Patent Publication Number: US-2016232838-A1

Title: Display device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of Korean Patent Application No. 10-2015-0017741 filed on Feb. 5, 2015, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     1. FILED 
     Exemplary embodiments relate to a display device, and more particularly, to a display device including a plurality of driving integrated circuits (ICs). 
     2. DISCUSSION OF THE BACKGROUND 
     As the “Information Society” continues to develop, the demand for thin, light-weight flat panel display (FPD) devices has steadily grown. Examples of FPD devices include a liquid crystal display (LCD) device, an electrophoretic display (EPD) device, an organic light-emitting display device, an inorganic electro-luminescent (EL) display device, a field emission display (FED) device, a surface-conduction electron-emitter display (SED) device, a plasma display panel (PDP) device, and a cathode ray tube (CRT) display device. 
     An FPD device includes a display area including a plurality of pixels arranged to display an image and a non-display area including a plurality of driving integrated circuits (ICs) disposed for driving the plurality of pixels. 
     The driving ICs disposed in the non-display area may be implemented as chips mounted on a display panel in a chip-on-glass (COG) manner or in a tape carrier package (TCP) manner using tape automated bonding (TAB). 
     The driving ICs mounted in the non-display area of the display panel are electrically connected to a controller on a printed circuit board (PCB) using a multi-drop method or a point-to-point method. 
     The point-to-point method, rather than a relatively low-speed multi-drop method, may have a relatively high speed for high-resolution and high-operating speed display devices. 
     The point-to-point method, however, connects the controller on the PCB one-on-one to the driving IC, and thus requires a relatively high number of wires to provide a high-speed interface. 
     In the point-to-point method, a high-speed interface is established using line-on-glass (LOG)-type transmission lines installed on a substrate. However, it is not easy to electrically connect the driving ICs, which are mounted in a COG manner and arranged along a horizontal direction, to the controller by using the LOG-type transmission lines, which are arranged along a vertical direction. Also, it is difficult to provide a high-speed interface due to the relatively high number of transmission lines required. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     Exemplary embodiments provide a display device including a high-speed interface by improving data transmission between a controller and a plurality of driving integrated circuits (ICs) provided in a non-display area, and thus may transmit data at high speed and provide a high-resolution image. 
     Exemplary embodiments may also provide a display device having a printed circuit board (PCB) with a reduced size such that the display panel may have a curvature or be formed of a flexible material. 
     Additional aspects will be set forth in the detailed description which follows, and, in part, will be apparent from the disclosure, or may be learned by practice of the inventive concept. 
     Exemplary embodiments disclose a display device, including: a display panel including: with pixels configured to display an image; driving integrated circuits (ICs) configured to generate and apply a pixel driving signal for driving the pixels; and at least one signal transmission unit configured to electrically connect the driving ICs to one another. The signal transmission unit is disposed on a surface of the display panel, spaced apart from the surface of the display panel by a first distance. The display device also includes a printed circuit board (PCB) including a controller configured to receive an image signal from an external source, generate a driving control signal, and apply the driving control signal to the driving ICs. 
     Exemplary embodiments also disclose a display device with a display area including pixels, the display being configured to display an image. A non-display area of the display device includes a first driving IC configured to apply a pixel driving signal to the pixels; and a second driving IC disposed adjacent to the first driving IC; and a controller electrically connected to the first driving IC, the controller configured to receive an image signal from an external source and configured to apply a driving control signal to the first driving IC. Each of the first driving IC and the second driving IC may include first pads disposed on first surfaces of the first driving IC and the second driving IC contacting the non-display area; and second pads disposed on second surfaces of the first driving IC and the second driving IC, the second surfaces being opposite to first surfaces. 
     The foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the inventive concept, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the inventive concept, and, together with the description, serve to explain principles of the inventive concept. 
         FIG. 1  is a schematic plan view of a display device according to one or more exemplary embodiments. 
         FIG. 2  is a schematic cross-sectional view illustrating exemplary connections between a plurality of driving ICs and a plurality of signal transmission units of the display device according to an exemplary embodiment. 
         FIGS. 3, 4, and 5  are schematic top plan views illustrating exemplary arrangements of the driving ICs and the signal transmission units illustrated in  FIG. 2 . 
         FIG. 6  is a schematic cross-sectional view illustrating exemplary connections between the driving ICs and the signal transmission units of the display device according to an exemplary embodiment. 
