Patent Publication Number: US-2023157109-A1

Title: Display device including an anisotropic conductive film

Description:
This application is a Continuation of co-pending U.S. patent application Ser. No. 16/268,027, filed on Feb. 5, 2019, which claims priority from Korean Patent Application No. 10-2018-0037625, filed on Mar. 30, 2018, in the Korean Intellectual Property Office, the disclosure of which is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a display device and, more specifically, to a display device having an anisotropic conductive film. 
     DISCUSSION OF THE RELATED ART 
     A display device is a machine configured to display an image, or a sequence of images, in response to a signal. Display devices are widely used in televisions, computer monitors, a personal digital assistants (PDAs), smart phones, personal computers (PCs), tablet computers, and other stationary and mobile devices. 
     The display device may include a display panel and a printed circuit board configured for driving the display panel. The printed circuit board and the display panel may be electrically connected to each other through an anisotropic conductive film (ACF) or the like. 
     An ACF includes conductive particles arranged within an insulating layer such as a resin layer. Because of the arrangement of the conductive particles, electricity may be conducted in a thickness direction of the ACF, while electricity is insulated in a surface direction (e.g. lengthwise direction) of the ACF. 
     SUMMARY 
     A display device includes a display panel having a display region and a pad region disposed in a periphery of the display region. The display panel further includes a pad portion disposed in the pad region. A printed circuit board is electrically connected to the pad portion. An anisotropic conductive film is interposed between the pad portion and the printed circuit board. The pad portion includes a first pad of which a lateral side and a Y axis that runs along a lengthwise direction of the display panel form a first angle greater than 0°. The anisotropic conductive film includes a plurality of conductive particles. The plurality of conductive particles are disposed at vertices of an imaginary quadrangle having a length of a first diagonal line shorter than a length of a second diagonal line when viewed from above. The second diagonal line and the Y axis form a second angle greater than 0°. The first angle and the second angle are acute angles. The first angle is greater than the second angle. 
     A display device includes a display substrate having a display region and a pad region disposed in a periphery of the display region. The display substrate further includes a pad disposed in the pad region. A printed circuit board is electrically connected to the pad. A lateral side of the pad and a Y axis that runs along a lengthwise direction of the display panel form a first angle greater than 0° and the pad includes a plurality of pad concave portions. Some of the plurality of pad concave portions are disposed at vertices of an imaginary quadrangle having a length of a first diagonal line shorter than a length of a second diagonal line. The second diagonal line and the Y axis form a second angle greater than 0°. The first angle and the second angle are acute angles. The first angle is greater than the second angle. 
     A display device includes a display panel having a display region and a non-display region. The non-display region includes a plurality of pads. A printed circuit board is electrically connected to the display panel via the plurality of pads. An anisotropic conductive film is interposed between the plurality of pads and the printed circuit board. At least some of the plurality of pads are disposed at an angle that is neither parallel not perpendicular with respect to a lengthwise or widthwise direction of the display panel. The anisotropic conductive film includes a plurality of conductive particles arranged within an insulator, the plurality of conductive particles being arranged in a triangular lattice. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects and features of the present disclosure will become more apparent by describing exemplary embodiments thereof in detail with reference to the attached drawings, in which: 
         FIGS.  1  and  2    are plan views illustrating a bonding process of a display panel and a printed circuit board in a display device according to an exemplary embodiment of the present disclosure; 
         FIG.  3    is an enlarged plan view illustrating a portion Q 1  of  FIG.  1   ; 
         FIG.  4    is an enlarged plan view illustrating a portion Q 2  of  FIG.  1   ; 
         FIG.  5    is a schematic cross-sectional view illustrating the display device of  FIG.  4    taken along line A 1 -A 1 ′ in a state in which the display panel and the printed circuit board are coupled; 
         FIG.  6    is a plan view illustrating a portion of an anisotropic conductive film shown in  FIG.  2   ; 
         FIG.  7    is an enlarged plan view illustrating a rectangular portion shown in  FIG.  6   ; 
         FIG.  8    is a plan view illustrating conductive particles of an anisotropic conductive film with a first pad in a display device according to an exemplary embodiment of the present disclosure; 
         FIG.  9    is a plan view illustrating conductive particles of an anisotropic conductive film and a first pad together in a display device according to a comparative example; 
         FIG.  10    is a plan view illustrating conductive particles of an anisotropic conductive film and a first pad together in a display device according to a comparative example; 
         FIG.  11    is a plan view illustrating a first pad of  FIG.  8   ; 
         FIG.  12    is a plan view illustrating a first connection electrode corresponding to the first pad of  FIG.  8   ; 
         FIG.  13    is an equivalent circuit diagram illustrating a pixel of  FIG.  1   ; 
         FIG.  14    is a plan view schematic circuit diagram illustrating a pixel of  FIG.  1   ; 
         FIG.  15    is a cross-sectional view taken along line A 2 -A 2 ′ of  FIG.  14   ; and 
         FIGS.  16  and  17    are plan views illustrating a bonding process of a display panel and a printed circuit board in a display device according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In describing exemplary embodiments of the present disclosure illustrated in the drawings, specific terminology is employed for sake of clarity. 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. 
     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. Same reference numerals may refer to the same constituent elements throughout the specification and drawings. 
     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. 
     Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. 
       FIGS.  1  and  2    are plan views illustrating a bonding process of a display panel and a printed circuit board in a display device according to an exemplary embodiment of the present disclosure. 
     Referring to  FIG.  1   , a display device  1  may include a display panel  100 , a printed circuit board  210 , and a data driving integrated circuit (IC). 
     The display panel  100  may have a rectangular shape in the plan view. The display panel  100  may include two short sides extending along an X axis and two long sides extending along a Y axis that is perpendicular to the X axis. The corners of the display panel  100 , at which the long sides and the short sides of the display panel  100  meet, may be right angles, but may alternatively be curved. A planar shape of the display panel  100  is not limited to that shown, and may be a circular shape or another shape such as an arbitrary shape. 
     The display panel  100  may include a display region DA displaying an image and a non-display region NA that does not display an image. In some exemplary embodiments of the present disclosure, the non-display region NA may be disposed in a periphery of the display region DA and may at least partially surround the display region DA. 
