TWI417255B - A manufacturing method of a glass plate and a manufacturing apparatus for a glass plate - Google Patents

Description

Glass plate manufacturing method and glass plate manufacturing device

The present invention relates to a method for producing a glass sheet using a down-draw method and a device for producing a glass sheet.

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

The overflow down-draw method in the down-draw method includes the steps of: causing the molten glass to overflow from the top of the formed body in the forming furnace, thereby forming a glass ribbon under the formed body; and causing the glass to be slowly cooled in the slow cooling furnace. The slow cooling furnace is used to slow the glass ribbon by reducing the strain or heat shrinkage inside the glass ribbon by drawing the glass ribbon between the pair of rolls to a desired thickness. Thereafter, the glass ribbon is cut into a specific size to form a glass plate, which is laminated on the top of the glass plate or transferred to a subsequent step. The pull-down 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 polycrystalline germanium TFT, the glass plate is heat-treated at a temperature of 400 ° C to 600 ° C in the display manufacturing step, but the glass plate is thermally contracted by the heat treatment after the heat treatment, and the size is slightly changed. . A slight change in the size causes a positional deviation of the TFT formation position formed on the glass plate with respect to the target position (pixel position), and as a result, a display failure of the liquid crystal display occurs. Further, in the liquid crystal display, the glass plate on which the TFT is formed and the color filter formed for each pixel The glass plates are opposed to each other, and a liquid crystal is disposed between the glass plates. However, if the glass plate on which the TFT is formed is slightly changed in size due to heat shrinkage, there is a case where the glass plate on which the color filter is formed cannot be accurately aligned in units of pixels. Therefore, in order to reduce variations in the size of the glass sheet, it is required that the heat shrinkage of the glass sheet is small. Furthermore, the heat shrinkage can be reduced by lowering the cooling rate in the slow cooling step of the glass ribbon.

Further, Patent Document 2 listed below discloses a technique of pressurizing the air pressure of the external environment of the furnace (the outer space of the furnace) of the forming furnace and/or the slow cooling furnace to reduce the plane strain of the glass sheet, thereby reducing the inside of the slow cooling furnace. The updraft generated along the glass ribbon thereby suppresses temperature variations in the slow cooling furnace.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-196879

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-173525

However, as described in Patent Document 2, only the air pressure in the outer space of the furnace is increased, and the air in the outer space of the furnace flows into the internal space of the forming furnace or the slow cooling furnace. In general, the temperature of the outer space of the furnace is about 200 to 1200 ° C lower than the temperature in the furnace environment of the forming furnace or the slow cooling furnace (the internal space of the furnace). Here, as described in Patent Document 2, there is a case where an air flow that rises in the slow cooling furnace, such as a cooling chamber or a cutting chamber, occurs, but even if an air flow occurs, the air flows in the slow cooling furnace. When it is raised, it is heated, so it has less influence on the temperature variation of the internal space of the furnace. With this When the air in the outer space of the furnace flows into the inner space of the furnace from the gap between the furnace wall of the forming furnace or the slow cooling furnace, since the air is not heated, the temperature difference from the temperature of the inner space of the furnace is large, In the internal space, a temperature difference occurs between the portion through which the inflowing air passes and the other portion thereof, which greatly affects the uniformity of the temperature of the internal space of the furnace. Here, in order to reduce the heat shrinkage rate and the plane strain, it is effective to accurately perform temperature management of the glass ribbon. However, if the glass ribbon passes through the furnace internal space of the forming furnace or the slow cooling furnace as described above, since the cooling rate of the glass ribbon is partially different, the heat shrinkage of the glass sheet is also uneven. In addition, the term "variation" means a case where the temperature is unintentionally changed from the set temperature.

In the slow cooling treatment (annealing treatment) of the method for producing a glass sheet of Patent Document 2, there is a case where the temperature in the slow cooling furnace cannot be maintained at the set temperature, and the unevenness of the heat shrinkage of the glass sheet becomes large. . Therefore, the glass plate is applied to a glass plate which is less uneven in heat shrinkage, for example, a glass plate for a flat panel display (particularly, a glass substrate for a liquid crystal display, or a glass substrate for an organic EL (electroluminescence) display). In the case of a glass substrate for a display in which an oxide semiconductor thin film transistor is formed, there is a problem that display defects occur.

Accordingly, an object of the present invention is to provide a method for producing a glass sheet which is capable of efficiently reducing uneven heat shrinkage when a glass sheet is produced by a down-draw method.

One aspect of the present invention is a method of manufacturing a glass sheet using a down-draw method, comprising: a melting step of melting a glass raw material to obtain molten glass; and a forming step of supplying the molten glass to a molded body provided in the forming furnace to form a glass ribbon, and forming a strip flow in the vertical direction of the glass ribbon; a slow cooling step of drawing the glass ribbon by means of a roller provided in the slow cooling furnace to be cooled in the slow cooling furnace; and a cutting step of cutting the cooled glass ribbon in the cutting space.

The forming furnace is placed vertically above the slow cooling furnace.

The internal space of the forming furnace in which the molded body is provided and the internal space of the slow cooling furnace in which the roller is provided are used as the internal space of the furnace, and the outer space of the forming furnace and the slow cooling furnace is set as the outer space of the furnace. The outer space of the furnace is a space partitioned by a partition wall for an atmospheric pressure environment, and the air pressure of the inner space of the furnace at the same position of the air pressure of at least a portion of the outer space of the furnace is reduced with respect to the flow direction of the glass ribbon. The way to adjust the air pressure.

Further, the outer space of the furnace is divided into a plurality of partial spaces in the vertical direction, and the difference between the air pressures of the inner spaces of the furnaces at the same positions of the air pressures of the partial spaces and the vertical direction of the partial spaces is When the uppermost partial space in the partial space is compared with the lowermost partial space, the air pressure is adjusted such that the difference between the uppermost portion and the lowermost portion becomes larger than the difference between the lowermost portions.

In this case, it is preferable to adjust the air pressure in such a manner that the air pressure in the outer space of the furnace is slower than the temperature of the slow cooling point corresponding to the glass ribbon. In the region between the position in the cold furnace and the position in the slow cooling furnace corresponding to the strain point temperature of the glass ribbon, the gas pressure at the same position relative to the inner space of the furnace is lowered.

Further, preferably, the air pressure of the at least a part of the outer space of the furnace is such that the difference between the air pressure in the inner space of the furnace and the air pressure in the outer space of the furnace is 40 Pa or less at the same position in the flow direction of the glass ribbon.

Preferably, the air pressure in the outer space of the furnace is adjusted in such a manner as to increase relative to atmospheric pressure.

Preferably, the outer space of the furnace includes an upper upper space with respect to a ceiling surface of the inner space of the forming furnace, and the upper space is adjusted in such a manner that air does not flow from the upper space into the inner space of the furnace. The pressure.

Preferably, the difference in the air pressure of the partial space increases toward the upper side.

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

Preferably, when the outer space of the furnace includes the first partial space at the same position as the molded body in the flow direction of the glass ribbon, the air pressure of the first partial space is at the same position as the flow direction of the glass ribbon. The difference in the air pressure in the internal space of the furnace is greater than 0 and is 40 Pa or less.

Preferably, the outer space of the furnace includes a second partial space located at the same position as the slow cooling furnace in the flow direction of the glass ribbon, and the air pressure in the inner space of the furnace of the slow cooling furnace and the second partial space Air pressure The difference is greater than 0 and is 40 Pa or less.

Preferably, the outer space of the furnace includes a first partial space located at the same position as the molded body and a second partial space located at the same position as the slow cooling furnace in the flow direction of the glass ribbon, and the When the first partial space is adjacent to the second partial space by the wall, the air pressure of the first partial space of the outer space of the furnace is larger than the air pressure of the second partial space, and the air pressure of the first partial space and the first The difference between the two parts of the air pressure is less than 20Pa.

Preferably, the outer space of the furnace includes a plurality of second partial spaces located at the same position as the slow cooling furnace, and the air pressure of the plurality of second partial spaces is higher toward the upstream side in the flow direction of the molten glass.

Preferably, the slow cooling step is such that the tensile stress acts on the central portion in the width direction of the glass ribbon, and acts in the flow direction of the glass ribbon, at least 150 ° C from the slow cooling point temperature of the glass ribbon. The temperature in the temperature range from the strain point temperature of the glass ribbon minus the temperature obtained by subtracting 200 ° C, the cooling rate of the central portion in the width direction of the glass ribbon is faster than the cooling speed of the both end portions, and the glass is made The state in which the temperature in the central portion in the width direction of the glass ribbon is higher than the both end portions changes to a state in which the temperature in the central portion is lower than the both end portions.

Preferably, the slow cooling step includes a first cooling step, a second cooling step, and a third cooling step. The first cooling step is a step of cooling the temperature of the central portion in the width direction of the glass ribbon to the slow cooling point temperature at the first average cooling rate. The second cooling step is a step of cooling the temperature of the central portion in the width direction of the glass ribbon from the slow cooling point temperature to the strain point temperature of -50 ° C at the second average cooling rate, and the third cooling step is a third average step. The cooling rate is such that the temperature of the central portion in the width direction of the glass ribbon is cooled from the strain point temperature of -50 ° C to the strain point temperature of -200 ° C, and the first average cooling rate is 5.0 ° C / sec or more, and the first average The 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 of the central portion of the glass ribbon in the first cooling step is preferably 5.5 ° C / sec to 50.0 ° C / sec. Further, the average cooling rate of the glass ribbon in the second cooling step is preferably from 0.5 to less than 5.5 ° C / sec. Further, the cooling rate in the central portion of the glass ribbon in the third cooling step is preferably from 1.5 ° C / sec to 7.0 ° C / sec.

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

Further, another aspect of the present invention is a manufacturing apparatus for a glass sheet using a down-draw method. The manufacturing apparatus includes: a melting device that melts a glass raw material to obtain molten glass; and a molding device that supplies the molten glass to a molded body provided in the forming furnace to form a glass ribbon, and forms a vertical direction of the glass ribbon band And flowing, and the glass ribbon is pulled by the roller provided in the slow cooling furnace to be cooled in the slow cooling furnace; and the cutting device cuts the cooled glass ribbon in the cutting space.

