JPH11228149A - Manufacture of glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide glass substrates having good quality and to shorten the manufacturing process for the glass substrates by annihilating shear marks generated in a gob formed by cutting molten glass subjected to dropping, etc., by a universal and simple method. SOLUTION: This method for manufacturing the glass substrates including a stage of press forming the molten glass 2 to a prescribed shape consists in press forming the gob 5 which is the molten glass 2 dropped or extruded to a press lower mold 1A by the press upper and lower molds 1A, 1B during or after heating. The press upper and lower molds preferably have contact parts which are directly mated without being interposed with the molten glass.

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.

Generally, such a method of manufacturing a glass substrate is divided into a blanking process and a substrate process, as shown in a flowchart of FIG. Here, in the blanking step, first, a molten glass material prepared to have a specific composition is poured into a press mold to perform press molding.

In this press molding, conventionally,
As shown in FIG. 10, the molten glass 52 extruded from the nozzle 51 is cut by a certain amount by a shear 53, and the molten glass 52 is dropped onto a lower die 55 surrounded by a cylindrical wall of a trunk die 54, and By pushing up the lower die 55 after covering the upper surface of the trunk die 54, the space surrounded by the upper die 56, the lower die 55 and the die 54 is densely filled with the molten glass 52, and the disk-shaped glass substrate 57 is removed. The method of manufacturing is adopted.

The glass substrate thus obtained is subjected to a crystallization treatment, and thereafter, the central portion of the glass substrate is cut to form an inner hole, and the presence or absence of a surface defect such as a chip or a crack is inspected. The glass substrate thus manufactured is called a blank.

Next, in the substrate process,
After lapping (primary lapping) the surface of the blank with an abrasive such as SiC fine powder, chamfering for processing the inner and outer diameters into predetermined dimensions and shapes is performed.
The surface is wrapped (secondary wrapping) and washed. The blank thus obtained is polished with cerium oxide fine powder to finish it to a predetermined smoothness, and then subjected to ultrasonic cleaning, IP
A cleaning is performed, and finally, the presence or absence of a surface defect or the like is inspected. The blank that has gone through the above steps is called a substrate. The substrate thus obtained is finally coated with a magnetic recording film.

[0008]

As described above, the conventional method of manufacturing a glass substrate as a product, that is, a substrate, includes many steps, and requires a long processing time such as lapping and polishing. There is a problem that the processing cost is high because it includes many steps in which the processing equipment cost and the processing consumable material cost are expensive. Further, in the formed glass substrate, there is also a problem that a raw material cost required for forming the glass substrate increases because there are many useless portions removed by lapping or the like. in addition,
In order to prevent chipping of the glass substrate and maintain mechanical strength, there is also a problem that a long processing time is required for chamfer processing which is important, and a special processing machine is required.

Further, the working environment, that is, the amount of molten glass dripped or extruded, the timing of cutting molten glass to be dropped, or the like, so that molten glass is always supplied to the press die by a certain amount. If the conditions such as viscosity control (temperature control) are not constant, there arises a problem that a glass substrate having a different thickness is formed each time.

Here, the molten glass cut by the shear and dropped on the lower press die is generally called “gob”, and is dropped onto the lower press die and on the lower press die. In some cases, the viscosity increases due to a decrease in the temperature from the time when the molding is performed to the time when the molding is actually performed, and the sufficient fluidity required at the time of the press molding cannot be obtained. In this case, even if the volume of the gob is a predetermined amount, there is a problem that it is not possible to press to a predetermined thickness and it is difficult to obtain a predetermined outer diameter.

In order to solve the problem of forming these glass substrates into a predetermined shape, as shown in FIG. 10, in a method of manufacturing a glass substrate in which a molten glass 52 is cut by a shear 53, the shear 53 comes into contact with the glass substrate. There is a quality problem in that defects called so-called "shear marks" such as shrinkage marks, scratches, and bubbles due to rapid cooling occur on the surface or inside of the molten glass 52.

In order to solve such a problem, a method of manufacturing a glass element which suppresses the generation of shear marks, particularly, mainly a lens, is disclosed in Japanese Patent Application Laid-Open Nos. 61-146721 and 2-34525. It is disclosed in, for example, JP-A-6-48746.

However, the methods for manufacturing glass elements disclosed in these publications have been made by examining the conditions and method of dripping molten glass without using a shear.
It lacks versatility in that the viscosity adjustment and dripping conditions of the molten glass must be set to appropriate values as appropriate for each glass material, and a predetermined shape unless the temperature conditions are set to keep the gob surface tension constant. It can be considered that this method requires strict control of the manufacturing conditions in that it is difficult to obtain the glass element.

