JPH11268919A - Preparation of glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a glass substrate having a definite thickness close to the product thickness and having good parallelism in which occurrence of sink mark is suppressed only by direct press by forming molten glass in ring-like shape when molten glass is dropped to a press lower mold. SOLUTION: In the conventional method (a), molten glass 6 from a nozzle 4 is dropped in disk-like state onto a press lower mold 1 and a gob 2 is formed. In the present invention method (b), molten glass 7 is dropped from a nozzle 5 onto a press lower mold so as to become a ring-like gob 3. Then, the gob 2 and the gob 3 are subjected to press molding to provide a prescribed glass substrate. Glass forming the ring-like gob 3 is pressed so as to spread in the circumference direction and central direction of a press type. Since moving distance R2 of the glass in this time is short, compared with moving distance R1 of the glass in the method (a), the press pressure is not increased and temperature distribution is made uniform and occurrence of a sink mark is suppressed and the parallelism can be suppressed to >=10 μm size.

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, with the rapid spread of computers, the capacity of OS software such as an operation system that affects the operability of the computer and various kinds of program software operating on the OS have been increased. The data created on these programs also tends to have a high capacity.

Accordingly, in the development of a hard disk as an information recording medium capable of recording / reading such a large amount of information at a high speed, hardness and smoothness have been changed in place of a conventional substrate using aluminum metal. In recent years, there has been an active movement to use a glass substrate having excellent characteristics, in particular, a glass substrate using crystallized glass.

In general, as a method of manufacturing such a glass substrate, as shown in FIG. 8, a certain amount of a molten glass 52 extruded from a nozzle 51 is cut by a shear 53, and the periphery is cut into a barrel shape. Lower mold 55 surrounded by 54 cylindrical walls
The molten glass 52 is densely filled in the space surrounded by the upper mold 56, the lower mold 55, and the mold 54 by dropping the upper mold 56, covering the upper surface of the mold 54 with the upper mold 56, and pushing up the lower mold 55. A method of manufacturing a disk-shaped glass substrate 57 is employed.

[0005]

In the above-described conventional method, the working environment, that is, the molten glass 52 is set so that the molten glass 52 is always supplied to the lower mold 55 by a constant amount.
If the conditions such as the dropping amount or extrusion amount, the timing of cutting the molten glass 52 to be dropped, or the viscosity adjustment (temperature management) of the molten glass 52 are made constant,
There is a problem that a glass substrate 57 having a different thickness is formed each time. As a result, a wasteful portion removed by lapping or the like increases, and a problem arises in that the cost of raw materials required for forming the glass substrate increases. In addition, chamfering, which is important in terms of preventing chipping of the glass substrate and maintaining mechanical strength, requires a long processing time and requires a special processing machine.

The molten glass 52 cut by the shear 53 and dropped on the lower mold 55 is generally called “gob”. The viscosity of the gob increases due to a drop in the temperature of the gob from the time of dropping to the time of actual press molding, and it may not be possible to obtain sufficient fluidity required at the time of press molding. In this case, even if the volume of the gob is set to a predetermined amount, it is not possible to press to a predetermined thickness, or deterioration of the press mold is promoted because the pressing pressure must be increased,
Such a problem arises.

On the other hand, in order to provide the gob with sufficient fluidity, the temperature of the molten glass 52 may be increased, but in this case, deterioration of the lower mold 55 and the like due to high-temperature oxidation and the like is promoted. Is not preferred.

Further, the gob is deformed at the time of pressing so that the gob can be pushed and spread from the center to the outer periphery. That is, since the temperature of the lower mold 55 where the molten glass 52 is dropped first rises and the temperature decreases toward the periphery, the peripheral portion of the pressed glass substrate 57 hardens first. However, there is a disadvantage that the central portion is slowly cured, and as a result, a depression called "sink" is formed in the central portion of the obtained glass substrate 57.

In order to obtain a predetermined degree of parallelism, the temperature of the glass substrate 57 on which sink marks have been generated is raised again to such a degree that the glass substrate 57 is softened, and a press process for performing fine adjustment of a shape called reheat pressing is performed. It was necessary to perform or to wrap the glass substrate 57 until sink was eliminated.

