Liquid crystal alignment composition, liquid crystal alignment film and liquid crystal display element

1. A liquid crystal photoalignment composition comprising:

a) at least one polyimide and/or polyamic acid compound (I) represented by the general Formula 1, comprising repeating structural units (1) and/or (2):

and/or a repeating structural unit represented by the general Formula 2, comprising repeating structural units (3) and/or (4):

where

A is a tetravalent organic residue of a tetracarboxylic dianhydride,

B is the divalent residue of a substituted or unsubstituted non-aromatic or aromatic diamine NH 2 —B—NH 2 without phenolic OH-groups,

M is the divalent residue of a substituted or unsubstituted aromatic diamine NH 2 -M-NH 2 carrying at least two phenolic OH-groups,

n and m are integers and the sum n+m has a value from 10 to 200, where m is greater than 0 and n is equal to 0 or greater than 0, and

under the proviso that at least 5 weight % of the aromatic diamine carrying phenolic OH groups NH 2 -M-NH 2 are present in 100 weight % of compound (I),

b) at least one photoactive compound (II) comprising photoalignment groups,

c) a solvent or solvent mixture,

d) optionally at least one additive,

and the amount of compound (I) is 50%-99.5% by weight of the sum of weights of compound (I) and compound (II);

wherein the substituted or unsubstituted aromatic diamine carrying at least two phenolic OH groups NH 2 -M-NH 2 is a bis-o-aminophenol carrying at least 2 phenolic OH groups and comprising 2 or 3 benzene rings in the molecular structure, where the phenolic OH groups are in para-position relative to the bridging group X and the amino groups are in ortho-position relative to the phenolic OH groups, as depicted in the following formulae:

and wherein Y represents a hydrogen atom, C 1 -C 4 alkyl group, C 1 -C 4 alkoxy group, Cl, F, Br or I, and p represents an integer from 1-3.

2. The liquid crystal photoalignment composition according to claim 1 , where the aromatic diamine carrying at least two phenolic OH groups NH 2 -M-NH 2 is selected from the bis-o-aminophenol compounds selected from the group consisting of:

3. The liquid crystal photoalignment composition according to claim 1 ,

where the polyimide and/or polyamic acid compound (I) is a copolymer comprising at least one molecular type of dianhydride and at least two molecular types of diamines, one being of the type NH 2 —B—NH 2 without phenolic OH groups and one being NH 2 -M-NH 2 carrying at least two phenolic OH groups, under the proviso that the amount of diamine NH 2 -M-NH 2 is 10% by weight relative to the total amount of diamines.

4. The liquid crystal photoalignment composition according to claim 1 , where the polyimide and/or polyamic acid compound (I) comprises at least one molecular type of dianhydride and one molecular type of diamine NH 2 -M-NH 2 containing phenolic OH groups.

5. The liquid crystal photoalignment composition according to claim 1 , where the compound (I) is a block copolymer comprising recurring block units

. . . [Block] b . . . [Block C] c . . .

where Block B comprises prepolymerized recurring structural units from at least one molecular type of dianhydride and at least one molecular type of diamine NH 2 —B—NH 2 without phenolic OH-groups, according to Formula 3:

and Block C comprises prepolymerized recurring structural units from at least one molecular type of dianhydride and at least one molecular type of diamine NH 2 -M-NH 2 containing phenolic OH-groups, according to Formula 4:

where A, B and M have the same meaning as given in claim 1 and

s, t, are integers indicating the number of recurring units in Block B and Block C, such that b*s+c*t is a value of 10 to 1000, under the proviso that at least 10 weight % of the recurring units of the Block C are present in 100 weight % of compound (I).

6. The liquid crystal photoalignment composition according to claim 1 , where the photoactive compound (II) comprising photoalignment groups is a monomer, oligomer, dendrimer, prepolymer or copolymer, where the photoalignment groups comprise functional groups selected from the group consisting of:

cinnamates, chalcones,

coumarines, quinolones, and

stilbenes,

where these functional groups can be unsubstituted or comprise substituents selected from the group consisting of:

fluorine, chlorine, bromine, cyano, C 1 -C 4 -alkoxy, carboxylic acid, ester groups with linear or branched C 1 -C 12 alkyl, optionally substituted with fluorine or cyano groups, linear or branched alkyl and cycloalkyl groups with 1-12 C atoms, optionally substituted with fluorine or cyano groups, and aromatic groups with 6-18 C atoms optionally substituted with fluorine or cyano groups.

7. The liquid crystal photoalignment composition according to claim 1 , where the photoactive compound (II) comprising photoalignment groups is an oligomer, polymer or copolymer.

8. The liquid crystal photoalignment composition according to claim 1 , where the photoactive compound (II) comprising photoalignment groups is a polyimide and/or polyamic acid oligomer or polymer.

9. A method of preparation of the liquid crystal photoalignment composition according to claim 1 , comprising mixing and/or blending together the components a) to d), providing the composition according to claim 1 for using it as a photoalignment film or coating material to align liquid crystalline compounds to fabricate structured or unstructured optical and electro-optical elements and devices.

10. A photoalignment film or coating layer prepared by the processes of

a) applying the composition according to claim 1 on a substrate to form a liquid crystal alignment film or coating layer,

b) optionally drying,

c) optionally heating the coated layer at 80° C. to 230° C.,

d) photoirradiating the photoalignment film or coating layer prepared via steps a) to c) with aligning light of a suitable wavelength to induce the anisotropy in the film or coating layer.

11. A photoalignment film or coating layer comprising a composition according to claim 1 .

12. A method of using the photoalignment film or coating layer according to claim 11 , comprising aligning liquid crystalline compounds with said photoalignment film or coating layer to fabricate structured or unstructured optical and electro-optical elements and devices.

13. Structured or unstructured optical and electro-optical elements and devices comprising the photoalignment film or coating layer according to claim 11 .