TW201702193A - Method for manufacturing glass substrate which is capable of reducing the variations in the thickness of the glass substrate - Google Patents

Abstract

The object of the present invention is to provide a method for manufacturing a glass substrate, which is capable of reducing the variations in the thickness of the glass substrate. The method for manufacturing the glass substrate comprises a shaping step, a transferring step, an acquiring step, a calculating step, and an adjusting step. The shaping step is to supply molten glass to a supply trench formed on the upper surface of the molded body such that the molten glass overflowing from two sides of the supply trench flows down along both side surfaces of the molded body, and the molten glass join in the lower end of the molded body to form a glass band. The transferring step is using a roller provided below the molded body to transfer the glass band formed in the shaping step downward at a specific speed. The acquiring step is to acquire the shape data in relation to the shapes of the molded body. The calculating step is, based on the shape data acquired from the acquiring step, to calculate the transferring speed in such a manner as to reduce the thickness deviation along the width direction of the glass band. The adjusting step is using the transferring speed calculated from the calculating step to adjust the transferring speed of the glass band.

Description

Method for manufacturing glass substrate

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

Glass substrates for flat panel displays (FPDs) such as liquid crystal displays and plasma displays require a high degree of flatness on the surface. Usually, such a glass substrate is produced by an overflow down-draw method. In the overflow down-draw method, as described in the patent document 1 (U.S. Patent No. 3,338,696), the molten glass which flows into the groove on the upper surface of the molded body and overflows from the groove flows through both side faces of the molded body, and is formed. The lower ends of the body merge to form a glass ribbon. The formed glass ribbon is stretched while being stretched downward. 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 in a high temperature atmosphere in the forming furnace. Further, the molded body is subjected to a load due to its own weight and the weight of the molten glass. Therefore, due to the long-term operation of the glass substrate manufacturing apparatus, the molded body is gradually deformed and deformed due to the thermal latent property of the material of the molded body. In particular, the central portion of the longitudinal direction of the molded body is likely to sag downward depending on the latent deformation. As a result, there is a problem in that the amount of molten glass that overflows from the central portion of the molded body is larger than the amount of molten glass that overflows from both end portions of the molded body, and the thickness of the central portion in the width direction of the formed glass ribbon increases. The thickness deviation of the glass substrate of the final product increases.

The latent deformation of the shaped body is deformed by using a glass having a higher liquidus temperature and a higher strain point In the manufacturing process of the glass substrate of the glass, the temperature of the molded body is likely to become high, which is particularly problematic. In addition, in recent years, as the size of the glass substrate has increased, the dimension of the longitudinal direction of the molded article has been increasing, and the deflection of the molded body due to the creeping deformation tends to be remarkable.

Accordingly, an object of the present invention is to provide a method for producing a glass substrate which can reduce variation in thickness of a glass substrate.

The method for producing a glass substrate of the present invention includes a molding step, a transporting step, an obtaining step, a calculating step, and an adjusting step. In the forming step, the 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 flows down the both sides of the formed body, so that the molten glass flowing down on both sides is formed. The lower ends of the body merge to form a glass ribbon. In the transporting step, the glass ribbon formed in the forming step is conveyed downward at a specific conveying speed by using a roller provided below the molded body. The obtaining step is to obtain shape data relating to the shape of the formed body. The calculation step is based on the shape data obtained in the acquisition step, and the conveyance speed is calculated such that the variation in the thickness of the glass ribbon in the width direction is reduced. The adjustment step adjusts the conveyance speed of the glass ribbon so as to be the conveyance speed calculated in the calculation step.

Further, in the method for producing a glass substrate of the present invention, preferably, the obtaining step is to obtain shape data based on the latent deformation of the molded body.

Further, in the method for producing a glass substrate of the present invention, preferably, the obtaining step is to obtain at least a shift amount in the vertical direction of the upper surface of the molded body as shape data. In this case, it is preferable that the larger the calculation amount is, the larger the value is calculated as the transport speed.

Further, in the method for producing a glass substrate of the present invention, it is preferable that the transport step is carried out by using a roll that sandwiches both end portions in the width direction of the glass ribbon, and the glass ribbon is conveyed while being cold, and based on the calculation step. The rotation speed of the conveyance speed control roller calculated in the middle.

Further, in the method for producing a glass substrate of the present invention, preferably, the obtaining step is to obtain shape data by obtaining a temporal change in the shape of the molded body by computer simulation.

The method for producing a glass substrate of the present invention can reduce the variation in thickness of the glass substrate.