[0010]

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to press-mold molten glass without performing reheat pressing, that is, An object of the present invention is to provide a glass substrate in which generation of sink is suppressed only by direct pressing, and to provide a method of manufacturing a glass substrate which is also effective in suppressing deterioration of a press die.

That is, according to the present invention, there is provided a method for producing a glass substrate including a step of press-forming molten glass into a predetermined shape using a press upper and lower mold, wherein the molten glass is dropped onto a lower press mold. A method for producing a glass substrate, wherein the molten glass is formed in a ring shape,
Is provided. According to such a method for manufacturing a glass substrate of the present invention, the molten glass is press-formed into a substrate having a parallelism of 10 μm or less.

Further, the press upper and lower dies used in the method of manufacturing a glass substrate of the present invention have a contact portion that can be directly fitted to each other without passing through the ring-shaped molten glass dropped on the lower press die. Are preferably used. Further, it is preferable that a space is provided on an outer peripheral portion of the press upper and lower molds to extrude a surplus volume portion of the dropped ring-shaped molten glass.

The shape of the glass substrate formed from the ring-shaped molten glass 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 and / or the outer peripheral portion and the main body. In this case, the shape of the notch Is also preferably in the shape of a chamfer. In addition, when the notch is formed in this way, if 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. . Note that the shape of the notch is preferably a V-shape.
In the present invention, the material of the glass substrate is S
An iO ₂ —Al ₂ O ₃ —Li ₂ O-based crystallized glass is preferably used.

[0015]

DETAILED DESCRIPTION OF THE INVENTION As described above, according to the method for manufacturing a glass substrate of the present invention, the occurrence of sink marks on a glass substrate obtained by direct pressing is suppressed. The process is extremely shortened, and as a result, the production cost can be significantly reduced. Hereinafter, embodiments of the present invention will be described with reference to a main example of a method for manufacturing a glass substrate having a flat ring shape used as a glass substrate for a hard disk or the like.

FIG. 1 is an explanatory diagram comparing the state of dripping of molten glass between the conventional method and the method for manufacturing a glass substrate of the present invention. As shown in FIG. 1A, in the conventional method, the molten glass 6 is dropped from the nozzle 4 in a disk shape on the press lower die 1, and the gob 2 is formed. On the other hand, in the method for producing a glass substrate of the present invention,
As shown in FIG. 1B, the molten glass 7 is dropped from the nozzle 5 onto the press lower die 1 so as to form the ring-shaped gob 3. Next, the gob 2 or the ring-shaped gob 3 is press-formed into a predetermined glass substrate shape. Such press forming is called direct pressing.

When the ring-shaped gob 3 is directly pressed, the glass forming the ring-shaped gob 3 is crushed so as to spread toward the outer periphery and the center of the press die. The moving distance of the glass at that time, for example, the moving distance R2 in the outer peripheral direction is shorter than the moving distance R1 of the glass when the gob 2 is directly pressed by the conventional method, so that the pressing pressure can be reduced. For example, there is an advantage that direct press can be easily performed.

By adjusting the inner and outer diameters of the ring-shaped gob 3 to be formed, the moving distance of the glass in the center direction of the ring-shaped gob 3 can be suppressed to about the moving distance R2 in the outer circumferential direction. , The glass of the ring-shaped gob 3
The movement to the center does not increase the pressure required for direct pressing.

Further, by forming the ring-shaped gob 3, the molten glass 7 is distributed over a wide area on the press lower die 1, so that the temperature distribution of the press lower die 1 is made uniform, Thereby, cooling and hardening of the ring-shaped gob 3 easily occur uniformly. Such uniformity of the temperature distribution of the lower press die 1 is the same in the upper press die (not shown).

Therefore, according to the present invention, the moving distance of the glass forming the ring-shaped gob 3 in the direct press is reduced and the temperature distribution in the press dies (the lower press die 1 and the upper press die) is made uniform. If this is the case, the occurrence of sink marks on the glass substrate to be formed is suppressed as compared with the conventional method, and the parallelism can be suppressed to 10 μm or less.

