JP5956009B2 - Glass substrate manufacturing method and glass substrate manufacturing apparatus - Google Patents

Description

  The present invention relates to a method for manufacturing a glass substrate, in which a glass substrate is manufactured by molding a molten glass produced by melting a glass raw material.

A glass substrate is generally manufactured through a process of forming molten glass from a glass raw material and then forming the molten glass into a glass substrate. The above process includes a step of removing minute bubbles contained in the molten glass (hereinafter also referred to as clarification) as necessary. The clarifier passes through a glass melt containing a clarifier such as As ₂ O _{3 in} the clarifier main body (hereinafter also simply referred to as the main body) while heating the main body of the tubular clarifier, and the redox of the clarifier is reduced. The reaction is performed by removing bubbles in the molten glass. 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). Conventionally, As ₂ O ₃ has been commonly used as a fining agent, but SnO ₂ , Fe ₂ O _{3 and the} like have come to be used from the viewpoint of environmental load in recent years.

In order to mass-produce high-quality glass substrates from high-temperature molten glass, it is desirable to consider that foreign substances that cause defects in the glass substrate do not enter the molten glass from any device that produces the glass substrate. It is. For this reason, the inner wall of the member in contact with the molten glass in the manufacturing process of the glass substrate 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 platinum group metal such as platinum or a platinum alloy is usually used as the material constituting the clarification tank body (Patent Document 1). Platinum or a platinum alloy is expensive but has a high melting point and excellent corrosion resistance against molten glass.
Although the temperature which heats a clarification tank main body at the time of a defoaming process changes with compositions of the glass substrate which should be shape | molded, it is about 1000-1650 degreeC.
When passing the above-mentioned molten glass through the clarification tank body, it is necessary to have a defoaming gas phase space of a certain width between the inner surface of the clarification tank body and the liquid surface of the molten glass. is there.

JP 2006-522001 Gazette

As described above, platinum or platinum alloy has a higher melting point than other substances, but when the temperature of the clarification tank body exceeds, for example, 1600 ° C., platinum or platinum alloy softens, so the strength of the clarification tank body Will fall.
Here, since the part which contact | connects gaseous-phase space among clarification tank main bodies is not in contact with molten glass, temperature becomes high compared with the part which contacts molten glass among clarification tank main bodies. That is, the portion of the clarification tank main body that is in contact with the gas phase space has a problem that the temperature is higher than the other areas of the clarification tank main body and the strength tends to decrease, so that deformation tends to occur. As said deformation | transformation, the deformation | transformation (hanging down) to the gravitational direction which advances with time is mentioned, for example. Note that the above-described deformation increases with time.
Or since the part which touches gaseous-phase space among the above-mentioned clarification tank main bodies thins by the secular change of the main body, there existed a subject that it would hang down in the gaseous-phase space direction (gravity direction).
About the above-mentioned part of a clarification tank main body hanging down, the following double causes can be considered.
1) The platinum or platinum alloy in the portion of the clarification tank main body that comes into contact with the gas phase space is volatilized, and the thickness of the portion of the clarification tank main body where the volatilization proceeds is reduced. For this reason, the intensity | strength of the upper part of a clarification tank main body falls, and the upper part of a clarification tank main body hangs down with dead weight with respect to the gaseous-phase space direction.
2) Due to the volatilization of 1 above, the thickness of the part where the volatilization of the clarification tank body has progressed becomes thin. For example, the density of the current supplied from the heater electrode for heating connected to the body increases, and as a result The temperature of the part where the volatilization of the tank body has progressed increases. For this reason, the intensity | strength of the upper part of a clarification tank main body falls, and the upper part of a clarification tank main body hangs down with dead weight with respect to the gaseous-phase space direction.
On the other hand, since the temperature of the molten glass that has passed through the clarification tank body is adjusted so as to decrease to a temperature corresponding to the viscosity suitable for molding, further, a transfer pipe that leads the molten glass after the clarification tank body to the molding process. Since there is no gas phase space, there is no problem of deformation due to heat or thinning due to aging in the transfer pipe.

When “deformation” or “sagging” occurs in the clarification tank body as described above, for example, in the case of a clarification tank configured to be covered with a refractory coating, between the outer upper part of the clarification tank and the coating A gap will be created. If air containing external oxygen is taken into the gap, volatilization of platinum or a platinum alloy may be promoted on the outer surface of the portion in contact with the gas phase space on the inner wall of the main body.
Similarly, the clarification tank main body is cracked due to “deformation” and “sagging”, and the inner wall of the main body is in contact with the molten glass flowing inside the main body, increasing the chance of foreign matter mixing in. was there.
In view of the above, the present invention intends to provide a glass substrate manufacturing method and a glass substrate manufacturing apparatus that can prevent deformation of the clarification tank body due to heat.
Alternatively, in the present invention, when the clarification tank main body is heated and defoamed in the glass substrate manufacturing process, even if the clarification tank main body is thinned by volatilization of the material, the portion in contact with the gas phase space of the main body is in the gas phase. An object of the present invention is to provide a glass substrate manufacturing method and a glass substrate manufacturing apparatus that do not hang down in the space direction.

