JP4438084B2 - Sheet glass forming method and sheet glass forming apparatus - Google Patents

Description

  The present invention relates to a sheet glass forming method and a sheet glass forming apparatus for forming a sheet glass by feeding between a pair of forming rollers that rotate molten glass, and in particular, a sheet glass forming method and a sheet glass suitable for a sheet glass made of crystalline glass. The present invention relates to a molding apparatus.

  In recent years, with the progress of computerization, the demand for transparent substrates with excellent heat resistance has increased. Quartz glass is known as having such high performance. Quartz glass is satisfactory at both high heat resistance and transparency. However, although there is a track record with photomasks, there is a limit to mass productivity, and there is a problem that expensive equipment is required to obtain a product with high transparency.

Compared to such quartz glass, borosilicate glass, aluminosilicate glass, and the like are not as good as quartz glass in terms of heat resistance, but they have the same transparency and are greatly superior in mass productivity. As a method for forming such glass into a plate shape, in Patent Document 1, molten glass supplied from a conduit is guided to a glass tank in which a heater is disposed above, and then toward the glass outflow direction. A sheet glass forming apparatus and a forming method are described which gradually become wider and flow on overflow ribs capable of being heated by electric current to be formed into sheet glass. Patent Document 2 discloses a sheet glass forming apparatus in which molten glass supplied from a conduit is led to a glass tank that gradually widens in the glass outflow direction using platinum, and is formed into a sheet glass by drawing with a pair of forming rollers. And a molding method are described. Further, in Patent Document 3, molten glass supplied from a conduit having a circular cross section gradually becomes wider in the glass outflow direction, flows out from a slit-like orifice that can be heated by electric current, and forms flat glass. An apparatus and a molding method are described. Patent Document 4 discloses a sheet glass forming apparatus for forming molten glass supplied from a conduit having a circular cross section into a rectangular glass container that can be energized and heated and extruding from a rectangular slit. A molding method is described. Patent Documents 5 and 6 describe a sheet glass forming apparatus and a forming method in which a band-shaped molten glass supplied from a feeder of a glass melting furnace is supplied to a pair of forming rollers and formed into a sheet glass.
JP-A-6-92660 JP-A-3-174332 Japanese Patent Laid-Open No. 2002-21934 JP-A-63-55127 Japanese Patent No. 71289 Japanese Patent No. 71285

  For example, an optical system of a liquid crystal projector may require heat resistance equal to or higher than that of quartz glass, and transparent crystalline glass can withstand this. However, when the transparent crystalline glass is formed into a plate shape, the conventional plate glass forming apparatus and forming method do not take into account the crystal precipitation in the molten glass that becomes very high temperature, and partially A so-called devitrification phenomenon occurs in which undesired crystals are precipitated, and there is a problem that performance such as appearance, translucency, and homogeneity as a glass product is partially lacked in transparency. In addition, even when producing an opaque crystalline glass plate product, the devitrified part is different from the surroundings, and the desired physical and chemical characteristics cannot be obtained, and a non-defective product cannot be obtained. There is.

  In addition, when devitrification occurs in the molten glass before molding, the portion locally becomes higher in viscosity or hardness than the surrounding molten glass, damages the surface of the molding roller, and an undesired pattern enters the plate glass surface. There is a problem that a plate glass having a predetermined effective width cannot be obtained.

  On the other hand, if the width of the dough supplied to the pair of forming rollers is significantly narrower than the width of the plate formed by the forming roller, there is a problem that the striae of the formed plate deteriorates, and the striae quality is good In order to obtain a wide crystalline plate glass, it was necessary to devise an apparatus for supplying a wide range of dough without devitrification to the forming roller.

  The present invention has been made in view of the above problems, and when forming a crystalline glass into a wide plate shape exceeding 400 mm to 2000 mm, it does not substantially cause devitrification, and is of striatal quality. It is an object of the present invention to provide a plate glass forming method and a forming apparatus that can efficiently form a good crystalline glass plate having a large plate width.