     A portion of the non-display region NA of the display panel  100  may be a pad region MA to which the printed circuit board  210  is coupled. In some exemplary embodiments of the present disclosure, the pad region MA may be disposed below the display panel  100  in the non-display region NA. 
     The display panel  100  may have a stacked structure including a base substrate  110 , a display element layer DSL, and a pad portion PDA. 
     The base substrate  110  may be made of an insulating material such as glass, quartz, a polymer resin, or the like. For example, the polymer material may include polyethersulphone (PES), polyacrylate (PA), polyarylate (PAR), polyetherimide (PEI), polyethylenenapthalate (PEN), polyethyleneterepthalate (PET), polyphenylenesulfide (PPS), polyallylate, polyimide (PI), polycarbonate (PC), cellulosetriacetate (CAT), cellulose acetate propionate (CAP), or a combination thereof. The base substrate  110  may include a metal. 
     The base substrate  110  may be a rigid substrate, which does not bend, or a flexible substrate, which is capable of being bent, folded, rolled, and the like. A material of the flexible substrate may be, for example, PI, but the present disclosure is not limited thereto. 
     The display element layer DSL may be disposed on the base substrate  110  in the display region DA. The display element layer DSL may include a plurality of pixels PX, and each of the pixels PX may be an element for displaying a portion of an image. In some exemplary embodiments of the present disclosure, each of the pixels PX may include an organic light-emitting diode. 
     The pad portion PDA may be disposed on the base substrate  110  in the pad region MA of the non-display region NA. The pad portion PDA may include a plurality of pads PD for receiving signals supplied from the printed circuit board  210 . 
     When a data driving IC for supplying a data signal to the pixel PX is mounted on the display panel  100  in the form of a chip, the pads PD may be used for supplying display data and control signals to the data driving IC. When the data driving IC is mounted on the printed circuit board  210  in the form of a chip, the pads PD may include data pads, which are electrically connected to data lines which supply data signals to the pixels PX, and control signal pads, which are electrically connected to control signal wires through which control signals are supplied to the data driving IC. 
     In some exemplary embodiments of the present disclosure, the printed circuit board  210  may be a flexible printed circuit board. In some exemplary embodiments of the present disclosure, as shown in  FIG.  1   , a connection electrode portion CNA corresponding to the pad portion PDA may be disposed on a rear surface of the printed circuit board  210 , for example, a surface facing the display panel  100 . The connection electrode portion CNA may include a plurality of connection electrodes CN for being electrically connected to the pads PD in one-to-one correspondence. 
     For example, a chip-on-film structure in which the data driving IC is mounted on the flexible printed circuit board  210  is shown in  FIG.  1   . 
     Referring to  FIG.  2   , the printed circuit board  210  is coupled to the pad region MA of the display panel  100 . An anisotropic conductive film  300  may be disposed between the display panel  100  and the printed circuit board  210 , and the display panel  100  and the printed circuit board  210  may be physically/electrically coupled to each other through the anisotropic conductive film  300 . 
     The anisotropic conductive film  300  is an adhesive film used for circuit connection and has anisotropic properties that conduct electricity in one direction (e.g., in a thickness direction) and insulate electricity in another direction (e.g., in a surface direction). The anisotropic conductive film  300  includes an insulating layer (e.g., a thermosetting insulating layer) having adhesiveness and a plurality of conductive particles disposed within the insulating layer. 
     When the connection electrodes CN of the printed circuit board  210  and the pads PD of the display panel  100  are arranged to face each other, the anisotropic conductive film  300  is interposed between the printed circuit board  210  and the display panel  100 . Thereafter, when heat and pressure are applied to the pad region MA of the display panel  100  by a tool, the conductive particles of the anisotropic conductive film  300  are in contact with the connection electrodes CN and the pads PD, and accordingly, the printed circuit board  210  and the display panel  100  are electrically connected to each other. Further, when the insulating layer of the anisotropic conductive film  300  is cured, the printed circuit board  210  is attached to the display panel  100 . 
       FIG.  3    is an enlarged plan view illustrating a portion Q 1  of  FIG.  1   , and shows various shapes of the pads disposed in the display panel. 
     Referring to  FIGS.  1  and  3   , a first pad group PG 1  may be disposed at a left side of the pad region MA of the display panel  100  with respect to a central line RL parallel to the Y axis. A second pad group PG 2  may be disposed at a right side of the pad region MA of the display panel  100 . According to an exemplary embodiment of the present disclosure, there are two pad groups: the first pad group PG 1  and the second pad group PG 2 . Further, a plurality of central lines RL may be disposed on the display panel  100 . Pad groups may be arranged in the same manner for each central line RL. However, for convenience of description, one central line RL is shown in the instant drawing. 
     The first pad group PG 1  may include a plurality of pads which extend along a line which forms an acute angle with respect to the central line RL. 
     For example, the first pad group PG 1  may include a first pad PD 11  which extends along a first line L 11 , a second pad PD 12  which extends along a second line L 12 , and a third pad PD 13  which extends along a third line L 13 . In some exemplary embodiments of the present disclosure, the first line L 11 , the second line L 12 , and the third line L 13  may converge on the same reference point C along with the central line RL, and each of the first line L 11 , the second line L 12 , and the third line L 13  may have a positive slope on a plane formed by the X axis and the Y axis. An acute angle formed by the first line L 11  and the central line RL may be a first angle a 11 , an acute angle formed by the second line L 12  and the central line RL may be a second angle a 12 , and an acute angle formed by the third line L 13  and the central line RL may be a third angle a 13 . Each of the first angle a 11 , the second angle a 12 , and the third angle a 13  may be greater than 0°. 
     The first pad PD 11 , the second pad PD 12 , and the third pad PD 13  may be arranged substantially parallel to the X axis, and may be sequentially arranged. 
