JP5921730B2 - Glass substrate manufacturing method and glass substrate manufacturing apparatus - Google Patents

Description

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

In general, the production of a glass substrate includes a step of forming molten glass from a glass raw material, followed by a clarification step, a stirring step, or a homogenization step, and then forming the molten glass into a glass substrate.
In any processing apparatus that performs the above steps, it is necessary to use an appropriate material for the member in contact with the molten glass depending on the temperature of the molten glass in contact with the member, the required quality of the glass substrate, and the like. That is, in order to mass-produce high-quality glass substrates from high-temperature molten glass, consideration should be given so that foreign substances that cause defects in the glass substrate are not mixed into the molten glass from any glass processing apparatus that manufactures the glass substrate. It is desirable to do. For example, since the molten glass is in a very high temperature state after it is generated and supplied to the molding process, the processing device for performing each process such as melting, clarification, supply, and stirring is platinum with high heat resistance. A member containing a group metal (for example, platinum) is used (for example, refer to Patent Document 1).
The above step includes a clarification step for removing minute bubbles contained in the molten glass. In a glass substrate used for a panel display such as a liquid crystal display or a plasma display or a flat panel display (FPD), it is necessary to eliminate defects due to bubbles remaining in the molten glass.
For this reason, the clarification process is performed in manufacture of the panel substrate and the glass substrate for FPD. The clarification is performed by passing a molten glass containing a clarifier through the clarifier tube body while heating the clarifier tube body, and removing bubbles in the molten glass by an oxidation-reduction reaction of the clarifier.
More specifically, a clarifier that releases oxygen by a reduction reaction is used, and the temperature of the molten glass melted further is raised in the clarifier tube to release oxygen by reducing the clarifier, and bubbles in the molten glass float up. After degassing, the temperature is lowered, and oxygen remaining without being degassed is used for oxidation of the reduced fining agent so as to be absorbed by the molten glass. A member containing a platinum group metal (for example, platinum) having high heat resistance is also used for the clarification tube in which the clarification step is performed at a high temperature.

JP 2010-111533 A

  The clarification step is a step in which the temperature of the molten glass is highest between the melting step and the forming step, and the clarification tube for performing the clarification step is heated to an extremely high temperature in order to heat the molten glass. Then, the platinum group metal used for the clarification tube is oxidized by oxygen generated by the reduction of the clarifier in the molten glass and volatilized as an oxide. On the other hand, the platinum group metal oxide is reduced at a position where the temperature of the clarification tube is locally lowered, and the reduced platinum group metal aggregates and adheres to the inner wall surface of the clarification tube. If a part of the platinum group metal adhering to the inner wall surface is mixed in the molten glass as a foreign substance, the quality of the glass substrate may be deteriorated. In particular, the clarification step is a step in which the temperature of the molten glass becomes the highest during the period from the melting step to the forming step, and therefore the clarification tube mainly performing the clarification step is heated to an extremely high temperature. For this reason, the volatilization of platinum group metals in the clarification tube is vigorous, and it is particularly desirable to reduce volatilization and aggregation of platinum group metals.

  The object of the present invention is to reduce the volatilization of platinum group metals used in glass processing equipment in the process of processing molten glass before forming a glass substrate, thereby suppressing foreign matter from being mixed into the molten glass. It is providing the manufacturing method and glass substrate manufacturing apparatus of a glass substrate which can be manufactured.

  The glass substrate manufacturing method and glass substrate manufacturing apparatus of the present invention include the following modes.

(Form 1)
Using at least a part of the inner wall made of a material containing a platinum group metal, and processing a molten glass containing a fining agent that releases oxygen by a reduction reaction,
In the process of processing the molten glass,
In the processing apparatus, the molten glass is caused to flow in a direction along a surface in contact with the gas phase space of the molten glass,
By adjusting the amount of oxygen released from the molten glass in the gas phase space formed by the inner wall of the processing apparatus and the surface of the molten glass, the gas is controlled so that volatilization of the platinum group metal is suppressed. Control the oxygen concentration in the phase space ,
The amount of released oxygen varies depending on the position of the molten glass in the flow direction,
By adjusting the distribution of the amount of released oxygen at the position in the flow direction of the molten glass,
A method for producing a glass substrate, comprising adjusting a distribution of oxygen concentration in a flow direction of the molten glass in the gas phase space so that volatilization of the platinum group metal is suppressed .

(Form 2)
A method for manufacturing a glass substrate for processing molten glass using a processing apparatus for processing molten glass,
When processing molten glass containing a fining agent that releases oxygen by a reduction reaction,
Supplying molten glass to the inside of the processing apparatus made of a material containing a platinum group metal at least a part of the inner wall so that a gas phase space is formed above the surface of the molten glass,
In the processing apparatus, the molten glass is caused to flow in a direction along a surface in contact with the gas phase space of the molten glass,
By adjusting the amount of oxygen released from the molten glass, the oxygen concentration in the gas phase space is controlled so that volatilization of the platinum group metal is suppressed ,
The amount of released oxygen varies depending on the position of the molten glass in the flow direction,
The distribution of oxygen concentration in the flow direction of the molten glass in the gas phase space is controlled by adjusting the distribution of the oxygen release amount at the position in the flow direction of the molten glass so that the volatilization of the platinum group metal is suppressed. A method for producing a glass substrate, wherein

(Form 3)
Using at least a part of the inner wall made of a material containing a platinum group metal, and processing a molten glass containing a fining agent that releases oxygen by a reduction reaction,
In the process of processing the molten glass,
In the processing apparatus, the molten glass is caused to flow in a direction along a surface in contact with the gas phase space of the molten glass,
By adjusting the amount of oxygen released from the molten glass in the gas phase space formed by the inner wall of the processing apparatus and the surface of the molten glass, the gas is controlled so that volatilization of the platinum group metal is suppressed. Control the oxygen concentration in the phase space,
The temperature of the inner wall in contact with the gas phase space in the processing apparatus has a temperature distribution along the flow direction of the molten glass,
In the processing of the molten glass, the bubble discharge amount maximum position in the flow direction of the molten glass at which the amount of bubbles discharged from the surface of the molten glass to the gas phase space becomes maximum, and the temperature distribution in the flow direction of the molten glass. The method for producing a glass substrate is characterized in that the maximum position of the bubble discharge amount is adjusted such that the maximum temperature position is spaced apart in the flow direction of the molten glass.

(Form 4)
A method for manufacturing a glass substrate for processing molten glass using a processing apparatus for processing molten glass,
When processing molten glass containing a fining agent that releases oxygen by a reduction reaction,
Supplying molten glass to the inside of the processing apparatus made of a material containing a platinum group metal at least a part of the inner wall so that a gas phase space is formed above the surface of the molten glass,
In the processing apparatus, the molten glass is caused to flow in a direction along a surface in contact with the gas phase space of the molten glass,
By adjusting the amount of oxygen released from the molten glass, the oxygen concentration in the gas phase space is controlled so that volatilization of the platinum group metal is suppressed,
The temperature of the inner wall in contact with the gas phase space in the processing apparatus has a temperature distribution along the flow direction of the molten glass,
In the processing of the molten glass, the bubble discharge amount maximum position in the flow direction of the molten glass at which the amount of bubbles discharged from the surface of the molten glass to the gas phase space becomes maximum, and the temperature distribution in the flow direction of the molten glass. The method for producing a glass substrate is characterized in that the maximum position of the bubble discharge amount is adjusted such that the maximum temperature position is spaced apart in the flow direction of the molten glass.

(Form 5)
The glass substrate contains 0.01 mol% to 0.3 mol% tin oxide,
The amount of oxygen released from the molten glass is the method for producing a glass substrate according to any one of Embodiments 1 to 4, wherein the amount of oxygen released is adjusted by the content of the tin oxide.

(Form 6)
The manufacturing method of the glass substrate as described in any one of form 1-5 which controls the said oxygen concentration by further adjusting the quantity of the oxygen discharged | emitted from the said gaseous-phase space outside the said processing apparatus.

(Form 7)
The manufacturing method of the glass substrate as described in any one of the forms 1-6 which supplies the gas which adjusted supply amount to the said gaseous-phase space so that the said oxygen concentration may become a predetermined range.

(Form 8)
The temperature of the processing device changes according to the position in the flow direction of the molten glass,
The distribution of the amount of released oxygen is predicted using computer simulation,
The processing condition is determined using the computer simulation so that the position where the amount of released oxygen in the flow direction of the molten glass is maximum is separated from the position where the temperature of the processing apparatus is maximum. 2. A method for producing a glass substrate according to 2.

(Form 9)
A method for manufacturing a glass substrate for processing molten glass using a processing apparatus for processing molten glass,
Having a step of melting glass raw material to produce molten glass,
Processing a molten glass containing a fining agent that releases oxygen by a reduction reaction;
In the process of processing the molten glass,
In the processing apparatus, at least a part of the inner wall is supplied with a molten glass in a processing apparatus made of a material containing a platinum group metal so that a gas phase space is formed above the surface of the molten glass. Flowing molten glass in a direction along the surface of the molten glass in contact with the gas phase space;
The temperature of the inner wall in contact with the gas phase space in the processing apparatus has a temperature distribution along the flow direction of the molten glass,
In the processing of the molten glass, the maximum amount of bubbles released in the flow direction of the molten glass at which the amount of bubbles released from the surface of the molten glass in contact with the gas phase space into the gas phase space is maximized, and the molten glass The method for producing a glass substrate, wherein the bubble discharge amount maximum position is adjusted so that the maximum temperature position of the temperature distribution in the flow direction is separated in the flow direction of the molten glass.

(Form 10)
The processing apparatus includes a clarification tube configured to degas at least the molten glass, wherein at least a part of the inner wall is made of a material containing a platinum group metal.
The process of processing the said molten glass is a manufacturing method of the glass substrate of any one of the forms 1-9 which is a clarification process including the defoaming process which defoams the said molten glass in the said clarification pipe | tube.

(Form 11)
The foam discharge maximum position is predicted using computer simulation,
Wherein As froth emission maximum position is spaced apart at said maximum temperature position to the flow direction of the molten glass, to determine the process conditions by using the computer simulation, in any one of embodiments 3, 4, 9 and 10 The manufacturing method of the glass substrate of description.

(Form 12)
Adjustment of the said bubble discharge | release amount maximum position is performed by adjustment of at least any one of the temperature distribution of the said molten glass, and the flow velocity of the said molten glass, It is any one of the form 3 , 4 , 9-11. Glass substrate manufacturing method.

(Form 13)
The said bubble discharge | release amount maximum position is a manufacturing method of the glass substrate as described in any one of form 3 , 4 , 9-12 located in the downstream of the flow of the said molten glass with respect to the said highest temperature position.

(Form 14)
The processing apparatus includes a clarification tube configured to degas at least the molten glass, wherein at least a part of the inner wall is made of a material containing a platinum group metal.
The clarification pipe is provided with an exhaust pipe that communicates the gas phase space and the atmosphere outside the processing apparatus,
The glass substrate according to any one of Embodiments 3 , 4 , 9 to 13, wherein an arrangement position of the exhaust pipe in a flow direction of the molten glass is between the bubble discharge amount maximum position and the maximum temperature position. Manufacturing method.

(Form 15)
The processing apparatus includes a clarification tube configured to degas at least the molten glass, wherein at least a part of the inner wall is made of a material containing a platinum group metal.
The clarification pipe is provided with an exhaust pipe that communicates the gas phase space and the atmosphere outside the clarification pipe,
The foam discharge maximum position and the arrangement position of the exhaust pipe in the flow direction of the molten glass are on the same side of the flow direction of the molten glass with respect to the maximum temperature position of the temperature distribution , glass substrate manufacturing method according to any one 9-14 of.

(Form 16)
A flange member extending outside the processing device is provided on the outer periphery of the processing device, and the arrangement position of the flange member in the flow direction of the molten glass includes the bubble discharge amount maximum position and the arrangement position of the exhaust pipe. The manufacturing method of the glass substrate of the form 14 or 15 which exists in area | regions other than the area | region between.

(Form 17)
The highest temperature position of the temperature distribution, the arrangement position of the exhaust pipe, and the maximum position of the bubble discharge amount are the highest temperature position, the arrangement position of the exhaust pipe, and the bubble from the upstream side in the flow direction of the molten glass. The manufacturing method of the glass substrate as described in any one of form 14-16 located in order of discharge | release amount maximum position.

(Form 18)
The processing apparatus is provided with an exhaust pipe that communicates the gas phase space and the atmosphere outside the processing apparatus,
The foam discharge amount maximum position and the arrangement position of the exhaust pipe in the flow direction of the molten glass are the same positions in the flow direction of the molten glass, and any one of forms 3 , 4 , 9 to 13 The manufacturing method of the glass substrate of description.

