Liquid crystal composition and liquid crystal display device

1. A liquid crystal composition having a nematic phase comprising at least one compound selected from a group of compounds represented by formula (1) as a first component and at least one compound selected from a group of compounds represented by formula (2-1) or (2-2) as a second component:

wherein R 1 is alkyl having 1 to 12 carbons or alkenyl having 2 to 12 carbons; R 2 and R 3 are independently alkyl having 1 to 12 carbons; Z 1 and Z 2 are independently a single bond or ethylene; Y 1 is fluorine or chlorine; and X 1 and X 2 are independently hydrogen or fluorine.

2. The liquid crystal composition according to claim 1 , wherein the second component is at least one compound selected from a group of compounds represented by formula (2-1).

3. The liquid crystal composition according to claim 1 , wherein the second component is at least one compound selected from a group of compounds represented by formula (2-2).

4. The liquid crystal composition according to claim 1 , wherein the second component is at least one compound selected from a group of compounds represented by formula (2-1) and at least one compound selected from a group of compounds represented by formula (2-2).

5. The liquid crystal composition according to claim 1 , wherein the ratio of the first component is in a range of from approximately 5% to approximately 30% by weight and the ratio of the second component is in a range of from approximately 30% to approximately 85% by weight, based on the total weight of the liquid crystal compounds.

6. The liquid crystal composition according to claim 1 , wherein the composition further comprises at least one compound selected from a group of compounds represented by formula (2-1) as a second component and at least one compound selected from a group of compounds represented by formula (3-1) as a third component:

wherein R 4 and R 5 are independently alkyl having 1 to 12 carbons; and X 3 , X 4 and X 5 are independently hydrogen or fluorine.

7. The liquid crystal composition according to claim 1 , wherein the composition further comprises at least one compound selected from a group of compounds represented by formula (2-1) as a second component and at least one compound selected from a group of compounds represented by formula (3-2) as a third component:

wherein R 6 and R 7 are independently alkyl having 1 to 12 carbons; A represents 1,4-cyclohexylene or 1,4-phenylene; and X 6 is hydrogen or fluorine.

8. The liquid crystal composition according to claim 1 , wherein the composition further comprises at least one compound selected from a group of compounds represented by formula (2-1) as a second component and at least one compound selected from a group of compounds represented by formula (3-1) and at least one compound selected from a group of compounds represented by formula (3-2) as a third component:

wherein R 4 , R 5 , R 6 and R 7 are independently alkyl having 1 to 12 carbons; A represents 1,4-cyclohexylene or 1,4-phenylene; and X 3 , X 4 , X 5 and X 6 are independently hydrogen or fluorine.

9. The liquid crystal composition according to claim 1 , wherein the composition further comprises at least one compound selected from a group of compounds represented by formula (2-2) as a second component, and at least one compound selected from a group of compounds represented by formula (3-1) as a third component:

wherein R 4 and R 5 are independently alkyl having 1 to 12 carbons; and X 3 , X 4 and X 5 are independently hydrogen or fluorine.

10. The liquid crystal composition according to claim 1 , wherein the composition further comprises at least one compound selected from a group of compounds represented by formula (2-2) as a second component and at least one compound selected from a group of compounds represented by formula (3-2) as a third component:

wherein R 6 and R 7 are independently alkyl having 1 to 12 carbons; A represents 1,4-cyclohexylene or 1,4-phenylene; and X 6 is hydrogen or fluorine.

11. The liquid crystal composition according to claim 1 , wherein the composition further comprises at least one compound selected from a group of compounds represented by formula (2-2) as a second component and at least one compound selected from a group of compounds represented by formula (3-1) and at least one compound selected from a group of compounds represented by formula (3-2) as a third component:

wherein R 4 , R 5 , R 6 and R 7 are independently alkyl having 1 to 12 carbons; A is 1,4-cyclohexylene or 1,4-phenylene; and X 3 , X 4 , X 5 and X 6 are independently hydrogen or fluorine.

12. The liquid crystal composition having a nematic phase according to claim 1 , wherein the composition comprises at least one compound selected from a group of compounds represented by formula (1), at least one compound selected from a group of compounds represented by formula (2-1) or formula (2-2) as a second component and at least one compound selected from a group of compounds represented by formula (3-1) and at least one compound selected from a group of compounds represented by formula (3-2) as a third component:

wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are independently alkyl having 1 to 12 carbons; Z 1 and Z 2 are independently a single bond or ethylene; Y 1 and X 6 are fluorine; X 1 , X 2 and X 4 are hydrogen; X 3 and X 5 are independently hydrogen or fluorine but at least one of X 3 and X 5 is fluorine; and A is 1,4-cyclohexylene.

