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 --SO.sub.3 M, --OH, --OSO.sub.3 M, --COOM, ##STR1## --NR. sub.2 and --⊕NR.sub.3 X. crclbar. 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° C. PPThe magnetic recording medium has an excellent running durability, still life and frictional property.