Multilayer optical compensator, liquid crystal display, and process

• US 20050134772A1
• Filed: 12/23/2003
• Published: 06/23/2005
• Est. Priority Date: 12/23/2003
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Eastman Kodak Company
• Inventors: Majumdar, Debasis, Nair, Mridula, Anderson, Charles C., Elman, James F., Yonkoski, Roger
• Granted Patent: US 6,995,395 B2
• Time in Patent Office: Days
• US Class Current: 349/117
• CPC Class Codes: B32B 27/08 of synthetic resin
• 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 1/133634 the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis

Abstract

Disclosed is a multilayer compensator polymeric film for a LC cell comprising two or more first layers having an out-of-plane birefringence not more negative than −0.005 and one or more second layers having an out-of-plane birefringence more negative than −0.005, wherein the second layers are amorphous and comprise selected polymeric materials having sufficient thickness so that the overall in-plane retardation (Re) of the compensator is from 0 to 300 nm and the out-of-plane retardation (Rth) of at least one of the one or more second layers is more negative than −20 nm wherein: (a) a first layer is present that is contiguous to a second layer and is between all of the second layers and all of the other first layers; (b) at least one of the second layers or one of the other first layers is a layer coated from an organic solvent; and (c) the contiguous first layer contains a polymer that is water soluble or water dispersible in an amount sufficient to impede the diffusion of the organic solvent between the other first layers and the second layers.

Claims

1. A multilayer compensator polymeric film for a LC cell comprising two or more first layers having an out-of-plane birefringence not more negative than −

0.005 and one or more second layers having an out-of-plane birefringence more negative than −

0.005, wherein the second layers are amorphous and comprise selected polymeric materials having sufficient thickness so that the overall in-plane retardation (Re) of the compensator is from 0 to 300 nm and the out-of-plane retardation (Rth) of at least one of the one or more second layers is more negative than −

20 nm wherein;

(a) a first layer is present that is contiguous to a second layer and is between all of the second layers and all of the other first layers;

(b) at least one of the second layers or one of the other first layers is a layer coated from an organic solvent; and

(c) the contiguous first layer contains a polymer that is water soluble or water dispersible in an amount sufficient to impede the diffusion of the organic solvent between the other first layers and the second layers.

2. The compensator of claim 1 wherein an organic solvent is contained in at least one of the layers.

3. The compensator of claim 1 wherein the organic solvent comprises one selected from the group consisting of aromatic or alkyl hydrocarbons, alcohols, esters, ketones, aldehydes, and halogenated analogues of the foregoing.

4. The compensator of claim 1 wherein the organic solvent comprises one selected from the group consisting of ethylacetate, propylacetate, butylacetate, acetone, methylethylketone, toluene, xylene, cycopentanone, cyclohexanone, and methylene chloride.

5. The compensator of claim 1 wherein each of the one or more first layers has an out-of-plane birefringence not more negative than −

0.005.

6. The compensator of claim 1 wherein each of the one or more second layers has an out-of-plane birefringence more negative than −

0.005.

7. The compensator of claim 1 wherein at least two of the first layers are contiguous.

8. The compensator of claim 1 wherein all of the first and second layers are contiguous.

9. The compensator of claim 1 wherein the combined second layers have a thickness of less than 30 micrometers.

10. The compensator of claim 1 wherein the combined second layers have a thickness of from 0.1 to 20 micrometers.

11. The compensator of claim 1 wherein the combined second layers have a thickness of from 1.0 to 10 micrometers.

12. The compensator of claim 1 wherein the combined second layers have a thickness of from 2 to 8 micrometers.

13. The compensator of claim 1 wherein the thickness of the combined first and second layers of the compensator is less than 115 micrometers.

14. The compensator of claim 1 wherein the thickness of the combined first and second layers of the compensator is from 20 to 105 micrometers.

15. The compensator of claim 1 wherein the thickness of the combined first and second layers of the compensator is from 40 to 100 micrometers.

16. The compensator of claim 1 wherein the Rth of at least one second layer is −

20 nm or more negative.

17. The compensator of claim 1 wherein the Rth of at least one second layer is from −

40 to −

600 nm.

18. The compensator of claim 1 wherein the Rth of at least one second layer is from −

60 to −

500 nm.

19. The compensator of claim 1 wherein the second layer comprises a polymer containing in the backbone a non-visible chromophore group and has a Tg above 180°

C.

20. The compensator of claim 1 wherein the Tg of the polymer is above 180°

C.

21. The compensator of claim 20 wherein the second layer comprises a polymer containing in the backbone a vinyl, carbonyl, amide, imide, ester, carbonate, aromatic, sulfone, or azo group.

