Patent Publication Number: US-2012038566-A1

Title: Touch display device

Description:
FIELD OF THE INVENTION 
     The present invention relates to a touch display device, and more particularly to a touch display panel with reduced frame width. 
     BACKGROUND OF THE INVENTION 
     The use of touch display devices can not only conserve the space for deploying conventional mouse and keyboard, but also provide more user-friendly operations, therefore becoming one of the major interfaces of the electronic devices or machines. Currently, the in-cell touch technology integrating the touch sensing element into the pixel structure can provide better contrast and brightness than the conventional touch display device and thus receives more and more attentions. 
       FIG. 1  illustrates the pixel structure  100  of a conventional touch display device, wherein the pixel structure  100  includes three sub-pixels: red (R), green (G), and blue (B). In general, each sub-pixel  110 ,  120 ,  130  includes a transistor and a pixel electrode and is driven by a gate line  140  and one of the three data lines  150 ,  152 , and  154 . For touch sensing function, each pixel structure is disposed with two sensing elements  160  and  162 , which sense x coordinate and y coordinate of the touch point, respectively. The structure of sensing elements  160  and  162  is typically a protrusion between the upper color filter substrate and the lower TFT array substrate of the display panel. When under pressing, the protrusion electrically conducts the upper substrate with the lower substrate. Thus, when an object touches the display panel, the sensing elements  160  and  162  of the pixel structure  100  corresponding to the touch position will generate a corresponding signal, wherein the signal can be transmitted to other circuitry of the display panel through the sensing lines  170  and  172  for further processing. 
       FIG. 2  illustrates a block diagram of the conventional touch display device  200 . The display device  200  includes a display panel  210 , Y-direction sensing circuits  220  and  222 , an X-direction sensing circuit  230 , gate-line driving circuits  240  and  242 , a data line driving circuit  250 , and a control chip  260 . The display panel  210  includes a plurality of pixel structures of  FIG. 1  arranged in matrix form, wherein the gate-line driving circuits  240 ,  242  and the data line driving circuit  250  update the display data in each pixel structure of the display panel  210 . The horizontal sensing element in each pixel structure (e.g. the sensing element  160  of  FIG. 1 ) is connected to the X-direction sensing circuit  230  through 2 n  sensing lines X( 1 ), X( 2 ), . . . , X( 2   n ). The vertical sensing element in each pixel structure (e.g. the sensing element  162  of  FIG. 1 ) is respectively connected to the 2 m  sensing lines Y( 1 ), Y( 2 ), . . . , Y( 2   m ), wherein the odd number sensing lines Y( 1 ), Y( 3 ), . . . , Y( 2   m −1), total 2 m−1  sensing lines, are connected to the Y-direction sensing circuit  220 , while the even number sensing lines Y( 2 ), Y( 4 ), . . . , Y( 2   m ), total 2 m−1  sensing lines, are connected to the Y-direction sensing circuit  222 . The control chip  260  receives and processes signals from the 2 n  sensing lines of the X-direction sensing circuit  230 , signals from the 2 m−1  sensing lines of the Y-direction sensing circuit  220 , and signals from the 2 −1  sensing lines of the Y-direction sensing circuit  222  to obtain data associated with the touch position on the display panel  210 . 
     Referring to  FIG. 2 , in order to prevent one side frame width of the touch display device  200  from widening, the sensing lines Y( 1 ), Y( 2 ), . . . , Y( 2   m ) are connected to two sides (e.g. left and right sides) of the display panel  210 , respectively. However, the Y-direction sensing circuit  220  or  222  still needs to output 2 m−1  sensing lines to the control chip  260 . Such huge amount of sensing lines will result in overlarge frame width (D). Moreover, the control chip  260  also requires a large amount of pins for receiving sensing signals. As the resolution of display panel  210  is promoted, the above problems become more serious. 
     Therefore, there is a need to provide a sensing circuit structure capable of effectively reducing the frame width of the touch display device and decreasing the amount of the pins required in the control chip. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and one aspect of the present invention is to provide a touch display device, which includes a digital logic circuit to significantly reduce the routing of the signal lines. 
