KR20140095457A - Method and apparatus for making glass sheet - Google Patents

Abstract

A method of manufacturing a glass substrate, comprising the steps of: forming a sheet glass in an upper space of a forming furnace chamber by an overflow method of a molten glass by a molding body; and forming the sheet glass into a lower space for cooling both end portions of the sheet glass Shed. And is partitioned by a heat insulating member between the upper space and the lower space. At this time, the temperature of the molten glass at the time of passing through the molding is not less than the liquid temperature, and the viscosity at both ends of the molten glass when passing through the lowermost end of the molding is 10 ^4.3 to 10 ⁶ dPa · sec, Wherein when the temperature of the central portion of the sheet glass in the lower space is in a temperature range from a temperature higher than the softening point to a vicinity of the standoff point so that the viscosity of both end portions of the sheet glass is 10 ^9.0 to 10 ^14.5 dPa · sec , A material having a heat insulating property is used for the heat insulating member.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing a glass substrate,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a glass substrate for manufacturing a glass substrate and an apparatus for manufacturing a glass substrate.

Conventionally, a method of manufacturing a glass substrate by an overflow down-draw method using a formed body has been used. Generally, in a molded article, when the temperature of the molten glass is maintained for a long period of time near the liquidus temperature, crystals are precipitated in the molten glass to cause devitrification.

The temperature of the molten glass at the time of supplying the molded body is made lower than that at the time of supplying the molten glass at the lower end of the molded body so as to be higher than that of the prior art in order to prevent the melting of the glass at the time of molding, And the temperature of the molten glass when passing through the lower end of the formed body is made smaller than 90 DEG C (Patent Document 1).

Japanese Patent No. 4511187

However, in the above technique, the temperature of the molten glass at the lowermost end of the formed body is made higher than the conventional one. Further, in the above technique, the temperature of the molten glass during molding is made sufficiently higher than the liquid temperature to prevent the slip. As described above, in the above technique, the temperature of the molten glass passing through the molded body must be made higher than in the prior art in order to prevent the generation of a slump in the glass. Therefore, the temperature of the molten glass at the lowermost end of the formed article becomes higher than that of the conventional art, and the viscosity of the glass becomes lower. Therefore, the force that the sheet glass which is generated when the sheet glass is separated from the molded article tends to shrink in the width direction can not be suppressed, The contraction of the glass increases. In addition, since the temperature of the molten glass at the lowermost end of the molded article becomes higher than the conventional one, the temperature of the space below the molded article rises due to heat transfer from the molten glass, It is impossible to sufficiently increase the viscosity at both ends of the film. As a result, the problem that the width of the sheet glass is shrunk becomes remarkable.

Therefore, in the method of manufacturing a glass substrate and the apparatus for manufacturing a glass substrate, it is possible to suppress the shrinkage of the glass sheet formed by using the formed body when the glass sheet is separated from the molded body, thereby securing the width of the targeted sheet glass A method of manufacturing a glass substrate and an apparatus for manufacturing a glass substrate.

The present invention includes the following aspects.

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

[Mode 1]

The production method thereof comprises:

A step of forming a sheet glass by overflowing the molten glass from the molded body in an upper space of the molding furnace surrounded by the furnace wall,

A step of passing the sheet glass through a slit-shaped gap formed by a heat insulating member that divides the molding furnace chamber into an upper space and a lower space;

And cooling the both end portions of the sheet glass in the lower space,

The heat insulating member

(1) In the step of molding the sheet glass, the temperature of the molten glass when the molten glass passes through the formed body is not lower than the liquidus temperature, and when the molten glass passes through the lowermost end of the formed body, The viscosity of both ends of the molten glass is 10 ^4.3 to 10 ⁶ dPa · sec,

(2) In the step of cooling the sheet glass, when the temperature of the central portion of the sheet glass is in a temperature range from the temperature higher than the softening point to the vicinity of the gradual point (slow cooling point) Is 10 ^9.0 to 10 ^14.5 dPa · sec, is used as the material of the glass substrate.

[Mode 2]

Wherein a thermal resistance between the upper space and the lower space of the heat insulating member is at least 0.2 m < 2 > K / W in an atmosphere temperature of the upper space.

[Mode 3]

In the lower space,

The temperature distribution in the width direction at the central portion of the sheet glass is made uniform and the temperature at both end portions of the sheet glass is made lower than the temperature at the central portion;

The temperature of the both end portions and the central portion is lower than the temperature of the both end portions and the central portion in the step of making the temperature lower than the temperature of the central portion and the width of the sheet glass from the center in the width direction of the central portion toward the both end portions And forming a temperature gradient in the direction of the surface of the glass substrate.

[Mode 4]

Wherein the glass substrate has a liquidus viscosity of 10 ^4.3 dPa · sec to 10 ^6.7 dPa · sec.

[Mode 5]

Wherein the glass substrate has a strain point of 670 캜 or higher.

[Mode 6]

A molding furnace surrounded by a furnace wall,

A heat insulating member dividing the molding furnace chamber into an upper space and a lower space and forming a slit-shaped gap through which the sheet glass passes;

A molded body provided in the upper space of the molding furnace for overflowing the molten glass to form a sheet glass,

And a cooling member for cooling both ends of the sheet glass in the lower space,

The heat insulating member

(1) In the step of forming the sheet glass, the temperature of the molten glass when the molten glass passes through the formed body is not lower than the liquidus temperature, and when the molten glass passes through the lowermost end of the formed body, The viscosity of both ends of the molten glass is 10 ^4.3 to 10 ⁶ dPa · sec,

(2) In the step of cooling the sheet glass, when the temperature of the central portion of the sheet glass is in the temperature range from the temperature higher than the softening point to the vicinity of the stand-off point, the viscosity of both ends of the sheet glass is 10 ^9.0 To 10 ^14.5 dPa · sec, wherein a material having a heat insulating property is used.

As the glass substrate, a glass having the following characteristics can be used.

[Mode 7]

And the liquid phase viscosity of the glass of the glass substrate is 10 ^4.3 dPa · sec to 10 ^6.7 dPa · sec. The method of manufacturing a glass substrate or the glass substrate manufacturing apparatus according to any one of the above modes 1 to 6.

[Mode 8]

The glass substrate manufacturing method or the glass substrate manufacturing apparatus according to any one of the first to seventh aspects, wherein the glass substrate contains zirconia.

[Mode 9]

The method of manufacturing a glass substrate according to any one of the first to eighth aspects, wherein the glass substrate contains tin oxide, or a glass substrate manufacturing apparatus.

[Mode 10]

The method according to any one of the first to ninth aspects, wherein the glass substrate is composed of an alkali-free glass substantially not containing an alkali metal oxide.

[Mode 11]

In the form described in any one of the first to ninth aspects, the glass substrate is preferably a glass substrate manufacturing method or a glass substrate manufacturing apparatus, which is made of an alkali-small-content glass containing 0.05 to 2.0% by mass of an alkali metal oxide .

[Mode 12]

The method of manufacturing a glass substrate according to any one of the first to eleventh aspects, wherein the molten glass is produced by electrospinning a glass raw material in a melting tank including a high-zirconia refractory material.

According to the method of manufacturing a glass substrate and the apparatus for manufacturing a glass substrate of the above-described form, it is possible to suppress contraction when the width of the glass sheet formed by using the formed body is separated from the molded body, .

1 is a view showing an example of a flow of a manufacturing method of a glass substrate according to the present embodiment.
Fig. 2 is a schematic configuration diagram of an example of a glass substrate manufacturing apparatus for carrying out the manufacturing method of the glass substrate of the present embodiment.
3 is a schematic structural view (cross-sectional view) of an example of a molding apparatus used in the method of manufacturing a glass substrate according to the present embodiment.
Fig. 4 is a schematic structural view (side view) of the molding apparatus shown in Fig.
Fig. 5 is a diagram showing an example of each mechanism connected to a control device and a control device used in the method of manufacturing a glass substrate according to the present embodiment.
6 is a diagram showing the atmospheric temperature obtained by temperature control based on a plurality of temperature profiles performed in the method of manufacturing a glass substrate according to the present embodiment.

