JP2015196609A - Manufacturing method for glass substrate and manufacturing apparatus for glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a heterogeneous base material containing a silica component much from flowing out from a dissolution bath.SOLUTION: A dissolution bath includes: a first side wall arranged in a front-rear direction; a second side wall arranged in parallel with the first side wall at an interval; a plurality of electrode pairs comprising a plurality of electrodes provided on the first side wall in the front-rear directions at intervals and a plurality of electrodes provided on the second side wall in the front-rear directions at intervals; and a front side wall connecting front end parts of the first side wall and second side wall to each other and a rear side wall connecting rear-side end parts of the first side wall and second side wall to each other. The distance between the rear-side electrode pair closest to the rear side wall among the plurality of electrode pairs to the rear side wall is shorter than a distance which is a half of the distance to another electrode pair adjoining the front side of the rear-side electrode pair. In dissolution process, a current is supplied between the rear-side electrode pairs so as to heat a molten glass between the rear-side electrode pairs and the rear side wall.

Description

  The present invention relates to a glass substrate manufacturing method and a glass substrate manufacturing apparatus for manufacturing a glass substrate.

  Generally, a glass substrate is produced through a process of forming molten glass from a glass raw material and then forming the molten glass into a glass substrate. The above process includes a melting process in which a glass raw material is melted to produce a molten glass.

  In the melting tank that performs the melting treatment, electrode pairs are provided on opposite side walls, and the molten glass is heated by energizing the molten glass accommodated in the melting tank with the electrode pair (electric heating) and heated. The glass raw material is melted by introducing the glass raw material into the molten glass (see, for example, Patent Document 1).

JP 2014-9133 A

  By the way, among the glass raw materials put into the melting tank, the silica component is harder to melt than the other components of the glass raw material. For this reason, there exists a tendency for the heterogeneous substrate with many silica components to gather on the liquid level of molten glass. In particular, the molten glass stays long in the vicinity of the liquid surface of the discharge portion where the molten glass is discharged from the melting tank, and the formation of a heterogeneous base that is difficult to melt is remarkable when the molten glass is held at a high temperature for a long time.

Since the molten glass in the melting tank is energized and heated, the space between the electrode pair becomes the highest temperature portion where the temperature is the highest, and the lower the temperature is, the lower the temperature portion becomes. For this reason, while an upward flow of the molten glass occurs in the high temperature portion, a downward flow of the molten glass occurs in the low temperature portion. For example, the wall surface on which the discharge part for discharging molten glass from the melting tank is generally located at a position away from the electrode pair and is cooled by heat radiation to the outside, so that a downward flow occurs along this wall surface. Cheap. For this reason, there is a possibility that the heterogeneous substrate collected on the liquid surface of the molten glass falls due to the downward flow in the vicinity of the discharge part and is discharged from the discharge part. Since the heterogeneous substrate having a large amount of silica component has a high viscosity, if the heterogeneous substrate is discharged from the melting tank without being completely melted, there is a possibility that striae may occur in the manufactured glass substrate.
In addition, since the electric resistance of the molten glass increases as the temperature decreases, current does not flow easily when the temperature of the molten glass decreases. For this reason, if a temperature difference occurs in the molten glass in a direction perpendicular to the flow direction of the current and a high temperature portion and a low temperature portion are formed, electricity flows more easily in the high temperature portion where the electrical resistance of the molten glass is smaller, and the temperature is likely to rise. On the other hand, the lower the temperature of the electrical resistance, the less the electricity flows and the temperature tends to decrease. As a result, there is a problem that the temperature difference between the high temperature portion and the low temperature portion is further increased, local convection is generated, and the flow velocity of the molten glass is increased, so that the downward flow is accelerated.

  An object of this invention is to provide the manufacturing method and manufacturing apparatus of a glass substrate which can suppress that the heterogeneous substrate with many silica components flows out of a melting tank, without melting.

