WO2013001834A1

WO2013001834A1 - Glass plate manufacturing method and glass plate manufacturing device

Info

Publication number: WO2013001834A1
Application number: PCT/JP2012/004231
Authority: WO
Inventors: 浩幸苅谷; 公彦中嶋
Original assignee: ＡｖａｎＳｔｒａｔｅ株式会社; アヴァンストレートコリアインコーポレイテッド
Priority date: 2011-06-30
Filing date: 2012-06-29
Publication date: 2013-01-03
Also published as: TWI417255B; TWI561482B; CN103108840A; JPWO2013001834A1; KR20130035252A; KR101442384B1; JP2016006007A; KR20140017417A; TW201328997A; CN103253848B; JP5778196B2; JP2013126946A; CN103253848A; JP6125572B2; JP5235249B1; TW201305069A; CN103108840B; KR101300934B1

Abstract

A glass plate manufacturing method comprises: a melting step for melting a glass starting material to obtain molten glass; a forming step for supplying the molten glass to a forming body provided in a forming furnace to form a glass ribbon and creating the flow of the glass ribbon; a slow cooling step for pulling the glass ribbon by a roller provided in a slow cooling furnace and cooling slowly the glass ribbon in the slow cooling furnace; and a cutting step for cutting the cooled glass ribbon in a cutting space. When the interior space of the forming furnace and the interior space of the slow cooling furnace are defined as a furnace interior space and the exterior spaces of the forming furnace and the slow cooling furnace are defined as a furnace exterior space, the furnace exterior space is a space separated from an atmospheric pressure atmosphere by a partition wall. The atmospheric pressure in the furnace exterior space is adjusted such that the atmospheric pressure in at least a part of the furnace exterior space is lower than the atmospheric pressure in the furnace interior space at the same position in the flow direction of the glass ribbon.

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 by a downdraw method.

Conventionally, for example, a downdraw method is used as a method for forming a glass substrate used in a flat panel display such as a liquid crystal display.
Among the downdraw methods, the overflow downdraw method includes a step of forming a glass ribbon below the formed body by allowing molten glass to overflow from the top of the formed body in a forming furnace, and a step of gradually cooling the glass ribbon in a slow cooling furnace. Including. The slow cooling furnace draws the glass ribbon between the pair of rollers and stretches the glass ribbon to a desired thickness, and then slowly cools the glass ribbon so as to reduce distortion and thermal shrinkage inside the glass ribbon. Thereafter, the glass ribbon is cut into a predetermined size to form a glass plate, which is laminated on a bundle of glass plates, or conveyed to the next step. About the downdraw method, it describes in the following patent document 1, for example.

For example, when a glass plate is used as a glass substrate for a liquid crystal display, a TFT (Thin Film Transistor) is formed on the surface of the glass sheet. For example, when the TFT is a polysilicon TFT, the glass plate is heat-treated at a temperature of 400 ° C. to 600 ° C. in the display manufacturing process. There is a case. This minute change in dimensions may cause a displacement of the TFT formation position formed on the glass plate with respect to the target position (pixel position), and as a result, display defects of the liquid crystal display may occur. In a liquid crystal display, a glass plate on which a TFT is formed and a glass plate on which a color filter is formed for each pixel are opposed to each other, and a liquid crystal is provided between the glass plates. However, if the glass plate on which the TFT is formed undergoes a minute dimensional change due to heat shrinkage, accurate alignment may not be possible in pixel units with the glass plate on which the color filter is formed. For this reason, in order to reduce the change of the dimension of a glass plate, it is calculated | required by the glass plate that heat contraction is small. The heat shrinkage can be reduced by lowering the cooling rate in the glass ribbon slow cooling step.

By the way, in Patent Document 2 below, in order to reduce the plane distortion of the glass plate, the pressure outside the furnace (space outside the furnace) of the forming furnace and / or the slow cooling furnace is pressurized and generated along the glass ribbon in the slow cooling furnace. The technique which suppresses the temperature fluctuation in a slow cooling furnace by reducing the upward airflow to perform is disclosed.

JP 2009-196879 A JP 2009-173525 A

However, as described in Patent Document 2, if the pressure in the furnace outer space is simply increased, the air in the furnace outer space may flow into the inner space of the forming furnace or the slow cooling furnace. In general, the temperature in the outer space of the furnace is about 200 to 1200 ° C. lower than the temperature in the furnace atmosphere (space inside the furnace) of the forming furnace or the slow cooling furnace. Here, as described in Patent Document 2, an air flow that rises from a cooling chamber, a cutting chamber, or the like into the slow cooling furnace may occur, but even if an air flow occurs, the air flow remains in the slow cooling furnace. As the temperature rises, the effect on temperature fluctuations in the furnace interior space is small. On the other hand, when the air in the furnace outer space flows into the furnace inner space from the gap between the furnace walls of the forming furnace and the slow cooling furnace, the air is not heated, so the temperature difference from the temperature of the furnace inner space is large. In the interior space of the furnace, a temperature difference occurs between the portion through which the inflowing air passes and the other portion, which greatly affects the temperature uniformity of the interior space of the furnace. Here, in order to reduce the thermal contraction rate and the plane strain, it is effective to accurately control the temperature of the glass ribbon. However, when the glass ribbon passes through the furnace interior space of the forming furnace or the slow cooling furnace whose temperature fluctuates as described above, the cooling rate of the glass ribbon is partially different, so that the thermal contraction of the glass plate also varies. The fluctuation indicates that the temperature changes unintentionally from the set temperature.

That is, in the slow cooling treatment (annealing treatment) of the glass plate manufacturing method of Patent Document 2, the temperature in the slow cooling furnace cannot be maintained at the set temperature, and the variation in thermal shrinkage of the glass plate may increase. For this reason, the glass plate is required to have a small variation in thermal shrinkage, for example, a glass plate for flat panel display (in particular, a glass substrate for liquid crystal display, a glass substrate for organic EL display, or an oxide semiconductor thin film transistor). When applied to a display glass substrate to be formed, there is a problem that display defects may occur.

Therefore, an object of the present invention is to provide a method for producing a glass plate that efficiently reduces variation in thermal shrinkage when producing a glass plate by a downdraw method.

One aspect of the present invention is a method for producing a glass plate by a downdraw method,
A melting step of melting glass raw material to obtain molten glass;
Forming the glass ribbon by supplying the molten glass to a molded body provided in a molding furnace, and forming a flow of the glass ribbon;
A slow cooling step of cooling the glass ribbon in the slow cooling furnace by pulling with a roller provided in the slow cooling furnace;
A cutting step of cutting the cooled glass ribbon in a cutting space.
When the internal space of the molding furnace provided with the molded body and the internal space of the slow cooling furnace provided with the roller are furnace internal spaces, and the external space of the molding furnace and the slow cooling furnace is a furnace external space, the furnace The external space is a space partitioned by a partition with respect to the atmospheric pressure atmosphere, and the atmospheric pressure of at least a part of the furnace external space is relative to the atmospheric pressure of the furnace internal space at the same position in the flow direction of the glass ribbon. The atmospheric pressure is adjusted to be low.

At this time, the atmospheric pressure in the outer space of the furnace is in a region between a position in the slow cooling furnace corresponding to the slow cooling point temperature of the glass ribbon and a position in the slow cooling furnace corresponding to the strain point temperature of the glass ribbon. It is preferable that the atmospheric pressure is adjusted so as to be lower than the atmospheric pressure at the same position in the furnace internal space.

Moreover, it is preferable that the difference between the pressure in the furnace internal space and the pressure in the furnace external space is 40 Pa or less at the same position in the flow direction of the glass ribbon with respect to the pressure of the at least part of the furnace external space. .

It is preferable that the pressure outside the furnace is adjusted to be higher than the atmospheric pressure.

The furnace outer space has an upper space located above the ceiling surface of the inner space of the molding furnace, and the upper space does not allow air to flow from the upper space into the furnace inner space. It is preferable that the air pressure in the upper space is adjusted.

The flow direction of the glass ribbon is a vertical direction, and the forming furnace is provided vertically above the slow cooling furnace. At this time, the furnace external space is divided into a plurality of partial spaces in the vertical direction, and the difference between the respective atmospheric pressure of the partial space and the atmospheric pressure of the furnace internal space at the same position in the vertical direction of the partial space, When comparing the uppermost partial space and the lowermost partial space of the partial spaces, the atmospheric pressure is adjusted such that the difference at the uppermost portion is larger than the difference at the lowermost portion. It is preferable.

It is preferable that the difference in the atmospheric pressure in the partial space increases as it goes upward.

The glass plate is, for example, a glass substrate for liquid crystal display on which a TFT (Thin Film Transistor) is formed.

When the outer space of the furnace includes a first partial space at the same position as the formed body in the flow direction of the glass ribbon, the furnace at the same position in the flow direction of the glass ribbon and the atmospheric pressure of the first partial space The difference in atmospheric pressure in the internal space is preferably greater than 0 and 40 Pa or less.

The furnace external space includes a second partial space located at the same position as the slow cooling furnace in the flow direction of the glass ribbon, and the difference between the atmospheric pressure of the furnace internal space of the slow cooling furnace and the atmospheric pressure of the second partial space is 0 It is preferably 40 Pa or less.

The furnace external space includes a first partial space located at the same position as the formed body and a second partial space located at the same position as the slow cooling furnace in the flow direction of the glass ribbon, and the first partial space and the first When two partial spaces are separated by a wall and adjacent to each other, the atmospheric pressure in the first partial space of the furnace external space is larger than the atmospheric pressure in the second partial space, and the atmospheric pressure in the first partial space and the second It is preferable that the difference in the atmospheric pressure of the partial space is smaller than 20 Pa.

The furnace outer space includes a plurality of second partial spaces at the same position as the slow cooling furnace, and the plurality of second partial spaces have higher atmospheric pressure toward the upstream side in the flow direction of the molten glass. preferable.

The slow cooling step includes
In the central part of the width direction of the glass ribbon, so that a tensile stress works in the flow direction of the glass ribbon,
At least in a temperature range from a temperature obtained by adding 150 ° C. to the annealing point temperature of the glass ribbon to a temperature obtained by subtracting 200 ° C. from the strain point temperature of the glass ribbon,
The cooling rate of the central part in the width direction of the glass ribbon is faster than the cooling rate of the both end parts,
It is preferable that the glass ribbon is changed from a state where the temperature of the central portion in the width direction of the glass ribbon is higher than the both end portions to a state where the temperature of the central portion is lower than the both end portions.

