GB953329A - Electroluminescent devices - Google Patents

Abstract

<PICT:0953329/C3/1> <PICT:0953329/C3/2> An electroluminescent device comprises a strip 10 of piezo-electric material, first and second contacts 12, 14 secured opposite one another to opposite surfaces of the strip, third and fourth contacts 18, 20 spaced from the contacts 12, 14 and secured opposite one another to opposite surfaces of the strip, an electroluminescent layer 24 on a surface of the strip between and spaced from the contacts 12, 18, a first transparent electrode 26 upon the exposed surface of the electroluminescent layer, a second electrode 28 upon the surface of the strip 10 remote from the layer 24 and opposite the electrode 26, and terminations 30, 32 fixed to each end of the strip 10 adapted to absorb substantially without reflection elastic waves reaching them from the strip. In modifications the second and fourth contacts 14, 20 and the second electrode 28 are electrically connected together, e.g. earthed, and can be constituted by a continuous electrode. Fig. 2 shows a circuit arrangement comprising means to apply a sawtooth pulse train between the first and second contacts 12, 14, means to apply a sawtooth pulse train between the third and fourth contacts 18, 20, and means to apply a spike pulse train between the first and second electrodes 26, 28. Means are provided for varying the relative timing of the pulses in the three trains and the three trains have such timing that a pulse occurs between the electrodes 26, 28 when elastic waves generated in the strip 10 by the pulses of the first two trains reach the same point on the strip. Means are provided for varying the recurrence frequency of at least one of the trains relatively to the other train or trains in such a manner that the point travels along the strip. Means are also provided to amplitude modulate the pulses in the third train. Specification 905,682 is referred to.