Process and materials for aligning liquid crystals and liquid crystal optical elements

• US 5,807,498 A
• Filed: 03/29/1996
• Issued: 09/15/1998
• Est. Priority Date: 03/29/1996
• Status: Expired due to Fees

• Current Assignee: Elsicon Incorporated
• Original Assignee: Alliant Techsystems Incorporated (Northrop Grumman Corporation)
• Inventors: Gibbons, Wayne M., Shannon, Paul J., Sun, Shao-Tang
• Primary Examiner(s): KELLY, CYNTHIA HARRIS
• Application Number:
  US08/624,945
• Time in Patent Office: 900 Days
• Field of Search: 252/299.01, 252/299.4, 428/1.2
• US Class Current: 252/299.4
• CPC Class Codes: C08G 73/10 Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
• CPC Class Codes: C08G 73/1039 comprising halogen-containing substituents
• CPC Class Codes: C08G 73/1042 Copolyimides derived from at least two different tetracarboxylic compounds or two different diamino compounds
• CPC Class Codes: C08G 73/1085 Polyimides with diamino moieties or tetracarboxylic segments containing heterocyclic moieties
• CPC Class Codes: C09K 2323/02 Alignment layer characterised by chemical composition
• CPC Class Codes: C09K 2323/025 Polyamide
• CPC Class Codes: C09K 2323/027 Polyimide
• CPC Class Codes: G02F 1/133723 Polyimide, polyamide-imide
• CPC Class Codes: G02F 1/133742 for homeotropic alignment
• CPC Class Codes: G02F 1/133753 with different alignment orientations or pretilt angles on a same surface, e.g. for grey scale or improved viewing angle
• CPC Class Codes: G02F 1/133788 by light irradiation, e.g. linearly polarised light photo-polymerisation
• CPC Class Codes: Y10S 359/90 Methods
• CPC Class Codes: Y10T 428/31721 Of polyimide

Abstract

A process for aligning liquid crystals adjacent to a surface of an optical alignment layer comprising: exposing at least one optical alignment layer, comprising anisotropically absorbing molecules, to polarized light; the polarized light having a wavelength within the absorption band of said anisotropically absorbing molecules; wherein the exposed anisotropically absorbing molecules induce alignment of a liquid crystal medium at an angle +and-θ with respect to the direction of the polarization of the incident light beam and along the surface of the optical alignment layer; and applying a liquid crystal medium to said optical alignment layer; wherein said anisotropically absorbing molecules consist essentially of diaryl ketones, is described. The invention also is directed to a liquid crystal optical storage medium, a liquid crystal display element, and a liquid crystal diffractive optical element made by the process of the invention and to novel polyimide compositions that are useful as optical alignment layers in the process of the invention.

Claims

1. A process for aligning liquid crystals adjacent to a surface of an optical alignment layer comprising:

(a) exposing at least one optical alignment layer, comprising anisotropically absorbing molecules, to polarized light;

the polarized light having a wavelength within the absorption band of said anisotropically absorbing molecules;

wherein the resulting exposed anisotropically absorbing molecules induce alignment of a liquid crystal medium at an angle + and -θ

with respect to the direction of the polarization of the incident light and along the surface of tie optical alignment layer;

(b) applying a liquid crystal medium to the optical alignment layer;

wherein the anisotropically absorbing molecules consist essentially of at least one diaryl ketone.

2. A process of claim 1 wherein the diaryl ketone comprises a polymer having a recurring structural element of the following formula I:

##STR39## wherein the structural element I has a covalent linkage from Q to at least one member selected from the group consisting of Q, Ar, and Ar'"'"';

Q is an organic radical with 1 to 100 atoms;

Ar and Ar'"'"' are independently selected from the group consisting of substituted and unsubstituted phenyl, fused polycyclic aromatic and heteroaromatic radicals.

3. A process of claim 2 wherein the polymer is a polyimide.

4. A process of claim 3 wherein the polyimide is the reaction product at least one diaryl ketone tetracarboxylic dianhydride and at least one diamine, which comprises at least one structural element of formula II ##STR40## wherein Q'"'"' is a divalent organic radical containing at least two carbon atoms;

X is independently selected from the group consisting of H, Cl, F, Br, R₁ and R₁ O--;

wherein R₁ is independently selected from C₁ -C₃ perflourinated alkyl chain, C₁ -C₃ partially flourinated alkyl chain and C₁ -C₈ hydrocarbon chain;

Z is selected from the group consisting of --S--, --SO₂ --, --O--, --CH₂ CH₂ --, --CH₂ --, --NR--, --C(CF₃)₂ --, --C(O)-- and a covalent bond, wherein R is a C₁ -C₄ hydrocarbon chain; and

m is 1 or 0.

