Glass substrate and method for manufacturing glass substrate

Abstract

To provide a glass substrate excellent in handleability during conveyance or processing, based on a new evaluation to the shape of the glass substrate.SOLUTION: In a glass substrate 1, which is a rectangular glass substrate 1 having a first side 2 along a board pulling direction X, and a second side 3 along a width direction Y orthogonal to the board pulling direction X, rectangular evaluation areas A-G are set on multiple positions along the direction of the second side 3, and in at least one evaluation area in the multiple evaluation areas A-G, front and back deflection differences W31a-W32a, W31b-W32b on two side 13a, 13b parallel to the second side 3 are different in terms of the positive and negative.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a glass substrate and a method for manufacturing a glass substrate. [Background technology]

[0002] In recent years, as the size and thickness of panel glass constituting, for example, a liquid crystal display, etc. increases, the size and thickness of the glass substrate used in the manufacture of the panel glass also inevitably increases. The manufacturing technology of this type of glass substrate is progressing at a rapid pace, and the current situation is that the level of shape precision required for the glass substrate is becoming extremely high.

[0003] Here, various evaluation methods have been proposed in the past to evaluate the shape accuracy of a glass substrate. For example, Patent Document 1 proposes a method of evaluating the shape accuracy of a glass substrate by using a warpage rate obtained by dividing the maximum separation distance between an ideal plane (e.g., the upper surface of a surface plate) and the rear surface of the glass substrate in a direction along a specific side when the glass substrate is placed on the ideal plane, by the total length of the specific side.

[0004] Patent Document 2 proposes a method for evaluating the shape of a glass substrate in a direction perpendicular to the drawing direction by setting a plurality of evaluation regions having a rectangular shape and different positions in a direction perpendicular to the drawing direction and measuring the front-back deflection difference in the plurality of evaluation regions. It also proposes a method for evaluating the change in the shape of a glass substrate in a direction perpendicular to the drawing direction by measuring the above-mentioned front-back deflection difference for a plurality of glass substrates and determining the amount of change in the front-back deflection difference in the same evaluation region between the plurality of glass substrates. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-199426 A [Patent Document 2] JP 2019-137587 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the manufacturing process of a glass substrate or in a process for manufacturing an electronic device by forming an electronic device on a glass substrate, the glass substrate may be transported while part of the main surface (rear surface) is supported from below, or processed while being held with positioning, as necessary. In such a case, even if the warpage or bending evaluated as the deformation of the entire glass substrate is small, the bending of the glass substrate due to its own weight while being supported as described above may appear as a deformation that may affect the transportation or processing. This type of deformation may cause unexpected situations such as contact with surrounding equipment, and is therefore an event that should be avoided as much as possible in terms of handling.

[0007] The evaluation method described in Patent Document 2 evaluates the shape or its change (variation) in a direction perpendicular to the drawing direction of the glass substrate based on the distribution of the difference in deflection between the front and back sides of the substrate in the direction. However, even if a glass substrate is evaluated by this method to have the shape or its change within an acceptable range, depending on the transportation or processing manner, the deflection due to its own weight may appear as a deformation that can affect transportation or processing.

[0008] In view of the above circumstances, a technical problem to be solved is to provide a glass substrate that is excellent in handleability during transportation or processing, based on a new evaluation of the shape of the glass substrate. [Means for solving the problem]

[0009] The above-mentioned problems are solved by a glass substrate according to the present invention, which is a rectangular glass substrate having a first side along the sheet drawing direction and a second side along the width direction perpendicular to the sheet drawing direction, and is characterized in that rectangular evaluation areas are set at a plurality of positions along the width direction, and in at least one of the plurality of evaluation areas, the difference in front-back deflection between two sides parallel to the second side is different in sign from the positive side.

[0010] As a result of intensively studying the deflection distribution in a glass substrate, the inventors have found that the shape in the drawing direction can be accurately grasped by properly evaluating the deflection distribution in the drawing direction, which has not been considered before. In addition, the inventors have found that the shape in the drawing direction affects the deflection due to the weight during transportation or processing. The glass substrate according to the present invention is made based on the above-mentioned findings, and is characterized in that rectangular evaluation areas are set at multiple positions along the width direction of the glass substrate perpendicular to the drawing direction, and in at least one evaluation area, the positive and negative front-back deflection difference is different between two sides parallel to a second side along the width direction of the glass substrate. A glass substrate having a shape in which the positive and negative front-back deflection difference is different between two sides along the width direction of the evaluation area has a shape in which the deflection direction is reversed in the drawing direction. In other words, the glass substrate has a wavy shape in the drawing direction. Therefore, if the glass substrate has the above-mentioned shape, it is possible to prevent the deflection due to the weight from becoming apparent in one direction and suppress deformation during transportation or processing. This makes it possible to stabilize the shape of the glass substrate during transportation or processing, thereby improving the handleability of the glass substrate.

[0011] In the glass substrate according to the present invention, in at least one of the plurality of evaluation regions, the difference between the front and back deflections in two sides parallel to the first side may be positive and negative, respectively.

[0012] In this way, if the glass substrate has a shape in which the difference in the front and back deflections is different not only in the width direction of the evaluation region but also on two sides along the sheet drawing direction of the evaluation region, the glass substrate has a wavy shape not only in the sheet drawing direction but also in the width direction, which makes the shape of the glass substrate more stable during transportation or processing, thereby further improving the handleability of the glass substrate.

[0013] In the glass substrate according to the present invention, each evaluation region may have a side along the width direction of 370 mm and a side along the sheet drawing direction of 470 mm.

