Vacuum coating on polymer films for outdoor applications

This paper discusses functionalization of ETFE webs by vacuum roll-to-roll deposition of permeation barrier layers and highly conductive transparent electrodes for outdoor applications. A 100 nm thick gas barrier layer (zinc-tin-oxide - ZTO) and a 60nm thick transparent conductive layer stack(indium-tin-oxide - ITO 25 nm - Ag 10 nm -ITO 25 nm) achieve a water vapor transmission rate of 0.01 g/m²d (at38°C/90% r.h.) and sheet resistance of< 6 O/sq on a commercial grade ETFE film. However, the elastic properties of ETFE as well as its creep-behavior require specific attention during roll-to-roll processing and for design of the functional layer stacks. Inconsequence, layer thicknesses and material selection must be balanced between functional performance and the ability to survive deformation of the polymer web. This paper compares functional performance and crack formation under strain load of different layer stacks on both PET and ETFE substrates.