The Kerr effect depends very strongly on the temperature and is associated with high operating voltages. The present invention relates to an electrically controllable optical element which comprises a cell (D) filled with a starting mixture (K) and having two substrates (1a, 1b) and a conductive layer (2a, 2b) applied onto the inner surface of the respective substrate (1a, 1b), wherein the starting mixture (K) comprises a mixture of dipolar, rod-shaped molecules (5) and semi-mesogenes (4) as active constituents, and wherein the starting mixture (K) forms a thin layer having a wide-meshed, anisotropic network (9) produced by photo-polymerization between the structured or/and flat conductive layers (2a, 2b), which are applied onto a substrate (1a, 1b), in a thin-film cell (D). According to the invention, an optically active surface profile (O) is incorporated on the inner surface of a substrate (1a or 1b) or into the substrate (1a or 1b) or both substrates (1a and 1b).

A polar compound has a high chemical stability, high ability to align liquid crystal molecules and high solubility in a liquid crystal composition, and causes no decrease of liquid crystallinity of the liquid crystal composition, a liquid crystal composition contains the compound, and a liquid crystal display device includes the composition. The compound is represented by formula (1), the composition contains the compound, and the liquid crystal display device uses the composition. ##STR00001## In formula (1), R.sup.1 is alkyl having 3 to 15 carbons, alkenyl having 4 to 15 carbons or the like; a is an integer from 2 to 12; and R.sup.2 is a group represented by formula (1a), formula (1b) or formula (1c). ##STR00002## In the formulas, S.sup.1 and S.sup.2 are independently a single bond, alkylene having 1 to 10 carbons; S.sup.3 is >CH— or >N—; S.sup.4 is >C< or >Si<; and X.sup.1 is —OH, —NH.sub.2 or the like.

A liquid-crystalline medium having a nematic phase, a dielectric anisotropy of 0.5 or more and a ratio of the dielectric constant perpendicular to the director (∈.sub.⊥) to the dielectric anisotropy (Δ∈), i.e. (∈.sub.⊥/Δ∈), of 2.0 or less and comprises one or more compounds of formula I

##STR00001##

wherein the parameters have the meaning given in the text.

An electro-optical display containing such a medium, particularly in an active-matrix display based on the IPS or FFS effect. Methods for using of the compounds of formula I for improvement of the transmission and/or response times of a liquid-crystalline medium which comprises one or more additional mesogenic compounds.

The present invention relates to compounds of formula M ##STR00001##
in which R.sup.M has the meaning indicated in claim 1, to liquid crystal mixture comprising the same, to the use of these liquid-crystal media, in particular in components for high-frequency technology, and to components of this type which contain media according to the invention, and to the production and use of these components. The components according to the invention are suitable, in particular, as phase shifters in the microwave and millimetre wave region, for microwave and millimetre wave array antennae and very particularly for so-called tunable “reflectarrays”.

The present invention is to find appropriate manufacturing conditions for obtaining a homogeneous scattering state, a homogeneous transparent state, and a homogeneous driving voltage state and to obtain a polymer dispersed liquid crystal display element that has homogeneous properties. A polymer dispersed liquid crystal display element having excellent homogeneity can be obtained by irradiating a light control layer-forming material containing a liquid crystal material and a polymerizable composition with ultraviolet light under specific ultraviolet irradiation conditions to polymerize the polymerizable composition.

The instant invention relates to mesogenic media exhibiting a blue phase, comprising one or both components selected from the two following components, components A and B, component A, comprising one or more compounds selected from the group of compounds of formula I-M, ##STR00001##
and component B, consisting of one or more compounds selected from the group of compounds of formula I-U, ##STR00002##
wherein the parameters are as specified in the text, preferably stabilized by a polymer, and their use in electro-optical light modulation elements and their respective use in displays, as well as to such displays.

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 (or high maximum temperature), a low minimum temperature of a liquid crystal phase, small viscosity, suitable optical anisotropy, large negative dielectric anisotropy, a suitable elastic constant and good compatibility with other liquid crystal compounds, a liquid crystal composition containing the compound, and a liquid crystal display device including the composition. The liquid crystal compound is represented by formula (1): ##STR00001##
in which, R.sup.a and R.sup.b are alkyl having 1 to 10 carbons; ring A.sup.1, ring A.sup.2 and ring A.sup.3 are 1,4-cyclohexylene, 1,4-phenylene; and ring N.sup.1 is 2,3-difluoro-1,4-phenylene; G is a divalent group represented by formula (pr-1) or (pr-2); ##STR00002##
in which, Z.sup.1, Z.sup.2, Z.sup.3 and Z.sup.4 are a single bond; and a, b and c are 0, 1 or 2.

A problem is to provide a liquid crystal compound satisfying at least one physical property such as high stability to heat and light, a high clearing point (or high maximum temperature), a low minimum temperature of a liquid crystal phase, small viscosity, suitable optical anisotropy, large dielectric anisotropy, a 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. A solution is a compound represented by formula (1). ##STR00001## In which, R.sup.1 is alkyl having 1 to 10 carbons or the like; Z.sup.1, Z.sup.2 and Z.sup.3 are independently a single bond, —COO—, —OCH.sub.2—, —CF.sub.2O— or the like, and at least one of Z.sup.1, Z.sup.2 and Z.sup.3 is —CF.sub.2O—; X.sup.1 is hydrogen, fluorine, —CF.sub.3 or —OCF.sub.3; and L.sup.1, L.sup.2, L.sup.3 and L.sup.4 are independently hydrogen, fluorine or chlorine.

The liquid crystal light modulator includes a first substrate (10) and a second substrate (20) disposed between two polarizers, and a pair of electrode structures (24, 24). The substrates include homeotropic alignment films (12) and (22), and at least one of the substrates has a function of aligning C-directors of liquid crystal molecules along one direction. The one direction forms an azimuth angle in the range of 35 to 55 degrees with the direction of the electric field generated by the pair of electrode structures (24, 24). A liquid crystal composition layer (31) contains a ferroelectric liquid crystal composition having a chiral smectic C phase or a liquid crystal composition that has an achiral smectic C phase and negative dielectric anisotropy. Light transmittance is modulated by the electric field generated by the electrode structures (24, 24) changing the birefringence index of the liquid crystal composition layer (31).

Mesogenic compounds of formula I-Z ##STR00001##
are suitable for use in mesogenic media. Such mesogenic media can exhibit a blue phase and comprise component A, consisting of one or more compounds of formula I-Z, and, optionally a component B, consisting of one or more compounds selected from the group of compounds of formulae
I-M and I-U, ##STR00002##
wherein the parameters are as defined herein. The media can also be stabilized by a polymer. The media can be used in electro-optical light modulation elements and displays.