     In one aspect of the present invention, by means of the digital logic circuit, the X-direction sensing lines and the Y-direction sensing lines in the touch display device are converted into signal lines in fewer amounts for outputting to the control chip. Due to the fewer amounts of the signal lines, not only the number of outputted signal lines can be reduced, but also the number of pins required in the control chip is decreased. 
     In one embodiment, the present invention provides a touch display device. The touch display device includes a display panel, a plurality of horizontal sensing lines, a horizontal encoder, and a control chip. The display panel includes a plurality of sensing elements arranged in matrix form, wherein the plurality of horizontal sensing lines are connected to the plurality of sensing elements, respectively. The horizontal encoder is coupled to the plurality of the horizontal sensing lines and provided for receiving and encoding a plurality of horizontal sensing signals from the plurality of horizontal sensing lines to output a plurality of horizontal encoded signals. The number of the plurality of horizontal encoded signals is less than the number of the plurality of horizontal sensing signals. The control chip is provided for receiving the plurality of horizontal encoded signals to obtain data associated with a touch position on the display panel. 
     In another aspect, the present invention provides an electronic apparatus including the touch display device described above, wherein the electronic apparatus is a mobile phone, a digital camera, a personal digital assistant, a laptop computer, a desktop computer, a television, a global positioning system, a head-up display, an aviation display, a digital frame, or a portable DVD player. 
     Other aspects of the present invention solve other problems and are disclosed and illustrated in detail with the embodiments below together with the aforesaid aspects. Various aspects of the present invention can be understood and implemented with the elements and combinations specified in the accompanied claims. However, it should be understood the foregoing contents and the following detailed description are only illustrative and not in a limited sense. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. While the invention is illustrated with preferred embodiments, those skilled in the art will understand the present invention is not limited to arrangements and elements described therein. In the drawings: 
         FIG. 1  illustrates a pixel structure of a conventional touch display device; 
         FIG. 2  illustrates a block diagram of a conventional touch display device; 
         FIG. 3  is a block diagram of a touch display device in accordance with one embodiment of the present invention; 
         FIG. 4  illustrates logic circuit diagrams of a 4-to-2 encoder and a 8-to-3 encoder; and 
         FIG. 5  illustrates a touch display device in accordance with another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention discloses a touch display device including at least one digital logic circuit for reducing the number of signal lines connected to the control chip to further reduce the frame width of the display device. The preferred embodiments of the present invention will now be described in greater details by referring to the following descriptions in reference with  FIG. 3  through  FIG. 5 . The devices, elements, and processing steps described in the following embodiments are provided to illustrate the present invention and are not intended to be restrictive of the scope of the present invention. 
       FIG. 3  is a block diagram of a touch display device  300  in accordance with one embodiment of the present invention. The touch display device  300  includes a display panel  310 , a vertical encoder  320 , a horizontal encoder  330 , a gate-line driving circuit  340 , a data-line driving circuit  350 , and a control chip  360 . 
     The display panel  310  includes a plurality of pixel structures  312  consisting of a TFT array substrate, a color filter substrate, and a liquid crystal layer sandwiched between the two substrates. In general, each pixel structure  312  can include three sub-pixels: red (R), green (G), blue (B), and each sub-pixel includes a thin film transistor (TFT) and a pixel electrode. The structure and function of elements in the pixel structure  312  are similar to those in the conventional liquid crystal display and will not be elaborated hereinafter. 
