TWI498291B - A glass substrate manufacturing method and a glass substrate manufacturing apparatus - Google Patents

Description

Glass substrate manufacturing method and glass substrate manufacturing device

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

Since the prior art, a method of manufacturing a glass substrate by using an overflow down-draw method of a formed body has been used. In general, when the temperature of the molten glass is maintained in the vicinity of the liquidus temperature for a long period of time in the molded body, crystals are precipitated in the molten glass to cause devitrification.

A technique (Patent Document 1) is known in which the temperature of the molten glass at the time of supplying the molded body is lower than the previous one in order to prevent devitrification of the glass during molding, and the temperature of the molten glass at the lower end of the formed body is higher than that of the prior art. The difference between the temperature of the molten glass when the molded body is supplied and the temperature of the molten glass when passing through the lower end of the molded body is less than 90 °C.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 4511187

However, the above technique is such that the temperature of the molten glass at the lowermost end portion of the formed body is higher than that of the prior art. Further, in the above technique, the temperature of the molten glass during molding is sufficiently higher than the liquidus temperature to prevent devitrification. As such, in order to prevent devitrification of the glass, the above technique must make the temperature of the molten glass passing through the formed body higher than before. Therefore, the temperature of the molten glass at the lowermost end portion of the molded body becomes higher than that of the prior art, and the viscosity of the glass becomes low, so that the force of the flat glass generated by the separation of the molded body in the width direction cannot be suppressed, thereby The shrinkage of the flat glass has become larger than before. Further, due to the melting of the lowermost end portion of the formed body Since the temperature of the glass becomes higher than the previous one, the temperature of the space below the molded body rises due to heat transfer from the molten glass, so that the both ends of the flat glass in the space below the molded body cannot be formed. The viscosity is raised sufficiently. As a result, the problem of shrinkage of the width of the flat glass becomes remarkable.

Therefore, an object of the present invention is to provide a method for producing a glass substrate and a glass substrate manufacturing apparatus which can suppress shrinkage of a glass flat plate formed by using a molded body when being separated from a molded body, thereby securing a target flat glass. width.

The present invention encompasses the following aspects.

One aspect of the present invention is a method of manufacturing a glass substrate.

[Scenario 1]

A method for producing a glass substrate, comprising: forming a flat glass by overflowing molten glass from a molded body in an upper space of a forming furnace chamber surrounded by a furnace wall; The forming furnace chamber is partitioned into a slit-like gap formed by the heat insulating members of the upper space and the lower space; and the both ends of the flat glass are cooled in the lower space; the heat insulating member is insulated In the step of forming the flat glass (1), the temperature of the molten glass when the molten glass passes through the molded body is equal to or higher than a liquidus temperature, and the molten glass passes through the lowermost end portion of the molded body. The viscosity of the two ends of the molten glass is 10 ^4.3 ~ 10 ⁶ dPa. And (2) in the step of cooling the flat glass, when the temperature of the central portion of the flat glass is in a temperature region from a temperature higher than a softening point to a vicinity of the annealing point, the both ends of the flat glass are made The viscosity of the part becomes 10 ^9.0 ~ 10 ^14.5 dPa. second.

[Surface 2]

A method of producing a glass substrate according to aspect 1, wherein a thermal resistance between the upper space of the heat insulating member and the lower space is 0.2 m ^{2 at an} ambient temperature of the upper space. K/W or above.

[Surface 3]

The method for producing a glass substrate according to aspect 1 or 2, wherein the lower space includes a step of uniformly making a temperature distribution in a width direction of the central portion of the flat glass and a temperature of both end portions of the flat glass a temperature lower than a temperature of the central portion; and a temperature at which the temperature of the both end portions and the central portion are lower than a temperature at which both ends of the flat glass are lower than a temperature of the central portion The temperature of the portion is low, and a temperature gradient is formed in the width direction of the flat glass from the center in the width direction of the central portion toward the both end portions.

[Surface 4]

The method for producing a glass substrate according to any one of the aspects 1 to 3, wherein the glass substrate has a liquid viscosity of 10 ^4.3 dPa. Seconds ~ 10 ^6.7 dPa. second.

[Surface 5]

The method for producing a glass substrate according to any one of the aspects 1 to 4, wherein the glass substrate has a strain point of 670 ° C or higher.

[Figure 6]

A glass substrate manufacturing apparatus comprising: a molding furnace chamber surrounded by a furnace wall; and a heat insulating member that divides the forming furnace chamber into an upper space and a lower space, and forms a slit shape through which the flat glass passes a gap formed in the upper space of the forming furnace chamber and overflowing the molten glass to form a flat glass; and a cooling member that cools both end portions of the flat glass in the lower space; In the step of forming the flat glass, the temperature of the molten glass when the molten glass passes through the molded body is at a liquidus temperature or higher, and the molten glass passes through the heat insulating member. The viscosity of the both ends of the molten glass at the lowermost end of the molded body is 10 ^4.3 to 10 ⁶ dPa. And (2) in the step of cooling the flat glass, when the temperature of the central portion of the flat glass is in a temperature region from a temperature higher than a softening point to a vicinity of an annealing point, both ends of the flat glass The viscosity becomes 10 ^9.0 ~ 10 ^14.5 dPa. second.

In the above glass substrate, glass having the following characteristics can be used.

[Stage 7]

The aspect of producing a glass substrate according to any one of methods 1 to 6 or a glass substrate manufacturing apparatus, wherein the liquid phase of the glass substrate of the glass viscosity of 10 ^4.3 dPa. Seconds ~ 10 ^6.7 dPa. second.

[Surface 8]

The method for producing a glass substrate according to any one of aspects 1 to 7, wherein the glass substrate contains zirconia.

[Surface 9]

The method for producing a glass substrate according to any one of aspects 1 to 8, wherein the glass substrate contains tin oxide.

[Surface 10]

The method for producing a glass substrate according to any one of aspects 1 to 9, wherein the glass substrate comprises an alkali-free glass substantially free of an alkali metal oxide.

[Stage 11]

The glass substrate manufacturing method or the glass substrate manufacturing apparatus according to any one of the aspects 1 to 9, wherein the glass substrate comprises a glass containing a trace amount of alkali containing 0.05 to 2.0% by mass of an alkali metal oxide.

[Surface 12]

The method for producing a glass substrate according to any one of aspects 1 to 11, wherein the molten glass is produced by electrically melting a glass raw material in a melting tank comprising a high zirconia refractory. .

According to the method for producing a glass substrate and the glass substrate manufacturing apparatus of the above aspect, it is possible to suppress shrinkage of the width of the glass flat plate formed by using the molded body when separating from the molded body, and to secure the width of the target flat glass.

10a, 10d‧‧‧ straight line

10b, 10c, 10e, 10f‧‧‧ curves

11‧‧‧melting device

12‧‧‧Clarification device

20a‧‧‧1st temperature distribution

20b‧‧‧2nd temperature distribution

20c‧‧‧3rd temperature distribution

23‧‧‧Upstream catheter

24‧‧‧Downstream catheter

32‧‧‧ Temperature Control Unit

40‧‧‧Forming device

41‧‧‧Formed body

41a‧‧‧ Lower end of the formed body

41b‧‧‧Top of the formed body

41c‧‧‧ Side of the formed body

50‧‧‧Parts

51‧‧‧Cooling roller

60‧‧‧Cooling unit

61‧‧‧Central cooling unit

62‧‧‧Central upper cooling unit

63a, 63b‧‧‧ central lower cooling unit

71‧‧‧End cooling unit

72‧‧‧End upper cooling unit

73‧‧‧Lower cooling unit

80‧‧‧ Annealing furnace

80a‧‧‧ top board

81‧‧‧ Pull down roller

90‧‧‧cutting device

91‧‧‧Control device

100‧‧‧Manufacturing device for glass substrates

FG‧‧‧ molten glass

SG‧‧ ‧ flat glass

X‧‧‧1st temperature difference

Y1‧‧‧2nd temperature difference

Y2‧‧‧3rd temperature difference

Fig. 1 is a view showing an example of a flow of a method for producing a glass substrate of the present embodiment.

FIG. 2 is a schematic configuration diagram showing an example of a glass substrate manufacturing apparatus for carrying out the method for producing a glass substrate of the present embodiment.

Fig. 3 is a schematic configuration view (cross-sectional view) showing an example of a molding apparatus used in the method for producing a glass substrate of the embodiment.

Fig. 4 is a schematic configuration view (side view) of the molding apparatus shown in Fig. 3.

Fig. 5 is a view showing an example of a control device used in the method for producing a glass substrate of the embodiment and each mechanism connected to the control device.

Fig. 6 is a view showing the ambient temperature obtained by temperature control based on a plurality of temperature distributions performed by the method for producing a glass substrate of the present embodiment.

(definition)

The following statements in this specification are defined as follows.

The end portion of the flat glass refers to a range within 150 mm from the edge of the flat glass in the width direction.

The central portion of the flat glass refers to the portion where the end portion of the flat glass is removed.