(Justice)

The following phrases in this specification are defined as follows.

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

The central portion of the sheet glass refers to the portion excluding the end portion of the sheet glass.

The strain point refers to the temperature of the glass when the glass viscosity is 10 ^14.5 dPa · sec.

The standing point refers to the temperature of the glass when the glass viscosity is 10 ¹³ dPa · sec.

The temperature region in the vicinity of the standing point means a temperature (glass standpoint + glass surface temperature + glass temperature) obtained by adding 100 占 폚 to the glass standpoint plus glass standpoint + 100 占 폚, Quot;) / 2]. ≪ / RTI >

The softening point refers to the temperature of the glass when the glass viscosity is 10 ^7.6 dPa · sec.

(Total configuration)

The method of manufacturing a glass substrate according to the present embodiment produces a glass substrate for a flat panel display such as a liquid crystal television, a plasma television, and a notebook computer. The glass substrate is manufactured using the down-draw method.

A plurality of steps (a method of manufacturing a glass substrate) up to the production of a glass substrate and a manufacturing apparatus 100 of a glass substrate used in a plurality of steps will be described with reference to Figs. 1 and 2. Fig.

The plurality of processes includes a melting step S1, a clarifying step S2, a molding step S3, a cooling step S4, and a cutting step S5.

The dissolving step S1 is a step of dissolving the glass raw material. As shown in Fig. 2, the raw material of the glass is put into the dissolution apparatus 11 arranged upstream. The raw material of the glass is dissolved in the melting tank of the melting apparatus 11 to be melted glass (FG). The molten glass FG is sent to the clarifying device 12 through the upstream pipe 23.

The firing step S2 is a step of removing bubbles in the molten glass FG. The molten glass FG in which the bubbles are removed in the refining apparatus 12 is then sent to the molding apparatus 40 through the downstream pipe 24.

The molding step S3 is a step of molding the molten glass (FG) into a sheet-shaped glass (sheet glass) SG. Specifically, the molten glass FG overflows from the molded body 41 after being sent to the molded body 41 contained in the molding apparatus 40. [ The overflowed molten glass (FG) flows down along the surface of the formed body 41. The molten glass FG then joins at the lowermost end of the formed body 41 to a sheet glass SG. At this time, the sheet glass SG passes through the slit-shaped gap formed by the partition member (heat insulating member) 50 and moves from the upper space to the lower space of the molding chamber. The partition member (heat insulating member) 50 divides the molding furnace chamber having the formed body 41 (see Fig. 3) into an upper space and a lower space.

The cooling step S4 is a step of cooling the sheet glass SG. The glass sheet is cooled to a temperature close to room temperature through a cooling step S4. Further, the thickness (plate thickness) of the glass substrate, the deflection amount of the glass substrate, and the amount of deformation of the glass substrate are determined according to the state of cooling in the molding step S1 and the cooling step S4.

The cutting step S5 is a step of cutting a sheet glass (SG) having a temperature close to room temperature to a predetermined size.

Further, the sheet glass SG (glass piece) cut to a predetermined size is then subjected to a process such as end-face machining to be a glass substrate.

In the embodiment described later, a glass having a strain point of the glass in the sheet glass SG of 640 캜 or more is used.

Hereinafter, the configuration of the molding apparatus 40 will be described with reference to Figs. 3 and 4. Fig. In the present embodiment, the width direction of the sheet glass SG means a direction crossing the direction in which the sheet glass SG descends (downward direction), that is, the horizontal direction.

(Configuration of molding apparatus)

3 and 4 show a schematic configuration of the molding apparatus 40. Fig. 3 is a sectional view of the molding apparatus 40. Fig. 4 is a side view of the molding apparatus 40. Fig. The molding apparatus 40 mainly includes a molding body 41, a partition member 50, a cooling roller 51, a cooling unit 60, a lowering roller 81, and a cutting device 90 have. Further, the molding apparatus 40 includes a control device 91 (see Fig. 5). The control device 91 controls the driving parts of the respective constituent elements included in the molding device 40. [

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

(Molded article)

The formed body 41 overflows the molten glass FG to form the molten glass FG into a sheet-shaped glass (sheet glass SG).

As shown in Fig. 3, the formed body 41 has a cross-sectional shape and a substantially pentagonal shape (a shape similar to a wedge shape). The tip of the approximately pentagonal shape corresponds to the lowermost end 41a of the formed body 41. [

The molten glass FG flowing into the molding body 41 overflows from the pair of top portions 41b of the molding body 41 and flows down while following a pair of side faces (surface) 41c of the molding body 41 . Thereafter, the molten glass FG joins at the lowermost end 41a of the formed body 41 to form a sheet glass SG. The viscosity of both ends of the molten glass when the molten glass passes through the lowermost end 41a of the formed body 41 is preferably from 10 ^4.3 to 10 ⁶ dPa · sec and from 10 ^4.4 to 10 ^5.4 dPa · sec, 10 ^4.6 ~ 10 ^5.2 dPa · sec.

(Partition member)

The partition member 50 is disposed near the merging point of the molten glass FG. 3, the partition member 50 is disposed on both sides in the thickness direction of the molten glass FG (sheet glass SG) joined at the confluence point. The partition member 50 is a heat insulating member. The partition member 50 is divided into an upper space of the molding furnace chamber located above the partition member 50 and a lower space of the molding furnace chamber located below the partition member 50, And the lower atmosphere to block the movement of heat from the upper side to the lower side of the partition member 50. [ The sheet glass SG passes through a slit-like gap formed by a pair of partition members (heat insulating members) 50 located on both sides in the thickness direction of the sheet glass SG, and moves to the lower space.

(Cooling roller)

The cooling roller 51 is a unit which is installed in a lower space of the molding furnace and heat-treats both end portions in the width direction of the sheet glass SG. The paired cooling rollers 51 are disposed on both sides in the thickness direction of the sheet glass SG and at both ends in the width direction of the sheet glass SG. That is, the cooling roller 51 is cooled by heat conduction by fitting the both end portions in the width direction of the sheet glass SG separated from the formed body 41 (quenching step). The cooling roller 51 may be air-cooled, for example, by an air-cooled pipe passed through the inside thereof.

The cooling roller 51 rapidly quenches both ends of the sheet glass SG so that the viscosity of both ends of the sheet glass SG becomes 10 ^9.0 to 10 ^14.5 dPa · sec. Further, by cooling the both ends of the sheet glass SG by the cooling roller 51, the shrinkage of the sheet glass SG in the width direction can be reduced, and the thickness of the sheet glass SG can be made uniform. Further, the flatness of the sheet glass SG can be maintained.

(Cooling unit)

The cooling unit 60 is a unit installed in the lower space of the molding furnace and performing heat treatment of the sheet glass SG. Specifically, the cooling unit 60 is a unit for cooling the sheet glass SG to a temperature region near the standoff point. The cooling unit 60 is located below the partition member 50 and is disposed on the ceiling plate 80a of the ceiling passage 80. [ The cooling unit 60 cools the upstream region of the sheet glass SG (upstream region cooling step). The upstream region of the sheet glass SG is a region of the sheet glass SG where the temperature of the central portion of the sheet glass SG is higher than the standpoint. The central portion of the sheet glass SG is a portion located between both ends of the sheet glass SG. Specifically, the upstream region includes a first temperature region and a second temperature region. The first temperature region is a region in which a sheet glass SG is formed from directly below the lowermost end portion 41a of the formed body 41 until the temperature at the central portion of the sheet glass SG becomes near the softening point (softening point ± 15 캜) . The second temperature range is a temperature range from the vicinity of the softening point to the temperature near the steeping point, at the central portion of the sheet glass SG. That is, the cooling unit 60 cools the sheet glass SG so that the temperature of the central portion of the sheet glass SG approaches the standoff point. The central portion of the sheet glass SG is then cooled to a temperature in the vicinity of room temperature through a deformation point in a thirst furnace 80 which will be described later (a downstream zone cooling step (quenching step)).

