28 May 2004 Patterned alignment of liquid crystals
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In this study the μ-rubbing technique is used to micro-pattern polyimide alignment layers using a metallic sphere at different loads. Optical and atomic force microscopy shows that the width of the patterns ranges from 12-40 μm and depth ranges from 2-14 nm. Our primary finding is that μ-rubbing induces planar alignment in polyimides. We performed μ-rubbing on pre-rubbed polyimide perpendicular to the rubbing direction. It is found that μ-rubbing erases the alignment properties of the pre-rubbing procedure. Liquid crystal cells were constructed using the pre-rubbed polyimide substrates with μ-rubbed patterns on one side and a homogeneously rubbed polyimide layer on the other side. Therefore the pre-rubbed polyimide layers are crossed and consequently a twisted nematic alignment is observed outside the micro-patterns. Within the micro-patterns, the directions of the pre-rubbing and μ-rubbing are parallel, a planar alignment observed. In another configuration, liquid crystal cells were made with pre-rubbed polyimide substrates having micro-patterns on both sides to give grid pattern with planar and twisted nematic configuration. Studies were extended to determine the pretilt of the micro patterned area.
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Soney Varghese, Soney Varghese, Sunil Narayanankutty, Sunil Narayanankutty, Cees W. M. Bastiaansen, Cees W. M. Bastiaansen, Gregory P. Crawford, Gregory P. Crawford, Dirk J. Broer, Dirk J. Broer, "Patterned alignment of liquid crystals", Proc. SPIE 5289, Liquid Crystal Materials, Devices, and Applications X and Projection Displays X, (28 May 2004); doi: 10.1117/12.522895; https://doi.org/10.1117/12.522895

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