CN113329978A - Method for forming glass plate - Google Patents

Abstract

In a method for press-forming a glass sheet, the glass sheet is sandwiched between two press molds, and a 1 st pressing force of 0.1MPa or less or no pressing force is applied to the glass center portion of the glass sheet in a mold closing direction, and a 2 nd pressing force of 0.1 to 10MPa is applied to the glass outer peripheral portion, thereby forming the glass sheet. Alternatively, a 1 st pressure of 0.1MPa or less is applied to the glass sheet from one of the pair of molding dies in the mold closing direction, the glass outer peripheral portion of the glass sheet is sandwiched between the pair of molding dies, a space is defined between the 1 st molding die and the glass sheet arranged in front in the mold closing direction on the inner peripheral side of the glass outer peripheral portion, and a negative pressure is supplied to the space to cause the glass sheet to adhere to the 1 st molding die.

Description

Method for forming glass plate

Technical Field

The present invention relates to a method for forming a glass sheet.

Background

Various methods of manufacturing a press-formed glass product by heating and softening a glass material accommodated in a forming die and pressing the glass material can be used. For example, there has been proposed a forming apparatus in which a plate-like glass material is sequentially conveyed to each of heating, pressing, and cooling stations provided in a chamber, and a press-formed product is continuously formed on each station (patent document 1).

In such a molding apparatus, the glass material is maintained at a heating temperature sufficient for processing the glass material by setting the molding die to a predetermined temperature during pressing. The glass material after molding is cooled and solidified, and finally cooled to a temperature of 200 ℃ or lower at which the molding die is not oxidized. As described above, the shape of the press mold is accurately transferred at the time of pressing, and the formed shape is held by cooling and solidifying, whereby the glass material becomes a press-formed product with high shape accuracy.

Patent document 1: international publication No. 2013/103102

However, in the molding apparatus as described above, along with the complication and mass production of the molded shape of the glass material, there is room for improvement in various aspects such as productivity of the molded product and quality of the shape/surface property.

Disclosure of Invention

The invention aims to provide a glass plate forming method which can reduce equipment cost and form a formed product with high shape precision and high production capacity even the formed product has a complex shape.

The present invention is constituted by the following structure.

(1) A method for forming a glass sheet into a desired shape by heating the glass sheet, comprising the steps of:

sandwiching the glass sheet between a pair of forming molds; and

the glass sheet is press-molded by the press mold by applying a 1 st pressing force of 0.1MPa or less to a glass central portion located inside the outer peripheral edge of the glass sheet in a mold closing direction or by not applying a pressing force to the glass central portion, and applying a 2 nd pressing force of 0.1 to 10MPa different from the 1 st pressing force to a glass outer peripheral portion located between the outer periphery of the glass central portion and the outer peripheral edge of the glass sheet in the mold closing direction.

(2) A method for forming a glass sheet into a desired shape by heating the glass sheet, comprising the steps of:

sandwiching the glass sheet between a pair of forming molds;

applying a pressurizing force of 0.1MPa or less to the glass sheet from one of the pair of molding dies in a mold clamping direction, and sandwiching an annular glass outer peripheral portion between an outer periphery of a glass central portion and an outer peripheral edge of the glass sheet between the pair of molding dies to define a space between a 1 st molding die disposed forward in the mold clamping direction and the glass sheet on an inner peripheral side of the glass outer peripheral portion, wherein the glass central portion is located inward of the outer peripheral edge of the glass sheet; and

negative pressure is supplied to the space defined between the glass sheet and the 1 st molding die, and the glass sheet is attracted to the 1 st molding die.

According to the present invention, even a molded article having a complicated shape can be molded with high shape accuracy and high throughput while reducing the equipment cost.

Drawings

Fig. 1 is a schematic process diagram showing a procedure for forming a glass plate into a curved shape.

Fig. 2 is a schematic configuration diagram of a molding apparatus.

Fig. 3 is a cross-sectional view of a multiple lamp heater.

Fig. 4 is a schematic plan view of the III-III line section shown in fig. 2 as viewed from above.

Fig. 5 is a schematic explanatory view showing a case where the lower mold is conveyed in the conveying direction from the preheating stage toward the cooling stage.

Fig. 6 is an enlarged cross-sectional view of the forming station.

Fig. 7 (a) is a cross-sectional view of the upper mold, and (B) is a cross-sectional view of the lower mold including the molding surface.

Fig. 8 is a rear view of the upper die as viewed from the direction B of fig. 7 (a).

Fig. 9 (a) is a cross-sectional view of an upper die of a modification, and (B) is a cross-sectional view of a lower die of the modification including a molding surface.

FIG. 10 is a top view of a glass sheet.

Fig. 11A is a schematic process explanatory view showing a case where the lower mold and the upper mold shown in (a) and (B) of fig. 7 are brought into contact with each other in stages to perform the forming process on the glass plate.

Fig. 11B is a schematic process explanatory view showing a case where the lower mold and the upper mold shown in (a) and (B) of fig. 7 are brought into contact with each other in stages to perform the forming process on the glass plate.

Fig. 11C is a schematic process explanatory view showing a case where the lower mold and the upper mold shown in (a) and (B) of fig. 7 are brought into contact with each other in stages to perform the forming process on the glass plate.

Fig. 12 is an explanatory view of a schematic process in a case where a glass sheet is formed by the 2 nd forming method.

Fig. 13A is a schematic process explanatory view showing a case where the glass plate is formed by bringing the lower mold and the upper mold of the modification shown in (a) and (B) of fig. 9 into contact with each other in stages.

Fig. 13B is a schematic process explanatory view showing a case where the glass plate is formed by bringing the lower mold and the upper mold of the modification shown in (a) and (B) of fig. 9 into contact with each other in stages.

Fig. 13C is a schematic process explanatory view showing a case where the glass plate is formed by bringing the lower mold and the upper mold of the modification shown in (a) and (B) of fig. 9 into contact with each other in stages.

Fig. 14 is an explanatory view of a schematic process in a case where a glass sheet is formed by the 4 th forming method.

Fig. 15 is a schematic configuration diagram of a molding apparatus including a plurality of preheating stages, a molding stage, and a plurality of cooling stages.

FIG. 16 is a graph showing an example of temperature changes of the lower mold and the glass sheet in the preheating stage, the forming stage, and the cooling stage.

Fig. 17 is a schematic configuration diagram of a conventional molding apparatus as a reference example.

Fig. 18 is a schematic configuration diagram of a molding apparatus showing another configuration example of the molding apparatus shown in fig. 15.

Fig. 19 (a) is a schematic cross-sectional view showing the molded shape of test examples 1 and 2, (B) is a schematic cross-sectional view showing the molded shape of test example 3, (C) is a schematic cross-sectional view showing the molded shape of test example 4, and (D) is a schematic cross-sectional view showing the molded shape of test example 5.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

Here, a specific example of a forming apparatus and a forming method for forming a glass plate into a shape having a curved surface shape at least in part will be described, but the present invention can also be modified in the configuration and order of the apparatus as appropriate depending on various manufacturing conditions such as a material to be used, a forming shape, and a size.

In the present specification, "to" indicating a numerical range is used in a sense of including numerical values before and after the range as a lower limit value and an upper limit value.

Outline of glass sheet Forming sequence

Fig. 1 is a schematic process diagram showing a procedure for forming a glass plate into a curved shape.

The glass sheet forming apparatus 100 is provided with a preheating stage 11, a forming stage 13, and a cooling stage 15 in this order, and further includes a loading section 19 for loading a glass sheet 17 before forming into the preheating stage 11, and an unloading section 21 for unloading a formed glass sheet 17A from the cooling stage 15.

The glass sheet 17 carried in is heated and softened in the preheating stage 11. The glass plate 17 heated and softened by the preheating stage 11 is press-formed into a desired shape on the forming stage 13. In the cooling stage 15, the glass sheet 17 formed on the forming stage 13 is slowly cooled to a temperature at which deformation can be suppressed.

The glass plate 17 is carried in and out from the loading unit 19 and the unloading unit 21 for each of the above-described units. That is, the glass sheet 17 before molding is placed on the lower mold (mold 1) 23 in the mounting section 19. The lower mold 23 on which the glass plate 17 is placed is conveyed to the preheating stage 11, and heated to a predetermined temperature in the preheating stage 11. The heated glass plate 17 is conveyed to the forming table 13 together with the lower mold 23.

In the forming table 13, the glass sheet 17 is clamped between an upper mold (2 nd molding mold) 25 and a lower mold 23 mounted on the forming table 13. Thereby, the glass plate 17 is formed into a curved shape. After the molding, the upper mold 25 is separated from the lower mold 23, and the glass plate 17A left after the processing of the lower mold 23 is conveyed to the cooling stage 15 together with the lower mold 23.

In the cooling stage 15, the heated glass sheet 17A is slowly cooled. The glass plate 17A after the slow cooling is taken out from the lower mold 23 by the unloading section 21 and carried out.

