Abstract:
An E-paper display device with touch sensing function includes a composite transparent electrodes layer including at least one layer of touch electrodes responding to a touch, a pixel electrode, and an electrophoretic medium contacting the composite transparent electrodes layer and arranged between the composite transparent electrodes layer and the pixel electrode. One of the at least one layer of touch electrodes forms a display layer with the pixel electrode and the electrophoretic medium. A driving circuit configured to detect the location of a user touch on the composite transparent electrodes layer and drive the electrophoretic medium layer for displaying content. With the use of the composite transparent electrodes layer, the light propagation efficiency can be effectively improved, and the manufacturing technology is simplified.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to electronic-paper (E-paper) display devices, especially to an E-paper display device with touch function. 
         [0003]    2. Description of Related Art 
         [0004]    For use as a E-paper display, a electrophoretic display is preferred over a liquid crystal display (LCD) because of a better reflectivity and contrast ratio. In addition, the electrophoretic display has low power consumption since it has bistable characteristic and can maintain content without needing a continuously applied voltage. The electrophoretic display is widely used for the screen of cell phone, E-book, PDA etc. 
         [0005]    A touch panel has been arranged on the electrophoretic display to employ a touch function. The touch panel is stacked on a surface of the electrophoretic display by a thin binder film. However, such a structure tends to reduce the reflectivity ratio of the electrophoretic display. Furthermore, assembling of the touch panel and electrophoretic display needs to be carried out in a sterile room for quality consideration. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0007]      FIG. 1  is a schematic view of an E-paper display device according to a first embodiment. 
           [0008]      FIG. 2  is a block diagram of the E-paper display device of  FIG. 1 . 
           [0009]      FIG. 3  is a flowchart of a control method applied in the E-paper display device of  FIG. 1 . 
           [0010]      FIG. 4  is a schematic view of an E-paper display device according to a second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    The disclosure, including the accompanying, is illustrated by way of example and not by way of limitation. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
         [0012]    Referring to  FIG. 1 , an E-paper display device  100  according to a first embodiment is disclosed. The E-paper display device  100  includes a covering layer  10 , a composite transparent electrodes layer  20 , an electrophoretic medium  30  and a pixel electrode  40 . 
         [0013]    The covering layer  10  is arranged on the surface of the E-paper display device  100  to protect the display from being scratched. The covering layer  10  may be a transparent film of high light propagation efficiency. 
         [0014]    In the first embodiment, the electrophoretic medium  30  is described as microcapsule electrophoretic medium with bistable characteristic. The electrophoretic medium  30  includes a plurality of microcapsules  301  containing electronic ink with first electrophoretic particles  302  with black pigment and second electrophoretic particles  303  with white pigment. 
         [0015]    The composite transparent electrodes layer  20  includes a first touch electrode  201 , a second touch electrode  202  and a plurality of spacers  203  arranged between the first touch electrode  201  and the second touch electrode  202  to separate the first touch electrode  201  from the second touch electrode  202 . The first touch electrode  201  and the second touch electrode  202  may be an electrically conductive and resistive layer made with indium tin oxides (ITO) film. The spacers  203  may be an array of transparent and insulating plastic having a thickness about 10˜40 micrometer. The composite transparent electrodes layer  20  includes two modes: a touch mode and a driving mode. When the surface of the E-paper display device  100  is touched under the touch mode, the two layers of touch electrodes  201 ,  202  are pressed together, the current variation of the first touch electrode  201  and the second touch electrode  202  indicates the location of the touch. In this embodiment, the E-paper display device  100  achieves the touch function by applying a resistive touch panel consisting of the first touch electrode  201 , the second touch electrode  202 , and the spacers  203 . 
