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

摘要

A liquid crystal compound selected from a group of compounds represented by formula (a): wherein Ra and Rb are each independently alkyl having 1 to 10 carbons, alkoxy having 1 to 9 carbons, alkoxyalkyl having 2 to 9 carbons, alkenyl having 2 to 10 carbons, alkenyloxy having 2 to 9 carbons, fluoroalkyl having 1 to 10 carbons or fluoroalkoxy having 1 to 9 carbons; ring A¹, ring A² and ring A³ are each independently trans-1,4-cyclohexylene, trans-1,3-dioxane-2,5-diyl, trans-tetrahydropyran-2,5-diyl, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, pyridine-2,5-diyl, 6-fluoropyridine-2,5-diyl or pyridazine-2,5-diyl; Z¹, Z² and Z³ are each independently a single bond, -(CH₂)₂-, -CH-CH-, -C≡C-, -CH₂O, -OCH₂-, -COO-, -OCO-, -OCF₂-, -CF₂O-, -CH₂CH₂OCF₂- or -CF₂OCH₂CH₂-; l, m and n are each independently 0, 1 or 2, provided that l+m+n is 0, 1, 2 or 3; one of X¹ and X² is fluorine, and the other is chlorine; Q is and atoms comprising the compound each may be an isotope thereof.