JP2018058756A - Glass substrate manufacturing method and glass substrate manufacturing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molten glass fining method capable of suppressing foreign objects of platinum group metal from mixing with molten glass.SOLUTION: In a molten glass fining method, a fining pipe 102 is formed of material containing platinum group metal, and molten glass is made to flow therethrough such that a gas phase space 120a is formed above a liquid surface. The fining pipe 102 includes, on a wall portion that comes into contact with the gas phase space, a vent hole 102a for exhausting gas inside the gas phase space 120a, and a supply hole 102b for supplying a gas inactive to the molten glass into the gas phase space 120a, and the vent hole and the supply hole are arranged spaced from each other in a flowing direction of the molten glass. Further in the method, the inactive gas is supplied from the supply hole 102a so that an oxygen concentration inside the gas phase space 120a becomes a target value or less, and meanwhile, when the oxygen concentration exceeds an allowable value, an amount of exhausting the gas from the vent hole 102a is reduced more than an amount of supplying the inert gas in a case of the oxygen concentration being the allowable value or less.SELECTED DRAWING: Figure 4

Description

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

  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 process of removing minute bubbles contained in the molten glass (hereinafter also referred to as clarification). The clarification is performed by passing the molten glass containing the clarifier in the clarifier while heating the main body (clarifier) of the clarifier and removing bubbles in the molten glass by the oxidation-reduction reaction of the clarifier. Is called. More specifically, after raising the temperature of the molten glass that has been melted and melted, the fining agent floats and defoamed, and then the temperature is lowered to melt the relatively small bubbles that remain without being defoamed. The glass is made to absorb. That is, clarification includes a defoaming process for rising and defoaming bubbles and an absorption process for absorbing small bubbles into the molten glass.

  The inner wall of the member in contact with the high-temperature molten glass before forming needs to be made of an appropriate material according to the temperature of the molten glass in contact with the member, the required quality of the glass substrate, and the like. For example, platinum group metals such as platinum and platinum alloys are usually used as the material constituting the above-mentioned clarification tube (Patent Document 1). Platinum group metals have a high melting point and are excellent in corrosion resistance against molten glass.

JP 2010-111533 A

When the molten glass passes through the refining tube in which the platinum group metal is used for the inner wall surface, the platinum group metal may be oxidized and volatilized in a portion of the heated inner wall surface that is in contact with the gas phase space. On the other hand, the platinum group metal oxide may be reduced at the position of the refining tube where the temperature is locally lowered and may adhere to the inner wall surface. The platinum group metal adhering to the inner wall surface may drop and be mixed into the molten glass and remain as a foreign substance in the glass substrate. There is a possibility that a glass substrate containing such a foreign substance is handled as a defective product.
In order to suppress such volatilization of the platinum group metal, it is known to flow an inert gas in the clarification tube to lower the oxygen concentration. However, it has been found that the oxygen concentration may not decrease even when an inert gas is allowed to flow.

  An object of this invention is to reduce the oxygen concentration in a clarification pipe | tube, and to suppress mixing of the foreign material of a platinum group metal into molten glass.

The present invention includes the following method for manufacturing a glass substrate and a glass substrate manufacturing apparatus.
(1): equipped with a clarification step of clarification of molten glass using a clarification tube,
In the clarification step, the clarification is performed while flowing the molten glass into the clarification tube so that a gas phase space is formed above the liquid surface of the molten glass,
The clarification tube is made of a material containing a platinum group metal, and has a vent hole for discharging the gas in the gas phase space on the wall portion in contact with the gas phase space, and a gas inert to the molten glass. A supply hole for supplying the gas phase space, and the vent hole and the supply hole are spaced apart from each other in the flow direction of the molten glass,
In the clarification step, the oxygen concentration is higher than the target value when the inert gas is supplied from the supply hole so that the oxygen concentration in the gas discharged from the vent hole is equal to or lower than the target value. A method for manufacturing a glass substrate, comprising: supplying the inert gas from the vent hole to the gas phase space when a first allowable value is exceeded.

(2): In the clarification step, when the inert gas is supplied from the supply hole, the oxygen concentration is lower than the first allowable value before the oxygen concentration exceeds the first allowable value, and the target When the second allowable value, which is an oxygen concentration higher than a value, is exceeded, the supply amount of the inert gas from the supply hole is determined from the supply hole when the oxygen concentration is equal to or less than the target value. The manufacturing method of the glass substrate as described in said (1) increased more than the supply amount of the said inert gas.

(3): The oxygen concentration becomes uneven in the flow direction due to the deformation of the wall portion between the vent hole and the supply hole with the use of the clarification tube. To suppress
The method for producing a glass substrate according to (1) or (2), wherein the inert gas is supplied.

(4): supplying the inert gas so as to reduce an inflow amount of outside air flowing into the gas phase space from an opening formed in the wall portion with use of the clarification tube, The manufacturing method of the glass substrate as described in any one of 1)-said (3).

(5): A correspondence relationship obtained in advance between the position of the opening formed in the wall portion with the use of the clarification tube and the change in the oxygen concentration that changes due to the opening. The method for producing a glass substrate according to any one of (1) to (4) above, wherein the position of the opening is specified from information on a change in the measured value of the oxygen concentration in the vent hole.

(6): The glass substrate according to (5), wherein the supply amount of the inert gas is adjusted according to the distance between the opening and the vent hole along the flow direction. Production method.

(7) The method for producing a glass substrate according to (5) or (6), wherein the inert gas is further supplied into the gas phase space from the opening having the specified position.

(8): In the clarification step, the inert gas is supplied from the supply hole at a controlled supply amount so that the oxygen concentration is equal to or lower than a target value, and the vent hole is controlled at a controlled discharge amount. Any one of the above (1) to (7), wherein when the oxygen concentration exceeds the first allowable value when the gas is discharged from the gas, the amount of the gas discharged from the vent hole is reduced. The manufacturing method of the glass substrate as described in any one.

(9): equipped with a clarification step of clarification of the molten glass using a clarification tube,
In the clarification step, the clarification is performed while flowing the molten glass into the clarification tube so that a gas phase space is formed above the liquid surface of the molten glass,
The clarification tube is made of a material containing a platinum group metal, and has a vent hole for discharging the gas in the gas phase space on the wall portion in contact with the gas phase space, and a gas inert to the molten glass. A supply hole for supplying the gas phase space, and the vent hole and the supply hole are spaced apart from each other in the flow direction of the molten glass,
In the clarification step, the inert gas is supplied from the supply hole at a supply amount controlled so that the oxygen concentration in the gas discharged from the vent hole is equal to or lower than a target value, and the controlled discharge is performed. When the gas is discharged from the vent hole in an amount, if the oxygen concentration exceeds a third allowable value higher than the target value, the gas discharge amount from the vent hole is reduced. A method for producing a glass substrate.

(10): In the clarification step, after reducing the amount of the gas discharged from the vent hole, the amount of the inert gas supplied from the supply hole is set to be equal to or less than the target value. The manufacturing method of the glass substrate as described in said (9) increased more than the supply amount of.

(11): The gas discharge amount is reduced so as to reduce an inflow amount of outside air flowing into the gas phase space from an opening formed in the wall portion with the use of the clarification tube. 9) The manufacturing method of the glass substrate as described in said (10).

