JPH08329454A - Production of glass substrate for magnetic disk - Google Patents

Abstract

PURPOSE: To prevent a glass substrate for a magnetic disk from bringing abrasive grains and metal particles sticking to the surface of the substrate in a lapping process to a subsequent polishing process and to reduce the rate of occurrence of flaws in the polishing process. CONSTITUTION: The principal surface of a glass substrate for a magnetic disk is lapped and etched to 0.1-3μm depth. The etched principal surface of the glass substrate is then polished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a glass substrate for a magnetic disk which reduces the occurrence rate of scratches on the surface.

[0002]

2. Description of the Related Art In a conventional method of manufacturing a glass substrate for a magnetic disk, a glass substrate is concentrically circularly processed, that is, a donut is circularly processed, and then lapping is performed by using free abrasive grains on a metal surface plate. (Lapping process), followed by a method of further polishing the lapping-processed surface using a polishing pad made of synthetic resin and loose abrasive grains having a finer grain size.

Between the lapping process and the polishing process, only the normal cleaning is performed, and the etching process for removing foreign matters on the surface of the disk glass substrate is not performed. As a result, in the polishing processing step subsequent to the lapping processing step, the abrasive particles having a larger particle diameter due to the lapping processing step and the metal particles generated from the lapping processing metal surface plate are brought in, and these are the surface of the glass substrate for the disk. This caused scratches and damage to the polishing pad.

As a method of performing the etching process, for example, Japanese Patent Laid-Open No. 7-230621 is known. This method has the main purpose of increasing the mechanical strength of the glass substrate for a disc by reducing the depth of scratches existing on the inner peripheral portion of the glass substrate for a disc, and for that purpose, the etching of the surface of the glass substrate is performed. It is conditioned that the depth should be deeper than 3 μm.

As still another example, there is a case where an etching process is performed as a means for forming a texture (fine irregularities on the surface of a magnetic disk) for improving friction and sliding characteristics with respect to a magnetic head.

However, in this method, since the polishing process is not performed after the etching process, an abnormal protrusion exceeding the surrounding texture height is formed on the surface of the disk glass substrate at the portion masked by the deposits such as dust. It When a magnetic disk manufactured by using such a glass substrate is rotated at a high speed of 3000 rpm or more and the magnetic head is flown on the surface of the disk at a height of 350 Å, for example, a head crash of the magnetic head and a magnetic disk There was a problem of causing local destruction of the surface.

Therefore, in this case, it is necessary to suppress the etching depth to, for example, 350 Å or less, but not only the removal of the abrasive grains is not sufficiently performed with such a small etching amount, but usually, It was almost impossible to control the etching depth in the liquid phase etching.

[0008]

SUMMARY OF THE INVENTION According to the present invention, the abrasive particles adhered to the surface of the glass substrate for a magnetic disk in the lapping process and the metal particles generated from the metal surface plate for the lapping process, which have been problems in the conventional method, are described below. It is an object of the present invention to prevent the scratches from being brought into the polishing process and reduce the occurrence rate of scratches in the polishing process.

[0009]

According to the present invention, after lapping the main surface of a glass substrate for a magnetic disk, the surface of the glass substrate is subjected to an etching treatment with a depth of 0.1 to 3 μm, and then the etching treatment is performed. Provided is a method for manufacturing a glass substrate for a magnetic disk, which comprises polishing the main surface of the glass substrate.

According to the present invention, etching treatment is performed with an etching solution between the lapping treatment step and the polishing step, so that the lapping treatment step adheres to the main surface and the inner and outer peripheral end surfaces of the glass substrate. This is because it was found that the fine particles generated from the abrasive grains and the metal surface plate can be completely removed.

In this case, if the etching is performed deeper than 3 μm, the mechanical strength can be greatly improved at the same time. However, if the main purpose is to remove foreign matters on the surface of the glass substrate for the disk, the depth of the etching process will be small. A sufficient effect is obtained with a thickness of about 0.1 to 3 μm. Furthermore, in the present invention, by performing a polishing process after the etching process, it is possible to remove minute protrusions on the surface of the glass substrate for a disk formed by the etching process.

As the etching solution in the present invention,
Various etching solutions used for etching the glass surface, for example, aqueous solution of hydrofluoric acid, HF-H ₂ SO ₄ solution,
NH ₄ F aqueous solution, H ₂ SiF ₆ aqueous solution, and various other glass etching solutions can be used.

In the present invention, the lapping treatment means a method of polishing using free abrasive grains dispersed in water or the like using a metal plate as described above, and is also simply called lapping treatment. On the other hand, the polishing treatment after the lapping treatment step in the present invention means loose abrasive grains dispersed in water etc. using a polishing pad made of synthetic resin (fine abrasive grains for lapping treatment, those having a low hardness are used. Will be done.)
Is used for polishing, and is also simply referred to as polishing or polishing.

In the present invention, the abrasive grains and the metal particles adhered to the surface of the glass substrate, which cannot be completely removed by the conventional cleaning, are subjected to the etching treatment after the lapping treatment step to dissolve them together with a part of the glass substrate surface. , Foreign matter from the surface of the glass substrate can be easily removed.

