TW201708136A - Method of heat treating glass substrate and method of manufacturing thereof characterized in that the glass substrate arranged in a transverse posture is heated at a temperature equal to or lower than the strain point - Google Patents

Abstract

Disclosed herein is a heat treatment method for reducing the heat shrinkage rate of a glass substrate 1 having a thickness of 300 micrometers or less, characterized in that the glass substrate 1 which is arranged in a transverse posture is heated at a temperature equal to or lower than the strain point under the condition that the central portion 1a of the glass substrate is located at a position higher than the peripheral portion 1b of the glass substrate. Preferably, the glass substrate before the heat treatment has a warp portion having a warpage amount of 300 micrometers or less, and the central portion of the glass substrate is located at a position within a range of 10 micrometers and 1000 micrometers higher than the peripheral portion of the glass substrate.

Description

Heat treatment method for glass substrate and method for producing glass substrate

The present invention relates to a heat treatment method for a glass substrate, and more particularly to a heat treatment method for reducing the heat shrinkage rate of a glass substrate having a small wall thickness.

As we all know, in recent years, mobile terminals such as smart phones and tablet-type terminals have rapidly spread, and the competition for technology development such as thinning, lightweight, and high-performance mobile terminals is fierce. The degree is increasing. In this case, a glass substrate which is a component of a flat panel display (hereinafter referred to as "FPD") such as a liquid crystal display or an organic electroluminescence (EL) display mounted on a mobile terminal device is used. It is indispensable that the wall thickness is small, the heat shrinkage rate is low (excellent in thermal dimensional stability), and the shape accuracy (especially flatness) is excellent.

In other words, in the manufacturing process of the FPD, a film formation process of a film-like circuit (circuit pattern) is usually performed on the surface of the glass substrate. However, in the film formation process, the glass substrate to be processed is exposed to a high temperature. Therefore, when the heat shrinkage rate of the glass substrate is large or the flatness is low, a circuit pattern of a predetermined accuracy cannot be formed on the surface of the glass substrate because the possibility of ensuring desired electrical characteristics is high.

Further, the glass substrate is being studied for use in a flexible device having excellent shape freedom or a wearable device used in a worn state. The glass substrate for such a component is required to be thinner than the glass substrate for FPD.

In addition, the glass substrate can be obtained, for example, by cutting a strip-shaped glass ribbon obtained by a down-draw method represented by an overflow downdraw method into a predetermined size, in the down-draw method. The faster the forming speed (plate stretching speed), the thinner the thickness of the glass ribbon. However, the faster the sheet stretching speed is, the shorter the cooling time becomes, and thus it is difficult to lower the heat shrinkage rate of the glass substrate. Further, as the sheet stretching speed is increased, the time for adjusting the shape of the sheet is also shortened, so that it is difficult to process the glass ribbon to a predetermined shape accuracy.

Therefore, for example, as described in Patent Document 1 below, heat treatment may be applied to the glass substrate for the purpose of improving the thermal dimensional stability or flatness of the glass substrate. In Patent Document 1, heat treatment is performed in a state where a glass substrate to be heat-treated is placed on a flat support substrate (heat-resistant glass ceramic plate). Furthermore, the heat treatment is also referred to as an annealing treatment. [Prior Art Document] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 5-330835

[Problems to be Solved by the Invention] As a result of the examination by the inventors of the present invention, it has been found that a glass substrate having a small thickness is used in the aspect disclosed in Patent Document 1 (specifically, a glass having a thickness of 300 μm or less) In the case where the heat treatment is applied to the substrate, particularly in a predetermined region (peripheral portion) including the end surface thereof, the glass substrate is likely to be highly lifted, and it is often impossible to ensure desired flatness.

In view of the above, an object of the present invention is to provide a heat treatment for reducing a heat shrinkage rate on a glass substrate having a thickness of 300 μm or less, thereby preventing the flatness of the glass substrate from being lowered as much as possible, thereby stabilizing A glass substrate having a low heat shrinkage rate and excellent flatness. [Means for solving the problem]

The present invention, which has been made to achieve the above object, is a heat treatment method for reducing the heat shrinkage rate of a glass substrate having a thickness of 300 μm or less, and is characterized in that the glass substrate disposed in a lateral position is subjected to The central portion is heated at a temperature lower than the strain point in a state where it is located higher than the peripheral portion. In the present invention, the term "lateral posture" has the same meaning as the flat posture, and the "peripheral portion" refers to a predetermined region including the end surface of the glass substrate.

As described above, when a glass substrate having a thickness of 300 μm or less is placed in a lateral position and the central portion of the glass substrate is placed at a position higher than the peripheral portion thereof (heat treatment is applied), In the heat treatment, the peripheral portion of the glass substrate is lifted, whereby the difference in height between the center portion and the peripheral portion is reduced, and a glass substrate having excellent flatness can be obtained after the heat treatment. Further, when the glass substrate is heated at a temperature higher than the strain point of the glass substrate, the strain existing in the substrate is released, and at the same time, a slight shape change is likely to occur, but the strain of the glass substrate is not more than the strain point. When the glass substrate is heated at a temperature, the amount of change in shape accompanying the release of strain can be reduced while reducing the heat shrinkage rate of the glass substrate. According to the above, a glass substrate having a small thickness and a low heat shrinkage ratio and excellent flatness can be obtained.

