TWI588105B - Method of manufacturing glass substrate and glass substrate manufacturing apparatus - Google Patents

Description

Glass substrate manufacturing method and glass substrate manufacturing device

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

Usually, a glass substrate is produced by the step of forming a molten glass from a glass raw material, and shaping|molding a molten glass into a glass substrate. The above steps include a step of treating the molten glass before forming, for example, a step of removing minute bubbles contained in the molten glass (hereinafter, also referred to as clarification). The clarification is carried out by heating the body of the clarification pipe while passing the molten glass containing the clarifying agent through the clarification pipe main body and removing the bubbles in the molten glass by the redox reaction of the clarifying agent. More specifically, the temperature of the molten glass which is coarsely melted is further increased to function as a clarifying agent, and after the bubbles are floated and defoamed, the molten glass is absorbed by incomplete defoaming by lowering the temperature. Relatively small bubbles. That is, the clarification includes a treatment for bubbling and defoaming bubbles (hereinafter also referred to as a defoaming treatment or a defoaming step) and a treatment for absorbing small bubbles into the molten glass (hereinafter also referred to as an absorption treatment or absorption step).

The inner wall of the member that is in contact with the molten glass of high temperature before molding needs to be composed of a suitable material depending on the temperature of the molten glass that is in contact with the member, the quality of the desired glass substrate, and the like. For example, it is known that a material constituting the above-mentioned clarification pipe body is usually a simple substance or an alloy of a platinum group metal (Patent Document 1). The platinum group metal has a high melting point and is excellent in corrosion resistance to molten glass.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-111533

If the molten glass is used as a treatment device for the inner wall surface of the platinum group metal, the platinum group metal volatilizes as an oxide in a portion of the heated inner surface which is in contact with the gas phase space (the atmosphere containing oxygen). On the other hand, the oxide of the platinum group metal is reduced at a position where the temperature of the treatment device is locally lowered, and the reduced platinum group metal adheres to the inner wall surface. The platinum group metal adhered to the inner wall surface is dropped and mixed into the molten glass, and is mixed as a foreign matter into the glass substrate.

In addition, in the glass substrate for a display, which is represented by a liquid crystal display, which is increasingly demanding in the recent years, the foreign matter derived from the aggregate of the volatile matter of the platinum group metal or the like is mixed into the molten glass. The problem has become bigger.

It is an object of the present invention to provide a method for reducing the temperature difference between a portion where the temperature of the processing device of the molten glass is locally lowered and the surrounding temperature, and setting it to a reference value or less, thereby making it possible to mix foreign matter into the glass substrate. A method for producing a glass substrate having a high quality glass substrate and a glass substrate manufacturing apparatus.

The invention has the following form:

(Form 1)

A method for producing a glass substrate, which comprises using a gas phase space formed by an inner wall and a surface of a molten glass, and at least a part of the inner wall contacting the gas phase space is made of a material containing a platinum group metal The molten glass is processed, and in the region where the processing device is in contact with the gas phase space, a high temperature region and a low temperature region having a lower temperature than the high temperature region are formed during the treatment of the molten glass, and support is provided outside the processing device. The processing device and the heat transfer medium that conducts heat from the high temperature region to the low temperature region, and The heat transfer amount of the heat transfer medium is adjusted so that the temperature difference between the high temperature region and the low temperature region is equal to or less than a reference value.

For example, the high temperature region may be a region of the processing device at a temperature in the range of 1600 ° C or higher, and the low temperature region may be a region in which the temperature of the processing device is within a temperature range of less than 1600 ° C. Alternatively, the high temperature region may be a region within a temperature range of the processing device at a temperature above 1620 ° C, and the low temperature region may be a region within a temperature range of the processing device at a temperature below 1590 ° C.

Alternatively, the electrode region in which the electrode is disposed in the processing device and the region in which the exhaust pipe is provided may be a low temperature region, and the region outside the low temperature region or the region between the electrode and the exhaust pipe may be a high temperature region.

Here, the processing apparatus includes a melting tank, a clarification device, a stirring tank or a forming device, a conveying pipe that transports the molten glass by the device pipes, and a supply pipe that supplies the glass to the devices. The treatment in the treatment apparatus includes: glass melting treatment, clarification treatment of molten glass, stirring treatment, forming treatment, and transportation processing and supply processing of molten glass.

When the temperature difference between the high temperature region and the low temperature region is equal to or lower than the reference value, the temperature difference between the high temperature region and the low temperature region is adjusted by the heat transfer amount of the heat transfer medium, and the temperature difference is equal to or lower than a predetermined reference value. Further, the reference value may be determined by the amount of aggregate of platinum precious metal in the target glass substrate. The heat transfer amount of the heat transfer medium is preferably adjusted so that the maximum temperature in the high temperature region is 1600 to 1750 ° C, and the lowest temperature in the low temperature region is 1300 to 1600 ° C. By lowering the temperature difference between the high temperature region and the low temperature region to be equal to or lower than the reference value, the amount of the platinum group metal volatilized in the high temperature region in the low temperature region can be reduced.

The platinum group metal means a metal composed of a single platinum group element and an alloy of a metal containing 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).

Preferably, the vapor pressure of the platinum group metal in the gas phase space is from 0.1 Pa to 15 Pa.

(Form 2)

A method for producing a glass substrate, which comprises using a gas phase space formed by an inner wall and a molten glass liquid surface, and at least a part of the inner wall contacting the gas phase space is made of a material containing a platinum group metal In the processing apparatus, in the processing apparatus, a high temperature region and a low temperature region are formed when the molten glass is processed, and the processing device is provided outside the processing device, and heat is supplied from the high temperature region to the low temperature. The region transmits the heat transfer medium, and the heat transfer amount of the heat transfer medium is adjusted to reduce the temperature difference between the high temperature region and the low temperature region.

(Form 3)

The method for producing a glass substrate according to the above aspect, wherein the reference value is 200° C. or less, and the heat transfer amount of the heat transfer medium is adjusted so that a temperature difference between the high temperature region and the low temperature region is 200° C. or less. .

(Form 4)

The method for producing a glass substrate according to any one of aspects 1 to 3, wherein the processing device and the heat transfer medium are covered with a refractory insulating brick, wherein the heat transfer medium is a refractory brick having a higher thermal conductivity than the refractory insulating brick, and The amount of heat transfer of the heat transfer medium is adjusted using either of the heat transfer rates and the arrangement of the heat transfer medium.

(Form 5)

The method for producing a glass substrate according to any one of the aspects 1 to 4, wherein the heat transfer amount of the heat transfer medium is determined by computer simulation.

Computer simulation can be performed, for example, by using a finite element method or a meshless method to create a model of a processing device, a heat transfer medium, and a gas phase space, and using the model for heat transfer analysis. Row.

