JP6616183B2 - Glass substrate manufacturing method and glass substrate manufacturing apparatus - Google Patents

Description

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

  Generally, a glass substrate is produced through a process of forming molten glass from a glass raw material and then forming the molten glass into a glass substrate. The above process includes a process of removing minute bubbles contained in the molten glass (hereinafter also referred to as clarification). The clarification is performed by passing a molten glass containing a clarifier in the clarifier tube body while heating the clarifier tube body, and removing bubbles in the molten glass by an oxidation-reduction reaction of the clarifier. More specifically, after raising the temperature of the molten glass that has been melted and melted, the fining agent floats and defoamed, and then the temperature is lowered to melt the relatively small bubbles that remain without being defoamed. The glass is made to absorb. That is, clarification includes a process for floating and defoaming bubbles (hereinafter also referred to as a defoaming process or a defoaming process) and a process for absorbing small bubbles into molten glass (hereinafter also referred to as an absorption process or an absorbing process).

  The inner wall of the member in contact with the high-temperature molten glass before forming needs to be made of an appropriate material according to the temperature of the molten glass in contact with the member, the required quality of the glass substrate, and the like. For example, it is known that a material constituting the above-mentioned clarification tube main body is usually a simple substance or an alloy of a platinum group metal (Patent Document 1). Platinum group metals have a high melting point and are excellent in corrosion resistance against molten glass.

JP 2010-111533 A

  In the clarification step, the molten glass passing through the clarification tube is heated by energizing the clarification tube made of a platinum group metal alone or an alloy to heat the clarification tube (electric heating). At this time, the temperature of the molten glass passing near the center of the clarification tube is lower than the temperature of the molten glass near the inner wall of the clarification tube. Further, the speed of the molten glass passing through the clarification tube is higher near the center of the pipe than near the inner wall of the clarification tube due to wall resistance. For this reason, the molten glass passing near the center of the clarification tube may pass through the clarification tube without being sufficiently heated, and the clarification may be insufficient.

  On the other hand, when the heating amount of the clarification tube is increased in order to increase the temperature of the molten glass near the center of the clarification tube, volatilization due to oxidation of a simple substance or an alloy of a platinum group metal constituting the clarification tube is promoted. When the volatilized metal oxide is reduced at a position where the temperature of the clarification tube is locally lowered, the reduced platinum group metal adheres to the inner wall surface of the clarification tube. The platinum group metal adhering to the inner wall surface may drop into the molten glass during the defoaming process and enter the glass substrate as a foreign substance.

In order to make the temperature of the molten glass in the clarification tube uniform, it is conceivable to provide a stirring means for stirring the molten glass in the clarification tube. However, if there is a stirring means in the gas phase space where bubbles rise in the clarification tube, the gas such as oxygen, CO ₂ , SO ₂ contained in the bubbles is discharged from the gas phase space to the outside of the clarification tube. May interfere. When the gas flow in the gas phase space is obstructed, the reduced platinum group metal adheres to the inner wall surface of the clarification tube, falls into the molten glass during the defoaming process, and enters the glass substrate as a foreign substance. There is a fear.

  An object of this invention is to provide the manufacturing method of the glass substrate which can stir the molten glass in a clarification tube uniformly, without preventing the flow of the gas of gaseous-phase space.

A first aspect of the present invention is a method for manufacturing a glass substrate,
The molten glass is heated from the upstream side to the downstream side while heating the molten glass, and the bubbles in the molten glass are discharged toward the gas phase space surrounded by the interface of the molten glass and the inner wall of the clarified tube. Clarification process,
An interface position control step for controlling the flow rate of the molten glass flowing into the clarified tube and the molten glass flowing out of the clarified tube so that the interface of the molten glass is at a predetermined position;
The clarification tube includes a plate member that suppresses the flow of the molten glass provided at a predetermined interval on the inner wall of the clarification tube, and an interface position measuring instrument that measures the position of the interface of the molten glass. And
In the interface position control step, based on the position of the interface of the molten glass measured by the interface position meter, the molten glass is adjusted so that the height of the interface of the molten glass coincides with the upper end of the plate member. Control the flow rate.
It is preferable that the plate member is provided to be inclined with respect to the longitudinal direction of the clarification tube.

  In the interface position control step, the inflow amount of the molten glass flowing into the clarification tube from a step upstream from the clarification step, and / or the molten glass flowing out from the clarification tube in a step downstream from the clarification step. It is preferable to control the position of the interface of the molten glass by adjusting the outflow amount.

