WO2015099157A1 - Method for producing glass substrate and glass-substrate production device - Google Patents

Abstract

Provided are a method for producing a glass substrate and a glass-substrate production device which make it possible to control the flow of molten glass even when there is a lot of molten-glass flow. When treating molten glass, the present invention: heats a treatment device by electrifying the treatment device in a manner such that the temperature of the molten glass inside the treatment device is within a range suitable for the treatment; controls the flow of the molten glass inside the treatment device using an amount of power for the electrification; and adjusts the amount of heat released to the exterior from the treatment device in a manner such that the amount of power is at or above the level at which it is possible to control the flow of the molten glass, and the temperature of the molten glass is in a temperature range in which it is possible to control the flow of the molten glass.

Description

Glass substrate manufacturing method and glass substrate manufacturing apparatus

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

A glass substrate is generally manufactured through a process of forming molten glass from a glass raw material and then forming the molten glass into a glass substrate. The above process includes a process of removing minute bubbles contained in the molten glass (hereinafter also referred to as clarification). The clarification is performed by passing a molten glass containing a clarifier in 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, the temperature of the molten glass that has been melted further is further raised to allow the fining agent to function and the bubbles to float and defoam. The glass is made to absorb. That is, clarification includes a process for floating and defoaming bubbles (hereinafter also referred to as a defoaming process or a defoaming process) and a process for absorbing small bubbles into molten glass (hereinafter also referred to as an absorption process or an absorbing process).

As a technique for heating the clarification tube in order to heat the molten glass in the clarification treatment, for example, a pair of flange-shaped electrodes are provided in the clarification tube, and the voltage is applied to the electrode pair to energize the clarification tube. A technique for heating is known (Patent Document 1).

Special table 2011-513173 gazette

In the above apparatus, the amount of heat applied to the molten glass in the clarification tube can be adjusted by the amount of current supplied to the clarification tube. For this reason, even if the flow volume of the molten glass which passes a clarification pipe | tube increases, the temperature of a molten glass can be raised to the temperature required for a defoaming process by increasing energization according to a flow volume.

One factor that determines the flow rate of the molten glass passing through the clarification tube is the viscosity of the molten glass. The viscosity of the molten glass is determined by the temperature of the molten glass, and the temperature of the molten glass is controlled by the amount of current supplied to the clarification tube. For this reason, the flow rate of the molten glass can be controlled by the energization amount to the clarifier tube outlet.
However, if the temperature in the low temperature region of the clarification tube is raised and the amount of heating in the subsequent process is reduced, the amount of current supplied to the clarification tube outlet becomes small, and the flow rate of the molten glass cannot be controlled. If the flow rate of the molten glass is large, the temperature of the molten glass cannot be lowered even if, for example, the energization amount at the clarification tube outlet is zero, and the flow rate of the molten glass cannot be controlled. If it becomes impossible to control the flow rate of the molten glass, there is a concern that a problem may occur that the molten glass overflows in the processing apparatus downstream of the clarification tube. Moreover, since it becomes difficult to lower | hang the temperature of a molten glass to the temperature required for an absorption process, there exists a problem that the reboyl bubble derived from nitrogen and a sulfur oxide will increase as a result.

In order to avoid the above problem, it is necessary to lower the temperature of the molten glass in the clarification tube. However, if the molten glass temperature is decreased by reducing the amount of current supplied to the clarification tube, the platinum group metal in the low temperature region. There is a risk of aggregation. Moreover, it becomes difficult to raise the molten glass temperature to the temperature required for the defoaming treatment described above, and a sufficient clarification effect cannot be obtained.

An object of the present invention is to provide a glass substrate manufacturing method and a glass substrate manufacturing apparatus capable of achieving both a refining effect and a flow control of a molten glass even when the flow rate of the molten glass is large.

The present invention has the following forms.
(Form 1)
A method for manufacturing a glass substrate using a processing apparatus for processing molten glass,
When processing molten glass,
Heating the processing device by energizing the processing device so that the temperature of the molten glass in the processing device is in a range suitable for the processing,
The flow rate of the molten glass in the processing device is controlled by the amount of electric power when energizing,
The amount of heat radiation from the processing device to the outside is set so that the amount of electric power is equal to or greater than the amount of electric power capable of controlling the flow rate of the molten glass, and the temperature of the molten glass is in a temperature range capable of controlling the flow rate of the molten glass. A method of manufacturing a glass substrate to be adjusted.

(Form 2)
A method for manufacturing a glass substrate using a processing apparatus for processing molten glass,
When processing molten glass,
Heating the processing device by energizing the processing device so that the temperature of the molten glass in the processing device is in a range suitable for the processing,
The flow rate of the molten glass in the processing device is controlled by the amount of current when the current is applied,
A method for producing a glass substrate, wherein the amount of heat released from the processing device to the outside is adjusted so as to be equal to or greater than an amount of current that enables flow control of the molten glass.

Here, the flow rate of the molten glass indicates the moving amount (volume or mass) of the molten glass per unit time.
Here, the processing apparatus includes a melting tank, a refining apparatus, a stirring tank and a forming apparatus, a transfer pipe for transferring molten glass through these apparatus tubes, and a supply pipe for supplying glass to these apparatuses. The processing in the processing apparatus includes glass melting processing, molten glass clarification processing, stirring processing, molding processing, and molten glass transfer processing and supply processing.

(Form 3)
The processing apparatus has a gas phase space formed by an inner wall and a molten glass liquid surface, and at least a portion of the inner wall in contact with the gas phase space is made of a material containing a platinum group metal,
In the processing apparatus, when processing the molten glass, a high temperature region and a low temperature region lower in temperature than the high temperature region are formed,
The manufacturing method of the glass substrate of the form 1 or 2 which adjusts the said thermal radiation amount so that the temperature difference of the said high temperature area | region and the said low temperature area | region may be 200 degrees C or less.
The platinum group metal means a metal composed of a single platinum group element and an alloy of a metal composed of a platinum group element. The platinum group elements are six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os) and iridium (Ir).
For example, the high temperature region may be a region where the temperature of the processing apparatus is in a temperature range of 1600 ° C. or higher, and the low temperature region may be a region where the temperature of the processing apparatus is in a temperature range of less than 1600 ° C. Alternatively, the high temperature region may be a region where the temperature of the processing apparatus is in a temperature range of 1620 ° C. or higher, and the low temperature region may be a region where the temperature of the processing apparatus is in a temperature range of 1590 ° C. or lower.
Alternatively, the electrode region, which is the region where the electrode provided in the processing apparatus is provided, and the region where the exhaust pipe is provided are the low temperature region, and the region other than the low temperature region or the region between the electrode and the exhaust pipe is the high temperature region. May be.
It is preferable to adjust the heat radiation amount so that the maximum temperature in the high temperature region is 1600 to 1750 ° C. and the minimum temperature in the low temperature region is 1300 to 1600 ° C. By reducing the temperature difference between the high temperature region and the low temperature region, the amount of aggregation of the platinum group metal volatilized in the high temperature region in the low temperature region can be reduced. In addition, the problem of mixing foreign substances derived from volatile aggregates such as the above platinum group metals into the molten glass is a display typified by a liquid crystal display whose quality requirements are becoming increasingly severe with the recent high definition. It becomes larger with the glass substrate. Therefore, the said form is suitable with the manufacturing method of the glass substrate for displays.

