KR101811508B1 - Method of making glass substrate, glass substrate and bundle of glass substrates - Google Patents

Abstract

A method of manufacturing a glass substrate which makes it difficult for the glass substrate to be deformed and makes it difficult to form irregularities on the main surface of the glass substrate is characterized in that at least a part of the wall in which the vapor phase space is formed by the introduction of the molten glass is made of a platinum group metal A molten glass treatment step in which an aggregate of volatiles of a platinum group metal volatilized from a wall existing in the vapor phase space is mixed as a foreign material when the molten glass is treated and a step of removing the aggregate of the platinum group metal volatilized from the molten glass in the molten glass treatment step And an aggregate treatment step of reducing the size of the aggregate so that the ratio of the number of aggregates of 50 mu m or less is 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 the aggregates having the maximum length of 50 m or less among all the platinum group metal flocculates contained in the glass substrate is 70%

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for manufacturing a glass substrate,

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

The glass substrate is generally produced through a step of producing a molten glass from a glass raw material, obtaining a refining step and a homogenizing step, and then molding the molten glass into a glass substrate. In order to mass-produce a glass substrate having a high quality from a molten glass at a high temperature, consideration is made so that foreign matter or the like which causes defects in the glass substrate is not mixed into the molten glass from any of the glass processing apparatuses for manufacturing the glass substrate Lt; / RTI > Therefore, the wall of the member in contact with the molten glass in the manufacturing process of the glass substrate needs to be made of a suitable material in accordance with the temperature of the molten glass in contact with the member, the quality of the required glass substrate, and the like.

For example, since the molten glass from the generation of the molten glass to the supply of the molten glass to the forming step becomes a very high temperature state, the apparatus for melting, refining, supplying, and agitating the molten glass contains platinum, which is a platinum group metal having high heat resistance Member is used (for example, Patent Document 1).

[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2010-111533

However, the platinum group metal becomes volatile as the temperature becomes high. When the volatiles of the platinum group metal coagulate, a part of the crystals as the aggregate is mixed into the molten glass as a foreign substance, which may cause deterioration of the quality of the glass substrate. Particularly, the cleaning process is a process in which the temperature of the molten glass is highest during the period from the dissolving process to the forming process, so that the cleaning tube, which mainly performs the cleaning process, is heated to a very high temperature. As a result, some of the aggregates obtained by flocculating the platinum group metal volatilized from the clarifying tube into the molten glass after the refining process are liable to become foreign substances and to be mixed.

When a foreign substance of the platinum group metal is mixed in the process of manufacturing the glass substrate, the glass substrate is deformed due to the difference in the coefficient of thermal expansion between the foreign substance of the platinum group metal and the glass, There is a problem of poor display of the display due to the fact that it exists in the vicinity of the main surface of the glass substrate to form irregularities on the main surface of the glass substrate and that the thin film transistor (TFT) provided on the main surface can not be uniformly formed It happens. In recent years, with the high definition of the screen display of the image display apparatus, in the glass substrate used for the display, the reduction of the foreign substances of the platinum group metal incorporated in the glass substrate is strongly demanded.

Thus, it is preferable to reduce the amount of foreign substances (aggregates) of the platinum group metal incorporated into the glass substrate. However, the temperature of the molten glass before molding is very high, and in particular, in the purifying tube for performing the refining step, oxygen which is a cause of volatilization of the platinum group metal can not be excluded from the gas phase space atmosphere of the purifying tube, The volatilization of platinum group metals can not be completely eliminated. Further, in the purifying tube, the temperature difference of the inner wall surface of the apparatus, which causes the volatiles of the platinum group metal to occur, can not be zero, and the volatilization of the platinum group metal can not be completely eliminated. Therefore, it is difficult to completely prevent the incorporation of foreign substances (agglomerates) of the platinum group metal in the molten glass during the manufacturing process.

Accordingly, it is an object of the present invention to provide a glass substrate production method, a glass substrate, and a glass substrate laminate which are difficult to cause the aforementioned problems even when foreign substances (agglomerates) of a platinum group metal are mixed in the glass substrate.

As described above, the inventors of the present invention have found that it is difficult to completely prevent foreign matter (agglomerates) of a platinum group metal from being mixed into the molten glass during the manufacturing process of the glass substrate, so that even when foreign substances (agglomerates) of the platinum group metal are mixed in the molten glass , It is difficult for the glass substrate to be deformed, and the shape of the foreign material which makes it difficult to make irregularities on the main surface of the glass substrate is sought. As a result, it is found that a maximum length of the platinum group metal of 50 탆 or less is less likely to cause deformation of the glass substrate, which makes it difficult to make irregularities on the main surface of the glass substrate. Further, (Agglomerates) of the platinum group metal having a maximum length of the platinum group metal of 50 m or less is 70% or more. Particularly, when the glass substrate is manufactured, it is effective to reduce the size of the foreign substance (agglomerate) of the platinum group metal incorporated in the molten glass, since it is difficult for the glass substrate to be deformed and it is difficult to make irregularities on the main surface of the glass substrate . This is an idea that can not be easily overcome from the prior art for reducing the absolute number of foreign substances (agglomerates) of the platinum group metal in order to suppress the occurrence of defective display.

That is, one mode of the present invention is a method for manufacturing a glass substrate. The method of manufacturing the glass substrate includes the following modes.

(First Embodiment)

A method of manufacturing a glass substrate,

A melting step of melting a glass raw material to produce a molten glass;

Wherein the molten glass has a space in which a surface of the molten glass and a vapor space surrounded by the wall are formed and at least a part of the wall is made of a material containing a platinum group metal, And a molten glass treatment step in which an aggregate of volatile substances of the platinum group metal volatilized from the wall existing in the vapor phase space is mixed with the molten glass as a foreign substance during the treatment of the molten glass,

And a flocculation treatment step of reducing the size of the flocculant mixed in the molten glass so that the ratio of the number of flocculants having a maximum length of 50 m or less among the flocculants mixed into the molten glass is 70% or more.

(Second Embodiment)

A method of manufacturing a glass substrate,

A melting step of melting a glass raw material to produce a molten glass;

Wherein said molten glass has a liquid phase composed of said molten glass and a vapor phase space formed from a wall of said molten glass and at least a part of a wall surrounding said vapor phase is made of a material containing a platinum group metal, A molten glass treatment step in which an aggregate of volatiles of a platinum group metal volatilized from the wall present in the vapor phase space is mixed with the molten glass as a foreign substance during the treatment of the molten glass,

And a step of reducing the size of the agglomerates mixed in the molten glass so that the ratio of the number of agglomerates having a maximum length of 50 탆 or less among the agglomerates mixed into the molten glass in the molten glass treatment step is 70% .

(Third Embodiment)

A method of manufacturing a glass substrate,

A melting step of melting a glass raw material to produce a molten glass;

Wherein the molten glass has a space in which a surface of the molten glass and a vapor space surrounded by the wall are formed and at least a part of the wall is made of a material containing a platinum group metal, And a molten glass treatment step in which an aggregate of volatile substances of the platinum group metal volatilized from the wall existing in the vapor phase space is mixed with the molten glass as a foreign substance during the treatment of the molten glass,

And 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 becomes small.

(Fourth Embodiment)

A method of manufacturing a glass substrate,

A melting step of melting a glass raw material to produce a molten glass;

Wherein said molten glass has a liquid phase composed of said molten glass and a vapor phase space formed from a wall of said molten glass and at least a part of a wall surrounding said vapor phase is made of a material containing a platinum group metal, And a molten glass treatment step in which the aggregate of volatile substances of the platinum group metal volatilized from the wall existing in the vapor phase space is mixed with the molten glass as a foreign substance during the treatment of the molten glass,

Further comprising an aggregate treatment step of controlling the amount of heat given to the aggregate so that the amount of heat imparted to the aggregate is equal to or greater than a minimum amount of heat that can reduce the size of the aggregate incorporated in the molten glass.

(Fifth Embodiment)

Wherein a difference between a maximum temperature and a minimum temperature of the wall in contact with the vapor phase space is set to 5 DEG C or more and the vapor phase space is made of any one of the first to fourth forms Of the glass substrate.

(Sixth embodiment)

Wherein the aggregate treatment step raises the temperature of the molten glass including the aggregate to be higher than the temperature of the molten glass in a region where the aggregate is mixed with the molten glass in the molten glass treatment step, And the method of manufacturing a glass substrate according to any one of the fifth to fifth aspects. Alternatively, in the aggregate treatment step, the temperature of the molten glass becomes the maximum temperature.

(Seventh Embodiment)

Wherein in the aggregate treatment step, the solubility of the aggregate in the molten glass is made higher than the solubility in the region in which the aggregate is mixed in the molten glass in the molten glass treatment step, A method of manufacturing a glass substrate according to any one of the preceding claims. Alternatively, the flocculation treatment step may be a step of increasing the solubility of the aggregate in the molten glass so as to reduce the size of the aggregate mixed in the molten glass. In the glass substrate of any one of the first to sixth aspects, Gt; Specifically, the flocculating material processing step is a step of reducing the size of the flocculated material mixed in the molten glass by heating and controlling the molten glass so as to increase the solubility of the flocculated material in the molten glass. A method of manufacturing a glass substrate according to any one of the preceding claims.

(Embodiment 8)

The glass processing apparatus is a purifying apparatus having a purifying tube,

The molten glass flows in the purifying tube,

Wherein the vapor phase space in the purifying tube is formed along the flow direction of the molten glass and the aggregate processing step is carried out in the glass tube described in any one of the first to seventh aspects, / RTI >

(Ninth embodiment)

Wherein in the molten glass treatment step, a fining treatment for reducing the number of bubbles in the molten glass is performed using tin oxide contained in the molten glass, the molten glass flows in the glass processing apparatus, The wall is formed with a temperature distribution along the flow direction of the molten glass and an oxygen concentration distribution is formed in the vapor space along the flow direction of the molten glass. Wherein the glass substrate is a glass substrate.

(Tenth Embodiment)

Wherein the flocculation treatment step is carried out in the glass treatment apparatus and the molten glass flows in the glass treatment apparatus and flows in the molten glass flowing in the glass treatment apparatus in the flow direction of the molten glass in the vapor phase, Is carried out with respect to the molten glass flowing at a position corresponding to the highest region of the glass substrate.

