Abstract:
An electrostatic capacitive touch sensor device includes sensing electrode provided at a plurality of positions, a high-frequency signal source that applies a high-frequency signal to the sensing electrode through a predetermined impedance element, a wiring portion that connects the sensing electrode and the impedance element, a shield portion provided to embrace the sensing electrodes and the connecting pattern, and a shield signal source that applies a shield signal to the shield portion and has the same phase and amplitude as the high-frequency signal source.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a Continuation Application of PCT Application No. PCT/JP2008/073633, filed Dec. 25, 2008, which was published under PCT Article 21(2) in Japanese. 
     
    
       [0002]    This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2008-094389, filed Mar. 31, 2008, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The present invention relates to an electrostatic capacitive touch sensor device for use in a switch device for operational input to, for example, an electronic device. 
         [0005]    2. Description of the Related Art 
         [0006]    Conventionally, in order to operate, for example, an audio device mounted in a car, a switch panel device is installed at a position on the dashboard allowing easy operation by the driver or passenger. Several switch panel devices as described are provided with electrostatic sensors. 
         [0007]    In a switch panel device of this type, a sensing electrode is formed at a portion of a panel section which an operator touches to operate the switch panel device. The sensing electrode is applied with a signal (voltage) output from a power supply. The sensing electrode is connected to a sensing circuit. 
         [0008]    When an operator touches the sensing electrode, a slight amount of current flows from the sensing electrode to the operator. Therefore, a voltage value changes in a download side of the sensing electrode between when an operator touches the sensing electrode and when the operator does not touch the sensing electrode. By detecting the change, the sensing circuit senses that the switch panel device has been operated. 
         [0009]    The sensing circuit is provided outside the panel section of the switch panel device. Therefore, a connection pattern for electrically connecting the sensing electrode to the sensing circuit is formed on the panel section. 
         [0010]    However, when an operator touches the connection pattern through the panel section, a slight amount of current then flows to the operator, and a voltage value in a download side of the connection pattern therefore changes. Even in this case, the sensing circuit detects change of the voltage value. As a result of this, the operator is recognized to have touched the sensing electrode. It is not preferred that the sensing circuit detects change in voltage which is caused by a touch of the operator on the connection pattern. 
         [0011]    Therefore, a shield electrode for covering the connection pattern is provided so that the sensing circuit may not detect a touch when an operator touches a connection pattern. Even when an operator touches a portion where the connection pattern is provided in the panel section, a current flows from the shield electrode to the operator while a current is restricted from flowing from the connection pattern to the operator. 
         [0012]    According to the prior art for a shield method of this type, the shield electrode is branched from between the sensing electrode and the sensing circuit. A technique of this type is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-268607. 
         [0013]    Therefore, in the case of using plural sensing electrodes to form a great number of operation switches like an operation switch for a car, plural independent shield electrodes respectively paired with the sensing electrodes, and plural independent circuit means are required between the shield electrodes and the sensing electrodes are required. Consequently, if a great number of operation switches are provided, not only the shield electrodes are difficult to be laid out but also costs for the circuit means for supplying signals to the shield electrodes increase. 
         [0014]    Further, in a car occupant sensing system disclosed in Jpn. Pat. Appln. KOKAI Publication No. 11-268607, a shield electrode is branched from between a sensing electrode and a sensing circuit. If electrical noise which propagates in the air is applied to the sensing electrode, a signal supplied to the shield electrode becomes an electrical signal equal to the noise, and the effect of shield against electrical noise decreases. 
         [0015]    That is, on a wiring connecting the sensing circuit and the sensing electrode, a voltage acting on the wiring changes owing to application of noise to the sensing electrode. Therefore, in the case of a structure in which a shield electrode is branched from a wiring connecting a sensing circuit and a sensing electrode, as disclosed in Patent Document 1, a voltage value applied to the shield electrode is influenced by change in voltage caused by noise affecting the sensing electrode. 
