Conductivity Enhanced Transparent Conductive Film and Method of Making the Same

Abstract

Disclosed herein is a method of fabricating a transparent conductive film, including preparing a carbon nanotube composite composition by blending a carbon nanotube in a solvent; coating the carbon nanotube composite composition on a base substrate to form a carbon nanotube composite film, and acid-treating the carbon nanotube composite film by dipping the carbon nanotube composite film in an acid solution, followed by washing the carbon nanotube composite film with distilled water and drying the washed carbon nanotube composite film to form a transparent electrode on the base substrate. The transparent conductive film can have excellent conductivity, transparency and bending properties following acid treatment, so that it can be used in touch screens and transparent electrodes of foldable flat panel displays. Further, the carbon nanotube composite conductive film can have improved conductivity while maintaining transparency after acid treatment.

That which is claimed is: 
     
         1 . A transparent conductive film comprising a transparent electrode comprising carbon nanotubes on a base substrate produced by the method of:
 preparing a carbon nanotube composite composition by blending carbon nanotubes in a solvent;   coating the carbon nanotube composite composition on the base substrate to form a carbon nanotube composite film; and   acid-treating the carbon nanotube composite film to form a transparent electrode on the base substrate by dipping the carbon nanotube composite film in an acid solution, followed by washing the carbon nanotube composite film with distilled water and drying the washed carbon nanotube composite film.   
     
     
         2 . The transparent conductive film according to  claim 1 , wherein the transparent electrode has a transmittance of 80% or more as measured at a wavelength of 550 nm using a UV/Vis spectrometer. 
     
     
         3 . The transparent conductive film according to  claim 1 , wherein the transparent electrode has a surface resistance of 1,000 Ω/cm 2  or less as measured by a 4-point probe method. 
     
     
         4 . The transparent conductive film according to  claim 1 , wherein the carbon nanotube composite composition further comprises a surfactant or a polymer binder. 
     
     
         5 . The transparent conductive film according to  claim 4 , wherein the carbon nanotube composite composition comprises 0.01 to 2 parts by weight of the surfactant and 0.01 to 2 parts by weight of the carbon nanotubes, based on 100 parts by weight of the solvent. 
     
     
         6 . The transparent conductive film according to  claim 5 , wherein the surfactant is sodium dodecyl sulfate (SDS) or sodium dodecyl benzene sulfonate (NaDDBS). 
     
     
         7 . The transparent conductive film according to  claim 4 , wherein the carbon nanotube composite composition comprises 0.05 to 1 part by weight of the polymer binder and 0.05 to 1 part by weight of carbon nanotubes, based on 100 parts by weight of the solvent. 
     
     
         8 . The transparent conductive film according to  claim 7 , wherein the polymer binder comprises a resin having ionic conductivity or ion exchange properties, the resin comprising fluorine atoms and a sulfonyl functional group. 
     
     
         9 . The transparent conductive film according to  claim 7 , wherein the polymer binder comprises a thermoplastic polymer comprising one or more functional groups selected from the group consisting of carboxyl, sulfonyl, phosphonyl, and sulfone imides. 
     
     
         10 . The transparent conductive film according to  claim 7 , wherein the polymer binder comprises a salt of potassium or sodium combined with one or more functional groups selected from the group consisting of carboxyl, sulfonyl, phosphonyl, and sulfone imides. 
     
     
         11 . The transparent conductive film according to  claim 7 , wherein the polymer binder and the carbon nanotubes are mixed in a ratio of 1:5 to 5:1. 
     
     
         12 . The transparent conductive film according to  claim 1 , wherein the solvent comprises a mixture solution of water and isopropyl alcohol in a volume ratio of 20:80 to 80:20. 
     
     
         13 . The transparent conductive film according to  claim 1 , wherein the base substrate is a polymer film comprising a polyester, polycarbonate, polyether sulfone, or acrylate-based polymer. 
     
     
         14 . The transparent conductive film according to  claim 13 , wherein the base substrate is a polymer film comprising polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), or a combination thereof. 
     
     
         15 . The transparent conductive film according to  claim 1 , wherein the base substrate is a glass substrate. 
     
     
         16 . The transparent conductive film according to  claim 1 , wherein the acid solution used in the acid-treatment has a pH in the range of −1 to 3. 
     
     
         17 . The transparent conductive film according to  claim 1 , wherein the acid solution comprises an acid selected from the group consisting of perchloric acid, nitric acid, hydrochloric acid, sulfuric acid, and mixtures thereof. 
     
     
         18 . The transparent conductive film according to  claim 1 , wherein the transparent conductive film comprises at least 90% by weight or more of single-walled or double-walled carbon nanotubes or a combination thereof. 
     
     
         19 . A transparent conductive film comprising an acid-treated transparent electrode comprising a carbon nanotube composite film on a base substrate, wherein said nanotube composite film comprises carbon nanotubes and a polymer binder.