4-Fluoro-3-trifluoromethylbenzenes, and their use in liquid-crystal mixtures

摘要

3-Trifluoromethylbenzenes of the formula (I) <IMAGE> in which the symbols have the following meanings: R<1> is H, a straight-chain or branched alkyl having 1 to 15 carbon atoms (with or without asymmetrical carbon atom), it also being possible for one or two non-adjacent -CH2- groups to be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -SO-CO-, -O-CO-O-, -CH=CH-, -C IDENTICAL C-, <IMAGE> or -Si(CH3)2-, and where, in addition, one or more H atoms of the alkyl radical may be substituted by F, Cl or CN; A<1>, A<2> and A<3> are identical or different and are 1,4-phenylene, pyrazine-2,5-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, in which one or two H atoms may be replaced by F, trans-1,4-cyclohexylene, 1,3,4-thiadiazole-2,5-diyl, 1,3-dioxane-2,5-diyl, naphthalene-2,6-diyl, bicyclo[2.2.2]octane-1,4-diyl or 1,4-dioxaborinane-2,5-diyl; M<1>, M<2> and M<3> are identical or different and are -CH2CH2-, -CH=CH-, -C IDENTICAL C-, -CH2CH2CH2CH2-, -CH2CH2CH2-O-, -O-CH2CH 2CH2-, -CH2CH2CO-O-, -OCO-CH2CH2-, -CH2O-, -OCH2-, -CO-O- or -O-CO-; k, l, m, n, o and p are zero or one, with the proviso that the sum k + m + o is greater than zero. The compounds according to the invention are chemically and photochemically stable. They are distinguished by low melting points and by favourable values for the anisotropy, the dielectric function and the refractive index.