TW201733935A - Glass substrate heat-processing method - Google Patents

Abstract

In this invention, the entirety of a glass substrate 2 having a thickness of 500 [mu]m or less is stacked onto a setter 1, and the glass substrate 2 is heat-processed in this state for the purpose of decreasing the heat-shrinking rate thereof. In this process, for the glass substrate 2, a substrate is used in which the edge portion strength when curved in such a manner that the front surface 2a side is convex and the edge portion strength when curved in such a manner that the back surface 2b side is convex are both 200 MPa or greater.

Description

Glass substrate heat treatment method

The present invention relates to a heat treatment method for a glass substrate which is subjected to heat treatment for lowering a heat shrinkage rate in a state in which a glass substrate and a setter are overlapped.

As is well known, in recent years, mobile terminals such as smart phones and tablet terminals are rapidly spreading, and technology development for high performance is progressing. With this, a flat panel display (hereinafter referred to as an FPD (flat panel display)) such as a liquid crystal display or an organic electroluminescence (EL) display mounted on a mobile terminal is required to have a high display performance. Fine image.

In the manufacturing process of the FPD, generally, a process of forming a transparent conductive film pattern containing indium tin oxide (ITO) or the like is performed on the surface of the glass substrate as the constituent member. At this time, in order to achieve high definition of the FPD, it is necessary to perform processing in a state where the glass substrate is exposed to a high temperature. Therefore, when a glass substrate having a high heat shrinkage rate is used as a processing target, the following problems may occur.

That is, since the dimensional stability of the glass substrate with respect to heat is low, it is difficult to form a transparent conductive film as designed, and the manufactured FPD may not exhibit the required high definition. Therefore, in order to avoid the occurrence of such a problem, it is required to reduce the heat shrinkage rate of the glass substrate as much as possible before the process is performed.

Here, Patent Document 1 discloses a heat treatment method for lowering the heat shrinkage rate of a glass substrate. In the method disclosed in this document, the glass substrate is subjected to heat treatment in a state where the entire glass substrate and the carrier (the heat-resistant glass ceramic plate in this document) are overlapped in a high-temperature slow cooling furnace. Further, in this document, a substrate having a thickness of 1 mm is exemplified as a glass substrate to be subjected to heat treatment.

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

[Problems to be Solved by the Invention] However, in the case where the glass substrate is subjected to heat treatment by the above method, the following problems are solved.

That is, regarding the performance required for the FPD, in addition to displaying a high-definition image, it is also required to be thin and lightweight. Therefore, as for the glass substrate which is a component of the FPD, the thinning of the glass substrate is progressing. However, when the heat treatment is performed on the glass substrate which has been thinned to a thickness of 500 μm or less by the above method, there is a problem in that the glass substrate on the carrier is easily broken at the end portion.

Further, it is assumed that the problem is caused by two points (A) and (B) below. (A) When the carrier and the glass substrate are cooled after the heat treatment, the two may inevitably adhere to each other and be in a state of being fixed to each other. (B) When both are cooled, a temperature difference occurs between the surface layer portion of the glass substrate and the inside, and a difference in thermal expansion occurs in the substrate. It is assumed that due to the above two points, a difference in thermal expansion occurs in the glass substrate fixed in the bracket, and stress acts on the substrate, and the stress causes the substrate to be damaged from the end portion having weak strength as a starting point.

The present invention has been made in view of the above-described problems, that is, a glass substrate having a thickness of 500 μm or less is subjected to heat treatment for reducing the heat shrinkage rate in a state of being overlapped with the carrier, and is prevented. Damage to the substrate.

[Means for Solving the Problem] The present invention has been made in order to solve the above problems, and is a method for heat-treating a glass substrate. The glass substrate is used in a state in which the entire glass substrate having a thickness of 500 μm or less is overlapped with the carrier. In the heat treatment method for reducing the heat shrinkage rate, the glass substrate heat treatment method is characterized in that the glass substrate is bent at the end portion when the surface side is convexly curved and the back surface side is convex. In the case where the end strength is 200 MPa or more.

In the method, the glass substrate to be heat-treated is a glass substrate having an end portion strength of 200 MPa or more in a case where either one of the front side and the back side is curved. In other words, a glass substrate having a thickness at which the end portion is broken from the end portion can be sufficiently prevented even when the thickness is as small as 500 μm or less. By this means, even when the entire glass substrate is overlapped with the carrier, heat treatment for lowering the heat shrinkage rate is performed, and it is possible to prevent the occurrence of a situation in which the glass substrate is damaged by the heat treatment.

In the method, the thickness of the glass substrate is preferably 300 μm or less.

For a glass substrate having a thickness of 300 μm or less, for example, it is difficult to remove microcracks included in the end portion by grinding, and the strength of the end portion can be improved. This is because the thickness of the glass substrate is extremely thin, so that the force acting on the end portion due to the grinding process is likely to cause damage to the glass substrate. However, in the method of the present invention, a glass substrate having sufficient end strength is used as the glass substrate to be heat-treated, so that it is not necessary to re-strengthen the strength of the end portion, and of course, no grinding processing is required. Therefore, when the thickness of the glass substrate is 300 μm or less, the effect of the method of the present invention can be applied more effectively and flexibly.

In the above method, it is preferable that the end portion of the glass substrate is a cut end portion formed by cutting the mother glass substrate by laser cutting when the glass substrate is cut out from the mother glass substrate.

The end strength of the cut end portion formed by laser cutting can be set to 200 MPa or more. Therefore, as long as the end portion of the glass substrate is a cut end portion formed by laser cutting, it is preferable to prevent breakage of the glass substrate.

In the above method, it is preferable that the surface of the surface and the back surface of the glass substrate that does not remain as a trace of the initial crack of the cutting starting point of the mother glass substrate is in contact with the carrier.

In the glass substrate, the portion (the portion on the end portion) where the trace of the initial crack as the starting point of the cutting remains is inevitably lower than the other portions. Further, the surface on the surface of the glass substrate and the surface on the back surface which is in contact with the carrier is more likely to exert a large stress accompanying the heat treatment than the surface on the side not contacting the side. Therefore, if the surface of the trace where the initial crack does not remain is brought into contact with the carrier, and the surface of the residual trace is not in contact with the carrier, the possibility that the glass substrate is broken as a starting point from the initial crack of the low strength can be excluded as much as possible. Therefore, the damage of the glass substrate can be prevented more reliably.