In the forming apparatus of this configuration, in addition to press forming in which the glass sheet 17 softened by heating is pressed by the lower mold 23 and the upper mold 25, bending by the weight of the glass sheet (self-weight bending forming), suction (vacuum suction) of the glass sheet to the forming surface of the forming mold, and pressure bonding (press blanking) of the glass sheet to the forming surface of the forming mold are combined and carried out in the forming table 13 according to the purpose. By selectively using such a plurality of pressure sources, curved surface forming with high shape accuracy can be performed. In the self-weight bending, the glass plate 17 is bent by its own weight by heating the glass plate 17 disposed on the lower mold 23, but controllability can be provided. For example, the bending start temperature and the press forming temperature due to the self-weight hardly diverge, and when the influence of the heating up to the press forming temperature on the self-weight bending is small, the self-weight bending is not applicable. On the other hand, when the deadweight forming time before and after the press is sufficient, the deadweight bending is applied because the shape after forming is affected by gravity. Thus, the deadweight bending can be controlled in accordance with the standby time and standby temperature before the press forming.

The above-described molding methods are the following molding methods.

(1) Press forming is a method of forming a glass sheet into a predetermined shape by placing the glass sheet between predetermined forming dies (a lower die and an upper die), applying a press load between the upper and lower forming dies in a state where the glass sheet is softened, and bending the glass sheet so that the glass sheet is bonded to the forming dies.

(2) The self-weight bending is a method of forming a glass plate into a predetermined shape by setting the glass plate on a predetermined forming mold, heating and softening the glass plate, and bending the glass plate by gravity to adhere the glass plate to the forming mold.

(3) Vacuum forming is performed by placing a glass sheet on a predetermined forming mold, for example, by placing a clamping forming mold on the glass sheet, and sealing the periphery of the glass sheet. Then, the closed space between the molding die and the glass plate is depressurized by a pump or the like, and a differential pressure is applied to the front surface and the back surface of the glass plate.

(4) In the press-and-blank molding method, a glass sheet is set on a predetermined molding die, for example, a pinch molding die is set on the glass sheet, and the periphery of the glass sheet is sealed. Then, a positive pressure is applied to the upper surface of the glass plate by compressed air, and a differential pressure is applied to the front surface and the back surface of the glass plate, thereby molding.

< glass Material to be shaped >

The glass plate to be molded has a thickness of, for example, 0.5mm or more, preferably 0.7mm or more. The thickness of the glass plate is 5mm or less, preferably 3mm or less, and more preferably 2mm or less. Within this range, the final product can have a strength that is less likely to break.

As the glass composition constituting the glass plate, alkali-free glass, soda lime silicate glass, aluminosilicate glass, borosilicate glass, lithium aluminosilicate glass, and borosilicate glass can be used. In particular, the glass forming apparatus of the present configuration is excellent when aluminosilicate or aluminoborosilicate is used for the glass sheet. These glass sheets have a high young's modulus, a high coefficient of expansion, and high thermal stress is generated by heating of the glass sheets. Therefore, the deviation from the desired bent shape of the glass sheet becomes large, and when the glass sheet is further subjected to the strengthening treatment, the values of the compressive stress may become uneven. In the glass forming apparatus of the present configuration, the glass plate is made of these glass compositions, and even when the glass plate is in a curved shape, the shape deviation can be reduced, and the variation in the compressive stress can be suppressed.

Specific examples of the glass composition include a glass containing 50 to 80% of SiO in terms of a composition expressed by mol% based on oxides₂0.1 to 25% of Al₂O₃3 to 30% of Li₂O+Na₂O+K₂O, 0 to 25% MgO, 0 to 25% CaO and 0 to 5% ZrO₂However, the method is not particularly limited. More specifically, the following glass compositions can be mentioned. For example, "0 to 25% of MgO" means that MgO is necessary, but may be contained at most 25%. (i) The glass of (i) is contained in a soda-lime-silicate glass, and the glasses of (ii) and (iii) are contained in an aluminosilicate glass. (v) The glass of (2) is contained in a lithium aluminosilicate glass.

(i) A composition comprising 63 to 73% of SiO in mol% based on the oxide₂0.1 to 5.2% of Al₂O₃10 to 16% of Na₂O, 0 to 1.5% of K₂O, 0-5% of Li₂O, 5-13% MgO and 4-10% CaO.

(ii) A composition comprising 50 to 74% of SiO in mol% based on the oxide₂1 to 10% of Al₂O₃6 to 14% of Na₂O, 3-11% of K₂O, 0-5% of Li₂O, 2-15% MgO, 0-6% CaO and 0-5% ZrO₂And SiO₂And Al₂O₃Sum of contents ofLess than 75% of Na₂O and K₂A glass having a total content of O of 12 to 25% and a total content of MgO and CaO of 7 to 15%.

(iii) A composition comprising 68 to 80% of SiO in mol% based on the oxide₂4 to 10% of Al₂O₃5 to 15% of Na₂O, 0 to 1% of K₂O, 0-5% of Li₂O, 4 to 15% of MgO and 0 to 1% of ZrO₂The glass of (2).

(iv) A composition comprising 67 to 75% of SiO in mol% based on the oxide₂0 to 4% of Al₂O₃7-15% of Na₂O, 1-9% of K₂O, 0-5% of Li₂O, 6 to 14% of MgO, and 0 to 1.5% of ZrO₂，SiO₂And Al₂O₃The total content of (a) is 71-75%, and Na₂O and K₂A glass containing 12 to 20% by weight of O in total and less than 1% by weight of CaO.

(v) A composition comprising 56 to 73% of SiO in mol% based on the oxide₂10 to 24% of Al₂O₃0 to 6% of B₂O₃0 to 6% of P₂O₅2 to 7% of Li₂O, 3-11% of Na₂O, 0 to 2% of K₂O, 0-8% of MgO, 0-2% of CaO, 0-5% of SrO, 0-5% of BaO, 0-5% of ZnO and 0-2% of TiO₂0 to 4% of ZrO₂The glass of (2).

< Structure of Forming device >

Hereinafter, one configuration example of the molding apparatus will be described in detail.

Fig. 2 is a schematic configuration diagram of the molding apparatus 100. Fig. 3 is a schematic plan view of the III-III line section shown in fig. 2 as viewed from above.

In the following description, the same reference numerals are given to members and portions that perform the same function, and the description thereof may be omitted or simplified. The embodiments described in the drawings are schematic in order to clarify the description of the present configuration, and are not intended to be accurately expressed in terms of the size and scale of an actual product.

In the forming apparatus 100 shown in fig. 2, the direction from the left side to the right side in the horizontal direction is defined as a conveyance direction TD of the glass sheet, and the preheating stage 11, the forming stage 13, and the cooling stage 15 are arranged in this order from the upstream side in the conveyance direction TD. Further, the preheating stage 11, the forming stage 13, and the cooling stage 15 are accommodated in the internal space of the chamber 27. The chamber 27 is purged with an inert gas such as nitrogen gas to reduce the gas concentration of the gas which adversely affects the glass forming.

The chamber 27 has: a carrying-in port 29 for carrying the glass plate and the lower mold 23 into the chamber 27; and a carrying-out port 31 for carrying out the formed glass plate and the lower mold 23. The loading unit 19 shown in fig. 1 is connected to the loading port 29, and the unloading unit 21 (not shown) shown in fig. 1 is connected to the unloading port 31 in the same manner. Further, the carrying-in port 29 and the carrying-out port 31 are provided with unshown shutters, and the shutters are closed except when the glass plate is carried in and out, whereby the atmosphere in the chamber 27 is kept constant. A plurality of openings 101 are formed in the cavity 27, and a support shaft 37 described later is inserted into each opening 101. The space between the support shaft 37 and the chamber 27 is sealed by a bellows structure not shown. In addition to the closed structure for closing the inert gas, the chamber 27 may be a semi-closed structure in which the inert gas is constantly supplied to make the inside of the chamber 27 positive in pressure.

In the preheating stage 11 shown in fig. 2, an upper heater (heating unit for raising temperature) 35 for heating the glass plate and the lower mold 23 to a desired heating temperature is disposed above the conveying surface of the glass plate. The upper heater 35 is preferably arranged to face the lower mold 23 and includes a plurality of lamp heaters 36 supported by a not-shown fixing frame as a heat source. As the lamp heater 36, for example, an infrared lamp heater is used. As the infrared lamp heater, for example, various known heaters such as a carbon filament lamp and a halogen lamp can be used, and any heating element can be used as long as it can perform radiation heating.

Fig. 3 is a cross-sectional view of the multiple lamp heater 36.

The lamp heater 36 has: a heating wire 36A that is energized to generate heat; and a tube material 36B made of quartz or the like surrounding the heating wire 36A. A ceramic coating 40 is formed on the inner or outer peripheral surface of the tube 36B so as to leave the irradiation window 38. The opening angle (center angle) θ of the irradiation window 38 with the heat-generating wire 36A as the center is determined by the distance Ld from the center of the lamp heater 36 to the lower mold 23 as the object to be heated and the arrangement pitch Lc of the lamp heater 36, so that the lower mold 23 is uniformly irradiated with the heat ray. Here, as an example, the opening angle θ is set to 60 °.

