Liquid-crystal display device and process for producing liquid-crystal display device

1. A liquid-crystal display device comprising

a pair of substrates;

a liquid crystal layer which is sandwiched between the substrates and which contains a liquid crystal material; and

a polymer layer which is disposed on a surface of each of the substrates and which controls the alignment of liquid crystal molecules,

the outermost surfaces of both the substrates comprising substantially no alignment film,

the polymer layer being obtained or obtainable by polymerizing two or more radical polymerizable monomer species added to the liquid crystal layer, and

at least one species of the one or more radical polymerizable monomer species being a compound represented by the following formula (1):

wherein

X 1 and X 2 may be the same as or different from each other, and represent acryloyl, methacryloyl, vinyl, or allyl;

a is 0 or 1;

b is 0 or 1;

c is 0 or 1;

R is a C1-C20 alkyl; and

each hydrogen atom may optionally be replaced by halogen, methyl, ethyl, or propyl; and

at least another one species of the one or more radical polymerizable monomer species has a cyclic structure and a single monofunctional polymerizable group.

2. The liquid-crystal display device according to claim 1 ,

wherein R in the compound of the formula (1) is a C4-C20 alkyl.

3. The liquid-crystal display device according to claim 1 ,

wherein R in the compound of the formula (1) is a C8-C20 alkyl.

4. The liquid-crystal display device according to claim 1 ,

wherein R in the compound of the formula (1) is a C16-C20 alkyl.

5. The liquid-crystal display device according to one of claims 1 - 2 ,

wherein the radical polymerizable monomer having the cyclic structure and the single monofunctional polymerizable group is a compound represented by the following formula (2):

wherein

X represents acrylate, methacrylate, acryloyloxy, methacryloyloxy, vinyl, or allyl;

m is an integer of 0 to 12;

a is 0 or 1;

b is 0 or 1;

R is a C1-C20 alkyl; and

each hydrogen atom may optionally be replaced by halogen, methyl, ethyl, or propyl.

6. The liquid-crystal display device according to claim 5 ,

wherein R in the compound of the formula (2) is a C4-C12 alkyl.

7. The liquid-crystal display device according to claim 5 ,

wherein R in the compound of the formula (2) is a C8-C12 alkyl.

8. The liquid-crystal display device according to claim 5 ,

wherein m in the compound of the formula (2) is an integer of 2 or greater.

9. The liquid-crystal display device according to claim 5 ,

wherein m in the compound of the formula (2) is an integer of 4 or greater.

10. The liquid-crystal display device according to claim 5 ,

wherein m in the compound of the formula (2) is an integer of 8 or greater.

11. The liquid-crystal display device according to claim 2 or 1 ,

wherein the proportion of the compound of the formula (1) is not lower than 0.5% by weight and not higher than 2.5% by weight in the whole liquid crystal composition constituting the liquid crystal layer before the polymerization.

12. The liquid-crystal display device according to claim 2 or 1 ,

wherein the ratio of the radical polymerizable monomer having a cyclic structure and a monofunctional polymerizable group is 10 mol % or more to the compound of the formula (1) before the polymerization.

13. The liquid-crystal display device according to claim 2 or 1 ,

wherein the liquid crystal material has negative dielectric constant anisotropy.

14. A process for producing a liquid-crystal display device, comprising the steps of:

injecting a liquid crystal composition that contains a liquid crystal material and one or more radical polymerizable monomer species into between a pair of substrates the outermost surfaces of which comprise substantially no alignment film;

applying light to the liquid crystal composition to polymerize the radical polymerizable monomers to thereby form a polymer layer which controls the alignment of liquid crystal molecules on a surface of each of the substrates; and

a heating step at a temperature not lower than a temperature 30° C. lower than a phase transition temperature of the liquid crystal material,

at least one species of the one or more radical polymerizable monomer species being a compound represented by the following formula (1):

wherein

X 1 and X 2 may be the same as or different from each other, and represent acryloyl, methacryloyl, vinyl, or allyl;

a is 0 or 1;

b is 0 or 1;

c is 0 or 1;

R is a C1-C20 alkyl; and

each hydrogen atom may optionally be replaced by halogen, methyl, ethyl, or propyl.

15. A process for producing a liquid-crystal display device, comprising the steps of:

injecting a liquid crystal composition that contains a liquid crystal material and one or more radical polymerizable monomer species into between a pair of substrates the outermost surfaces of which comprise substantially no alignment film;

annealing;

after the annealing step, applying light to the liquid crystal composition to polymerize the radical polymerizable monomers to thereby form a polymer layer which controls the alignment of liquid crystal molecules on a surface of each of the substrates,

at least one species of the one or more radical polymerizable monomer species being a compound represented by the following formula (1):

wherein

X 1 and X 2 may be the same as or different from each other, and represent acryloyl, methacryloyl, vinyl, or allyl;

a is 0 or 1;

b is 0 or 1;

c is 0 or 1;

R is a C1-C20 alkyl; and

each hydrogen atom may optionally be replaced by halogen, methyl, ethyl, or propyl.

16. The liquid-crystal display device according to claim 1 ,

wherein c in formula (1) is 0.

17. The liquid-crystal display device according to claim 1 ,

wherein c in formula (1) is 1.

18. The liquid-crystal display device according to claim 8 ,

wherein c in formula (1) is 0.

19. The liquid-crystal display device according to claim 8 ,

wherein c in formula (1) is 1.

20. The liquid-crystal display device according to claim 11 ,

wherein c in formula (1) is 0.

21. The liquid-crystal display device according to claim 11 ,

wherein c in formula (1) is 1.

22. The liquid-crystal display device according to claim 12 ,

wherein c in formula (1) is 0.

23. The liquid-crystal display device according to claim 12 ,

wherein c in formula (1) is 1.