KR101641806B1 - Apparatus and method for making glass sheet - Google Patents

Abstract

A method for producing a glass substrate is characterized in that in a melting tank, combustion heating in a gas phase by a combustion means and electrification heating conducted by flowing an electric current to a molten glass are used, and a glass raw material And a refining step of refining the molten glass using a redox reaction of tin oxide. The combustion heating and the energization heating are performed so that the ratio of the calorific value by the combustion heating to the calorific value by the energetic heating is not less than 1.0 and not more than 3.4. When making a molten glass to be a glass having a viscosity of 10 ^2.5 poise and having a temperature of 1580 캜 or higher, the ratio of the above calorific value should be 1.0 or higher and 2.8 or lower.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing a glass substrate,

The present invention relates to a manufacturing method of a glass substrate for manufacturing a glass substrate and a glass substrate manufacturing apparatus for implementing the manufacturing method.

2. Description of the Related Art In recent years, in the field of a display panel, high definition of a pixel is progressing for improving an image quality. With the advancement of high definition, it is desired that the glass substrate used for the display panel is of high quality. For example, there has been a demand for a glass substrate which is less likely to undergo dimensional changes in a glass substrate subjected to heat treatment at a high temperature during the manufacturing process of the panel, and has a small heat shrinkage. The glass substrate used for the liquid crystal display panel preferably contains no alkali metal oxide including Li ₂ O, Na ₂ O and K ₂ O, Glass that contains little or no water is used.

Generally, the above-described heat shrinkage of the glass substrate becomes smaller as the distortion point of the glass becomes higher. It is also known that the heat shrinkage of the glass substrate becomes smaller as the cooling rate during the manufacturing process of the glass substrate becomes smaller. Therefore, even with the same glass composition, by sufficiently reducing the cooling rate, it is possible to reduce the heat shrinkage to a required level. Particularly, when a glass substrate is manufactured from a molten glass by a float method, it is relatively easy to make the cooling rate slow by making the cooling furnace lengthened. However, when the glass substrate is manufactured by the down-draw method, Is difficult in terms of facility or operation operation. Therefore, in order to manufacture a glass substrate corresponding to a demand for heat shrinkage by the down-draw method, a glass having a glass composition with a higher degree of resistance than the conventional glass composition is used (Patent Document 1).

In addition, a known glass (Patent Document 2) which does not contain the alkali metal oxide or contains little or no alkali metal oxide as described above generally has a melting point higher than that of an alkali glass which does not interfere with the alkali metal oxide The temperature is high, and is insoluble. In the case of using such a glass, it is necessary to make the temperature of the molten glass in the melting step higher than that of the alkali glass in order to sufficiently dissolve the glass raw material to prevent the undissolved product, which is a defect of the glass substrate, there was.

Japanese Laid-Open Patent Publication No. 2010-6649 Japanese Laid-Open Patent Publication No. 2010-235444

However, if the glass composition is adjusted so that the point becomes higher, the viscosity at a high temperature region (for example, a temperature of 1,500 占 폚 or more) becomes high and the glass becomes insoluble. When the viscosity of the molten glass in the high temperature region is increased, it is necessary to sufficiently dissolve the glass raw material so as to prevent the undissolved product, which is a defect of the glass substrate, from flowing out to the subsequent step, I needed to do it.

Generally, in the case of making a molten glass as a glass raw material in a melting tank, the gaseous phase temperature is raised by heating with a burner using, for example, a combustion gas in the gas phase space in the melting tank to raise the temperature of the wall of the melting tank, Thereby dissolving the glass raw material introduced by the radiant heat. Further, in the melting tank, the molten glass generated by melting is heated by the radiant heat, and energized heating is carried out through the pair of electrodes in the liquid phase of the melting tank to make the molten glass have a desired temperature and viscosity.

However, if the temperature of the molten glass in the melting step is raised, a cleaning agent that promotes defoaming by generating bubbles in the refining step may generate oxygen in a floating state on the surface of the molten glass in the melting step , And releases the oxygen out of the molten glass. For this reason, there has been a problem that the refining ability of the refining agent is lowered and the bubbles can not be sufficiently reduced in the refining step.

In the case of producing a glass substrate of a hardly soluble glass which does not contain or hardly contain an alkali metal oxide, if the temperature of the molten glass is made too high in a melting process for producing a molten glass, The bubbles are generated in the melting process, and the bubbles are released from the molten glass. For this reason, there has been a problem that bubbles can not be sufficiently reduced in the refining process.

In addition, in recent years, the problem of the air bubbles has become more remarkable from the following reasons.

· From the viewpoint of environmental problems, As ₂ O ₃ And the refining effect is inferior in the As ₂ O ₃ contrast, tin oxide is used. Therefore, sufficient defoaming is not achieved in the refining process, and the problem of air bubbles is remarkable.

Since the viscosity of the molten glass in the high-temperature region is high, the rising speed of the bubbles in the refining process is slow. For this reason, sufficient defoaming can not be achieved in the refining step, and the problem of bubbles is remarkable.

Therefore, it is an object of the present invention to provide a glass substrate manufacturing method capable of reducing the occurrence of bubbles by sufficiently exhibiting the effect of a fining agent while reducing the occurrence of unheated products, even when a glass substrate is manufactured using a poorly soluble glass And a glass substrate manufacturing apparatus.

One aspect of the present invention is a method of manufacturing a glass substrate, including the following modes.

(Form 1)

A method of manufacturing a glass substrate,

In the melting tank, a glass having a viscosity of 10 ^2.5 poise and containing 15 vol% of tin oxide and having a temperature of 1580 캜 or higher is used by using combustion heating in a gas phase using a combustion means and current- A dissolving step of dissolving the glass raw material so that the glass raw material is dissolved,

And a refining step of refining the molten glass using a redox reaction of tin oxide,

Characterized in that the combustion heating and the energization heating are performed such that a ratio of a heating value by the combustion heating to a heating value by the energization heating is 1.0 or more and 2.8 or less.

(Form 2)

A method of manufacturing a glass substrate,

In the melting tank, by using combustion heating in a gas phase using a combustion means and electrification heating conducted by flowing an electric current to a molten glass, a glass containing SnO _{2 and} having a viscosity of 10 ^2.5 poise at a temperature of 1580 degrees or higher And a melting step of melting the glass raw material,

Characterized in that the combustion heating and the energization heating are performed so that the ratio of the amount of heat generated by the combustion heating to the amount of heat generated by the energetic heating is 1.5 or more and 2.8 or less.

(Form 3)

The method for producing a glass substrate according to form 1 or 2, wherein the glass substrate has a melting point of 680 캜 or higher.

(Mode 4)

A method of manufacturing a glass substrate,

A dissolution step of dissolving a glass raw material in a melting tank using combustion heating in a gas phase using a combustion means and electrification heating conducted by flowing an electric current in the molten glass so as to be glass having a melting point of 680 DEG C or higher, and,

And a refining step of refining the molten glass using a redox reaction of tin oxide,

Characterized in that the combustion heating and the energization heating are performed such that a ratio of a heating value by the combustion heating to a heating value by the energization heating is 1.0 or more and 2.8 or less.

(Mode 5)

Wherein the maximum temperature of the molten glass in the refining step is higher than the maximum temperature of the molten glass in the melting tank.

(Form 6)

The method for producing a glass substrate according to any one of claims 1 to 5, wherein the temperature of the thin portion of the ceiling surface covering the vapor phase space of the melting tank is 1610 캜 or lower.

(Form 7)

The method for producing a glass substrate according to any one of modes 1 to 6, wherein the content of the alkali metal oxide in the glass substrate is 0 mol% or more and 0.4 mol% or less.

(Form 8)

The glass substrate _{is, SiO 2, Al 2 O 3} , B 2 O 3, and the RO containing the (R is, Mg, Ca, of Sr, and Ba entire element contained in the glass substrate) at least, B ₂ O ₃ Is from 0 to 7 mol% based on the total amount of the glass composition.

