Patent Publication Number: US-2011050623-A1

Title: Organic conductive composition and touch panel input device including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of Korean Patent Application No. 10-2009-0081505 filed on Aug. 31, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an organic conductive composition and a touch panel input device including the same, and more particularly, to an organic conductive composition which has excellent transparency and low surface resistance, and a touch panel input device including the same. 
     2. Description of the Related Art 
     Recently, as computers, various household appliances, and communications devices have been digitalized and their performances have rapidly improved, the implementation of portable displays having large screens is increasingly demanded. In order to implement portable and flexible displays with large screens, a flexible display material is required which can be folded or rolled like a sheet of paper. 
     Therefore, electrode materials for display panels should be transparent and have low resistance. Furthermore, the electrode materials should have high flexibility such that they are mechanically stable even when a device is bent or folded. Moreover, the electrode materials should have a thermal expansion coefficient similar to that of a plastic substrate such that a short circuit does not occur and a change in surface resistance is not large even when the device is overheated. 
     Flexible electrode materials make it possible to manufacture a display in an arbitrary form. Therefore, such a display can be used in a portable display device, as a clothing trademark, a billboard, a product display stand price display tag, a large-sized electric illumination system, and the like, which can change colors or patterns. Hence, the utilization rate of the flexible display is high. 
     Currently, a chemical deposition method, a magneton sputtering method, and a reactive evaporation deposition method are being actively developed both domestically and internationally as methods of fabricating a transparent electrode. In the chemical deposition method, oxides and compounds of various metals such as indium, tin, zinc, titanium, and cesium are used. However, since a state of vacuum is required to coat a substrate with a metallic oxide, the manufacturing cost inevitably increases. 
     Recently, a method using a conductive polymer has been proposed as a method by which a transparent electrode can be manufactured at a low cost. When an electrode is manufactured using a conductive polymer, a variety of existing polymer coating methods may be used. Therefore, it is possible to reduce the manufacturing cost and the required number of operations. That is, a transparent electrode formed of a conductive polymer such as polyacetylene, polypyrrole, polyaniline, or polythiopene has more advantages in a manufacturing process than a transparent indium tin oxide (ITO) electrode, when the transparent electrode is applied to the process of manufacturing a flexible display or electronic illumination system. Furthermore, since the transparent electrode is more flexible and does not break easily, it may extend the lifespan of a device such as a touch screen which requires a very flexible electrode. Despite such advantages, however, the conductive polymer absorbs visible rays, and a conductivity characteristic of an organic electrode formed of the conductive polymer increases in proportion to the thickness of the electrode. Therefore, when a conductive film is applied to a small thickness to increase transmittance, surface resistance increases. In this case, it may be difficult to apply the organic electrode to the application fields of the transparent electrode such as touch panel and flexible display. In particular, when a transparent electrode is manufactured Using Baytron P, which is water-dispersed polythiopene obtained by separating a conductive polymer into nanoparticles, in order to improve the processibility of the conductive polymer; it exhibits a surface resistance of 1 MΩ/sq at a transmittance of 85%. Consequently, it may be difficult to use the electrode as a transparent electrode for a display. 
     Therefore, there is a need for the development of a transparent electrode material having excellent transparency and low surface resistance. 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention provides an organic conductive composition which has excellent transparency and low surface resistance, and a touch panel input device including the same. 
     According to an aspect of the present invention, there is provided an organic conductive composition including: 0.01 to 70 parts by weight of one or more conductive polymers selected from the group consisting of polythiopene, polyaniline, polyacetylene, polypyrrole, polyphenylenevinylene, and derivatives thereof; 0.01 to 40 parts by weight of one or more dopants selected from the group consisting of a sulfonate compound, a boron compound, a phosphate compound, and a conductive carbon black; and 1 to 40 parts by weight of one or more binders selected from the group consisting of alkyl glycidyl ether (meta) acrylate with a carbon number of 2 to 8, phenyl glycidyl ether (meta) acrylate, (meta) acrylate, multi-functional (meta) acrylate, ultraviolet (UV) or thermally curable epoxy, urethanes, and acrylic-urethane copolymer. 
     The organic conductive composition may further include one or more viscosity control agents selected from the group consisting of modified urethane, acrylic copolymer, hydroxy ethyl cellulose, and hydroxypropyl methyl cellulose. 
     The viscosity of the organic conductive composition may be controlled by adjusting a solid content of the binder. 
