Optical film

• US 6,613,421 B2
• Filed: 09/25/2001
• Issued: 09/02/2003
• Est. Priority Date: 12/21/1993
• Status: Expired due to Fees

• 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:
  US09/962,748
• Publication Number:
  US 20020031676A1
• Time in Patent Office: 707 Days
• Field of Search: 428/212, 428/332, 428/333, 428/910, 359/483, 359/487, 359/488, 359/489, 359/494, 359/500, 359/577, 359/580, 359/584, 359/581, 359/586, 359/589, 359/838, 359/839, 359/485, 359/350, 359/352, 359/359
• 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, mirror films with high reflectivity in two different planes of polarization for any incident direction over a wide bandwidth can be achieved.

Claims

1. A reflective mirror film, comprising:

a first reflective polarizer having a first transmission axis and a first extinction axis, wherein the first reflective polarizer transmits light polarized parallel to the first transmission axis and reflects light polarized parallel to the first extinction axis; and

a second reflective polarizer having a second transmission axis aligned with respect to the first transmission axis and a second extinction axis aligned with respect to the first extinction axis, such that he second reflective polarizer reflects at least some of the light transmitted by the first reflective polarizer;

wherein the first and second reflective polarizers each comprise a plurality of layers, and further wherein at least two of the plurality of layers exhibit a refractive index difference between layers in a first in-plane direction that is greater than a refractive index difference between layers in a second in-plane direction.

2. The reflective film of claim 1 wherein the first and second transmission axes are aligned at about 90 degrees.

3. The reflective mirror film of claim 1 wherein the first and second reflective polarizers are laminated together.

4. A mirror that substantially reflects light of two orthogonal polarizations, comprising a plurality of birefringent optical layers.

5. The mirror of claim 4, wherein the birefringent optical layers are arranged in an alternating fashion with second optical layers, the birefringent optical layers and the second optical layers comprising stretched polymeric materials.

6. The mirror of claim 5, wherein pairs of one of the birefringent optical layers and one of the second optical layers exhibit a refractive index difference along an in-plane direction of at least 0.05.

7. The mirror of claim 5, wherein pairs of one of the birefringent optical layers and one of the second optical layers exhibit a refractive index difference along each of two orthogonal in-plane directions of at least 0.05.

8. The mirror of claim 4, wherein the birefringent optical layers are uniaxially birefringent.

9. The mirror of claim 8, wherein the birefringent optical layers each have in-plane refractive indices nx, ny along orthogonal in-plane axes, and a refractive index nz along an axis perpendicular to the in-plane axes, and wherein nx=ny≠

nz.

10. The mirror of claim 4, wherein the mirror exhibits asymmetric transmission along different directions.

11. The mirror of claim 4, wherein the reflected light is in a first wavelength range but not in a second wavelength range.

12. The mirror of claim 11, wherein the first wavelength range comprises visible light wavelengths and the second wavelength range comprises infrared light wavelengths.

13. The mirror of claim 11, wherein the first wavelength range comprises infrared light wavelengths and the second wavelength range comprises visible light wavelengths.

14. The mirror of an of claims 4-9, wherein the plurality of birefringent optical layers form part of a quarterwave stack.

15. The mirror of any of claims 4-9 , wherein the plurality of birefringent optical layers each have an optical thickness in the range of 0.1 to 1 times a wavelength of the reflected light.