Patent GB-746502-A (GB)
Title: Electroluminescent display devices
IPC: G09F9/33
Filed: 1953-08-28
Abstract: 746,502. Electroluminescence. SYLVANIA ELECTRIC PRODUCTS, Inc. Aug. 28, 1953 [Aug. 28, 1952], No. 23870/53. Class 39 (1). [Also in Group XL (b)] An electroluminescent device for television display comprises a layer of phosphor material between two arrays of conductive grid-like elements, the elements of one array being inclined to those of the other array. The device comprises a transparent sheet 10, e.g. glass, coated with conductive strips 11, e.g. of silicon, tin or titanium chloride deposited in a reducing atmosphere, a superimposed layer of a phosphor 12, e.g. copper activated zinc sulphide embedded in a plasticized nitro-cellulose and further conductive strips 13, e.g. aluminium, chromium or stainless steel, applied to the phosphor by vacuum deposition to form a mirror surface. In Fig. 3, the exposed ends of elements 11, 13 are connected by sheets 16, 19 of insulating material carrying a printed raster of ribbon conductors to commutators 17, 20, the sheets being wrapped round and clamped to the drums of the commutators. The brushes 22, 25 are connected in circuit with an alternating source 28 and contacts 30, 31 through which passes a perforated tape 33 defining an animated display. The commutator drums are driven by the motor 24, step-down gearing ensuring the different speeds of rotation for the line and frame scanning. The screen 43 in the television receiving apparatus of Fig. 4 is controlled by an electrical delay line 39, 40 on one side and by interlaced connections to commutators 46, 48 on the other. The generator 52 applies two voltages of rectangular waveform displaced 180 degrees in phase through shunted condensers to the commutators. A synchronizing signal separator 55 coupled to the receiver 36 synchronizes the generator 52 and applies the pulses to the delay line 39, 40. Two-phase detectors 70, 70<SP>1</SP>, each comprise a transformer 62, 63, 64 diode rectifiers 65, 66, load resistors 67, 68, 69 and a lowpass filter. The motor 51 driving the commutators is energized by a D.C. amplifier 60 which is synchronized through the phase detector 701 and the separator 55, and also drives both the A.C. generator 61 feeding the transformer 62 of the phase detector 70, and the A.C. generator 74 feeding the phase detector 70<SP>1</SP>. The voltage applied to the horizontal lines 44 by each commutator in its particular half-cycle of operation is such that its difference relative to the pulse voltage on the vertical lines 42 equals the light threshold voltage of the electroluminescent screen, and the amplitude of the television signal applied to lines 42 determines the light output of the screen. A cathode-ray tube with two sets of conductive segments (Fig. 5, not shown) may replace the two commutators. In a modified display device suitable for P.P.I., Fig. 6 (not shown), one set of conductive elements is an array of concentric circles and a second array radiates from the centre of the circle. In Fig. 7 (not shown), a sheet of dielectric material separates the elements 13 from a conductor sheet and forms the capacitance elements of the delay line 39, 40 of Fig. 4. The inductances 39 may be formed on the surface of the dielectric material by printing or etched-foil techniques. Specifications 704,166, 731,345 and 735,752 are referred to.