Liquid crystal compound, liquid crystal composition and liquid crystal display device

1. A compound, represented by formula (1):

wherein, in formula (1),

R a and R b are independently alkyl having 1 to 30 carbons, and in the groups, at least one —CH 2 — may be replaced by —O—, —S—, —CO— or —SiH 2 —, at least one —CH 2 CH 2 — may be replaced by —CH═CH— or —C≡C—, and in the monovalent groups, at least one hydrogen may be replaced by fluorine or chlorine; and

X and Y are independently fluoroalkyl having 1 to 5 carbons, fluoroalkoxy having 1 to 5 carbons or pentafluorosulfanil, and one of X and Y may be fluorine.

2. The compound according to claim 1 , wherein, in formula (1),

R a and R b are independently alkyl having 1 to 20 carbons, and in the groups, at least one —CH 2 — may be replaced by —O— or —S—, one or two —CH 2 CH 2 — groups may be replaced by —CH═CH— or —C≡C—, and in the monovalent groups, at least one hydrogen may be replaced by fluorine or chlorine; and

X and Y are independently fluoroalkyl having 1 to 3 carbons, fluoroalkoxy having 1 to 3 carbons or pentafluorosulfanil, and one of X and Y may be fluorine.

3. The compound according to claim 1 , wherein, in formula (1),

R a and R b are independently alkyl having 1 to 15 carbons, and in the groups, at least one or two —CH 2 — groups may be replaced by —O—, one —CH 2 CH 2 — may be replaced by —CH═CH— or —C≡C—, and in the monovalent groups, at least one hydrogen may be replaced by fluorine; and

X is fluorine, fluoroalkyl having 1 to 3 carbons, fluoroalkoxy having 1 to 3 carbons or pentafluorosulfanil, and Y is fluoroalkyl having 1 to 3 carbons.

4. The compound according to claim 1 , represented by formula (1a):

wherein, in formula (1a),

R a and R b are independently alkyl having 1 to 10 carbons or alkoxy having 1 to 10 carbons; and Y is —CF 3 , —CF 2 H, —CFH 2 or fluorine.

5. The compound according to claim 4 , wherein, in formula (1a), R a is alkyl having 1 to 10 carbons and R b is alkoxy having 1 to 10 carbons; and Y is —CF 3 .

6. The compound according to claim 1 , represented by formula (1b):

wherein, in formula (1b),

R a and R b are independently alkyl having 1 to 10 carbons or alkoxy having 1 to 10 carbons; and Y is —CF 3 , —CF 2 H or —CFH 2 .

7. The compound according to claim 6 , wherein, in formula (1b), Ra and Rb are independently alkoxy having 1 to 10 carbons; and Y is —CF 3 .

8. A liquid crystal composition, containing at least one compound according to claim 1 .

9. The liquid crystal composition according to claim 8 , containing at least one compound selected from the group of compounds represented by formulas (2) to (4):

wherein, in formulas (2) to (4),

R 11 and R 12 are independently alkyl having 1 to 10 carbons or alkenyl having 2 to 10 carbons, and in the groups, at least one —CH 2 — may be replaced by —O—, and in the monovalent groups, at least one hydrogen may be replaced by fluorine;

ring B 1 , ring B 2 , ring B 3 and ring B 4 are independently 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; and

Z 11 , Z 12 and Z 13 are independently a single bond, —COO—, —CH 2 CH 2 —, —CH═CH— or —C≡C—.

10. The liquid crystal composition according to claim 8 , further containing at least one compound selected from the group of compounds represented by formulas (5) to (11):

wherein, in formulas (5) to (11),

R 13 , R 14 and R 15 are independently alkyl having 1 to 10 carbons or alkenyl having 2 to 10 carbons, and in the groups, at least one —CH 2 — may be replaced by —O—, and in the monovalent groups, at least one hydrogen may be replaced by fluorine, and R 15 may be hydrogen or fluorine;

ring C 1 , ring C 2 , ring C 3 and ring C 4 are independently 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene, 1,4-phenylene in which at least one hydrogen is replaced by fluorine, tetrahydropyran-2,5-diyl or decahydronaphthalene-2,6-diyl;

ring C 5 and ring C 6 are independently 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene, tetrahydropyran-2,5-diyl or decahydronaphthalene-2,6-diyl;

Z 14 , Z 15 , Z 16 and Z 17 are independently a single bond, —COO—, —CH 2 O—, —OCF 2 —, —CH 2 CH 2 — or —OCF 2 CH 2 CH 2 —;

L 11 and L 12 are independently fluorine or chlorine;

S 11 is hydrogen or methyl;

X is —CHF— or —CF 2 —; and

j, k, m, n, p, q, r and s are independently 0 or 1, a sum of k, m, n and p is 1 or 2, a sum of q, r and s is 0, 1, 2 or 3, and t is 1, 2 or 3.

11. The liquid crystal composition according to claim 8 , further containing at least one compound selected from the group of compounds represented by formulas (12) to (14):

wherein, in formulas (12) to (14),

R 16 is alkyl having 1 to 10 carbons or alkenyl having 2 to 10 carbons, and in the groups, at least one —CH 2 — may be replaced by —O—, and in the monovalent groups, at least one hydrogen may be replaced by fluorine;

X 11 is fluorine, chlorine, —CF 3 , —CHF 2 , —CH 2 F, —OCF 3 , —OCHF 2 , —OCF 2 CHF 2 or —OCF 2 CHFCF 3 ;

ring D 1 , ring D 2 and ring D 3 are independently 1,4-cyclohexylene, 1,4-phenylene, 1,4-phenylene in which at least one hydrogen is replaced by fluorine, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diy or pyrimidine-2,5-diyl;

Z 18 , Z 19 and Z 20 are independently a single bond, —COO—, —CH 2 O—, —CF 2 O—, —OCF 2 —, —CH 2 CH 2 —, —CH═CH—, —C≡C— or —(CH 2 ) 4 —; and

L 13 and L 14 are independently hydrogen or fluorine.

12. The liquid crystal composition according to claim 8 , further containing at least one compound selected from the group of compounds represented by formula (15):

wherein, in formula (15),

R 17 is alkyl having 1 to 10 carbons or alkenyl having 2 to 10 carbons, and in the groups, at least one —CH 2 — may be replaced by —O—, and in the monovalent groups, at least one hydrogen may be replaced by fluorine;

X 12 is —C≡N or —C≡C—C≡N;

ring E 1 is 1,4-cyclohexylene, 1,4-phenylene, 1,4-phenylene in which at least one hydrogen is replaced by fluorine, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl or pyrimidine-2,5-diyl;

Z 21 is a single bond, —COO—, —CH 2 O—, —CF 2 O—, —OCF 2 —, —CH 2 CH 2 — or —C≡C—;

L 15 and L 16 are independently hydrogen or fluorine; and

i is 1, 2, 3 or 4.

13. A liquid crystal display device, including the liquid crystal composition according to claim 8 .