Glass sheet and production method therefor

Abstract

Provided is a method for producing a glass sheet G, the method including a forming step S1 in which a molten glass Gm flowing down on both side surfaces 10 of a shaped body 3 is heated by heaters 16 provided to side walls 2a of a forming oven 2. When the temperature of the side walls 2 of the forming oven 2 which are in positions corresponding to the width-direction ends 3b, 3c of the shaped body 3, in the lower end 3a of the shaped body 3, is expressed by TRE (°C), then the difference between itself and the liquidus temperature TL (°C) of the glass sheet G, TRE-TL (°C), is 15-75°C.

Description

Glass plate and its manufacturing method

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

[0002] In recent years, the use of organic resin substrates as substrates for fabricating flexible organic EL displays has been attracting attention. However, due to the flexibility of organic resin substrates, it is difficult to directly form a semiconductor film on the substrate. Therefore, a process is required in which an organic resin layer is laminated on a carrier glass and then a semiconductor film is formed on the organic resin layer (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 in the upper part of a forming body having a generally wedge-shaped cross section, and the molten glass overflowing on both sides of the overflow groove flows 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).

[0004] International Publication No. 2018 / 199059 Japanese Patent Application Laid-Open No. 2021-195294

[0005] The glass plate used for the carrier glass is required to have the following properties: (1) small distortion of the glass plate to suppress pitch deviation of elements formed on the organic resin layer, (2) small warpage of the glass plate to suppress uneven film formation when organic resin is applied to the surface of the glass plate to form a film, and (3) small uneven thickness of the glass plate to ensure a uniform thickness of the organic resin layer.

[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] The present invention has as its technical object to appropriately control the temperature of molten glass supplied to a forming body.

[0008] (1) The present invention is intended to solve the above-mentioned problems, and is a method for manufacturing 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 increased to T RE (°C), the liquidus temperature T L (℃) 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 surface of the forming body, the temperature of the molten glass can be controlled by measuring the temperature of the side wall on which the heater is provided. Furthermore, the temperature at a position on the side wall of the forming furnace corresponding to the end of the lower end of the forming body in the width direction is determined as T RE (°C), the liquidus temperature T L (℃) RE -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, warpage, and thickness deviation of the glass ribbon formed by the forming body.

[0010] (2) In the method for manufacturing a glass plate described in (1) above, the 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 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.

[0011] The molten glass flowing down the side surface of the forming body tends to have a higher temperature at the widthwise middle portion of the lower end of the forming body and a lower temperature at the widthwise both end portions of the lower end of the forming body. When 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 portion 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 portion 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 manufacturing 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 portion 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 portion 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 (1) to (3), the glass plate may contain, in mass % calculated as oxide, 50 to 70% of SiO, 10 to 25% of AlO, 0.1 to 5% of BO, 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, the 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 (1) to (5) above, the 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 plate according to any one of (1) to (6) above, a conveying step may be provided in which the glass ribbon is conveyed downward while the widthwise ends of the glass ribbon are 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 widthwise direction.

[0019] The glass ribbon conveyed downward in the conveying step is annealed by passing through the interior of an annealing furnace having a predetermined temperature gradient. By independently arranging 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 intended to solve the above-mentioned problems, and is characterized by a rectangular glass plate having 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 sheet drawing direction, the number of protrusions due to wrinkles within a range of 1000 mm in the sheet 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 is 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 according to (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 plate 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 1,400° 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 oxides, 50 to 70% of SiO, 10 to 25% of AlO, 0.1 to 5% of BO, and 10 to 30% of MgO + CaO + SrO + BaO.

[0027] According to this configuration, a glass sheet having a small thermal shrinkage rate and high resistance to devitrification and melting property can be obtained, and 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.

