• Title/Summary/Keyword: homeotropic

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Liquid crystal alignment on patterned-alignment films

  • Lias, Jais Bin;Oo, Thet Naing;Yazawa, Tomohiro;Kimura, Munehiro;Akahane, Tadashi
    • Journal of Information Display
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    • v.12 no.2
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    • pp.101-107
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    • 2011
  • To come up with a bistable liquid crystal (LC) device using unpolarized UV light, single-step laser patterning on a photoalignment layer using a photomask was proposed to achieve an equilibrium configuration of LC molecules in contact with a periodically patterned substrate. The patterns were formed by stripes of alternating random planar and homeotropic anchoring on a submicrometer scale in the order of $0.5{\mu}m$. Two possible configurations of bistable LC cells that can be obtained by combining a micropatterned surface formed with alternating random-planar- and homeotropic-alignment with planar- or homeotropic-alignment surfaces were proposed. The alignment properties of the two proposed models were investigated, along with the microscopic switching behavior of micropatterned nematic LC cells.

Control of Pretilt Angle by UV exposure during Imidization of Polyimide for Homeotropic Alignment (수직 배향용 폴리미이드의 소성시에 UV 조사를 이용한 프리틸트각 제어)

  • 황정연;서대식;한은주;갬재형
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.11
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    • pp.950-953
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    • 2000
  • Aligning capabilities of nematic liquid crystal(NLC) using an in-situ photo-alignment method with obliquely polarized UV exposure on a polyimide (PI) surface for homeotropic alignment were studied. The high angle for NLC can be measured by obliquely UV exposure of 30°on the PI surface for 10∼20 min. The pretilt angle of NLC generated using the in-situ photo-alignment was higher than that of a conventional photo-alignment method. Finally, we suggest that the control of pretilt angle in NLC with obliquely polarized UV exposure during imidization of the polymer for homeotropic alignment is promising method to generate high pretilt angle.

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Homeotropic Alignment Effect of Liquid Crystal on the SiC Thin Film Layer (SiC 박막을 이용한 액정의 수직배향효과)

  • Park, Chang-Joon;Hwang, Jeoung-Yeon;Kang, Hyung-Ku;Kim, Young-Hwan;Seo, Dae-Shik;Ahn, Han-Jin;Kim, Kyung-Chan;Kim, Jong-Bok;Baik, Hong-Koo;Lim, Sung-Hoon;Park, Kyu-Chang;Jang, Jin
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.11a
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    • pp.502-505
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    • 2004
  • We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a SiC (Silicon Carbide) thin film. SiC thin film exhibits good chemical and thermal stability. The good thermal and chemical stability make SiC an attractive candidate for electronic applications. A homeotropic alignment of nematic liquid crystal by ion beam (IB) exposure on the SiC thin film surface was achieved. The about $87^{\circ}$ of stable pretilt angle was achieved at the range from $30^{\circ}$ to $45^{\circ}$ of incident angle. The good LC alignment is maintained by the ion beam alignment method on the SiC thin film surface until annealing temperature of $300^{\circ}C$. Consequently, homeotropic alignment effect of liquid crystal and the good thermal stability by the ion beam alignment method on the SiC thin film layer can be achieved.

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Liquid crystal alignment on rubbed self-assembled monolayers according to alkyl chain length (알킬 사슬 길이에 따른 러빙 처리된 자기 조립 단분자막의 액정 배향 연구)

  • Park, Hong-Gyu;Park, Mu-Hun
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.14 no.5
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    • pp.362-368
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    • 2021
  • A homeotropic liquid crystal (LC) alignment state on rubbed fluorinated self-assembled monolayers (FSAMs) is described according to alkyl chain length. A simple procedure, gas-phase method, for the preparation of FSAM was used. The average optical transmittance in the visible light range of FSAMs were 76.63% to 78.21%, which were superior to the conventional polyimide layer having a transmittance of 75.89%. In addition, the excellent homeotropic LC alignment characteristics of FSAMs were observed through pretilt angle measurement and polarized optical microscope images. By measuring the contact angles and the surface energies of FSAMs, it was confirmed that pretilt angles of LC molecules increased according to the alkyl chain length. High optical transparency and uniform homeotropic LC alignment characteristics of FSAMs showed the possibility of FSAMs as an LC alignment layers.