         FIG. 7  is a schematic top plan view illustrating the driving ICs and the signal transmission units of  FIG. 6 . 
         FIG. 8  is a schematic bottom plan view illustrating the driving ICs and the signal transmission units of  FIG. 6 . 
         FIG. 9  is a schematic cross-sectional view illustrating exemplary connections between the driving ICs and the signal transmission units of the display device according to an exemplary embodiment. 
         FIG. 10  is a schematic top plan view illustrating the driving ICs and the signal transmission units of  FIG. 9 . 
         FIG. 11  is a schematic cross-sectional view of an example of a driving IC of the display device according to an exemplary embodiment, taken along a sectional line I-I′ of  FIG. 3 . 
         FIG. 12  is a schematic cross-sectional view of an example of a driving IC of the display device according to an exemplary embodiment, taken along the sectional line I-I′ of  FIG. 3 . 
         FIG. 13  is a block diagram illustrating exemplary transmissions of signals in the display device according to an exemplary embodiment. 
         FIGS. 14, 15, and 16  are schematic plan views of first, second, and third driving ICs, respectively, illustrated in  FIG. 13 . 
         FIG. 17  is a block diagram illustrating an exemplary transmission of signals in the display device according to an exemplary embodiment. 
         FIGS. 18, 19, and 20  are schematic plan views of first, second, and third driving ICs, respectively, illustrated in  FIG. 17 . 
         FIG. 21  is a schematic block diagram illustrating exemplary transmissions of signals in the display device according to an exemplary embodiment. 
         FIG. 22  is a perspective view of a curved display device including a signal transmission substrate and a control substrate of the display device, according to an exemplary embodiment. 
         FIG. 23  is a schematic plan view of a display device according to an exemplary embodiment. 
         FIG. 24  is a schematic plan view of a display device according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various exemplary embodiments. It is apparent, however, that various exemplary embodiments may be practiced without these specific details or with one or more equivalent arrangements. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring various exemplary embodiments. 
     In the accompanying figures, the size and relative sizes of layers, films, panels, regions, etc., may be exaggerated for clarity and descriptive purposes. Also, like reference numerals denote like elements. 
     When an element or layer is referred to as being “on,” “connected to,” or “coupled to” another element or layer, it may be directly on, connected to, or coupled to the other element or layer or intervening elements or layers may be present. When, however, an element or layer is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. For the purposes of this disclosure, “at least one of X, Y, and Z” and “at least one selected from the group consisting of X, Y, and Z” may be construed as X only, Y only, Z only, or any combination of two or more of X, Y, and Z, such as, for instance, XYZ, XYY, YZ, and ZZ. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, and/or section from another element, component, region, layer, and/or section. Thus, a first element, component, region, layer, and/or section discussed below could be termed a second element, component, region, layer, and/or section without departing from the teachings of the present disclosure. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for descriptive purposes, and, thereby, to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the drawings. Spatially relative terms are intended to encompass different orientations of an apparatus in use, operation, and/or manufacture in addition to the orientation depicted in the drawings. For example, if the apparatus in the drawings is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. Furthermore, the apparatus may be otherwise oriented (e.g., rotated 90 degrees or at other orientations), and, as such, the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting. As used herein, the singular forms, “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Moreover, the terms “comprises,” “comprising,” “includes,” and/or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Various exemplary embodiments are described herein with reference to sectional illustrations that are schematic illustrations of idealized exemplary embodiments and/or intermediate structures. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, exemplary embodiments disclosed herein should not be construed as limited to the particular illustrated shapes of regions, but are to include deviations in shapes that result from, for instance, manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the drawings are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to be limiting. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure is a part. Terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense, unless expressly so defined herein. 
       FIG. 1  is a schematic plan view of a display device according to an exemplary embodiment. 
     Referring to  FIG. 1 , the display device according to an exemplary embodiment may include a panel substrate  100 , a signal transmission substrate  200  and a control substrate  300 . 
     The panel substrate  100  may include a first substrate  110  and a second substrate  120 . The first substrate  110  and the second substrate  120  may be formed of at least one of a glass material, an insulating material, and a flexible material. A plurality of light-emitting elements may be disposed between the first substrate  110  and the second substrate  120  to display an image, and an area where the light-emitting elements are disposed may be referred to as a display area DA. A non-display area NDA may refer to area where image is not displayed, and may be provided on the second substrate  120 . 
