• 제목/요약/키워드: Liquid Crystal Alignment

검색결과 493건 처리시간 0.027초

수직 광폴리머를 이용한 VA-1/4$\pi$셀의 전기 광학 특성 (Electro-optical Characteristics of in the Vertical-Alignment 1/4$\pi$ Cell Using Homeotroopic Photopolymer)

  • 황정연;서대식;김재형
    • 한국전기전자재료학회논문지
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    • 제14권8호
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    • pp.670-674
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    • 2001
  • The electro-optical (EO) performance in the vertical-alignment (VA) - 1/4$\pi$ cell photoaligned with polarized UV exposure on a homeotropic photopolymer surfaces was investigated. Excellent voltage-transmittance curve in the VA - 1/4$\pi$ cell photoaligned with polarized UV exposure for 3 min on the photopolymer containing cholesteryl group of 8% can be achieved. The V-T characteristics in the VA-1/4$\pi$ cell photoaligned on the photopolymer surface can be improved by increasing cholesteryl group. For response time measurement, the transmittance characteristics of the VA-1/4$\pi$ cell photopolymer surface was better than that of the VA-1/4$\pi$ cell rubbingaligned on a polyimide(PI) surface.

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Organosiloxanes with molecular microrelief for liquid crystal alignment

  • Mazaeva, Vera G.;Belyaev, Victor V.;Timofeyev, Sergey N.;Min'ko, Anatoliy A.
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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    • pp.948-950
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    • 2009
  • A few organosilicon compounds (OC) - both cyclic and linear siloxanes with different structure of the substituents - have been synthesized. Properties of the LC anchoring on OC films have been measured. The OC investigated provide the homogeneous planar alignment with LC tilt angle in the range from $0.7^{\circ}$ to $1.9^{\circ}$. An increase of the microrelief depth results in a small increase of the tilt angle. The azimuthal anchoring is better for the films of the OC without molecular microrelief or the OC comprising polar groups.

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Optimized electrode design to improve transmittance in the Patterned Vertical Alignment Liquid Crystal Display

  • Hwang, Seong-Jin;Kim, Youn-Sik;Lee, Seung-Hee;Lyu, Jae-Jin;Kim, Kyeong-Hyeon
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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    • pp.549-552
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    • 2007
  • Patterned vertical alignment (PVA) mode requires multi-domain to exhibit wide viewing angle whereas the transmittance is sacrificed. To overcome the demerit, a fine pattern was formed at folded region in PVA Z-shape electrode structure. In the present work fine patterns were formed near domain boundary regions where the unwanted field direction which causes the LC to tilt down in unwanted direction exists. Thereby transmittance is improved near those fine patterns. This method is very simple and more cost-effective process than the other methods. In this article, we show the method of fine pattern formation and its influence on LC molecule in PVA mode with Z-shape electrode structure.

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Statistical Modeling of Pretilt Angle Control using Ion-beam Alignment on Nitrogen Doped Diamond-like Carbon Thin Film

  • Kang, Hee-Jin;Lee, Jung-Hwan;Han, Jung-Min;Yun, Il-Gu;Seo, Dae-Shik
    • Transactions on Electrical and Electronic Materials
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    • 제7권6호
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    • pp.297-300
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    • 2006
  • The response surface modeling of the pretilt angle control using ion-beam (IB) alignment on nitrogen doped diamond-like carbon (NDLC) thin film layer is investigated. This modeling is used to analyze the variation of the pretilt angle under various process conditions. IB exposure angle and IB exposure time are considered as input factors. The analysis of variance technique is settled to analyze the statistical significance, and effect plots are also investigated to examine the relationships between the process parameters and the response. The model can allow us to reliably predict the pretilt angle with respect to the varying process conditions.