The so-called strain point means that the glass viscosity becomes 10 ^14.5 dPa. The temperature of the glass in seconds.

The so-called annealing point means that the glass viscosity is 10 ¹³ dPa. The temperature of the glass in seconds.

The temperature zone near the annealing point refers to the temperature obtained by adding the glass annealing point plus 100 ° C (glass annealing point + 100 ° C) to the glass strain point and the glass annealing point and dividing by 2 (the glass strain point). + glass annealing point) / 2) between the areas.

The so-called softening point means that the glass viscosity becomes 10 ^7.6 dPa. The temperature of the glass in seconds.

(overall)

The method for producing a glass substrate of the present embodiment is to manufacture a glass substrate for a flat panel display such as a liquid crystal television, a plasma TV, or a notebook computer. The glass substrate is manufactured using a down-draw method.

A plurality of steps (a method of manufacturing a glass substrate) and a manufacturing apparatus 100 for a glass substrate for a plurality of steps will be described with reference to FIGS. 1 and 2 .

The plurality of steps include a melting step S1, a clarifying step S2, a forming step S3, a cooling step S4, and a cutting step S5.

The melting step S1 is a step of melting the raw material of the glass. As shown in Fig. 2, the raw material of the glass is introduced into the melting device 11 disposed upstream. The raw material of the glass is melted in the melting tank of the melting device 11 to become molten glass FG. The molten glass FG is sent to the clarification device 12 through the upstream conduit 23.

The clarification step S2 is a step of removing bubbles in the molten glass FG. The molten glass FG obtained by removing bubbles in the clarification device 12 is then conveyed to the forming device 40 through the downstream conduit 24.

The forming step S3 is a step of forming the molten glass FG into a flat glass (plate glass) SG. Specifically, the molten glass FG is transferred to the forming included in the forming device 40. After the body 41, the molded body 41 overflows. The overflowed molten glass FG flows down the surface of the formed body 41. The molten glass FG is then merged at the lowermost end portion of the molded body 41 to become the sheet glass SG. At this time, the sheet glass SG moves from the upper space of the forming furnace chamber to the lower space by the slit-like gap formed by the partition member (heat insulating member) 50. The partition member (heat insulating member) 50 divides the forming furnace chamber having the molded body 41 (see FIG. 3) into an upper space and a lower space.

The cooling step S4 is a step of annealing the sheet glass SG. The glass plate is cooled to a temperature close to room temperature via a cooling step S4. Further, the thickness (thickness) of the glass substrate, the amount of warpage of the glass substrate, and the amount of strain of the glass substrate are determined according to the state of cooling in the forming step S1 and the cooling step S4.

The cutting step S5 is a step of cutting the sheet glass SG which is a temperature close to room temperature into a specific size.

Further, the sheet glass SG (glass sheet) cut into a specific size is then subjected to a step such as end surface processing to form a glass substrate.

In the embodiment described below, the glass having the flat glass SG has a strain point of 640 ° C or higher.

Hereinafter, the configuration of the molding apparatus 40 will be described with reference to Figs. 3 and 4 . In the present embodiment, the width direction of the sheet glass SG refers to a direction intersecting the direction in which the sheet glass SG flows down (downflow direction or downflow direction), that is, a horizontal direction.

(Composition of forming device)

First, FIG. 3 and FIG. 4 show the schematic configuration of the molding apparatus 40. 3 is a cross-sectional view of the forming device 40. 4 is a side view of the forming device 40. The molding apparatus 40 mainly includes a molded body 41, a partition member 50, a cooling roller 51, a cooling unit 60, a pull-down roller 81, and a cutting device 90. Further, the molding device 40 includes a control device 91 (see FIG. 9). The control device 91 controls the drive units of the respective configurations included in the molding device 40.

Hereinafter, each configuration included in the molding apparatus 40 will be described.

(formed body)

In the molded body 41, the molten glass FG is formed into a flat glass (flat glass SG) by overflowing the molten glass FG.

As shown in FIG. 3, the formed body 41 has a shape in which the cross-sectional shape is a substantially pentagonal shape (similar to the shape of a wedge shape). The front end of the substantially pentagon corresponds to the lowermost end portion 41a of the formed body 41.

The molten glass FG that has flowed into the molded body 41 overflows from the one of the molded bodies 41 to the top portion 41b, and flows down along one side of the molded body 41 to the side surface (surface) 41c. Thereafter, the molten glass FG merges at the lowermost end portion 41a of the molded body 41 to become the sheet glass SG. Further, the viscosity of the both ends of the molten glass when the molten glass passes through the lowermost end portion 41a of the molded body 41 is 10 ^4.3 to 10 ⁶ dPa. Seconds, preferably 10 ^4.4 ~ 10 ^5.4 dPa. Seconds, more preferably 10 ^4.6 ~ 10 ^5.2 dPa. second.

(separating member)

The partition member 50 is disposed in the vicinity of the junction point of the molten glass FG. Moreover, as shown in FIG. 3, the partition member 50 is arrange|positioned on the both sides of the thickness direction of the molten glass FG (flat glass SG) which joins the junction point. The partition member 50 is a heat insulating member. The partition member 50 is partitioned into an upper space of the forming furnace chamber located above the partitioning member 50 and a lower space of the forming furnace chamber located below, that is, by separating the upper side environment and the lower side environment of the merged point of the molten glass FG And the heat insulation is transmitted from the upper side of the partition member 50 toward the lower side. The sheet glass SG is moved to the lower space by a slit-like gap formed by the partition member (heat insulating member) 50 on one of the two sides in the thickness direction of the sheet glass SG.

(cooling roll)

The cooling roller 51 is a unit that is provided in the lower space of the forming furnace chamber and heat-treats both ends of the flat glass SG in the width direction. Further, the pair of cooling rolls 51 are disposed on both sides in the thickness direction of the sheet glass SG and at both end portions in the width direction of the sheet glass SG. In other words, the cooling roller 51 cools both ends in the width direction of the sheet glass SG separated from the molded body 41 by heat conduction (quenching step). The cooling roller 51 can also be used, for example, by Air cooling is carried out through the internal air-cooling pipe.

The cooling roller 51 is such that the viscosity of the both ends of the flat glass SG is 10 ^9.0 ~ 10 ^14.5 dPa. In the second mode, both ends of the flat glass SG are quenched. Further, by cooling the both ends of the sheet glass SG by the cooling rolls 51, the shrinkage in the width direction of the sheet glass SG can be reduced, and the thickness of the sheet glass SG can be made uniform. Moreover, the flatness of the sheet glass SG can be maintained.

(cooling unit)

The cooling unit 60 is a unit that is disposed in the lower space of the forming furnace chamber and performs heat treatment of the flat glass SG. Specifically, the cooling unit 60 is a unit that cools the sheet glass SG to a temperature region near the annealing point. The cooling unit 60 is disposed below the partition member 50 and above the top plate 80a of the annealing furnace 80. The cooling unit 60 cools the upstream region of the sheet glass SG (upstream region cooling step). The upstream region of the flat glass SG refers to a region in which the temperature of the central portion of the flat glass SG is higher than that of the flat glass SG at the annealing point. The central portion of the sheet glass SG is a portion sandwiched by both end portions of the sheet glass SG. Specifically, the first temperature region and the second temperature region are included in the upstream region. The first temperature region is a region of the sheet glass SG from the immediately below the lowermost end portion 41a of the molded body 41 to the temperature at the central portion of the sheet glass SG to the vicinity of the softening point (the softening point is within a range of ±15 ° C). In addition, the second temperature region refers to a temperature region in which the temperature in the central portion of the sheet glass SG is changed from the vicinity of the softening point to the vicinity of the annealing point. That is, the cooling unit 60 cools the sheet glass SG such that the temperature of the central portion of the sheet glass SG approaches the annealing point. The center portion of the sheet glass SG is thereafter cooled in the annealing furnace 80 described below to a temperature near room temperature via a strain point (downstream region cooling step (annealing step)).

The cooling unit 60 cools the sheet glass SG based on a plurality of temperature distributions such that the thickness and the amount of warpage of the sheet glass SG become desired values. That is, in the upstream region, a plurality of temperature distributions are set along the downward flow direction of the sheet glass SG. Here, the temperature distribution is a temperature distribution along the width direction of the sheet glass SG. In other words, the temperature distribution system The distribution of the ambient temperature to be the target. The cooling roller 51 and the cooling unit 60 control the ambient temperature so as to achieve a temperature distribution.

The cooling unit 60 includes a plurality of units for cooling. The temperature distribution of the sheet glass SG achieves a plurality of temperature distributions by independently controlling a plurality of cells. For example, the cooling unit 60 includes a central portion cooling unit 61 and two end portion cooling units 71, 71. As shown in FIG. 4, the central portion cooling unit 61 is disposed at the center in the width direction of the molding apparatus 40, and cools the central portion of the sheet glass SG (central portion cooling step). The central portion cooling unit 61 is disposed on both sides in the thickness direction of the sheet glass SG. The end portion cooling units 71 are disposed at positions adjacent to the central portion cooling unit 61, respectively. In other words, the end portion cooling unit 71 is disposed on both sides in the thickness direction of the sheet glass SG, and is opposed to the sheet glass SG, and cools both end portions and both end portions of the sheet glass SG (end portion cooling) step). Further, the central portion cooling unit 61 and the end portion cooling unit 71 are disposed at positions close to the sheet glass SG, respectively.

