TWI705943B - Manufacturing method of glass substrate - Google Patents

Abstract

The object of the present invention is to provide a method for manufacturing a glass substrate that can reduce the thickness deviation of the glass substrate. The manufacturing method of a glass substrate has a shaping|molding process, a conveyance process, an acquisition process, a calculation process, and an adjustment process. The forming step is to supply molten glass to the supply groove formed on the upper surface of the molded body, so that the molten glass overflowing from both sides of the supply groove flows down the two sides of the molded body, and merges the molten glass at the lower end of the molded body And forming the glass ribbon. The conveying step uses a roller set below the forming body to convey the glass ribbon formed in the forming step downward at a specific conveying speed. The obtaining step is to obtain shape data related to the shape of the formed body. The calculation step is based on the shape data acquired in the acquisition step to calculate the conveying speed so that the thickness deviation in the width direction of the glass ribbon becomes smaller. The adjustment step is to adjust the transport speed of the glass ribbon so as to be the transport speed calculated in the calculation step.

Description

Manufacturing method of glass substrate

The invention relates to a manufacturing method of a glass substrate.

Glass substrates used in flat panel displays (FPD) such as liquid crystal displays and plasma displays require high flatness on the surface. Generally, such glass substrates are manufactured by the overflow down-draw method. In the overflow down-draw method, as described in Patent Document 1 (U.S. Patent No. 3,338,696), the molten glass that flows into the groove on the upper surface of the molded body and overflows from the groove flows down through both sides of the molded body and is formed The lower end of the body merges to form a glass ribbon. The formed glass ribbon is stretched downward while being slowly cooled. The cooled glass ribbon is cut into a specific size to obtain a glass substrate.

In the overflow down-draw method, the formed body is placed under a high temperature atmosphere in the forming furnace. In addition, a load due to the weight of the dead weight and the molten glass is applied to the molded body. Therefore, due to the long-term operation of the glass substrate manufacturing device, the formed body gradually creeps and deforms due to the thermal creep characteristics of the material of the formed body. In particular, the central portion in the longitudinal direction of the molded body is likely to sag downward and bend due to creep deformation. As a result, there is a problem that the amount of molten glass that overflows from the center of the molded body becomes larger than the amount of molten glass that overflows from both ends of the molded body, and the thickness of the center portion in the width direction of the molded glass ribbon increases. The thickness deviation of the glass substrate of the final product increases.

The creep deformation of the formed body is when using glass with a higher liquidus temperature and a higher strain point In the manufacturing steps of the glass substrate of the glass, the temperature of the molded body tends to increase, which becomes a problem in particular. In addition, in recent years, with the increase in the size of glass substrates, the dimensions of the molded body in the longitudinal direction have been continuously increasing, and therefore, the bending of the molded body due to creep deformation tends to become significant.

Therefore, the object of the present invention is to provide a method for manufacturing a glass substrate capable of reducing the thickness deviation of the glass substrate.

The manufacturing method of the glass substrate of this invention has a shaping|molding process, a conveyance process, an acquisition process, a calculation process, and an adjustment process. The forming step is to supply molten glass to the supply groove formed on the upper surface of the molded body, so that the molten glass overflowing from both sides of the supply groove flows down along the two sides of the molded body, and the molten glass that flows down on both sides is formed The lower end of the body merges to form a glass ribbon. The conveying step uses rollers arranged below the forming body to convey the glass ribbon formed in the forming step downward at a specific conveying speed. The obtaining step is to obtain shape data related to the shape of the formed body. The calculation step is based on the shape data acquired in the acquisition step to calculate the conveying speed so that the thickness deviation in the width direction of the glass ribbon is reduced. The adjustment step is to adjust the transport speed of the glass ribbon so that it becomes the transport speed calculated in the calculation step.

Furthermore, in the manufacturing method of the glass substrate of the present invention, it is preferable that the obtaining step is to obtain shape data based on the creep deformation of the formed body.

Furthermore, in the manufacturing method of the glass substrate of the present invention, it is preferable that the obtaining step is to obtain at least the amount of displacement in the vertical direction of the upper surface of the molded body as the shape data. In this case, it is preferable that the larger the calculated step shift amount, the larger the calculated value is used as the transport speed.

Furthermore, in the method of manufacturing the glass substrate of the present invention, it is preferable that the conveying step is carried out by using rollers that hold the two ends of the glass ribbon in the width direction, while slowly cooling the glass ribbon, based on the calculation step The conveying speed calculated in the control roller rotation speed.

Furthermore, in the manufacturing method of the glass substrate of the present invention, it is preferable that the obtaining step is to obtain the time change of the shape of the molded body by computer simulation, thereby obtaining the shape data.

