WO2023181719A1 - Method for producing glass sheet - Google Patents

Abstract

This method for producing a glass sheet comprises the following (A) to (E). (A) Heat the glass sheet. (B) Bend the heated glass sheet along a mold provided on at least one side of the glass sheet. (C) Slowly cool the bent glass sheet. (D) Measure the surface shape of the slowly cooled glass sheet. (E) Modify the mold so that the deviation between the surface shape of the slowly cooled glass sheet and a target shape becomes small.

Description

Glass plate manufacturing method

The present disclosure relates to a method for manufacturing a glass plate.

The glass forming apparatus described in Patent Document 1 includes a heating furnace and a conveying means for conveying a glass plate inside the heating furnace. The heating furnace has a heating zone, a shape adjustment zone, and a slow cooling zone in this order, and the glass plate passes through the heating zone, shape adjustment zone, and slow cooling zone in this order. Glass forming equipment measures the shape of the glass plate in each of the heating zone and slow cooling zone, and based on the measurement results, adjusts the amount of heat received by the glass plate in the shape adjustment zone, and adjusts the shape of the glass plate. .

The method for forming a glass sheet described in Patent Document 2 includes obtaining the temperature distribution of the glass sheet, comparing the obtained temperature distribution with a reference temperature distribution, and matching the obtained temperature distribution with the reference temperature distribution. selectively heating the glass sheet to cause

Japanese Patent Application Publication No. 2005-350286 Japan Special Table No. 2018-528147

Conventionally, temperature control of glass plates has been performed in order to improve the molding precision of glass plates, but the molding precision of glass plates has been insufficient. This is because the glass plate is deformed after it is bent and formed along the mold. For example, when a glass plate is slowly cooled, the glass plate may be deformed. Furthermore, when pressing a glass plate when bending it along a mold, deformation called springback may occur when the press load is released. In any case, the glass plate may be deformed after bending.

One aspect of the present disclosure provides a technique that improves the molding accuracy of a glass plate.

A method for manufacturing a glass plate according to one aspect of the present disclosure includes the following (A) to (E). (A) Heating the glass plate. (B) Bending the heated glass plate along a mold provided on at least one side of the glass plate. (C) The bent glass plate is slowly cooled. (D) Measure the surface shape of the slowly cooled glass plate. (E) Correcting the shape of the mold so that the deviation between the surface shape of the slowly cooled glass plate and the target shape becomes smaller.

According to one aspect of the present disclosure, the surface shape of the glass plate is measured after slow cooling. After slow cooling, the glass plate becomes hard and does not deform. After slow cooling, the surface shape of the glass plate is measured, and the shape of the mold is modified based on the measurement results. By bending and forming a glass plate using the modified mold, the precision of forming the glass plate can be improved.

FIG. 1 is a flowchart showing a method for manufacturing a glass plate according to an embodiment. FIG. 2 is a cross-sectional view showing an example of step S101 and step S102 in FIG. FIG. 3 is a cross-sectional view showing an example of modification of the lower mold used for self-weight molding. FIG. 4 is a sectional view showing an example of modification of a lower mold used for press molding.

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

A method for manufacturing a glass plate according to one embodiment will be described with reference to FIGS. 1 to 4. As shown in FIG. 2, the method for manufacturing a glass plate includes, for example, bending a heated glass plate 2 along a lower die 3 provided on the lower side of the glass plate 2. The glass plate 2 may be a flat plate before being heated. The glass plate 2 is softened by being heated, and is bent and formed by its own weight, for example.

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 the lower mold 3 are provided with a glass plate 2 in between. The upper die may be placed on the glass plate 2 and push the glass plate 2 with its own weight, or it may be attached to a press and push the glass plate 2 with the driving force of the press.

The bent glass plate 2 may include a curved surface on its surface, or 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, for example, a radius of curvature of 10,000 mm or less. A plane means, for example, that the radius of curvature is greater than 10,000 mm.

