<title>Aging Properties of Optical Non-Erasable Disks.</title>

Abstract

The long term storage of DOR disks was studied for application as a long-term data storage medium with respect to degradation under high humidity conditions. For this purpose a standard test with high humidity (95%), and cyclic temperature (25 - 65°C) was used. Besides these accelerated aging tests on hermetically sealed sandwiches, we also investigated non-sealed disks in order to optimize the lacquer, the Te alloy composition and its thickness. During interruptions and after aging the relevant optical recorder parameters were measured. These were optical transmissivity, reflectivity, in-track clock-to-noise ratio, sig-nal-to-noise ratio of written data, threshold energy for ablative recording and the bit error rate. The various types of aging phenomena observed in the "open" sandwiches are discussed. Cyclic climate tests on open sandwiches with Te based alloy films containing 60 - 85% Te show that some alloy lacquer combinations have substantially decreased performance after 30 days of testing, whereas disks with pure Te films cannot withstand such severe conditions for more than a few days. Experiments on sealed disks show that the aging of sensitive films only starts after failure of the seal. On the basis of these experiments, the usability of OML disks is expected to exceed comfortably the requirements for application in long-term data storage under office conditions for periods of longer than ten years.