As described above, since the glass substrate manufactured by the method for manufacturing a glass substrate of the present invention has good parallelism, shape correction such as correction of parallelism by reheat pressing performed after direct pressing is performed. Since there is no need to perform this step, the manufacturing process can be shortened. In addition, since the pressure during direct pressing can be reduced and the temperature of the molten glass can be reduced, the load on the press die can be reduced, and there is an advantage that deterioration of the press die is suppressed. Hereinafter, the method for manufacturing a glass substrate of the present invention will be described in more detail.

First, in producing the molten glass 7,
A mixture of predetermined raw material powders having a predetermined composition, or a pre-synthesized glass powder or pellets is suitably used as a molten raw material. Further, as will be described later, since unnecessary portions such as an inner hole portion and an outer peripheral portion separated from the glass substrate once formed are easily collected, these can be reused. The type and composition of the glass used are not particularly limited. For example, as a glass substrate for a hard disk, SiO ₂ —Al ₂ O
_{A 3-} Li ₂ O-based crystallized glass is preferably used.

The molten glass 7 is supplied to the lower die for press 1 by being extruded or dropped from the nozzle 5. FIG. 2 is a sectional view showing an embodiment of the nozzle 5 suitably used in the present invention. The nozzle 5 includes a straight tube portion 8A connected to the glass melting furnace and a skirt portion 8B having a conical wall surface on which the molten glass 7 is dropped in a ring shape.

The molten glass 7 that hangs in a ring shape from the bottom surface of the skirt portion 8 B of the nozzle 5 is heated by a gas flame blown out from a gas burner 9 disposed at a predetermined position below the nozzle 5 when the predetermined length hangs down. Is reduced in viscosity and cut. The gas burner 9 is arranged in a ring shape so as to surround the molten glass 7. Further, such cutting of the molten glass 7 is superior to mechanical cutting using the shear 53 in that generation of shear marks on the surface of the ring-shaped gob 3 can be suppressed.

Thus, the ring-shaped gob 3 is formed on the lower press die 1. Here, in order to prevent rapid cooling and solidification of the molten glass 7 and generation of a large thermal stress due to the rapid cooling and solidification of the molten glass 7, the press lower mold 1 takes an appropriate temperature in consideration of the glass transition point of the molten glass 7 and the like. Is preferably preheated and held.

The ring-shaped gob 3 thus formed is
The upper die for press and the lower die for press 1 preheated to the same temperature as the lower die for press 1 are directly pressed under predetermined conditions to obtain a glass substrate.

In the production of a flat ring-shaped glass substrate such as a glass substrate for a hard disk, the shape of the glass substrate is determined in consideration of, for example, a method of processing the inner and outer diameters in a later step. FIG. 3 is a cross-sectional view in the radial direction of a glass substrate that is particularly preferably employed in the present invention.
The glass substrates 11 and 12 having any of these shapes are formed by extruding the main body portions 11A and 12A to be final glass substrates and the surplus supplied glass in the ring-shaped gob 3 to the outer peripheral portion and the central portion. Outer peripheral parts 11C and 12C
And inner holes 11B and 12B. In the production of the glass substrates 11 and 12, generally, the inner holes 11 are formed.
A hole is formed in the center of B.12B in accordance with the volume of the ring-shaped gob 3.

The trapezoidal shape shown in FIG.
The outer peripheral portion 11C is set to be thinner than the main body portion 11A in order to facilitate separation from the main body portion 11A in a later process, and the inner hole portion 11B of the main body portion 11A is formed.
In addition, a slope-shaped slope portion 14 is formed in a portion on the outer peripheral portion 11C side. In the wedge shape of FIG. 3B, a notch 13 is formed at a boundary between the inner hole 12B and the outer peripheral portion 12C and the main body 12A. As described later, a thermal shock is applied to the notch 13. By adding, it is possible to easily separate the inner hole portion 12B and the outer peripheral portion 12C from the main body portion 12A at the notch 13.

In the trapezoidal glass substrate 11 illustrated in FIG. 3A, it is preferable that the inclined portion 14 is designed so as to be a chamfer 16, which will be described later, that is, a chamfered portion. In the wedge-shaped glass substrate 12 shown in FIG. 3B, it is preferable that the notch 13 also serves as the chamfer 16. Such a chamfer 16 is important to prevent chipping of a glass substrate, which is a product, which is called a substrate, and to maintain mechanical strength. This is very important in that the indispensable chamfering process is omitted and the manufacturing process is shortened.

