Reflective polarizer display

• US 5,828,488 A
• Filed: 03/10/1995
• Issued: 10/27/1998
• Est. Priority Date: 12/21/1993
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Company
• Inventors: Cobb, Sanford Jr., Weber, Michael F., Ouderkirk, Andrew J., Stover, Carl A., Benson, Olester Jr., Jonza, James M., Wortman, David L.
• Primary Examiner(s): Shafer, Ricky D.
• Application Number:
  US08/402,349
• Time in Patent Office: 1,327 Days
• Field of Search: 359/485, 359/486, 359/487, 359/488, 359/490, 359/491, 359/492, 359/493, 359/494, 359/495, 359/496, 359/497, 359/498, 359/837, 362/19, 349/62, 349/96
• US Class Current: 359/485.02
• CPC Class Codes: B29C 55/023 using multilayered plates or sheets
• CPC Class Codes: B29D 11/00 Producing optical elements, e.g. lenses or prisms grinding or polishing of optical elements B24B; constructional form of optical elements G02B; optical parts of spectacles G02C7/00
• CPC Class Codes: B29K 2995/003 Reflective
• CPC Class Codes: B29K 2995/0034 Polarising
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: B32B 7/023 Optical properties
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/3025 Polarisers, i.e. arrangements capable of producing a definite output polarisation state from an unpolarised input state G02B5/3008, G02B5/3016 take precedence
• 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: 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

A brightness enhanced reflective polarizer includes a reflective polarizer and a structured surface material.

Claims

1. A brightness enhanced reflective polarizer which provides directional and polarization control of light incident upon it, comprising:

a reflective polarizer including a multiple layer stack of alternating layers of at least two different materials having a refractive index difference between the different materials along a first in-plane axis which is greater than a refractive index difference between the different materials along a second in-plane axis such that the reflective polarizer transmits light having a first polarization orientation and reflects light having a different polarization orientation; and

a first structured surface material adapted to reflect light having an angle of incidence between an axis normal to the first structured surface material and a first predetermined angle, and adapted to redirect and transmit light having an angle of incidence between the first predetermined angle and an axis parallel to the first structured surface material;

wherein the reflective polarizer and the first structured surface material operate together to control direction and polarization of light transmitted by the brightness enhanced reflective polarizer.

2. The brightness enhanced reflective polarizer of claim 1 wherein the first polarization orientation is polarized in a plane defined by the second in-plane axis.

3. The brightness enhanced reflective polarizer of claim 2, wherein the different polarization orientation is polarized in a plane defined by the first in-plane axis.

4. The brightness enhanced reflective polarizer of claim 1 wherein at least some of the reflected light of the different polarization orientation is converted to the first polarization orientation.

5. The brightness enhanced reflective polarizer of claim 4 wherein at least some of the converted light is transmitted by the reflective polarizer.

6. The brightness enhanced reflective polarizer of claim 1 wherein the reflective polarizer further has an average transmission of at least 80% for light incident normal to the reflective polarizer for light having the first polarization orientation.

7. The brightness enhanced reflective polarizer of claim 6 wherein the reflective polarizer further has an average transmission of at least 90% for light incident normal to the reflective polarizer for light having the first polarization orientation.

8. The brightness enhanced reflective polarizer of claim 1 wherein the reflective polarizer further has an average transmission of at least 70% for light incident 60°

from normal to the reflective polarizer for light having the first polarization orientation.

9. The brightness enhanced reflective polarizer of claim 8 wherein the reflective polarizer further has an average transmission of at least 80% for light incident 60°

from normal to the reflective polarizer for light having the first polarization orientation.

10. The brightness enhanced reflective polarizer of claim 9 wherein the reflective polarizer further has an average transmission of at least 90% for light incident 60°

from normal to the reflective polarizer for light having the first polarization orientation.

11. The brightness enhanced reflective polarizer of claim 10 wherein the reflective polarizer further has an average transmission of at least 95% for light incident 60°

from normal to the reflective polarizer for light having the first polarization orientation.

