MAGNETIC RECORDING MEDIUM

摘要

PURPOSE:To decrease permanent deformation and drop-out and to improve an S/N by incorporating at least silicone modified polyurethane and carbon black having a specific BET value in a back coating layer thereby improving the winding condition during high-speed traveling. CONSTITUTION:The above-mentioned purpose is achieved by incorporating at least silicone modified polyurethane and carbon black having 200-500m<2>/g BET value in a back coating layer. A polymer prepd. by using an active hydrogen compd. having at least >=1 siloxane bond, for example, the polysiloxanediol expressed by the general formula I as the active hydrogen compd. and bringing such compd. into reaction with isocyanate is preferred for the silicone modified polyurethane. The silicone modified polyurethane having a number average mol.wt. ranging 5,000-200,000 is preferred. The ratio of said polyurethane and other resins is preferably in a 75/25-25/75 range by weight. A preferred method for decreasing effectively the electric resistance of the back coating layer is to add carbon black having 200m<2>/g<=B<500m<2>/g BET value to the back coating layer.