KR101442384B1 - Method and apparatus for making glass sheet - Google Patents

Abstract

A manufacturing method of a glass plate includes a melting step of melting a glass raw material to obtain a molten glass, a molding step of supplying the molten glass to a molding body provided in the molding furnace to form a glass ribbon, A slow cooling step in which the ribbon is pulled by a roller provided in a gradual cooling furnace and cooled in the gradual cooling furnace, and a cutting step of cutting the cooled glass ribbon in a cutting space. Wherein the inner space of the molding furnace and the inner space of the annealing furnace are formed as furnace inner spaces and the outer space of the molding furnace and the annealing furnace is an outer furnace space, . The atmospheric pressure of at least a part of the furnace outer space is adjusted to be lower than the atmospheric pressure of the furnace inner space at the same position in the flow direction of the glass ribbon.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing a glass plate,

The present invention relates to a method of manufacturing a glass plate by a down-draw method and an apparatus for manufacturing a glass plate.

BACKGROUND ART Conventionally, a down-draw method is used as a method of forming a glass substrate used for a flat panel display such as a liquid crystal display.

The overflow down-draw method in the down-draw method includes a step of forming a glass ribbon under the molded body by making the molten glass overflow from the top of the molded body in the molding furnace, and a step of slowly cooling the glass ribbon in the gradual cool-down furnace. In the gradual cooling furnace, the glass ribbon is drawn between the pair of rollers and stretched to a desired thickness, and then the glass ribbon is slowly cooled to reduce distortion and heat shrinkage in the glass ribbon. Thereafter, the glass ribbon is cut into a predetermined size and made into a glass plate and laminated on a bundle of glass plates, or is conveyed to the next process. The down-draw method is described, for example, in Patent Document 1 below.

For example, when a glass plate is used for a glass substrate for a liquid crystal display, a TFT (Thin Film Transistor) is formed on the surface of the glass plate. 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. When the glass plate is thermally shrunk by cooling after the heat treatment, the size changes microscopically have. A minute change in the dimension may cause a positional shift with respect to the target position (pixel position) of the TFT formation position formed on the glass plate, resulting in a display failure of the liquid crystal display. Further, in a liquid crystal display, a liquid crystal is formed between 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. However, if the glass plate on which the TFT is formed causes a small dimensional change due to heat shrinkage, there is a case where accurate alignment with the glass plate on which the color filter is formed is impossible on a pixel-by-pixel basis. For this reason, in order to reduce the variation of the dimension of the glass plate, a glass plate with a small heat shrinkage is required. Further, the heat shrinkage can be reduced by lowering the cooling rate in the slow cooling step of the glass ribbon.

However, in Patent Document 2, in order to reduce the plane distortion of the glass plate, the air pressure in the furnace outer space (furnace outer space) of the molding furnace and / or the annealing furnace is pressurized, Thereby suppressing the temperature fluctuation in the annealing furnace.

Japanese Patent Application Laid-Open No. 2009-196879 Japanese Patent Application Laid-Open No. 2009-173525

However, as described in Patent Document 2, when the air pressure in the furnace outer space is simply increased, the air in the furnace outer space may flow into the inner space of the molding furnace or the annealing furnace. Generally, the temperature of the furnace outer space is lower than the temperature of the furnace atmosphere (furnace inner space) of the furnace or the annealing furnace by about 200 to 1200 ° C. Here, as described in Patent Document 2, there is a case where an air flow ascending in the slow cooling furnace is generated from a cooling chamber, a cutting chamber, or the like. Even if an air flow is generated, So that the influence on the temperature fluctuation of the internal space of the furnace is small. On the other hand, when 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 annealing furnace, the air is not heated, so the temperature difference between the furnace inner space and the furnace inner space is large, A temperature difference is generated between the portion through which the air passes and the other portion, which greatly affects the uniformity of the temperature of the inner space of the furnace. Here, in order to reduce the heat shrinkage rate and the plane distortion, it is effective to carry out temperature control of the glass ribbon with high precision. However, as described above, when the glass ribbon passes through the furnace inner space of the temperature-changed molding furnace or the gradual cooling furnace, the cooling rate of the glass ribbon is partially different, and thus the heat shrinkage of the glass plate also varies. Further, the fluctuation means that the temperature unintentionally changes from the set temperature.

That is, in the slow cooling process (annealing process) of the manufacturing method of the glass plate of Patent Document 2, the temperature in the slow cooling furnace can not be maintained at the set temperature, and the deviation of the heat shrinkage of the glass plate becomes large in some cases. Thus, the glass plate is required to have a small deviation of heat shrinkage, for example, a glass plate for a flat panel display (in particular, a glass substrate for a liquid crystal display, a glass substrate for an organic EL display, Glass substrate), there is a problem that display failure may occur.

Accordingly, it is an object of the present invention to provide a method of manufacturing a glass plate that effectively reduces the deviation of heat shrinkage during the production of the glass plate by the down-draw method.

One aspect of the present invention is a method of manufacturing a glass plate by a down-draw method,

A melting step of melting the glass raw material to obtain a molten glass,

A molding step of supplying the molten glass to a molded body provided in the molding furnace to form a glass ribbon and making a flow of the glass ribbon;

A slow cooling step in which the glass ribbon is pulled by a roller provided in a gradual cooling furnace and cooled in the gradual cooling furnace,

And a cutting step of cutting the cooled glass ribbon in a cutting space.

Wherein when the inner space of the molding furnace in which the molded body is provided and the inner space of the gradual furnace in which the rollers are provided are formed as furnace inner spaces and the outer space of the molding furnace and the annealing furnace is an outer furnace space, Wherein the atmospheric pressure is adjusted such that the atmospheric pressure of at least a part of the furnace outer space is lower than the atmospheric pressure of the furnace inner space at the same position in the flow direction of the glass ribbon .

At this time, in the region between the position in the annealing furnace corresponding to the standing cold spot temperature of the glass ribbon and the position in the annealing furnace corresponding to the distortion point temperature of the glass ribbon, It is preferable that the air pressure is adjusted so as to be lower than the air pressure at the same position of the inner space of the furnace.

It is preferable that the difference between the atmospheric pressure of the furnace inner space and the atmospheric pressure of the furnace outer 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 outer space.

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

Wherein the furnace outer space has an upper space located above the ceiling of the inner space of the molding furnace and the upper space has an upper space communicated with the upper space, The atmospheric pressure is preferably adjusted.

The flow direction of the glass ribbon is a vertical direction, and the molding furnace is installed vertically above the slow cooling furnace. In this case, the furnace outer space is divided into a plurality of subspaces in the vertical direction, and the difference between the respective pressures of the subspaces and the atmospheric pressure of the furnace inner space at the same position in the vertical direction of the subspaces, It is preferable that the air pressure is adjusted such that the difference at the uppermost portion is larger than the difference at the lowermost portion when compared between the uppermost partial space and the lowermost partial space of the partial space.

It is preferable that the difference of the atmospheric pressure in the subspace becomes larger toward the upper side.

The glass plate is, for example, a glass substrate for a liquid crystal display that forms a TFT (Thin Film Transistor) on the surface.

Wherein when the furnace outer space includes a first subspace 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 air pressure of the first subspace The difference in air pressure in the internal space is preferably greater than 0 and less than or equal to 40 Pa.

Wherein the furnace outer space includes a second partial space at the same position as the slow cooling path in the flow direction of the glass ribbon, and the difference between the air pressure of the furnace inner space of the annealing furnace and the air pressure of the second partial space is 0 And is preferably 40 Pa or less.

Wherein the furnace outer space includes a first subspace at the same position as the molded body in the flow direction of the glass ribbon and a second subspace at the same position as the slow furnace, Wherein when the two subspaces are divided and adjoined by the wall, the atmospheric pressure of the first subspace of the furnace outer space is larger than the atmospheric pressure of the second subspace, and the atmospheric pressure of the first subspace and the second portion It is preferable that the difference in the atmospheric pressure of the space is smaller than 20 Pa.

It is preferable that the furnace outer space includes a plurality of second subspaces at the same position as the slow cooling furnace and a plurality of the second subspaces preferably have a higher atmospheric pressure on the upstream side in the flow direction of the molten glass Do.

In the slow cooling step,

So that tensile stress acts on the central portion in the width direction of the glass ribbon in the flow direction of the glass ribbon,

In a temperature range from a temperature at which at least 150 占 폚 is added to a standing cold spot temperature of the glass ribbon to a temperature minus 200 占 폚 from a distortion point temperature of the glass ribbon,

The cooling rate at the central portion in the width direction of the glass ribbon is faster than the cooling rate at both ends,

It is preferable that the glass ribbon is changed in a state in which the temperature at the central portion in the width direction of the glass ribbon is higher than the temperature at the both end portions and the temperature at the central portion is lower than both ends.

The slow cooling step includes a first cooling step, a second cooling step and a third cooling step,

Wherein the first cooling step is a step of cooling the glass ribbon at a first average cooling rate until a temperature at a central portion in a width direction of the glass ribbon reaches a stand-

Wherein the second cooling step is a step of cooling the glass ribbon at a second average cooling rate until a temperature at a central portion in a width direction of the glass ribbon becomes from a stand-by cold point temperature to a strain point temperature of -50 占 폚,

The third cooling step is a step of cooling the glass ribbon at a third average cooling rate until the temperature at the center of the width direction of the glass ribbon becomes from the distortion point temperature of -50 캜 to the distortion point temperature of -200 캜,

It is preferable that the first average cooling rate is 5.0 deg. C / second or more, the first average cooling rate is faster than the third average cooling rate, and the third average cooling rate is faster than the second average cooling rate.

