Process of applying antistatic coating compositions to polyester films

Claim 1

Process for adhering an antistatic layer to a dimensionally stable polyester film support, which process comprises applying directly to an unstretched or only monoaxially stretched polyester film support an antistatic layer from an aqueous coating composition, drying said antistatic layer and stretching the polyester support carrying the dried antistatic layer biaxially or in a direction perpendicular to the first stretching operation, and heat-setting the thus coated and stretched polyester film, said aqueous coating composition consisting essentially of 30 to 80% by weight of an electroconductive polymer, 10 to 40% by weight of a stretch-improving agent for said polymer selected from the group consisting of (a) an aliphatic polyhydroxy compound, (b) caprolactam, (c) N,N'-dimethyl urea, and (d) an aliphatic or aromatic carboxylic or sulfonic acid and 10 to 40% by weight of a filler material selected from the group consisting of a non-electroconductive polymer of an α,β-ethylenically unsaturated monomer in dispersed particle form, an inorganic pigment, a silane compound hydrolyzable in situ to amorphous silicon dioxide, and gelatin, said electroconductive polymer having at least 50% of its recurring units carrying an electroconductive anionic or cationic group and imparting to said antistatic layer an electrical surface resistance lower than 1×10 10 ohm/sq area measured at 30% R.H.