(Mode 9)

Wherein the glass substrate comprises at least SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ and RO (RO is an entire element contained in the glass substrate among MgO, CaO, SrO and BaO) A method for producing a glass substrate according to any one of the first to eighth aspects.

(Mode 10)

The content of B ₂ O ₃ is 0 to 10 mol% or 0 to 5 mol%.

(Mode 11)

The method for producing a glass substrate according to form 9 or 10, wherein the content of SiO ₂ is 68 to 75 mol%.

(Form 12)

Wherein the glass substrate comprises B ₂ O ₃ and RO (RO is an amount of MgO, CaO, SrO and BaO), and SiO ₂ and Al ₂ O ₃ (2 x SiO ₂ ) + Al ₂ O ₃ ) / ((2 x B ₂ O ₃ ) + RO) is not less than 4.5, and the glass according to any one of the ninth to eleventh aspects / RTI >

(Form 13)

Wherein the glass substrate contains at least any one of MgO, CaO, SrO, and BaO and has a molar ratio (BaO + SrO) / RO (RO is an amount of MgO, CaO, SrO, and BaO) A method for manufacturing a glass substrate according to any one of claims 1 to 6.

(Form 14)

The method for producing a glass substrate according to any one of Forms 1 to 13, wherein the content of the alkali metal oxide in the glass substrate is 0 mol% or more and 0.4 mol% or less.

In the present specification, the content of alkali metal oxide refers to the sum of the contents of Li ₂ O, Na ₂ O and K ₂ O.

(Form 15)

The method for producing a glass substrate according to any one of the above forms 1 to 14, wherein the electrical resistivity (hereinafter also referred to as a resistivity) of the glass constituting the glass substrate in a molten glass at 1550 캜 is 100 Ω · cm or more.

(Form 16)

Wherein the glass substrate comprises:

SiO ₂ in an amount of 60 to 80 mol%, Al ₂ O ₃ Of the present invention contains 10 to 20 mol% of B ₂ O ₃ , 0 to 10 mol% of B ₂ O ₃ and 0 to 17 mol% of RO (RO is an amount of MgO, CaO, SrO and BaO) Wherein the glass substrate is a glass substrate.

(Mode 17)

The glass substrate may be a glass substrate for a flat panel display. It is preferable that the glass substrate is a glass substrate for an LTPS (Low Temperature Poly-Silicon) TFT (Thin Film Transistor) display or a glass substrate for an organic EL (electroluminescence) ≪ / RTI >

(Form 18)

The refining step may include a defoaming treatment in which the temperature of the molten glass is raised to 1630 DEG C or higher at a heating rate of 2 DEG C / min or more after the melting step to produce bubbles in the molten glass to perform defoaming, , And an absorption process for absorbing bubbles in the molten glass into the molten glass by lowering the molten glass.

(Form 19)

Wherein the degassing treatment raises the temperature of the molten glass to 1630 DEG C or higher at a heating rate of 2.5 DEG C / min or more.

(Form 20)

Wherein the refining step includes a degassing step of raising the temperature of the molten glass to 1630 DEG C or higher to generate bubbles in the molten glass to perform defoaming and a step of heating the molten glass to a temperature range of 1600 DEG C to 1500 DEG C Comprising the step of absorbing bubbles in the molten glass into the molten glass by lowering the temperature of the molten glass at a temperature lowering rate of 2 DEG C / min or more.

(Form 21)

A method of manufacturing a glass substrate,

A glass substrate containing tin oxide and having an alkali metal oxide content of 0 to 0.4 mol% is used as the melting furnace in the melting tank by using combustion heating in a gas phase using a combustion means and electric current heating conducted by flowing an electric current to the molten glass A melting step of melting the glass raw material so combined,

And a refining step of refining the molten glass using a redox reaction of tin oxide,

The combustion heating and the energization heating are performed so that the ratio of the amount of heat generated by the combustion heating to the amount of heat generated by the energized heating is not less than 1.0 and not more than 3.4.

(Form 22)

A method of manufacturing a glass substrate,

A glass substrate containing tin oxide and having an alkali metal oxide content of 0 to 0.4 mol% is used as the melting furnace in the melting tank by using combustion heating in a gas phase using a combustion means and electric current heating conducted by flowing an electric current to the molten glass And a dissolving step of dissolving the glass raw material so combined,

And the combustion heating and the energization heating are performed so that the ratio of the amount of heat generated by the combustion heating to the amount of heat generated by the energetic heating is not less than 1.5 and not more than 3.4.

(Form 23)

A method of manufacturing a glass substrate,

In the melting tank, combustion heating in a gas phase using a combustion means, and energization heating conducted by flowing an electric current to a molten glass are used, and a glass having a viscosity of 10 ^2.5 poise, including tin oxide, A melting step of melting the glass raw material so that the glass raw material is melted,

And a refining step of refining the molten glass using a redox reaction of tin oxide,

The combustion heating and the energization heating are performed so that the ratio of the amount of heat generated by the combustion heating to the amount of heat generated by the energized heating is not less than 1.0 and not more than 3.4.

(Form 24)

A method of manufacturing a glass substrate,

In the melting tank, combustion heating in a gas phase using a combustion means, and energization heating conducted by flowing an electric current to a molten glass are used, and a glass having a viscosity of 10 ^2.5 poise, including tin oxide, And a melting step of melting the glass raw material,

And the combustion heating and the energization heating are performed so that the ratio of the amount of heat generated by the combustion heating to the amount of heat generated by the energetic heating is not less than 1.5 and not more than 3.4.

(Form 25)

A melting vessel body having a vapor space and storing the molten glass,

Combustion means for heating the glass raw material and / or the molten glass by burning heating in the vapor space,

An electrode pair formed on a wall which is in contact with the molten glass to energize the glass raw material and / or the molten glass,

And a blue sign for purifying the molten glass using a redox reaction of tin oxide contained in the molten glass,

When making the molten glass using the combustion heating and the energization heating so that the glass becomes a glass having a viscosity of 10 ^2.5 poise at 1580 캜 or higher, the amount of heat generated by the combustion heating Wherein the burning heating and the energizing heating are performed so that the ratio is 1.0 or more and 2.8 or less.

(Form 26)

A melting vessel body having a vapor space and storing the molten glass,

Combustion means for heating the glass raw material and / or the molten glass by burning heating in the vapor space,

An electrode pair formed on a wall which is in contact with the molten glass to energize the glass raw material and / or the molten glass,

And a blue sign for purifying the molten glass using a redox reaction of tin oxide contained in the molten glass,

The ratio of the calorific value due to the combustion heating to the calorific value due to the energetic heating is set to be not less than 1.0 and not more than 2.8 when the molten glass is made by using the combustion heating and the energization heating so that the glass becomes a glass having a temperature of 680 캜 or more. , And the combustion heating and the energization heating are performed.

(Form 27)

A melting vessel body having a vapor space and storing the molten glass,

Combustion means for heating the glass raw material and / or the molten glass by burning heating in the vapor space,

An electrode pair formed on a wall which is in contact with the molten glass to energize the glass raw material and / or the molten glass,

And a blue sign for purifying the molten glass using a redox reaction of tin oxide contained in the molten glass,

When the molten glass is made using the burning heating and the energizing heating so as to be a glass substrate having an alkali metal oxide content of 0 to 0.4 mol%, the ratio of the calorific value by the combustion heating to the calorific value by the energetic heating Is carried out by burning heating and energizing heating so as to be not less than 1.0 and not more than 3.4.

(Form 28)

A melting vessel body having a vapor space and storing the molten glass,

Combustion means for heating the glass raw material and / or the molten glass by burning heating in the vapor space,

An electrode pair formed on a wall which is in contact with the molten glass to energize the glass raw material and / or the molten glass,

And a blue sign for purifying the molten glass using a redox reaction of tin oxide contained in the molten glass,

When the molten glass is made by using the combustion heating and the energization heating so that the glass becomes a glass having a viscosity of 10 ^2.5 poise at a temperature of 1500 ° C or higher, the amount of heat generated by the combustion heating Wherein the burning heating and the energizing heating are performed so that the ratio is not less than 1.0 and not more than 3.4.