     The organic conductive composition may further include one or more solvents selected from the group consisting of poly-alcohol, dimethyl sulfoxide (DMSO), N,N-dimethylformamide, ethylene glycol (EG), polyethylene glycol, meso-erythritol, aniline, acetone, methyl ethyl ketone, isopropyl alcohol, butyl alcohol, ethyl alcohol, methyl alcohol, dimethylacetamide, hexane, toluene, chloroform, cyclohexanone, distilled water, pyridine, methylnaphthalene, octadecylamine, tetrahydrofuran, dichlorobenzene, dimethylbenzene, trimethylbenzene, nitromethane, and acrylonitrile. The parts by weight of the solvent range from 2 to 95 parts by weight with respect to the entire composition. 
     According to another aspect of the present invention, there is provided a touch panel input device including: a first substrate; and a first organic conductive film formed on the first substrate and composed of an organic conductive composition, the organic conductive composition including: 0.01 to 70 parts by weight of one or more conductive polymers selected from the group consisting of polythiopene, polyaniline, polyacetylene, polypyrrole, polyphenylenevinylene, and derivatives thereof; 0.01 to 40 parts by weight of one or more dopants selected from the group consisting of a sulfonate compound, a boron compound, a phosphate compound, and a conductive carbon black; and 1 to 40 parts by weight of one or more binders selected from the group consisting of alkyl glycidyl ether (meta) acrylate with a carbon number of 2 to 8, phenyl glycidyl ether (meta) acrylate, (meta) acrylate, multi-functional (meta) acrylate, ultraviolet (UV) or thermally curable epoxy, urethanes, and acrylic-urethane copolymer. 
     The first substrate may be formed of polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylenenaphthalate (PEN), polyethersulfone (PES), or cyclo-olefin copolymer (COC). 
     The touch panel input device may further include a second substrate disposed opposite the first substrate; and a second organic conductive film formed on the second substrate. The first organic conductive film may be deformed by a touch to come into partial contact with the second organic conductive film. 
     The touch panel input device may further include a second substrate disposed opposite to the first substrate. The input device may detect a change in electrostatic capacity caused by a touch of the first substrate. 
     According to another aspect of the present invention, there is provided a method of manufacturing a touch panel input device, the method including: preparing an organic conductive composition, the organic conductive composition including 0.01 to 70 parts by weight of one or more conductive polymers selected from the group consisting of polythiopene, polyaniline, polyacetylene, polypyrrole, polyphenylenevinylene, and derivatives thereof; 0.01 to 40 parts by weight of one or more dopants selected from the group consisting of a sulfonate compound, a boron compound, a phosphate compound, and a conductive carbon black; and 1 to 40 parts by weight of one or more binders selected from the group consisting of alkyl glycidyl ether (meta) acrylate with a carbon number of 2 to 8, phenyl glycidyl ether (meta) acrylate, (meta) acrylate, multi-functional (meta) acrylate, ultraviolet (UV) or thermally curable epoxy, urethanes, and acrylic-urethane copolymer; and forming a first organic conductive film on the first substrate using the organic conductive composition. 
     The first organic conductive film may be formed by inkjet printing, screen printing, gravure printing, or offset printing. 
     The method may further include performing a surface treatment on a surface of the first substrate where the first organic conductive film is to be formed, in order to increase the surface tension of the first substrate, before forming the first organic conductive film on the first substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram illustrating a doping mechanism of poly-3,4-ethylenedioxythiophene (PEDOT) and polystyrene sulfonate; 
         FIG. 2  is a schematic cross-sectional view of a touch panel input device according to an embodiment of the present invention; and 
         FIG. 3  is a schematic cross-sectional view of a touch panel input device according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention relates to an organic conductive composition including a conductive polymer, a dopant lowering electric resistance, an acrylic binder, and a viscosity control agent. The organic conductive composition according to an embodiment of the present invention not only has excellent transparency, but also low surface resistance. Accordingly, the organic conductive composition may be suitable for use in a touch panel input device. Further, the organic conductive composition according to the embodiment of the present invention is composed of a similar material to a substrate of the input device and has a small difference in thermal expansion coefficient from the substrate. Therefore, the organic conductive composition may increase the durability of the input device. 
     Hereinafter, the respective components of the organic conductive composition will be described in detail. 
     The conductive polymer included in the organic conductive composition according to the embodiment of the present invention is not specifically limited. For example, polythiopene, polyaniline, polyacetylene, polypyrrole, polyphenylenevinylene, and derivatives thereof may be used as the conductive polymer, either in an independent or combined manner. 
     More specifically, poly3,4-ethylenedioxythiophene (hereinafter, referred to as PEDOT) expressed by following Chemical Formula I may be used as the polythiopene. 
     
