Direct-lit liquid crystal displays with laminated diffuser plates

• US 20060082698A1
• Filed: 10/15/2004
• Published: 04/20/2006
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Laumer, James W., Fabick, Ryan T., Park, Youngsoo, Gehlsen, Mark D., Epstein, Kenneth A., Rivard, Linda M., Emmons, Robert M., Seo, Kang-il, Kim, Chideuk, Ko, Byungsoo, Chen, Chingwen, Kim, Ji-Hyung, Lee, Ji-Hwa
• Granted Patent: US 7,446,827 B2
• Time in Patent Office: Days
• US Class Current: 349/61
• CPC Class Codes: G02F 1/133507 Films for enhancing the luminance
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 2201/086 UV absorbing

Abstract

In a directly-illuminated liquid crystal display (LCD), for example an LCD monitor or an LCD-TV, a number of light management films, including a diffuser layer, lie between the light source and the LCD panel to provide bright, uniform illumination. The diffuser layer is attached to a substrate which is separate from the light source and the LCD panel, or may be attached to either the LCD panel or, when using a two dimensional light source, to the light source. The other light management layers may also be attached to the separate substrate or to the LCD panel or two-dimensional light source. High levels of illumination uniformity at the LCD may be achieved with a uniform (non-patterned) diffuser, even with relatively low levels of diffusion, when the diffuser is used with a brightness enhancing layer.

Claims

1. A directly illuminated liquid crystal display (LCD) unit, comprising:

a light source;

an LCD panel; and

an arrangement of light management layers disposed between the light source and the LCD panel so that the light source illuminates the LCD panel through the arrangement of light management layers, the arrangement of light management layers comprising a diffuser plate, a brightness enhancing layer and a reflective polarizer, the diffuser plate being positioned closer to the one or more light sources than the brightness enhancing layer and the reflective polarizer, the diffuser plate comprising a substantially transparent substrate attached to a first diffusing layer that diffuses light propagating from the light source towards the LCD panel.

2. A unit as recited in claim 1, wherein the first diffusing layer comprises a matrix with a dispersed phase of diffusing particles.

3. A unit as recited in claim 2, wherein the first diffusing layer is attached directly to the substrate.

4. A unit as recited in claim 2, wherein the first diffusing layer is attached to the substrate via an adhesive layer disposed between the first diffusing layer and the substrate.

5. A unit as recited in claim 1, wherein the light source comprises a plurality of light sources.

6. A unit as recited in claim 1, wherein the arrangement of light management layers provides a spatially uniform diffusion characteristic.

7. A unit as recited in claim 1, wherein the substrate comprises a sheet of glass.

8. A unit as recited in claim 1, wherein the first diffusing layer is provided on a side of the substrate facing towards the array of light sources.

9. A unit as recited in claim 1, wherein the first diffusing layer is provided on a side of the substrate facing away from the array of light sources.

10. A unit as recited in claim 1, wherein the first diffusing layer is provided on a side of the substrate facing towards the array of light sources, and the diffuser plate further comprises a second diffusing layer provided on a side of the substrate facing away from the array of light sources.

11. A unit as recited in claim 1, wherein a first side of the brightness enhancing layer is attached to the diffuser plate.

12. A unit as recited in claim 11, wherein the reflective polarizer is attached to a second side of the brightness enhancing layer.

13. A unit as recited in claim 1, wherein a first side of the reflective polarizer is attached to the diffuser plate.

14. A unit as recited in claim 13, wherein the brightness enhancing layer is attached to a second side of the reflective polarizer.

15. A unit as recited in claim 1, wherein the reflective polarizer comprises a multilayer optical film reflective polarizer.

16. A unit as recited in claim 1, wherein the diffuser has a single pass optical transmission in the range of about 72%-95%.

17. A unit as recited in claim 16, wherein the diffuser has a single pass optical transmission in the range of about 75%-90%.

18. A unit as recited in claim 1, wherein a value of σ

/x is less than 1.5%, where x is the level of illumination light passing from the arrangement of light management layers to the LCD panel, averaged across the LCD panel, and σ

is the root mean square deviation in the level of illumination light across the arrangement of light management layers, and the diffuser plate has a single pass transmission of at least 72%.

19. A unit as recited in claim 18, wherein the value of σ

/x is less than 1.3%, and the diffuser plate has a single pass transmission of at least 75%

20. A unit as recited in claim 1, further comprising a controller coupled to control an image displayed by the LCD panel.

