JP2017014054A - Production method of glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a glass substrate capable of reducing a thickness deviation of the glass substrate.SOLUTION: The production method of the glass substrate includes, a molding step, a transporting step, an acquiring step, a calculating step and an adjusting step. In the molding step, molten glass is supplied to a supply groove formed on a top face of the mold, the mold glass overflown from both sides of the supply groove is flown down along both sides of the mold, and the molten glass is merged at a bottom end of the mold, to mold a glass ribbon. In the transporting step, the glass ribbon molded in the molding step is transported downward at a specified speed using a roll disposed below the mold. In the acquiring step, a shape data regarding the shape of the mold is acquired. In the calculating step, based on a shape data acquired in the acquiring step, a transporting speed is calculated so that thickness deviation of the glass ribbon in a width direction may be small. In the adjusting step, the transporting speed of the glass ribbon is adjusted so as to become the transporting speed calculated in the calculating step.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a method for manufacturing a glass substrate.

  A glass substrate used for a flat panel display (FPD) such as a liquid crystal display and a plasma display is required to have high flatness on the surface. Usually, such a glass substrate is manufactured by the overflow down draw method. In the overflow downdraw method, as described in Patent Document 1 (US Pat. No. 3,338,696), molten glass that has been poured into the groove on the upper surface of the molded body and overflowed from the groove is A glass ribbon is formed by flowing down along both side surfaces and joining at the lower end of the formed body. The formed glass ribbon is gradually cooled while being pulled downward. The cooled glass ribbon is cut into a predetermined dimension to obtain a glass substrate.

  In the overflow down draw method, the molded body is placed in a high-temperature atmosphere in a molding furnace. Further, a load due to its own weight and the weight of the molten glass is applied to the molded body. For this reason, the molded body gradually creep-deforms due to the thermal creep characteristics of the material of the molded body due to the long-term operation of the glass substrate manufacturing apparatus. In particular, the central portion in the longitudinal direction of the molded body is likely to sag downward due to creep deformation and bend easily. As a result, the amount of molten glass that overflows from the center of the molded body is greater than the amount of molten glass that overflows from both ends of the molded body, and the thickness of the central portion in the width direction of the glass ribbon to be molded increases. There was a problem that the thickness deviation of the glass substrate as the final product increased.

  Creep deformation of a molded body is a particular problem because the temperature of the molded body tends to be high in the manufacturing process of a glass substrate using glass having a high liquidus temperature and glass having a high strain point. In recent years, the size of the glass substrate has been increased, and the dimension in the longitudinal direction of the molded body has become longer. Therefore, the bending of the molded body due to creep deformation tends to become more prominent.

  Then, an object of this invention is to provide the manufacturing method of the glass substrate which can reduce the plate | board thickness deviation of a glass substrate.

  The manufacturing method of the glass substrate which concerns on this invention is equipped with a formation process, a conveyance process, an acquisition process, a calculation process, and an adjustment process. In the molding process, molten glass is supplied to the supply groove formed on the upper surface of the molded body, and the molten glass overflowing from both sides of the supply groove is caused to flow down along both side surfaces of the molded body, and the molten glass is flowed down on both sides. Are joined at the lower end of the molded body to form a glass ribbon. A conveyance process conveys the glass ribbon shape | molded by the formation process below with the predetermined | prescribed conveyance speed using the roll installed in the downward direction of the molded object. The acquisition step acquires shape data related to the shape of the molded body. In the calculation step, the conveyance speed is calculated based on the shape data acquired in the acquisition step so that the thickness deviation in the width direction of the glass ribbon is reduced. In the adjustment step, the conveyance speed of the glass ribbon is adjusted so that the conveyance speed calculated in the calculation step is obtained.

  Moreover, in the manufacturing method of the glass substrate which concerns on this invention, it is preferable that an acquisition process acquires the shape data based on the creep deformation of a molded object.

  Moreover, in the manufacturing method of the glass substrate which concerns on this invention, it is preferable that an acquisition process acquires at least the displacement amount of the vertical direction of the upper surface of a molded object as shape data. In this case, it is preferable that the calculation step calculates a larger value as the conveyance speed as the displacement amount is larger.

  Moreover, in the manufacturing method of the glass substrate which concerns on this invention, a conveyance process conveys a glass ribbon while gradually cooling using the roll which pinches | interposes the both ends of the width direction of a glass ribbon, and it is the conveyance speed calculated at the calculation process. It is preferable to control the rotation speed of the roll based on the above.

  Moreover, in the manufacturing method of the glass substrate which concerns on this invention, it is preferable that an acquisition process acquires shape data by calculating | requiring the time change of the shape of a molded object by computer simulation.

  The glass substrate manufacturing method according to the present invention can reduce the thickness deviation of the glass substrate.

It is a flowchart of the manufacturing method of the glass substrate which concerns on embodiment. It is a schematic diagram of the manufacturing apparatus of a glass substrate. It is a front view of a shaping | molding apparatus. It is a side view of a shaping | molding apparatus. It is a block diagram of a control apparatus. It is an example of the shape data of the molded object acquired by the acquisition part. It is an example of the graph of the temperature dependence change of the distortion rate of a molded object. It is an example of the graph of the stress dependence change of the distortion rate of a molded object. It is a graph which shows the relationship between the maximum upper surface displacement amount of a molded object, and the conveyance speed of a glass ribbon.

(1) Configuration of Glass Substrate Manufacturing Apparatus An embodiment of a glass substrate manufacturing method according to the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing an example of a glass substrate manufacturing method according to the present embodiment.

  As FIG. 1 shows, the manufacturing method of the glass substrate which concerns on this embodiment mainly has melting process S1, clarification process S2, stirring process S3, shaping | molding process S4, cooling process S5, and cutting process S6. Including.

In the melting step S1, the glass raw material is heated to obtain molten glass. The molten glass is stored in a melting tank and energized and heated to have a desired temperature. A fining agent is added to the glass raw material. From the viewpoint of reducing environmental burden, SnO ₂ is used as a clarifying agent.

