JP2014125363A - Glass substrate production apparatus, and production method of glass substrate for display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass substrate production apparatus capable of maintaining the quality of a glass plate by suppressing fluctuation of the temperature inside a furnace, and to provide a production method of a glass substrate for display.SOLUTION: A glass substrate production apparatus 300 for producing a glass substrate by a down-draw method includes a molding furnace 40 for molding a glass sheet by a down-draw method, an annealing furnace 50 for cooling the glass sheet G molded in the molding furnace 40, and a cutting chamber 60 for cutting the glass sheet G transferred continuously from the annealing furnace 50 to cut out the glass substrate. The cutting chamber 60 is provided in an underground space.

Description

  The present invention relates to a glass substrate manufacturing apparatus and a method for manufacturing a glass substrate for display.

  Conventionally, a down draw method is used as one method for forming a glass substrate used in a flat panel display such as a liquid crystal display.

  As equipment for forming a glass plate using the downdraw method, for example, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2009-196879), in a forming furnace, the molten glass is overflowed from the top so that Some include a molded body for forming a glass plate, a slow cooling furnace for slowly cooling the glass, and a cooling chamber.

  In recent years, glass substrates for liquid crystal displays have been required to reduce the absolute value of thermal shrinkage. For this purpose, glass having a high strain point in glass characteristics is formed by a downdraw method.

  However, even if glass with a high strain point is formed by the downdraw method, if the temperature conditions in the slow cooling furnace / cooling chamber are disturbed, not only the thermal shrinkage is reduced, but also the variation of the thermal shrinkage occurs in the plane of the glass substrate. There is also a problem that in-plane distortion increases.

  Therefore, the object of the present invention is to form a glass plate using the downdraw method, to reduce the absolute value of the thermal contraction of the glass plate using glass having a high strain point, and to reduce the variation of the thermal contraction in the plane. An object of the present invention is to provide a glass plate manufacturing apparatus and a glass plate manufacturing method for manufacturing a glass plate.

  The glass substrate manufacturing apparatus of the present invention is a glass substrate manufacturing apparatus using a downdraw method, and includes a forming furnace, a slow cooling furnace, and a cutting device. The forming furnace forms a glass sheet by a downdraw method. The slow cooling furnace cools the glass sheet formed in the forming furnace. The cutting chamber is formed spatially continuously with the slow cooling furnace. The cutting chamber is formed in the underground space, and a cutting device for cutting the glass sheet transferred from the slow cooling furnace into the size of the glass substrate is provided.

  Moreover, the glass substrate manufacturing apparatus includes a control unit. The control unit controls the atmospheric pressure from the forming furnace to the cutting chamber, and controls the atmospheric pressure in the slow cooling furnace to be higher than the atmospheric pressure in the underground space where the cutting chamber is provided. Moreover, an air current blocking means for suppressing an air current generated between the slow cooling furnace and the cutting chamber is provided.

  This glass substrate manufacturing method is a glass substrate manufacturing method by a downdraw method, and includes a melting step, a supplying step, a forming step, a slow cooling step, and a cutting step, and further includes atmospheric pressure control. In the melting step, the glass raw material is melted to obtain molten glass. In the supplying step, the molten glass is supplied to a molded body disposed inside the molding furnace. In the forming step, a glass sheet is formed in the formed body. In the slow cooling step, the temperature of the glass sheet transferred from the forming step is lowered by passing through a slow cooling furnace. In the cutting step, the glass sheet is cut into a glass substrate in a cutting chamber provided in the underground space. The atmospheric pressure in the slow cooling furnace is controlled to be higher than the atmospheric pressure in the underground space.

  In the present invention, a glass substrate with reduced heat shrinkability of the glass substrate can be provided.

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 substrate 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 internal space of the building for showing a furnace exterior space.

Hereinafter, a glass substrate manufacturing method for manufacturing a glass substrate using the glass manufacturing apparatus 100 of the present embodiment will be described with reference to the drawings.
(1) Overview of Glass Substrate Manufacturing Method FIG. 1 is a partial flowchart of the glass substrate manufacturing method according to this embodiment. Hereinafter, the manufacturing method of a glass substrate is demonstrated using FIG.

