The invention relates to a polymerisable LC medium with flat, negative or positive optical dispersion, a polymer film with flat, negative or positive optical dispersion obtainable from such a material, and the use of the polymerisable LC medium and polymer film in optical, electro optical, electronic, semiconducting or luminescent components or devices.

A liquid crystal display device having a liquid crystal composition, requiring neither an alignment film nor alignment treatment on a substrate. The problem is solved by a low molecular weight polar compound for homogeneously aligning a liquid crystal medium relative to the substrate, for example, the low molecular weight polar compound represented by formula (1).
Formula 95
M-P(1) In formula (1), M is a nonpolar group having 1 or more carbons, and P is a polar group.

The subject is to provide liquid crystal display device having 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 liquid crystal display device having a liquid crystal alignment film formed on the opposing surfaces of a pair of substrates, and a liquid crystal composition therebetween, wherein the liquid crystal alignment film includes a polymer derived from a polyamic acid having a photodegradable group, and the liquid crystal composition includes at least one compound represented by formula (1) as a first component: ##STR00001## R.sup.1 is alkyl having 1 to 12 carbons or the like; ring A is 1,4-cyclohexylene, 1,4-phenylene or the like; Z.sup.1 is a single bond or the like; X.sup.1 and X.sup.2 are hydrogen or fluorine; Y.sup.1 is fluorine or the like; and a is 1, 2, 3 or 4.

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.

Self-aligned liquid crystal materials and structures are disclosed. The structures can exhibit piezoelectric and flexoelectric properties.

The purpose of the invention is to control, by using a colorless alignment control monomer, the alignment of liquid crystal molecules of a liquid crystal display element that does not include an alignment film, and to provide a liquid crystal composition with which the colorless alignment control monomer exhibits excellent compatibility. The invention uses a liquid crystal display element that comprises an alignment control monomer including an aromatic ester that undergoes photo-Fries rearrangement by light irradiation, and that employs a liquid crystal composition having a positive dielectric anisotropy. The invention also uses the liquid crystal composition.

Shown is a compound represented by formula (1). For example, R.sup.1 is alkyl having 1 to 15 carbons; MES is a mesogen group having at least one ring; Sp.sup.1 is a single bond or alkylene having 1 to 10 carbons; M.sup.1 is methyl; and R.sup.2, M.sup.2 and M.sup.3 are hydrogen. ##STR00001##

A liquid crystal compound comprising a specific compound having a positive dielectric anisotropy as the first component, and a specific compound having a low viscosity as a second component. Further, the liquid crystal compound may contain a specific compound having a positive dielectric anisotropy as the third component, a specific compound having a maximum temperature or a low viscosity as the fourth component, or a specific compound having a negative dielectric anisotropy as the fifth component.

A liquid crystal composition includes a polymerizable compound (or polymer) and a polar compound, where the homeotropic alignment of liquid crystal molecules can be achieved by the action of these compounds, and a liquid crystal display device includes such a composition. A nematic liquid crystal composition has positive dielectric anisotropy and includes a polymerizable compound as a first additive and a polar compound as a second additive, and the composition may include a specific liquid crystal compound having a large positive dielectric anisotropy and a specific liquid crystal compound having a high maximum temperature or a small viscosity, and a liquid crystal display device includes such a 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 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.