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

1‧‧‧Glass substrate manufacturing equipment

2‧‧‧Molten glass

3‧‧‧Glass ribbon

10‧‧‧Melt Tank

20‧‧‧Clarification tube

30‧‧‧Stirring device

40‧‧‧Forming device

50a‧‧‧Transfer tube

50b‧‧‧Transfer tube

50c‧‧‧Transfer tube

60‧‧‧Upper forming space

62‧‧‧Form

62a‧‧‧Bottom

62b‧‧‧Supply groove

62c‧‧‧Upper surface

64‧‧‧Upper partition member

70‧‧‧Lower forming space

72‧‧‧Cooling Roll

74‧‧‧Temperature control unit

74a‧‧‧Central cooling unit

74b‧‧‧Side cooling unit

76‧‧‧Lower partition member

80‧‧‧Xuleng Space

82a‧‧‧Down roller (roller)

82b‧‧‧Down roller (roller)

82c‧‧‧Down roller (roller)

82d‧‧‧Down roller (roller)

82e‧‧‧Down roller (roller)

82f‧‧‧Down roller (roller)

82g‧‧‧Down roller (roller)

84a‧‧‧Heater

84b‧‧‧Heater

84c‧‧‧Heater

84d‧‧‧Heater

84e‧‧‧Heater

84f‧‧‧heater

84g‧‧‧Heater

86‧‧‧Insulation component

91‧‧‧Control device

98‧‧‧Cutting device

172‧‧‧Cooling roller drive motor

182‧‧‧Down roller drive motor

198‧‧‧Cutting device drive motor

S1‧‧‧Step

S2‧‧‧Step

S3‧‧‧Step

S4‧‧‧Step

S5‧‧‧Step

S6‧‧‧Step

L‧‧‧Maximum upper surface displacement

Fig. 1 is a flow chart of the manufacturing method of the glass substrate of the embodiment.

Fig. 2 is a schematic diagram of a manufacturing device of a glass substrate.

Figure 3 is a front view of the forming device.

Figure 4 is a side view of the forming device.

Figure 5 is a block diagram of the control device.

Fig. 6 is an example of the shape data of the formed body obtained by the obtaining unit.

Fig. 7 is an example of the temperature-dependent change curve of the strain rate of the formed body.

Figure 8 is an example of the stress-dependent change curve of the strain rate of the formed body.

Fig. 9 is a graph showing the relationship between the maximum displacement of the upper surface of the formed body and the conveying speed of the glass ribbon.

(1) Composition of glass substrate manufacturing equipment

With reference to the drawings, the embodiment of the manufacturing method of the glass substrate of the present invention will be described. Fig. 1 is a flowchart showing an example of a method of manufacturing a glass substrate of this embodiment.

As shown in FIG. 1, the manufacturing method of the glass substrate of this embodiment mainly includes melting step S1, clarification step S2, stirring step S3, forming step S4, cooling step S5, and cutting step S6.

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

In the clarification step S2, the molten glass obtained in the melting step S1 flows inside the clarification pipe to remove the gas contained in the molten glass, thereby clarifying the molten glass. First, in the clarification step S2, the temperature of the molten glass is increased. The clarifier added to the molten glass causes a reduction reaction due to the temperature rise, releasing oxygen. The bubbles containing CO ₂ , N ₂ , SO ₂ and other gas components contained in the molten glass absorb the oxygen generated by the reduction reaction of the clarifier. The bubble that has grown by absorbing oxygen floats to the surface of the molten glass, breaks the bubble and is eliminated. The gas contained in the eliminated bubbles is released into the gas phase space inside the clarification tube and discharged to the outside atmosphere. Then, in the clarification step S2, the temperature of the molten glass is lowered. Thereby, the reduced clarifying 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 degassed in the clarification step S2 is stirred to homogenize the components of the molten glass. Thereby, the uneven composition of molten glass, which causes the texture of the glass substrate, etc., is reduced.

In the forming step S4, the glass ribbon is continuously formed from the molten glass homogenized in the stirring step S3 using the overflow down-draw method.

In the cooling step S5, the glass ribbon formed in the forming step S4 is conveyed downward while being cooled. In the cooling step S5, the glass ribbon is gradually cooled while adjusting the temperature of the glass ribbon in such a way that the glass ribbon does not produce strain and warpage.

In the cutting step S6, the glass ribbon cooled in the cooling step S5 is cut into a specific size to obtain a glass substrate. After that, grinding and polishing of the end face of the glass substrate and cleaning of the glass substrate are performed. After that, the glass substrate is inspected for defects such as damage, and the glass substrates that pass the inspection are packaged and shipped as products.

FIG. 2 is a schematic diagram showing an example of the glass substrate manufacturing apparatus 1 of this embodiment. The glass substrate manufacturing apparatus 1 includes a melting tank 10, a clarification pipe 20, a stirring device 30, a forming device 40, and transfer pipes 50a, 50b, and 50c. The transfer pipe 50 a connects the melting tank 10 and the clarification pipe 20. The transfer pipe 50b connects the clarification pipe 20 and the stirring device 30. The transfer pipe 50c connects the stirring device 30 and the forming device 40.

The molten glass 2 obtained by the melting tank 10 in the melting step S1 flows into the clarification pipe 20 through the transfer pipe 50a. The molten glass 2 clarified by the clarification pipe 20 in the clarification step S2 flows into the stirring device 30 through the transfer pipe 50b. The molten glass 2 stirred by the stirring device 30 in the stirring step S3 flows into the forming device 40 through the transfer pipe 50c. In the forming step S4, the glass ribbon 3 is continuously formed from the molten glass 2 by the forming device 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 specific 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 for glass substrates for flat panel displays (FPD) such as liquid crystal displays, plasma displays, and organic EL displays. As the glass substrate for FPD, alkali-free glass, glass containing a small amount of alkali, glass for low temperature polysilicon (LTPS), or glass for oxide semiconductor is used. As a glass substrate for high-definition displays, glass with higher viscosity and higher strain point at high temperature is used. For example, glass used as a raw material for glass substrates for high-definition displays has a viscosity of 10 ^2.5 poise at 1500°C.

