Browsing by Author "Jeng, Shie-Chang"

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A polarizer-free flexible and reflective electrooptical switch using dye-doped liquid crystal gels
(2008-02-04)
Lin, Yi-Hsin
;
Yang, Jhih-Ming
;
Lin, Yan-Rung
;
Jeng, Shie-Chang
;
Liao, Chi-Chang
A polarizer-free flexible and reflective electro-optical switch using dye-doped liquid crystal (LC) gels is demonstrated. The electro-optical performances of both scattering and absorption based dye-doped LC gels depend on curing temperatures due to domain sizes of polymer networks. Such flexible electro-optical switch is bendable and trim-able because of the vertical polymer networks and gel-like materials. The dye-doped LC gel shows good reflectance similar to 55%, good contrast ratio similar to 450: 1 and fast response similar to 6.4ms at curing temperature 10 degrees C. The bending curvature is 21 mm. The dye-doped LC gels open a new window for trim-able electronic papers, decorative displays, electrically switchable curtains, and electrically switchable sun control film for the automobiles, homes or commercial buildings.
A Polarizes-free Flexible Display Using Dye-doped Liquid Crystal Gels
(2008)
Lin, Yi-Hsin
;
Yang, Chih-Ming
;
Lin, Yan-Rung
;
Jeng, Shie-Chang
;
Liao, Chi-Chang
A reflective type polarizes-free flexible displays using a dye-doped liquid crystal (LC) is demonstrated due to combining both scattering and absorption. A polarizer-free multi-switch using gradient dye-doped LC gels is also demonstrated. Such a gel-like flexible displav is bendable and trimable. The potential applications are e-papers and decorative displays.
Annealed zinc oxide films for controlling the alignment of liquid crystals
(2017-08-01)
Hu, Jia-Wei
;
Yang, Sheng-Hsiung
;
Jeng, Shie-Chang
;
光電系統研究所
;
照明與能源光電研究所
It is observed that the anchoring of LC molecules aligned on the ZnO film depends on the surface wettability. We demonstrate that the surface wettability of ZnO films fabricated by sol-gel process can be modified by annealing. The observations using the scanning electron microscope, photoluminescence and X-ray photoelectron spectroscopy for ZnO films have shown that the annealing can modify both the morphologies and chemical compositions of ZnO films, which in turn produces influences on the surface wettability. The surface wettability of as-prepared ZnO film can be controlled from 102 degrees to 60 degrees (contact angle (CA) of water) as the annealing temperature increases from 190 to 250 degrees C. Our experimental results show that the pretilt angles of LCs on ZnO films can be modified over a wide range from 89.5 degrees to 0.5 degrees as the CA of water on the ZnO films changes from 102 degrees to 60 degrees.
Applications of Tamm plasmon-liquid crystal devices
(1970-01-01)
Jeng, Shie-Chang
;
影像與生醫光電研究所
;
Institute of Imaging and Biomedical Photonics
The Tamm-plasmon-polariton (TPP) occurs at the interface between a metallic film and the photonic-crystal (PC) substrate. Unlike conventional surface-plasmon-polariton (SPP), TPP can be directly excited by both the transverse electric (TE) and transverse magnetic (TM) electromagnetic waves without using additional coupling optics. The fact that the optical functionality of most plasmonics devices is determined after fabrication limits their applications. Tunable SPP devices by applying liquid crystals (LCs) have been widely demonstrated due to their large birefringence and easy controllability via external stimuli. However, actively tuning TPP is difficult because the localised electric field is between the metallic film and PC substrate, the change of refractive index above the metallic film has only small influences on TPP. This article is intended to briefly review recent progress towards using LCs for actively tuning TPP devices. Not only TPP devices can gain benefits from LCs, we will also discuss the applications of TPP for measuring the anisotropy of the alignment films of LC devices. The sensitivity of the proposed scheme will be discussed.
