Patent Publication Number: US-11023010-B2

Title: Panel bottom sheet and display device including the same

Description:
This application is a continuation application of U.S. patent application Ser. No. 15/858,086 filed on Dec. 29, 2017, which claims priority under 35 USC § 119 to Korean Patent Application No. 10-2017-0077355, filed on Jun. 19, 2017, and all the benefits accruing therefrom under 35 U.S.C. § 119, the disclosures of which are incorporated herein in their entirety by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to a panel bottom sheet and a display device including the same. 
     2. Description of the Related Art 
     Organic light-emitting display devices have many advantages such as their excellent luminance, driving voltage, response speed characteristics and capability of realizing multiple colors, and thus have been applied to various products, including smart phones. A typical organic light-emitting display includes a display panel including organic light-emitting elements. In each of the organic light-emitting elements, a cathode electrode and an anode electrode are arranged to face each other with an organic light-emitting layer interposed therebetween. In response to a voltage applied to the cathode and anode electrodes, visible light is generated in the organic light emitting layer to which the cathode and anode electrodes are both connected. 
     A panel bottom sheet is attached to the bottom of a display panel of a display device. The panel bottom sheet may include various functional sheets for protecting the display panel against heat or an external shock. Also, the panel bottom sheet may further include an auxiliary input device (such as a digitizer) or a driving device that is difficult to place on the top of the display panel. 
     The auxiliary device such as a digitizer may include wiring patterns. The wiring patterns are generally formed of a metal. When the display device is used in an outdoor environment, the wiring patterns may become visible on the display screen of the display device because of reflected light by the wiring patterns which cause a serious deterioration of the display quality of the display device. 
     SUMMARY 
     Exemplary embodiments of the present disclosure provide a panel bottom sheet capable of reducing the visibility of wiring patterns. 
     Exemplary embodiments of the present disclosure also provide a display device capable of reducing the visibility of wiring patterns of a panel bottom sheet. 
     However, exemplary embodiments of the present disclosure are not restricted to those set forth herein. The above and other exemplary embodiments of the present disclosure will become more apparent to one of ordinary skill in the art to which the present disclosure pertains by referencing the detailed description of the present disclosure given below. 
     According to an exemplary embodiment of the present disclosure, there is provided a panel bottom sheet. The panel bottom sheet comprises a first base, a first light-absorbing layer disposed on a top surface or a bottom surface of the first base, a top bonding layer disposed above the first base and the first light-absorbing layer, an interlayer bonding layer disposed below the first base and the first light-absorbing layer, and a wiring pattern portion disposed below the interlayer bonding layer and including a plurality of wiring patterns. 
     According to an exemplary embodiment of the present disclosure, there is provided a display device. The display device comprises a display panel, and a panel bottom sheet disposed below the display panel, wherein the panel bottom sheet includes a first base, a first light-absorbing layer disposed on a top surface or a bottom surface of the first base, a top bonding layer disposed above the first base and the first light-absorbing layer, an interlayer bonding layer disposed below the first base and the first light-absorbing layer, and a wiring pattern portion disposed below the interlayer bonding layer and including a plurality of wiring patterns. 
     According to the aforementioned and other exemplary embodiments of the present disclosure, the visibility of wiring patterns can be reduced by reducing light reflected by wiring patterns or height differences formed by the wiring patterns. 
     Other features and exemplary embodiments may be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other exemplary embodiments and features of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which: 
         FIG. 1  is a perspective view of a display device according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is an exploded perspective view of the display device according to the exemplary embodiment of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along line III-III′ of  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of a panel bottom sheet according to an exemplary embodiment of the present disclosure; 
         FIG. 5  is a cross-sectional view illustrating the path of light in a panel bottom sheet in which a first light-absorbing layer is disposed on the top surface of a cover base; 
         FIG. 6  is a cross-sectional view illustrating the path of light in a panel bottom sheet in which a first light-absorbing layer is disposed on the bottom surface of a cover base; 
         FIG. 7  is a cross-sectional view of a panel bottom sheet according to another exemplary embodiment of the present disclosure; 
         FIG. 8  is a cross-sectional view of a panel bottom sheet according to another exemplary embodiment of the present disclosure; 
         FIGS. 9 and 10  are cross-sectional views of panel bottom sheets according to other exemplary embodiments of the present disclosure; 
         FIG. 11  is a cross-sectional view of a panel bottom sheet according to another exemplary embodiment of the present disclosure; 
         FIG. 12  is a layout view of a digitizer according to an exemplary embodiment of the present disclosure; 
         FIG. 13  is a cross-sectional view taken along line XIII-XIII′ of  FIG. 12 ; 
         FIG. 14  is a cross-sectional view showing the digitizer according to the exemplary embodiment of  FIG. 12  in a bent state; 
         FIG. 15  is a cross-sectional view of a digitizer according to another exemplary embodiment of the present disclosure; and 
         FIG. 16  is a layout view of a digitizer according to another exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Advantages and features of the present disclosure and methods of accomplishing the same may be understood more readily by reference to the following detailed description of exemplary embodiments and the accompanying drawings. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the present disclosure to those skilled in the art, and the present disclosure will only be defined within the scope of the appended claims. 
     Cases where elements or layers are referred to as being located “on” other elements or layers include all the cases where other layers or other elements are interposed directly on or between other elements. Meanwhile, cases where the elements are “directly on” indicate that no other element or layer is interposed therebetween. Same reference numerals refer to the same constituent elements throughout the specification. Term ‘and/or” includes each and every combination of one or more of the referenced items. 
     It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, a first element discussed below could be termed a second element without departing from the teachings of the present invention. Exemplary embodiments of the present disclosure will hereinafter be described with reference to the accompanying drawings. 
       FIG. 1  is a perspective view of a display device according to an exemplary embodiment of the present disclosure.  FIG. 2  is an exploded perspective view of the display device according to the exemplary embodiment of  FIG. 1 .  FIG. 3  is a cross-sectional view taken along line III-III′ of  FIG. 2 . 
     Referring to  FIGS. 1 through 3 , a display device  70  includes a display panel  20  and a panel bottom sheet  10  disposed below the display panel  20 . The display device  70  may further include a window  40  disposed above the display panel  20 . The display device  70  may further include a bracket  60  disposed below the panel bottom sheet  10 . 
     Unless specified otherwise, the terms “upper”, “top” or “top surface”, and “above,” as used herein, refer to a display surface side of the display panel  20 , and the terms “lower”, “bottom” or “bottom surface”, or “below,” as used herein, refer to an opposite side to the display surface side of the display panel  20 . 
     The display device  70  may be rectangular in a plan view. The display device  70  may have two long sides and two short sides. The long sides and the short sides of the display device  70  meet at a right angle. Alternatively, as illustrated in  FIG. 1 , the long sides and the short sides of the display device  70  meet to form curved surfaces, as illustrated in  FIG. 1 . The planar shape of the display device  70  is not particularly limited, and the display device  70  may be in a shape other than a rectangular shape such as, for example, a circular shape, in a plan view. 
     The display panel  20  is a panel for displaying an image and may be, for example, an organic light-emitting display panel. The display panel  20  will hereinafter be described as being an organic light-emitting display panel, but various types of display panels other than an organic light-emitting display panel, such as, for example, a liquid crystal display (LCD) panel, an electrophoretic display panel, or the like may be used as the display panel  20 . 
