Abstract: Disclosed is a disc cartridge comprising a cartridge case, a disc set rotatably in the cartridge case, and cleaning sheets secured to the inside of the cartridge case, wherein at least the disc side surface layer of each cleaning sheet, which is brought into direct sliding contact with the disc in operation, is almost entirely composed of ultrafine fibers having a diameter of less than 10 .mu.m producing an excellent disc cleaning effect on the disc, lessening the errors in the recording and reproducing operations of the disc.

Abstract: A disk cartridge which comprises a cartridge case receiving a magnetic disk and a cleaning sheet fixed by spot or line welding to the inner surfaces of the cartridge case such as to contact both sides of the magnetic disk; the density of the welding spots or lines is reduced or eliminated in the regions of the cleaning sheet which undergo the most pressure exerted by pressing pads on the recording/reproducing apparatus for the disk cartridge.

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 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 of non-woven fabric made mainly of acrylic fibers at least on the disk-facing side of the cleaning sheet and being fixed to the inside surfaces of the cartridge case by ultrasonic or heat welding has distinguished disk-handling characteristics and cartridge case-fixing characteristics.

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.