Laser patterning of printed silver for selective lighting of electroluminescence film

Abstract

We propose a method to use laser to pattern a 6.6 μm-thick Ag back electrode layer on electroluminescence (EL) film to electrically isolate designated regions towards the functionality of selective lighting. The laser processing system employs a 20 W, 1064 nm wavelength, nanosecond-pulsed, master oscillator power amplifier (MOPA) fibre laser as the laser source. A dynamic focusing configuration is adopted as a replacement of conventional telecentric lens setup for beam focusing and delivery, with a focal spot size of 33 μm and a speed as high as 3 m/s. The effects of processing parameters on ablated channel width, depth, quality, elemental composition and electrical isolation are investigated. It is found that a higher deposited laser energy causes kerf width and depth, as well as isolation reproducibility to increase, at a cost of increased chance of damage to surrounding electrode and substrate layer. Based on the findings, a processing recipe is established to isolate Ag electrode by producing channels as narrow as (41.3 ± 0.8) μm without introducing collateral damage to the film. Using selected parameter combinations from the processing window, the uniformity of laser ablation over a 300 × 200 mm2 scanning area is examined. Finally, using the raster scanning method, selective lighting over a designated area of 295 × 180 mm2 is demonstrated.