According to the method for manufacturing a glass substrate and the apparatus for manufacturing a glass substrate of this type, even when a glass substrate is manufactured by using glass as a refractory glass, the effect of the refining agent is sufficiently exhibited while reducing the occurrence of unheated products, Can be reduced.

1 is a view showing a flow of a manufacturing method of a glass substrate of the present embodiment.
Fig. 2 is a diagram schematically showing an example of a glass substrate manufacturing apparatus for performing a dissolving process to a cutting process in the present embodiment.
Fig. 3 is a view for explaining an example of a preferable form of the temperature history of the molten glass from the melting step to the molding step in the present embodiment.
Fig. 4 is a view for explaining an example of a blue sign used in the glass substrate producing apparatus of the present embodiment.
5 is a perspective view for explaining the outline of a melting vessel main body and its peripheral structure of a melting vessel used in the manufacturing method of the glass substrate of the present embodiment.
Fig. 6 is a view for explaining a cross section of the dissolving tank shown in Fig. 5;

Hereinafter, a method of manufacturing a glass substrate and a glass substrate manufacturing apparatus according to the present embodiment will be described.

(Overview of Manufacturing Method of Glass Substrate)

1 is a view showing a flow of a manufacturing method of a glass substrate of the present embodiment.

The glass substrate manufacturing method includes a melting step (ST1), a refining step (ST2), a homogenizing step (ST3), a supplying step (ST4), a molding step (ST5), a quenching step (ST7). In addition, it has a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like.

The dissolution step (ST1) is carried out in a dissolving tank. In a melting tank, a glass raw material is charged into a dissolution tank and dissolved by heating to produce a molten glass containing tin oxide. This molten glass is a molten glass having a high viscosity at a high temperature of 1580 DEG C or higher at a viscosity of 10 ^2.5 poise in any form. In another embodiment, the molten glass is a glass whose melting point (temperature corresponding to a viscosity of 10 ^14.5 dPa · sec) is 680 ° C. or higher. In another embodiment, the molten glass is a high-temperature viscous molten glass having a temperature of 1500 ° C or higher when the viscosity is 10 ^2.5 poise. In another embodiment, the molten glass is a glass substrate having a content of alkali metal oxide of 0 to 0.4 mol%. The glass raw material is combined in advance to be such a molten glass. Further, molten glass stored in the melting tank is flowed toward the downstream process from an outlet formed at one bottom of the inner sidewall of the melting tank.

The heating of the molten glass in the melting tank is carried out by, for example, burning heating in a gas phase using a combustion gas by a burner and electrification heating conducted by flowing an electric current through the molten glass, thereby producing a molten glass having a predetermined viscosity. Specifically, the charged glass raw material is floated on the liquid surface of the molten glass to be stored and heated by the heat radiation heat from the vapor space of the melting bath or the flame of the burner, heated by the molten glass heated by conduction, do. The molten glass thus produced is heated to a higher temperature. Further, the molten glass is heated to a higher temperature by heat radiation from the wall surface of the vapor space of the melting tank or from the flame of the burner. The molten glass contains tin oxide as a fining agent. As ₂ O ₃ , Sb ₂ O ₃ Is preferably substantially not contained in the molten glass in terms of environmental load. It is not substantially contained. Even if these substances are included, they are impurities. Specifically, these substances are preferably 0.1 mol% or less. At this point, at least tin oxide is used as a fining agent. Further, the glass raw material may be added with a cleaning agent in advance. In the melting tank, the molten glass is heated so that the glass raw material is completely dissolved so that unheated residues of the glass raw material do not flow out, and the predetermined viscosity becomes a suitable level for the post-process.

The purifying step (ST2) is carried out at least in the blue sign. In the purifying step, the molten glass is heated in a blue oven having a gas-phase space communicated with the atmosphere, whereby the volume of bubbles containing O ₂ , CO ₂ or SO ₂ contained in the molten glass is reduced by the amount of the purifying agent It absorbs oxygen and grows. As a result, the rising speed of the bubbles is raised, and the bubbles float on the surface of the molten glass and are released into the vapor phase space (defoaming treatment). Further, in the refining step, the reducing material obtained by the reducing reaction of the refining agent performs the oxidation reaction by lowering the temperature of the molten glass. As a result, gas components such as oxygen in the bubbles remaining in the molten glass are reabsorbed into the molten glass, and the bubbles disappear (absorption process). The oxidation reaction and the reduction reaction by the cleaning agent are performed by controlling the temperature of the molten glass. In the refining step, at least tin oxide is used as a fining agent.

In the homogenization step (ST3), the molten glass in the stirring tank supplied through the pipe extending from the blue sign is stirred using a stirrer to homogenize the glass components. Thereby, it is possible to reduce unevenness in the composition of the glass, which is a cause of malty or the like.

In the supplying step (ST4), the molten glass is supplied to the molding apparatus through the pipe extending from the stirring tank.

In the molding apparatus, the molding step (ST5) and the quenching step (ST6) are performed.

In the molding step (ST5), the molten glass is formed into a sheet glass to form a flow of the sheet glass. For forming, an overflow down-draw method is used.

In the quenching step (ST6), the formed sheet glass is cooled to a desired thickness so that internal deformation does not occur and no warping occurs.

In the cutting step (ST7), in the cutting apparatus, the sheet glass supplied from the molding apparatus is cut to a predetermined length to obtain a plate-like glass substrate.

Fig. 2 is a diagram schematically showing an example of a glass substrate manufacturing apparatus for performing the dissolving step (ST1) to cutting step (ST7) in the present embodiment. As shown in Fig. 2, this apparatus mainly has a dissolving apparatus 100, a molding apparatus 200, and a cutting apparatus 300. Fig. The melting apparatus 100 has a melting vessel 101, a blue bulb 102, a stirring vessel 103, and glass feed pipes 104, 105, and 106.

In the dissolving apparatus 101 shown in Fig. 2, the glass raw material is charged using the screw feeder 101a, and the molten glass MG obtained by dissolving the glass raw material is supplied to the molten glass MG Is heated. In the blue oven 102, the temperature of the molten glass MG is adjusted, and the refining of the molten glass MG is performed using the redox reaction of the refining agent. In the stirring tank 103, the molten glass MG is stirred and homogenized by the stirrer 103a. In the molding apparatus 200, the sheet glass SG is formed from the molten glass MG by an overflow down-draw method using the formed body 210. [

Fig. 3 is a view for explaining an example of a preferable form of the temperature history of the molten glass from the melting step to the molding step in the present embodiment.

In the melting tank 101, the temperature of the molten glass MG gradually increases from the temperature T1 at the time when the glass raw material is introduced to the temperature T3 at the time when the glass raw material enters the glass supply pipe 104. 3, T1 <T2 <T3, but T2 = T3 or T2> T3, or at least T1 <T3.

Fig. 4 is a view for explaining an example of blue sign 102. Fig. The blue sign 102 is a cylindrical container made of, for example, platinum or a gold alloy, and glass supply pipes 104 and 105 are connected to both ends in the longitudinal direction (left and right direction in FIG. 4). Metal flanges 102a and 102b are formed on both ends in the longitudinal direction of the blue sign 102 so as to protrude from the surface of the blue sign 102 to the outer peripheral side. A vent pipe 102c communicating the vapor phase space with the external atmosphere is formed at a midway point between both ends in the longitudinal direction of the blue sign 102. [ The gas discharged from the molten glass is discharged to the outside through the vent pipe 102c.

Electrodes (not shown) are mounted on the metallic flanges 102a and 102b, respectively, and the current from the electrodes is uniformly diffused around the blue screen 102. [ Electricity is conducted between the two electrodes mounted on the metal flanges 102a and 102b so that the blue sign 102 generates heat and the molten glass MG in the blue sign 102 is heated. The metal flange and the electrode are also formed in the glass supply pipe 104.

