Abstract:
A touch panel including upper and lower electrode substrates including upper and lower conductive layers, respectively; first and second electrodes respectively provided at bath ends of the upper conductive layer in a first direction for causing an electric potential distribution in the first direction; third and fourth electrodes respectively provided at both ends of the lower conductive layer in a second direction perpendicular to the first direction for causing an electric potential distribution in the second direction; a flexible substrate provided to be connected to the lower electrode substrate or the upper electrode substrate; a first resistor portion electrically connected to either of the first or second electrode and formed at the upper electrode substrate or the flexible substrate; and a second resistor portion connected to either of the third or fourth electrode and formed at the lower electrode substrate or the flexible substrate.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a touch panel. 
         [0003]    2. Description of the Related Art 
         [0004]    A touch panel is an input device usually provided in front of a display and capable of inputting data. A user can directly input data based on information visually grasped by viewing the display through the touch panel, so that the touch panel is used in various ways. 
         [0005]    A resistive touch panel is widely known. For the resistive touch panel, transparent conductive layers are respectively formed on an upper conductive substrate and on a lower conductive substrate where the transparent conductive layers are positioned to face each other. When force is applied to a point of the upper conductive substrate, the transparent conductive layers of the upper conductive substrate and the lower conductive substrate contact at that point. At this time, a potential gradient is generated on one of the transparent conductive layers so that a coordinate position of the pushed point can be detected by reading an electric potential of the other of the transparent conductive layers. 
         [0006]    Resistive touch panels mainly include a four-wire type and a five-wire type. For the four-wire type, electrodes for applying potential gradients in an X-axis direction and in a Y-axis direction are respectively provided on one and the other of the upper conductive substrate and the lower conductive substrate. For the five-wire type, electrodes for applying potential gradients in both the X-axis direction and the Y-axis are provided on the lower conductive substrate, and the upper conductive substrate functions as a probe to read an electric potential (see Patent Documents 1, 2 and 3). 
         [0007]    Specifically, with reference to  FIG. 1  and  FIG. 2 , the four-wire type touch panel is explained.  FIG. 1  is a cross-sectional view of a four-wire type touch panel.  FIG. 2  is a perspective view of the four-wire type touch panel. 
         [0008]    The four-wire type touch panel includes an upper electrode substrate including a film  10  and a transparent conductive layer  30  which is formed at one surface of the film  10 , a lower electrode substrate including a glass  20  and a transparent conductive layer  40  which is formed at one surface of the glass  20 , and a spacer  50 . The spacer  50  is provided between the transparent conductive layer  30  and the transparent conductive layer  40  such that the transparent conductive layer  30  and the transparent conductive layer  40  facing each other. The four-wire type touch panel is electrically connected to a host computer or the like through a cable, not shown in the drawings. 
         [0009]    Electrodes  31  and  32  are provided on the surface of the film  10 , on which the transparent conductive layer  30  is also formed, at both ends in an X-axis direction along a Y-axis direction. Similarly, electrodes  41  and  42  are provided on the surface of the glass  20 , on which the transparent conductive layer  40  is also formed, at both ends in the Y-axis direction along the X-axis direction. 
         [0010]    For the four-wire type touch panel, an operation of detecting a position of the touch panel while being touched is explained. 
         [0011]    First, as shown in  FIG. 3 , voltages are applied to the electrodes  31  and  32  of the upper electrode substrate. Specifically, the electrode  31  is grounded (0V) and the electrode  32  is applied with Vcc, for example, 5V. At this state, when a touch pen  60  or the like touches a point “A” of the touch panel, the transparent conductive layer  30  of the upper electrode substrate and the transparent conductive layer  40  of the lower electrode substrate contact at the point “A”. As a potential gradient is generated in the X-axis direction, the electric potential at the point “A” can be detected by measuring the electric potential of the transparent conductive layer  40  when the transparent conductive layer  30  and the transparent conductive layer  40  are contacted at the point “A”. The electric potential corresponds to a value of the voltage applied by the electrodes  32  and  31  and divided by the resistance of the transparent conductive layer  30  at the point “A” in the X-axis direction. The electric potential is detected by a voltage meter  70  through the electrode  41  provided on the transparent conductive layer  40 . Subsequently, as shown in  FIG. 4 , an X coordinate of the point “A” is detected based on the voltage “Va” measured by the voltage meter  70 . 
         [0012]    Next, as shown in  FIG. 5 , voltages are applied to the electrodes  41  and  42  of the lower electrode substrate. Specifically, the electrode  41  is grounded (0V) and the electrode  42  is applied with Vcc, for example, 5V. Similar to the above described upper electrode substrate, when the touch pen  60  or the like touches the point “A” of the touch panel, the transparent conductive layer  30  of the upper electrode substrate and the transparent conductive layer  40  of the lower electrode substrate contact at the point “A”. As the transparent conductive layer  40  is applied with voltages by the electrodes  41  and  42  to generate a potential gradient in the Y-axis direction and the transparent conductive layer  30  and the transparent conductive layer  40  are contacted at the point “A”, the electric potential at the point “A” can be detected by measuring the electric potential of the transparent conductive layer. The electric potential corresponds to a value of the voltage applied by the electrodes  41  and  42  and divided by the resistance of the transparent conductive layer  40  at the point “A” in the Y-axis direction. The electric potential is detected by a voltage meter  80  through the electrode  31  provided on the transparent conductive layer  30 . Subsequently, as shown in  FIG. 6 , a Y coordinate of the point “A” is detected based on the voltage “Vb” measured by the voltage meter  80 . 
         [0013]    With the above operations, the X coordinate and the Y coordinate of the point “A” can be obtained so that two-dimensional positions of the point “A” can be grasped. 
         [0014]    For the four-wire type touch panel, the operation in which the transparent conductive layer  30  of the upper electrode substrate is applied with voltages and the transparent conductive layer  40  of the lower electrode substrate detects the electric potential, and the operation in which the transparent conductive layer  40  of the lower electrode substrate is applied with voltages and the transparent conductive layer  30  of the upper electrode substrate detects the electric potential, are alternately performed to enable a successive positional detection. 
         [0015]    However, for the above described four-wire type touch panel, it is capable of detecting a position when a single point is touched, but it is impossible to detect plural positions when plural points are touched at the same time. 
