JPWO2016002814A1 - Glass substrate manufacturing method, glass substrate, and glass substrate laminate - Google Patents

Abstract

A glass substrate manufacturing method that makes it difficult for distortion to occur in the glass substrate and makes it difficult to form irregularities on the main surface of the glass substrate is that a gas phase space is formed by introducing molten glass, and at least a part of the wall is made of a platinum group metal. When processing molten glass in a glass processing device, a molten glass processing step in which agglomerates of platinum group metal volatiles volatilized from the walls that are present in the gas phase space are mixed as foreign matter, and in this molten glass processing step An aggregate treatment step for reducing the size of the aggregate so that the ratio of the number of aggregates having a maximum length of 50 μm or less among the aggregates mixed in the glass becomes 70% or more. The total volume of the glass substrate of the glass substrate laminate is 0.1 m 3 or more, and the ratio of the number of aggregates having a maximum length of 50 μm or less among all platinum group metal aggregates contained in the glass substrate is 70%. That's it.

Description

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

Generally, a glass substrate is produced through a step of forming molten glass from a glass raw material, obtaining a clarification step and a homogenization step, and then forming the molten glass into a glass substrate. By the way, in order to mass-produce high-quality glass substrates from high-temperature molten glass, consideration should be given so that foreign substances that cause defects in the glass substrate do not enter the molten glass from any glass processing apparatus that manufactures the glass substrate. It is desirable to do. For this reason, in the manufacturing process of a glass substrate, the wall of the member which contacts a molten glass needs to be comprised with an appropriate material according to the temperature of the molten glass which contacts the member, the quality of the required glass substrate, etc.
For example, since molten glass is produced at a very high temperature until it is supplied to the forming process after the molten glass is produced, the apparatus for melting, clarifying, supplying, and stirring the platinum, which is a platinum group metal having high heat resistance. The member to contain is used (for example, patent document 1).

JP 2010-111533 A

  However, platinum group metals are likely to volatilize as the temperature rises. When the volatiles of the platinum group metal are aggregated, a part of the crystals that are aggregates may be mixed into the molten glass as a foreign substance, which may cause deterioration of the quality of the glass substrate. In particular, since the clarification step is a step in which the temperature of the molten glass is highest during the period from the melting step to the forming step, the clarification tube mainly performing the clarification step is heated to an extremely high temperature. For this reason, in the molten glass after the clarification step, a part of the aggregate obtained by aggregation of the platinum group metal volatilized from the clarification tube is easily mixed as a foreign substance.

When foreign matter of platinum group metal is mixed in the glass substrate manufacturing process, the glass substrate is distorted due to the difference in thermal expansion coefficient between the platinum group metal foreign matter and glass, and this distortion causes display defects. The platinum group metal exists near the main surface of the glass substrate, forms irregularities on the main surface of the glass substrate, and the thin film transistor (TFT) provided on the main surface cannot be uniformly formed. Problems arise. 2. Description of the Related Art In recent years, with the increase in definition of screen display of image display devices, there has been a strong demand for reduction of platinum group metal foreign matter mixed in a glass substrate in a display.
Thus, it is preferable to reduce the amount of platinum group metal foreign matter (aggregates) mixed in the glass substrate. However, the temperature of the molten glass before forming is extremely high. In particular, in the clarification tube that performs the clarification process, oxygen that causes the volatilization of platinum group metals cannot be excluded from the gas phase space atmosphere of the clarification tube. The volatilization of platinum group metals cannot be completely eliminated. Further, in the clarification tube, the temperature difference of the inner wall surface of the apparatus, which causes aggregation of platinum group metal volatiles, cannot be reduced to 0, and the volatilization of the platinum group metal cannot be completely eliminated. For this reason, it is difficult to completely prevent foreign substances (aggregates) of the platinum group metal from being mixed into the molten glass during the manufacturing process.

  Accordingly, an object of the present invention is to provide a glass substrate manufacturing method, a glass substrate, and a glass substrate laminate that hardly cause the above problem even if foreign substances (aggregates) of a platinum group metal are mixed in the glass substrate. And

  As described above, the present inventor is difficult to completely prevent foreign substances (aggregates) of the platinum group metal from being mixed into the molten glass during the manufacturing process of the glass substrate. Even when a metal foreign substance (aggregate) was mixed, the glass substrate was hardly distorted, and the form of the foreign substance that made it difficult to make irregularities on the main surface of the glass substrate was sought. As a result, the maximum length of the platinum group metal of 50 μm or less is effective in making the glass substrate difficult to be distorted, making it difficult to make irregularities on the main surface of the glass substrate, and mixing into the glass substrate. A finding that it is effective that the ratio of the number of platinum group metal foreign matters (aggregates) having a maximum length of 50 μm or less among the platinum group metal foreign matters (aggregates) is 70% or more. Got. In particular, when manufacturing a glass substrate, reducing the size of platinum group metal foreign matter (aggregates) mixed in the molten glass makes it difficult for distortion to occur on the glass substrate and makes it difficult to create irregularities on the main surface of the glass substrate. The knowledge that it is effective in doing. This is a finding that cannot be easily conceived from the prior art for reducing the absolute number of foreign substances (aggregates) of platinum group metals in order to suppress the occurrence of display defects.

That is, one embodiment of the present invention is a method for manufacturing a glass substrate. The manufacturing method of the said glass substrate contains the following forms.
(First form)
The manufacturing method of the glass substrate is:
A melting step of melting glass raw material to produce molten glass;
A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal. In the step of treating the molten glass, the aggregate of platinum group metal volatiles volatilized from the wall, which is present in the gas phase space, is mixed into the molten glass as a foreign substance during the treatment of the molten glass. A molten glass processing step,
Among the aggregates mixed in the molten glass, the aggregates that reduce the size of the aggregate mixed in the molten glass so that the ratio of the number of aggregates having a maximum length of 50 μm or less is 70% or more. A processing step.

(Second form)
The manufacturing method of the glass substrate is:
A melting step of melting glass raw material to produce molten glass;
It has a liquid phase made of the molten glass, and a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal. A process of processing the molten glass in a glass processing apparatus, wherein during the processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the walls present in the gas phase space are treated as foreign matters. A molten glass processing step mixed in glass,
The size of the aggregates mixed in the molten glass so that the ratio of the number of aggregates having a maximum length of 50 μm or less among the aggregates mixed in the molten glass in the molten glass treatment step is 70% or more. An agglomerate treatment step for reducing the size of the aggregate.

(Third form)
The manufacturing method of the glass substrate is:
A melting step of melting glass raw material to produce molten glass;
A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal. In the step of treating the molten glass, the aggregate of platinum group metal volatiles volatilized from the wall, which is present in the gas phase space, is mixed into the molten glass as a foreign substance during the treatment of the molten glass. A molten glass processing step,
An agglomerate treatment step of adjusting the solubility of the agglomerates in the molten glass so that the size of the agglomerates mixed in the molten glass is reduced.

(4th form)
The manufacturing method of the glass substrate is:
A melting step of melting glass raw material to produce molten glass;
It has a liquid phase made of the molten glass, and a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal. A process of processing the molten glass in a glass processing apparatus, wherein during the processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the walls present in the gas phase space are treated as foreign matters. A molten glass processing step mixed in glass,
Furthermore, an aggregate treatment process for controlling the amount of heat applied to the aggregate so that the amount of heat applied to the aggregate is equal to or greater than a minimum amount of heat that can reduce the size of the aggregate mixed in the molten glass. Is provided.

(5th form)
In the method for manufacturing the glass substrate, the difference between the highest temperature and the lowest temperature of the wall in contact with the gas phase space is set to 5 ° C. or more, and the gas phase space contains oxygen. The manufacturing method of the glass substrate described in any one form.

(Sixth form)
The agglomerate treatment step raises the temperature of the molten glass containing the agglomerates so as to be higher than the temperature of the molten glass in the region where the agglomerates are mixed into the molten glass in the molten glass treatment step, The manufacturing method of the glass substrate described in any one form of the said 1st form-the said 5th form. Alternatively, in the agglomerate treatment step, the temperature of the molten glass becomes the maximum temperature.

(7th form)
In the agglomerate treatment step, the solubility of the agglomerate in the molten glass is made higher than the solubility in the region where the agglomerate is mixed into the molten glass in the molten glass treatment step, wherein the first form to the first The manufacturing method of the glass substrate described in any one form of 6 forms. Alternatively, the agglomerate treatment step reduces the size of the agglomerates mixed in the molten glass by increasing the solubility of the agglomerates in the molten glass, and any one of the first to sixth aspects. A method for manufacturing a glass substrate in one form. Specifically, in the agglomerate treatment step, the size of the agglomerates mixed in the molten glass is reduced by heating and controlling the molten glass so as to increase the solubility of the agglomerates in the molten glass. The manufacturing method of the glass substrate described in any one form of said form-said 6th form.

(8th form)
The glass processing apparatus is a clarification apparatus having a clarification tube,
The molten glass flows through the clarification tube,
The vapor phase space in the clarification tube is formed along the flow direction of the molten glass, and the agglomerate treatment step is performed in the clarification tube, any one of the first to seventh embodiments. The manufacturing method of the glass substrate described in one form.

(9th form)
In the molten glass treatment step, a clarification treatment is performed to reduce the number of bubbles in the molten glass using tin oxide contained in the molten glass, the molten glass flows through the glass treatment apparatus, and the gas phase space and A temperature distribution is formed along the flow direction of the molten glass on the wall in contact, and an oxygen concentration distribution is formed along the flow direction of the molten glass in the gas phase space. Form to manufacturing method of glass substrate described in any one form of said 8th form.

(10th form)
The agglomerate processing step is performed in the glass processing apparatus, the molten glass flows through the glass processing apparatus, and among the molten glass flowing through the glass processing apparatus, in the flow direction of the molten glass in the gas phase space, The manufacturing method of the glass substrate as described in any one form of the said 1st form-the said 9th form performed with respect to the molten glass which flows through the position corresponding to the area | region where oxygen concentration becomes the highest.

(Eleventh form)
The oxygen concentration in the gas phase space is more than 0% and 1.0% or less, and the difference between the maximum temperature and the minimum temperature of the wall in contact with the gas phase space is 5 ° C. or more, The manufacturing method of the glass substrate described in any one form of the said 1st form-the said 10th form made into degrees C or less.

(Twelfth embodiment)
The temperature of the molten glass in the agglomerate treatment step is controlled in a temperature range of 1670 ° C to 1730 ° C, and any one of the first to eleventh modes is controlled. The manufacturing method of the glass substrate described in 1 ..

(13th form)
In the molten glass treatment step, the temperature of the molten glass is controlled so that the temperature of the molten glass in the region where the agglomerates are mixed into the molten glass is in the temperature range of 1580 ° C to 1660 ° C. The manufacturing method of the glass substrate described in any one form of 12th form.