In addition, the heating region by the upper heater 35 (the region in which the lamp heaters 36 are arranged) is preferably wider than the outer edge of the lower mold 23 in the horizontal plane, and in this case, the entire lower mold 23 can be uniformly heated.

Above the upper heater 35, a water-cooling plate 39 supported by the support shaft 37 is disposed. A reflective film is preferably provided on the surface of the water-cooling plate 39 facing the upper heater 35. A flow path of cooling water is formed in the water-cooling plate 39, and the cooling water supplied and discharged through the support shaft 37 circulates. The water cooling plate 39 suppresses unnecessary heating of the peripheral members other than the lower mold 23 and the glass plate by the upper heater 35.

A heat diffusion plate 41 is disposed below the lower mold 23 with a gap. Further, a lower heater (heating unit for temperature increase) 43 is disposed below the heat diffusion plate 41. The heat diffusion plate 41 is made of a material having excellent thermal conductivity, and uniformly radiates and conducts heat generated by the lower heater 43 to the lower mold 23. As a material of the heat diffusion plate 41, for example, tungsten carbide, carbon, cemented carbide, copper, iron, stainless material, or the like can be used. The lower heater 43 may be a contact heating type stage heater, or the like, but may be a radiation heating type similar to the upper heater 35.

Further, a water cooling plate 47 is disposed below the lower heater 43. The water cooling plate 47 is supported by a support body 45 fixed to the lower portion of the chamber 27, and unnecessary heating of the peripheral components other than the heat diffusion plate 41 and the lower die 23 by the lower heater 43 is suppressed. The water cooling plate 47 has the same structure as the water cooling plate 39 described above, and supplies and discharges cooling water from the support body 45.

In the cooling stage 15, the gap between the lower mold 23 and the heat diffusion plate 41 is not particularly limited, but if it is too large, the heating efficiency is lowered, and if it is too small, it is difficult to suppress temperature variation of the glass sheet, and therefore the lower limit value of the gap is 1 mm. The upper limit of the gap is 10 mm.

The heat insulating frame 51 is disposed so as to surround the upper surface side of the lower mold 23 on which the glass plate is placed, and the outer periphery of the table on the side of the upper heater 35, the water-cooling plate 39, and the support shaft 37. The heat insulating frame 51 covers the side of the glass plate placed on the lower mold 23 disposed in the stage.

For example, a heat insulating plate made of calcium silicate as a main material can be used as the heat insulating frame 51. In addition, for example, a metal plate made of stainless steel or the like may be used. As shown in fig. 4, the heat insulating frame is preferably a frame having a rectangular horizontal cross section that surrounds a wide range outside the outer periphery of the lower mold 23. The heat insulating frame 51 may include a lid body covering an upper portion of the frame.

The heat insulating frames 53 and 55 having the same configuration are preferably disposed also on the forming table 13 and the cooling table 15. In order to improve the quality of the glass sheet to be formed, it is particularly important to reduce the temperature variation of the glass sheet in each stage. Therefore, it is preferable that all of the respective units are provided with the heat insulating frame. This makes it possible to make the temperature distribution in the internal space covered with the heat insulating frames 51, 53, and 55 uniform. Further, since the outside of the heat insulating frames 51, 53, and 55 is surrounded by the chamber 27, the inflow and outflow of heat to and from the outside is less likely to occur in the heat insulating frames 51, 53, and 55, and a more uniform temperature distribution is obtained. This improves the thermal efficiency, shortens the processing time in each stage, and reduces the temperature variation of the glass sheet in each stage.

As shown in fig. 4, lower molds 23 are disposed on the preheating stage 11, the forming stage 13, and the cooling stage 15, respectively. Each lower die 23 has a pair of die support bars 61 protruding outward from side surfaces 23a and 23b on both sides perpendicular to the conveying direction TD. Each mold support rod 61 is supported by mold conveying portions 63A, 63B arranged on both sides with the lower mold 23 interposed therebetween. Although the detailed explanation of the mechanism is omitted for the mold conveying units 63A and 63B, the plurality of lower molds 23 arranged along the respective stages are conveyed in the conveying direction TD by a conveying mechanism in which the conveying method is a walking beam method.

Fig. 5 is a schematic explanatory view of a case where the lower mold 23 is conveyed in the conveying direction TD from the preheating stage 11 toward the cooling stage 15.

The mold conveying units 63A and 63B support the mold support rods 61 protruding from the respective lower molds 23, and convey the lower molds 23 from the preheating stage 11 to the forming stage 13 and from the forming stage 13 to the cooling stage 15 simultaneously by a walking beam method. The vertical displacement of the lower mold 23 during the conveyance is performed within a range that does not interfere with the fixed-side members such as the heat insulating frames 51, 53, and 55 and the heat diffusion plate 41.

Next, the cooling stage 15 shown in fig. 2 will be explained.

A heat diffusion plate 65, an upper heater (temperature-lowering heating unit) 67 similar to the preheating stage 11, and a water cooling plate 59 are disposed in this order above the lower mold 23 of the cooling stage 15. The heat diffusion plate 65 has the same structure as the heat diffusion plate 41 described above. The water cooling plate 59 is supported by a support shaft 71 fixed to an upper portion of the chamber 27 and forming a flow path for the cooling water.

A heat diffusion plate 73, a lower heater (temperature lowering heating unit) 75, and a water cooling plate 77 are disposed below the lower mold 23 of the cooling stage 15, as in the preheating stage 11. The water cooling plate 77 is supported by a support body 79 fixed to the lower portion of the chamber 27, and suppresses unnecessary heating of the peripheral components other than the heat diffusion plate 73 and the lower die 23 by the lower heater 75. The water cooling plate 77 has the same structure as the water cooling plate 39 described above, and supplies and discharges cooling water from the support body 79.

The lower mold 23 of the cooling stage 15 and the heat diffusion plate 65 and the lower mold 23 and the heat diffusion plate 73 may be in close contact with each other, but the provision of the gap is preferable because the temperature distribution of the lower mold 23 can be made more uniform.

Next, the forming table 13 shown in fig. 2 will be explained.

Fig. 6 is an enlarged sectional view of the forming table 13.

An upper mold 25, a heat diffusion plate 81, an upper heater (heat-retaining heating unit) 83, a heat insulating plate 85, and a water cooling plate 87 are disposed in this order above the lower mold 23 of the molding table 13.

The upper mold 25 is connected to a plunger, not shown, and is supported to be movable up and down between a molding position where it is clamped to the lower mold 23 and a retracted position above the molding position. The upper mold 25 is disposed at the retracted position except for the molding when the lower mold 23 is conveyed. The upper mold 25 may be fixed inside the molding bed 13, and the lower mold 23 may be lifted to be clamped when the lower mold 23 is conveyed. In this case, the upper die moving mechanism can be omitted, and the facility cost can be reduced.

The water cooling plate 87 is supported by a support shaft 89 fixed to the upper portion of the chamber 27, and suppresses unnecessary heating of the peripheral components other than the upper die 25 and the heat diffusion plate 81 by the upper heater 83. The water cooling plate 87 has the same structure as the water cooling plate 39 described above, and supplies and discharges cooling water from the support shaft 89.

The heat insulating plate 85 can be made of a known heat insulating material such as ceramic, stainless steel, die steel, and high-speed steel (high-speed steel). When a metal-based material is used, it is preferable to perform coating treatment of CrN, TiN, TiAlN, or the like on the surface. The surface of the heat shield plate 85 may have a rough surface structure. In this case, a small gap is formed between the water cooling plate 39 and the heat insulating plate, and a further excellent heat insulating effect can be obtained.

A heat diffusion plate 91, a lower heater (heat-retaining heating unit) 93, a heat insulating plate 85, and a water cooling plate 97 are disposed in this order below the lower die 23 of the forming table 13. The water cooling plate 97 is supported by a support 99 fixed to the lower portion of the chamber 27, and unnecessary heating of the peripheral components other than the heat diffusion plate 91 and the lower die 23 by the lower heater 93 is suppressed. The water cooling plate 97 has the same structure as the water cooling plate 39 described above, and supplies and discharges cooling water from the support 99.

The upper mold 25 of the forming table 13 is attached to a cylinder, not shown, which is driven in the vertical direction, and is supported so as to be movable in the vertical direction by the driving of the cylinder. As the cylinder, an air cylinder, a hydraulic cylinder, a servo cylinder using an electric servo motor or the like, or the like can be used.

The upper mold 25 of the forming table 13 is in surface contact with the heat diffusion plate 81 so that heat from the upper heater 83 is uniformly conducted to the upper mold 25. The lower mold 23 of the molding table 3 is in surface contact with the heat diffusion plate 91, so that heat from the lower heater 93 is uniformly conducted to the lower mold 23. Further, depending on molding conditions and the like, the upper mold 25 and the heat diffusion plate 81 and the lower mold and the heat diffusion plate 91 may be separated from each other.

