Optical bodies including rough strippable boundary layers and asymmetric surface structures

• US 20060228092A1
• Filed: 04/05/2006
• Published: 10/12/2006
• Est. Priority Date: 04/06/2005
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Purcell, John P., Hebrink, Timothy J., Weber, Michael F., Taylor, Robert D., Derks, Kristopher J., Stover, Carl A., Strobel, Joan M., Jackson, Jeffery N., Bluem, Gregory L., Black, William B., Hamer, Kevin M., Rosell, Barry S., Denker, Martin E., Thompson, Richard J., Kobilansky, Anna A.
• Granted Patent: US 8,568,869 B2
• Time in Patent Office: Days
• US Class Current: 385/147
• CPC Class Codes: B29D 11/00788 Producing optical films
• CPC Class Codes: B32B 3/26 characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids foam layer B32B5/18; layer of synthetic resin characterised by fillers that create voids or cavities B32B27/205; characterised by an apertured layer
• CPC Class Codes: B32B 7/06 permitting easy separation
• CPC Class Codes: G02B 1/12 by surface treatment, e.g. by irradiation
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 5/0221 the surface having an irregular structure G02B5/0226 takes precedence
• CPC Class Codes: G02B 5/0257 creating an anisotropic diffusion characteristic, i.e. distributing output differently in two perpendicular axes
• CPC Class Codes: G02B 5/0268 characterized by the fabrication or manufacturing method
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24372 Particulate matter
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/254 Polymeric or resinous material

Abstract

Optical bodies are disclosed that include an optical film and at least one rough strippable skin layer. The at least one rough strippable skin layer can include a continuous phase and a disperse phase. In some embodiments, the at least one rough strippable skin layer can include a first polymer, a second polymer different from the first polymer and an additional material that is substantially immiscible in at least one of the first and second polymers. In some exemplary embodiments, a surface of the at least one rough strippable skin layer adjacent to the optical film comprises a plurality of protrusions and the adjacent surface of the optical film comprises a plurality of asymmetric depressions substantially corresponding to said plurality of protrusions. Methods of making such exemplary optical bodies are also disclosed.

Claims

1. An optical body, comprising:

a first optical film, a second optical film and at least one rough strippable boundary layer disposed between the first and second optical films adjacent to a surface of at least one of the first and second optical films;

wherein a surface of the rough strippable boundary layer disposed adjacent to an optical film comprises a first plurality of surface structures and the adjacent surface of the optical film comprises a second plurality of asymmetric surface structures substantially corresponding to said first plurality of surface structures.

2. The optical body of claim 1, wherein the asymmetric surface structures have a major dimension substantially collinear with a first axis of the optical body and a minor dimension substantially collinear with a second axis of the optical body.

3. The optical body of claim 2, wherein the asymmetric surface structures have an average ratio of the major dimension to the minor dimension of at least about 1.5.

8. The optical body of claim 1, wherein the rough strippable boundary layer comprises a continuous phase and a disperse phase.

9. The optical body of claim 8, wherein the continuous phase comprises a polypropylene, a polyester, a linear low density polyethylene, a nylon and copolymers thereof, syndiotactic polypropylene, linear low density polyethylene and random copolymer of propylene and ethylene.

10. The optical body of claim 8, wherein the disperse phase comprises at least one of:

styrene acrylonitrile, medium density polyethylene, modified polyethylene, polycarbonate and copolyester blend, C-caprolactone polymer, propylene random copolymer, poly(ethylene octene) copolymer, anti-static polymer, high density polyethylene, linear low density polyethylene, polymethyl methacrylate, and inorganic materials.

11. The optical body of claim 8, wherein the disperse phase comprises a plurality of beads.

12. The optical body of claim 1, wherein at least one rough strippable boundary layer further comprises a nucleating agent or a coloring agent.

13. The optical body of claim 1, wherein at least one of the optical films is selected from the group consisting of:

a multilayer polarizer, a multilayer reflector, an optical film having a continuous and a disperse phase, a layer comprising styrene acrylonitrile, a layer comprising polycarbonate, a layer comprising PET, a layer comprising a cycloaliphatic polyester/polycarbonate and any number or combination thereof.

14. The optical body of claim 1, wherein at least one of the optical films comprises at least one underskin layer.

15. The optical body of claim 14, wherein the underskin layer comprises styrene acrylonitrile, polycarbonate, PET or cycloaliphatic polyester/polycarbonate.

16. The optical body of claim 14, wherein the underskin layer comprises a first material and a second material substantially immiscible in the first material, said second material being polymeric or inorganic.

17. The optical body of claim 1, said optical body being substantially transparent.

18. The optical body of claim 1, wherein the optical body comprises a birefringent material.

19. The optical body of claim 1, further comprising at least one smooth strippable layer.

20. The optical body of claim 1, wherein the at least one rough strippable boundary layer further comprises voids.

4. The optical body of clam 2, wherein the asymmetric surface structures have an average major dimension from about 4 micron to about 40 microns.

5. The optical body of clam 2, wherein the asymmetric surface structures have an average depth from about 0.2 micron to about 4 microns.

