KR20120138838A - Glass substrate production method - Google Patents

Abstract

PURPOSE: A manufacturing method of glass substrates is provided to maintain the viscosity or convection of molten glasses by controlling joule heat based on the resistivity. CONSTITUTION: A manufacturing method of glass substrates comprises the following step: manufacturing molten glass by melting the raw material of the glass. The dissolution processing comprises the following steps: generating Joule heating by spilling current to the molten glass by arranging the molten glass between a pair of electrodes(114) and applying the voltage; calculating resistivity of the molten glass by measuring the current and voltage value; and controlling the Joule heating based on the calculated resistivity. The pair of electrodes is used as pairs. In each pair of the electrodes, the domain in which current flows is set up. In the resistivity calculation step, the resistivity is calculated from each domain. In the Joule heat modulating step, the Joule heat is controlled at each domain. [Reference numerals] (116) Control unit; (118) Computer

Description

Glass substrate manufacturing method {GLASS SUBSTRATE PRODUCTION METHOD}

The present invention relates to a method for producing a glass substrate.

Glass substrates used for flat panel displays (hereinafter referred to as FPDs), such as liquid crystal displays and plasma displays, have a thickness of, for example, 0.5 to 0.7 mm and a size of 300 x 400 mm to 2850 x 3050 mm.

The overflow down draw method is known as a manufacturing method of the glass substrate for FPD. In the overflow down draw method, in the forming furnace, the sheet glass is molded from the molten glass by overflowing the molten glass from the upper part of the molded body of the molten glass, and the molded sheet glass is slowly cooled and cut. Thereafter, the cut sheet glass is further cut to a predetermined size in accordance with the specification of the customer, washed, polished in one side, and shipped as a glass substrate for FDP.

Of the glass substrates for FPD, in particular, the glass substrates for liquid crystal display devices have a semiconductor element formed on the surface thereof, and therefore it is preferable that the glass substrates for liquid crystal display devices contain a small amount of alkali metal components that do not contain at all or do not affect the semiconductor elements or the like. Do.

In addition, the presence of bubbles in the glass substrate causes display defects. Therefore, the glass substrate with bubbles cannot be used as a glass substrate for FPD. For this reason, it is calculated | required that a bubble does not remain in a glass substrate.

In addition, when a glass composition nonuniformity (a glass composition is not uniform) exists in a glass substrate, the stripe-shaped defect called a stiffness arises, for example. This stria forms fine surface irregularities on the surface of the molten glass at the time of molding from the difference in the viscosity of the molten glass due to the heterogeneity of the glass composition, and the surface irregularities also remain on the glass substrate. For this reason, when this glass substrate is incorporated into a liquid crystal panel as a glass substrate for liquid crystal panels, an error may arise in a cell gap or it may cause display nonuniformity. For this reason, it is necessary to prevent the nonuniformity of glass composition, such as a stria, from occurring at the manufacturing stage of a glass substrate.

When manufacturing such a glass substrate, the electricity supply heating with respect to molten glass is performed conventionally.

As an example of such energization heating, the high frequency energization heating of the glass melting furnace using a some electrode pair is known. For example, Japanese Patent Application Laid-Open No. 04-367519 discloses a technique in which each electrode pair is connected to a separate power source, and each power source is individually controlled, so that a plurality of pairs of electrodes are controlled for each electrode pair. It is. In the dissolution tank using such energization heating, in order to make the viscosity and convection of a molten glass into a desired state, as described in Unexamined-Japanese-Patent No. 03-103328, for example, conventionally, the melting glass is made through a thermocouple. The temperature was measured.

[Patent Literature]

Patent Document 1: Japanese Patent Application Laid-Open No. 04-367519

Patent Document 2: Japanese Patent Application Laid-open No. 03-103328

Since a thermocouple is exposed to high temperature in a melting tank, for example, it may deteriorate in a comparatively short time, and an accurate temperature may not be measured. Moreover, since the location which can install a thermocouple is limited by the structure of the apparatus which melt | dissolves a glass raw material, the location which can measure temperature with a thermocouple is limited.

Therefore, this invention solves the said subject in the electricity supply heating of molten glass, and provides the manufacturing method of the glass substrate which can maintain the viscosity and convection of molten glass in a desired state.

The manufacturing method of the glass substrate which is one aspect of this invention includes the melting process which melt | dissolves the raw material of glass and produces | generates molten glass. In the melting step, the molten glass is disposed between a pair of electrodes, a voltage is applied, a step of passing a current through the molten glass to generate joule heat, and the value of the current and the voltage are measured to measure the molten glass. And a step of controlling the Joule heat based on the calculated specific resistance.

The process of controlling said joule heat may include the following process.

(1) When the viscosity and convection of the molten glass are in a desired state, the specific resistance of the molten glass is calculated by measuring the value of the current and the value of the voltage, and the calculated specific resistance is set as the target value of the specific resistance. fair.

(2) A step of comparing the calculated specific resistance with a target value of the specific resistance.

(3) A step of holding or increasing the value of the current so that the difference between the calculated specific resistance and the target value of the specific resistance becomes a value within a predetermined range.

In the process of said (1), you may measure the temperature of the said molten glass using temperature measuring means, such as a thermocouple, and may make the viscosity and convection of a molten glass into a desired state.

By calculating the value of the specific resistance of the molten glass and controlling the Joule heat generated in the molten glass based on the value of the specific resistance, the viscosity and convection of the molten glass can be maintained in a desired state, and a conventional temperature measuring means such as a thermocouple can be used. The problem of using can be solved.

1 is a diagram illustrating an example of a process of a method of manufacturing a glass substrate of the present embodiment.
It is sectional drawing which shows typically an example of the apparatus which performs the process from melt | dissolution to cutting | disconnection.
3 is a perspective view illustrating an example of a dissolution tank used in a dissolution step.
4 is a plan view illustrating the introduction of glass raw materials in a dissolution tank.
5A and 5B are explanatory diagrams of regions in which current flows between respective electrode pairs.
FIG. 6 is a diagram illustrating an example of a process of controlling Joule's heat by calculating a specific resistance.
It is a figure which shows an example of the process of controlling a joule heat by calculating temperature from a specific resistance.
It is typical sectional drawing explaining the convection of the molten glass inside a melting tank.
It is a figure explaining the convection of the molten glass in the conventional dissolution tank.

Hereinafter, the manufacturing method of the glass substrate of this embodiment is demonstrated. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the process of the manufacturing method of the glass substrate of this invention.

The glass substrate manufacturing method includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a molding step (ST5), a slow cooling step (ST6), and a cutting process. It mainly has a process (ST7). In addition, a plurality of glass substrates having a grinding step, a polishing step, a washing step, an inspection step, a packing step, and the like, and laminated at the packing step are conveyed to a supplier at a delivery destination.

