Organic materials for the use in optical layer systems

Ceramic materials such as SiO2 or Ta2O5 are widely used for optical interference coatings. These materials have a high hardness and mostly offer excellent optical properties. However, there is a growing demand not only for good optical properties and a high stability, but also for coatings with a high elasticity. Especially coatings on polymer substrates need layers with improved elasticity since cracks in the layers occur easily when the coated substrates were mechanically deformed. For such applications flexible layer materials using organics or even polymers are very promising. These may be used as pure organic layers of with organic-inorganic composites. Unfortunately the chemical reactions to form polymers layers are more complex than the reactions to form oxides. Thus the deposition techniques for polymer layers are much more varying. Other important issues are the deposition rate stability and the optical properties of the polymer layers like haze, refractive and absorption index. In this paper we compare different ways for the deposition of organic and polymer layers in the gas phase at low pressures. The methods used were: evaporation, sputtering, PECVD and thermal CVD techniques. The optical parameters (refractive index, absorption and haze) and some mechanical parameters (adhesion, crack onset strain) of the different polymer layers were characterized. It will be shown that excellent organic film properties can be obtained by the use of a suitable organic material and deposition process. Also shown will be results on composite materials to modify the optical properties.