Manufacturing method of glass plate

Abstract

To provide a technology for improving a molding accuracy of a glass plate.SOLUTION: A manufacturing method of a glass plate has (A)-(E) below. (A) The glass plate is heated. (B) The glass plate heated is bent-formed along a mold arranged in at least one side of the glass plate. (C) The glass plate bent-formed is gradually cooled. (D) A surface profile of the glass plate gradually cooled is measured. (E) A profile of the mold is modified such that a deviation between the surface profile of the glass plate gradually cooled and a target profile becomes small.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a glass sheet. [Background technology]

[0002] The glass forming apparatus described in Patent Document 1 includes a heating furnace and a conveying means for conveying a glass sheet inside the heating furnace. The heating furnace has a heating zone, a shape adjusting zone, and an annealing zone in this order, and the glass sheet passes through the heating zone, the shape adjusting zone, and the annealing zone in this order. The glass forming apparatus measures the shape of the glass sheet in each of the heating zone and the annealing zone, and adjusts the amount of heat received by the glass sheet in the shape adjusting zone based on the measurement results, thereby adjusting the shape of the glass sheet.

[0003] The method for forming a glass sheet described in Patent Document 2 includes acquiring a temperature distribution of the glass sheet, comparing the acquired temperature distribution with a reference temperature distribution, and selectively heating the glass sheet to match the acquired temperature distribution with the reference temperature distribution. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-350286 A [Patent Document 2] Special Publication No. 2018-528147 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally, the temperature of a glass sheet has been controlled in order to improve the forming accuracy of the glass sheet, but the forming accuracy of the glass sheet has been insufficient. This is because the glass sheet is deformed after being bent along a mold. For example, the glass sheet may be deformed by slowly cooling the glass sheet. In addition, when the glass sheet is pressed when bending the glass sheet along a mold, a deformation called springback may occur when the pressing load is released. In either case, the glass sheet may be deformed after bending.

[0006] One aspect of the present disclosure provides a technique for improving the forming accuracy of a glass sheet. [Means for solving the problem]

[0007] A method for producing a glass sheet according to one embodiment of the present disclosure includes the following steps (A) to (E): (A) heating a glass sheet; (B) bending the heated glass sheet along a mold provided on at least one side of the glass sheet; (C) annealing the bent glass sheet; (D) measuring a surface shape of the annealed glass sheet; and (E) modifying the shape of the mold so as to reduce a deviation between the surface shape of the annealed glass sheet and a target shape. Effect of the Invention

[0008] According to one aspect of the present disclosure, the surface shape of the glass sheet is measured after annealing. After annealing, the glass sheet is hardened and does not deform. The surface shape of the glass sheet is measured after annealing, and the shape of the mold is modified based on the measurement result. The glass sheet is bent and shaped using the modified mold, thereby improving the forming accuracy of the glass sheet. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a flowchart showing a method for manufacturing a glass plate according to one embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of step S101 and step S102 in FIG. [Diagram 3]FIG. 3 is a cross-sectional view showing an example of correction of a lower mold used in gravity molding. [Figure 4] FIG. 4 is a cross-sectional view showing an example of correction of a lower die used in press molding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding configurations are denoted by the same reference numerals, and the description may be omitted. In the specification, the symbol "~" indicating a numerical range means that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0011] A method for manufacturing a glass sheet according to an embodiment will be described with reference to Fig. 1 to Fig. 4. As shown in Fig. 2, the method for manufacturing a glass sheet includes, for example, bending a heated glass sheet 2 along a lower die 3 provided below the glass sheet 2. The glass sheet 2 may be flat before being heated. The glass sheet 2 is softened by being heated, and is bent, for example, by its own weight.

[0012] The lower mold 3 is an example of a mold. The mold is provided on at least one side of the glass plate 2. An upper mold (not shown) may be provided above the glass plate 2. The upper mold and lower mold 3 are provided with the glass plate 2 sandwiched between them. The upper mold may be placed on the glass plate 2 and press the glass plate 2 by its own weight, or may be attached to a press machine and press the glass plate 2 by the driving force of the press machine.

[0013] The bent glass sheet 2 may include a curved surface on its surface, and may partially include a flat surface. The curved surface may be a single curved surface or a double curved surface. A curved surface refers to a surface having a radius of curvature of 10,000 mm or less, for example. A flat surface refers to a surface having a radius of curvature of more than 10,000 mm, for example.