The forming furnace is placed vertically above the slow cooling furnace.

The internal space of the forming furnace in which the molded body is provided and the internal space of the slow cooling furnace in which the roller is provided are used as the internal space of the furnace, and the outer space of the forming furnace and the slow cooling furnace is set as the outer space of the furnace. At the time, the outer space of the furnace is a space separated by a partition wall for an atmospheric pressure environment.

The molding apparatus is provided with an air pressure control device that adjusts the air pressure in such a manner that the air pressure of at least a part of the outer space of the furnace is lowered with respect to the air pressure of the inner space of the furnace at the same position in the flow direction of the glass ribbon.

Further, the outer space of the furnace is divided into a plurality of partial spaces in the vertical direction, and the difference between the air pressures of the inner spaces of the furnaces at the same positions of the air pressures of the partial spaces and the vertical direction of the partial spaces is When the uppermost partial space in the partial space is compared with the lowermost partial space, the air pressure is adjusted such that the difference between the uppermost portion and the lowermost portion becomes larger than the difference between the lowermost portions.

Preferably, the air pressure control device adjusts the air flow between the atmosphere and the atmosphere to control the air pressure in the outer space of the furnace.

According to the method for producing a glass sheet of the above aspect, unevenness in heat shrinkage of the glass sheet can be efficiently reduced.

Hereinafter, a method of manufacturing a glass sheet and a manufacturing apparatus of the present invention will be described.

The following statements in this specification are defined as follows.

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

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

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

The slow cooling point temperature refers to the temperature of the glass plate with a log η of 13.

Fig. 1 is a view showing the flow of a method for producing a glass sheet of the present embodiment.

(Overall summary of the manufacturing method of glass plate)

The manufacturing method of the glass plate mainly includes a melting step (ST1), a clarification step (ST2), a homogenization step (ST3), a supply step (ST4), a forming step (ST5), a slow cooling step (ST6), and a cutting step (ST7). ). Further, a grinding step, a polishing step, a washing step, an inspection step, a packing step, and the like are included, and a plurality of glass sheets stacked in the packing step are conveyed to the ordering party.

Fig. 2 is a view schematically showing a manufacturing apparatus of a glass sheet which performs a melting step (ST1) to a cutting step (ST7). As shown in FIG. 2, the apparatus mainly includes a melting device 200, a forming device 300, and a cutting device 400. The melting apparatus 200 includes a melting tank 201, a clarification tank 202, a stirring tank 203, a first pipe 204, and a second pipe 205. The forming apparatus 300 will be described below.

In the melting step (ST1), the glass raw material supplied into the melting tank 201 is heated by a flame and an electric heater (not shown) to be melted, thereby obtaining melting. Melt the glass.

The clarification step (ST2) is carried out in the clarification tank 202, and by heating the molten glass in the clarification tank 202, the oxygen or SO ₂ bubbles contained in the molten glass are grown by the redox reaction of the clarifying agent and floated up to the liquid. The gas component of the bubble is released from the surface, or the gas component in the bubble is absorbed in the molten glass to eliminate the bubble.

In the homogenization step (ST3), the molten glass in the stirring tank 203 supplied through the first pipe 204 is stirred by a stirrer to homogenize the glass component.

In the supply step (ST4), the molten glass is supplied to the molding apparatus 300 through the second pipe 205.

The forming step (ST5) and the slow cooling step (ST6) are performed in the molding apparatus 300.

In the molding step (ST5), the molten glass is supplied to the molded body provided in the forming furnace to form the glass ribbon G (see FIG. 3). In the present embodiment, an overflow down-draw method using a molded body 310 to be described later is used. In the slow cooling step (ST6), the glass ribbon G which is formed and flows has a desired thickness, and the flat strain is not generated, and the heat shrinkage rate is not increased, and the roller is pulled and cooled.

In the cutting step (ST7), the glass ribbon G supplied from the molding apparatus 300 is cut into a specific length by the cutting device 400, thereby obtaining a plate-shaped glass plate G1 (see FIG. 3). The cut glass sheet G1 is further cut into a specific size to prepare a glass sheet G1 of a target size. Thereafter, the glass end face is ground and polished, and then cleaned to check for the presence or absence of bubbles or streaks. After abnormal defects, the glass plate G1 of the qualified product is bundled as a final product.

(Description of forming device)

3 and 4 are views mainly showing the configuration of a glass plate forming apparatus 300, FIG. 3 mainly showing a schematic side view of the forming apparatus 300, and FIG. 4 showing a schematic front view of the forming apparatus 300.

The glass plate formed in the forming apparatus 300 can be preferably used, for example, as a glass substrate for a flat panel display or a cover glass. 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 a display on which an oxide semiconductor thin film transistor is formed. Further, the glass plate formed in the molding apparatus 300 can also be used as a cover glass for a mobile terminal device or the like, a cover glass for a housing, a touch panel, a glass substrate for a solar cell, or a cover glass. It is particularly suitable for a glass substrate for a liquid crystal display having a polycrystalline germanium TFT.

The forming furnace 40 that performs the forming step (ST5) and the slow cooling furnace 50 that performs the slow cooling step (ST6) are surrounded by a furnace wall composed of refractory bricks such as refractory bricks, fire-resistant insulating bricks, or fiber-based heat insulating materials. . The forming furnace 40 is provided vertically above the slow cooling furnace 50. Further, the forming furnace 40 and the slow cooling furnace 50 are collectively referred to as a furnace 30. The molded body 310, the environmental isolation member 320, the cooling roller 330, the cooling unit 340, the conveying rollers 350a to 350h, and the pressure sensors 355, 360a to 360c are disposed in the furnace internal space surrounded by the furnace wall of the furnace 30 ( Refer to Figure 4).

As shown in FIG. 2, the molded body 310 is formed into a glass ribbon G by melting glass that has flowed from the melting device 200 through the second pipe 205. Thereby, in the forming device A flow of the glass ribbon G under the vertical is formed in 300. The formed body 310 is an elongated structure composed of refractory bricks or the like, and has a wedge shape as shown in FIG. A groove 312 serving as a flow path for guiding the molten glass is provided 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) provided in the molding apparatus 300. The molten glass that has flowed in through the second pipe 205 flows along the groove 312. The depth of the groove 312 is shallower downstream of the flow of the molten glass, so that the molten glass overflows from the groove 312 toward the lower side. In Figs. 3 and 4, the molten glass is indicated by reference numeral MG.

The molten glass overflowing from the groove 312 flows down the vertical side along the side walls of the both sides of the formed body 310. The molten glass flowing through the side walls merges at the lower end portion 313 of the formed body 310 shown in Fig. 3, and one glass ribbon G is formed. Thereby, the glass ribbon G flows down to the slow cooling furnace 50. The viscosity of the glass ribbon G at the time point from when the molded body 310 starts to flow down is, for example, 10 ^5.7 to 10 ^7.5 poise.

An environmental isolation member 320 is provided near the lower end portion 313 of the molded body 310. The environmental isolation member 320 is a pair of plate-shaped heat insulating members, and is configured to sandwich the glass ribbon G from both sides in the thickness direction. That is, in the environmental isolation member 320, a gap is left to the extent that it does not come into contact with the glass ribbon G. The environmental isolation member 320 blocks the movement of heat between the furnace interior space above the environmental isolation member 320 and the furnace interior space below by isolating the internal space of the forming furnace.

A cooling roll 330 is disposed below the environmental isolation member 320. The cooling roll 330 is in 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, and the glass ribbon G is pulled downward, and the thickness of the glass ribbon G is set to a desired thickness in the vicinity of both end portions, and The glass ribbon G is cooled (quickly cooled). The viscosity at both end portions of the glass ribbon is, for example, 10 ^9.0 to 10 ^10.5 poise by rapid cooling by the cooling roll 330. In the quenching-slow cooling step using the cooling roll 330, the viscosity of the both ends of the glass ribbon G can be maintained at, for example, 10 ^10.5 to 10 ^14.5 poise by cooling with a lower cooling function than the cooling function in the above quenching.

A cooling unit 340 is disposed below the cooling roller 330. The cooling unit 340 cools the glass ribbon G passing through the cooling roller 330. By the cooling by the cooling unit 340, the warpage of the glass ribbon G can be suppressed.

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

A pressure sensor 355 (see FIG. 4) for measuring the air pressure in the internal space of the furnace is provided in the internal space of the furnace 40. The pressure sensor 355 is disposed at the same position as the formed body 310 in the height direction (upper vertical). The height direction is above the paper surface in Figures 3 and 4. Since the glass ribbon G flows from the molded body 310 to the vertically downward direction, 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 inner space of the furnace of the slow cooling furnace 50.

On the other hand, outside the furnace wall of the forming furnace 40, a space partitioned by the partition wall of the building B by the partition wall for the atmospheric pressure environment, that is, the furnace outer spaces S1, S2, S3a to S3c is provided. The furnace outer space S1 is a ceiling surface with respect to the inner space of the forming furnace 40 and is located above the upper portion. between. The spaces are each separated by a bottom surface (bottom walls) 411, 412, 413a to 413c in the height direction. That is, the molding apparatus 300 is provided in the building B having a plurality of layers, and the furnace outer space (partial space) S1, S2, S3a to S3c partitioned by the bottom surface is provided in each layer. Further, below the furnace outer space S3c, a space S4 (cutting space) partitioned by walls is provided on the layer 414. The furnace wall is not provided in the space S4. The air pressures of the spaces are adjusted by air blowers 421, 422, 423a, 423b, 423c, and 424, which will be described later.

The furnace external space S1 is located in a space above the height direction of the molded body 310, and is vertically disposed above the space. The furnace external space S1 is provided with a pressure sensor 415 for measuring the atmospheric pressure of the external space of the furnace.

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

The furnace external spaces S3a to S3c are located below the furnace outer space S2, and are provided in the order of the furnace external spaces S3a to S3c from a higher height direction. The furnace external spaces S3a to S3c are provided on the bottom surfaces 413a to 413c. Further, pressure sensors 417a to 417c for measuring the air pressure of the furnace external spaces S3a to S3c are provided in each of the furnace external spaces S3a to S3c. In the inner space of the furnace surrounded by the furnace wall, a pressure sensor for measuring the air pressure in the inner space of the furnace is disposed at the same position in the height direction of the pressure sensors 417a to 417c. 360a~360c (refer to Figure 4).

