Abstract:
A composite touch panel includes a first insulating layer, a first conductive layer, a plurality of spacers, a second conductive layer and a second insulating layer in turn stacked on each other. The second conductive layer is applied with a predetermined first working voltage, and the voltages at four comers of the first conductive layer are measured. The composite touch panel is judged to work at a resistance mode when one of the measured voltages exceeds a first threshold, and a pressed position on the composite touch panel is determined. The composite touch panel is judged to work at a capacitance mode when all of the measured voltages are smaller than the first threshold. At the capacitance mode, whether a touch is present is judged, and the touch position is also determined when a touch is present.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a touch panel and method for operating the same, especially to composite touch panel and method for operating the same. 
         [0003]    2. Description of Prior Art 
         [0004]    Touch panel has extensive applications such as ATM, kiosk and industrial control. The touch panel can also be advantageously applied to smart phone or PDA to facilitate input function for laymen user. 
         [0005]    The touch panel can be classified into resistive type, capacitive type, sound wave type, IR type, electromagnetic type, touch-sensing type touch panel in terms of operation principles. More particularly, the resistive type senses a voltage corresponding to a pressing by finger or stylus. The capacitive type touch panel senses capacitance change caused by a touch of user finger, which draws little amount of current from the touch panel. 
         [0006]      FIG. 1  shows a schematic diagram of a prior art resistive type touch panel  40 , which mainly comprises a conductive base  42  (such as glass plate coated with conductive material), a conductive overlay  44  (such as polyester plate with conductive coating on inner side thereof), and a plurality of spacers  46  sandwiched between the conductive base  42  and the conductive overlay  44 . When a stylus is pressed against one point on the resistive type touch panel  40 , the conductive base  42  and the conductive overlay  44  are in contact at the pressed point. Therefore, a controller (not shown) can identify the X, Y coordinate of the pressed point. 
         [0007]      FIG. 2  shows a schematic diagram of a prior art capacitive type touch panel  50 , which mainly comprises a conductive base  52  (such as glass plate coated with conductive material) and electrodes  56 A- 56 D on four peripherals of the conductive base  52 . When user finger touches a point on the capacitive type touch panel  50 , the finger has electromagnetic coupling with the capacitive type touch panel  50  and draws small amount of current therefrom. A controller  54  can identify the touch position by measuring currents at electrodes  56 A- 56 D. The resistive type touch panel has the advantage of precise identification of pressed location. The capacitive type touch panel has the advantage of finger-input ability. The convenience for user can be enhanced when both advantages are provided. Taiwan patent No. M335736 discloses a dual-function touch panel, which comprises a capacitive type touch panel unit arranged on a resistive type touch panel unit. Two separate controllers are provided for the capacitive type touch panel unit and the resistive type touch panel unit, respectively. However, the dual-function touch panel requires four transparent conductive layers (such as ITO), the cost is increased. Moreover, the judgment of input location is difficult because separate controllers are used for the capacitive type touch panel unit and the resistive type touch panel unit, respectively. 
       SUMMARY OF THE INVENTION 
       [0008]    It is an object of the present invention to provide a composite touch panel with reduced cost and enhanced transparency. 
         [0009]    It is another object of the present invention to provide a composite touch panel which can prevent difficulty in identifying touch signal. 
         [0010]    Accordingly, the present invention provides a composite touch panel comprising: a first insulating layer; a first conductive layer; a plurality of spacers; a second conductive layer; a second insulating layer in turn stacked on each other; and a controller electrically connected to the first conductive layer and the second conductive layer. The controller is adapted to apply a first working voltage to the second conductive layer and to measure a sensed voltage on the first conductive layer, whereby controller identifies the composite touch panel to operate on a resistive mode or a capacitive mode. 
         [0011]    More particularly, the controller judges the composite touch panel to operate on a resistive mode when the sensed voltage at any one of the four corners of the conductive layer is larger than one half of the first working voltage. The controller judges the composite touch panel to operate on a capacitive mode when the sensed voltages at all of the four corners of the first electrodes are smaller than one half of the first working voltage. 
     