(Form 6)

The method for producing a glass substrate according to any one of aspects 1 to 5, wherein the processing device includes a clarification device for clarifying the molten glass, wherein the heat transfer medium is in contact with a high temperature region and a low temperature region of the clarification device. The temperature difference between the high temperature region and the low temperature region of the clarification tube is adjusted by adjusting the heat transfer amount of the heat transfer medium.

Preferably, the maximum temperature of the molten glass in the processing apparatus is from 1630 ° C to 1720 ° C. When the maximum temperature is 1630 ° C or higher, the clarifying agent in the molten glass can exhibit a clarifying effect. On the other hand, by setting the maximum temperature to 1720 ° C or lower, the temperature difference between the high temperature region and the low temperature region can be lowered to serve as a reference. Below the value, the reduction of the bubbles and the reduction of the amount of the platinum group metal can be simultaneously achieved.

As the clarifying agent, tin oxide is preferably used. It is preferred that the content of tin oxide in the molten glass is 0.01 to 0.3 mol%. If the content of tin oxide is too small, the bubbles cannot be sufficiently reduced. On the other hand, when the content of the tin oxide is too large, the amount of volatilization of tin oxide from the molten glass increases, and the problem that the volatilized tin oxide is mixed into the molten glass occurs. By setting the content of the tin oxide to 0.01 to 0.3 mol%, it is possible to sufficiently reduce the bubbles and suppress the incorporation of the aggregate of the tin oxide into the molten glass.

(Form 7)

A glass substrate manufacturing apparatus comprising: a processing apparatus having a gas phase space formed by an inner wall and a surface of a molten glass, wherein 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, and When the molten glass is treated, a high temperature region and a low temperature region having a lower temperature than the high temperature region are formed in the processing device; and a heat transfer medium disposed outside the processing device to support the processing device and to heat from the high temperature The region is conducted to the low temperature region, and the amount of heat transfer is adjusted such that the temperature difference between the high temperature region and the low temperature region is equal to or less than a reference value.

(Form 8)

A glass substrate manufacturing apparatus comprising: a processing apparatus having a gas phase space formed by an inner wall and a molten glass surface, wherein 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; And processing the molten glass to form a high temperature region and a low temperature region in the processing device; and a heat transfer medium disposed outside the processing device, supporting the processing device, and transferring heat from the high temperature region to the low temperature region Conduction, and the amount of heat transfer is adjusted in such a manner as to reduce the temperature difference between the high temperature region and the low temperature region.

(Form 9)

In any of the above aspects, it is preferred that the oxygen concentration in the gas phase space is 0 to 10%. By reducing the oxygen concentration, the amount of volatilization of the platinum group metal can be reduced.

Preferably, the vapor pressure of the platinum group metal in the gas phase space is from 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)

In any of the above aspects, it is preferred to further have an agglomerate treatment step of melting the aggregate of the platinum group metal mixed in the molten glass in the molten glass.

Preferably, the concentration of the platinum group metal dissolved in the molten glass at the start of the agglomerate treatment step is 0.05 to 20 ppm.

In the agglomerate treatment step, it is preferred to adjust the saturated solubility of the platinum group metal in the molten glass by setting the temperature of the molten glass to 1660 ° C to 1750 ° C.

The saturated solubility of the platinum group metal is preferably adjusted by adjusting the oxygen activity of the molten glass. For example, it is preferable to adjust the oxygen activity so that the index of the oxygen activity [Fe ³⁺ ]/([Fe ²⁺ ]+[Fe ³⁺ ]) is in the range of 0.2 to 0.5.

(Form 11)

In any of the above aspects, the agglomeration of the volatiles of the platinum group metal In the aggregate, for example, the ratio of the maximum length to the minimum length, that is, the aspect ratio is 100 or more. Further, for example, the aggregate of the platinum group metal has a maximum length of 50 μm to 300 μm and a minimum length of 0.5 μm to 2 μm. Here, the maximum length of the agglomerate of the platinum group metal refers to the length of the largest long side of the rectangle which is externally connected to the foreign matter image obtained by photographing the aggregate of the platinum group metal, and the minimum length means the above external connection. The length of the smallest short side of the rectangle.

Alternatively, the aggregate formed by the agglomeration of the volatiles of the platinum group metal may be a ratio of the maximum length to the minimum length, that is, an aspect ratio of 100 or more, and the maximum length of the aggregate of the platinum group metal is 100 μm or more. Good for 100μm~300μm.

(Form 12)

In any of the above aspects, the glass substrate is a glass substrate for a display. Further, the glass substrate is suitable for a glass substrate for an oxide semiconductor display or a glass substrate for LTPS (low temperature poly-silicon) display.

According to the present invention, it is possible to reduce the foreign matter from entering the glass substrate and to produce a glass substrate having a high quality.

100‧‧‧melting device

101‧‧‧melting tank

103‧‧‧Stirring tank

103a‧‧‧Agitator

104, 105‧‧‧ delivery tube

106‧‧‧Glass supply tube

120‧‧‧clarification tube (clarification device)

121a, 121b‧‧‧ electrodes

122‧‧‧Power supply unit

123‧‧‧Control device

127‧‧‧Exhaust pipe

130‧‧‧Heat transfer medium

140‧‧‧Insulation materials

200‧‧‧Molding device

Fig. 1 is a view showing an example of a procedure of a method for producing a glass substrate of the embodiment.

Fig. 2 is a view schematically showing an example of a device for performing the melting step to the cutting step shown in Fig. 1;

FIG. 3 is a schematic view showing the configuration of the clarification pipe 120.

4 is a cross-sectional view of the clarification tube 120.

Fig. 5 is a view showing an example of a temperature distribution in the longitudinal direction of the upper surface of the clarification pipe 120.

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

Fig. 1 is a view showing an example of a procedure of a method for producing a glass substrate of the embodiment.

(Overall outline of the manufacturing method of the glass substrate)

The method for producing a glass substrate mainly includes the following steps: a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a molding step (ST5), a slow cooling step (ST6), and cutting. Break step (ST7).

The melting step (ST1) is carried out in a melting tank. In the melting tank, molten glass is produced by putting a glass raw material into the liquid surface of the molten glass stored in the melting tank and heating it. Further, the molten glass is flowed downstream from one of the inner side walls of the melting tank to the bottom.