1‧‧‧Glass substrate manufacturing equipment

2‧‧‧Solid glass

3‧‧‧glass ribbon

10‧‧‧melting tank

20‧‧‧clarification tube

30‧‧‧Agitator

40‧‧‧Forming device

50a‧‧‧Transfer tube

50b‧‧‧Transfer tube

50c‧‧‧Transfer tube

60‧‧‧Upper forming space

62‧‧‧Formed body

62a‧‧‧Bottom

62b‧‧‧ supply trough

62c‧‧‧ upper surface

64‧‧‧Upper partition member

70‧‧‧ Lower forming space

72‧‧‧Cooling roller

74‧‧‧temperature adjustment unit

74a‧‧‧Central cooling unit

74b‧‧‧Side cooling unit

76‧‧‧Lower partition member

80‧‧‧Xu cold space

82a‧‧‧ Pull-down roller (roller)

82b‧‧‧ Pull down roller (roller)

82c‧‧‧ Pull down roller (roller)

82d‧‧‧ Pull down roller (roller)

82e‧‧‧ Pull down roller (roller)

82f‧‧‧ Pull down roller (roller)

82g‧‧‧ Pull down roller (roller)

84a‧‧‧heater

84b‧‧‧heater

84c‧‧‧heater

84d‧‧‧heater

84e‧‧‧heater

84f‧‧‧heater

84g‧‧‧heater

86‧‧‧Insulation members

91‧‧‧Control device

98‧‧‧cutting device

172‧‧‧Cooling roller drive motor

182‧‧‧ Pull-down roller drive motor

198‧‧‧cutting device drive motor

S1‧‧‧ steps

S2‧‧‧ steps

S3‧‧‧ steps

S4‧‧‧ steps

S5‧‧ steps

S6‧‧ steps

L‧‧‧Maximum upper surface displacement

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

Fig. 2 is a schematic view showing a manufacturing apparatus of a glass substrate.

Figure 3 is a front view of the forming apparatus.

Figure 4 is a side view of the forming apparatus.

Figure 5 is a block diagram of the control device.

Fig. 6 is an example of shape data of a molded body obtained by an acquisition unit.

Fig. 7 is an example of a curve of temperature dependence of strain rate of a molded body.

Fig. 8 is an example of a curve of stress dependence of strain rate of a formed body.

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

(1) Composition of a manufacturing apparatus for a glass substrate

An embodiment of a method of manufacturing a glass substrate of the present invention will be described with reference to the drawings. Fig. 1 is a flow chart showing an example of a method for producing a glass substrate of the present embodiment.

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

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 is electrically heated by means of a desired temperature. A clarifying agent is added to the glass raw material. From the viewpoint of reducing the environmental burden, SnO _{2 is} used as a fining 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 raised. The clarifying agent added to the molten glass causes a reduction reaction due to the temperature rise, and releases oxygen. The bubbles containing the gas components such as CO ₂ , N ₂ , and SO ₂ contained in the molten glass absorb the oxygen generated by the reduction reaction of the clarifying agent. The bubble which grows by absorbing oxygen floats on the liquid surface of the molten glass, and is broken by the bubble. The gas contained in the eliminated bubble is released into the gas phase space inside the clarification pipe and is 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 a gas component such as oxygen remaining in the molten glass.

In the stirring step S3, the molten glass from which the gas is removed in the clarification step S2 is stirred to homogenize the components of the molten glass. Thereby, the composition unevenness of the molten glass which is a texture of a 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 while being cooled 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 does not cause strain or 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. Thereafter, the end surface of the glass substrate is ground and polished, and the glass substrate is washed. Thereafter, the presence or absence of defects such as damage of the glass substrate is inspected, and the glass substrate which has passed the inspection is packaged and shipped as a product.

Fig. 2 is a schematic view showing an example of the glass substrate manufacturing apparatus 1 of the embodiment. The glass substrate manufacturing apparatus 1 includes a melting tank 10, a clarification pipe 20, a stirring device 30, a molding device 40, and transfer pipes 50a, 50b, and 50c. The transfer pipe 50a connects the melting tank 10 to the clarification pipe 20. The transfer pipe 50b connects the clarification pipe 20 to the stirring device 30. The transfer pipe 50c connects the stirring device 30 to 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 conveyed while being cooled 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 especially suitable for a glass substrate for flat panel displays (FPDs), such as a liquid crystal display, a plasma display, and an organic EL display. As the glass substrate for FPD, an alkali-free glass, a glass containing a small amount of alkali, a glass for low temperature polycrystalline silicon (LTPS), or a glass for an 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 which is a raw material for a glass substrate 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 to obtain molten glass 2. The glass raw material is prepared in such a manner as to obtain a glass substrate having a desired composition. As an example of the composition of the glass substrate, the alkali-free glass which is suitable as the glass substrate for FPD contains SiO ₂ : 50% by mass to 70% by mass, Al ₂ O ₃ : 10% by mass to 25% by mass, and B ₂ O ₃ : 1 mass. %~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, and 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.

