Abstract:
A method for molding glass, the method includes inserting glass into a chamber housing an upper plate, a lower plate facing the upper plate, and a heat radiation part that is configured to generate heat, placing the glass on the lower plate, moving the upper plate downward to press the glass, thereby molding the glass, applying heat to the glass, withdrawing the glass from the chamber, and forming a reinforcement layer at a surface of the glass by dipping the glass into a solution.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to, and the benefit of, Korean Patent Application No. 10-2015-0134058, filed on Sep. 22, 2015, the entire contents of which are incorporated herein by reference in their entirety. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure herein relates to an apparatus and a method for molding glass having a curvature. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, plastic, such as acryl, has previously been used for forming a window cover used for a display window of a mobile device, such as a mobile phone. However, as smart phone markets have expanded, touch functions, wear resistance, light transmittance, high dielectric constant, and the like have also expanded or improved. Thus, chemically tempered glass is primarily used. Materials for the chemically tempered window include a soda-lime based plate glass, which is for general products, and Gorilla Glass® (Gorilla Glass® is a registered trademark of Corning Incorporated, a New York corporation in the U.S.A.), which is mainly used for high end products. 
         [0006]    Glass material is increasingly used in various industrial fields, including use in covers of solar batteries, in flat displays, such as thin film transistor-liquid crystal displays (TFT-LCD), plasma display panels, and organic electroluminescent (EL) displays, and in covers for various mobile electronic devices. Thus, weight reduction and slimming of glass material may be desired. 
         [0007]    However, due to brittleness of glass material, achieving safety while also achieving weight reduction and slimming may be challenging. Accordingly, various reinforcing methods are researched for securing the safety of glass. A thermal reinforcing method and a chemical reinforcing method are used for tempering glass. 
         [0008]    Thermal reinforcement is a method in which a surface of the glass is heated at a high temperature, and then quenched, thereby generating compressive stress on the surface of the glass to strengthen the glass. However, when thermal reinforcement is performed, it may be difficult to uniformly transfer heat to the whole region of the glass due to the quick heating. As a result, the glass may be locally reinforced with different strengths. In addition, after the thermal reinforcement, the waviness and light transmittance of the glass are reduced, and the refractive index of the glass may be non-uniform. 
       SUMMARY 
       [0009]    The present disclosure provides a method for molding glass for a flexible display by using thicker glass while equally maintaining a level of a curvature. 
         [0010]    An embodiment of the inventive concept provides a method for molding glass, the method includes inserting glass into a chamber housing an upper plate, a lower plate facing the upper plate, and a heat radiation part that is configured to generate heat, placing the glass on the lower plate, moving the upper plate downward to press the glass, thereby molding the glass, applying heat to the glass, withdrawing the glass from the chamber, and forming a reinforcement layer at a surface of the glass by dipping the glass into a solution. 
         [0011]    The lower plate may include a convex top surface, and the upper plate may include a concave bottom surface that may be curved in a first direction. 
         [0012]    The glass may include molding the glass to include a curved shape that may be curved in the first direction. 
         [0013]    The heat to the glass may reduce stress of the glass. 
         [0014]    The heat may have a temperature of about 400° C. to about 900° C. 
         [0015]    The solution may include a potassium-nitrate solution. 
         [0016]    A surface of the glass may include first ions, and the solution may include second ions. 
         [0017]    The forming of the reinforcement layer at the surface of the glass may include heating the solution, and may include exchanging the first ions with the second ions. 
         [0018]    The first ions may include sodium ions. 
         [0019]    The second ions may include potassium ions. 
         [0020]    The forming of the reinforcement layer at the surface of the glass may include depositing the second ions at the surface of the glass. 
         [0021]    The upper plate may include a supporting plate having a flat shape, and a pressing part below the supporting plate, and may include a first curvature, and the lower plate may include a molding member facing the pressing part, and may include a convex shape corresponding to the first curvature, and an accommodating member defining a groove to insert the molding member. 
         [0022]    The glass may be configured to be placed between the molding member and the pressing part. 
         [0023]    The molding of the glass may include supporting a bottom surface of the glass with the molding part, and may include pressing a top surface of the glass with the pressing part. 