As a specific example of the press upper and lower dies used to form the ring-shaped gob 3 into these various shapes, as shown in FIGS. 4A and 4B, respectively. , (B) have trapezoidal dies 19A and 19B and wedge dies 20A.
20B.

Therefore, as shown in FIG. 4A, the pressing surfaces of the trapezoid molds 19A and 19B have deep grooves 21 for forming the main body 11A of the glass substrate 11 shown in FIG. It has a shallow groove portion 22 for forming the inner hole portion 11B and the outer peripheral portion 11C, and a slope portion 23 for forming a chamfer 16 formed between the inner hole portion 11B and the outer peripheral portion 11C and the main body portion 11A. . Also,
As shown in FIG. 4 (b), the pressing surfaces of the wedge shapes 20A and 20B correspond to the main body 12A, the inner hole 12B, and the outer peripheral portion 12C of the wedge-shaped glass substrate 12 shown in FIG. 3 (b).
And a V-shaped convex portion 25 for forming the notch 13.

The trapezoidal dies 19A and 19B and the wedge type 2
For press upper and lower dies such as 0A and 20B, see FIG.
As shown in (a) and (b), since the upper and lower molds have the contact portions 26 that are in direct contact with each other, the glass substrates 11 and 12 having a constant thickness can always be manufactured. .

When the wedges 20 A and 20 B are used, the processing accuracy is maintained such that the distance between the bottoms of the notches 13 formed on both surfaces of the glass substrate 12 is constant. Thereby, it is possible to control the processing shape in the case of performing the inner and outer diameter processing by chill cut described later to be substantially constant.

The surplus volume of the ring-shaped gob 3, that is, surplus glass unnecessary for forming the main bodies 11 A and 12 A is extruded into the space 27 and is formed on the outer peripheral parts 11 C and 12 C.
At this time, the space 27 is not completely filled so that a certain amount of space remains so that the surplus volume of the ring-shaped gob 3 does not enter the contact portion 26 at this time. Is preferred.

On the other hand, in the space of the press die that forms the inner holes 11B and 12B of the glass substrates 11 and 12, glass that exceeds the volume of the space is moved due to the movement of the surplus volume to the center. It is preferable to adjust the shape and volume of the ring-shaped gob 3 so as not to enter. This means that if there is glass that cannot be accommodated in the space where the inner hole portions 11B and 12B are to be formed, a pressing pressure is required so that the entire glass can be pushed again toward the outer peripheral portion. Because.

Considering the movement of the glass when the ring-shaped gob 3 is directly pressed, the ring-shaped gob 3
Is preferably formed on the groove 21 in the trapezoidal mold 19A, and on the groove 24 forming the main body 12A of the glass substrate 12 in the wedge mold 20A.

As the press upper and lower molds used in the method for manufacturing a glass substrate of the present invention, tungsten carbide and metal carbide having good thermal conductivity, good heat shock resistance, oxidation resistance, wear resistance and the like are used. Alternatively, a ceramic material such as a metal nitride is suitably used.

The shapes of the glass substrates 11 and 12 are as follows:
The shape is not limited to the trapezoidal shape and the wedge shape described above, and one surface may have a trapezoidal shape and the other surface may have a wedge shape. In this case, there is no restriction on which shape of the press upper die and the lower press die to use. Further, in the glass substrate 11 having a trapezoidal shape, the inner hole portion 11B, the outer peripheral portion 11C, and the
A trapezoidal wedge shape in which a notch 13 is formed at the boundary with A may be used. It goes without saying that the shape of the press surface of the press upper and lower dies used for forming such a trapezoidal wedge-shaped glass substrate is complementary to the surface shape of the glass substrate.

Next, the glass substrate 1 thus manufactured
The post-processing steps 1 and 12 will be described. Glass substrate 1
After the inner and outer diameters are processed after the direct pressing, the crystallization process is performed on 1 and 12.

Here, the inner and outer diameters of the trapezoidal glass substrate 11 shown in FIG. 3A are processed as shown in FIG. 5 by the inner and outer diameter concentric cup grindstones 41 (hereinafter simply referred to as “cup grindstones 4”).
1 ". ) Is preferably performed. The cup grindstone 41 is formed by arranging an inner diameter grindstone 41A and an outer diameter grindstone 41B concentrically. The cup grindstone 41 is pressed against the glass substrate 11 while rotating the cup grindstone 41, thereby forming an inner hole in the glass substrate 11. 11B and outer peripheral part 11C are cut from main part 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.