(Form 19)
A glass substrate manufacturing apparatus for processing molten glass using a processing apparatus for processing molten glass,
At least a part of the inner wall is made of a material containing a platinum group metal, and a molten glass containing a refining agent that releases oxygen by a reduction reaction is supplied to the inside, and a gas phase space is formed above the surface of the molten glass. A processing apparatus in which the molten glass flows in a direction along a surface in contact with the gas phase space of the molten glass ;
While adjusting the amount of oxygen released from the molten glass and adjusting the amount of oxygen discharged from the gas phase space, the oxygen concentration in the gas phase space is adjusted to be within a predetermined range. and a controller configured to,
The amount of released oxygen varies depending on the position of the molten glass in the flow direction,
The control device adjusts a distribution of the oxygen release amount at a position in the flow direction of the molten glass, so that the flow of the molten glass in the gas phase space is suppressed so that volatilization of the platinum group metal is suppressed. The glass substrate manufacturing apparatus characterized by adjusting the distribution of oxygen concentration in the glass substrate.

(Form 20)
A glass substrate manufacturing apparatus for processing molten glass using a processing apparatus for processing molten glass,
At least a part of the inner wall is made of a material containing a platinum group metal, and a molten glass containing a refining agent that releases oxygen by a reduction reaction is supplied to the inside, and a gas phase space is formed above the surface of the molten glass. A processing apparatus configured as follows:
While adjusting the amount of oxygen released from the molten glass and adjusting the amount of oxygen discharged from the gas phase space, the oxygen concentration in the gas phase space is adjusted to be within a predetermined range. The molten glass flows in a direction along a surface in contact with the gas phase space of the molten glass, and a control device,
The temperature of the inner wall in contact with the gas phase space in the processing apparatus has a temperature distribution along the flow direction of the molten glass,
The control device has a maximum bubble discharge amount position in the flow direction of the molten glass and a flow of the molten glass at which the amount of bubbles discharged from the surface of the molten glass to the gas phase space is maximized in the processing of the molten glass. Adjusting the bubble discharge amount maximum position so that the maximum temperature position of the temperature distribution in the direction is separated in the flow direction of the molten glass,
Or
A glass substrate manufacturing apparatus for processing molten glass using a processing apparatus for processing molten glass,
A melting tank for melting glass raw material to produce molten glass;
At least a part of the inner wall is made of a material containing a platinum group metal, and molten glass containing a refining agent that releases oxygen by a reduction reaction is supplied to the inside, and the molten glass is separated from the gas phase space of the molten glass. A gas phase space is formed in the upper part of the surface of the molten glass, and the temperature of the inner wall in contact with the gas phase space has a temperature distribution along the flow direction of the molten glass. And a processing device configured to
In the processing of the molten glass, the bubble discharge amount maximum position in the flow direction of the molten glass at which the amount of bubbles discharged from the surface of the molten glass to the gas phase space becomes maximum, and the temperature in the flow direction of the molten glass. The apparatus for producing a glass substrate, wherein the maximum position of the bubble discharge amount is adjusted such that the maximum temperature position of the distribution is separated in the flow direction of the molten glass.

(Form 21)
The said processing apparatus is a glass substrate manufacturing apparatus of the form 19 or 20 containing the clarification pipe | tube which defoams the said molten glass.

(Form 22)
In the method for manufacturing a glass substrate according to any one of Forms 1 to 18 , or any one of Forms 19 to 21, wherein the maximum temperature of the molten glass flowing inside the processing apparatus is 1630 ° C. to 1750 ° C. The glass substrate manufacturing apparatus of description.

(Form 23)
The method for producing a glass substrate according to any one of Forms 1 to 18 and 22, or a form 19 to 22, wherein the tin oxide content of the glass substrate is 0.01 mol% to 0.3 mol%. The glass substrate manufacturing apparatus as described in any one of these.

(Form 24)
The method for producing a glass substrate according to any one of Forms 1 to 18, 22 and 23, or Forms 19 to 23, wherein the vapor pressure of the platinum group metal in the gas phase space is 0.1 Pa to 15 Pa. The glass substrate manufacturing apparatus as described in any one of these.

(Form 25)
The agglomerates produced by agglomeration of oxides produced by volatilization of the platinum group metal (hereinafter, agglomerates of the platinum group metal) have an aspect ratio of 100 or more, which is a ratio of the maximum length to the minimum length, for example. The manufacturing method of the glass substrate as described in any one of the forms 1-18 and 22-24 which are these, or the glass substrate manufacturing apparatus as described in any one of the forms 19-24.
For example, the maximum length of the platinum group metal aggregate is 50 μm to 300 μm, and the minimum length is 0.5 μm to 2 μm. Here, the maximum length of the platinum group metal aggregate is the maximum long side length of the circumscribed rectangle circumscribing the image of the foreign material obtained by photographing the platinum group metal aggregate. The minimum length is And the length of the minimum short side of the circumscribed rectangle.
Alternatively, as the aggregate generated by the aggregation of the platinum group metal volatiles, the aspect ratio, which is the ratio of the maximum length to the minimum length, is 100 or more, and the maximum length of the platinum group metal aggregate is 100 μm. As mentioned above, Preferably, what is 100 micrometers-300 micrometers can be defined.

(Form 26)
The glass substrate is a glass substrate for display, or the glass substrate glass according to any one of Forms 19 to 25, or the method for producing a glass substrate according to any one of Forms 1 to 18 and 22 to 25. Board manufacturing equipment.
Moreover, the said glass substrate is suitable for the glass substrate for oxide semiconductor displays or the glass substrate for LTPS displays.

  According to the glass substrate manufacturing method and glass substrate manufacturing apparatus of each embodiment described above, in the processing step of the molten glass, for example, in the refining step, by suppressing the volatilization of the platinum group metal, foreign matter is mixed into the molten glass. Can be suppressed.

It is a flowchart which shows the process of the manufacturing method of a glass substrate. It is a schematic diagram which shows the structure of a glass substrate manufacturing apparatus. It is the schematic of the clarification tube of 1st Embodiment used for the manufacturing apparatus of FIG. It is a vertical sectional view in the longitudinal direction of the clarification tube of the first embodiment. It is a figure which shows the relationship between the position in the longitudinal direction of the clarification pipe | tube of 1st Embodiment, the temperature of the upper end part of the clarification pipe | tube 120, and oxygen release amount. It is an external view of the clarification pipe | tube which concerns on 2nd Embodiment. It is a figure showing the cross section of the clarification tube which concerns on 2nd Embodiment, and the temperature distribution of a clarification tube. It is a figure which shows the result of Experimental example 1. FIG.

Embodiments of a glass substrate manufacturing method and a glass processing apparatus according to the present invention will be described with reference to the drawings. In this specification, the suppression of foreign matters mixed into the molten glass by adjustment based on the oxygen concentration or the like means that the amount of foreign matters mixed into the molten glass is reduced compared to the case where the above adjustment is not performed. In addition, the amount of foreign matter mixed into the molten glass is included in zero, but the amount of foreign matter mixed into the molten glass is not limited to zero.
In the present specification, the upper part of the liquid level means a part that is vertically above the liquid level.
In the present specification, the upstream side of the molten glass flowing from the melting tank toward the forming apparatus refers to the side of the melting tank in which the molten glass is made with respect to the position of interest. Further, the downstream side of the molten glass refers to the side of the molding apparatus with respect to the position of interest.
In this specification, the inside of the processing apparatus refers to a space surrounded by the inner wall.
Moreover, the foreign material by the aggregate of a platinum group metal means the thing which has a linear shape elongated in one direction and the aspect ratio that is the ratio of the maximum length to the minimum length exceeds 100. For example, the maximum length of the platinum group metal aggregate is 50 μm to 300 μm, and the minimum length is 0.5 μm to 2 μm. Here, the maximum length of the platinum group metal aggregate is the maximum long side length of the circumscribed rectangle circumscribing the image of the foreign material obtained by photographing the platinum group metal aggregate. The minimum length is And the length of the minimum short side of the circumscribed rectangle.

(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 mainly includes a melting step (ST1), a clarification step (ST2), a stirring step (ST3), a forming step (ST4), a slow cooling step (ST5), and a cutting step (ST6).

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

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

  In the stirring 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.

The forming step (ST4) and the slow cooling step (ST5) are performed by a forming apparatus.
In the forming step (ST4), the molten glass is formed into a sheet glass to make a flow of the sheet glass. An overflow downdraw method is used for molding.
In the slow cooling step (ST5), 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 (ST6), the sheet glass after slow cooling is cut into a predetermined length to obtain a plate-like glass substrate. The cut glass substrate is further cut into a predetermined size to produce a glass substrate having a target size.

(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 120, 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 clarifying agent is added is charged into the melting tank, and a melting step (ST1) is performed. High-temperature (for example, 1500 ° C. to 1600 ° C.) molten glass melted in the melting tank 101 is supplied to the clarification tube 120 via the transfer tube 104. In the melting tank 101, the molten glass between the electrodes may be energized and heated by passing an electric current between at least one pair of electrodes. The glass raw material may be heated.

In the clarification tube 120, 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, the molten glass obtained in the melting tank 101 flows from the melting tank 101 through the transfer pipe 104 into the clarification pipe 120. The clarification tube 120, the transfer tubes 104 and 105, and the glass supply tube 106 are tubes made of a platinum group metal. The clarification tube 120 is provided with a heating means like the melting tank 101. At least the transfer pipe 104 is also provided with a heating means. In the clarification step ST2, the molten glass is clarified by raising the temperature of the molten glass. For example, the temperature of the molten glass in the clarification tube 120 is 1600 ° C to 1720 ° C. The molten glass clarified in the clarification tube 120 passes through the transfer tube 105 from the clarification tube 120 and flows into the stirring device 103. The molten glass is cooled when passing through the transfer tube 105. In this way, oxygen is released by the reductive reaction of the fining agent, and this released oxygen is absorbed by the bubbles contained in the molten glass. Bubbles having an increased bubble diameter by absorbing oxygen rise to the surface (liquid surface) of the molten glass, break up and disappear. Next, the temperature of the molten glass is lowered. Thereby, the reduced fining agent causes an oxidation reaction, and the molten glass absorbs oxygen remaining in the molten glass.
The clarified molten glass is supplied to the stirring vessel 103 through the transfer pipe 105.

In the stirring vessel 103, the molten glass is stirred by the stirrer 103a, and the stirring step (ST3) is performed. For example, in the stirring device 103, the temperature of the molten glass is 1250 ° C to 1450 ° C. For example, in the stirring device 103, the viscosity of the molten glass is 500 poise to 1300 poise. The molten glass stirred in the stirring tank 103 is supplied to the forming apparatus 200 through the glass supply pipe 106. When the molten glass passes through the transfer tube 106, it is cooled so as to have a viscosity suitable for forming the molten glass. For example, the molten glass is cooled to 1100 to 1300 ° C. In the forming apparatus 200, a sheet glass is formed from molten glass by an overflow down draw method (forming step ST4) and gradually cooled (slow cooling step ST5).
In the cutting device 300, a plate-shaped glass substrate cut out from the sheet glass is formed (cutting step ST6).

  The clarification tube 120, the stirring tank 103, the transfer tubes 104 and 105, and the glass supply tube 106 are made of a material in which at least a part of the inner wall contains a platinum group metal. More preferably, the clarification tube 120, the stirring tank 103, the transfer tubes 104 and 105, and the glass supply tube 106 are tubes made of a platinum group metal. In this specification, the “platinum group metal” means a metal composed of a platinum group element, and is used as a term including not only a metal composed of a single platinum group element but also an alloy of the platinum group element. Here, the platinum group element refers to six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), and iridium (Ir). Platinum group metals are expensive, but have a high melting point and excellent corrosion resistance against molten glass.

(Application example of glass substrate)
Aggregates of platinum group metals on the surface of the glass substrate are separated from the surface of the glass substrate in the panel manufacturing process using the glass substrate, so that the part of the detached surface becomes a recess, and the thin film formed on the glass substrate is uniform. In other words, there is a problem that a display defect of the screen is caused. Furthermore, if a platinum group metal aggregate is present in the glass substrate, distortion occurs due to the difference in thermal expansion coefficient between the glass and the platinum group metal in the slow cooling step, causing a display defect on the screen. For this reason, this embodiment is suitable for manufacturing a glass substrate for a display that is demanding for display defects on the screen. In particular, in the present embodiment, a glass substrate for an oxide semiconductor display using an oxide semiconductor such as IGZO (indium, gallium, zinc, oxygen) and LTPS (low-temperature polysilicon) are more demanding for screen display defects. It is suitable for a glass substrate for high-definition display such as a glass substrate for LTPS display using a semiconductor.
From the above, the glass substrate produced by the method for producing a glass substrate of the present embodiment is used for panel displays such as liquid crystal displays, plasma displays, and organic EL displays that are required to have a very low content of alkali metal oxides. It is suitable for a glass substrate for flat panel display (FPD). Moreover, it is suitable also for the glass substrate for oxide semiconductor displays or the glass substrate for LTPS displays. Furthermore, it is also suitable as a cover glass for protecting the display, a glass for magnetic disks, and a glass substrate for solar cells. As a glass substrate for a panel display or a flat panel display, non-alkali glass or glass containing a trace amount of alkali is used. Glass substrates for panel displays and flat panel displays have high viscosity at high temperatures. For example, the temperature of the molten glass having a viscosity of 10 ^2.5 poise is 1500 ° C. or higher.
As the glass substrate for display, the number of platinum group metal aggregates in the glass substrate is preferably 1000 pieces / m ³ or less, more preferably 100 pieces / m ³ or less, and 50 pieces / m 3. More preferably, it is ³ or less. The number of bubbles in the glass substrate is preferably 1000 / m ³ or less, more preferably 200 / m ³ or less, and even more preferably 50 / m ³ or less. Thus, by reducing the number of platinum metal aggregates and the number of bubbles in the glass substrate, the number of display defects of the display can be reduced, and the yield can be improved.

