KR101716996B1 - Method for manufacturing glass substrate and glass substrate manufacturing apparatus - Google Patents

Abstract

A manufacturing method of a glass substrate capable of reducing platinum foreign matter in a glass product includes a dissolving step, a refining step, and a molding step. The blue sign used in the fining process is a platinum or platinum alloy and has a flange-shaped electrode for electrically heating the blue sign. In the fining process, the blue sign is heated by energization so that the liquid level The electrode is cooled so as to suppress the heat generation of the electrode, and the cooling of the electrode is carried out in such a manner that the temperature of the wall of the blue oven is lower than the temperature of the air in the vapor space of the blue oven, The temperature is controlled so as to be in a range exceeding the temperature.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass substrate manufacturing method and a glass substrate manufacturing apparatus for melting glass raw materials to produce glass substrates. More particularly, the present invention relates to a cleaning process in a glass substrate manufacturing method.

The glass substrate is generally manufactured through a process of forming a molten glass from a glass raw material and then molding the molten glass into a glass substrate. The above-mentioned process includes a step of removing minute bubbles contained in the molten glass (hereinafter also referred to as refining). The refining is carried out by passing molten glass containing a refining agent through the blue-signing body (hereinafter, simply referred to as the body) while heating the body of the tube-shaped blue-sign, Is removed. More specifically, by raising the temperature of the molten glass to further raise the temperature of the molten glass to float the bubbles by floating the bubbles and lowering the temperature, the relatively small bubbles that can not be defoamed are absorbed into the molten glass . That is to say, the refining includes a process of flotation of bubbles (hereinafter also referred to as defoaming process or defoaming process) and a process of absorbing small bubbles into molten glass (hereinafter also referred to as an absorption process or an absorption process). Conventionally, As ₂ O ₃ has been generally used as a refining agent, but SnO ₂ has been used from the viewpoint of recent environmental load.

In mass production of glass substrates of high quality from molten glass at a high temperature, it is preferable to consider that foreign substances or the like which cause defects in the glass substrate are not mixed into the molten glass from any apparatus for manufacturing the glass substrate. Therefore, in the manufacturing process of the glass substrate, the inner wall of the member in contact with the molten glass needs to be made of an appropriate material in accordance with the temperature of the molten glass in contact with the member, the quality of the required glass substrate, and the like. For example, it is known that a platinum group metal such as platinum or a platinum alloy is usually used as a material for constituting the blue-signing body (Patent Document 1). Platinum or platinum alloys are expensive but have a high melting point and are excellent in corrosion resistance to molten glass.

The temperature for heating the blue oven body during the defoaming process varies depending on the composition of the glass substrate to be formed, but is about 1600 캜 to 1700 캜.

As a technique for heating the blue sign body, for example, a technique is known in which a pair of flange-shaped electrodes are provided on a blue sign body and a blue sign body is energized by applying voltage to the pair of electrodes 2). In addition, a flange-shaped electrode is provided with a water-cooled pipe made of copper or nickel.

Japanese Patent Publication No. 2006-522001 Japanese Patent Publication No. 2011-513173

In recent years, a platinum foreign matter contained in a glass substrate has become a problem.

For example, platinum foreign materials contained in glass substrates (glass substrates for FPD) used in flat panel displays such as liquid crystal displays (LCDs) and organic EL displays and the like are recently severely restricted. In addition, it is not limited to a flat panel display, and is also a problem in other applications.

However, as described in Patent Document 2, when the flange-shaped electrode is cooled in a water-cooled tube, the temperature locally falls at a position near the electrode of the blue sign.

On the other hand, when the inner surface of the blue sign body is made of platinum or a platinum alloy (platinum group metal), a portion in contact with the vapor phase space (atmosphere containing oxygen) is volatilized. The volatilized platinum or platinum alloy is condensed and adhered as a condensate at a locally lowered temperature position near the electrode of the blue sign. A part of the condensate may fall into the molten glass during the defoaming process and be mixed with the glass substrate as a platinum foreign matter.

In view of the above, it is an object of the present invention to provide a glass substrate manufacturing method and a glass substrate manufacturing apparatus capable of reducing the amount of platinum foreign matter in a glass product.

The present invention has the following aspects.

[Mode 1]

A method of manufacturing a glass substrate including a melting step, a cleaning step, and a molding step,

Wherein the blue pattern used in the finishing step is made of platinum or a platinum alloy and has a flange shaped electrode for energizing the blue pattern,

In the purifying step,

The defrosting is performed by passing the molten glass through the conduction-heated blue sign by adjusting the liquid level so as to have a vapor phase space,

Cooling the electrode to suppress heat generation of the electrode,

Wherein the cooling of the electrode is controlled such that the temperature of the wall of the blue sign exceeds a temperature at which the platinum vapor generated in the vapor space of the blue sign exceeds the condensation temperature.

[Mode 2]

In the purifying step,

Measuring the temperature of the electrode or the blue circle in the vicinity of the electrode,

The method of manufacturing a glass substrate according to claim 1, wherein the amount of cooling of the electrode is adjusted based on the measured temperature.

