JPS60172465A - Polishing of high-density magnetic disc substrate - Google Patents

Abstract

PURPOSE:To obtain a high-density magnetic disc substrate having a minute surface roughness in which the substrate surface has minute unevenness by polishing-working the substrate by using the polishing liquid containing the mixture of the grindgrains having a high hardness (Mohs hardness of 9 or more) and the grindgrains having a low hardness (Mohs hardness of 7 or less). CONSTITUTION:The figure shows the surface roughness curve of a magnetic disc substrate after the polishing work for the magnetic disc substrate applied with nonmagnetic nickel-polyphor plating onto an aluminum alloy surface by using the polishing liquid containing the mixture of aluminum oxide (grinding diameter of 0.3mum) having a Mohs hardness of 9 in the form of minute grindgrains with high hardness and silicon dioxide (grindgrain diameter of 0.4mum) having a Mohs hardness of 6 in the form of minute grindgrains with low hardness and the surface roughness is 0.01mumRmax, and the polished surface has minute uneveness. Thus, a high-density magnetic disc substrate with which the required surface roughness of the high-density magnetic disc is fullfilled and the close adhesion of a magnetic head onto the magnetic disc surface can be prevented can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for polishing magnetic disk substrates, particularly magnetic disk substrates that require high-precision processing, such as high-density magnetic disk substrates (for example, substrates for thin film media by plating or sputtering). .

In general, magnetic disk substrates are manufactured using an aluminum alloy surface, a non-magnetic nickel phosphorus plated surface formed on an aluminum alloy surface, or an anodized surface formed on an aluminum alloy surface, depending on the type of recording medium. And those that have been polished to the required surface roughness are used.

In such a magnetic disk device, the smaller the surface roughness of the magnetic disk substrate, the higher the recording density can be obtained.

Therefore, while the surface roughness of the magnetic disk substrate in a normal coated magnetic disk is 0.1 μmRmax, the surface roughness of a high-density magnetic disk is 0.1 μmRmax.
It is required to polish the surface to an extremely fine surface roughness of 01 PmRmmx.

However, when the surface roughness of the magnetic disk substrate becomes extremely small, a phenomenon occurs in which the magnetic head comes into close contact with the magnetic disk surface when stopped, and a motor with large rotational torque is required to rotate the magnetic disk again. Otherwise, the adhesion force may damage the thin film magnetic medium on the magnetic disk substrate.

Therefore, in order to manufacture high-density magnetic disk substrates, it is necessary to apply thin film magnetic media with minute surface roughness.
There is a need for a polishing method that achieves a high density air conductive disk substrate having a surface texture that prevents the magnetic head from adhering to the magnetic disk surface.

Figure 1 is a diagram illustrating the first example of the conventional polishing method, in which a magnetic disk substrate with non-magnetic nickel phosphorus plating applied on an aluminum alloy surface is oxidized with a Mohs hardness of 9, which is a highly hard micro abrasive. This figure shows a surface roughness curve of a magnetic disk substrate when it is subjected to boring processing using aluminum (abrasive grain size: 03 μm). In this case, the surface roughness of the magnetic disk substrate is 0.03 μmRmax, and although the magnetic head does not adhere to the magnetic disk surface, the required surface roughness of the high-density magnetic disk substrate, 0.01 #F7JRmax, is not satisfied. , which is insufficient as a high-density magnetic disk substrate.

Fig. 2 is a diagram for explaining a second example of the conventional polishing method, in which a magnetic disk substrate with non-magnetic nickel phosphorus plating applied on an aluminum alloy surface is coated with a highly hard ultrafine abrasive grain having a Mohs hardness of 9. of aluminum oxide (abrasive grain size 0.05
μm) 71i-The surface roughness of the magnetic disk substrate when subjected to boring processing is 0, OI P m'RmlL
Although the substrate has a rating of

Fig. 3 is a diagram for explaining the third example of the conventional polishing method, in which a magnetic disk substrate with non-magnetic nickel phosphorus plating applied on an aluminum alloy surface is polished with a Mohs hardness of 6, which is a low hardness micro abrasive. The surface roughness curve of a magnetic disk substrate is shown when it is subjected to a boring process using silicon dioxide (abrasive grain size: 0.04 pm).

