Alkylbyphenyloxyacetic acid esters and their use in smectic liqu

Details Alkylbyphenyloxyacetic acid esters and their use in smectic liqu Alkylbyphenyloxyacetic acid esters and their use in smectic liqu

1987-12-21

1990-03-27

Terapane, John F.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229901, 25229966, 25229961, 25229963, 25229964, 25229967, 25229968, 350350S, 560 59, 560 61, 560116, 560 8, 560 1, 560106, 560141, 544298, 544335, 546301, 546342, C09K 1912, C09K 1934, C09K 1930, G02F 113

Patent

active

049118633

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to liquid crystal mixtures and to compounds for use in them. The invention is particularly concerned with ferroelectric smectic liquid crystal mixtures and compounds. The invention also relates to electro-optical devices incorporating these mixtures.


DESCRIPTION OF THE INVENTION

Ferroelectric smectic liquid crystal materials utilize the ferroelectric properties of the chiral titlted smectic phase, ie the chiral smectic C, F, G, H, I, F and K phases (hereinafter designated S.sub.c.sup.* etc, the asterisk * denoting chirality). The S.sub.c.sup.* phase is most commonly sought for use in electro-optical devices as it is the most fluid, and it is also desirable that the material shows an S.sub.A phase at a temperature above the S.sub.c.sup.* phase, to assist in surface alignment.
Ferroelectric liquid crystal materials ideally have a low viscosity, a broad smectic liquid crystal temperature range, stability ect., and in particular should show a high spontaneous polarisation co-efficient (Ps, measured in nCcm.sup.-2). Although some single component materials show these properties, it has become common practice to use a mixture which shows a smectic phase. At least one of the compounds in the mixture is optically active (chiral) so as to induce the smectic phase shown by the mixture to be chiral, especially S.sub.C.sup.*. Such optically active compounds are called "chiral dopants".
According to the present invention a novel compound suitable for inclusion in a ferroelectric smectic liquid crystal mixture has a formula I: ##STR1## where R.sub.1 and R.sub.2 are independently selected from H, R, RO, ROOC, RCOO, RCOOCH(CH.sub.3)COO and COOCH(CH.sub.3)COOR where R is C.sub.1-12 alkyl, or from CN or halogen; ##STR2## is independently selected from: ##STR3## and these rings may carry one or more lateral substituents selected from halogen, CN or CH.sub.3 ; CH.sub.2, OCH.sub.2, CH.sub.2 O, CH.dbd.N, N.dbd.CH, N.dbd.N or a single bond; is 1, 2 or 3; CH.sub.2 or ##STR4## where W is C.sub.1-5 alkyl, phenyl, cyclohexyl, halogen or CN, provided that when W is CN then d or e is l, and further provided that rings ##STR5## when present have the same lateral substitution pattern.
Compounds of formula I are useful constituents of ferroelectric smectic liquid crystal mixtures. According to a second aspect of the invention there is provided a ferroelectric smectic liquid crystal mixture containing at least two compounds, at least one of which is a compound of formula I.
Suitability for use in such a mixture is among the factors determining the structural and other preferences discussed below.
The compound of formula I may be optically active, racemic, or non-optically active, but the mixture preferably contains at least one optically active compound of formula I.
The alkyl group R may be straight chain (--n), branched or when present in other than RCOOCH(CH.sub.3)COO or COOCH(CH.sub.3)COOR may be chiral. Preferably R.sub.1 and R.sub.2 are independently alkyl, alkoxy, alkanoyloxy or alkoxycarbonyl.
Preferred substituents when present of the rings ##STR6## are F. Compounds wherein one of these rings is ##STR7## are paricularly useful.
Preferably W in formula I is n-alkyl, especially methyl.
Preferred structures for the unit --X--Y--(Z)--.sub.z in formula I are listed in table 1 below:


TABLE 1 ______________________________________ ##STR8## 1.1 ##STR9## 1.2 ##STR10## 1.3 ##STR11## 1.4 ##STR12## 1.5 ##STR13## 1.6 ##STR14## 1.7 ##STR15## 1.8 ##STR16## 1.9 ##STR17## 1.10 OCH.sub.2COO 1.11 ______________________________________
Preferred structures for the unit ##STR18## in formula I are listed in table 2 below:


TABLE 2 ______________________________________ ##STR19## 2.1 ##STR20## 2.2 ##STR21## 2.3 ##STR22## 2.4 ##STR23## 2.5 ##STR24## 2.6 ##STR25## 2.7 ##STR26## 2.8 ##STR27## 2.9 ##STR28## 2.10 ______________________________________ lateral halogen substituent.
Preferred overall structures for the compound of formula I are listed in tab

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