TWI568696B - A glass substrate manufacturing method and a 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.

In general, the production of a glass substrate includes the steps of forming a molten glass from a glass raw material, passing through a clarification step, a stirring step, or a homogenization step, and thereafter forming the molten glass into a glass substrate.

In any of the above-described processing apparatuses, it is necessary to use a suitable material for the member that is in contact with the molten glass in accordance with the temperature of the molten glass that is in contact with the member, the quality of the desired glass substrate, and the like. In other words, in order to increase the amount of molten glass having a high-temperature molten glass, it is preferable to mix any of the glass processing apparatuses of the glass substrate into the molten glass without considering foreign matter which is a cause of the glass substrate defect. For example, after the molten glass is produced, the molten glass is in an extremely high temperature state before being supplied to the forming step. Therefore, a treatment apparatus for performing various processes such as melting, clarification, supply, and stirring is used as the platinum group metal having high heat resistance ( For example, a member of platinum (for example, refer to Patent Document 1).

In the above steps, a clarification step of removing minute bubbles contained in the molten glass is included. For a glass substrate used for a panel display such as a liquid crystal display or a plasma display or a flat panel display (FPD), defects due to air bubbles remaining in the molten glass must be excluded.

Therefore, in the manufacture of a panel display or a glass substrate for FPD, a clarification step is performed. The clarification is carried out by heating the body of the clarification pipe and passing the clarified agent-containing molten glass through the clarification pipe body, and removing the molten glass by the redox reaction of the clarifying agent. Bubbles in the glass.

More specifically, a clarifying agent which releases oxygen by a reduction reaction is used, and the temperature of the molten glass after the crude melting is further increased in the clarification pipe, whereby the oxygen is released by the reduction of the clarifying agent, thereby melting The bubbles in the glass float and defoam, and then the oxygen remaining in the incomplete defoaming is used for the oxidation of the reduced fining agent by lowering the temperature, whereby the molten glass absorbs the residual oxygen. Further, as the clarification tube which is subjected to the clarification step at a high temperature, a member containing a platinum group metal (for example, platinum) having high heat resistance is also used.

[Previous Technical Literature] [Patent Literature]

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

The clarification step is the step of the highest temperature of the molten glass between the melting step and the forming step, and in order to heat the molten glass, the clarification tube subjected to the clarification step is heated to an extremely high temperature. Thus, the platinum group metal used in the clarification tube is oxidized by oxygen generated by reduction of the clarifying agent in the molten glass, and volatilized in the form of an oxide. On the other hand, the oxide of the platinum group metal is reduced at a position where the temperature of the clarification tube is locally lowered, and the reduced platinum group metal is aggregated and adhered to the inner wall surface of the clarification tube. When a part of the platinum group metal attached to the inner wall surface is mixed as a foreign matter in the molten glass, the quality of the glass substrate is lowered. In particular, the clarification step is the step of the highest temperature of the molten glass between the melting step and the forming step, and therefore, in the clarification tube which mainly performs the clarification step, it is heated to an extremely high temperature. Therefore, the volatilization of the platinum group metal in the clarification tube is strong, and it is particularly desirable to reduce the volatilization and agglomeration of the platinum group metal.

An object of the present invention is to provide a method for producing a glass substrate which can reduce the volatilization of a platinum group metal used in a glass processing apparatus in a step of treating a molten glass before forming a glass substrate, thereby suppressing the incorporation of foreign matter into the molten glass. And glass substrate manufacturing equipment Set,

The method for producing a glass substrate of the present invention and the glass substrate manufacturing apparatus include the following aspects.

(Form 1)

A method for producing a glass substrate, comprising: a step of treating a molten glass containing a clarifying agent for releasing oxygen by a reduction reaction using a treatment device comprising at least a part of an inner wall containing a material containing a platinum group metal; In the step of treating the molten glass, the gas phase is controlled by adjusting the amount of oxygen released from the molten glass to the gas phase space formed by the inner wall of the processing device and the surface of the molten glass. The oxygen concentration of the space, thereby suppressing the volatilization of the above platinum group metal.

(Form 2)

A method for producing a glass substrate, which comprises treating a molten glass with a treatment device for treating molten glass, and treating the molten glass containing a clarifying agent that releases oxygen by a reduction reaction, on the surface of the molten glass The upper portion forms a gas phase space, and the molten glass is supplied to the inside of the processing device including at least a part of the inner wall containing the material of the platinum group metal, and the gas phase is controlled by adjusting the amount of oxygen released from the molten glass. The oxygen concentration of the space, thereby suppressing the volatilization of the above platinum group metal.

(Form 3)

The method for producing a glass substrate according to the aspect 1, wherein the glass substrate contains 0.011 mol% to 0.3 mol% of tin oxide, and the amount of oxygen released from the molten glass is determined by the content of the tin oxide. Tune whole.

(Form 4)

The method for producing a glass substrate according to any one of aspects 1 to 3, wherein the oxygen concentration is controlled by further adjusting an amount of oxygen discharged from the gas phase space to the outside of the processing device.

(Form 5)

The method for producing a glass substrate according to any one of the aspects 1 to 4, wherein the gas having the adjusted supply amount is supplied to the gas phase space such that the oxygen concentration is within a specific range.

(Form 6)

The method for producing a glass substrate according to any one of the aspects 1 to 5, wherein, in the processing apparatus, the molten glass flows in a direction in which the surface of the molten glass is in contact with the gas phase, and the amount of the oxygen is released. Depending on the position of the flow direction of the molten glass, the oxygen concentration in the flow direction of the molten glass in the gas phase space is adjusted by adjusting the distribution of the oxygen release amount at the position of the flow direction of the molten glass. The distribution is such that the volatilization of the platinum group metal described above is inhibited.

(Form 7)

The method for producing a glass substrate according to the aspect 6, wherein the temperature of the processing device changes according to a position of a flow direction of the molten glass, and the distribution of the oxygen release amount is predicted by using a computer simulation, and the computer simulation is used to make The processing conditions are determined such that the position at which the release amount of the oxygen in the flow direction of the molten glass is maximized is separated from the position at which the temperature of the processing device is the highest.

(Form 8)

The method for producing a glass substrate according to any one of the aspects 1 to 7, wherein in the processing apparatus, the molten glass flows in a direction of a surface of the molten glass in contact with the gas phase, and the gas is processed in the processing apparatus The temperature of the inner wall contacting the phase space has a temperature distribution along the flow direction of the molten glass, and in the treatment of the molten glass, the release amount of the bubbles released from the surface of the molten glass to the gas phase space is maximized. The maximum bubble discharge amount in the flow direction of the molten glass and the highest temperature position of the temperature distribution in the flow direction of the molten glass are adjusted to be the largest in the flow direction of the molten glass. position.

(Form 9)

A method for producing a glass substrate, which is characterized in that a molten glass is treated by a treatment device for treating molten glass, and includes a step of melting a glass raw material to produce molten glass, which comprises containing oxygen released by a reduction reaction. a step of treating the molten glass of the clarifying agent; in the step of treating the molten glass, supplying the molten glass to the inner wall at least a part of the inner wall to form a gas phase space on the surface of the molten glass a processing device formed of a metal material, and in the processing device, the molten glass flows in a direction of a surface of the molten glass that is in contact with the gas phase space, and the processing device is in contact with the gas phase space The temperature of the wall has a temperature distribution along the flow direction of the molten glass, and in the treatment of the molten glass, the release amount of the bubble released from the surface of the molten glass in contact with the gas phase space to the gas phase space The maximum position of the bubble release amount in the flow direction of the molten glass which is the largest Said flowing direction of molten glass The maximum temperature position of the above temperature distribution is adjusted so as to be spaced apart from each other in the flow direction of the molten glass.

(Form 10)

The method for producing a glass substrate according to the aspect 8 or 9, wherein the processing device includes a clarification tube in which at least a part of the inner wall is made of a material containing a platinum group metal and at least defoaming the molten glass, and the molten glass is subjected to the above The step of treating includes a clarification step of performing the defoaming treatment of the defoaming of the molten glass in the above-mentioned clarification tube.

(Form 11)

The method for producing a glass substrate according to any one of claims 8 to 10, wherein the maximum position of the bubble release amount is predicted by computer simulation, and the computer simulation is used to maximize the bubble discharge amount and the maximum temperature. The treatment conditions are determined such that the positions are spaced apart in the flow direction of the molten glass.

(Form 12)

The method for producing a glass substrate according to any one of aspects 8 to 11, wherein the adjustment of the maximum position of the bubble release amount is performed by adjusting at least one of a temperature distribution of the molten glass and a flow rate of the molten glass. .

(Form 13)

The method for producing a glass substrate according to any one of the aspects 8 to 12, wherein the maximum bubble discharge amount position is located on a downstream side of the flow direction of the molten glass with respect to the highest temperature position.

(Form 14)

The method for producing a glass substrate according to any one of aspects 8 to 13, wherein the processing device includes a clarification tube in which at least a part of the inner wall is made of a material containing a platinum group metal and at least defoaming the molten glass is performed, and The clarification pipe is provided to communicate with the gas phase space and the outer side of the processing device In the exhaust pipe of the atmosphere, the arrangement position of the exhaust pipe in the flow direction of the molten glass is between the maximum bubble discharge amount position and the highest temperature position.

(Form 15)

The method for producing a glass substrate according to any one of aspects 8 to 14, wherein the processing device includes a clarification tube in which at least a part of the inner wall is made of a material containing a platinum group metal and at least defoaming the molten glass is performed, and The clarification pipe is provided with an exhaust pipe that communicates the atmosphere between the gas phase space and the outside of the clarification pipe, and the position at which the bubble discharge amount is the maximum position and the position of the exhaust pipe in the flow direction of the molten glass is the temperature The highest temperature position of the distribution is based on the same side of the flow direction of the molten glass.

(Form 16)

The method for producing a glass substrate according to the aspect of the invention, wherein the flange member extending along the outer side of the processing device is provided on the outer periphery of the processing device, and the arrangement position of the flow direction of the molten glass of the flange member is An area other than the region between the maximum position of the bubble release amount and the position at which the exhaust pipe is disposed.

(Form 17)

The method for producing a glass substrate according to any one of the aspects of the present invention, wherein the maximum temperature position of the temperature distribution, the arrangement position of the exhaust pipe, and the maximum position of the bubble release amount are from a flow direction of the molten glass. The upstream side is sequentially the highest temperature position, the arrangement position of the exhaust pipe, and the maximum bubble discharge amount.

(Form 18)

The method for producing a glass substrate according to any one of the aspects 8 to 13, wherein the processing device is provided with an exhaust pipe that communicates the gas phase space and an atmosphere outside the processing device, and The position at which the bubble is released at the maximum position and the position at which the exhaust pipe is disposed in the flow direction of the molten glass is the same position in the flow direction of the molten glass.

(Form 19)

A glass substrate manufacturing apparatus which processes a molten glass using a processing apparatus for processing molten glass, and includes a processing apparatus configured to include at least a part of an inner wall containing a material containing a platinum group metal and internally a molten glass containing a clarifying agent that releases oxygen by a reduction reaction and forming a gas phase space above the surface of the molten glass; and a control device configured to be released from the molten glass by adjustment The amount of oxygen is adjusted and the amount of oxygen discharged from the gas phase space is adjusted so as to adjust the oxygen concentration in the gas phase space to a specific range.

(Form 20)

A glass substrate manufacturing apparatus characterized in that a molten glass is treated by a processing apparatus for processing molten glass, and includes: a melting tank that melts a glass raw material to produce molten glass; and a processing apparatus in the following manner a structure in which at least a part of the inner wall contains a material containing a platinum group metal, and is internally supplied with molten glass containing a clarifying agent that releases oxygen by a reduction reaction, and the molten glass is along the molten glass and the gas phase space Flowing in the direction of the contact surface, forming a gas phase space above the surface of the molten glass, and the temperature of the inner wall in contact with the gas phase space has a temperature distribution along the flow direction of the molten glass; treatment of the molten glass The maximum position of the amount of released bubbles in the flow direction of the molten glass in which the amount of released bubbles from the surface of the molten glass is released to the gas phase space is the highest, and the temperature in the flow direction of the molten glass The manner in which the highest temperature position of the distribution is separated in the flow direction of the molten glass Release the entire amount of the bubble maximum position.

(Form 21)

A method of producing a glass substrate according to the aspect 19 or 20, wherein the processing means comprises a clarification tube for performing defoaming of the molten glass.

(Form 22)

The method for producing a glass substrate according to any one of aspects 1 to 17, wherein the glass substrate manufacturing apparatus according to any one of aspects 19 to 21, wherein the maximum temperature of the molten glass flowing inside the processing apparatus is 1630 ° C. 1750 ° C.

