KR101411139B1 - Method for producing glass sheet - Google Patents

Abstract

The present invention relates to a process for producing a molten glass containing at least SnO ₂ from a molten bath (101) to a blue screen (102) through a first transfer pipe (105a) made of platinum or a platinum alloy And a purifying step of defoaming the bubbles contained in the molten glass out of the molten glass in the blue oven 102 made of platinum or a platinum alloy having a space for accommodating the gas by the molten glass. In the manufacturing method of the glass plate, the temperature of the molten glass is heated in the first conveyance pipe 105a (connecting pipe) to 1500 to 1690 DEG C, and the temperature of the molten glass is set to 1600 to 1780 DEG C . The temperature of the molten glass in the blue oven 102 is higher than the temperature of the molten glass in the first transfer pipe 105a (connecting pipe).

Description

[0001] METHOD FOR PRODUCING GLASS SHEET [0002]

The present invention relates to a method of manufacturing a glass plate.

Glass manufacturers have been troubled by bubbles formed in glass during manufacturing. Particularly, a glass substrate for a liquid crystal display device or a glass plate for a cover glass requires a very small amount of air bubbles. Therefore, in order to remove bubbles, refining of molten glass has been carried out, and various methods for refining have been developed. For example, Patent Document 1 (Japanese Patent Laid-Open Publication No. 2008-539162) proposes a technique of controlling the atmosphere around the blue circle in order to effectively purify the molten glass.

Japanese Patent Publication No. 2008-539162

The refining is also carried out by using a refining agent such as As ₂ O ₃ . However, recently, from the viewpoint of reducing the environmental load, it is required to limit the use of As ₂ O ₃ , which has been conventionally used, and which is highly toxic. Therefore, in place of As ₂ O _3, the temperature, that is hard, and when a temperature SnO to release oxygen _2, such as the refining function falling, exert the refining (degassing) function as compared to As ₂ O ₃ is used as a refining agent. For this reason, when SnO ₂ or the like is used as the fining agent, there is a problem that the number of bubbles in the glass plate can not be sufficiently reduced as compared with the case where As ₂ O ₃ is used as the fining agent.

The technique described in Patent Document 1 has a problem in that it can not sufficiently derive the refining function of the refining agent when a refining agent such as SnO ₂ other than As ₂ O ₃ which is an environmental load factor is used. In addition, recently, the demand for the number of bubbles in glass plates used in electric products such as displays has become stronger, and the technology described in Patent Document 1 can not sufficiently meet the demand.

The above-described method requires complicated atmosphere control, and facilities are complicated. Therefore, a simple and effective method for refining molten glass is still required.

An object of the present invention is to provide a method of manufacturing a glass plate capable of sufficiently reducing the number of bubbles even when a refining agent such as SnO ₂ other than As ₂ O ₃ is used. Another object of the present invention is to provide a method of manufacturing a glass plate capable of purifying a molten glass easily and effectively.

A method of manufacturing a glass plate according to the present invention comprises the steps of transporting a molten glass containing at least SnO ₂ from a melting tank to a blue screen through a platinum or platinum alloy connecting pipe, Or a purifying step of defoaming bubbles contained in the molten glass out of the molten glass in a blue sign made of a platinum alloy. The temperature of the molten glass in the connecting pipe is heated to 1500 to 1690 DEG C, the temperature of the molten glass in the blue oven is heated to 1600 to 1780 DEG C, and the temperature of the molten glass in the blue oven is the temperature .

In the method of manufacturing a glass sheet according to the present invention, since the molten glass is already heated to a temperature suitable for refining in the connecting pipe before being conveyed to the blue sign, the refining of the molten glass is promoted immediately after the molten glass is transferred to the blue sign . Therefore, according to the method for producing a glass sheet according to the present invention, even when a refining agent such as SnO ₂ other than As ₂ O ₃ is used, it is possible to sufficiently obtain the refining effect, and the number of bubbles in the glass plate can be sufficiently reduced.

In the method of manufacturing a glass plate according to the present invention, it is preferable that the temperature of the molten glass in the connecting pipe is heated to 1550 to 1690 占 폚 and the temperature of the molten glass is heated to 1620 to 1780 占 폚 in the blue oven.

A method of manufacturing a glass plate according to the present invention includes a melting step of melting and melting glass materials in a melting tank to produce a molten glass; And a cleaning process of heating and refining the molten glass in the blue screen. The molten glass flowing through the connecting pipe is heated by the connecting pipe to about 1600 DEG C to about 1650 DEG C, and the molten glass in the blue oven is heated to about 1650 DEG C to about 1700 DEG C by the blue oven.

Here, since the molten glass is already heated to a temperature suitable for refinement in the connecting pipe before being conveyed to the blue sign, the refining of the molten glass is promoted immediately after the molten glass is transferred to the blue sign. As described above, according to the manufacturing method of the glass sheet according to the present invention, it is possible to purify the molten glass easily and effectively.

Further, in the method of manufacturing a glass plate according to the present invention, it is preferable that the pressure applied to the molten glass in the connecting pipe is higher than the pressure applied to the molten glass in the blue sealing tank.

In the method of manufacturing a glass plate according to the present invention, it is preferable that the viscosity of the molten glass in the connecting pipe is 500 to 2000 poise and the viscosity of the molten glass in the blue oven is 200 to 800 poise.