In order to solve the above-mentioned problem, a first aspect of the present invention is a method for manufacturing a glass substrate including a melting process for melting a glass raw material to produce a molten glass,
The dissolution tank for performing the melting process is:
A first side wall disposed in the front-rear direction;
A second side wall spaced in parallel with the first side wall;
A plurality of electrodes provided at intervals in the front-rear direction on the first side wall; and a plurality of electrode pairs comprising a plurality of electrodes provided at intervals in the front-rear direction on the second side wall;
A front side wall connecting front end portions of the first side wall and the second side wall;
A rear side wall that connects rear end portions of the first side wall and the second side wall, and
Of the plurality of electrode pairs, the distance between the rear electrode pair closest to the rear side wall and the rear side wall is more than half the distance from the other electrode pair adjacent to the front side of the rear electrode pair. Short,
In the melting process, a current is allowed to flow between the rear electrode pair to heat the molten glass and the rear side wall between the rear electrode pair.

Of the plurality of electrodes, the distance between the front electrode pair closest to the front side wall and the front side wall is shorter than half the distance between the other electrode pair adjacent to the rear side of the front electrode pair,
In the melting process, it is preferable that a current is passed between the front electrode pair to heat the molten glass and the front side wall between the front electrode pair.

The melting tank includes three or more pairs of the electrodes,
It is preferable that the width of the electrodes constituting each electrode pair in the front-rear direction is the same.

A second aspect of the present invention is a glass substrate manufacturing apparatus including a melting tank that melts a glass raw material to produce a molten glass,
The melting tank is
A first side wall disposed in the front-rear direction;
A second side wall spaced in parallel with the first side wall;
A plurality of electrodes provided at intervals in the front-rear direction on the first side wall; and a plurality of electrode pairs comprising a plurality of electrodes provided at intervals in the front-rear direction on the second side wall;
A front side wall connecting front end portions of the first side wall and the second side wall;
A rear side wall that connects rear end portions of the first side wall and the second side wall, and
Of the plurality of electrode pairs, the distance between the rear electrode pair closest to the rear side wall and the rear side wall is more than half the distance from the other electrode pair adjacent to the front side of the rear electrode pair. It is short.

  According to the present invention, the molten glass is heated in the vicinity of the rear side wall by flowing a current between the rear side electrode pair provided on the rear side wall side and heating the molten glass and the rear side wall between the rear side electrode pair. The downward flow of the molten glass caused by cooling can be suppressed. For this reason, it can suppress that the heterogeneous base material with many silica components descend | falls from the liquid level of a molten glass by a downward flow without melting, and is discharged | emitted without melting.

It is a figure which shows the flow of the manufacturing method of a glass substrate. It is the schematic of the manufacturing apparatus of a glass substrate. It is a perspective view of the melting tank shown in FIG. FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3. It is a VV arrow sectional view of Drawing 4. It is a horizontal sectional view of the melting tank of a comparative example. FIG. 7 is a sectional view taken along arrow VII-VII in FIG. 6. It is a temperature distribution map by the simulation in the melting tank of an Example. It is a temperature distribution figure by simulation in the melting tank of a comparative example. It is the flow velocity distribution diagram which simulated the flow velocity of the molten glass of the melting tank of an Example. It is the flow velocity distribution map which simulated the flow velocity of the molten glass of the melting tank of a comparative example.

The glass substrate manufacturing method and glass substrate manufacturing apparatus of the present invention will be described below.
(Overall overview of glass substrate manufacturing method)
Drawing 1 is a figure showing an example of a process of a manufacturing method of a glass substrate of this embodiment. The glass substrate manufacturing method includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a molding step (ST5), a slow cooling step (ST6), and a cutting step ( ST7) is mainly included. In addition, a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like may be included. The manufactured glass substrate is laminated in a packing process as necessary, and is transported to a supplier.

In the melting step (ST1), molten glass is made by heating the glass raw material. The molten glass can be heated by energization heating in which electricity is supplied to the molten glass to generate heat. Further, the glass raw material can be melted by auxiliary heating with a burner flame.
In addition, molten glass contains a clarifier. As a fining agent, tin oxide, arsenous acid, antimony, and the like are known, but not particularly limited. However, it is preferable to use tin oxide as a clarifying agent from the viewpoint of reducing environmental burden.

In the clarification step (ST2), when the molten glass is heated, bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass are generated. This bubble grows by absorbing oxygen generated by the reductive reaction of the fining agent, and floats on the liquid surface of the molten glass and is released. Thereafter, in the clarification step, by reducing the temperature of the molten glass, the reducing substance obtained by the reduction reaction of the clarifier undergoes an oxidation reaction. Thereby, gas components, such as oxygen in the bubble which remain | survives in molten glass, are reabsorbed in molten glass, and a bubble lose | disappears. The oxidation reaction and reduction reaction by the fining agent are performed by controlling the temperature of the molten glass.
In addition, the clarification process can also use the reduced pressure defoaming system which grows the bubble which exists in molten glass in a reduced pressure atmosphere, and defoams. The vacuum degassing method is effective in that no clarifier is used. However, the vacuum degassing method makes the apparatus complicated and large. For this reason, it is preferable to employ | adopt the clarification method which raises molten glass temperature using a clarifier.