The heating of the molten glass in the melting tank is performed by heating the molten glass itself to heat it by heating, that is, heating, and it is also possible to apply a flame generated by the burner to melt the glass raw material. Further, the molten glass contains a clarifying agent. As the clarifying agent, tin oxide, arsenious acid, hydrazine, and the like are known, and are not particularly limited. However, in terms of reducing the environmental load, it is preferred to use tin oxide as a fining agent. The content of tin oxide in the glass substrate is preferably from 0.01 to 0.3 mol%, more preferably from 0.03 to 0.2 mol%. If the content of tin oxide is too small, the bubbles cannot be sufficiently reduced. On the other hand, when the content of the tin oxide is too large, the amount of volatilization of tin oxide from the molten glass increases, and the problem that the volatilized tin oxide is mixed into the molten glass occurs. Further, if the content of the tin oxide is too large, the amount of oxygen released from the molten glass to the gas phase space increases, and the oxygen concentration in the gas phase space rises excessively, and the amount of volatilization of the platinum group metal from the treatment device increases. By setting the content of the tin oxide to 0.01 to 0.3 mol%, the bubbles can be sufficiently reduced, and the aggregation of the tin oxide can be reduced to the molten glass. Further, the bubbles can be sufficiently reduced, and the amount of volatilization of the platinum group metal from the processing apparatus can be reduced.

Tin oxide has a lower clarifying function than the commonly used arsenious acid, but is preferably used as a clarifying agent in terms of a lower environmental load. However, since the clarifying function of tin oxide is lower than that of arsenious acid, in the case of using tin oxide, it is necessary to make the temperature of the molten glass MG in the clarification step of the molten glass MG higher than the previous one. Therefore, the amount of volatilization of the platinum group metal from the clarification tube will increase, and as a result, the problem that the platinum group metal is mixed as a foreign matter to the glass substrate becomes remarkable.

The clarification step (ST2) is carried out at least in the clarification tube. In the clarification step, by heating the molten glass in the clarification tube, the bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass absorb the oxygen generated by the reduction reaction of the clarifying agent, and the volume increases and floats out. To the liquid surface of the molten glass and released. Further, in the clarification step, the reducing substance obtained by the reduction reaction of the clarifying agent is subjected to an oxidation reaction by lowering the temperature of the molten glass. Thereby, the gas component such as oxygen in the bubbles remaining in the molten glass is again absorbed into the molten glass, and the bubbles disappear. The oxidation reaction and the reduction reaction using the clarifying agent are carried out by controlling the temperature of the molten glass. In the clarification step of this embodiment, a method of clarifying tin oxide as a clarifying agent will be described.

Further, the clarification step may be a vacuum defoaming method in which a space in a reduced pressure environment is produced in the clarification tube, and bubbles existing in the molten glass are grown and defoamed under a reduced pressure atmosphere. However, since the apparatus for the vacuum defoaming method is complicated and large, it is preferable to use a clarification method using a clarifying agent to raise the temperature of the molten glass.

In the homogenization step (ST3), the molten glass in the stirring tank supplied through the pipe extending from the clarification pipe is stirred by a stirrer to homogenize the glass component. Thereby, the composition unevenness of the glass which is a cause of a vein etc. 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 forming step (ST5) and the slow cooling step (ST6) are carried out in a forming apparatus.

In the forming step (ST5), the molten glass is formed into a flat glass and the flat glass is made flow. The forming can be carried out by an overflow down-draw method.

In the slow cooling step (ST6), the flat glass is formed into a desired thickness and the internal strain is not generated, and the flat glass is gradually cooled without causing warpage.

In the cutting step (ST7), in the cutting device, the plate glass supplied from the molding device is cut into a specific length to obtain a plate-shaped glass substrate. The cut glass substrate is further cut into a specific size to prepare a glass substrate of a target size.

Fig. 2 is a view schematically showing an example of an apparatus for performing the melting step (ST1) to the cutting step (ST7) of the present embodiment. As shown in FIG. 2, the apparatus mainly has a melting apparatus 100 and a forming apparatus 200. The melting apparatus 100 has a melting tank 101, a clarification pipe 120, a stirring tank 103, conveying pipes 104 and 105, and a glass supply pipe 106.

In the melting tank 101 shown in Fig. 2, a heating means such as a burner (not shown) is provided. A glass raw material to which a clarifying agent is added is introduced into the melting tank to carry out a melting step. The molten glass melted in the melting tank 101 is supplied to the clarification pipe 120 via the transfer pipe 104.

In the clarification pipe 120, the temperature of the molten glass MG is adjusted, and the clarification of the molten glass is performed by the oxidation-reduction reaction of a clarifier. The clarified molten glass is supplied to the stirring tank via the transfer pipe 105.

In the stirring tank 103, the molten glass is homogenized by stirring by the agitator 103a. The molten glass homogenized in the agitation tank 103 is supplied to the molding apparatus 200 via the glass supply pipe 106.

In the molding apparatus 200, molten glass is formed into a flat glass by an overflow down-draw method.

(constitution of clarification pipe)

Next, the configuration of the clarification pipe 120 will be described with reference to Fig. 3 . Fig. 3 is a schematic view showing the configuration of a clarification pipe 120 of the embodiment.

As shown in FIG. 3, the peripheral surface of the clarification pipe 120 is provided with electricity on the outer peripheral surface. The poles 121a and 121b are provided with an exhaust pipe 127 on the wall of the clarification pipe 120 that is in contact with the gas phase space. Further, the clarification tube 120 is preferably made of platinum, reinforced platinum or a platinum alloy.

The body of the clarification tube 120, the electrode 121, and the exhaust pipe 127 are all composed of a platinum group metal. In the present specification, the term "platinum group metal" means a metal containing a platinum group element, and is used as a term for not only a metal composed of a single platinum group element but also an alloy of a platinum group element. Here, the platinum group element means 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 are excellent in corrosion resistance to molten glass.

Further, in the present embodiment, a case where the clarification pipe 120 is composed of a platinum group metal will be described as a specific example, but a part of the clarification pipe 120 may be composed of a refractory or other metal.

The electrodes 121a and 121b are connected to the power supply device 122. By applying a voltage between the electrodes 121a and 121b, a current flows to the clarification pipe 120 between the electrodes 121a and 121b, and the clarification pipe 120 is electrically heated. By heating by the electric current, the body of the clarification pipe 120 is heated to a maximum temperature of, for example, 1600 ° C to 1750 ° C, more preferably 1630 ° C to 1750 ° C, and the molten glass supplied from the glass supply pipe 104 is heated to the highest temperature. The temperature suitable for defoaming is, for example, 1600 ° C to 1720 ° C, more preferably 1620 ° C to 1720 ° C, still more preferably 1630 ° C to 1720 ° C.

Further, by controlling the temperature of the molten glass by electric heating, the viscosity of the molten glass can be adjusted, and thereby the flow rate of the molten glass passing through the clarification pipe 120 can be adjusted.

Further, a temperature measuring device (such as a thermocouple or the like) (not shown) may be provided to the electrodes 121a and 121b. The temperature measuring device measures the temperatures of the electrodes 121a, 121b and outputs the measurement results to the control device 123.

The control device 123 controls the amount of current that the power source device 122 energizes the clarification tube 120, and thereby controls the temperature and flow rate of the molten glass passing through the clarification tube 120. The control device 123 includes a CPU (Central Processing Unit), a memory, and the like. brain.