         [0016]    As shown in  FIG. 7 , similar to that shown in  FIG. 3 , the electrodes  31  and  32  of the upper electrode substrate are applied with voltages, for example, the electrode  31  is grounded (0V) and the electrode  32  is applied with Vcc, 5V. At this state, if touch pens  61  and  62  or the like touch the touch panel at points “B” and “C”, respectively, at the same time, the coordinates of the points “B” and “C” cannot be detected. 
         [0017]    When the two points “B” and “C” of the touch panel are touched at the same time, the electric potential Vx at a middle point of the points “B” and “C” is detected at the transparent conductive layer  40 , as shown in  FIG. 8 . Therefore, even if two points are touched on the touch panel, as the detected electric potential is just a single value, it is detected as if a single point is touched. Thus, each of the two coordinates corresponding to the points “B” and “C” cannot be detected. 
         [0018]    Therefore, in Patent Document 4, a touch panel capable of detecting multi-touches by electrically connecting resistors to the transparent conductive layers  30  and  40 , respectively. 
       PATENT DOCUMENT 
       [0000]    
       
         [Patent Document 1] Japanese Laid-open Patent Publication No. 2004-272722 
         [Patent Document 2] Japanese Laid-open Patent Publication No. 2008-293129 
         [Patent Document 3] Japanese Laid-open Patent Publication No. H11-353101 
         [Patent Document 4] Japanese Laid-open Patent Publication No. 2009-176114 
       
     
         [0023]    However, for the touch panel disclosed in Patent Document 4, as the resistors are provided outside of the touch panel, this causes the size of the device to be larger and the cost of the touch panel to be higher. 
       SUMMARY OF THE INVENTION 
       [0024]    According to an embodiment, there is provided a touch panel including an upper electrode substrate including an upper conductive layer; a lower electrode substrate including a lower conductive layer; a first electrode and a second electrode respectively provided at both ends of the upper conductive layer in a first direction for causing an electric potential distribution in the first direction; a third electrode and a fourth electrode respectively provided at both ends of the lower conductive layer in a second direction perpendicular to the first direction for causing an electric potential distribution in the second direction; a flexible substrate provided to be connected to the lower electrode substrate or the upper electrode substrate; a first resistor portion electrically connected to either of the first electrode or the second electrode and formed at the upper electrode substrate or the flexible substrate; and a second resistor portion connected to either of the first the third electrode or the fourth electrode and formed at the lower electrode substrate or the flexible substrate. 
         [0025]    According to another embodiment, there is provided a touch panel including an upper electrode substrate including an upper conductive layer; a lower electrode substrate including a lower conductive layer; a first electrode and a second electrode respectively provided at both ends of the upper conductive layer in a first direction for causing an electric potential distribution in the first direction; a third electrode and a fourth electrode respectively provided at both ends of the lower conductive layer in a second direction perpendicular to the first direction for causing an electric potential distribution in the second direction; a first resistor portion electrically connected to either of the first electrode or the second electrode and formed at the upper electrode substrate; and a second resistor portion connected to either of the third electrode or the fourth electrode and formed at the lower electrode substrate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings. 
           [0027]      FIG. 1  is a cross-sectional view of a general four-wire type touch panel; 
           [0028]      FIG. 2  is a perspective view of a general four-wire type touch panel; 
           [0029]      FIG. 3  is a perspective view of a general four-wire type touch panel in which a coordinate in an X-axis direction is detected; 
           [0030]      FIG. 4  is a view for explaining an electric potential and a touched point in the X-axis direction; 
           [0031]      FIG. 5  is a perspective view of a general four-wire type touch panel in which a coordinate in a Y-axis direction is detected; 
           [0032]      FIG. 6  is a view for explaining an electric potential and a touched point in the Y-axis direction; 
           [0033]      FIG. 7  is a perspective view of a general four-wire type touch panel in which two points are touched; 
           [0034]      FIG. 8  is a view for explaining an electric potential and touched points when two points are touched; 
           [0035]      FIG. 9  is a plan view of an example of an upper electrode substrate of a touch panel of a first embodiment; 
           [0036]      FIG. 10  is a plan view of an example of a lower electrode substrate of a touch panel of the first embodiment; 
           [0037]      FIG. 11  is a perspective view of an example of the touch panel of the first embodiment; 
           [0038]      FIG. 12  is a perspective view of an example of the touch panel of the first embodiment; 
           [0039]      FIG. 13  is a cross-sectional view of an example of a resistor portion of the touch panel of the first embodiment; 
           [0040]      FIG. 14  is a cross-sectional view of another example of a resistor portion of the touch panel of the first embodiment; 
           [0041]      FIG. 15  is a plan view of an example of an upper electrode substrate of a touch panel of a second embodiment; 
           [0042]      FIG. 16  is a plan view of an example of a lower electrode substrate of a touch panel of the second embodiment; 
           [0043]      FIG. 17  is a plan view of an example of an upper electrode substrate of a touch panel of a third embodiment; 
           [0044]      FIG. 18  is a plan view of an example of a lower electrode substrate of a touch panel of the third embodiment; 
           [0045]      FIG. 19  is a plan view of an example of an upper electrode substrate of a touch panel of a fourth embodiment; 
           [0046]      FIG. 20  is a view of a resistor portion of the upper electrode substrate of the touch panel of the fourth embodiment; 
           [0047]      FIG. 21  is a plan view of an example of a lower electrode substrate of a touch panel of the fourth embodiment; 
           [0048]      FIG. 22  is a view of a resistor portion of the lower electrode substrate of the touch panel of the fourth embodiment; 
           [0049]      FIG. 23  is a cross-sectional view of the lower electrode substrate of the touch panel of the fourth embodiment; and 
           [0050]      FIG. 24  is a circuit diagram of the touch panel of the first embodiment showing the status corresponding to  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0051]    The invention will be described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purposes. 
         [0052]    It is to be noted that, in the explanation of the drawings, the same components are given the same reference numerals, and explanations are not repeated. 
       First Embodiment 
       [0053]    A touch panel of the first embodiment is explained. 
         [0054]      FIG. 9  is a plan view of an example of an upper electrode substrate  110  of a touch panel of a first embodiment.  FIG. 10  is a plan view of an example of a lower electrode substrate  120  of the touch panel of the first embodiment.  FIG. 11  and  FIG. 12  are perspective views of an example of the touch panel of the first embodiment. 
