OCB模式液晶光栅的光学特性研究
发布时间：2018-12-10 07:40
【摘要】：向列相液晶具有双折射特性与介电常数各向异性,可以通过较低的电场来控制其光学性能。由向列相液晶制作的液晶光栅具有重量轻、尺寸小、功耗低、寿命长、成本低、驱动电压低等特点,在平板显示,空间光通信装置,传感器等领域有很大的应用潜力。目前,液晶光栅应用的一个缺点就是响应速度慢,除此之外,在光束扫描、偏转、控制等功能上都符合实用化的要求。本文设计了一种OCB液晶光栅结构,光栅由两片ITO玻璃基板组成,一块基板上用光刻技术制做出叉指电极,另一块基板为连续电极,通过在两块基板之间施加电压,使液晶分子发生周期性的排列,入射光透过液晶层后产生相位差发生衍射现象,形成液晶光栅。OCB(光学补偿弯曲)模式是利用液晶分子在初始偏压下维持在弯曲状态,当加上驱动电压时可以快速的由弯曲变为垂直状态,且能抑制液晶分子偏转时产生的回流效应,与从平行状态变为垂直状态相比,响应时间显著降低。文中用混合平行取向PI和垂直取向PI方式得到使液晶与基板成5～6度预倾角的条件,制作出低预倾角OCB液晶光栅样品和平行液晶光栅样品,研究了对响应时间影响较大的因素液晶粘滞系数,盒厚和低预倾角下的偏压。对不同条件下的OCB液晶光栅和平行液晶光栅进行研究,发现液晶的粘滞系数越小,响应时间越短,盒厚越薄,响应时间越短,初始偏压越高,响应速度越快。在相同条件下,OCB液晶光栅响应速度明显高于平行液晶光栅,响应时间仅为平行光栅的三分之一。测量了不同盒厚条件下OCB液晶光栅和平行液晶光栅0级,1级以及2级的衍射效率,随着电压的升高0级衍射效率下降,1级和2级衍射效率都是先上升后略有下降。OCB模式液晶光栅1级和2级的最高衍射效率都高于平行模式液晶光栅,其12μ m样品1级最高衍射效率可以达到33%,随着盒厚的降低,响应速度提高,衍射效率下降,尚需进一步优化以得到高衍射效率的快速响应样本。
[Abstract]:Nematic liquid crystals have birefringence and anisotropy of dielectric constant, which can be controlled by low electric field. Liquid crystal gratings fabricated by nematic liquid crystal have the advantages of light weight, small size, low power consumption, long life, low cost and low driving voltage. It has great application potential in the fields of flat panel display, space optical communication device, sensor and so on. At present, one of the disadvantages of liquid crystal grating application is its slow response speed. In addition, it meets the practical requirements in beam scanning, deflection, control and other functions. In this paper, a structure of OCB liquid crystal grating is designed. The grating is composed of two ITO glass substrates. The cross finger electrode is fabricated by lithography on one substrate, and the other substrate is a continuous electrode, by applying voltage between the two substrates. The liquid crystal molecules are arranged periodically and the phase difference is diffracted when the incident light passes through the liquid crystal layer. The. OCB (optical compensation mode of liquid crystal grating is used to maintain the liquid crystal molecule in the bending state under the initial bias voltage. When the driving voltage is added, it can quickly change from bending to vertical state, and can restrain the reflux effect of liquid crystal molecule deflection. Compared with the parallel state to the vertical state, the response time is significantly reduced. In this paper, the conditions of predip angle between liquid crystal and substrate are obtained by mixing parallel orientation PI and vertically oriented PI. The low predip angle OCB grating sample and the parallel liquid crystal grating sample are fabricated. The factors affecting the response time, such as the viscosity coefficient of liquid crystal, the cell thickness and the bias voltage at low predip angle, are studied. The OCB and parallel liquid crystal gratings under different conditions are studied. It is found that the smaller the viscosity coefficient, the shorter the response time, the thinner the cell thickness, the shorter the response time, the higher the initial bias voltage and the faster the response speed. Under the same conditions, the response speed of the OCB liquid crystal grating is obviously higher than that of the parallel liquid crystal grating, and the response time is only 1/3 of that of the parallel liquid crystal grating. The diffraction efficiency of OCB liquid crystal grating and parallel liquid crystal grating of 0, 1 and 2 order are measured under different cell thickness. The diffraction efficiency of 0 order decreases with the increase of voltage. The first and second order diffraction efficiency of the OCB liquid crystal grating is higher than that of the parallel mode liquid crystal grating, and the maximum diffraction efficiency of the first order of the 12 渭 m sample can reach 330.The diffraction efficiency of the first order and the second order of the OCB mode liquid crystal grating are both higher than that of the parallel mode liquid crystal grating. With the decrease of the cell thickness, the response speed increases and the diffraction efficiency decreases. Further optimization is needed to obtain the fast response samples with high diffraction efficiency.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH74
