JP6110448B2 - Manufacturing method of glass substrate and stirring device - Google Patents

Description

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

  Generally, a glass substrate is produced through a process of forming molten glass from a glass raw material and then forming the molten glass into a glass substrate. Chemical and thermal homogeneity is a very important part in the process of forming excellent glass substrates. In the manufacturing process of the glass substrate described above, streaks (streaks) may be formed due to chemically different phases or viscosity differences. Such inhomogeneous components of the glass substrate result from various normal events during the melting process, including dissolution of sparingly soluble materials, stratification of the melt, volatilization of the glass surface, and temperature differences. This striae are streaked in the glass substrate in a visible state due to the difference in color and / or refractive index. Therefore, it is important to stir the molten glass in order to improve such glass heterogeneity. The molten glass is stirred by passing the molten glass through a stirring device provided downstream of the melting tank. In general, a stirring device for stirring molten glass is disposed above a stirring container for storing molten glass, a stirring container, and a lid (container cover) for covering the upper part, and the stirring container. And a stirrer (Patent Document 1, Patent Document 2). The stirrer has a rotating shaft that is rotated by a motor or the like, and a stirring blade (blade) that is attached to the outer peripheral surface of the rotating shaft by welding. The rotating shaft passes through a part of the lid. The stirring device is configured such that when the molten glass passes through the inside of the stirring vessel from the top to the bottom or from the bottom to the top, the stirring blade attached to the rotating shaft described above stirs and mixes the molten glass. ing. By stirring the molten glass in this manner, defects such as striae and stripes of the glass product are prevented.

In the stirring vessel, volatiles can be generated from molten glass or any component present in the stirring vessel. Some of the most volatile and disadvantageous oxides are those formed from Pt, B, and Sn. The main sources of oxides that can agglomerate (condense) in the molten glass include the hot platinum surface for PtO ₂ and the free surface of the molten glass for B ₂ O ₃ and SnO ₂ . The free surface of the molten glass means the surface of the molten glass that is exposed to the atmosphere in the stirring vessel. The atmosphere on the free surface of the molten glass may contain any or all of the aforementioned or other volatile materials, but since this atmosphere is hotter than the atmosphere outside the stirring vessel, the molten glass In the atmosphere on the free surface, the volatiles flow upward through an arbitrary opening such as an annular space between the rotating shaft of the stirrer and the lid covering the top of the stirring vessel. The rotating shaft generally cools as the distance from the free surface of the molten glass increases, so if the temperature of the rotating shaft and / or the cover (cover) is lower than the dew point of its oxide, the volatilization contained in the atmosphere of the stirred tank Objects may agglomerate on the surface of the rotating shaft. Agglomeration can occur on the surface of the agitator as well as on other relatively cool surfaces including the annular region of the agitator. When the generated aggregate reaches a sufficient size, the aggregate may break and fall onto the glass in the stirring vessel, causing inclusions or blister defects in the glass product after molding. Patent Document 1 describes a collar portion (holding member) that receives a falling foreign substance in which a gas phase space exists between the lid of the stirring tank and the surface of the molten glass.

Japanese Patent Laid-Open No. 2000-1000046 JP 2014-9136 A

  In recent years, the temperature of the molten glass flowing into the stirring tank has increased. When the temperature of the molten glass in the stirring tank rises, the concentration (vapor pressure) of volatiles in the gas phase space existing between the lid of the stirring tank and the surface of the molten glass increases, and it aggregates on the rotating shaft and falls. Volatile substances aggregated on the bottom surface of the holding member that holds the volatile substances. If a part of the aggregate aggregated on the bottom surface of the holding member falls and enters the molten glass as a foreign substance, the quality of the glass substrate may be deteriorated. In particular, in a glass substrate for a high-definition display, quality requirements regarding foreign matter contamination are severe.

  Then, an object of this invention is to provide the manufacturing method of a glass substrate which can reduce the foreign material mixed in a glass substrate, and a stirring apparatus. Moreover, it aims at providing the manufacturing method of a glass substrate which can suppress that a volatile substance aggregates on the holding member surface, and can prevent a foreign material from mixing in the molten glass in a stirring apparatus, and a stirring apparatus.

  The present invention includes the following forms.

[Form 1]
A glass substrate manufacturing method comprising a stirring step of stirring a molten glass produced by melting a glass raw material with a stirrer, and a forming step of forming the molten glass into a plate shape,
The stirring device
A stirring vessel made of a material containing a platinum group metal and containing molten glass;
A container cover provided above the stirring container;
A shaft made of a material containing a platinum group metal and having a protrusion protruding from the container cover to the upper side of the container cover; and a blade made of a material containing a platinum group metal attached to the shaft. A stirrer for stirring the molten glass in the stirring vessel;
A heat-resistant member that is installed outside the stirring vessel and forms a heating space in which the stirring vessel is installed inside;
A plurality of heating units installed at locations outside the stirring vessel in the heating space;
Holding the agglomerates formed by agglomerating the volatiles containing the platinum group metal or the glass raw material that volatilizes, and holding members provided on the protrusions,
The said holding member is provided in the position which becomes more than the temperature which the said volatile substance aggregates among the said protrusion parts in the said heating space, The manufacturing method of the glass substrate characterized by the above-mentioned.

[Form 2]
The temperature of the protruding portion decreases as the distance from the molten glass increases.
The said holding member is a manufacturing method of the glass substrate of the form 1 provided in the position on the said protrusion part of the said rotating shaft where the temperature of the said holding member is higher than the dew point of the said volatile matter.

[Form 3]
The vapor pressure of the volatiles that decreases as the volatiles flow upward through the clearance between the container cover and the shaft is less than the saturated vapor pressure of the volatiles that decreases as they move upward away from the molten glass. The manufacturing method of the glass substrate of the form 1 or 2 with which the said holding member is provided in a position.

[Form 4]
In the stirring step, the heating space is set such that a platinum vapor pressure in the heating space around the protrusion is 0.3 Pa to 5 Pa, and a temperature of the protrusion is equal to or higher than a temperature at which the platinum vapor pressure becomes a saturated vapor pressure. The manufacturing method of the glass substrate as described in any one of the forms 1-3 with which the said protrusion part is heated by a part.

[Form 5]
A glass substrate manufacturing method comprising a stirring step of stirring a molten glass produced by melting a glass raw material with a stirrer, and a forming step of forming the molten glass into a plate shape,
The stirring device
A stirring vessel made of a material containing a platinum group metal that houses molten glass;
A container cover provided above the stirring container;
A shaft made of a material containing a platinum group metal and having a protrusion protruding from the container cover to the upper side of the container cover; and a blade made of a material containing a platinum group metal attached to the shaft. A stirrer for stirring the molten glass in the stirring vessel;
A heat-resistant member that is installed outside the stirring vessel and forms a heating space in which the stirring vessel is installed inside;
A plurality of heating units installed at locations outside the stirring vessel in the heating space,
In the stirring step, the heating space is set such that a platinum vapor pressure in the heating space around the protrusion is 0.3 Pa to 5 Pa, and a temperature of the protrusion is equal to or higher than a temperature at which the platinum vapor pressure becomes a saturated vapor pressure. The protrusion is heated by the portion, and the method for manufacturing a glass substrate.

[Form 6]
The heating space is
An upper heating space above a middle height position of the heating space in the vertical direction;
A lower heating space below the intermediate height position,
The total output of the heating units arranged in the upper heating space is a method for manufacturing a glass substrate according to mode 5, wherein the total output of the heating units arranged in the lower heating space is larger.