  In order to achieve the above-described object, one embodiment of the present invention is a method for manufacturing a glass substrate. The said manufacturing method has the clarification process which heats molten glass and defoams inside the clarification tank main body comprised with the platinum group metal. A gas phase space is provided in the clarification tank body between the inner surface of the clarification tank body and the liquid surface of the molten glass. The clarification tank body is provided with a clarification tank shape holding means for preventing deformation of the clarification tank body in contact with the gas phase space due to heat.

In order to achieve the above-described object, another aspect of the present invention is to defoam by passing a molten glass containing a clarifier in the clarification tank body while heating the clarification tank body which is a tubular clarification tank. It is a manufacturing method of the glass substrate including the defoaming process which processes, Comprising: It is comprised as follows.
The clarification tank body is composed of platinum or a platinum alloy, and is provided between the inner surface of the clarification tank body and the liquid surface of the molten glass when passing the molten glass in which the clarification agent is blended in the clarification tank body. A clarification tank shape holding means for preventing a portion of the clarification tank body that comes into contact with the gas phase space from drooping in the direction of the gas phase space due to thinning, having a gas phase space for defoaming. Is provided.

It is preferable that the clarification tank shape holding means is provided so as to include at least a position where the temperature is highest in the longitudinal direction of the clarification tank body. For example, the clarification tank shape holding means is provided at a plurality of positions in the longitudinal direction of the clarification tank body. At this time, one of the plurality of positions where the clarification tank shape holding means is provided is a position where the temperature is highest in the longitudinal direction of the clarification tank body.
Furthermore, when the cross-sectional shape of the clarification tank main body is a circular shape, the clarification tank shape holding means is a portion where the temperature is highest among at least the arc portion of the outer surface of the clarification tank main body in contact with the gas phase space. It is preferable that it is provided so as to include.
Moreover, it is preferable that the said clarification tank main body is heated by an electrical heating from a viewpoint of energy efficiency.
It is preferable that the clarification tank main body is provided with a thermal spray film on at least the outer surface of the clarification tank main body in contact with the gas phase space.

At this time, a fireproof protective layer is provided outside the clarification tank body so as to cover the clarification tank body,
It is preferable that the clarification tank shape holding means is provided so as to hold the outer side of the clarification tank main body and the fireproof protective layer tightly.

  At this time, it is preferable that the temperature of the molten glass in the said clarification tank main body is 1600 degreeC or more.

  In addition, a layer of a refractory support is provided on the outside of the clarification tank body so as to cover the clarification tank body, and the clarification tank shape holding means is a member protruding outside the clarification tank body, The member preferably extends so that a tip portion of the member is located in a layer of the refractory support.

  Alternatively, the clarification tank shape holding means is a structure in the upper part of the clarification tank body, and a structure in which a relative position with respect to the clarification tank body is fixed, and the clarification tank body via the structure. It is also preferable that the suspension member is a suspension member that suspends the upper part, and is constituted by a suspension member having one end connected to the upper side of the outer surface of the clarification tank body and the other end connected to the structure.

  Further, the clarification tank shape holding means is arranged in a gap of the clarification tank body divided into a part or a plurality of the clarification tank body, and has one or more shapes corresponding to the cross-sectional shape of the clarification tank body. A reinforcing material is preferred.

  The fining agent is preferably tin oxide.

The molten glass may be composed of a composition having a temperature of 1300 ° C. or higher at which the viscosity becomes 10 ^2.5 poise.

  Furthermore, the glass substrate may be a glass substrate for LTPS (low temperature polysilicon) and / or a glass substrate for organic LE display. At this time, the strain point of the glass substrate may be 680 ° C. or higher. Moreover, it is preferable that the maximum temperature of the molten glass temperature in a clarification process is 1640 degreeC-1740 degreeC.

Moreover, the other aspect of this invention is a glass substrate manufacturing apparatus which has a clarification tank main body which is a tubular clarification tank for performing the defoaming process of molten glass in the manufacturing process of a glass substrate, Comprising: Has been.
The clarification tank body is made of a platinum group metal,
The internal space of the clarification tank main body comprises a defoaming gas phase space existing between the liquid surface of the molten glass,
A clarification tank shape holding means for holding the shape of the clarification tank main body for preventing the clarification tank main body at a position corresponding to the gas phase space from sagging is further provided.