Fig. 7 (a) is a sectional view of the upper mold 25, and (B) is a sectional view of the lower mold 23 including the molding surface 111. Fig. 8 is a rear view of the upper die 25 as viewed from the B direction of fig. 7 (a).

As shown in fig. 7 (a) and 8, the upper mold 25 disposed rearward in the mold clamping direction has an annular projection 113. The projection 113 is provided on the upper die 25 corresponding to the outer edge of the molding surface 111 of the lower die 23 shown in fig. 7 (B) so as to project toward the lower die 23. The projection 113 has an inclined surface 113a whose projection amount gradually increases from the outer periphery of the upper die 25 toward the center. The molding surface 111 is formed in a shape conforming to the molding shape of the glass sheet. That is, the inner side of the annular protrusion 113 shown in fig. 8 is a bottomed groove 25a having a flat bottom surface.

The lower mold 23 arranged forward in the mold clamping direction shown in fig. 7 (B) has a plurality of vacuum forming suction holes 115 opening in the forming surface 111. The suction hole 115 is connected to a suction source such as a suction pump not shown. The suction pump is driven to suck the gas in the space between the lower mold 23 and the glass sheet 17 at a predetermined time point, thereby bringing the glass sheet 17 into close contact with the molding surface 111.

The lower die 23 and the upper die 25 may be made of carbon, stainless steel, ceramics, cemented carbide, or the like. In particular, carbon is preferably used from the viewpoint of uniformizing the heat distribution.

The shape of the projection 113 of the upper mold 25 is not limited to this. The projection 113 may have a flat projection surface without forming the bottom groove 25 a.

Fig. 9 (a) is a cross-sectional view of an upper mold 25A of a modification, and (B) is a cross-sectional view of a lower mold 23A of the modification including a molding surface 111A.

The upper die 25A of the modification has a projection 113A projecting toward the lower die 23B of the modification. The protrusion 113A has an inclined surface 113A whose projection amount gradually increases from the outer periphery of the upper die 25A toward the center, and a flat top surface 113b is formed at the top.

The lower mold 23A has a molding surface 111A having a shape conforming to the molding shape of the glass plate, similarly to the lower mold 23 shown in fig. 7 (a). Suction holes 115 are provided at positions where the curvature of the molding surface 111A is maximized. In the case of this configuration, the region in a ring shape in a plan view connecting the inclined surface 111a corresponding to the inclined surface 113a of the upper mold 25A and the bottom surface 111b corresponding to the top surface 113b has the maximum curvature. A plurality of suction holes 115 are provided so as to open at least a part of the annular region.

In the present configuration, the projection 113A of the upper mold 25A and the molding surface 111A of the lower mold 23A are located at positions corresponding to each other, and the curvature of the projection 113A is smaller than the curvature of the molding surface 111A. Accordingly, when the glass plate 17 is sandwiched by the inclined surfaces 111a and 113a, the contact area with the glass plate 17 becomes small, and deformation and movement of the glass plate 17 become easy. This enables the glass sheet 17 to be faithfully aligned with the molding surface 111A, thereby improving the shape accuracy.

The respective upper heaters 35, 67, 83 and the respective lower heaters 43, 75, 93 in the preheating stage 11, the forming stage 13, and the cooling stage 15 shown in fig. 2 are connected to a temperature control unit, not shown, and are set to respective independent set temperatures. The temperature control unit realizes heating, heat retention, and slow cooling processes in each station by control operations such as proportional control, PI control, and PID control.

The forming apparatus 100 described above has the glass sheet conveyance direction TD set to the horizontal direction, but may be set to a direction inclined from the horizontal direction, such as the vertical direction. In this case, the lower mold 23 and the upper mold 25 may not be arranged vertically, but the viscosity of the glass sheet is not excessively lowered by adjusting the heating temperature of the glass sheet, whereby the glass sheet can be molded between the lower mold 23 and the upper mold 25 while suppressing the influence of gravity.

< glass plate Forming sequence >

Next, a specific procedure for forming the glass plate 17 into a curved shape and its operation will be described by using the forming apparatus 100 having the above-described configuration.

The glass plate 17 before molding is placed on the lower mold 23 of the loading unit 19 shown in fig. 1 by a transfer unit such as a robot arm, not shown, or by the hand of an operator.

The lower mold 23 of the loading unit 19 is conveyed to the preheating stage 11 by the mold conveying units 63A and 63B shown in fig. 4 in a state where the glass plate 17 is placed thereon. It is preferable to heat the lower mold 23 to a temperature higher than the normal temperature before the glass plate 17 is placed, because the heating time in the preheating stage 11 can be shortened. For example, the temperature of the lower mold 23 when the glass plate 17 is placed is preferably 300 ℃ or higher, and more preferably 500 ℃ or higher.

(preheating step)

In the preheating stage 11 shown in FIG. 2, the glass plate 17 on the lower mold 23 is heated by the upper heater 35 and the lower heater 43 until the target heating temperature (for example, 500 ℃ C. to 700 ℃ C.) is reached.

The temperature of the glass plate 17 suitable for press forming varies depending on the composition of the glass plate 17 itself, and if the temperature is too low, the glass plate 17 does not sufficiently soften. Therefore, the glass plate 17 is heated in the preheating stage 11 so that the glass transition temperature Tg is preferably equal to or higher than Tg, more preferably equal to or higher than Tg +40 ℃, and still more preferably equal to or higher than Tg +80 ℃. On the other hand, when the temperature of the glass plate 17 is too high, the glass plate 17 is softened too much and becomes a state unsuitable for maintaining the shape. Therefore, the glass sheet 17 is heated in the preheating stage 11 so as to be preferably Tg +200 ℃ or less, more preferably Tg +150 ℃ or less, and still more preferably Tg +120 ℃ or less.

From the same viewpoint as described above, the glass sheet 17 is preferably heated on the preheating stage 11 so that the viscosity thereof becomes 5.22 × 10¹¹Pa · s or more, more preferably 1.97X 10¹⁰Pa · s or more, more preferably 1.81X 10⁹Pa · s or more. Further, the glass plate 17 is heated on the preheating stage 11 so that the viscosity thereof is preferably 5.94 × 10⁶Pa · s or less, more preferably 4.16X 10⁷Pa · s or less, more preferably 1.65X 10⁸Pa · s or less.

From the viewpoint of the surface quality of the obtained glass sheet molded article, it is preferable to heat the glass sheet 17 uniformly on the preheating stage 11. That is, it is preferable to reduce the temperature variation of the glass sheet 17 during heating in the preheating stage 11. Specifically, the temperature variation of the glass sheet 17 during heating in the preheating stage 11 is preferably less than 30 ℃, more preferably less than 20 ℃, and still more preferably less than 10 ℃.

The temperature distribution of the region of the lower mold 23 in contact with the glass plate 17 during heating is preferably less than 30 ℃, more preferably less than 25 ℃, and still more preferably less than 20 ℃.

(Molding Process)

The glass plate 17 heated to the target heating temperature is conveyed to the forming table 13 together with the lower mold 23. The heated glass plate 17 is formed into a desired shape on the forming table 13 by applying an external force such as pressing in the mold clamping direction.

In the forming table 13, the upper mold 25 disposed at the retracted position is lowered, and the glass plate 17 is sandwiched between the lower mold 23 and the upper mold, thereby forming the glass plate 17. The details of the forming process will be described later. In the forming table 13, the temperature is kept by the upper heater 83 and the lower heater 93 so that the temperature of the glass sheet 17 heated by the preheating table 11 is maintained constant.

The temperature of the glass sheet 17 in the forming table 13 is preferably controlled to be 20 ℃ or lower from the temperature of the glass sheet heated in the preheating table 11. In addition, from the viewpoint of the surface quality of the obtained glass sheet molded body, it is preferable to heat the glass sheet 17 uniformly on the molding table 13. Specifically, the temperature deviation of the glass sheet 17 during the forming on the forming table 13 is preferably within 20 ℃.

After the glass plate 17 is formed, the upper mold 25 is raised and returned to the retracted position. Then, the lower mold 23 is conveyed to the cooling stage 15 together with the formed glass plate 17A.

(Cooling Process)

In the cooling stage 15, the set temperatures of the upper heater 67 and the lower heater 75 are set to be lower than the target heating temperature, and the glass plate 17A and the lower mold 23 are slowly cooled. In the cooling stage 15, the glass sheet 17 is slowly cooled until the shape of the heated and formed glass sheet 17A becomes stable.

The glass plate 17A is slowly cooled on the cooling stage 15 while adjusting the heating temperatures by the upper heater 67 and the lower heater 75. If the cooling rate in the cooling stage 15 is too high, the glass plate 17A is likely to be deteriorated and to have a temperature variation. Therefore, the cooling rate of the glass plate 17A in the cooling stage 15 is preferably set to 20 ℃ in 30 seconds, more preferably 30 ℃ and still more preferably 40 ℃. The temperature distribution of the glass plate 17A during cooling is preferably 30 ℃ or less, more preferably 25 ℃ or less, and further preferably 20 ℃ or less.

