Optical film

• US 6,296,927 B1
• Filed: 03/17/2000
• Issued: 10/02/2001
• 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:
  US09/527,452
• Time in Patent Office: 564 Days
• Field of Search: 428/212, 428/480, 428/910, 359/485, 359/487, 359/488, 359/494, 359/495, 359/500, 359/577, 359/580, 359/586, 359/589, 359/584
• 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

Birefringent optical films have a Brewster angle (the angle at which reflectance of p-polarized light goes to zero) which is very large or is nonexistent. This allows for the construction of multilayer mirrors and polarizers whose reflectivity for p-polarized light decreases slowly with angle of incidence, are independent of angle of incidence, or increase with angle of incidence away from the normal. As a result, multilayer films having high reflectivity (for both planes of polarization for any incident direction in the case of mirrors, and for the selected direction in the case of polarizers) over a wide bandwidth, can be achieved.

Claims

1. A polarizing film, comprising:

at least two layers, wherein each layer has a refractive index in a first in-plane direction, a second in-plane direction, and an out-of-plane direction, and further wherein a refractive index difference between at least two layers in the first in-plane direction is less than 0.05, wherein a refractive index difference between at least two layers in the second in-plane direction is less than 0.05, wherein a refractive index difference between at least two layers in the out-of-plane direction is greater than 0.0.

2. The polarizing film of claim 1 wherein reflectivity for p-polarized light increases monotonically with increasing angle of incidence.

3. A reflective polarizer for reflecting light having a first polarization orientation and transmitting light having a second polarization orientation, wherein the reflective polarizer comprises a plurality of layers and has a % RMS color for the transmitted polarization of less than 10% at an angle of at least 30 degrees from an axis perpendicular to the reflective polarizer over the bandwidth of interest.

4. The reflective polarizer of claim 3 wherein the reflective polarizer has a % RMS color for the transmitted polarization of less than 10% at an angle of at least 60 degrees from an axis perpendicular to the reflective polarizer.

5. The reflective polarizer of claim 3 wherein the reflective polarizer has a % RMS color for the transmitted polarization of less than 3.5% at an angle of at least 45 degrees from an axis perpendicular to the reflective polarizer.

6. The reflective polarizer of claim 5 wherein the reflective polarizer has a % RMS color for the transmitted polarization of less than 3.5% at an angle of at least 60 degrees from an axis perpendicular to the reflective polarizer.

7. The reflective polarizer of claim 3 wherein the reflective polarizer has a % RMS color for the transmitted polarization of less than 2.1% at an angle of at least 45 degrees from an axis perpendicular to the reflective polarizer.

8. The reflective polarizer of claim 7 wherein the reflective polarizer has a % RMS color for the transmitted polarization of less than 2.1% at an angle of at least 60 degrees from an axis perpendicular to the reflective polarizer.

9. The reflective polarizer of claim 3 wherein the reflective polarizer has a % RMS color for the transmitted polarization of less than 1.5% at an angle of at least 45 degrees from an axis perpendicular to the reflective polarizer.

10. The reflective polarizer of claim 9 wherein the reflective polarizer has a % RMS color for the transmitted polarization of less than 1.5% at an angle of at least 60 degrees from an axis perpendicular to the reflective polarizer.

11. The reflective polarizer of claim 3 wherein the % RMS color is determined according to the equation $\%$

 



RMS

 



color=∫

λ



1λ



 



2

((T-T_)2)1/2



λ

T_(λ



 



2-λ



 



1).

12. The reflective polarizer of claim 3 wherein the light having the first polarization orientation is polarized in a plane defined by a first in-plane direction and an out-of-plane direction.

13. The reflective polarizer of claim 12 wherein the light having the second polarization orientation is polarized in a plane defined by a second in-plane direction and the out-of-plane direction.

14. The reflective polarizer of claim 12 wherein the reflective polarizer exhibits a refractive index difference between at least two layers in the first in-plane direction that is greater than a refractive index difference between the at least two layers in the second in-plane direction.

15. The reflective polarizer of claim 14 wherein the refractive index difference in the first in-plane direction is greater than a refractive index difference between different material layers in the out-of-plane direction.

16. The reflective polarizer of claim 15 wherein the refractive index difference in the out-of-plane direction is less than 0.25.

17. The reflective polarizer of claim 16 wherein the refractive index difference in the out-of-plane direction is less than 0.11.

18. The reflective polarizer of claim 17 wherein the refractive index difference in the out-of-plane direction is less than 0.05.

19. The reflective polarizer of claim 18 wherein the refractive index difference in the out-of-plane direction is about 0.

20. A stack of two or more layers in which at least one layer is birefringent, and in which the z-axis refractive index of the birefringent layer is closer numerically in value to the z-axis refractive index of at least one other layer than to the highest in-plane refractive index of the birefringent layer.

21. A stack of two or more layers in which at least one layer is birefringent, and in which the z-axis refractive index of the birefringent layer is closely numerically in value to an in-plane refractive index of at least one other layer than to the highest in-plane refractive index of the birefringent layer.