(Form 23)

The method for producing a glass substrate according to any one of the aspects 1 to 18, wherein the content of the tin oxide of the glass substrate is 0.01 mol% to 0.3. Moer%.

(Form 24)

The method for producing a glass substrate according to any one of the aspects 1 to 18, 22, and 23, or the glass substrate manufacturing apparatus according to any one of aspects 19 to 23, wherein a vapor pressure of the platinum group metal in the gas phase space It is 0.1Pa~15Pa.

(Form 25)

The method for producing a glass substrate according to any one of aspects 1 to 24, wherein the glass substrate manufacturing apparatus according to any one of aspects 19 to 24, wherein the oxidation of the platinum group metal causes agglomeration of the oxide due to the oxidation Aggregates (hereinafter referred to as agglomerates of platinum group metals) generated by agglomeration of the substance have, for example, a ratio of the maximum length to the minimum length, that is, an aspect ratio of 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 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, as the aggregate generated by the agglomeration of the volatiles of the platinum group metal, the ratio of the maximum length to the minimum length, that is, the aspect ratio of 100 or more, and the platinum group can be specified. The maximum length of the agglomerates of the metal is 100 μm or more, preferably 100 μm to 300 μm.

(Form 26)

The method of producing a glass substrate according to any one of aspects 1 to 25, wherein the glass substrate is a glass substrate for a display.

Further, the glass substrate is preferably a glass substrate for an oxide semiconductor display or a glass substrate for LTPS (Low Temperature Poly-silicon) display.

According to the method for producing a glass substrate and the glass substrate manufacturing apparatus of the above aspects, in the processing step of the molten glass, for example, the clarification step, by suppressing volatilization of the platinum group metal, it is possible to suppress foreign matter from entering the molten glass.

100‧‧‧melting device

101‧‧‧melting tank

103‧‧‧Stirring tank

103a‧‧‧Agitator

104‧‧‧Transport

105‧‧‧ delivery tube

106‧‧‧Glass supply tube

120‧‧‧Clarification tank

120a‧‧‧ gas phase space

121a‧‧‧electrode

121b‧‧‧electrode

122‧‧‧Power supply unit

123‧‧‧Control device

124a‧‧‧ flushing gas supply pipe

124b‧‧‧ flushing gas supply pipe

125a‧‧‧ flushing gas supply device

125b‧‧‧ flushing gas supply device

127‧‧‧Exhaust pipe

128‧‧‧Oxygen concentration meter

200‧‧‧Forming device

300‧‧‧cutting device

A‧‧‧Maximum position of oxygen release

MG‧‧‧ molten glass

P‧‧‧Maximum temperature position

R‧‧‧Maximum temperature range

SG

Fig. 1 is a flow chart showing the steps of a method of manufacturing a glass substrate.

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

Fig. 3 is a schematic view showing a clarification pipe according to a first embodiment used in the manufacturing apparatus of Fig. 2;

Fig. 4 is a vertical sectional view in the longitudinal direction of the clarification pipe of the first embodiment.

Fig. 5 is a view showing the relationship between the position in the longitudinal direction of the clarification pipe according to the first embodiment, the temperature at the upper end portion of the clarification pipe 120, and the amount of released oxygen.

Fig. 6 is an external view of a clarification pipe according to a second embodiment.

Fig. 7 is a view showing a cross section of a clarification pipe and a temperature distribution of a clarification pipe in the second embodiment.

Fig. 8 is a view showing the results of Experimental Example 1.

A method of manufacturing a glass substrate and a glass for the present invention with reference to the drawings Embodiments of the processing apparatus will be described. In the present specification, the suppression of the incorporation of foreign matter into the molten glass by the adjustment of the oxygen concentration or the like means that the amount of foreign matter mixed into the molten glass is lowered with respect to the case where the above adjustment is not performed, and the foreign matter is mixed. The amount of molten glass is zero, but it is not limited to the case where the amount of foreign matter mixed into the molten glass is zero.

In the present specification, the upper portion of the liquid surface means a portion located above the liquid surface in the vertical direction.

In the present specification, the upstream side of the molten glass flowing from the melting tank to the molding apparatus means the side of the melting tank for manufacturing the molten glass with respect to the gazing position. Moreover, the downstream side of the said molten glass means the molding apparatus side with respect to a fixation position.

In the present specification, the inside of the processing device refers to a space surrounded by the inner wall.

Further, the foreign matter of the aggregate of the platinum group metal means, for example, a shape in which the one side is elongated and has a linear shape, and the ratio of the maximum length to the minimum length, that is, the aspect ratio exceeds 100. 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 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.

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

Fig. 1 is a view showing an example of a procedure of a method for producing a glass substrate of the embodiment. The manufacturing method of the glass substrate mainly includes a melting step (ST1), a clarification step (ST2), a stirring step (ST3), a molding step (ST4), a slow cooling step (ST5), and a cutting step (ST6).

In the melting step (ST1), molten glass is produced by heating a glass raw material. The heating of the molten glass can be performed by heating the molten glass itself to heat it. It is carried out by electric heating. Further, the glass raw material may be melted by auxiliary heating using a flame of a burner.

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 clarifying agent.

In the clarification step (ST2), bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass are generated by raising the temperature of the molten glass. The bubble absorbs oxygen generated by the reduction reaction of the clarifying agent to expand (grow) the diameter of the bubble, and floats to the liquid surface of the molten glass, that is, the free surface of the molten glass, and is broken and disappears, that is, the gas in the bubble is released. Out. Thereafter, in the clarification step, the reducing substance obtained by the reduction reaction of the clarifying agent undergoes 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 reabsorbed into the molten glass, and the diameter of the remaining bubbles is reduced, and the bubbles disappear. The oxidation reaction and the reduction reaction by the clarifying agent are carried out by controlling the temperature of the molten glass.

Further, the clarification step may also be a vacuum defoaming method in which the diameter of the bubbles existing in the molten glass is expanded to defoam under a reduced pressure atmosphere. The vacuum defoaming method is effective in terms of not using a clarifying agent. However, the apparatus for the vacuum defoaming method is complicated and large. Therefore, it is preferred to use a clarifying method using a clarifying agent to raise the temperature of the molten glass.

In the stirring step (ST3), the glass component is homogenized by stirring the molten glass using a stirrer. Thereby, it is possible to reduce the compositional unevenness of the glass which is a cause of streaks or the like.

The molding step (ST4) and the slow cooling step (ST5) are performed by a molding apparatus.

In the molding step (ST4), the molten glass is formed into a sheet glass to produce a sheet-like glass stream. An overflow down-draw method is used in forming.

In the slow cooling step (ST5), the sheet glass which is formed and flows becomes the desired thickness The cooling is performed in such a manner that internal strain is not generated and warpage is not generated.

In the cutting step (ST6), a sheet-shaped glass substrate is obtained by cutting the sheet glass after the slow cooling to a specific length. The cut glass substrate is further cut into a specific size to produce a glass substrate of a desired size.

(glass substrate manufacturing device)

Fig. 2 is a schematic view showing a glass substrate manufacturing apparatus which performs the melting step (ST1) to the cutting step (ST7) in the present embodiment. As shown in FIG. 2, the glass substrate manufacturing apparatus mainly includes a melting apparatus 100, a molding apparatus 200, and a cutting apparatus 300. The melting apparatus 100 includes a melting tank 101, a clarification pipe 120, a stirring tank 103, conveying pipes 104 and 105, and a glass supply pipe 106.

A heating device such as a burner (not shown) is provided in the melting tank 101 shown in Fig. 2 . A glass raw material to which a clarifying agent is added is introduced into the melting tank, and a melting step (ST1) is performed. The molten glass which is melted at the high temperature (for example, 1500 ° C - 1600 ° C) melted in the melting tank 101 is supplied to the clarification pipe 120 via the transfer pipe 104. Further, in the melting tank 101, the molten glass between the electrodes can be electrically heated by flowing a current between at least a pair of electrodes, and the burner can be assisted in addition to the electric heating. The flame, while heating the glass raw material.

In the clarification pipe 120, the temperature of the molten glass MG is adjusted, and the clarification step (ST2) of the molten glass is performed by the oxidation-reduction reaction of the clarifier.

Specifically, the molten glass obtained in the melting tank 101 flows into the clarification pipe 120 through the transfer pipe 104 from the melting tank 101. The clarification pipe 120, the conveying pipes 104 and 105, and the glass supply pipe 106 are pipes made of a platinum group metal. In the clarification pipe 120, a heating device is provided in the same manner as the melting tank 101. Further, at least the heating pipe is also provided in the conveying pipe 104. In the clarification step ST2, the molten glass is clarified by raising the temperature of the molten glass. For example, the temperature of the molten glass in the clarification tube 120 is 1600 ° C to 1720 ° C. The clarified molten glass in the clarification pipe 120 flows from the clarification pipe 120 through the delivery pipe 105 into the stirring device 103. Molten glass It is cooled when passing through the duct 105. Thus, oxygen is released by the reduction reaction of the clarifying agent, and the released oxygen is absorbed by the bubbles contained in the molten glass. The bubble that absorbs oxygen and has an increased bubble diameter floats to the surface (liquid level) of the molten glass, and is broken and disappears. Then, the temperature of the molten glass is lowered. Thereby, the reduced clarifying agent generates an oxidation reaction, and the molten glass absorbs oxygen remaining in the molten glass.

The clarified molten glass is supplied to the agitation vessel 103 via the transfer pipe 105.

In the stirring tank 103, the molten glass is stirred by the agitator 103a, and the stirring step (ST3) is performed. For example, in the stirring device 103, the temperature of the molten glass is 1250 ° C to 1450 ° C. For example, in the stirring device 103, the viscosity of the molten glass is 500 poise to 1300 poise. The molten glass stirred in the stirring tank 103 is supplied to the molding apparatus 200 via the glass supply pipe 106. When the molten glass passes through the transfer pipe 106, it is cooled so as to be suitable for the viscosity of the molten glass. For example, the molten glass is cooled to 1100 to 1300 °C. In the molding apparatus 200, the sheet glass is formed from the molten glass by the overflow down-draw method (forming step ST4), and the cooling is performed (slow cooling step ST5).

In the cutting device 300, a plate-shaped glass substrate cut out from the sheet glass is formed (cutting step ST6).

The clarification pipe 120, the agitation vessel 103, the transportation pipes 104 and 105, and the glass supply pipe 106 are formed of at least a part of the inner wall containing a material containing a platinum group metal. More preferably, the clarification pipe 120, the agitation vessel 103, the conveying pipes 104, 105, and the glass supply pipe 106 are all made of a platinum group metal. Further, in the present specification, the "platinum group metal" means a metal containing a platinum group element, which is used in a term that includes 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). Although the platinum group metal has a relatively high price, it has a high melting point and is excellent in corrosion resistance to molten glass.

(Application example of glass substrate)

Aggregates of platinum group metals present on the surface of the glass substrate, if a glass substrate is used In the panel manufacturing step, the surface of the glass substrate is desorbed, and the surface of the surface after desorption is a concave portion, and the film formed on the glass substrate is not uniformly formed, causing a problem of display defects of the screen. Further, when agglomerates of a platinum group metal are present in the glass substrate, strain is generated due to a difference in thermal expansion coefficient between the glass and the platinum group metal in the slow cooling step, which causes a problem of display defects on the screen. Therefore, this embodiment is suitable for manufacturing a glass substrate for a display which is strict in display defects on a screen. In particular, in the present embodiment, a glass substrate for an oxide semiconductor display using an oxide semiconductor such as IGZO (indium, gallium, zinc, or oxygen) and an LTPS display using LTPS (low temperature polysilicon) semiconductor are required to be stricter on display defects of the screen. A glass substrate for a high-definition display such as a glass substrate is preferred.

According to the above, the glass substrate produced by the method for producing a glass substrate of the present embodiment has a glass substrate or a flat panel display (FPD) for a panel display such as a liquid crystal display, a plasma display, or an organic EL display, which requires a very small amount of an alkali metal oxide. It is preferable to use a glass substrate. Further, it is also suitable for a glass substrate for an oxide semiconductor display or a glass substrate for an LTPS display. Further, it is also suitable as a cover glass for protecting a display, a glass for a magnetic disk, and a glass substrate for a solar cell. As the glass substrate for a panel display or a flat panel display, an alkali-free glass or a glass containing a small amount of alkali can be used. A glass substrate for a panel display or a flat panel display has a high viscosity at a high temperature. For example, the temperature of the molten glass having a viscosity of 10 ^2.5 poise is 1500 ° C or higher.