[0014] The glass plate 2 is, for example, soda-lime glass, aluminosilicate glass, borosilicate glass, or non-alkali glass. 2 OK 2 It means glass that is substantially free of alkali metal oxides such as O. Here, "substantially free of alkali metal oxides" means that the total content of alkali metal oxides is 0.1 mass % or less.

[0015] The glass constituting the glass plate 2 can be alkali-free glass, soda-lime glass, soda-lime silicate glass, aluminosilicate glass, borosilicate glass, lithium aluminosilicate glass, or borosilicate glass. In particular, when the glass plate 2 is used as a cover glass for a display device, glass containing an alkali metal oxide such as those shown below is preferable. Glass containing an alkali metal oxide can form a compressive stress layer on the glass surface and increase its strength by being subjected to a chemical strengthening treatment after molding.

[0016] A specific example of the glass composition is SiO 2 50% to 80%, Al 2 O 3 0.1%~25%, Li 2 O+Na 2 O+K 2 O 3% to 30%, MgO 0% to 25%, CaO 0% to 25% and ZrO 2 Examples of such glass compositions include, but are not limited to, glasses containing 0% to 5% of MgO. More specifically, examples of such glass compositions include the following glass compositions (i) to (v). For example, "containing 0% to 25% MgO" means that MgO is not essential but may be contained up to 25%. The following glass (i) is included in soda lime silicate glass, and the following glasses (ii), (iii), and (iv) are included in aluminosilicate glass. The following glass (v) is included in lithium aluminosilicate glass.

[0017] (i) Composition expressed in mole percent on an oxide basis, SiO 2 63% to 73%, Al2 O 3 0.1% to 5.2%, Na 2 O 10% to 16%, K 2 O 0% to 1.5%, Li 2 A glass containing 0%-5% O, 5%-13% MgO, and 4%-10% CaO.

[0018] (ii) The composition expressed in mole percent on an oxide basis is SiO 2 50% to 74%, Al 2 O 3 1% to 10%, Na 2 O 6% to 14%, K 2 O 3% to 11%, Li 2 O 0%-5%, MgO 2%-15%, CaO 0%-6% and ZrO 2 Contains 0% to 5% SiO 2 and Al 2 O 3 The total content of is 75% or less, Na 2 O and K 2 A glass having a total O content of 12% to 25%, and a total MgO and CaO content of 7% to 15%.

[0019] (iii) The composition expressed in mole percent on an oxide basis is SiO 2 68%~80%, Al 2 O 3 4% to 10%, Na 2 O 5% to 15%, K 2 O 0% to 1%, Li 2 O 0%-5%, MgO 4%-15% and ZrO 2 Glass containing 0% to 1%.

[0020] (iv) The composition expressed in mole percent on an oxide basis is SiO 2 67%~75%, Al 2 O 3 0% to 4%, Na 2 O 7% to 15%, K 2 O 1% to 9%, Li 2 O 0% to 5%, MgO 6% to 14%, and ZrO 2 Contains 0% to 1.5% SiO2 and Al 2 O 3 The total content of is 71% to 75%, Na 2 O and K 2 A glass having a total O content of 12% to 20%, and if CaO is contained, its content is less than 1%.

[0021] (v) The composition expressed in mole percent on an oxide basis is SiO 2 56% to 73%, Al 2 O 3 10% to 24%, B 2 O 3 0% to 6%, P 2 O 5 0% to 6%, Li 2 O2 to 7%, Na 2 O 3% to 11%, K 2 O 0%~2%, MgO 0%~8%, CaO 0%~2%, SrO 0%~5%, BaO 0%~5%, ZnO 0%~5%, TiO 2 0% to 2%, ZrO 2 Glass containing 0% to 4%.

[0022] The thickness of the glass plate 2 is preferably 0.2 mm or more, more preferably 0.8 mm or more, and even more preferably 1 mm or more. The thickness of the glass plate 2 is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 6 mm or less. When the glass plate 2 is a cover glass for an in-vehicle display device, the thickness of the glass plate 2 is preferably 0.8 mm or more and 3 mm or less.

[0023] As shown in Fig. 1, the method for manufacturing a glass sheet includes, for example, steps S101 to S105. As shown in Fig. 2, step S101 includes heating a glass sheet 2. The glass sheet 2 is softened by heating and becomes bendable. The glass sheet 2 is heated inside a heating furnace. The glass sheet 2 may be placed on a lower mold 3 and then carried into the heating furnace, or may be placed on the lower mold 3 after being carried into the heating furnace.

