Method for producing glass molded article and method for producing flattened mold cloth

Abstract

To reduce perspective distortion of a glass molded article obtained by subjecting a glass plate to a bending processing.SOLUTION: The present invention relates to a method for producing a glass molded article, the method including: attaching a flattened mold cloth, which is obtained by reducing irregularities on a surface of a mold cloth, to a forming mold; heating a glass plate to a temperature equal to or higher than a glass transition point; and press-forming the softened glass plate into a predetermined shape along the forming mold via the flattened mold cloth.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a glass molded product and a method for manufacturing a flattening mold cloth, and more particularly, to a method for manufacturing a glass molded product having a curved shape by bending a glass plate, and a method for manufacturing a flattening mold cloth used in the manufacture of the glass molded product.

Background Art

[0002] In recent years, window glasses for automobiles and window glasses for buildings having a curvature have been used in order to enhance the aesthetic appearance, light transmittance efficiency, etc. A glass having a curved shape (bent glass) is manufactured, for example, by heating a glass plate in a heating furnace to a temperature equal to or higher than the glass transition point and pressing it with a mold (mold) having a predetermined shape.

[0003] Regarding the press bending forming method of a glass plate, for example, in Patent Documents 1 and 2, a forming apparatus for bending a glass plate by sandwiching and press forming it between a female mold and a male mold has been proposed.

[0004] In this bending forming apparatus, generally, bent glass is formed including the following steps (1) to (3). (1) While transporting the glass plate, it is heated to a temperature equal to or higher than the glass transition point and placed on the female mold by a transfer machine having a positioning mechanism. (2) At the press position, the glass plate is pressed by the upper male mold and the lower female mold to form a predetermined bent shape. At this time, vacuum suction is also performed on the male mold side. (3) The glass plate after the press is completed is taken out while being adsorbed and held by the male mold, and then cooled. According to this forming apparatus, since the glass plate can be formed into a shape following the forming surface of the male mold, a bent glass having a desired shape can be formed by using a mold having a forming surface of a desired shape.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In a bending apparatus, in order to prevent a glass plate adsorbed and held by a male mold from remaining adsorbed to the male mold and not being released even after the vacuum state is released, the surface of the male mold is covered with a protective material called a mold cloth. Since the mold cloth generally uses a woven fabric in which yarns (spun yarns) made of refractory fibers are woven, there are fine irregularities on its surface, and when the glass plate is pressed, the irregularities on the surface of the mold cloth may be transferred to the surface of the glass plate. As a result, fine irregularities are generated on the surface of the glass plate, and a phenomenon called undulation (perspective distortion), such as the surface of the glass plate appearing wavy or objects appearing distorted depending on the viewing angle, may occur.

[0007] As a glass molded article having a curved surface, for example, there is a windshield of an automobile. Laminated glass is used for the windshield, but if there are irregularities on the surface of the glass plate, gaps will be formed between the glass plates when the glass plates are laminated, and the undulation phenomenon will be more likely to appear significantly. Since it is desired that the windshield has no perspective distortion that hinders the driver's visibility, it is desired to reduce the perspective distortion in the laminated glass.

[0008] In order to reduce such perspective distortion, conventionally, at the time of manufacturing bent glass, measures such as lowering the heating temperature of the glass plate, lowering the vacuum pressure, shortening the vacuum time, and shortening the pressing time have been taken. However, when these are done, it becomes difficult for the glass plate to bend into a desired shape, so there has been a problem that it is difficult to manufacture a glass molded article having a complex shape.

[0009] Therefore, an object of the present invention is to reduce the perspective distortion of a glass molded article obtained by bending a glass plate. [Means for Solving the Problems]

[0010] The inventors of the present invention have discovered that the higher the heating temperature of the glass plate, the easier it is for the unevenness on the surface of the mold cloth to be transferred to the glass surface. As a result of intensive studies, the inventors have found that based on this finding, by reducing the surface roughness of the mold cloth to be used, it is possible to perform bending processing into a desired shape while reducing perspective distortion without adjusting the processing conditions, and thus the present invention has been completed.

[0011] One aspect of the present invention relates to a method for manufacturing a glass molded article, which comprises attaching a planarized mold cloth with reduced unevenness on the surface of the mold cloth to a molding die, heating a glass plate to a temperature equal to or higher than the glass transition point, and pressing and molding the softened glass plate along the molding die through the planarized mold cloth into a predetermined shape.

[0012] Another aspect of the present invention relates to a method for manufacturing a planarized mold cloth, which comprises applying a pressure of 0.3 MPa or more to the plane of the mold cloth to reduce the unevenness on the surface of the mold cloth.

