JP6563230B2 - Glass substrate manufacturing method and glass substrate manufacturing apparatus - Google Patents

Description

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

Generally, the manufacturing method of a glass substrate has a melting process which heats a glass raw material and produces | generates a molten glass, and a shaping | molding process which shape | molds a glass substrate from molten glass, as described in patent document 1. . The method for producing a glass substrate further includes a refining step for removing minute bubbles contained in the molten glass between the melting step and the forming step. In the clarification step, bubbles in the molten glass are removed by an oxidation-reduction reaction of the clarifier by passing the molten glass containing a clarifier such as As ₂ O ₃ through a high-temperature clarifier. Specifically, first, by raising the temperature of the molten glass and causing the fining agent to function, bubbles contained in the molten glass are floated and removed on the liquid surface of the molten glass in the clarification tube. Next, the temperature of the molten glass is lowered, and fine bubbles remaining in the molten glass are absorbed by the molten glass and removed. The refining tube through which the molten glass passes has a gas phase space between the upper inner wall surface and the liquid surface of the molten glass. The gas phase space communicates with outside air, which is an external space of the clarification tube, through a ventilation tube connected to the clarification tube.

  In order to mass-produce a high-quality glass substrate from high-temperature molten glass, it is desirable that foreign substances that cause defects in the glass substrate do not enter the molten glass. Therefore, the inner wall of the member in contact with the molten glass needs to be made of an appropriate material according to the temperature of the molten glass in contact with the member and the required quality of the glass substrate. A platinum group metal is usually used for the inner wall of the member that contacts the molten glass. Hereinafter, the “platinum group metal” means a metal composed of a single platinum group element and a metal alloy composed of a platinum group element. The platinum group elements are six elements of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os) and iridium (Ir). Platinum group metals are expensive, but have a high melting point and excellent corrosion resistance against molten glass.

The temperature of the molten glass passing through the inside of the clarification tube varies depending on the composition of the glass substrate to be molded, and is 1000 ° C. to 1700 ° C. in the case of a glass substrate for a flat panel display (FPD). In recent years, SnO ₂ has been used as a refining agent instead of As ₂ O ₃ from the viewpoint of reducing environmental burden. SnO ₂ has a small refining effect as compared with _As 2 _{O 3,} in order to obtain the same refining effect and _As 2 _{O 3} is required to raise the temperature of the molten glass. Specifically, when using SnO ₂ as a fining agent, the temperature of the molten glass passing through the inside of the fining tube is set to 1500 ° C. to 1700 ° C.

JP 2006-522001 Gazette

In the method for producing a glass substrate using SnO ₂ as a fining agent, the inner wall of the fining tube is in contact with the high-temperature molten glass. At this time, the refining agent causes a reduction reaction by raising the temperature and releases oxygen. On the other hand, the foam containing the gas component contained in the molten glass absorbs oxygen generated by the reductive reaction of the fining agent. Bubbles that have grown by absorbing oxygen float on the liquid surface of the molten glass, break up and disappear. Moreover, platinum group metal volatilizes gradually from the inner wall of a clarification pipe | tube by use of a clarification pipe | tube over a long period of time. This volatile matter is discharged together with bubbles in the molten glass to the outside air through the gas phase space of the clarification tube and the ventilation tube. However, the platinum group metal volatiles become supersaturated as the temperature drops in the process of being discharged to the outside air. Therefore, there is a problem that solidified volatiles are likely to precipitate on the inner walls of the clarification tube and the ventilation tube. Hereinafter, the substance deposited on the inner wall of the clarification tube and the ventilation tube is referred to as “platinum foreign matter”. By measuring the oxygen concentration of this volatile matter, it is possible to predict the amount of bubbles that grow by absorbing oxygen, and to predict the precipitation of platinum foreign matter. However, since the inside of the vent pipe communicates with the outside air, the temperature tends to decrease, and platinum foreign matter is particularly likely to deposit on the inner wall of the vent pipe. Since the measurement tube for taking in oxygen and measuring the oxygen concentration is provided in the vent tube, there is a possibility that a platinum foreign substance is deposited on the measurement tube and falls. And when a platinum foreign material mixes in molten glass, it will become difficult to mass-produce a high quality glass substrate.

  Then, an object of this invention is to provide the manufacturing method of the glass substrate which can suppress that a foreign material mixes in molten glass in the clarification process of molten glass, and the manufacturing apparatus of a glass substrate.