[0014] By setting the size of the evaluation area to the above size, the shape of the glass substrate in the sheet drawing direction can be accurately evaluated. That is, it is possible to avoid a situation in which one of the peaks and valleys of the waviness shape that should be evaluated is missing from the evaluation area due to the size of the evaluation area being too small. It is also possible to avoid a situation in which the waviness shape in the sheet drawing direction is buried in one evaluation area due to the size of the evaluation area being too large.

[0015] In addition, in the glass substrate of the present invention, in all of the multiple evaluation areas, the difference in front-back deflection between two sides parallel to the first side may be -0.5 mm or more and +0.5 mm or less, and the difference in front-back deflection between two sides parallel to the second side may be -0.5 mm or more and +0.5 mm or less.

[0016] In this way, if the glass substrate has a difference in the front and back deflections of each evaluation region within the above-mentioned range, the substrate has a shape that is close to flat as a whole. Therefore, even if the substrate deflects due to its own weight during transportation or processing, the deflection is small.

[0017] In the glass substrate according to the present invention, the relatively shorter of the first and second sides may be 1100 mm or more and the relatively longer side may be 1300 mm or more, and the thickness dimension may be 200 μm or more and 1000 μm or less.

[0018] The above-mentioned deformation problem becomes prominent when a glass substrate having the above-mentioned size is manufactured by sheet drawing, and therefore the present invention is suitable for a glass substrate having the above-mentioned size.

[0019] The above-mentioned problems are also solved by a method for manufacturing a glass substrate according to the present invention. That is, this manufacturing method is a method for manufacturing a rectangular glass substrate having a first side along the sheet drawing direction and a second side along the width direction perpendicular to the sheet drawing direction, and is characterized in that it includes a forming step of forming a ribbon-shaped glass, a cutting step of cutting a glass substrate from the ribbon-shaped glass, a sampling step of sampling a rectangular sample glass having two sides parallel to the first side and the second side from the glass substrate, and a measuring step of measuring a difference in front-back deflection of the side parallel to the first side of the sample glass.

[0020] The method for manufacturing a glass substrate according to the present invention is based on the above findings, similar to the glass substrate according to the present invention, and is characterized in that a rectangular sample glass having two sides parallel to the first side and the second side is taken from a glass substrate cut out from a molded ribbon glass, and the difference in the front and back deflections of the sides along the drawing direction of the taken sample glass is measured. According to this method, the shape of the glass substrate in the drawing direction can be known from the deflection direction and the deflection magnitude of the sides along the drawing direction of the sample glass. From this, for example, the shape stability when a part of the glass substrate is supported from below can be evaluated, and a glass substrate having a shape stability of a predetermined level or higher can be selected. Therefore, according to the method for manufacturing a glass substrate according to the present invention, it is possible to provide a glass substrate that is excellent in handleability during transportation or processing.

[0021] In the method for manufacturing a glass substrate according to the present invention, in the measuring step, a difference in deflection between the front and back sides of each of two sides of the sample glass parallel to the first side may be measured.

[0022] By measuring the difference in the deflection between the front and back sides of two sides of one glass sample in this way, the number of glass samples required for measurement can be reduced, and it becomes possible to efficiently grasp the shape of the glass substrate in the sheet drawing direction.

[0023] The method for manufacturing a glass substrate according to the present invention may further include an evaluation step of evaluating whether a difference in front-back deflection of an edge parallel to the first edge of the sample glass measured in the measurement step is positive or negative.

[0024] In this way, by evaluating the positive and negative of the difference in the front and back warping of the side parallel to the first side, it is possible to grasp the partial warping direction of the glass substrate in the sheet drawing direction. Also, by evaluating the positive and negative of the difference in the front and back warping of the two parallel sides, it is possible to evaluate whether the glass substrate to be evaluated has a shape in which the warping direction is reversed in the width direction, in other words, whether the glass substrate has a wavy shape in the width direction. Therefore, it is possible to select a glass substrate that is less likely to deform during transportation or processing. Alternatively, it is possible to stably manufacture a glass substrate having a wavy shape in the width direction by adjusting the manufacturing conditions.

[0025] In the method for producing a glass substrate according to the present invention, in the measuring step, a difference in front-back deflection may be measured along each of two sides of the sample glass parallel to the second side.

[0026] According to this method, in addition to the shape of the glass substrate in the sheet drawing direction, the shape of the glass substrate in the width direction can be known from the deflection direction and the deflection magnitude of the side along the width direction of the sample glass. In particular, by measuring the front-back deflection difference at each of the two sides along the width direction as described above, the number of sample glasses required for measurement can be reduced. Therefore, it is possible to efficiently grasp the shape of the glass substrate in the width direction.

[0027] In this case, in the method for producing a glass substrate according to the present invention, the positive / negative difference in the front-back bending of the side parallel to the second side of the sample glass measured in the measuring step may be evaluated.

[0028] In this way, by evaluating the positive / negative difference in the front-back warping of two parallel sides along the width direction, it is possible to evaluate whether the glass substrate to be evaluated has a shape in which the warping direction is reversed in the sheet drawing direction, in other words, whether the glass substrate has a wavy shape in the sheet drawing direction. This makes it possible to select glass substrates that are less likely to deform during transportation or processing. Alternatively, by adjusting the manufacturing conditions, it becomes possible to stably manufacture glass substrates that have a wavy shape in the sheet drawing direction. Effect of the Invention

