Liquid-crystalline allenes of the formula I ##STR1## where M is a mesogenic group, R.sup.1 and R.sup.2 are hydrogen or a C-organic radical having 1-8 carbon atoms, R.sup.3 is a C-organic radical having 1-30 carbon atoms, X.sup.1 is --(CH.sub.2).sub.q --O--(CH.sub.2).sub.p --, --(CH.sub.2).sub.q --NR.sup.4 --(CH.sub.2).sub.p --, --(CH.sub.2).sub.q --CO--O--(CH.sub.2).sub.p --, --(CH.sub.2).sub.q --O--CO--(CH.sub.2).sub.p --, --(CH.sub.2).sub.q --CO--NR.sup.4 --(CH.sub.2).sub.p -- or --(CH.sub.2).sub.q --NR.sup.4 --CO--(CH.sub.2).sub.p --, R.sup.4 is hydrogen or an alkyl radical having 1-4 carbon atoms, p is from 1 to 20, and q is from 0 to 20, where the definitions of R.sup.2 and R.sup.3 can also be interchanged, are used in optical display elements.