In the above configuration, the glass substrate before the heat treatment can be a warped portion having a warpage amount of 300 μm or less.

In other words, in the present invention, a glass substrate having a warpage portion having a warpage amount of 300 μm or less can be preferably used in terms of improving flatness. In addition, the "warpage amount" here is a value measured by the non-contact glass substrate warpage measuring machine which is widely used commercially. In addition, the term "warping portion" as used herein refers to a portion that is deformed in the thickness direction of the glass substrate, and does not necessarily exist in the peripheral portion of the glass substrate, and may be present in the central portion of the glass substrate or the like.

The central portion of the glass substrate to be subjected to the heat treatment in the above-described manner is preferably located at a position higher than the peripheral portion of the glass substrate in a range of 10 μm or more and 1000 μm or less.

In this manner, the flatness of each of the glass substrates can be improved with heat treatment, and variations in flatness between the glass substrates after the heat treatment can be avoided as much as possible.

As a specific means for positioning the central portion of the glass substrate at a higher position than the peripheral portion, for example, it is conceivable to support the glass substrate from the lower side by a support member having a glass supporting surface formed in a convex curved shape.

It is also possible to make the glass support surface formed into a convex curved shape smaller than the glass substrate (which should be supported). In this manner, at least a part of the peripheral portion of the glass substrate extends beyond the outer side of the glass supporting surface. Therefore, if the glass substrate is gradually pulled up while holding the protruding portion of the glass substrate, the glass substrate can be separated from the supporting member. Therefore, the heat treatment step can be performed efficiently.

Further, in order to position the central portion of the glass substrate at a higher position than the peripheral portion, it may be supported from the lower side by a support member having a flat surface and a glass supporting surface smaller than the glass substrate.

In this case, as compared with the case where the glass substrate is supported by the glass supporting surface formed into a convex curved surface, the possibility that the glass substrate slides with respect to the glass supporting surface during the heat treatment can be reduced as much as possible, so that it is lowered. It is advantageous in that the lower surface of the glass substrate (the surface in contact with the glass supporting surface) is likely to cause minute defects.

Since the heat treatment method of the glass substrate of the present invention has the above-described advantages, it can be preferably applied to a glass substrate, particularly when a heat treatment is applied to a glass substrate for a flexible member or a body member having a small thickness.

The glass substrate is formed by cutting a glass film having a thickness of 300 μm or less, thereby obtaining a glass substrate having a thickness of 300 μm or less; and applying heat treatment to the glass substrate In the method of producing a glass substrate in the heat treatment step, the glass substrate having the low heat shrinkage ratio and excellent flatness can be stably mass-produced by applying the heat treatment method of the glass substrate of the present invention in the heat treatment step. [Effects of the Invention]

As described above, according to the present invention, as the heat treatment for reducing the heat shrinkage rate is applied to the glass substrate having a thickness of 300 μm or less, the flatness of the glass substrate can be prevented from being lowered as much as possible. Thereby, it is possible to stably mass-produce a glass substrate having a low heat shrinkage rate and excellent flatness.

Hereinafter, embodiments of the present invention will be described based on the drawings. Furthermore, the present invention relates to a specific method for heat-treating a glass substrate (in detail, a glass substrate having a thickness of 300 μm or less) obtained by a glass substrate production step by a subsequent heat treatment step. In the glass substrate production step, for example, a strip-shaped glass film formed by a known method such as an overflow down-draw method is cut into a predetermined size to obtain a glass substrate. Therefore, the detailed description regarding the glass substrate fabrication step will be omitted, and the heat treatment step will be described in detail below.

In the heat treatment step, the heat treatment for lowering the heat shrinkage rate of the glass substrate 1 is performed while adjusting the shape of the glass substrate 1 obtained by the glass substrate production step (flattening the glass substrate 1). In the heat treatment step, as shown in FIG. 1B, the glass substrate 1 to be heat-treated is introduced into the heat treatment apparatus in a state of being placed on the support member 2, that is, in a state where the support member 2 is supported from the lower side. (heat treatment furnace) to perform heating. Further, a cleaning step of cleaning the glass substrate 1 may be provided between the glass substrate forming step and the heat treatment step. When such a cleaning step is provided in advance, it is possible to prevent foreign matter adhering to the surface of the glass substrate 1 from being attached to the surface of the glass substrate 1 in association with heat treatment.

Hereinafter, the glass substrate 1 to be heat-treated and the support member 2 and the heat treatment apparatus 10 used in the heat treatment step will be described in detail.

