Glass sheet and method for manufacturing the same

Abstract

To properly control the temperature of a molten glass that is supplied to a molding.SOLUTION: A method for manufacturing a glass sheet G includes a molding step S1 of heating a molten glass Gm flowing down over both side surfaces 10 of a molding 3 with a heater 16 installed to a side wall part 2a of a molding furnace 2, where a difference TRE-TL(°C) from a liquid phase temperature TL(°C) of the glass sheet G is 15°C or more and 75°C or less where TRE(°C) represents the temperature of the side wall part 2 of the molding furnace 2 in a position corresponding to ends 3b, 3c in a width direction of the molding 3 of a lower end part 3a of the molding 3.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a glass plate and a method for producing the same. [Background technology]

[0002] In recent years, the use of an organic resin substrate as a substrate to fabricate a flexible organic EL display has been attracting attention. However, since the organic resin substrate is flexible, it is difficult to directly form a semiconductor film on the substrate. Therefore, a process is required in which a semiconductor film is formed on the organic resin layer in a state in which the organic resin layer is laminated on a carrier glass (see, for example, Patent Document 1).

[0003] The glass sheet used as the carrier glass is formed, for example, by the overflow downdraw method, in which molten glass is poured into an overflow groove provided on the upper part of a forming body having a substantially wedge-shaped cross section, and the molten glass overflowing on both sides of the overflow groove is allowed to flow down along both side surfaces of the forming body, and is fused and integrated at the lower end of the forming body, thereby continuously forming a glass ribbon (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 199059 [Patent Document 2] Patent Publication No. 2021-195294 Summary of the Invention [Problem to be solved by the invention]

[0005] The glass sheet used for the above carrier glass is required to have the following properties. (1) The distortion of the glass plate is small in order to suppress pitch deviation of the elements formed on the organic resin layer. (2) The warping of the glass plate is small in order to suppress unevenness in the film formation when an organic resin is applied to the surface of the glass plate to form a film. (3) In order to make the thickness of the organic resin layer uniform, the thickness deviation of the entire glass plate is small.

[0006] In order to produce a glass sheet satisfying the above-mentioned properties, it is necessary to appropriately control the temperature of the molten glass formed by the forming body.

[0007] An object of the present invention is to appropriately control the temperature of molten glass supplied to a forming body. [Means for solving the problem]

[0008] (1) The present invention is intended to solve the above problems, and is a method for producing a glass sheet, comprising a forming step of, by an overflow downdraw method, causing molten glass overflowing from a groove of a forming body arranged in a forming furnace to flow down along both side surfaces of the forming body, and then fusing the molten glass at a lower end of the forming body to form a glass ribbon, wherein in the forming step, the molten glass flowing down the both side surfaces of the forming body is heated by a heater provided on a side wall of the forming furnace, and the temperature of the side wall of the forming furnace at a position of the lower end of the forming body corresponding to an end of the forming body in the width direction is set to T RE (℃), the liquidus temperature of the glass plate, T L (℃) difference T RE -T L (°C) is 15°C or higher and 75°C or lower.

[0009] In the present invention, the molten glass supplied to the forming body is heated by a heater provided on the side wall of the forming furnace. In addition, since it is difficult to directly measure the temperature of the molten glass flowing down the side of the forming body, the temperature of the molten glass can be controlled by measuring the temperature of the side wall where the heater is provided. Furthermore, the temperature at a position on the side wall of the forming furnace that corresponds to the end of the lower end of the forming body in the width direction is determined as T RE (℃), the liquidus temperature of the glass plate, T L (℃) difference TRE -T L By setting the temperature (°C) to 15°C or higher and 75°C or lower, it becomes possible to appropriately control the temperature of the molten glass so as to minimize distortion, warping, and thickness deviation of the glass ribbon formed by the forming body.

[0010] (2) In the method for producing a glass plate described in (1) above, a temperature of the side wall portion at a position of the lower end of the formed body corresponding to the width direction end may be higher than a temperature of the side wall portion at a position of the lower end of the formed body corresponding to a width direction middle portion.

[0011] The molten glass flowing down the side surface of the forming body tends to have a high temperature at the widthwise middle of the lower end of the forming body and a low temperature at the widthwise both ends of the lower end of the forming body. If such a temperature difference occurs, there is a risk that distortion of the formed glass ribbon will increase. In the present invention, by setting the temperature of the side wall portion of the forming furnace at the position corresponding to the widthwise end of the lower end of the forming body to be higher than the temperature of the side wall portion at the position corresponding to the widthwise middle of the lower end of the forming body, it is possible to prevent an increase in distortion of the glass ribbon.

[0012] (3) In the method for producing a glass plate described in (2) above, a temperature difference between a temperature of the side wall portion at a position of the lower end of the formed body corresponding to the width direction end portion and a temperature of the side wall portion at a position of the lower end of the formed body corresponding to the width direction middle portion may be 10° C. or more and 50° C. or less.