The cooling unit 60 cools the sheet glass SG based on a plurality of temperature profiles so that the thickness and warpage of the sheet glass SG become a desired value. That is, in the upstream region, a plurality of temperature profiles are set along the downward direction of the sheet glass SG. Here, the temperature profile is a temperature distribution along the width direction of the sheet glass SG. In other words, the temperature profile is the distribution of the target ambient temperature. The above-described cooling roller 51 and the cooling unit 60 control the ambient temperature so as to realize the temperature profile.

The cooling unit 60 includes a plurality of cooling units. The temperature distribution of the sheet glass SG is realized by controlling a plurality of units independently so as to obtain a plurality of temperature profiles. For example, the cooling unit 60 includes a center cooling unit 61 and two end cooling units 71, 71. As shown in Fig. 4, the central 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 (center cooling step). The central cooling unit 61 is disposed on both sides in the thickness direction of the sheet glass SG. The end cooling units 71 are disposed at positions adjacent to the center cooling unit 61, respectively. That is, the end cooling unit 71 is disposed on both sides of the sheet glass SG in the thickness direction so as to face each other with the sheet glass SG interposed therebetween and cools both ends and both ends of the sheet glass SG Cooling process). Further, the center cooling unit 61 and the end cooling unit 71 are disposed at positions close to the sheet glass SG, respectively.

(Central cooling unit)

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

(Center upper cooling unit)

The center upper cooling unit 62 is located immediately below the partition member 50 described above. The center upper cooling unit 62 is a unit for realizing a temperature profile of a region that determines the thickness of the sheet glass SG. The region for determining the thickness of the sheet glass SG corresponds to the above-mentioned first temperature region. The center upper cooling unit 62 is controlled so as to make the thickness of the sheet glass SG uniform in the width direction (first center cooling step).

The center lower cooling units 63a and 63b are disposed below the center upper cooling unit 62 as described above. The center lower cooling units 63a and 63b are units for realizing the temperature profile of the region in which the control of the amount of warpage of the sheet glass SG is started. Here, the region in which the control of the deflection amount of the sheet glass SG is started corresponds to the second temperature region described above.

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

(End cooling unit)

The end cooling unit 71 cools both end portions of the sheet glass SG quenched by the cooling roller 51 continuously or stepwise along the downward direction of the sheet glass SG (end cooling step). The end cooling unit 71 operates at a cooling capability lower than that of the cooling roller 51. [ In other words, the amount of heat taken away from the end of the sheet glass SG by the end cooling unit 71 is small as compared with the amount of heat lost from the side of the sheet glass SG by the cooling roller 51. The end cooling units 71 are disposed on both sides of the center cooling unit 61, respectively, as described above (see Fig. 4). The end cooling unit 71 is arranged close to the surface of the sheet glass SG. The end cooling unit 71 cools both ends of the sheet glass SG so that the viscosity of both ends of the sheet glass SG is maintained within the range of 10 ^9.0 to 10 ^14.5 dPa · sec. The end cooling unit 71 preferably cools both ends of the sheet glass so that the viscosity of both ends of the sheet glass SG is maintained within the range of 10 ^10.5 to 10 ^14.5 dPa · sec.

When the amount of cooling in the end cooling unit 71 is small, the temperature of both ends of the sheet glass SG rises again, and the sheet glass SG shrinks in the width direction.

The end cooling unit 71 is composed of, for example, an upper end cooling unit 72 and a lower cooling unit 73 as shown in FIG. The single-phase unit cooling unit 72 and the single-stage lower cooling unit 73 are disposed along the downward direction of the sheet glass SG. The temperatures of the single-phase unit cooling unit 72 and the single-stage cooling unit 73 are adjusted independently of each other.

The single-phase unit cooling unit 72 is a unit for realizing a temperature profile of a region that influences the adjustment of the thickness and / or the deflection of the sheet glass SG (first end cooling step). The single-phase unit cooling unit 72 is located just below the above-described cooling roller 51, as shown in Fig. The sheet glass SG is cooled at a predetermined cooling rate mainly by radiant heat transfer of the single-phase unit cooling unit 72. [ Here, the predetermined cooling rate means that the plate width of the glass (SG) that has passed through the cooling roller (51) is prevented from shrinking, and the sheet glass (SG) Is a cooling rate at which cracks do not occur. That is, the single-phase unit cooling unit 72 cools the glass SG as much as possible without adversely affecting the sheet glass SG.

(Reduction roller)

The lowering roller (81) is disposed inside the throat (80). The throat passage 80 is a space disposed directly below the cooling unit 60. In the cooling furnace 80, the temperature of the sheet glass SG is cooled from the temperature in the vicinity of the standoff point to the temperature in the vicinity of room temperature (downstream zone cooling step (quenching step)).

(Cutting device)

The cutting device 90 cuts the sheet glass SG having passed through the thirst furnace 80 and cooled to a temperature near the room temperature to a predetermined size.

(controller)

The control device 91 is a control device for controlling the temperature of the cooling water supplied from the cooling unit 51 to the outside of the cooling unit 5, Temperature is controlled. By controlling this temperature, the temperature distribution of the sheet glass SG can be made to coincide with the predetermined temperature profile, as described below.

(Temperature profile)

Next, with reference to Fig. 6, the temperature profile used in the manufacturing method of the glass substrate according to the present embodiment and the control of each unit for cooling to realize the temperature profile will be described.

6, the broken-line regions indicate the arrangement of the cooling rollers 51 and the units 62, 63a, 63b, 72, and 73 included in the cooling unit. The curves 10b, 10c, 10e and 10f and the straight lines 10a and 10d included in the region divided by the broken line are formed by the cooling roller 51 or the units 62, 63a, 63b, 72 and 73 Which is included in the temperature profiles 20a, 20b and 20c to be realized.

In the present embodiment, as described above, the control device 91 independently controls the ambient temperature based on a plurality of temperature profiles in the downward direction of the sheet glass SG. The sheet glass SG is cooled so that a tensile force is applied toward the side of the sheet glass SG along the width direction of the sheet glass SG when the temperature of the sheet glass SG is in the predetermined temperature range. The predetermined temperature range is a temperature range from when the temperature of the sheet glass SG becomes higher than the softening point to near the standing point after the sheet glass SG is separated from the formed body 41. [ That is, the predetermined temperature region is the upstream region of the sheet glass SG described above.

The sheet glass SG after the molding 41 is separated has a viscosity of 10 ^5.7 to 10 ^7.5 dPa · sec. The sheet glass SG is cooled by the cooling roller 51 and the cooling unit 60, whereby the viscosity of the sheet glass SG is increased. That is, the viscosity (viscosity at the center portion and both ends) of the sheet glass SG is increased along the downward direction of the sheet glass SG. In other words, the viscosity of the sheet glass SG becomes higher on the downstream side of the sheet glass SG. In the present embodiment, both ends of the sheet glass SG are cooled by the cooling roller 51 and the end cooling unit 71 in the upstream region. Specifically, both ends of the sheet glass SG are cooled so as to keep the viscosity within the range of 10 ^9.0 to 10 ^14.5 dPa · sec. More specifically, the cooling roller 51 rapidly quenches both ends of the sheet glass so that the viscosity of the side portion of the sheet glass SG is within the range of 10 ^9.0 to 10 ^10.5 dPa · sec. Both ends of the sheet glass are cooled so that the viscosity at both ends of the sheet glass SG rapidly cooled by the heating roller 51 falls within the range of 10 ^10.5 to 10 ^14.5 dPa · sec.