One aspect of the present invention is a method for manufacturing a glass base plate,
A melting step of melting glass raw material to produce molten glass;
In the glass treatment apparatus comprising a made of platinum or a platinum alloy, wherein the clarification step of the molten glass flow to perform refining of the glass melt as vapor space is formed above the liquid surface of the molten glass,
A molding step of molding a glass substrate from the clarified molten glass,
In the glass processing apparatus,
An oxygen concentration meter that sucks gas from the gas phase space and measures the oxygen concentration in the gas;
A measuring tube which connects the oximeter with the vapor space,
A gas supplier connected to the measuring tube and supplying an inert gas to the measuring tube;
Heating means for heating the inert gas , and
The gas supplier supplies the inert gas heated by the heating means to the measuring tube when the oximeter stops the gas inhalation.
It is characterized by that.

  The gas supplier preferably supplies an inert gas of less than 2 liters / minute to the measuring tube.

The glass processing apparatus is provided with a thermometer for measuring the temperature of the gas,
The heating means preferably heats the inert gas so as to be higher than the temperature of the gas measured by the thermometer.

  The tip of the measuring tube is preferably made of an alloy of platinum and gold.

Another aspect of the present invention is a manufacturing apparatus for a glass board,
A melting device for melting glass raw material to produce molten glass;
A glass processing apparatus made of platinum or a platinum alloy that flows the molten glass so as to form a gas phase space above the liquid surface of the molten glass and clarifies the molten glass ; and
A molding apparatus for molding a glass substrate from the clarified molten glass,
In the glass processing apparatus,
An oxygen concentration meter that sucks gas from the gas phase space and measures the oxygen concentration in the gas;
A measuring tube which connects the oximeter with the vapor space,
A gas supplier connected to the measuring tube and supplying an inert gas to the measuring tube;
A heating device for heating the inert gas ,
The gas supply device supplies the inert gas heated by the heating device to the measurement tube when the oxygen concentration meter stops sucking the gas through the measurement tube.
It is characterized by that.

  According to the said aspect, it can suppress that a foreign material mixes in molten glass.

It is a flowchart which shows the process of the glass substrate manufacturing method which concerns on this embodiment. It is a schematic diagram which shows the structure of the glass substrate manufacturing apparatus which concerns on this embodiment. It is an external view of a clarification pipe. It is a schematic sectional drawing in the longitudinal direction of a clarification tube.

(1) Overall Configuration of Glass Substrate Manufacturing Apparatus An embodiment of a glass substrate manufacturing method and a glass substrate manufacturing apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an example of steps of the glass substrate manufacturing method according to the present embodiment.

As shown in FIG. 1, the glass substrate manufacturing method mainly includes a melting step S1, a clarification step S2, a stirring step S3, a forming step S4, a slow cooling step S5, and a cutting step S6.

In the melting step S1, the glass raw material is heated to obtain molten glass. The molten glass is stored in a melting tank and energized and heated to have a desired temperature. A fining agent is added to the glass raw material. From the viewpoint of reducing the environmental load, SnO ₂ is used as a fining agent.

In the clarification step S2, the molten glass flows through the clarification tube. First, the temperature of the molten glass is raised. The refining agent causes a reduction reaction with an increase in temperature to release oxygen. Bubbles containing gaseous components such as CO ₂ , N ₂ and SO ₂ contained in the molten glass absorb oxygen generated by the reductive reaction of the fining agent. Bubbles that have grown by absorbing oxygen float on the liquid surface of the molten glass, break up and disappear. The gas contained in the extinguished bubbles is discharged into the gas phase space in the clarification tube and finally discharged to the outside air. Next, in the refining step S2, the temperature of the molten glass is lowered. Thereby, the reduced fining agent causes an oxidation reaction and absorbs gas components such as oxygen remaining in the molten glass.

  In the stirring step S3, the clarified molten glass is stirred, and the components of the molten glass are homogenized. Thereby, the composition nonuniformity of the molten glass which is a cause of the striae etc. of a glass substrate is reduced. The homogenized molten glass is sent to the forming step S4.

  In the forming step S4, a glass ribbon is continuously formed from the molten glass by, for example, an overflow downdraw method or a float method.

  In the slow cooling step S5, the glass ribbon continuously formed in the forming step S4 is gradually cooled so as to have a desired thickness and to prevent distortion and warpage.

  In the cutting step S6, the glass ribbon slowly cooled in the slow cooling step S5 is cut into a predetermined length to obtain a glass sheet. The glass sheet is further cut into a predetermined size to obtain a glass substrate. Thereafter, the end surface of the glass substrate is ground and polished, and the glass substrate is cleaned. Further, the glass substrate is inspected for defects such as scratches, and the glass substrate that has passed the inspection is packed and shipped as a product.

