Optical film

• US 6,117,530 A
• Filed: 09/02/1998
• Issued: 09/12/2000
• Est. Priority Date: 12/21/1993
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Weber, Michael F., Ouderkirk, Andrew J., Stover, Carl A., Jonza, James M.
• Primary Examiner(s): Chen, Vivian
• Application Number:
  US09/145,371
• Time in Patent Office: 741 Days
• Field of Search: 428/212, 428/480, 428/910, 428/483, 359/483, 359/485, 359/487, 359/488, 359/494, 359/500, 359/495, 359/577, 359/580, 359/586, 359/589
• US Class Current: 428/212
• 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 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2995/003 Reflective
• CPC Class Codes: B29K 2995/0034 Polarising
• CPC Class Codes: B32B 2038/0028 Stretching, elongating
• CPC Class Codes: B32B 2323/00 Polyalkenes
• CPC Class Codes: B32B 2325/00 Polymers of vinyl-aromatic compounds, e.g. polystyrene
• CPC Class Codes: B32B 2333/08 Polymers of acrylic acid esters, e.g. PMA, i.e. polymethylacrylate
• CPC Class Codes: B32B 2367/00 Polyesters, e.g. PET, i.e. polyethylene terephthalate
• CPC Class Codes: B32B 2551/08 Mirrors
• 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 27/308 comprising acrylic (co)polymers
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: B32B 7/023 Optical properties
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding 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
• CPC Class Codes: Y10S 428/91 : Product with molecular orientation
• CPC Class Codes: Y10T 428/24942 : including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/26 : Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/261 : In terms of molecular thickness or light wave length
• CPC Class Codes: Y10T 428/31507 : Of polycarbonate
• CPC Class Codes: Y10T 428/3154 : Of fluorinated addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31616 : Next to polyester [e.g., alkyd]
• CPC Class Codes: Y10T 428/31786 : Of polyester [e.g., alkyd, etc.]
• CPC Class Codes: Y10T 428/31797 : Next to addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31935 : Ester, halide or nitrile of addition polymer
• CPC Class Codes: Y10T 428/31938 : Polymer of monoethylenically unsaturated hydrocarbon

Abstract

An optical film comprising a plurality of layers wherein the refractive index difference between the layers along at least one in-plane axis is greater than the refractive index difference between the layers along an out-of-plane axis. The film has an average reflectivity of at least 60% for a predetermined bandwidth of light incident at 60° from normal to the plane of the film, said light being polarized in a plane defined by the at least one in-plane axis and the out-of-plane axis.

Claims

1. A film, comprising:

a plurality of layers;

wherein at least two of the plurality of layers exhibit a refractive index difference between the layers along at least one in-plane axis that is greater than a refractive index difference between the layers along an out-of-plane axis;

and further wherein the film has an average reflectivity of at least 60% for light within an intended bandwidth incident at 60°

from normal to the plane of the film said light being polarized in a plane defined by the at least one in-plane axis and the out-of-plane axis.

2. The film of claim 1 wherein the at least two layers are adjacent.

3. The film of claim 1 wherein at least one of the at least two layers is birefringent.

4. The film of claim 3 wherein a refractive index along the out-of-plane axis of the birefringent layer is closer numerically to a refractive index along the out-of-plane axis of the other layer than to a highest in-plane refractive index of the birefringent layer.

5. The film of claim 1 wherein the plurality of layers comprise layers of at least two different materials.

6. The film of claim 5 wherein the plurality of layers comprise alternating layers of at least two different materials.

7. The film of claim 1 wherein the plurality of layers includes layers of a first material and layers of a second material.

8. The film of claim 7 wherein the first and second materials are coextrudable.

9. The film of claim 1 wherein the out-of-plane axis is perpendicular to the at least one in-plane axis.

10. The film of claim 1 wherein the film is oriented along the at least one in-plane axis.

11. The film of claim 1 wherein the refractive index difference along the at least one in-plane axis is at least 0.05.

12. The film of claim 1 wherein the refractive index difference along the at least one in-plane axis is at least 0.2.

13. The film of claim 1 wherein the refractive index difference along the at least one in-plane axis is at least 0.25.

14. The film of claim 1 wherein the refractive index difference along the at least one in-plane axis is at least 0.4.

15. The film of claim 1 wherein the refractive index difference along the out-of-plane axis is less than 0.25.

16. The film of claim 1 wherein the refractive index difference along the out-of-plane axis is less than 0.11.

17. The film of claim 1 wherein the refractive index difference along the out-of-plane axis is less than 0.075.

18. The film of claim 1 wherein the refractive index difference along the out-of-plane axis is less than 0.05.

19. The film of claim 1 wherein the refractive index difference along the out-of-plane axis is less than 0.04.

20. The film of claim 1 wherein the refractive index difference along the out-of-plane axis is less than 0.02.

21. The film of claim 1 wherein the refractive index difference along the out-of-plane axis is less than 0.01.

22. The film of claim 1 wherein the refractive index difference along the out-of-plane axis is about 0.

23. The film of claim 1 wherein a ratio of the refractive index difference along the out-of-plane axis to the refractive index difference along the first in-plane axis is less than 0.5.

