Patent Publication Number: US-9898152-B2

Title: Capacitive touch panel with low impedance that includes disconnected electrode strings

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a capacitive touch panel and a display device using the capacitive touch panel. 
     2. Description of the Prior Art 
     Display panels and flat screen display device using display panels are becoming the mainstream in the field of display devices. For instance, flat television for home use, liquid crystal monitor of the personal computer or of the laptop, display screen of mobile phone and digital camera are products which incorporate the display panel as essential component. As the product design is becoming user-oriented, the usability of the product calls for the touch input function of the display panel which becomes an emphasis in the development of the display device industry. 
     As  FIG. 1 a    shows, conventional Liquid Crystal Display (LCD) panel of with touch-input function includes a display panel  10  and a touch sensor  30 . The touch panel  30  is disposed on the display surface  11  of the display panel  10 . The images are displayed through the touch panel  30 . The majority of touch panels includes resistive and capacitive touch panels. 
     As for the resistive touch panel  30 , the operation principle includes using the voltage drop to locate the coordinates of the contact point. The touch panel  30  is composed of an upper layer and a lower layer and voltages are applied across two layers in two dimension. When the user physically points at the contact point, a conducting loop is created at the contact point. A voltage drop then occurs at the conducting loop which is then processed by the system. The system can then determine the location of the contact point. However the resistive touch panel  30  cannot accept multi-input simultaneously and also cannot process fingerprint recognition. Furthermore, a minimum applied pressure is required in order to create an effective conducting loop at the contact point, and thus the resistive touch panel  30  is subject to the limit of minimum applied force. 
     The operation principle of capacitive touch panel  30  is different to that of the resistive touch panel  30 . As for the conventional capacitive touch panel shown in  FIG. 1 b   , X direction electrodes  31  and Y direction electrodes  31  are respectively disposed on the upper and a lower layer. A difference in capacitance is created when the user physically points at the touch panel  30  using fingers or other objects. The system will be able to determine the contact point based on the difference in capacitance. As  FIG. 1 b    shows, the electrodes  31  on the same row or column form continuous electrode strings. The electrode strings are arranged in accordance with X direction and Y direction of coordinate system. Excessive amount of electrodes  31  on the same row or the same column may result in excessive resistance or capacitance in the overall system. Furthermore, rows or columns of the electrode strings will be checked separately and thus it will be difficult to reduce the detect time and reaction time of the overall system. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a capacitive touch panel with a lower overall system coupling capacitance and resistance. 
     It is another objective of the present invention to provide a capacitive touch panel with less detection time and reaction time. 
     It is another objective of the present invention to provide a capacitive touch panel with less system loading. 
     It is another objective of the present invention to provide a display device which incorporates the capacitive touch panel with less system loading. 
     The display device of the present invention includes a display panel and a capacitive touch panel. The capacitive touch panel is preferred to be disposed on the display surface of the display panel. The image on the display surface of the display panel is displayed outwards through the capacitive touch panel. When the user physically points at the image on the display surface, the capacitive touch panel will detect the contact point and send a signal to be processed by the back-end processor. 
     The capacitive touch panel includes a first electrode layer, a second electrode and a dielectric layer. The first electrode layer overlaps the second electrode layer. The dielectric layer is disposed between the first and the second electrode layers to provide signal isolation between the two layers. The first electrode layer includes a first A electrode string and a first B electrode string. The first A electrode string and the first B electrode string are both disposed along a first direction. Each of the first A electrode strings and of the first B electrode strings includes a plurality of first direction electrodes. The second electrode layer includes a plurality of second direction electrodes connected in series and disposed along a second direction. 
     The first A electrode strings and the first B electrode strings are disconnected in the first electrode layer and thus their signals are not common in the first electrode layer. However, the first A electrode strings and the first B electrode strings are simultaneously checked by the system for presence of signal variation. When signal variations are detected at both the first A electrode strings and the first B electrode strings, the system will regard the signal variations as created by the same cause. 