Effects of the Invention

[0013] According to the method for manufacturing a glass molded article of the present invention, a glass molded article with reduced perspective distortion can be obtained. The obtained glass molded article has little occurrence of perspective distortion and excellent appearance, so it is suitably used for laminated glass. Further, in the method for manufacturing a glass molded article of the present invention, even when the heating temperature of the glass plate is increased, the occurrence of perspective distortion is small, so more complex molding can be performed by increasing the heating temperature of the glass plate, and stress relaxation is facilitated, so cracking can be prevented. And according to the method for manufacturing a planarized mold cloth of the present invention, a mold cloth with small surface unevenness can be obtained. By manufacturing a glass molded article using this mold cloth, a glass molded article with reduced perspective distortion can be obtained.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, the present invention will be described, but the present invention is not limited by the examples in the following description. In this specification, "~" indicating a numerical range means including the numerical values described before and after it as the lower limit value and the upper limit value.

[0016] <Method for manufacturing a glass molded article> The method for manufacturing a glass molded article of the present invention includes attaching a planarized mold cloth with reduced unevenness (roughness) on the surface of a mold cloth to a molding die, heating a glass plate to a temperature equal to or higher than the glass transition point, and press-molding the softened glass plate along the molding die through the planarized mold cloth into a predetermined shape.

[0017] The present invention focuses on a mold cloth used when molding a glass plate, and is characterized in that the glass plate is bent and molded along a molding die through a planarized mold cloth with reduced unevenness (roughness) on the cloth surface. Thereby, the unevenness derived from the mold cloth transferred onto the surface of the glass becomes smaller, and thus the perspective distortion of the glass can be reduced. In particular, it is possible to suppress the occurrence of perspective distortion that is likely to be prominent in laminated glass. Further, by using the planarized mold cloth, it becomes unnecessary to adjust the processing conditions for reducing the perspective distortion during the production of bent glass, so that the production efficiency can be increased.

[0018] Hereinafter, embodiments of the method for manufacturing a glass molded article (bent glass) of the present invention will be specifically described.

[0019] FIG. 1 is a configuration diagram showing an example of a manufacturing apparatus 10 used in the method for manufacturing a glass molded article of the present invention, and FIG. 2 is a diagram for explaining an example of the operation procedure of the manufacturing apparatus 10 of FIG. 1. As shown in FIG. 1, the manufacturing apparatus 10 used for manufacturing a glass molded article includes a controller 28 and a transport conveyor 20 for transporting a heat-softened glass plate 12, and includes a press area and a cooling area from the upstream side to the downstream side in the transport direction of the glass plate 12. The transport conveyor 20 transports the heat-softened glass plate 12 to the press area, and the glass plate 12 is press-molded by a female mold 24 and a male mold 30 installed in the press area, and then cooled in the cooling area.

[0020] The glass plate 12 is inorganic glass. As the inorganic glass, for example, soda-lime glass, aluminosilicate glass, borosilicate glass, alkali-free glass, fused silica glass, etc. can be used without particular limitation. Among these, soda-lime glass is particularly preferred from the viewpoints of manufacturing cost and formability. The forming method of the glass plate 12 is not particularly limited. For example, in the case of inorganic glass, a glass plate formed by a float method or the like is preferred. As the glass plate 12, a glass that absorbs ultraviolet rays or infrared rays may be used. The glass plate 12 is preferably transparent, but may also be a glass plate colored to such an extent that the transparency is not impaired.

[0021] From the viewpoints of weight and perspective distortion, the thickness of the glass plate 12 is preferably 0.5 mm or more and 5.0 mm or less. More preferably, the thickness of the glass plate 12 is 1.6 mm or more. Further, a ceramic color paste containing a fusible glass frit containing a black pigment, for example, may be applied to the peripheral portion of the glass plate 12.

[0022] The means for heating the glass plate 12 is not particularly limited, but for example, heating in a heating furnace can be mentioned. As the heating furnace, it is preferable to use an electric heating furnace in terms of easy temperature adjustment. One heating furnace may be used, or a plurality of heating furnaces may be used for stepwise heating.

[0023] The glass plate 12 is heated to a temperature equal to or higher than the glass transition point of the glass plate 12. The glass transition point of the glass plate 12 varies depending on the composition of the glass, but is preferably 600 to 700 °C. The heating temperature can be adjusted by the controller 28.

[0024] In the present embodiment, first, the flat glass plate 12 cut into a predetermined shape is conveyed one by one in a heating furnace by a conveying conveyor 20 or the like, and after being heated to a predetermined bending forming temperature, it is carried into a press area.