At this time, the average cooling rate at the center of the glass ribbon in the first cooling step is preferably 5.5 to 50.0 DEG C / sec. In addition, the average cooling rate of the glass ribbon in the second cooling step is preferably less than 0.5 to 5.5 DEG C / second. In addition, the cooling rate at the center of the glass ribbon in the third cooling step is preferably 1.5 占 폚 / sec to 7.0 占 sec.

When the glass plate is a glass substrate on which a polysilicon (low-temperature polysilicon) TFT or an oxide semiconductor is formed, the glass distortion point temperature is preferably 675 DEG C or more, and more preferably, the distortion point temperature is 675 DEG C to 750 DEG C .

Further, another embodiment of the present invention is an apparatus for producing a glass plate by a down-draw method. The manufacturing apparatus includes:

A melting apparatus for melting a glass raw material to obtain a molten glass,

A molding device for supplying the molten glass to a molded body provided in the molding furnace to form a glass ribbon, to make a flow of the glass ribbon, to pull the glass ribbon with a roller provided in the annealing furnace and to cool the glass ribbon in the annealing furnace,

And a cutting device for cutting the cooled glass ribbon in a cutting space.

Wherein when the inner space of the molding furnace in which the molded body is provided and the inner space of the gradual furnace in which the rollers are provided are formed as furnace inner spaces and the outer space of the molding furnace and the annealing furnace is an outer furnace space, Is a space partitioned by a partition wall against an atmospheric pressure atmosphere.

A pressure control device for adjusting the air pressure so that the atmospheric pressure of at least a part of the furnace outer space is lower than the atmospheric pressure of the furnace inner space at the same position in the flow direction of the glass ribbon is provided in the molding apparatus.

Preferably, the atmospheric pressure control device is a device for adjusting the inflow of air between the air and the atmosphere to control the air pressure of the outside space of the furnace.

According to the manufacturing method of the glass plate of the above-mentioned form, deviation of heat shrinkage of the glass plate can be effectively reduced.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a flow of a manufacturing method of a glass plate according to the present embodiment. Fig.
Fig. 2 is a diagram schematically showing an apparatus for performing the dissolving process or cutting process according to the embodiment. Fig.
Fig. 3 is a schematic side view of a glass sheet forming apparatus in this embodiment. Fig.
Fig. 4 is a schematic front view of a glass sheet forming apparatus in this embodiment. Fig.
5 is a schematic view of a control system for controlling the amount of air sent by the blower used in the present embodiment.

Hereinafter, a method and apparatus for manufacturing a glass plate according to the present invention will be described.

The following phrases in this specification are defined as follows.

The central portion of the glass ribbon refers to the center of the width of the glass ribbon in the width direction of the glass ribbon.

The end of the glass ribbon refers to a range within 100 mm from the rim of the glass ribbon in the width direction.

The strain point temperature refers to the temperature of the glass plate having a log? Of 14.5 when the glass viscosity is?.

West cold point temperature refers to the temperature of glass plate with log? Of 13.

Fig. 1 is a diagram showing the flow of a manufacturing method of a glass plate according to the present embodiment.

(Overview of Manufacturing Method of Glass Plate)

The manufacturing method of the glass plate mainly includes the dissolving step (ST1), the refining step (ST2), the homogenizing step (ST3), the supplying step (ST4), the molding step (ST5), the slow cooling step (ST6) and the cutting step (ST7). In addition, a plurality of glass sheets stacked in the packing process having a grinding process, a polishing process, a cleaning process, an inspection process, a packing process, and the like are returned to the supplier.

Fig. 2 is a diagram schematically showing a manufacturing apparatus for a glass plate for performing the dissolving step (ST1) to the cutting step (ST7). The apparatus has a dissolving apparatus 200, a molding apparatus 300, and a cutting apparatus 400, as shown in Fig. The dissolving apparatus 200 has a dissolving tank 201, a blue oven 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 by a flame and electric heater (not shown) to obtain a molten glass.

Refining process (ST2) has a redox of blue sign (202) is performed said, by heating the molten glass in the blue sign (202), and bubbles of oxygen and SO ₂ Clarifier (淸澄劑) contained in the molten glass in the It grows by the reaction and floats on the liquid surface to release the gas component of the bubble 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 homogenized by stirring using a stirrer.

In the supplying step ST4, molten glass is supplied to the molding apparatus 300 through the second pipe 205. [

In the molding apparatus 300, a molding step (ST5) and a slow cooling step (ST6) are performed.

In the molding step ST5, the molten glass is supplied to the molded body provided in the molding furnace to form the glass ribbon G (see Fig. 3). In this embodiment, an overflow down-draw method using a formed body 310 to be described later is used. In the gradual cooling step (ST6), the formed glass ribbon G becomes a desired thickness, so that no plane distortion is generated, and the roller is pulled by the roller so that the heat shrinkage ratio is not increased.

In the cutting step ST7, the glass ribbon G fed from the molding apparatus 300 is cut to a predetermined length in the cutting apparatus 400 to obtain a glass plate G1 (see FIG. 3) in a plate shape. The cut glass plate G1 is further cut to a predetermined size to produce a glass plate G1 having a target size. Thereafter, after the grinding / polishing of the end face of the glass is carried out, cleaning is carried out and the presence or absence of abnormal defects such as bubbles or spots is checked, and then the glass plate G1 of the inspected product is packed as a final product.

(Explanation of the molding apparatus)

3 and 4 are views mainly showing the configuration of the glass sheet forming apparatus 300. Fig. 3 mainly shows a schematic side view of the molding apparatus 300, Fig. 4 is a schematic view of the molding apparatus 300, FIG.

The glass plate to be molded in the molding apparatus 300 is suitably used, for example, for a glass substrate or a cover glass for a flat panel display. 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 glass for display in which an oxide semiconductor thin film transistor is formed. The glass plate to be molded in the molding apparatus 300 can also be used as a cover glass for a display or a housing of a portable terminal device, a touch panel plate, a glass substrate for 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 annealing furnace 50 for performing the molding step ST5 and the slow cooling step ST6 is surrounded by a furnace wall made of refractory material such as refractory brick, fire-proof heat insulating brick or fiber-based heat insulating material. The shaping furnace 40 is provided vertically above the slow cooling furnace 50. The molding furnace 40 and the annealing furnace 50 are collectively referred to as a furnace 30. A cooling unit 330, a cooling unit 340, conveying rollers 350a to 350h, and a pressure sensor 355 (not shown) are disposed in the furnace inner space surrounded by the furnace wall of the furnace 30, , 360a to 360c (see Fig. 4) are provided.

The molded body 310 forms a molten glass flowing from the dissolving apparatus 200 through the second pipe 205 into a glass ribbon G as shown in Fig. Thereby, the flow of the glass ribbon G vertically downward in the molding apparatus 300 is made. The molded body 310 is an elongated structure made of refractory bricks 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 formed at the top of the formed body 310. The groove 312 is connected to the second pipe 205 at a supply port 311 (see FIG. 4) formed 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 becomes lower as the downstream of the flow of the molten glass becomes, and the molten glass overflows from the groove 312 toward the vertically downward direction. In Figs. 3 and 4, molten glass is indicated by reference symbol MG.

The molten glass overflowing from the grooves 312 flows vertically downward on the sidewalls of both sides of the formed body 310. The molten glass that has flowed through the sidewalls joins at the lower end 313 of the formed body 310 shown in Fig. 3, and a single glass ribbon G is formed. As a result, the glass ribbon G flows down toward the gradual cooling path 50. The viscosity of the glass ribbon G at the time when the dropping is started apart from the molded body 310 is, for example, 10 ^5.7 to 10 ^7.5 poise.

An atmosphere dividing member 320 is provided in the vicinity of the lower end 313 of the molded body 310. The atmosphere partitioning 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 dividing member 320 so as not to be in contact with the glass ribbon G. The atmosphere partitioning member 320 blocks the movement of heat between the furnace inner space above the atmosphere partitioning member 320 and the furnace inner space below by partitioning the inner space of the furnace.

A cooling roller 330 is provided below the atmosphere partitioning member 320. The cooling roller 330 comes into contact with the surface of the glass ribbon G in the vicinity of both end portions in the width direction of the glass ribbon G to lower the glass ribbon G down to a desired thickness And the glass ribbon (G) is cooled (quenched). By the quenching 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 quenching step or the gradual cooling step using the cooling roller 310, the viscosity of both ends of the glass ribbon G is maintained at 10 ^10.5 to 10 ^14.5 poise by cooling with the cooling function lower than the cooling function of the quenching do.

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 this cooling by the cooling unit 340, warping of the glass ribbon G is suppressed.

Feed rollers 350a to 350h are provided at predetermined intervals below the cooling unit 340 to pull the glass ribbon G downward. The space below the cooling unit 340 is a furnace inner space of the annealing furnace 50. Each of the conveying rollers 350a to 350h has a pair of rollers and is provided at both ends 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 air pressure in the furnace inner space is provided in the furnace inner space of the furnace 40. The pressure sensor 355 is provided at the same position in the height direction (vertical upward direction) with the formed body 310. The height direction is the upward direction of the paper in Figs. Since the glass ribbon G flows vertically downward from the formed 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 inner space of the slow cooling furnace 50. As shown in Fig.