The slow cooling step includes a first cooling step, a second cooling step, and a third cooling step,
The first cooling step is a step of cooling at the first average cooling rate until the temperature of the central portion in the width direction of the glass ribbon reaches the annealing point temperature,
The second cooling step is a step of cooling at the second average cooling rate until the temperature of the central portion in the width direction of the glass ribbon reaches the strain point temperature of −50 ° C. from the annealing point temperature,
The third cooling step is a step of cooling at a third average cooling rate until the temperature of the central portion in the width direction of the glass ribbon becomes a strain point temperature of −50 ° C. to a strain point temperature of −200 ° C.
The first average cooling rate is 5.0 ° C./second or more, the first average cooling rate is faster than the third average cooling rate, and the third average cooling rate is the second It is preferable that the cooling rate is higher than the average cooling rate.
At this time, the average cooling rate of the central portion of the glass ribbon in the first cooling step is preferably 5.5 ° C./second to 50.0 ° C./second. The average cooling rate of the glass ribbon in the second cooling step is preferably 0.5 to less than 5.5 ° C./second. Further, the cooling rate of the central portion of the glass ribbon in the third cooling step is preferably 1.5 ° C./second to 7.0 ° C./second.

When the glass plate is a polysilicon (low temperature polysilicon) TFT or a glass substrate on which an oxide semiconductor is formed, the strain point temperature of the glass is preferably 675 ° C. or higher, and the strain point temperature is 675 ° C. to 750 ° C. More preferably, it is ° C.

Another embodiment of the present invention is a glass plate manufacturing apparatus using a downdraw method. The manufacturing equipment
A melting apparatus for melting glass raw material to obtain molten glass;
The molten glass is supplied to a molded body provided in a molding furnace to form a glass ribbon, the flow of the glass ribbon is created, and the glass ribbon is pulled by a roller provided in the slow cooling furnace, and the slow cooling furnace A molding device for cooling inside,
And a cutting device for cutting the cooled glass ribbon in a cutting space.
When the internal space of the molding furnace provided with the molded body and the internal space of the slow cooling furnace provided with the roller are furnace internal spaces, and the external space of the molding furnace and the slow cooling furnace is a furnace external space, the furnace The external space is a space partitioned by a partition wall with respect to the atmospheric pressure atmosphere.
An air pressure control device for adjusting the air pressure is provided in the molding apparatus so that the air pressure in at least a part of the furnace outer space is lower than the air pressure in the furnace inner space at the same position in the flow direction of the glass ribbon. It has been.

It is preferable that the air pressure control device is a device that adjusts the inflow of air with the atmosphere in order to control the air pressure in the furnace outer space.

According to the method for producing a glass plate of the above aspect, variation in thermal contraction of the glass plate can be efficiently reduced.

It is a figure which shows the flow of the manufacturing method of the glass plate which is this embodiment. FIG. 2 is a diagram schematically showing an apparatus for performing a melting step to a cutting step according to the present embodiment. It is a schematic side view of the glass plate shaping | molding apparatus in this embodiment. It is a schematic front view of the glass plate shaping | molding apparatus in this embodiment. It is the schematic of the control system which controls the quantity of the air which the air blower used by this embodiment sends.

Hereinafter, the manufacturing method and manufacturing apparatus of the glass plate of this invention are demonstrated.
The following words and phrases in this specification are defined as follows.
The center part of a glass ribbon means the center of the width direction of a glass ribbon among the widths of the width direction of a glass ribbon.
The edge part of a glass ribbon means the range within 100 mm from the edge of the width direction of a glass ribbon.
The strain point temperature refers to the temperature of a glass plate having a log η of 14.5 when the glass viscosity is η.
The annealing point temperature refers to the temperature of a glass plate having a log η of 13.
FIG. 1 is a diagram showing a flow of a glass plate manufacturing method according to the present embodiment.

(Overall overview of glass plate manufacturing method)
The glass plate manufacturing method includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a forming step (ST5), and a slow cooling step (ST6). And a cutting step (ST7). In addition, a plurality of glass plates that have a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like and are stacked in the packing process are conveyed to a supplier.

FIG. 2 is a diagram schematically showing a glass plate manufacturing apparatus that performs the melting step (ST1) to the cutting step (ST7). As shown in FIG. 2, the apparatus mainly includes a melting apparatus 200, a molding apparatus 300, and a cutting apparatus 400. 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 molding apparatus 300 will be described later.

In the melting step (ST1), the glass raw material supplied into the melting tank 201 is heated and melted with a flame and an electric heater (not shown) to obtain molten glass.
The clarification step (ST2) is performed in the clarification tank 202, and by heating the molten glass in the clarification tank 202, oxygen and SO ₂ bubbles contained in the molten glass grow by the oxidation-reduction reaction of the clarifier. The bubble gas component is released by rising to the liquid surface, or the gas component in the bubble is absorbed into the molten glass and the bubble disappears.
In the homogenization step (ST3), the molten glass in the stirring tank 203 supplied through the first pipe 204 is stirred using a stirrer to homogenize the glass components.
In the supplying step (ST4), the molten glass is supplied to the molding apparatus 300 through the second pipe 205.

In the molding apparatus 300, a molding process (ST5) and a slow cooling process (ST6) are performed.
In the forming step (ST5), molten glass is supplied to a formed body provided in a forming furnace to form a glass ribbon G (see FIG. 3). In this embodiment, an overflow down draw method using a molded body 310 described later is used. In the slow cooling step (ST6), the glass ribbon G that has been molded and flowed has a desired thickness, and is cooled by being pulled by a roller so as not to cause a plane distortion and a thermal contraction rate. .
In the cutting step (ST7), the cutting device 400 cuts the glass ribbon G supplied from the forming device 300 into a predetermined length, thereby obtaining a plate-like glass plate G1 (see FIG. 3). The cut glass plate G1 is further cut into a predetermined size to produce a glass plate G1 having a target size. After this, the glass end face is ground and polished, then cleaned, and further inspected for the presence of abnormal defects such as bubbles and striae, and then the glass plate G1 that has passed the inspection is packed as the final product. Is done.

(Description of molding equipment)
3 and 4 are diagrams mainly showing a configuration of the glass sheet forming apparatus 300, FIG. 3 mainly shows a schematic side view of the forming apparatus 300, and FIG. 4 is a schematic front view of the forming apparatus 300. Indicates.
The glass plate molded by the molding apparatus 300 is suitably used for a glass substrate for flat panel display or a cover glass, for example. Examples of the glass substrate for a flat panel display include a glass substrate for a liquid crystal display, a glass substrate for an organic EL display, and a display glass on which an oxide semiconductor thin film transistor is formed. The glass plate molded by the molding apparatus 300 can also be used as a display for a portable terminal device, a cover glass for a housing, a touch panel plate, a glass substrate of a solar cell, or a cover glass. Particularly, it is suitable for a glass substrate for a liquid crystal display using a polysilicon TFT.

The forming furnace 40 for performing the forming step (ST5) and the slow cooling furnace 50 for performing the slow cooling step (ST6) are surrounded by a furnace wall composed of a refractory material such as a refractory brick, a refractory heat insulating brick, or a fiber-based heat insulating material. Has been. The molding furnace 40 is provided vertically above the slow cooling furnace 50. The forming furnace 40 and the slow cooling furnace 50 are collectively referred to as a furnace 30. In the furnace inner space surrounded by the furnace wall of the furnace 30, a molded body 310, an atmosphere partition member 320, a cooling roller 330, a cooling unit 340, conveying rollers 350a to 350h,

pressure sensors

355, 360a to 360c ( 4).
As shown in FIG. 2, the molded body 310 forms molten glass flowing from the melting device 200 through the second pipe 205 into a glass ribbon G. Thereby, the flow of the glass ribbon G of the vertically lower direction is made in the forming apparatus 300. The molded body 310 is a long and narrow structure made of refractory brick or the like, and has a wedge-shaped cross section as shown in FIG. A groove 312 serving as a flow path for guiding the molten glass is provided on the top of the molded body 310. The groove 312 is connected to the second pipe 205 at a supply port 311 (see FIG. 4) provided in the molding apparatus 300. The molten glass flowing through the second pipe 205 flows along the groove 312. The depth of the groove 312 is shallower toward the downstream side of the flow of the molten glass, so that the molten glass overflows vertically downward from the groove 312. 3 and 4, the molten glass is represented by the reference symbol MG.
The molten glass overflowing from the groove 312 travels down the side walls on both sides of the molded body 310 and flows down vertically. The molten glass that has flowed through the side walls merges at the lower end 313 of the molded body 310 shown in FIG. 3, and one glass ribbon G is formed. As a result, the glass ribbon G flows down toward the slow cooling furnace 50. The viscosity of the glass ribbon G at the time of starting to flow down after leaving the molded body 310 is, for example, 10 ^5.7 to 10 ^7.5 poise.

Near the lower end 313 of the molded body 310, an atmosphere partition member 320 is provided. The atmosphere partition member 320 is a pair of plate-like heat insulating members and is configured to sandwich the glass ribbon G from both sides in the thickness direction. That is, a gap is formed in the atmosphere partition member 320 so as not to contact the glass ribbon G. The atmosphere partition member 320 blocks the movement of heat between the furnace internal space above the atmosphere partition member 320 and the furnace internal space below by partitioning the molding furnace internal space.

A cooling roller 330 is provided below the atmosphere partition member 320. The cooling roller 330 is in contact with the surface of the glass ribbon G in the vicinity of both ends in the width direction of the glass ribbon G, pulls the glass ribbon G downward, and sets the thickness of the glass ribbon G to a desired thickness in the vicinity of both ends. At the same time, the glass ribbon G is cooled (rapidly cooled). Due to the rapid cooling by the cooling roller 330, the viscosity at both ends of the glass ribbon becomes, for example, 10 ^9.0 to 10 ^10.5 poise. In the rapid cooling to slow cooling process using the cooling roller 310, the viscosity at both ends of the glass ribbon G is, for example, 10 ^10.5 to 10 ^14.5 poise due to cooling with a cooling function lower than the cooling function in the rapid cooling. Maintained.
A cooling unit 340 is provided below the cooling roller 330. The cooling unit 340 cools the glass ribbon G that has passed through the cooling roller 330. By the cooling by the cooling unit 340, the warp of the glass ribbon G is suppressed.

Below the cooling unit 340, conveying rollers 350a to 350h are provided at predetermined intervals, and pull the glass ribbon G downward. The space below the cooling unit 340 is a furnace internal space of the slow cooling furnace 50. Each of the transport rollers 350a to 350h has a pair of rollers and is provided at both end portions in the width direction of the glass ribbon G so as to sandwich both sides of the glass ribbon G.

