Patent Publication Number: US-2022229531-A1

Title: Display device and watch

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of PCT Application No. PCT/JP2020/036916, filed Sep. 29, 2020, and based upon and claiming the benefit of priority from Japanese Patent Application No. 2019-184496, filed Oct. 7, 2019, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a display device and a watch. 
     BACKGROUND 
     In recent years, wearable devices with a touch detection function (for example, wristwatch wearable device, eye-glasses wearable devices, etc.) have been widely used. In such wearable devices, both display quality in image displaying and good operability by touching are required, and thus, various developments have been made. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a structural example of a display device of an embodiment. 
         FIG. 2  is a diagram illustrating an example of implementation of a touch controller, display controller, and CPU. 
         FIG. 3  is a diagram illustrating another example of the implementation of the touch controller, display controller, and CPU. 
         FIG. 4  is a diagram illustrating yet another example of the implementation of the touch controller, display controller, and CPU. 
         FIG. 5  is another plan view illustrating a structural example of the display device of the embodiment. 
         FIG. 6  is a schematic cross-sectional view of a structural example of a display panel, taken along line I-I of  FIG. 1 . 
         FIG. 7  is a schematic cross-sectional view of another structural example, which is different from the structural example of  FIG. 6 . 
         FIG. 8  is a schematic cross-sectional view of another structural example, which is different from the structural example of  FIG. 6 . 
         FIG. 9  is a schematic cross-sectional view of another structural example, which is different from the structural example of  FIG. 6 . 
         FIG. 10  is a diagram illustrating a first drive method which is one of drive methods for sensor electrodes. 
         FIG. 11  is a timing chart illustrating drive timing of the sensor electrodes in the first drive method. 
         FIG. 12  is a diagram illustrating a second drive method which is one of the drive methods for sensor electrodes. 
         FIG. 13  is a timing chart illustrating drive timing of the sensor electrodes in the second drive method. 
         FIG. 14  is a diagram illustrating a third drive method which is one of the drive methods for sensor electrodes. 
         FIG. 15  is a timing chart illustrating drive timing of the sensor electrodes in the third drive method. 
         FIG. 16  is a diagram illustrating a fourth drive method which is one of the drive methods for sensor electrodes. 
         FIG. 17  is a timing chart illustrating drive timing of the sensor electrodes in the fourth drive method. 
         FIG. 18  is a diagram illustrating an application example of the display device of the embodiment. 
         FIG. 19  is a diagram illustrating an example of principle of mutual-capacitive touch detection. 
         FIG. 20  is a diagram illustrating an example of principle of self-capacitive touch detection. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a display device includes a display part, a plurality of sensor electrodes and a controller. The display part is configured to display an image. The plurality of sensor electrodes are arranged to surround the display part. The controller is electrically connected to the sensor electrodes, and is configured to detect an object close to or contacting the sensor electrodes. The controller drives at least one of the sensor electrodes as a detection electrode and drives at least one of the sensor electrodes as a drive electrode. 
     According to another embodiment, a display device includes a display part, a plurality of sensor electrodes and a controller. The display part is configured to display an image. The plurality of sensor electrodes are arranged to surround the display part. The controller is electrically connected to the sensor electrodes and is configured to detect an object approaching or contacting the sensor electrodes. The controller selects M sensor electrodes from the sensor electrodes, outputs a drive signal to detect an approaching or contacting object to the selected M sensor electrodes, and receives a detection signal output in response to the input of the drive signal from the selected M sensor electrodes. 
     Embodiments will be described hereinafter with reference to the accompanying drawings. 
     The disclosure is merely an example, and proper changes within the spirit of the invention, which are easily conceivable by a skilled person, are included in the scope of the invention as a matter of course. In addition, in some cases, in order to make the description clearer, the widths, thicknesses, shapes, etc., of the respective parts are schematically illustrated in the drawings, compared to the actual modes. However, the schematic illustration is merely an example, and adds no restrictions to the interpretation of the invention. Besides, in the specification and drawings, the same or similar elements as or to those described in connection with preceding drawings or those exhibiting similar functions are denoted by like reference numerals, and a detailed description thereof is omitted unless otherwise necessary. 
     In the present embodiment, as an example of a display device, a display device with a touch detection function will be explained. There are various touch detection methods, such as optical, resistive, capacitive, and electromagnetic induction. Among the above methods, capacitive touch detection is based on the change in capacitance caused by an approaching or contacting object (e.g., a finger), and has advantages such as a relatively simple structure and low power consumption. In the present embodiment, a display device with a touch detection function using the capacitance method will be mainly explained. 
     Note that, the capacitance method will include a mutual-capacitive method, which generates an electric field using a pair of transmitting electrodes (drive electrodes) and receiving electrodes (detection electrodes) arranged in a state of separation from each other, and detects the change in the electric field (decrease in capacitance) accompanying an approaching or contacting object, and a self-capacitive method, which detects the change in capacitance (increase in capacitance) accompanying an approaching or contacting object using a single electrode. 
       FIG. 1  is a plan view illustrating a structural example of a display device DSP of an embodiment. In  FIG. 1 , the structure mainly related to the touch detection function is illustrated. In one example, a first direction X, second direction Y, and third direction Z are orthogonal to each other, but they may intersect at angles other than  90  degrees. The first direction X and the second direction Y correspond to the directions parallel to the main surface of the substrate of the display device DSP, and the third direction Z corresponds to the thickness direction of the display device DSP. In the present application, the direction toward the tip of the arrow indicating the third direction Z may be referred to as the upward direction, and the direction from the tip of the arrow to the opposite direction may be referred to as the downward direction. Assuming that there is an observation position for observing the display device DSP at the tip of the arrow indicating the third direction Z, and from this observation position, looking toward the X-Y plane defined by the first direction X and the second direction Y will be referred to as plan view. 
