1
|
Ju J, Chatterjee D, Voyles PM, Bock H, Ediger MD. Vapor-to-glass preparation of biaxially aligned organic semiconductors. J Chem Phys 2023; 159:211101. [PMID: 38038197 DOI: 10.1063/5.0174819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Accepted: 11/02/2023] [Indexed: 12/02/2023] Open
Abstract
Physical vapor deposition (PVD) provides a route to prepare highly stable and anisotropic organic glasses that are utilized in multi-layer structures such as organic light-emitting devices. While previous work has demonstrated that anisotropic glasses with uniaxial symmetry can be prepared by PVD, here, we prepare biaxially aligned glasses in which molecular orientation has a preferred in-plane direction. With the collective effect of the surface equilibration mechanism and template growth on an aligned substrate, macroscopic biaxial alignment is achieved in depositions as much as 180 K below the clearing point TLC-iso (and 50 K below the glass transition temperature Tg) with single-component disk-like (phenanthroperylene ester) and rod-like (itraconazole) mesogens. The preparation of biaxially aligned organic semiconductors adds a new dimension of structural control for vapor-deposited glasses and may enable polarized emission and in-plane control of charge mobility.
Collapse
Affiliation(s)
- Jianzhu Ju
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Debaditya Chatterjee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Paul M Voyles
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Harald Bock
- Centre de Recherche Paul Pascal, CNRS & Université de Bordeaux, 33600 Pessac, France
| | - Mark D Ediger
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| |
Collapse
|
2
|
Hierarchically self-constructed alignment layer of comb-shaped amphiphilic copolymers for spontaneous and stable vertical orientation of liquid crystals. J Mol Liq 2023. [DOI: 10.1016/j.molliq.2023.121247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
|
3
|
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.
Collapse
|
4
|
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
| |
Collapse
|
5
|
Orientation-induced properties of anisotropic polyacrylamide thin layer via plasma treatment in liquid crystal system. Eur Polym J 2022. [DOI: 10.1016/j.eurpolymj.2021.110937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
6
|
Kim DH, Lee DW, Oh JY, Lee JH, Won J, Jang JI, Jeong HC, Seo DS. Physicochemically modified high-resolution tin oxide thin film using soft imprinting. RSC Adv 2022; 12:26696-26703. [PMID: 36275172 PMCID: PMC9487481 DOI: 10.1039/d2ra04459e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 09/13/2022] [Indexed: 11/21/2022] Open
Abstract
We carried out nanoimprinting lithography on solution-processed tin oxide (SnO) film for use as a liquid crystal (LC) alignment layer, for which we used a parallel configuration.
Collapse
Affiliation(s)
- Dong Hyun Kim
- Department of Electrical and Electronic Engineering, Information Display Device Laboratory, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - Dong Wook Lee
- Department of Electrical and Electronic Engineering, Information Display Device Laboratory, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - Jin Young Oh
- Department of Electrical and Electronic Engineering, Information Display Device Laboratory, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - Ju Hwan Lee
- Department of Electrical and Electronic Engineering, Information Display Device Laboratory, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - Jonghoon Won
- Department of Electrical and Electronic Engineering, Information Display Device Laboratory, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - Jong In Jang
- Department of Smart Manufacturing Engineering, Changwon National University, 20 Changwondaehak-ro, Changwon, Gyeongnam 51140, Republic of Korea
- Department of Electrical Electronic and Control Engineering, Changwon National University, 20 Changwondaehak-ro, Changwon, Gyeongnam 51140, Republic of Korea
| | - Hae-Chang Jeong
- Department of Smart Manufacturing Engineering, Changwon National University, 20 Changwondaehak-ro, Changwon, Gyeongnam 51140, Republic of Korea
- Department of Electrical Electronic and Control Engineering, Changwon National University, 20 Changwondaehak-ro, Changwon, Gyeongnam 51140, Republic of Korea
| | - Dae-Shik Seo
- Department of Electrical and Electronic Engineering, Information Display Device Laboratory, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749, Republic of Korea
| |
Collapse
|
7
|
Oh JY, Kim EM, Heo GS, Kim DH, Lee D, Jeong HC, Seo DS. Superior nanopatterns via adjustable nanoimprint lithography on aluminum oxide in high-K thin films with ultraviolet curable polymer. RSC Adv 2022; 12:88-93. [PMID: 35424521 PMCID: PMC8978656 DOI: 10.1039/d1ra08425a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 12/04/2021] [Indexed: 12/04/2022] Open
Abstract
The present study substantiate that ultraviolet-nanoimprint lithography (UV-NIL) can be used to transfer a one-dimensional nano-pattern onto a high-k thin film of aluminum oxide mixed with a UV photocuring agent. Polydimethylsiloxane (PDMS) molds fabricated on silicon wafers were made using deep ultraviolet laser interference lithography in order to investigate one-dimension nanopatterns. These imprinted nano-patterns induce geometric deformations in the liquid crystal (LC), creating collective and elastic properties, which act as a guide for homogeneous alignment. The nanoimprint method can process a large area, so it can be processed much easier, faster, and more accurately than the conventional rubbing method. Moreover, the optical properties of the nano-imprinted aluminum oxide (AlO) thin-film are about 1.5p% superior to that of conventional commercialized cells, so it has a high effect on the luminance and color gamut of the display. After pattern imprinting, atomic force microscope (AFM) was performed to confirm the result. We can compared the cycle of AlO mixed with UV photocuring agent PDMS pattern cycle, the period is 776 and 750 nm, the width is 468 and 450 nm, the spacing is 292 and 300 nm, and the height is 40 and 30 nm. The nano-imprinted film appears to replicate the width, amplitude, and spacing of the PDMS template. In addition, X-ray photoelectron spectroscopy was performed to determine the chemical properties of the thin film and it was confirmed that UV irradiation induces oxidation, thus increases the intensity significantly. The binding energies of Al 2p and C–O spectra were situated at 74.27 ± 0.5 eV and 531.78 ± 0.5 eV, respectively. The present study substantiate that ultraviolet-nanoimprint lithography (UV-NIL) can be used to transfer a one-dimensional nano-pattern onto a high-k thin film of aluminum oxide mixed with a UV photocuring agent.![]()
Collapse
Affiliation(s)
- Jin Young Oh
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - Eun-Mi Kim
- National Center for Nanoprocess and Equipment, Korea Institute of Industrial Technology, 6 Cheomdangwagi-ro 208beon-gil, Buk-gu, Gwangju 500-480, South Korea
| | - Gi-Seok Heo
- National Center for Nanoprocess and Equipment, Korea Institute of Industrial Technology, 6 Cheomdangwagi-ro 208beon-gil, Buk-gu, Gwangju 500-480, South Korea
| | - Dong Hyun Kim
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - DongWook Lee
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemun-gu, Seoul 120-749, Republic of Korea
| | - Hae-Chang Jeong
- Electrical Engineering, Changwon National University, 20 changwondaehak-ro, Unichang-gu, Changwon, Gyeonnam, 51140, Korea
| | - Dae-Shik Seo
- IT Nano Electronic Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemun-gu, Seoul 120-749, Republic of Korea
| |
Collapse
|
8
|
Lee DW, Lee JH, Kim EM, Heo GS, Kim DH, Oh JY, Liu Y, Seo DS. Surface modification of a poly(ethylene-co-vinyl acetate) layer by ion beam irradiation for the uniform alignment of liquid crystals. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116700] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
9
|
Cui D, MacLeod JM, Rosei F. Planar Anchoring of C 70 Liquid Crystals Using a Covalent Organic Framework Template. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2019; 15:e1903294. [PMID: 31513362 DOI: 10.1002/smll.201903294] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/12/2019] [Indexed: 06/10/2023]
Abstract
The surface-induced anchoring effect is a well-developed technique to control the growth of liquid crystals (LCs). Nevertheless, a defined nanometer-scale template has never been used to induce the anchored growth of LCs with molecular building units. Scanning tunneling microscopy results at the solid/liquid interface reveal that a 2D covalent organic framework (COF-1) can offer an anchoring effect to template C70 molecules into forming several LC mesophases, which cannot be obtained under other conditions. Through comparison with the C60 system, a stepwise breakdown in ordering of C70 LC is observed. The process is described in terms of the effects of molecular anisotropy on the epitaxial growth of molecular crystals. The results suggest that using a surface-confined template to anchor the initial layer of LC molecules can be a modular and potentially broadly applicable approach for organizing molecular mesogens into LCs.
