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Lee DW, Kim DH, Oh JY, Kim DH, Choi SH, Kim JA, Park HG, Seo DS. Self-Aligned Liquid Crystals on Anisotropic Nano/Microstructured Lanthanum Yttrium Strontium Oxide Layer. MATERIALS (BASEL, SWITZERLAND) 2022; 15:6843. [PMID: 36234184 PMCID: PMC9570725 DOI: 10.3390/ma15196843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 09/27/2022] [Accepted: 09/28/2022] [Indexed: 06/16/2023]
Abstract
We propose an efficient alignment method for liquid crystals (LCs). A brush-coating method handles film deposition and LC alignment treatment simultaneously herein, meaning a reduction in the conventional alignment layer treatment process steps. A lanthanum yttrium strontium oxide (LaYSrO) film prepared by the sol-gel process was used for the alignment layer. Topographical details of the brush-coated LaYSrO films (compared with spin-coated films) were investigated by atomic force microscopy. Spin-coated LaYSrO meant that the film formation alone without orientation treatment represented an isotropic surface. On the other hand, the 270 °C-cured brush-coated LaYSrO showed nano/microstructure with directionality. It indicates that brush-hair sweeping induced shearing stress on the sol state of the LaYSrO, which results in surface anisotropy for LC alignment. The uniform LC alignment state was confirmed by polarized optical microscopy and pretilt analysis. The brush-coated LaYSrO shows fine optical transparency compared to plain and indium-tin-oxide coated glasses, and thermal stability up to 150 °C for LC alignment. Competitive electro-optical performances of the brush-coated LaYSrO were verified in a twisted-nematic LC system compared to those of the conventionally used polyimide layer. Consequently, we expect that the brush-coating process can be an innovative technology for LC alignment.
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Affiliation(s)
- Dong-Wook Lee
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
| | - Dong-Hyun Kim
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
| | - Jin-Young Oh
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
| | - Dae-Hyun Kim
- Department of Smart Electric, Korea Polytechnic, 23 Yeomjeon-ro, 333beon-gil, Nam-gu, Incheon 22121, Korea
| | - Se-Hoon Choi
- Department of Smart Manufacturing Engineering, Changwon National University, 20-1 Changwon Daehak-ro, Uichang-gu, Changwon, Gyeongnam 51140, Korea
| | - Jin-Ah Kim
- Department of Smart Manufacturing Engineering, Changwon National University, 20-1 Changwon Daehak-ro, Uichang-gu, Changwon, Gyeongnam 51140, Korea
| | - Hong-Gyu Park
- Department of Smart Manufacturing Engineering, Changwon National University, 20-1 Changwon Daehak-ro, Uichang-gu, Changwon, Gyeongnam 51140, Korea
- Department of Electrical, Electronic, Control Engineering, Changwon National University, 20-1 Changwondaehak-ro, Uichang-gu, Changwon, Gyeongnam 51140, Korea
| | - Dae-Shik Seo
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Korea
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Lee DW, Kim EM, Heo GS, Kim DH, Oh JY, Liu Y, Seo DS. Physicochemically Constructed Unidirectional Aluminum Bismuth Gallium Zinc Oxide Film for Enhanced Nematic Liquid Crystal System Using a Brush-Coating Method. Chemphyschem 2022; 23:e202200263. [PMID: 35798631 DOI: 10.1002/cphc.202200263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 06/15/2022] [Indexed: 11/10/2022]
Abstract
We proposed a convenient brush coating method for liquid crystal (LC) alignment. This method conducted film deposition and alignment layer treatment process simultaneously. Aluminum bismuth gallium zinc oxide (AlBiGaZnO) was used as an alignment layer. After the curing process, a unidirectional AlBiGaZnO film was formed and the surface morphology and chemical composition was verified using scanning electron microscopy and X-ray photoelectron spectroscopy. This oriented structure of the surface was produced by shear-stress which originated from brush movement. That structure induced a surface anisotropic characteristic and resulted in a uniform LC alignment. The uniform and homogeneous LC alignment state on the film was confirmed using polarized optical microscopy and pre-tilt angle analysis. The brush coated AlBiGaZnO film exhibited excellent thermal budget for advanced LC system. The film exhibited enhanced electro-optical performance with a low operating voltage. These results demonstrate the potential of LC alignment technology via the brush coating method.
