Patent ID: 6961952

Claim:
A disk cartridge comprising: an optical disk for recording/reproducing information, and a cartridge case rotatable accommodating the optical disk, wherein the cartridge case includes a front portion, a rear portion, and two side portions, wherein each of the two side portions is disposed substantially parallel to a direction of insertion of the disk cartridge into a disk driving device and said front portion is provided with a notched area, wherein the notched area allows an arm mounted on the disk driving device to approach the optical disk from said notched area and to move within the notched area substantially perpendicular to the direction of insertion when the disk cartridge is inserted in the disk driving device for recording/reproducing information through a head supported by the arm, wherein the optical disk has a center hub at the center thereof, and the cartridge case has a counterbore formed in a recess form on an inside wall on a side opposite to a side where a drive shaft for rotating the optical disk is inserted, the counterbore facing the center hub.