JP7636708B2 - Glass substrate and method for manufacturing glass substrate - Google Patents

Description

The present invention relates to a glass substrate and a method for manufacturing a glass substrate.

In recent years, as the glass panels that make up liquid crystal displays and the like have become larger and thinner, the glass substrates used to manufacture the glass panels have inevitably become larger and thinner as well. The technology for manufacturing this type of glass substrate is advancing at a rapid pace, and the current situation is that the level of shape precision required of glass substrates is becoming extremely high.

Here, various evaluation methods have been proposed 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 using a warpage rate obtained by dividing the maximum separation distance between an ideal plane and the back surface of the glass substrate in a direction along a specified side when the glass substrate is placed on an ideal plane (e.g., the top surface of a surface plate) by the total length of the specified side.

Patent Document 2 also proposes a method for evaluating the shape of a glass substrate in a direction perpendicular to the drawing direction by setting multiple rectangular evaluation regions at different positions in a direction perpendicular to the drawing direction and measuring the difference in front and back deflection in the multiple evaluation regions. It also proposes a method for evaluating the change in shape of a glass substrate in a direction perpendicular to the drawing direction by measuring the difference in front and back deflection as described above for multiple glass substrates and determining the amount of change in the difference in front and back deflection in the same evaluation region between the multiple glass substrates.

JP 2013-199426 A JP 2019-137587 A

In the manufacturing process of glass substrates or in the process of manufacturing electronic devices by forming electronic devices on glass substrates, glass substrates may be transported with part of their main surface (rear surface) supported from below, or processed while being held in position. In such cases, even if the warping or bending evaluated as deformation of the entire glass substrate is small, the bending of the glass substrate due to its own weight while supported as described above may appear as deformation that can affect transportation or processing. This type of deformation should be avoided as much as possible from the standpoint of ease of handling, as it may lead to unexpected situations such as contact with surrounding equipment.

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 the shape or its change of a glass substrate is evaluated by this method as being within an acceptable range, depending on the transportation or processing mode, the deflection due to its own weight may appear as a deformation that may affect transportation or processing.

In light of the above, the technical problem to be solved is to provide a glass substrate that is easy to handle during transportation or processing, based on a new evaluation of the shape of the glass substrate.

The above problem is solved by the glass substrate of the present invention. That is, this glass substrate 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 multiple positions along the width direction, and in at least one of the multiple evaluation areas, the difference in front-back deflection between the two sides parallel to the second side is different in sign.

As a result of the inventors' intensive study of the deflection distribution in the glass substrate, they 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 until now. They have also 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 perpendicular to the drawing direction of the glass substrate, and in at least one evaluation area, the positive and negative differences in the front and back deflections on two sides parallel to the second side along the width direction of the glass substrate are different. A glass substrate having a shape in which the positive and negative differences in the front and back deflections on two sides along the width direction of the evaluation area are different in this way 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 stabilizes the shape of the glass substrate during transportation or processing, making it easier to handle the glass substrate.

In addition, in the glass substrate according to the present invention, in at least one of the multiple evaluation regions, the difference in front-back deflection between two sides parallel to the first side may be positive or negative.

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 area but also on two sides along the sheet drawing direction of the evaluation area, the glass substrate has a wavy shape not only in the sheet drawing direction but also in the width direction. This makes the shape of the glass substrate more stable during transportation or processing, making it possible to further improve the handleability of the glass substrate.

Furthermore, in the glass substrate according to the present invention, the side along the width direction of each evaluation area may be 370 mm, and the side along the sheet drawing direction may be 470 mm.

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. In other words, it is possible to avoid a situation in which the size of the evaluation area is too small, resulting in either the peaks or valleys of the waviness shape that should be evaluated being missing from the evaluation area. It is also possible to avoid a situation in which the size of the evaluation area is too large, resulting in the waviness shape in the sheet drawing direction being buried in one evaluation area.

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

If the glass substrate has a front-back deflection difference in each evaluation area that falls within the above-mentioned range, the overall shape will be close to flat. Therefore, even if deflection occurs due to its own weight during transportation or processing, the deflection will be small.

In addition, 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.

The above-mentioned deformation problem becomes more pronounced when glass substrates of the above sizes are manufactured by sheet drawing. Therefore, the present invention is suitable for glass substrates of the above sizes.