  FIG. 2 is a schematic diagram illustrating an example of the configuration of the glass substrate manufacturing apparatus 200 according to the present embodiment. The glass substrate manufacturing apparatus 200 includes a melting tank 40, a clarification tube 41, a stirring device 100, a molding device 42, and transfer tubes 43a, 43b, and 43c. The transfer pipe 43 a connects the melting tank 40 and the clarification pipe 41. The transfer pipe 43 b connects the clarification pipe 41 and the stirring device 100. The transfer pipe 43 c connects the stirring device 100 and the molding device 42. In the present embodiment, the melting tank 40, the clarification tube 41, the stirring device 100, the molding device 42, and the transfer tubes 43a, 43b, and 43 through which the molten glass G flows correspond to the glass processing device.

  The molten glass G produced in the melting tank 40 passes through the transfer pipe 43a and flows into the clarification pipe 41. The molten glass G clarified by the clarification tube 41 passes through the transfer tube 43b and flows into the stirring device 100. The molten glass G stirred by the stirring device 100 passes through the transfer pipe 43 c and flows into the molding device 42. In the forming apparatus 42, the glass ribbon GR is formed from the molten glass G by the overflow downdraw method. The glass ribbon GR is cut into a predetermined size in a later process, and a glass substrate is manufactured. The dimension of the glass substrate in the width direction is, for example, 500 mm to 3500 mm. The dimension of the glass substrate in the length direction is, for example, 500 mm to 3500 mm.

The glass substrate manufactured by the glass substrate manufacturing method and the glass substrate manufacturing apparatus according to the present invention is particularly suitable as a glass substrate for a flat panel display (FPD) such as a liquid crystal display, a plasma display, and an organic EL display. ing. As the glass substrate for FPD, non-alkali glass or alkali-containing glass is used. A glass substrate for FPD has high viscosity at high temperatures. For example, the temperature of the molten glass having a viscosity of 10 ^2.5 poise is 1500 ° C. or higher.

The melting tank 40 includes heating means (not shown) such as a burner. In the melting tank 40, the glass raw material is melted by the heating means, and the molten glass G is generated. The glass raw material is prepared so that a glass having a desired composition can be substantially obtained. As an example of the glass composition, non-alkali glass suitable as a glass substrate for FPD is SiO ₂ : 50 mass% to 70 mass%, Al ₂ O ₃ : 0 mass% to 25 mass%, B ₂ O ₃ : 1. Mass% to 15 mass%, MgO: 0 mass% to 10 mass%, CaO: 0 mass% to 20 mass%, SrO: 0 mass% to 20 mass%, BaO: 0 mass% to 10 mass%. Here, the total content of MgO, CaO, SrO and BaO is 5% by mass to 30% by mass.

Moreover, you may use the alkali trace amount glass which contains a trace amount of alkali metals as a glass substrate for FPD. Alkaline trace containing glass, as component, 'comprises ₂ O, preferably, 0.2 wt% to 0.5 wt% R' of R 0.1 wt% to 0.5 wt% including the ₂ O. Here, R ′ is at least one selected from Li, Na and K. The total content of R ′ ₂ O may be less than 0.1% by mass.

In addition to the above components, the glass produced according to the present invention includes SnO ₂ : 0.01% by mass to 1% by mass (preferably 0.01% by mass to 0.5% by mass), Fe ₂ O ₃ : 0. You may further contain mass%-0.2 mass% (preferably 0.01 mass%-0.08 mass%). The glass produced by the present invention, in consideration of the environmental _load, substantially free of _{As 2 O 3, Sb 2 O} 3 , and PbO.

  The glass raw material prepared as described above is charged into the melting tank 40 using a raw material charging machine (not shown). The raw material input machine may input a glass raw material using a screw feeder, or may input a glass raw material using a bucket. In the melting tank 40, the glass raw material is heated and melted at a temperature according to its composition. Thereby, in the melting tank 40, the high temperature molten glass G of 1500-1600 degreeC is obtained, for example. In the melting tank 40, the molten glass G between the electrodes may be energized and heated by flowing a current between at least one pair of electrodes made of molybdenum, platinum, tin oxide, or the like. In addition, the glass raw material may be heated by supplementarily providing a flame with a burner.