In the temperature control of the sheet glass SG according to the present embodiment, a plurality of temperature profiles are respectively set in the width direction of the sheet glass SG and the downward direction of the sheet glass SG (temperature profile setting step). Specifically, the plurality of temperature profiles includes a first temperature profile 20a, a second temperature profile 20b, and a third temperature profile 20c, as shown in Fig. The first temperature profile 20a is located on the higher temperature side in the downward direction than the second temperature profile 20b. In addition, the second temperature profile 20b is located on the higher temperature side in the downward direction than the third temperature profile 20c.

The first temperature profile 20a is a temperature profile in which the temperature distribution in the width direction at the central portion in the width direction of the sheet glass SG is uniform and the temperature at both ends in the width direction of the sheet glass SG (SG). Here, the fact that the temperature distribution in the width direction is uniform means that the temperature distribution in the width direction is a value within a range of 占 0 占 폚 to 10 占 폚 with respect to a predetermined reference value (temperature). That is, both ends of the sheet glass SG are quenched on the basis of the first temperature profile 20a, and the temperature of the central portion of the sheet glass SG is higher than the temperature of both ends of the sheet glass SG, , And is controlled so as to be uniform in the width direction (plate thickness equalizing step). The first temperature profile 20a is set such that the temperature (average temperature) at the center of the sheet glass SG and the temperatures at both ends of the sheet glass SG become the first temperature difference X. [ The temperature distribution in the width direction at the central portion of the sheet glass SG is made uniform and the temperature at both end portions of the sheet glass SG is made lower than the temperature at the central portion in the plate thickness equalizing step. As a result, both ends of the sheet glass SG are cooled so as to suppress the contraction in the width direction, and the central portion of the sheet glass SG is cooled so as to make the sheet thickness uniform, so that the sheet thickness deviation of the sheet glass SG becomes small .

The second temperature profile 20b and the third temperature profile 20c are cooler than the first temperature profile 20a. The second temperature profile 20b and the third temperature profile 20c have a temperature gradient in the width direction at the center of the sheet glass SG. Concretely, the second temperature profile 20b and the third temperature profile 20c have the highest temperature at the center in the width direction of the sheet glass SG and the lowest temperatures at both ends of the sheet glass SG . More specifically, the second temperature profile 20b and the third temperature profile 20c gradually decrease in temperature from the center in the width direction of the sheet glass SG toward both ends of the sheet glass SG. That is, based on the second temperature profile 20b and the third temperature profile 20c, the temperature distribution in the width direction of the sheet glass SG is controlled to be a mountain shape (a curved line having a convex upper portion) ). That is, the warp reducing process cools the sheet glass SG while maintaining a temperature gradient (a curve having a convex upper portion). In other words, the warp reducing process cools the sheet glass SG so that the temperature distribution continuously keeps the shape of the curved line having the convex portions upward.

Further, the control of the temperature based on the second temperature profile 20b is carried out on the upstream side of the second temperature region with respect to the downward direction of the sheet glass SG. Further, the control based on the third temperature profile 20c is executed on the downstream side of the second temperature region with respect to the downward direction of the sheet glass SG. Here, it is preferable that the third temperature profile 20c is set to be larger than the second temperature profile 20b. Specifically, the second temperature profile 20b is set so 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. The third temperature profile 20c is set so 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 larger than the second temperature difference Y1. Further, the second temperature difference Y1 is larger than the first temperature difference X. [ That is, in the temperature profiles 20a to 20c, the temperature difference between the center portion and the end portion or the temperature difference between the center portion and the end portion increases along the downward direction of the sheet glass SG (X <Y1 <Y2).

The warp reducing process is a process in which the temperature gradient in the width direction of the sheet glass SG becomes smaller as the temperature of the sheet glass SG becomes closer to the point of deformation in the temperature region lower than the third temperature profile 20c The sheet glass SG is cooled so as to be reduced.

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

(Temperature control by center upper cooling unit)

In the center upper cooling unit 62, as described above, the temperature profile of the region determining the thickness of the sheet glass SG is realized (the first central portion cooling step). Concretely, the temperature distribution in the width direction of the center upper cooling unit 62 opposed to the sheet glass SG is uniform, so that the temperature in the width direction of the sheet glass SG becomes uniform (sub-profile 10a) .

The central lower cooling units 63a and 63b realize the temperature profile of the region where the adjustment of the amount of bending of the sheet glass SG is started as described above (the second central portion cooling step and the third central portion cooling step). Specifically, the center lower cooling units 63a and 63b are adjusted so that the temperature in the width direction of the sheet glass SG becomes a mountain-like shape (a curved line having convex portions). Specifically, the temperature at the center in the longitudinal direction of the center lower cooling units 63a and 63b is set to the highest temperature. Further, the temperature of both ends in the longitudinal direction of the center lower cooling units 63a and 63b is set to the lowest temperature. Further, the temperature is controlled to gradually decrease from the center toward both ends. In this way, the temperature in the width direction of the sheet glass SG becomes an acid type (sub profile 10b, sub profile 10c).

In the present embodiment, two center lower cooling units 63a and 63b are disposed along the downward direction of the sheet glass SG. The center lower cooling unit 63b disposed below the lower side of the sheet glass SG is controlled so as to form a temperature distribution with a larger curvature than the center lower cooling unit 63a disposed above. Concretely, as described above, the temperature lower than the temperature gradient (the temperature gradient between the central portion and the end portion) of the profile 10b realized by the center lower cooling unit 63a (see Y1 in FIG. 6) (See Y2 in Fig. 6) of the temperature profile 10c realized by the heaters 63a and 63b (Y1 &lt; Y2).

As described above, the cooling roller 51 realizes a temperature profile of a region that influences the uniformity of the thickness of the sheet glass SG (quenching step). The cooling roller 51 rapidly cools both ends of the joined glass at the lowermost end 41a of the formed body 41. [ That is, the atmosphere temperatures at both ends and both ends of the sheet glass SG become lower than the ambient temperature around the central portion of the sheet glass SG (sub profile 10d).

The single-phase unit cooling unit 72 realizes the temperature profile of the region that influences the adjustment of the thickness and / or the deflection of the sheet glass SG (first end cooling step), as described above. The single-phase unit cooling unit 72 applies a temperature lower than the temperature given to the sheet glass SG by the upper center cooling unit 62 and the lower center cooling unit 63a to the sheet glass SG. That is, the atmosphere temperatures at both ends and both ends of the sheet glass SG become lower than the ambient temperature around the central portion of the sheet glass SG (sub profile 10e).

In the lower cooling unit 73, as described above, the temperature profile of the region that influences the adjustment of the amount of deflection of the sheet glass SG is realized (the second end cooling step). The lower cooling unit 73 applies a temperature lower than the temperature given to the sheet glass SG by the center lower cooling units 63a and 63b to the sheet glass SG. That is, the atmosphere temperature at both ends of the sheet glass SG becomes lower than the atmosphere temperature at the central portion of the sheet glass SG (sub profile 10f).