     In the display area DA, a plurality of scan lines SL, a plurality of data lines DL, and a plurality of pixels P may be disposed. Each of the pixels P may include at least one switching element, for example, thin-film transistors (TFTs), which may be turned on or off according to a control signal applied thereto from the control substrate  300 , and a light-emitting element that may emit light under the control of the switching elements. 
     The non-display area NDA may include a plurality of driving integrated circuits (ICs)  121  connected to the scan lines SL and the data lines DL in the display area DA and configured to apply driving control signals to drive the pixels P disposed in the display area DA, a plurality of signal transmission units  122  configured to electrically connect the driving ICs  121  and transmitting signals between the driving ICs  121 , power lines ELVDD and ELVSS configured to apply power to the display area DA, and line-on-glass (LOG)-type transmission lines LOG configured to transmit signals between the driving ICs  121  and the signal transmission substrate  200 . The driving ICs  121  may be mounted on the second substrate  120  in a chip-on-glass (COG) manner. Referring to  FIG. 1 , the power lines ELVDD and ELVSS are disposed in the non-display area NDA, but the exemplary embodiments are not limited thereto. The power lines ELVDD and ELVSS may not be disposed on the signal transmission substrate  200 . The driving ICs  121  may include at least one main driving ICs  121 M. The main driving ICs  121 M may be connected to the signal transmission substrate  200  and/or the control substrate  300 . 
     The driving ICs  121  may include one or more main driving ICs  121 M, and therefore, some of the driving ICs  121  may be main driving ICs  121 M, and a display device according to an exemplary embodiment may include at least one main driving ICs  121 M. Accordingly, some of the driving ICs  121 , i.e., the main driving ICs  121 M, may be connected to the signal transmission substrate  200  and/or the control substrate  300 , and as a result, the size of the signal transmission substrate  200  and/or the control substrate  300  may be reduced. Each of the driving ICs  121  may include at least one pad on at least one of the top surface, bottom surface, and side surfaces thereof, and the signal transmission units  122  may be electrically connected to the pads of the driving ICs  121 . The connections between the driving ICs  121  and the signal transmission units  122  will be described later in detail. 
     The signal transmission substrate  200  may be disposed between the panel substrate  100  and the control substrate  300  and may electrically connect the panel substrate  100  and the control substrate  300 . The signal transmission substrate  200  may transmit data and control signals received from the control substrate  300  to the panel substrate  100 . The signal transmission substrate  200  may be a printed circuit board (PCB) formed of a flexible material, i.e., a flexible PCB (FPCB). 
     The control substrate  300  may include a controller  310 , which is electrically connected to the panel substrate  100  via the signal transmission substrate  200  and controls the operation of the driving ICs  121 . 
     The controller  310  may be electrically connected via the signal transmission substrate  200  to some of the driving ICs  121 , and particularly, the main driving ICs  121 M, of the panel substrate  100 . The controller  310  may generate a data signal based on source data input thereto from an external source (not illustrated), may generate a control signal for controlling the driving timing of the driving ICs  121 , and may transmit the data signal and the control signal to the main driving ICs  121 M. 
       FIG. 2  is a schematic cross-sectional view illustrating exemplary connections between the driving ICs  121  and the signal transmission units  122 , and  FIGS. 3, 4, and 5  are schematic top plan views illustrating exemplary arrangements of the driving ICs  121  and the signal transmission units  122 , according to an exemplary embodiment. 
     For convenience, the driving ICs  121  and the signal transmission units  122  will hereinafter be described, with reference to first, second, and third driving ICs  121   a ,  121   b , and  121   c  and first and second signal transmission units  122   a  and  122   b.    
     Referring to  FIG. 2 , the display device according to an exemplary embodiment may include the first, second, and third driving ICs  121   a ,  121   b , and  121   c , which are mounted on the second substrate  120 . The first, second, and third driving ICs  121   a ,  121   b , and  121   c  may be electrically connected to one another by the first and second signal transmission units  122   a  and  122   b , which connect a plurality of pads  1211 ,  1212   a ,  1212   b , or  1213  that are arranged on a first and/or second side of the top surface, the side surface and/or the bottom surface of the first, second, and third driving IC  121   a ,  121   b , and  121   c . The first and second signal transmission units  122   a  and  122   b  may be metal plates (for example, metal foils) and/or FPCBs. The first and second signal transmission units  122   a  and  122   b  may be disposed spaced apart from the second substrate  120  by a first distance d, which may be substantially the thickness of the driving ICs. An insulating material may be disposed in the gaps between the second substrate  120  and the first and second signal transmission units  122   a  and  122   b  to reduce or prevent signal interference between the power lines ELVDD and ELVSS or the LOG-type transmission lines LOG, which are disposed on the second substrate  120 . At least one of the first, second, and third driving ICs  121   a ,  121   b , and  121   c  may be main driving ICs  121 M, which receive the data signal and the control signal from the control substrate  300 . Since the first, second, and third driving ICs  121   a ,  121   b , and  121   c  transmit signals to one another via the first and second signal transmission units  122   a  and  122   b , an interface for high-speed data transmission may be provided. 
