Roll-to-Roll Technology on Pilot Scale for Transparent Ultra-High Multilayer barriers
Thin transparent layers on polymer films are used to drastically enhance the permeation barrier properties of polymer webs while at the same time maintaining the flexibility and optical transparency. Applications range from food packaging films to encapsulation films for solar cells or flexible electronics. Very low water vapor and oxygen transmission rates are required for the encapsulation of flexible OPV devices and OLEDs. This paper introduces a new technology for manufacturing ultra-high permeation barrier films using a roll-to-roll coating process. This multilayer barrier is based on reactively sputtered oxide barrier layers and an interlayer of inorganic-organic hybrid polymers (ORMOCER®s). The multilayer barrier is compared to other high barrier technologies and evaluated regarding barrier performance, optical transparency, surface properties and reproducibility. The water vapor transmission rate (WVTR) has been measured using different methods for different sample sizes and test conditions. The measurement limit of a MOCON Aquatran® system (5·10-4 g/(m²d)) has been reached with a three layer stack at 38°C / 90% relative humidity. The technology is now being used for a pilot production of barrier films. Coated rolls with a width of 400 mm and several 100 m in length can be provided for development purposes. In addition to the barrier layers, further layers can be applied to the polymer film to provide a mechanical protection, a smoothing layer for further processing or transparent conductive layers for e.g. manufacturing of flexible organic solar cells or flexible OLEDs. Applications such as using the barrier film as either a substrate for organic electronic devices or for the encapsulation of such devices will be discussed.