[0013] (4) In the method for producing a glass plate according to any one of the above (1) to (3), the glass plate may contain, in mass % calculated as oxide, 50 to 70% of SiO2, 10 to 25% of Al2O3, 0.1 to 5% of B2O3, and 10 to 30% of MgO+CaO+SrO+BaO.

[0014] (5) In the method for producing a glass plate according to any one of (1) to (4) above, a temperature of the side wall portion at a position of the lower end of the formed body corresponding to the width direction end may be 1200° C. or higher and 1350° C. or lower.

[0015] If the temperature of the lower end of the formed body is high, the warping of the glass sheet may worsen, and if the temperature of the lower end of the formed body is low, the glass sheet may devitrify. By setting the temperature of the side wall portion at the position corresponding to the width direction end of the lower end of the formed body to 1200°C or more and 1350°C or less, the occurrence of these problems can be suppressed.

[0016] (6) In the method for producing a glass plate according to any one of the above (1) to (5), a distance between the lower end of the formed body and the side wall portion may be 100 mm or more and 250 mm or less.

[0017] According to this configuration, the molten glass flowing through the lower end of the forming body can be suitably heated by the heater and the side wall of the forming furnace.

[0018] (7) In the method for manufacturing a glass sheet according to any one of (1) to (6) above, a conveying step may be provided in which the glass ribbon is conveyed downward while an end portion in a width direction of the glass ribbon is clamped between conveying rollers, and the conveying rollers may be independently arranged on one end side and the other end side of the glass ribbon in the width direction.

[0019] The glass ribbon conveyed downward in the conveying step is annealed by passing through the inside of an annealing furnace having a predetermined temperature gradient. By independently disposing the conveying rollers at one end side and the other end side in the width direction of the glass ribbon, the temperature inside the annealing furnace can be accurately adjusted, and distortion and thickness deviation of the glass ribbon can be reduced.

[0020] (8) The present invention is aimed at solving the above-mentioned problems, and is characterized in that a rectangular glass plate has a distortion of 0.8 nm or less, an overall thickness deviation of 12 μm or less, a warpage of 55 μm or less, and on an edge along the plate drawing direction, the number of protrusions due to wrinkles within an area of ​​1000 mm in the plate drawing direction is 1 or less.

[0021] According to this configuration, since the number of projections due to distortion, overall thickness deviation, warpage, and wrinkles falls within the above range, the glass plate becomes suitable for manufacturing flexible organic EL devices.

[0022] (9) The length of each side of the glass plate described in (8) above may be 1000 mm or more and 3500 mm or less.

[0023] (10) The glass plate according to (8) or (9) above may have a thickness of 0.3 mm or more and 1.0 mm or less.

[0024] (11) The glass sheet according to any one of (8) to (10) above may have a liquidus temperature of 1100° C. or higher and 1400° C. or lower.

[0025] If the liquidus temperature is 1400° C. or lower, devitrified crystals are less likely to precipitate when the glass is formed by the overflow downdraw method, and productivity can be improved.

[0026] (12) The glass plate according to any one of (8) to (11) above may contain, in mass % calculated as oxide, 50 to 70% of SiO2, 10 to 25% of Al2O3, 0.1 to 5% of B2O3, and 10 to 30% of MgO+CaO+SrO+BaO.

[0027] According to this configuration, it is possible to obtain a glass sheet having a small thermal shrinkage rate and high resistance to devitrification and melting property, and the glass sheet can be suitably used as a carrier glass.

[0028] (13) The glass plate according to any one of (8) to (12) above may be a carrier glass for transporting an organic resin substrate. Effect of the Invention

[0029] According to the present invention, the temperature of the molten glass supplied to the forming body can be appropriately controlled. [Brief description of the drawings]

[0030] [Figure 1] FIG. 2 is a side view showing the glass sheet manufacturing apparatus. [Diagram 2] FIG. 2 is a front view showing the glass sheet manufacturing apparatus. [Diagram 3] FIG. 2 is an enlarged side view showing the periphery of the molded body. [Figure 4] FIG. [Diagram 5] 1 is a flowchart showing a method for manufacturing a glass plate. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. 2 is a side view showing the state of the formed glass ribbon. [Figure 11] FIG. 2 is a cross-sectional view of a glass ribbon. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figures 1 to 11 show an embodiment of a glass plate and a method for producing the same according to the present invention.

[0032] 1 to 3, a glass sheet manufacturing apparatus 1 used in this method includes a forming furnace 2, an annealing furnace 4, a cooling chamber 5, and a cutting chamber 6. The forming furnace 2 and the annealing furnace 4, the annealing furnace 4 and the cooling chamber 5, and the cooling chamber 5 and the cutting chamber 6 are separated by partition members (e.g., floor surfaces of a building) F1, F2, and F3, respectively, having openings (e.g., slits) through which the glass ribbon Gr passes.