     As shown in  FIG. 1 , the display device DSP includes a display panel PNL, flexible printed circuit board FPC 1 , and printed circuit board PCB. The display panel PNL and the printed circuit board PCB are electrically connected via the flexible printed circuit board FPC 1 . Specifically, the terminal part T of the display panel PNL and the connection part CN of the printed circuit board PCB are electrically connected via the flexible printed circuit board FPC 1 . 
     The display panel PNL includes a display part DA that displays images and a frame-like non-display part NDA that surrounds the display part DA. Of a plurality of concentric circles of  FIG. 1 , the area represented by the innermost circle corresponds to the display part DA, and the area between the outermost circle and the innermost circle corresponds to the non-display part NDA. Note that,  FIG. 1  illustrates a case where the display part DA is circular in shape and the non-display part NDA surrounding the display part DA is also of the same shape, but no limitation is intended thereby, and the display part DA may not be circular and the non-display part NDA may not be circular. For example, the display part DA may be a rectangular shape, and the non-display part NDA may be a different shape from the display part DA. For example, the display part DA may be a rectangular shape. Furthermore, if the display part DA is rectangular, the non-display part NDA may be circular, which is a different shape from the display part DA. 
     In the non-display part NDA, a plurality of sensor electrodes SE 1  to SE 8  are arranged to surround the display part DA.  FIG. 1  illustrates eight sensor electrodes SE 1  to SE 8 ; however, the number of sensor electrodes placed in the non-display part NDA is not limited thereto, and any number of sensor electrodes may be arranged to surround the non-display part NDA. Although described later, the sensor electrodes SE 1  to SE 8  are electrically connected to sensor pads SP 1  to SP 8  via conductive materials (conductive beads)  31  included in sealing  30 . Furthermore, sensor wiring lines SL 1  to SL 8  extending from the sensor pads SP 1  to SP 8  are electrically connected to the terminal part T located in the non-display part NDA. In  FIG. 1 , a case where the sensor wiring lines SL 1  to SL 8  extend along the periphery of the sensor electrode SE 1  to SE 8  is shown; however, the sensor wiring lines SL 1  to SL 8  may extend in any other shape. The sensor wiring lines SL 1  to SL 8  are all to input drive signals (Tx signals) to the sensor electrodes SE 1  to SE 8 , and to output detection signals (RxAFE signals) from sensor electrodes SE 1  to SE 8 . 
     Scan line drive circuits GD 1  and GD 2  are arranged in the right and left sides of the non-display part NDA. The scan line drive circuits GD 1  and GD 2  and sensor electrodes SE 1  to SE 8  overlap with each other in the plan view. Since the scan line drive circuits GD 1  and GD 2  will be described later, the detailed explanation is omitted here. 
     On the printed circuit board PCB, a touch controller TC, display controller DC, CPU 1 , and the like are arranged. The touch controller TC outputs drive signals (Tx signals) to the sensor electrodes SE 1  to SE 8  arranged in the display panel PNL, and receives input of detection signals (RxAFE signals) output from the sensor electrodes SE 1  to SE 8  (that is, detects an approaching or contacting object). The display controller DC outputs video signals representing images on the display part DA of the display panel PNL and control signals for controlling scan line drive circuits GD 1  and GD 2 . The CPU  1  outputs synchronization signals that define the operation timing of the touch controller TC and the display controller DC, and executes operations in response to touches indicated by detection signals received for input by the touch controller TC. 
       FIG. 1  illustrates a case where the touch controller TC, the display controller DC, and the CPU 1  are realized by a single semiconductor chip; however, the implementation is not limited thereto, and as in  FIG. 2 , only the touch controller TC may be separated and each part may be mounted on the printed circuit board PCB, or as in  FIG. 3 , the touch controller TC and the CPU  1  may be mounted separately on the printed circuit board PCB, and the display controller DC may be mounted on the display panel PNL using Chip On Glass (COG), or as in  FIG. 4 , only the CPU  1  may be mounted on the printed circuit board PCB, and the touch controller TC and the display controller DC may be mounted on the display panel PNL by COG. 
       FIG. 5  is another plan view of a structural example of the display device DSP. In  FIG. 5 , the structure mainly related to the image display function is illustrated. As in  FIG. 5 , the display panel PNL includes n scan lines G (G 1  to Gn) in the display part DA and m signal lines S (S 1  to Sm) in the display part DA. Note that, both n and m are positive integers, and n may be equal to m, or n may be different from m. The scan lines G extend in the first direction X, and are arranged along the second direction Y at intervals. The signal lines S extend in the second direction Y, and are arranged along the first direction X at intervals. In the area defined by scan lines G and signal lines S, pixels PX are arranged. That is, the display panel PNL includes a large number of pixels PX arranged in a matrix in the first direction X and the second direction Y in the display part DA. 
     As shown in  FIG. 5  in an enlarged manner, each pixel PX includes a switching element SW, pixel electrode PE, common electrode CE, liquid crystal layer LC, and the like. The switching element SW includes a thin-film transistor (TFT), for example, and is electrically connected to the scan line G and the signal line S. The scan line G is electrically connected to the switching element SW in each of the pixels PX aligned in the first direction X. The signal line S is electrically connected to the switching element SW of each of the pixels PX aligned in the second direction Y. The pixel electrode PE is electrically connected to the switching element SW. Each of the pixel electrodes PE is opposed to the common electrode CE, and the electric field generated between the pixel electrode PE and the common electrode CE drives the liquid crystal layer LC. The capacitance CS is formed, for example, between the electrodes of the same potential as the common electrode CE and the electrodes of the same potential as the pixel electrode PE. 
     At least one end of the scan line G is electrically connected to at least one of the scan line drive circuits GD 1  and GD 2 . The scan line drive circuits GD 1  and GD 2  are electrically connected to the terminal part T, and control signals from display controller DC are input thereto. The scan line drive circuits GD 1  and GD 2  write video signals to each pixel PX according to the input control signals. One end of the signal line S is electrically connected to the terminal part T, and the video signals from the display controller DC are input to the signal line S. 