(11th form)

Wherein the oxygen concentration in the vapor phase space is set to more than 0% and not more than 1.0%, and a difference between a maximum temperature and a minimum temperature of the wall in contact with the vapor space is 5 ° C or more and 100 ° C or less, To (10), wherein the glass substrate is a glass substrate.

(Twelfth Mode)

The glass substrate according to any one of the first to eleventh aspects, wherein the temperature of the molten glass is controlled so that the temperature of the molten glass in the aggregate treatment step is in the range of 1670 캜 to 1730 캜 ≪ / RTI >

(Thirteenth Aspect)

Wherein the temperature of the molten glass is controlled so that the temperature of the molten glass in the region where the aggregate is mixed into the molten glass in the molten glass treatment step is in the range of 1580 캜 to 1660 캜. Wherein the glass substrate is a glass substrate.

(Fourteenth Aspect)

The method of manufacturing a glass substrate according to any one of the first to thirteenth aspects, wherein the molten glass treatment step includes the aggregate treatment step.

(15th form)

The method for manufacturing a glass substrate according to any one of the first to fourteenth aspects, wherein the glass substrate is a glass substrate for display.

(Sixteenth Aspect)

The method for producing a glass substrate according to any one of the first to fifteenth aspects, wherein the concentration of the platinum group metal dissolved in the molten glass at the start of the agglomerate treatment process is 0.05 to 20 ppm.

(17th form)

In the flocculation treatment step, the saturation solubility of the platinum group metal in the molten glass is adjusted in the range of [Fe ^{3 +} ] / ([Fe ^{2 +} ] + [Fe ^{3 +} ]) A method for manufacturing a glass substrate according to any one of the first to sixteenth aspects.

(18th form)

The glass substrate according to any one of the first to seventeenth aspects, wherein the content of the alkali metal oxide is 0 to 0.5% by mass.

(19th form)

A melting step of melting a glass raw material to produce a molten glass;

Wherein the molten glass has a space in which a surface of the molten glass and a vapor space surrounded by the wall are formed and at least a part of the wall is made of a material containing a platinum group metal, A molten glass treatment step in which an aggregate of volatiles of a platinum group metal volatilized from the wall present in the vapor phase space is mixed with the molten glass as a foreign substance during the treatment of the molten glass,

And an aggregate treatment step of dissolving at least a part of the agglomerates mixed in the molten glass in the molten glass in the molten glass treatment step,

Wherein the concentration of the platinum group metal dissolved in the molten glass at the start of the flocculation treatment process is set to 0.05 to 20 ppm.

(Twentieth Embodiment)

A dissolving step of dissolving a glass raw material to produce a molten glass,

Wherein a vapor phase space surrounded by the surface and the wall of the molten glass is formed by the introduction of the molten glass and at least a part of the wall contacting the vapor phase is formed of a material containing a platinum group metal, A molten glass treatment step in which an aggregate of volatiles of a platinum group metal volatilized from the wall existing in the vapor phase space is mixed with the molten glass during the treatment of the molten glass,

And an aggregate treatment step of dissolving at least a part of the agglomerates mixed in the molten glass in the molten glass treatment step in the molten glass,

In the aggregate treatment step, the number of defects of the aggregate contained in the glass substrate to be newly manufactured is set to an allowable level, and the number of defects of the aggregate detected on the glass substrate produced by using the glass treatment apparatus Wherein the saturation solubility of the aggregated platinum group metal is adjusted by adjusting the temperature of the glass.

Here, in the flocculation treatment step, the temperature of the molten glass is preferably adjusted to be in the range of 1660 to 1750 DEG C in order to adjust saturation solubility of the flocculated product.

(Twenty-first Embodiment)

A dissolving step of dissolving a glass raw material to produce a molten glass,

Wherein a vapor phase space surrounded by the surface and the wall of the molten glass is formed by the introduction of the molten glass and at least a part of the wall contacting the vapor phase is formed of a material containing a platinum group metal, A molten glass treatment step in which an aggregate of volatiles of a platinum group metal volatilized from the wall existing in the vapor phase space is mixed with the molten glass during the treatment of the molten glass,

And an aggregate treatment step of dissolving at least a part of the agglomerates mixed in the molten glass in the molten glass treatment step in the molten glass,

[Fe ^{3 +} ] / ([Fe ^{2 +} ] + [Fe ^{3 +} ]) of the glass substrate is adjusted in the range of 0.2 to 0.5 in the aggregate treatment step so that the number of defects of the aggregate contained in the glass substrate is at an allowable level To adjust the saturation solubility of the platinum group metal in the molten glass.

Here, the [Fe ^{3 +} ] / ([Fe ^{2 +} ] + [Fe ^{3 +} ]) may be adjusted by adjusting at least one of the content of tin oxide contained in the glass substrate and the content of the oxide contained in the glass raw material Is preferably adjusted.

According to another aspect of the present invention, there is provided a glass substrate laminate comprising a plurality of glass substrates laminated. At this time, the following twenty-second embodiment is included.

(Twenty-second Mode)

Wherein the total volume of the glass substrates in the glass substrate laminate is 0.1 m 3 or more and the ratio of the number of the aggregates having a maximum length of 50 m or less among all the aggregates of the platinum group metal contained in the glass substrate is 70% Glass substrate laminate.

According to another aspect of the present invention, there is provided a glass substrate comprising the following 23rd mode.

(23rd form)

Wherein the ratio of the number of agglomerates having a maximum length of 50 탆 or less among the agglomerates of the platinum group metal contained in the glass substrate is 70% or more.

Still another aspect of the present invention is a glass substrate manufacturing apparatus. The glass substrate manufacturing apparatus includes the following modes.

(Twenty-fourth Aspect)

In the glass substrate manufacturing apparatus,

A melting apparatus for melting glass raw materials to produce molten glass,

And a space in which a vapor phase space surrounded by the surface and the wall of the molten glass is formed by the introduction of the molten glass, wherein at least a part of the wall is made of a material containing a platinum group metal, A glass processing device in which an aggregate of volatiles of a platinum group metal volatilized from the wall existing in the vapor phase space is mixed into the molten glass as a foreign substance when the molten glass is processed,

And processing means for reducing the size of the agglomerates mixed in the molten glass so that the ratio of the number of agglomerates having a maximum length of 50 μm or less among the agglomerates incorporated into the molten glass in the molten glass processing step is 70% or more.

Another aspect of the present invention is a glass substrate manufacturing apparatus. The glass substrate manufacturing apparatus includes the following modes.

(Twenty-fifth Aspect)

In the glass substrate manufacturing apparatus,

A melting apparatus for melting glass raw materials to produce molten glass,

And a space in which a vapor phase space surrounded by the surface and the wall of the molten glass is formed by the introduction of the molten glass, wherein at least a part of the wall is made of a material containing a platinum group metal, And a glass processing apparatus in which an aggregate of volatile substances of the platinum group metal volatilized from the wall existing in the vapor phase space is mixed into the molten glass as a foreign substance when the molten glass is processed,

And means for adjusting the solubility of the aggregate in the molten glass so that the size of the aggregate mixed into the molten glass becomes smaller.

(26th form)

The method for manufacturing a glass substrate according to any one of the first to fifteenth aspects, the glass substrate laminate according to the twenty-second aspect, the glass substrate according to the twenty-third aspect, and the glass substrate producing apparatus according to the twenty- Type glass substrate is a glass substrate having a strain point of 650 DEG C or more.

The method for manufacturing a glass substrate according to any one of the first to fifteenth aspects, the glass substrate laminate according to the twenty-second aspect, the glass substrate according to the twenty-third aspect, and the glass substrate producing apparatus according to the twenty- Is used as a glass substrate for a liquid crystal display, a glass substrate for an organic EL (Electro-Luminescence) display, or a glass substrate for a display using an LTPS (Low Temperature Poly-silicon) thin film semiconductor.

According to the glass substrate manufacturing method, the glass substrate, the glass substrate laminate and the glass substrate manufacturing apparatus described above, even if foreign substances (agglomerates) of the platinum group metal are mixed into the glass substrate, the glass substrate is hardly deformed, It is possible to make it difficult to form the concave / As a result, the yield during the production of the glass substrate is improved.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a flowchart showing a process of a method of manufacturing a glass substrate according to an embodiment.
2 is a schematic diagram showing a configuration of a glass substrate manufacturing apparatus according to the embodiment.
3 is an external view mainly showing a purifying pipe according to the embodiment.
4 is a cross-sectional view showing the inside of the purifying tube according to the embodiment and an example of the temperature profile of the purifying tube.
5 is a graph showing the relationship between the maximum temperature of the molten glass and the ratio of the foreign material.

The method of manufacturing a glass substrate of the present embodiment is a method of manufacturing a glass substrate having a space in which a surface of a molten glass and a vapor space enclosed by a wall are formed by the introduction of molten glass and at least a part of the wall is composed of a glass A glass processing apparatus comprising a processing apparatus, for example, a liquid phase made of molten glass, a vapor phase space formed from the liquid surface and the wall of the molten glass, and at least a part of a wall surrounding the vapor phase is made of a material containing a platinum group metal The molten glass is treated (molten glass processing step). During the processing of the molten glass, aggregates of volatiles of the platinum group metal which are present in the vapor phase space and volatilized from the wall are mixed into the molten glass as foreign matter. A process of reducing the size of the agglomerates mixed in the molten glass is performed so that the ratio of the number of agglomerates having a maximum length of 50 탆 or less among the agglomerates incorporated into the molten glass is 70% or more (agglomerate processing step). Alternatively, the solubility of the foreign matter (agglomerate) in the molten glass is adjusted so that the size of the agglomerates mixed into the molten glass becomes small. For example, the amount of heat given to a foreign substance (agglomerate) is controlled so that the amount of heat given to the foreign substance (agglomerate) is equal to or more than a minimum amount of heat that can reduce the size of the foreign substance (agglomerate) fair).

By reducing the size of the foreign substance (agglomerate) of the platinum group metal incorporated into the glass substrate in this way, it is difficult for the glass substrate to be deformed, making it difficult to form the irregularities on the main surface of the glass substrate. This improves the conventional problems and improves the production yield of the glass substrate.

