JP5288386B2 - Glass plate manufacturing method and glass plate manufacturing apparatus - Google Patents

Abstract

When producing a glass sheet, a glass raw material is melted to create molten glass, the molten glass is molded using the downdraw method, a glass ribbon is formed, and the glass ribbon is drawn downwards and annealed while being sandwiched between a plurality of roller pairs disposed along the conveyance direction for the glass ribbon. During molding, both ends of the glass ribbon are cooled while the glass ribbon continues to be sandwiched between the roller pairs and drawn downwards. Each roller in a first roller pair, which is one of the roller pairs used either in molding or annealing, is rotatably driven on the basis of a roller rotation speed determined so as to compensate for roller diameter change.

Description

  The present invention relates to a glass plate manufacturing method and a glass plate manufacturing apparatus.

  In the glass plate manufacturing method using the downdraw method, the glass ribbon is drawn downward while being held between the pair of conveying rollers, and thus is stretched to a desired thickness, and further, no distortion occurs inside. In addition, cooling is performed so that the glass ribbon does not warp. Thereafter, the glass ribbon is cut into a predetermined size and stacked on each other with a slip sheet interposed therebetween, or further conveyed and processed in the next process (for example, shape processing, chemical strengthening treatment by ion exchange). .

  As a conventional glass plate manufacturing method using the down draw method, the rotational drive is controlled so that the same load is applied to each of the transport rollers of the transport roller pair, and slip caused by the difference in outer diameter between the transport rollers It is known that one of the conveying rollers is prevented from idling by preventing this (Patent Document 1). According to this, the glass surface and the conveyance roller can be prevented from being damaged.

  By the way, in a slow cooling furnace in which the ambient temperature and the temperature of the glass ribbon change in the glass ribbon transport direction, the relative speed between the peripheral speed of the transport roller provided at each position in the glass ribbon transport direction and the transport speed of the glass ribbon. Is preferably 0, but the coefficient of thermal expansion of the glass and the coefficient of thermal expansion of the conveying roller are different, and the temperature dependency thereof is also different. There is a difference in speed. Such a difference in relative speed is also caused by a change in the atmospheric temperature in the slow cooling furnace or the temperature of the glass ribbon due to, for example, a change in the conveyance speed or thickness of the glass ribbon, or a change in the airflow generated in the slow cooling furnace.

  Therefore, as in Patent Document 1, even if control is performed so that the loads on the conveyance rollers of the conveyance roller pair are equal, the actual conveyance speed of the glass ribbon generated between the plurality of conveyance roller pairs. The difference in the relative speed between the transport speed and the peripheral speed of the transport roller cannot be eliminated, and the occurrence of scratches on the glass surface due to slip cannot be prevented.

  In addition, if the relative speed is not constant between the required transport speed, which is the target speed of transport of the glass ribbon, and the peripheral speed of the transport roller, among the plurality of transport roller pairs, that is, if a difference in relative speed occurs, the glass ribbon If the actual transport speed is slower than the required transport speed, the glass ribbon will be deformed too much above the pair of transport rollers. Conversely, if the actual transport speed is faster than the required transport speed, the glass ribbon will be pulled downward. There is a risk of cracking due to fine scratches generated on the surface.

  Moreover, the glass plate manufacturing apparatus changes over time by continuously forming and slowly cooling the glass ribbon for a long period of time. For this reason, even if the manufacturing conditions in molding and slow cooling are initially set so that a high-quality (small internal strain and warpage) glass plate can be manufactured, it is not always possible to maintain a high-quality glass plate by continuous operation over a long period of time. In particular, the diameter of the conveying roller in contact with the glass ribbon changes and greatly affects the quality of the glass plate.

Special table 2008-501605

  Therefore, in order to solve the above problems, the present invention has as a first object to maintain the production of a high-quality glass plate even if the production equipment changes over time by continuous production of the glass plate for a long period of time. Provided is a method for producing a glass plate. The second purpose is to maintain the peripheral speed distribution of the transport roller changed by the change in the diameter of the transport roller in the set peripheral speed distribution, and between the transport roller pair, the peripheral speed of the transport roller and the transport speed of the glass ribbon. It is possible to prevent a difference in the relative speed of the glass plate, and thereby to provide a glass plate manufacturing method and a glass plate manufacturing apparatus capable of manufacturing a glass plate excellent in surface quality.

Another aspect of the present invention is a method for manufacturing a glass substrate.
The manufacturing method is
Melting process for melting glass raw material to make molten glass;
Molding a molten glass using a downdraw method to form a glass ribbon;
A slow cooling step in which the glass ribbon is slowly cooled by being pulled downward while being sandwiched by a plurality of roller pairs provided along the conveying direction of the glass ribbon.
The slow cooling step includes
Each roller of the first roller pair, which is at least one of the roller pairs, is rotationally driven based on the rotational speed of the roller determined so as to compensate for a change in the diameter of the roller ,
Each roller of the first roller pair is provided in a temperature region in which the temperature of at least the center of the glass ribbon in the slow cooling step is a glass transition point or more and a softening point or less,
In the slow cooling step, the rotational speed of each roller of the first roller pair is determined so as to compensate for a change in the diameter of each roller of the first roller pair, and each roller of the first roller pair is driven to rotate. .

At that time, the slow cooling step,
A detection step of detecting a change in the diameter of each roller of the first roller pair by a detection unit provided along the conveyance direction of the glass ribbon;
And a speed control step of determining a rotational speed of each roller based on the detected diameter change of each roller of the first roller pair and rotationally driving each roller of the first roller pair. preferable.

In the molding step and the slow cooling step, it is preferable to control the temperature of the glass ribbon as follows.
In the region where the temperature of the central portion of the glass ribbon is equal to or higher than the glass softening point, the end portion in the width direction of the glass ribbon is lower than the temperature of the central region sandwiched between the end portions, and the temperature of the central region is approximately Control to be uniform.
Furthermore, the temperature in the width direction of the glass ribbon is such that the tensile stress in the transport direction acts on the center portion of the glass ribbon in the region where the temperature of the center portion of the glass ribbon is below the softening point and near the strain point. The ribbon is controlled so as to decrease from the center to the end.
Further, in the forming step and the slow cooling step, the glass ribbon is configured such that there is no temperature gradient between the end portion and the center portion in the width direction of the glass ribbon in the temperature region near the glass strain point of the glass ribbon. To control the temperature distribution.

In the slow cooling step,
In the region where the temperature of the central portion of the glass ribbon is less than the vicinity of the strain point, the glass ribbon is lowered from the end in the width direction toward the central portion so that tensile stress in the transport direction acts on the central portion of the glass ribbon. Thus, it is preferable to control the temperature distribution of the glass ribbon.

The slow cooling step includes
A first cooling step of cooling at a first average cooling rate until the temperature of the central portion of the glass ribbon reaches a slow cooling point;
A second cooling step of cooling at a second average cooling rate until the temperature of the central portion reaches a strain point of −50 ° C. from the annealing point;
It is preferable to include a third cooling step of cooling at a third average cooling rate until the temperature of the central portion becomes from the strain point of −50 ° C. to the strain point of −200 ° C.
In this case, the first average cooling rate is 5.0 ° C./second or more, the first average cooling rate is faster than the third average cooling rate, and the third average cooling rate is: Faster than the second average cooling rate.

The rotational speed of each roller of the first roller pair is adjusted so as to compensate for the deviation of the peripheral speed caused by the change in the diameter of each roller of the first roller pair due to the thermal expansion of each roller of the first roller pair. It is preferable to determine and rotate each roller of the first roller pair.

  In addition, the rotational speed of each roller of the first roller pair is compensated for the deviation of the peripheral speed caused by the diameter change of each roller of the first roller pair due to the wear of each roller of the first roller pair. It is also preferable that each of the first roller pair is rotationally driven.

Among the plurality of roller pairs, a roller pair having a roller driven to rotate based on a rotation speed of the roller determined so as to compensate for a change in the diameter of the roller is a second roller pair in addition to the first roller pair. Can be included.
In this case, the manufacturing method includes a detection step of detecting a change in the diameter of each of the first roller pair and the second roller pair by a plurality of detection units provided along the conveyance direction of the glass ribbon. . The diameter of each roller is set so that the relative speed between the peripheral speed of the roller and the conveying speed of the glass ribbon is constant between each roller of the first roller pair and each roller of the second roller pair. The rotational speed of each roller that compensates for the change is determined.

In the manufacturing method, the temperature of the glass ribbon is detected by a glass state detection unit that detects the state of the glass ribbon provided along the conveyance direction of the glass ribbon,
Using the glass thermal expansion coefficient at the detected temperature of the glass ribbon, a change in the transport speed of the glass ribbon due to the thermal expansion of the glass ribbon is detected, and the transport speed of the glass ribbon and the peripheral speed of the roller It is also preferable to determine the rotational speed of each roller of the first roller pair so as to compensate for the deviation.

  The thickness of the glass plate formed by gradually cooling the glass ribbon is, for example, 0.5 mm or less.

