JPH11228150A - Manufacture of glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of shrink marks without requiring a reheat press, to obtain a substrate having good parallelism and to suppress the deterioration with lapse of time by use of press molds by spirally dropping molten glass press formed by the upper and lower molds onto the lower mold. SOLUTION: At the time of starting the dropping of the molten glass 3, the lower mold 2 rotates toward an arrow K within the horizontal plane around the center of the press plane. On the other hand, a nozzle 1 for dropping the molten glass 3 exists on the center of the lower mold 2 but the position of the nozzle 1 is fixed and, therefore, the position where the molten glass 3 is dropped is fixed. Next, when the lower mold 2 is kept rotated and is uniaxially moved in the radiol direction M of the lower mold 2 concurrently with the start of dropping of the molten glass 3, the molten glass 3 is dropped over the entire part of the press plane of the lower mold 2 while drawing spirals. When the dropping position of the molten glass 3, arrives at the prescribed outer peripheral part of the lower mold 2, the molten glass 3 is cut by a shear 5 and the spiral molten glass 4 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a glass substrate used as a substrate for a hard disk used mainly as an information recording medium of a computer.

[0002]

2. Description of the Related Art In recent years, the spread of computers and the increase in the capacity of various types of software have been advancing. With this trend, hard disks as information recording media capable of recording / reading a large amount of information at high speed have been developed. In the development, a glass substrate having excellent hardness and smoothness, particularly a glass substrate using crystallized glass, has been actively used instead of a conventional substrate using aluminum metal.

Generally, as shown in FIG. 9, such a glass substrate is manufactured by pouring a molten glass material prepared to a specific composition into a press mold and press-molding the same. That is, the molten glass 52 extruded from the nozzle 51 is cut by a certain amount by a shear 53, dropped onto a lower die 55 surrounded by a cylindrical wall of a die 54, and the upper die 56 is used to cut the upper surface of the die 54. Then, the space between the upper mold 56, the lower mold 55, and the body mold 54 is densely filled with the molten glass 52, and a disk-shaped glass substrate 57 is formed. Have been.

[0004]

Problems to be Solved by the Invention Here, the nozzle 51
The molten glass 52 extruded or dropped from is generally referred to as a “gob”, but the gob is pressed so as to be spread out, so that the moving distance of the glass when the gob is deformed becomes long. As a result, there is a drawback that a large press pressure is required, or a press at a higher temperature is forced to lower the viscosity of the gob, and deterioration of the press mold is easily promoted.

In most cases, the gob is at a high temperature of 1000 ° C. or higher. On the other hand, a press die such as the lower die 55 is heated to a high temperature of 300 ° C. to 700 ° C. in consideration of the glass transition point of the molten glass 52 and the like in order to avoid generation of thermal stress due to rapid cooling of the molten glass 52. It is preheated, but not to the temperature of the gob.

Therefore, as shown in FIG. 8, the lower mold 55 in contact with the gob 58 has a temperature gradient such that the temperature becomes higher at the center and becomes lower toward the outer periphery due to heat conduction from the gob 58. Occurs. When the upper mold 56 is brought into close contact with the gob 58, a temperature gradient similar to that of the lower mold 55 is generated in the upper mold 56.

The gob 58 is pressed so as to be spread by the upper mold 56 and the lower mold 55 in which such a temperature gradient is generated, so that the glass substrate 57 to be formed also moves from the center to the outer periphery. A temperature gradient occurs such that the temperature decreases. Thus, in the glass substrate 57, the outer peripheral portion cools faster, while the central portion cools slowly. As shown in FIG. 8, the central portion of the glass substrate 57 is smaller than the outer peripheral portion. Shrinkage in the thickness direction due to curing becomes large, and a depression called “sink” occurs in which the thickness of the central portion is smaller than that of the outer peripheral portion. When the sink marks 59 occur, the parallelism of the glass substrate 57 is significantly reduced.