Melting process (ST1) is performed in a dissolution tank. In the melting step, the glass raw material is intermittently dispersed in a plurality of locations on the liquid surface of the molten glass accumulated in the melting tank to produce molten glass with a uniform temperature of the surface layer including the liquid surface. Moreover, molten glass flows toward a subsequent process from the outflow port formed in the bottom part of the inner wall which opposes in the longitudinal direction of the rectangular dissolution tank among the inner wall of a dissolution tank.

Here, the temperature of the molten glass of the lower layer located below the surface layer is made uniform in the longitudinal direction of a melting tank, and the temperature difference of the molten glass in the longitudinal direction of a melting tank is made as small as possible. For that purpose, the amount of heat for heating the lower layer of the molten glass is such that both ends of the dissolution tank in the longitudinal direction of the dissolution tank are larger than the central portion of the dissolution tank in the longitudinal direction. This is because the heat of the molten glass is more likely to be taken away from the center portion at both ends in the longitudinal direction of the melting tank. As a result, convection caused by the temperature distribution of the molten glass in the longitudinal direction of the melting tank is prevented from occurring in the lower molten glass, and the molten glass is flowed from the outlet to the subsequent step while the temperature distribution in the lower layer of the molten glass is uniform. .

In this embodiment, the "surface layer" of the molten glass shows the area | region containing the liquid surface within 5% or less of the range from the liquid level toward the bottom of the melting tank, and the "lower layer" of the molten glass shows the area | regions other than a surface layer. . In addition, the "bottom part" in which the outlet port is formed represents a region near the bottom face of the dissolution tank as part of the lower layer. In this embodiment, a "bottom part" means the area | region whose depth from the bottom face in the depth direction of a dissolution tank is 1/2 or less of the depth between a liquid level and the bottom part of a dissolution tank.

The glass raw material is thrown into the whole surface over 80% or more of the liquid level of the molten glass of a melting tank. As a method of adding the glass raw material, a method of dispersing and injecting the glass raw material into the molten glass may be used by inverting the bucket containing the glass raw material. In addition, the method of injecting a glass raw material may be the method of conveying and disperse | distributing a glass raw material using a belt conveyor, or the method of putting into a whole surface at once. In addition, the method of injecting a glass raw material may be the method of disperse | distributing a glass raw material with a screw feeder, or the method of putting into a whole surface at once. In embodiment mentioned later, a glass raw material is thrown in by the input method using a bucket.

When a current is applied to the molten glass by applying a voltage between the electrodes of the melting tank, the molten glass generates Joule heat. Increasing this joule heat may increase the temperature of the molten glass, and decreasing it may lower the temperature of the molten glass. In addition to the heating by the energization of the molten glass, the glass raw material may be dissolved by using the heat of the burner's flame as an auxiliary.

A clarifier is added to a glass raw material. As the clarifier, SnO ₂ , As ₂ O ₃ , Sb ₂ O _3, and the like are known, but are not particularly limited. However, from the viewpoint of reducing the environmental load, it is preferable to use SnO ₂ (tin oxide) as a clarifier.

The clarification process ST2 is performed at least in a clarification tank. In the clarification process, the molten glass in a clarification tank is heated up. In this process, the clarifier becomes a substance which releases oxygen by a reduction reaction and later acts as a reducing agent. Bubbles containing O ₂ , CO ₂ or SO ₂ contained in the molten glass absorb and grow O ₂ generated by the reduction reaction of the clarifier, and float on the liquid level of the molten glass to disappear. The clarification process is performed inside a container made of platinum or platinum alloy.

Thereafter, in the clarification step, the temperature of the molten glass is lowered. In this process, the reducing agent obtained by the reduction reaction of the clarifier undergoes an oxidation reaction. Thereby, the gas components of O ₂ and the like in the air bubbles remaining in the molten glass is re-uptake in the molten glass, the bubble disappears.

Oxidation reaction and reduction reaction by a clarifier are performed by controlling the temperature of a molten glass. The clarification process can also use the pressure reduction degassing system which makes a pressure reduction atmosphere in a clarification tank, grows the bubble which exists in a molten glass in a pressure reduction atmosphere, and degasses. In this case, it is effective at not using a clarifier. In embodiment mentioned later, tin oxide is used as a clarifier.

In homogenization process ST3, the glass component is homogenized by stirring the molten glass in the stirring tank supplied through the piping extended from the clarification tank using a stirrer. Thereby, the composition nonuniformity of the glass which is a cause of stria etc. can be reduced. In addition, you may install one stirring tank or two.

In supply process ST4, molten glass is supplied to a shaping | molding apparatus through the piping extended from a stirring tank.

In the shaping | molding apparatus, shaping | molding process ST5 and slow cooling process ST6 are performed.

In the molding step ST5, the molten glass is molded into sheet glass to create a flow of the sheet glass. Molding can use the overflow downdraw method or the float method. In the present embodiment described later, the over download method is used.

In slow cooling process ST6, the sheet glass shape | molded and flows becomes desired thickness, and it cools so that internal distortion does not generate | occur | produce and a curvature does not generate | occur | produce.

In cutting process ST7, in a cutting device, the sheet glass supplied from the shaping | molding apparatus is cut | disconnected to predetermined length, and a plate-shaped glass plate is obtained. The cut glass plate is also cut to a predetermined size to produce a glass substrate of a target size. After that, the end surface of the glass substrate is ground and polished, the glass substrate is washed, and the presence or absence of abnormal defects such as bubbles and stria is inspected, and then the glass plate of the inspection passed product is packed as a final product.

FIG. 2: is a figure which shows typically an example of the apparatus which performs the melting process (ST1)-the cutting process (ST7) in this embodiment. As shown in FIG. 2, the apparatus mainly includes a melting apparatus 100, a molding apparatus 200, and a cutting device 300. The dissolution apparatus 100 has a dissolution tank 101, a clarification tank 102, a stirring tank 103, and glass supply pipes 104, 105, and 106.

In the melting apparatus 101 of the example shown in FIG. 2, the injection of a glass raw material is performed using the bucket 101d. In the clarification tank 102, the temperature of molten glass MG is adjusted, and clarification of molten glass MG is performed using the redox reaction of a clarifier. In the stirring vessel 103, the molten glass MG is stirred and homogenized by the stirrer 103a. In the shaping | molding apparatus 200, sheet glass SG is shape | molded from molten glass MG by the overflow down draw method using the molded object 210. FIG.

3 is a perspective view illustrating a schematic configuration of the dissolution tank 101 of the present embodiment.

