Deposition of Hard Coating Film on Polymer Surface by Plasma CVD

Polycarbonate (PC) resin is widely used for automobile parts. In order to improve its abrasion-proof and ultraviolet (UV) shielding abilities, we studied the effects of applying SiO₂/ZnO two-film-coating to polycarbonates by using a RF plasma CVD method with hexamethyldisilane (HMDS) and diethylzinc (DEZ).

We found that both the deposition rate of ZnO thin films and the characteristics of the film depended on the substance temperature. Deposition rates of the ZnO thin films decreased, and the ultraviolet shielding ability improved, as the substance temperature rose. We also found ZnO-coated PC plates to show a remarkable protection against UV radiation; their surfaces remained smooth and suffered less discoloration even after a 1000-hour-irradiation of UV light in a xenon arc weatherability test. SiO₂ films deposited on ZnO films using HDMS with oxygen had very hard surface characteristics and we feel that they may be used in coating hard films on automotive headlamp lenses.