  The molten glass G obtained in the melting tank 40 passes through the transfer pipe 43 a from the melting tank 40 and flows into the clarification pipe 41. The clarification tube 41 and the transfer tubes 43a, 43b, and 43c are tubes made of platinum or a platinum alloy. The clarification tube 41 is provided with a heating means similar to the melting tank 40. In the clarification tube 41, the molten glass G is clarified by further raising the temperature. For example, in the clarification tube 41, the temperature of the molten glass G is raised to 1500 ° C to 1700 ° C.

  The molten glass G clarified in the clarification tube 41 passes through the transfer tube 43b from the clarification tube 41 and flows into the stirring device 100. The molten glass G is cooled when passing through the transfer tube 43b. In the stirring device 100, the molten glass G is stirred at a temperature lower than the temperature of the molten glass G passing through the clarification tube 41. For example, in the stirring device 100, the temperature of the molten glass G is 1250 ° C to 1450 ° C. For example, in the stirring device 100, the viscosity of the molten glass G is 500 poise to 1300 poise. The molten glass G is stirred and homogenized in the stirring device 100.

  The molten glass G homogenized by the stirrer 100 flows from the stirrer 100 through the transfer pipe 43 c and flows into the molding device 42. When the molten glass G passes through the transfer tube 43c, it is cooled so as to have a viscosity suitable for forming the molten glass G. For example, the molten glass G is cooled to around 1200 ° C. In the shaping | molding apparatus 42, the molten glass G is shape | molded by the overflow downdraw method. Specifically, the molten glass G that has flowed into the molding apparatus 42 is supplied to a molded body 52 installed inside a molding furnace (not shown). The formed body 52 is formed of refractory bricks and has a wedge-shaped cross-sectional shape. A groove is formed on the upper surface of the molded body 52 along the longitudinal direction of the molded body 52. The molten glass G is supplied to the groove on the upper surface of the molded body 52. The molten glass G overflowing from the groove flows down along the pair of side surfaces of the molded body 52. A pair of molten glass G which flowed down the side surface of the molded body 52 joins at the lower end of the molded body 52, and the glass ribbon GR is continuously molded. The glass ribbon GR is gradually cooled as it flows downward, and then cut into a glass sheet having a desired length.

(2) Structure of clarification tube Next, the detailed structure of the clarification tube 41 is demonstrated. FIG. 3 is an external view of the clarification tube 41. FIG. 4 is a schematic cross-sectional view of the clarification tube 41 cut vertically along the longitudinal direction of the clarification tube 41. As shown in FIG. 3, the clarification tube 41 is provided with a ventilation tube 41a and a pair of heating electrodes 41b. Inside the clarification tube 41, the molten glass G flows in a state where the gas phase space 41c is formed upward. That is, the liquid surface LS of the molten glass G exists in the clarification tube 41 as shown in FIG. The internal space of the vent pipe 41a communicates with the gas phase space 41c. Moreover, the clarification tube 41 is energized and heated by passing a current between the pair of heating electrodes 41b. Thereby, the molten glass G which passes the inside of the clarification tube 41 is heated and clarified. Moreover, the oxygen partial pressure in the flow path is kept low by flowing an inert gas into the gas phase space 41 c in the clarification tube 41. The inert gas is supplied through a pipe from an inert gas supply source (not shown) through a vent pipe 41a provided in the clarification pipe 41, for example. The supply amount of the inert gas is not particularly limited, but it is preferable that the supply amount of the inert gas is large because the oxygen supply pressure decreases and the platinum or the platinum alloy hardly volatilizes as the supply amount increases. In the clarification process of the molten glass G, bubbles containing gas components such as CO ₂ , N ₂ , and SO ₂ contained in the molten glass G absorb oxygen generated by the reductive reaction of the clarifier. Bubbles grown by absorbing oxygen float on the liquid surface LS of the molten glass G, break up and disappear. The gas contained in the extinguished bubbles is released into the gas phase space 41c in the clarification tube 41, and is discharged to the outside air through the vent tube 41a.

The heating electrode 41 b is a flange-shaped electrode plate that is attached to each of both ends of the clarification tube 41. The heating electrode 41b is connected to a power source (not shown). By supplying electric power to the heating electrode 41b, a current flows through the clarification tube 41 between the pair of heating electrodes 41b, and the clarification tube 41 is energized and heated. Thereby, finer tube 41, for example, is heated to 1700 ° C., molten glass G flowing in the finer tube 41, the temperature of the reduction reaction of SnO ₂ is a fining agent contained in the molten glass G occurs, for example, 1600 C. to 1650.degree. By controlling the current flowing through the clarification tube 41, the temperature of the molten glass flowing inside the clarification tube 41 can be controlled. Note that the number and position of the heating electrodes 41b attached to the clarification tube 41 may be appropriately determined according to the material, inner diameter and length of the clarification tube 41, the position of the ventilation tube 41a, and the like.

