JP5642832B2 - Manufacturing method of glass plate - Google Patents

Description

  The present invention relates to a glass plate manufacturing method and a glass plate manufacturing apparatus, and more specifically, to a glass plate manufacturing method and a glass plate manufacturing apparatus by an overflow downdraw method.

  The overflow down-draw method is (1) supplying molten glass to a forming device having a wedge-shaped cross section in which a molten glass supply groove is formed, and (2) forming molten glass overflowing from the supply groove. Guide to a pair of wall surfaces corresponding to both side surfaces of the wedge shape in the apparatus, let it flow down along the wall surface, and (3) fuse the molten glass flowing down each wall surface at the lower end of the molding apparatus to continue the glass ribbon It is a method of forming automatically. The obtained glass ribbon is then cut into a desired size through steps such as thickness adjustment and slow cooling to form a glass plate. The overflow downdraw method is suitable for manufacturing a large area and thin glass plate, for example, a glass substrate used for a flat panel display (FPD) such as a liquid crystal display, an organic EL display, and a plasma display.

  A pair of guides formed opposite to each other so as to protrude from both end portions in the width direction of the forming apparatus, more specifically, both end portions in the width direction of the wall surface where the molten glass flows down. May be provided. The width of the molten glass flowing down along the wall surface is regulated by the arrangement of the guides. Patent Document 1 (Japanese Patent Laid-Open No. 2010-189220) discloses a molding apparatus including a guide having a specific shape. Patent Document 1 describes that the forming apparatus can form a glass ribbon having stable shapes at both ends (ear portions) even when the viscosity of the molten glass is relatively high.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2010-215428) discloses a technique for preventing a defective shape of an end portion of a glass ribbon. More specifically, in Patent Document 2, a heater is disposed in a space between the lower end of the forming apparatus and the glass ribbon transport roll located closest to the apparatus, and the glass ribbon immediately after fusion is formed by the heater. A technique for forming and conveying a glass ribbon while locally heating the end portion is disclosed.

JP 2010-189220 A JP 2010-215428 A

  When using a molding device equipped with a guide in the overflow down draw method, when trying to mold a glass having a small liquidus viscosity, devitrification occurs in the molten glass flowing down the vicinity of the guide, that is, the end in the width direction of the molded glass ribbon. There is a problem that devitrification is likely to occur in a portion (hereinafter, “end portion in the width direction” is simply referred to as “end portion”). Patent Document 1 does not describe such devitrification at the end of the glass ribbon. In Patent Document 2, only the molten glass in the vicinity of the lower end of the guide is devitrified by heating the lower end of the guide with a heater disposed between the lower end of the forming apparatus and a transport roll located downstream of the forming apparatus. It is described that it can be prevented from being stored for a long time in a temperature range in which it is likely to occur. However, in the technique of Patent Document 2, only the lower end of the guide is heated by the heater, and it cannot be said that devitrification of the molten glass flowing down the vicinity of the guide can be sufficiently suppressed. In particular, when the liquid phase viscosity of the glass composition constituting the molten glass is small, it is difficult to suppress devitrification at the end of the molded glass ribbon. Examples of the glass composition having a low liquidus viscosity include a glass composition for low-temperature polysilicon (p-Si) having an increased strain point in order to reduce the thermal shrinkage rate.

  An object of the present invention is a glass plate manufacturing method and manufacturing apparatus by an overflow downdraw method, which has a high effect of suppressing devitrification at the end of a molded glass ribbon, and is a liquid of a glass composition constituting a molten glass An object of the present invention is to provide a manufacturing method and a manufacturing apparatus capable of obtaining the effect of suppressing devitrification at the end portion even though the phase viscosity is small.

  The glass plate manufacturing method of the present invention induces molten glass that overflows on both sides of the supply groove and flows from both ends of the upper surface, and is fused at the lower end. And forming a glass ribbon by an overflow down draw method using a forming apparatus including a pair of wall surfaces to be a glass ribbon. In the manufacturing method of the glass plate of this invention, the liquid phase viscosity of the glass composition which comprises the said molten glass is 120,000 dPa * s or less, and the liquidus temperature of the said glass composition is 1100 degreeC-1250 degreeC. In the forming step in the method for producing a glass plate of the present invention, (1) the fusion is performed by a pair of guides formed to face each other at both ends in the width direction of the wall surface so as to protrude from the ends. The glass is allowed to flow down along the wall surface while regulating the width of the molten glass, and (2) the liquid in the vicinity of the guide in the molten glass flowing down until the viscosity reaches the lower end from the upper surface of the molding apparatus. The part is heated along the guide so as to keep the phase viscosity below.

  The glass plate manufacturing method and manufacturing apparatus of the present invention are highly effective in suppressing devitrification at the end of the molded glass ribbon. According to the manufacturing method or the manufacturing apparatus of the glass plate of the present invention, although the liquid phase viscosity of the glass composition constituting the molten glass is as small as 120,000 dPa · s or less, the effect of suppressing devitrification at the end is obtained. be able to.

It is a schematic diagram which shows an example of the shaping | molding apparatus which can be used for the manufacturing method of this invention. It is a schematic diagram which shows an example of the manufacturing method of this invention using the apparatus shown in FIG. In the manufacturing method of this invention, it is a schematic diagram which shows an example of the heating apparatus which heats the part near the guide in molten glass. In the manufacturing method of this invention, it is a schematic diagram which shows another example of the heating apparatus which heats the part of the molten glass near the guide. It is a schematic diagram which shows another example of the manufacturing method of this invention using the apparatus shown in FIG. It is a schematic diagram which shows an example of arrangement | positioning of the electrode at the time of carrying out the electricity heating of the guide of the shaping | molding apparatus which can be used for the manufacturing method of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are examples of the present invention, and the present invention is not limited to these embodiments.

  FIG. 1 shows an example of a molding apparatus that can be used in the manufacturing method of the present invention, and FIG. 2 shows an example of the manufacturing method of the present invention using the molding apparatus shown in FIG. The forming apparatus 1 induces the upper surface 3 on which the supply groove 2 to which molten glass is supplied and the molten glass that overflows on both sides of the supply groove 2 and flows down from both end portions 3a and 3b of the upper surface 3. A pair of wall surfaces 5 (only one wall surface is shown in FIGS. 1 and 2) fused to the lower end 4 to form a glass ribbon 50 and both end portions 5 a and 5 b in the width direction of the wall surface 5 are formed. A pair of guides 6a and 6b is provided. The guides 6a and 6b are formed to face each other so as to protrude from the end portions 5a and 5b, respectively. The molten glass overflowing from the supply groove 2 flows down each of the pair of wall surfaces 5. The wall surface 5 has a vertical wall surface in which the molten glass overflowing from the supply groove 2 flows down in the vertical direction, and an inclined wall surface connected to the vertical wall surface that guides the molten glass flowing down the vertical wall surface to the lower end 4 of the molding apparatus. . A pair of flows of the molten glass flowing down the wall surface 5 merges at the lower end 4 of the molding apparatus 1 and merges with each other. At this time, the width of the molten glass flowing down along the wall surface 5 is regulated by the guides 6a and 6b. For example, the glass ribbon 50 having a high uniformity in thickness in the width direction is continuously formed. The lower end 4 of the molding apparatus 1 forms a linear ridge line in which a pair of wall surfaces 5 (inclined wall surfaces) are connected. Reference numeral 2 a shown in FIGS. 1 and 2 is the bottom surface 2 a of the supply groove 2, and reference numeral 7 shown in FIG. 2 is the liquid surface 7 of the molten glass supplied to the supply groove 2.