In the above method, it is preferable to use a rectangular substrate which is formed by cutting the mother glass substrate to form each of the four sides as the glass substrate, and to leave only one trace of the initial crack on the glass substrate.

According to this, the four sides of the rectangular glass substrate are cut end portions formed by laser cutting, and the traces of the initial cracks remaining on the glass substrate are suppressed to only one, so that the glass substrate can be more reliably prevented from being damaged.

In the above method, the end portion of the glass substrate may be a fuse end portion formed by fusing the mother glass substrate by laser fusing when the glass substrate is cut out from the mother glass substrate.

The end strength of the fusing end portion formed by the laser fusing can be set to 200 MPa or more. Therefore, as long as the end portion of the glass substrate is a fusing end portion formed by laser fusing, it is preferable to prevent breakage of the glass substrate.

In the above method, the end portion of the glass substrate may be a cut end formed by performing a cutting step of cutting the mother glass substrate along the line to cut when the glass substrate is cut from the mother glass substrate. The cutting step may further include: a bending step of bending a portion of the mother glass substrate including the planned cutting line; and a crack forming step of forming a cut from the convex curved surface side of the mother glass substrate Crack at the starting point.

The strength of the end portion of the cut end portion formed by the execution of the cutting step can be set to 200 MPa or more. Therefore, as long as the end portion of the glass substrate is such a cut end portion, it is preferable to prevent breakage of the glass substrate.

In the above method, when the surface of the glass substrate and the back surface are bent in a convex manner, the surface having a higher end strength is preferably in contact with the carrier.

As described above, the surface on the side of the glass substrate and the surface on the back surface that is in contact with the carrier is more likely to exert a large stress accompanying the heat treatment than the surface on the non-contact side. Therefore, when the surface having a higher end strength when the film is bent is protruded, that is, the surface having less defects in which the glass substrate is broken can be brought into contact with the carrier, the damage of the glass substrate can be more reliably prevented.

[Effects of the Invention] In the present invention, as the glass substrate to be subjected to the heat treatment, the glass substrate is used, that is, the thickness of the end portion which is damaged at the end portion can be sufficiently prevented even when the thickness is as small as 500 μm or less. In this way, when the heat treatment for lowering the heat shrinkage rate is performed on the glass substrate having a thickness of 500 μm or less, the substrate can be prevented from being damaged.

Hereinafter, a heat treatment method of a glass substrate according to an embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1 , the heat treatment method of the glass substrate of the embodiment of the present invention is a method in which a plurality of glass substrates 2 supported by the carrier 1 are placed in a plurality of layers in the heat treatment furnace 3 in a plurality of layers. The substrate 2 is subjected to a heat treatment for lowering the heat shrinkage rate. In the heat treatment method, as each of the glass substrates 2, a substrate having a thickness of 500 μm or less and a surface of the surface 2a bent in a convex manner is used (hereinafter, the surface is convexly curved) The strength of the end portion when the back surface 2b side is convexly curved (hereinafter, the end portion strength when the back surface is convexly curved) is 200 MPa or more.

Here, in the heat treatment method, "the glass substrate 2 having an end portion strength at the time of surface convex bending and an end portion strength at a back surface convex bending of 200 MPa or more" means that the following "cutting step" to "average" are performed. As a result of each step of the end strength calculation step, the glass substrate 2 having an end strength at the time of surface convex bending and an end strength at the time of back convex bending was 200 MPa or more.

"Cutting step": A plurality of glass substrates 2 (Fig. 2, Figs. 3a to 3f) cut out from the plurality of mother glass substrates 4 manufactured under the same manufacturing conditions and cut by the same cutting conditions are obtained. "Sample taking step": From the plurality of glass substrates 2 obtained by the cutting step, 40 pieces were randomly taken as the sample glass substrate 2X for the two-point bending test. "Testing procedure": half of the 40 sample glass substrates 2X (hereinafter referred to as sample group A) taken in the step of the sample, and the respective surface 2Xa sides are bent in a convex manner to perform a two-point bending test. Further, the remaining half (hereinafter referred to as sample B group) was bent in a convex manner on the respective back surface 2Xb sides to perform a two-point bending test (Fig. 4a, Fig. 4b). "Average end strength calculation step": For each of the sample A group and the sample B group, only the sample glass substrate 2X which was broken by the end portion 2Xc as a starting point in the two-point bending test was extracted, and the calculation was based on the two-point bending test. The average value of the end strengths of the respective sample glass substrates 2X (hereinafter referred to as the average end strength A and the average end strength B). When the average end strength A and the average end strength B are both 200 MPa or more, each of the glass substrates 2 which are not taken as the sample glass substrate 2X in the sample taking step is regarded as When the surface is convexly curved, the strength of the end portion and the strength of the end portion when the back surface is convexly curved are both 200 MPa or more.

Hereinafter, each step of the cutting step to the average end portion strength calculating step will be described in detail.

<Cutting Step> In the cutting step, various cutting methods can be employed by cutting the glass substrate 2 by cutting each of the plurality of mother glass substrates 4 under the same cutting conditions. However, it is limited to a cutting method in which the average end strength A and the average end strength B calculated in the subsequent average end strength calculation step are both 200 MPa or more. A cutting method that satisfies this condition will be exemplified later. Further, the cut glass substrate 2 can have any shape and size as long as it is cut in the same shape and the same size. In the present embodiment, a description will be given of a case where the mother glass substrate 4 is cut by laser cutting, and the rectangular glass substrate 2 is cut out from each mother glass substrate 4, thereby performing a cutting step. .

Hereinafter, the cutting device 5 for laser cutting of the mother glass substrate 4 will be described.

As shown in FIG. 2, the cutting device 5 is provided with a processing table 6 that can horizontally move in a state in which the mother glass substrate 4 is supported from below, and a laser irradiator that irradiates the mother glass substrate 4 supported on the processing table 6 with the laser beam 7 8. The refrigerant injection nozzle 10 that injects the refrigerant 9 to the mother glass substrate 4.

The processing table 6 is movable in the X direction shown in FIG. 2 and the Y direction orthogonal to the X direction. The laser illuminator 8 is disposed in a state of being fixed at a fixed point, and the laser beam 7 is irradiated along the planned cutting line 11 of the mother glass substrate 4 as the processing table 6 moves in the X direction or the Y direction, thereby being on the mother glass substrate 4 The heating unit 12 that heats the laser 7 is formed (the case where the processing table 6 is moved in the X direction is illustrated in FIG. 2). Similarly to the laser illuminator 8, the refrigerant jetting nozzle 10 is provided in a state of being fixed at a fixed point, and ejects the refrigerant 9 toward the heating unit 12, and cools a part of the heating unit 12, thereby forming a cooling portion 13 on the mother glass substrate 4. .