One embodiment of the present invention is a glass plate manufacturing apparatus. The device is
A molding apparatus for molding a glass ribbon from molten glass using a downdraw method;
And a slow cooling device that cools the glass ribbon while pulling it downward while sandwiching it with a plurality of pairs of transport rollers.
The slow cooling device includes the plurality of conveyance roller pairs, a detection control unit, and a drive unit.
The plurality of transport roller pairs are provided along the transport direction of the glass ribbon, and transport the glass ribbon by drawing the glass ribbon downward.
The said detection control part is provided along the conveyance direction of the said glass ribbon, and is provided with the some conveyance roller state detection part which detects the diameter change of the conveyance roller of the said conveyance roller pair.
The drive unit maintains a peripheral speed distribution between the plurality of transport roller pairs when a relative speed between the peripheral speed of the transport roller and the transport speed of the glass ribbon is constant between the plurality of transport roller pairs. Then, the transport roller is driven to rotate based on the rotation speed of each transport roller determined based on the detected diameter change of the transport roller.
Furthermore, each roller of the first roller pair, which is at least one of the transport roller pairs, has a temperature at least at the center of the glass ribbon in the slow cooling device that is not less than the glass transition point and not more than the softening point. The slow cooling device determines a rotational speed of each roller of the first roller pair so as to compensate for a change in the diameter of each roller of the first roller pair, and the first roller pair Each roller is driven to rotate.

The transport roller state detection unit detects a change in the diameter of the transport roller based on the temperature of the transport roller,
The drive unit detects the temperature of the transport roller so as to compensate for a deviation from the peripheral speed distribution of the peripheral speed of the transport roller caused by a change in the diameter of the roller due to thermal expansion of the transport roller. It is preferable that the transport roller is rotationally driven based on the rotational speed of each transport roller determined using the roller thermal expansion coefficient.

  The detection unit further includes a plurality of glass state detection units provided along a conveyance direction of the glass ribbon to detect the state of the glass ribbon, and the driving unit is set based on the state of the glass ribbon. It is preferable that the transport roller is driven to rotate based on the peripheral speed distribution.

The glass state detection unit detects the temperature of the glass ribbon,
The driving unit uses the glass thermal expansion coefficient at the detected temperature of the glass ribbon, and the peripheral speed distribution set according to the change in the conveyance speed of the glass ribbon due to the thermal expansion of the glass ribbon. It is preferable that the transport roller is rotationally driven based on the base.

The transport roller state detection unit detects a change in the diameter of the transport roller based on an amount of wear of the transport roller,
The drive unit is determined to compensate for a deviation from the peripheral speed distribution of the peripheral speed of the transport roller, which is caused by a change in the diameter of the transport roller due to the detected wear of the transport roller. It is preferable that the transport roller is rotationally driven based on the rotational speed of the transport roller.

  The thickness of the glass plate formed by gradually cooling the glass ribbon is, for example, 0.5 mm or less.

  In the method for producing a glass plate described above, the production of a high-quality glass plate can be maintained by continuous production of the glass plate for a long period of time, even if production equipment such as a conveyance roller in contact with the glass ribbon changes with time. In addition, the glass plate manufacturing method and the glass plate manufacturing apparatus described above maintain a peripheral speed distribution in which the peripheral speed of the transport roller, which has changed due to a change in the diameter of the transport roller, is maintained, and a transport roller between a plurality of transport roller pairs. It is possible to prevent a difference from occurring in the relative speed between the peripheral speed and the glass ribbon transport speed. Thereby, the glass plate excellent in surface quality can be manufactured.

It is a figure which shows an example of the flow of the manufacturing method of the glass plate of this embodiment. It is a figure which shows an example of the flow of a slow cooling process. It is a top view explaining the inside of the glass plate manufacturing apparatus of 1st Embodiment of this invention. FIG. 4 is a cross-sectional view taken along line IV in FIG. 3. It is a block diagram explaining the structure of the control system which controls the rotational drive of a conveyance roller pair. It is a block diagram explaining the structure of the control system which controls the rotational drive of the conveyance roller pair of the glass plate manufacturing apparatus of 2nd Embodiment of this invention.

Hereinafter, the manufacturing method and glass plate manufacturing apparatus of the glass plate of this invention are demonstrated in detail.
In the manufacturing method and the manufacturing apparatus of the glass plate according to this embodiment or the modified example thereof, at least of the roller pair (cooling roller pair, conveying roller pair) used in the forming step and the slow cooling step which are one step of the glass plate manufacturing method. Each roller of any one roller pair (first roller pair) is rotationally driven based on the rotational speed of the roller determined so as to compensate for the change in the diameter of the roller. Further, in the slow cooling step, each roller of at least one of the plurality of transport roller pairs (first roller pair) is based on the rotational speed of the roller determined so as to compensate for the change in the roller diameter. , Is driven to rotate. The rotational speed of such a roller is determined so as to compensate for the diameter change by detecting the diameter change of each roller of the first roller pair by measurement. That is, the rotational speed of the roller is feedback controlled according to the detection result of the roller diameter change. Alternatively, the rotational speed of the rollers is determined based on information on the number of days used for each roller of the first roller pair. That is, the rotation speed of the rollers is sequentially determined based on information on the usage period of each roller. “Information on the number of days of use” is used for conversion of the change of the roller diameter based on the wear of the first roller pair, and the rotation speed of the roller is determined based on the conversion value of the change of the roller diameter. There may be a single first roller pair or a plurality of first roller pairs for determining the rotational speed of such rollers. “Compensating for changes in roller diameter” means that even if the diameter of each roller of the first roller pair changes, the appropriate peripheral speed of the roller before the diameter change is maintained in consideration of the change in diameter. means.

Moreover, the following words and phrases in this specification are defined as follows.
The vicinity of the annealing point refers to a range of log η = 12.5 to 13.5 with respect to the viscosity η of the glass.
The annealing point of glass means a temperature at which log η = 13 with respect to the viscosity η of the glass.
The strain point of glass means a temperature at which log η = 14.5 with respect to the viscosity η of the glass.
The vicinity of the strain point of the glass refers to a temperature range where log η = 14 to 15 with respect to the viscosity η of the glass.
The central region of the glass ribbon refers to a range within 85% of the width from the center in the width direction of the glass ribbon in the width in the width direction of the glass ribbon.
The center portion of the glass ribbon refers to the center in the width direction of the glass ribbon.
That the temperature in the central region of the glass ribbon is substantially uniform means that the temperature is within an allowable range of ± 20 ° C.
The edge part of a glass ribbon means the range within 200 mm from the edge of the width direction of a glass ribbon.

(Glass plate manufacturing method)
Drawing 1 is a figure explaining an example of the flow of the manufacturing method of the glass plate of this embodiment. The glass plate manufacturing method includes a melting step (step S10), a clarification step (step S20), a stirring step (step S30), a forming step (step S40), a slow cooling step (step S50), It mainly includes a process (step S60) and a shape processing process (step S70).

In the melting step (step S10), in a melting furnace (not shown), the glass raw material is heated to a high temperature by indirect heating from above and direct heating by passing an electric current through the glass to produce molten glass. The melting of the glass may be performed by other methods.
Next, a clarification process is performed (step S20). In the clarification step, the defoaming of bubbles in the molten glass is promoted by increasing the temperature of the molten glass in a state where the molten glass is stored in a liquid tank (not shown), for example, compared with the heating in the melting step. . Thereby, the bubble content rate in the glass plate finally obtained can be reduced, and a yield can be improved.
The clarification step may be performed by other methods. For example, in the state where the molten glass is stored in the liquid tank, bubbles in the molten glass may be removed using a clarifier. The fining agent is not particularly limited, and for example, metal oxides such as tin oxide and iron oxide are used. Specifically, the clarification step in this case is performed by a redox reaction of a metal oxide whose valence fluctuates in the molten glass. In the molten glass at a high temperature, the metal oxide releases oxygen by a reduction reaction, and this oxygen becomes a gas, and bubbles in the molten glass grow and float on the liquid surface. Thereby, bubbles in the molten glass are defoamed. Or the bubble of oxygen gas takes in the gas in the other bubble in a molten glass, grows, and floats on the liquid level of a molten glass. Thereby, bubbles in the molten glass are defoamed. Further, when the temperature of the molten glass is lowered, the metal oxide absorbs oxygen remaining in the molten glass due to the oxidation reaction, and reduces bubbles in the molten glass.
Next, a stirring process is performed (step S30). In the stirring step, the molten glass is mechanically stirred by a stirring device in order to maintain the chemical and thermal uniformity of the glass. Thereby, nonuniformity of the glass such as striae can be suppressed.

  Next, a molding process is performed (step S40). In the molding process, a downdraw method is used. The down draw method including overflow down draw, slot down draw, and the like is a known method using, for example, Japanese Patent No. 3586142 or the apparatus shown in FIGS. The molding process in the downdraw method will be described later. Thereby, a sheet-like glass ribbon having a predetermined thickness and width is formed. As a molding method, an overflow downdraw is most preferable among the downdraw methods, but a slot downdraw may be used. The forming step includes a step of cooling both ends of the glass ribbon while drawing the glass ribbon formed by the forming with a pair of rollers and pulling it downward in the conveying direction (downstream direction).