Further, as the glass substrate for FPD, a glass containing a trace amount of alkali containing an alkali metal may be used. The glass containing a trace amount of alkali contains 0.1% by mass to 0.5% by mass of R' ₂ O, preferably 0.2% by mass to 0.5% by mass of R' ₂ O. Here, R' is at least one selected from the group consisting of Li, Na, and K. The total content of R' ₂ O may be less than 0.1% by mass.

Further, the glass substrate produced 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), and Fe ₂ O ₃ : 0% by mass to 0.2%. % by mass (preferably 0.01% by mass to 0.08% by mass). In addition, 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 environmental burden.

The glass raw material prepared in the above-described composition is supplied to the melting tank 10 using a raw material dispenser (not shown). The raw material input machine can use a screw feeder to input glass raw materials, and a bucket can also be used to input glass raw materials. In the melting tank 10, the glass raw material is heated to a temperature corresponding to its composition and the like to be melted. In the melting tank 10, a molten glass 2 having a high temperature of, for example, 1500 ° C to 1600 ° C is obtained. In the melting tank 10, the molten glass 2 between the electrodes can be electrically heated by flowing an electric current between at least one pair of electrodes formed of molybdenum, platinum, tin oxide, or the like, and can be burned in addition to the electric heating. 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. A heating mechanism is provided in the clarification pipe 20 similarly to the melting tank 10. In the clarification pipe 20, the molten glass 2 is further heated and clarified. For example, in the clarification pipe 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 and homogenized in the stirring device 30.

The homogenized molten glass 2 in the stirring device 30 passes through the transfer tube 50c from the stirring device 30 It flows into the forming device 40. When the molten glass 2 passes through the transfer pipe 50c, it is cooled so as to have a viscosity suitable for the formation of the molten glass 2. For example, the molten glass 2 is cooled to about 1200 °C.

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

(2) Composition of the forming device

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

The molding apparatus 40 has a space surrounded by a furnace wall (not shown) including a refractory such as refractory brick. This space is used to form the glass ribbon 3 from the molten glass 2 and to cool the space of the glass ribbon 3. This space is composed of three spaces of the upper forming space 60, the lower forming space 70, and the undercooling 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 quenching 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 50c is formed into the glass ribbon 3. The lower forming space 70 is a space below the upper forming space 60, and is used to cool the glass ribbon 3 to a space around the cold spot of the glass. The space under the lower forming space 70 of the X-cool space 80 is a space for the glass ribbon 3 to be gradually cooled.

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

(2-1) Shaped body

The formed body 62 is provided in the upper forming space 60. The molded body 62 is used to overflow the molten glass 2 The glass ribbon 3 is formed by flowing. As shown in Fig. 4, the formed body 62 has a cross-sectional shape similar to a wedge-shaped pentagon. The tip end of the cross-sectional shape of the formed body 62 corresponds to the lower end 62a of the formed body 62. The formed body 62 is made of refractory brick.

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

The molten glass 2 sent from the stirring device 30 to the molding device 40 flows into the supply groove 62b of the molded body 62 via the transfer pipe 50c. The molten glass 2 overflowing from the supply groove 62b of the molded body 62 flows down through both side faces of the molded body 62, and merges in the vicinity of the lower end 62a of the molded body 62. The molten glass 2 after the merging falls in the vertical direction by gravity, and is formed 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 molding space 60, it is conveyed downward while being cooled by the lower molding space 70 and the cold space 80. The temperature of the glass ribbon 3 immediately after the upper molding space 60 is formed is 1100 ° C or more, and the viscosity is 25000 poise to 350,000 poise. For example, in the case of manufacturing a glass substrate for a high-definition display, the strain band of the glass ribbon 3 formed by the molded body 62 is 655 ° C to 750 ° C, preferably 680 ° C to 730 ° C, near the lower end 62a of the formed body 62. The fused molten glass 2 has a viscosity of 25,000 poise to 100,000 poise, preferably 32,000 poise to 80,000 poise.

(2-2) Upper partition member

The upper partition member 64 is a pair of plate-shaped heat insulating members provided in the vicinity of the lower end 62a of the molded body 62. As shown in FIG. 4, the upper partition members 64 are disposed on both sides in the thickness direction of the glass ribbon 3. The upper partitioning member 64 partitions the upper forming space 60 and the lower forming space 70, and suppresses the movement of heat from the upper forming space 60 to the lower forming space 70.

