CN107879598B

CN107879598B - Method for manufacturing glass substrate, and glass substrate manufacturing apparatus

Info

Publication number: CN107879598B
Application number: CN201710897766.8A
Authority: CN
Inventors: 张钧奕
Original assignee: Anhan Vision Co ltd; Anhan Vision Holding Co ltd
Current assignee: Anhan Vision Co ltd; Anhan Vision Holding Co ltd
Priority date: 2016-09-30
Filing date: 2017-09-28
Publication date: 2020-09-15
Anticipated expiration: 2037-09-28
Also published as: CN107879598A

Abstract

The present invention relates to a method for manufacturing a glass substrate and an apparatus for manufacturing a glass substrate. The invention aims to reduce the oxygen concentration in a fining tube and inhibit foreign matters of platinum group metals from mixing into molten glass. The method for producing a glass substrate of the present invention includes a fining step for fining molten glass using a fining tube. In the fining step, the molten glass is fined while flowing into the fining tube so that a gas phase space is formed above the liquid surface of the molten glass. The clarifying pipe is made of a material containing a platinum group metal, and has, on a wall portion in contact with the gas phase space: a vent hole for discharging 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 vent hole and the supply hole are arranged to be spaced from each other in the flow direction of the molten glass. In the clarification step, the inert gas is supplied from the supply hole so that the oxygen concentration in the gas phase space becomes equal to or lower than a target value, and when the oxygen concentration exceeds an allowable value higher than the target value, the amount of gas discharged from the vent hole is made smaller than the amount of gas supplied when the oxygen concentration is equal to or lower than the allowable value.

Description

Method for manufacturing glass substrate, and glass substrate manufacturing apparatus

Technical Field

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

Background

The glass substrate is generally produced through a step of producing molten glass from a glass raw material and then forming the molten glass into a glass substrate. The above step includes a step of removing fine bubbles included in the molten glass (hereinafter, also referred to as fining). Fining is performed by heating the main body (fining tube) of the fining vessel, passing molten glass with a fining agent mixed therein through the fining tube, and removing bubbles from the molten glass by the redox reaction of the fining agent. More specifically, the temperature of the molten glass after the rough melting is further raised to cause the refining agent to function and cause bubbles to float and defoam, and then the temperature is lowered to cause the molten glass to absorb relatively small bubbles remaining without being completely defoamed. That is, the fining includes a defoaming treatment for defoaming bubbles floating and an absorption treatment for absorbing small bubbles in the molten glass.

The inner wall of the member in contact with the high-temperature molten glass before molding must be made of an appropriate material depending on 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 generally used as the material constituting the clarifying pipe (patent document 1). The platinum group metal has a high melting point and is excellent in corrosion resistance to molten glass.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent application laid-open No. 2010-111533

Disclosure of Invention

[ problems to be solved by the invention ]

When the molten glass passes through a fining tube using platinum group metals as the inner wall surface, the platinum group metals may be oxidized and volatilized in a portion of the heated inner wall surface in contact with the gas phase space. On the other hand, the platinum group metal oxide may be reduced at a position of the clarifying pipe where the temperature is locally lowered and may be attached to the inner wall surface. The platinum group metal adhering to the inner wall surface may fall down and be mixed into the molten glass, and may remain as foreign matter in the glass substrate. There is a concern that a glass substrate containing such foreign matter may be handled as a defective product.

In order to suppress such volatilization of platinum group metals, it is known to reduce the oxygen concentration by flowing an inert gas into a fining tube. However, it was found that the oxygen concentration did not decrease even when the inert gas was flowed.

The purpose of the present invention is to reduce the oxygen concentration in a fining tube and to suppress the mixing of foreign matter of platinum group metals into molten glass.

[ means for solving problems ]

The present invention includes a glass substrate manufacturing method and a glass substrate manufacturing apparatus according to the following embodiments.

(1): a method for manufacturing a glass substrate, characterized by comprising a fining step for fining molten glass using a fining tube,

in the fining step, the fining is performed while the molten glass is caused to flow into the fining tube so as to form a gas phase space above a liquid surface of the molten glass,

the clarifying pipe is made of a material containing a platinum group metal, and has, on a wall portion in contact with the gas phase space: a vent hole for discharging 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 vent hole and the supply hole are arranged to be spaced from each other in a flow direction of the molten glass,

in the clarifying step, when the inert gas is supplied from the supply hole so that the oxygen concentration in the gas discharged from the vent hole becomes a target value or less, the inert gas is supplied from the vent hole to the gas phase space when the oxygen concentration exceeds a 1 st allowable value that is higher than the target value.

(2): the method for producing a glass substrate according to the item (1), wherein in the fining step, when the inert gas is supplied from the supply hole, if a 2 nd allowable value, which is an oxygen concentration lower than the 1 st allowable value and higher than the target value, is exceeded before the oxygen concentration exceeds the 1 st allowable value, the amount of inert gas supplied from the supply hole is made larger than the amount of inert gas supplied from the supply hole if the oxygen concentration is equal to or less than the target value.

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

(4): the method for manufacturing a glass substrate according to any one of the above (1) to (3), wherein the inert gas is supplied so as to reduce an inflow amount of an external gas flowing into the gas phase space from an opening formed in the wall portion with use of the finer tube.

(5): the method for manufacturing a glass substrate according to any one of the above (1) to (4), wherein the position of the opening formed in the wall portion is specified from information on a change in the measured value of the oxygen concentration in the vent hole, using a predetermined correspondence between the position of the opening and a change in the oxygen concentration that changes due to the opening, the change being caused by the use of the finer tube.

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

(7): the method for manufacturing a glass substrate according to the item (5) or (6), wherein the inert gas is further supplied into the gas phase space from the opening hole at the specified position.

(8): the method for producing a glass substrate according to any one of the above (1) to (7), wherein in the fining step, when the inert gas is supplied from the supply hole in a controlled supply amount so that the oxygen concentration becomes a target value or less and the gas is discharged from the vent hole in a controlled discharge amount, the discharge amount of the gas from the vent hole is reduced when the oxygen concentration exceeds the 1 st allowable value.

(9): a method for manufacturing a glass substrate, characterized by comprising a fining step for fining molten glass using a fining tube,

in the clarifying step, when the inert gas is supplied from the supply hole in a controlled supply amount so that the oxygen concentration in the gas discharged from the vent hole becomes a target value or less and the gas is discharged from the vent hole in a controlled discharge amount, the discharge amount of the gas from the vent hole is reduced in a case where the oxygen concentration exceeds a 3 rd allowable value that is higher than the target value.

(10): the method for producing a glass substrate according to the item (9), wherein in the fining step, after the amount of gas discharged from the vent hole is reduced, the amount of inert gas supplied from the supply hole is made larger than that in the case where the oxygen concentration is equal to or less than the target value.

(11): the method for producing a glass substrate according to the item (9) or (10), in which an amount of the discharged gas is reduced so as to reduce an inflow amount of the outside gas flowing into the gas phase space from the opening formed in the wall portion with use of the finer tube.