Collapse
Affiliation(s)
- Daling Cui
- Centre Énergie, Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boulevard Lionel-Boulet, Varennes, Québec, J3 × 1S2, Canada
| | - Jennifer M MacLeod
- Centre Énergie, Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boulevard Lionel-Boulet, Varennes, Québec, J3 × 1S2, Canada
- School of Chemistry Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, 4000, QLD, Australia
| | - Federico Rosei
- Centre Énergie, Matériaux et Télécommunications, Institut National de la Recherche Scientifique, 1650 Boulevard Lionel-Boulet, Varennes, Québec, J3 × 1S2, Canada
| |
Collapse
|
10
|
Jeong HC, Lee JH, Won J, Oh BY, Kim DH, Lee DW, Song IH, Liu Y, Seo DS. One-dimensional surface wrinkling for twisted nematic liquid crystal display based on ultraviolet nanoimprint lithography. OPTICS EXPRESS 2019; 27:18094-18101. [PMID: 31252757 DOI: 10.1364/oe.27.018094] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 05/26/2019] [Indexed: 06/09/2023]
Abstract
Surface wrinkling method is used to fabricate a 1-dimensional nanostructure. The structure is transferred to an ultraviolet cured polymer which is used as an alignment layer. The anisotropic geometry serves as a guide for aligning liquid crystal molecules uniformly without defects. The TN-LC cell showed a successful LC switching, with a response time of 20.5 ms, and a threshold voltage of 2.00 V. It also exhibited high thermal stability above 180°C. The proposed UV-cured polymers with 1-D nano wrinkle geometry can be a candidate for alternative alignment techniques, for advanced liquid crystal devices with high thermal budgets.
Collapse
|
11
|
Lee JH, Jeong HC, Won J, Oh BY, Kim DH, Lee DW, Liu Y, Seo DS. Nano pattern transfer on acrylic polymers with UV irradiation for liquid crystal alignment. POLYMER 2019. [DOI: 10.1016/j.polymer.2018.12.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
12
|
Abstract
In this paper, we review liquid-crystal-on-silicon (LCoS) technology and focus on its new application in emerging augmented reality (AR) displays. In the first part, the LCoS working principles of three commonly adopted LC modes—vertical alignment and twist nematic for amplitude modulation, and homogeneous alignment for phase modulation—are introduced and their pros and cons evaluated. In the second part, the fringing field effect is analyzed, and a novel pretilt angle patterning method for suppressing the effect is presented. Moreover, we illustrate how to integrate the LCoS panel in an AR display system. Both currently available intensity modulators and under-developing holographic displays are covered, with special emphases on achieving high image quality, such as a fast response time and high-resolution. The rapidly increasing application of LCoS in AR head-mounted displays and head-up displays is foreseeable.
Collapse
|
13
|
Artyushkova K, Pylypenko S. Application of surface analysis methods to study alignment mechanism and orientation of liquid crystals. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.01.071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
14
|
Shen TZ, Hong SH, Lee JH, Kang SG, Lee B, Whang D, Song JK. Selectivity of Threefold Symmetry in Epitaxial Alignment of Liquid Crystal Molecules on Macroscale Single-Crystal Graphene. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1802441. [PMID: 30073697 DOI: 10.1002/adma.201802441] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 07/04/2018] [Indexed: 06/08/2023]
Abstract
Epitaxial alignment of organic liquid crystal (LC) molecules on single-crystal graphene (SCG), an effective epitaxial molecular assembly template, can be used in alignment-layer-free liquid crystal displays. However, selectivity among the threefold symmetric easy axes of LCs on graphene is not well understood, which limits its application. Here, sixfold symmetric radial LC domains are demonstrated by dropping an LC droplet on clean SCG, which reveals that the graphene surface does not have an intrinsic preferential direction. Instead, the first contact geometry of the LC molecules determines the direction. Despite its strong anchoring energy on graphene, the LC alignment direction is readily erasable and rewritable, contrary to previous understanding. In addition, the quality of the threefold symmetric alignment is sensitive to alien residue and graphene imperfections, which can be used to detect infinitesimal impurities or structural defects on the graphene. Based on this unique epitaxial behavior of LCs on SCG, an alignment-layer-free electro-optical LC device and LC alignment duplication, which can result in practical graphene-based flexible LC devices, are realized.
Collapse
Affiliation(s)
- Tian-Zi Shen
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Korea
| | - Seung-Ho Hong
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Korea
| | - Jae-Hyun Lee
- Department of Energy Systems Research and Department of Materials Science and Engineering, Ajou University, Suwon, Gyeonggi-do, 16499, Korea
| | - Seog-Gyun Kang
- SKKU Advanced Institute of Nanotechnology, School of Advanced Material Science and Engineering, Sungkyunkwan University (SKKU), Suwon, Gyeonggi-do, 16419, Korea
| | - Bomi Lee
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Korea
| | - Dongmok Whang
- SKKU Advanced Institute of Nanotechnology, School of Advanced Material Science and Engineering, Sungkyunkwan University (SKKU), Suwon, Gyeonggi-do, 16419, Korea
| | - Jang-Kun Song
- Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon, Gyeonggi-do, 16419, Korea
| |
Collapse
|
15
|
Dhara P, Bhandaru N, Das A, Mukherjee R. Transition from Spin Dewetting to continuous film in spin coating of Liquid Crystal 5CB. Sci Rep 2018; 8:7169. [PMID: 29740096 PMCID: PMC5940909 DOI: 10.1038/s41598-018-25504-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Accepted: 04/13/2018] [Indexed: 12/03/2022] Open
Abstract
Spin dewetting refers to spontaneous rupture of the dispensed solution layer during spin coating, resulting in isolated but periodic, regular sized domains of the solute and is pre-dominant when the solute concentration (Cn) is very low. In this article we report how the morphology of liquid crystal (LC) 5CB thin films coated on flat and patterned PMMA substrate transform from spin dewetted droplets to continuous films with increase in Cn. We further show that within the spin dewetted regime, with gradual increase in the solute concentration, periodicity of the isotropic droplets (λD) as well as their mean diameter (dD), gradually decreases, till the film becomes continuous at a critical concentration (Cn*). Interestingly, the trend that λD reduces with increase in Cn is exact opposite to what is observed in thermal/solvent vapor induced dewetting of a thin film. The spin dewetted droplets exhibit transient Radial texture, in contrast to Schlieren texture observed in elongated threads and continuous films of 5CB, which remains in the Nematic phase at room temperature. Finally we show that by casting the film on a grating patterned substrate it becomes possible to align the spin dewetted droplets along the contours substrate patterns.
