Light pipe having one or more integral diffusers

• US 6,386,721 B1
• Filed: 07/08/1999
• Issued: 05/14/2002
• Est. Priority Date: 07/08/1999
• Status: Expired due to Term

• Current Assignee: Luminit LLC
• Original Assignee: Physical Optics Corporation
• Inventors: Hosseini, Abbas, Savant, Gajendra
• Primary Examiner(s): CARIASO, ALAN B
• Application Number:
  US09/349,280
• Time in Patent Office: 1,041 Days
• Field of Search: 362/26, 362/31, 362/330, 362/333, 362/339, 362/355, 362/558, 359/599, 349/64
• US Class Current: 362/619
• 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

Abstract

A light pipe for a backlight assembly has a front surface and a back surface. The back surface includes an integral surface diffuser microstructure formed thereon. The front surface may also have an integral surface diffuser microstructure formed thereon as well. A backlight assembly has a reflective surface adjacent the back surface of the light pipe and a separate diffuser film layer disposed against the front surface. A pair of brightness enhancing film layers for collimating light are placed adjacent the diffuser film layer. A protective layer is disposed over the brightness enhancing film layers. The integral diffusers on the front and back surfaces of the light pipe significantly enhance the brightness and light distribution uniformity of the assembly without adding additional components or reducing other performance characteristics of the assembly.

Claims

1. A light pipe for a backlight assembly, the light pipe comprising:

a front surface;

a back surface opposite the front surface; and

an integral diffuser including at least one region of surface micro-structures formed in the back surface, wherein the integral diffuser comprises a central region of surface structures having at least one lateral edge and a lateral region of surface micro-structures adjacent to each lateral edge.

2. The light pipe of claim 1, wherein all the surface micro-structures produce identical light output characteristics when light is directed through the light pipe.

3. The light pipe of claim 1, wherein each region produces different light output characteristics when light is directed through the light pipe.

4. The light pipe of claim 1, wherein the surface micro-structures produce elliptical light output when light is directed through the light pipe.

5. The light pipe of claim 4, wherein the elliptical light output from at least one of the regions is between approximately 80°

-120°

horizontal and between approximately 5°

-30°

vertical over the entire surface area of the light pipe when light is directed through the light pipe.

6. The light pipe of claim 5, wherein the elliptical light output from at least one of the regions is approximately 95°

horizontal and approximately 25°

vertical over the entire surface area of the light pipe when light is directed through the light pipe.

7. The light pipe of claim 1, further comprising an integral diffuser including at least one region of surface micro-structures formed on the front surface.

8. The light pipe of claim 7, wherein the integral diffuser in the front surface has at least two regions of surface micro-structures.

9. The light pipe of claim 7, wherein the surface micro-structures formed in the front surface produce circular light output when light is directed through the light pipe.

10. The light pipe of claim 7, wherein the circular light output has an angle between approximately 0.5°

and 5.0°

when light is directed through the light pipe.

11. A backlight assembly for a display comprising:

a light pipe including;

a front surface,

a back surface, and,

an integral surface diffuser including at least one region of surface micro-structures formed in the back surface of the light pipe wherein the integral diffuser comprises a central region of surface structures having at least one lateral edge and a lateral region of surface micro-structures adjacent to each lateral edge; and

,

at least one light source located adjacent an edge of the light pipe.

12. The backlight assembly of claim 11, wherein all the surface micro-structures produce identical light output characteristics when light is directed through the light pipe.

13. The backlight assembly of claim 11, wherein each region produces different light output characteristics when light is directed through the light pipe.

14. The backlight assembly of claim 11, wherein the surface micro-structures produce elliptical light output when light is directed through the light pipe.

15. The backlight assembly of claim 14, wherein the elliptical light output from at least one of the regions is about 95°

horizontal and 25°

vertical over the entire surface area of the light pipe when light is directed through the light pipe.

16. The backlight assembly of claim 11, further comprising a diffuser layer disposed adjacent the front surface of the light pipe.

17. The backlight assembly of claim 16, further comprising at least one brightness enhancing layer disposed adjacent the diffuser layer.

18. The backlight assembly of claim 17, further comprising a protective layer wherein the at least one brightness enhancing layer is disposed between the protective layer and the diffuser layer.

19. The backlight assembly of claim 17, wherein each brightness enhancing layer includes a plurality of integral optical elements.

20. The backlight assembly of claim 11, further comprising an integral surface diffuser including at least one region of surface micro-structures formed in the front surface of the light pipe.

21. The backlight assembly of claim 20, further comprising a diffuser layer disposed adjacent the front surface of the light pipe, and at least one brightness enhancing layer disposed adjacent the diffuser layer.

22. The backlight assembly of claim 21, wherein an air gap is formed between the surface micro-structures formed in the front surface of the light pipe and the diffuser layer disposed adjacent the front surface of the light pipe.

23. The backlight assembly of claim 22, wherein the surface micro-structures formed in the front surface produce circular light output when light is directed through the light pipe.

24. The backlight assembly of claim 23, wherein the circular light output has an angle between approximately 0.5°

and 5.0°

when light is directed through the light pipe.

25. The backlight assembly of claim 16, further comprising a reflective layer disposed adjacent the surface micro-structures formed in the back surface of the light pipe.

26. A method of enhancing the uniformity and brightness of light output produced by a backlight assembly comprising:

providing a backlight assembly including;

a light pipe having;

a front surface,

a back surface, and,

an integral surface diffuser including at least one region of surface micro-structures formed in the back surface of the light pipe wherein the integral surface diffuser comprises a central region of surface structures having at least one lateral edge and a lateral region of surface micro-structures adjacent to each lateral edge.

27. The method of claim 26, further comprising,

an integral surface diffuser including at least one region of surface micro-structures formed in the front surface of the light pipe, and,

a diffuser layer disposed adjacent the front surface of the light pipe; wherein an air gap is formed between the surface micro-structures formed in the front surface of the light pipe and the diffuser layer disposed adjacent the front surface of the light pipe.

28. The method of claim 27 wherein each region in the back surface produces an elliptical light output at an angle approximately 95°

horizontal and approximately 25°

vertical; and

each region in the front surface products a circular light output of approximately 1°

when light is directed through the light pipe.

29. The method of claim 26, wherein the central region produces an elliptical light output of approximately 95°

by 15° and

each lateral diffuser produces an elliptical output of approximately 95°

by 25°

when light is directed through the light pipe.

30. The method of claim 29, further comprising an integral surface diffuser including at least one region of surface micro-structures formed in the front surface of the light pipe, wherein the surface microstructures in the front surface produce a circular light output of between approximately 0.5°

and 5.0°

when light is directed through the light pipe.