  As shown in FIG. 2, a heater 8 is disposed in the vicinity of each of the guides 6 a and 6 b so as to extend from the upper surface 3 side to the lower end 4 side of the molding apparatus 1, and is shown in FIG. 2 in the molding apparatus 1. In addition, the heaters 8 are arranged on the side as well as the side shown in FIG. 2, and the portions near the guides 6a and 6b in the molten glass flowing down the pair of wall surfaces 5 are The heater 8 is heated. This heating is performed until the viscosity of the portion near the guides 6a and 6b in the molten glass flowing down the wall surface 5 reaches the lower end 4 from the upper surface 3 of the molding apparatus 1 (the portion of the molten glass flows down from the upper surface 3 of the molding apparatus 1). Until the lower end 4), and is performed along the guides 6a and 6b so as to be less than the liquid phase viscosity of the glass composition constituting the molten glass (hereinafter, also simply referred to as “liquid phase viscosity”).

  In the formation of a glass ribbon by the overflow down draw method using a forming apparatus equipped with a guide (and production of a glass plate obtained by cooling the ribbon), in the vicinity of the guide, that is, the end of the glass ribbon to be formed (reference numeral shown in FIG. 2) Devitrification is likely to occur in 50a). This is the temperature at which the molding furnace in which the molding apparatus is housed is intended not only to form the glass ribbon but also to cool the molten glass for the purpose of making the molten glass suitable for molding at the lower end of the molding apparatus. That is, since it is usually set to a temperature lower than the molten glass, the temperature of the molten glass in the vicinity of the guide is likely to be lower than the temperature of the other part in the molten glass because heat is taken away by the guide. In addition, due to such a decrease in temperature and physical resistance due to contact with the guide, the flow rate of the molten glass in the vicinity of the guide tends to be lower than other portions of the molten glass, and until it leaves the forming device after coming into contact with the guide This is probably because it takes a long time to complete.

  According to the technique of Patent Document 2 (Japanese Patent Laid-Open No. 2010-215428), there is a possibility that devitrification occurring at the lower end of the guide can be suppressed. However, in the technique of Patent Document 2, it is difficult to suppress devitrification occurring in an area upstream from the lower end of the guide, particularly in the initial stage when the molten glass starts to cool down in contact with the guide. It cannot be solved by heating the lower end. Further, glass compositions having a high liquidus temperature and a low liquidus viscosity, such as non-alkali glass suitable for use in FPD glass substrates and alkali-containing glass, such as liquids used in the production method of the present invention. Such devitrification is particularly likely to occur when molding a glass ribbon composed of a glass composition having a phase viscosity of 120,000 dPa · s or less and a liquidus temperature in the range of 1100 ° C. to 1250 ° C.

  In the manufacturing method of the present invention, the viscosity of the portion near the guides 6 a and 6 b in the molten glass flowing down the wall surface 5 of the molding apparatus 1 is kept below the liquid phase viscosity from the upper surface 3 to the lower end 4 of the molding apparatus 1. The portion of the molten glass is heated along the guides 6a and 6b (so that the temperature of the portion becomes equal to or higher than the liquid phase temperature from the upper surface 3 to the lower end 4 of the molding apparatus 1). Thereby, the high effect which suppresses devitrification in the part (edge part of molten glass) near the guide of molten glass is acquired, and the glass composition which comprises molten glass has a small liquidus viscosity of 120,000 dPa * s or less. And also when it has a liquidus temperature of the range of 1100 degreeC-1250 degreeC, generation | occurrence | production of the devitrification in the said edge part is suppressed.

  In the present specification, the liquidus temperature is the equilibrium temperature between the melt and the initial phase of the crystal, and is the temperature above which no crystal is present. It is the viscosity that becomes the phase temperature.

  In the manufacturing method of the present invention, the temperature in the vicinity of the guides 6a and 6b in the molten glass flowing down the wall surface 5 of the molding apparatus 1 is 10 ° C. or more than the liquidus temperature from the upper surface 3 to the lower end 4 of the molding apparatus 1. It is preferable to heat the part so that the temperature is high, and it is more preferable to heat the part so that the temperature is 15 ° C. or more higher than the liquidus temperature. In these cases, the occurrence of devitrification at the end of the glass ribbon to be molded is more reliably suppressed. The specific liquidus temperature varies depending on the composition of the glass composition.

  In the manufacturing method of the present invention, in the molding step, the temperature of the portion in the vicinity of the guides 6a and 6b in the molten glass flowing down the wall surface 5 of the molding apparatus 1 is higher than the liquid phase temperature from the upper surface 3 to the lower end 4 of the molding apparatus 1. Heating the part along the guide so as to be higher by 10 ° C to 150 ° C (more than 10 ° C higher than the liquidus temperature and lower than the liquidus temperature plus 150 ° C). preferable. Thereby, the deformation | transformation of the shaping | molding apparatus 1 and the shrinkage | contraction of the width direction in the glass ribbon 50 after shaping | molding can be suppressed. In the molten glass flowing down the wall surface 5 of the molding apparatus 1, the temperature in the vicinity of the guides 6 a and 6 b is 15 ° C. to 100 ° C. higher than the liquid phase temperature from the upper surface 3 to the lower end 4 of the molding apparatus 1. More preferably, the part is heated along the guide.

  Combining with the rapid cooling of the end portion after the molten glass leaves the molding apparatus 1 (rapid cooling of the end portion of the glass ribbon 50) further suppresses the occurrence of devitrification at the end portion.

  According to the manufacturing method of the present invention, the portion near the guides 6a and 6b in the molten glass flowing down the wall surface 5 of the molding apparatus 1 is not heated, but the temperature of the part reaches from the upper surface 3 to the lower end 4 of the molding apparatus 1. Devitrification is theoretically suppressed by setting the temperature of the entire molten glass flowing down the molding apparatus 1 to be sufficiently higher than the liquidus temperature so as to be sufficiently higher than the liquidus temperature. However, when manufacturing a glass having a high liquidus temperature, in reality, such a method cannot be applied to the overflow downdraw method. This is because there is a viscosity of the molten glass suitable for forming the glass ribbon by the overflow downdraw method (in order to prevent the following problems such as the slack of the glass ribbon and the shrinkage of the width of the glass ribbon, The viscosity of the molten glass at the lower end of the molding apparatus is preferably 40000 dPa · s or more, and more preferably 70000 dPa · s or more). When the temperature of the entire molten glass flowing down the molding apparatus is sufficiently higher than the liquid phase temperature so that the temperature in the vicinity of the guide in the molten glass is sufficiently higher than the liquid phase temperature, or at the lower end of the molding apparatus. If the heating is excessively performed, the viscosity of the molten glass at the lower end of the molding apparatus may be smaller than the appropriate range. Then, the viscosity of the glass ribbon after leaving the molding device does not rise sufficiently, and the glass ribbon falls at a speed equal to or higher than the tensile speed by the transport roll arranged on the downstream side of the molding device, and the glass ribbon on the roll This causes problems such as loosening and shrinking of the width of the glass ribbon. In addition, the higher the temperature of the molding apparatus, the more the creep phenomenon of the molding apparatus becomes more prominent, and there arises a problem that the central portion of the glass ribbon hangs down as time elapses from the start of molding. Considering the thickness desired for the glass plate and the temperature control of the glass ribbon performed in the slow cooling step after molding, there is a limit to the increase in the tensile speed by the transport roll (the glass ribbon performed in the slow cooling step). In view of the temperature control, the conveying speed of the glass ribbon is preferably 50 to 500 m / hour, preferably 100 to 400 m / hour, and preferably 120 to 300 m / hour). If the width of the glass ribbon to be formed shrinks, the product width as a glass plate cannot be secured. When the creep phenomenon becomes remarkable, the uniformity of the thickness of the glass plate to be manufactured is lowered.