(12): the method for manufacturing a glass substrate according to any one of the above (9) to (11), wherein the position of the opening formed in the wall portion is specified from information on a change in the measured value of the oxygen concentration in the vent hole, using a predetermined correspondence between the position of the opening and the change in the oxygen concentration that changes due to the opening, the change being caused by the use of the finer tube.

(13) The method for manufacturing a glass substrate according to the item (12), wherein an amount of the gas discharged is adjusted according to a distance between the vent hole and the vent hole along the flow direction.

(14) The method for manufacturing a glass substrate according to the item (12) or (13), wherein the inert gas is further supplied into the gas phase space from an opening hole which specifies the position.

(15) The method for manufacturing a glass substrate according to any one of the items (5) to (7) and (12) to (14), wherein a diameter of the opening is 50% or more of a diameter of the vent hole.

(16) The method for producing a glass substrate according to any one of the above (1) to (15), wherein a supply amount of the inert gas is adjusted so that bubbles are not generated in the refined molten glass.

(17): a glass substrate manufacturing apparatus is characterized by comprising:

a fining tube for fining molten glass while passing the molten glass through the fining tube so as to form a gas phase space above a liquid surface of the molten glass, the fining tube being made of a material containing a platinum group metal, and having, on a wall portion in contact with the gas phase space: a vent hole for discharging 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 vent hole and the supply hole are arranged to be spaced apart from each other in a flow direction of the molten glass;

an inert gas supply device for supplying the inert gas into the gas phase space; and

a control device that controls the inert gas supply device in the following manner: when the inert gas is supplied from the supply hole so that the oxygen concentration in the gas discharged from the vent hole becomes equal to or lower than a target value, the inert gas is supplied from the vent hole to the gas phase space when the oxygen concentration exceeds a 1 st allowable value that is higher than the target value.

(18): a glass substrate manufacturing apparatus is characterized by comprising:

a control device that controls the inert gas supply device in the following manner: when the inert gas is supplied from the supply hole in a controlled supply amount so that the oxygen concentration in the gas discharged from the vent hole becomes a target value or less and the gas is discharged from the vent hole in a controlled discharge amount, the discharge amount of the gas from the vent hole is reduced when the oxygen concentration exceeds a 3 rd permissible value that is higher than the target value.

[ Effect of the invention ]

According to the present invention, the concentration of oxygen in the fining tube can be reduced to suppress the mixing of foreign matter of platinum group metals into the molten glass.

Drawings

Fig. 1 is a flowchart showing a method for manufacturing a glass substrate.

Fig. 2 is a schematic view of a glass substrate manufacturing apparatus.

FIG. 3 is a schematic view of the fining tube shown in FIG. 2.

Fig. 4(a) is an explanatory view for explaining a damaged fining tube in embodiment 1, and (b) is an explanatory view for explaining supply of inert gas from the vent hole in embodiment 1.

Fig. 5(a) is an explanatory view for explaining a damaged fining tube in embodiment 2, and (b) is an explanatory view for explaining reduction in the amount of gas discharged from the vent hole in embodiment 2.

Detailed Description

The following describes a method and an apparatus for manufacturing a glass substrate according to the present embodiment.

(Overall outline of the method for producing glass substrate)

Fig. 1 is a diagram showing an example of the steps of the method for manufacturing a glass substrate according to the present embodiment. The method for manufacturing a glass substrate mainly includes a melting step (ST1), a refining step (ST2), a homogenizing step (ST3), a supplying step (ST4), a forming step (ST5), a slow cooling step (ST6), and a cutting step (ST 7). Further, the method may further include a grinding step, a polishing step, a washing step, an inspection step, a packaging step, and the like. The manufactured glass substrates are laminated as necessary in a packing step, and are transported to a purchaser.

In the melting step (ST1), molten glass is produced by heating glass raw materials.

In the fining step (ST2), the temperature of the molten glass is raised to generate a molten glass containing oxygen and CO contained in the molten glass₂Or SO₂The bubble of (2). The bubbles absorb oxygen generated by a reduction reaction of a fining agent (tin oxide or the like) contained in the molten glass, grow, float to the liquid surface of the molten glass, and are released. Then, in the fining 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 fining agent. As a result, gas components such as oxygen remaining in the bubbles in the molten glass are absorbed again into the molten glass, and the bubbles are extinguished.

In the homogenization step (ST3), the molten glass is stirred by a stirrer to homogenize the glass components. This can reduce the composition unevenness of the glass, which causes the occurrence of streaks and the like. The homogenization step is carried out in a stirring tank described below.

In the supply step (ST4), the homogenized molten glass is supplied to a forming apparatus.

The forming step (ST5) and the slow cooling step (ST6) are performed by a forming apparatus.

In the forming step (ST5), the molten glass is formed into a sheet glass that is a ribbon-shaped glass having a specific thickness, and a fluid of the sheet glass is formed. In the forming, a float method, a melting method (overflow down draw method), or the like is used, but in the melting method, it is not easy to extend a slow cooling device on a production line, and therefore the melting method is suitable for a method for producing a glass substrate including off-line heat treatment (described below).

In the slow cooling step (ST6), the sheet glass that has been molded and flowed is cooled so that the sheet glass has a desired thickness and internal strain, and further so that warpage does not occur.

In the cutting step (ST7), the sheet glass after slow cooling is cut into a specific length to obtain a plate-shaped glass substrate. The operation of cutting the sheet glass into a green sheet of a specific length may also be referred to as cutting the sheet. The glass substrate obtained by the plate cutting is further cut into a specific size to produce a glass substrate of a target size.

In the cutting step (ST7), the glass substrate obtained by cutting may be, for example, clamped and held by a conveyance mechanism (not shown), and may be guided and conveyed to a furnace in which the heat treatment step is performed, and then subjected to heat treatment. The glass substrate after the cutting or the heat treatment is further conveyed to a cutting device and cut into a product size to obtain a glass substrate. The following steps are performed, for example, on the glass substrate obtained in the cutting step (ST 7).

In the grinding step and the polishing step, end face machining including grinding, polishing, and chamfering of the end face of the glass substrate is performed. In the cleaning step, the glass substrate after the end surface processing is cleaned in order to remove fine foreign matters or stains on the glass surface (1 st cleaning). After the 1 st 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 (cleaning 2), and in the inspection step, optical inspection is performed to confirm whether the cleaned glass substrate has a flaw including a flaw, dust, stain, or optical defect. In the packing step, the glass substrates whose quality is confirmed by inspection are packed in a tray as a laminated body alternately laminated with paper for protecting the glass substrates. The bundled glass substrates are shipped to the purchaser.

(overview of the glass substrate manufacturing apparatus as a whole)

Fig. 2 is a schematic view of the 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 fining tube 102, a stirring tank 103,

transfer tubes

104 and 105, and a glass supply tube 106.

The melting tank 101 shown in FIG. 2 is provided with a heating means such as a burner, not shown. The glass raw material to which the refining agent is added is charged into the melting vessel 101 and melted (ST 1). The molten glass melted in the melting tank 101 is supplied to the fining tube 102 through the transfer tube 104.

