Patent Publication Number: US-2022214770-A1

Title: Touch sensing unit and display device including the same

Description:
This application is a Continuation of co-pending U.S. patent application Ser. No. 17/148,534, filed on Jan. 13, 2021, which is a Continuation of U.S. patent application Ser. No. 16/359,711 filed on Jul. 2, 2019 w claims priority to Korean Patent Application No. 10-2018-0112025 filed on Sep. 19, 2018 in the Korean Intellectual Property Office, the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a display device and, more specifically, to a touch sensing unit and a display device including the same. 
     DISCUSSION OF THE RELATED ART 
     Display devices are an important component of various products, as they may be used in displaying multimedia. There are many different types of display devices available today. Examples of commonly used display devices include organic light-emitting display (OLED) devices and liquid-crystal display (LCD) devices. 
     Modern user interfaces, such as those used in smartphones and tablet computers, commonly utilize touch as a primary means of input. To sense the touch of a user, a touch sensing unit may be used. Touch sensing units may be incorporated into a display device so that a single surface may be used for displaying multimedia and sensing touch input. For example, a touch sensor may be attached to one surface of a display panel or may be fabricated integrally with a display panel. A user can input information by pressing or touching the touch sensing unit while viewing images displayed on the screen of the display device. 
     SUMMARY 
     A touch sensing unit, includes a plurality of first sensing electrodes and a plurality of second sensing electrodes intersecting with and insulated from the plurality of first sensing electrodes. The plurality of first sensing electrodes includes a plurality of first sensor portions and a plurality of first connection portions connecting each of the plurality of first sensor portions with one another. The plurality of second sensing electrodes includes a plurality of second sensor portions, a plurality of stem sensors extended from the plurality of second sensor portions, and a plurality of second connection portions connecting each of the plurality of sensor portions with one another. Each of the plurality of first sensor portions includes a plurality of depressions indented inwardly. Each of the plurality of stem sensors is disposed such that it is at least partially surrounded by a respective depression of the plurality of depressions. 
     A display device includes a base layer having a display area and a non-display area at least partially surrounding the display. A plurality of first signal lines is disposed on a first side border of the non-display area. A plurality of second signal lines is disposed on a second side border of the non-display area. A ground line is disposed on a third border of the non-display area. A plurality of first sensing electrodes is disposed in the display area and is connected to the plurality of first signal lines. A plurality of second sensing electrodes is disposed in the display area, is connected to the plurality of second signal lines, and intersects with and is insulated from the plurality of first sensing electrodes. A plurality of ground electrodes disposed in the display area, connected to the ground line, and disposed between the plurality of first sensing electrodes and the plurality of second sensing electrodes. Each of the ground electrodes of the plurality of ground electrodes are insulated from the plurality of first sensing electrodes and the plurality of second sensing electrodes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the present disclosure and many of the attendant aspects thereof will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which: 
         FIG. 1  is a plan view illustrating an organic light-emitting display device according to an exemplary embodiment of the present disclosure; 
         FIG. 2  is a cross-sectional view of an organic light-emitting display device according to an exemplary embodiment of the present disclosure; 
         FIG. 3  is a cross-sectional view schematically illustrating a structure of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 4  is a plan view schematically illustrating an arrangement of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 5  is a layout view illustrating an area AA 1  of the touch sensing unit shown in  FIG. 4 , according to an exemplary embodiment of the present disclosure; 
         FIG. 6  is an enlarged view of area AA 2  of  FIG. 5 ; 
         FIG. 7  is a cross-sectional view taken along line I 1 -I 1 ′ of  FIG. 6  in the touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 8  is a cross-sectional view taken along line I 2 -I 2 ′ of  FIG. 5  in the touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 9  is an equivalent circuit diagram illustrating a touch sensing unit when a touch event has occurred according to an exemplary embodiment of the present disclosure; 
         FIG. 10  is a layout view illustrating a part of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 11  is a cross-sectional view taken along line II 1 -II 1 ′ of  FIG. 10  in a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 12  is a plan view schematically illustrating an arrangement of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 13  is a layout view illustrating a portion corresponding to area AB 1  in the touch sensing unit of  FIG. 12 ; 
         FIG. 14  is a layout view illustrating a portion corresponding to area AB 2  in the touch sensing unit of  FIG. 12 ; 
         FIG. 15  is a cross-sectional view illustrating a touch sensing unit, taken along line III 1 -III 1 ′ of  FIG. 13 , according to an exemplary embodiment of the present disclosure; 
         FIG. 16  is a cross-sectional view illustrating a touch sensing unit, taken along line III 2 -III 2 ′ of  FIG. 14 , according to an exemplary embodiment of the present disclosure; 
         FIG. 17  is an equivalent circuit diagram illustrating a touch sensing unit when a touch event has occurred according to an exemplary embodiment of the present disclosure; 
         FIG. 18  is a layout view illustrating a part of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 19  is a cross-sectional view of a touch sensing unit, taken along line IV 1 -IV 1 ′ of  FIG. 18 , according to an exemplary embodiment of the present disclosure; 
         FIG. 20  is a layout view illustrating a part of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 21  is a plan view schematically illustrating an arrangement of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 22  is a layout view illustrating a portion corresponding to area AC 1  in the touch sensing unit of  FIG. 21 ; 
         FIG. 23  is a layout view illustrating a portion corresponding to area AC 2  in the touch sensing unit of  FIG. 21 ; 
         FIG. 24  is a cross-sectional view illustrating a touch sensing unit, taken along line V 1 -V 1 ′ of  FIG. 23 , according to an exemplary embodiment of the present disclosure; 
         FIG. 25  is a cross-sectional view illustrating a touch sensing unit, taken along line V 2 -V 2 ′ of  FIG. 23 , according to an exemplary embodiment of the present disclosure; 
         FIG. 26  is a plan view schematically illustrating an arrangement of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 27  is a layout view illustrating a portion corresponding to area AD 1  of the touch sensing unit of  FIG. 26 ; 
         FIGS. 28 and 29  are layout views illustrating a part of touch sensing units according to exemplary embodiments of the present disclosure; 
         FIG. 30  is a plan view schematically illustrating an arrangement of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 31  is a layout view illustrating a portion corresponding to area AF 1  of the touch sensing unit of  FIG. 30 ; 
         FIG. 32  is a layout view illustrating a part of touch sensing units according to an exemplary embodiment of the present disclosure; 
         FIG. 33  is a layout view illustrating a part of a touch sensing unit according to an exemplary embodiment of the present disclosure; 
         FIG. 34  is an enlarged view illustrating area AG 1  of  FIG. 1 ; 
         FIG. 35  is a cross-sectional view taken along line VI 1 -VI 1 ′ of  FIG. 34 ; and 
         FIG. 36  is a perspective view illustrating an organic light-emitting display device according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present disclosure and many of the attendant aspects thereof may be understood more readily by reference to the following detailed description of embodiments and the accompanying drawings. The inventive concept may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the inventive concept to those skilled in the art. 
     It will be understood that when an element or layer is referred to as being “on”, “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. 
     Display devices, according to a variety of exemplary embodiments of the present disclosure, may be used as a display screen of a variety of devices that display video or still image. The various display devices may be configured to display video or still images either monoscopically or stereoscopically. These display devices may be incorporated into portable electronic devices such as a mobile communications terminal, a smart phone, a tablet PC, a laptop computer, a smart watch, and a navigation device, as well as stationary electronic devices, such as a television, a monitor, an electronic billboard, and a smart household device, such as an Internet of Things device. 
     Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, an organic light-emitting display device will be described as an example of a display device. It is, however, to be understood that the present disclosure is not limited thereto. The display device, according to exemplary embodiments of the present disclosure, can also be applied to other display devices such as a liquid-crystal display device, a field emission display device, an electrophoretic device, a quantum-dot display device, or a micro LED display device, without departing from the scope of the present disclosure. Like reference numerals may denote like elements throughout the specification and the drawings. 
       FIG. 1  is a plan view of an organic light-emitting display device according to an exemplary embodiment of the present disclosure.  FIG. 2  is a cross-sectional view of the organic light-emitting display device according to an exemplary embodiment of the present disclosure. 
     Referring to  FIG. 1 , the organic light-emitting display device  1  may have a substantially rectangular shape that is longer in a first direction dr 1  than in a second direction dr 2 , according to an exemplary embodiment of the present disclosure. For example, the border of the organic light-emitting display device  1  may include longer sides extended in the first direction dr 1  and shorter sides extended in the second direction dr 2 . 
     As used herein, for convenience of illustration, the vertical direction in the drawings is defined as a first direction dr 1 , and the horizontal direction is defined as a second direction dr 2 . In addition, a direction orthogonal to the first direction dr 1  and to the second direction dr 2  is defined as a third direction dr 3  and may extend in the direction out from the page. In addition, as inclined directions different from the first direction dr 1  and the second direction dr 2  on the plane, a direction extended in the upper left direction with respect to the imaginary reference point is defined as a fourth direction dr 4 , a direction extended in the upper right direction with respect to the imaginary reference point is defined as a fifth direction dr 5 , a direction extended in the lower left direction with respect to the imaginary, reference point is defined as a sixth direction dr 6 , and a direction extended in the lower right direction with respect to the imaginary reference point is defined as a seventh direction dr 7 . It is to be noted that the exemplary embodiments of the present disclosure are not limited by the directions defined above and the first to seventh directions dr 1  to dr 7  are relative directions provided for illustrative purposes. 
     The organic light-emitting display device  1  may include a display area DA 1  and a non-display area NDA. 
     The display area DA 1  is defined as an area for displaying images. The organic light-emitting display device  1  may include a plurality of pixels that are entirely disposed within the display area DA 1 . The display area DA 1  may also be used as an area for recognizing a user&#39;s touch input as well as the area for displaying images. 
