Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1989-05-15
1993-03-30
Stoll, Robert L.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229962, 25229963, 25229965, 25229966, 25229967, C09K 1934, C09K 1932, C09K 1930, C09K 1920
Patent
active
051981491
DESCRIPTION:
BRIEF SUMMARY
The invention relates to chiral, tilted, smectic liquid-crystal media having at least two liquid-crystal components and at least one chiral doping agent, at least one compound containing the structural element 2,3-difluoro-1,4-phenylene, excepting fluorinated oligophenyls of the formula 1 ##STR1## wherein a is 0 or 1 and wherein the terminal substituents R.sub.1, R.sub.2 and R.sub.3 independently of one another are each alkyl or alkenyl radical which has up to 15 C. atoms and is optionally substituted by CN or by at least one halogen atom and in which one or more non-adjacent CH.sub.2 groups of these radicals can also be replaced by --O--, --S--, --CO--, --O--CO--, --CO--O--, --O--CO--O-- or --C.tbd.--, one of these radicals R.sub.1 and R.sub.2 is also a group of formula, ##STR2## in one of the following pairs of lateral substituents the two substituents are fluorine
The invention relates in particular to media which contain at least one compound of the formula I ##STR3## wherein R.sup.1 and R.sup.2 are alkyl having 1 to 15 C atoms or alkenyl having 3-15 C atoms, each of which, independently of one another, is unsubstituted, monosubstituted by cyano or at least monosubstituted by fluorine or chlorine, it being also possible for a CH.sub.2 group in these radicals to be replaced in each case by --O--, --CO--, --O--CO--, --CO--O-- or --O--CO--O--, and one of the radicals R.sup.1 and R.sup.2 also denotes an organic radical Q* which induces chirality and which has an asymmetric carbon atom,
A.sup.1 and A.sup.2, independently of one another, are each 1,4-phenylene wherein one or two CH groups can also be replaced by N, 1,4-cyclohexylene wherein one or two non-adjacent CH.sub.2 groups can also be replaced by O atoms and/or S atoms, piperidine-1,4-diyl, 1,4-bicyclo(2,2,2)octylene, 1,3,4-thiadiazole-2,5-diyl, naphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl, each of which is unsubstituted or substituted by one or two F and/or Cl atoms and/or CH.sub.3 groups and/or CN groups,
Z.sup.1 and Z.sup.2 are each --CO--O--, --O--CO--, --CH.sub.2 CH.sub.2 --, --OCH.sub.2 --, --CH.sub.2 O--, --C.tbd.C-- or a single bond,
m and n are each 0, 1 or 2 and (m+n) is 1 or 2, subject to the proviso that one or two of the groups Z.sup.1 and/or Z.sup.2 present in the molecule of the formula I are --CO--O--, --O--CO--, --CH.sub.2 CH.sub.2 --, --OCH.sub.2 --, --CH.sub.2 O-- or --C.tbd.C--, if A.sup.1 and A.sup.2 independently of one another are each 1,4-phenylene which is unsubstituted or substituted by one or two F atoms.
Compounds of the formula 1 and/or chiral, tilted, smectic, liquid-crystal media containing oligophenyls of the formula 1 form the subject of International Patent Application PCT/EP 88/00724.
Chiral, tilted, smectic liquid-crystal media having ferroelectric properties can be prepared by adding a suitable chiral doping agent to base mixtures containing one or more tilted smectic phases (L. A. Beresnev et al., Mol. Cryst. Liq. Cryst. 89, 327 (1982); H. R. Brand et al., J. Physique 44 (lett.), L-771 (1983)). Phases of this type can be used as dielectrics for high-speed displays based on the principle of SSFLC technology described by Clark and Lagerwall (N. A. Clark and S. T. Lagerwall, Appl. Phys. Lett. 36, 899 (1980); U.S. Pat. No. 4,367,924), based on the ferroelectric properties of the chiral, tilted medium. In this medium, the longitudinally extended molecules are arranged in layers and the molecules have an angle of tilt to the layer perpendicular. In proceeding from layer to layer, the direction of tilt changes by a small angle in respect to an axis vertical to the layers, so that a helical structure is formed. In displays based on the SSFLC technology, the smectic layers are arranged perpendicularly to the plates of the cell. The helical arrangement of the directions of tilt of the molecules is suppressed by means of a very small distance between the plates (approx. 1-2 .mu.m). By this means, the longitudinal axes of the molecules are forced to arrange themselves in a plane parallel to the plates of the
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Coates David
Geelhaar Thomas
Greenfield Simon
Krause Joachim
Reiffenrath Volker
Harris C.
Merck Patent Gesellschaft mit beschrankter Haftung
Stoll Robert L.
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