[0033] The forming furnace 2 is an apparatus for forming a glass ribbon Gr from molten glass Gm by an overflow downdraw method. In the forming furnace 2, a forming body 3 for forming a glass ribbon Gr from the molten glass Gm and a first conveying roller 7 for cooling both ends in the width direction X of the glass ribbon Gr formed by the forming body 3 are arranged. The forming body 3 and the first conveying roller 7 are surrounded by a furnace wall of the forming furnace 2. The furnace wall of the forming furnace 2 includes a side wall portion 2a and a ceiling portion 2b.

[0034] The formed body 3 is made of a long refractory material along the width direction X of the glass ribbon Gr to be formed. Examples of the refractory material include zircon, zirconia, alumina, magnesia, and xenotime.

[0035] An overflow groove (groove portion) 8 is formed in the top of the forming body 3 along the width direction X. A supply pipe 9 is connected to one end side of the overflow groove 8 in the width direction X. Molten glass Gm is supplied into the overflow groove 8 through this supply pipe 9.

[0036] The forming body 3 has a pair of side surfaces 10 along which the molten glass Gm overflowing from the overflow groove 8 flows. Each of the side surfaces 10 of the forming body 3 includes a vertical surface portion 11 having a planar shape along the vertical direction, and an inclined surface portion 12 that is continuous with the lower side of the vertical surface portion 11 and has a planar shape inclined with respect to the vertical direction.

[0037] The vertical surfaces 11 are planes parallel to each other. The inclined surfaces 12 are planes inclined so as to approach each other as they extend downward. That is, the formed body 3 has a wedge shape tapering downward due to the formation of the inclined surfaces 12, and the corner where the inclined surfaces 12 intersect forms the lower end portion 3a of the formed body 3. The vertical surfaces 11 may be changed in shape to an inclined surface or a curved surface, or may be omitted.

[0038] Guide portions 3b and 3c for regulating the flow of molten glass Gm are provided at the ends of the formed body 3 in the width direction X. The molten glass Gm flows down the side surface 10 of the formed body 3 while maintaining a constant width dimension by being regulated by the guide portions 3b and 3c.

[0039] The first conveying rollers 7 are configured as a pair of rollers that sandwich each end of the glass ribbon Gr in the width direction X below the forming body 3. The first conveying rollers 7 are cantilever type rollers (separate rollers) and are arranged on one end side and the other end side of the glass ribbon Gr so as to independently sandwich each end of the glass ribbon Gr in the width direction X. The first conveying rollers 7 have a structure in which a fluid circulates therein, and are constantly cooled. The first conveying rollers 7 are also called cooling rollers or edge rollers.

[0040] As shown in Figure 3, the outer surface of the side wall portion 2a is provided with a first side heater 15 for heating the upper side of the molded body 3, a second side heater 16 for heating the lower side of the molded body 3, and a ceiling heater 17 for heating the top of the molded body 3.

[0041] The first side heater 15 is disposed on an upper outer surface of the side wall 2a of the forming furnace 2. The second side heater 16 is disposed on a lower outer surface of the side wall 2a of the forming furnace 2. The ceiling heater 17 is disposed on an outer surface of the ceiling 2b of the forming furnace 2.

[0042] 4, the first side heater 15 includes a plurality of heaters 15a-15g arranged linearly along the width direction X. The second side heater 16 includes heaters 16a-16g arranged linearly along the width direction X. Each of the heaters 15a-15g, 16a-16g is formed of, for example, a panel heater, but is not limited to this configuration.

[0043] 3 and 4, the outer surface of the side wall 2a is provided with a first side thermometer 18 for measuring the temperature of the side wall 2a at a position corresponding to the first side heater 15, a second side thermometer 19 for measuring the temperature of the side wall 2a at a position corresponding to the second side heater 16, and a ceiling thermometer 20 for measuring the temperature of the ceiling 2b at a position corresponding to the ceiling heater 17. Each of the thermometers 18 to 20 is formed of, for example, a thermocouple, but is not limited to this configuration.

[0044] 3, the side wall 2a of the forming furnace 2 is separated horizontally from the side surface 10 of the formed body 3 by a distance D1 at a position where the first side thermometer 18 is provided. This distance D1 is preferably 30 mm or more and 100 mm or less.

[0045] The side wall 2a of the forming furnace 2 is separated horizontally from the lower end 3a of the formed body 3 by a distance D2 at a position where the second side thermometer 19 is provided. This distance D2 is preferably 100 mm or more and 250 mm or less.

[0046] 4, the first side thermometer 18 includes a plurality of thermometers 18a-18g corresponding to the plurality of heaters 15a-15g in the first side heater 15. Each of the thermometers 18a-18g is inserted into an insertion hole formed in the center of the corresponding heater 15a-15g and is in contact with the side wall 2a. This allows each of the thermometers 18a-18g to measure the temperature of the side wall 2a at that position.