6. The optical body of clam 2, wherein the asymmetric surface structures have an average minor dimension from about 0.2 micron to about 5 microns.

7. The optical body of clam 1, wherein the optical film having asymmetric surface structures is characterized by a haze of at least about 10%.

21. An optical body comprising:

a first optical film, a second optical film and at least one strippable boundary layer disposed between the first and second optical films adjacent to a surface of at least one of the first and second optical films, the strippable boundary layer comprising a first polymer and a second polymer that is substantially immiscible in the first polymer;

wherein a surface of the strippable boundary layer disposed adjacent to an optical film comprises a first plurality of surface structures and the adjacent surface of the optical film comprises a second plurality of asymmetric surface structures substantially corresponding to said first plurality of surface structures.

22. The optical body of claim 21, wherein the first polymer has crystallinity that is lower than crystallinity of the second polymer.

23. The optical body of claim 21, wherein the strippable boundary layer further comprises a third polymer.

24. The optical body of claim 21, wherein the first polymer is selected from the group consisting of:

syndiotactic polypropylene, linear low density polyethylene and random copolymer of propylene and ethylene.

25. The optical body of claim 21, wherein the second polymer is selected from the group consisting of:

styrene acrylonitrile, medium density polyethylene, modified polyethylene, polycarbonate and copolyester blend, ε

-caprolactone polymer, propylene random copolymer, poly(ethylene octene) copolymer, anti-static polymer, high density polyethylene, linear low density polyethylene and polymethyl methacrylate.

26. The optical body of claim 21, wherein the optical film is selected from the group consisting of:

a multilayer polarizer, a multilayer reflector, an optical film having a continuous and a disperse phase, a layer comprising styrene acrylonitrile, a layer comprising polycarbonate, a layer comprising PET, a layer comprising a cycloaliphatic polyester/polycarbonate and any number or combination thereof.

27. The optical body of claim 21, wherein the optical film comprises at least one underskin layer.

28. The optical body of claim 27, wherein the underskin layer comprises styrene acrylonitrile, polycarbonate, PET or cycloaliphatic polyester/polycarbonate.

29. The optical body of claim 27, wherein the underskin layer comprises a first material and a second material substantially immiscible in the first material, said second material being polymeric or inorganic.

30. The optical body of claim 21, wherein the rough strippable boundary layer further comprises voids.

31. A method of processing an optical body, comprising the steps of:

providing an optical body comprising at least one strippable boundary layer between a first optical film and a second optical film; and

stretching the optical body;

wherein in the stretched optical body a surface of the strippable boundary layer disposed adjacent to an optical film comprises a first plurality of surface structures and the adjacent surface of the optical film comprises a second plurality of asymmetric surface structures substantially corresponding to said first plurality of surface structures.

32. The method of claim 31, wherein the optical body is stretched biaxially.

33. The method of claim 31, wherein the optical body is stretched substantially uniaxially.

34. The method of claim 33, wherein stretching the optical body comprises:

conveying the optical body into a stretching region;

stretching the optical body to increase a transverse dimension of the optical body while conveying the opposing edges of the optical body along generally diverging paths in a machine direction, wherein the generally diverging paths are configured and arranged to provide a machine direction draw ratio (MDDR), a normal direction draw ratio (NDDR) and a transverse direction draw ratio (TDDR) that approach the following relationship;

MDDR=NDDR=(TDDR)<sup>−

1/2</sup>

during the stretching.

35. The method of claim 34, wherein the diverging paths comprise a curvilinear segment.

36. The method of claim 34, wherein the diverging paths are linear approximations of a curvilinear segment.

37. The method of claim 34, wherein the diverging paths are coplanar.

38. The method of claim 34, wherein the minimum value of the extent of uniaxial character, U, is at least 0.7, wherein U is defined as

U=(1/MDDR−

1)/(TDDR^1/2−

1).

39. The method of claim 34, wherein the optical body is stretched to a draw ratio in excess of four within the stretcher by moving the opposing edge portions along diverging non-linear paths, wherein, during the stretching, the minimum value of the extent of uniaxial character, U, is at least 0.7 over a final portion of the stretching after achieving a TDDR of 2.5 and U is less than 1 at the end of the stretching, wherein U is defined as

U=(1/MDDR−

1)/(TDDR^1/2−

1)

wherein MDDR is the machine direction draw ratio and TDDR is the transverse direction draw ratio as measured between the diverging paths.

40. The method of claim 31, wherein in the stretched optical body at least one of the first and second optical films comprises a reflective polarizer.

41. The method of claim 31, wherein stretching the film comprises stretching the optical body to a draw ratio in excess of four.

42. The method of claim 31, further comprising providing the optical body to the stretcher in a continuous manner from a roll of film.

43. The method of claim 31, further comprising coextruding the optical body in-line with stretching.

44. The method of claim 43, wherein coextruding the optical body comprises multiplication and the at least one boundary layer is added prior to multiplication.

45. The method of claim 31, wherein the stretched film comprises at least one material with indices of refraction in a length direction corresponding to the machine direction and a thickness direction that are substantially the same but substantially different from an index of refraction in a width direction.