Patent Publication Number: US-2013234979-A1

Title: Touch cell applied to capacitive touch panel and associated capacitive touch panel

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a capacitive touch panel, and more particularly, to a touch cell of a capacitive touch panel having a fish-bone shaped electrode. 
     2. Description of the Prior Art 
     Please refer to  FIG. 1 , which is a diagram illustrating a portion of elements of a capacitive touch panel  100 . Referring to  FIG. 1 , the capacitive touch panel  100  includes a scan signal transmitting circuit  110 , a detecting circuit  120  and a plurality of touch cells  130  ( FIG. 1  merely shows three touch cells of a channel), where the touch cell includes a first electrode  132  and a second electrode  134 , and each of the first electrode  132  and the second electrode  134  has a triangular pattern (or a sawtooth pattern). In the operations of the capacitive touch panel  100 , the scan signal transmitting circuit  110  transmits a scan signal Vs to the first electrode  132  of the touch cell  130 , and the detecting circuit  120  immediately detects changes of a voltage of the second electrode  134  to obtain capacitance variation information of the touch cell  130 , and the capacitance variation information of the touch cell  130  is used to determine whether a touch point is on the touch cell  130  or not. Because the operations of the capacitive touch panel  100  are known by a person skilled in this art, further descriptions are therefore omitted here. 
     However, in the operations of the touch panel  100 , because a coupling capacitance between the first electrode  132  and the second electrode  134  of the touch cell  130  is small, a touch sensibility and a signal to noise ratio (SNR) of the touch panel  100  are not good. 
     SUMMARY OF THE INVENTION 
     It is therefore an objective of the present invention to provide a capacitive touch panel whose touch cell has a fish-bone shaped electrode, to solve the above-mentioned problems. 
     According to one embodiment of the present invention, a touch cell applied to a capacitive touch panel includes a first electrode and a second electrode, where the first electrode is connected to a scan signal transmitting circuit of the capacitive touch panel, and is utilized for receiving a scan signal, and the second electrode is connected to a detecting circuit of the capacitive touch panel. In addition, the second electrode is not connected to the first electrode, the second electrode has a fish-bone pattern, and a width of a tail of branches of the fish-bone pattern is greater than a width of a head of the branches of the fish-bone pattern. 
     According to another embodiment of the present invention, a touch cell applied to a capacitive touch panel includes a first electrode and a second electrode, where the first electrode is connected to a scan signal transmitting circuit of the capacitive touch panel, and is utilized for receiving a scan signal, and the second electrode is connected to a detecting circuit of the capacitive touch panel. In addition, the second electrode is not connected to the first electrode, the second electrode has a fish-bone pattern, and there is no first electrode positioned between the lines and the braches of the fish-bone pattern nearest to the lines. 
     According to another embodiment of the present invention, a capacitive touch panel includes a scan signal transmitting circuit, a detecting circuit and a plurality of touch cells, where each of the touch cells includes a first electrode and a second electrode, where the first electrode is connected to the scan signal transmitting circuit of the capacitive touch panel, and is utilized for receiving a scan signal, and the second electrode is connected to the detecting circuit. In addition, the second electrode is not connected to the first electrode, the second electrode has a fish-bone pattern, and a width of a tail of branches of the fish-bone pattern is greater than a width of a head of the branches of the fish-bone pattern. 
     According to another embodiment of the present invention, a capacitive touch panel includes a scan signal transmitting circuit, a detecting circuit and a plurality of touch cells, where each of the touch cells includes a first electrode and a second electrode, where the first electrode is connected to the scan signal transmitting circuit of the capacitive touch panel, and is utilized for receiving a scan signal, and the second electrode is connected to the detecting circuit. In addition, the second electrode is not connected to the first electrode, the second electrode has a fish-bone pattern, and there is no first electrode positioned between the lines and the braches of the fish-bone pattern nearest to the lines. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a portion of elements of a capacitive touch panel. 
         FIG. 2  is a diagram illustrating a capacitive touch panel according to one embodiment of the present invention. 
         FIG. 3  is a diagram illustrating a touch cell according to another embodiment of the present invention. 
         FIG. 4  is a diagram illustrating a touch cell according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 2 , which is a capacitive touch panel  200  according to one embodiment of the present invention. As shown in  FIG. 2 , the capacitive touch panel  200  includes a scan signal transmitting circuit  210 , a detecting circuit  220  and a plurality of touch cells  230 , where each of the touch cells has a first electrode  232  and a second electrode  234 , the second electrode  234  is not connected to the first electrode  232 , the second electrode  234  has a fish-bone pattern, and a width of a tail of branches of the fish-bone pattern is greater than a width of a head of the branches of the fish-bone pattern. In addition, both the first electrode  232  and the second electrode  234  are indium tin oxide (ITO) electrodes fabricated in the same layer. 
     In addition, in the touch cell  230  shown in  FIG. 2 , the tail width of each of the branches of the fish-bone pattern is greater than the head width of the branch of the fish-bone pattern. However, in other embodiment of the present invention, the tail widths of only a portion of the branches of the fish-bone pattern is greater than the head widths of the branches of the fish-bone pattern, and the widths of the other braches can be uniform or be other designs. These alternative designs shall fall within the scope of the present invention. 
     In the operations of the capacitive touch panel  200 , the scan signal transmitting circuit  210  transmits a scan signal Vs to the first electrode  232  of the touch cell  230 , and the detecting circuit  220  immediately detects changes of a voltage of the second electrode  234  to obtain capacitance variation information of the touch cell  230 , and the capacitance variation information of the touch cell  230  is used to determine whether a touch point is on the touch cell  230  or not. Because the operations of the scan signal transmitting circuit  210  and the detecting circuit  220  are known by a person skilled in this art, further descriptions are therefore omitted here. 
     Referring to the touch cell  230  shown in  FIG. 2 , because the first electrode  232  and the second electrode  234  have a greater coupling area (i.e., a longer channel length between the first electrode  232  and the second electrode  234 ), the detecting circuit  220  will detect a larger coupling capacitance between the first electrode  232  and the second electrode  234 , and it is meant that the touch sensibility and the SNR will be better. In detail, please refer to the following table that shows comparisons of measuring results of the prior touch cell  130  shown in  FIG. 1  and the touch cell  230  shown in  FIG. 2 , the touch cell  230  has greater coupling capacitance, and a different between a coupling capacitance C non-touch  (i.e., no touch point is on the touch cell) and a coupling capacitance C touch  (i.e., a touch point is on the touch cell) of the touch cell  230  is also greater than that of the touch cell  130 . 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                 Coupling 
                 Coupling 
                   