Further, as the glass substrate for a display, the number of agglomerates of the platinum group metal in the glass substrate is preferably 1000/m ³ or less, more preferably 100 / m ³ or less, still more preferably 50 / m ³ the following. Further, the number of bubbles in the glass substrate is preferably 1000 pieces/m ³ or less, more preferably 200 pieces/m ³ or less, still more preferably 50 pieces/m ³ or less. As described above, by reducing the number of platinum metal agglomerates and the number of bubbles in the glass substrate, the number of display defects on the display can be reduced, and the yield can be improved.

(glass composition)

In the melting tank 101, the glass raw material is melted by a heating means (not shown) to produce molten glass. The glass raw materials are prepared in such a manner that the glass of the desired composition can be obtained substantially. As an example of the composition of the glass, a preferred alkali-free glass for a glass substrate for a panel display or a flat panel display contains SiO ₂ : 50% by mass to 70% by mass, and Al ₂ O ₃ : 10% by mass to 25% by mass, and B ₂ O ₃ : 0% by mass to 15% by mass, MgO: 0% by mass to 10% by mass, CaO: 0% by mass to 20% by mass, SrO: 0% by mass to 20% by mass, BaO: 0% by mass to 10% by mass . Here, the total content of MgO, CaO, SrO, and BaO is 5% by mass to 30% by mass.

Alternatively, the glass substrate preferably used for the glass substrate for an oxide semiconductor display and the glass substrate for LTPS display contains SiO ₂ : 55 mass % to 70 mass %, Al ₂ O ₃ : 15 mass % to 25 mass %, and B ₂ O ₃ : 0% by mass to 10% by mass, MgO: 0% by mass to 10% by mass, CaO: 0% by mass to 20% by mass, SrO: 0% by mass to 20% by mass, and BaO: 0% by mass to 10% by mass. Here, the total content of MgO, CaO, SrO, and BaO is 5% by mass to 30% by mass. In this case, the glass substrate is more preferably contained in an amount of 60% by mass to 70% by mass of SiO ₂ and 3% by mass to 10% by mass of BaO.

As the glass substrate for a panel display or a flat panel display, in addition to the alkali-free glass, a glass containing a trace amount of an alkali metal containing a trace amount of alkali can also be used. When the glass of the glass substrate is an alkali-free glass containing tin oxide or a glass containing a trace amount of alkali containing tin oxide, the following volatilization of the platinum group metal used in the inner wall of the glass processing apparatus of the present embodiment is suppressed. The effect of the foreign matter of the agglomerates of the platinum group metal mixed into the molten glass becomes remarkable. Compared to alkali glass, the glass of alkali-free glass or glass containing a small amount of alkali has a higher viscosity. By increasing the melting temperature in the melting step, more tin oxide is reduced in the melting step. Therefore, in order to obtain a clarifying effect, it is necessary to increase the temperature of the molten glass in the clarification step, promote the reduction of tin oxide, and make the molten glass The viscosity is reduced. Further, since tin oxide has a higher temperature for promoting the reduction reaction than arsenious acid or ruthenium which has been used as a clarifying agent, it is necessary to increase the temperature of the inner wall of the clarification pipe 120 in order to increase the temperature of the molten glass to promote clarification. In other words, in the case of producing a glass substrate containing an anti-alkali glass substrate containing tin oxide or a glass containing a small amount of alkali containing tin oxide, it is necessary to increase the temperature of the molten glass in the clarification step, and therefore, volatilization of the platinum group metal is likely to occur.

Further, 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). Further, the glass containing a trace amount of alkali is a glass in which the content of the alkali metal oxide (the total amount of Li ₂ O, K ₂ O, and Na ₂ O) exceeds 0 and 0.8 mol% or less. The glass containing a trace amount of alkali contains, for example, 0.1% by mass to 0.5% by mass of an alkali metal oxide, and preferably 0.2% by mass to 0.5% by mass of an alkali metal oxide. Here, the alkali metal oxide is at least one selected from the group consisting of Li ₂ O, Na ₂ O, and K ₂ O. The total content of the alkali metal oxide may be less than 0.1% by mass. Even if the content of the alkali metal oxide in the glass substrate is 0 to 0.8 mol%, the aggregate of the platinum group metal can be suppressed from being mixed into the molten glass as a foreign matter by the following method.

The glass substrate produced in the present embodiment may further contain 0.01% by mass to 1% by mass (preferably 0.01% by mass to 0.5% by mass) of SnO ₂ and 0% by mass to 0.2% in addition to the above components. % (preferably 0.01% by mass to 0.08% by mass) of Fe ₂ O ₃ . In view of the environmental load, the glass substrate produced by the present embodiment preferably contains no or substantially no As ₂ O ₃ , Sb ₂ O ₃ and PbO.

Further, as the glass substrate produced by the present embodiment, a glass substrate having the following glass composition is further exemplified. Therefore, the glass raw material is prepared in such a manner that the glass substrate has the following glass composition.

For example, in terms of mole%, it contains: 55 to 75 mol% of SiO ₂ , 5 to 20 mol% of Al ₂ O ₃ , 0 to 15 mol% of B ₂ O ₃ , and 5 to 20 mol % RO (RO is the total amount of MgO, CaO, SrO and BaO), 0 to 0.4 mol% of R' ₂ O (R' is the total amount of Li ₂ O, K ₂ O and Na ₂ O), 0.01~ 0.4 mol% of SnO ₂ . 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), Mohr 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 one example of a glass having a high temperature viscosity. Regarding the glass having a high temperature viscosity, it is generally necessary to increase the temperature of the molten glass in the clarification step, and therefore, volatilization of the platinum group metal is liable to occur. In other words, when the glass substrate having such a composition is produced, the effect of the present embodiment, that is, 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 shows, for example, 1300 ° C or more.

The molten glass used in the present embodiment may have a glass composition having a viscosity of 10 to ^2.5 poise and a temperature of 1,500 to 1,700 °C. Such a glass is a glass having a high temperature and high viscosity, and a glass having a high temperature and high viscosity generally needs to increase the temperature of the molten glass in the clarification step, and therefore, volatilization of the platinum group metal is liable to occur. In other words, the effect of the present embodiment, that is, the effect of suppressing the aggregation of the platinum group metal as a foreign matter in the molten glass, is remarkable even in the case of the glass composition having a high temperature and high viscosity.

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 high strain point tends to have a high temperature of the molten glass when the viscosity is 10 ^2.5 poise. In other words, in the case of producing a glass substrate having a higher strain point, the effect of the present embodiment, that is, the effect of suppressing the aggregation of the platinum group metal as a foreign matter into the molten glass is remarkable. Moreover, since it is used for a high-definition display, the glass having a higher strain point has a stricter requirement for 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 inhibiting the incorporation of foreign matter of the aggregate of the platinum group metal.

In the case where the glass raw material is melted so that the temperature of the molten glass containing tin oxide and having a viscosity of 10 ^2.5 poise is 1500 ° C or higher, the above-described effects of the present embodiment become more remarkable, and the viscosity is 10 The temperature of the molten glass at ^2.5 poise is, for example, 1500 ° C to 1700 ° C, and may be 1550 ° C to 1650 ° C.

If the content of the clarifying agent such as tin oxide contained in the molten glass changes, the amount of oxygen released from the molten glass to the gas phase space also changes. In terms of suppressing the volatilization of the platinum group metal, the oxygen concentration in the gas phase space is preferably controlled (adjusted) by the content of tin oxide. Therefore, in terms of suppressing volatilization of platinum or a platinum alloy or the like, the content of tin oxide is preferably limited to 0.01 to 0.3 mol%, preferably 0.03 to 0.2 mol%. If the content of the tin oxide is large, there is a problem that secondary crystallization of tin oxide occurs in the molten glass, which is not preferable. Further, when 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 excessively rises, and the amount of volatilization of the platinum group metal from the treatment device increases. If the content of the tin oxide is too small, the defoaming of the bubbles of the molten glass is not sufficient.

(Configuration of the clarification pipe of the first embodiment)

Next, the configuration of the clarification tube 120 of the first embodiment will be described with reference to Figs. 3 and 4 . Fig. 3 is a schematic view showing the configuration of the clarification pipe 120 of the first embodiment. 4 is a vertical cross-sectional view in the longitudinal direction of the clarification pipe 120.

As shown in FIGS. 3 and 4, electrodes 121a and 121b are provided on the outer peripheral surfaces of both ends in the longitudinal direction of the clarification pipe 120, and an exhaust pipe 127 is provided on the wall of the clarification pipe 120 that is in contact with the gas phase space. That is, the clarification step of the present embodiment is a step of treating molten glass containing a clarifying agent that releases oxygen by a reduction reaction, and in the clarification step, at least a part of the inner wall contains a material containing a platinum group metal. Inside the processing apparatus, the molten glass is supplied so as to form a gas phase space above the surface of the molten glass. Further, in the clarification pipe 120, the molten glass flows in the longitudinal direction of the clarification pipe 120.

Further, a heat insulating material (for example, refractory bricks, fire-resistant heat insulating bricks, etc.) (not shown) may be provided outside the clarification pipe 120.

The electrodes 121a and 121b and the exhaust pipe 127 of the clarification pipe 120 are composed of the above-mentioned platinum group metal.

Furthermore, in the present embodiment, the case where the clarification tube 120 is composed of a platinum group metal is A specific example will be described, 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 through the clarification pipe 120 between the electrodes 121a and 121b, and the clarification pipe 120 is electrically heated. By the electric heating, the maximum temperature of the main body of the clarification pipe 120 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 transfer pipe 104 is heated to The temperature suitable for defoaming is, for example, 1600 ° C to 1720 ° C, more preferably 1620 ° C to 1720 ° C.

Further, by controlling the temperature of the molten glass by electric heating, the viscosity of the molten glass is adjusted, whereby 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) (not shown) may be provided on the electrodes 121a and 121b. The temperature measuring device measures the temperatures of the electrodes 121a and 121b, and outputs the measured 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, thereby controlling the temperature and flow rate of the molten glass passing through the clarification tube 120. The control device 123 is a computer including a CPU, a memory, and the like.

As shown in FIGS. 3 and 4, the electrode 121a may be provided with a flushing gas supplied to the vapor phase space 120a above the surface (liquid level) of the molten glass in contact with the gas phase space in the clarification tube 120. Gas supply pipe 124a. Similarly, the electrode 121b may be provided with a flushing gas supply pipe 124b for supplying the flushing gas to the gas phase space 120a above the surface (liquid surface) of the molten glass which is in contact with the gas phase space in the clarification pipe 120.

In the present embodiment, the flushing gas supply pipe 124a is connected to the flushing gas supply device 125a, and the flushing gas is supplied from the flushing gas supply device 125a to the gas phase space in the clarification pipe 120 via the flushing gas supply pipe 124a from the upstream side of the molten glass. 120a. Similarly, the flushing gas supply pipe 124b is connected to the flushing gas supply device 125b, and the flushing gas is supplied from the flushing gas supply device 125b via the flushing gas supply pipe 124b from the downstream side of the molten glass. The gas phase space 120a in the clarification tube 120 is supplied. Here, the upstream side and the downstream side mean the upstream side and the downstream side with respect to the center position of the gas phase space 120a in the direction in which the molten glass flows.

The amount of the flushing gas supplied from the flushing gas supply pipes 124a, 124b can be adjusted by adjusting the inner diameters of the flushing gas supply pipes 124a, 124b.

As the flushing gas, a gas inert to platinum and a gas having a lower reactivity with platinum group metal than oxygen can be used. Specifically, nitrogen (N ₂ ), a rare gas (for example, argon (Ar)), or the like can be used. In addition, in FIG. 4, as a flushing gas, nitrogen gas was mentioned as an example.

The flushing gas supply devices 125a and 125b are controlled by the control device 123 to adjust the supply amount and the supply pressure of the flushing gas.

An exhaust pipe 127 is provided in the wall of the clarification pipe 120 that is in contact with the gas phase space. The exhaust pipe 127 is disposed above the gas phase space 120a. The exhaust pipe 127 is preferably disposed between the upstream end portion and the downstream end portion in the flow direction of the molten glass in the clarification pipe 120. The exhaust pipe 127 may also have a shape protruding from the outer wall surface of the clarification pipe 120 toward the outer side in a chimney shape. The exhaust pipe 127 communicates the gas phase space 120a (refer to FIG. 4) with the outer space of the clarification pipe 120.