In the homogenization step (ST3), the glass component is homogenized by stirring the molten glass using a stirrer. Thereby, the composition unevenness of the glass which is a cause of striae or the like can be reduced.
In the supplying step (ST4), the molten glass that has been stirred is supplied to the molding apparatus.

The molding step (ST5) and the slow cooling step (ST6) are performed by a molding apparatus.
In the forming step (ST5), the molten glass is formed into a sheet glass to make a flow of the sheet glass. An overflow downdraw method is used for molding.
In the slow cooling step (ST6), the sheet glass that has been formed and flowed is cooled to a desired thickness, so that internal distortion does not occur and warpage does not occur.
In the cutting step (ST7), the sheet glass after slow cooling is cut into a predetermined length to obtain a plate-like glass substrate. The cut glass substrate is further cut into a predetermined size to produce a glass substrate having a target size.

FIG. 2 is a schematic view of a glass substrate manufacturing apparatus that performs the melting step (ST1) to the cutting step (ST7) in the present embodiment. As shown in FIG. 2, the glass substrate manufacturing apparatus mainly includes a melting apparatus 100, a forming apparatus 200, and a cutting apparatus 300. The melting apparatus 100 includes a melting tank 110, a clarification pipe 102, a stirring tank 103, transfer pipes 104 and 105, and a glass supply pipe 106.
The melting tank 110 shown in FIG. 2 is provided with heating means such as a burner (not shown). A glass raw material to which a clarifying agent is added is charged into the melting tank, and a melting step (ST1) is performed. The molten glass melted in the melting tank 110 is supplied to the clarification tube 102 via the transfer tube 104.
In the clarification tube 102, the temperature of the molten glass MG is adjusted, and the clarification step (ST2) of the molten glass is performed using the oxidation-reduction reaction of the clarifier. The clarified molten glass is supplied to the stirring vessel 103 through the transfer pipe 105.
In the stirring vessel 103, the molten glass is stirred by the stirrer 103a and the homogenization step (ST3) is performed. The molten glass homogenized in the stirring tank 103 is supplied to the forming apparatus 200 through the glass supply pipe 106 (supply process ST4).
In the forming apparatus 200, a sheet glass is formed from molten glass by an overflow down draw method (forming step ST5) and gradually cooled (slow cooling step ST6).
In the cutting device 300, a plate-shaped glass substrate cut out from the sheet glass is formed (cutting step ST7).

(Configuration of melting tank)
Next, with reference to FIGS. 3-5, the structure of the melting tank 110 is demonstrated. 3 is a perspective view of the melting tank 110, FIG. 4 is a cross-sectional view taken along arrows IV-IV in FIG. 3, and FIG. 5 is a cross-sectional view taken along arrows V-V in FIG.
As shown in FIGS. 3 to 5, the melting tank 110 includes a front side wall 120, a rear side wall 130, a first side wall 140, a second side wall 150, a bottom part 160, a compression part 170, and a rear side. An electrode pair 181, a front electrode pair 182, and a power supply device 190 are provided. 3 to 5 is the front side, and the right side in FIGS. 3 to 5 is the rear side.

As shown in FIG. 5, the front side wall 120 is provided vertically at the front end portion of the bottom portion 160. The front side wall 120 connects the front end portions of the first side wall 140 and the second side wall 150.
As shown in FIG. 5, the rear side wall 130 is provided vertically at the end (rear side end) of the bottom 160 opposite to the front side wall 120. The rear side wall 130 connects the rear end portions of the first side wall 140 and the second side wall 150.
As shown in FIG. 4, the first side wall 140 is provided vertically from the bottom 160 so as to extend from one end of the front side wall 120 to one end of the rear side wall 130.
As shown in FIG. 4, the second side wall 150 extends from the other end of the front side wall 120 to the other end of the rear side wall 130, and the second side wall 150 forms a space between the front side wall 120 and the rear side wall 130. 1 is provided vertically from the bottom 160 so as to be sandwiched between the first side wall 140 and the first side wall 140.
The bottom 160 is horizontally provided so as to connect the lower end portions of the front side wall 120, the rear side wall 130, the first side wall 140, and the second side wall 150.
The discharge part 131 is provided in a region closer to the rear side wall 130 than the front side wall 120 of the bottom part 160, or in the rear side wall 130. 3 to 5, the discharge part 131 is provided on the rear side wall 130. The molten glass in the melting tank 110 is discharged from the discharge unit 131 to the transfer pipe 104.