In the conventional method of manufacturing a glass substrate, in order to correct the sink mark 59 and improve the parallelism, the glass substrate 57 is further deformed under heating conditions to perform fine adjustment of the shape. It was necessary to carry out a press molding called. On the other hand, there is a method of producing a thick glass substrate 57 in consideration of the sink mark 59 at the time of molding the gob 58 without performing reheat pressing, and adjusting the parallelism and the thickness by polishing. There is a problem in that uneven thickness occurs. Further, it is conceivable that the press surfaces of the upper mold 56 and the lower mold 55 have a curved surface in consideration of the sink mark 59 so that the parallelism of the entire glass substrate 57 after curing becomes good. ,
There is a problem in the labor of an experiment for setting the pressing conditions and the shape, and also in the processing cost of the mold.

[0009]

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems of the prior art, and it is an object of the present invention to eliminate the need for reheat pressing and to prevent the occurrence of sink marks. The object of the present invention is to make it possible to produce a glass substrate having good parallelism in press molding of molten glass, and at the same time, to contribute to suppression of deterioration with time due to the use of a press die.

That is, according to the present invention, there is provided a method for producing a glass substrate in which molten glass is press-molded into a predetermined shape using an upper mold and a lower mold, wherein the molten glass is dropped onto the lower mold. A method for manufacturing a glass substrate, wherein a molten glass is formed in a spiral shape on the lower mold.

Here, as a method of forming the molten glass in a spiral shape, the position where the molten glass is dropped is fixed,
And, a method in which the lower mold is rotated uniaxially in the radial direction while rotating, or a method in which the lower mold is rotated at a fixed position, and the drop position of the molten glass is uniaxially moved in the radial direction of the lower mold is suitably used. Can be Thus, the molten glass is pressed into a substrate having a parallelism of 10 μm or less.

The upper mold and the lower mold used in the method for manufacturing a glass substrate of the present invention include a contact portion where they can be directly joined together without using the spiral molten glass dropped on the lower mold. Those having are preferably used. Further, it is preferable that a space is provided on the outer peripheral portion of the upper mold and the lower mold to extrude the surplus volume portion of the dropped spiral molten glass.

The shape of the glass substrate formed from the molten glass in a spiral shape by the method for manufacturing a glass substrate of the present invention may be a trapezoidal shape in which the thickness of the inner hole and / or the outer periphery is smaller than that of the main body. Here, it is preferable that the slope formed at the boundary between the inner hole and / or the outer periphery and the main body has a chamfer shape.

On the other hand, the shape of the glass substrate to be formed may be a wedge shape in which a notch is formed at the boundary between the inner hole portion and / or the outer peripheral portion and the main body portion.
It is also preferred that the shape of the notch be the shape of a chamfer. In addition, when the notch is formed in this manner, when a crack is generated in the notch by applying a thermal shock to the bottom of the notch, the inner hole and / or the outer peripheral portion can be easily separated from the main body. it can.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, according to the method for manufacturing a glass substrate of the present invention, the occurrence of sink marks on the glass substrate is prevented by a simple method, and the parallelism is reduced without the need for reheat pressing. An excellent glass substrate can be obtained at the stage of molten glass press molding.

Hereinafter, embodiments of the present invention will be described mainly with reference to a method of manufacturing a flat ring-shaped glass substrate. However, the method of manufacturing a glass substrate of the present invention includes manufacturing glass substrates of various other shapes. Can be used. Therefore, it goes without saying that the present invention is not limited to the following embodiments.

FIG. 1 is an explanatory diagram showing a step of press-molding molten glass in the method for producing a glass substrate of the present invention. In the present invention, the molten glass is formed in a spiral shape on the lower mold, that is, on the pressed surface of the lower mold. First, when the molten glass is dropped on the lower mold, the molten glass is dropped. There is a method in which the position is fixed and the lower die is rotated uniaxially in the radial direction while rotating.

That is, in FIG. 1, the molten glass 3
At the start of the dropping, the lower die 2 is rotating in the direction of arrow K in the horizontal plane about the center of the press surface. On the other hand, the nozzle 1 for dropping the molten glass 3 is on the center of the lower mold 2, but the position of the nozzle 1 is fixed, and therefore, the position for dropping the molten glass 3 is constant.

