A two-layer film consisting of a tacky layer (air side) and a porous nontacky layer (release-paper side) was prepared by casting blend emulsion on a release paper, in which 150-nm 2-ethylhexyl acrylate-2-methoxyethyl acrylate-acrylic acid terpolymer particles having high storage stability and 542-nm ethyl acrylate-methyl methacrylate copolymer particles having low storage stability were dispersed. Both emulsion particles were produced by emulsifier-free emulsion copolymerizations. The difference of tackiness between both surfaces increased with increases in the film-formation time and the concentration of electrolytes in the blend emulsion, and resulted in the two-layer film. The film had a high water vapor permeability, which is also needed for medical adhesive tape. (C) 2003 Wiley Periodicals, Inc.