[Form 7]
The strain point of the said glass substrate is a manufacturing method of the glass substrate as described in any one of the forms 1-6 which is 680 degreeC or more.

[Form 8]
A stirring device for stirring molten glass produced by melting glass raw materials,
A stirring vessel made of a material containing a platinum group metal and containing molten glass;
A container cover provided above the stirring container;
A shaft made of a material containing a platinum group metal and having a protrusion protruding from the container cover to the upper side of the container cover; and a blade made of a material containing a platinum group metal attached to the shaft. A stirrer for stirring the molten glass in the stirring vessel;
A heat-resistant member that is installed outside the stirring vessel and forms a heating space in which the stirring vessel is installed inside;
A plurality of heating units installed at locations outside the stirring vessel in the heating space;
Holding the agglomerates formed by agglomeration of the platinum group metal or the glass raw material that volatilizes, and holding members provided on the protrusions,
The said holding member is provided in the position which becomes more than the temperature which the said volatile substance aggregates among the said protrusion parts in the said heating space, The stirring apparatus characterized by the above-mentioned.

[Form 9]
A stirring device for stirring molten glass produced by melting glass raw materials,
A stirring vessel made of a material containing a platinum group metal and containing molten glass;
A container cover provided above the stirring container;
A shaft made of a material containing a platinum group metal and having a protrusion protruding from the container cover to the upper side of the container cover; and a blade made of a material containing a platinum group metal attached to the shaft. A stirrer for stirring the molten glass in the stirring vessel;
A heat-resistant member that is installed outside the stirring vessel and forms a heating space in which the stirring vessel is installed inside;
A plurality of heating units installed at locations outside the stirring vessel in the heating space,
The heating part has a platinum vapor pressure in the heating space around the protrusion of 0.3 Pa to 5 Pa, and the protrusion has a temperature equal to or higher than a temperature at which the platinum vapor pressure becomes a saturated vapor pressure. A stirrer characterized by heating the part.

  According to the above-mentioned form, it can suppress that a volatile substance aggregates on the holding member surface, and can prevent that a foreign material mixes in the molten glass in a stirring apparatus. Furthermore, foreign substances mixed in the glass substrate can be reduced.

It is a figure which shows an example of the flow of the manufacturing method of the glass substrate of this invention. It is a figure which shows typically an example of the apparatus which performs the melting process thru | or cutting process in this invention. It is a longitudinal cross-sectional view which shows an example of the stirring apparatus in Embodiment 1. It is a figure which shows the relationship between the distance from the surface of a molten glass to a holding member, and the temperature of the holding member. It is the figure which showed the relationship between the distance from the surface of a molten glass to a holding member, and the saturated vapor pressure and vapor pressure of volatilized platinum. It is the figure which showed the relationship between the distance from the surface of a molten glass to a holding member, and the vapor pressure difference which pulled the vapor pressure of platinum from the saturated vapor pressure of platinum. It is a side view which shows an example of the stirring apparatus of Embodiment 2. It is a top view of only the stirring container and the stirrer of the stirring apparatus shown in FIG. It is a figure explaining the flow of the molten glass stirred with the stirring apparatus in Embodiment 2. FIG. It is a figure explaining the heat generating body used in the Example.

Hereinafter, embodiments of the present invention will be described in detail.
(Overall overview of glass substrate manufacturing method)
FIG. 1 is a diagram showing a flow of a glass substrate manufacturing method according to an embodiment of the present invention.
The glass substrate manufacturing method includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a forming step (ST5), a cooling step (ST6), Cutting step (ST7). Moreover, the manufacturing method of a glass substrate has other processes, such as a grinding process, a grinding | polishing process, a washing | cleaning process, an inspection process, and a packing process. The plurality of glass plates stacked in the packing process are transported to a supplier (customer) as a delivery destination.

  FIG. 2 is a diagram schematically showing an apparatus for performing the melting step (ST1) to the cutting step (ST7). As shown in FIG. 2, the apparatus mainly includes a melting apparatus 100, a forming apparatus 200, and a cutting apparatus 300. The melting apparatus 100 includes a melting tank 101, a clarification tank 102, a stirring tank (stirring container) 103, a first pipe 104, a second pipe 105, and a third pipe 106. The melting tank 101 and the clarification tank 102 are connected by a first pipe 104, the clarification tank 102 and the stirring tank 103 are connected by a second pipe 105, and the stirring tank 103 and the molding apparatus 200 are connected by a third pipe 106. Has been. The stirring device including the stirring tank 103 will be described later.

In the melting step (ST1), for example, molten glass MG of 1520 ° C. to 1620 ° C. is obtained by melting the glass raw material supplied in the melting tank 101 by heating with a flame and an electric heater (not shown). The clarification step (ST2) is performed in the clarification tank 102, and is included in the molten glass MG by heating the molten glass MG in the clarification tank 102 supplied from the melting tank 101 through the first pipe 104. Oxygen and SO ₂ bubbles are absorbed by O ₂ released by the redox reaction of the fining agent and grow and float on the surface of the molten glass, or gas components in the bubbles are contained in the molten glass MG. Absorbed and the bubbles disappear. The temperature of the molten glass MG in the clarification tank 102 is preferably 1600 ° C to 1800 ° C, more preferably 1630 ° C to 1750 ° C, and further preferably 1650 ° C to 1750 ° C.

  In the homogenization step (ST3), the glass component MG is homogenized by stirring the molten glass MG in the stirring tank 103 supplied from the clarification tank 102 through the second pipe 105 using the stirrer 107. Specifically, since the molten glass MG is cooled when passing through the second pipe 105, the molten glass MG having a temperature lower than that of the molten glass MG in the clarification tank 102 is stirred in the stirring tank 103. In the stirring tank 103, the temperature of the molten glass MG is set within a range of 1400 ° C. to 1550 ° C., for example, and the viscosity of the molten glass G is adjusted within a range of 2500 dPa · s to 450 dPa · s, for example. It is preferable that stirring of the glass MG is performed. Molten glass MG is homogenized by being stirred in stirring tank 103.

  2 is lowered while the molten glass MG supplied from the upper part of the stirring tank 103 is stirred by the stirrer 107, and the lowered molten glass MG flows out of the third pipe 106, which will be described later. Thus, the molten glass MG supplied from the lower part of the stirring tank 103 may be raised while being stirred by the stirrer 107, and the elevated molten glass MG may be discharged from the third pipe 106.

  In the supply step (ST4), the molten glass MG is supplied from the stirring vessel 103 to the molding apparatus 200 through the third pipe 106. When the molten glass MG passes through the third pipe 106, it is cooled to a temperature suitable for molding by the molding apparatus 200, for example, 1200 ° C.

In the molding apparatus 200, a molding process (ST5) and a cooling process (ST6) are performed.
In the forming step (ST5), the molten glass MG is formed into a sheet glass SG to make a flow of the sheet glass SG. For example, an overflow down draw method using the molded body 210 is used. In this case, the flow direction of the sheet glass SG is vertically downward. In the cooling step (ST6), the sheet glass SG that is formed and flows has a desired thickness, and is cooled so that warpage and distortion due to cooling do not occur.
Specifically, the molten glass MG overflowing from the upper part of the molding apparatus 200 flows downward along the side wall of the molded body of the molding apparatus 200, so that the sheet glass SG is continuously molded from the lower end of the molded body. The The sheet glass ribbon SG is gradually cooled as it goes downward. The strain point of the glass substrate is preferably 680 ° C. or higher, and more preferably 700 ° C. or higher.

