Glass plate, method for manufacturing glass plate, method for manufacturing glass plate with resin film, method for manufacturing resin film, and glass plate manufacturing apparatus

Abstract

A rectangular glass sheet 1 has first edges 1y extending along a sheet-pulling direction Y and second edges 1x extending along a width direction X. The lengths of the first edges 1y and the second edges 1x are at least 1000 mm. The thickness of the glass sheet 1 is 0.1-2.0 mm. When five rectangular assessment regions A-E having the same size are sequentially set from one end in the width direction X, the absolute value of the average of the obverse-reverse warp differences X1-X2 in the width direction X in the assessment regions A-E is 0.06-0.8 mm.

Description

Glass plate, glass plate manufacturing method, and glass plate manufacturing apparatus

[0001] The present invention relates to a curved glass sheet and a manufacturing technique thereof.

[0002] 2. Description of the Related Art In the manufacturing process of electronic devices such as panel displays (for example, liquid crystal displays, organic EL displays, and plastic organic EL displays), a film formation step is carried out to form a film on a glass plate (mother glass).

[0003] As an example of this film formation process, Patent Document 1 discloses a method for producing a thin film device by forming a metal film on the convex surface of a glass plate having a curved dome or bowl shape through a film formation process involving heating, and then cooling the thin film device to near room temperature (including natural cooling).

[0004] According to this technique, during the cooling process of a thin-film device on which a metal film is formed, tensile stress acts on the metal film because the thermal expansion coefficient of the metal film is larger than that of the glass plate, which is expected to flatten the shape of the glass plate and, ultimately, the thin-film device.

[0005] The same document also discloses a method for producing a curved glass sheet by adjusting the thermal profile and thermal history during the formation of a glass ribbon using an overflow downdraw method or the like.

[0006] Furthermore, the same document discloses that the shape of a glass plate cut out from the above-mentioned glass ribbon is measured in a zero-gravity state in order to know the shape of the glass plate.

[0007] On the other hand, Patent Document 2 discloses the introduction of the concept of a difference in front and back deflection in evaluating the curved shape of a glass plate.

[0008] In detail, the document discloses that a plurality of evaluation regions are set on a glass plate, the deflection of sample glass corresponding to these regions is measured to determine the difference between the deflection on the front and back sides, and the curved shape of the glass plate is evaluated based on this difference between the deflection on the front and back sides.

[0009] Patent Publication No. 2018-506497 International Publication No. 2022 / 097537

[0010] Incidentally, Patent Document 1 merely discloses an apparatus for manufacturing a curved glass sheet, which is an apparatus having a general configuration for manufacturing a glass sheet by an overflow downdraw method (see FIG. 13 in the same document). Therefore, as described above, it is difficult to obtain a glass sheet having an appropriate curved shape for performing a film formation treatment involving heating, simply by adjusting the thermal profile or thermal history during the formation of a glass ribbon.

[0011] Here, the film formation process involving heating refers to, for example, a process in which a film material is applied to the main surface of a glass plate and then baked to harden the film material. In the following description, the "film formation process involving heating" will be simply referred to as the "thermal film formation process."

[0012] Furthermore, as disclosed in Patent Document 1, when the shape of a glass plate is measured in a state of zero gravity, there is a risk of large measurement errors occurring, and the measurement and post-processing take time, making it difficult to accurately and quickly measure the shape of the glass plate and obtain a glass plate with a curved shape suitable for performing a thermal film-forming process.

[0013] Furthermore, a glass sheet formed by a down-draw method or a float method has a sheet drawing direction and a width direction perpendicular to the sheet drawing direction, but Patent Document 1 does not distinguish between the sheet drawing direction and the width direction when measuring and evaluating the glass sheet, which results in insufficient measurement and evaluation to obtain a glass sheet having an appropriate curved shape for performing a thermal film-forming treatment.

[0014] On the other hand, in Patent Document 2, measurements and evaluations are performed separately in the sheet drawing direction and the width direction, but the technical solution disclosed in this document is for properly adsorbing the convex surface of a curved glass sheet to an adsorption surface plate. Therefore, even if the technical solution disclosed in this document is applied to a technical solution for performing a thermal film formation process on a curved glass sheet, it is not possible to obtain an appropriate configuration and effect.

[0015] The present inventors have also conducted research into forming a resin film on the convex surface of a curved glass plate by a thermal film-forming process, flattening the glass plate by cooling, and then peeling the resin film from the glass plate to use the film in the manufacture of electronic devices. In this research, if the glass plate is not flattened when cooled to near room temperature, peeling the resin film from the glass plate becomes difficult. Therefore, in this case too, it is important to obtain a glass plate with an appropriate curved shape for the thermal film-forming process.

[0016] In view of the above, an object of the present invention is to provide a glass plate having a curved shape suitable for carrying out a thermal film-forming treatment, and a manufacturing technique thereof.

[0017] (a) A first aspect of the present invention, which has been devised to solve the above-mentioned problems, is a rectangular glass plate having a first main surface and a second main surface on the back side of the first main surface, a first side along the sheet drawing direction and a second side along the width direction perpendicular to the sheet drawing direction, wherein the lengths of the first side and the second side are 1000 mm or more and the plate thickness is 0.1 mm or more and 2.0 mm or less, and is characterized in that when five rectangular evaluation areas of the same size are set in order from one end side in the width direction, the absolute value of the average value of the front-to-back deflection differences in the width direction of the five evaluation areas, which is calculated by the following formula (1), is 0.06 mm or more and 0.8 mm or less. Front-to-back deflection difference=(X1−X2) (1) X1: deflection [mm] in the width direction of the sample glass corresponding to the evaluation area where the front-to-back deflection difference is measured when the first main surface faces downwards, and X2: deflection [mm] in the width direction of the sample glass corresponding to the evaluation area where the front-to-back deflection difference is measured when the second main surface faces downwards.

[0018] According to this configuration, the glass sheet has a curved shape in which either the first or second principal surface is convex in the width direction. Furthermore, since the absolute value of the average value of the front-to-back deflection difference is 0.06 mm or more and 0.8 mm or less, the degree of curvature of the glass sheet in the width direction is large. Therefore, when a thermal film formation process is performed on the convex surface of the glass sheet, the shape of the glass sheet can be flattened when cooled to near room temperature, even if the thermal expansion coefficient of the film is significantly higher than that of the glass sheet. Therefore, even when cooled to near room temperature, it is possible to avoid a situation in which the shape of the glass sheet becomes improperly curved due to the difference in thermal expansion between the film and the glass sheet. This makes it possible to obtain a glass sheet with an appropriate curved shape for performing a thermal film formation process.

[0019] (b) In the above configuration (a), it is preferable that the average value of the difference in front and back deflection in the width direction of the five evaluation areas is 0.15 mm or more.

[0020] In this way, it is possible to more reliably obtain a glass sheet having an appropriate curved shape for carrying out the thermal film-forming treatment.

[0021] (c) In the configuration of (a) or (b) above, it is preferable that the average value of the difference in front-to-back deflection in the width direction of the five evaluation areas is positive, and that the difference in front-to-back deflection in the width direction of the five evaluation areas is all greater than -0.2 mm and less than 1.0 mm.

[0022] In this way, the glass plate has a curved shape with a convex first principal surface because the average value of the difference in the front-to-back deflections is positive (greater than 0). Furthermore, because the difference in the front-to-back deflections is −0.2 mm or more and 1.0 mm or less, the variation in the difference in the front-to-back deflections in the width direction of the glass plate can be reduced. This allows the first principal surface to have a smoothly curved convex surface over the entire length or substantially the entire length in the width direction. Therefore, when the glass plate is used to form a film on the first principal surface to manufacture a film-coated device, the thermal film-forming process on the first principal surface is properly performed, and a high-quality film-coated device can be obtained. Furthermore, when the glass plate is used to peel the film from a film-coated glass plate obtained by forming a film on the first principal surface, in addition to optimizing the thermal film-forming process, the film-peeling operation is properly performed.