The glass plate 17A after the slow cooling is conveyed to the outside of the chamber 27, and then taken out through the unloading section 21 as shown in fig. 1. In the unloading section 21, the glass sheet 17A after molding and slow cooling placed on a lower mold having a temperature of 300 ° or more, preferably 500 ° or more, is taken out from the mold surface. The glass plate 17 may be taken out by a transfer unit such as a robot arm, not shown, or by the hand of an operator.

< homogenization effect of temperature distribution >

The uniform temperature distribution of the glass plates 17, 17A is achieved by the synergistic effect of the heat sealing effect of the heat insulating frames 51, 53, 55, the high heat shielding effect of the chambers 27 outside the heat insulating frames 51, 53, 55 to the outside, the uniform heating effect of the heat diffusion plates 41, 65, 73, 81, 91 to the heaters, and the like. Further, radiation heating by the upper heater 35 of the preheating stage 11, heat conduction heating by the lower heater 43, heat conduction heating by the upper heater 83 and the lower heater 93 of the forming stage 13, and radiation heating by the upper heater 67 and the lower heater 75 via the heat diffusion plates 65 and 73 in the case of cooling the stage are performed, whereby different heating systems are provided for the respective stages. Further, the upper heater and the lower heater of each stage can be heated at respective set temperatures independently, and thus, extremely precise temperature control can be performed.

By independently controlling the heating of each heater in each of these stages, the temperature distribution of the glass plates 17 and 17A can be made uniform at a high level. Further, fine adjustment according to the position is facilitated, and the heat treatment as designed can be accurately realized. Further, since the heated atmosphere is enclosed by the heat insulating frames 51, 53, and 55 and the chamber 27, the outflow of heat to the outside is suppressed, and as a result, the responsiveness of heating control and temperature reduction control is improved, and a desired temperature can be reached uniformly and in a short time.

The mold conveying units 63A and 63B convey the lower mold 23 by the walking beam method, and therefore, the inter-stage movement speed is increased. This suppresses heat loss due to heat dissipation between stages, and also achieves uniformity of temperature distribution.

The heat diffusion plates 41, 65, 73, 81, and 91 can be omitted depending on molding conditions, but the temperature variation of the glass plates 17 and 17A in each stage can be suppressed to be small by providing the heat diffusion plates.

< details of the Forming Process >

Next, a method of molding the glass sheet 17 in the molding table 13 and a structure of a molding die will be described in detail.

First, the shape of the glass sheet 17 for forming is defined.

Fig. 10 is a plan view of the glass plate 17.

The glass plate 17 has a glass central portion 121 located inside the glass-shaped outer peripheral edge 17a, and a glass outer peripheral portion 123 extending from the central portion outer periphery 121a of the glass central portion 121 to the outer peripheral edge 17 a. In fig. 10, the outer peripheral portion 123 is hatched. In the forming step, at least a part of the glass central portion 121 is formed into a curved surface shape.

(1 st Forming method)

Fig. 11A, 11B, and 11C are schematic process explanatory views showing a case where the glass sheet 17 is formed by bringing the lower mold 23 and the upper mold 25 shown in fig. 7 (a) and (B) into contact with each other in stages.

As shown in fig. 11A, the glass sheet 17 is placed on the molding surface 111 of the lower mold 23 in a state where the outer peripheral edge 17a of the glass sheet 17 is in contact therewith. When the upper mold 25 is lowered toward the lower mold 23, the protrusion 113 of the upper mold 25 comes into contact with the glass plate 17 placed on the lower mold 23.

The upper mold 25 has a portion in contact with the glass plate 17 and a portion out of contact with the glass plate, and only the inclined surface 113a of the protrusion 113 is in contact with the glass outer peripheral portion 123 of the glass plate 17. Then, as shown in fig. 10B, when the upper mold 25 is further lowered, the glass plate 17 is pressed into a shape protruding downward due to the inclination of the inclined surface 113a of the protrusion 113. That is, even if the upper mold 25 only annularly contacts the glass plate 17, the glass plate 17 can be deformed toward the lower mold 23. The glass plate 17 is also deflected downward by its own weight and deformed to follow the molding surface 111 of the lower mold 23.

Next, as shown in fig. 11C, the glass sheet 17 is vacuum-sucked to the forming surface 111 by supplying a negative pressure from the suction holes 115. Thereby, the glass plate 17 is closely attached to the molding surface 111, and the curved surface shape of the molding surface 111 is transferred to the glass plate 17. This makes it possible to reliably bring a portion that is not easily brought into close contact with the glass plate 17 and the molding surface 111 by press molding only, and to easily mold even a complicated shape that is difficult to be brought into close contact with only by press molding.

The positions, the number, the sizes, and the like of the suction holes 115 are not particularly limited, and the suction holes 115 are preferably formed in the molding surface 111 only in portions where the glass plate 17 is not easily adhered by press molding. The size of the suction holes 115 is preferably adjusted to such an extent that no trace of the suction holes 115 remains in the glass plate 17 or that even if the trace remains, the trace is not conspicuous.

In general, in press forming of a glass sheet, the entire surface of the glass sheet is sandwiched and formed in contact with a forming mold. Therefore, the glass plate is molded at a relatively low temperature in order to ensure the surface quality of the resulting glass plate molded product. Therefore, a relatively long time is required to deform the glass plate into a desired shape. Therefore, when a complicated shape is formed, it is difficult to form the molded article in a low temperature range where surface quality can be ensured. On the other hand, when the lower mold 23 and the upper mold 25 configured as described above are used for molding, the upper mold 25 does not contact the glass central portion 121 of the glass plate 17. Therefore, even when the glass sheet is molded at a relatively high temperature, a glass sheet molded article having excellent surface quality can be obtained without causing adverse effects such as surface roughening due to contact with the molding die in the glass central portion 121. In this way, the molding table 13 of the present configuration can perform molding at a relatively high temperature, and thus can complete molding in a short time. That is, by using the above-described press mold, a glass sheet molded product having excellent surface quality can be obtained in a short time.

The lower mold 23 and the upper mold 25 of the present configuration are molds for obtaining a glass sheet molded product in which the entire glass central portion 121 is bent with a constant curvature, but the shapes of the lower mold 23 and the upper mold 25 are not limited to the shapes illustrated in the drawings. The shapes of the lower mold 23 and the upper mold 25 can be changed as appropriate according to the target shape of the molding.

The lower die 23 and the upper die 25 of the present configuration realize a combination of press forming, vacuum forming, and gravity-based bending forming, but can be formed by only press forming other than vacuum forming and weight-based forming depending on the material, forming conditions, and the like.

(No. 2 Molding method)

In the 1 st forming method, three types of forming, i.e., press forming, vacuum forming, and bending by gravity, are combined, but in the 2 nd forming method, press forming is further combined.

Fig. 12 is an explanatory view of a schematic process in a case where the glass plate 17 is formed by the 2 nd forming method. The molding die in this case has the same structure as the molding die of the molding method 1 except that the gas ejection holes 125 for the void molding are formed inside the annular protrusion 113 of the upper die 25B.

The gas ejection holes 125 are usually provided in a portion of the upper mold 25B that does not contact the glass plate 17. The number, size, and the like of the gas ejection holes 125 are not particularly limited.

When the lower mold 23 and the upper mold 25B having the above-described configuration are used and press-formed and press-blank-formed together, the gas is discharged from the gas discharge holes 125 after the protrusion 113 of the upper mold 25B is brought into contact with the glass outer peripheral portion 123 of the glass plate 17. Then, the glass plate 17 is pressed against the molding surface 111 of the lower mold 23. That is, since the projection 113 is formed annularly and the contact with the glass plate 17 is also formed annularly, the closed space 129 is formed between the molding surface 111 of the lower mold 23 and the glass plate 17. Gas is supplied to the closed space 129, and the pressure in the closed space 129 becomes positive. The glass plate 17 is thereby pressed against the molding surface 111.

Further, by simultaneously performing the vacuum forming and the gravity-based forming together with the above-described press forming, the glass sheet 17 can be more quickly and reliably made to follow the forming surface 111, and the time required until the forming is completed can be shortened. In this way, by combining at least one of vacuum forming, pressure-air forming, and bending by gravity with press forming, it is possible to easily realize forming of a complicated shape, and it is possible to further shorten the forming time.

The vacuum forming and the press forming can be performed at any time during the press forming, and the order of the press forming, the vacuum forming, and the press forming may be the order of the press forming, the vacuum forming, and the press forming, and the vacuum forming. By performing press forming prior to vacuum forming and press forming, the glass sheet 17 can be more reliably positioned with respect to the forming surface 111.

Further, by performing the molding simultaneously, the adhesion between the glass plate 17 and the molding surface 111 can be further improved, and the processing of the shape in which wrinkles are easily generated in the glass plate 17 becomes easy.