[Mode 3]

In the purifying step,

Determining whether or not the temperature of the blue circle in the vicinity of the measured electrode or the electrode is within a predetermined temperature range and adjusting the cooling amount when the measured temperature is outside the predetermined temperature range, A method for producing a glass substrate according to the second aspect.

[Mode 4]

In the purifying step,

The method for producing a glass substrate according to any one of the first to third aspects, wherein tin oxide is used as a fining agent.

[Mode 5]

Wherein the electrode has a cooling pipe for passing the refrigerant therethrough,

In the purifying step,

The method of manufacturing a glass substrate according to any one of claims 1 to 4, wherein the cooling amount is adjusted by increasing or decreasing the amount of refrigerant passing through the cooling pipe.

[Mode 6]

The method of manufacturing a glass substrate according to Mode 5, wherein the coolant is a base.

[Mode 7]

1. A glass substrate manufacturing apparatus comprising a melting vessel, a blue sign, and a molding apparatus,

Wherein the blue sign comprises a platinum or platinum alloy and has a flange-shaped electrode for energizing the blue sign,

The electrode is cooled to suppress heat generation of the electrode,

Wherein the cooling of the electrode is controlled such that the temperature of the wall of the blue sign exceeds a temperature at which the platinum vapor generated in the vapor space of the blue sign is condensed.

According to the method for manufacturing a glass substrate and the apparatus for manufacturing a glass substrate of the present invention, it is possible to reduce a platinum particle of a glass product.

1 is a flow chart for explaining a simple process of a manufacturing method of a glass substrate according to the present embodiment.
2 is a schematic layout diagram of a glass substrate manufacturing apparatus according to the present embodiment.
3 is a schematic view showing the configuration of the blue sign of the present embodiment.
4 is a flowchart showing an example of a method of controlling the cooling of the electrode in the cleaning process according to the present embodiment.
5 is a diagram showing an example of the temperature distribution in the longitudinal direction of the blue sign.
6 is a diagram showing an example of the relationship between temperature and time of the electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a method for manufacturing a glass substrate of the present invention will be described with reference to the drawings.

Fig. 1 is a flow chart showing the steps of a method for manufacturing a glass substrate according to the present embodiment. As shown in Fig. 1, the glass substrate is mainly composed of a dissolving step (ST1), a clarifying step (ST2), a homogenizing step (ST3), a supplying step (ST4), a molding step (ST5) (ST7).

2 is a schematic view of a glass substrate manufacturing apparatus of the present embodiment manufactured through the dissolving step (ST1) to cutting step (ST7) described above, and schematically shows the arrangement of apparatuses used in each step.

2, the glass substrate manufacturing apparatus 200 includes a melting apparatus 40 for heating glass raw materials to produce molten glass, a blue screen 41 for purifying the molten glass, An agitation apparatus 100 for homogenizing, and a molding apparatus 42 for molding into a glass substrate. Further, it has glass supply pipes (43a, 43b, 43c) for transferring molten glass between the above-described devices. The glass feed pipes 43a, 43b and 43c and the blue sign 41 and the stirring device 100 for connecting between the respective devices up to the melting device 40 and the molding device 42 are made of a platinum group metal.

The melting apparatus 40 is made of refractory material such as refractory bricks. The melting apparatus 40 is provided with a heating means such as a burner that burns a combustion gas obtained by mixing fuel and oxygen or the like (not shown) and emits a flame.

Dissolving step (ST1) in, for example, by the fining agent it is such as SnO ₂ added to the glass raw material supplied into the melter 40, and dissolved by heating in the above-described heating means to obtain a molten glass MG. Specifically, a glass raw material is supplied to the liquid surface of the molten glass by using a raw material feeding device not shown. The glass raw material is heated by radiant heat from the flame of the burner. The glass raw material is heated and slowly dissolved by the above-mentioned heating means, and melted in the molten glass MG.

The heating means may be at least a pair of electrodes made of, for example, molybdenum, platinum or tin oxide. In this case, the molten glass MG may be energized and heated by flowing a current between the electrodes.

The glass raw material charged into the dissolution apparatus 40 is appropriately prepared according to the composition of the glass substrate to be produced. For example, in the case of producing a glass substrate for use as a TFT-type LCD substrate, the glass composition constituting the glass substrate is expressed in mass%

SiO ₂ : 50 to 70%

Al ₂ O ₃ : 0 to 25%

B ₂ O ₃ : 1 to 15%

MgO: 0 to 10%

CaO: 0 to 20%

SrO: 0 to 20%

BaO: 0 to 10%

RO: 5 to 30% (R is the sum of Mg, Ca, Sr and Ba)

Alkali-free glass.

In the present embodiment, the glass is made of alkali-free glass. However, the glass substrate may be an alkali-containing glass containing a trace amount of alkali metal. When an alkali metal is contained, the total amount of R ' ₂ O is 0.10% to 0.5%, preferably 0.20% to 0.5% (provided that R' is at least one species selected from Li, Na and K, It is preferable to include a substrate). Of course, the total of R ' ₂ O may be lower than 0.10%.