Method of forming a glass sheet according to the present invention, between a pair of heat-resistant rollers to rotate is provided a molten glass that has been guided by a conduit from a glass melting furnace to the interval for obtaining the thickness of the supply unit or al plants constant A sheet glass forming method of forming a sheet glass by solidifying the glass strip drawn from between the forming rollers into a flat shape, wherein the supply unit communicates without a step from the pipe-shaped portion of the conduit; and The conduit and the supply part are inclined so as to be lowered as they approach the forming roller, the supply part is made of a metal containing platinum, and gradually expands as it approaches the forming roller, and the upper part is opened. The heated portion is heated by energizing the supply section, and at the same time, the molten glass at the portion where the upper portion of the supply section is opened is heated from the upper space, so that the liquidus temperature of the glass is exceeded. 0 to 100 ° C. higher retained, and viscosity and supplying the molten glass is ¹⁰ 2.0 ^{to 10} 4.5 poise between said forming roller.

  In the present invention, it is important that the supply part is made of a metal containing platinum and gradually expands as it approaches the forming roller, and has an open shape at the top. If the structure is such that the molten glass is stored as described in Patent Documents 1 and 2, the molten glass is disturbed in the flow direction of the molten glass at that position, and the molten glass is highly homogenized in the upstream glass melting furnace. Although it becomes inhomogeneous, by making it the shape which expands continuously like this invention, it is hard to produce disorder in the flow direction of a molten glass, and it can maintain homogeneity. Also, if there is a discontinuous part between the molten glass conduit and the molten glass spreading part, the flow direction of the molten glass is disturbed at that position, so the supply part is a pipe-like part of the conduit It is preferable to communicate without any step. Further, when the supply part is not made of a metal containing platinum as in Patent Documents 5 and 6, efficient energization heating cannot be performed, and in the case of a high-temperature molten glass such as crystalline glass, a refractory brick or the like. As a result of erosion, foreign matter defects frequently occur and devitrification defects occur at the interface with the refractory. It is important that the supply part is made of a metal containing platinum.

Further, in the present invention, molten glass having a viscosity of 10 ^2.0 to 10 ^4.5 poise, which is maintained at 50 to 100 ° C. higher than the liquidus temperature of the glass by energizing and heating the supply unit, is supplied between the pair of forming rollers. It is important for preventing devitrification, and 10 ^3.0 to 10 ^3.5 poise is preferable for preventing devitrification stably. On the other hand, when the temperature of the molten glass becomes too high, the surface of the molding roller is deteriorated severely, and frequent roller replacement is required, resulting in an increase in the manufacturing cost of the plate glass. Moreover, it is difficult to instantaneously raise the temperature of the molten glass with only an indirect heating means, and when the temperature of the molten glass whose width has been expanded due to some disturbance locally decreases, the rate of temperature rise cannot catch up and the temperature is lost. Since there is a possibility of see-through, it is important that the supply unit can be heated by energization.

  Moreover, since the temperature of the molten glass supplied will be determined by the electrical heating of the structure part which is in contact with molten glass when a supply part is a structure as described in patent documents 3 and 4, especially, When forming a wide plate glass, a large temperature difference is generated, which causes a problem in terms of variation in plate thickness and other formability. In the present invention, by heating from the upper side in addition to the energization heating of the supply section, it is possible to heat the molten glass away from the supply section that cannot be covered only by the energization heating, and an undesired temperature distribution caused by the heating only by the energization Corresponding to the above, the low temperature portion is complemented by heating from above. In addition, by heating the molten glass in the part where the upper part of the supply unit is opened from the upper space, the atmosphere temperature in the upper space of the molten glass can be easily stabilized, and as a result, the temperature of the molten glass on the forming roller can be reduced. It can be stabilized.

  Furthermore, the plate glass forming method of the present invention is characterized in that the plate glass is crystalline glass.

  In general, crystalline glass has a considerably higher liquidus temperature and higher working temperature than ordinary glass, and devitrification tends to occur if there is a portion of the molten glass that is lower than a predetermined temperature. The plate glass forming method of the present invention is suitable for forming plate glass made of such crystalline glass.