  In the production method of the present invention, the temperature of the entire molten glass flowing down the wall surface of the molding apparatus is uniformly raised so that the temperature in the vicinity of the guide in the molten glass does not exceed the liquidus temperature. Devitrification is particularly likely to occur. By setting the temperature in the vicinity of the guide in the molten glass above the liquid phase temperature from the upper surface to the lower end of the molding apparatus, that is, local heating of the molten glass flowing down the wall surface of the molding apparatus. Thus, while suppressing the entire molten glass and the entire molding apparatus from being overheated, the viscosity of the part is made less than the liquid phase viscosity from the upper surface to the lower end of the molding apparatus, and devitrification occurring at the end of the glass ribbon is suppressed. be able to.

  In the production method of the present invention, the method of heating a portion in the vicinity of the guide in the molten glass along the guide can keep the viscosity of the portion below the liquid phase viscosity from the upper surface 3 to the lower end 4 of the molding apparatus 1. , Not limited.

  An example of the heating method is heating by a heating device arranged in the vicinity of the guides 6a and 6b so as to extend from the upper surface 3 side to the lower end 4 side of the molding device 1 as shown in FIG. According to this method, heating of the vicinity of the guide in the molten glass and control of the heating can be performed relatively easily.

  The heating device is not limited as long as the molten glass can be heated so that the viscosity of the molten glass in the part is less than the liquidus viscosity, that is, the temperature of the molten glass in the part is equal to or higher than the liquidus temperature. . The heating device is, for example, a heater.

  The type of the heater is limited as long as it can be used in the temperature atmosphere of a glass ribbon molding furnace and the viscosity of the portions near the guides 6a and 6b in the molten glass can be made less than the liquid viscosity by heating the molten glass with the heater. Not. The heating device includes one that heats molten glass using a laser or electromagnetic waves.

  The state of the arrangement of the heating device is arranged in the vicinity of the guide in the molding device so as to extend from the upper surface side to the lower end side of the molding device, and the viscosity of the portion near the guide in the molten glass flowing down the wall surface of the molding device is It is not limited as long as it can keep less than liquid phase viscosity from the upper surface to the lower end of the apparatus. As shown in FIG. 2, it is preferable that the heating device is arranged in each of “portions near the guides” that exist at four locations for one molding device 1.

  In the example shown in FIG. 2, the heater 8 is arrange | positioned so that the guides 6a and 6b may be followed as a heating apparatus. The shape of the heater 8 is a straight line extending from the upper surface side to the lower end side of the molding apparatus. The shape of the heater 8 may not be linear as long as it extends from the upper surface side to the lower end side of the molding device as a whole (as long as it is a shape along the guides 6a and 6b as a whole).

  For example, as shown in FIG. 3, the heating device may be a heater 8 disposed so as to extend vertically from the upper surface 3 side to the lower end 4 side of the molding device 1 in the vicinity of the guide 6 b in the molding device 1. . Although FIG. 3 shows the guide 6b side of the molding apparatus 1, the vertically extending heater 8 can be similarly arranged on the guide 6a side.

  For example, as shown in FIG. 4, the heating device includes a heater 8 disposed in the vicinity of the guide 6 b in the molding device 1 so as to extend along the wall surface 5 from the upper surface 3 side to the lower end 4 side of the molding device 1. It may be. Although FIG. 4 shows the guide 6b side of the molding apparatus 1, the heater 8 extending along the wall surface 5 can be similarly arranged on the guide 6a side.

  Regarding the positional relationship between the guides 6a and 6b and the heating device, the heating device (heater 8) may be disposed near the molten glass side of the guides 6a and 6b as shown in FIG. As shown, the guides 6a and 6b may be disposed in the vicinity of the opposite side of the molten glass. In the former case, the portions near the guides 6a and 6b in the molten glass can be directly heated by the heating device. In the latter case, the guides 6a and 6b are heated by the heating device, and the guides in the molten glass are heated by the heating device 6a and 6b, depending on the specific arrangement position of the heating device and the material constituting the guides 6a and 6b. It is also possible to heat the vicinity. From the viewpoint of heating efficiency, it is preferable to directly heat the portions near the guides 6a and 6b in the molten glass with a heating device.

  The specific heating control by the heating device is free as long as the viscosity of the portion near the guide in the molten glass flowing down the wall of the molding device can be kept below the liquid phase viscosity from the upper surface to the lower end of the molding device. Can be set. For example, the heating by the heating device may be continuous or intermittent. When a plurality of heating devices are arranged, heating by each heating device may be controlled independently. A plurality of heating sections may be set for one heating device, and heating by each heating section may be controlled independently.

  Another example of the heating method is a method in which a portion of the molten glass near the guides 6a and 6b is heated by causing the guides to generate heat.

  The method and degree of heating the guide are not limited as long as the viscosity of the portion near the guide in the molten glass flowing down the wall surface of the molding apparatus can be kept below the liquid phase viscosity from the upper surface to the lower end of the molding apparatus.

  In the production method of the present invention, the temperature in the vicinity of the guides 6a and 6b in the molten glass is maintained at the liquid phase temperature or higher from the upper surface to the lower end of the molding apparatus. For this reason, it is preferable to heat the guides 6a and 6b so that the temperature of the portion of the guides 6a and 6b that contacts the molten glass (the portion along the full length (path) through which the molten glass flows) is equal to or higher than the liquidus temperature. . The guides 6a and 6b may generate heat so that the temperature of the guides 6a and 6b as a whole is equal to or higher than the liquidus temperature.

  The heat generation of the guides 6a and 6b is preferably carried out so that the temperature of the portion of the guides 6a and 6b that is in contact with the molten glass is higher by 10 ° C. than the liquidus temperature, and is higher by 15 ° C. or higher. It is more preferable to carry out. In this case, the occurrence of devitrification at the end of the glass ribbon to be molded is more reliably suppressed.

