• 제목/요약/키워드: Crystal alignment

검색결과 538건 처리시간 0.028초

Chemical Structural Effects of Polyimides on the Alignment and Electro-optical Properties of Liquid Crystal Cells

  • Paek, Sang-Hyon;Wonseok Dong
    • Macromolecular Research
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    • 제12권3호
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    • pp.251-257
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    • 2004
  • The nature of the nematic liquid crystal (LC) alignment induced by the rubbed polyimide (PI) alignment layers (ALs) and the electro-optical (EO) properties of the LC cells are expected to depend on the chemical and physical features of the PI. By employing five pyromellitic dianhydride (PMDA)-type PIs having different functionalities, we have studied the effects of the PI's structure and chemistry on the alignment characteristics and the cell's EO properties. Increasing the flexibility of the PI increases the pretilt angle and tends to improve the alignment stability. On the other hand, the rigid, fluorinated PI displays poor stability for LCs and induces a less stable/uniform LC alignment and, subsequently, a small pre tilt angle. It also transpired that fluorination of the PI deteriorated the voltage-transmittance characteristics and the voltage holding ratio; increasing the flexibility of the PI structure improves these EO properties. The finding that the qualitative trends for the PI's functionalities are similar for both the alignment and EO properties suggests that the EO properties are closely related to the alignment characteristics, which are determined by short-range interactions between LC and PI molecules.

Imprinting of Liquid Crystal Alignment on Polymer Layers

  • Wook, Jung-Jong;Kim, Jae-Hoon
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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    • pp.611-614
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    • 2003
  • We have investigated electric field effect on the formation of phase separated composite organic film structure which is utilized by anisotropic phase separation from LC and prepolymer mixtures. Application of bias field resulted in a significant change in liquid crystal alignment between glass substrate and polymer layer. The liquid crystal molecules segregated into the inter-electrodes and formed twisted structure which is the result of imprinting of LC alignment by the bias field on polymer layers during polymerization process.

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네마틱 백정의 표면 액정 배향에관한 폴리이미드막의 분자 구조의 효과 (Effect of the Molecular Structure of Rubbed Polyimide Films for Surface Liquid Crystal Alignment of Nematic Liquid Crystal)

  • 서대식
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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    • pp.232-234
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    • 1996
  • We have investigated the effect of molecular structure of polymer of rubbed polyimide (PI) films for surface liquid crystal alignment. To obtain surface alignment effect of Polymer molecular structure, we measured the polar (out of plane-tilt) anchoring strength and surface ordering of 5CB on rubbed PI surfaces. We have found that the polar anchoring strength of 5CB is depend on the polymer molecular structure of these unidirectionally rubbed PI surfaces.

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새로운 이온빔을 이용한 $SiO_x$ 박막 표면의 액정 배향 효과 (Homeotropic Alignment Effect for Nematic Liquid Crystal on the $SiO_x$ Thin Film Layer by New Ion beam Exposure)

  • 최성호;김병용;한진우;오용철;서대식
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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    • pp.311-312
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    • 2006
  • We studied homeotropic alignment effect for a nematic liquid crystal (NLC) on the $SiO_x$, thin film irradiated by the new ion beam method $SiO_x$ thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) and were treated by the DuoPIGatron ion source. A uniform liquid crystal alignment effect was achieved over 2100 eV ion beam energy. Tilt angle were about $90^{\circ}$ and were not affected by various ion beam energy.

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무기막 NiOx의 정렬 패턴 전사를 이용한 액정의 배향 특성 연구 (A Study on the Liquid Crystal Orientation Characteristics of the Inorganic NiOx Film with Aligned Nanopattern Using Imprinting Process)

  • 오병윤
    • 한국전기전자재료학회논문지
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    • 제32권5호
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    • pp.357-360
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    • 2019
  • We demonstrate an alignment technology using an imprinting process on an inorganic NiOx film. The aligned nanopattern was fabricated on a silicon wafer by laser interference lithography. The aligned nano pattern was then imprinted onto the sol-gel driven NiOx film using an imprinting process at an annealing temperature of $150^{\circ}C$. After the imprinting process, parallel grooves had been formed on the NiOx film. Atomic force microscopy and water contact angle measurements were performed to confirm the parallel groove on the NiOx film. The grooves caused liquid crystal alignment through geometric restriction, similar to grooves formed by the rubbing process on polyimide. The liquid crystal cell exhibited a pretilt angle of $0.2^{\circ}$, which demonstrated homogeneous alignment.