     The non-display area NDA is defined as an area where no image is displayed. For example, none of the pixels are disposed within the non-display area NDA. The non-display area NDA may be disposed on the outer side of the display area DA 1  and may at least partially surround the display area DA 1 . 
     A speaker module, a camera module, a sensor module, etc. may be disposed in a certain part of the non-display area NDA. In an exemplary embodiment of the present disclosure, the sensor module may include a luminance sensor, a proximity sensor, an infrared sensor, and or an ultrasonic sensor. 
     Referring to  FIG. 2 , in an exemplary embodiment of the present disclosure, the organic light-emitting display device  1  may include a first substrate  10 , a circuit layer  20  disposed on the first substrate  10 , a light-emitting element layer  30  disposed on the circuit layer  20 , an encapsulation layer  40  disposed on the light-emitting element layer  30 , a touch layer  50  disposed on the encapsulation layer  40 , and a second substrate  60  disposed on the touch layer  50 . It is, however, to be understood that the present disclosure is not limited thereto. Each of the layers may be made up of either a signal layer or multiple layers. Another layer may be added or some of the layers described herein may be omitted, as desired. The stacked structure of the organic light-emitting display device  1  will be described later with reference to  FIG. 35 . 
     As shown in  FIG. 35 , the second substrate  60  includes a cover window  601 . The upper surface of the cover window  601  may be the surface on which a users input means (e.g. a finger or stylus) touches. 
     As shown in  FIG. 3 , the organic light-emitting display device  1  may include a touch sensing unit  50   a.  In an exemplary embodiment of the present disclosure, the touch sensing unit  50   a  may be disposed in the touch layer  50 . The arrangement of constituent elements of the touch sensing unit  50   a  will be described with reference to  FIGS. 3 and 4 . 
       FIG. 3  is a cross-sectional view schematically illustrating the structure of the touch sensing unit, according to an exemplary embodiment of the present disclosure.  FIG. 4  is a plan view schematically showing the arrangement of the touch sensing unit according to the above exemplary embodiment. 
     Referring to  FIGS. 3 and 4 , the touch sensing unit  50   a  may have a multi-layer structure and may be disposed on a base layer  51 . The touch sensing unit  50   a  includes pluralities of sensing electrodes  510  and  520 , a plurality of signal lines  530 ,  540  and  550  connected to the plurality of sensing electrodes  510  and  520 , and at least one insulating layer (e.g., a first touch insulating layer  53 ). The touch sensing unit  50   a  may be configured to sense an input from an external source by, for example, capacitive sensing. In general, the pluralities of sensing electrodes  510  and  520  are arranged in the area falling within the display area DA 1  described above, and the plurality of signal lines  530 ,  540  and  550  are arranged in the area falling within the non-display area NDA, and the at least one insulating layer  53  may be disposed over the entire surface of the display area DA 1  and the non-display area NDA. It is, however, to be understood that the present disclosure is not limited thereto. 
     As shown in  FIG. 3 , the touch sensing unit  50   a  may include, in an exemplary embodiment of the present disclosure, a first touch conductive layer  52 , a first touch insulating layer  53 , a second touch conductive layer  54  and a second touch insulating layer  55  stacked on one another in the third direction dr 3 . According to an exemplary embodiment of the present disclosure, the second touch insulating layer  55  may be omitted. 
     The touch sensing unit  50   a  may be disposed on the base layer  51 . The base layer  51  may correspond to the above-described encapsulation layer  40 . In an exemplary embodiment of the present disclosure, the base layer  51  may correspond to a second inorganic layer  451  (see  FIG. 35 ) of an encapsulation layer  450  (see  FIG. 35 ). For example, the first touch conductive layer  52  may be disposed directly on the second inorganic layer  451  of the encapsulation layer  450 . It is, however, to be understood that the present disclosure is not limited thereto. The organic light-emitting display device  1  may further include a touch buffer layer, which may work as the base layer  51 . The touch buffer layer may be disposed on the second inorganic layer of the encapsulation layer. The first touch conductive layer  52  may be disposed on the touch buffer layer. The touch buffer layer may be configured to smoothen the surface of the encapsulation layer  450  and to prevent permeation of moisture or air. The touch buffer layer may be an inorganic layer containing silicon nitride (SiNx). 
     Each of the first touch conductive layer  52  and the second touch conductive layer  54  may be made up of a single-layer or a stack of multiple layers stacked in the third direction dr 3 , when the touch conductive layer is made of a single layer, it may include a metal layer or a transparent conductive layer. The metal layer may, for example, include molybdenum, silver, titanium, copper, aluminum, and/or alloys thereof. The transparent conductive layer may include a transparent conductive oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), and/or indium tin zinc oxide (ITZO). In addition, the transparent conductive layer may include a conductive polymer such as PEDOT, metal nanowire, graphene, etc. 
     When the touch conductive layer is made of multiple layers, it may include multiple metal layers. The multiple metal layers may have a three-layer structure of, for example, titanium (Ti)/aluminum (Al)/titanium (Ti). The touch conductive layer may include at least one metal layer and at least one transparent conductive layer. 
     Each of the first touch conductive layer  52  and the second touch conductive layer  54  includes a plurality of patterns. In the following description, it is assumed that the first touch conductive layer  52  includes first conductive patterns, and the second touch conductive layer  54  includes second conductive patterns. Each of the first conductive patterns and the second conductive patterns may include signal lines  530 ,  540  and  550  and sensing electrodes  510  and  520 . 
     The stacked structure and material of the sensing electrodes  510  and  520  may be determined based on the desired sensitivity. The RC delay may affect the sensitivity. Since the resistance of the sensing electrodes  510  and  520  including the metal layer is smaller than that of the transparent conductive layer, the RC value is decreased. Therefore, the charging time of the capacitors defined between the sensing electrodes  510  and  520  is reduced. The sensing electrodes including, the transparent conductive layer are less visible by a user as compared to the metal layer, and the input area is increased so as to increase the capacitance of the capacitors. 
     In an exemplary embodiment of the present disclosure, the sensing electrodes, including the metal layer, may have a mesh shape to prevent them from being seen by a user. It is, however, to be understood that the present disclosure is not limited thereto. The thickness of the encapsulation layer  450  may be adjusted so that the noise generated by the constituent elements of the light-emitting element layer  30  does not affect the touch sensing unit  50   a.  Each of the first touch insulating layer  53  and the second touch insulating layer  55  may be made up of a single layer or multiple layers. Each of the first touch insulating layer  53  and the second touch insulating layer  55  may include an inorganic material, an organic material, and/or an organic-inorganic composite material. The inorganic material may include aluminum oxide, titanium oxide, silicon oxide, silicon oxynitride, zirconium oxide, and/or hafnium oxide. The organic material may include an acrylic resin, a methacrylic resin, a polyisoprene, a vinyl resin, an epoxy resin, a urethane resin, a cellulose resin, a siloxane resin, a polyimide resin, a polyimide resin, and/or a perylene resin. 
     As shown in  FIG. 4 , the sensing electrodes  510  and  520  may be disposed in the area falling within the display area DA 1  of the organic light-emitting display device, and the signal lines  530 ,  540  and  550  may be disposed in the area falling within the non-display area NDA. Therefore, the areas corresponding to the display area DA 1  and the non-display area NDA, respectively, may be defined in the base layer  51 . 
     The sensing electrodes  510  and  520  include a plurality of first sensing electrodes  510  and a plurality of second sensing electrodes  520 . In the exemplary embodiment, it is assumed that the first sensing electrodes  510  are sensing electrodes, while, the second sensing electrodes  520  are driving electrode. Alternatively, the first sensing electrodes  510  may be driving electrodes while the second sensing electrodes  520  may be sensing electrodes. 
     The first sensing electrodes  510  intersect with the second sensing electrodes  520 . The first sensing electrodes  510  are extended in the second direction dr 2  and are arranged in parallel to each other. The second sensing electrodes  520  are extended in the first direction dr 1  and are arranged in parallel to each other. The first sensing electrodes  510  and the second sensing electrodes  520  may be insulated from one another and, for example, may be spaced apart from each other. 
     The first sensing electrodes  510  and the second sensing electrodes  520  may sense an external input by mutual-capacitance sensing. Also, the coordinates of an external input may be obtained by mutual-capacitance sensing during a first period of time and then the coordinates of the external input may be re-obtained by self-capacitance sensing during a second period of time. 
     Each of the first sensing electrodes  510  includes first sensor portions  511  and first connection portions  512 . The first sensor portions  511  are arranged in the second direction dr 2 . Each of the first connection portions  512  connects two adjacent ones of the first sensor portions  511 . The first sensor portions  511  and the first connection portions  512  may be disposed on the same layer. The two adjacent ones of the first sensor portions  511  may be substantially physically connected with each other through the first connection portions  512 . 
     Each of the second sensing electrodes  520  includes second sensor portions  521  and second connection portions  522 . The second sensor portions  521  are arranged in the first direction dr 1 . Each of the second connection portions  522  connects two adjacent ones of the second sensor portions  521 . The second sensor portions  521  may be disposed on a layer different from the second connection portions  522 . The second connection portions  522  may be disposed on a layer different from the first connection portions  512  and may traverse the first connection portions  512  such that they are insulated from each other. 
     The second sensing electrodes  520  may further include stem sensors  523  labeled  523   a  to  523   d.  The stem sensors may extend from the second sensor portions  521 . Each of the stem sensors  523   a  to  523   d  may have a shape that penetrates into the first sensor portions  511 . This will be described in detail later with reference to  FIG. 5 . 