       FIG. 6  is a cross-sectional view of an example of a display panel PNL, taken along line I-I of  FIG. 1 .  FIG. 6  illustrates a case where the sensor electrode SE is placed in the second substrate SUB 2  side. Note that, in the following, the structure of the display part DA side and the structure of the non-display part NDA side will be explained. 
     The display panel PNL includes a first substrate SUB 1 , second substrate SUB 2 , liquid crystal layer LC, sealing  30 , and backlight unit BL. The first substrate SUB 1  and second substrate SUB 2  are formed as flat plates parallel to the X-Y plane. The first substrate SUB 1  and the second substrate SUB 2  overlap with each other in a plan view, and adhered together by the sealing  30 . The liquid crystal layer LC is held between the first substrate SUB 1  and the second substrate SUB 2 , and sealed by the sealing  30 . The backlight unit BL is placed behind the first substrate SUB 1  as an illumination device to illuminate the display panel PNL. Various types of backlight units can be used for the backlight unit BL, and for example, a backlight unit using a light emitting diode (LED), or a cold cathode fluorescent lamp (CCFL) as a light source can be used. Although this is not shown in  FIG. 6 , a cover member is placed on the second substrate SUB 2 . Furthermore, in the non-display part NDA side, a light-shielding layer is placed between the second substrate SUB 2  and the cover member which is not shown. 
     In the display part DA side, the first substrate SUB 1  includes, as in  FIG. 6 , a transparent substrate  10 , switching element SW, planarization film  11 , pixel electrode PE, and alignment film ALl. The first substrate SUB 1  includes the scan line G, signal line S, and the like, as in  FIG. 5 , in addition to the elements described above; however, they are omitted in  FIG. 6 . 
     The transparent substrate  10  includes a main surface (lower surface)  10 A and a main surface (upper surface)  10 B in the opposite side of the main surface  10 A. The switching element SW is placed in the main surface  10 B side. The planarization film  11  includes at least one or more insulating films, and covers the switching element SW. The pixel electrodes PE are arranged in each pixel PX on the planarization film  11 . The alignment film AL 1  covers the pixel electrodes PE. 
     In  FIG. 6 , the switching element SW is illustrated in a simplified manner, but in reality, the switching element SW includes a semiconductor layer and various electrodes. Furthermore, although not shown in  FIG. 6 , the switching element SW and the pixel electrode PE are electrically connected to each other through an opening formed in the planarization film  11 . Furthermore, as described above, the scan line G and signal line S, which are omitted in  FIG. 6 , are placed between the transparent substrate  10  and the planarization film  11 , for example. 
     In the display part DA side, the second substrate SUB 2  includes, as in  FIG. 6 , a transparent substrate  20 , light-shielding film BM, color filter CF, overcoat layer OC, common electrode CE, and alignment film AL 2 . 
     The transparent substrate  20  includes a main surface (lower surface)  20 A and a main surface (upper surface)  20 B inn the opposite side of the main surface  20 A. The main surface  20 A of the transparent substrate  20  is opposed to the main surface  10 B of the transparent substrate  10 . The light-shielding film BM divides the pixels PX. The color filter CF is opposed to the pixel electrodes PE, and a part thereof overlaps the light-shielding film BM. The color filter CF includes a red color filter, green color filter, blue color filter, and the like. The overcoat layer OC covers the color filter CF. The common electrode CE is disposed over the pixels PX, and is opposed to the plurality of pixel electrodes PE in the third direction Z. Furthermore, the common electrode CE covers the overcoat layer OC. The alignment film AL 2  covers the common electrode CE. 
     The liquid crystal layer LC is disposed between the main surface  10 B and the main surface  20 A, and is in contact with the alignment films AL 1  and AL 2 . 
     The transparent substrates  10  and  20  are insulating substrates such as glass substrates or plastic substrates. The planarization film  11  is formed by a transparent insulating material such as silicon oxide, silicon nitride, silicon oxynitride, or acrylic resin. In one example, the planarization film  11  includes an inorganic insulating film and an organic insulating film. The pixel electrode PE and the common electrode CE are formed of transparent conductive materials such as indium tin oxide (ITO) and indium zinc oxide (IZO). The light-shielding layer BM is formed of an opaque metal material, for example, molybdenum (Mo), aluminum (Al), tungsten (W), titanium (Ti), silver (Ag), etc. Alignment films AL 1  and AL 2  are horizontal alignment films having alignment restriction force which is substantially parallel to the X-Y plane. The alignment restriction force may be applied by rubbing treatment or photo-alignment treatment. 
     In the non-display part NDA side, the first substrate SUB 1  includes, as in  FIG. 6 , a transparent substrate  10 , sensor wiring line SL, planarization film  11 , sensor pad part SP, and alignment film AL 1 . Note that, the structure already described for the display part DA side will be omitted from the detailed explanation. 
     The sensor wiring line SL is placed on the transparent substrate  10 . The sensor wiring line SL is arranged on the same layer as the switching element SW in the display part DA side. The sensor pad SP is placed on the planarization film  11 . The sensor pad SP is placed on the same layer as the pixel electrode PE in the display part DA side, and is formed of the same transparent conductive material as the pixel electrode PE. The sensor wiring line SL and the sensor pad SP are electrically connected through the opening formed in the planarization film  11 . 
     The terminal T is located in the main surface  10 B of the transparent substrate  10  that does not face the main surface  20 A. The terminal part T is electrically connected to the flexible printed circuit board FPC 1 . The terminal T is formed by covering a metal material such as Al with ITO or the like to prevent corrosion. 
     In the non-display part NDA side, the second substrate SUB 2  includes, as in  FIG. 6 , a transparent substrate  20 , light-shielding film BM, overcoat layer OC, sensor electrode SE, and alignment film AL 2 . Note that the structure already described for the display part DA side will be omitted from the detailed explanation. 
