Current Optics and Photonics

Optical Society of Korea (한국광학회)
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Ellipsometric Characterization of Rubbed Polyimide Alignment Layer in Relation with Distribution of Liquid Crystal Molecules in Twisted Nematic Cell

  • Received : 2018.03.06
  • Accepted : 2018.03.29
  • Published : 2018.04.25
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Abstract

Ultra-small optical anisotropy of a rubbed polyimide (PI) alignment layer is quantitatively characterized using the improved reflection ellipsometer. Twisted nematic (TN) cells are fabricated using the rubbed PIs of known surface anisotropy as alignment layers. Distribution of liquid crystal (LC) molecules in the TN cell is characterized using transmission ellipsometry. The retardation of the rubbed PI surface increases as rubbing strength increases. The tilt angle of the optic axis of the rubbed PI surface decreases as rubbing strength especially as the angular speed of the rubbing roller increases. Pretilt angle of LC molecules in the TN cell shows strong correlation with tilt angle of the optic axis of the rubbed PI surface. Both the apparent order parameter and the effective twist angle of the LC molecules in the TN cell decrease as the pretilt angle of LC molecules increases.

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References

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