Next, with the start of the dropping of the molten glass 3,
When the lower mold 2 is rotated and uniaxially moved in the radial direction of the lower mold 2, that is, when the lower mold 2 is moved uniaxially in the lateral direction indicated by an arrow L in FIG. No. 2 is dropped on the entire press surface. When the dropping position of the molten glass 3 reaches a predetermined outer peripheral portion of the lower mold 2, the molten glass 3 is cut by a shear 5, thereby forming a spiral molten glass 4 (hereinafter, “processed molten glass 4”). 4 ") is formed. When the molten glass 4 to be processed is formed, it is preferable to adjust the dripping conditions of the molten glass 3 such as viscosity so that the molten glass 3 is not interrupted.

Note that the dropping start position of the molten glass 3 is
The position is not necessarily limited to the center of the lower mold 2 and is set to a suitable position as appropriate according to the shape of the glass substrate to be formed. For example, when a flat ring-shaped glass substrate having an inner hole is formed, the glass which is dropped at the center of the lower mold 2 and press-formed becomes a portion which is finally separated from the main body of the glass substrate. In such a case, it is preferable to start dropping the molten glass 3 from a position slightly outside the center of the lower mold 2.

Similarly to the above-described method, as a method of forming the molten glass 4 to be processed on the pressed surface of the lower mold 2,
There is a method in which the lower mold 2 is rotated at a fixed position, and the position at which the molten glass 3 is dropped is uniaxially moved in the radial direction of the lower mold 2, that is, the position of the nozzle 1 at which the molten glass 3 is dropped is moved. However, generally, the nozzle 1 for dropping the molten glass 3 is composed of platinum and a furnace for heating the platinum.
, And integrated with a furnace for melting the glass raw material, the method of moving the lower mold 2 is considered preferable, and is actually practical.

In any of these methods, the lower mold 2
Alternatively, it is preferable that the uniaxial movement speed of the nozzle 1 and the rotation speed of the lower mold 2 are set so that the molten glass 3 is dropped on the press surface of the lower mold 2 as uniformly as possible. For example, FIG. 2 shows a part of the cross-sectional shape of the lower mold 2 and the molten glass 4 to be processed. Here, the cross-sectional diameter D of the molten glass 4 at a certain position and the cross-section of the molten glass 4 to be processed are adjacent. The distance P between the centers is preferably set so that the adjacent molten glass 4 is in contact with each other in a state where the molten glass 4 to be processed is deformed into a substantially elliptical shape over time due to surface tension or own weight.

Next, the molten glass 4 to be processed thus formed is pressed into a predetermined shape by pressing the upper mold 6 against the lower mold 2. The glass substrate 7 obtained by removing the upper mold 6 from the lower mold 2 is subjected to inner and outer diameter processing according to the shape of the formed glass substrate 7 and gradually cooled.
Alternatively, the inner and outer diameters are processed after being gradually cooled.

As described above, in the method for manufacturing a glass substrate of the present invention, the molten glass 4 to be processed is
Is formed by dripping the entirety on the press surface of the lower mold 2, so that the conventional gob 58 is formed only at the center of the lower mold 2,
Since the moving distance of the molten glass 4 to be processed is shorter than in the method of press molding, a glass substrate 7 having a uniform thickness can be produced, and the press molding pressure can be reduced. On the other hand, it is not necessary to perform press molding in a state where the viscosity of the molten glass 4 to be processed is maintained at a high temperature and the viscosity is reduced. Thereby, deterioration of the upper and lower dies 2 and 6 is substantially suppressed.

In the lower mold 2 and the upper mold 6 used for pressing, the glass transition of the molten glass 3 is performed in order to prevent the molten glass 3 from cooling and solidifying rapidly and generating a large thermal stress. It is preheated and held at an appropriate temperature in consideration of points, etc., but its outer periphery has a large area in contact with the atmosphere, so it has high heat dissipation, so the center has a high temperature and the outer periphery has a high temperature. In many cases, a temperature gradient is generated such that the temperature becomes low.

On the other hand, if the molten glass 3 is dropped in a spiral from the center of the lower mold 2 toward the outer periphery, the molten glass 3 that has already been dropped is naturally cooled. Contrary to the upper mold 6, the molten glass 4 to be processed has a temperature gradient such that the temperature increases from the center to the outer periphery.