    
     
       BRIEF DESCRIPTION OF DRAWING 
         [0012]    The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes an exemplary embodiment of the invention, taken in conjunction with the accompanying drawings. 
           [0013]      FIG. 1  shows a schematic diagram of a prior art resistive type touch panel. 
           [0014]      FIG. 2  shows a schematic diagram of a prior art capacitive type touch panel. 
           [0015]      FIGS. 3A and 3B  show two sectional views for the composite touch panel  100  according to the present invention. 
           [0016]      FIG. 4A  shows the top view of the first conductive layer of the composite touch panel according to the present invention. 
           [0017]      FIG. 4B  shows the top view of the second conductive layer of the composite touch panel according to the present invention. 
           [0018]      FIG. 5A  shows the top view of the first conductive layer of the composite touch panel according to another preferred embodiment of the present invention. 
           [0019]      FIG. 5B  shows the top view of the second conductive layer of the composite touch panel according to another preferred embodiment of the present invention. 
           [0020]      FIG. 6  shows the flowchart of the method for operating the composite touch panel according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]      FIGS. 3A and 3B  show two sectional views for the composite touch panel  100  according to the present invention. The composite touch panel  100  comprises a first insulating layer  12 A, a first conductive layer  14 A, a plurality of spacers  16 , a second conductive layer  14 B and a second insulating layer  12 B in turn stacked on each other, and further comprises a controller  10  electrically connected to the first conductive layer  14 A and the second conductive layer  14 B through electrodes (not shown, and will be detailed later). In above description, the first conductive layer  14 A and the second conductive layer  14 B can be made of indium tin oxide (ITO) or antimony-tin oxide (ATO). 
         [0022]      FIG. 4A  shows the top view of the first conductive layer  14 A of the composite touch panel  100  according to the present invention.  FIG. 4B  shows the top view of the second conductive layer  14 B of the composite touch panel  100  according to the present invention. As shown in those figures, the first conductive layer  14 A comprises four first electrodes  22 A,  22 B,  22 C and  22 D at four corners thereof. The second conductive layer  14 B comprises four second electrodes  24 A,  24 B,  24 C and  24 D on four lateral sides thereof, where the second electrodes  24 A and  24 B are corresponding to X axis, and the second electrodes  24 C and  24 D are corresponding to Y axis. The first conductive layer  14 A with the first electrodes  22 A,  22 B,  22 C and  22 D can provide capacitive touch input. The second conductive layer  14 B with the second electrodes  24 A,  24 B,  24 C and  24 D can provide resistive touch input when it is used with the first conductive layer  14 A having the first electrodes  22 A,  22 B,  22 C and  22 D.  FIG. 6  shows the flowchart of the method for operating the composite touch panel  100  according to the present invention. First a composite touch panel  100  with the structure shown in  FIGS. 3A ,  3 B,  4 A and  4 B is provided (S 100 ). A first working voltage is applied to the second conductive layer  14 B (S 102 ) and a sensed voltage is measured at the first conductive layer  14 A. If the sensed voltage is larger than a first threshold (it means a pressing is present on the composite touch panel  100 ), a resistive mode operation is conducted to identify the pressed location (S 112 ). If the sensed voltage is not larger than the first threshold (it means a pressing is not present on the composite touch panel  100 ), a capacitive mode operation is conducted to identify whether a touch is present and to identify the touch location (S 114 ). 