In the cutting step (ST7), the sheet glass SG supplied from the forming apparatus 200 is cut into a predetermined length in the cutting apparatus 300, thereby obtaining a plate-shaped glass substrate.
After this, after the end surface of the glass substrate is ground and polished, the glass substrate is cleaned, and further, the presence or absence of abnormal defects such as bubbles and striae is inspected. Packaged as a final product.

The glass substrates manufactured in the following Embodiments 1 and 2 and modifications are suitably used for, for example, a liquid crystal display glass substrate, an organic EL display glass substrate, and a cover glass. In addition, the glass substrate can also be used as a display for a portable terminal device, a cover glass for a housing, a touch panel plate, a glass substrate for a solar cell, or a cover glass. In particular, it is suitable for a glass substrate for a liquid crystal display using a polysilicon TFT (Thin Film Transistor).
Moreover, the thickness of a glass substrate is 0.05 mm-1.5 mm, for example. The thickness is preferably 0.05 to 1.2 mm, more preferably 0.3 to 1.0 mm, still more preferably 0.3 to 0.8 mm, and particularly preferably 0.3 to 0.5 mm.
Furthermore, the length of the glass substrate in the width direction is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm. On the other hand, the length of the glass substrate in the vertical direction is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm.

(Composition of glass substrate)
As the glass used for the glass substrate, for example, borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, soda lime glass, alkali silicate glass, alkali aluminosilicate glass, and alkali aluminogermanate glass can be applied. The glass applicable to the present invention is not limited to the above.

The glass composition of a glass substrate can mention the following, for example. The content rate display of the composition shown below is mass%.
SiO ₂ 50~70%,
Al ₂ O ₃ 0-25%,
B ₂ O ₃ 0-15%,
MgO 0-10%,
CaO 0-20%,
SrO 0-20%,
BaO 0-15%,
RO 5-30% (where R is the total amount of Mg, Ca, Sr and Ba),
It is preferable that it is an alkali free glass containing.

In addition, although it was set as the alkali free glass in said glass composition example, the glass substrate may be the alkali trace amount containing glass containing a trace amount of alkali metals. When an alkali metal is contained, the total of R ′ ₂ O is 0.10% or more and 0.5% or less, preferably 0.20% or more and 0.5% or less (where R ′ is selected from Li, Na, and K) It is preferable that the glass substrate G contains at least one kind. Of course, the total of R ′ ₂ O may be less than 0.10%. In order to facilitate melting of the glass, the content of iron oxide in the glass is 0.01 to 0.2% (preferably 0.01 to 0.08%) from the viewpoint of reducing the specific resistance. More preferably. Further, the content of tin oxide (SnO ₂ ) added as a fining agent is more preferably 0.01 to 1% (preferably 0.01 to 0.5%).

Moreover, as an example of the composition of glass, non-alkali glass and fine alkali glass are SiO ₂ 57 mass% to 70 mass%,
Al ₂ O ₃ 15% by mass to 25% by mass,
B ₂ O ₃ 0% by mass to 13% by mass,
MgO 0% by mass to 15% by mass,
CaO 0% by mass to 20% by mass,
SrO 0% by mass to 20% by mass,
BaO 0% by mass to 10% by mass,
Na ₂ O 0% by mass to 1% by mass,
K ₂ O 0% by mass to 1% by mass,
As ₂ O ₃ 0% by mass to 1% by mass,
Sb ₂ O ₃ 0% by mass to 1% by mass,
SnO ₂ 0% by mass to 1% by mass,
Fe ₂ O ₃ 0% by mass to 1% by mass,
It consists of 0 to 1% by mass of ZrO ₂ .
Here, regarding the glass having the above composition, each content of Fe ₂ O ₃ , As ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ is a component of Fe, As, Sb or Sn having a plurality of valences. These are values converted as Fe ₂ O ₃ , As ₂ O ₃ , Sb ₂ O ₃ or SnO ₂ , respectively.

  In Embodiments 1 and 2 described below, a melting step (the above-described melting step) for melting a glass raw material to obtain a molten glass, and a stirring step for stirring the molten glass obtained in the melting step with a stirring device ( And a forming step of forming a glass substrate from the molten glass stirred in the stirring step.

(Embodiment 1)
FIG. 3 is a longitudinal sectional view illustrating an example of the stirring device 120 according to the first embodiment.
A stirring device 120 shown in FIG. 3 includes a stirring tank (stirring container) 103, a lid (container cover) 110 that covers an upper part of the stirring tank 103, and a stirrer 107 disposed inside the stirring tank 103. The stirrer 107 includes a rotating shaft 108 arranged in a vertical direction, and a stirring blade (blade) 109 attached to a side peripheral surface below the rotating shaft 108. The rotating shaft 108 has a protruding portion that protrudes from the lid (container cover) 110 to above the lid 110. The rotation shaft 108 has a holding member 117 for holding agglomerates such as falling Pt and Sn at the protruding portion. As described above, the second pipe 105 and the third pipe 106 are connected to the stirring tank 103, and the molten glass MG supplied from the clarification tank 102 through the second pipe 105 into the stirring tank 103 is The glass components are homogenized by stirring using the stirrer 107, and the homogenized molten glass MG is supplied from the stirring tank 103 to the molding apparatus 200 through the third pipe 106.
In FIG. 2 described above, only the agitation tank 103 and the agitator 107 are shown, but the detailed configuration is as shown in FIG.

  The periphery of the stirring tank 103 and the lid 110 covering the upper part of the stirring tank 103 is covered with a first refractory material 111. And it has the heating part (not shown) which consists of a heat generating body which heats the atmosphere (heating space 112) outside this 1st refractory material 111. That is, in the first embodiment, an indirect heating method is employed as a method for heating the stirring vessel 103. The heating space 112 heated by the heating means is further covered with a second refractory material (heat resistant member) 113. The first refractory material 111 and the second refractory material 113 are refractories such as refractory bricks, refractory heat insulating bricks, or fiber heat insulating materials.

The first refractory material 111 and the second refractory material 113 are refractories such as refractory bricks, refractory heat insulating bricks, or fiber-based heat insulating materials, and are heat resistant members. Further, by installing a heat insulating brick on the ceiling surface of the refractory brick 113, the temperature of the upper portion of the heating space 112 rises and the temperature of the rotating shaft 108 and the holding member 117 also rises. ₂ , SnO ₂ volatiles are prevented from aggregating on the surfaces of the rotating shaft 108 and the holding member 117 due to the reduction of the temperature difference of PtO ₂ and SnO ₂ volatiles. Here, the volatile matter is formed from components existing in the glass raw material or the stirring tank, and examples thereof include PtO ₂ , B ₂ O ₃ , and SnO ₂ .

  Further, the upper portion of the rotating shaft 108 passes through the lid 110 and the first refractory material 111 thereon, and further passes through the second refractory material 113 and is connected to a rotating means (not shown). ing. The rotating shaft 108 is built in the stirring tank 103 and is supported by a support member (not shown) provided in the vicinity of the lid 110 on the stirring tank 103 and the first refractory material 111 that rotatably supports the rotating shaft 108. ing. When the rotation means rotates the support member, the rotation shaft 108 supported by the support member rotates. A first gap (clearance) 115 is provided between the rotary shaft 108 and the lid 110 and the first refractory material 111 thereon, and the rotary shaft 108 and the second refractory material. A second gap (clearance) 116 is provided between the material 113.

