Vacuum roll-to-roll technologies for transparent barrier films
Thin transparent layers on polymer films are being used to drastically enhance the permeation barrier properties of polymer films while at the same time maintaining the flexibility and optical transparency of the polymer film. Applications range from food packaging films to encapsulation films for solar cells or flexible electronics. This paper reviews and compares several technologies for the making of transparent barrier coatings by vacuum roll-to-roll coating. Plasma-activated deposition of alumina layers may be used for highly productive deposition of barrier layers on PET but also on CPP and BOPP. An example of the industrial use of this technology will be given. The potential of this process for high barrier films will be discussed. Reactive magnetron sputtering is suitable for the deposition of barrier films with high thickness uniformity and over a wide thickness range. The barrier properties of different materials will be presented in comparison to other technologies. A magnetron based PECVD process may be used to deposit an interlayer in multilayer structures in-line to magnetron sputtering. A critical issue here is the defect generation during the deposition process. In this paper, also an all-in-vacuum multilayer barrier technology will be presented and compared to the different single layer and other multilayer approaches.