         [0023]    More particularly, the controller  10  first applies a first working voltage Vcc to all second electrodes  24 A,  24 B,  24 C and  24 D of the second conductive layer  14 B. The controller  10  then measures the sensed voltages VA, VB, VC and VD of the four first electrodes  22 A,  22 B,  22 C and  22 D, respectively, on the first conductive layer  14 A. If any one of the sensed voltages VA, VB, VC and VD is larger than a first threshold Vth 1 , for example, Vcc/2, it means a pressing is present on the composite touch panel  100  as shown in  FIG. 3B , and a partial voltage of the first working voltage Vcc is present on the first electrodes  22 A,  22 B,  22 C and  22 D through the pressed location. A resistive mode operation is conducted to identify the pressed location. When all of the sensed voltages VA, VB, VC and VD are smaller than the first threshold Vth 1  (it means a pressing is not present on the composite touch panel  100 ), a capacitive mode operation is conducted to identify whether a touch is present and to identify the touch location. 
         [0024]    In resistive mode operation, the controller  10  first applies the first working voltage Vcc and a ground voltage to the second electrodes  24 A,  24 B, respectively, which are corresponding to X axis. The controller  10  further sets the second electrodes  24 C and  24 D as floating. The controller  10  measures a sensed voltage Vx at any one of the first electrodes  22 A,  22 B,  22 C and  22 D. The X coordinate for the pressed location can be expressed as: 
         [0000]        X=K 1+ K 2×( Vx/Vcc ) 
         [0025]    where K 1  is an offset constant and K 2  is a scale constant. This is well known art and the detailed description thereof is omitted here for simplicity. 
         [0026]    Afterward, the controller  10  applies the first working voltage Vcc and the ground voltage to the second electrodes  24 C,  24 D, respectively, which are corresponding to Y axis. The controller  10  further sets the second electrodes  24 A and  24 B as floating. The controller  10  measures a sensed voltage Vy at any one of the first electrodes  22 A,  22 B,  22 C and  22 D. The Y coordinate for the pressed location can be expressed as: 
         [0000]        Y=K 3+ K 4×( Vy/Vcc ) 
         [0027]    where K 3  is an offset constant and K 4  is a scale constant. The detailed description thereof is also omitted here for simplicity. In this way, the coordinate (X,Y) of the pressed location can be identified. 
         [0028]    In capacitive mode operation, the controller  10  first applies the ground voltage to the second electrodes  24 A,  24 B,  24 C and  24 D of the second conductive layer  14 B to provide shielding effect. The controller  10  then applies a second working voltage Vdd to the first conductive layer  14 A and measures the currents IA, IB, IC and ID present on the four first electrodes  22 A,  22 B,  22 C and  22 D respectively. When any one of the currents IA, IB, IC and ID is zero, the controller  10  can judge that no touch is present on the composite touch panel  100 . When all of the currents IA, IB, IC and ID are non-zero, the controller  10  can judge that a touch is presnet on the composite touch panel  100  and the X, Y coordinates for touch location can be determined as: 
         [0000]    
       
