JP2000317837A - Polishing method for disc substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To polish a high-hardness disc substrate with high productivity by spraying polishing abrasive grains with a specified grain diameter or a mixed liquid of polishing abrasive grains and a liquid to the disc substrate by pressurized air. SOLUTION: A glass substrate 6 (crystallized galss) with a diameter of 2.5 inch is used as a substrate to be polished. The polishing abrasive grains (media) are alumina abrasive grains, and the centric grain size is 40 μm (preferably 20 to 60 μm). The pressure of a liquid (water) is 1.2 kgf/mm2, the air pressure is 2.5 kgf/mm2 and the feed speed of a gun 1 is 5 mm/sec. The concentration of polishing abrasive grains to the liquid is 20 vol.%. Then, polishing is performed unitl the polishing amount of the substrate surface reaches about 240 μm. A nozzle 2 of the polishing gun is 90 mm long and 2 mm wide. As a result, the maximum surface roughness (Rmax) after polishing is smaller than 5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for polishing a magnetic disk substrate, and more particularly to a disk substrate polishing method effective for polishing a hard glass magnetic disk substrate.

[0002]

2. Description of the Related Art A magnetic disk used for a hard disk or the like of a computer is required to rotate at a higher speed in order to increase a data capacity. In order to enable such high-speed rotation, it is necessary to improve the flatness of the disk substrate and to increase the rigidity of the disk substrate. Such a substrate having high rigidity includes a hard glass substrate, for example, a hard material such as amorphous glass, crystallized glass, and ceramics.

Usually, in order to obtain a flat surface, a magnetic disk substrate is subjected to one or two lapping processes on the front and rear surfaces thereof, and then rough-polished and finish-polished.

[0004]

However, a material having a high hardness has a drawback that, although it has a high rigidity, it is extremely difficult to process, requires much time for polishing, and has extremely low productivity. Polishing using a diamond grindstone has the disadvantage that although the grindability is good, the productivity is similarly low.

The present invention has been made in view of the above problems, and has as its object to provide a disk substrate polishing method capable of polishing a hard disk substrate with high productivity.

[0006]

According to the present invention, there is provided a method for polishing a disk substrate, comprising: blowing abrasive grains having a particle size of 20 to 60 μm or a mixture of the abrasive grains and a liquid onto the disk substrate by pressurized air. And polishing the surface of the disk substrate.

The disk substrate is, for example, a hard glass substrate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing a polishing gun used in the method of the embodiment of the present invention.
The polishing gun 1 has a passage 3 for compressed air and a passage 4 for only abrasive grains, a mixture of air and abrasive grains or a mixture of water and abrasive grains. The nozzles 3 and 4 join in a mixing chamber 5 in the gun 1 and are ejected downward from a nozzle 2 thereunder. Also, nozzle 2
Is a slit having a wide ejection area of the mixed liquid, and the polishing gun 1 moves at a constant speed parallel to the surface in a direction perpendicular to the width direction of the ejection area of the nozzle 2.

The center particle diameter of the abrasive grains is 20 to 60 μm. If the center particle size of the abrasive grains is larger than 60 μm, the surface roughness after processing becomes large, and the intended specifications are not satisfied. When the center particle diameter of the abrasive grains is smaller than 20 μm, the processing efficiency is reduced. The type of abrasive grains can be qualitatively applied as long as it is harder than the workpiece and has a polygonal shape. Specific examples include ceramics such as SiC (silicon carbide) and ZrO ₂ (zirconia). Powder, metal oxide or diamond powder.

When the magnetic disk substrate 6 is polished using the polishing gun 1 configured as described above, only the abrasive grains or a mixture of water and abrasive grains is mixed through the passage 4. The mixture is supplied to the chamber 5 at a constant speed, and pressurized compressed air is sent into the mixing chamber through the passage 3. Thus, a mixture of water and abrasive grains is sprayed from the nozzle 2 toward the disk substrate 6 by compressed air.

As described above, in this embodiment, the surface of the disk substrate 6 is polished by spraying only the abrasive particles or the abrasive particles mixed with water onto the disk substrate 6 at high speed by the ejection energy of the compressed air. . Therefore, according to this embodiment, the surface of a hard substrate such as a hard glass plate can be polished at an extremely high speed. Thus, according to the present invention,
Processing at a higher speed than the grinding method is possible, and post-processing is shortened by lowering the surface roughness after processing,
The polishing time in the final surface finish can be reduced.

In this embodiment, the polishing is performed by moving the gun in one direction. However, the moving direction of the gun and the shape and size of the nozzle can be arbitrarily set.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A disk substrate is polished by a method according to an embodiment of the present invention, and its polishing characteristics will be described in comparison with comparative examples.

A glass substrate (crystallized glass) having a diameter of 2.5 inches was used as a substrate to be polished. The abrasive grains (media) are alumina-based abrasive grains, and the center particle diameter is as shown in Table 1 below. Other conditions are liquid (water)
The pressure was 1.2 kgf / mm ² , the air pressure was 2.5 kgf / mm ² , and the feed rate of the gun was 5 mm / sec. The concentration of the abrasive grains in the liquid is 20% by volume.

The polishing was performed until the polishing amount on the substrate surface became about 240 μm. Polishing gun nozzle is 90m long
m, width 2 mm. In Table 1, the evaluation criteria were as follows: 最大 when the maximum surface roughness (Rmax) after polishing was less than 5 μm, ○ when it was 5 to 10 μm, and X when it was greater than 10 μm. The central particle diameter of the abrasive grains is a median diameter corresponding to 50% of the cumulative particle size distribution of the number of particles (Metal Handbook, pp. 940-941, properties of 14.4 powder, test method, 14.4.1 powder characteristics, (i) particle size and particle size distribution).

[0016]

[Table 1]

As is clear from Table 1, in the case of Examples 1 to 4, the abrasive grains are 40 to 60 μm.
In each case, processed surfaces with sufficiently small maximum surface roughness were obtained. On the other hand, in Comparative Examples 1 to 4, the surface roughness after processing was poor.

[0018]

As described above, according to the present invention,
The abrasive grains are carried by the pressurized air, or the mixture of the abrasive grains and the liquid is carried by the pressurized air and blown toward the disk substrate, so that the surface of the hard disk substrate is polished with high productivity. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a polishing gun used in a method according to an embodiment of the present invention.

[Explanation of symbols]

 1: Polishing gun 2: Nozzle 3: Compressed air passage 4: Mixed liquid of water and abrasive grains 5: Mixing chamber

Claims (3)

[Claims] 1. A method for polishing a disk substrate, comprising: polishing a surface of the disk substrate by blowing abrasive grains having a center particle diameter of 20 to 60 μm onto the disk substrate by pressurized air. 2. The disk substrate according to claim 1, wherein a surface of the disk substrate is polished by spraying a mixture of polishing abrasive particles having a center particle diameter of 20 to 60 μm and a liquid onto the disk substrate by pressurized air. Polishing method. 3. The method according to claim 1, wherein the disk substrate is a hard glass substrate.