WO2015166972A1

WO2015166972A1 - Method for manufacturing glass plate, and device for manufacturing glass plate

Info

Publication number: WO2015166972A1
Application number: PCT/JP2015/062918
Authority: WO
Inventors: 諒鈴木
Original assignee: ＡｖａｎＳｔｒａｔｅ株式会社
Priority date: 2014-04-30
Filing date: 2015-04-30
Publication date: 2015-11-05
Also published as: JPWO2015166972A1; CN105705465A; TWI592373B; KR101798305B1; CN105705465B; KR20150140627A; TW201545998A; JP5937759B2

Abstract

　A method for manufacturing a glass plate by a downflow method, the method provided with a forming step for forming molten glass into a sheet-shaped glass plate, and an annealing step for annealing the glass sheet formed in the forming step using a plurality of heaters in an annealing space surrounded by furnace walls, the heaters for controlling the temperature in the annealing space, while conveying the glass sheet vertically downward. In the annealing step, the amount of retained head retained by the glass plate is determined together with the amount of heat in the annealing space using the amount of heat generated by the heaters, the distortion of the glass plate is determined on the basis of a pre-established relationship between the amount of retained heat and the distortion of the glass plate, and the amount of heat from the heaters is controlled, and the amount of retained heat in the glass plate is thereby corrected, and distortion of the glass plate is suppressed.

Description

Glass plate manufacturing method and glass plate manufacturing apparatus

The present invention relates to a glass plate manufacturing method and a glass plate manufacturing apparatus capable of reducing warpage and distortion of the glass plate.

Conventionally, a method of manufacturing a glass plate using a downdraw method has been used. In the downdraw method, molten glass is poured into a molded body, and then the molten glass is allowed to overflow from the top of the molded body. The overflowed molten glass flows down along both side surfaces of the molded body and joins at the lower end of the molded body to form a sheet-like glass plate. Thereafter, the glass plate is pulled downward by a roller and cut into a predetermined length.
However, the glass sheet is thermally contracted until it is pulled downward and cut to a predetermined length, which causes warpage and distortion (residual stress). Such warpage and distortion cause display defects when the glass plate is used as, for example, a liquid crystal display (LCD) substrate.

Patent Document 1 describes a method for producing a glass plate for making the thickness of the glass plate as uniform as possible and reducing warpage and distortion. Specifically, the first temperature control step in which the end of the glass plate in the width direction is lower than the temperature of the central region sandwiched between the ends, and the temperature of the central region is uniform, In the second temperature control step in which the temperature in the width direction of the glass plate decreases from the center portion toward the end portion, and in the temperature region near the glass strain point, the end portion and the center portion in the width direction of the glass plate A glass plate manufacturing method including a glass plate cooling step, in which a glass strain point temperature control step is performed, including a third temperature control step that eliminates a temperature gradient from the above is described.

International Publication No. 2012/133384

Although the curvature and distortion of the glass plate obtained by using the method for producing a glass plate described in Patent Document 1 can be reduced as compared with the conventional method, the distortion of the obtained glass plate may not be formed as desired. . Therefore, as a result of the present inventors diligently examining and advancing research, the reason why the distortion of the glass plate is not formed as desired is that in the slow cooling space where the glass plate having a correlation with the distortion of the glass plate is gradually cooled. And found that the warpage and distortion of the glass plate can be reduced by controlling the amount of heat generated by the heater that controls the temperature of the slow cooling space. It came to do.

The present invention includes the following forms.
(Form 1)
A method for producing a glass plate by a downdraw method,
A molding process for molding the molten glass into a sheet-like glass plate;
Slow cooling in which the glass plate formed in the forming step is gradually cooled using a plurality of heaters for controlling the temperature in the slow cooling space in the slow cooling space surrounded by the furnace wall while being conveyed vertically downward. A process,
In the cooling step, the amount of heat held by the glass plate is obtained together with the amount of heat in the slow cooling space using the amount of heat generated by the heater, and the amount of heat held and the distortion of the glass plate are determined in advance. Based on the relationship, the strain of the glass plate is obtained,
By controlling the amount of heat of the heater, the amount of heat retained by the glass plate is corrected, and distortion of the glass plate is suppressed,
The manufacturing method of the glass plate characterized by the above-mentioned.

(Form 2)
Dividing the slow cooling space into a plurality of spaces in the vertical direction, and controlling the temperature in the space using a plurality of heaters in each space;
Based on the results of determining the strain of the glass plate in each space, the amount of heat generated by the heater is controlled.
The manufacturing method of the glass plate of the form 1 characterized by the above-mentioned.

(Form 3)
The strain of the glass plate is determined by thermal fluid analysis simulation and viscoelastic model analysis simulation.
The manufacturing method of the glass plate of the

form

1 or 2 characterized by the above-mentioned.

(Form 4)
The slow cooling space is divided into a plurality of spaces in the vertical direction,
In the thermal fluid analysis simulation, the retained heat amount of the glass plate when entering each of the plurality of spaces is defined as the retained heat amount when entering the glass plate, and the retained heat amount of the glass plate during the approach and the heating value of the heater. The manufacturing method of the glass plate of the form 3 which calculates | requires the calorie | heat amount of the said glass plate in each of these space of the said glass plate by giving.