The clarification pipe is provided with a ventilation pipe that protrudes outward of the clarification pipe on the outer wall surface of the clarification pipe and communicates the gas phase space with the outside air,
The interface position meter is preferably guided from the outside of the clarification tube through the vent tube, and measures the position of the interface of the molten glass.

A second aspect of the present invention is a glass substrate manufacturing apparatus,
A clarification tube in which a clarification step is performed in which a molten glass is flowed from an upstream side to a downstream side while heating, and bubbles in the molten glass are discharged toward a gas phase space surrounded by an interface and an inner wall of the molten glass. Including
The clarification tube includes a plate member that suppresses the flow of the molten glass provided at a predetermined interval on the inner wall of the clarification tube, and an interface position measuring instrument that measures the position of the interface of the molten glass. And
In the clarification tube, based on the position of the interface of the molten glass measured by the interface position meter, the flow rate of the molten glass is adjusted so that the height of the interface of the molten glass coincides with the upper end of the plate member. Be controlled.

  According to the manufacturing method of the glass plate of the above-mentioned aspect, the molten glass in a clarification pipe | tube can be stirred uniformly, without preventing the gas flow of gaseous-phase space.

It is a figure which shows the flow of the manufacturing method of this embodiment. It is the schematic of the manufacturing apparatus of a glass substrate. It is the schematic of the clarification pipe | tube shown in FIG. It is a vertical sectional view in the longitudinal direction of the clarification tube. It is the figure which showed the shear rate obtained by the simulation of the vertical cross section in the longitudinal direction of a clarification pipe | tube, (a) is the figure which showed the shear rate when not providing a 2nd board member in a clarification pipe | tube, b) shows the shear rate when the height position of the interface of the molten glass coincides with the position of the upper end portion of the second plate member, and the second plate member and the third plate member are inclined. FIG.

Hereinafter, the manufacturing method of the glass substrate of this invention is demonstrated.
(Overall overview of glass substrate manufacturing method)
Drawing 1 is a figure showing an example of a process of a manufacturing method of a glass substrate of this embodiment. The glass substrate manufacturing method includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a molding step (ST5), a slow cooling step (ST6), and a cutting step ( ST7) is mainly included. In addition, a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like may be included. The manufactured glass substrate is laminated in a packing process as necessary, and is transported to a supplier.

  In the melting step (ST1), molten glass is made by heating the glass raw material.

In the clarification step (ST2), when the molten glass is heated, bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass are generated. The bubbles grow by taking in (absorbing) oxygen generated by the reduction reaction of the fining agent (tin oxide or the like) contained in the molten glass, and float on the liquid surface of the molten glass to be released. Thereafter, in the clarification step, by reducing the temperature of the molten glass, the reducing substance obtained by the reduction reaction of the clarifier undergoes an oxidation reaction. Thereby, gas components, such as oxygen in the bubble which remain | survives in molten glass, are reabsorbed in molten glass, and a bubble lose | disappears. The oxidation reaction and reduction reaction by the fining agent are performed by controlling the temperature of the molten glass.

  In addition, the clarification process can also use the reduced pressure defoaming system which grows the bubble which exists in molten glass in a reduced pressure atmosphere, and defoams. The vacuum degassing method is effective in that no clarifier is used. However, the vacuum degassing method makes the apparatus complicated and large. For this reason, it is preferable to employ | adopt the clarification method which raises molten glass temperature using a clarifier.

  In the homogenization step (ST3), the glass component is homogenized by stirring the molten glass using a stirrer. Thereby, the composition unevenness of the glass which is a cause of striae or the like can be reduced. A homogenization process is performed in the stirring tank mentioned later.

  In the supplying step (ST4), the stirred molten glass is supplied to the molding apparatus.

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

  In the forming step (ST5), the molten glass is formed into a sheet glass to make a flow of the sheet glass. An overflow downdraw method is used for molding.

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

  In the cutting step (ST7), the sheet glass after slow cooling is cut into a predetermined length to obtain a plate-like glass substrate. The cut glass substrate is further cut into a predetermined size to produce a glass substrate having a target size.

  FIG. 2 is a schematic view of a glass substrate manufacturing apparatus that performs the melting step (ST1) to the cutting step (ST8) in the present embodiment. As shown in FIG. 2, the glass substrate manufacturing apparatus mainly includes a melting apparatus 100, a forming apparatus 200, and a cutting apparatus 300. The melting apparatus 100 includes a melting tank 101, a clarification pipe 120, a stirring tank 103, transfer pipes 104 and 105, and a glass supply pipe 106.