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

In addition, as a glass substrate for FPD, a trace alkali-containing glass containing a trace amount of alkali metal can also be used. Trace amounts of glass-containing base containing 0.1 mass% to 0.5 mass% of R _'2 O, is preferably 0.2 mass% to 0.5 mass% of R' ₂ O. Here, R'is at least one selected from Li, Na, and K. R _'2 O of the total content may also be less than 0.1% by mass.

In addition, the glass substrate manufactured by the glass substrate manufacturing apparatus 1 may further contain SnO ₂ : 0.01% by mass to 1% by mass (preferably 0.01% by mass to 0.5% by mass), Fe ₂ O ₃ : 0% by mass to 0.2 Mass% (preferably 0.01% by mass to 0.08% by mass). Furthermore, the glass substrate manufactured by the glass substrate manufacturing apparatus 1 does not substantially contain As ₂ O ₃ , Sb ₂ O ₃ and PbO from the viewpoint of reducing the burden on the environment.

The glass raw material prepared to have the above-mentioned composition is charged into the melting tank 10 using a raw material feeder (not shown). The raw material feeder can use a screw feeder to feed glass raw materials, or use a bucket to feed glass raw materials. In the melting tank 10, the glass raw material is heated to a temperature corresponding to the composition and the like to melt. In the melting tank 10, a high-temperature molten glass 2 of, for example, 1500°C to 1600°C is obtained. In the melting tank 10, the molten glass 2 between the electrodes can be energized and heated by passing an electric current between at least one pair of electrodes formed of molybdenum, platinum, or tin oxide. In addition, it can also be heated by burning. The flame of the device assists in heating the glass material.

The molten glass 2 obtained in the melting tank 10 flows into the clarification pipe 20 from the melting tank 10 through the transfer pipe 50a. The clarification pipe 20 and the transfer pipes 50a, 50b, and 50c are pipes made of platinum or platinum alloy. The clarification pipe 20 is provided with a heating mechanism similarly to the melting tank 10. In the clarification pipe 20, the molten glass 2 is further heated up and 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 pipe 20 flows into the stirring device 30 from the clarification pipe 20 through the transfer pipe 50b. The molten glass 2 is cooled while passing through the transfer pipe 50b. In the stirring device 30, the molten glass 2 is stirred at a temperature lower than the temperature of the molten glass 2 passing through the clarification pipe 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 by the stirring device 30 to be homogenized.

The molten glass 2 homogenized in the stirring device 30 passes through the transfer pipe 50c from the stirring device 30 And flow into the forming device 40. When the molten glass 2 passes through the transfer pipe 50c, it is cooled to have a viscosity suitable for the molding of the molten glass 2. For example, molten glass 2 is cooled to about 1200 degreeC.

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

(2) The composition of the forming device

FIG. 3 is a front view of the forming device 40. FIG. 3 shows the forming device 40 viewed along the direction perpendicular to the surface of the glass ribbon 3 formed by the forming device 40. FIG. 4 is a side view of the forming device 40. FIG. 4 shows the forming device 40 viewed in a direction parallel to the surface of the glass ribbon 3 formed by the forming device 40.

The forming device 40 has a space enclosed by a furnace wall (not shown) containing refractory materials such as refractory bricks. This space is for forming the glass ribbon 3 from the molten glass 2 and cooling the glass ribbon 3. This space is composed of three spaces: the upper forming space 60, the lower forming space 70, and the cooling space 80.

The forming step S4 is performed in the upper forming space 60. The cooling step S5 is performed in the lower forming space 70 and the slow cooling space 80. The upper forming space 60 is a space for forming the molten glass 2 supplied from the stirring device 30 to the forming device 40 via the transfer pipe 50c into the glass ribbon 3. The lower forming space 70 is a space below the upper forming space 60, and is a space for the glass ribbon 3 to be rapidly cooled to about the cooling point of the glass. The Xu Leng space 80 is a space below the lower forming space 70 and is a space for the glass ribbon 3 to gradually cool down.

The forming device 40 mainly includes a formed body 62, an upper partition member 64, a cooling roller 72, a temperature adjustment unit 74, a lower partition member 76, a pull-down roller 82a to 82g, a heater 84a to 84g, a heat insulating member 86, a cutting device 98, And control device 91. Next, each constituent element of the molding device 40 will be described.