Collapse
Affiliation(s)
- Palash Dhara
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, Pin-721302, India
| | - Nandini Bhandaru
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, Pin-721302, India
| | - Anuja Das
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, Pin-721302, India
| | - Rabibrata Mukherjee
- Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, Pin-721302, India.
| |
Collapse
|
16
|
Kumar P, Oh SY, Baliyan VK, Kundu S, Lee SH, Kang SW. Topographically induced homeotropic alignment of liquid crystals on self-assembled opal crystals. OPTICS EXPRESS 2018; 26:8385-8396. [PMID: 29715806 DOI: 10.1364/oe.26.008385] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 03/13/2018] [Indexed: 06/08/2023]
Abstract
The surface of multilayered opal crystals resulted in homeotropic alignment of liquid crystal (LC), originated from the surface topography of opal crystals rather than a chemical nature of the nanoparticles. The polar anchoring energy (5.51 × 10-5 J/m2) of the crystal surface for nematic LC molecules was in a similar range to the conventional polyimide alignment layer (2.11 × 10-5 J/m2) used for commercial applications. The critical length scale for anchoring transition was approximately Lw = ~1 μm. If a diameter of particle d << 1 μm for opal crystals, LC molecules preferred to anchor vertically to the surface to minimize elastic free energy of bulk LCs. The LC favored a planar anchoring if d >> 1 μm. The results provide crucial insights to understand the homeotropic alignment of LCs on solid surfaces and therefore offer opportunities to develop novel materials for a vertical alignment of LCs.
Collapse
|
17
|
Ishige R, Tanaka K, Ando S. In Situ Analysis of Chain Orientation Behavior in Thin Film Aromatic Polyimides by Variable Temperature pMAIRS during Thermal Imidization. MACROMOL CHEM PHYS 2017. [DOI: 10.1002/macp.201700370] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ryohei Ishige
- Department of Chemical Science and Engineering; School of Materials and Chemical Technology; Tokyo Institute of Technology; E4-5, 2-12-1 Ookayama Meguro-ku Tokyo 152-8552 Japan
| | - Kazuyuki Tanaka
- Department of Chemical Science and Engineering; School of Materials and Chemical Technology; Tokyo Institute of Technology; E4-5, 2-12-1 Ookayama Meguro-ku Tokyo 152-8552 Japan
| | - Shinji Ando
- Department of Chemical Science and Engineering; School of Materials and Chemical Technology; Tokyo Institute of Technology; E4-5, 2-12-1 Ookayama Meguro-ku Tokyo 152-8552 Japan
| |
Collapse
|
18
|
Choi GJ, Van Le Q, Choi KS, Kwon KC, Jang HW, Gwag JS, Kim SY. Polarized Light-Emitting Diodes Based on Patterned MoS 2 Nanosheet Hole Transport Layer. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29. [PMID: 28731270 DOI: 10.1002/adma.201702598] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 06/24/2017] [Indexed: 05/08/2023]
Abstract
Here, this study successfully fabricates few-layer MoS2 nanosheets from (NH4 )2 MoS4 and applies them as the hole transport layer as well as the template for highly polarized organic light-emitting diodes (OLEDs). The obtained material consists of polycrystalline MoS2 nanosheets with thicknesses of 2 nm. The MoS2 nanosheets are patterned by rubbing/ion-beam treatment. The Raman spectra shows that {poly(9,9-dioctylfluorene-alt-benzothiadiazole), poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)]} (F8BT) on patterned MoS2 exhibits distinctive polarization behavior. It is discovered that patterned MoS2 not only improves the device efficiency but also changes the polarization behavior of the devices owing to the alignment of F8BT. This work demonstrates a highly efficient polarized OLED with a polarization ratio of 62.5:1 in the emission spectrum (166.7:1 at the peak intensity of 540 nm), which meets the manufacturing requirement. In addition, the use of patterned MoS2 nanosheets not only tunes the polarization of the OLEDs but also dramatically improves the device performance as compared with that of devices using untreated MoS2 .
Collapse
Affiliation(s)
- Gyu Jin Choi
- Department of Physics, Yeungnam University, 280 Daehak-Ro, Gyeongsan, 38541, Republic of Korea
| | - Quyet Van Le
- School of Chemical Engineering and Materials Science, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul, 06974, Republic of Korea
| | - Kyoung Soon Choi
- Advanced Nano-Surface Research Group, Korea Basic Science Institute, Daejeon, 305-333, Republic of Korea
| | - Ki Chang Kwon
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Ho Won Jang
- Department of Materials Science and Engineering, Research Institute of Advanced Materials, Seoul National University, Seoul, 08826, Republic of Korea
| | - Jin Seog Gwag
- Department of Physics, Yeungnam University, 280 Daehak-Ro, Gyeongsan, 38541, Republic of Korea
| | - Soo Young Kim
- School of Chemical Engineering and Materials Science, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul, 06974, Republic of Korea
| |
Collapse
|
19
|
Sidiq S, Prasad GVRK, Mukhopadhaya A, Pal SK. Poly(l-lysine)-Coated Liquid Crystal Droplets for Cell-Based Sensing Applications. J Phys Chem B 2017; 121:4247-4256. [DOI: 10.1021/acs.jpcb.7b00551] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sumyra Sidiq
- Department
of Chemical Sciences and §Department of Biological Sciences, Indian Institute of Science Education and Research Mohali (IISERM), Knowledge
City, Sector-81, SAS Nagar, Mohali 140306, India
| | - G. V. R. Krishna Prasad
- Department
of Chemical Sciences and §Department of Biological Sciences, Indian Institute of Science Education and Research Mohali (IISERM), Knowledge
City, Sector-81, SAS Nagar, Mohali 140306, India
| | - Arunika Mukhopadhaya
- Department
of Chemical Sciences and §Department of Biological Sciences, Indian Institute of Science Education and Research Mohali (IISERM), Knowledge
City, Sector-81, SAS Nagar, Mohali 140306, India
| | - Santanu Kumar Pal
- Department
of Chemical Sciences and §Department of Biological Sciences, Indian Institute of Science Education and Research Mohali (IISERM), Knowledge
City, Sector-81, SAS Nagar, Mohali 140306, India
| |
Collapse
|
20
|
Shehzad MA, Hussain S, Lee J, Jung J, Lee N, Kim G, Seo Y. Study of Grains and Boundaries of Molybdenum Diselenide and Tungsten Diselenide Using Liquid Crystal. NANO LETTERS 2017; 17:1474-1481. [PMID: 28207266 DOI: 10.1021/acs.nanolett.6b04491] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Direct observation of grains and boundaries is a vital factor in altering the electrical and optoelectronic properties of transition metal dichalcogenides (TMDs), that is, MoSe2 and WSe2. Here, we report visualization of grains and boundaries of chemical vapor deposition grown MoSe2 and WSe2 on silicon, using optical birefringence of two-dimensional layer covered with nematic liquid crystal (LC). An in-depth study was performed to determine the alignment orientation of LC molecules and their correlation with other grains. Interestingly, we found that alignment of liquid crystal has discrete preferential orientations. From computational simulations, higher adsorption energy for the armchair direction was found to force LC molecules to align on it, compared to that of the zigzag direction. We believe that these TMDs with three-fold symmetric alignment could be utilized for display applications.