(central cooling unit)

The central portion cooling unit 61 cools the central portion of the sheet glass SG stepwise in the downward direction of the sheet glass SG (central portion cooling step). The central portion cooling unit 61 includes a central upper cooling unit 62 and central lower cooling units 63a and 63b. The center upper cooling unit 62 and the two center lower cooling units 63a and 63b are disposed along the downward flow direction of the sheet glass SG. The temperatures of the central upper cooling unit 62 and each of the central lower cooling units 63a and 63b are independently adjusted.

(central upper cooling unit)

The central upper cooling unit 62 is located directly below the partition member 50. The central upper cooling unit 62 is a unit for realizing a temperature distribution of a region determining the thickness of the sheet glass SG. The region determining the thickness of the sheet glass SG corresponds to the first temperature region described above. The center upper cooling unit 62 is controlled such that the thickness of the sheet glass SG is uniform in the width direction (first central portion cooling step).

The center lower cooling units 63a and 63b are disposed below the center upper cooling unit 62 as described above. The central lower cooling units 63a, 63b are means for realizing the temperature distribution of the region where the amount of warpage of the sheet glass SG is controlled. Here, the region in which the amount of warpage of the sheet glass SG is controlled is controlled to correspond to the second temperature region.

The center lower cooling unit 63a is on the upstream side of the second temperature region, and performs temperature control of the sheet glass SG (second center portion cooling step). The center lower cooling unit 63b is on the downstream side of the second temperature region, and performs temperature control of the sheet glass SG (third center portion cooling step). It is preferable that the central lower cooling unit 63a and the central lower cooling unit 63b have the same configuration.

(end cooling unit)

The end portion cooling unit 71 continuously or stepwise cools both end portions of the sheet glass SG quenched by the cooling rolls 51 in the flow direction of the sheet glass SG (end portion cooling step). The end portion cooling unit 71 operates at a lower cooling capacity than the cooling roll 51. In other words, the amount of heat deprived by the end portion cooling unit 71 from the end portion of the sheet glass SG is less than the amount of heat deprived by the cooling roller 51 from the side portion of the sheet glass SG. The end portion cooling units 71 are disposed on both sides of the central portion cooling unit 61 as described above (see FIG. 4). The end portion cooling unit 71 is disposed close to the surface of the sheet glass SG. The end cooling unit 71 is configured to maintain the viscosity of both ends of the flat glass SG at 10 ^9.0 ~ 10 ^14.5 dPa. In the range of seconds, both ends of the flat glass SG are cooled. Furthermore, the end cooling unit 71 preferably maintains the viscosity of the two ends of the flat glass SG at 10 ^10.5 ~ 10 ^14.5 dPa. In the range of seconds, the ends of the flat glass are cooled.

When the amount of cooling of the end portion cooling unit 71 is small, the temperature at both end portions of the sheet glass SG rises again, causing the sheet glass SG to contract in the width direction.

As shown in FIG. 4, the end cooling unit 71 includes, for example, an end upper cooling unit 72 and an end lower cooling unit 73. The end upper cooling unit 72 and the end lower cooling unit 73 are disposed along the downward flow direction of the sheet glass SG. Moreover, the upper end cooling unit 72 and the lower end cooling unit The temperature of 73 is adjusted independently.

The end upper cooling unit 72 is a unit for realizing the temperature distribution of the region affected by the adjustment of the thickness and/or the amount of warpage of the sheet glass SG (first end portion cooling step). The end upper cooling unit 72 is located directly below the cooling roller 51 as shown in FIG. The flat glass SG is primarily cooled by the radiant heat transfer of the upper end cooling unit 72 at a desired cooling rate. Here, the required cooling rate refers to a cooling rate at which the shrinkage of the sheet width of the glass SG passing through the cooling roll 51 is suppressed, and the flat glass SG is not cracked during the cooling process after the end lower cooling unit 73. That is, the end upper portion cooling unit 72 maximizes the cooling of the glass SG within a range that does not adversely affect the sheet glass SG.

(pull down roller)

The pull-down roller 81 is disposed inside the annealing furnace 80. The annealing furnace 80 is disposed in a space directly below the cooling unit 60. In the annealing furnace 80, the temperature of the sheet glass SG is cooled from the temperature near the annealing point to a temperature near the room temperature (downstream region cooling step (annealing step)).

(cutting device)

The cutting device 90 cuts the sheet glass SG that has been cooled to a temperature near room temperature by the annealing furnace 80 to a specific size.

(control device)

The control device 91 controls, for example, the temperatures of the cooling roller 51, the center upper cooling unit 62, the end upper cooling unit 72, the end lower cooling unit 73, and the center lower cooling units 63a and 63b. As explained below, the temperature distribution of the sheet glass SG can be made to coincide with a specific temperature distribution by the control of the temperature.

(Temperature Distribution)

Next, the temperature distribution used in the method for producing a glass substrate of the present embodiment and the control of each unit for cooling the temperature distribution will be described with reference to Fig. 6 .

In Fig. 6, the area indicated by the broken line indicates each of the cooling roller 51 and the cooling unit. Configuration of units 62, 63a, 63b, 72, 73. Further, the curves 10b, 10c, 10e, 10f and the straight lines 10a, 10d included in the area divided by the broken lines are temperature distributions 20a, 20b realized by the cooling rolls 51 or the respective units 62, 63a, 63b, 72, 73, The distribution of the children contained in 20c.

In the present embodiment, as described above, the control device 91 independently controls the ambient temperature based on the plurality of temperature distributions in the downward flow direction of the sheet glass SG. When the temperature of the sheet glass SG is in a specific temperature region, the sheet glass SG is cooled by applying tension to the side portion of the sheet glass SG in the width direction of the sheet glass SG. The specific temperature region refers to a temperature region in which the temperature of the sheet glass SG changes from a temperature higher than the softening point to a vicinity of the annealing point after the sheet glass SG is separated from the molded body 41. That is, the specific temperature region refers to the upstream region of the above-described sheet glass SG.

The flat glass SG after separating the formed body 41 has 10 ^5.7 ~ 10 ^7.5 dPa. The viscosity of seconds. The sheet glass SG is cooled by the cooling roller 51 and the cooling unit 60 to have a high viscosity. That is, the viscosity (the viscosity of the center portion and the both end portions) of the sheet glass SG becomes higher in the downward direction of the sheet glass SG. In other words, the viscosity of the sheet glass SG is higher as it goes toward the downstream side of the sheet glass SG. This embodiment is in the upstream region, and both ends of the sheet glass SG are cooled by the cooling roller 51 and the end portion cooling unit 71. Specifically, the two ends of the flat glass SG are maintained at a viscosity of 10 ^9.0 ~ 10 ^14.5 dPa. Cool down in the range of seconds. More specifically, the viscosity of the cooling roller 51 at the side of the flat glass SG is 10 ^9.0 ~ 10 ^10.5 dPa. In the range of seconds, both ends of the flat glass are quenched, and the viscosity of the end portions of the flat glass SG quenched by the cooling fins 51 is 10 ^10.5 ~ 10 ^14.5 dPa. The ends of the flat glass are cooled in a range of seconds.

Under the control of the temperature of the sheet glass SG of the present embodiment, a plurality of temperature distributions are set in the width direction of the sheet glass SG and the flow direction of the sheet glass SG (temperature distribution setting step). Specifically, as shown in FIG. 6, the plurality of temperature distributions include the first temperature distribution 20a, the second temperature distribution 20b, and the third temperature distribution 20c. First temperature distribution The 20a system is located on the high temperature side in the downflow direction compared to the second temperature distribution 20b. Further, the second temperature distribution 20b is located on the high temperature side in the downflow direction from the third temperature distribution 20c.

The temperature distribution in the width direction of the center portion in the width direction of the sheet glass SG in the first temperature distribution 20a is uniform, and the temperature at both end portions (both sides) of the flat glass SG in the width direction is lower than the temperature in the central portion of the sheet glass SG. . Here, the uniform temperature distribution in the width direction means that the temperature distribution in the width direction is a value within a range of ±0° C. to 10° C. with respect to a specific reference value (temperature). In other words, the both ends of the sheet glass SG are quenched based on the first temperature distribution 20a, and the temperature in the central portion of the sheet glass SG is controlled to be higher than the temperature at both end portions of the sheet glass SG, and in the width direction. The temperature becomes uniform (the thickness uniformization step). Further, the first temperature distribution 20a is set such that the temperature (average temperature) at the central portion of the sheet glass SG and the temperature at both end portions of the sheet glass SG become the first temperature difference X. In the step of equalizing the thickness of the sheet, the temperature distribution in the width direction of the central portion of the sheet glass SG is made uniform, and the temperature at both end portions of the sheet glass SG is lower than the temperature at the central portion. In this way, the end portions of the sheet glass SG are cooled so as to be contracted in the width direction, and the central portion of the sheet glass SG is cooled so that the thickness of the sheet glass SG is uniform. Therefore, the thickness of the sheet glass SG is reduced. The deviation becomes smaller.