(2-1) Formed body

The molded body 62 is provided in the upper molding space 60. The formed body 62 is used to overflow the molten glass 2 Flow and shape the glass ribbon 3. As shown in FIG. 4, the formed body 62 has a cross-sectional shape of a pentagon similar to a wedge. The tip 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 50c communicating with the supply groove 62b 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 from the stirring device 30 to the forming device 40 flows into the supply groove 62b of the forming body 62 through the transfer pipe 50c. The molten glass 2 overflowing from the supply groove 62b of the molded body 62 flows down while passing through both side surfaces of the molded body 62, and merges near the lower end 62a of the molded body 62. The merged molten glass 2 falls in a vertical direction due to gravity, and is shaped into a plate shape. Thereby, the glass ribbon 3 is continuously formed in the vicinity of the lower end 62a of the molded body 62. After the formed glass ribbon 3 flows down in the upper forming space 60, it is conveyed downward while being cooled in the lower forming space 70 and the slow cooling space 80. The temperature of the glass ribbon 3 just after being formed in the upper forming space 60 is above 1100°C, and the viscosity is 25000 poise to 350000 poise. For example, in the case of manufacturing glass substrates for high-definition displays, the strain point of the glass ribbon 3 formed from the molded body 62 is 655°C to 750°C, preferably 680°C to 730°C, near the lower end 62a of the molded body 62 The viscosity of the fused molten glass 2 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-shaped heat insulating members provided near the lower end 62a of the molded body 62. As shown in FIG. 4, the upper partition members 64 are arranged 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 to suppress 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 forming space 70. The cooling roller 72 is arranged at Right below the upper partition member 64. As shown in FIG. 3, the cooling roll 72 is arrange|positioned at the both sides of the width direction of the glass ribbon 3. As shown in FIG. As shown in FIG. 4, the cooling rolls 72 are arranged on both sides of the glass ribbon 3 in the thickness direction. The glass ribbon 3 is clamped by the cooling roller 72 at the both sides of the width direction. The cooling roller 72 cools the glass ribbon 3 sent from the upper forming space 60.

In the lower forming space 70, both sides of the glass ribbon 3 in the width direction are clamped by two pairs of cooling rolls 72, respectively. By pressing the cooling roller 72 toward the surfaces of both sides of the glass ribbon 3, the contact area between the cooling roller 72 and the glass ribbon 3 becomes larger, and the glass ribbon 3 is efficiently cooled by the cooling roller 72. The cooling roll 72 applies to the glass ribbon 3 a force which opposes the force which pulls the glass ribbon 3 downward by the pull-down rolls 82a-82g mentioned later. Furthermore, the thickness of the glass ribbon 3 is determined based on the difference between the rotation speed of the cooling roll 72 and the rotation speed of the pull-down roll 82a disposed at the top.

The cooling roller 72 has an air cooling pipe inside. The cooling roller 72 is always cooled by the air cooling pipe. The cooling roll 72 is in contact with the glass ribbon 3 by pinching both sides of the glass ribbon 3 in the width direction. Thereby, heat is transferred from the glass ribbon 3 to the cooling roll 72, so the both sides of the width direction of the glass ribbon 3 are cooled. The viscosity of the both sides in the width direction of the glass ribbon 3 cooled by 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 by adjusting the position of the cooling roller 72 using a spring, for example. The greater the contact load, the stronger the force of the cooling roller 72 pressing the glass ribbon 3.

(2-4) Temperature adjustment unit

The temperature adjustment unit 74 is installed in the lower forming space 70. The temperature adjustment unit 74 is disposed below the upper partition member 64 and above the lower partition member 76.

In the lower forming space 70, the glass ribbon 3 is cooled until the temperature of the center part in the width direction of the glass ribbon 3 drops to about a slow cooling 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 for heating or cooling 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. In the width direction of the glass ribbon 3 of the central cooling unit 74a The temperature of the heart is adjusted. The side cooling unit 74b adjusts the temperature of both sides of the glass ribbon 3 in the width direction. Here, the center part in the width direction of the glass ribbon 3 refers to an area sandwiched by both sides of the glass ribbon 3 in the width direction.

In the lower forming space 70, as shown in FIG. 3, a plurality of center portion cooling units 74a and a plurality of side portion cooling units 74b are respectively arranged along the vertical direction in which the glass ribbon 3 flows down. The central part cooling unit 74a is arranged so as to face the surface of the central part of the glass ribbon 3 in the width direction. The side part cooling unit 74b is arrange|positioned so that it may oppose the surface of the both sides of the width direction of the glass ribbon 3.

The temperature adjustment unit 74 is controlled by the control device 91. Each center cooling unit 74a and each side 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-shaped heat insulating members disposed below the temperature adjustment unit 74. As shown in FIG. 4, the lower partition members 76 are provided on both sides of the glass ribbon 3 in the thickness direction. The lower partition member 76 partitions the lower forming space 70 and the slow cooling space 80 in the vertical direction, and suppresses the movement of heat from the lower forming space 70 to the slow cooling space 80.

(2-6) Pull down roller

The pull-down rollers 82a~82g are cantilever rollers installed in the Xu Leng Space 80. In the cold space 80, the pull-down roll 82a, the pull-down roll 82b, ..., the pull-down roll 82f, and the pull-down roll 82g are arranged at intervals from above to below. The pull-down roller 82a is arranged at the top, and the pull-down roller 82g is arranged at the bottom.

As shown in FIG. 3, the pull-down rollers 82a-82g are arrange|positioned at the both sides of the width direction of the glass ribbon 3, respectively. As shown in FIG. 4, the pull-down rollers 82a-82g are respectively arrange|positioned on the both sides of the thickness direction of the glass ribbon 3. That is, the both sides of the width direction of the glass ribbon 3 are pinched|interposed by 2 pairs of pull-down rollers 82a, 2 pairs of pull-down rollers 82b,..., 2 pairs of pull-down rollers 82f, and 2 pairs of pull-down rollers 82g from top to bottom.