       
         
         
             
             
         
       
     
     The polythiopene has high electrical conductivity and environmental affinity. The polythiopene has a disadvantage in that it is not easily dissolved. However, when the polythiopene is used with a dopant, the solubility thereof may increase. 
     The content of the conductive polymer may range from 0.01 to 70 parts by weight with respect to the entire composition. When the content is less than 0.01 parts by weight, the electrical conductivity of the organic conductive composition may decrease. Furthermore, when the content exceeds 70 parts by weight, the solubility or transparency thereof may decrease. 
     A Lewis acid capable of accepting electrons may be used as the dopant which is included in the organic conductive composition to lower electrical resistance. In the organic conductive composition according to the embodiment of the present invention, the dopant serves to increase the solubility of the conductive polymer and lower electrical resistance to improve the electrical conductivity of the organic conductive composition. 
     The dopant is not specifically limited. A sulfonate compound, a boron compound, a phosphate compound, a conductive carbon black and so on may be taken as examples of the dopant. They may be used in an independent or combined manner. 
     Polystyrene sulfonate, benzene sulfonate, alkylnaphthalene sulfonate, methane sulfonate, camphor sulfonate, naphthalene sulfonate, or para-toluene sulphonate may be taken as an example of the sulfonate compound. Tetrafluoroboron may be taken as an example of the boron compound. Hexafluoro phosphate or poly alkylenedioxythiophene may be taken as an example of the phosphate compound. 
     When the PEDOT is used as the conductive polymer and the polystyrene sulfonate is used as the dopant, the solubility of the PEDOT increases, which makes it easy to process the PEDOT in a desired form.  FIG. 1  is a diagram illustrating a doping mechanism of the PEDOT and the polystyrene sulfonate. Referring to  FIG. 1 , S atoms of thiophene in the PEDOT lose an electron to exhibit a positive charge, and the polystyrene sulfonates lose H′ to exhibit a negative charge. At this time, the conjugation between double bonds existing in the PEDOT causes an electric current to flow. 
     The content of the dopant may range from 0.01 to 40 parts by weight with respect to the entire composition. When the content is less than 0.01 parts by weight, the solubility of the conductive polymer may decrease, and the electrical resistance may increase. On the other hand, when the content exceeds 40 parts by weight, the transparency may decrease. 
     The binder included in the organic conductive composition according to the embodiment of the present invention serves to improve the viscosity of the organic conductive composition. Alkyl glycidyl ether (meta) acrylate with a carbon number of 2 to 8, phenyl glycidyl ether (meta) acrylate, (meta) acrylate, multi-functional (meta) acrylate, ultraviolet (UV) or thermally curable epoxy, urethanes, or an acrylic-urethane copolymer may be taken as an example of the binder. They may be used in an independent or combined manner. 
     The content of the binder may range from 1 to 40 parts by weight with respect to the entire composition. When the content is less than 1 part by weight, an adhesive force with a substrate may decrease. When the content exceeds 40 parts by weight, the electrical conductivity may decrease. 
     The viscosity of the organic conductive composition according to the embodiment of the present invention may be controlled by adjusting a solid content of the binder. That is, the viscosity of the organic conductive composition may be controlled depending on a printing method which is applied to a process of forming an organic conductive film. 
     For example, when the binder has a solid content of 33 to 45 wt %, the viscosity may range from 500 to 1000 mPas and is suitable for screen printing. When the binder has a solid content of 25 to 30 wt %, the viscosity may range from 50 to 300 mPas and is suitable for gravure printing. 
     Alternatively, the viscosity may be controlled using an organic viscosity control agent. 
     Modified urethane, acrylic copolymer, hydroxy ethyl cellulose, hydroxypropyl methyl cellulose and so on may be used as the viscosity control agent which may be applied to the embodiment of the present invention. They may be used independently, or two or more of them may be combined to be used. 
     The content of the viscosity control agent may range from 0 to 5 parts by weight with respect to the entire composition. When the content exceeds 30 parts by weight, the electrical conductivity may decrease. 
     A solvent included in the organic conductive composition according to the embodiment of the present invention is not specifically limited. Poly-alcohol, dimethyl sulfoxide (DMSO), N,N-dimethylformamide, ethylene glycol (EG), polyethylene glycol, meso-erythritol, aniline, acetone, methyl ethyl ketone, isopropyl alcohol, butyl alcohol, ethyl alcohol, methyl alcohol, dimethylacetamide, hexane, toluene, chloroform, cyclohexanone, distilled water, pyridine, methylnaphthalene, octadecylamine, tetrahydrofuran, dichlorobenzene, dimethylbenzene, trimethylbenzene, nitromethane, acrylonitrile and so on may be taken as examples of the solvent. They may be used independently, or two or more of them may be combined to be used. 
