Abstract: 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, andq 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.

Abstract: The chiral group of the formula ##STR1## is used as a constituent of liquid-crystalline compounds.

Abstract: Liquid-crystalline compounds of the formulae I and II;Z.sup.1 -(X.sup.1 -R.sup.1 -y-M).sub.m IZ.sup.2 -(X.sup.2 -R.sup.1 -Y-M).sub.n IIwhere Z.sup.1 is the radical of an m-valent alcohol an m-valent acid or certain trivalent triazine derivatives; Z.sup.2 is an n-valent radical of a monocyclic or polycyclic aromatic compound; X.sup.1 is a chemical bond or -CO-; X.sup.2 is -O-, -S-, -CO-O-, -O-CO-, -SO.sub.2 -, -SO.sub.2 -O-, -O-SO.sub.2 -O-, -NR.sup.4- , -CO-NR.sup.4 -, -NR.sup.4 -O- or -CO-N<, where R.sup.4 is H or C.sub.1 -C.sub.8 -alkyl; m and n are 3 to 6; R.sup.1 is a C.sub.2 2-C.sub.20 -bridge having 2 to 12 bridging members, which may be interrupted by -O-, -S- or -NR.sup.4 -, each of these hetero units being separated by at least 2 carbon atoms; Y is a chemical bond, -O-, -S-, -CO-O-, -O-CO-, -NR.sup.4 -, -CO-NR.sup.4 - or -NR.sup.4 -CO.sup. -; M is a mesogenic group. These compounds are suitable for the production of optical and electro-optical data carriers and display elements.

Abstract: 2,5-substituted 1,3,4-thiadiazoles of the general formula ##STR1##The aforementioned compounds are used in amounts of 0.1 to 80 mole percent in mixtures for electrooptical arrangements for the modulation of transmitted and reflected light, as well as for the colored or black-and-white display of numerals, symbols and moving or still pictures. The compounds endow the liquid-crystalline mixtures with an extended phase field of the smectic C phase, negative dielectric anisotropy and the property of forming optically active C phases upon admixture with optically active compounds.

Abstract: Liquid crystalline 2,6-disubstituted trans-1,3-dioxadecalins of the general formula ##STR1## are well suited as components of low double refraction for mixtures which are utilized in opto-electronic components.

Abstract: A mixing component for nematic liquid-crystalline substances used in optoelectronic components for the rendition of numbers, symbols and images. The object of the invention is to reduce, in components for nematic liquid crystal substances, the threshold and operating voltages. It has been found, that the addition of one or more 1-oxa-2,6,7-trioxane-1-phospha-bicyclo-derivatives having the general formula ##STR1## wherein ##STR2## with R.sup.1 =C.sub.n H.sub.2n+1 --, C.sub.n H.sub.2n+1 O--, C.sub.n H.sub.2n+1 COO--, C.sub.n H.sub.2n+1 OCOO--, R.sup.2 +C.sub.n H.sub.2n=1 --with n=an integer from 1 to 10to nematic liquid crystal substances, considerably reduces the operating voltage.