A constant current is flowed between the metal flange 102a of the blue lamp 102 and the unillustrated metal flange of the glass supply pipe 104 so that the platinum or platinum alloy pipe of the glass supply pipe 104 is heated by energization, The molten glass MG is heated at a temperature at which the tin oxide abruptly releases oxygen from the temperature T3 by flowing a constant current between the metal flange 102a of the sealing ring 102 and the metal flange 102b of the blue sealing ring 102 The temperature raising rate is preferably 2 ° C / min or more, more preferably 2.5 ° C / min or more, until T4 (for example, 1630 ° C or higher, more preferably 1630-1700 ° C and further preferably 1650-1700 ° C) . More preferably, the temperature of the molten glass (MG) is preferably raised to 1,630 DEG C or more at a temperature raising rate of 2.5 DEG C / min or more. It this case, it is desirable that the temperature rising rate in the above range, when the temperature raising rate in the above range, O ₂ This is because the emission amount of the gas increases very rapidly. Further, the larger the difference between the temperatures T3 and T4 is, the more the amount of O ₂ released by the tin oxide in the molten glass MG is increased, and the defoaming is accelerated. Therefore, it is preferable that the temperature T4 is, for example, 50 DEG C or more higher than the temperature T3. Therefore, it is preferable that the maximum temperature of the molten glass when refining is higher than the maximum temperature of the molten glass in the melting tank.

Further, the molten glass MG entering the blue oven 102 is maintained at a temperature T5 substantially equal to the temperature T4 from the temperature T4. The temperature of the molten glass MG at the temperature T3 to the temperature T5 is regulated by the method of energizing the blue sign in the present embodiment, but the present invention is not limited to this method. For example, the temperature control may be performed using indirect heating by a heater (not shown) disposed around the blue circle.

At this time, the molten glass (MG) is heated to 1630 DEG C or higher, thereby promoting the reaction of oxygen release of tin oxide, which is a refining agent. As a result, a large amount of oxygen is released into the molten glass MG. Existing bubbles in the molten glass (MG) can be prevented from diffusing into the expansion of the bubble diameter by the synergistic effect of the pressure of the gas component in the bubbles caused by the temperature rise of the molten glass (MG) The bubbles are diffused into the bubbles to overlap each other, and the bubble diameter is enlarged by the synergistic effect.

The expanded bubble diameter accelerates the rising speed of the bubble in accordance with the Stokes' law, and promotes the bubble rise and breakage.

The bubbles in the molten glass MG are floated on the surface of the molten glass MG and the bubbles in the molten glass MG are scattered on the surface of the molten glass MG, Whereby the molten glass MG is defoamed.

3, the degassing treatment is performed in a period in which the temperature of the molten glass MG rises from the temperature T3 to the temperature T4 and thereafter is maintained at the temperature T5 substantially equal to the temperature T4. In Fig. 3, T4 and T5 are substantially the same, but T4 &lt; T5 or T4 &gt; T5.

In addition, a place where the temperature of the molten glass MG reaches the temperature T4 may be the glass supply pipe 104 or the blue sign 102. [

The first highest temperature of the molten glass MG when the molten glass MG flows through the glass supply pipe 104 is the highest temperature of the molten glass MG when flowing through the blue oven 102 Equal to or higher than that. Thereby, when the molten glass MG moves from the glass supply pipe 104 to the blue oven 102, since the temperature of the molten glass MG is sufficiently high and maintained above the temperature at which the reaction of releasing oxygen of the refining agent occurs, The blue sign 102 does not require heating to further raise the molten glass MG. Therefore, the heating temperature of the blue sign 102 can be suppressed to be lower than the conventional one. Therefore, it is possible to suppress the volatilization of platinum from the blue sign 102 made of platinum or a platinum alloy, and to prevent the foreign substances such as platinum crystals adhering to the inner wall surface of the blue sign 102 by the volatilization of the platinum, It is possible to manufacture a glass substrate having few defects caused by contamination, that is, defects caused by foreign substances. It is preferable that the temperature of the molten glass MG reaches the first highest temperature while the molten glass MG flows through the glass supply pipe 104. [ In this case, as compared with the case where the molten glass reaches the first maximum temperature and the second maximum temperature at the connection position of the glass supply pipe 104 and the blue oven 102, the heating temperature of the blue oven 102 is lowered, Volatilization of the platinum can be more easily suppressed from the blue sign 102 made of the platinum alloy.

The molten glass MG flowing from the blue oven 102 to the glass supply pipe 105 absorbs the remaining bubbles and is supplied from the temperature T5 through the temperature T6 (for example, 1600 deg. C) (Which is a temperature suitable for the stirring process and is different from that of the glass seed (germ) species and the stirring device 103, but is, for example, 1500 ° C.).

The lowering of the temperature of the molten glass MG does not cause the foaming and de-foaming to occur, and the pressure of the gas component in the small bubbles remaining in the molten glass MG is lowered, and the bubble diameter becomes smaller. Also, when the temperature of the molten glass (MG) becomes 1600 DEG C or less, a part of the tin oxide which releases oxygen tends to absorb oxygen and return to the original tin oxide. Therefore, the oxygen in the remaining bubbles in the molten glass MG is reabsorbed in the molten glass MG, so that the small bubbles become smaller. This small bubble is absorbed by the molten glass (MG), and the small bubble finally disappears.

The treatment for absorbing oxygen which is a gas component in the bubbles by the reaction of absorbing oxygen of the SnO 2 is an absorption process and is performed during a period in which the temperature decreases from the temperature T 5 to the temperature T 6 through the temperature T 6. In Fig. 3, the cooling rate of the temperatures T5 to T6 is faster than the cooling rate of the temperatures T6 to T7, but the cooling rate of the temperatures T5 to T6 may be slower than the cooling rate of the temperatures T6 to T7. It is preferable that the temperature of the molten glass MG is lowered at a temperature lowering rate of 2 占 폚 / min or more at a temperature of 1600 占 폚 to 1500 占 폚 at least during this absorption process, and a more preferable temperature lowering rate is 2.5 占 폚 / min or more. In the absorption process, the molten glass (MG) is heated to a temperature within the range of 1500 占 폚 or lower (specifically, a range from 1500 占 폚 to the molten glass temperature when supplied to the molding process, for example, 1500 占 폚 to 1300 占 폚) Is preferably slower than the temperature lowering rate in the temperature range of 1600 캜 to 1500 캜.

In view of the improvement of the productivity of the glass substrate and the reduction of the facility cost, the molten glass (MG) has a melting point lower than 1500 deg. C (specifically, from 1500 deg. Range, for example, 1500 ° C to 1300 ° C), is preferably faster than the rate of temperature decrease in the temperature range of 1600 ° C to 1500 ° C. When such temperature control of the molten glass MG is carried out, it is preferable to provide a flow rate adjusting device for adjusting the amount of the molten glass MG to be supplied to the molding step.

After the absorption treatment or during the absorption treatment, the molten glass MG enters the stirring tank 103. The stirring tank 103 reduces the composition unevenness in the molten glass MG and homogenizes the molten glass MG. Further, in the stirring tank 103, the above absorption process may be continued. Thereafter, the molten glass MG is cooled down until the temperature T8 suitable for molding in the molding step, for example, 1200 to 1300 deg.

The molten glass MG is supplied to the molding apparatus 200 via the history history of the molten glass MG.

