Chiral alkenylaryl 2,3-epoxyalkyl ethers, and the use thereof in

Details Chiral alkenylaryl 2,3-epoxyalkyl ethers, and the use thereof in Chiral alkenylaryl 2,3-epoxyalkyl ethers, and the use thereof in

1993-01-21

1994-11-01

Wu, Susan

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229901, 504238, 504239, 504242, 504304, 504336, 549555, 549560, C09K 1934, C07D40512, C07D30312

Patent

active

053605764

DESCRIPTION:

BRIEF SUMMARY
Particularly in the last decade, liquid crystals have found their way into various industrial areas in which electro-optical and display device properties are required (for example in watch, calculator and typewriter displays). These display devices are based on the dielectric alignment effects in the nematic, cholesteric and/or smectic phases of the liquid-crystalline compounds, the dielectric anisotropy causing the molecular long axis of the compounds to adopt a preferential alignment in an applied electric field. The usual response times in these display devices are rather too long for many other potential areas of application of liquid crystals, which are per se very promising chemical compounds for industry due to their unique properties. This disadvantage is particularly noticeable if, as is necessarily the case in relatively large display element areas, a large number of pixels must be addressed, which would mean the production costs of equipment containing these relatively large areas, such as video equipment, oscillographs or TV, radar, EDP or wordprocessor screens, would be too high.
In addition to nematic and cholesteric liquid crystals, tilted smectic liquid-crystal phases have also been increasing in importance for practical applications for some years. If such tilted smectic phases, in particular smectic C (S.sub.c or SmC) phases are treated with suitable dopes which exhibit or induce in the liquid-crystal phase spontaneous polarization (P.sub.s), the phases can be converted into a ferroelectric liquid-crystal phase (P.sub.s specified in nC.cm.sup.-2); in this respect, see, for example, Lagerwall et al. in the paper "Ferroelectric Liquid Crystals for Displays", SID Symposium, October Meeting, 1985, San Diego (USA). Compared with conventional TN ("twisted nematic") cells, these ferroelectric liquid-crystal phases have response times which are faster by a factor of approximately 1000, so that, also due to other positive properties, such as a possibility of bistable switching, they are good potential candidates for the abovementioned areas of application (for example via matrix addressing).
At the 11th International Liquid-Crystal Conference (30.6. to 4.7.1986) in Berkeley, U.S.A, D. M. Walba presented ferroelectric liquid crystals which contain chiral 2,3-epoxyalkyl side chains and have the following formula: ##STR1## The compound containing a C.sub.10 -alkyl or C.sub.3 -alkyl radical has an SmC* phase between 75.degree. C. and 80.degree. C.; the response time (75.degree. C., 15 V/ .mu.m) is 14 .mu.sec, and the value for the spontaneous polarization P.sub.s is 45 nC/cm.sup.2.
DE-A 36 33 968 describes compounds of the formula (I) ##STR2## where the symbols have the following meanings: R.sup.1 is straight-chain or branched (C.sub.1 -C.sub.12)alkyl, it being possible for one or two non-adjacent CH.sub.2 groups to be replaced by O and/or S atoms, straight-chain (C.sub.1 -C.sub.10)alkyl or branched (C.sub.3 -C.sub.10)alkyl, R.sup.2, R.sup.3 and R.sup.4 not simultaneously being H.
These compounds induce high spontaneous polarization in liquid-crystalline mixtures.
The object of the present invention is to indicate unsaturated compounds which increase the phase width in LC mixtures and depress the melting point of the mixtures, which have high values for the inherent or spontaneous polarization P.sub.s, induced in liquid-crystal phases and contain structural elements which also make them "compatible" (i.e. miscible) with other components in liquid-crystal systems, since, inter alia, the mesogenic part of the molecules is frequently responsible for good "compatibility" with the other mixture components in liquid-crystal systems; these compounds need not necessarily themselves be liquid-crystalline, in particular need not necessarily have an S.sub.m C phase.
The invention proceeds from known chiral compounds containing a mesogenic aromatic unit and a chiral unit containing a heterocyclic three-membered ring.
The compounds according to the invention have the formula ##STR3## in which the symbols have the

REFERENCES:
patent: 4876028 (1989-10-01), Hemmerling et al.
patent: 4927244 (1990-05-01), Bahr et al.
patent: 4973425 (1990-11-01), Kazuhiko et al.
patent: 4988459 (1991-01-01), Scherowsky et al.
patent: 5206751 (1993-04-01), Escher et al.
D. M. Walba et al., Internationale Flussigkeitsknoferenz, (1986), "Synthesis and Some Properties of a New Class of Ferroelectric and Chiral Nematic Liquid Crystals Containing the 2,3-Epoxy Alcohol Unit".

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