Browsing by Author "King, Jinn-Shing"

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Effect of backbone on the biaxial retardation of polyimide films in uniaxial stretch
(2007-05-15)
King, Jinn-Shing
;
Whang, Wha-Tzong
;
Lee, Wen-Chin
;
Chang, Li-Ming
;
材料科學與工程學系
A biaxial-retardation film prepared from the uniaxial-stretched polyimide (PI) film was developed for compensating the viewing angle of liquid-crystal displays. Good uniformity of in-plane bireffingence in well-stretched PI films was observed visually with two crossed polarizers. The prism coupling method was used to measure the n(x), n(y), n(z), and thickness of the stretched PI films. The birefringence variations of n, - n, (difference of refractive indices between x- and y-axes) and n(x) - n(z) during the stretching process were highly affected by PI structure. The polarizability tensors and intrinsic birefringences of the PI repeat units were estimated by Gaussian 98W. It was found that the stretch-induced birefringence is more related to the average polarizability per volume at the low elongation period. (C) 2006 Elsevier B.V. All rights reserved.
Structural effect on stretch-induced birefringence in polyimide films
(2007-10-01)
King, Jinn-Shing
;
Lee, Wen-Chin
;
Chang, Li-Ming
;
Whang, Wha-Tzong
;
材料科學與工程學系
Seven polyimides (Pls) of low glass transition temperature were synthesized and their films were uniaxially stretched to observe the variation in their in-plane birefringence (An). The intrinsic birefringences (triangle n degrees) of their polymer chains were also estimated using the experimental average refractive indices and computationally calculated polarizability tensors. The observed stretch-induced An was markedly affected by the PI structure. A model that shows a good fit to experimental data is proposed to predict the orientation degree of PI chains in different PI films. The model, when combined with the analysis of the estimated An's, is useful in explaining the behavior of stretch-induced triangle ns in PI films.