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

[0030] Fig. 1 is a side view showing a glass sheet manufacturing apparatus; Fig. 2 is a front view showing a glass sheet manufacturing apparatus; Fig. 3 is an enlarged side view showing the periphery of a formed body; Fig. 4 is an enlarged front view showing a formed body; Fig. 5 is a flowchart showing a method for manufacturing a glass sheet; Fig. 6 is a front view showing an inspection step; Fig. 7 is a front view showing the inspection step; Fig. 8 is a perspective view of a glass sheet; Fig. 9 is a perspective view of a glass sheet; Fig. 10 is a side view showing a state of a formed glass ribbon; Fig. 11 is a cross-sectional view of the glass ribbon.

[0031] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. Figures 1 to 11 show an embodiment of a glass plate and a method for manufacturing 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., floors of a building) F1, F2, and F3, respectively, each having an opening (e.g., a slit) 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 the overflow downdraw method. Arranged within the forming furnace 2 are a forming body 3 that forms the glass ribbon Gr from the molten glass Gm, and first conveying rollers 7 that cool both ends in the width direction X of the glass ribbon Gr formed by the forming body 3. The forming body 3 and the first conveying rollers 7 are surrounded by furnace walls of the forming furnace 2. The furnace walls of the forming furnace 2 include side wall portions 2a and a ceiling portion 2b.

[0034] The formed body 3 is formed 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 at the top of the forming body 3 along the width direction X. A supply pipe 9 is connected to one end 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 3a of the formed body 3. The vertical surfaces 11 may be modified to have an inclined surface or a curved surface, or may be omitted.

[0038] Guide portions 3 b, 3 c 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 is regulated by these guide portions 3 b, 3 c, and flows down the side surface 10 of the formed body 3 while maintaining a constant width dimension.

[0039] The first conveying rollers 7 are configured as a pair of rollers below the forming body 3, which sandwich each end of the glass ribbon Gr in the width direction X. 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 inside them, 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 that heats the upper side of the formed body 3, a second side heater 16 that heats the lower side of the formed body 3, and a ceiling heater 17 that heats the top of the formed body 3.

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

[0042] 4, the first side heater 15 includes a plurality of heaters 15a to 15g arranged linearly along the width direction X. The second side heater 16 includes heaters 16a to 16g arranged linearly along the width direction X. Each of the heaters 15a to 15g and 16a to 16g is configured, for example, by 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 by a distance D1 from the side surface 10 of the formed body 3 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 by a distance D2 from the lower end 3a of the formed body 3 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 to 18g corresponding to the plurality of heaters 15a to 15g in the first side heater 15. Each of the thermometers 18a to 18g is inserted into an insertion hole formed in the center of the corresponding heater 15a to 15g and is in contact with the side wall portion 2a. This allows each of the thermometers 18a to 18g to measure the temperature of the side wall portion 2a at that position.

[0047] 4, the second side thermometer 19 includes a plurality of thermometers 19a to 19g corresponding to the plurality of heaters 16a to 16g in the second side heater 16. Each of the thermometers 19a to 19g is inserted into an insertion hole formed in the center of the corresponding heater 16a to 16g and is in contact with the side wall portion 2a. This allows each of the thermometers 19a to 19g to measure the temperature of the side wall portion 2a at a position corresponding to the lower end portion 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 in the internal space of the annealing furnace 4 can be adjusted by, for example, a heating device such as a heater arranged 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 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 multiple stages in the vertical direction.

[0050] The second conveying rollers 13 pinch 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 will be referred to as the sheet drawing direction A.

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

[0052] 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 multiple 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 arranged in the cutting chamber 6. The method for cutting the glass ribbon Gr by the cutting device is, but is not limited to, 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. The cutting method by the cutting device may also be, for example, laser cleaving or laser fusing.

[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 the 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 flows down along the respective vertical surface portions 11 and inclined surface portions 12 and rejoins at the lower end portion 3 a. In this way, a belt-shaped glass ribbon Gr is continuously formed from the molten glass Gm.

[0057] In the forming step S1, the forming 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 forming body 3. Furthermore, the first side heater 15 heats the molten glass Gm flowing on the upper part (vertical surface portion 11) of the forming body 3. Then, the second side heater 16 heats the molten glass Gm flowing on the lower part (inclined surface portion 12) of the forming body 3.

