Recording Mechanism of Overcoated Metallized Dye Layers on Polycarbonate Substrates

The recording mechanism of a so-called CD-Recordable is reported; the disc consists of a pregrooved polycarbonate substrate, a dye, a metal reflector and an overcoat. After recording, bumps on the pregrooved substrate and pits at the dye/metal interface are observed. A method to determine the complex refractive index of a dye is explained and it will be shown how to obtain both a high reflection and a high modulation. From optical and thermal calculations and from recording experiments it is shown that two threshold temperatures are involved, associated with the softening of polycarbonate at 170°C and with a transition of the dye at 265°C.