In the method of manufacturing a glass plate according to the present invention, it is preferable that the cross-sectional area perpendicular to the longitudinal direction of the connection pipe is smaller than the cross-sectional area perpendicular to the longitudinal direction of the blue sign.

Further, in the method of manufacturing a glass plate according to the present invention, it is preferable that heating of the connection pipe is performed by energization heating, and heating of the blue sign is performed by energization heating.

Further, in the manufacturing method of a glass sheet according to the present invention, the glass plate is 0.10% by weight greater than 2.0 mass% of R _'2 O (However, R' preferably containing at least one jongim selected from Li, Na and K) Do. In the present specification, R ' ₂ O represents the total amount of Li ₂ O, Na ₂ O and K ₂ O.

In the method for producing a glass plate according to the present invention, it is preferable that the glass plate is an alkali-free glass substantially free of R ' ₂ O (provided that R' is at least one selected from Li, Na and K).

Further, in the production method of the glass sheet according to the present invention, it is preferable that the temperature at which log? = 2.5 is 1500 占 폚 to 1750 占 폚.

Further, in the method of manufacturing a glass sheet according to the present invention, after the molten glass is heated to 1600 DEG C or higher by a blue sign, the molten glass is cooled at a temperature lowering rate of 2 DEG C / min or more in a temperature range of 1600 DEG C to 1500 DEG C desirable.

Further, in the method of manufacturing a glass plate according to the present invention, it is preferable that the molten glass is allowed to flow in contact with the connecting pipe all around the inner diameter of the connecting pipe.

Further, in the method of manufacturing a glass plate according to the present invention, it is preferable that the glass plate contains the following composition.

(a) 50 to 70% by mass of SiO ₂ ,

(b) 5 to 18 mass% of B ₂ O ₃ ,

(c) 10 to 25% by mass of Al ₂ O ₃ ,

(d) 0 to 10% by mass of MgO,

(e) 0 to 20% by mass of CaO,

(f) 0 to 20 mass% of SrO,

(o) BaO: 0 to 10 mass%

(p) RO: 5 to 20 mass% (provided that R is at least one selected from Mg, Ca, Sr and Ba).

Further, in the method of manufacturing a glass plate according to the present invention, it is preferable that the melting vessel and the blue vessel are connected so that the connecting tube is inclined from the melting vessel to the blue vessel.

Further, in the method of manufacturing a glass plate according to the present invention, it is preferable that the blue sign has a wall of a predetermined thickness, and the connecting pipe has a wall made of refractory metal that is thicker than the wall thickness of the blue sign.

In the present specification, RO represents the total amount of MgO, CaO, SrO, and BaO.

According to the method for producing a glass sheet according to the present invention, even when a refining agent such as SnO ₂ other than As ₂ O ₃ is used, the number of bubbles can be sufficiently reduced. In addition, it is possible to purify the molten glass easily and effectively.

1 is a flow chart of a method of manufacturing a glass plate according to an embodiment of the present invention.
2 is a schematic view of a glass sheet production line according to an embodiment of the present invention.
[Fig. 3] An enlarged view of a melting tank, a connecting pipe and a blue sign.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The following description relates to an example of the present invention, and the present invention is not limited thereto.

(1) Manufacturing method of glass plate

A method of manufacturing a glass sheet according to an embodiment of the present invention includes a series of steps shown in the flowchart of FIG. 1, and uses the glass sheet manufacturing line 100 shown in FIG.

(1-1) A step performed in a first furnace

The glass raw material is first dissolved in the dissolution step (step S101). The raw material is introduced into the first furnace melting tank 101 and heated to a predetermined first temperature T1. T1 is preferably, for example, 1450 to 1650 deg. C, and preferably, 1500 deg. C to 1630 deg. Further, T1 is preferably a glass substrate for a flat panel display having the following composition (2), particularly preferably a glass substrate for a liquid crystal display or a glass substrate for an organic EL display: R ' ₂ O And K, or in the case of an alkali-free glass plate containing no more than 0.10% by mass and no more than 2.0% by mass of R ' ₂ O, Deg.] C, more preferably 1550 deg. C or more and less than 1630 deg. By setting the lower limit temperature as described above, it becomes possible to sufficiently dissolve the glass raw material, and generation of bubbles due to the undissolved product such as silica can be suppressed. On the other hand, by setting the upper limit temperature as described above, it is possible to prevent a purifying agent such as SnO ₂ from severely releasing a gas component (for example, oxygen) in the dissolving bath 101 and exert a purifying function of the purifying agent in the purifying step . The heated raw material is melted to form a molten glass. The molten glass is conveyed through the first conveyance pipe 105a (connection pipe) to the blue sign 102 where the next refining process (step S102) is performed. In other words, the molten glass is conveyed from the melting tank 101 to the blue oven 102 through the first conveyance pipe 105a (platinum or platinum alloy connecting pipe).

The temperature of the molten glass in the vicinity of the region to which the melting tank 101 and the first transfer pipe 105a (platinum or platinum alloy connecting pipe) are connected is preferably 1500 占 폚 to 1690 占 폚, more preferably 1550 占 폚 to 1650 占 폚 Is more preferable.