In the clarification step S2, the molten glass obtained in the melting step S1 flows through the clarification tube, and the gas contained in the molten glass is removed, whereby the molten glass is clarified. First, in the refining step S2, the temperature of the molten glass is raised. The refining agent added to the molten glass causes a reduction reaction by raising the temperature and releases oxygen. Bubbles containing gas components such as CO ₂ , N ₂ and SO ₂ contained in the molten glass absorb oxygen generated by the reductive reaction of the fining agent. Bubbles that have grown by absorbing oxygen float on the liquid surface of the molten glass, break up and disappear. The gas contained in the extinguished bubbles is discharged into the gas phase space inside the clarification tube and discharged to the outside air. Next, in the refining step S2, the temperature of the molten glass is lowered. Thereby, the reduced fining agent causes an oxidation reaction and absorbs gas components such as oxygen remaining in the molten glass.

  In the stirring step S3, the molten glass from which the gas has been removed in the refining step S2 is stirred, and the components of the molten glass are homogenized. Thereby, the nonuniformity of the composition of the molten glass that is the cause of the striae of the glass substrate is reduced.

  In the forming step S4, a glass ribbon is continuously formed from the molten glass homogenized in the stirring step S3 using an overflow downdraw method.

  In the cooling step S5, the glass ribbon formed in the forming step S4 is cooled while being conveyed downward. In the cooling step S5, the glass ribbon is gradually cooled while adjusting the temperature of the glass ribbon so that the glass ribbon is not distorted and warped.

  In cutting process S6, the glass ribbon cooled by cooling process S5 is cut | disconnected by a predetermined dimension, and a glass substrate is obtained. Thereafter, the end surface of the glass substrate is ground and polished, and the glass substrate is cleaned. Thereafter, the glass substrate is inspected for defects such as scratches, and the glass substrate that has passed the inspection is packed and shipped as a product.

  FIG. 2 is a schematic diagram illustrating an example of the glass substrate manufacturing apparatus 1 according to the present embodiment. The glass substrate manufacturing apparatus 1 includes a melting tank 10, a clarification tube 20, a stirring device 30, a molding device 40, and transfer tubes 50a, 50b, and 50c. The transfer pipe 50 a connects the melting tank 10 and the clarification pipe 20. The transfer pipe 50 b connects the clarification pipe 20 and the stirring device 30. The transfer pipe 50 c connects the stirring device 30 and the molding device 40.

  The molten glass 2 obtained in the melting tank 10 in the melting step S1 passes through the transfer pipe 50a and flows into the clarification pipe 20. The molten glass 2 clarified by the clarification tube 20 in the clarification step S2 passes through the transfer tube 50b and flows into the stirring device 30. The molten glass 2 stirred by the stirring device 30 in the stirring step S3 passes through the transfer pipe 50c and flows into the molding device 40. In the forming step S4, the glass ribbon 3 is continuously formed from the molten glass 2 by the forming apparatus 40. In the cooling step S5, the glass ribbon 3 is cooled while being conveyed downward. In the cutting step S6, the cooled glass ribbon 3 is cut into a predetermined size to obtain a glass substrate. The width of the glass substrate is, for example, 500 mm to 3500 mm, and the length is, for example, 500 mm to 3500 mm. The thickness of the glass substrate is, for example, 0.2 mm to 0.8 mm.

The glass substrate manufactured by the glass substrate manufacturing apparatus 1 is particularly suitable as a glass substrate for a flat panel display (FPD) such as a liquid crystal display, a plasma display, and an organic EL display. As the glass substrate for FPD, non-alkali glass, alkali-containing glass, glass for low-temperature polysilicon (LTPS), or glass for oxide semiconductor is used. As a glass substrate for a high-definition display, a glass having a high viscosity and a high strain point at a high temperature is used. For example, glass used as a raw material for a glass substrate for a high-definition display has a viscosity of 10 ^2.5 poise at 1500 ° C.

In the melting tank 10, the glass raw material is melted to obtain the molten glass 2. The glass raw material is prepared so that a glass substrate having a desired composition can be obtained. As an example of the composition of the glass substrate, non-alkali glass suitable as a glass substrate for FPD is SiO ₂ : 50 mass% to 70 mass%, Al ₂ O ₃ : 10 mass% to 25 mass%, B ₂ O ₃ : 1% by mass to 18% by mass, MgO: 0% by mass to 10% by mass, CaO: 0% by mass to 20% by mass, SrO: 0% by mass to 20% by mass, BaO: 0% by mass to 10% by mass . Here, the total content of MgO, CaO, SrO and BaO is 5% by mass to 30% by mass.

In addition, a glass containing a trace amount of alkali metal containing a trace amount of alkali metal may be used as a glass substrate for FPD. Alkaline trace containing glass 'includes a ₂ O, preferably, 0.2 wt% to 0.5 wt% R' of R 0.1 wt% to 0.5 wt% including the ₂ O. Here, R ′ is at least one selected from Li, Na and K. The total content of R ′ ₂ O may be less than 0.1% by mass.

The glass substrate manufactured by the glass substrate manufacturing apparatus _1, SnO 2: 0.01 wt% to 1 wt% (preferably 0.01 mass% to 0.5 _{mass%), Fe 2 O 3:} 0 You may further contain mass%-0.2 mass% (preferably 0.01 mass%-0.08 mass%). The glass substrate manufactured by the glass substrate manufacturing apparatus 1, from the viewpoint of environmental load reduction, substantially free of _{As 2 O 3, Sb 2 O} 3 , and PbO.

  The glass raw material prepared to have the above composition is charged into the melting tank 10 using a raw material charging machine (not shown). The raw material input machine may input a glass raw material using a screw feeder, or may input a glass raw material using a bucket. In the melting tank 10, the glass raw material is heated and melted at a temperature according to its composition. In the melting tank 10, the high temperature molten glass 2 of 1500 degreeC-1600 degreeC is obtained, for example. In the melting tank 10, the molten glass 2 between the electrodes may be energized and heated by passing a current between at least one pair of electrodes formed of molybdenum, platinum, tin oxide or the like. The glass raw material may be supplementarily heated by a burner flame.