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

Further, air blowers 421, 422, 423a, and 423b are provided to the furnace outer spaces S1, S2, S3a to S3c, and the space S4, respectively, outside the partition walls of the partition furnace outer spaces S1, S2, S3a to S3c, and the space S4. , 423c, 424. The air sent from the air by the blowers 421, 422, 423a, 423b, 423c, and 424 is supplied to the furnace outer spaces S1, S2, S3a to S3c, and the space S4 through the pipes, respectively. The amount of air sent by the blowers 421, 422, 423a, 423b, 423c, and 424 is determined based on a drive signal from a drive unit 510, which will be described later. The blowers 421, 422, 423a, 423b, 423c, and 424 function as air pressure control devices that adjust the flow of air between the atmosphere and the outside of the furnace spaces S1, S2, S3a to S3c, and the space S4.

Fig. 5 is a schematic view showing a control system for controlling the amount of air fed into the blowers 421, 422, 423a, 423b, 423c, and 424.

The control system includes pressure sensors 355, 360a-360c disposed in the inner space of the furnace, pressure sensors 415, 416, 417a-417c, 418 disposed in the outer space of each furnace, the control device 500, the driving unit 510, and the blower 421. , 422, 423a, 423b, 423c, 424.

The control device 500 uses the measurement results of the air pressure in the internal space of the furnace transmitted from the pressure sensors 355, 360a to 360c, and the measurement of the air pressure in the external space of the furnace transmitted from the pressure sensors 415, 416, 417a to 417c, 418. And generating a control signal for adjusting the blowers 421, 422, 423a, and 423b such that the difference between the air pressures at the same position in the height direction of the furnace inner space and the outer space of the furnace is adjusted to a set range. 423c, 424 The amount of air sent from the atmosphere. The generated control signal is sent to the drive unit 510.

The drive unit 510 generates a drive signal for individually adjusting the amount of air fed by the blowers 421, 422, 423a, 423b, 423c, 424 based on the control signal. The drive unit 510 transmits a drive signal to each of the blowers 421, 422, 423a, 423b, 423c, 424.

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

Here, the amount of air sent to the blowers 421, 422, 423a, 423b, 423c, and 424 is such that the air pressure in the furnace internal space S2, S3a to S3c is lower than the air pressure in the furnace internal space at the same position in the height direction. The way is to adjust the air pressure in the outer space of each furnace.

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

When the difference between the above-mentioned air pressures exceeds the above range, a large amount of air flows out from the furnace internal space to the furnace outer space S2 from the gap of the furnace wall, thereby increasing the rise of the air in the internal space of the furnace. On the other hand, when the difference in the air pressure is less than the above range, air flows from the furnace outer space S2 into the furnace internal space from the gap of the furnace wall, and the temperature distribution in the furnace internal space is uneven. borrow By adjusting the difference in the air pressure to the above range, it is possible to prevent the low-temperature air from flowing into the furnace internal space of the forming furnace 40 from the furnace outer space S2. Therefore, unevenness in the temperature of the internal space of the furnace can be suppressed. Thereby, unevenness in the cooling rate and unevenness in the thickness of the glass ribbon G can be suppressed. In addition, the unevenness of temperature means that the temperature is unintentionally changed from a preset temperature.

On the other hand, the difference between the air pressure between the internal space of the slow cooling furnace 50 and the external space S3a to S3c of the furnace is more than 0 and 40 Pa or less, preferably 2 to 35 Pa, more preferably 2 to 25 Pa, and further preferably It is 3 to 23 Pa, and more preferably 5 to 20 Pa. Very good for 10~20Pa. When the difference in the air pressure exceeds the above range, a large amount of air flows out from the furnace internal space to the furnace external space S3a to S3c from the gap of the furnace wall, thereby increasing the rise of the air in the internal space of the furnace. On the other hand, when the difference in the air pressure is less than the above range, air flows from the furnace outer space S3a to S3c into the furnace internal space from the gap of the furnace wall, and the temperature distribution in the furnace internal space is uneven. By adjusting the difference in the air pressure to the above range, it is possible to prevent the low-temperature air from flowing into the furnace internal space from the furnace external space S3a to S3c, thereby suppressing the temperature unevenness in the furnace interior space. Thereby, deformation, warpage, unevenness of plane strain, and unevenness of heat shrinkage of the glass ribbon G can be suppressed. Further, it is preferable that the difference between the furnace external spaces S3a to S3c and the air pressure in the furnace internal space increases toward the upper side. The temperature of the inner space of the furnace is higher toward the upper side, and it is considered that the influence of the inflow of air lower than the temperature inside the furnace becomes large.

At this time, the difference in air pressure between the furnace outer space S3c and the space S4 is preferably 0 < (the air pressure of the furnace outer space S3c - the air pressure of the space S4), more preferably 0 < (the air pressure of the furnace outer space S3c - the air pressure of the space S4) <20Pa, further preferably 1 Pa < (air pressure of the furnace outer space S3c - air pressure of the space S4) < 15 Pa, more preferably 2 Pa < (pressure of the furnace outer space S3c - air pressure of the space S4) < 15 Pa.

Further, the difference in air pressure between the space S2 outside the furnace and the space S3a outside the furnace is preferably 0 < (pressure of the space S2 outside the furnace - pressure of the outer space S3a of the furnace), more preferably 0 < (pressure of the external space S2 of the furnace - The air pressure of the furnace outer space S3a is <20 Pa, and further preferably 1 Pa < (the air pressure of the furnace outer space S2 - the air pressure of the furnace outer space S3a) < 15 Pa, more preferably 2 Pa < (the air pressure of the furnace external space S2 - the furnace external space) S3a pressure) <15Pa.

Further, the difference in air pressure between the furnace outer space S1 and the furnace outer space S2 is preferably 0 < (air pressure of the furnace outer space S1 - air pressure of the furnace outer space S2), more preferably 0 < (air pressure of the furnace outer space S1 - furnace exterior The gas pressure of the space S2 is <30 Pa, and further preferably 1 Pa < (the gas pressure of the furnace outer space S1 - the gas pressure of the furnace outer space S2) < 25 Pa, more preferably 2 Pa < (the gas pressure of the furnace external space S1 - the furnace outer space S2) Air pressure) <15Pa. If the air pressure difference between the furnace outer space S3c and the space S4, the air pressure difference between the furnace outer space S2 and the furnace outer space S3a, and the air pressure difference between the furnace outer space S1 and the furnace outer space S2 are too large, the furnace outer space S1 and the furnace outer space S2 The absolute value of the air pressure in the external space S3a to S3c of the furnace becomes too large, so that air flows into the internal space of the furnace from the external space of the furnace. Therefore, there is a problem that the temperature in the internal space of the furnace fluctuates. Further, there is a case where local airflow is concentrated in the outer space of the furnace, and the flow velocity of the airflow is locally increased, and the air pressure stability of the outer space of the furnace is lowered, and as a result, the temperature in the inner space of the furnace is also generated. The problem of unevenness.

Further, in the present embodiment, the air pressure in the furnace internal space at the same position in the height direction is lowered by the air pressure in the outer space of all the furnaces. The air pressure in the outer space of the furnace is adjusted, but the air pressure in the outer space of the furnace can also be adjusted in such a manner that the air pressure of at least a part of the outer space of the furnace is reduced with respect to the air pressure in the inner space of the furnace at the same position in the height direction. In this case, it is preferable that in a region between the position in the slow cooling furnace corresponding to the slow cooling point temperature of the glass ribbon G and the position in the slow cooling furnace corresponding to the strain point temperature of the glass ribbon G, The air pressure in the outer space of the furnace is adjusted in such a manner that the air pressure in the inner space of the furnace at the same position in the height direction is lowered. The position corresponding to the slow cooling point temperature is, for example, the position in the height direction of the furnace outer space S3a, and the position corresponding to the strain point temperature is located, for example, in the height direction of the furnace outer space S3b. Since the glass ribbon G is cured in the above-mentioned region, it is most likely to affect the plane strain or heat shrinkage of the glass. Therefore, it is preferable to adjust the gas pressure efficiently in the above region to suppress the inflow of air from the outer space of the furnace. Thereby, the temperature unevenness of the internal space of the furnace is suppressed.

Further, by adjusting the air pressure in the outer space of the furnace at the same position in the height direction corresponding to the region in which the temperature of the glass ribbon G in the internal space of the slow cooling furnace 50 is equal to or lower than the strain point temperature, the air can be suppressed from the outer space of the furnace. The inflow can suppress the unevenness of the temperature in the region, and the warpage of the glass ribbon G can be prevented by the suppression. Here, the glass ribbon G is a continuous sheet before being cut from the forming furnace 40. Therefore, when the warp shape of the glass ribbon G changes in a region where the temperature of the glass ribbon G becomes equal to or lower than the strain point temperature, it also affects the glass ribbon which becomes a region above the strain point temperature, resulting in plane strain or heat shrinkage. Uneven. As described above, by suppressing the temperature unevenness in the region where the temperature of the glass ribbon G becomes equal to or lower than the strain point temperature, unevenness in warpage, plane strain, and heat shrinkage can be suppressed.

Further, the pressure sensor 415 located at a position in the height direction of the inner space of the furnace is preferably configured to measure the air pressure of the outer space S1 of the furnace so that the air does not flow into the inner space of the furnace from the outer space S1 of the furnace by the blower 421. Adjust the furnace outer space S1.