삼성의 LCD-SPVA 및 -PSVA모드 개발사(開發史)와 액정주입 ODF 공정

  • 유재진;신성태
    • 인포메이션 디스플레이
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    • 제22권4호
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    • pp.34-44
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    • 2021
  • 90년대 초 LCD (Liquid Crystal Display)는 연관된 반도체 산업과 함께 제2산업의 쌀로 불리며 정부와 관련업계의 높은 관심 속에 큰 성장을 이루었다. 삼성은 일본 기업에 비해 LCD 개발을 늦게 시작했지만 패널 대형화와 넓은 광시야각을 구현한 PVA (Patterned Vertical Alignment) 모드 (mode)를 실현하고, 여기에 더하여 측면 시인성 문제까지 해결한 공정이 단순하며 높은 대비비를 구현하는 SPVA (Super Patterned Vertical Alignment) 및 PSVA (Polymer-Stabilized Vertical Alignment) 모드를 개발하였다. 이와 동시에 새로운 액정 주입 방식인 ODF (One Drop Filling) 기술을 최초로 양산에 접목함으로써 LCD 산업에서 경쟁사들이 따라올 수 없는 훨씬 앞선 제1 주자가 되었다. 이 보고서는 삼성이 SPVA와 PSVA 모드를 역경 속에서 타사들과 어떻게 경쟁하며 발전시켜 왔는가에 대한 내용과 ODF 기술에 대해 삼성의 고유 자산권을 침해하지 않는 범위 내에서 서술하고자 한다. ※ 대비비: 화면의 백색상태 (white state)와 암흑 상태 (black state)의 광비 (光比)

Transmittance Improvement with Reversed Fishbone-Shape Electrode in Vertical Alignment Liquid Crystal Display

  • Lim, Young Jin;Kim, Hyo Joong;Kim, Min Su;Kim, Gi Heon;Kim, Yong Hae;Lee, Gi-Dong;Lee, Seung Hee
    • Journal of the Optical Society of Korea
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    • 제20권6호
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    • pp.794-798
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    • 2016
  • A polymer-stabilized vertical alignment (PS-VA) mode with fishbone-shaped pixel electrode structure is mainly used in large-sized liquid crystal displays (LCDs) owing to its advantages such as wide viewing angle, good transmittance and fast response time. One drawback of this mode is a main bone electrode, which crosses in the center of a pixel. It causes the transmittance to decrease badly because LCs cannot be reoriented in this region, and thus, it is particularly unfavorable in an ultra-high-definition LCD. Here, we propose an innovative structure with the main bone electrode relocated to the edge area in a pixel, and investigate how this reverse directed fishbone-shaped pixel electrode structure affects electro-optic characteristics. The proposed structure shows enhanced electro-optic performance, such as the higher transmittance and the faster response time than the conventional VA mode with fishbone-shaped pixel electrode structure.

The Alignment of Liquid Crystals on the Film Surfaces of Soluble Aromatic Polyimides Bearing t-Butylphenyl and Trimethylsilylphenyl Side Groups

  • Hahm, Suk-Gyu;Jin, Kyeong-Sik;Park, Sam-Dae;Ree, Moon-Hor;Kim, Hyung-Sun;Kwon, Soon-Ki;Kim, Yun-Hi
    • Macromolecular Research
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    • 제17권12호
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    • pp.976-986
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    • 2009
  • With the study goal of firstly elucidating the anisotropic interactions between oriented polymer chain segments and liquid crystal (LC) molecules, and secondly of determining the contributions of the chemical components of the polymer segments to the film surface topography, LC alignment, pretilt, and anchoring energy, we synthesized three dianhydrides, 1,4-bis(4'-t-butylphenyl)pyromellitic dianhydride (BBPD), 1,4-bis(4'-trimethylsilylphenyl)pyromellitic dianhydride(BTPD), and 2,2'-bis(4"-tert-butylphenyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride (BBBPAn), and a series of their organosoluble polyirnides, BBPD-ODA, BBPD-MDA, BBPD-FDA, BTPD-FDA, and BBBPAn-FDA, which contain the diamines 4,4'-oxydianiline (ODA), 4,4'-methylenediamine (MDA), and 4,4'-(hexafluoroisopropylidene)dianiline (FDA). All the polyimides were determined to be positive birefringent polymers, regardless of the chemical components. Although all the rubbed polyimide films exhibited microgrooves which were created by rubbing process, the film surface topography varied depending on the polyimides. In all the rubbed films, the polymer chains were unidirectionally oriented along the rubbing direction. However, the degree of in-plane birefringence in the rubbed film varied depending on the polyimides. The rubbing-aligned polymer chains in the polyimide films effectively induced the alignment of nematic LCs along their orientation directors by anisotropic interactions between the preferentially oriented polymer chain segments and the LCs. The azimuthal and polar anchoring energies of the LCs ranged from $0.45{\times}10^{-4}\;-\;1.37{\times}10^{-4}\;J/m^2$ and from $0.86{\times}10^{-5}\;-\;4.26{\times}10^{-5}\;J/m^2$, respectively, depending on the polyimides. The pretilt angles of the LCs were in the range $0.10-0.62^{\circ}$. In summary, the soluble aromatic polyimides reported here are promising LC alignment layer candidates for the production of advanced LC display devices.

