Backlight system with multilayer optical film reflector

• US 20020141194A1
• Filed: 01/22/2002
• Published: 10/03/2002
• Est. Priority Date: 06/26/1995
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Cobb, Sanford Jr., Weber, Michael F., Ouderkirk, Andrew J., Wortman, David L., Cull, Brian D.
• Granted Patent: US 6,905,220 B2
• Time in Patent Office: Days
• US Class Current: 362/309
• CPC Class Codes: B32B 2307/416 Reflective
• CPC Class Codes: B32B 2325/00 Polymers of vinyl-aromatic compounds, e.g. polystyrene
• CPC Class Codes: B32B 2327/12 containing fluorine
• CPC Class Codes: B32B 2333/12 Polymers of methacrylic acid esters, e.g. PMMA, i.e. polymethylmethacrylate
• CPC Class Codes: B32B 2367/00 Polyesters, e.g. PET, i.e. polyethylene terephthalate
• CPC Class Codes: B32B 2551/00 Optical elements
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/302 comprising aromatic vinyl (co)polymers, e.g. styrenic (co)polymers
• CPC Class Codes: B32B 27/304 comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: G02B 5/0841 comprising organic materials, e.g. polymers
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02B 6/0043 provided on the surface of the 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 6/0061 to provide homogeneous light output intensity
• CPC Class Codes: G02B 6/0065 Manufacturing aspects; Material aspects
• CPC Class Codes: G02F 1/133536 : Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133545 : Dielectric stack polarisers
• CPC Class Codes: G02F 1/13362 : providing polarized light, e.g. by converting a polarisation component into another one

Abstract

The present invention includes a backlight system incorporating a back reflector and/or a lamp cavity reflector constructed of a multilayer optical film.

Claims

1. A backlight system comprising:

a) a light guide defining a back surface;

b) a light source optically connected to the light guide, the light source emitting light into the light guide; and

c) a back reflector proximate the back surface of the light guide, the back reflector comprising a multilayer optical film which reflects at least about 80% of normal light and at least about 80% of light incident at an angle of 60 degrees from normal.

2. A backlight system according to claim 1, wherein the back reflector reflects at least about 90% of normally incident light.

3. A backlight system according to claim 1, wherein the back reflector reflects at least about 95% of normally incident light.

4. A backlight system according to claim 1, wherein the back reflector reflects at least about 98% of normally incident light.

5. A backlight system according to claim 1, wherein the back reflector reflects at least about 99% of normally incident light.

6. A backlight system according to claim 1, wherein the back reflector reflects at least about 90% of the light incident at an angle of 60 degrees from normal.

7. A backlight system according to claim 1, wherein the back reflector reflects at least about 95% of the light incident at an angle of 60 degrees from normal.

8. A backlight system according to claim 1, wherein the back reflector reflects at least about 98% of the light incident at an angle of 60 degrees from normal.

9. A backlight system according to claim 1, wherein the back reflector reflects at least about 99% of the light incident at an angle of 60 degrees from normal.

10. A backlight system according to claim 1, further comprising diffusing means for diffusing light reflected from the back reflector towards the back surface of the light guide.

11. A backlight system according to claim 10, wherein the diffusing means comprises diffusing particles within at least one layer of the multilayer optical film.

12. A backlight system according to claim 10, wherein the diffusing means comprises diffusing particles located on a surface of the multilayer optical film.

13. A backlight system according to claim 10, wherein the diffusing means comprises a diffusing film located between the back reflector and the back surface of the light guide.

14. A backlight system according to claim 1, wherein the back surface of the light guide is formed by the back reflector.

15. A backlight system according to claim 1, further comprising a lamp cavity reflector located about at least a portion of the light source, the lamp cavity reflector directing light from light source generally towards an edge of the light guide, the lamp cavity reflector further comprising a multilayer optical film which reflects at least about 80% of normal light and at least about 80% of light incident at an angle of 60 degrees from normal.

16. A backlight system according to claim 15, wherein the lamp cavity reflector reflects at least about 90% of normally incident light.

17. A backlight system according to claim 15, wherein the lamp cavity reflector reflects at least about 95% of normally incident light.

18. A backlight system according to claim 15, wherein the lamp cavity reflector reflects at least about 98% of normally incident light.

19. A backlight system according to claim 15, wherein the lamp cavity reflector reflects at least about 99% of normally incident light.

20. A backlight system according to claim 15, wherein the lamp cavity reflector reflects at least about 90% of the light incident at an angle of 60 degrees from normal.

21. A backlight system according to claim 15, wherein the lamp cavity reflector reflects at least about 95% of the light incident at an angle of 60 degrees from normal.

22. A backlight system according to claim 15, wherein the lamp cavity reflector reflects at least about 98% of the light incident at an angle of 60 degrees from normal.

23. A backlight system according to claim 15, wherein the lamp cavity reflector reflects at least about 99% of the light incident at an angle of 60 degrees from normal.

25. A backlight system according to claim 24, further comprising diffusing means for diffusing light reflected from the back reflector towards the back surface of the light guide.

