Patent Publication Number: US-2004051699-A1

Title: Transparent touch panel and method of manufacturing the touch panel

Description:
TECHNICAL FIELD  
       [0001] The present invention relates to a transparent touch panel used for switching the operation in various kinds of electronic apparatus, and a method for manufacturing the transparent touch panel.  
       BACKGROUND ART  
       [0002] The function of recent electronic apparatus has become diversified and more sophisticated. An increasing number of such electronic apparatus employs a transparent touch panel (hereinafter referred to as TTP) in the front of an LCD or the like display devices disposed in the apparatus as means for switching the operation. An operator viewing a display screen through a TTP can switch operation of the apparatus by selecting one of items among the letters, symbols or pictograms shown in the screen representing respective functions and designating a desired function through the TTP. A conventional TTP used for the purpose is described in the following with reference to the drawings in FIG. 4 through FIG. 6. FIG. 4 shows plan view of a conventional TTP. FIG. 5A and FIG. 5B show plan view of upper substrate and that of lower substrate, respectively, of a conventional TTP. Referring to FIG. 5A, the upper substrate  1  is made with a transparent film such as polyethylene terephthalate(PET), polycarbonate(PC), etc. A transparent upper conductive layer  2  is provided on the reverse surface of the transparent film. Transparent conductive layer  2  is formed of a transparent indium oxide-tin oxide, or the like metal oxide through vacuum deposition, sputtering or the like method.  
       [0003] A pair of upper electrodes  3  and  4  are formed by printing a conductive paste of silver, carbon, etc. As shown in FIG. 5A, the upper electrodes  3  and  4  are provided at both sides of upper conductive layer  2 ; by first removing the upper conductive layer  2  selectively by means of etching or laser beam cutting, and then the upper electrode is formed stretching in the removed lane on upper substrate  1 . Respective ends of the upper electrodes form upper lead-out sections  3 A and  4 A.  
       [0004] Referring to FIG. 5B, a transparent lower conductive layer  6  is formed in the same manner as the upper conductive layer  2 , on the upper surface of a transparent lower substrate  5  made of glass, acrylic resin, PC resin, etc. A pair of lower electrodes  7  and  8  are formed along the both sides of lower conductive layer  6  in the direction perpendicular to upper electrodes  3 ,  4  of upper conductive layer  2 . Respective ends of the lower electrodes form lower lead-out sections  7 A and  8 A. A plurality of dot spacers (not shown in the drawing) is provided at a regular interval on the upper surface of lower conductive layer  6 , for the purpose of maintaining a certain specific clearance with respect to the upper conductive layer  2 . The dot spacers are made of epoxy resin, silicone resin or the like insulating resin.  
       [0005] Upper substrate  1  and lower substrate  5  are attached together at the outer circumference using a frame-shaped spacer  9  which has an adhesive on both of the upper and lower surfaces, as shown in FIG. 4. Thus, the upper conductive layer  2  and the lower conductive layer  6  are disposed opposing to each other with a certain specific gap. In the lead-out sections of upper substrate  1  and lower substrate  5 , there is a wiring substrate  10  having a plurality of wiring patterns on the lower surface sandwiched by the substrates.  
       [0006] Referring to FIG. 6, an anisotropic conductive adhesive  11  is applied in the space formed by respective lead-out sections of upper and lower substrates  1 ,  5  and the wiring pattern of wiring board  10 . Upper lead-out sections  3 A and  4 A of upper substrate  1  are connected respectively to wiring patterns  12 A and  13 A disposed on the upper surface of wiring substrate  10 .  
       [0007] The wiring patterns  12 A,  13 A are connected via through holes filled with a conductive agent to wiring patterns  12 ,  13  disposed on the lower surface. Lower lead-out sections  7 A,  8 A of lower substrate  5  are connected to wiring patterns  14 ,  15  disposed on the lower surface of wiring substrate  10  by the anisotropic conductive adhesive  11 . In the above-configured TTP, each of the wiring patterns of wiring substrate  10  is connected with a detection circuit of an electronic apparatus via a connector or other connecting means. When upper substrate  1  is pressed from the above at a certain location with a finger tip, pen, etc., the upper substrate  1  bends, and upper conductive layer  2  makes contact with lower conductive layer  6  at the location. The pressed location is identified at the detection circuit, based on the respective resistance ratio between upper electrodes  3 ,  4  and lower electrodes  7 ,  8 .  
