TN and STN liquid-crystal displays

A TN or STN liquid-crystal display comprising:

• two outer plates, which, together with a frame, form a cell,
• a nematic liquid-crystal mixture of positive dielectric anisotropy located in the cell,
• electrode layers with alignment layers on the insides of the outer plates,
• a tilt angle between the longitudinal axis of the molecules at the surface of the outer plates and the outer plates of from 0 degree to 30 degrees, and
• a twist angle of the liquid-crystal mixture in the cell from alignment layer to alignment layer with a value of between 22.5° and 600°,
• the nematic liquid-crystal mixture comprising:
• a) 15-80% by weight of a liquid-crystalline component A consisting of one or more compounds having a dielectric anisotropy of greater than +1.5;
• b) 20-85% by weight of a liquid-crystalline component B consisting of one or more compounds having a dielectric anisotropy of from −1.5 to +1.5;
• c) 0-20% by weight of a liquid-crystalline component D consisting of one or more compounds having a dielectric anisotropy of below −1.5, and
• d) optionally, an optically active component C in such an amount that the ratio between the layer thickness, separation of the outer plates, and the natural pitch of the chiral nematic liquid-crystal mixture is from about 0.2 to 1.3,
• wherein the liquid-crystal mixture comprises at least one compound of the formula I
• in which
• R1 is an alkyl or alkenyl radical having 1 to 12 carbon atoms which is unsubstituted, monosubstituted by CN or CF3 or monosubstituted to per halo-substituted by halogen, and in which, one or two CH2 groups are optionally replaced by —O—, —S—,
• —CO—, —CO—O—, —O—CO— or —O—CO—O— in such a way that O atoms are not linked directly to one another,
• R2 has one of the meanings indicated for R1 or is X,
• X is F, Cl, CN, OCN, NCS, SCN or a halogenated alkyl, alkenyl, alkoxy or alkenyloxy radical having 1 to 6 carbon atoms,
• L1 and L2 are each, independently of one another, H or F, A is trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 3-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene or 1,3-dioxane-2,5-diyl, and
• u is 0 or 1, and
• wherein the nematic liquid crystal mixture further comprises at least one alkenyl compound of the formula II
• in which
• R3 is an alkenyl group having 2 to 7 carbon atoms,
• R4 has one of the meanings indicated for R1 is or Q—Y,
• Q is CF2, OCF2, CFH, OCFH or a single bond,
• Y is F or Cl,
• L1 and L2 are each, independently of one another, H or F, and
• m is 0 or 1.