Patent Publication Number: US-2023161345-A1

Title: Method of manufacturing window and window for display device

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a Continuation of co-pending U.S. patent application Ser. No. 17/487,288, filed on Sep. 28, 2021, which claims priority under 35 USC § 119 to Korean Patent Application No. 10-2021-0020676 filed on Feb. 16, 2021 in the Korean Intellectual Property Office (KIPO), the entire disclosure of which is herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a method of manufacturing a window. More particularly, the present disclosure relates to a window applied to various display devices and a method of manufacturing the window. 
     DISCUSSION OF THE RELATED ART 
     A display device is an electronic device that provides visual information to a user. Recently, display devices have been developed that are bendable, foldable, or rollable. These display panels are, in some cases, able to be bent, folded, or rolled during the manufacturing process and are then locked into a desired shape. On other cases, these display panels may be repeatedly bent, folded, or rolled during use. 
     The display device may include a window for protecting a display panel that generates an image. In these cases, both the display panel and the window might be flexible. 
     The window may be cut to correspond to the size of the display device during a manufacturing process. A cut surface of the window may be chemically polished with an etchant in order to remove defects or the like of the cut surface of the window. However, when the cut surface of the window is chemically polished, grains are formed on an edge of the window by a chemical reaction between the etchant and the window, and as an outer surface of the edge of the window is angled, an impact strength of the window may decrease. 
     SUMMARY 
     A method of manufacturing a window of a display device, the method includes alternately stacking a plurality of windows and a plurality of adhesive layers into a single stack; cutting the single stack; polishing a cut surface of the single stack using a polishing pad while a slurry is applied to the cut surface of the single stack; curing the single stack, and separating each of the plurality of windows from the single stack after the single stack has been cured. The polishing pad has an elastic modulus that is less than an elastic modulus of the window. 
     The curing may include exposing the single stack to UV light and emerging the single stack into a bath of hot water. 
     The polishing of the cut surface of the single stack may include polishing each of the plurality of adhesive layers shorter than each of the plurality of windows such that edges of each of the plurality of windows extend past corresponding edges of each of the plurality of adhesive layers. 
     A method of manufacturing a window includes cutting a window having a uniform thickness of about 20 μm to about 100 μm and polishing a cut surface of the window with a polishing pad having an elastic modulus that is less than an elastic modulus of the window, while applying a slurry to the cut surface of the window. 
     The window may include glass and/or plastic. 
     A hardness of the polishing pad may be less than a hardness of the window. 
     The polishing pad may include a fabric, wool, and/or a polymer. 
     The slurry may include cerium(IV) oxide (CeO 2 ). 
     Polishing the cut surface of the window may include polishing the window to remove a length measured from an edge of the window that is equal to about 10% to about 200% of the thickness of the window. 
     The method may further include, before cutting the window, or after cutting the window and before polishing the cut surface of the window, forming a first adhesive layer and a second adhesive layer on a first surface of the window and a second surface of the window that is opposite to the first surface of the window, respectively. 
     An elastic modulus of each of the first adhesive layer and the second adhesive layer may be less than the elastic modulus of the window. 
     A hardness of each of the first adhesive layer and the second adhesive layer may be less than a hardness of the window. 
     Each of the first adhesive layer and the second adhesive layer may include a resin, an optically clear adhesive (OCA), a rosin, and/or a wax. 
     The method may further include, after polishing the cut surface of the window, curing each of the window, the first adhesive layer, and the second adhesive layer and separating the first adhesive layer and the second adhesive layer from the window. 
     The method may further include, after cutting the window and before polishing the cut surface of the window, disposing the window between a first support and a second support. 
     An area of each of the first support and the second support may be less than an area of the window. 
     A window for a display device includes a flat portion having a uniform thickness of about 20 μm to about 100 μm and a chamfer portion disposed on at least a portion of an edge of the flat portion, having a thickness less than the thickness of the flat portion, and having an outer surface of a curved shape protruding from the flat portion. 
     A roughness of the outer surface of the chamfer portion may be about 0.5 nm to about 10 nm. 
     A distance from an edge of the chamfer portion to the edge of the flat portion may be in a range of about 10% to about 200% of the thickness of the flat portion. 
     The chamfer portion may include a first curved portion adjacent to a first surface of the flat portion and a second curved portion adjacent to a second surface of the flat portion opposite to the first surface. A radius of curvature of each of the first curved portion and the second curved portion may be in a range of about 10% to about 50% of the thickness of the flat portion. 
