JP2014062043A - Plate glass blank and manufacturing method of the same, and manufacturing method of cover glass plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a cover glass plate, which allows easily manufacturing of a cover glass plate having high-precision surface shapes on its both sides, and to provide a plate glass blank suitable for the manufacturing method, and a manufacturing method of the plate glass blank.SOLUTION: In a drop step (A), a constant amount of molten glass 3 is dropped to a lower mold 1 having a concavity part 1a. In a press step (C), the molten glass 3 on the lower mold 1 is pressed with an upper mold 2 having a concavity part 2a for molding to fill the concavity part 2a of the upper mold 2 with the molten glass 3 for forming a first plane s1, and to fill the concavity part 1a of the lower mold 1 with the molten glass 3 to form a second plane S2 having concavity and convex parts. In processing steps from (D) to (G), surface-grinding or -polishing is performed to flatten the second plane S2 to produce a cover glass plate 8.

Description

  The present invention relates to plate glass blanks, a method for manufacturing the same, and a method for manufacturing a cover glass plate. More specifically, for example, the present invention relates to a plate glass blank used for a cover glass plate provided on an image display surface of a smartphone, a manufacturing method thereof, and a cover glass plate manufacturing method.

  A digital device having an image display function (for example, a mobile phone, a smartphone, a mobile computer, etc.) is usually provided with a cover glass plate for protecting the image display surface. The cover glass plate is manufactured by cutting a large area plate glass formed into a flat plate shape into a predetermined size. For this reason, the outer frame processing is required after cutting the plate glass. That is, it is necessary to perform outline frame processing that smoothly chamfers or rounds the boundaries of the side surfaces that form four corners and four sides of a rectangular plate glass (see, for example, Patent Document 1). Moreover, although the need to change the specification of the surface of the cover glass plate from a flat surface to a curved surface has been increasing in recent years, post-processing is required to make the surface of the plate glass formed into a flat plate into a curved surface.

JP 2009-280452 A

  If high-precision molding transfer is performed on molten glass with a mold, the outer frame processing of the cover glass plate and the post-processing of the cover glass plate surface become unnecessary. However, the back surface of the molding surface needs to be polished. In order to ensure the accuracy of the molding surface, it is necessary to increase the molding thickness as much as possible. Therefore, the polishing cost for the back surface increases, and as a result, the processing cost increases.

  The present invention has been made in view of such a situation, and an object of the present invention is to produce a cover glass plate that can easily produce a cover glass plate having a highly accurate surface shape on both sides. An object of the present invention is to provide a sheet glass blank suitable for its production and a method for producing a sheet glass blank.

  In order to achieve the above object, the sheet glass blank of the first invention is a sheet glass blank for a cover glass sheet, and the back surface of the molding surface formed by the mold is subjected to surface grinding or surface polishing. It is a surface and has a recessed part and a convex part in the to-be-processed surface, It is characterized by the above-mentioned.

  The glass sheet blank of the second invention is characterized in that, in the first invention, the convex portion is provided on the outermost periphery of the surface to be processed.

  The glass sheet blank of the third invention is characterized in that, in the second invention, an area of the convex portion occupying the work surface is 1/4 or more of the whole work surface.

  The glass sheet blank of the fourth invention is characterized in that, in any one of the first to third inventions, the shape of the concave portion is a circular shape, a square shape, a honeycomb shape or a mesh shape.

  In the sheet glass blanks of the fifth invention according to any one of the first to fourth inventions, an area of the convex portion occupying the processing surface is 1/2 of an area of the concave portion occupying the processing surface. It is characterized by the following.

  In the glass glass blanks of the sixth invention, in any one of the first to fifth inventions, the side surface of the recess has a taper shape of 3 ° or more with respect to the normal line of the bottom surface of the recess. Features.

  The manufacturing method of the sheet glass blanks of 7th invention is a manufacturing method of the sheet glass blanks for cover glass plates which concerns on any one invention of the said 1st-6th, Comprising: A fixed amount is provided to the lower metal mold | die which has a recessed part. A dropping step of dropping molten glass, and pressing the molten glass on the lower mold with an upper mold having a molding recess, the molten glass is filled into the recess of the upper mold and the first surface is And a pressing step of forming a second surface having a concave portion and a convex portion by filling the concave portion of the lower mold with molten glass.

