| 摘要 |
PURPOSE: To provide a magnetic recording medium excellent in running durability by specifying a binder for ferromagnetic powder forming a magnetic layer and the ferromagnetic powder. CONSTITUTION: At least one magnetic layer contg. ferromagnetic powder dispersed in a binder is formed on a nonmagnetic substrate. Polyurethane having a polar group and 2×10<-5> -2×10<-3> eq/g epoxy group in each molecule and having a wt. average mol.wt. of 10,000-100,000 is incorporated as the binder and ferromagnetic metal powder contg. 5-60at.% Co is used as the ferromagnetic powder. Epoxy groups of the polyurethane bond to the terminals of the principal chain of the polyurethane. The polar groups of the polyurethane are SO3 M, SO4 M, COOM or PO3 M2 (M is one or more kinds of groups selected from among alkali metals and ammonium) and the amt. of the polar groups is 1×10<-5> -2×10<-4> eq/g.
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