A thin film electroluminescent element has a color changing layer doped with green luminescent material and red fluorescent material and separated from an electroluminescent layer for generating blue light for converting the blue light to green light and the green light to red light, and the separation...http://www.google.de/patents/US5717289?utm_source=gb-gplus-sharePatent US5717289 - Thin film electroluminescent element easily regulating emitted light to white 