  As shown in FIG. 1, the glass substrate is manufactured through various processes including a melting process T1, a clarification process T2, a molding process T3, a slow cooling process T4, and a cutting process T5. Hereinafter, these steps will be described.

In the melting step T1, molten glass is obtained by heating and melting the glass raw material. Glass raw material _is made of the composition, such as SiO 2, _Al 2 _{O 3, specifically,} SiO 2, _Al 2 _{O 3} is contained more than 80 mol%.

  In the clarification step T2, the molten glass is clarified. Specifically, the gas component contained in the molten glass is released from the molten glass, or the gas component contained in the molten glass is absorbed into the molten glass. The clarified molten glass is supplied to the molding apparatus 300 through the transfer tube 205.

  In the forming step T3, the molten glass is formed into a glass sheet G. In the present embodiment, the molten glass forms a plate-like sheet glass G by an overflow downdraw method.

  In the slow cooling step T4, the sheet glass G formed in the forming step T5 is cooled.

  In the cutting step T5, the cooled sheet glass G is cut every predetermined length to manufacture a glass substrate.

  The glass substrate G1 (see FIG. 3 and the like) cut for each predetermined length is further cut and ground, polished, cleaned, and inspected to become a glass substrate, which is a flat such as a liquid crystal display. Applies to panel displays.

(2) Outline of Glass Substrate Manufacturing Apparatus 100 FIG. 2 is a schematic diagram mainly showing a melting apparatus 200 included in the glass substrate manufacturing apparatus 100. FIG. 3 is a schematic view showing the inside of the building B in which various devices included in the glass substrate manufacturing apparatus 100 are accommodated or attached (in FIG. 3, the forming apparatus 300, the furnace 30, and the like are shown). Shown by schematic cross-sectional schematic). Hereinafter, the glass substrate manufacturing apparatus 100 will be described.

  The glass substrate manufacturing apparatus 100 mainly includes a melting apparatus 200 (see FIG. 2), a forming apparatus 300 (see FIGS. 2 and 3), and a cutting apparatus 400 (see FIG. 3). The melting device 200, the molding device 300, and the cutting device 400 are disposed in the building B (see FIG. 3).

(2-1) Structure of dissolution apparatus 200 The dissolution apparatus 200 is an apparatus for performing the dissolution process T1 and the clarification process T2.

  As shown in FIG. 2, the dissolution apparatus 200 includes a dissolution tank 201, a clarification tank 203, and a transfer pipe 205.

  The melting tank 201 is a tank for melting the glass raw material. In the dissolution tank 201, the dissolution step T1 is performed.

  The clarification tank 203 is a tank for removing bubbles from the molten glass melted in the melting tank 201. By further heating the molten glass fed from the melting tank 201 in the clarification tank 203, defoaming of bubbles in the molten glass is promoted. In the clarification tank 203, a clarification step T2 is performed.

(2-2) Configuration of Molding Device 300 FIG. 4 is a schematic side view of the molding device 300.

  The molding apparatus 300 is an apparatus for performing the molding process T3 and the slow cooling process T4.

  The molding apparatus 300 includes a molded body 310, an atmosphere partition member 320, a cooling roller 330, a cooling unit 340, feed rollers 350a to 350h, and temperature adjustment units 360a to 360g (see FIG. 4). Hereinafter, these configurations will be described.

(2-2-1) Molded body 310
As shown in FIG. 3, the molded body 310 is located in an upper portion of the molding apparatus 300 and has a function of molding the molten glass flowing from the melting apparatus 200 into a band-shaped glass (that is, a glass sheet G). The molded body 310 has a wedge-shaped cross section cut in the vertical direction, and is formed of bricks.

  As shown in FIG. 4, a supply port 311 is formed in the molded body 310 on the upstream side in the flow path direction through which the molten glass flows. Molten glass flowing from the transfer pipe 205 of the melting device 200 is supplied to the molded body 310 (forming device 300) through the supply port 311.

  A groove 312 (see FIG. 3) opened upward is formed in the molded body 310 along the longitudinal direction thereof. The groove 312 is formed so as to gradually become shallower from the upstream side in the flow direction of the molten glass toward the downstream side.

(2-2-2) 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 so as to be substantially horizontal 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 air.

(2-2-3) 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 lowers the molten glass to the downstream side in the first direction, thereby forming the glass sheet G to a desired thickness and cooling it. In the following description, the direction in which the glass sheet G flows is defined as the first direction.

