• Title, Summary, Keyword: Dielectric liquid

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Novel Liquid Crystal Compounds and Its Mixtures for VA-TFT-LCD TV Application

  • Kim, Y.B.;Roh, S.D.
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.471-474
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    • 2002
  • Three-ring types liquid crystalline compounds having fluoro and isothiocyanate substituent were synthesized and their physical and electro-optical properties were measured to evaluate the applications to active matrix VA liquid crystal displays. The tetrakis(triphenylphosphine)palladium(0) catalyzed cross coupling of aryl boronic acids with aryl halides is used to prepare trans-4'-Alkoxy-2,3-difluoro-3'-isothiocyanato-4-(4-alkylcyclohexyl}-biphenyl series. The synthesized compounds showed the nematic liquid crystalline phase and the negative dielectric anisotropy. The prepared mixtures showed faster response time and lower threshold voltage than their host mixture.

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Vertical Alignment Nematic Liquid Crystal Display with Patterned Electrode Using Positive Liquid Crystal Materials

  • Shin, Hun-Ki;Yoon, Tae-Hoon;Kim, Jae-Chang
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.499-501
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    • 2007
  • We propose a vertical-alignment liquid crystal display with patterned electrodes using a positive dielectric anisotropic liquid crystal. In this structure, the threshold and on-state voltages are reduced compared with previous vertical-alignment configuration with positive liquid crystal.

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High Speed Response Time of Nematic Liquid Crystal Mixtures for LCD Monitor and TV Applications

  • Kim, Y.B.;Hur, I.K.
    • Journal of Information Display
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    • v.2 no.3
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    • pp.32-38
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    • 2001
  • The most important parameter for TV application of LCD is a fast switching time for the display of moving image. To achieve faster switching time, the novel LC single materials with large dielectric anisotropies ($16{\sim}20$), high clearing temperatures ($195.5{\sim}237.4^{\circ}C$), broad nematic ranges (up to 169.9 $^{\circ}C$) and high birefringence ($0.254{\sim}0.2200$) were developed. KUR-series LC mixtures blended these single materials having significantly higher clearing temperatures and dielectric anisotropy values compared with conventional LC mixture. Especially, their clearing temperatures are $10{\sim}30^{\circ}C$ higher than their host mixture. These LC mixtures showing about lOms of high-speed switching time in Tv/Monitor of TFT LCD, is short enough to be addressed in a single time frame of 60Hz (16.7 ms). The threshold voltage $V_{th}$ was low enough to operate at a driving voltage of 5 V. The VHR values were found to be high enough for TFT-LCD in wide temperature range. Our novel LC mixtures are suitable materials for the inclusion in to LC mixtures for TV application of TN-LCD

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The Dielectric Characteristics of Turn-to-Turn Insulation for DC Reactor Type HTSFCL (DC reactor type 고온호전도 한류기의 턴간 절연 특성)

  • 백승명;정종만;이창화;류엔반둥;김상현
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.12S
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    • pp.1299-1304
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    • 2003
  • Fault current limiters (FCL) are extensively needed to suppress fault currents, especially for trunk power systems heavily connected to high voltage/large current transmission lines. Due to its ideal electrical behavior, high-temperature superconductor fault current limiter (HTSFCL) becomes one of the most important developing trends of limiters in power system. This paper describes the result of an investigation of the dielectric characteristics of turn-to-turn insulation for pancake and solenoid type reactor coil in liquid nitrogen. The influence of thickness in a variety length, on AC, DC and impulse surface flashover has been investigated. Also, the relationships between the number of turn and breakdown characteristics were clarified. The information gathered in this test series should be helpful in the design of liquid nitrogen filled DC reactor type HTSFCL.

The Characteristics of Electrical Breakdown and Tensile Stress of Dielectric Paper for Insulation of HTS Cable (고온 초전도 케이블 절연을 위한 절연지의 인장응력 및 절연파괴 특성)

  • Kim, Young-Seok;Kwak, Dong-Soon;Kim, Hae-Jong;Kim, Sang-Hyun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.61-64
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    • 2003
  • The degradation of the dielectric properties of insulating papers that were used under loaded conditions at cryogenic temperature was paid attention. Electrical and tensile stress properties of dielectric paper at cryogenic temperature have been investigated to optimum insulating design of high-Tc superconducting(HTS) cable. Tensile strength of PPLP in liquid nitrogen was high more than that of air, but tensile strain could know that decrease sharply. According as tensile strength increases, the breakdown stress of PPLP in liquid nitrogen was decreased.

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Cell Gap Dependent Electrode-Optic Characteristics of Fringe-Field Switching Mode using a Liquid Crystal with Negative Dielectric Anisotropy (유전율 이방성의 음인 액정을 이용한 Fringe-Field Switching mode의 cell gap 변화에 따른 전기광학 특성)

  • 정송희;김향율;이종문;이승희
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.10
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    • pp.914-922
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    • 2003
  • The FFS (fringe-field switching) mode was known to exhibit both a wide viewing angle and high transmittance, especially when using a liquid crystal with negative dielectric anisotropy. We have studied cell gap-dependent electrode-optic characteristics of the FFS mode using the LC with negative dielectric anisotropy. In case of a small cell gap of 2 ${\mu}$m, the transmittance at the center of pixel and common electrodes is relatively low because effect of surface anchoring that holds the LC to the initial state is larger than that in a large cell gap of 4 .urn such that the LCs in those regions cannot rotate enough. However, in case of a large cell gap of 4 .urn, the effect of surface anchoring becomes relatively small so that the LCs at the center of pixel and common electrode can be twisted enough by applied voltage, giving rise to high transmittance. Therefore, we can conclude that the light efficiency is dependent on the cell gap.

