• Title/Summary/Keyword: Rubbed polyimide

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Electro-optical characteristics of liquid crystal alignment layer modified by ion beam irradiation (액정배향막 표면 개질에 따른 전기광학적 특성연구)

  • Oh, Byeong-Yun;Seo, Dae-Shik
    • Proceedings of the IEEK Conference
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    • 2008.06a
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    • pp.513-514
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    • 2008
  • The potential of non-rubbing technology for applying to display devices was demonstrated by irradiating a high density argon ion beam (IB) on a polyimide (PI) as a liquid crystal alignment layer. The superior electro-optical characteristics were obtained, compared to rubbed PI, Although the low pretilt angle was created on the IB irradiated PI.

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New Photo-Alignment Materials for LCD as a Non-Rubbing Method.

  • Kumano, Atsushi;Takeuchi, Yasumasa;Nakata, Shoichi;Kimura, Masayuki
    • 한국정보디스플레이학회:학술대회논문집
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    • 2002.08a
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    • pp.953-956
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    • 2002
  • We successfully developed new photo-alignment materials which can be treated with linearly polarized UV (LPUV) light in near UV region. The alignment films were also shown to provide with surface anchoring as strong as that on rubbed polyimide when exposed to the LPUV light with warming up the substrate. It can be also able to control pretilt angle by introduction of alkyl side chain.

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Image Sticking Property in the In-Plane Switching Liquid Crystal Display by Residual DC Voltage Measurements

  • Jeon, Yong-Je;Seo, Dae-Shik;Kim, Jae-Hyung;Kim, Hyang-Yul
    • KIEE International Transactions on Electrophysics and Applications
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    • v.11C no.4
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    • pp.142-145
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    • 2001
  • The residual DC phenomena in the in-plane switching(IPS)-liquid crystal display(LCD) by the voltage-transmittance (V-T) and capacitance-voltage (C-V) hysteresis method on rubbed polyimide (PI) surfaces were studied. We found that the residual DC voltage in the IPS-LCD was decreasing with the increasing concentration of cyano LCs. The residual DC voltage of the IPS-LCD can be improved by the high polarity of cyano LCs.

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Thermal Stability of Polarized UV Exposed Polyimide Films for Liquid Crystal Display (편광 자외선이 조사된 액정 디스플레이용 폴리이미드 필름의 열 안정성)

  • 김일형;김욱수;하기룡
    • Polymer(Korea)
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    • v.26 no.4
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    • pp.431-438
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    • 2002
  • We studied the orientation behavior and thermal stability of polyimide (PI) molecules under irradiation of polarized UV (PUV) using polarized fourier transform infrared (FTIR) spectroscopy. In the case of PUV-exposed PI films, the remaining PI molecules after photo-degradation showed molecular orientation perpendicular to the irradiated PUV polarization direction predominantly, due to the preferential degradation of PI molecules parallel to the irradiated PUV Polarization direction. On the other hand, the rubbing of PI films induced reorientation of the PI molecules parallel to the rubbing direction. We also investigated the thermal stability of the alignment layers furled by rubbing and PUV irradiation on the PI films using Polarized FTIR. The thermal stability of the PUV irradiated PI alignment layer is lower than that of the rubbed PI layer due to the fragmentation reaction of the PI by PUV.

Polarized Light Emission of Liquid Crystalline Polymer Blends (액정성 고분자 블렌드의 편발광)

  • 김영철;조현남;김동영;홍재민;송남웅
    • Polymer(Korea)
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    • v.24 no.2
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    • pp.211-219
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    • 2000
  • Fluorene-based light emitting polymer blends with liquid crystalline characteristics were studied on effective energy transfer and dichroic characteristics. Incorporating 0.5 wt% of the non-liquid crystalline into the liquid crystalline polymer suppressed the PL emission at 420 nm on photoexcitation at 360 nm, but generated a new PL emission of the non-liquid crystalline polymer at 480 nm. The highest PL intensity at 480 nm, which was 13 times stronger than those of the two polymers before blending, was observed for a blend with 2.0 wt% of the non-liquid crystalline polymer. When the molecules of the blends were aligned on a rubbed polyimide surface by a heating-cooling process, the dichroic ratio and the order parameter were 2.0 and 0.25, respectively. Time-correlated single photon counting (TCSPC) study revealed that the time required for energy transfer between the two chromophores was shortened by 93 ps when the blends were aligned on the rubbed polyimide surface by the heating-cooling process. The thermal treatment also enhanced the energy transfer efficiency by 9%.