  Here, the molded body 310, the atmosphere partition member 320, and the cooling roller 330 are covered with the molding furnace 40 disposed in the building B. The molding furnace 40 has a rectangular parallelepiped shape in which a space opened downward is formed. In the molding furnace 40, a molding process T3 is performed.

(2-2-4) Cooling unit 340
The cooling unit 340 is disposed below the molding furnace 40. The cooling unit 340 cools the glass sheet G flowing through the cooling roller 330 to the downstream side in the first direction. This cooling effect can reduce the warpage of the glass plate.

(2-2-5) Feed rollers 350a to 350h
The feed rollers 350a to 350h are disposed below the cooling roller 330 with a predetermined interval in the first direction. Further, the feed rollers 350a to 350h are disposed on both sides in the thickness direction of the glass sheet G, respectively. The feed rollers 350a to 350h pull the glass sheet G downstream in the first direction.

(2-2-6) Temperature adjustment units 360a to 360g
The temperature adjustment units 360a to 360g are devices for adjusting the ambient temperature in the vicinity of the glass sheet G (specifically, keeping warm or raising the temperature), and a plurality of the temperature adjustment units 360a to 360g are arranged in the width direction of the glass sheet G. Has been.

  Here, the feed rollers 350 a to 350 h and the temperature adjustment units 360 a to 360 g are covered with the slow cooling furnace 50. The slow cooling furnace 50 has a substantially rectangular parallelepiped shape in which a space penetrating in the first direction is formed.

  In the slow cooling furnace 50, the glass sheet G is gradually cooled by the feed rollers 350a to 350h being pulled downstream in the first direction (the transition from the viscous region to the elastic region through the viscoelastic region). Slow cooling step T4 is performed. In the slow cooling step T4, the temperature adjustment units 360a to 360g adjust the atmospheric temperature of the glass sheet G so that the internal distortion of the glass plate is suppressed.

  In addition, a plurality of temperature sensors as atmosphere temperature detecting means for detecting the atmosphere temperature of the glass sheet G are arranged in the vicinity of each of the temperature adjustment units 360a to 360g along the width direction of the glass sheet G. Here, the plurality of temperature sensors are referred to as a temperature sensor unit 380 (see FIG. 5).

(2-3) Cutting device 400
In the cutting device 400, the cutting step T5 is performed. The cutting device 400 is provided in the cutting chamber 60 provided in the underground space D2. The cutting device 400 is a device that cuts the plate-like glass sheet G flowing down downstream in the first direction in the forming device 300 from a direction perpendicular to the longitudinal surface thereof. Thereby, the plate-shaped glass sheet G becomes a plurality of glass substrates G1 having a predetermined length.

(3) Control device 500
FIG. 5 is a control block diagram of the control device 500.

  First, 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 substrate manufacturing apparatus 100.

  Specifically, as shown in FIG. 5, the control device 500 controls the temperature adjustment of the temperature adjustment units 360 a to 360 g, the first for driving the cooling roller 330, the feed rollers 350 a to 350 h, the cutting device 400, and the like. The drive control of the drive unit 390 (for example, motor) and the 2nd drive unit 450 (after-mentioned) is performed. The temperature adjustment control of the temperature adjustment units 360a to 360g is performed based on the ambient temperature of the glass sheet G detected by the temperature sensor unit 380.

  In addition, the control device 500 further controls the atmospheric pressure in the internal region of the building B. This will be described later. The various sensors shown in FIG. 5 will also be described later.

(4) Molding of glass sheet G in molding apparatus 300 Hereinafter, a process in which the glass sheet G is molded in the molding apparatus 300 will be described.

  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 of 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 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 plate-like glass sheet G and cooled. The glass sheet G pulled down by the cooling roller 330 is further pulled down by the feed rollers 350a to 350h and gradually cooled. The glass sheet G pulled down by the feed rollers 350a to 350h is then cut into a plurality of glass substrates G1 by a cutting device 400 at predetermined lengths.

(5) Control of atmospheric pressure in the inner region of the building B FIG. 3 is a schematic diagram showing the inner region of the building B for showing the furnace outer region S.