A pressure sensor 355 (see FIG. 4) for measuring the pressure inside the furnace internal space is provided in the furnace internal space of the molding furnace 40. The pressure sensor 355 is provided at the same position as the molded body 310 in the height direction (vertically upward direction). The height direction is the upward direction of the drawing in FIGS. Since the glass ribbon G flows vertically downward from the molded body 310, the flow direction of the glass ribbon G is opposite to the height direction. Pressure sensors 360a to 360c (see FIG. 4) are provided in the furnace internal space of the slow cooling furnace 50.

On the other hand, outside the furnace wall of the forming furnace 40, spaces partitioned by the partition walls of the building B with respect to the atmospheric pressure atmosphere by the partition walls, that is, furnace exterior spaces S1, S2, S3a to S3c are provided. The furnace outer space S <b> 1 is an upper space located further above the ceiling surface of the inner space of the molding furnace 40. Each of these spaces is delimited by floor surfaces (floor walls) 411, 412, 413a to 413c in the height direction. That is, the molding apparatus 300 is provided in a building B having a plurality of floors, and furnace external spaces (partial spaces) S1, S2, S3a to S3c divided into a plurality by the floor surface are provided on each floor. Furthermore, a space S4 (cutting space) partitioned by walls on the floor 414 is provided below the furnace external space S3c. In the space S4, no furnace wall is provided. The air pressure in these spaces is adjusted by

blowers

421, 422, 423a, 423b, 423c, and 424, which will be described later.
The furnace outside space S1 is a space vertically above the position in the height direction of the molded body 310, and a pressure sensor 415 for measuring the pressure in the furnace outside space is provided in the furnace outside space S1.
The furnace exterior space S2 is a space provided on the floor surface 412, and the molded body 310 is disposed in the furnace interior space corresponding to this space. Further, a pressure sensor 416 for measuring the atmospheric pressure in the furnace external space S2 is provided in the furnace external space S2. In the furnace internal space surrounded by the furnace wall, a pressure sensor 355 for measuring the pressure in the furnace internal space is provided at the same position in the height direction of the pressure sensor 416 (see FIG. 4).
The furnace outside spaces S3a to S3c are spaces provided below the furnace outside space S2 in the order of the furnace outside spaces S3a to 3c from the highest in the height direction. The furnace outer spaces S3a to 3c are provided on the floor surfaces 413a to 413c. In addition, pressure sensors 417a to 417c for measuring the atmospheric pressure in the furnace external spaces 3a to 3c are provided in the furnace external spaces S3a to S3c, respectively. In the furnace internal space surrounded by the furnace wall, pressure sensors 360a to 360c for measuring the pressure in the furnace internal space are provided at the same position in the height direction of the pressure sensors 417a to 417c (see FIG. 4).
In this embodiment, the

pressure sensors

355, 360a to 360c are provided at each position in the furnace internal space, but the pressure sensor may be inserted into each position in the furnace internal space to measure the pressure. .

In addition, outside the partition walls separating the furnace outside spaces S1, S2, S3a to S3c and the space S4, the

fans

421, 422, 423a, 423b, 423c, and 424 are provided. Air sent from the atmosphere by the

blowers

421, 422, 423a, 423b, 423c, and 424 is supplied to each of the furnace external spaces S1, S2, S3a to S3c, and the space S4 through a pipe. The amount of air sent by the

blowers

421, 422, 423a, 423b, 423c, 424 is determined by a drive signal from the drive unit 510 described later. The

blowers

421, 422, 423a, 423b, 423c, and 424 are pressure control that adjusts the inflow of air to the atmosphere in order to control the respective air pressures in the furnace exterior spaces S1, S2, S3a to S3c, and the space S4 Functions as a device.

FIG. 5 is a schematic diagram of a control system that controls the amount of air that the

blowers

421, 422, 423a, 423b, 423c, and 424 send.
The control system includes

pressure sensors

355, 360a to 360c provided in the furnace internal space,

pressure sensors

415, 416, 417a to 417c, 418 provided in the furnace external space, the control device 500, and the drive unit 510. And

blowers

421, 422, 423a, 423b, 423c, and 424.
The control device 500 includes a measurement result of the atmospheric pressure in the furnace internal space sent from each of the

pressure sensors

355, 360a to 360c, and a measurement result of the atmospheric pressure in the furnace external space sent from the

pressure sensors

415, 416, 417a to 417c, 418. , The

blowers

421, 422, 423a, 423b, 423c, 424 are sent from the atmosphere so that the difference in atmospheric pressure at the same position in the height direction in the furnace inner space and the furnace outer space is adjusted to a set range. A control signal for adjusting the amount of air is generated. The generated control signal is sent to the drive unit 510.
The drive unit 510 generates a drive signal for individually adjusting the amount of air sent by the

blowers

421, 422, 423a, 423b, 423c, and 424 based on the control signal. The drive unit 510 sends drive signals to the

fans

421, 422, 423a, 423b, 423c, and 424, respectively.
In the present embodiment, the control device 500 and the drive unit 510 automatically control the air feed amount, but the operator may adjust the air feed amount manually.

Here, the amount of air sent from the

fans

421, 422, 423a, 423b, 423c, 424 is such that the pressure in the furnace outer space S2, S3a to S3c is lower than the pressure in the furnace inner space at the same position in the height direction. Thus, the atmospheric pressure in each furnace external space is adjusted.
The difference in atmospheric pressure between the furnace inner space and the furnace outer space S2 of the molding furnace 40 is more than 0 to 40 Pa, preferably 4 to 35 Pa, more preferably 8 to 30 Pa, and more preferably 10 to 27 Pa. It is more preferable that the pressure is 10 to 25 Pa.

If the difference in the atmospheric pressure exceeds the above range, a large amount of air may flow out of the gap between the furnace walls from the furnace inner space toward the furnace outer space S2, and the air rise in the furnace inner space is increased. On the other hand, if the difference between the atmospheric pressures is less than the above range, air may flow in from the gap between the furnace walls from the furnace outer space S2 toward the furnace inner space, and the temperature distribution in the furnace inner space varies. By adjusting the difference in atmospheric pressure to the above range, it is possible to prevent low temperature air from flowing into the furnace internal space of the molding furnace 40 from the furnace external space S2. For this reason, the dispersion | variation in the temperature of furnace interior space can be suppressed. Thereby, the dispersion | variation in cooling rate and by extension, the dispersion | variation in the plate | board thickness of the glass ribbon G can be suppressed. The temperature variation means that the temperature changes unintentionally from a preset temperature.

On the other hand, the difference in atmospheric pressure between the inner space of the slow cooling furnace 50 and the outer space S3a to S3c is more than 0 to 40 Pa, preferably 2 to 35 Pa, more preferably 2 to 25 Pa, The pressure is more preferably 3 to 23 Pa, and further preferably 5 to 20 Pa. Particularly preferred is 10 to 20 Pa. If the difference in the atmospheric pressure exceeds the above range, a large amount of air may flow out of the gap between the furnace walls from the furnace inner space toward the furnace outer space S3a to S3c, increasing the air rise in the furnace inner space. . On the other hand, if the difference in the atmospheric pressure is less than the above range, air may flow in from the gaps in the furnace wall from the furnace outer space S3a to S3c toward the furnace inner space, and the temperature distribution in the furnace inner space varies. By adjusting the difference in the atmospheric pressure to the above range, it is possible to prevent low-temperature air from flowing into the furnace internal space of the slow cooling furnace 50 from the furnace external spaces S3a to S3c, so that the temperature variation in the furnace internal space can be suppressed. Thereby, the deformation | transformation of the glass ribbon G, a curvature, the dispersion | variation in a plane distortion, and the dispersion | variation in heat shrink can be suppressed. Further, it is preferable that the difference in atmospheric pressure between the furnace outer spaces S3a to S3c and the furnace inner space increases as it goes upward. It is considered that the temperature of the furnace internal space becomes higher as it goes upward, and the influence of the inflow of air at a temperature lower than that of the furnace internal space is increased.

At this time, the pressure difference between the furnace external space S3c and the space S4 is preferably 0 <(pressure in the furnace external space S3c−pressure in the space S4), and 0 <(pressure in the furnace external space S3c−pressure in the space S4). Atmospheric pressure) <20 Pa is more preferable, and 1 Pa <(atmospheric pressure in the furnace outer space S3c−atmospheric pressure in the space S4) <15 Pa is further preferable, and 2Pa <(atmospheric pressure in the outer furnace space S3c−atmospheric pressure in the space S4). More preferably, it is <15 Pa.
Further, the pressure difference between the furnace outside lower space S2 and the furnace outside space S3a is preferably 0 <(the pressure in the furnace outside lower space S2−the pressure in the furnace outside space S3a), and 0 <(the furnace outside space S2 More preferably, the atmospheric pressure—the atmospheric pressure of the furnace outer space S3a) <20 Pa, and more preferably 1 Pa <(the atmospheric pressure of the outer furnace space S2—the atmospheric pressure of the outer furnace space S3a) <15 Pa, more preferably 2 Pa <(the outer furnace space). It is more preferable that the pressure of S2−the pressure of the furnace outer space S3a) <15 Pa.

The pressure difference between the furnace outside space S1 and the furnace outside space S2 is preferably 0 <(atmosphere pressure in the furnace outside space S1−atmospheric pressure in the furnace outside space S2), and 0 <(atmospheric pressure in the furnace outside space S1− It is more preferable that the pressure in the furnace outer space S2) <30 Pa, and it is more preferable that 1 Pa <(the pressure in the furnace outer space S1−the pressure in the furnace outer space S2) <25 Pa, more preferably 2 Pa <(in the furnace outer space S1). More preferably, the pressure is equal to the atmospheric pressure of the furnace outer space S2. If the pressure difference between the furnace outside space S3c and the space S4, the pressure difference between the furnace outside space S2 and the furnace outside space S3a, and the pressure difference between the furnace outside space S1 and the furnace outside space S2 are too large, the furnace outside space S1 The absolute values of the atmospheric pressure in the furnace outer space S2 and the furnace outer spaces S3a to S3c become too large, and air flows from the furnace outer space into the furnace inner space. For this reason, there exists a possibility that the problem that the temperature in a furnace interior space may fluctuate arises. Furthermore, there is a possibility that the local airflow concentration in the external space of the furnace or the flow velocity of the airflow is locally increased, and the atmospheric pressure stability of the external space of the furnace may be lowered. There is also a possibility that the problem that the temperature varies will occur.