In the fining tube 102, the temperature of the molten glass MG is adjusted, and a fining step of the molten glass is performed by the redox reaction of the fining agent (ST 2). Specifically, the molten glass in the fining tube 102 is heated to increase the temperature of the molten glass, thereby making the molten glass contain oxygen and CO contained in the molten glass₂Or SO₂The bubbles absorb oxygen generated by the reduction reaction of the fining agent, grow, float to the surface of the molten glass, and are released into the gas phase space. Then, the temperature of the molten glass is lowered, whereby a reduced substance generated by the reduction reaction of the fining agent is subjected to an oxidation reaction. As a result, gas components such as oxygen remaining in the bubbles in the molten glass are again absorbed into the molten glass, and the bubbles are extinguished. The clarified molten glass is supplied to the stirring tank 103 through the transfer pipe 105.

In the stirring tank 103, the molten glass is stirred by the stirrer 103a to perform the homogenization step (ST 3). The molten glass homogenized in the stirring tank 103 is supplied to the forming apparatus 200 via the glass supply pipe 106 (supply step ST 4).

In the forming apparatus 200, the sheet glass SG is formed from the molten glass by, for example, the overflow downdraw method (forming step ST5) and slowly cooled (slow cooling step ST 6).

In the cutting device 300, a plate-like glass substrate cut out of the sheet glass SG is formed (cutting step ST 7).

(constitution of clarifying tube)

Next, the structure of the clarifying pipe 102 will be described with reference to fig. 3. Fig. 3 is a schematic view showing the structure of the clarifying pipe 102.

The clarifying pipe 102 is a tubular member made of a material containing a platinum group metal. The platinum group metal refers to 6 elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), and iridium (Ir). The material containing a platinum group metal is a material containing a single element of a platinum group metal or an alloy containing a platinum group metal. For example, platinum or a platinum alloy is used.

Flange-

like electrodes

121a, 121b, and 121c are connected to the outer peripheral surface of the fining tube 102. In the example shown in fig. 3, the electrodes 121a to 121c are disposed at 3 positions, i.e., at both ends and the center in the longitudinal direction of the fining tube 102. The electrodes 121a to 121c are connected to a power supply device 122. By applying a voltage between the

electrodes

121a and 121b and between the

electrodes

121b and 121c, respectively, a current flows between the

electrodes

121a and 121b and between the

electrodes

121b and 121c, respectively, and the clarifying pipe 102 is heated by energization.

By this energization heating, the highest temperature of the finer tube 102 is heated between the

electrodes

121a and 121b to a temperature of, for example, 1600 to 1750 ℃, more preferably 1630 to 1750 ℃, and the highest temperature of the molten glass flowing through the finer tube 102 is heated to a temperature suitable for defoaming, 1600 to 1720 ℃, more preferably 1620 to 1720 ℃. Further, between the

electrodes

121b and 121c, the heating is performed so that the highest temperature of the finer tube 102 becomes, for example, 1590 ℃ to 1670 ℃, more preferably 1620 ℃ to 1670 ℃, and the highest temperature of the molten glass flowing through the finer tube 102 is heated to 1590 ℃ to 1640 ℃, more preferably 1610 ℃ to 1640 ℃ which is a temperature suitable for absorption.

The power supply device 122 is controlled by the control device 123. The controller 123 controls the amount of current supplied to the fining tube 102 from the power supply 122, thereby controlling the temperature of the molten glass passing through the fining tube 102. The control device 123 is a computer including a CPU (Central Processing Unit), a memory, and the like.

The electrodes 121a to 121c are cooled with water or air. Therefore, in the fining tube 102, a region in which the temperature is locally decreased is formed in accordance with the arrangement position of the electrodes 121a to 121 c.

The number of electrodes provided in the fining tube 102 is not limited to 3, and may be 2 or 4 or more.

In the fining step (ST2), the molten glass is fined while flowing into the finer tube 102 so that a gas-phase space 120a is formed above the liquid surface of the molten glass. The clarifying pipe 102 is formed on the wall portion contacting the gas phase space 120a as shown in fig. 4(a) and 4 (b): a vent hole 102a for discharging gas in the gas phase space; and a supply hole 102b for supplying a gas inert to the molten glass (hereinafter referred to as an inert gas) into the gas phase space. Fig. 4(a) and 4(b) are vertical sectional views showing a section along the longitudinal direction of the clarifying pipe 102. The vent holes 102a and the supply holes 102b are arranged to be spaced apart from each other in the flow direction of the molten glass.

The vent hole 102a does not include a hole (for example, the opening 131 described below) formed as the clarifying pipe 102 is used. The discharge of the gas from the vent hole 102a may be continued during the clarification step (ST2) or may be performed intermittently. For example, the gas may not be discharged from the vent hole 102a during the period in which the inert gas described below is supplied. 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 exists. A vent 127 communicates the vapor space 120a with the space (e.g., atmosphere) outside of the finer tube 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 portion. The vent hole 102a and the vent pipe 127 are disposed, for example, at a position where the molten glass has a highest temperature in the fining step (ST2) or in the vicinity of the downstream side thereof. The vent hole 102a and the vent tube 127 are provided between the

electrodes

121a and 121b in the example shown in fig. 3.

A suction device 129 for sucking the gas and floating objects in the gas phase space 120a is provided in the duct 127. The pressure on the side of the breather pipe 127 can be reduced (by about 10Pa, for example, compared to the atmospheric pressure) by the suction device 129. The suction means 129 are controlled by the control means 123. The suction pressure is controlled by the suction device 129, whereby the concentration of oxygen in the gas phase space 120a can be reduced. In addition, by controlling the suction pressure, the amount of the inert gas supplied from the inert

gas supply devices

125 and 126 described below to the gas phase space 120a can be adjusted.

The vent pipe 127 is surrounded by a heat insulating member (described below), and the opening degree of the vent pipe 127 can be adjusted by adjusting the size of the gap of the heat insulating member disposed near the upper end of the vent pipe 127. The gas is discharged from the vent hole 102a by suction by the suction device 129, and by a difference in gas pressure between the inside and the outside of the clarifying pipe 102. The discharge amount of the gas from the vent hole 102a is adjusted by adjusting the suction pressure of the suction device 129 or the opening degree of the vent pipe 127.

An oxygen concentration meter 128 is provided in the vent pipe 127. The oxygen concentration meter 128 measures the oxygen concentration of the gas discharged from the vent hole 102a, and outputs the measurement signal to the control device 123. The signal of the oxygen concentration 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 based on the signal of the oxygen concentration, and generates a control signal for adjusting the supply amount and the supply pressure of the inert gas. The control device 123 generates a control signal to adjust the suction pressure of the suction device 129 or the opening degree of the vent pipe 127 based on the signal of the oxygen concentration. The generated control signal is sent to the inert gas supply means 125, 126 or the suction means 129 or a not-shown adjusting means that adjusts the opening degree of the breather pipe 127. Thereby, the supply amount and supply pressure of the inert gas are adjusted, or the discharge amount of the gas from the vent hole 102a is adjusted. Hereinafter, 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 as the oxygen concentration in the gas phase space.