[0025] At a predetermined position in the press area, a female mold 24, which is an example of a lower mold for pressing, is provided. When the glass plate 12 is conveyed to the predetermined position in the press area, the female mold 24 rises from the standby position below the conveying conveyor 20 to a predetermined raised position. Therefore, when the glass plate 12 is conveyed to the above-mentioned predetermined position, it is transferred from the conveying conveyor 20 to the female mold 24.

[0026] As shown in Fig. 2(A), the female mold 24 supports the glass plate 12 from below. In this example, the female mold 24 is a press ring formed in a ring shape along the contour of the glass plate 12 so as to support the peripheral edge (end face or near the end face) of the glass plate 12. Note that the upper surface shape of the female mold 24 may support the entire circumference of the glass plate 12 or may support a part of the glass plate 12. Further, the upper surface shape of the female mold 24 can correspond to the curved shape of the glass plate 12 bent in the above-mentioned conveying direction or orthogonal direction.

[0027] The female mold 24 is movable up and down between a standby position below the conveying conveyor 20 and an upper press position. When the glass plate 12 is transferred from the conveying conveyor 20 at a predetermined raised position, the female mold 24 then rises from the predetermined raised position to a press position above the conveying conveyor 20 with the glass plate 12 placed thereon.

[0028] Above the conveying conveyor 20 in the press area, a male mold 30, which is a mold for molding, is disposed, and the glass plate 12 is sandwiched and pressed between the female mold 24 and the male mold 30. The male mold 30 has a lower surface formed in a shape corresponding to the entire surface of the glass plate 12 to be bent. In this example, the male mold 30 is a press mold formed convex downward. The lower surface shape of the male mold 30 can correspond to the curved shape of the glass plate 12 bent in the conveying direction and the orthogonal direction.

[0029] The female mold 24 and the male mold 30 are an example of a pair of molds constituting a main molding press device for press-molding the glass plate 12. The female mold 24 and the male mold 30 are arranged vertically with the conveying conveyor 20 interposed therebetween, and the upper surface shape of the female mold 24 and the lower surface shape of the male mold 30 match the predetermined shape of the glass molded product.

[0030] On the lower surface of the male mold 30, a number of air suction holes are formed. The glass plate 12 is sucked from the female mold 24 side to the male mold 30 side by air suction through these air suction holes and is sucked and held on the lower surface of the male mold 30. In this air suction, a high suction pressure is applied to lift the glass plate 12 against gravity so that it conforms to the lower surface of the male mold 30.

[0031] In the present embodiment, a mold cloth (not shown) is attached along the lower surface of the male mold 30 (that is, the surface on the side in contact with the glass plate 12). The mold cloth is a protective material for preventing the glass plate 12 from adhering to the male mold 30 and not being released after the air suction by the male mold 30 is released.

[0032] The mold cloth is a knitted fabric knitted from yarns (spun yarns) made of refractory fibers. Examples of the fibers forming the mold cloth include fibers made of metal, ceramic (glass fiber), heat-resistant resin (polyparaphenylene terephthalamide, polybenzoxazole (PBO), etc.). These may be used alone or in combination of two or more.

[0033] Since the mold cloth is knitted with yarns, there are fine irregularities on its surface. Therefore, when the glass plate 12 is heated to above the glass transition point and press-molded along the male mold 30, the irregularities on the surface of the mold cloth may be transferred to the surface of the glass plate 12. Therefore, in the present embodiment, a flattened mold cloth with reduced irregularities on the cross surface as described later is used.

[0034] When the press forming of the glass plate 12 by the female mold 24 and the male mold 30 is completed, the female mold 24 descends. At this time, as shown in FIG. 2(B), the male mold 30 sucks and holds the press-formed glass plate 12 by air suction from the air suction holes. In this embodiment, since suction is performed through the flattening mold cloth, even if a high suction pressure as described above is applied for suction and holding, the unevenness transferred to the glass surface is small, and the occurrence of perspective distortion of the glass molded product can be suppressed.

[0035] Subsequently, the press-formed glass 12 is cooled. In this embodiment, the manufacturing apparatus 10 includes a transfer shuttle 32 on which the glass plate 12 after press forming is placed, and the press-formed glass plate 12 is transferred from the press area to the cooling area by the transfer shuttle 32. The transfer shuttle 32 has a cooling mold 36 attached and fixed to a pedestal 34. The cooling mold 36 supports the glass plate 12 from below. In this example, the cooling mold 36 is a female ring formed in a ring shape along the contour of the glass plate 12 so as to support the peripheral portion (end face or near the end face) of the glass plate 12. Note that the upper surface shape of the cooling mold 36 may support the entire circumference of the glass plate 12 or may support a part of the glass plate 12. Further, the upper surface shape of the cooling mold 36 can correspond to the curved shape of the glass plate 12 that is bent and formed in the above-described transport direction and orthogonal direction.