  According to an eighth aspect of the present invention, there is provided a cover glass plate manufacturing method comprising: a dropping step of dropping a certain amount of molten glass into a lower mold having a recess; and a molten glass on the lower mold with an upper mold having a molding recess. To form a first surface by filling molten glass in the concave portion of the upper mold, and forming a second surface having concave and convex portions by filling the molten glass in the concave portion of the lower mold. And a pressing step for performing flattening by subjecting the second surface to surface grinding or surface polishing.

  According to a ninth aspect of the present invention, in the eighth aspect of the invention, the convex portion is provided on the outermost periphery of the second surface.

  The method for producing a cover glass plate according to a tenth aspect of the invention is characterized in that, in the ninth aspect, the area of the convex portion occupying the second surface is ¼ or more of the entire surface to be processed. .

  According to an eleventh aspect of the present invention, there is provided a cover glass plate manufacturing method according to any one of the eighth to tenth aspects, wherein the concave portion of the second surface has a circular shape, a square shape, a honeycomb shape, or a mesh shape. It is characterized by.

  The method for producing a cover glass plate according to a twelfth aspect of the present invention is the method according to any one of the eighth to eleventh aspects, wherein the area of the convex portion occupying the second surface is the area of the concave portion occupying the second surface. Or less than 1/2.

  The method for producing a cover glass plate according to a thirteenth aspect of the present invention is the method of any one of the eighth to twelfth aspects, wherein the side surface of the concave portion of the second surface is 3 ° or more with respect to the normal line of the bottom surface of the concave portion. It is characterized by having a tapered shape.

  If surface grinding or surface polishing is performed on the back surface of the molding surface formed by a mold, a highly accurate surface shape can be obtained on both surfaces. However, in order to ensure the accuracy of the molding surface, it is necessary to secure as much molding thickness as possible. As the molding thickness increases, the processing load of grinding or polishing increases. If the surface to be processed is a surface having a concave portion and a convex portion, the processing load of grinding or polishing is reduced, and the dressing effect of the polishing grindstone is also obtained by the unevenness. Therefore, if flat glass blanks having concave and convex portions on the back side of the molding surface are used, flattening at a predetermined position can be easily performed by surface grinding or surface polishing, so that processing time can be reduced and processing cost can be reduced. Thus, a cover glass plate having a highly accurate surface shape on both sides can be easily manufactured.

  If the convex part is arranged on the outermost periphery of the surface having the concave part and the convex part, the central part becomes relatively thin, the amount of glass shrinkage is reduced, the solidification of the glass in the peripheral part is alleviated, and the warpage of the plate glass blanks is reduced. Therefore, the transfer accuracy of the molding surface can be easily improved. And if the area of the convex part which occupies the surface which has a concave part and a convex part is 1/4 or more of the whole, the effect will become still larger.

  Although the degree of warpage varies depending on the thickness and size of the plate glass blanks, if the concave portion is reinforced by making it into a circular shape, square shape, honeycomb shape or mesh shape, the warpage of the plate glass blanks can be effectively reduced. Can do. If the area of the convex part occupying the surface having the concave part and the convex part is 1/2 or less of the area of the concave part, it is possible to effectively achieve both surface accuracy and workability. Further, if the side surface of the concave portion has a draft taper shape of 3 ° or more with respect to the normal line of the bottom surface of the concave portion, the releasability can be easily improved.

The manufacturing process figure which shows 1st Embodiment of the manufacturing method of a cover glass plate. The manufacturing process figure which shows 2nd Embodiment of the manufacturing method of a cover glass plate. The bottom view which shows the specific example of plate glass blanks.

  Hereinafter, the plate glass blanks and cover glass plate which implemented this invention, and those manufacturing methods are demonstrated, referring drawings. In addition, the same code | symbol is mutually attached | subjected to a mutually the same part of specific examples etc., and duplication description is abbreviate | omitted suitably.