     The chamfer portion may have a uniform radius of curvature. The radius of curvature may be in a range of about 50% to about 100% of the thickness of the flat portion. 
     The chamfer portion may have different radiuses of curvature along the outer surface of the chamfer portion. The radius of curvature on an edge of the chamfer portion may be in a range of about 20% to about 200% of the thickness of the flat portion. 
     The outer surface of the chamfer portion adjacent to a surface of the flat portion may have an angle of about 10 degrees to about 30 degrees with respect to a plane extending from the surface of the flat portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the present disclosure and many of the attendant aspects thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG.  1    is a flowchart illustrating a method of manufacturing a window according to an embodiment of the present disclosure: 
         FIGS.  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 , and  9    are diagrams illustrating a method of manufacturing a window according to an embodiment of the present disclosure; 
         FIG.  10    is a flowchart illustrating a method of manufacturing a window according to an embodiment of the present disclosure; 
         FIGS.  11  and  12    are diagrams illustrating a method of manufacturing a window according to an embodiment of the present disclosure; 
         FIG.  13    is a flowchart illustrating a method of manufacturing a window according to an embodiment of the present disclosure: 
         FIG.  14    is a diagram illustrating a method of manufacturing a window according to an embodiment of the present disclosure; 
         FIG.  15    is a plan view illustrating a window for a display device according to embodiments of the present disclosure; 
         FIG.  16    is a perspective view illustrating a window for a display device according to an embodiment of the present disclosure; 
         FIG.  17    is a perspective view illustrating a window for a display device according to an embodiment of the present disclosure; 
         FIG.  18    is a perspective view illustrating a window for a display device according to an embodiment of the present disclosure; and 
         FIG.  19    is a perspective view illustrating a window for a display device according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereinafter, methods of manufacturing windows and windows for display devices in accordance with embodiments of the present disclosure will be explained in detail with reference to the accompanying drawings. 
     Hereinafter, a method of manufacturing a window according to an embodiment of the present disclosure will be described with reference to  FIGS.  1  to  9   . 
       FIG.  1    is a flowchart illustrating a method of manufacturing a window according to an embodiment of the present disclosure. 
     Referring to  FIG.  1   , a method of manufacturing a window according to an embodiment of the present disclosure may include alternately stacking windows and adhesive layers (S 110 ), cutting the stacked windows and the adhesive layers (S 120 ), polishing cut surfaces of the stacked windows and the adhesive layers (S 130 ), UV-curing the stacked windows and the adhesive layers (S 140 ), heat-curing the stacked windows and the adhesive layers (S 150 ), and separating the individual windows and the adhesive layers from the stack (S 160 ). 
       FIGS.  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 , and  9    are diagrams illustrating a method of manufacturing a window according to an embodiment of the present disclosure. 
     Referring to  FIGS.  1  and  2   , the windows  100  and the adhesive layers  200  may be stacked (S 110 ). The windows  100  and the adhesive layers  200  may be alternately stacked, one-by-one, along a first direction DR 1 . Each window  100  may be a window for a display device. In an embodiment of the present disclosure, each window  100  may be a window for a flexible display device. Each window  100  may protect components of a display device, and an image generated by the display device may be displayed through the window  100  as the window may be transparent to visible light. As the windows  100  and the adhesive layers  200  are alternately stacked, a plurality of windows  100  may be cut together in a subsequent process, and a cutting time and a cutting cost of the windows  100  may be reduced as compared to a process in which each window  100  is individually cut. 
     Each window  100  may include a flexible material. For example, each window  100  may include thin glass and/or plastic. The thin glass may be of a thickness that allows for flexibility without cracking or otherwise breaking. 
     Each window  100  may have a uniform thickness TH. The thickness TH of each window  100  may be defined as a length of the window  100  in the first direction DR 1 . The thickness TH of each window  100  may be about 20 μm to about 100 μm. When the thickness TH of the window  100  is less than about 20 μm, handling of the window  100  may be difficult, and the window  100  might not sufficiently protect the components of the display device. When the thickness TH of the window  100  is greater than about 100 μm, the flexible characteristic of the window  100  may decrease, and a flexural strength of the window  100  may decrease. 