[0024] The heating furnace may be of a batch type or a continuous type. A continuous type heating furnace may be equipped with a conveyor for transporting the lower mold 3, or may be of a continuous transport type. A continuous transport type heating furnace is divided into a plurality of zones along the transport path. The glass sheet 2 is placed on the lower mold 3 and passes through a plurality of zones together with the lower mold 3. The upper mold may be placed on the glass sheet 2 and passes through a plurality of zones together with the glass sheet 2, or may be attached to a press machine installed in an intermediate zone. The upper mold can also be used in a batch type heating furnace.

[0025] Step S101 may include controlling the output of the heater 5 so as to reduce the deviation between the measured temperature of the glass plate 2 and the target temperature. The heater 5 is, for example, a carbon heater, a halogen heater, or a sheathed heater. Controlling the output of the heater 5 includes controlling the supply current to the heater 5.

[0026] The target temperature of the glass sheet 2 is set in step S102 described below so that the shape of the glass sheet 2 matches the shape of the lower mold 3. A plurality of target temperatures of the glass sheet 2 may be set in association with the coordinates of the surface (e.g., the upper surface or the lower surface) of the glass sheet 2. The target temperature of the glass sheet 2 is set, for example, according to the curvature of the surface of the glass sheet 2. The smaller the curvature, the higher the target temperature is set.

[0027] The target temperature of the glass sheet 2 may be changed according to the deviation between the surface shape of the glass sheet 2 measured in step S104, which will be described later, and the target shape. In step S102, which is performed after correcting the target temperature, the shape of the glass sheet 2 can be made to match the shape of the lower mold 3. However, as will be described in detail later, the glass sheet 2 may be deformed after step S102. Therefore, simply changing the target temperature of the glass sheet 2 does not provide sufficient forming precision for the glass sheet 2.

[0028] The target temperature of the glass plate 2 is, for example, 10 7.9 dPa·s~10 12.7 The temperature range is set to correspond to the viscosity range of 10 dPa·s. 7.9If the viscosity of the glass is 10 dPa·s or more, the deformation of the glass plate 2 is gentle, and it is possible to prevent the glass plate 2 from being marked by the mold such as the lower mold 3. 12.7 If the bending temperature is less than 10 dPa·s, the glass sheet 2 can be bent. 8.5 dPa·s~10 11.5 It is set within the temperature range that corresponds to the viscosity range in dPa·s.

[0029] The measured temperature of the glass plate 2 is obtained using, for example, a radiation thermometer or a thermocouple. The coordinates at which the measured temperature of the glass plate 2 is obtained and the coordinates at which the target temperature of the glass plate 2 is set are the same. The temperature measurement of the glass plate 2 may be performed for all the glass plates 2, or may be performed for some of the glass plates 2. The temperature measurement of the glass plate 2 is performed at least when the target shape or glass material of the glass plate 2 is changed.

[0030] A plurality of heaters 5 may be provided. When viewed from above, the heaters may be arranged in parallel stripes or in a matrix. Step S101 may include controlling the outputs of the heaters 5 individually. A complex temperature distribution can be imparted to the glass plate 2.

[0031] In step S102, the glass sheet 2 heated in step S101 is bent along a lower mold 3 provided below the glass sheet 2. The glass sheet 2 is softened by being heated, and is bent, for example, by its own weight. The bent glass sheet 2 includes a curved surface on its surface. The radius of curvature of the curved surface is preferably 10 mm or more, more preferably 30 mm or more, and even more preferably 50 mm or more. The radius of curvature of the curved surface is, for example, 10,000 mm or less, preferably 5,000 mm or less, and more preferably 3,000 mm or less.

[0032] The lower die 3 is an example of a die. The die is provided on at least one side of the glass plate 2. An upper die (not shown) may be provided above the glass plate 2. The upper die may be placed on the glass plate 2 and press the glass plate 2 by its own weight, or may be attached to a press machine and press the glass plate 2 by the driving force of the press machine. The upper die is configured similarly to the lower die 3.

[0033] The lower die 3 has, for example, a plurality of pins 31 that are parallel to each other. The longitudinal direction of the pins 31 is, for example, the vertical direction. When viewed from the longitudinal direction of the pins 31, the plurality of pins 31 may be arranged in a staggered manner or in a matrix. When viewed from the longitudinal direction of the pins 31, the tips of the pins 31 are circular, but may also be polygonal.

[0034] Step S102 involves bending the glass sheet 2 along the tips (e.g., upper ends) of the pins 31. The tips of the pins 31 include an upwardly convex dome-shaped curved surface, which supports the glass sheet 2 from below. This makes it possible to prevent local stress concentration in the glass sheet 2. The curved surface is, for example, hemispherical, and the curvature is determined taking into account the curvature of the glass sheet 2, etc.