In this embodiment, the pressure in the furnace outer space is adjusted so that the pressure in all the furnace outer spaces is lower than the pressure in the furnace inner space at the same position in the height direction. The pressure in the outer space of the furnace may be adjusted so that the pressure in at least a part of the furnace becomes lower than the pressure in the furnace inner space at the same position in the height direction. In this case, in the region between the position in the slow cooling furnace corresponding to the annealing point temperature of the glass ribbon G and the position in the annealing furnace corresponding to the strain point temperature of the glass ribbon G, the atmospheric pressure in the outside space of the furnace is high. It is preferable to adjust so that it may become low with respect to the atmospheric | air pressure of the furnace internal space in the same position of a direction. The position corresponding to the annealing point temperature is, for example, a position in the height direction of the furnace outside space S3a, and the position corresponding to the strain point temperature is, for example, a position in the height direction of the furnace outside space S3b. In the above region, the glass ribbon G is solidified and most affects the plane distortion and thermal shrinkage of the glass. Therefore, the air pressure is efficiently adjusted in the above region to suppress the inflow of air from the outside space of the furnace. By doing so, it is preferable to suppress variations in temperature in the furnace internal space.
Furthermore, by adjusting the atmospheric pressure in the external space of the furnace at the same position in the height direction corresponding to the region where the temperature of the glass ribbon G is equal to or lower than the strain point temperature in the internal space of the slow cooling furnace 50, the air from the external space of the furnace Inflow can be suppressed, and variations in temperature in this region can be suppressed, and warpage of the glass ribbon G can be prevented by this suppression. Here, the glass ribbon G is one continuous plate until it is cut from the molding furnace 40. Therefore, if the warp shape of the glass ribbon G changes in a region where the temperature of the glass ribbon G is equal to or lower than the strain point temperature, it also affects the glass ribbon in the region where the temperature is higher than the strain point temperature, resulting in variations in plane strain and thermal shrinkage. Will occur. As described above, that is, by suppressing variations in temperature in the region where the temperature of the glass ribbon G is equal to or lower than the strain point temperature, variations in warpage, plane strain, and thermal shrinkage can be suppressed.

Further, the pressure sensor 415 at a position in the height direction where there is no furnace internal space is used to adjust the furnace external space S1 by the blower 421 so that air does not flow from the furnace external space S1 into the furnace internal space. It is preferable to measure the atmospheric pressure.
There is a gap around the axis of the cooling roller 310 and the conveying rollers 350a to 350h in the furnace wall that divides the furnace internal space and the furnace external space, and further, the furnace wall and the floor surface that separate the furnace internal space and the furnace external space There is a gap in the connection portion with 411 or the like. For this reason, when there is a certain pressure difference or more, an air flow is likely to occur between the furnace internal space and the furnace external space. Therefore, it is preferable to adjust the atmospheric pressure of the furnace outer space surrounding the furnace inner space. In particular, the space of the forming furnace 40 in the furnace internal space is located at the most upstream position in the furnace internal space, and the atmospheric pressure is high and the temperature in the space is also high. It is not preferable that air flows out from the ceiling surface of the internal space of the forming furnace 40 to the external space S1 because the flow of air in the internal space of the furnace is promoted by the chimney effect. Therefore, in order to prevent the outflow of air to the furnace exterior space S1, the atmospheric pressure in the furnace exterior space S1 is increased. However, if the atmospheric pressure in the furnace external space S1 is excessively increased, air tends to easily flow from the furnace external space S1 into the furnace internal space. In this case, the cold air flowing from the furnace outer space S1 is not preferable because it forms the glass ribbon with the molded body 310 in the space of the molding furnace 40 and affects the viscosity of the molten glass being molded. It also affects the cooling of the glass ribbon in the slow cooling step. For this reason, the pressure sensor 415 measures the atmospheric pressure in the furnace external space S1 in order to adjust the furnace external space S1 by the blower 421 so that air does not flow into the furnace internal space from the furnace external space S1. That is, on the ceiling surface of the molding furnace 40 in which no cooling roller or conveyance roller is provided, the pressure in the molding furnace external space S1 is set so that air does not flow from the gap between the ceiling surfaces into the furnace internal space from the furnace external space S1. It is preferably adjusted by the blower 421.

The pressure sensor 418 is used for measuring the atmospheric pressure in the space S4. For example, it is preferable that the air pressure in the space S4 is adjusted so that the space S4 is further lower than the lowest air pressure in the furnace internal space. At this time, it is preferable that the pressure in the space S4 is adjusted to be equal to or higher than the atmospheric pressure. On the other hand, when the atmospheric pressure in the space S4 is equal to or higher than a predetermined pressure, air tends to flow into the furnace internal space, and there is a concern that the temperature of the furnace internal space is affected. Therefore, the atmospheric pressure in the space S4 is adjusted to be equal to or higher than atmospheric pressure and lower than a predetermined pressure. More specifically, the pressure in the space S4 is adjusted to be equal to or higher than the atmospheric pressure and equal to or lower than the lowest pressure in the furnace internal space (the lowest pressure in the furnace internal space). For example, the pressure in the space S4 is preferably 0 <(the pressure in the space S4−the atmospheric pressure), more preferably 0 <(the pressure in the space S4−the atmospheric pressure) <40 Pa, more preferably 5Pa <(the space S4 (Atmospheric pressure−atmospheric pressure) <40 Pa is more preferable.
By adjusting the atmospheric pressure in the space S4 as described above, the air flowing from the space S4 to the furnace internal space can be reduced.

The

air blowers

421, 422, 423a, 423b, 423c, 424 are adjusted so that the air pressure in any space is higher than the atmospheric pressure by sending air into the furnace outer spaces S1, S2, S3a to S3c and the space S4. However, increasing the atmospheric pressure of these spaces with respect to the atmospheric pressure prevents a large amount of air from flowing from the outside of the building B into the outside space S1, S2, S3a to S3c and the space S4. This is for efficiently adjusting the atmospheric pressure in the spaces S1, S2, S3a to S3c, S4.
Further, the atmospheric pressure in the furnace internal space becomes higher as the position in the height direction is higher. This is due to the fact that the air that has reached a high temperature moves upward in an ascending current. Thus, even if a temperature distribution is generated in the furnace internal space and a distribution is generated in the atmospheric pressure, the atmospheric pressure in the external space of the furnace is adjusted according to the atmospheric pressure distribution. This is to suppress the flow of air into the furnace internal space due to the difference between the pressure in the furnace external space and the pressure in the furnace internal space, and to suppress the occurrence of air convection due to air leakage into the furnace external space. It is. For this reason, a pressure sensor is provided in the furnace inner space at the same position in the height direction as the pressure sensor provided in each of the furnace outer space. Thus, when pressure distribution occurs in the furnace internal space, the difference between the atmospheric pressure in the furnace external space and the atmospheric pressure in the furnace internal space at the same position in the height direction of the furnace external space is calculated as the position in the height direction. It is preferable to adjust so that it may change with. For example, when a comparison is made between the uppermost furnace outer space S2 and the lowermost furnace outer space S3c among the furnace outer spaces S2, S3a to S3c in which the furnace inner space exists at the same position in the height direction, It is preferable that the difference in atmospheric pressure is adjusted so as to be larger than the difference in atmospheric pressure at the bottom. For example, the difference in the atmospheric pressure may be set so as to increase as the position in the height direction increases. This is because in the furnace internal space in the slow cooling furnace, the higher the position in the height direction, the higher the temperature, so the temperature difference with the glass ribbon G when cold air flows in increases, and the higher the position in the height direction, This is to prevent the temperature variation of the glass ribbon G from becoming large.
Moreover, it is preferable that the atmospheric | air pressure of a furnace exterior space is so high that the position of the height direction is high, ie, the upstream position of the flow direction of a glass ribbon. Thereby, the magnitude | size of the upward airflow which generate | occur | produces along a furnace wall can be reduced in a furnace exterior space. In other words, since the temperature of the furnace internal space near the furnace wall can be prevented from fluctuating due to the temperature fluctuation of the furnace wall due to the rising air flow generated along the furnace wall, the temperature variation in the furnace internal space can also be suppressed.

(Cooling of glass ribbon)
In this embodiment, variation in thermal shrinkage of the glass plate can be reduced, but furthermore, by adjusting the cooling rate of the molded glass ribbon, deformation of the glass plate is suppressed in addition to variation in thermal shrinkage. In addition, warpage can be suppressed and the absolute value of the heat shrinkage rate can be reduced.
Specifically, in the slow cooling process in which the glass ribbon is slowly transported using a roller, 200 ° C. is subtracted from the strain point temperature of the glass ribbon from the temperature obtained by adding 150 ° C. to the slow cooling point temperature of the glass ribbon. Define the temperature range up to the temperature. At this time, at least in the above temperature region, the cooling rate at the center in the width direction of the glass ribbon is faster than the cooling rate at both ends of the glass ribbon, and the temperature at the center in the width direction of the glass ribbon is higher than both ends of the glass ribbon. It is preferable to change the glass ribbon from a higher state to a state where the temperature at the center is lower than both ends. Thereby, a tensile stress can work in the flow direction of the glass ribbon at the center in the width direction of the glass ribbon. By applying a tensile stress in the flow direction of the glass ribbon, it is possible to further suppress the warpage of the glass ribbon, and thus the glass plate.