[0036] The transfer shuttle 32 is capable of reciprocating between the press area and the cooling area on the rail 26. After the glass plate 12 is press formed by the female mold 24 and the male mold 30 and sucked and held on the lower surface of the male mold 30, and the female mold 24 descends to the above standby position, it moves directly below the male mold 30 in the press area.

[0037] When the transfer shuttle 32 moves to a position facing the male mold 30 and the suction and holding of the glass plate 12 by air suction of the male mold 30 is released, as shown in FIG. 2(C), the glass plate 12 is transferred from the lower surface of the male mold 30 onto the cooling mold 36 of the transfer shuttle 32.

[0038] When the glass plate 12 is transferred onto the cooling mold 36 of the transfer shuttle 32, the transfer shuttle 32 moves toward the cooling area, and the glass plate 12 is cooled in the cooling area.

[0039] In the cooling area, the glass plate 12 is cooled until its temperature becomes lower than the glass transition point. When producing unstrengthened glass such as that used for laminated glass, it is preferable to anneal the glass plate slowly. When producing strengthened glass, it is preferable to cool the glass plate by ejecting cooling air from the cooling device 38 to form a high compressive stress layer on the surface of the glass plate for strengthening. Examples of the cooling device include a blower. When the glass plate 12 is cooled, the deformation of the glass plate 12 stops. In FIG. 2, (D) shows the manufacturing apparatus 10 in this state.

[0040] The cooled glass plate 12 is separated from the cooling mold 36 by a separating means and temporarily supported. Thereafter, the transfer shuttle 32 retracts to the press area. After the transfer shuttle 32 retracts to the press area, the unloading shuttle 39 enters the cooling area, and the glass plate 12 temporarily supported by the separating means is transferred onto the mold of the unloading shuttle 39. When the glass plate 12 is transferred onto the mold of the unloading shuttle 39, thereafter, the unloading shuttle 39 is carried out to the inspection area.

[0041] The maximum value MAX of the perspective distortion when measured under the condition of using the distortion inspector LABSCAN manufactured by ISRA-VISION Co., Ltd. with Filter 4.5.0 and an attachment angle of 30 degrees is preferably 120 mdpt or less for the glass formed product manufactured by the manufacturing method of this embodiment. More specifically, the maximum value MAX of the perspective distortion of the glass molded product is obtained by imaging the glass molded product using the "LABSCAN" manufactured by ISRA-VISION Co., Ltd. with Filter 4.5.0 and an attachment angle of 30 degrees, and measuring the maximum value of the perspective distortion in the image. Note that the measurement of the perspective distortion using the distortion inspector LABSCAN is preferably performed with the glass products laminated.

[0042] When the maximum value MAX of such perspective distortion is 120 mdpt or less, the surface does not appear wavy, and the distortion is small even when looking at an object through the glass. The maximum value MAX of the perspective distortion is more preferably 110 mdpt or less, even more preferably 100 mdpt or less, and particularly preferably 90 mdpt or less. Since the smaller the maximum value MAX of the perspective distortion, the smaller the unevenness on the surface of the glass molded product, which is preferable, the lower limit value is not particularly limited.

[0043] <Method for manufacturing a flattening mold cloth> The above-mentioned flattening mold cloth used in the method for manufacturing a glass molded product of the present invention is manufactured by applying a pressure of 0.3 MPa or more to the plane of the mold cloth to reduce the unevenness (roughness) on the surface of the mold cloth.

[0044] Since the flattening mold cloth obtained by performing the above flattening method has small unevenness on the cross surface, a glass molded product with reduced perspective distortion can be obtained when a glass plate is bent and molded using the flattening mold cloth.

[0045] As the mold cloth used in this embodiment, a commercially available mold cloth may be used, or a used mold cloth that has been used several times may be used, or a mold cloth produced by a knitting machine may be used. Also, the materials described above can be used for the mold cloth.

[0046] In this embodiment, a pressure of 0.3 MPa or more is applied to the plane of the mold cloth. By applying a pressure of 0.3 MPa or more to the mold cloth for treatment, the unevenness on the surface of the cloth can be flattened. Such pressure is preferably 0.5 MPa or more, more preferably 0.6 MPa or more, further preferably 1.0 MPa or more, even more preferably 2.5 MPa or more, particularly preferably 3.5 MPa or more, and most preferably 4.5 MPa or more. Also, since the flattening effect is balanced even when the pressure is increased, from the perspective of cross protection, the upper limit of the pressure is preferably 30 MPa or less, more preferably 20 MPa or less, and further preferably 10 MPa or less. That is, the pressure applied to the mold cloth is preferably in the range of 0.3 to 30 MPa.