[0047] 4, the second side thermometer 19 includes a plurality of thermometers 19a-19g corresponding to the plurality of heaters 16a-16g in the second side heater 16. Each of the thermometers 19a-19g is inserted into an insertion hole formed in the center of the corresponding heater 16a-16g and is in contact with the side wall 2a. This allows each of the thermometers 19a-19g to measure the temperature of the side wall 2a at a position corresponding to the lower end 3a of the formed body 3.

[0048] The annealing furnace 4 is a region for reducing warpage and distortion of the glass ribbon Gr. The internal space of the annealing furnace 4 has a predetermined temperature gradient downward. The temperature gradient of the internal space of the annealing furnace 4 can be adjusted by, for example, a heating device such as a heater disposed on the inner wall of the annealing furnace 4.

[0049] Second conveying rollers 13 are arranged in the annealing furnace 4. The second conveying rollers 13 are also called annealer rollers. The second conveying rollers 13 are cantilever type rollers (separate rollers) and are arranged on one end side and the other end side of the glass ribbon Gr so as to independently hold each end of the glass ribbon Gr in the width direction X. The second conveying rollers 13 are provided in a plurality of stages in the vertical direction.

[0050] The second conveyor rollers 13 hold both ends of the glass ribbon Gr in the width direction, and convey and lower the glass ribbon Gr while applying an appropriate tension to the glass ribbon Gr. Hereinafter, the longitudinal direction of the glass ribbon Gr is referred to as a sheet drawing direction A.

[0051] The cooling chamber 5 is a region for cooling the glass ribbon Gr to approximately room temperature. The cooling chamber 5 is open to the outside atmosphere at room temperature, and does not include a heating device such as a heater.

[0052] The third conveying rollers 14 are arranged in the cooling chamber 5. The third conveying rollers 14 are cantilever type rollers (separate rollers) and are arranged on one end side and the other end side of the glass ribbon Gr so as to independently hold each end of the glass ribbon Gr in the width direction X. The third conveying rollers 14 are provided in a plurality of stages in the vertical direction.

[0053] In this embodiment, both ends in the width direction X of the glass ribbon Gr obtained by the manufacturing apparatus 1 include ear portions (unnecessary portions) that are thicker than the central portion in the width direction X due to the influence of shrinkage during the molding process, etc.

[0054] The cutting chamber 6 is an area for cutting the glass ribbon Gr to a predetermined size to obtain a glass sheet G as a glass article. A cutting device (not shown) for cutting the glass ribbon Gr is disposed in the cutting chamber 6. The method for cutting the glass ribbon Gr by the cutting device is scribe cutting, in which a scribe line is formed on the glass ribbon Gr and then the glass ribbon Gr is bent and broken along the scribe line, but is not limited thereto. The cutting method by the cutting device may be, for example, laser cleaving or laser melting.

[0055] Hereinafter, a method for manufacturing a glass sheet G using the manufacturing apparatus 1 having the above configuration will be described. As shown in Fig. 5, this method includes a forming step S1, an annealing step S2, a cooling step S3, a first cutting step S4, a second cutting step S5, and an inspection step S6.

[0056] In the forming step S1, a glass ribbon Gr is formed from the molten glass Gm by an overflow downdraw method. Specifically, in the forming furnace 2, the molten glass Gm is supplied to the overflow groove 8 of the forming body 3, and the molten glass Gm that overflows from the overflow groove 8 onto both side surfaces 10 is caused to flow down along the respective vertical surface portions 11 and inclined surface portions 12 and rejoined at the lower end portion 3a. In this way, a band-shaped glass ribbon Gr is continuously formed from the molten glass Gm.

[0057] In the forming step S1, the formed body 3 is heated by heaters 15, 16, and 17 provided on the furnace wall. That is, in the forming step S1, the ceiling heater 17 heats the molten glass Gm supplied to the overflow groove 8 of the formed body 3. Furthermore, the first side heater 15 heats the molten glass Gm flowing on the upper part (vertical surface portion 11) of the formed body 3. Then, the second side heater 16 heats the molten glass Gm flowing on the lower part (inclined surface portion 12) of the formed body 3.

[0058] In the molding step S1, the temperature of the side wall portion 2a of the furnace wall where the first side heater 15 and the second side heater 16 are arranged is measured by a first side thermometer 18 and a second side thermometer 19. In addition, the temperature of the ceiling portion 2b of the furnace wall where the ceiling heater 17 is arranged is measured by a ceiling thermometer 20.