12. The brightness enhanced reflective polarizer of claim 1 wherein the reflective polarizer further has an average reflectance of at least 60% for light incident normal to the reflective polarizer for light having the different polarization orientation.

13. The brightness enhanced reflective polarizer of claim 12 wherein the reflective polarizer further has an average reflectance of at least 80% for light incident normal to the reflective polarizer for light having the different polarization orientation.

14. The brightness enhanced reflective polarizer of claim 13 wherein the reflective polarizer further has an average reflectance of at least 90% for light incident normal to the reflective polarizer for light having the different polarization orientation.

15. The brightness enhanced reflective polarizer of claim 14 wherein the reflective polarizer further has an average reflectance of at least 95% for light incident normal to the reflective polarizer for light having the different polarization orientation.

16. The brightness enhanced reflective polarizer of claim 1 wherein a first of the two different material comprises a napthalene dicarboxylic acid polyester.

17. The brightness enhanced reflective polarizer of claim 16 wherein the first material is a poly(ethylene naphthalate).

18. The brightness enhanced reflective polarizer of claim 17 wherein a second of the two different materials is a copolyester comprising napthalate and terephthalate units.

19. The brightness enhanced reflective polarizer of claim 17 wherein a second of the two different materials is a polystyrene.

20. The brightness enhanced reflective polarizer of claim 1 wherein the reflective polarizer is planar.

21. The brightness enhanced reflective polarizer of claim 1 wherein the multiple layer stack is oriented along the first in-plane axis.

22. The brightness enhanced reflective polarizer of claim 1 wherein the reflective polarizer has a % RMS color of less than 10% at 30 degrees from the normal.

23. The brightness enhanced reflective polarizer of claim 22 wherein the reflective polarizer has a % RMS color of less than 2.1% at 60 degrees from the normal.

24. The brightness enhanced reflective polarizer of claim 1 wherein the structured surface material is positioned to receive the light of the first polarization orientation transmitted by the reflective polarizer.

25. The brightness enhanced reflective polarizer of claim 1 wherein the reflective polarizer is positioned to receive the light transmitted by the structured surface material.

26. The brightness enhanced reflective polarizer of claim 1 wherein the first structured surface material has a smooth side and a structured side.

27. The brightness enhanced reflective polarizer of claim 26 wherein the structured side comprises a plurality of triangular prisms.

28. The brightness enhanced reflective polarizer of claim 27 wherein the structured side comprises an array of triangular prisms.

29. The brightness enhanced reflective polarizer of claim 28 wherein the array of triangular prisms defines an axis of orientation.

30. The brightness enhanced reflective polarizer of claim 29 wherein the axis of orientation of the first structured surface material is aligned with the first in-plane axis of the reflective polarizer.

31. The brightness enhanced reflective polarizer of claim 27 wherein the triangular prisms are isosceles triangular prisms.

32. The brightness enhanced reflective polarizer of claim 27 wherein the triangular prisms have included angles in the range of 70 degrees to 110 degrees.

33. The brightness enhanced reflective polarizer of claim 32 wherein the triangular prisms have included angles of about 90 degrees.

34. The brightness enhanced reflective polarizer of claim 32 wherein the smooth side of the first structured surface material is positioned toward the reflective polarizer.

35. The brightness enhanced reflective polarizer of claim 32 wherein the structured side of the first structured surface material is positioned toward the reflective polarizer.

36. The brightness enhanced reflective polarizer of claim 1 wherein there is an air gap between the reflective polarizer and the first structured surface material.

37. The brightness enhanced reflective polarizer of claim 1 wherein the reflective polarizer and the first structured surface material form a unitary structure.

38. The brightness enhanced reflective polarizer of claim 1 further including a second structured surface material.

39. The brightness enhanced reflective polarizer of claim 38 wherein the second structured surface material is adapted to reflect light having an angle of incidence between an axis normal to the second structured surface material and a second predetermined angle, and adapted to redirect and transmit light having an angle of incidence between the second predetermined angle and an axis parallel to the second structured surface material.