     Referring to  FIGS. 3, 4, and 5 , the first, second or third driving IC  121   a ,  121   b , and  121   c  may include plurality of through silicon vias (TSVs)  1202 , and a plurality of pads may be disposed on the bottom surfaces of each of the first, second, and third driving ICs  121   a ,  121   b , and  121   c  that contacts the second substrate  120 , and on the top surfaces of each of the first, second, and third driving ICs  121   a ,  121   b , and  121   c.    
     The first and second driving ICs  121   a  and  121   b  may be electrically connected by the first signal transmission unit  122   a , which connects a plurality of first pads  1211  that are disposed on a second side of the top surface of the first driving IC  121   a  and a plurality of  2   a  pads  1212   a  that are formed on a first side of the top surface of the second driving IC  121   b . when the first driving IC  121   a  is the main driving IC  121 M configured to receive data and the control signal from the control substrate  300 , the first pads  1211  on the first side of the top surface of the first driving IC  121   a  may be signal transmitting pads Tx, which transmit the control signal generated by the first driving IC  121   a  based on the received data and control signal to the second driving IC  121   b , and the  2   a  pads  1212   a  disposed on the first side of the top surface of the second driving IC  121   b  may be signal receiving pads Rx, which receive the control signal generated by the first driving IC  121   a . The transmission of signals between the first and second driving ICs  121   a  and  121   b  will be described later in detail. 
     The second and third driving ICs  121   b  and  121   c  may be electrically connected by the second signal transmission unit  122   b , which connects a plurality of  2   b  pads  1212   b  disposed on a second side of the top surface of the second driving IC  121   b  and a plurality of third pads  1213  disposed on a first side of the top surface of the third driving IC  121   c.    
     The first pads  1211 , the  2   a  and  2   b  pads  1212   a  and  1212   b , and the third pads  1213 , which are disposed on the top surfaces of the first, second, and third driving ICs  121   a ,  121   b , and  121   c , respectively, may be arranged in a vertical direction in a single column on one side of the top surfaces of the first, second, and third driving ICs  121   a ,  121   b , and  121   c , respectively, as illustrated in  FIGS. 3 and 4 , or may be arranged in the vertical direction in two or more columns on one side of the top surfaces of the first, second, and third driving ICs  121   a ,  121   b , and  121   c , respectively, as illustrated in  FIG. 5 . 
     The first signal transmission unit  122   a  may be disposed over all of the first pads  1211  disposed on a second side of the first driving IC  121   a  and all of the  2   a  pads  1212   a  disposed on the first side of the second driving IC  121   b , and the second signal transmission unit  122   b  may be disposed over all of the  2   b  pads  1212   b  disposed on the second side of the second driving IC  121   b  and all of the third pads  1213  disposed on the first side of the third driving IC  121   c , as illustrated in  FIGS. 3 and 5 . The first signal transmission unit  122   a  may be disposed over some of the first pads  1211  and some of the  2   a  pads  1212   a , and the second signal transmission unit  122   b  may be disposed over some of the  2   b  pads  1212   b  and some of the third pads  1213 , as illustrated in  FIG. 4 . 
       FIG. 6  is a schematic cross-sectional view illustrating exemplary connections between the driving ICs  121  and the signal transmission units  122  of the display device according to an exemplary embodiment,  FIG. 7  is a schematic top plan view illustrating the driving ICs  121  and the signal transmission units  122  of  FIG. 6 , and  FIG. 8  is a schematic bottom plan view illustrating the driving ICs  121  and the signal transmission units  122  of  FIG. 6 . 
