Light fixture containing optical film

• US 6,297,906 B1
• Filed: 02/28/1997
• Issued: 10/02/2001
• Est. Priority Date: 02/29/1996
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Majumdar, Biswaroop, Carlson, Lockwood W., Kotz, Arthur L., Weber, Michael F., Ouderkirk, Andrew J., Nevitt, Timothy J., Stover, Carl A., Allen, Richard C.
• Primary Examiner(s): SCHUBERG, DARREN E
• Application Number:
  US08/807,270
• Time in Patent Office: 1,677 Days
• Field of Search: 359/491, 359/492, 359/494, 359/495, 359/500, 252/585, 427/163.1, 362/257, 362/307, 362/310, 362/311, 362/317, 362/326, 362/341, 362/351
• US Class Current: 359/489.12
• CPC Class Codes: G02B 5/3008 comprising dielectric particles, e.g. birefringent crystals embedded in a matrix
• 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 1/133545 Dielectric stack polarisers

Abstract

An optical film is provided which comprises an antireflective layer and a disperse phase of polymeric particles disposed within a continuous birefringent matrix. The film is oriented, typically by stretching, in one or more directions. The size and shape of the disperse phase particles, the volume fraction of the disperse phase, the film thickness, and the amount of orientation are chosen to attain a desired degree of diffuse reflection and total transmission of electromagnetic radiation of a desired wavelength in the resulting film.

Claims

1. A light fixture, comprising:

a light source; and

an optical element comprising a polymeric first phase and a second phase disposed within said first phase, said second phase being discontinuous along at least two of any three mutually perpendicular axes;

wherein said first and second phases have indices of refraction which differ along a first axis by more than about 0.05 and which differ along a second axis orthogonal to said first axis by less than about 0.05, wherein said optical element has a total reflectivity of greater than about 50% for light emitted by said light source which is polarized along a first axis and a total transmission of greater than about 50% for light emitted by said light source which is polarized along a second axis, and wherein said second axis is orthogonal to said first axis.

2. The fixture of claim 1, wherein said optical element is a reflective element.

3. The fixture of claim 1, wherein said optical element is a polarizing element.

4. The fixture of claim 1, wherein said optical element is both a reflective element and a polarizing element.

5. The fixture of claim 1, wherein said fixture further comprises housing means for housing said light source and said optical element, and wherein said optical element is a reflective film disposed on an interior surface of said housing means.

6. The fixture of claim 1, wherein said fixture further comprises housing means for housing said light source and said optical element, wherein said housing means is equipped with at least one aperture for emitting light from said housing means, and wherein said optical element is disposed between said light source and said aperture.

7. The fixture of claim 6, wherein said optical element is a polarizer.

8. The fixture of claim 1, wherein said light source is a diffuse light source.

9. The fixture of claim 1, wherein said first phase has a birefringence of at least about 0.1.

10. The fixture of claim 1, wherein said first phase has a birefringence of at least about 0.15.

11. The fixture of claim 1, wherein said first phase has a birefringence of at least about 0.2.

12. The fixture of claim 1, wherein said second phase has a birefringence of less than about 0.02.

13. The fixture of claim 1, wherein said second phase has a birefringence of less than about 0.01.

14. The fixture of claim 1, wherein said second phase has an index of refraction which differs from said first phase by more than about 0.1 along said first axis.

15. The fixture of claim 1, wherein said second phase has an index of refraction which differs from said first phase by more than about 0.15 along said first axis.

16. The fixture of claim 1, wherein said second phase has an index of refraction which differs from said first phase by more than about 0.2 along said first axis.

17. The fixture of claim 1, wherein said second phase has an index of refraction which differs from said first phase by less than about 0.03 along said second axis.

18. The fixture of claim 1, wherein said second phase has an index of refraction which differs from said first phase by less than about 0.01 along said second axis.

19. The fixture of claim 1, wherein said first and second phases taken together have a diffuse reflectivity along said at least one axis of at least about 50% for both polarizations of electromagnetic radiation.

20. The fixture of claim 1, wherein said optical body has a total reflectivity of greater than about 50% for a first polarization of electromagnetic radiation and a total transmission of greater than about 50% for a second polarization of electromagnetic radiation orthogonal to said first polarization.

21. The fixture of claim 20, wherein said optical body has a total reflectivity of greater than about 60% for said first polarization of electromagnetic radiation.

22. The fixture of claim 20, wherein said optical body has a total reflectivity of greater than about 70% for said first polarization of electromagnetic radiation.