         [0024]    The glass may include molding the glass to have a shape corresponding to the first curvature. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The accompanying drawings are included to provide a further understanding of embodiments of the inventive concept, and are incorporated in, and constitute a part of, this specification. The drawings illustrate embodiments of the inventive concept and, together with the description, serve to explain aspects of embodiments of the inventive concept. In the drawings: 
           [0026]      FIG. 1  is a perspective view of a mechanism for molding glass according to an embodiment of the present invention; 
           [0027]      FIG. 2  is a view illustrating a lower plate of a glass molding mechanism according to an embodiment of the present invention; 
           [0028]      FIG. 3  is a view of glass between plates according to an embodiment of the present invention; 
           [0029]      FIG. 4  is a view illustrating a method for molding the glass according to an embodiment of the present invention; 
           [0030]      FIG. 5  is a view illustrating a method for heat-treating the glass according to an embodiment of the present invention; 
           [0031]      FIG. 6  is a view illustrating a method for chemically tempering the glass according to an embodiment of the present invention; 
           [0032]      FIG. 7  is a view of dipped glass according to an embodiment of the present invention; 
           [0033]      FIG. 8  is an enlarged view of a surface of the ion-exchanging glass in  FIG. 7 ; 
           [0034]      FIG. 9  is a view illustrating an ion arrangement of the glass that is ion-exchanged according to an embodiment of the present invention; and 
           [0035]      FIG. 10  is a view of the molded glass according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    Features of the inventive concept and methods of accomplishing the same may be understood more readily by reference to the following detailed description of embodiments and the accompanying drawings. The inventive concept may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Hereinafter, example embodiments will be described in more detail with reference to the accompanying drawings, in which like reference numbers refer to like elements throughout. The present invention, however, may be embodied in various different forms, and should not be construed as being limited to only the illustrated embodiments herein. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete, and will fully convey the aspects and features of the present invention to those skilled in the art. Accordingly, processes, elements, and techniques that are not necessary to those having ordinary skill in the art for a complete understanding of the aspects and features of the present invention may not be described. Unless otherwise noted, like reference numerals denote like elements throughout the attached drawings and the written description, and thus, descriptions thereof will not be repeated. In the drawings, the relative sizes of elements, layers, and regions may be exaggerated for clarity. 
         [0037]    It will be understood that, although the terms “first,” “second,” “third,” etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. 
         [0038]    Thus, a first element, component, region, layer or section described below could be termed a second element, component, region, layer or section, without departing from the spirit and scope of the present invention. 
         [0039]    Spatially relative terms, such as “beneath,” “below,” “lower,” “under,” “above,” “upper,” and the like, may be used herein for ease of explanation to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or in operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” or “under” other elements or features would then be oriented “above” the other elements or features. Thus, the example terms “below” and “under” can encompass both an orientation of above and below. The device may be otherwise oriented (e.g., rotated  90  degrees or at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly. 
         [0040]    It will be understood that when an element or layer is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it can be directly on, connected to, or coupled to the other element or layer, or one or more intervening elements or layers may be present. In addition, it will also be understood that when an element or layer is referred to as being “between” two elements or layers, it can be the only element or layer between the two elements or layers, or one or more intervening elements or layers may also be present. 
         [0041]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and “including,” when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
         [0042]    As used herein, the term “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Further, the use of “may” when describing embodiments of the present invention refers to “one or more embodiments of the present invention.” As used herein, the terms “use,” “using,” and “used” may be considered synonymous with the terms “utilize,” “utilizing,” and “utilized,” respectively. Also, the term “exemplary” is intended to refer to an example or illustration. 
         [0043]    The electronic or electric devices and/or any other relevant devices or components according to embodiments of the present invention described herein may be implemented utilizing any suitable hardware, firmware (e.g. an application-specific integrated circuit), software, or a combination of software, firmware, and hardware. For example, the various components of these devices may be formed on one integrated circuit (IC) chip or on separate IC chips. Further, the various components of these devices may be implemented on a flexible printed circuit film, a tape carrier package (TCP), a printed circuit board (PCB), or formed on one substrate. Further, the various components of these devices may be a process or thread, running on one or more processors, in one or more computing devices, executing computer program instructions and interacting with other system components for performing the various functionalities described herein. The computer program instructions are stored in a memory which may be implemented in a computing device using a standard memory device, such as, for example, a random access memory (RAM). The computer program instructions may also be stored in other non-transitory computer readable media such as, for example, a CD-ROM, flash drive, or the like. Also, a person of skill in the art should recognize that the functionality of various computing devices may be combined or integrated into a single computing device, or the functionality of a particular computing device may be distributed across one or more other computing devices without departing from the spirit and scope of the exemplary embodiments of the present invention. 
         [0044]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and/or the present specification, and should not be interpreted in an idealized or overly formal sense, unless expressly so defined herein. 
         [0045]      FIG. 1  is a perspective view of a mechanism for molding glass according to an embodiment of the present invention. 