On the outside of the furnace wall of the forming furnace 40, spaces partitioned by the partition walls of the building B, that is, furnace outer spaces S1, S2, S3a to S3c, are formed by the partition walls. The furnace outer space S1 is an upper space located further above the ceiling surface of the inner space of the forming furnace 40. [ Each of these spaces is partitioned by bottom surfaces (bottom walls) 411, 412, 413a to 413c with respect to the height direction. That is, the molding apparatus 300 is installed in the building B having a plurality of floors, and the furnace exterior space (subspace) S1, S2, S3a to S3c partitioned by the floor surface is formed on each floor . In addition, a space S4 (cutting space) partitioned by a wall is formed on the floor 414 under the furnace outer space S3c. No furnace wall is provided in the space S4. The air pressures in these spaces are adjusted by blowers 421, 422, 423a, 423b, 423c, and 424, respectively, which will be described later.

The furnace outer space S1 is a space vertically above the position in the height direction of the formed body 310 and the furnace outer space S1 is provided with a pressure sensor 415 for measuring the atmospheric pressure of the furnace outer space.

The furnace outer space S2 is a space formed on the bottom surface 412, and the formed body 310 is disposed in the furnace inner space corresponding to this space. In addition, a pressure sensor 416 for measuring the air pressure in the furnace outer space S2 is provided in the furnace outer space S2. A pressure sensor 355 for measuring the pressure of the inner space of the furnace is provided at the same position in the height direction of the pressure sensor 416 in the furnace inner space surrounded by the furnace wall (see FIG. 4).

The furnace outer spaces S3a to S3c are spaces formed in the order of the furnace outer space S3a to S3c from the higher side in the downward direction of the furnace outer space S2. The furnace outer spaces S3a to S3c are formed on the bottom surfaces 413a to 413c. In each of the furnace outer spaces S3a to S3c, pressure sensors 417a to 417c for measuring the atmospheric pressures of the furnace outer spaces S3a to S3c are provided. In the inner space surrounded by the furnace walls, pressure sensors 360a to 360c for measuring the air pressure in the furnace inner space are provided at the same positions in the height direction of the pressure sensors 417a to 417c (see FIG. 4).

In this embodiment, the pressure sensors 355 and 360a to 360c are provided at the respective positions of the internal space of the furnace, but the pressure sensor may be inserted at each position of the furnace internal space to measure the pressure.

The outside space S1, S2, S3a to S3c, and the space S4 are provided outside the partition wall for partitioning the outside space S1, S2, S3a to S3c and the space S4, respectively Blowers 421, 422, 423a, 423b, 423c, and 424 are provided. The air sent from the atmosphere by the blowers 421, 422, 423a, 423b, 423c, and 424 is supplied to the outside space S1, S2, S3a to S3c and the space S4 through the pipe. The amount of air sent by the blowers 421, 422, 423a, 423b, 423c, and 424 is determined by a driving signal from a drive unit 510, which will be described later. The blowers 421, 422, 423a, 423b, 423c, and 424 are provided in order to control the inflow of air into and out of the atmosphere in order to control the atmospheric pressure of each of the outdoor outer spaces S1, S2, S3a to S3c, And functions as an air pressure control device for adjusting.

5 is a schematic diagram of a control system for controlling the amount of air delivered by the blowers 421, 422, 423a, 423b, 423c, 424.

The control system includes pressure sensors 355 and 360a to 360c installed in the furnace space, pressure sensors 415, 416, 417a to 417c and 418 installed in the respective furnace spaces, a control device 500, Unit 510 and blowers 421, 422, 423a, 423b, 423c, and 424, respectively.

The control device 500 compares the measurement result of the atmospheric pressure in the internal space of the furnace that is sent from each of the pressure sensors 355 and 360a to 360c and the measurement result of the atmospheric pressure 422, 423a, 423b, 423c, 424 so that the difference in air pressure at the same position in the height direction in the furnace inner space and the furnace outer space is adjusted to the set range by using the measurement result of the air pressure at the blower 421, Generates a control signal for adjusting the amount of air sent from the atmosphere. The generated control signal is sent to the drive unit 510.

The drive unit 510 generates drive signals for individually adjusting the amount of air to be blown by the blowers 421, 422, 423a, 423b, 423c, and 424 based on the control signals. The driving unit 510 sends driving signals to the blowers 421, 422, 423a, 423b, 423c, and 424, respectively.

In the present embodiment, the control device 500 and the drive unit 510 automatically control the amount of air to be supplied, but the operator may manually adjust the amount of air to be supplied.

The amount of air sent by the blowers 421, 422, 423a, 423b, 423c, and 424 depends on the air pressure in the furnace outer space S2, S3a to S3c at the same position in the height direction The air pressure of the outside space of each furnace is adjusted to be lower.

The difference in air pressure between the furnace inner space and the furnace outer space S2 of the furnace 40 is more than 0 to 40 Pa, preferably 4 to 35 Pa, more preferably 8 to 30 Pa, more preferably 10 to 27 Pa More preferably 10 to 25 Pa, and still more preferably 10 to 25 Pa.

If the difference in air pressure exceeds the above range, a large amount of air may flow out of the gap between the furnace wall and the furnace inner space S2 from the furnace inner space, thereby increasing the rise of air in the furnace inner space. On the other hand, if the difference of the air pressure falls below the above range, there is a possibility that air flows from the gap between the furnace wall toward the furnace inner space from the furnace outer space S2, and the temperature distribution of the furnace inner space changes. It is possible to prevent the inflow of the low temperature air from the furnace outer space S2 into the furnace inner space of the furnace 40 by adjusting the difference of the atmospheric pressure within the above range. As a result, it is possible to suppress the variation in the temperature of the internal space of the furnace. Thus, it is possible to suppress the deviation of the cooling speed and the deviation of the thickness of the glass ribbon G. [ Incidentally, the temperature variation means that the temperature unintentionally changes from a preset temperature.

On the other hand, the difference in air pressure between the furnace inner space and the furnace outer space S3a to S3c of the annealing furnace 50 is more than 0 to 40 Pa, preferably 2 to 35 Pa, more preferably 2 to 25 Pa, More preferably from 3 to 23 Pa, still more preferably from 5 to 20 Pa. Particularly preferably 10 to 20 Pa. If the difference in air pressure exceeds the above range, there is a possibility that a large amount of air will flow out from the gap between the furnace walls from the furnace inner space toward the furnace outer spaces S3a to S3c, thereby increasing the rise of the air in the furnace inner space . On the other hand, if the difference in the air pressure falls below the above range, there is a possibility that air flows from the gaps between the furnace walls toward the furnace inner space from the furnace outer spaces S3a to S3c, and the temperature distribution in the furnace inner space is varied. By adjusting the difference in air pressure within the above range, inflow of low-temperature air from the furnace outer spaces S3a to S3c into the furnace inner space of the annealing furnace 50 can be prevented, . This makes it possible to suppress variations in the deformation, warpage, plane distortion, and deviation of heat shrinkage of the glass ribbon (G). Further, it is preferable that the difference in the atmospheric pressure between the furnace outer spaces (S3a to S3c) and the furnace inner space increases toward the upper side. The temperature of the inner space of the furnace increases toward the upper side and the influences due to the inflow of air at a lower temperature than the inner space of the furnace are considered to be larger.

At this time, it is preferable that the difference in air pressure between the furnace outer space S3c and the space S4 is 0 < (the atmospheric pressure in the atmospheric pressure space S4 at the furnace outer space S3c) (Air pressure in the atmospheric pressure-space S4) <20 Pa, more preferably 1 Pa <atmospheric pressure in the outer space S3c in the outer space S3c <15 Pa and more preferably 2 Pa < (The atmospheric pressure in the atmospheric pressure-space S4 in the step S3c) < 15 Pa.

The difference in air pressure between the furnace outer lower space S2 and the furnace outer space S3a is preferably 0 <(air pressure in the furnace outer space S2 and the outer space S3a in the furnace outer space S2), 0 < (The atmospheric pressure of the outer space S2 at the outer space S2a and the atmospheric pressure of the outer space S3a of the outer space S2) is preferably less than 20 Pa and more preferably 1 Pa < More preferably 2 Pa < (atmospheric pressure of the outer space S2 and atmospheric pressure of the outer space S3a of the furnace) < 15 Pa.

The difference in air pressure between the furnace outer space S1 and the furnace outer space S2 is preferably 0 <(atmospheric pressure in the furnace outer space S1 - atmospheric pressure in the furnace outer space S2) (The atmospheric pressure of the outer space S2 in the furnace outer space S1) is more preferably <30 Pa, and more preferably 1 Pa <(the atmospheric pressure in the outer furnace space S1 and the atmospheric pressure in the furnace outer space S2) , And more preferably 2 Pa <(air pressure in the outer space S1 and air pressure in the outer space S2 in the furnace) <15 Pa. The air pressure difference between the furnace outer space S3c and the space S4 and the atmospheric pressure difference between the furnace outer space S2 and the furnace outer space S3a and the atmospheric pressure difference between the furnace outer space S1 and the furnace outer space S2 The absolute value of the atmospheric pressure of the furnace outer space S1, the furnace outer space S2, and the furnace outer spaces S3a to S3c becomes excessively large, and air flows into the furnace inner space from the furnace outer space. This may cause a problem that the temperature inside the furnace space is fluctuated. In addition, concentration of local air currents in the external space of the furnace or locally rapid flow of the air current may occur, which may lower the stability of the atmospheric pressure of the external space, and as a result, the temperature in the internal space of the furnace may fluctuate There is a possibility that a problem may arise.