  The heat generation of the guides 6a and 6b is preferably carried out so that the temperature of the portion of the guides 6a and 6b that is in contact with the molten glass is higher by 10 ° C to 150 ° C than the liquidus temperature, and is higher by 15 ° C to 100 ° C. It is more preferable to carry out the temperature. In this case, deformation of the molding apparatus 1 and shrinkage in the width direction of the glass ribbon 50 after molding can be suppressed.

  An example of a method for generating heat from the guide is heating by a heating device such as a heater. As for the arrangement and control of the heating device for that purpose, as long as the viscosity of the molten glass near the guides 6a and 6b can be made less than the liquid phase viscosity from the upper surface to the lower end of the molding device by the guide generated by the heating device. , Not limited. One example thereof is heating of the guides 6a and 6b by a heating device (heater 8) arranged so as to extend from the upper surface 3 side to the lower end 4 side of the molding device 1 in the vicinity of the guides 6a and 6b shown in FIG. . Apart from this, for example, a heater that generates heat due to an electric current may be arranged on the surfaces of the guides 6a and 6b, or may be embedded in the surfaces of the guides 6a and 6b. The surface in that case is, for example, the surface opposite to the surface facing the molten glass in the guides 6a and 6b (the surface not contacting the molten glass).

  Another example of a method of generating heat in the guide is heat generation (energization heat generation) due to energization of the guides 6a and 6b when the guides 6a and 6b are made of metal. In the manufacturing method of the present invention, the guides 6a and 6b may be made of metal, and portions of the molten glass near the guides 6a and 6b may be heated by energizing the guides 6a and 6b to generate heat. This method has high thermal efficiency and temperature control is relatively easy.

  A specific method for generating heat in the guides 6a and 6b by energization is not limited. An electrode may be connected to each of the guides 6a and 6b, and a current may be passed through the guides 6a and 6b via the electrodes. The number and arrangement of electrodes connected to each guide can be arbitrarily set. The electrode may be connected to the surface facing the molten glass in the guides 6a and 6b or may be connected to the surface opposite to the surface.

  FIG. 6 shows an arrangement example of electrodes for energizing heat generation in the guide 6b. In the example shown in FIG. 6, the electrodes 11a, 11b, and 11c are connected to one place near the lower end of the guide 6b and two places that are spaced from each other near the upper end. By flowing a current between the electrodes 11a-11b and 11a-11c, the portion of the guide 6b that contacts the molten glass can be heated. Further, the potential of each electrode may be set so that a current flows between the electrodes 11b-11c. Similarly, electrodes can be arranged for the guide 6a.

  When the guides 6a and 6b are heated by energization, the composition of the metal that constitutes the portion of the guides 6a and 6b that contacts the molten glass is different from the metal that constitutes the other part of the guides 6a and 6b. You may make the emitted-heat amount in the part which contact | connects larger than the said other part. In this case, the thermal efficiency for making the viscosity in the vicinity of the guide in the molten glass less than the liquid phase viscosity becomes higher. The composition of the metal in each part can be determined, for example, by the conductivity indicated by the composition.

  The guides 6a and 6b may generate heat by using both energization heat generation by passing a current through the guide and heating by a heating device. Different heat generation methods may be employed for the guide 6a and the guide 6b.

  The heat generation temperature of the guides 6a and 6b (including the heating temperature by the heating device) may be equal to or higher than the liquidus temperature, preferably 10 ° C higher than the liquidus temperature, more preferably 15 ° C higher than the liquidus temperature. . Further, the heat generation temperature of the guides 6a and 6b is preferably a temperature that is 10 ° C to 150 ° C higher than the liquidus temperature, and more preferably a temperature that is 15 ° C to 100 ° C higher than the liquidus temperature. When the guide is made of metal, particularly when it is made of platinum or a platinum alloy having a high thermal conductivity, the heat generation temperature of the guides 6a and 6b is almost equal to the temperature in the vicinity of the guide in the molten glass. .

  In the manufacturing method of the present invention, for heating the portion near the guide in the molten glass, heating by the heating device and heating by heat generation of the guide may be used in combination.

  In the manufacturing method of this invention, you may use together the heating with respect to the molten glass by the heating apparatus arrange | positioned so that it may extend in the horizontal direction in the vicinity of a shaping | molding apparatus as needed.

  Except for the case where the guides 6a and 6b generate heat, the configuration (shape, material, etc.) of each part in the molding apparatus 1 may be the same as the configuration of the part in a known molding apparatus used for the overflow downdraw method. For example, the parts other than the guides 6a and 6b in the molding apparatus 1 are usually made of refractory bricks.

Although the material which comprises the guides 6a and 6b is not limited, Since heat resistance and fire resistance are high and it is hard to contaminate molten glass, it is preferable to comprise with platinum or a platinum alloy. Although this does not depend on the heating method of the vicinity of the guide in the molten glass, it is particularly preferable when the heating is performed by causing the guide to generate heat. Since platinum and platinum alloys have high thermal conductivity, glass ribbon molding by the conventional overflow downdraw method using a guide made of platinum or platinum alloy reduces the temperature in the vicinity of the guide in the molten glass. It tends to be devitrified at the end. However, when heating the portion near the guide in the molten glass by heating the guide, the guide is made of heat by using the guide with platinum or a platinum alloy and using the high thermal conductivity in reverse. The thermal efficiency of 6a, 6b can be increased, and the temperature control becomes easier.

  Regardless of the heating method in the vicinity of the guide in the molten glass, the shape and size of the guides 6a and 6b may be the same as those in a known molding apparatus used in the overflow downdraw method. The height from the wall surface of the pair of guides in the molding apparatus is lower than the thickness of the molten glass flowing on the wall surface in the range where the molten glass does not get over the pair of guides in the entire region where the guide protrudes from the inclined wall surface. It is preferable that it is set. Thereby, the ear part of the glass ribbon to be molded is prevented from opening in a bifurcated shape (when the cut surface in the width direction of the glass ribbon is viewed, the ear part becomes Y-shaped), and the glass ribbon to be molded The shape of the ear can be stabilized. When the shape of the ear portion is opened in a bifurcated shape, a greater stress is required in the process of cutting the glass ribbon than in the case where the ear portion is not. More specifically, if the shape of the ear portion is opened in a bifurcated shape, the stress required for cutting increases when the glass ribbon is cut by applying stress after cutting the glass ribbon with a cutter. . When the stress necessary for cutting the glass ribbon is increased, the glass ribbon may be cut from a region other than the cut line formed by the cutter, and in this case, a cutting failure occurs. Moreover, when the shape of the ear | edge part is open in a bifurcated shape, it will become easy to break a glass ribbon. That is, by setting the guide to the above preferable configuration, the occurrence of cutting failure of the glass ribbon is suppressed, or cracking of the glass ribbon is suppressed, and the glass plate can be produced stably and continuously.

  The height of the guide from the wall surface in the molding apparatus is preferably lower as the position is lower in the molding apparatus. It is preferable that the lower end 4 of the forming device is a linear ridge line in which the inclined wall surfaces on both sides are connected, and the height of the pair of guides on the inclined wall surface is 0 (zero) at the position of the ridge line. Thereby, it is further suppressed that the ear | edge part of a glass ribbon opens in a bifurcated shape, and a glass plate can be produced more stably and continuously.