26. A backlight system according to claim 1, wherein the multilayer optical film further comprises:

(a) a first layer comprising an oriented birefringent polymer, the first layer having an average thickness of not more than about 0.5 microns; and

(b) a second layer of a selected second polymer, each second layer having an average thickness of not more than 0.5 microns.

27. A backlight system according to claim 26, wherein the first layer of the multilayer optical film comprises a crystalline naphthalene dicarboxylic acid polyester.

28. A backlight system according to claim 26, wherein the multilayer optical film comprises a plurality of the first and second layers, wherein one of the second layers is located between each adjacent pair of first layers.

29. A backlight system according to claim 28, wherein the first and second layers of the multilayer optical film are adhered to each other.

30. A backlight system according to claim 26, wherein the multilayer optical film comprises at least fifty of each of the first and second layers.

31. A backlight system according to claim 26, wherein the oriented birefringent polymer has been stretched in at least two in-plane directions.

32. A backlight system according to claim 26, wherein the oriented birefringent polymer is more birefringent than the second polymer, and further wherein the refractive index of one polymer is higher than the other polymer.

33. A backlight system according to claim 32, wherein the higher index of refraction is at least 0.05 higher.

34. A backlight system according to claim 32, wherein the higher index of refraction is at least 0.10 higher.

35. A backlight system according to claim 32, wherein the higher index of refraction is at least 0.20 higher.

36. A backlight system according to claim 27, wherein the naphthalene dicarboxylic acid polyester is a poly(ethylene naphthalate).

37. A backlight system according to claim 27, wherein the naphthalene dicarboxylic acid polyester is a copolyester comprising naphthalate units and terephthalate units.

38. A backlight system according to claim 27, wherein the second polymer is a polyester.

39. A backlight system according to claim 38, wherein the second polymer comprises naphthalene units.

40. A backlight system according to claim 38, wherein the second polymer is a copolyester comprising naphthalate units and terephthalate units.

41. A backlight system according to claim 27, wherein the second polymer is a polystyrene.

42. A backlight system according to claim 27, wherein the second polymer is a fluoropolymer.

43. A backlight system according to claim 27, wherein the second polymer is a polyacrylate, polymethacrylate, or polyolefin.

24. A backlight system comprising:

a) a light guide defining a back surface;

b) a light source optically connected to the light guide, the light source emitting light into the light guide;

c) a back reflector proximate the back surface of the light guide, the back reflector comprising a multilayer optical film which reflects at least about 90% of normal light and at least about 80% of light incident at an angle of 60 degrees from normal; and

d) a lamp cavity reflector located about at least a portion of the light source, the lamp cavity reflector directing light from light source generally towards an edge of the light guide, the lamp cavity reflector further comprising the multilayer optical film.

44. A backlight system comprising:

a) a light guide defining a back surface;

b) a light source optically connected to the light guide, the light source emitting light into the light guide;

c) a back reflector proximate the back surface of the light guide, the back reflector comprising a multilayer optical film which reflects at least about 90% of normal light and at least about 80% of light incident at an angle of 60 degrees from normal, the multilayer optical film further comprising;

(1) a first layer comprising a biaxially oriented birefringent polymer, the first layer having an average thickness of not more than about 0.5 microns; and

(2) a second layer of a selected second polymer, each second layer having an average thickness of not more than 0.5 microns; and

d) a lamp cavity reflector located about at least a portion of the light source, the lamp cavity reflector directing light from light source generally towards an edge of the light guide, the lamp cavity reflector further comprising the multilayer optical film.

46. A backlight system according to claim 45, wherein the lamp cavity reflector reflects at least about 90% of normally incident light.

47. A backlight system according to claim 45, wherein the lamp cavity reflector reflects at least about 95% of normally incident light.

48. A backlight system according to claim 45, wherein the lamp cavity reflector reflects at least about 98% of normally incident light.

49. A backlight system according to claim 45, wherein the lamp cavity reflector reflects at least about 99% of normally incident light.

50. A backlight system according to claim 45, wherein the lamp cavity reflector reflects at least about 90% of the light incident at an angle of 60 degrees from normal.

51. A backlight system according to claim 45, wherein the lamp cavity reflector reflects at least about 95% of the light incident at an angle of 60 degrees from normal.

52. A backlight system according to claim 45, wherein the lamp cavity reflector reflects at least about 98% of the light incident at an angle of 60 degrees from normal.

53. A backlight system according to claim 45, wherein the lamp cavity reflector reflects at least about 99% of the light incident at an angle of 60 degrees from normal.

45. A backlight system comprising:

a) a light guide defining a back surface;

b) a light source optically connected to the light guide, the light source emitting light into the light guide; and

c) a lamp cavity reflector located about at least a portion of the light source, the lamp cavity reflector directing light from light source generally towards an edge of the light guide, the lamp cavity reflector further comprising a multilayer optical film which reflects at least about 80% of normal light and at least about 80% of light incident at an angle of 60 degrees from normal.