Browsing by Author "Jiang, Meng-Dan"

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DOPANT EFFECTS OF PHOTOREACTIVE ZnO NANOPARTICLES ON FAST RESPONSE LC MATERIALS IN OPTICAL COMPENSATED BEND (OCB) MODE LIQUID CRYSTAL DISPLAYS
(2010-11-01)
Lin, Hong-Cheu
;
Jiang, Meng-Dan
;
Wang, Ling-Yung
;
Chen, Wei-Hong
;
Chen, Szu-Fen
Photoreactive ZnO nanoparticles containing surface-modified acrylate groups were synthesized and applied to improve the threshold voltage in optical compensated bend (OCB) mode liquid crystal display (LCD) cells. The dopant effects of ZnO nanoparticles with or without commercial reactive monomer additives (1 wt% doping ratio) on the values of threshold voltage (V-th) and response time in OCB cells were explored by applying different voltages to photo-reactive ZnO nanoparticles during UV curing processes in OCB cells to compare the influences of doped ZnO nanoparticles. As a result, we successfully eliminated or reduced the splay state of OCB mode and thus reduced threshold voltage. However, lower transmissions and higher values of the response time were observed in OCB cells doped with photoreactive ZnO nanoparticles, and the decreasing of V-th, is independent of various doping materials. Moreover, lower transmission and high response time could be improved through sequential voltage-applied procedures, i.e., bend black mode (10 V) -> bend white mode (2.5 V), under the immobile minimum threshold voltage at the bent state during UV curing processes to achieve lower pre-transition and fast response time properties by only doping photoreactive ZnO nanoparticles.
DOPANT EFFECTS OF PHOTOREACTIVE ZnO NANOPARTICLES ON FAST RESPONSE LC MATERIALS IN OPTICAL COMPENSATED BEND (OCB) MODE LIQUID CRYSTAL DISPLAYS
(2010-11-01)
Lin, Hong-Cheu
;
Jiang, Meng-Dan
;
Wang, Ling-Yung
;
Chen, Wei-Hong
;
Chen, Szu-Fen
Photoreactive ZnO nanoparticles containing surface-modified acrylate groups were synthesized and applied to improve the threshold voltage in optical compensated bend (OCB) mode liquid crystal display (LCD) cells. The dopant effects of ZnO nanoparticles with or without commercial reactive monomer additives (1 wt% doping ratio) on the values of threshold voltage (V(th)) and response time in OCB cells were explored by applying different voltages to photo-reactive ZnO nanoparticles during UV curing processes in OCB cells to compare the influences of doped ZnO nanoparticles. As a result, we successfully eliminated or reduced the splay state of OCB mode and thus reduced threshold voltage. However, lower transmissions and higher values of the response time were observed in OCB cells doped with photoreactive ZnO nanoparticles, and the decreasing of V(th), is independent of various doping materials. Moreover, lower transmission and high response time could be improved through sequential voltage-applied procedures, i.e., bend black mode (10 V) -> bend white mode (2.5 V), under the immobile minimum threshold voltage at the bent state during UV curing processes to achieve lower pre-transition and fast response time properties by only doping photoreactive ZnO nanoparticles.
Improvement of fast responsive LC materials by bent-core dopants in optical compensated bend mode liquid crystal displays
(2011-03-01)
Lin, Hong-Cheu
;
Wang, Ling-Yung
;
Jiang, Meng-Dan
;
Tsai, Shin-Yi
;
Chen, Szu-Fen Fenny
Stabilization of bend configuration in optical compensated bend (OCB) mode cells by doping bent-core molecules was developed in this study. The values of response time (t) and threshold voltage (V(th)) in OCB cells were dependent not only on the concentration but also on the shape, dipole direction, and flexible chain length of the doping molecules. Experimental results showed that the total response time (t(total)) and threshold voltage (V(th)) of OCB cells could be reduced by doping bent-core molecules, and smaller t values produced by reducing flexible chain lengths. In addition, attaining smaller V(th) values could be achieved by reducing polarization of bent-core molecules. In general, higher concentrations of dopants normally induced shorter field-on response time (t(on)) and a minimum field-off response time (t(off)) occurred at 0.5% of doping concentration, where the fastest total response time (t(total)) values were achieved.
Optimizing hole-injection in organic electroluminescent devices by modifying CuPc/NPB interface
(2011-09-01)
Jiang, Meng-Dan
;
Lee, Pei-Yu
;
Chiu, Tien-Lung
;
Lin, Hong-Cheu
;
Lee, Jiun-Haw
This investigation discusses the performance of an organic light-emitting device (OLED) with ultraviolet (UV) illuminated and remote pulsed Ar plasma (RPAP), treated copper phthalcyanine (CuPc) thin film on an indium tin oxide anode as the hole-blocking layer. UV treatment increased the driving voltage, the current efficiency decreased at the same time due to the poor sticking probability of NPB on the CuPc surface. By contrast, the driving voltage reduction and current efficiency enhancement were achieved at the same time for the OLED with the RPAP treated CuPc. Besides this, in such device, the thickness of CuPc affects seldom the current density-voltage-luminance characteristics. The surface characteristics of these processed CuPc thin films were investigated by using atomic force microscope, contact angle and X-ray photoelectron spectroscopy measurements, which showed the CuPc/, N,N'-bis-(1-naphthyl)-N,N'-dipheny1-1,1'-bipheny1-4,4'-diamine (NPB) interface was crucial to not only the interface energy barrier, but also the following NPB growth, mode. (C) 2011 Elsevier B.V. All rights reserved.
