LIGHTING DEVICES WITH PATTERNED PRINTING OF DIFFRACTIVE EXTRACTION FEATURES

摘要

Extended area lighting devices include a light guide and diffractive surface features on a major surface of the light guide, at least some diffractive surface features adapted to couple guided-mode light out of the light guide. The diffractive features include first and second diffractive features disposed on respective first and second portions of the major surface. A patterned light transmissive layer, including a second light transmissive medium, optically contacts the second diffractive features but not the first diffractive features. A first light transmissive medium optically contacts the first but not the second diffractive features. The first and second portions may define indicia, and the first and second diffractive features provide low distortion for viewing objects through the light guide such that the indicia is not readily apparent to users when guided-mode light does not propagate within the light guide. Optical films having such diffractive features are also disclosed.