Molding apparatus of the glass sheet according to the present invention, between a pair of heat-resistant rollers to rotate is provided a molten glass that has been guided by a conduit from a glass melting furnace to the interval for obtaining the thickness of the supply unit or al plants constant A sheet glass forming device for forming a sheet glass by solidifying the glass strip drawn from between the forming rollers into a flat shape, wherein the supply unit communicates without a step from the pipe-shaped portion of the conduit; and The conduit and the supply part are inclined so as to be lowered as they approach the forming roller, the supply part is made of a metal containing platinum, and gradually expands as it approaches the forming roller, and the upper part is opened. The power supply unit is connected to a power supply unit that is electrically heated to control the temperature in the width direction of the molten glass, and above the supply unit. The molten glass opened portion by heating from the upper space, characterized in that it comprises a heating means for temperature control.

  As a supply unit used in the present invention, platinum having a predetermined thickness or more that has a desired erosion resistance and heat resistance with respect to a molten glass molded at a high temperature such as crystalline glass, and that can be energized and heated. It is important that it is made of a platinum alloy. In addition, the shape of the supply portion has a substantially fan shape that gradually expands as it approaches the forming roller, and that the upper portion is open is important in adjusting the temperature of the molten glass. Further, as described above, it is preferable that the supply portion communicates from the pipe-shaped portion of the conduit without any step.

In addition, as a power supply connected to the supply unit, the temperature control function that can maintain the temperature of the molten glass in the expanded and expanded supply unit above the liquidus temperature at which devitrification does not occur and close to the working temperature It is necessary to have As a temperature detector, temperature detection by a thermocouple made of platinum or the like, and as an output controller, a viscosity suitable for forming the temperature of molten glass by energizing a supply unit made of platinum or platinum alloy is 10 ^2.0 to 10 It can be used if it can be controlled within the range of ^4.5 poise, and preferably can be controlled within the range of 10 ^3.0 to 10 ^3.5 poise.

  In addition, the sheet glass forming apparatus of the present invention includes a heating means for controlling the temperature by heating the molten glass at a position where the upper portion of the supply unit is opened from the upper space.

  In the present invention, the heating means for heating and controlling the temperature from above and / or the side of the upper space includes a silicon carbide (abbreviation: SIC) heating element, a nickel-chromium alloy wire (abbreviation: nichrome wire). And the like, and a U-shaped SIC heating element is preferable in terms of the heating structure from above. As the temperature control means by the heating means, a platinum thermocouple can be used as the temperature detector, and a PID controller or the like is preferable in terms of temperature control.

  As the heat-resistant forming roller used in the present invention, high chromium steel or other heat-resistant metal considering corrosion resistance and creep deformation resistance to molten glass can be used.

According to the method for forming sheet glass according to the present invention, the molten glass is supplied from a supply part of the glass melting furnace between a pair of rotating heat-resistant rollers provided at intervals for obtaining a predetermined plate thickness, and the forming is performed. A sheet glass forming method for forming a sheet glass by solidifying a band-shaped glass drawn from between rollers into a flat shape, wherein the supply unit is made of a metal containing platinum and gradually expands as it approaches the forming roller. The liquidus temperature of the glass has a shape that is open and open at the top, energizes and heats the supply unit, and at the same time, heats the molten glass at the site where the top of the supply unit is open from the upper space. Since a molten glass which is maintained at a temperature higher by 50 to 100 ° C. and has a viscosity of 10 ^2.0 to 10 ^4.5 poise is supplied between the molding rollers, even a glass having a high liquidus temperature is devitrified. It is possible to form a plate glass having a width wider than that of the prior art without causing any problems.

  Further, according to the method for forming a plate glass of the present invention, since the plate glass is made of crystalline glass, a practically excellent effect capable of efficiently producing a plate glass made of crystallized glass having no unprecedented wide devitrification. It plays.