The second temperature distribution 20b and the third temperature distribution 20c are lower than the first temperature distribution 20a. Further, the second temperature distribution 20b and the third temperature distribution 20c have a temperature gradient in the width direction at the central portion of the sheet glass SG. Specifically, the second temperature distribution 20b and the third temperature distribution 20c are the highest temperatures in the center of the width direction of the sheet glass SG, and the temperatures of the both ends of the sheet glass SG are the lowest. More specifically, the second temperature distribution 20b and the third temperature distribution 20c gradually decrease in temperature as the center of the flat glass SG is oriented toward the both ends of the sheet glass SG. In other words, based on the second temperature distribution 20b and the third temperature distribution 20c, the temperature distribution in the width direction of the sheet glass SG is controlled so as to have a mountain shape (a curve having an upward convex shape) (warpage reduction step). That is, the warpage reduction step cools the sheet glass SG while maintaining a temperature gradient (having a curve convex upward). In other words, the warpage reduction step The sheet glass SG is cooled in such a manner that the temperature distribution continuously maintains the shape of the curve having the upward convex shape.

Further, the control based on the temperature of the second temperature distribution 20b is performed on the upstream side of the second temperature region with respect to the downward flow direction of the sheet glass SG. Further, the control system based on the third temperature distribution 20c is executed on the downstream side of the second temperature region with respect to the downward flow direction of the sheet glass SG. Here, it is preferable to set the third temperature distribution 20c to be larger than the second temperature distribution 20b. Specifically, the second temperature distribution 20b is set such that the temperature of the center of the sheet glass SG and the temperature of the end portion of the sheet glass SG become the second temperature difference Y1. Further, the third temperature distribution 20c is set such that the temperature of the central portion of the sheet glass SG and the temperature of the end portion of the sheet glass SG become the third temperature difference Y2. The third temperature difference Y2 is greater than the second temperature difference Y1. Furthermore, the second temperature difference Y1 is greater than the first temperature difference X. That is, the temperature distributions 20a to 20c are in the downward flow direction of the sheet glass SG, and the temperature difference between the center portion and the end portion or the temperature difference between the center portion and the end portion is increased (X < Y1 < Y2).

Further, the warpage reduction step is performed in a temperature region in which the third temperature distribution 20c is lower than the temperature, and the temperature gradient in the width direction of the flat glass SG decreases as the temperature of the flat glass SG approaches the vicinity of the strain point, and the flat plate is cooled. Glass SG.

Hereinafter, the temperature control of each unit will be described in detail.

(temperature control of the central upper cooling unit)

The center upper cooling unit 62 realizes the temperature distribution of the region in which the thickness of the sheet glass SG is determined as described above (first central portion cooling step). Specifically, since the temperature distribution in the width direction of the center upper cooling unit 62 opposed to the sheet glass SG is uniform, the temperature in the width direction of the sheet glass SG becomes uniform (sub-distribution 10a).

The central lower cooling units 63a and 63b realize the temperature distribution of the region in which the amount of warpage of the sheet glass SG is adjusted as described above (the second central portion cooling step and the third central portion cooling step). Specifically, the central lower cooling units 63a and 63b adjust the temperature in the width direction of the sheet glass SG so as to have a mountain shape (having a curve convex upward). With The body has the highest temperature at the center in the longitudinal direction of the central lower cooling units 63a and 63b. Further, the temperatures of both end portions in the longitudinal direction of the central lower cooling units 63a and 63b are set to the lowest temperatures. Further, the temperature is controlled so as to gradually decrease from the center toward both ends. In this way, the temperature in the width direction of the sheet glass SG becomes a mountain shape (sub-distribution 10b, sub-distribution 10c).

Further, in the present embodiment, two central lower cooling units 63a and 63b are disposed along the downward flow direction of the sheet glass SG. The central lower cooling unit 63b disposed below the flow direction of the sheet glass SG is controlled so as to form a temperature distribution larger than the curve of the upper central cooling unit 63a disposed above. Specifically, as described above, the temperature gradient (refer to Y2 of FIG. 6) of the temperature distribution 10c realized by the central lower cooling unit 63b is larger than the temperature gradient (center of the distribution 10b realized by the central lower cooling unit 63a) Temperature gradient between the part and the end) (refer to Y1 of Fig. 6) (Y1 < Y2).

As described above, the cooling roller 51 realizes the temperature distribution (quenching step) of the region that affects the uniformity of the thickness of the sheet glass SG. The cooling roller 51 quenches both end portions of the glass that joins the lowermost end portion 41a of the molded body 41. In other words, the ambient temperature at both end portions and both end portions of the sheet glass SG is a temperature lower than the ambient temperature around the central portion of the sheet glass SG (sub-distribution 10d).

The end upper cooling unit 72 realizes the temperature distribution of the region that affects the thickness and/or the amount of warpage of the sheet glass SG as described above (first end portion cooling step). The end upper cooling unit 72 supplies the sheet glass SG with a temperature lower than the temperature at which the center upper cooling unit 62 and the central lower cooling unit 63a are applied to the sheet glass SG. In other words, the ambient temperature at both end portions and both end portions of the sheet glass SG is a temperature lower than the ambient temperature around the central portion of the sheet glass SG (sub-distribution 10e).

The end lower cooling unit 73 realizes the temperature distribution of the region that affects the adjustment of the amount of warpage of the sheet glass SG as described above (the second side portion cooling step). The lower end cooling unit 73 applies lower temperature to the sheet glass SG than the central lower cooling units 63a, 63b. The temperature is imparted to the sheet glass SG. In other words, the ambient temperature at both end portions of the sheet glass SG is lower than the ambient temperature of the central portion of the sheet glass SG (sub-distribution 10f).

The temperature control of the sheet glass SG is performed via the control device 91, the cooling roller 51, and each unit. In the upper space of the forming furnace chamber in which the molded body 41 is located, a high temperature temperature environment is maintained so that the molten glass is formed at a specific viscosity. On the other hand, in the lower space of the forming furnace chamber which is partitioned from the upper space by the partition member (heat insulating member) 50, the sheet glass SG which is formed from the molten glass by the forming is cooled. Therefore, a heat insulating member having excellent heat insulating properties is used for the partition member 50 so that heat transfer from the upper space to the lower space is less likely to occur. Specifically, a material having heat insulating properties is used for the heat insulating member so that (1) when the flat glass SG is molded, the temperature of the molten glass FG when the molten glass FG passes through the molded body 41 is equal to or higher than the liquidus temperature. The viscosity of both ends of the molten glass FG when the molten glass FG passes through the lowermost end portion of the molded body 41 becomes 10 ^4.3 to 10 ⁶ dPa. Second, and (2) when cooling the flat glass SG, when the temperature of the central portion of the flat glass SG is in a temperature region from the temperature higher than the softening point to the vicinity of the annealing point, the viscosity of the both ends of the flat glass SG Become 10 ^9.0 ~ 10 ^14.5 dPa. second.

At this time, the thermal resistance between the upper space and the lower space of the ambient temperature of the upper space of the partition member (heat insulating member) 50 and the partition member 50 is preferably 0.2 m ² . K/W or above. The temperature distribution which can suppress the shrinkage of the sheet glass SG in the lower space can be achieved by using the partition member 50 including such a heat resistance. Specifically, the thermal resistance of the partition member 50 is less than 0.2 m ² . At the time of K/W, both ends of the plate glass SG quenched by the cooling roll 51 and the end portion cooling unit 71 are affected by the heat transmitted from the upper space toward the lower space, so that the temperature drop is suppressed, and the temperature cannot be increased. Viscosity required. In this case, since the viscosity of the both ends of the sheet glass SG is not high, the sheet glass SG is easily contracted in the width direction by the surface tension when the sheet glass SG is formed by the separation of the molded body 41. Therefore, it is difficult to ensure the target width of the sheet glass SG. However, the thermal resistance of the partition member (heat insulating member) 50 can be set to 0.2 m ² . Above K/W, the both ends of the quenched flat glass SG are reduced in heat from the upper space toward the lower space, and are cooled along a specific temperature distribution. The thermal resistance of the partition member 50 is preferably 0.3 m ² . Above K/W, more preferably 0.4m ² . K/W or above. Further, in order to make the thermal resistance extremely large, it is necessary to make the thickness of the partition member 50 extremely thick, for example, which is not preferable. Therefore, the thermal resistance of the partition member 50 is preferably 0.2 to 2 m ² . K/W, more preferably 0.4~2m ² . K/W.

In the partition member (insulation member) 50 having such thermal resistance, the thermal conductivity is 0.1 to 0.4 W/m. K, more preferably 0.1~0.25W/m. K material. As the partition member (heat insulating member) 50, for example, a ceramic fiber board having a high alumina content is used.