  In the present embodiment, the furnace 30 including the molding furnace 40 in which the molded body 310 and the like are disposed, the slow cooling furnace 50 in which the feed rollers 350a to 350h and the like are disposed, and the inner surface portion 10 of the building B covering the furnace 30 (on the cover portion). The external pressure S of the furnace external space S, that is, the internal space of the building B and the external space of the furnace 30 is controlled.

  The furnace outer space S is divided into a plurality of spaces by floors 411, 412 and 413 arranged in the building B. That is, the floors 411, 412 and 413 have a role as partition members for dividing the furnace outside space S into a plurality of spaces.

  Specifically, the furnace outer space S is divided by the floors 411, 412, and 413 into a molding furnace outer upper space S1, a molding furnace outer lower space S2, a slow cooling furnace outer space S3, and a slow cooling furnace lower space S4. .

The forming furnace exterior upper space S1 is a space sandwiched between the floor 411 and the upper part of the building B in the furnace exterior space S. The floor 411 is disposed at a height position close to the position of the upper portion of the molded body 310 and close to the upper portion of the furnace 40.
On the floor 411, the dissolution tank 201, the clarification tank 202, and the transfer pipe 205 shown in FIG. 2 are installed so as to have a predetermined height difference. Specifically, on the floor 411, the molten glass is transferred from the melting furnace 201 to the molded body 310 so as to be lowered by a predetermined height, and is supplied to the supply port 311 of the molded body 310.

  The molding furnace outer lower space S2 is a space formed downstream of the molding furnace outer upper space S1 in the first direction. Specifically, the forming furnace outside lower space S <b> 2 is a space sandwiched between the floor 411, the floor 412, and the cooling unit 340 in the furnace outside space S. Further, the molding furnace outer lower space S2 includes a region corresponding to the installation position of the molding furnace 40 (specifically, the installation position and the height position of the molding furnace 40 are the same). The floor 412 is disposed at a height position close to the lower portion of the cooling unit 340.

  The slow cooling furnace external space S3 is a space formed on the downstream side in the first direction with respect to the molding furnace external lower space S2. The slow cooling furnace outer space S3 is a space sandwiched between the floor 412 and the floor 413 in the furnace outer space S. The slow cooling furnace external space S3 includes a region corresponding to the installation position of the slow cooling furnace 50 (specifically, the installation position and the height position of the slow cooling furnace 50 are the same). The floor 413 is arranged at a height position close to the ground surface.

  The atmospheric temperature of the glass sheet G flowing through the in-furnace space D1 of the slow cooling furnace outer space S3 is the same as that of the slow cooling furnace outer space S3 (that is, the distance from the lower surface of the floor 412 to the upper surface of the floor 413). For example, the space where the temperature is 800 ° C. to 250 ° C., or the slow cooling furnace outer space S3 is a region where the glass sheet G flowing in the furnace space D1 is (slow cooling point + 5 ° C.) to (strain point−50 ° C.). It is a space to include.

The slow cooling furnace lower space S4 is a space formed on the downstream side in the first direction of the slow cooling furnace external space S3. The slow cooling furnace lower space S4 is defined by the floor 413 located at substantially the same height as the ground surface in the furnace outer space S and the outer surface 10B of the underground structure of the building B, and excludes the cutting chamber 60 provided with the cutting device 400. It is.
In the cutting chamber 60, the glass sheet G that flows in the first direction in the molding apparatus 300 is cut into predetermined lengths by the cutting apparatus 400.

(5-2) Atmospheric pressure control In the atmospheric pressure control, by pressurizing the furnace external space S, the atmospheric pressure in the furnace external space S is increased toward the upstream side in the first direction. Specifically, in the atmospheric pressure control, the atmospheric pressure in a plurality of spaces (that is, the upper space S1 outside the molding furnace, the lower space S2 outside the molding furnace, the outer space S3 of the slow cooling furnace, and the lower space S4 of the slow cooling furnace) is independently controlled. By doing this, the value of the atmospheric pressure in each space is such that the forming furnace outside upper space S1> the forming furnace outside lower space S2> the slow cooling furnace outer space S3> the slow cooling furnace lower space S4.

  In order to perform the atmospheric pressure control, the outer side of the molding furnace outer space S1, the molding furnace outer lower space S2, the slow cooling furnace outer space S3, and the outer side of the slow cooling furnace lower space S4 (that is, the outside through the wall portion of the building B). Blowers 421, 422, 423, and 424 for pressurizing each space are arranged in the space.