     Referring to  FIGS. 6, 7, and 8 , the first signal transmission unit  122   a  does not electrically connect pads disposed on the top surfaces of the first driving IC  121   a  and the second driving IC  121   b , and the second signal transmission unit  122   b  does not electrically connect pads disposed on the top surface of the second driving IC  121   b  and the third driving IC  121   c . Instead, the first signal transmission unit  122   a  may be connected to the pads disposed on the top surface of the first driving IC  121   a  on second side thereof and pads disposed on the bottom surface of the second driving ICs  121   b  on the first side thereof. The pads disposed on the bottom surface of the first, second, and third driving ICs  121   a ,  121   b  and  121   c  may be pads that are typically disposed on the second substrate  120  for transmitting signals to and/or receiving signals from the signal transmission substrate  200  and/or the control substrate  300 . The pads disposed on the top surface of the first, second, and third driving ICs  121   a ,  121   b , and  121   c  may be arranged according to the TSVs  1202 . 
     The first and second driving ICs  121   a  and  121   b  may be electrically connected by the first signal transmission unit  122   a , and the first signal transmission unit  122   a  connects the first pads  1211  disposed on a second side of the top surface of the first driving IC  121   a  and  2   b _ a  pads  1212   b _ a  that are disposed on a first side of the bottom surface of the second driving IC  121   b.    
     The second and third driving ICs  121   b  and  121   c  may be electrically connected by the second signal transmission unit  122   b , and the second signal transmission unit  122   b  connects a plurality of  2   b  pads  1212   b  that are disposed on a second side of the top surface of the second driving IC  121   b  and  3   b _ a  pads  1213   b _ a  that are disposed on a first side of the bottom surface of the third driving IC  121   c.    
     The first and second signal transmission units  122   a  and  122   b  may be flexible metal plates and/or FPCBs. 
       FIG. 9  is a schematic cross-sectional view illustrating exemplary connections between the driving ICs  121  and the signal transmission units  122  of the display device according to an exemplary embodiment, and  FIG. 10  is a schematic top plan view illustrating the driving ICs  121  and the signal transmission units  122  of  FIG. 9 . 
     Referring to  FIGS. 9 and 10 , a plurality of pads may be disposed on the sides of first, second, and third driving ICs  121   a ,  121   b , and  121   c  corresponding to the TSVs  1202 . 
     Accordingly, first and second signal transmission units  122   a  and  122   b  may connect the pads on the sides of the first, second, and third driving ICs  121   a ,  121   b , and  121   c , as illustrated in  FIG. 10 , to transmit signals between the first, second, and third driving ICs  121   a ,  121   b , and  121   c.    
     The driving ICs  121  may have a plurality of pads disposed on the top surface and/or bottom surface thereof, or may have a plurality of pads on the sides thereof, instead of at the top surface thereof. A plurality of pads may be disposed on the top surface or the sides of the driving ICs  121  and are electrically connected by the signal transmission units  122  to transmit data and the control signal therebetween, and therefore, the number of LOG-type transmission lines “LOG” disposed on the second substrate  120  may be reduced. Thus, larger data transmission may be enabled and a high-speed interface may be secured by the arrangement of pads at the top surface or the sides of the driving ICs  121 . There are two methods for arranging pads at the top surface or the sides of the driving ICs  121 , and these two methods will hereinafter be described with reference to  FIGS. 11 and 12 . 
       FIG. 11  is a schematic cross-sectional view of an example of a driving IC  121  of the display device according to an exemplary embodiment, taken along a sectional line I-I′ of  FIG. 3 . 
     Referring to  FIG. 11 , the driving IC  121  may be mounted on the second substrate  120 , and a bottom pad, i.e., a second pad  1211 B, may be disposed on a bottom surface of the driving IC  121  that contacts the second substrate  120 . 
     A first metal dielectric layer  1201  may be disposed on the second pad  1211 B. The first metal dielectric layer  1201  may be coated with an insulating material (not shown), and may include first and second metal wires M 1  and M 2  electrically connected to the second pad  1211 B, and a first metal contact MC 1  electrically connecting the second pad  1211 B and the first and second metal wires M 1  and M 2 . 
     A TSV  1202  may be formed above the first metal dielectric layer  1201  to penetrate a wafer  1204  of the driving IC  121  where electric elements, such as a transistor, are disposed. An insulating layer  1203  may be formed on the sidewalls of the TSV  1202  insulating the TSV  1202  from the electric elements formed in the wafer  1204 . 
     A second metal dielectric layer  1205  may be disposed on the TSV  1202 . The second metal dielectric layer  1205  may be coated with an insulating material (not shown) and may include third and fourth metal wires M 3  and M 4  electrically connected to the TSV  1202 , and a second metal contact MC 2  electrically connecting the TSV  1202  and the third and fourth metal wires M 3  and M 4 . 