[0023] (d) In the configuration (c) above, it is preferable that the first principal surface is a guaranteed surface and the second principal surface is a non-guaranteed surface.

[0024] This is a preferred embodiment, as it allows a film to be formed on the safe surface of the glass plate.

[0025] (e) In any of the above configurations (a) to (d), it is preferable that the difference between the maximum value and the minimum value of the difference in front-to-back deflection in the width direction of the five evaluation areas is 2.0 mm or less.

[0026] This arrangement can more reliably reduce the variation in the difference in the deflection between the front and back surfaces of the glass sheet in the width direction, thereby enabling the convex surface of the glass sheet to be smoothly curved over the entire or substantially entire length in the width direction, and thus achieving the same advantages as those described above even more reliably.

[0027] (f) In any one of the above (a) to (e), the linear thermal expansion coefficient at 30 to 380°C is 30 x 10 -7 / ℃ or more 50 × 10 -7 / °C or less is preferred.

[0028] Here, a polyimide resin film may be formed on the convex surface of the glass plate according to the first aspect of the present invention. In this case, the linear thermal expansion coefficient of the resin film is within the above-mentioned range. Therefore, by appropriately addressing the difference in thermal expansion between the resin film and the glass plate, the shape of the glass plate can be more reliably flattened when cooled to near room temperature.

[0029] (g) In any of the above configurations (a) to (f), it is preferable that the thermal shrinkage rate when held at 500° C. for 1 hour is 30 ppm or less.

[0030] This suppresses shrinkage (compaction) of the glass plate when a thermal film formation process is performed on the convex surface of the glass plate. Such a characteristic is particularly required for high-resolution displays. Therefore, the present configuration makes the glass plate suitable for use as a glass plate for high-resolution displays.

[0031] (h) In any of the above configurations (a) to (g), it is preferable that the transmittance in the plate thickness direction at a wavelength of 308 nm is 60% or more and 85% or less.

[0032] Here, a polyimide resin film may be formed on the convex surface of the glass plate according to the first aspect of the present invention by a thermal film-forming process. In this case, the glass plate may be used to peel a film from a film-coated glass plate obtained by forming a film on the glass plate. In this case, an ultraviolet laser may be used as a method for peeling the polyimide resin film from the glass plate. Considering that the wavelength of the ultraviolet laser is 308 nm, the glass plate has an appropriate transmittance in the thickness direction in that wavelength range. This allows the work of peeling the polyimide resin film from the glass plate to be performed appropriately and reliably.

[0033] (i) In any of the above structures (a) to (h), the glass composition preferably contains, in mole percent, 60 to 70% SiO, 9.5 to 17% AlO, 0 to 9% BO, 0 to less than 1% LiO+NaO+KO, 0 to 8% MgO, 2 to 15% CaO, 0 to 10% SrO, and 0.1 to 5% BaO.

[0034] In this way, the liquidus viscosity and Young's modulus can be increased.

[0035] (j) In any of the above structures (a) to (h), the glass composition preferably contains, in mole percent, 62 to 72% SiO, 9.5 to 16% AlO, 1 to 8% BO, 0 to less than 1% LiO+NaO+KO, 1 to 9% MgO, 2 to 10% CaO, 0.1 to 5% SrO, and 0.1 to 5% BaO.

[0036] In this way, the liquidus viscosity and Young's modulus can be increased.

[0037] (k) In any of the above structures (a) to (h), the glass composition preferably contains, in mole percent, 67 to 77% SiO, 9 to 14% AlO, 0 to 3% BO, 0 to less than 1% LiO+NaO+KO, 0 to 5% MgO, 0 to 10% CaO, 0 to 5% SrO, and 0 to 7% BaO.

[0038] This makes it easier to increase the strain point to 730°C or higher.

[0039] (l) A second aspect of the present invention, which has been invented to solve the above-mentioned problems, is a method for manufacturing a glass sheet, comprising: a forming step of forming a glass ribbon from molten glass; an annealing step of annealing the glass ribbon while conveying it by a conveying device; and a cutting step of cutting the annealed glass ribbon into rectangular glass sheets, wherein the glass ribbon has a first main surface and a second main surface on the back side of the first main surface, and a sheet thickness of 0.1 mm or more and 2.0 mm or less, and the annealing step is characterized in that both widthwise end portions of the glass ribbon are supported from the first main surface side and the second main surface side by a plurality of roller pairs in the conveying device, and both widthwise end portions of the glass ribbon are supported from only the second main surface side by a bias roller biased toward the first main surface side of the glass ribbon at at least one location in the conveying direction of the glass ribbon in the conveying device.

[0040] According to this configuration, the glass sheet according to the first aspect of the present invention can be appropriately manufactured. More specifically, according to this manufacturing method, a glass ribbon having a more appropriately curved shape can be obtained, compared to a case where, for example, at least one location on the conveying path, both widthwise end portions of the glass ribbon are supported from both main surface sides by a pair of biasing rollers biased toward the first main surface of the glass ribbon. That is, when both widthwise end portions of the glass ribbon are supported from both main surface sides by a pair of biasing rollers, even if the glass ribbon has a curved shape such that the first main surface is convex at the widthwise center portion, both widthwise end portions are sandwiched between the pair of biasing rollers and become flat. In contrast, when both widthwise end portions of the glass ribbon are supported only from the second main surface side by the biasing rollers, the widthwise end portions are not sandwiched, and therefore not only the widthwise center portion but also both widthwise end portions are curved toward the first main surface side. This allows the degree of curvature of the glass ribbon and therefore the glass sheet in the width direction to be increased. As a result, a glass sheet having the same advantages as the glass sheet according to the first aspect of the present invention can be obtained.

[0041] (m) In the above configuration (l), it is preferable that the first principal surface is a guaranteed surface and the second principal surface is a non-guaranteed surface.

[0042] This provides a glass plate having a curved shape with a convex guaranteed surface, which is a preferred embodiment since it allows a film to be formed on the guaranteed surface.

[0043] (n) In the configuration of (l) or (m) above, it is preferable that the bias amount of the bias roller is 1 mm or more and 20 mm or less.

[0044] In this way, the degree of curvature in the width direction of the resulting glass sheet can be made sufficiently large.

[0045] (o) A third aspect of the present invention, which has been invented to solve the above-mentioned problems, is a glass plate manufacturing apparatus including: a forming furnace that forms, from molten glass, a glass ribbon having a first main surface and a second main surface behind the first main surface; an annealing furnace that anneals the glass ribbon while conveying it using a conveying device; and a cutting device that cuts the annealed glass ribbon into rectangular glass plates, wherein the conveying device is characterized by including: a plurality of roller pairs that support both widthwise end portions of the glass ribbon from the first main surface side and the second main surface side; and a bias roller that is provided at at least one location on a conveying path of the glass ribbon and is biased toward the first main surface side of the glass ribbon to support both widthwise end portions of the glass ribbon from only the second main surface side.

[0046] This manufacturing apparatus can implement the manufacturing method according to the second aspect of the present invention described above, and can therefore provide substantially the same effects as those of the manufacturing method.

[0047] According to the present invention, a glass plate having a curved shape suitable for carrying out a thermal film-forming treatment and a manufacturing technique thereof are provided.

