Chiral compounds

Details Chiral compounds Chiral compounds

1996-09-16

1998-05-19

Wu, Shean C.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229961, 25229963, 549364, C09K 1932, C09K 1934, C09K 1930, C07D49304

Patent

active

057531412

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/EP45/00866, filed on Mar. 9, 1995.
Chiral, smectic, liquid-crystalline materials which on cooling from the liquid-crystalline phase solidify in a glass-like manner with formation of a layer structure are employed for many purposes, as is known, in the electrooptical field. Examples which may be mentioned here are optical storage systems (DE-A-3 827 603 and DE-A-3 917 196), electrophotography (DE-A-3 930 667), liquid-crystalline display elements such as displays (Mol. Cryst. Liq. Cryst., 114, (1990) 151) and also, in the case of simultaneously present ferroelectric behavior, electrical storage systems Ferroelectrics, 104, (1990) 241).
In the layer structure of ferroelectric S.sub.c * phases, the molecular long axes are inclined within the individual layer to the layer perpendiculars z. The direction of this inclination is given by the director n; the angle between z and n is the tilt angle .THETA.. S.sub.c * phases exhibit two stable states having a different direction of n, which can be switched between by applying an electric field (electrooptical effect).
S.sub.c * phases occur in low-molecular-weight, liquid-crystalline materials, in oligomesogens and in polymeric ferroelectric materials, the essential properties of the S.sub.c * phases agreeing.
The liquid-crystalline materials prepared until now, however, have disadvantages, for example low spontaneous polarization, low phase width, no stable, tilted smectic glass at room temperature or excessively slow switching.
The occurrence of the liquid-crystalline S.sub.c * phase is affected to a considerable extent by all groups of the molecule, ie. side group A, mesogenic group M and the chiral group, such that the smallest changes in the molecular structure can induce S.sub.c * phases or cause them to disappear.
The chiral group especially is of crucial importance for the achievement of spontaneous polarization, due to its structure and special function.
The present invention is based on the object of finding chiral groups for liquid-crystalline materials which affect the liquid-crystalline properties as little as possible, simultaneously induce high spontaneous polarizations and are synthetically accessible.
The invention therefore relates to compounds of the general formula I ##STR2## and where the radicals A independently of one another are C.sub.1 - to C.sub.30 -alkyl which may be substituted by fluorine, chlorine, bromine or cyano and may be interrupted by O, S, NH, NCH.sub.3, COO or OCO, COO or OCO and aromatic or aliphatic ring system of the general formula II CH.sub.2 O, OCH.sub.2, CH.dbd.N or N.dbd.CH, 1,3,4-thiadiazol-2,5-ylene or 2,5-pyrimidylene which may be substituted by fluorine, chlorine, bromine, iodine, cyano, hydroxyl, methoxy or methyl, and other than 0.
The invention particularly relates to compounds of the general formula I where the radicals C.sub.6 - to C.sub.14 -alkyl, which may be interrupted by O, COO or OCO,
The use of the compounds according to the invention for the construction of recording layers for laser optical and electrical recording elements, in electrophotography, for the production of latent charge images, for the construction or as a component of liquid-crystalline display elements and also as colored reflectors is likewise a subject of the invention.
The mesogenic molecular moiety M consists of an aromatic or aliphatic ring system of the general formula II CH.sub.2 O, OCH.sub.2, CH.dbd.N or N.dbd.CH, 1,3,4-thiadiazol-2,5-ylene or 2,5-pyrimidylene which may be substituted by fluorine, chlorine, bromine, iodine, cyano, hydroxyl, methoxy or methyl, and
Examples of particularly preferred Z.sup.1 groups are ##STR3##
The units A--Y--(M--Y).sub.n according to the invention, where A, Y and M have the meaning indicated above, are accessible in principle by generally known synthesis processes, as are described eg. in DE-A-3 917 186 and in Mol.Cryst.Liq.Cryst.191, (1991) 231.
All reactions were monitored by thin-layer chromatography (TLC) on silica gel ready-to-use film GF 254 (Merck). Detection

REFERENCES:
Mol.Cryst. . . . Liq. Cryst.,, 1984, vol. 114, pp. 151-187.
Ferroelectrics, 1990, vol. 104, pp. 241-256.

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