(1-2) Process in connection pipe

In the first transfer pipe 105a (connecting pipe), the molten glass is preferably heated to a third temperature T3 higher than T1. Specifically, it is preferable that T3 is higher than T1 by 50 DEG C or more. It is also preferable that T3 is higher than T1 by 100 DEG C or more. T1 is preferably from 1450 DEG C to 1650 DEG C, while T3 is preferably from 1500 DEG C to 1720 DEG C, and more preferably from about 1550 DEG C to about 1690 DEG C. [ At this time, the viscosity of the molten glass in the first transfer pipe 105a (connecting pipe) is preferably 500 to 2000 poise. For example, in the case of a glass substrate for a flat panel display having the following composition (2), T 1 is preferably about 1,500 ° C to 1,610 ° C (for example, about 1,550 ° C) And more preferably from about 1600 캜 to about 1650 캜. At this time, the viscosity of the molten glass in the first transfer pipe 105a (connecting pipe) is preferably 500 to 2000 poise. By doing so, the molten glass can be transferred to the blue marking 102 (second furnace) where the next cleaning process (step S102) is performed while the molten glass is at a temperature suitable for clarification to be described later or a temperature close thereto, The purifying can be effectively promoted from the entrance of the blue sign 102. Thus, the staying time of the molten glass in the blue oven 102 can be relatively shortened, and the time during which the molten glass is exposed to the atmosphere can be shortened, so that the diffusion of SO ₂ into the existing bubbles in the molten glass It can be suppressed from being promoted. It is also possible to prevent nitrogen or the like in the atmosphere from dissolving in the molten glass. Here, when the diffusion of SO ₂ into the existing bubbles in the molten glass is promoted, SO ₂ having a low solubility in the molten glass may remain as bubbles in the glass plate. On the other hand, when nitrogen or the like is dissolved in the molten glass, it is considered that N ₂ is generated as reboil bubbles in the process of lowering the temperature of the molten glass. In other words, if the staying time of the molten glass in the blue sign 102 can be made relatively short, reboiler bubbles such as SO ₂ and N ₂ can be suppressed and the number of bubbles in the glass plate can be reduced. On the other hand, if the temperature of the molten glass is to be increased higher than the upper limit temperature, the temperature of the first transfer pipe 105a (connecting pipe) is set to be lower than the melting point of the platinum or platinum alloy constituting the first transfer pipe 105a The first conveying pipe 105a (connecting pipe) may be eroded, which is not preferable. Further, it is preferable that T3 is equal to or lower than a second temperature T2 at which the molten glass reaches and is heated in the blue screen 102 to be described later.

Here, the temperature suitable for refining the molten glass varies depending on the composition of the refining agent and glass used. The glass plate of the present embodiment contains SnO ₂ as a fining agent. The temperature at which SnO ₂ functions as a refining agent, that is, the temperature at which oxygen effectively starts to emit, is 1600 ° C or higher, and the oxygen is severely released as the temperature rises. That is, when SnO ₂ is contained as a refining agent, the temperature suitable for refining is not lower than 1620 ° C, and more preferably not lower than 1650 ° C. On the other hand, the glass sheet shown in this embodiment is R _'2 O (However, R' is at least one jongim selected from Li, Na and K) a non-alkali glass plate that is substantially free of, or R _'2 O to 0.10% by weight By mass and not more than 2.0% by mass. As described above, the alkali-free or alkali-containing glass has a high viscosity (high-temperature viscosity) at a high temperature as compared with a glass containing more than 2.0% by mass of alkali. For example, the temperature at which the alkali-free glass or alkali-alkali-containing glass becomes log? = 2.5 is 1500 占 폚 to 1750 占 폚.

Here, the rate at which the bubbles rise in the molten glass is influenced by the viscosity of the molten glass, and the lower the viscosity of the molten glass, the higher the rate of rise of the bubbles. In order to perform refining efficiently, the viscosity of the molten glass in the blue oven 102 is preferably 200 to 800 poise, for example. Therefore, in order to purify an alkali-free glass or an alkali-alkali-containing glass, it is necessary to further raise the temperature of the molten glass as compared with the alkali glass in order to lower the viscosity of the molten glass. More specifically, in the production of an alkali-free glass plate or an alkali-alkali-containing glass plate, it is preferable that the temperature of the molten glass in the blue oven 102 is, for example, 1650 ° C or higher. The above-mentioned clarification means that bubbles in the molten glass are discharged out of the molten glass to defoam.

The heating of the molten glass is carried out by energizing the first transfer pipe 105a (connection pipe) made of refractory metal by the electric heating apparatus 201 having the feed terminals 201a and 201b, It is preferable to carry out heating. It is preferable that the feed terminals 201a and 201b are attached to both ends of the first conveyance pipe 105a (connection pipe). Thus made of platinum or platinum alloy in the first transfer pipe (105a) (connecting pipe), the molten glass to by heat conduction, sufficiently exploiting the fining effect of the in the manufacture of glass containing SnO _2, SnO ₂ as a fining agents It is possible to easily realize the temperature control.

The cross-sectional area perpendicular to the longitudinal direction of the first conveyance pipe 105a (connection pipe) is preferably smaller than the cross-sectional area perpendicular to the longitudinal direction of the blue sign 102. That is, the cross-sectional area perpendicular to the longitudinal direction of the blue sign 102 is preferably larger than the cross-sectional area perpendicular to the longitudinal direction of the first conveyance pipe 105a (connection pipe).

