Abstract: An information memory medium (10) includes disk-shaped substrates (30a, 30b) and recording layers (32a, 32b). It also has a centering member (38a, 38b) whose coefficient of thermal expansion resembles that of the substrates (30a, 30b). Two flat magnetic members (40a, 40b) are situated in annular depressions (68a, 68b) provided in the centering member. The annular depressions are larger than the magnetic members so that differences in thermal expansion can be absorbed.

Abstract: An information processing apparatus includes an optical disk and a drive mechanism for rotating the disk. The disk comprises a disk-shaped body and an attractable portion at the central portion of the body. The attractable portion has an attractable member projecting from the body. A center hole, defining the center of rotation of the body, is cut in the attractable member. The drive mechanism includes a turntable which is rotated by a motor. A depression is formed in a support surface of the turntable. A magnetic attraction unit is arranged in the depression so as to magnetically attract the attractable portion, whereby the attractable member is housed in the depression and the surface of the body is in contact with the support surface.

Abstract: A disc data reproducing apparatus, including a rotating mechanism for rotating the disc about a central axis, an optical head disposed opposite the disc for receiving data from the disc, and a moving mechanism for moving the optical head along the radial direction of the disc. The optical head is disposed on one side of the central axis of the rotating mechanism and the moving mechanism is disposed on the other side of the central axis so as to reduce the space requirements for housing the head and moving mechanism within the apparatus.

Abstract: An optical disk comprising a disk-like body having two base plates made of synthetic resin and two recording layers formed on the base plates, respectively. The body is formed by bonding the base plates, with a spacer interposed therebetween, such that the recording layers face each other. The disk further comprises two centering members, each projecting from the surface of the center portion of one base plate. Each centering member is made of synthetic resin, and one magnetic member is mounted on the centering member. The centering member is inserted in a hole formed in the center portion of the body. The centering member has a center hole defining the center of rotation of the body, and also three projections formed in the surface thereof which faces away from the recording layer. The magnetic member has three engaging holes and is mounted on the centering member, with the projections of the centering member fitted in the engaging holes.

Abstract: An information memory medium adapted for processing information with a drive mechanism including a turntable which has a support surface and a magnetic attraction member. The information memory medium includes a disk-shaped body, and an attractable member and a label disposed on the body. The label represents a manufacturer, recording sides, and type of the disk, etc., and is located on a portion of the body other than the surface where the attractable member is disposed and other than where the support surface comes in contact with the body.

Abstract: An optical disk comprising a disk-like body having two base plates made of synthetic resin and two recording layers formed on the base plates, respectively. The body is formed by bonding the base plates, with a spacer interposed therebetween, such that the recording layers face each other. The disk further comprises two centering members, each projecting from the surface of the center portion of each base plate. Each centering member is made of synthetic resin, and one magnetic member is mounted on the centering member. The centering member is inserted in a hole formed in the center portion of the body. The centering member has a center hole defining the center of rotation of the body, and also a recess for holding the magnetic member. Four through-holes are formed in the bottom of the recess. The magnetic member has four projections and is held in the recess, with the projections inserted into the through-holes of the bottom of the recess.