The invention is a liquid crystal composition satisfying at least one of characteristics or having a suitable balance regarding at least two of the characteristics such as a high maximum temperature of a nematic phase, a low minimum temperature of the nematic phase, small viscosity, suitable optical anisotropy, large dielectric anisotropy, large specific resistance, and high stability to ultraviolet light and heat. The liquid crystal composition has the nematic phase, and contains a specific compound having large dielectric anisotropy as a first component and a specific compound having small viscosity as a second component, and may contain a specific compound having a high maximum temperature or small viscosity as a third component, and a specific compound having large dielectric anisotropy as a fourth component, and a liquid crystal display device includes the composition.

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.

A polymerizable compound-containing liquid crystal composition of the present invention relates to a liquid crystal composition containing a polymerizable compound represented by general formula (I) and a compound represented by general formula (II) and can be used for a liquid crystal display device imparted with liquid crystal aligning ability by polymerization. The polymerizable liquid crystal composition is required to cause no precipitation in a wide temperature range and have a low viscosity corresponding to fast switching, and a liquid crystal display device using the composition is required to have more stable alignment after polymerization and to cause no defect in display characteristics. In the present invention, the problems can be solved using a specified compound.

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.

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.

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 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.

A liquid crystal composition includes one or more of compounds represented by general formula (i) below and one or more of compounds represented by general formula (ii) below. In the formulae, R.sup.11a and R.sup.21a each independently represent an alkyl group having 1 to 8 carbon atoms where one CH.sub.2 or two or more non-adjacent CH.sub.2 in the alkyl group may each independently be substituted with CHCH, CC, O, CO, COO, or OCO; one or more hydrogen atoms in the alkyl group may be substituted with a fluorine atom or a chlorine atom; X.sup.11a, X.sup.12a, X.sup.13a, X.sup.14a, and X.sup.21a each independently represent a hydrogen atom or a fluorine atom; A.sup.21a, A.sup.22a, and A.sup.23a each independently represent a trans-1,4-cyclohexylene group or a 1,4-phenylene group whose hydrogen atom may be substituted with a fluorine atom or a chlorine atom. ##STR00001##

There is provided a liquid crystal composition having a sufficiently low viscosity (), a sufficiently low rotational viscosity (1), a high elastic constant (K.sub.33), and negative with a high absolute value without decreasing the refractive index anisotropy (n) and the nematic phase-isotropic liquid phase transition temperature (T.sub.ni); and a liquid crystal display device with a VA mode or the like that uses the liquid crystal composition and has high display quality and high response speed. The liquid crystal display device that uses the liquid crystal composition of the present invention has a distinguished feature of high-speed response and is particularly useful as an active matrix driving liquid crystal display device. The liquid crystal display device is applicable to a VA mode, PSVA mode, PSA mode, IPS mode, or ECB mode liquid crystal display device.

There is provided a liquid crystal composition containing at least any one of compounds represented by General Formula (i) and at least any one of compounds represented by General Formula (ii). ##STR00001##