[0014]

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 of the present invention is to provide a versatile and simple method for eliminating a shear mark. Another object of the present invention is to provide a high quality glass substrate and shorten the manufacturing process of the glass substrate.

That is, according to the present invention, there is provided a method for producing a glass substrate including a step of press-molding molten glass into a predetermined shape, wherein the molten glass dropped or extruded onto a lower press die is heated, and And a method of manufacturing a glass substrate, wherein press molding is performed by a press upper and lower mold.

In the method for producing a glass substrate of the present invention, a press upper and lower mold having a contact portion that can be directly fitted without using a molten glass is preferably used. It is preferable to use one in which a space for extruding the molten glass is formed in the outer peripheral portion. And it is preferable to form a chamfer in the glass substrate formed using such a press upper and lower mold at a boundary portion between the inner hole portion and / or the outer peripheral portion and the main body portion in the glass substrate.

It is also preferable that the glass substrate has a trapezoidal shape in which the thickness of the inner hole portion and / or the outer peripheral portion is smaller than that of the main body portion, and 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 preferable to use a wedge shape in which is inserted. Here, as the shape of the notch, a V-shape is preferably adopted, and means for separating the inner hole and / or the outer peripheral portion from the main body at the notch by applying a thermal shock to the notch is preferably adopted. Can be In addition, as the glass substrate, a SiO ₂ —Al ₂ O ₃ —Li ₂ O-based crystallized glass is preferably used.

[0018]

DETAILED DESCRIPTION OF THE INVENTION As described above, according to the method for manufacturing a glass substrate of the present invention, the shearing mark on the gob is eliminated by a simple method to achieve homogenization, and the gob has a suitable fluidity at the time of pressing. To have
It is possible to reliably press-mold the gob to a predetermined thickness.

Hereinafter, a method for manufacturing a glass substrate having a flat ring shape used as a glass substrate for a hard disk or the like will be described with reference to an embodiment of the present invention. The method is not limited to the production of the glass substrate for a hard disk exemplified above, but can be used for the production of various other glass substrates. Therefore, it goes without saying that the present invention is not limited to the following embodiments.

FIG. 1 is an explanatory view showing a method for forming a glass substrate in the method for manufacturing a glass substrate of the present invention. First, a molten glass 2 is pressed from a nozzle 4 into a press lower mold 1A.
And the molten glass 2 is cut by the shear 3 so that a given amount is supplied.
To form At this time, a cut mark by the shear 3 called a shear mark 6 is formed on the gob 5.

Next, the gob 5 is heated to such a degree that the shear mark 6 disappears and the entire gob 5 has a substantially flat shape, so that the gob 5 has a proper viscosity and fluidity.
The upper press die 1B is pressed against the lower press die 1A and pressed to produce a glass substrate 11 having a predetermined shape. In the next step, it is preferable to perform the inner and outer diameter processing on the glass substrate 11 thus press-formed. However, the glass substrate 11 may be sent to a subsequent step such as a reheat press step or a slow cooling step without performing the inner and outer diameter processing. .

As described above, the method for producing a glass substrate of the present invention is a method for producing a glass substrate including the step of press-molding molten glass into a predetermined shape. Press molding is performed with a press upper and lower mold while heating or after heating the glass. Hereinafter, each of these steps will be described in detail.

First, in producing the molten glass 2,
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, since unnecessary portions such as an inner hole portion and an outer peripheral portion which are separated from the glass substrate once formed in the post-processing step can be 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 2 is extruded or dropped from the nozzle 4 so that the lower die 1A for pressing is pressed.
Supplied to. Here, in order to prevent the rapid cooling and solidification of the molten glass 2 and the occurrence of a large thermal stress due to the rapid cooling and solidification of the molten glass 2, the pressing lower mold 1A takes an appropriate temperature in consideration of the glass transition point of the molten glass 2 and the like. Is preferably preheated and held.

A certain amount of molten glass 2 is pressed into a lower mold 1A.
The molten glass 2 is cut by the shear 3 so as to be supplied to
A gob 5 is formed. At this time, the cut portion of the gob 5 is cooled by the temperature difference from the shear 3, and the gob 5 comes into contact with the atmosphere, so that the surface temperature becomes lower than the internal temperature and the viscosity increases. Then, when the outer surface portion having a higher viscosity tries to fall into the interior having a lower viscosity, bubbles may be trapped therein.
Defects such as shrink marks, bubbles and scratches, which are referred to as shear marks 6, occur.

If press molding is performed with the shear mark 6 left, traces of the shear mark 6 may remain on the formed glass substrate, and partial thickness unevenness may occur. Therefore, in order to prevent such various defects from remaining on the substrate, which is a product, sufficient polishing (lapping) must be performed. As in the conventional method for manufacturing a glass substrate, a large amount of labor is required for the processing step. Must be paid.