The cutting device 5 uses the thermal stress generated by the temperature difference between the heating portion 12 and the cooling portion 13 which are formed adjacent to each other, and starts from the initial crack 14 formed on the end portion 4a of the mother glass substrate 4, along the planned cutting line 11. The cutting portion 15 is formed, thereby cutting the mother glass substrate 4.

Here, in the case where the shape of the glass substrate 2 cut from the mother glass substrate 4 is a rectangle, the size of the glass substrate 2 is preferably 300 mm square or more, more preferably 400 mm square or more, and still more preferably 500. More than mm square, the best is 600 mm square.

Further, the thickness of the glass substrate 2 is preferably 300 μm or less, more preferably 200 μm or less, still more preferably 150 μm or less, and most preferably 100 μm or less. The smaller the thickness of the glass substrate 2, the greater the contribution to the reduction and weight reduction of the product (for example, FPD) in which the glass substrate 2 is a component, and the flexibility can be imparted. However, if the thickness of the glass substrate 2 is too small, the minimum strength required for the glass substrate 2 cannot be ensured. Therefore, the thickness of the glass substrate 2 is preferably 5 μm or more.

Further, the strain point of the glass substrate 2 is preferably 600 ° C or higher, more preferably 650 ° C or higher, still more preferably 680 ° C or higher, and most preferably 700 ° C or higher. In addition, the strain point referred to herein is a value measured based on the method specified by American Society for Testing and Materials (ASTM) C336.

The glass substrate 2 having the size, the plate thickness, and the strain point may include, for example, bismuth silicate glass, cerium oxide glass, borosilicate glass, soda glass, alkali-free glass, or the like. In the present embodiment, a glass substrate 2 containing the alkali-free glass which is less likely 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. Further, the content of the alkali component is preferably 1000 ppm or less, more preferably 500 ppm or less, and most preferably 300 ppm or less.

Hereinafter, an aspect in which the glass substrate 2 is cut out from each mother glass substrate 4 by using the dicing apparatus 5 will be described with reference to FIGS. 3a to 3f. In addition, in FIGS. 3a to 3f, illustration of the processing table 6, the laser illuminator 8, and the refrigerant injection nozzle 10 which are provided in the cutting device 5 is abbreviate|omitted.

As shown in FIG. 3a, the mother glass substrate 4 includes a glass substrate 2 (a portion to which a hatching is applied) as a target to be cut. The glass substrate 2 is a rectangular substrate having a pair of long sides 2c, long sides 2d, a pair of short sides 2e, and short sides 2f. First, as shown in FIG. 3b, a first initial crack 16 is formed with respect to the end portion 4a of the mother glass substrate 4, with the first initial crack 16 as a starting point, and a first cut extending along the long side 2c of the glass substrate 2. The first cutting portion 18 is gradually formed on the predetermined line 17, thereby cutting the long side 2c of the four sides.

Next, as shown in FIG. 3c, a second initial crack 19 is formed with respect to the end portion 4a of the mother glass substrate 4, with the second initial crack 19 as a starting point, and a second extending along the short side 2e of the glass substrate 2. The second cutting portion 21 is gradually formed on the cutting planned line 20, whereby the short side 2e is cut. Further, the portion including the trace of the first initial crack 16 is removed from the mother glass substrate 4 as the short side 2e is cut. Next, as shown in FIG. 3d, a third initial crack 22 is formed with respect to the end portion 4a of the mother glass substrate 4, with the third initial crack 22 as a starting point, and a third extending along the short side 2f of the glass substrate 2. The third cutting portion 24 is gradually formed on the cutting planned line 23, thereby cutting the short side 2f.

Finally, as shown in FIG. 3e, a fourth initial crack 25 is formed with respect to the end portion 4a of the mother glass substrate 4, with the fourth initial crack 25 as a starting point, and a fourth cut extending along the long side 2d of the glass substrate 2. The fourth cutting portion 27 is gradually formed on the predetermined line 26, and the last remaining long side 2d among the four sides is cut. When the cutting of the long side 2d is completed, as shown in FIG. 3f, the glass substrate 2 on each side of which the four sides are formed is cut by the cutting of the mother glass substrate 4. That is, the end portion 2g of the glass substrate 2 is a cut end portion formed by laser cutting. Further, the portion including the trace of the second initial crack 19 and the trace of the third initial crack 22 is removed from the mother glass substrate 4 with the cutting of the long side 2d. Thereby, only one trace of the fourth initial crack 25 among the traces of the first initial crack 16 to the fourth initial crack 25 remains in the glass substrate 2.

By sequentially cutting the glass substrate 2 from the mother glass substrate 4 for each of the plurality of mother glass substrates 4, a plurality of glass substrates 2 cut under the same cutting conditions are obtained. With the above, the cutting step is completed.

<Sample Taking Step> In the sample taking step, 40 pieces were taken from the plurality of glass substrates 2 as the sample glass substrate 2X. One half of the 40 sample glass substrates 2X was taken as the sample group A, and the remaining half was taken as the sample group B.

<Testing procedure> As shown in FIG. 4a, each of the sample glass substrates 2X belonging to the sample A group has a surface 2Xa side (a surface side where the trace of the fourth initial crack 25 does not remain) is U in a convex manner. The test was performed by bending the characters. On the other hand, as shown in FIG. 4b, each of the sample glass substrates 2X belonging to the sample B group has a U-shaped convex side on the back surface 2Xb side (the surface side on which the traces of the fourth initial crack 25 remain). The test was performed by bending.

Specifically, in a state in which the sample glass substrate 2X is sandwiched between the pair of upper and lower plates 28 and the plate body 28, the upper plate body 28 is lowered at a speed of 50 mm/min, thereby gradually increasing the sample glass substrate. The curvature of the 2X curved part. The lowering of the upper body 28 is continued until the sample glass substrate 2X is broken. The two-point bending test was performed on all of the sample glass substrates 2X belonging to the sample A group and all the sample glass substrates 2X belonging to the sample B group in this order. According to the above, the test procedure is completed.

