Roll to Roll Deposition of Transparent Electrodes on Permeation Barrier Coatings
The European project PI-SCALE has set an objective to create a virtual pilot manufacturing line for various types of OLED lighting devices. An important part of this virtual pilot line is the roll-to-roll sputtering of the anode layer. An indium tinoxide (ITO) layer with a sheet resistance below 30 Osq (ohm/square) was sputtered onto a continuously moving polyethylene terephthalate (PET) film substrate using a rotatable magnetron. The sputtering performance of a bonded ITO target was compared to the performance of a plasma sprayed ITO target. It was demonstrated that the variation of the hydrogen content of the sputtering gas atmosphere can serve as a powerful parameter for the optimization of the layer properties. This gas was varied between zero and ten percent of the total gas flow. The PET film was equipped with a planarizing layer and a permeation barrier coating on top of it. It was shown how the permeation barrier is prevented from getting deteriorated by conveying the film. The removal of a protective interleaf film directly before entering the sputtering zone turned out to be decisive for the layer quality. The same holds true for the application of a protective interleaf immediately after leaving the sputtering zone. By applying these two steps, the permeation barrier could be kept below 1×10-3 g/m2day, which is the lower limit of the applied coulometric measurement device.