In such a method for producing a glass substrate and a melting process for melting a glass raw material to produce a molten glass and heating the molten glass, Burning heating in the gas phase and electrification heating conducted by passing current through the molten glass are used. Particularly, in order to make a glass substrate having a small heat shrinkage, a glass having poor solubility, for example, a glass having a high viscosity at a temperature of 1580 DEG C or higher when the viscosity is 10 ^2.5 poise or higher, a glass having a melting point of 680 DEG C or higher, A glass having a high viscosity at a high temperature of 1,500 ° C or higher at 10 ^2.5 poise, a glass having a high glass transition temperature and having an alkali metal oxide content of 0 to 0.4 mol% (an alkali-free glass or an alkali Containing glass) is used, it is possible to provide a glass composition which is not resistant to abuse, has a high viscosity at a high temperature and is not high in viscosity, and a glass composition which has a higher melting point than the alkali glass containing an alkali metal oxide in an amount of more than 0.4 mol% The amount of heat generated by the combustion heating and the energization heating by the heater is increased.

At this time, in the present embodiment, the ratio of the amount of heat generated by the combustion heating to the amount of heat generated by the energized heating (hereinafter referred to as the heating amount ratio) is determined, and combustion heating and energization heating are performed. Hereinafter, heating of the molten glass in the melting tank will be described in detail.

(Melting tank)

Fig. 5 is a perspective view for explaining the outline of the structure of the dissolution tank 101 and the structure around the dissolution tank 101, and Fig. 6 is a view for explaining a section of the dissolution tank 101. Fig. 6 is the longitudinal direction of the melting vessel 101. The cross section shown in Fig. 6 is a position in the longitudinal direction in which the electrode 114 shown in Fig. 5 is formed, assuming that the direction from the inlet of the glass raw material to the outflow port of the molten glass, Of the dissolution tank 101 in the present invention.

In the present embodiment, the melting vessel 101 mainly has a melting vessel body 110, a burner 112, an electrode pair 114, and a thin portion 118.

The melting vessel body 110 has a vapor space at the upper portion and a portion for storing the molten glass at the lower portion. The melting vessel body 110 contains tin oxide and stores a molten glass having a temperature of 1580 degrees or more when the viscosity is 10 ^2.5 poise. In the melting vessel main body 110, the combined glass raw material is put into the liquid surface of the already-stored molten glass MG and floats on a part of the liquid surface thereof. This glass raw material is melted and becomes molten glass. Since the glass raw material floats on a part of the liquid surface of the molten glass, the foam layer formed on the liquid surface by mixing the gas generated from the molten glass and the impurities which are not sufficiently dissolved does not exist in a part of the liquid surface. Therefore, in addition to the radiant heat of the vapor phase space described later, the glass raw material also receives heat flowing through the molten glass heated by conduction, and the glass raw material is dissolved.

The burner 112 is provided in three pairs of mutually opposed walls at three different positions in the longitudinal direction on the wall facing each other out of the vapor space partition walls 116 surrounding the vapor space of the melting vessel body 110 . 5, only the burner 112 installed inside the melting vessel main body 110 is shown. In the burner 112, a combustion gas obtained by mixing fuel gas and oxygen or the like is burned to generate a flame. The flow rate of the combustion gas supplied from the gas source 112a (see FIG. 5) to the burner 112 is adjusted by using the flow rate regulator 112b. In the flow rate regulator 112b, the flow rate of the combustion gas is controlled by a control signal from the computer 122. The combustion gas is, for example, a mixed gas of methane and oxygen. Also, the type of the fuel gas is not limited to methane. Instead of mixing the fuel gas with oxygen, the fuel gas and air may be mixed, or they may be separately transferred into the melting tank without mixing.

The electrode pair 114 is formed in three pairs so that the molten glass is opposed to each other at three different positions in the longitudinal direction of the sidewall of the melting vessel body 110 for heating the molten glass. 5, only electrodes of the electrode pair 114 formed on the sidewall of the front side of the melting vessel body 110 are shown. As the electrode pair 114, for example, a conductive material having heat resistance such as tin oxide or molybdenum is used. The electrode pair 114 is connected to the current control device 120 and receives the supply of the controlled current from the current control device 120. The current control device 120 is connected to the computer 122 and controlled by the control signal of the computer 122 to control the total amount of current flowing through the electrode pair 114. [ Thus, the computer 122 generates a control signal for controlling the flow rate of the combustion gas and a control signal for controlling the current passed through the electrode pair 114. [

At this time, the flow rate of the combustion gas and the flow rate of the current are controlled so that the above-described calorific value ratio is included in the predetermined range. In the present embodiment, the computer 122 controls the flow rate of the combustion gas and the flow rate of the current, but the operator can also set and control the flow rate of the combustion gas and the flow rate of the current. In this case, the flow rate of the combustion gas and the flow rate of the current are controlled so that the above-described calorific value ratio becomes 1.0 to 3.4, preferably 1.5 to 3.4.

In the present embodiment, the burner 112 for generating the flame by burning the combustion gas is used as the combustion means. In this embodiment, the combustion means is not limited to the burner 112, It would be. 5, three burners 112 are provided. However, the burners 112 may be disposed alternately on only one side of the wall or on both sides of the wall. The number of the burners 112 and the number of the electrode pairs 114 is not particularly limited and may be at least two.

The vapor space partition wall 116 is a part of the melting vessel body 110 and is a wall formed on the upper part of the retention portion of the molten glass. A burner 112 is formed on the wall. A raw material inlet 101b is formed in the vapor space partition wall 116 and a glass raw material is supplied by the screw feeder 101a (see FIG. 2) through the raw material inlet 101b. An outlet 104a is formed in the vicinity of the bottom of the melting vessel body 110 on the side wall opposite to the raw material inlet 101b of the melting vessel body 110. [ The melting tank 101 flows molten glass from the outlet 104a toward the post-process. The feedstock may be introduced by a feeding method other than the screw feeder. The position of the raw material charging port 101b is not limited to the position shown in Fig. 5, and may be formed at any position of the vapor space partition wall 116. [

The thin portion 118 is a ceiling wall for closing the vapor phase space of the melting tank 101. A temperature sensor 118a (see Fig. 6) is provided at the end of the thin portion 118. [ It is more preferable that the temperature sensor 118a be mounted on the outside of the thin portion 118 and a plurality of the temperature sensors 118a are provided in the longitudinal direction of the thin portion 118. [

Both the melting vessel main body 110 and the thin portion 118 are made of refractory bricks having heat resistance against the temperature of the molten glass.

A ridge portion 124 of a laminated structure constituted by refractory bricks is formed in the lower portion of the melting vessel body 110. The rug 124 has a heat insulating layer of a four-layer structure in the example shown in Fig. The layer structure of the rug 124 is not limited to a four-layer structure. Refractory bricks having a higher heat-resistant temperature than the refractory bricks used for the rug 124 are used in the bottom wall 110c of the melting tank 101. [ The refractory bricks having a high heat resistance temperature are dense refractory bricks having a low porosity, and thus the thermal conductivity is relatively high. For this reason, in the ridge portion 124, refractory bricks having high thermal insulation and lower thermal conductivity than the refractory bricks used for the bottom wall 110c are used to improve the heat insulating property. Since the refractory bricks having a low thermal conductivity are refractory bricks having a high porosity, the heat resistance temperature is lower than that of refractory bricks having a high thermal conductivity. Such a layer structure is employed in the dissolution tank 110. In this embodiment, a portion including the bottom wall 110c of the melting vessel body 110 and the ridge 124 is referred to as a bottom portion 126 of the melting vessel 110. [

In the melting vessel 101, when the glass raw material is melted to form a molten glass, the calorific value ratio of the calorific value by the combustion heating to the calorific value by the energetic heating is not less than 1.0 and not more than 3.4, preferably not less than 1.5 and not more than 3.4 Combustion heating and electrification heating are performed. Specifically, when a high-temperature high-viscosity glass having a viscosity of 10 ^2,5 poise or more at a temperature of 10 ^2.5 poise or a glass having a temperature of 680 ° C. or higher is used for a glass substrate used for a high-precision display, The combustion heating and the energization heating are carried out so that the ratio of the calorific value of the calorific value due to the combustion heating to the calorific value is not less than 1.0 and not more than 2.8, preferably not less than 1.5 and not more than 2.8. When a glass having a high glass transition temperature and a glass transition temperature of 1500 ° C or higher at a viscosity of 10 ^2.5 poise or a glass having an alkali metal oxide content of 0 to 0.4 mol% is used, And preferably not less than 1.5 and not more than 3.4. Such heating is realized by controlling the supply amount of the combustion gas and the supply amount of the electric current by the control signal from the computer 122 or by setting of the operator.