An oxygen concentration meter 128 is provided in the exhaust pipe 127. The oxygen concentration meter 128 measures the amount of gas passing through the exhaust pipe 127 and the oxygen concentration, and outputs the measurement signal to the control device 123. The oxygen concentration meter 128 is not particularly limited, and a known oxygen concentration meter can be used.

In the present embodiment, the release from the molten glass is controlled by adjusting, for example, the content of the clarifying agent, the temperature of the molten glass, the viscosity of the molten glass, the type of the glass raw material, the temperature history of the molten glass, or a combination thereof. The amount of oxygen. The control of the amount of oxygen released is carried out by adjusting at least one of the content of the clarifying agent, the temperature and viscosity of the molten glass, the type of the glass raw material, and the temperature history of the molten glass as described below.

(content of clarifying agent)

For example, if the content of the clarifying agent is increased, it is released into the gas phase space in the clarification tube 120. The amount of oxygen in 120a increases. On the other hand, if the content of the clarifying agent is reduced, the amount of oxygen released from the molten glass can be reduced.

Further, if the amount of the clarifying agent is too small, the bubbles remaining in the molten glass cannot be sufficiently reduced. Therefore, the content of the clarifying agent is, for example, 0.01 mol% to 0.3 mol%, preferably 0.03 mol% to 0.2 mol% or 0.01 to 0.5 mass%, in the case of tin oxide. That is, in the present embodiment, by adjusting the content of tin oxide of the glass substrate within a range of 0.01 mol% to 0.3 mol%, the oxygen concentration in the gas phase space is adjusted, thereby simultaneously reducing the generation of the clarifying agent. Bubbles and inhibition of the volatilization of platinum group metals.

(temperature and viscosity of molten glass)

The temperature of the molten glass can be adjusted by the temperature of the clarification tube 120. When the temperature of the molten glass is raised, the amount of oxygen released from the molten glass by the reduction reaction of the clarifying agent increases. If the temperature of the molten glass is low, the amount of oxygen generated is small, and the clarifying effect cannot be sufficiently obtained. Further, when the temperature of the molten glass is low, the viscosity of the molten glass increases, and the floating speed of the bubbles becomes slow. Therefore, the gas phase space 120a does not release the bubbles in the molten glass, and the clarification cannot be sufficiently performed.

On the other hand, if the temperature of the clarification pipe 120 is raised in order to raise the temperature of the molten glass, the problem of volatilization of the platinum group metal arises. Therefore, in order to suppress the volatilization of the platinum group metal and maintain the generation of bubbles, the temperature of the clarification pipe 120 is controlled, for example, at 1600 to 1750 °C. Thereby, the maximum temperature of the molten glass in the clarification pipe 120 is 1630 ° C to 1750 ° C, preferably 1650 ° C to 1750 ° C. At this time, the minimum viscosity of the molten glass is 200 to 800 poise. That is, in the present embodiment, by adjusting the maximum temperature of the clarification tube in the clarification step to a range of 1600 ° C to 1750 ° C, the oxygen concentration in the gas phase space is adjusted, thereby simultaneously reducing the bubbles generated by the clarifying agent and It inhibits the volatilization of platinum group metals.

(Type of glass raw material)

The amount of oxygen contained in the molten glass depends on the amount of oxide contained in the glass raw material. Variety. Therefore, by adjusting the type and amount of the glass raw material, specifically, by adjusting the amount of the oxide contained in the glass raw material, the amount of oxygen released into the gas phase space 120a in the clarification pipe 120 can be adjusted.

(temperature history of molten glass)

In the step before the clarification step (melting step), there is also a case where a reducing reaction for generating a clarifying agent releases oxygen from the molten glass, and therefore, the amount of oxygen released into the gas phase space 120a in the clarification pipe 120 is according to the clarification step. The amount of oxygen released from the molten glass in the previous step (melting step) varies. Therefore, the amount of oxygen released into the gas phase space 120a in the clarification pipe 120 can be adjusted by the melting temperature of the melting tank 101 or the like. Specifically, the lower the temperature in the melting step, the more the reduction reaction of the clarifying agent in the melting step is reduced, and the amount of oxygen released from the molten glass in the melting step is decreased, and therefore, the gas released into the clarification tube 120 is released. The amount of oxygen in the phase space 120a increases. However, if the melting temperature in the melting step is too low, there is a problem that the glass raw material cannot be sufficiently melted. If the melting temperature in the melting step is too high, the reduction reaction of the clarifying agent excessively increases, and as a result, the clarification step cannot be sufficiently obtained. The problem of clarifying the effect. Therefore, for example, by adjusting the maximum temperature of the molten glass temperature in the melting step to a range of 1500 ° C to 1610 ° C, the oxygen concentration in the gas phase space in the clarification pipe 120 is adjusted, thereby simultaneously achieving full melting and suppression of the glass raw material. Volatilization of the platinum group metal constituting the wall of the clarification tube 120.

Further, the amount of reduction reaction of the clarifying agent also changes depending on the rate of temperature rise of the molten glass after the melting step. Specifically, the faster the temperature rise rate of the molten glass after the melting step, the more the reduction reaction of the clarifying agent is promoted. However, if the temperature increase rate is too fast, the temperature of the delivery tube 104 and the clarification tube 120 becomes too high, resulting in melting of the delivery tube 104 and the clarification tube 120 or an increase in the volatilization of the platinum group metal of the delivery tube 104 and the clarification tube 120. The problem is that if the rate of temperature rise is too slow, there is a problem that the clarifying effect in the clarification step cannot be sufficiently obtained. Therefore, for example, when the temperature of the molten glass is raised to 1630 ° C or higher in the transfer pipe 104, the temperature increase rate of the molten glass in the transfer pipe is adjusted to be in the range of 3 ° C / min to 20 ° C / min. And adjusting the oxygen concentration in the gas phase space in the clarification tube 120 in which the temperature of the molten glass is raised to 1630 ° C or higher at the temperature increase rate, thereby simultaneously reducing the bubbles generated by the clarifying agent and suppressing the platinum group metal. Volatile. More preferably, the temperature of the molten glass is raised to a temperature of 1630 ° C or higher at a temperature increase rate of 3 ° C / min to 10 ° C / min to adjust the temperature increase rate and the temperature of the molten glass.

In order to suppress volatilization of the platinum group metal, it is preferred to adjust the oxygen concentration in the gas phase space 120a to 0 to 10%. Further, when the oxygen concentration in the gas phase space 120a is 0%, volatilization of the platinum group metal can be suppressed. Therefore, in terms of suppressing volatilization of the platinum group metal, the oxygen concentration is preferably 0%. However, in order to always make the oxygen concentration of the gas phase space 120a 0%, there is a problem that the content of the clarifying agent is extremely reduced or the cost is low. Therefore, in order to achieve clarification or low cost and to suppress volatilization of the platinum group metal, it is preferred to The oxygen concentration in the gas phase space 120a is adjusted so as to be 0.01% or more. Further, it is preferable to adjust the oxygen concentration in the gas phase space 120a to be 10% or less. In order to simultaneously suppress the volatilization of the platinum group metal and reduce the number of bubbles, it is preferably adjusted in a range of 0.1% or more and 3.0% or less, more preferably in a range of 0.1% or more and 1.0% or less. It is preferable to adjust in the range of 0.3% or more and 0.7% or less. Here, if the oxygen concentration in the gas phase space becomes too small, the oxygen concentration released from the molten glass to the gas phase space 120a increases due to the difference in oxygen concentration between the molten glass and the gas phase space, and the molten glass is excessively reduced. As a result, bubbles of sulfur oxides, nitrogen, or the like remain in the glass substrate after the formation. On the other hand, when the oxygen concentration is too large, the platinum group metal is promoted to volatilize, and the amount of the platinum group metal which is volatilized is increased. Further, if the oxygen concentration in the gas phase space is too large, the difference in oxygen concentration between the molten glass and the gas phase space becomes too small, and oxygen is hardly released from the molten glass to the gas phase space 120a, and as a result, bubbles such as oxygen remain in the glass substrate. The amount increases.

Further, in the present embodiment, by adjusting the temperature distribution of the molten glass, the flow rate of the molten glass, and the content of the clarifying agent, the position of the longitudinal direction of the clarification pipe 120 may be The distribution of the amount of oxygen released from the molten glass, the amount of oxygen released from the liquid surface (liquid level) of the molten glass in contact with the gas phase space to the gas phase space becomes the position of the flow direction of the molten glass which becomes the largest (The maximum position of oxygen release) is adjusted. Thereby, the distribution of the oxygen concentration in the gas phase space 120a can be controlled.

In the present embodiment, the position at which the oxygen release amount is the largest is separated from the flow direction of the molten glass in the flow direction of the molten glass having the highest temperature of the molten glass (the highest temperature position). Adjustment.

Furthermore, the higher the temperature, the more the volatilization of the platinum group metal is promoted. Therefore, the highest temperature position becomes a temperature condition in which the platinum group metal is most likely to be strongly volatilized. Further, the more the oxygen content is, the more volatile the platinum group metal is.

Therefore, the maximum position of the oxygen release amount is adjusted by separating the maximum position of the oxygen release amount from the highest temperature position in the flow direction of the molten glass, thereby contacting the gas phase space at the maximum position of the oxygen release amount. The amount of oxygen in the bubbles released from the surface (liquid level) of the molten glass flows to the highest temperature position. Therefore, the oxygen released from the defoaming of the molten glass flows into the highest temperature position where the platinum group metal is strongly volatilized from the wall of the clarification tube 120, and the volatilization of the platinum group metal is promoted as compared with the case at the highest temperature position. The volatilization of the platinum group metal is reduced. Therefore, it is possible to suppress the fact that the volatile matter of the platinum group metal is aggregated on the wall of the clarification pipe 120 to form an aggregate, and one part of the aggregate is desorbed in the form of fine particles, and foreign matter is mixed in the molten glass. This aspect will be described below.

Fig. 5 is a view showing the relationship between the position in the longitudinal direction of the clarification pipe 120 (the position in the flow direction of the molten glass) and the temperature at the upper end portion of the clarification pipe 120 and the amount of released oxygen. In Fig. 5, the horizontal axis represents the position in the flow direction of the molten glass, that is, the position in the longitudinal direction of the clarification pipe 120, and the vertical axis on the left side represents the temperature of the clarification pipe 120, and the vertical axis on the right side represents the oxygen release amount.

The solid line curve of Fig. 5 indicates the relationship between the position in the longitudinal direction and the temperature of the clarification pipe 120. In the clarification tube 120 of the present embodiment, the electrodes 121a and 121b have a flange shape. Moreover, since the heat dissipation function is high, the temperature in the vicinity of both ends of the clarification pipe 120 is likely to locally become a low temperature. Further, since the exhaust pipe 127 also protrudes from the clarification pipe 120, the temperature in the vicinity of the exhaust pipe 127 of the clarification pipe 120 is also likely to locally become a low temperature. Therefore, the temperature of the wall of the clarification pipe 120 changes depending on the position of the flow direction of the molten glass.

For example, the vicinity of both ends of the clarification pipe 120 (that is, the vicinity of the electrodes 121a and 121b) and the vicinity of the exhaust pipe 127 are regions which are low in temperature in the flow direction of the molten glass. On the other hand, the intermediate portion between the exhaust pipe 127 and the electrodes 121a and 121b is a region where the temperature is high in the position in the flow direction of the molten glass. The lowest temperature among the temperature distributions of the clarification pipe 120 is such that the clarification pipe 120 is electrically heated by the electrodes 121a and 121b, whereby the temperature is 1500 ° C or higher.

FIG. 5 shows an example of the temperature distribution of the clarification pipe 120. In this temperature distribution, the position where the temperature becomes the highest temperature T _max °C in the longitudinal direction (the highest temperature position) is represented by P.

Here, the highest temperature position is not limited to the position P, but has an allowable range around the position P. The allowable range of the highest temperature position is preferably a temperature range in the range of (T _max -20) ° C to T _max ° C, and further preferably a temperature range in the range of (T _max -10) ° C to T _max ° C, in particular A temperature region within the range of (T _max -5) °C~T _max °C. Thereafter, the highest temperature position having the allowable range is referred to as the highest temperature position range R. In Fig. 5, the temperature region in the range of (T _max -20) ° C to T _max ° C represents the highest temperature position range R.

