Optical discs with cover sheets and pressure equalization of the enclosed air

Abstract

An optical disc is disclosed having a substrate in which data can be written on or read from, such optical disc has a transparent cover sheet which is held at a desired spacing from the substrate at least at an inner radius and an outer radius. In order to prevent the transparent cover sheet from deflecting due to pressure differences between the outside atmosphere and the air in the space between the substrate surface and the transparent cover sheet, a plurality of air passages in the transparent cover sheet are provided near an inflection point where on one lateral side of the point the transparent sheet will bulge and on the other lateral side it will be depressed due to centrifugal force acting upon air entrapped between the transparent cover sheet and the substrate surface during disc rotation in an optical disc drive. This arrangement equalizes the pressure in the air space between the transparent cover sheet and the substrate surface and the outside atmosphere.

Dependencies are inferred from the claim text.