The above-mentioned problem is also solved by the glass substrate manufacturing method 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 process for forming a ribbon-shaped glass, a cutting process for cutting a glass substrate from the ribbon-shaped glass, a collection process for collecting a rectangular sample glass from the glass substrate having two sides parallel to the first side and the second side, respectively, and a measurement process for measuring the difference in front and back deflection of the side parallel to the first side of the sample glass.

The manufacturing method of the glass substrate according to the present invention, like the glass substrate according to the present invention, is based on the above-mentioned findings, 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-shaped glass, and the difference in the front and back deflections of the side along the sheet drawing direction of the taken sample glass is measured. According to this method, the shape of the glass substrate in the sheet drawing direction can be known from the deflection direction and the deflection magnitude of the side along the sheet drawing direction of the sample glass. From this, it is possible to evaluate the shape stability when a part of the glass substrate is supported from below, for example, and to select glass substrates with shape stability at a predetermined level or higher. Therefore, according to the manufacturing method of the glass substrate according to the present invention, it is possible to provide a glass substrate with excellent handleability during transportation or processing.

In addition, in the glass substrate manufacturing method according to the present invention, the measurement step may measure the difference in front and back deflection along two sides of the sample glass parallel to the first side.

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

The glass substrate manufacturing method according to the present invention may further include an evaluation step for evaluating the positive or negative difference in the front and back deflections of the side parallel to the first side of the sample glass measured in the measurement step.

In this way, by evaluating the positive/negative difference in the front/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. In addition, by evaluating the positive/negative difference in the front/back warping of 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. 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 width direction.

In addition, in the glass substrate manufacturing method according to the present invention, the measurement step may measure the difference in front and back deflection along two sides of the sample glass parallel to the second side.

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 bending direction and the magnitude of bending of the sides along the width direction of the sample glass. In particular, by measuring the difference in bending between the front and back sides of each of the two sides along the width direction as described above, the number of sample glasses required for measurement can be reduced. This makes it possible to efficiently grasp the shape of the glass substrate in the width direction.

In this case, in the glass substrate manufacturing method according to the present invention, the difference in the front and back deflections of the side parallel to the second side of the sample glass measured in the measurement step may be evaluated as positive or negative.

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 being 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.

As described above, according to the present invention, it is possible to provide a glass substrate that is easy to handle during transportation or processing, based on a new evaluation of the shape of the glass substrate.

FIG. 1 is a plan view of a glass substrate according to an embodiment of the present invention. 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. 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 from the direction of an 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 from the direction of an arrow A2. 3A is a side view of another sample glass in which a difference in front and back deflection is measured by the method shown in FIG. 2, as seen from the direction of arrow A1, and FIG. 3B is a side view of another sample glass in which a difference in front and back deflection is measured by the method shown in FIG. 2, as seen from the direction of arrow A2. 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. 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. 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. 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. 8A is a side view of another sample glass in 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 another sample glass in which a difference in front and back deflection is measured by the method shown in FIG. 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. 6. FIG. 11 is a perspective view showing the state of the glass ribbon in the annealing zone of FIG. FIG. 12 is a cross-sectional view taken along the D1-D1 cutting line of the glass ribbon shown in FIG. FIG. 12 is a cross-sectional view taken along the D2-D2 cutting line of the glass ribbon shown in FIG. 12 is a longitudinal cross-sectional view taken along the E1-E1 cutting line of the glass ribbon shown in FIG. 11. 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. 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. 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.

One embodiment of the present invention will be described below with reference to Figures 1 to 14.

Figure 1 shows a plan view of a glass substrate 1 according to this embodiment. This 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.

The glass substrate 1 has a first side 2 along the 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 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.

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 darkroom 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.

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 evaluated using the difference in the deflection between the front and back surfaces.

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 single glass substrate 1 is set with multiple evaluation areas A to G 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 that they are spaced apart at equal intervals L in the direction along the second side 3. In this case, each evaluation area 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, for example, in a film formation process in a process for manufacturing an electronic device.

Here, each evaluation area A to G is rectangular, and the shape and size of each evaluation area 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 area A to G given here are only examples, and the size of each evaluation area 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, if it is not possible to set all the evaluation areas 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 areas A to G may be set alternately in each row so as to form two rows along the width direction, as shown in FIG. 1.

