WO2019189594A1 - Intermediate glass plate manufacturing method, glass plate manufacturing method, and intermediate glass plate - Google Patents

Abstract

In the present invention, when manufacturing an intermediate glass plate from a glass raw plate, the principal surfaces on both sides of the glass raw plate are heated while the glass raw plate is supported using a jig so that the glass raw plate does not contact a heating source. While the glass raw plate which has been heated is being supported using the jig, the principal surfaces on both sides of the glass raw plate which has been heated are pressurized by being brought into contact simultaneously with a pair of dies so as to mold the intermediate glass plate. Each of the principal surfaces on both sides of the intermediate glass plate includes a peripheral region and a center region which is provided so as to be surrounded by the peripheral region. The plate thickness in the center regions is thinner than the plate thickness in the peripheral regions. The center regions are provided so as to oppose each other.

Description

Intermediate glass plate manufacturing method, glass plate manufacturing method, and intermediate glass plate

The present invention relates to an intermediate glass plate production method for producing an intermediate glass plate from a glass base plate, a glass plate production method for producing a glass plate using the intermediate glass plate, and an intermediate glass plate.

A hard disk device for data recording uses a magnetic disk in which a magnetic layer is provided on a disk-shaped nonmagnetic magnetic glass substrate.
When manufacturing a glass substrate for a magnetic disk, grinding (lapping) or polishing is performed on a main surface of a glass plate that is a base of the glass substrate for a magnetic disk that is a final product. The main surface of the glass plate is ground so as to have a predetermined thickness, and then the fine cracks formed by grinding are removed and the surface irregularities after grinding are smoothed. Is called. By providing a magnetic layer on the polished glass plate, a magnetic disk glass substrate satisfying the surface quality of the hard disk substrate can be obtained. The surface quality includes, for example, surface irregularities of a glass substrate that allows a hard disk to be read and written without error in a hard disk drive device.

The glass plate that is the base of such a glass substrate is formed by forming the molten glass into a sheet glass using a float method or a downdraw method, cutting out the glass base plate from the sheet glass, or forming a lump of molten glass as a mold, A glass base plate is produced by pressing from above and below, and the glass base plate can be obtained by shape processing.
For example, when a glass substrate for a magnetic disk is produced from a glass base plate produced by a float process, the surface roughness of the main surface after precision polishing of the glass substrate is sufficiently low, and the occurrence of defects and foreign matter is remarkable. Polishing processing using colloidal silica slurry which can be controlled is known (patent document 1).

JP 2017-190395 A

However, since the thickness of the glass base plate made by the float process is distributed with a variation of about several tens of μm among a plurality of glass base plates, grinding (in which the plate thickness is kept within a predetermined range before polishing) Lapping) is required. At this time, it is necessary to increase the grinding allowance by setting the average thickness of the glass base plates to be thick in advance in consideration of the variation in the thickness of the glass base plates. In grinding, for example, fixed abrasive grains and the main surface of the glass base plate are brought into contact with each other and rubbed. Therefore, in grinding with a large grinding allowance, the grinding time until the predetermined grinding allowance is reached is long. The productivity of the glass plate is low.
Also, since the average plate thickness varies between lots consisting of multiple glass base plates before grinding (because the average plate thickness varies between lots), the average plate thickness of each lot is measured. Therefore, the grinding conditions including the grinding time had to be adjusted as appropriate, which was a factor in reducing the production efficiency of the final product glass plate.
Furthermore, the thickness of the glass base plate made from the float process may vary greatly within a single glass base plate. In such a case, it is necessary to perform grinding with a large grinding allowance, and the grinding time is long. For this reason, the productivity of the glass plate as the final product may be low.
As described above, the average plate thickness varies between the glass base plates, and the fact that there is a large thickness distribution within one glass base plate and the plate thickness varies within one plate is the target plate thickness. It is not preferable in terms of productivity when producing a glass plate.

Therefore, the present invention can suppress the variation of the thickness of the intermediate glass plate before becoming the glass plate as the final product, and can omit the grinding treatment performed before the polishing treatment of the main surface, or the grinding treatment An object of the present invention is to provide a method for producing an intermediate glass plate capable of reducing the time required for the production, a method for producing a glass plate as a final product from the intermediate glass plate, and an intermediate glass plate .

One embodiment of the present invention is a method for producing an intermediate glass plate from a glass base plate. The method is
While supporting the glass base plate using a jig, heat treatment is performed using the heating source with the main surfaces on both sides of the glass base plate not in contact with the heating source,
While supporting the heated glass base plate using the jig, the main surfaces on both sides of the heated glass base plate are simultaneously brought into contact with a pair of molds and pressed to form an intermediate glass plate. Pressure treatment to
Is provided.

In the heat treatment, the glass base plate is preferably heated by radiant heat from a heating source provided on both sides of the glass base plate.

The minimum temperature of the main surface of the pressure-treated portion of the main surface that is pressurized by the pressure treatment is a glass transition temperature Tg + 330 ° C. or higher and a glass transition temperature Tg + 430 ° C. or lower, and the temperature distribution of the pressure-treated portion. In the heat treatment, it is preferable to heat the main surfaces on both sides of the glass base plate so that the temperature difference at 50 ° C. or less. More preferably, the temperature difference in the temperature distribution of the pressure-treated portion is 20 ° C. or less. It is even more preferable that the temperature difference in the temperature distribution of the pressure-treated portion is 10 ° C. or less.

The heating rate of the main surface in the heat treatment is preferably 55 ° C./second or more. Furthermore, the temperature rising rate is more preferably 70 ° C./second or more.

In the pressurizing treatment, it is preferable that a part of the main surface of the glass base plate is pressed against the mold and the remaining part is not pressed with the mold.

In the pressurizing process, the glass base plate is pressurized by gradually reducing the distance between the pair of molds until the pressure received by the mold from the glass base plate reaches a predetermined upper limit. Is preferred.

In the pressurizing process, the glass base plate is pressurized by gradually reducing the distance between the pair of molds until the distance between the pair of molds reaches a preset distance. preferable.

It is preferable that the decrease in the same place of the temperature on the main surface of the glass base plate to be subjected to the pressurization treatment is 100 ° C. or less from the temperature heated by the heat treatment.
The decrease is more preferably 60 ° C. or lower.

In the pressure treatment, the glass base plate is disposed so that the main surface of the glass base plate faces in the horizontal direction, and the pair of molds are sandwiched between the glass base plates from both sides in the horizontal direction. It is preferable to pressurize the glass base plate.

The glass base plate that performs the pressure treatment moves from the processing device that performs the heat treatment to the processing device that performs the pressure treatment,
The pressure treatment is preferably performed when the glass base plate stops moving.

It is preferable that the edge of the glass base plate is supported by being fixed by the jig so that the glass base plate is not displaced during the heat treatment and the pressure treatment.

In the intermediate glass plate before post-processing that is performed first after the pressure treatment, the difference between the maximum plate thickness and the minimum plate thickness in the pressure-treated portion of the glass base plate pressed by the mold is 2 μm or less. Is preferable.

The difference between the maximum plate thickness and the minimum plate thickness in the plate thickness distribution of the glass base plate before the heat treatment is preferably 0.5 to 20 μm.

Another embodiment of the present invention is a method for producing a glass plate. The manufacturing method is
The intermediate glass plate manufactured by the method for manufacturing the intermediate glass plate, a process of cutting out the pressure-treated portion pressed by the mold into a predetermined shape, and the main surface of the cut-out pressure-treated portion. A polishing process for polishing is included.

The difference in plate thickness at the same place between the pressure-treated portion before the post-treatment first performed after the pressure treatment and the glass plate after the polishing treatment is 40 μm or less.
It is preferable.

Yet another embodiment of the present invention is an intermediate glass plate.
Each of the main surfaces on both sides of the intermediate glass plate includes a peripheral region, and a central region provided surrounded by the peripheral region,
The plate thickness in the central region is thinner than the plate thickness in the peripheral region,
The central regions of the main surfaces on both sides are provided to face each other.