Furthermore, the slow cooling step can include a first cooling step, a second cooling step, and a third cooling step.
The first cooling step is a step of cooling at the first average cooling rate until the temperature of the central portion in the width direction of the glass ribbon reaches the annealing point temperature.
The second cooling step is a step of cooling at the second average cooling rate until the temperature of the central portion in the width direction of the glass ribbon reaches the strain point temperature of −50 ° C. from the annealing point temperature.
The third cooling step is a step of cooling at the third average cooling rate until the temperature of the central portion in the width direction of the glass ribbon changes from the strain point temperature of −50 ° C. to the strain point temperature of −200 ° C.
In this case, the first average cooling rate is 5 ° C./second or more, the first average cooling rate is faster than the third average cooling rate, and the third average cooling rate is the second average cooling rate. It is preferable to make it faster. That is, the average cooling rate is, in descending order, the first average cooling rate, the third average cooling rate, and the second average cooling rate.
At this time, the average cooling rate of the central portion of the glass ribbon in the first cooling step is preferably 5.5 ° C./second to 50 ° C./second. If the average cooling rate at the central portion of the glass ribbon in the first cooling step is less than 5.5 ° C./second, the productivity is lowered. On the other hand, when the average cooling rate of the central portion of the glass ribbon in the first cooling step exceeds 50 ° C./second, it becomes difficult to control the temperature distribution in the width direction of the glass ribbon to suppress plane distortion and warpage. It is not preferable. The average cooling rate at the center of the glass ribbon in the first cooling step is more preferably 8 ° C./second to 16.5 ° C./second.
The average cooling rate of the glass ribbon in the second cooling step (thermal shrinkage reduction treatment step) is preferably 0.5 to 5.5 ° C./second. When the average cooling rate at the central portion of the glass ribbon in the second cooling step is less than 0.5 ° C./second, the slow cooling device becomes long, the manufacturing equipment becomes huge, and the productivity decreases. On the other hand, at 5.5 ° C./second or more, the heat shrinkage rate cannot be sufficiently reduced. The average cooling rate at the center of the glass ribbon in the second cooling step is more preferably 0.5 ° C./second to 5.5 ° C./second.
On the other hand, the cooling rate of the central portion of the glass ribbon in the third cooling step is not particularly limited, but is preferably 1.5 ° C./second to 7 ° C./second. If the cooling rate of the central part of the glass ribbon in the third cooling step is less than 1.5 ° C./second, the productivity is lowered. On the other hand, at 7 ° C./second or more, the glass ribbon may be cracked due to excessive quenching of the glass ribbon. From the above, the cooling rate of the central portion of the glass ribbon in the third cooling step is preferably 1.5 ° C./second to 7 ° C./second, more preferably 2 ° C./second to 5.5 ° C./second. It is.
The cooling rate in the flow direction of the glass ribbon affects the heat shrinkage of the glass plate to be manufactured. However, in the slow cooling step, by setting the cooling rate, it is possible to obtain a glass plate having a suitable heat shrinkage rate while improving the production amount of the glass plate.
Such a cooling rate is performed by controlling the temperature using a heater (not shown) provided in the furnace internal space.
In addition, a thermal contraction rate can also be made small by providing a thermal contraction reduction process (offline annealing) process separately after a slow cooling process. However, if an offline annealing step is provided separately from the slow cooling step, there is a problem that productivity is lowered and costs are increased. Therefore, as described above, it is preferable to keep the thermal shrinkage rate within a predetermined range by performing a thermal shrinkage reduction process (online annealing) in which the cooling rate of the glass plate is controlled in the slow cooling step. That is, the slow cooling process preferably includes a heat shrinkage reduction process. In addition, the said 2nd cooling process corresponds to a thermal contraction reduction process process among slow cooling processes.

(Glass plate)
As the glass used for the glass plate of the present embodiment, for example, borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, soda lime glass, alkali silicate glass, alkali aluminosilicate glass, alkali aluminogermanate glass, etc. can be applied. it can. The glass applicable to the present invention is not limited to the above.

(Glass composition 1)
Examples of the glass composition of the glass plate used in the present embodiment include the following.
The content rate display of the composition shown below is mass%.
SiO ₂ : 40 to 70%,
Al ₂ O ₃ : 2 to 25%,
B ₂ O ₃ : 0 to 20%,
MgO: 0 to 10%,
CaO: 0 to 15%,
SrO: 0 to 10%,
BaO: 0 to 15%,
ZnO: 0 to 10%,
ZrO ₂ : 0 to 10%,
Refiner: 0-2%,
It is an alkali-free glass.

(Glass composition 2)
Moreover, the alkali free glass of the following composition is also illustrated. The indications in parentheses below are the preferred contents of each component, and the ones described later are more preferred.
SiO ₂ : 50 to 70% (55 to 65%, 57 to 64%, 58 to 62%),
Al ₂ O ₃ : 2 to 25% (10 to 20%, 12 to 18%, 15 to 18%),
B ₂ O ₃ : 0 to 20% (5 to 15%, 6 to 13%, 7 to 12%).
At this time, the following components may be included as optional components.
MgO: 0 to 10% (lower limit is 0.01%, lower limit is 0.5%, upper limit is 5%, upper limit is 4%, upper limit is 2%),
CaO: 0 to 20% (lower limit is 1%, lower limit is 3%, lower limit is 4%, upper limit is 9%, upper limit is 8%,
Upper limit is 7%, upper limit is 6%),
SrO: 0 to 20% (lower limit is 0.5%, lower limit is 3%, upper limit is 9%, upper limit is 8%, upper limit is 7 %%, upper limit is 6%),
BaO: 0 to 10% (upper limit is 8%, upper limit is 3%, upper limit is 1%, upper limit is 0.2%),
ZrO ₂ : 0 to 10% (0 to 5%, 0 to 4%, 0 to 1%, 0 to 0.1%).

(Glass composition 3)
In particular,
SiO ₂ : 50 to 70%,
B ₂ O ₃ : 5 to 18%,
Al ₂ O ₃ : 0 to 25%,
MgO: 0 to 10%,
CaO: 0-20%,
SrO: 0 to 20%,
BaO: 0 to 10%,
RO: 5 to 20% (where R is at least one selected from Mg, Ca, Sr and Ba, and the glass plate contains),
It is preferable to contain.
Furthermore, the total of R ′ ₂ O exceeds 0.20% and is 2.0% or less (provided that R ′ is at least one selected from Li, Na and K, and is contained in the glass plate). It is preferable. Further, it is preferable that the total amount of fining agents is 0.05 to 1.5% and substantially free of As ₂ O ₃ , Sb ₂ O ₃ and PbO. More preferably, the iron oxide content in the glass is 0.01 to 0.2%.

(Glass composition 4)
Examples of the glass composition of the other glass plate used in the present embodiment include the following. By setting the glass plate to the composition shown below, the strain point temperature can be increased, and the thermal contraction of the glass plate can be further reduced. For this reason, the glass plate of the following composition is suitable for the glass substrate for liquid crystal displays and the glass substrate for organic EL displays, and is especially suitable for the glass substrate to which a polysilicon TFT is applied.
The content rate display of the composition shown below is mass%. The indications in parentheses below are the preferred contents of each component, and the ones described later are more preferred.
SiO ₂ : 57 to 75%,
Al ₂ O ₃ : 8 to 25%,
B ₂ O ₃ : 3 to less than 11%,
CaO: 0-20%,
MgO: 0 to 15%,
Non-alkali glass.
At this time, if one or more of the following mathematical formulas are satisfied, it is possible to improve the strain point temperature and reduce the weight of the glass while maintaining devitrification resistance and meltability. Suitable for substrates.
(SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ : 8 to 20% (9 to 17%, 9 to 15%, 9 to 12%)
SrO + BaO: 0 to 3.3% (0 to 1.5%, substantially free)
CaO / RO: 0.65% or more (0.8 to 1%, 0.9 to 1%) (However, R is at least one selected from Mg, Ca, Sr and Ba, and is contained in the glass plate) )
SiO ₂ + Al ₂ O ₃ : 75% or more (75 to 90%, 79 to 85%)
CaO / B ₂ O ₃ : 0.6% or more (0.9 to 3%, 1.0 to 2%, 1.1 to 1.5%)

In addition, although it was set as the alkali free glass in each said embodiment, the glass plate may contain a trace amount of alkali metals. When the alkali metal is contained, the total of R ′ ₂ O exceeds 0.20% and is 2.0% or less (provided that R ′ is at least one selected from Li, Na, and K, and is contained in the glass plate). It is preferable to contain. Further, it is preferable that the total amount of fining agents is 0.05 to 1.5% and substantially free of As ₂ O ₃ , Sb ₂ O ₃ and PbO. In order to facilitate melting of the glass, the content of iron oxide in the glass is more preferably 0.01 to 0.2% from the viewpoint of reducing the specific resistance.

(Glass composition 5)
Examples of the glass plate applied to the cover glass or the glass plate for solar cell after chemical strengthening include those in which the glass plate is in mass% and contains the following components.
SiO ₂ : 50 to 70% (55 to 65%, 57 to 64%, 57 to 62%),
Al ₂ O ₃ : 5 to 20% (9 to 18%, 12 to 17%),
Na ₂ O: 6-30% (7-20%, 8-18%, 10-15%).
At this time, the following composition may be included as an optional component.
Li ₂ O: 0 to 8% (0 to 6%, 0 to 2%, 0 to 0.6%, 0 to 0.4%, 0 to 0.2%),
B ₂ O ₃ : 0 to 5% (0 to 2%, 0 to 1%, 0 to 0.8%),
K ₂ O: 0 to 10% (lower limit is 1%, lower limit is 2%, upper limit is 6%, upper limit is 5%, upper limit is 4%).
MgO: 0 to 10% (lower limit is 1%, lower limit is 2%, lower limit is 3%, lower limit is 4%, upper limit is 9%, upper limit is 8%, upper limit is 7%),
CaO: 0 to 20% (lower limit is 0.1%, lower limit is 1%, lower limit is 2%, upper limit is 10%, upper limit is 5%, upper limit is 4%, upper limit is 3%),
ZrO ₂ : 0 to 10% (0 to 5%, 0 to 4%, 0 to 1%, 0 to 0.1%).

(Glass composition 6)
In recent years, flat panel displays that use polysilicon (low-temperature polysilicon) TFTs and oxide semiconductors instead of amorphous silicon TFTs (Thin Film Transistors) have been demanded in order to achieve further high-definition flat panel display assembly. Yes. Here, in the flat panel manufacturing process using the polysilicon TFT or the oxide semiconductor, there is a heat treatment process at a higher temperature than the flat panel manufacturing process using the amorphous silicon TFT. Therefore, a glass plate on which a polysilicon TFT or an oxide semiconductor is formed is required to have a low thermal shrinkage rate. In order to reduce the thermal shrinkage rate, it is preferable to increase the annealing conditions of the glass plate and the strain point temperature of the glass. In particular, for polysilicon TFTs and oxide semiconductors, a glass plate having a glass strain point temperature of 675 ° C. or higher (strain point temperature of 675 ° C. to 750 ° C.) is preferable, and a strain point temperature of 680 ° C. or higher (strain point temperature of 680 ° C.). A glass plate having a strain point temperature of 690 ° C. or higher (a strain point temperature of 690 ° C. to 750 ° C.) is particularly preferable.
As a composition of the glass plate whose strain point temperature of glass is 675 degreeC or more, for example, a glass plate is a mass% display and includes the following components.
SiO ₂ : 52 to 78%,
Al ₂ O ₃ : 3 to 25%,
B ₂ O ₃ : 3 to 15%,
RO (where RO is the total amount of all components contained in the glass plate among MgO, CaO, SrO and BaO): 3 to 20%,
A glass plate having a mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ in the range of 7 to 20.
In this case, it is preferable that the total content of SrO and BaO is less than 8% by mass in terms of reducing weight and reducing the thermal expansion coefficient. The total content of SrO and BaO is preferably 0 to 7%, more preferably 0 to 5%, still more preferably 0 to 3%, still more preferably 0 to 1%. In particular, when reducing the density of the glass plate, it is preferable that SrO and BaO are not substantially contained. The fact that it is not substantially contained means that it is not intentionally contained, and it is not excluded that SrO and BaO are inevitably mixed as impurities.
Furthermore, in order to further increase the strain point temperature, the mass ratio (SiO ₂ + Al ₂ O ₃ ) / RO is preferably 7.5 or more. Further, in order to increase the strain point temperature, the β-OH value is preferably set to 0.1 to 0.3 [mm ⁻¹ ]. On the other hand, in order to prevent current from flowing into the melting tank 201 instead of molten glass at the time of melting, the glass plate is made of R ₂ O (where R ₂ O is Li ₂ O, Na ₂ O and K ₂ O). The total amount of all components contained in the glass plate is preferably 0.01 to 0.8% by mass from the viewpoint of reducing the specific resistance of the glass. Alternatively, it is preferable to contain 0.01 to 1% by mass of Fe ₂ O ₃ in order to reduce the specific resistance of the glass. Further, the glass plate preferably has a CaO / RO of 0.65 or more in order to prevent an increase in the devitrification temperature while realizing a high strain point temperature. By setting the devitrification temperature to 1250 ° C. or lower, the overflow downdraw method can be applied. In consideration of application to mobile devices such as mobile communication terminals, the total content of SrO and BaO is preferably 0% or more and less than 2% from the viewpoint of weight reduction.

