The invention relates to bimesogenic compounds of formula I

##STR00001##

wherein R.sup.11, R.sup.12, MG.sup.11, MG.sup.12 and CG.sup.1 have the meaning given in claim 1, to the use of bimesogenic compounds of formula I in liquid crystal media and particular to flexoelectric liquid crystal devices comprising a liquid crystal medium according to the present invention.

The invention relates to bimesogenic compounds of formula I

##STR00001##

wherein R.sup.11, R.sup.12, MG.sup.11, MG.sup.12 and CG.sup.1 have the meaning given in claim 1, to the use of bimesogenic compounds of formula I in liquid crystal media and particular to flexoelectric liquid crystal devices comprising a liquid crystal medium according to the present invention.

To provide a liquid crystal display device, whereby transparency when no voltage is applied and scattering properties when a voltage is applied, are good, adhesion between a liquid crystal layer and a vertical liquid crystal alignment film is high, and its lifespan is long even in a severe environment. The liquid crystal display device has a liquid crystal layer formed by disposing a liquid crystal composition containing a liquid crystal and a polymerizable compound between a pair of substrates provided with electrodes, and irradiating and curing the composition with ultraviolet rays by an ultraviolet irradiation apparatus, and at least one of the substrates is provided with a liquid crystal alignment film to vertically align a liquid crystal, wherein the ultraviolet irradiation apparatus is an ultraviolet irradiation apparatus capable of controlling the irradiation light intensity and wavelength of the ultraviolet rays to be irradiated and the surface temperature of the pair of the substrates, the liquid crystal composition contains a compound represented by the formula [1], and the liquid crystal alignment film is a liquid crystal alignment film obtained from a liquid crystal alignment treating agent containing a polymer having a side chain structure represented by the formula [2-1] or formula [2-2].

X.sup.1-X.sup.2-X.sup.3-X.sup.4-X.sup.5-X.sup.6X.sup.7.sub.pX.sup.8  [1]

(X.sup.1 is a specific side chain structure; X.sup.2, X.sup.3, X.sup.4 and X.sup.6 are each a single bond, etc.; X.sup.5 and X.sup.7 are each a benzene ring, etc.; p is an integer of from 0 to 4; and X.sup.8 is a C.sub.1-18 alkyl group, etc.),

—Y.sup.1-Y.sup.2-Y.sup.3-Y.sup.4Y.sup.5.sub.nY.sup.6  [2-1]

(Y.sup.1, Y.sup.2 and Y.sup.3 are each a single bond; Y.sup.4 and Y.sup.5 are each a benzene ring, etc.; n is from 0 to 4; and Y.sup.6 is a C.sub.1-18 alkyl group, etc.,

—Y.sup.7-Y.sup.8  [2-2]

(Y.sup.7 is a single bond; and Y.sup.8 is a C.sub.8-22 alkyl group, etc.).

To provide a liquid crystal display device, whereby transparency when no voltage is applied and scattering properties when a voltage is applied, are good, adhesion between a liquid crystal layer and a vertical liquid crystal alignment film is high, and its lifespan is long even in a severe environment. The liquid crystal display device has a liquid crystal layer formed by disposing a liquid crystal composition containing a liquid crystal and a polymerizable compound between a pair of substrates provided with electrodes, and irradiating and curing the composition with ultraviolet rays by an ultraviolet irradiation apparatus, and at least one of the substrates is provided with a liquid crystal alignment film to vertically align a liquid crystal, wherein the ultraviolet irradiation apparatus is an ultraviolet irradiation apparatus capable of controlling the irradiation light intensity and wavelength of the ultraviolet rays to be irradiated and the surface temperature of the pair of the substrates, the liquid crystal composition contains a compound represented by the formula [1], and the liquid crystal alignment film is a liquid crystal alignment film obtained from a liquid crystal alignment treating agent containing a polymer having a side chain structure represented by the formula [2-1] or formula [2-2].