     The content of the solvent may range from 2 to 95 parts by weight with respect to the entire composition. The viscosity of the organic conductive composition may be properly controlled depending on the content of the solvent. 
     An organic conductive film formed of the organic conductive composition according to the embodiment of the present invention may exhibit a surface resistance of 2000 Ω/sq. or less. 
     As a result of an experiment, the surface resistance (ASTM D257) of the organic conductive film at a transparency of 83% or more had an average of 700 Ω/sq or less (as a result of five measurements). 
     Further, the elongation of the organic conductive film was measured to be 20 to 300%. The elongation of a polyethylene terephthalate (PET) film used in a touch panel input device ranges from 30 to 300% which is similar to that of the conductive film containing the organic conductive composition according to the embodiment of the present invention. 
     Since a conductive film formed of an inorganic material has a large difference in elongation from a substrate, a crack is highly likely to occur during an operation. However, since the conductive film containing the organic conductive composition according to the embodiment of the present invention has similar elongation to that of a substrate, a crack is not likely to occur. Therefore, the durability of the conductive film is expected to be excellent. Further, the conductive film containing the organic conductive composition according to the embodiment of the present invention has a thermal expansion coefficient of 30 to 60 ppm/° C. which is similar to that of a substrate (in a case of PET, 18-60 ppm/° C.). Therefore, the conductive film is not likely to be peeled off. 
     The present invention relates to a touch panel input device including a substrate and an organic conductive film formed on the substrate and containing an organic conductive composition including a conductive polymer, a dopant, and a binder. 
     The organic conductive film containing the above-described organic conductive composition may be applied to a touch panel input device requiring transparency and low surface resistance. 
     The substrate is not specifically limited as long as it is formed of a material upon which a conductive film is easy to form. Resin, glass and so on may be used as the substrate. 
     The substrate may be formed of a colored or colorless material depending on the intended use. When the substrate is provided as a display surface, a transparent material may be used. For example, PET, polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylenenaphthalate (PEN), polyethersulfone (PES), cyclo-olefin copolymer (COC) and so on may be used. 
     In this specification, the transparency includes colorless transparency, colored transparency, translucency, colored translucency and so on. 
     The conductive film is formed of the organic conductive composition including a conductive polymer, a dopant, and a binder. The specific components and contents of the organic conductive composition are as described above. 
     As described above, the organic conductive composition has excellent transparency, low surface resistance, and similar elongation and thermal expansion coefficient to that of the substrate. Accordingly, the conductive film is prevented from being peeled off from the substrate, which makes it possible to improve the durability of the touch panel input device. 
     Hereinafter, exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Like reference numerals in the drawings denote like elements, and thus their description will be omitted. 
       FIG. 2  is a schematic cross-sectional view of a touch panel input device according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the touch panel type input device according to the embodiment of the present invention includes a first substrate  11  and a first organic conductive film  12  which is formed on the first substrate  11  and composed of the above-described organic conductive composition including a conductive polymer, a dopant, and a binder. 
     Further, the input device includes a second substrate  13  disposed opposite the first substrate  11  and a second organic conductive film  14  formed on the second substrate  13 . Further, the input device includes electrodes  15  and  16  formed on the first and second organic conductive films  12  and  14 , respectively, and an insulating space  17  formed between the electrodes  15  and  16 . 
     The input device according to the embodiment of the present invention is a resistive overlay touch-panel-type input device, in which the first organic conductive film  12  is deformed by a touch to come into partial contact with the second organic conductive film  14 . In regions excluding the contact region, dot spacers  18  may be formed in order to provide electrical insulation. 
     The second substrate  13  may be formed of the same material as the first substrate  11 . Further, the second organic conductive film  14  may contain the above-described organic conductive composition. 
     Table 1 shows reflectances and light extraction efficiencies of the touch panel input device (using a PET substrate) according to this embodiment of the present invention and a touch panel input device including an indium tin oxide (ITO) film according to the related art. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Refractive 
                 Refractive 
                 Relative 
                   