         [0055]    Referring to  FIG. 9  to  FIG. 12 , the touch panel of the embodiment includes the upper electrode substrate  110  and the lower electrode substrate  120 . 
         [0056]    As shown in  FIG. 9 , the upper electrode substrate  110  includes a substantially rectangular insulating film substrate  111 , a transparent upper conductive layer  130  (an example of an upper conductive layer) formed at one surface of the insulating film substrate  111 , and electrodes  131  and  132  (examples of second and first electrodes) positioned near ends of the transparent upper conductive layer  130  in a Y-axis direction along an X-axis direction. 
         [0057]    The transparent upper conductive layer  130  is made of an Indium Tin Oxide (ITO) or the like. The electrodes  131  and  132  are respectively made of metal or the like. 
         [0058]    The touch panel of the embodiment further includes a first resistor portion  133  formed on the insulating film substrate  111  and connected to the electrode  132 . 
         [0059]    As shown in  FIG. 10 , the lower electrode substrate  120  includes a substantially rectangular glass substrate  121  corresponding to the upper electrode substrate  110 , a transparent lower conductive layer  140  (an example of a lower conductive layer) formed at one surface of the glass substrate  121 , and electrodes  141  and  142  (examples of fourth and third electrodes) positioned near ends of the transparent lower conductive layer  140  in the X-axis direction along the Y-axis direction. 
         [0060]    The transparent lower conductive layer  140  is made of an ITO or the like. The electrodes  141  and  142  are respectively made of metal or the like. 
         [0061]    The touch panel of the embodiment further includes a second resistor portion  143  formed on the glass substrate  121  and connected to the electrode  142 . 
         [0062]    Although not shown in the drawings, dot spacers or the like may be provided at the surface of the transparent upper conductive layer  130  or the transparent lower conductive layer  140 , in accordance with necessity. 
         [0063]    The upper electrode substrate  110  and the lower electrode substrate  120  are stacked such that the transparent upper conductive layer  130  and the transparent lower conductive layer  140  face each other and the peripheral portions of the upper electrode substrate  110  and the lower electrode substrate  120  are bonded by a double-sided tape, an adhesive resin, paste or the like. 
         [0064]    The touch panel of the embodiment further includes a flexible substrate  160  for connecting the electrodes  131 ,  132 ,  141  and  142  or the like with an external device. 
         [0065]      FIG. 11  and  FIG. 12  show resistors generated in the transparent upper conductive layer  130  and the transparent lower conductive layer  140  when points A and B are touched at the same time. 
         [0066]      FIG. 11  shows a status where a voltage Vcc is applied to the electrode  132  through the first resistor portion  133  while the electrode  131  is grounded (0V) at the upper electrode substrate  110 . 
         [0067]      FIG. 12  shows a status where a voltage Vcc is applied to the electrode  142  through the second resistor portion  143  while the electrode  141  is grounded (0V) at the lower electrode substrate  120 . 
         [0068]    As shown in  FIG. 11  and  FIG. 12 , for the touch panel of the embodiment, by generating electric potential distributions in the X-axis direction and the Y-axis direction alternately, and detecting the electric potentials in the generated electric potential distributions, an operation of multi-touch can be detected. 
         [0069]    Specifically, referring to  FIG. 12 , while applying the voltages Vcc and 0V between the electrodes  142  and  141  of the lower electrode substrate  120 , respectively, when the points A and B, which are positioned at different coordinates in the X-axis direction, are touched, the current also flows between the points A and B of the transparent upper conductive layer  130  of the upper electrode substrate  110 . This current causes the contact resistances ra and rb between the transparent conductive layers  140  and  130 , and the resistance R 2 ′ by the transparent upper conductive layer  130 . 
         [0070]      FIG. 24  shows a circuit diagram of the touch panel of the first embodiment showing the status corresponding to  FIG. 12 . In this case, between the voltages Vcc and 0V, the resistance R 4  of the second resistor portion  143 , the resistance R 1  of the transparent lower conductive layer  140  between the electrode  142  and the point “A”, the resistance R 2  between the points “A” and “B”, the resistance R 3  of the transparent lower conductive layer  140  between the point “B” and the electrode  141  exist. Further, a parallel circuit of the contact resistance ra, the resistance R 2 ′ of the transparent upper conductive layer  130  between the points “A” and “B”, and the contact resistance rb is generated with respect to the resistance R 2 . When such a parallel circuit is generated, the resistance R 5  between the electrodes  142  and  141  becomes lower compared with a case where only a single point is touched and such a parallel circuit is not generated. 
         [0071]    In this case, the voltage V 1  detected at the point ADX becomes V 1 =R 5 /(R 4 +R 5 ) where R 5 =R 1 +r 2 +R 3  (r 2  is the resistance value of the entire between the points “A” and “B”). 
         [0072]    At this time, the resistance R 4  of the second resistor portion  143  does not change and functions as a reference resistor. Thus, similar to the technique disclosed in Japanese Laid-open Patent Publication No. 2009-176114 (Patent Document 4), by detecting the voltage value at the point ADX, and comparing the detected voltage value with a predetermined threshold value, whether plural points are touched can be determined. Further, the longer the distance between the points “A” and “B”, the lower the resistance R 5  between the electrodes  142  and  141  becomes. Thus, the distance between the points “A” and “B” can be determined based on the detected voltage value. 
         [0073]    Similarly, for the case when two points, which are positioned at different coordinates in the Y-axis direction, are touched, whether the plural points are touched and the distance between the points can be detected by detecting the voltage value at the point ADY (see  FIG. 11 ). 
         [0074]    Referring back to  FIG. 9  and  FIG. 10 , for the insulating film substrate  111  composing the upper electrode substrate  110 , a material(s) selected from a group of polyethlene terephthalate, poly-carbonate, heat-resistant poly-carbonate, polyethylene naphthalate, polyethersulfone, cyclic polyolefin, polynorbornene, polyarylate, polypropylene, heat-resistant nylon and the like may be used. 
         [0075]    Further, for the lower electrode substrate  120 , a plastic substrate may be used instead of the glass substrate  121 . For the plastic substrate, a material(s) selected from poly-carbonate, heat-resistant poly-carbonate, polyacrylate, polymethacrylate, polyethylene naphthalate, polyethersulfone, cyclic polyolefin, polynorbornene, polyarylate, polypropylene, heat-resistant nylon and the like may be used. 