[0029] As described above, according to the present invention, it is possible to provide a glass substrate that is excellent in handleability during transportation or processing, based on a new evaluation of the shape of the glass substrate. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a plan view of a glass substrate according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a plan view for explaining a method for measuring a difference in deflection between the front and back of a side along the width direction of a sample glass cut out from a glass substrate. [Diagram 3] 3A is a side view of a sample glass for which a difference in front and back deflection is measured by the method shown in FIG. 2, as viewed in the direction of arrow A1, and FIG. 3B is a side view of a sample glass for which a difference in front and back deflection is measured by the method shown in FIG. 2, as viewed in the direction of arrow A2. [Figure 4] 3A and 3B are side views of another sample glass, the front-to-back deflection difference of which is measured by the method shown in FIG. 2, as viewed in the direction of arrow A1 and as viewed in the direction of arrow A2, respectively. [Diagram 5] 4 is a cross-sectional view taken along the line B1-B1 of FIG. 2 along the drawing direction of the glass substrate when the deflection shown in FIG. 3 occurs. [Figure 6] 5 is a cross-sectional view taken along the line B1-B1 of FIG. 2 along the drawing direction of the glass substrate when the deflection shown in FIG. 4 occurs. [Figure 7] FIG. 1 is a plan view for explaining a method for measuring a difference in deflection between the front and back sides of a sample glass cut out from a glass substrate along the sheet drawing direction. [Figure 8]8A is a side view of a sample glass for which a difference in front and back deflection is measured by the method shown in FIG. 7, as seen from the direction of an arrow C1, and FIG. 8B is a side view of a sample glass for which a difference in front and back deflection is measured by the method shown in FIG. [Figure 9] 8A is a side view of another sample glass in which the difference in deflection between the front and back sides is measured by the method shown in FIG. 7, as seen from the direction of the arrow C1, and FIG. 8B is a side view of another sample glass in which the difference in deflection between the front and back sides is measured by the method shown in FIG. [Figure 10] 7 is a vertical cross-sectional view showing a main part of a glass substrate manufacturing apparatus for manufacturing the glass substrate shown in FIG. [Figure 11] FIG. 11 is a perspective view showing a state of the glass ribbon in the annealing zone of FIG. [Figure 12] 12 is a cross-sectional view taken along the D1-D1 cutting line of the glass ribbon shown in FIG. 11. [Figure 13] FIG. 12 is a cross-sectional view taken along the D2-D2 cutting line of the glass ribbon shown in FIG. [Figure 14] 12 is a longitudinal sectional view taken along the E1-E1 cutting line of the glass ribbon shown in FIG. 11. [Figure 15] 1 is a graph showing evaluation results of differences in front and back deflections in the width direction in each evaluation region of a glass substrate for comparison with the present invention. [Figure 16] 1 is a graph showing evaluation results of differences in deflection between the front and back sides in the width direction in each evaluation region of a glass substrate according to the present invention. [Figure 17] 1 is a graph showing evaluation results of differences in deflection between the front and back surfaces in the sheet drawing direction in each evaluation area of ​​a glass substrate according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Hereinafter, one embodiment of the present invention will be described with reference to FIGS.

[0032] 1 is a plan view of a glass substrate 1 according to this embodiment. The glass substrate 1 is manufactured by a known forming method involving sheet drawing, such as a downdraw method, such as an overflow downdraw method or a slot downdraw method, or a float method. In this embodiment, a ribbon-shaped glass is formed by the overflow downdraw method (described in detail below), and a glass substrate 1 of a predetermined shape and size is obtained by cutting out the ribbon-shaped glass.

[0033] The glass substrate 1 has a first side 2 along the sheet drawing direction X resulting from the above-mentioned forming method, and a second side 3 along a direction (i.e., width direction) Y perpendicular to the sheet drawing direction X, and is generally rectangular. Here, it is preferable that the relatively shorter side of the first side 2 and the second side 3 is 1100 mm or more, and the relatively longer side is 1300 mm or more. On the other hand, it is preferable that the sizes of both the first side 2 and the second side 3 are 4000 mm or less. The thickness dimension of the glass substrate 1 is preferably 1000 μm or less, and more preferably 700 μm or less. On the other hand, the thickness dimension of the glass substrate 1 is preferably 200 μm or more, and more preferably 300 μm or more.

[0034] The drawing direction X of the glass substrate 1 can be observed as a striped pattern, for example, by irradiating light from a light source (e.g., a xenon light) while adjusting the angle of the glass substrate 1 in a dark room and projecting the transmitted light onto a screen. Therefore, even in the state of the glass substrate 1 after molding, the drawing direction X during molding can be identified.

[0035] The shape of the main surface 4 of the glass substrate 1, specifically, the shape of the main surface 4 in the direction along the width direction Y of the glass substrate 1 and the shape of the main surface 4 in the direction along the sheet drawing direction X are each evaluated using a difference in front and back deflection.

[0036] First, an example of a method for evaluating the shape of the main surface 4 in the direction along the width direction Y of the glass substrate 1 based on the difference in front and back deflection will be described. First, as shown in Fig. 1, a plurality of evaluation areas A to G are set on one glass substrate 1 at different positions in the direction along the second side 3. In this embodiment, seven evaluation areas A, B, C, D, E, F, and G are set so as to be spaced apart at equal intervals L in the direction along the second side 3. In this case, each of the evaluation areas A to G is set within an effective zone (not shown) on one main surface 4 of the glass substrate 1 where a thin film pattern is formed in a film formation process in a process of manufacturing an electronic device, for example.

[0037] Here, each of the evaluation regions A to G has a rectangular shape, and the shape and size of each evaluation region A to G are set so that, for example, the size of the side along the width direction Y is 370 mm and the size of the side along the sheet drawing direction X is 470 mm. Note that the shape and size of each evaluation region A to G given here are merely examples, and the size of each evaluation region A to G may be set so that, for example, the size of the side parallel to the first side 2 of the glass substrate 1 (sides 12a and 12b described later) is 10% or more and 30% or less of the size of the first side 2, and the size of the side parallel to the second side 3 (sides 13a and 13b described later) is 10% or more and 30% or less of the size of the second side 3. Note that, when it is not possible to set all the evaluation regions A to G in a single row along the width direction, for example, because the width dimension of the effective zone is small, seven evaluation regions A to G may be set alternately in each row along the width direction to form two rows.