The glass plate 2 is, for example, soda lime glass, aluminosilicate glass, borosilicate glass, or alkali-free glass. Alkali-free glass means glass that does not substantially contain alkali metal oxides such as Na ₂ O and K ₂ O. Here, "not substantially containing alkali metal oxides" means that the total content of alkali metal oxides is 0.1% by mass or less.

As the glass constituting the glass plate 2, alkali-free glass, soda lime glass, soda lime silicate glass, aluminosilicate glass, borosilicate glass, lithium aluminosilicate glass, and borosilicate glass can be used. In particular, when the glass plate 2 is used as a cover glass for a display device, it is preferably a glass containing an alkali metal oxide as shown below. Glass containing alkali metal oxides can be chemically strengthened after molding to form a compressive stress layer on the glass surface and increase its strength.

As a specific example of the glass composition, the composition expressed in mol% based on oxides is 50% to 80% of SiO ₂ , 0.1% to 25% of Al ₂ O ₃ , and Li ₂ O + Na ₂ O + K ₂ O. Examples include, but are not limited to, glasses containing 3% to 30% MgO, 0% to 25% MgO, 0% to 25% CaO, and 0% to 5% ZrO ₂ . More specifically, the following glass compositions (i) to (v) may be mentioned. Note that, for example, "contains 0% to 25% MgO" means that MgO is not essential, but may contain up to 25%. The glass (i) below is included in soda lime silicate glass, and the glasses (ii), (iii) and (iv) below are included in aluminosilicate glass. The following glass (v) is included in lithium aluminosilicate glass.

(i) Composition expressed in mol% based on oxides: 63% to 73% SiO ₂ , 0.1% to 5.2% Al ₂ O ₃ , 10% to 16% Na ₂ O, K A glass containing 0% to 1.5% of ₂ O, 0% to 5% of Li ₂ O, 5% to 13% of MgO, and 4% to 10% of CaO.

(ii) The composition expressed in mol% on an oxide basis is 50% to 74% of SiO ₂ , 1% to 10% of Al ₂ O ₃ , 6% to 14% of Na ₂ O , and 3% of K ₂ O % to 11%, Li ₂ O 0% to 5%, MgO 2% to 15%, CaO 0% to 6% and ZrO ₂ 0% to 5%, containing SiO ₂ and Al ₂ O _3. Glass having a total content of 75% or less, a total content of Na ₂ O and K ₂ O of 12% to 25%, and a total content of MgO and CaO of 7% to 15%.

(iii) The composition expressed in mol% on an oxide basis is 68% to 80% SiO ₂ , 4% to 10% Al ₂ O ₃ , 5% to 15% Na ₂ O , and 0% K ₂ O % to 1%, Li ₂ O 0% to 5%, MgO 4% to 15% and ZrO ₂ 0% to 1%.

(iv) The composition expressed in mol% on an oxide basis is 67% to 75% of SiO ₂ , 0% to 4% of Al ₂ O ₃ , 7% to 15% of Na ₂ O, and 1% of K ₂ O % to 9%, Li ₂ O 0% to 5%, MgO 6% to 14% and ZrO ₂ 0% to 1.5%, with a total content of SiO ₂ and Al ₂ O ₃ of 71%. % to 75%, the total content of Na ₂ O and K ₂ O is 12% to 20%, and if it contains CaO, the content is less than 1%.

(v) The composition expressed in mol% on an oxide basis is 56% to 73% of SiO ₂ , 10% to 24% of Al ₂ O ₃ , 0% to 6% of B ₂ O ₃ , and P ₂ O ₅ 0% to 6%, Li ₂ O 2% to 7%, Na ₂ O 3% to 11%, K ₂ O 0% to 2%, MgO 0% to 8%, CaO 0% to 2%, SrO 0% to 5%, BaO 0% to 5%, ZnO 0% to 5%, TiO ₂ 0% to 2%, and ZrO ₂ 0% to 4%.

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 a vehicle-mounted display device, the thickness of the glass plate 2 is preferably 0.8 mm or more and 3 mm or less.