The temperature control of the sheet glass SG is performed through the control device 91, the cooling roller 51, and the respective units. In the upper space of the molding furnace where the formed body 41 is located, a high-temperature atmosphere is maintained so that the molten glass is formed while maintaining a predetermined viscosity. On the other hand, in the lower space of the molding furnace chamber partitioned from the upper space by the partition member (heat insulating member) 50, the sheet glass SG formed by molding from the molten glass is cooled. As a result, a heat insulating member having excellent heat insulating property 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,

(1) When the sheet glass SG is molded, the temperature of the molten glass FG at the time when the molten glass FG passes through the formed body 41 is not lower than the liquidus temperature, and the molten glass FG is heated The viscosity of both ends of the molten glass FG at the time of passing through the lowermost end of the glass rod 41 is 10 ^4.3 to 10 ⁶ dPa · sec,

(2) When the sheet glass SG is cooled, when the temperature of the central portion of the sheet glass SG is in the temperature range from the temperature higher than the softening point to the vicinity of the stand-off point, A material having a heat insulating property is used for the heat insulating member so that the viscosity becomes 10 ^9.0 to 10 ^14.5 dPa · sec.

At this time, the thermal resistance between the upper space and the lower space in the upper space of the partition member (heat insulating member) 50 in contact with the partition member 50 is preferably 0.2 m 2 · K / W or more . By using the partition member 50 having such a thermal resistance, it is possible to realize a temperature profile that can suppress shrinkage of the sheet glass SG in the lower space. Concretely, both end portions of the sheet glass SG which is quenched by the cooling roller 51 and the end cooling unit 71 are separated from the upper space by a distance of 50 mm from the upper space when the heat resistance of the partition member 50 is less than 0.2 m 2 · K / The lowering of the temperature is suppressed by the influence of the heat transferred to the lower space, and the viscosity is not increased to a desired value. In this case, the viscosity of the both ends of the sheet glass SG is not high. Therefore, by the action of the surface tension when the sheet glass SG is formed apart from the molded body 41, Lt; / RTI &gt; This makes it difficult to secure the desired width of the sheet glass SG. However, by setting the heat resistance of the partition member (heat insulating member) 50 to 0.2 m &lt; 2 &gt; · K / W or more, both ends of the quenched sheet glass SG are reduced in the influence of heat moved from the upper space to the lower space, Can be cooled along a predetermined temperature profile. The heat resistance of the partition member 50 is preferably 0.3 m 2 · K / W or more, and more preferably 0.4 m 2 · K / W or more. Further, in order to make the thermal resistance extremely large, for example, it is necessary to make the thickness of the partition member 50 extremely large, which is not preferable. Therefore, the heat resistance of the partition member 50 is preferably 0.2 to 2 m 2 · K / W, more preferably 0.4 to 2 m 2 · K / W.

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

As a preferred form of the partitioning member 50, the thermal conductivity of the material on the surface of the partitioning member 50 in contact with the slit-shaped gap passing through when the sheet glass SG moves from the upper space to the lower space of the molding furnace The thermal conductivity at the atmospheric temperature of the upper space) is preferably 0.5 W / m · K or less. Particularly preferably, the partition member 50 is made of one material having a thermal conductivity (thermal conductivity at the atmospheric temperature of the upper space) of 0.25 W / mK or less. With this configuration, it is possible to make the plate resistance of the partition member 50 not excessively large, and to have a thermal resistance of 0.2 m 2 · K / W or more.

In the cooling of the sheet glass of the present embodiment, as shown in Fig. 6, the temperature distribution in the width direction at the central portion in the width direction of the sheet glass SG is made uniform, and the temperature distribution at the both ends of the sheet glass SG (Sheet thickness equalizing step) in which the temperature is lower than the temperature in the central portion in the width direction of the sheet glass SG and the temperature at both end portions and the central portion in this step are compared with each other at both ends of the sheet glass SG And a step of forming a temperature gradient in the width direction of the sheet glass SG from the center in the width direction of the sheet glass SG toward the both end portions. In order to realize these two processes, the control device 91 can control the temperature of the sheet glass SG using each unit and the cooling roller 51 or the like. In this embodiment, since the partition space 50 is provided, the movement of heat in the upper space of the molding furnace chamber and the lower space of the molding furnace chamber is sufficiently suppressed, Temperature control becomes possible.

In the above-described control of the temperature of the sheet glass SG, since the temperature distribution in the width direction at the central portion of the sheet glass SG is made uniform in the first step, not only the shrinkage in the widthwise direction of the sheet glass SG , And the sheet thickness deviation of the glass substrate made of sheet glass (SG) can be suppressed.

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 sheet glass SG is formed so as to extend from the center in the width direction of the sheet glass SG toward both ends, Thereby forming a temperature gradient in the width direction. At this time, the cooling amount at the central portion in the width direction of the sheet glass SG becomes larger than the cooling amount 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 both end portions in the width direction toward the central portion, so tensile stress acts on the central portion of the sheet glass SG. In particular, tensile stress acts on the central portion of the sheet glass SG in the downward and width directions of the sheet glass SG. It is also preferable that the tensile stress acting in the downward direction of the sheet glass SG is larger than the tensile stress acting in the width direction of the sheet glass SG in view of improving warp of the glass sheet. By this tensile stress, the sheet glass SG can be cooled while maintaining the flatness of the sheet glass SG, so that the amount of deflection of the sheet glass SG, and furthermore, the glass plate can be reduced.

Further, when the liquidus temperature of the glass is high, it is possible to prevent the glass from being deviated by using a molten glass having a temperature sufficiently higher than the liquidus temperature of the glass. However, in order to apply the overflow down-draw method, it is preferable that the viscosity of the molten glass at the lowermost end 41a of the formed body 41 is 10 ^4.3 dPa · sec or more at the central portion and both ends. The viscosity, 10 ^4.4 Pa · sec, and more preferably not less than, and more preferably not less than 10 ^4.6 dPa · s. The reason for securing such a viscosity is as follows. That is, the sheet glass SG spaced from the lowermost end 41a tends to fall down to the region held by the cooling roller 51 due to its own weight. This is because the dropping speed at this time differs depending on the viscosity of the molten glass at the lowermost end 41a of the formed body 41. [ When the viscosity of the molten glass at the lowermost end portion 41a is smaller than the above range, the speed at which the sheet glass SG tends to fall due to its own weight, compared with the pulling speed of the sheet glass SG by the cooling roller 51 So that the sheet glass SG may be loosened on the cooling roller 51 as a result. Therefore, it is preferable that the viscosity of the molten glass at the lowermost end 41a of the formed body 41 is 10 ^4.3 dPa · sec or more. If the speed of rotation of the lowering roller 81 positioned further downstream than the cooling roller 51 and the cooling roller 51 is sufficiently increased, the freeing of the glass ribbon is faster than the running speed of the cooling roller 51 and the lowering roller 81 The falling speed can be slowed down. However, in this case, in general, the thickness of the sheet glass SG to be obtained under the condition of a predetermined glass flow rate is predetermined, and in order to realize the temperature control of the glass ribbon performed in the downstream quenching step, It is practically undesirable to make the peripheral speed of the lower roller 51 and the lower roller 81 excessively high.

If the temperature of the molten glass at the lowermost end portion 41a of the formed body 41 is increased in order to perform molding at a viscosity lower than the numerical range of the viscosity of the molten glass described above, do. This makes it impossible to sufficiently increase the viscosity at both ends in the width direction of the sheet glass SG formed by joining the molten glass flowing on each of the wall surfaces of both sides of the molded body at the lowermost end 41a of the formed body 41. [ As a result, the width of the sheet glass SG is shrunk. If the width of the sheet glass SG is shrunk, there arises a problem that the width and the product width of the sheet glass SG immediately before the cutting can not be ensured. This problem becomes more remarkable as the liquidus temperature of the glass is higher (liquidus viscosity is smaller).

In the present embodiment, since the heat resistance of the partition member (insulating member) 50 is 0.2 m 2 · K / W or more, the movement of heat from the upper space to the lower space of the molding furnace is suppressed, The both ends of the quenched sheet glass SG are not affected by the heat that has moved from the upper space to the lower space and the predetermined viscosity is secured even if the atmosphere temperature in the upper space of the molding furnace is set high, . Therefore, the reduction of the width of the sheet glass SG can be suppressed.