Yet another embodiment of the present invention is also an intermediate glass plate.
Each of the main surfaces on both sides of the intermediate glass plate includes a peripheral region, and a central region provided surrounded by the peripheral region,
The plate thickness in the central region is thinner than the plate thickness in the peripheral region,
The central region is a press surface, and the peripheral region is a non-press surface.
The difference between the maximum plate thickness and the minimum plate thickness in the central region is preferably 2 μm or less.
The difference between the maximum plate thickness and the minimum plate thickness in the central region is preferably smaller than the difference between the maximum plate thickness and the minimum plate thickness in the peripheral region.

According to the above-described method for producing an intermediate glass plate, it is possible to provide a glass plate that suppresses variations in plate thickness. Therefore, by using the intermediate glass plate manufacturing method, the glass plate manufacturing method, and the intermediate glass plate, the grinding process of the main surface performed before the polishing process can be omitted, or the time taken for the grinding process Can be reduced.

It is a perspective view of an example of the glass plate produced as a final product which is one embodiment. (A), (b) is a figure which shows an example of the intermediate body glass plate which is one Embodiment. It is an external appearance perspective view of an example of the glass base plate which is one Embodiment. It is a figure explaining an example of the method of supporting the glass base plate which is one Embodiment. It is a figure explaining an example of the heat processing which is one Embodiment. It is a figure explaining an example of the pressurization process which is one Embodiment.

FIG. 1 is a perspective view of an example of a glass plate manufactured as a final product according to an embodiment. A glass plate 1 shown in FIG. 1 is an annular thin glass plate having a circular hole in the center. The glass plate 1 can be used as a glass substrate for a magnetic disk. When the glass plate 1 is used as a magnetic disk glass substrate, the size of the magnetic disk glass substrate is not limited, but the magnetic disk glass substrate is, for example, a magnetic disk glass having a nominal diameter of 2.5 inches or 3.5 inches. The size of the substrate. In the case of a glass substrate for a magnetic disk having a nominal diameter of 2.5 inches, for example, the outer diameter is 65 mm, the inner diameter of the circular hole is 20 mm, and the plate thickness is 0.3 to 1.3 mm. Although not shown, the glass plate 1 includes a chamfered surface interposed between the main surface and the side wall surface formed on each of the pair of main surfaces, the outer end surface, and the inner end surface. The side wall surface includes the center position of the glass plate 1 in the thickness direction. The inclination angle of the chamfered surface with respect to the main surface is not particularly limited, and is 45 °, for example. A magnetic layer is formed on the main surface of the glass plate 1 to produce a magnetic disk.

According to the conventional glass plate manufacturing method, such a glass plate 1 is cut out into a circular shape from a glass base plate as shown in FIG. 3, and by performing shape processing to open a circular hole concentric with the circular shape, A disk-shaped glass plate similar to the glass plate 1 is produced. Further, end face polishing is performed on the inner end face and the outer end face of the disk-shaped glass plate. Thereafter, the main surface is ground and further polished on the end-polished glass plate. At this time, for example, one grinding and two polishings (rough polishing and fine polishing) are performed. Thereby, the target board thickness and the surface quality of a glass plate which are requested | required of the glass substrate for magnetic discs, etc. can be achieved. However, since the time required for grinding and polishing of the glass plate is long and the productivity of the glass plate of the final product is low, it is preferable that the processing time for grinding and polishing is short. The time required for grinding and polishing is determined according to the average plate thickness and surface quality of the glass plate before grinding or polishing. For example, for a glass plate with an average thickness that is thicker than the target thickness, the grinding time is lengthened, the amount of machining allowance by grinding is increased, and polishing is performed to remove large cracks and the like caused by grinding. Time also has to be increased. Therefore, it is desirable that the surface of the glass plate before grinding is close to the target plate thickness and the required surface quality. The surface quality includes, for example, flatness and surface roughness.

As described above, the plate thickness of the glass sheet produced by the conventional float method and down draw method varies depending on the location, and the variation in the average plate thickness between the glass base plates cut into a predetermined shape from the glass sheet is large. Also, the glass plate produced by pressing a lump of molten glass also has a large variation in the average plate thickness between the glass plates. For this reason, the deviation of the average plate thickness with respect to the target plate thickness is large. Therefore, the time for grinding and polishing the glass plate so that the average plate thickness becomes the target plate thickness is extremely long.

Therefore, in the present embodiment, an intermediate glass plate serving as a base of the glass plate for polishing the main surface is manufactured by the manufacturing method described below.

(Intermediate glass plate and glass base plate)
2A and 2B are views showing an example of the intermediate glass plate produced in the present embodiment. The intermediate glass 10 shown in the figure has a rectangular outer shape. However, the outer shape may be circular or elliptical, and the outer shape is not particularly limited. In FIGS. 2A and 2B, the depth of the depression in the central region 14 is shown in an emphasized manner for easy understanding.

The intermediate glass plate 10 is a plate-like glass plate, and each of the main surfaces on both sides of the intermediate glass plate 10 includes a peripheral region 12 and a central region 14 that is recessed with respect to the peripheral region 12. Except for the inner edge of the peripheral region 12 in contact with the central region 14, the intermediate glass plate 10 has a substantially constant plate thickness. The substantially constant plate thickness in the peripheral region 12 means that the difference between the maximum plate thickness and the minimum plate thickness in the peripheral region 12 is within an allowable range. “Within an allowable range” means, for example, 100 μm or less. In some cases, the inner edge of the peripheral region 12 is provided with an annularly raised portion with respect to the peripheral region 12 having a substantially constant thickness so as to surround the peripheral region 12. The central region 14 is provided surrounded by the peripheral region 12. The plate thickness between the main surfaces in the central region 14 is thinner than the plate thickness between the main surfaces in the peripheral region 12. Specifically, the surface of the central region 14 is recessed at a certain depth with respect to the surface of the peripheral region portion 12. The constant depth means that it is depressed in the range of, for example, 10 μm to 30 μm from the average main surface position (center line of surface irregularities) of the central region 14. That is, the recess depth of the central region 14 is, for example, 10 μm to 30 μm.
The central region 14 is circular, but may be rectangular or elliptical.
It is preferable that the center area | region 14 is provided in the main surface of the both sides of the intermediate body 10, and fixed hollow depth is mutually the same in the main surface of both sides. Here, that the depths of the recesses are the same means that it is within an allowable range, and the allowable range is, for example, 6 μm or less.
Moreover, it is preferable that the center area | region 14 in the main surface of both sides is provided so that it may mutually oppose.

Here, the difference between the maximum plate thickness and the minimum plate thickness in the plate thickness distribution of the central region 14 is preferably 2 μm or less, and more preferably 1 μm or less. The difference between the maximum plate thickness and the minimum plate thickness in the central region 14 is preferably smaller than the difference between the maximum plate thickness and the minimum plate thickness in the peripheral region 12. A glass plate is cut out circularly from such a central region 14 to form a glass plate. This glass plate has little variation in thickness between glass plates, and the average plate thickness of any glass plate is close to the target plate thickness. There are few glass plates.
The arithmetic average roughness Ra (JIS B0601: 2001), which is an index of the surface roughness in the central region 14, is preferably 300 nm or less, and more preferably 200 nm or less. More preferably, it is 100 nm or less.
Moreover, it is preferable that there is no surface defect having a depth of 5 μm or more at any location in the central region 14.
Moreover, by producing the intermediate glass plate 10 using an intermediate glass plate manufacturing method described later, the central region 14 becomes a pressed surface and the peripheral region 12 becomes a non-pressed surface.