On the other hand, the curve of the single-dot chain line of Fig. 5 indicates the relationship between the position in the longitudinal direction and the amount of oxygen released. If the molten glass is heated in the clarification pipe 120, oxygen is released into the molten glass by the reduction reaction of the clarifying agent in the molten glass. The release of this oxygen occurs sharply. The released oxygen is absorbed by the bubbles in the molten glass to expand the diameter of the bubbles (bubble growth), or to become bubbles in the molten glass, to absorb the existing bubbles in the molten glass, and to expand the diameter of the bubbles (bubble growth). Overcoming the viscosity of the molten glass, the surface (liquid level) of the molten glass that is in contact with the gas phase space starts to float. At this time, the amount of released oxygen released from the surface (liquid level) of the molten glass becomes the largest in the longitudinal direction of the clarification pipe 120. The position (the maximum oxygen release amount) A is adjusted so as to be spaced apart from the maximum temperature position range R in the longitudinal direction of the clarification pipe 120 (the flow direction of the molten glass). Specifically, it is preferable to adjust the oxygen release amount maximum position A so as to be located on the downstream side of the molten glass flow with respect to the highest temperature position range R.

In general, the higher the temperature of the molten glass, the more active the reduction reaction of the clarifying agent releasing oxygen, the higher the temperature of the molten glass, and the smaller the viscosity of the molten glass becomes, the higher the floating speed of the molten glass is. fast. Further, in the region where the temperature of the inner wall in contact with the molten glass is higher, the temperature of the molten glass becomes higher, and therefore, the release of the bubbles from the molten glass becomes more active. Therefore, in general, the maximum oxygen release amount position A substantially coincides with the maximum temperature position range R. However, in the present embodiment, the oxygen release amount maximum position A is adjusted so as to separate the oxygen release amount maximum position A from the maximum temperature position range R as described above.

Furthermore, the distribution of oxygen release amount and oxygen release amount can be obtained by computer simulation. For example, the upper limit and the lower limit of the amount of released oxygen and the distribution of the amount of released oxygen are defined in advance by experiments or the like. In order to suppress an increase in the oxygen concentration in the gas phase space due to an increase in the amount of oxygen released, the volatilization of the platinum group metal is promoted, and the upper limit of the amount of oxygen released is set; the bubbles in the molten glass are not melted in order to reduce the amount of released oxygen. The diameter does not increase, the floating speed of the bubble does not increase, and the defoaming effect is lowered, and the lower limit of the oxygen release amount is set. Further, in the distribution of the oxygen release amount suitable for efficient defoaming and suppression of volatilization of the platinum group metal, it is also defined between the above upper limit and lower limit. In order to achieve the distribution of the target oxygen release amount and the target oxygen release amount between the upper limit and the lower limit, the clarification condition is obtained by computer simulation. The clarification conditions include, for example, one of or a combination of the content of the clarifying agent, the temperature of the molten glass, the viscosity of the molten glass, the type of the glass raw material, and the temperature history of the molten glass.

In the computer simulation, for example, the clarification pipe 120, the heat insulating material (not shown) provided around it, and the electric heating of the clarification pipe 120 are patterned to perform heat conduction simulation, and Using the simulation result, that is, the calculation result of the temperature and temperature distribution of the molten glass, the distribution of the oxygen release amount and the release amount of the clarifier is determined by using the relationship between the predetermined temperature of the molten glass and the oxygen release amount of the clarifying agent. Thereby, the reduction reaction in the molten glass is simulated, and further, the oxygen is absorbed by the predetermined bubble in the molten glass to expand the diameter of the bubble, and the bubble floating up the diameter is simulated, thereby predicting the release of oxygen. Quantity and its distribution.

Further, the clarification pipe 120, the heat insulating material (not shown) provided around the clarification pipe, and the electric heating of the clarification pipe 120 are patterned to perform heat conduction simulation, and the calculated value of the temperature of the molten glass, which is the result of the simulation, is used. The corresponding relationship between the temperature of the molten glass and the amount of oxygen released from the clarifying agent determines the amount of oxygen released from the clarifying agent to generate bubbles of a specific size, thereby simulating the redox reaction in the molten glass, and further, by melting the glass The bubble predetermined in the bubble absorbs oxygen to expand the diameter of the bubble, and simulates the floating of the bubble whose diameter is enlarged, so that the maximum position A of the oxygen release amount can be predicted. In this case, the overall release of oxygen can also be predicted. Such simulation can be performed on a computer using a well-known simulation program or the like. Further, a computer simulation can be used to determine the clarification condition in such a manner that the maximum oxygen release amount position A and the maximum temperature position range R are spaced apart from each other in the flow direction of the molten glass.

Here, the maximum oxygen release amount position A can be performed by adjusting at least one of the temperature distribution of the molten glass flowing in the clarification pipe 120, the flow rate of the molten glass, and the content and type of the clarifying agent. The temperature distribution of the molten glass affects the amount of oxygen released from the clarifying agent, the start position of the release of oxygen, and the floating speed of the bubbles in the molten glass. The temperature distribution of the molten glass can be adjusted, for example, by the heating amount of the clarification pipe 120 when the heating electrode 121b is heated by electric conduction or by adjusting the current distribution on the outer circumference of the clarification pipe 120. Further, the temperature distribution of the molten glass can be adjusted, for example, by adjusting the amount of heat radiated from the outer circumference of the clarification pipe 120 to the outside. The adjustment of the amount of heat dissipation is performed by adjusting the heat insulating properties (thermal conductivity, etc.) or thermal resistance (= (thickness of the heat insulating material) / thermal conductivity) of the heat insulating material surrounding the outer periphery of the clarification pipe 120. This adjustment parameter can be changed, and the oxygen release can be adjusted using computer simulation. The maximum position A is output.

The flow rate of the molten glass affects the distance from the start position of the release of oxygen in the molten glass to the position at which the oxygen is released from the surface (liquid level) of the molten glass. The adjustment of the flow rate of the molten glass can be adjusted, for example, by the temperature (viscosity) of the molten glass in the vicinity of the outlet of the molten glass of the clarification pipe 120 or by the amount of extraction of the molten glass in the apparatus of the subsequent step such as the forming apparatus 200. This adjustment parameter can be changed, and the maximum position A of the oxygen release amount can be adjusted using a computer simulation.

When actually manufacturing a glass substrate, each value of the above-mentioned adjustment parameter (clarification condition) when the maximum position A of the oxygen release amount adjusted by the computer simulation becomes the desired position is used.

In the present embodiment, the clarification pipe 120 is provided with an exhaust pipe 127 that communicates with the atmosphere outside the gas phase space 120a and the clarification pipe 120. The arrangement position of the exhaust pipe 127 in the flow direction of the molten glass is preferably between the maximum oxygen release amount position A and the highest temperature position range R. By arranging the arrangement position of the exhaust pipe 127 in this way, a large amount of oxygen release amount A of the bubble containing oxygen is released from the surface (liquid level) of the molten glass which is in contact with the gas phase space, and is released from the surface. Before the oxygen in the bubble flows to the highest temperature position range R by the gas flow, most of the oxygen is released from the exhaust pipe 127 to the outside of the clarification pipe 120a. Therefore, the possibility that the oxygen in the bubble released from the maximum oxygen release amount A flows to the highest temperature position range R is low, and the volatilization of the platinum group metal at the highest temperature position range R can be lowered.

The oxygen release maximum position A and the exhaust pipe 127 are preferably located on the same side with respect to the highest temperature position range R (including the highest temperature position P). That is, the maximum oxygen release amount position A and the exhaust pipe 127 are preferably located on the upstream side of the highest temperature position range R in the flow direction of the molten glass, or both on the downstream side of the higher temperature position range R. In this case, the possibility that the oxygen in the bubble released from the maximum oxygen release amount A flows to the highest temperature position range R is low, and the volatilization of the platinum group metal at the highest temperature position range R can be lowered.

For example, from the upstream side of the molten glass, the highest temperature position range R, the maximum oxygen release amount position A, and the exhaust pipe 127 may be sequentially disposed. In this case, the oxygen released at the maximum position A of the oxygen release flows in the direction of the exhaust pipe 127, and therefore, the oxygen released at the maximum position A of the oxygen release amount is difficult to be at the highest temperature of the molten glass. The gas phase space 120a near the position range R flows in a gas atmosphere having a relatively high temperature.

More preferably, from the upstream side of the molten glass, the highest temperature position range R, the arrangement position of the exhaust pipe 127, and the maximum oxygen release amount position A are sequentially arranged.

Further, the position where the oxygen release amount is the maximum position A and the position at which the exhaust pipe 127 is disposed may be set to the same position in the flow direction of the molten glass. By setting the oxygen release amount maximum position A and the arrangement position of the exhaust pipe 127 to the same position in the flow direction of the molten glass, the maximum release position A of the oxygen release amount can be obtained via the exhaust pipe 127 located above. The oxygen released from the surface (liquid level) of the molten glass is released to the outside of the clarification pipe 120. In this case, the oxygen released from the surface of the molten glass at the maximum oxygen release amount A flows to the exhaust pipe 127 without being diffused in the gas phase space 120a, and does not flow in the gas phase space 120a. Therefore, the oxygen released from the surface (liquid level) of the molten glass at the maximum position A of the oxygen release amount is hardly used for the volatilization of the platinum group metal. Further, the position where the maximum oxygen release amount A and the position of the exhaust pipe 127 are the same in the flow direction of the molten glass means that the flow direction of the molten glass is at the center of the exhaust pipe 127. The region within the range of the diameter of the tube of the exhaust pipe 127 having the center has the maximum position A of the oxygen release amount. Further, when the allowable range of the maximum position A of the oxygen release amount is specified at the maximum position A of the oxygen release amount, the allowable range may be partially overlapped with the region within the range of the size of the tube diameter.

In the present embodiment, a flange-shaped member (for example, electrodes 121a, 121b, etc.) extending along the outer side of the clarification pipe 120 is provided on the outer circumference of the clarification pipe 120. The flange-shaped member is preferably a region outside the region between the position where the maximum amount of oxygen is released and the position of the exhaust pipe 127 in the flow direction of the molten glass. That is, the member of the flange shape is preferably compared The position of the maximum oxygen release amount A and the exhaust pipe 127 is located on the upstream side of the molten glass, or on the downstream side of the molten glass as compared with the position of the maximum oxygen release amount A and the exhaust pipe 127. Since the amount of heat radiation from the flange-shaped member to the outside is large, the temperature of the portion of the clarification pipe 120 where the flange shape is provided is locally lowered. In this case, the volatile matter of the platinum group metal in the gas phase space 120a is cooled and reduced by passing through the vicinity of the flange-shaped member, and the reduced platinum group metal is aggregated on the inner wall surface of the clarification pipe 120. Happening. Therefore, it is preferable that a member having a flange shape is disposed in a region between the position A of the maximum oxygen release amount and the position at which the exhaust pipe 127 is disposed.

Further, in the present embodiment, the amount of oxygen discharged from the exhaust pipe 127 provided above the gas phase space 120a is adjusted.

The amount of oxygen discharged from the exhaust pipe 127 can be calculated by measuring the oxygen concentration of the gas discharged from the exhaust pipe 127 by the oxygen concentration meter 128, and measuring the total amount of gas discharged from the exhaust pipe 127. The amount of oxygen discharged from the exhaust pipe 127 is adjusted based on the oxygen concentration measured by the oxygen concentration meter 128, whereby the amount of oxygen discharged can be adjusted.

For example, a suction device for sucking gas in the gas phase space 120a is provided in the exhaust pipe 127, and by adjusting the output of the suction device, the total amount of gas discharged from the exhaust pipe 127 can be adjusted. Further, as shown in Fig. 4, when the flushing gas is supplied to the vapor phase space 120a, the amount of the flushing gas supplied to the gas phase space 120a can be adjusted by controlling the suction device.

In the present embodiment, the oxygen concentration of the gas phase space 120a is adjusted by adjusting the amount of oxygen released from the molten glass and adjusting the amount of oxygen discharged from the exhaust pipe 127 provided in the upper portion of the gas phase space 120a. Adjust to be in a specific range. Thereby, the platinum group metal can be suppressed from being volatilized by oxidation, and the precipitation amount of the platinum group metal which is produced by the reduction of the volatilized platinum group metal can be reduced. When tin oxide is used as a clarifying agent, the temperature range in which tin oxide exhibits a clarifying effect is higher than that in the case of using As ₂ O ₃ or Sb ₂ O ₃ , and volatilization of a platinum group metal becomes remarkable. The effect of the embodiment is particularly effective.

Furthermore, in the present embodiment, the flushing gas is supplied from the flushing gas supply pipe 124a. The flushing gas supply pipe 124b is supplied to the gas phase space 120a in the clarification pipe 120, and the oxygen released from the molten glass in the clarification pipe 120 can be discharged to lower the oxygen concentration in the gas phase space 120a. At this time, the supply amount of the flushing gas is adjusted based on the oxygen concentration measured by the oxygen concentration meter 128, and the oxygen concentration in the gas phase space 120a is adjusted to a specific range. Thereby, the platinum group metal can be suppressed from being volatilized by oxidation, and the precipitation amount of the platinum group metal which is produced by the reduction of the volatilized platinum group metal can be reduced.

