TW201600474A - Glass substrate manufacturing method and glass substrate - Google Patents

Abstract

The present invention relates to a glass substrate manufacturing method and a glass substrate. The glass substrate manufacturing method can increase the production efficiency and reduce the glass substrate thermal shrinkage rate and lower unevenness of the glass substrate thermal shrinkage rate. During the manufacturing process of the glass substrate, thermal treatment of the glass substrate is performed, and the overall glass substrate is subjected to thermal treatment at a temperature 60 to 260 DEG C lower than the strain point. The overall glass substrate is cooled from the thermal treatment temperature at a first rate down to a temperature 50 to 300 DEG C lower than the thermal treatment temperature, i.e. the middle temperature, and then the overall glass substrate is cooled from the middle temperature at a second rate faster than the first rate down to the room temperature.

Description

Method for manufacturing glass substrate and glass substrate

The present invention relates to a method for producing a glass substrate comprising a heat treatment step of a glass substrate, and a glass substrate.

In recent years, in the field of display panels, in order to improve image quality, the definition of pixels has been progressing. Along with the progress of the high definition, the dimensional accuracy of the glass substrate used for the display panel is also expected to be high. For example, in the manufacturing process of the display panel, the glass substrate is not easily changed in size even when heat-treated at a high temperature, and a glass substrate having a small heat shrinkage is required.

In general, the thermal shrinkage of the glass substrate is such that the higher the strain point of the glass, the smaller it is. Therefore, a method of changing the glass composition so as to increase the strain point in order to suppress the heat shrinkage rate is known (Patent Document 1). However, if the glass composition is changed so that the strain point becomes high, the devitrification temperature tends to increase, and there is a problem that it is difficult to produce a glass substrate.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Special Table 2014-503465

As a method of reducing the heat shrinkage of the glass substrate without causing difficulty in the production of the glass substrate, the glass substrate obtained by cutting the flat glass formed by the melt method or the like is subjected to heat treatment off-line (offline) Annealing method. However, offline In the case of the fire, when the temperature and temperature of the glass substrate are raised and lowered, a temperature difference occurs in the surface direction of the glass substrate, and the heat shrinkage rate is uneven in the surface direction of the glass substrate. Further, in the off-line annealing, when the temperature of the glass substrate is raised or lowered, if the temperature increase rate/temperature drop rate is increased, the heat shrinkage rate of the glass substrate is not reduced, and the temperature increase rate and the temperature decrease rate are slowed down. The production efficiency of the glass substrate is lowered.

Therefore, an object of the present invention is to provide a method for producing a glass substrate, which can improve the production efficiency of the glass substrate and reduce the heat shrinkage rate of the glass substrate, and can reduce the heat shrinkage rate in the glass. Unevenness in the direction of the surface of the substrate.

The method for producing a glass substrate of the present invention and the glass substrate include the following aspects.

(Form 1)

A method for producing a glass substrate, characterized in that it comprises a heat treatment step of a glass substrate, and the heat treatment step comprises the steps of: treating the entire glass substrate at a temperature lower than a strain point by a temperature of 60 ° C to 260 ° C, that is, a heat treatment temperature. Performing heat treatment; cooling the entire glass substrate from the heat treatment temperature to an intermediate temperature lower than the heat treatment temperature by 50 ° C to 300 ° C at a first speed; and after the heat treatment step, at a second speed faster than the first speed The entire glass substrate was cooled from the intermediate temperature to room temperature.

(Form 2)

A method for producing a glass substrate, characterized in that it comprises a heat treatment step of a glass substrate, and the heat treatment step comprises the steps of: heat treatment from room temperature until a temperature lower than a strain point by 60 ° C to 260 ° C That is, at the heat treatment temperature, the entire glass substrate is heated from the room temperature to an intermediate temperature lower than the heat treatment temperature by 50 ° C to 300 ° C at a third speed; and the glass substrate is entirely at a fourth speed slower than the third speed. Heating from the intermediate temperature to the heat treatment temperature; and heat treating the entire glass substrate at the heat treatment temperature.

(Form 3)

The method for producing a glass substrate according to the first aspect, wherein the heat treatment step comprises the step of: heat-treating from room temperature until the temperature is 60 ° C to 260 ° C lower than the strain point, that is, the heat treatment temperature, and the glass substrate is driven at a third speed. Heating the whole room temperature to an intermediate temperature lower than the heat treatment temperature by 50 ° C to 300 ° C; and heating the entire glass substrate from the intermediate temperature to the heat treatment temperature at a fourth speed slower than the third speed; The average speed of the first speed and the second speed is slower than the average speed of the third speed and the fourth speed.

(Form 4)

The method for producing a glass substrate according to any one of aspects 1 to 3, wherein the glass substrate has a strain point of 655 ° C or higher.

(Form 5)

The method of producing a glass substrate according to any one of the aspects of the present invention, wherein the glass substrate is formed by laminating a plurality of sheets in a thickness direction in a state in which the glass substrate is sandwiched between the sheet bodies. The laminate is heat treated.

(Form 6)

A method for producing a glass substrate, comprising: a heat treatment step comprising a single-layer glass substrate for a flat panel display, wherein the heat treatment step comprises: a heating maintaining step of heating the glass substrate to a heat treatment temperature in a range of 400 ° C to 600 ° C and maintaining the heat treatment temperature; and a cooling step of 0.5 ° C / min or more and less than 10 ° C / min The first temperature drop rate is obtained by cooling the glass substrate from the heat treatment temperature to a temperature lower than the heat treatment temperature by 50 ° C to 150 ° C, that is, an intermediate temperature of 10 ° C / min or more and less than 25 ° C / min. The above glass substrate was cooled.

(Form 7)

A method of producing a glass substrate according to aspect 6, wherein a semiconductor layer made of IGZO is formed on the glass substrate.

(Form 8)

A method of producing a glass substrate according to the aspect 6 or 7, wherein in the cooling step, the glass substrate is cooled at the second temperature drop rate, and then the glass substrate is further cooled to room temperature at the first temperature drop rate.

(Form 9)

The method for producing a glass substrate according to any one of the aspects 6 to 8, wherein in the heat treatment step, the glass substrate is horizontally placed in a furnace to perform the heating step, and heating is performed until the ambient temperature in the furnace becomes The above heat treatment temperature.

In the above heat treatment step, a heat treatment in a single sheet in which the plurality of sheets of the glass substrate are heat-treated one by one may be used.

(Form 10)

A glass substrate which is a glass substrate for liquid crystal display which is heat-treated at a heat treatment temperature in the range of 400 ° C to 600 ° C for 5 minutes to 30 minutes, and has a temperature of 500 ° C as the first evaluation temperature. 450 ° C as the second evaluation temperature, 550 ° C as the third evaluation temperature, and the glass substrate is maintained at each evaluation temperature for 30 minutes, and the heat shrinkage rate when the heat treatment is performed again is the first heat shrinkage ratio C1, the second Heat shrinkage rate C2 and the third heat shrinkage ratio C3, in this case, satisfy the relationship of |C1-C2|/|C3-C1|<0.28.

According to the method for producing a glass substrate and the glass substrate, the production efficiency of the glass substrate can be improved, the heat shrinkage rate of the glass substrate can be reduced, and the unevenness of the heat shrinkage rate of the glass substrate can be reduced.

10‧‧‧Layer

11‧‧‧ glass substrate

11a‧‧‧Edge area

11b‧‧‧Central area

12‧‧‧Sheet body

15a‧‧‧Insulation board

15b‧‧‧Insulation board

20‧‧‧ pallet

21‧‧‧Base Department

21a‧‧‧ Opening

22‧‧‧Loading Department

23‧‧‧ Back panel

40‧‧‧ furnace

41‧‧‧heating device

112‧‧‧Support components

140‧‧‧ furnace

141‧‧‧heating device

A‧‧‧ points

B‧‧‧ points

C1‧‧‧1st heat shrinkage rate

C2‧‧‧2nd heat shrinkage rate

C3‧‧‧3rd heat shrinkage rate

D, D1~D3‧‧‧ area

S1~S8‧‧‧Steps

S1, S2‧‧‧ heating rate

S3, S4, S5‧‧‧ cooling rate

T0~t5‧‧‧Time

Tm1~Tm4‧‧‧ Temperature

Fig. 1 is a flow chart showing an example of a flow of a method for producing a glass sheet according to the present embodiment.

Fig. 2 is a side view showing an example of a pallet in which a laminate of a glass substrate is placed in a heat treatment performed in the present embodiment.

Fig. 3(a) is a view showing a position on a glass substrate, and Fig. 3(b) is a view showing an example of a heat history at each position on the glass substrate.

Fig. 4 is a graph showing an example of the relationship between the area of the heat history difference and the strain.

Fig. 5 is a view showing an example of a temperature distribution when a glass substrate is subjected to heat treatment.

Fig. 6 (a) is a side view showing an example of a state in which the glass substrate is placed in the heat treatment performed in the embodiment, and (b) is a view of the glass substrate of (a) viewed from the bottom surface side.