     The display panel  20  includes a plurality of organic light-emitting elements disposed on a substrate. The substrate may be a rigid substrate formed of, for example, glass, or may be a flexible substrate formed of, for example, polyimide (PI). In a case where a PI substrate is used as the substrate, the display panel  20  may be a flexible panel such as a bendable panel, a foldable panel and a rollable panel. 
     The window  40  is disposed above the display panel  20 . The window  40  protects the display panel  20  from an external shock from the display surface side and allows the transmission of light emitted from the display panel  20 . The window  40  may be formed of, for example, glass. 
     The window  40  may be disposed to overlap with the display panel  20  and to cover the entire surface of the display panel  20 . The window  40  may be larger in size than the display panel  20 . For example, the window  40  may protrude beyond the display panel  20  on both short sides of the display device  70 . The window  40  may also protrude beyond the display panel  20  on both long sides of the display device  70 , but the distance by which the window  40  may protrude beyond the display panel  20  on both short sides of the display device  70  may be greater than the distance by which the window  40  may protrude beyond the display panel  20  on both long sides of the display device  70 . 
     In one exemplary embodiment, a touch member  30  may be disposed between the display panel  20  and the window  40 . The touch member  30  may be a rigid panel type, a flexible panel type, or a film type. The touch member  30  may have substantially the same size as the display panel  20  and may be disposed to overlap with the display panel  20  so that the sides thereof can be aligned with the sides of the display panel  20 , but the present disclosure is not limited thereto. The display panel  20  and the touch member  30  may be bonded together by a transparent bonding layer  52  such as an optically clear adhesive (OCA) or an optically clear resin (OCR), and the touch member  30  and the window  40  may be bonded together by a transparent bonding layer  53  such as an OCA or an OCR. The touch member  30  may be omitted, in which case, the display panel  20  and the window  40  may be bonded together by an OCA or an OCR. In one exemplary embodiment, the display panel  20  may include a touch member  30 . 
     The panel bottom sheet  10  is disposed below the display panel  20 . The panel bottom sheet  10  includes a top bonding layer ( 130  of  FIG. 4 ) at an uppermost portion thereof and may be attached to the bottom surface of the display panel  20  via the top bonding layer  130 . 
     The panel bottom sheet  10  may have substantially the same size as the display panel  20  and may be disposed to overlap with the display panel  20  so that the sides thereof can be aligned with the sides of the display panel  20 , but the present disclosure is not limited thereto. The panel bottom sheet  10  may perform a heat dissipation function, an electromagnetic shielding function, a pattern visibility prevention function, a grounding function, a buffer function, a reinforcement function, and/or a digitizing function, and may include at least one functional layer having at least one of these functions of the panel bottom sheet  10 . The functional layer may be provided in various forms such as a layer, a film, a sheet, a plate, or a panel. 
     The panel bottom sheet  10  may include one or more functional layers. In a case where the panel bottom sheet  10  includes a plurality of functional layers, the functional layers may be stacked to overlap with one another. The functional layers may be stacked directly on one another or may be stacked indirectly via bonding layers. 
     Various example of the panel bottom sheet  10  will be described later. 
     The bracket  60  is disposed below the panel bottom sheet  10 . The bracket  60  receives the window  40 , the touch member  30 , the display panel  20 , and the panel bottom sheet  10  therein. The bracket  60  may have a bottom surface and sidewalls. The bottom surface of the bracket  60  is opposite to the bottom surface of the panel bottom sheet  10 , and the sidewalls of the bracket  60  faces the sides of each of the window  40 , the touch member  30 , the display panel  20 , and the panel bottom sheet  10 . The panel bottom sheet  10  includes a bottom bonding member  450  of  FIG. 11  at a lowermost portion thereof and may be attached to the bottom surface of the bracket  60  via the bottom bonding member  450 . 
     Although not specifically illustrated, waterproof tapes may be disposed along the edges of the bottom surface of the bracket  60 . The waterproof tapes disposed along the long sides of the bracket  60  may be attached to the bottom surface of the panel bottom sheet  10 , and the waterproof tapes disposed along the short sides of the bracket  60  may be attached to the bottom surface of the window  40 . 
     In one exemplary embodiment, the display device  70  may include a flat area FA and bending areas BA connected to the flat area FA and disposed adjacent to the flat area FA. The flat area FA may be disposed substantially on one plane. The bending areas BA are not on the same plane as the flat area FA. For example, the bending areas BA may be bent downwardly from the plane where the flat area FA is disposed. 
     In one exemplary embodiment, the bending areas BA may have outwardly convex surfaces. In another exemplary embodiment, the bending areas BA may have flat surfaces that are disposed on a plane having a predetermined angle with respect to the plane of the flat area FA. 
     The bending areas BA may be provided on both long sides of the display device  70 , which is rectangular, or on one of the long sides of the display device  70 . Although not specifically illustrated, the display device  70  may also be bent on the short sides thereof. 
     The display panel  20 , the touch member  30 , the window  40 , and the panel bottom sheet  10  may all be positioned in both the flat area FA and the bending areas BA. 
     In an alternative exemplary embodiment, the display device  70  may be a flat display device only having the flat area FA. Thus, all the aspects of the display device  70  discussed herein, except for those specifically related to the bending areas BA, may be directly applicable not only to a bendable display device, but also to a flat display device. 
     The panel bottom sheet  10  will hereinafter be described in further detail. 
       FIG. 4  is a cross-sectional view of a panel bottom sheet according to an exemplary embodiment of the present disclosure. For convenience,  FIG. 4  illustrates a generally flat panel bottom sheet. The flat panel bottom sheet of  FIG. 4  maintains its shape when attached to a flat display panel. However, when attached to a curved display panel, the flat panel bottom sheet may be bent along the curved display panel and may have a flat area and bending areas. This directly applies not only to the panel bottom sheet of  FIG. 4 , but also to panel bottom sheets of  FIGS. 5 through 11 and 13 . 
     Referring to  FIG. 4 , a panel bottom sheet  11  includes a cover panel portion  100  and a wiring pattern portion  200  disposed below the cover panel portion  100 . 
     The cover panel portion  100  includes a cover base  110 , a first light-absorbing layer  120 , a top bonding layer  130  disposed on the top surface of the first light-absorbing layer  120 , a first release film  160  disposed on the top surface of the top bonding layer  130 , and a first interlayer bonding layer  140  disposed on the bottom surface of the cover base  110 . 
     The cover base  110  may be formed of polyethylene terephthalate (PET), PI, polycarbonate (PC), polyethylene (PE), polypropylene (PP), polysulfone (PSF), polymethyl methacrylate (PMMA), triacetyl cellulose (TAC), or a cyclo-olefin polymer (COP). 
     The first light-absorbing layer  120  is disposed on the top surface of the cover base  110 . The first light-absorbing layer  120  is disposed directly on the top surface of the cover base  110 . The first light-absorbing layer  120  may be disposed to completely cover wiring patterns  200   a . The first light-absorbing layer  120  may be disposed on the entire top surface of the cover base  110 . 
     The first light-absorbing layer  120  blocks transmission of light therethrough and thus prevents the wiring pattern  200   a  of a wiring pattern portion  200  from being visible from thereabove. The first light-absorbing layer  120  may comprise a light-absorbing material such as, for example, a black dye or pigment. The first light-absorbing layer  120  may comprise a black ink. The first light-absorbing layer  120  may be formed on the top surface of the cover base  110  by a coating or printing method. The first light-absorbing layer  120  will be described later in detail. 
     The top bonding layer  130  is disposed on the top surface of the first light-absorbing layer  120 . The top bonding layer  130  attaches the panel bottom sheet  11  to the bottom surface of the display panel  20 . The top bonding layer  130  may include an adhesive layer or a resin layer. For example, the top bonding layer  130  may comprise a polymer material such as a silicone polymer, a urethane polymer, a silicone-urethane (SU) hybrid polymer, an acrylic polymer, an isocyanate polymer, a polyvinyl alcohol polymer, a gelatin polymer, a vinyl polymer, a latex polymer, a polyester polymer, or a water-based polyester polymer. 
