Mesogenic compounds

In a nematic liquid crystalline medium, comprising at least two liquid crystalline compounds, the improvement wherein at least one compound is a mesogenic compound with a .omega.-CF.sub.3 -alkenyl or a .omega.-CF.sub.3 -alkynyl terminal group of formula I

• wherein
• R is an unsubstituted, a mono cyano or trifluoromethyl substituted or a mono-, oligo- or polyhalogeno-substituted alkyl or alkenyl residue having 1 to 15 carbon atoms, or such a residue wherein one or more CH.sub.2 groups are each independently replaced by --O--, --CO--, --CO--O--, --O--CO-- or --O--CO--O with the proviso that oxygen atoms are not directly attached to each other,
• the rings A and B independently are
• (a) a trans-1,4-cyclohexylene group, wherein one or more two non-adjacent CH.sub.2 groups may also be replaced by at least one of --O-- or --S-- or one or two CH groups may be replaced by N,
• (b) a 1,4-phenylene group, wherein one or two CH groups may be replaced by N,
• (c) 1,4-bicyclo-(2,2,2-octylene, 1,4-cyclohexenylene, napthalin-2,6-diyl or 1,3-cyclo-butylene,
• groups (a) and (b) being optionally substituted by one or more of halogen, cyano or methyl,
• Z is independently from each other --CO--O, --O--CO--, --CH.sub.2 CH.sub.2 --, --CH.sub.2 O--, --OCH.sub.3 --, --C.tbd.C, --CH.dbd.N--, --N.dbd.CH-- or a single bond,
• Q is --C.tbd.C or --CH.dbd.CH--,
• m is 1, 2 or 3 and
• n an o are independently from each other zero or integers from 1 to 10.