Photoinduced surface alignment for liquid crystal displays

Abstract

This review examines surface alignment of liquid crystals by exposure to light. Two distinct effects are discussed: illumination with polarized light induces a surface anisotropy to an alignment layer and hence a preferred in-plane orientation of the overlying liquid crystal director. Alternatively, a photochemical reaction of the alignment surface changes the liquid crystal anchoring conditions from homogeneous to homeotropic. We discuss how cis/trans isomerization, crosslinking and photodegradation are used to produce photoalignment layers and we show how the performance of the materials can be optimized by molecular design. Pretilted alignment is discussed and theoretical models are introduced to explain the photoalignment process. A range of display and non-display applications for photoalignment is presented.

Synthesis and Studies on Certain Semiconducting Copolyesteramides Containing 2, 5-Pyridine Dicarboxylic Acid and their Photocross linkable Blend Nanofibers

“…Photocrosslinkable polymers find potential applications in the preparation of photo curable coating, photocrosslinked hydrogels, optical lithographic materials, photo sensitizers, photo resists, photorefractive materials [6 ] and information storage devices. Polymers having photodimerizable groups find applications in immobilization of enzymes [7][8][9][10][11][12][13]. In the present investigation a. c conductivity of some of the synthesized novel random copolyesteramides containing 2, 5-pyridine dicarboxylic acid moiety in their main chain was determined using LCR meter.…”

The effect of phenoxymethyl side groups on the liquid crystal alignment behavior of polystyrene derivatives

“…[1][2][3][4][5][6] The mechanical rubbing of polyimide (PI) surfaces is the most commonly used technique for producing LC alignment layers, 7-21 which can induce stable homogeneous planar LC alignment 19,20 or homeotropic LC alignment. 14,18 The LC alignment properties such as the pretilt angle and electro-optical (E-O) performance on polyimide surfaces are known to be affected by the molecular structure of the polyimide such as the flexibility of the polymer backbone, isomeric structure of the mesogen end groups, spacer length, and spacer conformation in the side chains.…”

Photo-alignment of Low-molecular Mass Nematic Liquid Crystals on Photochemically Bifunctional Chalcone-epoxy Film by Irradiation of a Linearly Polarized UV Light

“…Therefore, the photo-alignment technique for LC display has received much attention in recent years because of its clean and photo-patternable system. [1][2][3][4][5][6][7] Many kinds of photoreactive polymers that can undergo anisotropic isomerization or photocrosslinking reactions have been reported for the photoalignment of LC. [3][4][5][6][7][8][9] Nematic liquid crystal (NLC) can be aligned either homogeneously or homeotropically on the photoreactive polymer film which is usually exposed to a linearly polarized light (LPL).…”

“…[1][2][3][4][5][6][7] Many kinds of photoreactive polymers that can undergo anisotropic isomerization or photocrosslinking reactions have been reported for the photoalignment of LC. [3][4][5][6][7][8][9] Nematic liquid crystal (NLC) can be aligned either homogeneously or homeotropically on the photoreactive polymer film which is usually exposed to a linearly polarized light (LPL). [10][11][12][13] For example, anisotropic [2+2] cycloaddition of polyvinylcinnamate (PVCi) film can induce irreversible low molecular weight-liquid crystal (LMW-LC) alignment.…”

“…[3][4][5][6][7][8][9]14 The orientational direction of LC molecules caused by linearly polarized light irradiation of polymers with photoreactive side chains including azobenzenes, cinnamates, and benzylidenephthalimidines is perpendicular to the electric field vector of actinic polarized light. 25 Thin films of chalcone-epoxy compound on a substrate plate were exposed to polarized UV light (λ = 300-360 nm) followed by the fabrication of LC cell using the above two plates coated with chalcone-epoxy compound.…”