     The adhesive layers  200  may serve to fix the stacked windows  100  to one another. Accordingly, the adhesive layers  200  may each include an adhesive material. For example, the adhesive layers  200  may each include a resin, an optically clear adhesive (OCA), a rosin, and/or a wax. 
     An elastic modulus of each adhesive layer  200  may be less than an elastic modulus of each window  100 . Further, a hardness of each adhesive layer  200  may be less than a hardness of each window  100 . 
     Referring to  FIGS.  1  and  3   , the stacked windows  100  and adhesive layers  200  may be cut (S 120 ). The stacked windows  100  and adhesive layers  200  may be cut together by a blade or laser beam  600 . For example, the stacked windows  100  and adhesive layers  200  may be cut using computer numerical control (CNC). As the stacked windows  100  and adhesive layers  200  are cut together, areas of the cut adhesive layers  200  may be substantially equal to areas of the cut windows  100 . This is to say, an area of each adhesive layer  200  is substantially equal to an area of each window  100 . 
     Each of the cut windows  100  may have a size corresponding to a size of one display device. For example, the window  100  may be cut such that each of the cut windows  100  is included in one display device. 
     Referring to  FIGS.  1  and  4   , the cut surfaces of the windows  100  and the adhesive layers  200  may be polished (S 130 ). The cut surfaces of the windows  100  and the adhesive layers  200  may correspond to edges of the cut windows  100  and adhesive layers  200 . 
     The cut surfaces of the windows  100  and the adhesive layers  200  may be polished with a polishing pad  300  while applying slurry  400  to the cut surfaces of the windows  100  and the adhesive layers  200 . The polishing pad  300  may rotate clockwise or counterclockwise along a rotation axis extending in the first direction DR 1 . The slurry  400  may contact the cut surfaces of the windows  100  due to the rotation of the polishing pad  300 , and may directly polish the cut surfaces of the windows  100 . 
     The polishing pad  300  may include a fabric, wool, and/or a polymer. The slurry  400  may include cerium(IV) oxide (CeO 2 ), which may be called “ceria”. 
     An elastic modulus of the polishing pad  300  may be less than an elastic modulus of each window  100 . Further, a hardness of the polishing pad  300  may be less than a hardness of each window  100 . 
       FIG.  5    is a diagram illustrating one window  100  and two adhesive layers  210  and  220 , before polishing, and  FIG.  6    is a diagram illustrating the window  100  and the adhesive layers  210  and  220  after polishing. 
     Referring to  FIGS.  5  and  6   , a first adhesive layer  210  may be formed on a first surface  101  of the cut window  100 , and a second adhesive layer  220  may be formed on a second surface  102  of the cut window  100  opposite to the first surface  101 . For example, the first surface  101  and the second surface  102  of the window  100  may be a lower surface and an upper surface of the window  100 , respectively. 
     The cut surfaces of the window  100  and the adhesive layers  210  and  220  before polishing may be parallel to each other. For example, the edges of the window  100  and the adhesive layers  210  and  220  before polishing might not protrude or recess in a second direction DR 2  crossing the first direction DR 1 . 
     Defects formed during the cutting process of the window  100  may remain on the cut surface of the window  100  before polishing. These defects, if left to remain on the cut surface of the window  100 , might reduce the bending strength of the window  100 . 
     A corner having a right-angled shape in a cross-sectional view may be formed at each of opposite ends of the cut surface of the window  100  before polishing. For example, the cut window  100  may have a rectangular prism shape in which all corners are right angles. However, the corners of the window  100  that were cut will have right angles even if one or more of the other corners of the window  100  are not at right angles. For example, the corner may be formed at each of a first end of the cut surface of the window  100  before polishing where the cut surface contacts the first surface  101  and a second end of the cut surface of the window  100  before polishing where the cut surface contacts the second surface  102 . 
     Edges of the window  100  and the adhesive layers  210  and  220  after polishing might not be parallel to each other. The edge of the window  100  after polishing may protrude in the second direction DR 2  farther than the edges of the adhesive layers  210  and  220  after polishing. 
     As the cut surface of the window  100  is polished, the defects that remain on the cut surface of the window  100  may be removed. Accordingly, the flexural strength of the window  100  may increase by polishing, and the flexural strength of the window  100  after polishing may be relatively large. 