[0015]

【Example】

[Example 1] Using a plate glass made of aluminoborosilicate glass with a thickness of about 1.1 mm, 100 concentric circular disk glass substrates (donut shape) each having an outer diameter of 65 mm and an inner diameter of 20 mm were processed, and these glass disks were processed. The main surface of the substrate was lapped by a plate thickness change amount (polishing amount) of about 400 μm by using a polishing machine using a cast iron surface plate and supplying free abrasive grains having an average particle diameter of 40 μm.

After that, an etching solution consisting of a hydrofluoric acid solution having a concentration of 2% was used and the depth of the glass substrate was set to 0.1.
After performing an etching treatment of μm, brush cleaning and ultrasonic cleaning with pure water were performed using a weak alkaline detergent.

After that, a polishing pad made of synthetic resin was supplied with cerium oxide having an average particle diameter of about 1 μm to perform polishing to a polishing amount of about 60 μm with a change in plate thickness, and then a weak alkaline detergent was used. Brush cleaning and ultrasonic cleaning with ultrapure water were performed to manufacture a sample of a glass substrate for a magnetic disk.

When the obtained glass substrate for magnetic disk was visually inspected under a light source of 10,000 lux, the ratio of scratches to the entire glass substrate (scratch occurrence rate) was visually observed.
Was 5%.

Example 2 A sample of a glass substrate for a magnetic disk was manufactured by the same method as in Example 1 except that the depth of etching after lapping was 2.8 μm.
When the obtained glass substrate for magnetic disk was similarly visually inspected, the scratch occurrence rate was 2%.

Example 3 (Comparative Example) A sample of a glass substrate for a magnetic disk was manufactured by the same method as in Example 1 except that the etching process after the lapping process was not performed. When the obtained glass substrate for magnetic disk was similarly visually inspected, the scratch occurrence rate was 15%.

Example 4 (Comparative Example) A magnetic disk glass substrate sample was manufactured in the same manner as in Example 1 except that the etching amount after lapping was 600 Å. When the obtained glass substrate for magnetic disk was visually inspected in the same manner, the scratch occurrence rate was 12%.

[Example 5] Using a plate glass made of soda lime silica glass and having a thickness of about 1.1 mm, an outer diameter of 65 m
m, an inner diameter of 20 mm, concentric circular disk glass substrates (donut shape) 100 each, and the main surface of these circular glass plates was polished using a metal surface plate, and the average particle size was 40 μm.
By lapping m loose abrasive grains, lapping treatment of about 400 μm was carried out with a variation in plate thickness (polishing amount).

After that, an etching solution consisting of a hydrofluoric acid solution having a concentration of 2% was used, and a depth of 0.1 was applied to the glass substrate.
After performing an etching treatment of μm, brush cleaning using a weak alkaline detergent and ultrasonic cleaning with pure water were performed.

After that, a cerium oxide having an average particle size of about 1 μm is supplied to a polishing pad made of a synthetic resin to perform polishing to a polishing amount of about 60 μm with a change in plate thickness, and then a weak alkaline detergent is used. Brush cleaning and ultrasonic cleaning with ultrapure water were performed to manufacture a sample glass substrate for a magnetic disk.

When the obtained glass substrate for a magnetic disk was visually inspected in the same manner, the scratch occurrence rate was 7%.

Example 6 A glass substrate sample for a magnetic disk was manufactured by the same method as in Example 5 except that the etching amount after lapping was 2.5 μm in depth. When the obtained glass substrate was subjected to the same visual inspection, the scratch occurrence rate was 5%.

[Example 7 (Comparative Example)] A sample of a glass substrate for a magnetic disk was manufactured by the same method as in Example 5 except that the lapping etching treatment was not performed. When the obtained glass substrate was visually inspected in the same manner, the scratch occurrence rate was 20%.

Example 8 (Comparative Example) A sample of a glass substrate for a magnetic disk was manufactured by the same method as in Example 5 except that the etching amount in the lapping process was 500 Å.
When the obtained glass substrate was subjected to the same visual inspection, the scratch occurrence rate was 18%.

[0029]

According to the present invention, the lapping treatment step is carried out for the abrasive particles adhered to the surface of the glass substrate for a magnetic disk and the metal particles generated from the polishing metal surface plate, which cannot be completely removed by the conventional cleaning. After that, the foreign matter on the surface of the glass substrate for a magnetic disk can be easily removed by performing an etching treatment and dissolving it together with a part of the surface of the glass substrate. Therefore, it is possible to prevent the abrasive grains adhered to the surface of the magnetic disk glass substrate in the lapping process and the metal particles generated from the metal plate for the lapping process from being brought into the polishing process of the next process, and the surface of the glass substrate for the magnetic disk after polishing The occurrence rate of scratches can be reduced.

Claims (2)

[Claims] 1. A main surface of a glass substrate for a magnetic disk is lapped, and then a depth of 0.1 is formed on the surface of the glass substrate.
A method for producing a glass substrate for a magnetic disk, which comprises subjecting the glass substrate to an etching treatment of ˜3 μm and then polishing the main surface of the etched glass substrate. 2. The method for producing a glass substrate for a magnetic disk according to claim 1, wherein the main surface of the glass substrate for a magnetic disk is etched with an etching solution containing hydrofluoric acid as a main component.