Then, the rotating shaft 108, the lid 110, and the first projection of the rotating shaft 108, which is located above the first refractory material 111 through which the rotating shaft 108 penetrates, protrude from the lid 110 and the first refractory material 111. A holding member 117 having a size that substantially covers the first gap 115 existing between the one refractory material 111 is provided. For this reason, the holding member 117 is a shielding member that prevents agglomerates of volatiles dropped from the ceiling or the like of the second refractory material 113 from entering the molten glass MG through the first gap 115. is there.
In the first embodiment, the holding member 117 is provided on the protruding portion of the rotary shaft 108 located in the heating space 112 above the first refractory material 111.
In addition, as a material of the stirring tank 103 and the stirrer 107 (the rotating shaft 108 and the stirring blade 109) constituting the stirring device 120, a platinum group metal such as platinum or a platinum alloy is used, but the holding member 117 is also used. It is preferable to use the same platinum group metal.

  In the stirring process using the stirring device 120 described above, the molten glass MG supplied from the clarification tank 102 to the stirring tank 103 through the second pipe 105 is guided from above to below in the stirring tank 103. The molten glass MG that has been stirred by the stirrer 107 and whose glass components are homogenized is supplied from the stirring vessel 103 to the molding apparatus 200 through the third pipe 106. In addition, when the molten glass MG is passed through the stirring device 120 and stirred, the position of the surface of the molten glass MG slightly moves up and down, so the lid 110 covering the upper part of the stirring tank 103 and the surface of the molten glass MG The positional relationship between the stirring tank 103 and the pipe 105 is adjusted so as to have a gas phase space 114 having a certain width therebetween. Further, in the first embodiment, the molten glass MG supplied into the stirring tank 103 is configured to be guided from the upper side to the lower side of the stirring tank 103, but not limited thereto, the inside of the stirring tank 103 is configured. May be configured to be guided from below to above.

In such a stirring step, as described above, when the molten glass MG is passed and stirred, the surface level of the molten glass MG goes up and down, so that the gap between the lid 110 of the stirring vessel 103 and the surface of the molten glass MG is increased. A gas phase space 114 having a certain size is provided. Since the gas phase space 114 contains oxygen, and the stirring vessel 103 is heated at a high temperature, the platinum group metal (material of the stirring vessel 103 and the stirrer 107) in contact with the gas phase space 114 is volatilized. Volatile platinum group metal volatiles (hereinafter referred to as platinum volatiles) in the vapor phase space 114 or volatiles such as B ₂ O ₃ and SnO ₂ volatilized from molten glass (hereinafter referred to as tin volatiles). The contained gas flows upward through a gap 115 existing between the rotating shaft 108 of the stirrer 107 and the lid 110 of the stirring tank 103.

  In the first embodiment, since the indirect heating method of heating the atmosphere (heating space 112) outside the first refractory material 111 covering the periphery of the stirring tank 103 and the lid 110 of the stirring tank 103 is employed, the gas phase An atmospheric temperature difference occurs between the rotary shaft 108 in the space 114, the inner wall of the second refractory material 113, and the atmosphere in the stirring vessel 103. Therefore, volatile substances aggregate and adhere to the rotary shaft 108 and the inner wall of the second refractory material 113. In order to prevent agglomerates of volatile matter that have aggregated and adhered to the rotary shaft 108, the inner wall of the second refractory material 113, and the like to fall and enter the molten glass MG through the first gap 115, the first gap 115 is provided. A holding member 117 having a size that substantially covers is provided.

  The gas containing platinum volatile matter or volatile matter such as tin, which has flowed into the upper heating space 112 through the first gap 115, further exists in the gap 116 existing between the rotary shaft 108 and the second refractory material 113. It flows upward through. As described above, since the heating space 112 is heated, the decrease in the atmospheric temperature in the heating space 112 is small, but a gas containing volatile materials such as platinum volatile matter and tin is passed through the gap 116 and is upward. When the temperature of the holding member 117 provided on the rotary shaft 108 is lower than the dew point of the volatile matter, for example, platinum, tin, etc. contained in the atmosphere. The volatile matter is aggregated and attached on the surface of the holding member 117. It deposits when the vapor pressure of platinum exceeds the saturated vapor pressure. In this way, a part of the aggregate of the volatile matter such as platinum and tin that has aggregated and adhered to the surface of the holding member 117 may be detached from the aggregate and fall into the molten glass MG.

As shown in FIG. 3, since the lower end of the rotating shaft 108 is in the molten glass MG, the rotating shaft 108 is heated (heated) by the molten glass MG. Since the temperature of the molten glass MG is higher than the temperatures of the refractory material 111, the gas phase space 114, etc., the temperature of the rotating shaft 108 is highest at the lower end in contact with the molten glass MG, and away from the molten glass MG. It goes down as it goes to. The holding member 117 is attached to the protruding portion of the rotating shaft 108, and heat is transmitted from below the rotating shaft 108 to warm it. For this reason, the temperature T of the holding member 117 changes according to the distance L from the surface of the molten glass MG to the holding member 117. The temperature T of the holding member 117 depends not only on the distance L from the surface of the molten glass MG but also on the temperature of the gas phase space 114 and the temperature of the heating space 112. Since the temperature of the gas phase space 114 and the temperature of the heating space 112 also decrease as the distance from the surface of the molten glass MG decreases, the temperature T of the holding member 117 is determined from the surface of the molten glass MG for ease of explanation here. A description will be given assuming that it depends on the distance L. FIG. 4 is a diagram showing the relationship between the distance L from the surface of the molten glass MG to the holding member 117 and the temperature T of the holding member 117. The temperature of the protrusion of the rotating shaft 108 decreases as the distance from the molten glass MG increases. Therefore, as shown in FIG. 4, the temperature T of the holding member 117 decreases as the position of the holding member 117 moves away from the surface of the molten glass MG, that is, as the distance L increases. When the temperature T of the holding member 117 is lowered, the temperature of the heating space 112 around the holding member 117 is also lowered, so that the saturated vapor pressure of the volatile matter is lowered. Then, the volatiles aggregate on the surface (mainly the bottom surface) of the holding member 117, the volatile aggregates adhere to the surface of the holding member 117, and a part of the aggregate may fall and enter the molten glass MG. is there. For this reason, the distance L from the surface of the molten glass MG to the holding member 117 is shortened so that the temperature T of the holding member 117 does not decrease, thereby suppressing aggregation of platinum or the like on the surface of the holding member 117. In addition, it is possible to prevent foreign matters from adhering to the surface of the holding member 117.
Moreover, the temperature of the protrusion part of the rotating shaft 108 falls, so that it leaves | separates from the molten glass accommodated in the stirring tank 103. FIG. At this time, the holding member 117 is preferably provided at a position on the rotary shaft 108 where the temperature of the holding member 117 is higher than the dew point of the volatile matter.

  On the other hand, the molar mass concentration of the platinum volatiles decreases as the distance from the surface of the molten glass MG increases. This is because the gas containing platinum volatiles, tin, and other volatiles in the gas phase space 114 flows upward through a gap 115 existing between the rotating shaft 108 of the stirrer 107 and the lid 110 of the stirring tank 103. It is because it spreads by going. Since the molar mass is proportional to the drop in vapor pressure according to Raoul's law, the vapor pressure of the volatile matter is higher as it is closer to the surface of the molten glass MG and lower as it is farther from the surface of the molten glass MG. In recent years, since the temperature of the molten glass MG flowing into the stirring vessel 103 has increased, the mass molar concentration and vapor pressure of volatiles such as platinum volatiles or tin have increased. For this reason, the closer the position of the holding member 117 provided on the rotating shaft 108 is to the surface of the molten glass MG, the more easily volatile substances such as platinum volatiles or tin aggregate on the surface of the holding member 117. Therefore, by providing the holding member 117 at a position away from the surface of the molten glass MG, the volatiles are prevented from aggregating on the surface of the holding member 117, and the volatile aggregates adhere to the surface of the holding member 117. Can be prevented.