     Since the elastic modulus and the hardness of the adhesive layers  210  and  220  are less than the elastic modulus and the hardness of the window  100 , respectively, the amount of polishing of the adhesive layers  210  and  220  by the polishing pad  300  and the slurry  400  may be greater than the amount of polishing of the window  100  by the polishing pad  300  and the slurry  400 . Accordingly, in addition to the cut surface of the window  100 , the first surface  101  of the window  100  in contact with the first adhesive layer  210  and the second surface  102  of the window  100  in contact with the second adhesive layer  220  may be polished. Accordingly, the window  100  after polishing may include a flat portion  100  that is not polished and a chamfer portion  120  that is polished. The flat portion  110  may overlap the polished adhesive layers  210  and  220 , and may have a uniform thickness TH. The chamfer portion  120  may be disposed on an edge of the flat portion  110 , and may protrude in the second direction DR 2  farther than the polished adhesive layers  210  and  220 . The chamfer portion  120  may correspond to a bezel of the display device including the window  100 . 
     The window  100  may be polished so as to reduce the length thereof in the DR 2  direction by about 10% to about 200% of the thickness TH of the window  100  in the DR 1  direction. A distance in the second direction DR 2  from the edge of the chamfer portion  120  to the edge of the flat portion  110  may be defined as a polishing distance PD, and the polishing distance PD may be about 10% to about 200% of the thickness TH of the window  100 . When the polishing distance PD is less than about 10% of the thickness TH of the window  100 , the polishing pad  300  might not sufficiently polish the cut surface of the window  100 . When the polishing distance PD is greater than about 200% of the thickness TH of the window  100 , a width of the chamfer portion  120  in the second direction DR 2  may increase to a predetermined width or more, accordingly, the bezel of the display device including the window  100  may increase by more than a predetermined width. 
     The polishing distance PD may be controlled based on a polishing pressure and a polishing time. The type of slurry used may also affect polishing distance PD. The polishing distance PD may be proportional to the polishing pressure and the polishing time. For example, the polishing distance PD may decrease as the polishing pressure and the polishing time decrease, and the polishing distance PD may increase as the polishing pressure and the polishing time increase. 
     Referring to  FIGS.  1  and  7   , the windows  100  and the adhesive layers  200  which are polished may be UV-cured (S 140 ). A UV curing machine  700  disposed in the first direction DR 1  from the windows  100  and the adhesive layers  200  which are polished may irradiate the windows  100  and the adhesive layers  200  with ultraviolet (UV) light, so that the windows  100  and the adhesive layers  200  may be UV-cured. The UV curing machine  700  may be or may include, for example, on or more UV lamp, bulb, light-emitting diode (LED), etc. 
     Referring to  FIGS.  1  and  8   , the windows  100  and the adhesive layers  200  which are UV-cured may be heat-cured (S 150 ). The windows  100  and the adhesive layers  200  which are UV-cured may be immersed in a water tank  800  containing hot water HW to heat-cure the windows  100  and the adhesive layers  200 . The hot water HW maybe of a temperature within a range from 22° C. to 100° C. 
     Referring to  FIGS.  1  and  9   , the windows  100  and the adhesive layers  200  which are heat-cured may be separated (S 160 ). The adhesive strengths of the adhesive layers  200  may be reduced through UV-curing and heat-curing, and accordingly, the windows  100  and the adhesive layers  200  may be easily separated from one another. 
     Hereinafter, a method of manufacturing a window according to an embodiment of the present disclosure will be described with reference to  FIGS.  10  to  12   . 
       FIG.  10    is a flowchart illustrating a method of manufacturing a window according to an embodiment of the present disclosure. 
     Referring to  FIG.  10   , a method of manufacturing a window according to an embodiment of the present disclosure may include cutting windows (S 210 ), stacking the windows and adhesive layers (S 220 ), polishing cut surfaces of the windows and the adhesive layers (S 230 ), UV-curing the windows and the adhesive layers (S 240 ), heat-curing the windows and the adhesive layers (S 250 ), and separating the windows and the adhesive layers (S 260 ). In a method for manufacturing the window according to an embodiment of the present disclosure, polishing the cut surfaces of the windows and the adhesive layers (S 230 ), UV-curing the windows and the adhesive layers (S 240 ), heat-curing the windows and the adhesive layers (S 250 ), and separating the windows and the adhesive layers (S 260 ) are substantially the same as or similar to polishing the cut surfaces of the windows and the adhesive layers (S 130 ), UV-curing the windows and the adhesive layers (S 140 ), heat-curing the windows and the adhesive layers (S 150 ), and separating the windows and the adhesive layers (S 160 ) of the method for manufacturing the window discussed above, respectively. Accordingly, to the extent that descriptions of steps S 230 , S 240 , S 250 , and S 260  are not provided herein, it may be assumed that these steps are at least similar to steps S 130 , S 140 , S 150 , and S 160 , respectively. 
