Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1988-01-04
1989-10-03
Gron, Teddy S.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229901, 2522995, 2522996, 25229962, 25229963, 25229964, 25229965, 25229966, 25229967, 350350R, 350350S, 549369, 570129, G02F 113, C09K 1934, C09K 1930, C09K 1920
Patent
active
048714690
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the use of trifluorotoluene derivatives of the formula I ##STR2## in which R.sup.1 is alkyl having 1 to 12 carbon atoms in which, in addition, one or more non-neighboring CH.sub.2 groups may be replaced by --O--, --CO--, --O--CO--, --CO--O--, --O--CO--O--, --CH--halogen, --CH--CN-- and/or --CH.dbd.CH--, 1,4-phenylene in which, in addition, one or more CH groups may be replaced by N, trans-1,4-cyclohexylene in which, in addition, one or more non-neighboring CH.sub.2 groups may be replaced by --O-- and/or --S--, or 1,4-bicyclo(2.2.2)octylene, each of which is unsubstituted or monosubstituted or polysubstituted by halogen, nitrile and/or CH.sub.3, --CO--O--, --O--CO--, --CH.sub.2 O--, --OCH.sub.2 --, --CH.sub.2 CH.sub.2 -- or a single bond, and liquid-crystalline phases, in particular chiral tilted smectic phases, containing compounds of the formula I. The invention furthermore relates to novel pyrimidine and pyridine compounds, novel cyclohexane derivatives and novel dioxane derivatives of the formula I.
Chiral tilted smectic liquid-crystallie phases having ferroelectric properties can be produced by adding a suitable chrial dope to base mixture having 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). Such phases can be used as dielectrics for rapidly switching displays which are based on the principle described by Clark and Lagerwall, of SSFLC technology (N. A. Clark and S. T. Lagerwall, Appl. Phys. Lett. 36, 899 (1980); U.S. Pat. No. 4,367,924) on the basis of the ferroelectric properties of the chiral tilted phase. In this phase, the extended molecules are arranged in layers, the molecules having a tilt angle to the layer perpendiculars. On proceeding from layer to layer, the tilt angle changes through a small angle with respect to an axis which is perpendicular to the layers, so that a helical structure is formed. In displays which are based on the principle of SSFLC technology, the smectic layers are arranged perpendicular to the plates of the cells. The helical arrangement of the tilt directions of the molecules is suppressed by a very small separation of the plates (about 1-2 .mu.m). The longitudinal axes of the molecule are thereby forced to arrange themselves in a plane parallel to the plates of the cell, whereby two distinct tilt orientations are produced. By applying a suitable alternating electrical field, it is possible to switch to and fro between these two states in the liquid-crystalline phase having spontaneous polarization. This switching process is significantly faster than in conventional twisted cells (TN-LCDs), which are based on nematic liquid crystals.
A major disadvantage for many applications of the materials currently available having chiral tilted smectic phases (such as, for example, Sc*) is that the S.sub.A phase, above the Sc* phase, which is necessary for good orientation capability in the display, often does not arise or not in the desired temperature range.
It has now been found that the use of compounds of the formula I as components of chiral tilted smectic mixtures can substantially lessen the disadvantages mentioned. The compounds of the formula I are thus highly suitable as components of chiral tilted smectic liquid-crystalline phases. In particular, chiral tilted smectic liquid-crystalline phases which have favorable ferroelectric phase regions, in particular broad Sc* phase regions, and are particularly stable chemically, and S.sub.A phases, above the Sc phase, which are favorable for the orientation in the display, have a favorable pitch height and have values for spontaneous polarization which are high for such phases, can be produced with their aid. P is the spontaneous polarization in nC/cm.sup.2.
The invention thus relates to the use of the compounds of the formula I as components of (chiral tilted) smectic liquid-crystalline phases. The invention furthermore relates to smectic liquid-crystalline phases, in particular chiral tilted s
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C.A. 107: 124957q (1987).
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Lebarny, P., et al., Mol. Cryst. Liq. Cryst., vol. 127, pp. 413-429 (1985).
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Eidenschink Rudolf
Geelhaar Thomas
Krause Joachim
Kurmeier Hans-Adolf
Poetsch Eike
Bescrankter Haftung
Gron Teddy S.
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