  The molten glass 2 obtained in the melting tank 10 passes through the transfer pipe 50 a from the melting tank 10 and flows into the clarification pipe 20. The clarification tube 20 and the transfer tubes 50a, 50b and 50c are tubes made of platinum or a platinum alloy. The clarification tube 20 is provided with heating means as in the melting tank 10. In the clarification tube 20, the molten glass 2 is further heated to be clarified. For example, in the clarification tube 20, the temperature of the molten glass 2 is raised to 1500 ° C to 1700 ° C.

  The molten glass 2 clarified in the clarification tube 20 passes through the transfer tube 50 b from the clarification tube 20 and flows into the stirring device 30. The molten glass 2 is cooled when passing through the transfer tube 50b. In the stirring device 30, the molten glass 2 is stirred at a temperature lower than the temperature of the molten glass 2 that passes through the clarification tube 20. For example, in the stirring device 30, the temperature of the molten glass 2 is 1250 ° C. to 1450 ° C., and the viscosity of the molten glass 2 is 500 poise to 1300 poise. The molten glass 2 is stirred and homogenized in the stirring device 30.

  The molten glass 2 homogenized by the stirring device 30 flows from the stirring device 30 through the transfer pipe 50 c and flows into the molding device 40. The molten glass 2 is cooled so as to have a viscosity suitable for forming the molten glass 2 when passing through the transfer tube 50c. For example, the molten glass 2 is cooled to around 1200 ° C.

  In the forming apparatus 40, the glass ribbon 3 is formed from the molten glass 2 by the overflow downdraw method. Next, the detailed configuration and operation of the molding apparatus 40 will be described.

(2) Configuration of Molding Device FIG. 3 is a front view of the molding device 40. FIG. 3 shows the forming apparatus 40 viewed along a direction perpendicular to the surface of the glass ribbon 3 formed by the forming apparatus 40. FIG. 4 is a side view of the molding apparatus 40. FIG. 4 shows the forming apparatus 40 viewed along a direction parallel to the surface of the glass ribbon 3 formed by the forming apparatus 40.

  The forming apparatus 40 has a space surrounded by a furnace wall (not shown) made of a refractory material such as a refractory brick. This space is a space in which the glass ribbon 3 is formed from the molten glass 2 and the glass ribbon 3 is cooled. This space includes three spaces, an upper molding space 60, a lower molding space 70, and a slow cooling space 80.

  The molding step S4 is performed in the upper molding space 60. The cooling step S5 is performed in the lower molding space 70 and the slow cooling space 80. The upper molding space 60 is a space in which the molten glass 2 supplied from the stirring device 30 to the molding device 40 via the transfer pipe 50 c is molded into the glass ribbon 3. The lower molding space 70 is a space below the upper molding space 60, and is a space where the glass ribbon 3 is rapidly cooled to the vicinity of the annealing point of the glass. The slow cooling space 80 is a space below the lower molding space 70 and is a space where the glass ribbon 3 is gradually cooled.

  The molding apparatus 40 mainly includes a molded body 62, an upper partition member 64, a cooling roll 72, a temperature adjustment unit 74, a lower partition member 76, pulling rolls 82a to 82g, heaters 84a to 84g, and a heat insulating member. 86, a cutting device 98, and a control device 91. Next, each component of the shaping | molding apparatus 40 is demonstrated.

(2-1) Molded Body The molded body 62 is installed in the upper molding space 60. The formed body 62 is used for forming the glass ribbon 3 by overflowing the molten glass 2. As shown in FIG. 4, the molded body 62 has a pentagonal cross-sectional shape similar to a wedge shape. The sharp end of the cross-sectional shape of the molded body 62 corresponds to the lower end 62 a of the molded body 62. The molded body 62 is made of refractory bricks.

  A supply groove 62 b is formed on the upper surface 62 c of the molded body 62 along the longitudinal direction of the molded body 62. A transfer pipe 50 c communicating with the supply groove 62 b is attached to the end of the molded body 62 in the longitudinal direction. The supply groove 62b is formed so as to gradually become shallower from one end communicating with the transfer pipe 50c toward the other end.

  The molten glass 2 sent to the shaping | molding apparatus 40 from the stirring apparatus 30 is poured into the supply groove | channel 62b of the molded object 62 via the transfer pipe 50c. The molten glass 2 overflowed from the supply groove 62 b of the molded body 62 flows down along both side surfaces of the molded body 62 and merges in the vicinity of the lower end 62 a of the molded body 62. The joined molten glass 2 falls in the vertical direction by gravity and is formed into a plate shape. Thereby, the glass ribbon 3 is continuously shape | molded in the vicinity of the lower end 62a of the molded object 62. FIG. The molded glass ribbon 3 flows down through the upper molding space 60 and then is conveyed downward while being cooled in the lower molding space 70 and the slow cooling space 80. The temperature of the glass ribbon 3 immediately after being molded in the upper molding space 60 is 1100 ° C. or higher, and the viscosity is 25000 poise to 350,000 poise. For example, when manufacturing a glass substrate for a high-definition display, the strain point of the glass ribbon 3 formed by the molded body 62 is 655 ° C. to 750 ° C., preferably 680 ° C. to 730 ° C. The viscosity of the molten glass 2 fused in the vicinity of the lower end 62a is 25000 poise to 100000 poise, preferably 32000 poise to 80000 poise.

(2-2) Upper Partition Member The upper partition member 64 is a pair of plate-like heat insulating members installed in the vicinity of the lower end 62 a of the molded body 62. As shown in FIG. 4, the upper partition member 64 is disposed on both sides of the glass ribbon 3 in the thickness direction. The upper partition member 64 partitions the upper molding space 60 and the lower molding space 70 and suppresses the movement of heat from the upper molding space 60 to the lower molding space 70.