Then, sample glass 11 with a position, shape, and size corresponding to each evaluation area A to G is taken from the glass substrate 1, and the same number of sample glass 11 as the number of evaluation areas A to G (7 in this case) is obtained per glass substrate 1. At this time, the sample glass 11 is taken from the glass substrate 1 so that one side 12a, 12b of the sample glass 11 is parallel to the drawing direction X of the glass substrate 1, and the other side 13a, 13b of the sample glass 11 is parallel to the width direction Y of the glass substrate 1.

After preparing a predetermined number of sample glasses 11 in this manner, the difference in front-back deflection of the sides 13a, 13b along the width direction Y of each sample glass 11 is measured. Specifically, as shown in FIG. 2, one main surface 11a of the sample glass 11 (for example, the main surface on the guaranteed side, here the main surface on the side included in one main surface 4 of the glass substrate 1) is turned up, and both ends of the sample glass 11 in the width direction Y are supported by a pair of support members 20, 20. At this time, the support span M of the sample glass 11 by the pair of support members 20, 20 is set to, for example, 350 mm. Then, in this state, the magnitude of the first deflection W31a (shown by the solid line in FIG. 3(a)) generated in one side 13a (for example, the downstream side 13a in relation to the sheet drawing direction X) of the two sides 13a, 13b along the width direction Y of the sample glass 11 is measured. Then, the sample glass 11 is turned over, and both ends of the sample glass 11 in the width direction Y are supported by a pair of support members 20, 20 with the other main surface 11b of the sample glass 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 on one side 13a of the sample glass 11 along the width direction Y is measured.

After measuring the first deflection W31a and the second deflection W32a in this manner, 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.

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

By performing the above operations on all the sample glass 11 corresponding to each evaluation area A to G, the direction and magnitude of the deflection in the multiple evaluation areas A to G across the entire width direction Y of the effective zone of the glass substrate 1 can be known. For example, as shown in FIG. 3(a), if the first deflection W31a occurring on one side 13a with one main surface 11a facing upward is larger than the second deflection W32a occurring on one side 13a with the other main surface 11b facing upward, the deflection direction in the area of the glass substrate 1 corresponding to one side 13a of the sample glass 11 is the direction in which one main surface 11a is concave, and the magnitude can be evaluated as the 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, the shape of the glass substrate 1 in the width direction Y can be grasped.

Furthermore, 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.

In this case, the positive and negative of the difference in front and back deflection W31a-W32a of one side 13a and the difference in front and 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 and back deflection W31a-W32a of one side 13a and the difference in front and back deflection W31b-W32b of the other side 13b are equal in positive and negative, the cross section along the sheet drawing direction X of the portion of the glass substrate 1 from which the sample glass 11 was taken (one of the evaluation areas A to G) forms a shape that is deflected in one direction from the front to the back, as shown in Figure 5.

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 differences W31a-W32a and W31b-W32b may differ (be reversed) between 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 of the glass substrate 1 from which the sample glass 11 was taken (any one of the evaluation areas A to G) 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 wavy shape, as shown in Figure 6. In this way, it is possible to grasp the shape of the glass substrate 1 in the drawing direction X.

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

First, a predetermined number of sample glasses 11 corresponding to the evaluation areas A to G shown in FIG. 2 are prepared, and then the difference in the front and back deflections of the sides 12a and 12b along the drawing direction X of each sample glass 11 is measured. Here, the sample glass 11 prepared may be the sample glass 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 sample glass 11 is facing upward, and both ends of the sample glass 11 in the drawing direction X are supported by a pair of support members 21, 21. At this time, the support span N of the sample glass 11 by the pair of support members 21, 21 is set to, for example, 450 mm. Then, in this state, the magnitude of the first deflection W21a (indicated by the solid line in FIG. 8(a)) generated in one side 12a (the left side 12a in FIG. 7) of the two sides 12a and 12b of the sample glass 11 along the drawing direction X is measured. After that, the sample glass 11 is turned over, and both ends of the sample glass 11 in the drawing direction X are supported by a pair of support members 21, 21 with the other main surface 11b of the sample glass 11 facing upward (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 sample glass 11 along the drawing direction X is measured.

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 between the front and back deflections of one edge 12a along the plate drawing direction X.

