Wide-area illumination panels employing flexible printed circuits and side-emitting LEDs

A wide-area lighting emitting panel, comprising:

• an optically transmissive sheet having a first broad-area surface, an opposing second broad-area surface, a first edge, an opposing second edge parallel to the first edge, a third edge perpendicular to the first and second edges, a fourth edge parallel to the third edge, a light mixing region adjacent to the first edge, and a two-dimensional light extraction region separated from the first edge by the light mixing region;
• a plurality of light extraction features distributed across the two-dimensional light extraction region with a density increasing along a direction from the first edge to the second edge and configured for extracting light from the optically transmissive sheet towards opposite sides of the optically transmissive sheet;
• a reflector positioned generally parallel to the optically transmissive sheet and configured to reflect light being extracted from the optically transmissive sheet;
• a light diffuser;
• a flexible optically transmissive prism sheet positioned parallel to the optically transmissive sheet and comprising a first prism film having a first array of parallel linear prisms facing away from the optically transmissive sheet and longitudinally extending between two edges of the flexible optically transmissive prism sheet;
• a flexible LED strip located adjacent to a surface of the light mixing region and extending parallel to the first edge, wherein the flexible LED strip comprises a flexible printed circuit having a major surface extending generally parallel to the first and second broad-area surfaces and disposed in direct or indirect contact with the surface of the light mixing region, and a linear array of electrically interconnected side-emitting LED packages mounted to the major surface such that a plane of a light emitting surface of each of the side-emitting LED packages is oriented perpendicular to the major surface;
• and
• a structural housing element at least partially encasing the linear array of electrically interconnected side-emitting LED packages and covering at least a portion of the light mixing region, the structural housing element comprising a linear channel formed from a metallic material and having an opening configured to provide a light passage from the linear array of electrically interconnected side-emitting LED packages towards the light mixing region;
• wherein at least a portion of the light mixing region has smooth and planar surfaces which are parallel to one another and generally free from the light extraction features, wherein the light mixing region is configured for mixing and guiding light towards the light extraction region using optical transmission and total internal reflection from the smooth and planar surfaces, wherein at least one of the electrically interconnected side-emitting LED packages has a height of less than 2 mm, wherein at least some of the plurality of light extraction features are separated from one another and from each of the first, second, third, and fourth edges by smooth and planar surface portions of the optically transmissive sheet, and wherein at least one of the plurality of light extraction features comprises a light-diffusing surface relief microstructure.