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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.
무기 박막을 이용한 이온빔 배향 FFS 셀의 전기광학특성에 관한 연구
황정연,박창준,정연학,김경찬,안한진,백홍구,서대식,Hwang, Jeoung-Yeon,Park, Chang-Joon,Jeong, Youn-Hak,Kim, Kyung-Chan,Ahn, Han-Jin,Baik, Hong-Koo,Seo, Dae-Shik 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.10
In this paper, we intend to make fringe-field switching (FFS) mode cell by the ion beam (IB) alignment method on the a-C:H thin film, to analyze electro-optical characteristics in this cell. We studied on the suitable inorganic thin film for fringe-field switching (FFS) cell and the aligning capabilities of nematic liquid crystal (NLC) using the alignment material of a-C:H thin film as working gas at 30 W rf bias condition. A high pretilt angle of about 5 $^{\circ}C$ by ion beam (IB) exposure on the a-C:H thin film surface was measured. Consequently, the high pretilt angle and the good thermal stability of LC alignment by the IB alignment method on the a-C:H thin film surface as working gas at 30 W rf bias condition can be achieved. An excellent voltage-transmittance (V -T) and response time curve of the IE-aligned FFS-LCD was observed with oblique IB exposure on the a-C:H thin films. Also, AC V-T hysteresis characteristics of the IB-aligned FFS-LCD with IE exposure on the a-C:H thin films is almost the same as that of the rubbing-aligned FFS cell on a polyimide (PI) surface.
Hydroxy Aromatic Polyimide계 광폴리머 표면을 이용한 광배향 TN 셀의 전기광학 특성
이휘원,황정연,최성호,서동학,서대식,Lee, Whee-Won,Hwang, Jeoung-Yeon,Choi, Sung-Ho,Suh, Dong-Hack,Seo, Dae-Shik 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.10
We synthesized the two types of photoalignment material of high thermal resistance with hydroxyl aromatic polyimide, and studied the liquid crystal (LC) aligning capabilities on the photopolymer layers. Also, electro-optical (EO) performances for the twisted-nematic (TN)-liquid crystal display (LCD) photoaligned with linearly polarized UV exposure were investigated. A good LC alignment with UV exposure on the two types of photopolymer surface can be obtained. The Voltage-transmittance (V-T) curve in the photoaligned TN cell with UV exposure was different from two type. The response time of photoaligned TN cell was measured about 21 ms in two alkyl chain and about 15 ms in four alkyl chain.
프로젝션 TV 적용을 위한 액정 디스플레이의 열적 안정성에 관한 연구
강희진,황정연,오용철,서대식,Kang, Hee-Jin,Hwang, Jeoung-Yeon,Oh, Yong-Cheul,Seo, Dae-Shik 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.11
We have investigated electro-optical characteristics in three kinds of twisted nematic (TN) cells on the polyimide surface. The threshold voltage and the response time of thermal stressed TN cells were same that of no thermal stressed TN cells. There were little change of value in these TN cells. On the other hand, transmittance of no thermal stressed TN cells were better than that of thermal stressed TN cells. Transmittances of TN cells on the polyimide surface decreased by increasing thermal stress time. Moreover, the residual DC of the thermal stressed TN cells increased as increasing thermal stress temperature and time. Therefore, thermal stability of TN cells were decreased gradually by giving high thermal stress for a long time.
새로운 이온빔장치를 사용한 Twisted Nematic-LCD의 전기광학특성
김상훈,황정연,장미혜,김귀열,서대식,Kim Sang-Hoon,Hwang Jeoung-Yeon,Jang Mi-Hye,Kim Gwi-Yeol,Seo Dae-Shik 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.6
We studied liquid crystal (LC) alignment with ion beam (IB) on polyimide and electro-optical characteristics of twisted nematic (TN)-liquid crystal display (LCD) on the polyimide surface using obliquely ion beam (IB) exposure with new IB type equipment. A good uniform alignment of the nematic liquid crystal (NLC) alignment with the ion beam exposure on the polyimide surface was observed. In addition, it can be achieved the good EO properties of the ion-beam-aligned TN-LCD on polyimide surface. Also, the EO characteristics of the ion-beam-aligned TN-LCD on a polyimide (PI) surface with ion beam exposure using new type IB equipment is same or more superior than ion-beam-aligned TN-LCD on a polyimide (PI) surface with ion beam exposure using Kaufman-type Ar ion gun.
전자빔증착법을 통한 SiO<sub>x</sub> 박막의 액정 배향 효과
강형구,한진우,강수희,김종환,김영환,황정연,서대식,Kang, Hyung-ku,Han, Jin-Woo,Kang, Soo-Hee,Kim, Jong-Hwan,Kim, Young-Hwan,Hwang, Jeoung-Yeon,Seo, Dae-Shik 한국전기전자재료학회 2005 전기전자재료학회논문지 Vol.18 No.11
By using $45^{\circ}$ obliqued evaporation method with electron beam system, uniformly vertical liquid crystal (LC) alignment was achieved. And a high pretilt angles of about $2.5^{\circ}$ were measured. Also, it was verified that there are no variations of pretilt angle as a function of $SiO_x$ thin film thickness 20 nm and 50 nm. A good LC alignment states were observed at annealing temperature of $250^{\circ}C$. Consequently, the high pretilt angle and the good thermal stability of LC alignment by $45^{\circ}$ obliqued electron beam evaporation method on the $SiO_x$ thin film can be achieved.