Specifically, it is preferable that the cross-sectional area of the blue sign 102 is greater than 100% of the cross-sectional area with respect to the inner diameter of the first conveyance pipe 105a (connection pipe). It is more preferable that the cross-sectional area of the blue sign 102 is larger than the cross-sectional area of the first conveyance pipe 105a (connection pipe) with respect to the inner diameter by 150% or more. For example, if the inner diameter of the first conveyance pipe 105a (connecting pipe) is 200 mm (cross-sectional area about 31416 mm ² ), the inner diameter of the blue sign 102 is about 316 mm, and the cross- mm < ² > Accordingly, when the molten glass is discharged from the first transfer pipe 105a (connecting pipe) to the blue screen 102, the pressure applied to the molten glass is reduced, and the gas components in the molten glass tend to escape out of the molten glass as bubbles So that the refining of the molten glass is promoted from the entrance of the blue sign 102. Here, the blue sign 102 has a space for accommodating the gas defoamed from the molten glass in the blue sign 102. That is, the pressure applied to the molten glass in the first transfer pipe 105a (connecting pipe) is made higher than the pressure applied to the molten glass in the blue screening vessel 102, so that the bubbles generated in the molten glass are supplied to the blue screen 102 And can be discharged to the space.

3, the first transfer pipe 105a (connection pipe) can connect the melting tank 101 and the blue sign 102 substantially horizontally as shown in FIG. 3, but the melting tank 101 and the blue sign 102 , So as to rise from the dissolution tank 101 to the blue sign 102 in an inclined manner. That is, the first conveyance pipe 105a (connection pipe) is arranged so that the molten glass passing through the first conveyance pipe 105a (connection pipe) rises from the melting vessel 101 toward the blue sign 102 on an inclined slope, It is preferable that the melting vessel 101 and the blue vessel 102 are connected to each other. The inclination is preferably from 15 degrees to less than 90 degrees, more preferably from 20 degrees to less than 90 degrees, further preferably from 30 degrees to less than 90 degrees. By doing so, a pressure due to its own weight is applied to the molten glass flowing in the first conveyance pipe 105a (connection pipe) excluding the downstream end of the first conveyance pipe 105a (connection pipe), but the pressure in the first conveyance pipe This pressure is not applied at the downstream end of the connecting pipe 105a (connecting pipe), that is, at the outlet to the blue oven 102, and is applied to the molten glass at the outlet of the first conveying pipe 105a Loss of pressure decreases. In such a reduced-pressure environment, the gas components in the molten glass tend to escape from the molten glass as bubbles, and the refining of the molten glass is promoted from the entrance of the blue sign 102.

Since the molten glass of high temperature flows into the first transfer pipe 105a (connecting pipe), it is preferable that the first transfer pipe 105a (connecting pipe) has a wall made of refractory metal, Platinum or a platinum alloy. It is preferable that the wall thickness of the first transfer pipe 105a (connection pipe) is thick. For example, the thickness of the wall is preferably about 1 mm or more. It is also preferable that the wall of the first conveyance pipe 105a (connection pipe) is thicker than the wall of the second hallow sign 102, which will be described later. It is preferable that the wall of the first conveyance pipe 105a (connection pipe) is 10% or more thicker than the wall of the blue sign 102. For example, if the wall thickness of the blue sign 102 is 1 mm, It is preferable that the wall of the connecting pipe 105a (connecting pipe) is 1.1 mm. It is preferable that the wall of the first conveyance pipe 105a (connection pipe) is thicker than the wall of the blue sign 102 by 20% or more. For example, if the wall thickness of the blue sign 102 is 1 mm, The wall of the transfer pipe 105a (connecting pipe) is preferably 1.2 mm. It is also preferable that the wall of the first conveyance pipe 105a (connection pipe) is 50% or more thicker than the wall of the blue sign 102. For example, if the wall thickness of the blue sign 102 is 1 mm, The wall of the transfer pipe 105a (connecting pipe) is preferably 1.5 mm. By doing so, the first conveyance pipe 105a (connection pipe) can be made to withstand even if the molten glass is heated to a high temperature of, for example, 1600 DEG C or more. Further, the strength of the wall of the first conveyance pipe 105a (connection pipe) against the pressure from the inside by the molten glass also increases.

Further, if there is a gap between the wall of the first transfer pipe 105a (connecting pipe) and the molten glass, the air in the gap becomes higher in temperature than the molten glass, so that the temperature of the first transfer pipe 105a The wall becomes hot, and the oxidation or volatilization of the refractory metal such as platinum or platinum alloy is promoted, so that the durability of the first transfer pipe 105a (connection pipe) is remarkably reduced. Therefore, in the first conveying pipe 105a (connecting pipe), the molten glass is conveyed in the state of being in contact with the entire circumference of the inner diameter of the first conveying pipe 105a (connecting pipe), that is, 105a (connecting pipe) without any gap therebetween. By doing so, breakage of the first conveyance pipe 105a (connection pipe) and shortening of its life can be prevented.