[0047] The method for applying pressure to the mold cloth is not particularly limited as long as the above pressure can be applied. For example, a method of roll-pressing the mold cloth using a roller press machine, a method of pressing the mold cloth between flat plates, a method of pinching using a roller press machine, a method of punching the mold cloth, etc. can be mentioned. Among them, it is preferable to perform either one of the roll-press treatment and the flat-plate press treatment, and from the perspective of production efficiency, the roll-press treatment that can be continuously processed is preferable.

[0048] In this embodiment, when applying pressure to the mold cloth, it is preferable to laminate a pressure-resistant auxiliary plate having a pressure resistance of 200 MPa or more on at least one of the opposing first surface and second surface of the mold cloth, and apply pressure through the pressure-resistant auxiliary plate. By applying pressure through the pressure-resistant auxiliary plate, the mold cloth can be uniformly pressurized and flattened more efficiently.

[0049] Examples of the pressure-resistant auxiliary plate include iron plates, steel plates, titanium plates, etc., and it is preferable to use at least one selected from the group consisting of these. Among them, from the perspective of pressure resistance, iron plates and steel plates are more preferable, and from the point of view of excellent rust resistance, it is even more preferable to use a steel plate.

[0050] The thickness of the pressure-resistant auxiliary plate is preferably in the range of 4 to 10 mm. When the thickness of the pressure-resistant auxiliary plate is 4 mm or more, deformation of the pressure-resistant auxiliary plate can be prevented, and when it is 10 mm or less, the working efficiency is improved. The thickness of the pressure-resistant auxiliary plate is more preferably 5 mm or more, even more preferably 6 mm or more, and more preferably 9 mm or less, even more preferably 8 mm or less.

[0051] The number of pressurization times and the pressurization time may be appropriately adjusted with the desired surface state as the target.

[0052] The planarized mold cloth produced by the manufacturing method of the present embodiment preferably has a maximum height difference Rz of the cross surface of 0.30 (1 / m) or less when measured by the following measurement method. [Measurement of maximum height difference Rz] As shown in FIG. 3, for a sample glass 41 formed into a 4000R spherical surface with a size of 50 cm × 50 cm, an iron plate 42 with a length of 50 cm, a width of 50 cm, and a thickness of 1 cm having a plurality of air suction holes around the outer peripheral portion and the in-plane central portion (20 cm × 20 cm) is installed in a vacuum generator 43 so that the inclination angle is 25°, and a small vacuum mold 40 is manufactured. A cloth is pasted on the iron plate 42, and a vinyl sheet (polyvinyl chloride (PVC)) with a thickness of 3 mm is covered thereon, and suction is performed with a vacuum generator 43 to obtain a laminate having a curved surface. Using "SCREENSCAN-Reflected Distortion" manufactured by ISRA VISION, which is a 3D measurement system capable of non-contact measurement of the curvature of the reflection surface, a reflected image of the vinyl sheet surface is obtained. The obtained reflected image is photographed with a camera to obtain a distribution image of 1 / R representing the strength of distortion. This distribution image is decomposed into 256 color difference gradations, and the 400 cm 2 (20 cm × 20 cm) region A of the central portion in the image is used to confirm the height difference of light and shade from the light and shade distribution, and the maximum value of the height difference of light and shade (maximum light and shade difference) is obtained as the maximum height difference Rz of the unevenness of the cross surface. Hereinafter, the method for evaluating the unevenness of the cross surface by this method is referred to as the "screen scan evaluation method".

[0053] More specifically, in the screen scan evaluation method, a laminate of a mold cloth and a vinyl sheet in a state of being sucked by the vacuum generating device 43 is set in a measurement MOLD "SCREENSCAN - Reflected Distortion" manufactured by ISRA VISION. A zebra image is projected onto the screen by a projector, and the reflected image is photographed by a camera installed above. When the projected reflected image is displaced from its original position, it represents "distortion". In this system, the value of the reciprocal 1 / R of the displaced distance is measured and converted into a distribution image so that the intensity of the distortion can be recognized. Then, the obtained distribution image is decomposed into 256 color difference gradations, and the height difference of light and shade is confirmed from the light and shade distribution in the area A of 400 cm 2 (20 cm × 20 cm), and the maximum value (maximum light and shade difference) of the height difference of light and shade is obtained.

[0054] As the vacuum generating device 43, a known vacuum generating device can be used, and examples include a vacuum cleaner, a vacuum pump, a suction machine, etc.

[0055] The suction pressure when sucking with the vacuum generating device 43 is not particularly limited as long as the vinyl sheet can be adhered to the cross surface, but it is preferable to perform vacuuming at a vacuum pressure of -50 kPa to -5 kPa. When the vacuum pressure is -5 kPa or less, the resin sheet can follow the unevenness on the surface of the cross material. The vacuum pressure is more preferably -10 kPa or less, further preferably -15 kPa or less, particularly preferably -25 kPa or less. Also, it is more preferably -45 kPa or more, further preferably -40 kPa or more, particularly preferably -35 kPa or more.

