共查询到20条相似文献,搜索用时 0 毫秒
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随着近几年液晶显示技术在诸多领域的广泛应用和新技术的推出,人们一直致力于改善液晶器件显示性能的研究。在液晶显示器应用中,电光特性是一个很重要的参数,介绍了采用激光测量的方法获得液晶的电光特性、阈值电压及视角特性。分析了液晶分子在交流电场作用下重新取向后的扭曲特性,测试了不同电压下液晶分子的透光率和扭曲角度,结果表明:该方法是可行的,向列相液晶具有0.92 V较低阈值电压和较为陡峭的电光曲线,水平方向上在-60~+50有较好的视角特性,垂直方向上在-40~+20有较好的视角特性。该结论为偏光器件的设计与制作提供了依据。 相似文献
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Stanisław A. Różański 《Phase Transitions》2019,92(1):79-86
The volume filling fraction dependence of the effective permittivity of the nematic liquid crystal 4-n-pentyl-4’-cyanobiphenyl embedded in different porous membranes and dispersed with aerosil nanoparticles was determined using broadband dielectric spectroscopy in the frequency range from 106 to 109 Hz. The experimental data were analyzed and compared with some existing theories based on the effective medium approximation and their modifications. The obtained effective permittivities as a function of the volume filling fraction lie between the lower limits of the Wiener and Hashin–Shtrikman bounds. The observed shift of the experimental points reflects the changes in the structure of the investigated composites. 相似文献
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Results of temperature studies of dielectric permittivity and mass density in binary mixtures are presented. The anomaly of dielectric permittivity as a function of temperature in nitrobenzene-n-alkanes binary mixtures has been studied. Molar dielectric permittivity which takes into account the anomaly of dielectric permittivity and the mass density anomaly has been introduced. 相似文献
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We theoretically study interfacial properties between two coexisting phases in mixtures of a flexible polymer and a low-molecular-weight liquid crystal. By numerically solving Euler equations for compositional and orientational order parameter fields, we calculate the order parameter profiles and interfacial tensions for nematic-isotropic and isotropic-isotropic phase equilibria. We find that the order parameter profiles are non-monotonic at some temperatures. The nematic-isotropic interfacial tension increases with decreasing temperature and is approximately proportional to (T - T(NI))(n) at temperatures below the nematic-isotropic transition temperature (T(NI)) of the pure nematogen. The value of the exponent n is strongly affected by the existence of a triple point. 相似文献
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We theoretically model the nucleation of nematic droplets during phase ordering in mixtures of a flexible polymer and a low-molecular-weight
liquid crystal. By appealing to classical nucleation theory (CNT), we calculate the energy barrier to nucleation and the size
of a critical nucleus. We study the influence of a metastable intermediate phase on the nucleation of the nematic. Below a
triple point in the phase diagram, there are two distinct mechanisms for the formation of a nematic nucleus: 1) direct nucleation
from the isotropic phase and 2) nucleation via a precursor metastable isotropic phase. We calculate the crossover concentration as a function of temperature, delineating
the regions of the phase diagram in which each mechanism prevails. In the latter case, the presence of a hidden metastable
isotropic-isotropic binodal may either promote or delay the nucleation of a nematic phase.
Received 9 August 2002
RID="a"
ID="a"e-mail: matuyama@chem.mie-u.ac.jp 相似文献
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We present a theory of the dielectric permittivity in which the intermolecular dipole-dipole correlations are treated explicitly. The results for the static permittivity agree with those which have previously been obtained by continuum calculations. The frequency dependence of the permittivity is related to two relaxation times which contain the effects of only short range intermolecular correlations. Approximate relationships are derived between these times and independently measurable properties. 相似文献
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Brillouin scattering has been used to obtain first order elastic constants in 8CB. In contrast to earlier measurements the interlayer constant is found to be finite as T approaches the smectic A—nematic transition. These results confirm recent theoretical predictions. 相似文献
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Eun Jeong Jeon Byoung Sun Jung Byeong Gyun Kang Myong-Hoon Lee Jeoung-Yeon Hwang Dae-Shik Seo Seung Hee Lee 《Current Applied Physics》2010,10(1):245-248
Optically compensated splay (OCS) mode, where the liquid crystals (LCs) are almost homeotropically aligned with rubbed surfaces at parallel directions and a mid-director orients parallel to the substrate, was known to show a wide-viewing-angle due to self-compensation effect. The device requires a setting voltage and phase transition time in order for LC to have a transition from almost vertical alignment to the splay state. The setting voltage, transition time, and response time of the device as a function of surface pretilt angle were studied. The results indicate that with decreasing surface pretilt angle in the OCS cell, both phase transition time and setting voltage decrease and response time becomes faster. 相似文献
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本文利用向列相液晶层作为激光偏振调控单元,涂覆于垂直腔面发射激光器(VCSEL)表面,测量并分析了不同温度下VCSEL正交线偏振光的阈值电流、峰值光功率和I-P特性. 实验结果表明:温度为293 K时,涂覆液晶后激光偏振第一跳变点和第二跳变点之间的电流值ΔI增大了2.2 mA,比无液晶时增大1倍. 温度为313 K、注入电流为3 mA时,两种正交线偏振光的光功率差ΔP由133.6 μW增大到248.8 μW,进一步增加了线偏振光的各向异性. 表面液晶层的引入有效地扩大了VCSEL的正交线偏振态稳定范围和光功率差,为实现液晶VCSEL高温单偏振稳定的设计和器件制备提供了理论和实验基础.