24. The film of claim 1 wherein a ratio of the refractive index difference along the out-of-plane axis to the refractive index difference along the first in-plane axis is less than 0.25.

25. The film of claim 1 wherein a ratio of the refractive index difference along the out-of-plane axis to the refractive index difference along the first in-plane axis is less than 0.1.

26. The film of claim 1 wherein a ratio of the refractive index difference along the out-of-plane axis to the refractive index difference along the first in-plane axis is less than 0.05.

27. The film of claim 1 wherein the film is a reflective polarizer.

28. The film of claim 1 wherein the film is an infrared reflective polarizer.

29. The film of claim 1 wherein the film is oriented along the at least one in-plane axis.

30. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a first in-plane axis that is greater than a refractive index difference between layers along a second in-plane axis.

31. The film of claim 30 wherein light of a first polarization orientation which is polarized in a plane defined by the first in-plane axis and the out-of-plane axis is reflected and wherein light of a second polarization orientation which is polarized in a plane defined by the second in-plane axis and the out-of-plane axis is transmitted.

32. The film of claim 31 wherein the light of the first and second polarization orientations is visible light.

33. The film of claim 31 wherein the light of the first and second polarization orientations is infrared light.

34. The film of claim 31 wherein the light of the first and second polarization orientations is red light.

35. The film of claim 31 wherein the light of the first and second polarization orientations is yellow light.

36. The film of claim 31 wherein the light of the first and second polarization orientations is blue light.

37. The film of claim 31 wherein the light of the first and second polarization orientations is green light.

38. The film of claim 31 wherein the light of the first and second polarization orientations is cyan light.

39. The film of claim 31 wherein the light of the first and second polarization orientations is magenta light.

40. The film of claim 31 wherein the light of the first and second polarization orientations has a bandwidth in the visible spectrum.

41. The film of claim 31 wherein the light of the first and second polarization orientations has a bandwidth of about 100 nm in the visible spectrum.

42. The film of claim 30 wherein the refractive index difference along the second in-plane axis is nonzero when the refractive index difference along the out-of-plane axis is nonzero.

43. The film of claim 42 wherein the refractive index difference along the second in-plane axis is of the same sign as the refractive index difference along the out-of-plane axis.

44. The film of claim 43 wherein the refractive index difference along the second in-plane axis and the refractive index difference along the out-of-plane axis are positive.

45. The film of claim 43 wherein the refractive index difference along the second in-plane axis and the refractive index difference along the out-of-plane axis are negative.

46. The film of claim 43 wherein the refractive index difference along the out-of-plane axis is greater than the refractive index difference along the second in-plane axis.

47. The film of claim 30 wherein the refractive index difference along the second in-plane axis is less than 0.05.

48. The film of claim 30 wherein the refractive index difference along the second in-plane axis is less than 0.02.

49. The film of claim 30 wherein the refractive index difference along the second in-plane axis is about 0.

50. The film of claim 30 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.

51. The film of claim 30 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 0.25.

52. The film of claim 30 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 0.1.

53. The film of claim 30 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 0.05.

54. The film of claim 30 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.

55. The film of claim 30 further having an average transmission of at least 80% for light incident normal to the film for light within an intended bandwidth having a first polarization orientation.

56. The film of claim 55 further having an average transmission of at least 85% for light incident normal to the film for light within an intended bandwidth having the first polarization orientation.

57. The film of claim 46 further having an average transmission of at least 60% for light incident 60°

from normal to the film for light within an intended bandwidth having the first polarization orientation.

58. The film of claim 57 further having an average transmission of at least 80% for light incident 60°

from normal to the film for light within an intended bandwidth having the first polarization orientation.

59. The film of claim 58 further having an average transmission of at least 90% for light incident 60°

from normal to the film for light within an intended bandwidth having a first polarization orientation.

60. The film of claim 59 further having an average transmission of at least 95% for light incident 60°

from normal to the film for light within an intended bandwidth having a first polarization orientation.

61. The film of claim 55 further having an average reflectance of at least 60% for light incident normal to the film for light within an intended bandwidth having a second polarization orientation.

