| 摘要 |
Disclosed is a tetracyclic compound of the formula I in which R1, R2 are each, independently of one another, an alkyl or alkenyl radical having up to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF3, or monosubstituted by halogen. One or more CH2 groups in these radicals may also, in each case independently of one another be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO- or -O-CO-O- such that the O atoms are not linked directly to one another. Z is -OCF2-, -CF2O- or a single bond. L1, L2, L3, and L4 are each, independently of one another, H or F. m is 1 or 2. Similar compounds, as well as liquid-crystalline media having these compounds, are also disclosed.
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