액정 디스플레이 배향막을 위한 이온빔 표면조사에 관한 연구 (Ion beam irradiation for surface modification of alignment layers in liquid crystal displays)

  • 오병윤;김병용;이강민;김영환;한정민;이상극;서대식
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2008년도 춘계학술대회 및 기술 세미나 논문집 디스플레이 광소자
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    • pp.41-41
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    • 2008
  • In general, polyimides (PIs) are used in alignment layers in liquid crystal displays (LCDs). The rubbing alignment technique has been widely used to align the LC molecules on the PI layer. Although this method is suitable for mass production of LCDs because of its simple process and high productivity, it has certain limitations. A rubbed PI surface includes debris left by the cloth, and the generation of electrostatic charges during the rubbing induces local defects, streaks, and a grating-like wavy surface due to nonuniform microgrooves that degrade the display resolution of computer displays and digital television. Additional washing and drying to remove the debris, and overwriting for multi-domain formation to improve the electro-optical characteristics such as the wide viewing angle, reduce the cost-effectiveness of the process. Therefore, an alternative to non-rubbing techniques without changing the LC alignment layer (i.e, PI) is proposed. The surface of LC alignment layers as a function of the ion beam (IE) energy was modified. Various pretilt angles were created on the IB-irradiated PI surfaces. After IB irradiation, the Ar ions did not change the morphology of the PI surface, indicating that the pretilt angle was not due to microgrooves. To verify the compositional behavior for the LC alignment, the chemical bonding states of the ill-irradiated PI surfaces were analyzed in detail by XPS. The chemical structure analysis showed that ability of LCs to align was due to the preferential orientation of the carbon network, which was caused by the breaking of C=O double bonds in the imide ring, parallel to the incident 18 direction. The potential of non-rubbing technology for fabricating display devices was further conformed by achieving the superior electro-optical characteristics, compared to rubbed PI.

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액정 디스플레이 시야각 향상을 위한 복합판의 편광특성 분석 (Polarization Analysis of Composite Optical Films for Viewing Angle Improvement of Liquid Crystal Display)

  • 류장위;김상열;김용기
    • 한국광학회지
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    • 제20권4호
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    • pp.241-248
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    • 2009
  • 액정 디스플레이에서 시야각 향상을 위해 사용하는 보상판과 편광판을 접합한 복합판의 광축 틀어짐 오차와 보상판의 $R_{in}$(in-plane retardation), $R_{th}$(out-of-plane retardation)를 동시에 결정하는 새로운 방법을 제시하였다. 보상판은 광축이 임의의 기울임각과 방위각을 갖는 o-판으로 하였으며, 확장된 존스 행렬법에 기반한 광학모델을 도입하여 복합판의 편광특성을 분석하였다. 입사각 0도와 50도에서 시료의 방위각을 360도 회전시키며 투과된 빛의 편광상태를 각각 계산한 후, 타원법의 모델링 분석기법을 적용하여 광축 틀어짐과 복합판의 기울임각과 방위각들을 역방계산하였다. 이 방법은 편광판과 보상판을 접합한 후에도 복합판의 성능평가를 할 수 있어 제조공정단계를 줄여 제조 원가를 절감하는데 기여할 수 있을 것으로 기대된다.

High Out-of-Plane Alignment of Liquid Crystalline Methacrylate Copolymer Bearing Photoreactive 4-Styrylpyridine Moiety

  • Kwak, Gi-Seop;Kong, Jong-Yun;Kim, Min-Woo;Hyun, Seok-Hee;Kim, Woo-Sik
    • Macromolecular Research
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    • 제17권4호
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    • pp.271-275
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    • 2009
  • This paper describes the out-of-plane order of a liquid crystalline(LC) methacrylate copolymer(3) comprised of a methacrylate(1) with a 4-styrylpyridine moiety as the photo-cyclodimerizable group and a benzoate moiety as the mesogenic group in the side chain, and another methacrylate(2) with a 4-(4-methoxyphenyl)benzoate moiety as the mesogenic group. The composition of 1 and 2 units in 3 was estimated to have a molar ratio of 54.2:45.8 by $^{1}H$ NMR spectroscopy. The X-ray diffraction study revealed that the copolymer forms a partial bilayer smectic structure. The copolymer gave rise to a high out-of-plane order parameter of about 0.74 in a wide LC temperature range of $110{\sim}160^{\circ}C$ after linearly polarized, UV light irradiation and subsequent annealing. Moreover, the external reflection IR analysis indicated that excess UV-light irradiation makes the out-of-plane LC structure of the copolymer appear in a higher and wider temperature range.