         [0076]    Further, although the example where the transparent upper conductive layer  130  and the transparent lower conductive layer  140  are made of ITO is descried in this embodiment, instead of ITO, a material which is transparent and has electric conductivity such as a material obtained by adding Al, Ga or the like to ZnO (zinc oxide), a material obtained by adding Sb or the like to SnO 2  (tin oxide) or the like may be used. 
         [0077]    For the touch panel of the embodiment, the first resistor portion  133  is provided at the upper electrode substrate  110 , and the second resistor portion  143  is provided at the lower electrode substrate  120 . 
         [0078]    As shown in  FIG. 9 , the first resistor portion  133  provided at the upper electrode substrate  110  may be formed by removing the transparent upper conductive layer  130  of the upper electrode substrate  110  at a region where the first resistor portion  133  is to be formed and then printing carbon paste for forming resistance (hereinafter, referred to as “resistance paste” as well) or the like at the region where the transparent upper conductive layer  130  is removed. Alternatively, the first resistor portion  133  may be formed by forming an insulating layer on the region of the transparent upper conductive layer  130  of the upper electrode substrate  110  where the first resistor portion  133  is to be formed, and then printing the carbon paste or the like on the insulating layer. 
         [0079]    The first resistor portion  133  is formed to function as a reference resistor for detecting multi-touches in the Y-axis direction based on a voltage value at a point (ADY) between the electrode  132  and the first resistor portion  133  when the predetermined voltages as described above are applied between an end of the first resistor portion  133 , which is opposite to an end connected to the electrode  132 , and the electrode  131  (similar to that shown in  FIG. 24 ). 
         [0080]    The first resistor portion  133  may be formed to have a resistance value greater than or equal to 25% and less than or equal to 200% of a resistance value of the transparent upper conductive layer  130  between the electrodes  131  and  132 . Preferably, the first resistor portion  133  may be formed to have a resistance value of about 70%, for example, of the resistance value of the transparent upper conductive layer  130  between the electrodes  131  and  132 . 
         [0081]    One end of the first resistor portion  133  is connected to the electrode  132  through a leader line or the like, while the other end of the first resistor portion  133  is connected to the flexible substrate  160  through a leader line or the like. 
         [0082]    As shown in  FIG. 10 , the second resistor portion  143  provided at the lower electrode substrate  120  may be formed by removing the transparent lower conductive layer  140  of the lower electrode substrate  120  at a region where the second resistor portion  143  is to be formed and then printing the carbon paste or the like at the region where the transparent lower conductive layer  140  is removed. Alternatively, the second resistor portion  143  may be formed by forming an insulating layer on the region of the transparent lower conductive layer  140  of the lower electrode substrate  120  where the second resistor portion  143  is to be formed, and then printing carbon paste or the like on the insulating layer. 
         [0083]    The second resistor portion  143  is formed to function as a reference resistor for detecting multi-touches in the X-axis direction based on a voltage value at a point (ADX) between the electrode  142  and the second resistor portion  143  when the predetermined voltages as described above are applied between an end of the second resistor portion  143 , which is opposite to an end connected to the electrode  142 , and the electrode  141  (see  FIG. 24 ). 
         [0084]    The second resistor portion  143  may be formed to have a resistance value greater than or equal to 25% and less than or equal to 200% of a resistance value of the transparent lower conductive layer  140  between the electrodes  141  and  142 . Preferably, the second resistor portion  143  may be formed to have a resistance value of about 70%, for example, of the resistance value of the transparent lower conductive layer  140  between the electrodes  141  and  142 . 
         [0085]    One end of the second resistor portion  143  is connected to the electrode  142  through a leader line or the like, while the other end of the second resistor portion  143  is connected to the flexible substrate  160  through a leader line or the like. 
         [0086]    Next, a method of manufacturing the touch panel of the embodiment is explained. 
         [0087]    First, a method of forming the lower electrode substrate  120  of the touch panel of the embodiment is explained with reference to  FIG. 10  and  FIG. 13 . An ITO layer, which becomes the transparent lower conductive layer  140 , is formed on the glass substrate  121  (having a thickness about 1.1 mm). Then, a peripheral portion of the ITO layer is removed by etching to form the transparent lower conductive layer  140 . At this time, the region of the ITO layer where the second resistor portion  143  is to be formed may be also removed. 
         [0088]    Then, dot spacers may be formed on the transparent lower conductive layer  140  by photoresist (not shown in the drawings). Subsequently, the electrodes  141  and  142 , the leader line or the like are formed on the transparent lower conductive layer  140  by screen printing using silver paste. Then, as shown in  FIG. 13 , the second resistor portion  143  is formed at a region on the glass substrate  121  where the transparent lower conductive layer  140  is removed. Specifically, the second resistor portion  143  is formed by printing carbon paste at the region on the glass substrate  121  where the transparent lower conductive layer  140  is removed, being dried and being baked. The second resistor portion  143  is formed to be electrically connected to the electrode  142  through the leader line or the like. 
         [0089]    Here, for an example, the resistance value of the second resistor portion  143  is 430Ω, and the resistance value of the transparent lower conductive layer  140  between the electrode  141  and the electrode  142  is 620Ω. Thus, the resistance value of the second resistor portion  143  is about 69% of the resistance value of the transparent lower conductive layer  140  between the electrode  141  and the electrode  142 . 
         [0090]    Alternatively, as shown in  FIG. 14 , the second resistor portion  143  may be formed on the transparent lower conductive layer  140  through an insulating layer  144 . In this example, the insulating layer  144  is formed at a region on the transparent lower conductive layer  140  where the second resistor portion  143  is to be formed by vapor deposition such as sputtering or the like, or printing. Then, the second resistor portion  143  is formed on the insulating layer  144  by printing or the like. 
         [0091]    A method of forming the upper electrode substrate  110  of the touch panel of the embodiment is explained with reference to  FIG. 9 . An ITO layer, which becomes the transparent upper conductive layer  130 , is formed on the insulating film substrate  111  (having a thickness of about 188 μm). Then, a peripheral portion of the ITO layer is removed by etching to form the transparent upper conductive layer  130 . At this time, the region of the ITO layer where the first resistor portion  133  is to be formed may be also removed. 
