A magnetic disc is disclosed, which comprises a disc-shaped magnetic recording medium having a magnetic layer comprising a ferromagnetic powder and a bimder and a case having a liner of a nonwoven fabric comprising a polyester fiber or a polycaryl-nitril fibre in a ratio of not less than 30% by weight. The binder of the magnetic recording medium comprises a modified polyurethane resin containing a a polar group selected from the group consisting of a -SO₃M group, a -OSO₃M group, a -COOM group, a -PO(OM)₂ group and a -OPO(OM)₂ group, in which M is a hydrogen atom or a alkali metal atom, or a hydroxyl group provided that the polar group may be formed an intramolecular salt.
本发明公开了一种磁性光盘,它包括一个圆盘状磁性记录介质,该磁性记录介质具有一个由
铁磁粉末和粘合剂组成的磁性层,以及一个外壳,外壳的内衬是由聚酯纤维或聚芳基氮纤维组成的无纺布,其重量比不低于 30%。磁记录介质的粘结剂包括改性聚
氨酯
树脂,其中含有选自由-SO₃M基团、-OSO₃M基团、-COOM基团、-PO(OM)₂基团和-OPO(OM)₂基团组成的组中的极性基团,其中M为氢原子或碱
金属原子或羟基,但极性基团可形成分子内盐。