Improvement of Overwrite Jitter of a Phase-Change Optical Disk with Al-Alloy Double-Reflective-Layer Structure

To obtain minimum overwrite jitter after 104 overwrites, the cause of degradation of readout waveforms after 104 overwrites was investigated by transmittance electron microscopy (TEM). To decrease the temperature of the recording film at the track center during recording, an Al-alloy double-reflective-layer structure is proposed. Two relationships, one between the thermal conductivity of the first reflective layer and the temperature of the recording film during recording and the other between the thermal conductivity and the readout waveforms after overwrites of more than 105 times, were investigated using thermal simulation and a digital versatile disk (DVD) disk tester. The optimized disk has a minimum overwrite jitter after 105 overwrites at a linear velocity of 6 m/s.