     The first A electrode strings and the first B electrode strings can be disposed along the same line or in parallel within the first electrode layer. When the first A electrode string and the first B electrode string are disposed on the same row along the first direction; the detected signal variation on the first A electrode string and on the first B electrode string shows that the contact point is situated on the row where the first A electrode string and the first B electrode string are disposed. The length and amount of first direction electrodes of the first A electrode strings and that of the first B electrode are less than the original electrode string before disconnection. The resistance and coupling capacitance of the first A electrode string and that of the first B electrode string is less than that of an electrode string before disconnection and this will reduce the overall system loading. 
     When the first A electrode string and the first B electrode string are disposed in parallel. The first A electrode strings and the first B electrode strings represent different coordinates along the orthogonal section direction. During detection for signal variation, the first A electrode strings and the first B electrode strings are categorized into the same group and are checked simultaneously for signal variation. The design of detecting for presence of signals variation at different electrode strings simultaneously will reduce the overall detection time required. 
     The present invention provides a manufacture method of the capacitive touch panel comprising firstly the step A, of forming the first electrode layer which includes the first A electrode strings and the first B electrode strings disposed along the first direction, such that the first A electrode strings. The first A electrode strings and the first B electrode strings will include a plurality of the first direction electrodes and are disconnected in the first electrode layer. Secondly the step B include forming a second electrode layer to overlap the first electrode layer and to include a plurality of second direction electrodes disposed in series and along a second direction. Finally the step C includes simultaneously detecting for presence of signal variation at the first A electrode strings and the first B electrode strings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
         FIG. 1 a    is the schematic diagram of a display device incorporating conventional touch panel; 
         FIG. 1 b    is the schematic diagram of a conventional capacitive touch panel; 
         FIG. 2  is the schematic diagram of an embodiment of the display device of the present invention; 
         FIG. 3  is the exploded diagram of an embodiment of the capacitive touch panel of the present invention; 
         FIG. 4 a    is the top view of an embodiment of the capacitive touch panel, wherein the first A electrode strings and the first B electrode strings are collinear; 
         FIG. 4 b    is the top view of another embodiment of the capacitive touch panel, wherein the first A electrode strings are first coupled together and then coupled with the first linking pads; 
         FIG. 5  is the top view of another embodiment of the capacitive touch panel; 
         FIG. 6 a    is the top view of another embodiment of the capacitive touch panel which comprises the second A electrode strings and the second B electrode strings; 
         FIG. 6 b    and  FIG. 6 c    is the top view of a variation embodiment of the capacitive touch panel shown in  FIG. 6   a;    
         FIG. 7  is the top view of another embodiment of the capacitive touch panel, wherein the first A electrode strings and the first B electrode strings are parallel; 
         FIG. 8 a    is the operation schematic diagram of the embodiment shown in  FIG. 7 . 
         FIG. 8 b    is a variation of the embodiment shown in  FIG. 7 ; 
         FIG. 9  is the flow chart of a manufacture method of the capacitive touch panel; 
         FIG. 10  and  FIG. 11  are variation embodiments of the manufacture method shown in  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention provides a capacitive touch panel and a display device incorporating the capacitive touch panel. The capacitive touch panel of the present invention includes an external adhesive capacitive touch panel and a capacitive touch panel integrated into a panel of display device. Furthermore, the above-mentioned display device mentioned includes a flat panel display device but is not limited thereto. The display panel is preferred to include a LCD panel, Organic Light Emitting Diode (OLED) display panel or other display panels. Furthermore, the LCD panel includes transmissive LCD panels, reflective LCD panels, transflective LCD panels and other types of LCD panel. 
     In an embodiment shown in  FIG. 2 , the display device  100  includes a display panel  110  and a capacitive touch panel  200 . The capacitive touch panel  200  is preferred to be disposed on a display surface  111  of the display panel  110 . The images of display panel  110  on the display surface  111  are displayed outwards through the capacitive touch panel  200 . When the user physically points at the images on the display surface  111 , the capacitive touch panel  200  will detect the contact point and transmit a signal to be processed by a back-end processor. However, in different embodiment, the capacitive touch panel of the present invention is not limited to the only use in the display device  100 ; it can also be used with other touch input devices and the touch panel may also be integrated in the LCD panel. 
