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1
Al-Zangana, Shakhawan. "Nano- and micro-particle doped liquid crystal phases." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/nano-and-microparticle-doped-liquid-crystal-phases(31dbb051-7d9c-4780-bda0-d58773846de0).html.
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This thesis presents the investigation of the liquid crystal (LC) - particle suspensions. Particles from nano- to micro-size, spherical to two-dimensional shapes, with different functionality are dispersed into nematic and smectic phases. The aim is to create ordered nanoparticle (NP) assemblies and thereby modify the common properties of the liquid crystal, such as dielectric anisotropy and electro-optical, revealing any interaction between particles and LC properties. It is found that for concentrations (>0.5vol%), the ferroelectric NPs have increased the sensitivity of the nematic liquid crystal to the electric field through electro-optical responses, which is seen by an enhancement in the dielectric anisotropy. This could be induced by the coupling of the electrical dipole moments in the spherical NPs with the LC director field. The electro-optical properties of the chiral smectic (SmC*) phase (tilt angle Θ, switching time τ_s and spontaneous polarisation P_s) are found to be independent of the concentration and sizes of the doped NPs. The relaxation frequency f_R of the Goldstone mode is faster in the ferroelectric NPs suspensions of 2.0vol% compared to the paraelectric NPs. In the graphene oxide (GO) - nematic LC (5CB) suspensions, the small GO sizes of mean size 560 nm are more easily dispersible than larger flakes of 2.8 micro metre mean size. As the GO concentration is increased, each of the threshold voltage and splay elastic constant dramatically increases, reaching saturation at ≈1.0wt%. The field driven switching-on time is practically not affected, while the purely elastically driven switching-off time is strongly sped-up. Interestingly, thermotropic and lyotropic LC phases are exhibited in the GO-5CB suspensions when heating the thermotropic liquid crystal into its isotropic phase. The isotropic phase of 5CB acts as a solvent for the GO particles, forming a lyotropic nematic phase with largely reduced birefringence. It is found that the nematic to isotropic phase transition is shifted toward higher temperature for the GO-5CB system compared to the BaTiO3-5CB system. Dispersions of different sizes of GO flakes are prepared in isotropic and nematic fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature range (25-60 ℃) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes were found to exhibit varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. The relaxation frequencies in the isotropic media were lower compared to the nematic medium. Relaxation frequencies (~10 kHz) are observed in the GO-isotropic media, which are reduced as the size of the GO flakes are decreased, are anticipated to be inherited from GO flakes. However, the fast relaxations (~100 kHz) that are observed in the nematic suspensions could imply strongly slowed down molecular relaxation modes of the nematogenic molecules. Finally, the phase diagram of lyotropic LC as a function of the lateral dimensions of the GO flakes, their concentration, geometrical confinement configuration and solvent polarity was investigated. Polarising optical microscopy was used to determine isotropic-biphasic-nematic phase evolution. The confinement volume and geometry of the sample relative to the GO size are shown to be vital to the observation of the lyotropic phase. GO LCs have the potential for a range of applications from display technologies to conductive fibres. The confinement related LC phase transition is critical toward their applications. It is also found that the stability of the LC phase is higher for the solvent of higher dielectric constant.
2
Gillespie, C. "Dye doped liquid crystal lasers." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599422.
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This thesis examines the emission properties of dye-doped liquid crystal lasers, which are of interest because they have the potential to provide compact, low threshold, tunable laser sources for applications ranging from medicine to displays. The primary aim is to provide the first detailed study of the interactions between liquid crystals (LCs) and laser dyes and to examine their effect upon the emission properties of dye-doped liquid crystal lasers. Five different dyes are examined and, in all cases, the LC host (a nematic mixture, E49) is shown to have a significant effect upon the properties of the dye, through a combination of general and specific solvent-solute interactions. Lasing is demonstrated from all five dyes in the chiral nematic (N*) mesophase. Conventional xanthene laser dyes, rhodamine 6G chloride and rhodamine B chloride, are shown to be unsuitable for N*LC lasers because their ionic nature and isotropic molecular shapes limit their solubility in LC materials. Emission is shown to occur preferentially at the long wavelength reflection band edge for small degrees of alignment of the dye in the LC host. Three elongated laser dyes (DCM, PM597 and PM580) are shown to be more compatible with E49. N*LC laser samples were made using dye concentrations in the range 0.5 wt% to 2.0 wt%. For each dye, slope efficiency (ηs) values were used to calculate relative quantum efficiency values, which decreased linearly as the concentration increased. ηs is shown to peak at a characteristic value corresponding to the balance between increasing absorbance and decreasing quantum efficiency with increasing dye concentration. The largest ηs demonstrated is 32%, which corresponds to 1.0 wt% PM597. The Eth of both PM597 and PM580 is shown to increase linearly with increasing concentration, whereas the Eth of DCM shows the opposite tendency. It is proposed that the different Eth trends indicate different quantum efficiency quenching mechanisms. Lasing was demonstrated from novel bimesogenic mixtures that showed wide temperature range blue phase I* (BP I*) mesophases. The preparation and properties of the BP I* samples are described. the nature of the laser emission is shown to depend upon the input energy used. For low inputs energies (<~ 3μJ/pulse), multimode lasing is demonstrated from the BP I* texture, whereas for high input energies (> ~ 3 μJ/pulse) random lasing is demonstrated from optically induced focal conic (N*) textures in the BP I* samples.
3
Wainwright, Stephen. "True liquid crystal templating of nanoparticle-doped mesoporous silica." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/1972/.
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Using true liquid crystal templating (TLCT), a one-pot method for preparing mesoporous silicas containing metal nanoparticles is available. The method leads to well-defined systems with possible applications is selective catalysis. Using this approach, a range of metal-doped variants of hexagonal silicas (general MCM-41 family) are prepared and show surface areas >1000 m2 g–1 and pore diameters of ca 30 Å. Specifically, palladium doped-MCM-41-like silicas are prepared and are shown to be active in the selective oxidation of crotyl alcohol and the activity of the system has been investigated as a function of both metal loading and the pore length – the latter affecting mass transport and therefore rate of conversion. Templating on Pluronic P123 leads to doped SBA-15-like materials, but in contrast to the findings with low-concentration templating as commonly reported, TLCT leads to materials with surface areas of about 400 m2 g–1, which is accounted for by the absence of micropores. Catalytic results from these SBA-15 materials will also be presented.
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Бордюг, Ганна Борисівна, and Аркадій Петрович Поліщук. "Fast photoconversion in viologen-doped lyotropic ionic liquid crystals." Thesis, Physikzentrum in Bad Honnef, 2017. http://er.nau.edu.ua/handle/NAU/32391.
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Coutino, Pedro. "Modeling and Characterization of Dye-Doped Guest-Host Liquid Crystal Eyewear." Kent State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=kent1449689683.
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Sigdel, Krishna P. "Phase transition studies of liquid crystal colloids with solvents and nano-solids." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-dissertations/137.