     In the non-display part NDA side, unlike the display part DA side, the light-shielding film BM is arranged over almost the entire surface of the transparent substrate  20 . The overcoat layer OC covers the light-shielding film BM. The sensor electrode SE is arranged in an island shape in the overcoat layer OC side, and is opposed to the sensor pad SP in the third direction Z. The sensor electrode SE is placed on the same layer as the common electrode CE on the display part DA side, and is formed of the same transparent conductive material as the common electrode CE. 
     The first substrate SUB 1  and the second substrate SUB 2  are adhered by the sealing  30 , and in the non-display part NDA, the sensor pad SP of the first substrate SUB 1  and the sensor electrode SE of the second In the non-display part NDA are electrically connected by the conductive material (conductive beads)  31  contained in the sealing  30 . 
       FIG. 6  illustrates a case where the liquid crystal mode of the display panel PNL is the so-called vertical field mode, which is classified into two categories according to the direction of the electric field applied to change the orientation of the liquid crystal molecules contained in the liquid crystal layer LC. However, the present structure is also applicable to the case where the liquid crystal mode is the so-called horizontal field mode. However, if the sensor electrode SE is placed on the second substrate SUB 2  side, it is possible to form the sensor electrode SE using the same transparent conductive material as the common electrode CE placed on the display part DA side in the vertical field mode, whereas in the case of horizontal field mode, the sensor electrode SE must be formed separately on the second substrate SUB 2 . Therefore, if the sensor electrode SE is to be placed in the second substrate SUB 2  side, it is preferable that the liquid crystal mode is the vertical field mode rather than the horizontal field mode. 
     The vertical field mode described above includes, for example, the Twisted Nematic (TN) mode and Vertical Alignment (VA) mode. The horizontal field mode described above includes, for example, In-Plane Switching (IPS) mode and Fringe Field Switching (FFS) mode, which is one of the IPS modes. 
       FIG. 7  is a cross-sectional view of a display panel PNL with a different structure from that of  FIG. 6 .  FIG. 7  illustrates a case where the sensor electrode SE is placed on the first substrate SUB 1  side. Note that, although this is omitted in  FIG. 7  as in  FIG. 6  above, a cover member is placed on the second substrate SUB 2 . Furthermore, in the non-display part NDA side, a light-shielding layer is placed between the second substrate SUB 2  and the cover member which is not shown. 
     As in  FIG. 7 , the sensor electrode SE may be placed in the first substrate SUB 1  side instead of the second substrate SUB 2  side.  FIG. 7  shows an example where the sensor electrode SE is placed in the first substrate SUB 1  side, in which the sensor electrode SE is placed on the same layer as the pixel electrode PE and is formed of the same transparent conductive material as pixel electrode PE. 
     If the sensor electrode SE is placed in the first substrate SUB 1  side, the first substrate SUB 1  does not need to conduct with the second substrate SUB 2  in the non-display part NDA, the sealing  30  does not need to contain conductive beads  31  as in  FIG. 7 . That is, the first substrate SUB 1  and second substrate SUB 2  may be adhered by sealing that does not contain conductive beads  31 . 
     Note that,  FIG. 7  illustrates a structure in which the pixel electrode PE and the common electrode CE are placed in the first substrate SUB 1  side, that is, when the liquid crystal mode of the display panel PNL is the horizontal field mode; however, the present structure is also applicable to the case where the liquid crystal mode is the vertical field mode. Furthermore, in  FIG. 7 , the pixel electrode PE is placed above the common electrode CE on the first substrate SUB 1  side; however, the positional relationship between the pixel electrode PE and the common electrode CE may be reversed. That is, the common electrode CE may be placed above the pixel electrode PE. 
     Furthermore,  FIG. 7  illustrates an example where the sensor electrode SE is placed on the same layer as the pixel electrode PE in the display part DA side; however, no limitation is intended thereby, and the sensor electrode SE may be placed on the same layer as the common electrode CE in the display part DA side, and formed of the same transparent conductive material as the common electrode CE. The sensor electrode SE may be placed on the same layer as the scan line G and signal line S in the display part DA side, and formed of the same metal material as the aforementioned lines. 
       FIG. 8  illustrates a cross section of a display panel PNL with a different structure from that of  FIG. 6 .  FIG. 8  illustrates an example where the sensor electrode SE is placed in the second substrate SUB 2  side, and on the main surface  20 B of the transparent substrate  20 . Although this is omitted from  FIG. 8  as in  FIGS. 6 and 7  above, a cover member is placed on the second substrate SUB 2 . Furthermore, in the non-display part NDA side, a light-shielding layer is placed between the second substrate SUB 2  and the cover member which is not shown. 
     As in  FIG. 8 , the sensor electrode SE may be placed on the main surface  20 B of the transparent substrate  20  in the second substrate SUB 2  side. In that case, the sensor electrode SE is electrically connected to the touch controller TC (printed circuit board PCB) via the flexible substrate FPC 2 . 
     When the sensor electrode SE is placed on the main surface  20 B of the transparent substrate  20 , the first substrate SUB 1  does not need to conduct with the second substrate SUB 2  in the non-display part NDA, and thus, the sealing  30  does not need to contain conductive beads  31  as in  FIG. 8 . That is, a sealing  30  that does not contain conductive beads  31  may be used for adhesion of the first substrate SUB 1  and second substrate SUB 2 . Furthermore, when the sensor electrode SE is placed on the main surface  20 B of the transparent substrate  20 , in the non-display part NDA, the metal layer corresponding to the sensor pad SP in  FIG. 6  and the metal layer ML 2  corresponding to the sensor wiring line SL of  FIG. 6  do not need electric connection therebetween. Thus, as in  FIG. 8 , an opening may not be formed in the planarization film  11 . Furthermore, if the sensor electrode SE is placed on the main surface  20 B of the transparent substrate  20 , in the non-display part NDA, the metal layer ML 3  corresponding to the sensor electrode SE of  FIG. 6  may not be formed. 