                   
                 Light 
               
               
                   
                 index of 
                 index of 
                 refractive 
                 Critical 
                   
                 extraction 
               
               
                   
                 medium n 1   
                 medium n 2   
                 index n = n 2 /n 1   
                 angle θ c   
                 Reflectance 
                 efficiency [%] 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Input device 
                 PET-ITO 
                 1.66 
                 1.95 
                 1.17 
                   
                 0.0065 
                   
               
               
                 according to 
                 ITO-package air 
                 1.95 
                 1.00 
                 0.51 
                 31 
                 0.1037 
                 7 
               
               
                 related art 
                 Package air-ITO 
                 1.00 
                 1.95 
                 1.95 
                   
                 0.1037 
               
               
                   
                 ITO-PET 
                 1.95 
                 1.66 
                 0.85 
                 58 
                 0.0065 
                 18 
               
               
                   
                 PET-outside 
                 1.66 
                 1.00 
                 0.60 
                 37 
                 0.0616 
                 9 
               
               
                 Input device 
                 PET-organic 
                 1.66 
                 1.47 
                 0.89 
                 62 
                 0.0037 
                 20 
               
               
                 according to 
                 conducive film 
               
               
                 present 
                 Organic conducive 
                 1.47 
                 1.00 
                 0.68 
                 43 
                 0.0362 
                 12 
               
               
                 invention 
                 film-package air 
               
               
                   
                 Package 
                 1.00 
                 1.47 
                 1.47 
                   
                 0.0362 
               
               
                   
                 air-organic 
               
               
                   
                 conducive film 
               
               
                   
                 Organic conducive 
                 1.47 
                 1.66 
                 1.13 
                   
                 0.0037 
               
               
                   
                 film-PET 
               
               
                   
                 PET-outside 
                 1.66 
                 1.00 
                 0.60 
                 37 
                 0.0616 
                 9 
               
               
                   
               
            
           
         
       
     
     Referring to Table 1, since the conductive film according to the embodiment of the present invention has a small difference in refractive index from PET; the critical angle therebetween is large. Accordingly, it can be seen that the light extraction efficiency is excellent. 
       FIG. 3  is a schematic cross-sectional view of a touch panel input device according to another embodiment of the present invention. 
     Referring to  FIG. 3 , the touch panel input device according to the embodiment of the present invention includes a first substrate  21  and a first organic conductive film  22  which is formed on the first substrate  21  and composed of the above-described organic conductive composition including a polymer, a dopant, and a binder. 
     Further, the input device includes a second substrate  23  disposed opposite the first substrate  21  and electrodes  24  and  25  formed on the first organic conductive film  22  and the second substrate  23 , respectively. The first organic conductive film  22  and the second substrate  23  may be bonded to each other through an optical clear adhesive (OCA)  26 . The touch-panel-type input device according to this embodiment of the present invention is a capacitive touch-panel-type input device which operates as the electrodes  24  and  25  detect a change in electrostatic capacity caused by a touch of the second substrate  23 . 
     The first organic conductive film  22  may be patterned in a stripe or diamond shape unlike the resistive overlay type. 
     Table 2 shows reflectances and light extraction efficiencies of the touch panel input device (using a PET substrate) according to this embodiment of the present invention and a touch panel input device including an ITO film according to the related art. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Refractive 
                 Refractive 
                 Relative 
                   
                   
                 Light 
               
               
                   
                 index of 
                 index of 
                 refractive 
                 Critical 
                   
                 extraction 
               
               
                   
                 medium n 1   
                 medium n 2   
                 index n = n 2 /n 1   
                 angle θ c   
                 Reflectance 
                 efficiency [%] 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Input device 
                 PET-ITO 
                 1.66 
                 1.95 
                 1.17 
                   
                 0.0065 
                   
               
               
                 according to 
                 ITO-OCA 
                 1.95 
                 1.47 
                 0.75 
                 49 
                 0.0197 
                 14 
               
               
                 related art 
                 OCA-PET 
                 1.47 
                 1.66 
                 1.13 
                   
                 0.0037 
                 32 
               
               
                   
                 PET-outside 
                 1.66 
                 1.00 
                 0.60 
                 37 
                 0.0616 
                 9 
               
