• 제목, 요약, 키워드: Dielectric liquid

검색결과 374건 처리시간 0.039초

액체유도체의 절연특성에 미치는 초음파의 영향 (Ultransonic Effect on the Break-Down Characteristics of Liquid Dielectrics)

  • 전춘생;김홍근;홍봉식
    • 전기의세계
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    • v.26 no.4
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    • pp.61-67
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    • 1977
  • This paper treats the Ultrasonic effects on the break down characteristics of Liquid Dielectric Material 1) Relative Dielectric constant, Es of Liquid Dielectric Material at a constant temperature decreases in proportion to the irradiated time of Ultrasonic radiation and its intensity, and reaches to a certain saturated value. The saturated value varies with the intensity of Ultrasonic radiation. 2) Power factor of Liquid Dielectric Material at a constant temperature increases in proportion tothe irradiated time of Ultrasonic radiation and its intensity, and reaches to a certain saturated value. The saturated value varies with the intensity of Ultrasonic radiation. 3) Relative resistance of Liquid Dielectric Material at a constant temperature decrease with the irradiated time of Ultrasonic radiation, but the effect of its intensity is very irregular. 4) Break-down strength of Liquid Dielectric Material, at a constant temperature decreases with the irradiated time of Ultrasonic radiation and its intensity, and then reaches to a saturated value.

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Fast(submillisecond) Switching of Nematic Liquid Crystals and Effects of Dielectric Dispersion; Theory and Experiment

  • Shiyanovskii, Sergij V.;Golovin, Andrii B.;Yin, Ye;Lavrentovich, Oleg D.
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.181-186
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    • 2005
  • We demonstrate that the finite rate of dielectric relaxation in liquid crystals which has been ignored previously causes profound effects in the fast dielectric reorientation of the director. The phenomenon is relevant for submillisecond switching of the director when the switching rate approaches the rate of dielectric relaxation through the reorientation of the molecular dipoles. A submillisecond switching ($15-400\;{\mu}s$ for an optical retardation shift $0.3-2.2\;{\mu}m$ in $10-15\;{\mu}m$ thick cells) is demonstrated for dual frequency nematic cells with high pretilt that maximizes the dielectric torque acting on the director. We propose the theory of dielectric response in which the electric displacement depends not only on the present (as in the standard theory) but also on the past values of electric field and director. We design an experiment in which the standard "instantaneous" model and our model predict effects of opposite signs; the experimental data support the latter model.

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Dielectric Relaxation in Electrooptical Switching of Nematics

  • Lavrentovich, Oleg D.;Wonderly, Hugh;Gu, Mingxia;Shiyanovskii, Sergei V.
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1283-1285
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    • 2008
  • We describe how the phenomenon of dielectric dispersion in nematic liquid crystals influences the director dynamics and thus the switching speed of nematic-based displays.

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Various Pattern-Forming States of Nematic Liquid Crystal Based on the Sign Inversion of Dielectric Anisotropy

  • Kang, Shin-Woong;Chien, Liang-Chy
    • Macromolecular research
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    • v.15 no.5
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    • pp.396-402
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    • 2007
  • The dielectric properties and various pattern-forming states of dual-frequency material in a nematic phase, as well as its mixture containing low concentrations of reactive monomers, are reported. The dielectric relaxation behaviors of nematic MLC 2048 are presented and compared to its mixture containing both mesogenic and nonmesogenic reactive monomers. The sign-inversion frequency of the dielectric anisotropy was significantly shifted on the addition of small amounts of the reactive monomers. However, all three mixtures used in this study essentially exhibited the same field-induced instabilities at different frequencies and voltage domains of the applied electric field. A broad band of modulated states were found to exist above a critical voltage and within a voltage dependent frequency band in the vicinity of the sign-inversion frequency, $f_I$, of the dielectric anisotropy. As the $f_I$ of the mixtures shifted, so did the bands of the modulated state of the different mixtures and the temperatures, which were well matched with the measured $f_I$ value.

Anomalously high dielectric strength and low frequency dielectric relaxation of a bent-core liquid crystal with a large kink angle

  • Srivastava, Anoop Kumar;Kim, Jongyoon;Yeo, Sunggu;Jeong, Jinyoung;Choi, E-Joon;Singh, Vijay;Lee, Ji-Hoon
    • Current Applied Physics
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    • v.17 no.6
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    • pp.858-863
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    • 2017
  • We investigated the dielectric dispersion property of a bent-core liquid crystal (BLC) with a large kink angle in the frequency range of 1.0 Hz-5.5 MHz in a planar aligned cell. Single dielectric dispersion was observed in the smectic A, nematic, and isotropic phase of the planar aligned sample. The dielectric strengths, relaxation frequencies, distribution parameters, and dc conductivity were measured as a function of temperature. The dielectric strength of the observed relaxation mode was anomalously high (~70), whereas the relaxation frequency was low at ~500 Hz. The relaxation mode observed in the planar aligned cell was attributed to the fluctuations in the polarization direction due to the cooperative motion of the molecules.

