disk was as shown in FIG. 3 (b), and the surface roughness of the substrate was the same as that of the substrate (FIG. 3 (a)), and no deterioration in surface roughness was observed.

In the magnetic head levitation test, the magnetic head was stably levated with a narrow levitation amount of about 0.2 μm.

Comparative Example Using the same high-purity aluminum alloy plate as used in Example 1, a disk substrate was manufactured by the conventional process shown in FIG. Fe was applied to this substrate under exactly the same conditions as in Example 1.
30. Film formation, γ-Fe, 0. The film was subjected to thermal oxidation treatment to obtain an iron oxide thin film magnetic disk. The surface roughness of this magnetic disk was as shown in FIG. 4, and obvious deterioration was expected.

Example 2゜Using the same high-purity aluminum alloy plate as in Example 1, a second
According to the process according to the present invention shown in the figure, after anodizing, the alloy plate is heat treated at 280°C for 3 hours prior to polishing the ψ surface, and then is polished to a mirror surface by grinding and polishing (6). Finished. The thus obtained disk substrate was coated with Fe50. After forming an iron oxide magnetic thin film mainly composed of
After oxidation treatment at 0°C for 1 hour, γ-Fe, 0. A4) An iron oxide magnetic thin film containing as the main component was prepared.

As in Example 1, the surface roughness of the magnetic disk produced in this manner was not different from that of the substrate after polishing.

As is clear from the above embodiments, according to the method of manufacturing a magnetic disk substrate according to the present invention, high performance is achieved without deterioration of surface properties even in the process of forming an iron oxide magnetic thin film medium magnetic disk. It becomes possible to manufacture disk substrates for continuous thin film magnetic disks.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional manufacturing process of an anodized aluminum alloy disk substrate. FIG. 2 is a diagram showing the manufacturing process of the aluminum alloy disk substrate according to the present invention. Figure 3(a) shows the surface roughness of a disk substrate manufactured using the manufacturing process of the present invention (7), and Figure 3(b) shows the surface roughness of an iron oxide magnetic thin film medium magnetic disk manufactured using the same. Diagram showing. FIG. 4 is a diagram showing the surface roughness of a magnetic disk manufactured using a disk substrate manufactured by a conventional method. (8) I M Figure 2

Claims (1)

[Claims] In a method for manufacturing an aluminum alloy magnetic disk substrate, which includes a step of forming an anodized film on the surface of an aluminum alloy plate and then mirror-finishing the surface, after forming the anodic film and prior to mirror-finishing, in the subsequent medium forming step. A magnetic disk substrate comprising the step of previously heat-treating the anodized aluminum alloy plate under the same or higher (or longer) conditions of either temperature or time, or both, compared to the heat treatment conditions. manufacturing method.