US Patent 7993721 Disc-shaped high-density recording mediums

Optical recording mediums comprising a substrate and a recording layer and a light transmitting layer sequentially disposed on the substrate; wherein the substrate comprises one or more parts selected from the group consisting of injection molded parts, injection molded sandwich structures having a molded surface layer and a molded core layer or two injection molded parts which are UV-bonded, and combinations thereof; and wherein the substrate has a Young's modulus E of at least 2.15 GPa and a Q factor of lower than 160 measured at 25° C. at 2000 Hz in accordance to ASTM E 756-05.