In the present embodiment, the amount of gas discharged from the exhaust pipe 127 is measured and the oxygen concentration is measured by the oxygen concentration meter 128 so that the amount of oxygen discharged from the exhaust pipe 127 (= the total amount of gas discharged from the exhaust pipe 127) The amount of supply of the flushing gas is adjusted such that the amount x oxygen concentration is in a specific range. That is, the signal from the total exhaust amount of the exhaust pipe 127 and the oxygen concentration in the exhaust gas measured by the oxygen concentration meter 128 is output to the control device 123, and the control device 123 controls based on the signal from the oxygen concentration meter 128. The gas supply devices 125a and 125b are flushed to adjust the supply amount and supply pressure of the flushing gas.

In the present embodiment, the amount of oxygen released from the molten glass in the clarification pipe 120 is adjusted so that the upstream side of the molten glass is more than the downstream side. Therefore, it is preferable to supply the upstream side from the molten glass. The flushing gas is more than the flushing gas supplied from the downstream side of the molten glass. That is, it is preferable that the amount of the flushing gas supplied from the flushing gas supply pipe 124a is larger than the amount of the flushing gas supplied from the flushing gas supply pipe 124b. By making the amount of the flushing gas supplied from the flushing gas supply pipe 124a larger than the amount of the flushing gas supplied from the flushing gas supply pipe 124b, it is possible to more efficiently dilute and discharge the oxygen released from the molten glass by the flushing gas.

Further, a suction device for sucking the gas in the gas phase space 120a may be provided in the exhaust pipe 127. By the suction device, the exhaust pipe 127 side is decompressed (for example, by about 10 Pa under pressure in the gas phase space 120a), whereby the oxygen in the gas phase space 120a can be efficiently discharged and rinsed. gas. Further, the amount of the flushing gas supplied to the gas phase space 120a can also be adjusted by controlling the suction means.

(Configuration of the clarification tube of the second embodiment)

Next, the configuration of the clarification tube 120 of the second embodiment will be described in detail. Further, the clarification device includes an exhaust pipe (vent pipe) 127, electrodes 121a and 121b, and a refractory protective layer and a refractory brick (not shown) which surround the outer periphery of the clarification pipe 120, in addition to the clarification pipe 120. FIG. 6 is an external view mainly showing the clarification pipe 120. Fig. 7 is a view showing an example of a cross-sectional view of the inside of the clarification pipe 120 and a temperature distribution of the clarification pipe.

An exhaust pipe (vent pipe) 127 and a pair of electrodes 121a and 121b are attached to the clarification pipe 120. Inside the clarification tube 120, a clarification step of the molten glass containing the clarifying agent for releasing oxygen by the reduction reaction is carried out. In the clarification step, the molten glass is supplied to the inside of the clarification pipe 120 in which at least a part of the inner wall contains the material containing the platinum group metal, and the clarification pipe is formed in such a manner that a vapor phase space is formed on the upper surface of the molten glass. In 120, the molten glass flows in the direction along the surface of the molten glass which is in contact with the gas phase space, specifically, in the longitudinal direction of the clarification pipe 120. The gas phase space is formed along the flow direction of the molten glass. At least a portion of the inner wall surrounding the gas phase space is composed of a material containing a platinum group metal. In the present embodiment, the entire wall surrounding the gas phase space is made of a material containing a platinum group metal.

The exhaust pipe (vent pipe) 127 is located in the middle of the flow direction of the molten glass, and is disposed on the inner wall in contact with the gas phase space, so that the gas phase space communicates with the atmosphere on the outer side of the clarification pipe 120. The exhaust pipe (vent pipe) 127 is preferably formed of a platinum group metal similarly to the clarification pipe 120. Regarding the exhaust pipe (vent pipe) 127, since the temperature of the exhaust pipe (vent pipe) 127 is liable to lower due to the heat dissipation function, a heating mechanism for heating the exhaust pipe (vent pipe) 127 may be provided.

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

Inside the clarification pipe 120, bubbles containing CO ₂ or SO ₂ contained in the molten glass are removed by a redox reaction of a clarifying agent added to the molten glass, for example, tin oxide. Specifically, first, the temperature of the molten glass is raised to reduce the clarifying agent, thereby generating oxygen bubbles in the molten glass. The bubbles containing the gas components such as CO ₂ , N ₂ , and SO ₂ contained in the molten glass absorb the oxygen generated by the reduction reaction of the clarifying agent. The bubble that absorbs oxygen and the diameter of the bubble expands (grows) floats to the surface (liquid level) of the molten glass that is in contact with the gas phase space, and the bubble is released, that is, the crack disappears. The gas contained in the bubble after disappearing is released into the gas phase space, and is discharged to the outside of the clarification pipe 120 through the exhaust pipe 127. In turn, the temperature of the molten glass is lowered to oxidize the reduced clarifying agent. Thereby, the oxygen of the bubbles remaining in the molten glass is dissolved in the molten glass and absorbed (absorption treatment). Thereby, the remaining bubbles become smaller and disappear. Thus, the bubbles contained in the molten glass are removed by the redox reaction of the clarifying agent.

Although not shown, a refractory protective layer is provided on the outer wall surface of the clarification pipe 120. A refractory brick is further disposed on the outer side of the refractory protective layer. The refractory bricks are placed on abutment (not shown).

In such a clarification pipe 120, the temperature of the wall of the clarification pipe 120 which is in contact with the gas phase space has a temperature distribution in the flow direction of the molten glass. Further, when the defoaming of the molten glass is performed, the amount of the bubbles released from the surface (liquid surface) of the molten glass which is in contact with the gas phase space to the gas phase space is maximized in the flow direction of the molten glass. The maximum position of the bubble release amount is adjusted such that the maximum position of the bubble release amount and the highest temperature position of the temperature distribution in the flow direction of the molten glass are spaced apart from each other in the flow direction of the molten glass.

Further, in the case of a platinum group metal, the higher the temperature of the inner wall, the more the volatilization is promoted. Therefore, the highest temperature position becomes a temperature condition in which the platinum group metal is most likely to be strongly volatilized. Further, the more the oxygen content is, the more volatile the platinum group metal is.

Therefore, the maximum position of the bubble release amount is adjusted such that the maximum bubble discharge amount position and the maximum temperature position are spaced apart from each other in the flow direction of the molten glass, and the maximum amount of bubble discharge is from the molten glass. The amount of oxygen in the bubble released from the surface (liquid level) flows to the highest temperature position. Therefore, the oxygen released from the defoaming of the molten glass flows into the highest temperature position where the platinum group metal is strongly volatilized from the wall of the clarification tube 120, and the volatilization of the platinum group metal is promoted as compared with the case at the highest temperature position. The volatilization of the platinum group metal is reduced. Therefore, it is possible to suppress the fact that the volatile matter of the platinum group metal is aggregated on the wall of the clarification pipe 120 to form an aggregate, and one part of the aggregate is desorbed in the form of fine particles, and foreign matter is mixed in the molten glass. This point will be described below.

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

In the clarification pipe 120 of the present embodiment, the electrode (flange member) 121a and 121b having a flange shape have a high heat dissipation function, so that the wall near the both ends of the clarification pipe 120 is melted along the edge of the inner wall. The inner wall of the periphery of the flow direction of the glass (the X direction: the longitudinal direction of the clarification pipe 120) is likely to be a low temperature as compared with the portion of the inner wall (the inner wall of the clarification pipe 120 that is in contact with the gas phase space). Moreover, since the exhaust pipe 127 also protrudes from the clarification pipe 120, the inner wall of the clarification pipe 120 in contact with the gas phase space in the vicinity of the exhaust pipe 127, and the inner wall of the inner wall in the X direction (the gas) The portion of the inner wall of the clarification pipe 120 that is in contact with the phase space is also liable to become a low temperature. Therefore, the temperature of the inner wall of the clarification pipe 120 in contact with the gas phase space has a temperature distribution in the X direction. The vicinity of both ends of the clarification pipe 120, that is, the inner wall near the end of the pair of electrodes 121a and 121b and the wall in the vicinity of the exhaust pipe 127 become a low temperature region having a lower temperature in the X direction, the exhaust pipe 127 and the electrode 121a, The middle portion between 121b becomes a high temperature region in the X direction. Even if the temperature in the temperature distribution of the inner wall is the lowest temperature, the clarification pipe 120 is electrically heated by the electrodes 121a and 121b, thereby achieving a high temperature, for example, a temperature of 1500 ° C or higher. Therefore, in the gas phase space, the platinum group metal constituting the clarification tube 120 is volatilized, and the volatiles of the platinum group metal are present. Fig. 7 shows an example of a temperature distribution. In this temperature distribution, the position in the X direction in which the temperature is the highest temperature T _max °C is represented by P.

Here, the highest temperature position of the temperature distribution is not limited to the position P, but has an allowable range around the position P. The allowable range of the highest temperature position is preferably a temperature range in the range of (T _max -20) ° C to T _max ° C, and further preferably a temperature range in the range of (T _max -10) ° C to T _max ° C, in particular A temperature region within the range of (T _max -5) °C~T _max °C. Thereafter, the highest temperature position having the allowable range is referred to as the highest temperature position R.

On the other hand, the molten glass is heated in the clarification pipe 120, and the clarifying agent undergoes a reduction reaction to start releasing oxygen into the molten glass. The release of this oxygen occurs sharply. The released oxygen is absorbed by the bubbles in the molten glass, so that the diameter of the bubbles is enlarged (bubbles are grown), or bubbles in the molten glass are absorbed to absorb the existing bubbles in the molten glass, and the diameter of the bubbles is expanded (growth) to overcome The viscosity of the molten glass starts to float toward the surface (liquid level) of the molten glass that is in contact with the gas phase space. At this time, the maximum amount of bubble release amount A in the longitudinal direction of the clarification pipe 120 from the surface (liquid level) of the molten glass is maximized, and the maximum temperature position R is separated from the above-mentioned maximum temperature position R in the X direction. . Specifically, it is preferably located on the downstream side of the flow of the molten glass with respect to the highest temperature position R.

In this manner, the bubble discharge amount maximum position A is adjusted such that the bubble discharge amount maximum position A is spaced apart from the highest temperature position R.

The maximum amount of bubble release A can be determined experimentally or by computer simulation. Calculated by prediction. In the case of computer simulation, the clarification pipe 120, the refractory protective layer (not shown) and the refractory bricks provided around the clarification pipe 120, and the heating source manufactured by the electric heating of the clarification pipe 120 are patterned to perform heat conduction simulation. And using the simulation result, that is, the calculated value of the temperature of the molten glass, using the corresponding relationship between the temperature of the predetermined molten glass and the amount of released oxygen of the clarifying agent, determining the amount of oxygen released from the clarifying agent to make the bubble of a specific size Produced to simulate the redox reaction in the molten glass, and further, the bubble is expanded by the predetermined bubble in the molten glass, and the diameter of the bubble is expanded, and the bubble floating up is expanded to simulate bubble release. The maximum position A. In this case, the release amount of the bubbles can also be predicted. Such simulation can be performed on a computer using a well-known simulation program or the like. Further, a computer simulation can be used to determine the clarification condition such that the bubble discharge maximum position A and the maximum temperature position R are spaced apart in the X direction.

Here, the bubble discharge maximum position A is preferably performed by adjusting at least one of the temperature distribution of the molten glass flowing in the clarification pipe 120 and the flow rate of the molten glass. The temperature distribution of the molten glass affects the amount of oxygen released from the clarifying agent, the start position of the release of oxygen, and the floating speed of the bubbles in the molten glass. The temperature distribution of the molten glass can be adjusted, for example, by the heating amount of the clarification pipe 120 when the heating electrode 121b is electrically heated, or by adjusting the current distribution on the outer circumference of the clarification pipe 120. Further, the temperature distribution of the molten glass can be adjusted, for example, by adjusting the amount of heat radiated from the outer circumference of the clarification pipe 120 to the outside. The amount of heat dissipation is adjusted by adjusting the thermal insulation properties (thermal conductivity, etc.) or thermal resistance (= (thickness of refractory protective layer or refractory brick) / thermal conductivity) of the refractory protective layer or refractory brick surrounding the outer circumference of the clarification pipe 120. get on. This adjustment parameter can be changed, and the maximum position A of the bubble release amount can be adjusted using a computer simulation.