The vent pipe 127 is connected to the inert gas supply 126. The inert gas supply device 126 can supply the inert gas from the inert gas supply device 126 to the gas phase space 120a via the breather 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 adjusts the supply amount and the supply pressure of the inert gas under the control of the control device 123. 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 102 a. When the inert gas is intermittently supplied, the inert gas can be supplied by blowing the inert gas into the breather pipe 127 when the suction by the suction device 129 is stopped. In the case of continuously supplying the inert gas, for example, a partition plate or another pipe having a smaller diameter than the vent pipe 127 may be arranged in the vent pipe 127 so as to divide the interior of the vent pipe 127 into a plurality of flow paths in a cross section perpendicular to the gas flow direction, and the inert gas may be supplied from a block different from the block where the gas is sucked by the suction device 129. Further, 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 exists. In the example shown in fig. 3, the supply hole 102b and the supply pipe 124 are provided between the

electrodes

121b and 121 c. 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 to adjust the supply amount and supply pressure of the inert gas. The inert gas introduced from the supply pipe 124 flows from the right to the left in fig. 3 along the flow direction of the molten glass.

The inert gas supplied from the inert

gas supply devices

125, 126 is preferably inert not only to the molten glass but also to the platinum group metal. For example, nitrogen (N) can be used₂) Rare gases (e.g., argon (Ar)), carbon monoxide (CO), and the like. Argon or carbon monoxide move more easily in the glass structure than nitrogen. Therefore, even when the inert gas dissolved in the molten glass is generated in the form of bubbles, the inert gas is easily sucked into the glass again during the transfer of the molten glass. Therefore, argon gas 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 becomes equal to or lower than the target value. In the following description, a case where the measurement value obtained by the oxygen concentration meter 128 is used 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 of the oxygen concentration at which volatilization of the platinum group metal can be favorably suppressed in the gas phase space 120a, and is, for example, 5%. From the viewpoint of suppressing the dissolution of the inert gas into the molten glass and suppressing the generation of bubbles of the dissolved inert gas, the lower limit of the target value is, for example, 0.1%, preferably 1%.

The finer tube 102 is coated with a cement casting material (not shown), and a heat insulating member (not shown) such as a firebrick is deposited on the outside thereof. That is, a heat insulating member is provided around the fining tube 102. The heat insulating member is disposed so as to be in contact with the electrodes 121a to 121c, the vent pipe 127, and the supply pipe 124, respectively.

(clarification step: embodiment 1)

Next, the supply of the inert gas performed in embodiment 1 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 holes 102 a) becomes equal to or lower than the target value, the inert gas is supplied from the vent holes 102a to the gas phase space 120a when the oxygen concentration exceeds the 1 st allowable value due to some cause (for example, deformation of the wall portion, or formation of an opening in the wall portion so that oxygen in the outside gas enters the gas phase space 120 a). For example, when the 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 becomes equal to or lower than the target value and the gas is discharged from the vent hole 102a at a controlled discharge amount, the inert gas is supplied from the vent hole 102a to the gas phase space 120a when the oxygen concentration rises and exceeds the 1 st allowable value. The allowable value 1 is a value of oxygen concentration at which the possibility of volatilization of the platinum group metal in the gas phase space 120a cannot be suppressed if the allowable value exceeds this value. The allowable value 1 is preferably 14 to 21%, for example, 20%, preferably 15%. When the oxygen concentration exceeds the 1 st 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 102 a. By supplying the inert gas into the gas phase space 120a from the vent hole 102a which is usually used as a discharge port for discharging the gas in the gas phase space 120a in this manner, the concentration of oxygen which becomes too high in the fining tube 102 can be reliably reduced, and volatilization of platinum group metals can be suppressed. When the oxygen concentration becomes the 1 st allowable value or less, the supply of the inert gas from the vent hole 102a may be stopped, or the supply of the inert gas may be continued until the oxygen concentration becomes the target value or less.

In the present embodiment, when the oxygen concentration (the oxygen concentration in the gas discharged from the vent hole 102 a) exceeds the 2 nd allowable value which is lower than the 1 st allowable value and higher than the target value before exceeding the 1 st allowable value, it is preferable that the supply amount of the inert gas from the supply hole 102b is larger than the supply amount in the case where the oxygen concentration is equal to or lower than the target value. The 2 nd allowable value is a value of oxygen concentration at which volatilization of the platinum group metal may not be sufficiently suppressed in the gas phase space 120a if the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102 a) exceeds the value. The allowable value 2 is preferably 7 to 11%, for example, 10%, preferably 8%. Specifically, when the oxygen concentration exceeds the 2 nd allowable value for some reason (for example, the wall portion is deformed, or an opening is formed in the wall portion), first, the inert gas supply device 125 and the suction device 129 are controlled so as to increase the supply amount of the inert gas from the supply hole 102 b. As a result, in the case where the oxygen concentration is decreased by increasing the supply amount of the inert gas from the supply hole 102b, the inert gas is not supplied from the vent hole 102 a. On the other hand, when the oxygen concentration cannot be reduced and exceeds the 1 st allowable value even if the supply amount of the inert gas from the supply hole 102b is increased, the inert gas supply device 126 is controlled to supply the inert gas from the vent pipe 127 as described above. In addition, the amount of the inert gas supplied from the supply hole 102b, which is increased by exceeding the 2 nd allowable value, may be maintained or may be further increased during the period in which the inert gas is supplied from the vent hole 102 a. In addition, when the oxygen concentration is equal to or lower than the 2 nd 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.

However, since the clarifying pipe 102 is maintained at a high temperature in the clarifying step (ST2), it may be damaged with use. Here, with reference to fig. 4(a) and 4(b), a case where the fining tube 102 is damaged will be described. Fig. 4(a) is an explanatory diagram for explaining a case where the oxygen concentration exceeds the 1 st allowable value. Fig. 4(b) is an explanatory diagram for explaining the supply of the inert gas in the case where the oxygen concentration exceeds the 1 st allowable value.

The clarifying pipe 102 may be deformed so that a wall portion contacting the gas phase space 120a may be inwardly sagged in use. In the portion deformed as described above (hereinafter, referred to as a deformed portion), the area of the gas flow path in the gas phase space 120a is reduced, and therefore the flow of the gas along the flow direction of the molten glass is likely to be stopped. In particular, when the deformation amount of the deformation portion 130 is large or the liquid surface of the molten glass rises, as shown in fig. 4(a), the lower end of the deformation portion 130 reaches the liquid surface of the molten glass, and the flow of the gas along the flow direction of the molten glass is blocked. As a result, the inert gas does not move to the portion of the gas phase space 120a opposite to the supply hole 102b with respect to the deformation portion 130, that is, the portion on the side where the vent hole 102a exists, and the oxygen concentration in this portion rises, and the oxygen concentration becomes uneven in the portion along the flow direction in the gas phase space 120 a.