(2-3) Cooling Roll The cooling roll 72 is a cantilever roll installed in the lower molding space 70. The cooling roll 72 is installed directly below the upper partition member 64. As shown in FIG. 3, the cooling rolls 72 are disposed on both sides in the width direction of the glass ribbon 3. As shown in FIG. 4, the cooling rolls 72 are disposed on both sides of the glass ribbon 3 in the thickness direction. The glass ribbon 3 is sandwiched between cooling rolls 72 on both sides in the width direction. The cooling roll 72 cools the glass ribbon 3 sent from the upper molding space 60.

  In the lower molding space 70, both side portions in the width direction of the glass ribbon 3 are sandwiched between two pairs of cooling rolls 72, respectively. When the cooling roll 72 is pressed toward the surface of the both sides of the glass ribbon 3, the contact area of the cooling roll 72 and the glass ribbon 3 becomes large, and the cooling of the glass ribbon 3 by the cooling roll 72 is performed efficiently. . The cooling roll 72 gives the glass ribbon 3 a force that opposes the force by which pulling rolls 82a to 82g described later pull the glass ribbon 3 downward. The thickness of the glass ribbon 3 is determined by the difference between the rotation speed of the cooling roll 72 and the rotation speed of the pulling roll 82a disposed at the uppermost position.

The cooling roll 72 has an air cooling tube inside. The cooling roll 72 is always cooled by an air cooling tube. The cooling roll 72 is brought into contact with the glass ribbon 3 by sandwiching both side portions in the width direction of the glass ribbon 3. Thereby, since heat is transmitted from the glass ribbon 3 to the cooling roll 72, both side portions in the width direction of the glass ribbon 3 are cooled. The viscosity of both side portions in the width direction of the glass ribbon 3 cooled in contact with the cooling roll 72 is, for example, 10 ^9.0 poise or more.

  The contact load between the cooling roll 72 and the glass ribbon 3 can be controlled by the control device 91. The contact load is controlled, for example, by adjusting the position of the cooling roll 72 using a spring. The larger the contact load, the stronger the force that the cooling roll 72 presses the glass ribbon 3.

(2-4) Temperature Control Unit The temperature control unit 74 is installed in the lower molding space 70. The temperature adjustment unit 74 is installed below the upper partition member 64 and above the lower partition member 76.

  In the lower molding space 70, the glass ribbon 3 is cooled until the temperature at the center in the width direction of the glass ribbon 3 decreases to the vicinity of the annealing point. The temperature adjustment unit 74 adjusts the temperature of the glass ribbon 3 cooled in the lower forming space 70. The temperature adjustment unit 74 is a unit that heats or cools the glass ribbon 3. As shown in FIG. 3, the temperature adjustment unit 74 includes a central cooling unit 74a and a side cooling unit 74b. The center cooling unit 74a adjusts the temperature of the center of the glass ribbon 3 in the width direction. The side cooling unit 74 b adjusts the temperature of both sides in the width direction of the glass ribbon 3. Here, the center portion in the width direction of the glass ribbon 3 means a region sandwiched between both side portions in the width direction of the glass ribbon 3.

  In the lower molding space 70, as shown in FIG. 3, a plurality of center cooling units 74a and a plurality of side cooling units 74b are arranged along the vertical direction, which is the direction in which the glass ribbon 3 flows down. Yes. The center part cooling unit 74a is arranged so as to face the surface of the center part of the glass ribbon 3 in the width direction. The side cooling unit 74b is disposed so as to face the surfaces of both side portions of the glass ribbon 3 in the width direction.

  The temperature adjustment unit 74 is controlled by the control device 91. Each center part cooling unit 74a and each side part cooling unit 74b can be independently controlled by the control device 91.

(2-5) Lower Partition Member The lower partition member 76 is a pair of plate-like heat insulating members installed below the temperature adjustment unit 74. As shown in FIG. 4, the lower partition member 76 is installed on both sides of the glass ribbon 3 in the thickness direction. The lower partition member 76 partitions the lower molding space 70 and the slow cooling space 80 in the vertical direction, and suppresses the movement of heat from the lower molding space 70 to the slow cooling space 80.

(2-6) Pull-down rolls The pull-down rolls 82 a to 82 g are cantilever rolls installed in the slow cooling space 80. In the slow cooling space 80, a pulling roll 82a, a pulling roll 82b,..., A pulling roll 82f, and a pulling roll 82g are arranged at intervals from above to below. The pulling roll 82a is disposed at the uppermost position, and the pulling roll 82g is disposed at the lowermost position.

  As shown in FIG. 3, the pulling rolls 82 a to 82 g are respectively disposed on both sides of the glass ribbon 3 in the width direction. As shown in FIG. 4, the pulling rolls 82 a to 82 g are respectively disposed on both sides of the glass ribbon 3 in the thickness direction. That is, the two sides of the glass ribbon 3 in the width direction are directed from the top to the bottom, two pairs of pulling rolls 82a, two pairs of pulling rolls 82b, ..., two pairs of pulling rolls 82f and two pairs of pulling rolls. It is sandwiched by 82g.

  The pulling rolls 82a to 82g pull the glass ribbon 3 downward in the vertical direction by rotating while sandwiching both end portions in the width direction of the glass ribbon 3 that has passed through the lower forming space 70. That is, the pulling rolls 82a to 82g are rolls for conveying the glass ribbon 3 downward.

  The angular velocities of the pulling rolls 82a to 82g can be controlled independently by the control device 91. The higher the angular speed of the pulling rolls 82a to 82g, the higher the speed at which the glass ribbon 3 is conveyed downward.

(2-7) Heater The heaters 84 a to 84 g are installed in the slow cooling space 80. As shown in FIG. 4, in the slow cooling space 80, the heater 84a, the heater 84b,..., The heater 84f and the heater 84g are arranged at intervals from the upper side to the lower side. The heaters 84a to 84g are respectively disposed on both sides of the glass ribbon 3 in the thickness direction. The pulling rolls 82a to 82g are disposed between the heaters 84a to 84g and the glass ribbon 3, respectively.