[0038] Then, glass samples 11 having positions, shapes and sizes corresponding to the evaluation regions A to G are taken from the glass substrate 1, and the number of glass samples 11 (here, seven) equal to the number of evaluation regions A to G is obtained per glass substrate 1. At this time, the glass samples 11 are taken from the glass substrate 1 such that one sides 12a, 12b of the glass sample 11 are parallel to the drawing direction X of the glass substrate 1 and the other sides 13a, 13b of the glass sample 11 are parallel to the width direction Y of the glass substrate 1.

[0039] After preparing a predetermined number of glass samples 11 in this manner, the difference in deflection between the front and back sides 13a, 13b of each glass sample 11 along the width direction Y is measured. Specifically, as shown in FIG. 2, one main surface 11a (e.g., the main surface on the side that becomes the guaranteed surface, here, the main surface on the side that is included in one main surface 4 of the glass substrate 1) of the glass sample 11 is turned up, and both ends of the glass sample 11 along the width direction Y are supported by a pair of support members 20, 20. At this time, the support span M of the glass sample 11 by the pair of support members 20, 20 is set to, for example, 350 mm. In this state, the magnitude of a first deflection W31a (indicated by a solid line in FIG. 3(a)) generated in one side 13a (e.g., the side 13a on the downstream side in terms of the sheet drawing direction X) of the two sides 13a, 13b along the width direction Y of the glass sample 11 is measured. Thereafter, the glass sample 11 is turned upside down, and both ends of the glass sample 11 in the width direction Y are supported by a pair of support members 20, 20 with the other main surface 11b of the glass sample 11 facing upward (as shown by the two-dot chain line in FIG. 3(a)). In this state, the magnitude of the second deflection W32a generated in one side 13a of the glass sample 11 along the width direction Y is measured.

[0040] In this manner, after measuring the first deflection W31a and the second deflection W32a, the value W31a-W32a obtained by subtracting the second deflection W32a from the first deflection W31a is obtained as the difference in the front and back deflections of one side 13a along the width direction Y.

[0041] In this embodiment, next, with one of the main surfaces 11a of the glass sample 11 facing upward, both ends of the glass sample 11 in the width direction Y are supported by a pair of supporting members 20, 20, and the magnitude of a first deflection W31b (indicated by a solid line in FIG. 3(b)) generated at the other side 13b of the glass sample 11 (the side 13b on the upstream side in relation to the sheet drawing direction X) is measured. Thereafter, the glass sample 11 is turned over, and with the other main surface 11b of the glass sample 11 facing upward, both ends of the glass sample 11 in the width direction Y are supported by a pair of supporting members 20, 20. Then, in this state, the magnitude of a second deflection W32b (indicated by a two-dot chain line in FIG. 3(b)) generated at the other side 13b of the glass sample 11 along the width direction Y is measured.

[0042] By carrying out the above-mentioned operation for all the sample glass 11 corresponding to each of the evaluation regions A to G, it is possible to know the direction and magnitude of the deflection in the multiple evaluation regions A to G over the entire width direction Y of the effective zone of the glass substrate 1. For example, as shown in FIG. 3(a), if a first deflection W31a occurring on one side 13a with one main surface 11a facing upward is larger than a second deflection W32a occurring on one side 13a with the other main surface 11b facing upward, the direction of the deflection in the region of the glass substrate 1 corresponding to one side 13a of the sample glass 11 is the direction in which the one main surface 11a is concave, and the magnitude of the deflection can be evaluated as a value obtained by subtracting the second deflection W32a from the first deflection W31a. Therefore, by measuring the deflection of one side 13a as described above, it is possible to grasp the shape of the glass substrate 1 in the width direction Y.

[0043] In addition, after measuring the first deflection W31b and the second deflection W32b in this manner, the value W31b-W32b obtained by subtracting the second deflection W32b from the first deflection W31b is obtained as the difference in the front and back deflections of the other side 13b along the width direction Y.

[0044] In this case, the positive and negative of the difference in front-back deflection W31a-W32a of one side 13a and the difference in front-back deflection W31b-W32b of the other side 13b obtained as described above are evaluated. As shown in Figures 3(a) and 3(b), when the difference in front-back deflection W31a-W32a of one side 13a and the difference in front-back deflection W31b-W32b of the other side 13b are equal in positive and negative, the cross section of the portion (any one of evaluation areas A to G) of the glass substrate 1 from which the sample glass 11 was taken along the sheet drawing direction X has a shape deflected in one direction from the front to the back as shown in Figure 5.

[0045] On the other hand, when the first deflection W31a (W31b) and the second deflection W32a (W32b) are measured at two sides 13a and 13b along the width direction Y of the sample glass 11, respectively, and the positive and negative of the front-back deflection difference W31a-W32a at one side 13a and the front-back deflection difference W31b-W32b at the other side 13b are evaluated, the positive and negative of the front-back deflection difference W31a-W32a and W31b-W32b may differ (be reversed) between the one side 13a and the other side 13b as shown in Figures 4(a) and 4(b). In this case, the cross section of the portion (any one of the evaluation areas A to G) of the glass substrate 1 from which the sample glass 11 was taken along the sheet drawing direction X has a shape in which the deflection direction is reversed in the sheet drawing direction X, that is, a so-called wavy shape, as shown in Figure 6. In this manner, the shape of the glass substrate 1 in the drawing direction X can be grasped.

[0046] Next, an example of a method for evaluating the shape of the glass substrate 1 along the drawing direction X based on the difference in deflection between the front and back sides will be described.