  In FIG. 1, 1st Embodiment of the manufacturing method of a cover glass plate is shown. This manufacturing method is shown in the molding step shown in the cross-sectional views of FIGS. 1A to 1C, the cross-sectional views of FIGS. 1D and 1E, and the bottom views of FIGS. 1F and 1G. And a processing step. In the forming step including the dropping step (A), the moving step (B), and the pressing step (C), the plate glass blanks 7 are formed by the direct pressing method, and in the processing steps (D) to (G), as a finished product The cover glass plate 8 is formed. The cover glass plate 8 is used, for example, to cover an image display surface of a digital device (for example, a mobile phone, a smartphone, a mobile computer, etc.) having an image display function.

  First, a fixed amount of molten glass 3 is dropped into the lower mold 1 having the recesses 1a in the dropping step (A). That is, the molten glass 3 obtained by melting in the melting furnace is poured out from the platinum nozzle 6 and cut by the blade 5, whereby a certain amount of the molten glass 3 is dropped onto the lower mold 1. In order to prevent the molten glass 3 from being rapidly cooled by the lower mold 1, the lower mold 1 is heated by the heater 4. Therefore, the molten glass 3 on the lower mold 1 is held and controlled in a state where a predetermined viscosity is maintained.

  In the next moving step (B), the lower mold 1 is moved to a predetermined position below the upper mold 2. Similarly to the lower mold 1, the upper mold 2 is heated by the heater 4 so that the molten glass 3 is not rapidly cooled by the upper mold 2. Accordingly, the molten glass 3 on the lower mold 1 is held and controlled in a state where a predetermined viscosity is maintained even when it contacts the upper mold 2.

  After waiting the lower mold 1 for a predetermined time in the moving step (B), the process proceeds to the pressing step (C). In the pressing step (C), the upper mold 2 having the molding recess 2 a is lowered, and the molten glass 3 on the lower mold 1 is pressed by the upper mold 2, whereby the molten glass 3 is converted into the upper mold. The sheet glass blanks (preliminary molded body) 7 having a protruding portion 7b is filled in the molding recess 2a of No. 2 and further protrudes from the recess 2a between the upper mold 2 and the lower mold 1 and into the recess 1a. Form. In this manner, the molding surface is transferred to the sheet glass blanks 7 up to the outer surface Sb (FIG. 1B) of the upper mold 2 by molding between the upper mold 2 and the lower mold 1. be able to.

  When the plate glass blanks 7 obtained in the pressing step (C) are released from the mold, the process proceeds to the processing steps (D) to (G). As shown in FIGS. 1 (D) and 1 (F), the plate glass blanks 7 are composed of a molded body 7a and a protruding portion 7b (shaded portion in FIG. 1 (D)). A first surface S1 (molding surface) is formed by the molten glass 3 filled in the concave portion 2a for molding of the upper mold 2, and the rectangular shape is formed by the molten glass 3 filled in the concave portion 1a of the lower mold 1. A second surface S2 (surface to be processed) having a concave portion T1 and a square-shaped convex portion T2 surrounding the periphery thereof is formed. By removing at least one of the surface grinding and the surface polishing in the processing step, the protruding portion 7b, which is an unnecessary portion, is completely removed from the sheet glass blanks 7 (that is, until the outer peripheral surface of the molded body 7a is reached). .), Only the molded body 7a remains. That is, as shown in FIGS. 1E and 1G, a cover glass plate 8 as a finished product is formed.

  Surface grinding / planar polishing for the protruding portion 7b is performed on the second surface S2. At this time, a plurality of plate glass blanks 7 are collectively ground with a polishing pad or a polishing grindstone, and then finely ground with a polishing pad. This is done by surface polishing. Switching from surface grinding to surface polishing can be easily performed by changing the polishing liquid used for the second surface S2. In addition, when it is not necessary to make the lower surface 8c of the cover glass plate 8 into a mirror surface, you may make it obtain desired smoothness by forming a film | membrane in the lower surface 8c. Examples of the coating include a scattering prevention film and a resin coat.

  Since the outer frame shape of the cover glass plate 8 is determined by the concave portion 2a of the upper mold 2, if all the protruding portions 7b are removed from the plate glass blanks 7 by surface grinding or surface polishing in the processing step, the outer frame processing of the cover glass plate 8 is performed. There is no need to perform (for example, four-frame outline processing corresponding to the rectangle of the image display surface). Further, since the surface shape of the cover glass plate 8 is determined by the recess 2a of the upper mold 2, there is no need to perform post-processing on the surface of the cover glass plate. Therefore, according to the configuration of this embodiment, the thin cover glass plate 8 having any outer frame shape and surface shape can be obtained without performing the outer frame processing of the cover glass plate 8 and the post-processing of the cover glass plate surface. It can be easily manufactured.

