Transparent diffusive oled substrate and method for producing such a substrate

The invention is drawn to a transparent diffusive OLED substrate comprising the following successive elements or layers: - a transparent flat substrate made of mineral glass having a refractive index of between 1.45 and 1.65, - a rough low index layer comprising mineral particles, said mineral particles being bonded to one side of the substrate by means of a low index enamel, the mineral particles near, at or protruding from the enamel's surface creating a surface roughness characterized by an arithmetical mean deviation R a comprised between 0.15 and 3 µm, the mineral particles and enamel both having a refractive index of between 1.45 and 1.65; - a high index planarization layer made of an enamel having a refractive index comprised between 1,8 and 2,1 covering the rough low index layer (b). It is also drawn to a method for preparing such a diffusive OLED substrate.