Surface Alignment with High Pretilt Angle Using the Photoreactive Fluorinated Polymer Films

Abstract

A newly developed fluorinated polymer film for liquid crystal alignment by applying ultra-violet (UV) irradiation or ion beam treatment is studied in this work. The surface alignment with high pretilt angle is achieved by the UV treatment. The induced pretilt angle by ion beam treatment on this photo-reactive polymer film, however, is relatively small. Surface analyses by x-ray photoemission spectroscopy and contact angle measurement are carried out to deduce the underlying mechanism. The result shows that the higher content of the fluorinated side-chain in polymer contribute to the lower surface energy and the higher pretilt angle. The atomic ratio of fluorine is largely decreased by ion beam treatments. The alignment uniformity and stability of the surfaces treated by linearly-polarized UV light and ion beam bombardment are also demonstrated.

Keywords:

• fluorinated polymer films
• ion beam
• nematic liquid crystals
• pretilt angle
• surface alignments
• ultraviolet irradiation

Acknowledgments

This work is supported in part by MOE-ATU Program and the National Science Council of R.O.C. under Grants No. NSC 95-2221-E-009-249 and PPAEU-II.