Abstract:
A capacitive touchpad with physical key function comprises a soft flexible first conductive layer; a second conductive layer; and a soft flexible insulator layer disposed between the first and the second conductive layers. The insulator layer has at least a through hole for the first conductive layer to connect to the second conductive layer while the touchpad is pressed and cause the voltages on the first or the second conductive layers to change and thus to trigger a predetermined key function.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention is related generally to a capacitive touchpad, and more particularly, to a capacitive touchpad with physical key function.  
       BACKGROUND OF THE INVENTION  
       [0002]     As shown in  FIG. 1  and  FIG. 2 , a conventional key-type input apparatus  100  and  200  change the potential stage of I/O of an integrated circuit  104  by applying a force to press a key  102  to detect if the key  102  is pressed. When the key  102  is not pressed, the potential of the I/O of the input apparatus  100  is high; when the key  102  is pressed, the potential of the I/O is low. When the key  102  is not pressed, the potential of the I/O of the input apparatus  200  is low; when the key  102  is pressed, the potential of the I/O changes to high. Since the potential stage varies with the force to determine if the key is pressed, there&#39;s an advantage of precise operation and low power consumption.  
         [0003]     As technology develops, the volumes of electronic devices get smaller, especially portable devices. But the size of a key-type input apparatus is limited due to the key, and becomes the barrier to minimize an electronic device. A touchpad that is thinner and lighter than a key is proposed as an input apparatus.  FIG. 3  is a section of a conventional capacitive touchpad  300 . The panel  302  and the substrate  306  are insulator. The conductive layer  308  is a first axis sensor, and the conductive layer  310  is a second axis sensor. An insulator layer  304  is disposed between the conductive layers  308  and  310  to separate the conductive layers  308  and  310 . The insulator layer  304  and the conductive layers  308  and  310  can be treated as a capacitor. When a finger  312  touches the touchpad  300 , the capacitance of the touched position changes, so the position of the finger  312  on the touchpad  300  is obtained. The sensing method of a capacitive touchpad can be referenced to U.S. Pat. No. 5,929,309. Since a capacitive touchpad  300  has the advantage of high resolution, it is proper to be used as a writing input apparatus. A capacitive touchpad  300  is operated using sensing method, it can&#39;t be operated as precise as a key-type input apparatus. A capacitive touchpad also has to scan continuously to sense the position of the finger and thus consumes much. Though there exists virtual key function on a touchpad, it also has to scan continuously to sense if a finger touches the virtual key.  
         [0004]     Thus, an input apparatus with the advantages of physical keys and capacitive touchpad is required.  
       SUMMARY OF THE INVENTION  
       [0005]     There is one object of the present invention to provide a capacitive touchpad with physical key function.  
         [0006]     According to the present invention, a capacitive touchpad with physical key function comprises a soft flexible first conductive layer under a panel; a second conductive layer and a soft flexible insulator layer between the first and the second conductive layers. There&#39;s a least one hole on the insulator layer. When a position corresponding to the hole is pressed, the first conductive layer deforms and connects to the second conductive layer. The voltage of the first or the second conductive layer changes and triggers a predetermined function.  
         [0007]     The capacitive touchpad according to the present invention is like a physical key that changes the potential by pressing to trigger a key function. So the present invention has the advantages of a capacitive touchpad and a physical key.  