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Liquid crystals (LCs) are anisotropic fluids that exhibit numerous thermodynamically stable phases in between an isotropic liquid and a three-dimensionally ordered solid. In their simplest ordered phase, the nematic, LCs show orientational order due to molecular self assembly and at the same time maintaining fluid flow properties. In the smectic phase, they show both orientational and partial translational order characterized by a 1-d density wave. Liquid crystalline substances have been extensively studied due to their applications and as important physical models of self-assembly. The effect of the disorder and impurities on LC systems is an important and challenging problem to the fundamental understanding of phases ordering or self-assembly and continually attracts the attention of researchers. The disordered systems often display complex and rich phenomena, being the generalization of the pure (ideal) systems. Disorder can dramatically alter the physical properties of multi-component, composite systems. In particular, the effect of disorder on phase transitions is important as the disorder typically couples to the order parameter, which can be usefully described as a random local field that is conjugate to the order parameter. This is usually realized in systems with random inclusions in a phase ordering media, e.g., a colloidal dispersion of solids in a complex fluid. Another form of disorder is presented by dilution effects, which imposes instead the random breaking or weakening of intermolecular bonds or interactions responsible for the phase ordering. Exploring a good physical system representing random dilution effects in a controlled manner offers a physical probe to unresolved problems in the understanding of mesophasic order. This Dissertation presents a series of studies of dilution and different form of disorder effect on liquid crystal phase transitions. We have used high-resolution AC-calorimetry, dielectric spectroscopy as well as polarizing microscopy to characterize the effects of solvent such as hexane, acetone, decane, and nanomaterials such as multiwall carbon nanotubes and ferroelectric nanoparticles on the phase transitions of several liquid crystals. The liquid crystals of interest are: pentylcyanobiphenyl (5CB), octylcyanobiphenyl (8CB), and decylcyanobiphenyl (10CB). Studies have been carried out as a function of solvent, nanotube, and nanoparticles concentration and temperature spanning the isotropic to nematic (I-N), nematic to smectic-A (N-SmA), and isotropic to smectic-A (I-SmA) phase transitions.
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Yu, Ming-Wei, and 余明韋. "Effects of Nano-Particles-Doped Polyimide on Liquid Crystal Cells." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/09458583288470443109.
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碩士逢甲大學
電機工程所
93
The purpose of this thesis is to study effects of nano-particle-doped polyimide on liquid crystal cells, to understand influence of nano-particle-doped polyimide on liquid crystal cells of interface trapped ions. The purpose of this thesis is including that 1. When high voltage static electricity is input on liquid crystal cells, image sticking is induced by Electro-Static Discharge. 2. The ions accumulate on the interface between polyimide and LC that can induce the phenomenon interface trapped ions in LC, this will influence the optical and electric property of liquid crystal cells. In our Experimental results, we found that 1. When nano-particle-doped concentration increase, the phenomenon interface trapped charge is less that can improve the duration of image sticking caused by ESD but can not influence voltage holding ratio and residual DC. 2. There doesn’t find any relations between threshold voltage of nano-particle-doped different concentrations. 3. From optical and electric measurement we establish the model of interface trapped ions in LC.
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Shie, Wun-Yi, and 謝文逸. "Study on Liquid Crystal Cells Doped with Nano-ITO Particles." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/43555129031062658258.
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碩士逢甲大學
電機工程所
96
In this study, it was found that nano-conductive powders doped in liquid crystal cells can significantly and effectively reduce the image sticking effect for the display suffering a short pulse of electro-static discharge (ESD) stress. Nano-scaled Tin-doped Indium Oxide (ITO) powders were uniformly solved in the LC cells to form a suspension solution. Both electrical and optical characteristics for the doped cells and those without intentional doping were compared. According to the measurement results from the normal voltage holding ratio (VHR), lower frequency of VHR, voltage-transmittances (V-T), enhance molecular reorientation (EMR), depressed molecular reorientation (DMR), EMR+DMR and ion density, it was shown that there is no difference between the two types of LC cells. This was shown that ion effect didn’t increase. And doping nano-ITO in LC wouldn’t have more ion effect from these measurement results. However, the capability of suffering high-voltage stress was profoundly improved for the doped cells in the ESD test. The possible reason for this finding will be discussed according to the breakdown theory of suspended particles in liquid. In order to demonstrate the possible reason, we measured induction charges of the cells by the capacitance in ESD stress. And induction charges of doping nano-ITO cells were lower than without intentional doping cells. With the results, it can be expected that the LC cells doped with conductive nano-particles would survive in worse environments while keeping their displaying characteristics unaffected. Further, a new model that conducting nanoparticles move in the liquid crystal after ESD stressing can be successfully built and explained for these results in the study.
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Chang, Chi-Peng, and 張志鵬. "Studies of liquid crystal Fresnel lenses doped with nano particles." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/77890551103566082335.
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碩士國立中山大學
物理學系研究所
101
A simple method to make a controllable liquid crystal Fresnel lens with bistable state is proposed based on a surface of polymerization and the characteristic of nanoparticles. The sample is fabricated by a homogeneous aligned substrate and a vertical aligned one of coating polymer film. However, it has low diffraction efficiency. We improve the patterned electrode type with etching electrode structure. Experimental results reveal that liquid crystal Fresnel lens which ITO etching pattern using the nanoparticles doped with liquid crystals has bistable state and high diffraction efficiency.
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Guo, Jia-hao, and 郭家豪. "Biphotonically controllable random lasing emissions from a dye-doped polymer-dispersed liquid crystal with nano-droplets." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/30693177684880425108.
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碩士國立成功大學
物理學系碩博士班
97
This thesis investigates a biphotonically controllable random lasing emission based on a dye-doped polymer-dispersed liquid crystal cell. Experimental results show that the intensity of the random lasing emission can decrease and increase with increasing the irradiated intensity of one green beam and decreasing the irradiated time of one red beam, respectively. The biphotoinc controllability of the random lasing emission can be attributable to two mechanisms: (1)After the irradiation of the green beam with increasing intensity, the concentration of the rod-like trans dyes transforming to curve cis-isomers may increase so that the LC droplets can be disturb to gradually change from nematic to isotropic phase. This may cause that the refractive indices of the LC droplet and the polymer gradually becomes match, which will induce the decrease of the diffusion constant (or scattering mean free path) of the fluorescence photons and thus the decrease of the scattering strength; in turn, the random lasing emission will decrease. (2)After turning off the green beam, the intensity of the random lasing emission can gradually recover once the cell is illuminated by one red beam with increasing irradiated time. This is because the concentration of the cis dyes transforming to the trans-isomers increases with increasing the irradiated time of the red beam via cis-trans back isomerization. The LC droplets will gradually recover from isotropic to nematic phase, and the refractive indices of the LC droplet and the polymer will gradually become mismatch. This will cause the increase of the diffusion constant of the fluorescence photons and thus the increase of the scattering strength; in turn, the intensity of the random lasing emission will gradually recover.
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Xiao, Ya-zhi, and 蕭雅之. "The study of Electro-Optical properties of ferroelectric Nano-powder doped with chiral smectic liquid crystal." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/51925681705917401312.