(Form 5)
When the glass plate flows through the plurality of spaces, the thermal fluid analysis simulation is performed in each of the plurality of spaces, and the second stage of the plurality of spaces when viewed from the upstream side in the flow direction of the glass plate. 5. The method for manufacturing a glass plate according to claim 4, wherein, in a subsequent space, a temperature distribution when the glass plate comes out in a space adjacent to the upstream side is used as a retained heat amount at the time of entering.

(Form 6)
An apparatus for producing a glass plate by a downdraw method,
A molded body for forming molten glass into a sheet-like glass plate;
While conveying the glass plate molded with the molded body vertically downward, a slow cooling space surrounded by the furnace wall,
A plurality of heaters for controlling the temperature in the slow cooling space and gradually cooling the glass plate,
The molding device includes:
The amount of heat held by the glass plate is obtained together with the amount of heat in the slow cooling space using the amount of heat generated by the heater, and based on a predetermined relationship between the amount of heat held and the strain of the glass plate. A first portion for determining the strain of the glass plate;
A glass plate manufacturing apparatus comprising: a second portion that corrects the amount of heat retained by the glass plate by controlling the heat amount of the heater and suppresses distortion of the glass plate.

According to the present invention, the warp and distortion of the glass plate can be reduced by controlling the amount of heat generated from the heater that controls the temperature of the slow cooling space.

It is a partial flowchart of the manufacturing method of the glass plate which concerns on this embodiment. It is a figure which mainly shows the melting apparatus contained in the manufacturing apparatus of the glass plate used for the manufacturing method of the glass plate which concerns on this embodiment. It is a schematic front view of a shaping | molding apparatus. It is a schematic side view of a shaping | molding apparatus. It is a control block diagram of a control apparatus. It is a partial enlarged view of the schematic front view of a shaping | molding apparatus. It is a schematic cross-sectional view of a shaping | molding apparatus. It is sectional drawing in the A line of FIG. It is a figure which shows the one-stage model of slow cooling space in this embodiment. It is a figure which shows the relationship between the temperature of a general glass, and a specific heat. It is a figure which shows the stress relaxation parameter of a glass plate. It is a figure which shows the structural relaxation parameter of a glass plate.

Hereinafter, a method for manufacturing a glass plate according to this embodiment, in which a glass plate is manufactured using a glass plate manufacturing apparatus, will be described with reference to the drawings.

(1) 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.
As shown in FIG. 1, the glass plate is manufactured through various processes including a melting process ST1, a clarification process ST2, a homogenization process ST3, a molding process ST4, a cooling process ST5, and a cutting process ST6. The Hereinafter, these steps will be described.

In the melting step ST1, the glass raw material is heated and melted. Glass raw materials, for _example, a composition, such as

SiO

2, _Al 2 _{O 3.} The molten glass raw material becomes molten glass.
In the clarification step ST2, 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.
In the homogenization step ST3, the molten glass is homogenized. In this step, the temperature of the molten glass that has been clarified is adjusted.
In the forming step ST4, the molten glass is formed into a sheet-like glass plate by a downdraw method (for example, an overflow downdraw method).

In the cooling step ST5, the glass plate formed in the forming step ST4 is cooled. In the cooling step ST5, the glass plate is cooled to near room temperature.
In the cutting step ST6, the glass plate cooled to near room temperature is cut into a glass plate every predetermined length.
In addition, the glass plate cut | disconnected for every predetermined length is cut | disconnected further after that, grinding | polishing, grinding | polishing, washing | cleaning, and an inspection are performed, it becomes a glass plate, and is used for flat panel displays, such as a liquid crystal display.

(2) Outline of Glass Plate Manufacturing Apparatus 100 FIG. 2 is a schematic diagram mainly showing a melting apparatus 200 included in the glass plate manufacturing apparatus 100. FIG. 3 is a schematic front view of a forming apparatus 300 included in the glass plate manufacturing apparatus 100. FIG. 4 is a schematic side view of the molding apparatus 300. Hereinafter, the glass plate manufacturing apparatus 100 will be described.

The glass plate manufacturing apparatus 100 mainly includes a melting apparatus 200 (see FIG. 2), a forming apparatus 300 (see FIGS. 3 to 4), and a cutting apparatus 400 (not shown).

(2-1) Configuration of Dissolution Device 200 The dissolution device 200 is a device for performing the dissolution step ST1, the clarification step ST2, and the homogenization step ST3.
As shown in FIG. 2, the dissolution apparatus 200 includes a dissolution tank 201, a clarification tank 202, a stirring tank 203, a first pipe 204, and a second pipe 205.
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. The clarification tank 202 is further heated with the molten glass fed from the melting tank 201, thereby promoting the defoaming of bubbles in the molten glass. In the clarification tank 202, a clarification step ST2 is performed.
The agitation tank 203 has an agitation device including a container for storing molten glass, a rotation shaft, and an agitation blade attached to the rotation shaft. As a container, a rotating shaft, and a stirring blade, although the thing made from platinum group elements, such as platinum, or the alloy of a platinum group element, for example can be used, it is not restricted to this. When the rotating shaft is rotated by driving a drive unit (not shown) such as a motor, the stirring blade attached to the rotating shaft stirs the molten glass. In the stirring tank 203, the homogenization step ST3 is performed.
The first pipe 204 and the second pipe 205 are pipes made of, for example, a platinum group element or a platinum group element alloy. The first pipe 204 is a pipe that connects the clarification tank 202 and the stirring tank 203. The second pipe 205 is a pipe that connects the stirring tank 203 and the molding apparatus 300.