  The melting tank 101 shown in FIG. 2 is provided with heating means such as a burner (not shown). A glass raw material to which a clarifying agent is added is charged into the melting tank, and a melting step (ST1) is performed. The molten glass melted in the melting tank 101 is supplied to the clarification tube 120 through the transfer tube 104.

In the clarification tube 120, the temperature of the molten glass MG is adjusted, and the clarification step (ST2) of the molten glass is performed using the oxidation-reduction reaction of the clarifier. Specifically, when the molten glass in the clarification tube 120 is heated, the bubbles containing oxygen, CO ₂ or SO ₂ contained in the molten glass take in oxygen generated by the reduction reaction of the clarifier. (Absorbs) and then rises to the liquid surface of the molten glass and is released into the gas phase space. Thereafter, by reducing the temperature of the molten glass, the reducing substance obtained by the reductive reaction of the fining agent undergoes an oxidation reaction. Thereby, gas components, such as oxygen in the bubble which remain | survives in molten glass, are reabsorbed in molten glass, and a bubble lose | disappears. The clarified molten glass is supplied to the stirring tank 103 via the transfer pipe 105.

  In the stirring vessel 103, the molten glass is stirred by the stirring bar 103a, and the homogenization step (ST3) is performed. The molten glass homogenized in the stirring tank 103 is supplied to the molding apparatus 200 through the glass supply pipe 106 (supply process ST4).

  In the forming apparatus 200, the sheet glass SG is formed from the molten glass by the overflow downdraw method (molding step ST5) and gradually cooled (slow cooling step ST6).

In the cutting device 300, a plate-like glass substrate cut out from the sheet glass SG is formed (cutting step ST7).
(Configuration of clarification tube)
Next, the configuration of the clarification tube 120 will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic perspective view showing the configuration of the clarification tube 120 of the embodiment, and FIG. 4 is a vertical sectional view in the longitudinal direction of the clarification tube 120.

  As shown in FIGS. 3 and 4, electrodes 121 a and 121 b are provided on the outer peripheral surfaces of both ends in the longitudinal direction of the clarification tube 120, and the walls are in contact with the gas phase space 120 a (see FIG. 4) of the clarification tube 120. Is provided with an exhaust pipe 127. Further, an interface position measuring instrument 128 is provided, and a sensor unit of the interface position measuring instrument 128 is introduced into the clarification tube 120 through the exhaust pipe 127, and the interface position of the molten glass is measured.

  The main body of the clarification tube 120, the electrodes 121a and 121b, and the exhaust pipe 127 are made of a platinum group metal. In this specification, the “platinum group metal” means a metal composed of a platinum group element, and is used as a term including not only a metal composed of a single platinum group element but also an alloy of the platinum group element. Here, the platinum group element refers to six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), and iridium (Ir). Platinum group metals are expensive, but have a high melting point and excellent corrosion resistance against molten glass.

  In the present embodiment, a case where the clarification tube 120 is made of a platinum group metal will be described as a specific example. However, a part of the clarification tube 120 may be made of a refractory or other metal. .

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

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

  The electrodes 121a and 121b may be provided with a temperature measurement device (thermocouple or the like) (not shown). The temperature measuring device measures the temperature of the electrodes 121 a and 121 b and outputs the measured result to the control device 123.

  The control device 123 controls the amount of current that the power supply device 122 supplies to the clarification tube 120, thereby controlling the temperature and flow rate of the molten glass passing through the clarification tube 120. The control device 123 is a computer including a CPU, a memory, and the like.

  An exhaust pipe 127 is provided on the wall of the clarification pipe 120 in contact with the gas phase space. The exhaust pipe 127 is provided above the gas phase space 120a. The exhaust pipe 127 is preferably provided at a position between the upstream end and the downstream end in the flow direction of the molten glass in the clarification pipe 120. The exhaust pipe 127 may have a shape protruding in a chimney shape from the outer wall surface of the main body of the clarification pipe 120 toward the outside. The exhaust pipe 127 communicates the gas phase space 120a (see FIG. 4) with the external space of the clarification pipe 120. By discharging the gas in the gas phase space 120a from the exhaust pipe 127, oxygen released from the molten glass in the clarification pipe 120 can be discharged. Thereby, it can suppress that a platinum group metal is oxidized and volatilizes, and can reduce the precipitation amount of the platinum group metal by reducing the volatilized platinum group metal.