It is preferable that the said clarification tank shape holding means in the manufacturing method of the said glass substrate and the said glass substrate manufacturing apparatus is a board member protruded to the outer side of the said clarification tank main body.
Moreover, it is preferable that the said plate member is provided at intervals in the longitudinal direction of the said clarification tank main body. At this time, it is preferable that the normal direction of the surface of the said plate member is a longitudinal direction of the said clarification tank main body. The thickness of the plate member is preferably 1 mm or more.

According to the glass substrate manufacturing method and the glass substrate manufacturing apparatus of the present invention, deformation of the clarification tank body due to heat can be prevented.
Alternatively, according to another glass substrate manufacturing method and glass substrate manufacturing apparatus of the present invention, even if a portion of the clarification tank main body that contacts the gas phase space is thinned due to aging, it hangs down in the gas phase space direction. There is no. Therefore, it is possible to avoid foreign matters from being mixed into the molten glass during the defoaming step, and a glass substrate with higher purity can be obtained.

It is a schematic block diagram of the glass substrate manufacturing apparatus for demonstrating the manufacturing method of the glass substrate of embodiment. It is the schematic which shows the basic composition of a clarification tank. It is the schematic of a clarification tank when a structure and a suspension member are used as a clarification tank shape holding means. It is a figure which shows an example of the shape and arrangement | positioning of a suspending member. It is the schematic of a clarification tank when using a ring-shaped reinforcement as a clarification tank shape holding means.

  Hereinafter, embodiments of a glass substrate manufacturing method and a glass substrate manufacturing apparatus according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram for explaining a glass substrate manufacturing method according to an embodiment, and shows a basic flow in manufacturing a glass substrate in a simplified manner.
A glass substrate manufacturing apparatus (hereinafter also simply referred to as an apparatus) 100 includes a melting tank 10 that heats a glass raw material to produce a molten glass, a clarification tank 30 that clarifies the molten glass, and a molding apparatus that molds the molten glass (FIG. (Not shown) and transfer pipes 20 and 40 for connecting them. The transfer pipe 20 connects the melting tank 10 and the clarification tank 30, and supplies the molten glass derived from the melting tank 10 to the clarification tank 30. The transfer pipe 40 connects the clarification tank 30 and a molding apparatus (not shown), and supplies the molten glass led out from the clarification tank 30 to the molding apparatus (not shown). In addition, between the clarification tank 30 and a shaping | molding apparatus, the stirring tank for stirring and homogenizing a molten glass may be arrange | positioned.

The glass raw material thrown into the melting tank 10 is suitably prepared according to the composition of the glass substrate to be manufactured. As an example, when manufacturing a glass substrate used as a TFT (Thin Film Transistor) type LCD (Liquid Crystal Display) substrate, the glass composition constituting the glass substrate is displayed in mass%,
SiO _2: 50~70%,
Al ₂ O _3: 0~25%,
B ₂ O ₃ : 1 to 15%,
MgO: 0 to 10%,
CaO: 0 to 20%,
SrO: 0 to 20%,
BaO: 0 to 10%,
RO: 5-30% (however, R is all the glass substrate contains among Mg, Ca, Sr and Ba),
It is preferable that it is an alkali free glass containing.
Although the alkali-free glass is used in this embodiment, the glass substrate may be a glass containing a trace amount of alkali containing a trace amount of alkali metal. When an alkali metal is contained, the total of R ′ ₂ O is 0.10% or more and 0.5% or less, preferably 0.20% or more and 0.5% or less (where R ′ is selected from Li, Na, and K) It is preferable that the glass substrate contains at least one kind. Of course, the total of R ′ ₂ O may be less than 0.10%.
Also, when applying the method of manufacturing a glass substrate of the present invention, the glass composition, in addition to the above components, and in _wt%, SnO 2: 0.01~1% (preferably 0.01 _{~0.5%), Fe 2 O 3} : 0~0.2% ( preferably containing from 0.01 to 0.08 percent), taking into account the environmental _{impact, As 2 O 3, Sb 2} O 3 And you may prepare a glass raw material so that PbO may not be included substantially.

The molten glass generated in the melting tank 10 is sent to the clarification tank 30 through the transfer pipe 20. In the clarification tank 30, the molten glass is maintained at a predetermined temperature (in the case of glass having the above composition, for example, 1500 ° C. or higher), and clarification including a defoaming step for removing bubbles contained in the molten glass is performed.
Further, the molten glass clarified in the clarification tank 30 is sent to the molding apparatus via the transfer pipe 40. The molten glass is a temperature suitable for molding in the transfer pipe 40 when it is sent from the clarification tank 30 to the molding apparatus (in the case of glass having the above composition, for example, 1200 ° C. when the overflow downdraw method is used as the molding method). To a degree). In the forming apparatus, the molten glass is formed into a glass substrate.