(Glass composition)
In the melting tank 101, a glass raw material is melted by a heating means (not shown) to produce molten glass. The glass raw material is prepared so that a glass having a desired composition can be substantially obtained. As an example of the glass composition, non-alkali glass suitable as a glass substrate for panel display or flat panel display is SiO ₂ : 50 mass% to 70 mass%, Al ₂ O ₃ : 10 mass% to 25 mass%, B ₂ O ₃ : 0% by mass to 15% by mass, MgO: 0% by mass to 10% by mass, CaO: 0% by mass to 20% by mass, SrO: 0% by mass to 20% by mass, BaO: 0% by mass to 10% by mass %. Here, the total content of MgO, CaO, SrO and BaO is 5% by mass to 30% by mass.
Alternatively, suitable glass substrate to the glass substrate and the LTPS glass substrate for a display for an oxide semiconductor display, SiO _2: 55 wt% to 70 wt%, Al ₂ O _3: 15 wt% to 25 wt%, B ₂ O ₃ : 0% by mass to 10% by mass, MgO: 0% by mass to 10% by mass, CaO: 0% by mass to 20% by mass, SrO: 0% by mass to 20% by mass, BaO: 0% by mass to 10% by mass To do. Here, the total content of MgO, CaO, SrO and BaO is 5% by mass to 30% by mass. At this time, it is more preferable that the glass substrate contains 60% by mass to 70% by mass of SiO ₂ and 3% by mass to 10% by mass of BaO.

As a glass substrate for a panel display or flat panel display, in addition to alkali-free glass, alkali trace glass containing a trace amount of alkali metal may be used. When the glass of the glass substrate is alkali-free glass containing tin oxide or alkali-containing glass containing tin oxide, a platinum group produced by volatilization of a platinum group metal used for the inner wall of the glass processing apparatus of this embodiment described later The effect of suppressing the foreign matter of the metal agglomerates from entering the molten glass is remarkable. The alkali-free glass or the alkali trace-containing glass has a glass viscosity higher than that of the alkali glass. Since a lot of tin oxide is reduced in the melting step by increasing the melting temperature in the melting step, the molten glass temperature in the clarification step is increased in order to obtain a clarification effect, and the reduction of tin oxide is promoted, and It is necessary to reduce the glass melt viscosity. In addition, tin oxide has a higher temperature that promotes the reduction reaction than arsenous acid and antimony that have been used as fining agents in the past, so that the temperature of the molten glass is increased to promote fining. The temperature of the inner wall of 120 needs to be increased. In other words, when producing a non-alkali glass substrate containing tin oxide or a glass substrate of alkali trace-containing glass containing tin oxide, it is necessary to increase the molten glass temperature in the refining step. Is likely to occur.
Note that the alkali-free glass substrate is glass that does not substantially contain alkali metal oxides (Li ₂ O, K ₂ O, and Na ₂ O). The alkali trace glass is a glass having an alkali metal oxide content (total amount of Li ₂ O, K ₂ O, and Na ₂ O) of more than 0 and 0.8 mol% or less. The alkali trace amount glass contains, for example, 0.1% by mass to 0.5% by mass of an alkali metal oxide as a component, and preferably 0.2% by mass to 0.5% by mass of an alkali metal oxide. . Here, the alkali metal oxide is at least one selected from Li ₂ O, Na ₂ O, and K ₂ O. The total content of alkali metal oxides may be less than 0.1% by mass. Even if the content of the alkali metal oxide in the glass substrate is 0 to 0.8 mol%, it is possible to suppress the agglomeration of platinum group metal as a foreign substance in the molten glass by the method described later. Can do.

In addition to the above components, the glass substrate produced according to the present embodiment has SnO ₂ 0.01 mass% to 1 mass% (preferably 0.01 mass% to 0.5 mass%), Fe ₂ O ₃ 0. You may further contain mass%-0.2 mass% (preferably 0.01 mass%-0.08 mass%). Glass substrate produced by the present embodiment, in consideration of the environmental impact, do not contain _{As 2 O 3, Sb 2 O} 3 and PbO, or does not substantially contain.

Moreover, the glass substrate of the following glass compositions is further illustrated as a glass substrate manufactured by this embodiment. Therefore, the glass raw material is prepared so that the glass substrate has the following glass composition.
For example, by mol%, SiO ₂ 55 to 75 mol%, Al ₂ O ₃ 5 to 20 mol%, B ₂ O ₃ 0 to 15 mol%, RO 5 to 20 mol% (RO is MgO, CaO, SrO and Total amount of BaO), R ′ ₂ O 0 to 0.4 mol% (R ′ is the total amount of Li ₂ O, K ₂ O, and Na ₂ O), SnO ₂ 0.01 to 0.4 mol%, contains. At this time, at least one of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , and RO (R is all elements contained in the glass substrate among Mg, Ca, Sr, and Ba) is included in a molar ratio. ((2 × SiO ₂ ) + Al ₂ O ₃ ) / ((2 × B ₂ O ₃ ) + RO) may be 4.0 or more. A glass having a molar ratio ((2 × SiO ₂ ) + Al ₂ O ₃ ) / ((2 × B ₂ O ₃ ) + RO) of 4.0 or more is an example of a glass having a high temperature viscosity. Glass with high viscosity at high temperature generally needs to raise the temperature of the molten glass in the refining process, and thus volatilization of platinum group metals is likely to occur. That is, when manufacturing a glass substrate having such a composition, the effect of this embodiment described later, that is, the effect of suppressing the inclusion of platinum group metal aggregates as foreign matter in the molten glass is remarkable. Become. In addition, high temperature viscosity shows the viscosity of glass when molten glass becomes high temperature, and high temperature here shows 1300 degreeC or more, for example.

The molten glass used in the present embodiment may have a glass composition having a temperature of 1500 to 1700 ° C. when the viscosity is 10 ^2.5 poise. Such a glass is a glass having a high temperature viscosity, and the glass having a high temperature viscosity generally needs to raise the temperature of the molten glass in the refining process, and thus the volatilization of the platinum group metal is likely to occur. That is, even if the glass composition has a high high temperature viscosity, the effect of the present embodiment described later, that is, the effect of suppressing the agglomeration of platinum group metal as a foreign substance in the molten glass becomes remarkable.

The strain point of the molten glass used in this embodiment may be 650 ° C. or higher, more preferably 660 ° C. or higher, further preferably 690 ° C. or higher, and particularly preferably 730 ° C. or higher. Further, a glass having a high strain point tends to increase the temperature of the molten glass at a viscosity of 10 ^2.5 poise. That is, as the glass substrate having a higher strain point is manufactured, the effect of the present embodiment described later, that is, the effect of suppressing the agglomeration of platinum group metal as a foreign substance in the molten glass becomes more prominent. In addition, since the glass having a higher strain point is used for a high-definition display, the demand for the problem that platinum group metal aggregates are mixed as foreign substances is severe. For this reason, the glass substrate having a higher strain point is more suitable for the present embodiment in which the platinum group metal aggregates can suppress foreign matter contamination.

Further, when the glass raw material is melted so that the temperature of the molten glass containing tin oxide and the viscosity of 10 ^2.5 poise becomes 1500 ° C. or more, the above effect of the present embodiment is more remarkable. The temperature of the molten glass when the viscosity is 10 ^2.5 poise is, for example, 1500 ° C. to 1700 ° C., and may be 1550 ° C. to 1650 ° C.
If the content of a fining agent, for example, tin oxide, contained in the molten glass changes, the amount of oxygen released from the molten glass into the gas phase space also changes. From the viewpoint of suppressing the volatilization of the platinum group metal, the oxygen concentration in the gas phase space is preferably controlled (adjusted) by the content of tin oxide. Therefore, from the point of suppressing volatilization of platinum or a platinum alloy or the like, the content of tin oxide is limited and is preferably 0.01 to 0.3 mol%, preferably 0.03 to 0.2 mol. If the content of tin oxide is large, there is a problem that secondary crystals of tin oxide are generated in the molten glass. If the tin oxide content is too high, the amount of oxygen released from the molten glass into the gas phase space increases, the oxygen concentration in the gas phase space increases too much, and the volatilization amount of platinum group metals from the processing equipment This increases the problem. When the content of tin oxide is too small, defoaming of the molten glass bubbles is not sufficient.

(Configuration of the clarification tube of the first embodiment)
Next, the configuration of the clarification tube 120 according to the first embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic view showing the configuration of the clarification tube 120 of the first embodiment, and FIG. 4 is a vertical sectional view in the longitudinal direction of the clarification tube 120.
As shown in FIGS. 3 and 4, electrodes 121 a and 121 b are provided on the outer peripheral surfaces at both ends in the length direction of the clarification tube 120, and an exhaust pipe is provided on the wall in contact with the gas phase space of the clarification tube 120. 127 is provided. That is, the clarification step of the present embodiment is a step of processing a molten glass containing a clarifier that releases oxygen by a reduction reaction. In this clarification step, at least a part of the inner wall is made of a material containing a platinum group metal. Inside the apparatus, the molten glass is supplied so that a gas phase space is formed above the surface of the molten glass. In the clarification tube 120, the molten glass flows in the longitudinal direction of the clarification tube 120.
Note that a heat insulating material (not shown) (for example, a refractory brick, a refractory heat insulating brick, or the like) may be provided outside the clarification tube 120.

In the clarification tube 120, the electrodes 121a and 121b and the exhaust pipe 127 are made of the above platinum group metal.
In the present embodiment, a case where the clarification tube 120 is made of a platinum group metal will be described as a specific example. However, a part of the clarification tube 120 may be made of a refractory or other metal. .

The electrodes 121 a and 121 b are connected to the power supply device 122. When a voltage is applied between the electrodes 121a and 121b, a current flows through the clarification tube 120 between the electrodes 121a and 121b, and the clarification tube 120 is energized and heated. By this energization heating, the maximum temperature of the main body of the clarification tube 120 is heated to, for example, 1600 ° C. to 1750 ° C., more preferably 1630 ° C. to 1750 ° C., and the maximum temperature of the molten glass supplied from the transfer tube 104 is The mixture is heated to a temperature suitable for defoaming, for example, 1600 ° C to 1720 ° C, more preferably 1620 ° C to 1720 ° C.
Further, by controlling the temperature of the molten glass by energization heating, the viscosity of the molten glass can be adjusted, and thereby the flow rate of the molten glass passing through the clarification tube 120 can be adjusted.

The electrodes 121a and 121b may be provided with a temperature measurement device (thermocouple or the like) (not shown). The temperature measuring device measures the temperature of the electrodes 121 a and 121 b and outputs the measured result to the control device 123.
The control device 123 controls the amount of current that the power supply device 122 supplies to the clarification tube 120, thereby controlling the temperature and flow rate of the molten glass passing through the clarification tube 120. The control device 123 is a computer including a CPU, a memory, and the like.

As shown in FIGS. 3 and 4, the electrode 121a has a purge gas supply pipe for supplying purge gas to the gas phase space 120a above the surface (liquid level) of the molten glass in contact with the gas phase space in the clarification tube 120. 124a may be provided. Similarly, the electrode 121b may be provided with a purge gas supply pipe 124b for supplying a purge gas to the gas phase space 120a above the surface (liquid level) of the molten glass in contact with the gas phase space in the clarification tube 120. Good.
In the present embodiment, the purge gas supply pipe 124a is connected to the purge gas supply apparatus 125a, and purge gas is supplied from the purge gas supply apparatus 125a to the gas phase space 120a in the clarification pipe 120 via the purge gas supply pipe 124a from the upstream side of the molten glass. Is done. Similarly, the purge gas supply pipe 124b is connected to the purge gas supply apparatus 125b, and purge gas is supplied from the purge gas supply apparatus 125b to the gas phase space 120a in the clarification pipe 120 through the purge gas supply pipe 124b from the downstream side of the molten glass. . Here, the upstream side and the downstream side mean the upstream side and the downstream side with respect to the center position of the gas phase space 120a in the direction in which the molten glass flows.
By adjusting the inner diameters of the purge gas supply pipes 124a and 124b, the amount of purge gas supplied from the purge gas supply pipes 124a and 124b can be adjusted.