     The first signal lines  530  are connected to first ends of the first sensing electrodes  510 . According to an exemplary embodiment of the present disclosure, the first signal lines  530  may be connected to the right ends of the first sensing electrodes  510  and may be extended generally in the first direction dr 1  along the right border of the area falling within the non-display area NDA. 
     The second signal lines  540  are connected to first ends of the second sensing electrodes  520 . According to an exemplary embodiment of the present disclosure, the second signal lines  540  may be connected to the upper ends of the second sensing electrodes  520  and may be bent so as to be extended generally along the left border. 
     The third signal lines  550  are connected to opposed ends of the second sensing electrodes  520 . According to an exemplary embodiment of the present disclosure, the third signal lines  550  may be connected to the lower ends of the second sensing electrodes  520  and may be disposed generally near the lower border. 
     As shown in the drawings, each of the second sensing electrodes  520  may be double-routed, whereas each of the first sensing electrodes  510  may be single-routed. The first sensing electrodes  510  may be applied with a first reference voltage signal, while the second sensing electrodes  520  may be applied with a second reference voltage signal. The first reference voltage signal applied to each of the first sensing electrodes  510  may have a voltage level that is lower than the voltage level of the second reference voltage signal applied to each of the second sensing electrodes  520 . 
     Since the second sensing electrodes  520  are applied with the signal having a higher voltage level, the voltage level in the touch sensing electrode may be greatly changed depending on the distance to the signal lines connected thereto. For example, if one signal line is connected to only one end of each of the second sensing electrodes  520 , the voltage level of the second sensor portions  521  adjacent to the end may be different from the voltage level of the second sensor portions  521  adjacent to the opposed end. In view of the above, the second signal lines  540  and the third signal lines  550  are connected to first ends and the opposed ends of the second sensing electrodes  520 , respectively, so that the difference in the voltage levels of the second sensor portions  521  between the two ends of the driving electrodes can be reduced. It is to be noted that the number of signal lines connected to the second sensing electrodes  520  and the arrangement of the signal lines are not limited to those shown in the drawings. 
     The touch sensing unit  50   a  may further include a ground line GNL. The ground line GNL may be disposed between the third signal lines  550  and the plurality of sensing electrodes. The ground line GNL may be applied with a third reference voltage signal (e.g., a voltage signal having the same level as the voltage signal applied to the common electrode). The third reference voltage signal may be, but is not limited to being, a voltage signal having a voltage level that is lower than that of the first and second reference voltage signals. The ground line GNL may prevent coupling between the third signal lines  550  and the plurality of sensing electrodes  510  and  520 . 
     The ground line GNL may be further disposed between the first signal lines  530  and the second signal lines  540  and between the second signal lines  540  and the third signal lines  550 . 
     In an exemplary embodiment of the present disclosure, a pad terminal area TPA may be formed on one side of the non-display area NDA of the organic light-emitting display device  1 . The pad terminal area TPA includes a plurality of pad terminals connected to the signal lines. The pad terminal area TPA may include a first pad terminal area TPA 1  connected to the first signal lines  530 , and a second pad terminal area TPA 2  connected to the second signal lines  540  and the third signal lines  550 . The second pad terminal area TPA 2  may include, but is not limited to including, a pad terminal connected to the ground line GNL. 
     In an exemplary embodiment of the present disclosure, the first pad terminal area TPA 1  may be disposed in a lower right area of the non-display area NDA, and the second pad terminal area TPA 2  may be disposed in a lower left area of the non-display area NDA. It is to be noted that the position of the pad terminal area TPA is not limited thereto. The position of the pad terminal area TPA may vary depending on the arrangement needed to establish electrical connections with other elements that may be connected to the touch member. 
     The first sensor portions  511  of the first sensing electrodes  510  and the second sensor portions  521  of the second sensing electrodes  520 , adjacent to each other, may for a plurality of unit sensing areas (for example, SUT 1  to SUT 4 ). For example, halves of the two first sensor portions  511  adjacent to each other in the second direction dr 2  and halves of the two second sensor portions  521  adjacent to each other in the first direction dr 1  may form a square or a rectangle shape, with the intersections between the first sensing electrodes  510  and the second sensing electrodes  520  in the center. The area defined by the half regions of the adjacent first sensor portions  511  and the second sensor portions  521  may be single unit sensing areas SUT 1  to SUT 4 . The plurality of unit sensing areas SUT 1  to SUT 4  may be arranged in row and column directions. The column direction may correspond to the first direction dr 1  and the row direction may correspond to the second direction dr 2 . 
     In each of the unit sensing areas SUT 1  to SUT 4 , the capacitance value between the adjacent driving electrodes and the sensing electrodes is measured to determine whether or not a touch input is made, and if so, the position of the touch input may be obtained as touch input coordinates. 
     Each of the unit sensing areas SUT 1  to SUT 4  may be larger than the emission region of one pixel, which will be described later. For example, each of the unit sensing areas SUT 1  to SUT 4  may cover a plurality of emission regions. The length of one side of each of the unit sensing areas SUT 1  to SUT 4  may be, for example, in the range of 3.5 mm to 4.5 mm, but these regions are not limited to being within this range. 
     Next, the arrangement of the sensing electrodes will be described with reference to  FIGS. 5 to 8 . 
       FIG. 5  is a layout view illustrating area AA 1  in  FIG. 4  in the touch sensing unit  50   a,  according to an exemplary embodiment of the present disclosure.  FIG. 6  is an enlarged view of area AA 2  in  FIG. 5 .  FIG. 7  is a cross-sectional view taken along line I 1 -I 1 ′ in  FIG. 6  in the touch sensing unit  50   a,  according to an exemplary embodiment of the present disclosure.  FIG. 8  is a cross-sectional view taken along line I 2 -I 2 ′ in  FIG. 5  in the touch sensing unit  50   a  according to an exemplary embodiment of the present disclosure. 
     It is to be noted that area AA 1  in  FIG. 4  is shown to include four unit sensing areas, e.g., the first to fourth unit sensing areas SUT 1  to SUT 4  arranged adjacent to one another in a matrix. For convenience of illustration, the sensing electrodes  510  and  520  disposed in the first unit sensing area SUT 1  will be described. It is to be understood that the description of the sensing electrodes disposed in the first unit sensing area SUT 1  can be equally applied to the sensing electrodes  510  and  520  disposed in the other unit sensing areas (for example, SUT 2  to SUT 4 ). 
     Referring to  FIGS. 5 to 8 , a plurality of first sensing electrodes  510  and a plurality of second sensing electrodes  520  are spaced apart from each other. The first sensing electrodes  510  may include a plurality of depressions  513   a  to  513   d.  The second sensing electrodes  520  may include a plurality of stem sensors  523   a  to  523   d  that are at least partially surrounded by the depressions  513   a  to  513   d  of the first sensing electrodes  510 , respectively. 
     The plurality of depressions  513   a  to  513   d  refer to the portions of the first sensor portions  511  indented inwardly. The stem sensors  523   a  to  523   d  refer to the protrusions that are extended from the second sensor portions  521  and at least partially surrounded by the depressions  513   a  to  513   d,  respectively. For example, the stem sensors  523   a  to  523   d  may have a shape that penetrates into the depressions  513   a  to  513   d  of the first sensor portions  511 , respectively. 
     The depressions  513   a  to  513   d  of the first sensing electrodes  510  and the respective stem sensors  523   a  to  523   d  of the second sensing electrodes  520  may be spaced apart from each other. 
     According to an exemplary embodiment of the present disclosure, with respect to the center of the first unit sensing area SUT 1  (the center of the first connection portion  512  in the drawings), the first sensing electrode  510  may include four depressions  513   a  to  513   d  and the second sensing electrode  520  may include four stem sensors  523   a  to  523   d.    
     The first sensing electrode  510  may include a first depression  513   a  that is indented in the fourth direction dr 4 , a second depression  513   b  that is indented in the fifth direction dr 5 , a third depression  513   c  that is indented in the sixth direction dr 6 , and a fourth depression  513   d  that is indented in the seventh direction dr 7 . The first and third depressions  513   a  and  513   c  may be formed in the same first sensor portion  511  as each other, and the second and the fourth depressions  513   b  and  513   d  may be formed in the same first sensor portion  511  as each other. 
     The second sensing electrode  520  may include a first stem sensor  523   a  extended in the fourth direction dr 4  from the second sensor portion  521 , a second stem sensor  523   b  extended in the fifth direction dr 5  from the second sensor portion  521 , a third stem sensor  523   c  extended in the sixth direction dr 6  from the second sensor portion  521 , and a fourth stem sensor  523   d  extended in the seventh direction dr 7  from the second sensor portion  521 . The first stem sensor  523   a  and the second stem sensor  523   b  may be formed in the same single second sensor portion  521 , and the third stem sensor  523   c  and the fourth stem sensor  523   d  may be formed in the same single second sensor portion  521 . 
     The first stern sensor  523   a  may be at least partially surrounded by the first depression  513   a,  the second stem sensor  523   b  may be at least partially surrounded by the second depression  513   b,  the third stem sensor  523   c  may be at least partially surrounded by the third depression  513   c,  and the fourth stem sensor  523   d  may be at least partially surrounded by the fourth depression  513   d.  The stem sensors  523   a  to  523   d  may be extended substantially parallel to the boundary lines between the second sensor portions  521  from which the stem sensors  523   a  to  523   d  are extended and the first sensor portions  511  disposed therebetween. 
     Since the second sensing electrodes  520  include the stem sensors  523   a  to  523   d,  the total length of the boundary lines between the first sensing electrodes  510  and the second sensing electrodes  520  may be increased, compared to when there is no stem sensors. Accordingly, the area where the capacitance can be generated between the first sensing electrodes  510  and the second sensing electrodes  520  is widened, so that the mutual capacitance C m  between first sensing electrodes  510  and the second sensing electrodes  520  can be increased. 