[0059] The output of the first side heater 15 is adjusted so that the temperature of the side wall 2a measured by the first side thermometer 18 is 1280° C. or more and 1320° C. or less. The second side heater 16 adjusts the temperature of the side wall 2a measured by the second side thermometer 19 to T R (℃), the liquidus temperature T L (℃) difference T R -T L The output of the second side heater 16 is adjusted so that the temperature (°C) of the side wall 2a at the position corresponding to the lower end 3a of the molded body 3 is within the above-mentioned temperature range. The temperature of the side wall 2a measured by the second side thermometer 19 is referred to as T R (°C) is preferably 1200°C or higher and 1350°C or lower. The output of ceiling heater 17 is adjusted so that the temperature of ceiling portion 2b measured by ceiling thermometer 20 is 1280°C or higher and 1340°C or lower.

[0060] By adjusting the temperature as described above, the temperature of the molten glass Gm supplied to the overflow groove 8 of the forming body 3 is suitably maintained by the ceiling heater 17. In addition, the temperature of the molten glass Gm flowing through the upper part of the forming body 3 is suitably maintained by the first side heater 15. In addition, the temperature of the molten glass Gm flowing through the lower part of the forming body 3 is suitably maintained by the second side heater 16.

[0061] In the first side heater 15, among the heaters 15a to 15g arranged in a row along the width direction X, the temperature of the portion of the side wall 2a heated by the heaters 15a, 15g located at the ends in the width direction X is higher than the temperature of the portion of the side wall 2a heated by the heater 15d located in the middle in the width direction X. In other words, the temperature of the side wall 2a at the positions corresponding to the ends (guide portions 3b, 3c) in the width direction X in the upper part of the formed body 3 is higher than the temperature of the side wall 2a at the position corresponding to the middle part 3d in the width direction X (see FIG. 4) in the upper part of the formed body 3. The temperature difference is preferably 10°C or more and 100°C or less.

[0062] In the second side heater 16, among the heaters 16a to 16g arranged in a row along the width direction X, the temperature of the portion of the side wall 2a heated by the heaters 16a, 16g located at the ends in the width direction X is higher than the temperature of the portion of the side wall 2a heated by the heater 16d located in the middle in the width direction X. In other words, the temperature of the side wall 2a at the positions corresponding to the ends (guide portions 3b, 3c) in the width direction X at the lower end 3a of the formed body 3 is higher than the temperature of the side wall 2a at the position corresponding to the middle portion 3d in the width direction X at the lower end 3a of the formed body 3. The temperature difference is preferably 10°C or more and 50°C or less.

[0063] In the forming step S1, the time it takes for the molten glass Gm to overflow from the overflow groove 8 of the formed body 3 and reach the lower end 3a of the formed body 3 is, for example, from 500 seconds to 1500 seconds, and preferably from 800 seconds to 1200 seconds.

[0064] In the annealing step S2, in the annealing furnace 4, the glass ribbon Gr is conveyed downward in a state in which the end portions in the width direction X of the glass ribbon Gr are clamped by the second conveyor rollers 13 (conveying step). The glass ribbon Gr is annealed by being conveyed downward in the annealing furnace 4.

[0065] In the subsequent cooling step S3, in the cooling chamber 5, the glass ribbon Gr that has been subjected to the gradual cooling step S2 is conveyed downward in a state in which the end portions in the width direction X of the glass ribbon Gr are clamped by the third conveyor rollers 14 (conveying step). The glass ribbon Gr is cooled to approximately room temperature by being conveyed downward in the cooling chamber 5.

[0066] In a first cutting step S4, in a cutting chamber 6, the glass ribbon Gr cooled in the cooling step S3 is cut into predetermined lengths in the width direction X to obtain a glass sheet G. In a subsequent second cutting step S5, edge portions (unnecessary portions) at both ends of the glass sheet G in the width direction X are cut and removed by means of scribing or the like.

[0067] In the inspection step S6, the shape and the like of the glass sheet G are inspected by the inspection device 21 to determine whether it is good or bad. Items inspected by the inspection device 21 include warping, uneven thickness, distortion, and the like of the glass sheet G, for example.

[0068] In the inspection process S6, the warp and thickness (uneven thickness) of the glass sheet G are inspected using an inspection device 21 shown in Fig. 6. The inspection device 21 includes a base 22 on which the glass sheet G is placed, and a measuring device 23 for measuring the warp and thickness of the glass sheet G.

[0069] The glass plate G is placed on the upper surface 22a of the surface plate 22. The measuring device 23 is constituted by, for example, a movable laser displacement meter, but is not limited to this configuration. The measuring device 23 is disposed above the surface plate 22. A groove having a width of 0.5 to 3 mm may be formed on the upper surface of the surface plate 22.

[0070] 6, the measuring device 23 irradiates the upper surface of the glass plate G with laser light L while moving above the glass plate G in a predetermined direction. The measuring device 23 measures the distance from the measuring device 23 to the upper surface of the glass plate G by receiving the laser light reflected from the upper surface of the glass plate G. The measuring device 23 performs this measurement for a plurality of measurement points set on the glass plate G. As a result, the difference in the measurement values ​​at each measurement point can be calculated as the amount of warping of the glass plate G.

