聚合物分散型液晶结构紫外光稳定性分析

Ultraviolet light stability of polymer structure based on polymer dispersed liquid crystal

聚合物分散型液晶组件技术是市面上常用的散射式光开关系统,且常常应用于具隐私保护性之电控切换窗户中。然而对于室外的应用,属于有机高分子材料的液晶材料与聚合物结构对于照射紫外光之稳定性与耐受性值得被讨论,尤其是较少被讨论之高分子聚合物结构的影响。本研究主要探讨不同聚合物结构之聚合物分散型液晶组件在紫外光照射下光电特性的变化,期待可以了解聚合物结构特性随曝光时间的变化并提出适当之改善方法。本实验藉由选择具有高紫外光稳定性之主体液晶搭配紫外固化胶调配聚合物分散型液晶预聚物,分别探讨不同固化胶比例与光强度等固化条件下,组件照射紫外光后对于光电特性造成的影响,以此了解各种聚合物形貌照射紫外光后之光电特性变化。实验结果显示,照射紫外光后,各种聚合物分散型液晶组件之临界电压仅仅些微提升,但下降时间剧烈地提高,以聚合物比例35%、固化强度2mW/cm^2为例,临界电压从15.57V些微提升至18.18V,下降时间从195.12ms大幅提升至925.26ms。此外,本研究亦发现相对于照射前,照射紫外光后之组件的下降时间对于电压施加时间长短相当敏感,且此现象可藉由调整固化光强度与固化胶浓度有抑制之趋势。本研究呈现了各种聚合物分散型液晶组件在照射紫外光后光电特性的变化,并了解聚合物结构的特性变化的影响。

Polymer dispersed liquid crystal（PDLC）is a commercially available technique which is already utilized to scattering mode light switching and also developed in electrically privacy-switching window.However,there is still essential to be discussed that the ultraviolet（UV）stability and tolerability in organic liquid crystal（LC）materials and polymer structure for outdoor applications,especially the rarely discussed polymer structure.The electro-optical（E-O）effects of UV light-irradiated PDLC in different curing condition are compared in this work.The understanding of UV stability inpolymer structure and the improved methods are expected.The precursor is prepared by the high UV stability host LC and optical adhesive（OA）.In order to realize the effect between different polymer structure morphology,the proportion of the optical adhesive and the curing intensity are discussed in this work.The results revealed that the threshold voltage only slightly rose but the response time dramatically increased.For example,the threshold voltage slightly rose from 15.57 Vto 18.18 V,the field off time dramatically increased from 195.12 ms to 925.26 ms under 35% OA concentration and 2mW/cm^2 curing intensity.In addition,it is observed that the response time after UV irradiation is more sensitive to the voltage duration time than before.This phenomenon can be suppressed by controlling the curing intensity and OA concentration.This work demonstrated the variation of E-O effect in different type of PDLC after irradiating UV light.The influence from polymer structure is realized.