  The interface position meter 128 includes a sensor unit that detects the interface position of the molten glass in the clarification tube 120 and a measurement unit that measures the interface position based on a signal (data) detected by the sensor unit. Here, the interface position is a boundary region between the liquid phase region in which the molten glass flows in the clarification tube 120 and the gas phase region (gas phase space) from which bubbles in the molten glass are released, and is the uppermost of the liquid phase region. Position, the lowest position of the gas phase region. The sensor unit of the interface position measuring instrument 128 is introduced into the clarification tube 120 through the exhaust pipe 127 and detects the interface position of the molten glass in the clarification tube 120. The measurement unit is connected to the sensor unit, and measures the interface position of the molten glass in the clarification tube 120 based on a signal (data) sent from the sensor unit. In this embodiment, the interface position of the molten glass in the clarification tube 120 is measured by the interface position meter 128, and the molten glass is melted so that the height of the interface of the molten glass coincides with the upper end portion of the second plate member 125 described later. Control the flow rate of glass.

  In the present embodiment, as shown in FIG. 4, the clarification tube 120 is disposed so as to extend in a substantially horizontal direction. A plate member group including a plurality of plate members 124, 125, and 126 is provided inside the clarification tube 120. The plate member group includes a first plate member group including a plurality of first plate members 124, a second plate member group including a plurality of second plate members 125, and a third plate member group including a plurality of third plate members 126. Including. The 1st board member 124, the 2nd board member 125, and the 3rd board member 126 are comprised from the platinum group metal similarly to the main body of the clarification pipe | tube 120. As shown in FIG.

  The plurality of first plate members 124 are provided at a first height spaced from the lowermost and uppermost portions of the inner wall of the clarification tube 120. The plurality of first plate members 124 are arranged at intervals in the longitudinal direction of the clarification tube 120. The first plate member 124 prevents the flow of the molten glass flowing in the longitudinal direction of the clarification tube 120 in the vicinity of the center of the clarification tube 120, and branches to the upper side of the first plate member 124 and the lower side of the first plate member 124. .

  The plurality of second plate members 125 are provided at a second height that is higher than the height (first height) of the first plate member 124 and spaced from the uppermost portion of the inner wall of the clarification tube 120. Yes. The plurality of second plate members 125 are arranged alternately with the plurality of first plate members 124 in the longitudinal direction of the fining tube 120. The second plate member 125 hinders the flow of the molten glass flowing in the longitudinal direction of the clarification tube 120 in the vicinity of the interface of the molten glass in the clarification tube 120, and the flow of the molten glass is lower than the second plate member 125 (the clarification tube (Near the center of). The plurality of second plate members 125 are provided to be inclined with respect to the longitudinal direction of the clarification tube 120. The inclination angle A1 of the plurality of second plate members 125 is, for example, in the range of 20 degrees to 70 degrees, more preferably 30 degrees to 60 degrees. When the 2nd board member 125 is provided in the clarification pipe | tube 120, as for the molten glass which collided with the 2nd board member 125, a flow stagnates temporarily and foreign glass may arise. However, by increasing the shear rate, the molten glass is stretched (stirred). The shear rate is a derivative of the fluid velocity, and its flow characteristics can be obtained by calculating the shear rate of the molten glass. The larger the shear response speed, the larger the difference in flow rate between adjacent molten glasses, the higher the stirring effect, and the more uniform the molten glass can be. On the other hand, the smaller the shear rate, the smaller the flow rate difference between adjacent molten glasses, and the lower the stirring effect. For this reason, by providing the 2nd board member 125, stirring efficiency is raised by improving the dispersion | variation in the shear rate of the molten glass which flows through the clarification pipe | tube 120, raising a shear rate. In addition, when small-sized impurities exist in the molten glass, they float on the interface (surface) of the molten glass and flow downstream without being stirred by the plurality of first plate members 124, so that these impurities affect the glass quality. May affect. Therefore, by providing a plurality of second plate members 125 inclined by a predetermined angle, the shear rate is increased, the molten glass is stirred by the plurality of second plate members 125, and the time spent in the clarification tube 120 is increased. The defoaming process can be promoted by increasing the length. At the lower end of the second plate member 125, the molten glass that has hit the second plate member 125 flows downward (toward the bottom of the clarification tube 120) along the second plate member 125, and a vortex is generated. The molten glass is agitated by this vortex. At the upper end portion of the second plate member 125, the molten glass that has hit the second plate member 125 flows upward (in the interface direction of the molten glass) along the second plate member 125. Since the flow rate of the molten glass is controlled so that the height position of the interface of the molten glass coincides with the position of the upper end portion of the second plate member 125, the molten glass that has flowed upward along the first plate member 124. Is stirred by the second plate member 125. By making the height position of the interface of the molten glass coincide with the position of the upper end portion of the second plate member 125, the impurities in the molten glass and the molten glass do not flow above the upper end portion of the second plate member 125. The second plate member 125 is agitated. Thereby, a defoaming process can be promoted. The distance D1 between the second plate members 125 is, for example, in the range of 100 mm to 500 m, more preferably 200 mm to 400 mm. If the distance D1 between the second plate members 125 is excessively widened, the molten glass flows from the upstream side to the downstream side without being stirred by the second plate member 125, so that the defoaming process is not promoted, and the second plate member 125. If the distance D1 between the two is too narrow, the flow of the molten glass is stagnated by the second plate member 125, the impurities in the molten glass float up to the interface (surface) of the molten glass, and this impurity is not glass quality. Will be affected. Therefore, by providing a plurality of second plate members 125 such that the distance D1 between the second plate members 125 is a predetermined interval, the defoaming process is promoted by increasing the shear rate and stirring the molten glass. Can be made.

