Surface relief gratings have been optically inscribed on azopolymer films on the interior surface of an empty liquid crystal (LC) cell. Uniform LC alignment is observed in the inscribed regions when the cell is filled. Since the microgrooves are on both sides, this may provide a higher degree of order than other techniques. The stability of the relief gratings and the transmittance of the azopolymer films can be further improved by photobleaching. This alignment technique could have useful applications in the in-plane switching LC displays.

The photopolymer material of poly(vinyl cinnamate) (PVCi) has been used to investigate the contribution of the anisotropic van der Waals force to the azimuthal anchoring energy in a pentyl cyanobiphenyl (5CB)/PVCi system. The optical anisotropy of a PVCi film is precisely controlled by varying the exposure time of linearly polarized UV light, and the azimuthal anchoring energy in the film is estimated by measuring the width of the Néel wall. The result shows that the azimuthal anchoring energy in the 5CB/PVCi system increases exponentially with increasing optical anisotropy, indicating the existence of additional contributions to the LC alignment.

In-plane switching liquid crystal displays (IPS-LCDs) have been fabricated by a photo-alignment method using poly (vinyl cinnamate), and the effect of the azimuthal anchoring energy on the electrooptical performance has been studied theoretically and experimentally. The results show a large reduction in the driving voltage of IPS samples with decreasing azimuthal anchoring energy, which demonstrates the usefulness of the photo-alignment method for fabricating IPS-LCDs.

The photopolymer material of polyvinyl cinnamate) (PVCi) has been used to align liquid crystal molecules using linearly-polarized UV light, and the LC alignment mechanism on the films has been investigated. Comparing the LC alignment on rubbed PVCi films with that on UV-exposed PVCi film, it is shown that the side chains of PVCi molecules strongly interact with the LC molecules on the PVCi films and thus the alignment mechanism on linearly-polarized UV-exposed PVCi films is due to the anisotropic van der Waals interaction between LC molecules and optically-anisotropic PVCi films arising from the photo-induced anisotropic side chain distribution on the films. We also study the thermal stability of UVexposed PVCi films, and clarify the improvement of the thermal stability with increasing UV exposure energy.

ABSTARCTThe photopolymer materials of poly(vinyl cinnamate)(PVCi) and polyimides showing homeotropic liquid crystal (LC) alignment have been used to control LC alignment on these films using linearly-polarized (LP-) UV exposure, and the LC alignment mechanism including pretilt angle generation on the films has been discussed. In the case of PVCi, an important contribution of non-dimerized side chains of PVCi molecules to the LC alignment is pointed out. On the other hand, LC alignmemnt on homeotropically alignment polymer films exposed to LP-UV light is shown to be determined through the interaction of LC with alkyl branches attached to the polymer. It is also shown that the photo-alignment method using these photopolymer matrerials are very promising technique for the fabrication of some attractive LCD modes such as in-plane switching and vertically-aligned display modes, and an example of the application of the photo-alignment method to the fabrication of in-plane switching device is presented.