Magnetic recording media and thermoplastic polyurethane resins therefor

摘要

A magnetic recording medium possessing a magnetic layer formed by application onto a non-magnetic support, of a magnetic coating containing magnetic particles dispersed in a binder which contains a polyurethane resin, together with carbon black particles at 5% by weight or more, based on the weight of the magnetic particles. The polyurethane resin to be used herein is composed of: (a) a polyester polyol having a molecular weight of 2000 or lower and containing at least one selected from aromatic dibasic acids and alicyclic dibasic acids at a ratio of 90 mol% or more of acid components; (b) a high molecular weight polyol having a molecular weight of 5000 or lower, which is at least one selected from (b1) polyester polyols each containing an aliphatic dibasic acid at a ratio of 90 mol% or more of acid components, (b2) polylactones, (b3) polyester polyols, and (b4) polycarbonate polyols; (c) an organic diisocyanate compound; and (d) an optional compound having a molecular weight of 500 or lower and containing at least two functional groups in one molecule, which are reactive with isocyanate groups.