  According to the production method of the present invention, when the liquid phase temperature of the glass composition constituting the molten glass is high and the liquid phase viscosity is small, for example, when the glass composition is an alkali-free glass, a glass containing a trace amount of alkali, etc. Moreover, the effect which suppresses devitrification in the edge part of the glass ribbon to shape | mold is acquired. That is, when the liquid phase temperature of the glass composition constituting the molten glass is high and the liquid phase viscosity is small, the advantages brought about by the production method of the present invention are great.

  In the production method of the present invention, the liquid phase viscosity of the glass composition constituting the molten glass is 120,000 dPa · s or less. In such a glass composition, the problem of devitrification at the end portion tends to occur in the conventional molding of a glass ribbon by the overflow down draw method. However, in the production method of the present invention, an effect of suppressing devitrification can be obtained.

  The liquid phase viscosity may be 100,000 dPa · s or less. In the glass composition having a liquid phase viscosity of 100000 dPa · s or less, the above-described devitrification problem becomes more prominent, but the production method of the present invention provides an effect of suppressing devitrification. The liquid phase viscosity is preferably 40,000 dPa · s or more from the viewpoint of stably forming the glass ribbon by the overflow downdraw method. The liquid phase viscosity is, for example, 50000 dPa · s or more and 120,000 dPa · s or less, 50000 dPa · s or more and 100000 dPa · s or less, or 50000 dPa · s or more and 80000 dPa · s or less.

  In the manufacturing method of this invention, the liquidus temperature of the glass composition which comprises molten glass is 1100 degreeC or more and 1250 degrees C or less. In such a glass composition, the problem of devitrification at the end portion tends to occur in the conventional molding of a glass ribbon by the overflow down draw method. However, in the production method of the present invention, an effect of suppressing devitrification can be obtained.

  In the production method of the present invention, the molten glass may contain zirconia and / or tin oxide. In the molten glass containing zirconia, the liquidus temperature of the glass composition increases as compared with the case where zirconia is not contained. In such a molten glass, the problem of devitrification at the end portion is likely to occur in the conventional glass ribbon forming by the overflow down draw method. However, in the production method of the present invention, an effect of suppressing devitrification can be obtained. In addition to the case where zirconia is originally contained in the molten glass as a component of the glass composition, zirconia is also eluted into the molten glass by using a melting tank and a molding apparatus configured using a high zirconia refractory. In particular, when a glass raw material is electrically melted using such a melting tank, the zirconia concentration in the molten glass tends to increase. That is, the production method of the present invention is more suitable when the glass raw material is electrically melted using a melting tank configured using a high zirconia refractory.

In addition, the melting tank configured using high zirconia refractories is less susceptible to erosion by glass than the melting tank configured using alumina electrocast refractories widely used in the past. As a long life. Moreover, foaming of molten glass can also be suppressed. Therefore, suitable for the formation of the melt temperature (viscosity 10 ^2.5 poise to become the temperature of the glass composition) is high glass composition, for example, non-alkali glass and alkali trace containing glass, the molten glass.

  In addition, when the molten glass formed in the melting tank is made of alkali-free glass or glass containing a small amount of alkali, the specific resistance of the glass composition tends to increase, and current tends to flow through the high zirconia refractory instead of the glass raw material. . When a current flows through the refractory, zirconia is eluted in the molten glass formed in the melting tank. That is, the production method of the present invention is further suitable when a molten glass of an alkali-free glass or a glass containing a trace amount of alkali is formed by electric melting using a melting tank configured using a high zirconia refractory. .

  For a glass substrate for FPD such as a liquid crystal display and an organic EL display, a glass plate composed of non-alkali glass or alkali-containing glass is preferable. This is because if alkaline components are eluted from the glass substrate in the panel manufacturing process, the characteristics of electronic devices such as thin film transistors (TFTs) may be deteriorated. That is, the manufacturing method of the present invention is to electrically melt a glass raw material using a melting tank composed of a high zirconia refractory, and to use an obtained molten glass to form a glass substrate for FPD by an overflow down draw method. It is particularly suitable for manufacturing. In addition, an alkali free glass means the glass composition which does not contain an alkali metal oxide substantially (it is less than 0.05 mass% in content rate). Alkali trace amount glass means the glass composition which contains 0.05-2.0 mass% of alkali metal oxides.

  In molten glass containing tin oxide, devitrification is likely to occur due to crystallization of tin oxide. Moreover, when coexisting with zirconia, tin oxide has an action of crystallizing zirconia. In such a molten glass, the problem of devitrification at the end is particularly likely to occur in the conventional molding of a glass ribbon by the overflow down draw method. However, in the production method of the present invention, an effect of suppressing devitrification can be obtained.

  In the production method of the present invention, the glass composition constituting the molten glass may be alkali-free glass or glass containing a trace amount of alkali. Compared to alkali glass containing alkali metal oxide in excess of 2.0% by mass, the liquidus temperature of such alkali-free glass or alkali-containing glass is high and the liquidus viscosity tends to be small, In the production method of the present invention, an effect of suppressing devitrification is obtained. As described above, this effect is particularly noticeable when an alkali-free glass or a glass containing a trace amount of alkali is formed by electric melting using a melting tank configured using a high zirconia refractory. It is.

  Note that alkali-free glass is suitable for the glass substrate for FPD from the viewpoint of preventing deterioration of characteristics of electronic elements such as TFTs. However, from the viewpoints of meltability and clarity, glass containing a trace amount of alkali is suitable for the glass substrate for FPD. By intentionally containing a small amount of alkali metal oxide to form a glass containing a small amount of alkali, the meltability and clarity of the glass composition are improved. For clarity, the basicity of the glass increases due to the presence of the alkali metal oxide, and the oxidation of the metal whose valence fluctuates is facilitated. In addition, when forming molten glass by electric melting of glass raw materials in a melting tank composed of high zirconia refractories, the specific resistance of glass can be reduced compared to non-alkali glass, The elution of zirconia to the glass can be suppressed, and the devitrification increase of the molten glass can be suppressed.

In the production method of the present invention, the glass composition constituting the molten glass may have a temperature (melting temperature) exhibiting a viscosity of 10 ^2.5 poise (1500 ° C. to 1750 ° C.). Since such a glass composition requires a high temperature at the time of melting, zirconia is likely to be eluted when a molten glass is formed by a melting tank configured using a high zirconia refractory. Even for such a glass composition, the production method of the present invention provides an effect of suppressing devitrification.

  The example of the glass composition from which the effect of devitrification suppression is especially acquired with the manufacturing method of this invention is shown below.