As the purge gas, a gas that is inert to platinum or a gas that is less reactive than oxygen can be used. Specifically, nitrogen (N ₂ ), a rare gas (eg, argon (Ar)), or the like can be used. In FIG. 4, nitrogen is described as an example of the purge gas.
The purge gas supply devices 125a and 125b are controlled by the control device 123, and the supply amount and supply pressure of the purge gas are adjusted.

An exhaust pipe 127 is provided on the wall of the clarification pipe 120 in contact with the gas phase space. The exhaust pipe 127 is provided above the gas phase space 120a. The exhaust pipe 127 is preferably provided at a position between the upstream end and the downstream end in the flow direction of the molten glass in the clarification pipe 120. The exhaust pipe 127 may have a shape protruding in a chimney shape from the outer wall surface of the main body of the clarification pipe 120 toward the outside. The exhaust pipe 127 communicates the gas phase space 120a (see FIG. 4) with the external space of the clarification pipe 120.
An oxygen concentration meter 128 is provided in the exhaust pipe 127. The oxygen concentration meter 128 measures the amount of gas passing through the exhaust pipe 127 and the oxygen concentration, and outputs the measurement signal to the control device 123. The oxygen concentration meter 128 is not particularly limited, and a known oxygen concentration meter is used.

  In this embodiment, for example, by adjusting one or a combination of the fining agent content, the temperature of the molten glass, the viscosity of the molten glass, the type of glass raw material, the temperature history of the molten glass, or the combination is released from the molten glass. The amount of oxygen produced is controlled. The amount of released oxygen is controlled by adjusting at least one of the fining agent content, molten glass temperature and viscosity, glass raw material type, and molten glass temperature history as described below.

(Content of clarifier)
For example, if the content of the fining agent increases, the amount of oxygen released into the gas phase space 120a in the fining tube 120 increases. On the other hand, if the content of the fining agent is reduced, the amount of oxygen released from the molten glass can be reduced.
If the amount of the clarifying agent is too small, bubbles remaining in the molten glass cannot be sufficiently reduced. Therefore, the content of the fining agent is, for example, 0.01 mol% to 0.3 mol%, preferably 0.03 mol% to 0.2 mol%, or 0.01 to 0.5 mol for tin oxide. It is preferable that it is mass%. That is, in this embodiment, the content of tin oxide in the glass substrate is adjusted in the range of 0.01 mol% to 0.3 mol%, and the oxygen concentration in the gas phase space is adjusted, thereby reducing bubbles by the clarifying agent. And suppression of volatilization of platinum group metals.

(Temperature and viscosity of molten glass)
The temperature of the molten glass can be adjusted by the temperature of the clarification tube 120. When the temperature of the molten glass is raised, the amount of oxygen released from the molten glass due to the reductive reaction of the fining agent increases. When the temperature of the molten glass is low, the amount of oxygen generated is small, and a clarification effect cannot be obtained sufficiently. On the other hand, when the temperature of the molten glass is low, the viscosity of the molten glass is increased, and the rising speed of the bubbles is decreased. For this reason, the gas phase space 120a is not released from the bubbles in the molten glass, and clarification cannot be performed sufficiently.
On the other hand, when the temperature of the clarification tube 120 is increased in order to increase the temperature of the molten glass, a problem of volatilization of the platinum group metal occurs. Therefore, in order to maintain the generation of bubbles while suppressing the volatilization of the platinum group metal, the temperature of the clarification tube 120 is controlled to be 1600 to 1750 ° C., for example. Thereby, the maximum temperature of the molten glass in the clarification tube 120 becomes 1630-1750 degreeC, Preferably it becomes 1650-1750 degreeC. At this time, the minimum viscosity of the molten glass is 200 to 800 poise. That is, in this embodiment, the maximum temperature of the clarification tube in the clarification step is adjusted in the range of 1600 ° C. to 1750 ° C., and the oxygen concentration in the gas phase space is adjusted, thereby reducing bubbles by the clarifier and volatilization of the platinum group metal. It is possible to achieve both suppression.

(Type of glass raw material)
The amount of oxygen contained in the molten glass varies depending on the amount of oxide contained in the glass raw material. For this reason, by adjusting the kind and amount of the glass raw material, specifically, by adjusting the amount of oxide contained in the glass raw material, the amount of oxygen released into the gas phase space 120a in the clarification tube 120 Can be adjusted.

(Temperature history of molten glass)
Since the reduction reaction of the clarifier occurs in the process prior to the clarification process (melting process) and oxygen may be released from the molten glass, it is released from the molten glass in the process prior to the clarification process (melting process). The amount of oxygen released into the gas phase space 120a in the clarification tube 120 varies depending on the amount of oxygen that is generated. For this reason, the amount of oxygen released into the gas phase space 120a in the clarification tube 120 can be adjusted by the melting temperature in the melting tank 101 or the like. Specifically, as the temperature in the melting process is lower, the reduction reaction of the clarifier in the melting process decreases, and the amount of oxygen released from the molten glass in the melting process decreases. The amount of oxygen released increases. However, if the melting temperature in the melting process is too low, there is a problem that the glass raw material cannot be melted sufficiently, and if the molten glass temperature in the melting process is too high, the reductive reaction of the fining agent increases too much, resulting in There arises a problem that the clarification effect in the clarification process cannot be sufficiently obtained. Therefore, for example, by adjusting the maximum temperature of the molten glass in the melting step in the range of 1500 ° C. to 1610 ° C. and adjusting the oxygen concentration in the gas phase space in the clarification tube 120, sufficient melting and clarification of the glass raw material. It is possible to achieve both suppression of volatilization of the platinum group metal constituting the wall of the tube 120.
Moreover, the amount of the reductive reaction of the fining agent changes depending on the temperature rising rate of the molten glass after the melting step. Specifically, the faster the rate of temperature rise of the molten glass after the melting step, the faster the refining agent reduction reaction. However, if the rate of temperature rise is too high, the temperature of the transfer tube 104 and the clarification tube 120 becomes too high, and the transfer tube 104 and the clarification tube 120 are melted and the platinum group metal in the transfer tube 104 and the clarification tube 120 is volatilized. The problem of increasing occurs, and if the rate of temperature rise is too slow, there arises a problem that the clarification effect in the clarification process cannot be sufficiently obtained. Therefore, for example, when the temperature of the molten glass is raised to 1630 ° C. or higher in the transfer pipe 104, the temperature rise rate of the molten glass in the transfer pipe is adjusted in the range of 3 ° C./min to 20 ° C./min. By adjusting the oxygen concentration in the gas phase space in the clarification tube 120 that raises the temperature of the molten glass to 1630 ° C. or higher at a speed, it is possible to achieve both foam reduction by a clarifier and suppression of platinum group metal volatilization. . More preferably, it is preferable to adjust the temperature rising rate and the molten glass temperature within a range in which the temperature of the molten glass is raised to 1630 ° C. or higher at a temperature rising rate of 3 ° C./min to 10 ° C./min.

  In order to suppress volatilization of the platinum group metal, it is preferable to adjust the oxygen concentration in the gas phase space 120a to be 0 to 10%. Note that if the oxygen concentration in the gas phase space 120a is set to 0%, the volatilization of the platinum group metal can be suppressed. Therefore, from the viewpoint of suppressing the volatilization of the platinum group metal, the oxygen concentration is preferably set to 0%. However, in order to always keep the oxygen concentration in the gas phase space 120a at 0%, there is a problem that the content of the fining agent is extremely reduced and the cost is high. In order to realize the above, it is preferable to adjust the oxygen concentration in the gas phase space 120a to be 0.01% or more. The oxygen concentration in the gas phase space 120a is preferably adjusted to 10% or less. In order to achieve both the suppression of volatilization of the platinum group metal and the reduction of the number of bubbles, the oxygen concentration is preferably adjusted to be in the range of 0.1% to 3.0%. It is more preferable to adjust so that it may become 0% or less range, and it is still more preferable to adjust so that it may become 0.3 to 0.7% of range. Here, if the oxygen concentration in the gas phase space becomes too small, the oxygen concentration difference between the molten glass and the gas phase space increases, so that the oxygen released from the molten glass into the gas phase space 120a increases, and the molten glass is reduced. As a result, air bubbles such as sulfur oxide and nitrogen may remain on the glass substrate after molding. On the other hand, if the oxygen concentration is too high, volatilization of the platinum group metal is promoted, and the amount of volatilized platinum group metal deposited may increase. Further, if the oxygen concentration in the gas phase space is too large, the difference in oxygen concentration between the molten glass and the gas phase space becomes too small, and oxygen is hardly released from the molten glass into the gas phase space 120a. The amount of bubbles such as oxygen remaining on the substrate increases.

  In this embodiment, the distribution of the amount of oxygen released from the molten glass at the longitudinal position of the clarification tube 120 by adjusting the temperature distribution of the molten glass, the flow rate of the molten glass, and the content of the clarifier. It is also possible to adjust the position in the flow direction of the molten glass (maximum oxygen release amount position) at which the amount of oxygen released from the liquid surface (liquid surface) of the molten glass in contact with the gas phase space is maximized. it can. Thereby, the distribution of oxygen concentration in the gas phase space 120a can be controlled.

In the present embodiment, the maximum oxygen release amount position is adjusted so as to be separated in the molten glass flow direction from the position in the molten glass flow direction (maximum temperature position) where the molten glass temperature is maximum. .
Note that the volatilization of the platinum group metal is promoted as the temperature increases. For this reason, the maximum temperature position is a temperature condition in which the platinum group metal is most easily volatilized. Moreover, the volatilization of the platinum group metal becomes more active as the atmosphere has a higher oxygen content.
Therefore, by adjusting the maximum oxygen release amount position so that the maximum oxygen release amount position and the maximum temperature position are separated from each other in the flow direction of the molten glass, Oxygen in the bubbles released from the surface (liquid level) is less likely to flow to the maximum temperature position. For this reason, the oxygen released by the defoaming of the molten glass flows into the highest temperature position where the platinum group metal volatilizes actively from the wall of the clarification tube 120, which is the highest compared to the case where the volatilization of the platinum group metal is promoted. Volatilization of the platinum group metal at the temperature position is reduced. For this reason, it is possible to prevent the volatiles of the platinum group metal from aggregating on the wall of the clarification tube 120 to form an aggregate, and a part of the aggregate is separated as fine particles and foreign matter is mixed into the molten glass. it can. This point will be described below.

  FIG. 5 is a diagram showing the relationship between the position in the longitudinal direction of the clarification tube 120 (position in the flow direction of the molten glass), the temperature of the upper end portion of the clarification tube 120, and the oxygen release amount. In FIG. 5, the horizontal axis represents the position in the flow direction of the molten glass, that is, the longitudinal position of the clarification tube 120, the left vertical axis represents the temperature of the clarification tube 120, and the right vertical axis represents the oxygen release amount. Represents.

The solid curve in FIG. 5 shows the relationship between the position in the longitudinal direction and the temperature of the clarification tube 120. In the clarification tube 120 of this embodiment, since the electrodes 121a and 121b are flange-shaped and have a high heat dissipation function, the temperature in the vicinity of both ends of the clarification tube 120 tends to be locally low. Further, since the exhaust pipe 127 also protrudes from the clarification pipe 120, the temperature in the vicinity of the exhaust pipe 127 of the clarification pipe 120 tends to be locally low. For this reason, the temperature of the wall of the clarification pipe | tube 120 changes according to the position of the flow direction of molten glass.
For example, the vicinity of both ends of the clarification tube 120 (that is, the vicinity of the electrodes 121a and 121b) and the vicinity of the exhaust pipe 127 are low-temperature regions at positions in the flow direction of the molten glass. On the other hand, an intermediate portion between the exhaust pipe 127 and the electrodes 121a and 121b becomes a high-temperature region at a position in the flow direction of the molten glass. The minimum temperature in the temperature distribution of the clarification tube 120 becomes a high temperature of, for example, 1500 ° C. or more due to energization heating of the clarification tube 120 by the electrodes 121a and 121b.
FIG. 5 shows an example of the temperature distribution of the clarification tube 120. In this temperature distribution, P represents the position in the longitudinal direction (maximum temperature position) where the temperature reaches the maximum temperature T _max ° C.
Here, the maximum temperature position is not limited to the position P, and has an allowable range around the position P. The allowable range of the maximum temperature position is preferably a temperature range within the range of (T _max −20) ° C. to T _max ° C, and more preferably within the range of (T _max −10) ° C. to T _max ° C. It is a temperature range, Especially preferably, it is a temperature range within the range of ( _Tmax- 5) degreeC- _Tmax degreeC. Hereinafter, the maximum temperature position having an allowable range is referred to as a maximum temperature position range R. In FIG. 5, the maximum temperature position range R is indicated by a temperature region within the range of (T _max −20) ° C. to T _max ° C.