Thus, since the temperature gradients of the upper and lower dies 2 and 6 and the molten glass 4 to be processed are opposite to each other, the temperature distribution of the glass substrate 7 at the time of press molding is entirely flattened. Thereby, the curing of the glass substrate 7 occurs uniformly, and the occurrence of sinks is suppressed. This is also considered to be one factor in obtaining the glass substrate 7 with good parallelism.

The preferred shape of the flat ring-shaped glass substrate having an inner hole manufactured by the above-described method for manufacturing a glass substrate of the present invention is a trapezoidal shape shown in FIGS. 3 (a) to 3 (c). , Wedge shape and trapezoidal wedge shape. In addition, each of these figures shows the glass substrates 11 to 1.
3 is a cross-sectional view showing the shape of the glass substrate in a direction perpendicular to the flat surface in the radial direction of FIG.
Also, the main body portions 11A to 13A to be the final glass substrates
A, the inner hole portions 11B to 13B, and the surplus volume portion of the molten glass 4 to be processed, that is, the outer peripheral portions 11C to 13C formed by extruding the excessively supplied glass to the outer periphery.

The trapezoidal glass substrate 11 shown in FIG.
The inner hole portion 11B and the outer peripheral portion 11C are set to be thinner than the main body portion 11A in order to facilitate separation from the main body portion 11A in a later step.
A gradient portion 14 is provided at a boundary between B and the outer peripheral portion 11C and the main body portion 11A. Here, the slope portion 14 is suitably set to a shape generally called a chamfer 16 after chamfering to be formed on a glass substrate as a product and removing corners.

As described above, by forming the chamfer 16 on the glass substrate 11 at the stage of press-molding the molten glass 4 to be processed, a disc-like shape as performed in a conventional method of manufacturing a glass substrate is obtained. A step of performing a cutting process for making an inner hole using the glass substrate and further performing a chamfering process can be omitted, thereby shortening the manufacturing process of the glass substrate and improving the productivity.

In the wedge-shaped glass substrate 12 shown in FIG. 3B, the inner hole 12 B, the outer peripheral portion 12 C, and the main body 1
A notch 15 is formed at the boundary with 2A, and the shape of the notch 15, that is, the shape of the slope portion of the notch 15 is suitably set to the shape of the chamfer 16. Also,
The trapezoidal wedge-shaped glass substrate 13 shown in FIG.
3B and the outer peripheral portion 13C in a trapezoidal shape thinner than the main body portion 13A.
A notch 15 is provided at the boundary between 3C and the main body 13A. Therefore, even in the trapezoidal wedge-shaped glass substrate 13, the notch 15 is set to the shape of the chamfer 16.

It is needless to say that the shape of the glass substrate manufactured by the present invention is not limited to those of the above glass substrates 11 to 13. A suitable shape is selected. For example, when manufacturing a glass substrate having an inner hole, the shape of one press surface is selected from trapezoidal shape, wedge shape, or trapezoidal wedge shape, and the other press surface is also arbitrary from these various shapes. , The shape of each surface of the glass substrate may be different. When a disc-shaped glass substrate having no inner hole is obtained, the inner hole portion need not be provided.

Next, the molten glass 4 to be processed is shown in FIG.
Specific examples of upper and lower dies for press used for molding into various shapes shown in (a) to (c) include:
As shown in FIGS. 4A to 4C, FIG.
(A) to (c) trapezoidal dies 19A and 19B and wedges 20A and 2 having shapes complementary to the shapes shown on the pressing surface.
OB and trapezoidal wedge shapes 21A and 21B.

Here, as shown in FIG. 4A, the pressing surfaces of the trapezoid molds 19A and 19B have a deep groove 22 for forming the main body 11A of the glass substrate 11, an inner hole 11B and an outer periphery. Groove portion 2 for forming portion 11C
3, the inner hole 11B, the outer periphery 11C, and the main body 1
1A (Chamfer 1)
6) has a slope portion 24 for forming the same.

