• Title/Summary/Keyword: Liquid crystal

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Molecular orientational surface structures of polymers for liquid crystal alignment

  • Ohe, Masahito
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.611-614
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    • 2006
  • Sum-frequency vibrational spectroscopy (SFVS) has been used to study the molecular orientations at the polymer surfaces for liquid crystal alignment. Various molecular orientations appear at the surface depending on various types of surface treatments and polymers.

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The Structural Effects on The Pretilt Angle of Alignment Materials with Alkylcyclohexylbenzene as a Side Chain in Polyimides

  • Lee, Jong-Beom;Lee, Hyun-Kyung;Park, Jae-Chul;Kim, Yong-Bae
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1188-1192
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    • 2004
  • Polyamic acid precursors were prepared by mixing various main chain dianhydrides, main chain diamines and side chain diamines. Copolyimide films with alkylcyclohexylbenzene as a side chain were prepared by thermal imidization of polyamic acid precursors. Pretilt angles on rubbed polyimides changed according to the side chain and main chain structures of the polyimide. Consequently, we found that LC pretilt angles of polyimide films with a liquid crystal structure as a side chain showed to be approximately 90$^{\circ}$ when a linear and rigid polyimide main chain and a side chain of suitable length were employed.

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Ferro-nematics and their outlook

  • West, John L.;Jakli, A.;Glushchenko, Anatoliy;Reznikov, Yuri
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.287-288
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    • 2004
  • We report on the development of ferronematic liquid crystals, new materials that consist of a dilute suspension of ferroelectric particles in a nematic liquid crystal host. The particles share their ferroelectric properties with the nematic liquid crystal and impose a spontaneous dielectric polarization of about 10 nC/$cm^2$ to the entire medium, typical for many ferroelectric liquid crystals. As expected, these new materials have enhanced dielectric anisotropy and are sensitive to the sign of an applied electric field. The potential of their use in a number of devices are discussed.

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X-ray Scattering Studies for Phase Separated Composite Organic Films

  • Choi, H.;Eom, K.E.;Wang, Q.;Kumar, S.;Kim, J.H.;Shin, S.T.
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1229-1232
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    • 2004
  • The ratio of optimized concentration on optical characteristics for phase-separated composite organic films (PSCOF) liquid crystal display is 30% of pre-polymer (NOA65) and 70% of ferroelectric liquid crystal (Felix). The layer structure in ferroelectric liquid crystal cell made by 30% NOA65 and 70% Felix materials is tilt-bookshelf layer structure. The angle of tilt-bookshelf structure are 17$^{\circ}$, 12$^{\circ}$ which are almost same of tilt angle of ferroelectric liquid crystal in Sm $C^{\ast}$ phase. We know that this result is from compensating the layer buckling. In this paper, we will discuss the effect of layer structure in PSCOF cell on ratio of concentration between pre-polymer and liquid crystal by x-ray measurements. We believe that technology of PSCOF is a good solution to solve the problems of align-defect and mechanical shock for future TV application and plastic LCD.

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Membrane from Liquid Crystal Composite of Cellulose Acetate and Poly (4-vinyl pyridine) (셀룰로오스 아세테이트와 폴리비닐 피리딘 액정중합체의 박막에 관한 연구)

  • Hong, Young-Keun;Cho, Bong-Heuy
    • Textile Coloration and Finishing
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    • v.3 no.2
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    • pp.43-48
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    • 1991
  • Cellulose acetate (CA) and poly-4-vinyl pyridine (PVP) in various weight proportions were mixed in a mixed solvent of trifluoroacetic acid: methylene chloride/6:4 (v:v). CA was miscible with PVP in that solvent system. CA/PVP/solvent show liquid crystal in a certain range of concentration and the nature of that liquid crystal was cholesteric. Films of the liquid crystal composite cast from the liquid crystal solutions of CA/PVP were tested in a viewpoint of biomembrane. Results show that considering permselectivity CA/PVP membrane is better than that of CA and CA/PVP membrane is closer to cell membrane.

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Bistable Liquid Crystal Device Realized on Microscopic Orientational Pattern

  • Kim, Jong-Hyun;Yoneya, Makoto;Yokoyama, Hiroshi
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.187-190
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    • 2005
  • Alignment pattern of checkerboard was constructed by the stylus of atomic force microscope. Orientational bistability of the nematic liquid crystal was realized on that frustrated surface alignment. Macroscopic orientational switching between two perpendicular directions took place by an appropriate in-plane electric field. The threshold electric fields decreased in both switching directions as temperature increased. The focused laser heated up only the limited domains in the cell including a light-absorbing medium. Irradiating the laser concurrently with an appropriate electric field, we switched the selected unit domains in the alignment pattern. The switched domains maintained stably the switched direction without the disturbance from the exterior. Extending and repeating this process, we realized extremely fine devices of bistable switching.

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Optimization of Chiral Dopant and Rubbing Direction in Liquid Crystal Display

  • Lee, Kyung-Jun;Park, Jun-Baek;Park, Jong-Min;Kim, Hoe-Chang;Seo, Jae-Ho;Kim, Yoo-Jin;Jung, Byung-Hwan
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.948-951
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    • 2007
  • In order to improve the performance of LCD, chiral dopant is added to liquid crystal mixture. When we decide the rubbing direction, we must consider the rotation direction of liquid crystal molecules by chiral dopant. When the rotation direction of liquid crystal molecules caused by dielectric torque decided by rubbing direction and that decided by chiral dopant are coincided, the performance of LCD would be improved along to our initial cell design intentions.

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Study on Pressure-dependent Dynamics of Liquid Crystal in a Twisted Nematic Liquid Crystal Cell with Thin Film Transistor (TFT를 이용한 비틀린 네마틱 액정 셀에서 외부 압력에 따른 액정 동력학에 관한 연구)

  • 고재완;김미숙;정연학;김향율;이승희
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.4
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    • pp.426-431
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    • 2004
  • We have studied the pressure-dependent liquid crystal's dynamics in a twisted nematic (TN) liquid crystal panel with thin film transistor by applying an external pressure to it. When the external pressure is applied to the panel in a dark state, the disclination lines were generated as a light leakage whereas they did not appear in a simple test cell that has only pixel and common electrodes. It was because the disclination lines were Provoked by the electric field between pixel electrode and data/gate bus line for active matrix driving. Consequently, the external pressure resulted in dynamic instability of the liquid crystal so that the disclination lines at the data/gate bus line intruded into the active area.

Vertical Alignment of Nematic Liquid Crystal on the SiC Thin Film Layer with Ion-beam Irradiation

  • Oh, Yong-Cheul;Lee, Dong-Gyu
    • Transactions on Electrical and Electronic Materials
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    • v.7 no.6
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    • pp.301-304
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    • 2006
  • We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of the SiC (Silicon Carbide) thin film. The SiC thin film exhibits good chemical and thermal stability. The good thermal and chemical stability make SiC an attractive candidate for electronic applications. A vertical alignment of nematic liquid crystal by atomic beam 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. Consequently, the vertical alignment effect of liquid crystal electro-optical characteristic by the atomic beam alignment method on the SiC thin film layer can be achieved.