         [0092]    Subsequently, the electrodes  131  and  132 , the leader line or the like are formed on the transparent upper conductive layer  130  by screen printing using silver paste. Then, similar to the second resistor portion  143  as shown in  FIG. 13 , the first resistor portion  133  is formed at a region on the insulating film substrate  111  where the transparent upper conductive layer  130  is removed. Specifically, the first resistor portion  133  is formed by printing carbon paste at the region on the insulating film substrate  111  where the transparent upper conductive layer  130  is removed, being dried and being baked. The first resistor portion  133  is formed to be electrically connected to the electrode  132  through the leader line or the like. 
         [0093]    Here, for an example, the resistance value of the first resistor portion  133  is 255Ω, and the resistance value of the transparent upper conductive layer  130  between the electrode  131  and the electrode  132  is 380Ω. Thus, the resistance value of the first resistor portion  133  is about 67% of the resistance value of the transparent upper conductive layer  130  between the electrode  131  and the electrode  132 . 
         [0094]    Alternatively, similar to the second resistor portion  143  as shown in  FIG. 14 , the first resistor portion  133  may be formed on the transparent upper conductive layer  130  through an insulating layer. In this example, the insulating layer is formed at a region on the transparent upper conductive layer  130  where the first resistor portion  133  is to be formed by vapor deposition such as sputtering or the like, or printing. Then, the first resistor portion  133  is formed on the insulating layer by printing or the like. 
         [0095]    Then, the upper electrode substrate  110  and the lower electrode substrate  120  are bonded such that the transparent upper conductive layer  130  and the transparent lower conductive layer  140  face each other by a double-sided tape or the like, not shown in the drawings. Then, the leader lines connected to the electrodes  131  and  132 , or the electrode  141  and  142  are connected to the flexible substrate  160  by a thermo-compression bonding or the like. 
         [0096]    Then, a control circuit for the touch panel is connected to the touch panel. 
         [0097]    Then, the operation of the touch panel is confirmed. As a result, the touch panel can properly detect a gesture operation such as enlarging, reducing, rotating or the like by multi-touches, so that a smooth operation will be performed. 
         [0098]    Further, a heat shock test (−40° C. to +85° C., each 0.5 hour, 1000 cycles) is performed. As a result, initial characteristics are maintained and a high reliability is confirmed. Further, a high temperature high humidity storage test (85° C., 85% (Relative Humidity: RH), 1000 hours) is performed. As a result, initial characteristics are maintained and no error is observed. 
         [0099]    Although the example where the second resistor portion  143  is formed by printing the carbon paste is described in this embodiment, a resistor chip (400Ω, for example), which is formed on the glass substrate  121  and is electrically connected to the electrode  142  through an electric conductive adhesive, may be used for the second resistor portion  143 . Similarly, a resistor chip, which is formed on the insulating film substrate  111  and is electrically connected to the electrode  132  through an electric conductive adhesive, may be used for the first resistor portion  133 . 
       Second Embodiment 
       [0100]    The second embodiment is explained. In this embodiment, resistor portions corresponding to the first resistor portion  133  and the second resistor portion  143  of the first embodiment are provided at a flexible substrate instead of providing the resistor portions on the upper electrode substrate  110  and the lower electrode substrate  120 . With this structure, an area of the touch panel can be enlarged. Further, as the upper electrode substrate and the lower electrode substrate of any type can be used, the cost of the touch panel can be reduced. 
         [0101]      FIG. 15  is a plan view of an example of an upper electrode substrate  210  of a touch panel of the second embodiment.  FIG. 16  is a plan view of an example of a lower electrode substrate  220  of the touch panel of the second embodiment. 
         [0102]    The touch panel of the embodiment is explained with reference to  FIG. 15  and  FIG. 16 . The touch panel of the embodiment includes the upper electrode substrate  210  and the lower electrode substrate  220 . 
         [0103]    As shown in  FIG. 15 , the upper electrode substrate  210  includes a substantially rectangular insulating film substrate  211 , the transparent upper conductive layer  130  formed at one surface of the insulating film substrate  211 , and the electrodes  131  and  132  positioned near ends of the transparent upper conductive layer  130  in the Y-axis direction along the X-axis direction. 
         [0104]    The transparent upper conductive layer  130  is made of an ITO or the like. The electrodes  131  and  132  are respectively made of metal or the like. 
         [0105]    As shown in  FIG. 16 , the lower electrode substrate  220  includes a substantially rectangular glass substrate  221  corresponding to the upper electrode substrate  210 , the transparent lower conductive layer  140  formed at one surface of the glass substrate  221 , and the electrodes  141  and  142  positioned near ends of the transparent lower conductive layer  140  in the X-axis direction along the Y-axis direction. 
         [0106]    The transparent lower conductive layer  140  is made of an ITO or the like. The electrodes  141  and  142  are respectively made of metal or the like. 
         [0107]    The upper electrode substrate  210  and the lower electrode substrate  220  are stacked such that the transparent upper conductive layer  130  and the transparent lower conductive layer  140  face each other and the peripheral portions of the upper electrode substrate  210  and the lower electrode substrate  220  are bonded by a double-sided tape, an adhesive resin, paste or the like. 
         [0108]    The touch panel of the embodiment further includes a flexible substrate  260  for connecting the electrodes  131 ,  132 ,  141  and  142  or the like with an external device. 
         [0109]    The touch panel of the embodiment further includes a first resistor chip  261  and a second resistor chip  262  provided in the flexible substrate  260 . The first resistor chip  261  is provided at a predetermined interconnect portion of the flexible substrate  260  such that the first resistor chip  261  is electrically connected with the electrode  132  of the upper electrode substrate  210 . The second resistor chip  262  is provided at a predetermined interconnect portion of the flexible substrate  260  such that the resistor chip  262  is electrically connected with the electrode  142  of the lower electrode substrate  220 . 
         [0110]    For the touch panel of the embodiment as well, similar to the touch panel of the first embodiment, a good characteristic can be obtained. Further, an area of the touch panel can be enlarged. Further, the touch panel having a multi-touch detecting function can be manufactured with a lower cost. 
       Third Embodiment 
       [0111]    The third embodiment is explained. In this embodiment, resistor portions are made of the same material as that of the transparent conductive layers of the upper electrode substrate and the lower electrode substrate, respectively. 