Next, clarification including the defoaming step will be described with reference to FIGS. FIG. 2 is a schematic view showing the basic configuration of the clarification tank 30, and shows the inside transparently.
The clarification tank 30 is mainly composed of a clarification tank main body (hereinafter also referred to as a main body) 1 and heater electrodes 1 a and 1 b connected to the main body 1. The main body 1 is a metal tube of platinum alloy such as platinum or platinum rhodium alloy, and generally has a cylindrical shape. The molten glass MG flows through the inside of the main body 1 using the pipe line of the main body 1 as a flow path. The heater electrodes 1a and 1b cause a current to flow from the outer peripheral wall surface of the main body 1 to the main body 1 and heat the outer peripheral wall of the main body 1 using Joule heat generated by the resistance of the main body 1 to bring the temperature of the molten glass MG to a predetermined temperature. The defoaming of the molten glass MG is carried out using a fining agent mixed with the molten glass MG.

The molten glass MG flowing through the inside of the main body 1 does not flow through the entire flow path cross section of the main body 1, but normally, the bubbles defoamed by the defoaming treatment of the molten glass MG are released above the inside of the main body 1. The gas phase space a exists. That is, inside the main body 1, a gas phase space a is provided between the inner surface of the main body 1 and the liquid level of the molten glass MG. By adjusting the liquid level of the molten glass MG flowing through the main body 1 of the clarification tank 30, the gas phase space a can obtain a predetermined size or can maintain a certain size. For example, a suitable method such as increasing or decreasing the amount of glass material put into the melting tank 10 may be adopted.
Further, a gas exhaust port (not shown) for releasing the gas component in the bubbles released from the gas phase space a to the atmosphere is provided at the upper part of the main body 1.

In the glass substrate manufacturing method or the glass substrate manufacturing apparatus according to the present embodiment, the clarification tank shape for preventing the portion of the clarification tank body 1 in contact with the gas phase space a from being deformed by heat in the clarification tank 30. Holding means 2 is provided.
In the glass substrate manufacturing method or the glass substrate manufacturing apparatus according to another embodiment, a portion of the clarification tank body 1 that contacts the gas phase space a hangs down in the direction of the gas phase space a due to thinning. A clarification tank shape holding means 2 is provided to prevent this.
The clarification tank shape holding means will be further described in detail with reference to FIGS.

FIG. 3 is a schematic view showing an example of the clarification tank 30, and is a cross-sectional view including the clarification tank 30. As shown in FIG. 3, the clarification tank 30 of this embodiment includes a suspension member 2 </ b> B as the clarification tank shape holding means 2. Alternatively, as another embodiment, the clarification tank 30 includes a structure 2A and a suspension member 2B as the clarification tank shape holding means 2. That is, in this embodiment, the clarification tank shape holding means 2 means the suspension member 2B, and in other embodiments, the clarification tank shape holding means 2 includes the structure 2A and the suspension member 2B. .
The structure 2A is a structure in which the relative position with respect to the main body 1 is fixed at the upper part of the clarification tank main body 1. Here, a fireproof protective layer (hereinafter also referred to as a protective layer) 2Aa that covers the periphery of the clarification tank body 1 and a fireproof support (hereinafter also referred to as a support) 2Ab that covers and supports the protective layer 2Aa. It is composed.
The suspension member 2B is a suspension member that suspends the upper portion of the main body 1 via the structure 2A. The suspension member 2B passes through the structure 2A (the protective layer 2Aa and the support 2Ab), one end 2Ba of the suspension member is connected to the upper side of the outer surface of the main body 1, and the other end 2Bb is connected to the structure 2A. Specifically, the other end 2Bb is connected in a state of being bent horizontally along the upper part of the outer surface of the support 2Ab (FIG. 3).

The protective layer 2Aa serves to prevent the non-uniform force from being applied to the main body 1 and to support it reliably. For example, the protective layer 2Aa can be formed using an amorphous refractory. The amorphous refractory means, as is well known, a refractory that can be formed into a desired shape upon use, and typically represented as a clay-like or powdery product, as represented by mortar and cement. It is commercially available. The material of the irregular refractory is not particularly limited as long as the periphery of the main body 1 can be protected, but castable cement, particularly alumina cement excellent in fire resistance and corrosion resistance is suitable.
Since the main body 1 is often formed with a thickness of, for example, about 1 mm, it is desirable to dispose the protective layer 2Aa in order to reliably withstand the internal pressure caused by the molten glass passing through the inside of the main body 1. . The thickness of the protective layer 2Aa is preferably 2.0 mm or more, particularly 10.0 mm or more. Even if the protective layer 2Aa is too thick, there is no particular hindrance, but 50 mm or less is appropriate from the viewpoint of reducing the amount of material used.