(12): A correspondence relationship obtained in advance between a position of an opening formed in the wall portion with use of the clarification tube and a change in the oxygen concentration that changes due to the opening. The method for producing a glass substrate according to any one of (9) to (11), wherein the position of the opening is specified from information on a change in the measured value of the oxygen concentration in the vent hole.

(13) The method for producing a glass substrate according to (12), wherein the gas discharge amount is adjusted according to the distance between the opening and the vent hole along the flow direction.

(14): Further, the method for producing a glass substrate according to (12) or (13), wherein the inert gas is supplied into the gas phase space from the opening whose position is specified.

(15): The diameter of the opening is 50% or more of the diameter of the air hole, and is described in any one of (5) to (7) and (12) to (14) above. Glass substrate manufacturing method.

(16): The glass substrate according to any one of (1) to (15), wherein the supply amount of the inert gas is adjusted so that bubbles are not generated in the molten glass after the clarification. Manufacturing method.

(17): A clarification tube for refining the molten glass while passing the molten glass so that a gas phase space is formed above the liquid surface of the molten glass, and is made of a material containing a platinum group metal. The wall portion in contact with the gas phase space has a vent hole for discharging the gas in the gas phase space and a supply hole for supplying a gas inert to the molten glass into the gas phase space. And the ventilation hole and the supply hole are arranged to be separated from each other in the flow direction of the molten glass,
An inert gas supply device for supplying the inert gas into the gas phase space;
When the inert gas is supplied from the supply hole such that the oxygen concentration in the gas discharged from the vent hole is equal to or lower than a target value, a first allowable value in which the oxygen concentration is higher than the target value. And a control device that controls the inert gas supply device so as to supply the inert gas from the vent hole to the gas-phase space when exceeding .

(18): A clarification tube for refining the molten glass while passing the molten glass so that a gas phase space is formed above the liquid surface of the molten glass, and is made of a material containing a platinum group metal. The wall portion in contact with the gas phase space has a vent hole for discharging the gas in the gas phase space and a supply hole for supplying a gas inert to the molten glass into the gas phase space. And the ventilation hole and the supply hole are arranged to be separated from each other in the flow direction of the molten glass,
An inert gas supply device for supplying the inert gas into the gas phase space;
The inert gas is supplied from the supply hole at a supply amount controlled so that the oxygen concentration in the gas discharged from the vent hole is equal to or less than a target value, and the vent hole is controlled at a controlled discharge amount. When the gas is discharged from the gas, if the oxygen concentration exceeds a third allowable value higher than the target value, the inert gas supply is performed so as to reduce the gas discharge amount from the vent hole. And a control device for controlling the apparatus.

  ADVANTAGE OF THE INVENTION According to this invention, the oxygen concentration in a clarification pipe | tube can be reduced and mixing to the molten glass of the foreign material of a platinum group metal can be suppressed.

It is a flowchart which shows the manufacturing method of a glass substrate. It is the schematic of a glass substrate manufacturing apparatus. It is the schematic of the clarification pipe | tube shown in FIG. (A) is a figure explaining the damaged clarification pipe | tube in 1st Embodiment, (b) is a figure explaining supply of the inert gas from the vent hole in 1st Embodiment. (A) is a figure explaining the damaged clarification pipe | tube in 2nd Embodiment, (b) is a figure explaining reduction of the discharge | emission amount of the gas from the vent hole in 2nd Embodiment.

Hereinafter, the manufacturing method and glass substrate manufacturing apparatus of the glass substrate of this embodiment are demonstrated.
(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.
In the clarification step (ST2), by raising the temperature of the molten glass, bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass are generated. This bubble grows by absorbing oxygen generated by the reduction reaction of a clarifying agent (tin oxide or the like) contained in the molten glass, and floats on the liquid surface of the molten glass and is released. Thereafter, in the clarification step, the temperature of the molten glass is lowered to promote the oxidation reaction of the reducing substance generated by the reduction reaction of the clarifier. 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.

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. A homogenization process is performed in the stirring tank mentioned later.
In the supplying step (ST4), the homogenized molten glass 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 that is a strip-shaped glass having a predetermined thickness, and a flow of the sheet glass is made. For the molding, a float method, a fusion method (overflow downdraw method), or the like is used. However, since it is difficult to lengthen the slow cooling device on the production line in the fusion method, offline heat treatment (described later) is included. A fusion method is suitable for the method of manufacturing the glass substrate.
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. Cutting a sheet glass into a base plate having a predetermined length is also referred to as a plate. The glass substrate obtained by sampling is further cut into a predetermined size to produce a glass substrate with a target size.

In the cutting step (ST7), the glass substrate obtained by the sampling may be guided and conveyed to a furnace for performing the heat treatment process while being pinched and held by a conveyance mechanism (not shown), and may be subjected to heat treatment. . The glass substrate after the plate collection or the heat treatment is further conveyed to a device for cutting, and is cut into a product size to obtain a glass substrate. For example, the following steps are performed on the glass substrate obtained in the cutting step (ST7).
In the grinding process and the polishing process, end face processing including grinding, polishing and corner cutting of the end face of the glass substrate is performed. The glass substrate after end face processing is cleaned (first cleaning) in order to remove fine foreign matters and dirt on the glass surface in the cleaning step. After the first cleaning, for example, a surface treatment including a roughening step and a rinsing step is performed on the glass substrate. After the surface treatment, the glass substrate is further cleaned (second cleaning), and the cleaned glass substrate is optically inspected for scratches, dust, dirt, or scratches including optical defects in the inspection process. In the packing process, a glass substrate that is suitable for quality by inspection is loaded and packed on a pallet as a laminated body alternately laminated with paper for protecting the glass substrate. The packed glass substrate is shipped to a supplier.

(Overall overview of glass substrate manufacturing equipment)
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 101, a clarification pipe 102, a stirring tank 103, transfer pipes 104 and 105, and a glass supply pipe 106.
The melting tank 101 shown in FIG. 2 is provided with heating means such as a burner (not shown). A glass raw material to which a fining agent is added is charged into the melting tank 101, and a melting step (ST1) is performed. The molten glass melted in the melting tank 101 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. Specifically, when the molten glass in the clarification tube 102 is heated, the bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass absorb oxygen generated by the reductive reaction of the clarifier. It grows and floats on the liquid surface of the molten glass and is released into the gas phase space. Then, the reducing substance produced | generated by the reductive reaction of a fining agent performs an oxidation reaction by lowering the temperature of molten glass. 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 clarified molten glass is supplied to the stirring tank 103 via the transfer pipe 105.
In the stirring tank 103, the molten glass is stirred by the stirrer 103a, and a homogenization process (ST3) is performed. The molten glass homogenized in the stirring tank 103 is supplied to the molding apparatus 200 through the glass supply pipe 106 (supply process ST4).
In the shaping | molding apparatus 200, the sheet glass SG is shape | molded from molten glass by the overflow down draw method, for example (molding process ST5), and it anneals (Slow cooling process ST6).
In the cutting device 300, a plate-like glass substrate cut out from the sheet glass SG is formed (cutting step ST7).

(Configuration of clarification tube)
Next, the configuration of the clarification tube 102 will be described with reference to FIG. FIG. 3 is a schematic view showing the configuration of the clarification tube 102.
The fining tube 102 is a tubular member made of a material containing a platinum group metal. The platinum group metal refers to six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), and iridium (Ir). As the material containing the platinum group metal, a material made of a platinum group metal made of a single element or an alloy of the platinum group metal is used. For example, platinum or a platinum alloy is used.