[0047] First, a predetermined number of glass samples 11 corresponding to the evaluation regions A to G shown in FIG. 2 are prepared, and then the difference in front-back deflection of the sides 12a, 12b of each glass sample 11 along the drawing direction X is measured. Here, the glass samples 11 prepared may be the glass samples 11 used when evaluating the shape along the width direction Y. Specifically, as shown in FIG. 7, one of the main surfaces 11a of the glass sample 11 is facing upward, and both ends of the glass sample 11 along the drawing direction X are supported by a pair of support members 21, 21. At this time, the support span N of the glass sample 11 by the pair of support members 21, 21 is set to, for example, 450 mm. In this state, the magnitude of the first deflection W21a (indicated by a solid line in FIG. 8(a)) generated in one side 12a (the left side 12a in FIG. 7) of the two sides 12a, 12b of the glass sample 11 along the drawing direction X is measured. Thereafter, the glass sample 11 is turned over so that the other main surface 11b of the glass sample 11 faces upward, and both ends of the glass sample 11 in the drawing direction X are supported by a pair of supporting members 21, 21 (as shown by the two-dot chain line in FIG. 8(a)). In this state, the magnitude of the second deflection W22a generated in one side 12a of the glass sample 11 along the drawing direction X is measured.

[0048] After measuring the first deflection W21a and the second deflection W22a in this manner, the value W21a-W22a obtained by subtracting the second deflection W22a from the first deflection W21a is obtained as the difference in the front and back deflections of one side 12a along the plate drawing direction X.

[0049] In this embodiment, next, with one of the main surfaces 11a of the glass sample 11 facing upward, both ends of the glass sample 11 in the drawing direction X are supported by a pair of supporting members 21, 21, and the magnitude of a first deflection W21b (indicated by a solid line in FIG. 8(b)) occurring at the other side 12b of the glass sample 11 (the right side 12b in FIG. 7) is measured. Thereafter, the glass sample 11 is turned over, and with the other main surface 11b of the glass sample 11 facing upward, both ends of the glass sample 11 in the drawing direction X are supported by a pair of supporting members 21, 21. Then, in this state, the magnitude of a second deflection W22b (indicated by a two-dot chain line in FIG. 8(b)) occurring at the other side 12b of the glass sample 11 along the drawing direction X is measured.

[0050] By carrying out the above-mentioned operation for all the sample glasses 11 corresponding to each of the evaluation regions A to G, it is possible to know the direction and magnitude of the deflection in the drawing direction X in the multiple evaluation regions A to G in the effective zone of the glass substrate 1. For example, as shown in FIG. 8(a), if a first deflection W21a occurring in one side 12a with one main surface 11a facing upward is larger than a second deflection W22a occurring in one side 12a with the other main surface 11b facing upward, the deflection direction in the region of the glass substrate 1 corresponding to one side 12a of the sample glass 11 is the direction in which one main surface 11a is concave, and the deflection magnitude can be evaluated as a value obtained by subtracting the second deflection W22a from the first deflection W21a. Therefore, by measuring the deflection of one side 12a as described above, it is possible to grasp the shape of the glass substrate 1 in the drawing direction X.

[0051] After measuring the first deflection W21b and the second deflection W22b in this manner, the value W21b-W22b obtained by subtracting the second deflection W22b from the first deflection W21b is obtained as the front-back deflection difference of the other side 12b along the plate drawing direction X.

[0052] In this case, the positive and negative of the difference in front-back deflection W21a-W22a of one side 12a and the difference in front-back deflection W21b-W22b of the other side 12b obtained as described above can be evaluated. As shown in Figures 8(a) and 8(b), when the difference in front-back deflection W21a-W22a of one side 12a and the difference in front-back deflection W21b-W22b of the other side 12b are equal in positive and negative, the cross section along the width direction Y of the portion (any one of the evaluation areas A to G) from which the sample glass 11 of the glass substrate 1 is taken has a shape that is deflected in one direction, front-back, although not shown.

[0053] On the other hand, when the first deflection W21a (W21b) and the second deflection W22a (W22b) are measured at two sides 12a and 12b along the sheet drawing direction X of the sample glass 11, respectively, and the positive and negative of the front-back deflection difference W21a-W22a at one side 12a and the front-back deflection difference W21b-W22b at the other side 12b are evaluated, the positive and negative of the front-back deflection difference W21a-W22a and W21b-W22b may differ (be reversed) between the one side 12a and the other side 12b, as shown in Figures 9(a) and 9(b). In this case, the cross section along the width direction Y of the portion (any one of the evaluation areas A to G) from which the sample glass 11 of the glass substrate 1 is taken has a shape (wavy shape) in which the deflection direction is reversed in the width direction Y, although not shown. In this manner, the shape of the glass substrate 1 in the width direction Y can be grasped.

[0054] In addition, in the glass substrate 1 evaluated as described above, in all of the evaluation regions A to G, the front-back deflection differences W21a-W22a and W21b-W22b in the two sides 12a and 12b parallel to the first side 2 are preferably -0.5 mm or more and +0.5 mm or less, and more preferably -0.3 mm or more and 0.3 mm or less. In addition, the front-back deflection differences W31a-W32a and W31b-W32b in the two sides 13a and 13b parallel to the second side 3 are preferably -0.5 mm or more and +0.5 mm or less, and more preferably -0.3 mm or more and 0.3 mm or less. In other words, when the handleability of the glass substrate 1 is taken into consideration in addition to the positive and negative front-to-back deflection difference mentioned above, in at least one of the evaluation regions A to G of the glass substrate 1, the positive and negative signs of the front-to-back deflection difference W31a-W32a of one side 13a along the width direction Y and the front-to-back deflection difference W31b-W32b of the other side 13b are reversed, and it is preferable that the absolute values ​​of the front-to-back deflection differences W21a-W22a, W21b-W22b, W31a-W32a, W31b-W32b of the four sides 12a, 12b, 13a, 13b in all of the evaluation regions A to G are all within 0.5 mm, and more preferably within 0.3 mm.