     In the embodiment, the display panel  310  is an in-cell touch panel, i.e. the sensing element is built in each pixel structure. Referring to  FIG. 3 , the pixel structure  312  includes a vertical sensing element  314  for sensing vertical position and a horizontal sensing element  316  for sensing horizontal position. The sensing elements  314  and  316  of the present invention can be any built-in sensing element commonly used in the touch panel, such as a protrusion structure between the TFT array substrate and the color filter substrate. When an object touches the display panel  310 , the sensing element corresponding to the touch position will electrically conduct the TFT array substrate and the color filter substrate, so as to determine the coordinates of the touch position by detecting the voltage drop caused by the short-circuit of the two substrates. It is noted that though each pixel includes one horizontal sensing element and one vertical sensing element in this embodiment, in other embodiments, the density of the sensing elements can be varied with the desired touch sensing resolution. 
     The sensing signal sensed by the vertical sensing element in each pixel structure can be outputted through the vertical sensing lines Y( 1 ), Y( 2 ), . . . , Y( 2   m ), wherein m is a positive integer. The sensing signal sensed by the horizontal sensing element in each pixel structure can be outputted through the horizontal sensing lines X( 1 ), X( 2 ), . . . , X( 2   n ), wherein n is a positive integer. In the embodiment, it is assumed that the number of the vertical sensing lines is 2 m , and the number of the horizontal sensing lines is 2 n . The number of the vertical or horizontal sensing lines is typically associated with the resolution of the display panel  310 . For example, if each pixel structure has 3 RGB sub-pixels, every 4 adjacent pixel structures in the horizontal direction are connected to a same vertical sensing line, every 4 adjacent pixel structures in the vertical direction are connected to a same horizontal sensing line, and the number of the vertical and horizontal sensing lines are respectively 2 m  and 2 n , then the resolution of the display panel  310  is (4×2 n )×3×(4×2 m ). 
     Referring to  FIG. 3  again, the gate-line driving circuit  340  and the data-line driving circuit  350  are configured to update the display data stored in each pixel structure of the display panel  310 . In general, each pixel structure can be driven by one gate line and three data lines. The gate-line driving circuit  340  can input the gate-line control signal through a plurality of gate lines (not shown) to drive the thin film transistor of the pixel structure. The data-line driving circuit  350  can send the display data signal to each pixel structure through a plurality of data lines (not shown). The structure and driving manner of the gate line and the data line are well known in the art and will not be described in detail, so as not to unnecessarily obscure the present invention. 
     Referring to  FIG. 3 , 2 m  vertical sensing lines Y( 1 ), Y( 2 ), . . . , Y( 2   m ) are connected to the vertical encoder  320 , and 2 n  horizontal sensing lines X( 1 ), X( 2 ), . . . , X( 2   n ) are connected to the horizontal encoder  330 . The vertical encoder  320  consists of a plurality of basic logic gates (typically OR logic gates), to encode 2 m  input signals into m output signals. In the embodiment, the vertical encoder  320  receives vertical sensing signals from the 2 m  vertical sensing lines Y( 1 ), Y( 2 ), . . . , Y( 2   m ) and encodes the 2 m  vertical sensing signals to obtain m vertical encoded signals  370 , wherein the m vertical encoded signals  370  correspond to the logic combinations of the 2 m  vertical sensing signals. Similarly, the horizontal encoder  330  receives and encodes horizontal sensing signals from the 2 n  horizontal sensing lines X( 1 ), X( 2 ), . . . , X( 2   n ) to obtain n horizontal encoded signals  375 . 
     In general, the vertical encoder  320  and the horizontal encoder  330  used in the present invention can be any common encoder configuration having output ports fewer than the input ports.  FIG. 4  illustrates logic circuits of a 4-to-2 (4 inputs and 2 outputs) encoder and an 8-to-3 (8 inputs and 3 outputs) encoder. From the teaching of the present invention and the embodiment of  FIG. 4 , those skilled in the art can easily recognize other 2 p -to-p ( 2   p  inputs and p outputs) encoder configuration. Referring to  FIG. 4 , the 4-to-2 encoder  400 A consists of two OR logic gates  402  and  404 , including 4 input ports I A0 ˜I A3  and 2 output ports Y A0 ˜Y A1 . Below shows the true value table of the 4-to-2 encoder  400 A. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                   
               
