The Anchoring Strength of Liquid Crystals on Polyimide Surfaces Treated by a Direct-Current Ion Beam Sputter

Abstract

In this work we report the alignment property of nematic liquid crystal with variable pretilt angle on surfaces treated by argon plasma. The scanning electron microscope (SEM) image indicates that nanoparticles are deposited on treated PI film. Groove-like aggregating structures are observed and the direction of aggregate tends to parallel to the ion beam direction. X-ray photoelectron spectroscopic (XPS) analysis confirms that γ-Fe₂O₃ nanoparticles were deposited on the surface of polyimide (PI) films. We also deduce that the maghemite is the main factor determining the pretilt angle while a competition exists between the homogeneous and homeotropic alignments.

Keywords:

• Anchoring strength
• ion beam
• nanoparticles
• polyimide films
• pretilt angle
• surface alignment

Acknowledgment

This work was supported by National Science Council, Republic of China, under grand number 96-2221-E-009-131-MY3 and Academia Sinica AS-98-TP-A10.