When the inner and outer diameters of the wedge-shaped glass substrate 12 shown in FIG. 3B are to be processed for the inner and outer diameters using the cup grindstone 41, the wedge-shaped glass substrate 12 is heated to a high temperature called a chill cut. A jig made of a cooled metal or the like is brought into contact with the notch 13 formed on the glass substrate 12, particularly, at the bottom where the thickness of the glass substrate 12 is the thinnest, and utilizing the thermal strain generated there. Thus, a method of cutting the glass substrate 12 at the position where the notch 13 is formed is suitably used, and processing can be performed easily and in a short time.

The chill cut needs to be performed in a state where the glass substrate 12 is heated to a predetermined temperature or higher. However, the glass substrate 12 immediately after directly pressing the ring-shaped gob 3 has a wedge shape of 20A · Since the glass substrate 12 is kept at a temperature higher than the preheating temperature of 20B, it is not necessary to heat the glass substrate 12 again.

FIG. 6 is an explanatory diagram of the chill cut. Here, a trapezoidal wedge-shaped glass substrate 17 is shown. The notch 13 provided on the glass substrate 17 is provided with a cooled concentric inner diameter processing blade 15A and an outer diameter processing blade 15B.
A metal jig 15 having a hole is brought into contact with the metal jig 15 to apply a thermal shock to generate a crack in the notch 13 so that the inner hole portion 17B
Then, the outer peripheral portion 17C is separated from the main body portion 17A. Here, as a shape of the notch 13 for satisfactorily performing the chill cut, a V-shape as shown in FIG. 3B or FIG. 6 is suitably adopted. It should be noted that the chill cut is preferably used even in the inner and outer diameter processing of the wedge-shaped glass substrate 12 shown in FIG.

The main bodies 11 A, 12 A, and 17 of the glass substrates 11, 12, and 17 obtained through the inner and outer diameter processing described above.
FIG. 7A shows a glass substrate 18 having a slope 14 or a notch 13 on its inner and outer circumferences, as shown in FIG.
Such a slope of the slope portion 14 and the notch 13 becomes the chamfer 16 itself to be formed on the inner and outer circumferences of the product.

Therefore, according to the method for manufacturing a glass substrate of the present invention, in the method for manufacturing a conventional glass substrate,
Since chamfering, which was separately indispensable, is performed simultaneously during direct pressing and inner / outer diameter processing of the ring-shaped gob 5, there is no need to provide a separate chamfering process. It is advantageous.

The glass substrate 18 thus manufactured
However, when the glass is crystallized glass, a crystallization treatment is performed after inner and outer diameter processing. Due to this crystallization process, a slight volume change occurs in the glass substrate 18, and the volume change causes the concentricity processing of the inner and outer diameters to be the next step (hereinafter referred to as “concentricity processing”). It is preferable to design the shape of the glass substrate, that is, the shape of the press upper and lower dies, so that the processing allowance in the above does not increase.

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 18 does not stand up. As an abrasive, an end surface polishing step is added by a nylon brush. Finally, both surfaces of the glass substrate are finely polished so that dimensional characteristics and surface characteristics required for the product are satisfied. In addition, as a method of fine polishing, using a resin grindstone of # 600,
A method in which the number of rotations is from 00 rpm to 5000 rpm is preferable.

As described above, the manufacturing method of the glass substrate of the present invention has been described by taking as an example the manufacture of a flat ring-shaped glass substrate for a hard disk. However, the present invention is not limited to this and can be used in various other ways. Can be used for producing a glass substrate. Therefore, it is needless to say that the present invention is not limited to the above embodiment.

For example, even when the press lower die 1 shown in FIG. 1 and the same press upper die are used,
By adjusting the inner and outer diameters of the nozzle 5 for dropping the molten glass 7 and dropping the ring-shaped gob 3, the ring-shaped gob 3 is deformed into a disk-shaped gob by utilizing the viscosity and surface tension of the ring-shaped gob 3 itself. By performing the press treatment, a disk-shaped glass substrate can be easily manufactured.

