JPWO2013042379A1 - Glass plate manufacturing method and glass plate manufacturing apparatus - Google Patents

Abstract

When manufacturing a glass plate, a glass raw material is melted to form molten glass, and the molten glass is supplied to a molded body disposed in a molding space surrounded by a molding furnace wall that is a furnace wall of a molding furnace. A sheet glass is molded from the molten glass supplied to the molded body using a downdraw method. Thereafter, the sheet glass is gradually cooled in a slow cooling space which is a space located below the molding space and surrounded by a slow cooling furnace wall which is a furnace wall of the slow cooling furnace. The gradually cooled sheet glass is cut into a glass plate in a cutting space located below the annealing furnace. At this time, the cutting space in the building inner space defined by the inner wall surface of the building accommodating the forming space, the slow cooling space, and the cutting space, the outer surface of the molding furnace wall, and the outer surface of the slow cooling furnace wall. The atmospheric pressure control is performed so that the atmospheric pressure in the furnace external space located above the building becomes larger than the atmospheric pressure outside the building.

Description

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

  Conventionally, there is a method of manufacturing a glass plate using various methods such as a downdraw method. For example, in the overflow downdraw method, which is one method for producing a glass plate, first, molten glass is supplied to a molded body disposed in a molding furnace. And the supplied molten glass is made to overflow from a molded object. Then, the molten glass overflowed is joined at the lower end of the molded body to form a continuous sheet-like glass (sheet glass). In addition, the sheet glass merged at the lower end of the formed body is further conveyed downward and gradually cooled in a slow cooling furnace. And the slowly cooled sheet glass is cut | disconnected by the desired magnitude | size in a cutting | disconnection space, and turns into a glass plate.

  When manufacturing a glass plate, it is calculated | required to produce stably the glass plate which satisfy | fills predetermined quality. For example, in the technique disclosed in Patent Document 1, when a glass plate is manufactured by using the overflow downdraw method, the pressure in the outer space of the forming furnace and / or the slow cooling furnace is increased along the sheet glass in the slow cooling furnace. Ascending airflow generated is reduced and temperature fluctuations in the slow cooling furnace are suppressed. And thereby, plane distortion is reduced.

JP 2009-173525 A

  However, there is a problem that a glass plate that satisfies a predetermined quality cannot be produced stably by simply pressurizing the pressure in the outer space of the forming furnace and / or the slow cooling furnace. For example, there is a problem in that particle adhesion to a sheet glass or a glass plate in a forming furnace or a slow cooling furnace cannot be sufficiently suppressed. If the particles adhere to the glass plate, there is a problem that the glass plate is damaged. In recent years, with an increase in the size of a glass plate, the amount of deflection of the glass plate in the final processing step (polishing, packing, etc.) of the glass plate and the display manufacturing process has increased. Therefore, the problem that the glass plate is damaged in the final processing step of the glass plate and the display manufacturing process due to the scratches on the glass plate due to the particles is remarkable.

  Then, this invention makes it a subject to solve the above problems, and to provide the manufacturing method of a glass plate and the manufacturing apparatus of a glass plate which can perform the stable production which satisfy | filled the predetermined quality of a glass plate.

The first aspect of the present invention is a method for producing a glass plate. The manufacturing method includes a melting step of melting a glass raw material to form molten glass, and supplying the molten glass to a molded body disposed in a molding space surrounded by a molding furnace wall that is a furnace wall of a molding furnace. A step of forming a sheet glass from molten glass in the molded body using a downdraw method, and a slow cooling furnace which is a space located below the molding space and is a furnace wall of the slow cooling furnace A slow cooling step of slow cooling in a slow cooling space surrounded by walls, and a cutting step of cutting the slowly cooled sheet glass in a cutting space located below the slow cooling furnace to form a glass plate.
Above the cutting space within the building space defined by the inner wall surface of the building that houses the molding space, the slow cooling space, and the cutting space, the outer surface of the molding furnace wall, and the outer surface of the slow cooling furnace wall. The atmospheric pressure control is performed so that the atmospheric pressure in the furnace outer space is larger than the atmospheric pressure outside the building.

  The second aspect of the present invention is a glass plate manufacturing apparatus. The manufacturing apparatus includes a forming furnace that is formed by surrounding a forming space for forming a sheet glass from molten glass with a forming furnace wall, and a slow cooling that gradually cools the sheet glass so as to be positioned below the forming furnace. A slow cooling furnace formed by surrounding the space with a wall of a slow cooling furnace, a cutting device disposed in a cutting space located below the slow cooling furnace and cutting the sheet glass that has been slowly cooled, the molding space, the slow cooling space, And the pressure in the furnace external space located above the cutting space in the building internal space defined by the inner wall surface of the building that houses the cutting space, the outer surface of the forming furnace wall, and the outer surface of the slow cooling furnace wall, Control means for performing atmospheric pressure control so as to increase with respect to the atmospheric pressure outside the building.

  As a preferred first embodiment, in the atmospheric pressure control, when the atmospheric pressure in the furnace exterior space is P1, and the atmospheric pressure outside the building is P2, the relationship 0 <P1-P2 ≦ 40 Pa is established. The atmospheric pressure in the outer space of the furnace is controlled.

  As a preferred second embodiment, in the atmospheric pressure control, when the atmospheric pressure in the cutting space is P3, the atmospheric pressure in the cutting space is further controlled so that the relationship 0 <P3-P2 ≦ 40 Pa is established.

  As a preferred third embodiment, in the atmospheric pressure control, the atmospheric pressure in the cutting space is controlled so that the atmospheric pressure in the slow cooling space is larger than the atmospheric pressure in the cutting space.

  As a preferred fourth embodiment, in the atmospheric pressure control, the atmospheric pressure in the furnace external space is controlled so that the atmospheric pressure in the furnace external space increases toward the upstream side in the flow direction of the sheet glass.

Further, as a preferred fifth embodiment, in the slow cooling step or the slow cooling space, in the central portion in the width direction of the sheet glass, a tension acts in the flow direction of the sheet glass,
At least in the temperature range where the temperature of the central portion in the width direction of the sheet glass is a temperature obtained by adding 200 ° C. from the strain point temperature of the glass to a temperature obtained by adding 150 ° C. to the annealing point temperature of the glass. Temperature control is performed so that the cooling rate at the center in the direction is faster than the cooling rate at both ends in the width direction.

Moreover, as a preferable sixth embodiment, in the molding step or the molding space, in the region where the temperature of the central portion in the width direction of the sheet glass is equal to or higher than the softening point temperature of the glass, both end portions in the width direction of the sheet glass are The temperature of the sheet glass is controlled so as to be lower than the temperature of the central portion sandwiched between the both end portions and uniform in the central portion. Furthermore, in the slow cooling step or the slow cooling space, the temperature of the central portion of the sheet glass is such that the tension in the flow direction of the sheet glass acts at the central portion in the width direction of the sheet glass. The temperature of the sheet glass is controlled so that the temperature distribution in the width direction of the sheet glass decreases from the central portion toward the both end portions in a region that is less than the strain point temperature of the glass. Furthermore, in the temperature region where the temperature of the central portion of the sheet glass is the strain point temperature of the glass, the temperature of the sheet glass is such that there is no temperature gradient between the both end portions in the width direction of the sheet glass and the central portion. Be controlled.
In the sixth embodiment, a temperature adjustment unit for controlling the temperature may be provided in a furnace space including the molding space and the slow cooling space.

  Further, as a preferred seventh embodiment, in the slow cooling step or the slow cooling space, in the central part in the width direction of the sheet glass, the tension in the flow direction of the sheet glass acts so that the central part of the sheet glass In the region where the temperature is lower than the strain point temperature of the glass, the temperature of the sheet glass is controlled so as to decrease from the both end portions of the sheet glass toward the central portion.

  Moreover, as a preferable eighth embodiment, in the slow cooling step or the slow cooling space, among the feed rollers for transporting the sheet glass, the downstream side of the position where the temperature of the sheet glass becomes the glass annealing point temperature. The peripheral speed of the feed roller provided in the sheet is 0.03 to 2% of the peripheral speed of the feed roller provided in the temperature region where the temperature of the sheet glass is not lower than the glass transition temperature and not higher than the softening temperature of the glass. Make it faster.

  Each of the first to eighth preferred embodiments can be applied to each of the glass plate manufacturing method of the first aspect and the glass plate manufacturing apparatus of the second aspect described above, and further, the first to eighth embodiments. The composite form combining at least two of the preferred forms can also be applied to the glass plate production method of the first aspect and the glass plate production apparatus of the second aspect.