In the present embodiment, the atmospheric pressure in the furnace outer space is adjusted so that the atmospheric pressure in all the furnace outer spaces is lower than the atmospheric pressure in the furnace inner space at the same position in the height direction. However, The air pressure in the furnace outer space may be adjusted so as to be lower than the atmospheric pressure in the furnace inner space at the same position of the furnace. In this case, in a region between the position in the annealing furnace corresponding to the stand-by 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 air- Direction with respect to the atmospheric pressure of the inner space of the furnace at the same position in the direction of the arrow. The position corresponding to the west cold point temperature is, for example, the position in the height direction of the furnace outer space S3a and the position corresponding to the distortion point temperature is, for example, the position in the height direction of the furnace outer space S3b . In this region, the glass ribbon G is solidified and affects the plane distortion and heat shrinkage of the glass most effectively. Therefore, by controlling the atmospheric pressure in the region effectively, the inflow of air from the furnace outer space is suppressed, It is preferable to suppress the deviation of the temperature in the case

By adjusting the atmospheric pressure in the furnace outer space at the same position in the height direction corresponding to the region where the temperature of the glass ribbon G is lower than the strain point temperature in the furnace inner space of the annealing furnace 50, It is possible to suppress the inflow of the glass ribbon G from the external space, to suppress the variation in the temperature of the region, and to prevent the glass ribbon G from being warped. Here, the glass ribbon G is a continuous sheet from the forming furnace 40 until it is cut. 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 distortion point temperature, it also affects the glass ribbon in the region where the distortion temperature becomes equal to or higher than the distortion point temperature, A deviation occurs. As described above, it is possible to suppress the deviation of the warp, the plane distortion and the heat shrinkage by suppressing the variation of the temperature in the region where the temperature of the glass ribbon G becomes the distortion point temperature or lower.

The pressure sensor 415 at the heightwise position without the inner space of the furnace adjusts the outer space S1 of the furnace 421 by the blower 421 so that air does not flow into the furnace inner space S1 from the furnace inner space S1 It is preferable to measure the atmospheric pressure of the furnace outer space S1.

On the wall of the furnace partitioning the furnace inner space and the furnace outer space, there is a gap around the axis of the cooling roller 310 and the conveying rollers 350a to 350h. Further, a furnace wall and a bottom surface 411 And the like. Therefore, when the difference in air pressure is greater than or equal to a certain degree, airflow easily occurs between the furnace inner space and the furnace outer space. Therefore, it is preferable to adjust the atmospheric pressure of the outer-furnace space surrounding the periphery of the furnace inner space. Particularly, the space of the molding furnace 40 in the furnace inner space is located at the most upstream position in the furnace inner space, so that the atmospheric pressure is high and the temperature in the space is high. The outflow of air from the ceiling of the inner space of the molding furnace 40 into the furnace outer space S1 is not preferable because it promotes the flow of air in the furnace inner space due to the chimney effect. Therefore, the air pressure in the furnace outer space S1 is increased to prevent the outflow of air into the furnace outer space S1. However, if the air pressure in the furnace outer space S1 is made excessively high, air can easily flow into the furnace inner space from the furnace outer space S1. In this case, the cold air introduced from the furnace outer space S1 is not preferable because it forms the glass ribbon in the molding body 310 in the space of the molding furnace 40, and thus affects the viscosity of the molten glass during molding. It also affects the cooling of the glass ribbon in the slow cooling step. The pressure sensor 415 adjusts the air pressure in the furnace outer space S1 so as to adjust the furnace outer space S1 by the blower 421 so that air does not flow into the furnace inner space S1 from the furnace outer space S1 . That is, in the ceiling of the molding furnace 40 where the cooling roller and the conveying roller are not provided, in order to prevent air from flowing into the furnace inner space from the furnace outer space S1, ) Is preferably adjusted by the blower 421. [0064]

The pressure sensor 418 is also used for measuring the atmospheric pressure in the space S4. For example, it is preferable that the atmospheric pressure in the space S4 is adjusted so that the space S4 becomes lower than the lowest atmospheric pressure in the furnace interior space. At this time, it is preferable that the atmospheric pressure in the space S4 is adjusted to be equal to or higher than the atmospheric pressure. On the other hand, when the air pressure in the space S4 becomes equal to or higher than the predetermined pressure, air easily flows into the furnace inner space, and the temperature of the furnace inner space may be influenced. Therefore, the atmospheric pressure in the space S4 is adjusted to be higher than the atmospheric pressure and lower than the predetermined pressure. More specifically, the atmospheric 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 atmospheric pressure in the furnace internal space (minimum atmospheric pressure in the furnace internal space). For example, it is preferable that the atmospheric pressure in the space S4 is 0 < (the atmospheric pressure in the space S4 - the atmospheric pressure), more preferably 0 < (Atmospheric pressure in the space S4-atmospheric pressure) < 40 Pa.

By adjusting the air pressure in the space S4 as described above, it is possible to reduce the air flowing from the space S4 into the furnace inner space.

The air blowers 421, 422, 423a, 423b, 423c, and 424 send air to the outdoor outer spaces S1, S2, S3a to S3c and the space S4 so that the atmospheric pressure in any space is adjusted Setting the air pressure of these spaces higher than the atmospheric pressure prevents a large amount of air from entering the outside space S1, S2, S3a to S3c and the outside of the building B in the space S4, To effectively adjust the air pressure of the external spaces S1, S2, S3a to S3c, and S4.

Further, the higher the position in the height direction, the higher the atmospheric pressure in the furnace inner space. This is due to the upward movement of the hot air into the upward flow. Thus, even if a temperature distribution occurs in the inner space of the furnace and distribution occurs in the atmospheric pressure, the atmospheric pressure in the furnace outer space is adjusted according to the atmospheric pressure distribution. This is to prevent air from flowing into the furnace inner space due to the difference between the atmospheric pressure of each of the furnace outer spaces and the atmospheric pressure of the furnace inner space, and to prevent air from leaking into the furnace outer space, As a result, a pressure sensor is installed in the furnace inner space at the same position in the height direction as the pressure sensor installed in each of the furnace outer spaces. In this way, when a pressure distribution occurs in the furnace inner space, the difference between each of the atmospheric pressures of the furnace outer space and the atmospheric pressure of the furnace inner space at the same position in the height direction of the furnace outer space, It is desirable to adjust it to change. For example, when the comparison is made between the uppermost non-outer space S2 and the lowermost non-outer space S3c among the non-outer spaces S2, S3a to S3c having the inner space at the same position in the height direction , It is preferable that the difference of the atmospheric pressure at the uppermost portion is adjusted to be larger than the difference of the atmospheric pressure at the lowermost portion. For example, the difference of the atmospheric pressure may be set to increase as the position in the height direction increases. This is because the higher the position in the height direction in the furnace inner space in the annealing furnace is, the higher the temperature is, the larger the temperature difference between the glass ribbon G and the glass ribbon G when the cool air is introduced, In order to prevent a variation in the temperature of the liquid.

It is also preferable that the air pressure in the furnace outer space is higher as the position in the height direction is higher, that is, the position on the upstream side in the direction in which the glass ribbon flows. As a result, the size of the upward flow generated along the furnace wall in the furnace exterior space can be reduced. That is, it is possible to suppress the fluctuation of the temperature of the furnace inner space near the furnace wall due to the temperature fluctuation of the furnace wall due to the upward flow generated along the furnace wall, so that the variation in the temperature of the furnace inner space can be suppressed.

(Cooling of the glass ribbon)

In this embodiment, the deviation of heat shrinkage of the glass sheet can be reduced, but by adjusting the cooling rate of the formed glass ribbon, it is possible to suppress the deformation of the glass sheet in addition to the deviation of heat shrinkage, to suppress the warpage and to reduce the absolute value of the heat shrinkage ratio .

Specifically, in the gradual cooling step of slowly cooling the glass ribbon while conveying the glass ribbon by using a roller, a temperature range from a temperature at which the glass ribbon's standing cold spot temperature is 150 占 폚 to a temperature at which the glass ribbon has a distortion point temperature minus 200 占 폚 is determined . The cooling rate at the central portion in the width direction of the glass ribbon is faster than the cooling rate at both ends of the glass ribbon in at least the temperature region and the temperature at the central portion in the width direction of the glass ribbon is higher than the temperature at the central portion It is preferable to change the glass ribbon to a state lower than both ends. Thereby, a tensile stress can be applied to the central portion in the width direction of the glass ribbon in the flow direction of the glass ribbon. The tensile stress acts in the flow direction of the glass ribbon, whereby the warpage of the glass ribbon and further the glass sheet can be further suppressed.

The slow cooling step may include a first cooling step, a second cooling step and a third cooling step.

The first cooling step is a step of cooling the glass ribbon at the first average cooling rate until the temperature at the central portion in the width direction of the glass ribbon reaches the stand-by temperature.

The second cooling step is a step of cooling the glass ribbon at a second average cooling rate until the temperature at the center of the glass ribbon in the width direction becomes from the stand-by cold point temperature to the strain point temperature -50 占 폚.

The third cooling step is a step of cooling the glass ribbon at the third average cooling rate until the temperature at the central portion in the width direction becomes from the distortion point temperature of -50 캜 to the distortion point temperature of -200 캜.

In this case, it is preferable that 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 faster than the second average cooling rate. That is, the average cooling rate is a first average cooling rate, a third average cooling rate, and a second average cooling rate in descending order.