On the other hand, the support 2Ab is disposed in the outermost layer of the structure 2A, supports the main body 1 and keeps it warm, and further protects the main body 1 from physical forces that may be applied from the outside. It is preferable to use a fixed refractory such as a refractory brick. Refractory bricks are often constructed by stacking a plurality of refractory bricks (solid bricks made of refractory) in a predetermined shape, and in many cases, a plurality of refractory fillers such as mortar are applied and fixed between them. Composed of bricks.
The refractory as used herein refers to a nonmetallic material that can withstand high temperatures as usual, specifically, a nonmetallic material having a refractory degree of 1000 ° C. or higher, preferably 1500 ° C. or higher. As is well known, the refractory is typically composed of oxides such as silica, alumina, zirconia, etc., and in some cases, the above oxides are blended with various components within the limit that does not impair the fire resistance. .

The suspension member 2B is made of, for example, platinum or a platinum alloy, which is the same material as the main body 1. One end 2Ba of the suspension member 2B is connected to the main body 1 by a suitable method such as welding. The other end 2Bb is connected to the upper side of the outer surface of the support 2Ab as already described. As shown in FIG. 3, the other end 2Bb may be bent horizontally along the upper portion of the outer surface of the support 2Ab, but may be connected using another suitable method.
The suspension member 2 </ b> B only needs to have a strength that prevents the portion of the main body 1 in contact with the gas phase space a from being deformed by heat or does not hang down in the direction of the gas phase space a. For example, they may be arranged one by one at regular intervals in the longitudinal direction of the tube of the main body 1 (FIGS. 3 and 4).
Here, the longitudinal direction of the tube refers to the flow direction of the molten glass MG through which the molten glass MG flows from the transfer tube 20 toward the transfer tube 40. FIG. 4 shows an example of the shape and arrangement of the suspension member 2B. The shape of the suspension member 2B is preferably a plate-like shape as in the example of FIG. 4, but is not limited to this as long as the shape of the clarification tank 30 can be maintained. The suspension member 2B shown in FIGS. 3 and 4 is a member projecting to the outside of the main body 1, and it is preferable that these members extend so that the tip portion of the member is located in the layer of the support 2Ab. Further, the suspension member 2B is provided so as to tightly hold the outside of the main body 1 and the fireproof protective layer 2Aa. Here, tightly holding means holding so that there is no gap between the outside of the main body 1 and the fireproof protective layer 2Aa.
In the configuration shown in FIG. 4, the suspension member 2B is a plate member, and this plate member is sandwiched between the supports 2Ab and is caused by a frictional force with the support 2Ab, or the plate member is attached to the support 2Ab with a bolt or the like. By fixing, the force which pulls the clarification tank main body 1 in the direction opposite to the force in the direction of gravity can be generated, and deformation of the clarification tank 30 can be suppressed. Thus, since the member extends so that the tip portion of the suspension member 2B is positioned on the layer of the support 2Ab, the temperature of the tip portion of the suspension member 2B is lower than the temperature of the main body 1. For this reason, the suspension member 2 </ b> B can prevent softening due to high temperature, and can effectively maintain the shape of the clarification tank 30.
The suspension member 2B, which is a plate member, is preferably provided at least at a position where the temperature is highest in the main body 1. For example, the suspension member 2 </ b> B is provided at a plurality of positions in the longitudinal direction of the main body 1. At this time, one of the plurality of positions where the suspension member 2 </ b> B is provided is a position where the temperature is highest in the longitudinal direction of the main body 1. This is because platinum or platinum alloy constituting the main body 1 softens and decreases in strength as the temperature rises, so that thermal deformation due to its own weight is likely to occur. However, for example, in the production of a glass substrate for display, the temperature of the main body 1 is 1600 ° C. or higher in most parts. . Therefore, as shown in FIG. 4, the suspension member 2 </ b> B that is a plate member is preferably provided with an interval in the longitudinal direction of the main body 1.
Of the glass substrates for display, particularly in the case of a glass substrate for LTPS (low temperature polysilicon) display and / or a glass substrate for organic EL display, the viscosity of glass (high temperature) is higher than that of other glass substrates for display glass. Therefore, it is necessary to increase the temperature of the molten glass at the time of refining compared to the time of manufacturing other glass substrates for display. Therefore, the strength reduction due to softening of platinum or platinum alloy of the main body 1 becomes remarkable, and the main body 1 is easily deformed. That is, in the production of the glass substrate for LTPS (low temperature polysilicon) display and / or the production of the glass substrate for organic EL display, the effect of preventing the clarification tank deformation by the clarification tank shape holding means 2 of the present invention becomes remarkable. As a glass substrate for LTPS (low temperature polysilicon) display and / or a glass substrate for organic EL display, a glass substrate having a strain point of 680 ° C. or higher, more preferably 700 ° C. or higher is preferably used. . In addition, since the viscosity at the same temperature tends to increase as the strain point increases, the higher the strain point glass, the higher the temperature of the clarification tank 30 is required for defoaming. It can be said that the effect of preventing clarification tank deformation by the clarification tank shape holding means 2 tends to be remarkable.
The interval at which the above-described suspension member 2B is provided is preferably 300 mm or less and 1 mm or more. More preferably, the interval is 150 mm or less, and further preferably, the interval is 50 mm or less. When the interval is extremely narrow, it is possible to ensure the prevention of deformation or sagging due to heat, but problems of workability and cost will emerge, so the optimal interval considering the length of the pipe etc. Shall be set to In particular, the normal direction of the suspension member 2 </ b> B is preferably the longitudinal direction of the main body 1 in that the shape of the clarification tank 30 is effectively retained. In addition, the thickness of the plate member is preferably 1 mm or more from the viewpoint of effectively holding the shape of the clarification tank 30. As an example, the suspension member 2B has a thickness of 1 mm and a width of about 10 mm.
Moreover, it is preferable that the suspension member 2B is connected to a region including at least the center portion of the arc portion that is in contact with the gas phase space a when the main body 1 is viewed in cross section. In other words, it is preferable that the suspension member 2B is connected to a region including a portion where the temperature is highest among arc portions in contact with the gas phase space a.
In addition, the suspension member 2B is 0.5% to 100%, more preferably 15% to 100%, more preferably 25% of the arc portion in contact with the gas phase space a when the main body 1 is viewed in cross section. It is desirable to connect to an area of ˜100%, particularly preferably 35% to 100%. Two or more suspension members 2B may be provided in the arc direction.