[0055] Next, an example of a method for manufacturing the glass substrate 1 having the above configuration will be described.

[0056] 10 is a vertical cross-sectional view showing a main part of a manufacturing apparatus 100 for manufacturing the glass substrate 1 according to this embodiment. The manufacturing apparatus 100 forms a glass ribbon 30 as a band-like glass that becomes the glass substrate 1 in a furnace 101 by an overflow downdraw method.

[0057] In detail, within the furnace 101, there are provided, from the top, a forming zone 102 where the forming process is performed, a slow cooling (annealing) zone 103 where the annealing process is performed, and a cooling zone 104 where the cooling process is performed, and downstream of the cooling zone 104, a cutting zone (not shown) where the cutting process is performed is provided.

[0058] In the forming zone 102, molten glass 31 is supplied to a formed body 121 having a wedge-shaped cross-sectional shape, and the molten glass 31 overflowing from the top of this formed body 121 is joined at the bottom end and allowed to flow down to form a band-shaped glass ribbon 30. In the annealing zone 103, the glass ribbon 30 formed in the forming zone 102 is annealed to suppress the occurrence of distortion inside the glass ribbon 30. In the cooling zone 104, the glass ribbon 30 annealed in the annealing zone 103 is cooled to room temperature or near room temperature. The glass ribbon 30 thus cooled is then cut to a predetermined size in a cutting zone (not shown), and glass substrates 1 are continuously produced.

[0059] In the annealing zone 103 and the cooling zone 104, a plurality of roller groups 106 are provided at a plurality of locations along the conveying path of the glass ribbon 30, each of which includes rollers 105 that rotate in the direction of the arrow in Fig. 10. As shown in Fig. 11, each of the roller groups 106 is configured by two pairs of rollers 105 (i.e., a total of four rollers 105) that respectively hold both ends of the glass ribbon 30 in the width direction Y, and in this embodiment, the two rollers 105 located on one side of the glass ribbon 30 in the width direction Y and the two rollers 105 located on the other side of the width direction Y are each connected and fixed to two roller shafts 107. Of course, the rollers 105 on one side and the rollers 105 on the other side may not be connected and fixed to each other by the roller shaft 107, and each of the rollers 105 may be cantilevered by the roller shaft 107.

[0060] In the annealing zone 103, as shown in Fig. 11, a part of the glass ribbon 30, which has a flat shape as a whole, is slightly curved. In detail, the glass ribbon 30 is curved at the center side in the width direction Y to form a curved portion 32 in the glass ribbon 30. In addition, the direction of the concave-convex of the curved portion 32 is reversed between the front and back directions at a predetermined position in the sheet drawing direction X of the glass ribbon 30.

[0061] In this embodiment, the first curved portion 33, which is located relatively upstream of the annealing zone 103 among the curved portions 32, has a shape in which the central portion in the width direction Y of the glass ribbon 30 is curved so that one main surface 30a side is concave and the other main surface 30b side is convex, as shown in Fig. 12. The state indicated by the dashed dotted line in Fig. 12 shows the state of the glass ribbon 30 when the first curved portion 33 is not formed, that is, the state of the flat glass ribbon 30.

[0062] On the other hand, the second curved portion 34, which is located relatively downstream of the annealing zone 103 among the curved portions 32, has a shape in which the central portion in the width direction Y of the glass ribbon 30 is curved so that one main surface 30a side is convex and the other main surface 30b side is concave, as shown in FIG. 13 .

[0063] The first curved portion 33 and the second curved portion 34 that are continuous in the sheet drawing direction X have a shape in which the convex direction is reversed between the upstream side and the downstream side, so that the first curved portion 33 and the second curved portion 34 are convex toward the back surface (the other main surface 30b) of the glass ribbon 30 on the upstream side and are convex toward the front surface (one main surface 30a) of the glass ribbon 30 on the downstream side, as shown in Fig. 11. That is, by providing the curved portions 32 (33, 34) having such a shape in the glass ribbon 30, the glass ribbon 30 has a shape curved along the sheet drawing direction X, as shown in Fig. 14, and the directions of the convex sides of the curved portions 33, 34 on the upstream side and the downstream side are reversed at the boundary of the reversal portion 35.

[0064] In the manufacturing method according to the present embodiment, the curved shape of the first curved portion 33 is repeatedly changed, and the curved shape of the second curved portion 34 is repeatedly changed. Specifically, the first curved portion 33 is first changed from a shape curved so that one of the main surfaces 30a is concave to a shape curved so that one of the main surfaces 30a is convex. The second curved portion 34 is also changed from a shape curved so that one of the main surfaces 30a is convex to a shape curved so that one of the main surfaces 30a is concave. Next, the first curved portion 33 is changed from a shape curved so that one of the main surfaces 30a is convex to a shape curved so that one of the main surfaces 30a is concave. The second curved portion 34 is also changed from a shape curved so that one of the main surfaces 30a is concave to a shape curved so that one of the main surfaces 30a is convex. As a result, the curved shapes of the first curved portion 33 and the second curved portion 34 return to the shapes shown in FIG. 11 to FIG. 14. Such changes in the curved shapes of the first curved portion 33 and the second curved portion 34 are repeated. One cycle of such changes may be performed in, for example, 1 to 3 seconds.

