Chiral aryloxypropionates, and the use thereof as dopes in liqui

Details Chiral aryloxypropionates, and the use thereof as dopes in liqui Chiral aryloxypropionates, and the use thereof as dopes in liqui

1989-05-05

1991-01-15

Maples, John S.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229966, 25229965, 25229964, 25229961, 25229901, 350350S, 544298, 544335, 560 59, 560 61, 560 73, C09K 1920, C07D23902, C07C 6976

Patent

active

049851721

DESCRIPTION:

BRIEF SUMMARY
Especially in the last decade, liquid crystals have been introduced into a very wide variety of industrial areas in which electrooptical and display device properties are in demand (e.g. in displays for watches, pocket calculators and typewriters). These display devices are based on dielectric alignment effects in nematic, cholesteric and/or smectic phases of liquid-crystalline compounds, where--caused by the dielectric anistropy--the longitudinal molecular axis of the compounds adopts a preferred alignment in an applied electrical field. The usual switching times in these display devices are rather too slow 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 when--which is necessaily the case in relatively large display element areas--it is necessary to address a large number of image points, which means that the production costs of equipment containing relatively large areas, such as video equipment, oscillographs or TV, radar, EDP or word processor screens, would be too high.
Besides nematic and cholesteric liquid crystals, tilted smectic liquid-crystal phases have in the last few years also become increasingly important. If suitable dopes which exhibit or induce in the liquid-crystal phase socalled spontaneous polarization (P.sub.s) are added to such tilted smectic phases, in particular smectic C (S.sub.c or SmC) phases, the phases can be converted into ferroelectric liquid-crystal phases (denomination of P.sub.s in nC.cm.sup.-2), in this respect, see, for example, Lagerwall et al. in the paper "Ferroelectric Liquid Crystals for Displays", SID Symposium, Oct. Meeting, 1985, San Diego (USA). Compared with customary TN ("twisted nematic") cells, these FLC phases have switching times which are faster by a factor of about 1,000. As a consequence of these and other positive properties, such as the possibility of bistable switching, they are good potential candidates for the abovementioned areas of application (for example via matrix addressing).
In WO-A 86/02937, compounds of the formula below ##STR2## which are 2-hydroxypropionates esterified on the hydroxyl group by arylcarboxylic acids and in which R may denote methyl, ethyl, propyl or n-butyl, are described, amongst others, as components of ferroelec-tric liquid-crystal mixtures.
The spontaneous polarization P.sub.s for these compounds (determined in a 10 mol-% mixture with racemic CE 8) is given as 72.6 nC.cm.sup.-2 (extrapolated to the pure substance) at a temperature 10.degree. below the S.sub.c.sup.* -S.sub.A transition; neither switching times nor other application-relevant parameters are given.
In EP-A 0,175,591, compounds of the formula below ##STR3## in which the symbols have the following meaning: R.sub.A : a linear, branched or cyclic, saturated or unsaturated hydrocarbon radical having 1 to 20 carbon atoms; ##STR4## where R.sup.1 to R.sup.5 denote alkyl or alkoxy groups having 1 to 20 carbon atoms and n and m denote 1 or 2, are described, amongst other compounds, as components of liquid-crystal mixtures. These compounds are described as being advantageous for achieving bistable behavior in ferroelectric liquid-crystal mixtures; optically active carbon atoms in -R.sub.B are not mentioned.
In WO-A 87/05012, which is not a prior publication, aryloxypropionic acid esters are described, but these differ from the compounds according to the invention in that the alkyl radical or alkoxy radical at the right-hand end of the molecule in the WO-A denotes C.sub.1 - to C.sub.12 -alkyl or C.sub.1 - to C.sub.12 -alkyloxy. Although it is stated (page 2, lines 31 to 34) that this alkyl group may be straight-chain, branded or "chiral", consideration of concrete compounds from Table 3 (p.4) and the definition for "R.sub.2 " (page 5, lines 2 to 4) shows that, however, only asymmetric carbon atoms which are linked to the remainder of the molecule via a carboxyl group come under the definition of R.sup.2.
The in

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