  Further, in order to perform atmospheric pressure control, a first pressure sensor 431 which is a detecting means for detecting the atmospheric pressure in the molding furnace outer upper space S1, the molding furnace outer lower space S2, the slow cooling furnace outer space S3, and the slow cooling furnace lower space S4, A two pressure sensor 432, a third pressure sensor 433, and a fourth pressure sensor 434 (see FIG. 5) are arranged in each space.

  In the atmospheric pressure control, by detecting the atmospheric pressure in the outer space S1 outside the molding furnace, the lower space S2 outside the molding furnace, the outer space S3 of the slow cooling furnace, and the lower space S4 of the slow cooling furnace, the atmospheric pressure in the outer space S is upstream in the first direction. The atmospheric pressure is increased. Specifically, in order to drive the blowers 421, 422, 423, and 424 by detecting the atmospheric pressure in the molding furnace outer upper space S1, the molding furnace outer lower space S2, the slow cooling furnace outer space S3, and the slow cooling furnace lower space S4. The second drive unit 450 (for example, a motor) is controlled (for example, the number of rotations in the case of a motor). Note that the detected atmospheric pressure data of each of the spaces S 1, S 2, S 3, and S 4 is stored as data in the control device 500.

Moreover, atmospheric pressure control is performed so that the pressure in the slow cooling furnace (furnace space D1) spatially continuous with the underground space D2 in which the cutting chamber is provided is higher than the pressure in the underground space D2. Specifically, the pressure in the in-furnace space D1 corresponding to the inside of the slow cooling furnace can be maintained by increasing the pressure in the slow cooling furnace outer space S3. Thereby, the pressure of the furnace space D1 is made higher than the underground space D2, and the inflow of air from the cutting chamber 60 to the slow cooling furnace 50 is suppressed. The pressure control in the furnace space D1 may be performed by pressure control in the slow cooling furnace outer space or pressure control in the cutting chamber. For example, the pressure balance may be controlled by directly controlling the pressure in the furnace space D1 and relatively lowering the pressure in the underground space D2.
Further, the pressure in the underground space D2 where the cutting chamber is provided is preferably controlled to be equal to or higher than the atmospheric pressure, and may be controlled to be substantially equal to the pressure in the slow cooling furnace lower space S4. This is to reduce the inflow and outflow of air between the slow cooling furnace lower space S4 and the underground space D2.

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

  The thickness of the glass plate is assumed to be 0.1 mm to 1.5 mm. And a more preferable upper limit will be 0.4 mm, 0.5 mm, 0.8 mm, 1.0 mm, and 1.2 mm if said in a preferable order. Furthermore, more preferable lower limit values are 0.3 mm, 0.2 mm, and 0.1 mm in a preferable order.

  Moreover, the magnitude | size of the glass plate assumes that the length of the width direction is 500 mm-3500 mm, and the length of a longitudinal direction is 500 mm-3500 mm. In addition, when a glass plate enlarges, it is necessary to enlarge a glass manufacturing apparatus. That is, since the furnace 30 including the forming furnace 40 and the slow cooling furnace 50 also tends to be enlarged, the furnace external space S is widened. When the furnace outside space S is widened, the upward air flow generated in the furnace outside space S is likely to be large. Moreover, the spatial connection part of the cutting chamber 60 and the slow cooling furnace 50 becomes large, and the movement of the air of the cutting chamber 60 and the slow cooling furnace tends to occur. That is, as the glass plate becomes larger, the temperature in the furnace and the furnace wall tends to become unstable, and the possibility that the temperature of the glass sheet G passing through the furnace fluctuates increases. Therefore, when the length of the glass plate in the width direction is 2000 mm or more, the effect of the present invention becomes remarkable. Furthermore, the effect of the present invention becomes more remarkable as the length in the width direction of the glass plate is 2500 mm or more and 3000 mm or more. In addition, the present invention is particularly useful when manufacturing a glass plate (for example, a glass plate for a liquid crystal display or a cover glass) that requires mass production.

  The types of glass plates are assumed to be borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, soda lime glass, alkali silicate glass, alkali aluminosilicate glass, and alkali aluminogermanate glass.