(2-2) Configuration of Molding Device 300 The molding device 300 is a device for performing the molding step ST4 and the cooling step ST5.
As shown in FIGS. 3 and 4, the molding apparatus 300 includes a molded body 310, an atmosphere partition member 320, a cooling roller 330, a cooling unit 340, pulling rollers 350a to 350e, and heaters 360a to 360e. . Hereinafter, these configurations will be described.

(2-2-1) Molded body 310
The molded body 310 is an apparatus for performing the molding process ST4.
As shown in FIG. 3, the molded body 310 is located in the upper part of the molding apparatus 300 and has a function of molding the molten glass flowing from the melting apparatus 200 into a sheet-like glass plate SG by the overflow down draw method. . The cross-sectional shape of the molded body 310 cut in the vertical direction is a wedge shape, and the molded body 3120 is made of, for example, refractory bricks.

As shown in FIG. 4, a supply port 311 is formed in the molded body 310 on the upstream side in the flow channel direction of the molten glass flowing from the melting device 200. Further, as shown in FIG. 4, the molded body 310 is formed with a groove portion 312 opened upward along the longitudinal direction thereof. The groove 312 is formed so as to gradually become shallower from the upstream side toward the downstream side in the flow channel direction of the molten glass.
The molten glass flowing from the melting device 200 toward the molding device 300 flows into the groove portion 312 of the molded body 310 via the supply port 311.
The molten glass that has flowed into the groove 312 of the molded body 310 overflows at the top of the groove 312 and flows down along both side surfaces 313 of the molded body 310. And the molten glass which flows down along the both side surfaces 313 of the molded object 310 joins in the lower part 314 of the molded object 310, and becomes the glass plate SG.

(2-2-2) Atmosphere partition member 320, heat insulating member 41
As shown in FIGS. 3 and 4, the atmosphere partition member 320 is a plate-like member disposed in the vicinity of the lower portion 314 of the molded body 310.
The atmosphere partition member 320 is disposed to be substantially horizontal on both sides in the thickness direction of the glass plate SG flowing down from the lower portion 314 of the molded body 310. 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. As shown in FIGS. 3 and 4, the molding apparatus 300 includes a molded body accommodation portion 410 that is a space above the atmosphere partition member 320, a molding zone 42a that is a space immediately below the atmosphere partition member 320, and a molding zone 42a. And a slow cooling zone 420 which is a space below the. The slow cooling zone 420 has a plurality of

slow cooling spaces

42b, 42c,. The molding zone 42a and the slow cooling spaces 42b to 42f are stacked in this order from the top to the bottom in the vertical direction. By being surrounded by the furnace wall, a forming zone 42a and a slow cooling zone 420 (slow cooling spaces 42b to 42f) are formed, and the glass plate SG is formed in the forming zone 42a and the slow cooling zone 420 (slow cooling spaces 42b to 42f). Moving.

The heat insulating member 41 is a plate-shaped heat insulating material that is disposed below the cooling roller 330 described later and on both sides in the thickness direction of the glass plate SG in the slow cooling zone 420. By partitioning the space below the heat insulating member 41 and the atmosphere partition member 320, the forming zone 42a and the slow cooling spaces 42b to 42f are formed. For example, as shown in FIG. 4, the heat insulating member 41 forms a molding zone 42a and a slow cooling space 42b. Moreover, the heat insulation member 41 forms the slow cooling space 42b and the slow cooling space 42c. As described above, the slow cooling spaces 42 b to 42 f are formed by being surrounded by the furnace wall and the heat insulating member 41. Each heat insulating member 41 suppresses heat transfer between the upper and lower spaces. For example, the heat insulating member 41 suppresses heat transfer between the molding zone 42a and the slow cooling space 42b, and the heat insulating member 41 suppresses heat transfer between the slow cooling space 42b and the slow cooling space 42c. .

(2-2-3) Cooling roller 330
The cooling roller 330 is disposed below the atmosphere partition member 320. Moreover, the cooling roller 330 is arrange | positioned so as to oppose the both ends of the thickness direction of the glass plate SG, and the both ends part of the width direction. The cooling roller 330 is air-cooled by an air-cooling tube passed through the cooling roller 330. Therefore, when the glass plate SG passes through the cooling roller 330, the glass plate SG is in contact with the air-cooled cooling roller 330. Both side portions in the thickness direction of the glass plate SG and both end portions in the width direction (hereinafter, the portions are referred to as glass plates). SG ears R and L) are cooled. Accordingly, the viscosity of the ear portion R, L is a predetermined value ^{(e.g., 10 9.0} poises) is above. Here, the ears R and L are thicker than the thickness of the central region (central part) in the width direction of the glass plate SG sandwiched between the ears R and L, and have a predetermined thickness. The central region (central portion) is a portion having a substantially uniform thickness that can be used as a product (glass substrate). The cooling roller 330 also has a role of pulling the glass plate SG downward by transmitting a driving force by the cooling roller driving motor 390 (see FIG. 5). The glass plate SG is stretched to a predetermined thickness by the cooling roller 330.