The flow rate of the molten glass affects the distance from the start position of the oxygen in the molten glass to the position at which the oxygen is released from the surface (liquid level) of the molten glass in contact with the gas phase. The flow rate of the molten glass can be adjusted, for example, by the temperature (viscosity) of the molten glass near the outlet of the molten glass of the clarification pipe 120 or by the forming apparatus 200 or the like. The amount of molten glass extracted by the apparatus of the subsequent step is adjusted. This adjustment parameter can be changed, and the maximum position A of the bubble release amount can be adjusted using a computer simulation.

In actual production of the glass substrate, each value of the above-mentioned adjustment parameter (clarification condition) when the bubble discharge maximum position A adjusted by the computer simulation becomes the desired position is used.

In the present embodiment, the clarification pipe 120 is provided with an exhaust pipe 127 that communicates with the atmosphere outside the gas phase space and the clarification pipe 120. At this time, the arrangement position of the exhaust pipe 127 in the X direction is preferably a bubble discharge. Between the maximum position A and the highest temperature position R. By arranging the arrangement position of the exhaust pipe 127 in this way, the maximum amount of bubble release amount released from the surface of the molten glass which is in contact with the gas phase space by a large amount of oxygen-containing gas bubbles is in the bubble released from the surface. Before the oxygen flows to the bubble discharge amount maximum position A by the gas flow, most of the oxygen is released from the exhaust pipe 127 to the outside of the clarification pipe 120a. Therefore, the possibility that the oxygen in the bubble released from the bubble discharge maximum position A flows to the highest temperature position R is low, and the volatilization of the platinum group metal at the highest temperature position R can be lowered.

The arrangement position of the exhaust pipe 127 at the maximum bubble discharge amount A and the X direction is preferably the same on the same side in the X direction with respect to the highest temperature position R of the temperature distribution of the wall of the clarification pipe 120. In this case, the possibility that the oxygen in the bubble released from the bubble discharge maximum position A flows to the highest temperature position R is also low, and the volatilization of the platinum group metal at the highest temperature position R can be lowered.

The maximum temperature position R, the arrangement position of the exhaust pipe 127, and the bubble discharge maximum position A are preferably the highest temperature position R from the upstream side in the X direction, the arrangement position of the exhaust pipe 127, and the bubble discharge. The maximum position A.

In the present embodiment, a flange-shaped member (flange member) including the electrodes 121a and 121b extending along the outer side of the clarification pipe 120 is provided on the outer circumference of the clarification pipe 120, and the arrangement position of the flange-shaped member in the X direction is higher. It is preferable that the region in the longitudinal direction is outside the region between the position A where the bubble discharge amount is maximum and the position at which the exhaust pipe 127 is disposed. The member of the flange shape has a large amount of heat dissipation to the outside of the exhaust pipe 127 due to its shape, and therefore, In the vicinity of the inner wall of the clarification pipe 120 of the flange-shaped member, the temperature is easily locally lowered. In this case, the volatile matter of the platinum group metal in the gas phase space is cooled by the vicinity of the inner wall of the member provided with the above-mentioned flange shape, and is agglomerated on the inner wall of the clarification pipe 120. Therefore, the arrangement position of the member having the flange shape is preferably a region outside the region between the position A of the bubble discharge amount maximum and the position where the exhaust pipe 127 is disposed.

In the present embodiment, the highest temperature position R, the arrangement position of the exhaust pipe 127, and the bubble discharge amount maximum position A are sequentially the highest temperature position R from the upstream side in the X direction, the arrangement position of the exhaust pipe 127, And the bubble discharge amount maximum position A, but the bubble discharge amount maximum position A and the arrangement position of the exhaust pipe 127 are located on the same side in the X direction (the longitudinal direction of the clarification pipe 120) based on the highest temperature position R. The maximum temperature position R, the arrangement position of the exhaust pipe 127, and the bubble discharge maximum position A are not limited. For example, it may be from the upstream side in the X direction in which the molten glass flows, in order to the highest temperature position R, the bubble discharge maximum position A, and the arrangement position of the exhaust pipe 127. In this case, the oxygen released at the maximum bubble discharge position A flows in the direction of the exhaust pipe 127, so that the oxygen released at the maximum bubble discharge position A is difficult to be at the highest temperature position of the molten glass. A gas atmosphere having a relatively high temperature in the gas phase space near R flows.

Further, the position at which the bubble discharge amount is maximum A and the position at which the exhaust pipe 127 is disposed may be the same position in the X direction. By setting the bubble discharge amount maximum position A and the arrangement position of the exhaust pipe 127 to the same position in the X direction, the oxygen released from the surface (liquid level) of the molten glass at the maximum bubble release amount A is obtained. The gas is discharged to the outside of the clarification pipe 120 via the exhaust pipe 127 located above, and therefore, the oxygen flows to the exhaust pipe 127 without being diffused in the gas phase space, and does not flow in the gas phase space. Therefore, the oxygen released from the surface (liquid level) of the molten glass at the maximum position A of the bubble release amount is hardly used for volatilization of the platinum group metal. In addition, the position where the bubble discharge maximum position A and the exhaust pipe 127 are disposed at the same position in the X direction means the center position of the tube in the X direction with respect to the exhaust pipe 127, and the exhaust pipe The area within the range of the diameter of the tube of 127 (the area along the X direction) has bubbles The maximum amount of release A is. Further, when the allowable range of the bubble discharge amount maximum position A is defined at the bubble discharge amount maximum position A, the allowable range may be partially overlapped with the region within the range of the tube diameter.

Even if the temperature of the inner wall of the clarification pipe 120 in contact with the gas phase space of the clarification pipe 120 is 1500 ° C or higher, in the present embodiment, since the volatilization of the platinum group metal is reduced and the agglomeration of the volatiles of the platinum group metal is suppressed, the present invention is The effects of the embodiments have also become remarkable.

Further, in any of the first embodiment and the second embodiment, the vapor pressure of the platinum group metal in the gas phase space is preferably adjusted to suppress volatilization of the platinum group metal. The vapor pressure of the platinum group metal in the gas phase space is preferably from 0.1 Pa to 15 Pa, preferably from 3 Pa to 10 Pa, in terms of suppressing volatilization and agglomeration of the platinum group metal.

Further, in the first embodiment and the second embodiment, the apparatus for treating the molten glass containing the clarifying agent that releases oxygen by the reduction reaction has been described using the clarification pipe 120, but is not necessarily limited to the clarification pipe. 120. The portion which is treated as a molten glass having a gas phase space and containing a clarifying agent which releases oxygen by a reduction reaction is not limited to the clarification tube.

(Experimental Example 1)

In order to confirm the effect of the first embodiment, the clarification pipe 120 of the first embodiment shown in Fig. 3 was used, and the clarification of the molten glass for one hour was carried out using tin oxide as a clarifying agent, and the above-described embodiment was adjusted. After this clarification, sheet glass of 2270 mm × 2000 mm and thickness of 0.5 mm was formed, and 100 glass substrates were produced.

At this time, in Examples 1 to 8, the oxygen release amount from the molten glass, the supply amount of the flushing gas (N ₂ ), and the suction amount of the exhaust pipe 127 were adjusted, and the oxygen concentration in the gas phase space 120a was adjusted. Range of 0.1% to 3%. The adjustment was as follows: the oxygen concentration in Example 1 was 0%, the oxygen concentration in Example 2 was 0.1%, the oxygen concentration in Example 3 was 0.3%, and the oxygen concentration in Example 4 was 0.5%. The oxygen concentration was 0.7%, the oxygen concentration of Example 6 was 1%, the oxygen concentration of Example 7 was 2%, and the oxygen concentration of Example 8 was 3%.

As a prior example, the adjustment of the oxygen concentration in the gas phase space 120a is not performed. At this time, the oxygen concentration was 21%. The platinum agglomerates of the glass substrate were examined by visual inspection, and the number of platinum agglomerates per 100 glass substrates was evaluated. Regarding the platinum agglomerate, a platinum foreign matter to be inspected is set to have an aspect ratio of 100 or more and a maximum length of 100 μm or more.

As a result of the above examination, the number of platinum agglomerates was 0.10 / m ³ , 1.2 / m ³ , 3.9 / m ³ , 7.4 / m ³ , 12 / m ^{3 in} the order of Examples 1 to 8. , 19 / m ³ , 57 / m ³ , 113 / m ³ . These results are less than the previous foreign matter amount of 4306 / m ³ . From this, it can be seen that Examples 1 to 8 can reduce the amount of foreign matter as compared with the previous examples. Further, the number of the bubbles remaining in the glass substrate as the defects of Examples 1 to 8 was 34/m ³ , 28 / m ³ , 19 / m ³ , 13 in the order of Examples 1 to 8. /m ³ , 11 / m ³ , 15 / m ³ , 88 / m ³ , 255 / m ³ . These results are less than the previous foreign matter amount of 19,201 / m ³ . Furthermore, the composition of the glass of the glass substrate is 66.6 mol% of SiO ₂ , 10.6 mol% of Al ₂ O ₃ , 11.0 mol % of B ₂ O ₃ , and the total amount of MgO, CaO, SrO and BaO is 11.4 Molar%, 0.15 mol% of SnO ₂ , 0.05% of Fe ₂ O ₃ , a total amount of alkali metal oxide of 0.2 mol%, a strain point of 660 ° C, and a viscosity of 10 ^2.5 poise of molten glass The temperature is 1570 °C.

Fig. 8 is a view showing the results of Examples 1 to 8 of Experimental Example 1. In Fig. 8, the results of other experimental examples are also plotted.

(Experimental Example 2)

In order to confirm the effect of the second embodiment, the clarification pipe 120 of the second embodiment shown in Fig. 6 was used, and the clarification of the molten glass for one hour was carried out using tin oxide as a clarifying agent, and the above-described embodiment was adjusted. Specifically, the temperature distribution of the molten glass is adjusted to change the bubble discharge maximum position A. After this clarification, sheet glass of 2270 mm × 2000 mm and thickness of 0.5 mm was formed, and 100 glass substrates were produced. At this time, in the embodiment 9, the maximum temperature position of the bubble release amount and the highest temperature position of the temperature distribution are in the flow of the molten glass. The temperature of the molten glass is adjusted in a moving manner. The position of the exhaust pipe 127 is set between the maximum bubble discharge amount position A in the flow direction of the molten glass and the highest temperature of the temperature distribution.

As a prior example, the adjustment of the maximum temperature of the bubble release amount maximum position A and the temperature distribution is not performed. In this case, the bubble discharge maximum position A substantially coincides with the maximum temperature of the temperature distribution.

The platinum agglomerates of the glass substrate were examined by visual inspection, and the number of platinum agglomerates per 100 glass substrates was evaluated.

In the platinum agglomerate, a platinum foreign matter having an aspect ratio of 100 or more and a maximum length of 100 μm or more is used as a foreign matter to be inspected.

As a result of the above inspection, in the case of Example 9, the number of platinum agglomerates generated by the platinum mixed in the glass substrate was 1/3 as compared with the previous example in which the bubble discharge maximum position A and the highest temperature of the temperature distribution were the same. the following. The number of bubbles remaining in the glass substrate as a defect in Example 9 was 300/m ³ or less. Thereby, in Example 9, it was confirmed that the number of platinum aggregates was reduced as compared with the previous example. Furthermore, the composition of the glass of the glass substrate is 66.6 mol% of SiO ₂ , 10.6 mol% of Al ₂ O ₃ , 11.0 mol % of B ₂ O ₃ , and the total amount of MgO, CaO, SrO and BaO is 11.4 Molar%, 0.15 mol% of SnO ₂ , 0.05% of Fe ₂ O ₃ , a total amount of alkali metal oxide of 0.2 mol%, a strain point of 660 ° C, and a viscosity of 10 ^2.5 poise of molten glass The temperature is 1570 °C.

(Experimental Example 3)

With respect to Experimental Example 1, the composition of the glass of the glass substrate was changed to 70 mol% of SiO ₂ , 12.9 mol% of Al ₂ O ₃ , 2.5 mol% of B ₂ O ₃ , 3.5 mol% of MgO, A glass substrate was produced in the same manner as in Example 1 except that 6 mol% of CaO, 1.5 mol% of SrO, 3.5 mol% of BaO, and 0.1 mol% of SnO ₂ were used. At this time, the strain point of the glass substrate was 745 °C.

As a result, it was found that platinum agglomeration can be reduced as in Experimental Example 1 as compared with the previous example. The number of objects.