As a preferred form of the partition member 50, the thermal conductivity (the upper space) of the material of the partition member 50 which is in contact with the slit-like gap through which the flat glass SG moves from the upper space of the forming furnace chamber to the lower space The thermal conductivity of the ambient temperature is preferably 0.5 W/m. Below K. More preferably, the partition member 50 includes a thermal conductivity (thermal conductivity of the ambient temperature of the upper space) of 0.25 W/m. 1 material below K. With this configuration, it is not necessary to excessively thicken the thickness of the partition member 50 to set the thermal resistance to 0.2 m ² . K/W or above.

As shown in FIG. 6, the cooling of the flat glass of the present embodiment includes the steps of uniformizing the temperature distribution in the width direction of the central portion in the width direction of the sheet glass SG, and lowering the temperature of both ends of the flat glass SG to be lower than that of the flat plate glass SG. Temperature of the central portion in the width direction of the glass SG (step of equalizing the thickness); and lowering the temperature of both end portions and the central portion of the sheet glass SG compared with the temperatures of the both end portions and the central portion in the step The temperature gradient is formed in the width direction of the sheet glass SG from the center of the width direction of the sheet glass SG toward both end portions. To achieve the two steps, the control unit 91 can control the temperature of the sheet glass SG using each unit, the cooling roller 51, and the like. In the present embodiment, by providing the partition member 50, the heat transfer between the upper space of the forming furnace chamber and the space below the forming furnace chamber is sufficiently suppressed, so that the temperature of the flat glass SG can be performed in the lower space of the forming furnace chamber. Control.

The temperature control of the sheet glass SG is performed in the first step to make the temperature distribution in the width direction of the central portion of the sheet glass SG uniform, so that not only the shrinkage in the width direction of the sheet glass SG but also the sheet glass SG can be suppressed. The thickness deviation of the produced glass substrate.

Further, in the next step, the temperature distribution in the width direction of the sheet glass SG is made lower than that in the first step, and the center of the width direction of the sheet glass SG is directed toward both end portions in the width direction of the sheet glass SG. A temperature gradient is formed on it. At this time, the amount of cooling in the central portion in the width direction of the sheet glass SG is larger than the amount of cooling at both end portions in the width direction of the sheet glass SG. As a result, the volume shrinkage ratio of the sheet glass SG increases from the both end portions in the width direction toward the center portion, so that the tensile stress acts on the center portion of the sheet glass SG. In particular, in the central portion of the sheet glass SG, tensile stress acts in the downward direction and the width direction of the sheet glass SG. Further, in terms of lifting the warpage of the glass sheet, it is preferable that the tensile stress acting upward in the downward direction of the flat glass SG is larger than the tensile stress acting in the width direction of the flat glass SG. By the tensile stress, the flatness of the sheet glass SG can be maintained while cooling, so that the amount of warpage of the sheet glass SG or even the glass sheet can be reduced.

Further, in the case where the temperature of the liquid phase of the glass is high, it is possible to prevent the devitrification of the glass by forming the molten glass having a temperature sufficiently higher than the liquidus temperature of the glass. However, for the application of overflow down draw method, the viscosity of the molten glass into the most compact portion 41 of the lower end 41a of the central portion and the both end portions is preferably 10 ^4.3 dPa. More than two seconds. The viscosity is preferably 10 ^4.4 dPa. More than second, and more preferably 10 ^4.6 dPa. More than two seconds. Ensuring this viscosity depends on the following reasons. That is, the sheet glass SG separated from the lowermost end portion 41a is intended to fall to the region sandwiched by the cooling roller 51 due to its own weight. The reason for this is that the falling speed at this time differs depending on the viscosity of the molten glass of the lowermost end portion 41a of the molded body 41. When the viscosity of the molten glass at the lowermost end portion 41a is smaller than the above range, the flat glass SG is more likely to fall due to its own weight than the stretching speed of the flat glass SG by the cooling roller 51, and finally exists. The flat glass SG is relaxed on the cooling roll 51. Therefore, the viscosity of the molten glass of the lowermost end portion 41a of the formed body 41 is preferably 10 ^4.3 dPa. More than two seconds. Further, if the circumferential speed of the cooling roller 51 and the lower cooling roller 51 located downstream of the downstream pulling roller 81 is sufficiently increased, the free fall speed of the glass ribbon can be made slower than the peripheral speed of the cooling roller 51 and the lowering roller 81. However, in this case, generally, not only the thickness of the sheet glass SG to be obtained under the condition of a specific glass flow rate but also the temperature control of the glass ribbon to be carried out in the downstream annealing step is excessively determined. The circumferential speed of the cooling roller 51 and the pull-down roller 81 is accelerated, which is not preferable in practical use.

In addition, in order to increase the temperature of the molten glass of the lowermost end portion 41a of the molded article 41 in order to form a viscosity lower than the numerical range of the viscosity of the molten glass, the ambient temperature of the downstream side of the molded article 41 rises. Therefore, the viscosity at both end portions in the width direction of the sheet glass SG formed by the joining of the molten glass flowing on the respective wall surfaces on both sides of the molded body is not sufficiently increased at the lowermost end portion 41a of the molded body 41. Therefore, the width of the sheet glass SG is contracted. If the width of the sheet glass SG is contracted, there is a problem that the width of the sheet glass SG immediately before cutting or the width of the product cannot be ensured. The problem is that the higher the liquid phase temperature of the glass (the smaller the liquid phase viscosity), the more significant.

In the present embodiment, the thermal resistance of the partition member (heat insulating member) 50 is set to 0.2 m ² . K/W or more, and suppresses the heat transfer from the upper space of the forming furnace chamber toward the lower space. Therefore, even if the liquidus temperature of the glass is high, the ambient temperature of the upper space of the forming furnace chamber is set high, and the quenched flat plate is set. Both ends of the glass SG may be protected from a specific viscosity by the heat transmitted from the upper space toward the lower space. Therefore, the reduction in the width of the sheet glass SG can be suppressed.

That is, when the glass having a high liquidus temperature (the liquid phase viscosity is small) is used, the effect of the present embodiment is remarkable. In this case, the thermal resistance is 0.2 m ² . The heat insulating member 50 of K/W or more is applied with tensile tension to both end portions of the flat glass SG so that the viscosity of both end portions of the flat glass SG is 10 ^9.0 to 10 ^14.5 dPa. In the second mode, the flat glass SG is cooled, thereby ensuring the width of the product.

(characteristics of glass)

The glass substrate produced by this embodiment is suitably used for the glass substrate for flat panel displays. Further, the glass substrate can also be used for a glass substrate which is required to form a LTPS (Low Temperature Poly Silicon), a TFT (Thin Film Transistor) or an oxide semiconductor, and which is subjected to high temperature treatment, which has a small heat shrinkage ratio. Further, it can be used for a cover glass such as a display device, a glass substrate for a magnetic disk, a glass substrate for a solar cell, or the like.

Moreover, the liquidus viscosity of the glass substrate of the present embodiment is preferably 10 ^4.3 dPa. Seconds ~ 10 ^6.7 dPa. second. In the forming step, in order to avoid devitrification of the glass, the viscosity of the lowermost end portion 41a of the molded body 41 must be made smaller than the liquidus viscosity, and therefore, the ambient temperature of the upper space of the forming furnace chamber is set higher than that of the lower space. Therefore, there is a large thermal step difference between the upper space and the lower space of the forming furnace chamber, so that heat transfer is likely to become large. In the present embodiment, the heat transfer from the upper space of the forming furnace chamber toward the lower space is suppressed, so that the shrinkage in the width direction of the sheet glass SG in the lower space of the forming furnace chamber can be suppressed. The glass having a higher liquidus viscosity can increase the viscosity of the lowermost end portion 41a of the molded body 41, so that the shrinkage of the flat glass SG in the width direction can be suppressed. Therefore, the liquidus viscosity of the glass substrate of the present embodiment is preferably 10 ^4.7 dPa. Seconds ~ 10 ^6.7 dPa. Seconds, more preferably 10 ⁵ dPa. Seconds ~ 10 ^6.7 dPa. second. Moreover, the liquidus viscosity of the glass substrate of the embodiment may also be 10 ^5.3 dPa. Less than seconds. The smaller the liquid phase viscosity of the glass, the higher the ambient temperature of the upper space of the forming furnace chamber is set. Therefore, the shrinkage in the width direction of the flat glass SG tends to be large as described above. That is, the liquid viscosity is 10 ^5.3 dPa. In the case of glass of a second or less, the effect of this embodiment becomes remarkable, if it is 10 ^4.3 ~ 10 ^5.3 dPa. Seconds, the effect is more significant, if it is 10 ^4.3 dPa. Seconds ~ 10 ^5.0 dPa. In seconds, the effect becomes more pronounced, if it is 10 ^4.3 dPa. Seconds ~ 10 ^4.9 dPa. In seconds, the effect becomes more significant, which is preferable in the above aspects. The viscosity in the liquid phase is less than 10 ^4.3 dPa. In the case of a second glass, the use of the overflow down-draw method becomes difficult.

