JPH05298667A - Aluminum alloy substrate for magnetic disk and magnetic disk - Google Patents

Abstract

PURPOSE:To prevent the warp of an NiP film and to provide a substrate for a magnetic disk and a magnetic disk excellent in property of preventing the adsorption of a magnetic head and having enhanced performance as a medium having high recording density. CONSTITUTION:The surface of an Al alloy disk as the body of a substrate is concentrically roughened so as to attain >=10Angstrom surface roughness Ra in a direction perpendicular to tangents of the resulting concentric circles. A hard dense layer such as an NiP film is formed on the roughened surface of the Al alloy disk.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy substrate for a magnetic disk and a magnetic disk, and in particular, it has excellent head adsorption prevention performance, enables improvement of medium performance and low flying height of the magnetic head, and high recording density medium. The present invention relates to an aluminum alloy substrate for a magnetic disk and a magnetic disk suitable as the magnetic disk.

[0002]

2. Description of the Related Art In recent years, with the increase in the amount of information, there has been a demand for an increase in the capacity of magnetic disks as external recording devices and an increase in the density of magnetic disk media.

When viewed from the magnetic head side to improve the recording density, it is effective to reduce the flying height in order to increase the recording density.
However, in order to reduce the flying height, it is important to optimize the smoothness or surface roughness required for the substrate.

At present, in high density recording technology, it is necessary to set the flying height to 0.3 μm or less. In this case, the surface roughness of the substrate should be set to 1/10 or less of the flying height. is necessary.

However, it is impossible to obtain such an extremely small surface roughness with the aluminum alloy substrate itself. Also, for the aluminum alloy substrate, in view of the limit of medium performance, etc., the coating medium using the aluminum alloy substrate which is the mainstream at present is replaced with an electroless NiP plating film on the aluminum alloy substrate to harden the surface, or The medium manufacturing method is changing to a thin film medium in which the substrate is made hard and dense to reduce defects to improve the surface roughness and a metal magnetic material is formed by a sputtering method or a plating method.

However, when the surface roughness is made as small as possible, there arises a problem that the magnetic head is attracted. In other words, such adsorption behavior, when the slider surface and the magnetic disk surface of the magnetic head is facing in and small distance in a very smooth, the gap is due molecules such as O _2, N ₂ or H ₂ O This is due to the generation of a large adsorption force due to the interfacial tension when it is filled up. When this attracting force is generated, not only the magnetic head scratches the magnetic disk and consumes a large amount of power when the motor is started, but in the worst case, the magnetic head is destroyed.

As a method of preventing the above phenomenon, the surface of the substrate is roughened with a tape coated with a fine abrasive in order to reduce the contact area between the magnetic head slider surface and the magnetic disk surface. Texture processing is generally performed.

When a Co—Cr alloy is sputtered as a magnetic film on a concentrically textured NiP film, the magnetic properties in the circumferential direction are greatly improved due to crystal magnetic anisotropy. It is also known.

[0009]

However, in the conventional texture treatment, concentric circular polishing stitches are formed on the NiP film by machining, so that a metal-specific return occurs. Therefore, it is difficult to reduce the flying height of the magnetic head.

The present invention has been made in view of the above problems, and a return process in a magnetic disk substrate is performed by concentrically roughening the surface of an aluminum alloy disk which is a base of an aluminum alloy substrate. It is an object of the present invention to provide a substrate for a high recording density magnetic disk and a magnetic disk which have excellent magnetic head adsorption preventing performance as a substrate for a high recording density medium and which can improve the medium performance.

[0011]

A surface of an aluminum alloy substrate for a magnetic disk according to the present invention is roughened concentrically, and a surface roughness Ra in a direction perpendicular to a tangent of the concentric circle is 10 Å or more. It is characterized by having an aluminum alloy disc and a hard dense layer formed on the surface of the aluminum alloy disc.

A magnetic disk according to the present invention is characterized in that a magnetic layer and a protective layer are sequentially formed on an aluminum alloy substrate constructed as described above.

[0013]

The inventors of the present invention have conducted intensive studies to prevent the return of the magnetic disk substrate having the NiP film as the hard and dense layer that is roughened concentrically, and as a result, as described above, the roughening treatment is performed. By changing the order and target of the process
It has been found that a smooth substrate with no return can be obtained. That is, in the present invention, before the formation of the NiP film, the aluminum alloy disc itself, which is the base body of the aluminum alloy substrate, is finely roughened concentrically to form a NiP film on the aluminum alloy disc. After forming the film, the conventional texture treatment is not performed. In this way, by forming the NiP film after roughening the aluminum alloy disc, the unevenness of the polishing mesh formed by the roughening treatment of the aluminum alloy disc is transferred to the NiP film on the surface. A magnetic disk substrate having the same unevenness on the surface as in the texture treatment of 1. can be obtained. Moreover, since the magnetic disk substrate is not subjected to the surface roughening treatment after the NiP film is formed, the occurrence of the return is avoided. Further, as a result of the concentric concavo-convex formation, the magnetic head can be prevented from being attracted, the medium performance can be improved, and the flying height of the magnetic head can be reduced. By lowering the flying height of the magnetic head, the recording density can be increased, and the present invention is extremely useful as a magnetic disk substrate and a magnetic disk for high recording density.