Molecular orientational surface structures of polymers for liquid crystal alignment

  • Ohe, Masahito
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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    • pp.611-614
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    • 2006
  • Sum-frequency vibrational spectroscopy (SFVS) has been used to study the molecular orientations at the polymer surfaces for liquid crystal alignment. Various molecular orientations appear at the surface depending on various types of surface treatments and polymers.

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Electro-optical Properties of Twisted Nematic Liquid Crystal Cell with Silver Nanowire Network Electrodes

  • Jang, Kyeong-Wook;Han, Jeong-Min;Shon, Jin-Geun
    • Journal of Electrical Engineering and Technology
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    • 제12권1호
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    • pp.284-287
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    • 2017
  • This paper introduces liquid crystal (LC) alignment and its electro-optical properties in the LC cells with silver nanowire (AgNW) networks. The AgNW network was used as an electrode of LC cell as a substitute for an indium-tin-oxide (ITO) film. LC alignment characteristics in the LC cell using AgNW networks, which have two different sheet resistances of $60{\Omega}/m^2$ and $80{\Omega}/m^2$, were observed. The LC alignment characteristics including pretilt angle, LC alignment state, and thermal stability are similar irrespective of sheet resistance of AgNW network. However, twisted-nematic (TN)-LC cell normally operated when using AgNW network with sheet resistance of $80{\Omega}/m^2$. Electrooptical properties of TN-LC cell exhibited competitive performance compared to those of TN-LC cell based on conventional ITO electrode, which allow new approaches to replace conventional ITO electrode in display technology.

측쇄기를 가진 폴리머의 폴리이미드 소성 방법에 따른 액정 배향 효과 (Liquid crystal alignment effects by imidization methods of the polyimide on the polymer with side chain.)

  • 서대식;김형규
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2000년도 춘계학술대회 논문집 디스플레이 광소자 분야
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    • pp.177-180
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    • 2000
  • In this study, we investigated the pretilt angle generation and liquid crystal (LC) alignment by ultraviolet (UV) exposure during imidization of polyimide on the polymer with side chain. The generated pretilt angle of nematic (N) LC using in-situ photo-alignment method was smaller than that of the conventional UV photo-alignment method. Also, the generated pretilt angle of NLC tends to increase by annealing.

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광배향기술을 이용한 액정배향의 기구 및 폴리이미드의 분자구조가 프리틸트각에 미치는 영향 (Liquid Crystal Alignment and Generation of Pretilt Angle by Using Photo-alignment Techniques on Different Polymer Molecules)

  • 서대식;황율연;이창훈
    • 한국전기전자재료학회논문지
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    • 제11권6호
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    • pp.477-480
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    • 1998
  • In this paper, we investigated the liquid crystal(LC) alignment and generation of pretilt angle by using photo-alignment techniques on two kinds of polyimide(PI) surface, It was found that the uniform alignment for nematic(N) LC is obtained in a cell with slanted UV light irradiation on PI surface without side chain. We successfully observed that the pretilt angle of NLC is generated about $3^{\circ}$ with an incident angle of 70 degree on the PI surface without side chain. It is considered that the pretilt angle generation in NLC is attributed to interaction between the LC molecules and the polymer surfaces.

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수직배향층에서의 네마틱액정의 프리틸트각 발생 (Pretilt Angle Generation for Nematic Liquid Crystal on a Homeotropic Alignment Layer)

  • 서대식;김형규;이승희
    • 한국전기전자재료학회논문지
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    • 제14권2호
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    • pp.130-132
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    • 2001
  • The mechanisms of pretilt angle generation in nematic liquid crystal (NLC) with negative dielectric anisotropy on a rubbed polyimide (PI) surface for homeotropic alignment were studied. The pretilt angle of negative type NLC was smaller than that of the positive type NLC for all rubbing strength regions on the rubbed PI surface. The pretilt angle generated in NLC does not attributable to steric interaction between the fluorine moiety of NLC and the polymer surface on the rubbed PI surface. Consequently, the mechanism of the pretilt angle generation for homeotropic alignment is different from the one for homogeneous alignment.

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