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0008]     These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which:  
         [0009]      FIG. 1  is a conventional key type input apparatus;  
         [0010]      FIG. 2  is another conventional key type input apparatus;  
         [0011]      FIG. 3  is a section view of a conventional capacitive touchpad;  
         [0012]      FIG. 4  is an exploded view of a capacitive touchpad according to the present invention;  
         [0013]      FIG. 5A  is a section view along AA direction of the touchpad in  FIG. 4 ;  
         [0014]      FIG. 5B  is another embodiment of the insulator layer  406  in  FIG. 5A ;  
         [0015]      FIG. 6  is an illustration of the pressed touchpad in  FIG. 5A ;  
         [0016]      FIG. 7  is another embodiment of the touchpad in  FIG. 4 ;  
         [0017]      FIG. 8  is an embodiment of a mobile phone or a phone using the structure in  FIG. 4 ;  
         [0018]      FIG. 9  is an expanded view and section view of the input apparatus in  FIG. 8 ;  
         [0019]      FIG. 10  is another embodiment of the structure in  FIG. 4  used as an input apparatus;  
         [0020]      FIG. 11  is an exploded view of anther capacitive touchpad according to the present invention;  
         [0021]      FIG. 12  is embodiment of a mobile phone or a phone using the structure in  FIG. 1   1 ;  
         [0022]      FIG. 13  is an expanded view of the input apparatus in  FIG. 12 ;  
         [0023]      FIG. 14  is another embodiment of the structure in  FIG. 11  used as an input apparatus;  
         [0024]      FIG. 15  is an embodiment of a structural capacitive touchpad using the structure in  FIG. 11 ;  
         [0025]      FIG. 16  is another embodiment of the touchpad in  FIG. 11 ; and  
         [0026]      FIG. 17  is yet another embodiment of the touchpad in  FIG. 11 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]      FIG. 4  is an exploded view of a capacitive touchpad  400  according to the present invention.  FIG. 5A  is a section view of the touchpad  400  along AA direction. In the capacitive touchpad  400 , the conductive layers  404  and  408  used as Y-axis sensor and X-axis sensor are separated by the insulator layer  406  between the panel  402  and the substrate  410 . As shown in  FIG. 5B , in other embodiments, the insulator layer  406  may comprise a plurality of insulator balls  406 ′. The panel  302 , conductive layers  404  and  408 , and insulator layer  406  are all made of soft flexible material. The insulator layer  406  has a hole on the insulator layer  406 . There is a key area  4022  on the panel  402  corresponding to the position of the hole  4062 . When a user presses on the key area  4022 , as shown in  FIG. 6 , the conductive layer  404  connects the conductive layer  408  through the hole  4022  of the insulator  406  and causes a change on the potential of conductive layer  404  or  408  and triggers a predetermined key function. The number and position of the key can be determined upon request, as shown in  FIG. 7 .  
         [0028]      FIG. 8  illustrates an embodiment using the structure in  FIG. 4  as the input apparatus  400  of a mobile phone or a phone.  FIG. 9  is the expanded view and section view of the input apparatus  500 . Please refer to  FIG. 9 , in the input apparatus  500 , the conductive layer  504  and  508  used as the first axis sensor and the second axis sensor are disposed between the panel  502  and the substrate  510 . An insulator layer  506  separates the conductive layers  504  and  508 . There are pluralities of holes  5062  in the insulator layer  506  corresponding to the key area  5022  on the panel. Please refer to  FIG. 8 , a capacitive detector  512  couples to the wires TY 0  to TY 8  on the conductive layer  504  and the wires TX 0  to TX 6  on the conductive layer  508  through a multiplexer  516  to actively provide a current to charge and discharge the parasitic capacitor on the conductive layers  504  and  508 . A voltage is further generated between the conductive layers  504  and  508 . When a user&#39;s finger touches the panel  502 , the parasitic capacitance at the touched place changes. The capacitance detector  512  detects the position of the changed capacitance to detect the position of the finger and the trace of movement to generate a corresponding response. The voltage detector  514  also couples to the wires TY 0  to TY 8  and TX 0  to TX 6  through the multiplexer  516  and provides a first voltage and a second voltage to the conductive layers  504  and  508 . When a used wants to dial a phone, touching the key area  5022  on the panel  502  such that the conductive layer  504  touches the conductive layer  508 . The potential detector  514  detects the changes on the first voltage of the conductive layer  504  or the second voltage of the conductive layer  508  and further determines the key area  5022  pressed by the user. When the present invention is utilized in different electronic devices, the shape and the number of keys vary, as the input apparatus  600  shown in  FIG. 10 .  
