A photoconductive material (11) coated on a drum, belt or sheet (22) is formed with a first photoconductive layer (11b) which is insensitive to red light, a second photoconductive layer (11d) which is sensitive to red light and a transparent insulating layer (11c) formed either between the photoconductive...http://www.google.de/patents/US4335194?utm_source=gb-gplus-sharePatent US4335194 - Two color electrophotographic process and material
