JP2012076974A - Method and device for manufacturing glass pane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a technology for manufacturing a glass pane suitably applicable to an electronic device such as a flat panel display and a solar cell panel by reducing dispersions in thermal shrinkage amount occurring by device production-related processing accompanied by heating of a glass pane scheduled after the production.SOLUTION: In the method for manufacturing a glass pane, a temperature-controllable continuous annealing furnace is used, to which a glass ribbon molded from molten glass is introduced, and the glass ribbon is annealed to be formed into a glass pane when passing through the continuous annealing furnace. The method for manufacturing a glass pane includes: a measurement process of measuring temperature of the glass ribbon passing through the continuous annealing furnace; and a computing process of continuously computing and predicting the thermal shrinkage quantity, which may occur when device production-related processing accompanied by heating is performed on the glass pane, from a temperature distribution of the glass ribbon measured during annealing the glass ribbon based on a correlation between variations in virtual temperature before and after the processing and the thermal shrinkage quantity.

Description

  The present invention relates to a glass plate manufacturing method by a float method and a glass plate manufacturing apparatus, and in particular, a glass plate manufacturing method and a glass plate that form a glass plate by continuously cooling a glass ribbon formed from molten glass. It relates to a manufacturing apparatus.

  As a method for forming a glass plate, a float method performed using a production line called a float bath is widely known. The glass plate manufactured by the float process can be used for electronic devices, such as a flat panel display (a liquid crystal display, a plasma display, an organic EL display, a field emission display etc.), a solar cell panel, for example.

  When processing the glass plate manufactured by the float process into a flat panel display, for example, an electrode, a partition, etc. are formed on the surface of a glass plate, another glass plate is laminated | stacked on it, and both are bonded together. At this time, a predetermined heat treatment is performed on both glass plates. This heat treatment is one of the device manufacturing related processes involving heating. When heat treatment is performed on a glass plate manufactured by the float process, a minute dimensional change called “heat shrinkage” occurs. The generation mechanism of heat shrinkage is explained as follows.

  The glass plate is generally composed of an amorphous body having a disordered atomic arrangement structure, and has a property of taking an atomic arrangement structure specific to temperature. For this reason, the glass plate immediately after manufacture has an atomic arrangement structure specific to the temperature according to the thermal history experienced in the step of slowly cooling the glass ribbon. From this, the atomic arrangement structure of the frozen glass ribbon can be expressed by a conceptual temperature, and this conceptual temperature is called “virtual temperature”.

  Here, when the heat treatment as described above is performed as a separate process on the glass plate after production, the atomic arrangement structure in the glass plate is heated from the atomic arrangement structure due to the thermal history experienced in the slow cooling step. It tries to change to an atomic arrangement structure intrinsic to temperature, that is, an atomic arrangement structure that is more stable at the heat treatment temperature. This change is called “glass structure relaxation” and occurs with volume shrinkage. Depending on the atomic arrangement structure of the glass plate, volume expansion may occur in the glass plate due to heat treatment, but the dimensional change of the glass plate during the production of the flat panel display is usually a change in the shrinking direction. .

  When such a dimensional change due to heat shrinkage occurs in a flat panel display in which two glass plates are bonded together, displacement may occur in the electrodes, partitions, etc. formed on the surface of each glass plate. . Further, the flat panel display itself may be warped. In recent years, with the increase in the definition of flat panel displays, the amount of heat shrinkage and the variation width generated by heat treatment have been regarded as important, and in particular, a glass plate with less variation in heat shrinkage is required.

  One simple method for suppressing thermal shrinkage itself is to use glass having a strain point higher than the heat treatment temperature as the glass plate. As molten glass cools, it exponentially increases in viscosity and eventually its structure freezes. The strain point is a temperature at which the glass structure is generally considered to be frozen, and is one of the guidelines for determining the schedule in the slow cooling process. A typical example of the glass having a high strain point is quartz glass. Quartz glass or the like has a high glass viscosity at the heat treatment temperature after the production of the glass plate, and a longer time is required because the atomic arrangement structure of the glass changes. For this reason, as a result, the thermal shrinkage in the heat treatment step is reduced. However, high strain point glass such as quartz glass is generally expensive, and it is difficult to industrially use it in large quantities as glass for flat panel displays.

  On the other hand, as a method of suppressing variation in the amount of heat shrinkage, by suppressing the amount of heat shrinkage between the two glass plates to be bonded within a predetermined range, the relative difference in the amount of heat shrinkage between the two glass plates is canceled out. There are known methods for eliminating such adverse effects. If the amount of heat shrinkage of the two glass plates is within a predetermined range, the positional deviation and warpage of the electrodes and the like in the flat panel display are substantially eliminated, so that the yield of products is improved. In addition, manufacturing time and energy costs can be saved.

In order to suppress variation in the amount of heat shrinkage, it is necessary to know in advance the amount of heat shrinkage of the glass plate generated by the heat treatment. Therefore, as a method for measuring the amount of heat shrinkage of the glass plate, there has been a method of directly measuring the amount of heat shrinkage of the sample cut out from the glass plate (see, for example, Non-Patent Document 1). According to Non-Patent Document 1, a parallel reference line is marked using a diamond pen at both ends of a glass plate, and then the glass plate is cut in half to obtain a measurement sample. One sample is heat treated and the other sample is not heat treated. The amount of heat shrinkage of the glass plate is obtained by matching the two samples and measuring the shift of the marking line. As shown in FIG. 5, the heat shrinkage amount is expressed as a ratio of the total shrinkage amount (ΔL ₁ + ΔL ₂ ) of the glass plate to the separation width length (ΔL ₀ ) of the two reference lines injured on the glass plate before the heat treatment. Expressed in units (ppm).

