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

Abstract

A backlight for an LCD display has an optically transmissive sheet with first and second broad-area surfaces, four edges, a light mixing region adjacent to a first edge, and a light extraction region. The mixing region has smooth planar surfaces for guiding light via total internal reflection. Light extraction features are distributed across the extraction region with increasing density toward the opposing edge. A flexible LED strip extends parallel to the first edge, with a flexible circuit and side-emitting LED packages of less than 2 mm in height. The LED packages have light emitting surfaces perpendicular to the circuit's major surface. A metallic housing partially encases the LED array with a linear channel providing light passage to the mixing region. At least one extraction feature has a surface relief microstructure separated from other features and edges by smooth planar portions of the sheet.