An exhaust pipe 127 is provided on the wall of the clarification pipe 120 that is in contact with the gas phase space. The exhaust pipe 127 may have a shape protruding from the outer surface of the outer wall of the clarification pipe 120 toward the outer side in a chimney shape. The exhaust pipe 127 communicates the gas phase space 120a which is a part of the inner space of the clarification pipe 120 with the outer space of the clarification pipe 120.

4 is a cross-sectional view of the clarification pipe 120 in the longitudinal direction of the body of the clarification pipe 120 and the longitudinal direction of the exhaust pipe 127. A heat transfer medium 130 is disposed on the outer wall surface of the body of the clarification pipe 120, the outer wall surfaces of the electrodes 121a and 121b, and the outer wall surface of the exhaust pipe 127, and the heat insulating material 140 is disposed outside the heat transfer medium 130.

The heat transfer medium 130 is made of a material having a higher thermal conductivity than the heat insulating material 140, abuts against the high temperature region and the low temperature region of the clarification pipe 120, and conducts heat from the high temperature region to the low temperature region via the heat transfer medium 130, thereby reducing the high temperature. The effect of the temperature difference between the zone and the low temperature zone. By adjusting the amount of heat transfer of the heat transfer medium 130, the temperature difference between the high temperature region and the low temperature region can be adjusted so that the temperature difference becomes equal to or lower than a predetermined reference value. The heat transfer medium 130 need not be disposed to abut the entire area of the clarification tube 120. Preferably, the heat transfer medium 130 is selectively provided at least in a portion that abuts against the high temperature region and a portion that abuts on the low temperature region, and the heat transfer medium 130 is provided to connect the two.

The thermal conductivity of the heat transfer medium 130 is preferably more than twice the thermal conductivity of the heat insulating material 140, more preferably five times or more. It is preferable to use a material having a thermal conductivity of 2 to 40 W/m‧K at 1000 ° C as the heat transfer medium 130. The heat transfer medium 130 can use a member having excellent fire resistance and high strength (stiffness). Specifically, an alumina electroformed refractory, a magnesia refractory, a tantalum carbide refractory or the like can be used as the heat transfer medium 130. By using such a material for the heat transfer medium 130, deformation of the clarification tube 120 can be prevented.

The heat transferred from the high temperature region to the low temperature region via the heat transfer medium 130 is preferably from 0.3 kW to 20 kW, more preferably from 0.5 kW to 15 kW.

The heat insulating material 140 is made of a material having a lower thermal conductivity than the heat transfer medium 130, and is adjusted. The effect of heat dissipation from the clarification tube 120 and the heat transfer medium 130 to the outside. It is preferable to use a material having a thermal conductivity of 0.1 to 1 W/m‧K at 1000 ° C as the heat insulating material 140. Specifically, porous bricks, ceramic fibers, or the like can be used as the heat insulating material 140.

Since the heat insulating medium 130 has a low heat insulating property, the clarification pipe 120 cannot be sufficiently insulated by only the heat transfer medium 130. On the other hand, the heat insulating material 140 provided on the outer side of the heat transfer medium 130 is excellent in heat insulating property, but tends to have low strength. For example, the higher the porosity of the insulating refractory brick, the higher the heat insulation, but the lower the strength. Therefore, deformation of the clarification device 120 cannot be prevented by only using the insulating refractory brick.

In the present embodiment, by providing a two-layer structure of the heat transfer medium 130 and the heat insulating material 140, the heat transfer medium 130 can be used to support the clarification pipe 120 and the heat insulating material 140 can be used for heat preservation.

Further, the high temperature region indicates a region where the temperature is higher than other regions. In the case of clarifying the tube 120, for example, the high temperature region may be a region in which the temperature of the clarification tube 120 is within a temperature range of 1600 ° C or higher, or may be a region in which the temperature of the clarification tube 120 is within a temperature range of 1620 ° C or higher. . Further, for example, the high temperature region may also include a region where the clarification pipe 120 becomes the highest temperature when the molten glass is processed. The low temperature region indicates a region where the temperature is lower than other regions, and specifically, a region where the temperature is lower than the high temperature region. In the case of clarifying the tube 120, the so-called low temperature region may be a region where the temperature of the clarification tube 120 is within a temperature range of less than 1600 ° C, or the temperature of the clarification tube 120 may be within a temperature range of 1590 ° C or lower. region. Further, for example, the low temperature region may include a region where the clarification pipe 120 becomes the lowest temperature when the molten glass is processed. For example, as described below, the region near the electrodes 121a and 121b of the clarification pipe and the vicinity of the exhaust pipe 127 becomes a low temperature region, and the region between the electrodes 121a and 121b and the exhaust pipe 127 becomes a high temperature region.

Fig. 5 is a view showing an example of a temperature distribution in the longitudinal direction of the upper surface of the clarification pipe 120, and the solid line is the temperature distribution of the clarification pipe 120 of the present embodiment, and the broken line is the previous clarification. The temperature distribution of the pigging. Since heat is radiated to the outside from the electrodes 121a and 121b and the exhaust pipe 127 in the vicinity of the electrodes 121a and 121b of the clarification pipe 120 and in the vicinity of the exhaust pipe 127, the temperature is likely to be lower than other regions of the clarification pipe 120. Specifically, in the case of the clarification tube 120 of the present embodiment, since the electrodes 121a and 121b having the flange shape have a high heat dissipation function, the temperature of the wall near the electrodes 121a and 121b is likely to be lower than that of the wall. Peripheral part. Further, for example, in order to suppress breakage due to overheating, the electrodes 121a and 121b are cooled by a liquid or a gas. Further, since the exhaust pipe 127 is also shaped to protrude from the clarification pipe 120, the temperature of the wall of the clarification pipe 120 which is in contact with the gas phase space 41c near the exhaust pipe 127 is also lower than the temperature of the periphery of the wall. Therefore, 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 pipe 120 of the present embodiment, the temperature of the clarification pipe 120 is not fixed, and a temperature difference is inevitably generated.

In the present embodiment, since the heat transfer medium 130 is provided on the outer wall surface of the main body of the clarification pipe 120, the outer wall surfaces of the electrodes 121a and 121b, and the outer wall surface of the exhaust pipe 127, the heat self-clarification pipe can be passed through the heat transfer medium 130. The high temperature region of 120 conducts to the low temperature region. Thereby, the temperature difference between the high temperature region and the low temperature region of the clarification pipe 120 can be suppressed within a specific range.

When the local temperature is lowered in the clarification pipe 120, the clarification is not sufficiently performed, and the quality of the bubble of the glass substrate to be formed is lowered. On the other hand, in the present embodiment, the heat transfer medium 130 can be used to alleviate the local temperature drop, and the temperature difference between the high temperature region and the low temperature region can be suppressed within a specific range. Therefore, the defoaming of the molten glass can be surely performed, and the bubble quality of the glass substrate to be formed can be improved.