         [0046]    Referring to  FIG. 1 , according to an embodiment of the inventive concept, a mechanism  100  for molding glass having a curvature (e.g., a predetermined curvature) (hereinafter, referred to as a molding mechanism  100 ) includes an upper plate  200  and a lower plate  300 , and glass  400  is placed between the upper plate  200  and the lower plate  300 . 
         [0047]    The glass  400  is between the upper plate  200  and the lower plate  300 . The glass  400  extends lengthwise (e.g., has a long side) in a first direction D 1 , and has a width (e.g., a short side) in a second direction D 2  crossing the first direction D 1 . The glass  400  may have a flat shape prior to being molded by the molding mechanism  100 . 
         [0048]    The glass  400  may have a radius of curvature in a range of about 1 mm to about 20 mm, and may have a thickness in a range of about 20 μm to about 200 μm. 
         [0049]    When the curvature and thickness of the glass  400  are below the abovementioned ranges, the substrate might not be strong enough to support a display device or the like. When the curvature and thickness of the glass  400  are above the abovementioned ranges, the substrate might not be flexible because the substrate is too thick. 
         [0050]    When the glass  400  is molded by the molding mechanism  100 , the glass  400  may be molded to have a curved surface (e.g., a surface having a predetermined curvature) in the first direction D 1 , and to have a flat shape (e.g., to be uncurved) in the second direction D 2 . 
         [0051]    The upper and lower plates  200 ,  300  of the molding mechanism  100  may be made of metal. Although the molding mechanism  100  according to an embodiment of the present invention is a mold that is formed of graphite, the present invention is not limited thereto. As a non-limiting example, the molding mechanism  100  may be made of ceramic, tungsten carbide (WC), silicon carbide (SiC), or the like. 
         [0052]    The upper plate  200  may be used for pressing the glass  400  so that the glass  400  is molded to have a curved surface. The upper plate  200  has a long side (e.g., extends lengthwise) in the first direction D 1 , and has a short side (e.g., extends widthwise) in the second direction D 2 . The upper plate  200  may include a supporting plate  210  having a flat shape, and may include a pressing part  220  below the supporting plate  210 . 
         [0053]    The supporting plate  210  and the pressing part  220  may each have a long side in the first direction D 1 , and a short side in the second direction D 2 . 
         [0054]    The pressing part  220  may be configured to be placed on the glass  400 , and the upper plate  200  may move downward to allow the pressing part  220  to press the glass  400 . The pressing part  220  is above the glass  400 , and has a first curvature that may be bent in the first direction D 1  (e.g., a first curvature that bends along the first direction D 1 ). 
         [0055]    When the upper plate  200  moves downward to press the glass  400 , the pressing part  220  may contact a top surface of the glass  400 , and a bottom surface of the glass  400  may contact an upper portion of a molding member  310  of the lower plate  300 , which also has the first curvature (e.g., has a shape corresponding to the first curvature). 
         [0056]    The lower plate  300  may include the molding member  310  on which the glass  400  is located, and may also include an accommodating member  320  configured to accommodate the molding member  310 . The glass  400  may be located on the molding member  310 . The accommodating member  320  may include a groove H recessed downward from a top surface of the accommodating member  320 , and the molding member  310  may be inserted into, and fixed within, the groove H. 
         [0057]    A top surface of the molding member  310  and a bottom surface of the pressing part  220  may face each other, and the top surface of the molding member  310  may have the same shape as (e.g., may correspond to the shape of) the bottom surface of the pressing part  220 . 
         [0058]    The lower plate  300  may include the molding member  310  configured to correspond to the pressing part  220 , and the molding member  310  may include a molding part (e.g., a surface of the molding member  310 )  311  having a convex shape having the same curvature as (e.g., corresponding to the curvature of) the pressing part  220 . 
         [0059]      FIGS. 2 to 4  are views illustrating a method for molding glass according to an embodiment of the present invention.  FIG. 2  is a view illustrating a lower plate of a glass molding mechanism,  FIG. 3  is a view of the glass located between the plates, and  FIG. 4  is a view illustrating the method for molding glass. 
         [0060]    In describing  FIGS. 2 to 4 , reference symbols for above-described components are given, and overlapped description for the components will be omitted. 
         [0061]    Referring to  FIG. 2 , the molding mechanism  100  is in a chamber  600 , and the upper plate  200  and the lower plate  300  face each other. The molding member  310  may be inserted into the groove H of the accommodating member  320 . 