[0035] The material of the pin 31 is not particularly limited, but may be, for example, stainless steel, heat-resistant steel, cemented carbide (e.g., tungsten carbide), ceramic (e.g., silicon carbide, silicon nitride, quartz), or carbon. A coating film may be formed on at least a portion of the pin 31. The coating film is a metal film, a ceramic film, or a carbon film.

[0036] The lower mold 3 may have a guide plate 32 in which a plurality of guide holes are formed, through which the pins 31 are inserted one by one. The plurality of guide holes may be arranged in a staggered manner or in a matrix, similar to the plurality of pins 31. The horizontal positions of the pins 31 can be regulated by the horizontal positions of the guide holes, and the pins 31 can be arranged in a desired pattern.

[0037] A plurality of guide plates 32 may be provided at intervals in the longitudinal direction of the pin 31 in order to suppress tilt of the pin 31. A flange 33 may be provided midway on the pin 31. The flange 33 moves between the pair of guide plates 32. The pair of guide plates 32 also play a role in defining the movable range of the pin 31.

[0038] A matrix 6 is provided below the lower mold 3. The matrix 6 has a contact surface 61 that comes into contact with the base ends (e.g., lower ends) of each of the multiple pins 31. The contact surface 61 defines the positions of the tips (e.g., upper ends) of each of the multiple pins 31. The shape of the contact surface 61 is determined based on the target shape of the glass plate 2.

[0039] The matrix 6 is disposed on the opposite side of the glass plate 2 with respect to the lower mold 3. Therefore, when the glass plate 2 is heated, the temperature of the matrix 6 can be made lower than that of the lower mold 3. This allows the matrix 6 to be molded from a material with low heat resistance, such as resin. As a result, the manufacturing time and manufacturing costs of the matrix 6 can be reduced. The matrix 6 is manufactured, for example, by a 3D printer.

[0040] The lower die 3 may be used separately from the matrix 6. Before separating the lower die 3 and the matrix 6, the tip positions of each of the multiple pins 31 may be fixed by a fixture, welding, or the like.

[0041] Although not shown, a heat-resistant cloth may be provided between the lower mold 3 and the glass plate 2. The heat-resistant cloth is, for example, a woven or non-woven fabric. By providing the heat-resistant cloth, it is possible to prevent the glass plate 2 from being locally and strongly pressed against the lower mold 3. The heat-resistant cloth contains, for example, stainless steel fibers or silica fibers.

[0042] The lower mold 3 is not limited to one having a plurality of parallel pins 31. The lower mold 3 may have the same shape as the matrix 6. The upper mold is similar to the lower mold.

[0043] Step S103 includes slowly cooling the glass sheet 2 bent in step S102. By slowly cooling the glass sheet 2, the glass sheet 2 may be deformed. When the glass sheet 2 is pressed in step S102, a deformation called springback may occur when the press load is released. In any case, the glass sheet 2 may be deformed after step S102 (bending).

[0044] In step S104, the surface shape of the glass sheet 2 annealed in step S103 is measured. After step S103 (annealing), the glass sheet 2 is hardened and does not deform. The surface shape of the annealed glass sheet 2 is measured by a three-dimensional measuring device. The three-dimensional measuring device may be of a contact type or a non-contact type. The surface shape may be measured on either the upper or lower surface during bending, or on both surfaces.

[0045] In step S105, the shape of the lower mold 3 is modified so as to reduce the deviation between the surface shape measured in step S104 and the target shape. By performing steps S101 to S105 again using the lower mold 3 whose shape has been modified, the surface shape of the glass sheet 2 after annealing can be made to coincide with the target shape, and the forming accuracy of the glass sheet 2 can be improved.

[0046] In step S105, the shape of the lower die 3 is modified so that the deviation between the surface shape of the glass sheet 2 slowly cooled in step S103 and the target shape is reduced, and the surface shape during bending deviates from the target shape. By intentionally deviating the surface shape during bending from the target shape, it is possible to deal with deformation after bending.

[0047] 2, the lower die 3 has a plurality of pins 31 that are parallel to each other. The glass sheet 2 is bent along the tips of the pins 31. In this case, step S105 includes relatively displacing the pins 31 in the longitudinal direction of the pins 31. Specifically, the matrix 6 is replaced, and the shape of the contact surface 61 of the matrix 6 is changed.

