A liquid crystal cell includes a pair of facing substrates having a photo-alignment film, and a liquid crystal layer. The liquid crystal material contains a liquid crystal compound having a structure represented by any of the following chemical formula (1-1) and chemical formula (1-2):

A.sub.1-C.sub.nF.sub.2nX.sub.1-A.sub.2(1-1)

A.sub.1-X.sub.1C.sub.nF.sub.2n+1(1-2)

in the chemical formula (1-1), A.sub.1 is a phenyl group, a phenylene group, a naphthyl group, a naphthylene group, a cyclohexyl group, or a cyclohexylene group; A.sub.2 is a phenyl group, a phenylene group, a naphthyl group, or a naphthylene group (provided that a hydrogen atom in functional groups A.sub.1 and A.sub.2 is optionally substituted by a fluoro group, a chloro group, a bromo group, a methyl group, or an ethyl group); X.sub.1 is an oxygen atom or a direct bond; and n is an integer of 1 to 6. The photo-alignment film is obtained by subjecting a polymer film to a photo-alignment treatment.

The disclosure shows a liquid-crystal composition having at least one or suitable balance regarding at least two of characteristics such as high maximum temperature of nematic phase, low minimum temperature thereof, small viscosity, suitable optical-anisotropy, large dielectric-anisotropy, large specific resistance, high stability to ultraviolet light and heat; and an AM device including the composition and having short response time, large voltage holding ratio, large contrast ratio or long life. The liquid-crystal composition has the nematic phase and contains a specific compound having small optical-anisotropy and large positive dielectric-anisotropy as first component, a specific compound having small viscosity as second component, and may contain a specific compound having high maximum temperature or small viscosity as third component, a specific compound having large positive-dielectric anisotropy as fourth component or a specific compound having negative dielectric-anisotropy as fifth component, and a liquid-crystal display device includes the composition.

The invention relates to a liquid-crystalline medium, preferably having a nematic phase and negative dielectric anisotropy, which comprises a) one or more compounds of formula I ##STR00001## and b) one or more compounds selected from the group of compounds of the formulae II and III ##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, IPS or FFS effect, to displays of this type which contain a liquid-crystalline medium of this type, and to the use of the compounds of formula I for reduction of the dispersion of the birefringence of a liquid-crystalline medium which comprises one or more compounds of the formulae II and/or III.

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

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 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.

To show a liquid crystal composition satisfying at least one of 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, high stability to ultraviolet light and heat; a liquid crystal composition having a suitable balance regarding at least two of the characteristics; and an AM device having a short response time, a large voltage holding ratio, a large contrast ratio, a long service life and so forth. The liquid crystal composition has the nematic phase and contains a specific compound having large dielectric anisotropy as a first component, and may contain a specific compound having a high maximum temperature or small viscosity as a second component, and a specific compound having large dielectric anisotropy as a third component, and a liquid crystal display device includes the composition.

There is provided a liquid crystal composition having a dielectric anisotropy () large in absolute value, a sufficiently low viscosity (), a sufficiently low rotational viscosity (.sub.1), and a high elastic constant (K.sub.33) without decreased refractive index anisotropy (n) or nematic phase-isotropic liquid phase transition temperature (T.sub.ni). A liquid crystal display device, such as a VA mode liquid crystal display device, including the liquid crystal composition has high response speed and good display quality with few or no display defects. The liquid crystal display device including the liquid crystal composition is useful as an active-matrix liquid crystal display device and is applicable as a liquid crystal display device such as a VA mode or PSVA mode liquid crystal display device.

There is provided a liquid crystal composition having the following properties without reductions in refractive index anisotropy (n) and nematic phase-isotropic liquid phase transition temperature (T.sub.ni): sufficiently small viscosity (), sufficiently small rotational viscosity (1), a large elastic constant (K.sub.33), and negative dielectric anisotropy () with a large absolute value. There is also provided a liquid crystal display device of, for example, a VA type in which such a liquid crystal composition is used and which has a high response speed and excellent display quality with defective display being eliminated or reduced. The liquid crystal display device using the liquid crystal composition of the present invention is useful as an active-matrix liquid crystal display device and can be used in liquid crystal display devices of, for instance, a VA mode and PSVA mode.