[Glass substrate] As shown in FIG. 1A, the glass substrate 1 has a rectangular shape in plan view, and its size is preferably 300 mm square or more, more preferably 400 mm square or more, and further preferably 500 mm square or more, and most preferably 600. Mm see above.

The thickness of the glass substrate 1 is 300 μm or less, preferably 200 μm or less, more preferably 150 μm or less, and most preferably 100 μm or less. The smaller the thickness of the glass substrate 1 is, the greater the contribution to the thinning or weight reduction of a product (for example, FPD) in which the glass substrate 1 is a component, and the flexibility can be imparted. However, if the thickness of the glass substrate 1 is too small, the strength required for the glass substrate 1 as a minimum cannot be ensured. Therefore, the thickness of the glass substrate 1 is preferably set to 5 μm or more.

The strain point of the glass substrate 1 is 600 ° C or higher, preferably 650 ° C or higher, more preferably 680 ° C or higher, and most preferably 700 ° C or higher. Further, the strain point referred to herein is a value measured by a method defined in American Society for Testing and Materials (ASTM) C336.

The glass substrate 1 having the above-described dimensions, thickness, and strain point can be formed, for example, by using bismuth silicate glass, cerium oxide glass, borosilicate glass, soda glass, alkali-free glass, or the like. In the present embodiment, the glass substrate 1 formed by the alkali-free glass which is most difficult to cause deterioration over the years is used. Here, the alkali-free glass means a glass which does not substantially contain an alkali component (alkali metal oxide), and specifically refers to a glass having an alkali component content of 3,000 ppm or less. The alkali-based glass is preferably used in an amount of 1000 ppm or less, more preferably 500 ppm or less, and most preferably 300 ppm or less.

Though the detailed illustration is omitted, the glass substrate 1 (the glass substrate 1 before heat treatment) which is a heat processing target has a warpage part, for example. The warpage amount of the warpage portion is preferably 300 μm or less, more preferably 200 μm or less, further preferably 150 μm or less, and most preferably 100 μm or less.

[Support member] As shown in FIG. 1A and FIG. 1B, the support member 2 is a glass substrate 1 to be heat-treated, which is disposed in a lateral position from the lower side (contact support), and the support member 2 of the present embodiment includes: The support portion 4 having the surface of the glass support surface 3 and the base portion 5 provided on the lower side of the support portion 4 and larger than the support portion 4 are provided. In the present embodiment, the glass support surface 3 is formed into a convex curved surface (convex spherical surface) that gradually transitions from the peripheral edge portion toward the central portion to a higher position, and is formed to have the same size as the glass substrate 1 to be supported. . Therefore, when the glass substrate 1 is placed on the glass supporting surface 3, the end surface 1c of the glass substrate 1 is not substantially in contact with the base portion 5. The glass supporting surface 3 is such that the central portion 1a of the glass substrate 1 is located at 10 μm to 1000 μm, preferably 20 μm to 1000 μm, more preferably 30 μm to 1000 μm, and most preferably 50 μm to 1000 μm. It is formed in a range higher than the peripheral portion 1b. Further, in FIG. 1B, the height difference between the central portion (top portion) and the peripheral portion of the glass supporting surface 3 is exaggerated for easy understanding.

The support member 2 of the present embodiment is formed by processing one plate-shaped member. In this case, if the difference in linear expansion coefficient between the glass substrate 1 and the support member 2 is large, the amount of deformation of the glass substrate 1 and the support member 2 during heat treatment is poor, and the glass substrate 1 is opposed to the support member 2 (glass support) The surface 3) is relatively movable, and there is a high possibility that minute defects such as scratches are generated on the lower surface of the glass substrate 1. Therefore, the support member 2 is preferably made of a material having a linear expansion coefficient equivalent to that of the glass substrate 1 (specifically, the difference in linear expansion coefficient from the glass substrate 1 at 30 ° C to 380 ° C is 5 × 10 ^-7 / ° C It is formed by the material inside, and it is especially preferable to use the glass which has the same composition as the glass substrate 1. Therefore, in the present embodiment, the support member 2 is formed by a plate-like member made of an alkali-free glass.

Further, the support member 2 may be formed using other glass materials such as bismuth silicate glass, ceria glass, or borosilicate glass. Of course, the support member 2 can also be formed using a heat-resistant material other than glass, such as ceramic or metal.

The thickness (maximum thickness) of the support member 2 is set in the range of 0.5 mm to 3.0 mm, and is preferably 0.5 mm to 2.5 mm, more preferably 0.5 mm to 2.0 mm, and still more preferably 0.7 mm to 2.0. Mm, preferably in the range of 1.0 mm to 2.0 mm. The reason for this is that, in the case where the thickness of the support member 2 is less than 0.5 mm, the possibility that the support member 2 is thermally deformed or the like is high; and in the case where the thickness of the support member 2 is more than 3.0 mm, the heat capacity of the support member 2 is changed. Large, resulting in large energy losses during heat treatment. Therefore, when the thickness of the support member 2 is set to the above range, the heat treatment of the glass substrate 1 can be performed with high precision and efficiency.