  In addition, a technique has been proposed in which the occurrence of heat shrinkage in a glass plate is allowed to some extent and the amount of heat shrinkage is controlled (see, for example, Patent Document 1). According to Patent Document 1, the thermal history experienced by the glass ribbon is adjusted by maintaining the glass ribbon passing through the continuous slow cooling furnace at a temperature lower than a predetermined temperature, and finally the control of the thermal shrinkage of the glass plate is attempted. ing. Patent Document 1 discloses that the ambient temperature of a continuous slow cooling furnace is controlled to control the amount of heat shrinkage.

JP-A-6-24775

Masayuki Yamane, 6 others, “Glass Engineering Handbook”, first edition, Asakura Shoten, July 5, 1999, p. 384

  However, there are several problems with the above prior art. The method described in Non-Patent Document 1 is to perform measurement using a glass plate that finally becomes a product or a test sample prepared from the glass plate. For this reason, the amount of heat shrinkage of the glass plate to be measured is found only after a certain measurement time has elapsed. Then, for example, if the time interval for actually measuring the amount of heat shrinkage is long, the amount of heat shrinkage of the glass plate will be out of the specified range until the measurement result becomes clear. The glass plate will continue to be manufactured. For this reason, the method of Non-Patent Document 1 has a problem that the yield of products deteriorates. In particular, when starting production of glass plates of different varieties, or when changing the thermal shrinkage characteristics of glass plates, the atmospheric temperature in the continuous annealing furnace will be changed in consideration of the thermal shrinkage characteristics of the glass. Whether or not the heat shrinkage amount is achieved cannot be determined until the heat shrinkage amount of the manufactured glass plate is measured by the method of Non-Patent Document 1 and the result is known. For this reason, a large amount of product loss may occur after changing the temperature condition in the slow cooling step.

  The method described in Patent Document 1 controls the ambient temperature near the temperature measurement point installed in the continuous slow cooling furnace. However, it is difficult to completely control the ambient temperature away from the temperature measurement point. Moreover, the temperature of the glass ribbon immediately before being carried into the continuous annealing furnace is likely to fluctuate due to the influence of the outside air temperature, the air current, and the like. As the temperature of the glass ribbon fluctuates, the thermal history experienced by the glass ribbon in a continuous slow cooling furnace will change. If it does so, it must be said that with the method of patent document 1, it is difficult to keep the thermal contraction amount of the glass plate manufactured from a glass ribbon within the predetermined range.

  Thus, in the present situation, a technology that can reliably control the heat shrinkage that can occur in the glass plate after manufacture has not been developed yet. The present invention has been made in view of the above-mentioned problems, and in manufacturing a glass plate obtained by slow cooling a glass ribbon formed by a float process, a device that involves heating a glass plate that is planned after the manufacturing. It is an object of the present invention to establish a technique for manufacturing a glass plate that can be suitably applied to an electronic device such as a flat panel display or a solar cell panel by reducing variations in the amount of heat shrinkage that may occur due to manufacturing-related processing.

The characteristic structure of the glass plate manufacturing method according to the present invention for solving the above problems is as follows.
Using a temperature-controllable continuous slow cooling furnace in which a glass ribbon formed from molten glass is introduced, the glass ribbon is slowly cooled while passing through the continuous slow cooling furnace to form a glass plate,
A measuring step for measuring the temperature of the glass ribbon passing through the continuous annealing furnace;
The amount of heat shrinkage that can occur when performing device manufacturing-related processing with heating on the glass plate is determined during the slow cooling of the glass ribbon based on the correlation between the amount of change in virtual temperature before and after the processing and the amount of heat shrinkage. A calculation process for continuously calculating and predicting from the measured temperature distribution of the glass ribbon,
Is to execute.

As described in the above problem, in the prior art, it has been very difficult to reliably control the heat shrinkage that can occur in the glass ribbon during the slow cooling process. For this reason, if device manufacturing related processing (for example, heat processing) accompanied by heating is performed after manufacturing a glass plate, variation in the amount of heat shrinkage occurs, which is suitable as glass for electronic devices such as flat panel displays and solar cell panels. It was difficult to obtain high quality glass plates that could be used.
Therefore, the present inventors paid attention to the fact that the amount of change in the virtual temperature of the glass plate and the amount of heat shrinkage are in a substantially proportional relationship, and as a result of intensive research, the heating applied to the glass plate after production was performed. It was found that using the correlation between the amount of change in the fictive temperature of the glass plate and the amount of heat shrinkage before and after the device manufacturing related process was very effective in predicting heat shrinkage.
From the above knowledge, in the glass plate manufacturing method of the present configuration, the amount of heat shrinkage that can occur when performing device manufacturing related processing with heating on the glass plate is calculated as the amount of change in virtual temperature before and after the processing and the amount of heat shrinkage. Based on the correlation, it is continuously calculated and predicted from the temperature distribution of the glass ribbon measured during the slow cooling of the glass ribbon. In particular, continuous operation is a unique feature of the present invention and is very effective in making accurate predictions. By performing such a process, variation in the amount of heat shrinkage that can occur when a device manufacturing-related process involving heating is performed on a manufactured glass plate can be reliably kept within a predetermined range. As a result, when two glass plates are bonded together, there is substantially no displacement or warpage between them. Therefore, the glass plate manufactured by the method of this invention can be utilized suitably for electronic devices, such as a flat panel display and a solar cell panel.