       [0008] In a conventional TTP as described in the above, a wiring substrate  10  is disposed between upper substrate  1  and lower substrate  5 , and three constituent parts, viz. the upper and lower lead-out sections and both surfaces of the wiring patterns, need to be assembled after they are precisely aligned with each other. Therefore, the operating productivity is low, and it takes a long time for the assembly.  
       [0009] The wiring substrate  10 , in which the wiring patterns  12 A,  13 A disposed on the upper surface are connected with the wiring patterns  12 ,  13  on the reverse surface via through holes, is expensive. Furthermore, when heating anisotropic conductive adhesive  11  for implementing a connection, the stacked structure of three constituent components, viz. upper substrate  1 , lower substrate  5  and wiring substrate  10 , readily causes a temperature difference within the stacked structure, which leads to a dispersion in the strength of adhesion and connection.  
       DISCLOSURE OF INVENTION  
       [0010] Addressing the above-described problems, the present invention offers a transparent touch panel having the following structure.  
       [0011] A transparent touch panel which comprises a transparent upper substrate having on the reverse surface a transparent upper conductive layer and an upper electrode extending along both sides of the upper conductive layer, extension of which electrodes forming a pair of upper lead-out sections at an end; a transparent lower substrate having on the upper surface a transparent lower conductive layer opposing to the upper conductive layer with a certain specific clearance and a lower electrode extending along both sides of the lower conductive layer in the direction perpendicular to the upper conductive layer, extension of which electrodes forming a pair of lower lead-out sections at an end; and a wiring substrate provided with a plurality of wiring patterns disposed on the reverse surface, which wiring patterns being glued and connected with the upper substrate or the lower substrate with an anisotropic conductive adhesive. In which touch panel, the lower substrate is provided with a pair of connection electrodes opposing to the upper lead-out sections; the connection electrodes being glued and connected at one end to the upper lead-out sections, while the other end of the connection electrodes and the lower lead-out sections to the wiring patterns of the wiring substrate. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012]FIG. 1 shows plan view of a TTP in accordance with an exemplary embodiment of the present invention.  
     [0013]FIG. 2A shows plan view of upper substrate of a TTP in accordance with an exemplary embodiment of the present invention.  
     [0014]FIG. 2B shows plan view of lower substrate of a TTP in accordance with an exemplary embodiment of the present invention.  
     [0015]FIG. 3 shows cross sectional view of a TTP in accordance with an exemplary embodiment of the present invention.  
     [0016]FIG. 4 shows plan view of a conventional TTP.  
     [0017]FIG. 5A shows plan view of upper substrate of a conventional TTP.  
     [0018]FIG. 5B shows plan view of lower substrate of a conventional TTP.  
     [0019]FIG. 6 shows cross sectional view of a conventional TTP. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
     [0020] Exemplary embodiment of the present invention is described with reference to the drawings, FIG. 1 through FIG. 3. In the drawings, those portions having the same structure as those in the conventional technologies are represented by using the same symbols, and the description on which portions will be simplified. The drawings are intended to offer the concepts of invention, they do not illustrate actual positions and dimensions.  
     [0021] (Exemplary Embodiment)  
     [0022] Referring to FIG. 1, an upper substrate  21  is made of a transparent film of PET, PC or the like material having an approximate thickness of 150-200 μm. On the reverse surface of which substrate, a transparent upper conductive layer  2  is provided by sputtering a material of an indium oxide-tin oxide system. Besides the above material, metals such as gold, silver, platinum, palladium, rhodium, etc., and metal oxides such as tin oxide, indium oxide, antimony oxide, etc. can be used as a material for the transparent conductive layer. The pair of upper electrodes  23 ,  24  is formed by printing a conductive paste of silver, carbon, etc.  
     [0023] Upper electrodes  23 ,  24  are provided by first removing the upper conductive layer  2  selectively at both sides by means of etching or laser beam cutting, and then the electrodes are formed extending in the removed lanes on the upper substrate  21 , as shown in FIG. 2A. Extension of which electrodes form a pair of upper lead-out sections  23 A and  24 A at an end.  