At this time, the average cooling rate at the center of the glass ribbon in the first cooling step is preferably 5.5 to 50 占 폚 / sec. If the average cooling rate at the center portion of the glass ribbon in the first cooling step is less than 5.5 deg. C / second, the productivity decreases. On the other hand, when the average cooling rate at the center of the glass ribbon in the first cooling step exceeds 50 deg. C / second, it is not preferable because control of the temperature distribution in the width direction of the glass ribbon, which is performed in order to suppress the plane distortion and warping, becomes difficult . The average cooling rate at the center portion of the glass ribbon in the first cooling step is more preferably 8 ° C / sec to 16.5 ° C / sec.

In addition, the average cooling rate of the glass ribbon in the second cooling step (heat shrinkage reduction processing step) is preferably less than 0.5 to 5.5 DEG C / second. If the average cooling rate at the central portion of the glass ribbon in the second cooling step is less than 0.5 占 폚 / second, the slow cooling apparatus becomes longer, resulting in a large manufacturing facility and lower productivity. On the other hand, the heat shrinkage rate can not be made sufficiently small at 5.5 deg. C / second or more. The average cooling rate at the center portion of the glass ribbon in the second cooling step is more preferably 0.5 占 폚 / second to 5.5 占 폚 / 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 / sec to 7 ° C / sec. If the cooling rate at the central portion of the glass ribbon in the third cooling step is less than 1.5 캜 / second, the productivity is lowered. On the other hand, when the temperature is higher than 7 ° C / second, the glass ribbon may be excessively quenched and the glass ribbon may be split. From the above, the cooling rate at the center of the glass ribbon in the third cooling step is preferably 15 deg. C / sec to 7 deg. C / sec, more preferably 2 deg. C / sec to 5.5 deg. C / sec.

The cooling rate in the flow direction of the glass ribbon affects the heat shrinkage of the glass sheet to be produced. However, in the gradual cooling step, by setting the cooling rate, it is possible to obtain a glass plate having a suitable heat shrinkage ratio while improving the production amount of the glass plate.

This cooling rate is performed by controlling the temperature by using a heater (not shown) provided in the furnace inner space.

In addition, by separately providing a heat shrinkage reduction process (offline annealing) process after the slow cooling process, the heat shrinkage rate can be reduced. However, if the off-line annealing process is installed separately from the slow cooling step, there is a problem that the productivity is lowered and the cost is increased. Therefore, as described above, it is preferable to set the heat shrinkage ratio within a predetermined range by performing a heat shrinkage reduction treatment (on-line annealing) such that the cooling rate of the glass sheet is controlled in the slow cooling step. That is, the slow cooling step preferably includes a heat shrinkage reduction treatment step. The second cooling step during the slow cooling step corresponds to the heat shrinkage reduction processing step.

(Glass plate)

The glass used for the glass plate of the present embodiment is not particularly limited and can be appropriately selected from the group consisting of borosilicate glass, aluminosilicate glass, aluminoborosilicate glass, soda lime glass, alkali silicate glass, alkali aluminosilicate glass, Can be applied. Further, the glass that can be applied to the present invention is not limited to the above.

(Glass composition 1)

The glass composition of the glass plate used in the present embodiment includes, for example, the following.

The content of the composition shown below is expressed in mass%.

40 to 70% SiO ₂ ,

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%,

Clarifying agent: 0 to 2%

Of alkali-free glass.

(Glass composition 2)

An alkali-free glass having the following composition is also exemplified. The indications in parentheses below are the preferable content ratios of the respective components, and the ratios described later are preferable.

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% (the lower limit is 0.01%, the lower limit is 0.5%, the upper limit is 5%, the upper limit is 4%, the 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% (the lower limit is 0.5%, the lower limit is 3%, the upper limit is 9%, the upper limit is 8%, the upper limit is 7%, the 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)

Especially,

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 to 20%

SrO: 0 to 20%

BaO: 0 to 10%

RO: 5 to 20% (R is at least one selected from Mg, Ca, Sr and Ba, and contains a glass plate)

.

Further, it is preferable that the total amount of R ' ₂ O is more than 0.20% and not more than 2.0% (provided that R' is at least one kind selected from Li, Na and K and contains a glass plate). It is also preferable that the total amount of the refining agent is 0.05 to 1.5%, and substantially no As ₂ O ₃ , Sb ₂ O ₃ and PbO are contained. It is more preferable that the content of iron oxide in the glass is 0.01 to 0.2%.

(Glass composition 4)

Glass compositions of the other glass plates used in the present embodiment include, for example, the following. When the glass plate has the composition shown below, the distortion point temperature can be increased and the heat shrinkage of the glass plate can be further reduced. As a result, the glass plate having the following composition is suitable for a glass substrate for a liquid crystal display or a glass substrate for an organic EL display, and is particularly suitable for a glass substrate to which a polysilicon TFT is applied.

The content of the composition shown below is expressed in mass%. The indications in parentheses below are the preferable content ratios of the respective components, and the ratios described later are preferable.

SiO ₂ : 57 to 75%

Al ₂ O ₃ : 8 to 25%

B ₂ O ₃ : 3 to less than 11%

CaO: 0 to 20%

MgO: 0 to 15%

Of alkali free glass.

At this time, if any one or more of the following expressions are satisfied, the distortion point temperature can be improved and the weight of the glass can be reduced while maintaining the resistance to devitrification and solubility, and thus it is more suitable for a glass substrate for a polysilicon TFT.

(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%) (wherein R is at least one selected from Mg, Ca, Sr and Ba and contains a glass plate)

SiO ₂ + Al ₂ O ₃ : 75% or more (75 to 90%, 79 to 85%)

CaO / B ₂ O ₃ : not less than 0.6% (0.9 to 3%, 1.0 to 2%, 1.1 to 1.5%)

In the above embodiments, the glass is made of alkali-free glass, but the glass plate may contain a trace amount of alkali metal. When an alkali metal is contained, it is preferable that the total amount of R ' ₂ O is more than 0.20% and not more than 2.0% (provided that R' is at least one selected from Li, Na and K and contains a glass plate) Do. It is also preferable that the total amount of the refining agent is 0.05 to 1.5%, and substantially no As ₂ O ₃ , Sb ₂ O ₃ and PbO are contained. From the standpoint of lowering the resistivity, it is more preferable that the content of the iron oxide in the glass is 0.01 to 0.2% in order to facilitate melting of the glass.

(Glass composition 5)

As a glass plate to be applied to a cover glass or a glass plate for a solar cell after chemical strengthening, for example, a glass plate includes the following components in mass%.

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 to 30% (7 to 20%, 8 to 18%, 10 to 15%)

At this time, the following composition may be included as optional components.

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% (the lower limit is 1%, the lower limit is 2%, the lower limit is 3%, the lower limit is 4%, the upper limit is 9%, the upper limit is 8%

CaO: 0 to 20% (the lower limit is 0.1%, the lower limit is 1%, the lower limit is 2%, the upper limit is 10%, the upper limit is 5%, the upper limit is 4%

ZrO ₂ : 0 to 10% (0 to 5%, 0 to 4%, 0 to 1%, 0 to 0.1%)

(Glass composition 6)

Recently, a flat panel display using a polysilicon (low-temperature polysilicon) TFT or an oxide semiconductor instead of an amorphous silicon TFT (Thin Film Transistor) has been required in order to achieve high-precision assembly of a flat panel display. Here, in a flat panel manufacturing process using a polysilicon TFT or an oxide semiconductor, there is a heat treatment process at a higher temperature than a flat panel manufacturing process using an amorphous silicon TFT. Therefore, a glass plate on which a polysilicon TFT or an oxide semiconductor is formed is required to have a low heat shrinkage ratio. In order to reduce the heat shrinkage ratio, it is preferable to increase the temperature of the glass-annealed condition and the temperature of the glass distortion point. Particularly, a glass plate having a distortion point temperature of 675 DEG C or higher (distortion point temperature 675 DEG C to 750 DEG C) is suitable for a polysilicon TFT or an oxide semiconductor, and a distortion point temperature of 680 DEG C or higher (distortion point temperature 680 DEG C to 750 DEG C) And a glass plate having a distortion point temperature of 690 DEG C or higher (distortion point temperature of 690 DEG C to 750 DEG C) is particularly suitable.

As the composition of the glass plate having a glass distortion point temperature of 675 DEG C or more, for example, the glass plate includes the following components in mass%.

52 to 78% of SiO ₂ ,

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%

Wherein the mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is in the range of 7-20.

In this case, it is preferable that the total content of SrO and BaO is less than 8 mass% from the viewpoint of weight reduction and thermal expansion coefficient reduction. 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 the case of lowering the density, it is preferable not to substantially contain SrO and BaO. Substantially no inclusion means not intentionally containing, and inevitably the inclusion of SrO and BaO as impurities is not excluded.

In order to further increase the distortion point temperature, the mass ratio (SrO ₂ + Al ₂ O ₃ ) / RO is preferably 7.5 or more. In order to increase the distortion point temperature, it is preferable to set the value of? -OH to 0.1 to 0.3 [mm ^-1 ]. On the other hand, in order to prevent current from flowing into the melting vessel 201 at the time of melting, the glass plate is made of R ₂ O (provided that R ₂ O is a whole of Li ₂ O, Na ₂ O and K ₂ O Is preferably 0.01 to 0.8% by mass in view 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 lower the specific resistance of the glass. In order to prevent an increase in the devitrification temperature while realizing a high distortion point temperature, the glass plate preferably has CaO / RO of 0.65 or more. By setting the slag temperature to 1250 占 폚 or lower, it becomes possible to apply the overflow down-draw method. Also, considering that it is applied to a mobile device such as a mobile communication terminal, it is preferable that the total content of SrO and BaO is 0% or more and less than 2% from the viewpoint of lightening.