In the glass plate manufacturing method according to the present invention,
A control step of controlling the internal temperature of the continuous slow cooling furnace based on the temperature of the glass ribbon measured in the measurement step is performed so that the predicted value of the heat shrinkage predicted in the calculation step falls within a specified range. It is preferable to do.

  According to the glass plate manufacturing method of this configuration, if it is predicted that the amount of heat shrinkage that may occur when performing device manufacturing-related processing with heating on the manufactured glass plate is outside the specified range, the internal temperature of the continuous slow cooling furnace Is controlled so that the amount of heat shrinkage falls within the specified range. Therefore, the variation in the amount of heat shrinkage can be reliably kept within a predetermined range, and as a result, a high-quality glass for electronic devices can be efficiently produced.

に基づいて求められることが好ましい。 In the glass plate manufacturing method according to the present invention,
The correlation between the amount of change in virtual temperature and the amount of heat shrinkage before and after the device manufacturing-related process with heating is expressed by the following equation (1) representing the amount of heat shrinkage, equation (2) representing the temporal variation of the virtual temperature, and Formula (3) representing relaxation time:

It is preferable that it is calculated | required based on.

  According to the glass plate manufacturing method of this configuration, the correlation between the amount of change in virtual temperature and the amount of heat shrinkage before and after the device manufacturing related process with heating is obtained based on the above formulas (1) to (3). Thus, the variation in the amount of heat shrinkage can be reliably kept within a predetermined range. Thereby, a high quality glass for electronic devices can be manufactured efficiently. In addition, what is necessary is just to discretize the differential equation of Formula (2) with an appropriate method.

In the glass plate manufacturing method according to the present invention,
In the calculation step, it is preferable that a time step introduced when the equation (2) is discretized is set to 1/10 to 1/1000 of the relaxation time τ.

  According to the glass plate manufacturing method of the present configuration, it is effective to set the time step introduced when the equation (2) is discretized to 1/10 to 1/1000 of the relaxation time τ in the calculation step. . If it is this range, even if the composition of a raw material glass, manufacturing conditions, a manufacturing scale, etc. change, the change of virtual temperature by the heat history which a glass ribbon experiences in a slow cooling process can be grasped | ascertained correctly. As a result, it is possible to improve the prediction accuracy of heat shrinkage that may occur when device manufacturing related processing involving heating is performed on the manufactured glass plate.

In the glass plate manufacturing method according to the present invention,
In the control step, the internal temperature of the continuous annealing furnace may be controlled so that the amount of heat shrinkage that can occur when device manufacturing-related processing involving heating is performed on the glass plate is within a specified range of a design value ± 20 ppm. preferable.

  According to the glass plate manufacturing method of this configuration, it is possible to efficiently manufacture a suitable glass plate by an electronic device such as a flat panel display or a solar cell panel by keeping the amount of heat shrinkage within a specified range of a design value ± 20 ppm. it can.

In the glass plate manufacturing method according to the present invention,
In the measurement step, the temperature is measured at least at a plurality of locations on the flow axis of the glass ribbon and at least a location from the inlet of the continuous annealing furnace to a point indicating the annealing point of the glass ribbon at −50 ° C. Is preferred.

  According to the glass plate manufacturing method of the present configuration, the glass plate after manufacture is heated in a state where the temperature range where the atomic arrangement structure of the glass ribbon is considered to be greatly relaxed is taken into consideration and included in the calculation region of the prediction calculation. Predict the amount of thermal shrinkage that can occur when performing device manufacturing related processing. Therefore, it is possible to efficiently produce a higher quality glass for electronic devices.

In the glass plate manufacturing method according to the present invention,
It is preferable that the continuous slow cooling furnace is configured to be capable of temperature control over at least a region including a point where temperature measurement is performed in the measurement step.

  According to the glass plate manufacturing method of the present configuration, when the predicted value of the heat shrinkage deviates from the specified range, it can be returned to the specified range by executing the temperature control of the continuous annealing furnace. Therefore, the variation in the amount of heat shrinkage can be reliably kept within a predetermined range, and as a result, a high-quality glass for electronic devices can be efficiently produced.

The characteristic configuration of the glass plate manufacturing apparatus according to the present invention for solving the above problems is as follows.
A glass plate manufacturing apparatus comprising a continuous annealing furnace capable of temperature control into which a glass ribbon formed from molten glass is introduced, wherein the glass ribbon is slowly cooled while passing through the continuous annealing furnace, and forms a glass plate,
Measuring means for measuring the temperature of the glass ribbon passing through the continuous slow cooling furnace;
The amount of heat shrinkage that can occur when performing device manufacturing-related processing with heating on the glass plate is determined during the slow cooling of the glass ribbon based on the correlation between the amount of change in virtual temperature before and after the processing and the amount of heat shrinkage. A calculation means for continuously calculating and predicting from the measured temperature distribution of the glass ribbon;
It is in having.