Although not shown in the drawings, the glass support surface 3 of the support member 2 may be configured by an inorganic film. In this case, when the glass substrate 1 is heated to a high temperature accompanying the heat treatment, the adhesion of the glass substrate 1 to the support member 2 can be avoided. Thereby, since the glass substrate 1 and the support member 2 can be easily separated after the heat treatment, the possibility that the glass substrate 1 is damaged or the like can be reduced as much as possible in association with the support member 2. Further, the inorganic film can be formed by a known method such as a sputtering method, a vacuum deposition method, a chemical vapor deposition (CVD) method, or a sol-gel method.

The inorganic film can be selected, for example, from indium tin oxide (ITO), Ti, Si, Au, Ag, Al, Cr, Cu, Mg, SiO ₂ , Al ₂ O ₃ , MgO, Y ₂ O ₃ , La ₂ O ₃ , Pr ₆ O ₁₁ , Sc ₂ O ₃ , WO ₃ , HfO ₂ , In ₂ O ₃ , ZrO ₂ , Nd ₂ O ₃ , Ta ₂ O ₅ , CeO ₂ , Nb ₂ O ₅ , TiO, TiO ₂ , one of Ti ₃ O ₅ , NiO, ZnO, SiN, AlN, or a combination of two or more layers. Among them, it is preferred to form an inorganic film by using an oxide such as ITO. The reason for this is that the oxide film is excellent in thermal stability and can be reused.

The surface roughness Ra of the inorganic film (the calculated average roughness Ra specified in Japanese Industrial Standards (JIS) B0601) is preferably 100 nm or less, more preferably 80 nm or less, and still more preferably 50 nm or less. The best is below 10 nm. The reason for this is that if the surface roughness Ra is larger than 100 nm, it is easy to interpose an air layer between the glass substrate 1 and the glass support surface 3, and during the heat treatment, the glass substrate 1 is easily slid relative to the glass support surface 3 ( The support state of the glass substrate 1 is easily destabilized).

However, when the surface roughness Ra of the inorganic film is too small, the adhesion of the glass substrate 1 to the inorganic film during the heat treatment is too high, and it is difficult to separate the glass substrate 1 from the support member 2 after the heat treatment. Therefore, the surface roughness Ra of the inorganic film is preferably 1.0 nm or more, more preferably 2.0 nm or more, and still more preferably 3.0 nm or more. Further, the surface roughness Ra of the inorganic film can be measured using a stylus type surface roughness meter or an atomic force microscope (AFM).

When the formation cost or strength of the inorganic film is considered, the thickness of the inorganic film is preferably 500 nm or less, more preferably 400 nm or less, and most preferably 300 nm or less. However, if the thickness of the inorganic film is too small, the effect of improving the separation property of the glass substrate 1 with respect to the support member 2 after heat treatment cannot be effectively obtained. Therefore, the thickness of the inorganic film is preferably set to 5 nm or more.

[Heat Treatment Apparatus] As shown in FIG. 2, the heat treatment apparatus 10 includes a glass chamber 11, a lifting table 13 that moves up and down with respect to the glass chamber 11 in a state in which the glass frame 12 is placed, and a furnace wall 14 that houses the glass chamber 11. And a heater 15 that heats the glass chamber 11 from the outside. The heat treatment apparatus 10 is disposed in a clean room. Briefly, the heat treatment step is performed in a clean room.

The glass chamber 11 has a lid-shaped cylindrical shape with a lower end open, and has a heat treatment space S inside. The glass chamber 11 is formed into a cylindrical shape by integrally molding quartz glass, and is formed by a continuous surface having no joints to form a heat treatment space S.

The glass frame 12 has a plurality of accommodating portions 16 that are provided in a plurality of stages in the vertical direction. Each of the accommodating portions 16 is formed by at least a pair of column portions 12a, column portions 12a, and column portions 12a that are erected on the lifting table 13. The shelf 12b to which the column portion 12a is detachably attached is formed. Both the column portion 12a and the shelf 12b are formed of quartz glass. In the present embodiment, a lattice-shaped frame is used as the shelf 12b, and a plurality of pin-shaped projections are provided on the upper surface of the shelf 12b. Further, the support member 2 (hereinafter also referred to as "assembly") of the glass substrate 1 supporting the lateral posture from the lower side is supported by the lower side from the pin-like projection.

The lifting table 13 has a mounting portion 13a made of quartz glass on which the glass frame 12 is placed. When the placing portion 13a is at the raised position, the lower end opening portion of the glass chamber 11 is blocked, and the glass frame 12 is disposed in the heat treatment space. S inside. On the other hand, when the placing portion 13a is lowered to the lowering position outside the drawing, the loading and unloading of the components is performed on (the respective housing portions 16) of the glass holder 12 placed on the placing portion 13a.