62. The film of claim 61 further having an average reflectance of at least 80% for light incident normal to the film for light within an intended bandwidth having the second polarization orientation.

63. The film of claim 62 further having an average reflectance of at least 90% for light incident normal to the film for light within an intended bandwidth having the second polarization orientation.

64. The film of claim 63 further having an average reflectance of at least 95% for light incident normal to the film for light within an intended bandwidth having the second polarization orientation.

65. The film of claim 1 wherein the film is oriented in a tenter along the at least one in-plane axis.

66. The film of claim 1 wherein the film is length oriented along the at least one in-plane axis.

67. The film of claim 1 further comprising an anti-reflective coating.

68. The film of claim 1 wherein at least two layers exhibit a refractive index difference between layers along a first in-plane axis and a refractive index difference between layers along a second in-plane axis, and a refractive index difference between layers along the out-of-plane axis such that there is no Brewster angle along the first in-plane axis.

69. The film of claim 1 wherein the at least two layers are birefringent.

70. The film of claim 1 wherein one of the at least two layers is birefringent and the other of the at least two layers is isotropic.

71. The film of claim 1 wherein the plurality of layers comprise birefringent materials.

72. The film of claim 1 wherein the plurality of layers comprise alternating layers of at least two birefringent materials.

73. The film of claim 1 wherein the plurality of layers comprise alternating layers of a birefringent material and an isotropic material.

74. The film of claim 1 wherein the refractive index difference along the out-of-plane axis, the refractive index difference along the first in-plane axis and a refractive index difference along a second in-plane axis are such that film has a Brewster angle of at least 45 degrees for light polarized along the first in-plane axis for an incident medium of index 1.6.

75. The film of claim 1 wherein the film is a mirror.

76. The film of claim 75 wherein the film is oriented along a first in-plane axis and is oriented along a second in-plane axis.

77. The film of claim 75 wherein the film is an infrared mirror.

78. The film of claim 75 wherein the film is a hot mirror.

79. The film of claim 75 wherein the film is a cold mirror.

80. The film of claim 1 wherein light of a first polarization orientation which is polarized in a plane defined by the at least one in-plane axis and the out-of-plane axis is reflected and wherein light of a second polarization orientation which is polarized in a plane defined by a second in-plane axis and the out-of-plane axis is reflected.

81. The film of claim 80 wherein the light of the first and second polarization orientations is visible light.

82. The film of claim 80 wherein the light of the first and second polarization orientations is infrared light.

83. The film of claim 80 wherein the light of the first and second polarization orientations is red light.

84. The film of claim 80 wherein the light of the first and second polarization orientations is yellow light.

85. The film of claim 80 wherein the light of the first and second polarization orientations is blue light.

86. The film of claim 80 wherein the light of the first and second polarization orientations is green light.

87. The film of claim 80 wherein the light of the first and second polarization orientations has a bandwidth in the visible spectrum.

88. The film of claim 80 wherein the light of the first and second polarization orientations has a bandwidth of about 100 nm in the visible spectrum.

89. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a second in-plane axis that is greater than a refractive index difference between layers along the out-of-plane axis.

90. The film of claim 89 wherein the refractive index difference along the first in-plane axis and a refractive index difference along the second in-plane axis are of the opposite sign as the refractive index difference along the out-of-plane axis.

91. The film of claim 90 wherein the refractive index differences along the first and second in-plane axes are negative and the refractive index difference along the out-of-plane axis is positive.

92. The film of claim 90 wherein the refractive index differences along the first and second in-plane axes are positive and the refractive index difference the out-of-plane axis is negative.

93. The film of claim 90 wherein the refractive index difference along the first in-plane axis is of the same sign as the refractive index difference along the second in-plane axis.

94. The film of claim 89 further having an average reflectance of at least 80% for light incident normal to the film for light within an intended bandwidth having the first and second polarization orientation.

95. The film of claim 94 further having an average reflectance of at least 90% for light incident normal to the film for light within an intended bandwidth having the first and second polarization orientations.

96. The film of claim 95 further having an average reflectance of at least 80% for light incident at sixty degrees from normal to the film for light within an intended bandwidth having the first and second polarization orientations.

97. The film of claim 96 further having an average reflectance of at least 90% for light incident normal at sixty degrees from normal to the film for light within an intended bandwidth having the first and second polarization orientations.

98. The film of claim 97 further having an average reflectance of at least 95% for light incident at sixty degrees from normal to the film for light within an intended bandwidth having the first and second polarization orientations.

99. The film of claim 89 wherein the refractive index differences along the first and second in-plane axes are at least 0.05.