Such an intermediate glass 10 is produced from the glass base plate 20 shown in FIG. FIG. 3 is an external perspective view of an example of the glass base plate 20 according to the embodiment.
The glass base plate 20 is a plate-like glass plate, and the outer shape of the glass base plate 20 shown in the figure is a rectangular shape, but it may be circular or elliptical, and the outer shape is not particularly limited.
The difference between the maximum plate thickness and the minimum plate thickness in the plate thickness distribution of the glass base plate 20 is preferably 0.5 μm to 20 μm. More preferably, the thickness is 0.5 μm to 10 μm. In the present embodiment, the glass base plate 20 is easily obtained from the glass base plate 20 because the central region 14 whose average plate thickness is in a predetermined range and whose surface quality of the main surface is improved is produced by the method described below. A glass plate that can be used is preferable. For this reason, the surface quality of the easily available glass base plate 20 may be inferior to some extent to the surface quality of the main surface of the central region 14. As the glass base plate 20, for example, a glass plate produced by a float method, a down draw method, or a press method is used. The arithmetic average roughness Ra of the glass base plate 20 by the float method or the downdraw method is 10 to 20 nm, and the arithmetic average roughness Ra of the glass base plate 20 by the press method is 0.1 to 1.0 μm.

The glass transition temperature Tg of the glass base plate 20, the intermediate glass plate 10, or the glass plate 1 is 450 to 800 ° C., which is achieved by efficiently heating the glass base plate 20 by the manufacturing method described later. It is preferable from the viewpoint of obtaining surface quality, and more preferably 480 to 750 ° C.

As the glass material of the glass base plate 20, that is, the glass material of the intermediate glass plate 10 and the glass plate 1, aluminosilicate glass, soda lime glass, borosilicate glass, or the like can be used. When producing a glass substrate for a magnetic disk, it is preferable to use an aluminosilicate glass that can be chemically strengthened and that can provide a glass substrate for a magnetic disk that is excellent in the flatness of the main surface and the strength of the substrate. it can. More preferably, it is an amorphous aluminosilicate glass.

The glass composition of the glass base plate 20, the intermediate glass plate 10, and the glass plate 1 is not limited, but according to one embodiment, converted to oxide standards and expressed in mol%,
50 to 75% of SiO ₂
Al ₂ O ₃ 1-15%,
A total of 5 to 35% of at least one component selected from Li ₂ O, Na ₂ O and K ₂ O;
0-20% in total of at least one component selected from MgO, CaO, SrO, BaO and ZnO;
0 to 10% in total of at least one component selected from ZrO ₂ , TiO ₂ , La ₂ O ₃ , Y ₂ O ₃ , Ta ₂ O ₅ , Nb ₂ O ₅ and HfO ₂ ;
An amorphous aluminosilicate glass having a composition having

Moreover, according to one embodiment, in mass% display,
SiO ₂ 57-75%,
Al ₂ O ₃ 5-20% (however, the total amount of SiO ₂ and Al ₂ O ₃ is 74% or more),
ZrO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , La ₂ O ₃ , Y ₂ O ₃ and TiO ₂ in total exceeding 0% and not more than 6%,
Li ₂ O exceeds 1% and is 9% or less,
Na ₂ O 5 to 28% (however, the mass ratio Li ₂ O / Na ₂ O is 0.5 or less),
0 to 6% of K ₂ O,
MgO 0-4%,
CaO exceeding 0% and 5% or less (however, the total amount of MgO and CaO is 5% or less, and the content of CaO is larger than the content of MgO), SrO + BaO is 0 to 3%,
An amorphous aluminosilicate glass having a composition having

According to one embodiment, as an essential component, SiO ₂ , Li ₂ O, Na ₂ O, and one or more alkaline earth metal oxides selected from the group consisting of MgO, CaO, SrO, and BaO are included. The molar ratio of the CaO content to the total content of MgO, CaO, SrO and BaO (CaO / (MgO + CaO + SrO + BaO)) may be 0.20 or less and the glass transition temperature may be 650 ° C. or more. When used in a glass substrate for a magnetic disk, the glass having such a composition is suitable for a glass substrate for a magnetic disk used for a magnetic disk for energy-assisted magnetic recording.

(Method for producing intermediate glass plate)
Hereinafter, a method of manufacturing (manufacturing) the intermediate glass plate 10 from the glass base plate 20 will be described.
The production method of the intermediate glass plate 10 is as follows:
(1) While supporting the glass base plate 20 using a jig, heat treatment is performed using the heating source so that both sides of the main surface of the glass base plate 20 are not in contact with the heating source;
(2) While supporting the heat-treated glass base plate 20 using a jig, the main glass surfaces on both sides of the heat-treated glass base plate 20 are simultaneously brought into contact with a pair of molds to pressurize the intermediate glass plate. Pressure treatment for molding 10.

FIG. 4 is a diagram illustrating an example of a method for supporting the glass base plate 20 before performing the heat treatment. FIG. 4 is a view of the main surface of the rectangular glass base plate 20 as viewed from the front. The glass base plate 20 is fixed to the carrier 30 by fixing the edge of the glass base plate 20 by the carrier 30 so that the glass base plate 20 is not displaced during the heat treatment and further during the pressure treatment. Supported. Specifically, the carrier 30 is composed of a pair of carrier plates 30a and 30b, and the glass base plate 20 is sandwiched from both sides of the glass base plate 20 by the carrier plates 30a and 30b. Each of the carrier plates 30a and 30b is provided with a through-hole 32 that is larger than the outer shape of the glass base plate 20 at a location facing each other when the glass base plate 20 is sandwiched between the carrier plates 30a and 30b. . Each of the carrier plates 30a and 30b protrudes from the inner edge of the hole 32 and has a pressing portion 34 for holding the glass base plate 20 at a location facing each other when the glass base plate 20 is sandwiched between the carrier plates 30a and 30b. Is provided. Therefore, by sandwiching the glass base plate 20 by the carrier plates 30a and 30b, the glass base plate 20 is sandwiched from both sides of the main surface of the glass base plate 20 by the pressing portions 34, and the edges of the glass base plate 20 are fixed. The Each of the main surfaces of the glass base plate 20 sandwiched between the carrier plates 30a and 30b is exposed from the holes 32. In this way, the glass base plate 20 supported by the carrier 30 is subjected to heat treatment and pressure treatment.
By fixing the edge of the glass base plate 20 with the pressing portion 34, during the heat treatment, a part of the glass base plate 20 becomes viscous due to heat and contracts due to the surface tension of the glass, and the glass base plate 20 is displaced. Can be suppressed. Further, it is possible to prevent the glass base plate 20 from being displaced by being pressed by the mold during the pressure treatment.

In the example shown in FIG. 4, three pressing portions 34 are provided on each side of the rectangular hole 32, and the edges of the glass base plate 20 are fixed by a total of twelve pressing portions 34. 30. However, the number of the pressing portions 34 is not particularly limited, and may be 16 or 8, for example. Further, the shape of the pressing portion 34 is not limited to that having a circular arc shape as illustrated.
If the holding part 34 fixes the edge of the glass base plate 20, the fixing part of the glass base plate 20 can be positioned outside the area where the mold presses in the pressurizing process described later. Although not particularly limited, for example, the position of the tip where the pressing portion 34 fixes the glass base plate 20 is preferably within a range of 0.5 to 4 mm from the edge of the glass base plate 20.

The size of the hole 32 is preferably determined according to the size of the glass base plate 20 so that the clearance distance between the edge of the glass base plate 20 and the edge of the hole 32 is in a predetermined range. When the clearance distance is equal to or less than the predetermined distance, the temperature difference between the edge of the glass base plate 20 and the central portion of the glass base plate 20 becomes large due to cooling by heat conduction from the carrier 30 to the outside during the heat treatment. The plate 20 is easily broken. The clearance distance is preferably at least 3 mm.
Further, the support of the glass base plate 20 by the carrier 30 is not limited to a method of pressing and fixing the edges of the glass base plate 20 at discrete positions in the form of the pressing portion 34, but pressing the glass base plate 20 continuously in a linear shape. A fixed method may be used. In addition, the edge of the glass base plate 20 is a chamfered surface when a chamfered surface is provided on the outer end surface of the glass base plate 20 at a location that is a certain distance from the outer peripheral edge of the main surface to the main surface side. including.