Self-Assembly of H-Bonded Side-Chain and Cross-Linking Copolymers Containing Diblock-Copolymeric Donors and Single/Double H-Bonded Light-Emitting Acceptors
(2009-09-15)
Lin, Hong-Cheu
;
Jiang, Meng-Dan
;
Wu, Shen-Chang
;
Jou, Leng-Long
;
Chou, Kai-Pin
A series of diblock-copolymers were synthesized through anionic polymerization of styrene and tert-butyl methacrylate (tBuA) with different monomer ratios, and analogous block-copolymeric derivatives (PS-b-PAA)s with monofunctional carboxylic acid groups were obtained by further hydrolyzation as hydrogen-bonded (H-bonded) proton donors. Via H-bonded interaction, these diblock-coplymeric donors (PS-b-PAA)s were incorporated with luminescent mono-pyridyl/bis-pyridyl acceptors to form single/double H-bonded supramolecules, that is, H-bonded side-chain/cross-linking copolymers, respectively. The supramolecular architectures formed by donor polymers and light-emitting acceptors were influenced by the ratio of acid blocks in the diblock copolymeric donors and the type of single/double H-bonded light-emitting acceptors. Their thermal and luminescent properties can be adjusted by H-bonds, and more than 100 nm of red-shifted photoluminescence (PL) emissions were observed, which depend on the degrees of the H-bonding interactions. Self-assembled phenomena of amphiphilic dibolck copolymers and their H-bonded complexes were confirmed by TEM micrographs, and supramolecular microphase separation of spherical micelle-like morphology was demonstrated to affect the photophysical properties. Polymer light-emitting diode (PLED) devices containing H-bonded complexes showed electroluminescence (EL) emissions of 503-560 nm under turn-on voltages of 7.5-9.0 V, maximum power efficiencies of 0.23-0.37 cd/A (at 100 mA/cm(2)), and maximum luminances of 318-519 cd/m(2) (around 25 V). (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4685-4702, 2009
THE INFLUENCE OF PROCESS PARAMETERS ON THE STRUCTURE AND MORPHOLOGY OF PULSED PLASMA-POLYMERIZED OCTAFLUOROTOLUENE FILMS
(2010-11-01)
Jiang, Meng-Dan
;
Wang, Ling-Yung
;
Lin, Hong-Cheu
;
Wei, Ta-Chin
;
Yang, Shih-Hsien
This work describes amorphous fluorinated polymer films deposited by pulsed plasma polymerizations of octafluorotoluene (PPP-OFT) monomers on ITO glass as the hole-injection layer of organic electroluminescent (EL) devices, in order to study the influence of sample position and duty cycle on PPP-OFT film characteristics, and also to find a good process to yield a higher retention degree of monomers and lower roughness of PPP-OFT fluorocarbon films. Experimental results revealed that PPP-OFT films deposited at positions far away from the RF coil and close to the monomer inlet showed less roughness than films deposited near the high RF-flux regions. In addition, the retention of the monomers in the PPP-OFT layer will be high if the deposition is conducted near the monomer inlet but some distance away from the RF electrode. Moreover, amorphous fluorinated polymer films can be deposited with higher fluorine to carbon (F/C) ratios and CF(2) contents at proper substrate positions by means of different sticking coefficients of free radicals dissociated by octafluorotoluene monomers.
Voltage Reduction and Lifetime Elongation of Organic Light-Emitting Diodes Using Photopolymerization for Fluorizated Polyxylylene Hole Injection Layer
(2012-03-01)
Jiang, Meng-Dan
;
Chiu, Tien-Lung
;
Lee, Pei-Yu
;
Yang, Shun-Po
;
Lin, Hong-Cheu
This study describes a novel method for manufacturing a hole injection layer of an organic light-emitting diode (OLED), comprising an ultraviolet (UV) reactive Br-fluorocarbon precursor (Br-CF2-C6F4-CF2-Br). The proposed method can be used to form a fluorizated polyxylylene film, demonstrating high repeatability on the anode as the hole injection layer of organic electroluminescent devices to enhance the hole injection, reduce the operating voltage of 1.2 V, and extend the operational lifetime by more than 150 times under a high current density of 125 mA/cm(2). Using a spin-coating process, the remaining precursor can be recycled to prevent wasting materials. UV curing without the solvent-removing process shortens manufacturing time. Hence, fabricating a high performance OLED using a simple, low-cost process is the aim of this study. (C) 2012 The Japan Society of Applied Physics