         [0112]      FIG. 17  is a plan view of an example of an upper electrode substrate  310  of a touch panel of the third embodiment.  FIG. 18  is a plan view of an example of a lower electrode substrate  320  of the touch panel of the third embodiment. 
         [0113]    The structure of the touch panel of the embodiment is explained with reference to  FIG. 17  and  FIG. 18 . The touch panel of the embodiment includes the upper electrode substrate  310  and the lower electrode substrate  320 . Here, in  FIG. 17  and  FIG. 18 , leader lines or the like are not shown. 
         [0114]    As shown in  FIG. 17 , the upper electrode substrate  310  includes a substantially rectangular insulating film substrate  311 , a transparent upper conductive layer  330  formed at one surface of the insulating film substrate  311 , electrodes  331  and  332  positioned near ends of the transparent upper conductive layer  330  in the Y-axis direction along the X-axis direction, an electrode  334 , and a first resistor portion  333  provided between the electrodes  332  and  334 . 
         [0115]    The transparent upper conductive layer  330  is made of an ITO or the like. The electrodes  331 ,  332  and  334  are respectively made of metal or the like. 
         [0116]    The first resistor portion  333  is made of the material same as that of the transparent upper conductive layer  330  of the upper electrode substrate  310 . The first resistor portion  333  may be formed by selectively removing a part of the transparent conductive layer ( 330 ), which is a periphery of a region which becomes the first resistor portion  333  by etching or the like. The first resistor portion  333  has the same function as the first resistor portion  133  of the first embodiment. It means that the first resistor portion  333  is formed by a part of the transparent conductive layer, the rest of which composes the electrode layer, and provided at the same level as the rest of the transparent conductive layer that composes the electrode. 
         [0117]    As shown in  FIG. 18 , the lower electrode substrate  320  includes a substantially rectangular glass substrate  321  corresponding to the upper electrode substrate  310 , a transparent lower conductive layer  340  formed at one surface of the glass substrate  321 , electrodes  341  and  342  positioned near ends of the transparent lower conductive layer  340  in the X-axis direction along the Y-axis direction, an electrode  344 , and a second resistor portion  343  provided between the electrodes  342  and  344 . 
         [0118]    The transparent lower conductive layer  340  is made of an ITO or the like. The electrodes  341   342 , and  332  are respectively made of metal or the like. 
         [0119]    The second resistor portion  343  is made of the material same as that of the transparent lower conductive layer  340  of the lower electrode substrate  320 . The second resistor portion  343  may be formed by selectively removing a part of the transparent conductive layer ( 340 ), which is a periphery of a region which becomes the second resistor portion  343 , by etching or the like. The second resistor portion  343  has the same function as the second resistor portion  143 . It means that the second resistor portion  343  is formed by a part of the transparent conductive layer, the rest of which composes the electrode layer, and provided at the same level as the rest of the transparent conductive layer that composes the electrode. 
         [0120]    The upper electrode substrate  310  and the lower electrode substrate  320  are stacked such that the transparent upper conductive layer  330  and the transparent lower conductive layer  340  face each other and peripheral portions of the upper electrode substrate  310  and the lower electrode substrate  320  are bonded by a double-sided tape, an adhesive resin, paste or the like. 
         [0121]    The touch panel of the embodiment further includes a flexible substrate (not shown in the drawing) for connecting the electrodes  331 ,  332 ,  334 ,  341 ,  342  and  344  or the like with an external device. 
         [0122]    The first resistor portion  333  may be formed as follows. First, a transparent conductive layer is formed on an entire surface of the insulating film substrate  311 . Then, a part of the transparent conductive layer at the upper side in  FIG. 17  other than the areas which become the first resistor portion  333  and the transparent upper conductive layer  330  is removed by laser ablation, dry-etching, wet-etching or the like so that the first resistor portion  333  and the transparent upper conductive layer  330  are patterned to be formed by the remaining portion(s). 
         [0123]    Similarly, the second resistor portion  343  may be formed as follows. First, a transparent conductive layer is formed on an entire surface of the glass substrate  321 . Then, a part of the transparent conductive layer at the left side in  FIG. 18  other than the areas which become the second resistor portion  343  and the transparent lower conductive layer  340  is removed by laser ablation, dry-etching, wet-etching or the like so that the second resistor portion  343  and the transparent lower conductive layer  340  are patterned to be formed by the remaining portion(s). 
         [0124]    In this embodiment, as the first resistor portion  333  and the second resistor portion  343  are made of the ITO or the like same as the transparent upper conductive layer  330  and the transparent lower conductive layer  340 , respectively, a process for mounting resistor chips is not necessary. Thus, the touch panel having a multi-touch detecting function can be manufactured with a lower cost. Further, as the first resistor portion  333  and the second resistor portion  343  are made of the material same as that of the transparent upper conductive layer  330  and the transparent lower conductive layer  340 , respectively, the characteristic of the first resistor portion  333  and the second resistor portion  343  changes in accordance with the change of the characteristic of the transparent upper conductive layer  330  and the transparent lower conductive layer  340  by an environment or elapsed time. 
         [0125]    This means that the relationship between the resistance value of the first resistor portion  333  between the electrode  332  and  334 , and the resistance value of the transparent upper conductive layer  330  between the electrodes  331  and  332 , does not change even by the environment or elapsed time. Similarly, the relationship between the resistance value of the second resistor portion  343  between the electrodes  342  and  344 , and the resistance value of the transparent lower conductive layer  340  between the electrodes  341  and  342  does not change even by the environment or elapsed time. 
         [0126]    Thus, according to the present embodiment, the accuracy of detection does not change largely based on the environment where the touch panel is placed or elapsed time. 
         [0127]    Further, the first resistor portion  333  and the second resistor portion  343  may be formed to be in a similar status as the transparent upper conductive layer  330  or the transparent lower conductive layer  340 , respectively. In that case, the characteristic of the first resistor portion  333  and the second resistor portion  343  can be maintained similar to that of the transparent upper conductive layer  330  and the transparent lower conductive layer  340 , respectively. Therefore, the first resistor portion  333  and the second resistor portion  343  can function as good reference resistors to maintain the relationships between the above described resistance values. 