[0056] Since the vinyl sheet follows the surface shape of the mold cloth, the maximum height difference Rz measured by the screen scan evaluation method is substantially equal to the maximum height difference Rz of the cross surface. When the maximum height difference Rz of the cross surface is 0.30 (1 / m) or less, the surface unevenness is reduced. Therefore, the transfer of the unevenness to the glass surface during the bending forming of the glass can be reduced, and the surface roughness of the glass molded product can be reduced. The maximum height difference Rz is more preferably 0.26 (1 / m) or less, and even more preferably 0.24 (1 / m) or less. Since the roughness of the cross surface becomes smaller as the maximum height difference Rz becomes smaller, the lower limit is not particularly limited.

[0057] In addition, the flattened mold cross produced by the manufacturing method of the present embodiment preferably has an average roughness Ra of the cross surface of 80 μm or less when measured by the following measurement method. [Measurement of average roughness Ra] In the above [Measurement of maximum height difference Rz], without using the sample glass 41, the cross and the vinyl sheet are brought into close contact to obtain a flat laminate, and the average roughness Ra of the cross surface in the set region is measured with an optical microscope.

[0058] As the optical microscope, a commercially available device can be used. For example, the one-shot 3D measuring instrument "VR6000" manufactured by KEYENCE Corporation can be used to measure the average roughness Ra of the cross surface. In the one-shot 3D measuring instrument, when a striped light pattern is irradiated on the sample surface, the thickness and shape of the striped pattern change according to the shape of the material, and the change is detected to measure the surface average roughness Ra of the cross. Hereinafter, the method for evaluating the unevenness of the cross surface using "VR6000" manufactured by KEYENCE Corporation is referred to as the "pattern light projection evaluation method".

[0059] When the average roughness Ra of the cross surface is 80 μm or less, it can be evaluated that the surface of the cross material is flattened. The average roughness Ra of the cross material surface is more preferably 70 μm or less, even more preferably 60 μm or less, and particularly preferably 50 μm or less. Since the roughness of the cross surface becomes smaller as the average roughness Ra becomes smaller, the lower limit is not particularly limited.

[0060] By manufacturing a glass molded product using the flattened mold cross obtained in this way, the transfer of the unevenness of the cross surface to the glass plate is suppressed, so that the occurrence of perspective distortion can be suppressed, and it is possible to cope with glass molded products with more complicated shapes.

[0061] The glass-formed product obtained by the method of the present embodiment has a small surface roughness, so it has little perspective distortion and can reduce the perspective distortion in laminated glass, and thus is suitably used for laminated glass applications.

Examples

[0062] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto. In the following description, the same components are used. Also, unless otherwise specified, "parts" and "%" represent "parts by mass" and "mass%". Examples 1, 3, and 5 are comparative examples, and Examples 2, 4, 6 to 8 are examples.

[0063] The measurement methods used in each example are as follows.

[0064] (Maximum height difference Rz of the mold cross surface) The maximum height difference Rz of the mold cross surface was measured by the screen scan evaluation method. As shown in Figure 3, for a sample glass 41 formed into a 4000R spherical surface with a size of 50 cm × 50 cm, an iron plate 42 with a plurality of air suction holes around the outer peripheral part and the in-plane central part (20 cm × 20 cm) and having a length of 50 cm, a width of 50 cm, and a thickness of 1 cm was installed on a vacuum cleaner (vacuum generator 43) so that the inclination angle was 25°, and a small vacuum mold 40 was fabricated. A mold cross was pasted on the iron plate 42, and a 3-mm-thick vinyl sheet (polyvinyl chloride (PVC)) was covered thereon, and suction was performed with a vacuum cleaner at a pressure of about -35 kPa to obtain a laminate having a curved surface. It was set in a measurement mold "SCREENSCAN - Reflected Distortion" manufactured by ISRA VISION. A zebra image was projected onto the screen by a projector, and the reflected image was photographed by a camera installed above to obtain a distribution image of 1 / R representing the strength of distortion. The obtained distribution image was decomposed into 256 color difference gradations, and the height difference of light and shade was confirmed from the light and shade distribution in the 400 cm 2 (20 cm × 20 cm) region A, and the maximum value (maximum light and shade difference) of the height difference of light and shade was obtained.