(3 rd Forming method)

Fig. 13A, 13B, and 13C are schematic process explanatory views showing a case where the lower mold 23A and the upper mold 25A of the modification shown in fig. 9 (a) and (B) are brought close to each other in stages to perform the forming process on the glass plate 17.

As shown in fig. 13A, the glass sheet 17 is placed on the molding surface 111A of the lower mold 23A in a state where the outer peripheral edge 17a of the glass sheet 17 is in contact therewith. When the upper mold 25A is lowered toward the lower mold 23A, the top surface 113b of the projection 113A of the upper mold 25A comes into contact with the glass sheet 17 placed on the molding surface 111A of the lower mold 23A.

At this time, the top surface 113b of the upper mold 25A comes into surface contact with the glass plate 17, thereby dispersing the pressure applied to the glass plate 17 with the lowering of the upper mold 25A. Namely, the light contact state is achieved. Then, as shown in fig. 13B, the upper mold 25 is further lowered, and the glass plate 17 is pressed into a downwardly convex shape with a light load (0.1MPa or less) by the inclined surface 113A of the protrusion 113A. At this time, a gap 117 communicating with the suction hole 115 is formed between the bottom surface 111b of the lower mold 23A and the glass plate 17. In other words, the top surface 113b of the protrusion 113A of the upper mold 25A and the bottom surface 111b of the molding surface 111A of the lower mold 23A are formed so as not to contact each other even when the molds are closed.

Next, as shown in fig. 13C, negative pressure is supplied from the suction holes 115 into the gap 117 to vacuum-adsorb the glass sheet 17 to the forming surface 111A. Thereby, the glass plate 17 is closely attached to the molding surface 111A, and the curved surface shape of the molding surface 111A is transferred to the glass plate 17. In the process of advancing the forming from fig. 13B to fig. 13C, the press pressure is preferably kept lower than the light load (0.1MPa or less) of fig. 13B.

The suction holes 115 are provided at the positions where the curvature of the molding surface 111A of the lower mold 23A is maximized, so that the gap 117 between the glass sheet 17 and the molding surface 111A disappears as the glass sheet 17 gradually comes into close contact with the molding surface 111A from the center side toward the peripheral side of the bottom surface 111 b. Then, the glass sheet 17 is finally brought into close contact with the portion of the forming surface 111A where the curvature is maximized. Thus, the glass plate 17 is delivered to the bottom surface 111b of the molding surface 111A of the lower mold 23A without a gap from the state of being in contact with the top surface 113b of the protrusion 113A of the upper mold 25A.

Further, since the glass outer peripheral portion 123 is lightly pressed between the inclined surface 113A of the upper mold 25A and the inclined surface 111a of the lower mold 23A, the glass outer peripheral portion 123 can be easily deformed toward the bottom surface 111b by suction from the suction holes 115. Therefore, the glass plate 17 is not locally constrained at the glass outer peripheral portion 123, but the entire glass plate 17 is bonded along the molding surface 111A with a substantially uniform pressure.

According to this molding method, the operation of transferring the shape of the glass plate 17 along the molding surface 111A of the lower mold 23A is performed substantially by vacuum suction. Therefore, since a uniform pressure distribution is generated in the glass surface, the indentation and the wrinkle due to the local die contact by the pressing of the upper die 25A are not generated on the plate surface of the glass plate 17, and high-quality molding can be performed. Further, since the metal sheet is processed into a desired shape by vacuum suction, even a complicated shape which is difficult to form only by pressing can be formed with high precision and high quality.

(4 th Forming method)

In the 4 th forming method, the 3 rd forming method is further combined with the press forming.

Fig. 14 is an explanatory view of a schematic process in a case where the glass plate 17 is formed by the 4 th forming method. The molding die in this case has the same configuration as the molding die of the 3 rd molding method, except that the gas ejection holes 125 for the void molding are formed in the protrusions 113A of the upper die 25C.

As in the case of the aforementioned 2 nd forming method, the openings of the gas ejection holes 125 are usually provided in the portion of the upper mold 25B that does not contact the glass plate 17. The number, size, and the like of the gas ejection holes 125 are not particularly limited.

When the lower mold 23A and the upper mold 25C having the above-described configuration are used and press-formed and press-blank-formed at the same time, the projection 113A of the upper mold 25C is brought into contact with the glass outer peripheral portion 123 of the glass plate 17, and then the gas is discharged from the gas discharge hole 125. Then, the glass plate 17 is pressed against the molding surface 111A of the lower mold 23A. That is, since the contact area between the protrusion 113A and the glass plate 17 is annular, the closed space 129 is formed between the molding surface 111A of the lower mold 23A and the glass plate 17. Gas is supplied to the closed space 129, and the pressure in the closed space 129 becomes positive. The glass plate 17 is thereby pressed against the molding surface 111A.

The gas ejection from the gas ejection holes 125 may be performed after the vacuum adsorption of the glass plate 17 by the suction holes 115, or may be performed before the vacuum adsorption.

< example of Structure of other Molding apparatus >

The glass-pane forming apparatus 100 may be configured to include a plurality of preheating stages 11 and a plurality of cooling stages 15.

Fig. 15 is a schematic configuration diagram of a molding apparatus 200 including a plurality of preheating stages 11, a molding stage 13, and a plurality of cooling stages 15.

The preheating stage 11 is provided at four places (PH1 to PH4) along the conveying direction TD of the lower mold 23, and the cooling stage 15 is provided at four places (C1 to C4) along the conveying direction TD of the lower mold 23. The forming table 13 is provided at one position between the preheating table 11 and the cooling table 15 (PM 1).

The heating temperature of the preheat stage 11 is set to be increased in stages along the conveyance direction TD from PH1 to PH 4. Thus, the lower mold 23 and the glass plate 17 are gradually heated up as they are conveyed in the conveying direction TD, and are heated to reach the target heating temperature, which is the molding temperature.

The heating temperature of C1 to C4 of the cooling stage 15 is set to be lowered stepwise along the conveyance direction TD. Thus, the lower mold 23 and the glass plate 17 are gradually cooled down as they are conveyed in the conveying direction TD, and are gradually cooled from the target heating temperature.

Fig. 16 is a graph showing an example of temperature changes of the lower mold 23 and the glass plate 17 in the preheating stage 11, the forming stage 13, and the cooling stage 15.

The glass plate 17 having a pH1 supplied from the loading section 19(LD) shown in FIG. 15 to the preheating stage 11 is placed on the lower mold 23 heated in advance to a predetermined temperature Tc and is cooled from room temperature T_RMHeating is started. The lower mold 23 and the glass sheet 17 are raised in temperature as they are conveyed to PH2, PH3, PH4, and reach the target heating temperature T as the molding temperature before being conveyed to the molding table 13(PM)_PM。

The glass sheet 17 is formed on the forming table 13(PM) while being held at a constant temperature of the target heating temperature TPM.

After the molding, the temperature of the lower mold 23 and the molded glass plate 17A gradually decrease as the temperature of C1 to C4 conveyed to the cooling stage 15. The glass sheet 17A conveyed from C4 to the unloading unit 21(ULD) shown in fig. 12 is naturally cooled.

In each of the preheating stage 11 and the cooling stage 15, temperature control is performed so that the lower mold 23 and the glass plates 17 and 17A are uniformly set at the respective stages. The larger the number of stages, the wider the temperature variation. In addition, from the viewpoint of the production interval time, it is preferable to reduce the number of stages. The number of the respective stations is appropriately set in accordance with the size, shape, and the like of the glass plate to be processed. For example, when the glass sheet is large in size and when a complicated shape is formed, it is preferable to increase the number of the preheating stages 11 and the cooling stages 15 in order to avoid a rapid temperature change.

Fig. 17 is a schematic diagram of a conventional molding apparatus as a reference example.

In the conventional molding apparatus, the glass sheet 17 is entirely pressed by the lower mold 131 and the upper mold 135, and the heating temperature is set to be lower than the above-described molding temperature (target set temperature). Therefore, the glass plate 17 needs to be held in a clamped state until the molded shape is stabilized. As a result, the molding time T_PM2Becomes longer than the forming time T shown in FIG. 13_PM1。

On the other hand, in the molding apparatus 200 of the present configuration shown in fig. 15, since the glass sheet 17 is molded by combining press molding, vacuum molding, press forming, and gravity-based molding that are only in contact with the outer periphery of the glass, the heating temperature can be set to a higher temperature than in the conventional art, and the glass sheet can be brought into close contact with the molding surface of the molding die by the synergistic effect of the respective molding, so that the molding shape can be quickly stabilized. That is, the glass sheet is less likely to rebound. This only requires one molding table 13, and can reduce equipment cost and improve throughput.

Further, by heating the temperature of the lower mold 23 to the predetermined temperature Tc in advance, the time until the temperature reaches the target set temperature can be further shortened, and the production interval time can be shortened.

FIG. 18 is a schematic view of a molding apparatus 300 showing another configuration example of the molding apparatus 200 shown in FIG. 15.

