• Title/Summary/Keyword: Photo-Alignment

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Liquid crystal alignment and generation of pretilt angle using an in-situ photo-alignment method (In-situ 광배향법을 이용한 액정 배향 및 프리틸트의 발생)

  • 서대식;김형규
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.336-339
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    • 2000
  • Effects of liquid crystal (LC) alignment using an in-situ photo-alignment method by linearly polarized UV exposure during imidization of polyirnide (PI) on the two kinds of PI surfaces with side chain were investigated. The generated pretilt angle in nematic (N) LC using an in-situ photo-alignment method was smaller than that of a conventional photo-alignment method for short UV exposure time. Also, the pretilt angle of the NLC using an in-situ photo-alignment method increases with increasing UV exposure time on the two kinds of the PI surfaces. Finally, the pretilt angle of NLC can be improved by annealing treatment.

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Liquid crystal alignment and photo-induced pretilt by imidization temperature. (소성온도에 따른 광유기된 프리틸트와 액정배향)

  • 서대식;김형규
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.11a
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    • pp.533-536
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    • 1999
  • In this study, we investigated pretilt angle generation and liquid crystal alignment by UV light irradiation during imidization of polyimide. Generated pretilt angle of NLC by using in-situ UV photo-alignment method was smaller than that of the conventional UV photo-alignment method. Also, generated pretilt angle of NLC tends to increase by annealing. We found that in-situ UV photo-alignment method has higher thermal stability of LC alignment, but it has a disadvantage to control pretilt angle.

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Control of Pretilt Angle by UV exposure during Imidization of Polyimide for Homeotropic Alignment (수직 배향용 폴리미이드의 소성시에 UV 조사를 이용한 프리틸트각 제어)

  • 황정연;서대식;한은주;갬재형
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.11
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    • pp.950-953
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    • 2000
  • Aligning capabilities of nematic liquid crystal(NLC) using an in-situ photo-alignment method with obliquely polarized UV exposure on a polyimide (PI) surface for homeotropic alignment were studied. The high angle for NLC can be measured by obliquely UV exposure of 30°on the PI surface for 10∼20 min. The pretilt angle of NLC generated using the in-situ photo-alignment was higher than that of a conventional photo-alignment method. Finally, we suggest that the control of pretilt angle in NLC with obliquely polarized UV exposure during imidization of the polymer for homeotropic alignment is promising method to generate high pretilt angle.

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Photo-Alignment Mechanism Study of Poly(siloxane cinnamate) (폴리(실록산 신나메이트)의 광배향 메커니즘 연구)

  • Choi Ji-Won;Lim Ji-Chul;Song Ki-Gook
    • Polymer(Korea)
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    • v.30 no.5
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    • pp.417-421
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    • 2006
  • Photo -alignment of poly (siloxane cinnamate) (PSCN) was studied to better understand the alignment mechanism of cynnamoyl groups under various process conditions. DSC and polarized microscope studies showed that the isotropic temperature oi PSCN was about $105^{\circ}C$ and the liquid crystallinity, once formed, did not completely disappear even when the temperature went into the isotropic regions. UV/Vis absorption study suggested that the photo - dimerization was the main photo alignment mechanism and it's efficiency could be enhanced through the self-alignment of PSCN. It was also found that photo-dimerization was in competition with photo-fries reaction and the photo- alignment of PSCN was interfered with the excessive UV because of the strong photo-fries reaction. However, photo - fries reaction could be suppressed by adjusting the UV wavelength.

Pretilt angle generation of vertically aligned nematic liquid crystal using a in-situ photoalignment method (In-situ 광배향법을 이용한 수직배향된 네마틱 액정의 프리틸트각 발생)

  • 김형규;황정연;서대식;한은주;김재형
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.11a
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    • pp.507-510
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    • 2000
  • Alignment effects for nematic liquid crystal (NLC) using an in-situ photo-alignment method with obliquely polarized UV exposure on a polyirnide (PI) surface for homeotropic alignment were studied. The high pretilt angle in NLC can be measured by obliquely W exposure of $30^{\circ}$ on the PI surface for 10~20 min. The pretilt angle of NLC generated using the in-situ photo-alignment was higher than that of a conventional photo-alignment method.

