| 摘要 |
Compounds of the general formula <IMAGE> I wherein R1 signifies alkyl or alkenyl with 1 to 12 and, respectively, 2 to 12 carbon atoms, which is unsubstituted or mono- or multiply-substituted with halogen and in which one methylene group can be replaced by -O-; R2 signifies alkyl or alkenyl with 1 to 12 and, respectively, 2 to 12 carbon atoms, which is unsubstituted or mono- or multiply-substituted with halogen and in which one or more methylene groups can be replaced by -O- and/or -COO- or -OOC-; Z1 signifies a single covalent bond or -CH2CH2-; A1, A2 each independently represent 1,4-phenylene, which is unsubstituted or mono- or multiply-substituted with halogen, or pyridine-2,5-diyl or pyrimidine-2,5-diyl; A3 represents 1,4-phenylene, which is unsubstituted or mono- or multiply-substituted with halogen, or pyridine-2,5-diyl, pyrimidine-2,5-diyl or trans-1,4-cyclohexylene; n is 0 or 1; with the proviso that at least one of rings A1, A2 or A3 signifies either pyridine-2,5-diyl or pyrimidine-2,5-diyl; and with the further proviso that, when n=0, R1 represents 1E-alkenyl and R2 represents alkyl, alkoxy or alkenyloxy, their manufacture and use in electro-optical devices as well as mixtures which contain said compounds are described in the present application.
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