Recording medium of air-sandwich structure

Abstract

Disclosed is an optical disk used as a recording medium of the type described as an air-sandwiched structure including two disk-shaped substrates, which are secured to each other by way of an inner and outer plastic spacer. Together, the two substrates and the inner and outer spacer define a closed inner space, and at least one inner surface of one of the two substrates is provided with a light-sensitive recording layer. Typically, such a recording layer is sensitive to high energy light such as that from a laser beam. Each of the disk-shaped substrates includes a central hole of equal size and shape, wherein the inner spacer is ring-shaped and is positioned with its central opening coaxial with the holes in the substrates. The improvement resides in that the inside diameter of the central hole of the inner spacer is larger than the diameter of the holes of the substrates, and in that a recessed seat is provided by recessed portions formed on both substrates adjacent to and around the holes of each substrate, for precisely fitting and aligning the inner spacer to both disk-shaped substrates. Such a structure ensures accurate positioning of the optical disk on a drive spindle without interference of excess adhesive used in securing the inner spacer to the substrates, as well as to ensure that the recording medium can be rotated with high precision.