23. The fixture of claim 20, wherein said optical body has a total transmission of greater than about 60% for said second polarization of electromagnetic radiation.

24. The fixture of claim 20, wherein said optical body has a total transmission of greater than about 70% for said second polarization of electromagnetic radiation.

25. The fixture of claim 1, wherein at least about 40% of light polarized orthogonal to a first polarization of light is transmitted through said optical body with an angle of deflection of less than about 8°

.

26. The fixture of claim 1, wherein at least about 60% of light polarized orthogonal to a first polarization of light is transmitted through said optical body with an angle of deflection of less than about 8°

.

27. The fixture of claim 1, wherein at least about 70% of light polarized orthogonal to a first polarization of light is transmitted through said optical body with an angle of deflection of less than about 8°

.

28. The fixture of claim 1, wherein said first phase comprises a thermoplastic resin.

29. The fixture of claim 28, wherein said thermoplastic resin is a syndiotactic vinyl aromatic polymer derived from a vinyl aromatic monomer.

30. The fixture of claim 28, wherein said thermoplastic resin comprises interpolymerized units of syndiotactic polystyrene.

31. The fixture of claim 28, wherein said thermoplastic resin comprises polyethylene naphthalate.

32. The fixture of claim 31, wherein said second phase comprises syndiotactic polystyrene.

33. The fixture of claim 28, wherein said second phase also comprises at least one thermoplastic polymer.

34. The fixture of claim 1, wherein said optical body is stretched to a stretch ratio of at least about 2.

35. The fixture of claim 1, wherein said optical body is stretched to a stretch ratio of at least about 4.

36. The fixture of claim 1, wherein said optical body is stretched to a stretch ratio of at least about 6.

37. The fixture of claim 1, wherein said first and second phases are immiscible.

38. The fixture of claim 1, wherein said second phase comprises a plurality of elongated masses whose major axes are substantially aligned along a common axis.

39. The fixture of claim 38, wherein said elongated masses have an aspect ratio of at least about 2.

40. The fixture of claim 38, wherein said elongated masses have an aspect ratio of at least about 5.

41. The fixture of claim 1, wherein said second phase comprises a plurality of rod-like structures.

42. The fixture of claim 1, wherein said optical body is oriented in at least two directions.

43. The fixture of claim 1, wherein said second phase is present in an amount of at least about 1% by volume relative to said first phase.

44. The fixture of claim 1, wherein said second phase is present in an amount of about 5% to about 50% by volume relative to said first phase.

45. The fixture of claim 1, wherein said second phase is present in an amount of about 15% to about 30% by volume relative to said first phase.

46. The fixture of claim 1, wherein said second phase is discontinuous along at least two of any three mutually perpendicular axes.

47. The fixture of claim 1, wherein said second phase is discontinuous along any three mutually perpendicular axes.

48. The fixture of claim 1, wherein the diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of visible, ultraviolet, or infrared electromagnetic radiation is at least about 30%.

49. The fixture of claim 1, wherein the extinction ratio of said optical body is greater than about 3.

50. The fixture of claim 1, wherein the extinction ratio of said optical body is greater than about 5.

51. The fixture of claim 1, wherein the extinction ratio of said optical body is greater than about 10.

52. The fixture of claim 1, wherein the optical body is a film, and wherein the index difference between said first and second phases is less than about 0.05 along an axis perpendicular to the surface of said film.

53. The fixture of claim 52, wherein the electromagnetic radiation is distributed anisotropically about the axis of specular reflection.

54. The fixture of claim 53, wherein said optical body is stretched in at least one direction, and wherein the diffusely reflected portion of said at least one polarization of electromagnetic radiation is distributed primarily along or near the surface of a cone whose axis is centered on the stretch direction and whose surface contains the specularly reflected direction.

55. The fixture of claim 53, wherein said second phase comprises elongated inclusions whose axes of elongation are aligned in a common direction, wherein said optical body is stretched in at least one direction, and wherein the diffusely reflected portion of said at least one polarization of electromagnetic radiation is distributed primarily along or near the surface of a cone whose axis is centered on the axis of elongation direction and whose surface contains the specularly reflected direction.

56. The fixture of claim 52, wherein the electromagnetic radiation is distributed anisotropically about the axis of specular transmission.

57. The fixture of claim 1, wherein said optical body is stretched in at least one direction, wherein at least about 40% of light polarized orthogonal to a first polarization of light is diffusely transmitted through said optical body, and wherein said diffusely transmitted rays are distributed primarily along or near the surface of a cone whose surface contains the spectrally transmitted direction and whose axis is centered on the stretch direction.

