Liquid-crystalline (LC) media having positive dielectric anisotropy and liquid-crystal displays (LCDs) containing these media, especially displays addressed by an active matrix and in particular energy saving LC displays of the TN, PS-TN, STN, TN-TFT, OCB, IPS, PS-IPS, FFS, HB-FFS, XB-FFS, PS-FFS, SA-HB-FFS, SA-XB-FFS, polymer stabilised SA-HB-FFS, polymer stabilised SA-XB-FFS, positive VA or positive PS-VA type. The media have an improved long-term stability against UV radiation and elevated temperatures.

The invention relates to a liquid-crystalline medium which comprises at least one compound of the formula I, ##STR00001##
in which R.sup.1, R.sup.1*, Z.sup.1, Z.sup.2 and L.sup.1-3 have the meanings defined herein, and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PS-VA, PALC, FFS, PS-FFS, PS-IPS or IPS effect.

The invention relates to a liquid-crystalline medium which comprises at least one compound of the formula I, ##STR00001##
in which
R.sup.1, R.sup.1*, Z.sup.1, Z.sup.2 and L.sup.1-3 have the meanings defined herein,
and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PS-VA, PALC, FFS, PS-FFS, PS-IPS or IPS effect.

The present invention provides a liquid-crystal display device capable of maintaining a high voltage holding ratio even without an alignment film. The liquid-crystal display device of the present invention includes a pair of substrates, a liquid crystal layer which is sandwiched between the substrates and which contains a liquid crystal material, and a polymer layer which is disposed on a surface of each of the substrates and which controls the alignment of liquid crystal molecules. The outermost surfaces of both the substrates comprise substantially no alignment film. The polymer layer is formed by polymerizing one or more radical polymerizable monomer species added to the liquid crystal layer. At least one species of the one or more radical polymerizable monomer species is a biphenyl compound having a specific structure.

The invention relates to a liquid-crystalline medium which comprises at least one compound of the formula I, ##STR00001## in which R.sup.1, R.sup.1*, Z.sup.1, Z.sup.2 and L.sup.1-3 have the meanings defined herein, and to the use thereof for an active-matrix display, in particular based on the VA, PSA, PS-VA, PALC, FFS, PS-FFS, PS-IPS or IPS effect.

The present invention provides a liquid crystal alignment film not only having an excellent alignment property and stability, but also having high film strength, and thus exhibiting excellent durability and a high residual image property, a method for preparing the same, and a liquid crystal display device using the same.

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

The present invention provides a liquid crystal display device that can retain a favorable VHR and a low residual DC voltage and minimize display unevenness such as stains and image sticking, in long-term use at high temperatures. The liquid crystal display device includes a first substrate including a pixel electrode; a second substrate facing the first substrate; a liquid crystal layer sandwiched between the first substrate and the second substrate; an aromatic polyimide-based alignment film disposed on at least one of the first substrate and the second substrate; and a radical generator capable of supplying a radical to the liquid crystal layer upon being irradiated with light, the liquid crystal layer containing a liquid crystal compound with an alkenyl group, the aromatic polyimide-based alignment film containing at least one polymer selected from a polyimide and a polyamic acid and being in no contact with the pixel electrode, the at least one polymer containing an aromatic tetracarboxylic dianhydride monomer unit.

The invention provides a liquid crystal display element hardly generating drop marks at the time of producing, and having high reliability and improved properties of a liquid crystal display element such as dielectric anisotropy, viscosity, a nematic phase upper limit temperature, or rotational viscosity (.sub.1) without deteriorating the properties of the liquid crystal display element and burn-in properties of the liquid crystal display element, and a method for producing the same. In addition, according to the invention, it is possible to effectively use the liquid crystal display element as a display element of a liquid crystal TV, a monitor, and the like, due to excellent high-response speed, a low frequency of occurrence of burn-in, a low frequency of generation of drop marks at the time of the producing, excellent properties of the liquid crystal display element, and high reliability.

A vertical alignment liquid crystal display includes a first substrate, a second substrate, a liquid crystal layer located between the first substrate and the second substrate, a first and a second passivation layers respectively located at inner sides of the first and the second substrates, a common electrode layer and a pixel electrode layer respectively located on the first and the second passivation layers. The liquid crystal layer includes liquid crystal molecules, auxiliary alignment agent and a polymer network penetrating the entire liquid crystal layer. The auxiliary alignment agent makes the liquid crystal molecules in the liquid crystal layer vertically aligned on the surfaces of the first and the second substrates. The polymer network stabilizes alignment of the liquid crystal molecules and enhances vertical alignment effect of the auxiliary alignment agent to the liquid crystal molecules.