Patent GB-972481-A (GB)
Title: Display device
IPC: H05B33/12
Filed: 1960-10-11
Abstract: <PICT:0972481/C4-C5/1> A solid state display device has an electroluminescent layer 12 common to a multitude of independently controllable display elements and a control structure 20 comprising a layer 22 of ferro-electric material having one surface contiguous with or in close proximity to one surface of the electroluminescent layer and being common to all of the display elements, and a multitude of first or control electrodes 23 disposed on the other surface of the ferro-electric layer, whereby each of the display elements is associated with one of the electrodes 23, each of the display elements including at least one non-linear condenser defined between its associated electrode 23 and a second electrode 24 disposed on said other surface of the layer 22, and the or each non-linear condenser being controlled with respect to its effective capacitance by input signals applied to the electrode 23.  Each of the display elements is associated with circuit means for impressing a time varying electric field across the electroluminescent layer 12, the magnitude of which is controlled in the area of a particular display element in accordance with the effective capacitance of the non-linear condenser or condensers associated with such display element. Each display element includes a second non-linear condenser defined between its associated first electrode 23 and a third electrode 25 disposed on said other surface of the ferro-electric layer 22, the circuit means, electroluminescent layer and non-linear condensers being so associated as to provide a bridge circuit for each display element with the electroluminescent layer being connected in the common branch of the bridge circuit.  A continuous transparent electrode 14 is disposed on the other surface of the electroluminescent layer 12 and a multitude of fourth electrodes 18 is disposed on the other surface of the layer 12, thereby defining a multitude of electroluminescent condensers, the condenser of each display element being connected in the common branch of the bridge circuit.  A series circuit of a first A.C. source and a D.C. source is connected between the transparent electrode 14 and the second electrodes 24 and a second A.C. source is connected between the electrode 14 and the third electrodes 25.  The input signals to the electrodes 23 can be supplied by directly coupled circuit means or by modulated electron beam bombardment as described in Specification 829,255.  The electroluminescent layer 12 can comprise copper activated zinc sulphide in a binder of polyvinyl chloride or glass, the electrode 14 tin oxide or gold, the electrodes 18 evaporated aluminium and the electrodes 23, 24 and 25 of etched silver. The ferro-electric layer 22 can comprise barium titanate, barium-strontium titanate, barium stannate, sodium columbate, sodium tantalate, potassium columbate or potassium tantalate. In a modified construction in which the ferroelectric layer 22 is contiguous with the electroluminescent layer 12 without intervening electrodes 18, an opaque grid of aluminium can be formed on the other surface of the electroluminescent layer.  Specifications 858,392, 858,393 and 972,482 also are referred to.