  Since the positional relationship between the concave portion 1a of the lower mold 1 and the concave portion 2a for molding of the upper mold 2 can be adjusted with high accuracy, surface grinding or surface polishing of the protruding portion 7b in the processing step is performed on the second surface S2. When performed on (FIGS. 1D and 1F), surface grinding or surface polishing in the processing step can be performed with high accuracy. Therefore, according to the configuration of this embodiment, it is possible to easily remove only the protruding portion 7b from the plate glass blanks 7.

  When all the protruding portions 7b are removed from the plate glass blanks 7, a portion (that is, a molded body main body 7a) consisting only of the molten glass 3 filled in the concave portion 2a for molding of the upper mold 2 remains, which is a finished product. The cover glass plate 8 is formed. The lower surface 8c of the cover glass plate 8 is formed by surface grinding or surface polishing (FIG. 1 (E)), but the other surfaces 8a and 8b are formed by the recessed portions 2a of the upper mold 2, so that the recessed portions 2a are high. The accuracy can be reflected in the surface accuracy of the upper surface 8a and the side surface 8b of the cover glass plate 8. For example, it is possible to mold the boundary between the upper surface 8a and the side surface 8b into a smooth curved surface. Therefore, according to the configuration of this embodiment, it is possible to control and improve the accuracy of the surfaces 8a and 8b other than the lower surface 8c of the cover glass plate 8. This configuration is particularly effective in forming highly viscous glass that is difficult to control.

  The shape of the upper surface 8 a of the cover glass plate 8 is determined by the shape of the recess 2 a filled with the molten glass 3. Therefore, as shown in FIG. 1B, if the surface shape of a part (or the whole) of the recess 2a is a curved surface, the surface shape of a part (or the whole) of the upper surface 8a of the cover glass plate 8 is changed. Can be curved. Therefore, according to the configuration of this embodiment, it is possible to easily meet the needs for changing the specification of the surface of the cover glass plate 8 from a flat surface to a curved surface.

  The plate glass blanks 7 are not limited to having a flat surface on the molded body main body 7a, but may have a concave surface or a convex surface on the molded body main body 7a. If the variation of the shape of the concave portion 2a of the upper mold 2 is increased, the cover glass plate 8 having various shapes (arbitrary curved surface; convex surface, concave surface; spherical surface, cylindrical surface, etc.) can be produced. When the molded body 7a has a convex surface, the thickness on the side surface is too thin and it is difficult to process the four-sided outer frame corresponding to the rectangle of the image display surface. However, according to the configuration of this embodiment, the side surface Even if the thickness is too thin, it is possible to easily remove all of the protruding portion 7b from the plate glass blanks 7 by surface grinding or surface polishing.

  Setting the upper surface 8a and the side surface 8b to be mirror surfaces acts in a direction to reduce the releasability with respect to the upper mold 2, but the presence of the protruding portion 7b improves the releasability with respect to the upper mold 2. For this reason, it becomes possible to stably maintain the state in which the plate glass blanks 7 are placed on the lower mold 1 after the pressing step (C), and the plate glass blanks 7 can be easily picked up from the lower mold 1. Further, when the outer surface Sb (FIG. 1 (B)) of the upper mold 2 that comes into contact with the protruding portion 7b in the pressing step (C) is made rougher than the inner surface Sa (FIG. 1 (B)) of the recess 2a, molding is performed. Separation of the rough surface portion occurs due to the glass shrinking action after completion and the release of the contact surface of the plate glass blanks is promoted, so that the release property of the plate glass blanks 7 can be effectively improved.