A pressing portion 170 indicated by a broken line in FIG. 3 is a ceiling wall that closes the gas phase space of the melting tank 110. The pressing portion 170 is provided with a charging portion 171 into which a glass raw material is charged, a burner 172, and the like. The insertion portion 171 is provided on the front side (left side in FIG. 3) of the compression portion 170, that is, on the opposite side to the discharge portion 131. In FIG. 5, the abutment portion 170 is omitted.
The raw glass charged from the charging portion 171 is stored and melted in a space surrounded by the front side wall 120, the rear side wall 130, the first side wall 140, the second side wall 150, the bottom portion 160, and the compression portion 170. .

For the front side wall 120, the rear side wall 130, the first side wall 140, the second side wall 150, the bottom part 160, and the compression part 170, members having excellent fire resistance and high strength (rigidity) are used. be able to. Specifically, an electroformed refractory, a refractory brick or a refractory heat insulating brick can be used.
In particular, the front side wall 120, the rear side wall 130, the first side wall 140, the second side wall 150, and the layer contacting the molten glass of the bottom 160 have excellent fire resistance and high strength (rigidity). A member that can withstand erosion from molten glass for a long period of time and has a high electrical resistivity is used. Specifically, an electrocast refractory can be used, and it is particularly preferable to use a zirconia electrocast refractory.

  On the outer side of the front side wall 120, the rear side wall 130, the first side wall 140, the second side wall 150, and the layer 160 in contact with the molten glass, a heat insulating layer composed of a plurality of layers is provided. The heat insulating layer plays a role of reducing the heat radiation amount of the layer in contact with the molten glass on the front side wall 120, the rear side wall 130, the first side wall 140, the second side wall 150, and the bottom 160. 4 and 5, three heat insulating layers are provided. A fireproof brick or a fireproof heat insulating brick can be used for the heat insulation layer. As the heat insulation layer, fire bricks or fire insulation bricks having fire resistance capable of withstanding the temperature predicted by each heat insulation layer can be used. For example, in the case of the three heat insulation layers shown in FIGS. 4 and 5, the innermost heat insulation layer is a high alumina fireproof insulation brick, the middle heat insulation layer is a mullite fireproof heat insulation brick, and the outermost heat insulation layer. Can use ceramic fiber.

  A plurality of electrodes are provided on the first side wall 140 and the second side wall 150 at intervals in the front-rear direction. 3 to 5, the first electrode 181a, the third electrode 182a, and the fifth electrode 183a are provided on the first side wall 140, and the second electrode 181b, the fourth electrode 182b, and the sixth electrode are provided on the second side wall. 183b is provided.

The rear electrode pair 181 includes a first electrode 181 a provided closest to the rear sidewall 130 of the first sidewall 140 and a second electrode provided closest to the rear sidewall 130 of the second sidewall 150. It consists of an electrode 181b.
The front electrode pair 182 includes a third electrode 182a provided closest to the front sidewall 120 of the first sidewall 140 and a fourth electrode provided closest to the front sidewall 120 of the second sidewall 150. 182b.
As shown in FIG. 4, the first electrode 181a and the second electrode 181b, and the third electrode 182a and the fourth electrode 182b are opposed to each other.

  One or more electrode pairs may be further provided between the rear electrode pair 181 and the front electrode pair 182. 3 to 5, one electrode pair 183 is provided between the rear electrode pair 181 and the front electrode pair 182. The electrode pair 183 includes a fifth electrode 183a and a sixth electrode 183b. The fifth electrode 183a is provided between the first electrode 181a and the third electrode 182a on the side wall of the first side wall 140. The sixth electrode 183b is provided between the second electrode 181b and the fourth electrode 182b on the side wall of the second side wall 150.