Flange-shaped electrodes 121 a, 121 b, 121 c are connected to the outer peripheral surface of the clarification tube 102. In the example shown in FIG. 3, the electrodes 121 a to 121 c are arranged at three positions, that is, both ends in the longitudinal direction of the clarification tube 102 and the center position. The electrodes 121a to 121c are connected to the power supply device 122. By applying a voltage between the electrodes 121a and 121b and between the electrodes 121b and 121c, a current flows between the electrodes 121a and 121b and between the electrodes 121b and 121c, and the clarification tube 102 is energized and heated. The
By this energization heating, the maximum temperature of the clarification tube 102 is heated between the electrodes 121a and 121b, for example, 1600 ° C to 1750 ° C, more preferably 1630 ° C to 1750 ° C, and the molten glass flowing in the clarification tube 102 is heated. The maximum temperature is heated to a temperature suitable for defoaming from 1600 ° C to 1720 ° C, more preferably from 1620 ° C to 1720 ° C. Further, between the electrodes 121b and 121c, the maximum temperature of the clarified tube 102 is heated to, for example, 1590 ° C to 1670 ° C, more preferably 1620 ° C to 1670 ° C, and the maximum temperature of the molten glass flowing in the clarified tube 102 is The temperature is suitable for absorption from 1590 ° C to 1640 ° C, more preferably from 1610 ° C to 1640 ° C.

The power supply device 122 is controlled by the control device 123. The control device 123 controls the amount of current that the power supply device 122 supplies to the clarification tube 102, and thereby controls the temperature of the molten glass that passes through the clarification tube 102. The control device 123 is a computer including a CPU, a memory, and the like.
The electrodes 121a to 121c are cooled using water or air. For this reason, in the clarification tube 102, a region where the temperature is locally lowered is formed corresponding to the arrangement position of the electrodes 121a to 121c.
The number of electrodes provided in the clarification tube 102 is not limited to three and may be two or four or more.

In the clarification step (ST2), clarification is performed while flowing the molten glass into the clarification tube 102 so that the gas phase space 120a is formed above the liquid surface of the molten glass. As shown in FIGS. 4 (a) and 4 (b), the clarification tube 102 is formed on the wall portion in contact with the gas phase space 120a, as shown in FIG. 4 (a) and FIG. On the other hand, a supply hole 102b for supplying an inert gas (hereinafter referred to as an inert gas) into the gas phase space is formed. FIG. 4A and FIG. 4B are vertical sectional views showing a section along the longitudinal direction of the clarification tube 102. The ventilation hole 102a and the supply hole 102b are spaced apart from each other in the flow direction of the molten glass.
The vent hole 102a does not include a hole (for example, an opening 131 described later) formed with the use of the clarification tube 102. The discharge of the gas from the vent hole 102a may be continuously performed during the clarification step (ST2) or may be performed intermittently. For example, during the supply of an inert gas described later, the gas need not be discharged from the vent hole 102a. The gas discharged from the vent hole 102a is a gas containing oxygen, and may contain an inert gas.

A vent pipe 127 is connected to the outer peripheral surface of the wall portion where the vent hole 102a is located. The ventilation pipe 127 communicates the gas phase space 120a and the external space (for example, the atmosphere) of the clarification pipe 102. In the example shown in FIG. 3, the vent pipe 127 is provided so as to extend vertically upward from the top of the wall. For example, in the clarification step (ST2), the vent hole 102a and the vent pipe 127 are disposed at a position where the molten glass reaches the maximum temperature or in the vicinity of the downstream side thereof. The vent hole 102a and the vent pipe 127 are provided between the electrodes 121a and 121b in the example shown in FIG.
The vent pipe 127 is provided with a suction device 129 for sucking the gas and suspended matter in the gas phase space 120a. The suction tube 129 can reduce the pressure on the side of the vent pipe 127 (for example, about 10 Pa from the atmospheric pressure). The suction device 129 is controlled by the control device 123. By controlling the suction pressure by the suction device 129, the concentration of oxygen in the gas phase space 120a can be reduced. Further, by controlling the suction pressure, it is possible to adjust the amount of the inert gas supplied from the inert gas supply devices 125 and 126 described later to the gas phase space 120a.

The vent pipe 127 is surrounded by a heat insulating member (described later), and the opening degree of the vent pipe 127 can be adjusted by adjusting the size of the gap between the heat insulating members arranged in the vicinity of the upper end of the vent pipe 127. it can. The discharge of gas from the vent hole 102a is performed not only by suction by the suction device 129 but also by a pressure difference between the inside and outside of the clarification tube 102. The amount of gas discharged from the vent hole 102a is adjusted by adjusting the suction pressure by the suction device 129 or the opening degree of the vent pipe 127.
The vent pipe 127 is provided with an oxygen concentration meter 128. The oxygen concentration meter 128 measures the oxygen concentration of the gas discharged from the vent hole 102 a and outputs the measurement signal to the control device 123. The oxygen concentration signal measured by the oxygen concentration meter 128 is output to the control device 123, and the control device 123 controls the inert gas supply devices 125 and 126 in accordance with the oxygen concentration signal to supply the inert gas supply amount. , Generating a control signal for adjusting the supply pressure. Further, the control device 123 generates a control signal so as to adjust the suction pressure by the suction device 129 or the opening degree of the vent pipe 127 according to the signal of the oxygen concentration. The generated control signal is transmitted to an inert gas supply device 125, 126 or an adjustment device (not shown) that adjusts the opening degree of the suction device 129 or the vent pipe 127. Thereby, the supply amount and supply pressure of the inert gas are adjusted, or the gas discharge amount from the vent hole 102a is adjusted. The measurement result of the oxygen concentration by the oxygen concentration meter 128, that is, the oxygen concentration in the gas discharged from the vent hole 102a will be described below as the oxygen concentration in the gas phase space.

  The vent pipe 127 is connected to the inert gas supply device 126. The inert gas supply device 126 can supply an inert gas from the inert gas supply device 126 to the gas phase space 120 a via the vent pipe 127. When the inert gas supply device 126 supplies the inert gas to the gas phase space 120a, the inert gas supply device 126 is controlled by the control device 123, and the supply amount and supply pressure of the inert gas are adjusted. The supply of the inert gas from the vent hole 102a can be performed simultaneously with the discharge of the gas from the vent hole 102a. When the inert gas is intermittently supplied, it can be performed by blowing into the ventilation pipe 127 when the suction by the suction device 129 is stopped. When supplying the inert gas continuously, for example, a partition plate that divides the inside of the ventilation pipe 127 into a plurality of flow paths in a cross section orthogonal to the air flow direction or another pipe having a smaller diameter than the ventilation pipe 127 is used. The inert gas may be supplied from a section different from the section where the gas is sucked by the suction device 129, which is disposed in the ventilation pipe 127. The supply amount of the inert gas from the vent pipe 127 may be larger than the discharge amount of the inert gas from the vent pipe 127.