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

By performing the above operations on all sample glasses 11 corresponding to each evaluation area A to G, the direction and magnitude of the deflection in the drawing direction X in the multiple evaluation areas A to G in the effective zone of the glass substrate 1 can be known. For example, as shown in FIG. 8(a), if the first deflection W21a occurring on one side 12a with one main surface 11a facing upward is larger than the second deflection W22a occurring on one side 12a with the other main surface 11b facing upward, the deflection direction in the area 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 magnitude can be evaluated as the 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, the shape of the glass substrate 1 in the drawing direction X can be grasped.

Furthermore, 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 difference in the front and back deflections of the other edge 12b along the plate drawing direction X.

In this case, the positive and negative of the difference in front-back bending W21a-W22a of one side 12a and the difference in front-back bending 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 bending W21a-W22a of one side 12a and the difference in front-back bending 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 evaluation areas A to G) from which the sample glass 11 of the glass substrate 1 was taken will have a shape that is bent in one direction, front to back, although this is not shown.

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 differences W21a-W22a and W21b-W22b may differ (be reversed) between 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 part (any one of the evaluation areas A to G) from which the sample glass 11 of the glass substrate 1 was taken has a shape (wavy shape) in which the deflection direction is reversed in the width direction Y, although not shown. In this way, it becomes possible to grasp the shape of the glass substrate 1 in the width direction Y.

In addition, in the glass substrate 1 evaluated as described above, in all of the evaluation areas 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-back deflection differences described above, the positive and negative of the front-back deflection difference W31a-W32a of one side 13a along the width direction Y in at least one of the evaluation areas A to G of the glass substrate 1 is reversed, and it is preferable that the absolute values of the front-back deflection differences W21a-W22a, W21b-W22b, W31a-W32a, and W31b-W32b of the four sides 12a, 12b, 13a, and 13b in all evaluation areas A to G are all within 0.5 mm, and more preferably within 0.3 mm.

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

Figure 10 is a vertical cross-sectional view showing the main parts of a manufacturing apparatus 100 for manufacturing the glass substrate 1 according to this embodiment. This manufacturing apparatus 100 forms a glass ribbon 30 as a band-shaped glass that becomes the glass substrate 1 in a furnace 101 by the overflow downdraw method.

In detail, within the furnace 101, from the top, there are provided 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, there is provided a cutting zone (not shown) where the cutting process is performed.

In the forming zone 102, molten glass 31 is supplied to a forming body 121 having a wedge-shaped cross-sectional shape, and the molten glass 31 overflowing from the top of this forming 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 prevent distortion from occurring inside. 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 manufactured.

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 is composed of 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, as shown in FIG. 11. 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 roller 105 may be cantilevered by the roller shaft 107.

In the annealing zone 103, as shown in FIG. 11, a portion of the glass ribbon 30, which is generally flat, 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 concaves and convexes of the curved portion 32 is reversed in the front and back directions at a predetermined position in the drawing direction X of the glass ribbon 30.

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 center of 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 shown by the dashed 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.

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 curved shape in which the center of the glass ribbon 30 in the width direction Y is convex on one main surface 30a side and concave on the other main surface 30b side, as shown in FIG. 13.

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

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 FIGS. 11 to 14. Such changes in the curved shape of the first curved portion 33 and the second curved portion 34 are repeated. One cycle of such changes may take, for example, 1 to 3 seconds.

As described above, when the shape of the glass substrate 1 cut from such a glass ribbon 30 is evaluated based on the difference in front and back warping along the sheet drawing direction X, the positive and negative of the front and back warping differences W31a-W32a and W31b-W32b of the two sides 13a and 13b along the width direction Y are reversed, as shown in Figures 4(a) and 4(b). That is, as shown in Figure 6, the glass substrate 1 has a wavy shape in the sheet drawing direction X. Therefore, with this wavy glass substrate 1, it is possible to prevent the warping due to its own weight from becoming apparent in one direction, and to suppress deformation during transportation or processing. As a result, the shape of the glass substrate 1 during transportation or processing is stable, making it possible to improve the handleability of the glass substrate 1.

Here, examples of methods for changing the curved shape of the first curved portion 33 and the second curved portion 34 of the glass ribbon 30 include the following means.

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.

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

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 plate drawing direction X change according to the amount of bending dt (see Figures 12 and 13) of the first curved portion 33 and the second curved portion 34. In other words, if the amount of bending dt is made small, for example, if the amount of bending dt is set 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 plate drawing direction X can be made to be -0.5 mm or more and +0.5 mm or less.

An example of the results of evaluating the shape accuracy of the glass substrate 1 manufactured in the above manner based on the difference in the deflection between the front and back sides is shown in Figures 15 to 17.