         [0128]    Further, the first resistor portion  333  and the second resistor portion  343  may be formed to be in a similar status as the transparent upper conductive layer  330  or the transparent lower conductive layer  340 , respectively. In that case, the characteristic of the first resistor portion  333  and the second resistor portion  343  can be maintained similar to that of the transparent upper conductive layer  330  and the transparent lower conductive layer  340 , respectively. Therefore, the first resistor portion  333  and the second resistor portion  343  can function as good reference resistors, as explained above with reference to  FIG. 24 , to maintain the relationships between the above described resistance values. 
         [0129]    For example, when the dot spacers (not shown in the drawings) are formed at a surface of the transparent upper conductive layer  330  or the transparent lower conductive layer  340 , similar dot spacers (not shown in the drawings) made of photoresist or the like may be formed at a surface of the first resistor portion  333  or the second resistor portion  343 . 
         [0130]    Further, the transparent conductive layers  330  and  340  are similar to the transparent conductive layers  130  and  140  of the first embodiment, the electrodes  331 ,  332 ,  341  and  342  are similar to the electrodes  131 ,  132 ,  141  and  142  of the first embodiment, respectively. Further the structure and the operation which are not described specifically are also the same as those of the first embodiment. 
         [0131]    Although the first resistor portion  333  and the second resistor portion  343  are formed at different sides of the transparent conductive layers  330  and  340  (the first resistor portion  333  is formed at the upper side while the second resistor portion  343  is formed at the left side in  FIG. 17  and  FIG. 18 , respectively), the first resistor portion  333  and the second resistor portion  343  may be formed at the same side of the transparent conductive layers  330  and  340 . 
       Fourth Embodiment 
       [0132]    The fourth embodiment is explained. In this embodiment, similar to the third embodiment, the resistor portions are made of the same material as that of the transparent conductive layers of the upper electrode substrate and the lower electrode substrate, respectively. Further, the first resistor portion and the second resistor portion are respectively made of plural blocks of the transparent conductive layer. 
         [0133]    With this structure, an area of the touch panel can be enlarged. 
         [0134]      FIG. 19  is a plan view of an example of an upper electrode substrate  410  of a touch panel of the fourth embodiment.  FIG. 20  is a view of a first resistor portion  433  of the upper electrode substrate  410  of the touch panel of the fourth embodiment.  FIG. 21  is a plan view of an example of a lower electrode substrate  420  of the touch panel of the fourth embodiment.  FIG. 22  is a view of a second resistor portion  443  of the lower electrode substrate  420  of the touch panel of the fourth embodiment. 
         [0135]    The touch panel of the embodiment is explained with reference to  FIG. 19  to  FIG. 22 . 
         [0136]    The touch panel of the embodiment includes the upper electrode substrate  410  and the lower electrode substrate  420 . In  FIG. 19  and  FIG. 21 , leader lines or the like are not shown. 
         [0137]    As shown in  FIG. 19 , the upper electrode substrate  410  includes a substantially rectangular insulating film substrate  411 , the transparent upper conductive layer  330  formed at one surface of the insulating film substrate  411 , the electrodes  331  and  332  positioned near ends of the transparent upper conductive layer  330  in the Y-axis direction along the X-axis direction, an electrode  434 , and a first resistor portion  433  provided between the electrodes  332  and  334 . 
         [0138]    The transparent upper conductive layer  330  is made of an ITO or the like. The electrodes  331 ,  332  and  434  are respectively made of metal or the like. 
         [0139]    In this embodiment, the first resistor portion  433  is provided with plural resistor blocks  433   a ,  433   b ,  433   c ,  433   d , . . . , and  433   x  separated in the X-axis direction. The resistor blocks  433   a  to  433   x  are positioned at the upper side of the transparent upper conductive layer  330  in this example. The resistor blocks  433   a  to  433   x  of the first resistor portion  433  are made of the same material as that of the transparent upper conductive layer  330  of the upper electrode substrate  410 . The resistor blocks  433   a  to  433   x  may be formed by selectively removing a part of the transparent conductive layer ( 330 ), which is a periphery of regions which eventually become the resistor blocks  433   a  to  433   x , by etching or the like. 
         [0140]    The plural resistor blocks  433   a  to  433   x  of the first resistor portion  433  are electrically connected with each other through wirings or electrodes such as the electrode  434  and the electrode  332 . The resistor blocks  433   a  to  433   x  may be connected with each other in parallel or serial based on the resistance value required for the first resistor portion  433 . In this embodiment, the case where the resistor blocks  433   a  to  433   x  of the first resistor portion  433  are connected with each other in parallel is shown in  FIG. 19 . As shown in  FIG. 20 , the resistor blocks  433   a  to  433   x  of the first resistor portion  433  of the fourth embodiment is similar to the structure where the first resistor portion  333  of the third embodiment is separated into plural resistor blocks along a direction in which the current flows. 
         [0141]    Referring back to  FIG. 19 , one end of the resistor blocks  433   a  to  433   x  are electrically connected to the electrode  332  and the other end of the resistor blocks  433   a  to  433   x  are electrically connected to the electrode  434 . 
         [0142]    Further, as shown in  FIG. 21 , the lower electrode substrate  420  includes a substantially rectangular glass substrate  421  corresponding to the upper electrode substrate  410 , the transparent lower conductive layer  340  formed at one surface of the glass substrate  421 , electrodes  341  and  342  positioned near ends of the transparent lower conductive layer  340  in the X-axis direction along the Y-axis direction, an electrode  344 , and a second resistor portion  443  provided between the electrodes  342  and  444 . 
         [0143]    The transparent lower conductive layer  340  is made of an ITO or the like. The electrodes  341   342 , and  444  are respectively made of metal or the like. 
         [0144]    In this embodiment, the second resistor portion  443  is provided with plural resistor blocks  443   a ,  443   b ,  443   c ,  443   d , . . . ,  443   w , and  443   x  separated in the Y-axis direction. The resistor blocks  443   a  to  443   x  are positioned at the left side of the transparent lower conductive layer  340 . The resistor blocks  443   a  to  443   x  of the second resistor portion  443  are made of the material same as that of the transparent lower conductive layer  340  of the lower electrode substrate  420 . The resistor blocks  443   a  to  443   x  may be formed by selectively removing a part of the transparent conductive layer ( 340 ), which is a periphery of regions which become the resistor blocks  443   a  to  443   x , by etching or the like. 