Further, as shown in FIG. 4B, the pressing surfaces of the wedge shapes 20 A and 20 B
12A, inner hole portion 12B and outer peripheral portion 12
It has a deep groove portion 25 for forming C and a V-shaped convex portion 26 for forming the notch 15. As shown in FIG. 4 (c), the pressing surfaces of the trapezoidal wedges 21A and 21B form a deep groove 27 for forming the main body 13A of the glass substrate 13, an inner hole 13B and an outer peripheral 13C. And a V-shaped projection 29 for forming the notch 15.

The trapezoidal dies 19A and 19B and the wedge type 20A
In the upper die and the lower die suitably used in the method for manufacturing the glass substrate of the present invention, such as 20B and trapezoidal wedge shapes 21A and 21B, the contact portions 30 where the respective dies are in direct contact with each other.
, The glass substrates 11 to 13 having a constant thickness
Can be manufactured. The surplus volume of the molten glass 4 to be processed, that is, the main body 11A
It is preferable to provide a space portion 31 in which excess glass unnecessary for formation of １３13A is extruded into the space portion 31 to become the outer peripheral portions 11C to 13C. At this time, in order to prevent the excess volume from entering the contact portion 30, the space 3
It is preferable that 1 is set to a size that does not completely fill and leaves a certain amount of space.

The upper mold and the lower mold preferably used in the method of manufacturing the glass substrate of the present invention such as the trapezoid molds 19A and 19B described above include tungsten carbide, metal carbide or metal nitride having good thermal conductivity. And the like are preferably used.

Next, a method for processing the inner and outer diameters of the glass substrates 11 to 13 having the respective shapes shown in FIGS. 3A to 3C will be described. The trapezoidal glass substrate 1 shown in FIG.
As shown in FIG. 5, it is preferable that the processing of No. 1 is performed using an inner and outer diameter concentric cup grindstone 41 (hereinafter, referred to as “cup grindstone 41”). The cup whetstone 41 has an inner diameter whetstone 4
1A and an outer diameter grindstone 41B are formed so as to be concentrically arranged, and the glass substrate 11 is rotated while rotating the cup grindstone 41.
To the inner hole 1 in the glass substrate 11.
1B and the outer peripheral portion 11C are cut from the main body 11A.

Here, the inner hole portion 11 B and the outer peripheral portion 11
Since C is formed thinner than the main body 11A, the processing time is shortened by a smaller cutting margin than when a single flat glass substrate is cut.
Since the wear of No. 1 is reduced, the processing cost can be reduced as a whole. Further, since the inner hole 11B and the outer periphery 11C separated from the main body 11A are obtained in a state of a lump of glass, it is easy to separate and wash them, and therefore, when manufacturing a glass substrate, It can be reused as a molten raw material.

For the inner and outer diameter processing using such a cup grindstone 41, the notch 15 is formed like the wedge-shaped and trapezoidal wedge-shaped glass substrates 12 and 13 shown in FIGS. 3 (b) and 3 (c). In this case, an inner / outer diameter processing method called chill cut is suitably used. Here, the chill cut is a notch 1 of the glass substrates 12 and 13 heated to a high temperature.
5, in particular, a jig made of a cooled metal or the like is brought into contact with the bottom portion where the thickness of the glass substrates 12 and 13 is the thinnest, and at the position where the notch 15 is formed, Since the glass substrates 12 and 13 are cut in the thickness direction, the processing can be performed easily and in a short time.

The chill cut is performed on the glass substrate 12.
Although it is necessary to perform the process in a state in which the glass substrate 13 is heated to a predetermined temperature or more, after the molten glass 4 to be processed is press-formed, the glass substrates 12 and 13 remain in a state of being placed on the lower molds 20A and 21A. The temperature of the upper and lower mold 20A
The glass substrates 12 and 13 do not need to be heated again because they are maintained at a high temperature of about 21 A preheating temperature.

FIG. 6 is an explanatory diagram of the chill cut. Here, a trapezoidal wedge-shaped glass substrate 13 is shown, and a metal jig 42 having a cooled concentric inner diameter processing blade 42A and an outer diameter processing blade 42B is brought into contact with a notch 15 provided on the glass substrate 13. Then, a thermal shock is applied to generate a crack at the notch 15, and the inner hole 13B and the outer peripheral portion 13C are separated from the main body 13A. Note that the shape of the notch 15 for satisfactorily performing chill cut is shown in FIG.
A V-shape as shown in FIG. 6B or FIG. 6 is preferably employed.