40. The brightness enhanced reflective polarizer of claim 39 wherein the second structured surface material includes a smooth side and a structured side.

41. The brightness enhanced reflective polarizer of claim 40 wherein the structured side of the second structured surface material includes a plurality of triangular prisms.

42. The brightness enhanced reflective polarizer of claim 41 wherein the structured side of the second structured surface material includes an array of triangular prisms, wherein the array defines an associated axis of orientation.

43. The brightness enhanced reflective polarizer of claim 42 wherein the axis of orientation of the first structured surface material is positioned with respect to the axis of orientation of the second structured surface material to provide two dimensional angular control of light transmitted by the first and second structured surface materials.

44. The brightness enhanced reflective polarizer of claim 43 wherein the axis of orientation of the first structured surface material is positioned at an angle greater than 0 degrees with respect to the axis of orientation of the second structured surface material.

45. The brightness enhanced reflective polarizer of claim 44 wherein the angle is about 90 degrees.

46. The brightness enhanced reflective polarizer of claim 44 wherein the angle is greater than 90 degrees.

47. The brightness enhanced reflective polarizer of claim 43 wherein the structured side of the first structured surface material is positioned toward the smooth side of the second structured surface material.

48. The brightness enhanced reflective polarizer of claim 47 wherein the structured side of the second structured surface material is positioned toward the reflective polarizer.

49. The brightness enhanced reflective polarizer of claim 48 wherein light is incident on the smooth side of the first structured surface material.

50. The brightness enhanced reflective polarizer of claim 43 wherein the reflective polarizer is positioned between the first and second structured surface materials.

51. The brightness enhanced reflective polarizer of claim 50 wherein the first structured surface material is positioned on a first side of the reflective polarizer such that its smooth side is toward the reflective polarizer, and further wherein the second structured surface material is positioned on a second side of the reflective polarizer such that its structured side is toward the reflective polarizer.

52. The brightness enhanced reflective polarizer of claim 51 wherein light is incident on the smooth side of the second surface material.

53. The brightness enhanced reflective polarizer of claim 1 wherein the refractive index difference along the first in-plane axis is greater than a refractive index difference between adjacent layers along a third out-of-plane axis.

54. The brightness enhanced reflective polarizer of claim 53 wherein the refractive index difference along the first in-plane axis is at least 0.05.

55. The brightness enhanced reflective polarizer of claim 54 wherein the refractive index difference an the first in-plane axis is greater than 0.2.

56. The brightness enhanced reflective polarizer of claim 53 wherein the refractive index difference along the second in-plane axis is less than 0.02.

57. The brightness enhanced reflective polarizer of claim 56 wherein the refractive index difference along the second in-plane axis is less than 0.01.

58. The brightness enhanced reflective polarizer of claim 57 wherein the refractive index difference along the second in-plane axis is about 0.

59. The brightness enhanced reflective polarizer of claim 53 wherein the refractive index difference along the third out-of-plane axis is less than 0.11.

60. The brightness enhanced reflective polarizer of claim 59 wherein the refractive index difference along the third out-of-plane axis is less than 0.05.

61. The brightness enhanced reflective polarizer of claim 60 wherein the refractive index difference along the third out-of-plane axis is less than 0.01.

62. The brightness enhanced reflective polarizer of claim 61 wherein the refractive index difference along the third out-of-plane axis is about 0.

63. The brightness enhanced reflective polarizer of claim 53 wherein a ratio of the refractive index difference along the second in-plane axis to the refractive index difference along the first in-plane axis is less than 0.5.

64. The brightness enhanced reflective polarizer of claim 53 wherein a ratio of the refractive index difference along the second in-plane axis to the refractive index difference along the first in-plane axis is about 0.

65. The brightness enhanced reflective polarizer of claim 53 wherein a ratio of the refractive index difference along the third out-of-plane axis to the refractive index difference along the first in-plane axis is about 0.

