TWI592373B - Manufacturing method of glass plate and manufacturing apparatus of glass plate - Google Patents

Description

Glass plate manufacturing method and glass plate manufacturing device

The present invention relates to a method for producing a glass sheet capable of reducing warpage and strain of a glass sheet, and a device for manufacturing the glass sheet.

Conventionally, a method of manufacturing a glass sheet by a down-draw method has been used. In the down-draw method, after the molten glass is poured into the formed body, the molten glass is allowed to overflow from the top of the formed body. The overflowed molten glass flows down along both sides of the formed body and merges at the lower end portions of the formed body, thereby forming a sheet-like glass plate. Thereafter, the glass sheet is stretched downward by the rolls and cut into a specific length.

However, the glass sheet is thermally contracted while being stretched downward and cut into a specific length, thereby causing warpage and strain (residual stress). Such warpage and strain can 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 sheet which is used to make the thickness of the glass sheet uniform as much as possible to reduce warpage and strain. Specifically, there is described a method of manufacturing a glass sheet including a cooling step of a glass sheet, the cooling step performing a temperature control step in a glass strain point, the temperature control step comprising: a first temperature control step of causing a glass sheet The temperature in the end portion in the width direction is lower than the temperature in the central portion sandwiched between the end portions, and the temperature in the central portion is made uniform; and the second temperature control step is to set the temperature in the width direction of the glass plate from The central portion is lowered toward the end portion; and the third temperature control step is performed in a temperature region near the glass strain point so that there is no temperature gradient between the end portion and the central portion of the glass sheet in the width direction.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2012/133843

There is a case where the warpage and strain of the glass sheet obtained by the method for producing a glass sheet described in Patent Document 1 can be reduced as compared with the prior art, but the strain of the obtained glass sheet is not formed as needed. Therefore, the inventors of the present invention have made efforts to investigate and advance the research, and as a result, have found that the strain of the glass sheet which is not formed as required is due to the temperature in the slow cooling space in which the glass sheet is slowly cooled in relation to the strain of the glass sheet. The control accuracy is insufficient, and it has been found that the warpage and strain of the glass sheet can be reduced by controlling the heat generated by the heater controlling the temperature of the slow cooling space, thereby completing the present invention.

The present invention encompasses the following aspects.

(Form 1)

A method for producing a glass sheet, characterized in that it is a pull-down method, and includes: a forming step of forming a molten glass into a sheet-shaped glass sheet; and a slow cooling step in which the forming step is performed The formed glass plate is conveyed downward in the vertical direction and is slowly cooled by a plurality of heaters for controlling the temperature in the slow cooling space in the slow cooling space surrounded by the furnace wall; in the cooling step, the cooling step is used The amount of heat released by the heater is obtained by combining the heat retained by the glass sheet with the heat of the space in the slow cooling space, and based on a predetermined relationship between the retained heat and the strain of the glass sheet. The strain of the glass plate, and the heat of the glass plate is corrected by controlling the heat of the heater, thereby The strain of the above glass plate is suppressed.

(Form 2)

The method for producing a glass sheet according to the first aspect, wherein the slow cooling space is divided into a plurality of spaces in the vertical direction, and a plurality of heaters are used in each space to control a temperature in the space, and based on The results of the strain of the glass plate were obtained in each of the above spaces, and the heat of the heater discharged from the heater was controlled.

(Form 3)

The method for producing a glass sheet according to aspect 1 or 2, wherein the strain of the glass sheet is obtained by thermal fluid analysis simulation and viscoelastic model analysis and simulation.

(Form 4)

The method for producing a glass sheet according to the third aspect, wherein the slow cooling space is divided into a plurality of spaces in the vertical direction, and in the thermal fluid analysis simulation, the glass sheet is entered into each of the plurality of spaces. The retained heat is set as the heat retained when the glass sheet enters, and the glass sheet is obtained in each of the plurality of spaces by providing the heat retained by the glass sheet at the time of entry and the heat release amount of the heater. The above glass plate retains heat.

(Form 5)

The method for producing a glass sheet according to claim 4, wherein the thermal fluid analysis simulation is performed in each of the plurality of spaces in the plurality of spaces, and the plurality of spaces are in the plurality of spaces. The upstream side of the flow direction of the glass sheet is a space after the second stage, and the temperature distribution when the glass sheet flows out in the space adjacent to the upstream side is used as the heat retention at the time of entry.

(Form 6)

A manufacturing apparatus for a glass sheet, characterized in that it uses a pull-down method and includes a forming device, the forming device comprising: a molded body in which molten glass is formed into a sheet-shaped glass plate; a slow cooling space in which a glass plate formed in the formed body is conveyed downward in a vertical direction and surrounded by a furnace wall; and a plurality of heaters, The glass plate is slowly cooled by controlling the temperature in the slow cooling space; the forming device has a first portion that uses the heat release amount emitted by the heater to maintain the heat retained by the glass plate and the slowing The heat of the space in the cold space is obtained together, and the strain of the glass plate is determined based on the predetermined relationship between the retained heat and the strain of the glass plate; and the second portion is corrected by controlling the heat of the heater. The glass plate retains heat, thereby suppressing the strain of the glass plate.