  As described above, the position where the holding member 117 is provided needs to be determined by the relationship between the saturation vapor pressure of volatile matter such as platinum volatile matter or tin (hereinafter sometimes simply referred to as volatile matter) and the vapor pressure of the volatile matter. is there. FIG. 5 is a diagram showing the relationship between the distance L from the surface of the molten glass MG to the holding member 117 and the saturated vapor pressure and vapor pressure of the volatile matter. The saturated vapor pressure of the volatile matter changes depending on the temperatures of the gas phase space 114 and the heating space 112, but the temperatures of the gas phase space 114 and the heating space 112 become lower as the distance from the surface of the molten glass MG decreases. As the distance L from the surface to the holding member 117 is longer, the distance is lower. For this reason, as shown by the solid line in the figure, the saturated vapor pressure of the volatile matter decreases as the distance L increases. Further, as described above, the vapor pressure of the volatile matter becomes smaller as the distance from the surface of the molten glass MG becomes smaller, and as shown by the broken line in FIG. . Here, when the vapor pressure of the volatile matter is smaller than the saturated vapor pressure of the volatile matter, the aggregation of the volatile matter on the surface of the holding member 117 can be suppressed. For this reason, the holding member 117 is provided at a position where the vapor pressure of the volatile matter is smaller than the saturated vapor pressure of the volatile matter. Volatile substances refer to volatile substances such as platinum group metal volatiles or tin. In addition, the holding member 117 is provided at a position on the protruding portion of the rotating shaft 108 that is equal to or higher than the temperature at which the volatiles aggregate. As shown in FIG. 5, the distance at which the vapor pressure of the volatile matter becomes smaller than the saturated vapor pressure of the volatile matter is from the distance L1 to the distance L2, and thus the holding member is within the range of the distance L1 to the distance L2 from the surface of the molten glass MG. By providing 117, it is possible to suppress volatiles from aggregating on the surface of the holding member 117. That is, the vapor pressure of the volatile matter that decreases as the volatile matter such as platinum volatile matter or tin flows upward through the first gap (clearance) 115 between the container cover 110 and the rotating shaft 108 is from the molten glass MG. It is preferable that the holding member 117 is provided at a position that is smaller than the saturated vapor pressure of the volatile matter that decreases as it moves away upward. For example, the position on the protruding portion of the rotating shaft 108 where the temperature T of the holding member 117 is 1310 ° C. to 1405 ° C., the position on the rotating shaft 108 where the temperature of the heating space 112 and the gas phase space 114 is 1310 ° C. to 1405 ° C. Alternatively, the holding member 117 is provided at a position on the protruding portion of the rotating shaft 108 where the temperature of the protruding portion of the rotating shaft 108 is 1310 ° C. to 1405 ° C. In this case, the position where the temperature T of the holding member 117 is 1310 ° C. is the distance L2, and the position where the temperature T of the holding member 117 is 1405 ° C. is the distance L1. By providing the holding member 117 at a position where the distances L1 and L2 are within this temperature range, aggregation of volatile substances on the surface of the holding member 117 can be suppressed.

  When the vapor pressure of the volatile material becomes smaller than the saturated vapor pressure of the volatile material, that is, when the vapor pressure difference obtained by subtracting the vapor pressure of the volatile material from the saturated vapor pressure of the volatile material becomes larger than 0, the volatilization occurs on the surface of the holding member 117. Although it is possible to suppress the agglomeration of the material, the saturated vapor pressure of the volatile matter and the vapor pressure of the volatile matter slightly change due to the temperature distribution in the vertical direction generated by the air flow upward from the surface of the molten glass MG. . For this reason, when the holding member 117 is in the vicinity of the distance L <b> 1 or the distance L <b> 2, volatile substances may aggregate on the surface of the holding member 117. In order to prevent the volatiles from aggregating on the surface of the holding member 117, the vapor pressure of the volatiles is saturated with the volatiles even when the temperature distribution in the vertical direction of the heating space 112 is changed by the air flow. It must be greater than the pressure. For example, when the amount of change in the vapor pressure of a volatile substance at a predetermined distance (positioned at the same height) is 0 to P1, the vapor pressure difference is held at a position where it is larger than P1, which is the maximum amount of change in vapor pressure. By providing the member 117, it is possible to prevent volatile substances from aggregating on the surface of the holding member 117. FIG. 6 shows the relationship between the distance L from the surface of the molten glass MG to the holding member 117 and the vapor pressure difference obtained by subtracting the vapor pressure of the volatile matter from the saturated vapor pressure of the volatile matter. As shown in the figure, the distance L from the surface of the molten glass MG to the holding member 117 corresponding to the range where the vapor pressure difference is larger than P1 is the distance L3 to the distance L4. For this reason, by providing the holding member 117 in the range from the distance L3 to the distance L4, it is possible to prevent volatile substances from aggregating on the surface of the holding member 117.

  The distances L1 to L2 from the surface of the molten glass MG that can prevent the volatiles from aggregating on the surface of the holding member 117 to the holding member 117, and the distance L4 from the distance L3 are the temperature of the molten glass MG and the first gap. It changes depending on the size of 115, the temperature of the heating space 112 heated by the heating means, the temperature of the gas phase space 114, the material of the holding member 117 and the rotating shaft 108, etc., and can be arbitrarily changed.

According to the first embodiment, in the stirring step of stirring the molten glass with the stirring device, the vapor pressure of the volatiles is adjusted so that the volatiles such as platinum volatiles or tin do not aggregate on the holding member 117. A holding member 117 is provided at a position lower than the saturated vapor pressure. For this reason, it can suppress that a volatile substance aggregates on the surface of the holding member 117, and can prevent some aggregates, such as aggregated platinum, entering molten glass MG as a foreign material.
Note that it is preferable to adjust the atmosphere of the heating space 112 so as to suppress aggregation of platinum volatiles or volatiles such as tin on the holding member 117. In this case, the heating space 112 is provided with a plurality of heating portions, which are heating elements installed outside the stirring tank (stirring vessel) 103, and platinum vapor around the protruding portion of the rotating shaft 108 in the heating space 112. The pressure is set to 0.3 Pa to 5 Pa, and the temperature of the protruding portion of the rotating shaft 108 is set to a temperature equal to or higher than a temperature at which the platinum vapor pressure becomes a saturated vapor pressure of the platinum volatiles. As described above, it is preferable that the protruding portion of the rotating shaft 108 is heated by the heating portion. This point will be described in the second embodiment.

(Embodiment 2)
FIG. 7 is a side view showing an example of the stirring device 120 of the second embodiment. The stirring device 120 mainly includes a stirring container 121, a container cover 121a, a stirrer 122, a heat-resistant tank 131, and a plurality of heating elements 132. The stirring vessel 121 and the stirrer 122 are made of a material containing a platinum group metal such as platinum or a platinum alloy. FIG. 8 is a top view of only the stirring container 121 and the stirrer 122 of the stirring device 120. In FIG. 8, a shielding member 125b described later is omitted.

