Abstract:
A touch panel includes a first and a second transparent substrates, a first and a second signal lines, a first polymeric conductive film, and a first and a second non-polymeric conductive films. The first signal line is formed on the first transparent substrate, the first polymeric conductive film is formed on the first transparent substrate, and the first non-polymeric conductive film is formed on the first polymeric conductive film. The second signal line is provided on the second transparent substrate, and the second non-polymeric conductive film is provided on the second transparent substrate.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims benefit of U.S. provisional application No. 61/031,408 filed on Feb. 26, 2008 under 35 U.S.C. § 119(e); the entire contents of which are hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a touch panel, particularly to a touch panel having transparent conductive films with excellent physical characteristics. 
         [0004]    2. Description of the Related Art 
         [0005]      FIG. 1  shows a schematic diagram of a conventional touch panel  100 . Referring to  FIG. 1 , the touch panel  100  includes a top electrode substrate  102  and a bottom electrode substrate  104  facing to each other. The top electrode substrate  102  includes a transparent substrate  110 , an ITO conductive film  112  formed on the transparent substrate  110 , and signal transmission lines  114 . The bottom electrode substrate  104  includes a transparent substrate  120 , an ITO conductive film  122  formed on the transparent substrate  120 , and signal transmission lines  124 . The top electrode substrate  102  and the bottom electrode substrate  104  are connected with each other by an adhesive AH. 
         [0006]    In the conventional design shown in  FIG. 1 , the ITO conductive films  112  and  122  are deposited on the transparent substrates  110  and  120 , respectively, through vacuum coating, and thus they are stably fabricated and have high electrical conductivity. However, under a critical condition where surface resistivity reaches 500 ohm, its bearable number of times for drawing a line on a touch screen is not allowed to exceed 50,000 to result in a comparatively limited operation life. Further, the ITO conductive films  112  and  122  each have a high refraction index and are liable to reflect incoming light to result in a light yellow screen color. The light yellow screen color may cause a shift in the color tone of a displayed image. Besides, the ITO conductive films  112  and  122  are prone to crack upon bending due to their inferior flexibility to sharply raise electrical resistances. 
         [0007]      FIG. 2  shows a schematic diagram of another conventional touch panel  200 . Referring to  FIG. 2 , the touch panel  200  includes a top electrode substrate  202  and a bottom electrode substrate  204  facing to each other. The top electrode substrate  202  includes a transparent substrate  210 , a polymeric conductive film  212  formed on the transparent substrate  210 , and signal transmission lines  214 . The bottom electrode substrate  204  includes a transparent substrate  220 , an ITO conductive film  222  formed on the transparent substrate  220 , and signal transmission lines  224 . The top electrode substrate  202  and the bottom electrode substrate  204  are connected with each other by an adhesive AH. 
         [0008]    In the conventional design shown in  FIG. 2 , the polymeric conductive film  212  formed on the transparent substrate  210  has competent flexibility to avoid crack and is not naturally light yellow thus not to influence the color tone of a displayed image. Besides, the polymeric conductive film  212  is deposited on the transparent substrate  210  at normal pressure to allow for comparatively low fabrication costs. However, the polymeric conductive film  212  has inferior electrical conductivity and high surface resistivity, which often cause inferior reliability and a drift to the linear response when one draws a line on the touch screen. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The invention relates to a touch panel capable of overcoming the disadvantages of conventional designs. 
         [0010]    According to an embodiment of the invention, a touch panel includes a first and a second transparent substrates, a first and a second signal lines, a first polymeric conductive film, a first non-polymeric conductive film, a second non-polymeric conductive film, and a plurality of insulating spacers. The first signal line is formed on the first transparent substrate, the first polymeric conductive film is formed on the first transparent substrate, and the first non-polymeric conductive film is formed on the first polymeric conductive film. The second signal line is provided on the second transparent substrate, the second non-polymeric conductive film is provided on the second transparent substrate, and the insulating spacers are provided between the first transparent substrate and the second transparent substrate. 