By providing the clarification tank shape holding means 2 as described above, in this embodiment, deformation of the clarification tank main body 1 due to heat can be reduced. Thereby, since generation | occurrence | production of the clearance gap into which air flows in between the outer surface of the part which touches gaseous-phase space among clarification tank main bodies 1 and a fireproof protective layer can be suppressed, gaseous-phase space among clarification tank main bodies 1 It is possible to prevent the volatilization of platinum or a platinum alloy from being promoted on the outer surface of the portion in contact with the surface. Furthermore, since the volatilization amount of the outer surface of the part in contact with the gas phase space in the clarification tank body 1 can be reduced, thinning in the part can be reduced. Thereby, since the current density of the outer surface of the part which touches gaseous-phase space among the clarification tank main bodies 1 can become higher than another area | region, it can suppress that temperature unintentionally rises, The problem of breakage and further increase in the amount of volatilization of the clarification tank body 1 can also be prevented.
Or in other embodiment, even if the part which the main body 1 contacts the gaseous-phase space a thins by volatilization of material, the part which contacts the gaseous-phase space of a main body does not hang down in the gaseous-phase space direction. Therefore, volatilization of platinum or platinum alloy is promoted at the portion of the inner wall that contacts the gas phase space, the clarification tank main body cracks due to drooping, or the inner wall of the main body contacts the molten glass flowing inside the main body Thus, there is no risk of increasing the chance of foreign matter being mixed in, and a glass substrate with higher purity can be obtained.
In particular, when the temperature of the molten glass in the main body 1 is set to 1600 ° C. or higher for the defoaming treatment, the main body 1 is heated higher than the temperature of the molten glass. For this reason, even high-temperature-resistant platinum or platinum alloy used for the main body 1 causes volatilization and strength reduction. For this reason, the shape of the clarification tank 30 can be effectively hold | maintained by using the suspension member 2B as shown in FIG. 3 or FIG.

Next, an example in which the clarification tank 30 includes the reinforcing material 2C as the clarification tank shape holding means 2 will be described with reference to FIG.
Here, a plurality of reinforcing materials 2C made of platinum or a platinum alloy, which is the same material as that of the main body 1, are arranged in the gap between the main bodies 1 divided into a plurality. The reinforcing material 2C has a shape corresponding to the cross-sectional shape of the clarification tank main body 1 and is formed in a ring shape with the same thickness as the main body 1 or slightly thicker, and is connected to the main body 1 by welding ( (A) and (b) of FIG.
By arranging such a reinforcing material 2C on the main body 1 at regular intervals, the reinforcing material 2C acts like a framework of the main body 1 and maintains the shape of the main body 1.
Like the suspension member 2B, the above-described interval is preferably 300 mm or less and 1 mm or more. More preferably, the interval is 150 mm or less. Further, as an example, the shape of the reinforcing material 2C is a hollow disk shape having a ring width of about 1 mm and a thickness of about 10 mm.
Even when the reinforcing material 2C is used, as in the case of using the structure 2A and the suspension member 2B, it is possible to prevent the portion in contact with the gas phase space a of the main body 1 from drooping in the direction of the gas phase space a. .

