• Title/Summary/Keyword: Polar anchoring energy

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Effects of Surface Order Parameter on Polar Anchoring Energy in NLC on Weakly Rubbed Polyimide Surface

  • Seo, Dae-Shik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.11 no.12
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    • pp.1128-1132
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    • 1998
  • We have investigated the relationship between the polar anchoring energy and the surface order parameter in nematic liquid crystal (NLC), 4-n-pentyl-4-cyanobiphenyl (5CB), on the two kinds of the weakly rubbed polyimide (PI) surfaces. The observed polar anchoring energy of 5CB is approximately 2${\times}10^{-4}(J/m^2$) and then increases with increasing the rubbing strength (RS) on weakly rubbed surface (RS=57mm) with side chain at $30^{\circ}C$; same results are obtained on weakly rubbed PI surface without side chain. The surface order parameter of 5CB on rubbed PI surfaces increases with increasing the RS at a weak rubbing region. The surface order parameter of 5CB is strongly related to the characteristics of PI material. Consequently, we suggest that the polar anchoring energy of NLC is strongly attributed to the surface order parameter on rubbed PI surfaces.

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Anchoring Strength Characteristics by the Washing Process after Rubbing on the Polyimide Layers

  • Lee, Sang-Keuk;Lee, Joon-Ung;Han, Jeong-Min;Hwang, Jeoung-Yeon;Paek, Seung-Kwon;Seo, Dae-Shik
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.07b
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    • pp.1078-1081
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    • 2003
  • The polar anchoring strength and surface ordering in a NLC, 4-n-pentyl-4'-cyanobiphenyl (5CB), on a rubbed polyimide (PI) surface containing trifluoromethyl moiety were studied. The large extrapolation length de of 5CB for washing process of water was measured at RS=114 mm. The polar anchoring energy of 5CB on the rubbed PI surface is decreased by the washing process. Also, the polar anchoring energy of 5CB increases with the rubbing strength on the PI surface. The surface ordering of 5CB for all washing processes is smaller than the non-washing process; it is attributed to the washing process.

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Polar Anchoring Strength and Surface Ordering in NLC by the Washing Process on Rubbed Polymer Surfaces Containing Trifluoromethyl Moiety

  • Lee, Sang-Keuk;Lee, Joon-Ung;Han, Jeong-Min;Hwang, Jeoung-Yeon;Seo, Dae-Shik;Paek, Seung-Kwon
    • Transactions on Electrical and Electronic Materials
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    • v.3 no.4
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    • pp.36-40
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    • 2002
  • The polar anchoring strength and surface ordering in a NLC,4-n-pentyl-4'-cyanobiphenyl (5CB), on a rubbed polyimide (PI) surface containing trifluoromethyl moiety were studied. The large extrapolation length de of 5CB for washing process of water was measured at RS=114 mm. The polar anchoring energy of 5CB on the rubbed PI surface is decreased by the washing process. Also, the polar anchoring energy of 5CB increases with the rubbing strength on the PI surface. The surface ordering of 5CB for all washing processes is smaller than the non-washing process; it is attributed to the washing process.

Polymer Layer Effects on Anchoring Strength and Surface Ordering in NLC, 5CB, by the Washing Process after Rubbing on the Polyimide Surfaces

  • Lee, Sang-Keuk;Han, Jeong-Min;Hwang, Jeoung-Yeon;Seo, Dae-Shik
    • Transactions on Electrical and Electronic Materials
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    • v.4 no.2
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    • pp.5-9
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    • 2003
  • The liquid crystal (LC) aligning capabilities by the washing processes after rubbing on the two kinds of the rubbed polyimide (Pl) surface were studied. The polar anchoring energy of 4-n-pentyl-4'-cyanobiphenyl (5CB) increased with the rubbing strength RS on the two kinds of the rubbed PI surface. The polar anchoring energy of 5CB on the rubbed PI surface with alkyl side chains is larger than the rubbed PI surface with CONH moiety. Also, the surface ordering of 5CB on the rubbed PI surface with alkyl side chains is larger than the rubbed PI surface with CONH moiety. Therefore, the surface ordering of 5CB strongly depends on the polymers and washing process.