  The plurality of third plate members 126 are provided at a third height that is lower than the height (first height) of the first plate member 124 without leaving a gap with the lowermost portion of the inner wall of the clarification tube 120. ing. The plurality of third plate members 126 are arranged alternately with the plurality of first plate members 124 in the longitudinal direction of the clarification tube 120 at intervals. The third plate member 126 hinders the flow of the molten glass flowing in the longitudinal direction of the clarification tube 120 at the lowermost part of the molten glass in the clarification tube 120, and the flow of the molten glass is higher than the third plate member 126 (of the clarification tube). (Near the center). The plurality of third plate members 126 are provided to be inclined with respect to the longitudinal direction of the clarification tube 120. The inclination angle B1 of the plurality of third plate members 126 is, for example, in the range of 20 degrees to 70 degrees, more preferably 30 degrees to 60 degrees. The interval between the third plate members 126 is, for example, in the range of 100 mm to 500 m, more preferably 200 mm to 400 mm.

  FIG. 5 is a diagram showing the shear rate obtained by simulation of the vertical cross section in the longitudinal direction of the clarification tube, (a) is a diagram showing the shear rate when the second plate member 125 is not provided, (B) shows the shear when the height position of the interface of the molten glass coincides with the position of the upper end portion of the second plate member 125 and the second plate member 125 and the third plate member 126 are inclined. It is a figure which shows speed. As shown in FIG. 5A, if the second plate member 125 is not provided, the shear rate is increased and stirring is performed in the vicinity where the first plate member 124 is provided (the central portion of the clarification tube 120). However, the shear rate was different between the vicinity of the interface of the molten glass and the vicinity of the bottom of the clarification tube 120, and the stirring unevenness of the molten glass was generated. Further, the molten glass flows in the vicinity of the interface of the molten glass, which is above the upper end portion of the first plate member 124, and the flow rate of the molten glass becomes faster than other regions. Since the molten glass flows from the upstream side to the downstream side without being stirred by the second plate member 125, the time for staying in the clarification tube 120 is shortened, and the defoaming process is not promoted. On the other hand, as shown in FIG. 5 (b), when the height position of the interface of the molten glass coincides with the position of the upper end portion of the second plate member 125, the molten glass is stirred by the second plate member 125 and sheared. The speed was high. Moreover, the shear rate was the same between the vicinity of the molten glass interface and the bottom of the clarification tube 120, and the molten glass was uniformly stirred in the clarification tube 120. Moreover, the molten glass which collided with the 2nd plate member 125 and the 3rd plate member 126 flows into the lower end part side of the 2nd plate member 125, and the upper end part side of the 3rd plate member 126, and becomes a vortex | eddy_current. For this reason, the molten glass flows from the upstream side to the downstream side while being agitated by the second plate member 125 and the third plate member 126, and the time for staying in the clarification tube 120 becomes longer, and the defoaming process is promoted.

