Liquid crystal medium

Abstract

A liquid crystalline medium containing (A) compound(s) with three 1,4-linked 6-membered rings in which one of the terminal rings is a fluorinated phenyl group and (B) 4-cyano-3-fluorophenyl benzoate derivative(s). A liquid crystalline (LC) medium (I) containing compound(s) of formula (A) and compound(s) of formula (B). Ra, Rb = H, 1-12C alkyl (optionally substituted with one CN or CF3 group or at least one halogen, and optionally with CH2 group(s) replaced by -O-, -S-, cyclobutane-1,3-diyl, -CH=CH-, -Cequivalent toC-, -CO-, -COO-, -OCO- or -OCOO-), -(A)-Z1-(B)-, -Cyc-Z1-Diox- or -Diox-Z1-Cyc-; (A), (B) = rings A, B as above; Cyc = trans-1,4-cyclohexylene; Diox = 1,3-dioxan-5,2-diyl; Z1, Z2 = -CH2CH2-, -(CH2)4-, -CH2-, -(CH2)3- or a single bond; L1-L8 = H or F; Y = F, Cl, SF5, NCS, OCN, SCN or a mono- or poly-halogenated 1-5C alkyl, alkoxy, alkenyl or alkenyloxy group. Independent claims are also included for (1) (1) electro-optical LC displays containing (I) (2) (2) TN or STN LC displays with two base plates forming a cell, a nematic LC mixture with positive dielectric anisotropy (DELTAe) in the cell, electrode layers with orientation layers on the inside of the base plates, an angle of incidence of 0-30 degrees between the base plates and the long axis of the molecules on their surface and a twist angle of 22.5-600 degrees from orientation layer to orientation layer in the cell, in which the nematic LC mixture comprises (a) 15-75 wt% of an LC component A consisting of compound(s) with a DELTAe of more than +1.5, (b) 25-85 wt% of an LC component B consisting of compound(s) with a DELTAe between -1.5 and +1.5, (c) 0-20 wt% of an LC component D consisting of compound(s) with a DELTAe of below -1.5 and (d) optionally an optically active component C in amounts such that the ratio between layer thickness (plate spacing) and natural pitch of the chiral nematic LC mixture = 0.2-1.3, and in which component A contains compound(s) of formula (A) and compound(s) of formula (B)

Description

field of invention

[0001] The present invention relates to liquid crystal media and to twisted nematic (TN) and super twisted nematic (STN) liquid crystal displays with very short response times and good steepness and angle dependence, and to novel nematics for use therein type liquid crystal mixture. Background technique

[0002] TN displays are known, see eg M. Schadt and W. Helfrich, Appl. Phys. Lett., 18, 127 (1971). STN displays are known, see for example EP0131216B1; DE3423993A1; EP0098070A2; M.Schadt and F.Leenhouts, 17th Freiburg Congress on Liquid Crystals (8.-10.04.87); K.Kawasaki et al., SID 87 Digest 391 ( 20.6); M. Schadt and F. Leenhouts, SID 87 Digest 372 (20.1); K. Katoh et al., Japanese Journal of Applied Physics, Vol.26, No.11, L1784-L1786 (1987); F. Leenhouts et al., Appl .Phys.Lett.50(21), 1468(1987); H.A.vanSprang and H.G.Koopman, J.Appl.Phys.62(5), 1734(1987); T.J.Scheffer and J.Nehring, Appl.Phys.Lett. 45 (10), 1021 (1984), M. Schadt and F. Leenhout...

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