The pull-down rollers 82a to 82g rotate while pinching both ends of the glass ribbon 3 in the width direction after passing through the lower forming space 70, thereby pulling the glass ribbon 3 downward in the vertical direction. which is, The pull-down rollers 82a to 82g are rollers for conveying the glass ribbon 3 downward.

The angular velocity of each pull-down roller 82a-82g can be independently controlled by the control device 91. The greater the angular velocity of the pull-down rollers 82a to 82g, the greater the speed at which the glass ribbon 3 is conveyed downward.

(2-7) Heater

The heaters 84a to 84g are installed in the Xu cold space 80. As shown in FIG. 4, in the cool space 80, the heater 84a, the heater 84b,..., the heater 84f, and the heater 84g are arrange|positioned at intervals from the top to the bottom. The heaters 84a to 84g are respectively arranged on both sides of the glass ribbon 3 in the thickness direction. The pull-down rollers 82a to 82g are arranged between the heaters 84a to 84g and the glass ribbon 3, respectively.

The heaters 84a to 84g radiate heat to the surface of the glass ribbon 3 to heat the glass ribbon 3. By using heaters 84a~84g, the temperature of the glass ribbon 3 conveyed downward can be adjusted in the cool space 80. Thereby, the heaters 84a to 84g can form a specific temperature distribution on the glass ribbon 3 in the conveying direction of the glass ribbon 3.

The output of each heater 84a~84g can be independently controlled by the control device 91. In addition, the heaters 84a to 84g may be 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 independently controlled by the control device 91. In this case, each heater 84a to 84g changes the heat generation amount according to the position of the glass ribbon 3 in the width direction, thereby forming a specific temperature distribution in the width direction of the glass ribbon 3.

Furthermore, near each heater 84a to 84g, a thermocouple (not shown) for measuring the ambient temperature of the cool space 80 is installed. The thermocouple measures, for example, the ambient temperature near the center part in the width direction of the glass ribbon 3 and the ambient temperature near both sides. The heaters 84a to 84g may also be controlled based on the ambient temperature of the cool space 80 measured by the thermocouple.

(2-8) Thermal insulation components

The heat insulation member 86 is installed in the Xu cold space 80. The heat insulation member 86 is installed in the height position between the two pull-down rollers 82a-82g adjacent to the conveyance direction of the glass ribbon 3. As shown in FIG. 4, the heat insulating member 86 is a pair of heat insulating plates horizontally arranged on both sides of the glass ribbon 3 in the thickness direction. The heat insulation member 86 partitions the cold space 80 in the vertical direction, and suppresses the heat movement in the vertical direction of the cold space 80.

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

(2-9) Cutting device

The cutting device 98 is installed in the space below the Xu cold space 80. The cutting device 98 cuts the glass ribbon 3 after passing through the slow cooling space 80 along the width direction of the glass ribbon 3 to a specific size. The glass ribbon 3 after passing through the cold space 80 is a flat glass ribbon 3 cooled to about room temperature.

The cutting device 98 cuts the glass ribbon 3 at specific time intervals. Thereby, when the conveying speed of the glass ribbon 3 is fixed, a glass substrate with a size close to the final product can be mass-produced.

(2-10) Control device

The control device 91 is a computer that mainly includes CPU, RAM, ROM, hard disk, etc. 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 roller drive motor 172, a temperature adjustment unit 74, a pull-down roller drive motor 182, heaters 84 a to 84 g, and a cutting device drive motor 198. The cooling roller drive motor 172 is a motor for controlling the position and rotation speed of the cooling roller 72. The pull-down roller drive motor 182 is a motor for independently controlling the position and rotation speed of each pull-down roller 82a to 82g. The cutting device driving motor 198 is a motor for controlling the time interval at which the cutting device 98 cuts the glass ribbon 3 and the like. The control device 91 obtains the state of each constituent element, and stores a program for controlling each constituent element.

The control device 91 can control the cooling roller drive motor 172 to obtain and adjust the contact load between the cooling roller 72 and the glass ribbon 3 on one of the side portions in the width direction clamping the glass ribbon 3. The control device 91 can control the pull-down roller drive motor 182 to obtain the twist of the rotating pull-down rollers 82a~82g Adjust the angular velocity of each pull-down roller 82a~82g. The control device 91 can obtain and adjust the output of the temperature adjustment unit 74 and the output of the heaters 84a to 84g. The control device 91 can control the cutting device drive motor 198 to obtain and adjust the time interval for the cutting device 98 to cut the glass ribbon 3, etc.

(3) Action of forming device

In the upper forming space 60, the molten glass 2 sent from the stirring device 30 to the forming device 40 via the transfer pipe 50c is supplied to the supply groove 62b formed on the upper surface 62c of the formed body 62. The molten glass 2 overflowing from the supply groove 62 b of the formed body 62 flows down through both side surfaces of the formed body 62 and merges near the lower end 62 a of the formed body 62. In the vicinity of the lower end 62a of the formed body 62, the glass ribbon 3 is continuously formed from the merged molten glass 2. The formed glass ribbon 3 is sent to the lower forming space 70.