In the case of applying the glass substrate production method of the present invention, the glass composition may contain SnO _{2 in an amount of} 0.01 to 1% (preferably 0.01 to 0.5%), Fe ₂ O ₃ : 0 to 0.2% (preferably 0.01 to 0.08%), and considering the environmental load, a glass raw material may be prepared so as not to contain As ₂ O ₃ , Sb ₂ O ₃ and PbO .

The following cleaning process (ST2) is performed in the bluezing process (41). In the refining step, the liquid level of the molten glass MG is adjusted so as to have a vapor phase space in the blue oven 41 to allow the molten glass MG to pass through. At this time, given that the molten glass MG in a blue sign (41) temperature by being heated up to (for the glass of the composition, for example more than 1600 ℃), including O _2, CO ₂ or SO ₂ contained in the molten glass MG The bubbles absorb O ₂ generated by the reduction reaction of a refining agent such as SnO ₂ , grow, and are discharged on the liquid surface of the molten glass MG. Thereafter, by lowering the temperature of the molten glass MG in the glass supply pipe 43b or the like, the SnO ₂ obtained by the reduction reaction of the refining agent such as SnO ₂ is subjected to the oxidation reaction and the gas component such as O ₂ in the bubbles remaining in the molten glass MG Is absorbed in the molten glass MG, and the bubbles disappear. The oxidation reaction and the reduction reaction by the cleaning agent are performed by controlling the temperature of the molten glass MG.

In the homogenization step (ST3), the molten glass MG in the stirring apparatus (100) supplied through the glass feed pipe (43b) is stirred using a stirrer to be described later to homogenize the glass components. The stirring apparatus 100 stirs the molten glass MG using one stirrer, but may also stir the molten glass MG using two or more stirrers.

In the supplying step ST4, the molten glass MG is supplied to the molding device 42 through the glass supply pipe 43c. The molten glass is cooled to a temperature suitable for molding (in the case of glass of the above composition, for example, about 1200 캜) in the glass supply pipe 43c when it is sent from the blue sign 41 to the molding apparatus.

In the molding apparatus 42, a molding step (ST5) and a slow cooling step (ST6) are performed.

In the molding step ST5, the molten glass MG is formed into the sheet-like glass 44, and the flow of the sheet-like glass 44 is made. In the slow cooling step (ST6), the sheet-like glass (44) to be formed and flowed has a desired thickness and is cooled so as not to cause internal deformation.

In the cutting step (ST7), the sheet-like glass (44) supplied from the molding machine (42) is cut to a predetermined length in a cutting device, not shown, to obtain a plate-like glass substrate. The cut glass substrate is further cut to a predetermined size to produce a glass substrate having a target size. Thereafter, the end face of the glass substrate is ground, polished, and the glass substrate is cleaned. After the presence or absence of defects such as bubbles, scratches, and contamination is inspected, the glass substrate of the inspected product is packaged as a final product.

[Composition of blue sign 41]

Next, the configuration of the blue sign 41 will be described with reference to Fig. 3 is a schematic view showing a configuration of the blue sign 41 of the embodiment. In the blue sign 41, the temperature of the wall of the blue sign 41 is controlled to be in a range exceeding the temperature at which the platinum vapor which condenses in the vapor space of the blue sign 41 is condensed.

As shown in Fig. 3, the blue sign 41 has a tubular shape and is made of platinum or a platinum alloy. Electrodes 50a and 50b are welded to the outer peripheral surfaces of both ends of the blue sign 41. [ The electrodes 50a and 50b are used for energizing the blue screen 41 and are connected to the power source device 52. [ A voltage is applied between the electrodes 50a and 50b so that a current flows into the blue bulb 41 between the electrodes 50a and 50b and the blue bulb 41 is energized and heated. By this energization heating, the blue sign 41 is heated to, for example, about 1650 캜 to 1700 캜, and the molten glass MG supplied from the glass supply pipe 43a is heated to a temperature suitable for defoaming, for example, Lt; / RTI >

Refrigerant supply devices 54a and 54b, temperature measuring devices 56a and 56b, and control devices 58a and 58b are connected to the electrodes 50a and 50b, respectively. Cooling tubes 502a and 502b are provided on the outer periphery of the electrodes 50a and 50b.