[0048] 11 is a plan view showing a glass plate according to an embodiment of the present invention. FIG. 12 is a plan view illustrating a method for measuring a difference in front-to-back deflection in the width direction of a glass sample cut out from a glass plate. FIG. 13 is a side view of a glass sample for which a difference in front-to-back deflection is measured by the method shown in FIG. 2, as viewed from the direction of arrow I. FIG. 14 is a plan view illustrating a method for measuring a difference in front-to-back deflection in the sheet drawing direction of a glass sample cut out from a glass plate. FIG. 15 is a side view of a glass sample for which a difference in front-to-back deflection is measured by the method shown in FIG. 4, as viewed from the direction of arrow II. FIG. 16 is a longitudinal sectional side view illustrating an example of use of a glass plate according to an embodiment of the present invention. FIG. 17 is a longitudinal sectional side view illustrating a schematic configuration of a glass plate manufacturing apparatus according to an embodiment of the present invention. FIG. 18 is a longitudinal front view illustrating a schematic configuration of a glass plate manufacturing apparatus according to an embodiment of the present invention, as viewed from the right side of the manufacturing apparatus of FIG. 7. FIG. 19 is an enlarged longitudinal sectional side view showing a main part of a glass plate manufacturing apparatus according to an embodiment of the present invention and a shape of a glass ribbon. FIG. 19 is a cross-sectional plan view cut along line D-D of FIG. 9. FIG. 11 is an enlarged longitudinal sectional side view showing a main part of a glass plate manufacturing apparatus and a shape of a glass ribbon, for explaining problems of the related art. FIG. 12 is a cross-sectional plan view cut along line E-E of FIG.

[0049] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A glass sheet, a glass sheet manufacturing apparatus, and a glass sheet manufacturing method according to embodiments of the present invention will be described below with reference to the accompanying drawings.

[0050] 1 , a glass sheet 1 according to this embodiment is produced by a known forming method, for example, a downdraw method such as an overflow downdraw method, a slot downdraw method, or a redraw method, or a float method. In this embodiment, a glass ribbon is formed by the overflow downdraw method, and a rectangular glass sheet 1 of a predetermined size is obtained by cutting from this glass ribbon.

[0051] The glass sheet 1 has a first side 1y extending along the drawing direction Y and a second side 1x extending along the width direction X perpendicular to the drawing direction Y. The drawing direction Y of the glass sheet 1 can be observed as a striped pattern, for example, by irradiating light from a light source (e.g., a xenon light) on the glass sheet 1 in a darkroom while adjusting the angle of the glass sheet 1 and projecting the transmitted light onto a screen. Therefore, the drawing direction Y during forming can be identified even for the glass sheet 1 after it has been cut out.

[0052] The glass plate 1 has a first main surface designated as a guaranteed surface 1a and a second main surface on the reverse side of the first main surface designated as a non-guaranteed surface 1b. The guaranteed surface 1a is guaranteed to have a predetermined quality, and is maintained in a non-contact state as much as possible during each step of the conveyance, processing, etc. of the glass plate 1. In contrast, the non-guaranteed surface 1b is a contact surface that comes into contact with a conveyance device or the like during each step of the conveyance, processing, etc.

[0053] An example of the glass plate 1 is a low-alkali glass plate for displays. Here, examples of the "display" include a liquid crystal display, an organic EL display, and a plastic organic EL display. Furthermore, "low-alkali glass" refers to glass with a low content of alkali components (alkali metal oxides) or glass that is substantially free of alkali components.

[0054] A specific composition of low-alkali glass preferably contains, in mole percent, 60 to 75% SiO, 5 to 20% AlO, 0 to 15% BO, 0 to less than 1% LiO + NaO + KO (total amount of LiO, NaO and KO), 0 to 10% MgO, 0 to 15% CaO, 0 to 10% SrO, and 0 to 10% BaO, and among these, the following glass composition examples are particularly preferred.

[0055] An example of the first glass composition contains, in mole percent, 60 to 70% SiO, 9.5 to 17% AlO (particularly 11 to 15%), 0 to 9% BO (particularly 5 to 7%), 0 to less than 1% LiO + NaO + KO (particularly 0 to 0.5%), 0 to 8% MgO (particularly 2 to 6%), 2 to 15% CaO (particularly 6 to 11%), 0 to 10% SrO (particularly 0.1 to 3%), and 0.1 to 5% BaO. This can increase the liquidus viscosity and Young's modulus.

[0056] An example of the second glass composition contains, in mole percent, 62 to 72% SiO, 9.5 to 16% (particularly 11 to 15%) AlO, 1 to 8% (particularly 2 to 4%) BO, 0 to less than 1% (particularly 0 to 0.5%) of LiO + NaO + KO, 1 to 9% (particularly 4 to 8%) MgO, 2 to 10% (particularly 3 to 8%) CaO, 0.1 to 5% (particularly 1 to 3%) SrO, and 0.1 to 5% (particularly 1 to 3%) BaO. This can increase the liquidus viscosity and Young's modulus.

[0057] An example of the third glass composition contains, in mole percent, 67-77% SiO, 9-14% AlO, 0-3% (particularly 0-less than 1%) BO, 0-1% (particularly 0-0.5%) of LiO + NaO + KO, 0-5% (particularly 2-5%) MgO, 0-10% (particularly 6-9%) CaO, 0-5% SrO, and 0-7% (particularly 3-6%) BaO. This makes it easier to raise the strain point to 730°C or higher.

[0058] SiO2 is a component that forms the skeleton of glass, raises the strain point, and enhances acid resistance. On the other hand, if the SiO2 content is high, the high-temperature viscosity increases, the melting property decreases, and devitrified crystals such as cristobalite tend to precipitate, raising the liquidus temperature.

[0059] Al2O3 is a component that forms the glass skeleton, raises the strain point, and increases the Young's modulus. On the other hand, if the Al2O3 content is high, devitrified crystals such as mullite and feldspar are likely to precipitate, raising the liquidus temperature.

[0060] B2O3 is a component that improves melting properties and devitrification resistance. On the other hand, a high B2O3 content lowers the strain point and Young's modulus, which increases the thermal shrinkage rate and makes pitch deviation more likely to occur during the panel manufacturing process.

[0061] MgO is a component that reduces high-temperature viscosity, improves melting property, and increases Young's modulus. On the other hand, a high MgO content promotes the precipitation of mullite, Mg- and Ba-derived crystals, and cristobalite crystals. Furthermore, a high MgO content significantly lowers the strain point.

[0062] CaO is a component that reduces high-temperature viscosity and significantly improves melting property without lowering the strain point. Furthermore, CaO is a component that reduces raw material costs because the raw material used is relatively inexpensive among alkaline earth metal oxides. Furthermore, CaO is a component that increases Young's modulus. CaO also has the effect of suppressing the precipitation of devitrified crystals containing Mg. On the other hand, a high CaO content makes it easier for anorthite devitrified crystals to precipitate and increases the density.

[0063] SrO is a component that suppresses phase separation and improves devitrification resistance. Furthermore, it is a component that reduces high-temperature viscosity and improves meltability without lowering the strain point. On the other hand, if the SrO content is high, feldspar-based devitrification crystals tend to precipitate in glasses containing a large amount of CaO, which can lead to a decrease in devitrification resistance. Furthermore, if the SrO content is high, the density tends to increase and the Young's modulus tends to decrease.

[0064] Among alkaline earth metal oxides, BaO is a component that is highly effective in suppressing the precipitation of mullite-based and anorthite-based devitrified crystals. On the other hand, if the BaO content is high, the density increases, the Young's modulus tends to decrease, and the high-temperature viscosity becomes too high, which tends to decrease the melting property.

[0065] The length of the first side 1y and the length of the second side 1x of the glass plate 1 are both 1000 mm or more, preferably 1200 mm or more, and more preferably 1500 mm or more. Furthermore, these lengths are 4000 mm or less, preferably 3000 mm or less, and more preferably 2000 mm. In this embodiment, the length of the first side 1y is 1500 mm, and the length of the second side 1x is 1850 mm.

[0066] The thickness of the glass plate 1 is 0.1 mm or more, preferably 0.2 mm or more, more preferably 0.3 mm or more, even more preferably 0.4 mm or more, and most preferably 0.5 mm or more. The thickness of the glass plate 1 is 2.0 mm or less, preferably 1.8 mm or less, more preferably 1.5 mm or less, even more preferably 1.2 mm or less, and most preferably 0.9 mm or less.