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Affiliation(s)
- Dong Wook Lee
- Yonsei University, Electrical and Electronic Engineering, KOREA, REPUBLIC OF
| | - Eun Mi Kim
- KITECH: Korea Institute of Industrial Technology, National Center for Nanoprocess and Equipment, KOREA, REPUBLIC OF
| | - Gi Seok Heo
- KITECH: Korea Institute of Industrial Technology, National Center for Nanoprocess and Equipment, KOREA, REPUBLIC OF
| | - Dong Hyun Kim
- Yonsei University, Electrical and Electronic Engineering, KOREA, REPUBLIC OF
| | - Jin Young Oh
- Yonsei University, Electrical and Electronic Engineering, KOREA, REPUBLIC OF
| | - Yang Liu
- Donghua University College of Information Science and Technology, College of Information Science and Technology, CHINA
| | - Dae-Shik Seo
- Yonsei University, Electrical and Electronic Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, 120-749, Seoul, KOREA, REPUBLIC OF
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Achievement of Unidirectional Aluminum Tin Oxide/UV-Curable Polymer Hybrid Film via UV Nanoimprinting Lithography for Uniform Liquid Crystal Alignment. CRYSTALS 2022. [DOI: 10.3390/cryst12060855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A uniform unidirectional nanostructure composed of aluminum tin oxide and ultraviolet (UV)-curable polymer is introduced herein. The nanostructure was produced by UV-nanoimprint lithography (UV-NIL), and the fabricated hybrid film was used as a uniform liquid crystal (LC) alignment layer. Atomic force microscopy and line profile analysis were performed to confirm a well-ordered nanostructure with 760 nm periodicity and 30 nm height. X-ray photoelectron spectroscopy analysis was also conducted to examine the chemical modifications to the hybrid film surface during UV exposure. Optical transmittance investigation of the nanopatterned hybrid film revealed its compatibility for LC device application. Stable, uniform, and homogeneous LC alignment on the hybrid film was confirmed by polarized optical microscopy observance and analysis of LC pretilt angle. The unidirectional structure on the film surface enabled uniform LC orientation along with surface anisotropy property. Hence, we expect that the proposed UV-NIL process can be applied to fabricate high-resolution unidirectional nanostructures with various inorganic/organic hybrid materials and that these nanostructures have high potential for next-generation LC systems.
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Lee DW, Won JH, Kim DH, Oh JY, Kim D, Liu Y, Seo D. Well‐ordered nanostructured organic/inorganic hybrid thin film construction via
UV
nanoimprint lithography applicable to liquid crystal systems. J Appl Polym Sci 2022. [DOI: 10.1002/app.52445] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Dong Wook Lee
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering Yonsei University Seoul South Korea
| | - Jong Hoon Won
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering Yonsei University Seoul South Korea
| | - Dong Hyun Kim
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering Yonsei University Seoul South Korea
| | - Jin Young Oh
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering Yonsei University Seoul South Korea
| | - Dae‐Hyun Kim
- Department of Smart Electric Korea Polytechnic Incheon South Korea
| | - Yang Liu
- College of Information Science and Technology Donghua University Shanghai China
| | - Dae‐Shik Seo
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering Yonsei University Seoul South Korea
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Sergan V, Sergan T, Dozov I, Joly S, Voss R. Orientational order induced by a polymer network in the isotropic phase of liquid crystal. Phys Rev E 2020; 101:052705. [PMID: 32575175 DOI: 10.1103/physreve.101.052705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 03/16/2020] [Indexed: 11/07/2022]
Abstract
We studied the paranematic ordering induced by a polymer network in the isotropic phase of a liquid crystal (LC) that occurs in polymer-stabilized cells with bend configuration of the LC director (π cells) fabricated via photopolymerization of photoreactive monomer RM 82 added in small concentrations (3-5 wt %) to a nematic LC [4-cyano-4'-pentylbiphenyl (5CB)] when low voltage was applied across the cell. The polymer network formed in the nematic phase of the LC consists of fine fibrils that are aligned along the LC director and thus mirror the bend deformation of the LC at the time of polymerization. When heated to temperatures above the nematic-to-isotropic (N-I) phase transition such highly ordered polymer network anchors LC molecules providing ordering of the LC around the fibrils which results in unusually high optical