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Home Vasodialators Alpha-hydroxy-carboxylic-acid-derivates-suitable-for-use-in-liquid-crystal-materials-and-devices

 Alpha-hydroxy carboxylic acid derivates suitable for use in liquid crystal materials and devices

Details
Inventors: Chan, Lawrence K. M.; Coates, David; Gemmell, Peter A.; Gray, George W.; Lacey, David; Toyne, Kenneth J.; Young, Daniel J. S.;
Assignee:
Primary Examiner: Stoll; Robert L.
Assistant Examiner: Treanor; Richard
Attorney, Agent or Firm:

Compounds which may be used as a dopant or host in a ferroelectric chiral smectic liquid crystal mixture. The compounds are characterized in that they are derivates of an X-hydroxy carboxylic acid and contain the chiral unit (I), in which Ro may be alkyl, alkoxy, halogen, formula (II), where b may be 0 to 3 and the phenyl ring may be substituted, and a is 0 or 1. The chiral unit is combined with a range of mesogenic combinations of groups. Lactic acid derivatives are described in detail (i.e. Ro.dbd.methyl) together with various preparative routes, for example the compound formula (III), which has dopant properties in a range of hosts.

DETAILED DESCRIPTION We claim: 1.
A lactic acid derivative having the formula: ##STR127## wherein R.
sub.
1 is alkyl or alkoxy an R.
sub.
2 is alkyl, the total number of carbon atoms in R.
sub.
1 plus R.
sub.
2 being 25 or less; W and X are independently selected from H and F; Y and Z are independently selected from H and Cl provided not more than one of Y and Z is Cl; n is 0 or 1 provided that if n is O then Y and Z are both H; and provided that if n is 1 then W and Y are both H.
2.
Derivative according to claim 1, wherein R.
sub.
1 is C.
sub.
5 -C.
sub.
12 n-alkyl or n-alkoxy; R.
sub.
2 is C.
sub.
1 -C.
sub.
5 n-alkyl and only one of W and X may be F.
3.
Derivative according to claim 1 or 2 having the formula: ##STR128## wherein either both of W and X are H, or one is H and the other is F.
4.
Derivative according to claim 3 wherein R.
sub.
1 is selected from the group consisting of n-pentyl, n-nonyl and n-octyloxy, and R.
sub.
2 is ethyl.
5.
Derivative according to claim 1 or 2 having a formula: ##STR129## 6.
Derivative according to claim 5 wherein R.
sub.
1 is selected from the group consisting of n-octyl, n-nonyl, n-decyl, n-octyloxy and n-nonyloxy, and R.
sub.
2 is ethyl.
7.
Liquid crystalline composition consisting of at least two compounds wherein at least one of said compounds is a compound as claimed in claim 1.
8.
Liquid crystalline composition according to claim 7 wherein the said compound of claim 1 is in an optically active form and induces a ferroelectric smectic phase in a smectic host.




Description:
The present invention relates to derivatives of .
alpha.
-hydroxy carboxylic acids suitable for use in liquid crystal materials and devices.
In particular the invention relates to ferroelectric liquid crystal materials, which show a tilted chiral smectic liquid crystal mesophase.
Such materials have been proposed for use in rapidly switched electro-optical devices, for example processing and storage devices and displays, based on the ferroelectric properties of the material in the tilted chiral smectic phase, eg as described by N A Clark and S T Lagerwall in `App Phys Lett` 36 P 899, (1980) (Reference 1)


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