GB1423011A - Light emitting devices - Google Patents

Abstract

1423011 Electroluminescence NORTHERN ELECTRIC CO Ltd 22 Feb 1973 [22 Feb 1972 24 Feb 1972] 8829/73 Heading C4S [Also in Divisions F4 and H1] A solid state light-emitting device comprises parabolic reflector 10, a semi-conductor electroluminescent element 1 at the focus, and encapsulating transparent insulating material with polylenticular lens formation 54 for spreading the light and central conical recess 53 of included angle such that light incident on the recess from the EL element is reflected outwards towards the reflector. PN-junction 2 may be formed in GaP : Zn, O (visible emitting). Pedestal 11 ensures no light is reflected on to the central part of the front face of the insulating material which is illuminated directly. The reflector provides electrical contact to negative lead 13. The lamp shown is circular, the reflector being a paraboloid rather than a parabolic cylinder. To improve the viewing angle (e.g. to 180 degrees), sectoring and/or increase in driving current may have to be accepted. Reflector 52 is composed of three conical sections 55, 56, 57(cf. also Fig. 2, not shown). Dotted lines (58) indicate light rays, and some light will also pass through flat base (59). Protective cup 60 may be a coloured transparent plastic to provide a filter. If the s/c element emits in the non-visible range, an upconverting phosphor (e.g. infra-red to visible) may be coated directly on the element or on a further support. Indicator and signal light applications are instanced. The EL source may be 0À015 inch square.