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.

The present invention relates to a liquid crystal alignment composition for the preparation of a liquid crystal alignment film having enhanced alignment property and stability and exhibiting a high voltage holding ratio, a method for preparing a liquid crystal alignment film using the same, and a liquid crystal alignment film and a liquid crystal display device using the same.

Provided are a composition for a liquid crystal alignment agent, a manufacturing method of a liquid crystal alignment film, a liquid crystal alignment film using the same, and a liquid crystal display device including the liquid crystal alignment film. More specifically, there are provided the manufacturing method of a liquid crystal alignment film capable of providing the liquid crystal alignment film in which light irradiation energy is able to be reduced, and alignment characteristic and stability are excellent and the voltage holding ratio and electrical characteristics are also excellent through a simple process including applying and drying the composition for a liquid crystal alignment agent on the substrate, directly performing light irradiation to conduct alignment treatment while a high-temperature heat treatment process is omitted, followed by curing by heat treatment, the liquid crystal alignment film, and the liquid crystal display device including the same.

Provided is a method of manufacturing new liquid crystal display device according to an embodiment of the present invention. Firstly, an alignment film is formed on a substrate. The alignment film is divided into a first alignment film formed using, as a precursor, liquid-state polyimide that contains a photodecomposition substance and a second alignment film formed using, as a precursor, a polyamic acid that does not contain a photodecomposition substance. UV light is irradiated to the alignment film, and decomposed substances formed by irradiation of the UV light is removed by an at least two-step removing process. By the method of manufacturing a liquid crystal display device according to the exemplary embodiment of the present disclosure, bright spots are minimized in pixels and a brightness of black is lowered, so that a liquid crystal display device with a high contrast ratio can be realized.

Shown is a liquid crystal display 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. A polymer sustained alignment mode liquid crystal display device includes an electrode group formed on one or both of a pair of substrates arranged with facing each other, a plurality of active devices connected to the electrode group, liquid crystal alignment films formed on surfaces facing each other of the pair of substrates, respectively, and a liquid crystal composition interposed between the pair of substrates, in which the liquid crystal alignment film contains at least one polymer selected from polyorganosiloxane, polyamic acid, polyamic acid ester and polyimide, and the liquid crystal composition contains a specific compound having negative dielectric anisotropy as a first component.

An alignment film for liquid crystal display device includes a first portion positioned towards to the liquid crystal layer and a second portion positioned away from the liquid crystal layer. The first portion provides improved anchoring force while the second portion exhibits a lower volume resistance than the first portion. Thus, AC image sticking and DC image sticking can be minimized at the same time.

An alignment layer composition including a copolymer of a dianhydride compound and a diamine compound, the copolymer including a repeating unit represented by chemical formula (1); and a repeating unit represented by chemical formula (2): ##STR00001##
wherein R.sub.1 is a tetravalent organic group derived from an alicyclic dianhydride or an aromatic dianhydride, and wherein R.sub.1 includes a phenyl ester group.

A liquid crystal display device is provided. An exemplary embodiment of the present invention provides a liquid crystal display device including: a first substrate; a thin film transistor disposed on the first substrate; a first electrode connected to the thin film transistor; and a first alignment layer disposed on the first electrode. The first alignment layer includes: a copolymer formed from at least one compound of cyclobutane dianhydride (CBDA) and a cyclobutane dianhydride derivative, and a first diaminean including alkylene group (C.sub.kH.sub.2k, k being a natural number); and a cross-linking agent including an alkylene group (C.sub.nH.sub.2n, n being a natural number), wherein the copolymer includes polyimide.

A photoalignment agent includes: a copolymer obtained from at least one of cyclobutane dianhydride (CBDA) and a cyclobutane dianhydride derivative, and a diamine; and a cross-linking agent including an alkylene group C.sub.nH.sub.2n, n being a natural number.

The present invention provides a liquid crystal display device in which even in the case of using a photo-alignment technique, excellent afterimage characteristics can be stably obtained. Provided is a liquid crystal display device including a TFT substrate having an alignment film, an opposed substrate which is arranged to face the TFT substrate and on which an alignment film is formed, and a liquid crystal layer sandwiched between the alignment films, wherein the alignment films are materials that can provide a liquid crystal alignment restraining force by irradiating polarized light, and the ratio of oxygen atoms on the surface of the alignment film is higher than that in the alignment film.