(2-3) Cooling roller

The cooling roller 72 is provided in a cantilever roller of the lower forming space 70. The cooling roller 72 is disposed at Directly below the upper partition member 64. As shown in FIG. 3, the cooling roll 72 is arrange|positioned in the both sides of the width direction of the glass ribbon 3. As shown in FIG. 4, the cooling rolls 72 are disposed on both sides in the thickness direction of the glass ribbon 3. The glass ribbon 3 is sandwiched by the cooling rolls 72 at both side portions in the width direction. The cooling roller 72 cools the glass ribbon 3 sent from the upper forming space 60.

In the lower molding space 70, both side portions in the width direction of the glass ribbon 3 are sandwiched by the pair of cooling rolls 72, respectively. By pressing the cooling rolls 72 toward the surfaces of both side portions of the glass ribbon 3, the contact area between the cooling rolls 72 and the glass ribbon 3 is increased, and the glass ribbon 3 is efficiently cooled by the cooling rolls 72. The cooling roller 72 applies a force against the glass ribbon 3 against the force of pulling the glass ribbon 3 downward by the lower rollers 82a to 82g which will be described later. Further, the thickness of the glass ribbon 3 is determined based on the difference between the rotational speed of the cooling roller 72 and the rotational speed of the uppermost lower pulling roller 82a.

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

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

(2-4) Temperature adjustment unit

The temperature adjustment unit 74 is disposed 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 temperature of the glass ribbon 3 cooled to the center portion in the width direction of the glass ribbon 3 is lowered to about the freezing point. The temperature adjustment unit 74 adjusts the temperature of the glass ribbon 3 to be 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 center portion cooling unit 74a and a side portion cooling unit 74b. The central portion cooling unit 74a is in the width direction of the glass ribbon 3 The temperature of the heart is adjusted. The side cooling unit 74b adjusts the temperature of both side portions in the width direction of the glass ribbon 3. Here, the center portion in the width direction of the glass ribbon 3 refers to a region sandwiched by both side portions in the width direction of the glass ribbon 3.

As shown in FIG. 3, in the lower molding space 70, a plurality of central portion cooling units 74a and a plurality of side cooling units 74b are disposed along the direction in which the glass ribbon 3 flows downward, that is, in the vertical direction. The center portion cooling unit 74a is disposed to face the surface of the center portion in the width direction of the glass ribbon 3. The side cooling unit 74b is disposed to face the surfaces of both side portions in the width direction of the glass ribbon 3.

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

(2-5) lower partition member

The lower partition member 76 is provided in a pair of plate-shaped heat insulating members below the temperature adjusting unit 74. As shown in FIG. 4, the lower partition members 76 are provided on both sides in the thickness direction of the glass ribbon 3. The lower partition member 76 partitions the lower forming space 70 and the cold space 80 in the vertical direction, and suppresses the movement of heat from the lower forming space 70 to the cold space 80.

(2-6) Pull down roller

The pull-down rolls 82a to 82g are cantilever rolls provided in the cold space 80. In the cold space 80, the pull-down roller 82a, the pull-down roller 82b, ..., the pull-down roller 82f, and the pull-down roller 82g are arranged at intervals from the upper side. The pull-down roller 82a is disposed at the uppermost position, and the pull-down roller 82g is disposed at the lowest position.

As shown in FIG. 3, the pull-down rolls 82a-82g are respectively arrange|positioned in the both sides of the width direction of the glass ribbon 3. As shown in FIG. 4, the pull-down rolls 82a to 82g are respectively disposed on both sides in the thickness direction of the glass ribbon 3. In other words, both side portions in the width direction of the glass ribbon 3 are sandwiched by the pair of pull-down rolls 82a, 2, the pull-down rolls 82b, ..., the pair of pull-down rolls 82f, and the pair of pull-down rolls 82g.

The pull-down rolls 82a to 82g are rotated while sandwiching both end portions in the width direction of the glass ribbon 3 which has passed through the lower molding space 70, whereby the glass ribbon 3 is pulled downward in the vertical direction. which is, The pull-down rolls 82a to 82g are rollers for conveying the glass ribbon 3 downward.

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

(2-7) heater

The heaters 84a to 84g are provided in the cold space 80. As shown in Fig. 4, in the cold space 80, the heater 84a, the heater 84b, ..., the heater 84f, and the heater 84g are arranged at intervals from above. The heaters 84a to 84g are disposed on both sides in the thickness direction of the glass ribbon 3, respectively. The pull-down rolls 82a to 82g are disposed between the heaters 84a to 84g and the glass ribbon 3, respectively.

The heaters 84a to 84g 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 can be adjusted in the cold space 80. Thereby, the heaters 84a to 84g can form a specific temperature distribution to the glass ribbon 3 in the conveying direction of the glass ribbon 3.