The first electrode 181a, the second electrode 181b, the third electrode 182a, the fourth electrode 182b, the fifth electrode 183a, and the sixth electrode 183b are made of a conductive material having heat resistance. As the conductive material having heat resistance, for example, tin oxide, molybdenum, platinum, or the like can be used.
Preferably, tin oxide is used, and each electrode is integrally formed by a plurality of tin oxide blocks.
The first electrode 181a, the second electrode 181b, the third electrode 182a, the fourth electrode 182b, the fifth electrode 183a, and the sixth electrode 183b preferably have the same width in the front-rear direction. The first electrode 181a, the second electrode 181b, the third electrode 182a, the fourth electrode 182b, the fifth electrode 183a, and the sixth electrode 183b preferably have the same height.

  In the present embodiment, among the plurality of electrode pairs 181, 182, 183, the distance between the rear electrode pair 181 closest to the rear side wall 130 and the rear side wall 130 is the other electrode adjacent to the front side of the rear electrode pair 181. It is preferable that the distance is shorter than half the distance to the pair 183. 3 to 5, the distance between the rear electrode pair 181 and the rear side wall 130 is zero.

  In the present embodiment, among the plurality of electrode pairs 181, 182, and 183, the distance between the front electrode pair 182 closest to the front side wall 120 and the front side wall 120 is the other distance adjacent to the rear side of the front electrode pair 182. It is preferable that the distance is shorter than half of the distance to the electrode pair 183. 3 to 5, the distance between the front electrode pair 182 and the front side wall 120 is zero.

  The power supply device 190 is connected to the first electrode 181a and the second electrode 181b of the rear electrode pair 181 and supplies power between the first electrode 181a and the second electrode 181b. When the power supply device 190 energizes the molten glass and the rear side wall 130 between the first electrode 181a and the second electrode 181b, the molten glass and the rear side wall 130 are heated.

  In the present embodiment, since the distance between the rear electrode pair 181 and the rear side wall 130 is shorter than the half of the distance with the other electrode pair 183 adjacent to the front side of the rear electrode pair 181, the rear electrode By flowing an electric current between the pair 181 and heating the molten glass and the rear side wall 130 between the rear electrode pair 181, it is possible to suppress the molten glass from being cooled in the vicinity of the rear side wall 130. Thereby, the downflow of the cooled molten glass produced in the vicinity of the rear side wall 130 can be suppressed. For this reason, it is possible to prevent the heterogeneous substrate having a large amount of silica component collected on the liquid surface of the molten glass from descending from the liquid surface of the molten glass by the downward flow in the vicinity of the discharge unit 131 and being discharged from the discharge unit 131. it can. Under the present circumstances, it is preferable to make the average temperature of the surface which contacts the molten glass of the rear side wall 130 higher than the average temperature of the molten glass in the melting tank 110. FIG.

  As described above, the molten glass has a lower electrical resistance as the temperature rises, but the refractory constituting the rear side wall 130 also has a lower electrical resistance as the temperature rises. For this reason, in the vicinity of the melting temperature of the molten glass (particularly in the vicinity of the melting temperature of the alkali-free glass or fine alkali glass), the electrical resistance of the rear side wall 130 is also reduced. For this reason, if the temperature of the rear side wall 130 is too high, the electrical resistance of the rear side wall 130 becomes smaller than the electrical resistance of the molten glass MG. In this state, the molten glass is not only easily heated, but the melting tank 110 may be damaged due to overheating of the rear side wall 130. Therefore, the temperature of the rear side wall 130 is adjusted to a temperature range in which the electric resistance of the rear side wall 130 is larger than the electric resistance of the molten glass MG. It can be adjusted by the arrangement of the rear electrode pair 181. Further, the temperature of the rear side wall 130 can be adjusted by the arrangement of the heat insulating layer, the thermal conductivity, and the like.

  In order to sufficiently obtain the effect of heating the rear side wall 130, the distance between the rear electrode pair 181 and the rear side wall 130 is ¼ or less of the distance between the rear electrode pair 181 and the other electrode pair 183. Preferably, the first electrode 181a is provided at the rearmost end portion of the inner wall surface of the first side wall 140, and the second electrode 181b is provided at the rearmost end portion of the inner wall surface of the second side wall 150. Further preferred.

