• Title/Summary/Keyword: Liquid Crystal Alignment

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Vertical Alignment of Liquid Crystals by Ordering Effect of Self-assembled Monolayers on the Ion-beam-irradiated Anisotropic Surface

  • Park, Ji-Sub;Seok, Keun-Yeong;Hwang, Soo-Won;Kim, Jae-Chang;Yoon, Tae-Hoon;Kim, Jae-Hoon;Kim, Hak-Rin
    • Journal of Information Display
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    • v.11 no.4
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    • pp.144-148
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    • 2010
  • In this paper, vertically aligned (VA) liquid crystal (LC) modes were investigated using the alkyl chain ordering effect of self-assembled monolayers (SAMs) prepared on the anisotropic inorganic surface. On the anisotropic surface prepared through oblique ion beam irradiations, the SAM molecules are adsorbed, producing macroscopic alkyl chain ordering, which can determine the pretilt direction of the vertically aligned LC molecules through the intermolecular interactions on the surface.

Wide-Viewing Display Configuration of Heilix-Deformed Ferroelectric Liquid Crystals

  • Lee, Ju-Hyun;You, Doo-Hwan;Park, Jae-Hong;Lee, Sin-Doo;Yu, Chang-Jae
    • Journal of Information Display
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    • v.1 no.1
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    • pp.20-24
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    • 2000
  • We propose on a novel vertical configuration (VC) for a helix-deformed ferroelectric liquid crystal (HDFLC) display that has fast response, high contrast, analog gray scale capability, and wide-viewing characteristics. In contrast to a conventional HDFLC in a planar geometry, smectic layers arrange themselves parallel to the substrates, and thus, extremely uniform alignment of molecules in large area is naturally achieved in our new configuration without additional processes such as the rubbing and/or electric field treatment. Moreover, with a proper design of electrode patterns on the same substrate, multidomain switching is easily realized without employing any complex process of alignment. Our new VC-HDFLC is expected to provide a viable technology to produce a next-generation large area LCD suitable for processing the dynamic image at a video-rate.

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Liquid Crystal Alignment on Treated Surfaces

  • Chung, Doo-Han;Shioda, Tatsutoshi;Okada, Yoshinori;Park, Byoung-Choo;Takezoe, Hideo
    • 한국정보디스플레이학회:학술대회논문집
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    • 2003.07a
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    • pp.1088-1091
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    • 2003
  • We have studied liquid crystal orientation on rubbed and photoaligned polymer surfaces. The following topics will be presented; (1) visualization of nonuniformity of rubbing, (2) competition between grooves and photoalignment and (3) alignment process of 5CB evaporated on treated surfaces. Through these topics, the importance of the intermolecular liquid crystalline interaction will be emphasized.

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Properties of liquid crystal alignment layers exposued to ion-beam irradiation enemies (이온빔 에너지에 따른 액정배향막의 전기광학적 특성연구)

  • Oh, Byeong-Yun;Lee, Kang-Min;Park, Hong-Gyu;Kim, Byoung-Yong;Kang, Dong-Hun;Han, Jin-Woo;Kim, Young-Hwan;Han, Jeong-Min;Lee, Sang-Keuk;Seo, Dae-Shik
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.11a
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    • pp.430-430
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    • 2007
  • In general, polyimides (PIs) are used in liquid crystal displays (LCDs) as alignment layer of liquid crystals (LCs). Up to date, the rubbing alignment technique has been widely used to align liquid crystals on the PI surface, which is suitable for mass-production of LCDs because of its simple process and high productivity. However, this method has some disadvantages. Rubbed PI surfaces include the debris left by the cloth and the generation of electrostatic charges during rubbing process. Therefore, rubbing-free techniques for LC alignment are strongly required in LCD technology. In this experiment, PI was uniformly coated on indium-tin-oxide electrode substrates to form LC alignment layers using a spin-coating method and the PI layers were subsequently imidized at 433 K for 1 h. The thickness of the PI layer was set at 50 nm. The LC alignment layer surfaces were exposed to an $Ar^+$ ion-beam under various ion-beam energies. The antiparallel cells and twisted-nematic (TN) cells for the measurement of pretile angle and electro-optical characteristics were fabricated with the cell gap of 60 and $5\;{\mu}m$, respectively. The LC cells were filled with nematic LC (NLC, MJ001929, Merck) and were assembled. The NLC alignment capability on ion-beam-treated PI was observed using photomicroscope and the pretilt angle of the NLC was measured by the crystal-rotation method at room temperature. Voltage-transmittance (V-T) and response time characteristics of the ion-beam irradiated TN cell were measured by a LCD evaluation system.

