New penta: and tetra:fluoro-benzene cpds. - useful in liquid crystal medium for electro=optical display esp. super-twist nematic display

摘要

New penta- or tetrafluorobenzene derivs. (I) are of the formula: n = 0-7; Q = -O-, -CH=CH- or a single bond; r = 0-5; s = 0-2; X = H or F; A = Z, Z-Ar, Ar-Z, Z-Cyc or 1,4-cyclohexenyl- -ene (IIA) or 1-hydroxy-1,4-cyclohexylene (IIB) of the formula: Z = a single bond, -(CH2)2- or -(CH2)4-; Ar = 1,4-phenylene or biphenyl-4,4'-diyl; Cyc = trans-1,4-cyclohexylene. (I) can be prepd. (not claimed) by standard methods, e.g. as described in Houben-Weyl, Methoden der Organischen Chemie, Georg-Thieme-Verlag, Stuttgart. USE/ADVANTAGE - (I) are claimed for use as components of liquid crystalline (LC) media for electrooptical displays. They are esp. useful in nematic media with positive dielectric anisotropy for use in STN and stable active matrix displays. The media have a wide nematic range, excellent nematogenicity down to low temps., excellent chemical stability, excellent elastic properties, little temp. dependence of the threshold voltage and/or small optical anisotropy. (I) also have good solubility for the other components of the media, high positive dielectric anisotropy and favourable viscosity.