A supply pipe 124 is connected to the outer peripheral surface of the wall portion where the supply hole 102b is located. In the example shown in FIG. 3, the supply hole 102b and the supply pipe 124 are provided between the electrodes 121b and 121c. The supply pipe 124 is connected to an inert gas supply device 125. The inert gas supply device 125 is controlled by the control device 123, and the supply amount and supply pressure of the inert gas are adjusted. The inert gas introduced from the supply pipe 124 flows from right to left in FIG. 3 along the flow direction of the molten glass.
It is preferable that the inert gas supplied from the inert gas supply devices 125 and 126 is inert not only to the molten glass but also to the platinum group metal. For example, nitrogen (N ₂ ), a rare gas (eg, argon (Ar)), carbon monoxide (CO), or the like can be used. Argon and carbon monoxide are more likely to move in the glass structure than nitrogen. Therefore, even when the inert gas melted in the molten glass is generated as bubbles, it is easily taken into the glass again during the transfer of the molten glass. Therefore, argon is preferably used in terms of bubble quality.
In the clarification step (ST2), the inert gas is supplied from the supply hole 102b so that the oxygen concentration in the gas phase space 120a is equal to or lower than the target value. In the following description, a case where a measured value by the oxygen concentration meter 128 is adopted as the oxygen concentration in the gas phase space 120a will be described as an example. The target value of the oxygen concentration is an upper limit value of the oxygen concentration that can preferably suppress the volatilization of the platinum group metal in the gas phase space 120a, for example, 5%. The lower limit of the target value is, for example, 0.1%, preferably 1% from the viewpoint of suppressing the inert gas from melting into the molten glass and suppressing the generation of bubbles of the dissolved inert gas.

  The clarification pipe | tube 102 is coat | covered with castable cement (not shown), and heat insulation members (not shown), such as a refractory brick, are piled up on the outer side. That is, a heat insulating member is provided around the clarification tube 102. The heat insulating member is disposed so as to be in contact with each of the electrodes 121 a to 121 c, the vent pipe 127, and the supply pipe 124.

(Clarification process: 1st Embodiment)
Next, the supply of the inert gas performed in the first embodiment of the clarification step (ST2) will be described.
In the present embodiment, even if the inert gas is supplied so that the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102a) is equal to or lower than the target value, the oxygen concentration is caused by some cause. (For example, when the wall portion is deformed, an opening is formed in the wall portion and oxygen in the outside air enters the gas phase space 120a) and the air hole 102a exceeds the first allowable value. To supply an inert gas to the gas phase space 120a. For example, an inert gas is supplied from the supply hole 102a at a controlled supply amount so that the oxygen concentration in the gas discharged from the vent hole 102a is equal to or less than a target value, and the vent hole is controlled at a controlled discharge amount. When the gas is discharged from 102a and the oxygen concentration increases and exceeds the first allowable value, an inert gas is supplied from the vent hole 102a to the gas phase space 120a. The first permissible value is an oxygen concentration value that, when exceeding this, is likely to prevent the volatilization of the platinum group metal in the gas phase space 120a. The first allowable value is preferably 14 to 21%, for example 20%, preferably 15%. When the oxygen concentration exceeds the first allowable value, specifically, the inert gas supply device 126 and the suction device 129 are controlled so that the inert gas is supplied from the vent hole 102a. As described above, the inert gas is supplied into the gas phase space 120a from the vent hole 102a that is normally used as a discharge port for discharging the gas in the gas phase space 120a, and thus becomes too high in the clarification tube 102. The oxygen concentration can be reliably reduced and volatilization of platinum group metals can be suppressed. When the oxygen concentration is equal to or lower than the first allowable value, the supply of the inert gas from the vent hole 102a may be stopped or continued until the oxygen concentration is equal to or lower than the target value.

  In the present embodiment, the second tolerance is lower than the first tolerance and higher than the target value before the oxygen concentration (oxygen concentration in the gas discharged from the vent 102a) exceeds the first tolerance. When the value is exceeded, it is preferable to increase the supply amount of the inert gas from the supply hole 102b more than the supply amount when the oxygen concentration is equal to or lower than the target value. The second allowable value is that if the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102a) exceeds this, volatilization of the platinum group metal cannot be sufficiently suppressed in the gas phase space 120a. Possible oxygen concentration value. The second allowable value is preferably 7 to 11%, for example, 10%, preferably 8%. Specifically, when the oxygen concentration exceeds the second allowable value due to some cause (for example, deformation of the wall portion or formation of an opening in the wall portion), first, the inertness from the supply hole 102b The inert gas supply device 125 and the suction device 129 are controlled so that the gas supply amount increases. As a result, when the oxygen concentration is reduced by increasing the supply amount of the inert gas from the supply hole 102b, the inert gas is not supplied from the vent hole 102a. On the other hand, if the supply amount of the inert gas from the supply hole 102b is increased, the oxygen concentration cannot be reduced, and if the first allowable value is exceeded, the inert gas is supplied from the vent pipe 127 as described above. Thus, the inert gas supply device 126 is controlled. During the supply of the inert gas from the vent hole 102a, the supply amount of the inert gas from the supply hole 102b increased by exceeding the second allowable value may be maintained, and further increased. May be. Further, when the oxygen concentration is equal to or lower than the second allowable value, the increased supply amount of the inert gas from the supply hole 102b may be returned to the supply amount before the increase.

By the way, since the clarification pipe | tube 102 is maintained at high temperature in a clarification process (ST2), it may be damaged with use. Here, with reference to FIG. 4 (a) and FIG.4 (b), the case where the clarification tube 102 is damaged is demonstrated. FIG. 4A is a diagram illustrating a case where the oxygen concentration exceeds the first allowable value. FIG. 4B is a diagram illustrating the supply of inert gas when the oxygen concentration exceeds the first allowable value.
The clarification tube 102 may be deformed so that the wall portion in contact with the gas phase space 120a hangs inward with use. In such a deformed portion (hereinafter referred to as a deformed portion), the area of the gas flow path in the gas phase space 120a becomes small, so that the gas flow along the flow direction of the molten glass tends to stagnate. In particular, when the deformation amount of the deforming portion 130 is large or when the liquid level of the molten glass rises, as shown in FIG. 4A, the lower end of the deforming portion 130 reaches the liquid surface of the molten glass, The gas flow along the flow direction of the molten glass is interrupted. As a result, the inert gas does not reach the portion of the gas phase space 120a opposite to the supply hole 102b with respect to the deformable portion 130, that is, the portion where the vent hole 102a is located, and the oxygen concentration in this portion increases. In the gas phase space 120a, the oxygen concentration becomes non-uniform at locations along the flow direction.
Further, depending on the conditions of the clarification step (ST2), the clarification tube 102 cannot easily avoid the volatilization of the platinum group metal from the wall portion, and the wall portion may be thinned. When the thinning progresses, as shown in FIG. 4A, an opening 131 that penetrates the wall may be formed. When the opening 131 is formed, outside air containing oxygen passes through the opening 131 and enters the gas phase space 120a so as to compensate for the amount of gas discharged from the vent hole 102a. In particular, when the amount of discharge is large due to suction by the suction device 129 or the opening of the vent hole 102a being large, the inflow amount of outside air containing oxygen is large, and the oxygen contained in the outside air causes a gas phase. The oxygen concentration in the space 120a tends to increase.
If the clarification tube 102 is damaged in this way, even if an inert gas is supplied from the supply hole 102b, the oxygen concentration cannot be maintained within the target value, and the possibility of exceeding the first allowable value increases.
Moreover, since the above-described heat insulating member is generally provided on the outer periphery of the clarification tube 102, even if the deformed portion 130 and the opening 131 are formed, it is difficult to notice the deformation portion 130 and the opening. Even if it is noticed that 131 has been formed, it is difficult to know their positions. For this reason, it has been difficult to take measures against an increase in the oxygen concentration in the gas phase space 120a.