(1-3) Step performed in the second furnace

In the next refining step (step S102), the molten glass is refined. Specifically, when the molten glass is heated to the predetermined second temperature (T2) in the blue sign 102, the gas component contained in the molten glass forms bubbles or vaporizes and escapes out of the molten glass. T2 is preferably higher than T1, and is preferably higher than T3. T2 is preferably from 1600 캜 to 1780 캜, and more preferably from 1620 캜 to 1780 캜. For example, in the case of a glass substrate for a flat panel display having the following composition (2), T2 is preferably from 1620 캜 to 1780 캜, more preferably from 1650 캜 to 1740 캜, Is more preferable. Accordingly, since the viscosity of the molten glass can be sufficiently reduced while preventing the blue sign 102 from being broken, a sufficient bubble floatation speed can be realized and the molten glass can be effectively refined. The heating of the molten glass is preferably carried out by energizing the blue sign 102 itself having a refractory metal wall by an electric heating device (not shown) provided with a power supply terminal (not shown) Do. The wall of the refractory metal is preferably platinum or platinum alloy. In this way heating of the blue sign (102) made of platinum or platinum alloy energized, in the manufacture of the glass plate containing SnO ₂ as a fining agent, facilitates the temperature control of the molten glass to fully derive the fining effect of the SnO ₂ .

When the melting temperature is raised in the first transfer pipe 105a (connection pipe) and the blue screen 102, the temperature of the molten glass is set to 1630 DEG C or higher, more preferably 1650 DEG C or higher, To 1740 占 폚. This is because if the heating rate is 2 ° C / min or more, the emission amount of O ₂ gas increases sharply. That is, when the temperature of the molten glass is raised to 1,630 ° C or more at a rate of temperature increase of 2 ° C / min or more, the temperature of the molten glass is increased to such an extent that volatilization is accelerated in the first transfer pipe 105a It is possible to sufficiently derive the finishing function of SnO ₂ without heating (for example, not exceeding 1740 ° C), and it is possible to prevent damage to the first conveyance pipe 105a (connection pipe) and blue screen 102 So that the number of bubbles in the glass plate can be reduced.

The refined molten glass is transferred to the stirring tank 103 through which the homogenizing process (step S103), which is the next process, is performed through the second transfer pipe 105b.

At this time, after the degassing treatment is performed by heating the temperature of the molten glass in the blue oven 102 to 1600 DEG C or higher, more preferably 1600 DEG C to 1780 DEG C, and more preferably 1620 DEG C to 1780 DEG C, It is preferable that the bubbles in the molten glass are absorbed (absorbed) in the molten glass by lowering the temperature at a temperature lowering rate of 2 DEG C / min or more in the temperature range of 1600 DEG C to 1500 DEG C. The reason why the molten glass is preferably cooled at a temperature lowering rate of 2 DEG C / min or more in the temperature range of 1600 DEG C to 1500 DEG C is as follows.

The blue sign (102), SnO ₂ is because the temperature at which the reduction and release oxygen melt above 1600 ℃ glass is raised, not only the blowing of oxygen a SnO ₂ is released to promote the air bubbles present in the molten glass, The diffusion of O ₂ , CO ₂ , and SO ₂ dissolved in the molten glass is accelerated, and O ₂ , CO ₂ , and SO ₂ dissolved in the molten glass are also blown into the bubbles. The solubility of the gas component in the molten glass changes depending on the glass component. In the case of SO ₂ , the solubility of the glass component is relatively high in the glass having a large content of the alkali metal component. However, In a small amount of an alkali-containing glass plate having a small amount, the solubility that can be dissolved in the molten glass is low. It is preferable that an alkali-free glass plate or an alkali-containing glass plate is originally not added with an S (sulfur) component artificially as a glass raw material. However, it is preferable to use as a raw material impurities or a combustion gas (natural gas, Gas and the like). Therefore, the S component contained as these impurities is oxidized to become SO ₂ , and diffuses into the air bubbles contained in the molten glass. SO ₂ remains as air bubbles because it is difficult to be reabsorbed. This phenomenon is very remarkable when SnO ₂ is used as a fining agent as compared with the case where conventional As ₂ O ₃ is used as a fining agent.

In the case of the glass composition using SnO ₂ as the refining agent, the longer the holding time at the high temperature of the molten glass is, the more the diffusion of SO ₂ into the existing bubbles in the molten glass is promoted. This is considered to be due to the fact that the temperature becomes high and the diffusion rate of SO _{2 in} the molten glass is accelerated and it is easy to enter the bubble.

Then, when the molten glass is cooled down, SnO ₂ obtained by reducing SnO ₂ tends to be oxidized by absorbing oxygen by the oxidation reaction. Therefore, O ₂ in the bubbles remaining in the molten glass is absorbed by SnO ₂ . However, the diffusion of SO ₂ or CO _{2 in} the molten glass into the existing bubbles is still maintained. Therefore, the gas component in the air bubbles downstream of the blue sign 102 has a higher concentration of SO ₂ and CO ₂ than air bubbles in the blue sign 102. Particularly, in a molten glass of an alkali-free or alkaline-containing glass, the solubility of SO _{2 in} the molten glass MG is small. Therefore, once SO ₂ is blown into bubbles as a gas, the SO ₂ is hardly absorbed into the molten glass in the absorption process.

For example, in the process from the second half of the blue sign 102 to the stirring tank 103, O ₂ in the bubbles is absorbed by SnO by the oxidation reaction of SnO, and SO ₂ and CO ₂ , It is possible to suppress the growth of bubbles by decreasing the diffusion of SO ₂ and CO ₂ into the existing bubbles by shortening this period.