There is a gap around the shaft of the cooling roll 330 and the transfer rolls 350a-350h in the inner wall of the isolator furnace and the furnace outer space, and further, the connection between the inner space of the partition furnace and the furnace wall and the bottom surface 411 of the furnace outer space exists. gap. Therefore, when the difference in the air pressure is present to some extent or more, it is easy to generate a flow of air between the inner space of the furnace and the outer space of the furnace. Therefore, it is preferable to adjust the air pressure of the outer space of the furnace surrounding the inner space of the furnace. In particular, the space of the forming furnace 40 in the inner space of the furnace is located at the most upstream side in the inner space of the furnace, the air pressure is high, and the temperature in the space is also high. When the air flows out from the ceiling surface of the internal space of the forming furnace 40 toward the furnace outer space S1, the flow of the air in the furnace interior space is promoted by the chimney effect, which is not preferable. Therefore, in order to prevent the air from flowing out to the furnace outer space S1, the air pressure in the furnace outer space S1 is increased. However, if the air pressure in the furnace outer space S1 is made too high, the air easily flows into the furnace internal space from the furnace outer space S1. In this case, since the glass ribbon is formed by the molded body 310 in the space of the forming furnace 40, the cold air flowing in from the furnace outer space S1 affects the viscosity of the molten glass during molding, which is not preferable. Moreover, it also affects the cooling of the glass ribbon in the slow cooling step. Therefore, the pressure sensor 415 measures the air pressure in the furnace outer space S1 to adjust the furnace outer space S1 by the blower 421 so that air does not flow from the furnace outer space S1 into the furnace inner space. That is, it is preferable that the air does not have a cooling roll or a conveying roller. The air pressure of the outer space S1 of the forming furnace is adjusted by the blower 421 from the ceiling surface of the furnace 40 from the gap of the ceiling surface into the furnace interior space S1.

Again, pressure sensor 418 can be used to measure air pressure in space S4. For example, it is preferred to adjust the air pressure of the space S4 such that the space S4 is lower than the lowest air pressure of the furnace interior space. In this case, it is preferable to adjust so that the gas pressure of the space S4 becomes the atmospheric pressure of atmospheric pressure or more. On the other hand, if the air pressure in the space S4 is equal to or higher than a specific pressure, it is feared that the air easily flows into the internal space of the furnace and affects the temperature of the internal space of the furnace. Therefore, the air pressure in the space S4 is adjusted so as to be at or above atmospheric pressure and not at a specific pressure. More specifically, the air pressure in the space S4 is adjusted so as to be equal to or higher than the atmospheric pressure and the lowest air pressure in the furnace internal space (the lowest air pressure in the furnace internal space). For example, the gas pressure in the space S4 is preferably 0 < (pressure of the space S4 - atmospheric pressure), more preferably 0 < (pressure of the space S4 - atmospheric pressure) < 40 Pa, and further preferably 5 Pa < (pressure of the space S4 - atmospheric pressure) <40Pa.

By adjusting the air pressure of the space S4 in the above manner, the air flowing into the internal space of the furnace from the space S4 can be reduced.

Further, the blowers 421, 422, 423a, 423b, 423c, and 424 are fed with air into the furnace outer spaces S1, S2, S3a to S3c, and the space S4, and the air pressure in any space is adjusted to be higher than the atmospheric pressure. The reason why the air pressure of the spaces is relatively high with respect to the atmospheric pressure is to prevent a large amount of air from flowing into the furnace outer spaces S1, S2, S3a to S3c and the space S4 from the outside of the building B, and efficiently adjust the furnace outer space S1. S2, S3a~S3c, S4 air pressure.

Further, regarding the air pressure in the internal space of the furnace, the higher the position in the height direction, the higher the air pressure. The reason for this is that the air that becomes high temperature moves upward by the ascending air current. Even if a temperature distribution is generated in the internal space of the furnace and a gas pressure distribution is generated as described above, the air pressure in the outer space of the furnace is adjusted in accordance with the pressure distribution. The object of the present invention is to suppress the flow of air into the internal space of the furnace by the difference between the respective air pressures in the outer space of the furnace and the air pressure in the inner space of the furnace, and to suppress the leakage of air into the outer space of the furnace to cause convection of air. Therefore, in the inner space of the furnace, a pressure sensor is disposed at the same position as the height direction of the pressure sensor respectively disposed in the outer space of the furnace. In the case where the pressure distribution is generated in the internal space of the furnace as described above, it is preferable to change the air pressure of the internal space of the furnace at the same position of the air pressure of the outer space of the furnace and the height direction of the outer space of the furnace according to the position in the height direction. The difference is adjusted in the way. For example, it is preferable to perform adjustment between the uppermost furnace outer space S2 and the lowermost furnace outer space S3c of the furnace outer space S2, S3a to S3c where the furnace internal space exists at the same position in the height direction. In comparison, the difference between the uppermost air pressure is larger than the lowermost air pressure. For example, it may be set such that the difference in the air pressure is increased as the position in the height direction becomes higher. In the inner space of the furnace of the slow cooling furnace, the higher the position in the height direction is, the higher the temperature is, and the temperature difference between the cold air and the glass ribbon G becomes larger, so the purpose is to prevent the position in the height direction from being higher, the glass belt G The greater the uneven temperature.

Further, the gas pressure in the outer space of the furnace is preferably higher as the position in the height direction is higher, that is, the position on the upstream side in the flow direction of the glass ribbon is higher. Thereby, the amount of updraft generated along the furnace wall in the outer space of the furnace can be reduced. In other words, it is possible to suppress the temperature fluctuation of the furnace wall caused by the upward flow generated along the furnace wall and to change the temperature of the furnace internal space in the vicinity of the furnace wall, thereby suppressing the temperature unevenness in the furnace interior space.

(cooling of glass ribbon)

In the present embodiment, unevenness in heat shrinkage of the glass sheet can be reduced, and further, by adjusting the cooling rate of the formed glass ribbon, the heat shrinkage is uneven, and deformation of the glass sheet can be suppressed, warpage can be suppressed, and reduction can be suppressed. The absolute value of the heat shrinkage rate.

Specifically, in the slow cooling step of slowly cooling the glass ribbon while using a roll, the temperature from the slow cooling point of the glass ribbon is increased by 150 ° C to the strain point temperature of the glass ribbon minus 200 ° C. The temperature range up to the temperature. In this case, it is preferable that at least in the temperature region, the cooling rate in the central portion in the width direction of the glass ribbon is faster than the cooling speed at both end portions of the glass ribbon, so that the temperature of the glass ribbon from the central portion in the width direction of the glass ribbon is high. In the state of the both ends of the glass ribbon, the temperature of the center portion is lower than the state of both end portions. Thereby, the tensile stress acts on the central portion in the width direction of the glass ribbon to function in the flow direction of the glass ribbon. By causing the tensile stress to act in the flow direction of the glass ribbon, the warpage of the glass ribbon and the glass sheet can be further suppressed.

Further, 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 temperature of the central portion in the width direction of the glass ribbon to the slow cooling point temperature at the first average cooling rate.

The second cooling step is to make the width direction of the glass ribbon at the second average cooling rate. The temperature at the central portion is cooled from the slow cooling point temperature to a strain point temperature of -50 °C.

The third cooling step is a step of cooling the temperature of the central portion in the width direction of the glass ribbon from the strain point temperature of -50 ° C to the strain point temperature of -200 ° C at the third average cooling rate.

In this case, it is preferable that the first average cooling rate is 5 ° C /sec 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 the first average cooling rate, the third average cooling rate, and the second average cooling rate in descending order.

At this time, the average cooling rate of the central portion of the glass ribbon in the first cooling step is preferably 5.5 ° C / sec to 50 ° C / sec. If the average cooling rate of the central portion of the glass ribbon in the first cooling step is less than 5.5 ° C / sec, the productivity is lowered. On the other hand, when the average cooling rate of the central portion of the glass ribbon in the first cooling step exceeds 50 ° C / sec, it is difficult to control the temperature distribution in the width direction of the glass ribbon to suppress the plane strain or warpage. Therefore, it is not good. The average cooling rate of the central portion of the glass ribbon in the first cooling step is more preferably from 8 ° C / sec to 16.5 ° C / sec.

Further, in the second cooling step (heat shrinkage reduction treatment step), the average cooling rate of the glass ribbon is preferably from 0.5 to less than 5.5 ° C / sec. When the average cooling rate of the central portion of the glass ribbon in the second cooling step is less than 0.5 ° C / sec, the slow cooling device becomes long, the manufacturing equipment is enlarged, and the productivity is lowered. On the other hand, when it is 5.5 ° C / sec or more, the heat shrinkage rate cannot be sufficiently reduced. The average cooling rate of the central portion of the glass ribbon in the second cooling step is preferably 0.5 ° C / sec to 5.5 ° C / second.

On the other hand, the cooling rate of the central portion of the glass ribbon in the third cooling step is not particularly limited, but is preferably 1.5 ° C / sec to 7 ° C / sec. If the cooling rate of the central portion of the glass ribbon in the third cooling step is less than 1.5 ° C / sec, the productivity is lowered. On the other hand, if it is 7 ° C / sec or more, there is a possibility that the glass ribbon is broken due to the rapid cooling of the glass ribbon. As described above, the cooling rate in the central portion of the glass ribbon in the third cooling step is preferably from 1.5 ° C / sec to 7 ° C / sec, more preferably from 2 ° C / sec to 5.5 ° C / sec.

The cooling rate of the glass ribbon in the direction of flow affects the thermal shrinkage of the manufactured glass sheet. However, by setting the above cooling rate in the slow cooling step, the amount of the glass sheet can be increased, and a glass sheet having a preferable heat shrinkage rate can be obtained.

Such a cooling rate can be performed by controlling the temperature using a heater (not shown) provided in the internal space of the furnace.

Further, by additionally providing a heat shrinkage reduction treatment (offline annealing) step after the slow cooling step, the heat shrinkage rate can be made small. However, if the offline annealing step is provided separately from the slow cooling step, there is a problem that the productivity is lowered and the cost is high. Therefore, it is preferable to control the heat shrinkage rate within a specific range by performing a heat shrinkage reduction process (on-line annealing) for controlling the cooling rate of the glass sheet in the slow cooling step as described above. That is, the slow cooling step preferably includes a heat shrinkage reduction treatment step. Further, in the slow cooling step, the second cooling step corresponds to a heat shrinkage reducing treatment step.

(glass plate)

The glass used in the glass plate of the present embodiment can be, for example, borosilicate glass. Glass, aluminum bismuth glass, aluminum borosilicate glass, soda lime glass, alkali bismuth glass, alkali aluminum bismuth glass, alkali aluminum bismuth glass, and the like. Further, the glass which can be used in the present invention is not limited to the above.

(glass composition 1)

The glass composition of the glass plate used in the present embodiment is exemplified by the following.