(2-2-4) Cooling unit 340
The cooling unit 340 is, for example, an air-cooling type cooling device, and cools the ambient temperature of the cooling roller 330 and the glass plate SG passing therebelow. Moreover, the cooling unit 340 is arranged in plural (for example, three) in the width direction of the glass plate SG and plural in the flow direction. Specifically, the cooling units 340 are arranged one by one so as to face the surfaces of the ears R and L of the glass plate SG, and one cooling unit 340 is arranged so as to face the surface of the central region. .

(2-2-5) Pulling rollers 350a to 350e
The pulling rollers 350a to 350e are arranged below the cooling roller 330 with a predetermined interval in the flow direction of the glass plate SG. Further, the pulling rollers 350a to 350e are respectively disposed in the slow cooling spaces 42b to 42f so as to face both sides in the thickness direction of the glass plate SG and to face both end portions in the width direction of the glass plate SG. The pulling rollers 350a to 350e are both side portions in the thickness direction of the glass plate SG in which the viscosities of the ear portions R and L are equal to or higher than a predetermined value in the cooling roller 330, while being in contact with both end portions in the width direction. Pull the glass plate SG downward. The pulling rollers 350a to 350e are driven by the driving force transmitted by the pulling roller driving motor 391 (see FIG. 5). The peripheral speed of the pulling rollers 350 a to 350 e is larger than the peripheral speed of the cooling roller 330. The circumferential speed of the pulling roller increases as it is arranged on the downstream side in the flow direction of the glass plate SG. That is, among the plurality of pulling rollers 350a to 350e, the peripheral speed of the pulling roller 350a is the lowest, and the peripheral speed of the pulling roller 350e is the highest.

(2-2-6) Heater (temperature control unit)
As shown in FIG. 3, the heaters (temperature control units) 360a to 360e are disposed in the molding zone 42a and the slow cooling spaces 42b to 42f below the cooling unit 340, respectively, and the molding zone 42a and the

slow cooling spaces

42b, 42c, Controls the ambient temperature of ... The heaters 360a to 360e control the ambient temperature in the vicinity of the glass sheet SG pulled downward by the pulling rollers 350a to 350e by controlling the output by the control device 500 described later (specifically, the ambient temperature Functions as a cooling device. Each of the heaters 360a to 360e includes heat generating portions 361a, 362a,... 366a arranged in a plurality (for example, three, six, etc.) in the width direction as shown in FIGS. The heat generating parts 361a to 366a are heat generating elements that release heat to the slow cooling space. The heat generating portions 361a to 366a are embedded in the furnace wall, and are configured to generate heat by being supplied with electric power. As shown in FIG. 6, the heat generating portions 361a to 366a are arranged in a line along the width direction of the glass plate SG at positions facing both sides of the glass plate SG. FIG. 6 shows the heat generating portions 361a to 366a provided in the slow cooling space 42b, but the heaters 360b to 360e having similar heat generating portions have an ambient temperature in the vicinity of the glass plate SG of the width of the glass plate SG. A predetermined temperature distribution (hereinafter referred to as “temperature profile”) is formed in the direction. In this way, the heaters 360a to 360e having the heat generating parts control the ambient temperature of the molding zone 42a and the slow cooling spaces 42b to 42f. Note that a plurality of heat generating portions of the heaters 360a to 360e may be arranged not only in the width direction of the glass plate SG but also in the flow direction of the glass plate SG.

Here, the atmospheric temperature of the glass plate SG pulled downward by the pulling rollers 350a to 350e is controlled by the heaters 360a to 360e (heat generating portions 361a to 366a) (specifically, the glass plate SG When the atmospheric temperature is controlled, the glass plate SG is temperature-controlled), so that the glass plate SG is cooled from the viscous region to the elastic region through the viscoelastic region.

Further, a thermocouple unit 380 (see FIGS. 5 to 7) for detecting the atmospheric temperature of each region of the glass plate SG is disposed in the vicinity of the heat generating portions 361a to 366a. The thermocouple unit 380 measures the ambient temperature of the slowly cooling spaces 42b to 42f that change as the heat generating portions 361a to 366a generate heat. The control device 500 acquires the ambient temperature measured by the thermocouple unit 380, and controls the amount of heat generated from the heat generating units 361a to 366a included in the heaters 360a to 360e based on the acquired ambient temperature. The glass plate SG is cooled by the cooling roller 330, the cooling unit 340, and the heaters 360a to 360e (heating units 361a to 366a) in the molding zone 42a and the slow cooling spaces 42b to 42f, which are regions below the lower portion 314 of the molded body 310. The going process is the cooling process ST5.

(2-3) Cutting device 400
In the cutting device 400, the cutting step ST6 is performed. The cutting device 400 is a device that cuts the glass plate SG flowing down in the forming device 300 from a direction perpendicular to the longitudinal surface thereof. Thereby, the sheet-like glass plate SG becomes a plurality of glass plates SG having a predetermined length. The cutting device 400 is driven by a cutting device drive motor 392 (see FIG. 5).