(14th form)
The method for manufacturing a glass substrate according to any one of the first to thirteenth modes, wherein the molten glass processing step includes the aggregate processing step.

(15th form)
The said glass substrate is a glass substrate for a display, The manufacturing method of the glass substrate described in any one form of the said 1st form-the said 14th form.

(16th form)
The concentration of the platinum group metal dissolved in the molten glass at the start of the agglomerate treatment step is 0.05 to 20 ppm, according to any one of the first to fifteenth embodiments. Glass substrate manufacturing method.

(Seventeenth Embodiment) In the aggregate treatment step, the platinum of the molten glass is within a range where [Fe ³⁺ ] / ([Fe ²⁺ ] + [Fe ³⁺ ]) of the glass substrate is 0.2 to 0.5. The manufacturing method of the glass substrate as described in any one of the said 1st form-the said 16th form which adjusts the saturation solubility of a group metal.

(18th form)
The said glass substrate is a manufacturing method of the glass substrate described in any one form of the said 1st form-the said 17th form whose content of an alkali metal oxide is 0-0.5 mass%.

(19th form)
A melting step of melting glass raw material to produce molten glass;
A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal. In the step of treating the molten glass, the aggregate of platinum group metal volatiles volatilized from the wall, which is present in the gas phase space, is mixed into the molten glass as a foreign substance during the treatment of the molten glass. Molten glass treatment process,
In the molten glass treatment step, an aggregate treatment step of dissolving at least a part of the aggregate mixed in the molten glass in the molten glass, and
The manufacturing method of the glass substrate characterized by making the density | concentration of the platinum group metal melt | dissolved in the said molten glass at the time of the said aggregate treatment process start into 0.05-20 ppm.

(20th form)
A melting process for melting glass raw materials to produce molten glass;
By using the glass processing apparatus, a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall in contact with the gas phase space is made of a material containing a platinum group metal. A molten glass in which aggregates of platinum group metal volatiles volatilized from the wall, which are present in the gas phase space, are mixed into the molten glass during the processing of the molten glass. Processing steps;
An agglomerate treatment step of dissolving at least a part of the agglomerates mixed in the molten glass in the molten glass treatment step,
In the agglomerate treatment step, the agglomerates detected in the glass substrate produced by using the glass processing apparatus so that the number of defects in the agglomerate contained in the newly produced glass substrate becomes an acceptable level. A method for producing a glass substrate, comprising adjusting the saturation solubility of the aggregate platinum group metal by adjusting the temperature of the molten glass based on the number of defects.
Here, in the agglomerate treatment step, the temperature of the molten glass is preferably adjusted in the range of 1660 to 1750 ° C. in order to adjust the saturated solubility of the agglomerates.

(21st form)
A melting process for melting glass raw materials to produce molten glass;
By using the glass processing apparatus, a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall in contact with the gas phase space is made of a material containing a platinum group metal. A molten glass in which aggregates of platinum group metal volatiles volatilized from the wall, which are present in the gas phase space, are mixed into the molten glass during the processing of the molten glass. Processing steps;
An agglomerate treatment step of dissolving at least a part of the agglomerates mixed in the molten glass in the molten glass treatment step,
In the agglomerate treatment step, [Fe ³⁺ ] / ([Fe ²⁺ ] + [Fe ³⁺ ]) of the glass substrate is set to 0.2 to so that the number of defects of the agglomerates contained in the glass substrate becomes an acceptable level. By adjusting in the range of 0.5, the saturation solubility of the said platinum group metal of the said molten glass is adjusted, The manufacturing method of the glass substrate characterized by the above-mentioned.
Here, [Fe ³⁺ ] / ([Fe ²⁺ ] + [Fe ³⁺ ]) regulates at least one of the content of tin oxide contained in the glass substrate and the content of oxide contained in the glass raw material. It is preferable to adjust by doing.

Another embodiment of the present invention is a glass substrate laminate in which a plurality of glass substrates are laminated. At this time, the following 22nd form is included.
(Twenty-second form)
The total volume of the glass substrates in the glass substrate laminate is 0.1 m ³ or more, and among the aggregates of all platinum group metals included in the glass substrate, the maximum number of aggregates having a maximum length of 50 μm or less. A glass substrate laminate, wherein the ratio is 70% or more.

Another embodiment of the present invention is a glass substrate, which includes the following twenty-third form.
(23rd form)
The ratio of the number of the aggregates whose maximum length is 50 micrometers or less among the aggregates of the platinum group metal which a glass substrate contains is 70% or more, The glass substrate characterized by the above-mentioned.

Furthermore, another embodiment of the present invention is a glass substrate manufacturing apparatus. The said glass substrate manufacturing apparatus contains the following forms.
(24th form)
Glass substrate manufacturing equipment
A melting device for melting glass raw material to produce molten glass;
The molten glass having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal. An apparatus for processing glass, wherein during processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the wall, which are present in the gas phase space, are mixed into the molten glass as foreign matter. When,
The size of the aggregates mixed in the molten glass so that the ratio of the number of aggregates having a maximum length of 50 μm or less among the aggregates mixed in the molten glass in the molten glass treatment step is 70% or more. And a processing means for reducing the size.

Furthermore, the other one aspect | mode of this invention is also a glass substrate manufacturing apparatus. The said glass substrate manufacturing apparatus contains the following forms.
(25th form)
Glass substrate manufacturing equipment
A melting device for melting glass raw material to produce molten glass;
The molten glass having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal. An apparatus for processing glass, wherein during processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the wall, which are present in the gas phase space, are mixed into the molten glass as foreign matter. And comprising
Means for adjusting the solubility of the aggregate in the molten glass so that the size of the aggregate mixed into the molten glass is reduced.

(26th form)
Moreover, the manufacturing method of the glass substrate of said 1st form-said 21st form, the glass substrate laminated body of said 22nd form, the glass substrate of said 23rd form, and the glass of said 24th, 25th form The said glass substrate in any one form of a substrate manufacturing apparatus is a glass substrate which has a strain point of 650 degreeC or more.

  Manufacturing method of glass substrate of said 1st form-said 21st form, glass substrate laminated body of said 22nd form, glass substrate of said 23rd form, and glass substrate manufacture of said 24th, 25th form The glass substrate in any one form of the apparatus is a glass substrate for liquid crystal display, a glass substrate for organic EL (Electro-Luminescence) display, or a glass substrate for display using LTPS (Low Temperature Poly-silicon) thin film semiconductor. Used as

  According to the glass substrate manufacturing method, the glass substrate, the glass substrate laminate, and the glass substrate manufacturing apparatus described above, even if a foreign substance (aggregate) of a platinum group metal is mixed in the glass substrate, the glass substrate is hardly distorted. It is possible to make it difficult to make irregularities on the main surface of the glass substrate. Thereby, the yield at the time of manufacture of a glass substrate improves.

It is a flowchart which shows the process of the manufacturing method of the glass substrate which concerns on embodiment. It is a schematic diagram which shows the structure of the glass substrate manufacturing apparatus which concerns on embodiment. It is the external view which mainly represented the clarification pipe | tube which concerns on embodiment. It is a figure showing an example of a temperature profile of a sectional view showing the inside of a clarification pipe concerning an embodiment, and a clarification pipe. It is a graph showing the relationship between the maximum temperature of a molten glass and the ratio of a foreign material.

The glass substrate manufacturing method of this embodiment has a space in which a gas phase space surrounded by the surface of the molten glass and the wall is formed by introducing molten glass, and at least a part of the wall is made of a platinum group metal. A glass processing apparatus composed of a material including, for example, a liquid phase made of molten glass, and a gas phase space formed by a liquid surface and a wall of the molten glass, and at least a part of the wall surrounding the gas phase space is A molten glass is processed in a glass processing apparatus composed of a material containing a platinum group metal (a molten glass processing step). During the processing of the molten glass, agglomerates of platinum group metal volatiles volatilized from the wall and existing in the gas phase space are mixed into the molten glass as foreign substances. A process of reducing the size of the aggregates mixed in the molten glass is performed so that the ratio of the number of aggregates having a maximum length of 50 μm or less among the aggregates mixed in the molten glass is 70% or more. (Aggregate treatment step). Or the solubility of the foreign material (aggregate) in molten glass is adjusted so that the magnitude | size of the aggregate mixed in molten glass may become small. For example, the amount of heat given to the foreign matter (aggregate) is controlled so that the amount of heat given to the foreign matter (aggregate) is not less than the minimum amount of heat that can reduce the size of the foreign matter (aggregate) mixed in the molten glass. (Aggregate treatment step).
Thus, by reducing the size of the foreign substance (aggregate) of the platinum group metal mixed in the glass substrate, it is difficult for the glass substrate to be distorted, and it is possible to make it difficult to make irregularities on the main surface of the glass substrate. For this reason, the conventional problem is improved and the manufacturing yield of the glass substrate is improved.
In the following description, as an example of controlling the conditions for adjusting the solubility so that the solubility of the aggregate in the molten glass is equal to or higher than the minimum solubility at which the aggregate can be dissolved in the molten glass to reduce the size, An example will be described in which the amount of heat applied to the aggregate is controlled so that the amount of heat applied to the aggregate is equal to or greater than the minimum amount of heat that can reduce the size of the aggregate mixed in the molten glass.

(Glass substrate manufacturing method and glass substrate manufacturing apparatus)
FIG. 1 is a flowchart showing an example of steps of the glass substrate manufacturing method according to the present embodiment. As shown in FIG. 1, the glass substrate manufacturing method mainly includes a melting step S1, a refining step S2, a stirring step S3, a forming step S4, a slow cooling step S5, and a cutting step S6.
FIG. 2 is a schematic diagram illustrating an example of the configuration of the glass substrate manufacturing apparatus 200 according to the present embodiment. The glass substrate manufacturing apparatus 200 includes a melting tank 40, a clarification tube 41, a stirring device 100, a molding device 42, and transfer tubes 43a, 43b, and 43c. The transfer pipe 43 a connects the melting tank 40 and the clarification pipe 41. The transfer pipe 43 b connects the clarification pipe 41 and the stirring device 100. The transfer pipe 43 c connects the stirring device 100 and the molding device 42.

In the melting step S1, molten glass is produced by melting glass raw materials. The molten glass is stored in the melting tank 40 and heated to have a desired temperature. The molten glass contains a fining agent. From the viewpoint of reducing the environmental load, tin oxide is suitably used as a fining agent.
In the melting tank 40, the glass raw material is heated and melted at a temperature according to its composition. Thereby, in the melting tank 40, the high temperature molten glass G of 1500 degreeC-1620 degreeC is obtained, for example. In the melting tank 40, the molten glass G between the electrodes may be energized and heated by passing an electric current between at least one pair of electrodes. In addition to the energization heating, a flame by the burner is supplementarily given. The glass raw material may be heated.