The electrode 50a is connected to the electrode 50b, the cooling pipe 502a to the cooling pipe 502b, the coolant supply device 54a to the coolant supply device 54b and the temperature measurement device 56a to measure the temperature The electrodes 50a and 50b will be collectively referred to as the electrodes 50 and the refrigerant supply devices 54a and 54b will be collectively referred to as the electrodes 50a and 50b as the electrodes 56a and 56b and the controller 58a have the same configurations as the controller 58b, The temperature measuring devices 56a and 56b are collectively referred to as a coolant supply device 54 and the temperature measuring devices 56a and 56b are collectively referred to as a temperature measuring device 56. The cooling pipes 502a and 502b are collectively referred to as a cooling pipe 502, 58a and 58b will be generically described as the control device 58. [

The electrode 50 is made of platinum or a platinum alloy. In this embodiment, a case where the electrode 50 is made of platinum or a platinum alloy will be described as a specific example, but a part of the electrode 50 may be made of another metal such as palladium, silver, or copper. For example, since platinum or a platinum alloy is expensive, palladium, silver, copper, or the like may be used in a place where the electrode 50 has a relatively low temperature. The electrodes 50 are formed in a plate shape and are welded to each other so that the electrodes 50 (50a, 50b) are substantially parallel to the outer peripheral surfaces of both ends of the blue screen 41. The electrode 50 is formed in a flange shape with a protruding portion partially protruded to be connected to the power source device 52. Since this protrusion protrudes from the blue sign 41, it is cooled by the outside air of the blue sign 41. [ As a result, the blue sign 41 near the electrode 50 is cooled.

The shape, mounting position, and mounting method of the electrode 50 may be arbitrary as long as a current flowing from the power source device 52 flows through the electrode 50 and the blue sign 41 to heat the molten glass MG.

To the electrode 50, a temperature measuring device 56 is connected. For example, the temperature measuring device 56 is composed of a thermocouple. The temperature measuring device 56 measures the temperature of the electrode 50 and outputs the measured result to the control device 58. [ The temperature measured by the temperature measuring device 56 is obtained by measuring the temperature of the blue circle near the electrode 50 instead of the temperature of the electrode 50 and controlling the temperature of the electrode 50 May be used. The vicinity of the electrode 50 means within a range of 50 cm from the position of the electrode 50.

In order to suppress the heat generation of the electrode 50, a cooling pipe 502 is provided so as to be in contact with the periphery of the electrode 50. That is, the electrode 50 is cooled by the cooling pipe 502, and heat generation is suppressed. That is, the fact that the electrode 50 is cooled to suppress the heat generation of the electrode 50 means that the heat of the electrode 50 sweated by the current is cooled and the temperature is suppressed.

The cooling pipe (502) is connected to the refrigerant supply device (54). The cooling pipe 502 has a tubular shape and has an inlet for receiving the refrigerant supplied from the refrigerant supply device 54 and a discharge port for discharging the supplied refrigerant to the refrigerant supply device 54. That is, the cooling pipe 502 is configured to cool the electrode 50 provided so as to contact the cooling pipe 502 by passing the coolant supplied from the coolant supply device 54.

The refrigerant may be a liquid such as water or a gas such as air.

In the present invention, it is more preferable that the refrigerant is a gas. When the refrigerant is a liquid such as water, the temperature is locally lowered in the vicinity of the electrode 50 of the blue sign 41 because the cooling ability is high.

If a local temperature drop occurs in the blue sign, refinement is not sufficiently carried out, and the bubble quality may be deteriorated. Further, the blue sign composed of platinum or platinum alloy has vapor phase space, so that platinum or platinum alloy is volatilized. The volatilized platinum or platinum alloy (referred to as platinum volatiles) is condensed at a locally lowered temperature in the vicinity of the electrode and attached as a condensate. A part of the condensate drops into the molten glass during the defoaming process and is mixed, which may lower the quality of the glass substrate. Therefore, in the present embodiment, the refrigerant is preferably a gas.

The cooling pipe 502 is made of metal. When the refrigerant supplied from the refrigerant supply device 54 is a liquid such as water, since the cooling ability is high, copper or nickel may be used for the metal, and it can withstand use. However, when the refrigerant supplied from the refrigerant supply device 54 is a gas, since the cooling ability is lower than that of the liquid, it is preferable to use a material that can not be oxidized in the high temperature air. Specifically, platinum, rhodium, silver, palladium, gold, or an alloy thereof is preferable. Silver is the cheapest among these materials and has a low electric resistance, so that heat generation can be suppressed. Therefore, the metal preferably contains silver and more preferably 90 mass% or more. Further, for example, when the electric current passing through the blue sign exceeds 3,000 amperes, the material of the cooling pipe material is preferably a material having a small electric resistance ratio and functioning as a bypass of the electric current, for example, copper, silver, Platinum can be used. When the electric current to be energized is less than 3,000 amperes, the problem of resistance heat generation of the cooling pipe material is small, so that stainless steel, nickel, cobalt or the like may be used. That is, the cooling pipe 502 may be configured to include any one of silver, platinum, copper, rhodium, palladium, gold, iron, cobalt, and nickel. When a material such as silver having a melting point lower than that of platinum is used for the cooling pipe 502, the periphery of the cooling pipe 502 may be covered with a refractory material such as refractory bricks to protect the cooling pipe 502.

The refrigerant supply device 54 is connected to the control device 58 and supplies the refrigerant to the cooling pipe 502 under the control of the control device 58. [ As the refrigerant, for example, compressed air or the like can be used.

The control device 58 is constituted by a computer including a CPU, a memory, and the like.