         [0011]    In one embodiment, a second polymeric conductive film is further provided between the second transparent substrate and the second non-polymeric conductive film. 
         [0012]    In one embodiment, the polymeric conductive film is made of a PEDOT/PSS conductive polymer, an unsaturated conjugate conductive polymer, a sulfur-containing conductive polymer, or an amine-containing conductive polymer. 
         [0013]    In one embodiment, the polymeric conductive film is made of a conductive polymer composite, and the conductive polymer composite is a PEDOT/PSS conductive polymer doped with inorganic conductive material, an unsaturated conjugate conductive polymer doped with inorganic conductive material, a sulfur-containing conductive polymer doped with inorganic conductive material, or an amine-containing conductive polymer doped with inorganic conductive material. 
         [0014]    In one embodiment, the polymeric conductive film is made of a conductive polymer composite, and the conductive polymer composite is made of a PEDOT/PSS conductive polymer doped with a carbon compound, an unsaturated conjugate conductive polymer doped with a carbon compound, a sulfur-containing conductive polymer doped with a carbon compound, or an amine-containing conductive polymer doped with a carbon compound. 
         [0015]    In one embodiment, the non-polymeric conductive film is made of a metallic oxide material such as ITO, IZO, GZO, AZO, or ZnO. 
         [0016]    According to the above embodiments, a transparent conductive composite that includes both a polymeric conductive film and a non-polymeric conductive film serves as a conductive layer for the touch screen of a touch panel. Hence, on one hand, the non-polymeric conductive film allows to improve electrical conductivity and reduce surface resistivity, with these characteristics being inherently inferior in a polymeric conductive film, to avoid a drift to the linear response when one draws a line on the touch screen of a touch panel. On the other hand, even the non-polymeric conductive film splits or cracks through repetitive drawing, the polymeric conductive film that has competent flexibility allows to maintain electrical conduction and thus increase the bearable number of times for drawing a line on a touch screen. 
         [0017]    Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  shows a schematic diagram of a conventional touch panel. 
           [0019]      FIG. 2  shows a schematic diagram of another conventional touch panel. 
           [0020]      FIG. 3  shows a schematic diagram of a touch panel according to an embodiment of the invention. 
           [0021]      FIG. 4  shows a schematic diagram of a touch panel according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” etc., is used with reference to the orientation of the Figure(s) being described. The components of the present invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. On the other hand, the drawings are only schematic and the sizes of components may be exaggerated for clarity. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. Similarly, “adjacent to” and variations thereof herein are used broadly and encompass directly and indirectly “adjacent to”. Therefore, the description of “A” component “adjacent to” “B” component herein may contain the situations that “A” component directly faces “B” component or one or more additional components are between “A” component and “B” component. Also, the description of “A” component “adjacent to” “B” component herein may contain the situations that “A” component is directly “adjacent to” “B” component or one or more additional components are between “A” component and “B” component. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
         [0023]      FIG. 3  shows a schematic diagram of a touch panel  10  according to an embodiment of the invention. Referring to  FIG. 3 , the touch panel  10  includes a top electrode substrate  12  and a bottom electrode substrate  14 . The top electrode substrate  12  includes a transparent substrate  20 , a polymeric conductive film  22  formed on the transparent substrate  20 , and a non-polymeric conductive film  24  formed on the polymeric conductive film  22 . The non-polymeric conductive film  24  substantially overlaps a touch screen of the touch panel  10 . At least one signal transmission line  26  is formed on the periphery of the polymeric conductive film  22  and is insulated by an insulating layer  28 . 