13. The liquid crystal composition according to claim 12 , wherein the ratio of the first component is in a range of from approximately 5% to approximately 30% by weight, the ratio of the second component is in a range of from approximately 30% to approximately 85% by weight and the ratio of the third component is in a range of from approximately 5% to approximately 40% by weight, based on the total weight of the liquid crystal compounds.

14. A liquid crystal composition having a nematic phase consisting essentially of at least one compound selected from a group of compounds represented by formula (1) as a first component, at least one compound selected from a group of compounds represented by formula (2-1) and at least one compound selected from a group of compounds represented by formula (2-2) as a second component, and at least one compound selected from a group of compounds represented by formula (3-1) or (3-2) as a third component:

wherein R 1 is alkyl having 1 to 12 carbons or alkenyl having 2 to 12 carbons; R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are independently alkyl having 1 to 12 carbons; A is 1,4-cyclohexylene or 1,4-phenylene; Z 1 and Z 2 are independently a single bond or ethylene; Y 1 is fluorine or chlorine; and X 1 , X 2 , X 3 , X 4 , X 5 and X 6 are independently hydrogen or fluorine.

15. The liquid crystal composition according to claim 14 , wherein the third component is at least one compound selected from a group of compounds represented by formula (3-1).

16. The liquid crystal composition according to claim 14 , wherein the third component is at least one compound selected from a group of compounds represented by formula (3-2).

17. The liquid crystal composition according to claim 14 , wherein the third component is at least one compound selected from a group of compounds represented by formula (3-1) and at least one compound selected from a group of compounds represented by formula (3-2).

18. The liquid crystal composition according to claim 14 , wherein in formula (1), R 1 is alkyl having 1 to 12 carbons, and Y 1 is fluorine; in formula (2-1), X 1 is hydrogen; in formula (2-2), X 2 is hydrogen; in formula (3-1), at least one of X 3 and X 5 is fluorine, and X 4 is hydrogen; and in formula (3-2), A is 1,4-cyclohexylene, and X 6 is fluorine.

19. The liquid crystal composition according to claim 14 , wherein the ratio of the first component is in a range of from approximately 5% to approximately 30% by weight, the ratio of the second component is in a range of from approximately 30% to approximately 85% by weight and the ratio of the third component is in a range of from approximately 5% to approximately 40% by weight, based on the total weight of the liquid crystal compounds.

20. A liquid crystal composition having a nematic phase comprising at least one compound selected from a group of compounds represented by formula (1) as a first component, at least one compound selected from a group of compounds represented by formula (2-1) and at least one compound selected from a group of compounds represented by formula (2-2) as a second component, at least one compound selected from a group of compounds represented by formula (3-1) or (3-2) as a third component and at least one compound selected from a group of compounds represented by formula (4) as a fourth component:

wherein R 1 is alkyl having 1 to 12 carbons or alkenyl having 2 to 12 carbons; R 2 , R 3 , R 4 , R 5 , R 6 , R 7 and R 8 are independently alkyl having 1 to 12 carbons; A is 1,4-cyclohexylene or 1,4-phenylene; Z 1 and Z 2 are independently a single bond or ethylene; X 1 , X 2 , X 3 , X 4 , X 5 , X 6 and X 7 are independently hydrogen or fluorine; Y 1 is fluorine or chlorine; and Y 2 is fluorine or trifluoromethoxy.

21. The liquid crystal composition according to one of claim 20 , wherein the ratio of the fourth component is in a range of from approximately 1% to approximately 10% by weight based on the total weight of the liquid crystal compounds.

22. The liquid crystal composition according to claim 1 , wherein the maximum temperature of a nematic phase is approximately 95° C. or more, the optical anisotropy (25° C.) at a wavelength of 589 nm is approximately 0.16 or more and the dielectric anisotropy (25° C.) at a frequency of 1 kHz is approximately 8 or more.

23. The liquid crystal composition according to claim 1 , wherein the composition further comprises an ultraviolet ray absorbent.

24. A liquid display device comprising the liquid crystal composition according to claim 1 .