In the following description, an example of controlling the conditions for adjusting the solubility so that the solubility of the aggregate in the molten glass is at least the minimum solubility that allows the aggregate to dissolve in the molten glass to reduce the size thereof, And the amount of heat applied to the agglomerates is controlled so as to be equal to or more than the minimum heat amount capable of reducing the size of the agglomerates incorporated into the molten glass.

(Manufacturing Method of Glass Substrate and Glass Substrate Manufacturing Apparatus)

Fig. 1 is a flow chart showing an example of a process of a manufacturing method of a glass substrate according to the present embodiment. As shown in Fig. 1, a method of manufacturing a glass substrate mainly includes a melting step S1, a clarifying step S2, a stirring step S3, a molding step S4, a slow cooling step S5, and a cutting step S6.

2 is a schematic diagram showing 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 vessel 40, a clarifying tube 41, a stirring device 100, a molding device 42, and transfer tubes 43a, 43b and 43c. The transfer pipe (43a) connects the melting tank (40) and the cleaning pipe (41). The transfer pipe 43b connects the purifying pipe 41 and the agitation device 100. The transfer pipe 43c connects the agitation apparatus 100 and the molding apparatus 42.

In the melting step S1, molten glass is produced by melting the glass raw material. The molten glass is stored in the melting tank 40 and heated to have a desired temperature. The molten glass contains a refining agent. From the viewpoint of environmental load reduction, 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 the composition and the like. Thus, in the melting tank 40, for example, a molten glass G having a high temperature of 1500 to 1620 占 폚 is obtained. Further, in the melting tank 40, the molten glass G between the electrodes may be heated by conduction of electric current between at least one pair of electrodes, and the flame by the burner is additionally provided in addition to the conduction heating, good.

The fining step S2 is performed inside the transfer pipe 43a and the cleaning pipe 41 through which the molten glass flows. Initially, the temperature of the molten glass is raised. The refining agent causes a reduction reaction by raising the temperature to release oxygen. The bubbles contained in the molten glass absorb the released oxygen and expand, and the molten glass floats on the surface in contact with the vapor phase, and is poured and disappears. That is, the defoaming process S2A is performed. Further, the temperature of the molten glass is raised from the middle of the defoaming process S2A or after the defoaming process S2A, and the flocculating process S2B for reducing the size of the aggregate of the platinum group metal incorporated in the defoaming process is performed . Thereafter, the temperature of the molten glass is lowered. As a result, the reduced refining agent causes an oxidation reaction to absorb gas components such as oxygen remaining in the molten glass. That is, the absorption processing step S2C is performed.

Concretely, the molten glass G obtained in the melting tank 40 flows from the melting tank 40 through the transfer pipe 43a and into the cleaning pipe 41. The purifying pipe 41 has a space in which a vapor space surrounded by the surface and the wall of the molten glass G is formed by the introduction of the molten glass G and at least a part of the wall is made of a material containing a platinum group metal. For example, at least a part of the liquid phase through which the molten glass flows, the vapor phase space formed from the liquid surface and the wall of the molten glass, and at least a part of the wall surrounding the vapor phase space is made of a material containing a platinum group metal. The transfer pipes 43a, 43b and 43c are pipes made of a platinum group metal. The platinum group metal means an alloy of a metal composed of a single platinum group element and a metal composed of a platinum group element. 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 suitably used. Platinum group metals have a high melting point and are excellent in corrosion resistance to molten glass. A heating means is provided in the purifying tube 41 in the same manner as the melting vessel 40. Also, at least the transfer pipe 43a is provided with a heating means.

In the refining step S2, the depletion treatment step of degassing by elevating the temperature of the molten glass G and the amount of heat imparted to foreign substances (agglomerates) of the platinum group metal incorporated into the molten glass are adjusted to separate or dissolve foreign substances (agglomerates) An aggregate treatment step of reducing the size of foreign substances (agglomerates) of the platinum group metal, and an absorption treatment step in which the molten glass is absorbed by the molten glass by lowering the temperature of the molten glass. In order to separate or dissolve foreign matters (agglomerates) mixed in the molten glass in the agglomerate treatment step to reduce the size of foreign substances (agglomerates) of platinum group metals, the amount of heat given to the foreign matter (agglomerates) Calories) or more. In this case, the amount of heat given to the foreign matter (agglomerate) in the molten glass is controlled so that the amount of heat given to the foreign matter (agglomerate) is equal to or more than the minimum amount of heat. The minimum amount of heat can be inspected in advance by experiment or the like. In the case where the minimum amount of heat is controlled to the temperature of the molten glass G, for example, the temperature of the molten glass G in the purifying pipe 41 is controlled within the range of 1580 캜 to 1730 캜, preferably in the range of 1670 캜 to 1730 캜 .

In the firing step S2, it is preferable that the temperature of the molten glass G flowing inside the transfer pipe 43a is gradually raised without lowering the temperature, from the viewpoint of sufficiently purifying the molten glass G. After the melting step S1, the molten glass G is preferably heated at a rate of 3 DEG C / min or more to 1630 DEG C or higher.

The maximum temperature of the molten glass G flowing through the transfer pipe 43a is preferably 1620 to 1690 캜 and preferably 1640 to 1670 캜. It is preferable that the temperature of the molten glass G at the inlet of the purifying tube which is the area where the transfer pipe 43a and the purifying pipe 41 are connected is 1610 캜 to 1680 캜 and 1630 캜 to 1660 캜. It is preferable that the temperature of the molten glass G at the outlet of the purifying tube which is the area connecting the purifying pipe 41 and the transfer pipe 43b is 1530 캜 to 1600 캜 and 1540 캜 to 1580 캜.

The refined molten glass G in the purifying pipe 41 flows from the purifying pipe 41 to the stirring device 100 through the transfer pipe 43b. The molten glass G is cooled when it passes through the transfer pipe 43b.

In the stirring step S3, the refined molten glass is stirred to homogenize the components of the molten glass. As a result, the unevenness of the composition of the molten glass, which is a cause of spalling of the glass substrate, is reduced. The homogenized molten glass is sent to the molding step S4.

Specifically, in the stirring apparatus 100, the molten glass G is agitated at a temperature lower than the temperature of the molten glass G passing through the purifying pipe 41. For example, in the stirring apparatus 100, the temperature of the molten glass G is 1250 캜 to 1450 캜. For example, in the stirring apparatus 100, the viscosity of the molten glass G is 500 poise to 1,300 poise. The molten glass G is stirred and homogenized in the stirring apparatus 100.

The molten glass G homogenized in the stirring apparatus 100 is introduced into the molding apparatus 42 from the stirring apparatus 100 through the transfer pipe 43c. The molten glass G is cooled so as to have a viscosity suitable for molding the molten glass G when it passes through the transfer pipe 43c. For example, the molten glass G is cooled to 1100 to 1300 占 폚.

The stirring step S3 of the present embodiment is performed after the fining step S2, but the stirring step S3 may be performed before the fining step 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 purifying pipe 41. [

In the molding step S4, the sheet glass is continuously formed from the molten glass by the overflow down-draw method or the float method.

Specifically, the molten glass G introduced into the molding apparatus 42 is supplied to a molded body 52 provided inside a molding furnace (not shown). On the upper surface of the molded body 52, a groove is formed along the longitudinal direction of the molded body 52. The molten glass G is supplied to the upper surface grooves of the molded body 52. The molten glass G overflowing from the groove flows downward along a pair of side surfaces of the molded body 52. The pair of molten glass G having the side surface of the molded body 52 lowered merges 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 molding step S4 has a desired thickness and is gradually cooled so as to prevent deformation and warping.

In the cutting step S6, the sheet glass that has been slowly cooled in the gradual cooling step S5 is cut to a predetermined length, and a glass sheet is obtained. The glass sheet is further cut to a predetermined size to obtain a glass substrate.

(Glass substrate laminate and glass substrate)

This embodiment provides a glass substrate laminate formed by laminating a plurality of glass substrates and a glass substrate.

The total volume of the glass substrate laminate of the present embodiment is 0.1 m 3 or more and the ratio of the number of aggregates having a maximum length of 50 탆 or less among aggregate platinum group metals contained in the glass substrate laminate is 70% . Such a glass substrate laminate can hardly cause deformation on the glass substrate as described later, making it difficult to form irregularities on the main surface of the glass substrate. Therefore, each of the glass substrates of the laminate is suitable for a glass substrate for a display, and is particularly effective for a glass substrate for a display panel which requires high precision in screen display.

The glass substrate of the present embodiment is characterized in that the ratio of the number of aggregates having a maximum length of 50 m or less among the aggregates of the platinum group metal contained in the glass substrate is 70% or more. With the glass substrate having such a constitution, deformation of the glass substrate is less likely to occur as described later, and it is possible to make the unevenness of the main surface of the glass substrate harder to be formed.

It is more preferable that the glass substrate laminate and the glass substrate have a ratio of the number of aggregates having a maximum length of 50 탆 or less among the contained platinum group metal aggregates of 90% or more. It is more preferable that the glass substrate laminate and the glass substrate have a ratio of the number of aggregates having a maximum length of 30 m or less among the aggregates of the platinum group metal contained therein to 90% or more.

As the glass used for the glass substrate, glass having a strain point of 600 캜 or higher is suitable for a glass substrate production method described later. More preferably, the strain point is 650 ° C or higher, more preferably 690 ° C or higher, and particularly preferably 730 ° C or higher.

(Application example of glass substrate)

The glass substrate produced by the glass substrate manufacturing method of the present embodiment is particularly suitable as a glass substrate for a display such as a liquid crystal display, a plasma display, an organic EL display or the like and a cover glass for protecting a display. A display using a glass substrate for a display includes an organic EL display, a liquid crystal display, and a curved display in which a display surface is curved, in addition to a flat panel display having a flat display surface. The glass substrate is a glass substrate for a high-precision display, for example, a glass substrate for a liquid crystal display, a glass substrate for an organic EL (Electro-Luminescence) display, a low temperature polysilicon (LTPS) thin film semiconductor, or an IGZO (Indium, Gallium, Zinc, Oxide) or the like is preferably used as a glass substrate for display using an oxide semiconductor.