     Each of the first pad PD 11 , the second pad PD 12 , and the third pad PD 13  may have a parallelogram shape, and a base of the parallelogram may be parallel to the X axis and a height of the parallelogram may be a length in a Y axis direction. Each of the first pad PD 11 , the second pad PD 12 , and the third pad PD 13  may have a parallelogram shape in which a height is greater than a length of a base. For example, when the second pad PD 12  is referred to as a first specific pad, a height H of the first specific pad PD 12  may be greater than a width W of the base of the first specific pad PD 12 . For example, each of the first pad PD 11 , the second pad PD 12 , and the third pad PD 13  may have a parallelogram shape elongated in the Y axis direction. Hereinafter, the “first specific pad” will be referred to as the “the second pad PD 12 .” 
     Each of the first pad PD 11 , the second pad PD 12 , and the third pad PD 13  may be obliquely tilted with respect to the Y axis, and may each include a lateral side having an acute angle greater than 0° with respect to the Y axis. 
     For example, a lateral side E 12  of the second pad PD 12  may have an acute angle greater than 0° with respect to the Y axis or the central line RL parallel to the Y axis. Further, the lateral side E 12  of the second pad PD 12  may be parallel to the second line L 12 . Therefore, the acute angle formed by the lateral side E 12  of the second pad PD 12  and the Y axis may be substantially the same as the second angle a 12  formed by the second line L 12  and the central line RL. 
     Similarly, an acute angle formed by a lateral side of the first pad PD 11  and the Y axis may be the first angle a 11 , and an acute angle formed by a lateral side of the third pad PD 13  and the Y axis may be the third angle a 13 . 
     In some exemplary embodiments of the present disclosure, each of the first angle a 11 , the second angle a 12 , and the third angle a 13  may have an angle in a range of 0° to 20°. Further, in some exemplary embodiments of the present disclosure, the second angle a 12  of the first specific pad PD 12  may be in a range of 5° to 20°. For example, the first specific pad PD 12  may be defined as a pad of which an acute angle formed by a lateral side and the Y axis is in a range of 5° to 20°, among the pads in the first pad group PG 1 . As will be described below, when the second angle a 12  of the first specific pad PD 12  is greater than 5°, an arrangement of the conductive particles  330  is determined in consideration of the second angle a 12  of the first specific pad PD 12  in order to increase the reliability of electrical connection. An upper limit of the second angle a 12  of the first specific pad PD 12  may be appropriately selected according to the structure of the display device  1 , and for example, the second angle a 12  may be 20° or less. 
     An acute angle formed by each of lateral sides of the pads and the Y axis may increase from the central line RL toward an edge of the display panel  100  in an X axis direction. 
     For example, among the first pad PD 11 , the second pad PD 12 , and the third pad PD 13 , the third pad PD 13  is relatively closest to the edge of the display panel  100  in the X axis direction, and the first pad PD 11  is closest to the central line RL. Further, the second pad PD 12  is disposed between the first pad PD 11  and the third pad PD 13 . In this case, the first angle a 11  formed by the lateral side of the first pad PD 11  and the Y axis may be smaller than the second angle a 12  formed by the lateral side of the second pad PD 12  and the Y axis, and the third angle a 13  formed by the lateral side of the third pad PD 13  and the Y axis may be greater than the second angle a 12 . 
     The second pad group PG 2  may include a fourth pad PD 21 , a fifth pad PD 22 , and a sixth pad PD 23 . The fourth pad PD 21  may extend along a fourth line L 21  symmetrical to the first line L 11  relative to the central line RL, the fifth pad PD 22  may extend along a fifth line L 22  symmetrical to the second line L 12  relative to the central line RL, and the sixth pad PD 23  may extend along a sixth line L 23  symmetrical to the third line L 13  relative to the central line RL. In some exemplary embodiments of the present disclosure, the fourth line L 21 , the fifth line L 22 , and the sixth line L 23  may converge on the same reference point C′ along with the central line RL like the first line L 11 , the second line L 12 , and the third line L 13 , and have a negative slope on the plane formed by the X axis and the Y axis. 
     An acute angle formed by the central line RL and the fourth line L 21  may be a fourth angle a 21 , and the fourth angle a 21  may be the same as the first angle a 11 . Similarly, a fifth angle a 22 , which is an acute angle formed by the central line RL and the fifth line L 22 , may be the same as the second angle a 12 , and a sixth angle a 23 , which is an acute angle formed by the central line RL and the sixth line L 23 , may be the same as the third angle a 13 . 
     The fourth pad PD 21 , the fifth pad PD 22 , and the sixth pad PD 23  may be respectively symmetrical to the first pad PD 11 , the second pad PD 12 , and the third pad PD 13  on the basis of the Y axis or the central line RL parallel to the Y axis. Therefore, an acute angle formal by a lateral side of each of the fourth pad PD 21 , the fifth pad PD 22 , and the sixth pad PD 23  and the Y axis may increase toward the edge of the display panel  100  in the X axis direction. 
     In some exemplary embodiments of the present disclosure, the display panel  100  may further include a reference pad PDC having a lateral side EC parallel to the central line RL. The reference pad PDC may be disposed between the first pad group PG 1  and the second pad group PG 2 , and the central line RL parallel to the Y axis may pass through the reference pad PDC. 
       FIG.  4    is an enlarged plan view illustrating a portion Q 2  of  FIG.  1   . 
     Referring to  FIGS.  1  and  4   , a first electrode group CNG 1  may be disposed at a left side of the connection electrode portion CNA on the rear surface of the printed circuit board  210  (e.g., the surface facing the display panel  100 ) with respect to the central line RL parallel to the Y axis, and a second electrode group CNG 2  may be disposed at a right side of the connection electrode portion CNA. 
     The first electrode group CNG 1  may include a first connection electrode CN 11  having a structure corresponding to the first pad PD 11 , a second connection electrode CN 12  having a structure corresponding to the second pad PD 12 , and a third connection electrode CNT 3  having a structure corresponding to the third pad PD 13 . The first connection electrode CN 11 , the second connection electrode CN 12 , and the third connection electrode CN 13  may have a parallelogramical shape having a height greater than a length of a base like the first pad PD 11 , the second pad PD 12 , and the third pad PD 13 . 