     According to an exemplary embodiment of the present disclosure, the first sensing electrodes  510  and the second sensing electrodes  520  may include electrodes in the form of a mesh. The first sensing electrodes  510  may include a plurality of first electrode lines  511   a  extended in the fourth direction dr 4 , and a plurality of second electrode lines  511   b  extended in the fifth direction dr 5  intersecting the fourth direction dr 4 , for example, at a right angle. The second sensing electrodes  520  may include a plurality of third electrode lines  521   a  extended in the fourth direction dr 4 , and a plurality of fourth electrode lines  521   b  extended in the fifth direction dr 5 . The emission regions PXA_R, PXA_G and PXA_B (see  FIG. 34 ) of a pixel may be formed in mesh holes formed by the first electrode lines  511   a  and the second electrode lines  511   b  intersecting each other and the third electrode lines  521   a  and the fourth electrode lines  521   b  intersecting each other, which will be described later with reference to  FIG. 34 . 
     The first electrode lines  511   a  and the second electrode lines  511   b,  which belong to one first sensing electrode  510 , may be physically connected to one another. On the other hand, the third electrode lines  521   a  and the fourth electrode lines  521   b,  which belong to one second sensing electrode  520 , might riot be physically connected to one another. The third electrode lines  521   a  and the fourth electrode lines  521   b,  which belong to one second sensor portion  521 , may be physically connected to one another. It is to be noted that the third electrode lines  521   a  and the fourth electrode lines  521   b  included in one of the second sensor portions  521  may be spaced apart from the third electrode lines and the fourth electrode lines included in another one of the second sensor portions. 
     Adjacent second sensor portions  521  may be electrically connected to one another by the second connection portions  522  disposed on a layer different from the second sensor portions  521 . For example, adjacent second sensor portions  521  may be electrically connected by two second connection portions  522   a  and  522   b.  Even if one of the second connection portions  522   a  and  522   b  is disconnected, the adjacent second sensor portions  521  can be electrically connected with each other by the other of the second connection portions  522   a  and  522   b.    
     The first connection portions  512  may be disposed not only between the adjacent first sensor portions  511  but also between the adjacent second sensor portions  521  and between the two second connection portions  522   a  and  522   b  adjacent to each other when viewed from the top. 
     Next, the stacked relationship between the first sensing electrodes  510  and the second sensing electrodes  520  will be described. 
     First, the second connection portions  522  may be disposed on the base layer  51 . The second connection portions  522  may correspond to the first touch conductive layer  52  described above. The first touch insulation layer  53  including the first contact holes CNT 1  may be disposed on the second connection portions  522 , and a part of the second connection portions  522  may be left exposed thereby. 
     The first sensor portions  511 , the first connection portions  512  and the second sensor portions  521  may be disposed on the first touch insulation layer  53 . The first sensor portions  511 , the first connection portions  512  and the second sensor portions  521  may correspond to the second touch conductive layer  54  described above. The second sensor portions  521  may be in contact with the second connection portions  522  exposed by the first contact holes CNT 1 . 
     The stem sensors  523   a  to  523   d  may be disposed in the same layer as the first sensor portions  511  including the depressions  513   a  to  513   d.  For example, the stem sensors  523   a  to  523   d  may correspond to the second touch conductive layer  54 . 
     Although the sensing electrodes include mesh-like electrode lines in the drawings, this is merely illustrative. In other implementations, the sensing electrodes may be implemented as common electrode patterns. Each of the common electrode patterns may overlap a plurality of emission regions (for example, PXA_R, PXA_G and PXA_B in  FIG. 34 ) in the third direction dr 3 . 
     Next, a touch event occurring in the unit sensing areas SUT 1  to SUT 4  will be described. 
       FIG. 9  is an equivalent circuit diagram illustrating the touch sensing unit  50   a  when a touch event has occurred, in accordance with an exemplary embodiment of the present disclosure. 
     When a touch event occurs, there is a change in the mutual capacitance C m  defined between the first sensing electrode  510  and the second sensing electrode  520  at the point of the touch event. Referring to  FIG. 9 , when a touch event occurs, a capacitance (hereinafter referred to as a touch capacitance) is formed between the two terminals of mutual capacitance C m . The touch capacitance may include two capacitances C ft  and C fr  connected in series. 
     The touch capacitance C ft  is formed between input means (e.g., a finger or stylus) and one of the first sensing electrode  510  and the second sensing electrode  520  that is applied with a detection signal DS. The touch capacitance C fr  is formed between input means and the other of the first sensing electrode  510  and the second sensing electrode  520 . A microprocessor may read out a sensing signal SS from the other sensing electrode and measure, from the sensing signal SS, a change in the capacitance ΔC m  occurring before and after the input from the input means. The change in the capacitance ΔC m  can be measured by sensing the current change of the sensing signal SS. 
       FIG. 9  further shows capacitances C bt  and C br  between the system ground (System GND) and the first sensing electrode and between the system ground (System GND) and the second sensing electrode, respectively, the capacitance between the system ground (System GND) and the ground, and the capacitance C fg  between the input means and the ground. The system ground (System GND) may refer to a voltage level applied to the second pixel electrode CE shown in  FIG. 35  or a comparable voltage level. In addition,  FIG. 9  shows an equivalent resistance r 1  between an input pad ISU-PDT and the sensing electrode to which the detection signal DS is applied, an equivalent resistance r 2  between an output pad ISU-PDR and the other sensing electrode, and equivalent resistances r 3 , r 4  and r 5  formed by the input means. 
     As the distance between the upper surface of the touch sensing unit  50   a  and the upper surface of the cover window  601  decreases, the touch capacitances C ft  and C fr  increase. For example, for a foldable organic light-emitting emitting display device, the distance between the upper surface of the touch sensing unit  50   a  and the upper surface of the cover window  601  may be less than 0.5 mm in order to provide effective folding characteristics. 
     As the distance between the upper surface of the touch sensing unit  50   a  and the upper surface of the cover window  601  decreases, the amount of the signal moving along a first path C 1  of  FIG. 9  is decreased and the amount of the signal moving along a second path C 2  of  FIG. 9  is increased. 
     In the touch sensing unit  50   a,  according to an exemplary embodiment of the present disclosure, the stem sensors  523   a  to  523   d  of the second sensing electrodes  520  are disposed in the depressions  513   a  to  513   d  of the first sensing electrodes  510 , respectively, such that the area between the sensing electrodes  510  and the second sensing electrodes  520  is increased, and accordingly the mutual capacitance C m  can be increased. 
     Hereinafter, a touch sensing unit, according to an exemplary embodiment of the present disclosure, will be described. In the following description, elements that are not described in detail may be assumed to be at least similar to corresponding elements that have already been described with respect to  FIGS. 1 to 9 . 
       FIG. 10  is a layout view illustrating a part of a touch sensing unit according to an exemplary embodiment of the present disclosure.  FIG. 11  is a cross-sectional view illustrating a touch sensing unit according to an exemplary embodiment of the present disclosure, taken along line II 1 -II 1 ′ of  FIG. 10 . The examples shown in  FIGS. 10 and 11  are modifications of the examples shown in  FIGS. 5 and 8 , respectively. 
     A touch sensing unit  50   a _ 1 , according to an exemplary embodiment of the present disclosure, shown in  FIGS. 10 and 11  is substantially identical to the touch sensing unit  50   a  shown in  FIGS. 5 and 8  except that the former further includes a plurality of dummy electrodes  561   a  to  561   d  and  562   a  to  562   d.    
     The touch sensing unit  50   a _ 1  may further include a plurality of dummy electrodes  561   a  to  561   d  and  562   a  to  562   d.  The dummy electrodes may be formed via the same process as the first sensing electrodes  510  and the second sensing electrodes  520 , so that they may include the same material and may have the same stacked structure. 
     The dummy electrodes  561   a  to  561   d  and  562   a  to  562   d  are floating electrodes and are not electrically connected to the first sensing electrodes  510  or the second sensing electrodes  520 . By disposing the dummy electrodes  561   a  to  561   d  and  562   a  to  562   d  in this manner, it is possible to make the boundary lines between the first sensor portions  511  and the second sensor portions  521  less noticeable. 
     When the first sensing, electrodes  510  and the second sensing electrodes  520  have a mesh shape, the dummy electrodes  561   a  to  561   d  and  562   a  and  562   d  may also have a mesh shape and may be spaced apart from the respective sensor portions by several mm. It is, however, to be understood that the present disclosure is not limited thereto. 
     The touch sensing unit  50   a _ 1  may include a plurality of first dummy electrodes  561   a  to  561   d  disposed between the first sensor portions  511  and the second sensor portions  521 , respectively, and a plurality of second dummy electrodes  562   a  to  562   d  disposed between the depressions  513   a  to  513   d  and the stem sensors  523   a  to  523   d,  respectively. In a single unit sensing region, the touch sensing unit  50   a _ 1  may include four first dummy electrodes  561   a  to  561   d  and four second dummy electrodes  562   a  to  562   d.    
     The first dummy electrodes  561   a  to  561   d  may be disposed between the first sensor portions  511  and the second sensor portions  521  to adjust the spacing therebetween. The boundary lines between the first sensor portions  511  and the second sensor portions  521  may be extended generally in the fourth to seventh directions dr 4  to dr 7 , respectively, with respect to the imaginary center point of the first unit sensing area SUT 1 . The four first sensor portions  511  may be disposed in a shape generally parallel to the directions of the boundary lines between the first sensor portions  511  and the second sensor portions  521 . 