As the glass substrate for display, an alkali-free glass or an alkali-small-content glass is used. The glass substrate for display has high viscosity at high temperature. For example, the temperature of the molten glass having a viscosity of 10 ^{2 5} poise is 1500 ° C or higher. Further, the alkali-free glass is a glass having a composition substantially not containing an alkali metal oxide (R ₂ O). The phrase "substantially free of alkali metal oxide" means that the alkali metal oxide is not added as a glass raw material except for impurities incorporated from raw materials and the like. For example, the content of alkali metal oxide is 0.1 mass% .

(Glass composition)

In the melting tank 40, the glass raw material is dissolved by a heating means (not shown), and a molten glass G is produced. The glass raw material is prepared so as to substantially obtain a glass having a desired composition. The alkali-free glass is suitable as a glass substrate for a display of an example of the glass composition, such as a glass substrate for a flat panel display (FPD) is, SiO ₂ 50 mass% to 70 mass%, Al ₂ O ₃ 0% by mass to 25% by weight, B ₂ O ₃ 0 mass% to 15 mass% of MgO, 0 mass% to 10 mass% of MgO, 0 mass% to 20 mass% of CaO, 0 mass% to 20 mass% of SrO, and 0 mass% to 10 mass% of BaO. Further, instead of 0% by mass to 10% by mass of BaO, 0% by mass to 20% by mass of BaO may be used. Here, the total content of MgO, CaO, SrO, and BaO is 5% by mass to 30% by mass.

As the glass substrate for display, an alkali-containing glass containing a slight amount of an alkali metal oxide may be used. The alkali-small-content glass contains R ' ₂ O in an amount of 0.1 mass% to 0.5 mass%, preferably 0.2 mass% to 0.5 mass% of R' ₂ O as a component. Here, R 'is at least one kind selected from Li, Na and K, and R' ₂ O is the sum of the contents 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, the glass substrate of the present embodiment contains an alkali-free glass, and a glass having an alkali metal oxide (R ' ₂ O) content of 0 to 0.5% by mass is appropriately used.

In addition to the above components, the glass produced by this embodiment may contain SnO ₂ (Preferably 0.01% by mass to 0.5% by mass) and 0% by mass to 0.2% by mass (preferably 0.01% by mass to 0.08% by mass) of Fe ₂ O ₃ . Further, it is preferable that the glass produced by the present invention does not substantially contain As ₂ O ₃ , Sb ₂ O ₃ and PbO in consideration of environmental load. For reducing the environmental load, tin oxide (SnO ₂ ) is preferably used as a fining agent.

In the present embodiment, the melting glass treatment step is referred to as a fining step and the molten glass treatment device is used as a cleaning device including the cleaning tube 41. However, the apparatus for performing the molten glass treatment step is not limited to the melting pot 40 and the molding apparatus 42 and is a device for performing a predetermined treatment on the molten glass. The glass processing apparatus may be, for example, a stirring apparatus or a transfer tube for transferring the molten glass in addition to the refining apparatus. Therefore, the treatment of the molten glass includes, besides the treatment for purifying the molten glass, a treatment for homogenizing the molten glass, a treatment for transporting the molten glass, and the like. Also, the aggregate treatment step S2B has been described by way of example in the cleaning step S2, but may be carried out, for example, in a stirring step S3 and a step of conveying the molten glass G by a transfer pipe. Also, even when the aggregate treatment step S2B is performed in the firing step S2, the aggregate treatment step S2B need not be performed before the absorption treatment step S2C as described above, but may be performed after the absorption treatment step S2C.

(Composition of the ceremony hall)

Next, the configuration of the cleaning tube 41 of the cleaning apparatus in this embodiment will be described in detail. The refining apparatus further includes a refractory brick and a refractory protective layer (not shown) surrounding the outer periphery of the vent pipe 41a, the heating electrode 41b and the purifying pipe 41 in addition to the purifying pipe 41. [ Fig. 3 is an external view showing mainly the cleaning tube 41. Fig. 4 is a cross-sectional view showing the inside of the purifying pipe 41 and an example of the temperature profile of the purifying pipe.

The purifying pipe 41 is provided with a vent pipe 41a and a pair of heating electrodes 41b. The purifying pipe (41) has a space in which a vapor space (41c) surrounded by the surface of the molten glass (G) and the wall is formed by introduction of the molten glass (G). For example, the cleaning tube 41 has therein a liquid phase in which the molten glass G flows, and a vapor phase space formed from the liquid surface and the wall of the molten glass G. The vapor space 41c is formed along the flow direction of the molten glass G. At least a part of the wall surrounding the vapor space 41c is made of a material containing a platinum group metal. In the present embodiment, the entire wall surrounding the vapor space 41c is made of a material containing a platinum group metal.

The vent pipe 41a is located in the middle of the direction in which the molten glass G flows and is provided in a wall in contact with the vapor space 41c to communicate the atmosphere outside the vapor pipe 41c with the outside of the cleaning pipe 41. [ Like the purifying pipe 41, the vent pipe 41a is preferably formed of a platinum group metal. Since the temperature of the vent pipe 41a is easily lowered by the heat radiation function of the vent pipe 41a, a heating mechanism for heating the vent pipe 41a may be provided.

The pair of heating electrodes 41b are flange-shaped electrode plates provided at both ends of the cleaning pipe 41a. The heating electrode 41b flows a current supplied from a power source (not shown) to the cleaning tube 41, and the cleaning tube 41 is energized and heated by this current. In the case of using tin oxide as the fining agent, for example, the wall of the cleaning tube 41 is heated so that the maximum temperature is 1670 캜 to 1750 캜, more preferably 1690 캜 to 1750 캜. The difference between the maximum temperature and the minimum temperature of the wall of the purifying pipe 41 is 5 DEG C or more, and the vapor 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. The molten glass G is preferably heated to a temperature at which foreign substances (agglomerates) of the platinum group metal are divided or dissolved, for example, 1670 DEG C or more, and more preferably 1680 DEG C or more. More specifically, it is preferable to be heated to 1670 캜 to 1730 캜, and more preferably to 1680 캜 to 1700 캜. If the maximum temperature of the molten glass G exceeds 1730 DEG C, the tube made of the platinum group metal constituting the cleaning tube 41a is likely to be damaged by the spallation. Further, the maximum temperature of the molten glass G can be calculated from the measured value of a thermocouple (not shown) installed in the cleaning tube 41.

The temperature of the molten glass G flowing in the inside of the purifying pipe 41 can be controlled by controlling the current flowing through the purifying pipe 41.

A pair of the heating electrodes 41b are provided in the cleaning tube 41, but the number of the heating electrodes 41b is not particularly limited. By controlling the amount of electric current of the heating electrode 41b, the temperature of the wall in contact with the vapor space 41c of the cleaning tube 41 is controlled in the range of, for example, 1500 to 1750 占 폚.

In the inside of the purifying pipe 41, bubbles containing CO ₂ or SO ₂ contained in the molten glass G are removed by a redox reaction of a fining agent contained in the molten glass G, for example, tin oxide. Specifically, at first, the temperature of the molten glass G is raised and the refining agent is reduced, thereby generating bubbles of oxygen in the molten glass G. Bubbles containing gas components such as CO ₂ , N ₂ and SO ₂ contained in the molten glass G are combined with the oxygen bubbles generated by the reduction reaction of the fining agent. The bubbles incorporated with the oxygen bubbles float on the surface of the molten glass G in contact with the vapor phase space to release the bubbles, that is, puff and disappear (defoaming treatment). The temperature of the molten glass G in this degassing treatment is 1610 캜 to 1730 캜, preferably 1640 캜 to 1710 캜. When the temperature is within the above range, the platinum group metal is vigorously volatilized from the wall of the cleaning tube 41. Since oxygen is released into the vapor phase space by defoaming, the oxygen concentration becomes high at the portion of the vapor phase space where the defoaming treatment is performed, and as a result, the volatilization of the platinum group metal is further enhanced. Along with this, since the concentration of the volatile matter of the platinum group metal contained in the vapor phase space becomes high, the volatilization of the platinum group metal contained in the vapor phase space tends to occur. Particularly, the volatiles of the platinum group metal at the position where the wall is partially cooled, for example, in the vicinity of the inlet of the purifying pipe 41, tend to agglomerate. Therefore, a part of the aggregate of the platinum group metal adhered to the wall of the cleaning tube 41 is dropped off, and is liable to be mixed into the molten glass G as foreign matter. For example, after the molten glass is introduced into the cleaning tube 41, the molten glass G is agglomerated and agglomerates of volatiles of the platinum group metal contained in the gaseous phase in the region where the temperature of the molten glass G is in the range of 1580 캜 to 1660 캜 Is likely to be incorporated.

Thus, an agglomerate treatment step for reducing the size of foreign substances (agglomerates) of the platinum group metal incorporated in the molten glass G is performed from the middle of the degassing treatment or after the completion of the degassing treatment.

The temperature of the molten glass G containing the foreign substance (agglomerate) of the platinum group metal is set so that 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 It is preferable to raise the temperature of the molten glass G so as to be higher than the temperature.

Further, in the case where the aggregate treatment step is performed from the middle of the defoaming treatment step, the defoaming treatment step and the aggregate treatment step are performed at the same time. In the case where the aggregate treatment step is performed from the middle of the defoaming treatment step, the defoaming treatment step and the aggregate treatment step may be performed at the same time. When the aggregate treatment step is performed from the middle of the defoaming treatment step, the molten glass reaches the maximum temperature in the aggregate treatment step. That is, the defoaming treatment step (molten glass treatment step) may include an aggregate treatment step.