  The clarification step S2 is performed inside the transfer pipe 43a and the clarification pipe 41 through which the molten glass flows. First, the temperature of the molten glass is raised. The refining agent causes a reduction reaction with an increase in temperature to release oxygen. Foam contained in the molten glass absorbs the released oxygen and expands, the molten glass floats on the surface in contact with the gas phase space, breaks up and disappears. That is, the defoaming process S2A is performed. Further, the agglomeration is performed in the middle of the defoaming treatment step S2A or after the defoaming treatment step S2A, and the temperature of the molten glass is increased to reduce the size of the platinum group metal agglomerates mixed in the defoaming treatment. The object processing step S2B is performed. Thereafter, the temperature of the molten glass is lowered. Thereby, the reduced fining agent causes an oxidation reaction and absorbs gas components such as oxygen remaining in the molten glass. That is, the absorption process step S2C is performed.

  Specifically, the molten glass G obtained in the melting tank 40 passes through the transfer pipe 43 a from the melting tank 40 and flows into the clarification pipe 41. The clarification tube 41 has a space in which a gas phase space surrounded by the surface and wall of the molten glass G is formed by introducing the molten glass G, and at least a part of the wall is made of a material containing a platinum group metal. Has been. For example, it has a liquid phase in which molten glass flows, a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal. Yes. The transfer pipes 43a, 43b, and 43c are platinum group metal pipes. The platinum group metal means a metal composed of a single platinum group element and a metal alloy composed of a platinum group element. The platinum group elements are six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os) and iridium (Ir). In the present embodiment, for example, an alloy of platinum and rhodium having a platinum content of 70% or more is preferably used. Platinum group metals have a high melting point and are excellent in corrosion resistance to molten glass. The clarification tube 41 is provided with a heating means similar to the melting tank 40. At least the transfer pipe 43a is also provided with a heating means.

In the clarification step S2, by adjusting the amount of heat given to the foreign substance (aggregate) of the platinum group metal mixed in the molten glass and the defoaming process step of defoaming the molten glass G by raising the temperature, The molten glass breaks or melts the foreign material (aggregate) to reduce the size of the platinum group metal foreign material (aggregate), and the molten glass cools the bubbles in the molten glass by cooling the molten glass. An absorption treatment process to absorb is performed. In the agglomerate treatment process, the amount of heat given to the foreign matter (aggregate) is reduced in order to reduce the size of the platinum group metal foreign matter (aggregate) by dividing or melting the foreign matter (aggregate) mixed in the molten glass. Must be greater than or equal to a predetermined amount of heat (minimum heat amount). In this case, the amount of heat given to the foreign matter (aggregate) in the molten glass is controlled so that the amount of heat given to the foreign matter (aggregate) becomes equal to or greater than the minimum heat amount. The minimum heat quantity can be examined in advance by experiments or the like. When controlling the minimum calorie | heat amount with the temperature of the molten glass G, the temperature of the molten glass G in the clarification pipe | tube 41 is controlled in the range of 1580 to 1730 degreeC, for example, Preferably, it is 1670 to 1730 degreeC.
In the clarification step S2, from the viewpoint of sufficiently clarifying the molten glass G, it is preferable that the temperature of the molten glass G flowing inside the transfer pipe 43a is sequentially raised without being lowered. After the melting step S1, the molten glass G is preferably heated up to 1630 ° C or higher at a rate of 3 ° C / min or higher.
The maximum temperature of the molten glass G flowing through the transfer tube 43a is 1620 ° C to 1690 ° C, and preferably 1640 ° C to 1670 ° C. Moreover, the temperature of the molten glass G in the clarification pipe | tube inlet which is an area | region which connects the transfer pipe | tube 43a and the clarification pipe | tube 41 is 1610 degreeC-1680 degreeC, and it is preferable that it is 1630 degreeC-1660 degreeC. Furthermore, the temperature of the molten glass G at the clarification tube outlet, which is a region connecting the clarification tube 41 and the transfer tube 43b, is 1530 ° C to 1600 ° C, and preferably 1540 ° C to 1580 ° C.
The molten glass G clarified in the clarification tube 41 passes through the transfer tube 43b from the clarification tube 41 and flows into the stirring device 100. The molten glass G is cooled when passing through the transfer tube 43b.

In the stirring step S3, the clarified molten glass is stirred, and the components of the molten glass are homogenized. Thereby, the composition nonuniformity of the molten glass which is a cause of the striae etc. of a glass substrate is reduced. The homogenized molten glass is sent to the forming step S4.
Specifically, in the stirring device 100, the molten glass G is stirred at a temperature lower than the temperature of the molten glass G passing through the clarification tube 41. For example, in the stirring device 100, the temperature of the molten glass G is 1250 ° C to 1450 ° C. For example, in the stirring device 100, the viscosity of the molten glass G is 500 poise to 1300 poise. The molten glass G is stirred and homogenized in the stirring device 100.
The molten glass G homogenized by the stirrer 100 flows from the stirrer 100 through the transfer pipe 43 c and flows into the molding device 42. When the molten glass G passes through the transfer tube 43c, it is cooled so as to have a viscosity suitable for forming the molten glass G. For example, the molten glass G is cooled to 1100 to 1300 ° C.
In addition, although stirring process S3 of this embodiment is performed after clarification process S2, stirring process S3 may be performed before clarification process S2. In this case, the temperature of the molten glass G in the stirring step S3 may be equal to or higher than the temperature of the molten glass G in the clarification tube 41.

In the forming step S4, the sheet glass is continuously formed from the molten glass by the overflow downdraw method or the float method.
Specifically, the molten glass G that has flowed into the molding apparatus 42 is supplied to a molded body 52 installed inside a molding furnace (not shown). A groove is formed on the upper surface of the molded body 52 along the longitudinal direction of the molded body 52. The molten glass G is supplied to the groove on the upper surface of the molded body 52. The molten glass G overflowing from the groove flows down along the pair of side surfaces of the molded body 52. A pair of molten glass G which flowed down the side surface of the molded body 52 joins at the lower end of the molded body 52, and the sheet glass GR is continuously molded.

In the slow cooling step S5, the sheet glass continuously formed in the forming step S4 has a desired thickness and is gradually cooled so as not to be distorted and warped.
In cutting process S6, the sheet glass annealed in slow cooling process S5 is cut | disconnected by predetermined length, and a glass sheet is obtained. The glass sheet is further cut into a predetermined size to obtain a glass substrate.

(Glass substrate laminate and glass substrate)
This embodiment provides a glass substrate laminate and a glass substrate formed by laminating a plurality of glass substrates.
The glass substrate laminate of the present embodiment has a total volume of 0.1 m ³ or more, and among the aggregates of all platinum group metals contained in the glass substrate laminate, the maximum length is 50 μm or less. The ratio of the number of is 70% or more. As will be described later, such a glass substrate laminate is less likely to be distorted in the glass substrate and can make it difficult to make irregularities on the main surface of the glass substrate. For this reason, each glass substrate of the said laminated body is suitable for the glass substrate for a display, and is especially effective in the glass substrate for display panels in which high definition is calculated | required in a screen display.
Further, the glass substrate of the present embodiment is characterized in that the ratio of the number of aggregates having a maximum length of 50 μm or less among the aggregates of platinum group metals included in the glass substrate is 70% or more. With the glass substrate having such a configuration, as described later, the glass substrate is less likely to be distorted, and the unevenness of the main surface of the glass substrate can be made more difficult to make.
In addition, as for a glass substrate laminated body and a glass substrate, it is more preferable that the ratio of the number of aggregates whose maximum length is 50 micrometers or less among the aggregates of the platinum group metal to contain is 90% or more. The glass substrate laminate and the glass substrate more preferably have a ratio of the number of aggregates having a maximum length of 30 μm or less among the aggregates of platinum group metal contained therein of 90% or more.
As the glass used for the glass substrate, a glass having a strain point of 600 ° C. or higher is suitable for the glass substrate manufacturing method described later. The strain point is more preferably 650 ° C. or higher, even more preferably 690 ° C. or higher, and particularly preferably 730 ° C. or higher.

(Application example of glass substrate)
The glass substrate produced by the method for producing a glass substrate of the present embodiment is particularly suitable as a glass substrate for a display such as a liquid crystal display, a plasma display, and an organic EL display, and a cover glass for protecting the display. The display using the glass substrate for display includes a flat panel display having a flat display surface, an organic EL display and a liquid crystal display, and a curved display having a curved display surface. The glass substrate is a glass substrate for a high-definition display, such as a glass substrate for a liquid crystal display, a glass substrate for an organic EL (Electro-Luminescence) display, an LTPS (Low Temperature Poly-silicon) thin film semiconductor, or an IGZO (Indium, Gallium, It is preferable to use as a glass substrate for display using an oxide semiconductor such as Zinc or Oxide.
As the glass substrate for display, non-alkali glass or alkali trace glass is used. The glass substrate for display has high viscosity at high temperatures. For example, the temperature of the molten glass having a viscosity of 10 ^2.5 poise is 1500 ° C. or higher. The alkali-free glass is a glass having a composition that does not substantially contain an alkali metal oxide (R ₂ O). “Alkali metal oxide is not practically contained” means a glass having a composition in which an alkali metal oxide is not added as a glass raw material except for impurities mixed in from the raw material and the like. It is less than 1% by mass.

(Glass composition)
In the melting tank 40, the glass raw material is melted by heating means (not shown), and molten glass G is generated. The glass raw material is prepared so that a glass having a desired composition can be substantially obtained. As an example of the composition of glass, non-alkali glass suitable as a glass substrate for display such as a glass substrate for flat panel display (FPD) is SiO ₂ 50 mass% to 70 mass%, Al ₂ O ₃ 0 mass% to 25 mass. %, B ₂ O ₃ 0% by mass to 15% by mass, MgO 0% by mass to 10% by mass, CaO 0% by mass to 20% by mass, SrO 0% by mass to 20% by mass, BaO 0% by mass to 10% by mass. contains. In addition, it is good also as BaO 0 mass%-20 mass% instead of BaO 0 mass%-10 mass%. Here, the total content of MgO, CaO, SrO and BaO is 5% by mass to 30% by mass.

Moreover, you may use the alkali trace amount containing glass which contains a trace amount of alkali metal oxides as a glass substrate for a display. The alkali-containing glass contains 0.1% by mass to 0.5% by mass of R ′ ₂ O as a component, and preferably 0.2% by mass to 0.5% by mass of R ′ ₂ O. Here, R ′ is at least one selected from Li, Na and K, and R ′ ₂ O is the total content of Li ₂ O, Na ₂ O and K ₂ O. The total content of R ′ ₂ O may be less than 0.1% by mass. Therefore, as the glass substrate of the present embodiment, a glass having an alkali metal oxide (R ′ ₂ O) content of 0 to 0.5% by mass including an alkali-free glass is suitably used.