In the present embodiment, the test was performed such that the pair of long sides 2c and the long sides 2d of the sample glass substrate 2X and the pair of short sides 2e and the pair of long sides 2c and the long sides 2d of the short sides 2f were bent. This is because the curvature of the sample glass substrate 2X is more easily maintained when the pair of long sides 2c and the long sides 2d are curved than when the pair of short sides 2e and short sides 2f are bent, so that the ends can be accurately grasped. Strength. Therefore, as a modification of the present embodiment, when the shape of the glass substrate 2 cut in the cutting step is different from the rectangular shape or the cutting step, the glass substrate 2 is cut by a cutting method different from laser cutting. In order to accurately grasp the end strength, it is preferable to test the sample glass substrate 2X by bending the sample glass substrate 2X so that the pair of the plate body 28 and the plate body 28 are easily fixed.

<Average End Strength Calculation Step> In the average end portion strength calculation step, first, only the sample glass group 2X that was damaged by the two-point bending test was extracted for each of the sample A group and the sample B group. 2Xc is the sample glass substrate 2X damaged by the starting point. In other words, only the sample glass substrate 2X which is broken by the pair of the long side 2c and the long side 2d as a starting point is extracted.

Next, each of the sample A group and the sample B group is calculated from each of the extracted sample glass substrates 2X according to the following formula 1 (reference: ST Gulati, SID 11 abstract, 652). End strength σ. Further, in Formula 1, E represents the Young's modulus of the sample glass substrate 2X, t represents the thickness of the sample glass substrate 2X, and D represents a pair of plates 28 and plates when the sample glass substrate 2X is broken at the end 2Xc as a starting point. The spacing of the bodies 28.

σ=1.198[E・t/(D-t)]...(Formula 1)

Finally, the average value of the end portion strength σ calculated from the above formula 1 is calculated for each of the sample group A and the sample group B, and the average end of the average value of the end portion strength σ in the sample group A is calculated. The average end strength B as the average value of the end strengths σ in the portion strength A and the sample B group. According to the above, the average end strength calculation step is completed.

Further, when the average end strength A and the average end strength B are both 200 MPa or more, each of the plurality of glass substrates 2 is taken as the sample glass substrate 2X in the sample taking step. It is considered that the end strength of the surface convex bending and the end strength of the back convex bending are both 200 MPa or more for the following reasons. In other words, the sample glass substrate 2X that has been damaged in the two-point bending test and the glass substrate 2 that is to be heat-treated are the substrates that are cut out from the respective mother glass substrates 4 manufactured under the same manufacturing conditions as each other by the same cutting conditions. They are thus considered to be substrates in substantially equal state with each other.

Here, in the cutting step, in the case of laser cutting in the cutting method which can be employed when the glass substrate 2 is cut from the mother glass substrate 4, the average end strength A and the average end can be obtained. The cutting conditions in which the partial strength B is set to 200 MPa or more are exemplified in Table 1 below. In addition, each of the cutting conditions shown in Table 1 is a four-side (a pair of long sides 2c, a long side 2d, a pair of short sides 2e, and a short side 2f) when the rectangular glass substrate 2 is cut out from the mother glass substrate 4. Cutting conditions common to the cutting of each side. Further, each item of "plate thickness", "laser output", "mist flow rate", "air pressure", "cutting speed", and "beam length" in Table 1 indicates the following items. "Thickness": the thickness of the mother glass substrate 4 (glass substrate (product name: OA-10G) manufactured by Nippon Electric Glass Co., Ltd.) and the glass substrate 2 cut from the mother glass substrate 4: "laser output": laser The output "mist flow rate" of the laser beam 7 irradiated by the illuminator 8: the flow rate per unit time of the refrigerant 9 (the mist formed by mixing the air and water) by the refrigerant injection nozzle 10: the refrigerant 9 (fog) The ejection pressure "cutting speed" of the air contained in the air: the speed at which the heating portion 12 and the cooling portion 13 formed on the mother glass substrate 4 relatively move with respect to the mother glass substrate 4 (equal to the speed at which the processing table 6 moves) "beam length" ": the length of the spot of the laser 7 along the line to cut 11 (length dimension L shown in Fig. 2)

[Table 1]

Under the four cutting conditions shown in Table 1, the average end strength A was 650 MPa, and the average end strength B was 600 Mpa. That is, the average end strength A and the average end strength B are both 200 MPa or more. Therefore, by performing the cutting step under the four cutting conditions, the plurality of glass substrates 2 obtained by cutting the glass substrate 2 from each of the mother glass substrates 4 are not used as the sample glass substrate in the sample taking step. The glass substrate 2 taken in 2X is subjected to heat treatment. In the glass substrate 2 cut under the four cutting conditions shown in Table 1, the pair of long sides 2c, long sides 2d, and a pair of short sides 2e and short sides 2f are included for every 1 mm. The number of defects (microcracks having a total length of 1 μm or more) is 10 or less. Regarding the number, each of the pair of long sides 2c, long sides 2d, and a pair of short sides 2e and short sides 2f is cut by scribing using a scribe wheel. In comparison, for a very small number, it is considered that the average end strength A and the average end strength B are factors which obtain a strength which greatly exceeds 200 MPa.

In addition, in the cutting method which can be used in the cutting step, the cutting method capable of setting the average end strength A and the average end strength B to 200 MPa or more is not limited to laser cutting. In the case of laser cutting or bending stress cutting as the cutting method in addition to the laser cutting, the average end strength A and the average end strength B can be set to 200 MPa or more. Further, the laser fusing or bending stress cutting is preferably performed when the thickness of the mother glass substrate 4 is 300 μm or less.

Hereinafter, a mode in the case where a laser fuse or a bending stress cut is used as the cutting method in the cutting step will be described. First, an embodiment in the case where the cutting step is performed by laser fusing will be described.

As shown in FIG. 5, the fuse device 29 is used for the laser blow of the mother glass substrate 4. The fuse device 29 includes a processing table 6 that supports the mother glass substrate 4 from below, a laser illuminator 8 that irradiates the mother glass substrate 4 with the laser beam 7, and an auxiliary gas injection nozzle 32 that is sprayed to make The first auxiliary gas 31 scattered by the molten glass 30 melted by the heat of the laser beam 7 is used.