(Form 4)
The treatment device is covered with a heat insulating material,
The method for manufacturing a glass substrate according to any one of Embodiments 1 to 3, wherein the heat radiation amount is controlled by adjusting a thermal resistance from the processing apparatus to an external space by the heat insulating material.
(Form 5)
The manufacturing method of the glass substrate of the form 4 which adjusts the said thermal resistance by adjusting the thermal conductivity and arrangement | positioning of the said heat insulating material.

(Form 6)
The said processing apparatus is a clarification apparatus which clarifies molten glass.
The clarifier is heated by energizing the clarifier so that the maximum temperature of the molten glass in the clarifier is equal to or higher than the temperature at which the reduction reaction of tin oxide contained in the molten glass occurs. The flow rate of the molten glass in the clarification device is controlled by the amount of electric power when the current is applied, and from the clarification device to the outside so that the amount of electric power is equal to or greater than the amount of electric power capable of controlling the flow rate of the molten glass. The method for producing a glass substrate according to any one of embodiments 1 to 5, wherein the amount of heat radiation is adjusted.

The maximum temperature of the molten glass in the processing apparatus is preferably 1630 ° C to 1720 ° C. When the maximum temperature is 1630 ° C. or higher, the fining agent in the molten glass can exert a clarification effect, and when it is 1720 ° C. or lower, the temperature difference between the high temperature region and the low temperature region can be reduced. It is possible to achieve both reduction of bubbles and reduction of the volatilization amount of the platinum group metal.
It is preferable to use tin oxide as a fining agent. The content of tin oxide in the molten glass is preferably 0.01 to 0.3 mol%. If the content of tin oxide is too small, bubbles cannot be sufficiently reduced. On the other hand, when the content of tin oxide is too large, the volatilization amount of tin oxide from the molten glass increases, and there arises a problem that aggregates of volatilized tin oxide are mixed into the molten glass. Also, if the tin oxide content is too high, the amount of oxygen released from the molten glass will increase too much, and the oxygen concentration in the gas phase space will increase, increasing the volatilization amount of platinum group metals from the processing equipment. The problem of end up occurs. By setting the content of tin oxide to 0.01 to 0.3 mol%, it is possible to reduce the mixture of tin oxide or platinum group metal aggregates into the molten glass while sufficiently reducing bubbles. Further, the volatilization amount of the platinum group metal from the processing apparatus can be reduced while sufficiently reducing bubbles.

(Form 7)
The clarification device is discharged from the clarification tube having a gas phase space through which bubbles in the molten glass are discharged, a first transfer tube to which the molten glass supplied into the clarification tube is transferred, and the clarification tube. A second transfer pipe through which the molten glass is transferred,
In the first transfer pipe, the clarification pipe, and the second transfer pipe, the defoaming treatment of the molten glass by the reductive reaction of the clarifier and the absorption treatment that absorbs the bubbles in the molten glass by the oxidation reaction of the clarifier. And
The amount of power to be applied to the first transfer pipe, the amount of power to be applied to the region for performing the defoaming process among the clarification pipe and the second transfer pipe, and the clarification pipe and the second transfer pipe The method of manufacturing a glass substrate according to mode 6, wherein the ratio of the amount of electric power applied to the region where the absorption treatment is performed is 1: 0.6 to 1: 0.1 to 0.4.

(Form 8)
The clarification device is discharged from the clarification tube having a gas phase space through which bubbles in the molten glass are discharged, a first transfer tube to which the molten glass supplied into the clarification tube is transferred, and the clarification tube. A second transfer pipe through which the molten glass is transferred,
In a partial region of the clarification tube, a defoaming treatment of the molten glass is performed by a reduction reaction of the clarifier,
In the other region of the clarification tube and the second transfer tube, an absorption treatment for absorbing bubbles in the molten glass by an oxidation reaction of the clarifier is performed,
The ratio of the amount of power applied to the first transfer pipe, the amount of power applied to a partial area of the clarification pipe, and the amount of power supplied to the other area of the clarification pipe is from 1: 0.6 to 1: The method for producing a glass substrate according to mode 6, wherein the ratio is 0.1 to 0.4.

(Form 9)
The processing device is discharged from the clarification tube having a gas phase space in which bubbles in the molten glass are discharged, a first transfer tube to which the molten glass supplied into the clarification tube is transferred, and the clarification tube. A second transfer pipe through which the molten glass is transferred,
In the clarification tube, the defoaming treatment of the molten glass is performed by the reduction reaction of the clarifier,
In the second transfer pipe, an absorption treatment for absorbing bubbles in the molten glass by an oxidation reaction of a clarifying agent is performed.
The ratio of the amount of power applied to the first transfer tube, the amount of power applied to the clarification tube, and the amount of power applied to the second transfer tube is 1: 0.6 to 1: 0.1 to The manufacturing method of the glass substrate of form 6 which is 0.4.

In Embodiments 7 to 9, the region where the defoaming treatment is performed refers to a region where the temperature is 1620 ° C. or higher. The maximum temperature of the molten glass in the region where the defoaming treatment is performed is preferably 1630 ° C. to 1720 ° C., and more preferably 1640 ° C. to 1720 ° C. The maximum temperature of the treatment apparatus in the region where defoaming treatment is performed is preferably 1630 ° C. to 1750 ° C., and more preferably 1640 ° C. to 1750 ° C. By setting it as this temperature range, volatilization of a platinum group metal can be reduced, fully performing the removal of the bubble by the reductive reaction of a clarifying agent.

In Embodiments 7 to 9, the region where the absorption treatment is performed refers to a region where the temperature is less than 1620 ° C. The temperature of the molten glass in the region where the absorption treatment is performed is preferably 1450 ° C. to 1620 ° C. By setting it as this temperature range, absorption of the bubble by the oxidation reaction of a clarifying agent can be performed effectively.

