JP6847620B2 - Glass substrate manufacturing method and glass substrate manufacturing equipment - Google Patents

Description

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

A glass substrate is generally manufactured through a process of producing molten glass from a glass raw material and then molding the molten glass into a glass substrate. The above-mentioned step includes a step of removing minute bubbles contained in the molten glass (hereinafter, also referred to as clarification). The clarification is performed by heating the main body (clarification tube) of the clarification tank, passing the molten glass containing the clarifying agent through the clarifying tube, and removing bubbles in the molten glass by the redox reaction of the clarifying agent. It is said. More specifically, the temperature of the coarsely melted molten glass is further raised to allow the clarifying agent to function to float and defoam the bubbles, and then the temperature is lowered to melt the relatively small bubbles remaining that cannot be completely defoamed. I try to make it absorb into the glass. That is, the clarification includes a defoaming treatment for floating and defoaming bubbles and an absorption treatment for absorbing small bubbles into the molten glass.

The inner wall of the member in contact with the high-temperature molten glass before molding 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, a platinum group metal such as platinum or a platinum alloy is usually used as the material constituting the above-mentioned clarification tube (Patent Document 1). Platinum group metals have a high melting point and are also excellent in corrosion resistance to molten glass.

Japanese Unexamined Patent Publication No. 2010-11153

When the molten glass passes through the clarification tube in which the platinum group metal is used for the inner wall surface, the platinum group metal may be oxidized and volatilized in the portion of the heated inner wall surface in contact with the vapor phase space. On the other hand, the oxide of the platinum group metal may be reduced at the position of the clarification tube whose temperature has dropped locally and may adhere to the inner wall surface. The platinum group metal adhering to the inner wall surface may fall and be mixed in the molten glass and remain as a foreign substance in the glass substrate. A glass substrate containing such a foreign substance may be treated as a defective product.
In order to suppress the volatilization of such platinum group metals, it is known that an inert gas is allowed to flow in the clarification tube to reduce the oxygen concentration. However, it was found that bubbles may be generated in the molten glass after clarification by flowing an inert gas. Such bubbles may remain on the glass substrate and be treated as optical defects, which may reduce the yield of the glass substrate.

An object of the present invention is to suppress the generation of bubbles in the molten glass after clarification while suppressing the aggregation of platinum group metals in the clarification tube.

The present invention provides the following (1) to ( 5 ).
(1) Provided with a clarification process for clarifying molten glass using a clarification tube.
In the clarification step, the clarification is performed using the clarifying agent contained in the molten glass while flowing the molten glass into the clarification tube so that a gas phase space is formed above the liquid surface of the molten glass.
The clarification tube is made of a material containing a platinum group metal, and a vent hole for discharging a gas in the gas phase space and a gas inert to the molten glass are provided in a wall portion in contact with the gas phase space. It has an introduction hole leading into the gas phase space, and the ventilation hole and the introduction hole are arranged apart from each other in the flow direction of the molten glass.
The clarification tube is provided along the flow direction of the molten glass to a first heating region for heating the molten glass so as to promote defoaming of the molten glass, and to the molten glass of bubbles remaining after the defoaming. Has a second heating region, which heats the molten glass to promote absorption of
The introduction hole is arranged in the second heating region.
In the clarification step, the inert gas is retained in the external space outside the clarification pipe adjacent to the introduction hole, and the gas is discharged from the ventilation hole, whereby the inert gas in the external space is discharged. A method for manufacturing a glass substrate, which comprises drawing a gas into the gas phase space and flowing the gas along the flow direction of the molten glass.

(2) the external space, members made of a refractory material positioned so as to surround the introduction hole from the outside of the finer tube, and a space defined by the finer tube, according to (1) Manufacturing method of glass substrate.

( 3 ) The method for producing a glass substrate according to (1) or (2) above , wherein the inert gas is argon gas.

( 4 ) Further, a transfer step of transferring the molten glass flowing out of the clarification pipe by using a transfer pipe connected to the downstream side of the clarification pipe in the flow direction is provided.
The glass according to any one of (1) to (3 ) above, wherein the difference between the maximum temperature of the molten glass in the clarification step and the minimum temperature of the molten glass in the transfer step is 200 ° C. or more. Substrate manufacturing method.