Further, the liquidus temperature of the glass substrate of the present embodiment is preferably from 1000 ° C to 1,250 ° C. The higher the liquidus temperature of the glass, the higher the ambient temperature of the upper space of the forming furnace chamber must be set to avoid the devitrification of the glass. Therefore, the step of heat between the upper space and the lower space of the forming furnace chamber is large, so that heat transfer is likely to become large. In the present embodiment, the heat transfer from the upper space of the forming furnace chamber toward the lower space is suppressed, so that the shrinkage in the width direction of the sheet glass SG in the lower space of the forming furnace chamber can be suppressed. In other words, from the viewpoint of reducing the amount of heat transfer from the upper space of the forming furnace chamber toward the lower space and reducing the shrinkage in the width direction of the sheet glass SG, the liquidus temperature of the glass substrate is preferably 1250 ° C or less, more preferably It is 1200 ° C or less, and more preferably 1105 ° C or less. Further, the liquid phase temperature of the glass substrate of the present embodiment may be 1150 ° C to 1250 ° C. The higher the liquidus temperature of the glass, the higher the ambient temperature of the upper space of the forming furnace chamber must be set to avoid the devitrification of the glass. In other words, when the glass having a liquid phase temperature of 1150 ° C or higher is used for the sheet glass SG, the effects of the embodiment are more remarkable. Further, the reason why the upper limit of the liquidus temperature of the glass is set to 1,250 ° C is that when the liquid phase temperature of the glass exceeds 1,250 ° C, there is a problem that the latent phenomenon of the molded body 41 is likely to occur. That is, in the present embodiment, since the liquidus temperature of the glass is from 1150 ° C to 1250 ° C, the effect of the present embodiment is remarkable, and if it is 1170 ° C to 1250 ° C, the effect becomes more remarkable, and if it is 1180 ° C to 1250 At °C, the effect becomes more remarkable. If it is 1200 ° C to 1250 ° C, the effect becomes more remarkable, and it is preferable in the above aspects.

The strain point of the glass substrate of the present embodiment is preferably 670 ° C or higher. When the strain point of the glass substrate is 670 ° C or more, the glass tends to have a high liquidus temperature, and there is a flaw in devitrification during the forming step. Therefore, in the case of using a glass having a strain point of 670 ° C or more, in order to suppress the occurrence of devitrification in the forming step, it is necessary to increase the temperature of the molten glass during molding as compared with the case of producing a glass which is less likely to cause devitrification. Therefore, the ambient temperature of the upper space of the forming furnace chamber in which the molded body 41 is located is also set high. Therefore, there is a large heat difference between the upper space and the lower space of the forming furnace chamber, and the heat transfer is likely to become large. In this embodiment, the thermal resistance is 0.2 m ² . The partition member 50 of K/W or more suppresses the heat transfer from the upper space of the forming furnace chamber toward the lower space, so that the shrinkage in the width direction of the sheet glass SG in the lower space of the forming furnace chamber can be suppressed. That is, when the strain point of the glass substrate is 670 ° C or more, the effect of the present embodiment is remarkable.

In the present embodiment, glass having a strain point of 670 ° C or higher can be used, and even a glass having a strain point of 675 ° C or higher, a strain point of 680 or more, and a glass having a strain point of 690 ° C or higher can be used to secure the flat glass. The width of the SG and the width of the product are significant in this respect. As the glass substrate forming the LTPS, the TFT, or the oxide semiconductor, it is preferable to use a glass having a strain point of 675 ° C or higher, and more preferably a glass having a strain point of 680 ° C or higher. Therefore, the glass substrate produced in the present embodiment is used as the glass substrate. A glass substrate forming an LTPS, a TFT or an oxide semiconductor is preferable.

Further, when the heat shrinkage rate of the glass substrate is 75 ppm or less, the strain point of the glass is generally high, and the liquidus temperature tends to be high. Even if it is necessary to manufacture a glass substrate having a heat shrinkage ratio of 75 ppm or less, a thermal resistance of 0.2 m ^{2 is used} . The partition member 50 of K/W or more suppresses the heat transfer from the upper space of the forming furnace chamber toward the lower space, so that the shrinkage in the width direction of the sheet glass SG in the lower space of the forming furnace chamber can be suppressed. Therefore, the sheet glass SG can suppress the shrinkage of the width of the sheet glass SG which is generated when the molded body 41 is separated, and ensures the width of the sheet glass SG. When a glass substrate having a glass having a heat shrinkage ratio of 75 ppm or less is used, an LTPS, a TFT, or an oxide semiconductor is formed on the glass substrate for the production of an image display device, and high temperature processing is performed to suppress an image. A problem such as a shift in the distance between pixels in the display device.

In addition, the heat shrinkage ratio is a value obtained by the following formula using the shrinkage amount of the glass substrate after heat treatment at a temperature rise and fall rate of 10/min and holding at 550 ° C for 2 hours.

Heat shrinkage ratio (ppm) = {shrinkage amount of glass substrate after heat treatment / length of glass substrate before heat treatment} × 10 ⁶

Further, the glass substrate of the present embodiment may contain zirconia. When the flat glass SG is produced and the glass substrate produced by the flat glass SG contains zirconia, the liquidus temperature of the glass rises. Therefore, in order to avoid devitrification of the glass, the molded body 41 must be reduced. In particular, the viscosity in the vicinity of the lowermost end portion 41a (the temperature of the molten glass is increased to such an extent that devitrification does not occur). In the present embodiment, even if the viscosity of the molten glass of the lowermost end portion 41a of the molded body 41 is small and the ambient temperature in the upper space is high, the thermal resistance is 0.2 m ² . The partition member 50 of K/W or more suppresses the heat transfer from the upper space toward the lower space, so that the shrinkage of the plate width in the lower space of the forming furnace chamber can be suppressed. Therefore, when such a glass is used, the effect of this embodiment becomes remarkable.

Moreover, it is preferable that the glass substrate of this embodiment contains tin oxide. Tin oxide is easily crystallized to cause devitrification. Therefore, in the case of producing a glass containing tin oxide, in order to avoid devitrification, it is necessary to reduce the viscosity of the molten glass in the vicinity of the molded body 41, particularly the lowermost end portion 41a (the molten glass temperature is such that no devitrification occurs) rise). In the present embodiment, the heat transfer from the upper space toward the lower space is suppressed, so that the shrinkage of the plate width in the lower space of the forming furnace chamber can be suppressed.

Further, when the melting tank of the melting apparatus 11 shown in Fig. 2 is composed of a furnace material such as a high zirconia refractory, the zirconia is melted from the high zirconia refractory in the melting step. The situation in molten glass. In this case, the concentration of zirconium oxide in the molten glass rises and the temperature of the liquid phase rises. Therefore, it is necessary to maintain the temperature of the molten glass at the time of molding at a high level. In the present embodiment, the heat transfer from the upper space toward the lower space is suppressed, so that the shrinkage of the plate width in the lower space of the forming furnace chamber can be suppressed. Therefore, when such a glass is used, the effect of this embodiment becomes remarkable.

(glass composition)

The glass substrate produced by this embodiment can be suitably used for a flat panel display, especially a glass substrate for liquid crystal displays. Such a glass substrate is, for example, represented by mass % and contains 50 to 70% of SiO ₂ , 5 to 25% of Al ₂ O ₃ , 0 to 15% of B ₂ O ₃ , 0 to 10% of MgO, and 0 to 20 % CaO, 0 to 20% SrO, 0 to 10% BaO, and 0 to 10% ZrO ₂ .

Further, the glass substrate produced in the present embodiment can be suitably used for a glass substrate in which an LTPS, a TFT or an oxide semiconductor is formed on the surface of the glass. Such a glass substrate is, for example, represented by mass %, containing 58 to 75% of SiO ₂ , 15 to 23% of Al ₂ O ₃ , 1 to 12% of B ₂ O ₃ , and 6 to 17% of RO (wherein , RO is the total amount of the total components contained in the glass plate of MgO, CaO, SrO, and BaO, and the strain point is 680 ° C or higher.

In this case, it is preferable to use a glass plate for LTPS or TFT if one or more of the following formulas are satisfied.

. In order to further increase the strain point, it is necessary to set (SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₂ : 8 to 50 and/or to make SiO ₂ + Al ₂ O ₃ : 75% or more.

. In order to further increase the strain point, it is necessary to make the mass ratio (SiO ₂ + Al ₂ O ₃ )/RO 7.5 or more.

. In order to lower the specific resistance of the glass, it is necessary to contain 0.01 to 1% by mass of Fe ₂ O ₃ .

. In order to achieve a higher strain point of the glass while preventing an increase in the liquidus temperature, CaO/RO must be made 0.65 or more.

Further, when it is considered to be applied to a mobile device such as a mobile communication terminal, the total content of SrO and BaO is preferably 0 to 5% by mass, more preferably 0 to 3.3% by mass, from the viewpoint of weight reduction. .