本文编号：2370217
[Abstract]:Nematic liquid crystals have birefringence and anisotropy of dielectric constant, which can be controlled by low electric field. Liquid crystal gratings fabricated by nematic liquid crystal have the advantages of light weight, small size, low power consumption, long life, low cost and low driving voltage. It has great application potential in the fields of flat panel display, space optical communication device, sensor and so on. At present, one of the disadvantages of liquid crystal grating application is its slow response speed. In addition, it meets the practical requirements in beam scanning, deflection, control and other functions. In this paper, a structure of OCB liquid crystal grating is designed. The grating is composed of two ITO glass substrates. The cross finger electrode is fabricated by lithography on one substrate, and the other substrate is a continuous electrode, by applying voltage between the two substrates. The liquid crystal molecules are arranged periodically and the phase difference is diffracted when the incident light passes through the liquid crystal layer. The. OCB (optical compensation mode of liquid crystal grating is used to maintain the liquid crystal molecule in the bending state under the initial bias voltage. When the driving voltage is added, it can quickly change from bending to vertical state, and can restrain the reflux effect of liquid crystal molecule deflection. Compared with the parallel state to the vertical state, the response time is significantly reduced. In this paper, the conditions of predip angle between liquid crystal and substrate are obtained by mixing parallel orientation PI and vertically oriented PI. The low predip angle OCB grating sample and the parallel liquid crystal grating sample are fabricated. The factors affecting the response time, such as the viscosity coefficient of liquid crystal, the cell thickness and the bias voltage at low predip angle, are studied. The OCB and parallel liquid crystal gratings under different conditions are studied. It is found that the smaller the viscosity coefficient, the shorter the response time, the thinner the cell thickness, the shorter the response time, the higher the initial bias voltage and the faster the response speed. Under the same conditions, the response speed of the OCB liquid crystal grating is obviously higher than that of the parallel liquid crystal grating, and the response time is only 1/3 of that of the parallel liquid crystal grating. The diffraction efficiency of OCB liquid crystal grating and parallel liquid crystal grating of 0, 1 and 2 order are measured under different cell thickness. The diffraction efficiency of 0 order decreases with the increase of voltage. The first and second order diffraction efficiency of the OCB liquid crystal grating is higher than that of the parallel mode liquid crystal grating, and the maximum diffraction efficiency of the first order of the 12 渭 m sample can reach 330.The diffraction efficiency of the first order and the second order of the OCB mode liquid crystal grating are both higher than that of the parallel mode liquid crystal grating. With the decrease of the cell thickness, the response speed increases and the diffraction efficiency decreases. Further optimization is needed to obtain the fast response samples with high diffraction efficiency.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TH74
【参考文献】
相关期刊论文 前1条
1 任洪文,黄锡珉,王宗凯,马凯;聚合物分散液晶(PDLC)光栅的制备及其光衍射特性[J];光散射学报;1997年Z1期
，本文编号：2370217
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