     Note that,  FIG. 8  illustrates an example where the pixel electrode PE is placed in the first substrate SUB 1  side and the common electrode CE is placed in the second substrate SUB 2  side. That is,  FIG. 8  illustrates an example where the liquid crystal mode of the display panel is the vertical field mode; however, the present structure is applicable to the case where the liquid crystal mode is the horizontal field mode. 
       FIG. 9  illustrates a structural example where the display panel PNL is a reflective display panel. 
     Each of the structures in  FIGS. 6 to 8  can be realized not only with a transmissive display panel in which the backlight unit BL is placed, but also with a reflective display panel. As an example,  FIG. 9  illustrates a case in which the sensor electrode SE is placed in the second substrate SUB 2  side; however, the sensor electrode SE may be placed in the first substrate SUB 1  side or may be placed on the main surface  20 B of the transparent substrate  20  in the second substrate SUB 2  side. Furthermore, although this is not shown in  FIG. 9  as in  FIGS. 6 to 8  above, the cover member is placed on the second substrate SUB  2 . Furthermore, in the non-display part NDA side, a light-shielding layer is placed between the second substrateSUB 2  and the cover member which is not shown. 
     In the reflective display panel PNL, the backlight unit is not placed behind the first substrate SUB 1 , and instead, a reflective electrode RE is placed on top of the pixel electrode PE. For example, Ag is used as the reflective electrode RE. The reflective electrode RE reflects the light incident from the second substrate SUB 2  side and directs the light to be incident on the liquid crystal layer LC, thereby illuminating the display panel PNL. Note that,  FIG. 9  illustrates a case where the reflective electrode RE is placed above the pixel electrode PE; however, no limitation is intended thereby, and the reflective electrode RE may be placed below the pixel electrode PE. 
     Next, referring to  FIGS. 10 and 11 , a first drive method which is one of the methods of driving sensor electrodes SE 1  to SE 8  provided with the display device DSP will be explained. In the case of the first drive method, the sensor electrodes SE 1  to SE 8  detect an approaching or contacting object (that is, detect touching) using the mutual capacitive method. 
     In the first drive method, as shown in the left side of  FIG. 10( a ) , at a certain timing, the odd-numbered sensors SE 1 , SE 3 , SE 5 , and SE 7  function as detection electrodes (Rx electrodes) to read detection signals, and the even-numbered sensor electrodes SE 2 , SE 4 , SE 6 , and SE 8  function as drive electrodes (Tx electrodes) to receive input of drive signals. Furthermore, in the first drive method, as shown in the right side of  FIG. 10( a ) , in the next timing following the aforementioned certain timing, the odd-numbered sensor electrodes SE 1 , SE 3 , SE 5 , and SE 7  function as drive electrodes to receive input of drive signals, and the even-numbered SE 2 , SE 4 , SE 6 , SE 8  function as detection electrodes to read detection signals. As above, the first drive method is designed so that the odd-numbered sensor electrodes and the even-numbered sensor electrodes function alternately between detection electrodes and drive electrodes. 
       FIG. 10( b )  illustrates an example of a switch circuit on/off of which is controlled by the touch controller TC to realize the first drive method. Note that, the switch circuit may be included in the touch controller TC or may be provided separately from the touch controller TC.  FIG. 10( b )  illustrates, as shown in the left side of  FIG. 10( a ) , connection state of a switch circuit in which the odd-numbered sensors SE 1 , SE 3 , SE 5 , and SE 7  function as detection electrodes, and the even-numbered sensor electrodes SE 2 , SE 4 , SE 6 , and SE 8  function as drive electrodes. In that case, the odd-numbered sensor electrodes SE 1 , SE 3 , SE 5 , and SE 7  are connected to the RxAFE wiring line to output detection signals, and the even-numbered sensor electrodes SE 2 , SE 4 , SE 6 , and SE 8  are connected to the Tx wiring line to receive the input of drive signals. 
       FIG. 11  is a timing chart illustrating the drive timing of sensor electrodes SE 1  to SE 8  using the first drive method. 
     Note that, in the present embodiment, one frame period includes a touch detection period TP to detect touching by sensor electrodes SE 1  to SE 8  placed in the non-display part NDA and a display period DP to display an image in the display part DA. Note that, in the present embodiment, a case where one frame period includes one touch detection period TP and one display period DP is considered; however, no limitation is intended thereby, and one frame period may include multiple touch detection periods TP and multiple display periods DP. 
     The first drive method includes, as shown in  FIG. 10  above, in the touch detection period TP, there are a period in which the odd-numbered sensor electrodes function as the detection electrodes and the even-numbered sensor electrodes function as the drive electrodes, and a period in which the even-numbered sensor electrodes function as the detection electrodes and the odd-numbered sensor electrodes function as the drive electrodes. Furthermore,  FIG. 11  illustrates that the odd-numbered sensor electrodes and the even-numbered sensor electrodes alternate between functioning as detection electrodes and functioning as drive electrodes. Note that, in the following, the period included in the touch detection period TP, from the time when the switch circuit described above transitions to one connection state to the time when it transitions to another connection state, will be referred to as the touch frame. 
     For this reason, in a first touch frame TP 1  included in the touch detection period TP of  FIG. 11 , the odd-numbered sensor electrodes SE 1 , SE 3 , SE 5 , and SE 7  function as detection electrodes, and reads the detection signals RxAFE 1  to RxAFE 4 , respectively, and the detection signals RxAFE 1  to RxAFE 4  are output to the touch controller TC. And, in the first touch frame TP 1 , the even-numbered sensor electrodes SE 2 , SE 4 , SE 6 , and SE 8  function as drive electrodes, and the sensor electrodes SE 2 , SE 4 , SE 6 , and SE 8  receive the input of the drive signals Tx from the touch controller TC. 