66. The brightness enhanced reflective polarizer of claim 53 wherein a ratio of the refractive index difference along the third out-of-plane axis to the refractive index difference along the first in-plane axis is less than 0.1.

67. The brightness enhanced reflective polarizer of claim 53 wherein a ratio of the refractive index difference along the third out-of-plane axis to the refractive index difference along the first in-plane axis is about 0.

68. The brightness enhanced reflective polarizer of claim 53 wherein an absolute value of the refractive index difference along the second in-plane axis is greater than zero when an absolute value of the refractive index difference along the third out-of-plane axis is greater than zero.

69. The brightness enhanced reflective polarizer of claim 68 wherein the refractive index difference along the second in-plane axis is in a range of about 0.01-0.02 when the refractive index difference along the third out-of-plane axis is about 0.1.

70. The brightness enhanced reflective polarizer of claim 68 wherein the refractive index difference along the second in-plane axis is of the same sign as the refractive index difference along the third out-of-plane axis is about 0.1.

71. The brightness enhanced reflective polarizer of claim 70 wherein the refractive index difference along the second in-plane axis and the refractive index difference along the third out-of-plane axis are positive.

72. The brightness enhanced reflective polarizer of claim 70 wherein the refractive index difference along the second in-plane axis and the refractive index difference along the third out-of-plane axis are negative.

73. The brightness enhanced reflective polarizer of claim 53 wherein the reflective polarizer has no Brewster angle.

74. The brightness enhanced reflective polarizer of claim 53 wherein the refractive index difference along the third out-of-plane axis is such that the reflective polarizer has no Brewster angle.

75. The brightness enhanced reflective polarizer of claim 53 wherein the refractive index difference along the third out-of-plane axis and the refractive index difference along the second in-plane axis are such that the reflective polarizer has a Brewster angle between 0-30 degrees.

76. The brightness enhanced reflective polarizer of claim 53 wherein the refractive index difference along the third out-of-plane axis and the refractive index difference along the second in-plane axis are such that the reflective polarizer has a Brewster angle between 30-60 degrees.

77. The brightness enhanced reflective polarizer of claim 53 wherein the refractive index difference along the third out-of-plane axis and the refractive index difference along the second in-plane axis are such that the reflective polarizer has a Brewster angle of at least 60 degrees.

78. The brightness enhanced reflective polarizer of claim 53 wherein the reflective polarizer has a % RMS color of less than 10% at an angle of at least 30 degrees from an axis perpendicular to the stack.

79. The brightness enhanced reflective polarizer of claim 78 wherein the reflective polarizer has a % RMS color of less than 3.5% at an angle of at least 45 degrees from an axis perpendicular to the stack.

80. The brightness enhanced reflective polarizer of claim 79 wherein the reflective polarizer has a % RMS color of less than 2.1% at an angle of at least 45 degrees from an axis perpendicular to the stack.

81. The brightness enhanced reflective polarizer of claim 80 wherein the reflective polarizer has a % RMS color of less than 1.5% at an angle of at least 60 degrees from an axis perpendicular to the stack.

82. A brightness enhanced reflective polarizer comprising:

a reflective polarizer adapted to transmit light having a first polarization orientation and to reflect light having a different polarization orientation, wherein the reflective polarizer comprises a multiple layer stack of alternating layers of at least two different materials, and wherein a refractive index difference between different material layers in a first in-plane direction is greater than a refractive index difference between different material layers in a second in-plane direction; and

a structured surface material having a smooth side and a structured side and positioned such that the light of the first polarization transmitted by the reflective polarizer is incident on the smooth side, the structured surface material adapted to reflect light having an angle of incidence between an axis normal to the structured surface material and a first predetermined angle, and adapted to redirect and transmit light having an angle of incidence between the first predetermined angle and an axis parallel to the first structured surface material;

wherein the structured side of the structured surface material comprises an array of triangular prisms, the array defining an axis of orientation of the structured surface material, the axis of orientation of the structured surface material is aligned with the first in-plane direction of the reflective polarizer, and further wherein the reflective polarizer and the structured surface material operate together to control direction and polarization of light transmitted by the brightness enhanced reflective polarizer.