Specifically, the temperature of the molten glass G is set to 1670 占 폚 or higher to control the amount of foreign substances (agglomerates) of the platinum group metal by dividing the molten glass G by controlling the amount of heat applied to foreign substances (agglomerates) of the platinum group metal incorporated into the molten glass, It is preferable to dissolve it. At this time, by performing the aggregate treatment process so that the ratio of the number of foreign substances having a maximum length of 50 mu m or less among the foreign substances (aggregates) of the platinum group metal incorporated into the molten glass G is 70% or more, And it is also possible to reduce the formation of irregularities on the main surface of the glass substrate. In order to obtain a foreign substance of such a size, it is preferable that the temperature of the molten glass G is maintained at 1670 占 폚 or more for 10 minutes or more, preferably 30 minutes or more. That is, the aggregate abatement treatment for reducing the size of the foreign substance (agglomerate) of the platinum group metal can reduce the size of the foreign substance (agglomerate) of the platinum group metal by maintaining the agglomerate abatement treatment at a temperature of 1670 캜 or higher for 10 minutes or longer.

In the present embodiment, the degree of solubility of the platinum group metal (coagulated material) mixed in the molten glass into the molten glass is controlled so that the molten glass is treated with a foreign substance (aggregate) of the platinum group metal in the molten glass It is also preferable to control the solubility so as to be higher than the solubility in the region to be incorporated. When the solubility of the foreign substance (agglomerate) in the molten glass G is increased, the temperature of the molten glass G is raised to increase the solubility of the agglomerate in the molten glass, or to raise the temperature of the molten glass G and / The amount of foreign matter (agglomerates) dissolved in the molten glass G can be increased.

In addition, the foreign substance (agglomerate) of the platinum group metal is linear and long in one direction. Therefore, the maximum length of the aggregate (foreign matter) of the platinum group metal refers to the length of the long side of the circumscribed rectangle circumscribing the foreign substance image when the foreign substance (aggregate) of the platinum group metal is photographed.

Before the flocculation treatment process, the proportion of foreign substances (aggregates) of the platinum group metal having a maximum length of 100 탆 or more exceeds 80%. In the present embodiment, the foreign substance (agglomerate) of the platinum group metal before the agglomerate treatment step refers to a foreign substance of the platinum group metal having an aspect ratio of more than 100 that is the ratio to the minimum length of the maximum length. For example, the maximum length of the foreign substance (agglomerate) of the platinum group metal is 50 탆 to 300 탆, and the minimum length is 0.5 탆 to 2 탆.

Thereafter, the temperature of the molten glass G is lowered to oxidize the reduced refining agent. Thereby, the oxygen of the bubbles remaining in the molten glass G is absorbed into the molten glass G (absorption process). In this way, the remaining bubbles become smaller and disappear. Thus, the bubbles contained in the molten glass G are removed by the redox reaction of the cleaning agent. Further, in the absorption treatment step S2C, the temperature of the molten glass G and the temperature of the wall of the cleaning tube 41 are lowered to 1580 DEG C or lower, and the oxygen concentration contained in the vapor space is lowered compared with the defoaming step S2A , The volatilization and agglomeration of the platinum group metal becomes difficult to be performed. As a result, in the absorption treatment step S2C, the possibility that a new platinum group metal aggregate becomes a foreign matter and is incorporated into the molten glass G is much lower than in the defoaming treatment step S2A.

Although not shown, a refractory protective layer is formed on the outer wall surface of the cleaning tube 41. A refractory brick is further provided on the outside of the refractory protective layer. The refractory bricks are mounted on a base (not shown). The amount of heat released from the purifying pipe 41 by the refractory protection layer and / or the refractory brick can be adjusted so that the temperature of the wall contacting the vapor space 41c of the purifying pipe 41 and / The temperature of the molten glass may be controlled.

4 shows an example of the temperature profile of the cleaning pipe 41 (the temperature profile in the X direction of the wall in contact with the vapor space 41c of the cleaning pipe 41) in accordance with the position of the cleaning pipe 41 in the X direction have. In the temperature profile, the temperature is the maximum temperature T _max between the end portion 41d (inlet) of the purifying pipe 41 on the side where the molten glass G flows and the vent pipe 41a. A temperature gradient is formed in which the temperature decreases from the position P of the maximum temperature T _max toward the end portion 41d of the cleaning tube 41. [ Similarly, a temperature gradient is formed such that the temperature decreases toward the position in the X direction of the vent pipe 41a from the position P of the maximum temperature T _max . The temperature gradient region is also formed between the position of the vent pipe 41a in the X direction and the end portion 41e (outlet) of the purifying pipe 41 on the side from which the molten glass G flows out . In such a temperature gradient range, the temperature difference between the maximum temperature and the minimum temperature in the temperature gradient range is more than 0 deg. C and not more than 150 deg. C, more preferably more than 0 deg. C and not more than 100 deg. have. As shown in Fig. 4, the defoaming process is started in the first half of the succeeding temperature rise period until the temperature of the wall reaches the maximum temperature T _max , and continues to at least the maximum temperature T _max . In addition, the agglomeration process is disclosed in the latter part of the temperature raising section including a maximum temperature T _max, continue at least until the maximum temperature T _max. The flocculation treatment process is started, for example, at a temperature of the molten glass G of 1670 DEG C or higher. Either the end of the defoaming treatment step or the end of the flocculating agent treatment step may be prioritized. However, from the viewpoint of the foreign matter of all the platinum group metals incorporated in the molten glass to be subjected to the flocculation treatment step, Is preferably at the same time as or after the end of the defoaming treatment step.

As described above, in this embodiment, the bubbles in the molten glass G are defoamed, but at this time, the aggregates of the volatiles of the platinum group metal volatilized from the walls are mixed into the molten glass G as foreign matter. The size of the agglomerates incorporated in the molten glass G is reduced so that the ratio of the number of foreign substances (agglomerates) having a maximum length of 50 μm or less among the foreign substances (agglomerates) mixed in the molten glass G is 70% or more. Alternatively, the amount of heat applied to the foreign substance of the platinum group metal is controlled so as to reduce the size of the impurity of the platinum group metal incorporated therein. Thus, even if a foreign substance of a platinum group metal is mixed into the glass substrate, deformation of the glass substrate is less likely to occur, making it difficult to make irregularities on the main surface of the glass substrate.

The difference in temperature between the maximum temperature and the minimum temperature of the wall in contact with the vapor phase space in the above-described cleaning tube 41 is 5 占 폚 or more, and even if the vapor phase space contains oxygen, that is, The size of the foreign substance of the platinum group metal contained in the molten glass can be reduced or the ratio of the number of foreign substances of the platinum group metal having the maximum length of 50 m or less can be 70% or more. Therefore, even if a foreign substance of a platinum group metal is mixed into the glass substrate, the glass substrate is less likely to be deformed, and it is possible to make it difficult to form irregularities on the main surface of the glass substrate.

When the aggregate treatment process is performed, 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 (agglomerate) of the platinum group metal is incorporated into the molten glass G in the molten glass treatment step It is preferable to raise the temperature to a high temperature. As a result, it is possible to separate or dissolve the foreign substance (agglomerate) of the platinum group metal by heat, and to surely reduce the size of the foreign substance (agglomerate) of the platinum group metal.

The glass processing apparatus is a purifying apparatus having a purifying pipe 41. The vaporizing space in the purifying pipe 41 is formed along the flow direction of the molten glass and the condensing process is performed in the purifying pipe 41 desirable. Since the temperature of the molten glass G in the cleaning tube 41 reaches the maximum temperature up to the molding step, it is possible to easily separate or dissolve the foreign substance (agglomerate) of the platinum group metal by heat.

In the glass treatment step of the present embodiment, the fining treatment for reducing the number of bubbles in the molten glass G is carried out by using the tin oxide contained in the molten glass G. In the wall contacting the vapor phase space in the glass processing apparatus, A temperature distribution is formed along the flow direction, and an oxygen concentration distribution is formed in the vapor phase space along the flow direction of the molten glass G. In such an apparatus, since there is an oxygen concentration distribution that affects the volatilization of the platinum group metal, aggregates of volatiles of the platinum group metal are likely to be formed, and the aggregates are liable to be incorporated into the molten glass as foreign matter. Even in such a case, since it is easy to reduce the size of the foreign substance (agglomerate) of the platinum group metal, the glass substrate is hardly deformed, and it is possible to make it difficult to make irregularities on the main surface of the glass substrate.

The agglomerate treatment step is preferably carried out in a glass treatment apparatus so as to include molten glass flowing in the molten glass flowing in the glass treatment apparatus at a position in the flow direction corresponding to the region where the oxygen concentration is highest in the vapor phase space . In the temperature profile shown in Fig. 4, defoaming treatment of the molten glass G at the maximum temperature T _max is performed most actively. Owing to the oxygen released from the bubbles, the oxygen concentration becomes the highest in the region in the vapor phase space near the maximum temperature T _max . For example, the agglomerate treatment process is performed on the molten glass passing through the position in the flow direction corresponding to the region in the vapor phase space where the oxygen concentration becomes the highest. As a result, the platinum group metal is volatilized actively due to the maximum oxygen concentration of the platinum group metal, and as a result, aggregates of the platinum group metal are liable to be generated. As a result, even if the platinum group metal aggregate is mixed into the molten glass as a foreign substance, .

The oxygen concentration in the vapor phase space of the purifying pipe 41 is set to more than 0% and not more than 1.0% and the difference between the maximum wall temperature and the minimum temperature of the purifying pipe 41 is set to 5 ° C or more and 100 ° C or less . Thereby, the volatilization of the platinum group metal can be suppressed and foreign substances of the platinum group metal incorporated into the molten glass G can be suppressed. However, even in this case, the foreign substance of the platinum group metal can not be completely zero. Thus, by reducing the size of the foreign substance of the platinum group metal, the glass substrate is hardly deformed, and the effect of the present embodiment, which makes it difficult to make irregularities on the main surface of the glass substrate, becomes even more remarkable. Further, since the volatilization of the platinum group metal can be suppressed, the lifetime of the apparatus composed of the platinum group metal such as the cleaning tube 41 can be improved.

