JP2002008224A - Method for producing glass substrate for disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a low-cost high-precision glass substrate for disk usable for a magnetic hard disk, etc. SOLUTION: A glass material is press-molded to produce a circular glass plate 5a having a larger outside diameter than the desired outside diameter of a disk and the center and periphery of the circular glass plate 5a are simultaneously or separately worked to the desired inside diameter and outside diameter. The outside diameter X of the circular glass plate 5a preferably satisfies the expression (the desired outside diameter)<X<=[(the desired outside diameter)+1.5×(the thickness of the objective substrate)].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a glass substrate for a disk used for a magnetic disk or the like by press molding.

[0002]

2. Description of the Related Art In recent years, with the spread of computers, demands for high performance such as miniaturization and high capacity of a hard disk, which is one of external storage devices, have been extremely increased.
At the same time, with the price reduction of computers, the price reduction of hard disks has been very demanded.

Conventionally, an aluminum alloy has been mainly used as a substrate material for a magnetic disk. However, since the aluminum alloy substrate has a low hardness, even if precision polishing is performed using high-precision abrasive grains and a polishing device, it is difficult to obtain a high-precision smooth surface because the polished surface is plastically deformed. Even if a nickel-phosphorus plating layer having higher hardness is formed on the substrate surface, it has become difficult to meet the demand for high precision.

[0004] In addition, the trend of miniaturization requires a reduction in the thickness of the disk, and it is becoming difficult for aluminum alloy substrates with low strength to meet the demand from this aspect as well.

[0005] Recent high-sensitivity magnetoresistive heads (M
The use of the (R head) requires a magnetic disk to reduce noise, and the substrate is required to cope with noise reduction by heat treatment after forming a magnetic film. However, from this aspect, it is becoming difficult for aluminum alloys to meet the demand.

In order to solve the above problems, new materials such as glass, ceramic, and carbon have been proposed as magnetic disk substrates. Among them, glass substrates have been widely studied, and some of them have already been put to practical use. The glass substrate has high strength, good heat resistance, high surface hardness, and can sufficiently meet the demand for high-precision smoothness by high-precision precision polishing.

Conventionally, a glass substrate for a magnetic disk has been cut into a predetermined size and then obtained in order to obtain a smooth surface.
It has been manufactured by a polishing method of precisely polishing glass substrates one by one. However, there are drawbacks that high precision is required for the polishing step, the number of steps is large, and the obtained glass substrate is very expensive.

[0008] By the way, the press molding method has been studied in the field of optical glass element production, and has already been put to practical use as a production method capable of high quality and high productivity.

[0009]

However, a technique for producing a thin and large-diameter glass substrate, such as a glass substrate for a disk, with high precision by a press molding method has not been established.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a disk glass substrate by press molding, which achieves both high density and high reliability of a disk glass substrate and can be mass-produced at low cost. .

[0011]

In order to solve the above-mentioned problems, a method of manufacturing a glass substrate for a disk according to the present invention comprises manufacturing a circular glass plate having a diameter larger than a desired outer diameter by press-molding glass. And a step of concentrically processing the central portion and the outer periphery of the circular glass plate so as to have desired inner and outer diameters.

According to another aspect of the present invention, there is provided a method for manufacturing a glass substrate for a disk, comprising: pressing a glass to form a circular glass plate having a diameter larger than a desired outer diameter; And forming a part or all of the outer free form surface concentrically into desired inner and outer diameters.

According to the above-described manufacturing method, it is inexpensive and
It is possible to manufacture a highly accurate glass substrate for a disk.

In this manufacturing method, preferably, the outer diameter of the press-formed circular glass plate is set so that (desired outer diameter) <X ≦ (desired outer diameter + 1.5 × substrate thickness). Perform a molding step.

By using a glass plate in this range,
The processing of the outer diameter can be performed within the free forming surface, and the chamfering of the outer periphery can be omitted.

