| 摘要 |
A compound expressed by the general formula (1):wherein R1 denotes an alkyl group having from 1 to 20 carbon atoms in which one or more methylene groups in said group may be replaced by oxygen atoms or -CH=CH- and one or more hydrogen atoms in said group may be replaced by flourine or chlorine atoms, with the proviso that two or more methylene groups may not be continuously replaced by oxygen atoms,Y1 denotes an alkoxy group having 1 to 5 carbon atoms, in which at least one hydrogen atom is replaced by a fluorine atom and one or more hydrogen atoms may be further replaced by chlorine atoms,Z1, Z2 and Z3 each independently denote a covalent bond, -CH2CH2-, -CH=CH-, -COO- or -CF2)-, with the proviso that at least one of Z1, Z2 and Z3 is -COO- or -CF2O-,rings A1, A2, A3 and A4 each independently denote trans-1,4-cyclohexylene, 3-cyclohexen-1,4-ylene, 3-fluoro-3-cyclohexen-1,4-ylene, pyrimidine-2,5-diyl, 1,3-dioxan-2,5-diyl, trans-1-sila-1,4-cyclohexylene, trans-4-sila-1,4-cyclohexylene, or 1,4-phenylene in which one or more hydrogen atoms may be replaced by fluorine atoms or chlorine atoms,andm and n denote 0 or 1,with the proviso that when Z1, Z2 or Z3 is -CF2O-, then at least two groups selected from rings A1, A2, A3 and A4 directly bonded to -CF2O- are both 1,4-phenylene in which one or more hydrogen atoms may be replaced by fluorine atoms or chlorine atoms, and any of the rings A1, A2 and A3 bonded with the carbon atoms of -CF2O- is 1,4-phenylene in which at least one hydrogen atom is replaced by fluorine or chlorine atoms.
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