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Electroluminescence characteristics of aromatic polyimides by vapor deposition polymerization
(2003)
Hsu, SC
;
Whang, WT
;
Chen, SC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Light emitting polyimide (PI) thin films are successfully prepared from two kinds of diamines: 2,5-Bis(4-aminophenyl)-1,3,4-oxadiazole (BAO) and 4,4'-(9-Fluorenylidene)dianiline (BAPF) reacting with 4,4'-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA) by vapor deposition polymerization (VDP). We succeed to reduce the thickness of the thin polyimide film to 150 Angstrom, and the threshold voltage of BAO-6FDA and BAPF-6FDA PI light-emitting diodes to 4.5 V and 6.5 V respectively. The root mean square of the surface roughness of the BAO-6FDA and BAPF-6FDA PI films are 8.8 Angstrom and 4.7 Angstrom respectively. But that of the BAO-6FDA film from wet coating process is 37.1 Angstrom. Apparently, VDP process is the better way to produce smooth polyimide film. The BAO-6FDA LED film emits a broader electroluminscence (EL) band, covering the full range of visible light (400 nm to 700 nm), than the BAPF-6FDA LED. However, the electroluminescence efficiency of BAPF-6FDA LED device is better than BAO-6FDA LED device. It is due to the better balance on the hole and electron injection in the former and better intermolecular charge transfer.
The synthesis and morphology characteristic study of BAO-ODPA polyimide/TiO2 nano hybrid films
(2003-04-01)
Chiang, PC
;
Whang, WT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Hybrid nanocomposite films of titanium dioxide (TiO2) in polyimide (PI) from 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (BAO) and 4,4'-1-oxydiphthalic anhydride (ODPA) have been successfully fabricated by an in situ sol-gel process. These nanocomposite films exhibit fair good optical transparency up to 40 wt% of TiO2 Content. X-ray diffraction spectroscopy shows three sharp peaks in pure BAO-ODPA PI. It results from the intermolecular regularity. However, the intermolecular regularity in the hybrid film is disrupted by the introduction of TiO2 nanoparticles with no sharp peak in XRD spectra. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results confirm the formation of TiO2 particles in PI matrix. The surface Ti content is much lower than the theoretical bulk content in all hybrid films. The ratio of the former to the latter increases with the TiO2 content and levels off at TiO2 wt% greater than or equal to 20. Transmission electron microscope (TEM) images show that the TiO2 phase is well dispersed in the polymer matrix. The size of the TiO2 phase increases from 10 to 40 nm when the TiO2 content is 5-30 wt%, respectively. (C) 2003 Elsevier Science Ltd. All rights reserved.
Effects of titania content and plasma treatment on the interfacial adhesion mechanism of nano titania-hybridized polyimide and copper system
(2004-06-03)
Chiang, PC
;
Whang, WT
;
Wu, SC
;
Chuang, KR
;
材料科學與工程學系
Nano-titania (TiO2) incorporated into polyimide (PI) matrix can significantly enhance the adhesion strength for PI/TiO2 hybrid film and copper system. Surface modifications by various plasma treatments (Ar, Ar/N-2 and Ar/O-2) were also applied in this study to improve the adhesion strength. The Ar/N2 plasma treatment is regarded as the more effective way in promoting the adhesion strength. The maximum adhesion value of 9.53 N/cm was obtained for the PI/TiO2-1 wt% hybrid film with Ar/N-2 plasma treatment. It is enhanced about 10 times as large as pristine PI. Furthermore, by Ar/O-2 plasma treatment, a weak boundary of copper oxide was formed at the interlayer between PI/TiO2 hybrid film and copper which decreases the adhesion strength. The effects of plasma treatment and content of nanosized TiO2 on the adhesion strength between PI/TiO2 hybrid film and copper system were studied. Atomic force microscope and contact angle analyses were used to measure the changes in surface morphology and surface energy as a result of plasma treatment. Besides, the interfacial states of peeled-off polymer side and copper side were investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Based on the result of XPS spectra, the peeled-off failure mode between PI/TiO2 hybrid film and copper was proposed in this study. (C) 2004 Elsevier Ltd. All rights reserved.
Synthesis and characteristics of polyimide/siloxane hybrid films for reliability adhesion
(2006-02-24)
Tsai, MH
;
Chiang, PC
;
Whang, WT
;
Ko, CJ
;
Huang, SL
Polyimide/siloxane (PISi) hybrid films from 2,2'-bis[4-(3-aminodiphenoxy)phenyl]sulfone (in-BAPS), 3,3'-oxydiphthatic anhydride (ODPA) and p-aminopropyltrimethoxysilane (APrTS) have been successfully fabricated by an in-situ sol-gel process. The APrTS is used to introduce siloxane structure and to be the end-capped agent to control the polymer block chain length in the range of 5000-20000 g/mol. The network structure of the PISi hybrid film is formed through the hydrolysis and condensation reactions. The PISi hybrid films with various polyimide block chain lengths are characterized with regard to the structure effect, mechanical properties, adhesion strength, adhesive melting flow and thermal stability. The result indicates that the more APrTS is contained, the shorter of the polyimide block chain length is formed and thus the lower inherent viscosity of APrTS-PAA is obtained. It is also suggested that the cross-linked density of the PISi hybrid film increases with the increase in the amount of APrTS. The network structure of the hybrid film reinforces the pure PI and makes the coefficient of thermal expansion (CTE) as well as adhesive melting flow decrease. Based on the dynamic mechanical analyses (DMA), the hybrid film with higher cross-linked density possesses superior mechanical property at elevated temperature. In addition, the introduction of APrTS causes an increase in thermal stability due to the network structure of hybrid film and the filler effect of the siloxane. (c) 2005 Elsevier B.V. All rights reserved.
The generation of biaxial optical anisotropies in polyimide films by an uniaxial stretch method
(2006-05-01)
King, JS
;
Whang, WT
;
Lee, WC
;
Chang, LM
;
材料科學與工程學系
A new biaxial-retardation film prepared from the uniaxial-stretched polyimide (PI) film was developed for compensating the viewing angle of liquid-crystal displays. A new aliphatic PI showing high transparence and low glass-transition temperature was firstly prepared for the biaxial-retardation film purpose. Both retardations in x-y and x-z planes of PI films were highly increased after stretching them uniaxially at 260 degrees C. Good uniformity of birefringence in well-stretched PI films was observed visually with two crossed polarizers. The birefringence variations of nx-ny (difference of refractive indexes between x- and y-axes) and nx-nZ during the stretching process were highly affected by PI structure.

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