Polymerizable liquid crystal compound, liquid crystal composition, optical anisotropic material and optical element

1. A compound represented by the following formula (1):

CH 2 ═CR 1 —COO-(L) k -E 1 -E 2 -E 3 -E 4 -R 2   (1)

provided that the symbols in the formula have the following meanings:

R 1 : a hydrogen atom or a methyl group;

R 2 : a C 1-8 alkyl group or a fluorine atom;

k: 0 or 1;

L: —(CH 2 ) p O— or —(CH 2 ) q — (wherein each of p and q which are independent of each other, is an integer of from 2 to 8);

E 1 : a 1,4-phenylene group;

E 2 , E 3 , E 4 : each independently a 1,4-phenylene group or a trans-1,4-cyclohexylene group and at least one of E 2 and E 3 is a trans-1,4-cyclohexylene group,

provided that the 1,4-phenylene group and trans-1,4-cyclohexylene group in E 1 to E 4 , may be such that a hydrogen atom bonded to a carbon atom in each group may be substituted by a fluorine atom, a chlorine atom or a methyl group.

2. The compound according to claim 1 , wherein when a 1,4-phenylene group is represented by -Ph- and a trans-1,4-cyclohexylene group is represented by -Cy-, -E 1 -E 2 -E 3 -E 4 - is -Ph-Cy-Ph-Ph-, -Ph-Ph-Cy-Cy- or -Ph-Ph-Cy-Ph-.

3. The compound according to claim 1 , wherein k is 1.

4. A liquid crystal composition containing at least 75 mass % of a polymerizable liquid crystal containing the compound as defined in claim 1 .

5. The liquid crystal composition according to claim 4 , wherein the polymerizable liquid crystal comprises from 30 to 95 mass % of at least one compound of formula (1), and from 5 to 70 mass % of at least one compound selected from the compounds of the following formulae (3-1) and (3-2):

CH 2 ═CR 3 —COO-(M) m -E 5 -E 6 - E 7 -R 4   (3-1)

CH 2 ═CR 5 —COO—(N) n -E 8 -E 9 -R 6   (3-2)

provided that the symbols in the formulae have the following meanings:

R 3 , R 5 : each independently a hydrogen atom or a methyl group;

R 4 , R 6 : each independently a C 1-8 alkyl group;

m, n: each independently 0 or 1;

M, N: each independently —(CH 2 ) s O— or —(CH 2 ) t — (provided that each of s and t which are independent of each other is an integer of from 2 to 8);

E 5 , E 6 , E 7 , E 8 , E 9 : each independently a 1,4-phenylene group or a trans-1,4-cyclohexylene group, provided that at least one of E 5 , E 6 and E 7 is a trans-1,4-cyclohexylene group,

provided that the above 1,4-phenylene group and trans-1,4-cyclohexylene group may be such that a hydrogen atom bonded to a carbon atom in each group may be substituted by a fluorine atom, a chlorine atom or a methyl group.

6. An optical anisotropic material made of a polymer obtained by polymerizing the liquid crystal composition as defined in claim 4 in a state where the liquid crystal composition shows a liquid crystal phase and in a state where the liquid crystal is aligned.

7. The optical anisotropic material according to claim 6 , which has a laser beam having a wavelength of from 300 to 450 nm impinging thereon.

8. An optical element having a structure such that the optical anisotropic material as defined in claim 6 is sandwiched between a pair of supports.

9. A diffraction element, which comprises the optical element as defined in claim 8 .

10. A phase plate, which comprises the optical element as defined in claim 8 .

11. The compound according to claim 1 , which is one of the following compounds:

where R 21 is a C1-8 alkyl group.

12. The compound according to claim 11 , wherein R 21 is a C 2-6 linear alkyl group.

13. The compound according to claim 11 , wherein p is an integer of from 4 to 6.

14. The compound according to claim 11 , which is one of the following compounds:

(1A-1),

(1A-3), and

(1A-5).

15. The compound according to claim 11 , which is one of the following compounds:

(1B-1),

(1B-3)

(1B-4), and

(1B-5).

16. The compound according to claim 11 , which is one of the following compounds:

(1C-1) and

(1C-2).

17. The liquid crystal composition according to claim 5 , wherein the polymerizable liquid crystal comprises from 5 to 70 mass % of at least one compound selected from the compounds of the following formulae:

CH 2 ═CR 3 —COO-Ph-Cy-Ph-R 4   (3-1-1)

CH 2 ═CR 3 —COO-Ph-Ph-Cy-R 4   (3-1-2)

CH 2 ═CR 5 —COO-Cy-Cy-R 6   (3-2-1)

wherein -Ph- is a 1,4-phenylene group and -Cy- is a trans-1,4-cyclohexylene group.