| 摘要 |
Compounds of the formula <IMAGE> I wherein A1 denotes a single covalent bond and A2 denotes 1,4-phenylene or trans-1,4-cyclohexylene or A1 denotes trans-1,4-cyclohexylene and A2 denotes a single covalent bond; X1 signifies fluorine or chlorine; X2 represents fluorine or, when X1 signifies chlorine, also hydrogen or chlorine; and R1 signifies 1E-alkenyl with 2 to 12 carbon atoms, their manufacture, liquid crystalline mixtures which contain such compounds and their use for electro-optical purposes.
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