[0065] (Average roughness Ra of the mold cloth surface) The average roughness Ra of the mold cloth surface was measured by the pattern light projection evaluation method. Using the small vacuum mold 40 with the configuration shown in Fig. 3, a flat laminate in which the cloth and the vinyl sheet were adhered without using the sample glass 41 was used to measure the average roughness Ra of the cloth surface with the Keyence Corporation one-shot 3D measuring instrument "VR6000".

[0066] (Maximum value MAX of the perspective distortion of the glass molded product) Using "LABSCAN" manufactured by ISRA-VISION, an image was obtained by imaging under the condition of Filter 4.5.0 and an attachment angle of 30 degrees, and the maximum value of the perspective distortion at the center of the image was measured.

[0067] (Test Example 1: Examples 1 to 4) (Example 1) Commercially available mold cloth A was used. The maximum height difference Rz of the surface of mold cloth A was 0.502 (1 / m). Using mold cloth A and the manufacturing apparatus shown in Fig. 1, a glass plate (soda lime glass) was heated to 640 to 660 °C and bent to obtain a spherical glass with a radius of curvature of 4000 mm.

[0068] (Example 2) The mold cloth A of Example 1 was installed on a roller press machine, a pressure-resistant auxiliary plate (SUS304, plate thickness 4 mm) was placed on the cloth, and a pressure of 0.6 MPa was applied from above the pressure-resistant auxiliary plate and the roller was reciprocated 3 times for pressing to obtain a flattened mold cloth. The maximum height difference Rz of the surface of the flattened mold cloth was 0.325 (1 / m). Using the obtained flattened mold cloth, a glass molded product was produced in the same manner as in Example 1.

[0069] (Example 3) Commercially available mold cloth B was used. The maximum height difference Rz of the surface of mold cloth B was 0.439 (1 / m). Using the mold cloth B, a glass molded article was produced in the same manner as in Example 1.

[0070] (Example 4) The mold cloth B of Example 3 was subjected to press treatment in the same manner as in Example 2 to obtain a flattened mold cloth. The maximum height difference Rz of the surface of the flattened mold cloth was 0.298 (1 / m). Using the obtained flattened mold cloth, a glass molded article was produced in the same manner as in Example 1.

[0071] The glass molded articles of Examples 1 to 4 were laminated to form a laminated glass, and the maximum value MAX of the perspective distortion was measured. The results are shown in Table 1 and FIGS. 4 to 5.

[0072]

Table 1

[0073] From Table 1 and FIGS. 4 to 5, when comparing Example 1 and Example 2, the flattened mold cloth produced in Example 2 had smaller irregularities on the cross surface than the mold cloth used in Example 1. When a glass molded article was produced using this flattened mold cloth, the irregularities on the surface of the glass molded article were reduced, and a glass molded article with a maximum value MAX of perspective distortion of 120 mdpt or less and reduced perspective distortion was obtained. Similarly, when comparing Example 3 and Example 4, Example 4 had reduced irregularities on the surface of the glass molded article compared to Example 3, and a glass molded article with reduced perspective distortion was obtained. Thus, it was found that the perspective distortion of the glass molded article can be reduced by flattening the mold cloth used.

[0074] <Test Example 2: Examples 5 to 8> (Example 5) A commercially available mold cloth A was used. The maximum height difference Rz of the surface of the mold cloth A was 0.502 (1 / m). Also, the average roughness Ra of the surface of the mold cloth A was 92.3 (μm). Using the mold cross A and the manufacturing apparatus shown in Fig. 1, a glass plate (soda lime glass) was heated to 640 - 660 °C and bent to obtain a spherical glass with a radius of curvature of 4000 mm. Note that Example 5 is the same as Example 1.

[0075] (Example 6) The mold cross A of Example 1 was installed in a cylinder press machine, a pressure - resistant auxiliary plate (SUS304, thickness 4 mm) was placed on the cross, and a pressure of 2.5 MPa was applied from above the pressure - resistant auxiliary plate and pressed to obtain a flattened mold cross. The maximum height difference Rz on the surface of the flattened mold cross was 0.286 (1 / m), and the average roughness Ra was 72.6 (μm). Using the obtained flattened mold cross, a glass molded product was produced in the same manner as in Example 5.

[0076] (Example 7) It was carried out in the same manner as in Example 6 except that a pressure of 4.75 MPa was applied and pressed. The maximum height difference Rz on the surface of the flattened mold cross produced in Example 7 was 0.243 (1 / m), and the average roughness Ra was 69.0 (μm). Using the obtained flattened mold cross, a glass molded product was produced in the same manner as in Example 5.

[0077] (Example 8) It was carried out in the same manner as in Example 6 except that a pressure of 7 MPa was applied and pressed. The maximum height difference Rz on the surface of the flattened mold cross produced in Example 8 was 0.231 (1 / m), and the average roughness Ra was 58.8 (μm). Using the obtained flattened mold cross, a glass molded product was produced in the same manner as in Example 5.