  Moreover, it is assumed that the maximum value of the internal strain of the glass plate is 1.7 nm or less. Preferably, it is 1.5 nm or less, More preferably, it is 1.0 nm or less, More preferably, it is 0.7 nm or less. The internal strain was measured with a birefringence measuring apparatus manufactured by UNIOPT.

  Further, it is assumed that the glass plate is used for flat panel displays (liquid crystal displays, plasma displays, etc.) used for AV devices (mobile terminals, etc.), panels for solar cells, and cover glasses.

(7) Features (7-1) In the present invention, a cutting chamber for cutting a glass substrate from a glass sheet is formed in the underground space, and the atmospheric pressure balance between the furnace internal space that is the inside of the slow cooling furnace and the underground space is controlled. . That is, a cutting chamber that is spatially continuous with a slow cooling furnace that cools the glass sheet is formed in the underground space to stabilize the airflow in the cutting chamber. And the full length of a slow cooling furnace is lengthened, without changing the height position of a molded object with the past. Thereby, variation in in-plane strain of the glass substrate and thermal shrinkage of the glass substrate that can occur in the annealing process of the display panel can be reduced.

  In the present embodiment, first, the air flow in the cutting chamber 60 is stabilized by providing the cutting chamber 60 in the underground space D2. And the structure which lengthened the full length of the 1st direction of the slow cooling furnace is provided, without raising the height position of the molded object 310 by providing the cutting chamber 60 in the basement.

  By stabilizing the airflow in the cutting chamber 60, air flowing from the cutting chamber 60 into the slow cooling furnace 50 is suppressed. Thereby, while keeping the temperature in the lowest stage of a slow cooling furnace high, the variation in temperature can be made small. As a result, the temperature of the glass sheet G can be kept higher than the room temperature even in the lowest stage of the slow cooling furnace. For example, the temperature of the glass sheet G can be set to 250 ° C. to 350 ° C. from the lowest stage of the slow cooling furnace to the outlet. Thereby, even in the second half of the slow cooling furnace, the temperature of the glass sheet G can be maintained in a temperature range effective for reducing the thermal shrinkage of the glass, for example, 450 ° C. to 650 ° C. Therefore, a glass substrate having a small thermal shrinkage is manufactured. be able to. As a method of measuring thermal shrinkage, the amount of shrinkage when annealing was repeated twice in an annealing apparatus was raised from room temperature to 550 ° C. (temperature raising time: 10 ° C./min) and held at 550 ° C. for 1 hour. It measured by the well-known marking method.

  In this embodiment, by providing the slow cooling furnace long, the residence time of the glass sheet G in the slow cooling furnace becomes long, and the thermal contraction of the glass substrate can be controlled. That is, it is possible to produce a glass substrate having a small heat shrinkage, for example, a heat shrinkage of 75 ppm or less, preferably 50 ppm or less, which is suitable for producing LTPS-TFT elements used in high-definition display panels.

  And in this embodiment, since it is not necessary to raise the height position of the molded object 310, it is not necessary to raise the height position of a melting furnace or an electrical path. Therefore, the structure is advantageous in terms of the earthquake resistance of the building without increasing the size of the entire building.

  Next, pressure control of the furnace outer space S will be described. In the present embodiment, the air inside the furnace 30 can be prevented from leaking into the furnace external space S in the furnace external space. Thereby, generation | occurrence | production of the updraft which rises along the surface of the glass sheet G can be suppressed, and the fluctuation | variation of the temperature inside the furnace 30 can be suppressed.

  Here, it is considered that the ascending airflow is generated not only ascending airflow rising along the surface of the glass plate but also along the outer surface of the furnace wall of the furnace. When an updraft is generated along the outer surface of the furnace wall of the furnace, it is assumed that the temperature of the outer surface of the furnace wall, and thus the inner surface, fluctuates. In this case, there is a concern that the temperature in the furnace may change. In this case, there is a concern that the quality of the manufactured glass plate is affected.