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

SiO ₂ : 40 to 70%, Al ₂ O ₃ : 2 to 25%, B ₂ O ₃ : 0 to 20%, MgO: 0 to 10%, CaO: 0 to 15%, SrO: 0 to 10%, BaO : 0~15%, ZnO: 0~10%, ZrO ₂ : 0~10%, clarifying agent: 0~2% alkali-free glass.

(glass composition 2)

Further, an alkali-free glass having the following composition can also be exemplified. The following description of the preferred content of each component in parentheses is described as being better in the latter case.

SiO ₂ : 50~70% (55~65%, 57~64%, 58~62%), Al ₂ O ₃ : 2~25% (10~20%, 12~18%, 15~18%), B ₂ O ₃ : 0 to 20% (5 to 15%, 6 to 13%, 7 to 12%).

In this case, the following components may be contained as an optional component.

MgO: 0~10% (lower limit is 0.01%, lower limit is 0.5%, upper limit is 5%, upper limit is 4%, upper limit is 2%), CaO: 0~20% (lower limit is 1%, lower limit is 3%, The lower limit is 4%, the upper limit is 9%, the upper limit is 8%, the upper limit is 7%, the upper limit is 6%), and SrO: 0 to 20% (the lower limit is 0.5%, the lower limit is 3%, the upper limit is 9%, and the upper limit is 8%, upper limit is 7%, upper limit is 6%), BaO: 0~10% (upper limit is 8%, upper limit is 3%, upper limit is 1%, upper limit is 0.2%), ZrO ₂ : 0~10% ( 0~5%, 0~4%, 0~1%, 0~0.1%).

(glass composition 3)

Particularly preferably, it contains: 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%, and SrO: 0 to 20%, BaO: 0 to 10%, and RO: 5 to 20% (wherein R is at least one selected from the group consisting of Mg, Ca, Sr, and Ba, and is contained in a glass plate).

Furthermore, it is preferable that the total content of R′ ₂ O is more than 0.20% and not more than 2.0% (wherein R′ is at least one selected from the group consisting of Li, Na, and K, and is contained in a glass plate). Further, it is preferable that the clarifying agent is contained in a total amount of 0.05 to 1.5%, and substantially no As ₂ O ₃ , Sb ₂ O _{3 or} PbO is contained. Further, the content of the iron oxide in the glass is more preferably 0.01 to 0.2%.

(glass composition 4)

The glass composition of the other glass plate used in this embodiment is mentioned, for example. By making the glass sheet into the composition shown below, the strain point temperature can be increased, and the heat shrinkage of the glass sheet can be further reduced. Therefore, the glass plate of the following composition is suitable for the glass substrate for liquid crystal displays or the glass substrate for organic electroluminescent displays, and is especially suitable for the glass substrate of the polycrystalline germanium TFT.

The content ratio of the composition shown below is expressed by mass%. The following description of the preferred content of each component in parentheses is described as being better in the latter case.

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%, and MgO: 0 to 15% of alkali-free glass.

In this case, if any one or more of the following formulas are satisfied, the devitrification resistance and the meltability can be maintained, and the strain point temperature can be improved and the glass can be made lighter. Therefore, it is more suitable for a polycrystalline germanium TFT glass substrate.

(SiO ₂ +Al ₂ O ₃ )/B ₂ O ₃ : 8~20% (9~17%, 9~15%, 9~12%)

SrO+BaO: 0~3.3% (0~1.5%, substantially not included)

CaO/RO: 0.65% or more (0.8 to 1%, 0.9 to 1%) (wherein R is at least one selected from the group consisting of Mg, Ca, Sr, and Ba, and is contained in a glass plate)

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

CaO/B ₂ O ₃ : 0.6% or more (0.9 to 3%, 1.0 to 2%, 1.1 to 1.5%)

Further, in the above embodiments, the alkali-free glass is used, but the glass plate may contain an alkali metal in a trace amount. In the case of containing an alkali metal, it is preferable that the total content of R' ₂ O is more than 0.20% and not more than 2.0% (wherein R' is at least one selected from the group consisting of Li, Na, and K, and is contained in a glass plate) . Further, it is preferable that the clarifying agent is contained in a total amount of 0.05 to 1.5%, and substantially no As ₂ O ₃ , Sb ₂ O _{3 or} PbO is contained. Further, in order to make the glass easy to melt, the content of iron oxide in the glass is preferably from 0.01 to 0.2% from the viewpoint of lowering the specific resistance.

(glass composition 5)

For example, a glass plate which is applied to a cover glass or a glass plate for a solar cell after chemical strengthening is exemplified as a glass plate containing the following components in mass%.

SiO ₂ : 50~70% (55~65%, 57~64%, 57~62%), Al ₂ O ₃ : 5~20% (9~18%, 12~17%), Na ₂ O:6 ~30% (7~20%, 8~18%, 10~15%).

In this case, the following composition may be contained as an optional component.

Li ₂ O: 0~8% (0~6%, 0~2%, 0~0.6%, 0~0.4%, 0~0.2%), B ₂ O ₃ :0~5% (0~2%, 0~1%, 0~0.8%), K ₂ O: 0~10% (lower limit is 1%, lower limit is 2%, upper limit is 6%, upper limit is 5%, upper limit is 4%).

MgO: 0~10% (lower limit is 1%, lower limit is 2%, lower limit is 3%, lower limit is 4%, upper limit is 9%, upper limit is 8%, upper limit is 7%), CaO: 0~20% ( 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%, the upper limit is 3%), and ZrO ₂ : 0 to 10% (0 to 5%, 0) ~4%, 0~1%, 0~0.1%).

(glass composition 6)

In recent years, in order to further achieve high definition of flat panel display assembly, it is required to use a polycrystalline germanium (low temperature polysilicon) TFT or an oxide semiconductor instead of a flat panel display using an amorphous germanium TFT (Thin Film Transistor). Here, in the flat plate manufacturing step using a polycrystalline germanium TFT or an oxide semiconductor, there is a heat treatment step in which the flat plate manufacturing step using an amorphous germanium TFT is high temperature. Therefore, for a glass plate forming a polycrystalline germanium TFT or an oxide semiconductor, a heat shrinkage ratio is required to be small. In order to lower the heat shrinkage rate, it is preferred to increase the slow cooling condition of the glass sheet and the strain point temperature of the glass. In particular, for a polycrystalline germanium TFT or an oxide semiconductor, a glass plate having a strain point temperature of 675 ° C or higher (strain point temperature of 675 ° C to 750 ° C) is preferable, and a strain point temperature of 680 ° C or higher is preferable. A glass plate having a temperature of 680 ° C to 750 ° C is particularly preferably a glass plate having a strain point temperature of 690 ° C or higher (strain point temperature of 690 ° C to 750 ° C).

The composition of the glass plate having a strain point temperature of 675 ° C or higher is, for example, a glass plate containing the following components in mass%.

SiO ₂ : 52 to 78%, Al ₂ O ₃ : 3 to 25%, B ₂ O ₃ : 3 to 15%, RO (where RO is the total composition of the glass plate in MgO, CaO, SrO and BaO) Amount: 3 to 20%, a mass ratio (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₃ is a glass plate in the range of 7 to 20.

In this case, in terms of weight reduction and reduction of thermal expansion coefficient, The total content of SrO and BaO is preferably less than 8% by mass. The total content of SrO and BaO is preferably from 0 to 7%, more preferably from 0 to 5%, further preferably from 0 to 3%, more preferably from 0 to 1%, especially in the case of lowering the density of the glass plate. Preferably, it does not substantially contain SrO and BaO. The term "substantially not contained" means that it is not intentionally contained, but it is not excluded that SrO and BaO are inevitably mixed as impurities.

Further, in order to further increase the strain point temperature, the mass ratio (SiO ₂ + Al ₂ O ₃ )/RO is preferably 7.5 or more. Further, in order to increase the strain point temperature, it is preferred to set the β-OH value to 0.1 to 0.3 [mm ^-1 ]. On the other hand, in order to reduce the specific resistance of the glass so that the current does not flow through the melting tank 201 during the melting, it is preferable that the glass plate contains R ₂ O (wherein R ₂ O is Li The total amount of the total components contained in the glass plate in ₂ O, Na ₂ O and K ₂ O is 0.01 to 0.8% by mass. Alternatively, in order to lower the specific resistance of the glass, it is preferable to contain 0.01 to 1% by mass of Fe ₂ O ₃ . Further, in order to achieve a high strain point temperature and prevent an increase in the devitrification temperature, the CaO/RO of the glass plate is preferably set to 0.65 or more. The overflow down-draw method can be applied by setting the devitrification temperature to 1250 ° C or lower. When it is considered to be applied to a mobile device or the like such as a mobile communication terminal, the total content of SrO and BaO is preferably 0% or more and less than 2% from the viewpoint of weight reduction.

(Description of each component)

SiO ₂ is a component of the glass of the glass plate, and has an effect of improving the chemical durability of the glass and the strain point temperature. When the content of SiO ₂ is too low, the effects of chemical durability and heat resistance cannot be sufficiently obtained. Further, the strain point temperature is lowered and the coefficient of thermal expansion is increased, so that the heat shrinkage rate is increased. When the content ratio of SiO ₂ is too high, devitrification of the glass is liable to occur, molding is difficult, and the viscosity is increased to make homogenization of the glass difficult. Moreover, since the specific resistance of the glass is increased, it is difficult to melt.

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

B ₂ O ₃ is a component that lowers the viscosity of the glass and promotes melting and clarification of the glass. When the content ratio of B ₂ O ₃ is too low, melting is difficult, and the acid resistance of the glass is lowered. Further, the devitrification resistance is lowered and the coefficient of thermal expansion is increased. On the other hand, when the content rate of B ₂ O ₃ is too high, the strain point temperature is lowered, so that heat resistance is lowered. In addition, the Yang type modulus is lowered. Further, due to the volatilization of B ₂ O ₃ during the melting of the glass, the unevenness of the glass becomes remarkable and streaks are likely to occur.