Further, in the clarification tube 120 containing a platinum group metal, the platinum group metal is oxidized and volatilized in the gas phase space. This volatilization in the high temperature region of the clarification tube 120 is particularly noticeable. The volatilized platinum group metal oxide is reduced in a region where the local temperature is lowered, and the solidified platinum group metal aggregates and adheres to the inner wall surface. The aggregate of the platinum group metal attached to the inner wall surface is dropped and mixed as a foreign matter into the molten glass in the clarification step, resulting in a decrease in the quality of the glass substrate. Hey. Particularly in the case where tin oxide is used as a clarifying agent, the problem of volatilization and adhesion becomes more conspicuous because the maximum temperature required for obtaining a clarifying effect is increased. By mitigating the local temperature drop, the temperature difference between the high temperature region and the low temperature region of the clarification tube 120 is suppressed to a specific range, and the aggregation of the platinum group metal can be prevented from adhering to the inner wall surface.

If the oxygen concentration in the gas phase space is set to 0%, the volatilization of the platinum group metal can be prevented. Therefore, from the viewpoint of preventing volatilization of the platinum group metal, it is preferred to set the oxygen concentration in the gas phase space to 0%. However, in order to keep the oxygen concentration in the gas phase space at 0% at all times, there is a problem that the content of the fining agent or the cost is extremely reduced. Therefore, in order to simultaneously achieve reduction of bubbles, low cost, and reduction of volatilization of platinum group metals, the oxygen concentration in the gas phase space 41c is preferably 0.01% or more. When the oxygen concentration in the gas phase space is too small, the difference in oxygen concentration between the molten glass and the gas phase space increases, and the amount of oxygen released from the molten glass to the gas phase space 120a increases, and the molten glass is excessively reduced. In the glass substrate after molding, bubbles such as sulfur oxides or nitrogen gas remain. On the other hand, if the oxygen concentration is too large, the volatilization of the platinum group metal is promoted, and the precipitation amount of the volatilized platinum group metal is increased. As apparent from the above, the oxygen concentration in the gas phase space is preferably from 0 to 30%, more preferably from 0.01 to 10%, still more preferably from 0.01 to 1%.

The vapor pressure of the platinum group metal in the gas phase space is preferably from 0.1 Pa to 15 Pa, more preferably from 3 Pa to 10 Pa. When the vapor of the platinum group metal is within this range, aggregation of the reduced platinum group metal to the inner wall surface can be suppressed.

Further, from the viewpoint of simultaneously suppressing the volatilization of the platinum group metal and the clarifying effect, the reference value of the temperature difference between the high temperature region and the low temperature region is preferably 50° C. or higher and 200° C. or lower, more preferably 70° C. or higher. 150. Below °C. When the temperature difference between the high temperature region and the low temperature region is 200 ° C or less, preferably 150 ° C or less, more preferably 100 ° C or less, the oxidation of the platinum group metal oxide which is oxidized in the high temperature region can be suppressed in the low temperature region, and the suppression can be suppressed. The solidified or agglomerated platinum group metal is mixed into the molten glass. On the other hand, if the temperature difference between the high temperature region and the low temperature region is 50 ° C or higher, more preferably 70 ° C or higher, the temperature of the molten glass can be set to A temperature range suitable for clarification reduces the number of bubbles. Further, the temperature difference between the high temperature region and the low temperature region may be a temperature difference between the highest temperature in the high temperature region and the lowest temperature in the low temperature region.

In order to set the temperature difference between the high temperature region and the low temperature region within the above range, the lowest 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 further preferably 1500 ° C or more. And below 1600 ° C. Further, the maximum temperature in the high temperature region is preferably 1600 ° C or more and 1750 ° C or less, more preferably 1600 ° C or more and 1720 ° C or less, and still more preferably 1610 ° C or more and 1700 ° C or less.

The temperature difference between the high temperature region and the low temperature region can be adjusted by adjusting the amount of heat transfer by the heat transfer medium 130. The adjustment of the amount of heat transfer can be performed by adjusting the thermal conductivity of the heat transfer medium 130 or the amount of the heat transfer medium 130.

Further, in the case where the heat transfer medium 130 is a refractory brick, the temperature difference between the high temperature region and the low temperature region can be controlled by adjusting the arrangement of the refractory bricks.

The amount of heat transfer when changing the thermal conductivity or the arrangement and amount of the heat transfer medium 130 can be calculated, for example, by using a hydrodynamic numerical calculation (computer simulation) of a 3D model produced by a finite element method or a meshless method. For example, a 3D model of the reproduction clarification tube 120, the heat transfer medium 130, the heat insulating material 140, the molten glass in the clarification tube 120, and the gas phase space is produced, divided into a limited number of regions (computation grid), and boundary conditions are defined. (Clarification of heat dissipation of the molten glass or the clarification tube 12 in the tube 12, etc.) and material properties (thermal conductivity, etc.). Then, iterative calculations using a computer are used to analyze the heat in and out of each computing grid. The optimum thermal conductivity or arrangement and amount of the heat transfer medium 130 and the heat insulating material 140 can be calculated by using computer simulation.

Further, the aggregate of the platinum group metal which is intended to be suppressed in the present embodiment has a shape of a unidirectionally elongated linear shape, and the aspect ratio of the maximum length to the minimum length, that is, the aspect ratio is 100 or more. For example, the aggregate length of the platinum group metal has a maximum length of 50 μm to 300 μm and a minimum length of 0.5 μm to 2 μm. Here, the maximum length of the agglomerate of the platinum group metal means that the foreign matter image obtained by photographing the aggregate of the platinum group metal is externally connected to the largest long side of the rectangle. The length, the minimum length, refers to the length of the smallest short side of the circumscribed rectangle.

According to this embodiment, it is possible to reduce the case where the aggregate of the platinum group metal is mixed as a foreign matter into the molten glass. However, in order to cope with the case where the aggregate of the platinum group metal is mixed into the molten glass, it is preferred to have an agglomerate treatment step of melting the aggregate of the platinum group metal in the molten glass. By melting the aggregate of the platinum group metal in the molten glass, the aggregate of the platinum group metal mixed in the glass substrate to be produced can be reduced.

The agglomerate treatment step described below is preferably carried out in a state where the concentration of the platinum group metal dissolved in the molten glass is 0.05 to 20 ppm. That is, it is preferable that the concentration of the platinum group metal dissolved in the molten glass at the start of the agglomerate treatment step is 0.05 to 20 ppm. The lower the concentration of the platinum group metal dissolved in the molten glass at the beginning of the coagulation treatment step, the more the dissolved amount of the platinum group metal in the molten glass dissolves. On the other hand, if the concentration of the platinum group metal is excessively lowered, the platinum group metal is eluted from the wall of the treatment apparatus which is in contact with the molten glass to the molten glass to melt the treatment apparatus.