The glass substrate for a hard disk currently has an average thickness of 0.645 mm as a product,
The parallelism is 6 μm or less, the flatness is 5 μm or less, and the surface roughness is required to be 0.1 μm or less in Ra. However, by the direct press of the ring-shaped gob, the average thickness is 0.7 mm, A glass substrate having a parallelism of 10 μm or less, a flatness of 10 μm or less, and a surface roughness Ra of 0.2 μm or less can be obtained.

Further, the crystallization process 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 0.69 mm,
A glass substrate having a shape with a parallelism of 10 μm or less, a flatness of 5 μm or less, and a surface roughness of 0.2 μm or less in Ra is obtained. Finally, the average required thickness of the product is 0.645 mm, the parallelism is 6 μm or less, and the flatness is 5 μm.
m or less and the surface roughness Ra of 0.1 or less are not satisfied, it is possible to obtain a glass substrate that satisfies the required shape for the product by precisely polishing with a # 600 resin grindstone. Become. Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

(Example) SiO ₂ was used as the molten glass.
There 77wt%, Al ₂ O ₃ is 5wt%, Li ₂ O is 5wt
%, The balance being SiO ₂ —Al ₂ O ₃ —L
i ₂ O-based glass was used. This glass is melted at 1400 ° C. in a glass melting furnace, and a cemented carbide press lower die (wedge type) that gives a wedge-shaped glass substrate preheated to 600 ° C. from a platinum nozzle kept at 1300 ° C. Was dropped in a ring shape. The nozzle used at this time has the shape shown in FIG. 2, and the outer diameter of the skirt is 60 mm.
φ, inner diameter is 30 mmφ. The cutting of the molten glass is performed by partially lowering the viscosity of the molten glass by a gas burner disposed below the nozzle so that the weight of the molten glass dropped on the press lower die becomes about 15 g. The cutting was performed.

Subsequently, a direct press is performed by pressing the upper press die preheated to 600 ° C. from above the formed ring-shaped gob against the lower press die, and pressing at 60 kg / cm ² for about 1 second. Was. Here, the glass substrate after the direct pressing is usually sent to the next step of the inner and outer diameter processing by chill cutting without cooling, but according to another test, the glass substrate formed at this stage has an average thickness. The value is 0.7 mm or less, and the parallelism is 1
It was confirmed that the finish was 0 μm or less.

Next, the upper press die is removed, and a cooled metal jig is applied to a notch portion of the glass substrate placed on the lower press die preheated to 600 ° C., thereby forming the inner hole portion and the outer peripheral portion. The inner and outer diameters were separated from the main body. Thereafter, the glass substrate is gradually cooled, and thus, the inner diameter becomes 2.
3.8mm ± 0.15mm, outer diameter 85.2 ± 0.15
mm glass substrate was obtained.

The obtained glass substrate was crystallized at 770 ° C. for 4 hours in a nitrogen atmosphere, and the average thickness was 0.68 mm, the parallelism was 7 μm, and the flatness was 5 μm.
m, 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,
Finally, by fine polishing with a # 600 resin grindstone, the average value of the thickness is 0.645 mm, the parallelism is 5 μm,
The flatness is 4 μm and the surface roughness is Ra at 0.08 μm.
A glass substrate (substrate) satisfying the required standard as a product was obtained. In addition, the wear amount of the press die after 10000 direct presses was 1 μm or less.

(Comparative Example) As a comparative example, a disk-shaped gob was formed by the conventional method shown in FIG. 1A, and the other conditions were the same as those of the above-described embodiment.
Direct press was performed. The parallelism of the glass substrate according to the comparative example thus manufactured was about 75 μm on average, and the wear amount of the press die after 10,000 times of direct pressing was about 3 μm.

[0058]

As described above, according to the method for manufacturing a glass substrate according to the present invention, only by direct pressing, the glass substrate has a constant thickness close to the product thickness, and has good parallelism with suppressed occurrence of sink marks. A glass substrate is manufactured.
This eliminates the need for reheat pressing,
The conventional method has the advantage that the processing time is longest and the equipment cost is high, and the processing steps such as lapping and polishing in the thickness direction are omitted. Further, since the inner and outer diameters can be easily processed and the chamfering is not required, the equipment cost and the processing cost can be reduced. Thus, according to the method for manufacturing a glass substrate of the present invention, a significant reduction in processing time and equipment cost can be achieved, and an excellent effect that an excellent quality glass substrate with a constant quality can be provided at low cost. To play.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram comparing the state of dropping molten glass between a conventional method and a method for manufacturing a glass substrate of the present invention.

