共查询到20条相似文献,搜索用时 140 毫秒
1.
2.
3.
高双折射液晶化合物的研究进展 总被引:1,自引:1,他引:0
近年来,液晶器件的响应速度得到了很大的改善,响应时间已经从25ms减少到3ms甚至更短。虽然这种改善与液晶层厚度的变薄有关,但主要原因应该归因于新型液晶材料的发展和使用。色序液晶显示能产生更高质量的图像,但前提是必须有能快速工作的液晶材料。液晶材料的旋转黏度系数、双折射和液晶层的厚度是影响液晶器件响应时间的3个主要因素。本文以液晶双折射这一因素为主线,从液晶化合物结构的角度介绍了影响液晶双折射数值的若干因素,包括中心环结构、中心基团上的桥键、极性基团和侧位-F对液晶双折射的影响等,延长分子的π电子共轭长度能有效提高液晶的双折射。本文列举了国内外已合成的高双折射向列相液晶的分子结构及双折射值,最后对高双折射液晶的研究进行了展望。 相似文献
4.
高Δn低粘度液晶的合成及性能研究 总被引:8,自引:8,他引:0
利用二苯乙炔为中心基团上的核心结构,合成了多种极性较低的液晶和几种含氟液晶单体化合物,并按10%的质量分数与商用液晶进行了混配,同时制成了平行排列的液晶盒.通过旋转粘度计分别测量了混合后的液晶溶液的粘度.利用光谱型椭偏仪测量了633 nm下的平行液晶盒的Δn,并且外推出了掺入的液晶单体的Δn,其结果与Vuks方程的计算结果吻合得很好.结果显示,二苯乙炔类液晶比传统的联苯类液晶的Δn有了显著提高,同时保持了相对较低的粘度,适合用于要求具有快速响应特性的液晶器件. 相似文献
5.
6.
中心环外侧嘧啶环作为液晶分子的极性介晶基团,能有效增大分子的偶极矩和分子间的作用力,提高分子的介电各向异性,降低液晶的驱动电压,也有利于形成近晶相液晶态。本文试图以嘧啶乙炔为中心结构单元,以异硫氰基为端基,设计合成了嘧啶乙炔类异硫氰基液晶化合物(nBTM-NCS)系列共5个化合物;它们都经过IR、~1H-NMR、~(13)C-NMR和MS光谱对其分子结构鉴定,经过差热分析仪(DSC)和偏光显微镜(POM)对其液晶性能进行检测。实验结果表明,所有化合物的分子结构均正确,具有近晶相态,其熔点较高并呈现奇偶效应;其光学各向异性达到0.45左右,介电常数21~24左右,可作为铁电液晶和聚合物分散液晶材料配方组分。 相似文献
7.
一、前言 液晶冠醚在1982年[1]出现以来,由于其同时具有冠醚和液晶所具有的性质,已越来越受琶人们的重视。作为液晶类的冠醚化合物,已在仿生物膜,手性识别,显示取向.分子离子器件等方面显示出很强的应用前景[2,3,4].液晶冠醚的应用,要求具有恰当的液晶温度范围,但在液晶冠醚的合成设计中,虽然可以通过对中心桥键、刚性及柔性链的长短等因素来调节液晶冠醚的熔点,但要较为准确也预计其熔点和液晶态温度范围是非常困难的,两将两种不同熔点的液晶混合,一般可得到低于每纯组分熔点的混合液晶。我们以单臂脂环液晶冠醚1和2,开展了它们的混合研究。 相似文献
8.
9.
10.
低分子和聚合物液晶物理性质研究、合成新材料和工艺方面的成就建立了光学仪器制造的新元件基础──光学液晶元件。光学液晶元件分为偏振型和光散射型。前者对偏振辐射进行变换,后者对自然辐射进行变换。液晶元件主要用于各种信息显示系统中,使用偏振效应的装置已获得很大发展。这可用它们所需能量较小和调制深度较大来解释。另一方面,光散射可控液晶元件不需要起偏器,并可连续或分立的控制辐射的角分布,实现图像的空间频率滤波,实现存储效应和改变介质的透明度,这就开创了独特的新应用领域。本综述讨论液晶元件在光学仪器中最有特征… 相似文献
11.
12.
以密度泛函理论为基础,利用Gaussian09程序包,通过Opt+Freq优化类型,以B3LYP/6-311g基组对10种不同数目及不同位置部分氟代的4-丁基-4’-[(4-丁基苯)乙炔]联苯液晶衍生物分子进行数值计算,根据氟原子的置换位置和数目对这些分子在太赫兹波段的光吸收情况进行了对比分析。结果表明,在太赫兹频段,氟原子置换的位置和数目会显著影响分子内其它官能团的吸收位置和强度。其中苯环内的C-H吸收会因为苯环上氟原子置换数目增加而减少,苯环上双氟原子的增加导致烷烃的吸收峰强度发生变化;对于炔烃,氟原子的置换会通过改变其偶极矩从而产生较强的吸收峰值。计算结果在分子官能团的吸收方面与文献报道的实验测量结果吻合得相当好。根据现有文献报道,作者还对比分析了0.3~3THz范围计算结果与相关文献的实验数据。总之,计算模拟结果能够较好地反应分子材料对太赫兹波的吸收状况,可为相关液晶分子的设计与合成提供参考。 相似文献
13.