         [0062]    The chamber  600  may include a vacuum pump for maintaining a vacuum state in the chamber  600 . The vacuum pump may be connected to the chamber  600  to adjust a pressure in the chamber  600 , thereby making a high vacuum environment in the chamber  600 . The vacuum pump may be connected to the outside of the chamber  600  having the high vacuum environment to discharge air in the chamber  600  to the outside. 
         [0063]    A heat radiation part  500  for heating the molding mechanism  100  is in the chamber  600 . A constitution in which the heat radiation part  500  heats the molding mechanism  100  will be described in detail with reference to  FIG. 5 . 
         [0064]    Referring to  FIG. 3 , the glass  400  may be placed on the molding member  310 , and a side surface of the glass  400  may contact an area (e.g., a predetermined area) of an upper portion of an inner surface of the accommodating member  320  in the groove H. 
         [0065]    The glass  400  may be inserted into the chamber  600  from the outside through a gate of the chamber  600 , and may be located on the molding member  310 . 
         [0066]    The upper plate  200  may move downward to press the glass  400  on the molding member  310 . 
         [0067]    Referring to  FIG. 4 , the upper plate  200  may move downward to contact the top surface of the glass  400 , and to then press the glass  400 . 
         [0068]    The glass  400  may be molded to have a curved surface having the same curvature as (e.g., corresponding to the curvature of) the molding member  310 . That is, when viewed from the second direction D 2 , the glass  400  may have a cross-section having a curved shape. 
         [0069]    The molding member  310  may face the upper plate  200 , and may contact a bottom surface of the glass  400  to support the glass  400 . Accordingly, the glass  400  on the lower plate  300  may be pressed by the upper plate  200  to form a curved surface. 
         [0070]    The molding member  310  may be located in the groove H defined by the lower plate  300 . That is, side and bottom surfaces of the molding member  310 , to the exclusion of the top surface of the molding member  310 , may respectively contact inner and bottom surfaces of the groove H. 
         [0071]    The flat glass  400  may be on the top surface of the molding member  310 . Both side surfaces of the glass  400  may contact the inner surface of the accommodating member  320  of the lower plate  300  in the groove H. The top surface of the molding member  310  may have substantially the same height as the top surface of the glass  400  after the molding. 
         [0072]    The upper plate  200  may be on the glass  400 , and the upper plate  200  may move downward to press the glass  400 . The pressing part  220  on a bottom surface of the upper plate  200  may press the glass  400  against the molding member  310 . That is, the pressing part  220  may press the glass  400  so that the glass  400  is molded to have substantially the same curvature shape as the pressing part  220 . 
         [0073]      FIG. 5  is a view illustrating a method for heat-treating the glass according to an embodiment of the present invention. In describing  FIGS. 4 and 5 , reference symbols for above-described components are given, and overlapped or repeated description for the components will be omitted. 
         [0074]    Referring to  FIG. 5 , the glass  400  between the lower and upper plates  300  and  200 , which are described in  FIGS. 2 and 4 , may be molded to have the curved surface in the chamber  600 , in which the upper plate  200 , the lower plate  300  facing the upper plate  200 , and the heat radiation part  500  for generating heat may be located. Thereafter, the heat radiation part  500  in the chamber  600  may generate heat. 
         [0075]    The upper and lower plates  200 ,  300  are heated, and the heat is transferred to the glass  400  by the plates  200 ,  300 . As a result, the heat may be applied to the glass  400 . 
         [0076]    The heat radiation part  500  may generate heat having a temperature of about 400° C. to about 900° C. When molded to have a curved surface, a resistance force may be generated in the glass  400  to correspond to a pressure applied by the plates  200 ,  300 . Herein, resistance force may be defined as stress. Due to the stress, the curved portion of the glass  400  may be damaged. 
         [0077]    When the heat is applied to the glass  400 , the stress generated in the glass  400  may be reduced or relieved. As a result, the damage of the glass  400  caused by the stress may be avoided. 
         [0078]    Also, because the thermal process is performed in a state in which the glass is fixed in the closed chamber  600 , even in a large sized glass, temperature distribution may be uniform over the glass  400 , and a thermal deformation of the glass  400  may be reduced or minimized. 
         [0079]    The heat radiation part  500  may include a control part for adjusting thermal temperature and time. When the glass  400  is heat-treated, the glass  400  may be heated (e.g., heated to a predetermined temperature) by the heat radiation part  500 , and may be maintained at the temperature for an amount time. The heat radiation part  500  may include a heater. 