Further, the glass substrate may be an alkali-free glass substantially free of an alkali metal oxide (Na ₂ O, K ₂ O, Li ₂ O) as described above, or an alkali metal oxide containing 0.05 to 2.0% by mass ( A glass containing a small amount of alkali of Na ₂ O, K ₂ O, and Li ₂ O). In the glass substrate for a flat panel display, if the alkali metal is eluted from the glass substrate in the panel manufacturing step, the TFT characteristics or the semiconductor characteristics are deteriorated. Therefore, it is preferable that the glass substrate does not substantially contain an alkali metal oxide or even contains It also contains 0.05 to 2.0% by mass.

Further, as long as the alkali metal is contained as much as possible, the deterioration of the TFT characteristics or the semiconductor characteristics or the thermal expansion of the glass can be suppressed in a fixed range, and the meltability and the clarification property can be improved. In addition, the glass containing a small amount of alkali can effectively reduce the specific resistance of the molten glass. Therefore, it is considered that the molten glass is easily energized during the electric melting, and the furnace material which constitutes the wall surface of the melting tank of the high zirconia-based refractory or the like is relatively opposed. It is difficult to energize. As a result, corrosion of the furnace material can be suppressed. Further, since zirconia can be reduced to be melted into the molten glass, the devitrification of the glass can be improved. From this point of view, it is more effective to use a glass containing a small amount of alkali.

In the above embodiment, the central upper cooling unit 62 controls the ambient temperature to be uniform in the width direction of the sheet glass SG (step of equalizing the thickness). Thereby, in the above embodiment, the thickness (wall thickness) of the sheet glass SG can be made uniform. However, the central upper cooling unit 62 may be configured to change the temperature in the width direction of the sheet glass SG. For example, the space formed inside the central cooling unit 62 may be divided into a plurality of spaces, and each space may be separately cooled, or a heat insulating material may be partially disposed inside the central cooling unit 62, thereby being changeable. Ambient temperature in the width direction. Therefore, even if the temperature of the central portion of the sheet glass SG is uniform, when the wall thickness in the width direction of the sheet glass SG cannot be uniformized due to some influence, the wall thickness of the sheet glass SG can be made uniform. Chemical.

[Experimental Example 1]

In order to confirm the effect of the present embodiment, a method of manufacturing a glass substrate was changed to produce a glass substrate.

(Example 1)

The glass substrate to be produced is melted in a melting tank of the melting device 11 to form a molten glass in such a manner that the glass substrate to be produced has the following composition. The molten glass was transferred to a clarification tank of the clarification device 12 via a tube made of a platinum alloy, and clarification of the molten glass was performed. Next, after the clarified molten glass was homogenized, the molten glass was supplied to the molded body 41, and the sheet glass SG was formed at a speed of about 2 m/min by an overflow down-draw method. At this time, the thermal resistance of the partition member (heat insulating member 50) used was set to 0.4 m ² . K/W. The viscosity of the both ends of the molten glass flowing in the lowermost end portion 41a of the formed body 41 is 10 ⁵ dPa. second. At this time, when the temperature of the central portion of the sheet glass SG is in a temperature region from the temperature higher than the softening point to the vicinity of the annealing point, tension is applied to both end portions of the sheet glass SG, and two of the flat glass SG are used. The viscosity of the end becomes 10 ^9.0 ~ 10 ^14.5 dPa. Cool down in seconds.

That is, a material having heat insulating properties is used for the heat insulating member 50 so that (1) when the flat glass SG is formed, the temperature of the molten glass FG when the molten glass FG passes through the molded body 41 is above the liquidus temperature, and is melted. When the glass FG passes through the lowermost end portion of the molded body 41, the viscosity of both ends of the molten glass FG becomes 10 ^4.3 to 10 ⁶ dPa. Second, and (2) when cooling the flat glass SG, when the temperature of the central portion of the flat glass SG is in a temperature region from the temperature higher than the softening point to the vicinity of the annealing point, the viscosity of the both ends of the flat glass SG Become 10 ^9.0 ~ 10 ^14.5 dPa. second. Thereafter, the sheet glass SG was cut, and a glass substrate for a flat panel display having a thickness of 0.7 mm and a size of 2200 mm × 2500 mm was produced. Further, the glass substrate for a flat panel display manufactured had a liquidus temperature of 1,125 ° C and a strain point of 660 ° C.

(The composition of the glass of Example 1)

SiO ₂ : 60% by mass, Al ₂ O ₃ : 19.5% by mass, B ₂ O ₃ : 10% by mass, CaO: 5.3% by mass, SrO: 5% by mass, and SnO ₂ : 0.2% by mass.

(Comparative Example 1)

In Comparative Example 1, a partition member (heat insulating material) having a heat resistance different from that of the partition member (heat insulating material) used in Example 1 was used. The thermal resistance of the partition member (insulation member) was set to 0.1 m ² . K/W.

Therefore, the following conditions are not satisfied: (1) When the sheet glass SG is formed, when the molten glass FG passes through the molded body 41, the temperature of the molten glass FG is equal to or higher than the liquidus temperature, and when the molten glass FG passes through the lowermost end portion of the molded body 41 The viscosity of the two ends of the molten glass FG is 10 ^4.3 ~ 10 ⁶ dPa. Second, and (2) when cooling the flat glass SG, when the temperature of the central portion of the flat glass SG is in a temperature region from the temperature higher than the softening point to the vicinity of the annealing point, the viscosity of the both ends of the flat glass SG Become 10 ^9.0 ~ 10 ^14.5 dPa. second.

A glass substrate was produced in the same manner as in Example 1 except for the above. The glass material of Comparative Example 1 was prepared in the same manner as the glass composition of Example 1, and a glass substrate was prepared to produce a glass substrate for a flat panel display.

(the amount of shrinkage of the width of the flat glass)

The amount of shrinkage of the flat glass of Example 1 and Comparative Example 1 in the width direction of the width of the molded body was measured. The amount of shrinkage in Example 1 was 180 mm, whereas the amount of shrinkage in Comparative Example 1 was 230 mm. Further, in the glass substrate produced by the production methods of Example 1 and Comparative Example 1, devitrification did not occur.

[Experimental Example 2]

Furthermore, in order to confirm the effect of this embodiment with the glass of the glass composition different from the said glass composition, the manufacturing method of a glass substrate was changed, and the glass substrate was manufactured.

(Example 2)

The glass substrate produced is a glass having the following glass composition, and the viscosity of the both ends of the molten glass flowing in the lowermost end portion 41a of the molded body 41 is 10 ^4.6 dPa. In seconds, the liquidus temperature of the glass substrate was 1230 ° C, and the strain point was 715 ° C. In addition to the above, the glass for flat panel display was produced in the same manner using the same thermal resistance of the partition member (heat insulating member) as in Example 1. Substrate.

(The composition of the glass of Example 2)

SiO ₂ : 61.5 mass%, Al ₂ O ₃ : 20 mass%, B ₂ O ₃ : 8.4 mass%, CaO: 10 mass%, and SnO ₂ : 0.1 mass%.

(Comparative Example 2)

In Comparative Example 2, a partition member having a heat resistance different from that used for the partition member of Example 2 was used. The thermal resistance of the partition member was set to 0.1 m ² . K/W.

Therefore, the following conditions are not satisfied: (1) When the sheet glass SG is formed, when the molten glass FG passes through the molded body 41, the temperature of the molten glass FG is equal to or higher than the liquidus temperature, and when the molten glass FG passes through the lowermost end portion of the molded body 41 The viscosity of the two ends of the molten glass FG is 10 ^4.3 ~ 10 ⁶ dPa. Second, and (2) when cooling the flat glass SG, when the temperature of the central portion of the flat glass SG is in a temperature region from the temperature higher than the softening point to the vicinity of the annealing point, the viscosity of the both ends of the flat glass SG Become 10 ^9.0 ~ 10 ^14.5 dPa. second.

A glass substrate was produced in the same manner as in Example 2 except for the above. The glass material of Comparative Example 2 was blended with the glass of the material of Example 2, and the glass substrate for flat panel display was manufactured.

(Example 3)

In Example 3, the glass substrate produced was a glass having the following glass composition, a liquidus temperature of 1200 ° C, and a strain point of 699 ° C. In addition to the above, the same partition member (heat insulating member) as in Example 2 was used. The thermal resistance was used to manufacture a glass substrate for a flat panel display in the same manner.

(The composition of the glass of Example 3)

SiO ₂ : 61.2% by mass, Al ₂ O ₃ : 19.5% by mass, B ₂ O ₃ : 9.0% by mass, K ₂ O: 0.19% by mass, CaO: 10% by mass, Fe ₂ O ₃ : 0.01% by mass, SnO ₂ : 0.1% by mass.

(Examples 4 to 7)

The thermal resistance of the partition member (heat insulating member) was changed to 0.2 m ² . K/W (Example 4), 0.6 m ² . K/W (Example 5), 1.0 m ² . K/W (Example 6), and 1.2 m ² . A glass substrate for a flat panel display was produced in the same manner as in Example 3 except that K/W (Example 7) was used.