Next, a slow cooling process is performed (step S50). In the slow cooling step, the glass ribbon formed into a sheet shape is cooled below the annealing point in the slow cooling furnace shown in FIGS. 3 and 4 by controlling the cooling rate so that distortion does not occur or is reduced. Specifically, a conveyance speed that is set in advance while the adjacent region adjacent to the width direction end of the glass ribbon in the width direction is sandwiched between a plurality of pairs of conveyance rollers provided in the conveyance direction of the glass ribbon. It is gradually cooled while being pulled down at.
FIG. 2 is a diagram illustrating an example of the flow of the slow cooling process. The slow cooling process includes a detection process (step S51), a speed determination process (step S52), and a speed control process (step S53). In addition, although the manufacturing method of the glass plate of this embodiment includes a detection process (step S51), a detection process is not performed like the modification mentioned later, and a slow cooling process is a speed determination process (step S52), And a speed control step (step S53).

  In the detection step (step S51), the diameter change of each conveyance roller of the plurality of conveyance roller pairs is performed by the plurality of detection units provided corresponding to the plurality of conveyance roller pairs described above along the conveyance direction of the glass ribbon. Is detected. As the diameter change of the transport roller, for example, the diameter change amount of the transport roller calculated based on the temperature of the transport roller or the wear amount of the transport roller can be mentioned. The detection unit in this case includes, for example, a temperature sensor or a distance measurement sensor described later, and a computer connected to these sensors. As the diameter, the diameter or radius of the transport roller is increased.

In the speed determination step (step S52), the relative speed between the peripheral speed of the transport roller and the transport speed of the glass ribbon is constant between the plurality of transport roller pairs, that is, when there is no difference in the relative speed. And the rotational speed of each transport roller is determined so as to maintain the set peripheral speed distribution based on the detected change in the diameter of the transport roller. As the peripheral speed distribution, for example, a peripheral speed ratio between a plurality of pairs of transport rollers and a specific peripheral speed of each transport roller are used. Here, since the relative speed when the glass ribbon is not scratched or deformed is 0, a difference in the relative speed means that the relative speed of a certain pair among the plurality of transport roller pairs is 0. This means that the relative speed of another pair has a distribution such that the relative speed is not zero.
When the change in the diameter of the conveyance roller is, for example, a thermal expansion amount (diameter change amount) of the conveyance roller calculated based on the temperature, specifically, the detection unit 37 and the speed determination unit 38 described later perform the change. As described above, the roller thermal expansion coefficient at the detected transport roller temperature is used to compensate for the deviation of the peripheral speed of the transport roller from the peripheral speed distribution caused by the change in the roller diameter caused by the thermal expansion of the transport roller. In other words, the rotational speed of the transport roller is determined so that the peripheral speed of each transport roller is maintained in the set peripheral speed distribution. The thermal expansion coefficient of the transport roller is stored in advance in the speed determination unit 38. In addition, the circumferential speed of a conveyance roller is determined by adjusting so that the formed glass ribbon may become the plate | board thickness of the glass plate to manufacture, for example.

  Further, for example, when the change in the diameter of the transport roller is the amount of change in the radius of the transport roller calculated based on the amount of wear, specifically, detection is performed as in the second embodiment described later. The peripheral speed of each transport roller was set so as to compensate for the deviation from the peripheral speed distribution of the peripheral speed of the transport roller caused by the change in the radius of the transport roller due to wear of the transport rollers. The rotation speed of the transport roller is determined so that the peripheral speed distribution is maintained.

  The speed determination unit 38 may determine the rotation speed of each transport roller based on the content input by the operator. In this case, the operator may calculate the rotation speed of each conveyance roller based on the detected change in the diameter of the conveyance roller so as to maintain the set peripheral speed distribution. For example, when the change in the diameter of the conveyance roller is the above-described amount of thermal expansion, the operator can change the diameter of the conveyance roller caused by the change in the roller diameter caused by the thermal expansion of the conveyance roller based on the detected temperature of the conveyance roller. The rotational speed of the transport roller may be calculated so as to compensate for the deviation of the peripheral speed from the peripheral speed distribution, that is, so that the peripheral speed of each transport roller is maintained at the set peripheral speed distribution. The calculated rotation speed of each transport roller is determined by the speed determination unit 38, and the rotation of the transport roller is controlled in the speed control step (step S53).

In the speed control process (step S53), the rotation of the transport roller is controlled based on the rotation speed determined in the speed determination process.
After the above slow cooling process, a plate-making process is performed (step S60). Specifically, the glass ribbon produced | generated continuously is cut | disconnected for every fixed length, and a glass plate is sampled.
Thereafter, a shape processing step is performed (step S70). In the shape processing step, the glass end face is ground and polished in addition to cutting into a predetermined glass plate size and shape. For the shape processing, a physical means using a cutter or a laser may be used, or a chemical means such as etching may be used.

  Further, in the forming step and the slow cooling step, in the region where the temperature of the central portion of the glass ribbon is equal to or higher than the glass softening point, in order to suppress shrinkage in the width direction of the glass ribbon, the end portion in the width direction of the glass ribbon is the end. It is preferable to control the temperature of the glass ribbon so that it is lower than the temperature of the central region sandwiched between the parts and the temperature of the central region is substantially uniform. At that time, the temperature in the width direction of the glass ribbon is the center of the glass ribbon so that the tensile stress in the transport direction acts on the center portion of the glass ribbon in the region where the temperature of the center portion of the glass ribbon is less than the softening point and near the strain point. It is preferable to control the temperature of the glass ribbon so as to decrease from the portion toward the end in terms of suppressing warpage of the glass plate. Furthermore, in the temperature region where the temperature of the glass ribbon is in the vicinity of the strain point, it is possible to control the temperature distribution of the glass ribbon so that there is no temperature gradient between the end portion in the width direction of the glass ribbon and the center portion. This is preferable in terms of suppressing internal distortion.

  Further, in the region where the temperature of the central portion of the glass ribbon is less than the vicinity of the strain point, the glass ribbon is lowered from the end in the width direction toward the central portion so that tensile stress in the transport direction acts on the central portion of the glass ribbon. In addition, it is preferable to control the temperature distribution of the glass ribbon in terms of suppressing warpage in the conveyance direction of the glass ribbon.

  Further, the slow cooling step includes a first cooling step of cooling at the first average cooling rate until the temperature of the central portion of the glass ribbon reaches a slow cooling point, and the temperature of the central portion of the glass ribbon is gradually cooled. From the point until the strain point reaches −50 ° C., the second cooling step of cooling at the second average cooling rate, and the temperature of the central portion of the glass ribbon reaches from the strain point −50 ° C. to the strain point −200 ° C. And a third cooling step of cooling at a third average cooling rate. In this case, the first average cooling rate is 5.0 ° C./second or more, the first average cooling rate is faster than the third average cooling rate, and the third average cooling rate is the second average cooling rate. Faster than the cooling rate. That is, the average cooling rate is, in descending order, the first average cooling rate, the third average cooling rate, and the second average cooling rate. The cooling rate in the conveyance direction of the glass ribbon affects the heat shrinkage of the glass plate to be manufactured. However, by setting the cooling rate in the slow cooling step as described above, it is possible to obtain a glass plate having a suitable heat shrinkage rate while improving the production amount of the glass plate.

  In addition to this, the method for producing a glass plate includes a cleaning step and an inspection step, but description of these steps is omitted. The clarification step and the stirring step can be omitted.

(Glass plate manufacturing equipment)
FIG.3 and FIG.4 is a schematic block diagram of the glass plate manufacturing apparatus 1 which is 1st Embodiment of this invention. The glass plate manufacturing apparatus 1 and the glass plate manufacturing method using the glass plate manufacturing apparatus 1 according to this embodiment include a glass substrate of a flat panel display such as a liquid crystal display device or an organic EL display device, and a display surface cover of a portable terminal. It is suitably applied to the production of glass. This is because liquid crystal display devices, organic EL display devices, and the like have recently been required to have high precision and high image quality, and a glass substrate used therefor is required to have high surface quality. Moreover, since the cover glass is applied to the display surface of the apparatus, the glass substrate used for the cover glass is required to have extremely high surface quality.
The glass plate manufacturing apparatus 1 manufactures the glass plate C from the molten glass A using the downdraw method. The glass plate manufacturing apparatus 1 includes a furnace chamber 11, a first slow cooling furnace 12, a second slow cooling furnace 13, and a sampling chamber (not shown) that are partitioned by heat insulating plates 21, 22, and 23 arranged in three locations in the vertical direction. Have. The heat insulating plates 21 to 23 are plate members made of a heat insulating material such as a ceramic fiber. The heat insulating plates 21 to 23 are respectively formed with transport holes 16 so that a glass ribbon B described later passes downward. In FIG. 3, the heat insulating plates 21 to 23 are not shown except for two places in the horizontal direction in contact with the furnace wall 15, which will be described later, for ease of understanding. On the back side, the two horizontal portions are connected together. 3 and 4 show an example in which partitioning is performed at three locations by a heat insulating plate, but the number and installation positions of the heat insulating plates are not particularly limited, and one or more heat insulating plates may be provided. That's fine. In addition, since the space which can control atmospheric temperature independently increases, so that there are many heat insulation plates, and adjustment of atmospheric temperature (adjustment of slow cooling conditions) becomes easy, the slow cooling apparatus 3 has two or more heat insulation plates. It is preferably provided and partitioned into a plurality of spaces. In other words, it is sufficient that one or more annealing furnaces are provided, but three or more are more preferably provided.