  In this invention, it is possible to suppress that a particle adheres to a glass plate.

The flowchart of a part of manufacturing method of the glass plate which concerns on this embodiment. The schematic diagram which mainly shows the melting | dissolving apparatus contained in a glass plate manufacturing apparatus. The schematic diagram which shows the inside of a building. The schematic side view of a shaping | molding apparatus. The schematic diagram which shows the inside of the building for demonstrating the space in a building. The control block diagram of a control apparatus. The schematic diagram which shows the inside of the building which concerns on the modification 1A. The schematic diagram which shows the inside of the building which concerns on the modification 1F.

The following words and phrases in this specification are defined as follows.
The center part of sheet glass means the center of the width direction of sheet glass among the width | variety of the width direction of sheet glass.
The edge part of sheet glass means the range within 100 mm from the edge of the width direction of sheet glass.
The strain point temperature refers to the temperature of a glass plate having a log η of 14.5 when the glass viscosity is η.
The annealing point temperature refers to the temperature of glass having a log η of 13.
The softening point temperature refers to the temperature of glass having a log η of 7.6.
The glass transition temperature refers to the temperature of the glass when the supercooled liquid changes to the glass state.

  The inventor of the present invention cannot realize sufficiently stable production only by pressurizing the pressure in the outer space of the forming furnace and / or the slow cooling furnace, because the magnitude of the pressure between the inside of the building and the outside of the building is small. I found that there is a relationship. More specifically, it has been found that the cause of lowering the quality of the glass plate is that air flows into the building from the outside of the building when the pressure inside the building is smaller than the pressure outside the building. Here, in order to prevent air from flowing into the building from the outside of the building, it is conceivable to improve the airtightness of the building, but it is extremely difficult to completely eliminate the gap between the buildings and complete the airtightness. Have difficulty. Since air flows from higher to lower pressure, if the pressure inside the building is smaller than the pressure outside the building, the air outside the building flows into the building through the gaps in the building. . Air flowing from the outside of the building through the gaps in the building causes particle adhesion to the glass plate and a decrease in accuracy of temperature control in the forming furnace and slow cooling furnace. And cannot be produced. Therefore, in order to solve the problem of the adhesion of particles on the glass plate, the inventor of the present invention increases the atmospheric pressure inside the building to the atmospheric pressure outside the building, so that the air outside the building is inside the building. It was found that it is only necessary to suppress the flow into the water. In addition, in order to suppress the decrease in accuracy of temperature control in the forming furnace and the slow cooling furnace, it was found that the difference between the pressure inside the building and the pressure outside the building should be controlled.

  Hereinafter, the manufacturing method of the glass plate which manufactures a glass plate using the glass plate manufacturing apparatus 100 of this embodiment is demonstrated, referring drawings.

(Outline of glass plate manufacturing method)
FIG. 1 is a partial flowchart of the glass plate manufacturing method according to the present embodiment. Hereinafter, the manufacturing method of a glass plate is demonstrated using FIG.

  The glass plate is manufactured through various processes in the building B. Specifically, as shown in FIG. 1, the glass plate has a melting step ST1, a refining step ST2, a homogenizing step ST3, a supplying step ST4, a forming step ST5, a slow cooling step ST6, and a cutting step. Manufactured through various processes including ST7. Hereinafter, these steps will be described.

  In melting step ST1, molten glass is obtained by heating and melting the glass raw material. In the clarification step ST2, the molten glass is clarified. In the homogenization step ST3, the molten glass is homogenized.

  In supply process ST4, it supplies to the shaping | molding apparatus 300 (refer FIG. 2) which shape | molds molten glass. In the forming step ST5, the molten glass is formed into a sheet-like sheet glass SG. The molten glass is preferably formed into a sheet-like sheet glass SG by a downdraw method, particularly an overflow downdraw method. In the slow cooling step ST6, the sheet glass SG formed in the forming step ST5 is gradually cooled. In the cutting step ST7, the slowly cooled sheet glass SG (see FIG. 3) is cut into a glass plate G (see FIG. 3) every predetermined length.

  In addition, the glass plate G cut | disconnected for every predetermined length is cut further after that, and grinding / polishing, washing | cleaning, and a test | inspection are performed, and what is expressed as a glass plate simply does not give a symbol. , Meaning the glass plate finally produced).

(Outline of glass plate manufacturing apparatus 100)
FIG. 2 is a schematic view mainly showing a melting apparatus 200 included in the glass plate manufacturing apparatus 100. FIG. 3 is a schematic diagram of the inside of the building B in which various apparatuses included in the glass plate manufacturing apparatus 100 are accommodated or attached (in FIG. 3, the forming apparatus 300, the forming furnace 40, and the slow cooling furnace 50 are illustrated. Etc. are shown by a schematic cross-sectional schematic diagram). Hereinafter, the glass plate manufacturing apparatus 100 will be described.

  The glass plate manufacturing apparatus 100 is disposed in the building B, and mainly includes a melting apparatus 200, a forming apparatus 300, and a cutting apparatus 400.

(Configuration of dissolution apparatus 200)
The dissolution apparatus 200 is an apparatus for performing the dissolution process ST1, the clarification process ST2, the homogenization process ST3, and the supply process ST4. As shown in FIG. 2, the dissolution apparatus 200 includes a dissolution tank 201, a clarification tank 202, and a stirring tank 203.

  The melting tank 201 is a tank for melting the glass raw material. In the dissolution tank 201, the dissolution step ST1 is performed. The clarification tank 202 is a tank for removing bubbles from the molten glass melted in the melting tank 201. In the clarification tank 202, a clarification step ST2 is performed. The stirring tank 203 stirs the molten glass. In the stirring tank 203, the homogenization step ST3 is performed. The melting tank 201, the clarification tank 202, the stirring tank 203, and the molding apparatus 300 are connected by a glass supply pipe including a first pipe 204 and a second pipe 205.

(Configuration of molding apparatus 300)
FIG. 4 is a schematic side view of the molding apparatus 300. FIG. 5 is a schematic diagram showing the inside of the building B for explaining the space S in the building.

The molding apparatus 300 is an apparatus for performing the molding process ST5 and the slow cooling process ST6.
The molding apparatus 300 mainly includes a molded body 310, an atmosphere partition member 320, a cooling roller 330, a cooling temperature adjustment unit 330a, feed rollers 340a to 340h, and temperature adjustment units 350a to 350g (see FIG. 4). And have.
Hereinafter, these configurations will be described.

(Molded body 310)
As shown in FIG. 3, the molded body 310 is located in the upper part of the molding apparatus 300, and the molten glass flowing from the melting apparatus 200 (indicated by reference numeral MG in FIGS. 3 and 4) is turned into a sheet-like sheet glass. Has the function of molding. The molded body 310 has a wedge-shaped cross section cut in the vertical direction, and is formed of bricks.

(Atmosphere partition member 320)
As shown in FIGS. 3 and 4, the atmosphere partition member 320 is a plate-like member disposed in the vicinity of the lower end 313 of the molded body 310. The atmosphere partition member 320 is arranged substantially horizontally on both sides in the thickness direction of the molten glass that merges at the lower end portion 313 of the molded body 310 and flows downstream in the first direction. The atmosphere partition member 320 functions as a heat insulating material. In other words, the atmosphere partition member 320 suppresses the movement of heat from the upper side to the lower side of the atmosphere partition member 320 by partitioning the upper and lower spaces thereof.

(Cooling roller 330)
The cooling roller 330 is disposed below the atmosphere partition member 320. Further, the cooling roller 330 is arranged at both sides in the thickness direction of the molten glass that joins at the lower end portion 313 of the molded body 310 and flows downstream in the first direction, and in the vicinity of both side portions in the width direction. The cooling roller 330 cools the molten glass by contacting both side portions in the width direction of the molten glass joined at the lower end 313 of the molded body 310. More specifically, the cooling roller 330 forms and cools the sheet glass SG to a desired thickness by pulling the molten glass downstream in the first direction. In the present specification, the direction in which the sheet glass SG flows is referred to as a first direction.

