The present invention relates to a compound of formula T

##STR00001##

as defined in claim 1, to a liquid crystal medium comprising a compound of formula T and to high-frequency components comprising 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 liquid-crystalline media (LC media) containing a low-molecular-weight, non-polymer component, and a combination of self-alignment additives for vertical alignment of two or more of the specified kinds (formulae IA to IM). The combination of two or more self-alignment additives affect homeotropic (vertical) alignment of the LC media at a surface or the cell surfaces of a liquid-crystal display (LC display).

A smectic A composition with the positive dielectric anisotropy exhibiting a monolayer smectic A structure (SmA.sub.1), which shows a phase transition from a smectic A phase to an isotropic phase (SmA-Iso) or a phase transition from a smectic A phase through a nematic phase to an isotropic phase (SmA-N-Iso) and includes at least two fluorinated compounds selected from the families of fluorinated derivatives of biphenyls and terphenyls expressed by the general formulae 1-12.

For ensuring of the high level of the conductivity the composition is doped with the ionic amidynium salts and/or the ionic potassium complexes of the crown ethers wherein the charge on the cation is delocalized. Such a structure of the ionic compound ensures the better solubility in the liquid crystalline fluorinated composition in comparison to that observed for quaternary ammonium salts.

For writing of the information the dynamic scattering effect (DS) was used, where the transition from a opaque (milky) state to a clear (transparent) state or reversal process is obtained by the change of the frequency of a driving alternating electric field.

The modification of the properties of the smectic A composition by adding of further components such as fluorinated four ring liquid crystal compounds or pyrimidine compounds or cyanocompounds is described.

A liquid-crystalline medium, preferably having a nematic phase and dielectric anisotropy of 0.5 or more, which comprises one or more compounds of each of formulae T and L

##STR00001##

in which the parameters have the meanings given in the claims and in the text. The use thereof in an electro-optical display, particularly in an active-matrix display based on the IPS or FFS effect, to displays of this type which contain a liquid-crystalline medium of this type. Also, the compounds of formulae T and L and their use for the 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 a liquid crystal (LC) medium comprising a compound of formula I

##STR00001## and one or more compounds selected from the group of compounds of the formulae IIA, IIB, IIC and IID,

##STR00002## as defined in claim 1, and to the use of the LC medium for optical, electro-optical and electronic purposes, in particular in LC displays, especially in IPS, FFS, VA or PS-VA displays.

The present invention relates to dielectrically positive liquid-crystalline media comprising one or more compounds of the formula I and II ##STR00001##
in which the parameters have the respective meanings indicated in claim 1, and to liquid-crystal displays, especially active-matrix displays and in particular displays of the vertically aligned mode, containing these media.

Provide are a liquid crystal compound represented by formula I, and a liquid crystal mixture comprising the compound ##STR00001## A lateral trifluoromethyl-containing liquid crystal compound having the structural characteristics of Formula I not only has a negative dielectric anisotropy (Δε), an appropriate optical anisotropy (Δn), a higher clearing point (CP), a prominent low-temperature miscibility with other liquid crystals, and a low rotary viscosity (γ1), but also has a good stability to UV and high temperatures, particularly, a negative dielectric anisotropy. Same can be applied to the formulation of liquid crystal compositions of positive and negative types, and it is particularly prominent that same has the advantages of a good solubility at low temperatures and a high transmittance.

A liquid crystal composition and a liquid crystal display device including the liquid crystal composition include at least one compound of general formula I and at least one compound of general formula II. Compared with the prior art, the liquid crystal composition has a smaller voltage change rate at high and low temperatures and a shorter low temperature response time, while maintaining an appropriate optical anisotropy, an appropriate clearing point, an appropriate absolute value of dielectric anisotropy, such that the liquid crystal display device having the liquid crystal composition has a better display and a faster response speed. ##STR00001##

A liquid-crystalline medium having a nematic phase containing one or more compounds of formula D

##STR00001##

the use thereof in an electro-optical display, particularly in an active-matrix display based on the IPS or FFS effect, displays of this type which contain a liquid-crystalline medium of this type and the use of the compounds of formula D for improvement of the contrast and/or response times of a liquid-crystalline medium which contain one or more additional mesogenic compounds, as well as certain compounds of formula D.

The present invention relates to a liquid crystal (LC) medium comprising polymerisable compounds, to a process for its preparation, to its use for optical, electro-optical and electronic purposes, in particular in LC displays, and to LC displays comprising it.