(1) Example This example of the glass composition for use as a glass substrate for the _FPD, SiO 2: 50 to 78 wt%, B ₂ O _3: 0~15 wt%, Al ₂ O _3: 3~25 wt%, It is a glass composition containing MgO: 0-10 mass%, CaO: 0-20 mass%, SrO: 0-20 mass%, BaO: 0-10 mass%, RO: 3-20 mass%. R is at least one element selected from Mg, Ca, Sr and Ba. RO indicates the total amount of MgO, CaO, SrO and BaO. More _preferably, SiO 2: 55 to 65 wt%, B ₂ O _3: 5~14 wt%, Al ₂ O _3: 13~20 wt%, MgO: 0 to 5 wt%, CaO: 2 to 10 wt% , SrO: 0 to 10% by mass, BaO: 0 to 4% by mass, RO: 7 to 17% by mass. From the viewpoint of preventing the deterioration of the characteristics of electronic devices such as TFTs, the glass composition is preferably substantially free of alkali metal oxides, that is, is alkali-free glass. From the viewpoint of improving the meltability and clarity of the glass composition, it is preferable to include a trace amount of an alkali metal oxide. In this case, the glass composition exceeds 0.05% by mass and is 2.0% by mass. % R ′ ₂ O or less, preferably more than 0.1% by mass and 2.0% by mass or less R ′ ₂ O. R ′ is at least one element selected from Li, Na and K. R ′ ₂ O represents the total amount of Li ₂ O, Na ₂ O and K ₂ O. The glass composition preferably contains substantially no As ₂ O ₃ and PbO as a fining agent (in terms of content, 0.05% by mass or less), and preferably contains at least tin oxide as a fining agent. Moreover, it is preferable that the content rate contains 0.01-0.2 mass% iron oxide.

  Considering that the weight reduction of FPD is demanded in recent years, the total content of SrO and BaO in the glass composition is preferably 0 to 10% by mass. In consideration of environmental impact as a product in addition to weight reduction, the content of BaO is preferably 0 to 2% by mass.

With such a glass composition, a glass plate that satisfies the characteristics required for a glass substrate for FPD can be realized. More specifically, a glass plate having a strain point of 650 ° C. or higher, a glass plate having a density of 2.6 g / cm ³ or lower, and a glass plate having a Young's modulus of 70 GPa or higher can be realized. Furthermore, a glass plate having a liquidus temperature of 1250 ° C. or lower can be realized, and such a glass plate can be manufactured by an overflow down draw method. However, since it is difficult to satisfy the above characteristics required for the glass substrate for FPD while realizing a liquidus temperature of less than 1050 ° C, the composition of the glass composition is adjusted so that the liquidus temperature is 1050 to 1250 ° C. It is preferable to adjust.

(2) Example of glass composition used as cover glass (chemical strengthening glass) This example is an example of a glass composition that can be used as a cover glass to be chemically strengthened or a glass plate for solar cells. This _example, SiO 2: 50-70 wt%, Al ₂ O _3: 5~20 wt%, Na ₂ O: 6~30 wt%, K ₂ O: 0~10 wt%, MgO: 0 Weight %, CaO: a glass composition containing 0 to 20% by mass.

(3) Example of glass composition used as glass substrate for polysilicon FPD In recent years, in order to realize further high definition of FPD, instead of α-Si · TFT, low-temperature p-Si · TFT or oxide semiconductor is used. Development of the used FPD is in progress. In the process of forming the low-temperature p-Si • TFT and the oxide semiconductor, the heat treatment is performed at a higher temperature than the step of forming the α-Si • TFT. For this reason, a small thermal contraction rate is calculated | required by the glass substrate in which low temperature p-Si * TFT and / or an oxide semiconductor are formed. In order to reduce the thermal shrinkage rate, it is preferable to increase the strain point of the glass composition, but a glass composition having a high strain point tends to decrease the liquidus viscosity. Further, a glass composition having a high strain point also tends to have a high liquidus temperature. Therefore, the production method of the present invention is suitable for producing a glass substrate for FPD with a low-temperature p-Si · TFT and a glass substrate for FPD with an oxide semiconductor.

  The strain point of the glass composition constituting the glass substrate for FPD mounted with low-temperature p-Si • TFT and the glass substrate for oxide semiconductor mounted FPD is, for example, 665 ° C. or higher, preferably 675 ° C. or higher, more preferably 680 ° C. or higher. Especially preferably, it is 690 degreeC or more. The liquid phase viscosity of the glass composition is, for example, 35000 dPa · s or more and 120,000 dPa · s or less, and 40000 dPa · s or more and 100,000 dPa · s or less in order to achieve both improvement in strain point and improvement in formability by the overflow downdraw method. The following is preferable, and more preferably 50000 dPa · s or more and 80000 dPa · s or less. In order to achieve both improvement of the strain point and improvement of formability by the overflow downdraw method, the liquidus temperature of the glass composition is, for example, 1100 to 1250 ° C, more preferably 1150 to 1250 ° C, and 1180. ˜1250 ° C. is more preferable, and 1200 to 1250 ° C. is particularly preferable.

Specific examples of the glass composition include SiO ₂ : 52 to 78% by mass, Al ₂ O ₃ : 3 to 25% by mass, B ₂ O ₃ : _{3 to} 15% by mass, RO (where RO is MgO, (Total content of CaO, SrO and BaO): a composition containing 3 to 20% by mass, a mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is 7.5 or more, and a strain point is It is a glass composition of 670 ° C. or higher. From the viewpoint of increasing the strain point of the glass composition, the mass ratio (SiO ₂ + Al ₂ O ₃ ) / RO is preferably 7 or more. From the same viewpoint, the β-OH value is preferably 0.1 to 0.3 [mm ⁻¹ ]. The glass composition is preferably an alkali-free glass. However, in consideration of lowering the specific resistance of the glass and suppressing elution of zirconia during electric melting, R ′ ₂ O (where R ′ ₂ O is Li ₂ The total content of O, Na ₂ O and K ₂ O) may be included in an amount of 0.01 to 0.8% by mass. The specific resistance of the glass can also be lowered by including 0.01 to 1% by mass of Fe ₂ O ₃ . In order to suppress an increase in the liquidus temperature while realizing a high strain point, the mass ratio CaO / RO in the glass composition is preferably 0.65 or more, and the mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is preferably 7.5 to 20. Considering that FPD is used for mobile devices and the like, the total content of SrO and BaO is preferably less than 0 to 2% by mass from the viewpoint of weight reduction.

  The production method of the present invention can include arbitrary steps other than those described above as long as the effects of the present invention are obtained.

  The said arbitrary process is a melting process which melts a glass raw material and forms molten glass, for example. The melting step may be a step of electrically melting at least the glass raw material in a melting tank configured using a high zirconia refractory. Such a process is suitable for forming a molten glass of an alkali-free glass and a glass containing a small amount of alkali. In this process, zirconia is eluted from the refractory into the molten glass (from the relationship of the specific resistance of the glass, when forming the molten glass of the alkali-free glass and the alkali-containing glass, particularly when forming the molten glass of the alkali-free glass. In the production method of the present invention, the devitrification of the end of the glass ribbon can be suppressed.

  Further, the melting step may be a step of electrically melting a glass raw material in a melting tank using a tin oxide electrode. In this step, tin oxide is eluted from the electrode into the molten glass, but in the production method of the present invention, devitrification of the end portion of the glass ribbon can be suppressed.

  The said arbitrary process is a clarification process which clarifies the molten glass formed with the melting tank, for example.

