Method and apparatus for making dual layer DVD discs

Abstract

An improved method and apparatus for making a dual-layer DVD disc that does not require a stamping step (typically, as part of the 2P prior art manufacturing process) during its manufacture. As proposed by Mueller, a polycarbonate substrate is molded and coated with a semireflective data layer in the usual way. A PMMA substrate is molded and coated with a fully reflective data layer. Adhesive is placed on the semireflective data layer, and the fully reflective data layer is transferred from its PMMA substrate to the polycarbonate substrate. The polycarbonate substrate thus ends up with two data layers in conformance with the DVD specifications, and the PMMA substrate can even be recycled for another use. However, instead of using a PMMA substrate that is larger than the polycarbonate substrate as proposed by Mueller, in the invention they have equal diameters. This allows conventional molding equipment to be used with no major changes. Also, while the substrates are sandwiched together, the equal diameters allow an edge milling operation to remove any adhesive that is trasfered to the PMMA substrate.

Dependencies are inferred from the claim text.