[0078] The glass molded products of Examples 5 - 8 were laminated to form a laminated glass, and the maximum value MAX of the perspective distortion was measured. The results are shown in Table 2 and Figs. 6 - 7.

[0079]

Table 2

[0080] From Table 2 and FIGS. 6 to 7, in Examples 6 to 8, the unevenness of the surface of the obtained flattened mold cloth was smaller than that of the mold cloth used in Example 5. The glass molded product produced using this flattened mold cloth had reduced surface unevenness and the maximum value MAX of perspective distortion also became smaller. In addition, since there was no significant change in the maximum value MAX of perspective distortion even when the press pressure was increased, it is considered that the reduction of surface roughness reached equilibrium.

[0081] As described above, the following matters are disclosed in this specification. <1>A method for manufacturing a glass molded product, comprising attaching a flattened mold cloth with reduced unevenness on the surface of a mold cloth to a molding die, heating a glass plate to a temperature equal to or higher than the glass transition point, and press-molding the softened glass plate along the molding die through the flattened mold cloth into a predetermined shape. <2>The method for manufacturing a glass molded product according to <1>, wherein a pressure of 0.3 MPa or more is applied to the plane of the mold cloth to obtain the flattened mold cloth. <3>The method for manufacturing a glass molded product according to <1> or <2>, wherein the maximum value of perspective distortion measured under the conditions of using a distortion inspector LABSCAN manufactured by ISRA-VISION, Filter 4.5.0, and an attachment angle of 30 degrees for the obtained glass molded product is 120 mdpt or less. <4>The method for manufacturing a glass molded product according to any one of <1> to <3>, which is a method for manufacturing a glass molded product for laminated glass. <5>A method for manufacturing a flattened mold cloth, comprising applying a pressure of 0.3 MPa or more to the plane of the mold cloth to reduce the unevenness on the surface of the mold cloth. <6>The method for manufacturing a flattened mold cloth according to <5>, wherein a pressure-resistant auxiliary plate having a pressure resistance of 200 MPa or more is laminated on at least one of the opposing first surface and second surface of the mold cloth, and the pressure is applied through the pressure-resistant auxiliary plate. <7>The method for manufacturing the planarized mold cloth according to <6>, wherein the pressure-resistant auxiliary plate is at least one metal plate selected from the group consisting of an iron plate, a steel plate, and a titanium plate. <8>The method for manufacturing the planarized mold cloth according to any one of <5> to <7>, wherein any one of a roll press treatment and a flat plate press treatment is performed on the mold cloth.

Explanation of reference numerals

[0082] 10 Manufacturing apparatus 12 Glass plate 20 Conveyor 24 Female mold 26 Rail 28 Controller 30 Male mold 32 Transfer shuttle 34 Pedestal 36 Cooling mold 38 Cooling device 39 Transfer shuttle 40 Vacuum mold 41 Sample glass 42 Iron plate 43 Vacuum generator

Claims

1. A flat mold cloth with reduced surface irregularities of the mold cloth is attached to a molding die, a glass plate is heated to a temperature equal to or higher than the glass transition point, and the softened glass plate is pressed into a predetermined shape along the molding die through the flat mold cloth. A method for manufacturing a glass molded product.

2. The method for manufacturing a glass molded product according to claim 1, wherein a pressure of 0.3 MPa or more is applied to the plane of the mold cloth to obtain the flat mold cloth.

3. When measuring the obtained glass molded product using a strain inspection device LABS CAN manufactured by ISRA-VISION with Filter 4.5.0 under the condition that the mounting angle is 30 degrees, the maximum value of the perspective distortion is 120 mdp t or less. The method for manufacturing a glass molded product according to claim 1 or 2.

4. The method for manufacturing a glass molded product according to claim 1 or 2, which is a method for manufacturing a glass molded product for laminated glass.

5. A method for manufacturing a flat mold cloth, wherein a pressure of 0.3 MPa or more is applied to the plane of the mold cloth to reduce the surface irregularities of the mold cloth.

6. A pressure-resistant auxiliary plate having a pressure resistance of 200 MPa or more is laminated on at least one of the opposing first and second surfaces of the mold cloth, and pressure is applied through the pressure-resistant auxiliary plate. The method for manufacturing a flat mold cloth according to claim 5.

7. The method for manufacturing a flat mold cloth according to claim 6, wherein the pressure-resistant auxiliary plate is at least one metal plate selected from the group consisting of an iron plate, a steel plate, and a titanium plate.

8. The method for manufacturing a flat mold cloth according to any one of claims 5 to 7, wherein any one of a roll press treatment and a flat plate press treatment is performed on the mold cloth.

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