Ulrike Schulz, Uwe B. Schallenberg, Norbert Kaiser
Fraunhofer-Institution for Applied Optics and Precision Engineering, Jena, Germany,
mso jena Mikroschichtoptik GmbH, Germany
“Abrasion resistant antireflection coating for plastics”, in Optical and Infrared Thin Films, Michael L. Fulton, Editor, Proceedings of SPIE Vol. 4094, 100-106 (2000)

Abstract:
Coating of plastics for optical applications is mostly intended to improve their mechanically durability and to provide a desired optical function. A potential layer system to realize an antireflection function and to improve the mechanical properties simultaneously is a combination of hard coating SiO2 with classical 4-layer antireflection system consisting of SiO₂ and Ta₂O₅. Plasma-Ion Assisted Deposition (Plasma-IAD) at room temperature has been applied for coating experiments on PMMA and Polycarbonate. The temperature on a polymere substrate can reach a critical value in respect to its low thermal stability, if thick layers Ta₂O₅ have to be deposited. The increase of temperature is mainly determined by the radiation heat of electron beam evaporator. With needle optimization, an alternative coating design has been developed. The design is characterized by low thickness of high refractive index layers, which add up to less than about 5% of the total multilayer thickness. The high refractive index layers are almost evenly distributed over the whole stack. The total thickness of this kind of coating is adjustable between 800 nm and about 2600 nm. The mechanical properties of the coating deposited on plastics correspond to that of a single SiO₂ layer of the same thickness.