The furnace wall 14 has a lid-shaped tubular shape with a lower end open, and the whole is made of a refractory. A heater 15 is attached to each of the side inner wall surface and the upper inner wall surface (top surface) of the furnace wall 14. As the heater 15, for example, a metal-based heating element represented by a nichrome-based heating element is used.

Although not shown in the drawings, a cooling unit (for example, a blower) that cools the glass chamber 11 from the outside may be separately provided in the heat treatment apparatus 10. By providing such a cooling unit in advance, the environment of the heat treatment space S heated by the heater 15 can be efficiently cooled.

Next, a heat treatment step performed by the heat treatment apparatus 10 having the above configuration will be described. In the heat treatment step, a temperature step, a heat retention step, and a temperature reduction step are sequentially performed.

Before the temperature raising step is performed, the placing portion 13a of the lifting platform 13 is placed at the lowered position, and the assembly is placed on each of the housing portions 16 of the glass holder 12, and then the lifting table 13 is moved upward to arrange the glass frame 12 in the glass chamber 11 Heat treatment space S inside. Further, the loading of the components with respect to the respective housing portions 16 (and the unloading of the components after heat treatment from the respective housing portions 16) is performed, for example, using a robot fork that supports the assembly from the lower side. At this time, the lower portion of the support member 2 is constituted by the base portion 5 having a large area, whereby the support area of the mechanical fork arm to the support member 2 is sufficiently ensured. Therefore, the loading and unloading of the components with respect to the respective housing portions 16 can be performed with high precision.

The temperature rising step is a step of raising the temperature of the glass substrate 1 to a predetermined temperature. Here, the temperature rise rate of the glass substrate 1 is 3° C./min or more, preferably 5° C./min or more, and more preferably 7° C./min or more. The output of the heater 15 is adjusted in such a manner as to increase the temperature. However, when the temperature rise rate of the glass substrate 1 is too fast, there is a high possibility that the glass substrate 1 is damaged or the like. Therefore, the temperature increase rate is preferably 30° C./min or less, more preferably 20° C./min or less.

In the heating step, the glass chamber 11 (the heat treatment space S in the inside) is heated from the outside until the temperature of the glass substrate 1 becomes the temperature equal to or lower than the strain point of the glass substrate 1. Specifically, when the strain point of the glass substrate 1 is T [unit: ° C], the temperature at which the glass chamber 11 is heated to the glass substrate 1 is preferably (T-30 ° C) or less, more preferably ( T-50 ° C) or less, more preferably (T-80 ° C) or less, and most preferably (T-100 ° C) or less. Thereby, the heat shrinkage rate of the glass substrate 1 can be reduced while preventing the undesired shape change of the glass substrate 1 as much as possible. However, if the glass substrate 1 is not sufficiently heated, the heat shrinkage rate of the glass substrate 1 cannot be appropriately lowered. Therefore, the glass chamber 11 is heated until the temperature of the glass substrate 1 becomes (T-200 ° C) or more.

In the heat retention step, the glass substrate 1 heated to a predetermined temperature is maintained for a predetermined period of time (specifically, 5 minutes to 120 minutes) while maintaining the predetermined temperature. Thereby, it is possible to appropriately reduce the heat shrinkage ratio of each of the glass substrates 1 while reducing the possibility of variation in shape between the glass substrates 1 as much as possible.

In the temperature lowering step, the temperature of the glass substrate 1 is gradually lowered. The cooling rate is preferably 1 ° C / min or more, more preferably 2 ° C / min or more, and still more preferably 5 ° C / min or more. Thereby, the productivity of the glass substrate 1 can be improved while shortening the processing time of the temperature decreasing step. However, if the temperature drop rate is too fast, the heat shrinkage rate of the glass substrate 1 cannot be sufficiently lowered, and the glass substrate 1 is warped or the like, and the shape accuracy of the glass substrate 1 is likely to be lowered. Therefore, the temperature drop rate is preferably 20 ° C / min or less, and more preferably 15 ° C / min or less.

In the heat treatment step, in particular, in the temperature lowering step, temperature distribution is likely to occur in the surface of the glass substrate 1 due to a difference in temperature drop rate in each portion of the glass substrate 1, and accordingly, the peripheral portion 1b of the glass substrate 1 is lifted up. The tendency (see Figure 3). In the present invention, in the glass substrate 1 disposed in the lateral position, the central portion 1a is placed in a higher position than the peripheral portion 1b, and heat treatment is applied to the glass substrate 1. Therefore, the peripheral portion 1b of the glass substrate 1 is accompanied by heat treatment. When the shape is lifted up, the height difference between the center portion 1a and the peripheral portion 1b can be reduced, and the glass substrate 1 having excellent flatness can be obtained after the heat treatment.

Though the heat treatment method of the glass substrate 1 of the embodiment of the present invention has been described above, the embodiment of the present invention is not limited thereto, and various modifications can be made without departing from the scope of the invention. In particular, various modifications can be made to the aspect in which the support member 2 at the time of heat treatment supports the glass substrate 1.