     In an exemplary embodiment of the present disclosure, in the first unit sensing area SUT 1 , the first dummy electrodes  561   a  to  561   d  may include a first dummy pattern  561   a  extended generally in the fourth direction dr 4  between the first sensor portion  511  and the second sensor portion  521 , a second dummy pattern  561   b  extended generally in the fifth direction dr 5  between the first sensor portion  511  and the second sensor portion  521 , a third dummy pattern  561   c  extended generally in the sixth direction dr 6  between the first sensor portion  511  and the second sensor portion  521 , and an eighth dummy pattern  561   d  extended generally in the seventh direction dr 7  between the first sensor portion  511  and the second sensor portion  521 . Although the first to fourth dummy patterns  561   a  to  561   d  are shown as having a rectangular shape in the drawings, this is merely illustrative and they may have various different shapes. 
     The second dummy electrodes  562   a  to  562   d  may be disposed between the depressions  513   a  to  513   d  of the first sensing electrodes  510  and the stem sensors  523   a  to  523   d  so as to adjust the spacing therebetween. For example, in the first unit sensing area SUT 1 , the second dummy electrodes  562   a  to  562   d  may include a fifth dummy pattern  562   a  disposed between the first depression  513   a  and the first stem sensor  523   a,  a sixth dummy pattern  562   b  disposed between the second depression  513   b  and the second stem sensor  523   b,  a seventh dummy pattern  562   c  disposed between the third depression  513   c  and the third stem sensor  523   c,  and an eighth dummy pattern  562   d  disposed between the fourth depression  513   d  and the fourth stem sensor  523   d.    
     The second dummy electrodes  562   a  to  562   d  may have a substantially U-shape and may be disposed to at least partially surround the stem sensors  523   a  to  523   d,  respectively. It is, however, to be understood that the present disclosure is not limited thereto and other configurations may be used. 
     The dummy electrodes  561   a  to  561   d  and  562   a  to  562   d  may be configured to adjust the distance between the first sensing electrodes  510  and the second sensing electrodes  520 . Accordingly, a change in the capacitance ΔC m  of the touch sensing unit  50   a _ 1  may be adjusted to meet the specifications required in the organic light-emitting display device. 
     Although the first unit sensing area SUT 1  includes the four first dummy electrodes  561   a  to  561   d  and the four second dummy electrodes  562   a  to  562   d  in  FIG. 10 , the numbers and locations thereof are not limited to those shown in  FIG. 10 . A single dummy electrode may be disposed such that it is divided into several pieces. Dummy electrodes may be disposed inside the sensing electrodes  510  and  520  to adjust the area of the sensing electrodes  510  and  520  (see  FIGS. 32 and 33 ). In such case, the dummy electrodes may be disposed inside the sensing electrodes  510  and  520  to adjust the area, so that the capacitance C m  of the sensing electrodes  510  and  520  can be adjusted. 
     By disposing the dummy electrodes  561   a  to  561   d  and  562   a  to  562   d  between the first sensor portions  511  and the second sensor portions  521 , the area where the first sensor portions  511  overlaps with the second sensor portions  521  is reduced. Accordingly, the touch capacitances C ft  and C fr  can be reduced. As a result, it is possible to increase a change in the capacitance ΔC m  before and after an input from the input means. 
     Since the area occupied by the first sensor portions  511  and the second sensor portions  521  becomes relatively small by the dummy electrodes  561   a  to  561   d  and  562   a  to  562   d,  the overlapping area with the system ground (System GND) is reduced. As a result, it is possible to reduce the influence by the fluctuation of the system ground (System GND). 
       FIG. 12  is a plan view schematically showing the arrangement of a touch sensing unit according to an exemplary embodiment of the present disclosure.  FIG. 13  is a layout view illustrating a portion corresponding to area AB 1  in the touch sensing unit of  FIG. 12 .  FIG. 14  is a layout view illustrating a portion corresponding to area AB 2  in the touch sensing unit of  FIG. 12 .  FIG. 15  is a cross-sectional view of the touch sensing unit  50   a  according to the above exemplary embodiment, taken along line III 1 -III 1 ′ of  FIG. 13 .  FIG. 16  is a cross-sectional view of the touch sensing unit according to the above exemplary embodiment, taken along line III 2 -III 2 ′ of  FIG. 14 .  FIG. 17  is an equivalent circuit diagram illustrating the touch sensing unit when a touch event has occurred, according to an exemplary embodiment of the present disclosure. 
     A touch sensing unit  50   a _ 2 , according to the exemplary embodiment shown in  FIGS. 12 to 17 , is substantially identical to the touch sensing unit  50   a  shown in  FIGS. 4 and 5  except that the former further includes first dummy electrodes  561   a  to  561   d  and ground electrodes  563   a  to  563   d.  In addition, the touch sensing unit  50   a _ 2  according to this exemplary embodiment is substantially identical to the touch sensing unit  50   a _ 1  shown in  FIGS. 10 and 11  except that second dummy electrodes  562   a  to  562   d  are replaced with ground electrodes  563   a  to  563   d.    
     The touch sensing unit  50   a _ 2  may further include a plurality of first dummy electrodes  561   a  to  561   d  and a plurality of ground electrodes  563 . The plurality of first dummy electrodes  561   a  to  561   d  and the plurality of ground electrodes  563  may be formed via the same process as the first sensing electrodes  510  and the second sensing electrodes  520 , and accordingly may include the same material and may have the same stacked structure. 
     The first dummy electrodes  561   a  to  561   d  are floating electrodes and are not electrically connected to the first sensing electrodes  510  and the second sensing electrodes  520 . The plurality of ground electrodes  563  are electrically connected to the ground line GNL and are not electrically connected to the first sensing electrodes  510  and the second sensing electrodes  520 . 
     The plurality of ground electrodes  563  may include a plurality of ground patterns and a plurality of third connection portions  564   a  electrically connecting the adjacent ground patterns with one another. 
     The plurality of ground patterns  563   a  to  563   d  may be arranged in a matrix form. For example, the first unit sensing area SUT 1  may include four ground patterns  563   a  to  563   d.  The four ground patterns  563   a  to  563   d  may be arranged in a matrix of two rows and two columns. The four ground patterns  563   a  to  563   d  may have a shape that is symmetrical with respect to the imaginary center point of the first unit sensing area SUT 1 . The plurality of second dummy electrodes  562   a  to  562   d  described above with respect to  FIGS. 10 and 11  may be replaced with the plurality of ground patterns  563   a  to  563   d.    
     In an exemplary embodiment of the present disclosure, the plurality of ground patterns  563   a  to  563   d  may include the first to fourth ground patterns  563   a  to  563   d  in the first unit sensing area SUT 1 . The first ground pattern  563   a  may be disposed between the first depression  513   a  and the first stem sensor  523   a.  The second ground pattern  563   b  may be disposed between the second depression  513   b  and the second stem sensor  523   b.  The third ground pattern  563   c  may be disposed between the third depression  513   c  and the third stem sensor  523   c.  The fourth ground pattern  563   d  may be disposed between the fourth depression  513   d  and the fourth stem sensor  523   d.  The ground pattern  563   a  to  563   d  may have a generally U-shape and may be disposed to surround the stem sensors  523   a  to  523   d,  respectively. It is, however, to be understood that the present disclosure is not limited thereto and other arrangements may be used. 
     Adjacent ones of the ground patterns  563   a  to  563   d  may be electrically connected with one another by the third connection portions  564   a.  In an exemplary embodiment of the present disclosure, the third connection portions may connect the ground patterns (e.g.,  563   a  and  563   b ) adjacent to each other in the row direction (the second direction dr 2 ). It is, however, to be understood that the present disclosure is not limited thereto and other arrangements may be used. 
     The plurality of third connection portions may be formed via the same process as the plurality of second connection portions  522 , and accordingly they may include the same material and may be formed in the same layer. For example, the third connection portions  564   a  may be formed in the first touch conductive layer  52 . 
     The first touch insulating layer  53  may further include second contact holes CNT 2  through which at least a part of the third connection portions  564   a  is exposed. The plurality of ground patterns  563   a  to  563   d  may be in contact with the third connection portions  564   a  via the second contact holes CNT 2 . 
     In an exemplary embodiment of the present disclosure the ground line GNL may be a double-line structure. For example, in the area falling within the non-display area NDA, the ground line GNL, may include a first ground line layer GNLa formed in the first touch conductive layer  52  and a second ground line layer GNLb formed in the second touch conductive layer  54 . 
     The first touch insulating layer  53  may include a plurality of third contact holes CNT 3  through which at least a part of the first ground line layer GNLa is exposed. The first ground line layer GNLa and the second ground line layer GNLb may be in contact with each other via the third contact holes CNT 3  of the first touch insulating layer  53 . 
     On the other hand, the ground patterns adjacent to the ground line GNL are connected to one another and may be connected to at least one of the first ground line layer GNLa and the second ground line layer GNLb. For example, the first ground line layer GNLa may be in contact with the ground pattern. In such case, the first ground line layer GNLa may be extended to an area falling within the display area DA 1 , and may be in contact with the ground patterns via the fourth contact holes of the first touch insulating layer  53  through which at least a part of the first ground line layer GNLa is exposed. 
     The spacing between the depressions  513   a  to  513   d  of the first sensing electrodes  510  and the stem sensors  523   a  to  523   d  can be adjusted by the ground patterns, so that a change in the capacitance ΔC m  of the touch sensing unit  50   a _ 2  can be adjusted. 
     Since the plurality of ground patterns  563   a  to  563   d  and the ground line GNL are all electrically connected, the plurality of ground patterns  563   a  to  563   d  may be applied with the third reference voltage signal. 
     A capacitance Csg between the input means and the system ground (System GND) can be formed. As a result, noise (so-called “re-transmission”) may occur. 