In this embodiment, the dissolution tank 101 is designed to make molten glass with the temperature of the surface layer containing a liquid level uniform. The glass raw material is thrown into the whole surface of the liquid surface 101c of the molten glass MG accumulated in the dissolution tank 101. The outlet port 104a is formed in the bottom of one inner wall of a pair of inner walls which oppose in the longitudinal direction of the rectangular dissolution tank 101 in plan view. The dissolution tank 101 flows molten glass MG from the outlet 104a toward the next process.

The dissolution tank 101 has an inner wall 110 made of refractory materials such as refractory bricks. The dissolution tank 101 has an inner space surrounded by the inner wall 110. The internal space of the dissolution tank 101 is divided into the liquid tank 101a and the upper space 101b. The liquid tank 101a accommodates the molten glass MG which the glass raw material thrown in the internal space melt | dissolved, heating. The upper space 101b is formed on the molten glass MG, and is a gaseous phase into which the glass raw material is injected.

In the inner wall 110 of the upper space 101b parallel to the longitudinal direction of the dissolution tank 101, a burner 112 is provided in which a combustion gas which mixes fuel and oxygen burns and emits a flame. The burner 112 heats the refractory of the upper space 101b with a flame to make the inner wall 110 high temperature. The glass raw material is heated by the radiant heat of the inner wall 110 at a high temperature and the gaseous atmosphere at a high temperature.

In the inner wall 110 on the opposite side to the inner wall 110 where the outlet 104a of the dissolution tank 101 is formed, a raw material input window 101f which leads to the upper space 101b is formed. Through this raw material input window 101f, the bucket 101d containing the glass raw material shown in FIG. 4 enters and exits the upper space 101b. The bucket 101d moves back and forth left and right on the liquid surface 101c of the molten glass MG in accordance with an instruction from the computer 118. The computer 118 sends an instruction to a bucket operating mechanism (not shown) to operate the bucket 101d via the control unit 116.

4 is a plan view illustrating the introduction of the glass raw material in the dissolution tank 101.

As shown in FIG. 4, the glass raw material is thrown in the whole surface with respect to the liquid level of the molten glass MG accumulate | stored in the dissolution tank 101. As shown in FIG. Thereby, molten glass MG with which the temperature of the surface layer containing a liquid level was made uniform is produced.

The dissolution tank 101 is provided with a bucket operation mechanism. The bucket operating mechanism moves to the area | region which aims at the bucket 101d, and inverts the top and bottom of the bucket 101d by the instruction | instruction of the computer 118, in the state in which the bucket 101d accommodated the glass raw material. The area | region where the bucket 101d throws in glass raw material, and the time interval which it throws in are predetermined so that the glass raw material may not disappear in the liquid surface 101c of molten glass MG. Therefore, in the dissolution tank 101, since it throws into the substantially whole surface of the liquid surface of molten glass MG, the glass raw material always covers the liquid surface 101c of molten glass MG.

As described above, one of the reasons for introducing the glass raw material into the dissolution tank 101 so that the glass raw material always covers the liquid surface 101c is that the heat of the molten glass MG is radiated to the upper space 101b in the gas phase through the liquid surface 101c. This is to prevent it. Thereby, the temperature of the surface layer containing the liquid surface of molten glass MG is equalized, the temperature is kept constant, and the temperature distribution of the horizontal direction is planarized. Another reason is to efficiently dissolve a low solubility (high melting temperature) raw material such as SiO ₂ (silica) in the glass raw material and prevent the raw material such as SiO ₂ from being left without melting.

A raw material having a high dissolution temperature such as SiO ₂ may be dissolved at a temperature lower than the dissolution temperature in the case where it is dissolved alone in a mixed state with another component, for example, a raw material such as B ₂ O ₃ (boron oxide). . In order to utilize the properties of such a raw material, the glass raw material is intermittently dispersed and injected so that the glass raw material always exists on the liquid surface 101c of the molten glass MG and covers the liquid surface 101c. As a result, the raw material such as B ₂ O _3, because the dissolution with a material such as SiO ₂ is difficult to melt, it is possible to prevent the raw material, such as SiO ₂ are left without greenery.

On the other hand, when the glass raw material is introduced only to a part of the liquid level of the molten glass, raw material components such as SiO _{2 which} are difficult to melt remain without melting, and the liquid level far from the injection position of the glass raw material is caused by convection of the molten glass. May float as a foreign material. Such heterogeneous raw materials may move to the lower layer of the molten glass, flow out from the outlet of the melting tank, and flow to the subsequent process depending on the convective state of the molten glass, and may be the cause of nonuniformity of glass composition such as striae.

In this embodiment, the glass raw material is thrown into the melting tank 101 with respect to the liquid level of molten glass MG. Therefore, the temperature in the surface layer containing the liquid level of molten glass MG becomes uniform. In addition, it is also possible to prevent the raw material components such as SiO ₂ from being left without melting.

A pair of electrodes extending from the longitudinal direction of the dissolution tank 101 and formed of a conductive material having heat resistance such as tin oxide or molybdenum on the inner walls 110a and 110b of the liquid tank 101a facing each other. 114 pairs are provided. In the present embodiment, the dissolution tank 101 includes three pairs of electrodes 114, but depending on the size of the dissolution tank, only the pair of electrodes 114 may be used. In the case of using the plurality of pairs of electrodes 114, two or four or more pairs of electrodes 114 may be used.

The three pairs of electrodes 114 are provided in the region corresponding to the lower layer of the molten glass MG among the inner walls 110a and 110b. The three pairs of electrodes 114 extend through the inner walls 110a and 110b from the outer side to the inner side of the inner walls 110a and 110b. In FIG. 3, each pair of electrodes 114 has an electrode 114 on the front side and an electrode 114 on the inner side not shown. Each pair of electrodes 114 is provided on the inner walls 110a and 110b so as to face each other with the molten glass MG disposed between the pairs of electrodes 114 interposed therebetween.

Each pair of electrodes 114 is energized by applying a voltage to the molten glass MG disposed between the pair of electrodes 114. By flowing an electric current through the molten glass MG, Joule heat is generated in the molten glass MG, and the molten glass MG is heated. In the dissolution tank 101, the molten glass MG is heated to 1500 degreeC or more, for example. The heated molten glass MG is sent to the clarification tank 102 via the glass supply pipe 104.

Although the burner 112 is provided in the upper space 101b in the dissolution tank 101 shown in FIG. 3, the burner 112 is not essential. For example, the glass raw material can be efficiently melt | dissolved by using burner 112 auxiliary | assistant in the molten glass with a specific resistance of 180 ohm * cm or more and comparatively large resistivity at 1500 degreeC.

When the molten glass MG is made by continuously dissolving the glass raw material, it is also possible to dissolve the glass raw material without using the burner 112. For example, by covering the liquid surface 101c of the molten glass MG with the glass raw material on the whole surface, heat radiation from the liquid surface 101c of the molten glass MG is prevented, and the fall of the temperature of the molten glass MG is suppressed, and The glass raw material can be dissolved by Joule heat emitted from the molten glass MG.

