Pleochroic dyes
AssigneeThe Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and Northern Ireland
InventorsDavid Coates, George W. Gray, Damien G. McDonnell
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Abstract
A dye compound suitable for use in solution with a liquid crystal material is characterized by one of the following formulae: ##STR1## (III) a derivative of (I) or (II) containing one or more simple lateral substituents or bridging groups on the benzene rings: ##STR2## where n.sub.1, n.sub.2, n.sub.3 are integers in the range 0 to 4, A is azo or azoxy, X is cyano, or nitro and Y.sub.1 and Y.sub.2 are one of the following: hydrogen, alkoxy, arylalkoxy or N.sub.R.sbsb.2.sup.R.sbsp.1 where R.sub.1 and R.sub.2 are alkyl, substituted alkyl or alkylene groups.
Claims11
A liquid crystal electro-optic device comprising two dielectric substrates at least one of which is optically transparent, at least one electrode on the inner surface of each substrate, and a layer of material sandwiched between the substrates, characterized in that said material is a liquid crystal twist-type nematic or cholesteric-to-nematic system which comprises a mixture of compounds each having a generalized formula ##STR43## wherein R is an alkyl or alkoxy group and m = 0 or 1, at least one of said compounds being cyanobiphenyl wherein m = 0, said material including in solution a dye having a formula selected from one of the following:
- (I) ##STR44## (II) a derivative of formula (I) wherein any of the lateral positions on any one of the benzene rings is substituted by one of the following substituents
- (i) a halogen atom
- (ii) a methyl group
- (iii) a halogen-substituted methyl group
- (iv) a methoxy group;
- (III) a derivative of formula (I) wherein any two of the lateral positions on any one of the benzene rings is bridged by a fused aromatic ring forming a naphthalene structure;
- wherein
- A is an azo or azoxy linkage group
- n.sub.1 and n.sub.2 are integers in the inclusive range 0 to 4 and Y.sub.1 and Y.sub.2 are each one of the following
- (i) hydrogen
- (ii) OR.sub.1 where R.sub.1 is an alkyl or arylalkyl group
- (iii) ##STR45## wherein R.sub.2 and R.sub.3 are each one of the following:
- a simple alkyl or substituted alkyl group or an alkylene group forming a reduced hetero-aromatic system with the terminal aromatic ring.
A liquid crystal electro-optic device comprising two dielectric substrates at least one of which is optically transparent, at least one electrode on the inner surface of each substrate, and a layer of material sandwiched between the substrates, characterized in that said material is a liquid crystal twist-type nematic or cholesteric-to-nematic system which comprises a mixture of compounds each having the formula ##STR53## wherein R is an alkyl or alkoxy group and m = 0 or 1, at least one of said compounds being a cyanobiphenyl wherein m = 0, said material including in solution a dye having a formula selected from one of the following:
- ##STR54## where Z is a hydrogen, methyl, or chlorine;
- ##STR55## where R is an alkyl group, particularly C.sub.7 H.sub.15 ;
- ##STR56## where Z is hydrogen or halogen;
- and ##STR57##
Dependencies are inferred from the claim text.