Applications of Tamm plasmon-liquid crystal devices
(2020-06-20)
Jeng, Shie-Chang
;
影像與生醫光電研究所
;
Institute of Imaging and Biomedical Photonics
The Tamm-plasmon-polariton (TPP) occurs at the interface between a metallic film and the photonic-crystal (PC) substrate. Unlike conventional surface-plasmon-polariton (SPP), TPP can be directly excited by both the transverse electric (TE) and transverse magnetic (TM) electromagnetic waves without using additional coupling optics. The fact that the optical functionality of most plasmonics devices is determined after fabrication limits their applications. Tunable SPP devices by applying liquid crystals (LCs) have been widely demonstrated due to their large birefringence and easy controllability via external stimuli. However, actively tuning TPP is difficult because the localised electric field is between the metallic film and PC substrate, the change of refractive index above the metallic film has only small influences on TPP. This article is intended to briefly review recent progress towards using LCs for actively tuning TPP devices. Not only TPP devices can gain benefits from LCs, we will also discuss the applications of TPP for measuring the anisotropy of the alignment films of LC devices. The sensitivity of the proposed scheme will be discussed.
Bistable liquid crystal devices with nanoparticle-coated polyimide alignment films
(2013-04-01)
Lee, Chuan-En
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Jeng, Shie-Chang
;
影像與生醫光電研究所
;
Institute of Imaging and Biomedical Photonics
Bistable hybrid-aligned nematic (HAN) liquid crystal devices (LCDs) with silica nanoparticle-coated polyimide alignment films were investigated. It was observed that the existence of the internal electric field produced from the triboelectrically charged silica nanoparticles layer and impurity ions in the LC reduced the total free energy of the HAN-LCD and stabilized the cell in the homeotropic state. The stable homeotropic state can be switched back to the HAN state by changing the ion distribution through a voltage pulse with proper polarity. The capability of controlling bistability through modification of ion density in the LC layer may have some applications, such as displaying a one-time password requiring a specific stable time. (C) 2013 Optical Society of America
Broadband cholesteric liquid crystal devices with poly(N-vinyl carbazole) microstructures
(2015-01-02)
Hu, Jia-Wei
;
Chen, Tai-An
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Jeng, Shie-Chang
;
光電系統研究所
;
影像與生醫光電研究所
The particular thermally induced phase separation (TIPS) method was developed by using poly(N-vinyl carbazole) (PVK) dissolved in liquid crystal (LC) layer recently. Permanent scattering is produced via the particular TIPS due to the formation of poly-domain LCs. In this work, we applied the particular TIPS to a conventional cholesteric LC (CLC) device. A broadband CLC device with a poly-domain structure was demonstrated by using the particular TIPS of CLC and PVK. The CLC device fabricated by two indium tin oxide glass substrates coated with PVK films generated the rough PVK layers and microstructures when the device was cooled from a temperature higher than the clear point of CLCs. The produced poly-domain planar texture of CLCs still preserved the bistability. A high cooling rate and PVK concentration both increased the reflection bandwidth of the CLC devices.
