Disk cartridge

A disk cartridge has a case comprising an upper and a lower shell halves (6, 7) for accommodating a disk. The case has a spindle insertion hole (8), a head insertion hole (9) and a shutter (10) for opening and closing the two holes (8, 9). The case has at least one of a disconnection preventing mechanism (25, 35; 39, 40) for preventing an elastic spring (23) for urging the shutter (10) from being disconnected from a slider (14) and a part of the case, a drive pin smooth motion mechanism (42) for moving a drive pin (P1, P2) on the slider (14), a shutter locking mechanism (56, 60) for locking the shutter (10) at a closing position, a disk center holding mechanism (85, 101, etc.) for supporting the disk at its center position, a disk periphery holding mechanism (18a, 19a) for holding the periphery of the disk, a writing protection mechanism (29a, 29b) for prevention new information from being recorded on the disk and a mechanism (417) for forming the case with a good outer appearance.