The concentration of the platinum group metal of the molten glass can be determined, for example, by sampling the molten glass in the clarification tube, cooling, pulverizing, and measuring by quantitative analysis using ICP (inductively coupled plasma).

In the agglomerate treatment step, the saturated solubility of the platinum group metal in the molten glass is adjusted by setting the temperature of the molten glass to 1660 ° C to 1750 ° C. By increasing the temperature of the molten glass, the saturated solubility of the platinum group metal in the molten glass can be increased, and the aggregate of the platinum group metal mixed in the molten glass can be dissolved. On the other hand, if the temperature of the molten glass is raised too much, the amount of volatilization of the glass component (for example, B ₂ O ₃ ) will increase, the glass composition will locally change, and the glass properties such as the thermal expansion coefficient or viscosity of the glass will locally change. The glass substrate has streaks such as veins. Moreover, when the temperature of the molten glass is raised, the amount of volatilization of the platinum group metal from the wall surface of the processing apparatus of the molten glass increases. Further, if the temperature of the molten glass is excessively increased, the wall of the processing apparatus is melted.

Further, if the temperature of the molten glass is excessively increased, the oxygen activity of the molten glass is lowered due to excessive defoaming. If the absorption process step in this state, will be dissolved in the molten glass because of SO _3, CO ₃ is reduced to produce an SO _2, CO _2. Since SO ₂ and CO _{2 are} less likely to be dissolved in the molten glass than SO ₃ and CO ₃ , they are likely to remain as bubbles, which may cause bubbles defects in the produced glass substrate.

Furthermore, the saturation solubility of the platinum group metal can also be adjusted by adjusting the pressure of the gas phase space facing the molten glass. Here, the pressure in the gas phase space means the total pressure of the gas contained in the gas phase space.

The gas phase space pressure can be adjusted, for example, by adjusting the amount of gas discharged into the gas phase space through the exhaust pipe 127 to the outside of the clarification pipe 120 (discharge amount) or the amount of gas supplied to the clarification pipe 120 such as an inert gas. The amount of gas released from the molten glass is released. The discharge amount can be adjusted, for example, by connecting the outlet of the exhaust pipe 127 of the clarification pipe 120 to the suction device, or narrowing the outlet or the like to adjust the pressure difference between the gas phase space and the atmosphere outside the clarification pipe 120. The amount of gas released from the molten glass can be adjusted, for example, by adjusting the amount of the clarifying agent contained in the molten glass and the blending ratio of the glass component. Further, the pressure in the gas phase space is higher or lower than the atmospheric pressure on the outer side of the clarification pipe 120, for example, based on the amount of gas released from the exhaust pipe 127.

If the pressure in the gas phase space is increased, the amount of dissolution of the aggregate of the platinum group metal increases. On the other hand, if the pressure in the gas phase space is excessively increased, the bubbles generated in the molten glass are less likely to be released from the surface of the molten glass in the defoaming treatment step, resulting in a poor clarification effect. Further, if the pressure in the gas phase space is excessively increased, the pressure difference from the atmosphere outside the clarification pipe 120 becomes large, and the flow velocity of the gas flow in the gas phase space increases. Therefore, it is difficult for the concentration of the platinum group metal in the gas phase space to rise to a saturated state, and therefore, the amount of volatilization of the platinum group metal from the wall of the clarification pipe 120 increases.

Further, the saturation solubility of the platinum group metal can also be adjusted by adjusting the oxygen activity of the molten glass. The oxygen activity of the molten glass means the amount of oxygen dissolved in the molten glass (except for the presence of bubbles in the molten glass). As an index of oxygen activity, [Fe ³⁺ ]/([Fe ²⁺ ]+[Fe ³⁺ ]) can be used. Here, the activities of Fe ²⁺ and Fe ³⁺ contained in the [Fe ²⁺ ] and [Fe ³⁺ ]-based molten glass are specifically expressed by mass percentage. [Fe ²⁺ ] and [Fe ³⁺ ] can be measured by spectrophotometry.

The amount of agglomerates of the platinum group metal can be increased by increasing the oxygen activity of the molten glass. On the other hand, if the oxygen activity is too high, the amount of oxygen released from the molten glass increases, and the platinum group metal is easily oxidized and volatilized. Moreover, the oxygen bubbles remain in the molten glass in the molten glass, and the oxygen bubbles remain, which is a cause of bubble defects generated in the produced glass substrate. Therefore, it is preferred to adjust the oxygen activity so that [Fe ³⁺ ]/([Fe ²⁺ ]+[Fe ³⁺ ]) is in the range of 0.2 to 0.5.

The oxygen activity of the molten glass can be adjusted, for example, by adjusting the amount of the clarifying agent contained in the molten glass and the oxide of the glass raw material in the melting step. Further, it may be adjusted by adjusting the temperature of the molten glass before the start of the agglomerate treatment step in the clarification step or by introducing an oxygen-containing gas into the molten glass before the start of the agglomerate treatment step.

[Examples]

In Examples 1 to 4, using the clarification device shown in FIG. 4, tin oxide was used as a clarifying agent, and clarification of the molten glass was performed for 1 hour, and the clarified molten glass was formed into a plate of 2270 mm × 2000 mm and a thickness of 0.5 mm. Glass, 100 glass substrates were produced. At this time, by adjusting the thermal conductivity of the heat transfer medium 130 and the heat insulating material 140, the amount of heat transfer from the region of the highest temperature of the clarification pipe to the regions around the electrodes 121a and 121b and the exhaust pipe 127 is adjusted. Thereby, the temperature difference between the temperature around the electrodes 121a and 121b and the exhaust pipe 127 and the maximum temperature of the clarification pipe can be maintained at the temperature shown in Table 1. Further, the heat transfer amount of Example 4 was 2 kW, and the heat transfer amounts of Examples 1 to 3 were 2 kW.

[Comparative example]

The heat transfer rate of the heat transfer medium and the heat insulating material is adjusted, and the heat transfer amount of the region from the highest temperature of the clarification pipe to the regions around the electrodes 121a and 121b and the exhaust pipe 127 is not adjusted, and the same method as in the embodiment is used. 100 glass substrates were produced. The result, the electrode The temperature difference between the temperature around 121a, 121b and the exhaust pipe 127 and the maximum temperature of the clarification pipe becomes the temperature shown in Table 1.

Further, in Examples 1 to 6 and Comparative Examples, the glass composition of the glass substrate was 66.6 mol% of SiO _{2 ,} 10.6 mol% of Al ₂ O _{3 , and} 11.0 mol% of B ₂ O ₃ , MgO, CaO, and SrO. And the total amount of BaO is 11.4 mol%, SnO ₂ is 0.15 mol%, Fe ₂ O ₃ is 0.05 mol%, alkali metal oxide is 0.2 mol%, strain point is 660 ° C, and viscosity is 10 ^2.5 poise. The temperature is 1570 °C.