Collapse
Affiliation(s)
- Muhammad Arslan Shehzad
- Graphene Research Institute, ‡Faculty of Nanotechnology and Advanced Materials Engineering, and §Department of Physics and Astronomy, Sejong University , Seoul 143-747, Republic of Korea
| | - Sajjad Hussain
- Graphene Research Institute, ‡Faculty of Nanotechnology and Advanced Materials Engineering, and §Department of Physics and Astronomy, Sejong University , Seoul 143-747, Republic of Korea
| | - Junsu Lee
- Graphene Research Institute, ‡Faculty of Nanotechnology and Advanced Materials Engineering, and §Department of Physics and Astronomy, Sejong University , Seoul 143-747, Republic of Korea
| | - Jongwan Jung
- Graphene Research Institute, ‡Faculty of Nanotechnology and Advanced Materials Engineering, and §Department of Physics and Astronomy, Sejong University , Seoul 143-747, Republic of Korea
| | - Naesung Lee
- Graphene Research Institute, ‡Faculty of Nanotechnology and Advanced Materials Engineering, and §Department of Physics and Astronomy, Sejong University , Seoul 143-747, Republic of Korea
| | - Gunn Kim
- Graphene Research Institute, ‡Faculty of Nanotechnology and Advanced Materials Engineering, and §Department of Physics and Astronomy, Sejong University , Seoul 143-747, Republic of Korea
| | - Yongho Seo
- Graphene Research Institute, ‡Faculty of Nanotechnology and Advanced Materials Engineering, and §Department of Physics and Astronomy, Sejong University , Seoul 143-747, Republic of Korea
| |
Collapse
|
21
|
Hahm SG, Lee SW, Suh J, Chae B, Kim SB, Lee SJ, Lee KH, Jung JC, Ree M. Rubbed Thin Films of Well-defined Brush Polyimides for Flat-Panel Liquid Crystal Displays: Surface Morphology, Molecular Orientation, and Liquid Crystal Alignability. HIGH PERFORM POLYM 2016. [DOI: 10.1177/0954008306068117] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
A series of well-defined brush polyimide (PI) composed of two 4- n-alkyloxyphenyloxy bristles per repeat unit on a semi-rigid poly(4,4′-methylenyldiphenylene pyromellitimide), Cm-PMDA-MDA PIs, were synthesized and their nanoscale thin films prepared by conventional spin-coating of their soluble poly(amic acid) precursor solutions and subsequent drying and thermal imidization in a nitrogen atmosphere. All the PIs were determined to be a positively birefringent polymer. The surface morphology and molecular orientation of each PI in films before and after rubbing were investigated in detail by atomic force microscopy, optical retardation analysis, and linearly polarized infrared spectroscopy. The sequence of the rubbing-induced polymer segmental orientations was further investigated in detail. In addition, the liquid crystal alignment and pretilt ability of the rubbed PI films were examined, and their thermal stability investigated. The present study provides important information on the sequence of the polymer segmental orientations induced by rubbing and additionally the mechanisms of the alignment and pretilt of liquid crystal molecules in contact with the rubbed PI film surface.
Collapse
Affiliation(s)
- Suk Gyu Hahm
- Department of Chemistry, Polymer Research Institute, BK21 Program, and Department of Materials Science & Engineering, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea
| | - Seung Woo Lee
- Department of Chemistry, Polymer Research Institute, BK21 Program, and Department of Materials Science & Engineering, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea
| | - Jinsuk Suh
- Department of Chemistry, Polymer Research Institute, BK21 Program, and Department of Materials Science & Engineering, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea
| | - Boknam Chae
- Department of Chemistry, Polymer Research Institute, BK21 Program, and Department of Materials Science & Engineering, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea
| | - Seung Bin Kim
- Department of Chemistry, Polymer Research Institute, BK21 Program, and Department of Materials Science & Engineering, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea
| | - Seong Joon Lee
- Department of Chemistry, Polymer Research Institute, BK21 Program, and Department of Materials Science & Engineering, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea
| | - Kyung Hoon Lee
- Department of Chemistry, Polymer Research Institute, BK21 Program, and Department of Materials Science & Engineering, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea
| | - Jin Chul Jung
- Department of Chemistry, Polymer Research Institute, BK21 Program, and Department of Materials Science & Engineering, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea
| | - Moonhor Ree
- Department of Chemistry, Polymer Research Institute, BK21 Program, and Department of Materials Science & Engineering, Pohang University of Science and Technology (Postech), Pohang 790-784, Republic of Korea
| |
Collapse
|
22
|
Liu Y, Lee JH, Seo DS. Ion beam fabrication of aluminum-doped zinc oxide layer for high-performance liquid crystals alignment. OPTICS EXPRESS 2016; 24:17424-17432. [PMID: 27464189 DOI: 10.1364/oe.24.017424] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In this paper, a 1.8 keV ion beam (IB) sputtered thin layer of aluminum-doped zinc oxide (AZO) with columnar AZO bumps covering the surface working as an alignment layer for the homogeneous alignment of liquid crystals (LC) is investigated. Bumpy AZO alignment layers in twisted nematic (TN) cells generated larger LC pre-tilt angles and thus enabled accelerated switching of LC, and the highly conductive bumpy AZO thin layers allowed super-fast release of accumulated charges, and led to low residual DC performance. These results indicate the promising applications of AZO bumps layer as alignment layer in LC devices.
Collapse
|
23
|
Mun HY, Jeong HC, Lee JH, Won JH, Park HG, Oh BY, Seo DS. Poly(styrene–maleic anhydride) films as alignment layers for liquid crystal systems via ion-beam irradiation. RSC Adv 2016. [DOI: 10.1039/c6ra16833g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We report an investigation of poly(styrene–maleic anhydride) (SMA) films as liquid crystal (LC) alignment layers fabricated by ion-beam (IB) irradiation.
Collapse
Affiliation(s)
- H.-Y. Mun
- Information Display Device Laboratory
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-gu
- Republic of Korea
| | - H.-C. Jeong
- Information Display Device Laboratory
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-gu
- Republic of Korea
| | - J. H. Lee
- Information Display Device Laboratory
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-gu
- Republic of Korea
| | - J.-H. Won
- Information Display Device Laboratory
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-gu
- Republic of Korea
| | - H.-G. Park
- School of Electrical, Electronic & Control Engineering
- Changwon National University
- Changwon-si
- Korea
| | - B.-Y. Oh
- ZeSHTech Co., Ltd
- Business Incubator
- Gwangju Institute of Science and Technology
- Gwangju
- Korea
| | - D.-S. Seo
- Information Display Device Laboratory
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seodaemun-gu
- Republic of Korea
| |
Collapse
|
24
|
Liu Y, Park HG, Lee JH, Seo DS, Kim EM, Heo GS. Electro-optical switching of liquid crystals sandwiched between ion-beam-spurted graphene quantum dots-doped PEDOT:PSS composite layers. OPTICS EXPRESS 2015; 23:34071-34081. [PMID: 26832063 DOI: 10.1364/oe.23.034071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
UNLABELLED Graphene quantum dots (GQDs)-doped PEDOT PSS composite layers were utilized to align liquid crystals (LCs) via an ion-beam (IB)-spurting pre-treatment process. LCs were homogeneously aligned between sandwiched GQDs/ PEDOT PSS composite thin layers, and the alignment of LCs was found to be affected by both the quantity of doped GQDs and IB-spurting intensity. Competitive electro-optical switching properties and non-residual DC performance of the cell equipped with GQDs/ PEDOT PSS composite alignment layers were obtained because of the enhanced field effect and charge transport induced by doped GQDs. Notably, using IB-spurted GQDs/ PEDOT PSS layers as alignment layers for next generation high-performance liquid crystal display (LCD) is promising.
Collapse
|
25
|
Molecular reorientation of polyimide film induced by thermal nanoimprint lithography and liquid crystals alignment on it. POLYMER 2015. [DOI: 10.1016/j.polymer.2015.06.062] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
26
|
Lee YG, Park HG, Jeong HC, Lee JH, Heo GS, Seo DS. Homogeneous liquid crystal alignment characteristics on solution-derived HfYGaO films treated with IB irradiation. OPTICS EXPRESS 2015; 23:17290-17300. [PMID: 26191738 DOI: 10.1364/oe.23.017290] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Solution-derived HfYGaO films have been treated by ion beam (IB) irradiation and used as liquid crystal (LC) alignment layers. Solution processing was adopted due to its simplicity, high throughput, and facile composition modification. Homogeneous and uniform LC alignment was achieved on the IB-irradiated HfYGaO films, and when these films were adopted in twisted nematic (TN) cells, electro-optical performance comparable to that of TN cells with conventional polyimide layers was achieved, with almost no capacitance-voltage hysteresis. Moreover, LC cells based on IB-irradiated HfYGaO films had a high thermal budget. The proposed IB-irradiated solution-derived HfYGaO films have considerable potential for use in advanced LC applications.
Collapse
|
27
|
Homogeneous self-aligned liquid crystals on wrinkled-wall poly(dimethylsiloxane) via localised ion-beam irradiation. Sci Rep 2015; 5:8641. [PMID: 25728372 DOI: 10.1038/srep08641] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 01/28/2015] [Indexed: 01/26/2023] Open
Abstract
We demonstrate self-aligned liquid crystals (LCs) using a wrinkled-wall polydimethylsiloxane (PDMS) wrinkle structure, which is a key factor to obtain a stable homogeneous alignment state with positive LCs. We constructed the wrinkled walls via localised surface exposure to IB radiation, which passed through a long length localised pattern mask. The creation of the wrinkled wall helped to align the LC molecules homogeneously because the wrinkled wall acted as a guide for the arrangement of positive LC molecules. In addition, we confirmed the stability of the alignment state as the width of the wrinkled wall was changed. Although this wrinkled-wall method is a non-contact method, LC alignment is achieved via an anisotropic topographical guide, which provides the LC molecules with stable homogeneous alignment.
Collapse
|
28
|
Lee JH, Jeong HC, Park HG, Seo DS. Hysteresis-free liquid crystal devices based on solution-derived oxide compound films treated by ion beam irradiation. RSC Adv 2015. [DOI: 10.1039/c5ra09337f] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Compounds with a high dielectric constant (high-k compounds) offer fast response times and low threshold voltages, and achieve a hysteresis-free LC device, thereby overcoming a image sticking issue.
Collapse
Affiliation(s)
- Ju Hwan Lee
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749
- Korea
| | - Hae-Chang Jeong
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749
- Korea
| | - Hong-Gyu Park
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749
- Korea
| | - Dae-Shik Seo
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749
- Korea
| |
Collapse
|
29
|
Park HG, Jeong HC, Park TK, Seo DS. Ion-beam-irradiated solution-derived tin oxide films for liquid crystal orientation. RSC Adv 2015. [DOI: 10.1039/c4ra12578a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We present the alignment characteristics of liquid crystal (LC) molecules on solution-derived tin(iv) oxide (SnO2) films.
Collapse
Affiliation(s)
- Hong-Gyu Park
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749
- Korea
| | - Hae-Chang Jeong
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749
- Korea
| | - Tae-Kyu Park
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749
- Korea
| | - Dae-Shik Seo
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749
- Korea
| |
Collapse
|
30
|
Lee JW, Park HG, Jeong HC, Jang SB, Park TK, Seo DS. High performance twisted nematic liquid crystal display with solution-derived YZO surface modification via ion-beam irradiation. OPTICS EXPRESS 2014; 22:31396-31403. [PMID: 25607088 DOI: 10.1364/oe.22.031396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Solution-derived YZO films were investigated as liquid crystal (LC) alignment layers modified by ion beam (IB) irradiation. Solution processing was adopted in place of the sputtering method for the deposition of YZO films as LC alignment layers. Uniform and homogeneous LC alignment was achieved to produce a high performance LC system. X-ray photoelectron spectroscopy analysis showed that surface reformation of YZO films by annealing and IB irradiation affects the uniformity of the LC alignment. Superior electro-optical characteristics of twisted nematic LC cells constructed from IB-irradiated YZO films were observed, which indicates that the proposed solution-derived YZO films have strong potential for use in the production of advanced LC displays.
Collapse
|
31
|
Chung HK, Lee WK, Park HG, Lee HM, Jeong HC, Cho MC, Seo DS. Polarized UV cured reactive mesogens for fast switching and low voltage driving liquid crystal device. OPTICS EXPRESS 2014; 22:21551-21559. [PMID: 25321534 DOI: 10.1364/oe.22.021551] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Uniaxial alignment of liquid crystals (LCs) is prerequisite for a vast number of LC applications. To accomplish stable and uniform LC orientation, an alignment process to orient the LCs is required. Herein, we demonstrate a simple strategy for fabricating novel LC alignment layers that ensures well aligned LC, superior switching without any capacitance hysteresis, low transmittance loss, and high thermal stability with sufficient anchoring action. Thin films of reactive mesogens (RMs) were transferred onto conventional homeotropic polyimides from a UV-cured RM stamp via contact printing. LC displays using defect free RM/PI polymeric stacks exhibited superior electro-optic (EO) properties to those containing rubbed PI layers. This approach allows for the fabrication of various-mode LC displays such as twisted nematic (TN), in-plane switching (IPS), and optically compensated bend (OCB) mode LCDs by changing the combinations of RMs, base PIs and LCs.
Collapse
|
32
|
Cattaneo L, Zhang J, Zuiddam M, Savoini M, Rasing T. Gaining control through frustration: two-fold approach for Liquid Crystal three-dimensional command layers. NANO LETTERS 2014; 14:3903-3907. [PMID: 24936774 DOI: 10.1021/nl501155h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The alignment of Liquid Crystal (LC) molecules, essential for their applications in optical devices such as displays, is usually controlled by functionalizing their confining surfaces by either patterning or by specific surfactants that induce either parallel or perpendicular molecular arrangement. Inducing a bistable alignment, such as in the new zenithal bistable displays, offers new opportunities in terms of new functionalities and lower energy consumption but a full understanding of such bistable alignment appears still complicated. Here we present a simple phenomenological model that includes surface topography and chemistry. The predicted orientational transitions and bistable states are in excellent agreement with experiments, thus making this a proper tool to design multistable 3D command layers.
Collapse
Affiliation(s)
- Laura Cattaneo
- Institute for Molecules and Materials, Radboud University Nijmegen , Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | | | | | | | | |
Collapse
|
33
|
Park HG, Lee HM, Jeong HC, Seo DS. Fast switching of liquid crystals on transferred reactive mesogens film via soft imprinting method. RSC Adv 2014. [DOI: 10.1039/c4ra06645f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Unidirectional alignment of liquid crystal (LC) molecules is a prerequisite for advanced LC devices.
Collapse
Affiliation(s)
- Hong-Gyu Park
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749, Korea
| | - Hak Moo Lee
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749, Korea
| | - Hae-Chang Jeong
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749, Korea
| | - Dae-Shik Seo
- Department of Electrical and Electronic Engineering
- Yonsei University
- Seoul 120-749, Korea
| |
Collapse
|
34
|
|
35
|
Jian SJ, Kou CS, Hwang J, Lee CD, Lin WC. Orientating layers with adjustable pretilt angles for liquid crystals deposited by a linear atmospheric pressure plasma source. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2013; 84:063501. [PMID: 23822339 DOI: 10.1063/1.4807695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A method for controlling the pretilt angles of liquid crystals (LC) was developed. Hexamethyldisiloxane polymer films were first deposited on indium tin oxide coated glass plates using a linear atmospheric pressure plasma source. The films were subsequently treated with the rubbing method for LC alignment. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy measurements were used to characterize the film composition, which could be varied to control the surface energy by adjusting the monomer feed rate and input power. The results of LC alignment experiments showed that the pretilt angle continuously increased from 0° to 90° with decreasing film surface energy.
Collapse
Affiliation(s)
- Shih-Jie Jian
- Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
| | | | | | | | | |
Collapse
|
36
|
Lee WK, Hwang SJ, Cho MJ, Park HG, Han JW, Song S, Jang JH, Seo DS. CIS-ZnS quantum dots for self-aligned liquid crystal molecules with superior electro-optic properties. NANOSCALE 2013; 5:193-199. [PMID: 23142966 DOI: 10.1039/c2nr32458j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We demonstrate self-aligned and high-performance liquid crystal (LC) systems doped with 1-dimensional (1D) chain-like clusters of CuInS(2) (CIS)-ZnS core-shell quantum dots (QDs). By changing the cell fabrication method of the LC-QD composites, we can selectively control the orientation of the LC molecules between the homogeneous and homeotropic states without conventional LC alignment layers. The homeotropic alignment of LCs was achieved by random dropcasting and the homogeneous alignment was performed using a capillary injection of LC-QDs due to the random or linear diffusion of QD clusters into ITO defects. The electrically compensated bend (ECB)- and vertically aligned (VA) mode LC displays (LCDs) containing our LC-QD composite both showed superior electro-optic (EO) properties. A 37.1% reduction in the threshold voltage (V(th)) and a 36.6% decrease in the response time were observed for ECB mode LCDs, and a 47.0% reduction in the V(th) and a 38.3% decrease in the response time were observed for VA mode LCDs, meaning that the proposed LC-QD composites have a great potential for the production of advanced flexible LCDs.
Collapse
Affiliation(s)
- Won-Kyu Lee
- Electronic Materials Research Institute, Kolon Central Research Park, Kolon Industries, Inc., Yongin 446-797, Republic of Korea
| | | | | | | | | | | | | | | |
Collapse
|
37
|
Liu YJ, Loh WW, Leong ESP, Kustandi TS, Sun XW, Teng JH. Nanoimprinted ultrafine line and space nanogratings for liquid crystal alignment. NANOTECHNOLOGY 2012; 23:465302. [PMID: 23092932 DOI: 10.1088/0957-4484/23/46/465302] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Ultrafine 50 nm line and space nanogratings were fabricated using nanoimprint lithography, and were further used as an alignment layer for liquid crystals. The surface morphologies of the nanogratings were characterized and their surface energies were estimated through the measurement of the contact angles for two different liquids. Experimental results show that the surface energies of the nanogratings are anisotropic: the surface free energy towards the direction parallel to the grating lines is higher than that in the direction perpendicular to the grating lines. Electro-optical characteristics were tested from a twisted nematic liquid crystal cell, which was assembled using two identical nanogratings. Experimental results show that such a kind of nanograting is promising as an alternative to the conventional rubbing process for liquid crystal alignment.
Collapse
Affiliation(s)
- Yan Jun Liu
- Institute of Materials Research and Engineering, Agency for Science Technology and Research (A*STAR), 3 Research Link, Singapore 117602, Singapore.