Fig. 7 is a view showing an example of a temperature history of a glass substrate.

FIG. 8 is a view showing an example of the result of heat shrinkage of the glass substrate when the glass substrate subjected to heat treatment in the present embodiment is heat-treated by the evaluation heat treatment method.

Hereinafter, a method of producing the glass substrate of the present invention will be described in detail.

Fig. 1 is a flow chart showing an example of a flow of a method for producing a glass sheet according to the present embodiment. The glass substrate to be produced is not particularly limited, and it is preferably, for example, a longitudinal dimension and a lateral dimension of 500 mm to 3500 mm, respectively. It is preferably a plate having a very thin rectangular shape in which the thickness of the glass substrate is 0.1 to 1.1 (mm), more preferably 0.75 mm or less.

First, the molten glass is formed into a sheet glass which is a specific thickness of a sheet glass by a known method such as a melting method or a floating method (step S1).

Next, the formed flat glass plate is cut into a glass substrate which is a plain plate of a specific length (step S2). The glass substrate obtained by cutting the sheet and the sheet body of the protective glass substrate are alternately laminated to form a laminate of the glass substrate (step S3). Next, the laminated body of the glass substrate is subjected to heat treatment (step S4). The processing of the step S3 and the processing of the step S4 are the heat treatment, that is, the annealing step of the embodiment. See below for details on the annealing step.

The glass substrate after the heat treatment is transferred to the cutting step, and is cut into the size of the product to obtain a glass substrate (step S5). After the surface of the obtained glass substrate is subjected to grinding, polishing, and chamfering of the end surface, the glass substrate is washed (step S6). An optical inspection is performed to confirm whether or not the glass substrate after the cleaning has damage including scratches, dust, dirt, or optical defects (step S7). The glass substrate having a suitable quality according to the inspection is stacked on the pallet in the form of a laminate which is alternately laminated with the paper of the protective glass substrate, and is bundled (step S8). The bundled glass substrate is shipped to the owner of the destination.

As such a glass substrate, a glass substrate having the following glass composition can be exemplified. That is, the raw material of the molten glass is prepared so as to produce a glass substrate having the following glass composition.

SiO ₂ 5~80 mol%, Al ₂ O ₃ 8-20 mol%, B ₂ O ₃ 0~12 mol%, RO 0~17 mol% (RO is the total of MgO, CaO, SrO and BaO the amount).

From the viewpoint of reducing the heat shrinkage ratio, SiO _{2 is} preferably from 60 to 75 mol%, more preferably from 63 to 72 mol%.

In RO, it is preferable that MgO is 0 to 10 mol%, CaO is 0 to 10 mol%, SrO is 0 to 10%, and BaO is 0 to 10%.

Further, it may be at least SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , and RO, and molar ratio ((2×SiO ₂ )+Al ₂ O ₃ )/((2×B ₂ O ₃ )+ RO) is a glass of 4.5 or more. Further, it is preferable to contain at least one of MgO, CaO, SrO, and BaO, and the molar ratio (BaO+SrO)/RO is 0.1 or more.

Further, the total content of B ₂ O ₃ expressed by mol% and the content ratio of RO represented by mol% are preferably 30 mol% or less, preferably 10 to 30 mol%.

Further, the content of the alkali metal oxide in the glass substrate having the glass composition may be 0 mol% or more and 0.4 mol% or less.

Further, the glass contains a metal oxide (tin oxide or iron oxide) having a total valence of 0.05 to 1.5 mol%, and does not necessarily contain substantially As ₂ O ₃ , Sb ₂ O ₃ and PbO. Any.

The glass substrate produced in the present embodiment is suitable as a glass substrate for a display, for example, a glass substrate for a flat panel display, a glass substrate for a liquid crystal display, or a glass substrate for an organic EL display.

Further, the glass substrate produced in the present embodiment is particularly suitable as a glass substrate for a LTPS (Low-temperature polysilicon)-TFT (Thin Film Transistor) display used for a high-definition display, or IGZO (Indium). An oxide semiconductor such as -Gallium-Zinc-Oxide, indium gallium zinc oxide, or a glass substrate for TFT display.

In the method of forming a flat glass from molten glass in the present embodiment, a floating method, a melting method, or the like is used. However, in the method of manufacturing a glass substrate including a glass substrate which is subjected to heat treatment in an off-line manner in the present embodiment, In the melting method (overflow down-draw method), it is difficult to make the slow cooling device on the production line long, and it is suitable for the melting method. The heat shrinkage rate of the glass substrate before the heat shrinkage rate is reduced by the heat treatment of the present embodiment is 80 ppm or less, and more preferably 40 ppm to 60 ppm.

Hereinafter, the annealing steps (first and second embodiments) of the present embodiment will be described. The off-line annealing described in this embodiment refers to a production line that is detached from the manufacture of a glass substrate. The glass substrate produced is annealed.

(annealing step of the first embodiment)

Next, the annealing step of the first embodiment will be described in detail.

First, the plurality of glass substrates 11 cut in a sheet shape in the step S2 and the plurality of sheet bodies 12 are alternately laminated one by one to form a laminated body 10 of a glass substrate (step S3). In the present embodiment, the laminated body 10 of the glass substrate in which the plurality of glass substrates 11 are laminated is heat-treated. However, the heat treatment may be performed in a single-piece heat treatment in which the glass substrate 11 is conveyed one by one. . Further, a method may be employed in which the glass substrates 11 are heat-treated by not stacking the glass substrates 11 and separating the plurality of glass substrates 11 by a predetermined distance.

FIG. 2 is a side view showing an example of the pallet 20 on which the laminated body 10 (hereinafter referred to as the laminated body 10) on which the glass substrate is placed. Here, the left direction of the paper surface of FIG. 2 is set to the front direction of the pallet 20, and the right direction of the paper surface of FIG. 2 is set to the direction behind the pallet 20. The paper surface direction of FIG. 2 is set to the upper direction, and the paper surface downward direction is set to the downward direction. In the pallet 20, the laminated body 10 is placed in the stacking direction as a substantially front-rear direction. The pallet 20 on which the laminated body 10 is placed is conveyed to the furnace 40, and the laminated body 10 is heat-processed in the furnace 40. The furnace 40 is provided with a heat generating device 41 for heating the environment (air) of the furnace 40, and the heat generating device 41 serves as a heat source to heat the environment of the furnace 40. When the heat treatment is performed, the inside of the furnace 40 becomes a closed space, and the heat of the environment is transmitted to the laminated body 10, and the heat treatment of the laminated body 10 (glass substrate 11) is performed. Here, the lamination direction of the laminated body 10 does not have to be completely coincident with the front-rear direction. For example, when the glass substrate 11 is erected obliquely as shown in FIG. 2, the angle formed by the lamination direction and the front-rear direction corresponds to an angle at which the glass substrate 11 is inclined with respect to the vertical direction. In addition, the laminated body 10 may be laid flat on the pallet 20 so that the laminated direction of the laminated body 10 may be the vertical direction.

The pallet 20 includes a base portion 21, a mounting portion 22, a back panel 23, and the like.

The base portion 21, the placing portion 22, and the back surface plate 23 include, for example, a metal such as steel, and are integrally formed by welding or the like.

The base 21 has a substantially rectangular plate shape, and an opening 21a for inserting the claws of the stacker is provided on the end surface.

The mounting portion 22 is fixed to the upper portion of the base 21, and the laminated body 10 of the glass substrate is placed on the upper portion of the mounting portion 22. Here, the upper surface of the placing portion 22 does not need to be completely horizontal. For example, when the glass substrate 11 is erected obliquely as shown in FIG. 2, the upper surface of the mounting portion 22 may be inclined in accordance with the rising angle of the glass substrate 11.

The back panel 23 has a substantially rectangular plate shape, and is fixed to the rear end of the mounting portion 22 substantially perpendicularly to the mounting portion 22 on the upper portion of the base 21 . The back panel 23 supports the end portion after the lamination direction of the laminated body 10 placed on the upper portion of the mounting portion 22. Here, the back panel 23 does not have to be completely vertical. For example, when the glass substrate 11 is erected obliquely as shown in FIG. 2, the back surface plate 23 may be inclined in accordance with the rising angle of the glass substrate 11.

Next, the laminated body 10 will be described. The laminated body 10 includes a plurality of glass substrates 11 and a plurality of sheet bodies 12.

The sheet body 12 is sandwiched between the glass substrates 11 . The sheet body 12 serves to prevent the laminated glass substrates 11 from adhering to each other. Therefore, the laminated body 10 of the glass substrate is formed by laminating a plurality of sheets in the thickness direction in a state in which the glass substrate 11 is sandwiched between the sheet bodies. The sheet body 12 can be made of a material having heat resistance to withstand the temperature at which the laminated body 10 is subjected to heat treatment. The sheet body 12 preferably has a thermal conductivity higher than that of the glass substrate 11.

As a material of such a sheet body 12, for example, one selected from the group consisting of carbon graphite, alumina fiber, cerium oxide fiber, and porous ceramic, or a combination thereof can be selected.