     For example, when the second connection electrode CN 12  corresponding to the first specific pad PD 12  is referred to as a first specific connection electrode, a height Ha of the first specific connection electrode CN 12  may be greater than a width Wa of a base of the first specific connection electrode CN 12 . In some exemplary embodiments of the present disclosure, the height Ha of the first specific connection electrode CN 12  may be the same as the height H of the first specific pad PD 12  and the width Wa of the base of the first specific connection electrode CN 12  may be substantially the same as the width W of the base of the first specific pad PD 12 , but the present disclosure is not limited thereto and the first specific pad PD 12  and the first specific connection electrode CN 12  may have different arrangements. 
     The first connection electrode CN 11  may have a structure corresponding to the first pad PD 11 , the second connection electrode CN 12  may have a structure corresponding to the second pad PD 12 , and the third connection electrode CN 13  may have a structure corresponding to the third pad PD 13 . Therefore, in some exemplary embodiments of the present disclosure, an acute angle formed by a lateral side E 12   a  of the first specific connection electrode CN 12  corresponding to the first specific pad PD 12  and the Y axis may be the second angle a 12 , which is equal to the acute angle formed by the lateral side E 12  of the first specific pad PD 12  and the Y axis. 
     The second electrode group CNG 2  may include a fourth connection electrode CN 21  having a structure corresponding to the fourth pad PD 21 , a fifth connection electrode CN 22  having a structure corresponding to the fifth pad PD 22 , and a sixth connection electrode CN 23  having a structure corresponding to the sixth pad PD 23 . 
     In addition, a description of each of the connection electrodes of the printed circuit board  210  is substantially the same as or similar to the description of each of the pads of the display panel  100 . 
     In some exemplary embodiments of the present disclosure, the connection electrode portion CNA of the printed circuit board  210  may further include a reference electrode CNC corresponding to the reference pad PDC. The reference electrode CNC may be disposed between the first electrode group CNG 1  and the second electrode group CNG 2 , and the central line RL parallel to the Y axis may pass through the reference electrode CNC. Further, a lateral side ECa of the reference electrode CNC may be parallel to the Y axis or the central line RL. 
     In the display device  1 , according to an exemplary embodiment of the present disclosure, the pads of the display panel  100  and the connection electrodes of the printed circuit board  210  are arranged obliquely with respect to the Y axis. Accordingly, an alignment margin between the display panel  100  and the printed circuit board  210  may be secured. 
       FIG.  5    is a schematic cross-sectional view of the display device taken along line A 1 -A 1 ′ of  FIG.  4    in a state in which the display panel and the printed circuit board are coupled. 
     Referring to  FIG.  5   , the anisotropic conductive film  300  is disposed between the first specific pad PD 12  and the first specific connection electrode CN 12 . 
     The anisotropic conductive film  300  includes an insulating layer  310  and a plurality of conductive particles  330  disposed in the insulating layer  310  as described above. Some of the conductive particles  330  are disposed between the first specific pad PD 12  and the first specific connection electrode CN 12  and are in contact with the first specific pad PD 12  and the first specific connection electrode CN 12 , and accordingly, the first specific pad PD 12  and the first specific connection electrode CN 12  are electrically connected. In some exemplary embodiments of the present disclosure, a plurality of conductive particles  330  may be disposed between the first specific pad PD 12  and the first specific connection electrode CN 12 . 
     In the process of coupling the display panel  100  and the printed circuit board  210 , pressure as well as heat is applied to the anisotropic conductive film  300 . Accordingly, traces pressed by the conductive particles  330 , which may be, a plurality of pad concave portions PCV, are formed in the first specific pad PD 12 . Similarly, traces pressed by the conductive particles  330 , which may be, a plurality of electrode concave portions CCV, are formed in the first specific connection electrode CN 12 . 
     The electrode concave portions CCV and the pad concave portions PCV are formed at positions corresponding to the conductive particles  330  disposed between the first specific pad PD 12  and the first specific connection electrode CN 12 . For example, the pad concave portions PCV and the electrode concave portions CCV may be formed at positions corresponding to each other and may at least partially overlap each other. Further, the conductive particles  330  may be disposed between the pad concave portions PCV and the electrode concave portions CCV. Further, the conductive particles  330  disposed between the first specific pad PD 12  and the first specific connection electrode CN 12  may simultaneously overlap the pad concave portions PCV and the electrode concave portions CCV. 
     When the conductive particles  330  are arranged at regular intervals, the pad concave portions PCV formed in the first specific pad PD 12  may be arranged to have substantially the same arrangement as the conductive particles  330 , and the electrode concave portions CCV formed in the first specific connection electrode CN 12  may also be arranged to have substantially the same arrangement as the conductive particles  330 . 
       FIG.  6    is a plan view illustrating a portion of the anisotropic conductive film shown in  FIG.  2   .  FIG.  7    is an enlarged plan view of a rectangular portion shown in  FIG.  6   .  FIG.  8    is a plan view illustrating conductive particles of an anisotropic conductive film and a first pad together in a display device according to an exemplary embodiment of the present disclosure.  FIG.  9    is a plan view showing conductive particles of an anisotropic conductive film and a first pad together in a display device according to a first comparative example, (“Comparative Example 1”), and  FIG.  10    is a plan view illustrating conductive particles of an anisotropic conductive film and a first pad together in a display device according to a second comparative example, (“Comparative Example 2”). 
     Referring to  FIGS.  6  to  10   , the plurality of conductive particles  330  of the anisotropic conductive film  300  included in the display device  1  are arranged to have a specific regularity as shown in  FIGS.  6  and  7   . For example, the conductive particles  330  may be disposed at vertices of an imaginary quadrangle DM of which a length of a first diagonal line SL is shorter than a length of a second diagonal line LL. It is to be understood that as used herein, the term “imaginary” means a quadrangle that does not exist in structure but exists merely as a manner of understanding the geometric arrangement of actual structures. For example, the imaginary quadrangles DM are mental constructs used to help understand the arrangement of the conductive particles  330 . In particular, the arrangement of the conductive particles  330  may be explained as being disposed at the vertices of a grid of regularly distributed rhombuses, as illustrated in the figures. 
     The arrangement of the conductive particles  330  may alternatively be described as being in a staggered matrix as the arrangement includes regular rows but columns that are staggered, or regular columns but rows that are staggered. This arrangement may also be referred to herein as a triangular lattice. 