The control device 58 receives the result of the temperature measured by the temperature measuring device 56 as described above and controls the refrigerant supply device 54 based on the measurement result. Thereby, the cooling amount of the electrode 50 is adjusted. For example, when the temperature measured by the temperature measuring device 56 is outside the predetermined temperature range, the control device 58 controls the refrigerant supply device 54 to adjust the amount of cooling. For example, the refrigerant supply amount is increased or decreased by a predetermined amount. Further, when the temperature is within the predetermined temperature range, the refrigerant supply device 54 is controlled so that the refrigerant supply amount supplied by the refrigerant supply device 54 is not changed.

More specifically, the control device 58 stores in advance a temperature range including at least one of the upper limit value and the lower limit value. Further, the control device 58 stores in advance a predetermined amount of refrigerant increase and decrease in the memory.

When the temperature measured by the temperature measuring device 56 exceeds the upper limit value, the control device 58 refers to the memory to determine the refrigerant increase amount. Further, the control device 58 controls the refrigerant supply device 54 and increases the refrigerant supply amount by the determined increase amount of the refrigerant.

On the other hand, when the lower limit value is exceeded, the refrigerant reduction amount is determined with reference to the memory. Further, the control device 58 controls the refrigerant supply device 54 and reduces the refrigerant supply amount by the determined amount.

For example, the upper limit value is a temperature at which the electrode 50 does not break or the like due to heat generation. Here, when the electrode 50 is made of platinum, the upper limit of the melting point of platinum is 1768 占 폚. Since the electrode 50 can be made of palladium or the like as described above, the upper limit value becomes the melting point of the material constituting the electrode 50. [ The lower limit value is a temperature at which the platinum vapor generated in the vapor phase space of the blue sign 41 does not condense. Since the temperature at which the platinum vapor does not condense in the vapor phase space of the blue oven 41 is equal to or higher than the temperature at which the temperature of the molten glass MG develops the refining of the refining agent (for example, tin oxide) The temperature of the MG should be the temperature at which the refining of the tin oxide occurs. The above-mentioned upper limit value is specifically 1720 占 폚. The above lower limit value is specifically 1300 占 폚, preferably 1400 占 폚.

The inventor of the present invention has found out that when the temperature of the flange-shaped electrode 50 is controlled to be 1300 캜 or higher as a result of the experiment, platinum does not condense (precipitate) in the blue sign. Further, the inventors of the present invention have found that the temperature of the flange-shaped electrode 50 can be controlled to be 1400 DEG C or more in order to reliably prevent platinum from being condensed (precipitated).

Therefore, in the present embodiment, the lower limit described above is 1300 캜, and more preferably 1400 캜.

[Cooling Adjustment Method of Electrode 50]

Next, a method of adjusting the cooling of the electrode 50 will be described in detail with reference to Fig. 4 is a flowchart showing an example of a method of controlling the cooling of the electrode 50 by the control device 58 in the finishing step ST2 according to the present embodiment.

4, in step 11 (ST11), the control device 58 determines whether or not the temperature measured by the temperature measuring device 56 (in the state where the refrigerant supply device 54 starts supplying the coolant) Measurement temperature). The temperature of the electrode 50 is lowest at the position where the electrode 50 is in contact with the cooling pipe 502 and gradually increases toward the position where the electrode 50 is in contact with the blue screen 41. The electrode 50 has the highest temperature at a position where it contacts the blue sign 41. In the blue sign 41, the temperature at which the electrode 50 is in contact with the electrode 50, Lower. 5 is a diagram showing an example of the temperature distribution in the longitudinal direction (flow direction) of the blue sign 41. Fig. When current is supplied to the blue bulb 41 made of platinum between the electrodes 50a and 50b to energize the blue bulb 41, the temperature T2 at the center in the longitudinal direction of the blue bulb 41 generally becomes the maximum temperature , The temperature T1 in the vicinity of the electrodes 50a and 50b at both ends in the longitudinal direction becomes the minimum temperature. The temperature of the gas phase space GP and the molten glass MG in the vicinity of the electrodes 50a and 50b is the lowest, and therefore platinum vapor may condense in the gas phase space GP near the electrodes 50a and 50b. For this reason, the temperature measuring apparatus 56 measures the temperature T1 which is the lowest in the vicinity of the electrodes 50a and 50b. Then, the control device 58 determines whether or not the temperature T1 is within the range from the upper limit value to the lower limit value in a step to be described later. Thus, the cooling of the electrodes 50a and 50b is controlled so that the temperature of the wall of the blue sign 41 becomes a range exceeding the temperature at which the platinum vapor generated in the vapor space GP condenses.

Further, when the control device 58 starts supplying refrigerant to the refrigerant supply device 54, the refrigerant supply amount may be an arbitrary amount. For example, the control device 58 may control the refrigerant supply device 54 so that the initial refrigerant supply amount is stored in the memory and the initial refrigerant supply amount is obtained.

