基于巯基化合物的聚合物分散液晶的电光性能研究

发布时间：2018-03-02 09:45

本文关键词： 聚合物分散液晶紫外光聚合巯基电光性能微观形貌　出处：《北京科技大学》2017年博士论文　论文类型：学位论文

【摘要】：聚合物分散液晶(Polymer Dispersed Liquid Crystal,PDLC)薄膜是将向列相液晶微滴均匀分散在高分子网络中而形成的复合材料。因其制备方法简单、不需要使用偏振片、基板内表面不需要取向处理、液晶层厚度不需要严格控制、可实现高亮度大面积柔性显示,目前已逐渐成为平板显示领域中研究的热点。在光阀、电控调光玻璃、大面积柔性显示及投影显示仪器等方面具有广泛的应用前景。本论文研究以丙烯酸酯/硫醇高分子网络为基体的PDLC材料、利用扫描电镜观察高分子网络的微观形貌、利用液晶综合参数测试仪测试PDLC薄膜的电光性能、利用紫外/可见/近红外分光光度计测试PDLC薄膜在不同波段光的透过率,研究PDLC薄膜的电光性能的优化方法并进行了综合分析。主要研究内容如下:(1)采用紫外光聚合法制备基于液晶/丙烯酸酯/硫醇的PDLC薄膜,研究了各组分的比例对PDLC薄膜电光性能的影响。实验结果表明:我们可以通过调控PDLC样品中液晶含量以及光可聚合单体硫醇的含量及其官能度对聚合物网络中的液晶微滴尺寸加以控制,从而使PDLC薄膜的电光性能得到优化,获得较低阈值电压的PDLC薄膜材料。(2)通过添加手性化合物制备基于胆甾相液晶/丙烯酸酯/硫醇的聚合物分散液晶(PDChLC)薄膜。实验结果表明:螺距是影响薄膜电光特性的主要因素。随着螺距的减小,薄膜的驱动电压和饱和电压呈逐渐增大的趋势,并且该薄膜的对比度进一步提高。和基于向列相液晶PDLC体系相比较,薄膜驱动电压和饱和电压有所升高,而关态透过率降低,对比度有所提高。这主要是由于胆甾相液晶的螺距越短,螺旋扭曲力就越大,因此驱动电压和饱和电压与螺距变化趋势相反。(3)研究了不同交联剂比率、紫外光强度及聚合温度对聚合物分散液晶薄膜电光性能的影响。研究表明交联剂比率对PDLC薄膜的聚合物网络形貌和液晶微滴尺寸有明显的影响。同时,PDLC薄膜中液晶微滴的尺寸随着聚合温度的上升先减小后增大,而随着紫外光强度的增加逐渐减小。
[Abstract]:Polymer Dispersed Liquid crystal crystal (PDLC) thin film is a composite material formed by uniformly dispersing nematic liquid crystal droplets in polymer networks. Because of its simple preparation method, no polarizer is needed, and the inner surface of the substrate does not need orientation treatment. The thickness of liquid crystal layer does not need to be strictly controlled, it can realize high brightness and large area flexible display, so it has gradually become a hot spot in the field of flat panel display. Large area flexible display and projection display instruments have wide application prospects. In this paper, the PDLC materials based on acrylate / mercaptan polymer network are studied, and the morphology of polymer networks is observed by scanning electron microscope (SEM). The electro-optic properties of PDLC films were tested by liquid crystal comprehensive parameter tester, and the transmittance of PDLC films in different bands was measured by ultraviolet / visible / near infrared spectrophotometer. The optimization method of electro-optic properties of PDLC thin films was studied and analyzed. The main contents were as follows: (1) the PDLC films based on liquid crystal / acrylate / mercaptan were prepared by UV photopolymerization. The effect of composition ratio on electrooptic properties of PDLC thin films was studied. The experimental results show that we can control the content of liquid crystal in PDLC sample, the content of photopolymeric monomer mercaptan and their functionalities on the properties of polymer networks. The size of liquid crystal droplets is controlled, Thus, the electro-optic properties of PDLC thin films are optimized. PDLC thin films with lower threshold voltage were prepared by adding chiral compounds to polymer dispersed liquid crystal films based on cholesteric liquid crystal / acrylate / mercaptan. The experimental results show that pitch is the key factor affecting the electrooptic properties of the films. As the pitch decreases, Compared with nematic liquid crystal liquid crystal (PDLC) system, the driving voltage and saturation voltage of the film are increased, but the off state transmittance is decreased, compared with the nematic liquid crystal PDLC system, the driving voltage and saturation voltage of the film are gradually increasing, and the contrast of the film is further improved. This is mainly because the shorter the pitch of the cholesteric liquid crystal is, the greater the twist force is, so the driving voltage and saturation voltage are opposite to the pitch. The effects of UV light intensity and polymerization temperature on the electrooptic properties of polymer dispersed liquid crystal films were studied. The results show that the ratio of crosslinking agent has a significant effect on the morphology of polymer networks and the size of liquid crystals in PDLC films. The size of microdroplets decreases first and then increases with the increase of polymerization temperature. However, the intensity of ultraviolet light decreases gradually with the increase of UV intensity.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O753.2;TB33

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