The optional step is, for example, a rapid cooling step for rapidly cooling the end portion of the glass ribbon to prevent devitrification after the glass ribbon is separated from the forming apparatus. In this step, it is preferable to quench the glass ribbon so that the viscosity of the end of the glass ribbon is 10 ⁹ to 10 ¹⁴ poise.

  The above optional step is a slow cooling step of slowly cooling the formed glass ribbon. The glass ribbon which passed through the slow cooling process is cut | disconnected to the desired size, and becomes various products. An example of a product is a glass substrate for FPD.

  The glass plate manufacturing apparatus which can implement the manufacturing method of this invention is equipped with the shaping | molding apparatus mentioned above in description of the manufacturing method of the said invention, for example.

  In this glass sheet manufacturing apparatus, the viscosity of the portion in the vicinity of the guide in the molten glass flowing down the wall surface of the molding apparatus is kept below the liquid phase viscosity of the glass composition constituting the molten glass from the upper surface to the lower end of the molding apparatus. Thus, the heating mechanism of the molten glass which heats the said part along a guide is provided.

  The configuration of the heating mechanism is not particularly limited. A heating mechanism is provided with the heating apparatus arrange | positioned so that it may extend in the vicinity of a guide from the upper surface side of a shaping | molding apparatus to a lower end side, for example. As the heating device, the heating device described in the description of the production method of the present invention can be used. The heating device is, for example, a heater. At this time, the heating mechanism can include a control mechanism that controls the heating device, a power source, a member that supplies power from the power source to the heating mechanism, a member that measures the temperature in the vicinity of the guide in the molten glass, and the like. . Further, the heating mechanism includes, for example, a heat generation mechanism for the guide. The structure of the heat generating mechanism is not particularly limited. When the guide is heated and heated, the heating mechanism includes, for example, a current (voltage) generator, a member that supplies current from the device to the guide (applies voltage), and an electrode that electrically connects the member and the guide. Prepare. When the guide is heated by a heating device such as a heater, the heat generation mechanism includes, for example, a heating device, a control mechanism that controls the heating device, a power source, and a member that supplies power from the power source to the heater.

  As long as the effect of the present invention is obtained, the glass plate manufacturing apparatus may include an arbitrary apparatus and mechanism other than the forming apparatus and the heating mechanism.

(Example)
In a melting tank using a high zirconia refractory, a glass material prepared to have the following composition was electrically melted to form a molten glass. Next, the formed molten glass was clarified at 1680 ° C. in a platinum alloy clarification tank, and then stirred in a stirring tank and cooled to 1250 ° C. Subsequently, the molten glass was supplied to the forming apparatus 1 shown in FIG. 1 through a platinum alloy guide member, and a glass ribbon was formed by the overflow down draw method. At this time, the temperature of the molten glass in the vicinity of the guides 6a and 6b flowing down the wall surface 5 is such that the current flows through the platinum alloy guides 6a and 6b to cause the guides to generate heat. The temperature was controlled so as not to fall below 1245 ° C., which was 15 ° C. higher than 1230 ° C., which was the liquid phase temperature of the product, and not to exceed 1330 ° C., which was 100 ° C. higher. The glass ribbon thus formed was cooled and gradually cooled and then cut to obtain a glass substrate for FPD having a thickness of 0.7 mm and a size of 2200 mm × 2500 mm. In addition, the liquid phase viscosity of the said glass composition was 50000 dPa * s, and the strain point was 715 degreeC.
SiO ₂ : 61.5% by mass,
Al ₂ O ₃ : 20% by mass,
B ₂ O ₃ : 8.4% by mass,
CaO: 10% by mass,
SnO ₂ : 0.1% by mass

  The obtained glass substrate was not devitrified including the end in the width direction. The product width was also secured.

(Comparative example)
According to the method described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2010-215428) that the guide did not generate heat, and the conveying roll located closest to the lower end of the molding apparatus and downstream of the molding apparatus A glass substrate for FPD was obtained in the same manner as in the example except that a heater was placed in the space between and the end of the glass ribbon moving downward from the lower end of the forming apparatus was locally heated. The heater was disposed below the molding device along the width direction of the molding device, and the temperature of the heater was controlled so that the temperature of the molten glass at the lower end of the molding device was equal to or higher than the liquidus temperature.

  The obtained glass substrate was devitrified at the end in the width direction. In the method described in Patent Document 2, it has been confirmed that it is difficult to suppress the devitrification of the end portion at the time of molding a glass ribbon with a glass composition having a high liquidus temperature and a low liquidus viscosity.

  This specification discloses the aspect shown below regarding the manufacturing method and glass plate manufacturing apparatus of a glass plate.

  In the first aspect, an upper surface on which a supply groove to which molten glass is supplied is formed, and molten glass that overflows on both sides of the supply groove and flows down from both ends of the upper surface is guided, fused at the lower end, and a glass ribbon A glass plate manufacturing method comprising a forming step of forming a glass ribbon by an overflow down-draw method using a forming apparatus comprising a pair of wall surfaces, wherein the liquid phase viscosity of the glass composition constituting the molten glass Is 120,000 dPa · s or less, and in the molding step, the molten glass is squeezed by a pair of guides formed opposite to each other so as to protrude from both ends in the width direction of the wall surface. The molten glass is allowed to flow down along the wall surface while restricting the width of the molten glass. To keep below the liquid phase viscosity from the top down to the bottom, to heat the parts along the guide, the manufacturing method of the glass plate.

  In the second aspect, the upper surface on which a supply groove to which molten glass is supplied is formed, and the molten glass that overflows on both sides of the supply groove and flows down from both ends of the upper surface is guided, fused at the lower end, and a glass ribbon A glass plate manufacturing method comprising a forming step of forming a glass ribbon by an overflow down-draw method using a forming apparatus comprising a pair of wall surfaces, wherein the liquid phase viscosity of the glass composition constituting the molten glass Is not more than 120,000 dPa · s, and the liquidus temperature is 1100 ° C. to 1250 ° C., and in the molding step, both end portions in the width direction of the wall surface are formed to face each other so as to protrude from the end portions. With the pair of guides, the molten glass is allowed to flow down along the wall surface while regulating the width of the molten glass. Serial viscosity of the guide near portions, so as to keep less than the liquid phase viscosity from the upper surface of the forming device until the lower end, to heat the parts along the guide, the manufacturing method of the glass plate.

  In the third aspect, in addition to the first or second aspect, in the molding step, the temperature of the portion in the vicinity of the guide in the molten glass flowing down is higher than the liquidus temperature until reaching the lower end from the upper surface of the molding apparatus. The manufacturing method of the glass plate which heats the said part along the said guide so that it may become 10 to 150 degreeC high.

  In addition to any one of the first to third aspects, the fourth aspect is arranged so that the heating of the portion of the molten glass extends from the upper surface side to the lower end side of the molding apparatus along the guide. A method for producing a glass plate, which is performed by a heating device.

In a fifth aspect, in addition to any one of the first to fourth aspects, the glass composition contains SiO ₂ : 50 to 78% by mass, B ₂ O ₃ : 0 to 15% by mass, Al ₂ O ₃ : 3 to 25% by mass, MgO: 0 to 10% by mass, CaO: 0 to 20% by mass, SrO: 0 to 20% by mass, BaO: 0 to 10% by mass, and RO (where RO is MgO, CaO, SrO And the total of BaO): A method for producing a glass plate, which is a glass composition containing 3 to 20% by mass.