| | | | | | | | | | | |
Collapse
|
38
|
Solomon D, Lehmann J, Wang J, Kinyangi J, Heymann K, Lu Y, Wirick S, Jacobsen C. Micro- and nano-environments of C sequestration in soil: a multi-elemental STXM-NEXAFS assessment of black C and organomineral associations. THE SCIENCE OF THE TOTAL ENVIRONMENT 2012; 438:372-388. [PMID: 23022722 DOI: 10.1016/j.scitotenv.2012.08.071] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Revised: 08/23/2012] [Accepted: 08/24/2012] [Indexed: 06/01/2023]
Abstract
Black C is an essential component of the terrestrial C pool and its formation is often credited as a CO(2) sink by transferring the fast-cycling C from the atmosphere-biosphere system into slower cycling C in the geosphere. This study is the first multi-element K- (C, N, Ca, Fe, Al and Si) soft-X-ray STXM-NEXAFS investigation conducted at a submicron-scale spatial resolution specifically targeting black C and its interaction with the mineral and non-black C organic matter in the organomineral assemblage. The STXM-NEXAFS micrographs and spectra demonstrated that pyrogenic C was dominated by quinoide, aromatic, phenol, ketone, alcohol, carboxylic and hydroxylated- and ether-linked C species. There was also evidence for the presence of pyridinic, pyridonic, pyrrolic, amine and nitril N functionalities. The non-black C organic matter contained amino acids, amino sugars, nucleic acids and polysaccharides known to exhibit negatively charged carboxylic, phenolic, enolic, thiolate and phosphate functionalities highly reactive towards metal ions and black C. The metal-rich mineral matrix was composed of phyllosilicate clay minerals, Fe and Al hydroxypolycations, oxides, hydroxides and oxyhydroxide that can attract and bind organic biopolymers. STXM-NEXAFS provided evidence for interactive association between pyrogenic C, non-black C organic matter and the mineral oxide and oxyhydroxide communities in the organomineral interface. These intimate associations occurred through a "two-way" direct linkage between black C and the mineral or non-black C organic matter or via a "three-way" indirect association where non-black C organic matter could serve as a molecular cross-linking agent binding black C with the mineral matrix or vice versa where inorganic oxides, hydroxides and polycations could act as a bridge to bind black C with non-black C organic matter. The binding and sequestration of black C in the investigated micro- and nano-C repository environments seem to be the combined action of physical entrapment in seemingly terminal biotic exclusion zone through the action of metal oxides and organic matter induced microaggregation and through molecular-level association ranging from ligand exchange, polyvalent cation bridging to weak hydrophobic interactions including van der Waals and H-bonding.
Collapse
|
39
|
Son PK, Choi SW, Kim SS, Gwag JS. Conductivity of ITO film amplified by multi-step ion beam-treatment on PET layers at room temperature. SURF INTERFACE ANAL 2012. [DOI: 10.1002/sia.5097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Phil Kook Son
- Department of Advanced Materials Engineering for Information and Electronics; Kyung Hee University; Yongin Gyeonggi-do 446-701 Republic of Korea
- Regional Innovation Center-Components and Materials for Information Display; Kyung Hee University; Yongin Gyeonggi-do 446-701 Republic of Korea
| | - Suk-Won Choi
- Department of Advanced Materials Engineering for Information and Electronics; Kyung Hee University; Yongin Gyeonggi-do 446-701 Republic of Korea
- Regional Innovation Center-Components and Materials for Information Display; Kyung Hee University; Yongin Gyeonggi-do 446-701 Republic of Korea
| | - Sung Soo Kim
- Department of Chemical Engineering; Kyung Hee University; Yongin Gyeonggi-do 446-701 Republic of Korea
- Regional Innovation Center-Components and Materials for Information Display; Kyung Hee University; Yongin Gyeonggi-do 446-701 Republic of Korea
| | - Jin Seog Gwag
- Department of Physics; Yeungnam University; Gyeongsan 712-749 Republic of Korea
| |
Collapse
|
40
|
Siqing S, Wu H, Yamaguchi H, Shinohara T, Sakata O, Takahara A. Grazing-incidence wide-angle X-ray diffraction study on molecular aggregation state of imprinted polyimide film before and after hard baking. Polym Bull (Berl) 2012. [DOI: 10.1007/s00289-012-0784-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
41
|
Lam RS, Metzler RA, Gilbert PU, Beniash E. Anisotropy of chemical bonds in collagen molecules studied by X-ray absorption near-edge structure (XANES) spectroscopy. ACS Chem Biol 2012; 7:476-80. [PMID: 22148847 DOI: 10.1021/cb200260d] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Collagen type I fibrils are the major building blocks of connective tissues. Collagen fibrils are anisotropic supramolecular structures, and their orientation can be revealed by polarized light microscopy and vibrational microspectroscopy. We hypothesized that the anisotropy of chemical bonds in the collagen molecules, and hence their orientation, might also be detected by X-ray photoemission electron spectromicroscopy (X-PEEM) and X-ray absorption near-edge structure (XANES) spectroscopy, which use linearly polarized synchrotron light. To test this hypothesis, we analyzed sections of rat-tail tendon, composed of parallel arrays of collagen fibrils. The results clearly indicate that XANES-PEEM is sensitive to collagen fibril orientation and, more specifically, to the orientations of carbonyl and amide bonds in collagen molecules. These data suggest that XANES-PEEM is a promising technique for characterizing the chemical composition and structural organization at the nanoscale of collagen-based connective tissues, including tendons, cartilage, and bone.
Collapse
Affiliation(s)
- Raymond S.K. Lam
- Department of Oral Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
15261, United States
| | - Rebecca A. Metzler
- Department
of Physics, University of Wisconsin, Madison,
Wisconsin 53706,
United States
| | - Pupa U.P.A. Gilbert
- Department
of Physics, University of Wisconsin, Madison,
Wisconsin 53706,
United States
| | - Elia Beniash
- Department of Oral Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
15261, United States
| |
Collapse
|
42
|
Ahn D, Jeong YC, Han M, Cho KY, Lee S, Park JK. Photo-configurable embossed liquid crystal alignment layer with high azimuthal anchoring strength. OPTICS EXPRESS 2012; 20:6835-6843. [PMID: 22418566 DOI: 10.1364/oe.20.006835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Herein we describe a photo-alignment layer of improved azimuthal anchoring energy comparable to conventional rubbing method. In order to address the inherent low anchoring stability of photo-alignment layer, we applied embossing technique to conventional photosensitive polymer film, based on the cinnamoyl photoreactive groups, to introduce physical micro-groove effect for additional anchoring energy. From this, 2.5 × 10⁻⁴ J/m² of azimuthal anchoring energy was achieved, which is considered as synergistic effect from both photoinduced chemical interaction and physical microgroove alignment. In this study, we conducted systematic study on change in anchoring energy as a function of both aspect ratio of embossed pattern and UV exposure dose. We also demonstrated fabrication of sophisticated multi-domain structure of LC cells and discussed theoretical interpretation through LC simulation.