     [0024] As shown in FIG. 2B, a transparent lower substrate  25  made of glass, acrylic resin, PC resin, etc. is provided, in the same manner as the upper conductive layer  2 , with a transparent lower conductive layer  6  formed on the upper surface. A pair of lower electrodes  27 ,  28  is provided extending from both sides of lower conductive layer  6 , which sides being perpendicular to the upper electrodes  23 ,  24  of upper conductive layer  2 . Extension of which electrodes form a pair of lower lead-out sections  27 A and  28 A at an end.  
     [0025] Next, a pair of connection electrodes  29 ,  30  is provided on lower substrate  25  by printing a conductive paste of silver, carbon, etc., which connection electrodes being independent of the lower electrodes  27 ,  28 . The respective connection electrodes are provided at one ends, which are opposing to upper lead-out sections  23 A,  24 A, with the left connection parts  29 A,  30 A; while the other ends, which are forming the right connection parts  29 B,  30 B, are disposed side by side with the lower lead-out sections  27 A,  28 A. A plurality of dot spacers (not shown) is provided at a certain specific interval on the upper surface of lower conductive layer  6 , for keeping a certain specific clearance against upper conductive layer  2 . The dot spacers are made of epoxy resin, silicone resin or other insulating resin. The upper substrate  21  and the lower substrate  25  are glued together at the outer circumference using a frame-shaped spacer  9  having an adhesive on both of the upper and lower surfaces, as shown in FIG. 1, so that upper conductive layer  2  and lower conductive layer  6  oppose to each other with a certain specific clearance in between.  
     [0026] Upper substrate  21  is provided with a cut  21 A for an area opposing to lower lead-out sections  27 A,  28 A and the right connection parts  29 B,  30 B. A wiring substrate  31  having a plurality of wiring patterns on the reverse surface is placed in the cut  21 A. As shown in FIG. 3, a cross sectional view, an anisotropic conductive adhesive  11  is applied in a space formed by respective lead-out sections of upper substrate  21  and lower substrate  25  and wiring patterns of wiring board  31 . Upper lead-out sections  23 A,  24 A of upper substrate  21  are glued and connected to the left connection parts  29 A,  30 A of lower substrate  25 , respectively. The anisotropic conductive adhesive  11  is produced by dispersing metal particles, metal, or conductive powder made of resin particles plated with a precious metal in a synthetic resin such as chloroprene rubber, polyester resin, epoxy resin, etc.  
     [0027] Wiring patterns  32 ,  33  disposed on the reverse surface of wiring substrate  31  are glued and connected to the right connection parts  29 B,  30 B, while wiring patterns  34 ,  35  to lower lead-out sections  27 A,  28 A, respectively.  
     [0028] A TTP in the present invention is thus structured. Respective wiring patterns of wiring substrate  31  are coupled with a detection circuit of an electronic apparatus via connector or the like means. When upper substrate  21  is pressed from the above at a certain location with a finger tip, pen, etc., the upper substrate  21  bends, and upper conductive layer  2  makes contact with lower conductive layer  6  at the location. The pressed location is identified at the detection circuit based on ratio of resistance between upper electrodes  23  and  24 , and lower electrodes  27  and  28 . Ratio of resistance between upper electrodes  23  and  24  is outputted from upper lead-out sections  23 A,  24 A via connection electrodes  29 ,  30  to wiring patterns  32 ,  33  disposed on the reverse surface of wiring substrate  31 .  
     [0029] Now in the following, a method for manufacturing the above-configured TTPs is described practically.  
