Study on application of UV-processed molecular alignment in liquid crystal devices

Photoalignment technique in liquid crystal devices (LCDs) fabrication processes is classified into a non-contact process which provides an anisotropy in liquid crystal (LC) alignment layer by exposing ultra violet (UV) light. The greatest benefit for using this technique is to avoid electrostati...

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Main Author:	Lais, Jais
Format:	Thesis
Language:	English
Published:	2011
Subjects:	TK Electrical engineering Electronics Nuclear engineering TK7800-8360 Electronics
Online Access:	http://eprints.uthm.edu.my/3005/1/24p%20JAIS%20LAIS.pdf
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spelling	my-uthm-ep.30052021-11-02T01:34:28Z Study on application of UV-processed molecular alignment in liquid crystal devices 2011 Lais, Jais TK Electrical engineering. Electronics Nuclear engineering TK7800-8360 Electronics Photoalignment technique in liquid crystal devices (LCDs) fabrication processes is classified into a non-contact process which provides an anisotropy in liquid crystal (LC) alignment layer by exposing ultra violet (UV) light. The greatest benefit for using this technique is to avoid electrostatic charges and impurities on the substrate. Moreover, photoalignment can realize the structures which has the required liquid crystal director azimuth with the selected area of the cell, thus viewing angle characteristics can be improved by the pixel dividing. In this study, the photoalignment technique was applied to the fabrication of a bistable type LCD and polymer-stabilized blue phase (PSBP) LCD. Most liquid crystal devices are monostable, which possesses only one possible state in absence of field. They requires continuous voltage application and frequent image refreshment, which is the cause of the energy consumption and limits the multiplexability. In other word, monostable devices have no intrinsic pixel memory and they need an active matrix or other external storage elements to obtain high multiplexing levels. Bistable type LCD have two (or more) stable states. Once an image displayed, the director state in each pixels is memorized for a long time, ranging from seconds up to years, until when the new image is overwritten. This intrinsic memory capability is a peculiar advantage of the bistable type LCD, provides a potential to reduce the power consumption, especially for the specific application which is unnecessary frequent update. In this study, to fabricate a bistable LCD (BLCD) by using unpolarized UV light irradiation, single-step laser patterning to photoalignment layer was proposed. Bistability can be achieved by two equilibrium configurations of LC director profile which is induced by a periodically patterned alignment layer on a substrate. The patterns were formed by stripes of alternating random planar and homeotropic anchoring in the order of 0.5 μm. In this work, two possible configurations of bistable LCD that can be obtained by combining a micropatterned surface formed with alternating random-planar- and homeotropic-alignment with planar- or homeotropic-alignment surfaces were proposed. The alignment properties of the two proposed BLCD models such as twisted angle, pretilt angle and its microscopic switching behavior and memory effect were investigated and determined. It was assumed that the formation of the two bulk orientational states will depend on the degree of depolarization of the laser light, the stripe periodicity and the effective anchoring strength of the patterned surface. 2011 Thesis http://eprints.uthm.edu.my/3005/ http://eprints.uthm.edu.my/3005/1/24p%20JAIS%20LAIS.pdf text en public phd doctoral Nagaoka University of Technology School of Engineering
institution	Universiti Tun Hussein Onn Malaysia
collection	UTHM Institutional Repository
language	English
topic	TK Electrical engineering Electronics Nuclear engineering TK7800-8360 Electronics
spellingShingle	TK Electrical engineering Electronics Nuclear engineering TK7800-8360 Electronics Lais, Jais Study on application of UV-processed molecular alignment in liquid crystal devices
description	Photoalignment technique in liquid crystal devices (LCDs) fabrication processes is classified into a non-contact process which provides an anisotropy in liquid crystal (LC) alignment layer by exposing ultra violet (UV) light. The greatest benefit for using this technique is to avoid electrostatic charges and impurities on the substrate. Moreover, photoalignment can realize the structures which has the required liquid crystal director azimuth with the selected area of the cell, thus viewing angle characteristics can be improved by the pixel dividing. In this study, the photoalignment technique was applied to the fabrication of a bistable type LCD and polymer-stabilized blue phase (PSBP) LCD. Most liquid crystal devices are monostable, which possesses only one possible state in absence of field. They requires continuous voltage application and frequent image refreshment, which is the cause of the energy consumption and limits the multiplexability. In other word, monostable devices have no intrinsic pixel memory and they need an active matrix or other external storage elements to obtain high multiplexing levels. Bistable type LCD have two (or more) stable states. Once an image displayed, the director state in each pixels is memorized for a long time, ranging from seconds up to years, until when the new image is overwritten. This intrinsic memory capability is a peculiar advantage of the bistable type LCD, provides a potential to reduce the power consumption, especially for the specific application which is unnecessary frequent update. In this study, to fabricate a bistable LCD (BLCD) by using unpolarized UV light irradiation, single-step laser patterning to photoalignment layer was proposed. Bistability can be achieved by two equilibrium configurations of LC director profile which is induced by a periodically patterned alignment layer on a substrate. The patterns were formed by stripes of alternating random planar and homeotropic anchoring in the order of 0.5 μm. In this work, two possible configurations of bistable LCD that can be obtained by combining a micropatterned surface formed with alternating random-planar- and homeotropic-alignment with planar- or homeotropic-alignment surfaces were proposed. The alignment properties of the two proposed BLCD models such as twisted angle, pretilt angle and its microscopic switching behavior and memory effect were investigated and determined. It was assumed that the formation of the two bulk orientational states will depend on the degree of depolarization of the laser light, the stripe periodicity and the effective anchoring strength of the patterned surface.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Lais, Jais
author_facet	Lais, Jais
author_sort	Lais, Jais
title	Study on application of UV-processed molecular alignment in liquid crystal devices
title_short	Study on application of UV-processed molecular alignment in liquid crystal devices
title_full	Study on application of UV-processed molecular alignment in liquid crystal devices
title_fullStr	Study on application of UV-processed molecular alignment in liquid crystal devices
title_full_unstemmed	Study on application of UV-processed molecular alignment in liquid crystal devices
title_sort	study on application of uv-processed molecular alignment in liquid crystal devices
granting_institution	Nagaoka University of Technology
granting_department	School of Engineering
publishDate	2011
url	http://eprints.uthm.edu.my/3005/1/24p%20JAIS%20LAIS.pdf
_version_	1747831010382315520

Study on application of UV-processed molecular alignment in liquid crystal devices

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