In order to increase the thermal conductivity in the in-plane direction of the glass substrate 11, it is preferable that the thickness of the sheet body 12 is thick. On the other hand, in order to reduce the volume of the laminated body 10, it is preferable that the thickness of the sheet body 12 is thin. Therefore, the thickness of the sheet body 12 is preferably about 0.02 mm to 2 mm. The area of the sheet body 12 is preferably the same as or larger than the area of the glass substrate 11 in terms of preventing the glass substrates 11 from adhering to each other.

Furthermore, it is also possible to intervene between any plurality of glass substrates 11 for heating the laminated body. A heating plate of 10 is used instead of the sheet body 12, or the heating plate is placed together with the sheet body 12. As the heating plate, for example, an electrode plate that generates heat by the flow of a current can be used. In this case, the resistance value of the electrode plate changes depending on the temperature of the electrode plate, and therefore the amount of current flowing through the electrode plate changes depending on the temperature of the electrode plate. Therefore, the temperature of the heating plate can be controlled based on the amount of current flowing through the electrode plates. Thereby, the heat distribution between the plurality of glass substrates 11 can be uniformly adjusted.

Further, as the sheet body 12, recycled paper or pulp paper can also be used.

In the present embodiment, the laminated body 10 is heat-treated in a state in which the laminated body 10 is sandwiched between the pair of heat insulating plates 15a and 15b.

The pair of heat insulating plates 15a and 15b are disposed at both end portions of the laminated body 10 in the stacking direction. In Fig. 2, the heat insulating plate 15a is disposed at the rear end portion, and the heat insulating plate 15b is disposed at the front end portion. The heat insulating members 15a and 15b contain a material having a lower thermal conductivity than the glass substrate. As the material having a thermal conductivity lower than that of the glass substrate, for example, one selected from the group consisting of ceramics, alumina, cerium oxide, and rock wool, or a combination thereof may be selected.

In order to maintain the heat insulating performance, the heat resistance of the heat insulating plates 15a, 15b is preferably 0.1 ° C / W or more. On the other hand, the thermal resistance of the heat insulating plates 15a and 15b is preferably 10 ° C / W or less in order not to hinder the heating and cooling of the glass substrate 11 disposed at the end portion of the laminated body 10 . In order to maintain the heat insulating property, it is preferable that the thickness of the heat insulating plates 15a, 15b is thick. On the other hand, in order to reduce the volume of the laminated body 10, it is preferable that the thickness of the heat insulating sheets 15a and 15b is thin. Therefore, the thickness of the heat insulating plates 15a and 15b is preferably about 10 to 50 mm. The area of the heat insulating plates 15a and 15b is preferably the same as or larger than the area of the glass substrate 11 in order to prevent the glass substrates 11 from the outer side of the lamination direction from being in close contact with each other.

When the both ends of the laminated body 10 in the laminating direction are sandwiched by the heat insulating sheets 15a and 15b, the glass substrate 11 located at the front end (front end portion) of the laminated body 10 is prevented from flowing from the environment to the main surface of the glass substrate 11 to the main surface. The heat of the glass substrate 11 can be a heat conduction pattern that flows outward from the surface of the main surface of the glass substrate 11 located in the center of the laminated direction of the glass substrate 11. The same form. That is, in all of the glass substrates 11 of the laminated layer, heat enters from the end portion including the edge of the glass substrate 11, and heat is transferred toward the central region surrounded by the end portion. As a result, the heat distribution of the plurality of laminated glass substrates 11 can be made uniform in the thickness direction.

Next, the heat treatment of step S4 will be described.

The layered body 10 produced by the process of step S3 is heat-treated in a manner that is off-line from the production line. In the heat treatment, the laminated body of the glass substrate is placed in a specific temperature environment for a specific period of time, and the heat distribution of the end portion of the glass substrate to the central portion surrounded by the end portion is made uniform, thereby making the end portion The strain distribution from the region to the central region is adjusted in such a manner that the strain distribution becomes uniform.

Specifically, the tray 20 on which the stacked body 10 is placed is carried into the furnace 40 for heat treatment, and the operation of the heat generating device 41 is controlled to heat the air (environment) in the furnace 40, thereby heating the glass substrate 11 Heat treatment is performed.

The heat treatment temperature is preferably in a temperature range from a strain point of the glass substrate 11 of -60 ° C to a temperature of a strain point of -260 ° C in terms of lowering the heat shrinkage rate and making the strain distribution of the glass substrate uniform. Here, the strain point refers to the strain point of ordinary glass, which is a temperature equivalent to a viscosity of 10 ^14.5 poise. The heat treatment time is, for example, 0.5 to 120 hours. The time history of the temperature in the environment during the heat treatment is not particularly limited, and the temperature of the environment is at a temperature of from -560 ° C at the strain point to a temperature in the range of the strain point of at least 0.5 hours, preferably at least 1 hour. If the temperature is less than 0.5 hour and 1 hour, the heat shrinkage rate is not sufficiently reduced. When the temperature is longer than 120 hours, the heat shrinkage rate is sufficiently reduced, but the production efficiency of the glass substrate 11 is lowered.

Further, the strain point varies depending on the type of the glass. In order to reduce the heat shrinkage, the glass substrate 11 preferably has a glass composition having a higher strain point, and the glass substrate 11 has a strain point of preferably 600 ° C or more. It is 655 ° C or more, for example, 661 ° C. In this case, the heat treatment temperature is a strain point (661 ° C) - (60 ° C ~ 260 ° C) = 601 ° C ~ 401 ° C. for The glass substrate for high-definition display is reduced in heat shrinkage of the glass substrate 11, and is not limited to the above temperature range. For example, the maximum temperature during heat treatment, that is, the heat treatment temperature may be 250 ° C to 700 ° C, or It is 300 ° C ~ 600 ° C, and can be 350 ° C ~ 600 ° C, or 400 ° C ~ 550 ° C.

The high temperature environment in which the laminate of the glass substrate is exposed is not particularly limited, and may be an environment having an oxygen content of 5 to 50%, or an atmospheric environment such as air.

3(a) and 3(b) are views showing an example of a thermal history at each position on the glass substrate 11. Here, the thermal history indicates the history of the temperature of the glass substrate 11 which changes due to the heat treatment. When the laminated body 10 of the glass substrate 11 is carried into the furnace 40 for heat treatment, and the ambient temperature in the furnace 40 is raised, the heat of the environment is transmitted to the glass substrate 11 from the outer side in the lamination direction of the laminated body 10. The edge region 11a of the glass substrate 11 including the edge receives heat conduction from a high temperature environment, and heats up faster than the central region 11b of the glass substrate 11 surrounded by the edge region 11a. Further, the ambient temperature is lowered, and the edge region 11a of the glass substrate 11 in a high temperature state is exposed to a low temperature environment to dissipate heat, thereby lowering the temperature faster than the central region 11b of the glass substrate 11. Therefore, as shown in FIGS. 3(a) and 3(b), on the glass substrate 11, the periphery of the point A is heated and cooled more rapidly than the periphery of the point B. If a difference occurs in the thermal history, the tensile stress and the compressive stress are generated from the edge region 11a to the central region 11b (from the periphery of the point A to the periphery of the point B), and strain is generated. In order to make the heat shrinkage rate in the plane of the glass substrate 11 uniform and suppress the occurrence of strain, it is necessary to eliminate the temperature variation difference between the edge region 11a of the glass substrate 11 and the central region 11b, that is, it is necessary to reduce the thermal history difference.

Here, the semiconductor layer made of LTPS or IGZO is formed on the glass substrate 11 at a temperature of 400 ° C to 600 ° C (at a strain point of 661 ° C, which is a temperature lower than the strain point by about 60 ° C to 260 ° C), It suffices that the heat shrinkage rate of the glass substrate 11 in this temperature range can be lowered. Therefore, in the present embodiment, heat treatment is performed so that the maximum temperature around the point A and the point B of the glass substrate 11 is in the temperature range of 400 ° C to 600 ° C. The heat shrinkage rate changes not only with the highest temperature when the glass substrate 11 is heat-treated, but also with The heat history changes. In particular, as shown in FIG. 3(b), heat from a heat treatment temperature (for example, 500 ° C) which is the highest temperature at the time of heat treatment to a temperature lower than the heat treatment temperature by 50 ° C to 300 ° C (for example, 450 ° C to 200 ° C) The history has a greater impact on the heat shrinkage rate. The heat shrinkage rate is heat-treated in the temperature region by heat treatment at a temperature at which the heat shrinkage rate is evaluated, in which the semiconductor layer composed of LTPS or IGZO is formed on the glass substrate 11, that is, for example, 400 ° C to 500 ° C. Small heat shrinkage rate. Further, in the temperature region of the temperature region of 400 ° C to 500 ° C or less, the heat shrinkage is also lowered. That is, the influence on the heat shrinkage rate is large at a temperature close to the temperature at which the heat shrinkage rate is evaluated, and the smaller the temperature is, the smaller the influence on the heat shrinkage rate is. Therefore, in the present embodiment, heat treatment is performed in a temperature range which is a heat treatment temperature at the highest temperature during heat treatment to a temperature lower than 50 ° C to 300 ° C to suppress a thermal history difference in the surface direction of the glass substrate 11 . Fig. 3(b) shows the thermal history difference in the temperature range of 300 °C to 500 °C. By reducing the thermal history difference (the area D in FIG. 3(b)) between the edge region 11a (the periphery of the dot A) of the glass substrate 11 and the central region 11b (the periphery of the dot B), the heat on the surface of the glass substrate 11 can be suppressed. The shrinkage rate is uneven, and the generation of strain is suppressed.