Each pair of electrodes 114 is connected to the control unit 116, respectively. In order to equalize the temperature distribution of the molten glass MG in the lower layer, the control unit 116 is configured to be able to control the power supplied to each of the electrodes 114 for each pair of opposed electrodes 114. . To each pair of electrodes 114, a single layer AC voltage is applied by the control unit 116.

The control unit 116 is further connected with the computer 118. The control unit 116 measures the magnitude of the voltage applied to the molten glass MG between the pair of electrodes 114 and the value of the current flowing through the molten glass MG between the pair of electrodes 114. The control unit 116 outputs information of the measured voltage and current values. Computer 118 receives these information output from control unit 116. The computer 118 calculates the specific resistance of the molten glass MG between the pair of electrodes 114 from the information of the values of the voltage and the current.

The computer 118 calculates, for example, the specific resistance p (Ω · m) of the molten glass MG between the pair of electrodes 114 based on the following equation (2).

In Equation 2, E is the voltage (V) applied to the molten glass MG between each pair of electrodes 114, I is the current (A) flowing in the molten glass MG between each pair of electrodes 114, S is each The cross-sectional area (m 2) of the molten glass MG through which current flows between the pair of electrodes 114, L is the distance m between the pair of electrodes 114. The cross-sectional area S and the length L are intrinsic values determined by the dissolution tank 101.

5A and 5B are plan views illustrating a method for obtaining a cross-sectional area S of the molten glass MG through which current flows between each pair of electrodes 114.

As shown in FIG. 5, each pair of electrodes 114 is disposed to face each other so as to cross the flow direction F of the molten glass MG on the inner walls 110a and 110b disposed on both sides of the molten glass MG. have. In addition, the electrode 114 of the third pair of opposed are arranged at a distance W ₁ from each other in the flow direction F of the molten glass MG. Here, the interval W ₁ is a distance between the edges of the adjacent electrodes 114 facing each other. The flow direction F conveniently shows the direction of the flow from the upstream as the whole of the molten glass MG to the downstream in the dissolution tank 101, and is a direction parallel to the inner walls 110a and 110b and toward the outlet 104a. In addition, the flow direction F is a direction along the longitudinal direction of the dissolution tank 101.

First, the area EA through which current flows for each pair of electrodes 114 is set. The boundary m of the energizing region EA is set to pass through the midpoint C of two electrodes 114 adjacent in the flow direction F. The midpoint C is the center of the heat resistant brick sandwiched between two adjacent electrodes 114. In other words, the intermediate point C is a point at which distances from two adjacent electrodes face each other. That is, the boundary m is in the vertical direction passing through the midpoint C between two electrodes 114 adjacent to the inner wall 110a and the midpoint C of two electrodes 114 adjacent to the inner wall 110b. It is a parallel plane. By this boundary m, the molten glass MG is virtually separated into the area | region EA of several square pillar shape corresponding to each pair of electrode 114. As shown in FIG.

That is, the cross-sectional area S of the energization area | region EA of molten glass MG is an area of the cross section parallel to the flow direction F and the vertical direction of area | region EA, as shown to FIG. 5 (b). Thus, the cross-sectional area S is obtained by the height (the depth of the molten glass MG) D to the liquid surface (101c) from the bottom surface (110e) of the melting vessel 101, the product of the width W ₂ of the area EA. Using the cross-sectional area S thus obtained, the specific resistance p of the molten glass MG between the pair of electrodes 114 can be obtained by the above equation (2).

When the specific resistance p of molten glass MG is calculated | required by the said method, as shown in FIG.5 (b), it is preferable that the area S1 of the electrode 114 with respect to the cross-sectional area S of the electricity supply area | region EA is as large as possible. . The ratio of the cross-sectional area S of the conduction area EA and the area S1 of the electrode 114 is not particularly limited. In this embodiment, S1 / S has a range of 1/3 or more and 1/2 or less, for example, from the strength and structural constraints of the dissolution tank 101. Thus, by making the area S1 of the electrode with respect to the cross-sectional area S of the electricity supply area | region EA of molten glass MG larger than before, it becomes possible to calculate the specific resistance (rho) of molten glass MG more correctly.

Based on the specific resistance p of the molten glass MG obtained by the above method, the Joule heat generated in the molten glass MG of each region EA corresponding to each pair of electrodes 114 can be controlled.

It is a figure explaining an example of the process of controlling the joule heat which generate | occur | produces in molten glass MG based on the specific resistance (rho) of molten glass MG.

In the sampling ST11 shown in FIG. 6, the information of the voltage E applied to the molten glass MG between the electrodes 114 of the respective regions EA corresponding to the pair of electrodes 114 shown in FIG. 5, and the respective regions EA Information of the value I of the current flowing through the molten glass MG is sent from the control unit 116 to the computer 118. The computer 118 stores the information of the voltage E and the current I of each area EA sent from the control unit 116. The computer 118 previously stores the cross-sectional area S, the distance L between the electrodes 114, and the target value of the specific resistance of the molten glass MG to be described later in each region EA.

In the calculation of the specific resistance (ST12) shown in FIG. 6, the computer 118 calculates each of the angles based on the information of the voltage E, the current I, the cross-sectional area S, and the distance L of each of the stored regions EA and the above expression (2). The resistivity p of the molten glass MG in the area EA is calculated.

In addition, the resistivity p of each area | region EA when the molten glass MG of the dissolution tank 101 is in the desired melt | dissolution state is computed previously, and the value can be preserve | saved in the computer 118 as a target value of specific resistance p. . In the step of determining the target value of the specific resistance p, for example, a desired melting state of the molten glass MG is made by using a temperature measuring means such as a thermocouple as in the prior art, and in that state by the computer 118 as described above. May be calculated. Moreover, the glass substrate manufactured from molten glass MG is previously taken out, it melt | dissolves in a crucible, etc., and the specific resistance corresponding to melting glass MG of a target viscosity and temperature may be calculated | required, and it may be set as the target value of specific resistance p.

In comparison of the specific resistance (ST13) shown in FIG. 6, the computer 118 compares the target value of the specific resistance p of each area EA with the calculated specific resistance p of each area EA.

In determination of the control amount (ST14) shown in FIG. 6, the computer 118 determines the control amount to be sent to the control unit 116 based on the result of the comparison of the specific resistance (ST13).

Specifically, in a certain area EA, when the calculated specific resistance p is larger than the target value or larger than the allowable range, the computer 118 generates a predetermined amount of Joule heat generated in the molten glass MG in the area EA. Give instructions to reduce.

In a certain area EA, if the calculated resistivity p is equal to or within an acceptable range, the computer 118 instructs to maintain the Joule heat generated in the molten glass MG in that area EA.

