Transparent coating systems for improving the environmental durability of transparency substrates

摘要

Transparent substrates having at least one surface coated with a transparent coating system to improve their environmental durability are described. The transparent coating system consists of a combination of components having different properties applied as separate layers to the transparent substrate. A thin layer of a silica-based adhesion promoter is applied directly to at least one surface of the substrate, followed by an organosilane primer layer, then a low modulus polyurethane layer, and, lastly, a thermoset aliphatic polyurethane layer. Alternatively, the low modulus polyurethane may also contain silanol groups or functional groups that can be hydrolyzed to silanol, thereby making a separate primer layer unnecessary.