In addition, the fining tube 102 may not be able to avoid the platinum group metals from volatilizing from the wall and thinning the wall, depending on the conditions of the fining step (ST 2). If the thickness is reduced, an opening 131 penetrating the wall may be formed as shown in fig. 4 (a). If the openings 131 are formed, the external gas containing oxygen is introduced into the gas phase space 120a through the openings 131 in such a manner as to compensate for the discharge amount of the gas from the vent hole 102 a. In particular, when the amount of discharge is increased by the suction of the suction device 129 or by the large opening degree of the vent hole 102a, the inflow amount of the outside air containing oxygen is large, and the oxygen concentration in the gas phase space 120a is likely to increase due to the oxygen contained in the outside air.

As described above, if the purge pipe 102 is damaged, the possibility that the oxygen concentration cannot be maintained within the target value and exceeds the 1 st allowable value is increased even if the inert gas is supplied from the supply hole 102 b.

Further, since the heat insulating material is usually provided on the outer periphery of the fining tube 102, even if the deformed portion 130 or the hole 131 is formed, it is not easy to find out the deformed portion 130 or the hole 131, and even if the deformed portion 130 or the hole 131 is formed, it is not easy to know the position of the deformed portion or the hole. Therefore, it is difficult to take measures against the increase in the oxygen concentration in the gas phase space 120 a.

In the present embodiment, when the oxygen concentration exceeds the 1 st allowable value, as shown in fig. 4(b), the inert gas is supplied from the vent hole 102a, whereby the inert gas is supplied to the portion opposite to the supply hole 102b with respect to the deformation portion 130, and the oxygen concentration in the gas phase space 120a on the side of the vent hole 102a with respect to the deformation portion 130 is reduced, whereby the unevenness of the oxygen concentration in the gas phase space 120a can be improved. In addition, the inert gas is supplied from the vent hole 102a, thereby suppressing the inflow of the external gas from the opening 131. This can reliably reduce the oxygen concentration in the gas phase space 120a, thereby suppressing volatilization of the platinum group metal. Therefore, even if the finer tube 102 is damaged, the glass substrate can be continuously manufactured (handled).

It is preferable to increase the amount of inert gas supplied from the supply hole 102b in addition to the supply of inert gas from the vent hole 102 a. Thus, for example, when the position of the formed deformed portion 130 in the tube axis direction (the flow direction of the molten glass) of the fining tube 102 is on the same side in the tube axis direction as the vent hole 102a and the supply hole 102b when viewed from the vent hole 102a and the supply hole 102b, the oxygen concentration can be reduced by increasing the amount of inert gas supplied from the supply hole 102b when the oxygen concentration exceeds the 2 nd allowable value. On the other hand, when the formed deformation portion 130 is located on a different side as viewed from the vent hole 102a and the supply hole 102b in the position of the clarifying pipe 102 in the pipe axial direction, the oxygen concentration exceeds the 2 nd allowable value, and the oxygen concentration does not decrease even if the supply amount of the inert gas from the supply hole 102b is increased, and even if the oxygen concentration exceeds the 1 st allowable value, the oxygen concentration can be reliably decreased by supplying the inert gas from the vent hole 102 a.

In the present embodiment, the position of the opening 131 (the position in the pipe axial direction of the fining tube 102) can be specified from the information on the change in the measurement value of the oxygen concentration in the vent hole 102a by utilizing a predetermined relationship between the position of the opening formed in the wall portion (the position in the pipe axial direction of the fining tube 102) and the change in the oxygen concentration caused by the opening 131 as the fining tube 102 is used. The correspondence relationship between the positions of the orifices 131 and the changes in the oxygen concentration can be obtained, for example, by obtaining the relationship between the conditions of the clarification step (ST2) and the oxygen concentration from the changes in the oxygen concentration when the conditions of the clarification step (ST2) are changed, and further obtaining the relationship between the conditions of the clarification step (ST2) and the oxygen concentration in the same manner using another clarification pipe 102 having different positions of the orifices 131 along the pipe axial direction of the clarification pipe 102, and obtaining the correspondence relationship from the obtained plurality of relationships. As the conditions for such a clarification step (ST2), for example, the 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 determined 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. As the measured value of the oxygen concentration, a correspondence relationship obtained by modeling the damaged fining tube 102 and the molten glass and simulating a change in the oxygen concentration due to the supply of the inert gas may be used.

In the present embodiment, the supply amount of the inert gas can be adjusted by specifying the position of the hole 131 and further according to the distance between the hole 131 and the vent hole 102a in the flow direction. The following are clarified by the study of the present inventors: the smaller the distance between the opening 131 and the vent hole 102a in the tube axial direction (the flow direction of the molten glass), that is, the closer the opening 131 is to the vent hole 102a, the higher the oxygen concentration in the gas-phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102 a). For this reason, it is considered that the closer the opening 131 is to the vent hole 102a, the stronger the force (e.g., suction pressure) of discharging the gas from the vent hole 102a acts, and the more the amount of the outside gas flowing in from the opening 131. 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 position-specified opening 131 and the vent hole 102 a. Specifically, the supply amount and the supply pressure of the inert gas by the inert gas supply device 126 are controlled based on the distance between the hole 131 and the vent hole 102 a.

Further, by specifying the position of the hole 131, it is possible to supply an inert gas into the gas phase space from the hole 131 specified at the specified position. Specifically, the heat insulating material disposed near the hole 131 at the specified position is partially removed, and the inert gas can be supplied from the hole 131 by connecting a supply pipe (not shown) similar to the supply pipe 124 to the wall of the fining tube 102 where the hole 131 exists, and connecting an inert gas supply device (not shown) similar to the inert gas supply device 125 to the supply pipe. This can further reduce the oxygen concentration in the gas phase space 120 a.

Further, by specifying the position of the opening 131, the heat insulating material in the vicinity of the opening 131 at the specified position can be partially removed, and the wall portion of the clarification pipe 102 in which the opening 131 is formed can be repaired.

As described above, in the clarification step (ST2), although 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 102 a) becomes equal to or lower than the target value, the inert gas is supplied from the vent hole 102a to the gas-phase space when the oxygen concentration rises for some reason and exceeds the 1 ST allowable value. This can reliably reduce the concentration of oxygen that becomes too high in the fining tube 102, thereby suppressing volatilization of platinum group metals from the fining tube 102, and thus preventing foreign matter of platinum group metals from mixing into the molten glass.

Further, when the oxygen concentration (the oxygen concentration in the gas discharged from the vent hole 102 a) exceeds the 2 nd allowable value, the oxygen concentration cannot be reduced even if the supply amount of the inert gas from the supply hole 102b is increased, and when the oxygen concentration exceeds the 1 st allowable value, the oxygen concentration can be reliably reduced by supplying the inert gas from the vent hole 102 a.