On the other hand, the dashed-dotted curve in FIG. 5 shows the relationship between the position in the longitudinal direction and the oxygen release amount. When the molten glass is heated in the clarification tube 120, oxygen is released into the molten glass by the reduction reaction of the clarifier in the molten glass. This release of oxygen occurs abruptly. The released oxygen is absorbed by bubbles in the molten glass and the diameter of the bubbles expands (bubbles grow), or becomes bubbles in the molten glass and absorbs the existing bubbles in the molten glass. The diameter of the glass expands (bubbles grow) and overcomes the viscosity of the molten glass and starts to float toward the surface (liquid surface) of the molten glass in contact with the gas phase space. At this time, the position in the longitudinal direction (maximum oxygen release amount position) A of the clarification tube 120 at which the amount of released oxygen from the surface (liquid level) of the molten glass is maximized is the maximum temperature position range R and the clarification tube. It is adjusted so as to be separated in the longitudinal direction of 120 (the flow direction of the molten glass). Specifically, it is preferable that the maximum oxygen release amount position A is adjusted with respect to the maximum temperature position range R so as to be located on the downstream side of the molten glass flow.
In general, the reductive reaction of the fining agent that releases oxygen becomes more active as the temperature of the molten glass becomes higher, and the higher the temperature of the molten glass, the lower the viscosity of the molten glass, and the higher the rising speed of the molten glass. In addition, the higher the temperature of the inner wall in contact with the molten glass, the higher the temperature of the molten glass, and therefore, the release of bubbles from the molten glass becomes more active. For this reason, in general, the maximum oxygen release amount position A and the maximum temperature position range R substantially coincide. However, in this embodiment, the maximum oxygen release amount position A is adjusted such that the maximum oxygen release amount position A is separated from the maximum temperature position range R as described above.

Note that the oxygen release amount and the distribution of the oxygen release amount can be obtained using computer simulation. For example, the upper limit and lower limit of the oxygen release amount and the distribution of the oxygen release amount are determined in advance by experiments or the like. The upper limit of the oxygen release amount is set in order to suppress the oxygen concentration in the gas phase space from increasing and the volatilization of the platinum group metal from being promoted by increasing the oxygen release amount. The lower limit of the oxygen release amount is set so that the bubble diameter in the glass does not increase, the bubble rising speed does not increase, and the defoaming effect is not low. Further, the oxygen release amount distribution suitable for suppressing efficient defoaming and volatilization of the platinum group metal is also determined between the upper limit and the lower limit. The clarification conditions can be extracted by using computer simulation so that the target oxygen release amount and the distribution of the target oxygen release amount such that the oxygen release amount is located between the upper limit and the lower limit are realized. . The fining conditions include, for example, one or a combination of a fining agent content, molten glass temperature, molten glass viscosity, glass raw material type, and molten glass temperature history.
In the computer simulation, for example, the clarification tube 120, a heat insulating material (not shown) provided around the clarification tube 120, and energization heating of the clarification tube 120 are modeled, and a heat conduction simulation is performed. By using the calculation result of the temperature distribution, the predetermined relationship between the temperature of the molten glass and the amount of oxygen released from the fining agent is used to determine the amount of oxygen released from the fining agent and the distribution of the amount released. By simulating the reduction reaction in the glass, and further by simulating the expansion of the bubble diameter and the rising of the bubble with a predetermined diameter in the molten glass by absorbing oxygen, the oxygen release amount and Its distribution can be predicted.
Furthermore, while conducting the heat conduction simulation by modeling the clarification tube 120, a heat insulating material (not shown) provided around the clarification tube 120, and the energization heating of the clarification tube 120, the calculated value of the temperature of the molten glass as the simulation result is calculated. By using the predetermined relationship between the temperature of the molten glass and the amount of oxygen released from the fining agent, the amount of oxygen released from the fining agent is determined and bubbles of a predetermined size are generated. Oxygen reduction maximum position A is simulated by simulating the oxidation-reduction reaction, and further, by simulating the expansion of the bubble diameter and the rising of the bubble whose diameter is increased by absorbing the oxygen in the molten glass. Can be predicted. In this case, the total amount of released oxygen can also be predicted. Such a simulation can be executed on a computer using a known simulation program or the like. The refining conditions can be determined using computer simulation so that the maximum oxygen release amount position A is separated from the maximum temperature position range R in the flow direction of the molten glass.

  Here, the maximum oxygen release amount position A can be adjusted by adjusting at least one of the temperature distribution of the molten glass flowing in the clarification tube 120, the flow rate of the molten glass, the content and type of the clarifier. The temperature distribution of the molten glass affects the amount of oxygen released from the fining agent and the oxygen release start position, as well as the bubble rising speed in the molten glass. The temperature distribution of the molten glass can be adjusted by, for example, the heating amount of the clarification tube 120 in the energization heating of the heating electrode 121b or by adjusting the current distribution on the circumference of the clarification tube 120. Moreover, the temperature distribution of the molten glass can be adjusted by adjusting the amount of heat released from the outer periphery of the clarification tube 120 to the outside, for example. The amount of heat release is adjusted by adjusting the heat insulating properties (thermal conductivity, etc.) and thermal resistance (= (heat insulating material thickness) / thermal conductivity) of the heat insulating material surrounding the outer periphery of the clarification tube 120. By changing such adjustment parameters, the maximum oxygen release amount position A can be adjusted using computer simulation.

The flow rate of the molten glass affects the distance from the oxygen release start position in the molten glass to the oxygen release position on the surface (liquid surface) of the molten glass. The flow rate of the molten glass is adjusted by, for example, the temperature (viscosity) of the molten glass in the vicinity of the molten glass outlet of the clarification tube 120 or the amount of molten glass drawn out by an apparatus located in a subsequent process such as the forming apparatus 200. be able to. By changing such adjustment parameters, the maximum oxygen release amount position A can be adjusted using computer simulation.
When actually manufacturing a glass substrate, each value (clarification condition) of the adjustment parameter when the maximum oxygen release amount position A adjusted by computer simulation is a desired position is used.

  In the present embodiment, the clarification pipe 120 is provided with an exhaust pipe 127 that communicates the gas phase space 120 a and the atmosphere outside the clarification pipe 120. The arrangement position of the exhaust pipe 127 in the flow direction of the molten glass is preferably between the maximum oxygen release amount position A and the maximum temperature position range R. By determining the arrangement position of the exhaust pipe 127 in this manner, the oxygen release amount maximum position A where a large amount of bubbles containing oxygen is released from the surface (liquid surface) of the molten glass in contact with the gas phase space is released from the surface. Before the oxygen in the generated bubbles flows to the maximum temperature position range R by the air flow, most of the oxygen is released from the exhaust pipe 127 to the outside of the clarification pipe 120a. For this reason, it is unlikely that oxygen in the bubbles released at the maximum oxygen release amount position A flows to the maximum temperature position range R, and volatilization of the platinum group metal in the maximum temperature position range R can be reduced.

It is preferable that both the maximum oxygen release amount position A and the exhaust pipe 127 are on the same side with respect to the maximum temperature position range R (including the maximum temperature position P). That is, the maximum oxygen release amount position A and the exhaust pipe 127 may both be upstream of the maximum temperature position range R in the molten glass flow direction, or both may be downstream of the maximum temperature position range R. preferable. In this case, it is unlikely that oxygen in the bubbles released at the maximum oxygen release amount position A flows to the maximum temperature position range R, and volatilization of the platinum group metal in the maximum temperature position range R can be reduced.
For example, the maximum temperature position range R, the maximum oxygen release amount position A, and the exhaust pipe 127 may be arranged in this order from the upstream side of the molten glass. In this case, the oxygen released at the maximum oxygen release amount position A flows in the direction of the exhaust pipe 127. Therefore, the oxygen released at the maximum oxygen release amount position A is a gas phase near the maximum temperature position range R of the molten glass. It is difficult to flow into a high-temperature atmosphere in the space 120a.
In particular, it is preferable to arrange the maximum temperature position range R, the arrangement position of the exhaust pipe 127, and the maximum oxygen release amount position A in this order from the upstream side of the molten glass.

  Further, the maximum oxygen release amount position A and the arrangement position of the exhaust pipe 127 can be the same position in the flow direction of the molten glass. By setting the oxygen release amount maximum position A and the exhaust pipe 127 to the same position in the flow direction of the molten glass, the oxygen released from the surface (liquid surface) of the molten glass at the oxygen release amount maximum position A is reduced. It can be discharged to the outside of the clarification tube 120 via the exhaust pipe 127 located above. In this case, oxygen released from the surface of the molten glass at the maximum oxygen release amount position A does not diffuse into the gas phase space 120a and flows toward the exhaust pipe 127 without flowing through the gas phase space 120a. For this reason, the oxygen released from the surface (liquid surface) of the molten glass at the maximum oxygen release amount position A is hardly used for volatilization of the platinum group metal. Note that the maximum oxygen release amount position A and the arrangement position of the exhaust pipe 127 are the same in the flow direction of the molten glass. In the flow direction of the molten glass, the exhaust pipe 127 is centered on the central position of the exhaust pipe 127. This means that the oxygen release amount maximum position A is in the region within the range of the tube diameter. When the allowable range of the maximum oxygen release amount position A is determined for the maximum oxygen release amount position A, this allowable range only needs to partially overlap the region within the range of the tube diameter dimension.

  In the present embodiment, a flange-shaped member (for example, electrodes 121a and 121b) extending outside the clarification tube 120 is provided on the outer periphery of the clarification tube 120. The flange-shaped member is preferably in a region other than the region between the maximum oxygen release amount position A and the position of the exhaust pipe 127 in the flow direction of the molten glass. That is, the flange-shaped member is located on the upstream side of the molten glass with respect to the oxygen release amount maximum position A and the position of the exhaust pipe 127, or on the downstream side of the molten glass with respect to the oxygen release amount maximum position A and the position of the exhaust pipe 127. Preferably there is. Since the amount of heat radiation from the flange-shaped member to the outside is large, the temperature in the vicinity of the portion of the clarification tube 120 where the flange-shaped member is provided is locally low. In this case, the platinum group metal volatiles in the gas phase space 120 a are cooled and reduced by passing in the vicinity of the flange-shaped member, and the reduced platinum group metal aggregates on the inner wall surface of the clarification tube 120. There is a case. For this reason, it is preferable that a flange-shaped member is not disposed in a region between the maximum oxygen release amount position A and the position where the exhaust pipe 127 is disposed.

In the present embodiment, the amount of oxygen exhausted from the exhaust pipe 127 provided in the upper part of the gas phase space 120a is adjusted.
The amount of oxygen exhausted from the exhaust pipe 127 is calculated by measuring the oxygen concentration of the gas exhausted from the exhaust pipe 127 with the oxygen concentration meter 128 and measuring the total amount of gas exhausted from the exhaust pipe 127. can do. By adjusting the total amount of gas discharged from the exhaust pipe 127 in accordance with the oxygen concentration measured by the oxygen concentration meter 128, the amount of oxygen discharged can be adjusted.

  For example, the exhaust pipe 127 is provided with a suction device that sucks the gas in the gas phase space 120a, and the total amount of gas discharged from the exhaust pipe 127 can be adjusted by adjusting the output of the suction device. As shown in FIG. 4, when supplying the purge gas to the gas phase space 120a, the amount of the purge gas supplied to the gas phase space 120a may be adjusted by controlling the suction device.

In the present embodiment, the gas phase space 120a is adjusted by adjusting the amount of oxygen released from the molten glass and adjusting the amount of oxygen discharged from the exhaust pipe 127 provided at the upper portion of the gas phase space 120a. The oxygen concentration is adjusted to be within a predetermined range. Thereby, it can suppress that a platinum group metal is oxidized and volatilizes, and can reduce the precipitation amount of the platinum group metal by reducing the volatilized platinum group metal. When tin oxide is used as a fining agent, the temperature range at which tin oxide exhibits a fining effect is higher than when As ₂ O ₃ and Sb ₂ O ₃ are used, and volatilization of the platinum group metal becomes significant. The effect of this embodiment is particularly effective.

  In this embodiment, by supplying purge gas from the purge gas supply pipe 124a and the purge gas supply pipe 124b to the gas phase space 120a in the clarification pipe 120, oxygen released from the molten glass in the clarification pipe 120 is discharged, The oxygen concentration in the gas phase space 120a can be reduced. At this time, by adjusting the supply amount of the purge gas in accordance with the oxygen concentration measured by the oxygen concentration meter 128, the oxygen concentration in the gas phase space 120a can be adjusted to be within a predetermined range. Thereby, it can suppress that a platinum group metal is oxidized and volatilizes, and can reduce the precipitation amount of the platinum group metal by reducing the volatilized platinum group metal.