         [0016]    As a result of this, the voltage value applied to the shield electrode is considered to change under influence of external noise. 
       BRIEF SUMMARY OF THE INVENTION 
       [0017]    An object of the present invention is to provide an electrostatic capacitive touch sensor device which simplifies a structure of shield electrodes in a touch switch device including a great number of operation switches and obtains high effect of shield against external electrical noise without causing an increase in number of circuit means for supplying signals to the shield electrodes. 
         [0018]    According to an aspect of the embodiments, an electrostatic capacitive touch sensor device includes a sensing electrode, a wiring portion that connects the sensing electrode and detector circuit, a shield portion provided around the sensing electrode and the wiring portion, and a shield signal source that applies voltage to the shield portion. The shield signal source is electrically connected to the sensing electrode through a predetermined impedance element and has a same phase and amplitude as the high-frequency signal source. 
         [0019]    Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0020]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
           [0021]      FIG. 1  is a perspective view illustrating an instrumental panel in which a panel device including a circuit device according to an embodiment of the present invention is built; 
           [0022]      FIG. 2  is a schematic view illustrating an area F 2  surrounded by a two-dot chain line in  FIG. 1 ; 
           [0023]      FIG. 3  is a cross-sectional view of a panel body illustrated along a line F 3 -F 3  denoted in  FIG. 2 ; 
           [0024]      FIG. 4  is a schematic view illustrating an area surrounded by F 4  denoted in  FIG. 1 ; 
           [0025]      FIG. 5  is a circuit diagram illustrating the circuit device illustrated in  FIG. 1 ; and 
           [0026]      FIG. 6  is a circuit diagram illustrating one signal processing circuit, a wiring, and a shield signal generation circuit. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    A panel device according to an embodiment of the present invention will now be described with reference to  FIGS. 1 to 6 . An electrostatic capacitive touch sensor device according to the present embodiment is exemplarily provided in a switch panel device  10 . The switch panel device  10  is a switch panel device, for example, for performing input operation on an audio device mounted on a car. 
         [0028]      FIG. 1  illustrates an instrument panel  20  in which the switch panel device  10  is built.  FIG. 1  also illustrates a state where the switch panel device  10  is disassembled. The switch panel device  10  includes a panel body  30 , a high frequency power supply  100 , and a circuit device  200 . The panel body  30  defines an exterior shape of the switch panel device  10 . The panel body  30  will be described in details later. 
         [0029]    The panel body  30  is provided with a touch sensing electrode  41 . As illustrated in  FIG. 1 , the touch sensing electrode  41  is an electrode which a car occupant touches when carrying out operation. Plural touch sensing electrodes  41  are provided in the panel body  30 . The touch sensing electrodes  41  are electrically connected to the circuit device  200  described later. 
         [0030]      FIG. 2  is a plan view illustrating an area F 2  enlarged, which is surrounded by a two-dot chain line in  FIG. 1 .  FIG. 2  illustrates the switch panel device  10  (panel body  30 ) viewed from outside, and illustrates only a vicinity of one of the plural touch sensing electrodes  41  formed in the switch panel device  10 . 
         [0031]    Vicinities of the respective touch sensing electrodes  41  in the panel body  30  may all have the same structure as each other. Therefore, the structure of the switch panel device  10  will be described with reference to a structure of a vicinity of one of the touch sensing electrode  41  illustrated in  FIG. 2 . 
         [0032]      FIG. 3  is a cross-sectional view of the panel body  30  illustrated along a line F 3 -F 3  in  FIG. 2 .  FIG. 3  is a cross-sectional view of the vicinity of one touch sensing electrode  41  in the panel body  30 . 
         [0033]    As illustrated in  FIG. 3 , the panel body  30  includes a touch sensing electrode  41 , a panel section  31 , a design layer  36 , a connection pattern  32 , a shield electrode  38 , and an insulating layer  34 . 