The smaller the area D formed by the difference between the thermal history of point A and the thermal history of point B, the smaller the value of strain. Fig. 4 is a graph showing an example of the relationship between the area of the heat history difference and the strain. As shown in the figure, when the strain is 2 kgf/cm ² or less, the glass substrate 11 is heat-treated so that the area becomes D1 or less. When the strain is 4 kgf/cm ² or less, the glass substrate 11 is heat-treated so that the area is D2 or less, and when the strain is 9 kgf/cm ² or less, the area is made D3 or less. The glass substrate 11 is heat treated in a manner. The values of the areas D1 to D3 correspond to the units of time x temperature. The values of the areas D1 to D3 can be arbitrarily changed in accordance with the size, thickness, composition, and the like of the glass substrate 11. Thereby, the temperature and time of the glass substrate 11 in the heat treatment can be appropriately changed according to the allowable value of the strain required when manufacturing the panel of the high-definition display.

Further, heat treatment is performed so that the temperature of the central region 11b (around the point B) of the glass substrate 11 reaches the highest temperature which is the same as the temperature of the edge region 11a (around the point A). By glass The temperature of the central region 11b (around the point B) of the glass substrate 11 reaches the maximum temperature, and the difference in thermal shrinkage ratio between the edge region 11a (around the point A) and the central region 11b (around the point B) becomes small, and the occurrence of strain can be reduced. The time during which the temperature of the central region 11b (around point B) continues (holds) the maximum temperature is arbitrary, and is, for example, 0.5 hours to 4 hours, more preferably 1 hour to 2 hours. In order to achieve a specific heat shrinkage rate, heat treatment is performed in such a manner that the temperature of the glass substrate 11 of the edge region 11a (around the periphery of the point A) to the central region 11b (the periphery of the dot B) reaches the highest temperature, in order to suppress the generation of strain to make the glass The heat treatment is performed in such a manner that the difference in thermal history in the surface direction of the substrate 11 becomes small.

Fig. 5 is a view showing an example of a temperature distribution when a glass substrate is subjected to heat treatment. As described above, the heat history at the highest temperature during heat treatment, that is, the heat treatment temperature (for example, a temperature lower than the strain point of 60 ° C to 260 ° C) to an intermediate temperature lower than the above heat treatment temperature by 50 ° C to 300 ° C, affects the heat shrinkage rate. Larger. In order to suppress the thermal history difference in the temperature range in the laminated glass substrate 11, it is necessary to make the intermediate temperature to the highest temperature (temperature gradient) slower (smooth) than the room temperature to the intermediate temperature (temperature gradient). In Fig. 5, the temperature increase rate S1 in the temperature region Tm1 to Tm2 having a small influence on the heat shrinkage is (Tm2-Tm1)/(t1-t0), and the temperature region Tm2 to Tm3 having a large influence on the heat shrinkage is The heating rate S2 is (Tm3-Tm2)/(t2-t1), and the speed S3 in the highest temperature region Tm3 is (Tm3-Tm3)/(t3-t2)=0, and the temperature region Tm3 having a large influence on the heat shrinkage The cooling rate S4 in ~Tm2 is (Tm2-Tm3)/(t4-t3), and the cooling rate S5 in the temperature region Tm2~Tm1 with less influence on heat shrinkage is (Tm1-Tm2)/(t5-t4) . Here, the temperature is Tm1 < Tm2 < Tm3, Tm1 = room temperature (for example, 25 ° C), Tm2 = intermediate temperature (for example, 300 ° C), and Tm3 = maximum temperature (for example, 500 ° C). Here, the room temperature is not limited to 25 ° C, for example, 1 ° C to 30 ° C. Further, the maximum temperature is not limited to 500 ° C, and may be any temperature of the strain point - (60 ° C to 260 ° C), the intermediate temperature is not limited to 300 ° C, and may be the highest temperature - (50 ° C ~ 300 ° C) temperature. The intermediate temperature varies with the maximum temperature, but the maximum temperature can also be set to the temperature in the range of strain point - (60 ° C ~ 260 ° C), and the intermediate temperature is fixed to 300 ° C. In this case, the maximum temperature rises to 300 ° C / Cooling rate is slower than 300 ° C to 25 ° C heating / cooling rate. Further, the temperature increase rate and the temperature decrease rate are average speeds at which the entire temperature of the glass substrate 11 is raised and lowered.

In the temperature rise time t0 to t2, the laminated body 10 is heat-treated so that the temperature increase rate S2 in the temperature regions Tm2 to Tm3 having a large influence on the heat shrinkage becomes the temperature increase rate S1 > the temperature increase rate S2. The temperature increase rate S1 in the temperature region where the influence on the heat shrinkage is small is, for example, 60 ° C / h to 300 ° C / h, more preferably 80 ° C / h ~ 250 ° C / h, and the temperature region having a large influence on the heat shrinkage The internal temperature increase rate S2 is, for example, 20 ° C / h to 60 ° C / h, more preferably 20 ° C / h ~ 40 ° C / h. The time t3-t2 at which the maximum temperature Tm3 is maintained is, for example, 0.5 hours to 4 hours, preferably 1 to 4 hours, more preferably 1 hour to 2 hours. Further, at the temperature drop time t3 to t5, the temperature drop rate S4 in the temperature regions Tm2 to Tm3 having a large influence on the heat shrinkage is determined as the temperature drop rate S5 > the temperature drop rate S4 by the absolute value of the temperature drop rate. Perform cooling (heat dissipation) processing. The cooling rate S4 in the temperature region where the influence on the heat shrinkage is large is, for example, -20 ° C / h ~ -60 ° C / h, more preferably -20 ° C / h ~ -40 ° C / h, the effect on heat shrinkage is more The temperature drop rate S5 in the small temperature region is, for example, -60 ° C / h to -300 ° C / h, more preferably - 80 ° C / h ~ -250 ° C / h. Further, with regard to heat shrinkage, the influence at the time of temperature drop is greater than the influence at the time of temperature rise. Therefore, the absolute value of the speed can be set to S2>S4, and the temperature drop rate S4 can be made slower than the temperature increase rate S2. Further, the temperature increase rate S1 and the average speed AS1 of the temperature increase rate S2 may be made slower than the average speed AS2 of the temperature drop rate S3 and the temperature drop rate S4, that is, the average speed AS1>the average speed AS2. In the temperature region of Tm2 to Tm1 (room temperature) which is less likely to cause strain due to heat shrinkage, the temperature increase rate and the temperature decrease rate are increased, and the temperature rise time and the temperature decrease time are shortened, thereby shortening the heat treatment of the laminated body 10. , the time of cooling treatment. Thereby, in the temperature regions Tm1 to Tm2 having a small influence on the reduction in the heat shrinkage rate, the heat treatment time can be shortened, and the production efficiency of the glass substrate 11 can be improved. On the other hand, in the temperature range Tm2 to Tm3 which is the intermediate temperature which is likely to cause strain due to the influence of heat shrinkage to the highest temperature during heat treatment, that is, the heat treatment temperature, the temperature increase rate and the temperature decrease rate are slowed, and the temperature rise time is prolonged. The cooling time, thereby suppressing the generation of strain. Thereby, the glass can be reduced The substrate 11 has uneven heat shrinkage rate and suppresses generation of strain, and further, the production efficiency of the glass substrate 11 can be improved.

The time during which heat is transferred from the heat source provided in the furnace 40 to the edge region 11a (around the point A) of the glass substrate 11 and the time when the heat is transferred from the heat source to the central region 11b (the periphery of the point B) is as shown in FIG. 3 ( b), the time from the heat source passing through the edge region 11a (around point A) to the central region 11b (around point B) is more time consuming. Therefore, after the time of heat transfer to the edge region 11a (around the point A), that is, the edge region 11a (around the point A) becomes an intermediate temperature of 300 ° C, the temperature increase rate is made intermediate from the room temperature to the edge region 11a (around the point A). The temperature rise rate is slow at 300 ° C (the temperature gradient is gentle). By slowing down the temperature increase rate, the speed at which the edge region 11a (around point A) is heated by the heat source is suppressed, and the time during which heat is transferred from the edge region 11a (around point A) to the central region 11b (around point B) is secured. Therefore, the difference between the thermal history of point A and the thermal history of point B becomes small. Further, regarding the heat dissipation, the heat dissipation time from the central region 11b (around the point B) via the edge region 11a (around the point A) is longer than the heat dissipation time from the region 11a (around the point A). Therefore, after the edge region 11a (around point A) is cooled (dissipated) to an intermediate temperature of 300 ° C, the temperature drop rate is slower than the edge region 11a (around point A) from the highest temperature to the intermediate temperature of 300 ° C. By such heat treatment/cooling treatment, it is possible to ensure the time during which heat is transmitted from the edge region 11a (around point A) to the central region 11b (around point B), and it is ensured that the central region 11b (around point B) is cooled. The time can suppress the thermal history difference in the temperature range from the intermediate temperature to the highest temperature (300 ° C ~ 500 ° C) which has a great influence on the heat shrinkage.