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Liquid Crystal Alignment on the Multiple Photo-treated Layers by the Interfered Laser Light

  • Lee, Eun-Kyu;Kim, Jong-Hyun
    • Journal of Information Display
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    • v.8 no.1
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    • pp.6-9
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    • 2007
  • Orientational alignment patterns have been proven to be that they are very useful for realizing diverse properties of liquid crystals. Here we produced the patterns combining interfered laser beams. A photo-isomerizable polymer including azo unit, which induces nematic liquid crystal alignment to the polarized laser light, was used as the alignment to layer. Double irradiations into two orthogonal directions brought the orientation patterns similar to the checkerboard. It indicates the possibility of bistability on those patterns.

Investigation of pretilt generation by UV light irradiation during imidization of polyimide (폴리이미드 소성 시에 UV 광조사를 이용한 프리틸트 발생에 대한 연구)

  • 서대식;김형규
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.1
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    • pp.75-79
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    • 2000
  • In this study, we investigated the pretilt angle generation and liquid crystal (LC) alignment by ultravi-olet (UV) light irradiation during imidization of polymide. The generated pretilt angle of nematic (N) LC by using the in-situ photo-alignment method was smaller than that of the conventional UV photo-alignment method. Also, generated pretilt angle of NLC tends to increase by annealing. In case of using the polymer(AL-3046), we found that the in-situ Uv photo-alignment method has higher thermal stability of LC alignment, but it has a disadvantage to control pretilt angle.

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Electro-optical properties of photo-aligned VA-LCD by irradiation of unpolarized UV light. (비편광 UV조사에 의한 광배향 VA-LCD의 전기광학특성)

  • 박두석;서대식
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1999.11a
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    • pp.545-548
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    • 1999
  • The electro-optical characteristics of photo-aligned vertical-alignment (VA)-liquid crystal display (LCD) with non-polarized ultraviolet (UV) light irradiation of 45\`on homeotropic polyimide (Pl) surface were investigated. LC alignment on photo-aligned VA-LCD is attributed to photo-depolymerized reaction of the polymer with non-polarized UV light irradiation on PI surface. We had good voltage-transmittance (V-T) characteristics of photo-aligned VA-LCD. The response time of photo-aligned VA-LCD was slower than that of the rubbing-aligned VA-LCD. Finally, we suggest that the slow response time of photo-aligned VA-LCD depends on the LC domain.

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Novel LCD's and novel LCD manufacturing;A new world of LCDs opened up by Photo-Rubbing

  • Yokoyama, Hiroshi;Kimura, Masayuki
    • 한국정보디스플레이학회:학술대회논문집
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    • 2006.08a
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    • pp.1601-1604
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    • 2006
  • A novel photo-alignment scheme using normally incident periodically intensity-modulated UV light has been developed and demonstrated to efficiently yield a stable pretilt angle of nematic liquid crystals by single exposure. The scheme, referred to as the "photo-rubbing", consists in unidirectional scan of the intensity-modulated UV light over the photo-alignment film, which causes asymmetrical photo-reactions in the film. We show here its successful application to multi-domain alignment processing. Thanks to the normal incidence, the photo-rubbing removes the instrumental disadvantages of the conventional oblique incidence technique, thereby providing a true practical solution for photo-alignment.

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Study of the Photo-alignment Technique through the Surface Modification

  • Song, Dong-Mee;Shin, Dong-Myung
    • 한국정보디스플레이학회:학술대회논문집
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    • 2000.01a
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    • pp.197-198
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    • 2000
  • A surface-assisted photo-control of the liquid crystal (LC) alignment has been achieved by modifying the topmost surface of the polyimide film with photo-reactive molecules. Recently, photo-alignment technique using a thin film of poly(vinyl cinnamates) have been reported. However their commercial potentiality is limited by their low thermal stability. To enhance thermal stability, we synthesized the chalcone derivatives as the photo-reactive molecules and introduced the materials on the surface-modified polyimide film.. We identified that the photo-chemical reaction of the chalcone derivatives occur in few minutes with irradiation of UV light. The photo-alignment characteristics of the modified polyimide films treated by polarized UV light and their LC cells are investigated as a function of exposure dose.

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