  Here, the molded body 310, the atmosphere partition member 320, and the cooling roller 330 are disposed in the molding space S1 (the space indicated by the diagonally oblique lines on the left in FIG. 5). The molding space S <b> 1 is a space surrounded by the inner surface of the molding furnace wall 41 that is the furnace wall of the molding furnace 40 and the plane FS <b> 1 including the upper surface of the partition member 42. The partition member 42 is a member that partitions the forming furnace 40 (the downstream end in the first direction of the forming furnace wall 41) and the slow cooling furnace 50 described later (the upstream end in the first direction of the slow cooling furnace wall 51 described later), For example, a flat plate member is used. The forming furnace wall 41 is a furnace wall of the forming furnace 40, and the cross-sectional shape cut along the first direction has a U-shape. In the molding furnace 40, a molding step ST5 is performed. A space composed of the molding space S1 and the slow cooling space S2 described later is referred to as a furnace space.

(Feed rollers 340a to 340h)
The feed rollers 340a to 340h are disposed below the cooling roller 330 with a predetermined interval in the first direction. The feed rollers 340a to 340h are respectively disposed on both sides in the thickness direction of the sheet glass SG. The feed rollers 340a to 340h pull the sheet glass SG downstream in the first direction.

(Temperature adjustment units 350a to 350g, cooling temperature adjustment unit 330a)
The temperature adjustment units 350a to 350g are devices for adjusting the temperature of the sheet glass SG, specifically, the ambient temperature in the vicinity of the sheet glass SG (specifically, raising the temperature), and a plurality of sheet glasses in the first direction. A plurality of SGs are arranged in the width direction of SG. The cooling temperature adjustment unit 330a is arranged below the cooling roller 330 in the first direction, and adjusts the temperature of the sheet glass SG, more precisely the ambient temperature in the vicinity of the sheet glass SG. The cooling temperature adjustment unit 330a cools so as to reduce the thickness and warpage of the high-temperature sheet glass SG immediately after molding.

Here, the cooling temperature adjustment unit 330a is disposed in the molding space S1 (the space indicated by the diagonally oblique lines in FIG. 5).
Further, the feed rollers 340a to 340h and the temperature adjustment units 350a to 350g are arranged in the slow cooling space S2 (the space shown by the diagonally oblique lines in FIG. 5). The slow cooling space S <b> 2 is a space formed by the slow cooling furnace 50 disposed below the molding furnace 40. More specifically, the space surrounded by the inner surface of the slow cooling furnace wall 51 that is the furnace wall of the slow cooling furnace 50, the flat surface FS2 including the lower surface of the partition member 42, and the flat surface FS3 including the downstream end surface of the slow cooling furnace wall 51 in the first direction. It is.

  In the slow cooling space S2, the sheet glass SG is gradually cooled by the feed rollers 340a to 340h being pulled downstream in the first direction (from the viscous region to the elastic region through the viscoelastic region). A slow cooling step ST6 is performed. In the slow cooling step ST6, the temperature adjustment units 350a to 350g adjust the temperature of the sheet glass SG so that the plane strain and the heat shrinkage rate of the sheet glass SG are suppressed. In addition, in the vicinity of each temperature adjustment unit 350a-350g, the several temperature sensor as an atmospheric temperature detection means to detect the atmospheric temperature of the vicinity of the sheet glass SG is arrange | positioned along the width direction of the sheet glass SG. . Here, the plurality of temperature sensors are referred to as a temperature sensor unit 380 (see FIG. 6).

(Cutting device 400)
The cutting device 400 performs a cutting process ST7. The cutting device 400 is disposed in a cutting space S3 (described later) located below the slow cooling furnace 50. The cutting device 400 cuts the sheet glass SG flowing down downstream in the first direction in the forming device 300 from a direction perpendicular to the longitudinal surface. Thereby, the sheet glass SG becomes a plurality of glass plates G having a predetermined length.

(Building space S)
The in-building space S is a space excluding the forming furnace wall 41, the forming space S1, the slow cooling furnace wall 51, and the slow cooling space S2 in the space surrounded by the inner surface of the building B (shaded hatching in FIG. 5). See section). The building space S is a space defined by the inner surface (inner wall surface) of the building B that houses the forming space S1, the slow cooling space S2, and the cutting space S3, the outer surface of the forming furnace wall 41, and the outer surface of the slow cooling furnace wall 51. It is.

  The building space S is divided into a plurality of spaces by floors 411, 412, and 413 arranged in the building B. The floors 411, 412 and 413 have a role as partition members for dividing the building space S into a plurality of spaces. Specifically, the building space S is divided into floors 411, 412, and 413 into a molding furnace outer upper space S 5, a molding furnace outer lower space S 6, a slow cooling furnace outer space S 7, and a cutting space S 3. However, the number of floors (the number of divisions in the building space) and the height position in the first direction where the floors are installed are not particularly limited.

  The forming furnace exterior upper space S5 is a space sandwiched between the floor 411 and the upper lower surface of the building B in the building space S. The height of the floor 411 is close to the position of the upper part of the molded body 310, and is disposed at the same height position as the upper part of the molding furnace wall 41.

  The molding furnace outer lower space S6 is a space formed on the downstream side in the first direction with respect to the molding furnace outer upper space S5. Specifically, the molding furnace outer lower space S6 is a space sandwiched between the floor 411 and the floor 412 in the building space S. The floor 412 is arranged so that the height position thereof is located in the vicinity of the downstream end of the forming furnace wall 41 in the first direction. The molding furnace outer lower space S6 includes a region A1 corresponding to the molded body 310 (specifically, the installation position and the height position of the molded body 310 are the same).

  The slow cooling furnace outer space S7 is a space formed on the downstream side in the first direction with respect to the molding furnace outer lower space S6. The slow cooling furnace outer space S7 is a space sandwiched between the floor 412 and the floor 413 in the building space S. The floor 413 is disposed at a height position close to the downstream end of the slow cooling furnace wall 51 in the first direction.

  Further, the slow cooling furnace external space S7 has the same temperature position as the slow cooling furnace external space S7 (that is, corresponding to the distance from the lower surface of the floor 412 to the upper surface of the floor 413) and the ambient temperature of the glass sheet G flowing through the slow cooling space S2 For example, the space is 800 ° C. to 110 ° C., or the slow cooling furnace external space S7 is such that the glass plate G flowing through the slow cooling space S2 is changed from (slow cooling point temperature + 5 ° C.) to (strain point temperature−50 ° C.). It is a space that includes a space.

  The cutting space S3 is a space formed on the downstream side in the first direction of the slow cooling furnace outer space S7. Specifically, the cut space S3 is a space sandwiched between the floor 413 and the upper surface of the lower part of the building B in the in-building space S.

  Here, the molding furnace wall 41 and the slow cooling furnace wall 51 are made of, for example, a refractory material or a heat insulating material. Moreover, the building B can be applied with a known refractory or the like generally used when building a building.

(Control device 500)
FIG. 6 is a control block diagram of the control device 500.
The control device 500 includes a CPU, a ROM, a RAM, a hard disk, and the like, and functions as a control unit that controls various devices included in the glass plate manufacturing apparatus 100.

  Specifically, as shown in FIG. 6, the control device 500 performs drive control of the first drive unit 390 that performs temperature adjustment control of the temperature adjustment units 350 a to 350 g, a cooling roller 330, feed rollers 340 a to 340 h, cutting Drive control of the second drive unit 450 for driving the device 400 and the like is performed. The temperature adjustment control of the cooling temperature adjustment unit 330a is performed based on the ambient temperature in the vicinity of the sheet glass SG detected by the temperature sensor unit provided in the molding space S1. Further, the temperature adjustment control of the temperature adjustment units 350a to 350g is performed based on the ambient temperature in the vicinity of the sheet glass SG detected by the temperature sensor unit 380.

  In addition, the control device 500 further controls the atmospheric pressure in the building space S formed by the inner surface of the building B. This will be described later. The various sensors shown in FIG. 6 will also be described later.

(Formation of sheet glass SG in the molding apparatus 300)
Hereinafter, the process in which the sheet glass SG is shape | molded in the shaping | molding apparatus 300 is demonstrated.

First, the molten glass supplied from the melting device 200 to the molded body 310 via the supply port 311 flows into the groove 312 (see FIG. 3) opened above the molded body 310. And it overflows in the groove part 312. The molten glass overflowed in the groove portion 312 flows downstream in the first direction along both side surfaces of the molded body 310 and merges at the lower end portion 313 as shown in FIG. The molten glass that has joined at the lower end 313 flows down to the downstream side in the first direction. The viscosity of the glass at the time of starting to flow down after leaving the molded body 310 is, for example, 10 ^5.7 to 10 ^7.5 poise.