In step 12 (ST12), the control device 58 determines whether or not the measurement temperature input from the temperature measurement device 56 exceeds the upper limit value. The control device 58 proceeds to the process of ST13 and when the measured temperature inputted from the temperature measuring device 56 exceeds the upper limit value (ST12; Y) And proceeds to processing. In the case where the measurement temperature exceeds the upper limit value (ST12; Y), since the vicinity of the electrode 50 and the electrode 50 is abnormally heated, the electrode 50 may be broken. For this reason, the control device 58 performs cooling of the electrode 50 in step 13 (ST13). On the other hand, in the case where the measurement temperature does not exceed the upper limit value (ST12; N), the temperature is appropriately controlled so that the electrode 50 is not likely to break. Therefore, in step 21 (ST21) Or not.

Step 13 (ST13)), the controller 58 refers to the memory to determine the amount of refrigerant to be increased. Further, the control device 58 controls the refrigerant supply device 54 to increase the refrigerant supply amount by the determined amount. 6 is a diagram showing an example of the relationship between temperature and time of the electrode 50. In Fig. The control device 58 determines that the measured temperature measured by the temperature measuring device 56 exceeds the upper limit value at time t1 (ST12; Controls the device 54 to increase the refrigerant supply amount, and controls the temperature of the electrode 50 to be lower than the upper limit value. If the control device 58 controls the refrigerant supply device 54 to increase the refrigerant supply amount, the temperature of the electrode 50 rises as shown by the dotted line in Fig. 6, It causes. The method of lowering the temperature of the electrode 50 is not limited to the method of increasing the amount of refrigerant supplied per unit time supplied by the refrigerant supply device 54 but also by increasing the supply time of the refrigerant (control execution time) Or the amount of current supplied by the power supply device 52 may be reduced.

In step 21 (ST21), the control device 58 determines whether or not the measured temperature input from the temperature measuring device 56 is less than the lower limit value. When the measured temperature inputted from the temperature measuring device 56 is lower than the lower limit value (ST21; Y), the control device 58 proceeds to the process of ST22. Otherwise, the process ends (ST21; N).

In step 22 (ST22), the controller 58 refers to the memory to determine the amount of refrigerant to be reduced. Further, the control device 58 controls the refrigerant supply device 54 and reduces the refrigerant supply amount by the determined amount. 6, when the measured temperature measured by the temperature measuring device 56 is lower than the lower limit value at the time t2 (ST21; Y), the control device 58 determines that the refrigerant supply The apparatus 54 is controlled to reduce the amount of cooling so that the temperature of the electrode 50 exceeds the lower limit value. If the control device 58 controls the refrigerant supply device 54 to reduce the amount of cooling, the temperature of the electrode 50 is lowered as shown by the dotted line in FIG. 6, and the temperature of the blue sign 41 The platinum vapor generated in the space is condensed or the refining agent (tin oxide) is refined. The method of raising the temperature of the electrode 50 is not only a method of reducing the amount of refrigerant supplied per unit time supplied by the refrigerant supply device 54 but also a method of shortening the supply time of the refrigerant (control execution time) Or the amount of current supplied by the power supply device 52 may be increased.

By repeating the above processing, the temperature of the electrode 50 can be controlled to fall within the range of the upper limit value to the lower limit value, and the platinum foreign matter of the glass product can be reduced.

Next, the operation of the present embodiment will be described.

In the refining step, a voltage is applied between the electrodes 50a and 50b so that a current flows through the blue screen 41 between the electrodes 50a and 50b, and the blue screen 41 is energized and heated. By being raised to by my heated blue sign (41) MG passes the molten glass, given that the molten glass MG temperature (in the case of a glass of the composition, for example more than 1600 ℃), O ₂ contained in the molten glass MG, Bubbles containing CO ₂ or SO ₂ absorb O ₂ generated by the reduction reaction of a refining agent such as SnO ₂ and grow, and are discharged on the surface of the molten glass MG. Thereafter, the temperature of the molten glass MG is lowered in the glass supply pipe 43b or the like, and the SnO ₂ subjected to the reduction reaction such as SnO ₂ is subjected to the oxidation reaction, so that the gas component such as O ₂ in the bubbles remaining in the molten glass MG The molten glass MG is absorbed and the bubbles disappear. The oxidation reaction and the reduction reaction by the cleaning agent are performed by controlling the temperature of the molten glass MG.

In order to suppress the heat generation of the electrode 50, a cooling pipe 502 is provided so as to be in contact with the periphery of the electrode 50. The cooling pipe (502) is connected to the refrigerant supply device (54). That is, the cooling pipe 502 passes the refrigerant supplied from the refrigerant supply device 54, thereby cooling the electrode 50 installed in contact with the cooling pipe 502.

Further, the cooling pipe 502 also serves to equalize the current density in the blue sign 41. When the cooling pipe 502 is not used, the current tends to go to the shortest distance to the blue bulb 41 only with the plate-shaped electrode 50, and the current density inside the blue bulb 41 is shifted upward All. On the other hand, the electrical resistance of the cooling tube 502 can be made small, and current is directed to the lower side of the blue bulb 41 through the cooling tube 502, whereby the current is bypassed and the bias of the current can be reduced .

At this time, the vapor phase space of the blue sign 41 has platinum vapor which is volatilized on the inner surface of the blue sign 41.