Further, the position of the hole 131 can be specified from the measured change in the oxygen concentration by utilizing a previously obtained correspondence between the position of the hole 131 in the wall portion along the tube axial direction of the finer tube 102 (the flow direction of the molten glass) and the change in the oxygen concentration due to the hole. Further, by supplying the inert gas from the opening 131 at the specified position, the oxygen concentration can be further reduced.

(clarification step: embodiment 2)

Next, the operation of discharging from the vent pipe 127 performed in embodiment 2 of the clarification step (ST2) will be described.

In the present embodiment, the following may be also used: 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 102 a) becomes equal to or lower than the target value, the oxygen concentration increases, as in the case of embodiment 1 of the above-described clarification step. In the present embodiment, when the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent holes 102 a) exceeds the 3 rd allowable value that is higher than the target value, the amount of gas discharged from the vent holes 102a is reduced. For example, when 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 becomes equal to or lower than a target value and the gas is discharged from the vent hole 102a at a controlled discharge amount, the discharge amount from the vent hole 102a is reduced when the value exceeds the 3 rd allowable value which is higher than the target value. It is considered that the reason for this increase in oxygen concentration is that oxygen enters the gas phase zone 120a due to some cause (for example, formation of an opening in the wall). The 3 rd permissible value is a value of oxygen concentration at which the possibility of volatilization of the platinum group metal in the gas phase space 120a cannot be suppressed increases if this value is exceeded. The allowable value 3 is preferably 14 to 21%, for example, 20%, preferably 15%. When the oxygen concentration exceeds the allowable value, specifically, the suction pressure of the suction device 129 is controlled or the opening degree of the breather pipe 127 is adjusted so as to reduce the amount of gas discharged from the breather hole 102 a. In this way, by reducing the discharge amount from the breather pipe 127, for example, by further reducing the discharge amount than the controlled discharge amount, the inflow amount of the outside air including oxygen gas into the gas phase space 120a can be reliably reduced, the oxygen gas concentration in the fining tube 102 that becomes too high can be reliably reduced, and volatilization of platinum group metals can be suppressed. When the oxygen concentration is equal to or lower than the 3 rd permissible value, the amount of gas discharged from the vent hole 102a may be increased to an amount exceeding the 3 rd permissible value or may be maintained. Here, the 3 rd allowable value is preferably the same as the 1 st allowable value in embodiment 1. Therefore, in embodiment 1, when the allowable value exceeds the 1 st allowable value (allowable value 3), it is preferable to supply the inert gas from the vent hole 102a to the gas phase space 120a and reduce the amount of gas discharged from the vent hole 102 a.

In the present embodiment, it is preferable that the amount of inert gas supplied from the supply holes 102b is made larger than that in the case where the oxygen concentration is equal to or lower than the target value after the amount of gas discharged from the vent holes 102a is reduced. Specifically, after the discharge amount of the gas from the vent hole 102a is reduced, the inert gas supply device 125 and the suction device 129 are controlled so as to increase the supply amount of the inert gas from the supply hole 102 b. If the amount of gas discharged from the gas vent holes 102a is reduced, the amount of inert gas discharged from the gas vent holes 102a can be suppressed to be small even if the amount of inert gas supplied from the supply holes 102b is increased, and the oxygen concentration in the gas phase space 120a can be efficiently reduced.

Since the clarifying pipe 102 is maintained at a high temperature in the clarifying step (ST2), it may be damaged with use. Here, a case where the fining tube 102 is damaged will be described with reference to fig. 5(a) and 5 (b). Fig. 4(a) is an explanatory diagram for explaining a case where the oxygen concentration exceeds the allowable value. Fig. 4(b) is an explanatory diagram for explaining reduction of the amount of gas discharged from the vent pipe 127 when the oxygen concentration exceeds the allowable value.

The fining tube 102 may not easily avoid volatilization of the platinum group metal from the wall portion and thinning of the wall portion depending on the conditions of the fining step (ST 2). If the thickness is reduced, an opening 131 penetrating the wall may be formed as shown in fig. 4 (a). If the openings 131 are formed, the external gas containing oxygen is introduced into the gas phase space 120a through the openings 131 in such a manner as to compensate for the discharge amount of the gas from the vent hole 102 a. In particular, when the amount of discharge is increased by the suction of the suction device 129 or by the large opening degree of the vent hole 102a, the inflow amount of the outside air containing oxygen is large, and the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent hole 102 a) is likely to increase by the oxygen contained in the outside air.

As described above, if the purge pipe 102 is damaged, the oxygen concentration cannot be maintained within the target value even if the inert gas is supplied from the supply hole 102b, and the possibility of exceeding the allowable value is increased.

Further, since the heat insulating material is usually provided on the outer periphery of the fining tube 102, even if the hole 131 is formed, the hole is not easily found, and even if the hole 131 is found, the position of the hole is not easily known. Therefore, it is difficult to take measures against the increase in the oxygen concentration in the gas phase space 120 a.

In the present embodiment, when the oxygen concentration exceeds the allowable value, the amount of the external air flowing from the opening 131 to compensate for the gas discharged from the vent hole 102a can be reduced by reducing the amount of the gas discharged from the vent hole 102a, as shown in fig. 4 (b). Therefore, the oxygen concentration in the gas phase space 120a can be reliably reduced, and volatilization of the platinum group metal can be suppressed. Therefore, even if the finer tube 102 is damaged, the glass substrate can be continuously manufactured (handled). In this case, it is preferable to increase the amount of inert gas supplied from the supply holes 102b in addition to reducing the amount of gas discharged from the vent holes 102 a.

In the present embodiment, as described in embodiment 1, the position of the opening 131 (the position in the pipe axial direction of the fining tube 102) can be specified from the information on the change in the measurement value of the oxygen concentration in the vent hole 102a by using a predetermined correspondence between the position of the opening formed in the wall portion with the use of the fining tube 102 (the position in the pipe axial direction of the fining tube 102) and the change in the oxygen concentration caused by the opening 131.

In the present embodiment, as in embodiment 1, the position of the opening 131 is specified, and the amount of gas to be discharged can be adjusted according to the distance between the opening 131 and the vent hole 102a in the flow direction.

Further, by specifying the position of the hole 131, it is possible to supply an inert gas into the gas phase space from the hole 131 specified at the specified position. Specifically, the heat insulating member disposed in the vicinity of the opening 131 at the specified position is opened, a supply pipe (not shown) similar to the supply pipe 124 is connected to the wall of the fining tube 102 where the opening 131 exists, an inert gas supply device (not shown) similar to the inert gas supply device 125 is connected to the supply pipe, and the inert gas can be supplied from the opening 131. This can further reduce the oxygen concentration in the gas phase space 120 a.

Further, by specifying the position of the opening 131, the heat insulating member in the vicinity of the opening 131 specified at the specified position can be opened, and the wall portion of the clarification pipe 102 in which the opening 131 is formed can be repaired.