  Although not shown in FIGS. 3 and 4, a refractory protective layer made of alumina cement or the like is provided on the outer wall surface of the clarification tube 41. A refractory brick is further provided on the outer wall surface of the refractory protective layer. The refractory brick is placed on a base (not shown). That is, the clarification tube 41 is supported from below by the refractory protective layer and the refractory brick.

  In addition, in order to prevent platinum foreign matter from falling on the molten glass, receiving portions may be provided in the vent pipe 41a and the measuring pipe 44. About the structure of a receiving part, the said content is considered including the content described in Unexamined-Japanese-Patent No. 2014-47124.

In the manufacturing method of the glass plate which concerns on this embodiment, the molten glass G produced | generated by heating a glass raw material is heated when passing the inside of the clarification pipe | tube 41. As shown in FIG. Inside the clarification tube 41, bubbles containing CO ₂ or SO ₂ contained in the molten glass G are removed by an oxidation-reduction reaction of SnO ₂ which is a clarifier added to the molten glass G. Specifically, first, the temperature of the molten glass G is raised to reduce the fining agent, thereby generating oxygen bubbles in the molten glass G. Bubbles containing gaseous components such as CO ₂ , N ₂ and SO ₂ contained in the molten glass G absorb oxygen generated by the reductive reaction of the clarifying agent. Bubbles grown by absorbing oxygen float on the liquid surface LS of the molten glass G, break up and disappear. The gas contained in the extinguished bubbles is released into the gas phase space 41c and discharged to the outside air through the vent pipe 41a.

  The ventilation pipe 41 a is attached to the outer wall surface of the clarification pipe 41 and projects outward from the clarification pipe 41. In the present embodiment, as shown in FIG. 4, the ventilation pipe 41 a is attached to the upper end portion of the outer wall surface of the clarification pipe 41 and protrudes in a chimney shape toward the upper side of the clarification pipe 41. The ventilation pipe 41 a communicates the gas phase space 41 c that is a part of the internal space of the clarification pipe 41 and the outside air that is the external space of the clarification pipe 41. The ventilation pipe 41a is formed of platinum or a platinum alloy in the same manner as the clarification pipe 41.

As shown in the figure, the vent pipe 41a has a measuring pipe 44 for taking in the gas in the gas phase space 41c passing through the vent pipe 41a, and an oxygen concentration meter for measuring the oxygen concentration of the gas taken in from the measuring pipe 44. 45 is provided. In addition, a gas supply unit 46 that supplies nitrogen (N ₂ ) to the measurement tube 44 is connected to the measurement tube 44. The measurement tube 44 is formed of platinum or a platinum alloy, for example, similarly to the ventilation tube 41 a, and is connected to the oxygen concentration meter 45 so that the gas is taken in from the measurement tube 44 and enters the oxygen concentration meter 45. The measuring tube 44 is formed to be narrower than the tube inner diameter of the vent tube 41a because it is sufficient to take in a gas that can measure the oxygen concentration of the gas in the gas phase space 41c. The inner diameter of the measuring tube 44 is 5 mm to 30 mm, more preferably 5 mm to 20 mm. Moreover, the measuring tube 44 consists of a thick tube of 0.5 mm-1.5 mm, for example. When the tube diameter of the measuring tube 44 is short, volatile substances are likely to precipitate in the tube of the measuring tube 44, and when the tube tube 44 has a long diameter, the amount of gas flowing from the measuring tube 44 to the gas phase space 41c increases. The phase space 41 c is cooled, and volatile substances are likely to precipitate near the gas intake port of the measuring tube 44. For this reason, the inner diameter of the measuring tube 44 is preferably 5 mm to 30 mm, more preferably 5 mm to 20 mm. Moreover, it is preferable that the front-end | tip part which takes in the gas of the measuring tube 44 consists of an alloy of platinum and gold | metal | money. An alloy of platinum and gold has higher wettability than platinum. Since the tip of the measuring tube 44 is likely to deposit (attach) volatiles, the wettability between the volatiles deposited on the tip of the measuring tube 44 and the tip of the measuring tube 44 is kept high. By reducing the contact angle with the measurement tube 44, volatile substances are less likely to be separated from the measurement tube 44. Thereby, it can suppress that the volatile matter which precipitated to the front-end | tip part of the measurement pipe | tube 44 falls.