(3) Control device 500
FIG. 5 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, the glass plate manufacturing apparatus 100 or the molding apparatus 300 includes a control device 500, and as shown in FIG. 5, the control device 500 includes various sensors (for example, the glass plate manufacturing apparatus 100). , Thermocouple unit 380, etc.) and switches (for example, main power switch 381 etc.), etc., and input instructions from an operator via an input device (not shown), etc., in response to the cooling unit 340, heaters 360a˜ 360e (heat generating units 361a to 366a), a cooling roller driving motor 390 that controls the operation of the cooling roller 330, a pulling roller driving motor 391 that controls the operation of the pulling rollers 350a to 350e, and a cutting device drive that controls the operation of the cutting device 400 Control of the motor 392 and the like is performed.

(4) Temperature control in cooling process ST5 Cooling process ST5 includes that the control apparatus 500 controls the temperature of the glass plate SG by controlling the cooling roller 330. FIG. Furthermore, the cooling step ST5 includes a temperature control step for controlling the temperature of the glass plate SG. Specifically, in the temperature control step, the temperature of the glass plate SG is controlled by controlling the heating unit 361a to 366a of the cooling unit 340 and the heaters 360a to 360e to control the ambient temperature of the glass plate SG. Control.

Further, the cooling step ST5 includes a heat amount control step for controlling the heat generation amount of the heat generating portions 361a to 366a so that the temperature of the glass plate SG falls within a predetermined temperature range at a predetermined height position (predetermined slow cooling space). In addition, the temperature of the glass plate SG has a predetermined temperature distribution in the width direction. That is, the temperature of the glass plate SG is controlled in the flow direction and the width direction.

The above-described heat quantity control step will be described below by taking the operation of the heat generating portions 361a to 366a as an example. In the heat amount control step, the amount of heat generated by the heat generating portions 361a to 366a is determined.

A procedure for determining the amount of heat generated by the heat generating units 361a to 366a will be described below. i) The control unit 500 initially sets the heat generating units 361a to 366a to a predetermined set temperature, and the ambient temperature in the vicinity of the glass plate SG is the width of the glass plate SG in the slow cooling spaces 42b to 42f (slow cooling zone 420). A predetermined temperature profile is formed in the direction.
ii) The amount of heat held by the glass plate SG (temperature of the glass plate SG) and the ambient temperature in the slow cooling spaces 42b to 42f (slow cooling zone 420) are obtained.
iii) Based on the temperature of the glass plate SG obtained in the above ii) and the atmospheric temperature in the slow cooling spaces 42b to 42f, the temperature distribution and strain distribution of the formed glass plate SG are obtained, and the obtained strain is reduced. As described above, the amount of heat (set temperature) generated by the heat generating portions 361a to 366a is controlled.

A method for obtaining the temperature distribution of the glass plate SG in order to control the amount of heat generated by the heat generating parts 361a to 366a (the set temperature of the heat generating parts 361a to 366a) will be described below. The method uses thermal fluid analysis simulation and viscoelastic analysis simulation.

<Thermal fluid analysis simulation>
In the thermal fluid analysis simulation, for example, a thermal fluid analysis is performed using a discretized model based on the finite element method. In the thermal fluid analysis, the amount of heater heat generated by the heat generating portions 361a to 366a is given, that is, the set temperature of the heat generating elements 361a to 366a is given, and the temperature distribution of the atmosphere of the slow cooling spaces 42b to 42f and the temperature distribution of the glass plate SG are obtained. As an unknown, a temperature distribution that is the amount of heat retained by the glass plate SG in the entire slow cooling space (slow cooling zone) is obtained. The simulation is performed under the following conditions.

1. Model The slow cooling space 42b of the slow cooling zone 420 divided into a plurality of stages in the flow direction of the glass plate SG is discretized as a mesh model, and the glass plate in the first slow cooling space 42b is analyzed using thermal fluid analysis. Obtain the temperature distribution of SG. At this time, the temperature distribution of the glass plate SG entering the slow cooling space 42b is determined in advance. Of the temperature distribution of the glass sheet SG in the first-stage slow cooling space 42b, the temperature distribution in the width direction when exiting from the slow cooling space 42b is the temperature of the glass sheet SG entering the second-stage slow cooling space 42c. Defined as distribution. Thus, the temperature distribution of the glass plate in each slow cooling space is calculated | required using the temperature distribution of the glass plate SG when approaching into the slow cooling space of each step | level. In this way, the temperature distribution of the glass plate SG in the entire slow cooling space is simulated.
FIG. 9 shows a model of the first-stage slow cooling space 42b as viewed from the flow direction of the glass plate SG. The amount of heat held by the glass plate SG when entering the slow cooling space 42b and the amount of heater heat (set temperature) of the heater 360a (heat generating portions 361a to 366a) are given, along with the ambient temperature in the slow cooling space 42b. The temperature distribution of the glass plate SG in the cold space 42b is obtained. Then, in the second and subsequent stages downstream from the first stage, the temperature distribution of the glass sheet SG is obtained in the same manner as in the first stage, and the obtained temperature distributions of the plurality of glass sheets SG are connected, so that the slow cooling spaces 42b˜ The temperature distribution of the glass plate SG in the entire 42f (slow cooling zone 420) is obtained.
(1) Amount of heat held by the glass plate SG when entering the slow cooling space 42b, (2) Amount of heater heat (set temperature) of the heater 360a (heat generating portions 361a to 366a), (3) Ambient temperature in the slow cooling space 42b The temperature distribution of the glass plate SG in the first-stage slow cooling space 42b is analyzed. The above (1) to (3) will be described as follows.