According to the present invention, the warpage and strain of the glass sheet can be reduced by controlling the amount of heat generated by the heater controlling the temperature of the slow cooling space.

41‧‧‧Insulation members

42a‧‧‧ forming area

42b~42f‧‧‧Slow space

100‧‧‧ glass plate manufacturing equipment

200‧‧‧melting device

201‧‧‧melting tank

202‧‧‧Clarification tank

203‧‧‧Stirring tank

204‧‧‧First piping

205‧‧‧Second piping

300‧‧‧Forming device

310‧‧‧Formed body

311‧‧‧ supply port

312‧‧‧ Groove Department

313‧‧‧Under the molded body

314‧‧‧Under the molded body

320‧‧‧Interval spacers

330‧‧‧Cooling roller (roller)

340‧‧‧Cooling unit

350a~350e‧‧‧Drawing roller (roller)

360a~360e‧‧‧heater

361a~366a‧‧‧heating department

380‧‧‧ thermocouple unit

381‧‧‧Main power switch

390‧‧‧Cooling roller drive motor

391‧‧‧Drawing roller drive motor

392‧‧‧cutting device drive motor

400‧‧‧cutting device

410‧‧‧Receiving Department

420‧‧‧ Slow cooling zone

500‧‧‧Control device

SG‧‧‧glass plate

ST1~ST6‧‧‧Steps

Fig. 1 is a partial flow chart showing a method of manufacturing a glass sheet of the embodiment.

Fig. 2 is a view mainly showing a melting device included in a manufacturing apparatus of a glass plate used in the method for producing a glass sheet of the embodiment.

Figure 3 is a schematic front view of the forming apparatus.

Figure 4 is a schematic side view of the forming apparatus.

Figure 5 is a control block diagram of the control device.

Fig. 6 is a partially enlarged plan view showing a schematic front view of the forming apparatus.

Figure 7 is a schematic cross-sectional view of the forming apparatus.

Figure 8 is a cross-sectional view taken along line A of Figure 7.

Fig. 9 is a view showing a model of a slow cooling space in the present embodiment.

Figure 10 is a graph showing the relationship between ordinary glass temperature and specific heat.

Figure 11 is a graph showing stress relaxation parameters of a glass sheet.

Figure 12 is a graph showing the structural relaxation parameters of a glass sheet.

Hereinafter, a method of manufacturing a glass sheet of the present embodiment in which a glass sheet is manufactured by using a glass plate manufacturing apparatus will be described with reference to the drawings.

(1) Outline of the manufacturing method of glass plate

Fig. 1 is a partial flow chart showing a method of manufacturing a glass sheet of the embodiment.

Hereinafter, a method of manufacturing a glass sheet will be described using FIG. 1 .

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

In the melting step ST1, the glass raw material is heated and melted. The glass raw material contains, for example, SiO ₂ , Al ₂ O ₃ or the like. 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. Further, in this step, the clarified molten glass is subjected to temperature adjustment.

In the forming step ST4, the molten glass is formed into a sheet-shaped glass plate by a down-draw method (for example, an overflow down-draw method).

In the cooling step ST5, cooling of the glass sheet formed in the forming step ST4 is performed. In this cooling step ST5, the glass plate is cooled to a temperature close to room temperature.

In the cutting step ST6, the glass plate which has been cooled to a temperature close to room temperature is cut for each specific length to prepare a glass plate.

Furthermore, the glass plate that has been cut for each specific length is further cut and then advanced. It is used for flat-panel display such as liquid crystal display by grinding, polishing, cleaning, and inspection to form a glass plate.

(2) Outline of the manufacturing apparatus 100 for glass sheets

FIG. 2 is a schematic view mainly showing a melting device 200 included in the manufacturing apparatus 100 for a glass sheet. 3 is a schematic front view of a molding apparatus 300 included in the apparatus 100 for manufacturing a glass sheet. 4 is a schematic side view of the forming apparatus 300. Hereinafter, the glass plate manufacturing apparatus 100 will be described.

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

(2-1) Composition of the melting device 200

The melting device 200 is a device for performing a melting step ST1, a clarification step ST2, and a homogenization step ST3.

As shown in FIG. 2, the melting apparatus 200 has a melting tank 201, a clarification tank 202, a stirring tank 203, a first piping 204, and a second piping 205.

The melting tank 201 is a tank for melting the glass raw material. In the melting tank 201, a melting 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 further heats the molten glass fed from the melting tank 201, thereby promoting defoaming of the bubbles in the molten glass. In the clarification tank 202, a clarification step ST2 is performed.

The stirring tank 203 has a stirring device including a container for accommodating molten glass, a rotating shaft, and a stirring blade attached to the rotating shaft. As the container, the rotating shaft, and the stirring blade, for example, a platinum group element such as platinum or an alloy of a platinum group element can be used, but it is not limited thereto. The rotating shaft is rotated by driving of a driving unit (not shown) such as a motor, whereby the stirring blade attached to the rotating shaft stirs the molten glass. In the stirring tank 203, a homogenization step ST3 is performed.