The molten glass flowing down to the downstream side in the first direction is pulled down to the downstream side in the first direction by sandwiching both ends in the width direction by the cooling rollers 330 arranged on both sides in the thickness direction. At this time, the molten glass is formed into a sheet-like sheet glass SG and cooled (rapidly cooled). Due to the rapid cooling by the cooling roller 330, the viscosity at both ends of the sheet glass is, for example, 10 ^9.0 to 10 ^10.5 poise. The sheet glass SG pulled down by the cooling roller 330 is further pulled down by the feed rollers 340a to 340h and gradually cooled.

  The sheet glass SG pulled down by the feed rollers 340a to 340h is then cut into a plurality of glass plates G by a cutting device 400 for each predetermined length.

(Control of atmospheric pressure in building space S)
In the present embodiment, the atmospheric pressure control of the furnace outside space S4 is performed. The furnace outer space S4 is a space that is surrounded by the outer surface of the forming furnace wall 41, the outer surface of the slow cooling furnace wall 51, and the inner surface of the building B, and is located above the cutting space S3, in other words, This is a space obtained by removing the cutting space S3 from the building space S (that is, a space constituted by the molding furnace outer upper space S5, the molding furnace outer lower space S6, and the slow cooling furnace outer space S7).

  The atmospheric pressure control process for performing atmospheric pressure control of the furnace outer space S4 is started, for example, at the time when the homogenization process ST3 is performed. That is, the atmospheric pressure control process is performed before the molding process ST5 and the slow cooling process ST6.

  In the present embodiment, in order to perform the atmospheric pressure control, outside the forming furnace outside upper space S5, the forming furnace outside lower space S6, and the slow cooling furnace outside space S7 (that is, outside through the wall of the building B), Blowers 421, 422, and 423 for pressurizing each space are disposed. Further, in order to perform the atmospheric pressure control, a first pressure sensor 431, a second pressure sensor 432, which are detection means for detecting the atmospheric pressure in the molding furnace outer upper space S5, the molding furnace outer lower space S6, and the slow cooling furnace outer space S7, And the 3rd pressure sensor 433 (refer to Drawing 6) is arranged in each space. In addition, the method of performing atmospheric pressure control is not limited to the method of performing air blowing, and a method of performing a combination of air blowing and exhaust air, a method of adjusting a pressure difference with a damper, or the like can be applied.

  In the atmospheric pressure control, the atmospheric pressure P1 in the outer space S4 is changed to the atmospheric pressure outside the building B (atmospheric pressure) by detecting the atmospheric pressure in each space S5, S6, S7 using various pressure sensors 431, 432, 433. ) The operation of the second drive unit 450 (for example, a motor) for driving the blowers 421, 422, and 423 so as to be larger than P2 (for example, the rotation speed in the case of a motor) is controlled outside the furnace. The atmospheric pressure in the space S4 is controlled.

  Specifically, the value obtained by subtracting P2 from P1 is controlled to be greater than 0 and 40 Pa or less. That is, the second drive unit 450 is controlled so that the relationship of the following formula 1 is established.

(Formula 1) 0 <P1-P2 ≦ 40 Pa
The value obtained by subtracting P2 from P1 is more preferably 1 to 40 Pa, further preferably 2 to 35 Pa, further preferably 3 to 25 Pa, and further preferably 4 to 15 Pa. .
Furthermore, in the atmospheric pressure control step, it is preferable that the atmospheric pressure in the furnace external space S4 is controlled so that the air pressure in the furnace external space S4 increases toward the upstream side in the flow direction of the sheet glass SG. More specifically, it is preferable that the atmospheric pressure in the molding furnace outer upper space S5> the atmospheric pressure in the molding furnace outer lower space S6> the atmospheric pressure in the slow cooling furnace outer space S7.

(Control of cooling of sheet glass SG)
In the present embodiment, cooling of the sheet glass SG can be controlled in the forming space S1 and the slow cooling space S2. Specifically, the following temperature control unit 330a, temperature adjustment units 350a to 350g, feed rollers 340a to 340h, and cooling roller 330 can be cooled in accordance with instructions from control device 500 as described below. .
For example, when the sheet glass SG is caused to flow downstream in the slow cooling space S2 using the cooling rollers 330 and the feed rollers 340a to 340h, the tension is effectively applied in the flow direction (first direction) of the sheet glass SG. Thereby, the curvature of the sheet glass SG can be suppressed. It is also possible to suppress the occurrence of wave-like deformation in an adjacent region adjacent to a portion that is sandwiched between the rollers and flows.
In order to exert tension effectively in the flow direction (first direction) of the sheet glass SG, for example, in the forming space S1, the temperature of the central portion in the width direction of the sheet glass SG is equal to or higher than the softening point temperature of the glass. In the region, the temperature of the sheet glass SG is controlled such that both end portions (ear portions) in the width direction of the sheet glass SG are lower than the temperature of the central portion and the temperature of the central portion is uniform. Furthermore, the temperature of the central portion in the width direction of the sheet glass SG is less than the softening point temperature and above the strain point temperature so that the tensile stress in the transport direction acts on the central portion in the width direction of the sheet glass SG. In this area, the temperature of the sheet glass SG is controlled so that the temperature distribution in the width direction of the sheet glass SG becomes lower from the center toward both ends. Furthermore, in the temperature region where the temperature of the center portion in the width direction of the sheet glass SG becomes the strain point temperature of the glass, the sheet is so formed that there is no temperature gradient between both end portions (ear portions) in the width direction of the sheet glass SG and the center portion. The temperature of the glass SG is controlled. Thereby, the tensile stress of a conveyance direction is applied to the center part of the width direction of the sheet glass SG.
In the temperature control of the sheet glass SG, it is assumed that the region where the temperature of the sheet glass SG is equal to or higher than the softening point temperature is in the molding space S1. Therefore, in order to perform the temperature control, a cooling temperature adjustment unit 330a is provided in the molding space S1. However, the area | region where the temperature of the sheet glass SG is more than a softening point temperature may exist in the slow cooling space S2. In this case, in order to perform the temperature control, a cooling temperature adjustment unit 330a is provided in the slow cooling space S2.

  Further, in the slow cooling space S2, the temperature of the central portion in the width direction of the sheet glass SG is less than the vicinity of the strain point temperature of the glass so that the tension in the conveyance direction acts on the central portion in the width direction of the sheet glass SG. , The temperature of the sheet glass SG can be controlled so as to decrease from both end portions (ear portions) in the width direction of the sheet glass SG toward the center portion in the width direction of the sheet glass SG. Thereby, in the area | region below the strain point temperature vicinity of the center part of the width direction of the sheet glass SG, tensile stress can always be applied to a conveyance direction in the center part of the width direction of the sheet glass SG.

In this embodiment, as will be described later, the variation in the thermal shrinkage rate of the glass plate can be reduced, and further, by adjusting the cooling rate of the formed sheet glass SG, in addition to the variation in the thermal shrinkage rate. In addition, the deformation of the glass plate can be suppressed, the warpage can be suppressed, and the absolute value of the heat shrinkage rate can be reduced.
Specifically, in the slow cooling space S2, when the sheet glass SG is gradually cooled using the feed rollers 340a to 340h, the sheet glass SG is heated from the temperature obtained by adding 150 ° C. to the annealing point temperature of the sheet glass SG. A temperature range from the strain point temperature of the glass SG to a temperature subtracted by 200 ° C. is determined. At this time, at least in the temperature region, the cooling rate at the center in the width direction of the sheet glass SG is faster than the cooling rate at both ends of the sheet glass SG, and the temperature at the center in the width direction of the sheet glass SG is the sheet glass SG. It is preferable to change the sheet glass SG from a state higher than the both ends to a state where the temperature at the center is lower than both ends. Thereby, it is possible to cause a tensile stress to act in the flow direction (first direction) of the sheet glass SG at the center in the width direction of the sheet glass SG. By applying a tensile stress in the flow direction of the sheet glass SG, it is possible to further suppress the warpage of the sheet glass SG and eventually the glass plate.
In the slow cooling step, the temperature of the central portion of the sheet glass SG is suppressed from the occurrence of the wave-shaped deformation as described above in the adjacent region adjacent to the portion of the sheet glass SG that is nipped and flows. The peripheral speed of the feed roller provided downstream from the position at which the annealing point becomes the temperature is provided in a temperature region in which the temperature of the central portion of the sheet glass SG is not less than the glass transition temperature and not more than the softening point temperature. It is preferably faster than the peripheral speed of the feed roller, for example, 0.03 to 2% faster. By adjusting the peripheral speed of the feed roller in this way, a tensile stress can be exerted in the flow direction (first direction) of the sheet glass SG.