By such heat treatment, the heat shrinkage rate of the glass substrate 11 can be set to 0 to 15 ppm. The heat shrinkage rate of the glass substrate 11 is preferably from 0 to 12 ppm, more preferably from 0 to 6 ppm. Such a heat shrinkage rate can be achieved by adjusting the glass composition of the glass substrate, the temperature of the heat treatment, and the heat treatment time.

In the present embodiment, the laminated body 10 is placed in a state in which the laminated body 10 of the glass substrate 11 is sandwiched between the pair of heat insulating plates 15a and 15b having a lower thermal conductivity than the glass substrate 11 in the lamination direction. The furnace 40 is carried into the heat treatment, and the ambient temperature in the furnace 40 is raised. Regarding the temperature gradient of the environment in the furnace 40, the heat distribution between the plurality of glass substrates 11 can be made uniform by making the temperature gradient from 300 ° C to 500 ° C gentler than the temperature gradient from room temperature to 300 ° C. Therefore, the unevenness of the heat shrinkage rate of each of the glass substrates 11 after the heat treatment can be reduced.

In this case, the heating plate may be placed at any position in the lamination direction of the laminated body 10, and the laminated body 10 may be heated by the heating plate so that the heat distribution between the plurality of glass substrates 11 is uniform.

Further, by using a material having a thermal conductivity higher than that of the glass substrate 11 as the sheet body 12, heat transfer in the in-plane direction of the glass substrate 11 can be promoted, and heat of the end portion and the central portion of the glass substrate 11 can be promoted. The distribution is consistent. Therefore, the unevenness of the heat shrinkage rate in the surface direction of the glass substrate 11 is suppressed, and the occurrence of strain due to the difference in the heat shrinkage rate is also suppressed, and the strain distribution of the glass substrate can be made uniform.

In the case of the monolithic method in which the glass substrate 11 is heat-treated one by one, the temperature increase rate and the temperature drop rate can be improved as compared with the case where the layered body 10 in which the glass substrate 11 is laminated is heat-treated. In the single-chip method, the heat treatment time can be shortened. Therefore, for example, the temperature increase rate S1=120°C/h to 400°C/h, the temperature increase rate S2=40°C/h to 120°C/h, and the maximum temperature Tm3 can be maintained. T3-t2=0.5 hours~2 hours, cooling rate S4=-40°C/h~-120°C/h, cooling rate S5=-120°C/h~-400°C/h.

Further, the temperature increase rate and the temperature decrease rate can be changed according to the thickness in the stacking direction of the laminated body 10. For example, when the thickness of the laminated body 10 in the lamination direction is 50 cm or less, the heat is rapidly transferred in the lamination direction, so that the heating rate S1 = 90 ° C / h - 300 ° C / h, and the heating rate S2 can be set. =30°C/h~90°C/h, the time to maintain the highest temperature Tm3 t3-t2=0.5 hours~3 hours, the cooling rate S4=-30°C/h~-90°C/h, the cooling rate S5=-90°C /h~-300°C/h. The thinner the thickness of the laminated body 10 in the lamination direction, the higher the temperature increase rate and the lowering speed. When the glass substrate 11 laminated in the lamination direction is one piece, that is, in the case of a single piece, the temperature increase rate and the temperature drop rate may be increased. Heat treatment is performed. which is The thickness of the laminated body 10 in the lamination direction is reduced, and the heat treatment can be performed without changing the magnitude relationship between the temperature increase rate and the temperature drop rate.

(annealing step of the second embodiment)

Next, the annealing step of the second embodiment will be described in detail. The second embodiment is a form of heat treatment in a one-piece manner in which a glass substrate is heat-treated one by one. The method for producing the glass substrate in the second embodiment is also carried out in the flow shown in Fig. 1 . In this case, when the glass substrate of step S3 is stacked, the glass substrate 11 is placed so as to be supported by the supporting member for supporting the glass substrate shown in FIG. 6(a) below.

Fig. 6(a) is a side view showing an example of the state in which the glass substrate 11 in the furnace is placed, and Fig. 6(b) is a view of the glass substrate 11 of Fig. 6(a) viewed from the bottom surface side. The glass substrate 11 is placed horizontally on the support member 112 provided in the furnace 140, and is heat-treated in the furnace 140. First, the glass substrate 11 cut in a plate shape by the step S2 shown in FIG. 1 is placed on the support member 112 in a manner supported by the support member 112 (step S3), and placed on the support member in the glass substrate 11. The heat treatment (annealing treatment) is performed in the state of 112 (step S4). In the present embodiment, heat is not performed in a state in which a plurality of glass substrates 11 are laminated without placing a single (single-layer) glass substrate 11 on the support member 112. Further, a single-piece heat treatment in which the glass substrate 11 placed on the support member 112 is transferred one by one and heat-treated is performed. Further, a plurality of sheets of the glass substrate 11 placed on the support member 112 may be placed in the furnace to heat-treat the glass substrates 11, and the glass substrate 11 and the support member 112 may be alternately laminated by the support member 112. Each of the glass substrates 11 is heat-treated by separating the glass substrates 11 by a specific distance.

The support member 112 is composed of, for example, a heat-resistant fiber member, carbon fiber, alumina fiber, cerium oxide fiber, porous ceramic, carbon graphite, carbon felt, metal member, or brick member, and is provided in a plurality of furnaces 140. The support member 112 supports the lower surface (bottom surface) of the glass substrate 11 in such a manner that the glass substrate 11 is substantially horizontal.

Furthermore, the number of support members 112 supporting the glass substrate 11 and the respective support members 112 are The position of the spacer and the supporting glass substrate 11 is arbitrary. Moreover, when the glass substrate 11 is heat-treated, the glass substrate 11 expands and deforms, and therefore the support member 112 preferably has flexibility.

The furnace 140 is provided with a plurality of heat generating devices 141 for heating the environment (air) of the furnace 140, and the heat generating device 141 serves as a heat source to heat the environment of the furnace 140. The heat generating device 141 is composed of, for example, a ceramic heater, a far-infrared heater, or a halogen heater, and heats the environment of the glass substrate 11 and the furnace 140 so that the temperature of the glass substrate 11 becomes the following thermal history. The heat of the environment is transmitted to the glass substrate 11, and the glass substrate 11 is heated by far infrared rays and infrared rays to heat the glass substrate 11 to a temperature in the range of 400 ° C to 600 ° C. When the heat treatment is performed, the inside of the furnace 140 becomes a closed space and is not easily affected by the outside of the furnace 140. The heat generating device 141 controls the amount of heat generation and the heat generation time so that the temperature distribution in the furnace 140 is substantially uniform. The temperature distribution in the furnace 140 may be substantially uniform, and the position and number of the heat generating device 141 in the furnace 140 may be arbitrary. The glass substrate 11 is supported by the support member 112, and a specific space is provided on the lower surface of the glass substrate 11. Since the temperature distribution in the furnace 140 is substantially uniform, the thermal history is the same on the upper surface of the glass substrate 11 and the lower surface of the glass substrate 11 supported by the support member 112. When a thermal history difference occurs between the upper surface and the lower surface of the glass substrate 11, the heat shrinkage rate is different between the upper surface and the lower surface, and tensile and compressive stresses are generated, so that warpage occurs. Therefore, the difference in temperature variation between the upper surface and the lower surface of the glass substrate 11 is eliminated, that is, the difference in thermal history is reduced.

Next, the heat treatment of step S4 will be described.

First, the heat generating device 141 is controlled so that the ambient temperature in the furnace 140 becomes the heat treatment temperature. Here, the heat treatment temperature refers to a temperature at which the semiconductor layer composed of LTPS or IGZO used in the high-definition display is formed on the glass substrate 11, specifically, a temperature in the range of 400 ° C to 600 ° C. The processing temperature of the glass substrate 11 when manufacturing a high-definition display is a temperature lower than the strain point of the glass (corresponding to a temperature of 10 ^14.5 poise, for example, 6601 ° C). If the heat shrinkage rate of the glass substrate is large in a temperature region lower than the processing temperature, the glass substrate is not suitable as a glass substrate for manufacturing a high-definition display. Therefore, the glass substrate 11 is heat-treated at a heat treatment temperature in a temperature range substantially equal to the processing temperature of the glass substrate on which the high-definition display is manufactured, that is, in the range of 400 ° C to 600 ° C, in a temperature region below the heat treatment temperature. The heat shrinkage ratio is 0 to 15 ppm, preferably 0 to 10 ppm, more preferably 0 to 6 ppm, and still more preferably 0 to 3 ppm.