In this embodiment, a temperature measuring device 56 is provided on the electrode 50, and the electrode 50 is controlled by the control device 58 to be higher than a predetermined temperature. The predetermined temperature is a temperature exceeding the temperature at which the platinum vapor generated in the vapor phase space of the blue sign 41 condenses. That is, the electrode 50 is controlled to be in a range exceeding the temperature at which the platinum vapor generated in the vapor phase space of the blue sign 41 is condensed. Therefore, the platinum vapor generated in the vapor phase space of the blue sign 41 can be prevented from condensing, and the platinum foreign matter can be prevented from being mixed into the glass.

In the above embodiment, examples in which the refrigerant supply devices 54a and 54b, the temperature measuring devices 56a and 56b, and the control devices 58a and 58b are connected to the electrodes 50a and 50b, respectively, The refrigerant supply devices 54 (54a and 54b), the temperature measuring devices 56 (56a and 56b), and the control devices 58 (58a and 58b) are connected to only one of the electrodes 50a and 50b .

In the embodiment described above, the temperature measuring device 56 is provided on the electrode 50, but it may be provided on the blue sign 41.

In the above embodiment, the blue sign 41 has a flange-shaped pair of electrodes 50a and 50b. However, the blue sign 41 may have only the electrode 50b, for example. In this case, for example, by providing an electrode (not shown) in the glass supply pipe 43a and flowing an electric current between the electrode 50b provided in the blue coloring cell 41 and the electrode provided in the glass supply pipe 43a And the blue sign 41 may be energized and energized.

Further, in the above embodiment, the control device 58 stores in advance the predetermined amount of refrigerant increase and decrease in the memory. However, the control device 58 may store, for example, the refrigerant increase amount and the decrease amount depending on the temperature in advance in the memory. That is, the control device 58 may determine the increase amount and the decrease amount of the refrigerant in accordance with the measurement temperature input from the temperature measurement device 56. [ Thus, the cooling accuracy can be improved.

In the above embodiment, the controller 58 determines the amount of increase and decrease of the refrigerant, controls the refrigerant supply device 54, and increases or decreases the refrigerant supply amount by the determined amount. However, instead of the control device 58, the operator (operator) may determine the amount of increase and decrease in the amount of refrigerant to control the refrigerant supply device 54, and increase or decrease the amount of refrigerant supplied by the determined amount.

Further, the amount of cooling may be changed in each of the electrodes 50a and 50b. For example, the temperature of the electrode 50a close to the glass supply pipe 43a may be made higher than the temperature of the electrode 50b close to the glass supply pipe 43b in order to promote refinement. Since the temperature for promoting refinement of the molten glass MG differs in the flow direction of the blue sign 41, the upper limit value of the temperature of the electrodes 50a and 50b is made the same, and as for the lower limit value of the temperature, The lower limit of the electrode 50a may be set to be higher than the lower limit of the electrode 50b (e.g., the lower limit of the temperature at the electrode 50a is 1400 占 폚 and the lower limit of the temperature at the electrode 50b is 1350 占 폚).

In addition, the shape of the projecting portion of the electrode 50 connected to the power source device 52 may be arbitrarily changed. The protruding portion of the electrode 50 protrudes from the blue sign 41 and thus the electrode 50 affected by the outside air is cooled and the vapor phase space of the blue sign 41 in the vicinity of the electrode 50 is also cooled. As a result, the projecting portion projecting from the blue sign 41 can be made linear, cooling by the outside air can be reduced, and cooling near the electrode 50 can be suppressed. It is also possible to suppress the cooling in the vicinity of the electrode 50 by keeping the protruding portion warm with a heat insulating material or the like.

[Example]

A glass substrate was produced by using the glass substrate producing apparatus described in the above-mentioned embodiments.

The temperature of the electrode 50 was controlled to be 1300 DEG C or more and 1720 DEG C or less.

As a result of confirming the platinum foreign matter contained in the produced glass substrate, the amount of platinum foreign matters contained in the glass substrate was lowered compared with the conventional method in which the temperature of the electrode 50 was not controlled, thereby improving the yield and quality of the product .

In the present specification, " platinum or platinum alloy (platinum group metal) " means a metal containing a platinum group element, and is used as a term including an alloy of a platinum group element as well as a metal containing a single platinum group element . Here, the platinum group element refers to six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os) and iridium (Ir).

Further, the present invention is particularly suitable for the production of a glass substrate using tin oxide (SnO ₂ ) as a fining agent. As the refining agent, arsenic (AS ₂ O ₃ ) has been generally used, but tin oxide (SnO ₂ ) has been used from the viewpoint of recent environmental load. Tin oxide has a weaker force of releasing bubbles in the defoaming process as compared with the abiotic acid, so it is necessary to lower the viscosity of the glass and to increase the defoaming effect, and as a result, it is necessary to purify at a high temperature. Therefore, in the case of using tin oxide (SnO ₂ ) as the refining agent, it is necessary to heat the blue oven to a high temperature as compared with the case of using arsenic (AS ₂ O ₃ ) If the temperature is lowered, the difference in temperature becomes larger, so that the problem of the above-described platinum foreign matter becomes more conspicuous. Therefore, the present invention is particularly suitable for the production of a glass substrate using tin oxide (SnO ₂ ) as a fining agent.