5. A process of claim 4 wherein Q'"'"' is a divalent radical selected from formulas III and IV ##STR41## wherein Z₁ is selected, independently, from the same group as Z;

each X₁ is independently selected from H, Cl, F, Br, R₁, --O--R₁, --S--R₁ and --N(R₂)--R₁ ;

wherein R₁ is independently selected from C₁ -C₃ perfluorinated alkyl chain, C₁ -C₃ partially fluorinated alkyl chain, and C₁ -C₈ hydrocarbon chain, and R₂ is independently selected from H and R₁ ; and

n is 1 to 4.

6. A process of claim 5 wherein the tetracarboxylic dianhydride from which the polyimide of structural formula II is derived is selected from the group consisting of 3,3'"'"',4,4'"'"'-benzophenonetetracarboxylic dianhydride and 2,2'"'"'-dichloro-4,4'"'"',5,5'"'"'-benzophenonetetracarboxylic dianhydride.

7. A process of claim 4 wherein the polyimide further comprises the reaction product of at least one alicyclic tetracarboxylic dianihydride and additionally at least one structural element of formula V ##STR42## wherein P is a tetravalent organic radical derived from said alicyclic tetracarboxylic dianhydride and Q'"'"' is as defined in claim 4.

8. A process of claim 7 wherein the alicyclic tetracarboxylic dianhydride is selected from 5-(2,5-dioxotetrahydro)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 2,3,5-tricarboxycyclopentaneacetic acid dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,3,4-cyclobutanetetracarboxylic dianhydride.

9. A process of claim 5 wherein Z₁ is selected from --C(O)-- and a covalent bond and X₁ is independently selected from H, --CF₃, --CH₃ and --CH₂ CH₃.

10. A process of claim 4 wherein the diaryl ketone tetracarboxylic dianhydride from which structural formula II is derived is 3,3'"'"',4,4'"'"'-benzophenonetetracarboxylic dianhydride and Q'"'"' is derived from at least one diamine selected from the group consisting of 2-(trifluoromethyl)-1,4-benzenediamine, 5-(trifluoromethyl)-1,3-benzenediamine, 2,2'"'"'-bis(trifluoromethyl)benzidene, 3,3'"'"'-bis(trifluoromethyl)benzidene and 4,4'"'"'-diaminobenzophenone.

11. A process of claim 7 wherein the tetracarboxylic dianhydride from which structural formula II is derived is 3,3'"'"',4,4'"'"'-benzophenonetetracarboxylic dianhydride, the alicyclic tetracarboxylic dianhydride from which structural formula V is derived is 5-(2,5-dioxotetrahydro)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, and Q'"'"' is derived from at least one diamine selected from the group consisting of 2-(trifluoromethyl)-1,4-benzenediamine, 5-(trifluoromethyl)-1,3-benzenediamine, 2,2'"'"'-bis(trifluoromethyl)benzidene, 3,3'"'"'-bis(trifluoromethyl)benzidene and 4,4'"'"'-diaminobenzophenone.

12. A process of claim 7 wherein the tetracarboxylic dianhydride from which structural formula II is derived is 3,3'"'"',4,4'"'"'-benzophenonetetracarboxylic dianhydride, the alicyclic tetracarboxylic dianhydride from which structural formula V is derived is 1,2,3,4-butanetetracarboxylic dianhydride, and Q'"'"' is derived from at least one diamine selected from the group consisting of 2-(trifluoromethyl)-1,4-benzenediamine, 5-(trifluoromethyl)-1,3-benzenediamine, 2,2'"'"'-bis(trifluoromethyl)benzidene, 3,3'"'"'-bis(trifluoromethyl)benzidene and 4,4'"'"'-diaminobenzophenone.

