The present invention relates to a liquid-crystalline medium (LC medium), to the use thereof for electro-optical purposes, and to LC displays containing this medium.

The invention relates to a liquid-crystalline medium based on a mixture of polar compounds having positive dielectric anisotropy, characterised in that it comprises one or more compounds of the formula I in a total concentration of ≥40%, ##STR00001##
in which the parameters have the meanings indicated in claim 1, and to the use of the liquid-crystalline medium for electro-optical purposes, in particular in liquid-crystal light valves for lighting devices for motor vehicles, and to liquid-crystal light valves which comprise this medium and lighting devices for motor vehicles which contain such liquid-crystal light valves.

A liquid crystal composition without requiring an alignment film or alignment treatment on a substrate. The problem is solved by a low molecular weight polar compound capable of homogeneously aligning a liquid crystal medium relative to the substrate, for example, a low molecular weight polar compound represented by formula (1):
M-P(1) In formula (1), M is a nonpolar group having 1 or more carbons, and P is a polar group.

A liquid crystal display device having a liquid crystal composition, requiring neither an alignment film nor alignment treatment on a substrate. The problem is solved by a low molecular weight polar compound for homogeneously aligning a liquid crystal medium relative to the substrate, for example, the low molecular weight polar compound represented by formula (1).
Formula 95
M-P(1) In formula (1), M is a nonpolar group having 1 or more carbons, and P is a polar group.

The problem is to provide a polymerizable compound having suitable polymerization reactivity, a high conversion ratio, low polymerization starting temperature, and high solubility in a liquid crystal composition; a liquid crystal composition containing the compound; and a liquid crystal display device including the composition.

A means thereof includes a compound represented by formula (1) and a liquid crystal composition containing the compound.

##STR00001##

In formula (1), R.sup.1, R.sup.2 and R.sup.3 are independently alkyl or the like; n is 0 or the like; ring A.sup.1 is phenyl or the like, and ring A.sup.2 and ring A.sup.3 are independently 1,4-phenylene or the like; Z.sup.1 and Z.sup.2 are independently a single bond or the like; Sp.sup.1 to Sp.sup.4 are a single bond or the like; a is 1 or the like; c, d and e are independently 0 or 1, and a sum of c, d and e is 1 or the like; and P.sup.1 to P.sup.4 are a polymerizable group, and at least one of P.sup.1 to P.sup.4 is a polymerizable group represented by formula (P-1).

##STR00002##

A means is a compound represented by formula (1) , a liquid crystal composition containing the compound, and a liquid crystal display device including the composition.

##STR00001##

In formula (1), R.sup.1 and R.sup.2 are independently alkyl having 1 to 15 carbons or the like; ring A.sup.1, ring A.sup.2 and ring A.sup.3 are independently 1,4-cyclohexylene, 1,4-phenylene or the like; and Z.sup.1, Z.sup.2 and Z.sup.3 are independently a single bond or the like.

A liquid crystal composite that contains a liquid crystal composition satisfying at least one of characteristics such as high maximum temperature, low minimum temperature, small viscosity, large optical anisotropy and large positive dielectric anisotropy, and that is suitable for dimming, or having a suitable balance regarding at least two of the characteristics; and a liquid crystal dimming device having the liquid crystal composite. The liquid crystal composite contains a polymer and a liquid crystal composition containing a specific compound having large positive dielectric anisotropy. The liquid crystal composite may further contain a specific compound having high maximum temperature or low minimum temperature; or a specific compound having large negative dielectric anisotropy.

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 dielectric anisotropy and a short helical pitch, or the liquid crystal composition having a suitable balance regarding at least two of the characteristics; and an AM device including the composition. The liquid crystal composition contains a specific optically active compound as an additive, and a specific compound having high maximum temperature or small viscosity as a first component, and may contain a specific compound having positive dielectric anisotropy as a second component, or a specific compound having negative dielectric anisotropy as a third component.

A liquid crystal compound is represented by formula (1): ##STR00001## In formula (1), R.sup.1 is alkyl or the like; ring A.sup.1 and ring A.sup.2 are independently 1,4-cyclohexylene, 1,4-phenylene or the like; Z.sup.1, Z.sup.2 and Z.sup.3 are independently a single bond, CF.sub.2O or the like; X.sup.1 is fluorine, chlorine, CF.sub.3 or the like; L.sup.1 and L.sup.2 are independently hydrogen, fluorine or the like; a and b are independently 0, 1, 2 or 3; and W is a group represented by formula (1a) or formula (1b); ##STR00002## In formula (1a) and formula (1b), L.sup.3 to L.sup.8 are independently hydrogen, fluorine or the like.

A liquid crystalline compound, a liquid crystal composition, and a liquid crystal display element are provided. The liquid crystalline compound satisfying at least one physical property among high stability against heat and light, high transparency, low minimum temperature of the liquid crystal phase, low viscosity, proper optical anisotropy, negatively large dielectric anisotropy, proper elastic constant, good compatibility with other liquid crystalline compounds at room temperature and low temperature. The liquid crystalline compound represented by formula (1).

##STR00001##