     In some exemplary embodiments of the present disclosure, the imaginary quadrangle DM may be a rectangle and/or a rhombus, having a constant value r in lengths of a first side S 1 , a second side S 2 , a third side S 3 , and a fourth side S 4 . When the imaginary quadrangle DM is a rhombus, the first diagonal line SL and the second diagonal line LL of the imaginary quadrangle DM may be perpendicular to each other. 
     In some exemplary embodiments of the present disclosure, the imaginary quadrangle DM is a rhombus, and may have a quadrangle in which two equilateral triangles are coupled, for example, a rhombus quadrangle having the value r of the length of the first diagonal line SL which is equal to the length of each of the first side S 1 , the second side S 2 , the third side S 3 , and the fourth side S 4 . Therefore, a distance between the conductive particles  330  closest to each other may be constant. 
     When the distance between the conductive particles  330  is too small, a short circuit may occur between adjacent conductive particles  330  within the insulating direction. Further, when the distance between the conductive particles  330  is too large, an open circuit may occur within the conductive direction. Therefore, in order to ensure the electrical connection between the pad of the display panel  100  and the connection electrode of the printed circuit board  210  without causing a short circuit, the conductive particles  330  are arranged at regular intervals, and particularly, the distance between the conductive particles  330  may be constant. In the display device  1 , according to an exemplary embodiment of the present disclosure, the conductive particles  330  of the anisotropic conductive film  300  are disposed at the vertices of the imaginary quadrangle DM having a quadrangle in which two equilateral triangles are coupled, and thus it is possible to prevent a short-circuit failure or a defect of electrical disconnection. 
     However, the shape of the imaginary quadrangle DM is not limited to the rhombus described above. In the process of applying the pressure to the anisotropic conductive film  300 , the arrangement of the conductive particles  330  may be partially changed. In this case, the shape of the imaginary quadrangle DM has the same value r as the lengths of the first side S 1 , the second side S 2 , the third side S 3 , and the fourth side S 4 , but may be a rhombus in which the length of the first diagonal line SL has a different value from that of the length of the first side S 1  or the like. Alternatively, the imaginary quadrangle DM may have a parallelogram shape, or have yet a different shape. For example, in some cases, the shape of the imaginary quadrangle DM may be changed within a limit that the length of the first diagonal line SL is shorter than the length of the second diagonal line LL. 
     The second diagonal line LL of the imaginary quadrangle DM may be tilted with respect to the Y axis or the reference line CL parallel to the Y axis. In some exemplary embodiments of the present disclosure, an acute angle formed by the second diagonal line LL and the Y axis or the reference line CL may be a seventh angle b 1 , and the seventh angle b 1  may be in a range of 0° to 15°. 
     Referring to a relationship between the first specific pad PD 12  and the arrangement of the conductive particles  330 , as shown in  FIG.  8   , the seventh angle b 1  formed by the second diagonal line LL of the imaginary quadrangle DM and the Y axis or the reference line CL) may be smaller than the second angle a 12  formed by the lateral side E 12  of the first specific pad PD 12  and the Y axis (or the reference line CL). 
     As described above, in some exemplary embodiments of the present disclosure, the second angle a 12 , which is an acute angle, may be in a range of 5° to 20°, and the seventh angle b 1 , which is an acute angle, may be in a range of 0° to 15°. Further, the seventh angle b 1  may be smaller than the second angle a 12  while both the range of the second angle a 12  and the range of the seventh angle b 1  described above are satisfied. 
     Each of the first side S 1 , the second side S 2 , the third side S 3 , and the fourth side S 4  of the imaginary quadrangle DM might not be parallel to the Y axis, and may also not be parallel to the lateral side E 12  of the first specific pad PD 12 . That is, the imaginary quadrangle DM might not include a side parallel to the Y axis, and might not include a side parallel to the lateral side E 12  of the first specific pad PD 12 . 
     When the imaginary quadrangle DM is a rhombus in which two equilateral triangles are coupled, one side of the imaginary quadrangle DM is parallel to the lateral side E 12  of the first specific pad PD 12  when the sum of the seventh angles b 1  and the second angles a 12  are 30°. Therefore, in order to prevent the above configuration, when the imaginary quadrangle DM is a rhombus in which two equilateral triangles are coupled, the second angle a 12  may be in a range of 5° to 20°, the seventh angle b 1 , which is an acute angle, may be in a range of 0° to 15°, the seventh angle b 1  may be smaller than the second angle a 12 , and the sum of the seventh angle b 1  and the second angles a 12  may be smaller than 30°. 
     The first specific pad PD 12  has a shape tilted with respect to the Y axis as described above. In this case, the number of the conductive particles  330  arranged on the first specific pad PD 12  may be changed according to the arrangement of the conductive particles  330 . For example, when the angle formed by the lateral side E 12  of the first specific pad PD 1  and the Y axis is greater than 5°, the arrangement of the conductive particles  330  may have a greater effect on the number of the conductive particles  330  arranged on the first specific pad PD 12 . 
     As the number of the conductive particles  330  arranged on the first specific pad PD 12  increases, the first specific pad PD 12  and the first specific connection electrode CN 12  may be electrically connected more stably. Further, as the number of the conductive particles  330  arranged on the tint specific pad PD 12  increases, the number of the conductive particles  330  which are not arranged on the first specific pad PD 12  decreases, and thus the probability of occurrence of a short circuit between adjacent pads is reduced by the conductive particles  330 . 
     According to an exemplary embodiment of the present disclosure, when the seventh angle b 1  formed by the second diagonal line LL of the imaginary quadrangle DM and the Y axis (or the reference line CL) is smaller than the second angle a 12  formed by the lateral side E 12  of the first specific pad PD 12  and the Y axis (or the reference line CL), the number of the conductive particles  330  overlapping the first specific pad PD 12  increases. Accordingly, the reliability of electrical connection between the first specific pad PD 12  and the first specific connection electrode CN 12  may be increased, and the probability of a short circuit occurring between adjacent pads may be reduced. 
     For example, according to an exemplary embodiment of the present disclosure, the number of the conductive particles  330  overlapping the first specific pad PD 12  is about eight as shown in  FIG.  8   . 