That is, the effect of the present embodiment is remarkable when a glass having a high liquidus temperature (low liquidus viscosity) is used. In this case, the heat insulating member 50 having a thermal resistance of 0.2 m 2 · K / W or more is used and the viscosity of both end portions of the sheet glass SG is adjusted to 10 ^9.0 to 10 ^The product width can be secured by cooling the sheet glass SG so as to be ^14.5 dPa · sec.

(Characteristics of glass)

The glass substrate produced in the present embodiment is suitably used for a glass substrate for a flat panel display. Further, the glass substrate can be used for a glass substrate which forms LTPS (Low Temperature Poly Silicon) TFT (Thin Film Transistor) or oxide semiconductor which requires a small heat shrinkage ratio and which performs high temperature processing. 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, and the like.

The glass substrate of the present embodiment preferably has a liquid viscosity of 10 ^4.3 dPa · sec to 10 ^6.7 dPa · sec. It is necessary to make the viscosity at the lowermost end 41a of the formed body 41 smaller than the liquid viscosity in the molding step so that the atmosphere temperature in the upper space of the forming furnace chamber becomes lower than the liquid viscosity, As shown in FIG. As a result, a large step of heat exists between the upper space and the lower space of the forming furnace chamber, and heat transfer is likely to increase. In this embodiment, since the movement of heat from the upper space to the lower space of the molding furnace is suppressed, contraction in the width direction of the sheet glass SG in the lower space of the molding furnace can be suppressed. Since the viscosity of the lowermost portion 41a of the formed body 41 can be increased as the glass has a high liquid viscosity, shrinkage in the width direction of the sheet glass SG described above can be suppressed. Therefore, the liquid-phase viscosity of the glass substrate of the present embodiment is preferably 10 ^4.7 dPa · sec to 10 ^6.7 dPa · sec, more preferably 10 ⁵ dPa · sec to 10 ^6.7 dPa · sec. The liquid phase viscosity of the glass substrate of the present embodiment may be 10 ^5.3 dPa · sec or less. The lower the liquid viscosity of the glass is, the higher the atmospheric temperature of the upper space of the molding furnace chamber is set. Therefore, the shrinkage of the sheet glass SG in the width direction tends to increase as described above. That is, in the case of using a glass having a liquid viscosity of 10 ^5.3 dPa · seconds or less, the effect of the present embodiment becomes remarkable, and the effect becomes remarkable when it is 10 ^4.3 to 10 ^5.3 dPa · second, and 10 ^4.3 dPa · sec to 10 ^5.0 dPa The effect becomes more remarkable in the case of seconds, and from 10 ^4.3 dPa · sec to 10 ^4.9 dPa · seconds in 10 seconds, the effect becomes more remarkable. In the case of a glass having a liquid viscosity of less than 10 ^4.3 dPa · sec, it is difficult to apply the overflow down-draw method.

The liquid phase temperature of the glass substrate of the present embodiment is preferably 1000 deg. C to 1250 deg. The higher the liquidus temperature of the glass is, the more the atmosphere temperature in the upper space of the molding furnace needs to be set to be high because the glass is not discharged. As a result, the step of the heat between the upper space and the lower space of the forming furnace chamber is large, and the heat is liable to move. In this embodiment, since the movement of heat from the upper space to the lower space of the molding furnace is suppressed, contraction in the width direction of the sheet glass SG in the lower space of the molding furnace can be suppressed. That is, from the viewpoint of reducing the amount of heat transfer from the upper space to the lower space of the molding furnace and reducing the shrinkage of the sheet glass SG in the width direction, the liquid temperature of the glass substrate is preferably 1250 DEG C or lower, More preferably 1200 DEG C or lower, and still more preferably 1105 DEG C or lower. The liquidus temperature of the glass substrate of the present embodiment may be 1150 ° C to 1250 ° C. The higher the liquidus temperature of the glass is, the more the atmosphere temperature in the upper space of the molding furnace needs to be set to be high because the glass is not discharged. That is, when the glass having the glass liquid temperature of 1150 DEG C or higher is used for the sheet glass (SG), the effect of the present embodiment becomes more remarkable. The reason why the upper limit of the liquidus temperature of the glass is set to 1250 캜 is that when the liquidus temperature of the glass exceeds 1250 캜, there is a fear that a creep phenomenon of the formed body 41 tends to occur. That is, in this embodiment, the effect of the present embodiment becomes remarkable when the liquidus temperature of the glass is 1150 to 1250 DEG C, and the effect is more remarkable when the temperature is 1170 to 1250 DEG C, and 1180 DEG C to 1250 DEG C And it is preferable from the standpoint that the effect becomes remarkable if the temperature is 1200 ° C to 1250 ° C.

The deformation point of the glass substrate of this embodiment is preferably 670 캜 or higher. When the strain point of the glass substrate is 670 占 폚 or higher, the glass tends to have a higher liquidus temperature, and there is a fear that a failure may occur in the molding process. Therefore, in the case of using glass having a strain point of 670 DEG C or higher, the temperature of the molten glass at the time of molding is made higher than that in the case of producing a glass which is less prone to release, in order to suppress the occurrence of devitrification in the molding step And the atmosphere temperature in the upper space of the molding furnace where the formed body 41 is located is also set to be high. Therefore, there is a large step of heat between the upper space and the lower space of the forming furnace chamber, and the heat transfer is likely to increase. In the present embodiment, the partition member 50 having a thermal resistance of 0.2 m 2 · K / W or more is used to suppress the movement of heat from the upper space to the lower space of the molding furnace, Shrinkage in the width direction of the glass SG can be suppressed. That is, when the strain point of the glass substrate is 670 DEG C or more, the effect of the present embodiment is remarkable.

In the present embodiment, glass having a strain point of 670 占 폚 or higher can be used as the glass substrate, glass having a strain point of 675 占 폚 or higher, a strain point of 680 占 폚 or higher, and even glass having a strain point of 690 占 폚 or higher can be used. The width and the product width can be ensured, the effect of the present embodiment is remarkable. As the glass substrate for forming the LTPS TFT or the oxide semiconductor, the glass having a strain point of 675 DEG C or higher is preferably used, and the glass having a strain point of 680 DEG C or higher is more preferably used. In the glass substrate produced by this embodiment, It is preferable as a glass substrate for forming LTPS TFT or oxide semiconductor.

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. The partition member 50 having a thermal resistance of 0.2 m 2 · K / W or more is used to suppress the movement of heat from the upper space to the lower space of the molding chamber even when a glass substrate having a heat shrinkage rate of 75 ppm or less is to be manufactured, Shrinkage in the width direction of the sheet glass SG in the lower space of the molding furnace can be suppressed. Therefore, contraction of the width of the sheet glass SG in the width direction, which occurs when the sheet glass SG is separated from the formed body 41, is suppressed, and the width of the sheet glass SG can be ensured. In the case of a glass substrate using a glass having a heat shrinkage of 75 ppm or less, even if LTPS TFT or an oxide semiconductor is formed on the glass substrate and a high temperature process is performed on the glass substrate for the production of an image display apparatus, And the like can be suppressed.

The heat shrinkage ratio is a value obtained by the following equation, using the shrinkage amount of the glass substrate after the heat treatment for holding at the elevation temperature rate of 10 / min and 550 DEG C for 2 hours.

Heat shrinkage rate (ppm) = shrinkage of glass substrate after heat treatment / length of glass substrate before heat treatment 占 10 ⁶

Further, the glass substrate of this embodiment may contain zirconia. In the case where the glass substrate SG made of sheet glass SG contains zirconia, the liquid temperature of the glass is elevated. Therefore, even in the case where the glass substrate 41 does not suffer from the release of the glass, , In particular, it is necessary to reduce the viscosity in the vicinity of the lowermost end portion 41a (to raise the temperature of the molten glass to such an extent that no slipping occurs). In this embodiment, the partition member 50 having a thermal resistance of 0.2 m 2 · K / W or more is used even if the viscosity of the molten glass at the lowermost end portion 41 a of the formed body 41 is small and the atmospheric temperature in the upper space is high The movement of heat from the upper space to the lower space is suppressed, so that shrinkage of the plate width in the lower space of the molding furnace can be suppressed. Therefore, when such a glass is used, the effect of the present embodiment becomes remarkable.

