【作者】 孙玉宝；

【导师】 傅广生；

【作者基本信息】 河北工业大学 ， 微电子学与固体电子学， 2010， 博士

【摘要】 液晶显示器已经广泛应用于各种显示领域,具有重量轻、薄型化和功耗少等优点,但是其响应时间特性还不能令人满意。传统的动力学理论对典型液晶显示模式进行了详细的理论研究,指出液晶材料参数和器件参数决定了响应时间,液晶材料参数主要为转动粘滞系数和弹性常数,器件参数包括液晶层厚度和驱动电压。对于复杂的液晶显示模式,很少人去详细地理论研究它们的响应时间特性,多是采用数值模拟、实验测试结果的理论分析。本文中采用小形变近似和连续体理论研究液晶显示模式中的动力学响应。研究了表面锚定能和表面粘滞系数在液晶显示器动力学响应中的影响,详细地研究共面转换、光学自补偿弯曲和垂面排列液晶显示模式中的响应时间,并对目前可实现亚微妙响应时间的双频液晶、铁电液晶和蓝相液晶显示模式的快速响应机制进行了研究。应用等效盒厚和求本征值方法研究了锚定能对指向矢响应时间的影响。详细研究了基板表面处液晶的动力学响应,通过数值模拟确定表面转动粘滞系数对基板表面处液晶的快响应和慢响应的影响。研究光学和指向矢响应时间之间的关系,研究扭曲形变和弯曲、展曲形变在光学响应时间上的差别。理论上给出展弯曲形变的光学下降响应时间至少比扭曲形变快一倍。对于复杂的显示模式,可以比较其中的扭曲和展弯曲形变的响应时间来确定显示模式的光学响应时间。研究共面转换模式中大摩擦角度、扭曲和超扭曲结构对响应时间的影响,得到了它们的响应时间公式,并通过模拟计算了它们的动力学响应过程,得到超扭曲结构具有4倍快于传统结构的响应速度。对比共面转换模式,研究了双面边缘场驱动沿面排列液晶显示模式的响应机制,对该显示模式的光学特性进行了理论分析。研究光学自补偿弯曲模式中展曲和弯曲状态的临界电压,展曲到弯曲的转变电压以及弯曲状态下的响应机制。理论上给出临界电压的理论公式。对展曲到弯曲的转变过程及转变电压,给出了模拟结果,并提出了用于测量表面转动粘滞系数的一种方法。理论上研究该显示模式的响应时间的公式,给出动力学响应机制。研究垂面排列显示模式中使用负性和正性液晶材料的差别,以及在动力学响应过程中,它们的响应时间的不同点。负性液晶显示模式的响应时间为经典结果,而正性液晶显示较复杂,共面转换模式的响应时间与负性液晶相同。对于三层电极驱动的显示模式,则在上升和下降过程都有电场参与,理论上给出下降响应时间公式。对于双面边缘场驱动垂面排列厚盒模式,因为在液晶在横向的变化周期远小于液晶层厚,因此该显示模式的响应时间受到横向周期的影响,理论上推导出该显示模式的下降响应时间公式。研究双频液晶、铁电液晶和蓝相液晶显示模式的动力学响应机制,给出了双频液晶的响应时间公式。分析了铁电液晶响应过程中的介电力和自发极化与电场之间的作用力大小,明确了铁电液晶快速响应特点的响应机制。对蓝相液晶显示模式的阈值电压和响应时间进行了理论分析,建立了一个简单模型,模拟计算了该显示模式的电光特性。更多还原

【Abstract】 Liquid crystal displays were widely used in many fields because of its light weight, thin panel and low power consumption, however, its response speed is not favorable. Some typical liquid crystal display modes were researched in detail using the classical dynamical theory, the results show that the factors affect the response time include the rotational viscosity and elastic parameters of liquid crystal, the thickness of the liquid crystal layer and the driven voltage. For the liquid crystal display mode with complex configuration, most people gave the theoretical analysis on the results of numerical simulation or experimental data. In this thesis, the dynamic responses of liquid crystal display modes were researched through the small deformation approximation and the continuum elastic theory. The effects of surface anchoring and surface viscosity on the dynamical response of liquid crysal display were researched, the response times of the in-plane switching, optically compensated bend and vertical alignment liquid crystal display modes were studied in detail, moreover, the response mechanism of the dual frequency, ferroelectric and blue phase liquid crystal display modes with submillisecond response times were analyzed.The anchoring energy’s effect on the director response time is studied by using effective cell gap and solving eigenvalue method. The dynamic responses of the liquid crystal near the substrates in the fast and slow response processes were analyzed in detail, and the effect of surface rotational viscosity is determined by the numerical simulation. The relationships of the director and optical response times were shown from the theoretical analysis, in the pure twist, splay and bend deformations. From the results, the optical decay response time of the splay and bend deformation is improved 2X at least than that of the twist deformation. In the cell with the three deformations, the optical response time is also determined by comparing the response times of the twist and splay-bend deformation.The effects of the rubbing angle, twist and super twist configuration on the response times were researched, and the equations of response times were obtained. The response time of the super twist configuration has four times faster than that of the conventional configuration from the theoretical analysis and numerical simulation of the dynamic response. The response mechanism of double fringe field switching driven homogeneous alignment liquid crystal is researched comparing with in-plane switching mode, and the optical characteristics of this mode is analyzed.The critical voltage and transition voltage of the splay to bend transition, and the response mechanism in the bend state were studied in the optically compensated bend liquid crystal display mode. The analytical equation to calculate the critical voltage is derived, the transition voltage and the transitional process are simulated, and moreover the transitional process can be used to measure the surface rotational viscosity. The equations of the response time were derived and the fast response mechanism was summarized.The difference of the response time for the vertical alignment liquid crystal display mode with negative and positive dielectric liquid crystal material were researched. The response time of the cell with negative liquid crystal is similar to that of the classical vertical alignment mode. The in-plane switching vertical alignment cell with positive liquid crystal is same as that of the cell with negative liquid crystal. The vertical alignment cell driven by the tri-layers electrodes, the electric field has an effect in the rise and decay processes, the decay response time is derived. In the double fringe field switching vertical alignment mode, the period of liquid crystal deformation in the transversal direction is less than the thickness of liquid crystal layer, and instead of the cell gap in lognitudinal direction, shows the cell gap effect on the response time, the equation of the decay response time is theoretically derived.The dynamic response mechanism of dual frequency liquid crystal, ferroelectric liquid crystal and blue phase liquid crystal modes were analyzed. The equations to calculate the response times of the dual frequency liquid crystal display are analyzed through the theoretical analysis. Through comparing the dielectric force and the force between the spontaneous polarization and the electric field, the fast response mechanism of the ferroelectric liquid crystal is clear. The threshold voltage and the response time of the blue phase liquid crystal mode were theoretically analyzed, and numerically simulate the electro-optic characteristics using a simple model.更多还原