Magnetic recording medium comprising a polyurethane resin coating residual groups derived from specified phosphorous containing compounds

A magnetic recording medium comprising a magnetic layer composed principallyof magnetic particles and a binder, characterized in that at least a portion of the binder is a polyurethane resin synthesized from a reactant mixture of components (1), (2), (3) and (4) set out below, containing one phosphoric acid group or one residualg roup derived from phosphoric acid per 3,000-200,000 number average molecular weight of the polyurethane resin, and having a number average molecular weight of 4,000-150,000:

• (1) a phosphorus compound (a) represented by a structural formula set out below or a phosphorus compound (b) represented by a structural formula set out below:
• ##STR5## wherein R.sup.1 is a hydrogen atom, a phenyl group, an aklyl group having 1-40 carbon atoms, or an alkylphenyl group having 1-40 carbon atoms, and n is an integer of 0-30;
• ##STR6## wherein R.sup.2 is a phenyl group, an alkyl group having 1-40 carbon atoms, or an alkylphenyl group having 1-40 carbon atoms;
• (2) an epoxy compound having at least two epoxy groups and/or an epoxy compound having one epoxy roupand at least one hydroxyl group;
• (3) a bifunctional isocyanate compound and/or a trifunctional isocyanate compound;
• and
• (4) a polyfunctional hydroxy compound having a number average molecular weight of 400-5,000.