(Experimental Example 4)

With respect to Experimental Example 2, the composition of the glass of the glass substrate was changed to 70 mol% of SiO ₂ , 12.9 mol% of Al ₂ O ₃ , 2.5 mol% of B ₂ O ₃ , and 3.5 mol% of MgO. A glass substrate was produced in the same manner as in Example 2 except that 6 mol% of CaO, 1.5 mol% of SrO, 3.5 mol% of BaO, and 0.1 mol% of SnO ₂ were used. At this time, the strain point of the glass substrate was 745 °C.

As a result, it was found that the number of platinum aggregates can be reduced as in Experimental Example 2 as compared with the previous examples.

In the above, the glass substrate manufacturing method and the glass substrate manufacturing apparatus of the present invention are described in detail. However, 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. In the above description, the clarification pipe has been described as an example of the treatment device. However, the present invention is not limited thereto, and the present invention may be applied to a melting tank, a stirring tank, a molding apparatus, a conveying pipe, and a supply pipe.

104‧‧‧Transport

105‧‧‧ delivery tube

120‧‧‧Clarification tank

120a‧‧‧ gas phase space

121a‧‧‧electrode

121b‧‧‧electrode

124a‧‧‧ flushing gas supply pipe

124b‧‧‧ flushing gas supply pipe

127‧‧‧Exhaust pipe

MG‧‧‧ molten glass

Claims (21)

A method for producing a glass substrate, comprising: a step of treating a molten glass containing a clarifying agent for releasing oxygen by a reduction reaction using a treatment device comprising at least a part of an inner wall containing a material containing a platinum group metal; In the step of treating the molten glass, in the processing apparatus, the molten glass flows in a direction of a surface of the molten glass in contact with the gas phase, and is released from the molten glass by adjustment The amount of oxygen in the gas phase space formed by the inner wall of the processing device and the surface of the molten glass is controlled to control the oxygen concentration of the gas phase space, thereby suppressing the volatilization of the platinum group metal, and the release amount of the oxygen is determined according to The position of the flow direction of the molten glass is changed, and the oxygen concentration in the flow direction of the molten glass in the gas phase space is adjusted by adjusting the distribution of the oxygen release amount at the position of the flow direction of the molten glass. The distribution is such that the volatilization of the platinum group metal described above is inhibited. A method for producing a glass substrate, which comprises treating a molten glass with a treatment device for treating molten glass, and treating the molten glass containing a clarifying agent that releases oxygen by a reduction reaction, on the surface of the molten glass The molten glass is supplied to the inside of the processing apparatus including at least a part of the inner wall including the material of the platinum group metal, and the molten glass is placed along the molten glass and the gas in the processing apparatus. Flow in the direction of the surface in contact with the phase space, Controlling the oxygen concentration in the gas phase space by adjusting the amount of oxygen released from the molten glass, thereby suppressing the volatilization of the platinum group metal, and the amount of the oxygen released varies according to the position of the flow direction of the molten glass. Adjusting the distribution of the oxygen concentration in the flow direction of the molten glass in the gas phase space by adjusting the distribution of the oxygen release amount at the position of the flow direction of the molten glass, thereby suppressing the platinum group metal Volatile. A method for producing a glass substrate, comprising: a step of treating a molten glass containing a clarifying agent for releasing oxygen by a reduction reaction using a treatment device comprising at least a part of an inner wall containing a material containing a platinum group metal; In the step of treating the molten glass, in the processing apparatus, the molten glass flows in a direction of a surface of the molten glass in contact with the gas phase, and is released from the molten glass by adjustment The amount of oxygen in the gas phase space formed by the inner wall of the processing device and the surface of the molten glass is controlled to control the oxygen concentration in the gas phase space, thereby suppressing the volatilization of the platinum group metal, and the gas phase in the processing device The temperature of the inner wall of the spatial contact has a temperature distribution along the flow direction of the molten glass, and in the treatment of the molten glass, the release amount of the bubbles released from the surface of the molten glass to the gas phase space is maximized. The maximum position of the bubble release amount in the flow direction of the molten glass and the flow side of the molten glass The position spaced above the highest temperature of the temperature distribution in the direction of flow of the molten glass above the bubble release amount adjusted maximum position. A method for producing a glass substrate, which comprises treating a molten glass with a treatment device for treating molten glass, and performing a molten glass containing a clarifying agent for releasing oxygen by a reduction reaction. In the processing apparatus, the molten glass is supplied to the inside of the processing apparatus in which at least a part of the inner wall contains a material containing a platinum group metal, so that the vapor-phase space is formed on the upper surface of the surface of the molten glass. The molten glass flows along a direction of the surface of the molten glass that is in spatial contact with the gas phase, and the oxygen concentration released from the molten glass is adjusted to control the oxygen concentration in the gas phase space, thereby suppressing the platinum group metal. Volatilizing, the temperature of the inner wall in contact with the gas phase space in the treatment device has a temperature distribution along the flow direction of the molten glass, and in the treatment of the molten glass, the surface of the molten glass is released to the gas phase space The maximum amount of bubble release in the flow direction of the molten glass in which the amount of bubbles is maximized is the highest temperature position of the temperature distribution in the flow direction of the molten glass in the flow direction of the molten glass. The mode adjusts the maximum position of the above bubble release amount. The method for producing a glass substrate according to any one of claims 1 to 4, wherein the glass substrate contains 0.01 mol% to 0.3 mol% of tin oxide, and the amount of oxygen released from the molten glass is oxidized by the above The tin content is adjusted. The method for producing a glass substrate according to any one of claims 1 to 4, wherein the oxygen concentration is controlled by further adjusting an amount of oxygen discharged from the gas phase space to the outside of the processing device. The method for producing a glass substrate according to any one of claims 1 to 4, wherein the gas having the adjusted supply amount is supplied to the gas phase space such that the oxygen concentration is within a specific range. The method for producing a glass substrate according to claim 1 or 2, wherein the temperature of the processing device is The degree of change in the flow direction of the molten glass is determined by computer simulation using a computer simulation to increase the amount of oxygen released in the flow direction of the molten glass. The maximum position is determined by the manner in which the temperature of the processing device is the highest. A method for producing a glass substrate, which is characterized in that a molten glass is treated by a treatment device for treating molten glass, and includes a step of melting a glass raw material to produce molten glass, which comprises containing oxygen released by a reduction reaction. a step of treating the molten glass of the clarifying agent; in the step of treating the molten glass, supplying the molten glass to the inner wall at least a part of the inner wall to form a gas phase space on the surface of the molten glass a processing device formed of a metal material, and in the processing device, the molten glass flows in a direction of a surface of the molten glass that is in contact with the gas phase space, and the processing device is in contact with the gas phase space The temperature of the wall has a temperature distribution along the flow direction of the molten glass, and in the treatment of the molten glass, the release amount of the bubble released from the surface of the molten glass in contact with the gas phase space to the gas phase space The maximum position of the bubble release amount in the flow direction of the molten glass which is the largest Spaced above the highest temperature of the temperature profile of the position of the flow direction of said molten glass to the flow direction of the molten glass above the bubble release amount adjusted maximum position. The method for producing a glass substrate according to any one of claims 1 to 4, wherein the processing device comprises at least a part of the inner wall made of a material containing a platinum group metal and at least defoaming the molten glass. Clarifying the tube, and the above step of treating the molten glass is carried out in the above-mentioned clarification tube The clarification step of the defoaming treatment of the defoaming of the above molten glass. The method for producing a glass substrate according to any one of claims 3, 4 and 9, wherein the maximum position of the bubble release amount is predicted by computer simulation, and the computer simulation is used to make the bubble discharge maximum position and the above The processing conditions are determined such that the highest temperature position is spaced apart in the flow direction of the molten glass. The method for producing a glass substrate according to any one of claims 3, 4 and 9, wherein the adjustment of the maximum position of the bubble release amount is performed by adjusting at least one of a temperature distribution of the molten glass and a flow rate of the molten glass. And proceed. The method for producing a glass substrate according to any one of claims 3, 4 and 9, wherein the bubble discharge amount maximum position is located on a downstream side of the flow direction of the molten glass with respect to the highest temperature position. The method for producing a glass substrate according to any one of claims 3, 4, wherein the processing device includes a clarification tube in which at least a part of the inner wall is made of a material containing a platinum group metal and at least defoaming of the molten glass is performed. And the clarification pipe is provided with an exhaust pipe that communicates the atmosphere between the gas phase space and the outside of the processing device, and the position of the exhaust pipe in the flow direction of the molten glass is the maximum position of the bubble release amount and Between the above highest temperature positions. The method for producing a glass substrate according to any one of claims 3, 4, wherein the processing device includes a clarification tube in which at least a part of the inner wall is made of a material containing a platinum group metal and at least defoaming of the molten glass is performed. And the clarification pipe is provided with an exhaust pipe that communicates the atmosphere between the gas phase space and the outside of the clarification pipe, wherein the maximum position of the bubble release amount and the arrangement position of the exhaust pipe in the flow direction of the molten glass are Based on the highest temperature position of the above temperature distribution Quasi-, on the same side of the flow direction of the above molten glass. The method of manufacturing a glass substrate according to claim 14, wherein a flange member extending along an outer side of the processing device is provided outside the processing device, and a position of a flow direction of the molten glass of the flange member is located at the bubble An area outside the region between the maximum position of the release amount and the position at which the exhaust pipe is disposed. The method of manufacturing a glass substrate according to claim 15, wherein a flange member extending along an outer side of the processing device is provided on an outer circumference of the processing device, and a position of a flow direction of the molten glass of the flange member is located at the bubble An area outside the region between the maximum position of the release amount and the position at which the exhaust pipe is disposed. A glass substrate manufacturing apparatus which processes a molten glass using a processing apparatus for processing molten glass, and includes a processing apparatus configured to include at least a part of an inner wall containing a material containing a platinum group metal and internally a molten glass containing a clarifying agent that releases oxygen by a reduction reaction is supplied and a vapor phase space is formed on a surface of the surface of the molten glass, and the molten glass flows in a direction of a surface of the molten glass that is in spatial contact with the gas phase. And a control device configured to adjust the amount of oxygen released from the molten glass and adjust the amount of oxygen discharged from the gas phase space such that the oxygen concentration in the gas phase space becomes a specific range Adjusting in such a manner that the amount of oxygen released varies according to the position of the flow direction of the molten glass, and the control device adjusts by adjusting the distribution of the amount of oxygen released at the position of the flow direction of the molten glass. Distribution of oxygen concentration in the flow direction of the above molten glass in the gas phase space Thereby suppressing the volatilization of the above-described platinum group metal. A glass substrate manufacturing apparatus using a processing device for processing molten glass The molten glass is processed, and includes a processing apparatus configured to: at least a part of the inner wall contains a material containing a platinum group metal, and is internally supplied with a molten glass containing a clarifying agent that releases oxygen by a reduction reaction And forming a gas phase space above the surface of the molten glass, wherein the molten glass flows in a direction of a surface of the molten glass in contact with the gas phase space; and a control device configured by: adjusting from the above The amount of oxygen released from the molten glass is adjusted and the amount of oxygen discharged from the gas phase space is adjusted to adjust the oxygen concentration in the gas phase space to a specific range, and the processing device is in contact with the gas phase space. The temperature of the wall has a temperature distribution along the flow direction of the molten glass, and the control device in the treatment of the molten glass causes the release amount of the bubbles released from the surface of the molten glass to the gas phase space to be the largest The maximum position of the bubble release amount in the flow direction of the molten glass and the flow direction of the molten glass The above-described embodiment the position spaced apart from the maximum temperature of the temperature distribution in the direction of flow of said molten glass to adjust the maximum amount of the bubble release position. A glass substrate manufacturing apparatus characterized in that a molten glass is treated by a processing apparatus for processing molten glass, and includes: a melting tank that melts a glass raw material to produce molten glass; and a processing apparatus in the following manner a structure in which at least a part of the inner wall contains a material containing a platinum group metal, and is internally supplied with molten glass containing a clarifying agent that releases oxygen by a reduction reaction, and the molten glass is along the molten glass and the gas phase space Flowing in the direction of the contact surface, forming a gas phase space above the surface of the molten glass, and the temperature of the inner wall in contact with the gas phase space has a temperature distribution along the flow direction of the molten glass; treatment of the molten glass In order to release the above surface from the molten glass The maximum temperature position of the bubble in the flow direction of the molten glass and the highest temperature position of the temperature distribution in the flow direction of the molten glass in the flow direction of the molten glass are the flow of the molten glass The maximum position of the bubble discharge amount is adjusted in a directionally spaced manner. The glass substrate manufacturing apparatus according to any one of claims 18 to 20, wherein the processing apparatus comprises a clarification tube for performing defoaming of the molten glass.