The first pipe 204 and the second pipe 205 are, for example, pipes containing an alloy of a platinum group element or a platinum group element. 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 forming device 300.

(2-2) Composition of Forming Apparatus 300

The forming apparatus 300 is a device for performing the forming 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 spacing member 320, a cooling roller 330, a cooling unit 340, stretching rolls 350a to 350e, and heaters 360a to 360e. Hereinafter, the configuration of the above will be described.

(2-2-1) formed body 310

The formed body 310 is a device for performing the forming step ST4.

As shown in FIG. 3, the formed body 310 is located above the forming apparatus 300, and has a function of forming the molten glass flowing from the melting apparatus 200 into a sheet-shaped glass sheet SG by an 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 brick.

As shown in FIG. 4, in the molded body 310, a supply port 311 is formed on the upstream side of the flow path of the molten glass flowing from the melting apparatus 200. Moreover, as shown in FIG. 4, in the molded object 310, the groove part 312 which opened upwards is formed along the longitudinal direction. The groove portion 312 is formed to gradually become shallower toward the downstream side from the upstream side in the flow path direction of the molten glass.

The molten glass flowing from the melting device 200 toward the forming device 300 flows to the groove portion 312 of the formed body 310 via the supply port 311.

The molten glass flowing to the groove portion 312 of the formed body 310 overflows at the top of the groove portion 312, and flows down the both side faces 313 of the formed body 310. Then, the molten glass which flows down along the both side surfaces 313 of the molded body 310 merges in the lower part 314 of the molded object 310, and becomes the glass plate SG.

(2-2-2) atmosphere spacing member 320, heat insulating member 41

As shown in FIGS. 3 and 4, the atmosphere spacing member 320 is disposed below the molded body 310. Plate-shaped member near 314.

The atmosphere spacing member 320 is disposed substantially horizontally on both sides in the thickness direction of the glass sheet SG flowing down from the lower portion 314 of the molded body 310. The atmosphere partition member 320 functions as a heat insulating material. That is, the ambience spacer member 320 suppresses the movement of heat from the upper side to the lower side of the ambience spacer member 320 by separating the air above and below it. As shown in FIGS. 3 and 4, the molding apparatus 300 has a space above the atmosphere partition member 320, that is, a molded body accommodating portion 410, a space directly below the ambience spacer 320, that is, a forming portion 42a, and a space below the forming portion 42a. Slow cooling zone 420. The slow cooling zone 420 has a plurality of slow cooling spaces 42b, 42c, ..., 42f. The forming zone 42a and the slow cooling spaces 42b to 42f are sequentially stacked from the upper side toward the lower side in the vertical direction. The forming zone 42a and the slow cooling zone 420 (slow cooling space 42b-42f) are formed by being surrounded by the furnace wall, and the glass plate SG moves in the forming zone 42a and the slow cooling zone 420 (slow cooling space 42b-42f).

The heat insulating member 41 is a plate-shaped heat insulating material disposed in the slow cooling zone 420 below the cooling roll 330 described below and on both sides in the thickness direction of the glass plate SG. The heat insulating member 41 forms the forming region 42a and the slow cooling spaces 42b to 42f by separating the space below the atmosphere spacing member 320. For example, as shown in FIG. 4, the heat insulating member 41 forms a forming zone 42a and a slow cooling space 42b. Further, the heat insulating member 41 forms a slow cooling space 42b and a slow cooling space 42c. In this manner, the slow cooling spaces 42b to 42f are formed by being surrounded by the furnace wall and the heat insulating member 41. Each of the heat insulating members 41 suppresses heat transfer between the upper and lower spaces. For example, the heat insulating member 41 suppresses heat transfer between the forming 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 ambience spacer 320. Further, the cooling rolls 330 are disposed on both sides in the thickness direction of the glass sheet SG, and are disposed to face opposite ends of the glass sheet SG in the width direction. The cooling roller 330 is air-cooled by an air cooling pipe that penetrates inside. Thus, when the glass sheet SG passes through the cooling roll 330, both sides of the glass sheet SG in contact with the air-cooled cooling roll 330 in the thickness direction and both end portions in the width direction thereof (hereinafter, this portion is referred to as glass) The ears R, L) of the plate SG are cooled. Thereby, the viscosity of the ear portions R and L is set to a specific value (for example, 10 ^9.0 poise) or more. Here, the ear portions R and L refer to a portion having a specific thickness in a central portion (central portion) in the width direction of the glass sheet SG sandwiched between the ear portions R and L, and the central portion (the central portion) The central portion is used as a portion of the product (glass substrate) having a substantially uniform thickness. The cooling roll 330 also has a function of stretching the glass plate SG downward by transmitting the driving force of the cooling roll drive motor 390 (see FIG. 5). The glass sheet SG is stretched to a specific thickness by the cooling roll 330.