As shown in FIG. 1, the method for manufacturing a glass plate includes, for example, steps S101 to S105. Step S101 includes heating the glass plate 2, as shown in FIG. The glass plate 2 is softened by heating and becomes bendable. The glass plate 2 is heated inside the heating furnace. The glass plate 2 may be placed on the 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.

The heating furnace may be a batch type or a continuous type. The continuous heating furnace may include a conveyor for conveying the lower mold 3, or may be of a continuous conveyance type. A continuous conveyance type heating furnace is divided into a plurality of zones along a conveyance path. The glass plate 2 is placed on the lower mold 3 and passes through a plurality of zones together with the lower mold 3. The upper die may be placed on the glass plate 2 and pass through a plurality of zones together with the glass plate 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.

Step S101 may include controlling the output of the heater 5 so that the deviation between the measured temperature of the glass plate 2 and the target temperature becomes small. 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 current supplied to the heater 5.

The target temperature of the glass plate 2 is set so that the shape of the glass plate 2 matches the shape of the lower mold 3 in step S102, which will be described later. A plurality of target temperatures for the glass plate 2 may be set in association with coordinates of the surface (for example, the upper surface or the lower surface) of the glass plate 2. The target temperature of the glass plate 2 is set, for example, according to the curvature of the surface of the glass plate 2. The smaller the curvature, the higher the target temperature is set.

Note that the target temperature of the glass plate 2 may be changed depending on the deviation between the surface shape of the glass plate 2 measured in step S104 described later and the target shape. In step S102 performed after correcting the target temperature, the shape of the glass plate 2 can be made to match the shape of the lower mold 3. However, as will be described in detail later, the glass plate 2 may be deformed after step S102. Therefore, simply changing the target temperature of the glass plate 2 is insufficient to form the glass plate 2 with sufficient precision.

The target temperature of the glass plate 2 is set within a temperature range corresponding to a viscosity range of, for example, 10 ^7.9 dPa·s to 10 ^12.7 dPa·s. If the viscosity of the glass is 10 ^7.9 dPa·s or more, the deformation of the glass plate 2 is gradual, and it is possible to suppress the formation of marks from molds such as the lower mold 3 on the glass plate 2. On the other hand, if the viscosity of the glass is 10 ^12.7 dPa·s or less, the glass plate 2 can be bent. The target temperature of the glass plate 2 is preferably set within a temperature range corresponding to a viscosity range of 10 ^8.5 dPa·s to 10 ^11.5 dPa·s.

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

A plurality of heaters 5 may be provided. When viewed from above, the plurality of heaters may be arranged in parallel to each other in stripes or in rows and columns. Step S101 may include individually controlling the outputs of the plurality of heaters 5. A complicated temperature distribution can be imparted to the glass plate 2.

In step S102, the glass plate 2 heated in step S101 is bent and formed along the lower mold 3 provided below the glass plate 2. The glass plate 2 is softened by being heated, and is bent and formed by its own weight, for example. The bent glass plate 2 includes a curved 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.

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 die may be placed on the glass plate 2 and push the glass plate 2 with its own weight, or it may be attached to a press and push the glass plate 2 with the driving force of the press. The upper mold is constructed similarly to the lower mold 3.

The lower mold 3 has, for example, a plurality of pins 31 that are parallel to each other. The longitudinal direction of the pin 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 rows and columns. When viewed from the longitudinal direction of the pin 31, the tip of the pin 31 has a circular shape, but may have a polygonal shape.

Step S102 includes bending and forming the glass plate 2 along the tips (for example, the upper ends) of each of the plurality of pins 31. The tip of the pin 31 includes an upwardly convex dome-shaped curved surface, which supports the glass plate 2 from below. Local stress concentration on the glass plate 2 can be suppressed. The curved surface is, for example, hemispherical, and its curvature is determined by taking into consideration the curvature of the glass plate 2 and the like.

The material of the pin 31 is not particularly limited, and is, for example, stainless steel, heat-resistant steel, cemented carbide (for example, tungsten carbide), ceramic (for example, 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.

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. Similar to the plurality of pins 31, the plurality of guide holes may be arranged in a staggered manner or in rows and columns. The horizontal position of the pins 31 can be regulated by the horizontal position of the guide hole, and the pins 31 can be arranged in a desired pattern.