[Counting of agglomerates of platinum group metals]

The glass substrates produced in Examples 1 to 6 and Comparative Examples were observed under an optical microscope, and the number of aggregates of platinum group metals in the glass substrate was counted. In addition, when the temperature difference between the highest temperature and the lowest temperature is 120 ° C, the number of agglomerates per 1 kg of the platinum group metal is set to 1, and the number of aggregates of the platinum group metal under each condition is expressed as a ratio. . Obviously, when the temperature difference is 250 ° C (comparative example), when the temperature difference is 50 ° C, 80 ° C, 100 ° C, 120 ° C, 170 ° C, 200 ° C (Examples 1 to 6), the glass can be suppressed. The amount of agglomerates of platinum group metals in the substrate. Further, as agglomerates of the platinum group metal, platinum foreign matters having an aspect ratio of 100 or more and a maximum length of 100 μm or more were counted.

The allowable level per unit mass of the number of defects caused by the agglomerates is, for example, 0.02/kg or less. In the glass substrates of Examples 1 to 6, the number of defects of the aggregate of the platinum group metal was within the allowable level. On the other hand, in the glass substrate of the comparative example, the number of defects of the foreign matter of the platinum group metal exceeded the allowable level.

(glass composition)

The effect of the present embodiment is remarkable in the case of an alkali-free glass substrate containing tin oxide or a low-alkali glass substrate containing tin oxide. The glass viscosity of alkali-free glass or low-alkali glass is higher than that of alkali glass. Therefore, in the melting step, the melting temperature must be raised, and a large amount of tin oxide is reduced in the melting step. Therefore, in order to obtain a clarifying effect, it is necessary to raise the temperature of the molten glass in the clarification step, further promote the reduction of tin oxide, and lower the molten glass. Viscosity. In other words, in the case of producing an alkali-free glass substrate containing tin oxide or a low-alkali glass substrate containing tin oxide, since the temperature of the molten glass in the clarification step must be increased, volatilization of platinum or a platinum alloy or the like is likely to occur. Here, in the present specification, the alkali-free glass substrate is a glass which does not substantially contain an alkali metal oxide (Li ₂ O, K ₂ O, and Na ₂ O). In addition, the low alkali glass is a glass in which the content of the alkali metal oxide (the content of Li ₂ O, K ₂ O, and Na ₂ O) exceeds 0 and is 0.8 mol% or less.

As the glass substrate produced in the present embodiment, a glass substrate having the following glass composition is exemplified. Therefore, the glass raw material is prepared in such a manner that the glass substrate has the following glass composition. The glass substrate produced in the present embodiment contains, for example, SiO ₂ 55 to 75 mol%, Al ₂ O ₃ 5 to 20 mol%, B ₂ O ₃ 0 to 15 mol%, and RO 5 to 20 mol% (RO is MgO, CaO, SrO, and The total amount of BaO) and R' ₂ O are 0 to 0.4 mol% (R' is a total amount of Li ₂ O, K ₂ O, and Na ₂ O), and SnO _{2 is} 0.01 to 0.4 mol%.

In this case, at least one of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , and RO (R is all of the elements contained in the glass substrate of Mg, Ca, Sr, and Ba) may be contained, and the 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 high temperature viscosity of 4.0 or more in a molar ratio of (2 × SiO ₂ ) + Al ₂ O ₃ ) / ((2 × B ₂ O ₃ ) + RO) is exemplified. A glass having a high temperature viscosity is generally required to raise the temperature of the molten glass in the clarification step, and therefore, volatilization of a platinum group metal (for example, platinum or a platinum alloy) is liable to occur. In other words, in the case of producing a glass substrate having such a composition, the effect of suppressing the aggregation of the platinum group metal as a foreign matter into the molten glass is remarkable. In addition, the high-temperature viscosity means the viscosity of the glass when the molten glass becomes a high temperature, and the high temperature here means, for example, 1300 ° C or more.

According to the present embodiment, even if the content of the alkali metal oxide in the glass substrate is 0 to 0.8 mol%, the aggregate of the platinum group metal can be prevented from being mixed into the molten glass as a foreign matter. Since the content of the alkali metal oxide is smaller, the viscosity at high temperature is higher. Therefore, the high-temperature viscosity of the glass having an alkali metal oxide content of 0 to 0.8 mol% is higher than the content of the alkali metal oxide exceeding 0.8 mol. % of the glass. A glass having a high viscosity at a high temperature generally needs to raise the temperature of the molten glass in the clarification step, and therefore, volatilization of a platinum group metal is liable to occur. In other words, when the glass having a high temperature and high viscosity is used, the effect of suppressing the aggregation of the platinum group metal as a foreign matter in the molten glass becomes remarkable.

The molten glass used in the present embodiment may have a glass composition having a viscosity of 10 ^2.5 poise and a temperature of 1500 to 1700 ° C and 1600 to 1700 ° C. As described above, a glass having a high temperature viscosity is generally required to raise the temperature of the molten glass in the clarification step, and therefore, volatilization of the platinum group metal is liable to occur. That is, even in the case of a high-temperature viscous glass composition, the above effects of the present embodiment are also remarkable.

The strain point of the molten glass used in the present 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, the glass having a higher strain point has a tendency to increase the temperature of the molten glass at a viscosity of 10 ^2.5 poise. That is, in the case of producing a glass substrate having a higher strain point, the above-described effects of the present embodiment are more remarkable. Further, the higher the strain point, the more the glass can be used for a high-definition display, and therefore, the stricter problem of the problem that the aggregate of the platinum group metal is mixed as a foreign matter. Therefore, the glass substrate having a higher strain point is more suitable for the present embodiment in which the aggregation of the platinum group metal can be suppressed.

In the case where the glass raw material is melted so that the temperature of the molten glass containing tin oxide and the viscosity is 10 ^2.5 poise is 1500 ° C or higher, the above effect of the embodiment becomes remarkable, and the viscosity is 10 ^2.5 poise. The temperature of the molten glass is, for example, 1500 ° C to 1700 ° C, and may be 1550 ° C to 1650 ° C.

When the aggregate of the platinum group metal located on the surface of the glass substrate is detached from the panel manufacturing step using the glass substrate, the portion which is detached becomes a concave portion, and the film formed on the glass substrate cannot be uniformly formed, thereby causing display defects of the screen. The problem. Further, when agglomerates of a platinum group metal are present in the glass substrate, there is a problem in that the film is deformed due to a difference in thermal expansion coefficient between the glass and the platinum group metal in the slow cooling step, which causes a display defect of the screen. Therefore, this embodiment is suitable for the manufacture of a glass substrate for a display which is strict in display defects of a screen. Particularly suitable for use in LTPS displays using oxide semiconductors such as IGZO (indium, gallium, zinc, and oxygen) for oxide semiconductor displays and LTPS displays using LTPS (low temperature polysilicon) semiconductors A glass substrate for a high-definition display such as a glass substrate.