  In the present embodiment, the amount of gas discharged from the exhaust pipe 127 is measured, the oxygen concentration is measured by the oxygen concentration meter 128, and the oxygen amount discharged from the exhaust pipe 127 (= exhausted from the exhaust pipe 127). The supply amount of the purge gas is adjusted so that the total amount of gas × oxygen concentration is within a predetermined range. That is, a signal of the total exhaust amount from the exhaust pipe 127 and the oxygen concentration in the exhaust gas measured by the oxygen concentration meter 128 is output to the control device 123, and the control device 123 supplies the purge gas in accordance with the signal from the oxygen concentration meter 128. The devices 125a and 125b are controlled to adjust the supply amount and supply pressure of the purge gas.

  In this embodiment, the amount of oxygen released from the molten glass in the clarification tube 120 is adjusted so that the upstream side of the molten glass is larger than the downstream side, and is supplied from the upstream side of the molten glass. It is preferable to increase the purge gas to be larger than the purge gas supplied from the downstream side of the molten glass. That is, it is preferable that the amount of purge gas supplied from the purge gas supply pipe 124a is larger than the amount of purge gas supplied from the purge gas supply pipe 124b. By making the amount of purge gas supplied from the purge gas supply pipe 124a larger than the amount of purge gas supplied from the purge gas supply pipe 124b, oxygen released from the molten glass is more efficiently diluted with the purge gas and discharged. Can do.

  The exhaust pipe 127 may be provided with a suction device that sucks the gas in the gas phase space 120a. By reducing the pressure on the exhaust pipe 127 side by the suction device (for example, about 10 Pa lower than the pressure in the gas phase space 120a), the oxygen and purge gas in the gas phase space 120a can be efficiently discharged. Further, the amount of purge gas supplied to the gas phase space 120a may be adjusted by controlling the suction device.

(Configuration of the clarification tube of the second embodiment)
Next, the structure of the clarification pipe | tube 120 of 2nd Embodiment is demonstrated in detail. In addition to the clarification pipe 120, the clarification apparatus includes an exhaust pipe (vent pipe) 127, electrodes 121a and 121b, and a refractory protective layer and a refractory brick (not shown) surrounding the outer periphery of the clarification pipe 120. FIG. 6 is an external view mainly showing the clarification tube 120. FIG. 7 is a cross-sectional view showing the inside of the clarification tube 120 and an example of the temperature distribution of the clarification tube.

  An exhaust pipe (vent pipe) 127 and a pair of electrodes 121 a and 121 b are attached to the clarification pipe 120. Inside the clarification tube 120, a clarification step of molten glass containing a clarifier that releases oxygen by a reduction reaction is performed. In this clarification step, molten glass is supplied into the clarification tube 120 made of a material containing a platinum group metal at least a part of the inner wall so that a gas phase space is formed above the surface of the molten glass, and In the clarification tube 120, the molten glass is caused to flow in a direction along the surface in contact with the gas phase space of the molten glass, specifically, in the longitudinal direction of the clarification tube 120. The gas phase space is formed along the flow direction of the molten glass. At least a part of the inner wall surrounding the gas phase space is made of a material containing a platinum group metal. In the present embodiment, the entire wall surrounding the gas phase space is made of a material containing a platinum group metal.

  The exhaust pipe (vent pipe) 127 is provided in the middle of the direction in which the molten glass flows, and is provided on the inner wall in contact with the gas phase space to communicate the gas phase space with the atmosphere outside the clarification tube 120. The exhaust pipe (vent pipe) 127 is preferably formed of a platinum group metal, like the clarification pipe 120. Since the temperature of the exhaust pipe (vent pipe) 127 is likely to decrease due to the heat dissipation function, the exhaust pipe (vent pipe) 127 may be provided with a heating mechanism for heating the exhaust pipe (vent pipe) 127.

  The pair of electrodes 121 a and 121 b are flange-shaped electrode plates provided at both ends of the clarification tube 120. The electrodes 121a and 121b cause a current supplied from a power source (not shown) to flow through the clarification tube 120, and the clarification tube 120 is energized and heated by this current. When tin oxide is used as the fining agent, for example, the fining tube 120 is heated so that the maximum temperature is 1600 ° C to 1750 ° C, more preferably 1630 ° C to 1750 ° C, and the molten glass has a maximum temperature of tin oxide reduction reaction. It is heated to the temperature at which it occurs, for example 1600 ° C to 1720 ° C, more preferably 1620 ° C to 1720 ° C. By controlling the current flowing through the clarification tube 120, the temperature of the molten glass flowing inside the clarification tube 120 can be controlled. Thus, the molten glass passing through the inside of the clarification tube 120 is heated and clarified. A pair of electrodes 121a and 121b are provided in the clarification tube 120, but the number of electrodes is not particularly limited. The temperature of the inner wall in contact with the gas phase space of the clarification tube 120 due to energization heating by the electrodes 121a and 121b is, for example, in the range of 1500 to 1750 ° C.

Inside the clarification tube 120, bubbles containing CO ₂ or SO ₂ contained in the molten glass are removed by the oxidation-reduction reaction of a clarifier added to the molten glass, for example, tin oxide. Specifically, first, the temperature of the molten glass is raised to reduce the fining agent, thereby generating oxygen bubbles in the molten glass. Bubbles containing gaseous components such as CO ₂ , N ₂ and SO ₂ contained in the molten glass absorb oxygen generated by the reductive reaction of the fining agent. Bubbles having expanded (grown up) by absorbing oxygen rise to the surface (liquid surface) of the molten glass in contact with the gas phase space and release the bubbles, that is, break up and disappear. The gas contained in the extinguished bubbles is released into the gas phase space and discharged to the outside of the clarification tube 120 through the exhaust pipe 127. Next, the temperature of the molten glass is lowered to oxidize the reduced fining agent. Thereby, the bubble oxygen remaining in the molten glass is dissolved and absorbed in the molten glass (absorption treatment). As a result, the remaining bubbles are reduced and disappear. In this way, bubbles contained in the molten glass are removed by the oxidation-reduction reaction of the clarifying agent.
Although not shown, a refractory protective layer is provided on the outer wall surface of the clarification tube 120. A refractory brick is further provided outside the refractory protective layer. The refractory brick is placed on a base (not shown).

In such a clarification tube 120, the temperature of the wall in contact with the gas phase space in the clarification tube 120 has a temperature distribution along the flow direction of the molten glass. When defoaming the molten glass, the maximum amount of bubbles released in the flow direction of the molten glass is the maximum amount of bubbles released from the surface (liquid level) of the molten glass in contact with the gas phase space to the gas phase space. The maximum position of the bubble discharge amount is adjusted so that the position and the maximum temperature position of the temperature distribution in the flow direction of the molten glass are separated from each other in the flow direction of the molten glass.
The platinum group metal promotes volatilization as the temperature of the inner wall increases. For this reason, the maximum temperature position is a temperature condition in which the platinum group metal is most easily volatilized. Moreover, the volatilization of the platinum group metal becomes more active as the atmosphere has a higher oxygen content.
Therefore, by adjusting the bubble discharge maximum position so that the maximum bubble discharge amount position and the maximum temperature position are separated in the flow direction of the molten glass, the surface of the molten glass (liquid The oxygen in the bubbles released from the surface) is less likely to flow to the maximum temperature position. For this reason, the oxygen released by the defoaming of the molten glass flows into the highest temperature position where the platinum group metal volatilizes actively from the wall of the clarification tube 120, which is the highest compared to the case where the volatilization of the platinum group metal is promoted. Volatilization of the platinum group metal at the temperature position is reduced. For this reason, it is possible to prevent the volatiles of the platinum group metal from aggregating on the wall of the clarification tube 120 to form an aggregate, and a part of the aggregate is separated as fine particles and foreign matter is mixed into the molten glass. it can. This point will be described below.

  FIG. 7 is a diagram illustrating the positional relationship between the cross section of the clarification tube 120 and the temperature distribution of the wall of the clarification tube 120. The upper part of FIG. 7 is a cross-sectional view of the clarification tube 120. The lower part of FIG. 7 is a graph showing the temperature distribution of the inner wall in contact with the gas phase space of the clarification tube 120. In the graph representing the temperature distribution of the inner wall in contact with the gas phase space of the clarification tube 120, the horizontal axis represents the position in the flow direction of the molten glass, that is, the position in the longitudinal direction of the clarification tube 120, and the vertical axis represents the clarification tube 120. Represents the temperature of the inner wall in contact with the gas phase space.

In the clarification tube 120 of this embodiment, since the electrodes (flange members) 121a and 121b having a flange shape have a high heat radiation function, the walls near both ends of the clarification tube 120 are in the flow direction of the molten glass (X The temperature tends to be lower than that of the peripheral inner wall along the direction: the longitudinal direction of the clarification tube 120 (the inner wall of the clarification tube 120 in contact with the gas phase space). Further, since the exhaust pipe 127 also protrudes from the clarification pipe 120, the inner wall of the clarification pipe 120 in contact with the gas phase space near the exhaust pipe 127 is also in contact with the inner wall (the gas phase space) around the inner wall along the X direction. The temperature tends to be lower than that of the inner wall of the clarification tube 120. For this reason, the temperature of the inner wall of the clarification tube 120 in contact with the gas phase space has a temperature distribution along the X direction. Near the both ends of the clarification pipe 120, that is, the inner wall near the ends of the pair of electrodes 121a and 121b and the wall near the exhaust pipe 127 become a low temperature region where the temperature is low in the X direction, and the exhaust pipe 127 and the electrodes 121a and 121b The intermediate part in the middle is a high temperature region where the temperature is high in the X direction. Even if the temperature in the temperature distribution of the inner wall is the lowest, the temperature is raised to a high temperature, for example, 1500 ° C. or more by energization heating of the fining tube 120 by the electrodes 121a and 121b. For this reason, the platinum group metal which comprises the clarification pipe | tube 120 volatilizes in gas phase space, and the volatile matter of a platinum group metal exists. FIG. 7 shows an example of the temperature distribution. In this temperature distribution, the position in the X direction where the temperature reaches the maximum temperature T _max ° C is represented by P.
Here, the maximum temperature position of the temperature distribution is not limited to the position P, and has an allowable range around the position P. The allowable range of the maximum temperature position is preferably a temperature range within the range of (T _max −20) ° C. to T _max ° C, and more preferably within the range of (T _max −10) ° C. to T _max ° C. It is a temperature range, Especially preferably, it is a temperature range within the range of ( _Tmax- 5) degreeC- _Tmax degreeC. Hereinafter, the highest temperature position having an allowable range is referred to as the highest temperature position R.

On the other hand, the molten glass is heated in the refining tube 120, and the refining agent undergoes a reduction reaction to start releasing oxygen into the molten glass. This release of oxygen occurs abruptly. The released oxygen is absorbed by the bubbles in the molten glass to enlarge (grow) the diameter of the bubbles, or becomes bubbles in the molten glass and absorbs the existing bubbles in the molten glass, resulting in the diameter of the bubbles. Is expanded (grown) to overcome the viscosity of the molten glass and start to float toward the surface (liquid surface) of the molten glass in contact with the gas phase space. At this time, the maximum bubble discharge amount position A in the longitudinal direction of the clarification tube 120 at which the discharge amount of bubbles released from the surface (liquid level) of the molten glass is maximized is separated from the maximum temperature position R in the X direction. Yes. Specifically, it is preferable that it is located on the downstream side of the flow of the molten glass with respect to the maximum temperature position R.
In this way, the bubble discharge amount maximum position A is adjusted so that the bubble discharge amount maximum position A is separated from the maximum temperature position R.

  The bubble discharge amount maximum position A can be obtained by experiments, but can also be obtained by prediction by computer simulation. In the case of computer simulation, a heat conduction simulation is performed by modeling the clarification tube 120, a refractory protective layer and a refractory brick (not shown) provided around the clarification tube 120, and a heating source created by energizing heating of the clarification tube 120. Using the calculated value of the molten glass temperature, which is the simulation result, the predetermined amount of oxygen released from the fining agent is determined by using a predetermined relationship between the temperature of the molten glass and the amount of oxygen released from the fining agent. By generating bubbles of the size, the oxidation-reduction reaction in the molten glass is simulated, and further, the bubbles that are predetermined in the molten glass absorb oxygen and the diameter of the bubbles expands and the expanded bubbles The bubble discharge amount maximum position A can be predicted by simulating the ascent of the bubble. In this case, the amount of foam released can also be predicted. Such a simulation can be executed on a computer using a known simulation program or the like. Then, the refining conditions can be determined using computer simulation so that the maximum bubble discharge amount position A is separated from the maximum temperature position R in the X direction.