Light efficiency of fringe-field switching nematic liquid crystal cell depending on dielectric anisotropy value of a liquid crystal

  • Ryu, Je-Woo;Lee, Ji-Youn;Park, Ji-Woong;Lee, Seung-Hee;Lee, Gi-Dong
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.560-563
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    • 2007
  • The light efficiency of fringe-field switching (FFS) mode was found to be dependent on the magnitude of dielectric anisotropy, indicating that the voltagedependent maximal effective cell retardation value in the on state is a function of magnitude of the dielectric anisotropy of the LC.

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Dependence of Dielectric Layer and Electrolyte on the Driving Performance of Electrowetting-Based Liquid Lens

  • Lee, June-Kyoo;Park, Kyung-Woo;Kim, Hak-Rin;Kong, Seong-Ho
    • Journal of Information Display
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    • v.11 no.2
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    • pp.84-90
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    • 2010
  • This paper presents the effects of a dielectric layer and an electrolyte on the driving performance of an electrowetting on dielectric (EWOD)-based liquid lens. The range of tunable focal length of the EWOD-based liquid lens was highly dependent on the conditions of the dielectric layer, which included an inorganic oxide layer and an organic hydrophobic layer. Moreover, experiments on the physical and optical durability of electrolyte by varying temperature conditions, were conducted and their results were discussed. Finally, the lens with a truncated-pyramid silicon cavity having a sidewall dielectrics and electrode was fabricated by anisotropic etching and other micro-electromechanical systems (MEMS) technologies in order to demonstrate its performance. The lens with $0.6-{\mu}m$-thick $SiO_2$ layer and 10 wt% LiCl-electrolyte exhibited brilliant focal-length tunability from infinity to 3.19 mm.

$ZnWO_4$ 소결특성 및 고주파 유전특성 (Sintering and Microwave Dielectric Properties of $ZnWO_4$)

  • 이경호;김용철
    • 한국전기전자재료학회:학술대회논문집
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    • pp.386-389
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    • 2001
  • In this study, development of a new LTCC material using non-glassy system was attempted with repsect to reducing the fabrication process steps and cost down. Lowering the sintering temperature can be achieved by liquid phase sintering. However, presence of liquid phases usually decrease dielectric properties, especially the quality factor. Therefore, the starting material must have quality factor as high as possible in microwave frequency range. And also, the material should have a low dielectric constant for enhancing the signal propagation speed. Regarding these factors, dielectric constants of various materials were estimated by the Clausius-Mosotti equation. Among them, $ZnWO_4$ was turned out the suitable LTCC material. $ZnWO_4$ can be sintered up to 98% of full density at $1050^{\circ}C$ for 3 hours. It's measured dielectric constant, quality factor, and temperature coefficient of resonant frequency were 15.5, 74380GHz, and $-70ppm/^{\circ}C$, respectively. In order to modify the dielectric properties and densification temperature, $B_{2}O_{3}$ and $V_{2}O_{5}$ were added to $ZnWO_4$. 40 mol% $B_{2}O_{3}$ addition reduced the dielectric constant from 15.5 to 12. And the temperature coefficient of resonant frequency was improved from -70 to $-7.6ppm/^{\circ}C$. However, sintering temperature did not change due to either lack of liquid phase or high viscosity of liquid phase. Incorporation of small amount of $V_{2}O_{5}$ in $ZnWO_{4}-B_{2}O_{3}$ system enhanced liquid phase sintering. 0.1 wt% $V_{2}O_{5}$ addition to the $0.6ZnWO_{4}-0.4B_{2}O_{3}$ system, reduced the sintering temperature down to $950^{\circ}C$. Dielectric constant, quality factor, and temperature coefficient of resonant frequency were 9.5, 16737GHz, and $-21.6ppm/^{\circ}C$, respectively.

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이중 주파수 액정을 적용한 액정 셔터의 고속 응답 특성 (Enhanced Electro-optical Characteristics of Liquid Crystal Shutter with a Dual Frequency Liquid Crystal Material)

  • 김대수;한승환;배건;전철규
    • 한국전기전자재료학회논문지
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    • v.27 no.5
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    • pp.303-306
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    • 2014
  • In this paper, by using a dual frequency liquid crystal material, we propose a liquid crystal device with a fast response characteristics. The dual frequency liquid crystal material has a positive dielectric anisotropy value at a low frequency. With a high frequency, the dielectric anisotropy becomes negative. Therefore, the relaxation process is governed by not only the elastic deformation, but also the dielectric interaction. The measured decay time and rise time were 0.88 ms and 0.33 ms, respectively.

Dielectric and Electro-Optical Properties of Ceramic Nanoparticles Doped Liquid Crystals

  • Porov, Preeti;Chandel, Vishal Singh;Manohar, Rajiv
    • Transactions on Electrical and Electronic Materials
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    • v.17 no.2
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    • pp.69-78
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    • 2016
  • Liquid crystals are important materials because of their applications in display technology and many other scientific applications. Different mixtures of liquid crystals and their doped samples have gained interest because a single liquid crystal compound cannot fulfill all the required parameters for the display application. The doping can be accomplished with dyes, polymers, or composite nanoparticles among other substance. The addition of nanoparticles can modify the physical properties of the host liquid crystal and enhances the performance of electro-optical devices. The present study is focused on investigations of possible changes in dielectric and electro optical properties of liquid crystals caused by doping with ceramic nanoparticles. Including smaller nanoparticles were found to be better candidates for use in suppressing the unwanted ion effects in liquid crystal displays.