LED light engine for backlighting a liquid crystal display

• US 7,220,040 B2
• Filed: 11/12/2004
• Issued: 05/22/2007
• Est. Priority Date: 11/12/2004
• Status: Expired due to Fees

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Lengyel, John Michael, Holmes, Jonathan Frank
• Primary Examiner(s): Alavi, Ali
• Assistant Examiner(s): Sawhney, Hargobind S.
• Application Number:
  US10/988,334
• Publication Number:
  US 20060104090A1
• Time in Patent Office: 921 Days
• Field of Search: 362/612, 362/608, 362/633
• US Class Current: 362/612
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side

Abstract

An edge-lit backlighting system for liquid crystal displays employs a number of light strips in the form of thin, light weight sections of a thermally conductive substrate each of which mounts a plurality of light engines having an array of densely packed, primary color light emitting diodes, which, when collectively illuminated, produce a white light of desired reference white chromaticity.

Claims

1. An edge-lit backlighting system for use with a liquid crystal display, comprising:

a heat exchanger;

at least one light strip including a plurality of light engines mounted at spaced intervals therealong, each of said light engines including a plurality of primary color light emitting diodes, said light emitting diodes being selected so that when illuminated the primary color light emitted therefrom is combined to collectively produce a white light of desired reference white chromaticity;

a separate protective casing for enclosing said light emitting diodes on each of said light engines, each of said protective casings protruding from the surface of said light engine;

a light guide mounted in position to receive said white light produced by said at least one light strip;

a light reflective sheet coupled to said at least one light strip, said light reflective sheet and said at least one light strip being mounted to said heat exchanger, said light reflective sheet having an upturned, peripheral edge formed with a plurality of spaced apertures, each of said apertures receiving one of said protective casings of a light engine to permit the transmission of white light to said light guide while said space along said at least one light strip between adjacent light engines is covered by said reflective sheet; and

at least one enhancement film overlying said light guide.

2. The system of claim 1 in which said at least one light strip includes a thermally conductive substrate formed in an elongated strip, said plurality of light engines being coupled to said elongated strip.

3. The system of claim 2 in which said elongated strip is a printed wiring board, said printed wiring board being formed with at least one metal heat spreader and a number of thermally conductive via, each of said light engines coupled to said elongated strip being positioned in thermal communication with said via.

4. The system of claim 3 in which said printed wiring board is formed with lines of weakness at intervals therealong in between said light engines, said printed wiring board being breakable at each of said lines of weakness to allow for the formation of a shortened strip of desired length.

5. The system of claim 3 further including a layer of thermally conductive material connected between said printed wiring board and said heat exchanger, said layer being flexible to form a seal at said printed wiring board and at said heat exchanger.

6. The system of claim 1 in which each of said protective casing is a clear section of low temperature glass ceramic material.