The present invention relates to a liquid crystal (LC) medium comprising a polymerizable compound, 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.

The present invention provides a polymerizable compound having high storage stability without causing crystal precipitation when added to a polymerizable composition. The present invention also provides a polymerizable composition containing the compound. When the filmy polymer produced through polymerization of the polymerizable composition is irradiated with UV light, it hardly discolors or peels from substrate. Further, the present invention provides a polymer produced through polymerization of the polymerizable composition and an optically anisotropic body using the polymer.

An object of the present invention is to provide a film capable of giving a necessary retardation without degrading the contrast. The present invention provides a retardation film formed from a composition which includes a polymer compound, a rod-like liquid crystal compound and a photo-reactive compound, wherein the polymer compound has a side chain which has one or more azo groups and/or cynnamate groups, and 3 or more and 10 or less arylene groups; the side chain further has an optionally substituted amino group, or a hydrocarbon group at the terminal; an absolute value of difference between an SP value of the polymer compound and an SP value of the photo-reactive compound is 1.1 or less; and an in-plane retardation of the film at wavelength of 550 nm is 10 nm or more and 200 nm or less.

An object of the present invention is to provide a film capable of giving a necessary retardation without degrading the contrast. The present invention provides a retardation film formed from a composition which includes a polymer compound, a rod-like liquid crystal compound and a photo-reactive compound, wherein the polymer compound has a side chain which has one or more azo groups and/or cynnamate groups, and 3 or more and 10 or less arylene groups; the side chain further has an optionally substituted amino group, or a hydrocarbon group at the terminal; an absolute value of difference between an SP value of the polymer compound and an SP value of the photo-reactive compound is 1.1 or less; and an in-plane retardation of the film at wavelength of 550 nm is 10 nm or more and 200 nm or less.

A polymer having a partial structure formed by performing radical polymerization with respect to a compound having a mesogenic group derived from at least one type of liquid crystal compound selected from a rod-like liquid crystal compound and a disk-like liquid crystal compound, and two or more polymerizable groups, in which the polymer is a branched polymer, and a composition containing the polymer, an optical film, and a liquid crystal display device.

There is provided a composition containing a discotic liquid crystal compound, a chiral agent, and a surfactant which can form a light reflecting layer formed by fixing a cholesteric liquid crystalline phase, which exhibits excellent durability under a hot and humid environment and excellent heat resistance, and has few alignment defects; a light reflecting film; a luminance-improving film; a backlight unit; and a liquid crystal display device.