High rate MW-PCVD processes for transparent hard coatings on PC plastic foils: first results and calculations for an up-scaling

A high rate microwave based plasma-CVD process for transparent hard coatings for large PC parts was established in the last years at the Fraunhofer ICT - showing deposition rates of up to 3 µm/ min. for the siloxanes HMDSO, TMDSO and OMCTS and a thickness uniformity of +/- 7 % on an area of ca. 0.5 sqm. This process is now also used to coat thin plastic foils, made from clear and black PC, which need scratch resistance because of their use as an outer skin of automotive body parts, and being laminated onto large parts made from fibre reinforced plastic compounds. In situ-measurements of the surface temperatures during coating show clearly the evidence of a good heat transfer to the substrate carrier to enlarge the effective deposition times, even for thinner foils. Taking into account, that the deposition rates of these PCVD process could be enlarged again by doubling pumping rates and MW plasma power, a roll-to-roll coating process for wipe and scratch resistant foils seems to be obtainable in the near future.