The present invention relates to a liquid-crystalline medium based on a mixture of polar compounds having negative dielectric anisotropy (), which is distinguished by the fact that it has a value for the ratio .sub.1/n.sup.2 in the range 6-45 with a clearing point of >60 C. and a of 2.3. Media of this type are particularly suitable for electro-optical displays having active-matrix addressing based on the ECB, PA LCD, FFS or IPS effect.

The invention relates to the compounds of the formula I and to a liquid-crystalline medium based on a mixture of polar compounds which contains at least one compound of the formula I ##STR00001##
in which R.sup.1, ring A.sup.1, L.sup.1, L.sup.2, L.sup.3, L.sup.4, L.sup.5, L.sup.6, L.sup.7, L.sup.8, Z.sup.1 and m have the meanings indicated in claim 1 and to the use of the LC mixtures in electro-optical displays, especially for the self-aligning VA mode.

The invention relates to an electro-optical liquid-crystal display having a re-alignment layer for re-alignment of the liquid crystals whose field has a component, crucial for the re-alignment, parallel to the liquid-crystal layer, containing a liquid-crystalline medium, characterized in that it comprises one or more compounds of the formula I1 to I3, (I1) (I2) (I3) and at least one compound of the formula II, in which the parameters R.sup.11, R.sup.11*, Z.sup.0, Sp, k, l, p, Y.sup.21 to Y.sup.22, R.sup.21 and R.sup.22 have the meanings indicated in claim 1.

A liquid crystal composition includes one or more compounds represented by Chemical Formula 1. ##STR00001## In Chemical Formula 1, ##STR00002##
are a cyclohexane or tetrahydropyran, and R1 and R2 are each independently hydrogen, a C1 to C8 alkyl group, a C2 to C8 alkenyl group, or a C1 to C8 alkoxy group.

The present invention provides a liquid crystal composition and a liquid crystal display device thereof. The liquid crystal composition comprises at least one compound of general formula I and at least one compound of general formula II. The liquid crystal composition has a larger vertical dielectric constant (?.sub.?), a larger ratio of the vertical dielectric constant to the absolute value of dielectric anisotropy (?.sub.?/|??|), a larger K.sub.ave value and a higher transmittance while maintaining an appropriate clearing point, an appropriate optical anisotropy, and an appropriate absolute value of the dielectric anisotropy, such that the liquid crystal display device comprising the same has a better contrast, a faster response speed and a better transmittance while maintaining an appropriate range of operating temperature and an appropriate threshold voltage. ##STR00001##

The invention relates to a liquid-crystalline medium comprising at least one compound of the formula I, ##STR00001##
in which
R.sup.1 and R.sup.2 have the meanings indicated in Claim 1,
and to the use thereof in electro-optical liquid-crystal displays.

A liquid-crystalline medium which comprises at least one compound of the formula I,

##STR00001## and one or more compounds of the formula ST

##STR00002## and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PA-VA, SS-VA, SA-VA, PS-VA, PALC, IPS, PS-IPS, UB-FFS, U-IPS, FFS or PS-FFS effect.

To provide a liquid crystal compound satisfying at least one of high stability to heat, light and so forth, a high clearing point, 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 compound is represented by formula (1-1). ##STR00001##
For example, R.sup.1 and R.sup.2 are independently hydrogen, alkyl having 1 to 10 carbons, alkenyl having 3 to 10 carbons and alkoxy having 1 to 9 carbons; ring A.sup.1 is 1,4-cyclohexylene; ring A.sup.2 and ring A.sup.3 are independently 1,4-cyclohexylene or 1,4-phenylene; Z.sup.1 is a single bond or (CH.sub.2).sub.2; l is 0 or 1, m and n are 0, 1 or 2, a sum: l+m+n is 0, 1 or 2; x is 0 or 1.

Shown is a compound represented by formula (1). For example, R.sup.1 is alkyl having 1 to 15 carbons; MES is a mesogen group having at least one ring; Sp.sup.1 is a single bond or alkylene having 1 to 10 carbons; M.sup.1 is methyl; and R.sup.2, M.sup.2 and M.sup.3 are hydrogen.

##STR00001##

Provided is a liquid crystal compound satisfying at least one of physical properties such as high stability to heat and light, a high clearing point (or high maximum temperature), 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 compound, represented by formula (1): ##STR00001##
wherein, in formula (1), R.sup.1 is alkoxy having 1 to 9 carbons or the like; R.sup.2 is alkenyl having 2 to 10 carbons; Z.sup.1 and Z.sup.2 are independently a single bond, CH.sub.2CH.sub.2, CHCH or the like; and a and b are independently 0 or 1.