Browsing by Author "Lin, Song-Shiang"

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Mechanism in determining pretilt angle of liquid crystals aligned on fluorinated copolymer films
(2009-08-07)
Wu, Hsin-Ying
;
Wang, Chih-Yu
;
Lin, Chia-Jen
;
Pan, Ru-Pin
;
Lin, Song-Shiang
This work explores the surface treatment of copolymer materials with fluorinated carbonyl groups in various mole fractions by ultraviolet irradiation and ion-beam (IB) bombardment and its effect on liquid crystal (LC) surface alignments. X-ray photoemission spectroscopic analysis confirms that the content of the grafted CF(2) side chains dominates the pretilt angle. A significant increase in oxygen content is responsible for the increase in the polar surface energy during IB treatment. Finally, the polar component of the surface energy dominates the pretilt angle of the LCs.
Surface Alignment with High Pretilt Angle Using the Photoreactive Fluorinated Polymer Films
(2009)
Wu, Hsin-Ying
;
Wang, Chih-Yu
;
Lin, Chia-Jen
;
Pan, Ru-Pin
;
Lin, Song-Shiang
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.