     A first pad  1211 T may be disposed on the second metal dielectric layer  1205  and on the top surface of the driving IC  121 . 
     More specifically, by forming the TSV  1202  through the wafer  1204  of the driving IC  121 , the first pad  1211 T may be formed on the top surface of the driving IC  121 , but exemplary embodiments are not limited thereto. That is, the first pad  1211 T may be disposed as illustrated in  FIG. 12 , which does not include forming the TSV. 
       FIG. 12  is a schematic cross-sectional view of another example of a driving IC  121  of the display device according to an exemplary embodiment, taken along the sectional line I-I′ of  FIG. 3 . 
     Referring to  FIG. 12 , a driving IC  121  may be mounted on the second substrate  120 . A second pad  1211 B may be disposed at the bottom surface of a wafer  1204  for transmitting signals to and/or receiving signals from the signal transmission substrate  200 , and a first pad  1211 T may be disposed on the top surface of the wafer  1204  for transmitting signals to or receiving signals from the driving IC  121 . The first and second pads  1211 T and  1211 B may be formed of a metal coil, and thus may transmit signals due to the magnetic coupling therebetween. 
     When the first and second pads  1211 T and  1211 B are formed of a metal material, the driving IC  121  may also include an induction coil  1211 C disposed on the bottom surface of the wafer  1204  contacting the second pad  1211 B. The induction coil  1211 C may induce signal coupled between the first and second pads  1211 T and  1211 B, and thus may transmit signal between the first and second pads  1211 T and  1211 B without the TSV. 
     Referring to  FIGS. 11 and 12 , the driving ICs  121  may include a high-speed interface by including the TSV through the wafer  1204 , by including the first and second pads  1211 T and  1211 B formed of a metal coil, or by including the induction coil  1211 C at the bottom of the wafer  1204 . That is, since pads can also be disposed on the top surface of the driving ICs  121  as well as the bottom surface of the driving ICs  121 . Therefore, the display device according to an exemplary embodiment may reduce any limits in the amount of data transmission using the LOG-type transmission lines LOG on the second substrate  120  and improve the data processing speed of the display device. Accordingly, the display device according to the current exemplary embodiment may transmit larger data and may provide a high-quality image with a high resolution. 
     The transmission of signals between the driving ICs  121  and the controller  310  will hereinafter be described with reference to  FIGS. 13, 14, 15, and 16 , in which driving ICs are arranged in a master-slave manner. 
       FIG. 13  is a block diagram illustrating exemplary transmissions of signals in the display device according to an exemplary embodiment, and  FIGS. 14, 15, and 16  are schematic plan views of the first, second, and third driving ICs  121   a ,  121   b  and  121   c , respectively, illustrated in  FIG. 13 . 
     Referring to  FIG. 13 , data and a control signal applied by the controller  310  may be transmitted to the first driving IC  121   a . Therefore, the first driving IC  121   a  may be a main driving IC  121 M. 
     The first driving IC  121   a , i.e. a main driving IC  121 M, may generate and transmit a pixel driving signal to the panel substrate  100  based on the data and the control signal received from the controller  310 , and may transmit data that is not processed by the first driving IC  121   a  to the second driving IC  121   b . The first driving IC  121   a  may operate as a master for the second driving IC  121   b . The first driving IC  121   a  may be electrically connected to the controller  310  via the signal transmission substrate  200  and may be electrically connected to the second driving IC  121   b  via a signal transmission unit  122 . Accordingly, referring to  FIG. 14 , the first pads  1211 , which are disposed on the first driving IC  121   a , may be signal transmitting pads  1211 Tx configured to transmit signals to the second driving IC  121   b.    
     The second driving IC  121   b  may generate and transmit a pixel driving signal to the panel substrate  100  based on data and a control signal received from the first driving IC  121   a , and may transmit data is not to processed by the second driving IC  121   b  to the third driving IC  121   c . The second driving IC  121   b  may operate as a master for the third driving IC  121   c . The second driving IC  121   b  may be electrically connected to the first and third driving IC  121   a  and  121   c  via a signal transmission unit  122 . Accordingly, referring to  FIG. 15 , the second driving IC  121   b  may include signal receiving pads  1212 Rx configured to receive data and a control signal from the first driving IC  121   a  and signal transmitting pads  1212 Tx configured to transmit data and a control signal to the third driving IC  121   c . That is, the  2   a  pads  1212   a  disposed on the first side of the second driving IC  121   b  may correspond to the signal receiving pads  1212 Rx, and the  2   b  pads  1212   b  disposed on the second side of the second driving IC  121   b  may correspond to the signal transmitting pads  1212 Tx. 