Next, after the ambient temperature in the furnace 140 becomes the heat treatment temperature, the glass substrate 11 is placed substantially horizontally on the support member 112 in the furnace 140, and the input port of the glass substrate 11 in the furnace 140 is closed to the inside of the furnace 140. Become a closed space. The glass substrate 11 is placed in the furnace 140 in a state where the ambient temperature in the furnace 140 is the heat treatment temperature, whereby the glass substrate 11 can be heated in a short time.

Furthermore, when there is a difference between the temperature of the glass substrate 11 and the ambient temperature in the furnace 140, the glass substrate 11 is thermally deformed (thermally expanded) when the glass substrate 11 is placed in the furnace 140, and the glass may be preliminarily The substrate 11 is heated and then placed in the furnace 140. By heating the glass substrate 11 in advance, it is possible to suppress the glass substrate 11 from being thermally deformed rapidly, and it is possible to reduce strain, warpage, recesses, and the like which are generated in the glass substrate 11. Moreover, damage to the glass substrate 11 due to friction between the glass substrate 11 and the support member 112 can also be suppressed.

Next, the heat generating device 141 is controlled to heat the glass substrate 11 at a temperature increase rate of 20 ° C / min or more to less than 120 ° C / min until the heat treatment temperature is the highest temperature at the time of heat treatment in the range of 400 ° C to 600 ° C. The step of heating the temperature of the glass substrate 11 to the heat treatment temperature is a heating step. After the heating step, the temperature of the glass substrate 11 is maintained at the heat treatment temperature for 5 minutes to 120 minutes. The step of continuously maintaining the temperature of the glass substrate 11 in the state of the heat treatment temperature is a maintaining step. In the maintaining step, the temperature of the glass substrate 11 may vary from 400 ° C to 600 ° C, and the temperature of the glass substrate 11 may not be fixed. For example, it can also be slower than the temperature increase rate of 20 ° C / min to 120 ° C / min, or The speed at which the first temperature drop rate is slower than 0.5 ° C / min to 10 ° C / min is maintained so that the temperature of the glass substrate 11 is in the range of 400 ° C to 600 ° C. After the maintenance step, the glass substrate 11 is cooled from the heat treatment temperature to a first intermediate temperature lower than the heat treatment temperature by 50 ° C to 150 ° C at a first temperature drop rate of 0.5 ° C / min or more to less than 10 ° C / min. After the glass substrate 11 is cooled at the first temperature drop rate, the glass substrate 11 is cooled from the first intermediate temperature to the second intermediate temperature at a second temperature drop rate of 10 ° C / min or more to less than 25 ° C / min. After the glass substrate 11 was cooled at the second temperature drop rate, the glass substrate 11 was further cooled from the second intermediate temperature to room temperature at the first temperature drop rate. The step of cooling the temperature of the glass substrate 11 from the heat treatment temperature to room temperature is a cooling step, and the cooling at the heat treatment temperature to the first intermediate temperature is the first cooling step, and the cooling from the first intermediate temperature to the second intermediate temperature is the second cooling step. The cooling from the second intermediate temperature to room temperature is the third cooling step.

FIG. 7 is a view showing the heat history of the glass substrate 11. Here, the thermal history represents the history of the temperature of the glass substrate 11 which varies with the heat treatment in the furnace 140. The temperature shown in the figure is Tm1 < Tm2 < Tm3 < Tm4, Tm1 = room temperature (for example, 25 ° C), Tm2 = second intermediate temperature (for example, 200 ° C), and Tm3 = first intermediate temperature (for example, 400 ° C) ), Tm4 = heat treatment temperature (for example, 500 ° C).

The heating step, the maintaining step, the speed in each cooling step, and the range of time are shown below.

(1) Heating step: t1-t0=5 minutes~20 minutes, Tm4-Tm1=400°C~600°C, heating rate S1=(Tm4-Tm1)/(t1-t0)=20°C/min~120°C/ Minutes; (2) Maintenance steps: t2-t1=5 minutes to 120 minutes, Tm4-Tm4=0, speed S2=(Tm4-Tm4)/(t2-t1)=0°C/min; (3) first cooling Step: t3-t2=15 minutes~100 minutes, Tm4-Tm3=50°C~150°C, cooling rate S3 (first cooling rate)=(Tm4-Tm3)/(t3-t2)=0.5°C/min~10 °C/min; (4) second cooling step: t4-t3=10 minutes~15 minutes, Tm3-Tm2=150°C~250°C, The cooling rate S4 (second cooling rate) is (Tm3-Tm2)/(t4-t3)=10°C/min~25°C/min; (5) the third cooling step: t5-t4=15 minutes~100 minutes, Tm2-Tm1=50°C~150°C, cooling rate S5 (first cooling rate)=(Tm2-Tm1)/(t5-t4)=0.5°C/min~10°C/min.

Here, the room temperature is not limited to 25 ° C, for example, 0 ° C to 30 ° C. Further, the heat treatment temperature is not limited to 500 ° C, and may be any temperature of 400 ° C to 600 ° C, and the first intermediate temperature is not limited to 400 ° C, and may be any temperature of the heat treatment temperature - (50 ° C to 150 ° C). The second intermediate temperature is a temperature in the range of 150 ° C to 250 ° C, and may be fixed at 200 ° C. Further, the temperature increase rate and the temperature decrease rate are average speeds at which the entire temperature of the glass substrate 11 is raised and lowered.

When the heating step is compared with the maintenance step and the cooling step, the influence on the heat shrinkage of the glass substrate 11 is small, and the strain due to the unevenness of the heat shrinkage rate is less likely to occur, so the processing time (=Tm4-Tm1) is also It can be shorter, and it can also make the heating rate faster. In the heating step, the heating rate is increased by shortening the processing time, and the production efficiency of the glass substrate 11 can be improved.

The maintenance step has a large influence on the heat shrinkage of the glass substrate 11 in the same manner as the cooling step, and can be reduced by making the processing time of the cooling step (= t5 - t2) longer than the processing time (= t2 - t1) of the sustaining step. Heat shrinkage rate. Therefore, the production efficiency of the glass substrate 11 can be improved by making the processing time of the maintaining step shorter than the processing time of the cooling step. By extending the processing time of the maintenance step, the low heat shrinkage rate of the glass substrate 11 can be achieved. Therefore, the processing time of the maintenance step can be arbitrarily changed according to the heat shrinkage ratio required for the glass substrate 11, whereby the glass substrate 11 can be realized. Increased production efficiency and reduced heat shrinkage. Further, the thinner the thickness of the glass substrate 11, the faster the heat is transferred to the inside of the glass substrate 11, so that the processing time of the maintenance step can be shortened according to the thinness of the thickness of the glass substrate 11. In addition, the temperature of the maintenance step, that is, the heat treatment temperature is based on the temperature at which the semiconductor layer made of LTPS or IGZO used in the high-definition display is formed on the glass substrate 11, and therefore It may be the same temperature range as the formation temperature, or may be a temperature lower than the strain point of the glass. Since it is not necessary to raise the temperature in the furnace 40 to the strain point of the glass, the heating cost becomes low, and the heat shrinkage rate of the glass substrate 11 can be reduced at a low cost.

Further, the strain point varies depending on the type of the glass. In order to reduce the heat shrinkage, the glass substrate 11 preferably has a glass composition having a higher strain point, and the glass substrate 11 has a strain point of preferably 600 ° C or more. It is 655 ° C or more, for example, 661 ° C.

Since the first cooling step has a large influence on the heat shrinkage of the glass substrate 11, the processing time (=t3-t2) is longer than the processing time (=t4-t3) of the second cooling step, and the cooling rate S3 is lower than the second cooling step. The cooling rate S4 is slow. In the heat treatment of the heat treatment temperature to the first intermediate temperature (for example, 400 ° C) which has a large influence on the heat shrinkage of the glass substrate 11, the treatment time is made longer than the other steps, and the temperature drop rate is slowed, whereby the glass substrate can be reduced. The uneven heat shrinkage rate of 11 can suppress the generation of strain.

Since the second cooling step has a small influence on the heat shrinkage of the glass substrate 11, the processing time (=t4-t3) is shorter than the processing time (=t3-t2) of the first cooling step, and the cooling rate S4 is lower than the first cooling step. The cooling rate S3 is fast. The region from the first intermediate temperature to the second intermediate temperature has less influence on the heat shrinkage of the glass substrate 11 than the temperature region in which the heat treatment temperature is to the first intermediate temperature, and strain which is not generated due to unevenness in heat shrinkage rate is less likely to occur. . Therefore, in the second cooling step, the processing time is made shorter than the first cooling step, and the temperature drop rate is increased, whereby the production efficiency of the glass substrate 11 can be improved.