     As  FIG. 3  shows, the capacitive touch panel  200  includes a first electrode layer  300 , a second electrode layer  500  and a dielectric layer  250 . The first electrode layer  300  is disposed on the second electrode layer  500 . The dielectric layer  250  is disposed between the first electrode layer  300  and the second electrode layer  500  to provide the required signal isolation. The first electrode layer  300  includes a plurality of first A electrode strings and first B electrode strings disposed along a first direction  410 . Each of the first A electrode strings  310  and first B electrode strings  320  respectively includes a plurality of first direction electrodes  350 . As  FIG. 3  shows, the second electrode layer  500  includes a plurality of second direction electrodes  550  connected in series along a second direction  420 . In the present embodiment, the first direction  410  is preferred to be orthogonal to the second direction  420 . However, in different embodiment, the first direction  410  may also cross the second direction  420  in angles other than 90 degree. The signal variation in the first direction electrodes  350  and the second direction electrodes  550  will be detected for determining the position on the capacitive touch panel physically pointed by the user. Furthermore, in different embodiments, when only contact point of a single dimension is required, the second electrode layer  500  can be omitted in the embodiment. 
     As it can be seen from the top view of  FIG. 4 a   , the first A electrode strings  310  and the first B electrode strings  320  are disposed along the same direction; and interlace with the electrodes strings formed by second direction electrodes  550  to form a grid shape structure. In other words, the first A electrode strings  310  and the first B electrode strings  320  cross the electrode strings formed by second direction electrodes  550 , with the dielectric layer  250  disposed in between. As  FIG. 4 a    shows, other than the electrodes distributed on the perimeter of first electrode layer  300 , each of the first direction electrodes  350  is disposed between the adjacent second direction electrodes  550 . Each of the second direction electrodes  550  is disposed between the adjacent first A electrode strings  310  or/and first B electrode strings  320 . In this way, the first direction electrodes  350  and the second direction electrodes  550  are disposed in a faveolate shape on the capacitive touch panel  200 . Each of the first direction electrodes  350  is disposed between four second direction electrodes  550  disposed in a shape of the 2×2 matrix. Each of the second direction electrodes  550  is also disposed between four first direction electrodes  350  disposed in a shape of the 2×2 matrix. However, in different embodiments, the first direction electrodes  350  and the second direction electrodes  550  can be distributed in a shape of a matrix, in an orderly pattern or in an irregular pattern. 
     As  FIG. 4 a    shows, the first A electrode strings  310  and the first B electrode strings  320  are disconnected in the first electrode layer  300 . The first A electrode strings  310  and the first B electrode strings  320  will not electrically communicate with each other; and their signals are therefore not common in the first electrode layer  300 . However, the first A electrode strings  310  and the first B electrode strings  320  are simultaneously checked by the system for presence of signal variation. In other words, the first A electrode strings  310  and the first B electrode strings  320  are categorised as the same group and are checked simultaneously. Thus signal variations simultaneously detected in the first A electrode strings  310  or in the first B electrode strings  320  will be regarded as created by the same cause. 
     In an embodiment shown in  FIG. 4 a   , the first A electrode strings  310  and the first B electrode strings  320  are collinear in a first direction  410 . In other words, the first A electrode string  310  and the first B electrode string  320  can be regards as made from an electrode string cut into two halves and distributed along a first direction  410 . In the present embodiment, the first A electrode strings  310  and the first B electrode strings represent the same Y-coordinate with respect to the orthogonal second direction  420 . A detected signal on the first A electrode strings  310  and the first B electrode strings indicate that the location physically pointed by the user is situated on the same row as that of the first A electrode strings  310  and the first B electrode strings. The disconnected electrode string has shorter length and less amount of electrodes; and thus the resistance and coupling capacitance are less than that of the original electrode string before disconnection. The disconnection will reduce the overall loading of the system. 
     As  FIG. 4 a    shows, the first A electrode strings  310  and the first B electrode strings  320  are coupled together via the extended conducting wire and then connected to the back-end system. In the present embodiment, the capacitive touch panel  200  includes a first linking pad  610  and a second linking pad  620  disposed outside of the first electrode layer  300  respectively. The first A electrode strings  310  and the first B electrode strings  320  couple with the first linking pads  610  and the second linking pads  620  respectively. The system will be able to detect the signal variations on the first A electrode strings  310  and the first B electrode strings via the first linking pads  610  and the second linking pads  620 , and then determines the coordinate on the second direction  420  physically pointed by the user. 