Further, if press molding is performed in a state where the viscosity of the gob 5 is increased, sufficient fluidity is not ensured and press molding to a predetermined thickness cannot be performed. In this case as well, there is a problem that sufficient thickness polishing must be performed as in the case of removing the trace of the shear mark 6 described above. Therefore, it is necessary to remove the shear mark 6 and reduce the fluidity of the gob 5 to an appropriate value before press molding.

Therefore, in the present invention, before the gob 5 is press-formed, the gob 5 is placed on the press lower mold 1A.
Is heated to such an extent that the entire gob 5 has a substantially flat shape due to the surface tension, so that the gob 5 has a proper viscosity and fluidity. Here, the method of heating the gob 5 includes heating with a flame such as an acetylene burner, high-frequency induction heating,
Various methods such as near-infrared heating and heating with an electric heater can be mentioned as typical examples.

The viscosity of the heated gob 5 is preferably about 10 ⁵ poise or less, but when the upper press mold 1B is pressed against the lower press mold 1A, the press surface of the upper press mold 1B is Heating and melting to a low viscosity state that does not contact with water must be avoided.

In this way, the shear mark 6 disappears by heating, and the gob 5 maintained at an appropriate viscosity is formed by the press upper die 1B and the press lower die 1A preheated to the same temperature as the press lower die 1A. Press molded glass substrate 11
Becomes

As a method of performing such a series of steps, at a position where the molten glass 2 is cut by the shear 3 to form the gob 5, the gob 5 is heated to have a predetermined viscosity and shape. The lower press die 1A is moved to a position where the upper press die 1B is set, and the press upper die 1A.
There is a method of press molding into a predetermined shape according to 1B. After the gob 5 is formed, the gob 5 is moved together with the press lower die 1A to a predetermined position where the gob 5 is heated and heated to have a predetermined viscosity and shape.
A method in which A is moved to a position where the upper press die 1B is installed, and press-formed into a predetermined shape by the press upper and lower dies 1A and 1B is also suitably adopted.

Further, after the gob 5 is heated at a position where the gob 5 is formed to have a predetermined viscosity and shape, the lower press die 1A is moved to a position where the upper press die 1B is installed. There is also a method of heating at two places, for example, heating 5 and press-molding with press upper and lower dies 1A and 1B.

As described above, the heating of the gob 5 may be performed at any stage after the formation of the gob 5 and before the press molding, but the pressing takes a long time from the time when the heating of the gob 5 is completed. It is preferable that the process be performed in a state where the viscosity of the entire gob 5 is maintained at a constant level. Therefore, after the gob 5 is formed, the gob 5 may be continuously heated until the upper press die is pressed against the lower press die.

The shape of the glass substrate 11 is determined in consideration of a method of processing the inner and outer diameters in a later step, and the like. As a particularly preferable shape, the shape of the glass substrate 11 shown in FIG. Trapezoidal shapes and wedge shapes as shown. The glass substrate 11 having any of these shapes has a main body 11A to be a final glass substrate and an outer peripheral portion 11C formed by extruding surplus glass out of the supplied molten glass 2 to the outer periphery. When a glass substrate having an inner hole such as a flat ring shape is manufactured, it is preferable to provide the inner hole portion 11 </ b> B in the glass substrate 11.

The trapezoidal shape shown in FIG. 2A is an embodiment suitable for manufacturing a flat ring-shaped glass substrate having an inner hole. The inner hole portion 11B and the outer peripheral portion 11C are formed in a later step. In order to facilitate separation from the main body 11A, it is set to be thinner than the main body 11A,
A slope 14 is formed in a portion of the main body 11A on the side of the inner hole 11B and the outer periphery 11C. In the wedge shape of FIG. 2B, a notch 1 is formed at a boundary between the inner hole 11B and / or the outer peripheral portion 11C and the main body 11A.
3 are formed, and the notch 13 is formed as described later.
By applying a thermal shock to the main body 11, the inner hole 11 </ b> B and the outer
A.

In the trapezoidal glass substrate 11 illustrated in FIG. 2A, it is preferable that the inclined portion 14 is designed to be a chamfer 16, which will be described later, that is, a chamfered portion. In the wedge-shaped glass substrate 11 shown in FIG. 2B, it is preferable that the notch 13 also serves as the chamfer 16. Such a chamfer 16 prevents chipping of a product substrate,
Although important in maintaining the mechanical strength, in the present invention, the importance in terms of shortening the processing step by omitting the chamfer processing step which is indispensable in the method of manufacturing a glass substrate according to the prior art is omitted. Is very high.