[0058] In the molding step S1, the temperatures of the side wall portions 2a of the furnace wall where the first side heater 15 and the second side heater 16 are arranged are measured by the first side thermometer 18 and the 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 the 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 (°C), the liquidus temperature T L (℃) R -T L The output of the second side heater 16 is adjusted so that the temperature T (°C) of the side wall 2a at the position corresponding to the lower end 3a of the formed body 3 is within the above temperature range. RThe temperature (°C) is preferably 1200°C or higher and 1350°C or lower. The output of the ceiling heater 17 is adjusted so that the temperature of the ceiling portion 2b measured by the 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. Furthermore, the temperature of the molten glass Gm flowing above the forming body 3 is suitably maintained by the first side heater 15. Furthermore, the temperature of the molten glass Gm flowing below the forming body 3 is suitably maintained by the second side heater 16.

[0061] In the first side heater 15, among the multiple 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 in the width direction X (guide portions 3b, 3c) 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 portion 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 multiple 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 in the width direction X (guide portions 3b, 3c) 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 forming body 3 and reach the lower end 3a of the forming body 3 is, for example, 500 seconds or more and 1500 seconds or less, preferably 800 seconds or more and 1200 seconds or less.

[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 of the glass ribbon Gr in the width direction X are sandwiched between the second conveying 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 annealing step S2 is conveyed downward in a state in which the end portions in the width direction X of the glass ribbon Gr are sandwiched between the third conveyor rollers 14 (conveying step). By being conveyed downward in the cooling chamber 5, the glass ribbon Gr is cooled to near room temperature.

[0066] In the first cutting step S4, in the 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 glass sheets G. In the subsequent second cutting step S5, ear 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 warpage, uneven thickness, distortion, and the like of the glass sheet G, for example.

[0068] In the inspection step S6, the warpage 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 surface plate 22 on which the glass sheet G is placed, and a measuring device 23 for measuring the warpage and thickness of the glass sheet G.

[0069] The glass plate G is placed on an upper surface 22a of a surface plate 22. The measuring device 23 is configured, for example, by 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 sheet G with laser light L while moving above the glass sheet G in a predetermined direction. The measuring device 23 measures the distance from the measuring device 23 to the upper surface of the glass sheet G by receiving the laser light reflected from the upper surface of the glass sheet G. The measuring device 23 performs this measurement at a plurality of measurement points set on the glass sheet G. As a result, the difference between the measurement values ​​at each measurement point can be calculated as the amount of warping of the glass sheet G.

[0071] Hereinafter, a case where the thickness (thickness deviation) of a 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 a surface plate 22. Specifically, the inspection device 21 measures the thickness of the glass sheet G at a position between adjacent surface plates 22 while moving the measuring device 23. The measuring device 23 irradiates both the upper surface and the lower surface of the glass sheet G with laser light L while moving. The measuring 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 optical path length as the thickness of the glass sheet G. The degree of thickness deviation of the glass sheet G can be confirmed by calculating the difference between the maximum and minimum values ​​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 its warpage. A plurality of ejection holes for ejecting a fluid (e.g., a gas) are formed on the upper surface 25a of the surface plate 25. As shown in Fig. 7 , the inspection device 24 ejects the fluid from the ejection holes of the surface plate 25, causing the glass sheet G to float 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 a glass plate G, a birefringence measuring device is preferably used that measures the birefringence of the glass plate G using, for example, a common path interferometer based on the optical heterodyne method and Fourier analysis. 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 of the glass plate G, such as distortion. 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 step S6, the quality of the glass sheet G is determined based on the measurement values ​​of the glass sheet G measured as described above (evaluation step). In this evaluation step, the measurement values ​​are compared with predetermined reference values ​​(threshold values). If the measurement values ​​of the glass sheet G are within the range of the reference values, the glass sheet G is determined 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 determined to be "defective."

