Heretofore, as an electrically conductive paste of this type, an electrically conductive paste in which an electrically conductive filler (B) is uniformly dispersed in a resin (A) has been disclosed (for example, see Patent document 1.). In this electrically conductive paste, the resin (A) is an aqueous dispersion (A1) of a conjugated double bond polymer containing a polyanion based on a sulfonated or sulfated rubber as a dopant, and as the resin (A), an aqueous dispersion (A2) of a conjugated double bond polymer containing a polymeric polyanion which contains an aromatic group showing high electrical conductivity may be further contained as a dopant within the range which does not impair extensibility. In addition, the electrically conductive filler (B) is a metal powder (B1) having an average grain diameter of 0.5-10 μm, and formulation amounts of the resin (A) and the electrically conductive filler (B) in the solid content of the electrically conductive paste are 50-80 vol. % and 20-50 vol. %, respectively. The above-mentioned metal powder (B1) may be mentioned noble metal powders such as silver powder, gold powder, platinum powder, palladium powder, etc., and base metal powders such as copper powder, nickel powder, aluminum powder, brass powder, etc. Further, as the above-mentioned electrically conductive filler, it is preferable to contain metal nanoparticles (B3) having an average grain diameter of 2-100 nm. As the metal nanoparticles (B3), there may be mentioned silver, bismuth, platinum, gold, nickel, tin, copper and zinc, and from the viewpoint of electrical conductivity, there may be mentioned copper, silver, platinum and gold, and it is particularly preferable that either one of or both of silver and copper is/are contained as a main component(s) (50 mass % or more).
In the electrically conductive paste thus constituted, the metal powder (B1) is uniformly dispersed in the resin (A) having stretchability and electrical conductivity, so that, by forming an effective electrically conductive network, the electrically conductive film formed by using the electrically conductive paste has high electrical conductivity, and can retain its high electrical conductivity even when the electrically conductive film is stretched. Also, when either one of or both of silver powder and copper powder is/are used as the metal powder (B1) and as the main component (50 mass % or more), a coating film showing high electrical conductivity can be obtained and it is advantageous from the viewpoint of cost. In addition, by further formulating metal nanoparticles (B3) in the electrically conductive paste as an electrically conductive filler, electrical conductivity can be improved and printability can be also improved. Further, the metal nanoparticles (B3) have the function of imparting electrical conductivity between the electrically conductive networks, so that it can be expected to improve electrical conductivity of the electrically conductive film.
USPTO Backgrounds
USPTO Backgrounds