(2-2-4) Cooling unit 340

The cooling unit 340 is, for example, an air-cooling type cooling device that cools the cooling roll 330 and the ambient temperature of the glass plate SG passing thereunder. Further, the cooling unit 340 is disposed in plural (for example, three) in the width direction of the glass sheet SG, and a plurality of the cooling units 340 are disposed in the flow direction. Specifically, the cooling unit 340 is disposed one by one so as to face the surfaces of the ear portions R and L of the glass sheet SG, and is disposed to face the surface of the central portion.

(2-2-5) stretching rolls 350a~350e

The stretching rolls 350a to 350e are disposed below the cooling rolls 330 and are disposed at a predetermined interval in the flow direction of the glass sheets SG. Further, the stretching rolls 350a to 350e are disposed on both sides in the thickness direction of the glass sheet SG, and are disposed in the slow cooling spaces 42b to 42f so as to oppose the both end portions in the width direction of the glass sheet SG. Further, the stretching rolls 350a to 350e are in contact with both end portions in the thickness direction of the glass plate SG having a viscosity equal to or greater than a specific value in the ear portions R and L of the cooling roll 330, and are in contact with each other in the width direction. The glass plate SG is stretched downward. Further, the stretching rolls 350a to 350e are driven by transmitting the driving force of the stretching roll driving motor 391 (see FIG. 5). The peripheral speed of the stretching rolls 350a to 350e is greater than the peripheral speed of the cooling roll 330. The peripheral speed of the stretching rolls becomes larger as it is disposed on the downstream side in the flow direction of the glass sheet SG. That is, among the plurality of stretching rolls 350a to 350e, the peripheral speed of the stretching roll 350a is the smallest, and the peripheral speed of the stretching roll 350e is the largest.

(2-2-6) heater (temperature control unit)

As shown in FIG. 3, heaters (temperature control units) 360a to 360e are respectively disposed in the forming region 42a and the slow cooling spaces 42b to 42f below the cooling unit 340, and the atmosphere of the forming region 42a and the slow cooling spaces 42b, 42c, ... Temperature is controlled. The heaters 360a to 360e function as the following cooling means, that is, by controlling the output by the control device 500 described below, the temperature of the atmosphere near the glass sheet SG pulled downward by the stretching rolls 350a to 350e is controlled (specifically In other words, the ambient temperature is raised). Further, as shown in FIGS. 6 and 7, each of the heaters 360a to 360e has a plurality of (for example, three, six, or the like) heat radiating portions 361a, 362a, ..., 366a arranged in the width direction. The heat radiating portions 361a to 366a are heat radiating bodies that release heat to the slow cooling space. The heat radiating portions 361a to 366a are configured to be embedded in the furnace wall and each of which is supplied with electric power to radiate heat. As shown in FIG. 6, the heat radiating portions 361a to 366a are arranged in a line along the width direction of the glass sheet SG at a position facing the both sides of the glass sheet SG. Fig. 6 shows the heat radiating portions 361a to 366a provided in the slow cooling space 42b, and the heaters 360b to 360e having the same heat radiating portion form a specific temperature in the width direction of the glass plate SG by the ambient temperature in the vicinity of the glass plate SG. The distribution (hereinafter referred to as "temperature distribution") is set. In this manner, the heaters 360a to 360e having the heat radiation portion control the atmosphere temperatures of the forming region 42a and the slow cooling spaces 42b to 42f. In addition, the heat radiating portion of each of the heaters 360a to 360e may be configured not only in a plurality of directions in the width direction of the glass sheet SG but also in a plurality of flow directions in the glass sheet SG.

Here, the ambient temperature of the glass sheet SG pulled downward by the stretching rolls 350a to 350e is temperature-controlled by the heaters 360a to 360e (heat radiating portions 361a to 366a) (specifically, by controlling the ambient temperature of the glass sheet SG) On the other hand, the glass plate SG is subjected to temperature control, whereby the self-adhesive region of the glass plate SG is moved to the elastic region through the viscoelastic region.

Further, in the vicinity of the heat radiation portions 361a to 366a, thermocouple units 380 (see FIGS. 5 to 7) for detecting the ambient temperature of each region of the glass sheet SG are disposed. The thermocouple unit 380 measures the ambient temperature of the slow cooling spaces 42b to 42f which are changed by the heat release of the heat radiating portions 361a to 366a. set. The control device 500 acquires the ambient temperature measured by the thermocouple unit 380, and controls the amount of heat released from the heat radiating portions 361a to 366a provided in the heaters 360a to 360e based on the acquired ambient temperature. The step of cooling the glass sheet SG by the cooling roller 330, the cooling unit 340, and the heaters 360a to 360e (the heat radiating portions 361a to 366a) in the region below the lower portion 314 of the molded body 310, that is, the forming region 42a and the slow cooling spaces 42b to 42f To cool step 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 sheet SG that has flowed down from the molding apparatus 300 from a direction perpendicular to the longitudinal surface of the glass sheet SG. Thereby, the sheet-shaped glass plate SG becomes a plurality of glass plates SG having a specific 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 (Central Processing Unit), a ROM (Read-Only Memory), a RAM (Random-Access Memory), a hard disk, etc., and serves as a pair of glasses. The control unit that controls the various devices included in the manufacturing apparatus 100 of the board functions.