  The heaters 84 a to 84 g radiate heat toward the surface of the glass ribbon 3 to heat the glass ribbon 3. By using the heaters 84a to 84g, the temperature of the glass ribbon 3 conveyed downward in the slow cooling space 80 can be adjusted. Accordingly, the heaters 84 a to 84 g can form a predetermined temperature distribution on the glass ribbon 3 in the conveyance direction of the glass ribbon 3.

  The outputs of the heaters 84a to 84g can be controlled independently by the control device 91. The heaters 84a to 84g are divided into a plurality of heater subunits (not shown) along the width direction of the glass ribbon 3, and the output of each heater subunit can be controlled independently by the controller 91. Also good. In this case, the heaters 84 a to 84 g can form a predetermined temperature distribution in the width direction of the glass ribbon 3 by changing the heat generation amount according to the position in the width direction of the glass ribbon 3.

  In addition, the thermocouple (not shown) which measures the temperature of the atmosphere of the slow cooling space 80 is installed in the vicinity of each heater 84a-84g. The thermocouple measures, for example, the ambient temperature near the center of the glass ribbon 3 in the width direction and the ambient temperature near both sides. The heaters 84a to 84g may be controlled based on the temperature of the atmosphere of the slow cooling space 80 measured by a thermocouple.

(2-8) Heat insulation member The heat insulation member 86 is installed in the slow cooling space 80. The heat insulating member 86 is installed at a height position between two pulling rolls 82 a to 82 g adjacent along the conveying direction of the glass ribbon 3. As shown in FIG. 4, the heat insulating member 86 is a pair of heat insulating plates arranged horizontally on both sides of the glass ribbon 3 in the thickness direction. The heat insulating member 86 partitions the slow cooling space 80 in the vertical direction and suppresses the movement of heat in the vertical direction in the slow cooling space 80.

  The heat insulating member 86 is installed so as not to contact the glass ribbon 3 conveyed downward. Moreover, the heat insulation member 86 is installed so that the distance to the surface of the glass ribbon 3 can be adjusted. Thereby, the heat insulating member 86 suppresses the movement of heat between the space above the heat insulating member 86 and the space below the heat insulating member 86.

(2-9) Cutting Device The cutting device 98 is installed in a space below the slow cooling space 80. The cutting device 98 cuts the glass ribbon 3 that has passed through the slow cooling space 80 along the width direction of the glass ribbon 3 for each predetermined dimension. The glass ribbon 3 that has passed through the slow cooling space 80 is a flat glass ribbon 3 that is cooled to near room temperature.

  The cutting device 98 cuts the glass ribbon 3 at predetermined time intervals. Thereby, when the conveyance speed of the glass ribbon 3 is constant, the glass substrate which has a dimension close | similar to a final product is mass-produced.

(2-10) Control Device The control device 91 is a computer mainly composed of a CPU, RAM, ROM, hard disk, and the like. FIG. 5 is a block diagram of the control device 91. As shown in FIG. 5, the control device 91 is connected to a cooling roll drive motor 172, a temperature adjustment unit 74, a pulling roll drive motor 182, heaters 84 a to 84 g and a cutting device drive motor 198. The cooling roll drive motor 172 is a motor for controlling the position and rotational speed of the cooling roll 72. The pulling roll drive motor 182 is a motor for independently controlling the positions and rotational speeds of the pulling rolls 82a to 82g. The cutting device drive motor 198 is a motor for controlling a time interval or the like at which the cutting device 98 cuts the glass ribbon 3. The control device 91 stores a program for acquiring the state of each component and controlling each component.

  The control device 91 can acquire and adjust the contact load between the pair of cooling rolls 72 and the glass ribbon 3 that sandwich the side portion in the width direction of the glass ribbon 3 by controlling the cooling roll drive motor 172. The control device 91 can control the pulling roll drive motor 182 to acquire the torques of the rotating pulling rolls 82a to 82g and adjust the angular velocities of the pulling rolls 82a to 82g. The control device 91 can acquire and adjust the output of the temperature adjustment unit 74 and the outputs of the heaters 84a to 84g. The control device 91 can control the cutting device drive motor 198 to acquire and adjust the time interval or the like at which the cutting device 98 cuts the glass ribbon 3.

(3) Operation of Molding Device In the upper molding space 60, the molten glass 2 sent from the stirring device 30 to the molding device 40 via the transfer pipe 50c enters the supply groove 62b formed on the upper surface 62c of the molded body 62. Supplied. The molten glass 2 overflowed from the supply groove 62 b of the molded body 62 flows down along both side surfaces of the molded body 62 and joins in the vicinity of the lower end 62 a of the molded body 62. In the vicinity of the lower end 62a of the formed body 62, the glass ribbon 3 is continuously formed from the molten glass 2 that has joined. The molded glass ribbon 3 is sent to the lower molding space 70.

  In the lower molding space 70, both side portions of the glass ribbon 3 in the width direction are brought into contact with the cooling roll 72 and rapidly cooled. Moreover, the temperature of the glass ribbon 3 is adjusted by the temperature adjustment unit 74 until the temperature of the center part of the width direction of the glass ribbon 3 falls to a slow cooling point. The glass ribbon 3 cooled while being conveyed downward by the cooling roll 72 is sent to the slow cooling space 80.

  In the slow cooling space 80, the glass ribbon 3 is gradually cooled while being pulled down by the pulling rolls 82a to 82g. The temperature of the glass ribbon 3 is controlled by the heaters 84 a to 84 g so that a predetermined temperature distribution is formed along the width direction of the glass ribbon 3. In the slow cooling space 80, the temperature of the glass ribbon 3 gradually decreases from the vicinity of the slow cooling point to a temperature lower than a temperature 200 ° C. lower than the strain point.