         [0034]    The panel section  31  defines an exterior shape of the switch panel device  10  (panel body  30 ). The panel section  31  is made of a resin sheet  35 . The resin sheet  35  is formed of, for example, transparent resins. 
         [0035]    The touch sensing electrode  41  is provided on one surface  31   a  of the panel section  31 . An operator touches the touch sensing electrode  41  through the panel section  31  (i.e., from above the panel section  31 ). The operator touches the touch sensing electrode  41  from a side of the other surface  31   b  opposite to the surface  31   a . The surface  31   b  is exposed to a car cabin. 
         [0036]    The design layer  36  is stacked on the one surface  31   a  of the panel section  31 , and defines colors, decorative patterns and the like of the panel body  30 . Colors and decorative patterns of the panel body  30  are recognized by seeing the design layer  36  through the panel section  31 . The design layer  36  is formed by printing, for example, an ink and the like to form the design layer  36 . The design layer  36  is not layered in an area of a vicinity of the touch sensing electrode  41  including the touch sensing electrode  41 . 
         [0037]    The connection pattern  32  is formed in a side of the surface  31   a  of the panel section  31 . The connection pattern  32  is electrically connected to the touch sensing electrode  41 , and is provided to electrically connect the touch sensing electrode  41  to the sensing circuit  200  described later. The connection patter  32  has a property of conducting electricity. The connection pattern  32  is formed by printing, for example, an ink having a property of conducting electricity. 
         [0038]    In the present invention, the side of the surface  31   a  is intended to refer to a side where the surface  31   a  exists. Therefore, being provided in the side of the surface  31   a  is a concept including a case of being provided on the one surface  31   a  and another case of not being provided on the surface  31   a  but being provided in the side where the surface  31   a  exists in relation to the panel section  31  as a boundary. Therefore, in actual, the connection pattern  32  which is provided on an insulating layer  34  described later is not formed on the surface  31   a  but is formed in the side of the surface  31   a.    
         [0039]    As illustrated in  FIG. 1 , a circuit device  200  is located outside the panel body  30 . Therefore, the connection pattern  32  extends to, for example, an edge  31   c  of the panel section  31 , and is electrically connected to a first wiring  37   a .  FIG. 4  schematically illustrates an area surrounded by  FIG. 4 .  FIG. 4  schematically illustrates a vicinity of an edge  31   c  of the panel section  31 . As illustrated in  FIG. 4 , the connection pattern  32  extends also to the edge  31   c.    
         [0040]    As illustrated in  FIGS. 1 and 4 , the connection pattern  32  is electrically connected to the circuit device  200  through a pair of wirings  37   a  from the edge  31   c . Therefore, the touch sensing electrode  41  is electrically connected to the circuit device  200  through the connection pattern  32  and the first wirings  37   a.    
         [0041]    As illustrated in  FIG. 3 , the shield electrode  38  is located between the connection pattern  32  and the design layer  36 , and is stacked on the design layer  36 . The shield electrode  38  has an area covering the connection pattern  32 . The shield electrode  38  has a property of conducting electricity. 
         [0042]    The shield electrode  38  is electrically connected to the circuit device  200  described later, and is applied with a voltage having the same amplitude and phase as a voltage applied to the touch sensing electrode  41 . 
         [0043]    As a result of this, even when an operator touches a part of the panel section  31  where the connection pattern  32  is provided from the side of the surface  31   b  of panel section  31 , a current flows from the shield electrode  38  to the operator. A current is thereby restricted from the connection pattern  32  to the operator. 
         [0044]    Therefore, in an area of the panel section  31  where the connection pattern  32  is formed, the shield electrode  38  is formed, and the connection pattern  32  and the shield electrode  38  are opposed to each other. The shield electrode  38  is formed by printing, for example, an ink having a property of conducting electricity. 
         [0045]    As illustrated in  FIG. 3 , the shield electrode  38  is neither formed on the touch sensing electrode  41  nor in the vicinity of the touch sensing electrode  41 . Therefore, the shield electrode  38  and the touch sensing electrode  41  are not electrically connected to each other. 