     In an embodiment shown in  FIG. 4 a    and  FIG. 4 b   , the first electrode layer  300  includes a plurality of first A electrode strings  310  disposed in parallel. The first electrode layer  300  also includes a plurality of first B electrode strings  320  collinear to the first A electrode strings  310 . First A electrode strings have the same length and the same amount of first direction electrodes  350  connected in series. First B electrode strings  320  have the same length and the same amount of first direction electrodes  350 . However, in an embodiment shown in  FIG. 5 , part of the adjacent first A electrode strings  310  have different length and also include different amount of first direction electrodes  350  connected in series. Similarly, the corresponding first B electrode strings  320  have length and amount of first direction electrodes  350  which complement that of the first A electrode strings  310 . The adjacent first B electrode strings  320  therefore have different length and amount of electrodes. As  FIG. 5  shows, in the present embodiment, the gap between first A electrode strings  310  and the corresponding first B electrode strings  320  is distributed in an indented shape and not the linear shape shown in  FIG. 4 a    and  FIG. 4 b   . This space design will average the lightness variation due to the space between the first A electrode strings  310  and the corresponding first B electrode strings  320 . This design will also make the space between the first A electrode strings  310  and the first B electrode strings  320  less visible. 
     In an embodiment shown in  FIG. 6 a   , part of the adjacent second direction electrodes  550  can be connected in series to form second A electrode strings  510  and the adjacent part of the adjacent second direction electrodes  550  can be connected in series to form second B electrode strings  520 . The second A electrodes strings  510  and the second B electrode strings  520  are disconnected in the second electrode layer  500 . The second A electrode strings  310  and the second B electrode strings  320  will not electrically communicate with each other and their signals are therefore not common in the second electrode layer  300 . However, the second A electrode strings  310  and the second B electrode strings  320  are simultaneously detected for presence of signal variation. In other words, the second A electrode strings  310  and the second B electrode strings  320  are classified into the same group and are checked simultaneously. Thus signal variations detected in the first A electrode strings  310  or in the first B electrode strings  320  will be regarded as created by the same cause. 
     In an embodiment shown in  FIG. 6 a   , the second A electrode strings  510  and the second B electrode strings  520  are collinear along the second direction  420 . In other words, the second A electrode strings  510  and the second B electrode string  520  can regarded as a single electrode string cut into two halves and distributed along the second direction  420 . In the present embodiment, the second A electrode string  510  and second B electrode string  520  are collinear and therefore have the same Y-coordinate along the first direction  410 . A detected signal variation on the second A electrode string  310  and the second B electrode string indicates that the location physically pointed by the user is on the row collinear to the second A electrode string  310  and the second B electrode string. The disconnected second electrode string has shorter length and fewer electrodes; and thus has less resistance and coupling capacitance than that of the original electrode string before disconnection. This design reduces the overall loading of the system. 
     As  FIG. 6 a    shows, the second A electrode strings  510  and the second B electrode strings  520  couple with the back-end system via conducting wires extended from upper and lower ends of the second electrode layer  500 . In the present embodiment, the capacitive touch panel includes a plurality of third linking pads  630  and fourth linking pads  640 . The system can detect signal variations on the second A electrode strings  510  and the second B electrode strings  520  via the third linking pads  630  and the fourth linking pads  640 ; and then determines the coordinate of the location physically pointed by the user. 
     In an embodiment shown in  FIG. 6 b   , only the third linking pads  630  are disposed outside of the third electrode layer  500 . The second A electrode strings  510  and the second B electrode strings  520  are coupled together with conducting wires and then coupled to the third linking pads  630 . In this way the second A electrode strings  510  and the second B electrode strings  520  are disposed in parallel. The system can detect signals on the second A electrode string  510  and the second B electrode string  520  via a single third linking pad  630 ; and then determine the coordinate of the pointed location by the user. 
