A Printed Electroluminescent Matrix Display: Implementation Details and Technical Solutions

Abstract

Electroluminescence (EL) of commercial phosphor pastes was investigated and an equivalent circuit of the EL stack was determined. The model was used to develop a simple driver electronics capable to operate electroluminescent displays (ELD) with a good contrast and visibility. Flexible displays with a passive matrix of 32 × 5 pixels and up to 11 pictogram elements were produced by screen printing on PET foil and combined with the driver to form a standalone unit. Several demonstrators with the ELDs integrated into a bag or a back pack were manufactured with the primary goal to allow traffic signalling for cyclists or skaters during the dark periods of day; the displays were controlled wirelessly using either a smartphone or a dedicated control device. Present work describes technical implementation details of the printed electroluminescent display and its driving electronics. The following aspects are discussed: empirical model of the EL stack, intensity of emitted light in dependence of driving voltage and frequency, waveforms used for driving the ELD, implemented driver circuit, layout and packaging considerations for the display module.