For example, in the embodiment described above, the glass substrate 1 is supported from the lower side by the support member 2 having the glass support surface 3 having the same size as the glass substrate 1 to be heat-treated, but the glass support surface 3 is also As shown in FIG. 4, the glass substrate 1 which is a heat processing target is larger, and as shown in FIG. 5, it is smaller than the glass substrate 1 which is a heat processing target.

In particular, as shown in FIG. 5 (the same as FIG. 6 and FIG. 7 described later), the glass substrate 1 is supported by the support member 2 having the glass support surface 3 smaller than the glass substrate 1 from the lower side. The peripheral portion 1b protrudes to the outside of the glass supporting surface 3, and forms a projecting portion P that does not come into contact with the glass supporting surface 3. The projecting portion P can be effectively used as a handle portion when the glass substrate 1 is separated from the support member 2 after the heat treatment, so that the glass substrate 1 can be easily separated from the support member 2. Therefore, the setting of the glass substrate 1 as the heat treatment target relative to the support member 2 (the fabrication of the assembly), the loading of the assembly with respect to the heat treatment apparatus 10, the heat treatment, the unloading of the assembly from the heat treatment apparatus 10, and the glass substrate 1 can be reduced. The support member 2 separates the cycle time required for this series of heat treatment processes, thereby performing the heat treatment step efficiently.

In addition, although the glass substrate 1 is supported from the lower side by the support member 2 which has the glass support surface 3 formed in the convex curved surface (convex spherical surface), it can also be formed by the use as shown in FIG. The support member 2 which is the flat glass support surface 3 supports the glass substrate 1 from the lower side. In this case, the glass support surface 3 is made larger than the glass substrate 1 so that the central portion 1a of the glass substrate 1 is located higher than the peripheral edge portion 1b (in other words, the peripheral portion 1b of the glass substrate 1 is suspended downward). small. As described above, when the glass substrate 1 is supported by the glass supporting surface 3 formed as a flat surface, the glass can be effectively reduced in the process of heat treatment as compared with the case where the glass substrate 1 is supported by the glass supporting surface 3 formed in a convex curved shape. The substrate 1 slides with respect to the glass support surface 3, and as a result, there is a possibility that minute defects such as scratches are generated on the lower surface of the glass substrate 1.

Further, as shown in FIGS. 5 to 7 , when the peripheral edge portion 1 b of the glass substrate 1 is extended to the outside of the glass supporting surface 3 to support the glass substrate 1 , it is preferable to heat the glass substrate 1 during the heat treatment. The end surface 1c determines the amount of protrusion of the glass substrate 1 so as not to come into contact with other members (the shelf 12b of the glass holder 12, the base portion 5 of the support member 2, and the like). The reason for this is that when the end surface 1c of the glass substrate 1 is in contact with another member, breakage or the like starting from the end surface 1c is likely to occur.

In the embodiment described above, in particular, in the embodiment shown in FIGS. 1 and 7, the support portion 4 and the base portion 5 constituting the support member 2 are integrally formed, and may be individually used by appropriate means. The formed support portion 4 is joined to the base portion 5 to be integrated to form the support member 2. In this case, the support portion 4 and the base portion 5 may be formed of the same type of material, or may be formed of materials different from each other, and the support portion 4 having the glass support surface 3 preferably has the same function as the glass substrate 1. The material of the coefficient of linear expansion (specifically, a material having a difference in linear expansion coefficient from the glass substrate 1 of 5 × 10 ^-7 /° C. at 30 ° C to 380 ° C) is particularly preferably used with a glass substrate. A glass of the same composition is formed.

Further, the heat treatment method of the glass substrate 1 of the present invention is a heat treatment apparatus other than the heat treatment apparatus 10 shown in FIG. 3, for example, a roller conveyor, a belt conveyor, or a moving beam (walking) An on-line type heat treatment device such as a beam) and a heat treatment device such as a batch type, a continuous transfer type, or a sheet-by-chip method can also be preferably used when heat treatment is applied to the glass substrate 1. Further, when a heat treatment is applied to the glass substrate 1 by using an in-line heat treatment apparatus using a roller conveyor in the transport mechanism, as shown in FIG. 1 or FIG. 7, it is preferable to use a base portion having a larger glass support surface 3. The support member 2 of 5 supports the glass substrate 1 as a heat processing target from the lower side. The reason for this is that the arrangement pitch of the rollers constituting the roller conveyor can be increased (the number of the rollers is reduced), so that it is easy to enjoy the advantage that the cost of the heat treatment device can be reduced, and the height level between the rollers can be easily performed. The adjustment can prevent the flaw of the glass substrate 1 (component) at the time of conveyance as much as possible.