     Then, in a second touch frame TP 2 , which is a touch frame included in the touch detection period TP and follows the first touch frame TP, the odd-numbered sensor electrodes SE 1 , SE 3 , SE 5 , and SE 7  function as drive electrodes, and the sensor electrodes SE 1 , SE 3 , SE 5 , and SE 7  receive input of the drive signals Tx from the touch controller TC. And, in the second touch frame TP 2 , the even-numbered sensor electrodes SE 2 , SE 4 , SE 6 , and SE 8  function as detection electrodes, and the sensor electrodes SE 2 , SE 4 , SE 6 , and SE 8  read detection signals RxAFE 1  to RxAFE 4 , respectively, and output the detection signals RxAFE 1  to RxAFE 4  to the touch controller TC. 
     When the first touch frame TP 1  and the second touch frame TP 2  are completed, the touch detection period TP ends, and the period transitions to the display period DP. When the display period DP ends, this one frame period ends, and the period transitions to the next one frame period. 
     If the waveforms of the detection signals RxAFE 1  to RxAFE 4  output from the sensor electrodes SE 1  to SE 8  in the touch detection period TP are different from the waveform in a case where an object does not approach or contact the sensor electrodes SE 1  to SE 8 , the touch controller TC detects that an object is approaching or contacting the sensor electrodes outputting the detection signals with different waveform and two sensor electrodes adjacent to the aforementioned sensor electrode. Note that, the waveform in the case where an does not approach or contact the sensor electrodes SE 1  to SE 8  is, for example, preliminarily stored in a memory or the like, which is not shown. 
     In the first drive method, the sensor electrodes shall be driven such that the odd-numbered sensor electrodes SE 1 , SE 3 , SE 5 , and SE 7  and the even-numbered sensor electrodes SE 2 , SE 4 , SE 6 , and SE 8  are alternately switched, and thus, the touch detection period TP should include two touch frames, such as the first touch frame TP 1  and the second touch frame TP 2 . According thereto, the number (types) of touch frames of the touch detection period TP can be low, and thus, there is no need for a switch circuit with a complicated configuration, or complicated control of the switch circuit, which means that the present embodiment is easily achieved. 
     Next, referring to  FIGS. 12 and 13 , a second drive method which is one of the methods of driving sensor electrodes SE 1  to SE 8  installed in the display device DSP will be explained. In the second drive method, sensor electrodes SE 1  to SE 8  detect an approaching or contacting object (that is, detect touching) using the mutual capacitive method. 
     In the second drive method, as in the left side of  FIG. 12( a ) , in a certain touch frame, one sensor electrode among the sensor electrodes functions as a detection electrode to read detection signals, and two sensor electrodes adjacent to the sensor electrode that functions as the detection electrode function as drive electrodes to receive input of drive signals. The other sensor electrodes do not function as either detection electrodes or drive electrodes. Note that, in  FIG. 12( a ) , the case where sensor electrodes functioning as detection electrodes are sequentially shifted in the clockwise direction for each touch frame is illustrated. However, no limitation is intended thereby, and the sensor electrode functioning as the detection electrode may shift sequentially in the counterclockwise direction for each touch frame. 
       FIG. 12( b )  illustrates an example of a switch circuit on/off of which is controlled by the touch controller TC to realize the second drive method. In  FIG. 12( b ) , as in the left side of  FIG. 12( a ) , the connection state of the switch circuit in a case where the sensor electrode SE 2  functions as the detection electrode, and the two sensor electrodes SE 1  and SE 3  adjacent to the aforementioned sensor electrode SE 2  function as drive electrodes is illustrated. In this case, the sensor electrode SE 2  is connected to the RxAFE wiring line to output the detection signal, and sensor electrodes SE 1  and SE 3  are connected to the Tx wiring line to receive input of drive signals, while the other sensor electrodes SE 4  to SE 8  are connected to a DC wiring line to which a DC voltage is applied to prevent them from functioning as either detection electrode or drive electrode. 
     Note that, the other sensor electrodes SE 4  to SE 8  are not connected to any of the wiring lines, and may be floating. In this case, a DC wiring line can be omitted, which simplifies the circuit configuration and reduces the circuit size. Alternatively, the other sensor electrodes SE 4  to SE 8  may be connected to the Tx wiring line. In this case, although the power consumption increases slightly compared to the case where they are connected to the DC wiring line or are floating, it is possible to have, for example, a function to reduce parasitic capacitance and the influence of noise by using the drive signal Tx input to sensor electrodes SE 4  to SE 8  as a so-called guard signal. 
       FIG. 13  is a timing chart illustrating the drive timing of sensor electrodes SE 1  to SE 8  using the second drive method. 
     The second drive method is characterized, as in  FIG. 12  above, such that in one touch frame included in the touch detection period TP, one sensor electrode functions as a detection electrode, and two sensor electrodes adjacent to the detection electrode function as drive electrodes, wherein the detection electrode is shifted sequentially in each touch frame. 
     Therefore, in the first touch frame TP 11  included in the touch detection period TP of  FIG. 13 , the sensor electrode SE 2  functions as the detection electrode, and the sensor electrode SE 2  reads the detection signal RxAFE to be output to the touch controller TC. And, in the first touch frame TP 11 , two sensor electrodes SE 1  and SE 3  adjacent to the sensor electrode SE 2  function as drive electrodes, and these sensor electrodes SE 1  and SE 3  receive the input of the drive signal Tx from the touch controller TC. Note that, the other sensor electrodes SE 4  to SE 8  are connected to the DC wiring line, or are floating, or receiving the input of the drive signal Tx that functions as a guard signal, and thus, they do not function as either a detection electrode or a drive electrode. 
     The second touch frame TP 12  is a touch frame included in the touch detection period TP and follows the first touch frame TP 11  described above. In the second touch frame TP 12 , the sensor electrode SE 3  functions as the detection electrode, and reads the detection signal RxAFE to be output to the touch controller TC. The sensor electrode SE 3  adjacent clockwise to the sensor electrode SE 2  which has functioned as the detection electrode in the first touch frame TP 11 . And, in the second touch frame TP 12 , the two sensor electrodes SE 2  and SE 4  adjacent to the sensor electrode SE 3  function as the drive electrodes, and the two sensor electrodes SE 2  and SE 4  receive the input of the drive signal Tx from the touch controller TC. Note that, the other sensor electrodes SE 1 , and SE 5  to SE 8  are connected to the DC wiring line, or floating, or receiving the input of the drive signal Tx that functions as a guard signal, and thus, they do not function either as detection electrodes or as drive electrodes. 