         [0016]    The second touch electrode  202  further contacts with the electrophoretic medium  30 , and acts as a common electrode layer under the driving mode. The second touch electrode  202 , the electrophoretic medium  30  and the pixel electrode  40  forms a display layer  56 . An adhesive layer (not shown), adheres the pixel electrode  40  to the electrophoretic medium  30 . The pixel electrode  40  includes a plurality of Thin-film transistors (TFTs), the pixel electrode  40  is used to generate a pixel voltage supplied through the TFT to generate an electric potential difference relating to the common voltage supplied to the second touch electrode  202  (the common electrode). Under the driving mode, the electric potential applied to the second touch electrode  202  and the pixel electrode  40  causes the first electrophoretic particles  302  and the second electrophoretic particles  303  to move to the electrodes attracting those particles, thereby displaying content such as an image. 
         [0017]    Referring to  FIG. 2 , the E-paper display device  100  further includes a power source  57  and a drive circuit  50  used to detect the location of the touch on the composite transparent electrodes layer  20  and drive the display layer  56  for displaying the content. 
         [0018]    The driving circuit  50  includes a touch control unit  52 , a center control unit  53 , an electrode switching unit  55  and an content control unit  54 . The touch control unit  52  is connected between the composite transparent electrode layer  20  and the center control unit  53 . The content control unit  54  is connected between the display layer  56  and the center control unit  53 . The electrode switching unit  55  is connected to the center control unit  53 , the composite transparent electrode layer  20  and the display layer  56 . 
         [0019]    The electrode switching unit  55  is used to switch the composite transparent electrodes layer  20  between the touch mode and the driving mode. The power source  57  is connected to the composite transparent electrodes layer  20  under the touch mode, and to the second touch electrode  202  and the pixel electrode  40  under the driving mode. The electrode switching unit  55  may be an electronic switching circuit including a metal oxide semiconductor field effect transistor (MOSFET). 
         [0020]    The touch control unit  52  includes an electronic signal detection module  521  and a touch analysis module  522 . The electronic signal detection module  521  is connected to the composite transparent electrodes layer  20 . The power source  57  generates an electric field between the first touch electrode  201  and the second touch electrode  202 . When the surface of the E-paper display device  100  is touched under the touch mode, the two layers of touch electrodes  201 ,  202  are pressed together, the current on the first touch electrode  201  and the second touch electrode  202  changes. The electronic signal detection module  521  detects and collects the current variation of the two layers of touch electrodes  201 ,  202 , and sends the current variation data to the touch analysis module  522 . The touch analysis module  522  identifies the location of the touch by analyzing the current variation data, and sends the data about the location of the touch to the center control unit  53 . 
         [0021]    The center control unit  53  identifies whether the content on the E-paper display device  100  needs to be changed according the location of the touch. If the content on the E-paper display device  100  needs to be changed, the center control unit  53  sends a first switching command to the electrode switching unit  55  and a driving signal to the content control unit  54 . If the content on the E-paper display device  100  does not need to be changed, the center control unit  53  executes the command corresponding to the location of the touch, and the electronic signal detection module  521  keeps on detecting and collecting the current variation of the first touch electrode  201  and the second touch electrode  202 . For example, when the location of the touch corresponds to the command “return to previous menu”, the center control unit  53  sends a first switch command to the electrode switching unit  55  and sends a driving signal to the content control unit  54 , so that the E-paper display device  100  returns to the previous menu. If the location of the touch point corresponding to “turn the volume up”, the center control unit  53  just executes the command “turn the volume up” to turn up the volume of the E-paper display device  100 . 
         [0022]    After receiving the first switch command from the center control unit  53 , the electrode switching unit  55  disconnects the connection between the power source  57  and the composite transparent electrodes layer  20  to remove the electric filed formed between the first touch electrode  201  and the second touch electrode  202 . In addition, connects the power source  57  to the second touch electrode  202  and the pixel electrode  40 , to switch the composite transparent electrodes layer  20  from the touch mode to the driving mode. 
         [0023]    After the content control unit  54  receives the driving signal from the center control unit  53 , the content control unit  54  controls the pixel voltage to change the optical state of the electrophoretic medium  30 , to refresh the content on the E-paper display device  100 . 