MgO and CaO reduce the viscosity of the glass and promote the melting and clarifying components of the glass. Further, since Mg and Ca have a small ratio of increasing the density of the glass in the alkaline earth metal, it is advantageous in that the obtained glass is made lighter and the meltability component is improved. However, if the content ratio of MgO and CaO is too high, the strain point temperature is lowered. Further, the chemical durability of the glass is lowered. Further, CaO is a component which is effective in improving the meltability of the glass without lowering the specific resistance and increasing the devitrification temperature of the glass. because Therefore, it is preferable to contain the glass at a high strain point temperature. Further, since MgO causes the devitrification temperature of the glass to rise, it is preferable that it is substantially not contained when the devitrification temperature is lowered.

SrO and BaO are components that reduce the viscosity of the glass and promote the melting and clarification of the glass. Further, it is also a component which improves the oxidizability of the glass raw material and improves the clarity. However, when the content ratio of SrO and BaO is too high, the density of the glass is increased, the weight of the glass sheet cannot be reduced, and the chemical durability of the glass is lowered. Further, in order to reduce the environmental burden, it is preferable that substantially no BaO is contained. Further, in the present specification, the term "substantially no BaO" means less than 0.01% by mass, and is not intentionally contained except for impurities.

Li ₂ O, Na ₂ O, and K ₂ O are components which lower the viscosity of the glass and improve the meltability or formability of the glass. When the content ratio of Li ₂ O, Na ₂ O or K ₂ O is too low, the meltability of the glass is lowered, and the cost for melting is improved. On the other hand, when the content ratio of Li ₂ O, Na ₂ O, or K ₂ O is too high, devitrification resistance due to deterioration of the glass balance occurs.

In addition, Li ₂ O, Na ₂ O, and K ₂ O are used because the characteristics of the TFT are deteriorated from elution from the glass, and the thermal expansion coefficient of the glass is increased to break the substrate during heat treatment. In the case of a glass substrate for a liquid crystal display or a glass substrate for an organic EL display, it is preferably substantially not contained. However, since the glass is intentionally contained in a specific amount of the above-mentioned components, the deterioration of the characteristics of the TFT or the thermal expansion of the glass can be suppressed within a fixed range, and the alkalinity of the glass can be increased, so that the metal having a valence number is easily oxidized. Play clarification. Therefore, the combined amount of Li ₂ O, Na ₂ O, and K ₂ O is 0 to 2.0%, more preferably 0.1 to 1.0%, still more preferably 0.2 to 0.5%. Further, preferably not contain Li ₂ O, Na ₂ O, and containing such components eluted from the glass is the most difficult of the deterioration of the TFT characteristics of K ₂ O. 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 that increases the viscosity or strain point temperature near the devitrification temperature of the glass. Further, ZrO _{2 is} also a component for improving the heat resistance of the glass. However, if the content ratio of ZrO ₂ is too high, the devitrification temperature is increased and the devitrification resistance is lowered.

TiO ₂ is a component that lowers the high temperature viscosity of glass. However, if the content of TiO ₂ is too high, the devitrification resistance is lowered. Further, the glass is colored, and it is not suitable for use in a cover glass or the like for displaying a screen of an electronic device. Moreover, since the ultraviolet ray transmittance is lowered by coloring the glass, when the treatment with the ultraviolet ray curable resin is performed, there is a problem that the ultraviolet ray curable resin cannot be sufficiently cured.

A clarifying agent may be added to the glass of the glass plate as a component for defoaming the bubbles in the glass. The clarifying agent is not particularly limited as long as it has a small environmental burden and excellent glass clarification, and examples thereof include metal oxidation selected from the group consisting of tin oxide, iron oxide, cerium oxide, cerium oxide, molybdenum oxide, and tungsten oxide. At least one of the things.

Further, As ₂ O ₃ , Sb ₂ O ₃ and PbO have substances which cause a reaction in which the valence fluctuates in the molten glass to clarify the glass, but are due to As ₂ O ₃ , Sb ₂ O ₃ and PbO. It is a substance that has a large environmental burden, and therefore it is preferably substantially not contained. In addition, in the present specification, substantially no inclusion of As ₂ O ₃ , Sb ₂ O ₃ and PbO means that it is less than 0.01% by mass and is not intentionally contained except for impurities.

The thickness of the glass plate of this embodiment is, for example, 0.1 mm to 1.5 mm. It is preferably 0.1 to 1.2 mm, more preferably 0.3 to 1.0 mm, still more preferably 0.3 to 0.8 mm, and particularly preferably 0.3 to 0.5 mm. Here, the thinner the glass sheet, the smaller the heat retention of the glass, and thus the control of the glass temperature distribution in the forming furnace 40 and the slow cooling furnace 50 is more difficult. Therefore, by using the method of the present embodiment which stabilizes the temperature of the internal space of the furnace for a glass plate having a thickness of 0.5 mm or less, deformation, warpage, unevenness of plane strain, and unevenness of heat shrinkage of the glass sheet are suppressed. The effect is greater.

The length of the glass sheet in the width direction of the embodiment is, for example, 500 mm to 3,500 mm, preferably 1,000 mm to 3,500 mm, and more preferably 2000 mm to 3,500 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, more preferably 2000 mm to 3500 mm.

Further, when the glass sheet is increased in size, the glass manufacturing apparatus is also increased in size in accordance with the size of the glass sheet. That is, when the glass plate is increased in size, the furnace including the forming furnace 40 or the slow cooling furnace 50 is also increased in size. Therefore, the internal space of the furnace is increased, and when the low-temperature air flows into the internal space of the furnace from the outside space of the furnace, the influence of the cooling of the glass ribbon G is different in the width direction of the glass ribbon G. Therefore, there is unevenness in the width direction of the glass ribbon G in the region corresponding to the slow cooling point temperature to the strain point temperature of the glass ribbon G, and the glass ribbon G is unevenly formed by the time from the slow cooling point temperature to the strain point temperature. situation. As a result, the heat shrinkage of the glass ribbon G also causes unevenness in the width direction. Therefore, when the length of the glass sheet in the width direction is 2000 mm or more, the effect of the embodiment is that the deformation, warpage, and plane strain of the glass sheet are suppressed. The effect of unevenness in both heat and shrinkage becomes large. Further, when the length in the width direction of the glass sheet is 2,500 mm or more and 3,000 mm or more, the effect of the present embodiment is more remarkable.

(Characteristics of glass plate: heat shrinkage rate)

When the glass plate produced in the present embodiment is left to stand in a temperature environment of 550 ° C for 2 hours, the heat shrinkage rate is 110 ppm or less, 80 ppm or less, 50 ppm or less, preferably 40 ppm or less, more preferably 35 ppm or less, and further preferably 30 ppm or less, particularly preferably 20 ppm or less. In particular, the glass plate forming the polycrystalline germanium TFT is preferably 50 ppm or less. Further, the heat shrinkage ratio was calculated from the amount of heat shrinkage/initial length × 10 ⁶ (ppm). As a method of measuring the heat shrinkage rate, the following method can be exemplified.

1. Use a diamond pen to draw parallel alignments at the ends of the glass.

2. The glass plate was cut into half in a direction perpendicular to the alignment, and one of them was heat-treated (the above treatment was performed at 550 ° C for 2 hours).

3. Dock the heat treated glass plate with another glass plate and measure the amount of deviation of the alignment.

(Characteristics of glass plates: uneven heat shrinkage rate)

In particular, in the case where a TFT is formed on a glass plate in the production of a display, the unevenness of the heat shrinkage ratio is more likely to cause display failure of the display panel than the heat shrinkage rate. In this respect, it is important to suppress the unevenness of the heat shrinkage rate. Further, the unevenness of the heat shrinkage rate of the glass plate is preferably ±3.05% or less. Here, the unevenness of the heat shrinkage ratio refers to the measurement of the heat shrinkage rate at the position of the three portions in the width direction of the glass sheet by the above method (for example, the position near the both end portions of the center portion and the width direction). When the bit The upper (+) and lower (-) limits of the measured values relative to the average of the values. The unevenness of heat shrinkage of the glass sheet is preferably ±3.0% or less, more preferably ±2.85% or less, further preferably ±2.7% or less, and further preferably ±2.65% or less. In particular, when a high strain point glass produced by reducing the glass composition of the heat shrinkage ratio is selected, the unevenness of the heat shrinkage ratio is preferably ±3.0% or less. It is preferably ±2.8% or less, more preferably ±2.7% or less, still more preferably ±2.6% or less. Here, in the present specification, the high strain point glass means a glass having a strain point temperature of 680 ° C or higher.

(Characteristics of glass plate: plane strain)

Further, the maximum value of the plane strain of the glass sheet (the maximum value of the hysteresis value) is preferably 1.7 nm or less. It is preferably 1.3 nm or less, more preferably 1.0 nm or less, still more preferably 0.7 nm or less. Further, the plane strain is measured, for example, by a birefringence measuring device manufactured by Uniopt. Here, since the liquid crystal display requires high-precision assembly, the method of the present embodiment which can reduce the plane strain of the glass plate is particularly preferably used for the production of a glass substrate for a liquid crystal display.

(glass plate: warp)

When the warpage of the glass sheet is measured by the following method, the maximum value of the warpage is in the range of 0 to 0.2 mm, preferably 0 to 0.15 mm, more preferably 0 to 0.1 mm or less, and further preferably 0. ~0.05mm or less, especially preferably 0~0.05mm or less.

The measurement of warpage is:

1. First, cut a small number of small plates (a rectangular plate of about 400 mm square) from the glass plate.

2. Next, for each of the small plates, the warping of the four portions of the corner and the four portions of the central portion were measured on the front and back surfaces (that is, the warpage of the total of 16 portions was measured). For example, in the case of measuring the warpage of eight small plates, measurement data of warpage of 16 parts × 8 pieces, that is, 128 parts is obtained.

3. Confirm whether the maximum value in the measurement data obtained in the above 2 is within the above range. Further, in the present embodiment, the maximum value of the warpage measured by a plurality of small plates is used as the warpage of the glass plate.

[Experiment 1]

In order to confirm the effect of the present embodiment, a glass plate is produced by variously changing the method for producing a glass plate, and further heat treatment is performed under the same conditions as in the case of producing a liquid crystal display, and the heat shrinkage rate and the plane strain are measured by the above method. The unevenness of the heat shrinkage rate of each person is obtained.

