Thomson-csf

Alain Beguin

Jean-Claude Dubois

Annie Zann

The invention concerns a substance of diester type, i.e. an organic compound with three benzene nuclei joined by --COO-- groups, exhibiting at least one mesomorphic phase of smectic type. The substance of the invention answers to the formula: ##STR1## where R.sub.1 is an alkyl or alkoxy radical and R.sub.2 an alkyl. In the case where R.sub.1 is an octyl and R.sub.2 a pentyl there is a dielectric isotropy frequency of 30 kHz, i.e. a frequency where the dielectric anistropy changes sign. Application to field-effect display devices with dual-frequency memory.

Liquid crystal of diester type exhibiting a smectic phase, with low

The invention relates to an organic compound having an enantiotropic or monotropic mesomorphous phase. The compound according to the invention complies with the general chemical formula: ##STR1## in which R is an alkyl radical, R' another alkyl radical or an alkoxy radical and the symbol  is a radical which can either be an aromatic nucleus or a radical with two aromatic nuclei or a cyclohexane radical or contain at least one cyclohexane radical or a heterocycle of type ##STR2##

Mesomorphous 4-alkoxytetrafluorobenzoic acid esters

A family of diphenylic esters are disclosed, which, within certain temperature ranges exhibit mesomorphic phases, either smectic or nematic, having the general formula: ##STR1## where R.sub.1 is C.sub.n H.sub.2n+1 O or C.sub.n H.sub.2n+1 in which n is an integer of from 1 to 10,

Diphenylic esters exhibiting mesomorphic phases

A family of organic compounds having at least one mesomorphic phase of nematic type and, in respect of some compounds, one or more smetic phases. The liquid crystals according to the invention satisfy general formula: ##STR1## in which R.sub.1 is an alkyl or alkoxy group having n carbon atoms (n being an integer of 1 to 10) X designates the bromine or the cyano group, Y is a methyl group.

Family of liquid crystals of the disubstitute diester type

A liquid crystal composition with high negative dielectric anisotropy, which is capable of exhibiting a high dynamic light scattering effect and of inducing similar characteristics into mixtures of the liquid crystal and another nematic liquid crystal and which derives an advantage from a larger mesomorphic temperature range, which comprises at least one compound of the formula: ##STR1## wherein R represents NO.sub.2, bromine or cyano; R.sub.1 is an alkyl or alkoxy group and R.sub.2 is an alkyl group.

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Paris, France

Alain Beguin