(5) is made of a material containing a platinum group metal, while the flow of the molten glass as the gas phase space is formed above the liquid surface of the molten glass, using a clearing agent contained in the molten glass refining a finer tube for performing, before the wall portion in contact with Kiki phase space, the vent hole for discharging gas in the gas phase space, a gas inert to the molten glass in the gas phase space A clarification tube having an introduction hole for guiding, and the ventilation hole and the introduction hole arranged apart from each other in the flow direction of the molten glass,
An enclosure made of a refractory material arranged so as to surround the introduction hole from the outside of the clarification pipe,
An inert gas supply device that supplies the inert gas into the enclosure,
A suction device that sucks and discharges the gas from the ventilation holes,
A control device that controls the suction device so that the inert gas in the enclosure is drawn into the gas phase space by discharging the gas from the ventilation holes and flows along the flow direction of the molten glass. And with
The clarification tube is provided along the flow direction of the molten glass to a first heating region for heating the molten glass so as to promote defoaming of the molten glass, and to the molten glass of bubbles remaining after the defoaming. Has a second heating region, which heats the molten glass to promote absorption of
A glass substrate manufacturing apparatus, wherein the introduction hole is arranged in the second heating region.

According to the present invention, it is possible to suppress the generation of bubbles in the molten glass after clarification while suppressing the aggregation of platinum group metals in the clarification tube.

It is a flow chart which shows the manufacturing method of a glass substrate. It is the schematic of the glass substrate manufacturing apparatus. It is the schematic of the clarification pipe shown in FIG. It is a vertical sectional view in the longitudinal direction of the clarification pipe shown in FIG. It is a vertical sectional view in the longitudinal direction of a conventional clarification pipe.

Hereinafter, the glass substrate manufacturing method and the glass substrate manufacturing apparatus of the present embodiment will be described.
(Overview of manufacturing method of glass substrate)
FIG. 1 is a diagram showing an example of a process of the method for manufacturing a glass substrate of the present 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 (ST6). Mainly has ST7). In addition to this, it may have a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like. The manufactured glass substrates are laminated in the packing process as needed and transported to the supplier.

In the melting step (ST1), molten glass is produced by heating a glass raw material.
In the clarification step (ST2), the temperature of the molten glass is raised to generate bubbles containing _{oxygen, CO 2} or SO _{2 contained in the molten glass.} These bubbles absorb oxygen generated by the reduction reaction of the fining agent (tin oxide or the like) contained in the molten glass, grow, and float on the liquid surface of the molten glass and are released. After that, in the clarification step, the temperature of the molten glass is lowered to promote the oxidation reaction of the reducing substance produced by the reduction reaction of the clarifying agent. As a result, gas components such as oxygen in the bubbles remaining in the molten glass are reabsorbed in the molten glass, and the bubbles disappear.

In the homogenization step (ST3), the glass component is homogenized by stirring the molten glass with a stirrer. This makes it possible to reduce the uneven composition of the glass, which is a cause of veins and the like. The homogenization step is performed in a stirring tank described later.
In the feeding step (ST4), the homogenized molten glass is fed to the molding apparatus.

The molding step (ST5) and the slow cooling step (ST6) are performed by a molding apparatus.
In the molding step (ST5), the molten glass is molded into a sheet glass which is a strip of glass having a predetermined thickness to create a flow of the sheet glass. Float method, fusion method (overflow down draw method), etc. are used for molding, but since it is difficult to lengthen the slow cooling device on the production line by the fusion method, offline heat treatment (described later) is included. The fusion method is suitable as a method for manufacturing a glass substrate.
In the slow cooling step (ST6), the molded and flowing sheet glass has a desired thickness and is cooled so as not to cause internal strain and further to prevent warpage.
In the cutting step (ST7), a plate-shaped glass substrate is obtained by cutting the sheet glass after slow cooling to a predetermined length. Cutting the sheet glass into a base plate of a predetermined length is also called plate picking. The glass substrate obtained by the plate sampling is further cut into a predetermined size to produce a glass substrate having a target size.