  In the present embodiment, the distance between the front electrode pair 182 and the front side wall 120 is shorter than half the distance from the other electrode pair 183 adjacent to the rear side of the front electrode pair 182, so the front electrode By flowing a current between the pair 182 and heating the molten glass and the front side wall 120 between the front electrode pair 182, it is possible to suppress the molten glass from being cooled in the vicinity of the front side wall 120. Thereby, the downward flow of the cooled molten glass produced in the vicinity of the front side wall 120 can be suppressed. For this reason, the heterogeneous substrate with a lot of silica components collected on the liquid surface of the molten glass descends from the liquid surface of the molten glass by the downward flow in the vicinity of the charging unit 121, moves to the discharge unit 131 side along the bottom 160, It is possible to suppress discharge from the discharge unit 131. At this time, the temperature of the front side wall 120 is preferably made higher than the average temperature of the molten glass in the melting tank 110.

  In order to sufficiently obtain the effect of heating the front side wall 120, the distance between the front electrode pair 182 and the front side wall 120 is preferably ¼ or less of the distance between the front electrode pair 182 and the other electrode pair 183. More preferably, the third electrode 182a is provided at the foremost end portion of the inner wall surface of the first side wall 140, and the fourth electrode 182b is provided at the foremost end portion of the inner wall surface of the second side wall 150. .

  Furthermore, when the electrode pair 183 is provided between the rear electrode pair 181 and the front electrode pair 182, a high temperature region between the rear electrode pair 181 of the molten glass and a high temperature region between the front electrode pair 182 are provided. In the central region between the two, a downward flow of the molten glass caused by a relatively low temperature can be suppressed. For this reason, the heterogeneous substrate having a large amount of silica components collected on the liquid surface of the molten glass descends from the liquid surface of the molten glass due to the downward flow generated in the central region, and moves to the discharge unit 131 side along the bottom 160. It is possible to suppress the discharge from 131.

(Composition of glass substrate)
The glass substrate used by this embodiment contains the following compositions, for example.
SiO _2: 50~70%,
Al ₂ O _3: 0~25%,
B ₂ O ₃ : 1 to 15%,
MgO: 0 to 10%,
CaO: 0 to 20%,
SrO: 0 to 20%,
BaO: 0 to 10%,
RO: Alkali-free glass containing 5 to 30% (where R is the total amount of Mg, Ca, Sr and Ba).
The glass substrate G may be a glass containing a trace amount of alkali metal. When an alkali metal is contained, the total of R ′ ₂ O is 0.10% or more and 0.5% or less, preferably 0.20% or more and 0.5% or less (where R ′ is selected from Li, Na, and K) It is preferable that the glass substrate contains at least one kind. Of course, the total of R ′ ₂ O may be less than 0.10%.

〔Example〕
As shown in FIGS. 3 to 5, a melting tank 100 in which a rear electrode pair 181 is provided at an end portion on the rear side wall 130 side and a front electrode pair 182 is provided at an end portion on the front side wall 120 side is used. The simulation of the temperature distribution in the melting tank and the flow velocity distribution of the molten glass was performed.

[Comparative Example]
The simulation of the temperature distribution in a melting tank and the flow velocity distribution of a molten glass in the case of manufacturing molten glass using a melting tank as shown in FIG. 6, FIG. 7 was performed. 6 is a horizontal sectional view similar to FIG. 4, and FIG. 7 is a sectional view taken along the arrow VII-VII in FIG. In the melting tank 200 of the comparative example shown in FIGS. 6 and 7, the rear electrode pair 281 is provided away from the rear side wall 230, and the front electrode pair 282 is provided away from the front side wall 220. . 6 and 7, the same reference numerals are given to the same components as those in FIGS. 3 to 5, and description thereof is omitted.

  FIG. 8 is a temperature distribution diagram by simulation in the melting tank of the example, and FIG. 9 is a temperature distribution diagram by simulation in the melting tank of the comparative example. In the embodiment, the molten glass at the intermediate portion between the front side wall 120 and the rear side wall 130 has a uniform temperature distribution. On the other hand, in the comparative example, it can be seen that the molten glass reaches the high temperature of the molten glass in the vicinity of the front side wall 220 and in the vicinity of the rear side wall 230 at an intermediate portion between the front side wall 220 and the rear side wall 230. Moreover, in the Example, it turns out that the temperature of the discharge part 131 vicinity of the rear side wall 130 becomes higher temperature than a comparative example.