  Thus, by providing the 1st plate member 124, the 2nd plate member 125, and the 3rd plate member 126, not only the molten glass in the clarification tube 120 flows into the longitudinal direction of the clarification tube 120, but molten glass does not flow. Since it changes so that it may also move to an up-down direction, molten glass is stirred uniformly in the clarification pipe | tube 120, and the temperature of molten glass can be made uniform.

  As shown in FIG. 4, the second plate member 125 and the third plate member 126 may be at the same position in the longitudinal direction of the clarification tube 120. That is, the third plate member 126 may be provided below the second plate member 125.

  Here, at the position of the first plate member 124, the flow rate obtained by dividing the flow rate of the molten glass flowing above the first plate member 124 by the flow passage cross-sectional area above the first plate member, It is preferable to control the flow rate and flow rate of the molten glass flowing through the clarification tube 120 so that the flow rate of the molten glass flowing through the lower side is equal to the flow rate obtained by dividing the flow rate of the molten glass by the lower channel cross-sectional area of the first plate member 124. . By equalizing the flow rate of the molten glass flowing above the first plate member 124 and the flow rate of the molten glass flowing below the first plate member 124, the molten glass can be uniformly stirred in the clarification tube 120. .

  The flow rate of the molten glass flowing above the first plate member 124 and the flow rate of the molten glass flowing below the first plate member 124 can be adjusted by the amount of heating by the clarification tube 120.

  For example, by increasing the heating amount of the clarification tube 120, the temperature of the molten glass flowing under the first plate member 124, which is close to the inner wall of the clarification tube 120, is increased, and the viscosity is decreased. The flow velocity of the molten glass flowing under the member 124 can be increased. On the other hand, by decreasing the heating amount of the clarification tube 120, the temperature of the molten glass flowing under the first plate member 124, which is close to the inner wall of the clarification tube 120, is decreased, and the viscosity is increased, whereby the first plate The flow rate of the molten glass flowing under the member 124 can be lowered.

  Since the molten glass flowing on the upper side of the first plate member 124 is far from the inner wall of the clarification tube 120, the amount of change in temperature due to the change in the heating amount of the clarification tube 120 is the melt flowing on the lower side of the first plate member 124. Smaller than glass.

  In the present embodiment, the flow rate and flow rate of the molten glass are controlled so that the height of the interface of the molten glass MG in the clarification tube 120 matches the highest position of the upper end portion of the second plate member 125. That is, all of the first plate member 124, the second plate member 125, and the third plate member 126 are in the molten glass, and the first plate member 124, the second plate member 125, and the third plate member are in the vapor phase space 120a. 126, the height of the interface of the molten glass MG in the clarification tube 120 is adjusted.

  In order to change the height of the interface of the molten glass MG, the flow rate of the molten glass flowing through the transfer pipes 104 and 105 may be changed. The flow from the melting step that is upstream of the clarification step to the clarification step, that is, the inflow amount of molten glass that flows into the clarification tube, and / or the homogenization step that is the step downstream from the clarification step, The position of the interface of the molten glass is controlled by adjusting the outflow amount of the molten glass that flows out into the supply process and the forming process, that is, out of the clarification tube. For example, the flow rate of the molten glass flowing into the clarification tube 120 from the transfer tube 104 is made larger than the flow rate of the molten glass flowing out of the clarification tube 120 through the transfer tube 105, so that the interface of the molten glass MG in the clarification tube 120 can be obtained. Can raise the height. In order to control the flow rate of the molten glass in the transfer pipes 104 and 105, the temperature of the molten glass flowing through the transfer pipes 104 and 105 may be changed to adjust the viscosity of the molten glass. For example, the flow rate and flow rate of the molten glass can be increased by increasing the temperature of the molten glass and decreasing the viscosity of the molten glass. On the other hand, the flow rate and flow rate of the molten glass can be reduced by lowering the temperature of the molten glass and increasing the viscosity of the molten glass.

  In order to increase the height of the interface of the molten glass MG in the clarification tube 120, the charging time interval for charging the glass raw material into the melting tank 101 is shortened, more specifically, the charging time interval is 3 minutes to 2 minutes, 1 minute. Further, the input amount of the glass raw material is increased once, more specifically, the input amount of one time is changed from 100 kg to 200 kg and 300 kg. Thereby, the height of the interface of the molten glass MG in the clarification tube 120 can be raised. On the other hand, the flow rate of the molten glass flowing from the transfer tube 104 to the clarification tube 120 is made smaller than the flow rate of the molten glass flowing out of the clarification tube 120 by the transfer tube 105, so that the interface of the molten glass MG in the clarification tube 120 is reduced. The height can be lowered. In order to lower the height of the interface of the molten glass MG in the clarification tube 120, the charging time interval for charging the glass raw material into the melting tank 101 is lengthened, more specifically, the charging time interval is 3 minutes to 4 minutes, 5 minutes. In addition, the amount of glass material input at one time is reduced, more specifically, the amount of input at one time is changed from 100 kg to 80 kg and 50 kg. Thereby, the height of the interface of the molten glass MG in the clarification tube 120 can be lowered. The charging time interval and charging amount of the glass raw material can be arbitrarily changed within a range in which the glass raw material can be melted in the melting tank 101.

