• Title, Summary, Keyword: PDLC

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Dynamic Analysis of the PDLC-based Electro-Optic Modulator for Fault Identification of TFT-LCD (박막 트랜지스터 기판 검사를 위한 PDLC 응용 전기-광학 변환기의 동특성 분석)

  • 정광석;정대화;방규용
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.4
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    • pp.92-102
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    • 2003
  • To detect electrical faults of a TFT (Thin Film Transistor) panel for the LCD (Liquid Crystal Display), techniques of converting electric field to an image are used One of them is the PDLC (polymer-dispersed liquid crystal) modulator which changes light transmittance under electric field. The advantage of PDLC modulator in the electric field detection is that it can be used without physically contacting the TFT panel surface. Specific pattern signals are applied to the data and gate electrodes of the panel to charge the pixel electrodes and the image sensor detects the change of transmittance of PDLC positioned in proximity distance above the pixel electrodes. The image represents the status of electric field reflected on the PDLC so that the characteristic of the PDLC itself plays an important role to accurately quantify the defects of TFT panel. In this paper, the image of the PDLC modulator caused by the change of electric field of the pixel electrodes on the TFT panel is acquired and how the characteristics of PDLC reflect the change of electric field to the image is analyzed. When the holding time of PDLC is short, better contrast of electric field image can be obtained by changing the instance of applying the driving voltage to the PDLC.

A power supply including adjustable transmittance function of PDLC film (투과도 조절기능이 포함 된 PDLC 전원 공급 장치 개발)

  • Lee, Juchan;Lee, Jin-woo;Mok, Hyung soo
    • Proceedings of the KIPE Conference
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    • pp.115-116
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    • 2018
  • 본 논문은 Polymer Dispersed Liquid Crystal (PDLC) 필름의 투과도 조절을 위한 전원 공급 장치 개발을 목적으로 한다. PDLC의 경우 블라인드를 대신하여 많이 사용된다. 따라서 계절, 시간, 날씨 등의 환경적 요인으로 사용자의 요구 및 필요에 의해 투과도 조절기능이 요구된다. 하지만 현재 시스템은 변압기를 사용하여 PDLC 필름을 구동시켜 투과도 조절이 어렵다. 본 논문에서는 인버터 출력의 듀티 비를 조절하여 PDLC 필름의 투과도 조절을 구현하였다.

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The electro-optical characteristic comparison according to square wave driving method of PDLC (구형파 구동방식에 따른 PDLC의 전기광학적 특성 비교)

  • Lee, Ju chan;Mok, Hyung soo
    • Proceedings of the KIPE Conference
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    • pp.354-355
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    • 2019
  • 본 논문은 Polymer Dispersed Liquid Crystal(PDLC)의 구형파 구동방식에 따른 전기광학적 특성을 비교한다. 현재 PDLC는 변압기를 사용하여 전압가변이 힘들어 ON/OFF 기능으로만 사용한다. PDLC 구동시스템에 전력변환장치를 적용하면 전압가변이 용이하여 PDLC의 투과도 조절이 가능하다. 구형파 구동방식 중 인버터의 DC Link Voltage를 가변하는 방식과 Duty ratio를 가변하는 두 방식의 전기광학적 특성을 비교하였다. 이를 실험을 통하여 전기광학적 특성을 분석하였다.

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The Injection of PDLC Solution Mixture in a Reduced Pressure

  • Kim, Kang-Pil;Yang, Kee-Jeong;Kim, Dae-Hwan;Choi, Byeong-Dae
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.524-526
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    • 2007
  • Polymer dispersed liquid crystal (PDLC) films consist of micro-droplets of liquid crystals dispersed in a polymer matrix. To make wide area PDLC filled devices, it is necessary to develop reliable method of vacuum injection of PDLC solution instead of the capillary injection. However, well-known 2-ethylhexylacrylate (EHA), main element of a prepolymer, exhibits the volatility problems, when the PDLC solution is placed under the low pressure. In this study, we developed the vacuum injection process to fill a wide area cell. Experimental results indicate that the $V_{90}$(turn-on voltage) of the PDLC cell made by a vacuum injection method are lower than that of the PDLC cell made by a capillary injection method.

