The new media exhibit a ferroelectric nematic phase preferably at ambient temperature. They preferably comprise one or more compounds selected from the group of compounds of formulae IA, IB and IC, ##STR00001##
in which the variable groups have the meanings indicated in the text and in the claims. Use of the media for providing ferroelectric nematic materials and a method of operation of an electro-optical device are presented. The media may be useful for energy-saving displays and electrical appliances.

Provided is a liquid crystal composition having at least one of, or a suitable balance regarding at least two of, characteristics such as a high maximum temperature, a low minimum temperature, small viscosity, suitable optical anisotropy and large dielectric anisotropy, and an AM device including the composition. The liquid crystal composition contains a specific compound having positive dielectric anisotropy as a first component, a specific compound having small viscosity as a second component, and may contain a specific compound having positive dielectric anisotropy as a third component, a specific compound having a high maximum temperature or small viscosity as a fourth component or a specific compound having negative dielectric anisotropy as a fifth component.

To provide a liquid crystal compound having high polymerization reactivity, a high conversion ratio and high solubility in a liquid crystal composition, a polymerizable composition containing the compound, a liquid crystal composite prepared using the composition, and a liquid crystal display device including the composite. The liquid crystal display device prepared using the polymerizable composition containing the compound represented by formula (1): ##STR00001##
wherein, in formula (1), P.sup.1 to P.sup.6 are a polymerizable group; S.sup.1 to S.sup.6 are a single bond, alkylene or the like; a1, a3 and a4 are an integer from 0 to 4, a2 is an integer from 1 to 4; ring A.sup.1 to ring A.sup.4 are a divalent group derived from benzene, naphthalene, anthracene, pyrimidine, pyridine or the like; Z.sup.1 to Z.sup.3 are a single bond, alkylene or the like, and at least one of Z.sup.1, Z.sup.2 and Z.sup.3 is CC; and b1 is 0 or 1.

A liquid crystal composition contains an achiral component T and a chiral dopant and exhibiting an optically isotropic liquid crystal phase. The achiral component T contains at least one compound represented by formula (1). ##STR00001##
In formula (1), R.sup.1 is alkyl having 1 to 12 carbons, alkenyl having 2 to 12 carbons, or alkoxy having 1 to 11 carbons, ring A.sup.1 and ring A.sup.2 independently represent one of the following formulae: ##STR00002##
Z.sup.1, Z.sup.2 and Z.sup.3 are independently a single bond, (CH.sub.2).sub.2, COO, CF.sub.2O or CHCH, X.sup.1 is hydrogen, halogen, CF.sub.3, OCF.sub.3 or CN, L.sup.1, L.sup.2, L.sup.3 and L.sup.4 are independently hydrogen or halogen, and i is 0, 1 or 2.

A liquid crystal compound is provided that satisfies at least one physical property such as high stability to heat and light, a high clearing point, low minimum temperature of liquid crystal phase, small viscosity, suitable optical anisotropy, large dielectric anisotropy, suitable elastic constant and compatibility with other liquid crystal compounds. A liquid crystal composition containing the compound and a liquid crystal display device including the composition is also provided. The liquid crystal compound is represented by formula (1) ##STR00001##
in which R.sup.1 is alkyl having 1 to 10 carbons, rings A.sup.1, A.sup.3 and A.sup.4 are independently 1,4-phenylene, ring A.sup.2 is a divalent group represented by any one of formulas (Ch), (Cx) and (ch), ##STR00002##
Z.sup.1, Z.sup.2, Z.sup.3 and Z.sup.4 are a single bond, X.sup.1 is fluorine, L.sup.1 and L.sup.2 are fluorine, a, b and c are independently 0 or 1, and a sum of a, b and c is 0 or 1.

A problem is to provide a liquid crystal compound satisfying at least one physical property such as high stability to heat and light, high clearing point, low minimum temperature of liquid crystal phase, small viscosity, suitable optical anisotropy, large dielectric anisotropy, suitable elastic constant and excellent compatibility with other liquid crystal compounds, a liquid crystal composition containing the compound, and a liquid crystal display device including the composition. The compound is represented by formula (1). ##STR00001## In formula (1), for example, R.sup.1 is alkenyl; ring A.sup.1 and ring A.sup.2 are 1,4-cyclohexylene or 1,4-phenylene; Z.sup.1, Z.sup.2, Z.sup.3 are a single bond or COO; X.sup.1 is hydrogen or fluorine; L.sup.1, L.sup.2, L.sup.3 and L.sup.4 are hydrogen or fluorine; and a and b are each independently 0 or 1, a sum of a and b is 1, and when a is 1, at least one of ring A.sup.1 and ring A.sup.2 is 1,4-cyclohexylene.

A liquid crystal composition is provided containing a compound that is effective in preventing photolysis of the liquid crystal composition, and has high solubility in the liquid crystal composition. A liquid crystal display device including the composition is also provided. The liquid crystal composition contains a compound represented by formula (1), and a liquid crystal display device uses the composition: ##STR00001##
in which, in formula (1), R.sup.1 to R.sup.8 are hydrogen or alkyl having 1 to 4 carbons; ring A.sup.1 and ring A.sup.2 are cyclohexylene, phenylene, or naphthalenediyl; Z.sup.1, Z.sup.2 and Z.sup.3 are a single bond; and a and b are independently 1 or 2, and c is 0, 1 or 2.

A polymerizable compound is provided having suitable polymerization reactivity, high conversion and high compatibility in a liquid crystal composition, a polymerizable composition containing the compound, a liquid crystal composite prepared using the composition, and a liquid crystal display device having the composite. The polymerizable compound has at least one monovalent group (A). The polymerizable composition contains the compound. The liquid crystal composition and the liquid crystal composite is prepared using the polymerizable composition. The liquid crystal display device has the liquid crystal composite. ##STR00001##
In the monovalent group (A), R.sup.1 and R.sup.2 are independently alkyl having 1 to 3 carbons, and in the alkyl, at least one of hydrogen may be replaced by fluorine, and R.sup.3 is hydrogen or methyl.

To provide a compound having an effect for preventing photolysis of a liquid crystal composition, and having a high solubility in the liquid crystal composition, a liquid crystal composition containing the compound, and a liquid crystal display device including the composition. The compound is represented by formula (1), a liquid crystal composition contains the compound, and a liquid crystal display device includes the composition:
M(Z-Q).sub.a(R.sup.b).sub.b(1)
wherein, in formula (1), a is 1 to 4, and b is a numerical value: (4a); M is an organic group; Z is a single bond or the like; and Q is a monovalent group represented by formula (Q-1), (Q-2) or (Q-3), in which R.sup.a and R.sup.b are hydrogen, alkyl or the like. ##STR00001##

A liquid crystal medium has stability to heat, light and so forth, and significantly high dielectric anisotropy, and develops an optically isotropic liquid crystal phase. Moreover, various kinds of optical devices can be used in a wide temperature range and have a short response time, a large contrast ratio and low driving voltage. A liquid crystal composition contains achiral component T containing at least one compound 1 represented by formula (1) and a chiral agent, and develops the optically isotropic liquid crystal phase. ##STR00001## In formula (1), for examples, R.sup.1 is alkyl, L.sup.1 and L.sup.2 are each independently fluorine or hydrogen, and X.sup.1 is halogen.