  By subjecting the second surface S2 that is the back surface of the first surface S1 formed by the upper mold 2 to surface grinding or surface polishing, both the first surface S1 and the second surface S2 can have a highly accurate surface shape. . However, in order to ensure the accuracy of the first surface S1, it is necessary to secure as much molding thickness as possible, and the processing load for grinding or polishing increases as the molding thickness increases. If the second surface S2 has the concave portion T1 and the convex portion T2 as in this embodiment, the processing load of grinding or polishing is reduced, and the dressing effect of the grinding stone (the clogging of the grinding stone) is caused by the irregularities. Can also be obtained. Therefore, if the plate glass blanks 7 (FIGS. 1D and 1F) having the concave portion T1 and the convex portion T2 are used on the second surface S2, the second surface S2 is planarized at a predetermined position by surface grinding or surface polishing. Therefore, the processing time can be shortened and the processing cost can be reduced, and the cover glass plate 8 having a highly accurate surface shape on both the first surface S1 and the second surface S2 can be easily manufactured. It becomes.

  If the convex portion T2 is arranged on the outermost periphery of the second surface S2 as in this embodiment, the central portion is relatively thin and the glass shrinkage is reduced, and the solidification of the glass in the peripheral portion is alleviated. Since the warpage of the plate glass blanks 7 is reduced, the transfer accuracy of the first surface S1 can be easily improved. And if the area of convex part T2 which occupies 2nd surface S2 is 1/4 or more of the whole, the effect will become still larger.

  Since the mold temperature is lower than the dropped molten glass, the glass after dropping starts to solidify. Since the peripheral portion of the glass is easily solidified, if the convex portion T2 is not provided on the outermost periphery, when the upper die is pressed, the glass does not spread to the peripheral portion and the transfer accuracy is likely to deteriorate. In the pressed molded product, the glass temperature is higher in the central portion than in the peripheral portion. Since the shrinkage rate of the glass at the central part is higher than that at the peripheral part due to the high temperature, the shrinkage amount at the central part of the glass becomes large after the press (after the pressing of the upper mold), and the gold against the plate glass blanks 7 Insufficient transfer or warping of the mold. In the present embodiment, by providing the convex portion T2 on the outermost periphery, the thickness of the outermost periphery is increased and the heat capacity is increased, so that the outer periphery is difficult to cool, and the glass easily spreads to the periphery during pressing. In addition, by making the central portion relatively thin with respect to the outer peripheral portion, it is possible to balance the central portion having a large shrinkage rate and the peripheral portion having a small shrinkage rate, and the entire flat glass blank 7 has a uniform shrinkage amount. Transfer performance is improved.

  If the area of the convex portion T2 occupying the second surface S2 is ½ or less of the area of the concave portion T1, it is possible to effectively achieve both surface accuracy and workability. Further, if the side surface of the concave portion T1 has a draft taper shape of 3 ° or more with respect to the normal line of the bottom surface of the concave portion T1 (cross-hatched portion in FIG. 1F) (in FIG. 1D) Of the angle θ ≧ 3 °), the releasability can be easily improved.

  FIG. 2 shows a second embodiment of a method for manufacturing a cover glass plate. This manufacturing method is shown in the molding step shown in the cross-sectional views of FIGS. 2A to 2C, the cross-sectional views of FIGS. 2D and 2E, and the bottom views of FIGS. 2F and 2G. And a processing step. In the forming step including the dropping step (A), the moving step (B), and the pressing step (C), the plate glass blanks 7 are formed by the direct pressing method, and in the processing steps (D) to (G), as a finished product The cover glass plate 8 is formed. The cover glass plate 8 is used, for example, to cover an image display surface of a digital device (for example, a mobile phone, a smartphone, a mobile computer, etc.) having an image display function.

  First, a fixed amount of molten glass 3 is dropped into the lower mold 1 having the recesses 1a in the dropping step (A). That is, the molten glass 3 obtained by melting in the melting furnace is poured out from the platinum nozzle 6 and cut by the blade 5, whereby a certain amount of the molten glass 3 is dropped onto the lower mold 1. In order to prevent the molten glass 3 from being rapidly cooled by the lower mold 1, the lower mold 1 is heated by the heater 4. Therefore, the molten glass 3 on the lower mold 1 is held and controlled in a state where a predetermined viscosity is maintained.

  In the next moving step (B), the lower mold 1 is moved to a predetermined position below the upper mold 2. Similarly to the lower mold 1, the upper mold 2 is heated by the heater 4 so that the molten glass 3 is not rapidly cooled by the upper mold 2. Accordingly, the molten glass 3 on the lower mold 1 is held and controlled in a state where a predetermined viscosity is maintained even when it contacts the upper mold 2.