[0067] The shape of the glass sheet 1, in this case the shape along the width direction X of the glass sheet 1, can be evaluated using the difference in front-to-back deflection. A method for evaluating the shape of the glass sheet 1 along the width direction X using the difference in front-to-back deflection X1-X2 will be described below.

[0068] As shown in FIG. 1 , five rectangular evaluation areas A, B, C, D, and E are set on a single glass plate 1 at different positions in the width direction X. The evaluation areas A to E are set in order from one end of the width direction X. The evaluation areas B, C, and D are arranged in a line along the width direction X with no gaps between them. The evaluation areas A and E are also positioned in a different position in the drawing direction Y from the evaluation areas B to D. The evaluation area A partially overlaps with the evaluation area B in the width direction X, and the evaluation area E partially overlaps with the evaluation area D in the width direction X. In this embodiment, the five evaluation areas A to E are set over the entire length of the glass plate 1 in the width direction X, from one end to the other end. Here, each of the five evaluation areas A to E is rectangular, with a side 2x along the width direction X having a length of 400 mm and a side 2y along the drawing direction Y having a length of 500 mm.

[0069] Glass sample pieces 3 (see FIGS. 2 and 4), which are glass pieces with positions and sizes corresponding to the evaluation regions A to E, are collected from the glass plate 1, and five glass sample pieces 3 corresponding to the evaluation regions A to E are obtained for each glass plate 1. That is, the glass sample 3 has a side 3y along the sheet drawing direction Y, which corresponds to the side 2y of the evaluation regions A to E, and a side 3x along the width direction X, which corresponds to the side 2x of the evaluation regions A to E.

[0070] After preparing five glass samples 3 in this manner, the difference X1-X2 between the front and back deflections in the width direction X of each glass sample 3 is measured. Specifically, as shown in FIG. 2 , the guaranteed surface 3a of the glass sample 3 (the surface on the same side as the guaranteed surface 1a of the glass sheet 1) is placed downward, and both ends of the glass sample 3 in the width direction X are supported by a pair of support members 4. In this case, the support span M of the glass sample 3 by the pair of support members 4 is set to 380 mm when the length of the side 3x along the width direction X is 400 mm and the length of the side 3y along the drawing direction Y is 500 mm. In other cases, it is set to a value obtained by subtracting 20 mm from the length of the side 3x along the width direction X of the glass sample 3. In this state, the magnitude of the first deflection X1 (indicated by the solid line in the figure) of the glass sample 3 in the width direction X is measured, as shown in FIG. In this measurement, the first deflection X1 is measured for each of two parallel sides 3x along the width direction X of the glass sample 3, and the larger of the two values ​​is adopted as the first deflection X1. The magnitude of the adopted first deflection X1 is converted to the first deflection X1 when the support span M is 350 mm. For example, when the support span M is M1 (any value) mm, the conversion is performed by X1 × (350 / M1).

[0071] Similarly, the glass sample 3 is turned upside down, and both ends of the glass sample 3 in the width direction X are supported by a pair of support members 4 with the non-protected surface 3b of the glass sample 3 (the surface on the same side as the non-protected surface 1b of the glass plate 1) facing downward. In this state, as shown in FIG. 3 , the magnitude of the second deflection X2 (indicated by the dashed line in the figure) in the width direction X of the glass sample 3 is measured. In this measurement, the second deflection X2 is measured for each of two parallel sides 3x of the glass sample 3 along the width direction X, and the larger of the two measured values ​​is adopted as the second deflection X2. The magnitude of the adopted second deflection X2 is converted to the second deflection X2 when the support span M is 350 mm.

[0072] After measuring the first deflection X1 and the second deflection X2 in this manner, the difference in front and back deflection in the width direction X, X1-X2, is obtained by subtracting the second deflection X2 from the first deflection X1.

[0073] By performing the above-described procedure on all the glass sample 3 corresponding to each of the evaluation regions A to E, the shape in the width direction X in each of the evaluation regions A to E can be grasped. For example, as shown in FIG. 3 , when the first deflection X1 is larger than the second deflection X2 and the front-to-back deflection difference X1-X2 is positive (a value larger than 0), the guaranteed surface 3a of the glass sample 3 in the width direction X of the glass plate 1 becomes a convex surface, and the magnitude of the deflection can be evaluated by the absolute value of the front-to-back deflection difference X1-X2. On the other hand, when the first deflection X1 is smaller than the second deflection X2 and the front-to-back deflection difference X1-X2 is negative (a value smaller than 0) (not shown), the guaranteed surface 3a of the glass sample 3 in the width direction X of the glass plate 1 becomes a concave surface, and the magnitude of the deflection can be evaluated by the absolute value of the front-to-back deflection difference X1-X2. Here, when any linear region (cross section) along the width direction X is viewed on the glass sheet 1, the annealing conditions at each point on the linear region can be considered to be substantially the same even if the position in the sheet drawing direction Y is different. Therefore, the overall shape of the glass sheet 1 in the width direction X can be grasped simply by determining the difference X1-X2 between the front and back deflections of the glass sample 3 corresponding to each of the evaluation regions A to E.

[0074] In the same manner as above, the shape of the glass sheet 1 along the drawing direction Y can be evaluated based on the difference Y1-Y2 between the front and back deflections. This evaluation method will be described below.

[0075] Five glass samples 3 corresponding to evaluation regions A to E shown in FIG. 1 are prepared, and the difference Y1-Y2 between the front and back deflections of each glass sample 3 in the drawing direction Y is measured. The glass samples 3 prepared may be the same as those used to evaluate the shape along the width direction X. Specifically, as shown in FIG. 4, the glass sample 3 is held with its guaranteed surface 3a facing downward, and both ends of the glass sample 3 in the drawing direction Y are supported by a pair of support members 5. In this case, the support span N of the glass sample 3 by the pair of support members 5 is set to 480 mm when the length of the edge 3y along the drawing direction Y is 500 mm and the length of the edge 3x along the width direction X is 400 mm. In other cases, it is set to a value obtained by subtracting 20 mm from the length of the edge 3y of the glass sample 3 along the drawing direction Y. In this state, the magnitude of the first deflection Y1 (indicated by the solid line in the figure) of the glass sample 3 in the drawing direction Y is measured, as shown in FIG. 5. In this measurement, the first deflection Y1 is measured for each of two parallel sides 3y along the drawing direction Y of the sample glass 3, and the larger of the two values ​​is adopted as the first deflection Y1. The magnitude of the adopted first deflection Y1 is converted into the first deflection Y1 when the support span N is 350 mm.

[0076] Similarly, the glass sample 3 is turned over, with the non-support surface 3b of the glass sample 3 facing downward, and both ends of the glass sample 3 in the drawing direction Y are supported by a pair of support members 5. In this state, as shown in Figure 5, the magnitude of the second deflection Y2 of the glass sample 3 in the drawing direction Y (indicated by the dashed line in the figure) is measured. In this measurement, the second deflection Y2 is measured for each of two parallel edges 3y of the glass sample 3 along the drawing direction Y, and the larger of the two measured values ​​is used as the second deflection Y2. The magnitude of the second deflection Y2 thus measured is converted to the second deflection Y2 when the support span N is 350 mm.

[0077] After measuring the first deflection Y1 and the second deflection Y2 in this manner, the difference Y1-Y2 between the front and back deflections in the drawing direction Y is obtained by subtracting the second deflection Y2 from the first deflection Y1.