The laser illuminator 8 is provided in a state of being fixed at a fixed point, and a lens 8a for concentrating the laser beam 7 to be irradiated onto the mother glass substrate 4 is mounted inside. The laser illuminator 8 is connected to a gas introduction pipe 8b for introducing the second auxiliary gas 33 sprayed in the irradiation direction of the laser beam 7 to the inside. Further, the laser irradiator 8 is formed with a photographing ejection port 8c for respectively irradiating and ejecting the laser beam 7 and the second assist gas 33. The auxiliary gas injection nozzle 32 is inclined with respect to the surface 4b of the mother glass substrate 4, and is provided in a state of being fixed at a fixed point. The auxiliary gas injection nozzle 32 is formed in a tubular shape, and is capable of ejecting the first auxiliary gas 31 passing through the inside thereof toward the irradiation portion 34 of the laser beam 7. The processing table 6 is provided with a pair of the irradiation portions 34 of the laser beam 7. The pair of processing table 6 and the processing table 6 can move in synchronization with the direction perpendicular to the paper surface in FIG. 5 while supporting the mother glass substrate 4.

The fuse device 29 continuously irradiates the laser beam 7 from the laser irradiator 8 toward the mother glass substrate 4 with the movement of the two processing stages 6 and the processing table 6 supporting the mother glass substrate 4. Further, the first auxiliary gas 31 injected from the auxiliary gas injection nozzle 32 and the second auxiliary gas 33 injected from the laser illuminator 8 are used to disperse and remove the molten glass 30 melted by the irradiation unit 34 of the laser beam 7 by This melts the mother glass substrate 4.

As an example, when the glass substrate 2 is cut out from the mother glass substrate 4 having a thickness of 100 μm by the fuse device 29, if the laser output is 14 W, the spot diameter of the laser beam 7 (mother glass substrate) The diameter on the surface 4b of 4 is set to 75 μm, the pulse period/pulse width is set to 1000/180 μm, and the fusing speed (equal to the speed at which the two processing stations 6 and the processing table 6 move) is set to 20 mm/s, and the assist gas The inclination angle θ of the injection nozzle 32 with respect to the surface 4b of the mother glass substrate 4 is 35°, the flow rate of the first assist gas 31 is 20 L/min, and the flow rate of the second assist gas 33 is 10 L/min. Both the average end strength A and the average end strength B can be set to 200 MPa or more. The end portion 2g of the glass substrate 2 cut in the above-described manner is a fusing end portion formed by laser fusing.

Next, an embodiment in the case where the cutting step is performed by bending stress cutting will be described.

As shown in FIG. 6, the cutting device 35 is used for cutting the bending stress of the mother glass substrate 4. The cutting device 35 includes a support member 36 formed with a support surface 36a for supporting the mother glass substrate 4 from below, and a crack former 38 for cutting the predetermined line 37 of the mother glass substrate 4 supported by the support member 36 (FIG. 6) A crack is formed on the middle edge extending in the direction perpendicular to the paper surface.

The support surface 36a formed on the support member 36 is formed on a partial cylindrical surface which is curved at the same radius of curvature R, and the portion including the planned cutting line 37 of the mother glass substrate 4 supported by the support member 36 is bent in accordance with the partial cylindrical surface. Thereby, it is possible to impart bending stress to the portion. The crack former 38 can form a crack on the line to cut 37 by pressing the mother glass substrate 4 at the tip end portion thereof.

In the cutting step of the mother glass substrate 4 using the cutting device 35, first, a bending step is performed in which the mother glass substrate 4 is placed on the supporting member 36 to include the mother glass substrate 4 The portion where the predetermined line 37 is cut is bent in conformity with the support surface 36a. Next, a crack forming step is performed in which a crack which is a starting point of cutting is formed on the planned cutting line 37 from the convex curved surface 4c side of the mother glass substrate 4. By using the crack as the starting point of the cutting, the cutting portion is advanced along the entire length of the line to cut 37 by the bending stress applied to the portion including the line to cut 37, thereby cutting the mother glass substrate 4 .

As an example, when the glass substrate 2 is cut out from the mother glass substrate 4 having a thickness of 200 μm by the cutting device 35, the radius of curvature R of the support surface 36a is set to 250 mm (for the line to cut 37) The average end strength A and the average end strength B can be set to 200 MPa or more by imparting a bending stress of about 35 MPa. The end portion 2g of the glass substrate 2 cut out in the above-described manner is a cut end portion which is cut by bending stress.

Further, in addition to the laser blow or bending stress cut, even when the cutting step is performed by etching using hydrogen fluoride (HF) or the like, the average end strength A and the average end strength B can be also obtained. Both are set to 200 MPa or more.

<Heat Treatment Step> Hereinafter, a heat treatment step of performing heat treatment on the glass substrate 2 will be described. First, the form in which the glass substrate 2 overlaps with the carrier 1 supporting the glass substrate 2 and the bracket 1 which is preferable for use in the heat treatment step will be described.

As shown in FIG. 7, in the heat treatment step, the glass substrate 2 is heat-treated in a state in which the entire end of the glass substrate 2 having the end portion 2g as the cut end portion is overlapped with the carrier 1 which is slightly larger than the glass substrate 2. Regarding the glass substrate 2, the surface of the surface and the back surface where the trace of the fourth initial crack 25 does not remain is in contact with the carrier 1. That is, when the surface is bent in a convex manner, the surface having a higher end strength is brought into contact with the bracket 1. Further, the glass substrate 2 may be cleaned before being overlapped with the cradle 1. According to this, it is possible to prevent the foreign matter adhering during the process of obtaining the glass substrate 2 from being burned on the glass substrate 2 by the heat treatment.

In the case of the modification of the present embodiment, when the glass substrate 2 having the end portion 2g as the fuse end portion is overlapped with the bracket 1, the surface having a higher end strength when the projection is bent in a convex manner The contact with the carrier 1 is such that the surface on the irradiation target side of the laser 7 is brought into contact with the carrier 1 when the laser is blown. Further, as another modification, when the glass substrate 2 having the end portion 2g as the cut end portion is overlapped with the bracket 1, the surface having a higher end strength and the support are also bent when the end portion 2g is bent. Since the frame 1 is in contact with each other, the surface which is a concave curved surface when the bending stress is cut is brought into contact with the bracket 1.