     The first release film  160  is disposed on the top surface of the top bonding layer  130 . The first release film  160  covers and protects the top surface of the top bonding layer  130  when the panel bottom sheet  11  is yet to be attached to the display panel  20 . Then, when the panel bottom sheet  11  is attached to the display panel  20 , the first release film  160  is peeled off and thus exposes the top surface of the top bonding layer  130 , which becomes a bonding surface. 
     The first release film  160  may be placed in contact with the top bonding member  130 , but may not be completely attached on the top bonding member  130  so as to be able to be peeled off later. The first release film  160  may comprise PET, PC, PI, or paper. In order to improve the release force of the first release film  160 , the top surface of the first release film  160  may be treated with a silicon solution or coated with a release coating layer, but the present disclosure is not limited to this. 
     In some exemplary embodiments, the bottom surface of the first release film  160  may have an embossed shape. The embossed shape of the bottom surface of the first release film  16  may be transferred to the top surface of the top bonding layer  130 , which is attached to the first release film  16 , and as a result, the top surface of the top bonding layer  130  may have an embossed shape that is complementary to the embossed shape of the bottom surface of the first release film  160 . In a case where the top surface of the top bonding layer  130  has an embossed shape, the embossed shape of the top surface of the top bonding layer  130  serves as an air passage during the attachment of the panel bottom sheet  11  to the bottom surface of the display panel  20 , and may thus reduce air bubbles between the display panel  20  and the panel bottom sheet  11 . Once the top bonding layer  130  is completely attached to the bottom of the display panel  20 , the embossed shape of the top surface of the top bonding layer  130  may collapse and may be planarized, as illustrated in  FIG. 5 . 
     The first interlayer bonding layer  140  is disposed on the bottom surface of the cover base  110 . The first interlayer bonding layer  140  may bond the cover base  110  and the wiring pattern portion  200  together. That is, the first interlayer bonding layer  140  may bond the cover panel portion  100  to the wiring pattern portion  200 , which is disposed below the cover panel portion  100 . In the exemplary embodiment of  FIG. 4 , the first interlayer bonding layer  140  may be included in the cover panel portion  100 , but alternatively, the first interlayer bonding layer  140  may be included in the wiring pattern portion  200  or may be provided as a separate member. 
     The first interlayer bonding layer  140  may be formed of one of the aforementioned examples of the material of the top bonding layer  130 . 
     The wiring pattern portion  200  may include the wiring patterns  200   a  and a plurality of insulating layers ( 200   b  and  200   c ) covering the wiring patterns  200   a  from above and below, respectively. Specifically, the wiring pattern portion  200  may include a first insulating layer  200   b , the wiring patterns  200   a  disposed on the top surface of the first insulating layer  200   b , and a second insulating layer  200   c  covering the top surfaces of the wiring patterns  200   a . The wiring patterns  200   a  cover some parts of the top surface of the first insulating layer  200   b  and expose other parts of the top surface of the first insulating layer  200   b . The second insulating layer  200   c  may be disposed not only on the top surface and the sides of each of the wiring patterns  200   a , but also on the exposed parts of the top surfaces of the first insulating layer  200   b.    
     The wiring patterns  200   a  may comprise a metal material such as, for example, copper (Cu), silver (Ag), nickel (Ni), or tungsten (W). The wiring patterns  200   a  may be formed as single films or stacks of a plurality of films. In one exemplary embodiment, each of the wiring patterns  200   a  may be a double layered film including a lower Cu film and an upper Cu film. The wiring patterns  200   a  may be wirings or electrodes transmitting signals. Also, the wiring patterns  200   a  may be floating wirings or electrodes. 
     The first and second insulating layers  200   b  and  200   c  may comprise an organic insulating material, an inorganic insulating material, or an organic-inorganic hybrid insulating material or may comprise a bonding material such as an adhesive material. 
     In one exemplary embodiment, the wiring pattern portion  200  may be a digitizer. The digitizer, unlike an input device such as a keyboard or a mouse, receives information regarding a position on a screen, designated by a user. The digitizer recognizes the movement of, for example, a stylus pen, and converts the recognized movement into a digital signal. The digitizer may be provided in the form of a thin film or a panel. In a case where the wiring pattern portion  200  is a digitizer, the structure of the digitizer will be described later with reference to  FIGS. 12 through 15 . However, the present disclosure is not limited to this. That is, alternatively, other various members with wiring patterns, such as a printed circuit board (PCB) or a flexible PCB (FPCB), may be used as the wiring pattern portion  200 . 
     The cover base  110 , the first light-absorbing layer  120 , the top bonding layer  130 , the first release film  160 , and the first interlayer bonding layer  140  of the cover panel portion  100  and the first and second insulating layers  200   b  and  200   c  of the wiring pattern portion  200  may all overlap with one another, and the sides of each of the cover base  110 , the first light-absorbing layer  120 , the top bonding layer  130 , the first release film  160 , and the first interlayer bonding layer  140  of the cover panel portion  100  and the sides of each of the first and second insulating layers  200   b  and  200   c  of the wiring pattern portion  200  may all be aligned. The sides of each of the cover base  110 , the first light-absorbing layer  120 , the top bonding layer  130 , the first release film  160 , and the first interlayer bonding layer  140  of the cover panel portion  100  and the sides of each of the first and second insulating layers  200   b  and  200   c  of the wiring pattern portion  200  may be cutting planes. For example, in a case where the panel bottom sheet  11  is obtained by fabricating and cutting a mother panel bottom sheet, the sides of each of the first light-absorbing layer  120 , the top bonding layer  130 , the first release film  160 , and the first interlayer bonding layer  140  of the cover panel portion  100  and the sides of each of the first and second insulating layers  200   b  and  200   c  of the wiring pattern portion  200  may all be cutting planes and may all be aligned. 
     In a case where the wiring patterns  200   a  are formed of a material such as a metal, the wiring patterns  200   a  may have a high reflectivity and may thus be able to well reflect light incident from thereabove. However, if the light reflected by the wiring patterns  200   a  is emitted toward a display screen, the wiring patterns  200   a  may be recognized by a user, thereby adversely affecting the display quality of the display device  70 . 
     Since the wiring patterns  200   a  are formed only on parts of the top surface of the first insulating layer  200   b , height differences may be formed between areas where the wiring patterns  200   a  are disposed and areas where the wiring patterns  200   a  are not disposed. The height differences may be transferred onto the layers formed on the wiring patterns  200   a . That is, for convenience,  FIG. 4  illustrates an example in which the top surface of the second insulating layer  200   c  is flat, but the second insulating layer  200   c  may be conformally formed on the wiring patterns  200   a  and may thus have an uneven top surface, rather than a flat top surface. The uneven top surface of the second insulating layer  200   c  may affect the layers formed on the second insulating layer  200   c , i.e., the first interlayer bonding layer  140 , the cover base  110 , and the first light-absorbing layer  120 , and as a result, the surfaces of the first interlayer bonding layer  140 , the cover base  110 , and the first light-absorbing layer  120  may become at least partially uneven. The uneven surfaces of the first interlayer bonding layer  140 , the cover base  110 , and the first light-absorbing layer  120  may affect the reflectance or the reflection angle of incident light (i.e., the emission direction of reflected light) so that particular patterns may become visible on the display screen. 
     The first light-absorbing layer  120  prevents reflected light from being emitted toward the display screen. The first light-absorbing layer  120  primarily prevents light from being downwardly transmitted therethrough and also prevents reflected light from being upwardly transmitted therethrough. 
     In order to prevent the wiring patterns  200   a  from becoming visible, the first light-absorbing layer  120  may be formed to be sufficiently thick. If the thickness of the first light-absorbing layer  120  is about 2 μm or more, the first light-absorbing layer  120  may have an optical density (OD) of 3.4 or more and may thus be able to sufficiently lower the reflectivity of the wiring patterns  200   a  with respect to the display screen, and as a result, the wiring patterns  200   a  may be prevented from becoming visible. If the thickness of the first light-absorbing layer  120  is about 4 μm or more, the first light-absorbing layer  120  may have an OD of 4 or more, and as a result, the wiring patterns  200   a  may be prevented from becoming visible, even if height differences formed by the wiring patterns  200   a  make the surfaces of the layers formed on the wiring patterns  200   a  to have uneven surface. 
