Liquid crystal compounds having bis(trifluoromethyl) phenyl rings, liquid crystal compositions and liquid crystal display devices

Abstract

The compound (1) having 2,3-bis(trifluoromethyl)-1,4-phenylene is stable chemically and has excellent miscibility with other liquid crystal compounds, large and negative dielectric anisotropy and proper optical anisotropy. A liquid crystal composition comprising the compound has large specific resistance and a large voltage holding ratio, and that the composition is useful for a liquid crystal display element. The compound (1) is represented by formula (1):RaA—Z)—(A—Z—A—Z—A—Rb  (1)wherein Ra and Rb independently are alkyl having 1 to 20 carbons, any —CH— in the alkyl may be replaced by —O—, —S—, —CH═CH—, or —C≡C—, and any hydrogen may be replaced by halogen; A, A, A, and Aindependently are 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,3-dioxane-2,5-diyl, 1,4-phenylene, pyridine-2,5-diyl, pyrimidine-2,5-diyl, pyridazine-3,6-diyl, or 2,3-bis(trifluoromethyl)-1,4-phenylene, any hydrogen in these rings may be replaced by halogen, and at least one of A, A, A, and Ais 2,3-bis(trifluoromethyl)-1,4-phenylene; Z, Zand Zindependently are a single bond, —(CH)—, —(CF)—, —COO—, —OCO—, —CHO—, —OCH—, —CFO—, —OCF—, —CH═CH—, —CF═CF—, —C≡C—, —(CH)—, —(CH)O—, or —O(CH)—; m and n independently are 0 or 1.