  In this embodiment, when the oxygen concentration exceeds the first allowable value, the inert gas is supplied from the vent hole 102a as shown in FIG. The inert gas is also supplied to the portion on the opposite side of the hole 102b, and the oxygen concentration in the gas phase space 120a on the vent hole 102a side with respect to the deformed portion 130 is lowered, thereby the oxygen concentration in the gas phase space 120a. Non-uniformity is improved. In addition, by supplying an inert gas from the vent hole 102a, the inflow of outside air from the opening 131 can be suppressed. Thereby, the oxygen concentration in the gas phase space 120a can be reliably reduced, and volatilization of the platinum group metal can be suppressed. For this reason, even if the clarification tube 102 is damaged, the production (operation) of the glass substrate can be continued.

  In addition to supplying the inert gas from the vent hole 102a, it is preferable to increase the supply amount of the inert gas from the supply hole 102b. Thereby, for example, when the position of the deformed portion 130 to be formed in the tube axis direction (flowing direction of the molten glass) of the clarification tube 102 is on the same side in the tube axis direction when viewed from the vent hole 102a and the supply hole 102b. When the oxygen concentration exceeds the second allowable value, the oxygen concentration can be reduced by increasing the supply amount of the inert gas from the supply hole 102b. On the other hand, when the position of the deformed portion 130 formed in the tube axis direction of the clarification tube 102 is on a different side as viewed from the vent hole 102a and the supply hole 102b, the oxygen concentration exceeds the second allowable value, and the supply hole Even when the supply amount of the inert gas from 102b is increased, the inert gas is supplied from the vent hole 102a when the oxygen concentration exceeds the first allowable value even if the oxygen concentration does not decrease. Thus, the oxygen concentration can be reliably reduced.

  In the present embodiment, the position of the opening formed in the wall portion with the use of the clarification tube 102 (position in the tube axis direction of the clarification tube 102), and the change in the oxygen concentration that changes due to the opening 131 The position of the opening 131 (the position in the tube axis direction of the clarification tube 102) can be identified from the information on the change in the measured value of the oxygen concentration in the vent hole 102a using the relationship obtained in advance. The correspondence relationship between the position of the above-described opening 131 and the change in the oxygen concentration is, for example, from the change in the oxygen concentration when the condition of the clarification step (ST2) is changed, and the condition and oxygen concentration in the clarification step (ST2) Furthermore, the relationship between the conditions of the clarification step (ST2) and the oxygen concentration is similarly determined using another clarification tube 102 in which the position of the opening 131 along the tube axis direction of the clarification tube 102 is different. It can be obtained from a plurality of obtained relationships. As a condition for such a clarification step (ST2), for example, a supply pressure of an inert gas can be used. In this case, the relationship between the supply pressure of the inert gas and the oxygen concentration is obtained from the change in the measured value of the oxygen concentration when the supply pressure of the inert gas from the supply hole 102b is changed. Note that as a measured value of the oxygen concentration, a correspondence relationship obtained by modeling the damaged clarification tube 102 and the molten glass and simulating a change in oxygen concentration accompanying the supply of the inert gas may be used.

  In the present embodiment, by specifying the position of the opening 131, the supply amount of the inert gas is adjusted according to the distance between the opening 131 and the vent hole 102a along the flow direction. Can do. According to the inventor's research, the smaller the distance between the opening 131 and the ventilation hole 102a along the tube axis direction (the flow direction of the molten glass), that is, the closer the opening 131 is to the ventilation hole 102a, It was clarified that the oxygen concentration in the phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102a) becomes high. The reason for this is that the closer the opening 131 is to the vent hole 102a, the stronger the force (for example, suction pressure) for discharging the gas from the vent hole 102a, and the greater the amount of outside air flowing in from the opening 131. Conceivable. Therefore, the oxygen concentration in the gas phase space 120a can be appropriately controlled by adjusting the supply amount of the inert gas based on the distance between the opening 131 and the vent hole 102a whose positions are specified. Specifically, the supply amount and supply pressure of the inert gas by the inert gas supply device 126 are controlled based on the distance between the opening 131 and the vent hole 102a.

Further, by specifying the position of the opening 131, an inert gas can be supplied into the gas phase space from the opening 131 whose position has been specified. Specifically, the heat insulating member arranged in the vicinity of the opening 131 whose position is specified is partially removed, and a supply pipe (not shown) similar to the supply pipe 124 is replaced with the clarification pipe 102 where the opening 131 is located. And an inert gas supply device (not shown) similar to the inert gas supply device 125 can be connected to the supply pipe to supply the inert gas from the opening 131. . Thereby, the oxygen concentration in the gas phase space 120a can be further reduced.
Further, by specifying the position of the opening 131, the heat insulating member in the vicinity of the specified opening 131 is partially removed, and the wall portion of the clarification tube 102 in which the opening 131 is formed is repaired. You can also.

As described above, in the clarification step (ST2), the inert gas is supplied so that the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102a) is equal to or lower than the target value. Nevertheless, when the oxygen concentration rises for some reason and exceeds the first allowable value, the inert gas is supplied from the vent hole 102a to the gas phase space. Thereby, the oxygen concentration which became too high in the clarification tube 102 can be reliably reduced, volatilization of the platinum group metal group from the clarification tube 102 can be suppressed, and contamination of the foreign material of the platinum group metal into the molten glass can be prevented. Can be suppressed.
Further, when the oxygen concentration (the oxygen concentration in the gas discharged from the vent hole 102a) exceeds the second allowable value, the oxygen concentration can be reduced even if the supply amount of the inert gas from the supply hole 102b is increased. Even if the first allowable value is exceeded, the oxygen concentration can be reliably reduced by supplying the inert gas from the vent hole 102a.
Further, the correspondence relationship obtained in advance between the position of the opening 131 in the wall portion along the tube axis direction (flowing direction of the molten glass) of the clarification tube 102 and the change in oxygen concentration caused by the opening. Can be used to identify the position of the aperture 131 from the change in the measured oxygen concentration. Further, the oxygen concentration can be further lowered by supplying the inert gas from the opening 131 whose position is specified.

(Clarification process: second embodiment)
Next, the discharge from the vent pipe 127 performed in the second embodiment of the clarification step (ST2) will be described.
In this embodiment as well, in the same manner as in the first embodiment of the clarification step, the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102a) is inactive so as to be equal to or lower than the target value. Even if gas is supplied, the oxygen concentration may increase. In the present embodiment, when the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102a) exceeds a third allowable value higher than the target value, the gas from the vent hole 102a Reduce emissions. For example, the gas is supplied from the supply hole 102b at a controlled supply amount so that the oxygen concentration in the gas discharged from the vent hole 102a is equal to or less than the target value, and the gas is supplied from the ventilation hole 102a at a controlled discharge amount. When discharging, if the third allowable value higher than the target value is exceeded, the discharge amount from the vent hole 102a is reduced. Such an increase in the oxygen concentration is considered to be due to oxygen entering the gas phase section 120a due to some cause (for example, formation of an opening in the wall). If this third allowable value is exceeded, it is a value of the oxygen concentration that increases the possibility that the volatilization of the platinum group metal cannot be suppressed in the gas phase space 120a. The third tolerance is preferably 14 to 21%, for example 20%, and preferably 15%. When the oxygen concentration exceeds an allowable value, specifically, the suction pressure by the suction device 129 is controlled or the opening degree of the vent pipe 127 is adjusted so that the amount of gas discharged from the vent hole 102a is reduced. Is done. Thus, by reducing the discharge amount from the vent pipe 127, for example, by reducing the discharge amount from the controlled discharge amount, the inflow amount of outside air including oxygen entering the gas phase space 120a is reduced. The oxygen concentration that has become too high in the clarification tube 102 can be reliably reduced, and volatilization of the platinum group metals can be suppressed. When the oxygen concentration is equal to or lower than the third allowable value, the amount of gas discharged from the vent hole 102a may be increased to the amount discharged before exceeding the third allowable value or may be maintained. Here, the third tolerance value is preferably the same as the first tolerance value in the first embodiment. Therefore, when the first embodiment is performed, when the first allowable value (third allowable value) is exceeded, the inert gas is supplied from the vent hole 102a to the gas phase space 120a, and the gas from the vent hole 102a is supplied. It is preferable to reduce the discharge amount.