In Embodiments 7 to 9, the oxygen concentration in the gas phase space is preferably 0 to 10%. By reducing the oxygen concentration, the volatilization amount of the platinum group metal can be reduced.
The vapor pressure of the platinum group metal in the gas phase space is preferably 0.1 Pa to 15 Pa. When the vapor pressure of the platinum group metal is within this range, the reduced platinum group metal can be prevented from adhering to the inner wall surface.

(Form 10)
A processing apparatus for processing molten glass;
An energizer that heats the processing apparatus by energizing the processing apparatus so that the temperature of the molten glass in the processing apparatus is in a range suitable for the processing when the molten glass is processed;
A control device for controlling the flow rate of the molten glass in the processing device by the amount of electric power when energizing,
The amount of heat radiation from the processing device to the outside is such that the amount of electric power is equal to or greater than the amount of electric power capable of controlling the flow rate of the molten glass, and the temperature of the molten glass is within a temperature range capable of controlling the flow rate of the molten glass. Glass substrate manufacturing equipment that is being adjusted.

(Form 11)
A processing apparatus for processing molten glass;
An energizer that heats the processing apparatus by energizing the processing apparatus so that the temperature of the molten glass in the processing apparatus is in a range suitable for the processing when the molten glass is processed;
A control device for controlling the flow rate of the molten glass in the processing device by the amount of current when the current is applied;
The glass substrate manufacturing apparatus in which the amount of heat radiation from the processing apparatus to the outside is adjusted so as to be equal to or greater than the amount of current capable of controlling the flow rate of the molten glass.

(Form 12)
The processing apparatus has a gas phase space formed from an inner wall and a molten glass liquid surface, and at least a portion of the inner wall that is in contact with the gas phase space is made of a material containing a platinum group metal, and volatilizes the platinum group metal. The method for producing a glass substrate according to any one of Embodiments 1 to 11, wherein the aggregate formed by the aggregation of the product has an aspect ratio of 100 or more, which is a ratio of the maximum length to the minimum length, for example. Glass substrate manufacturing equipment. 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, the aggregate generated by the aggregation of the platinum group metal volatiles has an aspect ratio of 100 or more, which is a ratio of the maximum length to the minimum length, and the maximum length of the platinum group metal aggregate is 100 μm. The above may preferably be 100 μm to 300 μm.

(Form 13)
The glass substrate manufacturing method or glass substrate manufacturing apparatus according to any one of Embodiments 1 to 12, wherein the glass substrate is a glass substrate for display. Moreover, it is suitable for the glass substrate for oxide semiconductor displays or the glass substrate for LTPS displays.

According to the present invention, even when the flow rate of the molten glass is large, the clarification effect and the flow rate control of the molten glass can be realized.

It is a figure which shows an example of the process of the manufacturing method of the glass substrate of this embodiment. FIG. 2 is a view schematically showing an example of an apparatus for performing a melting process to a cutting process shown in FIG. It is the schematic which shows the structure of the clarification pipe | tube 120. FIG. It is sectional drawing of the clarification pipe | tube 120. FIG.

Hereinafter, the glass substrate manufacturing method and glass substrate manufacturing apparatus of the present invention will be described.

FIG. 1 is a diagram illustrating an example of a process of a glass substrate manufacturing method according to the present embodiment.

(Overall overview of glass substrate manufacturing method)
The glass substrate manufacturing method includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a forming step (ST5), and a slow cooling step (ST6). And a cutting step (ST7). In addition, a plurality of glass substrates that have a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like and are stacked in the packing process are transported to a supplier.

The melting step (ST1) is performed in a melting tank. In the melting tank, a glass raw material is poured into the liquid surface of the molten glass stored in the melting tank and heated to make molten glass. Furthermore, molten glass is poured toward the downstream process from the outlet provided in one bottom part of the inner side wall of the melting tank.
The heating of the molten glass in the melting tank can melt the glass raw material in addition to energizing heating, which is a method in which electricity flows through the molten glass itself to generate and heat itself, and supplementary flame is provided by a burner. 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. The content of tin oxide is preferably 0.01 to 0.3 mol%, and more preferably 0.03 to 0.2 mol%. If the content of tin oxide is too small, bubbles cannot be sufficiently reduced. On the other hand, when the content of tin oxide is too large, the volatilization amount of tin oxide from the molten glass increases, and there arises a problem that aggregates of volatilized tin oxide are mixed into the molten glass. Moreover, when there is too much content of a tin oxide, the oxygen released from molten glass will increase too much, and the problem that the volatilization amount of the platinum group metal from a processing apparatus will increase will arise. By setting the content of tin oxide to 0.01 to 0.3 mol%, it is possible to reduce the mixture of tin oxide aggregates into the molten glass while sufficiently reducing bubbles. Further, the volatilization amount of the platinum group metal from the processing apparatus can be reduced while sufficiently reducing bubbles.
Tin oxide has a lower refining function than arsenous acid that has been generally used, but can be suitably used as a refining agent in terms of low environmental burden. However, since the refining function of tin oxide is lower than that of arsenous acid, when tin oxide is used, the temperature of the molten glass MG during the refining process of the molten glass MG must be made higher than before. In addition, since the maximum temperature of the molten glass is increased, if the temperature in the low temperature region of the processing apparatus is increased in order to suppress the aggregation of the platinum group metal, the temperature of the molten glass of the molten glass becomes too high, and the flow rate due to current is increased. There is a problem that it becomes difficult to control. Therefore, the volatilization amount of the platinum group metal from the clarification tube which will be described later increases, and as a result, the problem that the platinum group metal is mixed as a foreign substance in the glass substrate becomes remarkable.

The clarification step (ST2) is performed at least in the clarification tube. The clarification step includes a defoaming process and an absorption process.
In the defoaming treatment, when the molten glass is heated, the bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass absorb oxygen generated by the reductive reaction of the fining agent, and the volume increases. Then, it floats on the liquid surface of the molten glass and is discharged. A defoaming process is performed in the area | region of the processing apparatus from which the temperature of a molten glass becomes 1620 degreeC or more, for example. A region of the processing apparatus in which the temperature of the molten glass is 1620 ° C. or higher is defined as “a region where defoaming is performed”. The temperature of the region where the defoaming treatment is performed is preferably 1620 ° C. to 1750 ° C.
The maximum temperature of the molten glass in the region where the defoaming treatment is performed is preferably 1630 ° C. to 1720 ° C., more preferably 1640 ° C. to 1720 ° C. The maximum temperature of the treatment apparatus in the region where defoaming treatment is performed is preferably 1630 ° C. to 1750 ° C., and more preferably 1640 ° C. to 1750 ° C. By setting it as this temperature range, volatilization of a platinum group metal can be reduced, fully performing the removal of the bubble by the reductive reaction of a clarifying agent.