(1-4)

In the next homogenization process (step S103), the molten glass is homogenized. Concretely, the molten glass is homogenized by stirring in a stirring tank 103 by a stirring blade (not shown) provided in the stirring tank 103. The molten glass conveyed to the stirring tank 103 is heated to a predetermined temperature range. The predetermined temperature range is preferably 1440 DEG C to 1500 DEG C in the case of a glass substrate for a flat panel display having the following composition (2). The homogenized molten glass is conveyed from the stirring tank 103 to the third conveyance pipe 105c.

In the next supply step (step S104), the molten glass is heated to a temperature suitable for molding in the third conveyance pipe 105c, and is conveyed to the molding apparatus 104 where the next molding step (step S105) is performed. The temperature suitable for molding is preferably about 1200 DEG C in the case of a glass substrate for a flat panel display having the following composition (2), for example. Particularly, in the case of using the overflow down-draw method in the following molding step, it is preferable that it is about 1300 to 1200 ° C in the most downstream region of the third conveyance pipe 105c.

In the next molding step (step S105), the molten glass is formed into a plate-like glass. In the present embodiment, the molten glass is continuously formed into a ribbon shape by an overflow down-draw method. The glass on the molded ribbon is cut to a glass plate. The overflow down-draw method is a method known per se. For example, as described in U.S. Patent No. 3,338,696, molten glass that flows into a formed body to flow over the outer surface of the formed body, And the portion joined at the bottom of the molded body is drawn downward to be formed into glass on a ribbon.

(2) Mixing of glass raw materials

The method of producing a glass plate according to the present invention is applicable to the production of all glass plates, but is particularly suitable for the production of glass substrates for flat panel displays such as liquid crystal display devices, organic EL display devices, and plasma display devices, or cover glasses for covering display portions .

In order to produce a glass sheet according to the present invention, glass raw materials are first combined to obtain a desired glass composition. For example, in the case of producing a glass substrate for a flat panel display, it is preferable to mix the raw materials so as to have the following composition.

(a) 50 to 70% by mass of SiO ₂ ,

(b) 5 to 18 mass% of B ₂ O ₃ ,

(c) 10 to 25% by mass of Al ₂ O ₃ ,

(d) 0 to 10% by mass of MgO,

(e) 0 to 20% by mass of CaO,

(f) 0 to 20 mass% of SrO,

(o) BaO: 0 to 10 mass%

(p) RO: 5 to 20 mass% (provided that R is at least one selected from Mg, Ca, Sr and Ba)

(q) R ' ₂ O: more than 0.10 mass% to 2.0 mass% (provided that R' is at least one selected from Li, Na and K)

(r) at least one kind of metal oxide selected from tin oxide, iron oxide and cerium oxide in a total amount of 0.05 to 1.5% by mass.

Also, (q) R ' ₂ O is not essential and may not be included. In this case, R 'is an alkali-free glass that does not contain ₂ O substantially, R from the glass plate, it is possible to reduce the fear that the destruction of the TFT ₂ O flows out. On the other hand, by containing (q) R ' ₂ O in excess of 0.10 mass% to 2.0 mass% or less on the other hand, the basicity of the glass can be increased while suppressing the deterioration of the TFT characteristics and the thermal expansion of the glass within a certain range, Thereby making it easy to improve the purifying property. In addition, since the resistivity of the glass can be lowered, it is preferable to conduct the electric melting in the melting tank 101.

Recently, a display using P-Si (low-temperature polysilicon) TFT or oxide semiconductor instead of? -Si TFT has been demanded to realize further high definition. Here, in a process of forming a P-Si (low-temperature polysilicon) TFT or an oxide semiconductor, there is a heat treatment process at a higher temperature than a process of forming an? -Si TFT. For this reason, a glass plate on which a P-Si (low-temperature polysilicon) TFT or an oxide semiconductor is formed is required to have a low heat shrinkage ratio. In order to reduce the heat shrinkage ratio, it is preferable to increase the strain point of the glass, but a glass having a high strain point tends to have a high viscosity (high temperature viscosity) at a high temperature. Therefore, it is necessary to raise the temperature of the molten glass in the blue sign 102. However, if the blue sign 102 is excessively heated to raise the temperature of the molten glass, the blue sign 102 may be damaged. That is, the present invention, which can sufficiently elucidate the clarifying effect of SnO ₂ in blue screen 102, is preferable for the production of high-strain point glass which tends to have high-temperature viscosity.

That is, for example, the present invention is preferable for the production of a glass plate having a strain point of 655 DEG C or higher. Especially, a glass plate having a strain point of 675 DEG C or higher, which is preferable for P-Si (low temperature polysilicon) TFT or oxide semiconductor, is preferable for the present invention, more preferably a glass plate having a strain point of 680 DEG C or higher, Do.

As a composition of the glass plate having a strain point of 675 DEG C or more, for example, the glass plate includes the following components in mass%.

