JPH0417119A - Magnetic disk substrate and its production - Google Patents

Abstract

PURPOSE:To form a surface pattern with its pitch and height of crests within desired ranges and to obtain good CSS characteristics by executing rough machining of blank by means of lathe turning so as to provide a helical pattern on the blank, subjecting this blank to base Ni-P plating and then to texturing by heating at specified temp. so that the helical pattern appears. CONSTITUTION:An aluminum blank punched into a specified size is chamfered and machined with a lathe to provide a desired helical pattern which is to appear by texturing. After the surface is smoothened by grinding, the blank is subjected to Ni-P treatment as base coating to form a Ni-P film of 15 - 30mum thickness. Then the blank after Ni-P treatment is polished to have a mirror surface and subjected to texturing by heating at 180 - 300 deg.C to release the residual strain due to machining so that the helical pattern appears on the Ni-P treated surface. Thus, the surface becomes a rough surface having a uniform pitch and height of crests in a simple process, and the contact-start- stop (CSS) characteristics of the medium can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a so-called sputtering type or plating type magnetic disk, in which a magnetic layer is formed by sputtering or plating, and a magnetic disk substrate obtained thereby.

[Conventional technology]

In general, among magnetic disks used for computers, so-called hard disks whose substrates are made of metal such as aluminum are broadly classified into sputtering type, coating type, and plating type hard disks, depending on the method of forming the magnetic layer.

Among these, sputter-type or plating-type hard disks are attracting attention because they provide higher recording density than coated-type hard disks.

The manufacturing method for this sputter type or plating type hard disk is to edge an aluminum blank by chamfer processing, give it a mirror finish by rough grinding and finish grinding, or by turning and finish grinding, and then apply a Ni-P base layer on this. After treatment and polishing, texture processing is performed, and then a magnetic layer is formed by sputtering or plating, and a lubricant is applied to form a media.

In order to meet the recent demands for high-density recording in such sputter-type or plated-type hard disks, the head and disk are being brought closer together as the storage capacity becomes larger and larger. At present, the flying height of the head tends to be less than 0.1 μm. Therefore, the frictional resistance between the head and the disk surface is large during start and stop when the head is close to the disk surface, and CSS (
It is desired to improve the contact start/stop) characteristics.

For this reason, conventional sputter-type or plating-type hard disks are subjected to texture processing before sputtering or plating in the manufacturing process. This texturing treatment consists of pressing and sliding a tape to which alumina particles are attached onto the mirror-finished disk surface to roughen the surface and improve the C8S characteristics.

[Problem that the invention seeks to solve]

However, in conventional texturing using a tape with alumina particles attached, the rough surface formed is affected by the alumina particle arrangement of the tape used, and it is difficult to obtain a rough surface with a uniform pitch and height. The risk of contact or collision between the head and the disk cannot be ignored, and furthermore, defects caused by texturing affect subsequent processes, resulting in media defects.

The present invention improves the conventional problems as described above, makes it possible to set the peak pitch and peak height within a desired range, and forms an ideal rough surface with good CSS characteristics. Moreover, it is an object of the present invention to provide a manufacturing method including a texturing step that can accomplish this through a simple process, and a magnetic disk substrate obtained thereby.

[Means for solving problems]

One aspect of the present invention is a method for manufacturing a magnetic disk in which a magnetic layer is formed by sputtering or plating, in which rough grinding of a blank is performed by turning, and texturing after Ni-P base treatment is heated in a temperature range of 180 to 300°C. The above object has been achieved by making the spiral shape produced by the turning process appear.

In the present invention, the turning process is performed at a pitch of 10 to 200 μm.
, the peak height may be 0.1 to 5 μm.

In addition, in the present invention, the turning process is performed with a mountain pitch of 20 to 50.
[mu]m, and the peak height can be set to 0.2 to 1 [mu]m.

Further, according to the present invention, a hard disk substrate obtained by texture processing as described above can be obtained.