In a certain area, when the calculated specific resistance p is smaller than the target value or smaller than the allowable range, the computer 118 gives an instruction to increase the Joule heat generated in the molten glass MG in the area EA by a predetermined amount. .

In the control ST15 of Joule row shown in FIG. 6, the control unit 116 controls Joule row generated in the molten glass MG of each area EA based on the instruction of the control amount sent from the computer 118.

Specifically, when the control unit 116 is instructed to reduce the Joule heat generated in the molten glass MG of a certain area EA, the control unit 116 is connected to the molten glass MG between the pair of electrodes 114 corresponding to the area EA. The target current value is set so that the value of the flowing current becomes a constant value which is smaller by a predetermined value than the original value.

When the control unit 116 is instructed to maintain the Joule heat generated in the molten glass MG of a region EA, the value of the current flowing in the molten glass MG between the pair of electrodes 114 corresponding to the region EA is Alternatively, the original target value is set as the target current value.

When the control unit 116 is instructed to increase the joule heat generated in the molten glass MG of a region EA, the value of the current flowing in the molten glass MG between the pair of electrodes 114 corresponding to the region EA is The target current value is set to be a constant value which is larger by a predetermined value than the original value.

The control unit 116 further controls the voltage applied to the molten glass MG between the pair of electrodes 114 to maintain the value of the current flowing in the molten glass MG at the target current value.

By the above control, the viscosity and the temperature of the molten glass MG of each area EA are maintained in a desired state without using a temperature measuring means such as a conventional thermocouple, and convection and melting of the molten glass MG of the dissolution tank 101 are performed. You can keep the state as you want.

Next, as one of the methods of controlling the Joule heat generated in the molten glass MG of each area | region EA based on the above-mentioned specific resistivity p, the temperature of the molten glass MG of each area | region EA further from the calculated specific resistance p of each area | region EA. A method of calculating the will be described.

FIG. 7: is a figure explaining the process which calculates | requires the temperature of molten glass MG from the computed specific resistance (rho), and controls the joule heat which generate | occur | produces in the molten glass of each area | region EA.

In this method, first, as the preliminary step (ST21), the relationship between the temperature and the specific resistance of the molten glass of the same component as the molten glass MG made by the dissolution tank 101 is determined in advance and recorded in the computer 118. In the step of calculating the relationship between the temperature of the molten glass MG and the specific resistance, the melting glass 101 may be measured using a temperature measuring means such as a thermocouple, for example, in the conventional manner. In addition, by calculating the specific resistance p by the computer 118 as described above, the relationship between the temperature of the molten glass MG and the specific resistance can be obtained. Moreover, you may obtain these correlations by taking out the glass substrate manufactured from molten glass MG previously, melt | dissolving in a crucible, etc., and measuring the temperature and specific resistance of the molten glass MG at that time.

The temperature of the molten glass MG can be expressed as a function of the specific resistance p, for example F (p). That is, the specific resistance p of molten glass MG and the temperature T (degreeC) of molten glass MG have the correlation shown by following formula (1).

In Equation 1, a and b are constants that depend on the glass composition.

By the preliminary step ST21, the values of the constants a and b are specified. The values of the constants a and b are stored in the computer 118 together with the above equation (1). In the preliminary step ST21, the target temperature of the molten glass MG of each region EA is set in advance, and the value is stored in the computer 118.

Since the sampling ST21 and the calculation of the specific resistance ST23 shown in FIG. 7 are the same as those of the sampling ST11 and the calculation of the specific resistance ST12 shown in FIG. 6, the description is omitted.

In calculation of temperature ST24 shown in FIG. 7, the computer 118 calculates the specific resistance p of each area | region EA computed, the constants a and b previously stored, and each area | region EA based on said Formula (1). The temperature T of molten glass MG in is computed.

In addition, the temperature T of each area | region EA when the molten glass MG of the dissolution tank 101 is in the desired melt | dissolution state is calculated previously, and the value can be preserve | saved in the computer 118 as a target value of temperature T. . In the step of setting the target value of the temperature T, for example, a desired dissolved state is created in the molten glass MG using a temperature measuring means such as a thermocouple as in the prior art, and in that state, the temperature T is performed by the computer 118 as described above. May be calculated.

In the comparison of temperature ST25 shown in FIG. 7, the computer 118 compares the target value of the temperature T of the stored area EA and the calculated temperature T of each area EA.

In determination ST26 of the control amount shown in FIG. 7, the control amount to be sent to the control unit 116 is determined based on the result of the comparison of the temperature ST25 described above.

Specifically, in a certain area EA, when the calculated temperature T is higher than the target value or higher than an allowable range, the computer 118 generates a predetermined amount of Joule heat generated in the molten glass MG in the area EA. Give instructions to reduce.

In a region EA, if the calculated temperature T is equal to or within an acceptable range, the computer 118 instructs to maintain the Joule heat generated in the molten glass MG in that region EA.

In a certain region, when the calculated temperature T is lower than the target value or lower than an allowable range, the computer 118 gives an instruction to increase the Joule heat generated in the molten glass MG in the region EA by a predetermined amount. .

Since the control ST27 of the row of lines shown in FIG. 7 is the same as the control ST15 of the row of lines shown in FIG. 6, description thereof is omitted.

By the said control, the melt | dissolution state of the molten glass MG of the dissolution tank 101 is a desired state, making the viscosity and temperature of the molten glass MG of each area | region EA into a desired state, without using a conventional temperature measuring apparatus, such as a thermocouple. You can do

In general, the molten glass MG near the inner walls 110c and 110d facing each other in the flow direction F tends to become low temperature by heat radiation from the inner walls 110c and 110d to the outside. For this reason, in this embodiment, the amount of heat which the molten glass MG generate | occur | produces in the both ends of the flow direction F of the dissolution tank 101 is made more than the amount of heat which the molten glass MG produces in the center part. Thereby, the temperature difference of molten glass MG in a lower layer is made as small as possible, the temperature of molten glass MG is made uniform, and the temperature distribution of the lower layer of molten glass MG is flattened.

FIG. 8: is a figure explaining the convection of the molten glass in the dissolution tank 101 in this embodiment. In this embodiment, the glass raw material is thrown in the whole surface with respect to the liquid level of the molten glass MG accumulate | stored in the melting tank 101, and the molten glass MG which the temperature of the surface layer containing the liquid surface 101c was made uniform is produced.

When this molten glass MG flows from the outlet 104a toward the subsequent process, convection resulting from the temperature distribution along the longitudinal direction (first direction) of the dissolution tank 104a in FIG. 3 occurs in the molten glass MG of the lower layer. Do not do it. That is, the lower molten glass MG is heated so that the temperature along the 1st direction of the lower molten glass MG becomes uniform. Specifically, the amount of heat for heating the molten glass MG at both ends of the melting tank 101 in the first direction is adjusted to be higher than the amount of heat for heating the molten glass MG at the central portion in the first direction of the melting tank 101.