Cholesteric liquid crystal devices with nanoparticle aggregation
(2010-10-11)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Hung, Yu-Hsiang
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
A broadband cholesteric liquid crystal (CLC) device with a multi-domain structure is demonstrated by using an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the CLC layer. The aggregation pattern of the self-assembled POSS nanoparticles depends on the concentration of POSS doped in the mixture of POSS/CLC and the cooling rate of the mixture from a temperature higher than the clear point. POSS-induced changes in the bulk and surface properties of the cholesteric cells, such as a promotion of homeotropic alignment, help to form a cholesteric structure with a broadband reflection of light; the latter can be used for improvement of bistable CLC devices. A higher POSS concentration and a higher cooling rate both improve the appearance of the black-white CLC device. (C) 2010 Optical Society of America
Cholesteric liquid crystal devices with nanoparticle aggregation
(2010-10-11)
Jeng, Shie-Chang
;
Hwang, Shug-June
;
Hung, Yu-Hsiang
;
Chen, Sheng-Chieh
;
影像與生醫光電研究所
A broadband cholesteric liquid crystal (CLC) device with a multi-domain structure is demonstrated by using an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the CLC layer. The aggregation pattern of the self-assembled POSS nanoparticles depends on the concentration of POSS doped in the mixture of POSS/CLC and the cooling rate of the mixture from a temperature higher than the clear point. POSS-induced changes in the bulk and surface properties of the cholesteric cells, such as a promotion of homeotropic alignment, help to form a cholesteric structure with a broadband reflection of light; the latter can be used for improvement of bistable CLC devices. A higher POSS concentration and a higher cooling rate both improve the appearance of the black-white CLC device. (C) 2010 Optical Society of America
Controlling the alignment of liquid crystals by nanoparticle-doped and UV-treated polyimide alignment films
(2012)
Jeng, Shie-Chang
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Hwang, Su-June
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Chen, Tai-An
;
Liu, Han-Shiang
;
Chen, Mu-Zhe
We have developed two approaches for controlling the pretilt angles of liquid crystal molecules by using conventional polyimide (PI) alignment materials either doping homogeneous PIs with Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticles or treating homeotropic PIs with ultraviolet light. These techniques are very simple and are compatible with current methods familiar in the LCD industry. The characteristics of modified PI alignment films and their applications for photonic devices are demonstrated in this paper.
Effects of ambient illuminance and electronic displays on users' visual performance for young and elderly users
(2010-09-01)
Wang, An-Hsiang
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Hwang, Su-Lun
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Kuo, Hui-Tzu
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Jeng, Shie-Chang
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影像與生醫光電研究所
This study investigated the effects of age (young participants aged 20-30 and elderly participants older than 60), ambient illuminance (50, 500, 1500, 3000, 6000, and 9000 lx) on participants' visual performance when using various electronic displays (conventional transmissive LCD, Ch-LC display, and E-ink display). Overall, the results indicated that participants' visual performance showed significant difference among various ambient illuminance conditions, electronic displays, and between two groups of participants. Significantly different visual performance was observed between young and elderly participants. The interaction among ambient illuminance, type of electronic display, and age had a significant effect on participants' visual performance. When participants used the E-ink display, both young and elderly participants had significantly worse visual performance under an ambient illuminance of 50 lx compared to other illuminance settings. When participants used the Ch-LC display, young participants had significantly worse visual performance under an ambient illuminance of 50 lx compared to other illuminance settings, but elderly participants had significantly better visual performance under an ambient illuminance higher than 1500 lx. When young participants used a conventional transmissive LCD, the ambient illuminance had no significant effect on their visual performance. When elderly participants use a conventional transmissive LCD, an illuminance of 50 and 6000 lx seem to have a detrimental effect on their visual performance.
Electrically switchable liquid crystal Fresnel lens using UV-modified alignment film
(2010-12-06)
Jeng, Shie-Chang
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Hwang, Shug-June
;
Horng, Jing-Shyang
;
Lin, Kuo-Ren
;
影像與生醫光電研究所
A simple method to make a switchable liquid crystal (LC) Fresnel lens with high diffraction efficiency and a low driving voltage was proposed based on the photo-induced surface modification of the vertical alignment layer. UV illumination alters the pretilt angle of alignment layers, a Fresnel zone-distribution hybrid alignment in the homeotropic LC cell can be straightforwardly achieved through UV exposure, yielding a concentric structure of the Fresnel phase LC lens. A remarkable diffraction efficiency of similar to 31.4%, close to the measured diffraction efficiency of the used Fresnel-zone-plate mask of 32%, was detected using a linearly polarized incident beam. (C)2010 Optical Society of America
Flexible and reflective polarizer-free liquid crystal displays using dye-doped liquid crystal gels
(2008)
Lin, Yi-Hsin
;
Yang, Jhih-Ming
;
Jeng, Shie-Chang
;
Lin, Yan-Rung
;
Liao, Chi-Chang
A flexible and reflective polarizer-free display using dye-doped liquid crystal (LC) gels is demonstrated. The electro-optical performances of both scattering and absorption based dye-doped LC gels depend on curing temperatures. The dye-doped LC gel shows good reflectance similar to 55%, good contrast ratio similar to 450:1 and fast response similar to 6.5ms at curing temperature 10 degrees C when UV curing intensity is 2.6 mW/cm(2). The EO performance depends on the curing temperature. The hysteresis is independent of sampling time duration. The bending curvature is 21 mm. The response of dye-doped LC gels is faster under bending due to the bending-induced sheared force of polymer networks. The dye-doped LC gels open a new window for trimable electronic papers, decorative displays and switchable curtains.
