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Hollow-cathode activated EB evaporation for oxide coating of plastic films

: Neumann, M.; Morgner, H.; Straach, S.

Mattox, V.H. ; Society of Vacuum Coaters -SVC-, Albuquerque/NM:
Society of Vacuum Coaters. 39th Annual Technical Conference 1996. Proceedings
Albuquerque: SVC, 1996
ISSN: 0737-5921
Society of Vacuum Coaters (Annual Technical Conference) <39, 1996, Philadelphia>
Fraunhofer FEP ()
hollow cathode; plasma source; reactive deposition; thermal evaporation; web coating

In the last years we reported in general about the hollow-cathode activated deposition of oxides on plastic films (HAD process). This paper describes the process and its possible variations in more detail. As a first variant we investigated the horizontal hollow-cathode discharge with two different anode configurations. A row of hollow-cathode systems arranged side by side across the web creates a dense plasma shield that is located directly below the substrate. Al2O3 coatings deposited via this plasma shield show a clear improvement of microstructure, hardness and abrasion resistance. A further remarkable improvement of the Al2O3 properties can be attained by a vertical hollow-cathode discharge between the aforementioned plasma shield near the substrate and an anode in the vicinity of the evaporator crucible. The electrical field in this vertical plasma discharge causes additional ions to move toward the substrate. As a result, non-columnar Al2O3 , coatings of some micrometers thickne ss with high density and outstanding abrasion resistance have been produced. Despite of the successful deposition of Al2O3 layers by plasma-activated reactive EB evaporation of Al we recommend to use EB evaporation preferably for such materials that really need this technique. This holds especially for the deposition of SiO2, TiO2, or ZrO2 layers. For the deposition of Al2O3 layers we recommend the reactive Al evaporation via boat evaporators in combination with the vertical HAD process. The installation of the necessary hollow-cathode systems including monitoring and oxygen supply in conventional aluminum roll coaters is possible.