         [0046]    This is because the shield electrode  38  and the touch sensing electrode  41  are prevented from being connected to each other in consideration of errors occurring in formation of the shield electrode  38  and errors occurring in formation of the panel body  30  (e.g., in the case of shape-forming). 
         [0047]    As illustrated in  FIG. 1 , the circuit device  200  is provided outside the panel body  30 . Therefore, as illustrated in  FIG. 4 , the shield electrode  38  extends to an edge  31   c  of the panel section  31 , and is electrically connected to a second wiring  37   b . The second wiring  37   b  is electrically connected to the circuit device  200 . The shield electrode  38  is electrically connected to the circuit device  200  through the second wiring  37   b.    
         [0048]    One connection pattern  32  is provided for each one of the touch sensing electrodes  41 . Accordingly, the switch panel device  10  includes plural connection patterns  32 . The connection patterns  32  are not electrically connected to each other. The shield electrodes  38  provided respectively for the connection patterns  32  are gathered into one set near the edge  31   c . The figure illustrates, as an example, a case that two connection patterns  32  are provided. However, what is described above applies to other cases in which a plurality of connection pattern  32 , for example three or four connection pattern  32 , are provided, too. 
         [0049]    As illustrated in  FIG. 3 , the insulating layer  34  is provided between the connection pattern  32  and the shield electrode  38 . Specifically, the insulating layer  34  is stacked on the shield electrode  38 , and the connection pattern  32  is stacked on the insulating layer  34 . 
         [0050]    The insulating layer  34  is formed in a manner that the shield electrode  38  and a layer of the connection pattern  32  are insulated from each other (not electrically connected to each other). The insulating layer  34  is desirably 5 MΩ or more. The insulating layer  34  is neither formed on the touch sensing electrode  41  nor in the vicinity of the touch sensing electrode  41 . The insulating layer  34  is formed by printing, for example, an insulating ink. 
         [0051]    In the panel body  30  formed as described above, the design layer  36  is stacked on the one surface  31   a  of the panel section  31 , and the touch sensing electrode  41  is formed as well. The shield electrode  38  is stacked on the design layer  36 . The insulating layer  34  is stacked on the shield electrode  38 . The connection pattern  32  is stacked on the insulating layer  34 . 
         [0052]    Next, the circuit device  200  will be described.  FIG. 5  is a circuit diagram illustrating the circuit device  200 . As illustrated in  FIG. 5 , the circuit device  200  is inserted between a high-frequency power supply  100  and the touch sensing electrodes  41  and the shield electrode  38 . The high-frequency power supply  100  applies a voltage to the touch sensing electrodes  41  and the shield electrode  38 . The circuit device  200  includes a signal processing circuit, a wiring  220 , and a shield signal generation circuit  300 , as denoted by a two-dot chain line in  FIG. 2 . 
         [0053]    One signal processing circuit is used for each one of the touch sensing electrodes  41 . Therefore,  FIG. 5  illustrates exemplarily a state that the circuit device  200  includes two signal processing circuits  210   a  and  210   b . Since the signal processing circuits  210   a  and  210   b  may have substantially the same structure as each other, one signal processing circuit  210   a  will be described as a representative example.  FIG. 2  illustrates the one signal processing circuit  210   a  as a representative of the signal processing circuits  210   a  and  210   b.    
         [0054]      FIG. 6  is a circuit diagram illustrating the one signal processing circuit  210   a , the wiring  220 , and the shield signal generation circuit  300 , which are used in  FIG. 5 . As denoted by a two-dot chain line in  FIG. 6 , the signal processing circuit  210   a  includes a detector circuit  230 , an amplifier circuit  240 , and a wave detector circuit  250 . A rectangular wave signal (voltage) output from the high-frequency power supply  100  passes through the detector circuit  230 , is next amplified through the amplifier circuit  240 , and is subsequently converted into a direct current through the wave detector circuit  250 . As illustrated in  FIG. 5 , the wave detector circuit  250  is connected to a control device  400 , and a signal which has passed through the wave detector circuit  250  is input to the control device  400 . 