  The stirring container 121 is a cylindrical container. The stirring vessel 121 has an upstream side conduit 123 attached to the lower side surface and a downstream side conduit 124 attached to the upper side surface. The upstream conduit 123 corresponds to the second pipe 105 shown in FIG. 2, and the downstream conduit 124 corresponds to the third pipe 106 shown in FIG. As shown in FIG. 8, the upstream side conduit 123 is located on the opposite side of the downstream side conduit 124 with the stirring vessel 121 interposed therebetween. In the stirring device 120, the molten glass MG flows into the stirring vessel 121 from the upstream side conduit 123, and is stirred by the stirrer 122 while being guided upward from below in the stirring vessel 121, and from the inside of the stirring vessel 121 to the downstream side conduit 124. Spill to The horizontal cross-sectional shape of the stirring vessel 121 may be an ellipse.

  The container cover 121a is provided above the stirring container 121. The container cover 121 a is in contact with the upper end surface of the stirring container 121 and corresponds to the lid of the stirring container 121. The container cover 121 a prevents foreign matter dropped from above the stirring container 121 from being mixed into the molten glass G in the stirring container 121. The container cover 121a suppresses the temperature of the molten glass MG in the stirring container 121 from decreasing.

  An upper opening 121b is formed in the container cover 121a. The upper opening 121b is a hole through which a rotation shaft 125 described later passes. A discharge port 121 c is formed on the bottom surface of the stirring vessel 121. A discharge pipe 128 extending in the vertical direction is connected to the discharge port 121c. The discharge pipe 128 is made of a material containing a platinum group metal such as platinum or a platinum alloy. The discharge pipe 128 is a pipe for discharging the molten glass MG in the stirring vessel 121 from the stirring vessel 121.

  The stirrer 122 is arrange | positioned in the stirring container 121, and is used in order to stir the molten glass MG. The stirrer 122 includes a rotating shaft 125 and a stirring blade (blade) 126 attached to the rotating shaft 125. The rotation shaft 125 has a protruding portion that protrudes from the container cover 121a to above the container cover 121a. The stirrer 122 is made of a material containing a platinum group metal, and more specifically, made of reinforced platinum. Reinforced platinum is a material rolled by dispersing an oxide such as zirconia in platinum or a platinum alloy. Reinforced platinum has a layered platinum grain boundary structure, and has higher creep strength and tensile strength at higher temperatures than platinum or platinum alloys. Therefore, reinforced platinum is a suitable material for the stirrer 122 in contact with the high-temperature molten glass MG.

  The stirrer 122 includes a cylindrical rotary shaft 125 disposed along the vertical direction, and a stirring blade 126 connected to the outer peripheral surface of the rotary shaft 125. The rotary shaft 125 rotates in the direction of the arrow in FIG. 8 around a center line L (see FIG. 7) that connects the center of the cylindrical upper surface and the center of the lower surface. The rotating shaft 125 is a tubular member having a hollow inside. The stirring blade 126 is formed of a tubular member that is thinner than the rotating shaft 125. The stirring blade 126 is composed of a plurality of support pipes 126a penetrating the rotating shaft 125 and a frame pipe 126b connecting both ends of the support pipe 126a. As shown in FIG. 8, when the stirring device 120 is viewed from the axial direction of the center line L, the plurality of support tubes 126a and the frame tube 126b overlap each other. The support tube 126a and the frame tube 126b are attached to the outer peripheral surface of the rotating shaft 125 by welding. The support tube 126a and the frame tube 126b may be an integral member.

  The heat-resistant tank 131 is installed in the external space of the stirring vessel 121 and forms a heating space 133. The heating space 133 is an internal space of the heat-resistant tank 131 in which the stirring vessel 121 is installed in the heating space 133. The heat-resistant tank 131 is comprised from heat-resistant members, such as a fireproof heat insulation brick and an alumina cement. The discharge pipe 128 penetrates the bottom of the heat-resistant tank 131 in the vertical direction. Although not shown, below the heat-resistant tank 131, the discharge pipe 128 is heated while being covered with a heat-resistant member. The heating space 133 includes an upper heating space 133a and a lower heating space 133b. The upper heating space 133a is a space above the intermediate height position of the heating space 133 in the vertical direction. The lower heating space 133b is a space below the intermediate height position of the heating space 133 in the vertical direction. In FIG. 7, the intermediate height position of the heating space 133 is indicated by a broken line.

  The rotating shaft 125 penetrates the upper opening 121b along the vertical direction in a state where an annular gap (clearance) 121d is formed between the rotating shaft 125 and the container cover 121a. The rotating shaft 125 has a protruding portion 125a protruding above the container cover 121a. The protrusion 125 a is a part of the rotating shaft 125 and is located in the heating space 133. The rotating shaft 125 passes through the ceiling surface of the heat-resistant tank 131 above the projecting portion 125a, and is connected to a motor (not shown) above the heat-resistant tank 131. The motor is a drive source that rotates the rotary shaft 125.

A cylindrical shielding member 125 b is attached to the protrusion 125 a of the rotating shaft 125. The shielding member 125b is the same as the holding member 117 shown in FIG. As shown in FIG. 8, the shielding member 125b covers the annular gap (clearance) 121d when viewed from above in the vertical direction. The shielding member 125b is a member for preventing foreign matter dropped from the ceiling or the like of the heat-resistant tank 131 from passing through the annular gap 121d and entering the molten glass MG.
The installation position of the shielding member 125b on the protrusion 125a is also a position that satisfies the same conditions as those of the holding member 117 of the first embodiment.
That is, the temperature of the protrusion 125a decreases as the distance from the molten glass MG increases, and the shielding member 125b is provided at a position on the protrusion 125a where the temperature of the shielding member 125b is higher than the dew point of the volatile matter. In addition, the volatile matter pressure, which decreases as the volatile matter flows upward through the annular gap (clearance) 121d between the container cover 121 and the rotary shaft 125, decreases as it moves away from the molten glass MG. The shielding member 125b is provided at a position smaller than the saturated vapor pressure.

  The plurality of heating elements 132 are installed in the heating space 133. The heating element 132 is a rod-like member that generates heat when energized and is made of silicon carbide or the like. The heating element 132 is arranged such that its longitudinal direction is along the horizontal direction. The output of each heating element 132 is individually adjusted. The heating element 132 heats the stirring vessel 121 and the stirrer 122 by radiation, and suppresses a decrease in the temperature of the molten glass MG in contact with the stirring vessel 121 and the stirrer 122. Further, as will be described later, the heating element 132 selectively heats the protruding portion 125a of the rotary shaft 125.

  In the second embodiment, as shown in FIG. 7, twelve heating elements 132 are installed in the heating space 133. Six heating elements 132 are installed in the upper heating space 133a, and six heating elements 132 are installed in the lower heating space 133b. Five heating elements 132 are installed above the upstream conduit 123, and one heating element 132 is installed below the upstream conduit 123. One heating element 132 is installed above the downstream conduit 124, and five heating elements 132 are installed below the downstream conduit 124. The five heating elements 132 installed above the upstream conduit 123 are installed at different height positions. The five heating elements 132 installed below the downstream conduit 124 are installed at different height positions.

  FIG. 9 is a diagram illustrating the flow of the molten glass MG stirred by the stirring device 120. The arrow shown by FIG. 9 represents the direction of the flow of molten glass MG. Inside the stirring vessel 121, the molten glass MG flows from the upstream side conduit 123. When the stirring device 120 is viewed from above, the stirrer 122 rotates around the center line L of the rotating shaft 125. The rotation direction of the stirrer 122 is determined based on the positional relationship between the upstream conduit 123 and the downstream conduit 124, and may be either clockwise or counterclockwise. In the second embodiment, the stirrer 122 rotates counterclockwise. Inside the stirring vessel 121, the molten glass MG is stirred by the stirrer 122 while being gradually guided from below to above. The stirred molten glass MG flows out from the inside of the stirring vessel 121 to the downstream conduit 124.