[0078] By performing the above-described procedure on all the glass samples 3 corresponding to the evaluation regions A to E, the shape in the drawing direction Y in each of the evaluation regions A to E can be grasped. For example, as shown in Figure 5, when the first deflection Y1 is larger than the second deflection Y2 and the front-to-back deflection difference Y1 - Y2 is positive, the guaranteed surface 3a of the glass sample 3 in the drawing direction Y has a convex shape, and the magnitude of the deflection can be evaluated by the absolute value of the front-to-back deflection difference Y1 - Y2. On the other hand, when the first deflection Y1 is smaller than the second deflection Y2 and the front-to-back deflection difference Y1 - Y2 is negative (not shown), the guaranteed surface 3a of the glass sample 3 in the drawing direction Y has a concave shape, and the magnitude of the deflection can be evaluated by the absolute value of the front-to-back deflection difference Y1 - Y2. Here, when any linear region (cross section) of the glass sheet 1 along the width direction X is viewed, the annealing conditions at each point on the linear region can be considered to be substantially the same even if the position in the sheet drawing direction Y is different. Therefore, the overall shape of the glass sheet 1 in the sheet drawing direction Y can be grasped simply by determining the difference Y1-Y2 between the front and back deflections of the glass sample 3 corresponding to each of the evaluation regions A to E.

[0079] When the shape of the glass plate 1 according to this embodiment is evaluated based on the difference in the front and back deflections, it has the following shape quality.

[0080] That is, the absolute value of the average value of the front-to-back deflection differences X1-X2 in the width direction X corresponding to the five evaluation regions A to E of the glass plate 1 is 0.06 mm or more and 0.8 mm or less. The lower limit of this absolute value is preferably 0.1 mm or more, 0.15 mm or more, 0.17 mm or more, more preferably 0.18 mm or more, and even more preferably 0.2 mm or more. On the other hand, the upper limit of this absolute value is preferably 0.6 mm or less, more preferably 0.5 mm or less, and even more preferably 0.4 mm or less.

[0081] Furthermore, the glass plate 1 has a positive average value of the front-to-back deflection difference X1-X2 in the width direction X corresponding to the five evaluation regions A to E. The glass plate 1 has a front-to-back deflection difference X1-X2 in the width direction X corresponding to the five evaluation regions A to E that is −0.2 mm or more and 1.0 mm or less. The lower limit of this front-to-back deflection difference X1-X2 is preferably −0.1 mm or more, more preferably 0 mm or more, and even more preferably 0.1 mm or more. On the other hand, the upper limit of this front-to-back deflection difference X1-X2 is preferably 0.9 mm or less, more preferably 0.85 mm or less, and even more preferably 0.8 mm or less.

[0082] Furthermore, the glass plate 1 has a difference between the maximum and minimum values ​​of the front-to-back deflection difference X1-X2 in the width direction X corresponding to the five evaluation regions A to E of 2.0 mm or less. This difference is preferably 1.5 mm or less, more preferably 1.3 mm, and even more preferably 1.0 mm.

[0083] For the above reasons, since the average value of the front-to-back deflection difference X1-X2 of the glass sheet 1 is positive, the guaranteed surface 1a has a curved shape that is convex in the width direction X. Moreover, since both values ​​of the front-to-back deflection difference X1-X2 are large, the degree of curvature of the convex surface is large. Furthermore, since the difference between the maximum and minimum values ​​of the front-to-back deflection difference X1-X2 is small, the convex surface is more reliably smoothly curved over the entire length or almost the entire length in the width direction X. Such a shape along the width direction X of the glass sheet 1 extends over the entire length in the sheet drawing direction Y.

[0084] FIG. 6 is a schematic diagram illustrating an example of use of a glass plate 1. In the first example, a thermal film formation process is performed on the guaranteed surface 1a of the glass plate 1, as indicated by reference symbol B1 in the figure. Specifically, a resin film material 6, such as polyimide, is applied to the guaranteed surface 1a of the glass plate 1, degassed and dried, and then baked to harden the film material 6, forming a resin film 6a. After baking, the glass plate 1 and resin film 6a are flattened by cooling to near room temperature, as indicated by reference symbol B2 in the figure (in the illustrated example, they are flat). The resin film 6a is then peeled off from the glass plate 1 using an ultraviolet laser, and the peeled resin film 6a is used in the manufacture of electronic devices such as displays. In this case, the flattened shape of the glass plate 1 allows the resin film 6a to be peeled off properly and reliably.

[0085] In a second example of use, as shown by reference symbol B1 in the figure, a thermal film formation process is performed on the guaranteed surface 1a of the glass plate 1 in the same manner as described above to form a film 6a such as an organic film (including a resin film) or an inorganic film (including a metal film). Then, as shown by reference symbol B2 in the figure, the glass plate 1 is cooled to near room temperature in the same manner as described above to flatten the shape. The glass plate 1 with the film 6a thus obtained is then used in the manufacture of electronic devices such as displays. Because of its flattened shape, the glass plate 1 with the film 6a is of high quality.

[0086] In relation to these use examples, the glass plate 1 has the following properties.

[0087] The glass plate 1 has a linear thermal expansion coefficient of 30×10 -7 / ℃ or more 50 × 10 -7 / °C or less. This is advantageous when forming the polyimide resin film 6a by a thermal film formation process on the guaranteed surface 1a of the glass plate 1. That is, since the linear thermal expansion coefficient of the polyimide resin film 6a is within the above-mentioned numerical range, it is possible to appropriately address the difference in thermal expansion between the resin film 6a and the glass plate 1, and more reliably flatten the shape of the glass plate 1 when cooled to near room temperature.

[0088] The glass plate 1 has a thermal shrinkage of 30 ppm or less when held at 500°C for 1 hour. This suppresses shrinkage (compaction) of the glass plate 1 when a thermal film formation process is performed on the protection surface 1a of the glass plate 1. Such a characteristic is particularly required for high-resolution displays. Therefore, the glass plate 1 is suitable for use as a glass plate for high-resolution displays. The "thermal shrinkage" is measured as follows: First, a 160 mm x 30 mm rectangular sample is prepared as a measurement sample. This rectangular sample is marked approximately 20 to 40 mm from the long edge with #1000 waterproof abrasive paper, and then folded in a direction perpendicular to the marking to obtain two test pieces. One of the folded test pieces is heat-treated under specified conditions, and then the heat-treated sample and the unheated sample are aligned and secured together with tape or the like. The predetermined heat treatment involves raising the temperature from room temperature to 500°C at a rate of 5°C / min, holding at 500°C for 1 hour, and then lowering the temperature from 500°C to room temperature at a rate of 5°C / min. In this state, the positional deviation of the markings (ΔL1, ΔL2) is read using a laser microscope, and the thermal shrinkage is calculated using the following formula (4): Thermal shrinkage [ppm] = (ΔL1 [μm] + ΔL2 [μm]) / 160 × 10 -3 ...(4)

[0089] The thermal shrinkage is preferably 30 ppm or less, 20 ppm or less, particularly preferably 15 ppm or less. In this way, when the glass plate 1 is used in the manufacture of a high-definition display, problems such as pattern misalignment are less likely to occur. If the thermal shrinkage is too low, the production efficiency of the glass plate 1 is likely to decrease. Therefore, the thermal shrinkage is preferably 1 ppm or more, 2 ppm or more, 3 ppm or more, 4 ppm or more, particularly preferably 5 ppm or more.

[0090] The glass plate 1 has a transmittance of 60% to 85% in the thickness direction at a wavelength of 308 nm. The transmittance can be measured using a spectrophotometer.

[0091] This is advantageous when forming a polyimide resin film 6a on the guaranteed surface 1a of the glass plate 1 by a thermal film-forming process and then peeling off the resin film 6a using an ultraviolet laser. That is, since the wavelength of the ultraviolet laser is 308 nm, the glass plate 1 has an appropriate transmittance in the thickness direction in the same wavelength range. This allows the polyimide resin film 6a to be peeled off from the glass plate 1 more appropriately and reliably.

[0092] In the glass sheet 1 according to the above embodiment, the guaranteed surface 1a has a curved shape that is convex in the width direction X, but the guaranteed surface 1a may also have a curved shape that is convex in both the width direction X and the drawing direction Y. The shape of such a glass sheet 1 along the drawing direction Y can be evaluated by the front-to-back deflection difference Y1-Y2 using the method described above. In this case, it is preferable that the average value of the front-to-back deflection difference Y1-Y2 in the drawing direction Y of the five evaluation regions A to E is positive. It is also preferable that the absolute value of the average value of the front-to-back deflection difference Y1-Y2 in the drawing direction Y of the five evaluation regions A to E is equal to the absolute value of the average value of the front-to-back deflection difference X1-X2 in the width direction X described above.