As specific examples of the press upper and lower dies 1A and 1B used to form the gob 5 into these various shapes, as shown in FIGS. 3A and 3B, respectively. ), Trapezoidal dies 19A and 19B and a wedge 20A having shapes complementary to the shapes shown in FIG.
20B.

Therefore, as shown in FIG. 3A, the pressing surfaces of the trapezoid dies 19A and 19B are
1, a deep groove 21 for forming the main body 11A, a shallow groove 22 for forming the inner hole 11B and the outer periphery 11C, and a space between the inner hole 11B and the outer periphery 11C and the main body 11A. A chamfer 16 to be formed. In addition, wedge type 20A
As shown in FIG. 3B, the pressed surface of B forms a deep groove 24 for forming the main body 11A, the inner hole 11B and the outer periphery 11C, and the notch 13 in the wedge-shaped glass substrate 11. V-shaped convex portion 25 for use.

The trapezoid molds 19A and 19B and the wedge mold 2
For the upper and lower press dies such as 0A and 20B, 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 substrate 11 having a constant thickness can always be manufactured. The surplus volume of the gob 5, that is, the main body 1
Excess glass unnecessary for forming 1A is extruded into the space portion 27 to become the outer peripheral portion 11C.
In order to prevent the surplus volume of the gob 5 from entering the space, it is preferable that the space 27 is not completely filled and is set to have a size in which a certain amount of space remains.

In the case where the wedge shapes 20A and 20B are used, the processing accuracy is maintained so that the interval between the bottoms of the opposing notches 13 formed on both surfaces of the glass substrate 11 is constant. Even when the inner and outer diameters are processed by chill cutting, which will be described later, the processed shape can be controlled to be substantially constant.

The contact portions 26 and the space portions 27 provided on these various press upper and lower dies are used for the glass substrate 1 described later.
The upper and lower dies for reheat press, in which the shape is corrected by press-forming while reheating 1, are also suitably formed. Also,
For the press upper and lower molds, those made of ceramics such as tungsten carbide or metal carbide or metal nitride having good thermal conductivity are preferably used, and such materials are also used for the reheat press upper and lower molds similarly. .

The glass substrate 11 obtained through the process that satisfies the above-described conditions has not only a uniform quality due to the disappearance of the shear mark 6, but also a uniform thickness,
The feature is that the polishing depth is shallow.

The shape of the glass substrate 11 is not limited to the trapezoidal shape and the wedge shape described above, and one surface may be formed into a trapezoidal shape and the other surface may be formed into a wedge shape. In this case, there is no restriction as to which shape of the upper die and the lower die to use. Further, the glass substrate may have a trapezoidal wedge shape such that a notch 13 is formed at the boundary between the inner peripheral portion 11B and the outer peripheral portion 11C of the glass substrate 11 on the main body 11A side. It goes without saying that the shape of the press surface of the press upper and lower dies used for molding such a trapezoidal wedge-shaped glass substrate is complementary to the surface shape of the glass substrate.

Next, the glass substrate 1 thus manufactured
1 post-processing step will be described. As shown in FIG.
The order of the post-processing is such that after the inner and outer diameters of the glass substrate 11 are processed, a press process called a reheat press for correcting the shape is performed, and then the glass substrate 11 is cooled slowly, and further subjected to a crystallization process. The method is roughly divided into a method of performing reheat pressing, correcting the shape, then gradually cooling, processing the inner and outer diameters, and crystallizing. Further, there is a method of correcting the shape of the glass substrate 11 by reheat pressing, performing a crystallization treatment, and then performing inner and outer diameter processing. However, once the crystallization is performed, the strength of the glass substrate becomes large. However, when the inner and outer diameters are processed by grinding, it is disadvantageous in that the load on the grinding wheel is increased.

Regardless of which post-process is adopted, only the order is different, and the working method in each working process is the same. Therefore, first, a method of processing the inner and outer diameters will be described. The inner and outer diameters of the trapezoidal glass substrate 11 shown in FIG. 2A are processed using inner and outer diameter concentric cup grindstones 41 (hereinafter simply referred to as “cup grindstones 41”) as shown in FIG. Is preferred. The cup grindstone 41 includes an inner grindstone 41A and an outer grindstone 41.
B are formed so as to be concentrically arranged, and the cup grindstone 4
By pressing 1 against the glass substrate 11 while rotating, the inner hole portion 11B and the outer peripheral portion 11C of the glass substrate 11 are cut from the main body portion 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 glass substrate 11 on which the notch 13 is formed are performed as in the wedge-shaped glass substrate 11 shown in FIG. In the notch 13 of the glass substrate 11 heated to a high temperature called chill cut,
A jig made of a cooled metal or the like is brought into contact with the bottom portion where the thickness of the glass substrate 11 is the thinnest, and the glass substrate 11 is cut at the position where the notch 13 is formed by utilizing the thermal strain generated there. The method is suitably used, and processing can be performed simply and in a short time.