  In a sixth aspect, in addition to any one of the first to fifth aspects, the lower end of the molding device is a linear ridge line in which the pair of wall surfaces are connected to each other, and the above-described wall surface in the molding device is from the wall surface. The method for producing a glass plate, wherein the height of the guide is lower at a position below the molding apparatus and is zero at the position of the ridgeline.

  A seventh aspect is a method for producing a glass plate, in addition to any one of the first to sixth aspects, heating the portion of the molten glass by causing the guide to generate heat.

  The eighth aspect is the method for producing a glass plate, in addition to any one of the first to seventh aspects, wherein the glass composition has a liquidus viscosity of 35000 dPa · s or more and 120,000 dPa · s or less.

  A 9th aspect is a manufacturing method of the glass plate whose liquidus temperature of the said glass composition is 1050 degreeC or more in addition to any one of the 1st-8th aspect.

  A tenth aspect is the method for producing a glass plate, in addition to any one of the first to ninth aspects, wherein the molten glass contains zirconia and / or tin oxide.

  The eleventh aspect is the method for producing a glass plate, in addition to any one of the first to tenth aspects, wherein the glass composition contains 0 to 2.0% by mass of an alkali metal oxide.

A twelfth aspect, in addition to any one of the first to eleventh aspect, the said glass composition, temperature exhibits a viscosity of 10 ^2.5 poise is from 1,500 to 1750 ° C., the manufacturing method of the glass plate.

Thirteenth aspect, in addition to any one of the first to twelfth aspect, wherein the glass composition, SiO _2: 52-78 wt%, Al ₂ O _3: 3~25 wt%, B ₂ O _3: 3-15% by mass, RO (provided that RO is the total of MgO, CaO, SrO and BaO): 3-20% by mass, and the mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is 7. The manufacturing method of the glass plate which is 5 or more and is a glass composition whose strain point is 670 degreeC or more.

  A fourteenth aspect is the method for producing a glass plate, in addition to any one of the first to thirteenth aspects, wherein the glass plate is a glass substrate for liquid crystal display or a glass substrate for organic EL display. The glass plate may be a glass substrate for a low-temperature p-Si • TFT mounted display.

  In the fifteenth aspect, in addition to any one of the first to fourteenth aspects, the temperature is controlled so that the viscosity of the molten glass at the lower end of the molding apparatus is 40000 dPa · s or more. .

  In addition to any one of the first to fifteenth aspects, the sixteenth aspect further has a slow cooling step of slowly cooling the glass ribbon formed in the molding step, and the conveyance speed of the glass ribbon in the slow cooling step The manufacturing method of the glass plate whose is 50-500 m / h.

  In the seventeenth aspect, in addition to any one of the first to sixteenth aspects, a melting step of obtaining the molten glass by melting a glass raw material using at least electric heating in a melting tank containing a high zirconia refractory. The manufacturing method of the glass plate which has further.

  According to an eighteenth aspect, an upper surface on which a supply groove for supplying molten glass is formed, and molten glass that overflows on both sides of the supply groove and flows down from both ends of the upper surface is guided and fused at the lower end, A pair of wall surfaces, and a pair of guides that are formed at both end portions in the width direction of the wall surface so as to protrude from the end portions and regulate the width of the molten glass flowing down along the wall surface, The viscosity of the portion near the guide in the flowing molten glass is kept below the liquid viscosity of the glass composition constituting the molten glass from the upper surface to the lower end of the molding device. And a heating mechanism for the molten glass that heats the portion along the guide.

  In addition to the eighteenth aspect, the nineteenth aspect is a glass plate manufacturing apparatus provided with a heating device that is disposed in the vicinity of the guide so as to extend from the upper surface side to the lower end side of the molding device.

  A twentieth aspect is the glass plate manufacturing apparatus according to the eighteenth or nineteenth aspect, wherein the heating mechanism includes a heat generation mechanism of the guide.

  In a twenty-first aspect, in addition to any one of the eighteenth to twentieth aspects, the lower end of the molding device is a linear ridge line in which the pair of wall surfaces are connected to each other, and the above-mentioned wall surface in the molding device is from the wall surface. The height of the guide is lower at a position below the molding apparatus and is zero at the position of the ridge line.

  The glass plate obtained by the production method of the present invention can be used for various applications, for example, a glass substrate of FPD.

DESCRIPTION OF SYMBOLS 1 Molding apparatus 2 Supply groove 3 Upper surface 3a, 3b (Upper surface) edge 4 Lower end 5 Wall surface 6a, 6b Guide 7 Liquid surface 8 Heating device 11a, 11b, 11c Electrode 50 Glass ribbon 50a (Glass ribbon) edge

Claims (5)

An upper surface on which a supply groove to which molten glass is supplied is formed; and a pair of wall surfaces that induces molten glass that overflows on both sides of the supply groove and flows down from both ends of the upper surface and is fused at the lower end to form a glass ribbon; , Using a forming apparatus comprising a glass plate having a forming step of forming a glass ribbon by an overflow down draw method,
The liquid phase viscosity of the glass composition constituting the molten glass is 120,000 dPa · s or less, the liquid phase temperature is 1100 ° C. to 1250 ° C.,
In the molding step,
From the upper surface to the lower end of the molding apparatus, the molten glass is converted into the molten glass by a pair of guides formed at both ends in the width direction of the wall surface so as to protrude from the end portions. Flow down along the wall while regulating the width of
By maintaining the viscosity of the portion in the vicinity of the guide in the flowing molten glass below the liquid phase viscosity from the upper surface to the lower end of the molding apparatus , devitrification occurs in the molten glass from the upper surface to the lower end. A method for manufacturing a glass plate, in which the part is heated along the guide so as not to exist.   In the molding step, along the guide, the temperature of the portion in the vicinity of the guide in the flowing molten glass is higher by 10 ° C. to 150 ° C. than the liquid phase temperature from the upper surface to the lower end of the molding device. The method for producing a glass plate according to claim 1, wherein the portion is heated.   The manufacturing method of the glass plate of Claim 1 or 2 which heats with respect to the said part of the said molten glass with the heating apparatus arrange | positioned so that it may extend from the upper surface side of the said shaping | molding apparatus to a lower end side along the said guide. The molding apparatus is connected to the vertical wall surface as the wall surface, the vertical wall surface where the molten glass overflowing from the supply groove flows down in the vertical direction, and the molten glass flowing down the vertical wall surface to the lower end. An inclined slope, and
The said guide is a manufacturing method of the glass plate in any one of Claims 1-3 currently formed over the said inclined wall surface from the said vertical wall surface. The lower end of the molding device is a linear ridge line connected between the pair of wall surfaces,
The height of the said guide from the said wall surface in the said shaping | molding apparatus becomes low in the position below the said shaping | molding apparatus, and is zero in the position of the said ridgeline of the glass plate in any one of Claims 1-4 . Production method.

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