Difluorooxymethane derivative and liquid crystal composition

A difluorooxymethane derivative expressed by the general formula (I) ##STR34## wherein each of l, m, and n is 0 or 1, rings A.sub. and A.sub.2 independently represent trans-1,4-cyclohexylene group, 1,4-phenylene group one or more hydrogen atoms in which six-membered ring may be replaced by a halogen atom, trans-1,3-dioxane-2,5-diyl, or pyrimidine-2,5-diyl, ring A.sub.3 represents 1,4-phenylene group one or more hydrogen atoms in which six-membered ring may be replaced by a halogen atom, trans-1,3-dioxane-2,5-diyl, or pyrimidine-2,5-diyl, Z.sub.1, Z.sub.2, and Z.sub.3 independently represent a covalent bond, --CH.sub.2 CH.sub.2 --, --COO--, --CF.sub.2 O--, --OCF.sub.2 --, --CH.sub.2 O--, --OCH.sub.2 --, --CH.dbd.CH--, or --C.tbd.C--, L.sub.1, L.sub.2, L.sub.3, and L.sub.4 independently represent hydrogen atom or a halogen atom, respectively, X represents a halogen atom, CN, CF.sub.3, OCF.sub.3, OCHF.sub.2, OCH.sub.2 F, or a linear or branched alkyl group or alkoxy group having 1 to 10 carbon atoms, or a linear or branched alkenyl group having 2 to 10 carbon atoms, and R represents a linear or branched alkyl group having 1 to 10 carbon atoms or a linear or branched alkenyl group having 2 to 10 carbon atoms, one or not adjacent 2 or more CH.sub.2, groups in the R may be replaced by oxygen atom, provided that in no case is X an alkyl group, alkoxy group, or alkenyl group, except in the case where Z.sub.1, Z.sub.2, or Z.sub.3 is --CF.sub.2 O--or --OCF.sub.2 --;

• that in the case where l is 0, then Z.sub.1 represents a covalent bond, in the case where m is 0,then Z.sub.2 represents a covalent bond, and in the case where n is 0, then Z.sub.3 represents a covalent bond;
• that when X represents other than CN group, at least one of L.sub.1 and L.sub.2 represents a halogen atom except in the case where both l and m are 1;
• and that in the case where both L.sub.1 and L.sub.2 represent hydrogen atom and X represents CN group, then at least one of L.sub.3 and L.sub.4 represents a halogen atom.