3 to 20 mass% of SiO ₂ , 3 to 25 mass% of Al ₂ O _3, 3 to 15 mass% of B ₂ O _3, 3 to 20 mass% of RO (RO is a total amount of MgO, CaO, SrO and BaO) The mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is preferably in the range of 7 or more. In order to further increase the strain point, the mass ratio (SiO ₂ + Al ₂ O ₃ ) / RO is preferably 7.5 or more. In order to increase the strain point, it is preferable that the value of? -OH is 0.1 to 0.3 mm ^-1 . On the other hand, R ₂ O (R ₂ O is the total amount of Li ₂ O, Na ₂ O and K ₂ O) is set to 0.01 to 0.8% by mass so that current does not flow in the melting vessel 101, It is preferable to lower the resistivity of the glass. Alternatively, the content of Fe ₂ O ₃ is preferably 0.01 to 1% by mass in order to lower the resistivity of the glass. In order to prevent an increase in devitrification temperature while realizing a high strain point, CaO / RO is preferably 0.65 or more. Alternatively, the mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is preferably in the range of 7.5 to 20. By setting the slag temperature to 1250 占 폚 or lower, the overflow down-draw method can be applied. Also, considering that it is applied to a mobile device and the like, it is preferable that the total content of SrO and BaO is less than 0 to 2 mass% in terms of weight reduction.

Further, the above-mentioned glass substrate for a flat panel display preferably does not substantially contain arsenic, and more preferably does not substantially contain arsenic and antimony. That is, even if these materials are included, they are impurities, and specifically, these materials are As ₂ O ₃ And It is preferably 0.1 mass% or less including an oxide of Sb ₂ O ₃ .

In addition to the above components, the glass of the present invention may contain various other oxides to control the various physical, melting, refining and shaping properties of the glass. Examples of such other oxides include, but are not limited to, SnO ₂ , TiO ₂ , MnO, ZnO, Nb ₂ O ₅ , MoO ₃ , Ta ₂ O ₅ , WO ₃ , Y ₂ O ₃ and La ₂ O ₃ have. Here, glass substrates for flat panel displays such as liquid crystal displays and organic EL displays are particularly strict in their demand for bubbles, so that at least the above-mentioned oxides preferably contain at least SnO ₂ having a high clarifying effect.

As the source of RO in (p) of (a) to (r), nitrate or carbonate can be used. Further, in order to increase the oxidizing property of the molten glass, it is more preferable to use nitrate as a supply source of RO at a ratio suitable for the process.

The glass plate produced in the present embodiment is produced continuously, unlike the method in which a batch of glass raw materials is supplied to the melting furnace to perform batch processing. The glass plate used in the production method of the present invention may be a glass plate having any thickness and width.

(3) Specific example

As described below, when the glass plate manufacturing method according to the present invention is actually used, bubbles in the glass can be effectively suppressed.

(Example)

First, the composition was composed of 60.9 mass% SiO ₂ , 11.6 mass% B ₂ O ₃ , 16.9 mass% Al ₂ O ₃ , 1.7 mass% MgO, 5.1 mass% CaO, 2.6 mass% SrO, , A glass containing 0.25% by mass of K ₂ O, 0.15% by mass of Fe ₂ O ₃ , and 0.13% by mass of SnO ₂ was produced. Subsequently, a raw material was charged into the dissolution tank 101, and a series of processes of the glass plate production method according to the present invention described above was performed using the glass plate production line 100 to produce a glass plate. That is, the molten glass is formed by heating the glass raw material to about 1550 DEG C in the melting tank 101, and the molten glass is passed through the first conveyance pipe 105a (connection pipe) made of platinum and rhodium, And the melted glass was heated in the blue oven 102 to about 1700 ° C. The cross-sectional area of the inner diameter of the first transfer pipe 105a (connection pipe) was about 40% of the cross-sectional area perpendicular to the longitudinal direction of the blue sign 102. In the first conveyance pipe 105a (connecting pipe), the molten glass was heated to about 1650 ° C. A glass plate having a thickness of 0.7 mm, a length of 2000 mm in the width direction, and a length of 2500 mm in the lengthwise direction was manufactured using the overflow down-draw method. The number of bubbles contained in the glass plate was measured, and the bubbles were 0.05 out of 1 kg of glass.

(Comparative Example 1)

In Comparative Example 1, a glass raw material was heated to about 1550 DEG C in the melting tank 101 to be melted to form a molten glass, and the molten glass was passed through a first transfer pipe 105a (connecting pipe) made of an alloy of platinum and rhodium And the molten glass is heated to about 1700 DEG C in the blue oven 102. In the first transfer pipe 105a (connecting pipe), the molten glass is heated to about 1480 DEG C , A method of manufacturing a glass plate was carried out in the same manner as in Example. The number of bubbles contained in the glass plate was measured, and the bubbles were 0.2 to 0.3 in 1 kg of glass. Further, the region where the molten glass reached approximately 1700 DEG C in the blue oven 102 was the downstream side in the flow direction of the molten glass as compared with the embodiment. In addition, the temperature of the blue sign 102 was higher than that of the example, and the volatilization amount of the blue sign 102 after the production of the glass sheet for one year was increased by 50 to 66% as compared with that of the first example.

(Comparative Example 2)

As Comparative Example 2, a glass raw material was heated and dissolved to about 1550 ° C in a melting tank 101 to form a molten glass, and the molten glass was passed through a first conveyance pipe 105a (connecting pipe) made of an alloy of platinum and rhodium The glass plate was manufactured in the same manner as in Example 1 except that the molten glass was transferred to the blue sign 102 through the blue sign 102 and the molten glass was heated to about 1630 ° C in the blue sign 102. The number of bubbles contained in the glass plate was measured, and the number of bubbles was 50 to 200 in 1 kg of glass.