关键词:
垂直腔面发射激光器
向列相液晶
偏振态 相似文献
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Correlation of magnetic anisotropy with dielectric anisotropy in fluorinated phenyl bicyclohexane liquid crystal 下载免费PDF全文
Temperature dependence of magnetic anisotropy of homologous nematic fluorinated phenyl bicyclohexane liquid crystals is measured by a magneto-electric method.The result shows that the diamagnetic property is slightly influenced by the positions and the numbers of fluorine atoms substituted at the phenyl ring.By investigating the correlation of the dielectric anisotropy with the magnetic anisotropy,a novel explanation is proposed for the behaviour of the molecular dipole-dipole dimerization in the polar liquid crystal compounds. 相似文献
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Blue phase (BP) temperature range of a chiral nematic liquid crystal (LC) mixture is dependent upon the host nematic LC chemical structure and chiral dopant concentration. In this study, we investigated BP phase transition behaviour and helical twisting power (HTP) using three chiral dopant concentrations of cyano compound chiral nematic LC mixtures incorporating three two-ring core structures in the host nematic LCs. The effect of the host nematic LC core structure, HTP and chiral dopant concentrations were considered on BP temperature ranges, for two types of complete BPI and BPII without isotropic phase (Iso) and two types of coexistence state of BPI+Iso and BPII+Iso. 相似文献
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We report the measurement of temperature-dependent dielectric parameters in some binary liquid crystal mixtures comprising of a hockey-stick-shaped mesogen 4-(3-decyloxyphenyliminomethyl) phenyl-4-decyloxycinnamate (SF7) and calamitic compound 4′-octyloxy-4-cyanobiphenyl (8OCB). All the investigated mixtures possess a large positive dielectric anisotropy (Δε), although a noticeable reduction has been found by increasing the diverse-shaped dopant concentration. Investigation on the pretransitional behavior in the vicinity of isotropic to nematic (I–N) phase transition suggesting a tricritical character for all the studied mixtures. Parameterization of dielectric permittivity close to the nematic to smectic-A (N–Sm-A) phase transition exhibits non-universal values of the critical exponents describing a second-order nature of the transition. Systematic variation of critical exponents against dopant concentration and McMillan ratio reveals a well consistency with those obtained from the high-resolution optical birefringence measurements. 相似文献
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Richard Alben 《Solid State Communications》1973,13(11):1783-1785
It is pointed out that a tricritical point analogous to that in He3-He4 mixtures should occur in mixtures of liquid crystals with first and second order nematic-smectic transitions. 相似文献
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Observation of relaxation modes in room temperature ferroelectric liquid crystal mixtures 总被引:1,自引:0,他引:1
The dielectric measurements in SmC* and SmA phases of a room temperature ferroelectric liquid crystal mixture FLC-6980 in
the cells of different thickness in planer alignment have been carried out in the frequency range 100 Hz to 1 MHz. A relaxation
mode (called NRM) whose dielectric increment is less than the Goldstone mode has been observed in the SmC* phase. This mode
appears due to the surface effect. Goldstone mode and the soft mode was observable in the vicinity of SmC*-SmA transition
temperature (T
C*A). The dielectric parameters of the Goldstone mode, new mode and the soft mode have been studied as a function of frequency
and temperature. The calculated values for fNRM, δεNRM and distribution parameter αNRM are found to be 325 kHz, 6 and 0.156 for 5μm thick planer cell at 37°C. It is seen that in the vicinity of theT
C*A, soft mode obeys the Curie-Weiss law given by mean field theory. The results have been compared with materials of large spontaneous
polarization. 相似文献
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We report for the first time the determination of the real part of the third order nonlinear susceptibilities
(3) (–, , 0, 0) in the isotropic phase of two nematic liquid crystalsp-(ethoxybenzylidine)-p-butylaniline (EBBA) andp-(methoxybenzylidene)-p-butylaniline (MBBA) from electrooptic Kerr effect experiments. The highest value of
(3) observed near nematic-to-isotropic transition temperature, at 632.8 nm is found to be 1.067×10–20 m2V–2 for EBBA and 6.602×10–20 m2V–2 for MBBA. 相似文献