Backlight Unit for LCD Displays with Waveguide-Integrated Ridge Structures and Side-Emitting LEDs

A backlight unit for LCD displays, comprising:

• a planar light transmissive sheet having a generally rectangular shape, a generally planar first broad-area surface, an opposing second broad-area surface, a first edge, and an opposing second edge which is parallel to the first edge, the planar light transmissive sheet configured to guide light along a direction from the first edge to the second edge using total internal reflection at each of the first and second broad-area surfaces;
• a patterned light extraction area located at a distance from the first edge;
• a light mixing area located between the first edge and the patterned light extraction area;
• a plurality of light extraction microstructures formed in or on the first broad-area surface and distributed over the patterned light extraction area according to a two-dimensional pattern;
• a plurality of notches formed in the first edge;
• a reflector positioned adjacent to one of the first or second broad-area surfaces;
• and
• a side-emitting LED strip positioned adjacent and optically coupled to the first edge of the planar light transmissive sheet, the side-emitting LED strip comprising:
• a flexible printed circuit having a major surface, and
• a linear array of side-emitting LED packages arranged along a length dimension of the flexible printed circuit with a regular spacing and mounted to the major surface,
• wherein a light-emitting surface of each of the side-emitting LED packages is oriented perpendicular to the major surface and has at least one dimension which is greater than a thickness of the planar light transmissive sheet, and
• wherein the major surface of the flexible printed circuit is oriented parallel to the planar light transmissive sheet and positioned directly or indirectly in contact with one of the first or second broad-area surfaces.

A backlight unit for LCD displays, comprising:

• a light transmissive sheet having a generally rectangular shape, a planar first broad-area surface, an opposing second broad-area surface, a first edge, and an opposing second edge, the light transmissive sheet configured to guide light along a direction from the first edge to the second edge using total internal reflection at the first and second broad-area surfaces;
• a patterned light extraction area located at a distance from the first edge;
• a generally rectangular light mixing area located between the first edge and the patterned light extraction area;
• a plurality of light extraction microstructures formed in or on at least one of the first and second broad-area surfaces and distributed over the patterned light extraction area according to a two-dimensional pattern;
• a linear array of discrete optical elements distributed along a length dimension of the first edge with a regular spacing, each of the discrete optical elements being formed from an optically transmissive material and attached to the first broad-area surface or the second broad-area surface;
• a reflector positioned adjacent to one of the first or second broad-area surfaces;
• and
• a side-emitting LED strip positioned adjacent and optically coupled to the first edge of the light transmissive sheet, the side-emitting LED strip comprising:
• a flexible printed circuit having a generally planar major surface, and
• a linear array of side-emitting LED packages arranged along a length dimension of the flexible printed circuit with a regular spacing and mounted to the generally planar major surface,
• wherein a light-emitting surface of each of the side-emitting LED packages is oriented perpendicular to the generally planar major surface and has at least one dimension which is greater than a thickness of the light transmissive sheet, and
• wherein the generally planar major surface is oriented parallel to the light transmissive sheet and positioned directly or indirectly in contact with the first or second broad-area surfaces.