The amount of heat generated by energized heating can be obtained by measuring the power consumption from a power system, not shown, and the amount of power consumption. (1 kW = 860 kcal / hour) from the power consumption (kW) to the calorific value (kcal / hour) by energization heating. Further, the power consumption may be obtained from the voltage applied to the electrode 114 and the current flowing through the electrode 114.

The calorific value of the combustion heating using the combustion gas is calculated by multiplying the calorific value per unit volume by the combustion of the combustion gas by the supply amount of the combustion gas per unit time (the flow rate of the combustion gas). For example, when the calorific value of the combustion gas used is 8900 kcall / Nm 3 and the flow rate is 50 Nm 3 / hour, the calorific value is 8900 x 50/860 = 517.4 kW. The amount of heat generated by the combustion heating may be controlled to be constant by, for example, a gas calorie controller. However, the gas calorie controller is not required to be provided in the present embodiment, and can be obtained by using the controlled flow rate of the gas.

The calorific value ratio used in the present embodiment is the ratio of the average calorific value per a certain period of time. Here, the predetermined time may be one hour or one day. In the following description, the ratio of the calorific value of the average value per day is taken as an example. The calorific value for obtaining the calorific value ratio may be a value in kcal / hour or a value in kW.

Here, when the calorific value ratio exceeds 3.4, the contribution of the calorific value due to the combustion heating becomes large and the temperature of the vapor phase becomes high. Therefore, tin oxide included in the glass raw material as the refining agent in the state of the glass raw material on the liquid surface of the molten glass Oxygen is released into the gas phase space and oxygen is diffused. Therefore, when the molten glass is defoamed in the subsequent refining step, sufficient oxygen is not supplied from the refining agent contained in the molten glass, and oxygen is absorbed into the bubbles contained in the molten glass to grow the molten glass. It is not possible to sufficiently emit the bubbles by floating the bubbles. That is, the defoaming treatment can not be sufficiently performed.

On the other hand, when the calorific value ratio is less than 1.0, the contribution of the calorific value due to energetic heating becomes relatively large, and the current that flows due to energetic heating increases. When the electric current is increased, the amount of erosion of the electrode is increased, and the amount of erosion of the refractory bricks constituting the dissolution tank 101 is increased, so that the life of the dissolution tank 101 is shortened.

A glass which does not substantially contain an alkali metal oxide or has a content of an alkali metal oxide of 0 mol% or more and 0.4 mol% or less or a glass having a viscosity of 10 ^2.5 poise is used at a high temperature The glass used for a glass substrate having a high viscosity, that is, a glass substrate for an active matrix type flat panel display tends to have a large resistivity of the molten glass, and at the temperature of the molten glass stored in the melting tank 101, The resistivity of the refractory brick of the bottom wall 110c of the refractory brick is approximately the same as that of the refractory brick. This tendency becomes particularly noticeable with respect to glass containing tin oxide and having a temperature of 1550 DEG C or higher at a viscosity of 10 ^2.5 poise or a glass having a melting point of 680 DEG C or higher. Therefore, a part of the current supplied to the electrode pair 114 flows into the bottom wall 110c of the melting vessel body 110, not the molten glass, so that the bottom wall 110c is energized and heated. Therefore, when the molten glass of the glass having a high electrical resistivity is made in the melting vessel 101, a large amount of current is supplied to the electrode pair 114 to flow into the bottom wall 110c in a large amount. As a result, The amount of heat generated by heating becomes large. By the increase in the amount of heat generated in the bottom wall 110c, heat accumulation occurs due to the heat insulating property of the bottom portion 126 of the dissolution tank 101. [ This heat and agglomeration may weaken the mechanical strength of the refractory bricks of the bottom portion 126 to generate thermal creep, which may cause deformation of the bottom portion 126. In addition, there is a possibility that the temperature of the refractory bricks exceeds the heat-resistant temperature by heat shrinkage, thereby causing melting loss. For this reason, it is not preferable that the contribution of the heat generation amount due to energization heating becomes excessive. In this respect, the calorific value ratio is set to 1.0 or more, preferably 1.5 or more. When the calorific value ratio is 1.0 to 3.4, preferably 1.5 to 3.4, the glass raw material is heated from the vicinity of the liquid surface of the molten glass below the glass raw material by energization heating to raise the temperature of the glass raw material. For this reason, most of the tin oxide which tries to release oxygen in the tin oxide in the glass raw material is not in the glass raw material but is located in the vicinity of the liquid surface of the molten glass below the glass raw material. Therefore, even if tin oxide releases oxygen, the released oxygen is not released into the vapor phase space, and is easily accommodated in the molten glass. Even if tin oxide causes a redox reaction below the liquid surface of the molten glass and releases oxygen because the rate of rise of the bubbles of oxygen is not sufficiently fast, it is not released into the vapor phase space , The oxygen in the molten glass remains, and the remaining oxygen can be used in the refining process. In this respect, the calorific value ratio is 1.0 to 3.4, preferably 1.5 to 3.4.

In this case, the temperature of the vapor phase space measured by the temperature sensor 118a provided in the thin portion 118 (see FIG. 6) is preferably limited to 1610 占 폚 or lower, and more preferably limited to 1600 占 폚 or lower. This makes it possible to suppress the release of oxygen from the tin oxide on the surface of the molten glass. This makes it possible to suppress the release of oxygen from tin oxide above the glass raw material on the surface of the molten glass and to reduce the generation of bubbles in the glass substrate.

As described above, in this embodiment, since the heating of the dissolution tank is performed by setting the calorific value ratio to 1.0 to 3.4, preferably 1.5 to 3.4, the release of oxygen from the tin oxide to the vapor phase space in the dissolution step can be suppressed. Therefore, the defoaming treatment in the refining step can be performed effectively. Further, since the heating ratio is adjusted to 1.0 to 3.4, preferably 1.5 to 3.4, that is, the heating is performed while balancing the heating values of the energization heating and the combustion heating, so that tin oxide in the molten glass releases oxygen to the vapor phase space The temperature of the molten glass can be increased.

In addition, the optimum calorific value ratio may be determined using a computer simulation. By using the information such as the glass raw material and the structure of the melting vessel (size and position of the electrode used for energizing heating), the temperature of the melting vessel and the state of convection of the molten glass are checked by changing the heating ratio, Can be determined.

(Glass composition 1)

As a glass substrate made of such a molten glass, a glass substrate having the following glass composition 1 is exemplified. In short, the glass raw materials are combined so as to have the following glass composition in the glass substrate.

60 to 80 mol% of SiO ₂ ,

10 to 20 mol% of Al ₂ O ₃ ,

0 to 10 mol% of B ₂ O ₃ ,

RO 0 to 17 mol% (RO is the sum of MgO, CaO, SrO and BaO).

Also, it may be 0 to 10 mol% of MgO, 0 to 10 mol% of CaO, 0 to 5% of SrO and 0 to 10% of BaO.

At this time, SiO ₂ Is 65 to 75 mol%, and more preferably 68 to 75 mol%, the effect of the present embodiment for reducing the generation of bubbles and unheated products becomes remarkable. In addition, the effect of the present embodiment for reducing the generation of bubbles and unheated products becomes more remarkable as the content of B ₂ O ₃ is 0 to 7 mol%, 0 to 5 mol%, and 0 to 2 mol%.