(Preferred form of glass plate)
The preferable form of the glass plate manufactured using the manufacturing method of the glass plate manufacturing apparatus and glass plate which concerns on this embodiment is demonstrated below. Note that the present invention is not limited to the following form.

  This embodiment is suitable for manufacturing a glass plate having a glass plate thickness of 0.01 mm to 1.5 mm. The thinner the glass plate, the smaller the amount of heat held by the glass. Therefore, temperature control of the sheet glass in the slow cooling space (here, temperature control in the width direction of the sheet glass as well as temperature control in the first direction of the sheet glass is included) ) Becomes difficult. Therefore, in manufacturing a glass plate having a plate thickness of 0.01 to 0.5 mm, there is a great merit in applying the present invention that can stabilize the forming space S1 and the slow cooling space S2. For the reasons described above, the present invention is also suitable for producing a glass film having a very small glass holding heat of 0.01 mm to 0.1 mm.

  The larger the glass plate, the more easily the plane distortion occurs, and the temperature control of the above-described sheet glass SG becomes difficult. Therefore, the effect of the present invention is remarkable in a glass plate having a length of 2000 mm or more in the width direction and a length of 2000 mm or more in the longitudinal direction.

  Moreover, it is preferable to apply a glass plate to a liquid crystal display and organic EL display with a severe quality requirement. In addition, it can be applied to a display such as a cover glass and a portable terminal, a cover glass for a casing, a touch panel, and a glass plate of a solar cell. In particular, it is suitable for a liquid crystal display using a low temperature poly silicon (LTPS) / TFT (Thin Film Transistor), which is demanding for a glass plate.

  Further, the glass plate is heated from 50 ° C. to 550 ° C. at 10 ° C./min, held at 550 ° C. for 1 hour, then cooled to 50 ° C. at 10 ° C./min, and again raised to 550 ° C. at 10 ° C./min. It is preferable that the heat shrinkage rate when the temperature is lowered to 50 ° C. at 10 ° C./min is 100 ppm or less after being heated and held at 550 ° C. for 1 hour. More preferably, it is 0-60 ppm, More preferably, it is 0-40 ppm, More preferably, it is 0-20 ppm.

The thermal contraction rate is calculated as Elongation / Initial length × 10 ⁶ (ppm). As a method for measuring the heat shrinkage rate, there are the following methods. First, put parallel marking lines on both ends of the glass plate using a diamond pen. Next, the glass plate is cut in half so as to be perpendicular to the marking line, and one is heat-treated (as described above, the heat treatment at 550 ° C. for 1 hour is repeated twice). And the glass plate after heat processing and the other glass plate are put together, and the gap | deviation amount of a marking line is measured.

  The variation in the heat shrinkage rate is more likely to cause a display defect in the display panel than when the heat shrinkage rate is high or low, particularly when a TFT is formed on a glass plate in the production of a display. In this respect, it is important to suppress variations in the heat shrinkage rate. The variation in the heat shrinkage rate of the glass plate manufactured in the embodiment is preferably ± 2.85% or less. Here, the variation in the heat shrinkage rate means that when the heat shrinkage rate is measured by the above method at three positions in the width direction of the glass plate (for example, the position of the central portion and the position in the vicinity of both end portions in the width direction). The upper limit (+) and lower limit (-) where the measured value at the position fluctuates with respect to these average values. The variation in thermal shrinkage is preferably less than ± 2.80%, more preferably ± 2.75% or less, and even more preferably ± 2.65% or less.

  Moreover, it is preferable that the maximum value of the plane distortion of a glass plate is 0-1.7 nm. Preferably it is 0-1.5 nm, More preferably, it is 0-1.0 nm, More preferably, it is 0-0.7 nm. The plane strain can be measured with a birefringence measuring apparatus manufactured by UNIOPT.

  Here, since the liquid crystal display and the organic EL display are required to be assembled with high precision, the present invention that can reduce the variation in the thermal shrinkage of the glass plate used for the liquid crystal display or the organic EL display It is particularly suitable for the production of a glass plate for a glass or a glass plate for an organic EL display.

  The warpage of the glass plate, when measured by the following method, has a maximum value of warpage ranging from 0 to 0.2 mm, preferably 0 to 0.15 mm, preferably 0 to 0.1 mm. More preferably, it is more preferably 0 to 0.05 mm, and still more preferably 0 to 0.05 mm.

  For the measurement of warpage, first, a plurality of small plates (about 400 mm square) are cut out from a glass plate. Next, for each of the small plates, the warpage of the four corners and the four central portions is measured on each of the front and back sides (that is, a total of 16 warpages are measured). For example, when the warpage of 8 small plates is measured, measurement data of 128 warpages is obtained at 16 locations × 8. And it assumes that the maximum value in the said measurement data is the above-mentioned range. In the present embodiment, the maximum value of warpage measured with a plurality of small plates is used as the warpage of the glass plate.

Moreover, as a glass plate for flat panel displays (a liquid crystal display, a plasma display, etc.), the glass plate is a mass% display and includes the following components.
SiO ₂ : 50 to 70% by mass,
Al ₂ O ₃ : 5 to 25% by mass,
B ₂ O ₃ : 0 to 15% 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,
ZrO _2: 0 wt%.

The glass plate used for the organic EL display, the glass plate on which LTPS / TFT is formed, or the glass plate on which the oxide semiconductor is formed is hotter than the glass plate on which α-Si (amorphous silicon) / TFT is formed. The shrinkage rate is required to be small. In order to reduce the thermal shrinkage rate, the time for the slow cooling step of the glass plate may be increased or the strain point temperature of the glass may be increased. However, if the time for the slow cooling step of the glass plate is lengthened, it is necessary to enlarge the production apparatus, which is not preferable. Examples of the glass plate having a small heat shrinkage rate include glass plates having the following composition and characteristics.
SiO _2: 52~78% by weight,
Al ₂ O ₃ : 3 to 25% by mass,
1 to 15% by mass of B ₂ O ₃
RO (however, RO is the total amount of all components contained in the glass plate among MgO, CaO, SrO and BaO): 3 to 20% by mass,
A glass plate having a strain point of 680 ° C. or higher and a thermal shrinkage measured by the method described above of 60 ppm or less.

Or
SiO _2: 57~75% by weight,
Al ₂ O ₃ : 8 to 25% by mass,
B ₂ O ₃ : 3 to 11% by mass (excluding 11% by mass),
CaO: 0 to 20% by mass,
MgO: 0 to 15% by mass,
Glass plate.

At this time, if one or more of the following conditions are satisfied, it is more suitable for a glass plate for LTPS / TFT.
In order to further increase the strain point temperature,
(SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is preferably 8 to 20 and / or SiO ₂ + Al ₂ O ₃ is preferably 75% by mass or more.
Moreover, the CaO _/ B 2 _{O 3} is preferably set to 0.6 or more.
Furthermore, in order to further increase the strain point temperature, the mass ratio (SiO ₂ + Al ₂ O ₃ ) / RO is preferably 7.5 or more.
Alternatively, in order to reduce the specific resistance of the glass, the Fe ₂ O ₃ preferably contains 0.01 to 1 wt%.
Further, the glass plate preferably has a CaO / RO of 0.65 or more in order to prevent an increase in the devitrification temperature while realizing a high strain point temperature.
In consideration of application to mobile devices such as mobile communication terminals, the total content of SrO and BaO is preferably 0 to 3.3% from the viewpoint of weight reduction.

Note that R ₂ O (where R ₂ O is the total amount of all components contained in the glass plate among Li ₂ O, Na ₂ O and K ₂ O) is eluted from the glass and deteriorates TFT characteristics. Therefore, when it is applied as a glass plate for a liquid crystal display, it is preferably substantially free (alkali-free glass). However, by deliberately containing a specific amount of the above components in the glass, the basicity of the glass is increased while suppressing the deterioration of the TFT characteristics, the oxidation of the metal whose valence fluctuates is facilitated, and the clarity is exhibited. It is possible. Moreover, since the specific resistance of glass can also be reduced, breakage of the melting tank in the melting step can be suppressed. Therefore, R ₂ O is 0 to 2.0%, more preferably 0.1 to 1.0%, and still more preferably 0.2 to 0.5%. Note that, among R ₂ O, it is preferable to contain K ₂ O which is most likely to be eluted from the glass and hardly deteriorate the TFT characteristics. The content of K ₂ O is 0 to 2.0%, more preferably 0.1 to 1.0%, and further preferably 0.2 to 0.5%.

