Backlight Using LED Parallel to Light Guide Surface

• US 20080266900A1
• Filed: 07/10/2008
• Published: 10/30/2008
• Est. Priority Date: 08/25/2006
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.), Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Harbers, Gerard, Pugh, Mark, Bierhuizen, Serge
• Granted Patent: US 8,061,884 B2
• Time in Patent Office: Days
• US Class Current: 362/609
• CPC Class Codes: G02B 6/0016 Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/002 by shaping at least a portion of the light guide, e.g. with collimating, focussing or diverging surfaces
• CPC Class Codes: G02B 6/0025 Diffusing sheet or layer; Prismatic sheet or layer
• CPC Class Codes: G02B 6/0031 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0068 Arrangements of plural sources, e.g. multi-colour light sources
• CPC Class Codes: G02B 6/0091 of the light source relative to the light guide G02B6/0021 takes precedence

Abstract

Various embodiments of corner-coupled backlights are described, where one or more white light LEDs are optically coupled to a truncated corner edge of a solid rectangular light guide backlight. The one or more LEDs are mounted in a small reflective cavity, whose output opening is coupled to the truncated corner of the light guide. The reflective cavity provides a more uniform light distribution at a wide variety of angles to the face of the truncated corner to better distribute light throughout the entire light guide volume. To enable a thinner light guide, the LED die is positioned in the reflective cavity so that the major light emitting surface of the LED is parallel to the top surface of the light guide. The reflective cavity reflects the upward LED light toward the edge of the light guide.

Claims

1. A light emitting device comprising:

a light emitting diode (LED) die having a major light emitting surface, the LED die being mounted on a submount surface;

a reflective cavity housing the LED die, the cavity having an opening for light to exit; and

a substantially rectangular light guide formed of a solid material having a top surface and an edge, the light guide adapted for supplying light as a backlight through the top surface of the light guide, the opening of the reflective cavity being optically coupled to the edge of the light guide for injecting light into the light guide;

wherein the LED die is housed within the reflective cavity such that the major light emitting surface and the submount surface are substantially parallel to the top surface of the light guide, whereby light emitted by the major light emitting surface of the LED die is reflected within the reflective cavity towards the edge of the light guide.

2. The device of claim 1 wherein the reflective cavity comprises a rectangular cavity.

3. The device of claim 1 wherein the reflective cavity comprises a rounded cavity.

4. The device of claim 1 wherein the reflective cavity comprises an elliptical cavity.

5. The device of claim 1 wherein the reflective cavity comprises a parabolic cavity.

6. The device of claim 1 wherein the edge of the light guide is a truncated corner edge.

7. The device of claim 6 wherein a face of the truncated corner has rounded features.

8. The device of claim 1 wherein the LED die is spaced from the edge.

9. The device of claim 1 wherein there is no lens over the LED die.

10. The device of claim 1 wherein the reflective cavity has reflective walls, wherein at least one wall extends over a surface of the light guide.

11. The device of claim 1 wherein the LED die includes a phosphor layer for creating white light.

12. The device of claim 1 further comprising a plurality of LED dies in the reflective cavity.

13. The device of claim 1 wherein the submount surface is outside of a plane of the light guide.

14. The device of claim 13 wherein the light guide has a bottom surface, wherein a portion of the submount surface is directly below the bottom surface of the light guide.

15. The device of claim 1 further comprising liquid crystal display layers over the light guide.