  According to the glass plate manufacturing apparatus of this structure, there can exist an effect substantially the same as the glass plate manufacturing method mentioned above. That is, in the glass plate manufacturing apparatus of this configuration, the amount of heat shrinkage that can occur when device manufacturing-related processing involving heating is performed on the glass plate is correlated with the amount of change in virtual temperature before and after the processing and the amount of heat shrinkage. Based on the temperature distribution of the glass ribbon measured during the slow cooling of the glass ribbon. In particular, continuous operation is a unique feature of the present invention and is very effective in making accurate predictions. By performing such processing by the calculation means, variations in the amount of thermal shrinkage that can occur when device manufacturing-related processing involving heating is performed on the manufactured glass plate can be reliably kept within a predetermined range. As a result, when two glass plates are bonded together, there is substantially no displacement or warpage between them. Therefore, the glass plate manufactured with the apparatus of this invention can be utilized suitably for electronic devices, such as a flat panel display and a solar cell panel.

FIG. 1 is a schematic view of a glass plate manufacturing apparatus used for carrying out the glass plate manufacturing method of the present invention. FIG. 2 is a flowchart for explaining the glass plate manufacturing method of the present invention. FIG. 3 is a graph that approximates the relationship between the two obtained as a result of repeated adjustment based on the measured values of the heat treatment temperature and the amount of heat shrinkage. FIG. 4 is a graph showing an example of heat amount adjustment. FIG. 5 is an explanatory diagram of a conventional method for measuring the amount of thermal shrinkage of a glass plate.

  Hereinafter, the embodiment regarding the glass plate manufacturing method and glass plate manufacturing apparatus of this invention is described based on FIGS. However, the present invention is not intended to be limited to the configurations described in the embodiments and drawings described below, and includes configurations equivalent thereto.

[Glass plate manufacturing equipment]
FIG. 1 is a schematic view of a glass plate manufacturing apparatus 100 used for carrying out the glass plate manufacturing method of the present invention. The glass plate manufacturing apparatus 100 of the present invention is configured as part of equipment for manufacturing various glass plates by the float method. The glass plate manufacturing apparatus 100 includes a continuous slow cooling furnace 10 capable of controlling the internal temperature. In FIG. 1, the continuous slow cooling furnace 10 is shown by the dotted line for description of the internal structure. The continuous slow cooling furnace 10 is provided with an introduction port 11 through which a glass ribbon A formed from molten glass is introduced, and a carry-out port 12 through which a glass plate A ′ formed by slow cooling of the glass ribbon A is carried out. Yes. Inside the continuous slow cooling furnace 10, rollers 13 for conveying the glass ribbon A are disposed at a plurality of locations. Further, a plurality of temperature control heaters 14 are installed over the entire interior of the continuous slow cooling furnace 10. In the present specification, the glass ribbon A and the glass plate A ′ are separated for convenience of explanation. However, the two may be generally referred to as “glass plate”, and of course, the present application may be handled as such. Is possible.

  Here, the glass plate manufacturing apparatus 100 includes a plurality of thermocouples 20 for measuring the temperature of the glass ribbon A and a computer 30 for performing various calculations as main components. Furthermore, the monitor 40 which displays the calculation result by the computer 30, and the alarm device 50 which issues a warning as needed based on the said calculation result are provided.

  The thermocouple 20 is a measuring means in the present invention. The thermocouple 20 includes a plurality of three lines along the conveying direction of the glass ribbon A so as to measure the temperature on the flow axis (center axis) of the glass ribbon A and the temperature on the left and right straight lines sandwiching the flow axis. It is arranged at the place. At this time, it is preferable to arrange the thermocouple 20 within 50 mm from the surface of the glass ribbon A. Thereby, the temperature of each part of the glass ribbon A can be accurately measured while the glass ribbon A passes through the continuous slow cooling furnace 10. The number of thermocouples 20 is not particularly limited, and may be increased up to about 6 lines in the width direction of the glass ribbon A. On one line, the thermocouples 20 are preferably provided at intervals of 1/10 of the total length of the continuous slow cooling furnace 10, and more preferably at intervals of 1/30. Thereby, the temperature distribution of the glass ribbon A can be measured with higher accuracy. The thermocouple 20 has at least a plurality of locations on the flow axis of the glass ribbon A and temperatures at locations from the inlet 11 of the continuous slow cooling furnace 10 to at least a point where the slow cooling point of the glass ribbon A shows −50 ° C. Is arranged to measure. With this arrangement, an area where the atomic arrangement structure of the glass ribbon A is considered to be greatly relaxed can be included as a minimum calculation area. In addition, in the temperature measurement of the glass ribbon A, when the direct measurement by the thermocouple 20 is difficult, the ambient temperature near the glass ribbon A may be measured and used instead. Further, a radiation thermometer may be used instead of the thermocouple 20 to measure the temperature of the glass ribbon A.