  The glass ribbon 3 that has passed through the slow cooling space 80 is further cooled to near room temperature, and is cut into a predetermined size by a cutting device 98 to obtain a glass substrate. Thereafter, polishing and cleaning of the end face of the glass substrate are performed. Thereafter, the glass substrate that has passed the predetermined inspection is packed and shipped as a product.

(4) Operation | movement of control apparatus The control apparatus 91 memorize | stores and executes at least three programs which consist of a conveyance part, an acquisition part, and a calculation part.

  A conveyance part conveys the glass ribbon 3 shape | molded by the molded object 62 below with the predetermined | prescribed conveyance speed in the slow cooling space 80 using the pull-down rolls 82a-82g installed in the downward direction of the molded object 62. FIG. The transport unit controls the pulling roll drive motor 182 to adjust the rotation speed of the pulling rolls 82a to 82g, thereby adjusting the transport speed of the glass ribbon 3.

  The acquisition unit acquires shape data relating to the current shape of the molded body 62. Specifically, the acquisition unit acquires shape data based on the creep characteristic parameter. The creep characteristic parameter is a parameter for reproducing the relationship among the stress applied to the molded body 62, the temperature of the molded body 62, and the strain rate of the molded body 62 due to creep deformation. Here, the stress applied to the molded body 62 is a force that compresses the molded body 62 along the longitudinal direction of the molded body 62. Further, it is assumed that the strain rate of the molded body 62 is constant regardless of time. Next, a method for determining the creep characteristic parameter will be described.

  First, the temperature dependent change of the molded body 62 of the strain rate of the molded body 62 under the condition that the stress applied to the molded body 62 is constant is measured. FIG. 7 is an example of a graph of a temperature-dependent change in the strain rate of the molded body 62. In FIG. 7, the magnitude of the stress applied to the molded body 62 is 2.0 MPa. The strain rate of the molded body 62 is calculated, for example, by measuring the amount of change in the shape of the molded body 62 by a four-point bending test of the molded body 62. In FIG. 7, the measured value of the strain rate of the molded body 62 is indicated by a black circle.

  Next, the stress-dependent change applied to the molded body 62 of the strain rate of the molded body 62 under the condition that the temperature of the molded body 62 is constant is measured. FIG. 8 is an example of a graph of a stress-dependent change in the strain rate of the molded body 62. In FIG. 8, the temperature of the molded body 62 is 1250 ° C. The strain rate of the molded body 62 is calculated, for example, by measuring the amount of change in the shape of the molded body 62 by laser measurement. In FIG. 8, the measured value of the strain rate of the molded body 62 is indicated by a black circle.

  Next, based on the following formula (1), creep characteristic parameters A, B, and n that can reproduce the measured values of the temperature-dependent change and the stress-dependent change of the strain rate of the molded body 62 are determined.

式（１）において、Ｒは８．３１４［Ｊ／ｍｏｌ・Ｋ］であり、ΔＨは４．５００×１０⁵［Ｊ／ｍｏｌ］であり、ε´は成形体６２の歪み速度［／ｈｏｕｒ］であり、σは成形体６２に加えられる応力［Ｐａ］であり、Ｔは成形体６２の温度［Ｋ］である。クリープ特性パラメータＡ［／ｈｏｕｒ］、Ｂ［／Ｐａ］およびｎは、式（１）により求められる歪み速度が、歪み速度の測定値にフィッティングするように決定される。図７および図８では、決定されたクリープ特性パラメータに基づいて式（１）から算出された成形体６２の歪み速度は、白抜きの四角で示されている。なお、図７および図８で用いられたクリープ特性パラメータＡ，Ｂ，ｎは、それぞれ、８．６４８×１０¹²［／ｈｏｕｒ］、４．４９１×１０^-9［／Ｐａ］、９．９８７×１０^-1である。

In the formula (1), R is 8.314 [J / mol · K], ΔH is 4.500 × 10 ⁵ [J / mol], and ε ′ is the strain rate [/ hour] of the molded body 62. Σ is the stress [Pa] applied to the molded body 62, and T is the temperature [K] of the molded body 62. Creep characteristic parameters A [/ hour], B [/ Pa] and n are determined so that the strain rate obtained by equation (1) fits the measured strain rate. 7 and 8, the strain rate of the molded body 62 calculated from the formula (1) based on the determined creep characteristic parameter is indicated by a white square. The creep property parameters A, B, and n used in FIGS. 7 and 8 are 8.648 × 10 ¹² [/ hour], 4.491 × 10 ⁻⁹ [/ Pa], and 9.987 ×, respectively. 10 ^-1 .

  The acquisition unit may verify the creep characteristic parameter after determining the creep characteristic parameter. The verification of the creep characteristic parameter is performed, for example, by modeling a strain rate measurement system of the molded body 62 and confirming by computer simulation whether or not the strain rate based on the determined creep characteristic parameter is obtained. .

  Then, the acquisition unit calculates the strain rate of the molded body 62 under a predetermined temperature and stress by using the determined creep characteristic parameter by computer simulation, and obtains the time change of the shape of the molded body 62. The shape data of the body 62 is acquired.

  FIG. 6 is an example of the shape data of the molded body 62 acquired by the acquisition unit. FIG. 6 shows the formed body 62 viewed along a direction perpendicular to the surface of the glass ribbon 3 formed by the formed body 62. In FIG. 6, the creep deformation of the molded body 62 is shown more emphasized than actual. In FIG. 6, the shape of the unused green body 62, that is, the shape of the green body 62 before creep deformation is indicated by a dotted line, and the current shape of the green body 62 after creep deformation is indicated by a solid line. ing.

  The acquisition unit acquires at least an upper surface displacement amount that is a vertical displacement amount of the upper surface 62c of the molded body 62 from the shape data based on the creep deformation of the molded body 62. In FIG. 6, the upper surface displacement amount is a vertical dimension between the upper surface 62c before creep deformation and the upper surface 62c after creep deformation. FIG. 6 shows a maximum upper surface displacement amount L that is the maximum value of the upper surface displacement amount in the longitudinal direction of the molded body 62.