The carrier 30 supporting the glass base plate 20 is set in a moving device (not shown) and moves to a heating device that performs heat treatment.

FIG. 5 is a diagram for explaining an example of the heat treatment. In the example shown in FIG. 5, the carrier 30 sandwiching the glass base plate 20 moves downward from the top in the drawing. During this movement, the glass base plate 20 is heated by passing through a position between the pair of heating sources 40a and 40b that is a fixed distance away from the heating sources 40a and 40b.

The heating sources 40a and 40b are constituted by heaters, for example. In order to heat the glass base plate 20 uniformly, the heat sources 40a and 40b are arranged so as to heat the glass base plate 20 in a non-contact manner at a position equidistant from the moving path of the glass base plate 20. 40b is provided. By uniformly heating the glass base plate 20, variations in thickness between the intermediate glass plates 10 can be suppressed. Further, heating the glass base plate 20 uniformly does not increase the maximum temperature of the glass base plate 20 more than necessary in order to secure the minimum temperature of the glass base plate 20 suitable for the pressure treatment, It is also preferable in that energy consumption for heat generation of the sources 40a and 40b can be suppressed. For this reason, when the heating sources 40a and 40b are configured by heat generating elements, the heat generating elements generate heat so that the temperature of the main surface of the glass base plate 20 has a desired temperature distribution and generate radiant heat. The arrangement has been adjusted. The temperature of the main surface can be measured using an infrared radiation thermometer, and the arrangement of the heating elements is adjusted based on the measurement result. Moreover, the temperature demonstrated below can be obtained using an infrared radiation thermometer.

The heating sources 40a and 40b generate a large amount of heat in order to rapidly raise the temperature of the main surface of the moving glass base plate 20, and the distance between the heating sources 40a and 40b and the main surface of the glass base plate 20 is as follows. narrow. It is preferable to raise the temperature of the main surface of the glass base plate 20 at a heating rate of 55 ° C./second or more. The temperature rising rate is more preferably 70 ° C./second or more. Since the temperature of the main surface of the glass base plate 20 is raised so that the glass is in a viscous state, the glass on the surface layer including the main surface tends to flow and tends to flow vertically downward according to gravity. Such a flow is not preferable for the intermediate glass plate 10 for obtaining a constant plate thickness. For this reason, the main surface of the glass base plate 20 is heated in a short time. Moreover, in order to make the glass in the surface layer including the main surface into a viscous state and not to make the glass in the central portion in the thickness direction of the glass base plate 20 sandwiched between the surface layers into a viscous state, The main surface is heated. For example, the heating time at each position of the glass base plate 20 is preferably within 15 seconds, and more preferably within 10 seconds.

In the heat treatment, the temperature increase rate of the glass base plate 20 is extremely high, so that there is a temperature difference between the surface layer including the main surface of the glass base plate 20 and the central portion of the glass base plate 20 in the thickness direction. The glass in the surface layer of the heated glass base plate 20 is in a viscous state, but the glass in the center is in an elastic state or a viscoelastic state. In this way, by differentiating the state of the surface layer and the central glass, at least a part of the glass in the viscous state is forced to flow by the mold in the pressurizing process so that the plate thickness approaches the target plate thickness. In addition, the surface quality can be improved by eliminating cracks and scratches on the surface layer of the glass base plate 20 before the heat treatment.

When the glass base plate 20 passes through the gap between the heating source 40a and the heating source 40b, the glass base plate 20 is separated from the heating sources 40a and 40b by the same distance in order to receive heat evenly from the heating sources 40a and 40b. And let it pass. Thereby, the temperature of the main surface of the both sides of the glass base plate 20 can be made substantially the same. If there is a difference in the temperatures of the main surfaces on both sides of the glass base plate 20, the pressure treatment cannot be performed uniformly on the surface layers on both sides, and variations in the plate thickness between the plates are likely to be induced.

The temperature difference between the maximum temperature and the minimum temperature in the temperature distribution of the temperature of the main surface of the glass base plate 20 to be heated is preferably 50 ° C. or less, more preferably 20 ° C. or less, and more preferably 10 ° C. or less. Is even more preferable. The temperature of the main surface of the heated glass base plate 20 is preferably at least the glass transition temperature Tg (° C.) + 330 ° C. and the glass transition temperature Tg (° C.) + 430 ° C. at the lowest temperature, and the glass transition temperature Tg (° C. ) + 360 ° C. or higher, and glass transition temperature Tg (° C.) + 400 ° C. or lower is more preferable.
Further, in the heat treatment, as shown in FIG. 5, when the glass base plate 20 is moved from the top to the bottom along the vertical direction, the temperature of the glass base plate 20 on the upper side is reduced. It is also preferable to make a slight temperature difference within an allowable range so as to be lower than the temperature. Thereby, it can suppress that the glass of a viscous state flows downward, and can prevent a plate | board thickness from fluctuating large within the heated glass base plate 20. FIG.

The example of the heat treatment shown in FIG. 5 is a mode in which the glass base plate 20 is moved downward from above and passed between the heating sources 40a and 40b, but the movement direction of the glass base plate 20 is downward. The movement is not limited to the direction, and may be a movement from the bottom to the top, or may be a horizontal direction or a direction inclined with respect to the horizontal. The heat treatment of the glass base plate 20 is not limited to a method of heating the glass base plate 20 while moving, but may be a method of heating the stationary glass base plate 20. However, after the heat treatment, in order to start the pressure treatment within a short time so that the temperature of the main surface does not decrease beyond the allowable range, it is preferable to heat the glass base plate 20 while moving.

Next, the heat-treated glass base plate 20 is subjected to pressure treatment. In the pressurizing process, the intermediate glass plate 10 is formed by pressing the glass base plate 20 by simultaneously contacting the main surfaces on both sides of the glass base plate 20 with a pair of molds. Here, in the “simultaneous contact”, in addition to the case where there is no shift in the timing of contact, the duration of 100 minutes and 1 ms of the duration of time during which the glass base plate 20 contacts the press surface of the mold 50a, 50b. It is preferable that a deviation in timing equal to or shorter than the shorter time is included as an allowable range.
As shown in FIG. 5, in the case of a system in which the glass base plate 20 is heated while moving the carrier 30 sandwiching the glass base plate 20, the movement of the carrier 30 that has come to the place of the pressurizing device is stopped and pressurized. It is preferable to start the process.

FIG. 6 is a diagram for explaining an example of the pressurizing process. As shown in FIG. 6, the molds 50a and 50b on both sides of the main surface of the glass base plate 20 that has stopped moving are brought into contact with the main surface until a predetermined pressure is reached, or the molds 50a and 50b The glass base plate 20 is pressurized by bringing the molds 50a and 50b closer to each other until the distance reaches a predetermined distance.
The press surfaces of the molds 50a and 50b are flat surfaces, the flatness is 3 μm or less, and the arithmetic average roughness Ra of the surface irregularities is a plane of 300 nm or less, preferably 200 nm or less, more preferably 100 nm or less. ing. The press surfaces of such dies 50a and 50b are preferably formed of a material such as WC (tungsten carbide) or SiC.

The temperature of the glass base plate 20 immediately before the start of the pressure treatment is a temperature at which the glass on the surface layer including the main surface is maintained in a viscous state by the heat treatment. Therefore, it is preferable to quickly move from the position of the heating sources 40a, 40b to the position of the molds 50a, 50b. At the time when the pressure treatment is disclosed (when the mold first comes into contact with the glass base plate 20), the temperature of the main surface of the glass base plate 20 is at least the glass transition temperature Tg (° C.) + 220 ° C. The temperature is preferably Tg (° C.) + 270 ° C. to glass transition temperature Tg (° C.) + 370 ° C.
On the other hand, the central portion of the glass base plate 20 maintains the temperature from the elastic state to the viscoelastic state from the time of the heat treatment.