     The thicker the first light-absorbing layer  120 , the higher the OD of the first light-absorbing layer  120 . However, the thickness of the first light-absorbing layer  120  may preferably be set to be about 10 μm or less in consideration of coating or printing efficiency, durability, and the thickness of the display device  70 . 
     In the exemplary embodiment of  FIG. 4 , the first light-absorbing layer  120  may be disposed on the top surface of the cover base  110 , but alternatively, the first light-absorbing layer  120  may be disposed on the bottom surface of the cover base  110 . The light absorption ratio of the first light-absorbing layer  120  may slightly differ depending on whether the first light-absorbing layer  120  is disposed on the top surface or the bottom surface of the cover base  110 , and this will hereinafter be described with reference to  FIGS. 5 and 6 . 
       FIG. 5  is a cross-sectional view illustrating the path of light in a panel bottom sheet in which a first light-absorbing layer is disposed on the top surface of a cover base.  FIG. 6  is a cross-sectional view illustrating the path of light in a panel bottom sheet in which a first light-absorbing layer is disposed on the bottom surface of a cover base.  FIGS. 5 and 6  illustrate a top bonding layer  131  as being attached on the bottom surface of a display panel  20 . In each of the panel bottom sheets of  FIGS. 5 and 6 , a first release film  160  is already removed and thus no longer exists, and the top surface of the top bonding layer  131  is planarized. 
     Referring to  FIG. 5 , light L 1  is obliquely incident on a display panel  20  and arrives at a first light-absorbing layer  120  through the top bonding layer  130 . The first light-absorbing layer  120  absorbs some of the light L 1  and transmits some of the light L 1  downwardly therethrough. The light transmitted downwardly through the first light-absorbing layer  120  is reflected by wiring patterns  200   a  to travel upwardly. The light traveling upwardly arrives at the first light-absorbing layer  120 , and the first light-absorbing layer  120  absorbs at least some of the light arriving thereat. Some of the light not absorbed by the first light-absorbing layer  120 , i.e., light L 2 , may be emitted upwardly through the top bonding layer  130 . Since a considerable amount of light can be absorbed by the first light-absorbing layer  120 , the amount of light (i.e., the light L 2 ) reflected from the wiring patterns  200   a  and then finally emitted through the first light-absorbing layer  120  is much smaller than the amount of original incident light (i.e., the light L 1 ). 
     Referring to  FIG. 6 , light L 1  is obliquely incident on a display panel  20  and arrives at a first light-absorbing layer  120  through the top bonding layer  131  and a cover base  110 . The light L 1  is reflected at the interface between the top bonding layer  131  and the cover base  110 . The reflectance and reflection angle of the reflected light, i.e., light L 3 , may vary depending on the degree of unevenness on the surface of the cover base  110 . 
     Light transmitted through the cover base  110  arrives at the first light-absorbing layer  120 , and some of the light arriving at the first light-absorbing layer  120 , i.e., light L 2 , may be absorbed by the first light-absorbing layer  120  and some of the light arriving at the first light-absorbing layer  120  may be transmitted through the first light-absorbing layer  120  and reflected by the wiring patterns  200   a  upwardly along substantially the same path as the light L 2  of  FIG. 5 . 
     In response to the light L 1  being obliquely incident on the side of the display panel  20 , the panel bottom sheet of  FIG. 6  emits more light than the panel bottom sheet of  FIG. 5  by as much as the light L 3 . Since light (such as the light L 2  and the light L 3 ) emitted from the panel bottom sheet of  FIG. 6  adversely affects the visibility of wiring patterns  200   a , the panel bottom sheet of  FIG. 5 , which emits a relatively small amount of light, may be more advantageous than the panel bottom sheet of  FIG. 6  in terms of preventing the wiring patterns  200   a  from becoming visible. The absolute amount of the light L 3  reflected at the interface between the top bonding layer  131  and the cover base  110  is not small even when the difference in refractive index between the top bonding layer  131  and the cover base  110  is small, and the visibility of the wiring patterns  200   a  may be varied by even a slight difference in emitted light. Thus, the difference between the panel bottom sheet of  FIG. 5  and the panel bottom sheet of  FIG. 6  may produce a significant difference in the visibility of the wiring patterns  200   a . Accordingly, in general circumstances, one of the panel bottom sheet of  FIG. 5  and the panel bottom sheet of  FIG. 6  may be chosen, but in a case where the wiring patterns  200   a  of the panel bottom sheet of  FIG. 6  appear visible, the panel bottom sheet of  FIG. 5  may be considered instead of the panel bottom sheet of  FIG. 6 . 
     Panel bottom sheets according to other exemplary embodiments of the present disclosure will hereinafter be described. In  FIGS. 4 through 11 , like reference numerals denote like elements, and thus, descriptions thereof will be omitted or at least simplified. 
       FIG. 7  is a cross-sectional view of a panel bottom sheet according to another exemplary embodiment of the present disclosure.  FIG. 7  shows that a plurality of light-absorbing layers can be provided. 
     Referring to  FIG. 7 , a panel bottom sheet  12  differs from the panel bottom sheet  11  of  FIG. 4  in that a cover panel portion  101  further includes a second light-absorbing layer  121  disposed on the bottom surface of a cover base  110 . That is, a first light-absorbing layer  120  is disposed on the top surface of the cover base  110 , and a second light-absorbing layer  121  is disposed on the bottom surface of the cover base  110 . A first interlayer bonding layer  140  is disposed on the bottom surface of the second light-absorbing layer  121 . The second light-absorbing layer  121  may be formed of the same material as the first light-absorbing layer  120 , but the present disclosure is not limited thereto. The second light-absorbing layer  121  may have the same size, and the sides of the second light-absorbing layer  121  may be aligned with the sides of the first light-absorbing layer  120 . 
     In the exemplary embodiment of  FIG. 7 , the first and second light-absorbing layers  120  and  121  are disposed on the top surface and the bottom surface, respectively, of the cover base  110 , and light L 1  obliquely incident on a display panel  20  may be absorbed by both the first and second light-absorbing layers  120  and  121 . Accordingly, the amount of reflected light finally emitted can be reduced. The light absorption ratio of the panel bottom sheet  12  is generally proportional to the sum of the thicknesses of the first and second light-absorbing layers  120  and  121 . Thus, in order for the panel bottom sheet  12  to have substantially the same OD as the panel bottom sheet  11  according to the exemplary embodiment of  FIG. 4 , the sum of the thicknesses of the first and second light-absorbing layers  120  and  121  may be set to be in the range of about 2 μm to about 10 μm. Alternatively, each of the thicknesses of the first and second light-absorbing layers  120  and  121  may be set to be in the range of about 2 μm to about 10 μm, in which case, the OD of the panel bottom sheet  12  may be further improved if the sum of the thicknesses of the first and second light-absorbing layers  120  and  121  exceeds 10 μm. For example, the first and second light-absorbing layers  120  and  121  may have the same thickness of about 4 μm, but the present disclosure is not limited thereto. 
       FIG. 8  is a cross-sectional view of a panel bottom sheet according to another exemplary embodiment of the present disclosure.  FIG. 8  shows that a plurality of light-absorbing layers can be provided. 
     Referring to  FIG. 8 , a cover panel portion  102  of a panel bottom sheet  13  includes first and second light-absorbing layers  122  and  123 . 
     The first light-absorbing layer  122  includes first through fourth unit layers  122   a  through  122   d , which are sequentially stacked on the top surface of a cover base  110  along an upward direction. A top bonding layer  130  is disposed on the top surface of the fourth unit layer  122   d.    
     The second light-absorbing layer  123  includes first through fourth unit layers  123   a  through  123   d , which are sequentially stacked on the bottom surface of the cover base  110  along a downward direction. A first interlayer bonding layer  140  is disposed on the bottom surface of the fourth unit layer  123   d.    
     The first through fourth unit layers  122   a  through  122   d  and the first through fourth unit layers  123   a  through  123   d  may be formed of the same material as the first light-absorbing layer  120 . The first through fourth unit layers  122   a  through  122   d  and the first through fourth unit layers  123   a  through  123   d  may comprise the same material, but the present disclosure is not limited thereto. 
