Liquid crystalline compound, liquid crystal composition comprising the liquid crystal-line compound, and liquid crystal display device using the liquid crystal composition

A liquid crystalline compound expressed by the general formula (1)

• wherein R1 represents an alkyl group having 1 to 20 carbon atoms one or more non-adjacent methylene groups in the alkyl group may be replaced by oxygen atom, sulfur atom, or vinylene group;
• Y1 represents an alkoxy group having 1 to 19 carbon atoms;
• X1 represents single bond, 1,2-ethylene group, or vinylene group, X2 represents single bond, 1,2-ethylene group, vinylene group, or —COO—, and X3 represents —COO—, provided that at least one of X1 and X2 represents 1,2-ethylene group or vinylene group, and at least one of X2 and X3 represents —COO—;
• ring A1 represents trans-1,4-cyclohexylene group, ring A2, ring A3, and ring A4 independently represent trans-1,4-cyclohexylene group CH2 group on which ring may be replaced by oxygen atom, or 1,4-phenylene group one or more hydrogen atoms of which may be replaced by fluorine atom or chlorine atom, provided that at least one ring of ring A3 and ring A4 represents 2,3-difluoro-1,4-phenylene group;
• and
• m and n are independently 0 or 1, provided that m+n is 1 or 2,
• when m=1, n=0, X1 represents 1,2-ethylene group, and X2 represents —COO—, then ring A2 represents 1,4-phenylene group at least one hydrogen atom in which group is replaced by fluorine atom;
• when m=0, n=1, and X1 represents 1,2-ethylene group, then ring A3 represents 1,4-phenylene group at least one hydrogen atom in which group is replaced by fluorine atom;
• when m=n=1, one of X1 and X2 represents 1,2-ethylene group, and the other represents single bond, then ring A3 represents 1,4-phenylene group at least one hydrogen atom in which group is replaced by fluorine atom.