  The computer 30 includes an arithmetic unit 31 as arithmetic means and a control unit 32 as control means for generating a control command based on the arithmetic result. The arithmetic unit 31 and the control unit 32 can be realized as hardware of the computer 30 in which a program is incorporated, for example. The arithmetic unit 31 performs device manufacturing-related processing with heating on the glass plate A ′ formed by slowly cooling the glass ribbon A by performing arithmetic processing executed in a “glass plate manufacturing method” described later. Predict the amount of heat shrinkage that can occur. In the present embodiment, the “device manufacturing related process with heating” is a heating process executed to form a structure such as an electrode or a partition on a glass plate laminated on two sheets. Based on the temperature of the glass ribbon A measured by the thermocouple 20 so that the predicted value of the thermal contraction in the glass plate A ′ predicted by the arithmetic unit 31 falls within the specified range, the control unit 32 is arranged inside the continuous slow cooling furnace 10. Control the temperature. This is performed by controlling the output of a plurality of heaters 14 provided inside the continuous slow cooling furnace 10. Control of the internal temperature of the continuous slow cooling furnace 10 is performed over at least a region including a point where the thermocouple 20 performs temperature measurement.

[Glass plate manufacturing method]
FIG. 2 is a flowchart for explaining the glass plate manufacturing method of the present invention (hereinafter referred to as “the present manufacturing method”). This manufacturing method is executed in steps 0 to 15. In the flowchart, a step in each process is indicated by a symbol “S”. This manufacturing method includes a measurement process and a calculation process, and further includes a control process. Hereinafter, each step will be described in detail.

<Measurement process>
When this manufacturing method is started (S0), the temperature (glass temperature) of the glass ribbon A passing through the continuous slow cooling furnace 10 is collected by the thermocouple 20 (S1). Here, the operator sets the glass temperature measurement time in the computer 30. When the measurement time has been reached (S2; YES), calculation related to heat shrinkage is started. When the measurement time has not yet been reached (S2; NO), the status of the glass ribbon A is displayed (S14), and the glass temperature collection (S1) is continued.

<Calculation process>
In the calculation step, the amount of heat shrinkage that may occur when performing device manufacturing related processing with heating on the glass plate A ′ formed by slowly cooling the glass ribbon A is expressed by the following equations (1), (2), And it estimates using Formula (3) (S3). This prediction is executed by a prediction subroutine (S21 to S23) shown separately in the upper left part of FIG. In the prediction subroutine, first, the virtual temperature of the current glass plate A ′ is predicted using Equation (2) and Equation (3) (S21). Next, the virtual temperature after the device manufacturing related processing with heating is calculated from the device manufacturing related processing conditions with heating scheduled for the glass plate A ′ after manufacturing, which is input in advance. 3) is used (S22). Finally, from the virtual temperature difference between step 21 and step 22, the amount of heat shrinkage that can occur in the glass plate A ′ after the device manufacturing related process with heating is predicted using equation (1). This prediction is based on the correlation between the virtual temperature change amount and the heat shrinkage amount in the glass plate A ′ before and after the device manufacturing-related process with heating, and the temperature distribution of the glass ribbon A measured during the slow cooling of the glass ribbon A. Is done from. These prediction subroutines are continuously executed.

  Specific contents of the calculation in the prediction subroutine will be described below. The correlation between the amount of change in the virtual temperature and the amount of heat shrinkage before and after the device manufacturing-related process with heating is as follows: Equation (1) representing the amount of heat shrinkage, Equation (2) representing time variation of the virtual temperature, and relaxation It is calculated based on the expression (3) representing time.

Here, the reference temperature T _ref is a temperature serving as a reference for calculation, and an arbitrary temperature is set. The relaxation time τ is a time in which the state of the atomic arrangement structure being changed becomes 1 / e (e: the base of natural logarithm) with respect to the state of the atomic arrangement structure before the change in the process of structural relaxation of the glass. is there. The distribution rate x is a ratio that apportions the influence of the current virtual temperature _Tf and the glass temperature T on the relaxation time. When x = 0, only the influence of the virtual temperature _Tf is reflected in the calculation, and when x = 1, only the influence of the glass temperature T is reflected in the calculation.

In formulas (1) and (3), k ₁ , k ₂ , and x are constants specific to glass. For example, a preliminary test in which the heating temperature and the heating time are arbitrarily combined is performed, and k ₁ , k ₂ , and x are repeated until Equation (3) approximates the measured value (actual value) of heat shrinkage at this time It is calculated by adjusting. In addition, what is necessary is just to discretize the differential equation of Formula (2) with an appropriate method. As an example, discretization by the difference method is shown below.

  In the following formula, a subscript (t) is added to the variable at time t. Further, a subscript (t−Δt) is added to the variable at time t−Δt that is Δt before time t. Here, Δt is a minute time step (time step).

  When the expression (2) is added with a time index, the expression (4) is obtained.

  When the difference is applied to the first derivative of the left side of Expression (4), Expression (5) is obtained.

  Substituting equation (5) into equation (4) yields equation (6).

When this is arranged with respect to T _f (t), Expression (7) which is a discretization expression of Expression (2) can be obtained.

  Further, assuming that there are a plurality of forms in which the atomic arrangement structure of glass is relaxed, the following formulas (8) and (9) can be used instead of formula (2).

