Provided is a liquid crystal composition having at least one of, or a suitable balance regarding at least two of, characteristics such as a high maximum temperature, a low minimum temperature, small viscosity, suitable optical anisotropy and large dielectric anisotropy, and an AM device including the composition. The liquid crystal composition contains a specific compound having positive dielectric anisotropy as a first component, a specific compound having small viscosity as a second component, and may contain a specific compound having positive dielectric anisotropy as a third component, a specific compound having a high maximum temperature or small viscosity as a fourth component or a specific compound having negative dielectric anisotropy as a fifth component.

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.

The present invention provides a liquid crystal composition having positive dielectric anisotropy and containing at least one compound represented by general formula (LC0): ##STR00001##
and at least one compound represented by general formula (LC1):
R.sup.11A.sup.11-Z.sup.11.sub.m.sub.11A.sup.12-Z.sup.12-A.sup.13-R.sup.12(LC1)
The liquid crystal composition according to the present invention has refractive index anisotropy (n) adjusted to the desired level and a decrease in nematic phase-isotropic liquid phase transition temperature (T.sub.ni) and an increase in the nematic phase lower limit temperature are suppressed so as to achieve a sufficiently low viscosity () without degrading the nematic phase temperature range. When the liquid crystal composition of the present invention is used to produce a liquid crystal display device, a highly practical and highly reliable liquid crystal display device with high response speed and capacity for low-voltage drive is obtained.

The invention relates to compounds of the formula I, and to a liquid-crystalline medium, preferably having a nematic phase and negative dielectric anisotropy, which comprises a) one or more compounds of the formula I

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

##STR00002##

in which the parameters have the respective meanings indicated in Claim 1, to the use thereof in an electro-optical display, particularly in an active-matrix display based on the VA, ECB, PALC, FFS or IPS effect,

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.

An object of the present invention is to provide a composition which has a positive , a liquid crystal phase over a wide temperature range, a low viscosity, an excellent solubility at low temperature, high specific resistance, high voltage holding ratio, and stability against heat or light, and further provide a liquid crystal display element such as an IPS type or a TN type, which has excellent display qualities by using the composition, and in which display defects such as burn-in or drop marks are hardly caused, at a high yield. The present invention provides a composition including one or more compounds represented by General Formula (i); and a compound represented by Formula (L-1-2.2), and a liquid crystal display element using the composition and an IPS element or a FFS element using the composition.

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 high stability to ultraviolet light, or having a suitable balance regarding at least two of the characteristics, and an AM device including the composition.

The liquid crystal composition contains a quencher as an additive, and may contain a specific compound having large positive dielectric anisotropy as a first component, a specific compound having high maximum temperature or small viscosity as a second component, or a specific compound having large negative dielectric anisotropy as a third component.

The subject is to show a liquid crystal display device having characteristics such as 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 means concerns a liquid crystal display device including a first substrate, a second substrate and a liquid crystal composition having positive dielectric anisotropy, which is placed between these substrates, wherein the liquid crystal composition has a nematic phase and includes at least one compound selected from the group of compounds represented by formula (1) as a first component: ##STR00001##
in formula (1), R.sup.1 is alkyl or the like; ring A is 1,4-phenylene or the like; Z.sup.1 is a single bond or the like; X.sup.1 and X.sup.2 is hydrogen or fluorine; Y.sup.1 is fluorine or the like; and m is 0, 1, 2, 3 or 4.

A liquid crystal composition contains a specific compound having positive dielectric anisotropy as a first component, and a specific compound having large negative dielectric anisotropy as a second component, and may contain a specific compound having high maximum temperature or small viscosity as a third component, or a specific compound having large negative dielectric anisotropy and low minimum temperature as a fourth component.