In this case, the surface roughness of the magnetic disk substrate is 0005μ
Although mRmax satisfies the required surface roughness of 0.01 μmRmH for high-density magnetic disk substrates, the substrate surface roughness curve is very smooth, which causes the magnetic head to come into close contact with the magnetic disk surface, resulting in high-density magnetic disks. This is not necessarily fully satisfactory as a magnetic disk substrate.

Generally, adhesion force is proportional to the contact area between two objects, so
In order to reduce the adhesion force, it is safe to use a surface texture that reduces the contact area, that is, a surface texture where the surface roughness is composed of fine lugs (polishing loci).

Therefore, as a high-density magnetic disk substrate, it has minute holes and its surface roughness is minute (0.01 μm).
Rmax).

The object of the present invention is to provide a method for polishing a high-density magnetic disk substrate that eliminates the above-mentioned conventional drawbacks.

According to the present invention, in a method of polishing a magnetic disk substrate, a magnetic disk is By subjecting the substrate to a boring process, it is possible to achieve a high-density magnetic disk substrate that has minute surface roughness and can prevent the magnetic head from coming into close contact with the substrate.

Next, one embodiment of the present invention will be described using FIG. 4. Figure 4 shows a magnetic disk substrate with non-magnetic nickel phosphorus plating on the aluminum alloy surface.Aluminum oxide with a Mohs hardness of 9 (abrasive grain size 0), which is a highly hard micro abrasive grain,
．． Silicon dioxide with a Mohs hardness of 6 (abrasive grain size 0.0
The surface of a magnetic disk substrate when it was subjected to boring processing (processing: Ittμm/20 minutes) using a polishing solution mixed with 4μm) (mixed N amount ratio: aluminum oxide: silicon dioxide: pure water = 3:5:10) Represents the Arasa curve. The polished surface of the magnetic disk substrate in the example of the present invention has fine grooves, and the surface roughness is 001 μmRmax. In the polishing method of the present invention, the effect of the high-hardness micro-abrasive grains to generate a surface texture with a polishing locus and the effect of the low-hardness micro-abrasive grains to reduce surface roughness mutually contribute to polishing. A polished surface with minute surface roughness can be obtained. Therefore, by the polishing method of the present invention, it is possible to achieve a high-density magnetic disk substrate that satisfies the required surface roughness of a high-density magnetic disk and can prevent the magnetic head from adhering to the magnetic disk surface.

In the method of the present invention, by changing the mixing ratio of high-hardness micro-abrasive grains and low-hardness micro-abrasive grains, the 6-surface roughness of the polished surface when using only high-hardness micro-abrasive grains can be reduced. Any surface roughness between the surface roughness of the polished surface when only fine abrasive grains of hardness are used can be selected.

In this case, as the mixing ratio of high-hardness micro-abrasive grains increases, the surface roughness of the polished surface increases, and as the mixing ratio of low-hardness micro-abrasive grains increases, the surface roughness of the polished surface decreases. .

As explained above, by a polishing method in which a magnetic TiSF substrate is subjected to a polishing process using a polishing liquid containing a mixture of fine abrasive grains with high hardness (Mohs hardness of 9 or more) and fine abrasive grains with low hardness (Mohs hardness of 7 or less), This method has the advantage that a high-density magnetic disk substrate with a fine surface roughness and a fine groove on the substrate surface can be produced.

In one embodiment of the present invention, aluminum oxide was used as the high-hardness abrasive grain and silicon dioxide was used as the low-hardness abrasive grain, but silicon carbide (Mohs hardness: 9) was used as the high-hardness abrasive grain.
), zirconium oxide (Mohs hardness: 6) may be used as a low-hardness abrasive grain.

[Brief explanation of the drawing]

1, 2, and 3 show surface roughness curves of a magnetic disk substrate obtained by a conventional polishing method, and FIG. 4 shows a surface roughness curve of a magnetic disk substrate obtained by a polishing method of the present invention. 71 Figure 2 Figure 73 Figure 4

Claims (1)

[Claims] A method for polishing a magnetic disk substrate, characterized by boring the magnetic disk substrate using a polishing liquid containing a mixture of high-hardness micro-abrasive grains with a Mohs hardness of 9 or more and low-hardness micro-abrasive grains with a Mohs hardness of 7 or less. A method for polishing high-density magnetic disk substrates.