The chill cut needs to be performed in a state where the glass substrate 11 is heated to a predetermined temperature or higher.
At least, the glass substrate 11 does not need to be heated again because it is maintained at a high temperature equal to or higher than the preheating temperature of the press upper and lower dies 1A and 1B.

FIG. 6 is an explanatory diagram of the chill cut. Here, as the glass substrate 11, a trapezoidal wedge-shaped one is described, and a notch 13 provided on the glass substrate 11 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, thereby generating a crack in the notch 13, and
Then, the outer peripheral portion 11C is separated from the main body 11A. In addition, as a shape of the notch 13 for satisfactorily performing the chill cut, a V-shape as shown in FIG. 2B or FIG. 6 is suitably adopted. It should be noted that the chill cut is preferably used even when processing the inner and outer diameters of the wedge-shaped glass substrate 11 shown in FIG.

As shown in FIG. 7A, the main body 11 A of the glass substrate 11 obtained through the above-described inner / outer diameter processing becomes a glass substrate 12 having a gradient portion 14 on the inner and outer circumferences. Such a slope portion 14 is a chamfer 1 to be formed on the inner and outer peripheries of a substrate as a final product.
6 or when the reheat press is performed in the next step, the formation of the chamfer 16 is facilitated.

Next, the reheat press will be described. The reheat press improves the dimensional accuracy such as the thickness, flatness, and parallelism of the glass substrates 11 and 12, and after the inner and outer diameter processing is performed, the gradient portion 14 in the glass substrate 12 shown in FIG. This is a step of deforming the glass substrate 12 so as to adjust to the shape of the chamfer 16 shown in FIG. On the other hand, without performing inner and outer diameter machining,
When the reheat press is performed, the inclined portion 14 of the glass substrate 11 in FIG. 2A and the inclined portion 14 of the notch 13 in the glass substrate 11 of FIG.
This is a step of obtaining the glass substrate 18 by deforming the glass substrate 11 so as to adjust the shape of the chamfer 16 shown in FIG.

Therefore, the glass substrates 11 and 12 to be processed in the reheat press need to be heated and maintained at a temperature high enough to soften so as to be deformed under the pressure during the reheat press. For this reason, the reheat press puts the glass substrates 11 and 12 to be processed on the reheat press lower mold preheated to a predetermined temperature, and from there,
This is performed by pressing a preheated reheat press upper die similarly to the lower die.

As a specific example of the reheat press upper and lower mold, a trapezoid mold 29A as shown in FIGS.
・ 29B, flat plate type 30A ・ 30B or wedge type 31A ・
31B and the like. Here, FIG.
Regarding the glass substrate 11 shown in (b), regardless of whether or not the inner and outer diameter processing is performed, for example, a slope portion 14 and a notch 13 are formed as a chamfer 16 in advance, and these are formed by a reheat press. When the shape does not change significantly, the flat plate types 30A and 30B are most preferably used. That is, the flat molds 30A and 30B are used mainly for fine adjustment of the shape. In this case, wedge shapes 31A and 31B or trapezoid shapes 29A and 29B can be used.

On the other hand, when press-molding the glass substrate 11, the slope portion 14 and the notch 13 are formed as a chamfer having an approximate size, and the shape of the chamfer having an accurate size is corrected by a reheat press later. Fur 1
6 or a reheat press to form the slope 14
When the shape of the notch 13 changes greatly, the trapezoidal dies 29A and 29B are most preferably used.
A.31B can also be used.

Further, in a case where reheat pressing is performed after the inner and outer diameter processing is performed on the glass substrate 11 and a defect such as a small chipping such as chipping occurs in the processing trace during the inner and outer diameter processing, a trapezoidal shape is used. By using the 29A / 29B or the wedge-shaped 31A / 31B, the defect of the inner / outer diameter processing trace can be repaired, and the chamfer 16 can be formed again.

In order to perform such deformation of the glass substrates 11 and 12, the pressing surfaces of the trapezoid molds 29 A and 29 B are provided with a deep groove 32 for adjusting the thickness and flatness of the glass substrates 11 and 12, and a slope 14. And notch 13 for chamfer 1
6 has a slope portion 33 for reshaping. Similarly, the wedge shapes 31A and 31B have a deep groove portion 36 for adjusting the thickness and flatness of the glass substrates 11 and 12, and a slope portion 35 for reshaping the slope portion 14 into the chamfer 16.