In the absorption treatment, by reducing the temperature of the molten glass, the reducing substance obtained by the reductive reaction of the fining agent undergoes an oxidation reaction. Thereby, gas components, such as oxygen in the bubble which remain | survives in molten glass, are reabsorbed in molten glass, and a bubble lose | disappears. The absorption processing is performed in a region downstream of the region where the degassing processing of the processing apparatus is performed and the temperature of the molten glass is less than 1620 ° C. A region of the processing apparatus in which the temperature of the molten glass is less than 1620 ° C. is referred to as “region for performing absorption treatment”. The temperature of the region where the absorption treatment is performed is preferably 1450 ° C. or more and less than 1620 ° C.
The temperature of the molten glass in the region where the absorption treatment is performed is preferably 1450 ° C. to 1620 ° C. By setting it as this temperature range, absorption of the bubble by the oxidation reaction of a clarifying agent can be performed effectively.

The oxidation reaction and reduction reaction by the fining agent are performed by controlling the temperature of the molten glass. In the clarification step of this embodiment, a clarification method using tin oxide as a clarifier will be described.
In the clarification step, a reduced pressure defoaming method can be used in which a space in a reduced pressure atmosphere is formed in a clarified tube, and bubbles existing in the molten glass are grown in a reduced pressure atmosphere and defoamed. In this case, it is effective in that no clarifier is used. However, since the vacuum defoaming method complicates and enlarges the apparatus, it is preferable to employ a clarification method that uses a clarifier and raises the temperature of the molten glass.

In the homogenization step (ST3), the glass component is homogenized by stirring the molten glass in the stirring tank supplied through the pipe extending from the clarification pipe using a stirrer. Thereby, the composition unevenness of the glass which is a cause of striae or the like can be reduced.
In the supply step (ST4), the molten glass is supplied to the molding apparatus through a pipe extending from the stirring tank.

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

FIG. 2 is a diagram schematically showing an example of an apparatus for performing the melting step (ST1) to the cutting step (ST7) in the present embodiment. As shown in FIG. 2, the apparatus mainly includes a melting apparatus 100 and a molding apparatus 200. The melting apparatus 100 includes a melting tank 101, a clarification pipe 120, a stirring tank 103, a first transfer pipe 104, a second transfer pipe 105, and a glass supply pipe 106.
The melting tank 101 shown in FIG. 2 is provided with heating means such as a burner (not shown). A glass raw material to which a fining agent is added is charged into the melting tank, and a melting process is performed. The molten glass melted in the melting tank 101 is supplied to the clarification tube 120 through the transfer tube 104.
In the clarification tube 120, the temperature of the molten glass MG is adjusted, and the clarification step of the molten glass is performed using the oxidation-reduction reaction of the clarifier. The clarified molten glass is supplied to the stirring tank through the transfer pipe 105. In the clarification step, the defoaming process may be performed in the transfer pipe 104. That is, the transfer pipe 104 may have a “region for performing a defoaming process”. In the clarification process, the absorption process may be performed in the transfer pipe 105. That is, the transfer pipe 105 may have an “area for performing an absorption process”.

The clarification tube 120 is provided with electrodes 121a and 121b. When a voltage is applied between the electrodes 121a and 121b, an electric current flows through the clarification tube 120 between the electrodes 121a and 121b, and the clarification tube 120 is provided. Is heated by energization. In addition, electrodes (not shown) are provided at both ends of the first transfer pipe 104 and the second transfer pipe 105, and when a voltage is applied between the electrodes, the first transfer pipe 104 and the second transfer pipe 104 are provided. A current flows through the first transfer pipe 105 and the first transfer pipe 104 and the second transfer pipe 105 are energized and heated. It is preferable that the electrodes 121a and 121b have a flange shape from the viewpoint of preventing damage due to overheating. In the case of the clarification tube 120 of this embodiment, since the electrodes 121a and 121b having a flange shape have a high heat dissipation function, the walls near the electrodes 121a and 121b are at a lower temperature than the peripheral portions of the walls. Furthermore, the electrodes 121a and 121b are cooled with a liquid or a gas in order to suppress damage due to overheating, for example. For this reason, the temperature of the wall of the clarification tube 120 in contact with the gas phase space necessarily has a temperature profile along the flow direction of the molten glass. In other words, in the case of the clarification tube 120 of the present embodiment, the temperature of the clarification tube 120 does not become constant, and a temperature difference inevitably occurs.

The amount of power to be applied to the first transfer pipe 104, the amount of power to be supplied to the region of the clarification tube 120 to be defoamed, and the power to be supplied to the region of the clarification tube 120 and the second transfer tube 105 to be subjected to the absorption process The amount ratio is preferably 1: 0.6 to 1: 0.1 to 0.4, and more preferably 1: 0.7 to 1: 0.15 to 0.4.

In addition, when defoaming processing is performed in a part of the clarification tube 120 and absorption processing is performed in another region of the clarification tube 120 and the second transfer tube 105, electric power to be supplied to the first transfer tube 104 The ratio of the amount of electric power applied to the region where the defoaming treatment of the clarification tube 120 is performed and the amount of electric power applied to the region where the absorption treatment of the clarification tube 120 is performed is 1: 0.6 to 1: 0. It is preferably 1 to 0.4, and preferably 1: 0.7 to 1: 0.15 to 0.4.

In addition, when the defoaming process is performed in the clarification tube 120 and the absorption process is performed only in the second transfer pipe 105, the amount of power to be supplied to the first transfer pipe 104, the amount of power to be supplied to the clarification pipe 120, In addition, the ratio of the amount of electric power applied to the second transfer pipe 105 is preferably 1: 0.6 to 1: 0.1 to 0.4, and 1: 0.7 to 1: 0.15 to It is preferable that it is 0.4.

In the stirring vessel 103, the molten glass is stirred and homogenized by the stirrer 103a. The molten glass homogenized in the stirring tank 103 is supplied to the forming apparatus 200 through the glass supply pipe 106.
In the forming apparatus 200, sheet glass is formed from molten glass by the overflow downdraw method.