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碩士國立臺灣科技大學
高分子系
97
This proposal was successful dispersion the ferroelectric particles ; BaTiO3 reach to nano size via surface modification and wet grinding appropriately , and confirm particles size by TEM,SEM,DLS. Then we doped dilute suspension of ferroelectric particles (≦1wt%) into ferroelectric liquid crystal (CS1024)host. By electro-optical measurement ,including dielectric properties、spontaneous polarization value、response time and V-shaped switching, we found that the CS1024+0.1wt%susp. have excellent performance in electro-optical properties, and enhanced application of ferroelectric liquid crystal.
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Nien, Che-wei, and 粘哲瑋. "Electro-Optic Properties of Cholesteric Liquid Crystals Doped With Ferroelectric Nano-Particles." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/86081022988734116773.
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碩士國立臺灣科技大學
高分子系
96
Our research was used cholesteric liquid crystal (E7+20wt%S-811) doping with low concentrations ferroelectric nanoparticles, measuration ferro-electric nanoparticles to affect the LC electro- optic propertie.The ferro-electric nanoparticles are BaTiO3 whose perovskite structure and particles size about 30nm.The relative concentrations of ferroelectric nanoparticles were adjusted to give the final compound of 0.1wt%, 0.2wt% and 0.3wt%.Than put LC into the cell, the cell gap was 4μm and anti-parallel alignment. Afterward discuss with diffation concentrations of ferroelectric nanoparticles which affect whit the LC phase transition temperature, dielectric permittivity,threshold voltage,optical response time, theread pitch etc. We found low concentrations of ferroelectric nanoparticles in LC , the physical properties of LC material would be improved.Because ferro- electric nanoparticles have the large dipole moment and polarizability,so strong interactions occur between the LC molecules and the particles.
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Hsieh, Yao-An, and 謝曜安. "Study on the molecular alignment and electro-optical properties of the nano-particle doped ferroelectric liquid crystal cells." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/79h2vd.
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碩士國立臺北科技大學
光電工程系研究所
98
We investigated the alignment and electro-optical properties of the ferroelectric liquid crystal (FLC) cells doped with nano-particle material. This study used three kinds of FLC cells where their alignment configuration are PI-free, planar alignment (PA) and vertical alignment (VA), respectively. The two substrate surfaces of these three kinds of cells were treated in two conditions, parallel rubbing and anti-parallel rubbing. Experimental results showed that the dispersed nano-particle induced the homeotropic helical molecular alignment in the PI-free FLC cell when the FLC/nano-particle mixture concentration was larger than 0.3%wt. The linear rotation of helical configuration with axis parallel to the substrate normal resulted in the obtaining of uniform dark state in this kind of cell. In the PA-FLC cell, the nano-particle induced homeotropic molecular configuration as well, but surface anchoring leads the helix to be unwound and formed tilted homeotropic alignment in the cell. The uniformity of the cell was reduced as the mixture concentration increased due to the light scattering, caused by the aggregation nano-particles. The electro-optical properties of these three kinds of FLC cells are clarified in detail in this thesis. For practical applications, the nano-prticle doped PI-free FLC cell is expect to be a potential candidate for the use of flexible liquid crystal display because of the unnecessary of high temperature process on baking polyimide film.
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Chen, Jian-Long, and 陳建龍. "Silica-doped liquid crystal capacitors." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/wfw34h.
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碩士國立交通大學
影像與生醫光電研究所
102
This work presents the bistable and tunable capacitors based on silica-doped liquid crystal devices. The driving power for bistable capacitors is applied only when the capacitance changes. It has attracted our interest due to its low power consumption particularly for the power harvesting micro-devices, which convert mechanical energy into electricity. In order to improve the power harvesting efficiency, a tunable capacitor is needed for adjusting the resonance frequency of power harvesting micro-devices to match the frequency of the external vibration in real time. The influences of driving frequency and voltage on the bistability, dielectric loss and tuning ratio of silica-doped liquid crystal (E7) capacitors were studied by dielectric spectroscopy in this work. The dual frequency liquid crystal was finally applied in the silica-doped liquid crystal capacitors to obtain switchable capacitance from the memory state.
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Hu, Chao-Yuan, and 胡朝淵. "Carbon Nanotube Doped Liquid Crystal Cells." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/77361541717659310073.
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Ciou, Guo-Yang, and 邱國揚. "Microsphere Doped Polymer Dispersed Liquid Crystal Films." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/82675603983491878873.
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碩士國立中央大學
光電科學與工程學系
101
In this study, we investigate the electro-optic properties of liquid crystal device which is fabricated by doping microspheres in liquid crystal and polymer dispersed cholesteric liquid crystal. It could be switched from light scattering state to transparent state by applying the electric field to control the refractive index matching between materials. In the first part of the experiment, we discuss microsphere doped liquid crystal device contrast ratio. In the second part of the experiment, we doped microspheres in PD-ChLC to decrease the transmission of the opaque state when the voltage is turned off result in increasing the contrast. Finally, we make a PD-ChLC device that is doped by 20% PMMA microspheres of 3μm in diameter. The operating voltage and the contrast are 38 V and 3.3:1, respectively. We find that the doping of microsphere in PDLC can not only decrease the operating voltage, but also reduce the amount of usage of monomer and liquid crystal. Thus, this technique can reduce the production cost.
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Lu, Yi Ju, and 呂易儒. "Effects of Liquid Crystal Polymer and Nano-particles on the Liquid Crystal Displays." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/03495349417163763005.
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碩士長庚大學
電子工程學系
99
For LCD display module, pre-tilt angles is a very important parameter, and the pre-tilt angle represents the angle of LC molecules and alignment layer (Polyimide, PI).Because of this angle, by applying voltage to the LC molecules can twist toward the consistent direction. In addition, this could also prevent create reverse twist which could defect the alignment when applying voltage to cell. We proposed two methods of controlling the pre-tilt angles, and we also compared and contrasted how these two methods have effects to LCD display module. One method is by directly rubbing alignment on the substrate with coating Indium Tin Oxide(ITO), and we will also utilize the characteristics of horizontal and vertical LCP on ITO. By controlling the different concentrations of horizontal and vertical LCP, it could produce net force (also called resultant force). Another method is to apply different concentrations of SiO2 nano-particles (AE130) doped in horizontal alignment PI and then be coating on ITO substrate to control the pre-tilt angles. The experiment demonstrates, by having different concentrations of horizontal and vertical LCP , the LC cell without coating alignment layer could also control the pre-tilt angles to be 17.45°,32.59°,and 46.52°, respectively. On the other hand, different concentrations of nano-particles doped in PI could induce the pre-tilt angles to be in the range of 2.3~10.5°, and in this condition, pre-tilt angles are inverse with concentrations of nano-particles.
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Yan-JhenHuang and 黃彥禎. "All-optically controllable dye-doped liquid crystal infiltrated photonic crystal fiber." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/83682521666859223535.