When the glass substrate 12 after the inner and outer diameter processing is reheat-pressed using these trapezoidal dies 29A / 29B or wedge-shaped 31A / 31B, the glass substrate 18 after the reheat press is re-pressed. Figure 7
A bulge 17 as shown in FIG. 2B is formed, and the inner and outer diameters may change. However, since the change is usually not large, it can be easily processed into a predetermined shape at the time of concentricity processing described later.

When the occurrence of the bulge 17 can be predicted from the volume of the glass substrate 18 or the like,
In the press forming of the gob 5 which is the pre-processing step, it is preferable to form the notch 13 or the slope portion 14 at a position in which the bulge 17 is taken into consideration. It is preferable to determine the inner and outer diameter machining positions.

On the other hand, the press surfaces of the flat plate dies 30 A and 30 B have only the deep groove portions 34, but in particular, FIG.
When the glass substrate 12 subjected to the inner and outer diameter processing shown in FIG.
Deformation easily occurs so that the area near the inner diameter processing mark swells toward the center and the area near the outer diameter processing mark swells toward the outer circumference, so that the dimensional accuracy of flatness and parallelism is improved compared to other shapes. Features that can be. As mentioned above,
Since the flat molds 30A and 30B are used for fine adjustment of the shape, the processed inner and outer diameter shapes are not greatly deformed, and are easily formed into a predetermined shape in concentricity processing described later.

As described above, even if the inner and outer diameters of the glass substrate 12 subjected to the inner and outer diameter processing are changed by the reheat press, the shape correction processing accompanying the change is performed by the glass substrate without performing the reheat press. Compared to a processing step in which the thickness and flatness of 12 are corrected by polishing such as lapping, they are advantageous in that they can be performed simultaneously with the subsequent steps, and that they can be processed easily and in a short time. .

Further, in the method for manufacturing a glass substrate of the present invention, the chamfering step, which is indispensable separately from the conventional method for manufacturing a glass substrate, is performed irrespective of the order of inner and outer diameter processing and reheat pressing. Since it is performed simultaneously during press forming and inner and outer diameter processing of the gob 5,
This is advantageous in terms of processing steps such as processing equipment and processing time in that there is no need to perform a chamfering step.

In this way, the glass substrate that has been subjected to both the inner and outer diameter processing and the reheat press processing is sent to the slow cooling step. However, when the glass substrate is crystallized glass, the glass substrate does not pass through the slow cooling step. Subsequently, a crystallization treatment can be performed. This crystallization treatment may be performed by reheating the material that has been gradually cooled after the reheat press.

The crystallization treatment causes a slight volume change in the glass substrate, and the volume change causes the concentricity processing of the inner and outer diameters of the final glass substrate (hereinafter referred to as “concentricity”) in the next step. It is preferable that the inner and outer diameter processing positions are set in consideration of the deformation of the glass substrates 11 and 12 in the reheat press so that the processing allowance in “processing” is not increased. On the other hand, when the material of the glass substrate does not require crystallization treatment, concentricity processing is performed after a slow cooling step after reheat pressing.

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 does not stand. If necessary, cerium oxide is removed. As an abrasive, an end surface polishing step is added by a nylon brush. And finally, to satisfy the glass substrate characteristics required for the substrate,
Both surfaces of the glass substrate are finely polished to produce a product substrate. As a method of fine polishing, a method of using a # 600 resin grindstone at a rotation speed of 1000 rpm to 5000 rpm is preferable.

According to the above-described method for manufacturing a glass substrate according to the present invention, as shown in the flowchart of FIG. 4, the steps up to the completion of the substrate, which is a substrate, are different from those of the conventional manufacturing method shown in FIG. To be extremely shortened. In addition, during the manufacturing process of the glass substrate, the processing time such as polishing and lapping in the thickness direction takes the longest, and the processing process that increases the equipment cost is omitted.

As described above, according to the method for manufacturing a glass substrate of the present invention, gob having no defect such as a shear mark is press-molded, so that an extra thickness in consideration of removal of a defect such as the conventional shear mark is used. It is not necessary to press-mold a glass substrate having
There is an advantage that a glass substrate having a good parallelism and the like having a constant thickness close to the thickness of the substrate can be obtained. Therefore, it is possible to omit the lapping step of the glass substrate surface, which is indispensable for the conventional method of manufacturing a glass substrate, and has been a major cause of the high cost of the substrate. It can be shallower than before. Therefore, when the lapping step is omitted, the lapping does not cause uneven wear on the glass substrate. Thus, the processing time and the equipment cost can be reduced.

