Enhanced LCD backlight

• US 7,278,775 B2
• Filed: 09/09/2005
• Issued: 10/09/2007
• Est. Priority Date: 09/09/2004
• Status: Active Grant

• Current Assignee: Fusion Optix Inc.
• Original Assignee: Fusion Optix Inc.
• Inventors: Yeo, Terence E., Coleman, Zane A.
• Primary Examiner(s): O'Shea; Sandra
• Assistant Examiner(s): Bennett; Zahra I.
• Application Number:
  US11/223,660
• Publication Number:
  US 20060056166A1
• Time in Patent Office: 760 Days
• Field of Search: 362/615, 362/627, 362/629, 362/623, 362/19
• US Class Current: 362/627
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/0041 provided in the bulk of the light guide
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0051 Diffusing sheet or layer
• CPC Class Codes: G02B 6/0053 Prismatic sheet or layer; Brightness enhancement element, sheet or layer
• CPC Class Codes: G02B 6/0055 Reflecting element, sheet or layer
• CPC Class Codes: G02B 6/0056 for producing polarisation effects, e.g. by a surface with polarizing properties or by an additional polarizing elements
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: G02B 6/0078 Side-by-side arrangements, e.g. for large area displays

Abstract

A light guide containing substantially aligned non-spherical particles provides more efficient control of light scattering. One or more regions containing ellipsoidal particles may be used and the particle sizes may vary between 2 and 100 microns in the smaller dimension. The light scattering regions may be substantially orthogonal in their axis of alignment. Alternatively, one or more asymmetrically scattering films can be used in combination with a backlight light guide and a reflector to produce an efficient backlight system. The light guides may be manufactured by embossing, stamping, or compression molding a light guide in a suitable light guide material containing asymmetric particles substantially aligned in one direction. The light scattering light guide or non-scattering light guide may be used with one or more light sources, collimating films or symmetric or asymmetric scattering films.

Claims

1. A light guide comprising:

a) at least one input surface and output surface wherein incident light exits the light guide when the total internal reflection condition is not satisfied; and

b) a first scattering region disposed to receive light from the input surface and direct light to the output surface, comprising a continuous phase material of refractive index n_x1 and a first dispersed phase material of refractive index n_x2 wherein |n_x1−

n_x2|>

0.001 and one or more of the first dispersed phase domains are non-spherical in shape and have a domain dimension in the x, y, or z direction in the range of about 0.005 to 1 cm.

2. The light guide of claim 1, wherein the first scattering region is disposed in between the input surface and the output surface.

3. The light guide of claim 1, wherein the first dispersed phase non-spherical domains are ellipsoidal in shape with their major axes on average aligned substantially parallel or perpendicular to the light emitting source.

4. The light guide of claim 1, wherein the input surface is at an angle θ

to the output surface.

5. The light guide of claim 4, wherein θ

is approximately 0 degrees such that the input surface is parallel to the output surface.

6. The light guide of claim 1, further comprising a second dispersed phase material of refractive index n_x3.

7. The light guide of claim 1, wherein the light scattering region is contained within an optical film that is optically coupled to a surface of the light guide.

8. The light guide of claim 1, wherein the concentration of the dispersed phase material in the continuous phase material varies spatially.

9. The light guide of claim 1, wherein the thickness of the region containing the dispersed phase material in the continuous phase material varies spatially.

10. The light guide of claim 1, wherein the dispersed phase domains are substantially confined in at least one zone, the zone having a thickness that is less than the total thickness of the light guide.

11. The light guide of claim 1, further comprising a second light scattering region containing a second dispersed phase material of refractive index n_x4.

12. The light guide of claim 11, wherein the second dispersed phase domains are ellipsoidal in shape.

13. The light guide of claim 12, wherein the ellipsoidal domains are aligned on average substantially parallel to a second light emitting source.

14. The light guide of claim 1, wherein the first dispersed phase domains are substantially confined in at least one zone, and further comprising one or more zones containing dispersed phase domains with intervening zones substantially free of dispersed phase domains.

15. A backlight assembly comprising:

a) a housing;

b) a light emitting source; and

c) the light guide of claim 1.

16. The backlight of claim 15, wherein the light emitting source is an array of light sources.

17. The backlight of claim 16, wherein the array of light sources is a substantially linear array.

18. The backlight of claim 15, wherein the light source is at least one cold cathode fluorescent lamp.

19. The backlight of claim 15, wherein the light source is at least one light emitting diode.

20. The backlight of claim 15, further comprising at least one region selected from the group consisting of hardcoat, anti-glare, anti-blocking, UV-absorbing, anti-static or anti-reflection region.

21. A display comprising a flat screen display panel and the backlight assembly of claim 15.

22. The backlight of claim 15, further comprising at least one region selected from the group consisting of light diffusing region, light collimating region, reflective region, absorptive polarizing region, or polarization dependant reflective region.

23. A liquid crystal display illuminated with the backlight of claim 22 wherein one or more of the features are disposed in the light path between the light source and the liquid crystal display.

24. The light guide of claim 1, wherein the light guide is bounded such that light rays traveling at an angle that is larger than a critical angle will reflect and remain within the light guide.

25. A backlight assembly comprising:

a) a housing;

b) a light emitting source;

c) a light guide comprising;

i. at least one input surface and output surface wherein incident light exits the light guide when the total internal reflection condition is not satisfied; and

ii. a first scattering region disposed to receive light from the input surface and direct light to the output surface, comprising a continuous phase material of refractive index nx1 and

a first dispersed phase material of refractive index nx2 wherein |nx1−

nx2|>

0.001 and one or more of the first dispersed phase domains are non-spherical in shape; and

d) wherein the backlight has a speckle contrast is below 80%.