[0093] <Glass plate manufacturing equipment>

[0094] 7 and 8 , the manufacturing apparatus 7 for a glass sheet 1 according to this embodiment includes a forming furnace 8, an annealing furnace 9 located below the forming furnace 8, a cooling zone 10 located below the annealing furnace 9, and a cutting device 11 located below the cooling zone 10. The forming furnace 8 and the annealing furnace 9, the annealing furnace 9 and the cooling zone 10, and the cooling zone 10 and the cutting device 11 are separated by partition members (for example, floors of a building) F1, F2, and F3, respectively, each having an opening (for example, a slit) through which the glass ribbon Gr passes.

[0095] The forming furnace 8 is a region for forming a glass ribbon Gr from the molten glass Gm by the overflow downdraw method. Inside the forming furnace 8, there are arranged a forming body 12 that forms the glass ribbon Gr from the molten glass Gm, and edge rollers 13 that cool both ends in the width direction X of the glass ribbon Gr formed by the forming body 12.

[0096] A groove (overflow groove) 14 is formed in the width direction at the top of the formed body 12. A supply pipe 15 is connected to one end of the groove 14. Molten glass Gm is supplied into the groove 14 through this supply pipe 15. The method of supplying the molten glass Gm is not limited to this. For example, the molten glass Gm may be supplied from both ends of the groove 14, or the molten glass Gm may be supplied from above the groove 14.

[0097] Each of the outer surfaces of the molded body 12 includes a vertical surface portion 16 that is a flat surface along the vertical direction, and an inclined surface portion 17 that is connected to the lower side of the vertical surface portion 16 and is a flat surface inclined with respect to the vertical direction. The vertical surface portions 16 are flat surfaces that are parallel to each other. The inclined surface portions 17 are flat surfaces that are inclined so that they approach each other as they extend downward. In other words, due to the formation of the inclined surface portions 17, the molded body 12 has a wedge shape that tapers downward when viewed from the side, and the corner where the inclined surface portions 17 intersect forms the lower end portion 12a of the molded body 12. The vertical surface portions 16 may be modified to have an inclined surface or a curved surface, or may be omitted.

[0098] The edge rollers 13 are configured as a pair of rollers that sandwich each end of the glass ribbon Gr in the width direction directly below the forming body 12. The edge rollers 13 are cantilever type rollers that are constantly internally cooled during the forming process. For this reason, the edge rollers 13 are sometimes referred to as cooling rollers.

[0099] The annealing furnace 9 is a region for reducing warpage and internal strain of the glass ribbon Gr. A first conveying device 18 is provided inside the annealing furnace 9. The first conveying device 18 includes annealer rollers 19. The annealer rollers 19 are basically configured as a pair of rollers that sandwich both widthwise ends of the glass ribbon Gr. The annealer rollers 19 may be double-supported rollers arranged to span the entire widthwise region of the glass ribbon Gr, but in this embodiment, they are cantilevered rollers. The annealer rollers 19 are provided in multiple stages (nine stages in the illustrated example) on the conveying path of the glass ribbon Gr along the vertical direction.

[0100] The cooling zone 10 is an area for cooling the glass ribbon Gr to near room temperature. A second conveying device 20 is provided inside the cooling zone 10. The second conveying device 20 includes conveying rollers 21. The conveying rollers 21 are configured as a pair of rollers that sandwich both widthwise ends of the glass ribbon Gr. The conveying rollers 21 may be double-supported rollers arranged to span the entire widthwise area of ​​the glass ribbon Gr, but in this embodiment, they are cantilevered rollers. The conveying rollers 21 are provided in multiple stages (five stages in the illustrated example) in the vertical direction.

[0101] The cutting device 11 includes a scribe line forming device 22. The scribe line forming device 22 is a device that forms a scribe line S on the first main surface Ga of the glass ribbon Gr that has descended from the cooling zone 10 at a scribe line forming position P1. In the present embodiment, the scribe line forming device 22 includes a wheel cutter 23 that forms a scribe line S along the width direction on the first main surface Ga of the glass ribbon Gr, and a support member 24 (e.g., a support bar or a support roller) that supports the second main surface Gb of the glass ribbon Gr at a position corresponding to the wheel cutter 23. The wheel cutter 23 and the support member 24 are configured to form the scribe line S across the entire width or a portion of the width of the glass ribbon Gr while moving in accordance with the glass ribbon Gr that moves continuously downward. The scribe line S may be formed by laser irradiation or the like.

[0102] The cutting device 11 further includes a slicing device 25. The slicing device 25 is a device that slicing the glass ribbon Gr along a scribe line S at a slicing position P2 provided below the scribe line forming position P1 to cut out the glass sheet 1r. In this embodiment, the slicing device 25 includes a slicing member 26 that abuts the region where the scribe line S is formed from the second main surface Gb side, and a gripping mechanism 27 that grips a lower region of the glass ribbon Gr below the slicing position P2. The slicing member 26 is configured as a plate-like body having a contact surface that contacts the entire width or part of the glass ribbon Gr. The gripping mechanism 27 includes chucks 28 provided at multiple locations in the upper and lower directions at both widthwise ends of the glass ribbon Gr, and arms 29 that hold the multiple chucks 28 at both widthwise ends.

[0103] The breaking and splitting member 26 and the gripping mechanism 27 perform the following operations. First, the multiple chucks 28 grip the glass ribbon Gr, and then the arm 29 moves the multiple chucks 28 in accordance with the descent of the glass ribbon Gr. At this time, the breaking and splitting member 26 also moves in accordance with the descent of the glass ribbon Gr. While these movements are being performed, the arm 29 performs an operation (operation in the C direction shown in FIG. 1 ) for bending the glass ribbon Gr with the breaking and splitting member 26 as a fulcrum. This applies bending stress to the scribe line S and its vicinity, and the glass ribbon Gr is bent and split in the width direction along the scribe line S. As a result of cutting by this bending and splitting, a glass plate 1r is cut out from the glass ribbon Gr.

[0104] In this embodiment, the glass ribbon Gr and the glass sheet 1r obtained by the manufacturing apparatus 7 have ears at both ends in the width direction X that are thicker than the central portion in the width direction X. The ears are formed due to the influence of shrinkage and the like during the molding process. The glass sheet 1r becomes the above-mentioned glass sheet 1 by removing the ears in a later process. The guaranteed surface (first main surface) 1a of this glass sheet 1 and the first main surface Ga of the glass ribbon Gr are surfaces on the same side in the sheet thickness direction.

[0105] Here, the first conveying device 18 provided inside the annealing furnace 9 will be described in detail. As shown in Fig. 7 , of the nine annealer rollers 19 provided in the vertical direction, the first to fourth annealer rollers 19 from the top and the sixth annealer roller 19 from the top support both widthwise end portions of the glass ribbon Gr from the first main surface Ga side and the second main surface Gb side. Therefore, these annealer rollers 19 clamp both widthwise end portions of the glass ribbon Gr.