               
                 Input device 
                 PET-organic 
                 1.66 
                 1.47 
                 0.89 
                 62 
                 0.0037 
                 20 
               
               
                 according to 
                 conducive film 
               
               
                 present 
                 Organic conducive 
                 1.47 
                 1.47 
                 1.00 
                 90 
                 0.0000 
               
               
                 invention 
                 film-OCA 
               
               
                   
                 OCA-PET 
                 1.47 
                 1.66 
                 1.13 
                   
                 0.037 
                 32 
               
               
                   
                 PET-outside 
                 1.66 
                 1.00 
                 0.60 
                 37 
                 0.0616 
                 9 
               
               
                   
               
            
           
         
       
     
     Referring to Table 2, since the conductive film according to the embodiment of the present invention has a small difference in refractive index from PET; the critical angle therebetween is large. Accordingly, it can be seen that the light extraction efficiency is excellent. 
     Hereinafter, a method of manufacturing the touch-panel-type input device according to the embodiment of the present invention will be described. 
     First, an organic conductive composition including a conductive polymer, a dopant, and a binder is prepared. The specific components and contents of the organic conductive composition have been already described above. 
     The organic conductive composition is used to form an organic conductive film on a substrate. The process of forming the conductive film using the organic conductive composition is not specifically limited. For example, inkjet printing, screen printing, gravure printing, or offset printing may be used. 
     More specifically, the viscosity of the organic conductive composition may be properly controlled depending on the applied printing method. 
     When the conductive film is formed by the inkjet printing, the viscosity of the organic conductive composition may range from 1 to 50 mPas. When the conductive film is formed by the screen printing, the viscosity of the organic conductive composition may range from 300 to 70,000 mPas. 
     The inkjet printing or screen printing is suitable for patterning and forming a conductive film. 
     When the conductive film is formed by the gravure printing, the viscosity of the organic conductive composition may range from 10 to 300 mPas. When the conductive film is formed by the offset printing, the viscosity of the organic conductive composition may range from 10,000 to 100,000 mPas. The gravure printing may be applied to pattern printing as well as the entire printing. 
     As the viscosity of the organic conductive composition is controlled in the above-described manner, the conductive film may be formed by the printing method. A conductive film using ITO according to the related art is formed by deposition, exposure, development and so on. Therefore, material consumption is high, and the formation process is complicated. 
     However, when the organic conductive composition according to the embodiment of the present invention is used, the conductive film may be formed by the printing and heat treatment process. Further, material consumption is low, and the formation process is simple. 
     Before the conductive film is formed, a surface treatment may be performed on a surface of the substrate where the conductive film is to be formed. The surface treatment may improve an adhesive force between the conductive film and the substrate. When the conductive film is formed of a composition including a conductive polymer according to the related art, an adhesive force between the conductive film and the substrate is so low that its product quality decreases. 
     In this embodiment of the present invention, the surface treatment performed on the substrate increases the surface tension of the substrate to thereby improve the adhesive force between the organic conductive composition and the substrate. 
     The surface treatment is not specifically limited. For example, infrared ray (IR) irradiation, plasma treatment, ion shower, UV irradiation, or corona treatment may be applied. 
     More specifically, since a PET film has a small surface tension of 30-45 dyne/cm, it is easily peeled off from the organic conductive film. However, the surface thereof may be polarized by the surface treatment such that the surface tension increases to 45-80 dyne/cm. Accordingly, the adhesive force between the PET film and the organic conductive film may increase to improve durability. 
     To manufacture the resistive overlay touch-panel-type input device shown in  FIG. 2 , a second organic conductive film is formed on the second substrate, and a second substrate is formed so as to be disposed opposite the first substrate. At this time, electrodes may be formed on the first and second organic conductive films, respectively, and an insulating spacer may be inserted between the electrodes. 
     To manufacture the capacitive touch-panel-type input device shown in  FIG. 3 , a second substrate is formed so as to be disposed opposite the first substrate, and electrodes may be formed between the first and second organic conductive films. 
     According to the embodiments of the present invention, the organic conductive composition has excellent transparency and low surface resistance. Accordingly, the organic conductive composition may be properly used in the touch panel input device. Further, the organic conductive composition is composed of a similar material to the substrate of the input device and has a small difference in thermal expansion coefficient from the substrate. Therefore, the organic conductive composition may increase the durability of the input device. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.