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碩士國立成功大學
光電科學與工程研究所
98
This thesis demonstrates for the first time an all-optically controllable dye-doped liquid crystal infiltrated photonic crystal fiber (DDLCIPCF). The transmittance in the core of the DDLCIPCF can decrease and then increase with a concomitant increasing red-shift of the core transmitted spectrum by increasing the irradiation time of one UV beam, and recovers with increasing the irradiation time of one green beam on the DDLCIPCF. The reversible all-optical controllability of the photonic band structure of the DDLCIPCF is attributable to the UV-beam-induced isothermal nematic(N) → scattering(S) → isotropic(I) transition and green-beam-induced isothermal I → S → N transition of the LCs via trans→cis and cis→trans back isomerizations of the azo dye, respectively, in the DDLC-filled regions of the cladding. During the light irradiation, the appearance of the scattering state and the variation of the index modulation between the core and cladding of the fiber cause the variation of the photonic band structure of the DDLCIPCF, in which the former and the latter lead to the variation of the core transmittance and the shift of the core transmitted spectrum of the DDLCIPCF.
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Chi, Ting-Ta, and 紀廷達. "Study of dye-doped cholesteric liquid crystal lasers." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/26669236590308201151.
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碩士國立成功大學
光電科學與工程研究所
95
This experiment demonstrates an inherent direction-tunable lasing effect in a dye-doped cholesteric liquid crystal (DDCLC) film. This novel lasing effect with continuous variation of wavelength of laser output was found and is blue-shifted as the detected polar angle increases. The photons propagating in different polar angle (θ) experience an effective pitch of P0．cos(θ) in one-dimensional cholesteric planar structure, where P0 is the original pitch of the CLCs in normal direction. In the reflection photonic band-edges, the photons experience a long dwelling time inside the periodic structure and its spontaneous and stimulated emission is strongly enhanced, generating the lasing effect. This direction-tunable lasing effect has not been observed before, we believe that this is because of the defect in the fabricated CLC cell. If the CLC cell is not perfect and includes many structural defects, the defect scattering of the normal lasing mode will significantly suppress the inherent direction-tunable lasing effect. Besides, the dependences of the polarization property and the pumping threshold energy of the laser output on the polar angle have also investigated.
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Lin, Jian-Hong, and 林建宏. "Bistable liquid crystal devices doped with aerosil nanoparticles." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/91939334757407266184.
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碩士國立交通大學
影像與生醫光電研究所
99
The electro-optical properties of liquid crystal devices based on light scattering have been investigated for nematic liquid crystal (LC) / nanoparticles (aerosil) composites. By applying ac electric field to the device , a normally scattering LCD become transparent due to LC molecules and aerosil network reorient toward the E-field. The former aerosil network is being broken and a new stable network is being formed. Besides, this transparent state is retained if the E-field is switched off. The influences of driving frequency、electric field and waveform on electro-optical characteristics of transmission, threshold voltage , memory effect and response time were studied. Then, we used the dual frequency liquid crystal /nanoparticles composites to switch the bistable mode. Finally, we tried a single ester positive compound to decrease the cross-over frequency of dual liquid crystal by the chemical synthetic method.
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You, Chang-Feng, and 游長峯. "Liquid crystal-doped liquid electrolytes for dye-sensitized solar cell applications." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/7k7k8u.
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博士國立彰化師範大學
光電科技研究所
105
We investigate the effects of liquid crystal (LC) dopant on the power conversion efficiency (PCE) of dye-sensitized solar cell (DSSC). The photovoltaic and electrochemical impedance spectra indicate that minute amounts of LC dopant decrease the short-current density of DSSC because the doped LCs reduce the electrochemical reaction rate between DSSC counter electrode and electrolyte. The doped LC impedes the degradation rates of DSSC because of the interaction between cyano groups of the doped LCs and organic solvent in the liquid electrolyte. Owing to the molecular interaction, the doped LCs increase the viscosity and stability, thereby inhibiting the evaporation rate of the liquid electrolyte. Next, the commercialized LCs are also doped into the DSSC. Results indicate that the polar fluoro groups of the commercialized LCs effectively interact with the cyano groups of the organic solvent in the liquid electrolyte, enhancing the long-term stability of the DSSC but without significantly reducing PCE of the DSSCs. The viscosity of the LC dopant is a key factor that affects the light–to–electrical energy conversion efficiency of the LC-doped DSSC. The short-current density and related PCE of the DSSC is not reduced because of the low viscosity of the doped fluorinated carbon-based LCs.
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Huang, Cheng-Wei, and 黃誠威. "Phase Separations in Silica Nanoparticle-doped Liquid Crystal Mixtures." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/fc9255.
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碩士國立交通大學
光電系統研究所
105
This work discusses the phase separation of silica nanoparticle-doped liquid crystal (LC) mixtures. We find that the phase separation of the LC mixtures involves the nucleation and growth of nematic domains followed by the aggregation of silica nanoparticles. The final morphology of LC mixtures after phase separation depends on the concentration and surface properties of silica nanoparticles. The temperature-dependent dielectric permittivity at 1 kHz and 10 Hz can reveal the clear point temperature and the onset of the aggregation of silica nanoparticles in LC mixtures, respectively.
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HUANG, YI-JEN, and 黃義仁. "Silica-nanoparticle-doped Hybrid Aligned Nematic Liquid Crystal Lens." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/76207279249576503616.
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碩士國立彰化師範大學
光電科技研究所
97
Electro-optical properties of the hybrid-aligned nematic liquid crystal lens and the silica-nanoparticle-doped one are investigated. Under DC voltage excitation, the silica nanoparticles accumulate on the planar side of the cell, creating agglomerates to stabilize the homeotropically aligned LCs, which is retained after switching off the voltage, giving the demonstrated devices bistable focusing characteristics. The silica-nanoparticle-doped liquid crystal lens has a shorter response time than non-dpoed one, due to the increased dielectric anisotropy or the increased LC viscosity.
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Lin, Zhi-zhong, and 林志忠. "Ferro/anti-ferroelectric liquid crystal doped with ferroelectric nanoparticles." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/sj763x.
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碩士國立臺灣科技大學
高分子系
95
We report on an approach to modify liquid crystals (LCs) by dispersing ferroelectric nanoparticles. The LC material is chiral smectic LC (MHPOBC). The ferroelectric nanoparticles are BaTiO3 whose perovskite structure and particles size about 100nm. The ferroelectric nanoparticles were doped into MHPOBC. The relative concentrations of component were adjusted to give the final compound of 1wt%, 10wt%, 20wt% and 30wt%. We found the physical properties of LC material would be improved at 1wt%. For example phase transition temperature decrease, dielectric constant and spontaneous polarization (Ps) increase, optical response time shortening etc. But when concentration was increased over 10wt%, electric-optical properties would be decreased. It means particles’ volume effects begin to disturb alignment of LC molecules. Finally high concentration caused LC phase to break down and disappear at 30wt%.
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廖柏軒. "Dynamical Behavior of Silica Nanoparticle-Doped Liquid Crystal Cells." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/72711347893744982464.