  FIG. 10 is a flow velocity distribution diagram simulating the flow rate of the molten glass in the vicinity of the rear side wall 130 of the melting tank of the example, and FIG. It is a flow velocity distribution map. In the comparative example, the downflow of the molten glass is generated in the vicinity of the rear side wall 230, whereas in the example, the downflow of the molten glass in the vicinity of the rear side wall 130 is suppressed.

As mentioned above, although the manufacturing method of the glass substrate of this invention was demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, you may make various improvement and a change. Of course.
Although the case where the discharge part 131 is provided in the rear side wall 130 has been described in the above embodiment, the present invention is not limited thereto, and the discharge part may be provided in the bottom part 160. Moreover, in the said embodiment, although the case where the injection | throwing-in part 121 into which a glass raw material was thrown in was provided in the front side wall 120 was demonstrated, you may throw in a glass raw material from the arbitrary positions of the upper part of the melting tank 110. .

  The glass substrate manufactured by the manufacturing method of this embodiment is used suitably for the glass substrate for liquid crystal displays, the glass substrate for organic EL displays, and a cover glass, for example. In addition, it can be used as a display for a portable terminal device, a cover glass for a casing, a touch panel plate, a glass substrate of a solar cell, or a cover glass. Particularly, it is suitable for a glass substrate for a liquid crystal display using a polysilicon TFT.

DESCRIPTION OF SYMBOLS 100 Melting apparatus 102 Clarification tank 103 Agitation tank 104, 105 Transfer pipe 106 Glass supply pipe 110 Melting tank 120, 420 Front side wall 130, 430 Rear side wall 131, 431 Discharge part 140, 440 1st side wall 150, 450 2nd side wall 160, 460 Bottom 170 Compressor 171 Input portion 181, 481 Rear electrode pair 181a, 481a First electrode 181b, 481b Second electrode 182, 482 Front electrode pair 182a, 482a Third electrode 182b, 482b Fourth electrode 183, 483 Electrode pair 183a, 483a Fifth electrode 183b, 483b Sixth electrode 190 Power supply device 200 Molding device 300 Cutting device

Claims (4)

A method for producing a glass substrate including a melting process for melting a glass raw material to produce a molten glass,
The dissolution tank for performing the melting process is:
A first side wall disposed in the front-rear direction;
A second side wall spaced in parallel with the first side wall;
A plurality of electrodes provided at intervals in the front-rear direction on the first side wall; and a plurality of electrode pairs comprising a plurality of electrodes provided at intervals in the front-rear direction on the second side wall;
A front side wall connecting front end portions of the first side wall and the second side wall;
A rear side wall that connects rear end portions of the first side wall and the second side wall, and
Of the plurality of electrode pairs, the distance between the rear electrode pair closest to the rear side wall and the rear side wall is more than half the distance from the other electrode pair adjacent to the front side of the rear electrode pair. Short,
In the melting process, a current is passed between the rear electrode pair to heat the molten glass and the rear side wall between the rear electrode pair. Of the plurality of electrodes, the distance between the front electrode pair closest to the front side wall and the front side wall is shorter than half the distance between the other electrode pair adjacent to the rear side of the front electrode pair,
2. The method for producing a glass substrate according to claim 1, wherein, in the melting process, a current is passed between the front electrode pair to heat the molten glass and the front side wall between the front electrode pair. The melting tank includes three or more pairs of the electrodes,
The manufacturing method of the glass substrate of Claim 1 or 2 with which the width | variety of the front-back direction of the electrode which comprises each electrode pair is the same. An apparatus for manufacturing a glass substrate,
Including a melting tank for melting glass raw material to produce molten glass,
The melting tank is
A first side wall disposed in the front-rear direction;
A second side wall spaced in parallel with the first side wall;
A plurality of electrodes provided at intervals in the front-rear direction on the first side wall; and a plurality of electrode pairs comprising a plurality of electrodes provided at intervals in the front-rear direction on the second side wall;
A front side wall connecting front end portions of the first side wall and the second side wall;
A rear side wall that connects rear end portions of the first side wall and the second side wall, and
Of the plurality of electrode pairs, the distance between the rear electrode pair closest to the rear side wall and the rear side wall is more than half the distance from the other electrode pair adjacent to the front side of the rear electrode pair. Short glass substrate manufacturing equipment.

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