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The electro-optical characteristics of PDLC (PDLC의 전기광학적 특성)

  • Kim, Won-Jae;Park, Se-Kwang
    • Journal of Sensor Science and Technology
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    • v.7 no.6
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    • pp.432-436
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    • 1998
  • Recently, the PDLC(Polymer Dispersed Liquid Crystal) is being developed lively to make a large display device using a liquid crystal. Because of low light loss, high brightness, and simple fabrication process, it is made easily to large display device, In this study, the response time and light transmittance by the applied voltage is measured to analyze the electro-optical characteristics of PDLC. The He-Ne laser is applied to the PDLC cell, the light transmittance is measured using the photodiode and the result is analyzed and displayed graphically by the digital oscilloscope. The result of comparison between the PDLC and the present LCD is used to study the potential as a display device.

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A Study on the Transmittance of PDLC Film by Variable Voltage (전압가변에 의한 PDLC 필름 투과도에 대한 연구)

  • Lee, Juchan;Mok, Hyung soo;Lee, Jin-woo
    • Proceedings of the KIPE Conference
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    • pp.452-453
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    • 2018
  • 이 논문은 Polymer Dispersed Liquid Crystal (PDLC) 필름 구동방식을 제안한다. 현재 시스템은 변압기를 사용하여 PDLC를 구동시켜 전압가변이 힘들어 ON/OFF 기능으로만 사용된다. 하지만 변압기를 사용하지 않고 인버터를 사용하면 전압가변이 용이하여 PDLC 필름의 투과도 조절이 용이하다. 인버터를 사용한 토플로지에서 출력전압을 정현파로 출력하게 되면 필터가 추가되어 하드웨어 제작 시 추가적인 비용이 발생하고 하드웨어의 부피가 증가하게 된다. 그래서 필터가 사용되지 않는 구형파 구동방식을 선정하였다. 이를 실험을 통해 보여준다.

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Optimization of Electro-Optical Properties of Acrylate-based Polymer-Dispersed Liquid Crystals for use in Transparent Conductive ZITO/Ag/ZITO Multilayer Films (투명 전도성 ZITO/Ag/ZITO 다층막 필름 적용을 위한 아크릴레이트 기반 고분자분산액정의 전기광학적 특성 최적화)

  • Cho, Jung-Dae;Kim, Yang-Bae;Heo, Gi-Seok;Kim, Eun-Mi;Hong, Jin-Who
    • Applied Chemistry for Engineering
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    • v.31 no.3
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    • pp.291-298
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    • 2020
  • ZITO/Ag/ZITO multilayer transparent electrodes at room temperature on glass substrates were prepared using RF/DC magnetron sputtering. Transparent conductive films with a sheet resistance of 9.4 Ω/㎡ and a transmittance of 83.2% at 550 nm were obtained for the multilayer structure comprising ZITO/Ag/ZITO (100/8/42 nm). The sheet resistance and transmittance of ZITO/Ag/ZITO multilayer films meant that they would be highly applicable for use in polymer-dispersed liquid crystal (PDLC)-based smart windows due to the ability to effectively block infrared rays (heat rays) and thereby act as an energy-saving smart glass. Effects of the thickness of the PDLC layer and the intensity of ultraviolet light (UV) on electro-optical properties, photopolymerization kinetics, and morphologies of difunctional urethane acrylate-based PDLC systems were investigated using new transparent conducting electrodes. A PDLC cell photo-cured using UV at an intensity of 2.0 mW/c㎡ with a 15 ㎛-thick PDLC layer showed outstanding off-state opacity, good on-state transmittance, and favorable driving voltage. Also, the PDLC-based smart window optimized in this study formed liquid crystal droplets with a favorable microstructure, having an average size range of 2~5 ㎛ for scattering light efficiently, which could contribute to its superior final performance.