[0065] In the case of a glass substrate 1 cut out from such a glass ribbon 30, when the shape in the direction along the sheet drawing direction X is evaluated based on the difference in front and back deflections as described above, the positive and negative of the front and back deflection differences W31a-W32a and W31b-W32b of the two sides 13a and 13b along the width direction Y are reversed as shown in Figs. 4(a) and 4(b). That is, as shown in Fig. 6, the glass substrate 1 has a wavy shape in the sheet drawing direction X. Therefore, the glass substrate 1 having this wavy shape can prevent the deflection due to its own weight from becoming apparent in one direction, and can suppress deformation during transportation or processing. As a result, the shape of the glass substrate 1 during transportation or processing is stable, and the handleability of the glass substrate 1 can be improved.

[0066] Here, examples of a method for changing the curved shapes of the first curved portion 33 and the second curved portion 34 of the glass ribbon 30 include the following means.

[0067] For example, the curved shapes of the first curved portion 33 and the second curved portion 34 may be changed by a mechanical external force. Specifically, for example, a contactor (not shown) may be abutted against the glass ribbon 30, and the curved shapes of the first curved portion 33 and the second curved portion 34 may be forcibly changed by the contactor.

[0068] If the glass substrate 1 is cut out from the glass ribbon 30 in which the curved shapes of the first curved portion 33 and the second curved portion 34 described above have been repeatedly changed, the positive and negative values ​​of the front-back deflection differences W21a-W22a and W21b-W22b of the two sides 12a, 12b along the sheet drawing direction X will also be reversed.

[0069] The front-back deflection differences W31a-W32a and W31b-W32b of the two sides 13a and 13b along the width direction Y and the front-back deflection differences W21a-W22a and W21b-W22b of the two sides 12a and 12b along the sheet drawing direction X change according to the bending amount dt (see FIGS. 12 and 13) of the first bending portion 33 and the second bending portion 34. In other words, if the bending amount dt is made small, for example, to 1 mm to 20 mm, the front-back deflection differences W31a-W32a and W31b-W32b of the two sides 13a and 13b along the width direction Y and the front-back deflection differences W21a-W22a and W21b-W22b of the two sides 12a and 12b along the sheet drawing direction X can be made to be -0.5 mm or more and +0.5 mm or less.

[0070] An example of the results of evaluating the shape accuracy of the glass substrate 1 manufactured as described above based on the above-mentioned difference in the deflection between the front and back surfaces is shown in FIGS.

[0071] Fig. 15 shows the evaluation results of the front-back deflection difference in the width direction Y in each evaluation area A to G of the glass substrate 1 for comparison with the present invention. Here, the front-back deflection difference in the width direction Y shown in Fig. 15 is expressed as the difference between the deflections W31a, W31b, W32a, and W32b measured at the same side 13a (13b) by measuring the deflections W31a, W32a (W31b, W32b) caused by the weight of the sample glass 11 that is taken from the glass substrate 1 to be evaluated corresponding to the evaluation areas A to G, as shown in Figs. 2 and 3. The solid line in Fig. 15 shows the distribution of the front-back deflection difference obtained by measuring the side 13b on the upstream side of the sample glass 11, and the dashed line in Fig. 15 shows the distribution of the front-back deflection difference W31a-W32a obtained by measuring the side 13a on the downstream side of the sample glass 11.

[0072] 16 shows the evaluation results of the difference in front and back deflection in the width direction Y in each of the evaluation regions A to G of the glass substrate 1 according to the present invention. The differences in front and back deflection in the width direction Y shown in Fig. 16 were obtained in the same manner as the differences in front and back deflection shown in Fig. 15, except that the glass substrate 1 to be evaluated is different, and were graphed in the same manner.

[0073] Fig. 17 shows the evaluation results of the difference in front-back deflection in the drawing direction Y in each of the evaluation areas A to G of the glass substrate 1 according to the present invention. Here, the difference in front-back deflection in the drawing direction X shown in Fig. 17 is expressed as the difference between the deflections W21a, W22a (W21b, W22b) measured on the same side 12a (12b) after a sample glass 11 corresponding to the evaluation areas A to G is taken from the glass substrate 1 to be evaluated, and deflections W21a, W21b, W22a, W22b caused by the weight of the sampled sample glass 11 are measured on two sides 12a, 12b along the drawing direction X, as shown in Figs. 7 and 8. Moreover, the solid line in FIG. 17 represents the distribution of the front-to-back deflection difference W21b-W22b obtained by measuring the side 12b on one side of the width direction of the sample glass 11, and the dashed line in FIG. 17 represents the distribution of the front-to-back deflection difference W21a-W22a obtained by measuring the side 12a on the other side of the width direction of the sample glass 11.

[0074] As shown in Figure 15, in the glass substrate 1 compared with the present invention, in all evaluation areas A to G, the positive and negative differences in the front and back deflections in the width direction Y at the downstream side 13a and the upstream side 13b are the same, or one of them is substantially zero.

[0075] 16, in glass substrate 1 according to the present invention, the positive and negative difference in the front and back deflections in the width direction Y is reversed in predetermined evaluation areas B and C. From this, it is presumed that in at least the areas of glass substrate 1 according to the present invention corresponding to evaluation areas B and C, the directions of the front and back deflections are reversed between the downstream side and the upstream side, forming a wavy shape in the sheet drawing direction X as shown in FIG.

[0076] 17, in the glass substrate 1 according to the present invention, the positive and negative difference in the front and back deflections in the sheet drawing direction X is reversed in a predetermined evaluation area A. From this, it is presumed that in at least the area of ​​the glass substrate 1 according to the present invention corresponding to the evaluation area A, the directions of the front and back deflections are reversed between one side and the other side in the width direction, forming a wavy shape in the width direction Y as shown in FIG.

[0077] Furthermore, as shown in Figures 16 and 17, in the glass substrate 1 of the present invention, in all of the multiple evaluation areas A to G, the absolute value of the difference in front-back deflection between the downstream side 13a and the upstream side 13b parallel to the width direction Y, and the absolute value of the difference in front-back deflection between the side 12a on one side in the width direction and the side 12b on the other side parallel to the sheet drawing direction X, are all within 0.2 mm.

