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Diamond-like Carbon 박막을 이용한 액정 배향 효과
황정연,조용민,서대식,노순준,이대규 한국전기전자재료학회 2002 전기전자재료학회논문지 Vol.15 No.5
We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a diamond like carbon (DLC) thin film. A high pretilt angle of about $3.5^{\circ}$ by ion beam(IB) exposure on the DLC thin film surface was measured. A good LC alignment by the IB alignment method on the DLC thin film surface was observed at annealing temperature of $200^{\circ}C$, and the alignment defect of the NLC was observed above annealing temperature of $220^{\circ}C$. Consequently, the high NLC pretilt angle and the good thermal stability of LC alignment by the IB alignment method on the DLC thin film surface can be achieved.
소성 조건 변화에 따른 수직 폴리이미드 표면에서 이용한 네마틱 액정의 틸트 제어
황정연,이경준,김강우,서대식,Hwang, Jeoung-Yeon,Lee, Kyung-Jun,Kim, Kang-Woo,Seo, Dae-Shik 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.6
The control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by hot plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. Especially, the low LC tilt angle of positive type NLC (Δ$\varepsilon$>0) on the rubbed homeotropic PI surface by increasing temperature and time was measured. The tilt angle of positive type NLC(Δ$\varepsilon$>0) is smaller than that of the negative type (Δ$\varepsilon$>0) on rubbed PI with increasing baking temperature and time. We consider that the tilt angle of NLC is decreased due to increasing the steric interaction between horizon component of permittivity $\varepsilon$ = of NLC and the stress of polymer side chain by high temperature. As the increase of baking temperature, we obtain that AFM (atomic force microscope) image of rubbed PI surface using Hot-plate method has formed better solid micro-groove structure than oven method.
폴리이미드 표면에서의 네마틱 액정의 틸트 제어를 이용한 High Tilted OCB(HTOCB) 모드
황정연,정연학,서대식,Hwang, Jeoung-Yeon,Jeong, Youn-Hak,Seo, Dae-Shik 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.7
In this paper, we have improved a novel high tilted optically compensated bend (OCB) (HTOCB) mode by using high tilt angle that was generated by the unique baking condition on the homeotropic alignment layer. The high tilt angle of liquid crystal (LC) was generated by new alignment process that tilt angle changed homeotropic state to homeogenous state using Hot-plate equipment; we obtained about $40\~50^{\circ}$ tilt angle with negative and positive dielectric anisotropy on the homeotropic polyimide (PI), and then LC tilt angle decreased as increasing baking temperature and time. At last, we obtained about $10^{\circ}$ with positive type NLC $({\Delta}n>0)$. Also, the LC tilt angle of positive type NLC $({\Delta}n>0)$ decreased as increasing rubbing strength at the same baking temperature and time. The novel LC operating mode (HTOCB) that used the high tilt angle by the new alignment method was improved. The response time of the novel HTOCB cell was faster than that of conventional OCB cell. We suggest that the developed the novel HTOCB cell using control of tilt angle on the homeotropic surface is a promising technique for the achievement of a fast response time and a high contrast ratio.
황정연,서대식 한국전기전자재료학회 2001 전기전자재료학회논문지 Vol.14 No.1
We have developed a new multidomain vertical-alignment (MVA) mode using a homeotropic photopolymer that provides a wider viewing angle for nematic liquidcrystal (NLC) with negative dielectric anisotropy. Good voltage-transmittance curves for he new MVA cell using the homeotropic photopolymer were observed. The viewing angle of the new MVA cell using the homeotropic photopolymer was wider than that of the conventional VA cell. The wide viewing angle using the new MVA cell is attributable to 4-domain by the ribs with UV exposure on the photopolymer.
새로운 광중합 가능한 폴리이미드계 몰리머을 이용한 액정 배향 특성
황정연,서대식,이상렬,김재형,한은주 한국전기전자재료학회 2001 전기전자재료학회논문지 Vol.14 No.5
We synthesized a new photo-crosslinkable polymer (polyimide (PI)-chalcone-biphenyl (BP)) and liquid crystal (LC) aligning capabilities for nematic (N) LC with obliquely polarized UV exposure on a photo-crosslinkable polymer were studied. The high pretilt angle in NLC was obtained by polarized UV exposure on a PI-Chal-BP surface for 3 min. The high pretilt angle generated in NLC is attributed to the biphenyl moieties and the photo-dimerized chalclone group of a photopolymer. Also, good thermal stability of a PI-Chal-BP were obtained by thermogravimetric analysis (TGA) measurement until 450$^{\circ}C$. Finally, good voltage-transmittance curves and response time were observed by UV exposure on a PI-Chal-BP surface for 3min.
