Chiral compounds

Details Chiral compounds Chiral compounds

1990-07-02

1993-01-19

Stoll, Robert L.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229963, 558426, 558431, 546275, 546276, 546290, 546296, 546300, 544242, 544316, 544335, 544336, 544357, 544239, 544224, 544238, C09K 1934, C07D21172, C07D23900, C07C25500

Patent

active

051805219

DESCRIPTION:

BRIEF SUMMARY
The invention relates to optically active compounds of the formula I
R.sup.1 -A.sup.1 -A.sup.1 is R.sup.1 -A-Z.sup.1, R.sup.1 -A.sup.4 -A-Z.sup.1 or R.sup.1 -A-A.sup.4 -Z.sup.1
R.sup.1 and R.sup.2 are each H, an alkyl group with 1-12 C atoms, wherein one or two non-adjacent CH.sub.2 --groups can also be replaced by O atoms and/or --CO--groups and/or --CO--O--groups and/or --CH.dbd.CH--groups and/or --CH halogen-- and/or --CHCN--groups, F, Cl, Br, Cn or R.sup.3 -A.sup.3 -Z.sup.2, is a 1,4-cyclohexylene or 1,4-cyclohexenylene group, wherein one or two non-adjacent CH.sub.2 groups can also be replaced by --O-- and/or --S--, which is substituted in the 2-, 3-, 5- or 6-position by hydroxyl, halogen, nitrile and/or an alkyl group or a fluorinated alkyl group with in each case 1-10 C atoms, wherein one or two non-adjacent CH.sub.2 groups can also be replaced by --O--, --CO--, --O--CO--, --CO--O-- and/or --CH.dbd.CH--, and which can optionally also be substituted in the 1- and/or 4-position by hydroxyl, halogen, nitrile and/or in alkyl group or a fluorinated alkyl group with in each case 1-4 C atoms, wherein one or two nonadjacent CH.sub.2 groups can also be replaced by --O--, --CO--, --O--CO--, --CO--O-- and/or --CH.dbd.CH--,
A.sup.2, A.sup.3 and A.sup.4 are each 1,4 -phenylene which is unsubstituted or substituted by one or two F and/or Cl atoms and/or CH.sub.3 - groups and/or CN- groups, 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 be replaced by O atoms and/or S atoms, piperidine- 1,4-diyl, 1,4-bicyclo(2,2,2)-octylene, decahydronaphthalene-2,6-diyl or 1,2,3,4-tetrahydronaphthalene-2,6-diyl groups, --OCH.sub.2 --, --CH.sub.2 O-- or a single bond and
R.sup.3 is H, an alkyl group with 1-12 C atoms, wherein one or two non-adjacent CH.sub.2 groups can also be replaced by O atoms and/or --CO-- groups and/or --CO--O--groups and/or --CH.dbd.CH-groups, F, Cl, Br or Cn.
Like similar compounds described in German Offenlegungsschrift 3,515,373, the compounds of the formula I can be used as components of chiral tilted smectic liquid crystal phases.
Chiral tilted smectic liquid crystal phases with ferroelectric properties can be prepared by adding a suitable chiral doping substance to base mixtures containing one or more tilted smectic phases (L. A. Beresnev et al., Mol. Cryst. Liq. Cryst. 89, 327 (1982); and H. R. Brand et al., J. Physique 44, (lett.), L-771 (1983)). Such phases can be used as dielectrics for rapid-switching 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); and U.S. Pat. No. 4,366,924) on the basis of the ferroelectric properties of the chiral titled phase. The elongated molecules are arranged in layers in this phase, the molecules having an angle of tilt to the layer perpendicular. On progressing from layer to layer, the direction of tilt changes by a small angle with respect to an axis perpendicular to the layers, so that a helical structure is formed. In displays based on the principle of SSFLC technology, the smectic layers are arranged vertically to the plates of the cell. The helical arrangement of the tilt directions of the molecules in suppressed by a very low distance between the plates (about 1-2 .mu.m). This means that the longitudinal axes of the molecules are forced to align themselves in a plane parallel to the plates of the cell, whereupon two preferential tilt orientations are formed. By applying a suitable alternating electrical field, switching backwards and forwards between these two states can be effected in the liquid crystal phase which displays spontaneous polarization. This switching operation is considerably faster than in conventional twisted cells (TN-LCD's) based on nematic liquid crystals.
A great disadvantage for many applications of the materials with chiral tilted smectic phases (such as, for example, Sc*) currently available is that the dielectric anisotropy has values greater than zero or, i

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