Stability issues of photopolymer layers in optical disks

Abstract

Photopolymerization (2P) processes are used to produce polymer layers that can be used for servo information in optical storage. The authors have studied the stability of such polymer layers in structures involving a substrates/polymer layer/magneto-optic disk package. They have found that (depending upon structures, coatings, materials) a wave structure can develop in the underlaying 2P layer, whichgrows continuously in amplitude (e.g. 100A to 1000A) when the structure is aged at elevated temperature. The associated periodicity was very regular (10 μm) and usually confined to the grooved areas of the disk. Experiments show that the compressive stress in the magneto-optic layer, which depends upon the deposition process parameters, is the driving force leading to creep of the 2P layer underneath.