Optical film

• US 20040043205A1
• Filed: 09/02/2003
• Published: 03/04/2004
• Est. Priority Date: 12/21/1993
• Status: Active Grant

• 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.
• Granted Patent: US 7,083,847 B2
• Time in Patent Office: Days
• 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 multilayered optical film, comprising a plurality of layers, wherein at least one of the plurality of layers is birefringent and wherein a refractive index difference between at least two layers along a z-axis perpendicular to the film is selected to provide a desired relationship of reflectivity as a function of incidence angle for p-polarized light.

2. The film of claim 1 wherein the film is biaxially birefringent.

3. The film of claim 2 wherein the film is asymmetrically biaxially birefringent.

4. The film of claim 1 wherein at least one of the plurality of layers comprises a first material, and wherein at least one other of the plurality of layers comprises a second material.

5. The film of claim 4 wherein the first material is positively birefringent and the second material is positively birefringent.

6. The film of claim 4 wherein the first material is negatively birefringent and the second material is negatively birefringent.

7. The film of claim 4 wherein the first material is positively birefringent and the second material is negatively birefringent.

8. The film of claim 4 wherein the first material is negatively birefringent and the second material is positively birefringent.

9. The film of claim 4 wherein the first material or the second material is isotropic.

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

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

12. The film of claim 1, wherein an interface is formed between the at least two layers, and wherein the desired relationship is a reflectivity of the interface that is substantially independent of incidence angle.

13. The film of claim 1, wherein an interface is formed between the at least two layers, and the at least two layers further have respective in-plane refractive indices n1x, n2x that are mismatched to define at least one reflection axis, and wherein the desired relationship is a reflectivity of the interface that increases monotonically with incidence angle for p-polarized light incident in a plane that includes the z-axis and the reflection axis.

14. The film of claim 1, wherein an interface is formed between the at least two layers, and wherein the desired relationship is a reflectivity of the interface that initially decreases with angle of incidence away from the z-axis.

15. The film of claim 1, wherein an interface is formed between the at least two layers, wherein the refractive index of the at least two layers along the z-axis is respectively n1z, n2z, and wherein the at least two layers further have respective in-plane refractive indices n1x, n1y and n2x, n2y, wherein n1x and n2x are substantially matched, wherein n1y and n2y are substantially matched, and wherein n1z and n2z are substantially mismatched, such that the interface is substantially transparent to s-polarized light at any angle and becomes increasingly reflective for p-polarized light at increasing angles of incidence.

16. The film of claim 1 in combination with a light source.