U.S. Philips Corporation

Jeroen J Vleggaar

Coen T Liedenbaum

Adrianus J Berntsen

Yang Yang

Petrus J Peters

Aemilianus G Staring

Jeroen J Horikx

Henri M Boots

Robert J Demandt

Martinus B Van Der Mark

Marcus G Van Munster

Hermanus F Schoo

An organic electroluminescent device includes an electroluminescent element, which is enclosed in a housing. The deterioration in uniformity of the luminous surface, which occurs when an electroluminescent device is stored or operated under ambient conditions, and which deterioration manifests itself, for example, in the form of 'dark spots', can be overcome to a substantial degree in accordance with the invention by using an airtight and waterproof housing which is sealed by a low-melting metal, such as a BiSn alloy.

Organic electroluminescent device with housing

The illumination system (1) has a substrate (2) and an active layer (3) comprising an electroluminescent material, in which the active layer (3) is present between a first, optically transparent electrode layer (5) and a second electrode layer (7). The illumination system (1) is characterized in that a light-scattering layer (28) comprising a medium having light-scattering properties is present in a forward direction (29) with respect to the active layer (3), in which the non-scattered fraction of a (collimated) light beam, when passed through the light-scattering layer (8) in the forward direction (29), is in the range between 0.05 and 0.8, preferably in the range between 0.1 and 0.5. The light-scattering properties of the medium are preferably stronger as the light is more obliquely incident, as is achieved by using birefringent particles and/or media. A very suitable light-scattering layer (28) is a (half) monolayer of TiO.sub.2 particles provided on the substrate (2), with an average size of the (spherical) particles of 0.1-1 .mu.m. The light output of the illumination system (1) is further improved by providing the edges of the substrate (2) with a reflective coating (26).

Electroluminescent illumination system with an active layer of a medium

A description is given of a method of providing an electroluminescent device (20) comprising an active layer (5) of conjugated 2,5-alkyl- or alkoxy-substituted poly(p-phenylene vinylene) with inactive regions (51) and emissive regions (52) by means of patterned irradiation with UV light. Both regions (51) and (52) of the active layer (5) show a clear difference in electroluminescence, electrical resistance and solubility. By means of the above-described effects, displays can be manufactured without making use of structured electrode layers (3) and (11).

Electroluminescent device

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Eindhoven, Netherlands

Jeroen J Vleggaar