In the cutting step (ST7), the glass substrate obtained by the plate sampling may be guided and transported to a furnace for which the heat treatment step is performed while being pinched and held by, for example, a transfer mechanism (not shown), and the heat treatment may be performed. .. The glass substrate after plate-cutting or heat treatment is further transported to a cutting device and cut to the size of a product to obtain a glass substrate. For the glass substrate obtained by the cutting step (ST7), for example, the following steps are performed.
In the grinding and polishing steps, end face processing including grinding, polishing and corner cutting of the end face of the glass substrate is performed. The glass substrate after the end face processing is cleaned (first cleaning) in order to remove fine foreign matter and dirt on the glass surface in the cleaning step. After the first cleaning, for example, the glass substrate is subjected to a surface treatment including a roughening step and a rinsing step. After the surface treatment, the glass substrate is further cleaned (second cleaning), and the cleaned glass substrate is optically inspected for scratches, dust, stains, or scratches including optical defects in the inspection step. In the packing process, the glass substrate whose quality is matched by the inspection is loaded on the pallet and packed as a laminated body alternately laminated with the paper protecting the glass substrate. The packed glass substrate is shipped to the supplier.

(Overview of glass substrate manufacturing equipment)
FIG. 2 is a schematic view of a glass substrate manufacturing apparatus that performs the melting step (ST1) to the cutting step (ST7) in the present embodiment. As shown in FIG. 2, the glass substrate manufacturing apparatus mainly includes a melting apparatus 100, a molding apparatus 200, and a cutting apparatus 300. The melting device 100 includes a melting tank 101, a clarification pipe 102, a stirring tank 103, transfer pipes 104 and 105, and a glass introduction pipe 106.
The melting tank 101 shown in FIG. 2 is provided with a heating means such as a burner (not shown). The glass raw material to which the fining agent is added is put into the melting tank 101, and the melting step (ST1) is performed. The molten glass melted in the melting tank 101 is supplied to the clarification pipe 102 via the transfer pipe 104.
In the clarification tube 102, the temperature of the molten glass MG is adjusted, and the clarification step (ST2) of the molten glass is performed by utilizing the redox reaction of the fining agent. Specifically, when the temperature of the molten glass in the clarifying tube 102 is raised _{, the bubbles containing oxygen, CO 2} or SO ₂ contained in the clarifying glass absorb the oxygen generated by the reduction reaction of the clarifying agent. It grows and floats on the liquid surface of the molten glass and is released into the vapor phase space. After that, by lowering the temperature of the molten glass, the reducing substance produced by the reduction reaction of the clarifying agent undergoes an oxidation reaction. As a result, gas components such as oxygen in the bubbles remaining in the molten glass are reabsorbed in the molten glass, and the bubbles disappear. The clarified molten glass is supplied to the stirring tank 103 via the transfer pipe 105.
In the stirring tank 103, the molten glass is stirred by the stirrer 103a to perform the homogenization step (ST3). The molten glass homogenized in the stirring tank 103 is supplied to the molding apparatus 200 via the glass introduction pipe 106 (supply step ST4).
In the molding apparatus 200, the sheet glass SG is molded from the molten glass (molding step ST5) and slowly cooled (slow cooling step ST6) by, for example, an overflow down draw method.
In the cutting device 300, a plate-shaped glass substrate cut out from the sheet glass SG is formed (cutting step ST7).

(Composition of clear pipe)
Next, the configuration of the clarification pipe 102 will be described with reference to FIG. FIG. 3 is a schematic view showing the configuration of the clarification pipe 102.
The clarification tube 102 is a tubular member made of a material containing a platinum group metal. The platinum group metal refers to the six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), and iridium (Ir). As the material containing a platinum group metal, a material composed of a platinum group metal composed of a single element or an alloy of a platinum group metal is used. For example, platinum or platinum alloys are used.

Flange-shaped electrodes 121a, 121b, 121c are connected to the outer peripheral surface of the clarification pipe 102. In the example shown in FIG. 3, the electrodes 121a to 121c are arranged at three positions at both ends and the center of the clarification tube 102 in the longitudinal direction. The electrodes 121a to 121c are connected to the power supply device 122. By applying a voltage between the electrodes 121a and 121b and between the electrodes 121b and 121c, a current flows between the electrodes 121a and 121b and between the electrodes 121b and 121c, respectively, and the clarification pipe 102 is energized and heated. To.
By this energization heating, the maximum temperature of the clarification tube 102 is heated to, for example, 1600 ° C. to 1750 ° C., more preferably 1630 ° C. to 1750 ° C. between the electrodes 121a and 121b, and the molten glass flowing in the clarification tube 102. The maximum temperature is 1600 ° C. to 1720 ° C., more preferably 1620 ° C. to 1720 ° C., which is suitable for defoaming. Further, between the electrodes 121b and 121c, the maximum temperature of the clarification tube 102 is heated to, for example, 1590 ° C. to 1670 ° C., more preferably 1620 ° C. to 1670 ° C., and the maximum temperature of the molten glass flowing in the clarification tube 102 is , The temperature suitable for absorption is 1590 ° C to 1640 ° C, more preferably 1610 ° C to 1640 ° C.