retardation of the cell, R_{cell}. We present a theoretical model that relates R_{cell} to the degree of order of the fibrils, the anchoring energy of the LC molecules on the surface of the polymer fibrils, and the fibril radius r_{0}. Fitting of the experimental R_{cell}(T) curves with the developed model reveals correlation of r_{0} with the nematic correlation length ξ_{0} which characterizes penetration of the nematic order in the isotropic phase of the LC. Accepting ξ_{0} as a material constant of about 1 nm leads to a very small radius of the fibrils, r_{0}∼1nm, which is also supported by other reported experimental data. High optical retardation and fast electro-optical response of the cells at the temperatures deep into the isotropic phase point toward the enhancement of the polymer-induced paranematic order by a well-oriented layer of LC molecules that are absorbed on the surface of fibrils. Application of high voltage at the isotropic phase temperatures results in high variations of the optical retardation of the cells. Characteristic on and off response times were about 10-100 μs, independent of the cell gap. Combination of large voltage-driven changes of the optical retardation occurring in the low-viscosity isotropic state with switching times that are at least two orders of magnitude shorter than the typical relaxation times of the cells operating in the nematic phase make such polymer-stabilized π cells very promising for application in fast electro-optical switches and light modulators.
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Affiliation(s)
- V Sergan
- California State University, Sacramento, 6000 J Street, Sacramento, California 95608, USA
| | - T Sergan
- California State University, Sacramento, 6000 J Street, Sacramento, California 95608, USA
| | - I Dozov
- PSC, Université de Picardie Jules Verne, 80039 Amiens, France
| | - S Joly
- PEDL Laboratory, PSA Technical Center, Route de Gisy, Case courrier VV009, 78943 Vélizy-Villacoublay, France
| | - R Voss
- California State University, Sacramento, 6000 J Street, Sacramento, California 95608, USA
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Li BX, Xiao RL, Paladugu S, Shiyanovskii SV, Lavrentovich OD. Dye-doped dual-frequency nematic cells as fast-switching polarization-independent shutters. OPTICS EXPRESS 2019; 27:3861-3866. [PMID: 30876010 DOI: 10.1364/oe.27.003861] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 12/04/2018] [Indexed: 05/27/2023]
Abstract
We present polarization-independent optical shutters with a sub-millisecond switching time. The approach utilizes dual-frequency nematics doped with a dichroic dye. Two nematic cells with orthogonal alignment are driven simultaneously by a low-frequency or high-frequency electric field to switch the shutter either into a transparent or a light-absorbing state. The switching speed is accelerated via special short pulses of high amplitude voltage. The approach can be used in a variety of electro-optical devices.
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Sergan V, Sergan TA, Bos PJ, Lu L, Herrera R, Sergan EV. Control of liquid crystal alignment using surface-localized low-density polymer networks and its applications to electro-optical devices. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.02.125] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Sergan T, Dozov I, Sergan V, Voss R. Comparative study of the anchoring strength of reactive mesogens and industrial polyimides used for the alignment of liquid crystals. Phys Rev E 2017; 95:052706. [PMID: 28618526 DOI: 10.1103/physreve.95.052706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Indexed: 11/07/2022]
Abstract
We measured the Rapini-Papoular polar anchoring strength coefficient W for 4^{'}-pentyl-4-cyanobiphenyl (5CB) on alignment layers formed by the reactive mesogen photopolymers RM 257, RM 82, and RM 84 [4,4^{'}-bis(acryloyl)biphenyl] (by Merck). These materials are commonly used for the photostabilization of the liquid crystal (LC) director in the bulk as well as at the surface of the LC layer via the formation of a loose polymer network that captures the director orientation. We developed a method of fabrication of alignment layers from these polymers, and estimated W from the measurements of the optical retardation as a function of applied voltage in uniformly aligned cells. We found that RM 257 yielded W of about 6×10^{-4}J/m^{2}, whereas RM 82 and RM 84 provided anchoring strengths of about 2×10^{-4} and 4×10^{-4}J/m^{2}, respectively. Subsequent heating of the sample either destroyed the alignment layer, or substantially decreased W to about 1×10^{-4}J/m^{2}, which was comparable to the anchoring strength of weakly rubbed commercial polyimides.