100. The film of claim 89 wherein the refractive index differences along the first and second in-plane axes are at least 0.2.

101. The film of claim 89 wherein the refractive index differences along the first and second in-plane axes are at least 0.25.

102. The film of claim 89 wherein the refractive index differences along the first and second in-plane axes are at least 0.4.

103. The film of claim 89 wherein the film has no Brewster angle for light polarized along the first and second in-plane axes for an incident medium of any index.

104. The film of claim 89 wherein the refractive index difference along the out-of-plane axis is such that the film has no Brewster angle for light polarized along the first and second in-plane axes for an incident medium of any index.

105. The film of claim 89 wherein the refractive index difference along the out-of-plane axis and the refractive index differences along the first and second in-plane axes are such that film has a Brewster angle of at least 45 degrees for light polarized along the first and second in-plane axes for an incident medium of index 1.6.

106. The film of claim 105 wherein the refractive index difference along the out-of-plane axis and the refractive index differences along the first and second in-plane axes are such that film has a Brewster angle of at least 60 degrees for light polarized along the first and second in-plane axes for an incident medium of index 1.6.

107. The film of claim 106 wherein the refractive index difference along the out-of-plane axis and the refractive index differences along the first and second in-plane axes are such that film has a Brewster angle of at least 70 degrees for light polarized along the first and second in-plane axes for an incident medium of index 1.6.

108. The film of claim 107 wherein the refractive index difference along the out-of-plane axis and the refractive index differences along the first and second in-plane axes are such that film has a Brewster angle of at least 80 degrees for light polarized along the first and second in-plane axes for an incident medium of index 1.6.

109. The film of claim 1 wherein the film has more than 2 layers.

110. The film of claim 1 wherein the film has at least 100 layers.

111. The film of claim 1 wherein the film has less than 2000 layers.

112. The film of claim 111 wherein the film has less than 1000 layers.

113. The film of claim 112 wherein the film has less than 500 layers.

114. The film of claim 1 wherein at least one of the plurality of layers is birefringent, and wherein a refractive index of the birefringent layer along the first in-plane axis is at least 0.05 greater than a refractive index of the birefringent layer along the out-of-plane axis.

115. The film of claim 1 wherein at least one of the plurality of layers is birefringent, and wherein a refractive index of the birefringent layer along a second in-plane axis is at least 0.05 greater than the refractive index of the birefringent layer along the out-of-plane axis.

116. The film of claim 1 wherein at least one of the plurality of layers is birefringent, and wherein a refractive index of the birefringent layer along the first in-plane axis is at least 0.05 greater than a refractive index of the birefringent layer along a second in-plane axis.

117. The film of claim 1 wherein the first in-plane axis and a second in-plane axis are perpendicular to each other.

118. The film of claim 117 wherein the out-of-plane axis is perpendicular to both the first and second in-plane axes.

119. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a first in-plane axis that is greater than a refractive index difference between layers along a second in-plane axis;

the film offer having a % RMS color of less than 10% at an angle of at least 45 degrees from an axis perpendicular to the film.

120. The reflective polarizer of claim 119 wherein the % RMS color is determined according to the equation ##EQU3##121.

121. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a first in-plane axis that is greater than a refractive index difference between layers along a second in-plane axis;

the film further having a % RMS color of less than 10% at an angle of at least 60 degrees from an axis perpendicular to the film.

122. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a first in-plane axis that is greater than a refractive index difference between layers along a second in-plane axis;

the film farther having a % RMS color of less than 8% at an angle of at least 45 degrees from an axis perpendicular to the film.

123. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a first in-plane axis that is greater than a refractive index difference between layers along a second in-plane axis;

the film further having a % RMS color of less than 8% at an angle of at least 60 degrees from an axis perpendicular to the film.

124. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a first in-plane axis that is greater than a refractive index difference between layers along a second in-plane axis;

the film further having a % RMS color of less than 3.5% at an angle of at least 45 degrees from an axis perpendicular to the film.

125. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a first in-plane axis that is greater than a refractive index difference between layers along a second in-plane axis;

the film further having a % RMS color of less than 3.5% at an angle of at least 60 degrees from an axis perpendicular to the film.

126. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a first in-plane axis that is greater than a refractive index difference between layers along a second in-plane axis;

the film further having a % RMS color of less than 2.1% at an angle of at least 45 degrees from an axis perpendicular to the film.

127. The film of claim 1 wherein at least two of the plurality of layers exhibit a refractive index difference between layers along a first in-plane axis that is greater than a refractive index difference between layers along a second in-plane axis;

the film further having a % RMS color of less than 2.1% at an angle of at least 60 degrees from an axis perpendicular to the film.