  The oxygen concentration meter 45 is, for example, any commercially available device that can measure the oxygen concentration, which includes a zirconia type, magnetic type, or electrode type measuring instrument. The oxygen concentration meter 45 measures the oxygen concentration of the gas taken in from the measurement tube 44. The oxygen concentration meter 45 determines whether or not the platinum group metal volatiles are likely to precipitate by measuring the oxygen concentration of the gas discharged to the outside air. Moreover, the oxygen concentration meter 45 predicts the amount of oxygen released from the refining agent in the refining tube 41 by measuring the amount of oxygen that floats on the liquid surface LS of the molten glass G and breaks and is released. Predict the precipitation of platinum foreign matter. When the oxygen concentration in the gas is high, bubbles are likely to grow by absorbing oxygen, so that the amount of volatilized platinum group metal volatiles contained in the bubbles is large, and platinum foreign matter is likely to precipitate. On the other hand, when the oxygen concentration in the gas is low, it is difficult for bubbles to grow by absorbing oxygen, and the amount of volatilized platinum group metal volatiles contained in the bubbles is small. For this reason, by measuring the oxygen concentration in the gas, it is possible to determine whether or not the platinum metal volatiles are likely to precipitate, and it is possible to predict the precipitation of platinum foreign matter.

  The gas supplier 46 is connected to the measuring tube 44 and supplies an inert gas, specifically nitrogen gas, to the measuring tube 44. The gas containing platinum group metal volatiles is discharged to the outside air through the vent pipe 41a, but in the process of being discharged to the outside air, the temperature is lowered and the gas becomes supersaturated. In particular, the gas containing platinum group metal volatiles taken in from the measuring tube 44 becomes supersaturated as the temperature decreases from the inlet of the measuring tube 44 toward the oximeter 45, and volatilizes in the measuring tube 44. Objects may precipitate and the measuring tube 44 may become clogged. If the measuring tube 44 is clogged with volatile substances (precipitates), the oxygen concentration of the gas cannot be stably measured. Further, volatile substances may fall from the measuring tube 44, and platinum foreign matter may be mixed into the molten glass. For this reason, in the standby state before the oxygen concentration meter 45 measures the oxygen concentration, the gas supply unit 46 supplies nitrogen to the measurement tube 44 and fills the inside of the tube with nitrogen. By suppressing the inflow of the gas containing the volatile matter, the measurement tube 44 is prevented from being clogged with the volatile matter. The gas supply unit 46 includes a heating unit that heats the inert gas to be supplied. When the temperature of the inert gas supplied to the measuring tube 44 is low, the gas containing platinum group metal volatiles taken in through the measuring tube 44 cooled by the inert gas is cooled, and the volatiles are contained in the measuring tube 44. May deposit and the measuring tube 44 may be clogged. For this reason, supplying the heated inert gas to the measuring tube 44 prevents the measuring tube 44 from being clogged with volatile substances. Thereby, oxygen concentration can be measured stably and it can suppress that a volatile matter falls and a platinum foreign material mixes into molten glass. The inert gas supplied by the gas supply unit 46 is optional as long as it is a gas inert to the platinum group metal, or a gas whose reactivity with the platinum group metal is lower than that of oxygen. Carbon oxide can be used.

  The thermometer 47 is composed of, for example, a thermocouple, and measures the temperature of the gas in the vicinity of the intake port through which the measurement tube 44 takes in the gas. When the temperature of nitrogen supplied from the gas supply device 46 is lower than the temperature of the gas in the gas phase space 41c, nitrogen supplied from the gas supply device 46 enters the gas phase space 41c through the measuring tube 44, and the gas phase space 41c. Will lower the temperature. When the temperature of the gas phase space 41c is lowered, volatile substances are likely to be precipitated. In particular, the deposit is generated and deposited near the entrance of the measuring tube 44, so that the measuring tube 44 may be blocked and clogged. . For this reason, by supplying nitrogen having a temperature higher than the temperature of the gas in the gas phase space 41 c to the measuring tube 44, it is possible to suppress deposition of volatile substances near the entrance of the measuring tube 44.