(4) Features

In the above embodiment, the glass raw material is heated and melted to a first temperature (T1), for example, about 1550 ° C in the first furnace melting tank 101, and the molten glass is melted in the melting bath 101 and the second And is conveyed to the first conveyance pipe 105a (connection pipe) which is a connection pipe for connecting the low noise sign 102. [ In the first transfer pipe 105a (connecting pipe), the molten glass is heated to a third temperature T3 higher than the heating temperature in the melting tank 101, for example, to about 1650 deg. In the blue sign 102, the molten glass is further heated to a second temperature T2 higher than the first temperature T1. The second temperature T2 is a temperature suitable for refinement of the molten glass, for example, 1650 占 폚 to 1700 占 폚 in the case of the glass substrate for a flat panel display according to the above embodiment. Since the molten glass is already heated to a temperature suitable for refining in the first conveyance pipe 105a (connection pipe) before being conveyed to the blue sign 102, the refining of the molten glass is performed by the molten glass, As shown in FIG. Therefore, according to the method for producing a glass sheet according to the present invention, even when a refining agent such as SnO ₂ other than As ₂ O ₃ is used, it is possible to sufficiently obtain the refining effect, and the number of bubbles in the glass plate can be sufficiently reduced. In addition, it is possible to purify the molten glass easily and effectively.

100 glass plate manufacturing line
101 Melting bath
102 blue sign
105a First conveying pipe (connecting pipe)
201 Electric heating device

Claims (14)

A step of transporting molten glass containing at least SnO ₂ from a melting tank to a blue screen through a platinum or platinum alloy connecting pipe,
In a blue sign made of platinum or a platinum alloy having a space for storing gas by defoaming, a purifying step of defoaming bubbles contained in the molten glass out of the molten glass
Lt; / RTI &
Heating the temperature of the molten glass in the connecting pipe to 1500 to 1690 DEG C,
The temperature of the molten glass in the blue oven is heated to 1600 캜 to 1780 캜,
Wherein the temperature of the molten glass in the blue oven is higher than the temperature of the molten glass in the connecting pipe. The method according to claim 1, wherein the temperature of the molten glass in the connecting pipe is heated to 1550 캜 to 1690 캜,
And the temperature of the molten glass is heated to 1620 캜 to 1780 캜 in the blue sign. A melting step of heating and melting the glass material in a melting tank to produce a molten glass;
Flowing the molten glass from the melting vessel through a connecting pipe made of platinum or a platinum alloy to a platinum or platinum alloy manufacturing vessel;
The molten glass is heated in the blue screen and is refined
/ RTI >
The molten glass flowing through the connecting pipe is heated by the connecting pipe to 1600 캜 to 1650 캜,
Wherein the molten glass in the blue oven is heated by the blue oven to 1650 캜 to 1700 캜. The method of manufacturing a glass plate according to any one of claims 1 to 3, wherein a pressure applied to the molten glass in the connecting pipe is higher than a pressure applied to the molten glass in the blue oven. 4. The method according to any one of claims 1 to 3, wherein the viscosity of the molten glass in the connecting tube is 500 to 2000 poise and the viscosity of the molten glass in the blue oven is 200 to 800 poise. The manufacturing method of a glass plate according to any one of claims 1 to 3, wherein the cross-sectional area perpendicular to the longitudinal direction of the connection pipe is smaller than the cross-sectional area perpendicular to the longitudinal direction of the blue sign. The manufacturing method of a glass plate according to any one of claims 1 to 3, wherein the connection pipe is heated by energization heating, and the blue label is heated by energization heating. The glass sheet according to any one of claims 1 to 3, wherein the glass plate contains more than 0.10% by mass and no more than 2.0% by mass of R ' ₂ O (provided that R' is at least one selected from Li, Na and K) Wherein the glass plate is a glass plate. The glass plate according to any one of claims 1 to 3, wherein the glass plate is a glass plate which is an alkali-free glass substantially not containing R ' ₂ O (provided that R' is at least one selected from Li, Na and K) ≪ / RTI > 4. The method for producing a glass plate according to any one of claims 1 to 3, wherein the temperature is 1500 deg. C to 1750 deg. The method according to any one of claims 1 to 3, wherein after the molten glass is heated to 1600 DEG C or higher by the blue sign, the molten glass is cooled at a temperature lower than 2 DEG C / min in a temperature range of 1600 DEG C to 1500 DEG C Wherein the temperature of the glass plate is lowered. The method of manufacturing a glass plate according to any one of claims 1 to 3, wherein the molten glass is allowed to flow in contact with the connection pipe at an entire periphery of the inner diameter of the connection pipe. The glass plate according to any one of claims 1 to 3, wherein the glass plate contains the following composition.
(a) 50 to 70% by mass of SiO ₂ ,
(b) 5 to 18 mass% of B ₂ O ₃ ,
(c) 10 to 25% by mass of Al ₂ O ₃ ,
(d) 0 to 10% by mass of MgO,
(e) 0 to 20% by mass of CaO,
(f) 0 to 20 mass% of SrO,
(o) BaO: 0 to 10 mass%
(p) RO: 5 to 20 mass% (provided that R is at least one selected from Mg, Ca, Sr and Ba). The glass plate according to any one of claims 1 to 3, wherein the viscosity of the molten glass in the connecting pipe is 500 to 2000 poise, the viscosity of the molten glass in the blue oven is 200 to 800 poise, And at most 2.0% by mass of R ' ₂ O (provided that R' is at least one selected from Li, Na and K).

Images