         [0055]    By detecting a signal which has passed through the signal processing circuit  210   a  or  210   b , the control device  400  detects that the touch sensing electrode  41  has been operated (touched). The control device  400  is connected to an audio device and controls operation of the audio device upon detection made as described above. 
         [0056]    As illustrated in  FIG. 6 , the detector circuit  230  is connected to the high-frequency power supply  100  through the wiring  220 . The detector circuit  230  includes a first inverter  231 , a first resistor  232 , a second resistor  233 , and a third resistor  234 . 
         [0057]    The first inverter  231 , first resistor  232 , and second resistor  233  are connected in series to one another. A series circuit constituted by the first inverter  231 , first resistor  232 , and second resistor  233  is connected in parallel with the third resistor  234 . The first inverter  231  is, for example, of HCU04 type. 
         [0058]    Resistance R 1  of the first resistor  232 , resistance R 2  of the second resistor  233 , and resistance R 3  of the third resistor  234  satisfy a relationship of R 1 +R 2 =R 3 . 
         [0059]    In the detector circuit  230 , a downstream side of the first resistor  232  and an upstream side of the second resistor  233  is electrically connected to the connection pattern  32 . 
         [0060]    The amplifier circuit  240  includes a first capacitor  241 , a second inverter  242 , a second capacitor  243 , and a fourth resistor  244 . The first capacitor  241 , second inverter  242 , and second capacitor  243  are connected in series. The fourth resistor  244  is connected in parallel with the second inverter  242 . 
         [0061]    The wave detector circuit  250  includes first and second rectifiers  251  and  252 , a third capacitor  253 , and a fifth resistor  254 . The first rectifier  251  is connected in series to the second capacitor  243 . The second rectifier  252  is connected, at one end, to a downstream side of the second capacitor  243  and an upstream side of the first rectifier  251 . The other end of the second rectifier  252  is grounded. The third capacitor  253  and fifth resistor  254  are connected, at one ends, to a downstream side of the first rectifier  251 , and are grounded at the other ends. 
         [0062]    When the control device  400  detects change (in voltage) of a signal, the control device  400  then detects that the touch sensing electrode  41  has been operated (touched through the panel section  31 ). 
         [0063]    As illustrated in  FIG. 5 , the other signal processing circuit  210   b  has substantially the same structure as described above. The first inverter  231  of the detector circuit  230  in the signal processing circuit  210   a  is used in common by the other signal processing circuit  210   b . Even if three or more signal processing circuits are used, the first inverter  231  is used in common. 
         [0064]    The wiring  220  connects the high-frequency power supply  100  to the signal processing circuits  210   a  and  210   b  (detector circuit  230 ). 
         [0065]    As illustrated in  FIGS. 5 and 6 , the shield signal generation circuit  300  is connected to upstream sides of the signal processing circuits  210   a  and  210   b  (detector circuit  230 ). The shield signal generation circuit  300  includes a third inverter  301 , a sixth resistor  302 , a seventh resistor  303 , a fourth inverter  304 , and an eighth resistor  305 . 
         [0066]    The third inverter  301  is built in an upstream side of the detector circuit  230  on the wiring  220 . The third inverter  301  is, for example, of HCU04 type. 
         [0067]    The sixth resistor  302  and seventh resistor  303  are connected in series, forming a series circuit. The series circuit constituted by the sixth and seventh resistors  302  and  307  is connected to the wiring  220 , in parallel with the third inverter  301 . The sixth resistor  302  is connected to a downstream side of the third inverter  301  and an upstream side of the detector circuit  230 . The seventh resistor  303  is connected to an upstream side of the third inverter  301 . 