Τ _i in the formula (9) is a relaxation time for each of a plurality of relaxation modes of the atomic arrangement structure of the glass, and C _i in the formula (8) is a ratio of each relaxation time. C _i and τ _i are values inherent to the glass, and can be obtained by repeatedly adjusting so as to approximate the measured values in the same manner as k ₁ , k ₂ , and x described above. FIG. 3 shows a graph approximating the relationship between the two obtained as a result of repeated adjustment based on the measured values of the heat treatment temperature and the amount of heat shrinkage. In addition, what is necessary is just to discretize the differential equation of Formula (9) by the method similar to the above.

  Moreover, when using Formula (8) and (9), the following formula | equation (10) can be used instead of Formula (3).

  After execution of the prediction subroutine, it is determined whether or not the heat shrinkage predicted based on the equations (1) to (3) is within a specified range (S4). The specified range is set such that, for example, the amount of thermal shrinkage that can occur when device manufacturing related processing involving heating is performed on the glass plate A ′ is the design value ± 20 ppm. Here, the design value is a theoretical heat shrinkage amount obtained by the device manufacturing related process with a predetermined heating. If it is determined that the amount of heat shrinkage is within the specified range (S4; YES), the status of the glass ribbon A is displayed (S14), and the glass temperature collection (S1) is continued. When it is determined that the amount of heat shrinkage is not within the specified range (S4; NO), the direction of deviation of the predicted value (whether the predicted value is less than or exceeds the reference value) is determined (S5). Here, when it is determined that the predicted heat shrinkage amount is larger than the specified range (that is, shrinks a lot), the heat amount applied to the glass ribbon A is increased (S6). On the other hand, when it is determined that the predicted heat shrinkage amount is smaller than the specified range (that is, it does not shrink so much), the heat amount applied to the glass ribbon A is decreased (S7). These step 6 and step 7 for adjusting the amount of heat are combined into a control process. The control process can be automatically executed by the computer 30, but may be executed manually by an operator. For example, when an abnormality such as an excessive temperature rise or a temperature drop occurs during the execution of the control process, the computer 30 issues an alarm from the alarm device 50 to notify the operator of the abnormality.

  The amount of heat adjustment in the control step can be executed by the following operation, for example. FIG. 4 is a graph showing an example of heat amount adjustment. The solid line (a) in the graph is the temperature of the glass ribbon A during normal operation. Here, when it is predicted that the glass plate A ′ after the device manufacturing-related process with heating changes in a direction shrinking from the specified range, the output of the heater 14 of the continuous slow cooling furnace 10 is increased. And it shifts to a high temperature side, as shown to a broken line (b), maintaining the profile of a continuous line (a). Thereby, the amount of change in the virtual temperature before and after the device manufacturing-related process with heating is reduced, and the amount of heat shrinkage that can occur in the glass plate A ′ after the device manufacturing-related process with heating can be reduced. On the other hand, when it is predicted that the glass sheet A ′ after the device manufacturing-related process involving heating changes in a direction that does not shrink from the specified range, the output of the heater 14 of the continuous slow cooling furnace 10 is lowered. And it shifts to the low temperature side, as shown by a dashed-dotted line (c), maintaining the profile of a continuous line (a). Thereby, the amount of change in the virtual temperature before and after the device manufacturing-related process with heating increases, and the amount of heat shrinkage that can occur in the glass plate A ′ after the device manufacturing-related process with heating can be increased.

  As another heat quantity adjustment method, a part of the gradient may be changed in the temperature profile shown in FIG. In the present invention, since the temperature of the glass plate is measured over time, it is easy to obtain a temperature gradient for each temperature measurement section. Therefore, by utilizing this, the current temperature gradient is compared with a preset temperature gradient, and the control process can be performed by adjusting the output of the heater 14 in a section where the temperature gradient is greatly changed. . For example, if the predicted value deviates in the direction of shrinkage from the amount of heat shrinkage predicted by the device manufacturing related process involving heating on the glass plate A ′, the temperature gradient in the corresponding section is reduced. On the other hand, when the predicted value deviates in a direction in which the glass plate A ′ is not shrunk from the amount of heat shrinkage predicted by the device manufacturing related process involving heating to the glass plate A ′, the temperature gradient in the corresponding section is increased.

  After performing the above control process, the same prediction as in step 3 is retried again (S8). The subroutine in step 8 is the same as the above-described prediction subroutine (S21 to S23). As a result of the prediction based on the retry, it is determined whether or not it is within the specified range as in Step 4 (S9). If it is determined that it is within the specified range (S9; YES), after setting the layer temperature (S13), which is the internal temperature of the continuous slow cooling furnace 10, the status of the glass ribbon A is displayed (S14) and the glass temperature is collected. Continue (S1). When it is determined that it is not within the specified range (S9; NO), it is determined whether or not the set number of trials remains (S10). If the number of trials remains (S10; present), the process returns to step 5 to predict the amount of heat shrinkage. If the number of trials does not remain (S10; none), the computer 30 requests the operator to make a determination (S11). When the operator operates the computer 30 to instruct the glass temperature (S12; present), after setting the layer temperature (S13), the status of the glass ribbon A is displayed (S14) and the glass temperature is collected (S1). ). When the operator does not operate the computer 30 (S12; none), the manufacturing method is terminated (S15).

