Optical film

• US 5,882,774 A
• Filed: 03/10/1995
• Issued: 03/16/1999
• Est. Priority Date: 12/21/1993
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Company
• Inventors: Weber, Michael F., Ouderkirk, Andrew J., Stover, Carl A., Jonza, James M.
• Primary Examiner(s): Chen, Vivian
• Application Number:
  US08/402,041
• Time in Patent Office: 1,467 Days
• Field of Search: 264/1.31, 264/1.34, 313/112, 359/359, 359/485, 359/487, 359/488, 359/493, 359/494, 359/500, 359/838, 359/577, 359/580, 359/587, 359/586, 359/588, 359/589, 359/584, 362/19, 385/11, 427/163.1, 428/480, 428/910, 428/421, 428/483, 428/522, 428/523
• 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 multilayer optical films in which the refractive indices in the thickness direction of two adjacent layers are substantially matched have a Brewster angle (the angle at which reflectance of p-polarized light goes to zero) which is very large or is nonexistant. 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 film, comprising:

a first layer comprising a first polymeric material; and

a second layer, contiguous to said first layer, comprising a second polymeric material;

wherein the absolute value of the difference in indices of refraction between said first and second layers is Δ

x, Δ

y, and Δ

z, respectively, for light polarized along first, second, and third mutually orthogonal axes, wherein said third axis is orthogonal to the plane of said film, wherein Δ

x is greater than about 0.05, and wherein Δ

z is less than about 0.05.

2. The film of claim 1, wherein Δ

z is less than about 0.02.

3. The film of claim 1, wherein Δ

z is less than about 0.01.

4. The film of claim 1, wherein Δ

x is greater than about 0.1.

5. The film of claim 1, wherein Δ

x is greater than about 0.2.

6. The film of claim 1, wherein Δ

y is less than about 0.05.

7. The film of claim 1, wherein Δ

y is less than about 0.02.

8. The film of claim 1, wherein Δ

y is greater than about 0.05.

9. The film of claim 1, wherein Δ

y is greater than about 0.1.

10. The film of claim 1, wherein said film has been stretched in at least one direction.

11. The film of claim 1, wherein said film has been stretched in at least one direction to at least twice that direction'"'"'s unstretched dimension.

12. The film of claim 1, wherein both of said first and second polymeric materials are polyesters.

13. The film of claim 1, wherein said second polymeric material is a polyacrylate.

14. The film of claim 12, wherein said second polymeric material is polymethylmethacrylate.

15. The film of claim 1, wherein said film has an average reflectivity, for at least one plane of polarization, of at least 50% over at least a 100 nm wide band.

16. The film of claim 1, wherein said film comprises at least 50 layers of said first polymeric material and at least 50 layers of said second polymeric material, and wherein said first polymeric material is a naphthalene dicarboxylic acid polyester.

17. The film of claim 1, wherein said first polymeric material comprises a naphthalene dicarboxylic acid polyester.

18. The film of claim 17, wherein said naphthalene dicarboxylic acid polyester has a higher index of refraction than said second polymer for light polarized along at least one of said first and second axes.

19. The film of claim 18, wherein said higher index of refraction is at least about 0.05 higher.

20. The film of claim 18, wherein said higher index of refraction is at least 0.10 higher.

21. The film of claim 17, wherein said naphthalene dicarboxylic acid polyester is more positively birefringent than said second polymeric material.

22. The film of claim 17, wherein said naphthalene dicarboxylic acid polyester is polyethylene naphthalate.

23. The film of claim 17, wherein said second polymeric material is a copolyester comprising naphthalate units and terephthalate units.

24. The film of claim 17, wherein said second polymeric material is a copolyester comprising naphthalate units and terephthalate units.

25. The film of claim 17, wherein said second polymeric material is a polystyrene.

26. The film of claim 17, wherein said second polymeric material is a fluoropolymer.

27. A film, comprising:

a first layer comprising a first polymeric material; and

a second layer, contiguous to said first layer, comprising a second polymeric material;

wherein the absolute value of the difference in index of refraction between said first and second polymeric material is Δ

x, Δ

y, and Δ

z, respectively, for light polarized along first, second, and third mutually orthogonal axes, wherein said third axis is orthogonal to the plane of said film, wherein Δ

z is less than 0.5 k, where k is the larger of Δ

x and Δ

y, and wherein k is at least about 0.05.

28. The film of claim 27, wherein both of said first and second polymeric materials are polyesters.

29. The film of claim 27, wherein Δ

z is less than about 0.03.

30. The film of claim 27, wherein Δ

x is greater than about 0.1.

31. The film of claim 27, wherein said film comprises at least 50 layers of said first polymeric material and at least 50 layers of said second polymeric material, and wherein said first polymeric material is a naphthalene dicarboxylic acid polyester.

32. The film of claim 27, wherein Δ

z is less than 0.25 k.

33. The film of claim 27, wherein Δ

z is less than 0.1 k.

34. The film of claim 27, wherein said first polymeric material comprises a naphthalene dicarboxylic acid polyester.

35. The film of claim 34, wherein said naphthalene dicarboxylic acid polyester has a higher index of refraction than said second polymer for light polarized along at least one of said first and second axes.

36. The film of claim 35, wherein said higher index of refraction is at least about 0.05 higher.

37. The film of claim 35, wherein said higher index of refraction is at least 0.10 higher.

38. The film of claim 34, wherein said naphthalene dicarboxylic acid polyester is more positively birefringent than said second polymeric material.

39. The film of claim 34, wherein said naphthalene dicarboxylic acid polyester is polyethylene naphthalate.

40. The film of claim 34, wherein said second polymeric material is a copolyester comprising naphthalate units and terephthalate units.

41. The film of claim 34, wherein said second polymeric material is a copolyester comprising naphthalate units and terephthalate units.

42. The film of claim 34, wherein said second polymeric material is a polystyrene.

43. The film of claim 34, wherein said second polymeric material in a fluoropolymer.

44. The film of claim 34, wherein said second polymeric material is a polyacrylate.

45. The film of claim 44, wherein said second polymeric material is polymethylmethacrylate.