(1) Retained heat amount of the glass plate SG when entering the slow cooling space 42b The retained heat amount (temperature distribution) of the glass plate SG is the position where the glass plate SG enters the slow cooling space 42b (in the slow cooling space 42b). It is measured using a temperature sensor (not shown) provided on the upstream side. Since the amount of molten glass flowing out of the molded body 310 is constant, the flow rate (conveying speed) of the glass plate SG is constant, and the glass plate SG when entering the slow cooling space 42b from the measured temperature (temperature distribution). The amount of heat retained can be obtained. Further, from the flow rate of the glass plate SG and the temperature of the molten glass flowing into the molded body 310, the retained heat amount (temperature distribution) of the glass plate SG when entering the slow cooling space 42b can be obtained.

(2) Heat generation amount (set temperature) of the heater 360a (heat generating portions 361a to 366a)
The amount of heat generated by each of the heat generating units 361a to 366a varies depending on the set temperature set by the control device 500. The heater heat amount generated by each of the heat generating units 361a to 366a based on the set temperature is obtained from the measurement result of a wattmeter (not shown) of the heat generating units 361a to 366a provided in the power supply apparatus. Therefore, when controlling the heat generation amount of the heat generating units 361a to 366a, the power supplied to each of the heat generating units 361a to 366a is controlled. Here, the preset temperature initially set in the heat generating portions 361a to 366a included in the heater 360a of the slow cooling space 42b is set to 700 ° C., for example. The heat generation amounts of the heat generating elements 361a to 366a may be the same, but the heat generation amount may be distributed. In addition, since the temperature of 700 ° C. that is initially set is an example, the temperatures of the heat generating portions 361a to 366a can be obtained as calculation results as unknown amounts. The inflow temperature of the glass plate SG is calculated as, for example, 700 ° C., and the inflow temperature of the glass plate SG can be set so that the measured temperature and the temperature of the calculation result coincide with each other. The actual current (A), voltage (V), and power factor of the heat generating parts 361a to 366a whose temperature is set are actually measured, and the heat generation amount (W) is obtained therefrom, and the heat generation density (W / m ³ ) Convert to the calculation conditions. Since the temperature is obtained as a calculation result (solution), the calculation result and the set temperature are compared, and the temperature is obtained by repeating the review of the conditions so that the match is good.

(3) Atmospheric temperature in the slow cooling space 42b The atmospheric temperature in the slow cooling space 42b varies depending on the amount of heat held by the glass plate SG and the amount of heater heat in the heat generating portions 361a to 366a. Assuming that the atmosphere of the slow cooling space 42b is an incompressible ideal gas, the natural convection caused by buoyancy and the heat transfer caused thereby are the same as the heat transfer of the glass plate SG. It is included in the thermal fluid analysis model of and coupled to solve. In the present embodiment, the atmospheric temperature in the slow cooling space 42b is solved as an unknown in the thermofluid analysis, but instead, the thermocouple unit 380 measures the atmospheric temperature in the slow cooling space 42b, The amount of heat held in the slow cooling space 42b (atmosphere temperature in the slow cooling space 42b) is obtained, and this heat amount is given as the ambient temperature in the slow cooling space 42b in the thermal fluid analysis to calculate the temperature distribution of the glass plate SG. May be.

2. Physical property values The physical property values of the materials constituting the glass plate SG and the slow cooling space 42b are as follows.
A. Glass plate SG
i) Density: 2500 [kg / m ³ ].
ii) Thermal conductivity: 1.1278 [W / mK].
iii) Specific heat: as shown in FIG.
B. Pulling rollers 350a-350e (stainless steel SUS304)
ii) Thermal conductivity: 16.0 [W / mK] (27 ° C.), 25.7 [W / mK] (727 ° C.).
C. Atmosphere partition member 320, heat insulating member 41, furnace wall (heat insulating material)
i) Thermal conductivity: 0.04 to 0.3 [W / mK].

3. Calculation conditions Since this is a steady-state calculation (a system that does not change over time), an algorithm for thermal fluid analysis is used. The flow is steady and the SIMPLE algorithm is used to couple the fluid flow, convection heat transfer, and radiant heat transfer, and solve using a single solver. As the solver, commercially available software can be used, and known general-purpose thermal fluid analysis software can be used. Here, in the thermal fluid analysis, the glass plate SG is treated as a fluid for calculation, but since the moving speed of the glass plate SG coincides with the conveying speed and is known, the flow velocity of the entire glass plate SG region is fixed and the calculation is performed. Do. Air is assumed to be an incompressible ideal gas, and heat transfer by natural convection is included in the calculation.

The temperature conditions of the glass plate SG in the first-stage slow cooling space 42b can be obtained by inputting the above conditions and physical property values into general-purpose thermal fluid analysis software for analysis.