At this _{time, SiO 2, Al 2 O 3} , B 2 O 3, and the RO (RO is, MgO, CaO, the total amount of SrO and BaO) to contain at least a molar ratio _{((2 × SiO 2) +} Al 2 O 3 ) / ((2 x B ₂ O ₃ ) + RO) is 4.5 or more, the effect of reducing the occurrence of bubbles and unheated products, which is the effect of the present embodiment, can be achieved. That is, a glass having a molar ratio ((2 x SiO ₂ ) + Al ₂ O ₃ ) / ((2 x B ₂ O ₃ ) + RO) of 4.5 or higher is a glass having a high high-temperature viscosity, Is set to be 1.0 to 2.8, preferably 1.5 to 2.8, as compared with the case where the calorific value ratio is outside the range of 1.0 to 2.8, and the calorific value ratio is outside the range of 1.5 to 2.8, The effect of this embodiment is remarkable. In addition, it is preferable that at least one of MgO, CaO, SrO and BaO and the molar ratio (BaO + SrO) / RO (RO is the sum of CaO, MgO, SrO and BaO) is 0.1 or more, It is preferable in that the point of weakness can be raised.

The sum of the content of B ₂ O ₃ in mol% and the content of RO in mol% is preferably 30 mol% or less, and more preferably 10 to 30 mol%.

In addition, the effect of the present embodiment which can reduce the generation of bubbles and unheated products can be achieved even when the content of the alkali metal oxide in the glass substrate of the glass composition 1 is 0 mol% or more and 0.4 mol% or less . The lower the content of the alkali metal oxide, the higher the high-temperature viscosity and the higher the resistivity. Thus, compared with the glass having an alkali metal oxide content exceeding 0.4 mol%, the glass having an alkali metal oxide content of 0 mol% Is high in high-temperature viscosity and resistivity. The higher the high-temperature viscosity, the slower the rate of rise of the bubbles in the molten glass, so that the refining is liable to become insufficient. When the glass having a high temperature viscosity is used, the calorific value ratio is set in the range of 1.0 to 2.8, more preferably in the range of 1.5 to 2.8, so that the generation of bubbles and unheated products can be suppressed The effect becomes remarkable. In addition, even when glass having a high specific resistance is used, it is possible to prevent melting loss or shortening of life of the melting tank.

(Glass composition 2)

As the glass substrate, there is exemplified a glass substrate having the following glass composition 2. Therefore, the glass raw materials are combined so that the following glass composition is contained in the glass substrate.

55 to 75 mol% of SiO ₂ ,

Al ₂ O ₃ : 5 to 20 mol%

B ₂ O ₃ : 0 to 15 mol%

RO: 5 to 20 mol%

(RO is the sum of MgO, CaO, SrO, and BaO)

R ' ₂ O: 0 to 0.4 mol% (R' is all elements of Li, K, and Na contained in the glass substrate).

At this time, it is preferable that at least one of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ and RO (R is any of the elements contained in the glass substrate among Mg, Ca, Sr and Ba) SiO ₂ ) + Al ₂ O ₃ ) / ((2 x B ₂ O ₃ ) + RO) may be 4.0 or more, and the effect of reducing the generation of bubbles and unheated products, which is the effect of the present embodiment have. That is, a glass having a molar ratio ((2 x SiO ₂ ) + Al ₂ O ₃ ) / ((2 x B ₂ O ₃ ) + RO) of 4.0 or more is one example of a glass having a high temperature viscosity. And the calorific value ratio is in the range of 1.0 to 3.4, preferably 1.5 to 3.4, the generation of bubbles and unheated products can be suppressed as compared with the case where the calorific value ratio is out of the range of 1.0 to 3.4, The effect of the present embodiment in which the amount is reduced is remarkable.

Even if the content of the alkali metal oxide in the glass substrate of the glass composition 2 is 0 mol% or more and 0.4 mol% or less, generation of bubbles and unheated products can be reduced. The glass having a content of alkali metal oxide of 0 mol% or more and 0.4 mol% or less has a higher alkali metal oxide content than that of glass having an alkali metal oxide content of 0.4 mol% or more because the content of the alkali metal oxide is lower, Viscosity is high. When the glass having a high temperature viscosity is used, the calorific value ratio is set to 1.0 to 3.4, preferably 1.5 to 3.4, so that the calorific value ratio is not more than 1.0 to 3.4, The effect of the present embodiment for reducing the occurrence of bubbles and unheated products becomes remarkable. In addition, even when glass having a high specific resistance is used, it is possible to prevent melting loss or shortening of life of the melting tank.

(Characteristics of glass substrate)

In the glass substrate of the present embodiment, the temperature when the viscosity is 10 ^2.5 poise may be 1500 to 1700 ° C, or may be 1590 to 1700 ° C or 1550 to 1650 ° C. The effect of this embodiment that the generation of bubbles and unheated products is reduced by setting the ratio of calorific value to be within the above-described range as the glass having a high temperature at a viscosity of 10 ^2.5 poise, that is, It becomes.

That is, it is possible to use the melting furnace in which the combustion heating in the gas phase using the combustion means and the energization heating in which the current is passed through the molten glass are used in the melting tank without excessively shortening the life of the melting tank, ^The glass raw material can be dissolved so that the glass at a temperature of ^2.5 ° C is 1500 ° C or higher.

The melting point of the molten glass for making the glass substrate of the present embodiment may be 650 DEG C or higher, more preferably 660 DEG C or higher, still more preferably 680 DEG C or higher, and particularly preferably 720 DEG C or higher. Further, since the temperature of the molten glass at a viscosity of 10 ^2.5 poise tends to be high, the effect of the present embodiment becomes remarkable. In addition, the higher the point, the lower the heat shrinkage during panel manufacture, and therefore, it is suitable as a high-precision display LTPS TFT display and a glass substrate for organic EL display.

The heat shrinkage of the glass substrate is preferably 0 to 20 ppm, more preferably 0 to 10 ppm, and even more preferably 0 to 5 ppm. Such a heat shrinkage ratio can be obtained by the following equation after the glass substrate is subjected to the heat treatment for maintaining the elevation temperature at a rate of 10 占 폚 / min and at 4500 占 폚 for 1 hour.

Heat shrinkage (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶

The specific resistance of the glass constituting the glass substrate according to the present embodiment in a molten glass at 1550 캜 may be 50 Ω · cm or more and may be 50 to 350 Ω · cm and may be 100 Ω · cm or more May be 100 to 350? · Cm, and may be 150 to 350? · Cm. The higher the resistivity is, the more the problem of the melting loss or the life shortening of the melting tank becomes remarkable, and the effect of the present embodiment which can prevent the melting loss or the life span of the melting tank becomes remarkable. In addition, if the glass substrate is desired to have a high squeeze, the temperature of the glass melt tends to increase at the resistivity and viscosity of 10 ^2.5 poise.

The glass substrate manufactured in the present embodiment is preferable for a glass substrate for a flat panel display. The glass substrate produced in this embodiment is preferable as a glass substrate for a liquid crystal display or a glass substrate for an organic EL display. Further, the glass substrate produced in this embodiment is particularly preferable as a glass substrate for LTPS TFT display, or a glass substrate for oxide semiconductor TFT display. The glass substrate produced in this embodiment is also preferable for a glass substrate for a liquid crystal display which requires a very small content of alkali metal oxide.

[Experimental Example 1]

In order to confirm the effect of this embodiment, a glass substrate was produced by making a molten glass in a melting tank. Concretely, the glass raw material was melted by using the melting tank 101 shown in Figs. 5 and 6 to prepare a molten glass, and thereafter, a refining step was performed, and a glass substrate was manufactured through the steps shown in Fig.

The glass composition of the prepared glass substrate was as follows.

70.5 mol% of SiO ₂ ,

10.9 mol% of Al ₂ O ₃ ,

7.4 mol% B ₂ O ₃ ,

MgO, CaO, SrO and BaO in an amount of 10.9 mol%.

The glass substrate thus produced had a flaw point of 709 DEG C and a specific resistance of 195 OMEGA cm at 1550 DEG C in a molten glass.

