Characterization and control of cure of polymer coatings on optical disks

Abstract

Polymer coatings are used extensively in optical disk technology, the majority being acrylate based formulations which are transparent and tough. For example, the servo pattern for tracking can be generated by a photopolymer process (2P), where a thin acrylate-based coating system is cured between a `stamper' and a treated glass substrate. In this study, we have extended this technology beyond current servo geometries to generate the small structures (0.6 micron pitch features) that are required for future substrates using the blue laser. The fidelity of replication is measured by scanning tunneling microscopy (STM) techniques. Acrylate based polymer lacquer coatings are also applied (by spin coating) to optical disks and compact disks to provide handling and anti-static protection. The term `corrosion protective coating 1' (PC1) refers to the coating on the film side of the disk and `scratch resistent protective coating 2' (PC2) refers to the anti-static, anti-scratch coating applied to the substrate side of the polymer disk. A number of analytical techniques have been developed to monitor the cure of these acrylate based systems. These include infrared spectroscopy, microhardness, various thermal methods (DMTA, TGA, TGA-MS) and extraction techniques. The usefulness of these techniques is discussed in terms of formulation optimization, cure optimization, and accelerated aging tests that reveal failure mechanisms.