Browsing by Author "Lin, Chi-Wen"

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Defect-free half-V-mode ferroelectric liquid-crystal device
(2010-11-01)
Lin, Chi-Wen
;
Chen, Huang-Ming Philip
;
光電工程學系
;
Department of Photonics
The horizontal chevron defect found in a half-V-mode ferroelectric-liquid-crystal (HV-FLC) device can be suppressed by lowering the FLC's total free energy. The energy levels between spontaneous polarization (P(S)) up and down domains were degenerated by asymmetrical-alignment treatments. The difference in the polar surface coefficient (gamma(2)) was the key to suppressing the alignment defect. Alignment layers with opposite surface polarities and different anchoring energies were applied to control the sign and value of gamma(2). The asymmetric cells of PI(rub) - PI(plasma) (rubbed polyimide and plasma-treated polyimide surfaces), PVA(rub) - PI(plasma) (rubbed polyvinyl alcohol and plasma-treated polyimide surfaces), and PVA(rub) - PI(rub) (both rubbed PI and PVA) alignment conditions presented defect-free alignment textures under a slow-cooling process. Among these different alignment treatments, the PVA(rub) - PI(rub) treated cell demonstrated the best alignment result, benefited by the largest difference in polar surface coefficient.
Defect-free half-V-mode ferroelectric liquid-crystal device
(2010-11-01)
Lin, Chi-Wen
;
Chen, Huang-Ming Philip
;
顯示科技研究所
;
Institute of Display
The horizontal chevron defect found in a half-V-mode ferroelectric-liquid-crystal (HV-FLC) device can be suppressed by lowering the FLC's total free energy. The energy levels between spontaneous polarization (P-S) up and down domains were degenerated by asymmetrical-alignment treatments. The difference in the polar surface coefficient (gamma(2)) was the key to suppressing the alignment defect. Alignment layers with opposite surface polarities and different anchoring energies were applied to control the sign and value of gamma(2). The asymmetric cells of PIrub - PIplasma (rubbed polyimide and plasma-treated polyimide surfaces), PVA(rub) - PIplasma (rubbed polyvinyl alcohol and plasma-treated polyimide surfaces), and PVA(rub) - PIrub (both rubbed PI and PVA) alignment conditions presented defect-free alignment textures under a slow-cooling process. Among these different alignment treatments, the PVA(rub) - PIrub treated cell demonstrated the best alignment result, benefited by the largest difference in polar surface coefficient.
Ferroelectric LC Binary Phase Grating Based on Striped Electrodes
(2011)
Lin, Chi-Wen
;
Chen, Huang-Ming Philip
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
Using the asymmetric alignment technique, based on double-side striped electrodes, the electrically tunable ferroelectric LC grating, approaching calculated diffraction efficiency is demonstrated. The width of thin striped electrodes is designed smaller than half of the grating pitch to compensate for the fringe field effect and thus improve the diffraction efficiency.
Free alignment defect, low driving voltage of half-V ferroelectric liquid crystal device
(2009-08-24)
Chen, Huang-Ming P.
;
Lin, Chi-Wen
;
光電工程學系
;
顯示科技研究所
;
Department of Photonics
The horizontal chevron alignment defect in half-V mode ferroelectric liquid crystal (FLC) cell can be reduced by asymmetrical alignment hybrid cell. The low free energy level generated from the interaction between spontaneous polarization and opposite polar alignment surfaces was found. As a result, uniformly aligned FLC cell can be achieved without applied external voltage. The R3206 FLC material is applied as model compound. The contrast ratio of R3206-70 is greatly enhanced from 76 to 780 with 1.0 ms response time under 5 V.
Low driving voltage with clean aligned ferroelectric liquid crystal devices
(2007)
Lin, Chi-Wen
;
Li, Kun-Zhan
;
Yang, Chin-Wei
;
Chen, Huang-Ming Philip
;
顯示科技研究所
Low driving voltage FLC material, R3206 with Vsat. at 3.5V (AZ Electronic Materials), and its mixtures were under evaluation for potential TFT display application. Poor alignment issue was overcome by the diluted pitch mixtures and asymmetric hybrid alignment cells. In the series of diluted pitch mixtures, the contrast and alignment are better than pure compound in pre-made cells (1.8 +/- 0.1 mu m, from EHC). In particular, the 70% R3206 mixture showed the best result with low driving voltage helow 5V and fast response time (T (on) + T (off)) under 1.1 ms. The hybrid alignment cell was successfully suppressed horizontal chevron defects and achieved the best contrast ratio of 750. These results provide promising FLC Materials with low driving voltage, well aligned, and fast switching for TFT-LCD application.
Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants
(2006-01-01)
Chen, Huang-Ming Philip
;
Tsai, Yun-Yen
;
Lin, Chi-Wen
;
Shieh, Han-Ping David
;
光電工程學系
A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 degrees C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 mu m pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.
Novel ferroelectric liquid crystals consisting glassy liquid crystal as chiral dopants - art. no. 63320G
(2006)
Chen, Huang-Ming Philip
;
Tsai, Yun-Yen
;
Lin, Chi-Wen
;
Shieh, Han-Ping David
;
光電工程學系
A series of ferroelectric liquid crystals consisting new glassy liquid crystals (GLCs) as chiral dopants were prepared and evaluated for their potentials in fast switching ability less than 1 ms. The properties of pure ferroelectric glassy liquid crystals (FGLCs) and mixtures were reported in this paper. In particular, the novel FGLC possessing wide chiral smectic C mesophase over 100 degrees C is able to suppress smectic A phase of host. The mixture containing 2.0 % GLC-1 performs greater alignment ability and higher contrast ratio than R2301 (Clariant, Japan) in a 2 mu m pre-made cell (EHC, Japan). These results indicate that novel FLC mixtures consisting glassy liquid crystals present a promising liquid crystal materials for fast switching field sequential color displays.
Polarization-independent filters for luminescent solar concentrators
(2011-01-10)
de Boer, Dick K. G.
;
Lin, Chi-Wen
;
Giesbers, Merijn P.
;
Cornelissen, Hugo J.
;
Debije, Michael G.
The efficiency of luminescent solar concentrators could be enhanced by use of wavelength-selective filters, reducing the amount of luminescent light lost. To accomplish this, polarization-independent filters with reflectivity >97% were made by combining layers of cholesteric liquid crystals, either a right-with a left-handed layer, or two right-handed layers with a half-lambda waveplate. Normal cholesteric filters have a reflection bandwidth which is narrower than the spectral and angular range of the luminescent emission. The reflection band is broadened from 80 to 200 nm by employing a pitch gradient in the cholesteric layer. The measured transmission bands compare well with calculations. (C) 2011 American Institute of Physics. [doi:10.1063/1.3541543]
Surface Polarity Controlled Horizontal Chevron Defect Free Surface Stabilized Ferroelectric Liquid Crystal Devices
(2009)
Lin, Chi-Wen
;
Hsu, Chih-I
;
Chen, Huang-Ming Philip
;
光電工程學系
;
Department of Photonics
The asymmetrical surface polarity controlled hybrid alignment technique was proposed to suppress the alignment defects of half V-shaped switching FLC materials. When the material was cooled from N* to SmC*, two kinds of layer arrangements were formed with opposite spontaneous polarization directions (Ps). Alignment layers with opposite surface polarity direction were utilized in asymmetrical hybrid cells and produced uni-surface-polarity direction. FLC Ps was only controlled by this surface polarity; therefore, double domains were suppressed into mono-domain. A 2.4 '' prototype TFT-LCD was presented with defect free alignment texture. This alignment technique provided promising FLC material with well alignment and fast switching for TFT-LCD application.
Well Aligned Half-V Ferroelectric Liquid Crystal in Asymmetrical Surface Polarity Controlled Alignment Cells
(2010)
Chen, Huang-Ming Philip
;
Lin, Chi-Wen
;
光電工程學系
;
Department of Photonics
Ferroelectric liquid crystals (FLCs) were known to possess fast response time under 1 ms. The low contrast ratio yielding from defect alignment, however, limited their display application. Based on FLC elastic free energy, the asymmetrical surface polarity controlled alignment was able to suppress the horizontal chevron defects in a half V-shaped switching FLC cell. It is due to the FLC's spontaneous polarization (Ps) pointed to one direction inducing by the opposite surface polarity in asymmetrical hybrid cell. The experimental approach of different alignment materials and different strengths of surface anchoring energies were evaluated in this study. The highest contrast ratio of 780: 1 at saturation voltage under 5 V was obtained. The asymmetrical surface polarity controlled alignment technique provided a promising FLC well alignment and fast switching result for TFT-LCD application.