  After waiting the lower mold 1 for a predetermined time in the moving step (B), the process proceeds to the pressing step (C). In the pressing step (C), the upper mold 2 having the molding recess 2 a is lowered, and the molten glass 3 on the lower mold 1 is pressed by the upper mold 2, whereby the molten glass 3 is converted into the upper mold. The sheet glass blanks (preliminary molded body) 7 having a protruding portion 7b is filled in the molding recess 2a of No. 2 and further protrudes from the recess 2a between the upper mold 2 and the lower mold 1 and into the recess 1a. Form. In this manner, the molding surface is transferred to the sheet glass blanks 7 up to the outer surface Sb (FIG. 2B) of the upper mold 2 by molding by protruding between the upper mold 2 and the lower mold 1. be able to.

  When the plate glass blanks 7 obtained in the pressing step (C) are released from the mold, the process proceeds to the processing steps (D) to (G). As shown in FIGS. 2D and 2F, the plate glass blanks 7 are composed of a molded body 7a and a protruding portion 7b (shaded portion in FIG. 2D). A first surface S1 (molding surface) is formed of the molten glass 3 filled in the molding recess 2a of the upper mold 2, and a plurality of molten glass 3 filled in the recess 1a of the lower mold 1 A second surface S2 (surface to be processed) having a circular concave portion T1 and a rectangular convex portion T2 formed so as to protrude relative to the circular concave portion T1 is formed. By removing at least one of the surface grinding and the surface polishing in the processing step, the protruding portion 7b, which is an unnecessary portion, is completely removed from the sheet glass blanks 7 (that is, until the outer peripheral surface of the molded body 7a is reached). .), Only the molded body 7a remains. That is, as shown in FIGS. 2E and 2G, a cover glass plate 8 as a finished product is formed.

  Surface grinding / planar polishing for the protruding portion 7b is performed on the second surface S2. At this time, a plurality of plate glass blanks 7 are collectively ground with a polishing pad or a polishing grindstone, and then finely ground with a polishing pad. This is done by surface polishing. Switching from surface grinding to surface polishing can be easily performed by changing the polishing liquid used for the second surface S2. In addition, when it is not necessary to make the lower surface 8c of the cover glass plate 8 into a mirror surface, you may make it obtain desired smoothness by forming a film | membrane in the lower surface 8c.

  Since the outer frame shape of the cover glass plate 8 is determined by the concave portion 2a of the upper mold 2, if all the protruding portions 7b are removed from the plate glass blanks 7 by surface grinding or surface polishing in the processing step, the outer frame processing of the cover glass plate 8 is performed. There is no need to perform (for example, four-frame outline processing corresponding to the rectangle of the image display surface). Further, since the surface shape of the cover glass plate 8 is determined by the recess 2a of the upper mold 2, there is no need to perform post-processing on the surface of the cover glass plate. Therefore, according to the configuration of this embodiment, the thin cover glass plate 8 having any outer frame shape and surface shape can be obtained without performing the outer frame processing of the cover glass plate 8 and the post-processing of the cover glass plate surface. It can be easily manufactured.

  Since the positional relationship between the concave portion 1a of the lower die 1 and the concave portion 2a for molding the upper die 2 can be adjusted with high accuracy, surface grinding or surface polishing of the protruding portion 7b in the processing step is performed in the pressing step. When performed on the two surfaces S2 (FIGS. 2D and 2F), surface grinding or surface polishing in the processing step can be performed with high accuracy. Therefore, according to the configuration of this embodiment, it is possible to easily remove only the protruding portion 7b from the plate glass blanks 7.

  When all the protruding portions 7b are removed from the plate glass blanks 7, a portion (that is, a molded body main body 7a) consisting only of the molten glass 3 filled in the concave portion 2a for molding of the upper mold 2 remains, which is a finished product. The cover glass plate 8 is formed. The lower surface 8c of the cover glass plate 8 is formed by surface grinding or surface polishing (FIG. 2 (E)), but the other surfaces 8a and 8b are formed by the recessed portion 2a of the upper mold 2, so that the recessed portion 2a is high. The accuracy can be reflected in the surface accuracy of the upper surface 8a and the side surface 8b of the cover glass plate 8. For example, it is possible to mold the boundary between the upper surface 8a and the side surface 8b into a smooth curved surface. Therefore, according to the configuration of this embodiment, it is possible to control and improve the accuracy of the surfaces 8a and 8b other than the lower surface 8c of the cover glass plate 8. This configuration is particularly effective in forming highly viscous glass that is difficult to control.

