Method of making backlight units for lcd displays using side-emitting leds and optical waveguides

A method of making a backlight unit for LCD displays, comprising:

• providing a thin and flexible light transmissive sheet having a first broad-area surface, an opposing second broad-area surface, a first edge, and an opposing second edge;
• forming a patterned light extraction area located at a distance from the first edge and a light mixing area located between the first edge and the patterned light extraction area by forming a plurality of light extraction microstructures in or on at least one of the first and second broad-area surfaces according to an area-distributed two-dimensional pattern;
• providing a side-emitting LED strip comprising a flexible printed circuit 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 a major surface of the flexible printed circuit such that a light-emitting surface of each of the side-emitting LED packages is oriented perpendicular to the major surface, wherein the light-emitting surface has a first dimension which is greater than a thickness of the light transmissive sheet;
• providing a plurality of flexible electrical contacts configured for electrically connecting the flexible printed circuit to a power supply;
• orienting the major surface of the flexible printed circuit parallel to the light transmissive sheet and positioning the major surface of the flexible printed circuit directly or indirectly in contact with the first or second broad-area surface;
• distributing an optically transmissive adhesive layer over at least a portion of the light mixing area;
• positioning a reflective layer on a first side of the light transmissive sheet;
• and
• covering two or more sides of the flexible printed circuit and at least a portion of the light mixing area using an opaque housing which comprises a metallic channel.

A method of making a backlight unit for LCD displays, comprising:

• providing a thin and flexible light transmissive sheet having a first broad-area surface, an opposing second broad-area surface, a first edge, and an opposing second edge;
• forming a patterned light extraction area located at a distance from the first edge and a light mixing area located between the first edge and the patterned light extraction area by forming a plurality of light extraction microstructures in or on at least one of the first and second broad-area surfaces according to an area-distributed two-dimensional pattern;
• providing a side-emitting LED strip comprising a planar printed circuit board and a linear array of side-emitting LED packages arranged along a length dimension of the planar printed circuit board with a regular spacing and mounted to the planar printed circuit board such that a light-emitting surface of each of the side-emitting LED packages is oriented perpendicular to the planar printed circuit board, wherein the light-emitting surface has a first dimension which is greater than a thickness of the light transmissive sheet;
• providing a plurality of electrical contacts configured for electrically connecting the planar printed circuit board to a power supply;
• orienting the planar printed circuit board parallel to a plane of the light transmissive sheet and positioning the planar printed circuit board directly or indirectly in contact with the first or second broad-area surface;
• positioning a reflective layer on a first side of the light transmissive sheet;
• and
• covering two or more sides of the planar printed circuit board and at least a portion of the light mixing area using an opaque housing which comprises a metallic heat conductive element,
• wherein each of the side-emitting LED packages having a generally rectangular shape with rounded corners and comprising a light-recycling cavity, one or more LED chips, an encapsulant, a reflective material, and a phosphor material.