Patent ID: 9221979
Filing Date: 2015-12-29
Classification: B22F,C09D,C22C,H01B,H05K

Abstract:
1. Copper particles having an average particle diameter of 0.05 to 2 μm as measured by observation using SEM, a BET specific surface area value (SSA) m and an oxygen content (O) % by weight of the copper particles satisfy a relationship represented by the following formula [2]: wherein a specific resistance of a conductive coating film incorporating the copper particles is not more than 500 μΩ·cm, wherein the conductive coating film is prepared by the following steps: charging a sand mill with a dispersion composition having the copper particles, the composition having 2.5 parts of a copolyester solution in a form of a 40% by weight solution in toluene/cyclohexanone in a 1/1 weight ratio, 9 parts of the copper particles, 3.5 parts of γ-butyrolactone, 5 parts of methyl ethyl ketone, and 0.2 parts of blocked isocyanate; dispersing the dispersion composition at 800 rpm for 2 hr with dispersing media of zirconia beads having a radius of 0.2 mm to obtain a copper paste; applying the obtained copper paste onto a 25 μm-thick polyimide film using an applicator such that the thickness of the coating film obtained after dried is 2 μm; subjecting the coating film to hot-air drying at 120° C. for 5 min, thereby obtaining a copper powder-containing coating film; and heat-treating the resulting copper powder-containing coating film is heat-treated with superheated steam at 350° C. for 5 min.