MAGNETIC COATING MATERIAL AND MAGNETIC RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To improve the dispensability of a magnetic coating material contg. carbon black at a high degree by dispersing magnetic particles with a sulfonic acid metal base-contg. polyurethane resin, adding the carbon black of a specific average grain size of a specific value or below at specific weight % thereto in an arbitrary stage before the end of the dispersion and further dispersing the carbon black. SOLUTION: This magnetic coating material contains the sulfonic acid metal base-contg. polyurethane resin and is obtd. by first dispersing the magnetic particles with a binder and adding the carbon black of the average grain size of <=40×m at 7 to 30 wt.% of the magnetic particles to the resin in the arbitrary stage before the end of the dispersion and further dispersing the carbon black. The stage to add the carbon black to the resin is preferably the stage up to 1/10 to 9/10 of the entire dispersion stage. The magnetic recording medium having the magnetic layer formed of such magnetic coating material is excellent in magnetic characteristics and is improved in durability as well. The light shielding function by the carbon black is improved as well.