As the glass material to be subjected to the press molding, a glass material obtained by dropping a predetermined amount of a heated and melted glass material, or a cylindrical glass material obtained by cutting a rod-shaped glass material into a circle by a diamond grindstone is used. be able to.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described with reference to the drawings. (Embodiment 1) FIG. 1 shows a press forming method of a glass substrate for a magnetic disk according to Embodiment 1 of the present invention, and
It is a conceptual diagram of the molding machine used at that time.

In FIG. 1, reference numeral 1 denotes a pair of upper and lower press forming dies. The material used for the press-molding mold of the present invention is not particularly limited. However, in order to prevent deformation due to repeated use, a material having excellent mechanical strength at the highest possible temperature and oxidation resistance at a high temperature Good thing is good.

In the figure, reference numeral 2 denotes a glass material. In this embodiment, aluminosilicate glass (softening point: 673 ° C., glass transition point: 506 ° C.) is used. It was installed between.

Here, as the glass material, an extremely inexpensive manufacturing method was used in which the glass material was heated and melted and dropped from a nozzle or the like, although the weight varied. The variation in the weight accuracy of this glass material was 8%.

In this state, the glass material 2 and the press molding die 1 are heated to 680 ° C. in the vicinity of the softening point of the glass material 2 in a nitrogen atmosphere by a pair of upper and lower press heads 4 incorporating the heater 3. After heating, weight 1.47x
Press at 10 ⁵ N to obtain the desired disc thickness of 0.6
A 35 mm circular glass substrate 5a was used (FIG. 2). The diameter of the circular glass substrate 5a formed at this time was 72.3 mm, which is larger than the desired disk diameter of 65.0 mm (FIG. 3).

This circular glass substrate 5a is placed on a concentric diamond grindstone 6 shown in FIG.
5mm, outer diameter of inner grinding wheel φ20 + 0.05 / 0.015
mm) at the same time, the desired outer diameter φ6
Disc 7a with 5.002 mm inner diameter φ20.03 mm
(FIG. 5). In addition, 5c shows a molding free surface of the outer periphery.

(Embodiment 2) As in Embodiment 1,
Using the molding machine shown in FIG. 1, aluminosilicate glass (softening point 660 ° C., glass transition point 4
The glass material 2 was placed between a pair of upper and lower press molding dies 1 at 90 ° C.).

Here, as the glass material 2, a rod-shaped glass material obtained by cutting a rod-shaped glass material with a diamond grindstone by a very inexpensive manufacturing method was used. However, the weight accuracy of the glass material 2 had a variation of 2%.

In this state, the glass material 2 and the press molding die 1 are heated to 665 ° C. near the softening point of the glass material 2 in a nitrogen atmosphere by a pair of upper and lower press heads 4 incorporating the heater 3. After heating, weight 1.77x
Press at 10 ⁵ N to obtain the desired disc thickness of 0.6
A circular glass substrate 5b having a size of 35 mm was obtained (FIG. 6).
At this time, the diameter of the formed circular glass substrate 5b is φ65.4 mm, which is larger than the desired disk diameter φ65.0 mm.
Met. That is, as shown in FIG. 6A, the diameter of the plane portion is φ64.7 mm, and the outer diameter including the free molding surface 5c is φ
The outer peripheral shape was 65.4 mm.

This circular glass substrate 5b is used as a cylindrical diamond grindstone 8 (grindstone outer diameter φ20 + 0.05 / 0.0) as shown in FIG.
15 mm) to obtain a glass disk 7b having a desired disk inner diameter φ20.01 mm (FIG. 8).

However, since the outer periphery of the disk 7b is the free surface 5c formed by molding, the disk 7b does not form a highly accurate perfect circle (roundness 70 μm), and has a diameter corresponding to the already processed inner diameter. The concentricity was as poor as 67 μm. Therefore, as shown in FIG. 9, after fixing the inner diameter of the disk with the inner diameter support rod 9, the outer diameter machining whetstone 10 is used to finish the roundness and concentricity with high accuracy (± 4 μm) while rotating, and to adjust the outer diameter. Set the diameter to the desired specification (φ65 ± 0.00
5 mm) (φ65.002 mm) (FIG. 10).