     The first through fourth unit layers  122   a  through  122   d  and the first through fourth unit layers  123   a  through  123   d  may all have the same thickness. The thickness of the first light-absorbing layer  122  may be determined by the sum of the thicknesses of the first through fourth unit layers  122   a  through  122   d , and the thickness of the second light-absorbing layer  123  may be determined by the sum of the thicknesses of the first through fourth unit layers  123   a  through  123   d . If the first through fourth unit layers  122   a  through  122   d  and the first through fourth unit layers  123   a  through  123   d  all have the same thickness of, for example, about 1 μm, the thicknesses of the first and second light-absorbing layers  122  and  123  may both be about 4 μm. 
     The first through fourth unit layers  122   a  through  122   d  and the first through fourth unit layers  123   a  through  123   d  may be formed by printing. The first unit layers  122   a  and  123   a  may be 1-degree printed layers, the second unit layers  122   b  and  123   b  may be 2-degree printed layers, the third unit layers  122   c  and  123   c  may be 3-degree printed layers, and the fourth unit layers  122   d  and  123   d  may be 4-degree printed layers. More vivid colors can be obtained by printing the same colors multiple times. In the exemplary embodiment of  FIG. 8 , the first through fourth unit layers  122   a  through  122   d  and the first through fourth unit layers  123   a  through  123   d  may all appear black, thereby achieving a vivid black color, and this means that the light absorption efficiency of the first and second light-absorbing layers  122  and  123  can be further improved. The first through fourth unit layers  122   a  through  122   d  and the first through fourth unit layers  123   a  through  123   d  may also be formed by a method other than printing. 
     In the exemplary embodiment of  FIG. 8 , the first and second light-absorbing layers  122  and  123  both include four unit layers, but the present disclosure is not limited thereto. That is, the first and second light-absorbing layers  122  and  123  may include two, three, or five or more unit layers. Also, the number of unit layers of the first light-absorbing layer  122  may differ from the number of unit layers of the second light-absorbing layer  123 . Since the OD of the cover panel portion  102  is generally proportional to the sum of the thicknesses of the unit layers of the first light-absorbing layer  122  and the thicknesses of the unit layers of the second light-absorbing layer  123 , the first and second light-absorbing layers  122  and  123  may be formed by stacking various numbers of unit layers in accordance with a desired OD. 
       FIGS. 9 and 10  are cross-sectional views of panel bottom sheets according to other exemplary embodiments of the present disclosure. Referring to  FIGS. 9 and 10 , panel bottom sheets  14  and  15  differ from the panel bottom sheet  12  according to the exemplary embodiment of  FIG. 7  in that they further include a buffer portion  300 . The buffer portion  300  may include a buffer member  310  and a second interlayer bonding layer  320 . 
     The buffer member  310  absorbs an external shock and thus prevents the display device  70  from being damaged. The buffer member  310  may be formed as a single film or a stack of a plurality of films. The buffer member  310  may be formed of a material with elasticity such as, for example, a polyurethane (PU) or PE resin. The buffer member  310  may be a cushion layer. 
     The second interlayer bonding layer  320  bonds the buffer member  310  to another member and may be formed of one of the aforementioned examples of the material of the top bonding layer  130  of the panel bottom sheet  11  according to the exemplary embodiment of  FIG. 4 . In the exemplary embodiments of  FIGS. 9 and 10 , the second interlayer bonding layer  320  may be included in the buffer portion  300 . Alternatively, the second interlayer bonding layer  320  may be included in another member or may be provided as a separate member. 
     In one exemplary embodiment, the buffer member  310  may be disposed between a cover panel portion  102  and a wiring pattern portion  200 , as illustrated in  FIG. 9 . In this example, the second interlayer bonding layer  320  is disposed on the bottom surface of the buffer member  310  and is bonded to the wiring pattern portion  200 . The top surface of the buffer member  310  is bonded to a first interlayer bonding layer  140 . 
     In another exemplary embodiment, the buffer member  310  may be disposed below the wiring pattern portion  200 , as illustrated in  FIG. 10 . In this example, the second interlayer bonding layer  320  is disposed on the top surface of the buffer member  310  and is bonded to the wiring pattern portion  200 . 
       FIG. 11  is a cross-sectional view of a panel bottom sheet according to another exemplary embodiment of the present disclosure. Referring to  FIG. 11 , a panel bottom sheet  16  differs from the panel bottom sheet  14  according to the exemplary embodiment of  FIG. 9  in that it further includes a heat dissipation portion  400 . 
     Specifically, the heat dissipation portion  400  may be disposed below a wiring pattern portion  200 . The heat dissipation portion  400  may include at least one heat dissipation layer.  FIG. 11  illustrates an example in which the heat dissipation portion  400  includes two heat dissipation layers, i.e., first and second heat dissipation layers  410  and  420 . 
     The first and second heat dissipation layers  410  and  420  may be formed of the same material or may be formed of materials having different heat dissipation characteristics. The first heat dissipation layer  410  may include, for example, a metal film such as a Cu or Ag film. The second heat dissipation layer  420  may include, for example, graphite or carbon nanotubes (CNTs). 
     The second heat dissipation layer  420  may be disposed above the first heat dissipation layer  410 . The first and second heat dissipation layers  410  and  420  may be disposed to overlap with each other. The second heat dissipation layer  420  may be smaller in size than the first heat dissipation layer  410 , and the sides of the second heat dissipation layer  420  may be positioned more inwardly than the sides of the first heat dissipation layer  410 . For example, in response to the panel bottom sheet  16  being bonded to a bent display panel  20 , the first heat dissipation layer  410  may be disposed in both a flat area FA and bending areas BA. On the other hand, the second heat dissipation layer  420  may be disposed in the flat area FA, but not in the bending areas BA. This type of arrangement may be employed in a case where the second heat dissipation layer  420  is formed of a material with relatively poor bending characteristics such as, for example, graphite, or is too thick to be properly bent. 
     The second heat dissipation layer  420  is covered by a third interlayer bonding layer  430 , and the third interlayer bonding layer  430  is bonded to the wiring pattern portion  200 , which is disposed above the third interlayer bonding layer  430 . A fourth interlayer bonding layer  440  may be interposed between the second heat dissipation layer  420  and the first heat dissipation layer  410  and may bond the second heat dissipation layer  420  and the first heat dissipation layer  410  together. The second heat dissipation layer  420  may expose edge portions of the fourth interlayer bonding layer  440 , and the top surfaces of the edge portions of the fourth interlayer bonding layer  440  may be placed in direct contact with, and bonded to, the third interlayer bonding layer  430 , which is disposed above the fourth interlayer bonding layer  440 . 
     The heat dissipation portion  400  may further include a bottom bonding member  450  and a second release film  460 . The bottom bonding member  450  may be disposed on the bottom surface of the first heat dissipation layer  410  and bonds the panel bottom sheet  16  to a bracket  60 , which may be disposed below the panel bottom sheet  16 , as illustrated in  FIG. 3 . 
     In one exemplary embodiment, the bottom bonding member  450  may be provided as a double-sided tape. The double-sided tape includes a tape base  451 , a first bonding layer  452  disposed on the bottom surface of the tape base  451 , and a second bonding layer  453  disposed on the top surface of the tape base  451 . The tape base  451  may be formed of PET, PI, PC, PE, PP, PSF, PMMA, TAC, or a COP. The first and second bonding layers  452  and  453  may be formed of one of the aforementioned examples of the material of the top bonding layer  130  of the panel bottom sheet  11  according to the exemplary embodiment of  FIG. 4 . Alternatively, the bottom bonding member  450  may include a single bonding layer or a plurality of bonding layers without having the tape base  451 . 
     The second release film  460  is disposed on the bottom surface of the bottom bonding member  450  and protects the bottom surface of the bottom bonding member  450 . The second release film  460  may be substantially the same as the first release film  130 .  FIG. 11  illustrates an example in which the second release film  460  has no embossed shape on the top surface thereof, but alternatively, the second release film  460 , like the first release film  131  having an embossed shape on the bottom surface thereof, may have an embossed shape on the top surface thereof. 
     The bottom bonding member  450 , like the second heat dissipation layer  420 , may be disposed in the flat area FA, but not in the bending areas BA. The sides of the bottom bonding member  450  may be aligned with, or positioned more inwardly than, the sides of the second heat dissipation layer  420 . A waterproof tape (not illustrated) may be attached to part of the bottom surface of the first heat dissipation layer  410  exposed by the bottom bonding member  450  and may be bonded to the bracket  60 . 