In order to obtain such a temperature of the glass base plate 20 at the start of the pressurizing process, the time interval from the end of heating by the heating sources 40a and 40b to the start of the pressurizing process may be 1.6 seconds or less. Preferably, it is 0.5 seconds or less.

The pressing of the glass base plates 50a and 50b may press the entire glass base plate 20, but according to one embodiment, the molds 50a and 50b may press a part of the glass base plate 20. preferable. For this reason, each type | mold 50a, 50b is comprised so that the glass base plate 20 can be simultaneously contacted and the glass base plate 20 can be pressurized with the same pressure. In the pressurization by the molds 50a and 50b, the glass in a viscous state on the surface layer including the main surface is pressurized and fluidized so as to be pushed out of the molds 50a and 50b. On the other hand, since the glass in the central portion is in an elastic state to a viscoelastic state, the flow of the glass due to the pressurization of the molds 50a and 50b is less or hardly compared to the glass on the main surface. That is, in the pressure treatment, at least a part of the glass on the surface layer flows to adjust the plate thickness of the glass base plate 20, whereby the flatness is high, the plate thickness distribution approaches a constant value, and is the target. It approaches the plate thickness. For this reason, it is preferable that the temperature distribution on the main surface at the time when the pressure treatment is disclosed is nearly uniform, and the temperatures on the main surfaces on both sides are preferably the same. The same temperature means that the temperature difference is within 5 ° C.

On the other hand, the temperature of the press surface in contact with the glass base plate 20 of the molds 50a and 50b is preferably (Tg−20 ° C.) or more and (Tg + 20 ° C.) or less, more preferably centered on the glass transition point Tg. The temperature is from (Tg−10 ° C.) to (Tg + 10 ° C.) with the glass transition point Tg as the center. Therefore, the temperature of the press surfaces of the molds 50 a and 50 b is lower than the temperature of the surface layer of the glass base plate 20. For this reason, the molds 50a and 50b are configured to cool while flowing at least a part of the glass in a viscous state on the surface layer of the glass base plate 20. The molds 50a and 50b are cooled by taking heat from the main surface of the glass base plate 20, but it is preferable that the cooling process at this time is substantially the same on both sides (they can be cooled substantially uniformly). Therefore, it is preferable that the heat conduction of the molds 50a and 50b be configured to be substantially the same. That is, it is preferable that the amounts of heat flowing from the glass base plate 20 to the mold 50a and the mold 50b are approximately equal to each other from the viewpoint of increasing flatness and reducing variation in plate thickness between the plates.

In the pressurizing apparatus, the glass base plate 20 is disposed so that the molds 50a and 50b are in contact with the glass base plate 20 at the same time, and the movement operation of the molds 50a and 50b is controlled. In the pressurizing process, from the time when the molds 50a and 50b contact the glass base plate 20 until the molds 50a and 50b come closest, that is, until the pushing operation of the molds 50a and 50b into the glass base plate 20 is completed. The time is preferably 50 milliseconds or less, and more preferably 10 milliseconds or less.

Duration of time during which the glass base plate 20 is in contact with the press surfaces of the molds 50a, 50b (time from when the molds 50a, 50b abut on the glass base plate 20 to when the molds 50a, 50b are separated from the glass base plate 20) ) Is preferably 50 milliseconds to 10 seconds. When the molds 50a and 50b are separated from the glass base plate 20, the glass on the surface layer of the glass base plate 20 is in an elastic state.

According to one embodiment, the molds 50a and 50b gradually reduce the distance between the molds 50a and 50b until the pressure received by the molds 50a and 50b from the glass base plate 20 reaches a predetermined upper limit. Thus, it is preferable that the glass base plate 20 is pressurized by a so-called pressure control method in that it can be realized by simple control of the molds 50a and 50b.
Moreover, according to one embodiment, the glass base plate 20 is made by gradually narrowing the distance between the molds 50a and 50b until the distance between the molds 50a and 50b becomes a preset distance. It is preferable to pressurize by the so-called position control method from the viewpoint that the average plate thickness can be a target plate thickness.

In the pressure control method, for example, the operation of the molds 50a and 50b can be controlled by controlling the rotational torque of a servo motor that is a drive source of the molds 50a and 50b. Since the rotational torque of the servo motor is proportional to the current flowing through the servo motor, the operation of the molds 50a and 50b can be controlled by controlling this current. The position control method can be performed, for example, by controlling the current of the servo motor while monitoring the distance between the molds 50a and 50b. Further, the position control system is provided with a guide pin protruding from one of the molds 50a and 50b with respect to the other mold, and when approaching a predetermined distance, the guide pin comes into contact with the other mold. The position control method can also be performed by preventing the molds 50a and 50b from physically approaching.

In the pressure treatment, the main surface of the glass base plate 20 may be arranged so as to face the vertical direction, and the mold may sandwich the glass base plate 20 from both sides in the vertical direction, but as shown in FIG. Placing the glass base plate 20 so that the main surface of the glass base plate 20 faces in the horizontal direction, and pressing the glass base plate 20 by sandwiching the glass base plate 20 from both sides of the molds 50a and 50b in the horizontal direction. Is preferred. By pressurizing the glass base plate 20 in this way, the glass in the viscous state on the surface layer including the main surfaces on both sides is subjected to gravity in the same direction until pressurization is started, and pressurization treatment by the molds 50a and 50b In this case, since the glass behaves symmetrically on both sides of the main surface, it is possible to reduce the factor that the surface quality of the main surface varies between the plates.
The glass base plate 20 thus pressure-treated can be removed from the carrier 30 to obtain the intermediate glass plate 10 shown in FIG.

In this embodiment, the glass plate 1 is produced from the intermediate glass plate 10 as described above. Hereinafter, the manufacturing method of the glass plate 1 which produces the glass plate 1 from the intermediate body glass plate 10 is demonstrated.
In the manufacturing method of the glass plate 1, a part of the central region 14 of the intermediate glass plate 10 is cut into a circular shape with respect to the intermediate glass plate 10 as shown in FIG. In addition, a concentric inner hole is formed, and a shape processing process is performed to form a disk-shaped glass plate. The shape processing process further includes a chamfering process for forming a chamfered surface on the end surface of the disk-shaped glass plate.

In the shape processing, for example, cutting using a scriber and chamfering using a general grindstone may be performed, but cutting using laser light and chamfering using laser light are preferably performed. . By performing cutting using laser light, the surface quality of the cut end face (outer end face, inner end face) can be improved, so there is no need for end face polishing or the end face polishing time can be greatly shortened. it can.
The method of cutting out the circular glass plate by the laser beam is not particularly limited. For example, the focal position of the laser beam is located in the thickness direction of the intermediate glass plate 10 and the focal position is the intermediate body. A method of forming a crack start portion in the intermediate glass plate 10 by moving the laser light relative to the intermediate glass plate 10 so as to draw a circle as viewed from the surface of the glass plate 10 can be mentioned. In this case, heating or the like is carried out from the formed crack starting portion, the crack is propagated toward the main surface of the intermediate glass plate 10, the glass plate is split, and the intermediate glass plate 10 is formed into a circular shape. cut.
The chamfering process using the laser beam is not particularly limited, and examples thereof include a method of chamfering the corner portion between the end surface and the main surface with a laser beam of a type different from the laser beam used for cutting out the glass plate. In this case, the laser beam to be used can be chamfered by irradiating the corner from a direction inclined at 30 to 60 degrees with respect to the main surface, and heating and softening the corner to evaporate. it can.