  The updraft that rises along the surface of the glass plate is considered to be generated by a chimney effect or by convection caused by a gas having a high temperature flowing in a region having a low temperature. Here, since it is difficult to completely eliminate the gap from the furnace wall, an upward air flow is generated by the chimney effect. Note that the upward airflow is likely to be generated in a region where a gap between members such as rollers provided in the furnace is large. Here, when the downdraw method is used, the region to be the product at the center of the glass plate is formed and gradually cooled without contact with the member. In other words, the members are not in contact with the vicinity of the product area at the center of the glass plate, the gap between the members becomes large, and an upward airflow is likely to occur.

  On the other hand, it is difficult to completely eliminate the gap from the inner wall of the building. For this reason, it is thought that an updraft is also generated in the space outside the furnace 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.

  On the other hand, in the present embodiment, the air flow rising along the outer surface of the furnace wall of the furnace 30 in the furnace external space S can be suppressed by increasing the pressure in the furnace external space S toward the upstream side. Thereby, the temperature of the outer surface of the furnace wall of the furnace 30 can be stabilized as much as possible. Therefore, the fluctuation | variation of the temperature inside the furnace 30 can be suppressed further.

(7-2)
In the present embodiment, floors 411, 412, and 413 that function as partition members for dividing into a plurality of spaces (in this embodiment, four spaces S1, S2, S3, and S4) are disposed in the furnace external space S. Has been.

  Here, the floors 411, 412 and 413 make it easy to divide the furnace exterior space S into a plurality of spaces. That is, the atmospheric pressure control is facilitated.

(7-3)
In the present embodiment, the furnace outer space S is divided into a molding furnace outer upper space S1, a molding furnace outer lower space S2, a slow cooling furnace outer space S3, and a slow cooling furnace lower space S4. Thereby, compared with the furnace exterior space S, the temperature difference of the 1st direction in the molding furnace exterior upper space S1, the molding furnace exterior lower space S2, the slow cooling furnace exterior space S3, and the slow cooling furnace downward space S4 becomes small. Therefore, even if an air flow rising along the outer wall of the furnace 30 is generated, the range of the air flow rising along the outer surface of the furnace wall of the furnace 30 can be narrowed (that is, the air in each of the spaces S1 to S4). Can keep the flow). That is, since the atmospheric pressure in the furnace outside space S is divided into a plurality of spaces and is increased toward the upstream side, the pressure rises across the plurality of spaces (for example, across at least two spaces S1 to S4). N) Generation of a large air flow can be suppressed. Thereby, the temperature of the outer surface of the furnace wall of the furnace 30 becomes more stable. Therefore, the influence on the temperature inside the furnace 30 can be reduced, and the temperature inside the furnace 30 can be further stabilized. Since the temperature inside the furnace 30 can be stabilized as much as possible, the temperature control of the glass sheet G can be accurately performed. Therefore, the internal distortion of the glass plate can be suppressed, and the quality of the glass plate can be improved.

(7-4)
In the present embodiment, the slow cooling furnace external space S3 has the same height as the slow cooling furnace external space S3 (ie, the atmosphere of the glass sheet G flowing in the furnace space S8 corresponding to the distance from the lower surface of the floor 412 to the upper surface of the floor 413). It is a space including a region where the temperature is 800 ° C. to 110 ° C. or a region where the glass sheet G flowing through the furnace space S8 is from (annealing point + 5 ° C.) to (strain point−200 ° C.). It is. That is, in the furnace space S8, a slow cooling step ST6, which is an important step related to the quality of the glass plate, is performed. Therefore, it is desirable that the temperature of the slow cooling furnace external space S3 is more stable than the other spaces S1, S2, and S4.

  In the present embodiment, as described above, the temperature of the outer surface of the furnace wall of the slow cooling furnace 50 can be stabilized as much as possible in the slow cooling furnace external space S3 that is the same outer space as the furnace space D1 in which the slow cooling step T4 is performed. it can. Therefore, fluctuations in the temperature of the furnace space D2 can be suppressed. Therefore, the quality of the glass plate can be improved.

(8) Modifications Although 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.