Collapse
Affiliation(s)
- Dowon Ahn
- Department of Chemical and Biomolecular Engineering, KAIST, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, South Korea
| | | | | | | | | | | |
Collapse
|
43
|
Son PK, Choi SW. Investigation of ion-beam-treated SiOx film surfaces for liquid crystal alignment. SURF INTERFACE ANAL 2012. [DOI: 10.1002/sia.4817] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Phil Kook Son
- Department of Advanced Materials Engineering for Information and Electronics and Regional Innovation Center-Components and Materials for Information Display; Kyung Hee University; Yongin; Gyeonggi-do; 446-701; Korea
| | - Suk-Won Choi
- Department of Advanced Materials Engineering for Information and Electronics and Regional Innovation Center-Components and Materials for Information Display; Kyung Hee University; Yongin; Gyeonggi-do; 446-701; Korea
| |
Collapse
|
44
|
Kang YG, Kim HJ, Park HG, Kim BY, Seo DS. Tin dioxide inorganic nanolevel films with different liquid crystal molecular orientations for application in liquid crystal displays (LCDs). ACTA ACUST UNITED AC 2012. [DOI: 10.1039/c2jm13689a] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
45
|
Hong-Gyu Park, Hae-Yun Jeong, Young-Hwan Kim, Byoung-Yong Kim, Jeong-Hwan Kim, Hongil Yoon, Dae-Shik Seo. Electrooptical Properties of Single-Walled Carbon-Nanotube Mixed Liquid-Crystal Cells With Rubbed and Ion-Beam-Treated Alignment Layers. ACTA ACUST UNITED AC 2011. [DOI: 10.1109/jdt.2011.2160841] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
46
|
Ho CY, Lin FH, Tao YT, Lee JY. Improvement in device performance from a mixture of a liquid crystal and photosensitive acrylic prepolymer with the photoinduced vertical alignment method. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2011; 12:065002. [PMID: 27877462 PMCID: PMC5090677 DOI: 10.1088/1468-6996/12/6/065002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 12/02/2011] [Accepted: 10/24/2011] [Indexed: 06/06/2023]
Abstract
In a multicomponent nematic liquid crystal (NLC) mixture of a liquid crystal (negative-type NLC) and a photosensitive acrylic prepolymer, photopolymerization upon UV irradiation induces the separation of the LC and photosensitive acrylic prepolymer layers, thereby leading to a vertical arrangement of LC molecules. In this study, we propose a simple vertical alignment method for LC molecules, by adding a chiral smectic A (SmA∗) liquid crystal having homeotropic texture characteristics to an NLC mixture solution. Measurements of electro-optical properties revealed that the addition of the SmA∗ LC not only strengthened the anchoring force of the copolymer alignment film surface, but also significantly enhanced the contrast ratio (∼73%), response time and grayscale switching performance of the device.
Collapse
Affiliation(s)
- Czung-Yu Ho
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
- Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan
| | - Fa-Hsin Lin
- Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan
| | - Yu-Tai Tao
- Institute of Chemistry, Academia Sinica, Taipei 115, Taiwan
| | - Jiunn-Yih Lee
- Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan
| |
Collapse
|
47
|
Abstract
Understanding electronic structure at the nanoscale is crucial to untangling fundamental physics puzzles such as phase separation and emergent behavior in complex magnetic oxides. Probes with the ability to see beyond surfaces on nanometer length and subpicosecond time scales can greatly enhance our understanding of these systems and will undoubtedly impact development of future information technologies. Polarized X-rays are an appealing choice of probe due to their penetrating power, elemental and magnetic specificity, and high spatial resolution. The resolution of traditional X-ray microscopes is limited by the nanometer precision required to fabricate X-ray optics. Here we present a novel approach to lensless imaging of an extended magnetic nanostructure, in which a scanned series of dichroic coherent diffraction patterns is recorded and numerically inverted to map its magnetic domain configuration. Unlike holographic methods, it does not require a reference wave or precision optics. In addition, it enables the imaging of samples with arbitrarily large spatial dimensions, at a spatial resolution limited solely by the coherent X-ray flux, wavelength, and stability of the sample with respect to the beam. It can readily be extended to nonmagnetic systems that exhibit circular or linear dichroism. We demonstrate this approach by imaging ferrimagnetic labyrinthine domains in a Gd/Fe multilayer with perpendicular anisotropy and follow the evolution of the domain structure through part of its magnetization hysteresis loop. This approach is scalable to imaging with diffraction-limited resolution, a prospect rapidly becoming a reality in view of the new generation of phenomenally brilliant X-ray sources.
Collapse
|
48
|
Gilbert PUPA, Young A, Coppersmith SN. Measurement of c-axis angular orientation in calcite (CaCO3) nanocrystals using X-ray absorption spectroscopy. Proc Natl Acad Sci U S A 2011; 108:11350-5. [PMID: 21693647 PMCID: PMC3136314 DOI: 10.1073/pnas.1107917108] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We demonstrate that the ability to manipulate the polarization of synchrotron radiation can be exploited to enhance the capabilities of X-ray absorption near-edge structure (XANES) spectroscopy, to include linear dichroism effects. By acquiring spectra at the same photon energies but different polarizations, and using a photoelectron emission spectromicroscope (PEEM), one can quantitatively determine the angular orientation of micro- and nanocrystals with a spatial resolution down to 10 nm. XANES-PEEM instruments are already present at most synchrotrons, hence these methods are readily available. The methods are demonstrated here on geologic calcite (CaCO(3)) and used to investigate the prismatic layer of a mollusk shell, Pinctada fucata. These XANES-PEEM data reveal multiply oriented nanocrystals within calcite prisms, previously thought to be monocrystalline. The subdivision into multiply oriented nanocrystals, spread by more than 50°, may explain the excellent mechanical properties of the prismatic layer, known for decades but never explained.
Collapse
Affiliation(s)
| | - Anthony Young
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | | |
Collapse
|
49
|
Kang YG, Park HG, Kim HJ, Kim YH, Oh BY, Kim BY, Kim DH, Seo DS. Superior optical properties of homogeneous liquid crystal alignment on a tin (IV) oxide surface sequentially modulated via ion beam irradiation. OPTICS EXPRESS 2010; 18:21594-21602. [PMID: 20941057 DOI: 10.1364/oe.18.021594] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We first investigated the alignment characteristics of tin (IV) oxide (SnO(2)) thin films deposited by radio-frequency (RF) magnetron sputtering. This study demonstrates that liquid crystal (LC) molecules could be aligned homogeneously by controlling the Ion Beam (IB) irradiation energy densities. We also show that the pretilt angle of the LC molecules has a close relation with the surface energy. X-ray photoelectron spectroscopy (XPS) indicates that a non-stoichiometric SnO(2-x) surface converted by ion beam irradiation can horizontally align the LC molecules. The measured electro-optical (EO) characteristics showed high performance, comparable with those of rubbed and ion-beam irradiated polyimide (PI) layers.
Collapse
Affiliation(s)
- Young-Gu Kang
- Information Display Device Laboratory, Department of Electrical and Electronic Engineering, Yonsei University 262 Seongsanno, Seodaemun-gu, Seoul 120-749, South Korea
| | | | | | | | | | | | | | | |
Collapse
|
50
|
Ahn D, Jeong YC, Lee S, Park JK. UV-driven in-plane rotation of a liquid crystal director in poly(vinyl cinnamate) films having microscale grooves. OPTICS LETTERS 2010; 35:3141-3143. [PMID: 20847805 DOI: 10.1364/ol.35.003141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The micropatterned poly(vinyl cinnamate) (PVCi) alignment layers are fabricated by a solvent-assisted micromolding method. Without UV irradiation, the alignment layer can induce the unidirectional liquid crystal (LC) orientation, which is influenced by topography-based anchoring energies. With photodimerization of PVCi by UV irradiation, we could modulate the anchoring energies caused by chemical interactions of the alignment layer. It is observed that these two different contributions compete against each other in determining LC rotation on the surface of the alignment layer. The rotation angle of LC directors could be controlled from 45° to 70° by simply changing the UV exposure dose.
Collapse
Affiliation(s)
- Dowon Ahn
- Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701, Korea
| | | | | | | |
Collapse
|