Cyclohexene derivative having alkenyl, liquid crystal composition and liquid crystal display device

Abstract

A liquid crystal compound selected from a group of compounds represented by formula (a): wherein Ra and Rb are each independently hydrogen, alkyl having 1 to 10 carbons or alkenyl having 2 to 10 carbons, provided that in the alkyl, —CH— may be replaced by —O—, but plural —O— are not adjacent to each other, and hydrogen may be replaced by fluorine; ring Aand ring Aare each independently trans-1,4-cyclohexylene or 1,4-phenylene, provided that one or two hydrogens of the 1,4-phenylene may be replaced by halogen, and in a 6-membered ring of these groups, one —CH— or two —CH— that are not adjacent to each other may be replaced by —O—, and one or two —CH═ may be replaced by —N═; Zand Zare each independently a single bond, —(CH)—, —(CH)—, —CH═CH—, —C≡—, —CHO—, —OCH—, —COO—, —OCO— or —OCF—; l and m are each independently 0, 1 or 2, provided that l+m is 0, 1, 2 or 3; and n is an integer of from 0 to 6, provided that in —(CH)—, —CH— may be replaced by —O—, but plural —O— are not adjacent to each other, and hydrogen may be replaced by fluorine.