22. The compensator of claim 20 wherein the non-visible chromophore group includes a carbonyl, amide, imide, ester, carbonate, phenyl, naphthyl, biphenyl, bisphenol, or thiophene group.

23. The compensator of claim 1 wherein the second layer comprises 1)poly(4,4′

-hexafluoroisopropylidene-bisphenol) terephthalate-co-isophthalate,

     2)poly(4,4′

-hexahydro-4,7-methanoindan-5-ylidene bisphenol)terephthalate,

     3) poly(4,4′

-isopropylidene-2,2′

6,6′

-tetrachlorobisphenol) terephthalate-co-isophthalate,

     4) poly(4,4′

-hexafluoroisopropylidene)-bisphenol-co-(2-norbomylidene)-bisphenol terephthalate,

     5) poly(4,4′

-hexahydro-4,7-methanoindan-S-ylidene)-bisphenol-co-(4,4′

-isopropylidene-2,2′

,6,6′

-tetrabromo)-bisphenol terephthalate, or

     6) poly(4,4′

-isopropylidene-bisphenol-co-4,4′

-(2-norbomylidene)bisphenol)terephthalate-co-isophthalate or copolymers of any of the foregoing.

24. The compensator of claim 1 wherein the second layer comprises poly(4,4′

-hexafluoroisopropylidene-bisphenol-co-4,4′

-(2-norbomylidene)bisphenol)terephthalate-co-isophthalate or copolymers thereof.

25. The compensator of claim 1 wherein the first layer comprises a polymer other than a polymer containing in the backbone a non-visible chromophore group having a Tg above 180°

C.

26. The compensator of claim 20 wherein the second layer comprises a polymer containing in the backbone a non-visible chromophore group that does not contain a chromophore off of the backbone

27. The compensator of claim 1 wherein one of the first layers comprises esters of cellulose, polycarbonate, cyclic polyolefin or polyarylate containing fluorene groups.

28. The compensator of claim 1 wherein one of the first layers comprises triacetylcellulose (TAC).

30. A liquid crystal (LC) display comprising a liquid crystal cell, crossed polarizers located one on each side of the cell, and at least one compensator of claim 1.

31. A liquid crystal (LC) display comprising a liquid crystal cell, crossed polarizers located one on each side of the cell, and at least one compensator of claim 2.

29. A multilayer compensator for an LC cell comprising one or more first layers and one or more second, wherein the second layers are amorphous and comprise selected polymeric materials, in which each second layer comprises a polymer containing in the backbone a non-visible chromophore group and has a Tg above 180°

C. and in which each first layer does not comprise such a polymer, the layers having sufficient thickness so that the overall in-plane retardation (Re) of the compensator is from 0 to 300 nm and the out-of-plane retardation (Rth) of at least one of the one or more second layers is more negative than −

20 nm.

32. A liquid crystal (LC) display comprising a liquid crystal cell, crossed polarizers located one on each side of the cell, and at least one compensator of claim 29.

33. The display of claim 29 wherein the liquid crystal cell is a vertically aligned or twisted nematic cell.

34. The display of claim 29 employing in-plane switching.

35. A process for forming a compensator polymeric film for a LC display comprising two or more first layers having an out-of-plane birefringence not more negative than −

0.005 and one or more second layers having an out-of-plane birefringence more negative than −

0.005, wherein the second layers are amorphous and comprise selected polymeric materials having sufficient thickness so that the overall in-plane retardation (Re) of the compensator is from 0 to 300 nm and the out-of-plane retardation (Rth) of at least one of the one or more second layers is more negative than −

20 nm wherein;

(a) at least one of the layers is coated from an organic coating solvent;

(b) a contiguous first and second layer are coated to separate any other first layers from any other second layers; and

(c) at least one of the contiguous first or second layers contains a polymer that is applied from water and is present in an amount sufficient to impede the diffusion of the organic solvent between the contiguous layers.

36. The process of claim 35 wherein an organic solvent is contained in at least one of the layers.

37. The process of claim 35 wherein the organic solvent comprises one selected from the group consisting of aromatic or alkyl hydrocarbons, alcohols, esters, ketones, aldehydes, and halogenated analogues of the foregoing.

38. The process of claim 35 wherein the organic solvent comprises one selected from the group consisting of ethylacetate, propylacetate, butylacetate, acetone, methylethylketone, toluene, xylene, cycopentanone, cyclohexanone, and methylene chloride.

39. The process of claim 35 wherein at least one of the contiguous first or second layers that contains a polymer that is applied from water and is present in an amount sufficient to impede the diffusion of the organic solvent between the contiguous layers is crosslinked.