Moreover, when the stirring process of the molten glass MG by the stirring apparatus 120 is performed for a long time, the glass foreign material which has a glass component different from the molten glass MG will be accumulate | stored gradually in the bottom part of the stirring container 121. FIG. The glass foreign material is a molten glass mainly composed of components having a higher specific gravity than other components among the glass components contained in the molten glass MG. Since the glass foreign matter causes the striae of the glass substrate manufactured by the glass manufacturing apparatus 100, it is discharged outside the stirring vessel 121 through the discharge pipe 128.
In addition, the temperature of the molten glass MG stirred by the stirring device 120 is suitable when it has a viscosity of 10 ^2.5 dPa · s and is 1450 ° C. to 1750 ° C., and is 1500 ° C. to 1750 ° C. It is more suitable in some cases, and it is more suitable in the case of 1530 ° C to 1750 ° C.

  Next, the selective heating of the protrusion 125a of the rotating shaft 125 by the heating element 132 installed in the heating space 133 will be described. In the second embodiment, the heating element 132 is set so that the platinum vapor pressure in the heating space 133 around the protrusion 125a is 0.3 Pa to 5 Pa and the temperature of the protrusion 125a is equal to or higher than the temperature at which the platinum vapor pressure becomes the saturated vapor pressure. Thus, the protrusion 125a is selectively heated. Here, the heating space 133 around the protrusion 125a is a space above the annular gap 121d.

  Further, the height positions and outputs of at least some of the heating elements 132 are determined before using the stirring device 120 so that the protrusion 125a is selectively heated by the heating elements 132 as described above. For example, the height position and output of the heating element 132 installed in the vicinity of the protrusion 125 a are adjusted in advance so that the protrusion 125 a is efficiently heated by the radiant heat from the heating element 132. Here, the heating elements 132 installed in the vicinity of the protruding portion 125a are, for example, six heating elements 132 arranged in the upper heating space 133a. As another example, the total output of the six heating elements 132 arranged in the upper heating space 133a is larger than the total output of the six heating elements 132 arranged in the lower heating space 133b. In addition, the output of the heating element 132 may be adjusted.

  In the manufacturing method of the glass substrate of the second embodiment, the protruding portion 125a of the rotating shaft 125 is equal to or higher than the temperature at which the platinum vapor pressure becomes the saturated vapor pressure by the heating unit 132 installed in the heating space 143 outside the stirring vessel 121. Is selectively heated. The protrusion 125a of the rotating shaft 125 exists in the heating space 133 and does not contact the high temperature molten glass MG in the stirring vessel 121. Therefore, the protruding portion 125a is a portion where the temperature is likely to decrease due to heat radiation as compared with other portions of the rotating shaft 125.

  In the second embodiment, the protrusion 125a of the rotating shaft 125 is selectively heated by the heating unit 132, so that volatiles such as tin volatilized from the molten glass MG and platinum volatilized from the stirring vessel 121 or the stirrer 122 are used. Volatile substances can be prevented from aggregating in the heating space 133 in the vicinity of the protruding portion 125a and adhering to the surface of the protruding portion 125a and the shielding member 125b. Of the various volatiles, platinum volatiles are the components with the highest temperature when showing a certain vapor pressure value. In other words, when comparing the saturated vapor pressure of various volatile components at a certain temperature, platinum volatiles are the volatile components that exhibit the lowest saturated vapor pressure. Therefore, in order to prevent platinum volatiles from aggregating and precipitating, the protrusion 125a is heated above the temperature at which the platinum vapor pressure becomes the saturation vapor pressure of the platinum volatiles. Aggregation of objects is suppressed. As a result, the volatile matter that aggregates and adheres to the protrusion 125a and the shielding member 125b peels off from the protrusion 125a and the shielding member 125b, passes through the annular gap 121d, and falls into the molten glass MG in the stirring vessel 121. Therefore, foreign matters derived from volatile substances are prevented from being mixed into the molten glass MG.

Therefore, the manufacturing method of the glass substrate which concerns on Embodiment 2 reduces the quantity of the volatile matter which aggregates around the protrusion part 125a of the rotating shaft 125 of the stirring apparatus 120, and suppresses that a foreign material mixes into molten glass MG. Foreign substances remaining in the molded glass substrate can be reduced. The glass substrate manufactured from the molten glass MG mixed with foreign substances is likely to cause striae. Therefore, the molten glass MG can be homogeneously agitated in the agitator 120 by suppressing foreign matter from being mixed into the molten glass MG in the agitation vessel 121. Thereby, generation | occurrence | production of striae is suppressed and a high quality glass product can be obtained.
In Embodiment 2, the strain point of the glass substrate is 680 ° C. or higher, preferably 700 ° C. or higher. Since the volatilization amount of the volatile component of the molten glass MG tends to increase as the strain point of the glass substrate increases, the effect of suppressing foreign matters from entering the molten glass MG becomes remarkable.

Modification A:
In the second embodiment, the cylindrical shielding member 125b is attached to the protruding portion 125a of the rotating shaft 125, but the shielding member 125b may not be attached to the protruding portion 125a. Also in this case, the protrusion 125a is selectively heated by the heating unit 132, thereby reducing the amount of volatiles that aggregate in the vicinity of the protrusion 125a and reducing foreign matters remaining in the molded glass substrate. be able to.

Modification B:
In the second embodiment, the height position and output of the heating element 132 are determined before the stirring device 120 is used so that the protrusion 125 a is selectively heated by the heating element 132. Here, the height position and output of the heating element 132 may be determined by computer simulation. For example, the temperature of the heating space 133 around the protrusion 125a may be calculated by a thermal fluid analysis simulation, and the height position and output of the heating element 132 may be determined.

Modification C:
In the second embodiment, inside the stirring vessel 121, the molten glass MG is stirred by the stirrer 122 while being gradually guided upward from below. However, the molten glass MG may be stirred by the stirrer 122 while being gradually guided downward from above as in the first embodiment.

Modification D:
In Embodiment 1 and Embodiment 2, the stirring device 120 is installed between the clarification tank 102 and the molding apparatus 200, and stirs the molten glass MG clarified in the clarification tank 102. However, the stirring device 120 of the first embodiment and the second embodiment may be installed between the melting tank 101 and the clarification tank 102. In this case, the stirring device 120 stirs the molten glass MG generated in the melting tank 101 and supplies the homogenized molten glass MG to the clarification tank 102. In addition, the two stirring apparatuses 120 may be installed between the melting tank 101 and the clarification tank 102, and between the clarification tank 102 and the shaping | molding apparatus 200. FIG.

(Example)
A thermal fluid analysis simulation for calculating the temperature distribution inside the stirring device 120 was performed using a model having the same configuration as the stirring device 120 in the second embodiment. As shown in FIG. 7, the flow velocity distribution of the molten glass MG at the moment when the main surface of the stirring blade 126 of the stirrer 122 is parallel to the flow direction of the molten glass MG in the stirring vessel 121 is represented by the flow of the molten glass MG. Was calculated under the condition that is a laminar flow. Next, various parameters set at the time of analysis will be described. The same reference numerals are used for the same components as those in the second embodiment.
(A) Inflow temperature of molten glass MG: 1460 ° C.
(B) Inflow of molten glass MG: 18 (t / day),
(C) Emissivity of heat-resistant tank 131 and stirring device 120: 0.9,
(D) Heat transfer coefficient of convection heat transfer in the heat-resistant tank 131: 10 W / m ² K
(E) Output of heating element 132: 2.0 kW to 8.0 kW
Under the above parameters, the temperature distribution inside the stirring device 120 was calculated for the following seven models.