The glass plate manufacturing apparatus 1 includes a forming device 2, a slow cooling device 3, and a plate-taking device 4.
The forming apparatus 2 is an apparatus for forming the glass ribbon B from the molten glass A using a downdraw method. The forming apparatus 2 has a furnace chamber 11 surrounded by a furnace wall 15 assembled with refractory bricks, block-shaped electroformed column refractories, or the like. In the furnace chamber 11, a molded body 10 and a roller pair (cooling roller pair) 17 are provided. The molded body 10 includes a groove 10a opened upward (see FIG. 4), and the molten glass A flows in the groove 10a. The molded body 10 is made of brick, for example. One pair of rollers 17 is provided at positions corresponding to both ends in the width direction of the molten glass A fused at the lower end of the molded body 10, and the glass ribbon is held while holding the molten glass A and pulling it downward. A pair of cooling rollers for cooling both ends of B. In addition, the left-right direction in the paper surface in FIG. 3 and the direction perpendicular to the paper surface in FIG. 3 and 4 is the transport direction of the glass ribbon B. 3 and 4, the molded body 10 and the roller pair 17 are installed without partitioning, but in order to facilitate adjustment of the slow cooling conditions, a partition plate is provided by providing a heat insulating plate therebetween. May be. Two or more pairs of rollers 17 may be installed.

At this time, during the molding process, when the temperature of the glass ribbon B is in a temperature range from a temperature higher than the softening point to the vicinity of the annealing point, the viscosity at both ends while applying tension toward both ends of the glass ribbon. Regarding η, cooling is preferably performed so that log η = 9.0 to 14.5. This cooling is performed, for example, by the roller pair 17 sandwiching both ends of the glass ribbon B.
By cooling both ends of the glass ribbon 17 by each roller of the roller pair 17 that is a cooling roller, the viscosity of both ends increases, so that the shrinkage of the width of the glass ribbon B can be suppressed.

(Slow cooling device)
The slow cooling device 3 cools the glass ribbon B while pulling it downward while holding the glass ribbon B between the plurality of conveying roller pairs 18 and 19. The slow cooling device 3 has a first slow cooling furnace 12 and a second slow cooling furnace 13 provided adjacent to the lower part of the furnace chamber 11. The first slow cooling furnace 12 and the second slow cooling furnace 13 are surrounded by the furnace wall 15 that also constitutes the furnace chamber 11. The slow cooling device 3 is provided with heating means that are arranged in the first slow cooling furnace 12 and the second slow cooling furnace 13 along the conveying direction of the glass ribbon B and are automatically controlled by a computer to be described later. The heating means is not particularly limited, and for example, an electric heater is used. In the first slow cooling furnace 12, three conveyance roller pairs 18 arranged in the conveyance direction of the glass ribbon B are provided. In the second slow cooling furnace 13, four transport roller pairs 19 arranged in the transport direction of the glass ribbon B are provided. Furthermore, the slow cooling device 3 includes a detection control unit 30 and a drive unit 32 (see FIG. 5). In addition, there is no restriction | limiting in the installation number of the conveyance roller pairs 18 and 19 in the slow cooling furnaces 12 and 13, and at least 1 or more should just be provided.

  The conveyance roller pairs 18 and 19 convey the glass ribbon B by drawing the glass ribbon B downward. Each conveyance roller pair 18 is on the same side with respect to the glass ribbon B as the four conveyance rollers 18a arranged on both sides of the glass ribbon B so as to sandwich a neighboring region adjacent to both ends in the width direction of the glass ribbon B. It has two drive shafts 18b arranged on both sides of the glass ribbon B for connecting the two transport rollers 18a. Each conveyance roller pair 19 is on the same side with respect to the glass ribbon B as the four conveyance rollers 19a disposed on both sides of the glass ribbon B so as to sandwich a neighboring region adjacent to both ends in the width direction of the glass ribbon B. It has two drive shafts 19b arranged on both sides of the glass ribbon B for connecting the two transport rollers 19a. In FIG. 3, both ends of the drive shafts 18b and 19b are not shown. In FIG. 3, the transport rollers 18a and 19a are not limited to those described above. For example, the conveying rollers 18a and 19a on the same surface side with respect to the glass ribbon B are not connected to each other by the driving shaft, and at the both ends in the width direction of the glass ribbon B, like the rollers of the roller pair 17. It may be arranged independently.

In the slow cooling device 3 that performs the slow cooling process, the glass ribbon B has a temperature profile of the glass ribbon B with a single distribution in the width direction, and then gradually decreases as the distribution of the single peak progresses downstream in the conveyance direction. It is preferable to control a heater or the like disposed around the. At that time, in a temperature region in the vicinity of the strain point of the glass ribbon B, a heater or the like (not shown) can be controlled so that the distribution of peaks is a straight linear distribution, that is, the temperature distribution in the width direction is constant. preferable. In other words, in the temperature range from the temperature obtained by adding 150 ° C. to the annealing point of the glass ribbon B to the strain point, the cooling rate at the center in the width direction of the glass ribbon is faster than the cooling rate at both ends in the width direction. It is preferable that the temperature profile be constant so that the temperature of the central portion in the width direction of the glass ribbon B is the same in the temperature region near the strain point from a state where the temperature is higher than both ends. By setting it as such temperature distribution, tensile stress acts toward the downstream side of the conveyance direction of a glass ribbon. For this reason, the glass ribbon B can suppress the curvature of a conveyance direction. In addition, since the temperature profile is uniform in the temperature region near the strain point, the internal strain can be reduced in the glass plate.
Furthermore, it is preferable to slowly cool the glass ribbon B at a temperature at which the temperature of the glass ribbon B becomes from the annealing point (strain point −50 ° C.) as compared with other temperature ranges. Thereby, the thermal contraction rate of the glass ribbon B can be reduced.
Furthermore, in the temperature region where the temperature of the glass ribbon B becomes a temperature obtained by subtracting 200 ° C. from the strain point, the temperature profile of the glass ribbon B becomes a valley along the width direction, and the depth of the valley is conveyed. It is preferable to control a heater or the like (not shown) so as to increase as it goes downstream in the direction, that is, so that the temperature at the center portion becomes gradually lower than both end portions. Thus, by gradually deepening the valleys in the temperature profile, a tensile stress can be applied toward the downstream side in the transport direction, so that warpage in the transport direction can be suppressed.

As shown in FIG. 5, the detection control unit 30 includes a computer (not shown) that functions as a conveyance roller state detection unit (hereinafter also simply referred to as a detection unit) 37 and a speed determination unit 38. FIG. 5 is a block diagram illustrating the configuration of a control system that controls the rotational drive of the transport roller pairs 18 and 19. The detection unit 37 includes a temperature sensor (glass state detection unit) 34 disposed in correspondence with the pair of conveyance rollers 18 and 19. The speed determining unit 38 is connected to the conveying roller pair 18 and 19 via the driving unit 32. Details of the detection control unit 30 will be described later.
The driving unit 32 rotationally drives the transport rollers 18a and 19a based on the rotational speeds of the transport rollers 18a and 19a determined by the speed determination unit 38. The drive unit 32 has a motor (not shown) provided corresponding to each of the conveyance roller pairs 18 and 19. In addition, the motor may not be provided corresponding to each conveyance roller pair 18, 19, and the number thereof may be smaller than the number of each conveyance roller pair 18, 19, for example. In this case, it is possible to use one having a gear that can change the speed ratio between the transport rollers 18a and 19a so that the plurality of transport rollers 18a and 19a are driven by a single motor. In this case, the driving force from the motor is transmitted to the transport rollers 18a and 19a via, for example, a universal joint.

(Detection control unit)
Here, the detection control unit 30 will be described in more detail. In addition, although the detection process (step S51) performed by the detection control unit 30 is performed in the present embodiment as described above, the detection process is not performed as in the modified example described later, and the slow cooling process is a speed determination process. And a speed control step. In this case, the detection control unit 30 is not used.
The temperature sensor 34 detects the temperature of the transport rollers 18a and 19a. As the temperature sensor 34, for example, a contact type or a non-contact type is used. Here, detecting the temperatures of the transport rollers 18a and 19a includes calculating the temperatures of the transport rollers 18a and 19a. Each temperature sensor 34 specifically detects the ambient temperature at the arrangement position in the first slow cooling furnace 12 and the second slow cooling furnace 13. And the temperature of conveyance roller 18a, 19a is calculated with reference to the temperature difference data memorize | stored in the memory | storage part 36 mentioned later of the speed determination part 38 in the detected atmospheric temperature. Based on the detected temperatures of the transport rollers 18a and 19a, the detection unit 37 calculates the amount of thermal expansion of the transport rollers 18a and 19a as a change in diameter, as will be described later.