     The third touch frame TP 13  following the second touch frame TP 12  and the frames thereafter function the same, and when all sensor electrodes SE 1  to SE 2  placed in the non-display part NDA function as detection electrodes once each in the eighth touch frame TP 18 , the touch detection period TP ends, transitioning to the display period DP. When the display period DP ends, this one frame period ends, transitioning to the next one frame period begins. 
     In this second drive method, one sensor electrode that functions as a detection electrode and two sensor electrodes that are adjacent to the sensor electrode and function as drive electrodes are driven in sets so that they are shifted sequentially. Since sensor electrodes other than this set do not function as detection electrodes or drive electrodes, it is possible to accurately identify the sensor electrode which an object has approached or contacted to. That is, it is possible to realize highly sensitive touch detection. Furthermore, in the second drive method, since only one sensor electrode functions as a detection electrode in one touch frame, the touch controller TC only needs to pay attention to the detection signal read from one sensor electrode in one touch frame, and therefore, the processing load on the touch controller TC can be reduced. 
     Now, referring to  FIGS. 14 and 15 , a third drive method which is one of the methods of driving sensor electrodes SE 1  to SE 8  of the display device DSP. Note that, in the third drive method, the sensor electrode SE 1  to SE 8  detect an approaching or contacting object (that is, detect touching) using the self-capacitance method. 
     In the third drive method, as described above, sensor electrodes SE 1  to SE 8  detect an approaching or contacting object using the self-capacitance method, and thus, as in  FIG. 14( a ) , each of the sensor electrodes SE 1  to SE 8  functions as a detection electrode (Rx electrode) that receives the input of the drive signal and reads the detection signal. 
       FIG. 14( b )  illustrates an example of a circuit configured to realize the third drive method. In this case, sensor electrodes SE 1  to SE 8  each function as the detection electrode, and thus, each sensor electrode SE 1  to SE 8  is connected to the RxAFE wiring line. 
       FIG. 15  is a timing chart illustrating the drive timing of sensor electrodes SE 1  to SE 8  using the third drive method. 
     The third drive method is characterized, as in  FIG. 14  above, such that each sensor electrode functions as a detection electrode in the touch detection period TP. Therefore, in the touch detection period TP in  FIG. 15 , each of the sensor electrodes SE 1  to SE 8  functions as the detection electrode, and the sensor electrodes SE 1  to SE 8  read the detection signals RxAFE 1  to RxAFE 8 , respectively, and output the detection signals RxAFE 1  to RxAFE 8  to the touch controller TC. 
     When the touch detection period TP ends, the transition is made to the display period DP, and when the display period DP ends, this frame period ends, and the transition to the next frame period is made. 
     In this third drive method, it is only necessary to drive the sensor electrode so that each sensor electrode SE 1  to SE 8  functions as a detection electrode, and thus, there is no need to configure the touch detection period TP with multiple touch frames, and the display period DP can be made longer. Furthermore, the third drive method does not require a switch circuit as in the first and second drive methods described above, and has the advantage of being easy to implement. 
     Next, referring to  FIGS. 16 and 17 , a fourth drive method which is one of the methods to drive sensor electrodes SE 1  to SE 8  of the display device DSP. Note that, in the fourth drive method, the sensor electrodes SE 1  to SE 8  detect an approaching or contacting object (that is, detect touching) using the self-capacitance method. 
     In the fourth drive method, as shown in the left side of  FIG. 16( a ) , M sensor electrodes ( 3  in the case of  FIG. 16 ) of multiple sensor electrodes are selected in a certain touch frame, wherein the M sensor electrodes function as detection electrodes to read detection signals, and the other sensor electrodes do not function detection electrodes. Note that, in  FIG. 16( a ) , a case where M sensor electrodes functioning as detection electrodes are newly selected shifting in the clockwise direction for each touch frame by N (one in  FIG. 16 ) is illustrated as an example; however, no limitation is intended thereby, and M sensor electrodes functioning as detection electrodes may be selected by shifting N electrodes in the counterclockwise direction for each touch frame. Note that, M and N are both positive integers, and N may be equal to M or different from M. 
       FIG. 16( b )  illustrates an example of a switch circuit on/off of which is controlled by the touch controller TC to realize the fourth drive method. In  FIG. 16( b ) , as in the left side of  FIG. 16( a ) , a connection state of the switch circuit in which three sensor electrodes SE 1  to SE 3  function as detection electrodes is illustrated. In this case, sensor electrodes SE 1  to SE 3  are connected to the RxAFE wiring line to output detection signals, and the other sensor electrodes SE 4  to SE 8  are connected to the DC wiring line to prevent them from functioning as detection electrodes. 
     Note that the other sensor electrodes SE 4  to SE 8  are not connected to any of the wiring lines, and may be floating. In this case, it is possible to omit DC wiring lines, which simplifies the circuit configuration and reduces the circuit size. Alternatively, the other sensor electrodes SE 4  to SE 8  may be connected to the guard wiring line. In this case, although the power consumption increases slightly compared to the case where they are connected to the DC wiring line or floating, so-called guard signals can be input to the sensor electrodes SE 4  to SE 8 . 
       FIG. 16  illustrates a bundled drive in which M consecutive sensor electrodes function as detection electrodes. However, the M sensor electrodes that function as detection electrodes may not necessarily be consecutive. Furthermore, M and N may both be set to one, one sensor electrode may sequentially function as a detection electrode for each touch frame. In this case, the switch circuit on/off of which is controlled by the touch controller TC should include at least one switch that is connected to each sensor wiring line extending from each sensor electrode. This makes it possible to simplify the circuit configuration and reduce the circuit size, and to minimize the processing load on the touch controller TC, for example. 