In addition to the above components, the glass produced according to the present embodiment has SnO ₂ 0.01 mass% to 1 mass% (preferably 0.01 mass% to 0.5 mass%), Fe ₂ O ₃ 0 mass. % To 0.2% by mass (preferably 0.01% to 0.08% by mass) may be further contained. The glass produced by the present invention, in consideration of environmental burden, it is preferred not to substantially contain _{As 2 O 3, Sb 2 O} 3 , and PbO. In order to reduce the environmental burden, tin oxide (SnO ₂ ) is preferably used as a fining agent.

  In the present embodiment, the molten glass treatment process is used as a clarification process, and the molten glass treatment apparatus is described as an example of a clarification apparatus including a clarification tube 41. However, an apparatus for performing a molten glass treatment process is described below. As long as it is a device that is provided between the melting tank 40 and the molding device 42 and performs a predetermined treatment on the molten glass, it is not particularly limited. In addition to the refining device, the glass processing device can be, for example, a stirring device or a transfer tube for transferring molten glass. Therefore, the treatment of the molten glass includes a treatment for homogenizing the molten glass, a treatment for transferring the molten glass, and the like in addition to the treatment for refining the molten glass. The agglomerate treatment step S2B has also been described with reference to an example performed in the clarification step S2, but may be performed in, for example, the stirring step S3 and a step of transferring the molten glass G using a transfer tube. Even if the aggregate treatment step S2B is performed in the clarification step S2, the aggregate treatment step S2B does not need to be performed before the absorption treatment step S2C as described above, and the absorption treatment step S2C It may be done later.

(Configuration of clarification tube)
Next, the structure of the clarification pipe | tube 41 of the clarification apparatus in this embodiment is demonstrated in detail. In addition to the clarification pipe 41, the clarification apparatus includes a vent pipe 41a, a heating electrode 41b, and a refractory protective layer (not shown) and a refractory brick that surround the outer periphery of the clarification pipe 41. FIG. 3 is an external view mainly showing the clarification tube 41. FIG. 4 is a sectional view showing the inside of the clarification tube 41 and an example of a temperature profile of the clarification tube.

  A ventilation pipe 41a and a pair of heating electrodes 41b are attached to the clarification pipe 41. The clarification tube 41 has a space in which a gas phase space 41c surrounded by the surface and wall of the molten glass G is formed by introducing the molten glass G therein. For example, the clarification tube 41 has a gas phase space formed by a liquid phase in which the molten glass G flows, a liquid surface of the molten glass G, and a wall. The gas phase space 41 c is formed along the flow direction of the molten glass G. At least a part of the wall surrounding the gas phase space 41c is made of a material containing a platinum group metal. In the present embodiment, the entire wall surrounding the gas phase space 41c is made of a material containing a platinum group metal.

  The vent pipe 41a is provided in the middle of the direction in which the molten glass G flows and is provided on a wall in contact with the gas phase space 41c, and communicates the gas phase space 41c with the atmosphere outside the clarification tube 41. The vent pipe 41a is preferably formed of a platinum group metal, like the clarification pipe 41. Since the temperature of the vent pipe 41a is likely to decrease due to the heat dissipation function, the vent pipe 41a may be provided with a heating mechanism for heating the vent pipe 41a.

The pair of heating electrodes 41b are flange-shaped electrode plates provided at both ends of the clarification tube 41a. The heating electrode 41b allows a current supplied from a power source (not shown) to flow through the clarification tube 41, and the clarification tube 41 is energized and heated by this current. When using tin oxide as a fining agent, for example, the wall of the fining tube 41 is heated so that the maximum temperature is 1670 ° C to 1750 ° C, more preferably 1690 ° C to 1750 ° C. The difference between the maximum temperature and the minimum temperature of the wall of the clarification tube 41 is 5 ° C. or more, and the gas phase space has oxygen. The temperature of the molten glass G is heated to a temperature at which the reduction reaction of tin oxide is promoted. Furthermore, the molten glass G is preferably heated to a temperature at which the foreign substance (aggregate) of the platinum group metal is divided or melted, for example, 1670 ° C. or higher, and more preferably 1680 ° C. or higher. More specifically, it is preferably heated to 1670 ° C to 1730 ° C, more preferably 1680 ° C to 1700 ° C. When the maximum temperature of the molten glass G exceeds 1730 ° C., a tube made of a platinum group metal constituting the clarification tube 41a is easily broken. The maximum temperature of the molten glass G can be calculated from the measured value of a thermocouple (not shown) provided in the clarification tube 41.
The temperature of the molten glass G flowing inside the clarification tube 41 can be controlled by controlling the current flowing through the clarification tube 41.
Although a pair of heating electrodes 41b are provided on the clarification tube 41, the number of heating electrodes 41b is not particularly limited. By controlling the amount of current of the heating electrode 41b, the temperature of the wall in contact with the gas phase space 41c of the clarification tube 41 is controlled within a range of 1500 to 1750 ° C., for example.

Inside the clarification tube 41, bubbles containing CO ₂ or SO ₂ contained in the molten glass G are removed by the oxidation-reduction reaction of a clarifier contained in the molten glass G, for example, tin oxide. Specifically, first, the temperature of the molten glass G is raised to reduce the fining agent, thereby generating oxygen bubbles in the molten glass G. Bubbles containing gaseous components such as CO ₂ , N ₂ and SO ₂ contained in the molten glass G are combined with oxygen bubbles generated by the reductive reaction of the fining agent. The bubbles combined with the oxygen bubbles float on the surface of the molten glass G in contact with the gas space and release the bubbles, that is, break up and disappear. (Defoaming process). The temperature of the molten glass G in this defoaming process is 1610 degreeC-1730 degreeC, Preferably it is 1640 degreeC-1710 degreeC. When the temperature is in the above range, the platinum group metal volatilizes vigorously from the wall of the clarification tube 41. Since oxygen is released into the gas phase space by defoaming, the oxygen concentration becomes high in the portion of the gas phase space where the defoaming treatment is performed, and as a result, the volatilization of the platinum group metal becomes more active. Along with this, the concentration of the volatiles of the platinum group metal contained in the gas phase space is increased, so that aggregation of the volatiles of the platinum group metal contained in the gas phase space is likely to occur. In particular, the volatiles of the platinum group metal tend to aggregate at a partially cooled position on the wall, for example, the wall near the inlet of the clarification tube 41. Therefore, a part of the aggregate of platinum group metal adhering to the wall of the clarification tube 41 falls off and easily enters the molten glass G as a foreign substance. For example, after molten glass flows into the clarification tube 41, in a region where the temperature of the molten glass G is 1580 ° C. to 1660 ° C., aggregation of platinum group metal volatiles contained in the gas phase space and aggregated molten glass G It is easy to mix in.
For this reason, the aggregate treatment process which reduces the magnitude | size of the foreign material (aggregate) of the platinum group metal mixed in the molten glass G from the middle of a defoaming process or after completion | finish of a defoaming process is performed.
When the agglomerate treatment process is performed after the defoaming process is finished, the temperature of the molten glass G containing the platinum group metal foreign matter (aggregate) is set to the region where the platinum group metal foreign matter (aggregate) is mixed into the molten glass G. It is preferable to raise the temperature of the molten glass G so as to be higher than the temperature of the molten glass at.
Moreover, when performing the aggregate processing process from the middle of a defoaming process, a defoaming process and an aggregate processing process are performed simultaneously. When performing the aggregate treatment process from the middle of the defoaming process, the defoaming process and the aggregate treatment process may be performed at the same time. When performing the aggregate treatment process from the middle of the defoaming treatment process, the molten glass reaches the maximum temperature in the aggregate treatment process. That is, the defoaming treatment process (molten glass treatment process) may include an aggregate treatment process.

In the agglomerate treatment step, by controlling the amount of heat applied to the platinum group metal foreign matter (aggregate) mixed in the molten glass, specifically, by setting the temperature of the molten glass G to 1670 ° C. or higher, the platinum group metal It is preferable to sever and melt metal foreign matters (aggregates). At this time, the aggregate processing step is performed so that the ratio of the number of foreign substances having a maximum length of 50 μm or less among the foreign substances (aggregates) of the platinum group metal mixed in the molten glass G is 70% or more. As a result, the distortion generated by the glass substrate is small, and the formation of irregularities on the main surface of the glass substrate is reduced. In order to make a foreign substance having such a size, it is preferable to maintain the temperature of the molten glass G at 1670 ° C. or higher for 10 minutes or longer, preferably 30 minutes or longer. That is, the aggregate reduction process for reducing the size of the platinum group metal foreign matter (aggregate) is maintained at a temperature of 1670 ° C. or more for 10 minutes or longer, thereby allowing the size of the platinum group metal foreign matter (aggregate) to be maintained. Can be reduced.
In the present embodiment, the solubility of the platinum group metal foreign matter (aggregate) mixed in the molten glass in the molten glass in the molten glass treatment step is determined based on the solubility of the platinum group metal foreign matter (aggregate) in the molten glass treatment step. It is also preferable to control the solubility so that the solubility is higher than the solubility in the region mixed with the molten glass. When the solubility of the foreign matter (aggregate) in the molten glass G is increased, the temperature of the molten glass G is increased to increase the solubility of the aggregate in the molten glass, or the temperature of the molten glass G is increased. By increasing the treatment time, the amount of foreign matters (aggregates) dissolved in the molten glass G can be increased.

The foreign substance (aggregate) of the platinum group metal is a linear object elongated in one direction. Therefore, the maximum length of the platinum group metal aggregate (foreign matter) refers to the length of the long side of the circumscribed rectangle circumscribing the image of the foreign matter when the foreign matter (aggregate) of the platinum group metal is photographed.
Before the agglomerate treatment step, the proportion of platinum group metal foreign matter (aggregate) having a maximum length of 100 μm or more exceeds 80%. Further, in the present embodiment, the platinum group metal foreign matter (aggregate) before the aggregate treatment step refers to a platinum group metal foreign matter having an aspect ratio of more than 100, which is a ratio of the maximum length to the minimum length. For example, the maximum length of the foreign substance (aggregate) of the platinum group metal is 50 μm to 300 μm, and the minimum length is 0.5 μm to 2 μm.

  Thereafter, the temperature of the molten glass G is lowered to oxidize the reduced fining agent. Thereby, the oxygen of the bubble which remains in the molten glass G is absorbed by the molten glass G (absorption process). Thus, the remaining bubbles are reduced and disappear. In this way, bubbles contained in the molten glass G are removed by the oxidation-reduction reaction of the clarifying agent. Moreover, in absorption process S2C, the temperature of the molten glass G and the temperature of the wall of the clarification tube 41 are falling to 1580 degrees C or less, and the oxygen concentration contained in gaseous-phase space falls compared with degassing process S2A. Therefore, volatilization and aggregation of the platinum group metal are difficult to perform. For this reason, in the absorption treatment step S2C, the possibility that new platinum group metal aggregates become foreign matters and enter the molten glass G is much lower than in the defoaming treatment step S2A.

