The present invention provides a compound represented by the general formula (i), which has a partial structure K.sup.i1 represented by one of the general formulae (K-1) to (K-6) and has a ring B with at least one P-Sp- group and with at least one R.sup.i2 (R.sup.i2 denotes a linear or branched alkyl group having 2 to 10 carbon atoms or a linear or branched halogenated alkyl group having 2 to 10 carbon atoms, CH.sub.2 in the alkyl or halogenated alkyl group is optionally substituted with CHCH, O, COO, or OCO, but O is not adjacent to another O). Thus, the compound in a liquid crystal composition adsorbs to substrates between which the liquid crystal composition (a liquid crystal layer) exists. The compound can hold vertically aligned liquid crystal molecules, can improve alignment stability, and can ensure low-temperature storage stability.

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 present invention relates to a liquid crystal (LC) medium comprising a terphenyl compound and at least two polymerizable compounds, to a process for its preparation, to its use for optical, electro-optical and electronic purposes, in particular in LC displays, especially in an LC display of the polymer sustained alignment (PSA) type, and to an LC display, especially a PSA display, comprising it.

To provide a liquid crystal display device that has a high off-response speed and a good balance between drive voltage and transmittance, is stable over time, and also has a high voltage holding ratio. A liquid crystal display device in which a liquid crystal layer containing a polymer network (A) and a liquid crystal composition (B) is disposed between two substrates having an electrode on at least one side thereof and having transparent properties on at least one side thereof, and the loss factor (tan ) (loss modulus/storage modulus) of the liquid crystal layer calculated from the storage modulus (Pa) and the loss modulus (Pa) in a sinusoidal vibration measured with a rheometer at 25 C. and at a measurement frequency of 1 Hz ranges from 0.1 to 1.

The present invention provides a liquid crystal display device that includes a retardation layer with excellent thermal stability and suppresses a decrease in contrast ratio caused by scattering even when the retardation layer has been formed by polymerizing reactive monomers. The liquid crystal display device includes a pair of substrates and a liquid crystal layer held between the substrates. At least one of the substrates includes a retardation layer that contains a polymer of at least one type of monomer. The at least one type of monomer includes a photo-alignment monomer represented by a certain formula.

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 negative dielectric anisotropy, large specific resistance, high stability to ultraviolet light and high stability to heat, or has a suitable balance regarding at least two of the characteristics; and an AM device having characteristics such as a short response time, a large voltage holding ratio, low threshold voltage, a large contrast ratio and a long service life. The liquid crystal composition may contain a specific compound having large negative dielectric anisotropy as a first component, a specific compound having high maximum temperature as a second component, a specific compound having negative dielectric anisotropy as a third component, or a specific compound having a polymerizable group as an additive component.

A liquid crystal composition that satisfies at least one of characteristics such as a high maximum temperature, a low minimum temperature, a wide temperature range of a liquid crystal phase, a small viscosity, a large optical anisotropy, a large positive or negative dielectric anisotropy, a large specific resistance, a high stability to light, a high stability to heat and a large elastic constant or that is suitably balanced between at least two of these characteristics. The means is use of a liquid crystal composition that includes a specific compound having a high maximum temperature or a small viscosity as a first component, and that may include a specific compound having a large positive dielectric anisotropy as a second component, or a specific compound having a large negative dielectric anisotropy as a third component or a specific compound having a polymerizable group as a first additive.

A polar compound having high chemical stability, high capability of aligning liquid crystal molecules, high solubility in a liquid crystal composition, and a large voltage holding ratio when the compound is used in a liquid crystal display device; and a composition containing the compound. The compound is represented by formula (1). In formula (1), for example, P.sup.1 is a group represented by any one of formulas (1b) to (1i), P.sup.2 is a group represented by formula (1d), Sp.sup.1 and Sp.sup.2 are a single bond, Z.sup.1, Z.sup.2, Z.sup.3, Z.sup.4 and Z.sup.5 are COO, and ring A.sup.1, ring A.sup.2, ring A.sup.3 and ring A.sup.4 are 1,4-phenylene:

##STR00001##

A liquid crystal composition that satisfies at least one of characteristics such as a high maximum temperature, a low minimum temperature, a small viscosity, a suitable optical anisotropy and a large negative dielectric anisotropy, or that has a suitable balance between at least two of these characteristics, and an AM device including this composition. The nematic liquid crystal composition includes a specific compound having a large negative dielectric anisotropy as a first component and a specific compound having a small viscosity as a second component, and may include a specific compound having a negative dielectric anisotropy as a third component, and a specific compound having a high maximum temperature or a small viscosity as a fourth component, or a specific compound having a polymerizable group as an additive.

A problem to be solved by the present invention is to provide a liquid crystal composition excellent in vertical alignment and compatibility and to provide a liquid crystal display device produced using the same. The problem is solved by a liquid crystal composition containing one or two or more kinds of self-aligning polymerizable monomers and one or two or more kinds of polymerizable monomers (or polymerizable compounds) having a specific chemical structure, and a liquid crystal display device produced using the same, specifically a liquid crystal composition containing a polymerizable monomer represented by General Formula (I) and a spontaneously aligning monomer which has a chemical structure different from that of the polymerizable monomer represented by General Formula (I), and has a polar group, and a liquid crystal display device containing the same.