In the longitudinal direction of the dissolution tank 101, the heating amount of the molten glass MG at both ends is greater than that at the central portion because heat is easily released to the outside from the inner walls 110c and 110d facing in the longitudinal direction. If adjustment of such heating amount is not performed, the temperature of the molten glass MG in the said both ends will tend to become low compared with a center part. For this reason, the electric power supplied to three pairs of electrodes 114 is closer to the electrode 114 near the both ends of the longitudinal direction of the dissolution tank 101 compared with the electrode 114 of the center part of the longitudinal direction of the dissolution tank 101. It is preferable to set so that it may increase. This also applies to the case where four or more pairs of electrodes 114 are provided in the dissolution tank.

As described above, in the present embodiment, the joule heat generated in the molten glass MG of each region EA is controlled based on the calculated specific resistance p of the molten glass MG of each region EA. Therefore, even if the amount of heat emitted to the outside in each region EA is different, the amount of Joule heat generated in the molten glass MG of each region EA is adjusted to maintain the target value of the specific resistance p or the target value of the temperature T.

As a result, the molten glass MG is guided to the outflow from the outlet 104a of the molten glass MG without causing convection due to the temperature distribution of the molten glass MG in the lower layer. As shown by the arrow shown in FIG. 8, molten glass MG flows toward the outlet 104a along the bottom face of the dissolution tank 101 in the part near the bottom face of the dissolution tank 101 of a lower layer. As it moves away from the bottom of the dissolution tank 101, the influence of the flow along the bottom of the dissolution tank 101 becomes small, and the molten glass MG flows from the surface layer toward the bottom of the dissolution tank 101 to sink.

As described above, in the present embodiment, since convection due to the temperature distribution of the molten glass MG does not occur in the lower layer, the variation in the glass composition due to the foreign material and the like can be suppressed. In contrast, when the temperature distribution of the molten glass MG is not uniform in the lower layer, the distribution of the temperature difference occurs between the lower layer and the surface layer where the temperature is uniform, so that convection of the hot spring is likely to occur.

It is a figure explaining the convection of the molten glass in the conventional dissolution tank. As shown in Fig. 9, in the conventional dissolution tank, in the region A, the molten glass is partially heated so as to form a hot spring, so that convection is promoted. For this reason, in the glass raw material charged into the portion of the molten glass surface, the melt hard material components such as SiO ₂ is moved by convection, e.g., a dissimilar material 120 of the silica rich is away from the input position of the glass raw material Easy to accumulate Moreover, the chance that this foreign material 120 will flow out from an outlet port along convection increases, and it becomes easy to become a cause of the nonuniformity of glass composition, such as stria.

The manufacturing method of the glass substrate of this embodiment is 1300 degreeC or more (for example, 1300 degreeC or more and 1650 degrees C or less), More preferably, the viscosity of molten glass with high viscosity, for example, 10 ^2.5 poise of molten glass, is more preferable. Molten glass which is 1500 degrees C or more (for example, 1500 degrees C or more and 1650 degrees C or less) can also be applied, and compared with the case of the conventional manufacturing method, the advantage which can suppress the nonuniformity of glass composition, such as striae, is large.

In the method of manufacturing the glass substrate of the present embodiment, even in a molten glass having a specific resistance of 180 Ω · cm or more at 1500 ° C., it is not necessary to apply excessive voltage in order to emphasize the hot spring, thereby preventing current from flowing in the refractory. can do. Therefore, it is possible while preventing easily cause devitrification of the glass ZrO ₂ (zirconia) is eluted from the inner wall in contact with the molten glass in the melting vessel MG 101, to suppress the non-uniformity of the glass composition. About the molten glass with such a large specific resistance, you may use together the heating by a burner in the melting tank 101. FIG.

In this embodiment, since the pair of electrodes 114 face each other, the temperature in the lower layer along the first direction of the molten glass MG can be effectively uniformized.

In this embodiment, since the electric power supplied to each pair of electrodes 114 is supplied so that both ends may increase compared with the center part of the longitudinal direction of the dissolution tank 101 in consideration of the discharge | release of the heat of the dissolution tank 101, It is easy to uniformize the temperature distribution in the flow direction F of the molten glass MG at.

In this embodiment, the temperature in the lower layer of the molten glass MG is uniformized so as not to cause convection caused by the temperature distribution of the molten glass. Therefore, in order to promote convection due to the temperature distribution of the molten glass as in the prior art, the molten glass does not need to be heated to an excessively high temperature at the expense of elution of the refractory constituting the dissolution tank 101. As a result, it becomes difficult easy ZrO ₂ become a cause of devitrification of the glass to elute from the inner wall in contact with the molten glass in the melting vessel MG 101. Therefore, the production method of the present embodiment is suitable for the corrosion resistance in the inner wall of the melting vessel 101 is made of a refractory material containing a fine ZrO ₂ component.

Hereinafter, the effect of this embodiment is demonstrated from a viewpoint of glass composition.

The composition of the glass substrate manufactured in this embodiment is constituted by the alumino-silicate glass, it may include SiO ₂ (silica), 50 mass% or more. By applying the manufacturing method of this embodiment to the aluminosilicate glass which has this composition, the nonuniformity of glass composition can be suppressed more effectively than before. The composition of the glass substrate manufactured in this embodiment, may include at least 55 mass% SiO _2, and may include SiO ₂ more than 60% by mass.

By applying the manufacturing method of this embodiment to the aluminosilicate glass which has these compositions, glass composition nonuniformity can be suppressed more effectively compared with the former. Including SiO ₂ at least 50% by weight, may be easy glass to occur dissimilar material composition of the silica-rich, since the molten glass MG is dissolved so that the convection from occurring due to a temperature distribution, from a heterogeneous material of the silica-rich outlet (104a) Can be prevented from leaking.

In addition, since the glass raw material is always added to the liquid surface 101c to have a constant thickness, it is prevented that SiO ₂ does not melt and remains, and foreign material 120 by SiO ₂ hardly occurs as shown in FIG. 9. .

Include a SiO ₂ more than 50% by weight and by using a glass substrate composition highly viscous glass of the molten glass MG, when the facilitating the convection of molten glass as in the prior art, the ZrO ₂ (zirconia) which contains the refractory constituting the melting vessel It may elute to molten glass and may cause the devitrification of glass.

However, in the present embodiment, since the temperature distribution of the molten glass MG in the lower layer is uniformized so as not to cause convection due to the temperature distribution of the molten glass MG, it is not necessary to heat the molten glass to an excessively high temperature as in the prior art. Therefore, it is possible to prevent the dissolution of ZrO ₂ (zirconia) from the refractory of the melting vessel 101. Further, the content by percentage of the upper limit of the glass composition of SiO ₂ is 70 mass%, for example.

