Process for forming silicon oxide coating on plastic material

Abstract

A gas-impermeable plastic vessel and a process for forming a film having uniform thickness and high gas-interception to a plastic vessel is disclosed. The plastic vessel, having a Tg higher than the coating temperature, excellent in gas-interception, is coated with a silicon oxide film having a refractive index of 1.4 to 1.5, a thickness of 300 Å to 2000 Å and composition of SiO (X=1.5 to 2.0). A high-frequency electrode is placed on the non-coated surface side a constant distance of not more than 10 mm from the electrode surface to the vessel surface. A ground electrode connection is placed in the coated surface side and the ground connection electrode is maintained a constant distance from the electrode surface to the vessel surface, which distance is greater than the distance from the high-frequency electrode surface to the vessel surface on which the coating is formed. A silicon oxide film having a uniform thickness is coated onto the surface which faces to the ground connection electrode by introducing plasma of the silicon oxide produced by CVD process in between the vessel and the ground connection electrode with a discharge having a pressure of 0.0005 to 0.05 torr.