Polymer Layer Effects on Anchoring Strength and Surface Ordering in NLC, 5CB, by the Washing Process after Rubbing on the Polyimide Surfaces

  • Lee, S.K.;Lee, J.U.;Han, J.M.;Hwang, J.Y.;Seo, D.S.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.11a
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    • pp.506-509
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    • 2003
  • The liquid crystal (LC) aligning capabilities by the washing processes after rubbing on the two kinds of the rubbed polyimide (PI) surface were studied. The polar anchoring energy of 4-n-pentyl-4'-cyanobiphenyl (5CB) increased with the rubbing strength RS on the two kinds of the rubbed PI surface. The polar anchoring energy of 5CB on the rubbed PI surface with alkyl side chains is larger than the rubbed PI surface with CONH moiety. Also, the surface ordering of 5CB on the rubbed PI surface with alkyl side chains is larger than the rubbed PI surface with CONH moiety. Therefore, the surface ordering of 5CB strongly depends on the polymers and washing process.

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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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    • 2009.10a
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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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Basic Properties of Cell Fabricated by Ion-beam Treatment for In-plane Switching LCD

  • Seo, Joo-Hong;Lee, Sung-Pil;Yoon, Tae-Hoon;Kim, Jae-Chang
    • Journal of Information Display
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    • v.7 no.1
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    • pp.12-18
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    • 2006
  • We investigated the horizontal alignment properties such as surface morphology, pretilt angle, and polar and azimuthal anchoring energy of organic alignment material-coated surface treated by ion beam. In this investigation the energy and incident angle of ion beam were changed. We also fabricated an in-plane switching (IPS) cell by ion beam alignment. The results showed similar voltage-transmittance characteristics to those of a rubbed cell and better dark state.

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.

Microscopic Studies and Simulations of Bloch Walls in Nematic Thin Films

  • Park, Jung-Ok;Zhou, Jian;Srinivasarao, Mohan
    • 한국정보디스플레이학회:학술대회논문집
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    • 2005.07a
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    • pp.493-495
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    • 2005
  • The director profiles of the Bloch walls are directly visualized using fluorescence confocal polarizing microscopy. Both pure twist Bloch walls and diffuse Bloch walls are analyzed. Polar anchoring energy was measured from optical simulation of the transmitted light interference pattern or the fluorescence intensity profile of a pure twist wall..

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Reduction of Gamma Distortion in Oblique Viewing Directions in Polymer-stabilized Vertical Alignment Liquid Crystal Mode

  • Kim, Hyo Joong;Lim, Young Jin;Murali, G.;Kim, Min Su;Kim, Gi Heon;Kim, Yong Hae;Lee, Gi-Dong;Lee, Seung Hee
    • Current Optics and Photonics
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    • v.1 no.2
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    • pp.157-162
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    • 2017
  • In large liquid crystal displays, the image quality in an oblique viewing direction is a crucial issue. From this perspective, 8-domain polymer-stabilized vertical alignment (PS-VA) mode has been developed to suppress the color shift in oblique viewing directions, compared to that in 4-domain PS-VA mode. To realize the 8-domain PS-VA, the four domains in a pixel are each divided into two regions, such that applying different electric potentials result in different tilt angles in these two regions, while keeping four azimuthal directions in each domain. However, applying different voltages in a pixel causes drawbacks, such as requiring additional processes to construct a capacitor and a transistor, which will further reduce the aperture ratio. Here we propose a different approach to form the 8-domain, by controlling surface polar anchoring energy and the width of patterned electrodes in two regions of a pixel. As a result, the gamma-distortion index (GDI), measured at an azimuthal angle of $0^{\circ}$, is reduced by about 23% and 8%, compared to that of a conventional 4-domain at polar angles of $30^{\circ}$ and $60^{\circ}$ respectively.