Specifically, the manufacturing apparatus 100 or the molding apparatus 300 of the glass sheet is provided with the control apparatus 500. As shown in FIG. 5, this control apparatus 500 receives various sensors (for example, the thermocouple unit 380) included in the manufacturing apparatus 100 of a glass plate. a signal such as a switch (for example, the main power switch 381 or the like), an input instruction input from an operator via an input device (not shown), or the like, and the cooling unit 340 and the heaters 360a to 360e (the heat radiating portion 361a) ~366a), a cooling roll drive motor 390 that controls the operation of the cooling roll 330, a drawing roll drive motor 391 that controls the operation of the stretching rolls 350a to 350e, and a cutting of the operation of the cutting device 400 The device drives the control of the motor 392 and the like.

(4) Temperature control in the cooling step ST5

The cooling step ST5 includes the control device 500 being controlled by controlling the cooling roller 330 The temperature of the glass plate SG. Further, the cooling step ST5 includes a temperature control step of temperature control of the glass sheet SG. Specifically, in the temperature control step, the heat radiation portions 361a to 366a of the cooling unit 340 and the heaters 360a to 360e are controlled to control the temperature of the glass plate SG, thereby controlling the temperature of the glass plate SG. Take control.

Further, the cooling step ST5 includes a heat control step of controlling the heat release amount of the heat radiation portions 361a to 366a so that the temperature of the glass sheet SG enters a specific temperature range at a specific height position (specific slow cooling space), and the glass plate is made The temperature of the SG has a specific temperature distribution in the width direction of the glass sheet SG. That is, the temperature of the glass sheet SG is controlled in the flow direction and the width direction of the glass sheet SG.

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

The procedure for determining the amount of heat generated by the heat radiating portions 361a to 366a will be described below. i) The control unit 500 initially sets the heat radiation units 361a to 366a to a specific set temperature, and causes the ambient temperature in the vicinity of the glass sheet SG to be in the width direction of the glass sheet SG in the slow cooling spaces 42b to 42f (slow cooling zone 420). A specific temperature profile is formed.

Ii) The ambient temperature in the heat retention (temperature of the glass plate SG) and the slow cooling space 42b to 42f (slow cooling zone 420) held by the glass plate SG is obtained.

Iii) Calculating the temperature distribution and strain distribution of the formed glass sheet SG based on the temperature of the glass sheet SG obtained in the above ii) and the ambient temperature in the slow cooling spaces 42b to 42f, and reducing the obtained The heat generated by the heat radiating portions 361a to 366a (set temperature) is controlled in a strain manner.

A method for determining the temperature distribution of the glass sheet SG in order to control the heat generated by the heat radiating portions 361a to 366a (the set temperature of the heat radiating portions 361a to 366a) will be described below. The method uses thermal fluid analysis simulation and viscoelastic analysis simulation.

<Thermal Fluid Analysis Simulation>

In thermal fluid analysis simulations, for example, thermal fluid analysis is performed using a discrete model based on a finite element method. In the thermal fluid analysis, the heater heat generated by the heat radiating portions 361a to 366a is provided, that is, the set temperatures of the heat radiating bodies 361a to 366a are provided, and the temperature distribution of the atmosphere of the slow cooling space 42b to 42f and the temperature distribution of the glass plate SG are provided. When the number is unknown, the heat distribution, that is, the temperature distribution of the glass sheet SG in the entire slow cooling space (slow cooling zone) is obtained. The simulation was carried out under the following conditions.

Model

The slow cooling space 42b, which is one of the plurality of sections separated into the slow cooling zone 420 in the flow direction of the glass sheet SG, is discretized as a mesh model, and the glass in the first section of the slow cooling space 42b is obtained by thermal fluid analysis. The temperature distribution of the plate SG. At this time, the temperature distribution of the glass sheet SG entering the slow cooling space 42b is predetermined. Further, the temperature distribution in the width direction when the temperature distribution of the glass sheet SG in the first slow cooling space 42b flows out from the slow cooling space 42b is defined as the temperature distribution of the glass sheet SG entering the second slow cooling space 42c. . In this manner, the temperature distribution of the glass sheets in each of the slow cooling spaces is determined using the temperature distribution of the glass sheets SG entering each of the slow cooling spaces. Thus, the temperature distribution of the glass sheet SG in the entire slow cooling space is simulated.