The molding apparatus 300 of this configuration includes a plurality of molding lines each having a preheating stage 11, a molding stage 13, and a cooling stage 15 shown in fig. 12. The forming apparatus 300 has a configuration in which two lines, i.e., the 1 st forming line 141 and the 2 nd forming line 143, are provided in fig. 18, but three or more lines may be provided.

The loading section 19 of the 1 st forming line 141 of the forming apparatus 300 is connected to the unloading section 21 of the 2 nd forming line 143, and the unloading section 21 of the 1 st forming line 141 is connected to the loading section 19 of the 2 nd forming line 143. Then, the lower mold 23 of the 1 st forming line 141 and the lower molds 23 of the 2 nd forming line 143 are used in common, and circulate through the respective lines.

According to this configuration, the lower mold 23 conveyed to the unloading section 21 of one molding line is returned to the loading section 19 of the other molding line, thereby suppressing the drop in the mold temperature and maintaining the temperature at or above the predetermined temperature Tc during the operation of the molding apparatus 300. This reduces the temperature change width of the lower mold 23, and reduces the temperature cycle load on the lower mold 23. In addition, energy consumption for heating can be suppressed, and running cost can be reduced.

Further, the installation space of the molding apparatus 200 can be reduced as compared with a configuration in which a plurality of molding lines are arranged in series, and thus the facility cost can also be reduced.

< details of the Forming Process >

Next, preferred molding conditions in the molding step of the molding table 13 will be described.

In the forming apparatuses 100, 200, and 300 having the present configuration, it is preferable to form a glass sheet based on the forming conditions shown below.

(pressure conditions)

In the press forming, different pressures are applied to respective regions of the glass central portion 121 and the glass peripheral portion 123 of the glass plate 17 shown in fig. 10, and the glass plate 17 is press-formed. Specifically, when vacuum forming or pressure forming is not performed, it is preferable that the pressure Pct applied to the glass central portion 121 is 0 to 0.1MPa, and the pressure Peg applied to the glass outer peripheral portion 123 is 0.1 to 10 MPa.

When the vacuum forming or the press forming is not performed, a pressure other than the gravity is not applied to the glass central portion 121 of the glass plate 17. On the other hand, the glass peripheral portion 123 of the glass sheet 17 is pressed higher than the glass central portion 121, and the glass sheet 17 is fixed to the molding die. This enables stable press forming without positional displacement of the glass plate 17. The deformation direction (downward projection or upward projection) and the deformation amount of the glass sheet 17 formed by press forming can be determined according to the inclination direction and the inclination angle of the projection 113 and the forming surface 111 (see fig. 7a and B) which are in contact with the glass sheet 17.

When the glass plate 17 is formed by press forming and vacuum forming, it is preferable that the pressure Pct applied to the glass central portion 121 by press forming is 0 to 0.1MPa and the pressure Peg applied to the glass outer peripheral portion 123 is 0.1 to 10 MPa. Then, the total of the pressures applied to the glass plate 17 by the press forming and the vacuum forming is set to a pressure where the pressure Peg of the glass outer peripheral portion 123 is higher than the pressure Pct of the glass central portion 121 (Peg > Pct).

When the glass plate 17 is formed by press forming, vacuum forming, and pressure forming in combination, it is preferable that the pressure Pct applied to the glass central portion 121 by the press is 0 to 0.1MPa, and the pressure Peg applied to the glass outer peripheral portion 123 is 0.1 to 10 MPa. Then, the total of the pressures applied to the glass plate 17 by the press forming, the vacuum forming, and the pressure-vacuum forming is a pressure at which the pressure Peg of the glass outer peripheral portion 123 is higher than the pressure Pct of the glass central portion 121 (Peg > Pct). In this case, since the pressure by the press-and-air forming is applied to the glass central portion 121 in addition to the vacuum forming, the pressure applied to the glass central portion is higher than in the case of only the press forming and the vacuum forming.

The above conditions may or may not include the bending effect by the self-weight forming before and after the press forming.

(temperature of glass plate)

When the glass plate 17 is formed into a desired shape, the lower limit of the temperature at the time of forming is preferably 400 ℃, more preferably Tg +40 ℃, and still more preferably Tg +80 ℃. The upper limit of the temperature during molding is preferably 750 ℃, more preferably 680 ℃, and still more preferably 650 ℃.

By setting the forming temperature in the above range, the formed shape of the glass plate 17 can be maintained for a short time, and the forming time can be shortened.

(tackiness of glass plate)

When the glass plate 17 is formed into a desired shape, the viscosity of the glass plate 17 at the time of forming differs depending on the type of the material of the glass plate 17, but is preferably 1 × 10 from the viewpoint of formability^-5Pa · s or less.

In particular, it is an index of formability

[ P: in-plane pressure, ρ: viscosity of]) Preferably, the thickness of the glass plate is 1X 10 at the outer periphery of the glass^-8.7～1×10^2.51X 10 in the center of the glass^-12～1×10^-0.5eg。

(dimensional accuracy of glass plate)

According to the above-described manufacturing apparatus and forming method, a glass sheet formed body having excellent shape accuracy can be obtained. As an evaluation index of the shape quality of the glass sheet molded body, for example, an in-plane shape deviation compared with a design shape (design surface) can be cited.

The in-plane shape deviation is defined as a deviation of the in-plane shape of a surface obtained by approximating the shape of the glass sheet molding to a curved surface so that the absolute value of the distance from the design surface in the normal direction is the minimum in the plane when the normal is set along the design shape, and the deviation of the deviation amount in the normal direction between the surface obtained by approximating the curved surface and the design surface.

The deviation in the in-plane shape of the glass sheet formed body obtained by the manufacturing apparatus and the forming method of the present configuration is preferably 0.6mm or less, and more preferably 0.4mm or less.

Table 1 summarizes the conditions and results of forming the glass sheets.

A glass plate (material: dragonttail) having a size of 100 × 50mm (thickness t 1.1mm) was formed by press forming using only bending by its own weight, press forming using only the entire surface, press forming using only the edge of the outer peripheral portion of the press glass, and forming using a combination of press forming and vacuum forming using the forming apparatus shown in fig. 1.

The glass plate molding shapes were test examples 1 and 2 having a single radius of curvature shown in fig. 19 (a), test example 3 having an S-shape shown in fig. 19 (B), test example 4 having a J-shape shown in fig. 19 (C), and test example 5 having a saddle shape shown in fig. 19 (D). The radius of curvature R in test example 1 was 2000mm, and the radius of curvature R in test example 2 was 800 mm. In test example 3 having the S-shape, the radius of curvature was 2000mm for R1, 100mm for R2 and 2000mm for R3 in this order from one end. The J-shaped test example 4 had a shape in which a curved surface having a curvature radius R of 50mm was connected from a flat shape. The saddle-shaped test example 5 has a convex surface with a radius of curvature R5 of 800mm and a concave surface with a radius of curvature R6 of 2000mm in a direction orthogonal to the convex surface.

In test examples 1 to 4, the full-face press forming pressure was set to 0.1MPa, and in test example 5, the full-face press forming pressure was set to both 0.1MPa or less and a pressure exceeding 0.1 MPa.

The molded bodies obtained by the respective molding methods were evaluated for production interval time, shape accuracy, and surface quality of molding. The evaluation criteria are as follows.

Production Interval time (time required for shaping)

Very good: less than 30s

O: 30s or more and less than 100s

And (delta): more than 100s and less than 200s

A tangle-solidup: more than 200s and less than 500s

X: over 501s

Shape accuracy (deviation from design shape)

Very good: less than 0.2mm

O: 0.2mm or more and less than 0.4mm

And (delta): 0.4mm or more and less than 0.6mm

A tangle-solidup: more than 0.6mm and less than 0.8mm

X: 1.0mm or more

Quality of area (number of defects counted based on image processing)

Very good: 0 to 5

O: 6 to 10

And (delta): 11 to 50

A tangle-solidup: 51 to 100

X: more than 101

[ Table 1]

In the case of only the dead-weight bending, neither of the test examples was able to accelerate the production interval time.

In the case of the full-surface press molding, when the pressure is set to 0.1Mpa or less, the full surface of the glass sheet comes into contact with the molding die, and therefore the surface roughness of the glass surface after molding increases, and the surface quality deteriorates. However, in test example 5, when a pressure exceeding 0.1MPa was applied, the surface quality was improved.

In the case of pressing only in the edge press forming, the results of good production interval time and shape accuracy, and particularly excellent surface quality were obtained in test examples 1 and 2 of single-curve shape. However, in test examples 3, 4, and 5 in which the molded shape became relatively complicated, the production interval time, the shape accuracy, and the surface quality were all Not Good (NG).

On the other hand, when the press forming and the vacuum forming were combined in the edge press forming, good results were obtained in test examples 1 to 4, and the surface quality was not satisfactory (NG) in test example 5. That is, in the case of the saddle shape of test example 5, good results were obtained if a pressure exceeding 0.1MPa was applied to the full-face press forming.