In the lower forming space 70, the both sides of the width direction of the glass ribbon 3 contact the cooling roll 72, and are quenched. In addition, the temperature of the glass ribbon 3 is adjusted by the temperature adjustment unit 74, so that the temperature of the center part in the width direction of the glass ribbon 3 is lowered to a slow cooling point. The glass ribbon 3 cooled while being transported downward by the cooling roller 72 is sent to the cooling space 80.

In the Xu cold space 80, the glass ribbon 3 is gradually cooled while being pulled down by the pull-down rollers 82a to 82g. The temperature of the glass ribbon 3 is controlled by the heaters 84a~84g in a manner to form a specific temperature distribution along the width direction of the glass ribbon 3. In the cold space 80, the temperature of the glass ribbon 3 starts from about the cold temperature and gradually decreases to a temperature lower than the temperature 200°C lower than the strain point.

The glass ribbon 3 after passing through the slow cooling space 80 is further cooled to about room temperature, and cut into a specific size by the cutting device 98 to obtain a glass substrate. After that, the end surface of the glass substrate is polished and cleaned. After that, the glass substrates that passed the specific inspection are packaged and shipped as products.

(4) Action of control device

The control device 91 memorizes at least 3 programs including the transport unit, the acquisition unit, and the calculation unit. Be executed.

The conveying part uses pull-down rollers 82a to 82g provided below the molded body 62, and conveys the glass ribbon 3 formed by the molded body 62 downward in the slow cooling space 80 at a specific conveying speed. The conveying part controls the pull-down roller drive motor 182 to adjust the rotation speed of each pull-down roller 82a to 82g, thereby adjusting the conveying speed of the glass ribbon 3.

The acquiring unit acquires shape data related to the current shape of the molded body 62. Specifically, the acquisition unit acquires shape data based on creep characteristic parameters. The creep characteristic parameter is a parameter used to reproduce the relationship between the stress applied to the formed body 62, the temperature of the formed body 62, and the strain rate of the formed body 62 caused by the 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. In addition, the strain rate of the molded body 62 is assumed to be fixed regardless of time. Next, the method of determining creep characteristic parameters is explained.

First, the temperature-dependent change of the strain rate of the formed body 62 is measured under the condition that the stress applied to the formed body 62 is constant. FIG. 7 is an example of the temperature-dependent change curve of the strain rate of the formed body 62. In FIG. 7, the magnitude of the stress applied to the formed body 62 is 2.0 MPa. The strain rate of the molded body 62 is calculated by measuring the amount of change in the shape of the molded body 62 in the 4-point bending test of the molded body 62, for example. In FIG. 7, the measured value of the strain rate of the formed body 62 is indicated by black circles.

Then, under the condition that the temperature of the formed body 62 is fixed, the strain rate of the formed body 62 is measured to change depending on the stress applied to the formed body 62. FIG. 8 is an example of the stress-dependent change curve of the strain rate of the formed 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 by measuring, for example, the amount of change in the shape of the molded body 62 measured by laser. In FIG. 8, the measured value of the strain rate of the formed body 62 is indicated by black circles.

Then, based on the following equation (1), the 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.

[Number 1]

In the formula (1), R is 8.314[J/mol‧K], △H is 4.500×10 ⁵ [J/mol], ε'is the strain rate of the formed body 62 [/hour], and σ is the application to the forming The stress [Pa] of the body 62, and T is the temperature [K] of the formed body 62. The creep characteristic parameters A[/hour], B[/Pa] and n are determined in a way that the strain rate obtained by formula (1) matches the measured value of the strain rate. In FIGS. 7 and 8, the strain rate of the formed body 62 calculated from the equation (1) based on the determined creep characteristic parameters is represented by a blank square. Furthermore, the creep characteristic parameters A, B, and n used in Fig. 7 and Fig. 8 are 8.648×10 ¹² [/hour], 4.491×10 ^-9 [/Pa], 9.987×10 ^{-1, respectively} .

Furthermore, the acquiring unit may also verify the creep characteristic parameters after determining the creep characteristic parameters. The verification of the creep characteristic parameters is carried out in the following manner: for example, the measurement system of the strain rate of the formed body 62 is modeled, and computer simulation is used to confirm whether the strain rate based on the determined creep characteristic parameters is obtained.

Then, the acquisition unit uses the determined creep characteristic parameters to calculate the strain rate of the formed body 62 at a specific temperature and stress by computer simulation, and obtains the time change of the shape of the formed body 62, thereby obtaining the shape of the formed body 62 Shape information.

FIG. 6 is an example of the shape data of the formed body 62 acquired by the acquiring unit. FIG. 6 shows the formed body 62 viewed along the direction perpendicular to the surface of the glass ribbon 3 formed by the formed body 62. In FIG. 6, the creep deformation of the formed body 62 is more conspicuously shown. In FIG. 6, the shape of the unused formed body 62, that is, the shape of the formed body 62 before creep deformation, is shown by a broken line, and the current shape of the formed body 62 after creep deformation is shown by a solid line.

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

The calculation part calculates the conveyance speed of the glass ribbon 3 in the slow cooling space 80 so that the thickness deviation of the width direction of the glass ribbon 3 may become small based on the shape data of the molded object 62 acquired by the acquisition part. The smaller the thickness deviation of the glass ribbon 3 in the width direction, the more uniform the thickness of the glass ribbon 3 in the width direction. Specifically, the larger the maximum upper surface displacement amount L of the calculating part system is, the larger the value is calculated as the conveying speed of the glass ribbon 3.