58. The fixture of claim 1, wherein said second phase comprises elongated inclusions whose axes of elongation are aligned in a common direction, wherein said optical body is stretched in at least one direction, and wherein the diffusely transmitted portion of said at least one polarization of electromagnetic radiation is distributed primarily along or near the surface of a cone whose axis is centered on the axis of elongation direction and whose surface contains the diffusely transmitted direction.

59. The fixture of claim 1, wherein the optical body is a film, and wherein the index difference between said first and second phases is less than about 0.02 along an axis perpendicular to the surface of said film.

60. In combination with a light source, an optical body comprising:

a first phase having a birefringence of at least about 0.05; and

a second phase, disposed within said first phase;

wherein the absolute value of the difference in index of refraction of said first and second phases is Δ

n₁ along a first axis and Δ

n₂ along a second axis orthogonal to said first axis, wherein the absolute value of the difference between Δ

n₁ and Δ

n₂ is at least about 0.05, and wherein the diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation is at least about 30%.

61. The optical body of claim 60, wherein the absolute value of the difference between Δ

n₁ and Δ

n₂ is at least about 0.1.

62. The optical body of claim 60, wherein said first phase has a larger birefringence than said second phase.

63. The optical body of claim 62, wherein the birefringence of said first phase is at least 0.02 greater than the birefringence of said second phase.

64. The optical body of claim 62, wherein the birefringence of said first phase is at least 0.05 greater than the birefringence of said second phase.

65. An optical body having a plurality of layers, wherein at least one of said plurality of layers comprises:

a first phase having a birefringence of at least about 0.05; and

a second phase which is discontinuous along at least two of any three mutually orthogonal axes;

wherein the absolute value of the difference in index of refraction of said first and second phases is Δ

n₁ along a first axis and Δ

n₂ along a second axis orthogonal to said first axis, wherein the absolute value of the difference between Δ

nand Δ

n₂ is at least about 0.05, and wherein the diffuse reflectivity of said first and second phases taken together along at least one axis for at least one polarization of electromagnetic radiation is at least about 30%.

66. A light fixture, comprising:

a light source; and

an optical film;

wherein said optical film comprises a polymeric first phase and a second phase disposed within said first phase, said second phase being discontinuous along at least two of any three mutually perpendicular axes;

wherein said first and second phases have indices of refraction which differ along a first axis by more than about 0.05 and which differ along a second axis orthogonal to said first axis by less than about 0.05.

67. A light fixture, comprising:

a light source;

reflecting means for reflecting light produced by said light source; and

polarizing means for polarizing light produced by said light source;

wherein at least one of said reflecting means and said polarizing means comprises a polymeric first phase and a second phase disposed within said first phase, said second phase being discontinuous along at least two of any three mutually perpendicular axes, and wherein said first and second phases have indices of refraction which differ along a first axis by more than about 0.05 and which differ along a second axis orthogonal to said first axis by less than about 0.05.

68. A light fixture, comprising:

a light source; and

a polarizer, in optical communication with said light source, said polarizer comprising a thermoplastic polymeric continuous phase and a disperse phase disposed within said continuous phase.

69. The light fixture of claim 68, wherein said polarizer diffusely reflects light emitted by the light source which is polarized along a first axis, and specularly transmits light emitted by the light source which is polarized along a second axis.

70. The light fixture of claim 69, wherein said first and second axes are orthogonal.

71. The light fixture of claim 68, wherein said continuous and disperse phases comprise first and second diverse thermoplastic polymers, respectively.

72. The light fixture of claim 68, wherein said light fixture has an output region through which light is directed out of the fixture, and wherein said polarizer is disposed across at least a portion of said output region.

73. The light fixture of claim 72, wherein said output region is equipped with at least one louver adapted to control the direction in which light is emitted from said fixture, and wherein said polarizer is a film disposed on the surface of said louver.

74. The light fixture of claim 73, wherein the surface of said louver over which said polarizing element is disposed is mirrored.

75. The light fixture of claim 69, wherein said fixture further comprises a reflector.

76. The light fixture of claim 75, wherein said light source is disposed between said reflector and said output region.

77. The light fixture of claim 75, wherein said reflector is a birefringent multilayer film.

78. The light fixture of claim 68, wherein said light source is enclosed within said polarizer.

79. The light fixture of claim 68, wherein said light source is a light bulb, and wherein said polarizer is disposed upon at least a portion of the surface of said bulb.