  The shape of the upper surface 8 a of the cover glass plate 8 is determined by the shape of the recess 2 a filled with the molten glass 3. Therefore, as shown in FIG. 2B, if the surface shape of a part (or the whole) of the recess 2a is a curved surface, the surface shape of a part (or the whole) of the upper surface 8a of the cover glass plate 8 is changed. Can be curved. Therefore, according to the configuration of this embodiment, it is possible to easily meet the needs for changing the specification of the surface of the cover glass plate 8 from a flat surface to a curved surface.

  The plate glass blanks 7 are not limited to having a flat surface on the molded body main body 7a, but may have a concave surface or a convex surface on the molded body main body 7a. If the variation of the shape of the concave portion 2a of the upper mold 2 is increased, the cover glass plate 8 having various shapes (arbitrary curved surface; convex surface, concave surface; spherical surface, cylindrical surface, etc.) can be produced. When the molded body 7a has a convex surface, the thickness on the side surface is too thin and it is difficult to process the four-sided outer frame corresponding to the rectangle of the image display surface. However, according to the configuration of this embodiment, the side surface Even if the thickness is too thin, it is possible to easily remove all of the protruding portion 7b from the plate glass blanks 7 by surface grinding or surface polishing.

  Setting the upper surface 8a and the side surface 8b to be mirror surfaces acts in a direction to reduce the releasability with respect to the upper mold 2, but the presence of the protruding portion 7b improves the releasability with respect to the upper mold 2. For this reason, it becomes possible to stably maintain the state in which the plate glass blanks 7 are placed on the lower mold 1 after the pressing step (C), and the plate glass blanks 7 can be easily picked up from the lower mold 1. Further, when the outer surface Sb (FIG. 2 (B)) of the upper mold 2 that comes into contact with the protruding portion 7b in the pressing step (C) is made rougher than the inner surface Sa (FIG. 2 (B)) of the recess 2a, molding is performed. Separation of the rough surface portion occurs due to the glass shrinking action after completion and the release of the contact surface of the plate glass blanks is promoted, so that the release property of the plate glass blanks 7 can be effectively improved.

  By subjecting the second surface S2 that is the back surface of the first surface S1 formed by the upper mold 2 to surface grinding or surface polishing, both the first surface S1 and the second surface S2 can have a highly accurate surface shape. . However, in order to ensure the accuracy of the first surface S1, it is necessary to secure as much molding thickness as possible, and the processing load for grinding or polishing increases as the molding thickness increases. If the second surface S2 has the concave portion T1 and the convex portion T2 as in this embodiment, the processing load of grinding or polishing is reduced, and the dressing effect of the grinding stone (the clogging of the grinding stone) is caused by the irregularities. Can also be obtained. Therefore, if the plate glass blanks 7 (FIGS. 2D and 2F) having the concave portion T1 and the convex portion T2 are used on the second surface S2, planarization at a predetermined position of the second surface S2 by surface grinding or surface polishing. Therefore, the processing time can be shortened and the processing cost can be reduced, and the cover glass plate 8 having a highly accurate surface shape on both the first surface S1 and the second surface S2 can be easily manufactured. It becomes.

  If the convex portion T2 is arranged on the outermost periphery of the second surface S2 as in this embodiment, the central portion is relatively thin and the glass shrinkage is reduced, and the solidification of the glass in the peripheral portion is alleviated. Since the warpage of the plate glass blanks 7 is reduced, the transfer accuracy of the first surface S1 can be easily improved. And if the area of convex part T2 which occupies 2nd surface S2 is 1/4 or more of the whole, the effect will become still larger. Although the degree of warpage varies depending on the thickness and size of the plate glass blanks 7, if reinforcing by arranging a plurality of circular recesses T1 (one in some cases) as in this embodiment, the plate glass blanks 7 Warpage can be effectively reduced.