A plurality of guide plates 32 may be provided at intervals in the longitudinal direction of the pin 31 in order to suppress the inclination of the pin 31. A flange 33 may be provided in the middle of the pin 31. The flange 33 moves between the pair of guide plates 32. The pair of guide plates 32 also serve to define the movable range of the pin 31.

A mother mold 6 is provided below the lower mold 3. The mother die 6 has a contact surface 61 that comes into contact with the base end (for example, the lower end) of each of the plurality of pins 31 . The contact surface 61 defines the position of each tip (eg, upper end) of the plurality of pins 31. The shape of the contact surface 61 is determined based on the target shape of the glass plate 2.

The mother mold 6 is placed on the opposite side of the glass plate 2 with respect to the lower mold 3. Therefore, when heating the glass plate 2, the temperature of the mother mold 6 can be lower than the temperature of the lower mold 3. Therefore, the mother mold 6 can be molded from a material with low heat resistance, such as resin. As a result, the manufacturing period and manufacturing cost of the mother mold 6 can be reduced. The mother mold 6 is manufactured using, for example, a 3D printer.

Note that the lower die 3 may be used separately from the mother die 6. Before separating the lower die 3 and the mother die 6, the positions of the tips of the plurality of pins 31 may be fixed using a fixture, welding, or the like.

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

Note that the lower mold 3 is not limited to having a plurality of pins 31 that are parallel to each other. As the lower die 3, one having the same shape as the mother die 6 may be used. The upper mold is also similar to the lower mold.

Step S103 includes slowly cooling the glass plate 2 bent and formed in step S102. By slowly cooling the glass plate 2, the glass plate 2 may be deformed. Note that when pressing the glass plate 2 in step S102, deformation called springback may occur by releasing the press load. In any case, the glass plate 2 may be deformed after step S102 (bending forming).

In step S104, the surface shape of the glass plate 2 slowly cooled in step S103 is measured. After step S103 (slow cooling), the glass plate 2 has become hard and will not be deformed. The surface shape of the slowly cooled glass plate 2 is measured using a three-dimensional measuring device. The three-dimensional measuring device may be a contact type or a non-contact type. The surface on which the surface shape is measured may be either the upper surface or the lower surface during bending, or both.

In step S105, the shape of the lower mold 3 is corrected so that the deviation between the surface shape measured in step S104 and the target shape becomes smaller. By performing steps S101 to S103 again using the lower mold 3 whose shape has been corrected, the surface shape of the glass plate 2 after slow cooling can match the target shape, and the molding accuracy of the glass plate 2 can be improved.

Note that after steps S101 to S103 are performed again, step S104 may be performed again. As a result, if the deviation is within the allowable range, steps S101 to S103 are performed again without performing step S105 again. On the other hand, if the deviation is outside the allowable range, step S105 is performed again, and then steps S101 to S103 are performed again.

In step S105, the shape of the lower die 3 is corrected so that the deviation between the surface shape of the glass plate 2 slowly cooled in step S103 and the target shape is reduced, and the surface shape during bending deviates from the target shape. . By purposely changing the surface shape during bending from the target shape, it is possible to cope with deformation after bending.

For example, as shown in FIG. 2, the lower mold 3 has a plurality of pins 31 that are parallel to each other. The glass plate 2 is bent and formed along the tips of each of the plurality of pins 31. In that case, step S105 includes relatively displacing the plurality of 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.

Next, with reference to FIG. 3, an example of modification of the lower mold 3 used for self-weight molding will be described. In FIG. 3, Zdesign indicates the target shape of the glass plate 2 after slow cooling, Zmold1 indicates the shape of the lower die 3 before correction, and Zglass indicates the shape of the glass plate 2 after bending and forming along the lower die 3 before correction and slow cooling. The measured surface shape of the glass plate 2 is shown, and Zmold2 shows the shape of the lower mold 3 after correction.