As shown in FIG. 7, each of the main bodies 11A to 13A of the glass substrates 11 to 13 obtained through the above-described inner and outer diameter processing becomes a glass substrate 17 having a gradient portion 14 on the inner and outer circumferences. . Such a gradient portion 14 becomes the chamfer 16 itself to be formed on the inner and outer peripheries of the substrate, which is the final product. However, in the concentricity processing described later, a slight shape adjustment may be performed.

As described above, with respect to the glass substrate 17 on which the inner and outer diameter processing has been completed, when the glass substrate 17 is made of crystallized glass, a crystallization process is subsequently performed. Here, when the inner and outer diameters are processed using the cup grindstone 41, the temperature is raised from room temperature to the crystallization temperature. To a crystallization treatment temperature.

By this crystallization process, the glass substrate 1
Since a slight volume change occurs in 7, the volume change causes a large amount of processing cost in the concentricity processing of the inner and outer diameters of the final glass substrate (hereinafter, referred to as “concentricity processing”) which is the next step. It is preferable that the inner and outer diameter processing positions are set so as not to be affected. When the material of the glass substrate 17 does not require crystallization, concentricity processing is performed after inner and outer diameter processing.

The concentricity processing is a step of finishing the concentricity with higher precision while grinding with a fine grindstone so that the edge of the processing end face of the glass substrate 17 does not stand. Is used as an abrasive, and an end surface polishing step is added by a nylon brush. Finally, the glass substrate 1 is made so as to satisfy the shape characteristics required for the product.
Both surfaces of 7 are finely polished. In addition, as a method of fine polishing, a resin grindstone of # 600 is used, and 1000 is used.
A method in which the rotation is performed at a rotation speed of from 5000 rpm to 5000 rpm is preferable.

According to the above-described method for producing a glass substrate according to the present invention, the reheat press step and the lapping (polishing) processing in the thickness direction, which are costly in terms of time and equipment, are performed in the conventional method. Since a processing step can be omitted, manufacturing cost of a glass substrate can be reduced.

The glass substrate for a hard disk currently has an average thickness of 0.645 mm, a parallelism of 6 μm or less, and a flatness of 5 μm as a product substrate.
m and a surface roughness of 0.1 μm or less in Ra are required, but according to the above-described method for producing a glass substrate of the present invention, the average value of the thickness is 0.9 m after press molding.
It is possible to obtain a glass substrate having a shape with m and parallelism of 10 μm or less.

Further, the crystallization treatment of the glass substrate
By performing in the range of about 0 ° C. to 800 ° C. for about 3 hours to 12 hours, the average thickness is 0.68 mm,
A glass substrate having a shape with a parallelism of 7 μm or less, a flatness of 5 μm or less, and a surface roughness Ra of 0.2 μm or less is obtained. Lastly, if the average required thickness of the substrate is 0.645 mm, the parallelism is 6 μm or less, the flatness is 5 μm or less, and the surface roughness is Ra and the specification of 0.1 or less is not satisfied, # 600 By precision polishing with the above resin grindstone, it becomes possible to obtain a glass substrate which satisfies the required shape for the substrate. Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[0050]

[Example] As molten glass, 77 wt% of SiO ₂ was used.
%, Al ₂ O ₃ was 5 wt%, Li ₂ O was 5 wt%, and the balance was a SiO ₂ —Al ₂ O ₃ —Li ₂ O-based glass composed of trace components. This glass is heated at 1400 ° C in a glass melting furnace.
From the nozzle held at 1300 ° C.
Diameter 120 for forming wedge-shaped glass substrate 12 of (b)
mm of the lower mold 20A. At this time, while rotating the lower mold 20A at a speed of one rotation per second, the molten glass was cut by a shear after four rotations after dropping. During this time, the drop position of the molten glass starts from a position 10 mm away from the center of the lower mold 20A, and the lower mold 2 moves in the outer peripheral direction.
By moving the lower mold 20A in one axis direction so that the position 45 mm away from the center of 0A becomes the end point, a spiral molten glass as shown in FIG. 10, ie, a molten glass to be processed, was obtained.

