Nanostructuring of ethylene tetrafluoroethylene films by a low pressure plasma treatment process
A vacuum plasma treatment is used to create stochastic nanostructures on ethylene tetrafluoroethylene (ETFE) films. Such nanostructures exhibit excellent anti-reflection (AR) properties. Therefore, nanostructures have good application potential in displays, large area organic electronics and solar cells. In this paper, a reactive dual-magnetron plasma process is used to prepare nanostructured surfaces on ETFE in a vacuum roll-to-roll coater. The influences of different process parameters like induced plasma power density and web speed on structure formation and surface properties were investigated. The best combination of high productivity and a high AR-effect of this single step etching process is achieved at 1.35 m/min by induced power density of 5.91 W/cm².Thereby a transmittance of 95.1 % at 600 nm wavelength has been reached. This results in an AR-effect of about 1.1 %. A higher transmittance may be achieved by using a three-step process. This process includes a pretreatment followed by the etching step and the deposition of a top coat. This yields a transmittance of 98.7 % at 600 nm wavelength for double side treatment. The resulting morphology and further properties of the treated ETFE film are discussed.