• Title/Summary/Keyword: Surface anchoring energy

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A Study on Electro-optical Characteristics Dependent on Surface Anchoring Energy in the Fringe-field Switching Mode (FFS 모드에서 표면 엥커링에너지에 따른 전기광학특성의 연구)

  • Yu, In-Ho;Zhong, Zhen-Xin;Jang, Won-Gun;Lee, Myong-Hoon;Lee, Seung Hee
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.18 no.11
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    • pp.1028-1032
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    • 2005
  • Liquid crystal (LC) alignment using a photoalignment method by irradiation of polarized ultraviolet (UV) on an alignment layer has been investigated. Photoalignment method exhibits weaker anchoring energy than rubbing method so that we have studied electro-optic characteristics of fringe-field switching (FFS) mode with alignment layers using the photo and rubbing alignment methods. The cell using photo alignment layer shows lower threshold and operation voltage than those using rubbed alignment layer. Also, the former method shows higher transmittance than that of the latter.

Effect of Surface anchoring energy on the Electro-Optical Characteristics in the Fringe-Field Switching mode (FFS 모드에서 표면 앵커링 에너지에 따른 전기광학특성의 연구)

  • Yu, In-Ho;Zhong, Zhen-Xin;Jang, Won-Gun;Lee, Myong-Hoon;Lee, Seung-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.05a
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    • pp.118-122
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    • 2005
  • Liquid crystal (LC) alignment using a photoalignment method by irradiation of polarized ultraviolet (UV) on an alignment layer has been investigated. Photoalignment method exhibits weaker anchoring energy than rubbing method so that we have studied electro-optic characteristics of fringe-field switching (FFS) mode with alignment layers using the photo and rubbing alignment methods. The cell using photo alignment layer shows lower threshold and operation voltage than those using rubbed alignment layer. Also. the former method shows higher transmittance than that of the latter.

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Basic Properties of Cell Fabricated by Ion-beam Treatment for In-plane Switching LCD

  • Seo, Joo-Hong;Lee, Sung-Pil;Yoon, Tae-Hoon;Kim, Jae-Chang
    • Journal of Information Display
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    • v.7 no.1
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    • pp.12-18
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    • 2006
  • We investigated the horizontal alignment properties such as surface morphology, pretilt angle, and polar and azimuthal anchoring energy of organic alignment material-coated surface treated by ion beam. In this investigation the energy and incident angle of ion beam were changed. We also fabricated an in-plane switching (IPS) cell by ion beam alignment. The results showed similar voltage-transmittance characteristics to those of a rubbed cell and better dark state.

The Characteristics of Photo-alignment with Photo-crosslinkable Polyimide (광 가교성 폴리이미드의 광배향 특성)

  • Shin, Dong-Muyng;Cho, Sun-Ju;Shon, Byoung-Choung;Choi, Jeong-Woo;Yi, Mi-Hie;Choi, Kil-Yeoung
    • Journal of the Korean Applied Science and Technology
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    • v.16 no.1
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    • pp.15-20
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    • 1999
  • Photo-crosslinkable polyimide(PI) which contains CF3 moiety was synthesized. Polarized UV light transformed ketone group of PI to hydroxyl group, which was confirmed by IR and UV-visible spectroscopy. We investigated the dichroic UV-absorption before and after photo-reaction with linearly polarized light. In particular we have attempted to clarify the relationship between the anisotropy of surface region and surface azimuthal anchoring energy and knew that the anchoring energy of photo-alignment PI is comparable with that of mechanical rubbing.

The Alignment of Liquid Crystals on the Film Surfaces of Soluble Aromatic Polyimides Bearing t-Butylphenyl and Trimethylsilylphenyl Side Groups

  • Hahm, Suk-Gyu;Jin, Kyeong-Sik;Park, Sam-Dae;Ree, Moon-Hor;Kim, Hyung-Sun;Kwon, Soon-Ki;Kim, Yun-Hi
    • Macromolecular Research
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    • v.17 no.12
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    • pp.976-986
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    • 2009
  • With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride(BTPD), and 2,2'-bis(4"-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyirnides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from $0.45{\times}10^{-4}\;-\;1.37{\times}10^{-4}\;J/m^2$ and from $0.86{\times}10^{-5}\;-\;4.26{\times}10^{-5}\;J/m^2$, respectively, depending on the polyimides. The pretilt angles of the LCs were in the range $0.10-0.62^{\circ}$. In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.