Moreover, as a glass plate applied to a cover glass or a glass plate for a solar cell after chemical strengthening, for example, the glass plate is represented by mass% and includes the following components.
SiO ₂ : 50 to 70% by mass,
Al ₂ O ₃ : 5 to 20% by mass,
Na ₂ O: 6 to 30 wt%,
Li ₂ O: 0 to 8% by mass,
B ₂ O ₃ : 0 to 5% by mass,
K ₂ O: 0 to 10% by mass,
MgO: 0 to 10% by mass,
CaO: 0 to 20% by mass,
ZrO _2: 0 wt%.

(Feature)
The air flowing into the building from outside the building through gaps in the building contains particles such as dust, so if it adheres to the sheet glass in the slow cooling furnace or the glass plate after cutting, it can cause scratches. It is possible to become. Moreover, when the said particle | grain flows into the updraft generated along the sheet glass in a slow cooling furnace, it will be considered that a particle adheres to a sheet glass and forms a bubble and a protrusion on the sheet glass surface. In such a case, since the surface quality of the glass plate is deteriorated, it may be difficult to produce a stable glass plate.

  In addition, the inside of the forming furnace and the slow cooling furnace is controlled by a heater so that the temperature does not fluctuate. However, in the forming furnace and the slow cooling furnace, there is a gap in addition to the region where the sheet glass is cut. It is extremely difficult to eliminate them completely. For this reason, if air outside the building flows into the building, the relationship between the pressure difference between the furnace outer space and the furnace inner space is disrupted, and the air in the furnace outer space is molded through the gap between the molding furnace and the slow cooling furnace. There is a risk that it will flow into the furnace or the slow cooling furnace and reduce the accuracy of temperature management control in the molding furnace or the slow cooling furnace. At this time, the temperature of the air flowing into the molding furnace or the slow cooling furnace is lower than the temperature in the temperature controlled molding furnace or slow cooling furnace. That is, only the area | region which contacted the air which flowed in the said shaping | molding furnace or a slow cooling furnace among molten glass and sheet glass will be rapidly cooled. For example, when a certain region of molten glass is locally quenched in a forming furnace, the viscosity of only the region increases, and after being formed into a sheet glass, when the sheet glass is stretched downstream with a roller, the viscosity of the sheet glass is increased. Only the high region cannot be sufficiently stretched, causing a deviation in the thickness of the glass plate. Further, as described above, in the annealing furnace, the temperature profile in the width direction of the sheet glass is controlled in order to reduce warpage, plane distortion, and thermal shrinkage. Therefore, when a certain region of the sheet glass is locally cooled in the slow cooling furnace, the heat shrinkage rate is locally increased only in the region, and thus the heat shrinkage rate varies.

  In order to solve the above-described problem, it is preferable to suppress the air outside the building from flowing into the building by making the pressure inside the building higher than the pressure outside the building. However, if the air pressure inside the building is made higher than the air pressure outside the building, a large amount of air inside the building will flow out to the outside of the building, and the air pressure and temperature inside the building will fluctuate. There is. Alternatively, if the pressure in the furnace outer space and / or the cutting space becomes too high, the amount of air flowing from the furnace outer space and / or the cutting space into the furnace inner space increases, and an upward air flow along the sheet glass tends to occur. Become. Therefore, the difference between the atmospheric pressure inside the building and the atmospheric pressure outside the building is preferably more than 0 to 40 Pa. That is, in the atmospheric pressure control of the present embodiment, it is preferable to control the blower so that a value obtained by subtracting the atmospheric pressure P2 outside the building B from the atmospheric pressure P1 in the furnace exterior space S4 is greater than 0 and equal to or less than 40 Pa.

  And, by controlling as described above, in addition to suppressing quality deterioration due to particles, it is possible to suppress glass plate quality deterioration such as warpage and thermal shrinkage variation, satisfying the quality of particle, warp and thermal shrinkage variation. A glass plate can be manufactured stably.

  In addition, by suppressing fluctuations in the temperature of the forming space S1, variations in the thickness of the glass plate can be suppressed.

  Further, the slow cooling space S2 is a space including a region in which the temperature of the sheet glass SG becomes a temperature in the vicinity of the strain point temperature from the vicinity of the slow cooling point temperature, but by suppressing temperature fluctuations in the slow cooling space S2, Variation in thermal shrinkage can be reduced. In addition, in the annealing space S2, since the fluctuation | variation of the atmospheric temperature of the sheet glass SG vicinity which becomes more than an annealing point can be suppressed, a deformation | transformation and curvature of a glass plate can be suppressed. Moreover, since the fluctuation | variation of the atmospheric temperature of the sheet glass SG vicinity used as the strain point temperature or less can be suppressed in slow cooling space S2, the curvature of a glass plate etc. can be suppressed. Here, the sheet glass SG is one continuous plate until it is cut. Therefore, if the warp shape of the sheet glass changes in the region where the temperature of the sheet glass is equal to or lower than the strain point temperature, the sheet glass in the region where the temperature is higher than the strain point temperature is also affected, and variation in the thermal shrinkage rate occurs. . On the other hand, in this embodiment, it is possible to suppress variations in warpage, plane distortion, and thermal shrinkage by suppressing changes in the ambient temperature in a region where the temperature of the sheet glass SG is equal to or lower than the strain point temperature.

  It is difficult to completely eliminate the gap from the building walls. For this reason, it is thought that an updraft is generated also in the furnace outer space due to the chimney effect. In addition, since the atmospheric temperature becomes higher near the furnace wall, an upward air flow is likely to be generated. Further, convection also occurs when a gas having a high temperature flows in a region having a low temperature. This is because the ambient temperature on the inner wall side of the building is considered to be lower than the furnace wall side. In other words, a descending airflow is generated along the inner wall of the building and an upward airflow is generated along the furnace wall, thereby generating a large convection.

  Therefore, in the present embodiment, the blower is controlled so that the atmospheric pressure in the furnace external space S4 increases toward the upstream side in the first direction. Thereby, in the furnace exterior space S4, the air flow rising along the outer surface of the forming furnace wall 41 of the forming furnace 40 and the slow cooling furnace wall 51 of the slow cooling furnace 50 can be suppressed. Therefore, the temperature of the outer surface of the forming furnace wall 41 and the slow cooling furnace wall 51 can be stabilized as much as possible. Therefore, fluctuations in the temperature of the molding space S1 and the slow cooling space S2 can be suppressed.

  The furnace outer space S4 is divided into a molding furnace outer upper space S5, a molding furnace outer lower space S6, and a slow cooling furnace outer space S7. Therefore, even if an air flow rising along the outer surface of the forming furnace wall 41 or the slow cooling furnace wall 51 is generated, the range of the air flow in the first direction can be narrowed (that is, the air flow in each of the spaces S5 to S7). ). That is, since the atmospheric pressure in the furnace external space S4 is distributed among a plurality of spaces and is increased toward the upstream side, the pressure rises across the plurality of spaces (for example, in at least two spaces S5 to S7). It is possible to suppress the generation of a large air flow (such as crossing).

  Thereby, the temperature of the outer surface of the shaping | molding furnace wall 41 and the slow cooling furnace wall 51 becomes more stable. Therefore, the influence on the temperature in molding space S1 and slow cooling space S2 can be reduced, and the temperature of molding space S1 and slow cooling space S2 can be stabilized more.

(Modification)
While the present embodiment has been described with reference to the drawings, the specific configuration is not limited to the above-described embodiment, and can be changed without departing from the scope of the invention.

(Modification 1A)
FIG. 7 is a schematic diagram showing the inside of the building B according to the modification 1A.
The rising airflow generated along the sheet glass soars the dust contained in the glass chips generated when the sheet glass is cut and the air flowing into the building from the outside of the building. It will adhere to the flowing sheet glass. The glass chips adhering to the sheet glass form bubbles and protrusions on the surface of the sheet glass, and deteriorate the quality of the surface of the glass plate. Dust also reduces the quality of the surface of the glass plate. In addition, the air flowing from the outside of the building into the building interior varies greatly depending on the conditions outside the building (temperature, wind speed, etc.), so the air flows into the building interior from the outside of the building. It becomes difficult to control the pressure and temperature of the inner space.

  Therefore, in the atmospheric pressure control in the atmospheric pressure control process, it is preferable to perform control so that the atmospheric pressure P3 in the cutting space S3 is larger than the atmospheric pressure P2 outside the building B. Thereby, it can prevent that the air containing dust etc. flows into the cutting space from the outside of a building, and can suppress the fall of the surface quality of a glass plate by extension.