The temperature of the molten glass G is controlled to be in the range of 1580 ° C to 1660 ° C in at least part of the molten glass treatment step so that the temperature of the molten glass G in the agglomerate treatment step is controlled to be 1670 ° C to 1730 ° C The defoaming treatment can be reliably performed and the size of the foreign substance (agglomerate) of the platinum group metal can be reliably reduced. That is, it is possible to reduce both the number of bubbles contained in the glass substrate and the reduction of the foreign substance of the platinum group metal having a maximum length of 50 mu m or more. In addition, when the oxygen concentration in the vapor-phase space of the cleaning tube 41 has a distribution depending on the place, foreign substances (agglomerates) of the platinum group metal are easily mixed into the molten glass G in the region where the oxygen concentration is higher than the predetermined value, It is preferable to adjust the temperature of the molten glass G to a temperature at which the size of foreign substances (agglomerates) of the platinum group metal can be reduced, for example, a temperature of 1680 캜 or more, even if foreign substances (agglomerates) More preferably, it is preferable to control the temperature of the molten glass so as to form the temperature distribution of the molten glass along the oxygen concentration distribution in the vapor phase space.

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

(Conditions for adjusting the solubility of the agglomerates)

As conditions for adjusting the solubility of the agglomerates, for example,

(a) the concentration of the platinum group metal dissolved in the molten glass,

(b) the temperature or temperature distribution of the molten glass (the amount of heat given to the aggregate)

(c) the pressure of the meteorological space,

(d) oxygen activity of the molten glass.

(a) the concentration of the platinum group metal dissolved in the molten glass

The lower the concentration of the platinum group metal dissolved in the molten glass at the start of the coagulation treatment process, the higher the solubility in which the platinum group metal in the molten glass dissolves in the platinum treatment process. The concentration of the platinum group metal in the molten glass can be determined by, for example, sampling the molten glass in the purifying pipe, cooling it, pulverizing it, and measuring using ICP quantitative analysis.

If the concentration of the platinum group metal is excessively low, the solubility of the aggregate of the platinum group metal increases, while the platinum group metal is eluted from the wall of the cleaning tube in contact with the molten glass to cause the melting of the cleaning tube.

From the viewpoint of suppressing the occurrence of such disadvantages, the concentration of the platinum group metal is adjusted.

The platinum group metal dissolved in the molten glass at the start of the flocculation treatment process in the cleaning pipe 41 is a platinum group metal which is eluted from the wall surface in contact with the molten glass such as the cleaning pipe 41 or the transfer pipe 43a It mainly comes from. The amount of the platinum group metal eluted from the wall surface depends on the temperature of the molten glass in the degassing treatment process before the transfer pipe 43a, the agglomeration treatment process, or the temperature of the wall surface of the cleaning pipe 41 in contact with the molten glass. Therefore, the concentration of the platinum group metal in the molten glass at the start of the agglomerate treatment process can be adjusted by adjusting the temperature or the temperature distribution of the wall surface of the transfer pipe 43a and the cleaning pipe 41. [ For example, by adjusting the current flowing through the cleaning tube 41, adjusting the current supplied to the heater disposed around the cleaning 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 agglomerate treatment process, the solubility of dissolving the platinum group metal in the molten glass at the start of the agglomerate 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 agglomerate treatment process is adjusted to 0.05 to 20 ppm.

Thus, even when the platinum group metal aggregate is mixed into the molten glass during the manufacturing process of the glass substrate, a glass substrate can be manufactured in which the number of defects of the platinum group metal aggregate is set at an allowable level.

(b) Temperature or temperature distribution of the molten glass

In the purifying pipe 41, the solubility of the aggregate of the platinum group metal mixed in the molten glass can be increased by increasing the temperature of the molten glass. The temperature or temperature distribution of the molten glass has been described in detail above, so that the description is omitted.

If the temperature of the molten glass is excessively increased, the amount of aggregation of the platinum group metal increases, while the following disadvantages arise.

ㆍ Increase of reboil bubble

If the temperature of the molten glass in the purifying pipe 41 is excessively high, defoaming is excessively performed in the defoaming process, so that the oxygen activity amount of the molten glass is lowered, and as a result, the molten glass is in a reduced state. In this state, when the absorption treatment process is carried out, excessive bubbles are generated in the molten glass in accordance with the following mechanism, and bubbles of the rebubbed bubbles may be present on the glass substrate. Specifically, the reboiler bubble is a bubble containing SO ₂ or CO ₂ generated due to sulfur or carbon contained as an impurity 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 likely to be produced. Since SO ₂ and CO ₂ are less soluble in molten glass than SO ₃ and CO ₃ , they tend to become bubbles. If such reoil bubbles are generated in a large amount, they may remain as bubble defects on the glass substrate, thereby deteriorating the quality of the glass substrate. The bubbles remaining on the glass substrate are detected by, for example, a laser microscope or naked eyes.

ㆍ Increase of volatile amount of glass component

When the temperature of the molten glass in the cleaning tube 41 is excessively increased, the component of the molten glass, for example, B ₂ O _3, is volatilized to a large extent in the vapor phase space. As a result, the glass composition locally changes, and the glass characteristics such as the coefficient of thermal expansion and the viscosity of the glass are locally changed, and streaks such as spots are generated on the glass substrate.

Increased volatility of platinum group metals

When the temperature of the molten glass in the cleaning tube 41 is excessively increased, the temperature of the vapor phase space in contact with the molten glass also increases. In addition, the amount of oxygen released into the gas phase by the defoaming treatment of the molten glass increases, As a result, the platinum group metal is easily volatilized from the wall of the purifying tube surrounding the vapor space. When the volatilization amount of the platinum group metal is increased, the concentration of the platinum group metal in the vapor phase is increased, and coagulation and mixing of the aggregate into the molten glass are apt to occur.

ㆍ Wrong loss of purifying pipe

If the temperature of the molten glass in the cleaning pipe 41 is excessively high, the wall of the cleaning pipe 41 contacting the molten glass may be damaged.

Adjustment of the temperature or temperature distribution of the molten glass in the cleaning tube 41 is performed from the viewpoint of suppressing the occurrence of such disadvantages.

(c) the pressure of the meteorological space

The solubility of the platinum group metal aggregate can be increased by increasing the pressure in the gas phase space 41c of the cleaning tube 41. [ The pressure of the vapor space means the voltage of the gas contained in the vapor space.

The adjustment of the pressure in the vapor space 41c can be performed by adjusting the amount of the gas in the vapor space 41c to be sucked to the outside of the purifying pipe 41 through the vent pipe 41a, For example, the amount of the inert gas supplied and the amount of the gas released from the molten glass. The amount of suction can be adjusted by connecting the outlet of the vent pipe 41a of the purifying pipe 41 to the suction device or by narrowing the outlet so that the atmosphere outside the vapor phase space 41c and the purifying pipe 41 By adjusting the magnitude of the pressure difference of the pressure difference. The emission amount of the gas emitted from the molten glass can be adjusted, for example, by adjusting the amount of the refining agent contained in the molten glass and the blending ratio of the glass component. The pressure in the gas phase space 41c is higher or lower than the atmospheric pressure outside the purifying pipe 41 can be obtained by the amount of gas discharged from the vent pipe 41a, for example.

The method of increasing the pressure of the gas phase space 41c in order to dissolve the foreign matter in the molten glass in the molten glass is not particularly limited as long as the amount of gas supplied into the cleaning tube 41, And adjusting the discharge amount of the gas emitted from the molten glass. The pressure in the vapor space 41c is preferably adjusted to a range of, for example, 0.8 to 1.2 atm.

When the pressure in the gas phase space 41c is excessively increased, the amount of platinum group metal aggregate dissolved increases, while the following disadvantages arise.

ㆍ Poor quality

If the pressure in the gas phase space 41c is excessively high, the bubbles generated in the molten glass in the defoaming process may be difficult to be released from the surface of the molten glass, resulting in poor purging.

Increased volatility of platinum group metals

When the pressure in the vapor space 41c is excessively high, the pressure difference between the air outside the cleaning tube 41 and the atmosphere increases, and the flow velocity of the airflow in the vapor space 41 increases. Because of this, the concentration of the platinum group metal in the vapor space 41c is not increased and it is difficult to be saturated, so that the volatilization amount of the platinum group metal from the wall of the cleaning tube 41 increases.

From the viewpoint of suppressing the occurrence of such disadvantages, pressure adjustment of the gas phase space is performed.

(d) Oxygen activity of the molten glass

In the purifying pipe 41, the solubility of the aggregate of the platinum group metal can be increased by raising the oxygen activity amount of the molten glass. The oxygen activity amount of the molten glass means the amount of oxygen dissolved in the molten glass (excluding bubbles present in the molten glass). In the present embodiment, [Fe ^{3 +} ] / ([Fe ^{2 +} ] + [Fe ^{3 +} ]) is used as an index of oxygen activity. Here, [Fe ^{2 +} ] and [Fe ^{3 +} ] are the activity values of Fe ^{2 +} and Fe ^{3 +} contained in the molten glass, specifically, the content is expressed as a percentage of mass and can be measured using a spectrophotometric method .

For example, in the defoaming step in the refining process, the temperature of the molten glass is increased, and oxygen dissolved in the molten glass is defoamed as bubbles, so that the oxygen activity amount of the molten glass is lowered. On the other hand, when the temperature of the molten glass is lowered in the refining step, the refining agent attracts oxygen, so the oxygen activity increases.

The oxygen activity of the molten glass can be adjusted, for example, by adjusting the amount of the refining agent or the glass raw material contained in the molten glass, in addition to adjusting the amount of the refining agent and the oxide contained in the molten glass in the melting step In addition to this, it is possible to adjust the temperature of the molten glass before the start of the agglomerate treatment process in the refining process, or to bubble the oxygen-containing gas in the molten glass before the agglomerate treatment process starts.

The adjustment of the oxygen activity amount in the molten glass may be performed together with the adjustment of the temperature or the temperature distribution of the molten glass. The adjustment of the oxygen activity amount in the molten glass may be performed together with the adjustment of the pressure in the gas phase space 41c. The adjustment of the oxygen activity amount in the molten glass is carried out by adjusting the amount of the fining agent contained in the molten glass or the amount of the oxide of the glass raw material as described above and also adjusting the temperature of the molten glass before the start of the agglomerate treatment process in the refining step Or by bubbling an oxygen-containing gas into the molten glass before the start of the agglomerate treatment process. It is preferable to adjust [Fe ^{3 +} ] / ([Fe ^{2 +} ] + [Fe ^{3 +} ]), which is an index of oxygen activity, in the range of, for example, 0.2 to 0.5 in the aggregate treatment process.