(Configuration of clarification tube)
Next, the configuration of the clarification tube 120 will be described with reference to FIG. FIG. 3 is a schematic diagram illustrating a configuration of the clarification tube 120 according to the embodiment.
As shown in FIG. 3, electrodes 121 a and 121 b are provided on the outer peripheral surfaces of both ends in the length direction of the clarification tube 120, and an exhaust pipe 127 is provided on the wall in contact with the gas phase space of the clarification tube 120. It has been. The clarification tube 120 is preferably made of platinum, reinforced platinum, or a platinum alloy.

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.
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 clarification tube 120 is heated so that the maximum temperature is, 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 glass supply tube 104 is It is heated to a temperature suitable for the defoaming treatment, for example, 1630 ° C. to 1720 ° C.
Further, by controlling the temperature of the molten glass by energization heating, the viscosity of the molten glass in the clarification tube 120 can be adjusted, and thereby the flow rate of the molten glass passing through the clarification tube 120 can be adjusted. In order to adjust the flow rate of the molten glass, the target power amount to be passed through the clarification tube 120 is more preferably 5 kW or more, and more preferably 10 kW or more. In particular, the target power amount to be energized at the outlet of the clarification tube 120 is preferably 5 kW or more, and more preferably 8 kW or more. By setting the power amount within the above range, the flow rate of the molten glass can be adjusted by the power amount.

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 is a computer including a CPU, a memory, and the like. The control device 123 controls the amount of current and the amount of power that the power supply device 122 supplies to the clarification tube 120. Thereby, the control apparatus 123 can adjust the temperature and flow velocity of the molten glass in the clarification tube 120.

An exhaust pipe 127 is provided on the wall in contact with the gas phase space of 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 120 a that is a part of the internal space of the clarification pipe 120 and the external space of the clarification pipe 120.

FIG. 4 is a cross-sectional view of the clarification tube 120 in the longitudinal direction of the main body of the clarification tube 120 and in the longitudinal direction of the exhaust pipe 127. A heat insulating material 140 is provided on the outer wall surface of the main body of the clarification tube 120, the outer wall surfaces of the electrodes 121 a and 121 b, and the outer wall surface of the exhaust pipe 127.

The heat insulating material 140 plays a role of keeping the fining tube 120 warm while supporting the fining tube 120 so as not to deform. As the heat insulating material 140, a member having excellent fire resistance and sufficiently high strength (rigidity) can be used.
In order to accurately control the amount of heat released from the clarification tube 120, it is preferable to use materials having different thermal conductivities as the heat insulating material 140. For example, a first heat insulating material having a higher thermal conductivity and a second heat insulating material having a lower thermal conductivity are used, and the first heat insulating material is disposed in a region that promotes heat dissipation of the clarification tube 120. By using the second heat insulating material for the region, the amount of heat released from each region of the clarification tube 120 can be adjusted.
It is not necessary to provide the first heat insulating material so as to contact the entire region of the clarification tube 120. It is preferable that the heat transfer medium 130 is selectively provided at least at a location that contacts the high temperature region and a location that contacts the low temperature region, and the heat transfer medium 130 is provided so as to connect both.
The thermal conductivity of the first heat insulating material is preferably at least twice that of the second heat insulating material, and more preferably at least five times.
It is preferable to use a material having a thermal conductivity of 2 to 40 W / m · K at 1000 ° C. as the first heat insulating material. Specifically, an alumina electrocast refractory, a magnesia refractory, a silicon carbide refractory, or the like can be used as the first heat insulating material.
As the second heat insulating material, a material having a thermal conductivity at 1000 ° C. of 0.1 to 1 W / m · K is preferably used. Specifically, porous brick, ceramic fiber, or the like can be used as the second heat insulating material.

The amount of heat released from the clarification tube 120 to the outside can be controlled by controlling the temperature and flow rate of the molten glass while the control device 123 supplies current to the clarification tube 120 so that the current amount is greater than or equal to the target current amount. It is adjusted to. This amount of heat radiation is the amount of heat radiation required when the flow rate of the molten glass passing through the clarification tube 120 is maximized. The amount of heat radiation can be controlled by adjusting the thermal resistance from the clarification tube 120 to the external space. For example, the thermal resistance can be adjusted by adjusting the thermal conductivity and arrangement of the first heat insulating material and the second heat insulating material used as the heat insulating material 140.

By reducing the thermal resistance from the clarification tube 120 to the external space, heat conduction from the clarification tube 120 to the external space through the heat insulating material 140 is promoted. As a result, the amount of power supplied to the clarified tube is equal to or greater than the amount of power that can control the flow rate of the molten glass. Can do.

In addition, the temperature difference between the high temperature region and the low temperature region of the clarification tube 120 is preferably 50 ° C. or more and 200 ° C. or less, and 70 ° C. or more and 150 ° C. or less from the viewpoint of achieving both suppression of volatilization of the platinum group metal and the clarification effect. It is more preferable that it is below ℃. Here, the high temperature region indicates a region having a higher temperature than other regions. In the case of the clarification tube 120, for example, the high temperature region may be a region where the temperature of the clarification tube 120 is in a temperature range of 1600 ° C. or higher, or a region in a temperature range of 1620 ° C. or higher. Further, for example, the high temperature region may include a region where the maximum temperature is reached when the clarification tube 120 processes the molten glass. The low temperature region indicates a region where the temperature is lower than that of other regions, and specifically indicates a region where the temperature is lower than that of the high temperature region. In the case of the clarification tube 120, the low temperature region may be a region where the temperature of the clarification tube 120 is in a temperature range of less than 1600 ° C or a temperature range of 1590 ° C or less. Further, for example, the low temperature region may include a region where the refining tube 120 is at the lowest temperature when the molten glass is processed. For example, the connection portion of the clarification tube 120 with the electrodes 121a and 121b and the connection portion with the exhaust pipe 127 are radiated to the outside from the electrodes 121a and 121b and the exhaust pipe 127. It tends to be low temperature compared to the area. That is, the region of the connection portion between the electrodes 121a and 121b of the clarification tube and the connection portion with the exhaust tube 127 is a low temperature region, and the region between the electrodes 121a and 121b and the exhaust tube 127 is a high temperature region.
In order to make the temperature difference between the high temperature region and the low temperature region within the above range, the minimum temperature in the low temperature region is preferably 1300 ° C. or more and 1600 ° C. or less, more preferably 1400 ° C. or more and 1600 ° C. or less, and 1500 ° C. The temperature is more preferably 1600 ° C. or lower. The maximum temperature in the high temperature region is preferably 1600 ° C. or higher and 1750 ° C. or lower, more preferably 1600 ° C. or higher and 1720 ° C. or lower, and further preferably 1610 ° C. or higher and 1700 ° C. or lower.