       FIGS.  11  and  12    are diagrams illustrating a method of manufacturing the window according to an embodiment of the present disclosure. 
     Referring to  FIGS.  10  and  11   , the windows  100  may be cut (S 210 ). Each of the windows  100  may be individually cut as opposed to being cut in a stack, as explained above. The window  100  may be cut by irradiating the window  100  with a laser beam LB from a laser cutter  900  disposed in the first direction DR 1  from the window  100 . Each of the cut windows  100  may have a size corresponding to the size of one display device. 
     Referring to  FIGS.  10  and  12   , the cut windows  100  and the adhesive layers  200  may be stacked (S 220 ). The windows  100  and the adhesive layers  200  may be alternately stacked along the first direction DR 1 . Areas of the adhesive layers  200  may be substantially equal to areas of the cut windows  100 . Thus, here, the windows  100  and adhesive layers  200  are stacked after cutting as opposed to prior to cutting, which was discussed above. 
       FIG.  13    is a flowchart illustrating a method of manufacturing a window according to an embodiment of the present disclosure. 
     Referring to  FIG.  13   , the method of manufacturing the window according to an embodiment of the present disclosure may include cutting a window (S 310 ), disposing the window between support members (S 320 ), and polishing a cut surface of the window (S 330 ). In the method for manufacturing the window according to an embodiment of the present disclosure, cutting the window (S 310 ) and polishing the cut surface of the window (S 330 ) are substantially the same as or similar to cutting the windows (S 210 ) and polishing the cut surfaces of the windows and the adhesive layers (S 230 ) of the method for manufacturing the window described above, respectively. Accordingly, to the extent that descriptions on the steps S 310  and S 330  are not provided, it may be assumed that these steps are at least similar to the steps of cutting S 210  and polishing S 230  discussed above, respectively. 
       FIG.  14    is a diagram illustrating a method of manufacturing a window according to an embodiment of the present disclosure. 
     Referring to  FIGS.  13  and  14   , the cut window  100  may be disposed between the supporting members  510  and  520  (S 310 ). A first support member  510  may be disposed on a first surface of the cut window  100 , and a second support member  520  may be disposed on a second surface of the cut window  100  opposite to the first surface. The support members  510  and  520  may support the window  100  in the process of polishing the cut window  100 . The support members  510  and  520  may each be a support block (referred to herein simply as “a support”) and these supports  510  and  520  may contain the window  100  and keep it in place by the force of the supports  510  and  520  pushing toward each other like a vice and/or by friction. 
     An area of each of the first support member  510  and the second support member  520  may be less than an area of the window  100  causing the window  100  to overhang the first support member  510  and the second support member  520 . Accordingly, in the process of polishing the cut surface of the window  100 , the first surface of the window  100  which contacts the first support member  510  and the second surface of the window  100  which contacts the second support member  520  as well as the cut surface of the window  100  may be polished. Accordingly, an edge of the polished window  100  may have a curved outer surface. 
     In a method of manufacturing a window according to an embodiment of the present disclosure, the process of stacking the window  100  and an adhesive layer, curing the window  100  and the adhesive layer, and separating the window  100  and the adhesive layer may be omitted because the cut surface of one window  100  is polished without the use of an adhesive layer. 
     In the prior art, a window may be polished in a chemical manner using an etchant. In this case, grains may be formed on a cut surface of the window by a chemical reaction between the etchant and the cut surface of the window, and accordingly, the roughness of the cut surface of the window may increase. When the roughness of the cut surface of the window increases, the impact strength of the cut surface of the window may decrease. In addition, when the window is polished in the chemical manner, an outer surface of an edge of the window may be angled, and accordingly, the impact strength of the cut surface of the window may decrease. 
     Further, in the prior art, chemical substances (e.g., hydrofluoric acid, sulfuric acid, nitric acid, phosphoric acid, etc.) included in the etchant used in chemical polishing may cause environmental pollution. Moreover, an etchant rinse process may be additionally required to remove the chemical substances. 