[0106] On the other hand, in the fifth and seventh annealer rollers 19 from the top, the annealer rollers 19 located on the second main surface Gb side of the glass ribbon Gr are biased toward the first main surface Ga side (hereinafter, these annealer rollers 19 will be referred to as biased rollers 19a). Both widthwise ends of the glass ribbon Gr are supported only from the second main surface Gb side by these biased rollers 19a. In other words, these biased rollers 19a press both widthwise ends of the glass ribbon Gr only from the second main surface Gb side. The biased roller 19a in the fifth annealer roller from the top is biased toward the first main surface Ga side with respect to the annealer roller 19 located on the second main surface Gb side of the fourth annealer roller 19 from the top. The seventh bias roller 19a from the top is biased toward the first main surface Ga with respect to the annealer roller 19 located on the second main surface Gb side of the sixth annealer roller 19 from the top. As shown in Fig. 9, the bias amount Lz by which these bias rollers 19a are biased toward the first main surface Ga with respect to the nearest annealer roller 19 on the upper side set to 1 mm or more and 20 mm or less. The lower limit of the bias amount Lz is more preferably 3 mm or more, and even more preferably 5 mm or more. The upper limit of the bias amount Lz is more preferably 15 mm or less, and even more preferably 10 mm or less. In this case, as shown in Figure 7, the annealer roller 19 located on the second main surface Gb side of the sixth annealer roller 19 from the top is not biased toward either the first main surface Ga side or the second main surface Gb side, with the bias roller 19a, the fifth annealer roller 19 from the top, as a reference.

[0107] 7 and 9 , biased opposing rollers 19b are provided at positions opposing the two biased rollers 19a in the thickness direction of the glass ribbon Gr. These biased opposing rollers 19b are spaced away from both widthwise ends of the glass ribbon Gr toward the first main surface Ga. In the present embodiment, the eighth and ninth annealer rollers 19 from the top do not sandwich both widthwise ends of the glass ribbon Gr, and in the illustrated example, are spaced away from both widthwise ends of the glass ribbon Gr toward both the first main surface Ga and the second main surface Gb. Therefore, inside the annealing furnace 9, using the biased roller 19a and biased opposing roller 19b provided at the lowest position as references, the annealer rollers 19 provided below them do not sandwich the glass ribbon Gr.

[0108] The two bias rollers 19a are preferably provided in a region where the temperature of the glass ribbon Gr is between the strain point and the softening point. 14.5 ~10 7.6 It is preferable that the bias rollers 19a are provided in a region where the viscosity becomes dPa s. In other words, it is preferable that both of the two bias rollers 19a are provided below the vertical center position of the transport path in the annealing furnace 9. Note that instead of providing the bias rollers 19a at two locations on the transport path in the annealing furnace 9 as in the illustrated example, they may be provided at one location on the transport path, or at three or more locations. In this case, too, it is preferable that the bias rollers 19a are provided below the vertical center position of the transport path in the annealing furnace 9. Furthermore, when the bias rollers 19a are provided at two locations on the transport path in the annealing furnace 9, the annealer rollers 19 other than the fifth and seventh rollers may be biased.

[0109] <Method for manufacturing glass sheet> The method for manufacturing the glass sheet 1 according to this embodiment is carried out mainly using the manufacturing apparatus 7 having the above-described configuration. This manufacturing method includes a forming step, an annealing step, a cooling step, and a cutting step.

[0110] In the forming step, in the forming furnace 8, molten glass Gm is supplied to the grooves 14 of the forming body 12, and the molten glass Gm overflowing on both sides of the grooves 14 flows down along the vertical surfaces 16 and the inclined surfaces 17 and meets again at the lower end 12 a. In this way, a glass ribbon Gr is continuously formed from the molten glass Gm.

[0111] In the annealing step, the glass ribbon Gr is annealed in the annealing furnace 9 while being conveyed downward by the first conveying device 18 .

[0112] In the cooling step, in the cooling zone 10, the glass ribbon Gr is cooled to near room temperature while being transported downward by the second transport device 20.

[0113] In the cutting step, the glass ribbon Gr is cut to obtain glass plates 1. Specifically, the cutting step includes a first cutting step of cutting the glass ribbon Gr in the width direction X at predetermined lengths to obtain glass plates 1r, and a second cutting step of cutting and removing the edge portions at both ends in the width direction of the glass plate 1r to obtain glass plates 1r.

[0114] Here, in the above-mentioned annealing step, the first conveying device 18 is provided with the bias roller 19a and the bias opposing roller 19b, and therefore the glass sheet 1 cut out from the glass ribbon Gr through the first and second cutting steps can be formed into the curved shape described above. More specifically, as shown in Figures 9 and 10 , the bias roller 19a supports the second main surface Gb sides of both widthwise end portions Gd of the glass ribbon Gr, and the bias opposing roller 19b is separated from both widthwise end portions Gd of the glass ribbon Gr, so that the widthwise central portion Gc of the glass ribbon Gr can be curved in a largely convex shape toward the first main surface Ga. In other words, as shown in Figure 10 , the widthwise end portions Gd of the glass ribbon Gr are not sandwiched between the bias roller 19a and the bias opposing roller 19b, and therefore not only the widthwise central portion Gc of the glass ribbon Gr but also both widthwise end portions Gd can be curved toward the first main surface Ga. This allows the first main surface 1a of the obtained glass plate 1 to be a convex surface with a large degree of curvature in the width direction.

[0115] In contrast, if both widthwise end portions Gd of the glass ribbon Gr are sandwiched between the biasing roller 19 a and the biasing opposing roller 19 b as shown in Figures 11 and 12, both widthwise end portions Gd will have a flat shape. As a result, only a narrow region of the widthwise central portion Gc of the glass ribbon Gr will be convexly curved toward the first main surface Ga. Therefore, the first main surface 1 a of the obtained glass sheet 1 will be a convex surface with a small degree of curvature in the width direction.

[0116] Moreover, in the annealing furnace 9 according to this embodiment, the biased roller 19 a and the biased opposing roller 19 b are provided at two locations on the conveying path of the glass ribbon Gr, so that the first main surface 1 a of the obtained glass plate 1 can be made into a convex surface with an even greater degree of curvature in the width direction.

[0117] Taking the above into consideration, the biased opposing roller 19 b does not have to be provided, but providing the biased opposing roller 19 b provides the following advantages. The biased roller 19 a and the biased opposing roller 19 b are installed so as to be movable in the thickness direction of the glass ribbon Gr. By providing the biased opposing roller 19 b, the annealer roller 19 to be biased can be selected depending on the manufacturing conditions of the glass sheet 1.

[0118] Furthermore, in the annealing step according to this embodiment, the biasing roller 19a is provided, so that the glass ribbon Gr is also curved convexly toward the first main surface Ga in the drawing direction. Therefore, the first main surface 1a of the obtained glass sheet 1 can also be convex in the drawing direction. Therefore, in this annealing step, the shape of the glass sheet 1 along the drawing direction can be made into the above-described shape.

[0119] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0120] The present inventors conducted a comparative test to confirm the effects of the present invention. In this test, glass plates according to Examples 1 to 6 and glass plates according to Comparative Examples 1 and 2 were prepared, and the difference in front-to-back deflection X1-X2 in the width direction X of each example was evaluated. The glass plates in each example were prepared using the manufacturing apparatus 7 described above. The difference in front-to-back deflection X1-X2 in each example was evaluated based on the method described above. Furthermore, in each example, a polyimide solution was applied to the first main surface of the glass plate, and the glass plate was subjected to a heat film formation treatment at 500°C for 5 hours. After cooling to near room temperature, the glass plate was evaluated for warpage. These evaluation results and evaluation results are shown in Table 1 below. In each example, a low-alkali glass plate for display was prepared, having a strain point of 780 to 830°C, a Young's modulus of 80 to 85 GPa, a thermal shrinkage of approximately 9 to 12 ppm when heat-treated at 500°C for 1 hour, and a thermal expansion coefficient of 35 to 40×10 -7 The material used was OA-31 manufactured by Nippon Electric Glass Co., Ltd., which has a temperature range of 100°C / °C. In each example, the thickness of the polyimide film after heat deposition was about 10 μm.