For the laser light used for cutting out the glass plate, for example, a YAG laser or a solid-state laser such as an ND: YAG laser is used. In this case, the wavelength of the laser light is in the range of 1030 nm to 1070 nm, for example. The laser beam is a pulse laser, and the pulse width of the laser beam is 10 ⁻¹² seconds or less (1 picosecond or less), so that excessive alteration of the glass at the focal position of the laser beam can be suppressed. It is preferable from the point. The optical energy of the laser light can be appropriately adjusted according to the pulse width and the repetition frequency of the pulse width. Providing excessive light energy with respect to the pulse width and repetition frequency tends to excessively alter the glass and tends to leave residue at the focal point.
As the laser beam used for the chamfering process, for example, a CO ₂ laser is preferably used. In this case, for example, a laser beam having a repetition period of 5 KHz or more and a power density per pulse per unit area of 100 W / cm ² or less can be used.

Next, the obtained disk-shaped glass plate is subjected to polishing of the main surface.
The polishing treatment includes first polishing and second polishing of the glass plate.
In the first polishing, the main surfaces on both sides of the glass plate are polished while the glass plate is held in a holding hole provided in a polishing carrier of a known double-side polishing apparatus. The purpose of the first polishing is to adjust minute surface irregularities (microwaveness, roughness).

In the first polishing treatment, the main surface of the glass plate is polished using a double-side polishing apparatus equipped with a planetary gear mechanism. Specifically, the main surfaces on both sides of the glass plate are polished while the glass plate is held in the holding holes provided in the holding member of the double-side polishing apparatus. The double-side polishing apparatus has a pair of upper and lower surface plates (upper surface plate and lower surface plate), and an annular plate-shaped polishing pad (for example, as a whole on the upper surface of the lower surface plate and the bottom surface of the upper surface plate) Resin polisher) is attached. A glass plate is sandwiched between the upper surface plate and the lower surface plate. Then, either the upper surface plate or the lower surface plate, or both of them are moved, and the glass plate and each surface plate are relatively moved while supplying a polishing slurry containing free abrasive grains. Both main surfaces of the plate can be polished. As the free abrasive grains used for the first polishing, for example, abrasive grains such as cerium oxide or zirconia are used. The size of the abrasive grains is preferably in the range of 0.5 to 3 μm in terms of average particle diameter (D50).

The glass plate may be chemically strengthened after the first polishing. In this case, for example, a mixed melt of potassium nitrate and sodium sulfate or the like is used as the chemical strengthening liquid, and the glass plate is immersed in the chemical strengthening liquid. Thereby, a compressive-stress layer can be formed on the surface of a glass plate by ion exchange.

Next, the second polishing is performed on the glass plate. The second polishing treatment aims at mirror polishing of the main surface. Also in the second polishing, a double-side polishing apparatus having the same configuration as the double-side polishing apparatus used for the first polishing is used. Specifically, the main surfaces on both sides of the glass plate are polished while the glass plate is held in the holding holes provided in the polishing carrier of the double-side polishing apparatus. In the second polishing process, the type and particle size of loose abrasive grains are different from those in the first polishing process, and the hardness of the resin polisher is different. The hardness of the resin polisher is preferably smaller than that during the first polishing process. For example, a polishing liquid containing colloidal silica as free abrasive grains is supplied between the polishing pad of the double-side polishing apparatus and the main surface of the glass plate, and the main surface of the glass plate is polished. The size of the abrasive grains used for the second polishing is preferably in the range of 5 to 50 nm in terms of average particle diameter (D50).
In the present embodiment, whether or not the chemical strengthening treatment is necessary may be appropriately selected in consideration of the glass composition and necessity. In addition to the first polishing and the second polishing, another polishing may be added, and the two main surfaces may be polished by one polishing process.
In this way, the final surface of the glass plate 1 satisfying the conditions required for the magnetic disk glass substrate or the like can be obtained by polishing the main surface of the glass plate.

In addition, the disk-shaped glass plate obtained by performing the shape processing treatment may be subjected to a grinding treatment before the first polishing. The variation in the plate thickness is small, and the difference between the average plate thickness and the target plate thickness can be reduced, so the machining allowance by grinding is less than the machining allowance in conventional grinding, and the grinding time must be shortened. Can do. Moreover, you may perform end surface grinding | polishing with respect to the inner side end surface and outer side end surface of a disk-shaped glass plate before performing 1st grinding | polishing.

As described above, after the shape processing including cutting and chamfering is performed from the intermediate glass plate 10 shown in FIG. 2A to obtain a disk-shaped glass plate, the main surface is polished. . The difference between the maximum plate thickness and the minimum plate thickness in the plate thickness distribution in the pressure-treated portion before the polishing treatment can be 2 μm or less. For this reason, grinding is not performed, or even if it is performed, the machining allowance is small. When polishing the main surface without grinding the main surface, the difference in plate thickness between the pressure-treated portion processed into a disk shape and the polished glass plate at the same place should be 40 μm or less. it can. Further, the machining allowance can be reduced to 20 μm or less by polishing one side of the main surface. Furthermore, even when the main surface is ground, the machining allowance by grinding can be reduced, so the difference in plate thickness at the same place between the pressure-processed portion processed into a disk shape and the glass plate after polishing treatment can be reduced to 40 μm. It can be:
The average plate thickness in the central region 14 of the intermediate glass plate 10 can be brought close to the target plate thickness to the extent that it is not necessary to grind the main surface of the glass plate. Since the variation can be reduced, it is not necessary to perform grinding, and the productivity when manufacturing the glass plate 1 that satisfies the target plate thickness and required quality is higher.

As described above, when manufacturing an intermediate glass plate from a glass base plate, both sides of the main surface of the glass base plate 20 are supported by the heating sources 40a and 40b while supporting the glass base plate 20 using a jig. Heat without contact. Thereafter, while supporting the glass base plate 20 using a jig, the main surfaces on both sides of the heat-treated glass base plate 20 are simultaneously brought into contact with the pair of molds 50a and 50b to pressurize the intermediate glass plate 10. Is molded. For this reason, in the pressurization process part of the intermediate body glass plate 10, the dispersion | variation in the plate thickness of the glass base plate 20 can be made small, and the dispersion | variation in the plate thickness in a board can also be made small. Furthermore, the flatness can be improved. For example, the variation in the average plate thickness between the plates in the pressure-treated portion (central region 14) of the intermediate glass plate 10 before the polishing treatment can be reduced to 1 μm or less. The difference between the maximum plate thickness and the minimum plate thickness can be 2 μm or less, and the flatness can be 4 μm or less. Furthermore, the distortion of the pressure-treated portion can be suppressed, and the retardation value can be made less than 5 nm.

Further, in the above heat treatment, the glass base plate 20 is heated by radiant heat from a heating source provided on both sides of the glass base plate 20, so that the main surface of the glass base plate 20 is efficiently and rapidly heated regardless of heat conduction. can do.

In the heat treatment, the minimum temperature of the main surface of the glass base plate 20 is the glass transition temperature Tg + 330 ° C. or more and the glass transition temperature Tg + 430 ° C. or less, and the temperature difference between the maximum temperature and the minimum temperature on the main surface is 50 ° C. or less. Therefore, the glass on the surface layer including the main surface of the glass base plate 20 can be brought into a viscous state, and can be made into a nearly uniform viscous state, and variations in plate thickness between the plates can be further suppressed. .

The heating rate of the main surface in the heat treatment is 55 ° C./second or more, so that the glass on the surface layer including the main surface of the glass base plate 20 becomes viscous and easily flows, according to gravity. The time to flow vertically downward is very short. For this reason, the change of the plate | board thickness of the glass base plate 20 from the plate | board thickness before heat processing is small. Thereby, the dispersion | variation in the board thickness between boards can be suppressed more.

In the pressurizing process, a part of the main surface of the glass base plate 20 is pressed against the molds 50a and 50b and the remaining part is not pressed by the molds 50a and 50b. In this type of pressure treatment, the glass base plate 20 can be supported using a portion that is not pressurized during the pressure treatment, so that the glass base plate 20 is prevented from being displaced at the start of the pressure treatment. Can do. In this regard, the method in which a part of the main surface of the glass base plate 20 is pressed against the molds 50 a and 50 b can perform a stable pressurizing process on the glass base plate 20.