  Moreover, the height of the interface of molten glass MG can be raised by making it smaller than the flow volume of the molten glass which flows out from the clarification tube 120. In order to raise the height of the interface of the molten glass MG in the clarification tube 120, the temperature of the molten glass flowing through the glass supply pipe 106 located downstream of the clarification tube 120 is lowered, more specifically, the temperature of the molten glass. From 1000 ° C. to 980 ° C. and 950 ° C. By suppressing the flow rate of the molten glass flowing through the glass supply pipe 106, the flow rate of the molten glass flowing out of the clarification tube 120 is suppressed, and therefore the height of the interface of the molten glass MG in the clarification tube 120 can be increased. . On the other hand, the height of the interface of the molten glass MG can be lowered by making it larger than the flow rate of the molten glass flowing out of the clarification tube 120. In order to lower the height of the interface of the molten glass MG in the clarification tube 120, the temperature of the molten glass flowing through the glass supply pipe 106 located downstream of the clarification tube 120 is increased. More specifically, the temperature of the molten glass is increased. From 1000 ° C. to 1020 ° C. and 1050 ° C. By increasing the flow rate of the molten glass flowing through the glass supply pipe 106, the flow rate of the molten glass flowing out from the clarification tube 120 increases, so that the height of the interface of the molten glass MG in the clarification tube 120 can be lowered. The position of changing the temperature of the molten glass and the temperature of the molten glass in the glass supply pipe 106 can be arbitrarily changed within a range in which the sheet glass SG can be formed in the forming apparatus 200.

Thus, the 1st board member 124, the 2nd board member 125, and the 3rd board member 126 are exposed in the gaseous-phase space 120a by adjusting the height of the interface of the molten glass MG in the clarification tube 120. Therefore, in the first plate member 124, the second plate member 125, and the third plate member 126, gases such as oxygen, CO ₂ , and SO ₂ released into the gas phase space 120a are directed to the exhaust pipe 127. Does not obstruct the flow.

Further, the first plate member 124, the second plate member 125, and the third plate member 126 are prevented from coming into contact with a gas such as oxygen, CO ₂ , SO _2, etc. released into the gas phase space 120a. It is possible to prevent the platinum group metal constituting the plate member 124, the second plate member 125, and the third plate member 126 from being volatilized by being oxidized.

  In addition, by temporarily increasing the flow rate of the molten glass and making the height of the interface of the molten glass MG in the clarification tube 120 higher than the upper end portion of the second plate member 125, small impurities existing in the molten glass are removed. You can also If the amount of the molten glass MG is continuously controlled so that the height of the interface of the molten glass MG coincides with the upper end of the second plate member 125, in the case of small impurities, the impurities float on the interface (surface) of the molten glass. It rises and gradually accumulates in the vicinity of the second plate member 125 and may flow downstream without being stirred by the second plate member 125, and this impurity may affect the glass quality. For this reason, by temporarily increasing the flow rate of the molten glass, impurities accumulated in the vicinity of the second plate member 125 are pushed downstream. Since the fixed amount of impurities keep flowing near the interface of the molten glass MG, the impurities can be efficiently removed by removing them in the stirring tank 103 in which the homogenization step (ST3) is performed.

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

  For the glass substrate produced by the method for producing a glass substrate of the present embodiment, an alkali-free boroaluminosilicate glass having a high strain point and a slow cooling point and good dimensional stability or a glass containing a trace amount of alkali is used.

