Hoechst Aktiengesellschaft

Merck Patent Gesellschaft MIT Beschrankter Haftung

Siemens Aktiengesellschaft

Feodor Oestreicher

Gerd Heppke

Detlef Lotzsch

Christian Bahr

Gunter Scherowsky

Annerose Gobl-Wunsch

Michael Krumrey

Heinz-Siegfried Kitzerow

Liquid crystal phases containing at least one optically active compound of the formula I ##STR1## wherein X.sup.1 and X.sup.2 independently of one another are each --CO--O-- or --O--CO--, one of X.sup.1 and X.sup.2 may also be --O--,

Liquid crystal phase

The novel esters of a chiral alcohol and a mesogenic carboxylic acid are characterized by the general formula (I) ##STR1## in which the symbols have the following meanings: n denotes 0 or 1,

Chiral esters of mesogenic carboxylic acids in liquid crystal phases

The chiral smetic liquid-crystalline compounds of the general formula (I)

Chiral smetic liquid crystals and glassy materials containing the same

The twistable liquid crystal phases contain at least two chiral compounds (admixtures), at least one exhibiting helix inversion and at least one other having a high twisting capacity. With the aid of this combination of chiral compounds possessing certain properties, it is possible to effect temperature compensation with a relatively small amount of added admixtures.

Liquid crystal phase containing admixtures which effect temperature

Chiral esters of mesogenic carboxylic acids

The new esters derived from a chiral compound containing two OH groups and at least one mesogenic carboxylic acid which have the general formula (I) ##STR1## in which X.sup.1 =O--H or O--CO--(C.sub.1 to C.sub.12)alkyl and X.sup.2 =O--MC or X.sup.1 and X.sup.2 denote O-MC independently of each other, where MC is the molecular radical of a mesogenic monocarboxylic acid after splitting off an OH group. The esters or esters substituted in the aromatic part of the phenolic part preferably find application as an admixture intwistable liquid crystal phases in which they produce a temperature compensation and a high degree of twisting.

Chiral phenolic esters of mesogenic carboxylic acids and their use as

The circular polarizer comprises a liquid crystal cell, the liquid crystal layer (8) of which is present as a so-called 'blue phase' and can be exposed to a variable electric field. The blue phase is an optically isotropic chiral phase which, like the cholesteric phase, reflects circularly polarized light within a narrow frequency band and accordingly, in this spectral region, transmits only light which is circularly polarized (in the opposite sense). Under the influence of the field, the reflection band changes its position and can be shifted almost continuously from blue to red by means of relatively small voltage changes. The circular polarizer can, by means of simple additional measures, for instance by including a color-neutral circular polarizer, be developed into a color modulator and, in particular, it also makes a multi-colored display of information possible.

Color-selective circular polarizer and its use

An optical system contains a liquid crystal cell (1), to the liquid crystal layer (11) of which an E-field can be applied transversely to the plane of the layer. A light source (3) sends to the liquid crystal cell (1) a beam of rays parallel to the field direction. The liquid crystal is in the form of a chiral, optically isotropic phase ('blue phase'). This phase has a field-dependent optical density for the incident light and is matched to the light wavelength such that no selective reflection takes place. Such a cell is also optically isotropic in the presence of an E-field, switches rapidly and requires no interface orientation. Its preferred fields of use are: intensity modulation of light of a given wavelength, or as a phase grid in a schlieren-optical system, an etalon in a laser, or a light switch.

Blue phase liquid crystal system, method of operation and its use

Liquid crystal phases containing at least one optically active compound of the formula I

Liquid crystal phases containing at least one chiral, compound with at least two chiral centers in the molecule which are adjacent or separated from one another by an acyclic chain, preferably at least one optically active compound of the formula I

An operable liquid crystal display device having threshold energy fields dependent on a finite temperature operating range is provided with a layer of a liquid crystal material positioned between the carrier plates of such device. The liquid crystal material includes a nematic carrier material and at least two doping chiral additives, one of which exhibits a clockwise twisting tendency and the other which exhibits a couter-clockwise twisting tendency. The twisting characteristic for the cholesteric phase has a temperature-dependent pitch and, under certain conditions, a temperature-dependent direction of rotation. With such a multiply-doped liquid crystal material and with the application of a controllable select energy field, such as electricity or magnetism to such material, selective display characteristic data can be generated by, for example, a temperature-independent pitch, a helix inversion, or a pitch which greatly increases or decreases with an increasing temperature within the finite temperature range. In such liquid crystal materials, the threshold field strengths are temperature-constant for different display effects or may be compensated to the temperature-dependency of other magnitudes, such as the temperature drift of a driving module designed as an integrated circuit.

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Berlin, Germany

Feodor Oestreicher