Effect of 2-HEA and EGPA Composition on the Electro-optical Properties of Polymer Dispersed Liquid Crystal (아크릴계 단량체 2-HEA와 EGPA의 조성에 따른 고분자 분산형 액정(PDLC)의 전기광학적 특성 평가)

  • Choi, Jongseon;Kim, Young Dae;Kim, So Yeon
    • Applied Chemistry for Engineering
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    • v.30 no.2
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    • pp.205-211
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    • 2019
  • Over the past several decades, the polymer dispersed liquid crystal (PDLC) has received particular attention as a material for developing smart window due to their electro-optical switchable properties. In this study, PDLC cells were fabricated using acrylate monomers, namely 2-hydroxyethyl acrylate (2-HEA) and ethylene glycol phenyl ether acrylate (EGPA), and the effect of the monomer composition on their electro-optical properties was investigated. The monomer mixture with a low viscosity (~10 cps) was easily filled between indium tin oxide (ITO) glasses by capillary action at room temperature. PDLC cells prepared using the mixture ratio of 1 : 9 (2-HEA : EGPA) did not show a complete opaque state at a 0 V condition but exhibited unstable electro-optical properties under an electric field. As the LC composition increased in the reaction mixture for PDLC cell preparation, the $V_{th}$ (threshold voltage) and $V_{sat}$ (saturation voltage) values as well as contrast ratio (CR) increased. $V_{th}$ and $V_{sat}$ values also increased with the cell gap thickness. PDLC cells with a $20{\mu}m$ cell gap thickness exhibited higher CR than those with 10 and $40{\mu}m$ cell gap thicknesses. Particularly, PDLC cells prepared using the mixture ratio of 7 : 3 (2-HEA : EGPA) showed excellent electro-optical properties such as a low driving voltage and high contrast ratio.

Electro-Optic Characteristics of Polymer Dispersed Liquid Crystal Cell with Transparent State Initially (초기에 투명한 상태인 고분자 분산형 액정셀의 전기 광학 특성)

  • 김미숙;원해경;송성훈;이명훈;이승희
    • Polymer(Korea)
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    • v.28 no.4
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    • pp.298-304
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    • 2004
  • We fabricated a polymer dispersed liquid crystal (PDLC) cell using LC with negative dielectric anisotropy and UV curable monomer exhibiting transparent state initially (called normally transparent (NT)) and studied the electro-optic characteristics. The NT PDLC cell made with the ratio of LC : monomer = 70/30 wt%, curing temperature of 20 $^{\circ}C$ and strong UV intensity of 198 ㎽/$\textrm{cm}^2$ had high contrast ratio and showed good electro-optic characteristics. In this condition, LC is aligned vertically on the substrate due to the vertical alignment layer and the polymer made with the UV exposure does not influence the alignment of the LC much. Therefore, the transmittance at the zero voltage is very high and the scattering state of the cell is good after applying the voltage because LC with negative dielectric anisotropy tries to align perpendicular to the field. And also, the NT PDLC cell showed better viewing angle characteristics than that in the normally scattering (NS) PDLC.

Droplet Size Distribution Effect on the Electro-Optical Properties of Emulsion Type Polymer Dispersed Liquid Crystal (에멀전 방식의 고분자 분산형 액정의 전기 광학 특성에 미치는 액적 크기 분포의 영향)

  • Yoo, Hee Sang;Oh, Nam-Seok;Yan, Jin;Kwon, Soon-Bum
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.28 no.7
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    • pp.439-445
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    • 2015
  • We established the emulsion method using membrane filter with precise control of LC droplet distribution in PDLC. PDLC cells with various LC droplet size distributions such as single droplet sizes of $1.0{\mu}m$, $1.9{\mu}m$ and $3.5{\mu}m$, the mixture of two different LC droplet sizes and the mixture of three different LC droplet sizes were fabricated and the electro-optical properties of the emulsion type PDLC cells with various droplet size distribution were investigated. In the appropriate droplet size range, the PDLCs with the single droplet sizes distributions have good electro optical properties than those with the mixture of three different LC droplet sizes. In addition, the PDLC cells with the mixture of two different LC droplet sizes have the better electro optical properties than those with single droplet sizes distribution. The PDLC cell with dual droplet size distribution of $1.0+1.9{\mu}m$ shown the best electro optical properties than the PDLC cells with other size distributions. This method enabled us to find the proper LC droplet size distribution for achieving both high transmittance and contrast ratio.