Poly[N-(phenyl)maleimide]계 광폴리머를 이용한 액정배향효과
황정연,서대식,김준영,이재호,김태호 한국전기전자재료학회 2001 전기전자재료학회논문지 Vol.14 No.10
The new phto-alignment material PMI5CA, poly{N-(phenyl)maleimide-co-3-[4-(pentyloxy) cinamate]porpyl-2-hydroxy-1-methacrylate}, was synthesized and the electro-optical (EO)characteristics in the vertical-aligned(VA) liquid crystal display (LCD) photo-aligned on the photopolymer surface were studied. Excellent Voltage-transmittance(V-T) characteristics in the VA-LCD photoaligned with polarized UV exposure of oblique direction on the pohotopolymer surface for 1 min can be achieve. The transmittance of the VA-LCD photoaligned on the photopolymer surface decreased with increasing UV exposure time. We suggest that decrease of transmittance in the VA-LCD photoaligned on the photopolymer surface is attributed to the dissociation of the ester linkage in the photodimerized cinnamate structure with increasing UV exposure time.
광중합 가능한 폴리머 표면에 in-situ 광배향법을 이용한 액정배향특성
황정연,정은아,서대식,정재형,한은주 한국전기전자재료학회 2001 전기전자재료학회논문지 Vol.14 No.11
Aligning capabilities for nematic liquid crystal (NLC) using a in-situ photodimerization method on various Photo-crosslinkable Polyimide (Pl) based polymer and blending photopolymer surfaces were investigated. High pretilt angle of the NLC can be measured by obliquely polarized UV exposure on a photo-crosslinkable polyimide based polymer surface containing biphenyl (BP), decyl (de), and cholesteryl (chol) group, respectively. However, the low pretilt angle of the NLC was measured by obliquely polarized UV exposure on the blending photopolymer (Pl and cinnamate materials) surfaces. Consequently, the pretilt angle of the NLC generated on the photo-crosslinkable polyimide based polymer surfaces using the in-situ photodimerization method was higher than that of the blending photopolymers.
새로운 광중합 가능한 폴리머의 프리틸트각 발생의 메카니즘
황정연,서대식,김재형 한국전기전자재료학회 2001 전기전자재료학회논문지 Vol.14 No.7
The mechanisms of pretilt angle generation for a nematic liquid cystal (NLC) using a photodimerization method with obliquely polarized UV exposure on the various new photo-crosslinkable polymer were studied. A good thermal stability of all the photo-crosslinkable polymers was obtained by thermogravimetric analysis (TGA) measurement until 450$\^{C}$. High pretilt angle of the NLC was observed by polarized UV exposure on the three kinds of the photo-crosslinkable polymers containing biphenyl(BP), decyl(de), and cholesteryl(chol) group, respectively. However, the low pretilt angle of the NLC was measured by obliquely polarized UV exposure on the two kinds of the photo-crosslinkable polymers containing fluorine and chalcone group. Consequently, the high NLC angle generated is attributable to the biphenyl and alkyl moieties, and photo-dimerized chalcone group of the photopolymer.
DLC 박막을 이용한 Ion Beam 배향 TN 셀의 전기광학특성에 관한 연구
황정연,조용민,노순준,이대규,백홍구,서대식 한국전기전자재료학회 2002 전기전자재료학회논문지 Vol.15 No.8
Electro-optical (EO) performances of the ion beam (IB) aligned twisted-nematic (TN)-liquid crystal display (LCD) with ion beam exposure on the new diamond-like carbon (DLC) thin film surface were investigated. A good voltage-transmittance (V-T) curve of the ion beam aligned TN-LCD with oblique ion beam exposure on the DLC thin film surface for 1 min was observed. Also, the fast response time of the ion beam aligned TN-LCD with oblique ion beam exposure on the DLC thin film surface for 1 min can be achieved. Finally, the residual DC voltage of the ion beam aligned TN-LCD on the DLC thin film surface is almost the same as that of the rubbing aligned TN-LCD on a polyimide (Pl) surface.