Fig. 9 shows a model of the first stage slow cooling space 42b as seen from the flow direction of the glass sheet SG. The heat retained by the glass sheet SG entering the slow cooling space 42b and the heater heat (set temperature) of the heater 360a (heat radiating portions 361a to 366a) are provided, and the glass sheet SG in the first stage slow cooling space 42b is provided. The temperature distribution is obtained together with the ambient temperature in the slow cooling space 42b. Further, in the slow cooling space after the second stage on the downstream side of the first stage, the temperature distribution of the glass sheet SG is obtained in the same manner as the first stage, and the temperature distribution of the plurality of glass sheets SG obtained is obtained. Together, the temperature distribution of the glass sheet SG of the entire slow cooling space 42b to 42f (slow cooling zone 420) is obtained.

Consider (1) heat retention of the glass sheet SG when entering the slow cooling space 42b, (2) heater heat (set temperature) of the heater 360a (heat radiating portions 361a to 366a), and (3) slow cooling space 42b The temperature distribution of the glass sheet SG in the first slow cooling space 42b is analyzed by the influence of the ambient temperature. The above (1) to (3) will be described as follows.

(1) The heat retention of the glass plate SG when entering the slow cooling space 42b

The heat retention (temperature distribution) of the glass plate SG is measured using a temperature sensor (not shown) provided at a position where the glass plate SG enters the slow cooling space 42b (on the upstream side of the slow cooling space 42b). Since the amount of molten glass flowing out from the molded body 310 is fixed, the flow rate (transport speed) of the glass sheet SG is fixed, and the glass sheet SG can be obtained when entering the slow cooling space 42b based on the measured temperature (temperature distribution). Heat. In addition, the heat retention (temperature distribution) of the glass sheet SG when entering the slow cooling space 42b can be obtained from the flow rate of the glass sheet SG and the temperature of the molten glass flowing into the molded body 310.

(2) Heat release amount of the heater 360a (heat radiating portions 361a to 366a) (set temperature)

The heat release amount of each of the heat radiation portions 361a to 366a changes according to the set temperature set by the control device 500. The heat of the heater discharged from each of the heat radiating portions 361a to 366a based on the set temperature is obtained based on the measurement results of a power meter (not shown) of the heat radiating portions 361a to 366a provided in the power supply device. Therefore, when the heat release amount of the heat radiation portions 361a to 366a is controlled, the electric power applied to each of the heat radiation portions 361a to 366a is controlled. Here, the set temperature initially set by the heat radiation portions 361a to 366a of the heater 360a of the slow cooling space 42b is set to, for example, 700 °C. The heat release amounts of the heat radiators 361a to 366a may be the same, and the heat release amount may be distributed. Further, since the initially set temperature of 700 ° C is exemplified, the temperature of the heat radiating portions 361 a to 366 a can also be obtained as an unknown result as a calculation result. The inflow temperature of the glass plate SG may be calculated, for example, at 700 ° C, and the inflow temperature of the glass plate SG may be set such that the measured temperature and the calculated temperature are in good agreement. The average current (A) of the heat radiating portions 361a to 366a set by the temperature. Voltage (V). The power factor was actually measured, and the amount of heat release (W) was calculated and converted into an exothermic density (W/m ³ ) as a calculation condition. The temperature is obtained in the form of a calculation result (solution), and thus can be obtained by comparing the calculation result with the set temperature and repeating the modification condition in such a manner as to achieve a good agreement.

(3) Ambient temperature in the slow cooling space 42b

The ambient temperature in the slow cooling space 42b changes according to the heat retained by the glass plate SG and the heater heat of the heat radiating portions 361a to 366a. The ambient temperature in the slow cooling space 42b is based on the assumption that the atmosphere of the slow cooling space 42b is an uncompressed ideal gas, and the natural convection caused by buoyancy and the heat transfer caused by the natural convection are included in the glass plate SG. The heat transfer is coupled in the same thermal fluid analysis model. Furthermore, in the present embodiment, the ambient temperature in the slow cooling space 42b is solved as an unknown number in the thermal fluid analysis, and instead, the ambient temperature in the slow cooling space 42b may be measured by the thermocouple unit 380. The heat held in the slow cooling space 42b (the ambient temperature in the slow cooling space 42b) is obtained, and this heat is supplied as the ambient temperature in the slow cooling space 42b in the thermal fluid analysis, thereby calculating the temperature of the glass plate SG. distributed.

2. Physical property value

The physical property values of the materials constituting the glass sheet 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 Figure 10.

B. Stretching rolls 350a~350e (stainless steel SUS304)

Ii) Thermal conductivity: 16.0 [W/mK] (27 ° C), 25.7 [W/mK] (727 ° C).

C. Atmosphere spacer member 320, heat insulating member 41, furnace wall (heat insulation material)

i) Thermal conductivity: 0.04~0.3 [W/mK].

3. Calculation conditions

Since it is a steady state calculation (calculation of a system whose time does not change), an algorithm of thermal fluid analysis is used. The flow is set to be stable, and the fluid flow, convective heat transfer, and radiation heat transfer are coupled using the SIMPLE algorithm and solved using a single solution. for For solving the program, a commercially available software can be used, and a well-known general thermal fluid analysis software can be used. Here, in the thermal fluid analysis, the glass plate SG is calculated as a fluid, and since the moving speed of the glass plate SG is known to be the same as the conveying speed, the flow rate of the entire glass plate SG region is fixed and calculated. Also, the air system is assumed to be an ideal gas that is not compressive, and the heat transfer caused by natural convection is included in the calculation.