The hard disk glass substrate currently has an average thickness of 0.6 as a substrate.
The shape of 45 mm, parallelism of 6 μm or less, flatness of 5 μm or less and surface roughness of 0.1 μm or less in Ra is required, but by the combination of the above gob press forming, inner and outer diameter processing, and reheat press, After the pressing step, a glass substrate having a shape having an average thickness of 1.0 mm or less and a parallelism of 0.2 mm or less is obtained. Further, after the reheat pressing, the glass has an average thickness of 0.7 mm and a parallelism of 0.7 mm. Is 10 μm or less, the flatness is 10 μm or less, and the surface roughness Ra is 0.2 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 0.69 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. 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.

[0069]

[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 maintained at 1300 ° C.
It was extruded into a press lower mold that gave a wedge-shaped glass substrate preheated to 0 ° C. At this time, the molten glass extruded by the shear provided near the nozzle end was cut into a gob so that the weight of the molten glass supplied to the lower mold became about 15 g.

Subsequently, while the gob was heated using an acetylene burner, the gob was pressed at 120 kg / cm ² for about 1 second by a press upper die preheated to 600 ° C. to perform press molding. Here, the glass substrate after press molding is usually sent to the next step without cooling, but according to another test, the average value of the thickness of the molded glass substrate at this stage is 0.9 mm or less. , Parallelism is 0.1m
m or less. FIG. 11 shows the measurement results. In addition, such a measurement of the thickness of the glass substrate was performed at a plurality of measurement points 37 set at regular intervals on arbitrary XY orthogonal coordinates on the glass substrate 11, as shown in FIG.

Next, after press molding, the upper mold is removed from the molded glass substrate, and the cooled metal jig is placed on the glass substrate while the glass substrate is placed on the lower mold preheated to 600 ° C. The inner and outer diameters were processed by chill cutting to separate the inner hole portion and the outer peripheral portion from the main body portion by applying to the formed notch. Thus, the glass substrate after the chill cutting after the inner and outer diameter processing was gradually cooled to obtain a glass substrate having an inner diameter of 23.8 mm ± 0.15 mm and an outer diameter of 85.2 mm ± 0.15 mm.

Next, the glass substrate after the inner and outer diameter processing is
It was transferred to the reheat press lower mold by the transfer arm. Here, a flat plate type was used as the reheat press upper and lower die. The temperature of the lower mold is preheated to 650 ° C., and the upper mold similarly preheated to 650 ° C. is pressed against the lower mold at a pressure of 30 kg / cm ^2.
Press processing was performed for about 0 seconds. After removing the upper mold, the reheat-pressed glass substrate thus obtained was transferred from the lower mold to an annealing furnace set at 450 ° C. by the transfer arm.
At this stage, the glass substrate after the slow cooling had an average thickness of 0.7 mm and a parallelism of 10 μm or less.

Further, crystallization treatment of the glass substrate was performed at 770 ° C. for 4 hours in a nitrogen atmosphere, and the average value of the thickness was 0.68 mm, the parallelism was 7 μm, the flatness was 5 μm, and the surface roughness was Ra at 0. A glass substrate having a concentricity of 7 μm or less was obtained by performing concentricity processing.
By fine polishing with a 600 resin grindstone, the average value of the thickness is 0.645 mm, the parallelism is 5 μm, and the flatness is 4 μm.
As a result, a glass substrate (substrate) satisfying the required standard as a product having a surface roughness Ra of 0.08 μm was obtained.

In comparison with the above-described embodiment, as a comparative example,
A press-molded glass substrate was produced without heating the gob and under the same conditions. As shown in FIG. 12, the glass substrate of this comparative example had a thickness after the first press molding of 1.3 mm or more and a parallelism of 100 μm or more, and could not be molded to a sufficiently thin thickness. The thickness measurement in this case was performed in the same manner as in the above-described embodiment.

Further, on the surface of the glass substrate, a shear mark in which bubbles were connected was observed. This is presumably because the gob was not heated, the shear mark remained, and the viscosity of the gob increased due to natural cooling, and a sufficient press treatment could not be performed.

[0076]

As described above, in the method for manufacturing a glass substrate of the present invention, gob having no defects such as shear marks is press-molded, so that extra thickness in consideration of removing defects such as conventional shear marks is used. There is an advantage that it is not necessary to press-mold a glass substrate having the above, and a glass substrate having a good parallelism and the like having a constant thickness close to the thickness of the substrate can be obtained from the time of gob press-forming. Therefore,
The lapping process of the glass substrate surface, which is indispensable for the conventional method of manufacturing a glass substrate and has been a major cause of the high cost of the substrate, can be omitted. No wear occurs. In addition, there is an advantage that the polishing allowance in the final polishing step can be made shallower than before. Further, since the formation of the chamfer is performed simultaneously with the press forming of the gob and the inner and outer diameter working, it is not necessary to separately perform a chamfering process. Thus, according to the method for manufacturing a glass substrate of the present invention, a great reduction in processing time and a reduction in equipment cost can be achieved, and an excellent effect of providing a glass substrate of excellent quality with a constant quality can be provided at low cost. To play.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for forming a glass substrate in a method for manufacturing a glass substrate of the present invention.

