JPWO2009148139A1 - Sheet glass manufacturing apparatus and sheet glass manufacturing method - Google Patents

Abstract

The present invention provides a plate glass manufacturing apparatus and a plate glass manufacturing method capable of manufacturing a high quality plate glass in which the occurrence of warpage and residual stress is suppressed. According to the glass plate manufacturing equipment of the present invention, the reheating preventing means is provided at the boundary between the forming part and the slow cooling part. By this reheating prevention means, it is possible to prevent the hydrogen gas in the molding part from entering the slow cooling part, thereby preventing the generation of a hydrogen flame, and thus preventing reheating of the glass ribbon. That is, in the glass plate manufacturing facility of the embodiment, hydrogen gas in the molding part can be prevented from entering the slow cooling part by the reheating prevention means provided at the boundary part between the molding part and the slow cooling part. It is possible to prevent reheating of the glass ribbon due to the hydrogen flame generated by the gas penetration.

Description

  The present invention relates to a sheet glass manufacturing apparatus by a float process and a method for manufacturing the same, and in particular, a sheet glass for manufacturing a sheet glass by transporting a high-temperature glass ribbon drawn from a molten metal bath in a reducing atmosphere to a slow cooling part that is an oxidizing atmosphere. The present invention relates to a manufacturing apparatus and a manufacturing method of plate glass.

  In glass plates such as glass plates for buildings, glass plates for automobiles, and glass plates for displays, a plate glass manufacturing apparatus and a manufacturing method by a float method using a float bath (molten tin bath) have been conventionally known (Patent Literature). 1).

  The method for producing plate glass by the float process is to supply molten glass onto the molten tin surface of the float bath and form the molten glass into a continuous sheet on the molten tin bath. This is a manufacturing method in which a high-temperature glass ribbon that has become a continuous glass plate is drawn out from the surface of the molten tin, and this is gradually cooled and cut into a glass plate of a predetermined size.

The glass ribbon is drawn from the surface of the molten tin bath by lifting and conveying the glass ribbon at the outlet of the molten tin bath by a roll called a lift-out roll. The location where the lift-out roll exists is hereinafter referred to as a dross box. This area where the float bath and the dross box are present is called a molded part. The drawn-out glass ribbon is gradually cooled in the connecting portion and the slow cooling furnace communicating with the slow cooling furnace on the downstream side of the dross box. The area where the connecting part and the slow cooling furnace exist is hereinafter referred to as a slow cooling part. The roll that supports and conveys the glass ribbon in this slow cooling section is hereinafter referred to as a slow cooling roll. Since the molten tin in the float bath is easily oxidized, the atmosphere of the float bath is reduced by a mixed gas of nitrogen (N ₂ ) gas and hydrogen (H ₂ ) gas (H ₂ concentration: 1 to 12%, oxygen (O _2). ) Concentration: 100 ppm or less) and kept at a positive pressure. The dross box communicating with the float bath is also maintained in a reducing atmosphere of positive pressure. Then, _{O 2} concentration in the oxidizing atmosphere annealing furnace is 5-21%.

International Publication WO 02/051767

  By the way, the conventional plate glass manufacturing apparatus by the float method is configured to allow the glass ribbon to pass from the forming part to the annealing furnace, although the forming part which is a reducing atmosphere and the annealing part which is an oxidizing atmosphere are partitioned by a partition wall. A slight gap is provided between the upper surface of the glass ribbon and the partition wall.

  For this reason, hydrogen gas in the dross box of the molding part leaks to the slow cooling part through the gap, and this reacts with oxygen in the vicinity of the high-temperature glass ribbon to generate a hydrogen flame. However, there was a problem that the glass ribbon that had been cooled rapidly was reheated by the hydrogen flame. Due to the reheating of the glass ribbon, the produced plate glass is warped or residual stress is generated, which causes a problem that the quality of the plate glass is deteriorated. In particular, reduction of warpage and residual stress is required in terms of the quality of glass plates for displays such as plasma display panels and liquid crystal display panels, and glass for electronic use (solar cell cover glass, magnetic disk substrate, etc.). In the dross box, since the bottom surface of the glass ribbon is continuously in contact with the entire width direction by the lift-out roll, the hydrogen gas is gradually cooled from between the bottom surface of the glass ribbon and the lift-out roll. There is no generation of hydrogen flame due to leakage to the part.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a plate glass manufacturing apparatus and a plate glass manufacturing method capable of manufacturing a high quality plate glass in which generation of warpage and residual stress is suppressed. And

  In order to achieve the above object, a glass ribbon formed on a float bath in a forming part maintained in a reducing atmosphere containing hydrogen gas is used to produce a glass ribbon manufacturing apparatus according to the present invention. In the sheet glass manufacturing apparatus for manufacturing sheet glass by transporting and slowly cooling the glass ribbon, the glass ribbon is reheated by the hydrogen flame caused by the hydrogen gas in the molded part at the boundary between the molded part and the gradually cooled part. A feature of preventing reheating is provided.

  In order to achieve the above object, the invention of the method for producing a plate glass of the present invention uses the production apparatus to slowly cool the glass ribbon so that the glass ribbon temperature in the slow cooling portion is equal to or lower than the glass ribbon temperature in the forming portion. It is characterized by doing.

  According to the present invention, the reheating prevention means provided at the boundary between the molding part and the slow cooling part can prevent hydrogen gas in the molding part from entering the slow cooling part. No flame is generated, and therefore reheating of the glass ribbon can be prevented. Thereby, since the glass ribbon which flows into a slow cooling part from a shaping | molding part is annealed so that the temperature may fall gradually, the quality plate glass which suppressed generation | occurrence | production of curvature and a residual stress can be manufactured.

  According to this invention, it is preferable that the said reheating prevention means consists of a heat-resistant fiber sheet in the part which contact | connects the said glass ribbon upper surface of the said reheating prevention means. Thereby, since the atmosphere of a shaping | molding part and the atmosphere of a slow cooling part are completely interrupted | blocked by the contact member (heat-resistant fiber sheet), it can prevent that the hydrogen gas of a shaping | molding part permeates into a slow cooling part. Further, as the heat-resistant fiber, the temperature of the glass ribbon drawn from the outlet of the float bath (temperature above the strain point and below the softening point, specifically, 510 to 840 ° C. in the case of soda lime glass for plasma display etc., liquid crystal In the case of non-alkali glass for display or the like, a material that can withstand a temperature of 670 to 950 ° C., that is, a fiber that can withstand a temperature of 950 ° C. or higher, particularly about 1000 ° C. or higher is preferable.

  According to this invention, it is preferable that the said heat-resistant fiber sheet is a carbon fiber or a silica fiber. From the viewpoint of low hardness and difficulty in scratching the glass ribbon, carbon fiber is more preferable than silica fiber. Even if the carbon fiber adheres to the upper surface of the glass ribbon, the carbon fiber burns out on the downstream side of the slow cooling portion, which is a relatively high-temperature oxidizing atmosphere, so that it does not cause defects such as dirt.

  The heat-resistant fibers are not limited to carbon fibers and silica fibers, and may be inorganic fibers such as alumina fibers, silicon carbide fibers, and metal fibers. As the fiber sheet, a felt-like sheet, a woven fabric, or a non-woven fabric sheet is preferable. Specifically, for example, a felt sheet of carbon fiber or a woven fabric of carbon fiber can be used. The heat resistant fiber sheet may be a fiber sheet composed of two or more kinds of inorganic fibers of different materials.

  According to the plate glass manufacturing apparatus and the plate glass manufacturing method according to the present invention, since the reheating preventing means is provided at the boundary between the forming portion and the slow cooling portion, the glass ribbon is reheated by the hydrogen flame caused by hydrogen gas. Thus, it is possible to manufacture a high-quality plate glass in which generation of warpage and residual stress is suppressed. The present invention is effective for the production of display glass plates.

Sectional drawing which showed the structure of the glass plate manufacturing equipment of embodiment. The graph which showed the temperature change of the glass ribbon which passes a slow cooling part from a dross box. The perspective view of the reheating prevention member installed in the glass plate manufacturing equipment of FIG.

  Hereinafter, preferred embodiments of a plate glass manufacturing apparatus and a plate glass manufacturing method of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view of a glass plate manufacturing facility 10 by a float method to which a plate glass manufacturing apparatus according to the present invention is applied. In the following description, the downstream side refers to the same direction as the movement direction of the glass ribbon 12 in FIG. 1 (in the direction of arrow A in FIG. 1), and the opposite side is referred to as the upstream side.

  The glass plate manufacturing facility 10 shown in FIG. 1 is provided with a forming part 14 and a slow cooling part 16 from the upstream side toward the downstream side. The forming unit 14 includes a float bath (molten metal bath) 18 and a dross box 20, and the slow cooling unit 16 includes a connecting unit 21 and a slow cooling furnace 22, and a slow cooling roll 23 that supports and conveys the glass ribbon 12 to the slow cooling furnace 22. Is provided.

The float bath 18 contains high-temperature molten tin 24, and molten glass is continuously supplied to the horizontal bath surface of the molten tin 24, whereby the glass ribbon 12 is formed toward the outlet 19 of the float bath 18. The The glass ribbon 12 is pulled up from the molten tin 24 by the lift-out rolls 26 </ b> A, 26 </ b> B, 26 </ b> C of the dross box 20 at the outlet 19 of the float bath 18 and is conveyed through the dross box 20. And this glass ribbon 12 is carried out to the slow cooling furnace 22 from the connection part 21, is cooled gradually while passing through this slow cooling furnace 22, and is manufactured to plate glass. Incidentally, the float bath 18 and dross box 20 is the atmosphere above the melting temperature of tin, it is necessary to hold as well known reduced to (non-oxidizing) atmosphere, the hydrogen from the nozzle (not shown) and nitrogen (N ₂₎ A gas mixture with (H ₂ ) is always supplied, preventing oxidation of the molten tin 24 and maintaining a positive pressure.

  On the other hand, a reheating preventing means 32, that is, a partition wall 15 is provided at the boundary between the molding unit 14 and the slow cooling unit 16, and the upper surface of the glass ribbon 12 is in contact with the partition wall 15 and below the partition wall 15. A heat-resistant fiber sheet 30 in contact therewith is provided. The heat-resistant fiber sheet 30 prevents the glass ribbon 12 from being reheated by the hydrogen flame generated when the hydrogen gas in the molding unit 14 enters the slow cooling unit 16.

  That is, in the glass plate manufacturing facility 10 of the embodiment, the hydrogen gas in the molding unit 14 enters the slow cooling unit 16 by the reheating prevention means 32 provided at the boundary between the molding unit 14 and the slow cooling unit 16. Since this can be prevented, reheating of the glass ribbon 12 due to the hydrogen flame generated by the penetration of hydrogen gas is prevented. Thereby, the reheating of the glass ribbon 12 due to the hydrogen flame generated when the hydrogen gas in the molding unit 14 enters the slow cooling unit 16 is prevented, and the temperature of the glass ribbon 12 in the slow cooling unit 16 is reduced. The glass ribbon 12 is gradually cooled so as to be equal to or lower than the temperature of the glass ribbon 12. Therefore, the manufactured plate glass has a good quality with reduced warpage and residual stress.

  FIG. 2 is a graph showing the temperature change of the glass ribbon for a plasma display panel that passes from the dross box 20 through the slow cooling part 16. The vertical axis of the graph shows the temperature of the glass ribbon 12, and the horizontal axis shows the distance from the outlet 19 of the molten metal bath 18 toward the slow cooling furnace 22. Further, in the graph, the solid line indicates the temperature change of the glass ribbon 12 when the reheating prevention means 32 of the embodiment is disposed at the boundary between the molded part 14 and the slow cooling part 16, and the two-dot chain line. Shows a temperature change when the glass ribbon 12 is reheated because a hydrogen flame is generated because the reheating preventing means 32 is not disposed at the boundary.

  In the form shown by the solid line in the graph, the reheating of the glass ribbon 12 due to the hydrogen flame generated by the hydrogen gas in the molding unit 14 entering the slow cooling unit 16 is prevented, and the glass ribbon 12 of the slow cooling unit 16 is prevented. The glass ribbon 12 is gradually cooled so that the temperature of the glass ribbon 12 becomes equal to or lower than the temperature of the glass ribbon 12 of the molding unit 14. Therefore, it becomes the plate glass of the quality which suppressed generation | occurrence | production of curvature and a residual stress.

  On the other hand, in the form shown by the two-dot chain line, since a hydrogen flame is generated between the forming portion 14 and the slow cooling portion 16, the glass ribbon that has gradually decreased in temperature from 650 ° C. is heated by the hydrogen flame. And reheated to 650-660 ° C. For this reason, it becomes the plate glass which the curvature and the residual stress generate | occur | produced. In addition, the difference with the temperature of the form shown with the continuous line corresponding to the peak temperature of the reheating is about 40 degreeC. In the case of soda lime glass, which is a glass ribbon for plasma display, the exit temperature of the glass ribbon at the exit 19 of the float bath 18 is about 650 ° C. as shown in FIG. The outlet temperature of the alkali glass is about 750 ° C. Note that the difference from the temperature corresponding to the peak temperature of reheating of the alkali-free glass is also about 40 ° C.

  By the way, it is preferable that the heat-resistant fiber sheet 30 is a contact member that is continuously in contact with the upper surface of the glass ribbon 12 over the entire length in the width direction of the glass ribbon 12 as shown in FIG. Thereby, since the atmosphere of the shaping | molding part 14 and the atmosphere of the slow cooling part 16 are completely interrupted | blocked, it can prevent reliably that the hydrogen gas of the shaping | molding part 14 permeates into the slow cooling part 16. FIG. The installation position of the heat resistant fiber sheet 30 is preferably directly above the most downstream liftout roll 26C.

  As an example, reheating prevention means is applied to a soda lime glass and a non-alkali glass ribbon that are continuously drawn from a float bath, and then gradually cooled. Reheating of the glass ribbon by the hydrogen flame is prevented, and the glass temperature of the slow cooling portion is equal to or lower than the glass temperature of the forming portion, so that the warp and residual stress of the glass ribbon are reduced.

INDUSTRIAL APPLICATION This invention can be utilized for manufacture of plate glass, such as a plate glass for buildings by the float process, a plate glass for motor vehicles, and a plate glass for displays.
In addition, the entire content of the specification, claims, drawings and abstract of Japanese Patent Application No. 2008-149616 filed on June 6, 2008 is cited here as disclosure of the specification of the present invention. Incorporated.

  DESCRIPTION OF SYMBOLS 10 ... Glass plate manufacturing equipment, 12 ... Glass ribbon, 14 ... Molding part, 15 ... Partition wall, 16 ... Slow cooling part, 18 ... Float bath, 19 ... Outlet, 20 ... Dross box, 21 ... Connection part, 22 ... Slow cooling furnace 24 ... Molten tin, 26A, 26B, 26C ... Lift-out roll, 30 ... Heat-resistant fiber sheet, 32 ... Reheating prevention means

Claims (4)

In a plate glass manufacturing apparatus for manufacturing a plate glass by transporting a glass ribbon formed on a float bath in a molding section maintained in a reducing atmosphere containing hydrogen gas to a slow cooling section in an oxidizing atmosphere and gradually cooling the glass ribbon,
Reheating prevention means for preventing reheating of the glass ribbon due to hydrogen flame caused by hydrogen gas in the forming portion is provided at a boundary portion between the forming portion and the slow cooling portion. apparatus.   The plate glass manufacturing apparatus according to claim 1, wherein a portion of the reheating preventing means that contacts the upper surface of the glass ribbon is formed of a heat-resistant fiber sheet.   The plate glass manufacturing apparatus according to claim 2, wherein the heat-resistant fiber sheet is carbon fiber or silica fiber.   A sheet glass characterized by using the sheet glass manufacturing apparatus according to any one of claims 1 to 3 to slowly cool the glass ribbon so that the glass ribbon temperature of the slow cooling part is equal to or lower than the glass ribbon temperature of the forming part. Manufacturing method.

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