The outputs of the heaters 84a-84g can be independently controlled by the control unit 91. Further, 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 outputs of the heater subunits may be independently controlled by the control device 91. In this case, each of the heaters 84a to 84g changes the amount of heat generation according to the position in the width direction of the glass ribbon 3, whereby a specific temperature distribution can be formed in the width direction of the glass ribbon 3.

Further, a thermocouple (not shown) for measuring the ambient temperature of the quenching space 80 is provided in the vicinity of each of the heaters 84a to 84g. The thermocouple measures, for example, the ambient temperature in the vicinity of the center portion in the width direction of the glass ribbon 3 and the ambient temperature in the vicinity of both side portions. The heaters 84a to 84g may also be controlled based on the ambient temperature of the cold space 80 measured by the thermocouple.

(2-8) Insulation member

The heat insulating member 86 is disposed in the cold space 80. The heat insulating member 86 is disposed at a height position between the two pull-down rolls 82a to 82g adjacent to each other in the conveyance direction of the glass ribbon 3. As shown in FIG. 4, the heat insulating member 86 is disposed horizontally on one of the two sides of the glass ribbon 3 in the thickness direction. The heat insulating member 86 partitions the quench space 80 in the vertical direction, and suppresses thermal movement in the vertical direction of the cold space 80.

The heat insulating member 86 is provided so as not to be in contact with the glass ribbon 3 that is transported downward. Moreover, the heat insulating member 86 is provided so that the distance from the surface of the glass ribbon 3 can be adjusted. Thereby, the heat insulating member 86 suppresses heat transfer 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 disposed in a space below the cold space 80. The cutting device 98 cuts the glass ribbon 3 that has passed through the cold space 80 in a width direction along the glass ribbon 3 in a specific size. The glass ribbon 3 after passing through the cold space 80 is cooled to a flat glass ribbon 3 of 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, the glass substrate which has a size close to the final product is mass-produced.

(2-10) Control device

The control device 91 mainly includes a computer such as a CPU, a RAM, a ROM, and a hard disk. 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 84a to 84g, and a cutting device drive motor 198. The cooling roller drive motor 172 is a motor for controlling the position of the cooling roller 72, the rotational speed, and the like. The pull-down roller drive motor 182 is a motor for independently controlling the position and rotation speed of each of the pull-down rollers 82a to 82g. The cutting device drive motor 198 is a motor for controlling the cutting device 98 to cut the time interval of the glass ribbon 3 or the like. The control device 91 acquires the state of each component and memorizes the program for controlling each component.

The control device 91 can control the cooling roller drive motor 172 to obtain and adjust the contact load between one of the side portions in the width direction of the holding glass ribbon 3 and the cooling roller 72 and the glass ribbon 3. The control device 91 can control the pull-down roller drive motor 182 to obtain the rotation of each of the pull-down rollers 82a-82g The angular velocity of each of the pull-down rolls 82a to 82g is adjusted. The control unit 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 for the cutting device 98 to cut the glass ribbon 3.

(3) Action of the forming device

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

In the lower molding space 70, both side portions in the width direction of the glass ribbon 3 are brought into contact with the cooling roller 72 to be quenched. Further, the temperature of the glass ribbon 3 is adjusted by the temperature adjusting unit 74 to lower the temperature of the central portion of the glass ribbon 3 in the width direction to the freezing point. The glass ribbon 3 cooled while being conveyed downward by the cooling roller 72 is sent to the cold space 80.

In the cold space 80, the glass ribbon 3 is gradually cooled by being pulled down by the pull-down rolls 82a to 82g. The temperature of the glass ribbon 3 is controlled by the heaters 84a to 84g so as 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 is gradually reduced from the temperature of the cold point to a temperature lower than the temperature of 200 ° C lower than the strain point.

The glass ribbon 3 after the cold space 80 is further cooled to about room temperature, and cut into a specific size by a cutting device 98 to obtain a glass substrate. Thereafter, polishing and washing of the end faces of the glass substrate are performed. Thereafter, the glass substrate which has passed the specific inspection is bundled and shipped as a product.

(4) Action of the control device

The control device 91 at least stores three programs including the transport unit, the acquisition unit, and the calculation unit. Implement it.

The conveyance unit uses the lower rolls 82a to 82g provided below the molded body 62, and conveys the glass ribbon 3 formed by the molded body 62 to the lower cold space 80 at a specific conveyance speed. The conveyance unit controls the pull-down roller drive motor 182 to adjust the rotation speed of each of the pull-down rollers 82a to 82g, thereby adjusting the conveyance speed of the glass ribbon 3.

