The present invention relates to a light-emitting, transparent, optionally flexible film system based on polymers, to a process for its production and to its use.
WO03/037031 and U.S. Pat. No. 5,780,965 describe light-emitting film systems which are formable and onto the back of which a material can be injected. In a first production step, the graphic design, the material for the front, transparent electrode, the inorganic luminescent agent and the material for the back electrode are printed onto a transparent substrate. When this film system is used directly, the back is insulated, for example, by means of a protective film. However, it is also possible for the system to be pre-formed after the printing process and then inserted into an injection-molding tool, in which a material is injected onto its back. By way of contacts attached to the electrodes in a suitable manner, it is possible to apply an alternating voltage field (e.g., 110 V, 400 Hz) with the aid of an inverter and to excite the luminescent agent for the emission of light. In U.S. Pat. No. 5,780,965, the material used for the transparent electrode is, for example, indium-doped tin oxide (ITO). In WO03/037031, Baytrone® chemicals for the production and processing of conductive substances which are commercially available from H.C. Stark GmbH & Co. KG are disclosed. The advantage of Baytron® chemicals over ITO is their better formability. The luminescent agent—which is generally doped tin oxides or tin sulfides—is dispersed in a paste suitable for a screen printing process. Such luminescent film systems have been used substantially for small-area applications because, inter alia, production is complex and the costs are high.