     In the exemplary embodiment of  FIG. 11 , the bottom bonding member  450  is included in the heat dissipation portion  400 , but may be provided as a separate member. Alternatively, the bottom bonding member  450  may be provided at lowermost portions of panel bottom sheets having various stack structures to bond the panel bottom sheets to the bracket  60 . For example, the bottom bonding member  450  may be disposed below the wiring pattern portion of the panel bottom sheet  12  according to the exemplary embodiment of  FIG. 7 . 
     A digitizer, which is used as the wiring pattern portion  200  of each of the panel bottom sheets  11  through  16  according to the exemplary embodiments of  FIGS. 4 and 7 through 11 , will hereinafter be described. 
       FIG. 12  is a layout view of a digitizer according to an exemplary embodiment of the present disclosure.  FIG. 13  is a cross-sectional view taken along line XIII-XIII′ of  FIG. 12 .  FIG. 14  is a cross-sectional view showing the digitizer according to the exemplary embodiment of  FIG. 12  in a bent state. 
     Referring to  FIGS. 12 through 14 , a digitizer  201  includes a base layer  210 , a first wiring layer  220  disposed on the top surface of the base layer  210 , and a second wiring layer  230  disposed on the bottom surface of the base layer  210 . The digitizer  201  may further include a first coverlay  240  covering the first wiring layer  220  from above, a second coverlay  250  covering the second wiring layer  230  from below, a signal shielding sheet  260  disposed below the second coverlay  250 , and a fifth interlayer bonding layer  261  interposed between the signal shielding sheet  260  and the second coverlay  250 . The top surface of the first coverlay  240  may be bonded to the bottom surface of the second interlayer bonding layer  320  of  FIG. 11 , and the bottom surface of the signal shielding sheet  260  may be bonded to the third interlayer bonding layer  430  of  FIG. 11 . 
     The base layer  210  provides space in which to form the first and second wiring layers  220  and  230 . The base layer  210  may be formed of an insulating material. The base layer  210  may comprise an inorganic material such as glass, or may comprise an organic material in order to realize flexibleness. For example, the base layer  210  may comprise at least one of PI, PET, PC, PE, PP, PSF, PMMA, TAC, and a COP. For example, the base layer  210  may comprise PI. 
     The first and second wiring layers  220  and  230  are disposed on the top surface and the bottom surface, respectively, of the base layer  210 . The first and second wiring layers  220  and  230  may be formed directly on the base layer  210 . The first and second wiring layers  220  and  230  may comprise a metal material such as Cu, Ag, Ni, or W.  FIGS. 12 through 14  illustrate an example in which the first and second wiring layers  220  and  230  are single films, but alternatively, each of the first and second wiring layers  220  and  230  may be formed as a stack of a plurality of films. For example, each of the first and second wiring layers  220  and  230  may include a stack of first and second Cu films. 
     The first wiring layer  220  includes a plurality of first wiring patterns  221  and first ground wirings  222 . The second wiring layer  230  includes a plurality of second wiring patterns  231  and second ground wirings  232 . 
     The first wiring patterns  221  may extend in a first direction, for example, a long-side direction. The second wiring patterns  231  may extend in a second direction, which intersects the first direction, for example, a short-side direction. The first wiring patterns  221  and the second wiring patterns  231  may be disposed mostly in a flat area FA, but not in bending areas BA. Alternatively, some of the first wiring patterns  221  and some of the second wiring patterns  231  may be disposed in the bending areas BA. 
     A number of first wiring patterns  221  may form a wiring pattern group, and a number of second wiring patterns  231  may form a wiring pattern group. For example, as illustrated in  FIG. 12 , five first or second wiring patterns  221  or  231  may form a single wiring pattern group, but the present disclosure is not limited thereto. That is, various numbers of first or second wiring patterns  221  or  231  form various numbers of wiring pattern groups. 
     The distance between wiring pattern groups formed by the first wiring patterns  221  or between wiring pattern groups formed by the second wiring patterns  231  may be greater than the distance between the first wiring patterns  221  or between the second wiring patterns  231 . In a case where the distance between wiring patterns or wiring pattern groups is large in a particular region, height differences formed in the particular region may be reflected onto the top of the particular region, and as a result, the wiring patterns or the wiring pattern groups may become visible. However, as already mentioned above, since the first light-absorbing layer  122  and/or the second light-absorbing layer  123  of  FIG. 11  may be disposed on the first wiring patterns  221  and the second wiring patterns  231 , the first wiring patterns  221  and the second wiring patterns  231  can be prevented from becoming visible. 
     Areas where the wiring pattern groups formed by the first wiring patterns  221  and the wiring pattern groups formed by the second wiring patterns  231  intersect each other may become coordinate electrode portions CE, which are basic units for position recognition. 
     The first ground wirings  222  and the second grounding wirings  232  are disposed in the bending areas BA. The first ground wirings  222  and the second grounding wirings  232  may extend in the same direction as the first wiring patterns  221 , i.e., in the long-side direction. The first ground wirings  222  and the second grounding wirings  232  may generally overlap with each other.  FIGS. 12 through 14  illustrate an example in which the first ground wirings  222  and the second grounding wirings  232  completely overlap with each other in a plan view, but the present disclosure is not limited thereto. 
     Each of the first ground wirings  222  and the second grounding wirings  232  include slits SL. The slits SL may extend in the first direction. Each of the first ground wirings  222  and the second grounding wirings  232  may be divided into sub-wirings, which are separated from one another by the slits SL but are connected to one another at the end of the corresponding first or second ground wiring  222  or  232 , but the present disclosure is not limited thereto. That is, the slits SL may be surrounded by each of the first ground wirings  222  and the second grounding wirings  232 , but the present disclosure is not limited thereto. Alternatively, the slits SL may extend to the end of each of the first ground wirings  222  and the second grounding wirings  232  so that the sub-wirings of each of the first ground wirings  222  and the second grounding wirings  232  may be separated from one another, even at the end of the corresponding first or second ground wiring  222  or  232 .  FIGS. 12 through 14  illustrate an example in which two slits SL are provided in each of the first ground wirings  222  and the second ground wirings  232  to divide the corresponding first or second ground wirings  222  or  232  into three sub-wirings, but alternatively, only one slit SL or three or more slits SL may be provided in each of the first ground wirings  222  and the second ground wirings  232 . The slits SL reduce bending stress. 
     Specifically, the first ground wirings  222  and the second ground wirings  232  have a relatively wide width. For example, the width of the first ground wirings  222  and the second ground wirings  232  may be greater than the width of the first wiring patterns  221  and the second wiring patterns  231 . If the first ground wirings  222  and the second ground wirings  232 , which are both disposed in the bending areas BA, have too large width, a considerable amount of stress may be applied to the bending areas BA during the attachment of a panel bottom sheet including the digitizer  201  to a display panel  20 . For example, in a case where the first ground wirings  222  and the second ground wirings  232  are formed of Cu, the bending resistance of the first ground wirings  222  and the second ground wirings  232  is relatively strong so that the panel bottom sheet including the digitizer  201  may not be able to be properly attached to the display panel  20  or that the bonding force between the panel bottom sheet including the digitizer  201  and the display panel  20  may weaken later. 
     In the exemplary embodiment of  FIGS. 12 through 14 , the slits SL are formed in each of the first ground wirings  222  and the second ground wirings  232 , thereby offering the same effect of reducing the width of the first ground wirings  222  and the second ground wirings  232 . That is, as illustrated in  FIG. 14 , flexibility can be secured in the slits SL where no wiring material is provided, and as a result, the first ground wirings  222  and the second ground wirings  232  can be properly bent. 