The power supply device 122 is controlled by the control device 123. The control device 123 controls the amount of current that the power supply device 122 energizes the clarification pipe 102, thereby controlling the temperature of the molten glass passing through the clarification pipe 102. The control device 123 is a computer including a CPU, a memory, and the like.
Further, the electrodes 121a to 121c are cooled by using water or air. Therefore, in the clarification tube 102, a region where the temperature is locally lowered is formed corresponding to the arrangement position of the electrodes 121a to 121c.
The number of electrodes provided on the clarification tube 102 is not limited to three, and may be two or four or more.

In the clarification step (ST2), clarification is performed while flowing the molten glass into the clarification tube 102 so that the vapor phase space 120a is formed above the liquid surface of the molten glass. As shown in FIG. 4, the clarification tube 102 has a vent hole 102a for discharging the gas in the gas phase space and a gas inert to the molten glass (hereinafter, referred to as the gas) on the wall portion in contact with the gas phase space 120a. An introduction hole 102b is formed to guide the (referred to as an inert gas) into the gas phase space. FIG. 4 is a vertical cross-sectional view of the clarification pipe 102 in the longitudinal direction. The ventilation holes 102a and the introduction holes 102b are arranged apart from each other in the flow direction of the molten glass.
The ventilation hole 102a does not include a hole (for example, an opening 131 described later) formed with the use of the clarification pipe 102. The discharge of the gas from the ventilation hole 102a may be continuously performed or intermittently performed during the clarification step (ST2). The gas discharged from the ventilation hole 102a is a gas containing oxygen, and may contain an inert gas.

The clarification pipe 102 is covered with castable cement (not shown), and heat insulating members (not shown) such as refractory bricks and members made of platinum group metal are stacked on the outside thereof. That is, a heat insulating member is provided around the clarification pipe 102. The heat insulating member is arranged so as to be in contact with each of the electrodes 121a to 121c and the ventilation pipe 127, which will be described later.

A ventilation pipe 127 is connected to the outer peripheral surface of the wall portion where the ventilation hole 102a is located. The ventilation pipe 127 communicates the gas phase space 120a with the space outside the clarification pipe 102 (for example, the atmosphere). In the example shown in FIG. 3, the ventilation pipe 127 is provided so as to extend vertically upward from the top of the wall portion. The ventilation holes 102a and the ventilation pipe 127 are arranged, for example, at a position where the molten glass reaches the maximum temperature in the clarification step (ST2), or near the downstream side thereof. The ventilation hole 102a and the ventilation pipe 127 are provided in the clarification pipe 102 region (first heating region) between the electrodes 121a and 121b in the example shown in FIG.
The ventilation pipe 127 is provided with a suction device 129 for sucking gas and suspended matter in the gas phase space 120a. The suction device 129 can reduce the pressure on the ventilation pipe 127 side (for example, about 10 Pa lower than the atmospheric pressure). The suction device 129 is controlled by the control device 123. By controlling the suction pressure by the suction device 129, the concentration of oxygen in the gas phase space 120a can be reduced. Further, by controlling the suction pressure, the amount of the inert gas supplied from the external space described later to the gas phase space 120a can be adjusted.

The ventilation pipe 127 is surrounded by a heat insulating member (described later), and the opening degree of the ventilation pipe 127 can be adjusted by adjusting the size of the gap of the heat insulating member arranged near the upper end of the ventilation pipe 127. it can. The gas is discharged from the ventilation hole 102a not only by suction by the suction device 129 but also by the pressure difference between the inside and outside of the clarification pipe 102.
The ventilation pipe 127 is provided with an oxygen concentration meter 128. The oxygen concentration meter 128 measures the oxygen concentration of the gas passing through the ventilation hole 102a, and outputs the measurement signal to the control device 123. The oxygen concentration signal measured by the oxygen concentration meter 128 is output to the control device 123, and the control device 123 controls the inert gas supply device 125 according to the oxygen concentration signal, and supplies and supplies the inert gas. Adjust the pressure.