The bracket 1 is a plate-like member. When the difference in thermal expansion coefficient between the glass substrate 2 and the carrier 1 is large, the expansion of the glass substrate 2 and the carrier 1 during heat treatment is inferior, and the glass substrate 2 may be damaged or the like. Therefore, as the material of the bracket 1, it is preferable to use a material having a thermal expansion coefficient equivalent to that of the glass substrate 2. Specifically, it is preferable to use a material having a difference in thermal expansion coefficient from the glass substrate 2 in a temperature range of 30 ° C to 380 ° C of 5 × 10 ^{- 7} / ° C or less. Further, it is preferable to use a glass having the same composition as that of the glass substrate 2. Therefore, in the present embodiment, the bracket 1 is made of a plate-like member made of an alkali-free glass.

In addition, the bracket 1 may also contain other glass materials such as bismuth silicate glass, bismuth oxide glass, and borosilicate glass. Further, a material containing a heat-resistant material other than glass, for example, a bracket 1 of ceramic or metal may be used.

The thickness of the bracket 1 is preferably from 0.5 mm to 3.0 mm, more preferably from 0.5 mm to 2.5 mm, further preferably from 0.5 mm to 2.0 mm, further preferably from 0.7 mm to 2.0 mm, and most preferably from 1.0 mm to ～ 2.0 mm. The reason for this is that, in the case where the thickness of the bracket 1 is less than 0.5 mm, the possibility that the bracket 1 is deformed with heat treatment is increased, and in the case where the thickness of the bracket 1 is larger than 3.0 mm, the heat capacity of the bracket 1 is increased. And the heat energy in the heat treatment will not disappear. Therefore, when the thickness of the bracket 1 is set within the above range, the heat treatment of the glass substrate 2 can be performed with high precision and efficiency.

Although not shown in FIG. 7, the contact portion with the glass substrate 2 in the bracket 1 may include an inorganic thin film. According to this, even when the glass substrate 2 reaches a high temperature accompanying the heat treatment, it is possible to avoid the occurrence of a situation in which the glass substrate 2 adheres to the carrier 1. Therefore, after the heat treatment step, the glass substrate 2 and the carrier 1 can be easily separated, and the possibility of damage to the glass substrate 2 accompanying separation from the carrier 1 can be eliminated as much as possible. Further, the inorganic thin 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 thin film may be, for example, selected from the group consisting of ITO, Ti, Si, Au, Ag, Al, Cr, Cu, Mg, SiO ₂ , Al ₂ O ₃ , MgO, Y ₂ O ₃ , La ₂ O ₃ , and 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 , Ti ₃ O ₅ , NiO, ZnO A film of any one of SiN and AlN or a film of two or more types is laminated. Further, an inorganic thin film made of an oxide such as ITO in the films is particularly preferable. The reason for this is that the film containing the oxide is excellent in dimensional stability of heat, and thus the carrier 1 forming the film can be repeatedly used for the heat treatment step.

The value of the surface roughness Ra of the inorganic thin 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. Below, the best is below 10 nm. The reason is that if the value of the surface roughness Ra is larger than 100 nm, the bubbles are easily interposed between the glass substrate 2 and the carrier 1. During the heat treatment, the glass substrate 2 is easily slid with respect to the carrier 1, and the carrier 1 is difficult to stabilize. The glass substrate 2 is supported.

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

Further, in consideration of the cost of forming the inorganic thin film or the strength of the inorganic thin film, the thickness thereof 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 thin film is too small, it is difficult to separate the glass substrate 2 from the carrier 1 after the heat treatment step. Therefore, the thickness of the inorganic thin film is preferably 5 nm or more.

Further, the contact portion with the glass substrate 2 in the bracket 1 can also be roughened. According to this, in the case where the contact portion includes the inorganic thin film as described above, even when the glass substrate 2 reaches a high temperature due to the heat treatment, the state in which the glass substrate 2 adheres to the carrier 1 can be avoided. occur. As a method of roughening, it can carry out by acid-processing, grinding, etc., using a fluoric acid.

Hereinafter, the heat treatment furnace 3 used for the heat treatment will be described.

As shown in Fig. 1, the heat treatment furnace 3 includes a glass chamber 39, a lifting table 41 that moves up and down with respect to the glass chamber 39 in a state in which the glass frame 40 is placed, and a furnace wall 42 that houses the glass chamber 39. And a heater 43 that heats the glass chamber 39 from the outside. The heat treatment furnace 3 is placed in a clean room, and the heat treatment step is performed in a clean room.

The glass chamber 39 is formed as a covered cylindrical body having an opening formed at its lower end, and a heat treatment space S is formed inside thereof. The glass chamber 39 is formed by integrally molding quartz glass, and the heat treatment space S is formed without seams.

The glass holder 40 has a housing portion 44 that is disposed in a plurality of layers, and each of the housing portions 44 includes a pair of column portions 40a provided on the elevation table 41, a column portion 40a, and a shelf 40b that can be attached to and detached from the column portion 40a and the column portion 40a. Both the column portion 40a and the shelf plate 40b are formed of quartz glass. In the present embodiment, a lattice-shaped frame body is used as the shelf plate 40b, and a plurality of pin-shaped projections are provided on the upper surface of the shelf plate 40b. Further, the bracket 1 of the glass substrate 2 that supports the flat posture from the lower side is supported by the lower side from the pin-like projection.

The lifting table 41 has a mounting portion 41a made of quartz glass on which the glass frame 40 is placed. When the mounting portion 41a is at the raised position, the opening formed at the lower end of the glass chamber 39 is closed, and the glass holder 40 is placed in the heat treatment. Within space S. On the other hand, when the placing portion 41a is lowered to the lowering position shown in the drawing, loading and unloading of the bracket 1 and the glass substrate 2 are performed on the respective housing portions 44 of the glass holder 40 placed on the placing portion 41a.

The furnace wall 42 is formed in a closed cylindrical shape having an opening at its lower end, and the entire body contains a refractory. A heater 43 is attached to the inner wall surface of the side wall of the furnace wall 42 and the inner wall surface of the top wall, respectively. As the heater 43, for example, a metal-based heating element typified by a nichrome-based heating element can be used.

Although not shown in FIG. 1, the heat treatment furnace 3 is provided with a cooling mechanism (for example, a blower) that cools the glass chamber 39 from the outside. By providing the cooling mechanism, the environment of the heat treatment space S heated by the heater 43 can be efficiently cooled.

Hereinafter, a mode of the heat treatment step using the heat treatment furnace 3 will be described. In the heat treatment step, the temperature increasing step, the holding step, and the cooling step are sequentially performed.

