Phase Change Optical Disks Having Recording Marks with Large Optical Phase Difference Suitable for Mark Edge Recording

We have developed a novel absorptivity control method for phase change optical disks with the aim of reducing overwriting jitter in mark edge recording without degradation of overwriting cyclability. To control absorptivity more easily, we have designed a disk with a small difference in reflectivity between the amorphous and the crystalline states, and with a large optical phase difference between the reflected light from those two states, which produces a high carrier-to-noise ratio. We have obtained significantly reduced overwriting jitter, down to 2.5 ns for the leading edge, as well as a sufficient overwriting cyclability of up to 105 times.