You may provide the air curtain which is not shown in figure in order to suppress an updraft between the furnace internal space which is the inside of a slow cooling furnace, and the underground space where a cutting device is provided.
The spatial connection between the slow cooling furnace 50 and the cutting chamber 60 is a gap provided in the floor 413 so as to have a sufficient width for the glass sheet to pass through. An air curtain is provided on the floor 413 as airflow blocking means so as to suppress the rising airflow generated on the surface of the glass sheet from flowing into the slow cooling furnace from the underground space through the spatial connection portion.
Specifically, the wind direction of the air curtain provided on the floor 413 on both sides of the glass sheet G is provided so as to be inclined with respect to the traveling direction of the glass sheet G so that air is blown into the surface of the glass sheet G. . Thereby, air can be blown against the glass sheet G from the air curtain, and the upward airflow that is generated on the surface of the glass sheet G and flows into the slow cooling furnace 50 from the cutting chamber 60 can be suppressed. Moreover, it can suppress that the glass powder accompanying a cutting | disconnection mixes in the slow cooling furnace 50 by an updraft.

  According to the present invention, variations in plate thickness and the like can be suppressed by suppressing temperature fluctuations in the forming furnace 40. In the gradual furnace 50, the deformation of the glass sheet can be suppressed by suppressing the fluctuation of the atmosphere in the furnace in the region where the temperature of the glass sheet is equal to or higher than the annealing point. Moreover, in the gradual furnace 50, by suppressing the fluctuation | variation of the temperature of the atmosphere in a furnace in the area | region where the temperature of a glass plate becomes an annealing point-strain point vicinity, generation | occurrence | production of the internal distortion of a glass plate can be suppressed. it can. Further, in the gradual furnace 50, warpage of the glass plate can be prevented by suppressing temperature fluctuation of the atmosphere in the furnace in the region where the temperature of the glass plate is below the strain point.

  As described above, the present invention can reduce the fluctuation of the glass slow cooling environment in the slow cooling furnace, and is particularly suitable for the production of a glass substrate for display having a small thermal shrinkage using a glass having a strain point of 690 ° C. or higher.

  In the present embodiment, the strain point indicates the temperature of the glass plate having a glass viscosity near log η14.5, and the annealing point indicates the temperature of the glass plate near log η13.

30 furnace 40 molding furnace 50 slow cooling furnace 60 cutting chamber 300 molding apparatus 400 cutting apparatus

Claims (8)

A molding furnace for molding a glass sheet by a downdraw method;
A slow cooling furnace for cooling the glass sheet formed in the forming furnace;
A cutting chamber provided with a cutting device for cutting the glass sheet continuously cut from the slow cooling furnace and cutting the glass substrate;
With
The glass substrate manufacturing apparatus, wherein the cutting chamber is provided in an underground space. The glass substrate manufacturing apparatus is
A control unit that performs atmospheric pressure control from at least the slow cooling furnace to the cutting chamber;
The control unit performs atmospheric pressure control so that the atmospheric pressure in the slow cooling furnace is higher than the atmospheric pressure in the underground space,
The glass substrate manufacturing apparatus according to claim 1. The atmospheric pressure control is performed so that the atmospheric pressure in the underground space is equal to or higher than atmospheric pressure.
The glass substrate manufacturing apparatus according to claim 1 or 2.   The glass substrate manufacturing apparatus in any one of Claim 1 to 3 with which the airflow interruption | blocking means for suppressing the airflow produced toward the inside of the said slow cooling furnace from the said cutting chamber is provided.   The glass substrate manufacturing apparatus according to claim 4, wherein the airflow blocking means is an air curtain that is blown toward the surface of the glass sheet. A method for producing a glass substrate by a downdraw method,
A melting step of melting glass raw material to form molten glass;
Supplying the molten glass to a molded body disposed inside the molding furnace;
A molding step of molding a glass sheet in the molded body;
A slow cooling step of lowering the temperature of the glass sheet moved from the forming step;
A cutting step of cutting out the glass substrate from the glass sheet moved from the slow cooling step;
With
A cutting device for cutting out the glass substrate in the cutting step is provided in an underground space,
Control the atmospheric pressure so that the atmospheric pressure in the slow cooling furnace is higher than the atmospheric pressure in the underground space,
Manufacturing method of glass substrate for display. The atmospheric pressure control is performed so that the atmospheric pressure in the underground space is equal to or higher than atmospheric pressure.
The manufacturing method of the glass substrate for displays of Claim 6. The manufacturing method of the glass substrate for a display of Claim 6 or 7 which sprays a fluid with respect to the airflow produced toward the inside of the slow cooling furnace from the said cutting chamber, and interrupts | blocks the said airflow.