Optical bodies including strippable boundary layers

• US 20060227421A1
• Filed: 04/06/2005
• Published: 10/12/2006
• Est. Priority Date: 04/06/2005
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Derks, Kristopher J., Denker, Martin E., Hebrink, Timothy J., Stover, Carl A., Jackson, Jeffery N.
• Application Number:
  US11/099,860
• Publication Number:
  US 20060227421A1
• Time in Patent Office: Days
• US Class Current: 359/485
• CPC Class Codes: B29C 55/023 using multilayered plates or sheets
• CPC Class Codes: B29C 55/08 transverse to the direction of feed
• CPC Class Codes: B29D 11/00644 polarizing
• CPC Class Codes: B29K 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2067/003 PET, i.e. poylethylene terephthalate
• CPC Class Codes: B32B 2307/42 Polarizing, birefringent, filtering
• CPC Class Codes: B32B 27/00 Layered products comprising a layer of synthetic resin fibrous or filamentary layer made of a synthetic resin B32B5/02; particulate layer made of a synthetic resin B32B5/16; foamed layer made of a synthetic resin B32B5/18
• CPC Class Codes: B32B 27/36 comprising polyesters
• CPC Class Codes: G02B 5/3041 comprising multiple thin layers, e.g. multilayer stacks
• 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

Abstract

The present disclosure is directed to optical bodies including a first optical film, a second optical film and one or more strippable boundary layers disposed between the first and second optical films. Each major surface of a strippable boundary layer may be disposed adjacent to an optical film or another strippable boundary layer. At least one of the first and second optical films may include a reflective polarizer. The present disclosure is also directed to methods of processing such optical bodies.

Claims

1. An optical body comprising a first optical film, a second optical film and one or more strippable boundary layers disposed between the first and second optical films such that each major surface of a strippable boundary layer is disposed adjacent to an optical film or another strippable boundary layer, wherein at least one of the first and second optical films comprises a reflective polarizer.

2. The optical body of claim 1, wherein the reflective polarizer is a diffuse reflective polarizer comprising a disperse polymeric phase and a continuous polymeric phase.

3. The optical body of claim 2, wherein the reflective polarizer has a thickness of no more than 1 mil.

4. The optical body of claim 2, wherein at least one of the disperse or continuous phase has an in-plane birefringence of at least 0.1.

5. The optical body of claim 1, further comprising a third optical film and at least one additional strippable boundary layer disposed between the third optical film and the second optical film.

6. The optical body of claim 1, wherein the reflective polarizer is a multilayer reflective polarizer comprising a plurality of first and second optical layers.

7. The optical body of claim 6, wherein the reflective polarizer has no more than optical layers.

8. The optical body of claim 6, wherein at least one of the first and second optical layers has an in-plane birefringence of at least 0.1.

9. The optical body of claim 1, wherein a strippable boundary layer comprises at least one of:

a fluropolymer, a polypropylene, a modified polypropylene, an aliphatic polyolefin, a polyethylene, a polyethylene copolymer, polymethylpentene, a cyclic olefin copolymer, a syndiotactic polymer, an atactic vinyl aromatic polymer, a polysyrene, and a copolymer of styrene.

10. The optical body of claim 1, further comprising at least one outer skin layer.

11. A method for processing an optical body, comprising:

providing 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;

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.

12. The method of claim 11, wherein the diverging paths are substantially parabolic.

13. The method of claim 11, wherein the diverging paths are linear approximations of substantially parabolic paths.

14. The method of claim 11, wherein the diverging paths are coplanar.

15. The method of claim 11, wherein in the stretched optical body at least one of the first and second optical films comprises a reflective polarizer.

16. The method of claim 11, wherein stretching the film comprises stretching the optical body to a draw ratio in excess of four.

17. The method of claim 11, wherein the step of stretching comprises moving the opposing edge portions along diverging paths that are substantially symmetrical about a center axis of the optical body.

18. The method of claim 11, further comprising providing the optical body to the stretcher in a continuous manner from a roll of film.

19. The method of claim 11, further comprising coextruding the optical body in-line with stretching.

21. The method of claim 11, 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.

22. The method of claim 11, 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).

20. The method of claim 20, wherein coextruding the optical body comprises multiplication and the at least one boundary layer is added prior to multiplication.

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

providing 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;

conveying the optical body within a stretcher along a machine direction while holding opposing edge portions of the optical body; and

stretching the optical body 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.

24. The method of claim 24, wherein the minimum value of the extent of uniaxial character is at least 0.8.

25. The method of claim 24, wherein the extent of uniaxial character, U, is at least 0.8 over a final portion of the stretching after achieving a TDDR of 2.0.

26. The method of claim 24, wherein at least one of the first and second optical films comprises a multilayer film having a plurality of alternating layers of different polymeric composition.

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

providing 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;

conveying the optical body within a stretcher along a machine direction while holding opposing edge portions of the optical body; and

stretching the optical body within the stretcher by moving the opposing edge portions along diverging non-linear paths, wherein, during the stretching of the optical body, the speed of the film along the machine direction decreases by a factor of approximately λ

^1/2 where λ

is the transverse direction draw ratio.

28. The method of claim 28, wherein at least one of the first and second optical film comprises a multilayer film having a plurality of alternating layers of different polymeric composition.