         [0068]    Resistance R 6  of the sixth resistor  302  and resistance R 7  of the seventh resistor  303  satisfy a relationship of a ratio of R 6  to R 7 =a ratio of R 1  to R 2 +R 3 . That is, R 6 :R 7 =R 1 :R 2 +R 3 . 
         [0069]    The fourth inverter  304  is connected, at one end, between the sixth and seventh resistors  302  and  303 , and is electrically connected, at the other end, to the shield electrode  38  through the second wiring  37   b . The fourth inverter  304  is, for example, of HCU04 type. The eighth resistor  305  is connected in parallel with the fourth inverter  304 . 
         [0070]    Resistance R 8  of the eighth resistor  305 , resistance R 6  of the sixth resistor  302 , and resistance R 7  of the seventh resistor  303  satisfy a relationship of R 8 =R 6 //R 7  (where “//” expresses parallel resistance). 
         [0071]    Next, operation of the circuit device  200  will be described. At first, operation of the signal processing circuits  210   a  and  210   b  will be described. A rectangular wave signal applied from the high-frequency power supply  100  passes through the wiring  220  and is then applied to the signal processing circuits  210   a  and  210   b . Halfway, the rectangular wave signal is inverted by the third inverter  301  provided on the wiring  220 . The inverted rectangular wave signal is applied to the first inverter  231  and the third resistor  234 . 
         [0072]    The rectangular wave signal applied to the first inverter  231  is further inverted by the first inverter  231 . The rectangular wave signal which has passed through the first inverter  231  comes to be put in the same state as output from the high-frequency power supply  100 . 
         [0073]    Subsequently, the rectangular wave signal which has passed through the first inverter  231  passes through the first resistor  232 . At this time, the rectangular wave signal is reduced and an amplitude thereof decreases accordingly. The rectangular wave signal which has passed through the first inverter  231  is applied to the touch sensing electrode  41 , and passes through the second resistor  233 . The rectangular wave signal passes through the second resistor  233  and is thereby reduced. Accordingly, the amplitude decreases much more. 
         [0074]    Meanwhile, a rectangular wave signal applied to the third resistor  234  passes through this third resistor  234 , and is thereby reduced. Accordingly, an amplitude thereof decreases. 
         [0075]    The rectangular wave signals which have passed through the second and third resistors  233  and  234  are synthesized at a cross point P 1  (a meeting point in the downstream side of the second and third resistors  233  and  234 ) 
         [0076]    As described above, resistance R 1  of the first resistor  232 +resistance R 2  of the second resistor  233 =resistance R 3  of the third resistor  234 . As a result of this, the rectangular wave signal which has passed through the first and second resistors  232  and  233 , and the rectangular wave signal which has passed through the third resistor  234  have an equal amplitude. However, the rectangular wave signal which has passed through the first and second resistors  232  and  233  has already passed through the first inverter  231 , and is therefore inverted relative to the rectangular wave signal which has passed through the third resistor  234 . 
         [0077]    Therefore, a signal synthesized at the cross point P 1  is flat. The signal synthesized at the cross point P 1  passes through the amplifier circuit  240  and the wave detector circuit  250 , and reaches the control device  400 . 
         [0078]    When an operator touches the touch sensing electrode  41  through the panel section  31 , a slight amount of current then flows from the touch sensing electrode  41  to the operator. As a result of this, an amplitude of a rectangular wave signal passing through the second resistor  233  of the signal processing circuit which is connected to the touched touch sensing electrode  41  becomes much smaller, compared with when the touch sensing electrode  41  is not touched by the operator. 
         [0079]    Since the amplitude of the rectangular wave signal which has passed through the second resistor  233  becomes much smaller, the rectangular wave signal synthesized at the cross point P 1  is not flat. By detecting this, the control device  400  detects that the operator has touched the touch sensing electrode  41 . 