     A plurality of ground patterns applied with the third reference voltage signal, whose voltage level is lower than that of the first reference voltage signal and the second reference voltage signal, is disposed between the first sensing electrodes  510  to which the first reference voltage signal is applied and the second sensing electrodes  520  to which the second reference voltage signal is applied, such that signal may flow to the system ground (System GND) along the third path C 3 . The noise (re-transmission) may be moved to the system ground (System GND) along to the third path C 3 . 
     For example, the amount of signal moving along the second path C 2  can be relatively reduced, and noise (so-called re-transmission) can be reduced. Therefore, the sensitivity (ΔC m /C m ) of the capacitance of the touch sensing unit  50   a _ 2  can be increased. 
     For example, by disposing the first dummy electrodes  561   a  to  561   d  and the ground patterns  563   a  to  563   d,  the area occupied by the first sensing electrodes  510  and the second sensing electrodes  520  becomes relatively small, such that the noise can be reduced. As the area occupied by the first sensing electrodes  510  and the second sensing electrodes  520  is reduced, a change in the capacitance C m  can be reduced. However, by increasing the length of the boundary lines between the depressions  513   a  to  513   d  of the first sensing patterns and the stem sensors  523   a  to  523   d,  it is possible to further reduce a change in the capacitance ΔC m . In addition, by disposing the ground patterns  563   a  to  563   d  between the depressions  513   a  to  513   d  of the first sensing electrodes  510  and the stem sensors  523   a  to  523   d,  the noise can be reduced, so that the sensitivity of the capacitance ΔC m /C m  can be increased. 
       FIG. 18  is a layout view illustrating a part of a touch sensing unit according to an exemplary embodiment of the present disclosure.  FIG. 19  is a cross-sectional view of the touch sensing unit according to the above exemplary embodiment, taken along line IV 1 -IV 1 ′ of  FIG. 18 . 
     A touch sensing unit  50   a _ 3 , according to the exemplary embodiment shown in  FIGS. 18 and 19 , is substantially identical to the touch sensing unit  50   a _ 2  of  FIGS. 13 and 15  except that the former further includes fourth connection portions  564   b  connecting ground patterns adjacent to each other in the column direction (the first direction dr 1 ) (e.g., ground patterns  563   a  and  563   c ) with each other in a single unit sensing area SUT 1 . 
     In the first unit sensing area SUT 1 , the touch sensing unit  50   a _ 3  may further include a plurality of fourth connection portions  564   b  that connects the first ground pattern  563   a  with the third around pattern  563   c  and connects the second ground pattern  563   b  with the fourth ground pattern  563   d.  The plurality of fourth connection portions  564   b  may be formed via the same process as the plurality of third connection portions  564   a  and the plurality of second connection portions  522 , and accordingly they may include the same material and may be formed in the same layer. For example, the fourth connection portions  564   b  may be formed in the first touch conductive layer  52 . 
     The first touch insulating layer  53  may further include fifth contact holes CMT 5  through which at least a part of the fourth connection portions  564   b  is exposed. The plurality of ground patterns  563   a  to  563   d  adjacent to one another in the column direction (the first direction dr 1 ) may be in contact with the third connection portions  564   a  via the fifth contact holes CNT 5  in a single unit sensing area. 
       FIG. 20  is a layout view illustrating a part of a touch sensing unit according to an exemplary embodiment of the present disclosure. 
     A touch sensing unit  50   a _ 4 , according to the exemplary embodiment shown in  FIG. 20 , is substantially identical to the touch sensing unit  50   a _ 3  of  FIG. 18  except that the former further includes fourth connection portions  564   c  connecting the ground patterns included in the unit sensing areas adjacent to each other in the column direction (the first direction dr 1 ) (e.g., unit sensing areas SUT 1  and SUT 3 ) with each other. 
     The touch sensing unit  50   a _ 4  may further include a plurality of fifth connection portions  564   c  included in each of the unit sensing areas adjacent to one another in the column direction (the first direction dr 1 ) and connecting a plurality of ground patterns adjacent to one another in the column direction (the first direction dr 1 ). The plurality of fifth connection portions  564   c  may be formed via the same process as the plurality of second to fourth connection portions  522 ,  564   a  and  564   b,  and accordingly they may include the same material and may be formed in the same layer. For example, the fifth connection portions  564   c  may be formed in the first touch conductive layer  52 . 
       FIG. 21  is a plan view schematically illustrating the arrangement of the touch sensing unit according to an exemplary embodiment of the present disclosure.  FIG. 22  is a layout view illustrating a portion corresponding to area AC 1  in the touch sensing unit of  FIG. 21 .  FIG. 23  is a layout view illustrating a portion corresponding to area AC 2  in the touch sensing unit of  FIG. 21 .  FIG. 24  is a cross-sectional view illustrating the touch sensing unit according to the above exemplary embodiment, taken along line V 1 -V 1 ′ of  FIG. 23 .  FIG. 25  is a cross-sectional view of the touch sensing unit according to the above exemplary embodiment, taken along line V 2 -V 2 ′ of  FIG. 23 . 
     A touch sensing unit  50   a _ 5  according to the exemplary embodiment shown in  FIGS. 21 to 25  is substantially identical to the touch sensing unit  50   a _ 4  of  FIG. 20  except that the third connection portions  564   a  are omitted and the arrangement of a ground line GNL is different. 
     The ground line GNL may be extended to the upper edge as well as the left edge of the area falling within the non-display area NDA. The ground line GNL may be disposed between the third signal lines  550  and the plurality of sensing electrodes  510  and  520  at the left edge. The ground line GNL may be disposed so as to intersect a sensing electrode extension  521   a  at the upper edge. 
     The sensing electrode extension  521   a  may work as a bridge electrode connecting the second sensing electrodes  520  with the third signal lines  550 . The extension of the second sensing electrodes  520  may be formed in the second touch conductive layer  54  and may be extended from first ends of the second sensing electrodes  520  to the area falling within the non-display area NDA. 
     The first touch insulating layer  53  may include a plurality of sixth contact holes CNT 6  through which at least a part of the second ground lines  540  (e.g.,  541 ) is exposed. The sensing electrode extension may be in contact with the second signal lines  540  via the sixth contact holes CNT 6  of the first touch insulating layer  53 . 
     The ground line GNL may be connected to the ground patterns adjacent to the ground line GNL in the region disposed at the upper edge. The ground line GNL may traverse the sensing electrode extension  521   a  in a region disposed at the upper edge. The ground line GNL may be insulated from the sensing electrode extension  521   a.    
     The ground line GNL may include a double-line structure at the left edge and a single-line structure at the upper edge. In an exemplary embodiment of the present disclosure, the ground line GNL at the upper edge may include only the first ground line layer GNLa. The ground line GNL may be insulated from the sensing electrode extension at the upper edge, and the first ground line layer GNLa may be extended to the area falling within the display area DA 1  to be connected to the ground patterns. 
     The plurality of ground patterns can maintain the electrical connection with the ground line GNL even if the third connection portions  564   a,  according to the above exemplary embodiment of the present disclosure, are omitted. 
     It is to be noted that the arrangement of the ground line GNL is not limited to that shown in the drawings. The ground line GNL may be disposed so as to intersect with the third signal lines  550  at the upper edge. In such case, the ground line may be disposed in the second touch conductive layer  54 , and the third signal lines  550  may be disposed in the first touch conductive layer  52  and insulated from one another. In addition, the ground line GNL and the ground patterns may be connected to one another through the fifth connection portions  564   c.    
       FIG. 26  is a plan view schematically illustrating the arrangement of the touch sensing unit according to an exemplary embodiment of the present disclosure.  FIG. 27  is a layout view illustrating a portion corresponding to area AD 1  in the touch sensing unit of  FIG. 26 . 
     A touch sensing unit  50   a _ 6 , according to the exemplary embodiment shown in  FIGS. 26 and 27 , is substantially identical to the touch sensing unit  50   a _ 2  shown in  FIGS. 12 and 13  except for the shape of stem sensors  523   a  to  523   d.    
     One of the stem sensors (e.g., a stem sensor  523   a ) may include one or more regions having different widths. For example, one of the stem sensors  523   a  to  523   d  may have a shape whose width alternates between being small and large in the direction that it is extended. One of the stem sensors  523   a  to  523   d  may include a first width  523 W 1  and a second width  523 W 2  that is larger than the first width  523 W 1 . In an exemplary embodiment of the present disclosure, the first width  523 W 1  may range approximately from 50 to and 150 μm, and the second width  523 W 2  may range approximately from 150 to 200 μm. For example, the stem sensors  523   a  to  523   d  may have a shape including saw-tooth-like longer sides. 
     The shape of the ground patterns  563   a  to  563   d  may substantially conform to the shape of the border of the stem sensors  523   a  to  523   d.  For example, the outer border of the ground patterns  563   a  to  563   d  may conform to the shape of the border of the depressions  513   a  to  513   d,  and the inner border of the ground patterns  563   a  to  563   d  may conform to the shape of the border of the stem sensors  523   a  to  523   d,  which has a saw-tooth shape. 
     The length of the boundary lines between the first sensing electrodes  510  and the second sensing electrodes  520  can be increased by the stem sensors  523   a  to  523   d.  Accordingly, it is possible to further reduce a change in the capacitance ΔC m . 
     Although the shape of the border of the depressions  513   a  to  513   d  is shown as being a straight line in the drawings, this is merely illustrative. The shape of the border of the depressions  513   a  to  513   d  may conform to the shape of the stem sensors  523   a  to  523   d,  which has a saw-tooth shape. 
     Hereinafter, modifications of this exemplary embodiment will be described with reference to  FIGS. 28 to 31 . 
       FIGS. 28 and 29  are layout views illustrating a part of touch sensing units according to exemplary embodiments of the present disclosure. 