Next, the temperature distribution of the glass plate SG in the second and subsequent slow cooling spaces 42c to 42f is obtained. For the second and subsequent slow cooling spaces 42c to 42f, a discrete mesh model is created in the same manner as the slow cooling space 42b. Specifically, in the mesh model, the retained heat amount of the glass plate SG flowing into the slow cooling spaces 42c to 42f is obtained as a result of the thermofluid analysis, and the retained heat amount of the glass plate SG when exiting the preceding slow cooling space. Use calorie (temperature distribution). That is, for example, the retained heat amount of the glass plate SG entering the second-stage slow cooling space 42c is obtained as a temperature (temperature distribution) in the first-stage slow cooling space 42b obtained as a result of the thermal fluid analysis. The amount of heat held by the glass plate SG when the glass plate SG flows out of the first-stage slow cooling space 42b is used.
Further, the set temperature of the heat generating portions 361a to 366a provided in the second-stage slow cooling space 42c is set to a temperature lower by 5 ° C. to 30 ° C., preferably 15 ° C. than that of the previous stage, toward the flow direction. Each time the stage is advanced, the set temperature is set to a temperature lowered in the range of 5 ° C. to 30 ° C., preferably a temperature lowered by 15 ° C.
The conditions for obtaining the temperature distribution of the entire glass plate SG in the second and subsequent slow cooling spaces 42c to 42f by thermal fluid analysis are the conditions used for the temperature distribution of the glass plate SG in the first cooling space 42b. Since the values are the same as the physical property values, description thereof is omitted.
As described above, in the thermal fluid analysis simulation, the retained heat amount of the glass plate when entering each of the plurality of slow cooling spaces is defined as the retained heat amount when the glass plate enters, and the retained heat amount of the glass plate and the heat generation of the heater when entering the glass plate. By giving the amount, the retained heat amount of the glass plate in each of the plurality of cooling spaces of the glass plate can be obtained. At this time, the thermal fluid analysis simulation is performed in each of the plurality of cooling spaces, and among the plurality of cooling spaces, the cooling spaces in the second and subsequent stages as viewed from the upstream side in the flow direction of the glass plate are adjacent to the upstream side. The temperature distribution at the time when the glass plate comes out of the cooling space can be used as the retained heat amount at the time of entering.
Thus, the temperature distribution of the glass sheet SG in the annealing space for each stage is obtained by thermofluid analysis, and a plurality of temperature distributions of the glass sheets SG in the annealing space for each stage are connected, whereby a plurality of the annealing spaces 42c of the plurality of stages are obtained. The temperature distribution of the glass plate SG in the entire region ~ 42f (slow cooling zone 420) can be obtained.

<Viscoelastic analysis simulation>
Using the amount of heat (temperature distribution) retained by the glass plate SG in the entire slow cooling spaces 42b to 42f (slow cooling zone 420) obtained by the above thermal fluid analysis, the strain distribution of the glass plate SG is determined by viscoelastic model analysis. Ask.
Specifically, the temperature distribution of the glass plate SG in the entire slow cooling spaces 42b to 42f obtained by the thermal fluid analysis, the physical property values of the glass plate SG, the stress relaxation parameters and the structural relaxation parameters of the glass plate SG are as follows: By inputting into known analysis software and performing analysis, viscoelastic model analysis is performed and the strain distribution of the glass plate is obtained. Specifically, the strain distribution is obtained in consideration of the stress relaxation parameter and the structure relaxation parameter. In the slow cooling spaces 42b to 42f, the temperature of the glass plate SG may be cooled in a non-uniform state in the width direction, and thermal stress is constantly generated due to the difference in shrinkage, and the stress is constantly relaxed. For this reason, in order to evaluate the residual stress remaining in the glass plate SG, it is necessary to consider not only thermal stress calculation due to shrinkage but also stress relaxation in which the stress decreases with time. For this reason, stress relaxation is taken into account by using a viscoelastic model of software for structural analysis. Moreover, in order to obtain | require a structure relaxation parameter, the shrinkage | contraction resulting from structure relaxation can also be considered. Shrinkage of the glass plate SG includes thermal expansion due to thermal expansion and thermal contraction that is contraction due to structural relaxation. Since the volume decreases when the glass plate SG is left at a high temperature for a long time, this is used as a structural relaxation parameter. Through the off-line experiment for estimating the structural relaxation parameter, the number of cycles is adjusted so that the structural relaxation parameter matches the shrinkage result of multiple heat treatments.
According to the result of the viscoelastic analysis, since the temperature distribution of the glass plate and the strain of the glass plate have a correlation, the correlation is obtained in advance, and based on this correlation, the temperature of the glass plate SG ( The strain distribution of the glass plate SG can be obtained from the (temperature distribution). The stress relaxation parameter and the structural relaxation parameter of the glass plate SG are as shown in FIGS.

As described above, the strain distribution of the glass plate SG can be obtained using the thermal fluid analysis and the viscoelastic model analysis.