By inputting the above conditions and physical property values to the general-purpose thermal fluid analysis software, the temperature distribution of the glass sheet SG in the first-stage slow cooling space 42b can be obtained.

Next, the temperature distribution of the glass sheet SG in the slow cooling spaces 42c to 42f after the second stage is obtained. Regarding the slow cooling spaces 42c to 42f after the second stage, a discretized mesh model is also produced in the same manner as the slow cooling space 42b. Specifically, in the mesh model, the heat retention of the glass sheet SG flowing into the slow cooling spaces 42c to 42f is determined by using the glass sheet SG which is obtained as a result of the thermal fluid analysis and flows out from the last slow cooling space. Keep heat (temperature distribution). That is, for example, for the heat retention of the glass sheet SG entering the second-stage slow cooling space 42c, the temperature (temperature distribution) obtained in the first-stage slow cooling space 42b obtained as a result of the thermal fluid analysis is used. When the glass plate SG flows out from the first slow cooling space 42b, the glass plate SG retains heat.

Further, the set temperature of the heat radiating 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 than the upper stage, preferably set to a temperature lower by 15 ° C, and is directed to the flow direction. For a period of advancement, the set temperature is set to a temperature which is lowered in the range of 5 ° C to 30 ° C, and it is preferably set to a temperature of 15 ° C per time.

The condition for determining the temperature distribution of the entire glass plate SG in the slow cooling space 42c to 42f after the second stage by the thermal fluid analysis and the temperature distribution of the glass plate SG in the first stage slow cooling space 42b are used. Since the conditions and physical property values are the same, the description is omitted.

In this way, in the thermal fluid analysis simulation, the heat retained by the glass sheet entering each of the plurality of slow cooling spaces is set as the heat retained when the glass sheet enters, and the heat retained by the glass sheet and the heater are provided. Heat, which can be used to determine the number of cooling of the glass plate The glass plate in each of the spaces retains heat. At this time, the thermal fluid analysis simulation is performed in each of the plurality of cooling spaces, and in the cooling space of the second stage after seeing from the upstream side of the flow direction of the glass plate in the plurality of cooling spaces, The temperature distribution of the glass sheet from the cooling space adjacent to the upstream side is used as the heat retention at the time of entry.

In this way, the temperature distribution of the glass sheet SG in each of the slow cooling spaces is obtained by thermal fluid analysis, and the temperature distribution of the glass sheets SG in each of the slow cooling spaces is connected in plurality. The temperature distribution of the glass sheet SG in the entire section of the slow cooling space 42c to 42f (the slow cooling zone 420).

<Viscoelastic Analysis Simulation>

Using the heat retention (temperature distribution) of the glass plate SG in the entire region (slow cooling zone 420) of the slow cooling space 42b to 42f obtained by the above thermal fluid analysis, the strain distribution of the glass plate SG is obtained by the viscoelastic model analysis. .

Specifically, the temperature distribution of the glass sheet SG in the entire region of the slow cooling space 42b to 42f obtained by the above thermal fluid analysis, the physical property value of the glass sheet SG, and the stress relaxation parameter and structural relaxation parameter of the glass sheet SG The analysis is performed by inputting to a known analysis software, thereby performing a viscoelastic model analysis to determine the strain distribution of the glass plate. Specifically, the strain distribution is obtained by considering the stress relaxation parameter and the structural relaxation parameter. In the slow cooling space 42b to 42f, the temperature of the glass sheet SG is not uniform in the width direction, and the thermal stress is continuously generated due to the difference in shrinkage, and the stress is continuously alleviated. Therefore, in order to evaluate the residual stress remaining on the glass sheet SG, it is necessary to perform not only the calculation of the thermal stress based on shrinkage but also the stress relaxation in which the stress is reduced with time. Therefore, stress relaxation is considered by using the viscoelastic model of the structural analysis software. Further, in order to determine the structural relaxation parameter, shrinkage due to structural relaxation may also be considered. The shrinkage of the glass sheet SG has a thermal expansion due to a decrease in temperature due to thermal expansion, and a heat expansion as a contraction due to structural relaxation. Since the volume of the glass plate SG is reduced when it is left at a high temperature for a long time, it is set as a structural relaxation parameter. By using The off-line experiment with the estimated structural relaxation parameters is to adjust the structural relaxation parameters in a manner consistent with the shrinkage results of the multiple heat treatments.

According to the results of the viscoelastic analysis, the temperature distribution of the glass plate has a correlation with the strain of the glass plate, so the correlation can be obtained in advance, and based on the correlation, the glass plate can be obtained from the temperature (temperature distribution) of the glass plate SG. Strain distribution of SG. The stress relaxation parameters of the glass sheet SG and the structural relaxation parameters described above are shown in Fig. 11 and Fig. 12, respectively, as measured by experiments.