Before the temperature raising step is performed, the mounting portion 41a of the lifting platform 41 is placed at the lowered position, and after the bracket 1 and the glass substrate 2 are loaded in the respective housing portions 44 of the glass holder 40, the lifting table 41 is moved upward to arrange the glass holder 40. The heat treatment space S in the glass chamber 39. Further, the loading of the accommodating portion 44 and the unloading of the accommodating portion 44 after the heat treatment of the cradle 1 and the glass substrate 2 can be performed, for example, by using a robot fork that can support the cradle 1 from below.

The temperature rising step is a step of raising the temperature of the glass substrate 2 to a predetermined temperature. Here, the glass substrate 2 is heated at 3 ° C / min or more, preferably 5 ° C / min or more, more preferably 7 ° C / min or more. The output of the heater 43 is adjusted in such a manner that the speed is increased. However, if the temperature rise rate of the glass substrate 2 is too fast, the possibility of breakage of the glass substrate 2 is increased. Therefore, the temperature increase rate is preferably 30° C./min or less, and more preferably 20° C./min or less.

Further, in the temperature increasing step, the heat treatment space S in the glass chamber 39 is heated from the outside until the temperature of the glass substrate 2 reaches a temperature equal to or lower than the strain point of the glass substrate 2. Specifically, when the strain point of the glass substrate 2 is set to [T] ° C, heating is performed until the temperature of the glass substrate 2 is preferably [T-30] ° C or less, more preferably [T-50] ° C or less. More preferably, it is [T-80] ° C or less, and most preferably [T-100] ° C or less. Thereby, variation in the improper shape of the glass substrate 2 can be prevented, and the heat shrinkage rate of the glass substrate 2 can be reduced. However, if the glass substrate 2 is not sufficiently heated, the heat shrinkage rate of the glass substrate 2 cannot be appropriately lowered, and thus the temperature until the glass substrate 2 is heated is [T-200] ° C or more.

In the heat retention step, the glass substrate 2 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, the possibility of occurrence of shape unevenness between the glass substrates 2 can be suppressed as much as possible, and the heat shrinkage rate of each of the glass substrates 2 can be appropriately reduced.

In the temperature lowering step, the temperature of the glass substrate 2 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 processing time of the temperature lowering step can be shortened, and the productivity of the glass substrate 2 can be improved. However, if the temperature drop rate is too fast, the heat shrinkage rate of the glass substrate 2 cannot be sufficiently lowered. Further, in addition, warpage or the like occurs in the glass substrate 2, and the shape of the glass substrate 2 is easily deteriorated. Therefore, the temperature drop rate is preferably 20 ° C / min or less, more preferably 15 ° C / min or less.

[Examples] As an example (Examples 1 to 4) of the present invention, a rectangular glass substrate cut out from a mother glass substrate under the respective conditions shown in Table 1 was subjected to heat shrinkage. After the heat treatment with a reduced rate, the ratio of breakage of the glass substrate was verified. Further, as a comparative example (Comparative Example 1 to Comparative Example 4), dicing was performed by cutting the scribe line of the mother glass substrate and applying bending stress to the periphery of the scribe line, thereby The rectangular glass substrate cut out from the mother glass substrate was cut, and the ratio of the damage of the glass substrate was verified after the heat treatment for lowering the heat shrinkage rate.

In each of the examples and the comparative examples, the size of the glass substrate was 730 mm × 920 mm. For the bracket, a bracket (a glass substrate (product name: OA-10G) manufactured by Nippon Electric Glass Co., Ltd.) in which an ITO film is formed at a contact portion with a glass substrate is used. The bracket measures 750 mm x 940 mm and has a plate thickness of 1.6 mm. The glass substrate and the carrier are respectively dried in a clean room and then dried. Thereafter, the glass substrate and the carrier were stacked, and the glass substrate was subjected to heat treatment under the conditions of a heat treatment temperature of 560 ° C and a heat treatment time of 60 min.

In each of the first to fourth embodiments, the ratio of the damage of the glass substrate was such that the surface of the glass substrate (the surface on which the trace of the initial crack did not remain) was brought into contact with the carrier and the back surface (the residual initial crack) The surface of the trace was verified in both cases in the case of contact with the bracket. Here, in each of the first to fourth embodiments, each of the glass substrate having the surface in contact with the carrier and the glass substrate having the back surface in contact with the carrier were prepared in two pieces. Then, the damage rate was calculated by counting the number of blocks of the damaged substrate in the 25 pieces.

In each of Comparative Examples 1 to 4, the back surface of the glass substrate (the surface on which the scribe line which is the starting point of the dicing was formed) was brought into contact with the holder to be verified. Further, in each of Comparative Examples 1 to 4, 25 glass substrates were prepared. Then, the damage rate was calculated by counting the number of blocks of the damaged substrate in 25 pieces. Further, the thicknesses of the glass substrates in Comparative Examples 1 to 4 correspond to the thicknesses of the glass substrates in Examples 1 to 4.

The results of the verification are shown in Table 2 below. Here, the value in the parentheses in Table 2 is the thickness of the glass substrate to be heat-treated.

[Table 2]

According to the results shown in Table 2, in Examples 1 to 4, the breakage ratio of the glass substrate was significantly lowered as compared with Comparative Examples 1 to 4. It is assumed that the results are obtained in Examples 1 to 4, when the surface of the glass substrate is convexly curved, and the end strength at the time of the back surface convex bending is 200 MPa or more, which is compared with Comparative Examples 1 to 4. The strength of the department is increased. Further, in Comparative Examples 1 to 4, the end strength (average end strength B) when the back surface was convexly curved was 150 MPa. In each of Comparative Example 1 to Comparative Example 4, each of the pair of long sides and the pair of short sides of the cut glass substrate has a defect (a microcrack having a total length of 1 μm or more) per 1 mm. The number is 35, and more defects than the 10th to the following Examples 1 to 4 are included.

In the heat treatment method of the glass substrate of the present invention, it is estimated that the glass substrate having a thickness of 500 μm or less can be prevented from being subjected to heat treatment for lowering the heat shrinkage rate in a state of being overlapped with the carrier. Broken.