Further, in the dissolving step, the molten glass was produced under the following dissolution conditions in which the above-described calorific value ratio was changed, and the number of defects in the bubbles and the undissolved product remaining in the produced glass substrate was examined. Table 1 below shows dissolution conditions and evaluation results. The thin portion temperature in the table is the temperature in the vapor space measured by the temperature sensor 118a (see Fig. 6) provided in the thin portion 118. [ Regarding the calorific value of the combustion heating, the calorific value in one day was obtained from the supply amount of the combustion gas per unit time and the calorific value of the combustion gas per unit volume. The amount of heat generated by the energization heating was obtained by measuring the current flowing into the electrode pair 114 and the voltage between the electrode pair 114 so as to calculate the heat generation amount in one day in the energization heating in the dissolution tank 110.

The number of bubbles and the number of defects of the undissolved component of the glass substrate were counted by naked eyes. The number of bubbles in the following Table 1 is expressed by the ratio in the case where the number of bubbles in Example 1 is one. The larger the ratio, the greater the number of bubbles.

In addition, the immersion amount of the dissolution tank after use of the dissolution tank in the dissolution process was specified, and the life of the dissolution tank was evaluated in three levels of levels A, B and C. Level A means that the amount of erosion is very small and the life of the dissolution tank is very long, the level B is the amount of erosion but the life of the dissolution tank is the allowable level and the level C means that the amount of erosion is large and the life time of the dissolution tank is short.

As shown in Tables 1 and 2, the glass substrates obtained in Examples 1, 2, and 3 are superior to the glass substrates obtained in Comparative Example 1 in terms of the number of bubbles and the number of defects in the undissolved product. In Comparative Example 2, the life of the melting tank was not within the permissible range, and in any of Examples 1 to 3, the life of the melting tank was very long and the length of the allowable level was long. From the above table, the effect of this embodiment is obvious.

[Experimental Example 2]

A glass substrate was produced in the same manner as in Experimental Example 1, using Glass Composition 2 different from the glass composition used in Experimental Example 1. [ The glass composition of Experimental Example 2 is as follows.

66.6 mol% of SiO ₂ ,

10.6 mol% of Al ₂ O ₃ ,

11.0 mol% of B ₂ O ₃ ,

The total amount of MgO, CaO, SrO and BaO was 11.4 mol%.

The glass substrate produced had a wax point of 660 캜 and a resistivity of 165 Ω · cm in the molten glass at 1550 캜.

In addition, the number of defects in bubbles and undissolved products remaining in the glass substrate produced by varying the dissolution conditions in the dissolution step were examined in the same manner as in Experimental Example 1. [ The calorific value ratio and the thin portion temperature were obtained in the same manner as in Experimental Example 1. [ The number of bubbles in Tables 3 and 4 is expressed as a ratio when the number of bubbles in Example 4 is 1. The larger the ratio, the greater the number of bubbles. In addition, the life of the dissolution tank was evaluated in the same manner as in Experimental Example 1. [

The glass substrates obtained in Examples 4 to 7 are superior to the glass substrates obtained in Comparative Example 3 in terms of the number of bubbles and the number of defects in the undissolved product. In Comparative Example 4, the life of the melting bath was not within the permissible range, but in Examples 4 to 7, the life of the melting bath was very long. From the above table, the effect of this embodiment is obvious.

While the present invention has been particularly shown and described with respect to a preferred embodiment thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Needless to say, it can be changed.

100: dissolution apparatus
101: Melting bath
101a: screw feeder
101b: feed inlet
101c: bottom wall
102: Blue sign
102a, 102b: metal flange
102c:
103: stirring tank
103a: Steller
104, 105, and 106: glass supply pipe
104a; Outlet
110: Melting tank body
112: Burner
112a: gas source
112b: Flow regulator
114: electrode pair
120: control unit
124:
122: computer
126:
200: forming device
210: molded article
300: Cutting device

Claims (11)

A method of manufacturing a glass substrate,
In the melting tank, combustion heating in a gas phase using a combustion means and electrification heating conducted by flowing an electric current to a molten glass are used, and a glass containing tin oxide and having a viscosity of 10 ^2.5 poise at a temperature of 1580 캜 or higher The ratio of the calorific value by the combustion heating to the calorific value by the energetic heating is 1.0 or more and 2.8 or less so that the amount of oxygen released from the tin oxide in the vapor phase space A dissolution step of suppressing the release of
And a refining step of refining the molten glass using a redox reaction of tin oxide. A method of manufacturing a glass substrate,
In the melting tank, combustion heating in a gas phase using a combustion means and electrification heating conducted by flowing an electric current to a molten glass are used, and a glass containing tin oxide and having a viscosity of 10 ^2.5 poise at a temperature of 1580 캜 or higher The ratio of the heating amount by the combustion heating to the heating amount by the energization heating is 1.5 or more and 2.8 or less so that the amount of oxygen released from the tin oxide in the vapor phase space And a dissolution step of suppressing the release of the glass substrate into the glass substrate. The method according to claim 1,
Wherein the maximum temperature of the molten glass in the refining step is higher than the maximum temperature of the molten glass in the melting tank. 4. The method according to any one of claims 1 to 3,
Wherein the glass substrate has a melting point of 680 캜 or higher. 4. The method according to any one of claims 1 to 3,
The content of the alkali metal oxide in the glass substrate is 0 mol% or more and 0.4 mol% or less. 4. The method according to any one of claims 1 to 3,
The glass substrate _{is, SiO 2, Al 2 O 3} , B 2 O 3, and the RO containing the (R is, Mg, Ca, of Sr, and Ba entire element contained in the glass substrate) at least, B ₂ O ₃ Is 0 to 7 mol%. 4. The method according to any one of claims 1 to 3,
Wherein the temperature of the thin portion of the ceiling surface covering the vapor phase space of the melting tank is 1610 캜 or less. A method of manufacturing a glass substrate,
In the melting tank, by using combustion heating in the gas phase using the combustion means and electrification heating conducted by flowing an electric current to the molten glass to dissolve the glass raw material so as to be glass having a melting point of 680 DEG C or higher including tin oxide So that the ratio of the calorific value due to the combustion heating to the calorific value by the energetic heating is 1.0 or more and 2.8 or less to suppress the release of the oxygen released from the tin oxide to the vapor phase space ,
And a refining step of refining the molten glass using a redox reaction of tin oxide. 9. The method according to any one of claims 1, 3 and 8,
The refining step may include a defoaming treatment in which the temperature of the molten glass is raised to 1,630 DEG C or more at a heating rate of 2.5 DEG C / min or more after the melting step to generate bubbles in the molten glass to perform degassing, And an absorption process for lowering the temperature of the molten glass so that bubbles in the molten glass are absorbed in the molten glass. A method of manufacturing a glass substrate,
A glass substrate containing tin oxide and having an alkali metal oxide content of 0 to 0.4 mol% is used as the melting furnace in the melting tank by using combustion heating in a gas phase using a combustion means and electric current heating conducted by flowing an electric current to the molten glass Wherein the ratio of the calorific value by the combustion heating to the calorific value by the energetic heating is 1.0 or more and 3.4 or less to dissolve oxygen released from the tin oxide, A dissolution step of suppressing the release into the space,
And a refining step of refining the molten glass using a redox reaction of tin oxide. A melting vessel body having a vapor space and storing the molten glass,
Combustion means for heating the glass raw material and / or the molten glass by burning heating in the vapor space,
An electrode pair formed on a wall which is in contact with the molten glass to energize the glass raw material and / or the molten glass,
And a blue sign for purifying the molten glass using a redox reaction of tin oxide contained in the molten glass,
When making the molten glass using the combustion heating and the energization heating so that the glass becomes a glass having a viscosity of 10 ^2.5 poise at 1580 캜 or higher, the amount of heat generated by the combustion heating Wherein the combustion heating and the energization heating are performed so that the ratio is 1.0 or more and 2.8 or less so as to suppress release of the oxygen emitted from the tin oxide to the vapor phase space of the dissolution tank.

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