Data Reliability Deterioration of Phase-Change Discs Caused by Lowering of Crystallization Speed of Amorphous Marks through a High Environmental Temperature Storage

Abstract

We describe details of a data reliability testing procedure of phase-change discs called “overwrite shelf” concerning structural relaxation of recorded amorphous marks in recording film, which should be considered when designing phase-change discs. The overwrite shelf denotes the erase performance of a previously recorded disc. We have found that data subjected to the overwrite shelf operation greatly deteriorates after the disc has been held at a high environmental temperature which is much below the crystallization temperature of the amorphous marks. This is considered to be due to the lowering of the crystallization speed of amorphous marks in phase-change discs through structural relaxation. Therefore, in order to avoid data destruction in the overwrite shelf operation, the crystallization speeds of phase-change discs should be designed to be faster than those expected from the initial properties, to compensate the lowering of crystallization speeds.