  In the present embodiment, after reducing the amount of gas discharged from the vent hole 102a, the amount of inert gas supplied from the supply hole 102b is increased more than the amount supplied when the oxygen concentration is equal to or lower than the target value. It is preferable. Specifically, after reducing the amount of gas discharged from the vent hole 102a, the inert gas supply device 125 and the suction device 129 are controlled so that the supply amount of the inert gas from the supply hole 102b increases. After the amount of gas discharged from the vent hole 102a is reduced, the amount of inert gas discharged from the vent hole 102a can be reduced even if the amount of inert gas supplied from the supply hole 102b is increased. The oxygen concentration in the gas phase space 120a can be lowered efficiently.

Since the clarification tube 102 is maintained at a high temperature in the clarification step (ST2), it may be damaged with use. Here, with reference to FIG. 5A and FIG. 5B, the case where the clarification tube 102 is damaged will be described. FIG. 4A is a diagram illustrating a case where the oxygen concentration exceeds an allowable value. FIG. 4B is a diagram for explaining a reduction in the amount of gas discharged from the vent pipe 127 when the oxygen concentration exceeds the allowable value.
In the clarification tube 102, volatilization of the platinum group metal from the wall is difficult to avoid depending on the condition of the clarification step (ST2), and the wall may be thin. When the thinning progresses, as shown in FIG. 4A, an opening 131 that penetrates the wall may be formed. When the opening 131 is formed, outside air containing oxygen passes through the opening 131 and enters the gas phase space 120a so as to supplement the amount of gas discharged from the vent hole 102a. In particular, when the amount of discharge is large due to suction by the suction device 129 and the opening of the vent hole 102a being large, the inflow amount of outside air containing oxygen is large, and the gas phase space is caused by oxygen contained in the outside air. The oxygen concentration in 120a (the oxygen concentration in the gas discharged from the vent hole 102a) tends to increase.
If the clarification tube 102 is damaged in this way, even if an inert gas is supplied from the supply hole 102b, the oxygen concentration cannot be maintained within the target value, and the possibility of exceeding the allowable value increases.
Also, since the outer periphery of the clarification tube 102 is generally provided with a heat insulating member, even if the opening 131 is formed, it is difficult to notice it, and it is assumed that the opening 131 has been formed. Even knowing their location is difficult. For this reason, it has been difficult to take measures against an increase in the oxygen concentration in the gas phase space 120a.

  In the present embodiment, when the oxygen concentration exceeds an allowable value, as shown in FIG. 4B, the gas discharged from the vent hole 102a is reduced by reducing the amount of gas discharged from the vent hole 102a. The amount of outside air flowing from the opening 131 can be reduced to compensate. For this reason, the oxygen concentration in the gas phase space 120a can be reliably reduced, and volatilization of the platinum group metal can be suppressed. For this reason, even if the clarification tube 102 is damaged, the production (operation) of the glass substrate can be continued. At this time, it is preferable to increase the supply amount of the inert gas from the supply hole 102b in addition to the reduction of the discharge amount of the gas from the vent hole 102a.

Also in this embodiment, as described in the first embodiment, the position of the opening formed in the wall portion with the use of the clarification tube 102 (position in the tube axis direction of the clarification tube 102) and the opening 131 The position of the opening 131 (the tube axis of the clarification tube 102 is obtained from information on the change in the measured value of the oxygen concentration in the vent hole 102a using the correspondence relationship obtained in advance with the change in the oxygen concentration caused by Position in the direction) can be specified.
Also in this embodiment, as in the first embodiment, by specifying the position of the opening 131, the gas is further changed according to the distance between the opening 131 and the vent hole 102a along the flow direction. The amount of discharge can be adjusted.

Further, by specifying the position of the opening 131, an inert gas can be supplied into the gas phase space from the opening 131 whose position has been specified. Specifically, a heat insulating member disposed near the opening 131 whose position is specified is opened, and a supply pipe (not shown) similar to the supply pipe 124 is placed on the wall of the clarification pipe 102 where the opening 131 is located. In addition to the connection, an inert gas supply device (not shown) similar to the inert gas supply device 125 can be connected to the supply pipe to supply the inert gas from the opening 131. Thereby, the oxygen concentration in the gas phase space 120a can be further reduced.
Further, by specifying the position of the opening 131, it is also possible to repair the wall portion of the clarification tube 102 in which the opening 131 is formed by opening a heat insulating member near the opening 131 whose position is specified.

According to the second embodiment, in the refining step (ST2), the inert gas is supplied so that the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102a) is equal to or lower than the target value. In spite of being performed, when the oxygen concentration increases and exceeds the third allowable value, the amount of gas discharged from the vent hole 102a is reduced. Thereby, the amount of oxygen flowing from the outside due to some cause can be reduced, and the oxygen concentration that has become too high in the clarification tube 102 can be reliably reduced. For this reason, volatilization of the platinum group metal from the clarification tube 102 can be suppressed, and mixing of foreign matter of the platinum group metal into the molten glass can be suppressed.
In addition, after reducing the gas discharge amount from the vent hole 127, the supply amount of the inert gas from the supply hole 102b is increased more than the supply amount when the oxygen concentration is equal to or lower than the target value, thereby efficiently. The oxygen concentration in the gas phase space 120a can be lowered.
Further, by reducing the amount of gas discharged from the vent hole 102a, the amount of outside air flowing into the gas phase space 120a from the opening 131 formed in the wall portion with the use of the clarification tube 102 is reduced. be able to.
Further, the position of the opening can be specified from the oxygen concentration using the relationship obtained in advance between the position of the opening 131 in the wall portion along the flow direction and the magnitude of the oxygen concentration.
Moreover, the correspondence relationship calculated | required previously between the position of the opening in the wall part along the pipe-axis direction (flow direction of a molten glass) of the clarification tube 102, and the change of the oxygen concentration which changes resulting from opening. The position of the opening 131 can be specified from the change in the oxygen concentration. Further, the oxygen concentration can be further lowered by supplying the inert gas from the opening 131 whose position is specified.
Further, the oxygen concentration in the gas phase space 120a (exhausted from the vent hole 102a) is adjusted by adjusting the gas discharge amount according to the distance between the opening 131 and the vent hole 102a along the flow direction. The oxygen concentration in the gas can be appropriately controlled.