     The third driving IC  121   c  may generate and transmit a pixel driving signal to the panel substrate  100  based on data and a control signal received from the second driving IC  121   b . Referring to  FIG. 16 , the third pads  1213 , which are disposed on the third driving IC  121   c , may be signal receiving pads  1213 Rx configured to receive data and a control signal from the second driving IC  121   b.    
       FIG. 17  is a block diagram illustrating exemplary transmissions of signals in the display device according to an exemplary embodiment, and  FIGS. 18, 19, and 20  are schematic plan views of the first, second, and third driving ICs  121   a ,  121   b  and  121   c , respectively, illustrated  FIG. 17 . 
     Referring to  FIG. 17 , data and a control signal applied by the controller  310  may be transmitted to the second driving IC  121   b . Therefore, the second driving IC  121   b  may be a main driving IC  121 M. 
     The first driving IC  121   a  may generate and transmit a pixel driving signal to the panel substrate  100  based on data and a control signal received from the second driving IC  121   b . The first driving IC  121   a  may be electrically connected to the second driving IC  121   b  via a signal transmission unit  122 . Accordingly, referring to  FIG. 18 , the first pads  1211 , which are disposed on the first driving IC  121   a , may be signal receiving pads  1211 Rx configured to receive signals from the second driving IC  121   b.    
     The second driving IC  121   b  may generate and transmit a pixel driving signal to the panel substrate  100  based on the data and the control signal received from the controller  310 , and may transmit data that is not processed by the second driving IC  121   b  to the first and third driving ICs  121   a  and  121   c . The second driving IC  121   b  may be a main driving IC  121 M. The second driving IC  121   b  may be electrically connected to the controller  310  via the signal transmission substrate  200  and may be electrically connected to the first and third driving ICs  121   a  and  121   c  via different signal transmission units  122 . Accordingly, referring to  FIG. 19 , the second driving IC  121   b  may include signal transmitting pads  1212 Tx on the first side configured to transmit signals to the first driving IC  121   a  and signal transmitting pads  1212 Tx on the second side configured to transmit signals to the third driving IC  121   c . That is, the  2   a  pads  1212   a  disposed on the first side of the second driving IC  121   b  and the  2   b  pads  1212   b  disposed on the second side of the second driving IC  121   b , may correspond to the signal transmitting pads  1212 Tx. 
     The third driving IC  121   c  may generate and transmit a pixel driving signal to the panel substrate  100  based on data and a control signal received from the second driving IC  121   b . Referring to  FIG. 20 , the third pads  1213 , which are disposed on the third driving IC  121   c , may be signal receiving pads  1213 Rx configured to receive data and a control signal from the second driving IC  121   b.    
       FIG. 21  is a schematic block diagram illustrating exemplary transmissions of signals in the display device according to an exemplary embodiment. 
     Referring to  FIG. 21 , data and a control signal applied by the controller  310  may be transmitted to the first and second driving ICs  121   a  and  121   b . Therefore, the first and second driving ICs  121   a  and  121   b  may be main driving ICs  121 M. 
     The first and second driving ICs  121   a  and  121   b  may generate and transmit a pixel driving signal to the panel substrate  100  based on the data and the control signal received from the controller  310 , and may transmit data that is not processed by the first and second driving ICs  121   a  and  121   b , to the third driving IC  121   c  and a fourth driving IC  121   d , respectively. The first and second driving ICs  121   a  and  121   b  may be electrically connected to the controller  310  via the signal transmission substrate  200 , and may be electrically connected to the third and fourth driving ICs  121   c  and  121   d , respectively, via different signal transmission units  122 . Accordingly, each of the first and second driving ICs  121   a  and  121   b , like the first driving IC  121   a  in the example of  FIG. 14 , may include signal transmitting pads for transmitting signals. 