  According to the sheet glass forming apparatus of the present invention, molten glass is supplied from a supply unit of a glass melting furnace between a pair of rotating heat-resistant rollers provided at intervals to obtain a predetermined plate thickness, and the forming is performed. A sheet glass forming apparatus for forming a sheet glass by solidifying a strip glass drawn from between rollers into a flat shape, wherein the supply unit is made of a metal containing platinum and gradually expands as the forming roller is approached. The power supply unit is connected to a power supply that can be heated and heated in the width direction of the molten glass. Since it is equipped with a heating means for controlling the temperature by heating the molten glass of the part where the upper part of the supply part is opened from the upper space, even glass having a high liquidus temperature does not cause devitrification than before. Method of forming flat glass of the present invention that it is possible to mold a wide plate glass can be carried out efficiently and stably by the.

  In addition, according to the sheet glass forming apparatus and the forming method of the present invention, it is provided with heating means for controlling the temperature by heating the molten glass in the part where the upper part of the supply part is opened from the upper space, and above the supply part. Is heated from the upper space, so that it can be compensated for by heating from the upper space for the low temperature portion corresponding to the undesired temperature distribution caused by heating only by energization heating, The atmosphere temperature in the upper space can be stabilized to prevent the devitrification of the molten glass finely, and a wider band-like molten glass can be supplied between the forming rollers. Since such strict temperature control is possible, even if the flow rate of the molten glass is reduced, it is possible to form a wide plate glass that has been impossible in the past.

  Hereinafter, an example of a sheet glass forming apparatus according to an embodiment of the present invention will be described in detail with reference to FIG. In the figure, 1 is a conduit from a glass melting furnace, 2 is a pipe-shaped portion of the conduit 1 and communicates without a step, gradually expanding as it approaches a pair of forming rollers, and has an open top. A metal supply unit containing platinum, 3 is a power supply unit capable of controlling the temperature in the width direction of the molten glass by energizing the supply unit 2, and 4 is a molten glass in a portion where the upper part of the supply unit is opened. 5 is a heating means for controlling the temperature by heating from above, 5 is a pair of forming rollers, 6 is a formed plate glass, and G is a molten glass.

As shown in FIG. 1 (A), the sheet glass forming apparatus of the present embodiment has a conduit 1 having an inner diameter of 54 mm and a supply unit 2 made of platinum having a thickness of 1 mm, and the supply unit 2 is supplied from a glass melting furnace. A fan-shaped portion 2a that gradually expands the molten glass G flowing out from the conduit 1 as it approaches the pair of forming rollers 5 is provided, and the upper portion of the fan-shaped portion 2a is opened, and its depth is 65 mm. Further, as shown in FIG. 1B, the temperature sensor 3a and the output control unit 3b capable of controlling the temperature within ± 1 ° C. in the width direction of the molten glass G by energizing and heating the electrode unit 2b of the supply unit 2. And the power supply unit 3 using the power supply unit 3c are connected. Further, the band-shaped molten glass G having a predetermined width, for example, about 400 mm, is maintained at 1430 ° C. or higher, which is 50 ° C. higher than the glass liquid phase temperature of 1380 ° C., and has a viscosity of 10 ^2.0. The upper space S by a plurality of heating elements 4a made of U-shaped SIC of the heating means 4 and the heating means 4 so as to have a working viscosity of 10 ^3.0 to 10 ^3.5 poise within 10 to ^4.5 poise. The temperature is controlled strictly at the working temperature by heating from the outside. The band-shaped molten glass G having a width of about 400 mm, which has been strictly controlled in temperature as described above, has a pair of rotating refractory metals provided with an interval for obtaining a predetermined plate thickness, for example, 2 mm. A sheet glass 6 supplied between the forming rollers 5 and pulled out from between the pair of forming rollers 5 is solidified in a flat shape by a roller conveyor 7 made of heat-resistant metal, and a plate glass 6 having a thickness of 2 mm and an overall width of 410 mm and an effective width of 410 mm is obtained. It is designed to be molded.

  The heating means 4 detects the temperature of the upper space S heated by the heating element 4a connected to the power supply unit 4b by a temperature sensor 4d of a platinum thermocouple, and the power supply unit 4b by a signal sent to the output control unit 4c. The output of is controlled.

  A forming method of this embodiment for forming a large plate glass having a thickness of 5 mm and an effective width of about 2 m using the plate glass forming apparatus will be described below.