The acquisition unit acquires shape data related to the current shape of the molded body 62. Specifically, the acquisition unit acquires the shape data based on the creeping characteristic parameter. The creep characteristic parameter is a parameter for reproducing the relationship between the stress applied to the formed body 62, the temperature of the formed body 62, and the strain rate of the molded body 62 due to the creep deformation. Here, the stress applied to the molded body 62 is a force that compresses the molded body 62 in the longitudinal direction of the molded body 62. Further, the strain rate of the molded body 62 is assumed to be fixed irrespective of time. Next, the method of determining the latent characteristic parameters will be described.

First, the temperature of the molded body 62 at the strain rate of the molded body 62 is changed under the condition that the stress applied to the molded body 62 is fixed. Fig. 7 is an example of a curve of temperature dependence of strain rate of the formed body 62. In Fig. 7, the magnitude of the stress applied to the formed body 62 was 2.0 MPa. 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 of the four-point bending test of the molded body 62. In Fig. 7, the measured value of the strain velocity of the molded body 62 is indicated by a black circle.

Then, under the condition that the temperature of the molded body 62 is fixed, the strain rate applied to the molded body 62 is changed to the stress dependence of the molded body 62. Fig. 8 is an example of a curve showing the stress dependence of the strain rate of the formed body 62. In Fig. 8, the temperature of the formed body 62 is 1,250 °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 the laser. In Fig. 8, the measured value of the strain rate of the molded body 62 is indicated by a black circle.

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

[Number 1]

In the formula (1), R is 8.314 [J/mol‧K], ΔH is 4.500 × 10 ⁵ [J/mol], ε' is the strain rate of the formed body 62 [/hour], and σ is applied to the forming. The stress [Pa] of the body 62, T is the temperature [K] of the formed body 62. The creeping characteristic parameters A[/hour], B[/Pa], and n are determined such that the strain rate obtained by the equation (1) matches the measured value of the strain rate. In FIGS. 7 and 8, the strain rate of the molded body 62 calculated from the equation (1) based on the determined creep characteristic parameter is indicated by a blank square. Further, the creep characteristic 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 × 10 ^{-1 , respectively} .

Furthermore, the acquisition unit may also verify the creep characteristic parameter after determining the creep characteristic parameter. The verification of the creep characteristic parameter is performed in such a manner that, for example, the measurement system of the strain rate of the formed body 62 is modeled, and it is confirmed 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 at a specific temperature and stress using a predetermined creep characteristic parameter by computer simulation, and obtains a time change of the shape of the molded body 62, thereby obtaining the molded body 62. Shape data.

Fig. 6 is an example of the shape data of the molded body 62 obtained by the acquisition unit. Fig. 6 shows a molded 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 formed body 62 is more conspicuously shown. In Fig. 6, the shape of the unused molded body 62, that is, the shape of the molded body 62 before the creep deformation is shown by a broken line, and the current shape of the molded body 62 after the latent deformation is shown by a solid line.

The acquisition unit obtains at least the surface displacement amount from the displacement amount in the vertical direction of the upper surface 62c of the molded body 62 from the shape data based on the latent deformation of the molded body 62. In FIG. 6, the upper surface displacement amount is the upper surface 62c before the creep deformation and the upper surface after the latent deformation. The size of the vertical direction between 62c. In Fig. 6, the maximum displacement amount L of the surface displacement amount in the longitudinal direction of the molded body 62 is shown.

The calculation unit calculates the conveyance speed of the glass ribbon 3 in the cold space 80 so that the variation in the thickness of the glass ribbon 3 in the width direction is small, based on the shape data of the molded body 62 obtained by the acquisition unit. The smaller the variation in the thickness of the glass ribbon 3 in the width direction, the more uniform the thickness of the glass ribbon 3 is in the width direction. Specifically, as the calculation unit maximum upper surface shift amount L is larger, the larger value is calculated as the conveyance speed of the glass ribbon 3 .

Moreover, the conveyance unit adjusts the rotation speed of each of the pull-down rolls 82a to 82g based on the conveyance speed of the glass ribbon 3 calculated by the calculation unit. Thereby, the conveyance unit adjusts the conveyance speed of the glass ribbon 3 to the value calculated by the calculation unit.

The control unit 91 can reduce the variation in the thickness of the glass ribbon 3 conveyed downward in the cold space 80 by the conveyance unit, the acquisition unit, and the calculation unit.

(5) Features

In the present embodiment, the molded body 62 is provided in an atmosphere of a high temperature in the upper molding space 60. In the molding step of the glass ribbon 3, the weight of the molded body 62 and the weight of the molten glass 2 supplied to the supply groove 62b are applied to the molded body 62. Therefore, as a result of the long-term operation of the glass substrate manufacturing apparatus 1, as shown in FIG. 6, the molded body 62 is gradually deformed and deformed by the thermal creep property of the material of the molded body 62. In particular, the central portion of the longitudinal direction of the molded body 62 is likely to hang down due to creep deformation. In FIG. 6, the maximum upper surface displacement amount L is the amount of surface displacement of the upper portion in the longitudinal direction of the molded body 62.