By the way, when the molten glass passes through the processing apparatus in which the platinum group metal is used for the inner wall surface, the platinum group metal is volatilized as an oxide in a portion in contact with the gas phase space (atmosphere containing oxygen) on the heated inner surface. For example, in the clarification tube 120 made of a platinum group metal, the platinum group metal is oxidized and volatilized in the gas phase space. This volatilization is particularly noticeable in the high temperature region of the clarification tube 120. On the other hand, the oxide of the platinum group metal is reduced at a position where the temperature is locally lowered (for example, around the electrode) of the processing apparatus, and the reduced platinum group metal aggregates and adheres (aggregates) to the inner wall surface. Aggregates of platinum group metals adhering to the inner wall surface fall into the molten glass and enter as foreign substances, which may cause a deterioration in the quality of the glass substrate. In particular, when tin oxide is used as a fining agent, the maximum temperature necessary for obtaining a fining effect is increased, so that the problem of volatilization and adhesion becomes more prominent. For this reason, it is conceivable to prevent aggregation of the platinum group metal by increasing the temperature of the region (low temperature region) where the temperature locally decreases in the processing apparatus. When the temperature difference between the high temperature region and the low temperature region is 200 ° C. or less, preferably 150 ° C. or less, the reduction of the oxide of the platinum group metal oxidized in the high temperature region can be reduced, and solidified platinum Group metal agglomerates rarely enter molten glass.
If the oxygen concentration in the gas phase space is 0%, volatilization of the platinum group metal can be prevented. For this reason, from the viewpoint of preventing volatilization of the platinum group metal, the oxygen concentration in the gas phase space is preferably 0%. However, in order to always keep the oxygen concentration in the gas phase space at 0%, there are problems that the content of the fining agent is extremely reduced and costs are increased. For this reason, in order to achieve both foam reduction, low cost, and reduction of platinum group metal volatilization, the oxygen concentration in the gas phase space is preferably 0.01% or more. 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 increases and the molten glass is reduced too much. As a result, there is a possibility that 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. From the above, the oxygen concentration in the gas phase space is preferably 0 to 30%, more preferably 0.1 to 10%, and still more preferably 0.1 to 1%. .
The vapor pressure of the platinum group metal in the gas phase space is preferably 0.1 Pa to 15 Pa, and more preferably 3 Pa to 10 Pa. When the vapor pressure of the platinum group metal is within this range, the reduced platinum group metal aggregates can be prevented from adhering to the inner wall surface.

On the other hand, when the temperature in the low temperature region is raised, the molten glass that has been cooled in the low temperature region is not cooled, so that molten glass that is higher in temperature than the target temperature flows out downstream. Since the optimum temperature for the molten glass flowing out downstream is determined, if the temperature in the low temperature region is raised, it is necessary to reduce the heating amount in the subsequent steps.
In the clarification tube 120, in order to prevent the reduction of platinum, the temperature of the molten glass increases when the amount of current supplied to the electrodes 121a and 121b is increased to increase the temperature in the vicinity of the electrodes 121a and 121b in the low temperature region. As a result, the amount of heating on the downstream side of the clarification tube 120 becomes small, so that the flow rate cannot be adjusted.
According to this embodiment, the temperature difference between the high temperature region and the low temperature region can be adjusted by adjusting the thermal conductivity, arrangement, and amount of the heat insulating material 140. Accordingly, it is possible to avoid the situation where the flow rate cannot be adjusted by increasing the energization amount to the electrodes 121a and 121b.

The amount of heat transfer when the thermal conductivity, arrangement, and amount of the heat insulating material 140 are changed should be calculated by, for example, computational fluid dynamic calculation (computer simulation) using a 3D model created by the finite element method or the mesh-free method. Can do. For example, a 3D model that reproduces the refining tube 120, the heat insulating material 140, the molten glass in the refining tube 120, and the gas phase space is created, and this is divided into a finite number of regions (calculation grids), and boundary conditions (the refining tube 12 The temperature of the inner glass and the gas phase space, the temperature of the external space, etc.) and the material properties (thermal conductivity, etc.). Next, the amount of heat in and out of each calculation grid is analyzed using iterative calculation by a computer. By using computer simulation, the optimum thermal conductivity, arrangement, and amount of the heat insulating material 140 can be easily calculated economically.

In addition, the platinum group metal aggregate to be suppressed in the present embodiment has a linear shape elongated in one direction, which is the ratio of the maximum length to the minimum length, and the aspect ratio is 100 or more. 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.

(Experimental example 1)
A glass substrate having a thickness of 2270 mm × 2000 mm and a thickness of 0.5 mm was prepared using tin oxide as a fining agent and using the manufacturing apparatus of the above embodiment. The glass composition of the glass substrate was as follows: SiO ₂ 66.6 mol%, Al ₂ O ₃ 10.6 mol%, B ₂ O ₃ 11.0 mol%, MgO, CaO, SrO and BaO combined 11.4 Mol%, SnO ₂ 0.15 mol%, Fe ₂ O ₃ 0.05 mol%, alkali metal oxide 0.2 mol%, the strain point is 660 ° C., and the viscosity is 10 ^2.5 poise. The temperature of the molten glass was 1570 ° C. In addition, by adjusting the amount of heat released from the clarification tube to the outside, the amount of power applied to the first transfer tube 104, the amount of power applied to the clarification tube 120, and the amount of power applied to the second transfer tube 105 The ratio was 1: 0.8: 0.3. As a result, a glass substrate having a number of bubbles equal to or less than the specified number could be produced without the molten glass overflowing from the processing apparatus. Moreover, the number of platinum group metal foreign matters mixed into the glass substrate could be suppressed to 0.001 piece / kg or less. In addition, as a foreign material of the platinum group metal, those having an aspect ratio of 100 or more and a maximum length of 100 μm or more were counted.

(Experimental example 2)
With respect to Experimental Example 1, the glass composition of the glass substrate to be manufactured 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%, to prepare a glass substrate in the same manner as in example 1 except that the _SnO 2 0.1 mol%. At this time, the strain point of the glass substrate was 745 ° C.
As a result, even if a glass substrate having a high strain point and a fining temperature higher than that of Experimental Example 1 is manufactured, a glass substrate having a number of bubbles equal to or less than a specified number is treated by the molten glass as in Experimental Example 1. It was found that it can be manufactured without overflowing. It was also found that the number of platinum group metals mixed into the glass substrate can be suppressed to 0.001 piece / kg or less.