21. A unit as recited in claim 20, wherein the controller comprises a computer.

22. A unit as recited in claim 20, wherein the controller comprises a television controller.

23. A directly illuminated liquid crystal display (LCD) unit, comprising:

a light source;

an LCD panel; and

an arrangement of light management layers disposed between the light sources and the LCD panel so that the light source illuminates the LCD panel through the arrangement of light management layers, the arrangement of light management layers comprising at least one diffuser layer and a brightness enhancing layer, a single pass transmission through the diffuser layer being greater than about 75%.

24. A unit as recited in claim 23, wherein the single pass transmission through the at least one diffuser layer is greater than about 80%.

25. A unit as recited in claim 23, wherein the single pass transmission through the at least one diffuser layer is greater than about 85%.

26. A unit as recited in claim 23, wherein the single pass transmission is averaged across the width of the diffuser layer.

27. A unit as recited in claim 23, wherein a value of σ

/x is less than 1.5%, where x is the level of illumination light passing from the arrangement of light management layers to the LCD panel, averaged across the LCD panel, and σ

is the root mean square deviation in the level of illumination light across the arrangement of light management layers.

28. A unit as recited in claim 27, wherein a value of σ

/x is less than 1.3%.

29. A unit as recited in claim 27, wherein a value of σ

/x is less than 1.0%.

30. A unit as recited in claim 23, wherein the at least one diffusing layer comprises a matrix with a dispersed phase of diffusing particles.

31. A unit as recited in claim 23, wherein the arrangement of light management layers further comprises a transparent substrate.

32. A unit as recited in claim 31, wherein the at least one diffusing layer comprises a first diffusing layer attached to the substrate.

33. A unit as recited in claim 31, wherein the substrate comprises a sheet of glass.

34. A unit as recited in claim 23, wherein the at least one diffusing layer provides has a spatially uniform diffusion characteristic.

35. A unit as recited in claim 23, wherein the at least one diffusing layer comprises at least two diffusing layers.

36. A unit as recited in claim 23, wherein the brightness enhancing layer is attached to a stack of optical layers, the stack of optical layers comprising the at least one diffuser layer.

37. A unit as recited in claim 23, wherein the arrangement of light management layers further comprises a reflective polarizer.

38. A unit as recited in claim 37, wherein the reflective polarizer is attached to a stack of optical layers attached together, the stack of optical layers comprising at least the one or more diffuser layer and a substrate.

39. A unit as recited in claim 23, wherein the light source comprises a plurality of light sources.

40. A unit as recited in claim 23, further comprising a controller coupled to control an image displayed by the LCD panel.

41. A unit as recited in claim 40, wherein the controller comprises a computer.

42. A unit as recited in claim 40, wherein the controller comprises a television controller.

43. A directly illuminated liquid crystal display (LCD) unit, comprising:

a flat fluorescent light source having an upper surface, the flat fluorescent light source being capable of emitting light through its upper surface;

an LCD panel; and

an arrangement of light management layers disposed between the flat fluorescent light source and the LCD panel, the arrangement of light management layers comprising at least a first diffuser layer and a brightness enhancing layer, at least one of the light management layers being attached to the upper surface of the flat fluorescent light source.

44. A unit as recited in claim 43, wherein the first diffuser layer is attached to the upper surface of the flat fluorescent light source.

45. A unit as recited in claim 44, wherein the first diffuser layer is attached directly to the upper surface of the flat fluorescent light source.

46. A unit as recited in claim 44, wherein the first diffuser layer is attached to the upper surface of the flat fluorescent light source via an adhesive layer.

47. A unit as recited in claim 44, wherein one of the brightness enhancing layer and a reflective polarizer is attached to the first diffuser layer, the first diffuser layer lying between the flat fluorescent light source and the one of the brightness enhancing layer and the reflective polarizer.

48. A unit as recited in claim 43, wherein the arrangement of light management layers provides a spatially uniform diffusion characteristic.

49. A unit as recited in claim 43, wherein the arrangement of light management layers comprises a stack comprising the diffusing layer, the brightness enhancing layer and a reflective polarizer attached together, the stack being attached to the flat fluorescent light source.

50. A unit as recited in claim 49, wherein the reflective polarizer lies closer to the LCD panel than the brightness enhancing film.

51. A unit as recited in claim 49, wherein the brightness enhancing film lies closer to the LCD panel than the reflective polarizer.