Further, the glass substrate of the present embodiment preferably contains tin oxide. Tin oxide is easily extracted to cause a slip. Therefore, in the case of producing a glass containing tin oxide, the viscosity of the molten glass in the vicinity of the molded body 41, particularly the lowermost end portion 41a is reduced (the molten glass It is necessary to raise the temperature. In this embodiment, since the movement of heat from the upper space to the lower space is suppressed, shrinkage of the plate width in the lower space of the molding furnace can be suppressed.

When the melting tank of the dissolving apparatus 11 shown in Fig. 2 is composed of a furnace material such as a high zirconia refractory material, zirconia may be eluted from the high zirconia refractory material into the molten glass in the melting process . In this case, the zirconia concentration in the molten glass rises and the liquidus temperature rises. Therefore, it is necessary to keep the temperature of the molten glass at the time of molding high. In this embodiment, since the movement of heat from the upper space to the lower space is suppressed, shrinkage of the plate width in the lower space of the molding furnace can be suppressed. Therefore, when such a glass is used, the effect of the present embodiment becomes remarkable.

(Glass composition)

The glass substrate manufactured by this embodiment can be suitably used for a flat panel display, particularly a glass substrate for a liquid crystal display. Such a glass substrate includes, for example, 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, 0 to 20% of CaO, 0 to 20% of SrO, 0 to 10% of BaO, and 0 to 10% of ZrO ₂ .

Further, the glass substrate manufactured by this embodiment can be suitably used for a glass substrate that forms LTPS TFT or oxide semiconductor on the surface of the glass. Such a glass substrate is, for example, expressed in terms of mass%: 58 to 75% of SiO ₂ , 15 to 23% of Al ₂ O ₃ , 1 to 12% of B ₂ O ₃ , RO (where RO is MgO, CaO, SrO And the total amount of the components contained in the glass plate in BaO) of 6 to 17% and a strain point of 680 캜 or more.

At this time, if any one or more of the following expressions are satisfied, it is more preferable for the glass plate for LTPS-TFT.

(SiO ₂ + Al ₂ O ₃ ) / B ₂ O ₂ : 8 to 50 and / or SiO ₂ + Al ₂ O ₃ : 75% or more in order to further increase the strain point.

To increase the strain point further, the mass ratio (SiO ₂ + Al ₂ O ₃ ) / RO should be at least 7.5.

Containing 0.01 to 1% by mass of Fe ₂ O ₃ in order to lower the resistivity of the glass.

CaO / RO of not less than 0.65 to prevent the rise of liquid temperature while realizing high strain point of glass.

In consideration of being applied to mobile devices such as mobile communication terminals, the total content of SrO and BaO is preferably 0 to 5 mass%, more preferably 0 to 3.3 mass% from the viewpoint of lightening.

Further, the glass substrate may be a non-alkali glass substantially containing no alkali metal oxide (Na ₂ O, K ₂ O, Li ₂ O) or an alkali metal oxide (Na ₂ O, K ₂ O, Li ₂ O) in an amount of 0.05 to 2.0% by mass. Since the glass substrate for a flat panel display is likely to deteriorate TFT characteristics and semiconductor characteristics when alkali metals are eluted from the glass substrate in the panel manufacturing process, the glass substrate does not substantially contain the alkali metal oxide, % By mass.

In addition, by containing a slight amount of an alkali metal such as an alkali-small-content glass, solubility and refinability can be improved while suppressing deterioration of TFT characteristics, semiconductor characteristics, and thermal expansion of glass within a certain range. Since the alkali-small-content glass can effectively lower the resistivity of the molten glass, the molten glass easily becomes electrically conductive during the melting of the molten glass, and the furnace material constituting the wall surface of the melting tank, such as relatively high- It is thought that electricity becomes difficult to pass through. As a result, erosion of the furnace can be suppressed. Further, since the elution of zirconia into the molten glass can be reduced, it is possible to improve the failure of the glass. In this respect, it is effective to use an alkali-containing glass.

In the above embodiment, the center upper cooling unit 62 is controlled so that the atmospheric temperature is uniform along the width direction of the sheet glass SG (plate thickness equalizing step). Thus, in the above embodiment, the thickness of the sheet glass SG can be made uniform. However, the center upper cooling unit 62 may use a configuration capable of changing the temperature along the width direction of the sheet glass SG. For example, it is possible to divide the space formed inside the central cooling unit 62 into a plurality of spaces, respectively, to cool each space, or to provide a constitution in which a part of the heat insulating material can be installed inside the central cooling unit 62 , The atmosphere temperature in the width direction may be changed. Even if the uniformity of the thickness of the sheet glass SG in the width direction can not be realized due to some influence even though the temperature of the central portion of the sheet glass SG is made uniform, The thickness can be made uniform.

[Experimental Example 1]

In order to confirm the effect of the present embodiment, a glass substrate was manufactured by changing the manufacturing method of the glass substrate.

(Example 1)

The glass raw material was dissolved in the melting tank of the dissolving apparatus 11 to obtain a molten glass so that the glass substrate to be produced had the following composition. The molten glass was conveyed through a tube made of a platinum alloy to the blue sign of the clarifying device 12, and the molten glass was refined. Subsequently, the molten glass after the refining was homogenized, the molten glass was supplied to the formed body 41, and the sheet glass SG was formed at a speed of about 2 m / min by the overflow down-draw method. At this time, the thermal resistance of the used partition member (the heat insulating member 50) was 0.4 m 2 · K / W. The viscosity at both ends of the molten glass flowing through the lowermost end 41a of the formed body 41 was 10 ⁵ dPa · sec. At this time, when the temperature of the central portion of the sheet glass SG is in the temperature range from the temperature higher than the softening point to the vicinity of the stand-off point, the sheet glass SG is heated while applying a tensile force toward both ends of the sheet glass SG. Can be cooled so that the viscosity at both ends thereof becomes 10 ^9.0 to 10 ^14.5 dPa · sec.

In other words,

(1) When the sheet glass SG is molded, the temperature of the molten glass FG at the time when the molten glass FG passes through the formed body 41 is not lower than the liquidus temperature, and the molten glass FG is heated The viscosity of both ends of the molten glass FG at the time of passing through the lowermost end of the glass rod 41 is 10 ^4.3 to 10 ⁶ dPa · sec,

(2) When the sheet glass SG is cooled, when the temperature of the central portion of the sheet glass SG is in the temperature range from the temperature higher than the softening point to the vicinity of the stand-off point, A material having a heat resistance of 10 ^9.0 to 10 ^14.5 dPa · sec was used for the heat insulating member 50. Thereafter, the sheet glass SG was cut to produce a glass substrate for a flat panel display having a thickness of 0.7 mm and a size of 2200 mm x 2500 mm. The liquid phase temperature of the glass substrate for a flat panel display thus manufactured was 1125 ° C and the strain point was 660 ° C.

(Glass Composition of Example 1)

SiO _2: 60 mass%, Al ₂ O _3: 19.5 wt%, B ₂ O _3: 10 mass%, CaO: 5.3% by weight, SrO: 5% by weight, SnO _2: 0.2% by weight

(Comparative Example 1)

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

Because of this,

(1) When the sheet glass SG is molded, the temperature of the molten glass FG at the time when the molten glass FG passes through the formed body 41 is not lower than the liquidus temperature, and the molten glass FG is heated The viscosity of both ends of the molten glass FG at the time of passing through the lowermost end of the glass rod 41 is 10 ^4.3 to 10 ⁶ dPa · sec,

(2) When the sheet glass SG is cooled, when the temperature of the central portion of the sheet glass SG is in the temperature range from the temperature higher than the softening point to the vicinity of the stand-off point, And the viscosity was 10 ^9.0 to 10 ^14.5 dPa · sec.