Subsequently, the upper mold 20 preheated to 600 ° C.
B was used to press-mold the molten glass to be processed at 60 kg / cm ² for about 1 second. The used upper mold 20B and lower mold 20A are made of cemented carbide. In this manner, the formed wedge-shaped glass substrate 12 is usually subjected to inner and outer diameter processing by chill cutting, but in a similar test, the dimensions were measured after press molding and then gradually cooled to obtain dimensions. It was confirmed that the glass substrate 12 had an average thickness of 0.9 mm or less and a parallelism of 10 μm or less.

Next, the upper mold 20 B is removed from the molded glass substrate 12, and the cooling metal jig 42 is used while the glass substrate 12 is mounted on the lower mold 20 A preheated to 600 ° C. Inner / outer diameter processing by chill cut is performed on the notch 15 formed in the glass substrate 12 so that the inner hole 12 is formed.
B and the outer peripheral portion 12C are separated from the main body portion 12A. The inner diameter of the glass substrate 12A thus obtained after slow cooling is 2
3.8mm ± 0.15mm, outer diameter 85.2 ± 0.
It was 15 mm.

Further, the crystallization treatment of the glass substrate is performed in a nitrogen atmosphere at 770 ° C. for 4 hours, and the average thickness is 0.68 mm or less, the parallelism is 7 μm or less, and the flatness is 5 μm.
m or less, a glass substrate having a surface roughness Ra of 0.02 μm or less is obtained, and then concentricity processing is performed to reduce the concentricity to 7 μm or less, and finally, a fine grinding is performed with a # 600 resin grindstone. , The average thickness is 0.645 mm, and the parallelism is about 5
μm, flatness is about 4 μm, surface roughness is about 0.08 μm in Ra
A substrate m satisfying the required standard for a hard disk substrate was obtained. Further, under the above conditions, the wear amount of the upper mold 20B and the lower mold 20A after producing 10,000 glass substrates 12 was 1 μm or less, respectively.

As a comparative example, a method in which a gob is formed and press-formed without rotating and lowering the lower mold 20A is used as a comparative example. A glass substrate was manufactured. However, in order to set the average thickness of the glass substrate 12 obtained at this time to about 0.9 mm, which is the same as in the above example, the press molding pressure had to be 120 kg / cm ² . However, the parallelism of the obtained glass substrate is about 75 on average.
The upper mold 20B and the lower mold 20A had a wear amount of 3 μm each after the production of 10,000 glass substrates.

[0055]

As described above, according to the method for manufacturing a glass substrate of the present invention, since the formed glass substrate is uniformly cured, the occurrence of sink marks is suppressed and the parallelism is improved. A glass substrate is obtained. In addition, a chamfer can be simultaneously formed on a glass substrate during press forming. As a result, the reheat press step, which is indispensable in the conventional method, and the lapping (polishing) processing step in the thickness direction, which is costly in terms of time and equipment, and further, the chamfer processing step can be omitted. This is an extremely excellent effect that the manufacturing cost of the glass substrate is extremely reduced. Further, since the pressure for press-molding the molten glass can be reduced, an effect of suppressing the deterioration over time of the lower mold and the upper mold used for press-molding is also exerted.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a method for forming a glass substrate in a method for manufacturing a glass substrate of the present invention.

FIG. 2 is an explanatory diagram relating to a shape of a molten glass to be processed in the method for manufacturing a glass substrate of the present invention.

3A and 3B are cross-sectional views illustrating an embodiment of a shape of a glass substrate formed by the method for manufacturing a glass substrate of the present invention, wherein FIG. 3A illustrates a trapezoidal shape, FIG.
(C) shows a trapezoidal wedge shape.

FIG. 4 is a cross-sectional view showing the shape of a press upper and lower mold used in the method of manufacturing a glass substrate of the present invention, wherein (a) shows a trapezoidal mold, (b) shows a wedge mold, and (c) shows 2 shows a trapezoidal wedge shape.

FIG. 5 is an explanatory diagram of inner and outer diameter processing using a cup grindstone in the method for manufacturing a glass substrate of the present invention.