As the clarification tank shape holding means, the structure 2A and the suspension member 2B and the reinforcing material 2C may be used in combination. In that case, it can be expected that the portion of the clarification tank 30 in contact with the gas phase space of the main body 1 is more effectively prevented from being deformed or sagging.
When forming in combination as described above, it is preferable that the position where the suspension member 2B is provided and the position where the reinforcing material 2C is provided do not overlap so that the shape of the clarification tank 30 is maintained. .

  Moreover, volatilization in the outer surface of the clarification tank main body 1 can be reduced by forming a sprayed film on the outer surface of the clarification tank main body 1. Therefore, from the viewpoint of preventing deformation of the fining tank and reducing volatilization, it is preferable to use the fining tank shape holding means 2 and thermal spraying of the outer surface of the fining tank body 1 in combination. It is preferable that the sprayed film is provided at least in a region where the temperature of the fining tank body 1 is highest. In addition, it is preferable that a thermal spray film is comprised including a refractory oxide, for example. Examples of the refractory oxide include zirconia, zirconia and Mg and / or Y compounds. Although it does not specifically limit as a thermal spraying method, Plasma spraying etc. can be used.

By the way, it is known that the glass substrate has different temperatures at which the clarification action is effectively exhibited depending on the clarifier used. For example, As ₂ O ₃ (arsenous acid) is excellent in the ability to remove bubbles, and the refining temperature (the temperature of the molten glass) is sufficient in the range of about 1500 ° C. However, since arsenous acid has a high environmental load, SnO ₂ (tin oxide) or the like has recently been used as a refining agent that does not have a high environmental load as described above. However, tin oxide has a weaker ability to release bubbles during the defoaming process than arsenous acid, so it is necessary to lower the viscosity of the glass to increase the defoaming effect, and therefore it is necessary to clarify at a high temperature. is there. For example, when tin oxide is used as a fining agent, the temperature of the molten glass in the main body 1 is preferably 1600 ° C. or higher, for example, 1600 ° C. to 1700 ° C., preferably 1630 ° C. to 1710 ° C., more preferably 1630 ° C. The temperature is raised to about ˜1720 ° C. That is, it is necessary to raise the temperature of the clarification tank 30 to near the heat resistance temperature of platinum or platinum alloy of the main body 1 constituting the clarification tank 30.
In particular, since the glass constituting the glass substrate for LTPS display and / or the glass substrate for organic EL display has a high viscosity, the maximum temperature of the molten glass in the refining process is 1640 ° C to 1740 ° C in order to sufficiently perform refining. It is preferable to do.

Further, in the clarification tank 30, the clarification tank 30 has a viscosity at which bubbles are likely to rise, preferably from 120 poise (poise) to 400 poise, so that the release reaction of oxygen in the clarifier is promoted. It is heated before being fed into. For example, alkali-containing glass (high-temperature viscous glass) containing only 2% by mass or less of the alkali-free glass or alkali metal oxide has a temperature of 10 ^2.5 poise at 1300 ° C. or higher, preferably 1400 ° C. or higher. Further, since it is preferably 1500 ° C. or higher, the temperature of the clarification tank body 1 is raised to 1700 ° C. or higher, preferably 1710 ° C. or higher, more preferably near 1720 ° C.
That is, it is necessary to raise the temperature of the clarification tank 30 to near the heat resistance temperature of platinum or platinum alloy of the main body 1 constituting the clarification tank 30.

The present invention is therefore particularly suitable for the production of glass substrates using tin oxide as a fining agent. The present invention is particularly suitable when a glass substrate is produced using a glass material having a high temperature viscosity. Specifically, it is particularly suitable for a case where the molten glass is made of a glass material having a temperature (melting temperature) of 10 ^2.5 poise of 1300 ° C. or higher. The melting temperature is preferably 1400 ° C. or higher, and more preferably made of a glass material that requires a melting temperature of 1500 ° C. or higher.