In the glass substrate 5b shown in FIG. 6 obtained by molding, the outer peripheral free molding surface 5c was formed in a region of φ64.7 to φ65.4 mm in the outer peripheral portion. Therefore, machining of the outer diameter can be performed within the free forming surface 5c, and chamfering of the outer periphery can be omitted.

Here, the outer free surface 5c does not have a geometric circular cross section due to slight uneven heat during molding. As a result of repeated experiments, the outer diameter of the circular glass plate 5b is It has been found that the thickness is at most 1.5 times the thickness of the substrate with respect to the desired outer diameter. If the outer diameter is formed within this range, the chamfering of the outer periphery can be omitted as described above.

In this embodiment, aluminosilicate glass is used as the glass material, but the same effect can be obtained with other glass materials. The manufacturing method of the glass material may be a method other than the columnar glass material and the molten dropping method. Further, the processing method and order of the center and the outer periphery are not limited to the present embodiment.

After the inner and outer diameters are processed, chamfering may be performed as necessary.

[0032]

According to the present invention, a high-quality disk glass substrate used for a magnetic disk or the like can be provided inexpensively and in large quantities by using an inexpensive glass material having poor weight accuracy. In addition, by performing the outer peripheral processing within the range of the outer peripheral free forming surface, it is possible to omit the outer peripheral chamfering processing.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a press forming machine and a forming method of a circular glass substrate used in Embodiments 1 and 2 of the present invention.

FIG. 2 is a schematic sectional view showing a state after molding of the press molding machine of FIG. 1;

FIGS. 3A and 3B schematically show a circular glass plate after press molding in Embodiment 1, wherein FIG. 3A is a cross-sectional view and FIG.

4A and 4B schematically show a method of processing a circular glass plate in the first embodiment, where FIG. 4A is a plan view and FIG.

FIGS. 5A and 5B show a disk glass substrate obtained in Embodiment 1, wherein FIG. 5A is a plan view and FIG.

FIGS. 6A and 6B schematically show a press-formed circular glass plate in Embodiment 2, wherein FIG. 6A is a cross-sectional view and FIG.

7A and 7B show a method of processing a central portion of a circular glass plate according to the second embodiment, where FIG. 7A is a plan view and FIG.

8A and 8B show a circular glass plate obtained in Embodiment 2, wherein FIG. 8A is a plan view and FIG.

FIG. 9 is a schematic cross-sectional view showing a method for processing the outer periphery of a circular glass plate in the second embodiment.

10A and 10B show a glass substrate for a disk obtained in Embodiment 2, wherein FIG. 10A is a cross-sectional view and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Press molding die 2 Glass material 3 Heater 4 Press head 5a Circular glass plate 5b Circular glass plate 5c Free forming surface of the outer periphery of a circular glass plate 6 Concentric grindstone 7a Disk glass substrate 7b Disk glass substrate 8 Cylindrical grindstone 9 Inside diameter support rod 10 Outside diameter processing whetstone

Continued on the front page (72) Inventor Takahisa Kondo 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 5D112 AA02 AA24 BA03 BA09 BA10 GA09

Claims (4)

[Claims] 1. A step of manufacturing a circular glass plate having a diameter larger than a desired outer diameter by press-molding glass; and forming a desired inner diameter and an outer diameter of the circular glass plate at a center portion and an outer periphery thereof concentrically. And manufacturing the glass substrate for a disk. 2. A step of manufacturing a circular glass plate having a diameter larger than a desired outer diameter by press-molding glass, and forming a part or the whole of a free surface of a central portion and an outer periphery of the circular glass plate. Processing the concentrically shaped inner and outer diameters into desired ones. 3. An outer diameter of the press-formed circular glass plate is (desired outer diameter) <X ≦ (desired outer diameter + 1.5 × substrate thickness). A manufacturing method of the glass substrate for a disk according to the above. 4. A glass material obtained by dropping a predetermined amount of a glass material heated and melted, or a cylindrical glass material obtained by cutting a rod-shaped glass material into a circle, as the glass material to be subjected to the press molding. The method for producing a glass substrate for a disk according to claim 1 or 2, wherein: