JP2012082107A - Plate glass forming apparatus and method of forming glass sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel plate glass forming apparatus which can inhibit devitrification in the lower top part of a molding, and a method of forming a glass sheet using the same.SOLUTION: The plate glass forming apparatus includes: an overflow groove 2a which overflows a molten glass G supplied to a top part to both sidewall surfaces 2b; the sidewall surfaces 2b which makes the molten glass flooding in the both sides of the overflow groove 2a flow under; and a cross-sectional substantially wedge-like molding 2 which has a lower top part 2c which fuses the molten glass which has flowed down in the both sidewall surfaces 2b, wherein at least the surface of the lower top part 2c consists of platinum or a platinum alloy, and a high-frequency heating coil 4 which heats the surface of the lower top 2c is prepared.

Description

  The present invention relates to a sheet glass forming apparatus for forming molten glass into a plate shape and a method for forming a sheet glass using the same.

  In general, when manufacturing thin plate glass, molten glass is supplied to an overflow groove formed on the upper part of a substantially wedge-shaped molded body, and the molten glass is overflowed from both sides of the overflow groove to form side wall surfaces on both sides of the molded body. After flowing down, a method is known in which each molten glass is fused at the lower top of the molded body, formed into a plate shape, and cut to obtain a plate glass. This forming method is generally called an overflow down draw method.

  As shown in FIG. 3, the molding apparatus used in the above molding method arranges a molded body 2 having a substantially wedge-shaped cross section and an overflow groove 2a at the top in a molding chamber 1a formed by a heat insulating wall 1. Then, the molten glass G is supplied to the overflow groove 2a of the molded body 2, overflowed, the side wall surfaces 2b on both sides of the molded body 2 are caused to flow down, and fused at the lower top portion 2c of the molded body 2, whereby the sheet glass SG is obtained. The molded body is drawn out through the opening 1b, and has a structure in which the heating element 3 is disposed on both sides of the molded body 2.

  This method and apparatus are suitable for the production of thin plate glasses such as glass substrates for liquid crystal displays, glass substrates for organic EL displays, cover glasses for solar cells, cover glasses for touch panels, and the like.

JP 60-11235 A JP 2003-81653 A JP 2008-69024 A JP 2009-518275 A International Application Publication No. WO2009 / 108338

  In the case of forming a sheet glass by the overflow down draw method, there is a problem in that devitrification occurs due to the temperature of the glass being lowered near the lower top of the formed body. As a method for solving this problem, it is effective to employ a method of heating the molded body, particularly the lower top portion of the molded body. Patent Documents 1 to 5 disclose methods for heating a molded body.

  Patent Document 1 discloses a configuration in which a heating element is provided in a fluid control body (corresponding to the molded body of the present invention), and the surface of the fluid control body is indirectly heated by the heat generation. However, in this configuration, it is necessary to install terminals for supplying current on both sides of the heating element, and there are equipment limitations. Further, since the heating element is embedded in the central portion of the fluid control body, it is difficult to adjust the lower top portion of the fluid control section to a desired temperature.

  Patent Document 2 discloses a configuration in which a heating source made of platinum or the like is disposed at the lower edge of the molded body (corresponding to the lower top of the molded body of the present invention), and the lower edge is directly heated by energization. Yes. However, this heating source needs to be connected to a power source, which is not only limited in terms of equipment but also difficult to heat uniformly in the width direction due to heat radiation from the terminal.

  Patent Document 3 discloses a configuration in which a fusion cell is directly heated by energizing and heating a platinum coating formed on the surface of a fusion cell (corresponding to the molded body of the present invention). However, with this configuration, it is difficult to subdivide the heating area and heat only necessary portions.

  In Patent Document 4, a conductive member made of platinum or the like is incorporated in the vicinity of the tip of the wedge-shaped body for molding (corresponding to the molded body of the present invention) (corresponding to the lower top of the molded body of the present invention), or the tip of the wedge-shaped body The structure which heats a front-end | tip part by forming these with an electroconductive member and energizing these is disclosed. However, this conductive member needs to be connected to a power source, and is not only limited in terms of equipment, but is also difficult to heat uniformly in the width direction due to heat radiation from the terminal.

  Patent Document 5 describes a configuration in which the tip of the molded body is heated by irradiation with energy having a frequency absorbed by the refractory of the molded body. However, in this configuration, it is difficult to heat only a specific part. In addition, it is very difficult to output the frequency at a high output, the equipment is expensive, and the size cannot be increased.

  An object of the present invention is to provide a novel sheet glass forming apparatus capable of preventing devitrification at the lower top portion of a formed body and a method for forming a sheet glass using the same.

  The sheet glass forming apparatus of the present invention includes an overflow groove for overflowing the molten glass supplied to the top to both side wall surfaces, a side wall surface for flowing the molten glass overflowing on both sides of the overflow groove, and a melt flowing down the both side wall surfaces. In a sheet glass forming apparatus having a substantially wedge-shaped molded body having a lower apex portion for fusing glass, at least the surface of the lower apex portion is made of platinum or a platinum alloy, and high-frequency induction heating means for heating the lower apex surface is provided. It is characterized by being provided.

  In the present invention, it is preferable that the high-frequency induction heating means includes a high-frequency heating coil, and the high-frequency heating coil is provided in the vicinity of the lower top portion of the molded body and separated from the lower top portion.

  In the present invention, the high-frequency heating coil is preferably substantially U-shaped and provided in the width direction of the molded body.

  In the present invention, it is preferable that the high-frequency heating coils are arranged symmetrically on both sides of the molded body.

  In the present invention, it is preferable that the feeding direction of the high-frequency heating coil arranged in the vicinity of the lower top is the same direction on both sides of the molded body.

  In the present invention, it is preferable that the arrangement position of the high-frequency heating coil arranged in the vicinity of the lower top portion is substantially the same height as the tip of the lower top portion of the molded body.

  In the present invention, the high-frequency heating coil is preferably fixed in the refractory.

  The glass sheet forming method of the present invention is characterized in that glass is formed into a plate shape using the above glass sheet forming apparatus.

  In the present invention, since the lower top portion of the molded body can be subjected to high-frequency induction heating, it is possible to prevent the glass from lowering the temperature at the lower top portion of the molded body and effectively suppress the devitrification of the glass caused by the temperature decrease. .

  In addition, there is no need to form a heating element or a conductor connected to an external power source on or inside the molded body.

It is explanatory drawing which shows the plate glass shaping | molding apparatus of this invention. It is explanatory drawing which shows the example of arrangement | positioning of a high frequency heating coil. It is explanatory drawing which shows the conventional plate glass shaping | molding apparatus.

  Hereinafter, the present invention will be described based on examples. FIG. 1 shows a preferred embodiment of the apparatus of the present invention. FIG. 1 (a) is a schematic explanatory view showing a cross section of the apparatus, and FIG. 1 (b) is a schematic explanatory view showing the front of the apparatus. The plate glass forming apparatus of the present invention is not limited to this.

  The sheet glass forming apparatus of the present invention has a substantially wedge-shaped cross section in a forming chamber 1a formed by a heat insulating wall 1, and allows an overflow groove 2a to flow down at the top and molten glass G overflowing on both sides of the overflow groove. The molded body 2 having the side wall surface 2b and the lower top portion 2c for fusing the molten glass G flowing down the both side wall surfaces is disposed.

  The lower top portion 2c of the molded body 2 has a structure covered with a coating made of platinum. In the present embodiment, the platinum coating is configured to be formed only on the lower top portion 2c, but a configuration covering the entire molded body 2 may be employed instead. The coating 2c may be formed of a platinum alloy such as platinum-rhodium instead of platinum.

  A heating element 3 is arranged in the molding chamber 1a so as to oppose both side wall surfaces of the molding 2, and the molding chamber is maintained at a desired temperature.

  Furthermore, high-frequency induction heating means capable of high-frequency induction heating of the platinum coating is provided in the molding chamber 1a.

  The high frequency induction heating means includes a high frequency power source (not shown) and a high frequency heating coil 4 connected to the high frequency power source. When a high-frequency current is passed through the high-frequency heating coil 4, a high-density eddy current is generated near the lower top 2c of the molded body due to electromagnetic induction, and the platinum film generates heat due to the Joule heat. By utilizing this heat generation, the molded body lower top portion 2c can be heated to prevent devitrification of the glass in contact with the molded body lower top portion 2c or the glass that is coming away from the lower top portion 2c.

  The shape of the high-frequency heating coil 4 is not particularly limited, but in this embodiment, it is a substantially U-shape that extends in the width direction of the molded body 2, and the straight portion extends over the entire width of the molded body 2. By adopting such a coil shape, it becomes easy to uniformly heat the entire width of the molded body 2 with a simple configuration.

  Further, the high frequency heating coil 4 is set apart from the molded body 2. The high-frequency heating coil 4 is preferably disposed symmetrically on both sides of the molded body 2. If it arrange | positions symmetrically, the heating conditions of both sides can be made the same. Moreover, it is preferable that the feeding direction of the coils on both sides arranged in the vicinity of the molded product lower top portion 2c is the same direction. If they are in the same direction, the directions of current flowing on both sides near the tip of the molded product lower top 2c are the same, and the tip can be efficiently heated without affecting each other. In order to make the feeding direction the same direction, two U-shaped coils may be arranged symmetrically with the molded body interposed therebetween, or may be connected by a single coil as shown in FIG. Moreover, it is preferable that the arrangement position of the high-frequency heating coil 4 arranged in the vicinity of the molded product lower top portion 2c is arranged at substantially the same height as the tip of the molded product lower top portion. If it arrange | positions at the same height, the molded object lower top part 2c front-end | tip will be heated and it is effective in suppressing devitrification generation | occurrence | production. The high-frequency heating coil 4 is preferably installed in a refractory that constitutes the heat insulating wall 1. If the high frequency heating coil 4 is installed in the refractory, the high frequency heating coil 4 and the molded body 2 can be reliably electrically insulated. In addition, the distance between the high-frequency heating coil 4 and the molded body 2 can always be kept constant, and the molded body lower top 2c can be stably heated.

  Next, a method for forming a sheet glass using the above-described sheet glass forming apparatus will be described. The method of the present invention is not necessarily limited to the following method.

  First, a glass raw material is vitrified and homogenized by a glass melting apparatus (not shown). The molten glass G thus obtained is continuously supplied to the overflow groove 2a of the molded body 2 through a molten glass supply pipe (not shown). The molten glass G supplied to the overflow groove 2a overflows from both sides of the overflow groove 2a and flows down along the both side walls 2b of the molded body. The molten glass G flowing down the surface of the molded body along the side wall surface 2b is eventually fused at the molded body lower top portion 2c to become a sheet glass SG. Here, the lower temperature of the glass is prevented by preliminarily heating the molded body lower top 2c by high-frequency induction heating means using high-frequency induction heating means.

  Furthermore, the both ends of the sheet glass SG which has left the compact lower top 2c are gripped by a cooling roller (not shown) to suppress contraction in the sheet width direction. Further, the sheet glass SG is stretched downward by a pulling roller and formed to have a desired plate thickness. Further, roll forming is performed as necessary, and the resultant is further put into a slow cooling furnace. After annealing, a plate glass can be obtained by cutting into a predetermined size.

  The method and apparatus of the present invention are suitable for producing a glass substrate for liquid crystal display, a glass substrate for organic EL display, a cover glass for solar cell, a cover glass for touch panel, and the like. In addition to these, it can also be suitably used for producing cover glass for image sensors such as CCD and CMOS, glass for semiconductor laser, substrate glass for microlens array, display protection glass and the like.

DESCRIPTION OF SYMBOLS 1 Heat insulating wall 2 Molded body 2a Overflow groove 2b Side wall surface 2c Lower top part 3 Heat generating body 4 High frequency heating coil G Molten glass SG Sheet glass

Claims (8)

  An overflow groove for overflowing the molten glass supplied to the top on both side wall surfaces, a side wall surface for flowing down the molten glass flowing on both sides of the overflow groove, and a lower top portion for fusing the molten glass flowing down on both side wall surfaces In a sheet glass forming apparatus having a substantially wedge-shaped molded body having at least the surface of the lower top portion is made of platinum or a platinum alloy, and high frequency induction heating means for heating the lower top portion surface is provided. Sheet glass forming equipment.   The plate glass forming apparatus according to claim 1, wherein the high-frequency induction heating means includes a high-frequency heating coil, and the high-frequency heating coil is provided in the vicinity of the lower top portion of the molded body and separated from the lower top portion.   The plate glass forming apparatus according to claim 2, wherein the high-frequency heating coil is substantially U-shaped and is provided in a width direction of the formed body.   The plate glass forming apparatus according to claim 3, wherein the high-frequency heating coils are symmetrically arranged on both sides of the formed body.   The sheet glass forming apparatus according to claim 4, wherein the feeding direction of the high-frequency heating coil disposed in the vicinity of the lower top portion is the same direction on both sides of the molded body.   The flat glass molding apparatus according to any one of claims 3 to 5, wherein the arrangement position of the high-frequency heating coil arranged in the vicinity of the lower top portion is substantially the same height as the tip of the lower top portion of the molded body.   The plate glass forming apparatus according to claim 2 or 3, wherein the high-frequency heating coil is fixed in a refractory. A plate glass forming method comprising forming glass into a plate shape using the plate glass forming apparatus according to claim 1.