  The first embodiment and the second embodiment described above are suitable because they exert a great effect when the diameter of the opening 131 is large. Even if the opening 131 is initially formed in the clarification tube 102 and has a small diameter, the opening 131 may increase with use. The small-diameter aperture 131 may be blocked by the molten glass leaking from it being cooled and solidified, but the large-diameter aperture 131 is difficult to block and tends to remain open. It has been found that the opening 131 having such a large diameter tends to increase the amount of outside air flowing in, and is particularly noticeable when the opening 131 has a size equal to or larger than that of the vent hole 102a. In the first embodiment described above, when the oxygen concentration exceeds the first allowable value, the inert gas is supplied from the vent hole 102a, whereby the opening 131 having a large diameter is formed. In addition, the oxygen concentration in the gas phase space 120a can be reliably reduced by supplying the inert gas from the vent hole 102a. In the second embodiment, as described above, the inert gas is supplied from the vent hole 102a when the oxygen concentration exceeds the third allowable value, whereby the opening 131 having a large diameter is formed. Even in this case, the oxygen concentration in the gas phase space 120a can be reliably reduced by reducing the amount of gas discharged from the vent hole 102a. The diameter of the aperture 131 refers to the maximum length of the aperture 131 projected on the surface where the wall portion of the clarification tube 102 extends. When the diameter of the opening 131 is large, specifically, the diameter of the opening 131 is 50% or more of the diameter of the vent hole 102a, and is 3 mm or more. The upper limit of the diameter of the opening 131 is not particularly limited, but is, for example, twice the diameter of the vent hole 102a and 10 mm.

  In 1st Embodiment and 2nd Embodiment mentioned above, it is preferable that the supply amount of an inert gas is adjusted so that a bubble may not generate | occur | produce in the molten glass after clarification. As described above, the molten glass after the defoaming treatment passes through the clarification tube 102 and is then transferred through the transfer tube 105 and the homogenization step (ST3) is performed in the stirring vessel 103. In this process, the temperature of the molten glass is lowered, but as a result of the local increase in temperature, the bubbles absorbed in the molten glass by the absorption treatment may be degassed again. Such bubbles can also be generated when the molten glass comes into contact with the stirrer 103a in the stirring vessel 103. It was found that such bubbles are likely to be generated when the pressure of the inert gas supplied to the gas phase space 120a is high in the clarification step (ST2). In the present embodiment, it is possible to prevent bubbles from remaining on the glass substrate by adjusting the pressure of the inert gas supplied to the gas phase space so that bubbles are not generated in the clarified molten glass. For example, it is preferable that the inert gas is distributed from the supply hole 102b and the opening 131 together with the vent hole 102a, or the flow area of each hole is increased to suppress the supply pressure within a low range. .

(Glass substrate)
The size of the glass substrate manufactured in the first embodiment and the second embodiment is not particularly limited. For example, the vertical dimension and the horizontal dimension are 500 mm to 3500 mm, 1500 mm to 3500 mm, 1800 to 3500 mm, 2000 mm to 3500 mm, respectively. It is preferable that it is 2000 mm-3500 mm.
The thickness of the glass substrate is, for example, 0.1 to 1.1 mm, more preferably a very thin rectangular plate of 0.75 mm or less, for example, 0.55 mm or less, and further 0.45 mm or less. Thickness is more preferred. The lower limit value of the thickness of the glass substrate is preferably 0.15 mm, and more preferably 0.25 mm.

<Glass composition>
As such a glass substrate, the glass substrate of the following glass compositions is illustrated. That is, the raw material of molten glass is prepared so that the glass substrate of the following glass compositions is manufactured.
SiO ₂ 55~80 mol%,
Al ₂ O ₃ 8-20 mol%,
B ₂ O ₃ 0 to 12 mol%,
RO 0 to 17 mol% (RO is the total amount of MgO, CaO, SrO and BaO).

SiO ₂ is preferably 60 to 75 mol%, and more preferably 63 to 72 mol%, from the viewpoint of reducing the heat shrinkage rate.
Among RO, it is preferable that MgO is 0-10 mol%, CaO is 0-15 mol%, SrO is 0-10%, and BaO is 0-10%.

Further, at least SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , and RO are included, and the molar ratio ((2 × SiO ₂ ) + Al ₂ O ₃ ) / ((2 × B ₂ O ₃ ) + RO) is 4. The glass which is 5 or more may be sufficient. In addition, it is preferable that at least one of MgO, CaO, SrO, and BaO is included, and the molar ratio (BaO + SrO) / RO is 0.1 or more.

The total content of 2-fold and mol% of RO for the content of mol% of B ₂ O ₃ is 30 mol% or less, it is preferred that preferably 10 to 30 mol%.
Moreover, 0 mol% or more and 0.4 mol% or less may be sufficient as the content rate of the alkali metal oxide in the glass substrate of the said glass composition.
Further, it contains 0.05 to 1.5 mol% of metal oxides (tin oxide and iron oxide) whose valence fluctuates in the glass, and substantially contains As ₂ O ₃ , Sb ₂ O ₃ and PbO. It is not essential but optional.

Moreover, it is preferable that an alkali-free boroaluminosilicate glass or alkali trace amount glass is used for the glass substrate manufactured by 1st Embodiment and 2nd Embodiment.
It is preferable that the glass substrate manufactured by 1st Embodiment and 2nd Embodiment consists of an alkali free glass containing the following compositions, for example.
As a glass composition of the glass substrate manufactured by 1st Embodiment and 2nd Embodiment, the following is mentioned, for example (mass% display).
SiO _2: 50~70% _{(preferably, 57~64%), Al 2 O} 3: 5~25% ( _{preferably, 12~18%), B 2 O} 3: 0~15% ( preferably, 6 ~ 13%), and may optionally contain the following composition. As optional components, MgO: 0 to 10% (preferably 0.5 to 4%), CaO: 0 to 20% (preferably 3 to 7%), SrO: 0 to 20% (preferably, from 0.5 to 8%, more preferably 3~7%), BaO: 0~10% ( preferably 0-3%, more preferably _{0~1%), ZrO 2: 0~10} % ( preferably 0 to 4%, more preferably 0 to 1%). Furthermore, it is more preferable that R ′ ₂ O: more than 0.10% and 2.0% or less (provided that R ′ is at least one selected from Li, Na, and K).

_{Alternatively,} SiO 2: _{50~70% (preferably, 55~65%), B 2 O} 3: 0~10% ( _{preferably, 0~5%, 1.3~5%),} Al 2 O 3: 10-25% (preferably 16-22%), MgO: 0-10% (preferably 0.5-4%), CaO: 0-20% (preferably 2-10%, 2-6 %), SrO: 0 to 20% (preferably 0 to 4%, 0.4 to 3%), BaO: 0 to 15% (preferably 4 to 11%), RO: 5 to 20% (preferably Is preferably 8 to 20%, 14 to 19%) (wherein R is at least one selected from Mg, Ca, Sr and Ba). Furthermore, it is more preferable that R ′ ₂ O contains more than 0.10% and 2.0% or less (provided that R ′ is at least one selected from Li, Na and K).

<Young's modulus>
As a Young's modulus of the glass substrate manufactured by 1st Embodiment and 2nd Embodiment, 72 GPa or more is preferable, for example, 75 GPa or more is more preferable, and 77 GPa or more is still more preferable.

<Strain point>
As a distortion rate of the glass substrate manufactured by 1st Embodiment and 2nd Embodiment, 650 degreeC or more is preferable, for example, 680 degreeC or more is more preferable, 700 degreeC or more and 720 degreeC or more are still more preferable.