[0071] Hereinafter, a case where the thickness (uneven thickness) of the glass sheet G is measured will be described. As shown in FIG. 6, the inspection device 21 measures the thickness of the glass sheet G in a state where the glass sheet G is placed on the upper surface 22a of the surface plate 22. Specifically, the inspection device 21 measures the thickness of the glass sheet G at a position between the adjacent surface plates 22 while moving the measurement device 23. The measurement device 23 irradiates both the upper surface and the lower surface of the glass sheet G with laser light L while moving. The measurement device 23 receives the laser light reflected from the upper surface and the laser light reflected from the lower surface, and can measure the difference in the optical path length as the thickness of the glass sheet G. The degree of uneven thickness of the glass sheet G can be confirmed by calculating the difference between the maximum value and the minimum value of the measured thickness.

[0072] As shown in Fig. 7, the inspection device 24 floats the glass sheet G from the surface plate 25 and measures the warpage. A plurality of nozzles for spraying a fluid (e.g., gas) are formed on the upper surface 25a of the surface plate 25. As shown in Fig. 7, the inspection device 24 sprays the fluid from the nozzles of the surface plate 25 and floats the glass sheet G above the surface plate 25. In this floated state, the measurement device 26 measures the distance between the measurement device 26 and the upper surface of the glass sheet G, similar to the example of Fig. 6.

[0073] When measuring the distortion of the glass plate G, a birefringence measuring device is preferably used that measures the birefringence of the glass plate G by using, for example, a common path interferometer using an optical heterodyne method and a Fourier analysis method. This birefringence measuring device can measure the magnitude and azimuth angle of retardation (retardation: phase difference due to birefringence) in order to evaluate the characteristics such as distortion of the glass plate G. This measuring device can calculate the distortion of the glass plate G based on the magnitude and azimuth angle of retardation. Note that the larger the retardation, the larger the distortion. When measuring the distortion of the glass plate G, the measurement is performed with the glass plate G placed on a surface plate.

[0074] In the inspection process S6, the quality of the glass sheet G is judged based on the measurement values ​​of the glass sheet G measured as described above (evaluation process). In this evaluation process, the measurement values ​​are compared with a predetermined reference value (threshold value). If the measurement values ​​of the glass sheet G are within the range of the reference values, the glass sheet G is judged to be "good". If the measurement values ​​of the glass sheet G are outside the range of the reference values, the glass sheet G is judged to be "defective".

[0075] 8 and 9 show a glass sheet G manufactured by the present method. As shown in Fig. 8, the glass sheet G manufactured by the present method is configured to have a rectangular shape. The length of one side of the glass sheet G is preferably 1000 mm or more and 3500 mm or less. The sheet thickness t of the glass sheet G is preferably 0.3 mm or more and 1.0 mm or less.

[0076] The glass sheet G includes a first side Ga, a second side Gb and a third side Gc intersecting (for example, forming a right angle) with the first side Ga, and a fourth side Gd facing the first side Ga. The first side Ga and the fourth side Gd are sides along the sheet drawing direction A. The second side Gb and the third side Gc are sides along a direction perpendicular to the sheet drawing direction, i.e., the width direction X of the glass ribbon Gr.

[0077] The drawing direction A of the glass sheet G 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 sheet G in a dark room and projecting the transmitted light onto a screen. Therefore, even in the state of the glass sheet G after forming, the drawing direction A during forming can be identified.

[0078] The distortion of the glass plate G is preferably 0.3 nm or more and 1.5 nm or less. When measuring the distortion of the glass plate G, the measurement is performed at measurement points with a pitch of 100 mm using the birefringence measuring device described above, and the maximum value of the retardation obtained is regarded as the distortion of the glass plate G. By making the distortion of the glass plate G 0.3 nm or more and 1.5 nm or less, when the glass plate G is used as a carrier glass for transporting an organic resin substrate, the pitch deviation of the element formed on the organic resin layer can be suppressed.

[0079] The warpage of the glass sheet G is preferably 20 μm or more and 100 μm or less. When measuring the warpage of the glass sheet G, the above-mentioned inspection device 21 is used to measure at measurement points with a pitch of 50 mm, and the maximum value of the obtained warpage is taken as the warpage of the glass sheet G. By making the warpage of the glass sheet G 20 μm or more and 100 μm or less, when the glass sheet G is used as a carrier glass for transporting an organic resin substrate, it is possible to suppress unevenness in film formation when an organic resin is applied to the surface of the glass sheet G to form a film.