The present invention is not limited to the above-described embodiments, and embodiments modified and applied by those skilled in the art based on the combination of the respective configurations of the embodiments, the description of the specification, and known techniques are also intended to be included in the scope of the present invention.

As described above, the following matters are disclosed in the present specification.

(1) A method for forming a glass sheet into a desired shape by heating the glass sheet, comprising the steps of:

sandwiching the glass sheet between a pair of forming molds; and

the glass sheet is press-molded by the press mold by applying a 1 st pressing force of 0.1MPa or less to a glass central portion located inside the outer peripheral edge of the glass sheet in a mold closing direction or by not applying a pressing force to the glass central portion, and applying a 2 nd pressing force of 0.1 to 10MPa different from the 1 st pressing force to a glass outer peripheral portion located between the outer periphery of the glass central portion and the outer peripheral edge of the glass sheet in the mold closing direction.

According to this glass sheet forming method, the glass central portion and the glass outer peripheral portion of the glass sheet are press-formed with different pressing forces, whereby deterioration in surface quality of the glass central portion having a low pressing force can be suppressed.

(2) The method of forming a glass sheet according to (1), characterized by comprising a step of applying a negative pressure between a 1 st forming mold disposed in front in the mold clamping direction and the glass sheet to cause the glass sheet to adhere to the 1 st forming mold.

According to this method for forming a glass sheet, the glass sheet can be attracted to the 1 st forming die by the negative pressure, and the glass sheet can be formed into a desired shape more reliably and at high speed.

(3) A method for forming a glass sheet into a desired shape by heating the glass sheet, comprising the steps of:

sandwiching the glass sheet between a pair of forming molds;

applying a pressurizing force of 0.1MPa or less to the glass sheet from one of the pair of molding dies in a mold clamping direction, and sandwiching an annular glass outer peripheral portion between an outer periphery of a glass central portion and an outer peripheral edge of the glass sheet between the pair of molding dies to define a space between a 1 st molding die disposed forward in the mold clamping direction and the glass sheet on an inner peripheral side of the glass outer peripheral portion, wherein the glass central portion is located inward of the outer peripheral edge of the glass sheet; and

negative pressure is supplied to the space defined between the glass sheet and the 1 st molding die, and the glass sheet is attracted to the 1 st molding die.

According to this glass sheet forming method, the operation of transferring the shape of the glass sheet along the forming surface of the 1 st forming mold is performed substantially by vacuum suction. Therefore, high-quality molding can be performed without generating indentations and wrinkles on the plate surface of the glass plate due to the press of the 2 nd molding die. Further, since the metal sheet is processed into a desired shape by vacuum suction, even a complicated shape which is difficult to form only by pressing can be formed with high precision and high quality.

(4) The method of forming a glass sheet according to (3), wherein a suction hole is provided in at least a part of a portion having a maximum curvature in the forming surface of the 1 st forming die to which the curved surface shape is transferred, and the negative pressure is supplied from the suction hole to the space.

According to this method of forming a glass sheet, the gap between the glass sheet and the forming surface gradually disappears toward the portion where the curvature is maximum as the negative pressure is supplied, and the glass sheet and the forming surface are brought into close contact with each other without leaving a gap therebetween.

(5) The method of forming a glass sheet as set forth in (3) or (4), wherein the pair of molding dies is provided with a protrusion in either one of the molding dies, and a concave molding surface corresponding to the protrusion in the other molding die,

the curvature of the protrusion is smaller than the curvature of the forming surface at a position corresponding to the protrusion and the forming surface.

According to this method of forming a glass sheet, when the glass sheet is sandwiched between the inclined surface of the protrusion and the inclined surface of the forming surface, the contact area with the glass sheet is reduced, and deformation and movement of the glass sheet are facilitated. This enables the glass sheet to be faithfully aligned with the molding surface, thereby improving the shape accuracy.

(6) The method of forming a glass sheet according to any one of (1) to (5), comprising a step of supplying a positive pressure between a 2 nd forming mold disposed rearward in the mold clamping direction and the glass sheet to press the glass sheet against a 1 st forming mold disposed forward in the mold clamping direction.

According to this glass sheet forming method, the glass center portion of the glass sheet is pressed against the 1 st forming die, so the glass sheet can be formed into a desired shape more reliably and at high speed.

(7) The method of forming a glass sheet according to any one of (1) to (6), wherein the forming of the glass sheet is performed by heating the glass sheet so that the viscosity of the glass sheet becomes 5.94 × 10⁶Pa·s～5.22×10¹¹Pa · s.

According to this method for forming a glass sheet, the glass sheet is made to have a viscosity excellent in formability, so that the glass sheet can be bonded to a forming mold well, and can be formed into a desired shape quickly.

(8) The method of forming a glass sheet according to any one of (1) to (7), wherein an in-plane shape deviation of the glass sheet formed body after the glass sheet is formed from a design shape is within 0.3 mm.

According to the method for forming a glass sheet, a glass sheet formed body having high shape accuracy can be obtained.

The present application is based on the japanese patent application (patent application 2019-21562) filed on 8.2.2019, the contents of which are incorporated by reference in the present application.

Description of the reference numerals

11 … preheating stage; 13 … forming station; 15 … cooling stage; 17. 17a … glass plate; 17a … outer periphery; 23. 23a … lower die (1 st forming die); 25. 25A, 25B, 25C … upper die (2 nd forming die); 27 … chamber; 35 … upper heater (heating part for heating); a 36 … lamp heater; 41 … heat diffusion plate; 43 … lower heater (heating part for heating); 51. 53, 55 … heat insulating frame; 63A, 63B … mold conveying parts; 65 … heat spreading plate; 67 … upper heater (heat retention heating part); 73 … heat spreading plate; 75 … lower heater (heating part for heat preservation); 81 … heat diffusion plate; 83 … upper heater (cooling heater); 91 … heat diffusion plate; 93 … lower heater (cooling heater); 100 … forming device; 111. 111a … forming side; 113. 113a … projection; 113a … inclined plane; 115 … suction holes; 121 … glass center; 121a … central portion outer periphery; 123 … glass peripheral portion; 125 … gas ejection holes; 131 … lower die (1 st forming die); 135 … upper die (2 nd forming die); 141 … form line 1 (forming line); 143 … form line 2 (forming line).

Claims (8)

1. A method for forming a glass sheet into a desired shape by heating the glass sheet, comprising the steps of:

sandwiching the glass sheet between a pair of forming molds; and

the glass sheet is press-molded by the press mold by applying a 1 st pressing force of 0.1MPa or less to a glass central portion located inside the outer peripheral edge of the glass sheet in a mold closing direction or by not applying a pressing force to the glass central portion, and applying a 2 nd pressing force of 0.1 to 10MPa different from the 1 st pressing force to a glass outer peripheral portion located between the outer periphery of the glass central portion and the outer peripheral edge of the glass sheet in the mold closing direction.

2. A method of forming glass sheets as in claim 1,

the method includes a step of supplying a negative pressure between a first molding die 1 disposed in front of the mold clamping direction and the glass sheet to cause the glass sheet to adhere to the first molding die 1.

3. A method for forming a glass sheet into a desired shape by heating the glass sheet, comprising the steps of:

sandwiching the glass sheet between a pair of forming molds;

applying a pressurizing force of 0.1MPa or less to the glass sheet from one of the pair of molding dies in a mold clamping direction, and sandwiching an annular glass outer peripheral portion between an outer periphery of a glass central portion and an outer peripheral edge of the glass sheet between the pair of molding dies to define a space between a 1 st molding die disposed forward in the mold clamping direction and the glass sheet on an inner peripheral side of the glass outer peripheral portion, wherein the glass central portion is located inward of the outer peripheral edge of the glass sheet; and

negative pressure is supplied to the space defined between the glass sheet and the 1 st molding die, and the glass sheet is attracted to the 1 st molding die.

4. A method for forming a glass sheet as claimed in claim 3,

suction holes are provided in at least a part of a portion of the molding surface of the 1 st molding die, to which the curved surface shape is transferred, having a maximum curvature, and negative pressure is supplied from the suction holes to the space.

5. A method for forming glass sheets as in claim 3 or 4,

the pair of molding dies has a protrusion on one of the molding dies, and a concave molding surface corresponding to the protrusion on the other molding die,

the curvature of the protrusion is smaller than the curvature of the forming surface at a position corresponding to the protrusion and the forming surface.

6. A method for forming a glass sheet according to any one of claims 1 to 5,

the method includes a step of supplying a positive pressure between the 2 nd molding die disposed rearward in the mold clamping direction and the glass sheet to press the glass sheet against the 1 st molding die disposed forward in the mold clamping direction.

7. A method for forming glass sheets according to any one of claims 1 to 6,

the glass plate is formed by heating the glass plate so that the viscosity of the glass plate becomes 5.94 x 10⁶Pa·s～5.22×10¹¹Pa · s.

8. A method for forming a glass sheet according to any one of claims 1 to 7,

the deviation of the in-plane shape of the glass sheet formed body after the glass sheet forming is within 0.3mm from the design shape.

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