<Heat shrinkage>
The thermal contraction rate of the glass substrate manufactured by the first embodiment and the second embodiment is, for example, 50 ppm or less, preferably 40 ppm or less, more preferably 30 ppm or less, and still more preferably 20 ppm or less. The range of the heat shrinkage rate of the glass substrate before reducing the heat shrinkage rate is preferably 10 ppm to 40 ppm.

The glass substrate manufactured in the first embodiment and the second embodiment is suitable as a glass substrate for a display including a glass substrate for a flat panel display and a glass substrate for a curved panel display. For example, a glass substrate for a liquid crystal display or It is suitable as a glass substrate for an organic EL display. Furthermore, the glass substrate manufactured in the first embodiment and the second embodiment is a glass for an oxide semiconductor display using an oxide semiconductor such as IGZO (indium, gallium, zinc, oxygen) used for a high-definition display. It is suitable for a glass substrate for LTPS display using a substrate and LTPS (low temperature polysilicon) semiconductor.
Moreover, the glass substrate manufactured by 1st Embodiment and 2nd Embodiment is applicable also to a cover glass, the glass for magnetic discs, the glass substrate for solar cells, etc.

  The glass substrate manufacturing method and glass substrate manufacturing apparatus of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention. Of course.

DESCRIPTION OF SYMBOLS 100 Melting apparatus 101 Melting tank 102 Clarification pipe | tube 102a Vent hole 102b Supply hole 103 Stirrer tank 103a Stirrer 104, 105 Transfer pipe 106 Glass supply pipe 120a Gas phase space 121a-121c Electrode 123 Control apparatus 124 Supply pipe 125,126 Supply of inert gas Device 127 Ventilation tube 130 Deformed portion 131 Opening hole 200 Molding device 300 Cutting device MG Molten glass SG Sheet glass

Claims (12)

It is equipped with a clarification process that clarifies molten glass using a clarification tube.
In the clarification step, the clarification is performed while flowing the molten glass into the clarification tube so that a gas phase space is formed above the liquid surface of the molten glass,
The clarification tube is made of a material containing a platinum group metal, and has a vent hole for discharging the gas in the gas phase space on the wall portion in contact with the gas phase space, and a gas inert to the molten glass. A supply hole for supplying the gas phase space, and the vent hole and the supply hole are spaced apart from each other in the flow direction of the molten glass,
In the clarification step, the oxygen concentration is higher than the target value when the inert gas is supplied from the supply hole so that the oxygen concentration in the gas discharged from the vent hole is equal to or lower than the target value. A method for manufacturing a glass substrate, comprising: supplying the inert gas from the vent hole to the gas phase space when a first allowable value is exceeded.   In the clarification step, when supplying the inert gas from the supply hole, oxygen is lower than the first allowable value and higher than the target value before the oxygen concentration exceeds the first allowable value. When the second allowable value, which is a concentration, is exceeded, the supply amount of the inert gas from the supply hole is changed to the inert gas from the supply hole when the oxygen concentration is equal to or lower than the target value. The manufacturing method of the glass substrate of Claim 1 which increases rather than the supply amount of gas.   Using the relationship obtained in advance between the position of the opening formed in the wall portion with the use of the clarification tube and the change in the oxygen concentration that changes due to the opening, the communication is performed. The manufacturing method of the glass substrate of Claim 1 or 2 which specifies the position of the said opening from the information of the change of the measured value of the said oxygen concentration in a pore.   Furthermore, the manufacturing method of the glass substrate of Claim 3 which supplies the said inert gas in the said gaseous-phase space from the opening which pinpointed the said position.   In the clarification step, the inert gas is supplied from the supply hole at a controlled supply amount so that the oxygen concentration is equal to or less than a target value, and the gas is discharged from the vent hole at a controlled discharge amount. 5. The glass substrate according to claim 1, wherein when the oxygen concentration exceeds the first allowable value during discharge, the amount of the gas discharged from the vent hole is reduced. Manufacturing method. It is equipped with a clarification process that clarifies molten glass using a clarification tube.
In the clarification step, the clarification is performed while flowing the molten glass into the clarification tube so that a gas phase space is formed above the liquid surface of the molten glass,
The clarification tube is made of a material containing a platinum group metal, and has a vent hole for discharging the gas in the gas phase space on the wall portion in contact with the gas phase space, and a gas inert to the molten glass. A supply hole for supplying the gas phase space, and the vent hole and the supply hole are spaced apart from each other in the flow direction of the molten glass,
In the clarification step, the inert gas is supplied from the supply hole at a supply amount controlled so that the oxygen concentration in the gas discharged from the vent hole is equal to or lower than a target value, and the controlled discharge is performed. When the gas is discharged from the vent hole in an amount, if the oxygen concentration exceeds a third allowable value higher than the target value, the gas discharge amount from the vent hole is reduced. A method for producing a glass substrate.   In the clarification step, after reducing the discharge amount of the gas from the vent hole, the supply amount of the inert gas from the supply hole is less than the supply amount when the oxygen concentration is equal to or less than the target value. The manufacturing method of the glass substrate of Claim 6 which also increases.   The exhaust amount of the gas is reduced so as to reduce an inflow amount of outside air flowing into the gas phase space from an opening formed in the wall portion with use of the clarification tube. The manufacturing method of the glass substrate of description.   Using the relationship obtained in advance between the position of the opening and the change in the oxygen concentration that changes due to the opening, the information on the change in the measured value of the oxygen concentration in the vent hole The manufacturing method of the glass substrate of any one of Claims 6-8 which specifies the position of an opening.   The manufacturing method of the glass substrate of Claim 9 which adjusts the discharge | emission amount of the said gas according to the magnitude | size of the distance of the said opening and the said vent hole along the said flow direction. A refining tube for refining the molten glass while passing the molten glass so that a gas phase space is formed above the liquid surface of the molten glass, the refining tube comprising a material containing a platinum group metal, and the gas phase The wall portion in contact with the space has a vent hole for discharging the gas in the gas phase space, and a supply hole for supplying a gas inert to the molten glass into the gas phase space. The pores and the supply holes are clarified tubes arranged apart from each other in the flow direction of the molten glass,
An inert gas supply device for supplying the inert gas into the gas phase space;
Control is performed to supply the inert gas from the supply hole such that the oxygen concentration in the gas discharged from the vent hole is equal to or lower than a target value, and the oxygen concentration is higher than the target value during the control. A control device that controls the inert gas supply device so as to supply the inert gas from the vent hole to the gas-phase space when the first allowable value is exceeded. Glass substrate manufacturing equipment. A refining tube for refining the molten glass while passing the molten glass so that a gas phase space is formed above the liquid surface of the molten glass, the refining tube comprising a material containing a platinum group metal, and the gas phase The wall portion in contact with the space has a vent hole for discharging the gas in the gas phase space, and a supply hole for supplying a gas inert to the molten glass into the gas phase space. The pores and the supply holes are clarified tubes arranged apart from each other in the flow direction of the molten glass,
An inert gas supply device for supplying the inert gas into the gas phase space;
The inert gas is supplied from the supply hole at a supply amount controlled so that the oxygen concentration in the gas discharged from the vent hole is equal to or less than a target value, and the vent hole is controlled at a controlled discharge amount. When the gas is discharged from the gas, if the oxygen concentration exceeds a third allowable value higher than the target value, the inert gas supply is performed so as to reduce the gas discharge amount from the vent hole. And a control device for controlling the apparatus.

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