Residual stresses in a digital versatile disc recordable

The residual stresses in a multi-layer digital versatile disc recordable (DVD-R) were studied. The DVD-R consisted of a recording layer, a reflective layer and a protective layer deposited on a polycarbonate substrate. After deposition of each layers, the bending curvatures of the substrate were measured successively and the corresponding residual stresses in each layer were calculated using a closed-form solution of bending of a multi-layer composite plate. The residual stresses were found to be compressive in the recording and reflective layers. In the protective layer, the stress was compressive near the bottom interface and tensile near the top free surface. The stress distribution in the thick substrate was close to a pure bending under compression near the bottom free surface and tension near the top interface. The bending and neutral axes were also determined and discussed.