As described above, the glass substrate produced in the present embodiment is suitable for a glass substrate for a display including a glass substrate for a flat panel display. A glass substrate for an oxide semiconductor display using an oxide semiconductor such as IGZO or a glass substrate for an LTPS display using an LTPS semiconductor. Moreover, the glass substrate manufactured in the present embodiment is suitable for A glass substrate for a liquid crystal display having an extremely low content of an alkali metal oxide. Further, it is also suitable for a glass substrate for an organic EL display. In other words, the method for producing a glass substrate of the present embodiment is suitable for the production of a glass substrate for a display, and is particularly suitable for the production of a glass substrate for a liquid crystal display.

Further, the glass substrate produced in the present embodiment can also be applied to a cover glass, a glass for a disk, a glass substrate for a solar cell, or the like.

The method of producing the glass substrate of the present invention has been described in detail above, but the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the spirit and scope of the invention.

For example, although not shown, a refrigerant may be circulated inside the circulation pipe by a circulation pipe provided with a refrigerant between the high temperature region and the low temperature region, and the refrigerant may be used as a heat transfer medium. In this case, the amount of heat transfer between the high temperature region and the low temperature region can be adjusted by controlling the circulation amount of the refrigerant, and the temperature difference between the high temperature region and the low temperature region can be adjusted.

The refrigerant circulating in the circulation pipe may be a liquid such as water or a gas such as air.

The circulating pipe can use a metal material having a higher melting point. Specifically, platinum, rhodium, silver, palladium, gold, or the like may be used as the material of the circulation tube.

In the above description, the present invention has been described mainly with the clarification pipe 120, but it is not limited to the clarification pipe 120, and may be other parts of the melting device 100 (melting tank 101, stirring tank 103, conveying pipe 104, 105, glass supply). The tube 106) or the forming device 200 is provided with a heat transfer medium 130 or a heat insulating material 140.

120‧‧‧clarification tube (clarification device)

121a, 121b‧‧‧ electrodes

127‧‧‧Exhaust pipe

130‧‧‧Heat transfer medium

140‧‧‧Insulation materials

Claims (9)

A method for producing a glass substrate, wherein the processing device is configured to treat a molten glass having a gas phase space formed by an inner wall and a surface of the molten glass, and at least a portion of the inner wall in contact with the gas phase space When the molten glass is treated by the material containing the platinum group metal in the processing apparatus, the high temperature region is formed on the inner wall in contact with the gas phase space, and the low temperature region is lower than the high temperature region, and the processing device is Providing at least one of an electrode for electrically heating the main body of the processing device or an exhaust pipe connecting the gas phase space and an outer space of the processing device to the body of the processing device and the electrode or the exhaust pipe Provided outside the heat transfer medium that supports the processing device and conducts heat from the high temperature region to the low temperature region, and the heat transfer medium has a heat transfer amount such that at least one of the electrode or the exhaust pipe is The temperature difference between the low temperature region and the high temperature region caused by the cause is less than or equal to the reference value. Type adjustment. The method of producing a glass substrate according to claim 1, wherein the reference value is determined according to the amount of aggregate of platinum precious metal in the target glass substrate. A method for producing a glass substrate, wherein the processing device is configured to treat a molten glass having a gas phase space formed by an inner wall and a molten glass surface, and at least the inner wall in contact with the gas phase space a part is composed of a material containing a platinum group metal, and when the molten glass is treated in the processing apparatus, a high temperature region is formed on the inner wall in contact with the gas phase space, and the temperature is lower than the high temperature region. In the low temperature region, the processing device is provided with at least one of an electrode for electrically heating the main body of the processing device or an exhaust pipe connecting the gas phase space and an outer space of the processing device, and the body of the processing device a heat transfer medium supporting the processing device and conducting heat from the high temperature region to the low temperature region is disposed outside the electrode or the exhaust pipe, and the heat transfer amount of the heat transfer medium is such that the electrode or the exhaust pipe At least one of them is adjusted in such a manner that the temperature difference between the low temperature region and the high temperature region is reduced. The method for producing a glass substrate according to any one of claims 1 to 3, wherein the heat transfer amount of the heat transfer medium is adjusted so that a temperature difference between the high temperature region and the low temperature region is 200 ° C or lower. The method for producing a glass substrate according to any one of claims 1 to 3, wherein the processing device and the heat transfer medium are covered by a refractory insulating brick, wherein the heat transfer medium is a refractory brick having a higher thermal conductivity than the refractory insulating brick, and The amount of heat transfer of the heat transfer medium is adjusted using either of the heat transfer rates and the arrangement of the heat transfer medium. The method for producing a glass substrate according to any one of claims 1 to 3, wherein the heat transfer amount of the heat transfer medium is determined by computer simulation. The method for producing a glass substrate according to any one of claims 1 to 3, wherein the processing device comprises a clarification device for clarifying the molten glass, wherein the heat transfer medium abuts between a high temperature region and a low temperature region of the clarification device, and The heat transfer amount of the heat transfer medium is adjusted to adjust the temperature difference between the high temperature region and the low temperature region of the clarification device. A glass substrate manufacturing apparatus comprising: a processing device and a heat transfer medium; the processing device having a gas phase space formed by an inner wall and a surface of the molten glass, and at least a portion of the inner wall contacting the gas phase space is composed of platinum a material of a group metal, and is provided with a body for forming a high temperature region on the inner wall in contact with the gas phase space and a low temperature region having a temperature lower than the high temperature region when the molten glass is processed, and At least one of an electrode electrically heated by the main body of the processing device or an exhaust pipe communicating with the gas phase space and an outer space of the processing device; the heat transfer medium being disposed on the body of the processing device and the electrode or the exhaust pipe Externally, the processing device is supported, and heat is conducted from the high temperature region to the low temperature region, and the heat transfer amount is the low temperature region and the high temperature region generated by causing at least one of the electrode or the exhaust pipe The temperature difference is adjusted so as to be equal to or less than the reference value. A glass substrate manufacturing apparatus comprising: a processing device and a heat transfer medium; wherein the processing device has a gas phase space formed by an inner wall and a molten glass surface, and at least a portion of the inner wall in contact with the gas phase space is included a material of a platinum group metal, and is provided with a body for forming a high temperature region on the inner wall in contact with the gas phase space and a low temperature region having a temperature lower than the high temperature region when the molten glass is processed, and At least one of an electrode that is electrically heated by the body of the processing device or an exhaust pipe that communicates between the gas phase space and an outer space of the processing device; the heat transfer medium is disposed on a body of the processing device and the electrode or the exhaust gas The outside of the tube supports the processing device, and conducts heat from the high temperature region to the low temperature region, and the heat transfer amount is the low temperature region generated by causing at least one of the electrode or the exhaust pipe The temperature difference in the high temperature region is adjusted in such a manner as to decrease.