When the molded body 62 is deformed in a latent manner as shown in FIG. 6, the amount of the molten glass 2 overflowing from the central portion in the longitudinal direction of the molded body 62 is larger than the molten glass overflowing from both ends in the longitudinal direction of the molded body 62. 2 amount. In this case, the thickness of the central portion in the width direction of the glass ribbon 3 formed by the molded body 62 increases, and the thickness of the central 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 variation in the thickness of the glass ribbon 3 in the width direction is increased, and the variation in the thickness of the glass substrate as the final product is increased.

In the glass substrate manufacturing apparatus 1 of the present embodiment, by adjusting the rotational speed of each of the pull-down rolls 82a to 82g, the transport speed of the glass ribbon 3 in the cold space 80 is adjusted, and the creep deformation due to the molded body 62 can be reduced. The thickness deviation of the glass ribbon 3 in the width direction. Second, explain its organization.

First, as shown in FIG. 6, the acquisition unit of the control device 91 of the glass substrate manufacturing apparatus 1 acquires shape data relating to the current shape of the molded body 62 which is subjected to the latent deformation. Then, the calculation unit of the control device 91 calculates the glass ribbon 3 which minimizes the variation in the thickness of the glass ribbon 3 conveyed downward in the cold space 80 based on the shape data of the molded body 62 obtained by the acquisition unit. Transfer speed. 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. 6 . Then, the conveyance unit 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 unit. Thereby, the control device 91 adjusts the conveying speed of the glass ribbon 3 in the cold space 80 based on the shape data of the latently deformed molded body 62. Fig. 9 is a graph showing the relationship between the maximum upper surface displacement amount L of the molded body 62 of the latent deformation and the conveying speed of the glass ribbon 3. As shown in FIG. 9, the control device 91 is configured such that the larger the maximum upper surface displacement amount L of the molded body 62 is, the more the rotation speed of each of the pull-down rolls 82a to 82g is increased, and the conveyance speed of the glass ribbon 3 is adjusted. 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 maximum upper surface displacement amount L of the latent-deformed molded body 62 is larger is larger as the transport speed calculated by the calculation unit is larger. As described above, the larger the maximum upper surface displacement amount L, the greater the thickness of the central portion in the width direction of the glass ribbon 3 is greater than the thickness at both end portions in the width direction. In this case, when the rotation speed of each of the pull-down rolls 82a to 82g is increased and the conveyance speed of the glass ribbon 3 in the cold space 80 is increased, the cooling rate of the glass ribbon 3 in the cold space 80 is increased, and the vertical direction is increased. The amount of shrinkage of the glass ribbon 3 (in the direction in which the glass ribbon 3 flows downward) also rises. The glass ribbon 3 has the largest amount of shrinkage in the portion having the largest thickness in the width direction, that is, the central portion in the width direction of the glass ribbon 3. The center of the width direction of the glass ribbon 3 The contraction in the vertical direction causes a tension in the width direction from the central portion in the width direction of the glass ribbon 3 toward both end portions in the width direction. As a result, the thickness of both end portions in the width direction of the glass ribbon 3 is increased, and the difference between the thickness of the central portion in the width direction of the glass ribbon 3 and the thickness of both end portions in the width direction is small.

Therefore, when the central portion of the longitudinal direction of the molded body 62 is lowered downward and is deflected by the latent deformation of the molded body 62, the conveyance speed of the glass ribbon 3 in the cold space 80 can be increased. 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 variation in the thickness of the glass substrate as the final product.

Further, in the production step of using a glass substrate having a high liquidus temperature and a glass substrate having a high strain point, the latent deformation of the molded body 62 is particularly likely to be a problem because the temperature of the molded body 62 is likely to become high. In addition, in recent years, as the size of the glass substrate is increased, the dimension of the longitudinal direction of the molded article is continuously increased, so that the deflection of the molded body 62 due to the creeping deformation tends to be remarkable. In the present embodiment, by adjusting the rotational speed of each of the pull-down rolls 82a to 82g, the transport speed of the glass ribbon 3 in the cold space 80 is adjusted, and the glass which is caused by the latent deformation of the molded body 62 can be effectively reduced. The thickness deviation of the belt 3 in the width direction.

(6) Variations

(6-1) Change A

In the embodiment, the acquisition unit of the control device 91 of the glass substrate manufacturing apparatus 1 obtains the shape data relating to the current shape of the molded body 62 by temporally changing the shape of the molded body 62 by computer simulation. However, the acquisition unit may obtain shape data related to the current shape of the molded body 62 by other methods.