         [0080]      FIGS. 6 to 7  are views illustrating a method for chemically tempering the glass according to an embodiment of the present invention. In describing  FIGS. 6 to 7 , reference symbols for above-described components are given, and overlapped or repeated description for the components will be omitted. 
         [0081]    Referring to  FIGS. 6 and 7 , first and second portions of the glass  400  may be molded such that the glass  400  has a curved surface, and then the heat-treated glass  400  may be withdrawn through the gate of the chamber  600 . A storage bath  700 , in which a solution  710  for dipping the withdrawn glass  400 , may be prepared. The glass  400  may be dipped into the solution  710  in the storage bath  700 . 
         [0082]    The solution  710  may include potassium nitrate (KNO 3 ). First ions  800  (see  FIG. 8 ) exist on the surface of the glass  400 , and the solution  710  may include second ions  900  (see  FIG. 8 ). The first ions  800  may be sodium ions (Na + ), and the second ions  900  may be potassium (K + ) ions. 
         [0083]    Hereinafter, the solution  710  is defined as a potassium nitrate solution  710 . The solution  710  is heated (e.g., heated to a predetermined temperature) to form a reinforcement layer on the surface of the glass  400 . A heating part for heating the solution  710  may be in the storage bath  700 . 
         [0084]    As a result of heating the solution  710  in which the glass  400  is dipped, a process of ion exchange that exchanges the first ions  800  at the surface of the glass  400  dipped in the solution  710  with the second ions  900  dipped in the solution  710 . Through the ion exchange, compressive stress may be formed on the surface of the glass  400  to temper the glass  400 . The glass tempering method may be referred to as a chemical reinforcement. 
         [0085]    The ion exchange is a reaction in which ions of an insoluble solid may be reversibly exchanged with other ions having the same sign (e.g., the ions of the insoluble solid and the other ions may both be positively charged or may both be negatively charged) as each other. For example, the ion exchange is exchanging one kind of ions that exist on a surface of a mineral contacting water, or on other positions, with another kind of ions that are dissolved in the water. Positive ions between the mineral and the solution may include calcium (Ca 2+ ), magnesium (Mg 2+ ), sodium (Na + ), and potassium (K + ). 
         [0086]    Accordingly, the reinforcement layer may be formed on the surface of the glass  400  by the solution  710 . 
         [0087]    Hereinafter, a constitution in which the reinforcement layer is formed on the glass  400  will be described in detail with reference to  FIGS. 8 to 10 .  FIGS. 8 to 10  are views illustrating a method for exchanging ions of the glass according to an embodiment of the present invention.  FIG. 8  is an enlarged view illustrating the surface, in which ions are exchanged, of the glass shown in  FIG. 7 ,  FIG. 9  is a view illustrating an ion arrangement of the ion-exchanged glass, and  FIG. 10  is a view of a molded glass. In describing  FIGS. 8 to 10 , reference symbols for above-described components are given, and overlapped description for the components will be omitted. 
         [0088]    Referring to  FIGS. 8 to 10 , the glass may be dipped into the heated solution  710 , and the first ions  800  existing on the surface of the glass  400  may escape from the surface of the glass  400 . The second ions  900  of the solution  710  permeate into the surface of the glass  400 , from which the first ions  800  are removed. That is, some of the second ions  900  may replace the first ions  800 . 
         [0089]    Although potassium ions, as the second ions  900 , each have a radius that is greater than that of sodium ions, as the first ions  800 . Accordingly, when the sodium ions  800  and the potassium ions  900  are ion-exchanged, the surface of the glass  400  may increase in strength. It should be noted that the method for chemical tempering the glass is not limited thereto. 
         [0090]    As a non-limiting example, microwaves may be emitted to the glass  400  to vibrate sodium ions  800  of the glass  400 , thereby loosening molecular binding structure of the glass  400 , and thereby generating heat caused by the vibration. Also, the potassium ions  900  in the solution  710  may react to the microwave to vibrate the glass  400 , and thus ion activity of the solution  710  may increase, and heat caused by the vibration may be generated. 
         [0091]    The glass  400  that is chemically tempered and heat-treated may have compressive stress that is greater than that of the glass  400  if it were not heat-treated. 
         [0092]    According to an embodiment of the present invention, the method for molding glass may apply the heat to the glass molded to have the curved surface to relieve the stress of the glass. 
         [0093]    Also, through the exchanging of ions, the compressive stress may be formed on the surface of the glass to temper the surface of the glass. 
         [0094]    It will be apparent to those skilled in the art that various modifications and variations can be made in the inventive concept. Thus, it is intended that the present disclosure covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.