         [0024]    The bottom electrode substrate  14  includes a transparent substrate  30 , a non-polymeric conductive film  32  formed on the transparent substrate  30 , and at least one signal transmission line  36 . The signal transmission line  36  is formed on the periphery of the non-polymeric conductive film  32  and is insulated by an insulating layer  38 . The top electrode substrate  12  and the bottom electrode substrate  14  are connected with each other through an adhesive AH, and multiple insulating spacers  34  are provided on the non-polymeric conductive film  32  to maintain a gap between the top electrode substrate  12  and the bottom electrode substrate  14 . The transparent substrates  20  and  30  may be made of polycarbonate (PC) plastic, polystyrene (PS) plastic, polyethylene terephthalate (PET) plastic, glass, or a polymer/inorganics composite such as a composite formed by adding SiO 2  into polycarbonate plastic or polyethylene terephthalate plastic. In one embodiment, the polymeric conductive film  22  is made of a PEDOT/PSS conductive polymer, an unsaturated conjugate conductive polymer, a sulfur-containing conductive polymer, or an amine-containing conductive polymer. In an alternate embodiment, the polymeric conductive film  22  is made of a conductive polymer composite, and the conductive polymer composite may be a PEDOT/PSS conductive polymer doped with inorganic conductive material (such as a conductive metal), an unsaturated conjugate conductive polymer doped with inorganic conductive material, a sulfur-containing conductive polymer doped with inorganic conductive material, or an amine-containing conductive polymer doped with inorganic conductive material. In an alternate embodiment, the polymeric conductive film  22  is made of another conductive polymer composite, and the conductive polymer composite may be made of a PEDOT/PSS conductive polymer doped with a carbon compound, an unsaturated conjugate conductive polymer doped with a carbon compound, a sulfur-containing conductive polymer doped with a carbon compound, or an amine-containing conductive polymer doped with a carbon compound. The carbon compound may be made from a carbon nanotube, a carbon fiber, or a bamboo charcoal. Further, in one embodiment, the non-polymeric conductive film  32  is made of metallic oxide such as ITO, IZO, GZO, AZO, or ZnO. Further, the metallic oxide may be sputtered on the polymeric conductive film  22 , and the adhesive AH may be a pressure sensitive adhesive. 
         [0025]      FIG. 4  shows a schematic diagram of a touch panel  40  according to another embodiment of the invention. This embodiment is similar to the embodiment shown in  FIG. 3 , except each of a top electrode substrate  42  and a bottom electrode substrate  44  have a polymeric conductive film and a non-polymeric conductive film. Referring to  FIG. 4 , in the top electrode substrate  42 , a polymeric conductive film  52  is formed on one surface of a transparent substrate  50  facing the bottom electrode substrate  44 , and a non-polymeric conductive film is formed on an entire surface of the polymeric conductive film  52 . In the bottom electrode substrate  44 , a polymeric conductive film  62  is formed on the transparent substrate  60 , and a non-polymeric conductive film  64  is formed on an entire surface of the polymeric conductive film  62 . 
         [0026]    According to the above embodiments, a transparent conductive composite that includes both a polymeric conductive film and a non-polymeric conductive film serves as a conductive layer for the touch screen of a touch panel. Hence, on one hand, the non-polymeric conductive film allows to improve electrical conductivity and reduce surface resistivity, with these characteristics being inherently inferior in a polymeric conductive film, to avoid a drift to the linear response when one draws a line on the touch screen of a touch panel. On the other hand, even the non-polymeric conductive film splits or cracks through repetitive drawing, the polymeric conductive film that has competent flexibility allows to maintain electrical conduction and thus increase the bearable number of times for drawing a line on a touch screen. According to the result of an experiment performed by the inventor, the touch panel in each of the above embodiments may endure 100,000 times of line drawing and not crack or bend even 130,000 times of line drawing is performed. Further, the natural light blue color of the polymeric conductive film may compensate the light yellow screen color of a touch panel to provide fine color tone. 
         [0027]    The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. Therefore, the term “the invention”, “the present invention” or the like does not necessarily limit the claim scope to a specific embodiment, and the reference to particularly preferred exemplary embodiments of the invention does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is limited only by the spirit and scope of the appended claims. The abstract of the disclosure is provided to comply with the rules requiring an abstract, which will allow a searcher to quickly ascertain the subject matter of the technical disclosure of any patent issued from this disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Any advantages and benefits described may not apply to all embodiments of the invention. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims. Moreover, no element and component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.