         [0145]    Similar to the plural resistor blocks  433   a  to  433   x  of the first resistor portion  433 , the resistor blocks  443   a  to  443   x  of the second resistor portion  443  are electrically connected with each other through wirings or electrodes. The resistor blocks  443   a  to  443   x  may be connected with each other in parallel or serial based on the resistance value required for the second resistor portion  443 . 
         [0146]    In this embodiment, the case where the resistor blocks  443   a  to  443   x  of the second resistor portion  443  are connected with each other in serial is shown in  FIG. 21 . Specifically, the adjacent resistor blocks of the resistor blocks  443   a  to  443   x  are connected through wirings  445   a  to  445   w , respectively. 
         [0147]    As shown in  FIG. 22 , the resistor blocks  443   a  to  443   x  of the second resistor portion  443  of the fourth embodiment is similar to the structure where the second resistor portion  343  of the third embodiment is separated into plural resistor blocks along a direction perpendicular to the direction in which the current flows. 
         [0148]    Referring back to  FIG. 21 , one end of the resistor block  433   x  is electrically connected to the electrode  342 , the other end of the resistor block  433   x  is electrically connected to the adjacent resistor block  443   w  through the wiring  445   w , . . . , the other end of the resistor block  443   b  is electrically connected to one end of the adjacent resistor block  443   a  through the wiring  445   a , and the other end of the resistor block  443   a  is electrically connected to the electrode  444 . 
         [0149]    In this embodiment, as the transparent upper conductive layer  330  and the transparent lower conductive layer  340  has a shape where the length in the X-axis direction is longer than the length in the Y-axis direction, the resistance value of the transparent lower conductive layer  340  between the electrodes  341  and  342  becomes greater than the resistance value of the transparent upper conductive layer  330  between the electrodes  331  and  332 . Thus, the second resistor portion  443  for the transparent lower conductive layer  340  is necessary to have a greater resistance value than the first resistor portion  433  for the transparent upper conductive layer  330 . Therefore, by connecting the resistor blocks  443   a  to  443   x  of the second resistor portion  443  in serial while connecting the resistor blocks  433   a  to  433   x  of the first resistor portion  433  in parallel, the resistance value of the second resistor portion  443  can be set greater, in this embodiment. 
         [0150]      FIG. 23  is a cross-sectional view of the lower electrode substrate  420  of the touch panel of the fourth embodiment taken along a  21 A- 21 B line. 
         [0151]    The upper electrode substrate  410  and the lower electrode substrate  420  are bonded by adhesive material  451  provided above the wiring  445   w  and a peripheral portion, and adhesive material  452  provided above the electrode  342 . In this embodiment, the adhesive material is not provided above the second resistor portion  443  such as the resistor portion  433   x  or the like nor above the transparent lower conductive layer  340 . With this structure, the characteristics of the first resistor portion  433 , the second resistor portion  443 , the transparent upper conductive layer  330 , and the transparent lower conductive layer  340  can be maintained. Further, with this structure, the characteristic of the first resistor portion  433  and the second resistor portion  443  can be maintained similar to that of the transparent upper conductive layer  330  and the transparent lower conductive layer  340 , respectively. Therefore, similar to as described above for the first resistor portion  333  and the second resistor portion  343 , the first resistor portion  433  and the second resistor portion  443  can function as good reference resistors to maintain the relationships between the above described resistance values. 
         [0152]    Further, similar to the transparent lower conductive layer  340 , dot spacers (not shown in the drawings) made of photoresist or the like may be formed on the second resistor portion  443  (resistor blocks  443   a  to  434   x ). 
         [0153]    Further, dot spacers may be formed on the transparent lower conductive layer  340 , and when the insulating dot spaces are formed on the transparent lower conductive layer  340 , similar dot spacers (not shown in the drawings) may be formed on the first resistor portion  433  (resistor blocks  433   a  to  433   x ) of the upper electrode substrate  410 . 
         [0154]    According to the touch panel of the embodiment, the first resistor portion  433  and the second resistor portion  443  are formed to be separated, respectively. Therefore, the width necessary for the first resistor portion  433  and the second resistor portion  443  on the insulating film substrate  311  and the glass substrate  321 , respectively, can be reduced. With this, an area of the touch panel can be enlarged. 
         [0155]    Although in this embodiment, the case where the plural resistor blocks  433   a  to  433   x  of the first resistor portion  433  are electrically connected with each other in parallel, while the resistor blocks  443   a  to  443   x  of the second resistor portion  443  are electrically connected with each other in serial, is shown, however, the following cases may be adapted based on the required resistance values, the number of resistor blocks, shapes of the resistor blocks or the like. 
         [0156]    For example, the resistor blocks  433   a  to  433   x  of the first resistor portion  433  may also be connected with each other in serial, while the resistor blocks  443   a  to  443   x  of the second resistor portion  443  are connected with each other in serial. Alternatively, the resistor blocks  443   a  to  443   x  of the second resistor portion  443  may also be connected with each other in parallel while the resistor blocks  433   a  to  433   x  of the first resistor portion  433  are connected with each other in parallel. Alternatively, the resistor blocks  433   a  to  433   x  of the first resistor portion  433  may be connected with each other in serial, while the resistor blocks  443   a  to  443   x  of the second resistor portion  443  are connected with each other in parallel. Further, alternatively, some blocks of the first resistor portion  433  or the second resistor portion  443  may be connected with each other in parallel, while other blocks of the first resistor portion  433  or the second resistor portion  443  are connected with each other in serial. Any combination can be adapted to adjust the resistance value of the first resistor portion  433  or the second resistor portion  443 . 
         [0157]    Further, the first resistor portion  433  and the second resistor portion  443  may be formed at the same side of the transparent conductive layers  330  and  340 . Specifically, the first resistor portion  433  and the second resistor portion  443  may be formed to overlap with each other when seen as a plan view. 
         [0158]    According to the embodiment, a touch panel capable of detecting multi-touches without the size of the touch panel becoming larger or the cost of the touch panel becoming higher can be provided. 
         [0159]    The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention. 
         [0160]    The present application is based on Japanese Priority Application No. 2011-97609 filed on Apr. 25, 2011, the entire contents of which are hereby incorporated herein by reference.