  Although not shown, a refractory protective layer is provided on the outer wall surface of the clarification tube 41. A refractory brick is further provided outside the refractory protective layer. The refractory brick is placed on a base (not shown). In addition, the temperature of the wall which contact | connects the gaseous phase space 41c of the clarification pipe | tube 41 and / or the inside of the clarification pipe | tube 41 is adjusted by adjusting the thermal radiation amount from the clarification pipe | tube 41 with a refractory protective layer and / or a refractory brick. The temperature may be controlled.

FIG. 4 shows an example of the temperature profile of the clarification tube 41 (the temperature profile in the X direction of the wall in contact with the gas phase space 41c of the clarification tube 41) expressed in accordance with the position of the clarification tube 41 in the X direction. In the temperature profile, the temperature is the maximum temperature T _max between the end 41d (inlet) of the clarification tube 41 on the side where the molten glass G flows and the vent tube 41a. A temperature gradient in which the temperature decreases from the position P of the maximum temperature T _max toward the end 41 d of the clarification tube 41 is formed. Similarly, a temperature gradient is formed in which the temperature decreases from the position P at the maximum temperature T _max toward the position in the X direction of the vent pipe 41a. In addition to the above, the temperature gradient region is also formed between the position in the X direction of the ventilation pipe 41a and the end 41e (exit) of the clarification pipe 41 on the side where the molten glass G flows out. . In such a temperature gradient region, the temperature difference between the maximum temperature and the minimum temperature in the temperature gradient region is more than 0 ° C. and 150 ° C. or less, more preferably more than 0 ° C. and 100 ° C. or less. . As shown in FIG. 4, the defoaming process starts at least in the first half of the temperature increase section that continues until the wall temperature reaches the maximum temperature _Tmax , and continues at least to the maximum temperature _Tmax . Also includes the maximum temperature T _max, starts aggregate processing steps in the second half of the temperature rising section, continues at least to the maximum temperature T _max. The aggregate treatment process starts, for example, when the temperature of the molten glass G is 1670 ° C. or higher. The end of the defoaming treatment step and the end of the agglomerate treatment step may be either, but the point that all the platinum group metal foreign matter mixed in the molten glass is the subject of the agglomerate treatment step. Therefore, the end of the agglomerate treatment process is preferably the same as or after the end of the defoaming treatment process.

  Thus, in this embodiment, the process which defoams the bubble in the molten glass G is performed, but the aggregate of the volatile matter of the platinum group metal volatilized from the wall mixes in the molten glass G as a foreign material at this time. The size of the agglomerates mixed in the molten glass G so that the ratio of the number of foreign substances (aggregates) having a maximum length of 50 μm or less among the foreign substances (aggregates) mixed in the molten glass G is 70% or more. Reduce the thickness. Alternatively, the amount of heat applied to the platinum group metal foreign matter is controlled so as to reduce the size of the mixed platinum group metal foreign matter. Thereby, even if a foreign substance of a platinum group metal is mixed in the glass substrate, the glass substrate is hardly distorted, and the main surface of the glass substrate can be hardly made uneven.

  Further, the difference between the maximum temperature and the minimum temperature of the wall in contact with the gas phase space in the clarification tube 41 described above is 5 ° C. or more, and the gas phase space is an atmosphere containing oxygen, that is, the platinum group metal. Even under conditions where agglomerates are likely to occur, the size of the platinum group metal foreign matter contained in the molten glass can be reduced, or the ratio of the number of platinum group metal foreign matters having a maximum length of 50 μm or less is 70%. This can be done. Therefore, even if a foreign substance of a platinum group metal is mixed in the glass substrate, the glass substrate is hardly distorted, and the main surface of the glass substrate can be hardly formed.

  Further, when performing the aggregate treatment step, the temperature of the molten glass G containing the aggregate is compared with the temperature of the molten glass in the region where the foreign substance (aggregate) of the platinum group metal is mixed into the molten glass G in the molten glass treatment step. It is preferable to raise the temperature so as to increase. Thereby, the foreign material (aggregate) of the platinum group metal can be divided or melted by heat, and the size of the foreign material (aggregate) of the platinum group metal can be reliably reduced.

  Further, the glass processing apparatus is a clarification apparatus having a clarification tube 41, the gas phase space in the clarification tube 41 is formed along the flow direction of the molten glass, and the agglomerate processing step is performed by the clarification tube 41. Are preferred. Since the temperature of the molten glass G in the clarification tube 41 reaches the maximum temperature until the molding step, the platinum group metal foreign matter (aggregates) can be easily divided or melted.

  In the glass treatment process of the present embodiment, a clarification treatment is performed to reduce the number of bubbles in the molten glass G using tin oxide contained in the molten glass G. A temperature distribution is formed along the flow direction of the glass, and an oxygen concentration distribution is formed along the flow direction of the molten glass G in the gas phase space. In such an apparatus, since there is an oxygen concentration distribution that affects the volatilization of the platinum group metal, agglomerates of platinum group metal volatiles are likely to be generated, and the agglomerates are easily mixed into the molten glass as foreign substances. Even in such a case, the size of the foreign substance (aggregate) of the platinum group metal can be easily reduced, so that the glass substrate is less likely to be distorted, and the main surface of the glass substrate can be hardly made uneven. .

The agglomerate processing step is performed in a glass processing apparatus, and among the molten glass flowing through the glass processing apparatus, the molten glass flowing in a position in the flow direction corresponding to the region where the oxygen concentration is highest in the gas phase space is included. Preferably, it is done. In the temperature profile shown in FIG. 4, the defoaming treatment of the molten glass G is most actively performed at the maximum temperature _Tmax . Thereby, the oxygen concentration is highest in the region in the gas phase space near the maximum temperature _Tmax due to the oxygen released from the bubbles. For example, the agglomerate treatment step is performed on the molten glass passing through a position in the flow direction corresponding to the region in the gas phase space where the oxygen concentration is highest. For this reason, platinum group metals are actively volatilized due to the maximum oxygen concentration, and as a result, platinum group metal aggregates are easily generated, and platinum group metal aggregates are formed as foreign substances in the molten glass. Even if it is mixed, the size of the foreign matter can be efficiently reduced.

  The oxygen concentration in the gas phase space of the clarification tube 41 is more than 0% and not more than 1.0%, and the difference between the highest temperature and the lowest temperature of the wall of the clarification tube 41 is 5 ° C. or more, 100 It is preferable to set it as below ℃. Thereby, volatilization of a platinum group metal can be suppressed and the foreign material of the platinum group metal mixed in the molten glass G can be suppressed. However, even in this case, the platinum group metal foreign matter cannot be made completely zero. For this reason, by reducing the size of the platinum group metal foreign matter, the glass substrate is less likely to be distorted, and the effects of the present embodiment that make it difficult to make irregularities on the main surface of the glass substrate become even more remarkable. Moreover, since the volatilization of the platinum group metal can be suppressed, the life of the apparatus composed of the platinum group metal such as the fining tube 41 can be improved.

  Moreover, the temperature of the molten glass G is controlled to be in a temperature range of 1580 ° C. to 1660 ° C. in at least a part of the molten glass treatment step, and the temperature of the molten glass G during the aggregate treatment step is 1670 ° C. to 1730 ° C. By controlling so as to be, it is possible to reliably perform the defoaming process and to reliably reduce the size of the foreign substance (aggregate) of the platinum group metal. That is, it is possible to achieve both the reduction of the number of bubbles contained in the glass substrate and the reduction of platinum group metal foreign matters having a maximum length of 50 μm or more. Further, when the oxygen concentration in the gas phase space of the clarification tube 41 has a distribution depending on the location, foreign substances (aggregates) of the platinum group metal are easily mixed into the molten glass G in a region where the oxygen concentration is higher than a predetermined value. The temperature of the molten glass G to a temperature that can reduce the size of the platinum group metal foreign matter (aggregate) even if platinum group metal foreign matter (aggregate) is mixed. Is preferably adjusted. More preferably, it is preferable to control the molten glass temperature so as to form a temperature distribution of the molten glass along the oxygen concentration distribution in the gas phase space.

  In the above-described embodiment, as an example of controlling the condition for adjusting the solubility of the aggregate in the molten glass, an example of controlling the amount of heat given to the aggregate has been described. However, the conditions for adjusting the solubility so that the solubility is equal to or higher than the minimum solubility include the following conditions including the control of the heat amount. The solubility can be adjusted by controlling these conditions or by controlling these conditions in combination.

(Conditions for adjusting the solubility of aggregates)
As a condition for adjusting the solubility of the aggregate, for example,
(A) the concentration of the platinum group metal dissolved in the molten glass;
(B) Temperature or temperature distribution of the molten glass (amount of heat given to the aggregate),
(C) pressure in the gas phase space;
(D) The oxygen activity of the molten glass.

(A) Concentration of platinum group metal dissolved in molten glass The lower the concentration of platinum group metal dissolved in the molten glass at the start of the agglomeration treatment process, the more the foreign substance of platinum group metal in the molten glass in the platinum treatment step. Solubility increases. The concentration of the platinum group metal in the molten glass can be determined, for example, by sampling the molten glass in the clarification tube, crushing after cooling, and measuring using ICP quantitative analysis.
If the platinum group metal concentration is too low, the solubility of the platinum group metal agglomerates will increase, but the platinum group metal will elute from the wall of the clarified tube in contact with the molten glass to the molten glass, causing the clarified tube to be damaged. It may happen.
From the viewpoint of suppressing the occurrence of such disadvantages, the concentration of the platinum group metal is adjusted.

In addition, the platinum group metal melt | dissolved in the molten glass at the time of the aggregate process process start in the clarification tube 41 originates mainly in the platinum group metal eluted from the wall surface which contacts molten glass, such as the clarification tube 41 and the transfer pipe 43a. The amount of platinum group metal eluting from the wall surface depends on the temperature of the transfer tube 43a, the temperature of the molten glass in the defoaming treatment step before the start of the agglomerate treatment step, or the temperature of the wall of the clarification tube 41 in contact with the molten glass. Therefore, by adjusting the temperature or temperature distribution of the wall surfaces of the transfer pipe 43a and the clarification pipe 41, the concentration of the platinum group metal of the molten glass at the start of the aggregate treatment process can be adjusted. For example, it can be performed by adjusting the current flowing through the clarification tube 41, adjusting the current supplied to the heater arranged around the clarification tube 41, or a combination thereof. By lowering the concentration of the platinum group metal dissolved in the molten glass at the start of the aggregate treatment process, the solubility of the platinum group metal in the molten glass at the start of the aggregate treatment process is increased. From this point, it is preferable that the concentration of the platinum group metal dissolved in the molten glass at the start of the aggregate treatment process is adjusted to 0.05 to 20 ppm.
As a result, even when platinum group metal aggregates are mixed into the molten glass during the glass substrate manufacturing process, a glass substrate having an acceptable number of defects in the platinum group metal aggregates can be manufactured.