Therefore, the concentric circular grinds formed on the surface of the aluminum alloy disk must have a surface roughness of 10 Å or more in the direction perpendicular to the tangent to the concentric circle. If the surface roughness is less than 10Å, the effect of preventing the adsorption by reducing the contact area with the magnetic head after forming the NiP film is not recognized. On the other hand, the surface roughness
If it is rougher than 1 μm, it takes a long time to finish and polish the NiP film, which increases the manufacturing cost. Therefore, the surface roughness of the aluminum alloy disc is preferably 1 μm or less. The surface roughness of the aluminum alloy substrate is
It is necessary to change the thickness of the NiP film and the magnetic characteristics according to the roughness required on the surface of the NiP film.

As the hard dense layer, conventionally, NiC is used.
Although uP, NiWP, FeNi and the like are used, it is preferable to use a NiP film from the viewpoint of plating properties and manufacturing cost.

Then, a magnetic layer and a protective layer are formed on the surface of the magnetic disk substrate having the above structure,
A magnetic disk is manufactured. As the magnetic layer, C
oNiCr, CoCrTa, CoCrPt and CoNi
There are P etc. Further, as the protective layer, C, ZrO ₂ , S
iO ₂ etc.

[0017]

EXAMPLES Next, examples of the present invention will be described in comparison with comparative examples.

First, a polished aluminum alloy disk, which is a substrate for forming a NiP film, is subjected to a concentric texture treatment under the following conditions using a polishing tape, and is subjected to a tangential line of a concentric circle at a right angle. Surface roughness Ra is 20
An aluminum alloy substrate for a magnetic disk of 0 angstrom was prepared.

Tape roughness: No. 2000 substrate rotation speed: 800 rpm Roll hardness: 90 Pressing load: 0.5-2.0 Kg / cm ² Abrasive: Yushiroken MIC-5 (manufactured by Yushiro Kagaku Co., Ltd.)
5% solution treatment time: 1 minute After that, a commercially available electroless NiP plating bath is used to coat the surface of the aluminum alloy substrate for magnetic disks with a NiP film as a hard dense layer by electroless plating to a thickness of 10 μm. did. Further, the surface of the NiP film was subjected to predetermined finishing polishing to prepare a magnetic disk substrate.

For comparison, the conventional ground aluminum alloy substrate was also subjected to NiP plating and finish polishing, and then subjected to concentric texture treatment with tape roughness number 4000 to prepare a magnetic disk substrate. did.

On both of these magnetic disk substrates, an inline type D.D. C. With a magnetron sputtering device, the Cr layer was 3000 Å, Co _62.5 Ni ₃₀ Cr
_{The 7.5} layer was 600 Å and the C layer was 300 Å. Then, the coercive force in the circumferential direction and the radial direction of the magnetic disk manufactured as described above is measured by a vibrating sample magnetometer (VS
M). The results are shown in Table 1 below.

[0022]

[Table 1]

Further, in order to evaluate the adsorbability of the magnetic head, the magnetic head was placed on the magnetic disk and an adsorption test was carried out under high temperature and high humidity (85% humidity, 65 ° C., 10 days). The results are also shown in Table 1 above.

As can be seen from Table 1, in the concentric texture-treated substrate using the aluminum alloy substrate according to the embodiment of the present invention, the magnetic head is not attracted and magnetic characteristics in the circumferential direction are not generated. Is significantly improved. The flying characteristics of the magnetic head are 0.07
As a result of performing a glide test with a low flying head of 5 μm (peripheral speed 10 m / sec), when the aluminum alloy substrate for a magnetic disk according to the present invention was used, traces of collision of the magnetic head with the film could not be confirmed. .. On the other hand, in the case of the aluminum alloy substrate for a magnetic disk of the comparative example manufactured by the conventional method, many collision marks were confirmed.

[0025]

As described above, according to the present invention,
Different from the conventional substrate machined to NiP film because the aluminum alloy disc itself which is the base of the aluminum alloy substrate for magnetic disk is subjected to concentric circular texture treatment and a hard dense layer such as NiP film is formed on it. , Ni
Since the return of the P film does not occur, the flying height of the magnetic head can be lowered, and the recording density can be further increased. Further, since the unevenness of the aluminum alloy disc of the base appears on the surface of the magnetic disk substrate, adsorption of the magnetic head can be avoided and the medium performance in the circumferential direction is improved. An excellent effect can be obtained as a disk substrate.

Claims (2)

[Claims] 1. A surface thereof is roughened in a concentric circle shape, and a surface roughness Ra in a direction perpendicular to a tangent line of the concentric circle is 10Å.
An aluminum alloy substrate for a magnetic disk, comprising the aluminum alloy disc described above and a hard dense layer formed on the surface of the aluminum alloy disc. 2. A magnetic disk comprising a magnetic layer and a protective layer formed in sequence on the aluminum alloy substrate according to claim 1.