1. Embodiment 1

The gas pressure difference between the temperature of the glass ribbon G in the inner space of the furnace as the temperature of the slow cooling point to the temperature of the strain point and the outer space of the furnace corresponding to the height direction of the region is 5 Pa (more specifically, 3 ~7Pa) to adjust the air pressure in the outer space of the furnace.

The glass plate manufactured is a glass substrate for liquid crystal display, and has a size of 2,200 mm × 2,500 mm and a thickness of 0.7 mm. The glass composition of the glass plate is as follows. The content rate 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

In the same manner as in the first embodiment, the pressure difference between the region in which the temperature of the glass ribbon G in the internal space of the furnace becomes the slow cooling point temperature to the strain point temperature and the outer space of the furnace corresponding to the height position of the region is 5 Pa (detailed The pressure of the external space of the furnace is adjusted in the manner of 3~7Pa).

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

The temperature of the glass ribbon G in the internal space of the furnace becomes the region of the slow cooling point temperature to the strain point temperature, and the air pressure difference from the furnace outer space corresponding to the height position of the region is 20 Pa (more specifically, 18 to 22 Pa). The production of a glass substrate for a liquid crystal display was carried out in the same manner as in Example 1.

4. Example 4

The temperature of the glass ribbon G in the internal space of the furnace becomes the region of the slow cooling point temperature to the strain point temperature, and the gas outside the furnace corresponding to the height position of the region. The production of a glass substrate for a liquid crystal display in which a polycrystalline germanium TFT was formed was carried out in the same manner as in Example 2 except that the pressure difference was 20 Pa (specifically, 18 to 22 Pa).

5. Example 5

The temperature of the glass ribbon G in the internal space of the furnace becomes the region of the slow cooling point temperature to the strain point temperature, and the air pressure difference from the furnace outer space corresponding to the height position of the region is 35 Pa (specifically, 33 to 37 Pa). The production of a glass substrate for a liquid crystal display was carried out in the same manner as in Example 1.

6. Example 6

The temperature of the glass ribbon G in the internal space of the furnace becomes the region of the slow cooling point temperature to the strain point temperature, and the air pressure difference from the furnace outer space corresponding to the height position of the region is 35 Pa (specifically, 33 to 37 Pa). Production of a glass substrate for a liquid crystal display in which a polycrystalline germanium TFT was formed was carried out in the same manner as in Example 2.

7. Example 7

The temperature of the glass ribbon G in the internal space of the furnace becomes the region of the slow cooling point temperature to the strain point temperature, and the air pressure difference from the furnace outer space corresponding to the height position of the region is 60 Pa (more specifically, 55 to 65 Pa). The production of a glass substrate for a liquid crystal display was carried out in the same manner as in Example 1.

8. Comparative example

The temperature of the glass ribbon G in the internal space of the furnace becomes the region of the slow cooling point temperature to the strain point temperature, and the air pressure difference from the furnace outer space corresponding to the height position of the region is -5 Pa (specifically, -6 to -4 Pa) (That is, the air pressure in the outer space of the furnace corresponding to the height position of the region is higher than the region where the temperature of the glass ribbon G becomes the slow cooling point temperature to the strain point temperature) In the same manner as in Example 1, the production of a glass substrate for a liquid crystal display was carried out.

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

The effect of the method of the present embodiment can be clarified based on the above table.

[Experiment 2]

Further, the glass raw material is melted to form molten glass, and after clarification and stirring, the molten glass is supplied to the molding apparatus 200, and a glass plate is produced by an overflow down-draw method. Thereafter, the glass plate was cut to produce a glass plate having a longitudinal direction of 1100 mm, a width direction of 1300 mm, and a thickness of 0.5 mm. At this time, the air pressure in the outer space of the furnace is controlled as shown in the following Table 2, so that the upstream side is higher. Further, the content ratio 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 strain (hysteresis) of the glass sheets produced in Examples 8 to 12 The maximum value) is 1.6 nm or less. Further, the warpage of the glass plate was 0.18 mm or less. In particular, the maximum strain (maximum hysteresis) of the glass sheets produced in Examples 9 to 11 was 1.0 nm or less. Further, the warpage of the glass plate is 0.15 mm or less.

In the eighth to twelfth embodiments, the furnace outer spaces S3a and S3b shown in Fig. 3 were connected to each other and the air pressure was controlled as one space. At this time, the outer space of the furnace is adjusted such that the temperature of the glass ribbon G becomes the region from the slow cooling point temperature to the strain point temperature and the air pressure difference between the furnace outer spaces S3a and S3b corresponding to the height position of the region is 10 to 20 Pa. The pressure. The air pressure in the furnace outer space S3c is adjusted so that the air pressure difference between the air pressure in the furnace outer space S3c and the corresponding position in the furnace internal space is 5 Pa (specifically, 3 to 7 Pa). Table 2 below shows the conditions and evaluation results of Examples 8 to 12.

P1: air pressure in the space above the outside of the forming furnace [Pa]

P2: Air pressure of the furnace outer space S2 [Pa]

P3: Air pressure of the external space S3a, S3b [Pa]

P4: Air pressure of space S4 [Pa]

According to Table 2, the higher the upstream side of the flow of the glass ribbon G, the higher the pressure in the outer space of the furnace, the lower the maximum strain and the warpage. Better words.

In summary, the present specification discloses the following aspects.

(Revelation 1)

A method for producing a glass sheet, comprising: using a down-draw method, comprising: a melting step of melting a glass raw material to obtain molten glass; and a forming step of supplying the molten glass to a forming furnace Forming a glass ribbon to form a strip stream of the glass ribbon; and a slow cooling step of drawing the glass ribbon by means of a roller disposed in the slow cooling furnace to be cooled in the slow cooling furnace; and cutting a step of cutting the cooled glass ribbon in a cutting space; and setting an inner space of the forming furnace provided with the molded body and an inner space of the slow cooling furnace provided with the roller as a furnace inner space When the outer space of the forming furnace and the slow cooling furnace is an outer space of the furnace, the outer space of the furnace is a space partitioned by a partition wall for an atmospheric pressure environment, and the air pressure of at least a part of the outer space of the furnace is opposite to The air pressure is adjusted in such a manner that the air pressure in the inner space of the furnace at the same position in the flow direction of the glass ribbon is lowered.

(Revelation 2)

The method for producing a glass plate according to the first aspect, wherein the air pressure is adjusted in such a manner that a gas pressure in the outer space of the furnace is at a position in the slow cooling furnace corresponding to a slow cooling point temperature of the glass ribbon, and a position corresponding to the glass In the region between the positions of the above-mentioned slow cooling furnace with the strain point temperature, The air pressure at the same position in the internal space of the furnace is lowered.

(Revelation 3)

The method for producing a glass sheet according to claim 1 or 2, wherein the air pressure of the at least a part of the outer space of the furnace is at the same position in the flow direction of the glass ribbon, the air pressure of the inner space of the furnace and the air pressure of the outer space of the furnace The difference is 40 Pa or less.

(Revelation 4)

A method of producing a glass sheet according to any one of claims 1 to 3, wherein the pressure of the outer space of the furnace is adjusted in such a manner as to increase relative to atmospheric pressure.

(Revelation 5)

The method for producing a glass sheet according to any one of the items 1 to 4, wherein the outer space of the furnace includes an upper upper space with respect to a ceiling surface of the inner space of the forming furnace, and the air does not self from the upper space. The air pressure of the upper space is adjusted in such a manner that the upper space flows into the internal space of the furnace.

(Revelation 6)

The method for producing a glass sheet according to any one of the items 1 to 5, wherein a flow direction of the glass ribbon is a vertical direction, and the forming furnace is disposed vertically above the slow cooling furnace, and the furnace outer space is vertically vertical. The direction is divided into a plurality of partial spaces, and the air pressure is adjusted in such a manner that the difference between the air pressure of each of the partial spaces and the air pressure of the inner space of the furnace at the same position in the vertical direction of the partial space is the most in the partial space. When the upper part of the space is compared with the lowermost part of the space, the above difference of the uppermost portion is higher than the above The above difference of the lowermost portion becomes large.

(Revelation 7)

A method of producing a glass sheet according to 6, wherein the difference in the gas pressure of the partial space increases toward the upper side.

(Revelation 8)

The method for producing a glass sheet according to any one of the items 1 to 7, wherein the glass sheet is a glass substrate for a liquid crystal display in which a TFT (Thin Film Transistor) is formed on the surface.

(Revelation 9)

The method for producing a glass sheet according to any one of the items 1 to 8, wherein the outer space of the furnace includes the first partial space at the same position as the shaped body in a flow direction of the glass ribbon, the first partial space The difference between the air pressure and the air pressure in the inner space of the furnace at the same position as the flow direction of the glass ribbon is greater than 0 and 40 Pa or less.

(Revelation 10)

The method for producing a glass sheet according to any one of the items 1 to 9, wherein the outer space of the furnace includes a second partial space located at the same position as the slow cooling furnace in a flow direction of the glass ribbon, and the slow cooling furnace The difference between the air pressure in the internal space of the furnace and the air pressure in the second partial space is greater than 0 and is 40 Pa or less.

(Revelation 11)

The method for producing a glass sheet according to any one of the items 1 to 10, wherein the furnace outer space includes a first portion space located at the same position as the molded body in the flow direction of the glass ribbon, and is located in the slow cooling furnace the same When the first partial space is adjacent to the second partial space by the wall, the air pressure of the first partial space of the furnace outer space is larger than the air pressure of the second partial space. The difference between the air pressure in the first partial space and the air pressure in the second partial space is less than 20 Pa.

(Revelation 12)

The method for producing a glass sheet according to any one of the items 1 to 11, wherein the furnace outer space includes a plurality of second partial spaces located at the same position as the slow cooling furnace, and the plurality of second partial spaces are in the molten glass The higher the flow direction, the higher the upstream side pressure.

(Revelation 13)

The method for producing a glass sheet according to any one of the items 1 to 12, wherein the slow cooling step is such that a tensile stress acts on a central portion in a width direction of the glass ribbon to function in a flow direction of the glass ribbon, at least Cooling in the central portion of the width direction of the glass ribbon in a temperature region from the temperature of the slow cooling point of the glass ribbon plus the temperature obtained by adding 150 ° C to the temperature of the strain point of the glass ribbon minus 200 ° C The speed is faster than the cooling speed of the both end portions, and the temperature of the glass ribbon from the central portion in the width direction of the glass ribbon is higher than the state of the both end portions, and the temperature of the central portion is lower than the state of the both end portions. .

