Liquid-crystalline media having one or more compounds of formula C ##STR00001##
and high-frequency components containing these media, especially microwave components for high-frequency devices, such as devices for shifting the phase of microwaves, tunable filters, tunable metamaterial structures, and electronic beam steering antennas (e.g. phased array antennas).

A compound is represented by general formula (I), a liquid-crystal composition contains this compound, and devices are made using this liquid-crystal composition.

##STR00001##

Having a large refractive-index anisotropy Δn and a sufficiently high Tni, highly compatible with liquid-crystal compositions, and exhibiting a high dielectric anisotropy in the radiofrequency range, the compound is a useful material for RF phase shifters, phased-array antennae, image recognition devices, distance meters, liquid-crystal displays, liquid-crystal lenses, and birefringent lenses for 3D image display, among other devices.

The present invention relates to liquid-crystalline media comprising one or more pleochroic compounds, and one or more compounds selected from the group of compounds of formulae I, II and III, ##STR00001##
in which the groups have the meanings as set forth in claim 1,
and to components comprising these media for high-frequency technology, in particular phase shifters and microwave array antennas.

Compounds of the formula I, liquid-crystalline media which contain at least one compound of the formula I and electro-optical displays which contain the LC mixtures, especially for the self-aligning VA, PSA, PS-VA, PVA, MVA, PM-VA, HT-VA or VA-IPS mode ##STR00001##
in which R.sub.1, R.sub.2, ring A.sub.1, Z.sub.1, Z.sub.2, Sp, P, L.sub.1, L.sub.2, r1, r2, r3, m, n, p1 and p2 have the meanings indicated above.

The present invention relates to an optical component comprising a liquid crystal (LC) medium, operable in the infrared region of the electromagnetic spectrum. The invention further relates to the use of said LC medium in the infrared (IR) region and to devices comprising said optical component. The present invention further relates to an LC medium comprising one or more compounds of the formulae I, II, and III

##STR00001##

##STR00002##

##STR00003##

in which the occurring groups and parameters have the meanings defined in claim 1, and preferably one or more compounds of the formula RO

##STR00004##

in which the occurring groups and parameters have the meanings defined in claim 2.

A steerable antenna having a plurality of radiating elements and a plurality of modifier elements configured for shifting phase and/or adjusting amplitude of a signal to be emitted by the radiating elements is disclosed. Each of the radiating elements is coupled to one of the modifier elements, wherein the modifier elements each comprise a liquid crystalline medium and wherein the modifier elements are configured such that the adjustment of the phase and/or amplitude is dependent on a state of the liquid crystalline medium. The steerable antenna further comprises a signal generator connected to the modifier elements and configured for generating a signal suited for dielectric heating of the liquid crystalline media of the modifier elements. Further aspects relate to a method for heating and/or controlling the temperature of the liquid crystalline medium of such a steerable antenna.

A method for preparing a switching element which is operable in and electrically switchable between an optically clear state and a scattering state, wherein one or more polymerisable mesogenic compounds provided in a layer containing a liquid-crystalline medium which comprises one or more mesogenic compounds, one or more chiral compounds and the one or more polymerisable mesogenic compounds are subjected to polymerisation in the presence of a direct current (DC) electric field in the layer. Also, a switching element obtained or respectively obtainable by carrying out the method and to the use of the switching element in a window.

The present invention relates to an optical article comprising a birefringent liquid crystal composition, said composition comprising more than 30% by weight based on the total weight of the composition of tolane compounds of formula R—S—Z.sup.1-A-Z.sup.2—NCS, in which R is a substituted or unsubstituted, linear or branched alkyl group, Z.sup.1 and Z.sup.2 are aryl groups, and A is an ethynyl group, an arylethynyl group or an ethynylarylethynyl group.

A method and apparatus for improved switching speed and/or tunability for radio-frequency (RF) devices are described. In one embodiment, a liquid crystal (LC) component comprises an LC structure in a mixture with right-handed (R) and left-handed (S) chiral dopants.

As a material used in an element used for phase control of an electromagnetic wave signal having a frequency of 1 GHz to 10 THz, a liquid crystal composition is required, which has a high upper limit temperature of a nematic phase, a low lower limit temperature of a nematic phase, large dielectric anisotropy and a small tan δ in a frequency region where the phase control of an electromagnetic wave signal is performed, and stability against heat, and which has an excellent balance of the characteristics. A liquid crystal composition which is used in an element for phase control of an electromagnetic wave signal having any frequency from 1 GHz to 10 THz, the liquid crystal composition containing at least one compound selected from compounds represented by Formula (1) as a first component.

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