[0080] The thickness deviation of the entire glass sheet G is preferably 1 μm or more and 30 μm or less. When measuring the thickness deviation of the entire glass sheet G, the above-mentioned inspection device 21 is used to measure at measurement points with a pitch of 10 mm, and the difference between the maximum and minimum plate thickness values ​​is taken as the thickness deviation of the glass sheet G. By making the thickness deviation of the entire glass sheet G 1 μm or more and 30 μm or less, when the glass sheet G is used as a carrier glass for transporting an organic resin substrate, the thickness of the organic resin layer can be made uniform.

[0081] The liquidus temperature of the glass plate G is preferably 1100° C. or more and 1400° C. or less. The “liquidus temperature” is defined as the temperature at which crystals (primary phase) precipitate when a glass powder that passes through a standard sieve of 30 mesh (sieve opening of 500 μm) and remains on a 50 mesh (sieve opening of 300 μm) is placed in a platinum boat and held in a temperature gradient furnace for 24 hours.

[0082] The glass plate G preferably contains, in mass % calculated as oxide, 50 to 70% of SiO2, 10 to 25% of Al2O3, 0.1 to 5% of B2O3, and 10 to 30% of MgO+CaO+SrO+BaO.

[0083] As shown in Fig. 9, the glass plate G may have a resin layer R formed on its surface. This resin layer R preferably contains at least one selected from the group consisting of polyimide, polyamideimide, polyetherimide, and polyesterimide. The resin layer R is formed by applying or coating a resin material onto the surface of the glass plate G.

[0084] According to the manufacturing method of the glass sheet G according to the present embodiment described above, by setting the temperature of the side wall portion 2a of the forming furnace 2 at the position corresponding to the lower end portion 3a of the formed body 3 to 1200°C or higher and 1350°C or lower, it is possible to minimize warping, uneven thickness, and distortion of the manufactured glass sheet G and to prevent devitrification of the glass sheet G.

[0085] The present inventors have confirmed that when the temperature of the side wall portion 2a of the forming furnace 2 exceeds 1350°C, the following defects are formed in the glass ribbon Gr (glass sheet G). That is, as shown in Figs. 10 and 11, a plurality of protrusions P due to wrinkles are formed in a part of the glass ribbon Gr formed by the forming body 3. The protrusions P are generated when the molten glass Gm is at a high temperature. This is considered to occur because a part of the formed glass ribbon Gr moves downward at a speed exceeding the conveying speed of the conveying rollers 7, 13, and 14.

[0086] According to this embodiment, by controlling the temperature of the side wall portion 2a of the forming furnace 2 in the forming step S1 to be within the above-mentioned temperature range, it is possible to prevent the generation of a plurality of protrusions P on the glass sheet G.

[0087] In the produced glass sheet G, it is preferable that the number of the above-mentioned protrusions P within a length of 1000 mm on the first side Ga or the fourth side Gd along the sheet drawing direction A is 1 or less. The protrusions P have a height H (see FIG. 11) from the surface of the glass sheet G of 5 μm or more and 80 μm or less, and a length D3 (see FIG. 11) in the sheet drawing direction A of 50 mm or more and 500 mm or less. The size and number of the protrusions P can be measured by the measurement method exemplified in FIG. 7.

[0088] The glass plate G produced by this method is suitably used as a carrier glass in producing devices such as flexible organic EL displays.

[0089] The present invention is not limited to the configuration of the above embodiment, nor is it limited to the above-mentioned effects and advantages. Various modifications of the present invention are possible without departing from the spirit and scope of the present invention.

[0090] In the above embodiment, the glass sheet G cut out from the glass ribbon Gr has been exemplified. However, the glass sheet according to the present invention is not limited to this and may include, for example, a glass roll obtained by winding up the glass ribbon Gr in a roll shape. EXAMPLES

[0091] The present inventors carried out a comparative test to confirm the effect of the manufacturing method of the glass plate of the present invention. In this test, a glass plate according to Example 1 and glass plates according to Comparative Examples 1 and 2 were manufactured, and the warp, distortion, and thickness deviation of the glass plate according to each example were measured, and the presence or absence of devitrification and the number of protrusions P were confirmed. For the glass plates according to Example 1 and Comparative Examples 1 and 2, only the temperature conditions of the side wall of the forming furnace at the position corresponding to the lower end of the formed body were changed, and the other manufacturing conditions and glass composition were the same. In Table 1, the temperature of the side wall of the forming furnace at the position corresponding to the end of the lower end of the formed body in the width direction of the formed body is set as T RE (°C), and the temperature of the side wall of the forming furnace at the position of the lower end of the formed body corresponding to the center of the formed body in the width direction is T RC (℃). [Table 1]

[0092] According to Table 1 above, the glass sheet according to Example 1 has a temperature T RE (℃) is the liquidus temperature T L (°C), it was possible to reduce warping, distortion, and thickness deviation. In addition, under the temperature conditions of Example 1, the temperature T RE Since the temperature (°C) is 1200°C or higher and 1350°C or lower, devitrification does not occur in the glass sheet, and no protrusions P are formed.

