The present invention provides a liquid crystal alignment agent having high thermal stability and high solvent solubility, and a liquid crystal panel in which occurrence of ghosting and stain and a decrease in contrast are suppressed even under environments at high temperatures long period of time. The present invention is a liquid crystal alignment agent including a copolymer including a structure represented by a chemical formula (1) below, and a solvent. In the formula, X is a specified structure including a cyclic hydrocarbon group, Y.sup.1 is a specified structure including a cyclic hydrocarbon group, R.sup.1 represents a homogeneous alignment group, a homeotropic alignment group, or a photoreactive functional group, and Z.sup.1 and Z.sup.2 are the same or different, and represent an —NH— group, an —O— group, or a —S— group. ##STR00001##

Compositions of azobenzene-containing, photomechanically active, copoly(amic acids) and linear copolyimides including an azobenzenediamine, a rigid dianhydride, and a flexible dianhydride are provided; and methods of making the same.

A photo-aligning liquid crystal alignment layer formed by using a photo-aligning liquid crystal aligning agent containing polyamic acid or a derivative thereof which is synthesized by using tetracarboxylic acid dianhydride having no photoreactive structure having a specific structure and diamine having no photoreactive structure having a specific structure together with at least one of tetracarboxylic acid dianhydride having a photoreactive structure and diamine having a photoreactive structure can reduce storage of residual DC in a liquid crystal display device. Further, the above alignment layer can shorten the relaxation time and can prevent afterimages from being generated.

The present invention provides an alignment film having excellent heat resistance and capable of suppressing generation of defects such as image sticking and stain, and a liquid crystal display device including the alignment film. The alignment film of the present invention contains a copolymer containing a repeating structural unit represented by the following formula (1), wherein X1 and X2 may be the same as or different from each other and are each represented by, for example, any of the following formulas (X-P1) to (X-P4); and Y is represented by, for example, any of the following formulas (Y-P1) to (Y-P4).

##STR00001##

The present invention relates to a liquid crystal display device including a pair of a substrate arranged opposite to each other, an electrode group disposed on one side or both sides of the pair of substrates facing each other, a plurality of active devices connected to the electrode group, a liquid crystal alignment film disposed on each facing side of the pair of substrates, and a liquid crystal layer interposed between the pair of substrates, wherein the liquid crystal alignment film is manufactured by irradiating linearly polarized light to a film obtained from polyamic acid or a derivative thereof having a photoisomerization structure in the main chain or a film being subject to heat-baking so as to provide alignment-controlling capability, and the liquid crystal layer is a liquid crystal composition having negative (−) dielectric anisotropy. By the present invention, a liquid crystal display device having improved image sticking characteristics and good alignment stability is provided.

The present invention provides a liquid crystal alignment agent having high thermal stability and high solvent solubility, and a liquid crystal panel in which occurrence of ghosting and stain and a decrease in contrast are suppressed even under environments at high temperatures long period of time. The present invention is a liquid crystal alignment agent including a copolymer including a structure represented by a chemical formula (1) below, and a solvent. In the formula, X is a specified structure including a cyclic hydrocarbon group, Y.sup.1 is a specified structure including a cyclic hydrocarbon group, R.sup.1 represents a homogeneous alignment group, a homeotropic alignment group, or a photoreactive functional group, and Z.sup.1 and Z.sup.2 are the same or different, and represent an NH group, an O group, or a S group.

##STR00001##

A healable and recyclable polyimide polymer resin includes a chemical structural unit represented by formula (I), which is defined in the description. The chemical structural unit represented by the formula (I) bonds to at least one condensation-polymerizable monomer, so as to form the healable and recyclable polyimide polymer resin, and the condensation-polymerizable monomer is a diamine monomer or a dianhydride monomer.

A tunable film apparatus is provided. The apparatus includes: first and second layers; a tunable liquid crystal layer disposed between the first and second layers; and a tuner configured to tune the liquid crystal layer to adjust a light diffusing angle of the tunable liquid crystal layer.

The present invention provides a liquid crystal display device that includes: a pair of substrates; a liquid crystal layer held between the substrates; and an alignment film disposed on a liquid crystal layer side surface of at least one of the substrates, the liquid crystal layer containing a liquid crystal material that has a nematic-isotropic phase transition temperature of 75 C. or lower and a nematic phase temperature range narrower than 100 C., the alignment film containing a first polymer and a second polymer, the first polymer having in its main chain at least one selected from a polyamic acid structure and a polyimide structure or a polysiloxane structure, the second polymer being obtained by polymerizing at least one monomer including at least one monomer containing an azobenzene group.

A liquid crystal cell according to the present invention includes two substrates facing each other and a liquid crystal layer between the substrates. The substrates have a photo-alignment film on at least one of opposing surfaces of the substrates. The photo-alignment film includes a polymer having a polyamic acid as a main chain. The polyamic acid is obtained through polymerization of a tetracarboxylic dianhydride having a bent structure and a diamine compound having an azobenzene group. The liquid crystal layer includes a first liquid crystal compound having an unsaturated bond and a second liquid crystal compound having at least one structure selected from the group consisting of structures represented by the following chemical formulas (1-1) and (1-2) and has a nematic-isotropic phase transition temperature of 90 C. or more.

(Formula 1-1) and (Formula 1-2)

##STR00001##