Moreover, the conveyance part adjusts the rotation speed of each pull-down roller 82a-82g based on the conveyance speed of the glass ribbon 3 calculated by the calculation part. Thereby, the 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 thickness deviation in the width direction of the glass ribbon 3 conveyed downward in the slow cooling space 80 by the conveyance part, the acquisition part, and the calculation part.

(5) Features

In this embodiment, the formed body 62 is set in the high temperature atmosphere of the upper forming space 60. In the forming step of the glass ribbon 3, a load due to the weight of the formed body 62 and the weight of the molten glass 2 supplied to the supply groove 62b is applied to the formed body 62. Therefore, due to the long-term operation of the glass substrate manufacturing apparatus 1, as shown in FIG. 6, the molded body 62 gradually creeps and deforms due to the thermal creep characteristics of the material of the molded body 62. In particular, the central portion in the longitudinal direction of the molded body 62 is likely to sag downward due to creep deformation. In FIG. 6, the maximum upper surface displacement amount L is the upper surface displacement amount of the central portion of the molded body 62 in the longitudinal direction.

If the molded body 62 creeps and deforms as shown in FIG. 6, the amount of molten glass 2 overflowing from the center portion of the molded body 62 in the longitudinal direction is more than the molten glass overflowing from both ends of the molded body 62 in the longitudinal direction The amount of 2. In this case, the thickness of the central part in the width direction of the glass ribbon 3 formed by the molded body 62 increases, and the thickness of the central part in the width direction of the glass ribbon 3 becomes larger than the thickness of both ends in the width direction. As a result, the thickness deviation of the width direction of the glass ribbon 3 may become large, and the thickness deviation of the glass substrate which is a final product may increase.

The glass substrate manufacturing apparatus 1 of this embodiment adjusts the rotation speed of the pull-down rollers 82a to 82g, and adjusts the conveying speed of the glass ribbon 3 in the cold space 80, thereby reducing creep deformation caused by the molded body 62 The thickness deviation of the glass ribbon 3 in the width direction. Next, explain its organization.

First, as shown in FIG. 6, the acquisition part of the control device 91 of the glass substrate manufacturing apparatus 1 acquires shape data related to the current shape of the creep-deformed molded body 62. Then, the calculation unit of the control device 91 calculates the glass ribbon 3 that minimizes the 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 Transport speed. Specifically, the calculation part calculates the conveyance speed of the glass ribbon 3 based on the maximum upper surface displacement amount L shown in FIG. Then, the conveyance section of the control device 91 adjusts the rotation speed of each of the pull-down rollers 82a to 82g so as to realize the conveyance speed calculated by the calculation section. Thereby, the control device 91 adjusts the conveying speed of the glass ribbon 3 in the slow cooling space 80 based on the shape data of the formed body 62 of creep deformation. 9 is a graph showing the relationship between the maximum upper surface displacement amount L of the creep-deformed formed body 62 and the conveying speed of the glass ribbon 3. As shown in FIG. 9, the control device 91 adjusts the conveying speed of the glass ribbon 3 so that the larger the maximum upper surface displacement amount L of the molded body 62 is, the more the rotation speed of the pull-down rollers 82a to 82g is increased. There is a correlation (linear relationship) between the maximum upper surface displacement amount L of the molded body 62 and the conveying speed of the glass ribbon 3.

Next, the reason why the larger the maximum upper surface displacement amount L of the creep-deformed molded body 62 is, the larger the conveying speed calculated by the calculation unit is. As described above, the greater the maximum upper surface displacement amount L, the greater the thickness of the center portion in the width direction of the glass ribbon 3 than the thickness of both ends in the width direction. In this case, if the rotation speed of each pull-down roller 82a~82g is increased, and the conveying speed of the glass ribbon 3 in the slow cooling space 80 is increased, the cooling speed of the glass ribbon 3 in the slow cooling space 80 will increase in the vertical direction (The downward direction of the glass ribbon 3) The shrinkage of the glass ribbon 3 also increases. In the part with the largest thickness in the width direction, that is, the central part of the glass ribbon 3 in the width direction, the glass ribbon 3 has the largest shrinkage. Because the center of the glass ribbon 3 in the width direction The contraction in the vertical direction exerts a tension in the width direction from the center of the glass ribbon 3 in the width direction toward the ends in the width direction. As a result, the thickness of the both ends of the width direction of the glass ribbon 3 becomes large, and the difference of the thickness of the center part of the width direction of the glass ribbon 3 and the thickness of the both ends of the width direction becomes small.

Therefore, when the center of the longitudinal direction of the molded body 62 is bent downward due to the creep deformation of the molded body 62, the conveying speed of the glass ribbon 3 in the slow cooling space 80 can be increased to reduce The thickness deviation of the small glass ribbon 3 in the width direction. As a result, the glass substrate manufacturing apparatus 1 can reduce the thickness deviation of the glass substrate as the final product.