         [0080]    Next, operation of the shield signal generation circuit  300  will be described. As illustrated in  FIG. 6 , the rectangular wave signal which has passed through the seventh resistor  303  and the rectangular wave signal which has passed through the third inverter  301  and the sixth resistor  302  are synthesized at a cross point P 2  (in the downstream side of the sixth and seventh resistors  302  and  303 ). 
         [0081]    The rectangular wave signal which has passed through the sixth resistor  302  passes the third inverter  301 , and is thereby inverted relative to the rectangular wave signal which has passed through the seventh resistor  303 . 
         [0082]    Further, as described above, R 6 :R 7 =R 1 :R 2 +R 3  is given. Accordingly, the signal synthesized at the cross point P 2  has an amplitude equal to the signal applied to the touch sensing electrode  41 , and is inverted relative to the signal applied to the touch sensing electrode  41 . 
         [0083]    Since the resistance R 8  of the eighth resistor  305  is set to R 8 =R 6 //R 7  (where “//” expresses parallel resistance), the fourth inverter  304  and eighth resistor  305  and the sixth resistor  302  and seventh resistor  303  form an inverting amplifier circuit having a gain 1. 
         [0084]    Accordingly, the rectangular wave signal which has passed through the cross point P 2  passes through the fourth inverter  304  and is thereby inverted. However, an amplitude thereof is equal to that at the cross point P 2 . 
         [0085]    Therefore, the signal which has passed through the fourth inverter  304  has the same potential and phase as the signal applied to the touch sensing electrode  41 . The signal generated by the shield signal generation circuit  300  is applied to the shield electrode  38  through the second wiring  37   b.    
         [0086]    In the circuit device  200  constructed as described above, change of a signal caused by an touch on the touch sensing electrode  41  by an operator influences the downstream side of the touch sensing electrode  41 . Specifically, the rectangular wave signal applied to the second resistor  233  is reduced, and therefore, an amplitude of the rectangular wave signal decreases. 
         [0087]    Thus, change of a signal caused by a touch on the touch sensing electrode  41  influences the detector circuit  230  and the downstream side of the detector circuit  230 . In the circuit device  200 , the shield signal generation circuit  300  is provided in the upstream side of the detector circuit  230 . 
         [0088]    Therefore, change of a signal caused by a touch on the touch sensing electrode  41  does not influence the shield signal generation circuit  300 . Accordingly, even when high-frequency noise and the like propagating in the space are applied to the touch sensing electrode  41 , the signal (voltage) applied to the shield electrode  38  does not change. 
         [0089]    As a result of this, reduction of shield effect against external noise can be restricted. Further, even in the case of constructing plural touch sensing electrodes  41 , only one circuit is enough to constitute the shield electrode  38  and the shield signal generation circuit  300 . Accordingly, shield wirings can be constructed with a simple structure, and increase of costs for the shield signal generation circuit can be restricted. 
         [0090]    In the present embodiment, the high-frequency power supply  100  outputs a rectangular wave signal. However, the embodiment is not limited hitherto. For example, a sign wave signal is available. In brief, any signal is available insofar as a synthesized wave is flat when forming a synthesized wave at the cross point P 1 . 
         [0091]    Also in the present embodiment, the circuit device  200  is used in a switch panel device for an audio device or the like. However, the embodiment is not limited hitherto. The circuit device  200  may be used in other devices. 
         [0092]    The present invention is not exactly limited to the embodiment described above but can be embodied with componential elements modified in a practical phase within a scope of not deviating from the subject matter of the invention. Further, various invention can be derived from appropriate combinations of plural componential elements disclosed in the embodiments described above. For example, several componential elements may be removed from the whole componential elements suggested in the above embodiments. Further, componential elements may be appropriately combined between different embodiments. 
         [0093]    The present invention can provide an electrostatic capacitive touch sensor device which is capable of forming a shield function by one shield signal source and shield electrodes constructed in one circuit, and obtains high shield effect against external noise. 
         [0094]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.