(Description of each component)

SiO ₂ is a component constituting the skeleton of the glass of the glass plate and has an effect of increasing the chemical durability of the glass and the temperature of the distortion point. If the content of SiO ₂ is too low, the effects of chemical durability and heat resistance are not sufficiently obtained. Further, since the distortion point temperature is lowered and the thermal expansion coefficient is increased, the heat shrinkage ratio is increased. If the content of SiO ₂ is too high, the glass tends to cause delamination, making it difficult to form, and the viscosity tends to rise, making it difficult to homogenize the glass. Further, since the specific resistance of the glass is increased, it is difficult to dissolve the glass.

Al ₂ O ₃ constitutes the skeleton of glass and has the effect of increasing the chemical durability of glass and the temperature of distortion point. It also has an effect of increasing the etching rate. If the content of Al ₂ O ₃ is too low, the effect of the chemical durability and heat resistance of the glass can not be sufficiently obtained. Also, the distortion point temperature and Young's modulus decrease. On the other hand, if the content of Al ₂ O ₃ is too high, the viscosity of the glass increases, which makes it difficult to dissolve and the acid resistance decreases. Further, since the specific resistance of the glass is increased, it is difficult to dissolve the glass.

B ₂ O ₃ is a component that promotes the dissolution and refinement of glass by lowering the viscosity of the glass. When the content of B ₂ O ₃ is too low, it is difficult to dissolve and the acid resistance of the glass deteriorates. Further, resistance to devitrification is lowered and the thermal expansion coefficient is increased. On the other hand, if the content of B ₂ O ₃ is excessively high, the distortion point temperature is lowered and the heat resistance is lowered. Also, the Young's modulus deteriorates. In addition, due to the volatilization of B ₂ O ₃ during the glass dissolution, the heterogeneity of the glass becomes remarkable, and consequently, fogging tends to occur.

MgO and CaO are components that promote the melting and refining of glass by lowering the viscosity of the glass. Further, Mg and Ca are advantageous components for improving the solubility while reducing the weight of the obtained glass because the proportion of the glass to increase the density of the alkaline earth metal is small. However, if the content of MgO and CaO is excessively high, the distortion point temperature is lowered. In addition, the chemical durability of the glass deteriorates. In addition, CaO is an effective component for lowering the resistivity and improving the solubility of glass without rapidly increasing the glass transition temperature. For this reason, it is preferable to contain it in a glass having a high strain point temperature. In order to raise the glass transition temperature of the glass, MgO is preferably not substantially contained when the glass transition temperature is lowered.

SrO and BaO are components that promote the melting and refining of glass by lowering the viscosity of the glass. It is also a component that increases the oxidizing property of the glass raw material and improves the refinability. However, if the content of SrO and BaO is excessively high, the density of the glass is increased, the weight of the glass plate is not reduced, and the chemical durability of the glass is lowered. It is preferable that BaO is not substantially contained in order to reduce the environmental load. Further, in the present specification, substantially not containing BaO means that the content is less than 0.01% by mass and is not intentionally contained except impurities.

Li ₂ O, Na ₂ O and K ₂ O decrease the viscosity of the glass to improve the solubility and moldability of the glass. When the content of Li ₂ O, Na ₂ O or K ₂ O is too low, the solubility of the glass is lowered and the cost for melting is increased.

On the other hand, if the content of Li ₂ O, Na ₂ O or K ₂ O is excessively high, loss of resistance to devitrification due to deterioration of the glass balance occurs.

In addition, since Li ₂ O, Na ₂ O and K ₂ O elute from the glass to deteriorate the characteristics of the TFT and increase the thermal expansion coefficient of the glass, there is a risk of destroying the substrate during the heat treatment, When it is applied as a glass substrate or a glass substrate for an organic EL display, it is preferably not substantially contained. However, by containing a specific amount of the above-described components in the glass, the basicity of the glass can be increased while suppressing the deterioration of the TFT characteristics and the thermal expansion of the glass within a certain range, It is possible. Therefore, the content of Li ₂ O, Na ₂ O, and K ₂ O is 0 to 2.0%, more preferably 0.1 to 1.0%, and further preferably 0.2 to 0.5%. In addition, it is preferable to not contain Li ₂ O and Na ₂ O, and to contain K ₂ O, which is most difficult to elute from the glass and deteriorate TFT characteristics, among the above components. The content of K ₂ O is 0 to 2.0%, more preferably 0.1 to 1.0%, still more preferably 0.2 to 0.5%.

ZrO ₂ is a component for increasing the viscosity or distortion point temperature near the glass transition temperature. ZrO ₂ is also a component for improving the heat resistance of glass. However, if the content of ZrO ₂ is excessively high, the melt temperature rises and the resistance to devitrification decreases.

TiO ₂ is a component that lowers the high temperature viscosity of glass. However, if the content of TiO ₂ is excessively high, resistance to devitrification is reduced. Further, the glass is colored, and application to a cover glass or the like of a display screen of an electronic apparatus is not preferable. In addition, since the ultraviolet transmittance is lowered because the glass is colored, there arises a problem that the ultraviolet curable resin can not be sufficiently cured when the ultraviolet curable resin is used.

In the glass of the glass plate, a refining agent may be added as a component for defoaming bubbles in the glass. The clinker is not particularly limited as long as it has a small environmental load and is excellent in the refinement of the glass. Examples of the clinker include at least one selected from metal oxides such as tin oxide, iron oxide, cerium oxide, terbium oxide, molybdenum oxide and tungsten oxide .

In addition, As ₂ O ₃ , Sb ₂ O _3, and PbO are substances having the effect of purifying the glass by generating a reaction accompanied by hydrolysis in the molten glass, while As ₂ O ₃ , Sb ₂ O _3, It is preferable that it is substantially not included. Further, in the present specification, substantially not containing As ₂ O ₃ , Sb ₂ O ₃ and PbO means that the content is less than 0.01% by mass and is not intentionally contained except impurities.

The thickness of the glass plate of the present embodiment is, for example, 0.1 mm to 1.5 mm. Preferably 0.1 to 1.2 mm, more preferably 0.3 to 1.0 mm, still more preferably 0.3 to 0.8 mm, particularly preferably 0.3 to 0.5 mm. Here, since the amount of heat retained in the glass is smaller for a thin glass plate, it is difficult to control the glass temperature distribution in the molding furnace 40 and the annealing furnace 50. [ Therefore, by applying the method of this embodiment capable of stabilizing the temperature of the inner space of the furnace, the glass plate having a thickness of 0.5 mm or less can suppress the variation, warping, deviation of plane distortion and deviation of heat shrinkage .

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 longitudinal direction is, for example, 500 mm to 3500 mm, preferably 1000 mm to 3500 mm, and more preferably 2000 mm to 3500 mm.

Further, when the glass plate is enlarged, the glass manufacturing apparatus is also increased in size corresponding to the size of the glass plate. That is, when the glass plate is enlarged, the size of the furnace including the molding furnace 40 and the annealing furnace 50 is increased. As a result, the inner space of the furnace becomes wider, and the influence of cooling of the glass ribbon (G) when the low-temperature air flows into the furnace inner space from the furnace outer space is different in the width direction of the glass ribbon (G). Therefore, the area corresponding to the temperature from the stand-by temperature to the distortion point of the glass ribbon G is varied in the width direction of the glass ribbon G, the time at which the glass ribbon G passes through the above- May fluctuate. As a result, the heat shrinkage of the glass ribbon G also varies in the width direction. Therefore, when the length of the glass plate in the width direction is 2000 mm or more, the effects of the present embodiment, namely, the effects of suppressing the deformation of the glass plate, the deviation of the glass plate, the deviation of the plane distortion, and the deviation of the heat shrinkage are increased. Further, as the length in the width direction of the glass plate becomes 2500 mm or more and 3000 mm or more, the effect of the present embodiment becomes remarkable.

(Characteristics of the glass plate: heat shrinkage ratio)

In the glass plate produced in the present embodiment, the heat shrinkage when left in a temperature atmosphere of 550 캜 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 Is preferably 30 ppm or less, and particularly preferably 20 ppm or less. Particularly, in a glass plate forming a polysilicon TFT, it is preferably 50 ppm or less. In addition, the heat shrinkage rate is calculated by the amount of heat shrinkage / initial length x 10 ⁶ (ppm). As a method of measuring the heat shrinkage percentage, the following methods are exemplified.

1. Use a diamond pen on both ends of the glass plate to draw a parallel ruled line.

2. The glass plate is cut in half in the direction perpendicular to the ruled line, and one of them is heat-treated (550 DEG C for 2 hours in the above).

3. Measure the deviation of the ruled line by bringing the glass plate after heat treatment into contact with the other glass plate.

