• Title/Summary/Keyword: van der waals(VDW)

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Washing Effects on Generation of Pretilt Angle in NLC, 5CB, on a Polyimide Surface with Trifluoromethyl Moieties

  • 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.1
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    • pp.21-23
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    • 2003
  • The washing effects on pretilt angle generation in a nematic liquid crystal (NLC), 4-n-pentyl-4'-cyanobiphenyl (5CB) on a rubbed polyimide (PI) surface with trifluoromethyl moiety have been successfully studied. The pretilt angle of 5CB is increased by the washing process on the rubbed PI surface. The surface tension on the rubbed PI surface increases with the rubbing strength RS and then saturated above RS: 150 mm. The pretilt angle of 5CB for all washing processes on the rubbed PI surface decreases with the surface tension. We have found that the pretilt angle of 5CB on the rubbed PI surface may be attributed van der walls (VDW) dispersion interaction between the LC molecules and the polymer surfaces having trifluoromethyl moieties.

Liquid Crystal Alignment on Multi-stacked Layer HfO2 Thin Films Using a Solution-process (용액 공정 기반의 다중 적층된 HfO2 박막 상에서의 액정 배향)

  • Kim, Dai-Hyun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.26 no.11
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    • pp.821-825
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    • 2013
  • Effect of multi-stacked layer (MSL), 0.1 mol (M) and 0.3 mol (M) hafnium oxide ($HfO_2$) alignment layers were fabricated via a solution-process for LCs orientation. The solutions were spin-coated and annealed in a furnace. MSL consists of three sub-layers using 0.1 M solution, mono-layer (ML) is composed of 0.3 M $HfO_2$ solution. Then ion-beam irradiation was treated with 1.8 keV for 2 min. $HfO_2$-based LC cells were investigated through photographs, pre-tilt angle using crystal rotation method, X-ray photoelectron spectroscopy (XPS) measurement, and surface roughness using atomic force microscopy(AFM) for their characteristic research. Good LC orientation characteristics were observed on MSL $HfO_2$ surface. The LC alignment mechanism on MSL $HfO_2$ and ML $HfO_2$ surfaces was attributed to van der Waals (VDW) interaction between the LC molecular and substrate surface.