Obviously, the method for manufacturing a glass substrate of the present invention is not limited to the manufacturing method of the embodiment. For example, the glass substrate production method of the present invention can be applied to glass raw materials other than the glass raw materials exemplified in the embodiment by using conventional raw materials.
Regarding the clarification tank holding means, for example, the structure is an upper part of the clarification tank main body 1 regardless of the shape of the structure 2A of the embodiment and is a structure whose relative position to the main body 1 is fixed. Other shapes may also be used. Further, the shape of the suspension member 2B and the reinforcing member 2C is not limited to the shape of the embodiment, and may be other suitable shapes. Moreover, what is necessary is just to provide at least any one of protective layer 2Aa and support body 2Ab. Furthermore, also about the space | interval which arrange | positions the suspension member 2B and the reinforcing material 2C, a suitable arrangement | positioning space | interval can be set with the magnitude | size and shape of the clarification tank to be used.
In the present specification, the “platinum group metal” means a gold group 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. That is, the “platinum group metal” includes platinum and a platinum alloy. 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.
Further, the clarification tank is preferably cylindrical as shown in the figure, but there is no limitation on its shape as long as a space for accommodating the molten glass MG is secured therein. For example, its outer shape is a rectangular parallelepiped. May be.
The present invention is suitable for manufacturing a glass substrate on which glass is formed by the overflow download method. In the overflow download method, molten glass is made to flow down along both side surfaces of the wedge-shaped molded body, and is merged at the lower end of the wedge-shaped molded body to form a sheet glass. Cool and cut. The overflow download method can achieve a smooth surface by stretching and cooling the molten glass vertically without touching anything. After that, the cut glass sheet is further cut into a predetermined size according to the customer's specifications, subjected to end face polishing, cleaning, etc., and shipped.
The present invention is suitable for manufacturing a glass substrate for FPD having a thickness of 0.5 to 0.7 mm and a size of 300 × 400 mm to 2850 × 3050 mm, for example.
In addition, since a semiconductor element is formed on the surface of a glass substrate for a liquid crystal display device, the alkali metal component is not included at all, or even if it is included, it is a trace amount that does not affect the semiconductor element. Is preferred. Moreover, since the glass substrate for liquid crystal display devices etc. will cause a display defect when a bubble exists in a glass substrate, it is preferable to reduce a bubble as much as possible. From these, in the glass substrate for liquid crystal display devices and the like, as described above, the glass composition, the temperature of the molten glass, the clarifying agent and the like are selected, so the present invention is suitable for the production of glass substrates for liquid crystal display devices and the like. Suitable.
In addition, various suitable modifications can be made without departing from the spirit of the invention.

1 Body (Clarification tank body)
2 Clarification tank shape holding means 2A Structure 2Aa Protective layer (fireproof protective layer)
2Ab support (fireproof support)
2B Hanging member 2Ba One end 2Bb The other end 2C Reinforcing material (clarification tank shape holding means)
DESCRIPTION OF SYMBOLS 10 Melting tank 20, 40 Transfer pipe 30 Clarification tank 100 Glass substrate manufacturing apparatus MG Molten glass a Gas-phase space

Claims (7)

A method of manufacturing a glass substrate,
The manufacturing method includes a defoaming step of performing a defoaming process by passing a molten glass in which a fining agent is blended in the clarification tank body while heating the clarification tank body which is a tubular clarification tank,
The clarification tank body is
Composed of platinum group metals,
When passing a molten glass containing a clarifying agent in the clarification tank body, it has a gas phase space for defoaming provided between the inner surface of the clarification tank body and the liquid surface of the molten glass,
Said refining vessel, for preventing portion in contact with the gas phase space of the refining vessel body that hangs down by its own weight in the vapor space direction by thinning volatilized, hanging over the fining vessel body A method for producing a glass substrate, comprising: a clarification tank shape holding means for holding the glass substrate. A fireproof protective layer is provided on the outside of the clarification tank body so as to cover the clarification tank body,
The said clarification tank shape holding means is a manufacturing method of the glass substrate of Claim 1 provided so that the outer side of the said clarification tank main body and the said fireproof protective layer may be hold | maintained closely. The manufacturing method of the glass substrate of Claim 1 or 2 whose maximum temperature of the molten glass in the said clarification tank main body is 1600 degreeC or more. A layer of a refractory support is provided on the outside of the clarification tank body so as to cover the clarification tank body,
The said clarification tank shape holding means is a member which protrudes to the outer side of the said clarification tank main body, The said member is extended so that the front-end | tip part of the said member may be located in the layer of the said refractory support body. The manufacturing method of the glass substrate of any one of -3 . The clarification tank shape holding means is
A structure in the upper part of the clarification tank body, wherein the relative position to the clarification tank body is fixed; and
A suspension member that suspends the upper part of the clarification tank body through the structure, one end is connected to the upper side of the outer surface of the clarification tank body, and the other end is connected to the structure, It is comprised by these. The manufacturing method of the glass substrate of any one of Claims 1-4 characterized by the above-mentioned. The said molten glass is a manufacturing method of the glass substrate of any one of Claims 1-5 containing a tin oxide. A glass substrate manufacturing apparatus having a clarification tank body that is a tubular clarification tank for performing defoaming treatment of molten glass in a manufacturing process of a glass substrate,
The clarification tank body is
Composed of platinum group metals,
The internal space of the clarification tank main body comprises a defoaming gas phase space existing between the liquid surface of the molten glass,
For preventing the sagging under its own weight into the vapor space direction by thinning the fining vessel body volatilizes position that corresponds to the vapor space, holding the shape hanging upper portion of the refining vessel body A glass substrate manufacturing apparatus, further comprising a clarification tank shape holding means.

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