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Affiliation(s)
- T Sergan
- California State University, Sacramento, 6000 J Street, Sacramento, California 95819, USA
| | - I Dozov
- Université de Picardie Jules Verne, 80039 Amiens, France
| | - V Sergan
- California State University, Sacramento, 6000 J Street, Sacramento, California 95819, USA
| | - R Voss
- California State University, Sacramento, 6000 J Street, Sacramento, California 95819, USA
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Belyaev VV, Solomatin AS, Chausov DN. Measurement of the liquid crystal pretilt angle in cells with homogeneous and inhomogeneous liquid crystal director configuration. APPLIED OPTICS 2013; 52:3012-3019. [PMID: 23669767 DOI: 10.1364/ao.52.003012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 03/26/2013] [Indexed: 06/02/2023]
Abstract
Optical and electro-optical methods of liquid crystal (LC) director pretilt angle measurement are described for LC cells with homogeneous and inhomogeneous LC director distribution. The LC pretilt on both LC substrates can have the same or opposite direction. The phase retardation difference of both extraordinary and ordinary polarized rays passing through an LC cell with homogeneous and inhomogeneous LC director distribution has been calculated versus the LC pretilt angle θ(0) on the cell's substrates in the range 0≤θ(0)≤90°. The experimental procedure for phase retardation difference determination by measurement of the LC cell transmission between crossed polarizers for cells with LC tilted alignment is described. The method developed can also be used in optical compensator design.
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Affiliation(s)
- Victor V Belyaev
- Laboratory for Theoretical and Applied Nanotechnology, Moscow Region State University, Moscow 105005, Russia.
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Zhao D, Zhou W, Cui X, Tian Y, Guo L, Yang H. Alignment of liquid crystals doped with nickel nanoparticles containing different morphologies. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2011; 23:5779-84. [PMID: 22102432 DOI: 10.1002/adma.201102611] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 09/24/2011] [Indexed: 05/22/2023]
Abstract
Uniform homeotropic and homogeneous alignment of liquid crystals (LCs) is facilely achieved by dispersing Ni nanoparticles (Ni NPs) into the LCs. The alignment mode depends on the morphology of the Ni NPs. The mechanism of NP-induced LC alignment is elucidated clearly, indicating that the perfect orientation arises from the adsorption of Ni NPs on the substrate.
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Affiliation(s)
- Dongyu Zhao
- School of Chemistry and Environment Science, Beijing University of Aeronautics and Astronautics, China
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11
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Interfacial molecular self-assembled films of amphiphilic disclike molecules induce uniform alignment of nematic liquid crystals. Colloids Surf A Physicochem Eng Asp 2011. [DOI: 10.1016/j.colsurfa.2011.03.059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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12
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Zhao D, Huang W, Cao H, Zheng Y, Wang G, Yang Z, Yang H. Homeotropic Alignment of Nematic Liquid Crystals by a Photocross-Linkable Organic Monomer Containing Dual Photofunctional Groups. J Phys Chem B 2009; 113:2961-5. [DOI: 10.1021/jp8101089] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Dongyu Zhao
- Department of Materials Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Wei Huang
- Department of Materials Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Hui Cao
- Department of Materials Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Yudong Zheng
- Department of Materials Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Guojie Wang
- Department of Materials Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Zhou Yang
- Department of Materials Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Huai Yang
- Department of Materials Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
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Sakamoto K, Abe N, Arafune R, Ushioda S. Orientation of the Backbone Structure of Polyimide with Alkyl Side-Chains: Determination by Infrared Absorption Spectroscopy. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259708041990] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- K. Sakamoto
- a Research Institute of Electrical Communication, Tohoku University 2-1-1 Katahira , Aoba-ku, Sendai , 980-77 , Japan
| | - N. Abe
- a Research Institute of Electrical Communication, Tohoku University 2-1-1 Katahira , Aoba-ku, Sendai , 980-77 , Japan
| | - R. Arafune
- a Research Institute of Electrical Communication, Tohoku University 2-1-1 Katahira , Aoba-ku, Sendai , 980-77 , Japan
| | - S. Ushioda
- a Research Institute of Electrical Communication, Tohoku University 2-1-1 Katahira , Aoba-ku, Sendai , 980-77 , Japan
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