Although Zmold1 matches the Zdesign as shown in FIG. 3, it may become inconsistent with the Zdesign by repeatedly modifying the lower mold 3. Note that the modification of the lower mold 3 may be performed only once. Zdesign, Zmold1, Zglass, and Zmold2 are each expressed as a distance from the surface (for example, the bottom surface or the top surface) of the horizontal glass plate before heating.

The glass plate 2 is, for example, bent and formed along the lower mold 3 by its own weight. In this case, as shown in FIG. 3, the shape of the lower die 3 after correction is, for example, expressed by the following formula (1).
Zmold2=Zmold1+(Zdesign-Zglass)...(1)
It can be found using By correcting the shape of the lower mold 3 using the above formula (1), it is possible to cope with deformation of the glass plate 2 caused by slow cooling of the glass plate 2.

Note that it is also possible to slowly cool the glass plate 2 so that the glass plate 2 is not deformed due to the slow cooling of the glass plate 2. However, the slow cooling time becomes longer and energy consumption increases. Moreover, when the heating furnace is of a continuous conveyance type, the length of the heating furnace becomes long, and the equipment cost of the heating furnace becomes high.

According to the present embodiment, the shape of the lower die 3 is corrected so that the deviation between the surface shape measured in step S104 and the target shape is reduced. By repeating steps S101 to S103 using the lower mold 3 whose shape has been corrected, a glass plate 2 with good molding accuracy can be obtained even if the annealing time is short.

Next, with reference to FIG. 4, an example of modification of the lower mold 3 used for press molding will be described. In FIG. 4, Zdesign, Zmold1, Zglass, and Zmold2 have the same meanings as in FIG. 3.

When the glass plate 2 is press-molded, deformation called springback may occur when the press load is released. Springback is an elastic deformation. Therefore, when springback occurs, as shown in FIG.
Zmold2=Zmold1×(Zdesign/Zglass)...(2)
It can be found using By correcting the shape of the lower mold 3 using the above formula (2), it is possible to obtain a glass plate 2 with good molding accuracy even when springback occurs.

The glass plate 2 obtained by the technique of the present disclosure is mounted on, for example, an automobile. The glass plate 2 is used as a windshield, a head-up display, a dashboard, a display device cover glass, a camera cover glass, a radar cover glass, a sensor cover glass, or the like. The front windshield is entirely or partially curved in a convex manner toward the outside of the vehicle. In recent years, cover glasses for in-vehicle display devices have been required to have complex curved shapes and high surface quality from the viewpoint of design, and the application of the technology of the present disclosure is of great significance.

Although the method for manufacturing a glass plate according to the present disclosure has been described above, the present disclosure is not limited to the above embodiments. 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.

This application claims priority based on Japanese Patent Application No. 2022-050351 filed with the Japan Patent Office on March 25, 2022, and the entire content of Japanese Patent Application No. 2022-050351 is incorporated into this application. .

2 Glass plate 3 Lower mold (mold)

Claims (5)

A method for manufacturing a glass plate having a curved surface, the method comprising:
heating the glass plate;
Bending the heated glass plate along a mold provided on at least one side of the glass plate;
Slowly cooling the bent and formed glass plate;
Measuring the surface shape of the slowly cooled glass plate;
modifying the shape of the mold so that the deviation between the surface shape of the slowly cooled glass plate and the target shape is reduced;
A method for manufacturing a glass plate, comprising: The glass according to claim 1, wherein heating the glass plate includes controlling an output of a heater that heats the glass plate so that a deviation between a measured temperature of the glass plate and a target temperature becomes small. Method of manufacturing the board. The method for manufacturing a glass plate according to claim 2, comprising changing the target temperature of the glass plate so that a deviation between the surface shape of the slowly cooled glass plate and the target shape becomes small. A plurality of the heaters are provided,
The method for manufacturing a glass plate according to claim 2 or 3, wherein heating the glass plate includes individually controlling outputs of the plurality of heaters. The mold has a plurality of pins parallel to each other,
Bending and forming the glass plate includes bending and forming the glass plate along the tips of each of the plurality of 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 the longitudinal direction of the pins.

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