  The shape of the recess T1 is not limited to a circular shape, and may be a shape that can be easily processed such as a square shape, a honeycomb shape, or a mesh shape. FIG. 3 shows another specific example of the plate glass blanks 7. In the plate glass blank 7 shown in FIG. 3A, the shape of the recess T1 on the second surface S2 is a square shape, and the plate glass blank 7 shown in FIG. 2B is the shape of the recess T1 on the second surface S2. Has a honeycomb shape. The shape of any of the recesses T1 is effective for reducing warpage of the plate glass blanks 7.

  If the area of the convex portion T2 occupying the second surface S2 is ½ or less of the area of the concave portion T1, it is possible to effectively achieve both surface accuracy and workability. Further, if the side surface of the concave portion T1 has a draft taper shape of 3 ° or more with respect to the normal line of the bottom surface of the concave portion T1 (cross-hatched portion in FIG. 2F) (in FIG. 2D) Of the angle θ ≧ 3 °), the releasability can be easily improved.

DESCRIPTION OF SYMBOLS 1 Lower mold 1a Concave part 2 Upper mold | type 2a Concave part 3 Molten glass 4 Heater 5 Blade 6 Platinum nozzle 7 Plate glass blanks (preliminary molded object)
7a molded body 7b protruding portion 8 cover glass plate 8a upper surface 8b side surface 8c lower surface T1 concave portion T2 convex portion S1 first surface (molding surface)
S2 2nd surface (surface to be processed)
Sa inner surface Sb outer surface

Claims (13)

  It is a plate glass blank for a cover glass plate, and the back surface of the molding surface formed by the mold is a processing surface on which surface grinding or surface polishing is performed, and the processing surface has a concave portion and a convex portion. Sheet glass blanks.   The plate glass blank according to claim 1, wherein the convex portion is provided on an outermost periphery of the processing surface.   The area of the said convex part which occupies for the said to-be-processed surface is 1/4 or more of the said to-be-processed surface, The plate glass blanks of Claim 2 characterized by the above-mentioned.   The shape of the said recessed part is circular shape, square shape, honeycomb shape, or mesh shape, The plate glass blanks of any one of Claims 1-3 characterized by the above-mentioned.   The area of the said convex part which occupies the said to-be-processed surface is 1/2 or less of the area of the said recessed part to occupy the said to-be-processed surface, The plate glass blanks of any one of Claims 1-4 characterized by the above-mentioned. .   The plate glass blanks according to any one of claims 1 to 5, wherein a side surface of the concave portion has a draft taper shape of 3 ° or more with respect to a normal line of a bottom surface of the concave portion. It is a manufacturing method of the plate glass blanks for cover glass plates of any one of Claims 1-6,
A dropping step of dropping a certain amount of molten glass into a lower mold having a recess;
By pressing the molten glass on the lower mold with an upper mold having a recess for molding, the concave portion of the lower mold is filled with molten glass to form a first surface, and the concave of the lower mold A pressing step of filling the molten glass with a second surface having a concave portion and a convex portion;
The manufacturing method of the plate glass blanks characterized by having. A dropping step of dropping a certain amount of molten glass into a lower mold having a recess;
By pressing the molten glass on the lower mold with an upper mold having a recess for molding, the concave portion of the lower mold is filled with molten glass to form a first surface, and the concave of the lower mold A pressing step of filling the molten glass with a second surface having a concave portion and a convex portion;
A processing step of planarizing the second surface by surface grinding or surface polishing;
The manufacturing method of the cover glass plate characterized by having.   The method for manufacturing a cover glass plate according to claim 8, wherein the convex portion is provided on the outermost periphery of the second surface.   10. The method for manufacturing a cover glass plate according to claim 9, wherein an area of the convex portion occupying the second surface is 1/4 or more of the entire processing surface.   The method for manufacturing a cover glass plate according to any one of claims 8 to 10, wherein the concave portion of the second surface has a circular shape, a square shape, a honeycomb shape, or a mesh shape.   The area of the said convex part which occupies for the said 2nd surface is 1/2 or less of the area of the said recessed part which occupies for the said 2nd surface, The cover glass of any one of Claims 8-11 characterized by the above-mentioned. A manufacturing method of a board.   The cover glass plate according to any one of claims 8 to 12, wherein a side surface of the concave portion of the second surface has a draft taper shape of 3 ° or more with respect to a normal line of a bottom surface of the concave portion. Manufacturing method.

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