(Description of each component)
SiO ₂ is a component constituting the glass skeleton of the glass plate, and has the effect of increasing the chemical durability and strain point temperature of the glass. When the content of SiO ₂ is too low, the effects of chemical durability and heat resistance cannot be obtained sufficiently. Furthermore, since the strain point temperature decreases and the thermal expansion coefficient increases, the thermal contraction rate increases. If the content of SiO ₂ is too high, the glass tends to be devitrified, making molding difficult, and increasing the viscosity, making it difficult to homogenize the glass. Moreover, since the specific resistance of glass is increased, melting becomes difficult.

Al ₂ O ₃ is a component forming a glass skeleton, and has an effect of increasing the chemical durability and strain point temperature of the glass. It also has the effect of increasing the etching rate. When the content of Al ₂ O ₃ is too low, the effects of chemical durability and heat resistance of the glass cannot be obtained sufficiently. In addition, the strain point temperature and Young's modulus are reduced. On the other hand, when the content ratio of Al ₂ O ₃ is too high, the viscosity of the glass increases to make it difficult to dissolve, and the acid resistance decreases. Moreover, since the specific resistance of glass is increased, melting becomes difficult.

B ₂ O ₃ is a component that lowers the viscosity of the glass and promotes melting and clarification of the glass. If the content of B ₂ O ₃ is too low, melting becomes difficult, and the acid resistance of the glass decreases. Moreover, devitrification resistance falls and a thermal expansion coefficient increases. On the other hand, if the content of B ₂ O ₃ is too high, the strain point temperature is lowered, so that the heat resistance is lowered. In addition, Young's modulus decreases. Moreover, due to the volatilization of B ₂ O ₃ during glass melting, glass non-uniformity becomes prominent and striae are likely to occur.

MgO and CaO are components that lower the viscosity of the glass and promote glass melting and fining. Further, Mg and Ca are advantageous components for improving the meltability while reducing the weight of the obtained glass because the ratio of increasing the density of the glass is small in the alkaline earth metal. However, if the content of MgO and CaO becomes too high, the strain point temperature is lowered. Furthermore, the chemical durability of the glass is reduced. CaO is an effective component for reducing the specific resistance and improving the meltability of the glass without rapidly increasing the devitrification temperature of the glass. Therefore, it is preferable to contain in the glass of high strain point temperature. Moreover, since MgO raises the devitrification temperature of glass, when reducing a devitrification temperature, it is preferable not to contain substantially.

SrO and BaO are components that lower the viscosity of the glass and promote glass melting and fining. Moreover, it is also a component which improves the oxidizability of a glass raw material and improves clarity. However, if the content of SrO and BaO becomes too high, the density of the glass increases, the weight of the glass plate cannot be reduced, and the chemical durability of the glass decreases. In order to reduce the environmental burden, BaO is preferably not substantially contained. In the present specification, “substantially free of BaO” means less than 0.01% by mass and is not intentionally contained except for impurities.

Li ₂ O, Na ₂ O, and K ₂ O are components that reduce the viscosity of the glass and improve the meltability and moldability of the glass. When Li 2 _O, Na 2 _O and K _{2 O} content is too low it reduces the melting properties of the glass, the higher the cost for the melting. On the other hand, if the content of Li ₂ O, Na ₂ O, or K ₂ O becomes too high, devitrification resistance decreases due to deterioration of the glass balance.

Note that Li ₂ O, Na ₂ O, and K ₂ O are components that may be eluted from the glass to deteriorate the TFT characteristics, and may increase the thermal expansion coefficient of the glass and damage the substrate during heat treatment. Therefore, when applied as a glass substrate for a liquid crystal display or a glass substrate for an organic EL display, it is preferably substantially not contained. However, by deliberately containing the above-mentioned components in the glass, the basicity of the glass is increased while the deterioration of the TFT characteristics and the thermal expansion of the glass are suppressed within a certain range, and the oxidation of the metal whose valence fluctuates. It is possible to make clear and exhibit clarity. Therefore, the total amount of Li ₂ O, Na ₂ O and K ₂ O is 0 to 2.0%, more preferably 0.1 to 1.0%, and still more preferably 0.2 to 0.5%. Incidentally, Li 2 _O, without Na 2 _O is allowed to contain, in the component, most glass eluted from be contained hardly K ₂ O which deteriorates the characteristics of the TFT are preferred. The content of K ₂ O is 0 to 2.0%, more preferably 0.1 to 1.0%, and further preferably 0.2 to 0.5%.

ZrO ₂ is a component that increases the viscosity near the devitrification temperature of glass and the strain point temperature. ZrO ₂ is also a component that improves the heat resistance of the glass. However, if the content of ZrO ₂ becomes too high, the devitrification temperature increases and the devitrification resistance decreases.

TiO ₂ is a component that lowers the high temperature viscosity of the glass. However, when the content of TiO ₂ becomes too high, the devitrification resistance is lowered. Furthermore, since the glass is colored, application to a cover glass of a display screen of an electronic device is not preferable. Further, since the glass is colored, the ultraviolet transmittance is reduced, and therefore, when the treatment using the ultraviolet curable resin is performed, there is a disadvantage that the ultraviolet curable resin cannot be sufficiently cured.

In the glass of the glass plate, a clarifier can be added as a component for defoaming bubbles in the glass. The fining agent is not particularly limited as long as it has a small environmental burden and excellent glass fining properties. For example, from a metal oxide such as tin oxide, iron oxide, cerium oxide, terbium oxide, molybdenum oxide and tungsten oxide. There may be mentioned at least one selected.

Note that As ₂ O ₃ , Sb ₂ O ₃ and PbO are substances having an effect of clarifying the glass by causing a reaction with valence fluctuation in the molten glass, but As ₂ O ₃ , Sb ₂ O ₃ and Since PbO is a substance having a large environmental load, it is preferable that PbO is not substantially contained. In the present specification, “substantially not containing As ₂ O ₃ , Sb ₂ O ₃ and PbO” means less than 0.01% by mass and intentionally not containing impurities.

The thickness of the glass plate of this embodiment is, for example, 0.1 mm to 1.5 mm. The thickness is preferably 0.1 to 1.2 mm, more preferably 0.3 to 1.0 mm, even more preferably 0.3 to 0.8 mm, and particularly preferably 0.3 to 0.5 mm. Here, the thinner the glass plate, the smaller the amount of heat held by the glass, making it difficult to control the glass temperature distribution in the forming furnace 40 and the slow cooling furnace 50. Therefore, a glass plate having a thickness of 0.5 mm or less is applied to the method of the present embodiment, which can stabilize the temperature of the furnace internal space, so that the glass plate is deformed, warped, and variations in plane distortion and heat shrinkage. This has a great effect of suppressing the variation of the image.

The length in the width direction of the glass plate of the present embodiment is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm. On the other hand, the length of the glass plate in the vertical direction is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm.
In addition, when a glass plate enlarges, a glass manufacturing apparatus will also be enlarged corresponding to the magnitude | size of a glass plate. That is, when the glass plate is enlarged, the furnace including the forming furnace 40 and the slow cooling furnace 50 is also enlarged. For this reason, the furnace internal space is widened, and when low-temperature air flows from the furnace external space into the furnace internal space, the influence on the cooling of the glass ribbon G differs in the width direction of the glass ribbon G. Accordingly, the region corresponding to the annealing point temperature to the strain point temperature of the glass ribbon G varies in the width direction of the glass ribbon G, and the time for the glass ribbon G to pass the annealing point temperature to the strain point temperature may vary. . As a result, the thermal contraction of the glass ribbon G also varies in the width direction. Therefore, when the length in the width direction of the glass plate is 2000 mm or more, the effect of the present embodiment, that is, the effect of suppressing the deformation, warpage, plane distortion variation, and thermal shrinkage variation of the glass plate is increased. Furthermore, the effect of this embodiment becomes remarkable, so that the length of the glass plate in the width direction is 2500 mm or more and 3000 mm or more.

(Characteristics of glass plate: thermal shrinkage)
In the glass plate produced in the present embodiment, the thermal shrinkage rate when left in a temperature atmosphere at 550 ° C. for 2 hours is 110 ppm or less, 80 ppm or less, 50 ppm or less, preferably 40 ppm or less, more preferably 35 ppm or less. Yes, more preferably 30 ppm or less, particularly preferably 20 ppm or less. In particular, in a glass plate for forming a polysilicon TFT, it is preferably 50 ppm or less. The heat shrinkage rate is calculated by heat shrinkage / initial length × 10 ⁶ (ppm). The following methods are exemplified as a method for measuring the heat shrinkage rate.
1. Put parallel marking lines on both ends of the glass plate using a diamond pen.
2. The glass plate is cut in half in a direction perpendicular to the marking line, and one of them is heat-treated (in the above, 550 ° C. for 2 hours).
3. The glass plate after the heat treatment and the other glass plate are put together to measure the amount of deviation of the marking line.

(Characteristics of glass plate: variation in thermal shrinkage)
The variation in the heat shrinkage rate is more likely to cause a display defect in the display panel than when the heat shrinkage rate is high or low, particularly when a TFT is formed on a glass plate in the production of a display. In this respect, it is important to suppress variations in the heat shrinkage rate. In addition, it is preferable that the dispersion | variation in the thermal contraction rate of a glass plate is +/- 3.05% or less. Here, the variation in the heat shrinkage rate means that when the heat shrinkage rate is measured by the above method at three positions in the width direction of the glass plate (for example, the position of the central portion and the position in the vicinity of both end portions in the width direction). The upper limit (+) and lower limit (−) at which the measured value at the position fluctuates with respect to the average value. The variation in thermal shrinkage of the glass plate is preferably ± 3.0% or less, more preferably ± 2.85% or less, still more preferably ± 2.7% or less, and further preferably ± 2.65% or less. . In particular, in a high strain point glass manufactured by selecting a glass composition that reduces the thermal shrinkage rate, the variation in the thermal shrinkage rate is preferably ± 3.0% or less. Preferably, it is ± 2.8% or less, more preferably ± 2.7% or less, and further preferably ± 2.6% or less. Here, in this specification, high strain point glass refers to glass having a strain point temperature of 680 ° C. or higher.