     In the embodiments of the present invention, the window  100  may be polished in a mechanical manner using the polishing pad  300  and the slurry  400 . In this case, grains might not be formed on the cut surface of the window  100 , and accordingly, the roughness of the cut surface of the window  100  may decrease. Accordingly, the impact strength of the cut surface of the window  100  may increase. Further, when the window  100  is polished in the mechanical manner, the outer surface of the edge of the window  100  may be formed to be rounded, and accordingly, the impact strength of the cut surface of the window  100  may increase. 
     Further, in the embodiments of the present invention, the slurry  400  used in mechanical polishing might not cause environmental pollution because the slurry  400  may simply be an abrasive compound that does not contain a chemical substance. Moreover, since no chemical substances are used in the polishing process of the window  100 , the etchant rinse process of the prior art may be omitted. 
     Hereinafter, a window for a display device according to embodiments of the present disclosure will be described with reference to  FIGS.  15  to  19   . 
       FIG.  15    is a plan view illustrating a window  100  for a display device according to embodiments of the present disclosure.  FIG.  16    is a perspective view illustrating a window  100  for a display device according to an embodiment of the present disclosure.  FIG.  16    may illustrate an example of an area A in  FIG.  15   . 
     Referring to  FIGS.  15  and  16   , a window  100  may include a flat portion  110  and a chamfer portion  120 . The flat portion  110  may have a rectangular shape with rounded corners in a plan view. However, the planar shape of the flat portion  110  is not necessarily limited thereto, and the flat portion  110  may have various planar shapes such as a polygonal planar shape, a circular planar shape, an elliptical planar shape, or the like. 
     The flat portion  110  may have a uniform thickness TH. The thickness TH of the flat portion  110  may be about 20 μm to about 100 μm. When the thickness TH of the flat portion  110  is less than about 20 μm, handling of the window  100  may be difficult, and the window  100  might not sufficiently protect the components of the display device. When the thickness TH of the flat portion  110  is greater than about 100 μm, the flexible characteristic of the window  100  may decrease. 
     The chamfer portion  120  may be disposed on at least a portion of an edge of the flat portion  110 . For example, the chamfer portion  120  may surround at least a portion of the flat portion  110 . In an embodiment of the present disclosure, as illustrated in  FIG.  15   , the chamfer portion  120  may be disposed on an entire edge of the flat portion  110  to fully surround the flat portion  110 . 
     The bezel of the display device may overlap at least the chamfer portion  120 . In an embodiment, the bezel of the display device may overlap an entirety of the chamfer portion  120  and a part of the flat portion  110  adjacent to the chamfer portion  120 , and a black matrix or other light-blocking pattern may be formed on the bezel. 
     The chamfer portion  120  may have a thickness less than the thickness TH of the flat portion  110 . The thickness of the chamfer portion  120  may decrease along the second direction DR 2  from the edge of the flat portion  110  toward the edge of the chamfer portion  120 . 
     The chamfer portion  120  may have a curved outer surface protruding from the flat portion  110 . The outer surface of the chamfer portion  120  may have a relatively small roughness. In an embodiment, the roughness of the outer surface of the chamfer portion  120  may be about 0.5 nm to about 10 nm. As described above, the window  100  may be polished in a mechanical manner using the polishing pad  300  and the slurry  400 , and accordingly, the outer surface of the chamfer portion  120  may have a relatively small roughness (i.e., it may be relatively smooth). Accordingly, the window  100  may have a relatively high impact strength. 
     A distance from the edge of the chamfer portion  120  to the edge of the flat portion  110  may be about 10% to about 200% of the thickness TH of the flat portion  110 . The distance from the edge of the chamfer portion  120  to the edge of the flat portion  110  in the second direction DR 2  may be defined as a polishing distance PD. When the polishing distance PD is less than about 10% of the thickness TH of the flat portion  110 , defects generated during the cutting process of the window  100  may remain on the outer surface of the chamfer portion  120 . When the polishing distance PD is greater than about 200% of the thickness TH of the flat portion  110 , the width of the chamfer portion  120  in the second direction DR 2  may increase to a predetermined width or more, and accordingly, the bezel of the display device including the window  100  may increase by more than a predetermined width. 