  The speed determination unit 38 has a storage unit 36. The storage unit 36 stores temperature difference data. The temperature difference data includes data on the difference between the atmospheric temperature of the slow cooling furnaces 12 and 13 and the temperature (surface temperature) of the transport rollers 18a and 19a at each atmospheric temperature, which is measured in advance when the slow cooling furnaces 12 and 13 are installed. The temperature difference data is stored differently depending on the structure of the slow cooling furnaces 12 and 13. The storage unit 36 further stores thermal expansion coefficients (hereinafter also referred to as roller thermal expansion coefficients) of the transport rollers 18a and 19a. The roller thermal expansion coefficient is determined from the material of the transport rollers 18a and 19a.

  The storage unit 36 also includes a rotational speed of each of the transport rollers 18a and 19a determined by the speed determination unit 38, a reference peripheral speed distribution set between the plurality of transport roller pairs 18 and 19, and each transport roller 18a. , 19a are further stored. The reference value of the diameter of each of the transport rollers 18a and 19a is a diameter at the time of a new article at normal temperature (for example, 25 degrees). The storage unit 36 also has conditions for achieving a reference peripheral velocity distribution (conveying roller temperature, glass ribbon temperature, glass ribbon thermal expansion coefficient, glass ribbon thickness, width, glass ribbon flow rate, etc. ) Is memorized.

  The speed determination unit 38 is provided between the plurality of conveyance roller pairs 18 and 19 when the relative speed between the circumferential speed of the conveyance rollers 18a and 19a and the conveyance speed of the glass ribbon B is constant between the plurality of conveyance roller pairs 18 and 19. Set the peripheral speed ratio (peripheral speed distribution). Next, the speed determination unit 38 is configured to maintain the peripheral speed ratio between the plurality of conveyance roller pairs 18 and 19 based on the change in the diameter of the conveyance rollers 18a and 19a calculated by the detection unit 37. The rotational speed of 19a is determined.

((Setting of peripheral speed ratio))
The peripheral speed ratio between the plurality of transport roller pairs 18 and 19 is set to 1.0, for example, so that all the transport rollers 18a and 19a have the same peripheral speed. The peripheral speed ratio set as a reference in this way is the peripheral speed ratio when the conventional glass ribbon B is gradually cooled without causing problems of scratches or shape deformation. The reference peripheral speed distribution is stored and held in the speed determination unit 38 together with conditions such as the temperature, thermal expansion coefficient, thickness, width, and glass flow rate of the glass ribbon B. As will be described later, this peripheral speed ratio is set by correcting the reference peripheral speed distribution when conditions of slow cooling such as the temperature of the glass ribbon B change.

  The relative speed between the conveyance speed of the glass ribbon B and the peripheral speed of the conveyance rollers 18a and 19a between the plurality of conveyance roller pairs 18 and 19 is more sure to slip between the glass ribbon B and the conveyance rollers 18a and 19a. From the viewpoint of preventing this, it is preferably 0.

Further, the speed determination unit 38 corrects and sets the reference peripheral speed ratio according to the temperature, the thermal expansion coefficient, the thickness, the glass flow rate, and the like of the glass ribbon B.
Specifically, a reference temperature in each pair of conveying rollers is set as a condition at that time in the peripheral speed ratio set as the reference peripheral speed distribution. Therefore, when the current temperature of the glass ribbon B changes with respect to this reference temperature, for example, when the temperature T ₁ changes to T ₂ , the difference in thermal expansion coefficient between the temperature difference between T ₂ and T ₁ is calculated. The speed determining unit 38 corrects the peripheral speed ratio set as the reference peripheral speed distribution. This is because the conveyance speed of the glass ribbon B changes depending on the coefficient of thermal expansion determined by the temperature of the glass ribbon B and the coefficient of thermal expansion. In this case, since the thermal expansion coefficient differs depending on the type of the glass ribbon B, the peripheral speed ratio may be more generally corrected using the difference in the thermal expansion coefficient in consideration of the thermal expansion coefficient and the temperature of the glass ribbon B. Such a peripheral speed ratio is corrected and set by changes in conditions such as the thickness, width, and glass flow rate of the glass ribbon B in addition to the temperature dependency of the glass ribbon B and the thermal expansion coefficient. Therefore, the conditions of the reference peripheral speed ratio such as the temperature of the glass ribbon B, the temperature-dependent characteristics of the thermal expansion coefficient, the thickness, the width, and the glass flow rate are stored and held in advance in the speed determination unit 38. The glass thermal expansion coefficient is determined from the composition of the molten glass. From the set peripheral speed ratio, the peripheral speeds of the respective transport roller pairs on the downstream side are calculated on the basis of the current peripheral speed of the transport roller pair on the most upstream side.
Thus, by correcting the peripheral speed ratio in accordance with the change in the state including the temperature of the glass ribbon B, it is possible to determine more appropriate rotation speeds of the transport rollers 18a and 19a.

((Determination of the rotation speed of the transport roller))
The speed determination unit 38 determines the rotation speed of each of the transport rollers 18a and 19a according to the following formula based on the calculated peripheral speed of each of the transport rollers 18a and 19a.
Rotational speed = peripheral speed / (diameter of thermally expanded conveying roller × π)

Here, when the ambient temperature detected at the arrangement position of each conveyance roller pair 18 and 19 in the slow cooling furnaces 12 and 13 has changed with respect to the temperature of the conveyance roller pair at the reference peripheral speed ratio described above. The rotational speeds of the transport rollers 18a and 19a are determined so as to maintain the above-described peripheral speed ratio.
Specifically, the detection unit 37 has the roller thermal expansion coefficient at the temperature of the conveyance rollers 18a and 19a and the conveyance roller 18a and 19a with respect to the conveyance rollers 18a and 19a whose temperature detected by the temperature sensor 34 has changed. With reference to the reference value of the diameter, the amount of expansion (the amount of change in diameter) of the transport roller 18a is calculated according to the following formula.
dD = β · D · ΔT
dD: Expansion amount β: Thermal expansion coefficient D: Reference value of the diameter of the transport roller ΔT: Temperature difference from the temperature of the transport roller set at the reference peripheral speed ratio

The speed determination unit 38 calculates a new rotation speed from the amount of change in the diameter of the conveyance roller 18a calculated by the detection unit 37 according to the following formula, assuming that the amount of change in the peripheral speed is 1, and the conveyance rollers 18a and 19a. Change the rotation speed.
New rotation speed = (peripheral speed + change amount of peripheral speed) / ((change diameter of transport roller + change amount of transport roller diameter) × π)

The rotation speed determined by the speed determination unit 38 is sent to the drive unit 32, and the rotation of the transport rollers 18a and 19a is controlled.
Further, the computer (not shown) uses heating means in the slow cooling furnaces 12 and 13 so that the atmospheric temperature in the slow cooling furnaces 12 and 13 is maintained within a predetermined temperature range based on the ambient temperature detected by the temperature sensor 34. Automatic control. The predetermined temperature range of the first slow cooling furnace 12 is set to, for example, 500 to 800 degrees. The predetermined temperature range of the second slow cooling furnace 13 is set to 200 to 500 degrees, for example. Thus, even if the atmospheric temperature in the slow cooling furnaces 12 and 13 is controlled, the temperature of the glass ribbon B and the temperatures of the transport rollers 18a and 19a change as described above. However, since this change is relatively small, even if the above-described reference peripheral speed ratio is corrected in accordance with the temperature, the correction amount is small, and the distribution of the set reference peripheral speed ratio is not greatly changed.

  The speed determination unit 38 may determine the rotation speeds of the transport rollers 18a and 19a based on the content input by the operator. In this case, the glass plate manufacturing apparatus 1 further includes an input unit (not shown) that receives an operator's input operation, and this input unit receives the rotation speeds of the transport rollers 18a and 19a input by the operator. The storage unit 36 does not store temperature difference data, roller thermal expansion coefficient, peripheral speed distribution, reference values of the diameters of the transport rollers 18a and 19a, conditions for achieving the reference peripheral speed distribution, and the like. It is often calculated and input by an operator based on temperature difference data, roller thermal expansion coefficient, peripheral speed distribution, reference value of the diameter of each of the transport rollers 18a and 19a, conditions for achieving the reference peripheral speed distribution, etc. What is necessary is just to memorize | store the performed rotation speed. The temperature difference data, the roller thermal expansion coefficient, the peripheral speed distribution, the reference value of the diameter of each of the transport rollers 18a and 19a, and the reference peripheral speed distribution may be calculated by an operator, and the calculated values are stored in the storage unit 36. May be remembered.

