Abstract:
A touch detecting circuit of the present invention is provided between a substrate and a bistable display film of a display. The touch detecting circuit includes a plurality of first electrodes along a first direction, a plurality of second electrodes along a second direction, and an insulating layer between the first electrodes and the second electrodes. The insulating layer has through holes, on opposite ends of which the first electrodes and the second electrodes are provided. Each of the second electrodes has a contact terminal not masking the entire through hole. The first electrodes will contact the second electrodes under an external force exertion and a resistance effect will occur to let the system terminal of the display detecting the location of the external force.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an optical display and more particularly, to a touch detecting circuit for a bistable electronic display. 
         [0003]    2. Description of the Related Art 
         [0004]    E-paper displays are provided to simulate the real papers with inked words or pictures. The E-paper display has many characters including better readability, portability, reusability, and download for update. The E-paper display needs power only when changing the picture. In other words, the power is off when reader reads the picture on the E-paper display that would reduce the power consumption thereof. Besides, there is no a backlight module in the E-paper display. The E-paper display is readable in a light environment that the cost thereof is lower. 
         [0005]    The E-paper displays have many advantages that the conventional books don&#39;t have. However, readers have to operate the keys thereon to turn pages that is inconvenient. Some E-paper displays are provided with a touch panel for a better operation. Such touch panel is stacked on the top of the E-paper display, and the touch panel has a glass substrate and other elements that such E-paper display is thicker and heavier. The drawbacks as described above may affect the displaying performance of the E-paper displays. We strongly believe that the E-paper display will have a wider application when above drawbacks are fixed. 
       SUMMARY OF THE INVENTION 
       [0006]    The primary objective of the present invention is to provide a touch detecting circuit for a bistable electronic display, which is built in the display and will not increase the thickness and the weight of the display, furthermore, it will not affect the displaying performance of the display. 
         [0007]    The secondary objective of the present invention is to provide a touch detecting circuit for a bistable electronic display, which has a better touch function. 
         [0008]    To achieve the objectives of the present invention, a touch detecting circuit of the present invention is provided between a substrate and a bistable display film of a display. The touch detecting circuit includes a plurality of first electrodes along a first direction, an insulating layer, and a plurality of second electrodes along a second direction. Each of the first electrodes has at least a first contact area. The insulating layer has through holes associated with the first contact areas of the first electrodes. The insulating layer is between the first electrodes and the second electrodes. Each of the second electrodes has a contact terminal not masking the entire through hole. The contact terminal has a second contact area, which keeps a distance from the corresponding first contact area. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a sectional view in a part of a preferred embodiment of the present invention; 
           [0010]      FIG. 2  is a sectional view of the preferred embodiment of the present invention; 
           [0011]      FIG. 3  is a sectional view along the  3 - 3  line of  FIG. 2 ; 
           [0012]      FIG. 4  is a sectional view along the  4 - 4  line of  FIG. 2 ; 
           [0013]      FIG. 5  is similar to  FIG. 3 , showing the vertical second electrode; 
           [0014]      FIG. 6  is similar to  FIG. 3 , showing the second electrode having the recess portion and the protrusion on a position corresponding to the through hole; 
           [0015]      FIG. 7  is similar to  FIG. 3 , showing the flat layer on the second electrode and the insulating layer; 
           [0016]      FIG. 8  is similar to  FIG. 2 , showing a plurality of electrodes in electrical connection together and connected to the system terminal of the display; 
           [0017]      FIG. 9  is similar to  FIG. 2 , showing the odd electrodes connected to the system terminal of the display; and 
           [0018]      FIG. 10  is an enlarged view in a part of the preferred embodiment of the present invention, showing the second electrode having the recess portion in communication with the trough hole of the insulating layer. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIGS. 1˜4  show a touch detecting circuit  10  of a bistable electronic display  100 . The display  100  has a substrate  102  and a bistable display film  106 . The substrate  102 , which constructs a bottom portion of the display  100 , has a thin film transistor array substrate  103  having a plurality of data lines  103   a  and scan lines  103   b,  and a surface layer  104 . The surface layer  104  is made of an insulating material to cover the data lines  103   a  and the scan lines  103   b.  The surface layer  104  has a flat surface  104   a.  The bistable display film  106 , which constructs a top portion of the display  100 , changes pictures shown thereon by an electric field. The display  100  further includes a system terminal  107  to detect and determine pressed positions of the touch detecting circuit  10 . The touch detecting circuit  10  of the preferred embodiment of the present invention is described in following: 
         [0020]    The touch detecting circuit  10 , which is provided between the substrate  102  and the bistable display film  106 , includes a plurality of first electrodes  102 , an insulating layer  14 , and a plurality of second electrodes  16 . 
         [0021]    The first electrodes  12  are provided on the surface  104   a  of the surface layer  104  along a first direction D 1 , each of which has a top side  121  higher than the surface  104   a,  and long lateral sides  122  and  123  adjacent to the top side  121 . In the present embodiment, each of the first electrodes  12  are electrically connected to the system terminal  107 . 
         [0022]    After the first electrodes  12  are made, the insulating layer  14  covers all of the first electrodes  12 . The insulating layer  14  has a top side  141  and a plurality of transverse through holes  142 . In the present embodiment, one first electrode  12  is associated with plural of the through holes  142 . As shown in  FIG. 1  and  FIG. 3 , each of the through holes has an opening end along a second direction D 2  having an opening with a width W 1  greater than widths W 2  of the first electrodes  12  along the second direction D 2 . With this definition, each of the top sides  121  of the first electrodes  12  has first contact areas  10   a  aligned with the through holes  142  respectively. Besides, there are gaps  143  and  144  between an inner sidewall of each through holes  142  and the long lateral sides  122  and  123  of each first electrode  12 . 