[0048] Next, an example of modification of the lower mold 3 used in gravity forming will be described with reference to Fig. 3. In Fig. 3, Zdesing indicates the target shape of the glass sheet 2 after annealing, Zmold1 indicates the shape of the lower mold 3 before modification, Zglass indicates the surface shape of the glass sheet 2 measured after bending along the lower mold 3 before modification and annealing, and Zmold2 indicates the shape of the lower mold 3 after modification.

[0049] Zmold1 coincides with Zdesing as shown in FIG. 3, but it may not coincide with Zdesing by repeatedly modifying the lower mold 3. Note that the modification of the lower mold 3 may be performed only once. Zdesing, Zmold1, Zglass, and Zmold2 are each represented by the distance from the surface (e.g., the lower surface or the upper surface) of the horizontal glass sheet before heating.

[0050] The glass sheet 2 is bent along the lower die 3, for example, by its own weight. In this case, as shown in FIG. 3, the shape of the lower die 3 after correction is determined, for example, by the following formula (1): Zmold2=Zmold1+(Zdesign-Zglass)...(1) By modifying the shape of the lower mold 3 using the above formula (1), it is possible to deal with deformation of the glass sheet 2 caused by the gradual cooling of the glass sheet 2.

[0051] It is also possible to slowly cool the glass sheet 2 so that the glass sheet 2 is not deformed by the slow cooling. However, this would result in a long cooling time and increased energy consumption. In addition, if the heating furnace is of a continuous conveying type, the length of the heating furnace would be long, resulting in high equipment costs for the heating furnace.

[0052] According to this embodiment, the shape of the lower mold 3 is modified so as to reduce the deviation between the surface shape measured in step S104 and the target shape. By repeating steps S101 to S105 using the lower mold 3 whose shape has been modified, it is possible to obtain a glass plate 2 with good forming accuracy even if the annealing time is short.

[0053] Next, an example of modification of the lower mold 3 used in press molding will be described with reference to Fig. 4. In Fig. 4, Zdesing, Zmold1, Zglass, and Zmold2 have the same meanings as in Fig. 3.

[0054] When the glass sheet 2 is press-molded, a deformation called springback may occur when the press load is released. Springback is an elastic deformation. When springback occurs, as shown in FIG. 4, the shape of the lower die 3 after correction is, for example, expressed by the following formula (2): Zmold2=Zmold1×(Zdesign / Zglass)...(2) By modifying the shape of the lower die 3 using the above formula (2), it is possible to obtain a glass sheet 2 with good forming accuracy even when springback occurs.

[0055] The glass plate 2 obtained by the technology of the present disclosure is mounted on, for example, an automobile. The glass plate 2 is used for a windshield, a head-up display, a dashboard, a cover glass for a display device, a cover glass for a camera, a cover glass for a radar, a cover glass for a sensor, and the like. The front windshield is curved convexly toward the outside of the vehicle as a whole or in part. In recent years, from the viewpoint of design, a complex curved shape and high surface quality are required for the cover glass of an in-vehicle display device, and therefore, there is great significance in applying the technology of the present disclosure.

[0056] Although the manufacturing method of the glass plate according to the present disclosure has been described above, the present disclosure is not limited to the above-mentioned embodiment. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure. [Explanation of symbols]

[0057] 2 Glass plate 3 Lower mold (mold)

Claims

1. A method for producing a glass plate including a curved surface, comprising the steps of: Heating the glass plate; bending the heated glass sheet along a mold provided on at least one side of the glass sheet; annealing the bent glass sheet; Measuring the surface shape of the annealed glass plate; Modifying the shape of the mold so that the deviation between the surface shape of the annealed glass sheet and a target shape is reduced; The method for producing a glass plate comprising the steps of:

2. The method for manufacturing a glass sheet according to claim 1 , wherein heating the glass sheet includes controlling an output of a heater that heats the glass sheet so that a deviation between a measured temperature of the glass sheet and a target temperature is reduced.

3. The method for manufacturing a glass sheet according to claim 2 , further comprising changing the target temperature of the glass sheet so that a deviation between the surface shape of the annealed glass sheet and the target shape becomes small.

4. The heater is provided in plurality, The method for manufacturing a glass sheet according to claim 2 or 3, wherein heating the glass sheet includes individually controlling outputs of a plurality of the heaters.

5. The mold has a plurality of pins parallel to each other, Bending the glass sheet includes bending the glass sheet along tips of the pins, The method for manufacturing a glass plate according to claim 1 , wherein modifying the shape of the mold includes relatively displacing the plurality of pins in a longitudinal direction of the pins.

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