     Touch sensing units  50   a _ 7  and  50   a _ 8 , according to the exemplary embodiments shown in  FIGS. 28 and 29 , are substantially identical to the touch sensing unit  50   a _ 6  shown in  FIG. 27  except that the formers further include at least one of third to fifth connection portions  564   a  to  564   c.    
     The touch sensing units  50   a _ 7  and  50   a _ 8 , according to the exemplary embodiments, are substantially identical to those described above with reference to  FIGS. 18 and 20  except for the shape of the ground lines GNL; and, therefore, the redundant description will be omitted. 
       FIG. 30  is a plan view schematically illustrating the arrangement of the touch sensing unit according to an exemplary embodiment of the present disclosure.  FIG. 31  is a layout view illustrating a portion corresponding to area AF 1  in the touch sensing unit of  FIG. 30 . 
     A touch sensing unit  50   a _ 9 , according to the exemplary embodiment shown in  FIGS. 30 and 31 , is substantially identical to the touch sensing unit  50   a _ 6  shown in  FIG. 27  except that the arrangement of a ground line GNL is different and that at least one of the third to fifth connection portions  564   a  to  564   c  is further included. 
     The touch sensing unit  50   a _ 9 , according to the exemplary embodiment, is substantially identical to that described above with reference to  FIGS. 21 and 22  except for the shape of the ground line GNL; and, therefore, the redundant description will be omitted. 
       FIG. 32  is a layout view illustrating a part of touch sensing units according to an exemplary embodiment of the present disclosure. 
     A touch sensing unit  50   a _ 10 , according to the exemplary embodiment shown in  FIG. 32 , is substantially identical to the touch sensing unit  50   a _ 6  of  FIG. 27  except that the former further includes third dummy electrodes  565 . 
     The touch sensing unit  50   a _ 10  may further include third dummy electrodes  565 . The third dummy electrodes  565  are disposed inside the first sensor portions  511  and may be spaced apart from the first sensor portions  511 . The third dummy electrodes  565  may be formed via the same process as the first and second sensor portions  521  and the first and second dummy electrodes  565   a  and  562   d,  and accordingly may include the same material and may be formed in the same layer. For example, the third dummy electrodes  565  may be formed in the second touch conductive layer  54 . 
     The third dummy electrodes  565  may have a variety of locations and shapes. Although one first sensor portion  511  includes two third dummy electrodes  565  and the third dummy electrodes  565  have a generally triangular shape in  FIG. 32 , this is merely illustrative. 
     By disposing the third dummy electrodes  565  in the first sensor portions  511 , the overlapping area between the input means (e.g., a user&#39;s finger) and the first sensor portions  511  is reduced Accordingly, the touch capacitances C ft  and C fr  can be reduced. As a result, it is possible to increase a change in the capacitance ΔC m  before and after an input from the input means. In addition, the overlap area with the system ground (System GND) is reduced. As a result, it is possible to reduce the influence by the fluctuation of the system ground (System GND). 
     In order to adjust a change in the capacitance ΔC m , the area occupied by the third dummy electrodes  555  may be adjusted, such that the area of the first sensor portions  511  can be adjusted. 
       FIG. 33  is a layout view illustrating a part of a touch sensing unit according to an exemplary embodiment of the present disclosure. 
     A touch sensing unit  50   a _ 11 , according to this exemplary embodiment shown in  FIG. 33 , is substantially identical to the touch sensing unit  50   a _ 10  of  FIG. 32  except that the former further includes fourth dummy electrodes  566 . 
     The touch sensing unit  50   a _ 11  may further include fourth dummy electrodes  566 . The fourth dummy electrodes  566  may be disposed inside the second sensor portions  521  and may be spaced apart from the second sensor portions  521 . The fourth dummy electrodes  566  may be formed via the same process as the first and second sensor portions  521  and the first to third dummy electrodes  565 , and accordingly may include the same material and may be formed in the same layer. For example, the fourth dummy electrodes  566  may be formed in the second touch conductive layer  54 . 
     The location and shape of the fourth dummy electrodes  566  may vary. Although one second sensor portion  521  includes two fourth dummy electrodes  566  and the fourth dummy electrodes  566  have a generally triangular shape in  FIG. 33 , this is merely illustrative and the fourth dummy electrodes  566  may have different shapes. 
     By disposing the third dummy electrodes  565  and the fourth dummy electrodes  566  in the first sensor portions  511  and the second sensor portions  521 , respectively, the area where the input means overlaps with the first sensor portions  511  and the second sensor portions  521  is reduced. Accordingly, the touch capacitances C ft  and C fr  can be reduced. As a result, it is possible to increase a change in the capacitance ΔC m  before and after an input from the input means. In addition, by disposing the third dummy electrodes  565  and the fourth dummy electrodes  566  in the first sensor portions  511  and the second sensor portions  521 , respectively, the overlapping area with the system ground (System GND) is reduced. As a result, it is possible to reduce the influence by the fluctuation of the system ground (System GND). 
     To adjust a change in the capacitance ΔC m  the area occupied by the fourth dummy electrodes  566  may be adjusted, such that the area of the second sensor portions  521  can be adjusted. 
     Hereinafter, organic light-emitting display devices including the touch sensing units  50   a,    50   a _ 1  to  50   a _ 11 , according to the above-described exemplary embodiments will be described. 
       FIG. 34  is an enlarged view of area AG 1  of  FIG. 1 .  FIG. 35  is a cross-sectional view taken along line VI 1 -VI 1 ′ of  FIG. 34 . 
     Referring to  FIG. 34 , the base layer  51  includes emission regions PXA_R, PXA_G and PXA_B, and a non-emission region disposed such that it at least partially surrounds the emission regions PXA_R, PXA_G and PXA_B and separating the emission regions PXA_R, PXA_G and PXA_B from one another. The emission regions PXA_R, PXA_G and PXA_B may be separated from one another by a pixel-defining layer PDL. For example, in the display area DA 1 , the portion overlapping the pixel-defining layer PDL may be the non-emission region, while the portions not overlapping the pixel defining layer PDL may be the emission regions PXA_R, PXA_G and PXA_B. In an exemplary embodiment of the present disclosure, the non-emission region may be in the form of a mesh, but the shape is not limited thereto. 
     The mesh pattern of each of the sensing electrodes  521  may define a plurality of mesh holes. The mesh holes may be formed in the emission regions PXA_R, PXA_G and PXA_B, respectively. The mesh holes may be included in the non-emission region. 
     The emission regions PXA_R, PXA_G and PXA_B may be sorted into groups by the colors of light generated in the organic light-emitting diodes. In the example shown in  FIG. 34 , three groups of emission regions PXA_R, PXA_G and PXA_B sorted by the colors of the light are depicted. 
     The emission regions PXA_R, PXA_G and PXA_B may have different areas depending on the colors of the light emitted from an organic emissive layer  312  (see  FIG. 35 ) of the organic light-emitting diode. The area of the emission regions PXA_R, PXA_G and PXA_B may be determined depending on the type of the organic light-emitting diode. For example, the emission regions PXA_R, PXA_G and PXA_B, may include a first emission region PXA_R, a second emission region PXA_G, and a third emission region PXA_B. The area of the third emission region PXA_B may be larger than the area of the first emission region PXA_R, and the area of the first emission region PXA_R may be larger than the area of the second emission region PXA_G. In this exemplary embodiment, the first emission region PXA_R emits red light, the second emission region PXA_G emits green light, and the third emission region PXA_B emits blue light. It is, however, to be understood that the present disclosure is not limited thereto. According to alternative arrangements, the first to third emission regions PXA_R, PXA_G and PXA_B may emit light of cyan, magenta and yellow, instead of the red, green and blue. 
     The mesh holes may be sorted into groups having different areas. For example, mesh holes may be sorted into three groups by the emission regions PXA_R, PXA_G and PXA_B associated therewith. 
     In the foregoing description, the mesh holes are formed in the emission regions PXA_R, PXA_G and PXA_B, respectively, but the present disclosure is not limited thereto. Each of the mesh holes may be associated with two or more emission regions PXA_R, PXA_G, and PXA_B. In addition, although the emitting regions PXA_R, PXA_G and PXA_B have different areas, this is merely illustrative. The emission regions PXA_R, PXA_G and PXA_B all may have the same size, and all of the mesh holes may also have the same size. 
     The shape of the mesh holes, when viewed from the top, is not limited to what is shown herein but may alternatively have a diamond shape or other polygonal shapes. The shape of the mesh holes, when viewed from the top, may have a polygonal shape with rounded corners. 
     As the first sensing electrodes  510  and the second sensing electrodes  520  have a mesh shape, the first sensing electrodes  510  and the second sensing electrodes  520  do not overlap the emission regions PXA_R, PXA_G and PXA_B and thus are not visible to a user who watches the organic light-emitting display device. In addition, in the first sensing electrodes  510  and the second sensing electrode  520 , the parasitic capacitance between the electrodes of the light-emitting element layer  30  can be reduced. 
     Referring to  FIG. 35 , a base substrate  101  may be a rigid, or flexible substrate. If the base substrate  101  is a rigid substrate, it may be a glass substrate, a quartz substrate, a glass ceramic substrate, and/or a crystalline glass substrate. If the base substrate  101  is a flexible substrate, it may be a film substrate including a polymer organic material or a plastic substrate. In addition, the base substrate  101  may include fiberglass reinforced plastic (FRP). 
     On the base substrate  101 , the display area DA 1  and the non-display area NA described above may be defined. 
     The base substrate  101  shown in  FIG. 35  may correspond to the first substrate  10  of  FIG. 2 . 
     A first buffer layer  201  is disposed on the base substrate  101 . The first buffer layer  201  smooths the surface of the base substrate  101  and prevents the permeation of moisture or air therethrough. The first buffer layer  201  may be an inorganic layer. The first buffer layer  201  may be made up of a single layer or multiple layers. 