FIG. 6 is an explanatory diagram of inner and outer diameter processing by chill cut in the method for manufacturing a glass substrate of the present invention.

FIG. 7 is a cross-sectional view showing one embodiment of the shape of the glass substrate after inner and outer diameter processing manufactured by the method for manufacturing a glass substrate of the present invention.

FIG. 8 is an explanatory diagram showing the occurrence of sink marks on a glass substrate.

FIG. 9 is an explanatory view showing a method for forming a glass substrate in a conventional method for manufacturing a glass substrate.

FIG. 10 is a plan view showing one embodiment of a shape of a molten glass to be processed formed by the method for manufacturing a glass substrate of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Nozzle, 2 ... Lower mold, 3 ... Molten glass, 4 ... Spiral molten glass (processed molten glass), 5 ... Shear,
6: upper mold, 7: glass substrate, 11 to 13: glass substrate,
11A to 13A: main body, 11B to 13B: inner hole, 1
1C to 13C: outer peripheral portion, 14: gradient portion, 15: notch,
16: chamfer, 17: glass substrate, 19A / 19
B: trapezoidal type, 20A / 20B ... wedge type, 21A / 21B ...
Trapezoidal wedge shape, 22: groove, 23: groove, 24: slope, 2
5 ... groove, 26 ... V-shaped convex, 27 ... groove, 28 ... groove,
29: V-shaped convex part, 30: contact part, 31: space part, 41 ...
Inner / outer diameter concentric cup grindstone (cup grindstone), 41A: inner diameter grindstone, 41B: outer diameter grindstone, 42: metal jig, 42A: inner diameter processing blade, 42B: outer diameter processing blade, 51: nozzle, 52: molten glass, 53 ... shear, 54 ... body type, 55 ... lower type, 5
6: upper mold, 57: glass substrate, 58: gob, 59: sink mark.

Continuation of front page (72) Inventor Toshiki Goto 2-56 Suda-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Insulator Co., Ltd.

Claims (8)

[Claims] 1. A method for producing a glass substrate, comprising pressing molten glass into a predetermined shape using an upper mold and a lower mold, wherein the molten glass is dropped onto the lower mold when the molten glass is dropped onto the lower mold. A method for manufacturing a glass substrate, which is formed in a spiral shape on a mold. 2. The method according to claim 1, further comprising: fixing the dropping position of the molten glass, and moving the lower die in a uniaxial direction while rotating the lower die, or rotating the lower die at a fixed position, and The method for manufacturing a glass substrate according to claim 1, wherein the molten glass is formed in a spiral shape on the lower mold by moving a dropping position of the glass uniaxially in a radial direction of the lower mold. 3. The method for producing a glass substrate according to claim 1, wherein said molten glass is press-molded into a substrate having a parallelism of 10 μm or less. 4. The method according to claim 1, wherein the upper mold and the lower mold are provided with contact portions that can be directly fitted to each other without interposing the spiral molten glass therebetween. The method for producing the glass substrate described in the above. 5. The method according to claim 1, wherein a space is formed in an outer peripheral portion of the upper mold and the lower mold so that an excess volume of the spiral molten glass is extruded. The method for producing the glass substrate described in the above. 6. A glass substrate formed from the spiral molten glass has a trapezoidal shape in which the thickness of an inner hole portion and / or an outer peripheral portion is smaller than that of a main body portion, and the shape of the inner hole portion and / or The method for manufacturing a glass substrate according to any one of claims 1 to 5, wherein a gradient portion formed at a boundary between the outer peripheral portion and the main body portion has a chamfer shape. 7. The shape of the glass substrate formed from the molten glass in a spiral shape is a wedge shape in which a notch is formed at a boundary between the inner hole and / or the outer peripheral portion and the main body, and the shape of the notch Is a shape of a chamfer, The method for manufacturing a glass substrate according to any one of claims 1 to 6, wherein 8. The method according to claim 1, wherein a thermal shock is applied to the bottom of the notch to cause a crack in the notch, thereby separating the inner hole and / or the outer periphery from the main body. 8. The method for producing a glass substrate according to 7.