The introduction pipe 124 is connected to the outer peripheral surface of the wall portion where the introduction hole 102b is located. In the example shown in FIG. 3, the introduction hole 102b and the introduction pipe 124 are provided in the region (second heating region) of the clarification pipe 102 between the electrodes 121b and 121c. On the outside of the clarification pipe 102 where the introduction hole 102b and the introduction pipe 124 are located, the heat insulating member is arranged with a gap from the introduction hole 102b and the introduction pipe 124, and as shown in FIG. 4, the introduction hole 102b and the introduction pipe 124 are arranged. An external space 140 surrounding the introduction pipe 124 is formed. In the example shown in FIG. 4, the external space 140 is defined by the surrounding surface of the enclosure 141, the supply pipe 142 described later, and the clarification pipe 102. The portion of the heat insulating member in contact with the external space 140 is referred to as an enclosure 141 in the following description.
Above the introduction pipe 124, a supply pipe 142 for supplying the inert gas into the external space 140 is arranged. The supply pipe 142 is connected to the inert gas supply device 125. The supply pipe 142 is made of, for example, a ceramic material or a metal material such as a platinum group metal or stainless steel. The inert gas supply device 125 is controlled by the control device 123, and the supply amount and supply pressure of the inert gas into the enclosure 141 are adjusted.
A lid (not shown) is arranged at the upper end of the introduction pipe 124 so as to block the gas flow path. The lid is provided with a plurality of small holes (for example, a diameter of 1 mm or less) that communicate with the external space 140 and the inside of the introduction pipe 124. When the inert gas supplied from the inert gas supply device 125 collides with the lid, the velocity component in the direction toward the gas phase space 120a is canceled.

The inert gas supplied from the inert gas supply device 125 is preferably inert not only to the molten glass but also to the platinum group metal. For example, nitrogen (N ₂ ), a rare gas (for example, argon (Ar)), carbon monoxide (CO) and the like can be used. Argon and carbon monoxide are more mobile in the glass structure than nitrogen. Therefore, even when the inert gas dissolved in the molten glass is generated as bubbles, it is easily taken into the glass again during the transfer of the molten glass, and the adoption of argon is preferred from the viewpoint of foam quality.

(Clearing process)
Next, the supply of the inert gas performed in the clarification step (ST2) will be described.
In the clarification step (ST2), the inert gas is supplied so that the oxygen concentration in the gas phase space 120a is within a certain range (for example, a range of 5% or less). Specifically, the oxygen concentration signal measured by the oxygen concentration meter 128 is output to the control device 123, and the control device 123 controls the inert gas supply device 125 and the suction device 129 in response to the oxygen concentration signal. Adjust the supply amount, supply pressure, and suction pressure of the inert gas. By supplying the inert gas in this way, the volatilization of the platinum group metal can be suppressed.

In such a supply of the inert gas, the inert gas is retained in the external space 140 and the gas is discharged from the ventilation hole 102a, so that the inert gas in the external space 140 is drawn into the gas phase space 120a and melted. It is performed by flowing along the flow direction of the glass. Specifically, the control device 123 controls the inert gas supply device 125 to surround the inert gas and supply it into the 141. At this time, the inert gas collides with the lid of the introduction pipe 102b and stays in the external space 140. The control device 123 further controls the suction device 129 to draw the inert gas in the enclosure 141 into the gas phase space 120a and adjust the suction pressure so as to flow along the flow direction of the molten glass. As a result, the inert gas staying in the external space 140 is introduced into the gas phase space 120a by laminar flow from a state where it does not have an initial velocity in the direction toward the gas phase space 120a, and is along the flow direction of the molten glass. Then, in FIG. 3, it flows from the right side to the left side.