         [0029]      FIG. 11  is an exploded view of another capacitive touchpad  700  according to the present invention. There is a capacitance-sensing conductive layer  704  with a plurality of first axis wires  7042  and a plurality of second axis wires  7044  therein and an insulator layer  706  between the panel  702  and the substrate  708 . A key area  7022  is on the panel  702 . When a user presses the key area  7022 , the wires  7042  and  7044  of the capacitance-sensing conductive layer  704  are pressed through the hole  7062  of the insulator layer  706  to contact the key operation conductor  7082  on the substrate  708 . Wires  7042  and  7044  are connected through the key operation conductor  7082 , and destroy the original charge and discharge mechanism to cause variation in potential to trigger a predetermined function. In such a structure, the number and position of the hole  7062  on the insulator layer  706  vary upon request, as the capacitive touchpad  700  in  FIG. 11 , in which the hole  7062  on the insulator layer  706  covers two first axis wires  7042  and two second axis wires  7044 . The capacitive touchpad  700 ′ in  FIG. 16  has a hole  7062  on the insulator layer  706  to cover one first axis wire  7042  and one second wire  7044 . The capacitive touchpad  700 ″ in  FIG. 17  has a hole  7062  on the insulator layer  706  that covers only on first axis wire  7042 . The insulator layer  706  can be formed of insulator balls.  
         [0030]      FIG. 12  illustrates an embodiment using the structure in  FIG. 11  as an input apparatus of a mobile phone or a phone.  FIG. 13  is the expanded view of the input apparatus  800 . In the control device  802  of the input apparatus  800 , the capacitance detector  804  couples to the first axis wires TX 0  to TX 5  and second axis wires TY 0  to TY 7  of the capacitance-sensing conductive layer  812  through a multiplexer  806  to provide a current to the parasitic capacitor of the capacitance-sensing conductive layer  612  to generate a voltage. When a user&#39;s finger touches the panel  810 , the capacitance detector  804  detects the parasitic capacitance of the first axis wires TX 0  to TX 5  and second axis wires TY 0  to TY 7  to generate minor changes and to detect the position of the finger and the trace of motion. When the uses presses the key area  8102  on the panel  810 , the capacitance-sensing conductive layer  812  contacts the key operation conductor  8162  on the substrate  816  through the hole  8142  on the insulator layer  814  to trigger the predetermined key function. To save power, standby mechanism can be implanted in the input apparatus  800 . When the control circuit  802  enters a standby mode, the key operation conductor  8162  pulls the potential to high or low by using pull-up or pull-down resistor. The capacitance-sensing conductive layer  812  also shifts to a low or a high voltage level to enter the most power-saving mode. To wake up the control circuit  802 , the key can be pressed to cause the capacitance-sensing conductive layer  812  to contact the key operation conductor  8162 . The potential detector  808  detects the voltage change of the key operation conductor  8162  or the capacitance-sensing conductive layer to wake up the control circuit  802 . When the present invention is utilized in different electronic devices, the shape and the number of keys can vary, as the input apparatus  900  shown in  FIG. 14 .  
         [0031]     The structure in  FIG. 11  can be used in a one-dimensional structure, as the capacitive touchpad  950  in  FIG. 15 . The capacitance-sensing conductive layer  954  and the insulator layer  956  are disposed between the panel  952  and the substrate  958 . The capacitance-sensing conductive layer  953  has a plurality of wire aligned to one direction. When a user presses the key area  9522  on the panel  952 , the capacitance-sensing conductive layer  954  couples the key operation conductor  9582  on the substrate  958  through the hole  9562  in the insulator layer  956  to trigger the predetermined function.  
         [0032]     While the present invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope thereof as set forth in the appended claims.