(Characteristics of the glass plate: variation of heat shrinkage rate)

The deviation of the heat shrinkage rate tends to cause a display failure in the display panel rather than a high and low heat shrinkage ratio particularly when a TFT is formed on a glass plate in the production of a display. In this respect, it is important to suppress the variation of the heat shrinkage rate. It is also preferable that the deviation of the heat shrinkage rate of the glass sheet is ± 3.05% or less. Here, the heat shrinkage deviations are measured when the heat shrinkage percentage is measured at the three positions in the width direction of the glass plate (for example, the position of the central portion and the positions near both ends in the width direction) (+) And the lower limit (-) that fluctuate with respect to these average values. The deviation of heat shrinkage of this glass sheet is preferably ± 3.0% or less, more preferably ± 2.85% or less, further preferably ± 2.7% or less, further preferably ± 2.65% or less. Particularly, in a high-distortion glass produced by selecting a glass composition which reduces the heat shrinkage, it is preferable that the variation of the heat shrinkage rate is not more than 3.0%. Preferably not more than 2.8%, more preferably not more than 2.7%, further preferably not more than 2.6%. Here, in the present specification, the high-distortion point glass refers to a glass having a distortion point temperature of 680 캜 or higher.

(Characteristics of glass plate: plane distortion)

It is also preferable that the maximum value of the plane distortion of the glass plate (the maximum value of the retardation value) is 1.7 nm or less. Preferably 1.3 nm or less, more preferably 1.0 nm or less, and further preferably 0.7 nm or less. The plane distortion is measured by, for example, a birefringence measuring device manufactured by Uni-Opt. Here, since the liquid crystal display is required to be assembled with high precision, the method of this embodiment capable of reducing the plane distortion of the glass plate is particularly suitably used for manufacturing the glass substrate for a liquid crystal display.

(Glass plate: warp)

The warpage of the glass plate is preferably in the range of from 0 to 0.2 mm, preferably from 0 to 0.15 mm, more preferably from 0 to 0.1 mm, and most preferably, Is 0 to 0.05 mm or less, and particularly preferably 0 to 0.05 mm or less.

The measurement of the warpage,

1. First, a plurality of small plates (a rectangular plate with one side of about 400 mm) are cut out from the glass plate.

2. Next, for each small plate, the warpage at four corners and four corners is measured at each of the front and back sides (i.e., a total of 16 deflections are measured). For example, when the warpage of eight small plates is measured, 128 pieces of measurement data of warpage are obtained in 16 places x 8 pieces.

Check whether the maximum value among the measurement data obtained in 3.2 is within the above-mentioned range. In this embodiment, the maximum value of the warpage measured on a plurality of small plates is defined as the warpage of the glass plate.

Experiment 1

In order to confirm the effect of the present embodiment, a method of manufacturing a glass plate by variously changing the manufacturing method of the glass plate and performing heat treatment under the same conditions as in the case of producing a liquid crystal display to measure the heat shrinkage and plane strain by the above- The deviation of the respective heat shrinkage ratios was determined.

1. Example 1

The difference in air pressure between the region where the temperature of the glass ribbon G in the furnace inner space becomes the west coolant temperature or the distortion point temperature and the outside space corresponding to the same position in the height direction of this region is 5 Pa (specifically, 3 to 7 Pa) The air pressure in the outside space was adjusted.

The produced glass plate is a glass substrate for a liquid crystal display, the size is 2200 mm x 2500 mm, and the thickness is 0.7 mm. The glass composition of the glass plate was as follows. The content is expressed in 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 the case of Example 1, the pressure difference between the region where the temperature of the glass ribbon (G) in the furnace space is from the cold point temperature to the distortion point temperature and the pressure in the furnace outside space corresponding to the height position of this region is 5 Pa 7 Pa) was adjusted.

The thickness of the produced glass plate is the same as in Example 1, but the glass composition is as follows (the content is expressed by mass%). The size of the glass plate is 1100 mm x 1300 mm. This glass plate is used as a glass substrate for a liquid crystal display which forms 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

Except that the pressure difference between the region where the temperature of the glass ribbon G in the furnace inner space is from the stand-by temperature to the distortion point temperature and the outside space corresponding to the height position of this region is 20 Pa (specifically, 18 to 22 Pa) , A glass substrate for a liquid crystal display was produced in the same manner as in Example 1. [

4. Example 4

Except that the pressure difference between the region where the temperature of the glass ribbon G in the furnace inner space is from the stand-by temperature to the distortion point temperature and the outside space corresponding to the height position of this region is 20 Pa (specifically, 18 to 22 Pa) , A glass substrate for a liquid crystal display in which a polysilicon TFT was formed was produced in the same manner as in Example 2. [

5. Example 5

Except that the pressure difference between the region where the temperature of the glass ribbon G in the furnace inner space is from the stand-by temperature to the distortion point temperature and the outside space corresponding to the height position of this region is 35 Pa (specifically, 33 to 37 Pa) , A glass substrate for a liquid crystal display was produced in the same manner as in Example 1. [

6. Example 6

Except that the pressure difference between the region where the temperature of the glass ribbon G in the furnace inner space is from the stand-by temperature to the distortion point temperature and the outside space corresponding to the height position of this region is 35 Pa (specifically, 33 to 37 Pa) , A glass substrate for a liquid crystal display in which a polysilicon TFT was formed was produced in the same manner as in Example 2. [

7. Example 7

A space in which the temperature of the glass ribbon G is in the range from the stand-by temperature to the distortion point temperature and the difference in air pressure in the furnace outer space corresponding to the height position of this region is 60 Pa (specifically, 55 to 65 Pa) A glass substrate for a liquid crystal display was produced in the same manner as in Example 1 except for the above.

8. Comparative Example

The air gap difference between the region where the temperature of the glass ribbon G in the furnace inner space becomes the west coolant temperature or the distortion point temperature and the outside space corresponding to the height position of this region is -5 Pa (specifically -6 to -4 Pa) (That is, a region where the temperature of the glass ribbon G is in the range from the stand-by temperature to the distortion point temperature, and the pressure in the out-of-furnace space corresponding to the height position of this region is higher) To prepare a glass substrate for a liquid crystal display.

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

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

Experiment 2

Further, the glass raw material was melted and refined and stirred as molten glass, and then melted glass was supplied to the molding apparatus 200 to produce a glass plate by an overflow down-draw method. Thereafter, the glass plate was cut to produce a glass plate having a length of 1100 mm, a width of 1300 mm, and a thickness of 0.5 mm. At this time, as shown in Table 2 below, the atmospheric pressure in the furnace outer space was controlled so as to be higher on the upstream side. The content of each component contained in the 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 distortion (maximum value of the retardation) of the glass plate produced in Examples 8 to 12 was 1.6 nm or less. The warp of the glass plate was 0.18 mm or less. In particular, the maximum distortion (maximum retardation) of the glass plate produced in Examples 9 to 11 was 1.0 nm or less. The warp of the glass plate was 0.15 mm or less.

In Examples 8 to 12, the atmospheric pressures were controlled by making the one of the outer open spaces S3a and S3b shown in FIG. 3 communicate with each other. At this time, the space of the glass ribbon G is set so that the temperature at which the temperature of the glass ribbon G becomes the cold point temperature or the distortion point temperature and the pressure difference between the outer openings S3a and S3b corresponding to the height position of this region become 10-20 Pa. Was adjusted. The atmospheric pressure in the furnace outer space S3c was adjusted so that the atmospheric pressure in the furnace outer space S3c and the atmospheric pressure difference at the corresponding positions of the furnace inner space were 5 Pa (3 to 7 Pa in detail). Table 2 below shows the conditions and evaluation results of Examples 8 to 12.

P1: atmospheric pressure [Pa] of the upper space S1 of the forming furnace

P2: atmospheric pressure [Pa] of the outside space S2 of the furnace

P3: atmospheric pressure [Pa] of the furnace outer spaces S3a and S3b,

P4: atmospheric pressure [Pa] in the space S4

It can be seen from Table 2 that the air pressure in the furnace outer space is controlled so as to become higher on the upstream side of the flow of the glass ribbon G in view of reducing the maximum distortion and warpage.

To summarize the above, this specification discloses the following modes.

(Initiation 1)

A method of manufacturing a glass plate by a down-draw method,

A melting step of melting the glass raw material to obtain a molten glass,

A molding step of supplying the molten glass to a molded body provided in the molding furnace to form a glass ribbon and making a flow of the glass ribbon;

A slow cooling step in which the glass ribbon is pulled by a roller provided in a gradual cooling furnace and cooled in the gradual cooling furnace,

And a cutting step of cutting the cooled glass ribbon in a cutting space,

Wherein when the inner space of the molding furnace in which the molded body is provided and the inner space of the gradual furnace in which the rollers are provided are formed as furnace inner spaces and the outer space of the molding furnace and the annealing furnace is an outer furnace space, Wherein the air pressure is adjusted such that the atmospheric pressure of at least a part of the furnace outer space is lower than the atmospheric pressure of the furnace inner space at the same position in the flow direction of the glass ribbon &Lt; / RTI &gt;

(Initiation 2)

The atmospheric pressure of the furnace outer space is set such that in the region between the position in the anneal furnace corresponding to the stand-by temperature of the glass ribbon and the position in the anneal furnace corresponding to the strain point temperature of the glass ribbon, Wherein the air pressure is adjusted so as to be lower than the air pressure at the same position of the glass plate.

(Initiation 3)

The glass sheet according to any one of the above 1 or 2, wherein a difference in air pressure between the furnace inner space and the furnace outer 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 a portion of the furnace outer space. &Lt; / RTI &gt;

(Initiation 4)

The method of manufacturing a glass plate according to any one of claims 1 to 3, wherein the atmospheric pressure in the furnace outer space is adjusted to be higher than atmospheric pressure.