Flexible and reflective polarizer-free liquid crystal displays using dye-doped liquid crystal gels - art. no. 691108
(2008-01-01)
Lin, Yi-Hsin
;
Yang, Jhih-Ming
;
Jeng, Shie-Chang
;
Lin, Yan-Rung
;
Liao, Chi-Chang
A flexible and reflective polarizer-free display using dye-doped liquid crystal (LC) gels is demonstrated. The electro-optical performances of both scattering and absorption based dye-doped LC gels depend on curing temperatures. The dye-doped LC gel shows good reflectance similar to 55%, good contrast ratio similar to 450:1 and fast response similar to 6.5ms at curing temperature 10 degrees C when UV curing intensity is 2.6 mW/cm(2). The EO performance depends on the curing temperature. The hysteresis is independent of sampling time duration. The bending curvature is 21 mm. The response of dye-doped LC gels is faster under bending due to the bending-induced sheared force of polymer networks. The dye-doped LC gels open a new window for trimable electronic papers, decorative displays and switchable curtains.
Flexible Homeotropic Liquid Crystal Displays Using Low-Glass-Transition-Temperature Poly(ethylene terephthalate) Substrates
(2010)
Teng, Wen-Yu
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Jeng, Shie-Chang
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Ding, Jau-Min
;
Kuo, Chia-Wei
;
Chin, Wei-Kuo
This research is aimed at fabricating flexible homeotropic liquid crystal displays (LCDs) using low-glass-transition-temperature poly(ethylene terephthalate) (PET) substrates. The low-temperature technique of nanoparticle-induced vertical alignment (NIVA) was successfully applied to the flexible homeotropic PET-LCD. The PET film generally exhibits birefringence, which greatly interferes with the phase retardation of light propagation in the LCD. This problem can be alleviated by adjusting the optical axis with respect to the axis of the polarizer. The resulting flexible PET-LCD exhibited a low threshold voltage of 2.1 V and a transmittance of 53% at 3.2 V in the flat state. (C) 2010 The Japan Society of Applied Physics
Growth of ZnO Nanorods and Their Applications for Liquid Crystal Devices
(2018-04-01)
Chen, Mu-Zhe
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Yang, Sheng-Hsiung
;
Jeng, Shie-Chang
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光電系統研究所
;
照明與能源光電研究所
Different morphologies of ZnO nanorods were synthesized by using the two-step hydrothermal method, and they were applied to liquid crystal (LC) alignment films. The morphology of the ZnO nanorods, including length, diameter, and density, were controlled by the growth time, which ranged from 16 to 26 min. The morphology and the chemical features both contributed to the surface wettability of the ZnO nanorods. The LC pretilt angle on the ZnO nanorods was successfully controlled from homeotropic (similar to 89.0 degrees) to homogeneous (similar to 1.7 degrees) alignments, as the contact angle of water on ZnO nanorods was changed from 93 to 28 with the growth time. The analysis of Xray diffraction and X-ray photoelectron spectroscopy showed that the crystallite size of ZnO nanorods increased with the growth time, while the oxygen vacancy decreased. The ZnO nanorods grown on the ITO glass substrate also improve the transmission of LCDs due to the antireflection effect.