(B) Temperature or temperature distribution of molten glass In the clarification tube 41, the solubility of the aggregates of platinum group metals mixed in the molten glass can be increased by increasing the temperature of the molten glass. Since the temperature or temperature distribution of the molten glass has been described above, the description thereof will be omitted.

If the temperature of the molten glass is too high, the amount of platinum group metal agglomerates will increase, but the following disadvantages will be caused.
・ Increase in reboiling bubbles If the temperature of the molten glass is excessively increased in the clarification tube 41, the defoaming process causes excessive defoaming, so that the oxygen activity of the molten glass is lowered. As a result, the molten glass is in a reduced state. become. In this state, when the absorption treatment process is performed, reboil bubbles may be excessively generated in the molten glass according to the following mechanism, and reboil bubble bubbles may remain on the glass substrate. Specifically, the reboil bubble is a bubble containing SO ₂ or CO ₂ generated due to sulfur and carbon contained as impurities in the molten glass. When the reduction state of the molten glass becomes longer in time, SO ₃ and CO ₃ dissolved in the molten glass are easily reduced, so that SO ₂ and CO ₂ are easily generated. Since SO ₂ and CO ₂ are less soluble in molten glass than SO ₃ and CO ₃ , they tend to be bubbles. When many reboiling bubbles are generated, they remain as bubble defects on the glass substrate, which may deteriorate the quality of the glass substrate. The bubbles remaining on the glass substrate are detected by, for example, a laser microscope or visual observation.
-Increase in volatilization amount of glass component If the temperature of the molten glass is excessively raised in the clarification tube 41, a component of the molten glass, for example, B ₂ O ₃ is volatilized in the gas phase space. As a result, the glass composition changes locally, and the glass properties such as the thermal expansion coefficient and viscosity of the glass change locally, causing streaks such as striae to occur in the glass substrate.
-Increase in volatilization amount of platinum group metal In the clarification tube 41, if the temperature of the molten glass is too high, the temperature of the gas phase space in contact with the molten glass also increases, and further, the gas phase space is removed by the defoaming treatment of the molten glass. As a result, the amount of oxygen released into the gas increases, and as a result, the platinum group metal tends to volatilize from the wall of the clarification tube surrounding the gas phase space. When the volatilization amount of the platinum group metal increases, the concentration of the platinum group metal in the gas phase space increases, and aggregation and mixing of the aggregate into the molten glass easily occur.
-Melting of the clarification tube In the clarification tube 41, if the temperature of the molten glass is too high, the wall of the clarification tube 41 in contact with the molten glass may be melted.
From the viewpoint of suppressing the occurrence of such disadvantages, the temperature or temperature distribution of the molten glass in the clarification tube 41 is adjusted.

(C) Pressure in Gas Phase Space The solubility of the platinum group metal aggregates can be increased by increasing the pressure in the gas phase space 41 c of the clarification tube 41. The pressure in the gas phase space means the total pressure of the gas contained in the gas phase space.
The adjustment of the pressure in the gas phase space 41c is, for example, an amount (suction amount) in which the gas in the gas phase space 41c is sucked to the outside of the clarification tube 41 through the vent pipe 41a, the gas into the clarification tube 41, For example, it can be performed by adjusting the supply amount of the inert gas and the discharge amount of the gas released from the molten glass. The amount of suction is, for example, the magnitude of the pressure difference between the gas phase space 41c and the atmosphere outside the clarification tube 41 by connecting the outlet of the ventilation tube 41a of the clarification tube 41 to a suction device or by narrowing the outlet. It can be adjusted by adjusting. The amount of gas released from the molten glass can be adjusted, for example, by adjusting the amount of fining agent contained in the molten glass and the mixing ratio of the glass components. In addition, it can be calculated | required by the amount of gas discharge | released from the vent pipe 41a that the pressure of the gaseous-phase space 41c is higher or lower than the atmospheric pressure of the outer side of the clarification pipe | tube 41, for example.
In order to melt the foreign matter in the molten glass in the molten glass, the method for increasing the pressure in the gas phase space 41c is as described above, such as the amount of gas supplied into the clarification tube 41, for example, the amount of inert gas supplied, or This can be done by adjusting the amount of gas released from the molten glass. The pressure in the gas phase space 41c is preferably adjusted in the range of 0.8 to 1.2 atm, for example.

If the pressure in the gas phase space 41c is increased too much, the dissolution amount of the platinum group metal agglomerates increases, but the following disadvantages are caused.
-Poor fining If the pressure in the gas phase space 41c is too high, bubbles generated in the molten glass are difficult to be released from the surface of the molten glass in the defoaming treatment step, which may lead to poor fining.
-Increase in volatilization amount of platinum group metal If the pressure in the gas phase space 41c is increased too much, the pressure difference with the atmosphere outside the clarification tube 41 increases, and the flow velocity of the air flow in the gas phase space 41 increases. . For this reason, since the density | concentration of the platinum group metal in the gaseous-phase space 41c does not rise and it is hard to become a saturated state, the volatilization amount of the platinum group metal from the wall of the clarification tube 41 increases.
From the viewpoint of suppressing the occurrence of such disadvantages, the pressure of the gas phase space is adjusted.

(D) Oxygen Activity of Molten Glass In the clarification tube 41, the solubility of the platinum group metal aggregate can be increased by increasing the oxygen activity of the molten glass. The oxygen activity of the molten glass means the amount of oxygen dissolved in the molten glass (excluding those present in the molten glass as bubbles). In the present embodiment, [Fe ³⁺ ] / ([Fe ²⁺ ] + [Fe ³⁺ ]) is used as an index of the oxygen activity. Here, [Fe ²⁺ ] and [Fe ³⁺ ] are the activities of Fe ²⁺ and Fe ³⁺ contained in the molten glass, specifically, the mass percentage display content, which is measured using a spectrophotometric method. can do.
For example, in the defoaming treatment step in the clarification step, the temperature of the molten glass is increased, and oxygen dissolved in the molten glass is defoamed as bubbles, so that the oxygen activity of the molten glass is lowered. On the other hand, when the temperature of the molten glass is lowered in the fining step, the fining agent takes in oxygen, so that the oxygen activity increases.
The oxygen activity of the molten glass is adjusted, for example, in the melting process by adjusting the amount of fining agent and oxide contained in the molten glass, as well as adjusting the amount of fining agent and oxide contained in the molten glass. In addition, in the refining process, the temperature of the molten glass before the start of the aggregate treatment process can be adjusted, or the oxygen-containing gas can be adjusted by bubbling the molten glass before the start of the aggregate treatment process. .
Adjustment of the oxygen activity in the molten glass may be performed together with adjustment of the temperature or temperature distribution of the molten glass. The adjustment of the oxygen activity in the molten glass may be performed together with the adjustment of the pressure of the gas phase space 41c. As described above, the oxygen activity in the molten glass is adjusted by adjusting the amount of fining agent contained in the molten glass or the oxide of the glass raw material, and in the clarification process, before the start of the aggregate treatment process. It can be adjusted by adjusting the temperature of the glass or by bubbling an oxygen-containing gas into the molten glass before the start of the aggregate treatment process. It is preferable to adjust [Fe ³⁺ ] / ([Fe ²⁺ ] + [Fe ³⁺ ]), which is an index of oxygen activity, in the range of 0.2 to 0.5, for example, during the aggregate treatment process.

When the oxygen activity of the molten glass is adjusted, if the oxygen activity of the molten glass is excessively increased, the dissolution amount of the platinum group metal aggregate is increased, but the following disadvantages are caused.
・ Increased volatility of platinum group metals If the oxygen activity of the molten glass is increased too much, the amount of oxygen released from the molten glass into the gas phase space during the defoaming process will increase, and the oxygen concentration in the gas phase space will increase. Therefore, the platinum group metal is easily oxidized and easily volatilized. When the platinum group metal is easily volatilized, aggregates of the platinum group metal are likely to be generated and easily mixed into the molten glass.
・ Remaining oxygen bubbles in the molten glass If the oxygen activity of the molten glass is increased too much, the reduced fining agent cannot take up oxygen in the absorption treatment process, and bubbles containing oxygen (oxygen bubbles) are contained in the molten glass. Since it is produced | generated and remains as a bubble in a glass substrate, it becomes easy to reduce the quality of a glass substrate.
From the viewpoint of suppressing the occurrence of such disadvantages, when increasing the amount of dissolved platinum group metal aggregates by adjusting the oxygen activity of the molten glass, it is adjusted by combining appropriate condition parameters (temperature of the molten glass, etc.) It is preferable to do.

Alternatively, the temperature adjustment of the molten glass may be feedback adjusted based on the number of defects in the aggregate. The temperature of the molten glass to be adjusted may be the temperature at the start of the agglomerate treatment process or may be the temperature during the agglomerate treatment process.
The defects of platinum group metal aggregates in the glass substrate are obtained by making light such as laser light incident on the surface of the glass substrate from an oblique direction and receiving the reflected light at each position of the glass substrate. It can detect by specifying the area | region which corresponds to the shape of the aggregate of a platinum group metal from the acquired image. Aggregate defects may be detected visually instead of using the apparatus in this way. The allowable level of the number of defects in the aggregate is, for example, 0.02 piece / kg or less when expressed in unit mass. The allowable level changes in accordance with specifications regarding distortion and irregularities on the main surface, which are required by the user of the glass substrate.
For example, when the number of defects detected in the glass substrate exceeds an allowable level, the temperature of the molten glass is increased to increase the saturation solubility of the platinum group metal in the molten glass, thereby mixing into the molten glass. Promotes the dissolution of aggregates. On the other hand, when the number of defects detected in the glass substrate is at an allowable level, the number can be lowered within a range higher than the upper limit of the number of defects at the allowable level and the temperature of the molten glass corresponding to the upper limit. In this way, by adjusting the temperature of the molten glass, the saturation solubility of the platinum group metal can be adjusted to an appropriate range. It is possible to suppress the deterioration of the quality of the glass substrate caused by the increase in bubbles and the like.
Specifically, when the glass processing apparatus is a clarification apparatus including a clarification tube, the temperature of the molten glass can be adjusted by passing an electric current through the clarification tube and conducting heating. The amount of current can be adjusted by the magnitude of the voltage applied to the heating electrode. Further, the temperature adjustment of the molten glass may be indirectly adjusted by a heater (not shown) disposed around the clarification tube in place of the electric heating or in combination with the electric heating. The heater is disposed, for example, inside or outside a refractory protective layer or a refractory brick. Moreover, temperature adjustment of molten glass may be performed by adjusting the heat dissipation from a clarification pipe | tube using a refractory material protective layer and a refractory brick.