(Comparative example)
A glass substrate was produced in the same manner as in Experimental Example 1 except that the amount of heat released from the clarification tube to the outside was not adjusted. At this time, the ratio of the amount of power applied to the first transfer tube 104, the amount of power applied to the clarification tube 120, and the amount of power applied to the second transfer tube 105 is 1: 1.5: 0.05. As a result, the number of bubbles containing nitrogen or sulfur oxide became a specified number or more.

(Glass composition)
The effect of this embodiment becomes remarkable when it is a non-alkali glass substrate containing tin oxide or a fine alkali glass substrate containing tin oxide. The alkali-free glass or fine alkali glass has a higher glass viscosity than the alkali glass. Therefore, it is necessary to increase the melting temperature in the melting process, and many tin oxides are reduced in the melting process. Therefore, in order to obtain a clarification effect, the molten glass temperature in the clarification process is increased to reduce the tin oxide. Is required to be further promoted and the viscosity of the molten glass needs to be lowered. In other words, when producing a non-alkali glass substrate containing tin oxide or a fine alkali glass substrate containing tin oxide, it is necessary to increase the molten glass temperature in the refining step. It is difficult to control by the amount of electric power when energized, and the volatilization of platinum group metal (for example, platinum or platinum alloy) is likely to occur. Here, in the present specification, the alkali-free glass substrate is a glass that substantially does not contain alkali metal oxides (Li ₂ O, K ₂ O, and Na ₂ O). The fine alkali 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 not more than 0.8 mol%.

As a glass substrate manufactured by this embodiment, the glass substrate of the following glass compositions is illustrated. Therefore, the glass raw material is prepared so that the glass substrate has the following glass composition. The glass substrate produced in the present embodiment includes, for example, 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 BaO total amount), 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 Contains 0.4 mol%.
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. High-viscosity glass generally requires a higher molten glass temperature in the refining process, so it is difficult to control the flow rate of the molten glass by the amount of electric power when the processing device is energized, and the platinum group metal volatilizes. Cheap. In other words, when manufacturing a glass substrate having such a composition, by adjusting the amount of heat released from the processing apparatus to the outside so that the temperature of the molten glass is in a temperature range in which the flow rate of the molten glass can be controlled, Makes it easy to control the flow rate of the molten glass by the amount of power when energizing the processing device, suppresses the inclusion of platinum group metal agglomerates as foreign matter in the molten glass, and adjusts the flow rate of the molten glass by the amount of power The effect of this embodiment becomes remarkable. 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.

According to this embodiment, even if the content of the alkali metal oxide in the glass substrate is 0 to 0.8 mol%, the flow rate of the molten glass can be controlled by the amount of electric power, and the platinum group is contained in the molten glass. It can suppress that the metal aggregate is mixed as a foreign material. The smaller the alkali metal oxide content, the higher the high-temperature viscosity. Therefore, a glass having an alkali metal oxide content of 0 to 0.8 mol% has an alkali metal oxide content of 0.8 mol%. High temperature viscosity is high compared to glass exceeding. Glass having high viscosity at high temperature generally needs to increase the temperature of the molten glass in the refining process, so that it is difficult to control the flow rate of the molten glass by the amount of electric power supplied to the processing apparatus, and the platinum group metal is likely to volatilize. That is, when using this glass having a high temperature viscosity, the temperature of the molten glass is in a temperature range in which the flow rate of the molten glass can be controlled while suppressing the agglomeration of the platinum group metal as a foreign substance in the molten glass. In addition, the effect of the present embodiment that makes it easy to control the flow rate of the molten glass by the amount of electric power when the processing apparatus is energized becomes remarkable by adjusting the amount of heat radiation from the processing apparatus to the outside.

The molten glass used in the present embodiment may have a glass composition in which the temperature is 1500 to 1700 ° C. when the viscosity is 10 ^2.5 poise. As described above, glass having a high temperature viscosity generally needs to increase the temperature of the molten glass in the refining process, so that it is difficult to control the flow rate of the molten glass by the amount of electric power supplied to the processing apparatus, and the volatilization of the platinum group metal. Is likely to occur. That is, even if it is a glass composition of high temperature viscosity, the said effect of this embodiment 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, the effect of this embodiment becomes more remarkable as the glass substrate having a higher strain point is manufactured. 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, which can suppress the inclusion of platinum group metal aggregates.

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. Thus, 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.

When the aggregate of platinum group metals located on the surface of the glass substrate is detached in the panel manufacturing process using the glass substrate, the detached portion becomes a recess, and the thin film formed on the glass substrate is not uniformly formed, and the screen Cause a display defect. 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, which has severe demands for display defects on the screen. In particular, glass substrates for oxide semiconductor displays using oxide semiconductors such as IGZO (indium, gallium, zinc, oxygen) and LTPS (low temperature polysilicon) semiconductors, which are more demanding for display defects on the screen. It is suitable for glass substrates for high-definition displays such as display glass substrates.
From the above, the glass substrate produced in the present embodiment is suitable for a glass substrate for display including a glass substrate for flat panel display. It is suitable for a glass substrate for oxide semiconductor display or a glass substrate for LTPS display. Moreover, the glass substrate manufactured by this embodiment is suitable for the glass substrate for liquid crystal displays by which it is calculated | required that content of an alkali metal oxide is very small. Moreover, it is suitable also for the glass substrate for organic EL displays. In other words, the manufacturing method of the glass substrate of this embodiment is suitable for manufacture of the glass substrate for displays, and is especially suitable for manufacture of the glass substrate for liquid crystal displays.
Moreover, the glass substrate manufactured by this embodiment is applicable also to a cover glass, the glass for magnetic discs, the glass substrate for solar cells, etc.

As mentioned above, although the manufacturing method of the glass substrate of this invention was demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, you may make various improvement and a change. Of course.

For example, although not shown in the figure, the amount of heat release may be adjusted by providing a refrigerant circulation pipe between the vicinity of the clarification pipe 120 and the outside of the heat insulating material 140 and circulating the refrigerant inside the circulation pipe. In this case, the heat radiation amount can be adjusted by controlling the circulation amount of the refrigerant.
The refrigerant circulated in the circulation pipe may be a liquid such as water or a gas such as air.
A metal material having a high melting point can be used for the circulation pipe. Specifically, platinum, rhodium, silver, palladium, gold, or an alloy thereof can be used as a material for the circulation pipe.

In the above description, the present invention has been described mainly with respect to the clarification tube 120. However, the present invention is not limited to the clarification tube 120, but other parts of the melting apparatus 100 (dissolution tank 101, stirring tank 103, transfer pipes 104 and 105, glass supply). The amount of heat released from the tube 106) or the molding apparatus 200 may be adjusted.

