Abstract: Proposed is a novel vinyl chloride-based copolymeric resin suitable as an electron beam-curable binder resin for forming a magnetic recording layer of a magnetic recording medium. The binder resin is a vinyl chloride-based copolymeric resin containing monomeric units having a hydroxy group which is reacted with an ethylenically unsaturated monomeric compound having an isocyanato group in a molecule and then subjected to a modification reaction with an amine compound. The magnetic recording medium, e.g., magnetic recording tape, prepared by using the binder resin is excellent in the surface properties such as gloss and traveling resistance as well as in the magnetic properties such as residual magnetic flux density and squareness ratio of the magnetic hysteresis loop.

Abstract: The invention provides a coating composition used for forming a magnetic layer on the surface of substrates to prepare magnetic recording media, e.g., recording tapes, of which the characteristic ingredient is a novel copolymeric resin. The copolymeric resin is a partial or complete saponification product of a copolymer obtained by the copolymerization of 4 types of comonomers in a spe-cified proportion including (1) vinyl chloride, (2) vinyl acetate, (3) a monomer having an ethylenically unsaturated polymerizable group and an epoxy group in the same molecule and (4) a monomer having an ethylenically unsaturated polymerizable group in the form of a sulfonic acid or a metal salt thereof. The vinyl acetate moiety is converted into a vinyl alcohol moiety partially or completely by the saponification.