V. deHalleux J.‐P. Calbert P. Brocorens J. Cornil J.‐P. Declercq J.‐L. Brdas Y. Geerts 《Advanced functional materials》2004,14(7):649-659
Tetraphenylpyrene has been selected as a discotic core to promote liquid‐crystalline fluorescent columns in view of its high fluorescence quantum yield in solution and ease of substitution by flexible lateral side chains. The synthesis and characterization of ten new derivatives of pyrene have been carried out; the pyrene core has been substituted at the 1,3,6,8‐positions by phenylene rings bearing alkoxy, ester, thioether, or tris(alkoxy)benzoate groups on the para position; the compounds have been characterized by mass spectrometry and 1H NMR and UV‐vis spectroscopies. In order to generate liquid‐crystalline phases, the nature, number, and size of the side chains as well as the degree of polarity around the tetraphenylpyrene core have been varied. However, the desired liquid‐crystalline behavior has not been observed. The supramolecular order together with the absorption and emission properties in solution and the solid state are discussed and compared to theoretical predictions. Quantum‐chemical calculations rationalize the high solid‐state fluorescence of a tetraphenylpyrene derivative for which the crystal structure has been determined. 相似文献
14.
A comparison of the performance of two input access mechanisms for multicast switching is presented. The first of these-a cyclic priority input access method-is a derivative of the ring token reservation method which eliminates the unfairness of the ordinary ring token reservation. It has the advantage of being relatively simple and easy to implement. A second approach employs a neural network to resolve output port conflict. While more difficult to implement, it has a delay-throughput performance advantage over the cyclic priority approach. The primary performance measurements are the switch throughput and the packet delay. A key assumption is that all copies of the same packet must be switched in the same slot 相似文献
15.
液晶盒边界效应对胆甾相液晶电控螺距的影响 总被引:1,自引:1,他引:0
研究了共面转换(IPS)液晶盒处于强锚定及弱锚定两种边界状态时横向电场与平面织构胆甾相液晶螺距的关系,探讨了液晶盒表面锚定对胆甾相液晶电控螺距的影响。理论结果表明,共面转换模式下电场可以调谐胆甾相液晶的反射光颜色,而边界锚定效应对电场调谐螺距有显著影响。这一结果为基于电控螺距原理的胆甾相液晶反射式彩色显示方案提供了理论上的依据。 相似文献
16.
17.
一、引言 相干反斯托克斯喇曼散射光谱(CARS)作为一种研究分子结构的手段,已在物理、化学、生物学以及相关的一些技术领域获得令人鼓舞的应用。它是基于两个和分子体系相作用的光波其频率差ω_1-ω_2和相应分子的振动模ω-r共振,对频率为ω_(as)=2ω_1-ω_2的四波混频光信号强度I_(as)的增强来获取该分子的振动结构信息的(图1(a))。当入射光束ω_2有较宽的频带结构,并满足ω_1-ω_2=ω_r的条件下,视分子振动模频率的不同,将有多条ω_(as)谱线同时出现, 相似文献
18.
《Microwave Theory and Techniques》1977,25(10):825-830
Wide-band balanced line microwave hybrids each consisting of lossless two-ports and a "reversed-phase hybrid ring" are presented. The two-ports can be designed for wide-band match and the new device is shown to have the same frequency independent properties as the basic hybrid ring. Two special two-ports are treated: one consists of open-circuited series stubs and short-circuited shunt stubs while the other consists of transmission-line cascades. The hybrid ring with matching stubs has been described previously, but is difficult to realize. The hybrid ring matched with transmission-line cascades is a new development which simplifies the practical realization. A complete synthesis procedure is presented and design data for 3-, 6-, 10-, and 15-dB coupling are tabulated. 相似文献
19.
The possibility of synthesis of the lead, arsenic, and bismuth chalcogenides with liquid encapsulation has been investigated.
The conditions and results of the synthesis of PbSe, PbS, PbTe, Bi2Te3, and As2Te3, as well as solid solutions in the systems PbSe-CdSe and Bi2Te3-Bi2Se3 are reported. The obtained materials have been used for fabrication of thin-film photodetectors and interference filters
for infrared radiation. Recommendations concerning the choice of fluxes for liquid encapsulation and the temperature conditions
of synthesis are given. 相似文献
20.
In this paper parallel metallic strips FSSs with a ring are introduced and analyzed by the WCIP method for their simple modeling characterized by independent resonant frequencies due to its non-coupled metallic elements. Two FSS structures are manufactured and measured. A FSSs synthesis approach is presented and the curves relating the desired resonant frequencies to the FSS metallic elements lengths responsible of theses frequencies are plotted. To test the synthesis, approach the two manufactured FSSs frequency responses are taken as the desired ones and the proposed synthesis approach is used to determine the metallic strips and the ring lengths for the FSSs unit cell. WCIP results are compared to measurements and a good agreement is observed. For complex pattern FSS the resonant frequencies sources are not always easy to be determined. Thus an equivalent FSS based on metallic strips and a ring can be used maintaining the same frequency response in the limit of the proposed approach. The synthesis approach is used to determine its equivalent FSS structure of a published complex FSS pattern. WCIP method and HFSS software results of the equivalent FSS are compared to published measurements and a good agreement is recorded. 相似文献