     The chamfer portion  120  may include a first curved portion  121  adjacent to a first surface  111  of the flat portion  110  and a second curved portion  122  adjacent to a second surface  112  of the flat portion  110  opposite to the first surface  111 . Each of a radius of curvature RC 1  of the first curved portion  121  and a radius of curvature RC 2  of the second curved portion  122  may be about 10% to about 50% of the thickness TH of the flat portion  110 . 
       FIG.  17    is a perspective view illustrating a window  100  for a display device according to an embodiment of the present disclosure.  FIG.  17    may illustrate an example of the area A in  FIG.  15   . 
     Referring to  FIG.  17   , the chamfer portion  120  may have a uniform radius of curvature RC 3 . The radius of curvature RC 3  of the chamfer portion  120  may be about 50% to about 100% of the thickness TH of the flat portion  110 . 
     The polishing pressure and the polishing time in the process of manufacturing the window  100  discussed here may be greater than the polishing pressure and the polishing time in the process of manufacturing the window  100  discussed above. For example, the polishing distance PD of the window  100  discussed here may be greater than the polishing distance PD of the window  100  discussed above. For example, the polishing distance PD of the window  100  discussed above may be about 20% to about 30% of the thickness TH of the flat portion  110 , and the polishing distance PD of the window  100  discussed here may be about 50% of the thickness TH of the flat portion  110 . 
       FIG.  18    is a perspective view illustrating a window  100  for a display device according to an embodiment of the present disclosure.  FIG.  18    may illustrate an example of the area A in  FIG.  15   .  FIG.  19    is a perspective view illustrating a window  100  for a display device according to an embodiment of the present disclosure.  FIG.  19    may illustrate an example of the area A in  FIG.  15   . 
     Referring to  FIGS.  18  and  19   , the chamfer portion  120  may have different radiuses of curvature from each other along the outer surface of the chamfer portion  120 . The radiuses of curvature RC 4  and RC 5  of the chamfer portion  120  at the edge of the chamfer portion  120  may be about 20% to about 200% of the thickness TH of the flat portion  110 . 
     The outer surface of the chamfer portion  120  adjacent to a surface of the flat portion  110  may have an included angle IA of about 10 degrees to about 30 degrees with respect to an imaginary surface extending from the surface of the flat portion  110 . For example, the included angle IA between the outer surface of the chamfer portion  120  adjacent to the second surface  112  of the flat portion  110  and an imaginary surface extending from the second surface  112  of the flat portion  110  may be about 10 degrees to about 30 degrees. 
     The polishing pressure and the polishing time in the process of manufacturing the window  100  according to an embodiment of the present disclosure may be greater than the polishing pressure and the polishing time in the process of manufacturing the window  100  according to the approach described above, respectively. For example, the polishing distance PD of the window  100  discussed here may be greater than the polishing distance PD of the window  100  discussed above. For example, the polishing distance PD of the window  100  discussed here may be about 100% of the thickness TH of the flat portion  110 . 
     The polishing pressure and polishing time in the process of manufacturing the window  100  according to an embodiment of the present disclosure may be greater than the polishing pressure and the polishing time in the process of manufacturing the window  100  discussed above, respectively. For example, the polishing distance PD of the window  100  discussed here may be greater than the polishing distance PD of the window  100  discussed above. For example, the polishing distance PD of the window  100  discussed here may be about 150% of the thickness TH of the flat portion  110 . 
     In the prior art, the window may be polished in a chemical manner. In this case, the roughness of the cut surface of the window may increase, and the outer surface of the edge of the window may be angled. Accordingly, the impact strength of the cut surface of the window may be reduced. 
     In an embodiments of the present invention, the window  100  may be polished in a mechanical manner. In this case, the roughness of the cut surface of the window  100  may be reduced, and the outer surface of the edge of the window  100  may be rounded. Accordingly, the impact strength of the cut surface of the window  100  may increase. 
     The window according to an embodiments of the present disclosure may be applied to a display device included in a computer monitor, a notebook computer, a mobile phone, a smart phone, a smart pad, a tablet computer, a personal media player (PMP), a personal digital assistant (PDA), an MP3 player, or the like. 
     Although the methods of manufacturing the windows and the windows for the display devices according to the embodiments have been described with reference to the drawings, the illustrated embodiments are examples, and may be modified and changed by a person having ordinary knowledge in the relevant technical field without departing from the technical spirit of the present disclosure.