Next, a method for suppressing volatiles deposited on the measuring tube 44 by supplying an inert gas (nitrogen) to the measuring tube 44 will be described.
First, the thermometer 47 measures the temperature of the gas in the vicinity of the intake port through which the measuring tube 44 takes in the gas. Next, the gas supplier 46 continues to supply an inert gas (nitrogen) having a temperature higher than the gas temperature measured by the thermometer 47 to the measuring tube 44. By continuing to supply the inert gas to the measurement tube 44, the measurement tube 44 is filled with the inert gas and the gas in the gas phase space 41 c is prevented from entering the measurement tube 44. It is possible to prevent the measurement tube 44 from clogging due to deposition of volatile substances. Moreover, since the clogging of the measuring tube 44 can be prevented, the oxygen concentration of the gas can be accurately measured by the oxygen concentration meter 45. Further, by supplying an inert gas having a temperature higher than the temperature of the gas in the gas phase space 41 c, it is possible to suppress volatiles from being deposited at the intake port of the measurement tube 44, so that the volatiles fall from the measurement tube 44. And it can suppress that a platinum foreign material mixes in molten glass. The amount of the inert gas supplied by the gas supplier 46 is, for example, 0.3 to 2 liters / minute. If the supply amount of the inert gas is small, the gas in the gas phase space 41 c may enter the measurement tube 44, and volatile substances may be deposited in the measurement tube 44. For this reason, it is preferable to supply 0.3 liter / min or more of inert gas, More preferably, it is 0.5 liter / min or more. Further, when the supply amount of the inert gas is large, the volatile matter deposited at the intake port of the measuring tube 44 is blown off by the inert gas, and the volatile matter may fall and platinum foreign matter may be mixed into the molten glass. Further, when the supply amount of the inert gas is large, a large amount of inert gas is supplied into the gas phase space 41c. Therefore, the oxygen in the gas phase space 41c measured by the oxygen concentration meter 45 changes, and the oxygen amount It is difficult to predict the precipitation of platinum foreign matter calculated from For this reason, it is preferable to supply an inert gas of less than 2 liters / minute, more preferably 1.5 liters / minute or less. Further, when supplying the inert gas, the measuring tube 44 is heated so that the temperature of the inert gas becomes higher than the temperature of the gas measured by the thermometer 47, and is discharged from the gas intake port of the measuring tube 44. The temperature of the inert gas can be increased.

  Next, when measuring the oxygen concentration of the gas, after the gas supply unit 46 stops supplying the inert gas, the oxygen concentration meter 45 takes in the gas in the gas phase space 41 c through the measurement tube 44. When the gas in the gas phase space 41 c enters the measurement tube 44, the gas is cooled in the measurement tube 44, and volatile substances may be deposited in the measurement tube 44. However, since the inert gas having a temperature higher than the temperature of the gas in the gas phase space 41 c has been supplied into the measurement tube 44 until immediately before, the temperature in the measurement tube 44 is kept high and volatilizes in the measurement tube 44. It is suppressed that a thing precipitates. Thereby, since clogging of the measuring tube 44 can be prevented, the oxygen concentration of the gas can be accurately measured by the oxygen concentration meter 45. Moreover, it can suppress that a volatile substance falls and a platinum foreign material mixes in molten glass.

  After the oxygen concentration meter 45 measures the oxygen concentration of the gas taken in from the measurement tube 44, the gas supply unit 46 supplies the inert gas to the measurement tube 44 again. As a result, the inert gas is again filled in the measuring tube 44, and the gas in the gas phase space 41c is prevented from entering the measuring tube 44, so that volatile substances are deposited in the measuring tube 44, and the measuring tube 44 Can be prevented from clogging.

  By repeating the above processing, it is possible to accurately measure the oxygen concentration of the gas in the gas phase space 41c while preventing the measurement tube 44 from being clogged, so that the amount of bubbles that grow by absorbing oxygen is predicted. Then, precipitation of platinum foreign matter can be predicted.

  As described above, in this embodiment, the measurement tube 44 is clogged with platinum group metal volatiles by continuously supplying a certain amount of inert gas to the measurement tube 44 before measuring the oxygen concentration of the gas. This can be prevented. Moreover, it can suppress that the volatile matter which deposits on the measuring tube 44 falls, and a platinum foreign material mixes into molten glass. In addition, since the measurement tube 44 can be prevented from being clogged, the oxygen concentration can be measured with high accuracy, and precipitation of platinum foreign matter can be predicted.

  Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.