  The calculation unit calculates the conveyance speed of the glass ribbon 3 in the slow cooling space 80 based on the shape data of the molded body 62 acquired by the acquisition unit so that the thickness deviation in the width direction of the glass ribbon 3 is reduced. . The smaller the thickness deviation in the width direction of the glass ribbon 3, the more uniform the thickness of the glass ribbon 3 in the width direction. Specifically, the calculation unit calculates a larger value as the conveyance speed of the glass ribbon 3 as the maximum upper surface displacement amount L is larger.

  Moreover, a conveyance part adjusts the rotational speed of each pulling roll 82a-82g based on the conveyance speed of the glass ribbon 3 calculated by the calculation part. Thereby, a conveyance part adjusts the conveyance speed of the glass ribbon 3 to the value calculated by the calculation part.

  The control device 91 can reduce the plate thickness deviation in the width direction of the glass ribbon 3 conveyed downward in the slow cooling space 80 by the conveyance unit, the acquisition unit, and the calculation unit.

(5) Features In this embodiment, the molded body 62 is installed in a high-temperature atmosphere in the upper molding space 60. In the molding process of the glass ribbon 3, a load is applied to the molded body 62 due to the weight of the molded body 62 and the weight of the molten glass 2 supplied to the supply groove 62b. Therefore, as the glass substrate manufacturing apparatus 1 is operated for many years, the molded body 62 gradually creep-deforms due to the thermal creep characteristics of the material of the molded body 62 as shown in FIG. In particular, the central portion in the longitudinal direction of the molded body 62 is likely to bend and hang down due to creep deformation. In FIG. 6, the maximum upper surface displacement amount L is the upper surface displacement amount at the center portion in the longitudinal direction of the molded body 62.

  When the molded body 62 is creep-deformed as shown in FIG. 6, the amount of the molten glass 2 overflowing from the center portion in the longitudinal direction of the molded body 62 causes the molten glass 2 overflowing from both ends in the longitudinal direction of the molded body 62. More than the amount. In this case, the thickness of the center portion in the width direction of the glass ribbon 3 formed by the molded body 62 increases, and the thickness of the center portion in the width direction of the glass ribbon 3 becomes larger than the thickness of both end portions in the width direction. As a result, the thickness deviation in the width direction of the glass ribbon 3 increases, and the thickness deviation of the glass substrate that is the final product may increase.

  The glass substrate manufacturing apparatus 1 of the present embodiment is caused by creep deformation of the formed body 62 by adjusting the rotation speed of the pulling rolls 82a to 82g and adjusting the conveyance speed of the glass ribbon 3 in the slow cooling space 80. The thickness deviation in the width direction of the glass ribbon 3 to be performed can be reduced. Next, the mechanism will be described.

  First, the acquisition part of the control apparatus 91 of the glass substrate manufacturing apparatus 1 acquires the shape data regarding the current shape of the molded body 62 that is creep-deformed as shown in FIG. Next, the calculation unit of the control device 91 has a minimum thickness deviation in the width direction of the glass ribbon 3 conveyed downward in the slow cooling space 80 based on the shape data of the molded body 62 acquired by the acquisition unit. Such a conveyance speed of the glass ribbon 3 is calculated. Specifically, the calculation unit calculates the conveyance speed of the glass ribbon 3 based on the maximum upper surface displacement amount L shown in FIG. Next, the conveyance part of the control apparatus 91 adjusts the rotational speed of each pulling roll 82a-82g so that the conveyance speed computed by the calculation part is implement | achieved. Thereby, the control apparatus 91 adjusts the conveyance speed of the glass ribbon 3 in the slow cooling space 80 based on the shape data of the molded object 62 which is creep-deforming. FIG. 9 is a graph showing the relationship between the maximum upper surface displacement amount L of the molded body 62 that is creep-deformed and the conveyance speed of the glass ribbon 3. As shown in FIG. 9, the control device 91 adjusts the conveyance speed of the glass ribbon 3 by increasing the rotational speed of each of the pulling rolls 82 a to 82 g as the maximum upper surface displacement amount L of the molded body 62 is larger. There is a correlation (linear relationship) between the maximum upper surface displacement amount L of the molded body 62 and the conveyance speed of the glass ribbon 3.

  Next, the reason why the conveyance speed calculated by the calculation unit increases as the maximum upper surface displacement amount L of the molded body 62 undergoing creep deformation increases. As described above, as the maximum upper surface displacement amount L is larger, the thickness of the central portion in the width direction of the glass ribbon 3 tends to be larger than the thickness of both end portions in the width direction. In this case, if the rotational speed of each pulling roll 82a-82g is raised and the conveyance speed of the glass ribbon 3 in the slow cooling space 80 is enlarged, the cooling speed of the glass ribbon 3 in the slow cooling space 80 will increase, and it will be perpendicular | vertical direction (glass The shrinkage amount of the glass ribbon 3 in the flow direction of the ribbon 3 also increases. In the central portion of the glass ribbon 3 in the width direction, which is the portion having the largest thickness in the width direction, the shrinkage amount of the glass ribbon 3 is maximized. By contraction in the vertical direction at the center in the width direction of the glass ribbon 3, tension in the width direction acts from the center in the width direction of the glass ribbon 3 toward both ends in the width direction. As a result, the thickness of both ends in the width direction of the glass ribbon 3 is increased, and the difference between the thickness of the center portion in the width direction of the glass ribbon 3 and the thickness of both ends in the width direction is decreased.

  Therefore, when the central portion in the longitudinal direction of the molded body 62 hangs downward and bends due to creep deformation of the molded body 62, by increasing the conveyance speed of the glass ribbon 3 in the slow cooling space 80, The thickness deviation in the width direction can be reduced. As a result, the glass substrate manufacturing apparatus 1 can reduce the thickness deviation of the glass substrate that is the final product.