Further, the present invention is particularly suitable for the production of a glass substrate in which the glass is an alkali-containing glass containing only trace amounts of alkali-free glass and alkali. Since the alkali-free glass or alkali-alkali-containing glass has a higher viscosity than a glass containing a larger amount of alkali than an alkali-alkali-containing glass, it is necessary to purify the glass at a higher temperature and it is necessary to heat the blue- .

When the blue sign is heated to a high temperature, when the temperature is locally lowered in the blue sign, the problem of the above-mentioned platinum foreign matter becomes more conspicuous. Therefore, the present invention is particularly suitable for the production of a glass substrate, which is an alkali-free glass containing only trace amounts of alkali-free glass and alkali. In addition, it is particularly suitable for the production of a glass substrate for a flat panel display (FPD) such as a glass substrate for a liquid crystal display or a glass substrate for an organic EL in which an alkali-free glass containing only trace amounts of alkali-free glass or alkali is used.

Examples of the glass substrate for FPD include glass substrates for liquid crystal displays and glass substrates for organic EL displays. The glass substrate for FPD has, for example, a thickness of 0.1 to 0.7 mm and a size of 300 x 400 mm to 2850 x 3050 mm. The present invention is advantageous in that defects of bubbles and platinum foreign substances are improved, It is suitable for the production of large glass.

The present invention is particularly suitable for manufacturing a glass substrate for low temperature polysilicon (LTPSS). A glass substrate for low temperature polysilicon (LTPS) is generally used by slimming a glass substrate by etching or the like. If the glass substrate is slipped by etching or the like, a platinum foreign substance contained in the glass substrate appears on the surface, and unevenness is formed on the glass surface, which is a problem. Therefore, the present invention is particularly suitable for producing a glass substrate for low temperature polysilicon (LTPS). A glass substrate for low temperature polysilicon (LTPS) is a glass substrate having a high strain point. For example, a glass substrate having a strain point of 675 DEG C or higher, preferably 680 DEG C or higher, more preferably 690 DEG C or higher can be given.

The present invention is particularly suitable in the case of producing a glass substrate for FPD. In recent years, in a flat panel display, a higher contrast is required, and a platinum particle, which has not become a problem in the past, becomes a problem with high contrast. Therefore, the present invention is particularly suitable for producing a glass substrate for FPD.

In addition, various modifications may be made without departing from the spirit and scope of the invention.

40: dissolution apparatus
41: Blue sign
42: Molding device
43a, 43b, and 43c:
52: Power supply
54a and 54b:
56a, 56b: temperature measuring device
58a, 58b:
100: stirring device
200: glass substrate manufacturing apparatus
502a, 502b: cooling pipe

Claims (7)

A method of manufacturing a glass substrate including a melting step, a cleaning step, and a molding step,
Wherein the blue sign used in the fining process has a cylindrical shape and is made of platinum or a platinum alloy, and a flange-shaped electrode for electrically heating the blue sign is connected to the outer peripheral face of the blue sign,
In the purifying step,
And the liquid level is adjusted so as to have a vapor phase space by passing the melted glass through the energization heating blue sign,
Cooling the electrode to suppress heat generation of the electrode,
The cooling of the electrode is performed by controlling the temperature of the electrode so that the temperature of the wall of the blue screen is in a range exceeding the temperature at which platinum vapor generated in the vapor space of the blue screen is condensed A method of manufacturing a glass substrate. The method according to claim 1,
Measuring the temperature of the electrode or the blue circle in the vicinity of the electrode,
And adjusting a cooling amount of the electrode based on the measured temperature. 3. The method according to claim 2,
Determining whether or not the temperature of the blue circle in the vicinity of the measured electrode or the electrode is within a predetermined temperature range and when the measured temperature is outside the predetermined temperature range, / RTI > 4. The method according to any one of claims 1 to 3,
Wherein the tin oxide is used as the fining agent. The refrigerating machine according to any one of claims 1 to 3, wherein the electrode has a cooling pipe for passing refrigerant,
In the purifying step,
Wherein the cooling amount is adjusted by increasing or decreasing the amount of the refrigerant passed through the cooling pipe. The method of manufacturing a glass substrate according to claim 5, wherein the coolant is a base. 1. A glass substrate manufacturing apparatus comprising a melting vessel, a blue sign, and a molding apparatus,
The blue sign has a tubular shape and is made of platinum or a platinum alloy. A flange-shaped electrode for electrically heating the blue sign is connected to the outer peripheral surface of the blue sign,
The electrode is cooled to suppress heat generation of the electrode,
The cooling of the electrode is performed by controlling the temperature of the electrode so that the temperature of the wall of the blue screen is in a range exceeding the temperature at which platinum vapor generated in the vapor space of the blue screen is condensed A glass substrate manufacturing apparatus.

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