(Starting 5)

Wherein the furnace outer space has an upper space located above the ceiling of the inner space of the molding furnace and the upper space has an upper space communicated with the upper space, A method for producing a glass plate according to any one of the first to fourth aspects, wherein the atmospheric pressure is adjusted.

(Initiation 6)

The flow direction of the glass ribbon is a vertical direction,

Wherein the molding furnace is installed vertically above the slow cooling furnace,

The furnace outer space is divided into a plurality of partial spaces in the vertical direction,

When the difference between the respective atmospheric pressures of the partial spaces and the atmospheric pressure of the furnace inner space at the same position in the vertical direction of the partial spaces is compared between the uppermost partial space and the lowermost partial space of the partial spaces , And the difference in the uppermost portion is adjusted so that the difference in the difference at the lowermost portion is larger than the difference at the lowermost portion.

(Initiation 7)

And the difference of the atmospheric pressure in the partial space becomes larger toward the upper side.

(Opening 8)

Wherein the glass plate is a glass substrate for a liquid crystal display that forms a TFT (Thin Film Transistor) on a surface thereof.

(Initiation 9)

Wherein when the furnace outer space includes a first subspace at the same position as the formed body in the flow direction of the glass ribbon, the furnace inner space at the same position in the flow direction of the glass ribbon with the air pressure of the first subspace A method for producing a glass plate according to any one of the first to eighth aspects, wherein a difference in air pressure in the space is greater than 0 and equal to or less than 40 Pa.

(Initiation 10)

Wherein the furnace outer space includes a second partial space at the same position as the slow cooling path in the flow direction of the glass ribbon, and the difference between the air pressure of the furnace inner space of the annealing furnace and the air pressure of the second partial space is 0 Wherein the glass transition temperature of the glass plate is greater than or equal to 40 Pa.

(Initiation 11)

Wherein the furnace outer space includes a first subspace at the same position as the molded body in the flow direction of the glass ribbon and a second subspace at the same position as the slow furnace, When the two partial spaces are adjoined by the wall and are adjacent to each other, the air pressure of the first subspace of the furnace outer space is larger than the air pressure of the second subspace, and the air pressure of the first subspace and the air pressure of the second subspace Is less than 20 Pa, wherein the difference of the atmospheric pressure of the glass plate is less than 20 Pa.

(Opening 12)

Wherein the furnace outer space includes a plurality of second subspaces at the same position as the slow cooling furnace and a plurality of the second subspaces have an air pressure higher at the upstream side in the flow direction of the molten glass, The method for producing a glass plate according to any one of 1 to 11.

(Initiation 13)

In the slow cooling step,

So that a tensile stress acts on the central portion in the width direction of the glass ribbon in the flow direction of the glass ribbon,

In a temperature range from a temperature at which at least 150 占 폚 is added to a standing cold spot temperature of the glass ribbon to a temperature minus 200 占 폚 from a distortion point temperature of the glass ribbon,

The cooling rate at the central portion in the width direction of the glass ribbon is faster than the cooling rate at both ends,

Wherein the glass ribbon is changed in a state in which the temperature at the central portion in the width direction of the glass ribbon is higher than that at the both end portions in a state in which the temperature of the central portion is lower than that at both end portions.

(Initiation 14)

The slow cooling step includes a first cooling step, a second cooling step and a third cooling step,

Wherein the first cooling step is a step of cooling the glass ribbon at a first average cooling rate until a temperature at a central portion in a width direction of the glass ribbon reaches a stand-

Wherein the second cooling step is a step of cooling the glass ribbon at a second average cooling rate until a temperature at a central portion in a width direction of the glass ribbon becomes from a stand-by cold point temperature to a strain point temperature of -50 占 폚,

The third cooling step is a step of cooling the glass ribbon at a third average cooling rate until the temperature at the center of the width direction of the glass ribbon becomes from the distortion point temperature of -50 캜 to the distortion point temperature of -200 캜,

Wherein the first average cooling rate is at least 5.0 占 폚 / second, the first average cooling rate is faster than the third average cooling rate, and the third average cooling rate is faster than the second average cooling rate. Wherein the glass plate is a glass plate.

(Initiation 15)

Wherein an average cooling rate at a central portion of the glass ribbon in the first cooling step is 5.5 deg. C / sec to 50.0 deg. C / sec.

(Initiation 16)

Wherein an average cooling rate of the glass ribbon in the second cooling step is less than 0.5 to 5.5 DEG C / second.

(Initiation 17)

Wherein the glass plate is a glass substrate for forming a polysilicon TFT or an oxide semiconductor, and a glass distortion point temperature is 675 DEG C or higher.

(Initiation 18)

An apparatus for manufacturing a glass plate by a down-draw method,

A melting apparatus for melting a glass raw material to obtain a molten glass,

A molding device for supplying the molten glass to a molded body provided in the molding furnace to form a glass ribbon, to make a flow of the glass ribbon, to pull the glass ribbon with a roller provided in the annealing furnace and to cool the glass ribbon in the annealing furnace,

And a cutting device for cutting the cooled glass ribbon in a cutting space,

Wherein when the inner space of the molding furnace in which the molded body is provided and the inner space of the gradual furnace in which the rollers are provided are formed as furnace inner spaces and the outer space of the molding furnace and the annealing furnace is an outer furnace space, Wherein at least a part of the air outside the furnace space is partitioned by the partition wall in relation to the atmospheric pressure atmosphere so that the atmospheric pressure of the at least a part of the furnace outer space is lower than the atmospheric pressure of the furnace inner space at the same position in the flow direction of the glass ribbon Wherein the control device is provided in the molding apparatus.

(Initiation 19)

Wherein the air pressure control device is an apparatus for adjusting the inflow of air between the air and the atmosphere to control the air pressure of the outside space of the furnace.

While the present invention has been particularly shown and described with respect to a preferred embodiment of the invention, it should be understood that various changes and modifications may be made without departing from the scope of the invention. to be.

30: No
40: Molding furnace
50: slowly cooled
200: dissolution apparatus
201: Melting bath
202: Blue sign
203: stirring tank
204: first piping
205: second piping
300: forming device
310: molded article
311: Supply port
312: Home
313: Lower end
320: atmosphere partition member
330: cooling roller
340: cooling unit
350a to 350h:
355, 360a, 360b, 360c, 415, 416, 417a, 417b, 417c, 418:
400: Cutting device
411, 412, 413a, 413b, 413c, 414:
421, 422, 423a, 423b, 423c, 424:
500: control device
510: drive unit

Claims (9)

A method of manufacturing a glass plate by a down-draw method,
A melting step of melting the glass raw material to obtain a molten glass,
A molding step of supplying the molten glass to a molded body provided in a molding furnace to form a glass ribbon and making a flow of the glass ribbon;
The glass ribbon is pulled by a roller provided in a gradual cooling furnace and cooled in the gradual cooling furnace
/ RTI &gt;
Wherein when the inner space of the molding furnace in which the molded body is provided and the inner space of the gradual furnace in which the rollers are provided are formed as furnace inner spaces and the outer space of the molding furnace and the annealing furnace is an outer furnace space, Is a space defined by a partition wall with respect to an atmospheric pressure atmosphere and the atmospheric pressure of at least a part of the furnace outer space is adjusted to be lower than the atmospheric pressure of the furnace inner space at the same position in the flow direction of the glass ribbon Wherein the glass plate is a glass plate. The method according to claim 1, wherein the atmospheric pressure of the furnace outer space is a difference between a position in the anneal furnace corresponding to a stand-by temperature of the glass ribbon and a position in the anneal furnace corresponding to a strain point temperature of the glass ribbon Wherein an adjustment of the air pressure is made to be lower with respect to the air pressure at the same position of the inner space of the furnace. The method according to claim 1 or 2, wherein a difference in air pressure between the furnace inner space and the furnace outer space 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 outer space 40 Pa or less. The method of manufacturing a glass plate according to claim 1 or 2, wherein the atmospheric pressure of the furnace outer space is adjusted to be higher than atmospheric pressure. 3. The apparatus according to claim 1 or 2, wherein the furnace outer space has an upper space located above the ceiling of the inner space of the molding furnace, And the air pressure in the upper space is adjusted so that air does not flow into the upper space. The method of manufacturing a glass plate according to claim 1 or 2, wherein the glass plate is a glass substrate for a liquid crystal display that forms a TFT (Thin Film Transistor) on the surface. 3. The method according to claim 1 or 2,
And a cutting step of cutting the glass ribbon cooled in the slow cooling step in a cutting space. As an apparatus for producing a glass plate by a down-draw method,
A melting apparatus for melting a glass raw material to obtain a molten glass,
Wherein the molten glass is supplied to a molded body provided in a molding furnace to form a glass ribbon to make a flow of the glass ribbon and to pull the glass ribbon with a roller provided in the gradual cooling furnace,
Lt; / RTI &gt;
Wherein when the inner space of the molding furnace in which the molded body is provided and the inner space of the gradual furnace in which the rollers are provided are formed as furnace inner spaces and the outer space of the molding furnace and the annealing furnace is an outer furnace space, Wherein the atmospheric pressure of at least a part of the outer space of the furnace is adjusted to be lower than the atmospheric pressure of the furnace inner space at the same position in the flow direction of the glass ribbon Wherein an air pressure control device is provided in the molding apparatus. The apparatus for manufacturing a glass plate according to claim 8, wherein the atmospheric pressure control device is an apparatus for adjusting the inflow of air with the external space to control the air pressure of the external space of the furnace.

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