FIG. 2 is an explanatory view showing one embodiment of a nozzle and a method for cutting molten glass used 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, and FIG. 3B illustrates a wedge shape.

FIG. 4 is an explanatory view showing an embodiment of the shape of a press upper and lower die used in the method for producing a glass substrate of the present invention, wherein (a) shows a trapezoidal shape and (b) shows a 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 the shape of a glass substrate obtained after inner and outer diameter processing in the method for manufacturing a glass substrate of the present invention.

FIG. 8 is an explanatory view showing a conventional glass substrate forming method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Press lower mold, 2 ... Gob, 3 ... Ring-shaped gob, 4 ... Nozzle, 5 ... Nozzle, 6 ... Molten glass, 7 ... Molten glass,
8A: straight pipe portion, 8B: hem portion, 9: gas burner, 11 ...
Glass substrate, 11A: main body, 11B: inner hole, 11C
... outer peripheral part, 12 ... glass substrate, 12A ... body part, 12B
... Inner hole part, 12C ... Outer peripheral part, 13 ... Notch, 14 ... Gradient part, 15 ... Metal jig, 15A ... Inner diameter processing blade, 15B ... Outer diameter processing blade, 16 ... Chamfer, 17 ... Glass substrate, 1
7A: body portion, 17B: inner hole portion, 17C: outer peripheral portion, 18
... Glass substrate, 19A / 19B ... Trapezoidal type, 20A / 20
B: wedge shape, 21: groove, 22: groove, 23: slope, 2
Reference numeral 4: groove portion, 25: V-shaped convex portion, 26: contact portion, 27: space portion, 41: inner and outer diameter concentric cup grindstones, 41: inner diameter grindstone, 4
1B: outer diameter grinding wheel, 51: nozzle, 52: molten glass, 5
3 ... shear, 54 ... trunk type, 55 ... lower type, 56 ... upper type, 5
7 ... Glass substrate.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hideto Sandaiji 2-56 Sudacho, Mizuho-ku, Nagoya-shi, Aichi Japan Inside Nihon Insulator Co., Ltd.

Claims (9)

[Claims] 1. A method for producing a glass substrate, comprising a step of press-molding molten glass into a predetermined shape using a press upper and lower mold, wherein when the molten glass is dropped on a lower press mold, the molten glass is formed into a ring. A method for manufacturing a glass substrate, wherein the glass substrate is formed into a shape. 2. The ring-shaped molten glass has a thickness of 10 μm.
The method for producing a glass substrate according to claim 1, wherein the glass substrate is press-molded into a glass substrate having the following parallelism. 3. The method for producing a glass substrate according to claim 1, wherein the press upper and lower dies are provided with contact portions which can be directly fitted to each other without interposing the ring-shaped molten glass therebetween. 4. The glass according to any one of claims 1 to 3, wherein a space is provided in an outer peripheral portion of the press upper and lower molds so that an excess volume of the ring-shaped molten glass is extruded. How to make a substrate. 5. The glass substrate formed from the ring-shaped molten glass has a trapezoidal shape in which the thickness of the inner hole and / or the outer periphery is smaller than that of the main body, and the shape of the inner hole and / or The method for manufacturing a glass substrate according to any one of claims 1 to 4, wherein a gradient portion formed at a boundary between the outer peripheral portion and the main body portion has a chamfer shape. 6. The shape of the glass substrate formed from the ring-shaped molten glass is a wedge shape in which a notch is formed at a boundary between an inner hole and / or an outer peripheral portion and a 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 5, wherein 7. The method for manufacturing a glass substrate according to claim 6, wherein the shape of the notch is V-shaped. 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 6 or 7. 9. The method according to claim 9, wherein the molten glass is SiO ₂ —Al ₂
O ₃ -Li ₂ O system a method for manufacturing a glass substrate according to any one of claims 1-8, characterized by using a crystallized glass.