When the oxygen activity amount of the molten glass is excessively increased at the time of adjusting the oxygen activity amount of the molten glass, the amount of the aggregate of the platinum group metal increases, while the following disadvantages arise.

Increased volatility of platinum group metals

If the oxygen activity amount of the molten glass is excessively increased, the amount of oxygen released from the molten glass to the vapor phase increases in the defoaming process, and the oxygen concentration in the vapor phase rises, so that the platinum group metal is easily oxidized and volatilized easily. If the platinum group metal is liable to volatilize, an aggregate of platinum group metal tends to be generated, and it is likely to be incorporated into the molten glass.

The remaining oxygen bubbles in the molten glass

If the oxygen activity amount of the molten glass is excessively increased, the reduced refining agent can not attract oxygen, and oxygen bubbles (oxygen bubbles) are generated in the molten glass and remain as bubbles in the glass substrate, And the quality of the substrate is easily deteriorated.

From the viewpoint of suppressing the occurrence of such disadvantages, when the amount of platinum group metal aggregate is increased by adjusting the oxygen activity amount of the molten glass, it is preferable to suitably adjust the combination of the condition parameters (the temperature of the molten glass, etc.) .

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 flocculation treatment process or may be the temperature in the middle of the flocculation treatment process.

The defect of the aggregate of the platinum group metal in the glass substrate is caused by causing light such as laser light to be incident on the surface of the glass substrate from the oblique direction and receiving the reflected light at each position of the glass substrate, Can be detected by specifying an area that matches the shape of the agglomerate of the metal. The defects of the agglomerates may be visually detected instead of using the apparatus. The allowable level of the number of defects of this aggregate is, for example, 0.02 pieces / kg or less when expressed in unit mass. The allowable level is changed in accordance with the specification of the deformation and the unevenness of the main surface required by the user of the glass substrate.

For example, when the number of defects detected in the glass substrate exceeds the 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 accelerating the dissolution of the agglomerates. On the other hand, when the number of defects detected in the glass substrate is at the permissible level, it can be made lower within the range higher than the upper limit value of the number of defects at the tolerance level and the temperature of the corresponding molten glass. By adjusting the temperature of the molten glass in this manner, the saturation solubility of the platinum group metal can be adjusted to an appropriate range, thereby causing the number of defects in the aggregate contained in the glass substrate to be at an allowable level, It is possible to suppress deterioration of the quality of the glass substrate.

Specifically, in the case where the glass processing apparatus is a clarifying apparatus including a purifying tube, the temperature adjustment of the molten glass can be carried out by supplying electric current to the purifying tube and energizing and heating it. The amount of current can be adjusted by the magnitude of the voltage applied to the heating electrode. The temperature adjustment of the molten glass may be indirectly adjusted by a heater (not shown) disposed around the cleaning tube in place of or in combination with energization heating. The heater is disposed, for example, inside or outside the refractory protective layer or the refractory brick. The temperature of the molten glass may be adjusted by adjusting the amount of heat released from the purifying pipe by using the refractory protection layer or the refractory brick.

The aggregate process, [Fe of the agglomerate glass substrate in addition to instead of the temperature adjustment of the molten glass so that the defect count is acceptable level, or temperature regulation, an indicator of oxygen hwalryang of the above-mentioned molten glass contained in the glass substrate ^{3 +} ] / ([Fe ^{2 +} ] + [Fe ^{3 +} ]) in the range of 0.2 to 0.5 to adjust the saturation solubility of the platinum group metal.

(Aggregate of platinum group metal after the aggregate treatment process)

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

In the present embodiment, when the temperature of the cleaning tube 41 is increased to raise the temperature of the molten glass G, the above-described effects of the present embodiment can be effectively exhibited.

For example, tin oxide is preferably used as the fining agent of the molten glass for reducing the environmental load. However, tin oxide is inferior to As ₂ O ₃ or Sb ₂ O _{3 at a} temperature at which the fining effect (oxidation reaction) high. Therefore, when tin oxide is used as the fining agent, it is necessary to raise the temperature of the cleaning tube 41 and increase the temperature of the fused glass G as compared with the case where As ₂ O ₃ or Sb ₂ O ₃ is used as the fining agent . That is, since tin oxide is used as the refining agent, the purifying tube 41 is more likely to be volatilized (oxidized) than in the prior art, and the problem of volatilization and agglomeration of the platinum group metal tends to occur. Thus, even if the amount of foreign substances (agglomerates) of the platinum group metal incorporated into the molten glass is increased by using tin oxide as the fining agent, the size of the foreign substance of the platinum group metal can be reduced as in the present embodiment, It is difficult for the substrate to be deformed, and the effect of making it difficult to make irregularities on the main surface of the glass substrate becomes remarkable. That is, it is possible to sufficiently reduce the amount of foreign matter (aggregate) causing display failure.

Further, in a molten glass having a high viscosity, the rising speed of bubbles is slow in the refining process, and it is difficult to purify the molten glass. In addition, even in the stirring step performed in the stirring apparatus 100, it is difficult to homogeneously stir molten glass having a high viscosity. Therefore, in order to sufficiently obtain the refining effect or homogenization of the molten glass, it is necessary to raise the temperature of the molten glass. Therefore, if the temperature of the glass processing apparatus is elevated in order to obtain a molten glass having a high temperature, the volatilization of the platinum group metal becomes severe in the glass processing step, and the amount of foreign matter (agglomerate) incorporated into the molten glass tends to increase. That is, the problem of volatilization and agglomeration of the platinum group metal tends to occur.

For example, a thin film transistor is formed on a glass substrate used for a display panel. In order not to adversely affect the operation of the thin film transistor, it is preferable to use an alkali-free glass or a glass containing a small amount of alkali for the glass substrate. Since the alkali-free glass or alkali-containing glass has a high viscosity as compared with an alkali-containing glass such as soda glass, the rising speed of the bubbles is slow in the refining process and it is difficult to purify the glass. For this reason, in order to sufficiently obtain the purifying effect, it is necessary to raise the temperature of the cleaning tube 41 and increase the temperature of the molten glass G. That is, since the object to be produced is an alkali-free glass or a glass containing a small amount of alkali, volatilization (oxidation) of the cleaning tube 41 is more likely to occur than alkali glass, and the problem of volatilization and agglomeration of the platinum group metal tends to occur. Even if the temperature of the cleaning tube 41 is increased to use an alkali-free glass or an alkali-containing glass as described above and the amount of foreign substances (agglomerates) of the platinum group metal incorporated in the molten glass increases, Likewise, since the size of the foreign substance of the platinum group metal can be reduced, the glass substrate is hardly deformed, and the effect of making it difficult to make irregularities on the main surface of the glass substrate becomes remarkable. That is, it is possible to sufficiently reduce the amount of foreign matter (aggregate) causing display failure.

The above-mentioned alkali-free glass or alkali-alkali-containing glass is a glass having a high strain point. Since the glass having a high strain point has a higher viscosity than a glass having a low strain point, the rising speed of bubbles in the cleaning process is slow and it is difficult to purify the glass. For this reason, in order to sufficiently obtain the purifying effect, it is necessary to raise the temperature of the cleaning tube 41 and increase the temperature of the molten glass G. That is, in the case of producing a glass having a high strain point, volatilization (oxidation) of the cleaning tube is more likely to occur than in the case of producing a glass having a low strain point, and the problem of volatilization and agglomeration of the platinum group metal tends to occur. Thus, even if the temperature of the cleaning tube 41 is increased to use a glass having a high strain point and the amount of foreign substances (agglomerates) of the platinum group metal in the molten glass increases, the platinum group metal The deformation of the glass substrate is less likely to occur, and the effect of making it difficult to make irregularities on the main surface of the glass substrate becomes remarkable. That is, it is possible to sufficiently reduce the amount of foreign matter (aggregate) causing display failure.

The glass substrate for display is required to have a strain point of 600 DEG C or higher, more preferably 650 DEG C or higher. However, if the strain point of the glass substrate is 600 DEG C or higher, it is preferable that the strain of the foreign substance (agglomerate) The effect of the present embodiment capable of sufficiently reducing the amount of the catalyst is remarkable. The glass substrate for a high-precision display is required to have a higher strain point, and the strain point is preferably 690 캜 or higher, and more preferably 730 캜 or higher. When the strain point is 690 DEG C or more and 730 DEG C or more as described above, the above-described effect of the present embodiment becomes more remarkable.

Further, the viscosity of molten glass comprising a tin oxide used in the present embodiment, more than 1500 ℃ temperature, for example at a temperature of 1700 to 1500 ℃ ℃, or 1550 to 1650 ℃ ℃, the viscosity 10 ^2.5 It is preferable that it is Poisson. In this case, the above-described effect of the present embodiment becomes more remarkable.

When the thickness of the glass substrate produced in the present embodiment is 0.005 mm to 0.8 mm, preferably 0.01 mm to 0.5 mm, and more preferably 0.01 mm to 0.2 mm, the above-described effects of the present embodiment Lt; / RTI > When such a glass substrate having a thin thickness is produced, foreign matter (aggregated material) appears on the glass surface, and surface irregularities are easily formed. In the present embodiment, the problem caused by such a plate thickness can be solved by the above-mentioned effects.

[Experimental Example]

In order to confirm the effect of the present embodiment, a glass substrate was manufactured in a manufacturing step including the aggregate treatment step S2B shown in Fig. 1 (Example). In the aggregate treatment step S2B, the amount of heat given to the aggregate was controlled.

The production conditions of the glass substrate are as follows.

The glass composition of the glass substrate was SiO ₂ 60.7% by weight, Al ₂ O ₃ 17% by mass, B ₂ O ₃ 11.5 mass%, MgO 2% by mass, 5.6% by weight CaO, SrO 3% by weight, SnO ₂ 0.2% by mass, a strain point of 660 캜, and a plate thickness of 0.4 mm.

Further, without performing the aggregate treatment step S2B shown in Fig. 1, a glass substrate was produced under the above-described production conditions in the conventional manufacturing step in which the absorption treatment step S2C was performed after the defoaming treatment step S2A. Specifically, in Examples 1 to 5 shown in the following Table 1, the maximum temperature of the molten glass G in the purifying pipe 41 is 1670 to 1720 캜, and the temperature of the molten glass G is 1670 캜 or higher I set the time to 40 minutes. On the other hand, in Examples 6 and 7, the maximum temperature of the molten glass G was set to be lower than 1670 캜, and the time when the temperature of the molten glass G became 1670 캜 or higher was set to 0 min.