FIGS. 2A and 2B are cross-sectional views showing an embodiment of a shape of a glass substrate formed by pressing in a method for manufacturing a glass substrate of the present invention, wherein FIG. 2A shows a trapezoidal shape, and FIG. .

3A and 3B are explanatory diagrams relating to the shape of a press upper and lower die used in the method of manufacturing a glass substrate of the present invention, wherein FIG. 3A shows a trapezoidal shape, and FIG. 3B shows a wedge shape.

FIG. 4 is a flowchart showing a method for manufacturing a glass substrate of the present invention.

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 illustrates a method for manufacturing a glass substrate of the present invention.
(A) is a cross-sectional view showing the shape of the glass substrate obtained after inner and outer diameter processing, (b) is a cross-sectional view showing an example of the shape of the glass substrate obtained by performing reheat pressing after inner and outer diameter processing, (C) is sectional drawing which shows an example of the shape of the glass substrate obtained by performing reheat press, without performing inner / outer diameter processing.

FIG. 8 is an explanatory diagram relating to the shape of a reheat press upper and lower die used in the method for producing a glass substrate of the present invention;
(A) shows a trapezoid type, (b) shows a flat type, (c)
Indicates a wedge shape.

FIG. 9 is a flowchart showing a conventional method for manufacturing a glass substrate.

FIG. 10 is an explanatory view showing a conventional method for forming a glass substrate.

FIG. 11 is a measurement result of a thickness distribution of a glass substrate in an example.

FIG. 12 is a measurement result of a thickness distribution of a glass substrate in a comparative example.

FIG. 13 is a plan view showing thickness measurement points of a glass substrate.

[Explanation of symbols]

1A: Press lower mold, 1B: Press upper mold, 2: Molten glass, 3: Shear, 4: Nozzle, 5: Gob, 6: Sher mark, 11: Glass substrate, 11A: Main body, 11B: Inner hole, 11C: outer peripheral portion, 12: glass substrate, 13: notch, 14: gradient portion, 15: metal jig, 15A: inner diameter processing blade, 15B: outer diameter processing blade, 16: chamfer, 17 ...
Bulge, 18: glass substrate, 19A / 19B: trapezoidal type,
20A / 20B: wedge-shaped, 21: groove, 22: groove, 23
... Slope, 24 ... Groove, 25 ... V-shaped convex, 26 ... Contact, 27 ... Space, 29A / 29B ... Trapezoid, 30A
30B: flat plate type, 31A / 31B: wedge type, 32: groove portion,
33 ... slope part, 34 ... groove part, 35 ... slope part, 36 ... groove part, 37 ... measurement point, 41 ... inner and outer diameter concentric cup grindstone, 41
A: inner diameter whetstone, 41B: outer diameter whetstone, 51: nozzle, 52
... molten glass, 53 ... shear, 54 ... trunk type, 55 ... lower die, 56 ... upper die, 57 ... glass substrate.

Continuation of front page (72) Inventor Toshiki Goto 2-56 Suda-cho, Mizuho-ku, Nagoya-shi, Aichi Japan 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, wherein the molten glass dropped or extruded on a lower press die is heated while heating, or after heating, is pressed up and down. A method for producing a glass substrate, wherein press molding is performed using a mold. 2. The method for producing a glass substrate according to claim 1, wherein the press upper and lower molds have a contact portion that can be directly fitted without passing through the molten glass. 3. The glass substrate according to claim 1, wherein the press upper and lower molds have a space for extruding an excess volume of the molten glass to an outer peripheral portion of the molten glass. Method. 4. A glass substrate formed by using the press upper and lower molds, wherein a chamfer is formed at a boundary portion between an inner hole portion and / or an outer peripheral portion and a main body portion of the glass substrate. A method for producing the glass substrate according to claim 1. 5. A glass substrate formed by using the press upper and lower molds, wherein the glass substrate 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. A method for producing the glass substrate according to claim 1. 6. A glass substrate formed by using the press upper and lower molds, wherein the glass substrate has a wedge shape with a notch at a boundary between an inner hole and / or an outer peripheral portion and a main body. The method for producing a glass substrate according to any one of claims 1 to 5. 7. The method for manufacturing a glass substrate according to claim 6, wherein the shape of the notch is V-shaped. 8. The glass substrate according to claim 6, wherein a thermal shock is applied to the notch to separate the inner hole portion and / or the outer peripheral portion from the main body portion at the notch. Method of manufacturing. 9. The method according to claim 1, wherein the glass substrate 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.