Further, it may comprise more than 60% by mass in total of SiO ₂ and Al ₂ O _3, the manufacturing method of this embodiment is applied to an aluminosilicate glass having the glass composition is, as compared with the conventional Consequently, to suppress the non-uniformity of the glass composition Can be. Further, it may comprise more than 65% by mass in total of SiO ₂ and Al ₂ O _3, it may also include the SiO ₂ and Al ₂ O _3, the total of 70 mass% or more.

Even the occur easy glass composition including SiO ₂ and Al ₂ O ₃ in total more than 60% by mass of heterogeneous material (120) of the silica-rich, since the molten glass MG is dissolved so that the convection from occurring due to the temperature distribution of the silica-rich It is possible to prevent the foreign material from flowing out of the outlet 104a.

In addition, since the glass raw material is always added to the liquid surface 101c to have a constant thickness, it is prevented that SiO ₂ does not melt and remains, and foreign material 120 by SiO ₂ hardly occurs as shown in FIG. 9. .

Including SiO ₂ and Al ₂ O ₃ in total more than 60% by weight and by using a glass substrate composition highly viscous glass of the molten glass MG, when the facilitating the convection of molten glass as in the prior art, containing a refractory constituting the melting vessel ZrO ₂ (zirconia) may be eluted to the molten glass, resulting in loss of glass.

However, in the present embodiment, since the temperature distribution of the molten glass MG in the lower layer is uniformed so as not to cause convection caused by the temperature distribution of the molten glass MG, there is no need to heat the molten glass to partly excessively high temperature as in the prior art. . Therefore, it is possible to prevent the dissolution of ZrO ₂ (zirconia) from the refractory of the melting vessel 101. Further, in the glass composition, the content by percentage of the upper limit of the sum of SiO ₂ and Al ₂ O ₃ is, for example, 95% by weight.

In addition, it is preferable that a glass substrate consists of aluminoborosilicate glass. B ₂ O ₃ (boron oxide) is dissolved at a low temperature compared to the SiO _2, also, to lower the melting temperature of the SiO _2. Therefore, in a glass composition with a high SiO ₂ content, it is effective to contain B ₂ O _{3 in} that it is difficult to generate a foreign material 120 (see FIG. 9).

The glass composition of a glass substrate can apply the following, for example. The content rate indication of the composition shown below is the mass%.

SiO ₂ : 50 to 70%,

B ₂ O ₃ : 5-18%,

Al ₂ O ₃ : 0-25%,

MgO: 0-10%,

CaO: 0-20%,

SrO: 0-20%,

BaO: 0 to 10%

RO: 5 to 20% (wherein R is at least one selected from Mg, Ca, Sr and Ba, and the glass substrate contains)

It is preferable that it is an alkali free glass containing.

In addition, the following composition can be applied as a composition of a glass substrate.

SiO ₂ : 50 to 70%,

B ₂ O ₃ : 1-10%,

Al ₂ O ₃ : 0-25%,

MgO: 0-10%,

CaO: 0-20%,

SrO: 0-20%,

BaO: 0 to 10%

RO: 5-30% (wherein R is the total amount of Mg, Ca, Sr and Ba)

It is also likewise preferable to be an alkali free glass containing.

In addition, in this embodiment, although it is set as the alkali free glass, the glass substrate may be alkali trace amount containing glass containing a trace amount of alkali metal. When an alkali metal, R 'is the sum of the ₂ O at least 0.10% less than 0.5%, preferably at least 0.20% less than 0.5% (however, R' is at least one selected from Li, Na and K, the glass It is preferable to include). Moreover, in order to make melting of glass easy, from a viewpoint of reducing specific resistance, it is more preferable that content of iron oxide in glass is 0.01 to 0.2%. In addition, it is preferred that _{As 2 O 3, Sb 2 O} 3 and that is substantially free of the PbO.

The manufacturing method of this embodiment can be effectively applied to a glass substrate for a liquid crystal display device. The glass substrate for a liquid crystal display device suppresses thermal expansion in a glass substrate and also does not reduce the characteristic of TFT (Thin Film Transistor) formed in a glass substrate, As mentioned above, an alkali metal component ( A trace amount is preferable even if it does not contain Li, Na, and K).

However, when the alkali metal component (Li, Na, and K) is not included or is contained in a small amount, the high temperature viscosity of the molten glass MG becomes high, so that the molten glass MG is partially heated to a high temperature to make a strong hot spring. There is a need.

On the other hand, in this embodiment, the glass raw material is thrown into the substantially whole surface of the liquid surface 101c of molten glass MG, and the temperature of molten glass MG is adjusted so that convection of molten glass MG may not generate | occur | produce. Therefore, it is not necessary to heat molten glass MG at high temperature partly in order to make temperature distribution of molten glass like conventionally. Therefore, the manufacturing method of this embodiment can be suitably applied to the glass substrate for liquid crystal display devices in the point which does not make the temperature of molten glass partially too high like the conventional one.

In addition, the glass raw material, as fining agents, SnO ₂ and the inclusion of (tin oxide), 0.01? 0.5 mass%, is preferred from the point that exhibited a reduced environmental load On the other hand, effective refining effect. In the present embodiment, from the viewpoint of reducing the environmental load, SnO ₂ is used as a clarifier, but in order to effectively function the clarification action of SnO ₂ , it is preferable not to make the dissolution temperature too high.

In this embodiment, it is not necessary to partially heat the molten glass excessively in order to emphasize the hot spring in the temperature of the molten glass MG as in the conventionally known manufacturing method. Therefore, in addition to preventing the elution of ZrO ₂ (zirconia) from the refractory of the dissolution tank 101, the clarification action of SnO ₂ can be effectively functioned.

In addition, in this embodiment, in order to more uniformize the temperature in the lower layer of the molten glass MG in the dissolution tank 101 more effectively, the heat insulation member is provided in the outer side wall of the dissolution tank 101 around the part in which the electrode 114 is provided. Is preferably installed. As a heat insulating material, the board member etc. which hardened heat insulating materials, such as glass wool and a ceramic fiber in plate shape, are used, for example. Thereby, heat dissipation from the outer side wall of the dissolution tank 101 can be prevented, the temperature of the molten glass MG can be uniformed more effectively in the dissolution tank 101, and the convection of the molten glass MG can be further reduced. .

As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to said embodiment. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the invention. The present invention is not limited by the above description, but only by the scope of the appended claims.

In addition, the said embodiment contains the following content.