     Referring to  FIG.  9   , the display device according to Comparative Example 1 illustrates the case in which the seventh angle b 1  and the second angle a 12  are substantially equal. According to Comparative Example 1, the number of the conductive particles  330  overlapping the first specific pad PD 12  is about six. 
     Referring to  FIG.  10   , the display device according to Comparative Example 2 illustrates the case in which the seventh angle b 1  is greater than the second angle a 12 , and particularly, illustrates the case in which one side of the imaginary quadrangle DM is parallel to the lateral side E 12  of the first specific pad PD 12 . According to Comparative Example 2, the number of the conductive particles  330  overlapping the first specific pad PD 12  is about five. 
     For example, the number of the conductive particles  330  overlapping the first specific pad PD 12  in the display device  1 , according to exemplary embodiments of the present disclosure, may be greater than the number of the conductive particles  330  overlapping the first specific pad PD 12  in each of Comparative Example 1 and Comparative Example 2. As a result, the display device  1 , according to exemplary embodiments of the present disclosure, has increased reliability of electrical connection. 
     Further, as the number of the conductive particles  330  overlapping the first specific pad PD 12  increases, the number of the conductive particles  330  which do not overlap the first specific pad PD 12  decreases. Therefore, the display device  1 , according to exemplary embodiments of the present invention, has a lower probability of occurrence of a short-circuit failure than in the Comparative Example 1 and the Comparative Example 2. 
       FIG.  11    is a plan view illustrating the first specific pad of  FIG.  8   , and  FIG.  12    is a plan view illustrating the first specific connection electrode corresponding to the first specific pad of  FIG.  8   . 
     Referring to  FIGS.  11  and  12   , the first specific pad PD 12  includes a plurality of pad concave portions PCV corresponding to the plurality of conductive particles  330  overlapping the plurality of pad concave portions PCV. Further, the first specific connection electrode CN 12  corresponding to the first specific pad PD 12  includes a plurality of electrode concave portions CCV corresponding to the respective pad concave portions PCV. The arrangement of the pad concave portions PCV may be substantially the same as the arrangement of the conductive particles  330  overlapping the first specific pad PD 12 . Therefore, like the conductive particles  330 , the pad concave portions PCV may be disposed at vertices overlapping the first specific pad PD 12 , among the vertices of the imaginary quadrangle DM. 
     An acute angle formed by the second diagonal line LL of the imaginary quadrangle DM and the Y axis may be the seventh angle b 1 , like the conductive particles  330 , and the seventh angle b 1  may be smaller than the second angle a 12  formed by the lateral side E 12  of the first specific pad PD 12  and the Y axis (or the reference line CL). In some exemplary embodiments of the present disclosure, the second angle a 12 , which is an acute angle, may be in a range of 5° to 20°, and the seventh angle b 1 , which is an acute angle, may be in a range of 0° to 15°. Further, the seventh angle b 1  may be smaller than the second angle a 12  while both the range of the second angle a 12  and the range of the seventh angle b 1  described above are satisfied. In addition, the description of the arrangement of the pad concave portions PCV and the relationship between the lateral side E 12  of the first specific pad PD 12  and the arrangement of the pad concave portions PCV are the same as those described above in the description of the conductive particles  330 . 
     Similarly, the arrangement of the electrode concave portions CCV may be substantially the same as the arrangement of the conductive particles  330  overlapping the first specific connection electrode CN 12  or the arrangement of the pad concave portions PCV. In addition, the acute angle formed by the lateral side E 12   a  of the first specific connection electrode CN 12  and the Y axis may be substantially equal to the second angle a 12 , and the shape of the first specific connection electrode CN 12  may be substantially the same as that of the first specific pad PD 12 . Therefore, the relationship between the electrode concave portions CCV and the first specific connection electrode CN 12  is the same as that described above in the description of the conductive particles  330 . 
     Hereinafter, the structure of the display panel  100  in the display region of the display device  1  will be described in detail with reference to  FIGS.  13  to  15   . 
       FIG.  13    is an equivalent circuit diagram illustrating a pixel of  FIG.  1   ,  FIG.  14    is a plan view schematic circuit diagram illustrating a pixel of  FIG.  1   , and  FIG.  15    is a cross-sectional view taken along line A 2 -A 2 ′ of  FIG.  14   . 
     Referring to  FIGS.  13  to  15   , one pixel PX of the display device may include a plurality of signal lines  121 ,  171 , and  172 , a plurality of transistors T 1  and T 2  connected to the plurality of signal lines  121 ,  171 , and  172 , a storage capacitor Cst, and an organic light-emitting diode OLED as shown in  FIG.  13   . 
     The transistors T 1  and T 2  include a switching transistor T 1  and a driving transistor T 2 . 
     The signal lines  121 ,  171 , and  172  include a plurality of gate lines  121  which transmit gate signals Sn (also referred to as scan signals), a plurality of data lines  171  which cross the gate lines  121  and transmit data signals Dm, and a plurality of driving voltage lines  172  which transmit a driving voltage ELVDD and extend in a direction parallel to the data lines  171 .  FIG.  12    shows one gate line  121 , one data line  171 , and one driving voltage line  172  as an example showing one pixel connected to one gate line  121 , one data line  171 , and one driving voltage line  172 , and in actuality, a plurality of gate lines  121 , a plurality of data lines  171 , and a plurality of driving voltage lines  172  may be formed. In some exemplary embodiments of the present disclosure, the plurality of gate lines  121  may extend in a direction parallel to the X axis, and the plurality of data lines  171  and the plurality of driving voltage lines  172  may extend in a direction parallel to the Y axis. 
     The switching transistor T 1  has a control terminal, an input terminal, and an output terminal. The control terminal of the switching transistor T 1  is connected to the gate line  121 , the input terminal is connected to the data line  171 , and the output terminal is connected to the driving transistor T 2 . The switching transistor T 1  transmits the data signal Dm applied to the data line  171  to the driving transistor T 2  in response to the gate signal Sn applied to the gate line  121 . 
     The driving transistor T 2  also has a control terminal, an input terminal, and an output terminal. The control terminal of the driving transistor T 2  is connected to the switching transistor T 1 , the input terminal is connected to the driving voltage line  172 , and the output terminal is connected to the organic light-emitting diode OLED. The driving transistor T 2  flows a driving current Id whose magnitude varies according to a voltage applied between the control terminal and the output terminal. 