     In the embodiment shown in  FIG. 6 a    and  FIG. 6 b   , the second electrode layer  500  includes a plurality of second A electrode strings  510  in parallel. The second electrode layer  500  also includes a plurality of second B electrode strings  520  collinear with the second A electrode strings  510 . Each of the second A electrode strings  510  has the same length and the same amount of second direction electrodes  550  connected in series. Each of the second B electrode string  520  has the same length and the same amount of second direction electrodes  550  connected in series. However, in the embodiment shown in  FIG. 6 c   , part of the adjacent second A electrode strings  510  disposed in parallel have different length and different amount of second direction electrodes  550  connected in series. Similarly, the corresponding second B electrode strings  520  have length and amount of second direction electrodes  550  which complement that of the second A electrode strings  510 , and thus the second B electrode string  520  and the adjacent second B electrode strings  520  have different length and amount of electrodes. As  FIG. 6 c    shows, in the present embodiment, space between second A electrode strings  510  and the corresponding second B electrode strings  520  has a distribution shape selected from a group of an indented shape, an oblique line shape and a trapezium shape, and not the linear shape shown in  FIG. 6 a    and  FIG. 6 b   . This design will average the lightness variation due to the space distribution between the second A electrode strings  510  and the corresponding second B electrode strings  520 . This design will also make the space between the second A electrode strings  510  and the second B electrode strings  520  less visible. 
     In an embodiment shown in  FIG. 7 , the first A electrode strings  310  and the first B electrode strings  320  are disposed in parallel and are not collinear in the first electrode layer  300 . The first A electrode strings  310  and the first B electrode strings  320  do not have the same Y-coordinate along the second direction  420 . The first A electrode strings  310  and the first B electrode strings  320  are not electrically coupled in the first electrode layer  300 , but all of these electrode strings are simultaneously detected for presence of signal variation. In other words, the first A electrode strings  310  and the first B electrode strings  320  will be regarded as being in the same group and checked simultaneously. This design will check different electrode strings simultaneously in order to saves the overall detection time. 
     As  FIG. 7  shows, in a more preferred embodiment, the first A electrode string  310  and the first B electrode string  320  disposed in parallel couple with each other outside of the first electrode layer  300 , then couple with the linking pads  600 , and afterwards couple with the back-end system. Furthermore, the present embodiment includes a plurality of first A electrode strings  310  and first B electrode strings  320 , wherein the first B electrode strings  320  corresponding to the adjacent first A electrode strings  310  are not adjacent to each other. In other words, if the first A electrode string  310  and the B electrode string  320  are paired, then the pair will have at most one electrode string adjacent to other pairs of electrode strings. The electrode string adjacent to other pairs may be a first A electrode string  310  or a first B electrode string  320 . 
     When the user physically points at the capacitive touch panel  200 , the user normally points at the two electrode strings adjacent to each other. One first A electrode string couples with one first B electrode string and thus a detected signal cannot indicate if the detected signal originates from signal the first A electrode string  310  or the first B electrode string  320 . If signal variations are detected at two adjacent first A electrode strings  310  which are coupled with B electrode strings  320  not adjacent to each other. The system will be able to determine that the contact point falls on the location where the two adjacent A electrode strings  310  pass through. 
     In the embodiment shown in  FIG. 8 , when the user physically points at the first electrode string  311 ; the system will detect signal variation from the first A electrode string  311  and from the first B electrode strings  321 . The contact point by the user covers both the first A electrode string  311  and the adjacent first A electrode string  312 , and thus the system will simultaneously detect signal variations at the first A electrode string  312  and the first B electrode strings  322 . The first A electrode string  311  is adjacent to the first electrode string  312  and thus the system will be able to determine the contact point by the user. Furthermore, in the embodiment shown in  FIG. 8 b   , three electrode strings  370  can be coupled to form a single group. Each group of electrode strings  370  will have at most one electrode string  370  adjacent to other group and this design will facilitate the determination of contact point by the user. 
     It should be indicated that the embodiments shown in  FIG. 7 ,  FIG. 8 a    and  FIG. 8 b    are applied to the first electrode layer  300 . However, in other embodiments, the design of using parallel electrode strings  370  can also be applied to the first direction electrodes  350  in the first electrode layer  300  and the second direction electrodes  550  in the second electrode layer  500 . Furthermore, the embodiment shown in  FIG. 7  may incorporate the design of collinear electrode string shown in  FIGS. 6 a , 6 b  and 6 c    and make the second direction electrodes  550  in the second electrode layer  500  into collinear electrode strings. 