     The third and fourth driving ICs  121   c  and  121   d  may generate and transmit a pixel driving signal to the panel substrate  100  based on data and a control signal received from the first and second driving ICs  121   a  and  121   b , respectively. Each of the third and fourth driving ICs  121   c  and  121   d , like the third driving IC  121   c  in the example of  FIG. 16 , may include signal receiving pads configured to receive data and a control signal. Each of the third and fourth driving ICs  121   c  and  121   d  may also include signal transmitting pads if there are other driving ICs  121  connected thereto via signal transmission units  122 . 
       FIG. 22  is a perspective view of a curved display device including the signal transmission substrate  200  and the control substrate  300  of the display device, according to an exemplary embodiment. 
     Referring to  FIG. 22 , a curved display device may include the signal transmission substrate  200  and the control substrate  300 , such that one or more main driving ICs  121 M may be included in an area with a relatively low curvature, i.e., an area with a high level of flatness. Accordingly, the reliability of the bonding among the driving ICs  121 , the signal transmission substrate  200  and the control substrate  300  may be improved. The signal transmission substrate  200  and the control substrate  300  may also be disposed to a display device with a flexible substrate, as well as a curved display device. 
       FIG. 23  is a schematic plan view of a display device according to an exemplary embodiment. Referring to  FIG. 23 , the display device according to an exemplary embodiment may include a panel substrate  100  and a control substrate  300 . 
     The display device according to an exemplary embodiment has a similar structure to the display device according to the pervious exemplary embodiments illustrated in of  FIG. 1 , but the signal transmission substrate  200  is omitted. Referring to  FIG. 23 , the control substrate  300  may be electrically connected to the panel substrate  100  without the signal transmission substrate  200 . 
       FIG. 24  is a schematic plan view of a display device according to an exemplary embodiment. Referring to  FIG. 24 , the display device according to an exemplary embodiment may include a panel substrate  500 , a plurality of signal transmission films  600  and a control substrate  700 . 
     The panel substrate  500  may include a first substrate  510  and a second substrate  520 . A plurality of light-emitting elements for displaying an image may be disposed between the first substrate  510  and the second substrate  520 , and an area where the light-emitting elements are disposed may be referred to as a display area DA. A non-display area NDA may refer to area where image is not displayed, and may be provided on the second substrate  520 . 
     In the display area DA, a plurality of scan lines SL, a plurality of data lines DL and a plurality of pixels P may be disposed. Each of the pixels P may include at least one switching elements, for example, thin-film transistor (TFTs), which may be turned on or off according to a control signal applied thereto from the control substrate  700 , and a light-emitting element that may emit light under the control of the switching elements. 
     The non-display area NDA may include a pad area including a plurality of pads connected to the scan lines SL and the data lines DL. The pad area may be connected to the signal transmission films  600 . 
     At least one signal transmission film  600  may be disposed between the panel substrate  500  and the control substrate  700 . The signal transmission films  600  may be configured to receive data and a control signal from the control substrate  700  and transmit the received data and the received control signal to the panel substrate  500 . The signal transmission films  600  may include flexible insulating films  610  formed of a polyimide (PI) material, driving ICs  620  mounted in the open areas of the flexible insulating films  210 , and signal transmission units  630  configured to transmit signals between the driving ICs  620  disposed on the signal transmission films  600 . The signal transmission films  600  including the driving ICs  620  mounted thereon may be referred to as chip-on-films (COFs). At least one of the signal transmission films  600  may be electrically connected to a controller  710 , which is mounted on the control substrate  700 . The at least one signal transmission film  600  is connected to the controller  710 , configured to transmit signal between the driving ICs  620  disposed on the signal transmission films  600  via the signal transmission units  630 . Therefore, the size of the control substrate  700 , which is formed of a rigid material, may be reduced, and thereby improving applicability to a curved and/or flexible display device. The connections, and the transmission of signals, between the driving ICs  620 , which are mounted on the signal transmission films  600 , and the signal transmission units  630  are the same as those in the exemplary embodiments illustrated in  FIGS. 3 to 21 , and thus, detailed descriptions thereof will be omitted. 
     The control substrate  700  may be electrically connected to the panel substrate  500  via the signal transmission films  600 , and may include the controller  710 , which may be configured to control the operation of the driving ICs  620  mounted on the signal transmission films  600 . The controller  710  is the same as its counterpart of  FIG. 1 , and thus, a detailed description thereof will be omitted. 
     Although certain exemplary embodiments and implementations have been described herein, other embodiments and modifications will be apparent from this description. Accordingly, the inventive concept is not limited to such embodiments, but rather to the broader scope of the presented claims and various obvious modifications and equivalent arrangements.