Abstract: Optically active dopants of the formula ##STR1## wherein A represents an optically active group selected from 1,1'-binaphthyl-2,2'-diyl, --CHR.sup.1 --CHR.sup.2 -- or --CH(COOR.sup.3)--CH(COOR.sup.4)--; Z denotes a group --(CH.sub.2).sub.4 --, --O(CH.sub.2).sub.3 -- or the trans form of --OCH.sub.2 --CH.dbd.CH--; R.sup.1 is hydrogen, methyl, phenyl or cyclohexyl; R.sup.2 is methyl, phenyl or cyclohexyl; R.sup.3 and R.sup.4 denote alkyl; Y stands for --CO-- or --CH.sub.2 --; ring B represents 1,4-phenylene or trans-1,4-cyclohexylene; and R is hydrogen, alkyl, alkoxy or cyano, liquid crystalline mixtures which contain such dopants and their use for optical and electro-optical purposes.

Abstract: A liquid crystal display (LCD) cell comprising a highly twisted nematic liquid crystal disposed between two electrode plates and polarizers and having a positive dielectric anisotropy. The optical path difference .DELTA.n.d is 0.2 to 0.7 .mu.m and the ratio d/p of thickness to pitch is 0.2 to 0.6. The absolute value of the twist angle .phi. can be between 120.degree. and 260.degree. for a right-hand twist or left-hand twist, the angle .psi. between the polarizers can be between 0.degree. and 180.degree. and the angle .beta. between the surface orientation direction and the polarization direction on the screen on the light incidence side can be between 0.degree. and 360.degree..

Abstract: A liquid crystal display (LCD) cell comprising a twist nematic liquid crystal disposed between two electrode plates and polarizers and having a positive dielectric anisotropy. The optical path difference .DELTA.n.d is 0.2 to 0.7 .mu.m. The absolute value of the twist angle .phi. can be between 10.degree. and 80.degree., the angle .psi. between the polarizers can be between 80.degree. and 110.degree. and the angle .theta. between the surface orientation direction and the polarization direction on the screen on the light incidence side can be between -10.degree. and 60.degree., preferably so that the polarizers are symmetrical of the nematic directors.

Abstract: A liquid crystal display wherein in order to obtain an improved contrast without diminishing the brightness of the display, the angle of twist is reduced in the case of a liquid crystal display according to the rotating cell principle, polarizers with greater extinction power are used and up to 3% by weight of a suitable dye is added. Thus, a largely achromatic display is also obtained.

Abstract: A liquid crystal display with a liquid crystal layer enclosed by two parallel plates which carry electrodes and on top thereof a first layer system of several dielectric electrodes having refractive indices smaller than 2.2 and a thickness of the layers above the base layer, under 200 nm. The liquid crystal display is characterized by the following features with respect to the first carrier plate.the electrode has a thickness d.sub.e, within the range according to 0<d.sub.e .ltoreq.30 nm or (m.lambda./2n.sub.e -10) nm.ltoreq.d.sub.e .ltoreq.(m.lambda./2n.sub.e +10) nm (.lambda.=550 nm, m=natural integer>0, n.sub.e =index of refraction of the electrode, nm=nanometer),the base layer has an index of refraction n.sub.b and a thickness d.sub.b, within the range according to 1.40.ltoreq.n.sub.b .ltoreq.1.50 and 20 nm.ltoreq.d.sub.b .ltoreq.50 nm or (m 300/n.sub.b -20) nm.ltoreq.d.sub.b .ltoreq.(m 300/n.sub.b +20) nm,the remaining layers of the first layer system have indices of refraction n.sub.

Abstract: A liquid crystal display enclosing between two parallel plates a liquid crystal layer which can be switched between two optically different states. The plate surfaces facing each other each carry a matching layer on top of which are the electrodes. On top of the electrode is a first layer system with a dielectric layer and a topmost orientation layer. The refraction index n.sub.u of the substrata is smaller than the index n.sub.e of the electrode. The index of the matching layer has the following relationship: ##EQU1## The matching layer has a thickness d.sub.a, according to: ##EQU2## wherein .lambda.=550 nm, m=natural integer >0, and nm=nanometer, The electrode has a thickness d.sub.e, according to: d.sub.e .ltoreq.