     The slits SL may also help prevent each of the first ground wirings  222  and the second ground wirings  232  from becoming visible. Specifically, in a case where the first ground wirings  222  and the second ground wirings  232  are formed to have no slits SL, the first ground wirings  222  and the second ground wirings  232  are highly likely to be visible from the outside because of strong reflections that may occur over their relatively large areas. On the other hand, in the exemplary embodiment of  FIGS. 12 through 14 , each of the first ground wirings  222  and the second ground wirings  232  is divided into sub-wirings by the slits SL. As a result, the reflectivity of the first ground wirings  222  and the second ground wirings  232  may be reduced, and as a result, the visibility of the first ground wirings  222  and the second ground wirings  232  may also be reduced. 
     A pad portion PAD is provided at one side of the base layer  210 . An external device such as a PCB or a FPCB is connected to the pad portion PAD. The first wiring patterns  221  and the second wiring patterns  231  are connected to the pad portion PAD so that the digitizer  201  can be communicated with the external device. 
     The pad portion PAD may comprise the material of the first wiring layer  220  and/or the material of the second wiring layer  230 . In a case where the pad portion PAD comprises both the materials of the first wiring layer  220  and the second wiring layer  230 , a PCB or FPC may be connected to the pad portion PAD, the first wiring patterns  221  and the first ground wirings  222  may be connected to part of the pad portion PAD corresponding to the first wiring layer  220 , and the second wiring patterns  231  and the second ground wirings  232  may be connected to part of the pad portion PAD corresponding to the second wiring layer  230 . 
     In one exemplary embodiment, the first and second wiring layers  220  and  230  may be electrically connected through via holes, and this will hereinafter be described with reference to  FIG. 15 . 
       FIG. 15  is a cross-sectional view of a digitizer according to another exemplary embodiment of the present disclosure. Referring to  FIG. 15 , a digitizer  202  may further include via holes VIA formed through a base layer  210  and connecting first and second wiring layers  220  and  230 . 
     For example, a first ground wiring  222  of the first wiring layer  220  and a second ground wiring  232  of the second wiring layer  230  are all wirings for grounding and may be short-circuited. The via holes VIA electrically connect the first and second ground wirings  222  and  232  to short-circuit the first and second ground wirings  222  and  232 . The via holes VIA may be formed in sub-wirings, respectively, of each of the first and second ground wirings  222  and  232 , divided by slits SL, as illustrated in  FIG. 15 . Alternatively, the via holes VIA may be formed only in part of each of the first and second ground wirings  222  and  232 . 
     The via holes VIA may be filled with the material of the first wiring layer  220 . In this case, the material of the first wiring layer  220  and the material filling the via holes VIA may not have any physical boundary therebetween. Alternatively, the via holes VIA may be filled with the material of the second wiring layer  230 . Still alternatively, the via holes VIA may be filled with a material other than the materials of the first and second wiring layers  220  and  230 . In this example, the boundaries between the material filling the via holes VIA and the first and second ground wirings  222  and  232  may be observed. 
     Although not specifically illustrated, the via holes VIA may also be formed through the base layer  210  through which the pad portions PAD which is formed of the material of the first wiring layer  220  and the second wiring patterns  230  are connected. For example, in a case where a pad portion PAD comprises only the material of the first wiring layer  220 , the pad portion PAD through which a control signal or an output signal of the second wiring patterns  230  is transmitted is connected to the second wiring patterns  230  through the via holes VIA. The first wiring layer  220  connected to the second wiring pattern  231  via the via holes VIA may be disposed on the outer side of the first wiring pattern  221 , which forms a coordinate electrode portion CE, for example, in or around a bent portion BA. 
     First and second coverlays  240  and  250 , which protect the first and second wiring layers  220  and  230 , respectively, may be formed of an insulating material. The first and second coverlays  240  and  250  may be formed as single films or stacks of a plurality of films. 
     For example, the first coverlay  240  may include a first coverlay bonding layer  242  and a first coverlay insulating layer  241  sequentially stacked in an upward direction, and the second coverlay  250  may include a second coverlay bonding layer  252  and a second coverlay insulating layer  251  sequentially stacked in a downward direction. 
     The first and second coverlay insulating layers  241  and  251  may be formed of at least one of PI, PET, PC, PE, PP, PSF, PMMA, TAC, and a COP. In one exemplary embodiment, the first and second coverlay insulating layers  241  and  251  may comprise PI. The first and second coverlay bonding layers  242  and  252  may be formed of one of the aforementioned examples of the material of the top bonding layer  130  of the panel bottom sheet  11  according to the exemplary embodiment of  FIG. 4 . The first and second coverlay bonding layers  242  and  252  may not be provided. 
     A signal shielding sheet  260  is disposed below the first and second wiring layers  220  and  230  and prevents signal interference. For example, in a case where an external device such as a PCB, FPCB, or a driving chip is disposed below a bracket  60 , the external device may cause signal interference during the input of signals with a stylus pen, and the signal shielding sheet  260  prevents this type of signal interference. The signal shielding sheet  260  may be formed of a ferromagnetic material comprising iron oxide such as, for example, ferrite. 
       FIG. 16  is a layout view of a digitizer according to another exemplary embodiment of the present disclosure. 
     Referring to  FIG. 16 , a digitizer  203  differs from the digitizer  201  according to the exemplary embodiment of  FIG. 12  in that it further includes a plurality of first floating wiring patterns  221   a  and a plurality of second floating wiring patterns  231   a.    
     The first floating wiring patterns  221   a  are disposed among wiring pattern groups formed by first wiring patterns  221 , and the second floating wiring patterns  231   a  are disposed among wiring pattern groups formed by second wiring patterns  231 . Since the first or second floating wiring patterns  221   a  or  231   a  are disposed among the wiring pattern groups formed by the first or second wiring patterns  221  or  231 , the gaps among the wiring pattern groups formed by the first or second wiring patterns  221  or  231  are filled. Accordingly, the same effect of reducing the distance between the wiring pattern groups formed by the first or second wiring patterns  221  or  231  can be offered, and as a result, the visibility of the first wiring patterns  221  and the second wiring patterns  231  can be reduced. 
     Examples 1 through 5 and Experimental Examples 1 and 2 in accordance with the present disclosure will hereinafter be described. 
     Example 1 
     The bottom surface of a PET base was coated with black ink to a thickness of 1 μm twice to form a black ink layer having a thickness of 2 μm. Thereafter, an adhesive was respectively applied to the top surface of the black ink layer to a thickness of 28 μm and to the bottom surface of the PET base to a thickness of 15 μm, thereby obtaining a cover panel film. 
     Example 2 
     A cover panel film was fabricated using the same method used to obtain the cover panel film according to Example 1 except for coating the bottom surface of a PET base with black ink to a thickness of 1 μm three times to form a black ink layer having a thickness of 3 μm. 
     Example 3 
     The top surface and the bottom surface of a PET base were both coated with black ink to a thickness of 1 μm twice to form a black ink layer having a thickness of 2 μm on each of the top and bottom surfaces of the PET base. Thereafter, an adhesive was respectively applied to the top surface of the black ink layer on the top surface of the PET base to a thickness of 28 μm and to the bottom surface of the black ink layer on the bottom surface of the PET base to a thickness of 15 μm, thereby obtaining a cover panel film. 
     Example 4 
     A cover panel film was fabricated using the same method used to obtain the cover panel film according to Example 3 except for coating both the top surface and the bottom surface of a PET base with black ink to a thickness of 1 μm three times to form a black ink layer having a thickness of 3 μm on each of the top and bottom surfaces of the PET base. 
     Example 5 
     A cover panel film was fabricated using the same method used to obtain the cover panel film according to Example 3 except for coating both the top surface and the bottom surface of a PET base with black ink to a thickness of 1 μm four times to form a black ink layer having a thickness of 4 μm on each of the top and bottom surfaces of the PET base. 
     Experimental Example 1: Measurement of OD 
     The ODs of the cover panel films according to Examples 1 through 5 were measured, and the results of the measurement are as shown in Table 1 below. OD is a logarithmic value of the ratio of an amount I 1  of light transmitted through a particular medium to an amount I 0  of light incident upon the particular medium, i.e., I 1 /I 0 . The higher the OD, the smaller the amount of light transmission, and the greater the amount of optical absorption. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Total Thickness of Black 
                   