The plate-taking device 4 has a plate-making chamber (not shown) arranged on the downstream side of the second slow cooling furnace 13. In the plate-making chamber, the glass ribbon B is cut at regular intervals, and the glass plate C is sampled. The thickness of the glass plate C is, for example, 0.7 mm or less, or 0.5 mm or less. In recent years, since flat panel displays have been required to be slim, flat display glass substrates such as liquid crystal displays and organic EL displays are also required to be thin. On the other hand, since the strength of the glass plate decreases as the thickness of the glass plate decreases, breakage easily occurs. Considering these things, it is preferable that the thickness of the glass plate for flat displays is 0.01-1.0 mm, It is more preferable that it is 0.05-0.7 mm, 0.05-0. More preferably, it is 5 mm. In addition, since intensity | strength falls as a thin glass plate, there exists a possibility that it may become easy to break by the damage | wound by the slip between the roller and glass ribbon which convey a glass ribbon. That is, as described above, the present embodiment that can suppress the slip between the roller and the glass ribbon is suitable for manufacturing a glass plate of 0.05 to 0.7 mm, for example. It is particularly suitable for the production of 5 mm thin glass.
Further, for example, the length in the width direction of the glass plate C may be 1000 mm or more, 1500 mm or more, 2000 mm or more, 2500 mm or more, and the length in the longitudinal direction may be 1000 mm or more, 1500 mm or more, 2000 mm or more, 2500 mm or more. Good. As the glass plate C increases in size, a relative speed difference (slip) tends to occur between the transport rollers 18a and 19a due to the weight of the glass ribbon. Therefore, when the length in the width direction of the glass plate C is 1000 mm or more, the relative speed difference tends to be easily generated, but the effect of preventing the relative speed difference from occurring is remarkable. In addition, the effect of this invention becomes so useful that the length of the width direction of the glass plate C is 1500 mm or more, 2000 mm or more, 2500 mm or more.

(Composition of glass plate)
As a glass plate manufactured with the glass plate manufacturing method and glass plate manufacturing apparatus mentioned above, the glass substrate for liquid crystal displays is mentioned suitably, for example.
The following glass composition is illustrated as a glass composition of the glass substrate for liquid crystal displays.
SiO ₂ 50~70% by weight,
B ₂ O ₃ 0-15% by mass,
Al ₂ O ₃ 5-25% by mass,
MgO 0-10% by mass,
CaO 0-20% by mass,
SrO 0-20% by mass,
BaO 0-10% by mass,
RO 5-20% by mass (provided that R is all components contained in the glass plate selected from Mg, Ca, Sr and Ba, and is at least one),
It is preferable to contain.
Furthermore, from the viewpoint of suppressing the destruction of TFT (Thin Film Transistor) formed on the glass substrate for liquid crystal display, non-alkali glass (glass containing substantially no alkali component) is preferable. On the other hand, in order to improve the meltability and clarity of the molten glass, a small amount of an alkali component may be included. in this case,
Regarding R ′ ₂ O, it exceeds 0.05% by mass and is 2.0% by mass or less, more preferably, R ′ ₂ O exceeds 0.1% by mass and is 2.0% by mass or less (provided that R ′ is Li, Na And all components contained in the glass plate selected from K and K, which are at least one kind).

According to the glass plate manufacturing apparatus 1 configured as described above, the rotational speed of each of the transport rollers 18a and 19a is controlled so as to compensate for the change in diameter that occurs in the transport rollers 18a and 19a. It is possible to suppress a difference in the relative speed between the peripheral speed of each of the transport rollers 18a and 19a and the transport speed of the glass ribbon B in the plurality of transport roller pairs 18 and 19 with higher accuracy. Thereby, the slip between the glass ribbon B and the conveyance rollers 18a and 19a can be prevented, and the quality of the glass plate surface can be improved.
In addition, the peripheral speed distribution of a plurality of pairs of transport rollers used for transporting the glass ribbon is corrected and set according to the temperature of the glass ribbon, so that the glass ribbon is not excessively prevented from being deformed. Moreover, it can prevent that a glass ribbon is pulled and a glass ribbon breaks because it becomes quicker than necessary. Such an effect is obtained when the glass conveying speed is high (for example, when the conveying speed is 200 m / or more), or when the strength of the glass ribbon is small and easily deformed, the thickness is 0.5 mm or less, preferably 0.05 to This is more remarkable in the production of 0.5 mm thin glass.

Note that the number of the plurality of conveying roller pairs is not particularly limited as long as it is at least two.
In the above-described example, the temperature sensor detects the atmospheric temperature in the slow cooling furnaces 12 and 13 and uses this to calculate the glass ribbon temperature and the conveyance roller temperature, but the glass ribbon temperature and the conveyance roller temperature are directly measured. May be. For this purpose, for example, a radiation thermometer for continuously measuring the temperature of the glass ribbon may be used as the glass state detecting unit, and for continuously measuring the temperature of the conveying roller as the conveying roller state detecting unit. The following thermometers may be used.
The peripheral speed ratio is not limited to that described above. Further, the speed determination unit 38 may calculate specific peripheral speeds of the transport rollers 18a and 19a as the peripheral speed distribution instead of the peripheral speed ratio. In this case, the reference peripheral speed distribution and the corrected peripheral speed are also set as specific speed values.
In this embodiment, in addition to adjusting the rotational speed so as to obtain a set peripheral speed distribution according to the change in the diameter of the transport roller, the peripheral speed distribution is changed to a reference peripheral speed distribution according to the temperature of the glass ribbon. Modify and set. However, the reference peripheral velocity distribution need not be corrected in accordance with the current temperature of the glass ribbon. However, it is preferable to correct the reference peripheral velocity distribution in accordance with the current temperature of the glass ribbon in terms of manufacturing a glass plate having excellent surface quality.

(Modification of the first embodiment)
In the first embodiment, the rotational speed of the transport rollers 18a and 19a is determined so as to compensate for the change in the diameter of the transport rollers that occurs in each roller of the transport roller pair 18 and 19, but in addition to the transport rollers 18a and 19a, The rotational speed of each roller of the roller pair 17 is determined so as to compensate for the change in diameter of each roller of the roller pair 17 used as the cooling roller pair in the molding process. Each roller of the roller pair 17 detects the state of each roller of the roller pair 17 using a detection unit such as the above-described conveyance roller state detection unit 37, and based on the detection result, each roller of the roller pair 17 is detected. The rotational speed of each roller of the roller pair 17 is determined so as to compensate for the diameter change.
In general, the peripheral speed of each roller of the roller pair 17 is set to an appropriate value so that the thickness distribution of the glass plate and the unevenness of the glass surface are minimized. Distribution and unevenness of the glass surface will be deteriorated.
That is, when the peripheral speed of the roller pair 17 changes, the amount of the glass ribbon B stretched between the lower end of the molded body 10 and the roller pair 17 and the glass performed between the roller pair 17 and the conveying roller pair 18. By changing the amount of stretching of the ribbon B, the temperature distribution in the width direction of the glass ribbon B between the lower end of the molded body 10 and the roller pair 17 and the glass ribbons of the roller pair 17 to the transport roller pairs 18 and 19 are changed. The thickness distribution in the width direction of the manufactured glass plate and the size of the irregularities on the glass surface are changed. For this reason, it is preferable that the rotational speed of each roller of the roller pair 17 is determined so as to compensate for a change in the diameter of each roller of the roller pair 17.

In this modification, the rotational speed is determined so as to compensate for the change in the diameter of each roller of the roller pair 17 used as the cooling roller pair in the molding process in addition to the rollers of the transport roller pair 18 and 19, but The rotational speed may be determined so as to compensate for a change in the diameter of each roller of at least one of the rollers of the roller pair 18, 19 and the roller pair 17.
In other words, it is not necessary to determine the rotation speed of the roller so as to compensate for the change in the diameter of the cooling roller or the conveyance roller, and it is not necessary to perform it for all rollers (cooling roller, conveyance roller), You may go.

For example, the rotational speed of the transport roller is determined so as to compensate for the change in the diameter of the transport roller provided in the region where the central portion of the glass ribbon B is equal to or lower than the softening point (temperature at which the viscosity η is log η = 7.65), By rotating the transport roller, slip of the glass ribbon B and the like can be suppressed, and generation of scratches on the surface of the glass ribbon B can be suppressed.
If the glass is above the softening point, the glass ribbon B is not sufficiently solidified, so that slip is unlikely to occur. On the other hand, slip is likely to occur in the glass ribbon B below the softening point. For this reason, it is preferable to determine the rotational speed of the conveyance roller so as to compensate for the change in the diameter of the conveyance roller provided in the region where the central portion of the glass ribbon B is below the softening point.