  In this case, a blower 424 for pressurizing the cutting space S3 is disposed outside the cutting space S3. The cutting space S3 is provided with a fourth pressure sensor (not shown) for detecting the atmospheric pressure P3 in the cutting space S3.

In addition, when the air pressure in the cutting space becomes equal to or higher than a predetermined pressure, an air flow flowing to the furnace (forming furnace and slow cooling furnace) is likely to be generated, and there is a concern that the temperature of the forming space and the slow cooling space may be affected.
Therefore, it is preferable to control the atmospheric pressure in the cutting space S3 so that the value obtained by subtracting the atmospheric pressure P2 outside the building B from the atmospheric pressure P3 in the cutting space S3 is greater than 0 and 40 Pa or less. That is, it is preferable to perform the atmospheric pressure control so that the following expression 2 is established.
(Formula 2) 0 <P3-P2 ≦ 40 Pa
Thereby, since the inflow of the air from the outside of the building B into the building B can be suppressed, it becomes easy to accurately perform the temperature control and the atmospheric pressure control of the cutting space S3 and consequently the building space S. Moreover, since the inflow of dust or the like into the cutting space S3 can be suppressed, it is possible to prevent the surface quality of the glass plate from deteriorating.

In addition to the above embodiment, in the atmospheric pressure control, the values detected by the fourth pressure sensor and the fifth pressure sensor (not shown) are monitored to control the blower 424 (that is, the atmospheric pressure in the cutting space S3 is controlled). The air pressure P4 in the slow cooling space S2 may be larger than the air pressure P3 in the cutting space S3. The fifth pressure sensor is a pressure sensor that detects the atmospheric pressure P4 in the slow cooling space S2.
Thereby, the airflow which flows from the cutting space S3 to the slow cooling space S2 can be suppressed. Further, the atmospheric pressure control may be performed so that the atmospheric pressure in the slow cooling space S2 increases toward the upstream side in the first direction. Thereby, the fluctuation | variation of the temperature of shaping | molding space S1 or slow cooling space S2 can be suppressed.

(Modification 1B)
In the above embodiment, the floors 411, 412 and 413 functioning as physical partition members are arranged to form a plurality of spaces. However, the present invention is not limited to this, and the upstream side in the first direction. If the atmospheric pressure control is performed so that the atmospheric pressure increases, the same effects as in the above embodiment are obtained.

(Modification 1C)
In the said embodiment, the furnace exterior space S4 is pressurized. However, it is not always necessary to make the pressure in the furnace outer space S4 larger than the pressure in the molding space S1 and the slow cooling space S2. For example, even if the pressure difference between the molding space S1 or the slow cooling space S2 and the pressure outside the furnace space S4 is reduced, the amount of air leaking from the pressure in the molding space S1 or the slow cooling space S2 can be reduced. It is effective because it can suppress the upward air flow that occurs along.

(Modification 1D)
FIG. 8 is a schematic diagram showing the inside of the building B according to the modification 1F. As shown in FIG. 8, the furnace external space S4 may be divided into three spaces, a forming furnace external space S10 including a forming furnace external upper space S5 and a forming furnace external lower space S6, and a slow cooling furnace external space S7. . Even in this case, the same effects as those of the above-described embodiment can be obtained.

  Further, it is not always necessary to increase the atmospheric pressure in the furnace external space S4 toward the upstream side in the first direction, and at least the atmospheric pressure in the molding furnace external space S10 is made higher than the atmospheric pressure in the slow cooling furnace external space S7. It is possible to suppress the generation of ascending airflow generated in the air. This is because the temperature difference between the temperature of the forming furnace wall 41 and the temperature of the slow cooling furnace wall 51 is particularly large, so that a larger upward air flow is likely to be generated from the slow cooling furnace wall 51 to the forming furnace wall 41. Further, as described above, in order to improve the quality of the glass plate, it is particularly preferable to reduce temperature fluctuations in the forming furnace 40 and the slow cooling furnace 50.

  Examples of the present invention will be described below.

(Example 1)
The pressure in the furnace outer space S4 was controlled so that the difference between the pressure in the furnace outer space S4 and the pressure P2 outside the building B was 5 Pa. And the glass plate for liquid crystal displays of thickness 0.7mm and magnitude | size 2200 mm x 2500 mm was manufactured. The content of each component of the glass plate was as follows.
SiO ₂ 60 mass%
Al ₂ O ₃ 19.5 mass%
B ₂ O ₃ 10% by mass
CaO 5% by mass
SrO 5% by mass
SnO ₂ 0.5% by mass

(Example 2)
A glass plate for a liquid crystal display was produced in the same manner as in Example 1 except that the difference between the pressure P1 in the furnace outer space S4 and the pressure P2 outside the building B was 20 Pa.

(Example 3)
A glass plate for a liquid crystal display was manufactured in the same manner as in Example 1 except that the difference between the pressure P1 in the furnace outer space S4 and the pressure P2 outside the building B was 35 Pa.

Example 4
A glass plate for a liquid crystal display was produced in the same manner as in Example 1 except that the difference between the pressure P1 in the furnace outer space S4 and the pressure P2 outside the building B was 50 Pa.

(Comparative Example 1)
Implemented except that the difference between the pressure P1 in the furnace outer space S4 and the pressure P2 outside the building B is -5 Pa (that is, the pressure P2 outside the building B is higher than the pressure in the furnace outer space S4). A glass plate for a liquid crystal display was produced in the same manner as in Example 1.

  And under the above conditions, the dispersion | variation in the heat shrink of the manufactured glass plate for liquid crystal displays was measured by the method mentioned above ((7) The method described in the preferable form of the glass plate). Moreover, when the surface of the glass plate for liquid crystal displays was observed visually and it was not able to confirm a crack, it was evaluated as NG when a crack was confirmed and it was evaluated. Table 1 below shows the measurement results of Examples 1 to 4 and Comparative Example 1.

As described above, if the atmospheric pressure in the furnace exterior space S4 is controlled so that 0 <P1-P2, the generation of scratches on the glass plate surface can be suppressed. Moreover, if the atmospheric pressure in the furnace outside space S4 is controlled so that 0 <P1-P2 ≦ 40 Pa, the variation in the thermal contraction rate can be further suppressed. The content of each component of the glass plate _{(wt%) is, SiO 2 61%, Al 2} O 3 19.5%, B 2 O 3 10%, CaO 9%, SnO 2 0.3%, R 2 Even if O was 0.2%, the same result as above was obtained.

40 Molding furnace 50 Slow cooling furnace 100 Glass plate manufacturing apparatus 310 Molded body B Building MG Molten glass

The first aspect of the present invention is a method for producing a glass plate. The manufacturing method includes a melting step of melting a glass raw material to form molten glass, and supplying the molten glass to a molded body disposed in a molding space surrounded by a molding furnace wall that is a furnace wall of a molding furnace. A step of forming a sheet glass from molten glass in the molded body using a downdraw method, and a slow cooling furnace which is a space located below the molding space and is a furnace wall of the slow cooling furnace A slow cooling step of slow cooling in a slow cooling space surrounded by walls, and a cutting step of cutting the slowly cooled sheet glass in a cutting space located below the slow cooling furnace to form a glass plate.
Above the cutting space within the building space defined by the inner wall surface of the building that houses the molding space, the slow cooling space, and the cutting space, the outer surface of the molding furnace wall, and the outer surface of the slow cooling furnace wall. The atmospheric pressure control is performed so that the atmospheric pressure in the furnace outer space is larger than the atmospheric pressure outside the building. In the atmospheric pressure control, when the atmospheric pressure in the furnace outer space is P1 and the atmospheric pressure outside the building is P2, the atmospheric pressure in the furnace outer space is controlled so that the relationship 0 <P1-P2 ≦ 40 Pa is satisfied. Yes.

The second aspect of the present invention is a glass plate manufacturing apparatus. The manufacturing apparatus includes a forming furnace that is formed by surrounding a forming space for forming a sheet glass from molten glass with a forming furnace wall, and a slow cooling that gradually cools the sheet glass so as to be positioned below the forming furnace. A slow cooling furnace formed by surrounding the space with a wall of a slow cooling furnace, a cutting device disposed in a cutting space located below the slow cooling furnace and cutting the sheet glass that has been slowly cooled, the molding space, the slow cooling space, And the pressure in the furnace external space located above the cutting space in the building internal space defined by the inner wall surface of the building that houses the cutting space, the outer surface of the forming furnace wall, and the outer surface of the slow cooling furnace wall, Control means for performing atmospheric pressure control so as to increase with respect to the atmospheric pressure outside the building. The said atmospheric | air pressure control means controls the atmospheric | air pressure of a furnace exterior space so that the relationship of 0 <P1-P2 <= 40Pa is materialized, when the atmospheric pressure of a furnace exterior space is set to P1, and the atmospheric pressure outside a building is set to P2. .