Since the third cooling step has a small influence on the heat shrinkage of the glass substrate 11, the glass substrate 11 can be cooled by any cooling rate. By lowering the temperature drop rate S5 of the third cooling step than the temperature decreasing rate S4 of the second cooling step, thermal deformation of the glass substrate 11 can be suppressed, and damage to the glass substrate 11 due to friction between the glass substrate 11 and the support member 12 can be suppressed. .

Further, since the third cooling step has little influence on the heat shrinkage of the glass substrate 11, the glass substrate 11 can be cooled by the cooling rate S4 of the second cooling step. By cooling at the temperature decreasing rate S4 in the third cooling step, the production efficiency of the glass substrate 11 can be improved.

By such heat treatment, the heat shrinkage rate of the glass substrate 11 can be set to 0 to 15 ppm. The heat shrinkage rate of the glass substrate 11 is preferably from 0 to 10 ppm, more preferably from 0 to 6 ppm. Such a heat shrinkage rate can be achieved by adjusting the glass composition of the glass substrate, the temperature of the heat treatment, and the heat treatment time. Further, in the temperature region where the influence on the heat shrinkage of the glass substrate is small, the processing time is shortened and the temperature increase rate and the temperature decrease rate are increased, whereby the production efficiency of the glass substrate 11 can be improved. Further, in the case of the single-piece glass substrate 11, heat is easily transferred to the surface of the glass substrate 11 uniformly. Therefore, by processing the glass substrate 11 by the heat treatment step of the present embodiment, the production of the glass substrate 11 can be improved. Efficiency and reduce heat shrinkage.

Next, the evaluation and evaluation results of the heat-treated (offline annealing) glass substrate 11 of the first embodiment or the second embodiment will be described. In this case, the glass substrate 11 is a glass substrate for a liquid crystal display which is heat-treated at a heat treatment temperature in the range of 400 ° C to 600 ° C for 5 minutes to 30 minutes.

In the evaluation of the glass substrate 11 after the heat treatment, the heat treatment furnace was introduced and heat treatment was again performed. The temperature to be evaluated is (1) 500 ° C, that is, the first evaluation temperature, (2) the second evaluation temperature (450 ° C) lower than the first evaluation temperature by 50 ° C, and (3) the third higher than the first evaluation temperature by 50 ° C. The temperature was evaluated (550 ° C). The heat shrinkage rate after off-line annealing may be a case where a semiconductor layer composed of LTPS or IGZO which is not used for a high-definition display is formed on the glass substrate 11 as the case may be. In particular, it is important to suppress a glass substrate in the vicinity of a temperature range of 400 ° C to 600 ° C which is a temperature region at which the temperature at which the semiconductor layer of the glass substrate 11 of the high-definition display is formed (this temperature is referred to as a processing temperature) is substantially equal. 11 heat shrinkage rate. Therefore, the heat shrinkage ratio of the glass substrate 11 is evaluated in a temperature region equal to the temperature at which the semiconductor layer in the glass substrate 11 of the high-definition display is formed.

The evaluation heat treatment method for evaluating the glass substrate 11 is set so that the temperature in the heat treatment furnace becomes the first evaluation temperature, the second evaluation temperature, and the third evaluation temperature, and the glass substrate 11 is put into the evaluation. Temperature heat treatment furnace, heat treatment After heat treatment in the furnace for 30 minutes, it was taken out from the heat treatment furnace and naturally cooled. The heat shrinkage ratio of the glass substrate 11 at the time of the evaluation heat treatment by this method is made into the 1st heat-shrinkage rate C1, the 2nd heat-shrinkage rate C2, and the 3rd heat-shrinkage rate C3, respectively. At this time, the glass substrate 11 suitable for manufacturing a high-definition display is a glass substrate satisfying the following relational expression.

Relational formula: |C1-C2|/|C3-C1|<0.28

Here, C1 = the first heat shrinkage rate when the first evaluation temperature is maintained for 30 minutes, C2 = the second heat shrinkage rate when the second evaluation temperature is maintained for 30 minutes, and C3 = when the third evaluation temperature is maintained for 30 minutes. The third heat shrinkage rate.

FIG. 8 is a view showing an example of a result of heat shrinkage of the glass substrate 11 when the glass substrate 11 subjected to heat treatment in the first embodiment is heat-treated by the evaluation heat treatment method. In a glass substrate suitable for manufacturing a high-definition display, the heat shrinkage rate is small below the processing temperature of the high-definition display. Therefore, the heat shrinkage ratio (C1 to C3) in the temperature range from the first evaluation temperature to the third evaluation temperature is lower than the heat shrinkage ratio (C1 to C2) in the temperature range from the first evaluation temperature to the second evaluation temperature. A glass substrate suitable for manufacturing a high-definition display can be realized. In the heat treatment of the first embodiment, the glass substrate 11 is treated at a heat treatment temperature Tm3 (400 ° C to 600 ° C). Therefore, as shown in FIG. 8 , the temperature is lower than the heat treatment temperature from the first evaluation temperature to the second evaluation temperature. The heat shrinkage rate in the region is reduced to less than 15 ppm. However, the decrease in the heat shrinkage rate in the temperature region from the first evaluation temperature to the heat treatment temperature of the third evaluation temperature is small, and the heat shrinkage ratio close to the heat shrinkage ratio (for example, 80 ppm) before the heat treatment is obtained. The glass substrate 11 is extremely suitable for manufacturing a high-definition display because the heat shrinkage rate in the temperature region which affects the manufacture of the high-definition display becomes extremely low as compared with the temperature region which does not affect the manufacture of the high-definition display. Moreover, by suppressing the decrease in the heat shrinkage rate of the glass substrate 11 in the temperature region exceeding the heat treatment temperature, unevenness in heat shrinkage and strain in the glass substrate 11 can be suppressed.

(Experimental example of the first embodiment)

In order to confirm the effect of the first embodiment, it is overflowed by one type of the melting method. A glass substrate having the following glass composition was produced by pulling. The strain point of the glass substrate was 660 °C.

‧ glass composition

SiO ₂ 67.0 mol%, Al ₂ O ₃ 10.6 mol %, B ₂ O ₃ 11.0 mol %, RO 11.4 mol % (RO is the total amount of MgO, CaO, SrO and BaO).

‧annealing

The glass substrate is subjected to heat treatment (also referred to as annealing) by the method of the first embodiment. In the embodiment, the glass substrate is laminated, and the temperature rise rate and the temperature drop rate are slower than the temperature range of 300 ° C to room temperature in the temperature range of 300 ° C to the highest temperature of the heat treatment temperature of 500 ° C, and the temperature rise time and the temperature decrease time are made. The heat treatment is carried out in a manner of lengthening. In the comparative example, the laminated body of the glass substrate was formed, and the temperature increase rate and the temperature decrease rate were not changed according to the temperature region, and the temperature increase rate and the temperature decrease rate were fixed at a constant speed, respectively, and heat treatment was performed (previous example).

‧ Determination of heat shrinkage rate

Before the heat treatment, the glass substrate was cut into a rectangular shape of a specific size, and a mark line was drawn at both end portions of the long side, and cut into two halves at the center of the short side to obtain two glass samples. One of the glass samples was subjected to heat treatment (temperature up rate was 10 ° C / min, and left at 450 ° C for 1 hour). The length of another glass sample that was not heat treated was measured. Further, the heat-treated glass sample is placed next to the untreated glass sample, and the offset of the mark line is measured by a laser microscope to determine the difference between the lengths of the glass samples, thereby obtaining the heat shrinkage of the sample. the amount. Using the difference between the amount of heat shrinkage and the length of the glass sample before the heat treatment, the heat shrinkage ratio was determined by the following formula. The heat shrinkage rate of the glass sample was defined as the heat shrinkage ratio of the glass substrate.

Heat shrinkage rate (ppm) = (difference) / (length of glass sample before heat treatment) × 10 ⁶

The heat shrinkage rate of the glass substrate before annealing was examined and found to be 50 ppm.

The heat shrinkage rate of the glass substrate after the annealing was examined. As a result, in the examples, the heat shrinkage rate of the glass substrate at the end portion in the stacking direction was 2 ppm, and the heat shrinkage rate of the glass substrate at the center portion in the stacking direction was 3 ppm. On the other hand, in the prior art, the heat shrinkage rate of the glass substrate at the end portion in the stacking direction was 10 ppm, and the heat shrinkage rate of the glass substrate at the center portion in the stacking direction was 18 ppm.

Further, in the examples, the thermal history difference between the edge region and the central region of the glass substrate was reduced, the thermal contraction rate of the edge region was 2 ppm, and the thermal contraction rate of the central region was 3 ppm. On the other hand, in the previous example, the heat shrinkage rate in the edge region was 11 ppm, and the heat shrinkage ratio in the center region was 18 ppm.

In this manner, by changing the temperature increase rate and the temperature decrease rate in accordance with the temperature region, the heat distribution between the plurality of glass substrates is uniformly adjusted in the heat treatment step, whereby the unevenness of the heat shrinkage rate of the glass substrate after the heat treatment can be reduced. .

