Disclosed are a liquid crystal composition and a liquid crystal display device. The liquid crystal composition comprises at least one compound of general formula I, at least one compound of general formula II, at least one compound of general formula III, and at least one compound of general formula IV. By compounding the four compounds, the composition can have advantages of a wide temperature range of nematic phase, a low viscosity and a low threshold voltage, and the liquid crystal display element can have a short response time and great power saving performance.

A stabilizer represented by formula I, wherein M represents cyclopentyl, cyclobutyl or cyclopropyl; Z.sub.1 and Z.sub.2 each independently represent a single bond, CH.sub.2, CH.sub.2CH.sub.2, O, CH.sub.2O, OCH.sub.2 or COO; ##STR00001## represents one or two of ##STR00002## and n represents 0, 1 or 2. ##STR00003##

The invention relates to a polymerisable LC medium with flat, negative or positive optical dispersion, a polymer film with flat, negative or positive optical dispersion obtainable from such a material, and the use of the polymerisable LC medium and polymer film in optical, electro optical, electronic, semiconducting or luminescent components or devices.

Liquid-crystalline media comprising one or more compounds of formula T

##STR00001##

as defined in claim 1, and high-frequency components comprising these media, especially microwave components for high-frequency devices, such as devices for shifting the phase of microwaves, tunable filters, tunable metamaterial structures, and electronic beam steering antennas, e.g. phased array antennas.

The invention relates to a liquid-crystalline medium, in particular based on a mixture of polar compounds, and to the use thereof for an active-matrix display, in particular based on the VA, SA-VA, IPS, PS-IPS, FFS, PS-FFS, UB-FFS or PS-UB-FFS effect.

There is provided an element which has large dielectric anisotropy and low dielectric loss in a high frequency range, has high reliability, and is used for phase control of an electromagnetic wave signal with a frequency of 1 MHz to 400 THz. An element in which a liquid crystal composition contains a compound represented by the following Formula (1) and has a refractive index anisotropy of 0.30 or more at a wavelength of 589 nm, and a polyimide alignment film contains 10% or more of a repeating unit represented by the following Formula (2) with respect to all repeating units:

##STR00001##

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.

A device using a liquid crystal medium exhibiting an optically isotropic liquid crystal phase, particularly, a blue phase liquid crystal medium for polarized light control application, in which reduction of an effective dielectric constant in a high frequency region is suppressed. A liquid crystal composition contains achiral component T, and has a liquid crystal phase optically exhibiting isotropy, in which achiral component T contains at least one compound selected from the group of compounds represented by formula (1) as a first component, at least one compound selected from the group of compounds represented by formula (2) and formula (3) as a second component, and is used for optical switching for controlling retardation by electric field-induced birefringence.

Compounds of the formula I,

##STR00001##

in which Y.sup.1 denotes O or CH.sub.2, and the groups R.sup.1, L.sup.1 to L.sup.6 and X.sup.1 have the meanings indicated in claim 1. A process for the preparation thereof, and liquid-crystalline media comprising at least one compound of the formula I and electro-optical displays containing a liquid-crystalline medium this type. The compounds of the formula I include, as structural element, a combination of a 1,4-substituted cyclohexene ring besides a dioxane or tetrahydropyran ring and a substituted biphenyl group.

The subject is to provide liquid crystal display device having a short response time, a large voltage holding ratio, a low threshold voltage, a large contrast ratio, a long service life and a small flicker rate. The liquid crystal display device having a liquid crystal alignment film formed on the opposing surfaces of a pair of substrates, and a liquid crystal composition therebetween, wherein the liquid crystal alignment film includes a polymer derived from a polyamic acid having a photodegradable group, and the liquid crystal composition includes at least one compound represented by formula (1) as a first component: ##STR00001## R.sup.1 is alkyl having 1 to 12 carbons or the like; ring A is 1,4-cyclohexylene, 1,4-phenylene or the like; Z.sup.1 is a single bond or the like; X.sup.1 and X.sup.2 are hydrogen or fluorine; Y.sup.1 is fluorine or the like; and a is 1, 2, 3 or 4.