As shown in FIG. 5, the amount of the inert gas supplied in this way is reduced in the molten glass as compared with the case where the inert gas is directly injected into the gas phase space 220a from the introduction hole 202a. It turned out to be done.
FIG. 5 is a vertical cross-sectional view of the conventional clarification pipe 202 in the longitudinal direction. In the example shown in FIG. 5, the inert gas supplied from the inert gas supply device (not shown) is supplied into the gas phase space 220a through the supply pipe 242 and the introduction pipe 224 connected to each other. .. In this case, since the inert gas is sprayed so as to act a dynamic pressure on the liquid surface of the molten glass, it is easily dissolved in the molten glass. The inert gas dissolved in the molten glass tends to appear as bubbles after clarification and remains on the glass substrate, which may deteriorate the quality of the glass substrate.
In the present embodiment, the inert gas is temporarily retained outside the clarification tube 102 and then supplied into the gas phase space 120a by being drawn into the gas phase space 120a, so that the inert gas is supplied into the gas phase space 120a with respect to the liquid surface of the molten glass. The acting pressure is smaller than that shown in FIG. 5, and the amount of the inert gas dissolved in the molten glass is reduced. Therefore, it is possible to suppress the generation of bubbles in the molten glass after clarification, and it is possible to obtain a glass substrate having high foam quality.

Specifically, in the present embodiment, an amount of inert gas required to make the oxygen concentration in the gas phase space 120a the same concentration is supplied to the gas phase space 120a at a slower flow rate than in the example shown in FIG. Alternatively, suction is performed from the ventilation pipe 127 having a larger opening than in the example shown in FIG. In the example shown in FIG. 5, the suction pressure by the suction device is smaller than the supply pressure of the inert gas supplied to the gas phase space, whereas in the present embodiment, the suction pressure by the suction device 129 is inactive. The pressure of the gas is greater than the pressure supplied into the gas phase space 120a.

In the present embodiment, it is preferable that the inert gas is drawn in through the introduction hole 102b provided in the second heating region of the clarification pipe 102. In the clarification tube 102, the defoaming treatment is performed in the first heating region, and the absorption treatment is performed in the second heating region. Therefore, the inert gas existing in the portion of the gas phase space 120a located in the second heating region is easily taken into the molten glass. In the present embodiment, as described above, the inert gas is temporarily retained outside the clarification tube 102 and then drawn into the gas phase space 120a to prevent the inert gas from melting into the molten glass. Can be done.

In the present embodiment, the inert gas is preferably argon gas from the viewpoint of suppressing the generation of bubbles in the molten glass after clarification.
Further, in order to suppress the aggregation of the platinum group metal volatilized in the vapor phase space 120a, it is preferable to preheat the inert gas in the enclosure 141. The residual heat temperature of the inert gas is preferably 500 ° C. or higher, for example.

This embodiment is suitable when the difference between the maximum temperature of the molten glass in the clarification step (ST2) and the minimum temperature of the molten glass in the transfer step is 200 ° C. or more. The transfer step is a step of transferring the molten glass flowing out of the clarification pipe 102 after the clarification step (ST2). In the transfer step, the molten glass is transferred in the transfer pipe 105 connected to the downstream side in the flow direction of the clarification pipe 102.
After the defoamed glass has passed through the clarification pipe 102, it is transferred into the transfer pipe 105, and the homogenization step (ST3) is performed in the stirring tank 103. A heating device is generally arranged on the outside of the transfer pipe 105, and the molten glass is transferred while being kept warm. In this process, the temperature of the molten glass is lowered, but as a result of the temperature rising locally, the bubbles absorbed by the molten glass by the absorption treatment may be defoamed again. It can also occur when the molten glass comes into contact with the stirrer 103a in the stirring tank 103. It was found that such bubbles are more likely to be generated as the temperature difference between the clarification step and the transfer step is larger. According to the present embodiment, even when the temperature difference between the clarification step and the transfer step is large, the inert gas is drawn into the vapor phase space 120a as described above, so that the inert gas can be transferred to the molten glass. Since the amount of dissolution is reduced, the generation of such bubbles can be suppressed.

Further, in the present embodiment, unlike the example shown in FIG. 5, the introduction pipe 124 and the supply pipe 142 are separated from each other, but even if a foreign substance is generated in the external space 140, the lid of the introduction pipe 124 is used. Therefore, it can be prevented from falling into the introduction pipe 124 and being mixed with the molten glass.

(Glass substrate)
The size of the glass substrate produced in the present embodiment is not particularly limited, but for example, the vertical dimension and the horizontal dimension are 500 mm to 3500 mm, 1500 mm to 3500 mm, 1800 to 3500 mm, 2000 mm to 3500 mm, and 2000 mm to 3500 mm, respectively. Is preferable.
The thickness of the glass substrate is, for example, 0.1 to 1.1 mm, more preferably 0.75 mm or less, and an extremely thin rectangular plate, for example, 0.55 mm or less, further 0.45 mm or less. The thickness is more preferable. The lower limit of the thickness of the glass substrate is preferably 0.15 mm, more preferably 0.25 mm.