According to embodiment 2, in the clarification step (ST2), the amount of gas discharged from the gas communication hole 102a is reduced when the oxygen concentration increases and exceeds the 3 rd allowable value even though 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 gas communication hole 102 a) becomes equal to or lower than the target value. This can reduce the amount of oxygen flowing into the outside for some reason, and can reliably reduce the oxygen concentration that becomes too high in the fining tube 102. Therefore, volatilization of platinum group metals from the fining tube 102 can be suppressed, and mixing of foreign matter of platinum group metals into the molten glass can be suppressed.

Further, by making the supply amount of the inert gas from the supply holes 102b larger than that in the case where the oxygen concentration is equal to or less than the target value after the discharge amount of the gas from the vent hole 127 is reduced, the oxygen concentration in the gas phase space 120a can be efficiently reduced.

Further, by reducing the amount of gas discharged from the vent hole 102a, the amount of external gas flowing into the gas phase space 120a from the opening 131 formed in the wall portion with the use of the purge pipe 102 can be reduced.

Further, the positions of the holes can be specified from the oxygen concentration by using a predetermined relationship between the positions of the holes 131 in the wall portion along the flow direction and the magnitude of the oxygen concentration.

Further, the position of the hole 131 can be specified from the change in the oxygen concentration by utilizing a previously obtained correspondence between the position of the hole in the wall portion along the tube axial direction (the flow direction of the molten glass) of the finer tube 102 and the change in the oxygen concentration that changes due to the hole. Further, by supplying the inert gas from the opening 131 at the specified position, the oxygen concentration can be further reduced.

In addition, by adjusting the amount of gas discharged according to the magnitude of the distance between the openings 131 and the vent holes 102a in the flow direction, the oxygen concentration in the gas phase space 120a (the oxygen concentration in the gas discharged from the vent holes 102 a) can be appropriately controlled.

The above-described embodiments 1 and 2 are preferable because a large effect is exerted when the diameter of the hole 131 is large. The openings 131 may be formed in the fining tube 102 with a small initial diameter, but may also increase with use. The small-diameter openings 131 may be closed by the molten glass leaked from the openings after cooling and solidifying, and the large-diameter openings 131 are not easily closed and are easily kept in an open state. It is found that such a large diameter hole 131 easily increases the inflow amount of the outside air, and becomes remarkable particularly when the size is equal to or larger than the size of the vent hole 102 a. In embodiment 1, when the oxygen concentration exceeds the 1 st allowable value, the inert gas is supplied from the vent hole 102a, and thus, even when the large-diameter hole 131 is formed, the oxygen concentration in the gas phase space 120a can be reliably reduced by supplying the inert gas from the vent hole 102 a. In embodiment 2, when the oxygen concentration exceeds the 3 rd permissible value as described above, the inert gas is supplied from the vent hole 102a, and therefore, even when the aperture 131 having a large diameter is formed, the oxygen concentration in the gas phase space 120a can be reliably reduced by reducing the amount of gas discharged from the vent hole 102 a. The diameter of the opening 131 is the maximum length of the opening 131 projected on the surface of the clarification tube 102 along which the wall extends. When the diameter of the hole 131 is large, specifically, the diameter of the hole 131 is 50% or more, 3mm or more of the diameter of the vent hole 102 a. The upper limit of the diameter of the hole 131 is not particularly limited, and is, for example, 10mm, which is 2 times the diameter of the vent hole 102 a.

In the above-described embodiment 1 and embodiment 2, the supply amount of the inert gas is preferably adjusted so that bubbles are not generated in the refined molten glass. The molten glass after the defoaming treatment passes through the clarifying pipe 102 as described above, is transferred in the transfer pipe 105, and is subjected to a homogenizing step in the stirring tank 103 (ST 3). In this process, although the temperature of the molten glass is lowered, the temperature may locally rise, and as a result, bubbles absorbed into the molten glass by the absorption treatment may be defoamed again. Such bubbles may be generated in the stirring tank 103 by the contact of the molten glass with the stirrer 103 a. It is found that such bubbles are likely to be generated in the clarification step (ST2) when the pressure of the inert gas supplied to the gas-phase space 120a is high. In the present embodiment, the pressure of the inert gas supplied to the gas phase space is adjusted so that bubbles are not generated in the refined molten glass, and thus, the bubbles can be suppressed from remaining in the glass substrate. For example, it is preferable to supply the inert gas from the vent hole 102a, the supply holes 102b, and the opening 131 in a dispersed manner, or to increase the flow path area of each hole to keep the supply pressure within a low range.

(glass substrate)

The size of the glass substrate produced in embodiment 1 and embodiment 2 is not particularly limited, but for example, the vertical and horizontal dimensions are preferably 500mm to 3500mm, 1500mm to 3500mm, 1800 mm to 3500mm, 2000mm to 3500mm, and 2000mm to 3500mm, respectively.

The thickness of the glass substrate is, for example, 0.1 to 1.1mm, more preferably 0.75mm or less, for example, more preferably 0.55mm or less, and still more preferably 0.45mm or less. The lower limit value of the thickness of the glass substrate is preferably 0.15mm, more preferably 0.25 mm.

< glass composition >

As such a glass substrate, the following glass composition glass substrate is exemplified. That is, the raw materials of the molten glass were prepared so as to produce a glass substrate having the following glass composition.

SiO₂55 to 80 mol%,

Al₂O₃8 to 20 mol%,

B₂O₃0 to 12 mol%,

RO 0 to 17 mol% (RO is the total amount of MgO, CaO, SrO and BaO).

From the viewpoint of reducing the thermal shrinkage ratio, SiO₂Preferably 60 to 75 mol%, and more preferably 63 to 72 mol%.

In the RO, MgO is preferably 0 to 10 mol%, CaO is 0 to 15 mol%, SrO is preferably 0 to 10%, and BaO is preferably 0 to 10%.

Further, the material may contain at least SiO₂、Al₂O₃、B₂O₃And RO in a molar ratio of ((2 × SiO)₂)+Al₂O₃)/((2×B₂O₃) + RO) is 4.5 or more. Preferably, the composition contains at least one of MgO, CaO, SrO, and BaO, and the molar ratio (BaO + SrO)/RO is 0.1 or more.

In addition, B is expressed in mol%₂O₃The total of 2 times the content of (b) and the content of RO in mol% is preferably 30 mol% or less, and preferably 10 to 30 mol%.

The content of the alkali metal oxide in the glass substrate having the glass composition may be 0 mol% or more and 0.4 mol% or less.

In addition, it is not necessary to include 0.05 to 1.5 mol% in total of oxides (tin oxide, iron oxide) of metals that vary in valence in the glass and substantially no As₂O₃、Sb₂O₃And PbO, but is arbitrary.

In addition, as the glass substrate manufactured according to embodiment 1 and embodiment 2, alkali-free boroaluminosilicate glass or glass containing a small amount of alkali is preferably used.

The glass substrate manufactured according to embodiment 1 and embodiment 2 preferably includes alkali-free glass having the following composition, for example.

Examples of the glass composition of the glass substrate produced according to embodiment 1 and embodiment 2 include the following (expressed by mass%).