     [0030] In the first place, an upper substrate  21  having on one of the surfaces a transparent upper conductive layer  2  formed through sputtering or other processes undergoes etching or laser beam cutting for selectively removing the upper conductive layer  2 . A pair of upper electrodes  23 ,  24  as well as upper lead-out sections  23 A,  24 A are formed in the removed region by printing a conductive paste of silver, carbon, etc., as illustrated in FIG. 2A. Thus an upper substrate  21  is provided. Next, in the same way as in the upper substrate, lower conductive layer  6  formed on the upper surface of lower substrate  25  is selectively removed, and then lower electrodes  27  and  28 , lower lead-out sections  27 A and  28 A, and connection electrodes  29  and  30  are provided at once by a screen printing process or the like method. Anisotropic conductive adhesive  11  is applied on the lower lead-out sections  27 A,  28 A and connection electrodes  29 ,  30  to provide a lower substrate  25  as shown in FIG. 2B. The lower substrate  25  and the upper substrate  21  are attached together by gluing the outer circumference via frame-shaped spacer  9 , so that upper lead-out sections  23 A,  24 A oppose to the left connection parts  29 A,  30 A, respectively. And then, wiring substrate  31  is placed so that the wiring patterns  32 ,  33  are on the right connection parts  29 B,  30 B, and the wiring patterns  34 ,  35  on lower lead-out sections  27 A,  28 A, respectively. As the final step, upper lead-out sections  23 A,  24 A of upper substrate  21 , and wiring patterns of wiring substrate  31  disposed in the cut  21 A of upper substrate  21  are heat-pressed altogether. The upper lead-out sections  23 A,  24 A are glued and connected to the left connection parts  29 A,  30 A, the wiring patterns  32 ,  33 ,  34  and  35  to the right connection parts  29 B,  30 B and lower lead-out sections  27 A,  28 A, respectively, by the anisotropic conductive adhesive  11  to provide a finished TTP as shown in FIG. 1.  
     [0031] As described in the above, a lower substrate  25  in the present embodiment is provided with a pair of connection electrodes  29 ,  30  in an area opposing to upper lead-out sections  23 A,  24 A. One end of the connection electrodes  29 ,  30 , or the left connection parts  29 A,  30 A, are glued and connected to upper lead-out sections  23 A,  24 A, while the other end, or the right connection parts  29 B,  30 B, and lower lead-out sections  27 A,  28 A are glued and connected to wiring patterns  32 ,  33 ,  34  and  35 , respectively, for forming a TTP. Namely, each part of the total structures of the TTP is formed of integration of two constituent components; namely, upper substrate  21  and lower substrate  25 , and wiring substrate  31  and lower substrate  25 . This structure results in an easy location aligning between the components, rendering the assembly operation easier and simpler.  
     [0032] Furthermore, since it employs a wiring board  31  that has a plurality of wiring patterns only on the reverse surface and no through hole, TTPs can be manufactured easily for a lower cost.  
     [0033] An upper substrate  21  in the present embodiment is provided with a cut  21 A in a region corresponding to lower lead-out sections  27 A,  28 A and the other end of connection electrodes, or the right connection parts  29 B,  30 B. A wiring substrate  31  is placed in the cut.  
     [0034] In the above-configured structure, there is no need of sandwiching a wiring substrate  31  between upper substrate  21  and lower substrate  25 . This further makes the assembly operation easier.  
     [0035] Furthermore, the gluing and connecting with heat and pressure in the present embodiment is conducted between two component items, viz. between upper substrate  21  and lower substrate  25 , and between wiring substrate  31  and lower substrate  25 . As a result, the temperature can be kept even among the components, and a stable gluing and connecting is implemented with the anisotropic conductive adhesive.  
     [0036] Furthermore, since the gluing and connecting operation in the present embodiment is carried out by placing wiring substrate  31  and upper substrate  21  on lower substrate  25  and then heat-pressing the upper and lower lead-out sections, connection electrodes and wiring patterns altogether with an anisotropic conductive adhesive  11 , inexpensive TTPs can be manufactured with ease.  
     [0037] In addition, a reinforcement layer may be provided by applying an adhesive agent for reinforcement in the vicinity of the gluing and connecting area, on at least one of the upper substrate  21  and the lower substrate  25 , or the wiring substrate  31  and the lower substrate  25 . When a wiring substrate  31  is connected with a connector the wiring substrate may be affected by an external force; the reinforcement layer is advantageous in protecting it from the external force and enhancing the connecting strength. Although the above descriptions have been based on a lower substrate  25  which is made of a glass or a resin having a certain rigidity, it may be formed of a flexible film of PET, PC, etc. in the same way as in the upper substrate  21 .  
     INDUSTRIAL APPLICABILITY  
     [0038] An easy-to-assemble and inexpensive TTPs are implemented in accordance with the present invention. The present invention also discloses a method for manufacturing such TTPs.