101 melting tank 103 stirring tank 104, 105 transfer pipe 105 glass supply pipe 120 clarification pipe (clarification apparatus)
121a, 121b Electrode 122 Power supply device 123 Control device 127 Exhaust pipe 140 Heat insulation material 200 Molding device

Claims (11)

1. A method for manufacturing a glass substrate using a processing apparatus for processing molten glass,
   When processing molten glass,
   Heating the processing device by energizing the processing device so that the temperature of the molten glass in the processing device is in a range suitable for the processing,
   The flow rate of the molten glass in the processing device is controlled by the amount of electric power when energizing,
   The amount of heat radiation from the processing device to the outside is set so that the amount of electric power is equal to or greater than the amount of electric power capable of controlling the flow rate of the molten glass, and the temperature of the molten glass is in a temperature range capable of controlling the flow rate of the molten glass. A method of manufacturing a glass substrate to be adjusted.
2. A method for manufacturing a glass substrate using a processing apparatus for processing molten glass,
   When processing molten glass,
   Heating the processing device by energizing the processing device so that the temperature of the molten glass in the processing device is in a range suitable for the processing,
   The flow rate of the molten glass in the processing device is controlled by the amount of current when the current is applied,
   A method for producing a glass substrate, wherein the amount of heat released from the processing device to the outside is adjusted so as to be equal to or greater than an amount of current that enables flow control of the molten glass.
3. The processing apparatus has a gas phase space formed by an inner wall and a molten glass liquid surface, and at least a portion of the inner wall in contact with the gas phase space is made of a material containing a platinum group metal,
   In the processing apparatus, a high temperature region is formed when the molten glass is processed, and a low temperature region lower in temperature than the high temperature region is formed when the molten glass is processed,
   The manufacturing method of the glass substrate of Claim 1 or 2 which adjusts the said thermal radiation amount so that the temperature difference of the said high temperature area | region and the said low temperature area | region will be 200 degrees C or less.
4. The treatment device is covered with a heat insulating material,
   The method for producing a glass substrate according to any one of claims 1 to 3, wherein the heat radiation amount is controlled by adjusting a thermal resistance from the processing apparatus to an external space by the heat insulating material.
5. The method for producing a glass substrate according to claim 4, wherein the thermal resistance is adjusted by adjusting a thermal conductivity and an arrangement of the heat insulating material.
6. The processing device is a clarification device for clarifying molten glass,
   The clarifier is heated by energizing the clarifier so that the maximum temperature of the molten glass in the clarifier is equal to or higher than the temperature at which the reduction reaction of tin oxide contained in the molten glass occurs.
   The flow rate of the molten glass in the clarification device is controlled by the amount of power when energizing,
   The production of a glass substrate according to any one of claims 1 to 5, wherein an amount of heat released from the clarifier to the outside is adjusted so that the amount of electric power is equal to or greater than an amount of electric power capable of controlling the flow rate of the molten glass. Method.
7. The clarification device is discharged from the clarification tube having a gas phase space through which bubbles in the molten glass are discharged, a first transfer tube to which the molten glass supplied into the clarification tube is transferred, and the clarification tube. A second transfer pipe through which the molten glass is transferred,
   In the first transfer pipe, the clarification pipe, and the second transfer pipe, the defoaming treatment of the molten glass by the reductive reaction of the clarifier and the absorption treatment that absorbs the bubbles in the molten glass by the oxidation reaction of the clarifier. And
   The amount of power to be applied to the first transfer pipe, the amount of power to be supplied to the area for performing the defoaming process in the clarification pipe, and the area for performing the absorption process among the clarification pipe and the second transfer pipe. The method for manufacturing a glass substrate according to claim 6, wherein the ratio of the amount of electric power applied to the current is 1: 0.6 to 1: 0.1 to 0.4.
8. The clarification device is discharged from the clarification tube having a gas phase space through which bubbles in the molten glass are discharged, a first transfer tube to which the molten glass supplied into the clarification tube is transferred, and the clarification tube. A second transfer pipe through which the molten glass is transferred,
   In a partial region of the clarification tube, a defoaming treatment of the molten glass is performed by a reduction reaction of the clarifier,
   In the other region of the clarification tube and the second transfer tube, an absorption treatment for absorbing bubbles in the molten glass by an oxidation reaction of the clarifier is performed,
   The ratio of the amount of power applied to the first transfer pipe, the amount of power applied to a partial area of the clarification pipe, and the amount of power supplied to the other area of the clarification pipe is from 1: 0.6 to The method for producing a glass substrate according to claim 6, wherein the ratio is 1: 0.05 to 0.4.
9. The processing device is discharged from the clarification tube having a gas phase space in which bubbles in the molten glass are discharged, a first transfer tube to which the molten glass supplied into the clarification tube is transferred, and the clarification tube. A second transfer pipe through which the molten glass is transferred,
   In the clarification tube, the defoaming treatment of the molten glass is performed by the reduction reaction of the clarifier,
   In the second transfer pipe, an absorption treatment for absorbing bubbles in the molten glass by an oxidation reaction of a clarifying agent is performed.
   The ratio of the amount of power applied to the first transfer tube, the amount of power applied to the clarification tube, and the amount of power applied to the second transfer tube is 1: 0.6 to 1: 0.1 to The manufacturing method of the glass substrate of Claim 6 which is 0.4.
10. A processing apparatus for processing molten glass;
    An energizer that heats the processing apparatus by energizing the processing apparatus so that the temperature of the molten glass in the processing apparatus is in a range suitable for the processing when the molten glass is processed;
    A control device for controlling the flow rate of the molten glass in the processing device by the amount of electric power when energizing,
    The amount of heat radiation from the processing device to the outside is such that the amount of electric power is equal to or greater than the amount of electric power capable of controlling the flow rate of the molten glass, and the temperature of the molten glass is within a temperature range capable of controlling the flow rate of the molten glass. Glass substrate manufacturing equipment that is being adjusted.
11. A processing apparatus for processing molten glass;
    An energizer that heats the processing apparatus by energizing the processing apparatus so that the temperature of the molten glass in the processing apparatus is in a range suitable for the processing when the molten glass is processed;
    A control device for controlling the flow rate of the molten glass in the processing device by the amount of current when the current is applied;
    The glass substrate manufacturing apparatus in which the amount of heat radiation from the processing apparatus to the outside is adjusted so as to be equal to or greater than the amount of current capable of controlling the flow rate of the molten glass.
    

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