May comprise SiO₂: 50-70% (preferably 57-64%) Al₂O₃: 5 to 25% (preferably 12 to 18%) of B₂O₃: 0 to 15% (preferably 6 to 13%), and further optionally contains the following composition. As the optionally contained component, MgO: 0 to 10% (preferably 0.5 to 4%), CaO: 0 to 20% (preferably 3 to 7%), SrO: 0 to 20% (preferably 0.5 to 8%, more preferably 3 to 7%), BaO: 0 to 10% (preferably 0 to 3%, more preferably 0 to 1%) ZrO₂: 0 to 10% (preferably 0 to 4%, more preferably 0 to 1%). Further, R 'is more preferably contained'₂O: more than 0.10% and not more than 2.0% (wherein R' is at least 1 selected from Li, Na and K).

Or, preferably, SiO₂: 50-70% (preferably 55-65%) of B₂O₃: 0 to 10% (preferably 0 to 5%, 1.3 to 5%) of Al₂O₃: 10 to 25% (preferably 16 to 22%), MgO: 0 to 10% (preferably 0.5 to 4%), CaO: 0 to 20% (preferably 2 to 10%, 2 to 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 8 to 20%, 14 to 19%) (wherein R is at least 1 selected from Mg, Ca, Sr and Ba). Still more preferably, R ' is contained in an amount of more than 0.10% and not more than 2.0% (wherein R ' is at least 1 selected from the group consisting of Li, Na and K) '₂O。

< Young's modulus >

The young's modulus of the glass substrate manufactured according to embodiment 1 and embodiment 2 is, for example, preferably 72GPa or more, more preferably 75GPa or more, and still more preferably 77GPa or more.

< strain point >

The strain rate of the glass substrate manufactured according to embodiment 1 and embodiment 2 is, for example, preferably 650 ℃ or higher, more preferably 680 ℃ or higher, and still more preferably 700 ℃ or higher and 720 ℃ or higher.

< Heat shrinkage >

The thermal shrinkage of the glass substrate produced according to embodiment 1 and embodiment 2 is, for example, 50ppm or less, preferably 40ppm or less, more preferably 30ppm or less, and still more preferably 20ppm or less. The range of the thermal shrinkage rate of the glass substrate before the thermal shrinkage rate is reduced is preferably 10ppm to 40 ppm.

The glass substrate produced in embodiment 1 and embodiment 2 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 a glass substrate for an organic EL (Electroluminescence) display. Furthermore, the glass substrates manufactured in embodiment 1 and embodiment 2 are suitable for glass substrates for oxide semiconductor displays using an oxide semiconductor such as IGZO (indium, gallium, zinc, oxygen) or the like used for high definition displays, and glass substrates for LTPS displays using an LTPS (Low-temperature polysilicon) semiconductor.

The glass substrates manufactured in embodiments 1 and 2 can also be applied to cover glass, magnetic disk glass, solar cell glass substrates, and the like.

Although the method and apparatus for manufacturing a glass substrate according to the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the scope of the present invention.

[ description of symbols ]

100 melting device

101 melting tank

102 clarification tube

102a vent hole

102b supply hole

103 stirring tank

103a stirrer

104. 105 transport pipe

106 glass supply pipe

120a gas phase space

121 a-121 c electrodes

123 control device

124 supply pipe

125. 126 inert gas supply device

127 vent pipe

130 deformation part

131 open pores

200 forming device

300 cutting device

MG molten glass

SG laminated glass

Claims

1. A method for manufacturing a glass substrate, characterized in that: comprises a fining step of fining molten glass using a fining tube, and

in the clarifying step, in the control of supplying the inert gas from the supply hole such that the oxygen concentration in the gas discharged from the vent hole becomes a target value or less, the inert gas is supplied from the vent hole to the gas phase space when the oxygen concentration exceeds a 1 st allowable value higher than the target value.

2. The glass substrate manufacturing method according to claim 1, wherein in the fining step, when the inert gas is supplied from the supply hole, in a case where a 2 nd allowable value, which is an oxygen concentration lower than the 1 st allowable value and higher than the target value, is exceeded before the oxygen concentration exceeds the 1 st allowable value, a supply amount of the inert gas from the supply hole is made larger than a supply amount of the inert gas from the supply hole in a case where the oxygen concentration is equal to or lower than the target value.

3. The method for producing a glass substrate according to claim 1 or 2, 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 by using a predetermined relationship between the position of the opening formed in the wall portion and a change in the oxygen concentration caused by the opening when the finer tube is used.

4. The method for manufacturing a glass substrate according to claim 3, wherein the inert gas is further supplied into the gas phase space from an opening hole for specifying the position.

5. The method for manufacturing a glass substrate according to claim 1 or 2, wherein in the fining step, when the inert gas is supplied from the supply hole in a controlled supply amount so that the oxygen concentration becomes equal to or less than a target value and the gas is discharged from the vent hole in a controlled discharge amount, the discharge amount of the gas from the vent hole is reduced when the oxygen concentration exceeds the 1 st allowable value.

6. A method for manufacturing a glass substrate, characterized in that: comprises a fining step of fining molten glass using a fining tube, and

in the clarifying step, in control in which the inert gas is supplied from the supply hole in a controlled supply amount so that an oxygen concentration in the gas discharged from the vent hole becomes a target value or less, and the gas is discharged from the vent hole in a controlled discharge amount, the discharge amount of the gas from the vent hole is reduced in a case where the oxygen concentration exceeds a 3 rd allowable value that is higher than the target value.

7. The method for manufacturing a glass substrate according to claim 6, wherein in the fining step, after the amount of gas discharged from the vent hole is reduced, the amount of inert gas supplied from the supply hole is made larger than that in a case where the oxygen concentration is equal to or less than the target value.

8. The method for producing a glass substrate according to claim 6 or 7, wherein an amount of the gas discharged is reduced so as to reduce an inflow amount of the outside gas flowing into the gas phase space from the opening formed in the wall portion with use of the finer tube.

9. The method for manufacturing a glass substrate according to claim 8, 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 by using a predetermined relationship between the position of the opening and a change in the oxygen concentration that changes due to the opening.

10. The method for manufacturing a glass substrate according to claim 9, wherein an amount of the gas discharged is adjusted according to a magnitude of a distance between the vent hole and the vent hole along the flow direction.

11. A glass substrate manufacturing apparatus is characterized by comprising:

and a controller that controls an operation of supplying the inert gas from the supply hole such that an oxygen concentration in the gas discharged from the vent hole becomes a target value or less, wherein in the control, the inert gas supply device is controlled such that the inert gas is supplied from the vent hole to the gas phase space when the oxygen concentration exceeds a 1 st allowable value higher than the target value.

12. A glass substrate manufacturing apparatus is characterized by comprising:

a control device that controls the inert gas supply device in the following manner: in the control of supplying the inert gas from the supply hole in a controlled supply amount so that the oxygen concentration in the gas discharged from the vent hole becomes a target value or less and discharging the gas from the vent hole in a controlled discharge amount, the discharge amount of the gas from the vent hole is reduced when the oxygen concentration exceeds a 3 rd allowable value that is higher than the target value.