(Model 1) All twelve heating elements 132 shown in FIG. 7 were used. The output of the heating element 132 was set to 2 kW.
(Model 2) In the configuration of Model 1, the height positions of the five heating elements 132 installed above the upstream side conduit 133 were set 60 mm above the case of Model 1.
(Model 3) In the configuration of Model 2, six of the twelve heating elements 132 were used. The six heating elements 132 used are the four heating elements 132 excluding the heating element 132 located at the lowermost position among the five heating elements 132 installed above the upstream conduit 133, and the downstream side. The heating element 132 is located at the uppermost position among the one heating element 132 installed above the conduit 134 and the five heating elements 132 installed below the downstream conduit 124. In FIG. 10, the six heating elements 132 used are hatched. The output of the heating element 132 was set to 2 kW.
(Model 4) Of the twelve heating elements 132, six heating elements 132 were used. The six heating elements 132 used are the same as in the model 3, but the positions of the heating elements 132 are the same as in the model 1. The output of the heating element 132 was set to 2 kW.
(Model 5) In the configuration of Model 4, the output of the heating element 132 was set to 4 kW.
(Model 6) In the configuration of Model 4, the output of the heating element 132 was set to 6 kW.
(Model 7) In the configuration of Model 4, the output of the heating element 132 was set to 8 kW.

  In order to confirm the effect that the protrusion 125a is selectively heated by the heating element 132, the first temperature at a point 20 mm above the shielding member 125b of the protrusion 125a and 20 mm below the shielding member 125b of the protrusion 125a. The results of the analysis of the second temperature at this point were compared. Next, the examination result will be described.

In the model 3, compared with the model 1, the first temperature and the second temperature showed higher values. That is, it was confirmed that the projecting portion 125a can be selectively heated by generating heat from the heating elements 132 (the six heating elements 132 hatched in FIG. 10) installed above in the heating space 133.
Moreover, regarding the models 4 to 7, the higher the output of the heating element 132, the higher the first temperature and the second temperature. The rate of change of the first temperature and the second temperature with respect to the output of the heating element 132 was 13.5 ° C./kW to 15.9 ° C./kW. That is, it was confirmed that the protrusion 125a can be selectively heated by increasing the output of the heating element 132.

  As mentioned above, although the manufacturing method and stirring apparatus of the glass substrate of this invention were demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, even if various improvement and a change are carried out. Of course it is good.

DESCRIPTION OF SYMBOLS 100 Melting apparatus 101 Melting tank 102 Clarification tank 103 Agitation tank 104 1st piping 105 2nd piping 106 3rd piping 107 Agitation machine 108,125 Rotating shaft 109,126 Stirring blade 110 Lid 111 1st refractory material 112,133 Heating space 113 Second refractory material 114 Gas phase space 115, 116 Gap 117 Holding member 120 Stirrer 121 Stirrer 121a Container cover 121b Upper opening 121c Discharge port 121d Annular gap 122 Stirrer 123 Upstream conduit 124 Downstream conduit 125 Rotating shaft 125a Projection 125b Shield member 126a Support tube 126b Frame tube 128 Discharge tube 131 Heat-resistant member 132 Heating element (heating unit)
133 Heating space 133a Upper heating space 133b Lower heating space 200 Molding device 210 Molded body 300 Cutting device

Claims (7)

A glass substrate manufacturing method comprising a stirring step of stirring a molten glass produced by melting a glass raw material with a stirrer, and a forming step of forming the molten glass into a plate shape,
The stirring device
A stirring vessel made of a material containing a platinum group metal and containing molten glass;
A container cover provided above the stirring container;
A shaft made of a material containing a platinum group metal and having a protrusion protruding from the container cover to the upper side of the container cover; and a blade made of a material containing a platinum group metal attached to the shaft. A stirrer for stirring the molten glass in the stirring vessel;
A heat-resistant member that is installed outside the stirring vessel and forms a heating space in which the stirring vessel is installed inside;
A plurality of heating units installed at locations outside the stirring vessel in the heating space;
Holding the agglomerates formed by agglomerating the volatiles containing the platinum group metal or the glass raw material that volatilizes, and holding members provided on the protrusions,
The holding member is provided at a position that is equal to or higher than the temperature at which the volatiles aggregate in the protrusion in the heating space .
A region is formed in which the vapor pressure of volatiles that decreases as it flows upward through the clearance between the container cover and the shaft is smaller than the saturated vapor pressure of volatiles that decreases as it moves upward away from the molten glass. As described above, the glass substrate is characterized in that the holding member is provided at a position in the region by adjusting the temperature distribution of the protruding portion, the temperature of which decreases as it moves away from the molten glass and moves upward. Manufacturing method. The temperature of the protruding portion decreases as the distance from the molten glass increases.
The method of manufacturing a glass substrate according to claim 1, wherein the holding member is provided at a position on the protruding portion of the shaft where a temperature of the holding member is higher than a dew point of the volatile matter. In the stirring step, the heating space is set such that a platinum vapor pressure in the heating space around the protrusion is 0.3 Pa to 5 Pa, and a temperature of the protrusion is equal to or higher than a temperature at which the platinum vapor pressure becomes a saturated vapor pressure. The manufacturing method of the glass substrate of Claim 1 or 2 with which the said protrusion part is heated by a part. The heating space is
An upper heating space above a middle height position of the heating space in the vertical direction;
A lower heating space below the intermediate height position,
The total output of the heating unit arranged in the upper heating space is larger than the total output of the heating unit arranged in the lower heating space,
The said holding member is a manufacturing method of the glass substrate of any one of Claims 1-3 provided in the said upper heating space . The strain point of the said glass substrate is a manufacturing method of the glass substrate of any one of Claims 1-4 which is 680 degreeC or more. A stirring device for stirring molten glass produced by melting glass raw materials,
A stirring vessel made of a material containing a platinum group metal and containing molten glass;
A container cover provided above the stirring container;
A shaft made of a material containing a platinum group metal and having a protrusion protruding from the container cover to the upper side of the container cover; and a blade made of a material containing a platinum group metal attached to the shaft. A stirrer for stirring the molten glass in the stirring vessel;
A heat-resistant member that is installed outside the stirring vessel and forms a heating space in which the stirring vessel is installed inside;
A plurality of heating units installed at locations outside the stirring vessel in the heating space;
Holding the agglomerates formed by agglomeration of the platinum group metal or the glass raw material that volatilizes, and holding members provided on the protrusions,
The holding member is provided at a position that is equal to or higher than the temperature at which the volatiles aggregate in the protrusion in the heating space .
A region is formed in which the vapor pressure of volatiles that decreases as it flows upward through the clearance between the container cover and the shaft is smaller than the saturated vapor pressure of volatiles that decreases as it moves upward away from the molten glass. As described above, the temperature distribution of the protruding portion, the temperature of which decreases as it goes away from the molten glass and moves upward, is adjusted by heating, and the holding member is provided at a position in the region. . The stirrer according to claim 6, wherein the platinum vapor pressure in the heating space around the protrusion is 0.3 Pa to 5 Pa .

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