Abstract: A magnetic disc cartridge comprising a cartridge case, a magnetic disc housed rotatably in the cartridge case, and a liner, which serves as a cleaning sheet, secured on the inner surface of the cartridge case, characterized in that the magnetic disc has a magnetic layer containing a ferromagnetic metal powder, a reinforcing powder, whose content is defined in the range of from 5 to 40% by weight, and a fatty acid ester with a melting point of 0.degree. C. or lower, and that at least the disc side surface layer of the cleaning sheet, which is brought into sliding contact directly with the magnetic layer, is almost entirely composed of rayon fiber, such that the magnetic disc cartridge of the present invention can provide a highly reliable magnetic disc cartridge having a magnetic disc which is excellent in durability and substantially error free.

Abstract: A disk cartridge which comprises a cartridge case, a disk rotatably encased in the cartridge case, and a cleaning sheet supported on the inside surface of the cartridge case by welding, the cartridge case being composed of a thermoplastic synthetic resin, and the cleaning sheet being composed at least of a mixed fabric of acrylic fibers and rayon fibers and being fixed to the inside surfaces of the cartridge case by welding has distinguished disk-handling characteristics and cartridge case-fixing characteristics.

Abstract: A magnetic recording medium suitable for high density recording comprising a non-magnetic substrate and a magnetic layer which contains a non-magnetic binder and ferromagnetic powder dispersed therein formed on said substrate, the coercive force of the magnetic layer being from 1,400 to 2,000 oersteds, the residual magnetic flux density being at least 1,100 gausses and a thickness of the layer being at least 0.5 .mu.m, which effectively works when it is used together with a magnetic head, a part of which near a magnetic gap, made of a magnetic material having saturation magnetic flux density of at least 7,000 gausses and which has a magnetic gap length of 0.15 to 0.4 .mu.m.

Abstract: A magnetic disc which comprises a non-magnetic support substrate and a magnetic layer thereon consisting of a magnetic coating comprising ferromagnetic powder, a binder, an aliphatic acid ester having a melting point not higher than 10.degree. C. and an aliphatic acid ester having a melting point from 15.degree. to 60.degree. C., the magnetic coating having improved lubricity and durability.

Abstract: A recording disc cartridge comprising a recording disc containing, at least in its surface layer, at least one compound selected from the group consisting of an aliphatic acid and its salt and derivative, a case in which the recording disc is rotatively contained, and a liner comprising polyester fiber which is interposed between the case and the recording disc with facing the disc, which has good durability and less drop out.

Abstract: In a recording disc cartridge having a recording disc rotatably supported by a hub assembly in a disc case, the hub assembly is formed by a hub body and a reinforcing metal plate laid on one of the surfaces of the hub body so as to prevent thermal deformation of the recording disc due to deformation of the hub body.

Abstract: A magnetic recording medium which comprises a substrate and a magnetic layer comprising magnetic powder and a resinous binder formed on the substrate, characterized in that the magnetic layer further comprises a lubricant and an unsaturated fatty acid ester, which is improved in durability.

Abstract: A magnetic recording medium improved in durability which comprises a substrate and a magnetic layer of about 1.0 to 10.mu. in thickness comprising magnetic particles and a binder and being formed on the substrate, characterized in that the magnetic layer further comprises (a) a liquid hydrocarbon having a melting or flowing point of about -20.degree. to -60.degree. C. with (b) .alpha.-iron oxide particles having a particle size of 0.5 to 2.mu. and/or (c) a higher fatty acid having a melting point of about 45.degree. C. or higher.