X.sup.1-X.sup.2-X.sup.3-X.sup.4-X.sup.5-X.sup.6X.sup.7.sub.pX.sup.8  [1]

(X.sup.1 is a specific side chain structure; X.sup.2, X.sup.3, X.sup.4 and X.sup.6 are each a single bond, etc.; X.sup.5 and X.sup.7 are each a benzene ring, etc.; p is an integer of from 0 to 4; and X.sup.8 is a C.sub.1-18 alkyl group, etc.),

—Y.sup.1-Y.sup.2-Y.sup.3-Y.sup.4Y.sup.5.sub.nY.sup.6  [2-1]

(Y.sup.1, Y.sup.2 and Y.sup.3 are each a single bond; Y.sup.4 and Y.sup.5 are each a benzene ring, etc.; n is from 0 to 4; and Y.sup.6 is a C.sub.1-18 alkyl group, etc.,

—Y.sup.7-Y.sup.8  [2-2]

(Y.sup.7 is a single bond; and Y.sup.8 is a C.sub.8-22 alkyl group, etc.).

The present invention relates to the technical field of liquid crystal displays, and particularly relates to a liquid crystal composition containing a 2-methyl-3,4,5-trifluorobenzene liquid crystal compound and use thereof, wherein the liquid crystal composition of the present invention comprises, in percentages by weight, 1-50% of one or more compounds represented by general formula I and 10-70% of one or more compounds represented by general formula II, and may further comprise 0-30% of compounds represented by general formula III and/or 6-45% of one or more compounds represented by general formulas IV to XIII The liquid crystal composition provided by the present invention has a low rotational viscosity and a large elastic constant, is presented as having a shorter response time, and can significantly improve the display effect of a liquid crystal display when applied to TN, IPS and FFS mode displays.

The present invention relates to the technical field of liquid crystal displays, and particularly relates to a liquid crystal composition containing a 2-methyl-3,4,5-trifluorobenzene liquid crystal compound and use thereof, wherein the liquid crystal composition of the present invention comprises, in percentages by weight, 1-50% of one or more compounds represented by general formula I and 10-70% of one or more compounds represented by general formula II, and may further comprise 0-30% of compounds represented by general formula III and/or 6-45% of one or more compounds represented by general formulas IV to XIII The liquid crystal composition provided by the present invention has a low rotational viscosity and a large elastic constant, is presented as having a shorter response time, and can significantly improve the display effect of a liquid crystal display when applied to TN, IPS and FFS mode displays.

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.

A liquid-crystalline medium, in particular based on a mixture of polar compounds, having compounds of formulae Y, CY, PY and/or LY, and compounds of formula S1 and/or S2:

##STR00001##

A liquid-crystalline medium, in particular based on a mixture of polar compounds, having compounds of formulae Y, CY, PY and/or LY, and compounds of formula S1 and/or S2:

##STR00001##

Provided is a liquid crystal compound that can obtain a high-speed response and a sufficient contrast ratio in switching of a display device. A compound represented by formula (1) described below is utilized.

##STR00001##

In formula (1), ring A is naphthylene, phenantolylene or anthracenylene, and in the groups, at least one piece of hydrogen may be replaced by halogen, —CH.sub.3, —C.sub.2H.sub.5, —CF.sub.3, —CHF.sub.2, —CH.sub.2F, —OCF.sub.3, —OCHF.sub.2 or —OCH.sub.2F; and X.sup.1, X.sup.2, X.sup.3, X.sup.4, X.sup.5, Y.sup.1, Y.sup.2, Y.sup.3, Y.sup.4 and Y.sup.5 are independently hydrogen or fluorine, but at least two or more of X.sup.1, X.sup.2, X.sup.3, X.sup.4, X.sup.5, Y.sup.1, Y.sup.2, Y.sup.3, Y.sup.4 and Y.sup.5 is fluorine.