1‧‧‧ Bracket 2‧‧‧Glass substrate 2a‧‧‧Surface 2b‧‧‧Back 2c, 2d‧‧‧Long side 2e, 2f‧‧‧ Short side 2g, 2Xc‧‧‧End 2X‧‧‧ Sample glass substrate 2Xa‧‧ ‧ Sample glass substrate surface 2Xb‧‧‧ Sample glass substrate back 3.‧‧‧ Heat treatment furnace 4‧‧‧ Mother glass substrate 4a‧‧‧End 4b‧‧‧ Surface 4c‧‧‧ convex Curved surface 5‧‧‧Cutting device 6‧‧‧Processing table 7‧‧‧Laser 8‧‧‧Laser illuminator 8a‧‧‧Lens 8b‧‧‧ gas introduction tube 8c‧‧‧Photo ejection port 9‧‧ ‧Refrigerant 10‧‧‧Refrigerant Spraying Machine 11‧‧‧ Cutting Line 12‧‧‧Heating Department 13‧‧‧Cooling Unit 14‧‧‧Initial Crack 15‧‧‧ Cutting Section 16‧‧‧ First Initial Crack 17‧ ‧‧First cutting line 18‧‧‧First cutting section 19‧‧‧Second initial crack 20‧‧‧Second cutting line 21‧‧‧Second cutting part 22‧‧‧ Third initial crack 23‧ ‧‧The third cutting line 24‧‧ Third cutting section 25‧‧‧ Fourth initial crack 26‧‧‧ fourth Cutting line 27‧‧‧4th cutting section 28‧‧‧Board body 29‧‧‧Fusing device 30‧‧‧Solid glass 31‧‧‧First auxiliary gas 32‧‧‧Assistant gas injection nozzle 33‧‧‧ Second auxiliary gas 34‧‧‧ Irradiation unit 35‧‧‧ Cutting device 36‧‧‧Support member 36a‧‧‧Support surface 37‧‧‧ Cutting line 38‧‧‧ Crack former 39‧‧‧ Glass chamber 40‧‧‧glass frame 40a‧‧‧column 40b‧‧‧shelf 41‧‧‧lifting platform 41a‧‧‧mounting section 42‧‧‧wall 43‧‧‧heater 44‧‧‧ accommodating part D ‧ ‧ ‧ interval R‧ ‧ radius of curvature S‧ ‧ heat treatment space t‧ ‧ board thickness X, Y‧ ‧ direction θ‧‧‧ angle of inclination L‧‧‧ length dimension

Fig. 1 is a vertical cross-sectional front view showing a heat treatment step in a method of heat-treating a glass substrate according to an embodiment of the present invention. 2 is a perspective view showing a cutting step in a method of heat-treating a glass substrate according to an embodiment of the present invention. Fig. 3a is a plan view showing a cutting step in a method of heat-treating a glass substrate according to an embodiment of the present invention. Fig. 3b is a plan view showing a cutting step in a method of heat-treating a glass substrate according to an embodiment of the present invention. Fig. 3c is a plan view showing a cutting step in a method of heat-treating a glass substrate according to an embodiment of the present invention. Fig. 3d is a plan view showing a cutting step in the heat treatment method of the glass substrate according to the embodiment of the present invention. Fig. 3e is a plan view showing a cutting step in a method of heat-treating a glass substrate according to an embodiment of the present invention. Fig. 3f is a plan view showing a cutting step in the heat treatment method of the glass substrate according to the embodiment of the present invention. Fig. 4a is a side view showing a test procedure in a method of heat-treating a glass substrate according to an embodiment of the present invention. Fig. 4b is a side view showing a test procedure in a method of heat-treating a glass substrate according to an embodiment of the present invention. FIG. 5 is a vertical cross-sectional front view showing a modification of the cutting step in the heat treatment method for a glass substrate according to the embodiment of the present invention. FIG. 6 is a vertical cross-sectional front view showing a modification of the cutting step in the heat treatment method for a glass substrate according to the embodiment of the present invention. FIG. 7 is a perspective view showing a heat treatment step in a heat treatment method for a glass substrate according to an embodiment of the present invention.

1‧‧‧ bracket

2‧‧‧ glass substrate

2a‧‧‧ surface

2b‧‧‧back

3‧‧‧heat treatment furnace

39‧‧‧ glass chamber

40‧‧‧glass shelf

40a‧‧‧ pillar

40b‧‧‧ board

41‧‧‧ Lifting table

41a‧‧‧Loading Department

42‧‧‧ furnace wall

43‧‧‧heater

44‧‧‧ Housing Department

S‧‧‧ Heat treatment space

Claims (8)

In a method of heat-treating a glass substrate, a heat treatment for lowering a heat shrinkage rate of the glass substrate is performed in a state in which the entire glass substrate having a thickness of 500 μm or less is overlapped with the carrier, and the heat treatment method for the glass substrate The glass substrate is a substrate having an end portion strength when the surface side is convexly curved and an end portion strength when the back surface side is convexly curved is 200 MPa or more. . The method for heat-treating a glass substrate according to claim 1, wherein the glass substrate has a thickness of 300 μm or less. The method for heat-treating a glass substrate according to claim 1 or 2, wherein the end portion of the glass substrate is cut by laser cutting when the glass substrate is cut from the mother glass substrate The cutting end portion formed by cutting the mother glass substrate. The method for heat-treating a glass substrate according to the third aspect of the invention, wherein a surface of the surface of the glass substrate and the back surface where no trace of the initial crack of the starting point of the mother glass substrate is not left remains. The bracket is in contact. The method for heat-treating a glass substrate according to claim 4, wherein, as the glass substrate, a rectangular substrate formed by cutting the mother glass substrate to form each of four sides is used, and the initial crack is formed. Only one trace remains on the glass substrate. The method for heat-treating a glass substrate according to claim 2, wherein the end portion of the glass substrate is such that the glass substrate is cut by a laser to cut the mother glass A fuse end formed by the substrate being blown. The method for heat-treating a glass substrate according to claim 2, wherein the end portion of the glass substrate is formed by cutting along a line to cut when the glass substrate is cut from the mother glass substrate a cutting end portion formed by the cutting step of cutting the mother glass substrate, the cutting step comprising: a bending step of bending a portion of the mother glass substrate including the planned cutting line; and a crack In the forming step, a crack which is a starting point of the cutting is formed on the planned cutting line side from the side of the convex curved surface of the mother glass substrate. The method for heat-treating a glass substrate according to claim 6 or 7, wherein, in the case where the surface of the glass substrate and the back surface are curved in a convex manner, the strength of the end portion is further increased. The high face is in contact with the bracket.