| abstract |
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 TiO2 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). |