Further, the heat treatment method of the glass substrate 1 of the present invention can also be preferably applied to a heat treatment of the glass substrate 1 which is to be pulled down by a method other than the overflow down-draw method, for example, a flow hole ( The glass film obtained by the slot down draw method, the roll out method, the float method, the updraw method, the redraw method, or the like is cut into a predetermined size. [Examples]

In order to confirm the usefulness of the present invention, in the case where heat treatment is applied to the glass substrate by applying the method of the present invention (specifically, heat treatment is applied to the glass substrate supported by the aspect shown in FIG. 7 of the present application, In the case where heat treatment is applied to the glass substrate by the method disclosed in Patent Document 1 (hereinafter also referred to as "Comparative Example"), the amount of warpage of the glass substrate is confirmed. The degree of change has changed.

In the case of carrying out the confirmation test, each of the examples and the comparative examples was prepared by assembling seven support members each including a glass substrate and supporting the substrate from the lower side, and applying heat treatment using the heat treatment apparatus 10 schematically shown in FIG. . The heat treatment conditions were such that the glass substrate at room temperature was heated to 560 ° C at a temperature increase rate of 10 ° C / min, and then held at 560 ° C for 60 minutes, and then the glass substrate was cooled to room temperature at a temperature drop rate of 3 ° C / min. .

A rectangular glass substrate of 320 mm × 400 nm having a thickness of 100 μm is prepared as a glass substrate to be subjected to a heat treatment target (measurement target) used in the confirmation test (specifically, an alkali-free glass substrate OA manufactured by Nippon Electric Glass Co., Ltd.) -10G). The main physical properties of the glass substrate were linear expansion coefficients at 30 ° C to 380 ° C: 38 × 10 ^-7 / ° C, strain points: 650 ° C, and cold spots: 710 ° C.

The support member of the example was prepared by using an alkali-free glass substrate (OA-10G) similar to the glass substrate to be measured. Specifically, it is prepared to fix a rectangular-shaped glass substrate of 300 mm × 380 mm having a thickness of 1.5 mm on the upper surface of a 740 mm × 940 mm rectangular-shaped glass substrate having a thickness of 0.5 mm, thereby being able to be used as a measurement target. A support member having a convex shape having a convex shape supported from the lower side in a state where the central portion of the glass substrate is located higher than the peripheral portion. Further, as the rectangular glass substrate disposed on the upper side, an inorganic film (ITO film) having a thickness of 180 nm was formed on the upper surface (glass supporting surface) by sputtering.

On the other hand, as a support member of a comparative example, a rectangular-shaped glass substrate (specifically, a 740 mm × 940 mm glass substrate (OA-10G) having a thickness of 0.5 mm) was prepared, in which the glass support surface was flat, and The glass support surface has a larger area than the glass substrate to be measured, and an ITO film having a thickness of 180 nm is formed on the glass support surface by a sputtering method. Therefore, the glass substrate of the comparative example is subjected to heat treatment in a state where there is no height difference between the central portion and the peripheral portion.

The test results of the confirmation test are shown in Table 1 below. In Table 1, the glass substrate of the example and the glass substrate of the comparative example are shown as sample No. 1-No. 7 and sample No. 8-No. 14, respectively.

[Table 1]

As is also clear from Table 1, in the examples, the values of the amount of warpage after heat treatment of all the samples were as small as 100 μm or less, and the average value of the amount of warpage was greatly lowered. In addition, the standard deviation of the amount of warpage is also greatly reduced. On the other hand, in the comparative example, the amount of warpage of all the samples increased after heat treatment, and the standard deviation of the amount of warpage also increased. Therefore, the heat treatment method of the present invention is useful for improving the flatness of each glass substrate and further suppressing variations in flatness between the glass substrates.

In addition to the above-described confirmation test, the degree of thermal shrinkage of the glass substrate, that is, the heat shrinkage ratio of the glass substrate, was evaluated in accordance with the heat treatment. The heat shrinkage rate of the glass substrate was measured by the order shown by the following (1)-(5). (1) As shown in Fig. 8A, a long strip sample G of 160 mm × 30 mm was prepared as a sample of a glass substrate. (2) The water-resistant abrasive paper having a particle size of 1000 is formed to extend in the short-side direction at a position shifted from the both end portions in the longitudinal direction of the long-length sample G to the center portion in the longitudinal direction by about 20 mm to 40 mm. Mark M, mark M. (3) As shown in Fig. 8B, the long sample G on which the mark M is formed is divided into two in the longitudinal direction, and the sample piece Ga and the sample piece Gb are produced. (4) Only one of the two sample pieces Ga and the sample piece Gb (here, the sample piece Gb) is heat-treated by the heat treatment apparatus. The heat treatment was carried out by raising the temperature from normal temperature to 500 ° C at a temperature increase rate of 5 ° C / min → holding at 500 ° C for 1 hour → cooling to room temperature at a temperature drop rate of 5 ° C / min. (5) After heat treatment is applied to the sample piece Gb in the above-described manner, as shown in FIG. 8C, the sample piece Ga to which the heat treatment is not applied is placed in parallel with the sample piece Gb to which the heat treatment is applied, and the laser microscope is used. The positional shift amount ΔL ₁ and the positional shift amount ΔL ₂ of the mark M between the two sample pieces Ga and the sample piece Gb are read, and the heat shrinkage rate [unit: ppm] is calculated based on the following formula. Further, L ₀ in the following formula is a distance between the mark M and the mark M before the heat treatment. Heat shrinkage rate = [{ΔL ₁ (μm) + ΔL ₂ (μm)} × 10 ³ ] / L ₀ (mm)

The heat shrinkage rate of the glass substrate measured and measured in the above-described order was 10 ppm or less and became a very small value.