(Experimental example of the second embodiment)

In order to confirm the effect of the second embodiment, a glass substrate having a glass composition similar to that of the experimental example of the first embodiment was produced by an overflow down-draw method. The thickness of the glass substrate was 0.5 mm, and the strain point of the glass substrate was 660 °C.

‧annealing

The glass substrate is subjected to heat treatment by the method of heat treatment in the second embodiment. In the embodiment, a piece of the glass substrate is placed on the supporting member, and the temperature decreasing rate of the temperature range of the heat treatment temperature of 500 ° C to the first intermediate temperature is slower than the temperature range of the first intermediate temperature to the second intermediate temperature. The heat treatment is performed in the same manner. In the comparative example, a glass substrate was placed on the support member in the same manner as in the example, and the temperature range of the heat treatment temperature of 500 ° C to the first intermediate temperature was compared with the temperature range from the first intermediate temperature to the second intermediate temperature. The heat treatment is performed in such a manner that the cooling rate is increased.

The measurement of the heat shrinkage rate is the same as the measurement of the heat shrinkage ratio in the first embodiment. The method is carried out. The heat shrinkage rate of the glass sample before the heat treatment was 40 to 50 ppm.

The heat treatment temperature = 500 ° C, the first intermediate temperature = 400 ° C, the second intermediate temperature = 200 ° C, and the maintenance time = 10 minutes, and the temperature increase rate, the first temperature drop rate, and the second temperature drop rate were changed, and the glass sample was The heat shrinkage ratio is compared. The results are shown in Table 1.

As shown in the first and second embodiments of Table 1, the heat of the glass substrate can be reduced in the range where the first temperature drop rate is slower than the second temperature drop rate and the temperature increase rate is 20 ° C / min or more to less than 120 ° C / min. The shrinkage rate and the unevenness of the heat shrinkage rate are also small. Further, as shown in Examples 1 to 6, the first temperature drop rate is 0.5 ° C / min or more to less than 10 ° C / min, and the second temperature drop rate is 10 ° C / min or more to less than 25 ° C / min. The heat shrinkage rate of the glass substrate can be reduced to 15 ppm or less, and the unevenness of the heat shrinkage rate is also small. Further, by making the first temperature drop rate having a large influence on the heat shrinkage rate slower, the heat shrinkage rate can be further reduced. Further, as shown in Comparative Examples 1 to 3, when the first temperature drop rate and the second temperature drop rate were outside the speed range of the present embodiment, the heat shrinkage rate of the glass substrate was reduced, but it exceeded 15 ppm, so that it was found that Effective heat treatment.

Next, the heat shrinkage ratio of the glass samples when the maintenance time in the heat treatment of the second embodiment was set to 0 minutes, 2 minutes, 5 minutes, 30 minutes, 60 minutes, 120 minutes, and 150 minutes was compared. Further, heat treatment temperature = 500 ° C, first intermediate temperature = 400 ° C, second intermediate temperature = 200 ° C, temperature increase rate = 50 ° C / minute, and first temperature drop rate Degree = 3 ° C / min, and second cooling rate = 13 ° C / min. The results are shown in Table 2.

As shown in Examples 1 to 6 of Table 2, by setting the holding time, the heat shrinkage rate of the glass substrate was 10 ppm or less, and the unevenness of the heat shrinkage rate was also small. By setting the maintenance time to 5 to 150 minutes, the heat shrinkage rate can be reduced to 10 ppm or less. In particular, in Examples 3 to 5 in which the holding time was 20 to 120 minutes, an excellent effect of a heat shrinkage rate of 7 ± 1 ppm or less was exhibited.

Next, the heat shrinkage ratio of the glass sample when the heat treatment temperature in the heat treatment in the second embodiment was set to 350 ° C, 400 ° C, 500 ° C, 600 ° C, and 650 ° C was compared. Further, the maintenance time = 10 minutes, the first intermediate temperature = 400 ° C, the second intermediate temperature = 200 ° C, the temperature increase rate = 50 ° C, the first temperature drop rate = 3 ° C / minute, and the second temperature drop rate = 13 ° C /minute. The results are shown in Table 3.

As shown in Examples 1 to 3 of Table 3, when the heat treatment temperature is 400 ° C or more to 600 ° C or less, the heat shrinkage rate of the glass substrate can be made substantially 10 ppm or less, and the unevenness of the heat shrinkage rate is also small. On the other hand, as shown in Comparative Example 1, when the heat treatment temperature was 350 ° C, the heat shrinkage rate of the glass substrate exceeded 15 ppm, and thus it was found that it was not an effective heat. Reason. Further, as shown in Comparative Example 2, when the heat treatment temperature is 650 ° C, the heat shrinkage rate of the glass substrate can be 15 ppm or less, but it is considered that the heat treatment is not effective from the viewpoint of thermal efficiency.

As described above, by changing the temperature drop rate depending on the temperature region, the heat shrinkage rate of the glass substrate after the heat treatment can be reduced.

In the above, the method of manufacturing the glass substrate of the present invention is described in detail. The present invention is not limited to the above-described embodiments and examples, and various modifications and changes can be made without departing from the spirit and scope of the invention.

S1~S8‧‧‧Steps

Claims (10)

A method for producing a glass substrate, characterized in that it comprises a heat treatment step of a glass substrate, and the heat treatment step comprises the steps of: treating the entire glass substrate at a temperature lower than a strain point by a temperature of 60 ° C to 260 ° C, that is, a heat treatment temperature. Performing heat treatment; cooling the entire glass substrate from the heat treatment temperature to an intermediate temperature lower than the heat treatment temperature by 50 ° C to 300 ° C at a first speed; and after the heat treatment step, at a second speed faster than the first speed The entire glass substrate was cooled from the intermediate temperature to room temperature. A method for producing a glass substrate, characterized in that it comprises a heat treatment step of a glass substrate, and the heat treatment step comprises the steps of: heat treatment from room temperature until a temperature lower than a strain point by 60 ° C to 260 ° C, that is, heat treatment At a temperature, the entire glass substrate is heated from the room temperature to an intermediate temperature lower than the heat treatment temperature by 50 ° C to 300 ° C at a third speed; and the glass substrate is entirely from the fourth speed slower than the third speed. The intermediate temperature is heated to the heat treatment temperature; and the entire glass substrate is heat-treated at the heat treatment temperature. The method for producing a glass substrate according to claim 1, wherein the heat treatment step comprises the step of: heat-treating from room temperature until a temperature lower than a strain point of 60 ° C to 260 ° C, that is, a heat treatment temperature, at a third speed The whole substrate is heated from the room temperature to an intermediate temperature lower than the heat treatment temperature by 50 ° C to 300 ° C; and the glass substrate is entirely from the above at a fourth speed slower than the third speed. The intermediate temperature is heated to the heat treatment temperature; and the average speed of the first speed and the second speed is slower than the average speed of the third speed and the fourth speed. The method for producing a glass substrate according to any one of claims 1 to 3, wherein the glass substrate has a strain point of 655 ° C or higher. The method of producing a glass substrate according to any one of claims 1 to 4, wherein in the heat treatment step, the glass substrate is formed by laminating a plurality of sheets in a thickness direction in a state of being sandwiched between the sheet bodies. The laminate is heat treated. A method for producing a glass substrate, comprising: a heat treatment step of a single-layer glass substrate for a flat panel display, wherein the heat treatment step comprises: a heating maintaining step of heating the glass substrate to 400 ° C to 600 ° C a heat treatment temperature in the range of maintaining the heat treatment temperature; and a cooling step of cooling the glass substrate from the heat treatment temperature to the heat treatment at a first temperature drop rate of 0.5 ° C / min or more and less than 10 ° C / min After the temperature is lower than the intermediate temperature of 50 ° C to 150 ° C, the glass substrate is cooled at a second temperature drop rate of from 10 ° C / min to less than 25 ° C / min. A method of producing a glass substrate according to claim 6, wherein a semiconductor layer made of IGZO is formed on the glass substrate. The method for producing a glass substrate according to claim 6 or 7, wherein in the cooling step, the glass substrate is cooled at the second temperature drop rate, and then the glass substrate is further cooled to room temperature at the first temperature drop rate. The method for producing a glass substrate according to any one of claims 6 to 8, wherein in the heat treatment step, before the heating step is performed by placing the glass substrate horizontally in a furnace, heating is performed until the ambient temperature in the furnace It becomes the above heat treatment temperature. A glass substrate which is a glass substrate for liquid crystal display which is heat-treated at a heat treatment temperature in the range of 400 ° C to 600 ° C for 5 minutes to 30 minutes, and has a temperature of 500 ° C as the first evaluation temperature. 450 ° C as the second evaluation temperature, 550 ° C as the third evaluation temperature, and the glass substrate is maintained at each evaluation temperature for 30 minutes, and the heat shrinkage rate when the heat treatment is performed again is the first heat shrinkage ratio C1, the second The heat shrinkage ratio C2 and the third heat shrinkage ratio C3 satisfy the relationship of |C1-C2|/|C3-C1|<0.28 in this case.