Here, it is preferable that the bubble discharge amount maximum position A is performed by adjusting at least one of the temperature distribution of the molten glass flowing in the clarification tube 120 and the flow rate of the molten glass. The temperature distribution of the molten glass affects the amount of oxygen released from the fining agent and the oxygen release start position, as well as the bubble rising speed in the molten glass. The temperature distribution of the molten glass can be adjusted by, for example, the heating amount of the clarification tube 120 in the energization heating of the heating electrode 121b or by adjusting the current distribution on the circumference of the clarification tube 120. Moreover, the temperature distribution of the molten glass can be adjusted by adjusting the amount of heat released from the outer periphery of the clarification tube 120 to the outside, for example. The amount of heat release can be adjusted by adjusting the heat insulation properties (thermal conductivity, etc.) and heat resistance (= (thickness of the refractory protective layer or refractory brick) / heat This is done by adjusting the conductivity. By changing such adjustment parameters, it is possible to adjust the bubble discharge amount maximum position A using computer simulation.
The flow rate of the molten glass affects the distance from the oxygen release start position in the molten glass to the oxygen release position on the surface (liquid surface) of the molten glass in contact with the gas phase space. The flow rate of the molten glass is adjusted by, for example, the temperature (viscosity) of the molten glass in the vicinity of the molten glass outlet of the clarification tube 120 or the amount of molten glass drawn out by an apparatus located in a subsequent process such as the forming apparatus 200. be able to. By changing such adjustment parameters, it is possible to adjust the bubble discharge amount maximum position A using computer simulation.
When actually manufacturing a glass substrate, each value (clarification condition) of the adjustment parameter when the bubble discharge maximum position A adjusted by computer simulation becomes a desired position is used.

  In the present embodiment, the clarification pipe 120 is provided with an exhaust pipe 127 that communicates the gas phase space and the atmosphere outside the clarification pipe 120. At this time, the arrangement position of the exhaust pipe 127 in the X direction is the maximum bubble discharge amount. It is preferably between the position A and the maximum temperature position R. By determining the arrangement position of the exhaust pipe 127 in this way, in the bubble discharge amount maximum position A where a large amount of bubbles containing oxygen is released from the surface in contact with the gas phase space of the molten glass, Most of the oxygen is released from the exhaust pipe 127 to the outside of the clarification pipe 120a before the oxygen flows to the bubble discharge amount maximum position A by the airflow. For this reason, it is unlikely that oxygen in the bubbles released at the bubble discharge amount maximum position A flows to the maximum temperature position R, and volatilization of the platinum group metal at the maximum temperature position R can be reduced.

It is preferable that the bubble discharge amount maximum position A and the arrangement position of the exhaust pipe 127 in the X direction are on the same side in the X direction on the basis of the maximum temperature position R of the temperature distribution of the wall of the clarification pipe 120. Even in this case, it is unlikely that oxygen in the bubbles released at the bubble discharge amount maximum position A flows to the highest temperature position R, and volatilization of the platinum group metal at the highest temperature position R can be reduced.
The maximum temperature position R, the arrangement position of the exhaust pipe 127, and the bubble discharge amount maximum position A are located in the order of the maximum temperature position R, the arrangement position of the exhaust pipe 127, and the bubble discharge amount maximum position A from the upstream side in the X direction. It is preferable.

  In the present embodiment, a flange-shaped member (flange member) including electrodes 121a and 121b extending outside the clarification tube 120 is provided on the outer periphery of the clarification tube 120. However, the arrangement position of the flange-shaped member in the X direction is In addition, it is preferable to be in the region in the longitudinal direction other than the region between the maximum bubble discharge amount position A and the position where the exhaust pipe 127 is disposed. Since the flange-shaped member has a large amount of heat radiation to the outside of the exhaust pipe 127 due to its shape, the temperature tends to be locally lowered in the vicinity of the inner wall of the clarification tube 120 provided with the flange-shaped member. In this case, the volatiles of the platinum group metal in the gas phase space may pass through the vicinity of the inner wall where the flange-shaped member is provided, so that the volatiles are cooled and aggregate on the inner wall of the clarification tube 120. is there. For this reason, it is preferable that the arrangement position of the flange-shaped member is in a region other than the region between the maximum bubble discharge amount position A and the arrangement position of the exhaust pipe 127.

  In the present embodiment, the maximum temperature position R, the arrangement position of the exhaust pipe 127, and the maximum bubble discharge amount position A are the highest temperature position R, the arrangement position of the exhaust pipe 127, and the maximum bubble discharge amount position from the upstream side in the X direction. Although it is located in the order of A, the maximum temperature as long as the foam discharge maximum position A and the arrangement position of the exhaust pipe 127 are on the same side in the X direction (the longitudinal direction of the clarification pipe 120) with respect to the maximum temperature position R. The position R, the arrangement position of the exhaust pipe 127, and the foam discharge maximum position A are not limited. For example, the maximum temperature position R, the maximum bubble discharge amount position A, and the arrangement position of the exhaust pipe 127 may be sequentially arranged from the upstream side in the X direction through which the molten glass flows. In this case, the oxygen released at the bubble discharge amount maximum position A flows in the direction of the exhaust pipe 127, so the oxygen released at the bubble discharge amount maximum position A is in the gas phase space near the maximum temperature position R of the molten glass. Difficult to flow in high temperature atmosphere.

  Moreover, the bubble discharge amount maximum position A and the arrangement position of the exhaust pipe 127 may be the same position in the X direction. By setting the foam discharge maximum position A and the exhaust pipe 127 at the same position in the X direction, oxygen released from the surface (liquid level) of the molten glass at the maximum foam discharge position A is positioned above. Since it is discharged to the outside of the clarification tube 120 via the exhaust pipe 127, oxygen travels toward the exhaust pipe 127 without diffusing into the gas phase space and without flowing through the gas phase space. For this reason, the oxygen released from the surface (liquid level) of the molten glass at the bubble discharge maximum position A is hardly used for volatilization of the platinum group metal. Note that setting the maximum bubble discharge amount position A and the position of the exhaust pipe 127 to the same position in the X direction means the range of the diameter of the exhaust pipe 127 relative to the center position of the pipe of the exhaust pipe 127 in the X direction. It means that the bubble discharge amount maximum position A is in the inner region (region along the X direction). Further, when the allowable range of the maximum bubble discharge amount position A is defined for the maximum bubble discharge amount position A, this allowable range only needs to partially overlap with the region within the range of the tube diameter dimension.

  Even if the temperature of the inner wall of the clarification tube 120 in contact with the gas phase space of the clarification tube 120 is 1500 ° C. or higher, in this embodiment, the volatilization of the platinum group metal is reduced and the aggregation of the volatiles of the platinum group metal is suppressed. Therefore, the effect of this embodiment becomes remarkable.

In both the first embodiment and the second embodiment, the vapor pressure of the platinum group metal in the gas phase space is preferably adjusted in order to suppress the volatilization of the platinum group metal. From the viewpoint of suppressing volatilization and aggregation of the platinum group metal, the vapor pressure of the platinum group metal in the gas phase space is preferably 0.1 Pa to 15 Pa, and preferably 3 Pa to 10 Pa.
Moreover, in 1st Embodiment and 2nd Embodiment, although demonstrated using the clarification tube 120 as an apparatus which processes the molten glass containing the clarifier which discharge | releases oxygen by a reductive reaction, it is not necessarily limited to the clarification tube 120. Not. It is not limited to a clarification tube, as long as it is a part that has a gas phase space and that processes molten glass containing a clarifier that releases oxygen by a reduction reaction.

(Experimental example 1)
In order to confirm the effect of the first embodiment, tin oxide is used as a clarifier, and the clarified tube 120 of the first embodiment shown in FIG. The form was adjusted. After this clarification, it was formed into a sheet glass of 2270 mm × 2000 mm and a thickness of 0.5 mm, and 100 glass substrates were produced.
At this time, in Examples 1 to 8, the oxygen release amount from the molten glass, the supply amount of the purge gas (N ₂ ), and the suction amount of the exhaust pipe 127 are adjusted, so that the oxygen concentration in the gas phase space 120a is 0.1%. Adjustment was made in the range of ˜3%. The oxygen concentration of Example 1 is 0%, the oxygen concentration of Example 2 is 0.1%, the oxygen concentration of Example 3 is 0.3%, the oxygen concentration of Example 4 is 0.5%, The oxygen concentration was adjusted to 0.7%, the oxygen concentration of Example 6 to 1%, the oxygen concentration of Example 7 to 2%, and the oxygen concentration of Example 8 to 3%.
As a conventional example, the oxygen concentration in the gas phase space 120a was not adjusted. At this time, the oxygen concentration was 21%. The platinum aggregates on the glass substrate were visually inspected and evaluated by the number of platinum aggregates per 100 sheets. Platinum agglomerates having an aspect ratio of 100 or more and a maximum length of 100 μm or more were defined as platinum foreign matters to be inspected.
As a result of the inspection, the number of platinum aggregates was 0.10 / m ³ , 1.2 / m ³ , 3.9 / m ³ , 7.4 / m ^{3 in} the order of Examples 1 to 8. 12 / m ³ , 19 / m ³ , 57 / m ³ , 113 / m ³ . These results are smaller than the amount of foreign matter 4306 / m ^{3 in} the conventional example. From this, in Examples 1-8, it turns out that the amount of foreign materials compared with a prior art example can be reduced. The number of bubbles remaining as defects in the glass substrates of Examples 1 to 8 was 34 / m ³ , 28 / m ³ , 19 / m ³ , 13 / in the order of Examples 1 to 8. They were m ³ , 11 pieces / m ³ , 15 pieces / m ³ , 88 pieces / m ³ , 255 pieces / m ³ . These results are smaller than the amount of foreign matter 19201 / m ³ of the conventional example. The glass composition of the glass _substrate, SiO 2 66.6 _{mol%, Al} 2 O 3 10.6 _{mol%, B} 2 O 3 11.0 mol%, MgO, CaO, SrO and BaO in total amount 11.4 Mol%, SnO ₂ 0.15 mol%, Fe ₂ O ₃ 0.05%, total amount of alkali metal oxides 0.2 mol%, strain point is 660 ° C., viscosity is 10 ^2.5 poise. The temperature of the molten glass at that time was 1570 ° C.
FIG. 8 is a diagram illustrating the results of Examples 1 to 8 of Experimental Example 1. In FIG. 8, the results of other examples are also plotted.

(Experimental example 2)
In order to confirm the effect of the second embodiment, tin oxide is used as a clarifier, and the clarified tube 120 of the second embodiment shown in FIG. The form was adjusted. Specifically, the bubble distribution maximum position A was changed by adjusting the temperature distribution of the molten glass. After this clarification, it was formed into a sheet glass of 2270 mm × 2000 mm and a thickness of 0.5 mm, and 100 glass substrates were produced. At this time, in Example 9, the temperature of the molten glass was adjusted so that the bubble discharge amount maximum position A and the maximum temperature position of the temperature distribution were separated in the flow direction of the molten glass. The position of the exhaust pipe 127 was between the maximum bubble discharge amount position A in the flow direction of the molten glass and the maximum temperature position of the temperature distribution.
As a conventional example, adjustment between the maximum bubble discharge amount position A and the maximum temperature position of the temperature distribution was not performed. In this case, the maximum bubble discharge amount position A and the maximum temperature position of the temperature distribution were substantially the same.
The platinum aggregates on the glass substrate were visually inspected and evaluated by the number of platinum aggregates per 100 sheets.
The platinum agglomerate had an aspect ratio of 100 or more and a platinum foreign matter having a maximum length of 100 μm or more was used as a foreign matter to be inspected.
As a result of the above inspection, compared to the conventional example in which the bubble discharge amount maximum position A coincides with the maximum temperature position of the temperature distribution, in Example 9, the number of platinum aggregates due to platinum mixed in the glass substrate is 1 / 3 or less. In Example 9, the number of bubbles remaining as defects on the glass substrate was 300 / m ³ or less. Met. Thereby, in Example 9, it has confirmed that the number of platinum aggregates compared with a prior art example was reduced. The glass composition of the glass _substrate, SiO 2 66.6 _{mol%, Al} 2 O 3 10.6 _{mol%, B} 2 O 3 11.0 mol%, MgO, CaO, SrO and BaO in total amount 11.4 Mol%, SnO ₂ 0.15 mol%, Fe ₂ O ₃ 0.05%, total amount of alkali metal oxides 0.2 mol%, strain point is 660 ° C., viscosity is 10 ^2.5 poise. The temperature of the molten glass at that time was 1570 ° C.

(Experimental example 3)
With respect to Experimental Example 1, the glass composition of the glass substrate was SiO ₂ 70 mol%, Al ₂ O ₃ 12.9 mol%, B ₂ O ₃ 2.5 mol%, MgO 3.5 mol%, CaO 6 mol. %, SrO 1.5 mol%, BaO 3.5 mol%, SnO ₂ 0.1 mol%, and a glass substrate was produced in the same manner as in Example 1. At this time, the strain point of the glass substrate was 745 ° C.
As a result, as in Experimental Example 1, it was found that the number of platinum aggregates can be reduced compared to the conventional example.