(Characteristics of glass plate: plane strain)
Moreover, it is preferable that the maximum value (flat value of retardation value) of the plane distortion of a glass plate is 1.7 nm or less. Preferably, it is 1.3 nm or less, More preferably, it is 1.0 nm or less, More preferably, it is 0.7 nm or less. The plane strain is measured by, for example, a birefringence measuring device manufactured by UNIOPT. Here, since the liquid crystal display is required to be assembled with high accuracy, the method of the present embodiment capable of reducing the plane distortion of the glass plate is particularly preferably used for manufacturing a glass substrate for a liquid crystal display.

(Glass plate: Warpage)
The warpage of the glass plate, when measured by the following method, has a maximum warpage in the range of 0 to 0.2 mm, preferably 0 to 0.15 mm, more preferably 0 to 0.1 mm. Or less, more preferably 0 to 0.05 mm or less, and particularly preferably 0 to 0.05 mm or less.
The measurement of warpage is
1. First, a plurality of small plates (about 400 mm square plates) are cut out from a glass plate.
2. Next, for each of the small plates, the warpage of the four corners and the four central portions is measured on each of the front and back sides (that is, a total of 16 warpages are measured). For example, when the warpage of 8 small plates is measured, measurement data of 128 warpages is obtained at 16 locations × 8.
Check whether the maximum value in the measurement data obtained in 3.2 is within the above range. In the present embodiment, the maximum value of warpage measured with a plurality of small plates is taken as the warpage of the glass plate.

Experiment 1

In order to confirm the effect of the present embodiment, the glass plate is manufactured by variously changing the manufacturing method of the glass plate, and further heat treatment is performed under the same conditions as when the liquid crystal display is manufactured, and the heat shrinkage rate is obtained by the method described above In addition, the plane strain was measured, and the variation of the thermal shrinkage rate was obtained.

1. Example 1
In the inner space of the furnace, the pressure difference between the region where the temperature of the glass ribbon G is the annealing point temperature to the strain point temperature and the outer space corresponding to the same position in the height direction of this region is 5 Pa (in detail) Was adjusted to 3 to 7 Pa).
The manufactured glass plate is a glass substrate for a liquid crystal display, and has a size of 2200 mm × 2500 mm and a thickness of 0.7 mm. The glass composition of the glass plate was as follows. The content rate is expressed by mass%.
SiO ₂ 60%
Al ₂ O ₃ 19.5%
B ₂ O ₃ 10%
CaO 5%
SrO 5%
SnO ₂ 0.5%

2. Example 2
As in Example 1, the pressure difference between the region in the furnace internal space where the temperature of the glass ribbon G is between the annealing point temperature and the strain point temperature and the space outside the furnace corresponding to the height position of this region is The pressure in the external space of the furnace was adjusted so as to be 5 Pa (specifically, 3 to 7 Pa).
Although the thickness of the manufactured glass plate is the same as Example 1, glass composition is as follows (a content rate is a mass% display). In addition, the magnitude | size of a glass plate is 1100 mm x 1300 mm. This glass plate is used as a glass substrate for a liquid crystal display for forming a polysilicon TFT.
SiO ₂ 66%
Al ₂ O ₃ 17.5%
B ₂ O ₃ 7.5%
CaO 8.5%
SnO ₂ 0.5%

3. Example 3
In the inner space of the furnace, the pressure difference between the region where the temperature of the glass ribbon G is the annealing point temperature to the strain point temperature and the outer space of the furnace corresponding to the height position of this region is 20 Pa (specifically, 18 to A glass substrate for a liquid crystal display was produced in the same manner as in Example 1 except that the pressure was 22 Pa).

4). Example 4
In the inner space of the furnace, the pressure difference between the region where the temperature of the glass ribbon G is the annealing point temperature to the strain point temperature and the outer space of the furnace corresponding to the height position of this region is 20 Pa (specifically, 18 to The glass substrate for liquid crystal display which forms a polysilicon TFT was manufactured by the method similar to Example 2 except being 22Pa).

5. Example 5
In the interior space of the furnace, the pressure difference between the region where the temperature of the glass ribbon G is the annealing point temperature to the strain point temperature and the space outside the furnace corresponding to the height position of this region is 35 Pa (specifically 33 to A glass substrate for a liquid crystal display was produced in the same manner as in Example 1 except that the pressure was 37 Pa).

6). Example 6
In the interior space of the furnace, the pressure difference between the region where the temperature of the glass ribbon G is the annealing point temperature to the strain point temperature and the space outside the furnace corresponding to the height position of this region is 35 Pa (specifically 33 to The glass substrate for liquid crystal display which forms a polysilicon TFT by the method similar to Example 2 except having been 37 Pa) was manufactured.

7). Example 7
In the inner space of the furnace, the pressure difference between the region where the temperature of the glass ribbon G is the annealing point temperature to the strain point temperature and the outer space of the furnace corresponding to the height position of this region is 60 Pa (specifically 55 to A glass substrate for a liquid crystal display was produced in the same manner as in Example 1 except that the pressure was 65 Pa).

8). Comparative Example In the furnace internal space, the pressure difference between the region where the temperature of the glass ribbon G is between the annealing point temperature and the strain point temperature and the space outside the furnace corresponding to the height position of this region is −5 Pa (in detail) Is −6 to −4 Pa) (that is, the pressure in the external space corresponding to the height position of this region is higher than that in the region where the temperature of the glass ribbon G is the annealing point temperature to the strain point temperature) A glass substrate for a liquid crystal display was produced in the same manner as in Example 1 except that.

Table 1 below shows the evaluation results of Examples 1 to 7 and Comparative Example.

From the above table, the effect of the method of the present embodiment is clear.

Experiment 2

Further, after melting the glass raw material to obtain molten glass, clarification and stirring were performed, the molten glass was supplied to the forming apparatus 200, and a glass plate was produced by the overflow down draw method. Thereafter, the glass plate was cut to produce a glass plate having a longitudinal direction of 1100 mm, a width direction of 1300 mm, and a thickness of 0.5 mm. At this time, the atmospheric pressure in the furnace outer space was controlled to be higher toward the upstream side as shown in Table 2 below. In addition, the content rate of each component contained in a molten glass is as follows.

SiO ₂ 60%
Al ₂ O ₃ 19.5%
B ₂ O ₃ 10%
CaO 5%
SrO 5%
SnO ₂ 0.5%

At this time, the maximum strain (maximum value of retardation) of the glass plates produced in Examples 8 to 12 was 1.6 nm or less. Moreover, the curvature of the glass plate was 0.18 mm or less. In particular, the maximum strain (maximum retardation value) of the glass plates produced in Examples 9 to 11 was 1.0 nm or less. Moreover, the curvature of the glass plate was 0.15 mm or less.

In Examples 8 to 12, the furnace external spaces S3a and S3b shown in FIG. 3 were connected to control the atmospheric pressure as one space. At that time, the pressure difference between the region where the temperature of the glass ribbon G is the annealing point temperature to the strain point temperature and the furnace external space S3a, S3b corresponding to the height position of this region is 10 to 20 Pa. The pressure in the space outside the furnace was adjusted. The air pressure in the furnace external space S3c was adjusted so that the difference between the air pressure in the furnace external space S3c and the pressure in the corresponding position in the furnace internal space was 5 Pa (specifically, 3 to 7 Pa). Table 2 below shows the conditions and evaluation results of Examples 8 to 12.

P1: Air pressure [Pa] in the upper space S1 outside the forming furnace
P2: Pressure in the furnace outer space S2 [Pa]
P3: Pressure in the furnace outer space S3a, S3b [Pa]
P4: Pressure in space S4 [Pa]

From Table 2, it can be seen that it is preferable to control the atmospheric pressure in the outside space of the furnace so that the upstream side of the flow of the glass ribbon G becomes higher in terms of reducing the maximum strain and warpage.

In summary, the present specification discloses the following forms.

(Disclosure 1)
A method for producing a glass plate by a downdraw method,
A melting step of melting glass raw material to obtain molten glass;
Forming the glass ribbon by supplying the molten glass to a molded body provided in a molding furnace, and forming a flow of the glass ribbon;
A slow cooling step of cooling the glass ribbon in the slow cooling furnace by pulling with a roller provided in the slow cooling furnace;
Cutting the cooled glass ribbon in a cutting space, and
When the internal space of the molding furnace provided with the molded body and the internal space of the slow cooling furnace provided with the roller are furnace internal spaces, and the external space of the molding furnace and the slow cooling furnace is a furnace external space, the furnace The external space is a space partitioned by a partition with respect to the atmospheric pressure atmosphere, and the atmospheric pressure of at least a part of the furnace external space is relative to the atmospheric pressure of the furnace internal space at the same position in the flow direction of the glass ribbon. A method for producing a glass plate, wherein the atmospheric pressure is adjusted so as to be low.

(Disclosure 2)
The pressure in the outer space of the furnace is in the region between the position in the slow cooling furnace corresponding to the slow cooling point temperature of the glass ribbon and the position in the slow cooling furnace corresponding to the strain point temperature of the glass ribbon. The manufacturing method of the glass plate of Claim 1 by which the atmospheric pressure is adjusted so that it may become low with respect to the atmospheric pressure in the same position of internal space.

(Disclosure 3)
Disclosure 1 or 2, wherein the difference between the atmospheric pressure in the furnace internal space and the atmospheric pressure in the furnace external space is 40 Pa or less at the same position in the flow direction of the glass ribbon with respect to the atmospheric pressure of the at least part of the furnace external space. The manufacturing method of the glass plate of description.

(Disclosure 4)
The method for producing a glass plate according to any one of disclosures 1 to 3, wherein the pressure in the space outside the furnace is adjusted to be higher than the atmospheric pressure.

(Disclosure 5)
The furnace outer space has an upper space located above the ceiling surface of the inner space of the molding furnace, and the upper space does not allow air to flow from the upper space into the furnace inner space. The method for producing a glass plate according to any one of disclosures 1 to 4, wherein the pressure in the upper space is adjusted.