  Further, in a glass substrate manufacturing process using glass having a high liquidus temperature and glass having a high strain point, creep deformation of the molded body 62 is particularly problematic because the temperature of the molded body 62 tends to increase. In recent years, the size of the glass substrate has been increased, and the size of the molded body in the longitudinal direction has become longer. Therefore, the bending of the molded body 62 due to creep deformation tends to become more prominent. In the present embodiment, the width of the glass ribbon 3 caused by creep deformation of the molded body 62 is adjusted by adjusting the rotation speed of each pulling roll 82a to 82g and adjusting the conveyance speed of the glass ribbon 3 in the slow cooling space 80. The thickness deviation in the direction can be effectively reduced.

(6) Modification (6-1) Modification A
In the embodiment, the acquisition unit of the control device 91 of the glass substrate manufacturing apparatus 1 acquires shape data related to the current shape of the molded body 62 by obtaining a temporal change in the shape of the molded body 62 by computer simulation. However, the acquisition unit may acquire shape data related to the current shape of the molded body 62 by another method.

  For example, the acquisition unit may acquire shape data based on an actual measurement value of the shape of the molded body 62. In this case, it is necessary to collect and analyze data related to the actual measurement value of the shape of the molded body 62 and data related to the usage conditions of the molded body 62 in advance. The usage conditions of the molded body 62 are various parameters related to the molded body 62, such as the operating time of the glass substrate manufacturing apparatus 1, the temperature of the molten glass 2, the viscosity of the molten glass 2, and the temperature of the upper molding space 60. is there. The acquisition unit predicts and acquires the shape data of the molded body 62 currently used based on the correlation between the data related to the actual measurement value of the shape of the molded body 62 and the data related to the use conditions of the molded body 62.

  Further, the acquisition unit may acquire shape data based on an actual measurement value of the thickness of the glass ribbon 3 formed by the formed body 62. In this case, the acquisition unit predicts and acquires the shape data of the molded body 62 currently used based on the data regarding the measured value of the thickness of the glass ribbon 3 in the width direction.

(6-2) Modification B
In the embodiment, the controller 91 of the glass substrate manufacturing apparatus 1 adjusts the conveyance speed of the glass ribbon 3 in the slow cooling space 80 by adjusting the rotation speeds of the pulling rolls 82a to 82g. However, the control device 91 may adjust the rotation speed of each of the pulling rolls 82a to 82g and adjust the amount of the molten glass 2 supplied to the supply groove 62b of the molded body 62.

  If the conveyance speed of the glass ribbon 3 in the slow cooling space 80 is made high, the thickness of the glass ribbon 3 shape | molded by the molded object 62 will become small. On the other hand, when the amount of the molten glass 2 supplied to the supply groove 62b of the molded body 62 is increased, the thickness of the glass ribbon 3 molded by the molded body 62 increases. Therefore, the control device 91 is molded by the molded body 62 by increasing the rotation speed of each of the pulling rolls 82a to 82g and increasing the amount of the molten glass 2 supplied to the supply groove 62b of the molded body 62. While maintaining the thickness of the glass ribbon 3, an increase in the thickness deviation in the width direction of the glass ribbon 3 due to the creep deformation of the molded body 62 can be suppressed.

(6-3) Modification C
In the embodiment, the calculation unit of the control device 91 of the glass substrate manufacturing apparatus 1 uses the maximum upper surface displacement amount L shown in FIG. 6 as the shape data of the molded body 62, and the larger the maximum upper surface displacement amount L, the larger the glass ribbon 3. A larger value is calculated as the transport speed. However, the calculation unit may calculate the conveyance speed of the glass ribbon 3 using other parameters related to the shape data of the molded body 62.

  For example, the calculation unit uses the glass ribbon as a parameter related to the shape data of the molded body 62 based on the curvature of the upper surface 62c or the lower end 62a of the molded body 62 when viewed along the direction perpendicular to the surface of the glass ribbon 3. 3 may be calculated. For example, as the curvature of the upper surface 62c or the lower end 62a of the molded body 62 is larger, the calculating unit calculates a larger value as the conveyance speed of the glass ribbon 3 because the bent amount of the molded body 62 due to creep deformation is larger.

2 Molten glass 3 Glass ribbon 62 Molded body 62a Lower end 62b Supply groove 62c Upper surface 82a-82g Pulling roll (roll)

U.S. Pat. No. 3,338,696

Claims (5)

The molten glass is supplied to a supply groove formed on the upper surface of the molded body, the molten glass overflowing from both sides of the supply groove is caused to flow down along both side surfaces of the molded body, and the molten glass is flowed down on both side surfaces. A molding step of forming a glass ribbon by joining glass at the lower end of the molded body; and
Using a roll installed below the molded body, a conveyance step of conveying the glass ribbon molded in the molding step downward at a predetermined conveyance speed;
An acquisition step of acquiring shape data relating to the shape of the molded body;
Based on the shape data acquired in the acquisition step, the calculation step of calculating the transport speed so that the thickness deviation in the width direction of the glass ribbon is reduced,
An adjusting step of adjusting the transport speed of the glass ribbon so as to be the transport speed calculated in the calculation step;
A method for producing a glass substrate. The acquisition step acquires the shape data based on creep deformation of the molded body.
The manufacturing method of the glass substrate of Claim 1. The acquisition step acquires at least a vertical displacement amount of the upper surface of the molded body as the shape data,
The calculation step calculates a larger value as the transport speed as the displacement amount is larger.
The manufacturing method of the glass substrate of Claim 2. The conveyance step conveys the glass ribbon while gradually cooling using the rolls sandwiching both end portions in the width direction of the glass ribbon, and the rotation speed of the roll is based on the conveyance speed calculated in the calculation step. To control the
The manufacturing method of the glass substrate of any one of Claim 1 to 3. The obtaining step obtains the shape data by obtaining a time change of the shape by computer simulation,
The manufacturing method of the glass substrate of any one of Claim 1 to 4.

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