Provided are a liquid crystal compound satisfying at least one of physical properties such as high stability to heat or light, a high clearing point (or high maximum temperature), low minimum temperature of a liquid crystal phase, small viscosity, large 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.

A compound is represented by formula (1):

##STR00001## In formula (1), R.sup.1 and R.sup.2 are independently hydrogen or alkyl having 1 to 15 carbons; and A.sup.1, A.sup.2 and A.sup.3 are independently 1,4-cyclohexylene or 1,4-phenylene; Z.sup.1, Z.sup.2 and Z.sup.3 are independently a single bond; Y.sup.1, Y.sup.2, Y.sup.3 and Y.sup.4 are independently hydrogen, fluorine or the like; and a, b and c are independently 0 or 1, and a sum of a, b and c is 0 to 3.

The invention relates to a liquid-crystalline medium, having particular dielectric properties, in that it has: either a dielectric constant perpendicular to the director (.sub.) in the range of 2 or more to less 8 or less and at the same time a ratio of the dielectric constant perpendicular to the director (.sub.) to the dielectric anisotropy (), i.e. (.sub./) of 1.0 or more or or a dielectric constant perpendicular to the director (.sub.) of 8 or more and a dielectric anisotropy () of 26 or less and
preferably comprises one or more compounds having a high dielectric constant perpendicular to the director (.sub.) and a high average dielectric constant (.sub.av.). These compounds are suitable for use in an electro-optical display, particularly in an active-matrix display based on the IPS or FFS effect.

The present invention provides a polymerizable cholesteric liquid crystal composition containing: one or two or more polymerizable liquid crystal compounds (I) having two or more polymerizable functional groups in the molecule; a chiral compound (III); a polymerization initiator (IV); optionally a non-silicon compound (V) having a repeating unit; and optionally one or two or more polymerizable liquid crystal compounds (II) having one polymerizable functional group. An optically anisotropic body formed from a polymerizable liquid crystal composition according to the present invention is also provided.

Compounds of formula I, and liquid-crystalline media, preferably having a nematic phase and negative dielectric anisotropy, comprising: a) one or more compounds of formula I

##STR00001## and one or more other compounds selected from: b) one or more compounds of formula II

##STR00002## and/or c) one or more compounds selected from compounds of formulae III-1 to III-4 and B

##STR00003##

Use thereof in electro-optical displays, particularly in active-matrix displays based on the VA, ECB, PALC, FFS or IPS effect and use of compounds of formula I for stabilisation of liquid-crystalline media which comprise one or more compounds of formula II and/or one or more compounds selected from compounds of formulae III-1 to III-4 and B.

Compounds of the formula I, and liquid-crystalline media, preferably having a nematic phase and negative dielectric anisotropy, comprising a) one or more compounds of the formula I

##STR00001## and one or more compounds selected from b) one or more compounds of formula II

##STR00002## and/or c) one or more compounds selected from compounds of formulae III-1 to III-4 and formula B

##STR00003##

Methods for making and using these liquid-crystalline media in electro-optical displays, particularly in active-matrix displays based on the VA, ECB, PALC, FFS or IPS effect and the displays which contain these media. Methods for stabilizing liquid-crystalline media with compounds of formula I, where the liquid-crystalline media comprise one or more compounds of the formula II and one or more compounds selected from compounds of the formulae III-1 to III-4 and formula B.

Provided are a liquid crystal composition satisfying at least one of characteristics such as high maximum temperature, low minimum temperature, small viscosity, suitable optical anisotropy, large negative dielectric anisotropy, large specific resistance, high stability to ultraviolet light and high stability to heat, or has a suitable balance regarding at least two of the characteristics; and an AM device having characteristics such as a short response time, a large voltage holding ratio, low threshold voltage, a large contrast ratio and a long service life. The liquid crystal composition may contain a specific compound having large negative dielectric anisotropy as a first component, a specific compound having high maximum temperature as a second component, a specific compound having negative dielectric anisotropy as a third component, or a specific compound having a polymerizable group as an additive component.

Disclosed are dibenzofuran and dibenzothiophene derivatives of the general formula I, ##STR00001##
in which X.sup.1, X.sup.2, W, Y, R, A, Z and m have the meaning defined in claim 1, to a process for the preparation thereof, to the use thereof as components in liquid-crystalline media, and to electro-optical display elements which contain the liquid-crystalline media according to the invention.

Provided are liquid crystal compounds and mixtures incorporating the same. The liquid crystal compounds of the invention generally comprise a cyclopentane group and at least two other rings. In one embodiment, the liquid crystal compounds of the invention comprise a cyclopentane group and at least two other rings, one of which is a fused ring system.

The present invention relates to polymers that include residues of at least one monomer represented by the following Formula (I). With reference to Formula (I), at least one of E1 and E2 independently is, or is independently substituted with, at least one reactive group, such as a (meth)acryloyl group. Monomers represented by Formula (I) and monomer residues thereof have alignment properties, such as photoalignment properties. The present invention also relates to alignment layers that include such polymers, and articles of manufacture, such as optical elements, that include one or more such alignment layers.

##STR00001##

The present invention relates to a liquid crystalline medium comprising a polymerizable compound, to a process for its preparation, to its use for optical, electro-optical and electronic purposes, in particular in liquid crystalline displays, especially in a liquid crystalline display of the polymer sustained alignment (PSA) type, and to a liquid crystalline display, especially a PSA display, comprising it.