Claims (16)

A melting step of melting glass raw material to form molten glass;
Supplying the molten glass to a molded body disposed in a molding space surrounded by a molding furnace wall that is a furnace wall of a molding furnace;
A molding step of molding sheet glass from molten glass in the molded body using a downdraw method;
A slow cooling step of slowly cooling the sheet glass in a slow cooling space that is a space located below the molding space and surrounded by a slow cooling furnace wall that is a furnace wall of the slow cooling furnace;
A step of cutting the slowly cooled sheet glass in a cutting space located below the slow cooling furnace to form a glass plate,
Above the cutting space within the building space defined by the inner wall surface of the building that houses the molding space, the slow cooling space, and the cutting space, the outer surface of the molding furnace wall, and the outer surface of the slow cooling furnace wall. The manufacturing method of the glass plate by which atmospheric | air pressure control is performed so that the atmospheric | air pressure of the furnace exterior space located may become large with respect to the atmospheric pressure outside the said building. In the atmospheric pressure control step,
When the pressure outside the furnace is P1, and the pressure outside the building is P2,
0 <P1-P2 ≦ 40Pa
To control the atmospheric pressure in the outside space of the furnace so that the relationship of
The manufacturing method of the glass plate of Claim 1. In the atmospheric pressure control step,
When the atmospheric pressure in the cutting space is P3 and the atmospheric pressure outside the building is P2,
0 <P3-P2 ≦ 40Pa
Further controlling the pressure in the cutting space so that the relationship of
The manufacturing method of the glass plate of Claim 1. In the atmospheric pressure control step, the atmospheric pressure of the cutting space is controlled so that the atmospheric pressure of the slow cooling space becomes larger than the atmospheric pressure of the cutting space.
The manufacturing method of the glass plate of Claim 3. In the atmospheric pressure control step, the atmospheric pressure in the furnace external space is controlled so that the atmospheric pressure in the furnace external space increases toward the upstream side in the flow direction of the sheet glass.
The manufacturing method of the glass plate of Claim 3 or 4. In the slow cooling step,
In the center of the width direction of the sheet glass, so that tension works in the flow direction of the sheet glass,
At least in the temperature region where the temperature of the central portion in the width direction of the sheet glass is a temperature obtained by adding 200 ° C. from the strain point temperature of the glass from the temperature obtained by adding 150 ° C. to the annealing point temperature of the glass,
The manufacturing method of the glass plate of any one of Claims 1-5 which controls temperature so that the cooling rate of the center part of the width direction of the said sheet glass may become faster than the cooling rate of the both ends of the said width direction. . In the region where the temperature of the center portion in the width direction of the sheet glass is equal to or higher than the softening point temperature of the glass, both ends in the width direction of the sheet glass are lower than the temperature of the center portion sandwiched between the both ends, and the center Control the temperature of the sheet glass so that the temperature of the part is uniform,
In the central portion of the sheet glass in the width direction, the temperature of the central portion of the sheet glass is less than the softening point temperature of the glass so that tension in the flow direction of the sheet glass works. Control the temperature of the sheet glass so that the temperature distribution in the width direction of the sheet glass becomes lower from the center toward the both ends,
In the temperature region where the temperature of the central portion of the sheet glass becomes the strain point temperature of the glass, the temperature of the sheet glass is controlled so that there is no temperature gradient between the both end portions and the central portion in the width direction of the sheet glass. The manufacturing method of the glass plate of any one of Claims 1-6.   In the central portion of the sheet glass in the width direction, in the region where the temperature of the central portion of the sheet glass is lower than the strain point temperature of the glass so that tension in the flow direction of the sheet glass works, from the both end portions of the sheet glass The manufacturing method of the glass plate of any one of Claims 1-7 which controls the temperature of the said sheet glass so that it becomes low toward the said center part.   In the slow cooling step, among the feed rollers that transport the sheet glass, the peripheral speed of the feed roller provided on the downstream side of the position where the temperature of the sheet glass becomes the slow cooling point temperature of the glass is set to the sheet glass. 9. The method according to claim 1, wherein the temperature is 0.03 to 2% faster than the peripheral speed of the feed roller provided in a temperature region in which the temperature is not lower than the glass transition temperature and not higher than the softening temperature of the glass. The manufacturing method of the glass plate of description. A molding furnace for forming a molding space for molding sheet glass from molten glass by surrounding the molding furnace wall;
A slow cooling furnace formed by surrounding a slow cooling space for gradually cooling the sheet glass with a wall of the slow cooling furnace so as to be positioned below the molding furnace,
A cutting device that is disposed in a cutting space located below the slow cooling furnace and that cuts the slowly cooled sheet glass;
Above the cutting space within the building space defined by the inner wall surface of the building that houses the molding space, the slow cooling space, and the cutting space, the outer surface of the molding furnace wall, and the outer surface of the slow cooling furnace wall. An apparatus for manufacturing a glass plate, comprising: an atmospheric pressure control unit configured to perform atmospheric pressure control so that an atmospheric pressure of a furnace outer space located is larger than an atmospheric pressure outside the building.   The said atmospheric | air pressure control means is a manufacturing apparatus of the glass plate of Claim 10 containing the air blower which sends air in the said furnace exterior space from the outside of the said building.   The atmospheric pressure control means includes a pressure sensor that is provided in the furnace external space and measures the atmospheric pressure of the furnace external space, and the atmospheric pressure in the furnace external space is outside the building by the detection result of the pressure sensor. The manufacturing apparatus of the glass plate of Claim 11 containing the control apparatus for driving the said air blower so that it may become large with respect to atmospheric pressure. Furthermore, in the slow cooling space, at the center in the width direction of the sheet glass, so that tension acts in the flow direction of the sheet glass,
At least in the temperature region where the temperature of the central portion in the width direction of the sheet glass is a temperature obtained by adding 200 ° C. from the strain point temperature of the glass from the temperature obtained by adding 150 ° C. to the annealing point temperature of the glass,
The temperature adjustment unit which temperature-controls so that the cooling rate of the center part of the width direction of the said sheet glass may become faster than the cooling rate of the both ends of the said width direction is described in any one of Claims 10-12. Glass plate manufacturing equipment. In the furnace space consisting of the molding space and the slow cooling space,
In the region where the temperature of the center portion in the width direction of the sheet glass is equal to or higher than the softening point temperature of the glass, both ends in the width direction of the sheet glass are lower than the temperature of the center portion sandwiched between the both ends, and the center Control the temperature of the sheet glass so that the temperature of the part is uniform,
In the central portion of the sheet glass in the width direction, the temperature of the central portion of the sheet glass is less than the softening point temperature of the glass so that tension in the flow direction of the sheet glass works. Control the temperature of the sheet glass so that the temperature distribution in the width direction of the sheet glass becomes lower from the center toward the both ends,
In the temperature region where the temperature of the central portion of the sheet glass becomes the strain point temperature of the glass, the temperature of the sheet glass is controlled so that there is no temperature gradient between the both end portions and the central portion in the width direction of the sheet glass. The manufacturing apparatus of the glass plate of any one of Claims 10-13 in which the temperature adjustment unit is provided. In the slow cooling space,
In the central portion of the sheet glass in the width direction, in the region where the temperature of the central portion of the sheet glass is lower than the strain point temperature of the glass so that tension in the flow direction of the sheet glass works, from the both end portions of the sheet glass The manufacturing apparatus of the glass plate of any one of Claims 10-14 in which the temperature adjustment unit which controls the temperature of the said sheet glass so that it becomes low toward the said center part is provided.   The slow cooling space is provided with a feed roller for transporting the sheet glass, and the feed roller provided on the downstream side of the feed roller from the position where the temperature of the sheet glass is the glass annealing point temperature. The peripheral speed of the sheet glass rotates 0.03 to 2% faster than the peripheral speed of the feed roller provided in a temperature region in which the temperature of the sheet glass is equal to or higher than the glass transition temperature and lower than or equal to the softening temperature of the glass. The manufacturing apparatus of the glass plate of any one of 10-15.

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