       FIG. 17  is a timing chart illustrating the drive timing of the sensor electrodes SE 1  to SE 8  using the fourth drive method. 
     The fourth drive method is characterized, as in  FIG. 16  above, such that M sensor electrodes are selected in one touch frame included in the touch detection period TP, and the M sensor electrodes functioning as detection electrodes are shifted by N for each touch frame. Note that, in  FIG. 17 , M is set to 3 and N is set to 1 in the clockwise direction. 
     Therefore, in the first touch frame TP 21  included in the touch detection period TP of  FIG. 17 , three sensor electrodes SE 1  to SE 3  function as detection electrodes, and the sensor electrodes SE 1  to SE 3  read the detection signals RxAFE to be output to the touch controller TC. Note that the other sensor electrodes SE 4  to SE 8  are either connected to the DC wiring line, or floating, or receiving the input of the guard signal, and do not function as detection electrodes. 
     Then, in the second touch frame TP 22  included in the touch detection period TP, which follows the first touch frame TP 21 , the three sensors the three sensor electrodes SE 2  to SE 4  which are shifted by one electrode in the clockwise direction from the three sensor electrodes SE 1  to SE 3  which have functioned as detection electrodes in the first touch frame TP 21  function as detection electrodes, and the sensor electrodes SE 2  to SE 4  read the detection signal RxAFE to be output to the touch controller TC. Note that, the other sensor electrodes SE 1 , and SE 5  to SE 8  are connected to the DC wiring line, or floating, or receiving the input of the guard signal, and do not function as detection electrodes. 
     The third touch frame TP 23  following the second touch frame TP 22  and the frames thereafter are operated in the same manner, and all sensor electrodes SE 1  to SE 2  that are placed in the non-display part NDA function as the detection electrode for the same number of times (three times in this example) in the eighth touch frame TP 28 , the touch detection period TP ends, transitioning to the display period DP. When the display period DP ends, this one frame period ends, and the transition to the next frame period is made. 
     In this fourth drive method, M sensor electrodes functioning as detection electrodes are selected, and the M sensor electrodes are driven in bundles (bundled driving), and M sensor electrodes functioning as the detection electrodes are selected shifting by N for each touch frame. Therefore, it is possible to receive the input of detection signals RxAFE while maintaining the predetermined resolution, and it is possible to accurately identify the sensor electrode with which an object is approaching or contacting. That is, it is possible to realize highly sensitive touch detection. 
       FIG. 18  shows an example of application of the display device DSP of the embodiment. As in  FIG. 18 , the display device DSP is applied to, for example, a wristwatch  100 . In this case, time and other information are displayed in the display part DA of the display device DSP, and the display device DSP responds to a predetermined gesture when sensor electrodes located in the non-display part NDA are touched (for example, a gesture of touching the circumferential part of the watch so as to rotate it clockwise by one rotation, a gesture of touching the circumferential part of the watch so as to rotate it counterclockwise by one rotation, a gesture of tapping), and therefore, it is possible to realize the operation according to the detected predetermined gesture. 
     Referring to  FIGS. 19 and 20 , the principle of capacitive touch detection used in the embodiment will be explained. 
       FIG. 19  illustrates an example of the principle of touch detection by the mutual capacitive method. A capacitance Cc exists between the drive electrode Tx and the detection electrode Rx, which are facing each other. When a drive signal is supplied to the drive electrode Tx from the drive circuit  200   a  , the current flows to the detection electrode Rx through the capacitance Cc, and a detection signal of a predetermined waveform is read from the detection electrode Rx. On the other hand, when an object (a conductor such as a finger) approaches or contacts therewith, a capacitance is generated between the object and detection electrode Rx. In this state, the waveform of the detection signal read from the detection electrode Rx when the drive signal is supplied to the drive electrode Tx changes because of the capacitance generated between the object and the detection electrode Rx. The detection circuit  300   a  detects an approaching or contacting object based on the change in the waveform of the detection signal. 
       FIG. 20  illustrates an example of the principle of touch detection by the self-capacitance method. The voltage divided by the voltage of the power supply Vdd by the resistor division is supplied to the detection electrode Rx as the bias voltage. A drive signal with a predetermined waveform is supplied from the drive circuit  200   b  to the detection electrode Rx by capacitive coupling, etc., and the detection signal of a predetermined waveform is read from the detection electrode Rx. At this time, the amplitude of the detection electrode changes when the capacitance caused by a finger or the like is loaded on the detection electrode Rx. In  FIG. 20 , the amplitude of detection electrode Rx decreases. Therefore, in the equivalent circuit illustrated in  FIG. 20 , the detection circuit  300   b  detects the amplitude of the detection electrode Rx. Therefore, in the equivalent circuit illustrated in  FIG. 20 , the detection circuit  300   b  detects the amplitude of detection electrode Rx to detect the presence or absence of an approaching or contacting external proximity object such as a finger. Note that the self-detection circuit is not limited to the circuit illustrated in  FIG. 20 , and any circuit method may be adopted as long as the presence or absence of an external proximate object such as a finger can be detected using only the detection electrodes. 
     According to an embodiment described above, it is possible to suitably drive sensor electrodes SE 1  to SE 8  located in the non-display part NDA by various drive methods, and it is possible to provide a display device and a watch that have both display quality when displaying images and excellent operability by touch. 
     A skilled person would conceive various changes and modifications of the present invention within the scope of the technical concept of the invention, and naturally, such changes and modifications are encompassed by the scope of the present invention. For example, if a skilled person adds/deletes/alters a structural element or design to/from/in the above-described embodiments, or adds/deletes/alters a step or a condition to/from/in the above-described embodiment, as long as they fall within the scope and spirit of the present invention, such addition, deletion, and altercation are encompassed by the scope of the present invention. 
     Furthermore, regarding the present embodiments, any advantage and effect those will be obvious from the description of the specification or arbitrarily conceived by a skilled person are naturally considered achievable by the present invention.