     The storage capacitor Cst is connected between the control terminal and the input terminal of the driving transistor T 2 . The storage capacitor Cst charges the data signal applied to the control terminal of the driving transistor T 2  and maintains the data signal after the switching transistor T 1  is turned off. 
     The organic light-emitting diode OLED has an anode connected to the output terminal of the driving transistor T 2 , and a cathode connected to a common voltage ELVSS. The organic light-emitting diode OLED emits light with intensity that depends on the magnitude of the driving current Id of the driving transistor T 2 . The luminance of each pixel is adjusted by adjusting the emission intensity of the organic light-emitting diode OLED for each pixel, so that an image is displayed. 
     A connection relationship between the transistors T 1  and T 2 , the storage capacitor Cst, and the organic light-emitting diode OLED is not limited to that described above, and may be variously changed. 
     Referring to  FIGS.  14  and  15   , a display element layer DSL is disposed on the base substrate  110 . 
     Hereinafter, a structure of the display element layer DSL will be described. 
     A buffer layer  120  is disposed on the base substrate  110 , and a semiconductor layer  130  is formed on the buffer layer  120 . The semiconductor layer  130  includes a switching semiconductor layer  135   a  and a driving semiconductor layer  135   b,  which are formed at positions spaced apart from each other. The semiconductor layer  130  may be made of a polycrystalline silicon material or an oxide semiconductor material. 
     Each of the synching semiconductor layer  135   a  and the driving semiconductor layer  135   b  includes a channel  1355 , and includes a source region  1356  and a drain region  1357  which are disposed at both sides of the channel  1355 . 
     A gate insulating film  140  may be disposed on the switching semiconductor layer  135   a  and the driving semiconductor layer  135   b.  The gate lines  121 , a switching gate electrode  125   a,  a driving gate electrode  125   b  and a first storage capacitor plate  128  may be disposed on the gate insulating film  140 . 
     The gate lines  121  may extend in the X axis direction and may transmit the gate signal Sn. The switching, gate electrode  125   a  protrudes from the gate lines  121  over the switching semiconductor layer  135   a.  The driving gate electrode  125   b  protrudes from the first storage capacitor plate  128  over the driving semiconductor layer  135   b.  Each of the switching gate electrode  125   a  and the driving gate electrode  125   b  at least partially overlaps the channel  1355 . 
     A gate pad  129  connected to an end of the gate line  121  is disposed on the gate insulating film  140 . The gate pad  129  is disposed in the non-display region NA of the display panel  100 . 
     An interlayer insulating film  160  is disposed on the gate insulating film  140 , the gate lines  121 , the driving gate electrode  125   b,  and the first storage capacitor plate  128 , and contact holes  61  and  62  are formed in the gate insulating film  140  and the interlayer insulating film  160  to expose at least a portion of an upper surface of the semiconductor layer  130 . For example, the contact holes  61  and  62  may expose the source region  1356  and the drain region  1357  of the semiconductor layer  130 . Further, a storage contact hole  63  overlapping a portion of the first storage capacitor plate  128  may be formed in the interlayer insulating film  160 . 
     The data lines  171 , the driving voltage line  172 , a switching source electrode  176   a,  a driving source electrode  176   b,  a second storage capacitor plate  178 , a switching drain electrode  177   a,  and a driving drain electrode  177   b  may be disposed on the interlayer insulating film  160 . 
     The data line  171  transmits the data signal Dm, crosses the gate lines  121 , and extends in the Y axis direction. The driving voltage line  172  transmits the driving voltage ELVDD, and is separated from the data line  171  to extend in a direction parallel to the data line  171 . 
     The switching source electrode  176   a  may protrude from the data line  171  toward the switching semiconductor layer  135   a,  and the driving source electrode  176   b  may protrude from the driving voltage line  172  toward the driving semiconductor layer  135   b.  Each of the switching source electrode  176   a  and the driving source electrode  176   b  is connected to the source region  1356  through the contact hole  61 . 
     Each of the switching drain electrode  177   a  and the driving drain electrode  177   b  is connected to the drain region  1357  through the contact hole  62 . 
     The switching drain electrode  177   a  may extend to be electrically connected to the first storage capacitor plate  128  and the driving gate electrode  125   b  through the storage contact hole  63  formed in the interlayer insulating film  160 . 
     The second storage capacitor plate  178  may protrude from the driving voltage lines  172  and may be polymerized with the first storage capacitor plate  128 , and the first storage capacitor plate  128  and the second storage capacitor plate  178  may form the storage capacitor Cst using the interlayer insulating film  160  as a dielectric. 
     The switching semiconductor layer  135   a,  the switching gate electrode  125   a,  the switching source electrode  176   a,  and the switching drain electrode  177   a  form the switching transistor T 1 , and the driving semiconductor layer  135   b,  the driving gate electrode  125   b,  the driving source electrode  176   b,  and the driving drain electrode  177   b  form the driving transistor T 2 . 
     In some exemplary embodiments of the present disclosure, the data line  171  may be electrically connected to the pad PD disposed in the pad region MA of the display panel  100 . For example, the end of the data line  171  may be connected to the pad PD, but the present disclosure is not limited thereto. In some exemplary embodiments of the present disclosure, the data line  171  and the pad PD may be electrically connected to each other through a separate wire. 
     A protective film  180  is formed on the data lines  171 , the driving voltage lines  172 , the switching source electrode  176   a,  the driving source electrode  176   b,  the second storage capacitor plate  178 , the switching drain electrode  177   a,  and the driving drain electrode  177   b.  A contact hole  81  is formed in the protective film  180  to expose at least a portion of the driving drain electrode  177   b.    
     A pixel electrode  191  is formed on the protective film  180 . The pixel electrode  191  is electrically connected to the driving drain electrode  177   b  of the driving transistor T 2  through the contact hole  81 , and is an anode electrode of the organic light-emitting diode OLED. 
     A pixel definition film  350  is formed on the protective film  180 . The pixel definition film  350  has a pixel opening  351  overlapping the pixel electrode  191 . 