52. A unit as recited in claim 43, wherein the single pass transmission through the first diffuser layer and any other diffuser layer in the arrangement of light management films is in the range of about 72%-95%.

53. A unit as recited in claim 52, wherein the single pass transmission is in the range of about 75%-90%.

54. A unit as recited in claim 43, wherein a value of σ

/x is less than 1.5%, where x is the level of illumination light passing from the arrangement of light management films to the LCD panel, averaged across the LCD panel, and σ

is the root mean square deviation in the level of illumination light across the arrangement of light management films, and the first diffuser layer has a single pass transmission of at least 72%.

55. A unit as recited in claim 54, wherein the value of σ

/x is less than 1.3%, and the diffuser plate has a single pass transmission of at least 75%

56. A unit as recited in claim 43, further comprising a controller coupled to control an image displayed by the LCD panel.

57. A unit as recited in claim 56, wherein the controller comprises a computer.

58. A unit as recited in claim 56, wherein the controller comprises a television controller.

59. A directly illuminated liquid crystal display (LCD) unit, comprising:

a light source;

an LCD panel comprising an upper plate, a lower plate and a liquid crystal layer disposed between the upper and lower plates, the lower plate facing the light source, the lower plate comprising an absorbing polarizer; and

an arrangement of light management films disposed between the light source and the LCD panel so that the light source illuminates the LCD panel through the arrangement of light management films, the arrangement of light management films comprising at least a first diffuser layer, at least the first diffuser layer being attached to a lower surface of the lower plate of the LCD panel.

60. A unit as recited in claim 59, wherein the arrangement of light management films further comprises a reflective polarizer attached to the lower plate.

61. A unit as recited in claim 59, wherein the arrangement of light management films further comprises a brightness enhancing layer attached to the lower plate.

62. A unit as recited in claim 59, wherein the arrangement of light management films comprises a stack of least a brightness enhancing layer and a reflective polarizer attached together, the stack being attached to the lower plate of the LCD panel.

63. A unit as recited in claim 62, wherein the stack comprises the first diffuser layer.

64. A unit as recited in claim 59, wherein the arrangement of light management films provides a spatially uniform diffusion characteristic.

65. A unit as recited in claim 59, wherein the single pass transmission through the first diffuser layer and any other diffuser in the arrangement of light management films is in the range of about 72%-95%.

66. A unit as recited in claim 65, wherein the single pass transmission is in the range of about 85%-90%.

67. A unit as recited in claim 59, wherein a value of σ

/x is less than 1.5%, where x is the level of illumination light passing from the arrangement of light management films to the LCD panel, averaged across the LCD panel, and σ

is the root mean square deviation in the level of illumination light across the arrangement of light management films.

68. A unit as recited in claim 67, wherein the single pass transmission through the first diffuser layer and any other diffuser in the arrangement of light management films is in the range of about 72%-95%.

69. A unit as recited in claim 67, wherein the value of σ

/x is less than 1.3%, and the diffuser plate has a single pass transmission of at least 75%

70. A unit as recited in claim 59, wherein the arrangement of light management films further comprises a reflective polarizer and a brightness enhancing layer attached to the lower plate of the LCD panel, the reflective polarizer being disposed between the brightness enhancing layer and the lower panel.

71. A unit as recited in claim 59, wherein the arrangement of light management films further comprises a reflective polarizer and a brightness enhancing layer attached to the lower plate of the LCD panel, the brightness enhancing layer being disposed between the reflective polarizer and the lower panel.

72. A unit as recited in claim 59, further comprising a controller coupled to control an image displayed by the LCD panel.

73. A unit as recited in claim 72, wherein the controller comprises a computer.

74. A unit as recited in claim 72, wherein the controller comprises a television controller.

75. A directly illuminated liquid crystal display (LCD) unit, comprising:

a light source;

an LCD panel; and

an arrangement of light management layers disposed between the light source and the LCD panel so that the light source illuminates the LCD panel through the arrangement of light management layers, the arrangement of light management layers comprising a diffuser plate and at least one of a brightness enhancing layer and a reflective polarizer, the diffuser plate comprising a substantially transparent substrate attached to a first diffusing layer that diffuses light propagating from the one or more light sources towards the LCD panel.

76. A unit as recited in claim 75, wherein the at least one of a brightness enhancing layer and a reflective polarizer is attached to the diffuser plate.