According to the above, the strain distribution of the glass plate SG can be obtained by thermal fluid analysis and viscoelastic model analysis.

The strain distribution of the glass sheet SG obtained by the above method is determined based on the amount of heat generation in the initial state in which the set temperatures of the heat radiating portions 361a to 366a are set to 700 ° C, and the set temperatures of the heat radiating portions 361a to 366a are changed. The strain distribution of the glass plate SG also changes. Since the relationship between the change in the set temperature of the heat radiating portions 361a to 366a and the strain change of the glass plate SG is obtained by using the thermal fluid analysis and the viscoelastic model analysis, it can be controlled by suppressing the strain distribution of the glass plate SG. The set temperatures of the heat radiating portions 361a to 366a reduce the warpage and strain of the glass sheet SG.

Further, the strain measuring device (strain measuring sensor) may be placed in the slow cooling spaces 42b to 42f to measure the warpage, strain, and temperature distribution of the glass plate SG. Strain measurement and temperature measurement (thermocouple) are measured differently, but they can also be measured in the same place.

Further, the heat retention (temperature distribution) of the glass sheet SG may be changed by being sandwiched by the stretching rolls 350a to 350e. At this time, the heat retention (temperature distribution) of the stretching rolls 350a to 350e is measured by the thermocouple unit 380 or the heat detecting sensor provided by the stretching rolls 350a to 350e. The warpage and strain of the glass sheet SG can also be obtained by performing simulation using both the heat retained by the stretching rolls 350a to 350e and the retained heat of the glass sheet SG.

Specifically, when performing the above-described thermal fluid analysis simulation, a mesh model of the stretching rolls 350a to 350e may be added to each model of the slow cooling space, and the mesh of the stretching rolls 350a to 350e may be determined based on the above measurement results. The model retains heat and solves the ambient temperature of the slow cooling space and the temperature distribution of the glass sheet SG by imparting a set temperature to the heat radiating portion. Thereby, the temperature distribution of the glass plate SG can be obtained more accurately.

In the above, the method for producing the glass sheet of the present invention and the apparatus for producing the glass sheet are described in detail. The present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the spirit and scope of the invention. .

42b‧‧‧Slow space

361a~366a‧‧‧heating department

SG‧‧‧glass plate

Claims (6)

A method for producing a glass sheet, characterized in that it is a pull-down method, and includes: a forming step of forming a molten glass into a sheet-shaped glass sheet; and a slow cooling step in which the forming step is performed The formed glass sheet is conveyed downward in the vertical direction and is slowly cooled by a plurality of heaters that control the temperature in the slow cooling space in the slow cooling space surrounded by the furnace wall; in the slow cooling step, Using the amount of heat released by the heater, the heat retained by the glass plate is obtained together with the heat of the space in the slow cooling space, and is determined based on a predetermined relationship between the retained heat and the strain of the glass plate. The strain of the glass sheet is corrected by controlling the heat of the heater to suppress the heat retained by the glass sheet, thereby suppressing the strain of the glass sheet. The method for manufacturing a glass sheet according to claim 1, wherein the slow cooling space is divided into a plurality of spaces in the vertical direction, and a plurality of heaters are used to control the temperature in the space in each space, and based on the above The results of the strain of the glass plate were determined in each space, and the heat of the heater discharged from the heater was controlled. The method for producing a glass sheet according to claim 1 or 2, wherein the strain of the glass sheet is determined by a thermal fluid analysis simulation and a viscoelastic model analysis simulation. The method for producing a glass sheet according to claim 3, wherein the slow cooling space is divided into a plurality of spaces in the vertical direction, and in the thermal fluid analysis simulation, the glass plate is entered into each of the plurality of spaces. The heat retention is set to retain the heat when the glass plate enters, and The amount of heat retained by the glass sheet in each of the plurality of spaces is determined by the heat retained by the glass sheet at the time of entry and the amount of heat released by the heater. The method of manufacturing a glass sheet according to claim 4, wherein said glass frit is flowed in said plurality of spaces, said thermal fluid analysis simulation being performed in each of said plurality of spaces, and said plurality of spaces The upstream side of the flow direction of the glass sheet is seen as the space after the second stage, and the temperature distribution when the glass sheet flows out in the space adjacent to the upstream side is used as the heat retention at the time of entry. A glass plate manufacturing apparatus characterized by using a down-draw method and comprising a molding device comprising: a molded body which forms a molten glass into a sheet-shaped glass plate; a slow cooling space, which The glass plate formed in the molded body is conveyed downward in the vertical direction and surrounded by the furnace wall; and a plurality of heaters control the temperature in the slow cooling space to slowly cool the glass plate; The forming device has a first portion that uses the amount of heat released by the heater to obtain the heat retained by the glass sheet together with the heat of the space in the slow cooling space, and based on the retained heat and the glass sheet The predetermined relationship between the strains is used to determine the strain of the glass sheet; and the second portion is configured to correct the heat retained by the glass sheet by controlling the heat of the heater to suppress the strain of the glass sheet.