     An organic light-emitting layer  370  may be disposed in the pixel opening  351  of the pixel definition film  350 . The organic light-emitting layer  370  may include a plurality of layers including at least one of a light-emitting layer, a hole injecting layer (HIL), a hole transporting layer (HTL), an electron transporting layer (ETL), and an electron injecting layer (EIL). When the organic light-emitting layer  370  includes all of the above layers, the HIL may be disposed on the pixel electrode  191 , which is an anode electrode, and the HTL, the light-emitting layer, the ETL, and the EIL may be sequentially stacked on the HIL. 
     In some exemplary embodiments of the present disclosure, the organic light-emitting layer  370  may include a red organic light-emitting layer which emits red light, a green organic light-emitting layer which emits green light, or a blue organic light-emitting layer which emits blue light. The red organic light-emitting layer, the green organic light-emitting layer, and the blue organic light-emitting layer are formed in a red pixel, a green pixel, and a blue pixel, respectively, to realize a color image. 
     A common electrode  270  is disposed on the pixel definition film  350  and the organic light-emitting layer  370 . The common electrode  270  becomes a cathode electrode of the organic light-emitting diode OLED. The pixel electrode  191 , the organic light-emitting layer  370 , and the common electrode  270  form the organic light-emitting diode OLED. 
     The case in which the display device, according to exemplary embodiments of the present disclosure, is an organic light-emitting display device has been described above. 
     However, the present disclosure is not limited thereto, and the display device, according to exemplary embodiments of the present disclosure may be a display device other than the organic light-emitting display device, for example, a liquid crystal display device or the like. 
       FIGS.  16  and  17    are plan views showing a bonding process of a display panel and a printed circuit board in a display device according to an exemplary embodiment of the present disclosure. 
     Referring to  FIGS.  16  and  17   , a display device  2 , according to an exemplary embodiment of the present disclosure, includes a display panel  100   a,  a data driving IC formed in the form of a chip, which is mounted on the display panel  100   a,  and a printed circuit board  210 . 
     The display panel  100   a  differs from the display panel  100  of the display device  1  shown in  FIGS.  1  and  2    in that a pad region MA includes a first chip pad portion PDB 1  and a second chip pad portion PDB 2  which are electrically connected to the data driving IC formed in the form of a chip, and other elements of the display panel  100   a  are substantially the same as or similar to those of the display panel  100  of the display device  1  shown in  FIGS.  1  and  2   . Therefore, to the extent that descriptions of some elements is not provided, it may be assumed that the undescribed elements are at least similar to those of the display panel  100  of the display device  1  shown in  FIGS.  1  and  2    that have already been described. 
     The first chip pad portion PDB 1  is electrically connected to the data driving IC and the data line of the display element layer DSL and transmits a driving signal from the data driving IC to the pixel PX of the display element layer DSL. In some exemplary embodiments of the present disclosure, the first chip pad portion PDB 1  may include a plurality of first chip pads PDa, and some of the first chip pads PDa may have a shape tilted with respect to the Y axis, similar to the pads PD of the pad portion PDA. 
     The second chip pad portion PDB 2  is a portion which electrically connects the data driving IC to the pad portion PDA, and transmits a control signal or power from a main circuit board or the like electrically connected to the printed circuit board  210 , to the data driving IC. In some exemplary embodiments of the present disclosure, the second chip pad portion PDB 2  may include a plurality of second chip pads PDb, and some of the second chip pads PDb may have a shape tilted with respect to the Y axis, similar to the pads PD of the pad portion PDA. 
     The data driving IC may include a first circuit pad portion IA 1  and a second circuit pad portion IA 2  on a surface facing the display panel  100   a,  for example, on a rear surface of the printed circuit board  210 . 
     The first circuit pad portion IA 1  may be electrically connected to the first chip pad portion PDB 1 , and the second circuit pad portion IA 2  may be electrically connected to the second chip pad portion PDB 2 . 
     The first circuit pad portion IA 1  may include a plurality of first circuit pads ICN 1 , and the first circuit pad ICN 1  may have a shape corresponding to the first chip pad PDa. 
     The second circuit pad portion IA 2  may include a plurality of second circuit pads ICN 2 , and the second circuit pad ICN 2  may have a shape corresponding to the second chip pad PDb. 
     An anisotropic conductive film  300   a  may be disposed between the display panel  100   a  and the data driving IC formed in the form of a chip, and the display panel  100   a  and the data driving IC may be physically and/or electrically coupled to each other through the anisotropic conductive film  300   a.    
     For example, in some exemplary embodiments of the present disclosure, when the base substrate  110  of the display panel  100   a  is made of glass, the data driving IC may be mounted on the display panel  100   a  in the form of a chip-on-glass (COG), or when the base substrate  110  of the display panel  100   a  is made of plastic or the like, the data driving IC may be mounted on the display panel  100   a  in the form of a chip-on-plastic (COP). 
     The anisotropic conductive film  300   a  may have substantially the same structure as the anisotropic conductive film  300 . For example, the anisotropic conductive film  300   a  may include an insulating layer and a plurality of conductive particles disposed in the insulating layer, and the conductive particles in the anisotropic conductive film  300   a  may be arranged in the same manner as the conductive particles  330  of the anisotropic conductive film  300 . 
     The first circuit pads ICN 1  and the first chip pads PDa may be electrically connected to each other through the conductive particles of the anisotropic conductive film  300   a.  In the same manner, the second circuit pads ICN 2  and the second chip pads PDb may be electrically connected to each other through the conductive particles of the anisotropic conductive film  300   a.    
     A relationship between an arrangement of the conductive particles in the anisotropic conductive film  300   a  and the tilted angle of the first chip pad PDa, a relationship between an arrangement of the conductive particles in the anisotropic conductive film  300   a  and the tilted angle of the second chip pad PDb, and the like may be substantially the same as or similar to the relationship between the arrangement of the conductive particles  330  in the anisotropic conductive film  300  and the first specific pad PD 12  described above. 
     According to exemplary embodiments of the present disclosure, a display device having increased reliability can be provided. 
     Exemplary embodiments described herein are illustrative, and many variations can be introduced without departing from the spirit of the disclosure or from the scope of the appended claims. For example, elements and/or features of different exemplary embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.