The number of foreign substances (agglomerates) of platinum group metals in a plurality of 0.1 m 3 glass substrates produced in this manner was counted using an optical microscope and the maximum length of foreign substances (agglomerates) of platinum group metals was measured . Then, the ratio of the number of foreign substances having a maximum length of 50 占 퐉 or less among all the platinum group metal foreign substances (aggregates) mixed in the glass substrate was determined. The obtained ratio is shown in Table 1 together with the maximum temperature. The foreign matter ratios of Examples 1 to 5 were 70% or more in any of the glass substrates, and the foreign matter ratios in Examples 6 and 7 were 35% or less for both glass substrates. 5 is a graph showing the relationship between the maximum temperature of the molten glass and the ratio of the foreign material. As can be seen from Fig. 5, the proportion of foreign matter having a maximum length of 50 mu m or less rapidly increased by setting the maximum temperature of the molten glass at 1660 DEG C to 1670 DEG C or more, and became 70% or more at a temperature of 1670 DEG C or more. At 1690 占 폚 or more, the ratio of foreign matter having a maximum length of 50 占 퐉 or less becomes 92% or more, and particularly, at 1700 占 폚 or more, the ratio of foreign matter having a maximum length of 50 占 퐉 or less is 100%. Thus, in the case of controlling the amount of heat applied to the foreign substance under the conditions of this experimental example, by setting the maximum temperature of the molten glass to 1670 DEG C or higher, preferably 1690 DEG C or higher, more preferably 1700 DEG C or higher, It is preferable to give the information. Under the conditions of this experimental example, the maximum temperature of 1670 占 폚 is the lower limit temperature of the maximum temperature at which the ratio of the foreign substance having the maximum length of 50 占 퐉 or less is 70%, but it is not necessarily essential that the maximum temperature is 1670 占 폚 or higher. It is possible to realize the ratio of the foreign matter having the maximum length of 50 탆 or less to 70% even by adjusting the solubility of the aggregate (foreign matter).

Although the present invention has been described in detail with respect to the method for producing a glass substrate, the glass substrate and the glass substrate laminate according to the present invention, the present invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the gist of the present invention. Of course, it is good to change.

40: Melting bath
41: Purification Hall
41a: vent pipe
41b: heating electrode
41c: weather space
42: Molding device
52: molded article
43a, 43b, and 43c:
100: stirring device
200: glass substrate manufacturing apparatus

Claims (19)

A melting step of melting a glass raw material to produce a molten glass;
Wherein the molten glass is introduced into the tube of the glass processing apparatus having a space in which a surface of the molten glass and a space surrounded by the wall are formed and at least a part of the wall is made of a material containing a platinum group metal Wherein the molten glass is subjected to a treatment while flowing the molten glass, wherein the molten glass treatment step in which the aggregate of the volatile substances of the platinum group metal volatilized from the wall present in the vapor phase space is mixed with the molten glass as a foreign substance and,
The temperature of the molten glass in the tube of the glass processing apparatus is set to 1670 占 폚 or higher so that the ratio of the number of agglomerates having a maximum length of 50 占 퐉 or less among the agglomerates mixed in the molten glass is 70% And an agglomerate treatment step for reducing the size of agglomerates incorporated into the glass,
Wherein the pipe of the glass processing apparatus is provided with a vent pipe for communicating the gas phase space with the atmosphere outside the glass processing apparatus, and wherein the molten glass flowing through the pipe of the glass processing apparatus has a maximum Wherein the temperature position is located between an inlet where the molten glass is introduced into the pipe of the glass processing apparatus and a position of the vent pipe in the flow direction of the molten glass. A melting step of melting a glass raw material to produce a molten glass;
In a tube of a glass processing apparatus having a liquid phase made of the molten glass and a vapor phase space formed from the liquid surface and the wall of the molten glass and at least a part of the wall surrounding the vapor phase is made of a material containing a platinum group metal, A molten glass treatment step in which the aggregate of volatiles of the platinum group metal volatilized from the wall present in the vapor phase space is mixed with the molten glass as a foreign substance during the treatment of the molten glass,
The temperature of the molten glass in the tube of the glass processing apparatus is set to 1670 DEG C or more so that the ratio of the number of agglomerates having a maximum length of 50 mu m or less among the agglomerates mixed in the molten glass in the molten glass processing step is 70% And an agglomerate treatment step of reducing the size of agglomerates mixed in the molten glass,
Wherein the pipe of the glass processing apparatus is provided with a vent pipe for communicating the gas phase space with the atmosphere outside the glass processing apparatus, and wherein the molten glass flowing through the pipe of the glass processing apparatus has a maximum Wherein the temperature position is located between an inlet where the molten glass is introduced into the pipe of the glass processing apparatus and a position of the vent pipe in the flow direction of the molten glass. A melting step of melting a glass raw material to produce a molten glass;
Wherein the molten glass has a space in which a surface of the molten glass and a vapor space surrounded by the wall are formed and at least a part of the wall is made of a material containing a platinum group metal, A molten glass treatment step in which an aggregate of volatile products of the platinum group metal volatilized from the wall existing in the vapor phase space is mixed with the molten glass as a foreign substance during the treatment of the molten glass,
An agglomerate treatment step of adjusting the solubility of the agglomerate in the molten glass so that the temperature of the molten glass in the tube of the glass processing apparatus is set to 1670 DEG C or higher so as to reduce the size of agglomerates mixed in the molten glass; And,
Wherein the pipe of the glass processing apparatus is provided with a vent pipe for communicating the gas phase space with the atmosphere outside the glass processing apparatus, and wherein the molten glass flowing through the pipe of the glass processing apparatus has a maximum Wherein the temperature position is located between an inlet where the molten glass is introduced into the pipe of the glass processing apparatus and a position of the vent pipe in the flow direction of the molten glass. A melting step of melting a glass raw material to produce a molten glass;
In a tube of a glass processing apparatus having a liquid phase made of the molten glass and a vapor phase space formed from the liquid surface and the wall of the molten glass and at least a part of the wall surrounding the vapor phase is made of a material containing a platinum group metal, A molten glass treatment step in which the aggregate of volatiles of the platinum group metal volatilized from the wall present in the vapor phase space is mixed with the molten glass as a foreign substance during the treatment of the molten glass,
The temperature of the molten glass in the tube of the glass processing apparatus is set to 1670 占 폚 or more so that the amount of heat given to the aggregate is equal to or more than a minimum amount of heat capable of reducing the size of the agglomerate incorporated in the molten glass, And an aggregate treatment step of controlling the amount of heat applied to the aggregate,
Wherein the pipe of the glass processing apparatus is provided with a vent pipe for communicating the gas phase space with the atmosphere outside the glass processing apparatus, and wherein the molten glass flowing through the pipe of the glass processing apparatus has a maximum Wherein the temperature position is located between an inlet where the molten glass is introduced into the pipe of the glass processing apparatus and a position of the vent pipe in the flow direction of the molten glass. 5. The method according to any one of claims 1 to 4,
The difference between the maximum temperature and the minimum temperature of the wall in contact with the vapor space is set to 5 DEG C or more,
Wherein the vapor phase space contains oxygen. 5. The method according to any one of claims 1 to 4,
In the aggregate treatment step, the temperature of the molten glass containing the aggregate is raised so as to be higher than the temperature of the molten glass in the region where the aggregate is mixed in the molten glass in the molten glass treatment step Way. 5. The method according to any one of claims 1 to 4,
Wherein the solubility of the agglomerate in the molten glass is higher than the solubility of the agglomerate in the molten glass in the molten glass treatment step. 5. The method according to any one of claims 1 to 4,
The glass processing apparatus is a purifying apparatus having a purifying tube,
Wherein the vapor phase space in the purifying tube is formed along the flow direction of the molten glass,
Wherein the flocculation treatment is performed in the clarifying tube. 5. The method according to any one of claims 1 to 4,
In the above-mentioned molten glass treatment step, a fining treatment for reducing the number of bubbles in the molten glass is performed using tin oxide contained in the molten glass,
Wherein a temperature distribution is formed in the wall in contact with the vapor space along the flow direction of the molten glass,
Wherein an oxygen concentration distribution is formed in the vapor phase space along the flow direction of the molten glass. 5. The method according to any one of claims 1 to 4,
Wherein the flocculation treatment step is carried out in the glass treatment apparatus and the molten glass flowing in a position corresponding to the region where the oxygen concentration is the highest in the flow direction of the molten glass in the vapor phase among the molten glass flowing in the glass treatment apparatus Is performed on the glass substrate. 5. The method according to any one of claims 1 to 4,
Wherein the oxygen concentration in the vapor phase space is set to more than 0% and not more than 1.0%, and a difference between a maximum temperature and a minimum temperature of the wall in contact with the vapor phase is 5 ° C or more and 150 ° C or less Way. 5. The method according to any one of claims 1 to 4,
Wherein the temperature of the molten glass is controlled so that the temperature of the molten glass in the aggregate treatment step is in the range of 1670 캜 to 1730 캜. 5. The method according to any one of claims 1 to 4,
Wherein the temperature of the molten glass is controlled so that the temperature of the molten glass in the region where the aggregate is mixed into the molten glass in the molten glass treatment step is in the range of 1580 캜 to 1660 캜. 5. The method according to any one of claims 1 to 4,
Wherein the molten glass treatment step includes the aggregate treatment step. 5. The method according to any one of claims 1 to 4,
Wherein the glass substrate is a glass substrate for display. 5. The method according to any one of claims 1 to 4,
Wherein the concentration of the platinum group metal dissolved in the molten glass at the start of the agglomerate treatment process is set to 0.05 to 20 ppm. 5. The method according to any one of claims 1 to 4,
In the flocculation treatment step, a glass for adjusting the saturation solubility of the platinum group metal in the molten glass in the range of [Fe ³⁺ ] / ([Fe ²⁺ ] + [Fe ³⁺ ] / RTI > delete delete

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