First, the molten glass G is sufficiently stirred and clarified in a glass melting furnace, homogenized, and then guided to the conduit 1 as shown in FIG. When the molten glass G flows from the conduit 1 to the supply part 2 that is energized and heated by the power supply device 3, the molten glass G gradually expands as it approaches the forming roller 5 in the fan-shaped part 2 a of the supply part 2. The molten glass G on the fan-shaped part 2a whose upper part is opened from the upper space S which is 1600 ° C. widened and is heated by the heating means 4 is heated. By this heating, the belt-shaped molten glass G is maintained at 1430 ° C. or higher, which is 50 ° C. higher than the glass liquid phase temperature of 1380 ° C., and has a working viscosity of 10 ^3.0 to 10 ^3.5 poise. . The belt-like molten glass G that has been strictly temperature-controlled and brought to the working temperature in this way is supplied between a pair of rotating heat-resistant forming rollers 5 provided at intervals to obtain a plate thickness of 5 mm, The glass strip drawn from between the forming rollers 5 is solidified in a flat shape by a heat-resistant roller conveyor 7 and has a thickness of 5 mm and a total width of 2.3 m. The effective width excluding the deformed portions at both ends is about A 2 m plate glass 6 is formed.

  The plate glass 6 thus obtained was crystallized at a predetermined heat treatment condition at a later date, and when striae due to undesired crystal precipitation was observed using an inspection device or a laser interferometer through a polarizing plate, it was effective. No striae at a level that would hinder use in an optical system such as a liquid crystal projector were observed at the site, and the site had good homogeneity. Properties such as thermal expansion, bending strength, and transmittance were desired values over the entire surface.

  The present invention is applicable when molding another material having a narrow working temperature range with a pair of molding rollers.

It is explanatory drawing of the shaping | molding apparatus of the plate glass which concerns on this invention, Comprising: (A) is a top view, (B) is XX sectional drawing of (A), (C) is YY sectional drawing of (B).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conduit 2 Supply part 2a Fan part 2b Electrode part 3 Electric power supply device 3a Temperature sensor 3b Output control part 3c Power supply part 4 Heating means 4a Heat generating body 4b Power supply part 4c Output control part 4d Temperature sensor 5 Molding roller 6 Sheet glass 7 Roller conveyor G Molten glass S Upper space

Claims (3)

Fed between a pair of heat-resistant rollers to rotate is provided a molten glass that has been guided by a conduit from a glass melting furnace to the interval for obtaining the thickness of the supply unit or al plants constant, drawn from between the molding roller A sheet glass forming method of solidifying the strip glass into a flat shape to form a sheet glass,
The supply portion communicates from the pipe-shaped portion of the conduit without a step, and the conduit and the supply portion are inclined so as to descend as approaching the forming roller,
The supply part is made of a platinum-containing metal, has a shape that gradually expands as it approaches the forming roller, and has an open shape at the top. The molten glass having a viscosity of 10 ^2.0 to 10 ^4.5 poise is maintained at a temperature higher by 50 to 100 ° C. than the liquid phase temperature of the glass by heating the molten glass at the upper part of the glass from the upper space. Is supplied between the forming rollers.   The plate glass forming method according to claim 1, wherein the plate glass is made of crystalline glass. Fed between a pair of heat-resistant rollers to rotate is provided a molten glass that has been guided by a conduit from a glass melting furnace to the interval for obtaining the thickness of the supply unit or al plants constant, drawn from between the molding roller A sheet glass forming apparatus for forming a sheet glass by solidifying the strip-shaped glass into a flat shape,
The supply portion communicates from the pipe-shaped portion of the conduit without a step, and the conduit and the supply portion are inclined so as to descend as approaching the forming roller,
The supply part is made of a platinum-containing metal and has a shape that gradually expands as it approaches the forming roller, and the upper part is opened. A power supply device capable of controlling the temperature in the width direction of the glass is connected, and heating means is provided for heating the molten glass at a portion where the upper portion of the supply unit is opened to control the temperature from the upper space. An apparatus for forming a glass sheet, characterized in that:

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