In the agglomerate treatment step, the above-mentioned index of the oxygen activity of the molten glass is used in place of or in addition to the temperature adjustment of the molten glass so that the number of defects of the agglomerates contained in the glass substrate becomes an acceptable level. It is preferable to adjust the saturation solubility of the platinum group metal by adjusting [Fe ³⁺ ] / ([Fe ²⁺ ] + [Fe ³⁺ ]) of the glass substrate in the range of 0.2 to 0.5.

(Aggregates of platinum group metals after the aggregate treatment process)
The ratio of the number of foreign substances (aggregates) having a maximum length of more than 50 μm among the platinum group metal foreign substances (aggregates) contained in the molten glass, the glass substrate, or the glass substrate laminate after the aggregate treatment step is 30 Decrease to less than%.

In this embodiment, in order to raise the temperature of the molten glass G, when making the temperature of the clarification tube 41 high, the effect mentioned above of this embodiment can be exhibited effectively.
For example, tin oxide is preferably used as a clarifier for molten glass in order to reduce environmental impact. However, tin oxide has a clarification effect (oxidation reaction) as compared with As ₂ O ₃ and Sb ₂ O _3. The temperature obtained is high. For this reason, when the tin oxide is used as a clarifier, the temperature of the clarification tube 41 is increased as compared with the case where As ₂ O ₃ or Sb ₂ O ₃ is used as a clarifier. Need to be high. That is, since tin oxide is used as a fining agent, volatilization (oxidation) of the fining tube 41 is more likely to occur than before, and the problem of volatilization and aggregation of platinum group metals is likely to occur. Thus, even if the amount of platinum group metal foreign matter (aggregates) mixed in the molten glass is increased by using tin oxide as a fining agent, the size of the platinum group metal foreign matter is increased as in this embodiment. Since the thickness of the glass substrate can be reduced, the glass substrate is less likely to be distorted, and the effect of making it difficult to make irregularities on the main surface of the glass substrate becomes significant. That is, the amount of foreign matters (aggregates) that cause display defects can be sufficiently reduced.

In addition, molten glass with high viscosity has a low bubble rising speed in the refining process and is difficult to clarify. Further, even in the stirring step performed by the stirring device 100, it is difficult to uniformly stir molten glass having high viscosity. Therefore, in order to sufficiently obtain the refining effect or the homogenization of the molten glass, it is necessary to increase the temperature of the molten glass. For this reason, if the temperature of the glass processing apparatus is also increased in order to obtain a molten glass having a high temperature, volatilization of the platinum group metal becomes intense in the glass processing step, and the amount of foreign matters (aggregates) mixed into the molten glass increases. easy. That is, the problem of volatilization and aggregation of platinum group metals is likely to occur.
For example, although a thin film transistor is formed on a glass substrate used for a display panel, it is preferable to use alkali-free glass or glass containing a trace amount of alkali so as not to adversely affect the operation of the thin film transistor. Since alkali-free glass or glass containing a small amount of alkali is higher in viscosity than alkali-containing glass such as soda glass, it is difficult to clarify because the speed of foam rise is slow in the fining process. For this reason, in order to fully obtain the clarification effect, it is necessary to raise the temperature of the clarification tube 41 and to raise the temperature of the molten glass G. That is, since the object to be manufactured is alkali-free glass or glass containing a small amount of alkali, volatilization (oxidation) of the clarification tube 41 is more likely to occur than alkali glass, and the problem of volatilization and aggregation of platinum group metals is likely to occur. Thus, even if the amount of foreign matter (aggregates) of platinum group metal mixed into the molten glass is increased by increasing the temperature of the clarification tube 41 in order to use alkali-free glass or glass containing a small amount of alkali, Since the size of the foreign material of the platinum group metal can be reduced as in the embodiment, the effect that the glass substrate is hardly distorted and the main surface of the glass substrate can be made difficult to make uneven is remarkable. . That is, the amount of foreign matters (aggregates) that cause display defects can be sufficiently reduced.

The alkali-free glass or alkali trace glass described above is a glass having a high strain point. A glass having a high strain point has a higher viscosity than a glass having a low strain point, and therefore, the rising speed of bubbles is slow in the refining process, and it is difficult to clarify. For this reason, in order to fully obtain the clarification effect, it is necessary to raise the temperature of the clarification tube 41 and to raise the temperature of the molten glass G. That is, when producing a glass with a high strain point, the clarification tube is more likely to volatilize (oxidize) than when producing a glass with a low strain point, and the problem of volatilization and aggregation of platinum group metals is likely to occur. Thus, in order to use glass with a high strain point, even if the temperature of the clarification tube 41 is increased and the amount of foreign matter (aggregates) of the platinum group metal mixed in the molten glass increases, As described above, since the size of the platinum group metal foreign matter can be reduced, the glass substrate is less likely to be distorted, and the effect of making it difficult to make irregularities on the main surface of the glass substrate becomes significant. That is, the amount of foreign matters (aggregates) that cause display defects can be sufficiently reduced.
The glass substrate for display is required to have a strain point of the glass substrate of 600 ° C. or higher, more preferably 650 ° C. or higher. However, if the strain point of the glass substrate is 600 ° C. or higher, a display defect is caused. The effect of the present embodiment that can sufficiently reduce the amount of foreign matters (aggregates) having such a size becomes remarkable. Moreover, the glass substrate for high-definition displays is required to have a higher strain point, and the strain point is preferably 690 ° C. or higher, and more preferably 730 ° C. or higher. As described above, when the strain point is 690 ° C. or higher and 730 ° C. or higher, the above-described effect of the present embodiment becomes more remarkable.
Moreover, the viscosity of the molten glass containing tin oxide used in the present embodiment is 10 ^2.5 poise at a temperature of 1500 ° C. or higher, for example, 1500 ° C. to 1700 ° C., or 1550 ° C. to 1650 ° C. It is preferable. In this case, the above-described effect of the present embodiment becomes more remarkable.
Further, when the thickness of the glass substrate manufactured in this embodiment is 0.005 mm to 0.8 mm, preferably 0.01 mm to 0.5 mm, more preferably 0.01 mm to 0.2 mm, this embodiment The above-mentioned effect becomes more remarkable. When such a thin glass substrate is produced, foreign substances (aggregates) appear on the glass surface and surface irregularities are easily formed. In the present embodiment, such a problem due to the plate thickness can be solved by the above-described effects.

[Experimental example]
In order to confirm the effect of this embodiment, the glass substrate was produced by the manufacturing process including the aggregate processing process S2B shown in FIG. 1 (Example). In the aggregate processing step S2B, the amount of heat given to the aggregate was controlled.
The conditions for producing the glass substrate are as follows.
The glass composition of the glass substrate is as follows: SiO ₂ 60.7 mass%, Al ₂ O ₃ 17 mass%, B ₂ O ₃ 11.5 mass%, MgO 2 mass%, CaO 5.6 mass%, SrO 3 mass%. SnO ₂ 0.2 mass%, the strain point was 660 ° C., and the plate thickness was 0.4 mm.
Moreover, the glass substrate was produced on the above-mentioned production conditions by the conventional manufacturing process which performed the absorption process S2C after the defoaming process S2A, without performing the aggregate treatment process S2B shown in FIG. Specifically, in Examples 1 to 5 shown in Table 1 below, the maximum temperature of the molten glass G in the clarification tube 41 is set to 1670 ° C. to 1720 ° C., and the time for the temperature of the molten glass G to be 1670 ° C. or higher is 40 minutes. did. On the other hand, in Examples 6 and 7, the maximum temperature of the molten glass G was set to less than 1670 ° C, and the time during which the temperature of the molten glass G was 1670 ° C or higher was set to 0 minutes.

The number of foreign substances (aggregates) of the platinum group metal on the plurality of 0.1 m ³ glass substrates thus prepared is counted using an optical microscope, and the maximum length of the foreign substances (aggregates) of the platinum group metal is counted. Was measured. And the ratio of the number of the foreign material whose maximum length is 50 micrometers or less among the foreign materials (aggregate) of all the platinum group metals mixed in a glass substrate was calculated | required. The obtained ratio is shown in Table 1 below together with the maximum temperature. The percentage of foreign matter in Examples 1 to 5 was 70% or more in any glass substrate, but the percentage of foreign matter in Examples 6 and 7 was 35% or less in any glass substrate. FIG. 5 is a graph showing the relationship between the maximum temperature of the molten glass and the ratio of foreign matter. As can be seen from FIG. 5, the ratio of foreign matter having a maximum length of 50 μm or less rapidly increases when the maximum temperature of the molten glass is increased from 1660 ° C. to 1670 ° C. or higher, and is 70% or higher at a temperature of 1670 ° C. or higher. It became. At 1690 ° C. or higher, the ratio of foreign matters having a maximum length of 50 μm or less was 92% or higher. In particular, at 1700 ° C. or higher, the ratio of foreign matters having a maximum length of 50 μm or lower was 100%. From this, when controlling the amount of heat given to the foreign material under the conditions of this experimental example, the maximum temperature of the molten glass is set to 1670 ° C. or higher, preferably 1690 ° C. or higher, more preferably 1700 ° C. or higher, to give heat to the foreign material. It turns out that it is preferable. Under the conditions of this experimental example, the maximum temperature of 1670 ° C. is the lower limit temperature of the maximum temperature at which the ratio of foreign matter having a maximum length of 50 μm or less is 70%, but it is essential that the maximum temperature is 1670 ° C. or more. Instead, adjusting the solubility of the agglomerates (foreign substances) by other methods can also realize the ratio of foreign substances having a maximum length of 50 μm or less to 70%.

  As mentioned above, although the manufacturing method of the glass substrate of this invention, the glass substrate, and the glass substrate laminated body were 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, it is various improvement. Of course, you may make changes.

40 Melting tank 41 Clarification tube 41a Ventilation tube 41b Heating electrode 41c Gas phase space 42 Molding device 52 Molded bodies 43a, 43b. 43c Transfer pipe 100 Stirrer 200 Glass substrate manufacturing apparatus

That is, one embodiment of the present invention is a method for manufacturing a glass substrate. The manufacturing method of the said glass substrate contains the following forms.
(First form)
The manufacturing method of the glass substrate is:
A melting step of melting glass raw material to produce molten glass;
A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal. The molten glass is flowed in the tube of the molten glass, and when the molten glass is processed, aggregates of platinum group metal volatiles volatilized from the wall, which are present in the gas phase space, are treated as foreign matter as the molten glass. Molten glass processing step mixed in,
In the tube of the glass processing apparatus, the temperature of the molten glass is set to 1670 so that the ratio of the number of aggregates having a maximum length of 50 μm or less among the aggregates mixed in the molten glass is 70% or more. An agglomerate treatment step for reducing the size of the agglomerates mixed in the molten glass at a temperature higher than or equal to ° C.
The pipe of the glass processing apparatus is provided with a vent pipe communicating with the gas phase space and the atmosphere outside the glass processing apparatus, and becomes the maximum temperature of the molten glass flowing through the pipe of the glass processing apparatus. The maximum temperature position in the flow direction is between the inlet where the molten glass is introduced into the tube of the glass processing apparatus and the position of the vent tube in the flow direction of the molten glass.