     The present invention provides a method of manufacturing the capacitive electrode touch panel. As  FIG. 9  shows, the step  910  includes forming a first electrode layer having first A electrode strings and first B electrode strings distributed along a first direction. This step also includes disposing a plurality of first direction electrodes on each first A electrode string and each first B electrode strings; and making the first A electrode string and the first B electrode string disconnected from each other in the first electrode layer. The step of forming the first electrode layer includes various semi-conductor processes such as etching, deposition, coating or other processes. 
     The step  930  includes forming a second electrode layer having a plurality of second direction electrodes connected in series along the second direction. The second electrode layer is disposed on the first electrode layer. The second direction is preferred to be orthogonal to the first direction. However, the second direction may cross the first direction in angles other than 90 degree. The method of forming the second electrode layer includes various semi-conductor processes, such as etching, deposition, coating or other processes. Furthermore, the present step is preferred to form a dielectric layer within the first electrode layer, within the second electrode layer or between the two electrode layers, in order to electrically isolate the first electrodes and the second electrodes. 
     The step  950  includes detecting for signal variation at the first A electrode strings and the first B electrode strings simultaneously. This step can be executed by using the system to detect for signal variation via the first linking pads and the second linking pads coupled with the first A electrode strings and the first B electrode strings respectively. This step can also be executed by first coupling the first A electrode string and the B electrode string into a pair, and then using the system end to simultaneously detect for signal variation via a single linking pad coupled with the pair of first A electrode string and the first B electrode string. 
     In an embodiment shown in  FIG. 10 , the step  910  includes step  1010 , step  1030  and step  1050 . The step  1010  includes forming a plurality of first A electrode strings disposed in parallel and forming corresponding first B electrode strings. The step  1030  includes making the first A electrode strings and the corresponding first B electrode strings collinear along the first direction. The step  1050  includes disposing the adjacent first A electrode strings having different lengths and different amount of first direction electrodes. In this design, the space between the first A electrode strings and first B electrode strings has a distribution shape selected from a group of an indented shape, an oblique shape and a trapezium shape. This design will average the lightness variation due to the space distribution between the first A electrode strings  510  and the corresponding first B electrode strings  520 . This design will also make the space between the second A electrode strings  510  and the second B electrode strings  520  less visible. Furthermore, the length and the amount of first direction electrodes of the first A electrode strings and of the first B electrode strings are less than that of original electrode strings before disconnection. This design will reduce the overall loading of the system. 
     In an embodiment shown in  FIG. 11 , the step  910  may include step  1110  and step  1130 . The step  1110  includes disposing a plurality of first A electrode strings and first B electrode strings in parallel but not collinear. The step  1130  includes coupling two adjacent first A electrode strings with two first B electrode strings which are not adjacent to each other. 
     When the user physically points at the touch panel; normally two adjacent electrode strings will be pointed simultaneously. The first A electrode string couples with the first B electrode string and thus a signal variation cannot indicate whether which electrode string is contacted. In step  1150 , if signal variations are simultaneously detected at the adjacent first A electrode strings; because the two first B electrode strings corresponding to the above-mentioned first A electrode strings are not adjacent to each other. Thus in the step  1170 , the system will determine if the signal variations occur at the adjacent first A electrode strings. In other words, the area pointed by the user falls on the position passed through by the adjacent first A electrode strings. 
     It needs to be emphasized that the second direction electrodes in the second electrode layer can be manufactured by the methods shown in the  FIG. 8 ,  FIG. 9  and  FIG. 10 . The production method and structure of the first direction electrodes and the second direction electrodes can be adjusted to increase the diversity in design in order to satisfy demands from various products. 
     The above is a detailed description of the particular embodiment of the invention which is not intended to limit the invention to the embodiment described. It is recognized that modifications within the scope of the invention will occur to a person skilled in the art. Such modifications and equivalents of the invention are intended for inclusion within the scope of this invention.