<Glass composition>
Examples of such a glass substrate include a glass substrate having the following glass composition. That is, the raw materials for the molten glass are prepared so that a glass substrate having the following glass composition is produced.
SiO ₂ 55-80 mol%,
Al ₂ O ₃ 8-20 mol%,
B ₂ O ₃ 0 to 12 mol%,
RO 0 to 17 mol% (RO is the total amount of MgO, CaO, SrO and BaO).

SiO ₂ is preferably 60 to 75 mol%, more preferably 63 to 72 mol% from the viewpoint of reducing the heat shrinkage rate.
Of the RO, MgO is preferably 0 to 10 mol%, CaO is 0 to 15 mol%, SrO is 0 to 10%, and BaO is 0 to 10%.

Further, it _{contains at least SiO 2} , Al ₂ O ₃ , B ₂ O ₃ , and RO, and the molar ratio ((2 × SiO ₂ ) + Al ₂ O ₃ ) / ((2 × B ₂ O ₃ ) + RO) is 4. It may be glass having 5 or more. Further, it is preferable that at least one of MgO, CaO, SrO, and BaO is contained, and the molar ratio (BaO + SrO) / RO is 0.1 or more.

Further, _{the total of twice the content of B 2} O ₃ in mol% and the content of RO in mol% is preferably 30 mol% or less, preferably 10 to 30 mol%.
Further, the content of the alkali metal oxide in the glass substrate having the above glass composition may be 0 mol% or more and 0.4 mol% or less.
In addition, it contains a total of 0.05 to 1.5 mol% of metal oxides (tin oxide, iron oxide) whose valence fluctuates in glass, _{and substantially contains As 2} O ₃ , Sb ₂ O _3, and PbO. Not being required is not mandatory but optional.

Further, it is preferable that non-alkali boroaluminosilicate glass or glass containing a trace amount of alkali is used for the glass substrate produced by the present embodiment.
The glass substrate produced by this embodiment is preferably made of non-alkali glass containing, for example, the following composition.
Examples of the glass composition of the glass substrate produced by the present embodiment include the following (indicated by mass%).
SiO ₂ : 50 to 70% (preferably 57 to 64%), Al ₂ O ₃ : 5 to 25% (preferably 12 to 18%), B ₂ O ₃ : 0 to 15% (preferably 6). ~ 13%) may be included, and the composition shown below may be optionally included. As optionally contained components, MgO: 0 to 10% (preferably 0.5 to 4%), CaO: 0 to 20% (preferably 3 to 7%), SrO: 0 to 20% (preferably, preferably). 0.5-8%, more preferably 3-7%), BaO: 0-10% (preferably 0-3%, more preferably 0-1%), ZrO ₂ : 0-10% (preferably) , 0-4%, more preferably 0-1%). Additionally, R _'2 O: 2.0% greater than the 0.10% or less (, R' is Li, at least one selected from Na and K) more preferably contains a.

Alternatively, SiO ₂ : 50 to 70% (preferably 55 to 65%), B ₂ O ₃ : 0 to 10% (preferably 0 to 5%, 1.3 to 5%), Al ₂ O ₃ : 10-25% (preferably 16-22%), MgO: 0-10% (preferably 0.5-4%), CaO: 0-20% (preferably 2-10%, 2-6) %), SrO: 0 to 20% (preferably 0 to 4%, 0.4 to 3%), BaO: 0 to 15% (preferably 4 to 11%), RO: 5 to 20% (preferably). Is preferably contained (8 to 20%, 14 to 19%), where R is at least one selected from Mg, Ca, Sr and Ba). Additionally, R _'2 O is 2.0% or less than 0.10% (however, R' is Li, at least one selected from Na and K) more preferably contains a.

<Young's modulus>
As the Young's modulus of the glass substrate produced by the present embodiment, for example, 72 GPa or more is preferable, 75 GPa or more is more preferable, and 77 GPa or more is further preferable.

<Distortion point>
As the distortion rate of the glass substrate produced by the present embodiment, for example, 650 ° C. or higher is preferable, 680 ° C. or higher is more preferable, and 700 ° C. or higher and 720 ° C. or higher are even more preferable.