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Study on the Alignment of the LC near Spacer in a Homogeneously Aligned LC Cell (수평배향된 액정셀에서의 스페이서 주변 액정 배향 연구)

  • 정연학;김성운;이종문;이승희
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.10
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    • pp.902-908
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    • 2002
  • Homogeneously aligned nematic liquid crystal displays (LCDs) driven by in-plane or fringe field were known to exhibit wide viewing angle and appeared to be black in the off state. However, the existence of spacers inside the cell causes the deformation of the liquid crystal molecules. Such a deformation of the liquid crystal causes light-leakage in the dark state, which lowers contrast ratio of the display. We found that the light-leakage due to deformation of the LC director near the spacer mainly depends on the dielectric anisotropy and the ratio of elastic constants of the LC. In this paper, the mechanism on deformation of the LC near spacer is investigated by optical polarizing microscopy.

Statistical Modeling of the Pretilt Angle Control in Nematic Liquid Crystal using In-situ Photoalignment Method on Plastic Substrate

  • Kang, Hee-Jin;Lee, Jung-Hwan;Yun, Il-Gu;Seo, Dae-Shik
    • Transactions on Electrical and Electronic Materials
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    • v.7 no.3
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    • pp.145-148
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    • 2006
  • In this study, the response surface modeling of the pretilt angle control using in-situ photoalignment method with oblique UV exposure .on plastic substrate is investigated. The pretilt angle is the main factor to determine the alignment of the liquid crystal display. The response surface model is used to analyze the variation of the pretilt angle on the various process conditions. Heating temperature and UV exposure time are considered as input factors. The liquid crystal (LC) pretilt angle increased with increasing heating temperature and UV exposure time. The analysis of variance is used to analyze the statistical significance and the effect plots are also investigated to examine the relationship between the process parameters and the response.

Electro-optical Properties of Twisted Nematic Liquid Crystal Displays Fabricated with TIPS-pentacene Doping

  • Lee, Jin-Woo
    • Transactions on Electrical and Electronic Materials
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    • v.14 no.2
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    • pp.82-85
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    • 2013
  • This paper introduces 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) doped liquid crystal (LC) alignment properties on a rubbed polyimide (PI) layer as a function of the doping concentration of TIPS pentacene. Pretilt angles, photomicrographs, and electro-optical properties of TIPS pentacene doped LCs were comparable to those of pure LCs. However, TIPS pentacene in a LC medium supported twisted nematic-liquid crystal displays (TN-LCDs) to improve electro-optical properties. The threshold voltages observed in the TN cells decreased as the TIPS pentacene concentration increased. In addition, suitable response times were observed in TN cells.

Fabrication of $32{\times}32$ Flat Panel Display Using Liquid Crystal (액정을 이용한 $32{\times}32$ 평판표시기의 제작)

  • Kim Jeong Gyoo;Kim Choong Ki;Kyung Chong Min
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.23 no.1
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    • pp.46-49
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    • 1986
  • A 32x32 liquid crystal (LC) flat panel display using two-dimensional array of PMOS switches and capacitors is designed and fabricated. Standard PMOS process was followed to fabricate the switch and capacitor array on silicon wafer, on the top of which guest-host effect liquid crystal was wmployed as an electro-optical material for optical switching and liquid crystal display(LCD) with its external drive circuitry was basically successful. Remaining problems to be solved are improvement of contrast ratio, good surface alignment and uniformity.

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Investigation on Liquid Crystal Alignment Effects of SiNx Thin Film Irradiated by Ion Beam (이온 빔 조사된 SiNx 박막의 액정 배향 효과에 관한 연구)

  • Lee, Sang-Keuk;Kim, Young-Hwan;Kim, Byoung-Yong;Han, Jin-Woo;Kang, Dong-Hun;Kim, Jong-Hwan;Seo, Dae-Shik
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.398-398
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    • 2007
  • Most recently, the Liquid Crystal (LC) aligning capabilities achieved by ion beam exposure on the diamond-like carbon (DLC) thin film layer have been successfully studied. The DLC thin films have a high mechanical hardness, a high electrical resistance, optical transparency and chemical inertness. Nitrogen doped Diamond Like Carbon (NDLC) thin films exhibit properties similar to those of the DLC films and better thermal stability than the DLC films because C:N bonding in the NDLC film is stronger against thermal stress than C:H bonding in the DLC thin films. Moreover, our research group has already studied ion beam alignment method using the NDLC thin films. The nematic liquid crystal (NLC) alignment effects treated on the SiNx thin film layers using ion beam irradiation for three kinds of N rations was successfully studied for the first time. The SiNx thin film was deposited by plasma-enhanced chemical vapor deposition (PECVD) and used three kinds of N rations. In order to characterize the films, the atomic force microscopy (AFM) image was observed. The good LC aligning capabilities treated on the SiNx thin film with ion beam exposure for all N rations can be achieved. The low pretilt angles for a NLC treated on the SiNx thin film with ion beam irradiation were measure.

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