Polymerizable mixtures
A mixture which is polymerizable to polymers exhibiting a high optical anisotropy which is stable during polymerization. The mixture contains a first monomer or (and/or) oligomer having two or more polymerizable functional groups and optionally a mesogenic group; a second monomer or oligomer bearing at least one mesogenic group having an aromatic double ring structure and only one polymerizable group; and from 1 to 50% by weight of a monomer non-polymerizable with the first or second monomer, but which also contains a mesogenic group having an aromatic double ring structure.
1. A polymerizable mixture (P) comprising
A) at least one monomer or oligomer (A), each monomer or oligomer (A) having at least two polymerizable functional groups selected from the group consisting of (meth)acrylate ester, epoxy, and vinyl ether groups,
B) at least one liquid crystalline monomer or oligomer (B), each monomer or oligomer (B) having at least one mesogenic group having an aromatic double ring structure, and having a single polymerizable functional group selected from the group consisting of (meth)acrylate ester, epoxy, and vinyl ether groups,
C) from 1 to less than 50% by weight, based on the weight of the polymerizable mixture, of one or more monomers (C) which have at least one mesogenic group having an aromatic double ring structure and contain no group which reacts substantially with the polymerizable functional groups of the monomers or oligomers (A) and (B) during polymerization of said polymerizable mixture,
said mixture, when polymerized, forming a stable polymer film.
2. The mixture of claim 1 , in which the aromatic double ring structures are selected from the group consisting of a) two monocyclic groups each of which are linked by a single bond and are selected from the group consisting of unsubstituted and substituted 1,4-phenylene, 2,5-pyridinylene, and 2,5-pyrenylene, b) aromatic double rings selected from the group consisting of unsubstituted and substituted 2,6-naphthylidene, 2,7-naphthylidene and 1,4-naphthylidene, and c) mixtures thereof.
3. The mixture of claim 1 , wherein the mesogenic groups comprise carboxylic esters and alcohols based on phenyl, biphenyl, cyanobiphenyl, naphthyl and cyanonaphthyl derivatives, or combinations of these groups.
4. The mixture of claim 2 , wherein the mesogenic groups comprise carboxylic esters and alcohols based on phenyl, biphenyl, cyanobiphenyl, naphthyl and cyanonaphthyl derivatives, or combinations of these groups.
5. The mixture of claim 1 , wherein the monomers or oligomers (A) have at least one mesogenic group.
6. The mixture of claim 2 , wherein the monomers or oligomers (A) have at least one mesogenic group.
7. The mixture of claim 3 , wherein the monomers or oligomers (A) have at least one mesogenic group.
8. The mixture of claim 1 , which contains from 5 to 95% by weight of monomer or oligomer (A).
9. The mixture of claim 1 , which contains from 5 to 95% by weight of liquid crystalline monomer or oligomer (B).
10. An optically anisotropic polymer (F), prepared by polymerizing the polymerizable mixture (P) of claim 1 .
11. An optically anisotropic polymer (F), prepared by polymerizing the polymerizable mixture (P) of claim 2 .
12. An optically anisotropic polymer (F), prepared by polymerizing the polymerizable mixture (P) of claim 3 .
13. An optically anisotropic polymer (F), prepared by polymerizing the polymerizable mixture (P) of claim 5 .
14. The polymer (F) of claim 10 which is a nematic polymer in which the optical anisotropy Δn is greater than 0.18.
15. The optically anisotropic polymer (F) of claim 10 which is a cholesteric polymer (F) in which the optical anisotropy Δn is greater than 0.16.
16. A process for the preparation of an optically anisotropic polymer (F) comprising applying a polymerizable mixture (P) of claim 1 to a substrate, orienting the mixture, and a polymerizing the polymerizable mixture.
17. A process for the preparation of an optically anisotropic polymer (F) comprising applying a polymerizable mixture (P) of claim 2 to a substrate, orienting the mixture, and a polymerizing the polymerizable mixture.
18. A process for the preparation of an optically anisotropic polymer (F) comprising applying a polymerizable mixture (P) of claim 3 to a substrate, orienting the mixture, and a polymerizing the polymerizable mixture.
19. A process for the preparation of an optically anisotropic polymer (F) comprising applying a polymerizable mixture (P) of claim 5 to a substrate, orienting the mixture, and a polymerizing the polymerizable mixture.
20. The polymer film of claim 11 , which has a hardness greater than 0.12 measured using a Berkovitch diamond tip.