Heat-curable plate for picture or video signals - with central circular recess contg. flat ring, to eliminate surface deformation

摘要

Input-output media plate for optically readable picture or video signals in the form of surface structures is made of heat-curable material, e.g. based on PVC, styrene-acrylonitrile copolymer or polymethyl methacrylate, and has a central circular recess in which is inserted a flat ring, of dimensionally stable material. At the outer edge of the ring is pref. a thin flange-like annular attachment which is countersunk in a further recess in the body of the plate. At the outer edge of the plate may be a stabilising ring of L-shaped cross-section partly resting on one side of the plate and partly encompassing its outer edge. Surface deformation due to thermal stress occurring during mfr. is eliminated.