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Pile Contact Depth Effects in Rubbed Polyimide(PI) Films

  • Kim, Gi-Jeong;Gwon, Hyeok-Min;Lee, Sang-Mun;Lee, Cheol-Gu;Gwak, Mu-Seon;Kim, Bong-Su
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.398-398
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    • 2010
  • To determine the molecular directionality of PI chains depending on rubbing condition, we measured the angle resolved near edge X-ray absorption fine structure (NEXAFS) spectra at C K-edge of the rubbed PI films. Twisted nematic mode PI (PI-TN) and in plane switching mode PI (PI-IPS) were introduced to examine the effect of rubbing conditions on the chain directionality. The average tilt angle a of the PI molecules was estimated through the measured intensity change of $C=C\;{\pi}^*$ in NEXAFS C K-edge spectrum by controlling the stage speed and the pile contact depth. After rubbing, the irregular molecular direction changed to a regular direction with a molecular tilt angle of $51.2^{\circ}$ for PI-TN and $49.6^{\circ}$ for PI-IPS at the rubbing condition of the roll speed of 1000 rpm, stage speed of 50 mm/sec, and file contact depth of 0.3 mm. The molecular tilt angle $\alpha$ was linearly decreased in the PI-TN and PI-IPS samples with increasing depth of the pile contact.

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No-bias-bend pi cell using the rubbed polyimide mixture

  • Kim, Dae-Hyeon;Park, Hong-Gyu;Kim, Yeong-Hwan;Kim, Byeong-Yong;Ok, Cheol-Ho;Han, Jeong-Min;Seo, Dae-Sik
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.11a
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    • pp.186-186
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    • 2009
  • Most liquid crystal display modes, including the twisted nematic (TN) $mode^1$, the in-plane switching (IPS) $mode^2$, the fringe field switching (FFS) $mode^3$, and the vertically aligned (VA) $mode^4$ are based on either a horizontal or a vertical alignment. However, for some applications, such as no-bias-bend (NBB) pi cell or bistable bend-splay display, an intermediate pretilt angle is essential$^5$. NBB pi cells have been a focus of interest because of their fast response time; however, the reliable control of the intermediate pretilt angle of liquid crystals that is required for the fabrication of NBB pi cells is challenging. The controllable pre-tilt angle of liquid crystals was investigated using a blend of horizontal and vertical polyimide prepared by a rubbing method. Various pretilt angles in the range from 0^{\circ}$ to 90^{\circ}$ were achieved as a function of the vertical polyimide content. We observed uniform liquid crystal alignment on the rubbing-treated blended polyimide layer. A NBB pi cell with an intermediate pretilt angle of 47.8^{\circ}$ was manufactured. This cell had no initial bias voltage and a low threshold voltage, which indicates that it has low power consumption. In addition, the response time of the NBB pi cell was rapid.

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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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    • v.17 no.12
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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.

Analysis of Properties of Rubbed Polyimide Alignment Layer and Rubbing Effect of Various Rubbing Cloths for LCD Fabrication (LCD 제조용 러빙포 물성에 따른 러빙된 폴리이미드 배향막의 특성 및 러빙효과 분석)

  • Ahn, Hong-Jun;Lee, Jang-Ju;Ahn, Jong-Soo;Park, Kyung-Chul;Noh, Jae-Gyu;Yoo, Dong-Yeon;Paek, Sang-Hyon
    • Polymer(Korea)
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    • v.35 no.5
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    • pp.385-389
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    • 2011
  • In rubbing process, process factors, the properties of alignment layer and the physical properties of rubbing cloth have acted as important variables. These factors affect the orientation properties of the alignment layer by rubbed extent that is determined by rubbing density and rubbing force. In this work, we studied the effects of rubbing cloths with different pile density and rigidity on rubbing density(length) and rubbing force. As the pile density and rigidity of rubbing cloths increased, the birefringence and the surface roughness of the rubbed alignment layers became bigger, but the characteristics of rubbing-effect had differed each other. The pile density of rubbing cloths which was related with the number of pile, affected the rubbing density(length). On the other hand, the pile rigidity of rubbing was closely related to rubbing force rather than the rubbing density(length).

Effects of UV light irradiation condition and imidization temperature for the generation of pretilt angle on polyimide surfaces (폴리이미드 표면에서의 프리틸트각 발생에 대한 UV조사 조건과 이미드화온도의 영향)

  • Yu, Mun-Sang;Seo, Dae-Shik;Hwang, Jeoung-Yeon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 1998.11a
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    • pp.61-64
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    • 1998
  • We have investigated the effects of ultraviolet (UV) light irradiation condition and imidization temperature for the generation of pretilt angle in nematic liquid crystal (NLC) on the two kinds of the polyimide (PI) surfaces. High pretilt angle of NLC is generated with oblique p-polarized UV light irradiation of 30$^{\circ}$ on PI surface for 20 min. Also, the high pretilt angle of NLC is generated with oblique p-polarized UV light irradiation of 10-30$^{\circ}$ on PI surface at 20min. The pretilt angle of NLC decreases with increasing the imidization temperature on all rubbed PI surfaces ; the pretilt angle of NLC with oblique p-polarized UV light irradiation of 30$^{\circ}$on PI surface decreases with increasing the imidization temperature. The high pretilt angle of NLC is observed due to high photo-depolymerization reaction by low surface energy at low imidization temperature. We suggest that the pretilt angle of NLC is strongly attributed to the photo-depolymerization reaction with the UV light irradiation condition and imidization temperature.

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