         
           
             X 
             = 
             
               
                 K 
                  
                 
                     
                 
                  
                 5 
               
               + 
               
                 K 
                  
                 
                     
                 
                  
                 6 
                  
                 
                   
                     IB 
                     + 
                     ID 
                   
                   
                     IA 
                     + 
                     IB 
                     + 
                     IC 
                     + 
                     ID 
                   
                 
               
             
           
         
       
       
         
           
             Y 
             = 
             
               
                 K 
                  
                 
                     
                 
                  
                 7 
               
               + 
               
                 K 
                  
                 
                     
                 
                  
                 8 
                  
                 
                   
                     IC 
                     + 
                     ID 
                   
                   
                     IA 
                     + 
                     IB 
                     + 
                     IC 
                     + 
                     ID 
                   
                 
               
             
           
         
       
     
         [0029]    where K 5  and K 7  are offset constants, and K 6  and K 8  are scale constants. This is well known art and the detailed description thereof is omitted here for simplicity. In this way, the coordinate (X,Y) of the touch location can be identified. 
         [0030]      FIG. 5A  shows the top view of the first conductive layer  14 A of the composite touch panel  100  according to another preferred embodiment of the present invention.  FIG. 5B  shows the top view of the second conductive layer  14 B of the composite touch panel  100  according to another preferred embodiment of the present invention. The second conductive layer  14 B shown in  FIG. 5B  is substantially the same as that in  FIG. 4B  and, therefore, the detailed description is omitted here. The first conductive layer  14 A of the composite touch panel  100  according to another preferred embodiment of the present invention can be etched into a plurality of conductive strips  14 C, where the conductive strips  14 C are electrically connected to electrodes S 1 -S 12 . Therefore, the first conductive layer  14 A of the composite touch panel  100  can provide projected capacitive touch input through the electrodes S 1 -S 12 . The second conductive layer  14 B with the second electrodes  24 A,  24 B,  24 C and  24 D can provide resistive touch input when it is used with the first conductive layer  14 A having the electrodes S 1 -S 12 . 
         [0031]    In the operation of the composite touch panel  100  shown in  FIGS. 5A and 5B , the controller  10  first applies a first working voltage Vcc to all second electrodes  24 A,  24 B,  24 C and  24 D of the second conductive layer  14 B. The controller  10  then measures the sensed voltages V 1 -V 12  of the electrodes S 1 -S 12 , respectively, on the first conductive layer  14 A. If any one (for example, voltage Vn of electrode Sn) of the sensed voltages V 1 -V 12  is larger than a first threshold Vth 1 , for example, Vcc/2, it means a pressing is present on the composite touch panel  100  as shown in  FIG. 3B . A resistive mode operation is conducted to identify the pressed location. When all of the sensed voltages V 1 -V 12  are smaller than the first threshold Vth 1  (it means a pressing is not present on the composite touch panel  100 ), a capacitive mode operation is conducted to identify whether a touch is present and to identify the touch location. 
         [0032]    In resistive mode operation, the controller  10  first applies the first working voltage Vcc and a ground voltage to the second electrodes  24 A,  24 B, respectively, which are corresponding to X axis. The controller  10  further sets the second electrodes  24 C and  24 D as floating. The controller  10  measures a sensed voltage Vx at the electrode Sn. The X coordinate for the pressed location can be expressed as: 
         [0000]        X=K 1+ K 2×( Vx/Vcc ) 
         [0033]    where K 1  is an offset constant and K 2  is a scale constant. This is well known art and the detailed description thereof is omitted here for simplicity. 
         [0034]    Afterward, the controller  10  applies the first working voltage Vcc and the ground voltage to the second electrodes  24 C,  24 D, respectively, which are corresponding to Y axis. The controller  10  further sets the second electrodes  24 A and  24 B as floating. The controller  10  measures a sensed voltage Vy at the electrode Sn. The Y coordinate for the pressed location can be expressed as: 
         [0000]        Y=K 3+ K 4×( Vy/Vcc ) 
         [0035]    where K 3  is an offset constant and K 4  is a scale constant. The detailed description thereof is also omitted here for simplicity. In this way, the coordinate (X,Y) of the pressed location can be identified. 
         [0036]    In capacitive mode operation, the controller  10  first applies the ground voltage to the second electrodes  24 A,  24 B,  24 C and  24 D of the second conductive layer  14 B to provide shielding effect. The controller  10  then applies a second working voltage Vdd to the electrodes S 1 -S 12  of the first conductive layer  14 A sequentially and measures the voltages V 1 -V 12  of the electrodes S 1 -S 12  respectively. When all of the sensed voltages V 1 -V 12  of the electrodes S 1 -S 12  are smaller than a second threshold Vth 2 , it means no conductive object is in touch with the composite touch panel  100 . 
         [0037]    On the contrary, when any one of the voltages V 1 -V 12  of the electrodes S 1 -S 12  is larger than the second threshold Vth 2 , it means that a conductive object is in touch with the composite touch panel  100 . The touch location can be identified by interpolating the sensed voltages V 1 -V 12  of the electrodes S 1 -S 12 , or by other prior art method for projected capacitive touch panel. In this way, the coordinate (X,Y) of the touch location can be identified.