(Experimental example 4)
Against experimental example 2, the glass composition of the glass substrate, _SiO 2 70 _{mol%, Al} 2 O 3 12.9 _{mol%, B 2} O 3 2.5 mol%, MgO 3.5 mol%, CaO 6 moles %, SrO 1.5 mol%, BaO 3.5 mol%, SnO ₂ 0.1 mol%, and a glass substrate was produced in the same manner as in Example 2. At this time, the strain point of the glass substrate was 745 ° C.
As a result, as in Experimental Example 2, it was found that the number of platinum aggregates can be reduced compared to the conventional example.

  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. In the above description, a clarification tube has been described as an example of the processing apparatus. However, the present invention is not limited to this, and the present invention may be applied to a melting tank, a stirring tank, a molding apparatus, a transfer pipe, and a supply pipe.

DESCRIPTION OF SYMBOLS 100 Melting apparatus 101 Melting tank 103 Stirring tank 104, 105 Transfer pipe 106 Glass supply pipe 120 Clarification tank 121a, 121b Electrode 122 Power supply apparatus 123 Control apparatus 124a, 124b Purge gas supply pipe 125a, 125b Purge gas supply apparatus 127 Exhaust pipe 128 Oxygen meter 200 Forming device 300 Cutting device A Oxygen release maximum position P Maximum temperature position R Maximum temperature position range

Claims (20)

Using at least a part of the inner wall made of a material containing a platinum group metal, and processing a molten glass containing a fining agent that releases oxygen by a reduction reaction,
In the process of processing the molten glass,
In the processing apparatus, the molten glass is caused to flow in a direction along a surface in contact with the gas phase space of the molten glass,
By adjusting the amount of oxygen released from the molten glass in the gas phase space formed by the inner wall of the processing apparatus and the surface of the molten glass, the gas is controlled so that volatilization of the platinum group metal is suppressed. Control the oxygen concentration in the phase space ,
The amount of released oxygen varies depending on the position of the molten glass in the flow direction,
By adjusting the distribution of the amount of released oxygen at the position in the flow direction of the molten glass,
A method for producing a glass substrate, comprising adjusting a distribution of oxygen concentration in a flow direction of the molten glass in the gas phase space so that volatilization of the platinum group metal is suppressed . A method for manufacturing a glass substrate for processing molten glass using a processing apparatus for processing molten glass,
When processing molten glass containing a fining agent that releases oxygen by a reduction reaction,
Supplying molten glass to the inside of the processing apparatus made of a material containing a platinum group metal at least a part of the inner wall so that a gas phase space is formed above the surface of the molten glass,
In the processing apparatus, the molten glass is caused to flow in a direction along a surface in contact with the gas phase space of the molten glass,
By adjusting the amount of oxygen released from the molten glass, the oxygen concentration in the gas phase space is controlled so that volatilization of the platinum group metal is suppressed ,
The amount of released oxygen varies depending on the position of the molten glass in the flow direction,
The distribution of oxygen concentration in the flow direction of the molten glass in the gas phase space is controlled by adjusting the distribution of the oxygen release amount at the position in the flow direction of the molten glass so that the volatilization of the platinum group metal is suppressed. A method for producing a glass substrate, wherein Using at least a part of the inner wall made of a material containing a platinum group metal, and processing a molten glass containing a fining agent that releases oxygen by a reduction reaction,
In the process of processing the molten glass,
In the processing apparatus, the molten glass is caused to flow in a direction along a surface in contact with the gas phase space of the molten glass,
By adjusting the amount of oxygen released from the molten glass in the gas phase space formed by the inner wall of the processing apparatus and the surface of the molten glass, the gas is controlled so that volatilization of the platinum group metal is suppressed. Control the oxygen concentration in the phase space,
The temperature of the inner wall in contact with the gas phase space in the processing apparatus has a temperature distribution along the flow direction of the molten glass,
In the processing of the molten glass, the bubble discharge amount maximum position in the flow direction of the molten glass at which the amount of bubbles discharged from the surface of the molten glass to the gas phase space becomes maximum, and the temperature distribution in the flow direction of the molten glass. The method for producing a glass substrate is characterized in that the maximum position of the bubble discharge amount is adjusted such that the maximum temperature position is spaced apart in the flow direction of the molten glass. A method for manufacturing a glass substrate for processing molten glass using a processing apparatus for processing molten glass,
When processing molten glass containing a fining agent that releases oxygen by a reduction reaction,
Supplying molten glass to the inside of the processing apparatus made of a material containing a platinum group metal at least a part of the inner wall so that a gas phase space is formed above the surface of the molten glass,
In the processing apparatus, the molten glass is caused to flow in a direction along a surface in contact with the gas phase space of the molten glass,
By adjusting the amount of oxygen released from the molten glass, the oxygen concentration in the gas phase space is controlled so that volatilization of the platinum group metal is suppressed,
The temperature of the inner wall in contact with the gas phase space in the processing apparatus has a temperature distribution along the flow direction of the molten glass,
In the processing of the molten glass, the bubble discharge amount maximum position in the flow direction of the molten glass at which the amount of bubbles discharged from the surface of the molten glass to the gas phase space becomes maximum, and the temperature distribution in the flow direction of the molten glass. The method for producing a glass substrate is characterized in that the maximum position of the bubble discharge amount is adjusted such that the maximum temperature position is spaced apart in the flow direction of the molten glass. The glass substrate contains 0.01 mol% to 0.3 mol% tin oxide,
The amount of oxygen released from the molten glass, the is adjusted by the content of tin oxide, a manufacturing method of a glass substrate according to any one of claims 1 to 4. The method for manufacturing a glass substrate according to any one of claims 1 to 5 , wherein the oxygen concentration is controlled by further adjusting an amount of oxygen discharged from the gas phase space to the outside of the processing apparatus. The way the oxygen concentration of the predetermined range, method of manufacturing a glass substrate according to adjusted gas supply amount in any one of the gas phase supplied to the space, claim 1-6. The temperature of the processing device changes according to the position in the flow direction of the molten glass,
The distribution of the amount of released oxygen is predicted using computer simulation,
The released amount of the oxygen in the flow direction of the molten glass becomes maximum position, so as to be separated from a position where the temperature of the processor is the highest, to determine the process conditions by using the computer simulation, according to claim 1 Or the manufacturing method of the glass substrate of 2 . A method for manufacturing a glass substrate for processing molten glass using a processing apparatus for processing molten glass,
Having a step of melting glass raw material to produce molten glass,
Processing a molten glass containing a fining agent that releases oxygen by a reduction reaction;
In the process of processing the molten glass,
In the processing apparatus, at least a part of the inner wall is supplied with a molten glass in a processing apparatus made of a material containing a platinum group metal so that a gas phase space is formed above the surface of the molten glass. Flowing molten glass in a direction along the surface of the molten glass in contact with the gas phase space;
The temperature of the inner wall in contact with the gas phase space in the processing apparatus has a temperature distribution along the flow direction of the molten glass,
In the processing of the molten glass, the maximum amount of bubbles released in the flow direction of the molten glass at which the amount of bubbles released from the surface of the molten glass in contact with the gas phase space into the gas phase space is maximized, and the molten glass The method for producing a glass substrate, wherein the bubble discharge amount maximum position is adjusted so that the maximum temperature position of the temperature distribution in the flow direction is separated in the flow direction of the molten glass. The processing apparatus includes a clarification tube configured to degas at least the molten glass, wherein at least a part of the inner wall is made of a material containing a platinum group metal.
The method for producing a glass substrate according to any one of claims 1 to 9 , wherein the step of treating the molten glass is a clarification step including a defoaming treatment for defoaming the molten glass in the clarification tube. The foam discharge maximum position is predicted using computer simulation,
The processing conditions are determined using the computer simulation so that the maximum position of the bubble discharge amount is separated from the maximum temperature position in the flow direction of the molten glass, or any one of claims 3, 4, 9, and 10. The manufacturing method of the glass substrate as described in a term. The adjustment of the bubble discharge amount maximum position is performed by adjusting at least one of a temperature distribution of the molten glass and a flow rate of the molten glass, according to any one of claims 3, 4, 9 to 11. The manufacturing method of the glass substrate of description. The said foam discharge | release amount maximum position is a manufacturing method of the glass substrate of any one of Claim 3, 4, 9-12 located in the downstream of the flow of the said molten glass with respect to the said highest temperature position. The processing apparatus includes a clarification tube configured to degas at least the molten glass, wherein at least a part of the inner wall is made of a material containing a platinum group metal.
The clarification pipe is provided with an exhaust pipe that communicates the gas phase space and the atmosphere outside the processing apparatus,
The glass according to any one of claims 3, 4, 9 to 13, wherein an arrangement position of the exhaust pipe in a flow direction of the molten glass is between the maximum bubble discharge amount position and the maximum temperature position. A method for manufacturing a substrate. The processing apparatus includes a clarification tube configured to degas at least the molten glass, wherein at least a part of the inner wall is made of a material containing a platinum group metal.
The clarification pipe is provided with an exhaust pipe that communicates the gas phase space and the atmosphere outside the clarification pipe,
Said foam emission maximum position, the arrangement position of the exhaust pipe in the flow direction of the molten glass is at the same side of the flow direction of the molten glass the highest temperature position of the temperature distribution as a reference, according to claim 3, 4 the method of manufacturing a glass substrate according to any one 9-14 of.   A flange member extending outside the processing device is provided on the outer periphery of the processing device, and the arrangement position of the flange member in the flow direction of the molten glass includes the bubble discharge amount maximum position and the arrangement position of the exhaust pipe. The manufacturing method of the glass substrate of Claim 14 or 15 which exists in area | regions other than the area | region between. A glass substrate manufacturing apparatus for processing molten glass using a processing apparatus for processing molten glass,
At least a part of the inner wall is made of a material containing a platinum group metal, and a molten glass containing a refining agent that releases oxygen by a reduction reaction is supplied to the inside, and a gas phase space is formed above the surface of the molten glass. A processing apparatus in which the molten glass flows in a direction along a surface in contact with the gas phase space of the molten glass ;
While adjusting the amount of oxygen released from the molten glass and adjusting the amount of oxygen discharged from the gas phase space, the oxygen concentration in the gas phase space is adjusted to be within a predetermined range. Bei example and a control device configured to,
The amount of released oxygen varies depending on the position of the molten glass in the flow direction,
The control device adjusts a distribution of the oxygen release amount at a position in the flow direction of the molten glass, so that the flow of the molten glass in the gas phase space is suppressed so that volatilization of the platinum group metal is suppressed. The glass substrate manufacturing apparatus characterized by adjusting the distribution of oxygen concentration in the glass substrate. A glass substrate manufacturing apparatus for processing molten glass using a processing apparatus for processing molten glass,
At least a part of the inner wall is made of a material containing a platinum group metal, and a molten glass containing a refining agent that releases oxygen by a reduction reaction is supplied to the inside, and a gas phase space is formed above the surface of the molten glass. A processing apparatus in which the molten glass flows in a direction along a surface in contact with the gas phase space of the molten glass;
While adjusting the amount of oxygen released from the molten glass and adjusting the amount of oxygen discharged from the gas phase space, the oxygen concentration in the gas phase space is adjusted to be within a predetermined range. And a control device configured to
The temperature of the inner wall in contact with the gas phase space in the processing apparatus has a temperature distribution along the flow direction of the molten glass,
The control device has a maximum bubble discharge amount position in the flow direction of the molten glass and a flow of the molten glass at which the amount of bubbles discharged from the surface of the molten glass to the gas phase space is maximized in the processing of the molten glass. The apparatus for producing a glass substrate, wherein the bubble discharge amount maximum position is adjusted such that the maximum temperature position of the temperature distribution in the direction is separated in the flow direction of the molten glass. A glass substrate manufacturing apparatus for processing molten glass using a processing apparatus for processing molten glass,
A melting tank for melting glass raw material to produce molten glass;
At least a part of the inner wall is made of a material containing a platinum group metal, and molten glass containing a refining agent that releases oxygen by a reduction reaction is supplied to the inside, and the molten glass is separated from the gas phase space of the molten glass. A gas phase space is formed in the upper part of the surface of the molten glass, and the temperature of the inner wall in contact with the gas phase space has a temperature distribution along the flow direction of the molten glass. And a processing device configured to
In the processing of the molten glass, the bubble discharge amount maximum position in the flow direction of the molten glass at which the amount of bubbles discharged from the surface of the molten glass to the gas phase space becomes maximum, and the temperature in the flow direction of the molten glass. The apparatus for producing a glass substrate, wherein the maximum position of the bubble discharge amount is adjusted such that the maximum temperature position of the distribution is separated in the flow direction of the molten glass. The said processing apparatus is a glass substrate manufacturing apparatus of any one of Claims 17-19 containing the clarification pipe | tube which defoams the said molten glass.

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