(Second form)
The manufacturing method of the glass substrate is:
A melting step of melting glass raw material to produce molten glass;
It has a liquid phase made of the molten glass, and a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal. A process of pouring the molten glass in a tube of a glass processing apparatus , and an aggregate of platinum group metal volatiles volatilized from the wall and present in the gas phase space during the processing of the molten glass As a molten glass processing step mixed in the molten glass,
In the tube of the glass processing apparatus , the molten metal is mixed so that the ratio of the number of aggregates having a maximum length of 50 μm or less among the aggregates mixed in the molten glass in the molten glass treatment step is 70% or more. And agglomerate treatment step for reducing the size of the agglomerates mixed in the molten glass by setting the glass temperature to 1670 ° C. or higher .
The pipe of the glass processing apparatus is provided with a vent pipe communicating with the gas phase space and the atmosphere outside the glass processing apparatus, and becomes the maximum temperature of the molten glass flowing through the pipe of the glass processing apparatus. The maximum temperature position in the flow direction is between the inlet where the molten glass is introduced into the tube of the glass processing apparatus and the position of the vent tube in the flow direction of the molten glass .

(Third form)
The manufacturing method of the glass substrate is:
A melting step of melting glass raw material to produce molten glass;
A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal. The molten glass is flowed in the tube of the molten glass, and when the molten glass is processed, aggregates of platinum group metal volatiles volatilized from the wall, which are present in the gas phase space, are treated as foreign matter as the molten glass. A molten glass processing step mixed in,
Aggregation that adjusts the solubility of the aggregate in the molten glass by setting the temperature of the molten glass to 1670 ° C. or higher in the tube of the glass processing apparatus so that the size of the aggregate mixed in the molten glass is reduced. A material processing step,
The pipe of the glass processing apparatus is provided with a vent pipe communicating with the gas phase space and the atmosphere outside the glass processing apparatus, and becomes the maximum temperature of the molten glass flowing through the pipe of the glass processing apparatus. The maximum temperature position in the flow direction is between the inlet where the molten glass is introduced into the tube of the glass processing apparatus and the position of the vent tube in the flow direction of the molten glass .

(4th form)
The manufacturing method of the glass substrate is:
A melting step of melting glass raw material to produce molten glass;
It has a liquid phase made of the molten glass, and a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal. A process of pouring the molten glass in a tube of a glass processing apparatus , and an aggregate of platinum group metal volatiles volatilized from the wall and present in the gas phase space during the processing of the molten glass As a molten glass processing step mixed in the molten glass as,
Further, in the tube of the glass processing apparatus, the temperature of the molten glass is set so that the amount of heat given to the agglomerates is not less than the minimum amount of heat that can reduce the size of the agglomerates mixed in the molten glass. An agglomerate treatment step for controlling the amount of heat given to the agglomerates at 1670 ° C. or higher ,
The pipe of the glass processing apparatus is provided with a vent pipe communicating with the gas phase space and the atmosphere outside the glass processing apparatus, and becomes the maximum temperature of the molten glass flowing through the pipe of the glass processing apparatus. The maximum temperature position in the flow direction is between the inlet where the molten glass is introduced into the tube of the glass processing apparatus and the position of the vent tube in the flow direction of the molten glass .

(8th form)
The glass processing apparatus is a clarification apparatus having a clarification tube,
The vapor phase space in the clarification tube is formed along the flow direction of the molten glass, and the agglomerate treatment step is performed in the clarification tube, any one of the first to seventh embodiments. The manufacturing method of the glass substrate described in one form.

(9th form)
In the molten glass treatment step, a clarification treatment is performed to reduce the number of bubbles in the molten glass using tin oxide contained in the molten glass, and the wall in contact with the gas phase space has a flow of the molten glass. A temperature distribution is formed along a direction, and an oxygen concentration distribution is formed in the gas phase space along a flow direction of the molten glass. Any one of the first to eighth embodiments The manufacturing method of the glass substrate described in the form.

(10th form)
The agglomerate treatment step is performed in the glass treatment apparatus, and among the molten glass flowing through the glass treatment apparatus, the position corresponding to the region where the oxygen concentration is highest in the flow direction of the molten glass in the gas phase space. The manufacturing method of the glass substrate described in any one of the said 1st form-the said 9th form performed with respect to the flowing molten glass.

Claims (19)

A melting step of melting glass raw material to produce molten glass;
A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal. In the step of treating the molten glass, the aggregate of platinum group metal volatiles volatilized from the wall, which is present in the gas phase space, is mixed into the molten glass as a foreign substance during the treatment of the molten glass. A molten glass processing step,
Among the aggregates mixed in the molten glass, the aggregates that reduce the size of the aggregate mixed in the molten glass so that the ratio of the number of aggregates having a maximum length of 50 μm or less is 70% or more. A method for producing a glass substrate, comprising a treatment step. A melting step of melting glass raw material to produce molten glass;
It has a liquid phase made of the molten glass, and a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal. A process of processing the molten glass in a glass processing apparatus, wherein during the processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the walls present in the gas phase space are treated as foreign matters. A molten glass processing step mixed in glass,
The size of the aggregates mixed in the molten glass so that the ratio of the number of aggregates having a maximum length of 50 μm or less among the aggregates mixed in the molten glass in the molten glass treatment step is 70% or more. A method for producing a glass substrate, comprising: A melting step of melting glass raw material to produce molten glass;
A glass processing apparatus having a space in which a gas phase space surrounded by a surface and a wall of the molten glass is formed by introducing the molten glass, and at least a part of the wall is made of a material containing a platinum group metal. In the step of treating the molten glass, the aggregate of platinum group metal volatiles volatilized from the wall, which is present in the gas phase space, is mixed into the molten glass as a foreign substance during the treatment of the molten glass. A molten glass processing step,
A method for producing a glass substrate, comprising: an aggregate treatment step of adjusting the solubility of the aggregate in the molten glass so that the size of the aggregate mixed into the molten glass is reduced. A melting step of melting glass raw material to produce molten glass;
It has a liquid phase made of the molten glass, and a gas phase space formed from the liquid surface and walls of the molten glass, and at least a part of the wall surrounding the gas phase space is made of a material containing a platinum group metal. A process of processing the molten glass in a glass processing apparatus, wherein during the processing of the molten glass, aggregates of platinum group metal volatiles volatilized from the walls present in the gas phase space are treated as foreign matters. A molten glass processing step mixed in glass,
Furthermore, an aggregate treatment process for controlling the amount of heat applied to the aggregate so that the amount of heat applied to the aggregate is equal to or greater than a minimum amount of heat that can reduce the size of the aggregate mixed in the molten glass. A method for producing a glass substrate, comprising: The difference between the maximum temperature and the minimum temperature of the wall in contact with the gas phase space is 5 ° C. or more,
The method for producing a glass substrate according to claim 1, wherein the gas phase space contains oxygen.   In the agglomerate treatment step, the temperature of the molten glass containing the agglomerates is raised so as to be higher than the temperature of the molten glass in the region where the agglomerates are mixed into the molten glass in the molten glass treatment step. The manufacturing method of the glass substrate of any one of Claims 1-5.   In the said aggregate treatment process, the solubility to the molten glass of the said aggregate is made high compared with the said solubility in the area | region in which the aggregate mixes with molten glass in the said molten glass treatment process. 2. A method for producing a glass substrate according to item 1. The glass processing apparatus is a clarification apparatus having a clarification tube,
The molten glass flows through the clarification tube,
The gas phase space in the fining tube is formed along the direction of the flow of the molten glass,
The said aggregate processing process is a manufacturing method of the glass substrate of any one of Claims 1-7 performed by the said clarification tube. In the molten glass treatment step, a clarification treatment is performed to reduce the number of bubbles in the molten glass using tin oxide contained in the molten glass,
The molten glass flows through the glass processing apparatus,
In the wall in contact with the gas phase space, a temperature distribution is formed along the flow direction of the molten glass,
The method for manufacturing a glass substrate according to claim 1, wherein an oxygen concentration distribution is formed in the gas phase space along a flow direction of the molten glass. The molten glass flows through the glass processing apparatus,
The agglomerate treatment step is performed in the glass treatment apparatus, and among the molten glass flowing through the glass treatment apparatus, the position corresponding to the region where the oxygen concentration is highest in the flow direction of the molten glass in the gas phase space. The manufacturing method of the glass substrate of any one of Claims 1-9 performed with respect to the flowing molten glass.   The oxygen concentration in the gas phase space is more than 0% and 1.0% or less, and the difference between the maximum temperature and the minimum temperature of the wall in contact with the gas phase space is 5 ° C. or more, 150 The manufacturing method of the glass substrate of any one of Claims 1-10 made into degrees C or less.   The manufacturing of the glass substrate of any one of Claims 1-11 which controls the temperature of a molten glass so that the temperature of the said molten glass in the said aggregate processing process shall be 1670 degreeC-1730 degreeC temperature range. Method.   The temperature of a molten glass is controlled so that the temperature of the said molten glass in the area | region where the aggregate mixes in a molten glass in the said molten glass processing process shall be 1580 to 1660 degreeC. The manufacturing method of the glass substrate of Claim 1.   The said molten glass processing process is a manufacturing method of the glass substrate of any one of Claims 1-13 including the said aggregate processing process.   The said glass substrate is a manufacturing method of the glass substrate of any one of Claims 1-14 which is a glass substrate for displays.   The manufacturing method of the glass substrate of any one of Claims 1-15 which makes the density | concentration of the platinum group metal melt | dissolved in the said molten glass at the time of the said aggregate treatment process start 0.05-20 ppm. In the agglomerate treatment step, the saturation solubility of the platinum group metal of the molten glass is adjusted so that [Fe ³⁺ ] / ([Fe ²⁺ ] + [Fe ³⁺ ]) of the glass substrate is 0.2 to 0.5. The manufacturing method of the glass substrate of any one of Claims 1-16 adjusted.
A glass substrate laminate formed by laminating a plurality of glass substrates,
The total volume of the glass substrate of the glass substrate laminate is 0.1 m ³ or more,
The ratio of the number of aggregates having a maximum length of 50 μm or less among the aggregates of all platinum group metals contained in the glass substrate laminate is 70% or more.   The ratio of the number of the aggregates whose maximum length is 50 micrometers or less among the aggregates of the platinum group metal which a glass substrate contains is 70% or more, The glass substrate characterized by the above-mentioned.

Images