[For production]

In the present invention, texturing is performed by heating in a temperature range of 180 to 300°C, so this heat treatment releases the residual stress along the spiral shape formed by turning, and the spiral shape during turning is released. The shape reappears on the base Ni-P coated surface which has been polished to a mirror finish. Texturing by this heating allows the pitch of the spiral ridges to remain as is, and the height of the ridges to appear in accordance with the heating temperature.

Therefore, the roughness of the textured surface can be arbitrarily controlled by turning.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is a process explanatory diagram for manufacturing a sputter type hard disk. In FIG. 1, an aluminum blank (FIG. 1(a)) punched to a predetermined size is edged by chamfer processing, and then turned. In this turning process, a desired spiral shape to be created by texture processing is processed by turning, and the turning pitch is preferably 10 to 200 Pm, more preferably 20 to 50 μm, and the peak height is is preferably 0.1 to 5 μm, more preferably 0.2 to 1 μm (FIG. 1(b)). This was ground to make the surface smooth (Fig. 1(c)), and then Ni-P treatment was applied as an undercoat.
A film is formed (FIG. 1(d)). This undercoat 1-1 is required to be a non-magnetized film, and in the present invention, this undercoat is a Ni--P film formed according to a conventional method. After the base Ni-P treatment, polishing is performed to achieve a mirror finish (Fig. 1 (,)), and then texture processing is performed. The texture processing of the present invention is 180 to 30
This is done by heating to 0°C to release the residual stress during the turning process in step (b), and making the turning spiral pattern appear on the mirror-finished base Ni-P treated surface (first step). Figure (f)). If the heating temperature is less than 180°C, the release of residual stress will be insufficient and the appearance of the spiral pattern will become unclear, while if the heating temperature exceeds 300°C, the underlying Ni-P film will become magnetic.

In the present invention, a sputter type or plating type hard disk substrate having a turned spiral shape can be obtained by performing the turning process so that the crest pitch and crest height are as described above.

After texture processing in this manner, a magnetic layer is formed to a thickness of 200 to 500 layers by sputtering or plating. Normally, the magnetic layer can be formed by sputtering, plating, or other coating methods, but for example, when coating is used, the coating thickness is about 1 μm, and the mountain shape formed by the texturing described above is buried. Therefore, in the present invention, the magnetic layer is formed by sputtering or plating, which is the so-called sputter type or plating type hard disk. After sputtering or plating, a lubricant is applied by a conventional method to obtain media.

Examples are shown below.

〔Example〕

An aluminum blank with a thickness of 1 mm and an outer diameter of 3 mm.
It was punched into a 5-inch donut-shaped disk, edged by chamfer processing, and then turned so that the pitch of the ridges was 50 μm and the height of the ridges was 0.5 μm. After grinding this to a smooth surface, Nj, −
A Ni--P film with a thickness of 20 μm was formed by P treatment.

This Ni--P coated surface was polished to give a mirror finish.

Next, heat treatment as texturing was performed at different temperatures. Table 1 shows the relationship between the heating temperature and the peak height that appeared.

A first surface substrate is obtained, and hard disks manufactured using this substrate have fewer media defects due to texture processing.

[Brief explanation of drawings]

FIG. 1 is a process explanatory diagram for carrying out the method of the present invention. Note that Ra is preferably at least 30 Å or more. 〔Effect of the invention〕

Claims (1)

[Claims] 1. In a method for manufacturing a magnetic disk in which a magnetic layer is formed by sputtering or plating, rough grinding of a blank is performed by turning, and texture processing after base Ni-P plating is performed at 180 to 300°C. A method for manufacturing a magnetic disk, characterized in that the spiral shape produced by the turning process is revealed by heating in a temperature range. 2. Turning is performed with a pitch of 10 to 200 μm and a height of 0.
The method according to claim 1, wherein the method is carried out so that the thickness is 1 to 5 μm. 3. Turning with a pitch of 20 to 50 μm and a height of 0.2
2. The method according to claim 1, wherein the method is carried out so that the thickness is 1 .mu.m. 4. A magnetic disk substrate obtained by the method according to any one of claims 1 to 3.