The glass substrate to which this embodiment is applied is made of an alkali-free glass having the following composition, for example.
SiO _2: 56-65% by weight
Al ₂ O ₃ : 15-19% by mass
B ₂ O _3: 8-13 wt%
MgO: 1-3% by mass
CaO: 4-7% by mass
SrO: 1-4% by mass
BaO: 0-2 mass%
Na ₂ O: 0-1% by mass
K ₂ O: 0-1 wt%
As ₂ O ₃ : 0-1% by mass
Sb ₂ O _3: 0-1 wt%
SnO ₂ : 0-1% by mass
Fe ₂ O ₃ : 0-1% by mass
ZrO ₂ : 0-1% by mass
The glass substrate manufactured by this embodiment is suitable for the glass substrate for a display containing the glass substrate for flat panel displays. It is suitable for an oxide semiconductor display glass substrate using an oxide semiconductor such as IGZO (indium, gallium, zinc, oxygen) and an LTPS display glass substrate using an LTPS (low temperature polysilicon) semiconductor. Moreover, the glass substrate manufactured by this embodiment is suitable for the glass substrate for liquid crystal displays by which it is calculated | required that content of an alkali metal oxide is very small. Moreover, it is suitable also for the glass substrate for organic EL displays. In other words, the manufacturing method of the glass substrate of this embodiment is suitable for manufacture of the glass substrate for displays, and is especially suitable for manufacture of the glass substrate for liquid crystal displays. In addition, it can be used as a display for a portable terminal device, a cover glass for a casing, a touch panel plate, a glass substrate of a solar cell, or a cover glass. Particularly, it is suitable for a glass substrate for a liquid crystal display using a polysilicon TFT.

  Moreover, the glass substrate manufactured by this embodiment is applicable also to a cover glass, the glass for magnetic discs, the glass substrate for solar cells, etc.

DESCRIPTION OF SYMBOLS 100 Melting apparatus 101 Melting tank 102 Clarification pipe 103 Stirring tank 103a Stirrer 104, 105 Transfer pipe 106 Glass supply pipe 120 Clarification pipe 120a Gas phase space 121a, 121b Electrode 122 Power supply apparatus 123 Control apparatus 124 First plate member 125 Second plate Member 126 Third plate member 127 Exhaust pipe 128 Interface position meter 200 Molding device 300 Cutting device MG Molten glass SG Sheet glass

Claims (5)

A method of manufacturing a glass substrate,
The molten glass is heated from the upstream side to the downstream side while heating the molten glass, and the bubbles in the molten glass are discharged toward the gas phase space surrounded by the interface of the molten glass and the inner wall of the clarified tube. Clarification process,
An interface position control step for controlling the flow rate of the molten glass flowing into the clarified tube and the molten glass flowing out of the clarified tube so that the interface of the molten glass is at a predetermined position;
The clarification tube includes a plate member that suppresses the flow of the molten glass provided at a predetermined interval on the inner wall of the clarification tube, and an interface position measuring instrument that measures the position of the interface of the molten glass. And
In the interface position control step, based on the position of the interface of the molten glass measured by the interface position meter, the molten glass is adjusted so that the height of the interface of the molten glass coincides with the upper end of the plate member. Control the flow rate,
A method for producing a glass substrate, comprising: The plate member is provided to be inclined with respect to the longitudinal direction of the clarification tube.
The method for producing a glass substrate according to claim 1. In the interface position control step, the inflow amount of the molten glass flowing into the clarification tube from a step upstream from the clarification step, and / or the molten glass flowing out from the clarification tube in a step downstream from the clarification step. By adjusting the outflow amount, the position of the interface of the molten glass is controlled,
The manufacturing method of the glass substrate of Claim 1 or 2 characterized by the above-mentioned. The clarification pipe is provided with a ventilation pipe that protrudes outward of the clarification pipe on the outer wall surface of the clarification pipe and communicates the gas phase space with the outside air,
The interface position meter is guided from the outside of the clarification tube through the vent tube, and measures the position of the interface of the molten glass.
The manufacturing method of the glass substrate as described in any one of Claim 1 to 3 characterized by the above-mentioned. An apparatus for manufacturing a glass substrate,
A clarification tube in which a clarification step is performed in which a molten glass is flowed from an upstream side to a downstream side while heating, and bubbles in the molten glass are discharged toward a gas phase space surrounded by an interface and an inner wall of the molten glass. Including
The clarification tube includes a plate member that suppresses the flow of the molten glass provided at a predetermined interval on the inner wall of the clarification tube, and an interface position measuring instrument that measures the position of the interface of the molten glass. And
In the clarification tube, based on the position of the interface of the molten glass measured by the interface position meter, the flow rate of the molten glass is adjusted so that the height of the interface of the molten glass coincides with the upper end of the plate member. Controlled,
An apparatus for producing a glass substrate.

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