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碩士國立彰化師範大學
光電科技研究所
101
This thesis discusses dynamical behavior of the silica nanoparticle(SN)-doped liquid crystal (LC) cells. When the LC-SN mixture is filled into the cell, the doped SNs move toward margin of the cell, owing to the drag force generated from the interface between LCs and sealant. With alternate current (AC) voltage, the doped SNs are rapidly moved, due to the surface charges of SNs and the dielectrophoretic force in the cell. The moving speed of SNs markedly depends on amplitude and frequency of the applied voltage, and the employed LC materials. The AC high voltage also causes SNs at margin and center of the cell to have different accumulation conditions, affecting the electro-optical properties of the cell. At the center of the cell, the pretilt angle and the response time of the cell increase with SN concentrations; whereas at the margin of the cell,the pretilt angle and the response time of the cell are independent on the doped SN concentrations.
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Lin, Kuo-Ren, and 林國仁. "Nonlinear Optical Properties of Nanopraticle doped Cholesteric Liquid Crystal." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/45045476710937570516.
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碩士國立聯合大學
光電工程學系碩士班
99
Due to high nonlinear effect of liquid crystal (LC), LC has a considerable potential application on the field of nonlinear optics. In recent years, nanoparticles-doped liquid crystal composite materials have attracted considerable attention. In this thesis, I have studied the impact of an aggregation of polyhedral oligomeric silsesquioxane (POSS) nanoparticles doped in cholesteric liquid crystal cell on the nonlinear second harmonic generation. By controlling the cooling rate and doped concentration of POSS particles, the dispersed properties of aggregated POSS nanoparticels, which would induce many interfaces and disrupt the helical axis of CLC molecules were regulated. The generation of second harmonic signal is contributed by the interfaces between LC molecules and POSS aggregated clusters, as well as from the interfaces of the adjacent cholesteric focal conic domains with different helical axis. As a result, a significant second harmonic effect will be generated. We used polarized optical microscope to observe the aggregated morphology of the nano-particles clusters under different process conditions. In addition, Q-switched Nd:YAG laser was applied to measure the second harmonic generation of nanoparticles-doped CLC composite material. The experimental results demonstrated the cooling rate and POSS-doped concentration significantly influenced the dispersion of nanopraticle aggregation and the second harmonic signal intensity of CLC composite film.
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Chen, Jin-Yi, and 陳晉懿. "Polarization holographic gratings in dye-doped liquid-crystal films." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/84411394113597256354.
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Wu, Kuan-Ju, and 吳冠儒. "Unique properties of semiconductor and liquid crystal nano composites." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/05964410063982002830.
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碩士國立臺灣大學
物理研究所
95
Abstract In this thesis we report the study of optical and electrical properties on the composites based on liquid crystals and CdS nanorods. Quite interesting results have been obtained from our studies, which are very useful for the understanding as well as application of these materials. They are presented as follow. The novel nanocomposite device reveals a very unique and useful behavior that the polarization of the emission from semiconductor nanorods can be controlled by an external bias. The large magnitude of polarization anisotropy of 0.63 can be quantitatively interpreted very well in terms of the dielectric contrast between semiconductor and liquid crystal. Our approach is quite general, which is applicable to other nanomaterials, and it utilizes the currently mature liquid crystal display technology. The results open up new possible applications for one-dimensional semiconductor nanostructures in smart optoelectronic applications, including optical switches, integrated photonic devices, as well as electrochromatic gadgets in the near future.
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Wu, Kuan-Ju. "Unique properties of semiconductor and liquid crystal nano composites." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0607200717320500.
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Tsung-HanWu and 吳宗翰. "Optically controllable liquid crystal display based on azo dye-doped cholesteric liquid crystals." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/73816579139294959994.
Full textAbstract:
碩士國立成功大學
物理學系碩博士班
100
In this study, we report an all optically switchable display device based on azo chiral(Q1-3c-S)-doped nematic liquid crystal. The bright and dark states of the display device are at planar texture and focal conic texture, respectively, and can be repeatedly switched between each other. Notably, the bright state is achieved using the Bragg reflection of the planar textures is selected in infrared region. Moreover, the grayscales can also be achieved by illuminating the cell with purple light for different irradiation duration. The mechanism for switching the device between bright and dark states is described as follows. Briefly, the pitch length of the used material can be elongated and shortened by illuminating with purple and green light, respectively. When the pitch length is elongated, the free energy focal conic texture will be enhanced and the focal conic texture will be switched to planar texture. Moreover, the switching of textures from planar to focal conic can be obtained optically resulting from the disturbance of photo-isomerized azo molecules. It is also found that if the irradiation duration with purple light is too long, resulting in too much cis-isomers of the azo chiral material, the order parameter of the cholesteric liquid crystal is reduced so that the transmittance of the planar texture decreases. Yet, after blocking off the purple light from the sample, the transmission will recovers to the initial value. The cause can be understood since the cis-isomers will transfer to trans-isomers naturally, that is dark relaxation. About the demonstration of grayscales, the surface of treatment with weak anchoring (planar alignment) onto only one substrate of the LC device can be adopted to improve the stability of grayscales. Finally, we also demonstrate an all optically switchable display device that is optically addressable, erasable and rewritable.
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Wu, Yin-Chen, and 吳尹塵. "Study on the alignment of liquid crystal and surface propertiesin a liquid crystal cell doped with POSS nanopartcles." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/46028804227820909288.
Full textAbstract:
碩士中原大學
物理研究所
99
Adding 1 wt % polyhedral oligomeric slisequioxa POSS nanoparticles in the liquid crystals can change the planar alignment of liquid crystal (LC) cell into vertical alignment at the room temperature. In this paper, the alignment properties of POSS at different temperatures were investigated. When the temperature increased, pretilt angle of the POSS-doped LC cell decreased. Once the temperature reached 64.61<sup>。</sup>C, the pretilt angle is 4<sup>。</sup> and the POSS-doped LC cell becomes planar-aligned. From the measurement of the contact angles between the POSS-doped liquid crystals and the alignment layer, and the relationship between contact angle and surface energy, we conclude that the decrease of the pretilt angle as the temperature increases is the result of the increase of the surface energy.
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Jyun-WeiLin and 林俊瑋. "Low-Voltage Tunable Color in Full Visible Region Using Ferroelectric Liquid Crystal Doped Cholesteric Liquid Crystal Smart Materials." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/7ees22.
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碩士國立成功大學
光電科學與工程學系
105
This thesis mainly focused on three topics. The first is the investigation for the temperature-tuning of the reflective color of the ferroelectric liquid crystal doped cholesteric liquid crystal (FLC-CLC) across the entire visible region. The second topic is the study for electrical tuning of the reflective color of the FLC-CLC across the entire visible region in a low DC voltage range by using the high electrothermal feature of the ITO film. The third one is the investigation for electrical tuning of the reflective color of the FLC-CLC across the entire visible region by merging a flexible graphene electrothermal heater with the coaxial electrospinng technique. Experimental results show that the smectic-cholesteric phase transition temperature can be increased to near the room temperature such that the helix untwists significantly at near the transition temperature and thus the reflection band significantly red-shifts with a complete band structure. The reflection band or color of the FLC-CLC sample can be tuned across the wide band of the entire visible region when the ITO substrate of the sample is simply applied at a low DC voltage regime (〈 5 V). In addition, the FLC-CLC microfibers are electrospun and sprayed on the flexible graphene electrothermal heater film. The reflection band or color of the microfibers can also be tuned electrically across the wide band of the entire visible region at a moderate DC voltage regime (〈 24 V) on the graphene film. The planar or microfibers sample both possess a high reversibility and repeatability for the above-mentioned thermal and electrical tunabilities of the reflective band or color. Based on the above-mentioned experimental results, the electrically tunable FLC-CLC planar sample with ITO substrates and microfibers sample are highly potential for the applications of smart displays and lasers and smart sensors and textiles, respectively.
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Hsu, Kuei-Chu, and 徐桂珠. "Studies of Photorefractive Effect on Dye-Doped Liquid Crystal Films." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/25823830779404911783.
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碩士國立成功大學
物理學系
88
In this thesis, we study the dynamic behavior of the photorefractive effect on Dye Doped Liquid Crystal (DDLC) films. The two pump beams derived from a Krypton Ion Laser (l=568.4nm) set up a periodic interference of light on the DDLC sample, generating a phase grating. From the dynamic first order diffraction intensity of the probe beam (He-Ne Laser, l=632.8nm), we believe that the photoexcited dye molecules are diffusing slowly and then adsorbing onto the inner surfaces. These dye molecules induce a negative reorientational nonlinearity to the liquid crystal molecules in the high-intensity regions of interference patterns. After suitable illumination time, the photographs (SEM and AFM) show that the Methyl Red molecules adsorb onto the surfaces and form laser-induced ripple structures. These photoexcited dye molecules exert an intermolecular torque inducing transient dynamic sliding followed by permanent reorientation. Under an application of an external voltage, the space charge field effect and the intermolecular torque are competing each other. Finally, the strong negative nonlinearity induces a permanent grating. We can switch off the grating by applying an external voltage. The study of the application for optical data storage is underway.
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蔣振宇. "Polarization holographic gratings in dye doped polymer dispersed liquid crystal." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/90102087583840987278.
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碩士國立彰化師範大學
光電科技研究所
97
Polarization holographic gratings written by two orthogonally (sand p-) polarized writing beams in dye doped liquid crystal (DDLC), CdSe nanocrystals doped DDLC and dye doped polymer dispersed liquid crystal (DDPDCL) are demonstrated. Two writing beams generate a light field with a spatial variation of polarization state. The dyes are excited by the different polarization state of the light field. The liquid crystals are reoriented by the azo-dyes owing to host-guest effect. The orientation of liquid crystals molecules contribute to the index change in the material sample and lead to generation of polarization gratings. In this thesis, we have investigated the recording, reading, and erasable property of polarization holographic gratings in dye doped liquid crystal (DDLC), nanocrystals CdSe doped DDLC and dye doped polymer dispersed liquid crystal (DDPDCL).
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Te-WeiChang and 章德威. "Study of azo-dye doped nematic liquid crystal containing colloids." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/sg9upa.
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碩士國立成功大學
光電科學與工程學系
102
In this thesis, interactions of laser beam with an azo dye-doped nematic liquid crystal containing micron-sized colloids are investigated. Manipulations of colloids caused by both unfocused and focused laser beams are investigated. Key word ：Azo-dye, Nematic colloids, Optical trapping, Phase separation, DDLC.
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Chang, Wei-Hong, and 張維宏. "Laser-induced diffractive gratings in dye-doped liquid-crystal films." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/53426356954535935277.
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碩士國立成功大學
光電科學與工程研究所
95
The laser-induced diffractive gratings are investigated in azo dye-doped liquid crystal(DDLC) films. The formation of the gratings are owing to the laser-induced fine and homogeneous dye adsorption and laser-induced ripple structure. Which causes, respectively, the 40° and -50° twisted nematic(TN) structures. The gratings have great diffractive properties, such as high diffraction efficiency (~25%), high polarization independence (~90%), and electrical switch-ability.
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Chen, Tung-Ho, and 陳東河. "Electro-optical properties of nematic liquid crystal doped with nanoparticles." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/10150544245304377861.
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碩士國立臺灣大學
物理研究所
94
Nematic liquid crystal is the most common material for liquid crystal display (LCD). Some papers reported that the electro-optical properties of nematic liquid crystal could be changed with doped nanotubes. Those changes can improve the threshold voltage significantly. We plan to know if doping some different nanoparticles can change electro-optical properties in nematic liquid crystal. We use one commercial liquid crystal material MJ991597 to be our host and doped with nano-diamond powder and nano-TiO2, respectively. The concentrations are 0.1 %, 0.3 % and 0.5% for nano-diamond powder and nano-TiO2 . We measured the transmittance (voltage-transmittance curve), the ion effect (voltage-current curve), and the capacity of the liquid crystal device. We found that nano-dopants could change the electro-optical properties significantly compared with pure MJ991597. From our research, we know that the electro-optical properties can be improved by doping some nanoparticles to decrease the threshold voltage and ion effect. In other word, we can improve the performance of LCD and increase efficiency by doping nanoparticles.
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Cheng, Hsien-Hui, and 鄭憲徽. "Photoalignment in dye-doped liquid crystal films and its applications." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/77007932363470077785.
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碩士國立成功大學
物理學系碩博士班
94
The applications of photo-induced dye adsorption in dye-doped liquid crystal(DDLC) film for liquid crystal(LC) alignment using single pump beam have been extensively studied recently . In this thesis, we heat a DDLC cell to isotropic and pump the LC cell with various intensity to make a homogenous alignment. We observe dye absorption on the two ITO glass substrates in LC cell pumped with different intensity , and optimize the conditions to make a good homogenous alignment. We verify that the azo dyes(Methyl Red) in DDLC films pumped by a low-power beam are adsorbed with their long axis perpendicular to the polarization of the pump beam. In addition, we prove that azo dyes in the isotropic LC cell can adsorb on two glass substrates pumped with a suitable intensity. Based on the optimized conditions we fabricate a LC grating using a photomask, and a continuous homogenous LC grating using a polarization hologram. The measured results show that the diffractive property of these two kinds LC gratings, are polarization independent, and can be used as an electrically tunable beam splitter.
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Hung, Shang-Po, and 洪尚伯. "Dielectric spectroscopy of liquid crystal devices doped with silver nanoparticles." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/92271424273324149038.
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碩士國立交通大學
光電系統研究所
102
The applications of liquid crystal devices (LCDs) doped with metal nanoparticles have been investigated intensively and demonstrated recently. However, the study of the influences of the aggregation of nanoparticles on the electro-optical properties of LCDs is scarce. The capacitance amplification of the LCD doped with metal nanoparticles was reported by Kobayashi et. al. recently. They claimed that the phenomenon may be due to a special nature of the oscillating extra charges, which occurred in the region between the LC and nanoparticles, and produced an effective negative dielectric constant of the metal nanoparticles. In this work, we studied the dielectric spectroscopy of LCDs doped with silver nanoparticles in the frequency range of 50–105 Hz. The dielectric spectroscopy of a binary composite material can be well described by the Maxwell–Wagner polarization for spherical particle suspensions. We have observed that the silver nanoparticles aggregated and formed different sizes of clusters in LCDs. Therefore, the Maxwell–Wagner–Sillars model suitable for different shapes of particle suspensions was applied to analyze our data. Our results showed that the dielectric constant of silver clusters in LCDs was positive regardless of frequency, which was different from the results reported by Kobayashi et. al.
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Lee, Yu-Ren, and 李育仁. "Electro-Optical Effects of Dye Doped Cholesteric Liquid Crystal Device." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/e9uq4n.
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碩士國立臺灣科技大學
高分子系
94
This study discussed electro-optical effects of dye doped cholesteric liquid crystal devices. We studied the electro-optical effects by using dichroic dye mixing in cholesteric liquid crystal device and through parameters, such as operation voltage, light transmittance, contrast ratio and response time, against the related dependence of cholesteric liquid crystal device cell gap, dye weight percent, and cholesteric liquid crystal pitch. The experimental results show that smaller cell gap, longer pitch, and lower percentage of dichroic dye got lower operation voltage and shorter period of response time. Moreover, with the same cell gap, the cholesteric liquid crystal device with longer pitch performed a narrow and ascent curve in light transmittance, contrast ratio and reflection characters. By the doping dichroic dye, it achieved a contrast effect and viewing angle on either side without any polarizer.
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Tsui, Chih-Yu, and 崔志宇. "Substrate morphology studies of photo-prepolymer-doped liquid crystal cells." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/26057468158976730900.
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碩士國立彰化師範大學
光電科技研究所
104
This thesis investigates the polymer morphology on the substrate surface of the LC cell doped with photo-prepolymer NOA65. The polymer morphology is determined by the surface of the substrate, exposure parameter, and rubbing treatment. During exposure process, the monomers move toward the substrate surfaces due to the photo-induced phase separation induced by the interaction between the LCs, substrate surfaces, and monomers. After polymerization, the microstructures such as gravels and polymer films are formed on the substrate surfaces of the cell. The obtained results also reveal that the photo-induced phase separations can be classified as isotropic and anisotropic phase separations, determined by the extent of the interaction between monomers and substrate surfaces. Furthermore, the polymerization morphology is related to the exposure parameter. It is also found that the polymerized microstructures on the substrate surfaces create periodic structure along the rubbing direction of the LC cell when the substrate is coated with homogeneous or homeotropic polyimide, which can provide sufficient anchoring energy to align the LC molecules. The amplitude and the uniformity of the formed gravels is dependent on the curing intensity and the curing voltage of the LC cell.
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Lo, Chun-Hsiang, and 羅春祥. "An Electrically Tunable Polarizer Using Dye-doped Liquid Crystal Gels." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/29891624402054075389.
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碩士國立交通大學
顯示科技研究所
97
An electrically tunable polarizer using dye-doped liquid crystal (LC) gels is demonstrated. The main mechanism of such a polarizer is a combination of the light absorption and the scattering owning to dichroic dyes and poly-domains resulting from polymer networks. In this thesis, we observe the morphologies of dye-doped liquid crystal gels by a scanning electron microscopy. The polymer networks perpendicular to the glass substrates are chain-linked by lots of nano-sized polymer grains. The sizes of poly-domains and polymer grains depend on curing temperatures and monomer concentrations. The domain sizes of polymer networks and the sizes of polymer grains increase by increasing the curing temperature. The domain sizes have influence on electro-optical properties of the electrically tunable polarizers. In our experiments, the maximum contrast ratio of the polarizer can be electrically tuned is around 5:1~10:1 at 10�aC curing temperature. The operating voltage is around 30 Vrms. The response time is around ~ 6ms. The optical analysis based on the scattering theory and the absorption theory is discussed as well. Furthermore, we focus on the color issue of dye-doped LC gels LC gels and provide several methods to improve the colors. One application of electrically tunable iris is also demonstrated.
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Jian, Bo-Ru, and 簡伯儒. "Dielectric Study of a Liquid Crystal Doped with Carbon Nanotubes." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/22917264578475054568.
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碩士中原大學
物理研究所
98
This thesis focuses on the ionic effect in liquid crystals doped with multiwalled carbon nanotubes (CNTs). By dielectric spectroscopy, the electrode-polarization process dictated by both the concentration and the diffusion constant of impurity ions and, thus, can be monitored, which is particularly useful for interpretation of the dopant effect on the ion transport. From the results of voltage-holding-ratio (VHR) measurements, one can investigate whether CNTs as a dopant has the potential application in display devices by “purifying” liquid crystals. The results show that a minute amount (< 0.05 wt.%) of CNTs as a dopant not only localize impurity ions via the formation of the charge-transfer complex to reduce the measured ion concentration but also hinder ion transport to result in a smaller diffusion constant in the suspension. When the CNT concentration is larger than 0.05 wt.%, the CNTs were prone to aggregate and cause the undesired effect. The VHR results reveal that doping CNTs in a liquid-crystal cell raises the VHR by 26% and extend the life time of the cell. Our study concludes that CNTs as an additive can suppress the ionic effect, allowing its potential application in TFT–LCD devices.
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Yu-MengLin and 林郁孟. "All-optically switchable dye-doped blue phase liquid crystal laser." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/16933745814160752574.
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Hsu, Tang-Wei, and 許唐維. "Characteristics and Applications of Silica Nanoparticle-Doped Liquid Crystal Devices." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/22695894060952348828.
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碩士國立交通大學
影像與生醫光電研究所
99
With doping silica nanoparticles in a hybrid aligned nematic (HAN) liquid crystal device (LCD), the electrophoretic effect of nanoparticles was observed by applying a pulse voltage. Under a pulse voltage excitation, the silica nanoparticles accumulated on the homogeneous alignment (HA) layer, and it changed the alignment property near the HA layer. The stabilization of silica nanoparticles on the HA layer provided a stable vertically aligned LC cell even switching off the voltage. This work studied the influences of liquid crystal, alignment material, thickness of alignment layer, nanoparticles and concentration of nanoparticles on the bistability of HAN LCDs. In addition, the technique of achieving bistable HAN LCDs was applied on a bistable Guest-Host (G-H) LCD. The characteristic of bistable G-H LCD was studied in this work.
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Jia-HengDai and 戴嘉恆. "All-inorganic perovskite quantum dots doped cholesteric liquid crystal laser." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/rg2d8a.
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碩士國立成功大學
光電科學與工程學系
106
This work demonstrated for the first time an highly efficient all-inorganic perovskite quantum dots doped CLC (AIPQD-CLC) laser. The AIPQD material as an efficient optical gain medium in the optical resonator of the CLC planar texture can be obtained by pre-underdoing a low-cost solvothermal process.. Experimental results show that the AIPQD lattice structure corresponds to the black orthorhombic phase of CsSnI3 perovskite. The ge value and linewidth of the lasing signal from the AIPQD-CLC laser measured are around 1.8 and 0.21 nm, respectively. The aggregation of the AIPQDs in the CLC may significantly decrease the lasing performance. In second part, the position of the bandedge can be changed by changing the composition ratio of the chiral and LC such that the lasing wavelength of the AIPQD-CLC laser can be tuned. Experimental results show that both the absorption and photoluminescence (PL) of the QDs may competitively influence the lasing threshold. Additionally, the energy threshold of the AIPQD-CLC laser can be as low as 1.86 μJ/pulse. Including the lasing threshold, ge value and linewidth, the performances of the AIPQD-CLC laser are nearly comparable with those based on traditional dye-doped CLC lasers. In third part, the thermal, AC and DC electrical tuning features of the AIPQD-CLC laser were demonstarted. The AIPQD-CLC laser exhibited a high potential to become a new class of candidates for photonic applications, particularly in multi-tunable light-emitting devices.
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Liao, Chi-Chang, and 廖奇璋. "Studies of Photorefractive Effect and Optical Storage Applications in Dye-Doped Liquid-Crystal and Polymer-Dispersed Liquid-Crystal Films." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/37155788312944487754.
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博士國立成功大學
物理學系碩博士班
91
In this thesis, we study the photorefractive effect and optical storage in the dye-doped liquid-crystal (DDLC) and polymer-dispersed liquid-crystal films. The dynamic behavior of a holographic grating induced in a homeotropically aligned DDLC film is firstly investigated.In the presence of an applied dc voltage, photoexcited azo dyes, Methyl Red (MR), induce a photorefractive grating and then diffuse and are adsorbed onto cell substrates, generating a surface-alignment grating. The former is 90o phase shifted with respect to the light-interference pattern set up by the writing beams. The latter is in phase with the interference pattern. The transition from the former to the latter grating effect induces a dynamic change in from two-beam coupling (TBC) of the two writing beams. Next we investigate a fast optical recording material based on dye-doped polymer-dispersed liquid-crystal (DDPDLC) film. The result shows that a holographic grating is written in this film with a single Q-switched Nd:YAG laser pulse that has a duration of ~ 6 ns. Such a grating is due to the reorientation effect of the liquid-crystal molecules through interaction with the photoinduced adsorption of the azo dyes. The grating thus formed is permanent but electrically switchable. Fabrication of the sample is simple, but the sensitivity and the speed of the storage are high and fast, respectively. These properties make practive uses of the grating possible. Finally we study the light-induced reorientation effects on a homeotropical DDLC cell using the holographic grating setup. The photo-excited MR dyes diffuse and adsorb onto the substrate, thus forming a ripple structure. The adsorbed dyes and laser-induced ripple structure then reorient the liquid crystal molecules and induce a holographic grating. In the case of the grating written with two s-polarized beams, the direction of the adsorbed dyes is orthogonal to the ripple direction. Initially, the LC directors are reoriented primarily by the adsorbed dyes. However, given sufficiently large ripple groove amplitude,the torque imposed by the ripple grooves overcomes that owing to the adsorbed dyes, and the LCs are realigned along the groove direction.
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Lu, Chia-Yu, and 呂佳諭. "Studies of laser-induced gratings on dye-doped liquid crystal films." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/60896194154357607203.
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碩士國立成功大學
物理學系
88
Abstract Dye-doped liquid crystals (DDLCs) have potential for uses in optical holographic storage and display owing to its large light-induced reorientation effect. It is a novel material for application in optical recording. It requires low-intensity writing beams (0.3J/cm2). The resolution can reach 103 lines/mm. The storage can preserve as long as one year, and can be repeatedly writing and erasing by heating and different polarized light. In addition, DDLC can be used as display devices switched optically. It is different from the conventional device which is usually controlled electrically. The orientation of liquid crystal molecules can be changed by polarized light. Although the DDLC has many applications, the basic mechanism in light-induced reorientation is not clear yet. In this thesis, we use dynamic holographic technique and polarimetric technique to study the microscopic mechanism of the dynamic holographic grating in planar nematic liquid crystal (NLC) films doped with Methyl Red (MR). The results show that the LC molecules are reoriented parallelly and orthogonally to the polarization of the pump light in different time scale. Varying the polarization in the pump and the probe beams, we observe two different phase gratings which result from different LC molecular orientation affected by MR concentration gradient and diffusion. Both the qualitative explanation and the quantitative fitting are given to account for the experimental results.
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Tai, Chia-Chun, and 戴嘉駿. "Electro-Optical Properties of Homeotropic Liquid Crystal Doped with Carbon Nanosolids." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/15772292448634405547.
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碩士中原大學
應用物理研究所
93
In the pass two years, research projects conducted in our laboratory have indicated that carbon-nanotube dopant in liquid-crystal cells can effectively reduce the threshold and driving voltages, and yet the dopant would not enhance the ion-charge effect. In this work, we investigated several physical properties, such as the threshold voltage, driving voltage, time-evolved transmittance and time-evolved capacitance, of vertical-aligned liquid-crystal cells doped with carbon nanosolids in the presence of dc or ac voltage. Experimental evidence points out that the doped cells have lower threshold and driving voltages under external dc voltage. Furthermore, in the presence of ac voltage, the threshold and driving voltages of the cells are affected by the frequency. The higher the frequency is, the higher the threshold and driving voltages of the cells become. In addition, the threshold and driving voltages of the doped cells become lower in some specific frequency. Moreover, we found that doping carbon nanosolids in liquid crystal does not increase ion charge. In contrast, it suppresses ion-charge effects.
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Cheng, Ko-Ting, and 鄭恪亭. "Studies of Biphotonic Effect based onDye-Doped Nematic Liquid Crystal films." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/7m966z.
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碩士國立成功大學
物理學系碩博士班
91
The applications of dye adsorption in a dye-doped liquid crystal (DDLC) film by using single pump beam have been extensively studied in recent decades. In this thesis, we study the biphotonic (red and green light) effect based on the DDLC films, and observe the adsorption, aggregation and separation phenomena. The formed patterns under different intensities of two laser beams and temperatures are investigated. Specifically, the relations between the laser-induced ripple structures of adsorbed dyes are observed using a scanning electron microscope (SEM). We conclude that the direction of the adsorbed azo dyes (Methyl Red) in DDLC films pumped by a low-power excited beam is perpendicular to the polarization of excited beam. In addition, we prove that the red light and temperature can restrain the green light from causing the adsorption of azo dyes. Moreover, different polarization of excited beams can cause some different biphotonic effects. We propose the mechanism that accounts for the separation phenomenon of aggregated dyes, and for the ripple structure of the adsorbed dyes observed under SEM. An easy numerical method is also give to prove the phenomena. Based on the obtained results, some further experiments in this system are designed and given in the conclusion chapter.