Liquid crystal alignment by polyhedral oligomeric silsesquioxane (POSS)-polyimide nanocomposites
(2013-05-01)
Liu, Han-Shiang
;
Jeng, Shie-Chang
;
光電系統研究所
;
影像與生醫光電研究所
;
Institute of Photonic System
Polyimide (PI) films are widely used in the liquid crystal display (LCD) industry to align liquid crystal (LC) molecules in a specific orientation with a pretilt angle 0(p) on the PI alignment films. It was observed that physical dispersion of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in commercial homogenous PIs decreases the surface energy of the PI alignment films and generates a controllable 0(p) in the range 0 degrees < 0(p) < 90 degrees, which is not easily achieved by complicate PI synthesis. Characteristics of POSS-PI nanocomposites were studied to investigate the influence of FOSS nanoparticles on PIs. Increased absorption in the infrared spectra and decreased decomposition temperature and glass transition temperature with POSS doped concentration in PI were observed due to the increase in free volume of POSS-PI nanocomposites. Such nanoscale hybridization suggests a novel approach to tune the properties of PIs through modification of molecular interaction. A fast response no-bias optically-compensated bend (OCB) LCD with a pretilt angle of 68 degrees was also demonstrated in this work. (C) 2013 Elsevier B.V. All rights reserved.
Liquid crystal alignment on zinc oxide nanowire arrays for LCDs applications
(2013-12-02)
Chen, Mu-Zhe
;
Chen, Wei-Sheng
;
Jeng, Shie-Chang
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Yang, Sheng-Hsiung
;
Chung, Yueh-Feng
The zinc oxide (ZnO) nanowire arrays on the indium tin oxide (ITO) glass substrates were fabricated by using the two-step hydrothermal method. A high transmittance similar to 92% of ZnO nanowire arrays on ITO substrate in the visible region was obtained. It was observed that the liquid crystal (LC) directors were aligned vertically to the (ZnO) nanowire arrays. The properties of ZnO nanowire arrays as vertical liquid crystal (LC) alignment layers and their applications for hybrid-aligned nematic LC modes were investigated in this work. (C)2013 Optical Society of America
Liquid crystal alignment on ZnO nanostructure films
(2016-01-01)
Chung, Yueh-Feng
;
Chen, Mu-Zhe
;
Yang, Sheng-Hsiung
;
Jeng, Shie-Chang
;
光電系統研究所
The study of liquid crystal (LC) alignment is important for fundamental researches and industrial applications. The tunable pretilt angles of liquid crystal (LC) molecules aligned on the inorganic zinc oxide (ZnO) nanostructure films with controllable surface wettability are demonstrated in this work. The ZnO nanostructure films are deposited on the ITO-glass substrates by the two-steps hydrothermal process, and their wettability can be modified by annealing. Our experimental results show that the pretilt angles of LCs on ZnO nanostructure films can be successfully adjusted over a wide range from similar to 90 degrees to similar to 0 degrees as the surface energy on the ZnO nanostructure films changes from similar to 30 to similar to 70 mJ/m. Finally, we have applied this technique to fabricate a no-bias optically-compensated bend (OCB) LCD with ZnO nanostructure films annealed at 235 degrees C.
Liquid-Crystal Active Tamm-Plasmon Devices
(2018-06-20)
Cheng, Hao-Chi
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Kuo, Ching-Yung
;
Hung, Yu-Ju
;
Chen, Kuo-Ping
;
Jeng, Shie-Chang
We demonstrate a liquid-crystal (LC)-tuned Tamm-plasmon (TP) resonance device. The term TP polariton refers to plasmonic resonance at the interface between a photonic crystal (PC) and a metallic film. We formulate a precise optical analysis of the proposed device using the transfer-matrix method. A single resonance dip in the photonic band-gap region guarantees that the thickness of the LC layer between the PC and the metallic film can be as small as about 180 nm. Tuning phase retardation in the LC layer is shown to shift the resonance wavelength tens of nanometers, depending on the birefringence and width of the LC layer. Simulation results are in good agreement with the experimental data.