83. A brightness enhanced reflective polarizer comprising:

a first structured surface material adapted to reflect light having an angle of incidence between an axis normal to the first structured surface material and a first predetermined angle, and adapted to redirect and transmit light having an angle of incidence between the first predetermined angle and an axis parallel to the first structured surface material, the first structured surface material including a smooth side and a structured side, the structured side including an array of triangular prisms which define an axis of orientation;

a second structured surface material, positioned to receive light transmitted by the first structured surface material, and adapted to reflect light having an angle of incidence between an axis normal to the second structured surface material and a second predetermined angle, and adapted to redirect and transmit light having an angle of incidence between the second predetermined angle and an axis parallel to the second structured surface material, the second structured surface material including a smooth side and a structured side, the structured side including an array of triangular prisms which define an axis of orientation;

wherein the axis of orientation of the second structured surface material is orientated at an angle greater than 0 degrees with respect to the axis of orientation of the first structured surface material; and

a reflective polarizer adapted to transmit light having a first polarization orientation and to reflect light having a different polarization orientation, wherein the reflective polarizer comprises a multilayer stack of alternating layers of a first material and a second material, wherein a refractive index difference between layers of the first and second materials is greater in a first in-plane direction than a refractive index difference between layers of the first and second materials in a second in-plane direction;

wherein the reflective polarizer, the first structured surface material, and the second structured surface material provide polarization and two dimensional directional control of light transmitted by the brightness enhanced reflective polarizer.

84. A brightness enhanced display, comprising:

a structured surface material adapted to transmit an input wedge of light incident on the structured surface material at incident angles within a first predetermined group of angles, the transmitted light being refracted by the structured surface material into an output wedge of light which is narrower than the input wedge of light; and

a reflective polarizer including a first and second polymeric materials, at least one of the first and second polymeric materials being birefringent such that a refractive index difference between the first and second polymeric materials for light having a first polarization state is large enough to substantially reflect the light having the first polarization state and a refractive index difference between the first and second polymeric materials for light having a second polarization state is small enough to substantially transmit the light having the second polarization state.

85. A display as recited in claim 84, further comprising a polarization converter disposed in the display to receive light reflected by the reflective polarizer, alter the polarization state of the reflected light and redirect the altered light back towards the reflective polarizer.

86. A display as recited in claim 84, wherein the structured surface material is further adapted to reflect light incident on the structured surface material at incident angles within a second predetermined group of angles.

87. A display as recited in claim 86, further comprising a diffuse reflector disposed to receive light reflected by the reflective polarizer and to receive light reflected by the structured surface material, the diffuse reflector alters a direction and polarization state of the received light and redirects the altered light back toward the reflective polarizer and the structured surface material.

88. A display as recited in claim 84, further comprising:

an optical cavity; and

a display module selectively altering a polarization state of light transmitted through the display module, the structured surface material and the reflective polarizer being disposed between the optical cavity and the display module.

89. A display as recited in claim 88, wherein the reflective polarizer reflects light having the first polarization state towards the optical cavity and the optical cavity alters the polarization state of the light reflected by the reflective polarizer and redirects the light back towards the reflective polarizer.

90. A display as recited in claim 89, wherein the structured surface material is further adapted to reflect light incident on the structured surface material at incident angles within a second predetermined group of angles.

91. A display as recited in claim 90, wherein the optical cavity receives light reflected by the structured surface material and redirects at least a portion of the light back towards the structured surface material at an angle of incidence within the first predetermined group of angles.

92. A display as recited in claim 91, wherein the structured surface material, reflective polarizer and optical cavity cooperatively interact to at least double on-axis illumination brightness of the display module.