     On the first buffer layer  201 , a plurality of thin-film transistors TR 1 , TR 2  and TR 3  are disposed. The plurality of thin-film transistors TR 1 , TR 2  and TR 3  may be driving thin-film transistors. 
     Each of the thin-film transistors TR 1 , TR 2  and TR 3  may include a first thin-film transistor TR 1 , a second thin-film transistor TR 2  and a third thin-film transistor TR 3 . The thin-film transistors TR 1 , TR 2 , and TR 3  may be disposed in emission regions PXA_R, PXA_G, and PXA_B, respectively. For example, the first thin-film transistor TR 1  may be disposed in the first emission region PXA_R, the second thin-film transistor TR 2  may be disposed in the second emission region PXA_G and the third thin-film transistor TR 3  may be disposed in the third emission region PXA_B. 
     The thin-film transistors TR 1 , TR 2  and TR 3  may include semiconductor layers A 1 , A 2  and A 3 , gate electrodes G 1 , G 2  and G 3 , source electrodes S 1 , S 2  and S 3 , and drain electrodes D 1 , D 2  and D 3 , respectively. More specifically, the semiconductor layers A 1 , A 2 , and A 3  are disposed on the first buffer layer  201 . The semiconductor layers A 1 , A 2  and A 3  may include an amorphous silicon, a poly silicon, a low-temperature poly silicon, and an organic semiconductor. In an exemplary embodiment of the present disclosure, the semiconductor layers A 1 , A 2  and A 3  may be oxide semiconductors. The semiconductor layer A 1 , A 2  and A 3  may include a channel region, and a source region and a drain region which are disposed on the sides of the channel region, respectively, and are doped with impurities. 
     A gate insulating layer  211  is disposed on the semiconductor layers A 1 , A 2  and A 3 . The gate insulating layer  211  may be an inorganic layer. The gate insulating layer  211  may be made up of a single layer or multiple layers. 
     On the gate insulating layer  211 , the gate electrodes G 1 , G 2  and G 3  are disposed. The gate electrodes G 1 , G 2  and G 3  may be made of a conductive metal material. For example, the gate electrodes G 1 , G 2  and G 3  may include molybdenum (Mo), aluminum (Al), copper (Cu), and/or titanium (Ti). The gate electrodes G 1 , G 2  and G 3  may be made of a single layer or multiple layers. 
     An interlayer dielectric layer  212  is disposed on the gate electrodes G 1 , G 2  and G 3 . The interlayer dielectric layer  212  may be an inorganic layer. The interlayer dielectric layer  212  may be made up of a single layer or multiple layers. 
     The source electrodes S 1 , S 2  and S 3  and the drain electrodes D 1 , D 2  and D 3  are disposed on the interlayer dielectric layer  212 . The source electrodes S 1 , S 2  and S 3  and the drain electrodes D 1 , D 2  and D 3  are made of a conductive metal material. For example, the source electrodes S 1 , S 2  and S 3  and the drain electrodes D 1 , D 2  and D 3  may include aluminum (Al), copper (Cu), titanium (Ti), and or molybdenum (Mo). 
     The source electrodes S 1 , S 2  and S 3  and the drain electrodes D 1 , D 2  and D 3  may be electrically connected to the source regions and the drain regions of the semiconductor layers A 1 , A 2  and A 3 , respectively, through contact holes that pass through the interlayer dielectric layer  212  and the gate insulating layer  211 . 
     The organic light-emitting display device  1  may further include a storage capacitor and a switching thin-film transistor on the base substrate  101 . 
     A protective layer  220  is disposed on the source electrodes S 1 , S 2  and S 3  and the drain electrodes D 1 , D 2  and D 3 . The protective layer  220  covers the circuitry including the thin-film transistors TR 1 , TR 2  and TR 3 . The protective layer  220  may be a passivation layer or a planarizing layer. The passivation layer may include SiO2, SiNx, etc., and the planarization layer may include materials such as acrylic and polyimide. The protective layer  220  may include both the passivation layer and the planarization layer. In such case, the passivation layer may be disposed over the source electrodes S 1 , S 2  and S 3 , the drain electrodes D 1 , D 2  and D 3 , and the interlayer dielectric layer  212 , and the planarization layer may be disposed on the passivation layer. The upper surface of the protective layer  220  may be flat. 
     The first buffer layer  201  and the protective layer  220  shown in  FIG. 35  may correspond to the circuit layer  20  of  FIG. 2 . 
     A plurality of first pixel electrodes  311  is disposed on the protective layer  220 . The first pixel electrode  311  may be disposed in each of the emission regions PXA_R, PXA_G and PXA_B. In addition, each of the first electrodes  311  may be an anode electrode of the respective organic light-emitting diodes. 
     The first electrodes  311  may be electrically connected to the drain electrodes D 1 , D 2  and D 3  (or the source electrodes S 1 , S 2  and S 3 ) disposed on the base substrate  101  through the via holes passing through the protective layer  220 , respectively. 
     The first pixel electrodes  311  may have different areas in accordance with the areas of the emission regions PXA_R, PXA_G, and PXA_B. 
     The first pixel electrodes  311  may be made of a material having a high work function. The first pixel electrodes  311  may include indium-tin-oxide (ITO), indium-zinc-oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), and/or a material having a work function within a range of cofunctions of the aforementioned materials. 
     A pixel-defining layer PDL is disposed over the first pixel electrodes  311 . The pixel-defining layer PDL includes a plurality of openings. At least a part of each of the first pixel electrodes  311  is exposed via the respective openings. The openings may have different widths in accordance with the areas of the emission regions PXA_R, PXA_G and PXA_B. 
     The pixel-defining layer PDL may include an organic material or an inorganic material. In an exemplary embodiment of the present disclosure, the pixel-defining layer PDL may include a material such as a photoresist, a polyimide resin, an acrylic resin, a silicon compound and a polyacrylic resin. 
     An organic emissive layer  312  is disposed on the first electrode  311  exposed by the pixel-defining layer PDL. 
     A second pixel electrode  313  is disposed on the organic emissive layer  312 . The second pixel electrode  313  may be a common electrode extended across all the pixels In addition, the second pixel electrode  313  may work as the cathode electrodes of organic light-emitting diode. 
     The second pixel electrode  313  may be made of a material having a low work function. The second pixel electrode  313  may include Li, Ca, LiF/Ca, LiF/Al, Al, Mg, Ag, Pt, Pd, Ni, Au, Nd, Ir, Cr, BaF, Ba, or a compound or mixture thereof, e.g., a mixture of Ag and Mg. A low work function material may be any material having a work function within the range of work functions of the above-named materials. The second pixel electrode  313  may be connected to a power line through an electrode formed in the same layer as the first pixel electrodes  311 . 
     The first pixel electrodes  311 , the organic emissive layer  312  and the second pixel electrode  313  may form the organic light-emitting diodes (OLEDs). In addition, the first pixel electrodes  311  and the second pixel electrode  313  shown in  FIG. 35  may correspond to the light-emitting element layer  30  of  FIG. 2 . 
     The encapsulation layer  450  may be disposed on the second pixel electrode  313 . The encapsulation layer  450  includes an inorganic layer and an organic layer. The encapsulation layer  450  may include a plurality of layers stacked on one another. As shown in  FIG. 35 , the encapsulation layer  450  may be made up of multiple layers including a first inorganic layer  451 , an organic layer  452 , and a second inorganic layer  453  which are stacked on one another in this order. The first inorganic layer  451  and the second inorganic layer  453  may include silicon oxide (SiOx), silicon nitride (SiNx) and/or silicon oxynitride (SiONx). The organic layer  452  may include epoxy, acrylate and/or urethane acrylate. 
     The encapsulation layer  450  shown in  FIG. 35  may correspond to the encapsulation layer  40  of  FIG. 2 . 
     The touch sensing unit  50   a  may be disposed on the encapsulation layer  450  in order. The touch sensing unit  50   a  may correspond to the touch layer  50  of  FIG. 2 . 
     The cover window  601  may be disposed on the touch layer  50 . The cover window  601  can protect the light-emitting element layer  30 , the circuit layer  20  or the touch layer  50  from scratches by an external object. The cover window  601  may be attached to the touch layer  50  by an adhesive member  610  such as an optically clear adhesive (OCA) or an optically clear resin (OCR). 
     The cover window  601  shown in  FIG. 35  may correspond to the second substrate  60  of  FIG. 2  including the adhesive member  610 . 
     An optical member such as an anti-reflection film and a polarizing film may be disposed on or under the cover window  601 , or a color filter may be disposed under the cover window  601 . 
       FIG. 36  is a perspective view of an organic light-emitting display device according to an exemplary embodiment of the present disclosure. The organic light-emitting display device  2  of  FIG. 36  is a modification in which the organic light-emitting display device  1  of  FIG. 1  is bendable. 
     The organic light-emitting display device  2  may be foldable. For example, the base substrate  101  may be a flexible substrate having excellent flexibility so that it may be bent upon itself without cracking or breaking. The first and second touch insulating layers  53  and  55  may include one or more of the organic materials listed above. 
     The organic light-emitting display device  2 , according to an exemplary embodiment of the present disclosure, may include a bending area BA that can be bent with respect to a bending axis, a first non-banding area NBA 1 , and a second non-banding area NBA 2  which are not bent. The bending area BA may include a portion of a display area DA and a non-display area NDA, and similarly, portions of the display area DA and the non-display area NDA may be part of the non-bending areas NBA 1  and NBA 2 . 
     The effects of the present invention are not limited by the foregoing, and other various effects are anticipated herein. 
     Although various exemplary embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention.