Abstract:
The invention provides a touch panel that exhibits high strength at the joints with external circuits, and that does not require high-temperature treatment for formation of the joints. The touch panel of the invention comprises a pair of electrode members, each having a construction with a transparent base and a transparent conductive layer laminated on the transparent base, situated separate and opposing each other with their transparent conductive layers facing, wherein the electrode member has a body section and lead sections formed by protrusions of the transparent base and transparent conductive layer from an edge of the body section, and a pair of extraction electrodes are formed on the side of the transparent conductive layer opposite the transparent base, the pair of extraction electrodes opposing each other in the body section and each extending to the lead sections.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a touch panel and to a method for producing it. 
         [0003]    2. Related Background Art 
         [0004]    Resistance film-type touch panels are known that have a structure with a pair of electrode members, each comprising a transparent conductive layer on a transparent base, laid together so that the transparent conductive layers are facing each other across a spacer or the like. In such touch panels, one of the electrode members is pressed to contact the other electrode member and create current between the transparent conductive layers, thereby allowing detection of the location that was pressed. 
         [0005]    Such touch panels require connection of the transparent conductive layer with an external circuit for detection of current. 
         [0006]    The connection has conventionally been made using a flexible printed circuit board (FPC) (see Japanese Unexamined Patent Publication No. 2003-29930 and Japanese Unexamined Patent Publication No. 2004-259640). 
       SUMMARY OF THE INVENTION 
       [0007]    However, since connection with an FPC requires connection of the FPC with the transparent conductive layer, the strength of the joint tends to be weakened. In addition, connection of the FPC usually requires treatment at relatively high temperature, and high-temperature treatment can cause expansion of the transparent base and cracking of the transparent conductive layer, thereby potentially resulting in poor characteristics of the transparent conductive layer, which may include a lack of uniform distribution of the resistance value in the in-plane direction. 
         [0008]    The present invention has been accomplished in light of these circumstances, and its object is to provide a touch panel that exhibits high strength at joints with external circuits, and that does not require high-temperature treatment for formation of the joints, as well as a method for producing it. 
         [0009]    In order to achieve this object, the touch panel of the invention is a touch panel comprising a pair of electrode members, each having a construction with a transparent base and a transparent conductive layer laminated on the transparent base, situated separate and opposing each other with their transparent conductive layers facing, wherein the electrode member has a body and lead sections formed by protrusions of the transparent base and transparent conductive layer from the edge of the body, and a pair of extraction electrodes are formed on the side of the transparent conductive layer opposite the transparent base, the pair of extraction electrodes opposing each other in the body and each extending to the lead sections. 
         [0010]    Since the touch panel of the invention has extraction electrodes that extend out from the body section at the lead sections of the electrode members, it is possible to connect the transparent conductive layers with external circuits using the lead sections. The lead sections are formed integrally with the electrode members because each transparent base and transparent conductive layer composing the electrode member is protruding, and therefore the strength of the joint is not reduced as with connection using a conventional FPC, and high strength is exhibited when connection is made to external circuits. In addition, since the lead sections are formed integrally with the electrode member, there is no need for high-temperature treatment as with connection of FPCs and the characteristics are not impaired as a result. 
         [0011]    Since the touch panel of the invention can be connected to an external circuit or the like by the lead sections formed integrally with the electrode members, it may be used as a unit with pre-formed joints, thus increasing the degree of freedom for application as a touch panel. Specifically, since the touch panel of the invention has the lead sections at the joints formed in an integral fashion, it can be mounted on any display device and simply connected by the lead sections, thus allowing the function of the touch panel to be easily incorporated into the display device. Also, since the lead sections at the joints are integrally formed, a panel that has been applied to one display device can be easily removed and applied to a different display device. 
         [0012]    In the touch panel of the invention, the extraction electrodes formed on at least one of the electrode members may lead out in a manner wrapping around the edges of the lead sections from the transparent conductive layer side to the transparent base side. Since the extraction electrodes formed on the opposing electrode members are facing each other they will normally be positioned on opposite sides of the lead sections, but if extraction electrodes are leading out and wrapped around to the transparent base side of the lead sections as described above, they will be able to wrap around to the same side as the lead sections of the other extraction electrodes. Having the extraction electrodes arranged on the same side of the lead sections in this manner may be advantageous for connecting external circuits and the like with the lead sections of the touch panel. 
         [0013]    The invention further provides a method for producing a touch panel, which comprises a first step of obtaining electrode members comprising a transparent conductive layer formed on a transparent base, and having a body section and lead sections formed by protrusion of the transparent base and transparent conductive layer from the edges of the body section, a second step of forming a pair of extraction electrodes on the side of the transparent conductive layer of the electrode member opposite the transparent base, so that they are situated opposing each other in the body section and each extend to the lead sections, and a third step of laying together a pair of electrode members on which extraction electrodes have been formed so that the transparent conductive layers are facing each other. 
         [0014]    This method for producing a touch panel can satisfactorily produce a touch panel according to the invention having lead sections integrally formed with the electrode members. In addition, since the electrode members are formed with pre-formed lead sections in this method, there is no need for the high temperature treatment required when a connecting FPC or the like is provided afterwards. Deterioration in the characteristics caused by treatment for connection is thus drastically reduced. 
         [0015]    In the production method of the invention, the transparent conductive layer is preferably formed by transfer or coating of a transparent conductive layer-forming material on the transparent base. This will allow a uniform transparent conductive layer to be formed more easily, and will also facilitate formation of the transparent conductive layer along the shapes of the lead sections when lead sections are provided by pre-working of the transparent base. 
         [0016]    The extraction electrodes are preferably formed by coating the extraction electrode-forming material on the side of the transparent conductive layer in the electrode member opposite the transparent base side. This will facilitate formation of the extraction electrodes in the desired shapes, and is advantageous for forming extraction electrodes that lead out through the lead sections. 
         [0017]    The extraction electrodes that lead out through the lead sections may also be formed by dipping the lead sections in the extraction electrode-forming material. This will permit formation of extraction electrodes on both sides of the lead sections in a more convenient manner, and will allow the extraction electrodes to be more easily led out to the transparent base side of the lead sections. 
         [0018]    According to the invention it is possible to provide a touch panel that exhibits high strength at joints with external circuits, and that does not require high-temperature treatment for formation of the joints, as well as a method for producing it. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is an exploded perspective view showing a touch panel according to a preferred embodiment. 
           [0020]      FIG. 2  is a schematic perspective view showing parts of the lead sections of a touch panel. 
           [0021]      FIG. 3  is a schematic perspective view showing parts of the lead sections of extraction electrodes leading out to the transparent base side. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    Preferred embodiments of the invention will now be explained with reference to the accompanying drawings. Throughout the explanation of the drawings, corresponding elements will be referred to by like reference numerals and will be explained only once. Also, the dimensional proportions depicted in the drawings are not necessarily limitative. 
         [0023]    The construction of a touch panel according to a preferred embodiment will be explained first. 
         [0024]      FIG. 1  is an exploded perspective view showing a touch panel according to the preferred embodiment. The touch panel  100  shown in  FIG. 1  has a structure wherein an upper electrode member  10  comprising a transparent conductive layer  14  laminated on a transparent base  12  and a lower electrode member  20  comprising a transparent conductive layer  24  laminated on a transparent base  22  are situated in a mutually opposing manner with their transparent conductive layers  14 ,  24  facing each other. 
         [0025]    The transparent bases  12 ,  22  are composed of a material that is transparent to visible light. As examples of the transparent bases  12 ,  22  there may be mentioned bases made of polyester resins such as polyethylene terephthalate (PET), polyolefin resins such as polyethylene and polypropylene, or polycarbonate resins, acrylic resins, norbornane-based resins (ARTON by JSR, ZEONOR by Zeon Corp., and the like), and polyethersulfone (PES). Glass may also be used instead of these resins. The material for the transparent bases  12 ,  22  is not limited to those mentioned above and may be a different type of transparent base material. 
         [0026]    If resin films are used for the transparent bases  12 ,  22 , the touch panel  100  will undergo shape deformation more easily and will have a smaller thickness and lighter weight, thus increasing the degree of design freedom for the display device in which the touch panel  100  is used. 
         [0027]    The transparent conductive layers  14 ,  24  are composed of conductive materials that are transparent to visible light, such as a transparent conductive oxides, for example. As transparent conductive oxides there may be mentioned indium oxide or indium oxide doped with one or more elements selected from among tin, zinc and tellurium, tin oxide or tin oxide doped with one or more elements selected from among antimony, zinc and fluorine, zinc oxide or zinc oxide doped with one or more elements selected from among aluminum, gallium, indium and boron, and titanium oxide doped with one or more elements selected from among niobium, molybdenum and tantalum. Conductive polymers may also be used instead of oxides. Tin-doped indium oxide (ITO) is a suitable structural material for the transparent conductive layers  14 ,  24 . The transparent conductive layers  14 ,  24  may also be layers with a structure in which powder composed of ITO or other transparent conductive particles is fixed with a resin. 
         [0028]    The upper electrode member  10  and lower electrode member  20  are attached via a spacer  50  between the transparent conductive layers  14 ,  24 . The spacer  50  is situated along the perimeter of the touch panel  100 , and is composed of an insulating resin or the like. The spacer  50  causes the upper electrode member  10  and lower electrode member  20  to be placed apart in such a manner that the transparent conductive layer  14  and transparent conductive layer  24  are not in contact in the absence of pressing force. 
         [0029]    Although the spacer  50  is provided around approximately the entire perimeter of the touch panel  100  in this embodiment, it may be provided only around part of the edges instead of the entire perimeter of the touch panel  100 , and if necessary it may even be provided in the interior. Also, while not shown, a plurality of dot spacers may be provided on the inner surface of the transparent conductive layer  14  or  24  in the interior region of the upper electrode member  10  or lower electrode member  20 . 
         [0030]    The upper electrode member  10  has a form comprising a rectangular body section  10   a  and two lead sections  10   b  formed on one side of the body section  10   a . The two lead sections  10   b  are formed by protrusion of the transparent base  12  and transparent conductive layer  14  from the body section  10   a  in the direction perpendicular to the side of the electrode member  10 , and more specifically to the direction of lamination of the transparent base  12  and transparent conductive layer  14 , and they are integral with the body section  10   a.    
         [0031]    Similarly, the lower electrode member  20  also has a rectangular body section  20   a  and two lead sections  20   b  formed by the transparent base  22  and transparent conductive layer  24  protruding from one side of the body section  20   a . The two lead sections  10   b  of the upper electrode member  10  and the two lead sections  20   b  of the lower electrode member  20  are formed so as to lead out from the same side of the touch panel  100 . The lead section  10   b  and lead section  20   b  have an alternate placement so that they do not overlap. 
         [0032]    A pair of extraction electrodes  30  composed of a conducting material such as a metal (for example, Ag) are provided on the inner surface of the transparent conductive layer  14  in the upper electrode member  10 . The pair of extraction electrodes  30  are formed in the body section  10   a  parallel along a pair of opposing sides of the touch panel  100 . The pair of extraction electrodes  30  also have lead wires  30   a  that extend from the parallel formed sections to the lead sections  10   b.    
         [0033]    The pair of extraction electrodes  30  lead out to different lead sections  10   b . That is, the extraction electrode  30  near the lead sections  10   b  has a lead wire  30   a  formed protruding from its side, extending from the body section  10   a  to a lead section  10   b . Also, the extraction electrode  30  far from the lead sections  10   b  has a lead wire  30   a  formed running around the area near the edges of the body section  10   a  and extending to the other lead section  10   b.    
         [0034]    A pair of extraction electrodes  40  are also formed on the inner surface of the transparent conductive layer  24  of the lower electrode member  20 , similar to the upper electrode member  10 . The pair of extraction electrodes  40  are formed in the body section  20   a  parallel along a different pair of opposing sides of the touch panel  100  than the extraction electrodes  30  of the upper electrode member  10 . That is, the sections of the extraction electrodes  30  and the extraction electrodes  40  formed parallel to the body sections  10   a ,  20   a  are in a positional relationship with mutually crossing, and preferably orthogonal, directions. 
         [0035]    The pair of extraction electrodes  40  of the lower electrode member  20 , as well, each have lead wires  40   a  extending from the sections parallel to the body section  20   a  to the lead sections  20   b , and running around the area near the edges of the body section  20   a  if necessary. The pair of extraction electrodes  40  lead out to different lead sections  20   b  by their respective lead wires  40   a.    
         [0036]      FIG. 2  is a schematic perspective view showing part of the lead sections of a touch panel. The spacer  50  is not shown in  FIG. 2  for simplicity. 
         [0037]    In the touch panel  100  shown in  FIG. 2 , the lead sections  10   b  where the extraction electrodes  30  lead out and the lead sections  20   b  where the extraction electrodes  40  lead out are bent so that their tips are situated on the same plane. A single terminal is thus formed by the two lead sections  10   b  and the two lead sections  20   b . This facilitates connection of an external circuit or the like for the touch panel  100 . 
         [0038]    When a touch panel  100  having such a construction is used, the upper electrode member  10  and lower electrode member  20  function as a movable side and a fixed side, respectively, and the touch panel  100  may be placed on a display device so that the movable upper electrode member  10  is on the surface. In the normal state of the touch panel  100 , the upper electrode member  10  and lower electrode member  20  are not in contact and no current flows between them. 
         [0039]    When the movable upper electrode member  10  is pressed during use, however, the transparent conductive layers  14 ,  24  of both electrode members  10 ,  20  contact at that section and current flow takes place there. In this state, the voltage between the pair of extraction electrodes  30  formed on the upper electrode member  10  or between the pair of extraction electrodes  40  formed on the lower electrode member  20  is detected at the electrode to which the voltage has been applied. This detected voltage value can be used to determine the distance from the pair of extraction electrodes  30 ,  40  that are parallel in the body sections  10   a ,  20   a  to the location where electrification has occurred. The pressing location can thus be identified. 
         [0040]    The lead sections  10   b ,  20   b , where the extraction electrodes  30 ,  40  lead out, protrude from the body sections  10   a ,  20   a  of the touch panel  100 , collectively forming a terminal. The touch panel  100  can therefore be connected externally by this terminal, thus eliminating the need for separate connection with an FPC as in the prior art. Such voltage data can therefore be easily extracted from the touch panel  100 , so that a touch panel function can be more easily imparted to any display device. 
         [0041]    A preferred method for producing a touch panel  100  having the structure described above will now be explained. 
         [0042]    First, an upper electrode member  10  and a lower electrode member  20  are each prepared for production of the touch panel  100 . Since they can be formed in the same manner, the upper electrode member  10  alone will be described as an example. 
         [0043]    The upper electrode member  10  can be obtained by preparing a transparent base  12  and forming a transparent conductive layer  14  on it. Formation of the transparent conductive layer  14  on the transparent base  12  may be accomplished as appropriate depending on the structural material of the transparent conductive layer  14 . For example, an ITO layer may be formed by a physical build-up method such as vapor deposition or sputtering. Alternatively, a layer (sheet) made of ITO or the like may be pre-formed and transferred onto the transparent base  12 . For a layer having transparent conductive particles fixed in the resin, the layer may be formed by dispersing the particles in a solvent, directly coating the solution onto the transparent base  12  by a prescribed method, and drying. For formation of a transparent conductive layer  14  composed of a conductive polymer, the conductive polymer is preferably coated onto the transparent base  12  and dried by some method, as mentioned above. 
         [0044]    The upper electrode member  10  also comprises a body section  10   a  and lead sections  10   b , as above. The upper electrode member  10  with this shape can be obtained by forming the transparent conductive layer  14  on the transparent base  12  and then cutting it to the required shape. After the transparent base  12  has been cut to the shape corresponding to the body section  10   a  and lead sections  10   b , the transparent conductive layer  14  may be formed on its surface. In this case, the transparent conductive layer  14  can be easily matched to the shape of the transparent base  12  by forming the material for the transparent conductive layer  14  onto the transparent base  12  using a method of transfer or coating. An upper electrode member  10  comprising the integrally formed body section  10   a  and lead sections  10   b  can thus be obtained. 
         [0045]    Either or both the upper/lower electrode members  10 ,  20  may have dot spacers provided on their transparent conductive layers  14 ,  24  if necessary. A dot spacer is formed from a photocuring resin, by placing the resin at a prescribed location and curing it with light, for example. 
         [0046]    Next, extraction electrodes  30 ,  40  having prescribed patterns are formed on the respective surfaces of the transparent conductive layers  14 ,  24 . The extraction electrodes  30 ,  40  can also be formed by appropriate methods depending on their structural materials. The extraction electrodes  30 ,  40  are most preferably formed by coating the material for the extraction electrodes, such as conductive paste, by a printing method such as screen printing, and then drying it. 
         [0047]    Coating in this manner will allow the conductive paste to easily adopt the prescribed shape. It is therefore advantageous for forming extraction electrodes  30 ,  40  with complex shapes with the lead wires  30   a ,  30   b . The conductive paste used may be a mixture of a material such as the metal for the extraction electrodes  30 ,  40 , with a binder or solvent. 
         [0048]    After the attachment described below, an adhesive spacer  50  is situated on either or both the upper/lower electrode members  10 ,  20  on which the extraction electrodes  30 ,  40  have been formed. The adhesive is formed on the transparent conductive layer  14  or  24  of the upper electrode member  10  or lower electrode member  20 , in such a manner that the desired spacer  50  shape is obtained. The adhesive is preferably formed by coating with a dispenser or by screen printing, and it may be dried after coating if necessary. The adhesive for the spacer  50  may be provided on both the upper and lower electrode members  10 ,  20 , and it may be formed separately so that the spacer  50  as a whole is formed following the shapes of the extraction electrodes  30 ,  40 . 
         [0049]    The upper electrode member  10  and lower electrode member  20 , on which the extraction electrodes  30 ,  40  and the adhesive for the spacer  50  have been formed in the manner described above, are placed together with their transparent conductive layers  14 ,  24  facing each other and are attached via the adhesive. The upper electrode member  10  and lower electrode member  20  are placed so that the extraction electrodes  30 ,  40  are in the prescribed positional relationship mentioned above (the directions of the body sections are perpendicular). Such attachment by itself allows the adhesive to function as the spacer  50 , but if necessary the adhesive may be dried or cured as well. A touch panel  100  having the construction described above is thus obtained. 
         [0050]    Preferred embodiments of the touch panel and method for producing it were described above, but the invention is not necessarily limited to these embodiments and may be appropriately modified within ranges that still maintain the gist of the invention. 
         [0051]    For example, the extraction electrodes  30 ,  40  in the embodiment described above were described as leading out only on one side of the respective lead sections  10   b ,  20   b  (the transparent conductive layer  14 ,  24  sides). Therefore, when the lead sections  10   b  and lead sections  20   b  are combined as a single terminal, the extraction electrodes  30  and extraction electrodes  40  are on opposite sides (see  FIG. 2 ). As an alternative for the invention, however, at least one pair of extraction electrodes  30 ,  40  may lead out in the lead sections  10   b ,  20   b  from the transparent conductive layer  14 ,  24  side to the transparent base  12 ,  22  side, by wrapping around the edges of the lead sections  10   b ,  20   b.    
         [0052]      FIG. 3  is a schematic perspective view showing parts of the lead sections of extraction electrodes leading out to the transparent base side. The lead sections  10   b ,  20   b  shown in  FIG. 3  are entirely covered by the extraction electrodes  30  (lead wire  30   a ),  40  (lead wire  40   a ). The extraction electrodes  30 ,  40  lead out around the lead sections  10   b ,  20   b  so that they cover their surfaces not only on the transparent conductive layer  14 ,  24  sides but also the transparent base  12 ,  22  sides. With this construction it is possible to connect both the extraction electrodes  30 ,  40  on the same side when the lead sections  10   b  and  20   b  are combined as a single terminal. External connection by the lead sections  10   b ,  20   b  can often be facilitated as a result. 
         [0053]    The lead sections  10   b ,  20   b  having this construction can be formed by dipping the lead section  10   b ,  20   b  portions in the material for the extraction electrodes  30 ,  40 . This will allow easier formation of the extraction electrodes  30 ,  40  covering the entirety of the lead sections  10   b ,  20   b.    
         [0054]    With dipping, the extraction electrodes  30 ,  40  at the body section  10   a ,  20   b  portions can be formed by the coating described above. Also, when the extraction electrodes  30 ,  40  of the body sections  10   a ,  20   a  are formed by coating, they may be led out to at least parts of the lead sections  10   b ,  20   b . This will permit more satisfactory electrical connection between the extraction electrodes  30 ,  40  formed on the body sections  10   a ,  20   a  and the extraction electrodes  30 ,  40  formed covering the lead sections  10   b ,  20   b.    
         [0055]    The method for forming the extraction electrodes  30 ,  40  up to the transparent base  12 ,  22  sides of the lead sections  10   b ,  20   b  is not limited to dipping. For example, simple application can be used to form the extraction electrodes  30 ,  40  so that they wrap around the lead sections  10   b ,  20   b . Also, in cases where the extraction electrodes  30 ,  40  are to wrap around from the transparent conductive layer  14 ,  24  sides to the transparent base  12 ,  22  sides, instead of covering the entirety of the lead sections  10   b ,  20   b  with the extraction electrodes  30 ,  40  as described above, the extraction electrodes  30 ,  40  that are already leading straight out as shown in  FIGS. 1 and 2  may continue to the opposite side by wrapping around the sides (edges) of the lead sections  10   b ,  20   b.    
         [0056]    Also, while the upper electrode member  10  and lower electrode member  20  each had two lead sections  10   b  and lead sections  20   b  in the embodiment described above, this is not restrictive and the number of lead sections formed on each electrode member may be 1, or 3 or more, depending on the number of electrodes required to lead out from the body section. Also, two or more extraction electrodes may lead out from a single lead section. When many lead sections are present in the electrode members, extraction electrodes may not be leading out to some of the lead sections. 
         [0057]    Also, while all of the lead sections  10   b ,  20   b  were formed protruding from the same side of the touch panel  100  for this embodiment, this is not restrictive and several lead sections may be provided on different sides of the touch panel, depending on the manner in which the touch panel is to be connected.