Turn-to-Turn Dielectric Characteristics of Coils for HTSFCL (고온초전도 한류기용 코일의 턴간 절연 특성)

  • Baek, Seung-Myeong;Joung, Jong-Man;Lee, Chang-Hwa;Nguyen, Van Dung;Kim, Sang-Hyun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.15-18
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    • 2003
  • Fault current limiters (FCL) are extensively needed to suppress fault currents, especially for trunk power systems heavily connected to high voltage/large current transmission lines. Due to its ideal electrical behavior, high-temperature superconductor fault current limiter (HTSFCL) becomes one of the most important developing trends of limiters in power system. This paper describes the result of an investigation of the dielectric characteristics of turn-to-turn insulation for pancake and solenoid type reactor coil in liquid nitrogen. The influence of thickness in a variety length, on AC, DC and impulse surface flashover has been investigated. Also, the relationships between the number of turn and breakdown characteristics were clarified. The information gathered in this test series should be helpful in the design of liquid nitrogen filled DC reactor type HTSFCL.

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Study on Retardation Value of Fringe-Field Driven Homogeneously Aligned Nematic Liquid Crystal Cell using Liquid Crystals with Positive Dielectric Anisotropy (유전율 이방성이 양인 액정을 이용한 Fringe-Field Driven 수평 배향셀의 위상지연값 연구)

  • 정송희;김향율;송성훈;이승희
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.3
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    • pp.305-310
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    • 2004
  • We have studied the optimal phase retardation value of a homogeneously aligned liquid crystal (LC) driven by fringe-field when using the LC with positive dielectric anisotropy. In general, the transmittance of a homogeneous aligned LC cell under crossed polarizer is maximum when a twist angle of LC by in-plane rotation is 45$^{\circ}$ with polarizer and the cell retardation becomes λ/2. However, the device using the LC with positive dielectric anisotropy does not follow this since the degree of rotation of the LC is dependent on electrode position and in addition the LCs tilt up along the fringe-field. At the center of common and pixel electrode, the LC is most twisted around a middle position of a cell whereas at the edge position of pixel electrode, the LC is most twisted near bottom surface of a cell. Consequently, the optimal phase retardation of the device becomes much larger than λ/2 and the transmittance can be described using the combination of the in-plane switching and twisted nematic mode.

Low Temperature sintering of $Al_2O_3-TiO_2$ ceramics (저온소결 $Al_2O_3-TiO_2$ 세라믹의 마이크로파 유전특성에 관한 연구)

  • Lim, Eun-Kyeong;Kim, Chang-Il;Park, Yong-Jun;Lee, Young-Jin;Nahn, Shan;Paik, Jong-Hoo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.252-252
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    • 2007
  • $Al_2O_3-TiO_2$(AT)ceramics shows great promise as a dielectric material for millimeter-wave use. The sintering temperature of AT ceramics was approximately $1450^{\circ}C$ and decreased to $900^{\circ}C$ with the addition of BaCu(B2O5) (BCB) ceramic powder. The presence, of the liquid phase was responsible for the decrease of the sintering temperature. The liquid phase is considered to have a composition similar to the BaO-deficient BCB. The Q-value initially increased with the addition of BCB, but decreased considerably when a large amount of BCB was added, because of the presence of the liquid phase. Good microwave dielectric properties of $Q{\times}f\;=\;16,200\;GHz$, ${\varepsilon}_r\;=\;9$ and ${\tau}_f\;=\;-4\;ppm/^{\circ}C$ were obtained for the 20.0 mol% BCB-added AT ceramics sintered at $900^{\circ}C$ for 2 h.

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Asymmetric Electrohydrodynamic Flow of Dielectric Liquid around Symmetric Coplanar Electrodes (대칭형상의 평판 전극 주위의 비대칭 절연유체 유동)

  • Baek, Kwang Hyun;Cho, Dong Sik;Suh, Yong Kweon
    • Journal of the Korean Society of Visualization
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    • v.11 no.1
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    • pp.48-52
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    • 2013
  • This paper presents experimental observation of asymmetric electrohydrodynamic flow generated around a pair of symmetric coplanar electrodes. Electrodes are attached on the bottom of the cavity containing a dielectric liquid, i.e., a mixture of dodecane and 0.5% wt Span80. In the first experiment, an AC voltage of 1500 V is applied with the frequency varying in the range 10~500 hz and the left electrode being grounded. The flow patterns show that the center line of vortices is unexpectedly tilted to the left side. If the right side electrode is grounded, the center line is tilted to the right side. The magnitude of the fluid velocity shows an irregular variation with the frequency in the range 10 Hz~100 Hz, beyond which it simply decays. In the second experiment, we applied fixed AC with 1000 V and 60 Hz superposed by DC voltage varying in the range -1000 V ~ +1000 V. The center line of the flow pattern is tilted to the right side with positive DC voltage and to the left side with negative DC. We have managed to show that the flow pattern can be symmetric with a suitable combination of DC and AC, e.g., DC 850 V plus AC 1000 V with the frequency 10 Hz.