A liquid crystal composition is provided containing a compound that is effective in preventing photolysis of the liquid crystal composition, and has high solubility in the liquid crystal composition. A liquid crystal display device including the composition is also provided. The liquid crystal composition contains a compound represented by formula (1), and a liquid crystal display device uses the composition: ##STR00001##
in which, in formula (1), R.sup.1 to R.sup.8 are hydrogen or alkyl having 1 to 4 carbons; ring A.sup.1 and ring A.sup.2 are cyclohexylene, phenylene, or naphthalenediyl; Z.sup.1, Z.sup.2 and Z.sup.3 are a single bond; and a and b are independently 1 or 2, and c is 0, 1 or 2.

To show a liquid crystal compound satisfying at least one of physical properties such as high chemical stability, a high clearing point, a low minimum temperature of a liquid crystal phase, low viscosity, large 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).

##STR00001##

The present invention relates to a switch element, which is thermoresponsive and which switches between a less transmissive state for radiant energy and a more transmissive state for radiant energy, and which comprises a liquid-crystalline medium. The invention furthermore relates to the use of the switch element for the regulation of radiant energy flow between interior spaces and the environment and for the regulation of the temperature of interior spaces. The invention furthermore relates to a liquid-crystalline medium, characterised in that it comprises 5-95% of a compound of the formula (I), in particular for use in the switch elements according to the invention.

A compound represented by formula (1), a liquid crystal composition, a liquid crystal display device are described. ##STR00001##
In formula (1), for example, the ring A.sup.1 and the ring A.sup.4 are phenylene or cyclohexylene; Z.sup.1, Z.sup.2, Z.sup.3 and Z.sup.4 are a single bond or alkylene having 1 to 6 carbons; L.sup.1 is a single bond; s and t are 0; and P.sup.1, P.sup.2, P.sup.3 and P.sup.4 are a polymerizable group.

The present invention relates to nematic liquid-crystal media of negative dielectric anisotropy which have a peak time (t.sub.max.) of 0.25 ms or less, which is determined as described in the disclosure, and which preferably have a value of the quotient of the peak time and the square of the birefringence (t.sub.max/n.sup.2) of 22 ms or less, and to the use of these liquid-crystal media in liquid-crystal displays, and to these liquid-crystal displays.

A liquid crystal composition includes one or more compounds represented by Chemical Formula 1: ##STR00001## wherein in Chemical Formula 1, A1, A2, L.sub.1 to L.sub.8, R, R, Z.sub.1 to Z.sub.3, n1, and n2 are the same as described in the specification.

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 present invention relates to liquid-crystalline media comprising one or more compounds selected from the group of compounds of formulae I, II and III, ##STR00001##
in which the parameters R.sup.1-R.sup.3, Z.sup.21, Z.sup.31, Z.sup.32 and rings A.sup.11, A.sup.12, A.sup.13, A.sup.21, A.sup.22, A.sup.31, and A.sup.32 are as defined herein, and to components comprising these media for high-frequency technology, in particular phase shifters and microwave array antennas.

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.

It is an object of the present invention to provide a liquid crystal composition having a positive as well as a liquid crystal phase in a wide temperature range, good solubility at low temperature, excellent adaptability to an ODF process, high specific resistance, a high voltage holding ratio, and stability to heat and light. In order to achieve this object, a liquid crystal composition containing a compound represented by Formula (i) and a compound represented by Formula (ii) is provided.