Further, in the above-described slow cooling step, at least the rotation speed of the transport roller so as to compensate for a change in the diameter of the transport roller provided in a temperature region where the temperature of the glass ribbon B is at least the glass transition point and below the softening point. The effect of suppressing the plastic deformation of the glass ribbon B is increased. Therefore, it is preferable to determine the rotation speed of the conveying roller so as to compensate for a change in the diameter of the conveying roller provided in a temperature region in which at least the temperature of the central portion of the glass ribbon B is not less than the glass transition point and not more than the softening point.
Further, since the diameter of the conveyance roller provided in the temperature region where the temperature of the central portion of the glass ribbon B is not less than the glass transition point and not more than the softening point is likely to change, the diameter change of the conveyance roller provided in this region is compensated. It is preferable to determine the rotation speed of the transport roller.
When the glass temperature is higher than the softening point, the compressive stress acting on the glass is instantly relieved, so that the glass ribbon B hardly undergoes wave-shaped plastic deformation. On the other hand, when the glass temperature is lower than the glass transition point, the viscosity of the glass ribbon B is sufficiently increased, so that the corrugated plastic deformation hardly occurs.
Also, the upstream roller tends to change in roller diameter due to wear or thermal expansion. That is, it is preferable to determine the rotation speed of the conveying roller so as to compensate for a change in the diameter of the conveying roller provided at least in a temperature region where the temperature is not less than the glass transition point and not more than the softening point.

Further, the rotation speed of the conveyance roller is determined so as to compensate for the change in the diameter of the conveyance roller provided in the temperature region where the temperature of the central portion of the glass ribbon B is from the annealing point (strain point—50 ° C.), By rotating the transport roller, plastic deformation of the glass ribbon can be suppressed.
Thus, depending on which characteristic of the glass ribbon B is to be improved, the location of the conveyance roller that determines the rotation speed so as to compensate for the change in the diameter of the roller varies.

(Second Embodiment)
Next, the glass plate manufacturing apparatus which is 2nd Embodiment of this invention is demonstrated.
Here, the description will be made paying attention to the difference from the first embodiment.
The conveyance roller state detection unit 37 according to the first embodiment includes a temperature sensor 34 that detects the temperature of the conveyance roller. The conveyance roller state detection unit (hereinafter also simply referred to as a detection unit) 47 according to the second embodiment is illustrated in FIG. As shown in FIG. 6, a distance measurement sensor 44 for detecting the wear amount of the transport roller is included. FIG. 6 is a block diagram illustrating the configuration of a control system that controls the rotational driving of the transport roller pairs 18 and 19 according to the second embodiment. In FIG. 6, elements indicated by the same reference numerals as those in the first embodiment are not different from the configurations described in the first embodiment.

A plurality of distance measuring sensors 44 are provided corresponding to the respective transport roller pairs 18 and 19. The distance measuring sensor 44 detects the driving shaft interval. The drive shaft spacing is such that the drive shafts 18b and 19b connect the conveying rollers 18a and 19a on the same side with respect to the glass ribbon B, and the drive shaft 18b disposed opposite to the drive shafts 18b and 19b. , 19b. The pair of transport rollers 18 and 19 sandwich the glass ribbon B in a state where the pair of transport rollers 18a and 19a are urged to each other. Therefore, in the detection unit 47, the amount of wear of each of the transport rollers 18a and 19a is caused by the amount of change of the roller radius calculated according to the following formula from the roller radius when new, due to the wear of the transport rollers 18a and 19a. Detected as In this equation, since the thickness of the glass ribbon B is constant at the positions of the transport rollers 18a and 19a, the roller radius is calculated by measuring the distance between the drive shafts 18b and 19b.
Roller radius = (drive shaft interval-glass ribbon thickness) / 2

The speed determination unit 48 of the detection control unit 40 determines the peripheral speed ratio of the peripheral speeds of the transport rollers 18a and 19a caused by the change in the radius of the transport rollers 18a and 19a due to the detected wear of the transport rollers 18a and 19a. The rotational speeds of the transport rollers 18a and 19a are determined so as to compensate for the deviation.
In the second embodiment, the radius change calculated based on the wear state is used as the diameter change of the transport rollers 18a and 19a. However, the wear roller 18a, 19a used in the first embodiment uses this wear state. It can also be applied together with the temperature of 19a. In this case, the diameters of the transport rollers 18a and 19a vary with the amount of wear and also with thermal expansion. The rotational speeds of the transport rollers 18a and 19a can be calculated so that the peripheral speed of the transport rollers that changes with the change in diameter is maintained at the peripheral speed ratio.
Furthermore, in addition to changes in the diameters of the transport rollers 18a and 19a, a change in the transport speed of the glass ribbon B that changes according to the temperature of the glass ribbon B due to the thermal expansion of the glass ribbon B as a state of the glass ribbon B is integrated and applied. You can also

According to the second embodiment described above, it is possible to compensate for a deviation from the peripheral speed ratio of the peripheral speed of the transport roller due to a diameter change due to wear of the transport rollers 18a and 19a.
In this glass plate manufacturing apparatus, the distance measurement sensor 44 replaces the distance between the drive shafts 18b and 19b of the transport roller pair 18 and 19 with the origin of the drive shafts 18b and 19b of the transport roller pair 18 and 19. It may be configured to detect the amount of wear by reading the deviation from the position. The origin position is a center position where the drive shafts 18b and 19b are located when the transport rollers 18a and 19a are new, and is stored in the storage unit 46. The amount of wear of the transport rollers 18a and 19a is detected using the deviation of the drive shafts 18b and 19b from the origin position of the pair of transport rollers 18 and 19, and the roller diameter of the transport rollers thus worn can be calculated.
The diameters of the transport rollers 18a and 19a are not limited to being calculated by the detection unit 47, and may be calculated by an operator based on the amount of wear, for example. In this case, based on the diameters of the transport rollers 18a and 19a calculated by the operator and input to the speed determination unit 48, the rotation speeds of the transport rollers 18a and 19a are calculated by the speed determination unit 48. Alternatively, the rotational speeds of the transport rollers 18a and 19a may be further calculated based on the diameters of the transport rollers 18a and 19a calculated by the operator, and the calculation result may be input to the speed determination unit 48. The rotation speed calculated or input by the speed determination unit 48 is determined by the speed determination unit 48 and transmitted to the drive unit 32. Further, the wear amount and the origin position of the transport rollers 18 a and 19 a may be calculated by the operator, and the calculated values may be stored in the storage unit 46.

(Modification of the second embodiment)
Instead of the distance measuring sensor 44 of the glass plate manufacturing apparatus according to the second embodiment, a change in the diameter of the conveyance roller calculated based on the number of days of use of the conveyance rollers 18a and 19a is counted as a change in the diameter of the conveyance rollers 18a and 19a. An apparatus may be used. For example, the device that counts the diameter change sends the usage days of the transport rollers 18 a and 19 a to the speed determination unit 48. The speed determination unit 48 replaces the amount of wear from the new roller diameter when the transport rollers 18a and 19a stored in the storage unit 46 of the speed determination unit 48 are replaced in the past. The amount of wear per day is calculated based on these and the number of days used. Next, the new roller diameter stored in the storage unit 46 is referred to, and the roller diameter is calculated according to the following formula. At this time, it is assumed that the product of the amount of wear per day × the number of days of use corresponds to the amount of wear of the transport rollers 18a and 19a, as shown in the following formula using the number of days of use sent from the device for counting the diameter change. Detected.
Roller diameter = new diameter-(amount of wear per day x number of days used)
In the storage unit 46, the speed determination unit 48 stores past replacement results and roller diameters when new for each of the transport rollers 18a and 19a.
According to this modification, the deviation from the peripheral speed ratio of the peripheral speeds of the transport rollers 18a and 19a caused by the change in the diameter of the transport rollers 18a and 19a can be compensated by a simpler method. The amount of wear per day can be calculated by an operator and stored in the storage unit 46. The diameter change of the transport rollers 18a and 19a due to the wear amount may be calculated by the operator and transmitted to the detection control unit 40 or the drive unit 32. Further, the wear amount of the roller diameter when it was replaced in the past and the number of days used until the replacement may be calculated by the operator, and the calculated value may be stored in the storage unit 46.
Thus, in this modification, the transport rollers 18a and 19a are rotationally driven based on the rotational speed of the rollers determined based on the number of days of use of the transport rollers 18a and 19a so as to compensate for the change in the diameter of the rollers. . In this modification, as in the first and second embodiments, the state of the transport roller is not detected by the transport roller state detection unit, and the roller rotation speed is not determined based on the detection result, but the transport roller 18a. , 19a is different from the first and second embodiments in that the roller rotational speed is sequentially determined based on the number of days used.

  In addition, the modification of 1st Embodiment or 1st Embodiment and the modification of 2nd Embodiment or 2nd Embodiment can also be combined. By combining the modification of the first embodiment or the first embodiment with the modification of the second embodiment or the second embodiment, the modification of the first embodiment or the first embodiment, the second embodiment or the first embodiment. The deviation from the peripheral speed ratio can be compensated more accurately than in the case where the modification of the second embodiment is applied alone.

