Abstract:
A method for manufacturing a curved glass sheet is provided. The method includes: providing a mold and a furnace; placing the mold in the furnace, the mold including a first mold, a second mold, and a mold core, the first mold defining a receiving space; a bottom surface in the receiving space defining at least one guiding groove, a bottom surface in the at least one guiding groove defining at least one air outlet, the mold core defining a mold cavity and a plurality of micro-holes; placing a raw glass sheet on the second mold; controlling a temperature in the furnace to heat the raw glass sheet; extracting air in the receiving space of the mold via the at least one outlet, to force the raw glass sheet to bend until contacting a bottom surface in the mold cavity; and cooling the mold to form a curved glass sheet.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a divisional application of U.S. patent application Ser. No. 14/211,498, filed on Mar. 14, 2014, which claims priority to Chinese Application No. 201310102756.2 filed on Mar. 28, 2013, the contents of which are entirely incorporated by reference herein. 
    
    
     FIELD 
     The present disclosure generally relates to a method for manufacturing a glass sheet, and particularly to a method for manufacturing a curved glass sheet. 
     BACKGROUND 
     In recent years, curved glass sheets are employed as glazing display panels in electronic devices such as mobile phones. Such curved glass sheets are conventionally produced by gravity bending methods. In a typical gravity bending method, a raw glass sheet is heated to a temperature which is equal to or higher than a glass transition temperature of the raw glass sheet, and then the glass sheet is conveyed to a first mold having an inner concave surface. The raw glass sheet is pressed to the inner concave surface by gravity to form the curved glass sheet. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the method for manufacturing curved glass sheet and the mold employed in the same. Moreover, in the drawings like reference numerals designate corresponding parts throughout the several views. Wherever possible, the same reference numerals are used throughout the drawings to refer to the same or like elements of an embodiment. 
         FIG. 1  shows an exploded, isometric view of an embodiment of a mold, including a mold core. 
         FIG. 2  shows an assembled, isometric view of the mold of  FIG. 1 . 
         FIG. 3  is a flowchart showing a method for manufacturing a curved glass sheet using the mold of  FIG. 1 . 
         FIG. 4  shows a cross-section of the mold of  FIG. 1  in a first state of use. 
         FIG. 5  shows a cross-section of the mold of  FIG. 1  in a second state of use. 
         FIG. 6  shows a cross-section of the mold of  FIG. 1  in a third state of use. 
         FIG. 7  is a flowchart showing a method for manufacturing the mold core of the mold of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean “at least one.” 
       FIGS. 1 and 2  show an embodiment of a mold  100  for manufacturing a curved glass sheet  300 . The curved glass sheet  300  can be obtained from a raw glass sheet  200  (shown in  FIG. 4 ). The mold  100  can include a first mold  10 , an second mold  30  matching with the first mold  10 , and a mold core  50  located between the first mold  10  and the second mold  30 . 
     The first mold  10  can be substantially cuboid and can include a mounting surface  11  facing the mold core  50 . The mounting surface  11  can define a receiving space  111  matching with the mold core  50  for receiving the mold core  50 . A bottom surface  113  in the receiving space  111  can support the mold core  50  and can define a plurality of guiding grooves  115  spaced from each other. A bottom surface  117  (see  FIG. 1 ) in each guiding groove  115  can define an air outlet  119  communicating with the receiving space  111 . In an illustrated embodiment, five guiding grooves  115  are defined in the bottom surface  113 . Each of four corners of the mounting surface  11  can define an aligning hole  13 , for positioning the second mold  30 . 
     The second mold  30  can be substantially rectangular and plate-like and can include a mounting surface  31  away from the first mold  10 . The mounting surface  31  can define a receiving groove  33  in a substantially center portion for receiving the raw glass sheet  200 . A support surface  331  can be formed in the receiving groove  33  for supporting the raw glass sheet  200 . An opening  335  can be defined in a center portion of the support surface  331 . The opening  335  can be substantially rectangular, and corners of the opening  335  can be chamfered. The second mold  30  can further include a plurality of positioning posts  35  at corners of the second mold  30  towards the first mold  10 . Each positioning post  35  can correspond to one aligning hole  13 , such that each positioning post  35  can be inserted into the corresponding aligning hole  13  for positioning the second mold  30 . In other embodiments, the receiving groove  33  can be omitted, such that the opening  335  is directly defined in the mounting surface  31 , and the raw glass sheet  200  is placed directly on the mounting surface  31  covering the opening  335 . In the illustrated embodiment, the support surface  331  is substantially parallel to the mounting surface  31 . In other embodiments, the support surface  331  can be a planar surface or curved surface inclined to the mounting surface  31 . 