[0093] The glass sheet according to Comparative Example 1 had a temperature T RE (℃) is the liquidus temperature T L (°C), the temperature T RE Because the temperature (℃) is less than 1200℃, devitrification occurs in the glass sheet.

[0094] The glass sheet according to Comparative Example 2 had a temperature T RE (℃) is the liquidus temperature T L (°C), the temperature T RE Since the alloy was manufactured under conditions where the temperature (℃) was above 1350℃, the number of protrusions P is two. [Explanation of symbols]

[0095] 2 Molding furnace 2a Side wall of the forming furnace 3. Molded body 3a Lower end of molded body 3b Guide portion (widthwise end portion of molded body) 3c Guide portion (widthwise end portion of molded body) 3d: Middle part of the molded body in the width direction 7 First conveyor roller 8 Overflow groove (groove) 10 Side of molded body 13 Second conveyor roller 14 Third conveyor roller 15 First side heater 16 Second side heater A Drawing direction D2 Distance between the side wall of the forming furnace and the bottom end of the formed body G Glass plate Ga: First edge of glass sheet (edge ​​along the sheet drawing direction) Gd The fourth side of the glass sheet (the side along the sheet drawing direction) Gm Molten Glass Gr Glass ribbon P protrusion R resin layer S1 Molding process t Thickness of glass plate

Claims

1. A method for producing a glass sheet, comprising a forming step of causing molten glass overflowing from a groove of a forming body arranged in a forming furnace to flow down along both side surfaces of the forming body by an overflow downdraw method, and then fusing the molten glass at a lower end of the forming body to form a glass ribbon, In the forming step, the molten glass flowing down the both side surfaces of the forming body is heated by a heater provided in a side wall portion of the forming furnace, The temperature of the side wall of the forming furnace at a position of the lower end of the formed body corresponding to the end of the formed body in the width direction is defined as T ＲＥ (° C.), the liquidus temperature T Ｌ (℃) difference T ＲＥ -T Ｌ (°C) is 15°C or more and 75°C or less.

2. 2. The method for manufacturing a glass plate according to claim 1, wherein the temperature of the side wall portion at a position of the lower end of the formed body corresponding to the width direction end is higher than the temperature of the side wall portion at a position of the lower end of the formed body corresponding to the width direction middle portion.

3. 3. The method for manufacturing a glass plate according to claim 2, wherein a temperature difference between a temperature of the side wall portion at a position of the lower end of the formed body corresponding to the width direction end portion and a temperature of the side wall portion at a position of the lower end of the formed body corresponding to the width direction middle portion is 10° C. or more and 50° C. or less.

4. The glass plate contains, in terms of oxide, SiO ２ 50-70%, Al ２ O ３ 10-25%, B ２ O ３ 4. The method for producing a glass plate according to claim 1, further comprising: 0.1 to 5% of MgO; and 10 to 30% of MgO+CaO+SrO+BaO.

5. 4. The method for manufacturing a glass plate according to claim 1, wherein a temperature of the side wall portion at a position of the lower end of the formed body corresponding to the end in the width direction is 1200° C. or higher and 1350° C. or lower.

6. 4. The method for manufacturing a glass plate according to claim 1, wherein a distance between the lower end of the formed body and the side wall portion is 100 mm or more and 250 mm or less.

7. A conveying step of conveying the glass ribbon downward in a state in which an end portion in a width direction of the glass ribbon is sandwiched between conveying rollers, The method for manufacturing a glass sheet according to any one of claims 1 to 3, wherein the transport rollers are independently arranged on one end side and the other end side in the width direction of the glass ribbon.

8. A rectangular glass plate, The distortion is 0.8 nm or less, The overall thickness deviation is 12 μm or less, The warpage is 55 μm or less, A glass sheet, characterized in that, on an edge along a sheet drawing direction, the number of protrusions due to wrinkles within an area of ​​1000 mm in the sheet drawing direction is 1 or less.

9. 9. The glass plate according to claim 8, wherein the length of each side of the glass plate is 1000 mm or more and 3500 mm or less.

10. 10. The glass plate according to claim 8, wherein the glass plate has a thickness of 0.3 mm or more and 1.0 mm or less.

11. 10. The glass plate according to claim 8, wherein the liquidus temperature of the glass plate is 1100°C or higher and 1400°C or lower.

12. The glass plate contains, in terms of oxide, SiO ２ 50-70%, Al ２ O ３ 10-25%, B ２ O ３ 10. The glass plate according to claim 8, further comprising 0.1 to 5% of CaO, and 10 to 30% of MgO+CaO+SrO+BaO.

13. 10. The glass plate according to claim 8, wherein the glass plate is a carrier glass for transporting an organic resin substrate.

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