By the way, although it has been described in the above calculation step that the prediction subroutine is executed based on the equations (1) to (3), in the actual calculation, the computer 30 repeatedly calculates the discretized equation (2). ing. The calculation accuracy of equation (2) at this time depends on the time step (time step) introduced when equation (2) is discretized. If the time step is too rough, the calculation accuracy of the virtual temperature T _f calculated by the equation (2) is deteriorated. As a result, the accuracy of predicting the amount of heat shrinkage in equation (1) also deteriorates. Therefore, in order to accurately predict the amount of heat shrinkage, it is necessary to continuously execute the calculation process at an appropriate time step. In the present invention, it is effective to set the calculation time step to 1/10 to 1/1000 of the relaxation time τ. Preferably, the time step of calculation is set to 1/100 to 1/1000 of the relaxation time τ. If the time step of the calculation is set to at least 1/10 to 1/1000 of the relaxation time τ, the glass ribbon A experiences in the slow cooling process even if the composition, production conditions, production scale, etc. of the raw glass changes. It is possible to accurately grasp changes in virtual temperature due to thermal history. As a result, it is possible to improve the prediction accuracy of heat shrinkage that may occur when device manufacturing related processing involving heating is performed on the manufactured glass plate A ′. When the time step of the calculation is made larger than 1/10 of the relaxation time τ, the relaxation phenomenon of the glass atomic arrangement structure cannot be sufficiently resolved, the calculation error increases, and the reliability of the prediction result decreases. On the other hand, even if the time is less than 1/1000 of the relaxation time τ, the calculation accuracy is hardly improved, but since the calculation amount increases, it takes time for prediction.

  Hereinafter, as an example, an apparatus corresponding to the glass plate manufacturing apparatus 100 was actually used, and the amount of heat shrinkage that could occur in the glass plate was predicted. First, the prediction accuracy was confirmed by the time step of the calculation. The time step was changed based on the relaxation time τ, and the virtual temperature of the glass ribbon A was obtained. Three time steps: 1 second (1/10 of the relaxation time τ), 0 under the conditions where the relaxation time τ is 10 seconds, the heat treatment temperature is 650 ° C. (constant), and the initial value of the fictive temperature is 680 ° C. The calculation was performed for 1 second (1/100 of relaxation time τ) and 0.01 second (1/1000 of relaxation time τ). As a result, the virtual temperature of the glass ribbon A after 10 seconds is 661.6 ° C. at time step 1 second, 661.1 ° C. at time step 0.1 second, and 661.0 ° C. at time step 0.01 second. became. Since the fictive temperature values under these three conditions are substantially the same, the reliability of the calculation result under the above conditions is considered to be high.

  For comparison, calculation was performed for the time step of 10 seconds (1/1 of the relaxation time τ) and 0.001 second (1/10000 of the relaxation time τ) under the same conditions as described above. As a result, the virtual temperature of the glass ribbon A after 10 seconds had reached 665.0 ° C. at the time step of 10 seconds. This greatly deviated from the fictive temperature (661.0 ° C. to 661.6 ° C.) obtained by the calculation of 1/10 to 1/1000 of the relaxation time τ. On the other hand, at a time step of 0.001 seconds, the temperature was 661.0 ° C., which was almost the same as the calculation result of 1/10 to 1/1000 of the relaxation time τ, but the calculation load increased due to the shortening of the time step.

  Next, the following Example 1 and Example 2 were implemented. In these examples, 5 lines were set in the width direction of the glass ribbon transported inside the continuous slow cooling furnace, and radiation thermometers were provided at intervals of 1/12 of the total length of the continuous slow cooling furnace in the transport direction for each line. . And the temperature of the glass ribbon was measured with time.

<Example 1>
Based on the above-mentioned formulas (1) to (3), the amount of heat shrinkage that can occur in the glass plate was predicted by the device manufacturing-related process with heating scheduled after manufacturing. Here, the allowable range of heat shrinkage was set to −440 ± 10 ppm. Table 1 shows the predicted value of the heat shrinkage of the glass plate during the implementation period (measurement time) of Example 1 and the heat shrinkage of the glass plate actually measured after manufacturing. In addition, the value shown in Table 1 is a result in the center line among the 5 lines installed in the width direction of the glass ribbon described above.

  When the predicted value of the amount of heat shrinkage deviated from the allowable range, the operator planned to correct the temperature of the glass ribbon by adjusting the internal atmospheric temperature of the continuous slow cooling furnace. Since the predicted value was stable during the implementation period of 1, the temperature adjustment was unnecessary as a result.

<Example 2>
In an apparatus for continuously producing a glass plate as in the present invention, the thickness of the glass plate is generally controlled by the conveyance speed of the glass ribbon. When changing the thickness of the glass plate, the thermal history experienced by the glass ribbon also changes as the conveying speed changes. For this reason, the operation of changing the temperature distribution in the continuous slow cooling furnace at the same time and keeping the amount of heat shrinkage that can occur in the glass plate within the specified range is performed. Example 2 is an example in which the present invention is applied when the thickness of the glass plate is changed.

  First, based on the formulas (1) to (3), the temperature distribution of the continuous slow cooling furnace in which the amount of heat shrinkage after changing the conveyance speed becomes a specified value was determined. For this, assuming a plurality of patterns of temperature distribution in the continuous slow cooling furnace, substituting each assumed temperature distribution into equations (1) to (3) as appropriate, and performing repeated calculations, the heat shrinkage amount becomes a specified value. At least one pattern of temperature distribution that is close was selected.

