Ferromagnetic thin film magnetic recording medium having an intermediate layer containing ultrafine particles and a polar group containing binder resin having a loss tangent peak temperature in a specified range

摘要

A ferromagnetic thin film type magnetic recording medium is disclosed, comprising a nonmagnetic intermediate layer formed between a nonmagnetic support and a magnetic layer, the intermediate layer containing a binder resin and ultrafine particles, wherein the ultrafine particles have a diameter of from 5 to 250 nm and (a) the binder resin has as a polar group at least one group selected from the group consisting of -SO3M, -OH, -OSO3M, -COOM, -NR2 and -(+)NR3X(-) wherein M is H, Li, Na, K or a hydrocarbon group, R is H, or an alkyl group, and X is a halogen atom, or (b) the peak temperature of the loss tangent (tan) of the binder resin is from 10 to 90 DEG C. The magnetic recording medium has an excellent running durability, still life and frictional property.