Homeotropic Alignment Effect for Nematic Liquid Crystal on the SiOx Thin Film Layer by New Ion Beam Exposure

  • Han, Jeong-Min;Choi, Sung-Ho;Kim, Byoung-Yong;Han, Jin-Woo;Hwang, Jeoung-Yeon;Ok, Chul-Ho;Seo, Dae-Shik
    • Transactions on Electrical and Electronic Materials
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    • v.7 no.6
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    • pp.293-296
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    • 2006
  • We studied homeotropic alignment effect for a nematic liquid crystal (NLC) on the $SiO_{x}$ thin film irradiated by the new ion beam method. $SiO_{x}$ thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) and were treated by the DuoPIGatron ion source. A uniform liquid crystal alignment effect was achieved over 2100 eV ion beam energy. Tilt angle were about $90^{\circ}$ and were not affected by various ion beam energy.

Control of tilt angle in the Nematic Liquid Crystal as a Function of the Baking Temperature (소성 온도 변화를 이용한 네마틱 액정의 틸트 제어)

  • Lee, Kyung-Jun;Hwang, Jeoung-Yeon;Kim, Kang-Woo;Seo, Dae-Shik
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.11a
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    • pp.67-70
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    • 2003
  • The control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by hot plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. Especially, the low LC tilt angle of positive type NLC ($\Delta\varepsilon$ >0) on the rubbed homeotropic PI surface by increasing temperature and time was measured. The tilt angle of positive type NLC ($\Delta\varepsilon$ >0) is smaller than that of the negative type ($\Delta\varepsilon$ >0) on rubbed PI with increasing baking temperature and time. We consider that the tilt angle of NLC is decreased due to increasing the steric interaction between horizon component of permittivity $\varepsilon$ = of NLC and the stress of polymer side chain by high temperature.

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Locked Super Homeotropic Liquid Crystal Mode with Wide Viewing Angle using patterned polymer

  • Park, S.H.;Song, I.S.;Kim, W.C.;Oh, S.T.;Lee, S.H.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.1185-1187
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    • 2004
  • We have studied a liquid crystal (LC) mode, named locked super homeotropic (LSH), where the LCs aligned homeotropically are locked by surrounding walls such as cubic, hexagonal and cylinder. In the device, the vertically aligned LCs tilt down symmetrically around the center of the cell when a voltage is applied and thus it exhibits wide viewing angle. In addition, since the LCs is locked in micro domains the LCs do not flow to the bottom of the panel by gravity.

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Novel Alignment Layers for Ion Beam Method and the Orientations of Liquid Crystal

  • Ahn, Han-Jin;Kim, Kyung-Chan;Kim, Jong-Bok;Baik, Hong-Koo;Park, Chang-Joon;Hwang, Jeoung-Yeon;Seo, Dae-Shik
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.1155-1158
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    • 2004
  • Various inorganic alignment layers of nematic liquid crystal (NLC) molecules were investigated. Ar ion beam (IB) irradiation was utilized for alignment method and homogenous and homeotropic orientations with tilt angle were obtained on the suitable inorganic thin films. Proper doping materials were added to diamond-like carbon (DLC) films. In the case of homogeneous alignment, nitrogen doping affected the increase of pretilt angle, while the fluorine bonding in the DLC films was induced the tilted homeotropic alignment cause its extreme hydrophobic property. These results showed that ion beam irradiation method could be applied to the various alignment mode of NLC such as IPS, TN and MVA.

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A Novel ECB cell using bend structure for Nematic Liquid Crystal on Rubbed Polyimide Surface

  • Hwang, J.Y.;Kim, K.W.;Seo, D.S.
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.1137-1141
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    • 2004
  • In this paper, we have improved a novel ECB mode using bend structure with high tilt angle in the unique condition by Hot plate equipment. The new control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by Hot plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. We suggest that the development of the novel ECB cell using control of tilt angle on the homeotropic surface is a promising technique for the achievement of fast response time and high contrast ratio.

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Controllable Pretilt Angles for Liquid Crystal Molecules using a Rubbing Treated Mixture Layer

  • Kim, Dae-Hyun;Park, Hong-Gyu;Kim, Young-Hwan;Kim, Byoung-Yong;Ok, Chul-Ho;Seo, Dae-Shik
    • Transactions on Electrical and Electronic Materials
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    • v.10 no.4
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    • pp.140-142
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    • 2009
  • We have investigated the continuous pretilt angle generation for liquid crystals using a rubbing treated mixture layer consisting of homogeneous and homeotropic polyimides. Various pretilt angles in the range from $0^{\circ}$ to $60^{\circ}$ were achieved as a function of the concentration of homeotropic PI. The transmittance characteristics used to measure the pretilt angle showed that the pretilt angles were measured with a high reliability. We observed uniform liquid crystal alignment on the rubbing treated mixture layer.