The strain distribution of the glass plate SG obtained by the above-described method is obtained from the heat generation amount in the initial state where the set temperature of the heat generating portions 361a to 366a is 700 ° C., and the set temperature of the heat generating portions 361a to 366a is changed. Thereby, the strain distribution of the glass plate SG also changes. By using the thermal fluid analysis and the viscoelastic model analysis, the relationship between the change in the set temperature of the heat generating portions 361a to 366a and the strain change in the glass plate SG is obtained, so that the strain distribution in the glass plate SG is suppressed. By controlling the set temperature of the heat generating portions 361a to 366a, the warp and distortion of the glass plate SG can be reduced.

Note that a warp, strain, and temperature distribution of the glass plate SG can be measured by providing a strain measuring device (strain measuring sensor) in the slow cooling spaces 42b to 42f. Strain measurement and temperature measurement (thermocouple) are separate measurements, but both can be measured at the same location.

Further, the retained heat amount (temperature distribution) of the glass plate SG may be changed by being sandwiched between the pulling rollers 350a to 350e. In this case, the retained heat amount (temperature distribution) included in the pulling rollers 350a to 350e is measured by the thermocouple unit 380 or the heat amount detection sensor included in the pulling rollers 350a to 350e. It is also possible to obtain warpage and distortion of the glass plate SG by performing a simulation using both the amount of heat retained by the pulling rollers 350a to 350e and the amount of heat retained by the glass plate SG.

Specifically, when performing the above-described thermal fluid analysis simulation, the mesh model of the pulling rollers 350a to 350e is added to the model of each slow cooling space, and the amount of heat held by the mesh model of the pulling rollers 350a to 350e is measured as described above. The temperature distribution of the slow cooling space and the temperature distribution of the glass plate SG may be solved by giving a set temperature to the heat generating portion. Thereby, the temperature distribution of the glass plate SG can be calculated | required more correctly.

As mentioned above, although the manufacturing method of the glass plate of this invention and the manufacturing apparatus of the glass plate were demonstrated in detail, this invention is not limited to the said embodiment, In the range which does not deviate from the main point of this invention, various improvement or change Of course, you may do it.

DESCRIPTION OF SYMBOLS 100 Glass plate manufacturing apparatus 310 Molded body 313 Lower part of molded body 330 Cooling roller (roller)
350a-350e Pulling roller (roller)
360a to 360e Heater 361a to 366a Heat generating part 420 Slow cooling zone 42a Molding zone 42b to 42f Slow cooling space SG Glass plate

Claims

A method for producing a glass plate by a downdraw method,
A molding process for molding the molten glass into a sheet-like glass plate;
Slow cooling in which the glass plate formed in the forming step is gradually cooled using a plurality of heaters for controlling the temperature in the slow cooling space in the slow cooling space surrounded by the furnace wall while being conveyed vertically downward. A process,
In the cooling step, the amount of heat held by the glass plate is obtained together with the amount of heat in the slow cooling space using the amount of heat generated by the heater, and the amount of heat held and the distortion of the glass plate are determined in advance. Based on the relationship, the strain of the glass plate is obtained,
By controlling the amount of heat of the heater, the amount of heat retained by the glass plate is corrected, and distortion of the glass plate is suppressed,
The manufacturing method of the glass plate characterized by the above-mentioned.
Dividing the slow cooling space into a plurality of spaces in the vertical direction, and controlling the temperature in the space using a plurality of heaters in each space;
Based on the results of determining the strain of the glass plate in each space, the amount of heat generated by the heater is controlled.
The manufacturing method of the glass plate of Claim 1 characterized by the above-mentioned.
The strain of the glass plate is determined by thermal fluid analysis simulation and viscoelastic model analysis simulation.
The manufacturing method of the glass plate of Claim 1 or 2 characterized by the above-mentioned.
The slow cooling space is divided into a plurality of spaces in the vertical direction,
In the thermal fluid analysis simulation, the retained heat amount of the glass plate when entering each of the plurality of spaces is defined as the retained heat amount when entering the glass plate, and the retained heat amount of the glass plate during the approach and the heating value of the heater. The manufacturing method of the glass plate of Claim 3 which calculates | requires the retained heat amount of the said glass plate in each of these space of the said glass plate by giving.
When the glass plate flows through the plurality of spaces, the thermal fluid analysis simulation is performed in each of the plurality of spaces, and the second stage of the plurality of spaces when viewed from the upstream side in the flow direction of the glass plate. 5. The method for manufacturing a glass plate according to claim 4, wherein, in a subsequent space, a temperature distribution when the glass plate comes out in a space adjacent to the upstream side is used as a retained heat amount at the time of entering.
An apparatus for producing a glass plate by a downdraw method,
A molded body for forming molten glass into a sheet-like glass plate;
While conveying the glass plate molded with the molded body vertically downward, a slow cooling space surrounded by the furnace wall,
A plurality of heaters for controlling the temperature in the slow cooling space and gradually cooling the glass plate,
The molding device includes:
The amount of heat held by the glass plate is obtained together with the amount of heat in the slow cooling space using the amount of heat generated by the heater, and based on a predetermined relationship between the amount of heat held and the strain of the glass plate. A first portion for determining the strain of the glass plate;
A glass plate manufacturing apparatus comprising: a second portion that corrects the amount of heat retained by the glass plate by controlling the heat amount of the heater and suppresses distortion of the glass plate.