(Disclosure 6)
The flow direction of the glass ribbon is a vertical direction,
The molding furnace is provided vertically above the slow cooling furnace,
The furnace outer space is divided into a plurality of partial spaces in the vertical direction,
The difference between each atmospheric pressure in the partial space and the atmospheric pressure in the furnace internal space at the same position in the vertical direction of the partial space is compared between the uppermost partial space and the lowermost partial space. The method for producing a glass sheet according to any one of claims 1 to 5, wherein the atmospheric pressure is adjusted so that the difference at the uppermost portion is larger than the difference at the lowermost portion.

(Disclosure 7)
The manufacturing method of the glass plate of Claim 6 with which the said difference of the said atmospheric | air pressure of the said partial space becomes large, so that it goes upwards.

(Disclosure 8)
The glass plate manufacturing method according to any one of disclosures 1 to 7, wherein the glass plate is a glass substrate for a liquid crystal display on which a TFT (Thin Film Transistor) is formed.

(Disclosure 9)
When the outer space of the furnace includes a first partial space at the same position as the formed body in the flow direction of the glass ribbon, the furnace at the same position in the flow direction of the glass ribbon and the atmospheric pressure of the first partial space The method for producing a glass plate according to any one of disclosures 1 to 8, wherein a difference in atmospheric pressure in the internal space is greater than 0 and 40 Pa or less.

(Disclosure 10)
The furnace outer space includes a second partial space located at the same position as the slow cooling furnace in the flow direction of the glass ribbon, and the difference between the atmospheric pressure of the furnace internal space of the slow cooling furnace and the atmospheric pressure of the second partial space is 0 The method for producing a glass plate according to any one of Disclosures 1 to 9, which is largely 40 Pa or less.

(Disclosure 11)
The furnace external space includes a first partial space located at the same position as the formed body and a second partial space located at the same position as the slow cooling furnace in the flow direction of the glass ribbon, and the first partial space and the first When two partial spaces are separated by a wall and adjacent to each other, the atmospheric pressure in the first partial space of the furnace external space is larger than the atmospheric pressure in the second partial space, and the atmospheric pressure in the first partial space and the second The method for producing a glass plate according to any one of disclosures 1 to 10, wherein the difference in atmospheric pressure in the partial space is less than 20 Pa.

(Disclosure 12)
The furnace exterior space includes a plurality of second partial spaces at the same position as the slow cooling furnace, and the plurality of the second partial spaces have a higher atmospheric pressure toward the upstream side in the flow direction of the molten glass. 12. A method for producing a glass plate according to any one of.

(Disclosure 13)
The slow cooling step includes
In the central part of the width direction of the glass ribbon, so that a tensile stress works in the flow direction of the glass ribbon,
At least in a temperature range from a temperature obtained by adding 150 ° C. to the annealing point temperature of the glass ribbon to a temperature obtained by subtracting 200 ° C. from the strain point temperature of the glass ribbon,
The cooling rate of the central part in the width direction of the glass ribbon is faster than the cooling rate of the both end parts,
The disclosure 1 to 12, wherein the glass ribbon is changed from a state in which a temperature in a central portion in the width direction of the glass ribbon is higher than the both end portions to a state in which the temperature in the central portion is lower than the both end portions. Manufacturing method of glass plate.

(Disclosure 14)
The slow cooling step includes a first cooling step, a second cooling step, and a third cooling step,
The first cooling step is a step of cooling at the first average cooling rate until the temperature of the central portion in the width direction of the glass ribbon reaches the annealing point temperature,
The second cooling step is a step of cooling at the second average cooling rate until the temperature of the central portion in the width direction of the glass ribbon reaches the strain point temperature of −50 ° C. from the annealing point temperature,
The third cooling step is a step of cooling at a third average cooling rate until the temperature of the central portion in the width direction of the glass ribbon becomes a strain point temperature of −50 ° C. to a strain point temperature of −200 ° C.
The first average cooling rate is 5.0 ° C./second or more, the first average cooling rate is faster than the third average cooling rate, and the third average cooling rate is the second 14. The method for producing a glass plate according to any one of disclosures 1 to 13, wherein the glass plate is made faster than the average cooling rate.

(Disclosure 15)
The method for producing a glass sheet according to disclosure 14, wherein an average cooling rate of a central portion of the glass ribbon in the first cooling step is 5.5 ° C / second to 50.0 ° C / second.

(Disclosure 16)
The method for producing a glass plate according to disclosure 14, wherein an average cooling rate of the glass ribbon in the second cooling step is 0.5 to less than 5.5 ° C / second.

(Disclosure 17)
The method for producing a glass plate according to any one of disclosures 1 to 16, wherein the glass plate is a glass substrate on which a polysilicon TFT or an oxide semiconductor is formed, and a strain point temperature of the glass is 675 ° C. or higher.

(Disclosure 18)
An apparatus for producing a glass plate by a downdraw method,
A melting apparatus for melting glass raw material to obtain molten glass;
The molten glass is supplied to a molded body provided in a molding furnace to form a glass ribbon, the flow of the glass ribbon is created, and the glass ribbon is pulled by a roller provided in the slow cooling furnace, and the slow cooling furnace A molding device for cooling inside,
A cutting device for cutting the cooled glass ribbon in a cutting space,
When the internal space of the molding furnace provided with the molded body and the internal space of the slow cooling furnace provided with the roller are furnace internal spaces, and the external space of the molding furnace and the slow cooling furnace is a furnace external space, the furnace The external space is a space partitioned by a partition with respect to the atmospheric pressure atmosphere, and the atmospheric pressure of at least a part of the furnace external space is relative to the atmospheric pressure of the furnace internal space at the same position in the flow direction of the glass ribbon. An apparatus for producing a glass plate, characterized in that an atmospheric pressure control device for adjusting the atmospheric pressure is provided in the molding apparatus so as to be lowered.

(Disclosure 19)
The glass plate manufacturing apparatus according to disclosure 18, wherein the atmospheric pressure control device is a device that adjusts the inflow of air to and from the atmosphere in order to control the atmospheric pressure in the furnace exterior space.

As mentioned above, although the manufacturing method and manufacturing apparatus of the glass plate of this invention 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, even if various improvement and a change are carried out. Of course it is good.

30 furnace 40 molding furnace 50 slow cooling furnace 200 melting apparatus 201 melting tank 202 clarification tank 203 stirring tank 204 first pipe 205 second pipe 300 molding apparatus 310 molded body 311 supply port 312 groove 313 lower end 320 atmosphere partition member 330 cooling roller 340 Cooling units 350a to

350h Conveying rollers

355, 360a, 360b, 360c, 415, 416, 417a, 417b, 417c, 418 Pressure sensor 400

Cutting devices

411, 412, 413a, 413b, 413c, 414 Floor surfaces 421, 422, 423a, 423b, 423c, 424 Blower 500 Controller 510 Drive unit

Claims

A method for producing a glass plate by a downdraw method,
A melting step of melting glass raw material to obtain molten glass;
Forming the glass ribbon by supplying the molten glass to a molded body provided in a molding furnace, and forming a flow of the glass ribbon;
A slow cooling step of cooling the glass ribbon in the slow cooling furnace by pulling with a roller provided in the slow cooling furnace;
Cutting the cooled glass ribbon in a cutting space, and
When the internal space of the molding furnace provided with the molded body and the internal space of the slow cooling furnace provided with the roller are furnace internal spaces, and the external space of the molding furnace and the slow cooling furnace is a furnace external space, the furnace The external space is a space partitioned by a partition with respect to the atmospheric pressure atmosphere, and the atmospheric pressure of at least a part of the furnace external space is relative to the atmospheric pressure of the furnace internal space at the same position in the flow direction of the glass ribbon. A method for producing a glass plate, wherein the atmospheric pressure is adjusted so as to be low.
The pressure in the outer space of the furnace is in the region between the position in the slow cooling furnace corresponding to the annealing temperature of the glass ribbon and the position in the annealing furnace corresponding to the strain temperature of the glass ribbon. The manufacturing method of the glass plate of Claim 1 by which adjustment of atmospheric pressure is carried out so that it may become low with respect to the atmospheric pressure in the same position of internal space.
3. The difference between the pressure in the furnace internal space and the pressure in the furnace external space is 40 Pa or less at the same position in the flow direction of the glass ribbon with respect to the pressure of the at least a part of the furnace external space. The manufacturing method of the glass plate of description.
The method for producing a glass sheet according to any one of claims 1 to 3, wherein the pressure in the space outside the furnace is adjusted to be higher than the atmospheric pressure.
The furnace outer space has an upper space located above the ceiling surface of the inner space of the molding furnace, and the upper space does not allow air to flow from the upper space into the furnace inner space. The method for producing a glass plate according to any one of claims 1 to 4, wherein an air pressure in the upper space is adjusted.
The flow direction of the glass ribbon is a vertical direction,
The molding furnace is provided vertically above the slow cooling furnace,
The furnace outer space is divided into a plurality of partial spaces in the vertical direction,
The difference between each atmospheric pressure in the partial space and the atmospheric pressure in the furnace internal space at the same position in the vertical direction of the partial space is compared between the uppermost partial space and the lowermost partial space. The method for producing a glass sheet according to any one of claims 1 to 5, wherein the atmospheric pressure is adjusted so that the difference at the uppermost portion is larger than the difference at the lowermost portion. .
The method for producing a glass plate according to claim 6, wherein the difference in the atmospheric pressure in the partial space increases as it goes upward.
The method for producing a glass plate according to any one of claims 1 to 7, wherein the glass plate is a glass substrate for a liquid crystal display on which a TFT (Thin Film Transistor) is formed.
An apparatus for producing a glass plate by a downdraw method,
A melting apparatus for melting glass raw material to obtain molten glass;
The molten glass is supplied to a molded body provided in a molding furnace to form a glass ribbon, the flow of the glass ribbon is created, and the glass ribbon is pulled by a roller provided in the slow cooling furnace, and the slow cooling furnace A molding device for cooling inside,
A cutting device for cutting the cooled glass ribbon in a cutting space,
When the internal space of the molding furnace provided with the molded body and the internal space of the slow cooling furnace provided with the roller are furnace internal spaces, and the external space of the molding furnace and the slow cooling furnace is a furnace external space, the furnace The external space is a space partitioned by a partition with respect to the atmospheric pressure atmosphere, and the atmospheric pressure of at least a part of the furnace external space is relative to the atmospheric pressure of the furnace internal space at the same position in the flow direction of the glass ribbon. An apparatus for producing a glass plate, characterized in that an atmospheric pressure control device for adjusting the atmospheric pressure is provided in the molding apparatus so as to be lowered.
The said atmospheric | air pressure control apparatus is an apparatus which adjusts inflow of air between the said exterior spaces, in order to control the atmospheric | air pressure of the said furnace exterior space, The manufacturing apparatus of the glass plate of Claim 9.