In addition, in the manufacturing process of a glass substrate using glass with a higher liquidus temperature and glass with a higher strain point, the creep deformation of the molded body 62 is particularly likely to become a problem because the temperature of the molded body 62 tends to increase. In addition, in recent years, with the increase in the size of the glass substrate, the dimension in the longitudinal direction of the molded body has been continuously increasing, and therefore, the bending of the molded body 62 due to creep deformation tends to become remarkable. In this embodiment, by adjusting the rotation speed of each pull-down roller 82a~82g, and adjusting the conveying speed of the glass ribbon 3 in the cold space 80, the glass caused by the creep deformation of the formed body 62 can be effectively reduced Thickness deviation in the width direction of belt 3.

(6) Variations

(6-1) Variation A

In the embodiment, the acquisition unit of the control device 91 of the glass substrate manufacturing apparatus 1 obtains the time change of the shape of the molded body 62 by computer simulation, thereby obtaining shape data related to the current shape of the molded body 62. However, the obtaining part may also obtain shape data related to the current shape of the molded body 62 by other methods.

For example, the acquiring unit may also acquire shape data based on actual measured values of the shape of the molded body 62. In this case, it is necessary to collect and analyze data related to the actual measured value of the shape of the molded body 62 and data related to the use conditions of the molded body 62 in advance. The use 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 forming space 60. number. The acquiring unit predicts and acquires the shape data of the currently used molded body 62 based on the correlation between the data related to the actual measured value of the shape of the molded body 62 and the data related to the use condition of the molded body 62.

Moreover, the acquisition part may acquire shape data based on the actual measured value of the plate thickness of the glass ribbon 3 molded by the molded body 62. In this case, the acquisition unit predicts and acquires the shape data of the currently used molded body 62 based on the data related to the actual measured value of the thickness of the glass ribbon 3 in the width direction.

(6-2) Variation B

In the embodiment, the control device 91 of the glass substrate manufacturing apparatus 1 adjusts the rotation speed of the pull-down rollers 82a to 82g, and adjusts the conveying speed of the glass ribbon 3 in the cold space 80. However, the control device 91 may also adjust the rotation speed of the respective pull-down rolls 82a to 82g, and adjust the amount of the molten glass 2 supplied to the supply groove 62b of the formed body 62.

If the conveying speed of the glass ribbon 3 in the slow cooling space 80 is increased, the thickness of the glass ribbon 3 formed by the forming body 62 becomes smaller. On the other hand, if the amount of 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 becomes larger. Therefore, the control device 91 increases the rotation speed of the pull-down rolls 82a to 82g, and increases the amount of molten glass 2 supplied to the supply groove 62b of the molded body 62, thereby maintaining the glass ribbon 3 formed by the molded body 62. This thickness suppresses the increase in the thickness deviation of the glass ribbon 3 in the width direction caused by the creep deformation of the molded body 62.

(6-3) Variation 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. The larger the maximum upper surface displacement amount L, the greater The larger value is calculated as the conveying speed of the glass ribbon 3. However, the calculation unit may also use other parameters related to the shape data of the molded body 62 to calculate the conveying speed of the glass ribbon 3.

For example, the calculation part can also be used as a parameter related to the shape data of the formed body 62, based on The curvature of the upper surface 62c or the lower end 62a of the formed body 62 when viewed in the direction perpendicular to the surface of the glass ribbon 3 is used to calculate the conveying speed of the glass ribbon 3. For example, in the calculation section, the greater the curvature of the upper surface 62c or the lower end 62a of the molded body 62, the greater the amount of deflection of the molded body 62 due to creep deformation, so the larger value is calculated as the conveying speed of the glass ribbon 3 .

[Prior Technical Literature]

[Patent Document] US Patent No. 3,338,696

62‧‧‧Form

62a‧‧‧Bottom

62c‧‧‧Upper surface

L‧‧‧Maximum upper surface displacement

Claims (5)

A method of manufacturing a glass substrate, comprising: a forming step of supplying molten glass to a supply groove formed on the upper surface of a molded body, and causing the molten glass overflowing from both sides of the supply groove to follow the molded body The two sides flow down, and the molten glass that flows down on the two sides merges at the lower end of the shaped body to form a glass ribbon; the conveying step is to use rollers arranged below the shaped body at a specific conveying speed The glass ribbon formed in the above forming step is conveyed below; the obtaining step is to obtain shape data related to the shape of the formed body; the calculation step is based on the shape data obtained in the obtaining step, and the glass ribbon is Calculate the conveying speed by reducing the thickness deviation in the width direction; and the adjustment step, which is to adjust the conveying speed of the glass ribbon so as to become the conveying speed calculated in the calculating step; and The step is to obtain the shape data based on the creep deformation of the formed body. The method for manufacturing a glass substrate of claim 1, wherein the obtaining step obtains at least the amount of displacement in the vertical direction of the upper surface of the molded body as the shape data, and the calculation step is that the greater the amount of displacement, then The larger value is calculated as the above-mentioned conveying speed. The method for manufacturing a glass substrate according to claim 1 or 2, wherein the conveying step uses the rollers that clamp the both ends of the glass ribbon in the width direction while slowly cooling the glass ribbon and conveys it based on the calculation step described above The above-mentioned conveying speed calculated in the above controls the rotation speed of the above-mentioned roller. The method for manufacturing a glass substrate of claim 1 or 2, wherein the obtaining step obtains the time change of the shape by computer simulation, thereby obtaining the shape data. The method for manufacturing a glass substrate according to claim 3, wherein the obtaining step obtains the time change of the shape by computer simulation, thereby obtaining the shape data.

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