(1) The manufacturing method of a glass substrate includes the melting process which melt | dissolves a glass raw material in a dissolution tank. In the said melting process, a glass raw material is thrown into the substantially whole surface of the liquid level of the molten glass accumulate | stored in the melting tank, and the molten glass which the temperature of the surface layer containing a liquid level is uniform is made. The molten glass flows from the outlet formed in the bottom of the inner sidewall facing the first direction among the inner sidewalls of the dissolution tank toward the subsequent process. When flowing the molten glass, the temperature of the lower layer of the molten glass located below the surface layer in the depth direction of the molten glass so that convection due to the temperature distribution of the molten glass in the lower layer does not occur. By adjusting at least the amount of heat provided to the molten glass which is located at both ends of the first direction, the molten glass is flowed from the outlet to the subsequent step while equalizing the temperature distribution along the first direction of the molten glass of the lower layer. .

(2) In the method for manufacturing a glass substrate of (1), in order to make the temperature distribution in the lower layer uniform, the inner side wall parallel to the first direction of the dissolution tank in the depth direction corresponding to the lower layer. In the portion, a plurality of pairs of electrodes are provided to energize and heat the molten glass located in the lower layer by flowing a current in a direction parallel to the liquid level. Each pair of the plurality of pairs of electrodes faces each other in a direction orthogonal to the first direction.

(3) In the method for manufacturing a glass substrate of (2), the power supplied to the plurality of pairs of electrodes is the first in comparison with the electrode located in the center portion of the first direction of the dissolution tank in the first direction. The electrode side located in the both sides of the said dissolution tank of the direction is high.

(4) The method for producing a glass substrate according to any one of (1) to (3), wherein the inner sidewall contacting the molten glass of the dissolution tank is made of a refractory containing zirconia as a component.

(5) The method for producing a glass substrate of any one of (1) to (3), wherein the temperature of the molten glass at 10 ^2.5 poise is 1300 ° C or higher.

(6) The method for producing a glass substrate according to any one of (1) to (3), wherein the glass substrate to be manufactured is made of aluminosilicate glass and contains 50% by mass or more of SiO ₂ .

In the production method of the glass substrate 7 (6), a glass substrate on which the preparation is made up as an aluminosilicate glass, and the SiO ₂ and Al ₂ O ₃ containing 60 wt% or more in total.

(8) The method for producing a glass substrate according to any one of (1) to (7), wherein the glass substrate to be produced is composed of an alkali free glass or an alkali trace amount containing glass.

(9) In the method for producing a glass substrate according to any one of (1) to (8), the specific resistance of the molten glass at 1500 ° C. is 180 Ω · cm or more.

(10) In the method for producing a glass substrate according to any one of (1) to (9), tin oxide is added to the glass raw material as a clarifier.

(11) In the manufacturing method of the glass substrate of (2), the heat insulation member is provided in the outer side wall of the said dissolution tank around the part in which the said several pair of electrode is provided.

100: dissolution device
101: dissolution tank
101a: liquid tank
101b: upper space
101c: face value
101d: bucket
101f: Raw material input window
102: clarification
103: stirring tank
103a: stirrer
104, 105, 106: glass supply pipe
110: inner wall
110a, 110b, 110c, 110d: inner wall
110e: Bottom
112: burner
114: electrode
116: control unit
118: computer
120: heterogeneous raw material
200: forming apparatus
210: molded body
300: cutting device

Claims (12)

A melting step of melting the raw material of the glass to produce the molten glass;
The dissolution step,
Arranging the molten glass between a pair of electrodes and applying a voltage to flow a current through the molten glass to generate Joule heat;
Calculating a specific resistance of the molten glass by measuring a value of the current and a value of the voltage;
Controlling the Joule heat based on the calculated specific resistance;
Method for producing a glass substrate. The method of claim 1,
In the dissolution step, a plurality of pairs of the pair of electrodes are used, and a region in which the current flows for each of the pair of electrodes is set,
In the step of calculating the specific resistance, the specific resistance is calculated for each of the regions,
In the step of controlling the row of rows, the method of manufacturing a glass substrate for controlling the row of rows for each region. The method of claim 1,
The dissolution step,
And a preliminary step of obtaining a correlation between the temperature of the molten glass and the specific resistance of the molten glass,
The step of controlling the joule heat,
Setting a target temperature of the molten glass;
Calculating a temperature of the molten glass based on the correlation and the calculated specific resistance;
And a step of controlling Joule's heat generated in the molten glass based on a result of comparing the calculated temperature with the target temperature. The method of claim 3,
In the dissolution step, a plurality of pairs of the pair of electrodes are used, and a region in which the current flows for each of the pair of electrodes is set,
In the step of calculating the specific resistance, the specific resistance is calculated for each of the regions,
In the step of calculating the temperature, the temperature is calculated for each of the regions,
In the step of controlling the row of rows, the method of manufacturing a glass substrate for controlling the row of rows for each region. The method according to claim 3 or 4,
The step of controlling the joule heat,
Obtaining the current value for generating Joule's heat in the molten glass so as to maintain the calculated temperature at the target temperature, and setting the current value to a target current value;
And controlling the voltage to maintain the current value at the target current value. 6. The method according to any one of claims 3 to 5,
In the preliminary process,
The temperature is set to T, the specific resistance is set to ρ, and the expression representing the correlation:
[Equation 1]

Find the constants a and b in,
In the step of calculating the temperature,
A method of manufacturing a glass substrate which calculates the temperature T by substituting the specific resistance p in Equation 1. The method according to claim 2 or 4,
The pair of electrodes are arranged opposite to each other on both sides of the molten glass so as to cross the flow direction from the upstream to the downstream of the molten glass,
The plurality of pairs of electrodes are arranged at intervals from each other in the flow direction,
The boundary of the said area | region is set so that it may pass through the intermediate point of the said electrode adjacent to the said flow direction. 8. The method according to any one of claims 1 to 7,
In the step of calculating the specific resistance,
The current value is I, the voltage is E, the cross-sectional area of the molten glass through which the current flows is S, the distance between the pair of electrodes is L, the resistivity is ρ, Expressions representing these relationships:
&Quot; (2) "

Based on the above, the specific resistance ρ is calculated. The method according to any one of claims 1 to 8,
In the dissolution process,
The manufacturing method of the glass substrate which disperse | distributes and inputs the said raw material so that the liquid surface of the said molten glass may be covered. 10. The method according to any one of claims 1 to 9,
The electrode is a method of manufacturing a glass substrate is a tin oxide electrode. 11. The method according to any one of claims 1 to 10,
After the dissolution step,
Clarifying the molten glass;
It has a process of molding the molten glass into a glass substrate,
The manufacturing method of the glass substrate which performs the process of clarifying the said molten glass in the inside of the container made from platinum or a platinum alloy. 12. The method according to any one of claims 1 to 11,
The said glass substrate is a manufacturing method of the glass substrate which is a glass substrate for flat panel displays.

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