Abstract

Plastic substrates take a major place in the optics industry today¹. They are less fragile than glass and can be easily molded in any shape. However, considerable effort is needed to improve the quality of optical coatings on such substrate, particularly to increase their adhesion and scratch resistance. These difficulties are mainly due to the softness and low surface energy of the polymer surfaces. Plasma deposition is an attracting approach to deposit good quality optical filters at a high rate and a favorable cost. Various pretreatments can be applied in order to increase the adhesion of coatings on plastics, such as predeposition of a hard layer,² or surface modification by plasma pretreatment.³ Due to a synergistic effect of ions, photons and free radicals with exposed polymer surfaces, PECVD on plastics has been found to create a physically thick “interphase”.³–⁵ In this work, we study this interfacial region between silicon-compound films and a polycarbonate (PC) substrate. Evidence of the presence of an interphase will be demonstrated by spectroscopic ellipsometry (SE) and spectrophotometric measurements, and its impact on the performance of optical filters will be shown.

© 1998 Optical Society of America