<Heat shrinkage rate>
The heat shrinkage of the glass substrate produced by the present embodiment is, for example, 50 ppm or less, preferably 40 ppm or less, more preferably 30 ppm or less, and even more preferably 20 ppm or less. The range of the heat shrinkage of the glass substrate before reducing the heat shrinkage is preferably 10 ppm to 40 ppm.

The glass substrate manufactured in this embodiment is suitable as a glass substrate for a flat panel display and a glass substrate for a display including a glass substrate for a curved panel display. For example, a glass substrate for a liquid crystal display or a glass for an organic EL display. Suitable as a substrate. Further, the glass substrate manufactured in this embodiment includes a glass substrate for an oxide semiconductor display using an oxide semiconductor such as IGZO (indium, gallium, zinc, oxygen) used for a high-definition display, and LTPS (low). It is suitable for a glass substrate for LTPS display using a (temperature polysilicon) semiconductor.
Further, the glass substrate manufactured in this embodiment can be applied to a cover glass, a glass for a magnetic disk, a glass substrate for a solar cell, and the like.

Although the glass substrate manufacturing method and the glass substrate manufacturing apparatus of the present invention have been described in detail above, the present invention is not limited to the above embodiment, and various improvements and changes are made without departing from the gist of the present invention. Of course, it may be.

100 Melting device 101 Melting tank 102 Clarifying pipe 102a Ventilation hole 102b Introduction hole 103 Stirring tank 103a Stirrer 104, 105 Transfer pipe 106 Glass introduction pipe 120a Gas phase space 121a to 121c Electrode 123 Control device 124 Introduction pipe 125 Inactive gas supply device 127 Ventilation tube 200 Molding device 300 Cutting device MG Melted glass SG Sheet glass

Claims (3)

Equipped with a clarification process for clarifying molten glass using a clarification tube
In the clarification step, the clarification is performed using the clarifying agent contained in the molten glass while flowing the molten glass into the clarification tube so that a gas phase space is formed above the liquid surface of the molten glass.
The clarification tube is made of a material containing a platinum group metal, and a vent hole for discharging a gas in the gas phase space and a gas inert to the molten glass are provided in a wall portion in contact with the gas phase space. It has an introduction hole leading into the gas phase space, and the ventilation hole and the introduction hole are arranged apart from each other in the flow direction of the molten glass.
The clarification tube is provided along the flow direction of the molten glass to a first heating region for heating the molten glass so as to promote defoaming of the molten glass, and to the molten glass of bubbles remaining after the defoaming. Has a second heating region, which heats the molten glass to promote absorption of
The introduction hole is arranged in the second heating region.
In the clarification step, the inert gas is retained in the external space outside the clarification pipe adjacent to the introduction hole, and the gas is discharged from the ventilation hole, whereby the inert gas in the external space is discharged. A method for manufacturing a glass substrate, which comprises drawing a gas into the gas phase space and flowing the gas along the flow direction of the molten glass. The production of the glass substrate according to claim 1, wherein the external space is a member made of a refractory material arranged so as to surround the introduction hole from the outside of the clarification pipe, and a space defined by the clarification pipe. Method. Is formed of a material containing a platinum group metal, the with the flow of the molten glass so that the gas phase space is formed above the liquid surface of the molten glass, fining is performed with a fining agent contained in the molten glass refining a tube, the wall portion in contact with the front Kiki phase space, the vent hole for discharging gas in the gas phase space, introduction hole leading to a gas inert to the molten glass in the gas phase space And, the ventilation hole and the introduction hole are arranged apart from each other in the flow direction of the molten glass.
An enclosure made of a refractory material arranged so as to surround the introduction hole from the outside of the clarification pipe,
An inert gas supply device that supplies the inert gas into the enclosure,
A suction device that sucks and discharges the gas from the ventilation holes,
A control device that controls the suction device so that the inert gas in the enclosure is drawn into the gas phase space by discharging the gas from the ventilation holes and flows along the flow direction of the molten glass. And with
The clarification tube is provided along the flow direction of the molten glass to a first heating region for heating the molten glass so as to promote defoaming of the molten glass, and to the molten glass of bubbles remaining after the defoaming. Has a second heating region, which heats the molten glass to promote absorption of
A glass substrate manufacturing apparatus, wherein the introduction hole is arranged in the second heating region.

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