Gravure printing of Ag electrodes for electroluminescent lighting

Electroluminescent lighting (EL) is a form of printed lighting on flexible film processed traditionally using screen printing technique for small areas or panel sized formats. Roll to roll slot coating of EL inks (phosphor, dielectric and Ag conductor) was implemented to increase productivity for large area printed electronics applications. However, material cost remains a big concern for widespread industry adoption of printed lighting. In this work, the Ag electrode thickness on printed lighting was successfully reduced by two thirds by conversion of slot coating to gravure printing. A wide range of printing thicknesses and sheet resistivities were produced by varying gravure cell design. A minimum print thickness range of 5∼7 μm was found feasible without defects with sheet resistance of 210 Ω/sq. This was achieved by gravure cell depth of 75 μm. Printing layer thickness can be increased easily by increasing gravure cell depth. Print layer thickness under 5 μm generated porosities. The printed lighting brightness was almost unchanged by reduced electrode thickness.