A glass substrate was produced in the same manner as in Example 1 except for the above. A glass substrate for a flat panel display was produced by combining glass raw materials such that the glass composition of Comparative Example 1 was the same as the glass composition of Example 1.

(The shrinkage amount of the width of the sheet glass)

The shrinkage amount in the width direction of the sheet glass in Example 1 and Comparative Example 1 with respect to the width of the formed article was measured. The shrinkage amount of Example 1 was 180 mm, while the shrinkage amount of Comparative Example 1 was 230 mm. No devitrification occurred on the glass substrate produced by the manufacturing method of Example 1 and Comparative Example 1. [

[Experimental Example 2]

Further, in order to confirm the effect of the present embodiment in the glass having the glass composition different from the above-mentioned glass composition, a manufacturing method of the glass substrate was changed to manufacture a glass substrate.

(Example 2)

The glass substrate to be manufactured is a glass having the following glass composition and the viscosity at both ends of the molten glass flowing through the lowermost end portion 41a of the formed body 41 is 10 ^4.6 dPa.second and the liquidus temperature of the glass substrate is 1,230.degree. 715 DEG C, a glass substrate for a flat panel display was manufactured in the same manner using the same thermal resistance of the partition member (insulating member) as in Example 1. [

(Glass Composition of Example 2)

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

(Comparative Example 2)

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

Because of this,

(1) When the sheet glass SG is molded, the temperature of the molten glass FG at the time when the molten glass FG passes through the formed body 41 is not lower than the liquidus temperature, and the molten glass FG is heated The viscosity of both ends of the molten glass FG at the time of passing through the lowermost end of the glass rod 41 is 10 ^4.3 to 10 ⁶ dPa · sec,

(2) When the sheet glass SG is cooled, when the temperature of the central portion of the sheet glass SG is in the temperature range from the temperature higher than the softening point to the vicinity of the stand-off point, And the viscosity was 10 ^9.0 to 10 ^14.5 dPa · sec.

A glass substrate was produced in the same manner as in Example 2 except for the above. A glass substrate for a flat panel display was produced by combining glass raw materials so that the glass of Comparative Example 2 had the same composition as the glass of Example 2.

(Example 3)

The thermal resistance of the partition member (insulating member) in Example 3 is the same as that of Example 2 except that the glass substrate to be manufactured is a glass having the following glass composition, the liquidus temperature is 1200 캜 and the strain point is 699 캜, A glass substrate for a flat panel display was manufactured.

(Glass Composition of Example 3)

SiO _2: 61.2% by weight, Al ₂ O _3: 19.5 wt%, B ₂ O _3: 9.0 wt%, K ₂ O: 0.19 mass%, CaO: 10 weight%, Fe ₂ O _3: 0.01 mass%, SnO ₂ : 0.1 mass%

(Examples 4 to 7)

The heat resistance of the partition member (heat insulating member) is set to 0.2 m2 K / W (Example 4), 0.6 m2 K / W (Example 5), 1.0 m2 K / W (Example 6) K / W (Example 7), the same glass as in Example 3 was used, and a glass substrate for a flat panel display was manufactured in the same manner.

(Comparative Example 3)

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

Because of this,

(1) When the sheet glass SG is molded, the temperature of the molten glass FG at the time when the molten glass FG passes through the formed body 41 is not lower than the liquidus temperature, and the molten glass FG is heated The viscosity of both ends of the molten glass FG at the time of passing through the lowermost end of the glass rod 41 is 10 ^4.3 to 10 ⁶ dPa · sec,

(2) When the sheet glass SG is cooled, when the temperature of the central portion of the sheet glass SG is in the temperature range from the temperature higher than the softening point to the vicinity of the stand-off point, And the viscosity was 10 ^9.0 to 10 ^14.5 dPa · sec.

A glass substrate was produced in the same manner as in Example 3 except for the above. A glass substrate for a flat panel display was manufactured by combining glass raw materials so that the glass of Comparative Example 3 had the same glass composition as the glass of Example 3.

(The shrinkage amount of the width of the sheet glass)

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

From the above Experimental Examples 1 and 2, the effect of this embodiment is clear. In addition, it is preferable to use a partition member (heat insulating material) having a thermal resistance of 0.2 m 2 · K / W or more to cool the sheet glass so that the viscosity at both ends of the sheet glass is 10 ^9.0 to 10 ^14.5 dPa · sec, Which is preferable.

While the present invention has been particularly shown and described with respect to a preferred embodiment thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Needless to say, it can be changed.

32: Temperature control unit
41: molded article
41a: Lower end of the molded article
41b:
50: partition member
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: Single phase cooling unit
73: Lower cooling unit

Claims (6)

A step of forming a sheet glass by overflowing the molten glass from the molded body in an upper space of the molding furnace surrounded by the furnace wall,
A step of passing the sheet glass through a slit-shaped gap formed by a heat insulating member that divides the molding furnace chamber into an upper space and a lower space;
And cooling the both end portions of the sheet glass in the lower space,
The heat insulating member
(1) In the step of molding the sheet glass, the temperature of the molten glass when the molten glass passes through the formed body is not lower than the liquidus temperature, and when the molten glass passes through the lowermost end of the formed body, The viscosity of both ends of the molten glass is 10 ^4.3 to 10 ⁶ dPa · sec,
Also,
(2) In the step of cooling the sheet glass, when the temperature of the central portion of the sheet glass is in a temperature range from the temperature higher than the softening point to the vicinity of the gradual point (slow cooling point) Is 10 ^9.0 to 10 ^14.5 dPa · sec, is used as the glass substrate. The method according to claim 1,
Wherein a thermal resistance between the upper space and the lower space of the heat insulating member is 0.2 m 2 K · W or more at an atmosphere temperature of the upper space. 3. The method according to claim 1 or 2,
In the lower space,
The temperature distribution in the width direction at the central portion of the sheet glass is made uniform and the temperature at both end portions of the sheet glass is made lower than the temperature at the central portion;
The temperature of the both end portions and the central portion is lower than the temperature of the both end portions and the central portion in the step of lowering the temperature of the central portion, And forming a temperature gradient in the width direction. 4. The method according to any one of claims 1 to 3,
Wherein a liquidus viscosity of the glass in the sheet glass is 10 ^4.3 dPa · sec to 10 ^6.7 dPa · sec. 5. The method according to any one of claims 1 to 4,
Wherein a strain point of the glass substrate is 670 캜 or higher. A molding furnace surrounded by a furnace wall,
A heat insulating member dividing the molding furnace chamber into an upper space and a lower space and forming a slit-shaped gap through which the sheet glass passes;
A molded body provided in the upper space of the molding furnace for overflowing the molten glass to form a sheet glass,
And a cooling member for cooling both ends of the sheet glass in the lower space,
The heat insulating member
(1) In the step of molding the sheet glass, the temperature of the molten glass when the molten glass passes through the formed body is not lower than the liquidus temperature, and when the molten glass passes through the lowermost end of the formed body, The viscosity of both ends of the molten glass is 10 ^4.3 to 10 ⁶ dPa · sec,
Also,
(2) In the step of cooling the sheet glass, when the temperature of the central portion of the sheet glass is in the temperature range from the temperature higher than the softening point to the vicinity of the stand-off point, the viscosity of both ends of the sheet glass is 10 ^9.0 To 10 ^14.5 dPa · sec.

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