For example, the acquisition unit may acquire the shape data based on the actual measured value of the shape of the molded body 62. In this case, it is necessary to collect and analyze the data relating to the actual measured value of the shape of the molded body 62 and the data relating to the use conditions of the molded body 62. The conditions of use of the molded article 62 are various parameters associated with the molded body 62 such as the operation 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. number. The acquisition unit predicts and obtains the shape data of the currently used molded body 62 based on the correlation between the measured values of the shape of the molded body 62 and the data relating to the use conditions of the molded body 62.

Further, the acquisition unit can obtain the shape data based on the measured value of the thickness of the glass ribbon 3 formed by the molded body 62. In this case, the acquisition unit predicts and obtains the shape data of the currently used molded body 62 based on the data relating to the measured value of the thickness of the glass ribbon 3 in the width direction.

(6-2) Change B

In the embodiment, the control device 91 of the glass substrate manufacturing apparatus 1 adjusts the rotational speed of each of the pull-down rolls 82a to 82g, and adjusts the transport speed of the glass ribbon 3 in the quenching space 80. However, the control device 91 can also adjust the rotational speed of each of the 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.

When the conveying speed of the glass ribbon 3 in the cold space 80 is increased, the thickness of the glass ribbon 3 formed by the molded body 62 becomes 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 formed by the molded body 62 becomes large. Therefore, the control device 91 increases the rotational speed of each of the pull-down rolls 82a to 82g and increases the amount of the molten glass 2 supplied to the supply groove 62b of the formed body 62, whereby the glass ribbon 3 formed by the formed body 62 can be maintained while maintaining The thickness of the glass ribbon 3 due to the latent deformation of the molded body 62 is suppressed from increasing in thickness variation.

(6-3) Change C

In the calculation unit of the control unit 91 of the glass substrate manufacturing apparatus 1, the maximum upper surface shift amount L shown in FIG. 6 is used as the shape data of the molded body 62, and the maximum upper surface shift amount L is larger. The larger value is calculated as the conveying speed of the glass ribbon 3. However, the calculation unit may calculate the conveyance speed of the glass ribbon 3 by using other parameters related to the shape data of the molded body 62.

For example, the calculation unit may also serve as a parameter related to the shape data of the molded body 62. The conveyance speed of the glass ribbon 3 is calculated by the curvature of the upper surface 62c or the lower end 62a of the molded body 62 when viewed in a direction perpendicular to the surface of the glass ribbon 3. For example, the larger the curvature of the upper surface 62c or the lower end 62a of the molded body 62, the larger the amount of deflection of the molded body 62 due to the creep deformation, and the larger the value is calculated as the transport speed of the glass ribbon 3. .

[Previous Technical Literature]

[Patent Document] U.S. Patent No. 3,338,696

62‧‧‧Formed body

62a‧‧‧Bottom

62c‧‧‧ upper surface

L‧‧‧Maximum upper surface displacement

Claims (5)

A method for producing a glass substrate, comprising: a molding step of supplying molten glass to a supply groove formed on an upper surface of the molded body, and the molten glass overflowing from both sides of the supply groove along the molded body The two sides are flowed down, and the molten glass which flows down on the both side surfaces is merged at the lower end of the molded body to form a glass ribbon, and the transporting step is performed by using a roller provided below the molded body at a specific conveying speed. The glass ribbon formed in the forming step is conveyed downward; the obtaining step is to obtain shape data related to the shape of the molded body; and the calculating step is based on the shape data obtained in the obtaining step, and the glass ribbon is The conveyance speed is calculated so that the variation in the thickness direction in the width direction is small, and the adjustment step is to adjust the conveyance speed of the glass ribbon so as to be the conveyance speed calculated in the calculation step. The method for producing a glass substrate according to claim 1, wherein the obtaining step obtains the shape data based on the latent deformation of the molded body. The method for producing a glass substrate according to claim 2, wherein the obtaining step obtains at least a shift amount in a vertical direction of the upper surface of the molded body as the shape data, and the calculating step is such that the shift amount is larger. The larger value is calculated as the above-described transfer speed. The method for producing a glass substrate according to any one of claims 1 to 3, wherein the transporting step is performed by using the roller that sandwiches both end portions in the width direction of the glass ribbon, and the glass ribbon is conveyed while being cold-cooled. Calculated above The above-described transport speed calculated in the step controls the rotational speed of the roller. The method for producing a glass substrate according to any one of claims 1 to 4, wherein the obtaining step obtains the shape data by obtaining a time change of the shape by computer simulation.