  Next, it was judged whether or not the determined temperature distribution could be realized in a continuous annealing furnace. This was judged in consideration of the capacity of a plurality of heating facilities installed inside a continuous slow cooling furnace and the capacity of a cooling facility. A feasible temperature distribution pattern was set.

  Based on the production method of the present invention, during the production of the glass plate, the amount of heat shrinkage that can occur in the glass plate after production is continuously calculated and predicted, and if the predicted value fluctuates, the internal temperature control of the continuous annealing furnace is performed. Carried out. Here, the specified range of heat shrinkage was set to −435 ± 10 ppm. The predicted value of the heat shrinkage amount of the glass plate during the implementation period (measurement time) of Example 2, the heat shrinkage amount of the glass plate actually measured after manufacturing, and the actual measurement value of the heat shrinkage amount before the thickness change of the glass plate It shows in Table 2.

  Also in Example 2, since the predicted value was stable during the implementation period, temperature adjustment was unnecessary as a result.

<Discussion>
From the results of Example 1 and Example 2, if the present invention is applied to the production of a glass plate, the amount of heat shrinkage of the glass plate, which is first revealed after device manufacturing-related processing with heating that is originally carried out after production, is reduced to glass. It can be grasped during the manufacture of the board. Further, when the thermal shrinkage of the glass plate is likely to deviate from the allowable range, it can be within the allowable range by performing temperature control. Therefore, product loss is reduced and yield is improved. In addition, manufacturing time and energy costs can be saved. Furthermore, even when the glass plate type is changed, the amount of heat shrinkage of the changed glass plate can be quickly kept within a new allowable range, so that the production efficiency of the glass plate is improved.

  The glass plate manufacturing method and glass plate manufacturing apparatus of the present invention are, for example, glass plates used for electronic devices such as flat panel displays (liquid crystal displays, plasma displays, organic EL displays, field emission displays, etc.) and solar battery panels. Can be used for manufacturing.

DESCRIPTION OF SYMBOLS 10 Continuous slow cooling furnace 11 Inlet 12 Carry-out 13 Roller 14 Heater 20 Thermocouple (measuring means)
30 Computer 31 Calculation unit (calculation means)
32 Control unit (control means)
40 Monitor 50 Alarm 100 Glass plate manufacturing equipment A Glass ribbon A 'Glass plate

Claims (8)

Using a temperature-controllable continuous slow cooling furnace in which a glass ribbon formed from molten glass is introduced, the glass ribbon is slowly cooled while passing through the continuous slow cooling furnace to form a glass plate,
A measuring step for measuring the temperature of the glass ribbon passing through the continuous annealing furnace;
The amount of heat shrinkage that can occur when performing device manufacturing-related processing with heating on the glass plate is determined during the slow cooling of the glass ribbon based on the correlation between the amount of change in virtual temperature before and after the processing and the amount of heat shrinkage. A calculation process for continuously calculating and predicting from the measured temperature distribution of the glass ribbon,
The glass plate manufacturing method which performs.   A control step of controlling the internal temperature of the continuous slow cooling furnace based on the temperature of the glass ribbon measured in the measurement step is performed so that the predicted value of the heat shrinkage predicted in the calculation step falls within a specified range. The glass plate manufacturing method of Claim 1 to do. The correlation between the amount of change in virtual temperature and the amount of heat shrinkage before and after the device manufacturing-related process with heating is expressed by the following equation (1) representing the amount of heat shrinkage, equation (2) representing the temporal variation of the virtual temperature, and Formula (3) representing relaxation time:

The glass plate manufacturing method of Claim 1 or 2 calculated | required based on this.   The glass plate manufacturing method of Claim 3 which sets the time step introduce | transduced when the said Formula (2) is discretized in the said calculating process to 1/10-1/1000 of relaxation time (tau).   In the control step, the internal temperature of the continuous annealing furnace is controlled so that the amount of heat shrinkage that may occur when device manufacturing-related processing involving heating is performed on the glass plate is within a specified range of a design value ± 20 ppm. The glass plate manufacturing method as described in any one of 2-4.   In the measurement step, the temperature is measured at at least a plurality of locations on the flow axis of the glass ribbon, and at least a location from the inlet of the continuous annealing furnace to a location at which the glass ribbon has an annealing point of −50 ° C. Item 6. The glass plate production method according to any one of Items 1 to 5.   The said continuous slow cooling furnace is a glass plate manufacturing method of Claim 6 comprised so that temperature control is possible over the area | region including the point which performs a temperature measurement in the said measurement process at least. A glass plate manufacturing apparatus comprising a continuous annealing furnace capable of temperature control into which a glass ribbon formed from molten glass is introduced, wherein the glass ribbon is slowly cooled while passing through the continuous annealing furnace, and forms a glass plate,
Measuring means for measuring the temperature of the glass ribbon passing through the continuous slow cooling furnace;
The amount of heat shrinkage that can occur when performing device manufacturing-related processing with heating on the glass plate is determined during the slow cooling of the glass ribbon based on the correlation between the amount of change in virtual temperature before and after the processing and the amount of heat shrinkage. A calculation means for continuously calculating and predicting from the measured temperature distribution of the glass ribbon;
The glass plate manufacturing apparatus provided with.

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