80. The light fixture of claim 79, wherein said light source is a fluorescent bulb.

81. A smoke detection system, comprising the light fixture of claim 68.

82. The light fixture of claim 68, wherein said light source is enclosed within a housing having an aperture through which light is emitted from said light fixture, and wherein said polarizer is disposed across at least a portion of said aperture.

83. The light fixture of claim 68, wherein said light source is a diffuse light source.

84. The light fixture of claim 68, wherein said light fixture further comprises a light pipe.

85. The light fixture of claim 84, wherein said light source is solar radiation.

86. The light fixture of claim 68, further comprising a depolarizing element.

87. The light fixture of claim 68, wherein said light source has a first light emitting region and a second region adapted to depolarize the light emitted in said first region.

88. The light fixture of claim 68, wherein said depolarizing element is in optical communication with said polarizing element.

89. The light fixture of claim 68, comprising first and second polarizing elements, wherein the axis of transmission of the first polarizing element is adjustable with respect to the axis of transmission of the second polarizing element.

90. The fixture of claim 68, wherein said fixture further comprises housing means for housing said light source and said polarizer, wherein said housing means is equipped with at least one aperture for emitting light from said housing means, and wherein said polarizer is disposed between said light source and said aperture.

91. The fixture of claim 68, wherein said continuous phase has a birefringence of at least about 0.1.

92. The fixture of claim 68, wherein said disperse phase has a birefringence of less than about 0.02.

93. The fixture of claim 68, wherein said continuous and disperse phases taken together have a total diffuse reflectivity along at least one axis of at least about 30% for light emitted by said light source.

94. The fixture of claim 68, wherein said continuous phase is a polyester.

95. The fixture of claim 68, wherein said disperse phase is present in an amount of at least about 1% by volume relative to said continuous phase.

96. The fixture of claim 68, wherein said disperse phase is present in an amount of about 5% to about 50% by volume relative to said continuous phase.

97. The fixture of claim 68, wherein said polarizer is a film, and wherein the refractive index difference between said continuous phase and said disperse phase is at least 0.05 for visible light polarized along a first in-plane axis and is less than 0.05 for visible light polarized along a second in-plane axis.

98. The fixture of claim 97, wherein said first and second axes are orthogonal.

99. The fixture of claim 68, wherein said polarizer is a film, and wherein the absolute value of the difference in index of refraction of said continuous and disperse phases is Δ

n₁ for visible light polarized along a first in-plane axis and Δ

n₂ for visible light polarized along a second in-plane axis, and wherein the absolute value of the difference between Δ

n₁ and Δ

n₂ is at least about 0.05.

100. The fixture of claim 99, wherein said first and second axes are orthogonal.

101. The fixture of claim 99, wherein the absolute value of the difference between Δ

n₁ and Δ

n₂ is at least about 0.1.

102. The fixture of claim 68, wherein said polarizer is a film, and wherein the difference in indices of refraction between said first and second phases is less than about 0.05 for visible light polarized along an axis perpendicular to the surface of said film.

103. A light fixture, comprising:

a housing element with a light source disposed therein, said housing element having at least one opening for emitting light; and

a diffusely reflective optical element, disposed within the optical path between said light source and said opening, said optical element comprising a continuous phase and a disperse phase, disposed within said continuous phase, said continuous and disperse phases comprising diverse thermoplastic polymers.

104. The light fixture of claim 103, wherein said optical element is a diffusely reflective polarizer.

105. The light fixture of claim 103, wherein said optical element is a diffusely reflective mirror.

106. The light fixture of claim 103, wherein said optical element has a total diffuse reflectivity of at least about 30%.

107. The light fixture of claim 103, wherein said optical element is a film, and wherein said continuous and disperse phases have a difference in index of refraction of at least 0.05 for visible light polarized along a first in-plane axis of the film.

108. The film of claim 107, wherein said continuous and disperse phases have a difference in index of retraction of at least 0.05 for visible light polarized along a second in-plane axis which is orthogonal to said first in-plane axis.

109. The film of claim 107, wherein said continuous and disperse phases have a difference in index of refraction of less than 0.05 for visible light polarized along a second in-plane axis which is orthogonal to said first in-plane axis.

110. A light fixture, comprising:

a light source; and

a polarizer, in optical communication with said light source, said polarizer being adapted to predominantly reflect light produced by said light source which is polarized along a first axis, and being further adapted to predominantly transmit light produced by said light source which is polarized along a second axis;

wherein said polarizer comprises a thermoplastic polymeric continuous phase and a polymeric disperse phase disposed within said continuous phase.

111. The light fixture of claim 110, wherein said polarizer is a free standing film.