According to one embodiment, in the pressure treatment, the distance between the molds 50a and 50b is gradually reduced until the pressure received by the molds 50a and 50b from the glass base plate 20 reaches a predetermined upper limit. It is preferable to pressurize the base plate 20. Thereby, control of the plate | board thickness of the intermediate body glass plate 10 is realizable by simple control of metal mold | die 50a, 50b.
Further, according to one embodiment, in the pressurizing process, the distance between the molds 50a and 50b is gradually reduced until the distance between the molds 50a and 50b reaches a preset distance. It is also preferable to pressurize the base plate 20. Thereby, the average board thickness in the center area | region 12 of the intermediate body glass plate 10 can be made into target board thickness.

It is preferable that the decrease in the temperature on the main surface of the glass base plate 20 to be subjected to the pressure treatment from the temperature in the heat treatment (temperature drop in the same place) is 100 ° C. or less. More preferably, it is 60 degrees C or less. Such a temperature decrease has a small amount of decrease from the temperature of the glass base plate 20 heated higher than the glass transition temperature Tg, and while maintaining the viscosity state of the glass in the surface layer including the main surface of the glass base plate 20, The pressure treatment of the glass base plate 20 can be performed effectively.

In the pressure treatment, the glass base plate 20 is arranged so that the main surface of the glass base plate 20 faces the horizontal direction, and the glass base plate 20 is sandwiched between the molds 50a and 50b from both sides in the horizontal direction. It is preferable to pressurize the plate 20. Thus, by pressing the glass base plate 20 from both sides in the horizontal direction, the glass in the viscous state on the surface layer including the main surfaces on both sides receives gravity in the same direction until pressing is started. Factors in which the surface quality varies between plates can be reduced.

The glass base plate 20 is moved from a heating device that performs heat treatment to a pressure device that performs pressure treatment, and the pressure treatment is preferably performed when the glass base plate 20 stops moving. Thereby, the dispersion | variation in the board thickness between boards can be suppressed. When pressure treatment is performed during the movement of the glass base plate 20, when the main surface of the glass base plate 20 comes into contact with the molds 50a and 50b, a part of the glass on the surface layer is displaced by the inertia due to the movement, and the plate The variation in the plate thickness along the moving direction is likely to increase.

The edge of the glass base plate 20 is preferably supported by the carrier 30 by being fixed by the carrier 30 (jigs) so that the glass base plate 20 is not displaced during the heat treatment and the pressure treatment. Thereby, it can suppress that the glass base plate 20 displaces by the thermal contraction of the glass base plate 20 during heat processing, and increases the dispersion | variation in the plate | board thickness between board | plates. , 50b abuts on the glass base plate 20, the position of the glass base plate 20 does not change and the glass base plate 20 is pressurized, so that the plate thickness between the plates is larger than when the glass base plate 20 is not supported. Can be suppressed. In addition, if the edges of the glass base plate 20 are not fixed during the heat treatment, the glass base plate 20 is shrunk by heating, which increases the variation in the plate thickness within the plate, and further increases the plate thickness variation between the plates. Absent.

The maximum plate thickness and the minimum plate thickness in the plate thickness distribution of the pressed portion of the glass base plate 20 pressed by the molds 50a and 50b after the pressing process and before the first post-processing performed after the pressing process. Can be reduced to 2 μm or less by the pressure treatment.
The difference between the maximum plate thickness and the minimum plate thickness in the plate thickness distribution of the glass base plate 20 before the heat treatment is 0.5 to 20 μm.
As described above, the difference between the maximum plate thickness and the minimum plate thickness in the plate thickness distribution of the glass base plate 20 can be reduced by the pressurizing process, and thereafter, it is necessary to perform grinding so that the plate thickness is within a predetermined range. Moreover, since the machining allowance in grinding can be reduced as compared with the prior art, the productivity of the glass plate 1 satisfying a predetermined surface quality can be improved.

Moreover, when manufacturing the glass plate 1 which satisfies predetermined surface quality as shown in FIG. 1, the pressurization process part of the intermediate glass plate 1 0 produced through the said heat processing and pressurization process is made into predetermined shape. And the main surface of the cut-out processed portion is polished. At this time, the difference in plate thickness at the same place between the cut-out pressure-treated portion and the polished glass plate can be 40 μm or less. The variation in the thickness between the plates of the pressure treatment part of the intermediate glass plate 20 is small and can approach the target plate thickness, so there is no need to grind, and even if grinding, the amount of machining allowance is Less than conventional. Thus, the machining allowance in polishing can be reduced, and the difference in plate thickness at the same place between the cut-out pressure-treated portion and the glass plate after polishing can be made 40 μm or less. When only the polishing is performed without grinding the main surface, the machining allowance on one side by polishing can be set to 20 μm or less.

(Conventional example, Example)
In order to confirm the effect of this embodiment, the intermediate glass plate 10 is produced from the glass base plate 20 using the method for manufacturing the intermediate glass plate 10 shown in FIGS. The variation of the plate thickness within the plate was examined.
The target plate thickness in the central region 14 of the intermediate glass plate 10 to be produced is 820 μm,
An 80 mm × 80 mm rectangular glass plate (average plate thickness: 830 μm to 870 μm, glass transition temperature Tg: 500 ° C.) was prepared as the glass base plate 20. The intermediate glass plate 10 was produced by using 10 glass base plates 20 in each of the following examples. Variation in the plate thickness between the glass base plates 20 (average plate thickness variation between glass plates) is more than 20 μm, variation in plate thickness (maximum difference between maximum plate thickness and minimum plate thickness) Was over 4.0 μm.
As the heating sources 40a and 40b, a Kanthal wire heater adjusted so that the heating of the glass base plate 20 is uniform is used, and the temperature of the main surface of the place that becomes the pressurizing process part by the heating process of the heating time of 10 seconds from the room temperature. And heated to at least 780 ° C. or higher.
The pressing surfaces of the molds 50a and 50b were circular with a diameter of 70 mm. The pressure applied in the pressure treatment was 30 MPa, and the temperature of the pressure surface was 480 ° C.
In addition, the edge of the glass base plate 20 was fixed at 12 places on the circumference as shown in FIG.

Table 1 below shows the specifications and evaluation results of each example.
“Temperature of the main surface after heat treatment (° C.)” in Table 1 is a value measured by an infrared radiation thermometer provided in the heat treatment apparatus. Indicates the minimum temperature.
“Temperature difference between maximum temperature and minimum temperature (° C.)” in Table 1 indicates the temperature difference between the maximum temperature and the minimum temperature of the pressure-treated portion of the main surface to be pressed.
“Heating rate of heat treatment (° C./second)” in Table 1 represents a value obtained by dividing the temperature increase due to the heat treatment by the heat treatment time.
The “decrease of the pre-pressurization temperature from the temperature immediately after the heat treatment (° C.)” in Table 1 is obtained by measuring with an infrared radiation thermometer provided in the vicinity of the pressurization surfaces of the molds 50a and 50b. It shows the decrease in the same place from the temperature heated by the heat treatment of the temperature on the main surface of the pressurized treatment portion to be pressurized just before the pressure treatment.
“Evaluation of variation in plate thickness” in the evaluation results in Table 1 is the difference between the maximum value and the minimum value of the average plate thickness in the central region 14 (pressurized portion) in the 10 intermediate glass plates 10 (plate The result of dividing the sheet thickness variation) between the following levels. Further, “Evaluation of difference between maximum plate thickness and minimum plate thickness” is the largest difference among the difference between the maximum plate thickness and the minimum plate thickness in the central region 14 (pressurized portion) of each of the 10 intermediate glass plates. The result of dividing (variation in plate thickness within the plate) by the following levels is shown.
Level C is rejected, and levels AA, A, and B are acceptable.
Level AA: 0.5 μm or less Level A: More than 0.5 μm, 1 μm or less Level B: More than 1 μm, 2 μm or less Level C: More than 2 μm

