Electroluminescent Display

Although there is considerable interest today in electroluminescent display devices, interest in this subject has varied greatly in the past. As far back as 1937 Destriau carried out experiments on phosphor powders and discovered that luminescence could be produced by the direct application of an electric field.3 Unfortunately his work was either ignored or looked upon with suspicion by the scientific community until 1950 when workers at the Sylvania Co. demonstrated that practical largetrea luminescent panels12 could be made, bsed on Destriau's work. The ensuing few years saw much activity as individuals at various laboratories undertook the study of electrically addressing such panels with the thought of flat-panel TV displays as their ultimate goal. The confidence tnd euphoria initially prevailing soon gave way to widespread pessimism as it became evident that some very difficult problems stood in the way. Aside from the fact that relatively high voltages were required to excite electroluminescent layers, the low average brightness obtained under pulsed or intermittent excitation when sequentially addressing elements seemed discouraging. In addition it was found that the addressing of selected elements by arrays of X-Y conductors caused excessive excitation of other elements, making the contrast of any image impractically low. Equally discouraging was the fact that the operating life of early layers was frequently only a few hundred hours.