As described above, the present invention is useful in reducing the heat shrinkage rate of a glass substrate having a thickness of 300 μm or less while improving the flatness of the glass substrate.

1‧‧‧ glass substrate
1a‧‧‧Central Department
1b‧‧‧The Peripheral Department
1c‧‧‧ end face
2‧‧‧Support members
3‧‧‧glass support surface
4‧‧‧Support
5‧‧‧ base
10‧‧‧ Heat treatment unit
11‧‧‧ glass chamber
12‧‧‧glass shelf
12a‧‧‧ pillar
12b‧‧‧Shelf
13‧‧‧ Lifting table
13a‧‧‧Loading Department
14‧‧‧ furnace wall
15‧‧‧heater
16‧‧‧Receiving Department
G‧‧‧Long strip sample
Ga, Gb‧‧‧ Samples
L ₀ ‧‧‧ Separation distance between mark M and mark M before heat treatment
M‧‧‧ mark
P‧‧‧Outreach
S‧‧‧ Heat treatment space ΔL ₁ , ΔL ₂ ‧‧‧ position offset

Fig. 1A is a plan view schematically showing a supporting state of a glass substrate when the heat treatment method of the present invention is performed. Fig. 1B is a cross-sectional view taken along the line X-X of Fig. 1A. Fig. 2 is a schematic cross-sectional view showing a heat treatment apparatus used in carrying out the heat treatment method of the present invention. 3 is an enlarged view schematically showing a form of deformation occurring in a peripheral portion of a glass substrate in accordance with heat treatment. 4 is a cross-sectional view showing a modification of the supporting state of the glass substrate when the heat treatment method of the present invention is performed. FIG. 5 is a cross-sectional view showing a modification of the supporting state of the glass substrate when the heat treatment method of the present invention is performed. Fig. 6 is a cross-sectional view showing a modification of the supporting state of the glass substrate when the heat treatment method of the present invention is performed. FIG. 7 is a cross-sectional view showing a modification of the supporting state of the glass substrate when the heat treatment method of the present invention is performed. 8A is a schematic view for explaining a procedure for measuring a heat shrinkage ratio of a glass substrate. 8B is a schematic view for explaining a procedure for measuring the heat shrinkage rate of the glass substrate. 8C is a schematic view for explaining a procedure for measuring the heat shrinkage rate of the glass substrate.

1‧‧‧ glass substrate

1a‧‧‧Central Department

1b‧‧‧The Peripheral Department

1c‧‧‧ end face

2‧‧‧Support members

3‧‧‧glass support surface

4‧‧‧Support

5‧‧‧ base

Claims (8)

A heat treatment method for a glass substrate, which is a heat treatment method for reducing a heat shrinkage rate of a glass substrate having a thickness of 300 μm or less, wherein the glass substrate heat treatment method is characterized by: the glass substrate disposed in a lateral posture The heating is performed at a temperature lower than the strain point in a state where the central portion thereof is located at a position higher than the peripheral portion. The method for heat-treating a glass substrate according to the first aspect of the invention, wherein the glass substrate before the heat treatment has a warpage portion having a warpage amount of 300 μm or less. The method for heat-treating a glass substrate according to the first or second aspect of the invention, wherein the central portion of the glass substrate is located in a range of 10 μm or more and 1000 μm or less in comparison with a peripheral portion of the glass substrate Higher position. The method for heat-treating a glass substrate according to any one of the first aspect, wherein the glass substrate is supported from a lower side by a support member having a convex glass-shaped support surface. The method for heat-treating a glass substrate according to claim 4, wherein the glass supporting surface is made smaller than the glass substrate. The method for heat-treating a glass substrate according to any one of claims 1 to 3, wherein the method further comprises a support member having a flat surface and a glass support surface smaller than the glass substrate. The lower side supports the glass substrate. The method for heat-treating a glass substrate according to any one of claims 1 to 6, wherein the glass substrate is used for a flexible member or for a portable member. A method for producing a glass substrate, comprising: a step of preparing a glass substrate, forming a strip-shaped glass film having a thickness of 300 μm or less, and cutting the glass film to obtain a glass substrate having a thickness of 300 μm or less And a heat treatment step of applying heat treatment to the glass substrate by a heat treatment method of the glass substrate according to any one of claims 1 to 7.