[0121]

[0122] According to Table 1 above, the glass plates according to Examples 1 to 6 all had positive average values ​​of the front-to-back deflection difference X1-X2 in the width direction X of the five evaluation areas A to E, and all of these average values ​​were within the numerical range of 0.06 to 0.4 mm, so no warping occurred after firing. On the other hand, in Comparative Example 1, the average value of the front-to-back deflection difference X1-X2 in the width direction X of the five evaluation areas A to E was 0.05 mm, which was smaller than in Examples 1 to 6, so warping occurred after firing so as to be convex toward the non-guaranteed surface (second main surface). Furthermore, in Comparative Example 2, the average value of the front-to-back deflection difference X1-X2 in the width direction X of the five evaluation areas A to E was 0.9 mm, which was larger than in Examples 1 to 6, so warping occurred after firing so as to be convex toward the guaranteed surface (first main surface). Taking this into consideration, it can be inferred that the upper limit of the average value of the front and back deflection differences X1-X2 in the width direction X of the five evaluation areas A to E should be 0.8 mm and the lower limit should be 0.06 mm.

[0123] Furthermore, according to Table 1 above, the glass plates according to Examples 1 to 6 had a smoothly curved shape over the entire width of the glass plate, and no warping occurred after firing, because the difference between the maximum and minimum values ​​of the front-to-back deflection difference X1-X2 in the width direction X of the five evaluation areas A to E was within the numerical range of 0.2 to 0.8 mm. In Comparative Example 1, the difference between the maximum and minimum values ​​of the front-to-back deflection difference X1-X2 in the width direction X of the five evaluation areas A to E was 0.2 mm, so the glass plate had a smoothly curved shape over the entire width of the glass plate, but as mentioned above, the average value was 0.05 mm, so warping occurred after firing. On the other hand, in Comparative Example 2, the difference between the maximum and minimum values ​​of the front-to-back deflection difference X1-X2 in the width direction X of the five evaluation areas A to E was 2.3 mm, which was larger than that of Examples 1 to 6, so the glass plate did not have a smoothly curved shape over the entire width of the glass plate, and further, warping occurred after firing.

[0124] DESCRIPTION OF SYMBOLS 1 Glass sheet 1a First main surface (guaranteed surface) of glass sheet 1b Second main surface (non-guaranteed surface) of glass sheet 1x Side along the width direction of glass sheet 1y Side along the sheet drawing direction of glass sheet 7 Manufacturing device 8 Forming furnace 9 Lehr 18 First conveying device (conveying device in lehr) 19 Annealer roller 19a Bias roller Ga First main surface of glass ribbon Gb Second main surface of glass ribbon Gd Both ends in the width direction of glass ribbon Gr Glass ribbon Lz Bias amount of bias roller X Width direction X1 Deflection in the width direction Y Sheet drawing direction Y1 Deflection in the sheet drawing direction

Claims

1. A rectangular glass plate having a first main surface and a second main surface on the back side of the first main surface, a first side along the sheet drawing direction, and a second side along the width direction perpendicular to the sheet drawing direction, wherein the lengths of the first side and the second side are 1000 mm or more, and the plate thickness is 0.1 mm or more and 2.0 mm or less, A glass plate characterized in that, when five rectangular evaluation areas of the same size are set in order from one end side of the width direction, the absolute value of the average value of the front-to-back deflection difference in the width direction of the five evaluation areas calculated by the following formula (1) is 0.06 mm or more and 0.8 mm or less. Difference in front and back deflection = (X1 - X2) (1) X1: Deflection [mm] in the width direction of the sample glass corresponding to the evaluation area for measuring the difference in front and back deflections when the first main surface faces downward. X2: Deflection [mm] in the width direction of the sample glass corresponding to the evaluation area for measuring the difference in deflection between the front and back surfaces when the second main surface is facing downward.

2. 2. The glass plate according to claim 1, wherein an average value of the difference in front and back deflections in the width direction of the five evaluation regions is 0.15 mm or more.

3. The average value of the difference in front and back deflection in the width direction of the five evaluation areas is positive, 2. The glass plate according to claim 1, wherein the difference in front-to-back deflection in the width direction of each of the five evaluation regions is −0.2 mm or more and 1.0 mm or less.

4. 4. The glass plate according to claim 3, wherein the first main surface is a guaranteed surface and the second main surface is a non-guaranteed surface.

5. 5. The glass plate according to claim 1, wherein a difference between a maximum value and a minimum value of the difference in front-to-back deflection in the width direction in the five evaluation regions is 2.0 mm or less.

6. The linear thermal expansion coefficient at 30 to 380°C is 30 x 10 －７ / ℃ or more 50 × 10 －７ 5. The glass plate according to claim 1, wherein the glass plate has a viscosity of 1 / °C or less.

7. 5. The glass plate according to claim 1, wherein the glass plate has a thermal shrinkage of 30 ppm or less when held at 500° C. for 1 hour.

8. 5. The glass plate according to claim 1, wherein the transmittance in the plate thickness direction at a wavelength of 308 nm is 60% or more and 85% or less.

9. The glass composition is, in mol%, SiO ２ 60-70%, Al ２ O ３ 9.5-17%, B ２ O ３ 0-9%, Li ２ O + Na ２ O+K ２ 5. The glass plate according to claim 1, comprising 0 to less than 1% of O, 0 to 8% of MgO, 2 to 15% of CaO, 0 to 10% of SrO, and 0.1 to 5% of BaO.

10. The glass composition is, in mol%, SiO ２ 62-72%, Al ２ O ３ 9.5-16%, B ２ O ３ 1-8% Li ２ O + Na ２ O+K ２ 5. The glass plate according to claim 1, comprising 0 to less than 1% of O, 1 to 9% of MgO, 2 to 10% of CaO, 0.1 to 5% of SrO, and 0.1 to 5% of BaO.

11. The glass composition is, in mol%, SiO ２ 67-77%, Al ２ O ３ 9-14%, B ２ O ３ 0-3%, Li ２ O + Na ２ O+K ２ 5. The glass plate according to claim 1, comprising from 0 to less than 1% of O, from 0 to 5% of MgO, from 0 to 10% of CaO, from 0 to 5% of SrO, and from 0 to 7% of BaO.

12. A method for manufacturing a glass plate with a resin film, comprising: an application step of applying a resin film material to a glass plate described in any one of claims 1 to 4; and a firing step of forming a resin film by firing and hardening the resin film material applied to the glass plate.

13. A method for manufacturing a resin film, comprising a peeling step of irradiating an ultraviolet laser onto a glass plate with a resin film manufactured by the method for manufacturing a glass plate with a resin film described in claim 12, thereby peeling off the resin film from the glass plate.

14. A method for manufacturing a glass sheet, comprising: a forming step of forming a glass ribbon from molten glass; an annealing step of annealing the glass ribbon while conveying it by a conveying device; and a cutting step of cutting the annealed glass ribbon into rectangular glass sheets, the glass ribbon has a first main surface and a second main surface on a back side of the first main surface, and has a sheet thickness of 0.1 mm or more and 2.0 mm or less, In the annealing step, both widthwise end portions of the glass ribbon are supported from the first main surface side and the second main surface side by a plurality of roller pairs in the conveying device, and both widthwise end portions of the glass ribbon are supported from only the second main surface side by a bias roller biased toward the first main surface side of the glass ribbon at at least one location in the conveying direction of the glass ribbon in the conveying device.

15. 15. The method for manufacturing a glass plate according to claim 14, wherein the first main surface is a guaranteed surface and the second main surface is a non-guaranteed surface.

16. 16. The method for manufacturing a glass sheet according to claim 14, wherein the bias amount of the bias roller is 1 mm or more and 20 mm or less.

17. A glass sheet manufacturing apparatus including: a forming furnace that forms, from molten glass, a glass ribbon having a first main surface and a second main surface on a back side of the first main surface; an annealing furnace that anneales the glass ribbon while conveying it by a conveying device; and a cutting device that cuts the annealed glass ribbon into a rectangular glass sheet, the conveying device includes: a plurality of roller pairs that support both widthwise end portions of the glass ribbon from the first main surface side and the second main surface side; and a biasing roller that is provided at at least one location on a conveying path of the glass ribbon and is biased toward the first main surface side of the glass ribbon to support both widthwise end portions of the glass ribbon from only the second main surface side.