               
                   
                 I A3   
                 I A2   
                 I A1   
                 I A0   
                 Y A1   
                 Y A0   
               
               
                   
                   
               
             
            
               
                   
                 0 
                 0 
                 0 
                 1 
                 0 
                 0 
               
               
                   
                 0 
                 0 
                 1 
                 0 
                 0 
                 1 
               
               
                   
                 0 
                 1 
                 0 
                 0 
                 1 
                 0 
               
               
                   
                 1 
                 0 
                 0 
                 0 
                 1 
                 1 
               
               
                   
                   
               
            
           
         
       
     
     Referring to  FIG. 4  again, the 8-to-3 encoder  400 B consists of three OR logic gates  412 ,  414 , and  416 , including 8 input ports I B0 ˜I B7  and 3 output ports Y B0 ˜Y B2 . Below shows the true value table of the 8-to-3 encoder  400 B. 
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
             
               
                   
               
               
                 I B7   
                 I B6   
                 I B5   
                 I B4   
                 I B3   
                 I B2   
                 I B1   
                 I B0   
                 Y B2   
                 Y B1   
                 Y B0   
               
               
                   
               
             
            
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 1 
                 0 
                 0 
                 0 
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 1 
                 0 
                 0 
                 0 
                 1 
               
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 1 
                 0 
                 0 
                 0 
                 1 
                 0 
               
               
                 0 
                 0 
                 0 
                 0 
                 1 
                 0 
                 0 
                 0 
                 0 
                 1 
                 1 
               
               
                 0 
                 0 
                 0 
                 1 
                 0 
                 0 
                 0 
                 0 
                 1 
                 0 
                 0 
               
               
                 0 
                 0 
                 1 
                 0 
                 0 
                 0 
                 0 
                 0 
                 1 
                 0 
                 1 
               
               
                 0 
                 1 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 1 
                 1 
                 0 
               
               
                 1 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 1 
                 1 
                 1 
               
               
                   
               
            
           
         
       
     
     Returning to  FIG. 3 , after the encoders  320  and  330  encode the received 2 m  vertical sensing signals and 2 n  horizontal sensing signals, the encoders  320  and  330  output the m vertical encoded signals  370  and the n horizontal encoded signals  375  respectively to the control chip  360 . The control chip  360  can determine the vertical coordinate and the horizontal coordinate of the touch position based on the received encoded signals  370  and  375 . In the embodiment, after the 2 m  and 2 n  sensing lines are encoded through the encoders  320  and  330 , the number of sensing lines can be reduced to m and n. As such, not only the frame width of the display device  300  can be reduced, but also the number of the pins required in the control chip  360  is decreased. 
     In the embodiment of  FIG. 3 , the vertical encoder  320  is disposed on the left side of the display panel  310 . For the layout balance, the gate-line driving circuit  340  is thus disposed on the right side of the display panel  310 . However, it is noted that the relative position of elements in the touch display device  300  is not limited thereto, which can be modified as appropriate, for example, as shown in the touch display device  500  of  FIG. 5  (later described). 
       FIG. 5  illustrates a block diagram of the touch display device  500  in accordance with another embodiment of the present invention. The touch display device  500  includes a display panel  510 , a first vertical encoder  520 , a second vertical encoder  522 , a horizontal encoder  530 , gate-line driving circuits  540  and  542 , a data-line driving circuit  550 , and a control chip  560 . The working principle of elements in the touch display panel  500  is identical to those in the  FIG. 3  and not elaborated hereinafter. Compared to the embodiment of  FIG. 3 , the touch display panel  500  of  FIG. 5  has two gate-line driving circuits  540  and  542  each to drive one half of the plurality of pixel structures in the display panel  510 . Moreover, in the embodiment of  FIG. 5 , the odd number vertical sensing lines Y( 1 ), Y( 3 ), . . . , Y( 2   m −1) are connected to the first vertical encoder  520  located on the left side of the display panel  510 , while the even number vertical sensing lines Y( 2 ), Y( 4 ), . . . , Y( 2   m ) are connected to the second vertical encoder  522  located on the right side of the display panel  510 . In other words, the vertical encoders  520  and  522  each receives sensing signals from 2 m−1  vertical sensing lines and outputs m−1 vertical encoded signals  570  and  572  to the control chip  560 . Similarly, the horizontal encoder  530  receives sensing signals from 2 n  horizontal sensing lines and outputs n horizontal encoded signals  575  to the control chip  560 . In the embodiment, with the arrangement of the encoders  520  and  522 , the gate-line driving circuits  540  and  542  can be disposed on left and right sides of the display panel  510  to obtain a better layout balance. 
     Compared to the conventional touch display device, in which all horizontal and vertical sensing lines are directly routing connected to the control chip, the touch display panel of the present invention adds a simple digital logic circuit to significantly reduce the number of sensing lines connected to the control chip. Consequently, the present invention can not only decrease the number of pins for external connection required in the control chip, but also reduce the overall dimension of the touch display device to further reduce the manufacturing cost. 
     The foregoing preferred embodiments are provided to illustrate and disclose the technical features of the present invention, and are not intended to be restrictive of the scope of the present invention. Hence, all equivalent variations or modifications made to the foregoing embodiments without departing from the spirit embodied in the disclosure of the present invention should fall within the scope of the present invention as set forth in the appended claims.