화학공학소재연구정보센터
홈 로그인 로그아웃 연락처 사이트맵
Applied Chemistry for Engineering, Vol.30, No.2, 205-211, April, 2019
DOI10.14478/ace.2019.1002  Export Citation
아크릴계 단량체 2-HEA와 EGPA의 조성에 따른 고분자 분산형 액정(PDLC)의 전기광학적 특성 평가
Effect of 2-HEA and EGPA Composition on the Electro-optical Properties of Polymer Dispersed Liquid Crystal
최종선1, 김영대1, 김소연1, 2, †
  • 1충남대학교 에너지과학기술대학원
  • 2충남대학교 사범대학 화학공학교육과
Jongseon Choi1, Young Dae Kim1, and So Yeon Kim1, 2, †
  • 1Graduate school of Energy Science and Technology, Chungnam National University, Daejeon 34134, South Korea
  • 2Department of Chemical Engineering Education, College of Education, Chungnam National University, Daejeon 34134, South Korea
E-mail:
초록
지난 수십 년 동안 고분자 분산형 액정(polymer dispersed liquid crystal, PDLC)은 전기광학적으로 전환이 가능한 특성으로 인해 빛의 투과도를 자유롭게 조절할 수 있는 smart window를 개발하는 물질로서 주목을 받아왔다. 본 연구에서는 높은 구동전압과 낮은 명암비 등의 PDLC 문제점을 해결하기 위해 아크릴계 단량체 2-hydroxyethyl acrylate (2-HEA)와 ethylene glycol phenyl ether acrylate (EGPA)의 조성이 PDLC의 전기광학 특성에 미치는 영향을 평가하였다. 상온에서 10 cps 이하의 낮은 점도를 나타내는 2-HEA와 EGPA 단량체를 사용하여 제조하는 경우 보다 쉽게 capillary action에 의해서 indium tin oxide (ITO) glass 사이에 주입하는 공정이 가능하였다. Phenyl group를 포함한 EGPA 단량체가 대부분으로 이루어진 1 : 9인 단량체 혼합물로 만들어진 PDLC cell의 경우 전기장을 인가하지 않은 경우에도 불투명한 상태가 관측되지 않았고 인가 전압에 따라 매우 불안정한 투과율을 나타내었다. Cell gap thickness가 증가함에 따라 문턱전압 (threshold voltage, Vth)과 포화전압(saturation voltage, Vsat)도 증가하는 경향을 나타내었으며, 20 μm의 cell gap thickness 를 갖는 PDLC cell이 10과 40 μm의 경우 보다 상대적으로 높은 명암비를 나타내었다. 특히, 7 : 3 비율의 2-HEA : EGPA 단량체 혼합물을 사용하여 제조된 PDLC cell의 경우가 낮은 구동전압과 높은 명암비의 가장 우수한 전기광학적 특성을 나타내었다.
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 Vth (threshold voltage) and Vsat (saturation voltage) values as well as contrast ratio (CR) increased. Vth and Vsat values also increased with the cell gap thickness. PDLC cells with a 20 μm cell gap thickness exhibited higher CR than those with 10 and 40 μ 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.
Keywords:Polymer dispersed liquid crystal;Smart window;2-HEA;EGPA;Electro-optical properties
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