         [0024]    The content control unit  54  sends a finished signal to the center control unit  53  when the refresh of the content on the E-paper display device  100  is completed, the center control unit  53  sends a second switching command to the electrode switching unit  55  according to the finished signal. After receiving the second switching command from the center control unit  53 , the electrode switching unit  55  disconnects the connection between the power source  57  and the display layer  56  to remove the electric field formed between the second touch electrode  202  and the pixel electrode  40 . Moreover, connects the power source  57  to the first touch electrode  201  and the second touch electrode  202 , to switch the composite transparent electrodes layer  20  from the driving mode to the touch mode. The electronic signal detection module  521  starts to detect and collect the current variation of the first touch electrode  201  and the second touch electrode  202 . 
         [0025]    Referring to  FIG. 3 , a flowchart of a control method is applied in the E-paper display device  100 . 
         [0026]    In step S 61 , the electronic signal detection module  521  detects and collects the current variation of the first touch electrode  201  and the second touch electrode  202 , and sends the current variation data to the touch analysis module  522 . 
         [0027]    In step S 62 , the touch analysis module  522  identifies the location of the touch by analyzing the current variation data sent by the electronic signal detection module  521 , and sends the data about the location of the touch point to the center control unit  53 . 
         [0028]    In step S 63 , the center control unit  53  identifies whether the content on the E-paper display device  100  needs to be changed according the location of the touch. If so, the center control unit  53  sends a first switching command to the electrode switching unit  55 , sends a driving signal to the content control unit  54 , and the procedure goes to step S 64 ; if not, the center control unit  53  executes the command corresponding to the location of the touch, and the procedure goes back to step S 61 . 
         [0029]    In step S 64 , the electrode switching unit  55  switches the composite transparent electrodes layer  20  from the touch mode to the driving mode according the first switch command. 
         [0030]    In step S 65 , the content control unit  54  controls the pixel voltage to change the optical state of the electrophoretic medium  30  according the driving signal, to refresh the content on the E-paper display device  100 . 
         [0031]    In step S 66 , the content control unit  54  sends a finish signal to the center control unit  53  when the refresh of the content on the E-paper display device  100  is completed. 
         [0032]    In step S 67 , the center control unit  53  sends a second switching command to the electrode switching unit  55  according to the finish signal. 
         [0033]    In step S 68 , the electrode switching unit  55  switches the composite transparent electrodes layer  20  from the driving mode to the touch mode according the second switch command, and the procedure goes back to step S 61 . 
         [0034]    Referring to  FIG. 4 , an E-paper display device  102  according to a second embodiment is disclosed. The E-paper display device  102  includes a covering layer  12 , a composite transparent electrodes layer  22 , an electrophoretic medium  32  and a pixel electrode  42 . 
         [0035]    The second embodiment is similar to the first embodiment, the difference between the second embodiment and the first embodiment is that the composite transparent electrodes layer  22  just includes a layer of touch electrode  221 . The composite transparent electrodes layer  22  also includes a touch mode and a driving mode. A small voltage is applied to the touch electrode  221 , resulting in a uniform electrostatic field. When a conductor, such as a human finger, touches the surface of the E-paper display device  100 , a capacitor is dynamically formed. The location of the touch can be determined indirectly from the change in the capacitance as measured from the four corners of the touch electrode  221 . In the second embodiment, the E-paper display device  102  achieves the touch function by applying a surface capacitive touch panel including the touch electrode  221 . 
         [0036]    The touch electrode  221  also acts as a common electrode layer under the driving mode. The pixel voltage applied to the touch electrode  221  and the pixel electrode  42  causes the electrophoretic medium  32  to change optical state, thus to refresh the content on the E-paper display device  100 . 
         [0037]    It is to be understood, however, that even though numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with details of the structure and function of the present disclosure, the present disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.