         [0023]    After the insulating layer  14  is made, insulating support pads (not shown) are provided in the through holes  142  of the insulating layer  14 . The support pads cover the first electrodes  12  in the through holes  142 . The support pads are conventional devices, so we do not describe the detail here. After that, a metal foil is deposited on the top side  141  of the insulating layer  14 , and is performed with photo resistor coating, exposure, development, and etching to make the second electrodes  16 . The second electrodes  16 , which are parallel and along the second direction D 2  orthogonal to the first direction D 1 , are electrically connected to the system terminal  107  respectively. In above process, the top side  141  of the insulating layer  14  is higher than the support pads so that each of the second electrodes  16  forms contact terminals  161  in the through holes  142 . In the present preferred embodiment, the contact terminals  161  are U-shaped. As shown in  FIG. 4 , each of the through holes  142  of the insulating layer  16  of the present embodiment has an opening along the first direction D 1  having a width W 3  greater than a width W 4  of the contact terminal  161  of each second electrode  16  along the first direction D 1 . This is convenient for removal of the support pads. After the support pads are removed, each of the contact terminals  161  is suspended to form a second contact area  10   b  facing the first electrode  12 . There is a distance between each of the second contact areas  10   b  and the corresponding first contact area  10   a.    
         [0024]      FIG. 5  shows a vertical second electrode  17  because that the support pads are even with the top side  141  of the insulating layer  14 . When the support pads are higher than the top side  141  of the insulating layer  14 , it will get second electrodes  18  having recess portions  181  as shown in  FIG. 6 . To enhance the contact between the electrodes, as shown in  FIG. 6 , it may provide a protrusion  182  projected from a bottom of the recess portion  181  and a protrusion  124  on the first electrode  12  associated with the protrusion  182 . 
         [0025]    In above embodiment, when one presses the bistable display film  106 , the pressing force will deform the contact terminal  161  of the second electrode  16  thereunder that the second contact area  10   b  touches the corresponding first contact area  10   a  and a resistance effect is occurred. In this time, the system terminal  107  will identify the location of the pressing force immediately according to the change of current resistance for the following operation. 
         [0026]    With the description above, the touch detecting circuit  10  of the present invention is built in the display  100  that fixes the problem of thicker and heavier of the conventional device with a touch panel. The present invention has no effect on the optical display performance of the bistable display film  106 . In addition, the present invention provides the gaps  143  and  144  between the first electrodes  12  and the inner sidewalls of the through holes  142  to prevent the edges of the through holes  142  from crashing because of the pressure to keep a well touch sensing relation between the first contact areas  10   a  and the second contact areas  10   b.    
         [0027]    In addition, the first electrodes  12  of the present invention are right on the tops of the corresponding data lines  103   a,  and the second electrodes  16  are right on the tops of the corresponding scan lines  103   b.  However, they can be made on a pixel area  103   c  constructed by the orthogonal data lines  103   a  and the scan lines  103   b.  Besides, it is not necessary for the through holes  142  of the insulating layer  14  having to be associated with each of the first electrodes  12 . For example, the first line of the through holes  142  is on the top of the first of the first electrodes  12 , and the second line of the through holes  142  is on the top of the third of the first electrodes  12 . In addition, to enhance the lamination of the bistable display film  106 , the present invention may provide a covering layer  191 , which is made of an insulating material, on the second electrodes  16 , as shown in  FIG. 7 , and then provide a flat layer  192  on the covering layer  191  to enhance the lamination of the bistable display film  106 . 
         [0028]    Besides the first electrodes  12  and the second electrodes  14  may be electrically connected to the system terminal  107  respectively, they may be divided into groups. As shown in  FIG. 8 , the electrodes in the same group are electrical connected together first, and then connected to the system terminal  107 . It is mentioned that in each of the groups, a distance from the first to the last of the first (second) electrode  12   a ( 12   b ) is less than or identical to 0.7 cm. This is because that the electrodes are very fine, and it is about 0.7 cm when a tip of finger touches the electrodes, so that the groups may provide the system terminal  107  sensing the correct touching position. In addition, the connection of the electrodes and the system terminal  107  may be done as shown in  FIG. 9  which only odd electrodes  12  are connected to the system terminal  107 . There may be two or more electrodes not connected to the system terminal  107  between the electrodes  12  connected to system terminal  107 . However, a distance of the distribution of the electrodes  12  should be less than 0.7 cm for the correct position sensing. Referring to  FIG. 2 , a distance between the neighboring first electrodes  12  and the neighboring second electrodes  16  should be less than 0.7 cm also for the condition of touching by finger. On contrary, in the condition of touching by pen, the distance between the neighboring first electrodes  12  (or the neighboring second electrodes  16 ) should be narrower. 
         [0029]    In the embodiments as described above, widths of the second contact areas of the second electrodes along the first direction are less than that of the through holes of the insulating layer along the first direction. This character makes it easier to clean the support pads made of insulating material. There are some other ways to achieve the above objective. For example, referring to  FIG. 10 , widths of the through holes  21  of the insulating layer  20  along the first direction D 1  are less than that of the contact areas  221  of the second electrodes  22  along the first direction D 1 . Furthermore, each of the second electrodes  22  has a recess portion  222  associated with the through holes  21  and two gaps  223  on opposite sides of the recess portion  222  communicated with outside that also may help the step of cleaning the support pads. The second electrode  22  is provided with a protrusion  224  on a bottom side of the recess portion  222 , and the first electrode  24  is provided with a protrusion  242  on the first contact area  241  to enhance the contact of the electrodes. 
         [0030]    Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.