Figure 15 shows the evaluation results of the front-back deflection difference in the width direction Y in each evaluation area A to G of a glass substrate 1 for comparison with the present invention. Here, the front-back deflection difference in the width direction Y shown in Figure 15 is expressed as the difference between the deflections W31a, W31b, W32a, and W32b measured on the same side 13a (13b) after taking a sample glass 11 corresponding to the evaluation areas A to G from the glass substrate 1 to be evaluated as shown in Figures 2 and 3 and measuring the deflections W31a, W31b, W32a, and W32b caused by the weight of the two sides 13a and 13b of the sampled sample glass 11 along the width direction Y. The solid line in Figure 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 Figure 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.

Figure 16 shows the evaluation results of the difference in front and back deflection in the width direction Y in each evaluation area A to G of the glass substrate 1 according to the present invention. Here, the differences in front and back deflection in the width direction Y shown in Figure 16 were obtained in the same manner as the differences in front and back deflection shown in Figure 15, and were graphed in the same manner, except that the glass substrate 1 being evaluated is different.

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

As shown in FIG. 15, in the glass substrate 1 for comparison 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 of the downstream side 13a and the upstream side 13b match, or one of them is substantially zero.

In contrast, as shown in Figure 16, in the glass substrate 1 according to the present invention, the positive and negative difference in the front and back deflection in the width direction Y is reversed in the predetermined evaluation areas B and C. From this, it is presumed that in at least the areas of the glass substrate 1 according to the present invention corresponding to the evaluation areas B and C, the direction of the front and back deflection is reversed between the downstream side and the upstream side, forming a wavy shape in the sheet drawing direction X as shown in Figure 6.

As shown in Figure 17, in the glass substrate 1 according to the present invention, the positive and negative difference in the front and back deflection in the 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 direction of the front and back deflection is reversed between one side and the other side in the width direction, forming a wavy shape in the width direction Y as shown in Figure 6.

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

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

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 difference in front and back deflection may be obtained for each glass sample 11.

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

In the above embodiment, a case was exemplified in which multiple glass samples 11 were taken from one glass substrate 1 corresponding to the evaluation areas A to G, and the difference in front and back deflection of each glass sample 11 was measured, but other methods can also be used. For example, multiple glass substrates 1 manufactured on the same production line are obtained, and a number of glass samples 11 corresponding to the evaluation area are taken from each obtained glass substrate 1. Then, the front and back deflection differences of each side 12a, 12b, 13a, and 13b of each glass sample 11 are obtained, and the average or maximum value of the multiple front and back deflection differences obtained in the same evaluation area is calculated, thereby evaluating the front and back deflection difference in the evaluation area.

In the above embodiment, the glass ribbon 30 is formed by the overflow downdraw method. However, the glass ribbon 30 may be formed by other downdraw methods such as the slot downdraw method or the redraw method, or by the float method.

The glass substrate 1 described above can be used as a glass substrate or cover glass for displays such as liquid crystal displays and organic electroluminescence displays.

1 Glass substrate 2 Side along the sheet drawing direction 3 Side along the width direction 4 Main surface 11 Sample glass 11a, 11b Main surface 12a, 12b Side along the sheet drawing direction 13a, 13b Side along the width direction 20, 20, 21, 21 Support member 30 Glass ribbon 30a, 30b Main surface 31 Molten glass 32, 33, 34 Curved portion 35 Inverted portion 100 Manufacturing apparatus 101 Furnace 102 Forming zone 103 Annealing zone 104 Cooling zone 105 Roller 106 Roller group 107 Roller shaft 121 Formed body A, B, C, D, E, F, G Evaluation area M, N Support span W21a, W21b, W22a, W22b Deflection of side along the sheet drawing direction W31a, W31b, W32a, W32b Deflection of side along the width direction X Plate drawing direction Y Width direction

Claims (9)

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 . The glass substrate according to claim 1, wherein in at least one of the multiple evaluation areas, the difference in front-back deflection between two sides parallel to the first side is different in sign. In all of the plurality of evaluation regions,
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 a 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. 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 side is 1300 mm or more, and the thickness dimension is 200 µm or more and 1000 µm or less. 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. 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. 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. 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. The method for manufacturing a glass substrate according to claim 8 , 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 second side measured in the measurement step is positive or negative.

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