13. A process of claim 3 wherein the polyimide is the reaction product of at least one tetracarboxylic dianhydride and at least one diaminobenzophenone, which comprises at least one structural element of formula VI ##STR43## wherein M is a tetravalent organic radical derived from said tetracarboxylic dianhydride containing at least two carbon atoms, no more than two carbonyl groups of the dianhydride being attached to any one carbon atom of the tetravalent radical;

and X is as described in claim 4.

14. A process of claim 13 wherein the diaminobenzophenone from which formula VI is derived is 4,4'"'"'-diaminobenzophenone.

15. A process of claim 13 wherein the tetracarboxylic dianhydride from which M is derived is an alicyclic tetracarboxylic dianhydride.

16. A process of claim 15 wherein the alicyclic tetracarboxylic dianhydride is selected from 5-(2,5-dioxotetrahydro)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 2,3,5-tricarboxycyclopentaneacetic acid dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,3,4-cyclobutanetetracarboxylic dianhydride.

17. A process of claim 13 wherein the diamine from which formula VI is derived is 4,4'"'"'-diaminobenzophenone and the tetracarboxylic dianhydride from which M is derived is selected from the group consisting of 5-(2,5-dioxotetrahydro)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 2,3,5-tricarboxycyclopentaneacetic acid dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,3,4-cyclobutanetetracarboxylic dianhydride.

18. A process of claim 1 wherein the optical alignment layer is exposed by delivery of 0.001 to 2000 Joules/cm², within the absorption band of the anisotropically absorbing molecules, to the optical alignment layer.

19. A process of claim 1 wherein the polarized light is from a laser.

20. A process of claim 1 wherein the polarized light is from a source selected from the group consisting of:

mercury arc, xenon lamp, deuterium and quartz tungsten halogen lamps, and black lights;

in combination with a polarizer.

21. A process of claim 1 wherein the optical alignment layer is exposed in a scanning mode.

22. A process of claim 1 wherein the optical alignment layer is exposed in two steps comprising:

(a) exposing at least one optical alignment layer to polarized light at a normal incidence, and

(b) subsequently exposing the optical alignment layer to polarized light at an oblique incidence.

23. A process of claim 1 wherein the optical alignment layer is exposed in two steps comprising:

(a) exposing the optical aligmnent layer to polarized light of a first direction of linear polarization of the incident light beam, and

(b) exposing the optical alignment layer to polarized light of a second direction of linear polarization of the incident light beam.

24. A process of claim 1 wherein the optical alignment layer is exposed in two steps comprising:

(a) exposing the optical alignment layer to polarized light of a first direction of linear polarization of the incident light, and

(b) exposing the optical alignment layer to polarized light of a second direction of linear polarization of the incident light, at an oblique incidence.

25. A process of claim 1 wherein the polarized light has at least one wavelength of about 150 to 800 nm.

26. A process of claim 1 wherein the polarized light has at least one wavelength of about from 150 to 400 nm.

27. A process of claim 1 wherein the polarized light has at least one wavelength of about from 300 to 400 nm.

28. A process of claim 1 wherein the applying of a liquid crystal medium comprises capillary filling a cell.

29. A process of claim 1 wherein the applying of a liquid crystal medium comprises casting of the liquid crystal medium onto an optical alignment layer.

30. A process of claim 1 wherein the liquid crystal medium is selected from the group consisting of nematic liquid crystals, ferroelectric liquid crystals, polymerizable nematic liquid crystals and nematic liquid crystalline polymers.

31. A process of claim 1 wherein the liquid crystal medium is selected from the group consisting of nematic liquid crystals and polymerizable nematic liquid crystals.

32. A process of claim 2 wherein Ar and Ar'"'"' are independently selected from aromatic radicals of the formulas:

##STR44## wherein X'"'"' is independently selected from the group of monovalent organic radical of 1 to 100 atoms, a divalent organic group of 1 to 20 atoms connecting Ar and Ar'"'"' to form a ring, and a covalent bond connecting Ar and Ar'"'"' to form a ring;

t is 0 to 4;

wherein q=1 to 3 and said polymer has a molecular weight between 600 and 5 million Daltons.

33. A liquid crystal optical storage medium containing aligned liquid crystals resulting from the process of claim 1.

34. A liquid crystal display element containing an aligned liquid crystal resulting from the process of claim 1.

35. A diffractive optical element containing an aligned liquid crystal resulting from the process of claim 1.