               
               
                   
                 capacitance C non-touch   
                 capacitance C touch   
               
               
                   
                 when no touch 
                 when a touch 
                 Difference 
               
               
                   
                 point is on the 
                 point is on the 
                 between C non-touch   
               
               
                   
                 touch cell 
                 touch cell 
                 and C touch   
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Prior art 
                 1.04 pF 
                 0.675 pF 
                 0.365 pF 
               
               
                 touch cell 
               
               
                 130 
               
               
                 Touch cell 
                 2.13 pF 
                 1.672 pF 
                 0.458 pF 
               
               
                 230 
               
               
                   
               
            
           
         
       
     
     In addition, when a user uses the capacitive touch panel  200 , the user&#39;s finger may be simultaneously put on many lines connected between the touch cells  230  and the detecting circuit  220 . Therefore, the detecting circuit  220  may detect a little coupling capacitance variation even when there is no touch point on the touch cell  230 , causing the error of detection. To solve this problem, in another embodiment of the present invention, the touch cell  230  of the touch panel  200  can be replaced by the touch cell  330  shown in  FIG. 3 , where the touch cell  330  includes a first electrode  332  and a second electrode  334 , and there is no first electrode  332  positioned between branches of the fish-bone shaped second electrode  334 , nearest to the lines connected to the detecting circuit  220 , and the lines connected to the detecting circuit  220  (i.e., there is no first electrode  332  positioned between the branches ( 334 _ 1  and  334 _ 2 ) and the lines connected to the detecting circuit  220 ). 
     In addition, in another embodiment of the present invention, the touch cell  230  of the touch panel  200  can be replaced by the couch cell  430  shown in  FIG. 4 , where the touch cell  430  includes a first electrode  432  and a second electrode  434 , and there is no first electrode  432  positioned between branches of the fish-bone shaped second electrode  434 , nearest to the lines connected to the detecting circuit  220 , and the lines connected to the detecting circuit  220  (i.e., there is no first electrode  432  positioned between the branches ( 434 _ 1  and  434 _ 2 ) and the lines connected to the detecting circuit  220 ). 
     In the touch cells  330  and  430  shown in  FIG. 3  and  FIG. 4 , respectively, because there is no first electrode ( 332  and  432 ) positioned between the second electrode ( 334  and  434 ) and the lines, for each of the touch cell, the coupling capacitance between the second electrode of the touch cell and the lines connected between the other touch cells and the detecting circuit  220  can be decreased. Therefore, the detecting circuit  220  can determine the coupling capacitance more precisely. 
     It is noted that, the size, width, pitch and ratio of the first electrode and the second electrode shown in  FIGS. 2-4  are for illustrative purposes only, and are not limitations of the present invention. In a practical design, the size, width, pitch and ratio of the first electrode and the second electrode can be determined according to a designer&#39;s consideration. 
     Briefly summarized, in the capacitive touch panel of the present invention, the touch cell includes a first electrode connected to a scan signal transmitting circuit and a second electrode connected to a detecting circuit, where the second electrode has a fish-bone pattern, and a width of a tail of branches of the fish-bone pattern is greater than a width of a head of the branches of the fish-bone pattern. In addition, in another embodiment, there is no first electrode positioned between the second electrode and a plurality of lines. Therefore, compared with the prior art technique, the capacitive touch panel of the present invention has better touch sensibility and the SNR. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.