               
               
                   
                 Examples 
                 Ink Layer(s) (μm) 
                 OD 
               
               
                   
                   
               
             
            
               
                   
                 Example 1 
                 2 
                 3.4 
               
               
                   
                 Example 2 
                 3 
                 4.4 
               
               
                   
                 Example 3 
                 4 
                 5.0 
               
               
                   
                 Example 4 
                 6 
                 6.2 
               
               
                   
                 Example 5 
                 8 
                 6.5 
               
               
                   
                   
               
            
           
         
       
     
     Experimental Example 2: Measurement of Reflectance 
     Reflectance measurement was conducted by placing a digitizer below each of the cover panel films according to Examples 2 and 5. Referring to Table 2 below, “Top” denotes a location near one short side of each of the cover panel films according to Examples 2 and 5, which are rectangular in shape, “Middle” denotes a location in the middle of each of the cover panel films according to Examples 2 and 5, and “Bottom” denotes a location near the other short side of each of the cover panel films according to Examples 2 and 5. Reflectance measurements obtained from the cover panel films according to Examples 2 and 5 are as shown in Table 2 below. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Measurement Location 
                 Reflectance 
               
               
                   
                   
               
             
            
               
                   
                 Example 2 
                 Top 
                 4.931 
               
               
                   
                   
                 Middle 
                 4.950 
               
               
                   
                   
                 Bottom 
                 4.874 
               
               
                   
                   
                 Average 
                 4.918 
               
               
                   
                 Example 5 
                 Top 
                 4.849 
               
               
                   
                   
                 Middle 
                 4.864 
               
               
                   
                   
                 Bottom 
                 4.832 
               
               
                   
                   
                 Average 
                 4.848 
               
               
                   
                   
               
            
           
         
       
     
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the inventive concept of the present disclosure. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the inventive concept of the present disclosure. Additionally, the features of various implementing embodiments may be combined to form further exemplary embodiments of the present disclosure.