(Comparative Example 3)

In Comparative Example 3, a partition member having a heat resistance different from that used in the partition member of Example 3 was used. The thermal resistance of the partition member was set to 0.1 m ² . K/W.

Therefore, the following conditions are not satisfied: (1) When the sheet glass SG is formed, when the molten glass FG passes through the molded body 41, the temperature of the molten glass FG is equal to or higher than the liquidus temperature, and when the molten glass FG passes through the lowermost end portion of the molded body 41 The viscosity of the two ends of the molten glass FG is 10 ^4.3 ~ 10 ⁶ dPa. Second, and (2) when cooling the flat glass SG, when the temperature of the central portion of the flat glass SG is in a temperature region from the temperature higher than the softening point to the vicinity of the annealing point, the viscosity of the both ends of the flat glass SG Become 10 ^9.0 ~ 10 ^14.5 dPa. second.

A glass substrate was produced in the same manner as in Example 3 except for the above. The glass material of Comparative Example 3 was blended with the glass composition of the glass of Example 3, and a glass substrate for flat panel display was produced.

(the amount of shrinkage of the width of the flat glass)

The amount of shrinkage of the sheet glass in the production methods of Examples 2 to 7 and Comparative Examples 2 to 3 with respect to the width direction of the molded body width was measured. The shrinkage amount of Examples 2 to 4 was 190 mm or less, the shrinkage amount of Example 5 was 170 mm or less, the shrinkage amount of Example 6 was 160 mm or less, and the shrinkage amount of Example 7 was 150 mm or less. In contrast, Comparative Example 2 and The shrinkage amount of Example 3 exceeded 220 mm.

According to the above Experimental Examples 1 and 2, the effects of the present embodiment are remarkable. Further, it is understood that the heat resistance used is 0.2 m ² . For the partition member (heat insulation material) of K/W or more, the viscosity at both ends of the flat glass is 10 ^9.0 ~ 10 ^14.5 dPa. It is preferable to perform cooling in a second manner to suppress the amount of shrinkage of the flat glass.

In the above, the glass substrate manufacturing method and the glass substrate manufacturing apparatus of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments or examples, and it is of course possible to carry out the invention without departing from the spirit of the invention. Various improvements or changes.

40‧‧‧Forming device

41‧‧‧Formed body

41a‧‧‧ Lower end of the formed body

41b‧‧‧Top of the formed body

41c‧‧‧ Side of the formed body

50‧‧‧Parts

51‧‧‧Cooling roller

60‧‧‧Cooling unit

61‧‧‧Central cooling unit

62‧‧‧Central upper cooling unit

63a, 63b‧‧‧ central lower cooling unit

80‧‧‧ Annealing furnace

80a‧‧‧ top board

81‧‧‧ Pull down roller

90‧‧‧cutting device

FG‧‧‧ molten glass

SG‧‧ ‧ flat glass

Claims (10)

A method for producing a glass substrate, comprising: forming a flat glass by overflowing molten glass from a molded body in an upper space of a forming furnace chamber surrounded by a furnace wall; and passing the flat glass through a slit-like gap, The gap is formed by a heat insulating member that divides the forming furnace chamber into an upper space and a lower space; and in the lower space, both end portions of the flat glass are cooled; wherein the both ends of the flat glass are cooled The method comprises the steps of making the viscosity of the two ends of the flat glass by a cooling roller of 10 ^9.0 ~ 10 ^10.5 dPa. In the case where the cooling member is cooled, the heat insulating member is made of a heat insulating material so that (1) in the step of molding the flat glass, the temperature of the molten glass when the molten glass passes through the molded body is a liquid phase. The viscosity of the both ends of the molten glass when the molten glass passes through the lowermost end portion of the molded body is 10 ^4.3 to 10 ⁶ dPa. Second, and (2) in the step of cooling the flat glass, when the temperature of the central portion of the flat glass is at a temperature from the softening point plus 15 ° C to the glass strain point and the glass annealing point are added and then divided by 2 when the temperature of the region until the temperature of the resultant, comprising satisfied by the cooling and of the cooling roll and the viscosity of both end portions of the above-described flat glass becomes 10 ^9.0 ~ 10 ^14.5 dPa. Cooling in seconds. The method of manufacturing a glass substrate according to claim 1, wherein the thermal resistance between the upper space of the heat insulating member and the lower space is 0.2 m ² in an ambient temperature of the upper space. K/W or above. A method of manufacturing a glass substrate according to claim 1, wherein the lower space includes the following steps: a temperature distribution in a width direction of the central portion of the flat glass is made uniform, and a temperature of both end portions of the flat glass is lower than a temperature of the central portion; and a temperature of the both end portions and the central portion is compared with The temperature of the both end portions and the central portion in the step of lowering the temperature of the both end portions of the flat glass is lower than the center of the central portion in the width direction toward the both end portions A temperature gradient is formed in the width direction of the flat glass. The method for producing a glass substrate according to claim 2, wherein the lower space includes a step of uniformly making a temperature distribution in a width direction of the central portion of the flat glass and lowering a temperature of both end portions of the flat glass a temperature of the central portion; and the both end portions and the center of the step in which the temperature of the both end portions and the central portion are lower than a temperature at which both ends of the flat glass are lower than a temperature of the central portion The temperature of the portion is lower, and a temperature gradient is formed in the width direction of the flat glass from the center in the width direction of the central portion toward the both end portions. The method for producing a glass substrate according to any one of claims 1 to 4, wherein the liquid phase viscosity of the glass in the flat glass is 10 ^4.3 dPa. Seconds ~ 10 ^6.7 dPa. second. The method for producing a glass substrate according to any one of claims 1 to 4, wherein the glass substrate has a strain point of 670 ° C or higher. The method for producing a glass substrate according to any one of the preceding claims, wherein the glass substrate has a strain point of 670 ° C or higher. The method for producing a glass substrate according to any one of claims 1 to 4, wherein the step of cooling the both ends includes the viscosity of both ends of the flat glass being 10 ^9.0 to 10 ^10.5 dPa by a cooling roll. . Cooling is performed in a second manner, and after the cooling, the end portions are cooled by a lower cooling capacity than the cooling roller by the end portion cooling unit spaced apart from the flat glass, so that the both end portions are The viscosity becomes 10 ^9.0 ~ 10 ^14.5 dPa. second. A method for producing a glass substrate, comprising: forming a flat glass by overflowing molten glass from a molded body in an upper space of a forming furnace chamber surrounded by a furnace wall; and passing the flat glass through a slit-like gap, The gap is formed by a heat insulating member that partitions the forming furnace chamber into an upper space and a lower space; and in the lower space, both end portions of the flat glass are cooled; wherein the heat insulating member is insulated In the step of molding the flat glass, the temperature of the molten glass when the molten glass passes through the molded body is equal to or higher than a liquidus temperature, and the molten glass passes through the lowermost end portion of the molded body. The viscosity of the two ends of the molten glass is 10 ^4.3 ~ 10 ⁶ dPa. Second, and (2) in the step of cooling the flat glass, when the temperature of the central portion of the flat glass is at a temperature from the softening point plus 15 ° C to the glass strain point and the glass annealing point are added and then divided by 2 When the temperature is obtained in the temperature range, the viscosity of the both ends of the flat glass is 10 ^9.0 ~ 10 ^14.5 dPa. a second heat treatment unit provided by contacting the flat glass when the temperature of the central portion of the flat glass is in the temperature region after the flat glass is separated from the molded body in the step of cooling the both ends of the flat glass Heat treatment is performed on both end portions of the flat glass, and then the two end portions of the flat glass are heat-treated by a second heat treatment unit provided to leave the flat glass, and stretching is applied to the both end portions of the flat glass. Tension, while maintaining the viscosity of the two ends at 10 ^9.0 ~ 10 ^14.5 dPa. Within the range of seconds. A glass substrate manufacturing apparatus comprising: a molding furnace chamber surrounded by a furnace wall; and a heat insulating member that divides the forming furnace chamber into an upper space and a lower space to form a slit shape through which the flat glass passes a molded body provided in the upper space of the forming furnace chamber to overflow the molten glass to form a flat glass; and a cooling member that cools both end portions of the flat glass in the lower space; the cooling The member is included such that the viscosity of the two ends of the flat glass is 10 ^9.0 ~ 10 ^10.5 dPa. a cooling roll for cooling both end portions of the flat glass, wherein the heat insulating member is made of a heat insulating material, wherein (1) the step of forming the flat glass, the molten glass passes through the molded body The temperature of the molten glass is equal to or higher than the liquidus temperature, and the viscosity of the both ends of the molten glass when the molten glass passes through the lowermost end of the molded body is 10 ^4.3 to 10 ⁶ dPa. Second, and (2) in the step of cooling the flat glass, when the temperature of the central portion of the flat glass is at a temperature from the softening point plus 15 ° C to the glass strain point and the glass annealing point are added and then divided by 2 when the temperature of the region until the temperature of the resultant, comprising satisfied by the cooling and of the cooling roll and the viscosity of both end portions of the above-described flat glass becomes 10 ^9.0 ~ 10 ^14.5 dPa. Cooling in seconds.