[0075] 8 and 9 show a glass sheet G produced by this method. As shown in Fig. 8, the glass sheet G produced by this 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 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 that intersect with (for example, form a right angle with) the first side Ga, and a fourth side Gd that faces the first side Ga. The first side Ga and the fourth side Gd are sides that extend along the sheet drawing direction A. The second side Gb and the third side Gc are sides that extend in a direction perpendicular to the sheet drawing direction, i.e., along 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) on the glass sheet G in a darkroom while adjusting the angle of the glass sheet G and projecting the transmitted light onto a screen. Therefore, the drawing direction A during forming can be identified even in the state of the glass sheet G after forming.

[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 100 mm pitch using the birefringence measuring device described above, and the maximum value of the obtained retardation magnitude is taken as the distortion of the glass plate G. By setting the distortion of the glass plate G to 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, pitch deviation of elements 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 spaced 50 mm apart, and the maximum value of the obtained warpage is taken as the warpage of the glass sheet G. By setting the warpage of the glass sheet G to 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, uneven film formation can be suppressed when an organic resin is applied to the surface of the glass sheet G to form a film.

[0080] The overall thickness deviation of the glass sheet G is preferably 1 μm or more and 30 μm or less. When measuring the overall thickness deviation of the glass sheet G, the above-mentioned inspection device 21 is used to measure at measurement points at 10 mm intervals, and the difference between the maximum and minimum plate thickness values ​​is taken as the thickness deviation of the glass sheet G. By setting the overall thickness deviation of the glass sheet G to 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 higher and 1400° C. or lower. The “liquidus temperature” is defined as the value measured by placing glass powder that passes through a standard 30 mesh sieve (sieve opening 500 μm) and remains on a 50 mesh sieve (sieve opening 300 μm) in a platinum boat and holding the boat in a temperature gradient furnace for 24 hours, and then measuring the temperature at which crystals (primary phase) precipitate.

[0082] The glass sheet G preferably contains, in mass % calculated as oxides, 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] 9 , a glass sheet 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 sheet 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 2 a of the forming furnace 2 at the position corresponding to the lower end portion 3 a of the formed body 3 to 1200°C or higher and 1350°C or lower, it is possible to minimize warpage, uneven thickness, and distortion of the glass sheet G to be manufactured and to prevent devitrification of the glass sheet G.

[0085] The present inventors have confirmed that when the temperature of the side wall portion 2 a 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 Fig. 10 and Fig. 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. It is considered that these protrusions P are formed because, due to the high temperature of the molten glass Gm, a part of the formed glass ribbon Gr moves downward at a speed that exceeds the conveying speed of the conveying rollers 7, 13, and 14.

[0086] According to the present embodiment, by controlling the temperature of the side wall portion 2 a of the forming furnace 2 in the forming step S1 so that it is within the above-mentioned temperature range, it is possible to prevent the generation of multiple 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 be 1 or less within a length of 1000 mm on the first side Ga or the fourth side Gd along the drawing direction A. The protrusions P have a height H (see FIG. 11 ) from the surface of the glass sheet G of 5 μm to 80 μm, and a length D3 (see FIG. 11 ) in the drawing direction A of 50 mm to 500 mm. 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 when producing devices such as flexible organic EL displays.

[0089] The present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. The present invention can be modified in various ways without departing from the spirit of the present invention.

[0090] In the above embodiment, the glass sheet G cut out from the glass ribbon Gr is exemplified, but the glass sheet according to the present invention is not limited to this and includes, for example, a glass roll obtained by winding the glass ribbon Gr into a roll.

[0091] The present inventors conducted a comparative test to confirm the effect of the manufacturing method of a 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 warpage, 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 portion of the forming furnace at a 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 portion of the forming furnace at a position corresponding to the end of the lower end of the formed body in the width direction is set to T RE (°C), and the temperature of the side wall of the forming furnace at a position of the lower end of the formed body corresponding to the center of the formed body in the width direction is T RC (℃).

