Hoechst Aktiengesellschaft

Hans-Rolf Dubal

Dieter Ohlendorf

Claus Escher

Rainer Wingen

Ingrid Muller

Wolfgang Hemmerling

Mikio Murakami

Gerhard Illian

Takamasa Harada

Yoshio Inoguchi

Arnold Schneller

Gunter Scherowsky

Otto Herrmann-Schonherr

Jurgen Gay

Gerd Heppke

Norbert Rosch

Michael Feldhues

Peter Wegener

Thomas Mecklenburg

Detlef Lotzsch

Christian Bahr

Heinz Rieger

Hans-Otto Drotloff

Michael Brekner

Karl Pampus

Armin De Meijere

Optically active 1,3-dioxolane derivatives which carry a mesogenic radical in the 4-position and have the general formula (I) ##STR1## are suitable for use as doping agents in liquid-crystal mixtures--in particular ferroelectric liquid-crystal mixtures. The symbols in the general formula have the following meanings:

Optically active 1,3-dioxolane derivatives carrying a mesogenic radical

Optically active, mesogenic 1,3-dioxolane-4-carboxylates are suitable as dopes in liquid-crystal mixtures. They result in liquid-crystalline ferroelectric phases having short switching times and in electroclinic phases having large electroclinic coefficients. Their particular advantage is that they induce a helix of very large pitch, meaning that helix compensation by further dopes is unnecessary. In addition, the 1,3-dioxolane-4-carboxylates exhibit high UV stability.

Use of optically active 1,3-dioxolane-4-carboxylates as dopes in

Ferroelectric liquid-crystal systems having high spontaneous polarization, in particular &gt;35 nC cm.sup.-2, and good orientation properties in the ferroelectric phase, in particular the S.sub.C * phase, contain at least three different optically active compounds, preferably as dopes in a base mixture which is not itself optically active and has a nematic phase above the smectic phase. The optically active compounds are selected so that they do not all induce a helix of the same rotation sense in the nematic phase. Their relative concentrations are selected so that the total resultant pitch of the helix throughout the cholesteric phase is not less than 10 .mu.m.

Ferroelectric liquid-crystal systems having three or more chiral

Disclosed and claimed are liquid-crystalline cyclopropylalkyl or -alkenyl or heterocyclic compounds, process for their preparation, and their use in liquid-crystalline mixtures. The novel cyclopropylalkyl or -alkenyl or heterocyclic compounds are of the general formula ##STR1## In this formula A.sup.1, A.sup.2 and A.sup.3 are unsubstituted or substituted, aromatic or heteroaromatic molecular components such as 1,4-phenylene or pyrimidine-2,5-diyl which are linked via a single bond (in the case where k and m=0) or via functional groups M.sup.1 and M.sup.2, such as CO--O or CH.sub.2 --O; j, k, l, m and n are zero, 1 or 2. The radicals R.sup.2, R.sup.3 and R.sup.4 are H or alkyl/alkenyl, R.sup.1 is alkyl/alkenyl or one of the substitutents known from LC chemistry such as an .alpha.-haloalkanoic acid radical. At least one of the components A.sup.1, A.sup.2 and A.sup.3 can be heteroaromatic, and G is alkylene or alkenylene.

Cyclopropylaklyl or -alkenyl or heterocyclic compounds, process for

Ferroelectric liquid-crystal display of high contrast and brightness. The use of alignment layers containing compounds having an amphiphilicity-providing effect increases the contrast and brightness of the image in FLC displays.

Ferroelectric liquid-crystal display of high contrast and brightness

The use of optically active tetrahydrofuran-2-carboxylic acid esters as dopants in liquid-crystal mixtures, liquid-crystal mixtures containing same and novel optically active tetrahydrofuran-2-carboxylic acid esters. Optically active tetrahydrofuran-2-carboxylic acid esters containing a mesogenic molecular building unit are suitable as dopants in liquid-crystal mixtures. They result in liquid-crystalline ferroelectric phases having short switching times and in electroclinic phases having large electroclinic coefficients. A further advantage is that they induce a helix having a very small pitch so that they are also suitable for helix compensation in LC mixtures. The compounds are symbolized by the general formula: ##STR1## in which the symbols and indices essentially denote: R.sup.1 =alkyl/alkenyl or tetrahydrofurancarbonyloxy or -thio; j, l, n=zero, 1 or 2; k, m=zero or 1; --A.sup.1, --A.sup.2, --A.sup.3 =phenylene, cycloalkylene or corresponding heterocyclates containing nitrogen, oxygen or sulfur; --M.sup.1, --M.sup.2 =bridges such as --CO--O, --OCH.sub.2 or --CH.dbd.CH; X=oxygen or sulfur.

Use of optically active tetrahydrofuran-2-carboxylic acid esters as

Ferroelectric liquid-crystalline mixtures

Use of optically active carboxylic esters of oxygen-containing heterocycles as doping substances in liquid crystal mixtures and liquid crystal mixtures containing them. Optically active 1,3-dioxolane-4-carboxylic esters and oxirane-2-carboxylic esters of the general formula (I)

Optically active carboxylic esters of oxygen-containing heterocycles as

Ferroelectric liquid crystal with positive dielectric anisotropy,

The novel silylalkyl or silylalkenyl compounds correspond to the general formula (I) ##STR1## Here the symbols A.sup.1, A.sup.2, A.sup.3 denote aromatic or heteroaromatic molecular units such as 1,4-phenylene or pyrimidine-2,5-diyl which are combined via a single bond (for k, m=0) or via functional groups M.sup.1,M.sup.2 such as CO--O or CH.sub.2 --O; j, k, l, m, n are zero or 1 (j+l+n=2 or 3). The radicals R.sup.2, R.sup.3, R.sup.4, R.sup.5 are hydrogen or alkyl/alkenyl, cycloalkyl, and the radicals R.sup.6, R.sup.7, R.sup.8 have a comparable meaning (hydrogen); R.sup.1 is alkyl/alkenyl or one of the substituents known from LC chemistry such as an .alpha.-haloalkanoic radical. In some cases compounds have wide and polymorphous liquid crystalline phases.

Organosilylalkyl or organosilylalkenyl compounds, process for preparing

Use of fluorinated aromatic polyamides as orientation layer for

Optically active 1,3-dioxolane derivatives of the general formula (I) ##STR1## are suitable as doping substances in liquid crystal mixtures. The symbols in the general formula have the following meaning:

Optically active esters of 5-ethyl- and

Liquid-crystalline mixtures, in particular ferroelectric

Ferroelectric liquid crystal display having gray steps or a continuous

Preparation of specially substituted aromatic polyamides containing structural units of the formula I mentioned and copolyamides containing at least 10 mol % of structural units of the formula I and structural units of the formula II mentioned and their use as orientation layer in liquid crystal display elements and/or liquid crystal switching elements.

Substituted aromatic polyamides as orientation layers for liquid crystal

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Konigstein/Taunus, Germany

Hans-Rolf Dubal