Thomson-csf

Max-planck-gesellschaft Zur F&#xf6;rderung Der Wissenschaften E. V.

Jean P Billard

Jean-Claude Dubois

Michel Hareng

Serge Le Berre

Annie Zann

Jean Claude Dubois

Jean-Noel Perbet

Pierre Le Barny

Lydie Thirant

Annie Beguin

Herbert Zimmermann

Raphi Poupko

Zeev Luz

The invention relates to hexa-substituted tribenzocyclononatriene derivats constituting a new type of liquid crystals with novel 'pyramidal' mesophases. The compounds of the invention differ from the known liquid crystals in their different steric molecular structure. Their molecules consist of a rigid central nucleus of pyramidal structure, the chains of substituents being symmetrically attached to the basis of the pyramid. The compounds of the invention have an electric dipole moment and can be excited in the electric field. Therefore, they are suitable for use in memory devices and/or electro-optical display means.

Pyramidal liquid crystals

The invention relates to an organic compound obtained by synthesis from 3,5-dihydroxybenzoic acid. The compound according to the invention is in accordance with the following general formula: ##STR1## in which R stands for an organic group of the alkyl, alkoxy or alkyl carboxylate type having 1 to 15 carbon atoms and in which X designates a nitrile or halogene group.

Diphenyl benzoates and its use as a dopant for smectic liquid crystals

A process wherein certain disc-like liquid crystals, which locally undergo heating and then rapid cooling on either side of the transition temperature between two mesophases permit the liquid crystal to become diffuse with an adequate contrast to be used for display purposes. The following liquid crystals can be utilized, i.e. triphenylene derivatives of formulas: ##STR1##

Display process using a thermo-optical effect with a memory in a thin

Cholesteric liquid crystals of the so-called reentrant mesogenic type obtained by mixing a substance such as a cholesterol ester having molecules of the 'chiral' type with a liquid crystal of the so-called reentrant nematic type such as a substance corresponding to the general formula: ##STR1## where R is an alkyl or alkoxy or alkylcarbonate group with:

Cholesteric liquid crystal of the reentrant type and a

A mixture of liquid crystals having a mesophase of the disc-like with wires-type, where a sensitivity to the electrical field can be observed and application can be made to visual display cells. The mixture comprises two hexasubstituted triphenylene derivatives, to the nucleus of which are fixed six identical radicals in positions 2, 3, 6, 7, 10 and 11, which can be alkyl, alkoxy, alkylcarboxylate, alkylbenzoate, and alkoxybenzoate radicals. The electro-optical devices can either be of the variable birefringence type when the liquid crystal molecules have their optical axes parallel to one another and to the walls of a display cell, or of the type with a variable rotatory power under the action of an electrical field when a helical type arrangement is used, or finally, under the effect of a relatively strong field, of the type with dynamic light diffusion.

Mixture of disc-like liquid crystals, electro-optical device using such

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Paris, France

Jean P Billard