[0078] Although one embodiment of the present invention has been described above, the glass substrate and the method for manufacturing a glass substrate according to the present invention are not limited to the above embodiment and may take various forms within the scope of the present invention.

[0079] For example, in the above embodiment, seven evaluation areas A to G are set for one glass substrate 1, and seven corresponding glass samples 11 (the same number as the evaluation areas) are taken, but of course this is not limited to this. For example, three to ten evaluation areas may be set for one glass substrate 1, and the same number of glass samples 11 as the set evaluation areas may be taken from the glass substrate 1, and the front-back deflection difference may be obtained for each of the glass samples 11.

[0080] The size of the evaluation region (i.e., the glass sample 11) is not limited to the above-mentioned dimensions, and may be, for example, a side along the width direction Y of 250 mm or more and 600 mm or less. The size of a side of the evaluation region (glass sample 11) along the drawing direction X of 300 mm or more and 700 mm or less. The support spans M and N are also not limited to the above-mentioned dimensions, and may be, for example, set to 80 to 98% of the size of a side of the glass sample 11 parallel to the width direction Y or the drawing direction X.

[0081] In the above embodiment, a case has been exemplified in which a plurality of glass samples 11 are taken from one glass substrate 1 corresponding to the evaluation regions A to G, and the difference in front and back deflection of each of the glass samples 11 is measured, but other methods can be used. For example, a plurality of glass substrates 1 manufactured on the same manufacturing line are obtained, and glass samples 11 in the number corresponding to the evaluation regions are taken from each of the obtained glass substrates 1. Then, the difference in front and back deflection of each side 12a, 12b, 13a, and 13b of each glass sample 11 is obtained, and the average or maximum value of the plurality of differences in front and back deflection obtained in the same evaluation region is obtained, so that the difference in front and back deflection in the evaluation region can be evaluated.

[0082] In addition, in the above embodiment, the case where the glass ribbon 30 is formed by the overflow downdraw method has been described. However, the glass ribbon 30 may be formed by, for example, other downdraw methods such as a slot downdraw method or a redraw method, or a float method.

[0083] Moreover, the glass substrate 1 according to the above description can be applied to, for example, glass substrates and cover glasses of displays such as liquid crystal displays and organic EL displays. [Explanation of symbols]

[0084] 1 Glass substrate 2 Edge along the drawing direction 3 Edge along the width direction 4 Main surface 11 Sample glass 11a,11b Main surface 12a, 12b Edges along the plate drawing direction 13a, 13b Sides along the width direction 20,20,21,21 Support member 30 Glass Ribbon 30a,30b Main surface 31 Molten Glass 32, 33, 34 Curved section 35 Reversal section 100 Manufacturing equipment 101 Furnace 102 Forming Zone 103 Slow cooling zone 104 Cooling Zone 105 Lola 106 Roller Group 107 Roller shaft 121 Molded body A,B,C,D,E,F,G Evaluation Areas M,N Support span W21a, W21b, W22a, W22b Deflection of edges along the plate drawing direction W31a, W31b, W32a, W32b Deflection of sides along the width direction X Drawing direction Y Width direction

Claims

1. A rectangular glass substrate having a first side along a drawing direction and a second side along a width direction perpendicular to the drawing direction, a plurality of rectangular evaluation areas are set at positions along the direction of the second side, and in at least one of the plurality of evaluation areas, the difference in front-back deflection between two sides parallel to the second side is different in positive and negative, The second side of each of the evaluation areas is 370 mm and the first side is 470 mm; The glass substrate has seven evaluation regions set within an effective zone so as to be equally spaced apart in a direction along the second side.

2. 2 . The glass substrate according to claim 1 , wherein in at least one of the plurality of evaluation regions, the difference in front-back deflection between two sides parallel to the first side is different in sign from the positive one.

3. In all of the multiple evaluation areas, The difference in front-back deflection in each of the two sides parallel to the first side is −0.5 mm or more and +0.5 mm or less, 3. The glass substrate according to claim 1, wherein the difference in front-back deflection in each of the two sides parallel to the second side is −0.5 mm or more and +0.5 mm or less.

4. The glass substrate according to any one of claims 1 to 3, wherein the relatively shorter of the first and second sides is 1100 mm or more and the relatively longer of the first and second sides is 1300 mm or more, and the thickness dimension is 200 μm or more and 1000 μm or less.

5. A method for manufacturing a rectangular glass substrate having a first side along a drawing direction and a second side along a width direction perpendicular to the drawing direction, comprising: forming a ribbon of glass; a cutting step of cutting the glass substrate from the ribbon glass; a step of extracting a rectangular glass sample from the glass substrate, the rectangular glass sample having two sides parallel to the first side and the second side; and measuring a difference in deflection between the front and back sides of the sample glass along a side parallel to the first side.

6. 6. The method for manufacturing a glass substrate according to claim 5, wherein in the measuring step, the difference in the front and back deflections is measured for each of two sides of the sample glass parallel to the first side.

7. The method for manufacturing a glass substrate according to claim 5 or 6, further comprising an evaluation step of evaluating whether a difference between the front and back deflections of the side of the sample glass parallel to the first side measured in the measurement step is positive or negative.

8. 8. The method for manufacturing a glass substrate according to claim 5, wherein in the measuring step, the difference in front-back deflection is measured for each of two sides of the sample glass parallel to the second side.

9. The method for manufacturing a glass substrate according to claim 8 , further comprising an evaluation step of evaluating whether a difference in front-back deflection of a side of the sample glass parallel to the second side measured in the measurement step is positive or negative.

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