고성능 LCD를 위한 광배향과 셀 모드

Abstract

Alignments of liquid crystals in LCD panel industries are of classical research issues, but there are no reliable technologies available as to date, except for the rubbing process that are used in the commercial applications. This review will focus on recent progresses made in photoalignment and alignment structure of cells. Photoalignment utilize polarized light to modify the surface structure of materials, which can be categorized to photoisomerization, photodegradation, photodimerization and/or surface relief grating. Photoisomerization uses the cis/trans transition of isomers of azo-compounds; photodegradation degrades the polyimide film by shining polarized light; photodimerization usually cyclize the neighboring double bonds with cinnamates or cumarine group; and surface relief grating forms surface fringes on the film of azo-compounds. All these methods can control the alignment states of liquid crystals, governed by pretilt angles and anchoring energies of liquid crystals on the surfaces. In addition, some of the recently proposed cell modes for a wide viewing angle and a fast response are also introduced.