Example 1
The amount of nitrogen supplied by the gas supply unit 46 is changed between 0.3 liters / minute and 2.0 liters / minute, and the measurement tube 44 is blocked by the volatile matter of the platinum group metal deposited on the measurement tube 44. The condition was observed. A measuring tube 44 with a diameter of 10 mm was used. Further, since the gas in the gas phase space 41c measured by the thermometer 47 was 1400 ° C. to 1450 ° C., nitrogen higher than this temperature was supplied. Table 1 shows the results of the state of the volatile matter changing depending on the nitrogen supply amount.

  As shown in Table 1, when the amount of nitrogen supplied to the measuring tube 44 was 0.5 liters / minute to 2.0 liters / minute, no volatile matter was deposited in the measuring tube 44. However, when the amount of nitrogen supplied to the measuring tube 44 was 2.0 liters / minute, linear platinum was generated in the clarification tube 41 and mixed into the molten glass. This is probably because the amount of nitrogen supplied to the measuring tube 44 has increased. For this reason, it was found that the appropriate amount of nitrogen supplied to the measuring tube 44 is less than 2.0 liters / minute. Further, when the amount of nitrogen supplied to the measuring tube 44 was 0.1 liter / min, the measuring tube 44 was completely blocked by volatile substances. When the measuring tube 44 is completely blocked, it is obvious that when the nitrogen or gas is allowed to pass through the measuring tube 44, volatile substances are peeled off from the measuring tube 44 and platinum foreign matter is mixed into the molten glass. Became.

  From the above results, the amount of nitrogen supplied to the measuring tube 44, that is, the amount of nitrogen released from the gas intake port of the measuring tube 44 into the gas phase space 41c is more than 0.1 liter / minute to 2.0 liter / minute. Less than, more preferably 0.5 liters / minute to 1.5 liters / minute, and if the nitrogen supply amount is within this range, the volatiles deposited on the measuring tube 44 peel off, and the molten glass It was found that contamination as platinum foreign matter can be suppressed.

  Although the manufacturing method of the glass plate and the manufacturing apparatus of the glass plate of the present invention have been described in detail, the present invention is not limited to the above-described embodiment, and various improvements and modifications are made without departing from the gist of the present invention. Of course it is also good.

DESCRIPTION OF SYMBOLS 41 Clearing pipe 41a Venting pipe 41b Heating electrode 41c Gas phase space 44 Measuring pipe 45 Oxygen concentration meter 46 Gas supply 47 Thermometer 200 Glass plate manufacturing apparatus G Molten glass LS Liquid glass surface

Claims (5)

A melting step of melting glass raw material to produce molten glass;
In the glass treatment apparatus comprising a made of platinum or a platinum alloy, wherein the clarification step of the molten glass flow to perform refining of the molten glass as vapor space is formed above the liquid surface of the molten glass,
A molding step of molding a glass substrate from the clarified molten glass,
In the glass processing apparatus,
An oxygen concentration meter that sucks gas from the gas phase space and measures the oxygen concentration in the gas;
A measuring tube which connects the oximeter with the vapor space,
A gas supplier connected to the measuring tube and supplying an inert gas to the measuring tube;
Heating means for heating the inert gas , and
The gas supplier supplies the inert gas heated by the heating means to the measuring tube when the oximeter stops the gas inhalation.
A method for producing a glass substrate, comprising: The gas supplier supplies an inert gas of less than 2 liters / minute to the measuring tube;
The method for producing a glass substrate according to claim 1. The glass processing apparatus is provided with a thermometer for measuring the temperature of the gas,
The heating means heats the inert gas to be higher than the temperature of the gas measured by the thermometer,
The manufacturing method of the glass substrate of Claim 1 or 2 characterized by the above-mentioned. The tip of the measuring tube is made of an alloy of platinum and gold.
The manufacturing method of the glass substrate as described in any one of Claim 1 to 3 characterized by the above-mentioned. A melting device for melting glass raw material to produce molten glass;
A glass processing apparatus made of platinum or a platinum alloy that flows the molten glass so as to form a gas phase space above the liquid surface of the molten glass and clarifies the molten glass ; and
A molding apparatus for molding a glass substrate from the clarified molten glass,
In the glass processing apparatus,
An oxygen concentration meter that sucks gas from the gas phase space and measures the oxygen concentration in the gas;
A measuring tube which connects the oximeter with the vapor space,
A gas supplier connected to the measuring tube and supplying an inert gas to the measuring tube;
A heating device for heating the inert gas ,
The gas supply device supplies the inert gas heated by the heating device to the measurement tube when the oxygen concentration meter stops sucking the gas through the measurement tube.
An apparatus for producing a glass substrate.

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