JPS60169594A - Manufacture of alumite substrate for high density magnetic recording material - Google Patents

Abstract

PURPOSE:To manufacture the titled alumite substrate free from black spots and having superior smoothness and heat resistance by anodizing Al in a sulfamic acid soln. having a specified concn. at a specified bath temp., a specified current density and a specified voltage. CONSTITUTION:An Al or Al alloy material is anodizing by electrolysis in a sulfamic acid soln. having >=1wt%, preferably 5-18wt% concn. at 10-80 deg.C, preferably 20-50 deg.C bath temp., 0.1-10A/dm<2>, preferably 0.5-5A/dm<2> current density and 10-100V, preferably 20-80V voltage. The electrolysis time is about 10- 15min. It is preferable that the Al or Al alloy material has low Fe and Si contents.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a high-density magnetic recording Aikawa alumite substrate that has no black spot defects and has excellent smoothness, heat resistance, etc.

It has excellent abrasion resistance, which is required for magnetic recording substrates such as magnetic disks, has good abrasiveness, makes it easy to obtain a highly accurate smooth surface, and can easily form multiple thin magnetic layers on the surface. As a material, anodized aluminum or aluminum alloy is used. However, in this alumite substrate, impurities such as iron and silicon that are present in the aluminum or aluminum alloy crystallize as intermetallic compounds, and these are scattered on the old surface and this part becomes extremely small during the alumite treatment. A so-called black spot defect, which is an alumite coating defect, occurs. Initially, this defect is very small on the submicron scale, but as the alumite film grows, it expands and becomes a black spot defect in an alumite layer with a film thickness of 5 μm or more. Since these are focused minute defects of 5 to 10 μm in size, the larger the number, the more signal errors occur in the magnetic recording material, which is undesirable. In addition, when making a high-intelligence magnetic recording plate, α
-Fe3st is deposited by sputtering or other method and heated to 300-400°C to form γ-Fez03.
Is it necessary to heat the alumite layer at such a high temperature?There is a problem that cracks occur in the alumite film, which can easily cause product defects. The thickness of the coating must be extremely thin, which causes a decrease in the consistency of the alumite plate.

As a result of repeated efforts to solve these problems, the present inventors recognized that the objective could be achieved by selecting electrolytic conditions using a sulfamino acid solution as an electrolytic bath, and developed the present invention. This is what was done. That is, in the present invention, aluminum or aluminum alloy material is heated in a sulfamino acid solution having an IM quantity coefficient or higher at a bath temperature of 10 to 80°C.
Current density 0.1-10 A/d+□2. voltage 10~10
This is a method for manufacturing an alumite substrate for high-density magnetic recording materials, which is anodized at a temperature of 0.

As the aluminum or aluminum alloy used in the present invention, an ordinary plate material can be used, but from the viewpoint of black spot defects, it is preferable to use a material with a small content of iron, silica, etc.

A sulfamino acid solution is used as the alumite electrolytic bath, and the concentration of sulfamino acid (1% by weight) is
It can be used in a range of over saturated sweetness.

It is preferable to maintain it within the range of 5 to 18 weight coefficients. When the concentration is less than 1 weight, the conductivity of the solution becomes low, and the above is meaningless. In addition.

Removing a small amount of sulfuric acid from the sulfamic acid electrolyte can improve the conductivity, film structure, stability, etc. of the bath.

It is economical and effective to maintain the bath temperature in the range of 10 to 80°C, preferably 20 to 50°C.

The electrolysis time is not particularly limited, but it is preferable to electrolyze for 10 to 15 minutes, although a longer treatment time will result in a thicker film.

The voltage is in the range of 10-100V, preferably 20-80V, and the current density is 01-10A/dn, 2. Preferably, it is carried out within the range of 0.5 to 5 A/dm2.

The alumite substrate obtained in this way has almost no microscopic black spots and is resistant to henodokrano
Even if the film thickness σ is grown to 10 μm or more in order to improve the durability, large black spots are not observed. Furthermore, it has excellent heat resistance and does not generate cracks even when heated and held at 300 to 400° C. for forming a magnetic film.

Next, the aluminum alloy side (A2-3% M7 alloy) was
Current density IA/dr, ? using a 15 wt steamed sulfamino acid solution kept at 0°C. Alumite substrates were prepared with films of various thicknesses formed by applying direct current electrical angle heating for 20 to 80 minutes, and the occurrence of sunspots and crank formation by heating to 350°C for 2 hours, as well as the coatings related to henodecanoic/yellow resistance. Hardness was measured.

The results are shown in the table below. For comparison, we also show the results of similar tests on an alumite substrate made using a conventional sulfuric acid bath.Evaluation of sunspots was performed in a microscopic field of view (0.36mj).
O indicates 2.5 μm or less, Δ indicates 35 μm or less, and × indicates no more than 1 black spot of 5 μm or less.

The crank was evaluated by observing the alumite board after heat treatment under a microscope. O indicates no cracks at all, △ indicates partially cracked, and Evaluation.

○ indicates 250H.
V or more, △ is 200-250Hv, X is 200H
Indicates that it is less than or equal to v.

[edited] Sulfur bath: Sulfuric acid bath Sulfuric acid bath As shown in the table above, alumite substrates treated with alumite using the sulfamino acid solution of the present invention have no or almost no black spots or cracks. However, in the sulfuric acid bath, which is the typical conventional alumite treatment method,
It can be seen that it is not possible to obtain a substrate that satisfies all three characteristics of black spots, cracks, and hardness.

In the present invention, the electrolytic conditions are selected using aluminum or aluminum alloy as a sulfamino acid solution in the electrolytic bath. It was possible to solve the problems of crack generation and heat crush resistance, and to produce an alumite substrate having excellent properties against these problems, and excellent young fruits were observed.

Next, an example of the method of the present invention will be described.

Example Aluminum alloy material for high-density magnetic recording (At-3%My
An alloy (inner diameter: 75mm, outer diameter: 200mm, thickness: 2mm) was subjected to specified surface polishing, washed with a non-erosive detergent, and then heated and maintained at 40°C in a sulfamino acid solution of 15% by weight. The current density was kept constant at I Vdm'' as an anode, and the voltage was varied from 20 to 27 V to form a pale white smooth alumite film of 10 μm. The treatment time was 40 minutes. Ta.

I4I et al. 11 Examine the alumite film with a microscope, /6
- or black spot defects were not observed. Further, after further heat-treating this film at 350° C. for 2 hours, it was observed under a microscope and no cracks were observed. In addition.

The Vickers hardness of the film was 290 Hv.

Comparative Example After using the same monthly fee as in the example and applying the same pretreatment,
It was immersed in a 15% sulfuric acid solution maintained at 10° C., and a direct current of 1.2 A/dm 2 was applied as an anode. The voltage was about 15V, and a 10 μm transparent alumite film was formed in 30 minutes. The alumite film prepared by I44 had a satisfactory Vickers hardness, but black spots and cracks were noticeable, and it was inferior to the film made of sulfamino acid.

Patent applicant: Nippon Light Metal Co., Ltd.

Claims (1)

[Claims] 1) Aluminum or aluminum alloy is heated in a sulfamino acid solution of 1% or more by weight at a bath temperature of 10 to 80°C and a current density of 01 to 10 A/dm2. % pressure 10~100V
1. A method for producing an alumite substrate for high-density magnetic recording material, characterized by alumite treatment.