Roll to roll deposition of transparent electrodes on permeation barrier coatings

The European project PI-SCALE has set the aim 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 ITO layer with a sheet resistance below 30 Ohm/square was sputtered onto PET substrate at room temperature 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 could serve as a powerful parameter for the optimization of the layer properties. The amount of hydrogen gas was varied between zero and ten percent of the total gas flow.

PET film (Melinex ST 504) was used as the substrate . The film was equipped with a planarizing layer and a permeation barrier coating on top of it.

It was shown how the permeation barrier was prevented from getting deteriorated by conveying the film and by the ITO sputtering process. The removal of a protective interlayer film directly before entering the sputtering zone had turned out to be decisive for the layer quality. The same held  true for the application of a protective interleaf immediately after leaving the sputtering zone. By incorporating these two steps the permeation barrier could be kept below 1x10-3 g/m2day, which is the lower detection limit of the applied  coulometric measurement device.

The paper provides a short outlook on the subsequent manufacturing steps towards the OLED device as well as to the ways to achieve lower sheet resistance values compared to ITO.