     The mold core  50  can be substantially cuboid, and can be made of composite ceramic in which B content (wt %) and N content (wt %) is higher than 70%. In other embodiments, the mold core  50  can also be made of ceramic fiber, such as Si—B—N ceramic fiber. The mold core  50  can be received in the receiving space  111 , and can include a first surface  51  and a second surface  53  opposite to the first surface  51 . The first surface  51  can face to the second mold  30 . The second surface  53  can face to the first mold  10 . A plurality of through micro-holes  55  can be defined through the first surface  51  and the second surface  53 , such that the opening  335  can be in communication with the guiding grooves  115 . The diameter of each micro-hole  55  can be smaller than about 1 mm. In the illustrated embodiment, the diameter of each micro-hole can be about 0.3 mm. The first surface  51  can define a mold cavity  57  corresponding to the opening  335 . A shape of the mold cavity  57  can match with a shape of the curved glass sheet  300 . In the illustrated embodiment, a bottom surface  571  in the mold cavity  57  can be an arc. The micro-holes  55  can extend along crisscross directions, and the micro-holes  55  can be arranged in a matrix. In the illustrated embodiment, a shape of the mold core  50  matches with the receiving space  111 , so that when the second mold  30  is positioned on the first mold  10 , the second mold  30  contacts with the first surface  51  of the mold core  50 . In other embodiments, the micro-holes  55  can be defined only corresponding to mold cavity  57 . The diameter of each micro-hole  55  can be changed, for example the diameter can be 0.5 mm. 
     In assembly, the mold core  50  can be received in the receiving space  111  and mounted on the bottom surface  113 , and can be located on a side of the guiding grooves  115  away from the air outlet  119 . The side surface of the second mold  30  opposite to the mounting surface  31  can contact the mounting surface  11  of the first mold  10  and the first surface  51  of the mold core  50 . The positioning posts  35  can be inserted into the corresponding positioning holes  13 . The opening  335  of the second mold  30  can be communicated to the guiding grooves  115  of the first mold  10  via the micro-holes  55 . 
       FIG. 3  shows an embodiment of a method for manufacturing the curved glass sheet employing a mold, which can be as described above, with the raw glass sheet. 
     In  101 , the mold described as above and a furnace (not shown) are provided. A temperature in the furnace can be controlled. 
     In  102 , the raw glass sheet (shown in  FIG. 4 ) can be provided and placed on the support surface of the second mold, and can cover the opening of the second mold. In  102 , the mold can be in a first state of use. 
     In  103 , the furnace can be evacuated to be in a substantially vacuum state, and then protective gas can be introduced into the furnace. In the illustrated embodiment, the protective gas is nitrogen gas. 
     In  104 , the temperature in the furnace can be controlled, and the raw glass sheet can be heated to a temperature about the glass transition temperature of the raw glass sheet. In the illustrated embodiment, a temperature difference between the heated temperature of the raw glass sheet and the glass transition temperature of the raw glass sheet is smaller than or equal to about Celsius degrees. 
     In  105 , the mold can be extracted via the air outlet of the first mold, such that a side of the raw glass sheet adjacent to the first mold forms a zone of negative pressure, an opposite side of the raw glass sheet away from the first mold forms a zone of positive pressure. Thus, the raw glass sheet can be bent and adhered to the bottom surface of the mold cavity. In  105 , the mold can be in a second state of use. There can be many guiding grooves evenly defined in the bottom surface of the receiving space, such that when extracting the mold via the outlet, the gas in the mold cavity can be evenly extracted via the micro-holes and the guiding grooves. Thus, stress can be uniformly applied on the raw glass sheet, and the raw glass sheet can bend until tightly adhered to the bottom surface of the mold cavity. In addition, the micro-holes can extend crisscrossing, such that the zone of negative pressure in a side of the raw glass sheet adjacent to the first mold can be quickly formed. 
     In  106 , after the raw glass sheet is cooled, gas can be introduced into the mold cavity via the outlet, and the mold can be in a third state of use (shown in  FIG. 6 ). Then, the mold can be taken out from the furnace, and the curved glass sheet can be obtained. 
       FIG. 7  shows an embodiment of a method for manufacturing the mold of the embodiment is illustrated as follows. 
     In  201 , composite ceramic powders can be provided as raw material, and can be pressed to form a first layer. B content (wt %) and N content (wt %) of the composite ceramic powders is higher than 70%. 
     In  202 , an organic net can be placed on the first layer of the composite ceramic powders, and can be pressed. In the illustrated embodiment, the diameter of each organic line of the organic net is about 0.3 mm. In other embodiments, the diameter of each organic line of the organic net can be about 0.5 mm. 
     In  203 , composite ceramic powders can be placed on the organic net and pressed to form a second layer. 
     In  204 ,  202  and  203  can be repeated, and the composite ceramic powders can be pressed to be a predetermined thickness, such that a first preformed mold can be obtained. 
     In  205 , a furnace can be provided, and the first preformed perform can be sintered to form a second preformed mold. 
     In  206 , the second preformed mold can be sintered in an atmosphere of air or oxygen, and thus the organics of the organic net can be oxidized, such that a third preformed mold with a plurality of micro-holes in matrix can be formed. In the illustrated embodiment, a sintered temperature of second preformed mold is 700 Celsius degrees. The diameter of each micro-hole can be about 0.3 mm. 
     In  207 , the exterior of the third preformed mold can be shaped, and a mold cavity corresponding to the curved glass sheet can be machined, thus, forming the mold core. 
     In an alternative embodiment, a number of the guiding grooves can be one or more than one, and a number of the air outlet corresponding to each guiding groove can be one or more than one. The raw glass sheet can be directly put on the first surface of the mold core during manufacturing the curved glass sheet. When a profile of the curved glass sheet is not so important, the guiding grooves can be omitted, and the air outlets can be directly defined in the bottom surface received in the receiving space. 
     It is to be understood, however, that even through numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.