(Revelation 14)

The method for producing a glass sheet according to any one of the items 1 to 13, wherein the slow cooling step includes a first cooling step, a second cooling step, and a third cooling step, wherein the first cooling step is performed at a first average cooling rate a step of cooling the temperature in the central portion in the width direction of the glass ribbon to the slow cooling point temperature, wherein the second cooling step cools the temperature in the central portion in the width direction of the glass ribbon from the slow cooling point temperature to the second average cooling rate In the step of the strain point temperature of -50 ° C, the third cooling step is to cool the temperature of the central portion in the width direction of the glass ribbon from the strain point temperature of -50 ° C to the strain point temperature of -200 ° C at the third average cooling rate. In the step, the first average cooling rate is 5.0 ° C / sec 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.

(Revelation 15)

A method of producing a glass sheet according to claim 14, wherein an average cooling rate of a central portion of the glass ribbon in the first cooling step is 5.5 ° C / sec to 50.0 ° C / sec.

(Revelation 16)

A method of producing a glass sheet according to claim 14, wherein the average cooling rate of the glass ribbon in the second cooling step is from 0.5 to less than 5.5 ° C / sec.

(Revelation 17)

The method for producing a glass sheet according to any one of the items 1 to 16, wherein the glass sheet is a glass substrate of a polycrystalline germanium TFT or an oxide semiconductor, The strain point temperature of the glass is 675 ° C or higher.

(Revelation 18)

A glass plate manufacturing apparatus characterized by using a down-draw method, comprising: a melting device that melts a glass raw material to obtain molten glass; and a molding device that supplies the molten glass to a forming machine provided in the forming furnace Forming a glass ribbon, forming a strip stream of the glass ribbon, pulling the glass ribbon by means of a roller disposed in the slow cooling furnace to be cooled in the slow cooling furnace; and cutting the device, cutting the cut space The glass ribbon is cooled, and the inner space of the forming furnace in which the molded body is provided and the inner space of the slow cooling furnace in which the roller is provided are used as the inner space of the furnace, and the forming furnace and the slow cooling furnace are When the external space is set as the outer space of the furnace, the outer space of the furnace is a space partitioned by the partition wall for the atmospheric pressure environment, and the forming device is provided with a gas pressure control device for adjusting the air pressure in such a manner as to make the outer space of the furnace At least a portion of the gas pressure is reduced relative to the gas pressure in the furnace interior space at the same position in the flow direction of the glass ribbon.

(Revelation 19)

A manufacturing apparatus for a glass sheet according to claim 18, wherein said air pressure control means is means for adjusting the inflow of air with the atmosphere to control the air pressure in the outer space of said furnace.

The method for manufacturing the glass sheet of the present invention and the manufacturing apparatus have been described in detail above, but the present invention is not limited to the above embodiment, and of course, it is not necessary to take off Various modifications and changes are possible within the scope of the spirit of the invention.

30‧‧‧ furnace

40‧‧‧forming furnace

50‧‧‧ Slow cooling furnace

200‧‧‧melting device

201‧‧‧melting tank

202‧‧‧Clarification tank

203‧‧‧Stirring tank

204‧‧‧1st piping

205‧‧‧2nd piping

300‧‧‧Forming device

310‧‧‧Formed body

311‧‧‧ supply port

312‧‧‧ slot

313‧‧‧ bottom end

320‧‧‧Environmental isolation components

330‧‧‧Cooling roller

340‧‧‧Cooling unit

350a~350h‧‧‧Transport roller

355, 360a, 360b, 360c‧‧‧ pressure sensors

400‧‧‧cutting device

411, 412, 413a, 413b, 413c, 414‧‧‧ bottom

415, 416, 417a, 417b, 417c, 418‧‧ ‧ pressure sensors

421, 422, 423a, 423b, 423c, 424‧‧ ‧ blower

500‧‧‧Control device

510‧‧‧ drive unit

B‧‧‧Buildings

G‧‧‧glass ribbon

G1‧‧‧ glass plate

MG‧‧‧ molten glass

S1, S2, S3a~S3c‧‧‧ furnace external space

S4‧‧‧ space (cut space)

Fig. 1 is a view showing the flow of a method for producing a glass sheet of the present embodiment.

Fig. 2 is a view schematically showing an apparatus for performing the melting step to the cutting step of the embodiment.

Fig. 3 is a side view showing the outline of a molding apparatus for a glass sheet of the embodiment.

Fig. 4 is a schematic front view showing a molding apparatus for a glass sheet of the embodiment.

Fig. 5 is a schematic view showing a control system for controlling the amount of air to be fed by the air blower used in the embodiment.

30‧‧‧ furnace

40‧‧‧forming furnace

50‧‧‧ Slow cooling furnace

300‧‧‧Forming device

310‧‧‧Formed body

312‧‧‧ slot

313‧‧‧ bottom end

320‧‧‧Environmental isolation components

330‧‧‧Cooling roller

340‧‧‧Cooling unit

350a~350h‧‧‧Transport roller

400‧‧‧cutting device

411, 412, 413a, 413b, 413c, 414‧‧‧ bottom

415, 416, 417a, 417b, 417c, 418‧‧ ‧ pressure sensors

421, 422, 423a, 423b, 423c, 424‧‧ ‧ blower

B‧‧‧Buildings

G‧‧‧glass ribbon

G1‧‧‧ glass plate

MG‧‧‧ molten glass

S1, S2, S3a~S3c‧‧‧ furnace external space

S4‧‧‧ space (cut space)

Claims (9)

A method for producing a glass sheet, comprising: using a down-draw method, comprising: a melting step of melting a glass raw material to obtain molten glass; and a forming step of supplying the molten glass to a forming furnace a molded body to form a glass ribbon to form a flow in the vertical direction of the glass ribbon; and a slow cooling step of drawing the glass ribbon by a roller disposed in the slow cooling furnace to be cooled in the slow cooling furnace; And a cutting step of cutting the cooled glass ribbon in a cutting space; wherein the forming furnace is disposed vertically above the slow cooling furnace, and is inside the forming furnace in which the molded body is provided The space and the internal space of the slow cooling furnace provided with the above-mentioned rolls are used as the inner space of the furnace, and when the outer space of the forming furnace and the slow cooling furnace is set as the outer space of the furnace, the outer space of the furnace is a partition wall for the atmospheric pressure environment. Separating the space, and the inner space of the furnace at the same position as the air pressure of at least a portion of the outer space of the furnace relative to the flow direction of the glass ribbon The air pressure is adjusted in such a manner that the air pressure is reduced, and the outer space of the furnace is divided into a plurality of partial spaces in the vertical direction, and the furnace is placed at the same position as the vertical direction of the partial space in the vertical direction of the partial space. When the difference between the air pressures in the internal space is compared between the uppermost partial space and the lowermost partial space in the partial space, the difference between the uppermost portion and the lowermost portion is lower than the lowermost portion. The air pressure is adjusted in such a manner that the difference is increased. The method for producing a glass sheet according to claim 1, wherein the air pressure is adjusted in such a manner that the air pressure in the outer space of the furnace is at a position in the slow cooling furnace corresponding to the slow cooling point temperature of the glass ribbon and corresponds to the above In the region between the positions in the slow cooling furnace of the strain point temperature of the glass ribbon, the gas pressure at the same position relative to the inner space of the furnace is lowered. The method for producing a glass sheet according to claim 1, wherein the air pressure of the at least a part of the outer space of the furnace is at the same position in the flow direction of the glass ribbon, the air pressure of the inner space of the furnace and the air pressure of the outer space of the furnace The difference is 40 Pa or less. The method for producing a glass sheet according to claim 2, wherein the air pressure of the at least a part of the outer space of the furnace is at the same position in the flow direction of the glass ribbon, the air pressure of the inner space of the furnace and the air pressure of the outer space of the furnace The difference is 40 Pa or less. The method for producing a glass sheet according to any one of claims 1 to 4, wherein the outer space of the furnace includes an upper upper space with respect to a ceiling surface of the inner space of the forming furnace, and air is not used for the upper space The air pressure of the upper space is adjusted in such a manner that the upper space flows into the inner space of the furnace. The method for producing a glass sheet according to any one of claims 1 to 4, wherein the difference in the gas pressure of the partial space increases toward the upper side. The method for producing a glass sheet according to any one of the preceding claims, wherein the difference in the gas pressure of the partial space increases toward the upper side. A manufacturing device for a glass plate, characterized in that: Further, the present invention includes: a melting device that melts a glass raw material to obtain molten glass; and a molding device that supplies the molten glass to a molded body provided in the forming furnace to form a glass ribbon, and forms a vertical direction of the glass ribbon Carrying a stream, and pulling the glass ribbon by means of a roller disposed in the slow cooling furnace to be cooled in the slow cooling furnace; and cutting means for cutting the cooled glass ribbon in the cutting space; wherein the forming The furnace is disposed vertically above the slow cooling furnace, and the internal space of the forming furnace in which the molded body is provided and the internal space of the slow cooling furnace in which the roller is provided are used as a furnace internal space, and the forming furnace is When the external space of the slow cooling furnace is set as the outer space of the furnace, the outer space of the furnace is a space partitioned by a partition wall for an atmospheric pressure environment, and the forming device is provided with a gas pressure control device that adjusts the air pressure as follows: The air pressure of the inner space of the furnace at the same position of the air pressure of at least a part of the outer space of the furnace relative to the flow direction of the glass ribbon And the outer space of the furnace is divided into a plurality of partial spaces in the vertical direction, and the difference between the air pressure of the inner space of the furnace at the same position of the air pressure of the partial space and the vertical direction of the partial space is When the uppermost partial space in the partial space is compared with the lowermost partial space, the air pressure is adjusted such that the difference between the uppermost portion and the lowermost portion becomes larger than the difference between the lowermost portions. The manufacturing apparatus of the glass plate of claim 8, wherein the above air pressure control device A means for adjusting the flow of air between the outer space and the outer space to control the air pressure in the outer space of the furnace.