(Example)
In order to investigate the effect of the present invention, a glass plate is manufactured according to the following method using a conventional glass plate manufacturing apparatus and the glass plate manufacturing apparatus of the present embodiment, and the wavy uneven deformation generated in the glass plate is measured. did. In addition, all used the glass plate manufacturing apparatus is the glass plate manufacturing apparatus 1 by the downdraw method shown in FIG.3 and FIG.4, and the glass used the aluminosilicate glass containing the component shown below.
SiO ₂ 60% by mass,
Al ₂ O ₃ 19.5 mass%,
B ₂ O ₃ 10% by mass,
CaO 5 mass%,
5% by mass of SrO,
SnO ₂ 0.5% by mass.

  In Example 1, according to the first embodiment described above, the speed determining unit 38 determines the rotational speed of each of the transport rollers 18a and 19a, and controls the rotational drive of each of the transport rollers 18a and 19a based on the determined rotational speed. Then, a glass substrate for a liquid crystal display having a thickness of 0.7 mm and a length of 2000 mm in the width direction and a length of 2500 mm in the length direction was manufactured. The peripheral speeds of the transport rollers 18a and 19a as the peripheral speed ratio are all the same. The temperature of the glass ribbon and the temperature of the conveying roller were measured using a contact-type temperature sensor.

  In Example 2, a glass substrate for a liquid crystal display was manufactured in the same manner as in Example 1 except that the rotational speeds of the transport rollers 18a and 19a were determined by the speed determination unit 48 according to the second embodiment described above. Specifically, the wear amount of the transport rollers 18 a and 19 a was calculated using the driving shaft interval measured by the distance measuring sensor 44. In addition to the amount of change in roller diameter due to the amount of wear of the transport rollers 18a and 19a, the rotational speed of the transport rollers 18a and 19a was calculated in consideration of the amount of change in roller diameter due to the temperature of the transport rollers 18a and 19a.

  In the third embodiment, in determining the rotational speeds of the transport rollers 18a and 19a, the peripheral speeds of the respective transport rollers 18a and 19a are all changed to 1.1 times that of the first embodiment, and a 0.5 mm thick liquid crystal display is used. A glass substrate for a liquid crystal display was produced in the same manner as in Example 1 except that a glass substrate for production was produced.

In Comparative Examples 1 and 2, the speed determination unit was under the same conditions as in Examples 1 and 2 except that the rotation speed based on the state of the glass ribbon and the diameter change of the transport rollers 18a and 19a was not performed. went.
About the obtained glass substrate for liquid crystal displays of Examples 1-3 and Comparative Examples 1 and 2, the presence or absence of the damage | wound of the glass substrate surface for liquid crystal displays was confirmed visually, and the deformation | transformation of the waveform was measured using the thickness gauge. . In the case of a glass substrate for a liquid crystal display having a thickness of 0.7 mm, the wave shape was assumed to satisfy the surface quality if it was within 0.4 mm in the thickness direction. In a glass substrate for a liquid crystal display having a thickness of 0.5 mm, a surface quality of 0.2 mm or less was satisfied in the thickness direction.

  As for the glass substrate for liquid crystal displays of the comparative examples 1 and 2 obtained using the conventional manufacturing apparatus, the damage | wound was confirmed on the glass surface visually. In both cases, a wave-shaped deformation of 0.5 mm occurred in the thickness direction.

  On the other hand, the glass substrate for liquid crystal displays of Examples 1-3 obtained using the manufacturing apparatus 1 of the present embodiment could not confirm any scratches on the glass surface by visual observation. Moreover, about the deformation | transformation of a waveform, Example 1 had a deformation | transformation of about 0.2 mm in the thickness direction. In Example 2, deformation of about 0.1 mm occurred in the thickness direction. In Example 3, deformation of 0.02 mm or less occurred in the thickness direction. Examples 1 to 3 all satisfied the surface quality described above.

  As mentioned above, although the manufacturing method and glass plate manufacturing apparatus of the present invention were explained in detail, the present invention is not limited to the above-mentioned embodiment, and various improvements and changes are made without departing from the gist of the present invention. Of course.

DESCRIPTION OF SYMBOLS 1 Glass plate manufacturing apparatus 2 Molding apparatus 3 Gradation apparatus 18, 19 Conveyance roller pair 18a, 19a Conveyance roller 30, 40 Detection control part 32 Drive part 34 Temperature sensor (glass state detection part)
37, 47 Conveyance roller state detection unit 38, 48 Speed determination unit A Molten glass B Glass ribbon C Glass plate S10 Melting step S40 Molding step S50 Slow cooling step S51 Detection step S52 Speed determination step S53 Speed control step

Claims (7)

Melting process for melting glass raw material to make molten glass;
Molding a molten glass using a downdraw method to form a glass ribbon;
A slow cooling step of slowly cooling the glass ribbon by pulling it downward while being sandwiched by a plurality of roller pairs provided along the conveying direction of the glass ribbon,
The slow cooling step includes
Each roller of the first roller pair, which is at least one of the roller pairs, is rotationally driven based on the rotational speed of the roller determined so as to compensate for a change in the diameter of the roller,
Each roller of the first roller pair is provided in a temperature region in which the temperature of at least the center of the glass ribbon in the slow cooling step is a glass transition point or more and a softening point or less,
In the slow cooling step, the rotational speed of each roller of the first roller pair is determined so as to compensate for a change in the diameter of each roller of the first roller pair, and each roller of the first roller pair is driven to rotate. The manufacturing method of the glass plate characterized by the above-mentioned. In the molding step and the slow cooling step,
In the region where the temperature of the central portion of the glass ribbon is equal to or higher than the glass softening point, the end portion in the width direction of the glass ribbon is lower than the temperature of the central region sandwiched between the end portions, and the temperature of the central region is approximately Control to be uniform,
In the region where the temperature of the central portion of the glass ribbon is below the softening point and near the strain point, the temperature in the width direction of the glass ribbon is such that the tensile stress in the transport direction acts on the central portion of the glass ribbon. Control to lower from the center to the end,
The temperature distribution of the glass ribbon is controlled so that there is no temperature gradient between an end portion and a center portion in the width direction of the glass ribbon in a temperature region near the glass strain point of the glass ribbon. Manufacturing method of glass plate. In the slow cooling step,
In the region where the temperature of the central portion of the glass ribbon is less than the vicinity of the strain point, the glass ribbon is lowered from the end in the width direction toward the central portion so that tensile stress in the transport direction acts on the central portion of the glass ribbon. Thus, the manufacturing method of the glass plate of Claim 1 or 2 which controls the temperature distribution of the said glass ribbon. The slow cooling step includes
A first cooling step of cooling at a first average cooling rate until the temperature of the central portion of the glass ribbon reaches a slow cooling point;
A second cooling step of cooling at a second average cooling rate until the temperature of the central portion reaches a strain point of −50 ° C. from the annealing point;
A third cooling step of cooling at a third average cooling rate until the temperature of the central portion reaches the strain point of −200 ° C. from the strain point of −50 ° C., and
The first average cooling rate is 5.0 ° C./second or more,
The first average cooling rate is faster than the third average cooling rate;
The method for producing a glass sheet according to any one of claims 1 to 3 , wherein the third average cooling rate is faster than the second average cooling rate. The rotational speed of each roller of the first roller pair is adjusted so as to compensate for the deviation of the peripheral speed caused by the change in the diameter of each roller of the first roller pair due to the thermal expansion of each roller of the first roller pair. determined, the respective rollers are driven rotation of the first roller pair, a manufacturing method of a glass plate according to any one of claims 1-4. The thickness of the glass plate formed by cooling the said glass ribbon is 0.5 mm or less, The manufacturing method of the glass plate of any one of Claims 1-5 . A molding apparatus for molding a glass ribbon from molten glass using a downdraw method;
A slow cooling device that slowly cools the glass ribbon while pulling it downward while sandwiching it with a plurality of pairs of transport rollers,
The slow cooling device includes the plurality of conveying roller pairs, a detection control unit, and a driving unit,
The plurality of conveyance roller pairs are provided along a conveyance direction of the glass ribbon, and convey the glass ribbon by drawing the glass ribbon downward.
The detection control unit
A plurality of conveyance roller state detection units that are provided along the conveyance direction of the glass ribbon and detect a change in the diameter of the conveyance roller of the conveyance roller pair,
The drive unit maintains a peripheral speed distribution between the plurality of transport roller pairs when a relative speed between the peripheral speed of the transport roller and the transport speed of the glass ribbon is constant between the plurality of transport roller pairs. In addition, based on the rotational speed of each of the transport rollers determined based on the detected diameter change of the transport roller, the transport rollers are driven to rotate ,
Furthermore, each roller of the first roller pair, which is at least one of the transport roller pairs, has a temperature at least at the center of the glass ribbon in the slow cooling device that is not less than the glass transition point and not more than the softening point. In the temperature range
In the slow cooling device, the rotational speed of each roller of the first roller pair is determined so as to compensate for a change in the diameter of each roller of the first roller pair, and each roller of the first roller pair is driven to rotate. The glass plate manufacturing apparatus characterized by the above-mentioned.

Images