All evaluations in Examples 1 to 5 are levels AA, A, and B, and there is no level C. Variation in the plate thickness between the intermediate glass plates 10 in any of Examples 1 to 5 (“plate thickness”) Evaluation of variation in the sheet thickness)) and variation in the plate thickness ("Evaluation of difference between the maximum plate thickness and the minimum plate thickness") are also caused by variations in the plate thickness of the glass base plate 20 exceeding 4.0 μm and in the plate. It was smaller than the variation of the plate thickness.
Further, from the comparison of Examples 1 to 3, the minimum temperature of the main surface of the pressure treatment portion of the main surface is the glass transition temperature Tg + 330 ° C. or more and the glass transition temperature Tg + 430 ° C. or less, and in the temperature distribution of the pressure treatment portion Variation in the plate thickness between the plates of Example 1 that satisfies the temperature difference of 20 ° C. or less (“Evaluation of plate thickness variation”) and the variation in the plate thickness within the plate (“maximum plate thickness and minimum plate thickness” The difference evaluation “)” was smaller than the variation in the plate thickness between the plates of Examples 2 and 3 that did not satisfy this condition and the variation in the plate thickness within the plate.
Further, from the comparison between Examples 1 and 4, the plate thickness variation (“Evaluation of plate thickness variation”) between the plates of Example 1 in which the heating rate of the main surface in the heat treatment is 55 ° C./second or more and Variations in the plate thickness within the plate (“Evaluation of difference between maximum plate thickness and minimum plate thickness”) are the variations in the plate thickness between the plates of Example 4 where the rate of temperature increase is less than 55 ° C./second, and the plates in the plate. It was smaller than the thickness variation.
Moreover, from the comparison of Examples 1 and 5, the decrease in the same place from the temperature heated by the heat treatment of the main surface of the glass base plate subjected to the pressure treatment is 100 ° C. or less. Variation in plate thickness between plates (“Evaluation of plate thickness variation”) and variation in plate thickness (“Evaluation of difference between maximum plate thickness and minimum plate thickness”) It was small compared with the dispersion | variation in the board thickness of the board of a certain Example 5, and the dispersion | variation in the board thickness in a board.
From this, the effect of this embodiment is clear.

As mentioned above, although the manufacturing method of the intermediate glass plate of this invention, the manufacturing method of a glass plate, and the intermediate glass plate were demonstrated in detail, this invention is not limited to the said embodiment, and does not deviate from the main point of this invention. Of course, various improvements and changes may be made in the range.

DESCRIPTION OF SYMBOLS 1 Glass plate 10 Intermediate glass plate 12 Peripheral area | region 14 Central area | region 20 Glass base plate 30 Carrier 30a, 30b Carrier plate 32 Hole 34 Holding | maintenance part 40a, 40b Heat source 50a, 50b type

Claims (19)

1. A method for producing an intermediate glass plate from a glass base plate,
   While supporting the glass base plate using a jig, heat treatment is performed using the heating source with the main surfaces on both sides of the glass base plate not in contact with the heating source,
   While supporting the heated glass base plate using the jig, the main surfaces on both sides of the heated glass base plate are simultaneously brought into contact with a pair of molds and pressed to form an intermediate glass plate. Pressure treatment to
   The manufacturing method of the intermediate body glass plate characterized by the above-mentioned.
2. The method for producing an intermediate glass plate according to claim 1, wherein, in the heat treatment, the glass base plate is heated by radiant heat from a heating source provided on both sides of the glass base plate.
3. The minimum temperature of the main surface of the pressure-treated portion of the main surface that is pressurized by the pressure treatment is a glass transition temperature Tg + 330 ° C. or higher and a glass transition temperature Tg + 430 ° C. or lower, and the temperature distribution of the pressure-treated portion. The method for producing an intermediate glass plate according to claim 1 or 2, wherein in the heat treatment, main surfaces on both sides of the glass base plate are heated so that a temperature difference in the heat treatment is 50 ° C or less.
4. The method for producing an intermediate glass sheet according to any one of claims 1 to 3, wherein a temperature increase rate of the main surface in the heat treatment is 55 ° C / second or more.
5. 5. The pressurizing treatment according to claim 1, wherein a part of the main surface of the glass base plate is pressed against the mold and pressed, and the remaining part is not pressed with the mold. The manufacturing method of the glass plate of description.
6. In the pressurizing process, the glass base plate is pressurized by gradually reducing the distance between the pair of molds until the pressure received by the mold from the glass base plate reaches a predetermined upper limit. Item 6. The method for producing an intermediate glass sheet according to any one of Items 1 to 5.
7. The pressurizing process pressurizes the glass base plate by gradually reducing the distance between the pair of molds until the distance between the pair of molds reaches a preset distance. 6. The method for producing an intermediate glass plate according to any one of 1 to 5.
8. The decrease in temperature at the same place from the temperature heated by the heat treatment of the temperature on the main surface of the glass base plate subjected to the pressure treatment is 100 ° C. or less. The manufacturing method of the intermediate body glass plate of description.
9. In the pressure treatment, the glass base plate is disposed so that the main surface of the glass base plate faces in the horizontal direction, and the pair of molds are sandwiched between the glass base plates from both sides in the horizontal direction. The method for producing an intermediate glass plate according to any one of claims 1 to 8, wherein the glass base plate is pressurized.
10. The glass base plate that performs the pressure treatment moves from the processing device that performs the heat treatment to the processing device that performs the pressure treatment,
    The method for producing an intermediate glass sheet according to any one of claims 1 to 9, wherein the pressure treatment is performed when the movement of the glass base plate is stopped.
11. The edge of the glass base plate is supported by being fixed by the jig so that the glass base plate is not displaced during the heat treatment and the pressure treatment. The manufacturing method of the intermediate body glass plate of 1 item | term.
12. In the intermediate glass plate before post-processing that is performed first after the pressure treatment, the difference between the maximum plate thickness and the minimum plate thickness in the pressure-treated portion of the glass base plate pressed by the mold is 2 μm or less. The method for producing an intermediate glass plate according to any one of claims 1 to 11.
13. The intermediate glass plate according to any one of claims 1 to 12, wherein a difference between a maximum plate thickness and a minimum plate thickness in a plate thickness distribution of the glass base plate before the heat treatment is 0.5 to 20 µm. Production method.
14. A method of manufacturing a glass plate,
    A process of cutting a pressure-treated portion pressed by the mold of the intermediate glass sheet produced by the method for producing an intermediate glass sheet according to any one of claims 1 to 13 into a predetermined shape; A method for producing a glass plate, comprising: a polishing treatment for polishing a main surface of the cut-out processed pressure portion.
15. The difference in plate thickness at the same place between the pressure-treated portion before the post-treatment first performed after the pressure treatment and the glass plate after the polishing treatment is 40 μm or less.
    The manufacturing method of the glass plate of Claim 14.
16. An intermediate glass plate,
    Each of the main surfaces on both sides of the intermediate glass plate includes a peripheral region, and a central region provided surrounded by the peripheral region,
    The plate thickness in the central region is thinner than the plate thickness in the peripheral region,
    The intermediate glass plate, wherein the central regions of the main surfaces on both sides are provided to face each other.
17. An intermediate glass plate,
    Each of the main surfaces on both sides of the intermediate glass plate includes a peripheral region, and a central region provided surrounded by the peripheral region,
    The plate thickness in the central region is thinner than the plate thickness in the peripheral region,
    The intermediate glass plate, wherein the central region is a press surface and the peripheral region is a non-press surface.
18. The intermediate glass plate according to claim 16 or 17, wherein a difference between the maximum plate thickness and the minimum plate thickness in the central region is 2 µm or less.
19. The intermediate glass plate according to any one of claims 16 to 18, wherein a difference between the maximum plate thickness and the minimum plate thickness in the central region is smaller than a difference between the maximum plate thickness and the minimum plate thickness in the peripheral region.

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