[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 warpage, 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 has a temperature T RE (℃) is the liquidus temperature T L (°C), the temperature T RE Since the temperature (°C) is less than 1200°C, devitrification occurs in the glass sheet.

[0094] The glass sheet according to Comparative Example 2 has a temperature T RE (℃) is the liquidus temperature T L (°C), the temperature T RE Since the alloy was manufactured under the condition that the temperature (°C) was higher than 1350°C, the number of protrusions P was two.

[0095] DESCRIPTION OF SYMBOLS 2 Forming furnace 2a Side wall of forming furnace 3 Formed body 3a Lower end of formed body 3b Guide portion (widthwise end of formed body) 3c Guide portion (widthwise end of formed body) 3d Widthwise middle portion of formed body 7 First conveying roller 8 Overflow groove (groove portion) 10 Side of formed body 13 Second conveying roller 14 Third conveying roller 15 First side heater 16 Second side heater A Sheet drawing direction D2 Distance between side wall of forming furnace and lower end of formed body G Glass sheet Ga First side of glass sheet (side along the sheet drawing direction) Gd Fourth side of glass sheet (side along the sheet drawing direction) Gm Molten glass Gr Glass ribbon P Protrusion R Resin layer S1 Forming process t Thickness of glass sheet

Claims

1. A method for manufacturing a glass sheet, comprising a forming step of forming a glass ribbon by forming molten glass overflowing from a groove of a forming body arranged in a forming furnace by an overflow downdraw method, flowing down along both side surfaces of the forming body, and fusing the molten glass at a lower end of the forming body, 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 the width direction end of the forming body is set to 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. The method for manufacturing a glass plate as described in claim 1, characterized in that the temperature of the side wall portion at a position of the lower end of the formed body corresponding to the widthwise 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 widthwise middle portion.

3. The method for manufacturing a glass plate as described in claim 2, characterized in that the temperature difference between the temperature of the side wall portion at a position of the lower end of the molded body corresponding to the widthwise end portion and the temperature of the side wall portion at a position of the lower end of the molded body corresponding to the widthwise middle portion is 10°C or more and 50°C or less.

4. The method for manufacturing a glass plate according to any one of claims 1 to 3, characterized in that the glass plate contains, in mass % calculated as oxide, 50 to 70% SiO2, 10 to 25% Al2O3, 0.1 to 5% B2O3, and 10 to 30% MgO + CaO + SrO + BaO.

5. A method for manufacturing a glass plate as described in any one of claims 1 to 3, characterized in that the temperature of the side wall portion at the position of the lower end of the formed body corresponding to the widthwise end is 1200°C or higher and 1350°C or lower.

6. A method for manufacturing a glass plate according to any one of claims 1 to 3, characterized in that the 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 method for manufacturing a glass sheet as described in any one of claims 1 to 3, characterized in that it comprises a conveying step of conveying the glass ribbon downward while clamping the widthwise ends of the glass ribbon between conveying rollers, the conveying rollers being independently arranged on one end side and the other end side of the glass ribbon in the widthwise direction.

8. A rectangular glass plate having 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 sheet drawing direction, the number of protrusions due to wrinkles within a range of 1000 mm in the sheet drawing direction is 1 or less.

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. The glass plate according to claim 8 or 9, characterized in that the thickness of the glass plate is 0.3 mm or more and 1.0 mm or less.

11. The glass plate according to claim 8 or 9, characterized in that the liquidus temperature of the glass plate is 1100°C or higher and 1400°C or lower.

12. The glass plate according to claim 8 or 9, characterized in that the glass plate contains, in mass % calculated as oxide, 50 to 70% SiO2, 10 to 25% Al2O3, 0.1 to 5% B2O3, and 10 to 30% MgO + CaO + SrO + BaO.

13. The glass plate according to claim 8 or 9, characterized in that the glass plate is a carrier glass for transporting an organic resin substrate.

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