Electro-optical Characterization of Transmission Holographic PDLC with Surfactant

  • Woo, Ju-Yeon;Kim, Eun-Hee;Kim, Byung-Kyu
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.1204-1207
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    • 2004
  • The effects of surfactant on the electro-optic properties of holographic polymer dispersed liquid crystal(HPDLC) have been studied hoping to increase the diffraction efficiency and to reduce the anchoring energy at interfaces. Octanoic acid(OA) was used as sulfactant. The 2,2,2 trifluoroethyl acrylate(TFEA) was added to the monomer mixture to enhance the phase separation and improve optical properties. The morphology of holographic gratings was examined using scanning electron microscopy(SEM). Addition of surfactant was likely to reduce the surface anchoring of the nematic droplet with the polymer surface which favors lowering of the swiching field and to improve the optical qualities.

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Improvement in the electro-optical properties of PDLCs (고분자 분산형 액정 표시소자의 전기광학적 특성 개선)

  • 최기석;박우상;박세근
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1998.06a
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    • pp.125-128
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    • 1998
  • The electro-optical properties of PDLCs ( Polymer Dispersed Liquid Crystals ) that have been interested for applications to projection display devices lately are significantly improved. For this improvement, we optimized not only the material parameters of liquid crystal and polymer but also the process conditions. Using TL series liquid crystals and polymer PN393 provided from Merck, we obtained the optimized process conditions such as cell gap, LC concentration, curing temperature and curing time. Under these conditions, we have achieved PDLC cells of threshold voltage 2.6V. contrast ratio 260 and negligible hysteresis.

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Asperities on the Surface of Plate-like Alumina and their Effect on Nacre-inspired Alumina-PMMA Composites

  • Kim, Bo-Yeon;Lee, Yoonjoo;Kim, Soo-Ryong;Shin, Dong-Geun;Kwon, Woo-Teck;Choi, Duck-Kyun;Kim, Younghee
    • Journal of the Korean Ceramic Society
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    • v.52 no.4
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    • pp.248-252
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    • 2015
  • Natural materials often have unique mechanical properties, such as the hierarchical structure of nacre formed through mineral bridges or asperities created between an inorganic particle and a natural-layer surface. As these asperities produce an exceptional shear resistance, in this study, we aimed to emulate the natural structure of nacre by synthesizing inorganic asperities and mineral bridges with different temperatures in the range of $1100-1300^{\circ}C$ and clay contents from 10 - 50 wt%. Following the infiltration of methyl methacrylate, we measured the mechanical properties to assess whether they were improved by the asperities. It was confirmed that the asperities improved the bending strength by 10%, and the anchoring effect was observed on the fracture surface.

Characteristics and Stability of Liquid Crystal Alignment for Interfacial Properties of Polyimide-Liquid Crystal (폴리이미드-액정 계면의 특성에 따른 액정 배향의 특성 및 안정성)

  • 동원석;이미혜;백상현
    • Polymer(Korea)
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    • v.27 no.5
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    • pp.484-492
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    • 2003
  • How the characteristics and stability of the rubbing-induced alignment of nematic liquid crystals (LCs) relate to the interfacial characteristics of LC-polyimide has been studied. The characteristics of the LC alignment (such as the LC texture, the pretilt angle, and the anchoring energy) and their thermal stability have been investigated for 5 polyimides synthesized for this work. The work showed that the rubbed polyimide alignment layer induces the strong LC anchoring and that the characteristics and stability of LC alignment are determined by the short-ranged interactions between LC and polyimide molecules at the alignment layer surface. The increased flexibility of the polyimide accelerates thermal imidization, increases the pretilt angle, and improves the alignment stability. It also turned out that fluorination of the polyimide tends to deteriorate the alignment uniformity and stability. No distinct differences in the alignment characteristics were shown for the aromatic- and alicyclic-dianhydride polyimides.

Liquid Crystal Alignment on Solid Substrates

  • Kim, Jae-Hoon;Shi, Yushan;Kumar, Satyendra
    • 한국정보디스플레이학회:학술대회논문집
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    • 2005.07a
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    • pp.755-758
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    • 2005
  • The mechanism responsible for liquid crystal (LC) alignment on solid substrates treated with mechanical rubbing or polarized UV is not understood. The results of x-ray reflectivity study of LC alignment on a large number of different alignment layers show that the anisotropy in the surface roughness of the substrate completely determines the LC alignment. The anchoring energy depends on the degree of roughness anisotropy and chemical interactions between the substrate and LC molecules.

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