聚合物分散液晶薄膜的极化特性及其对电光性能的影响  

Polarization characteristics of polymer dispersed liquid crystal films and their effects on electro-optical properties

作　　者：陈昊鹏 聂永杰 李国倡 魏艳慧 胡昊 鲁广昊 李盛涛[1] 朱远惟[1,2] Chen Hao-Peng;Nie Yong-Jie;Li Guo-Chang;Wei Yan-Hui;Hu Hao;Lu Guang-Hao;Li Sheng-Tao;Zhu Yuan-Wei(State Key Laboratory of Electrical Insulation and Power Equipment,Xi’an Jiaotong University,Xi’an 710049,China;Frontier Institute of Science and Technology,Xi’an Jiaotong University,Xi’an 710054,China;Electric Power Research Institute,Yunnan Power Gird Co.,Ltd.,Kunming 650217,China;College of Automation and Electronic Engineering,Qingdao University of Science and Technology,Qingdao 266000,China)

机构地区：[1]西安交通大学,电力设备电气绝缘国家重点实验室,西安710049 [2]西安交通大学,前沿科学技术研究院,西安710054 [3]云南电网有限责任公司电力科学研究院,昆明650217 [4]青岛科技大学,自动化与电子工程学院,青岛266000

出　　处：《物理学报》2023年第17期320-327,共8页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51907148);中国南方电网科技项目(批准号:YNKJXM20190717);云南省基础研究计划(批准号:202001AU070062);电工材料电气绝缘全国重点实验室(批准号:EIPE23407)资助的课题.

摘　　要：液晶含量和外加电场类型是影响聚合物分散液晶薄膜电光性能的重要因素,而对薄膜微观形貌的分析并不能直接反映电光性能的变化机理.因此本文以液晶材料E7和光聚物NOA65共混制备的聚合物分散液晶薄膜作为研究对象,通过对其极化特性的研究,揭示了在不同液晶含量和不同类型电场下极化过程对薄膜电光性能的调控规律和微观机制.结果表明,在10^(-1)—10^(6)Hz频率范围内,薄膜在低频、中频和高频存在3个松弛极化过程,分别为热离子极化、界面极化和转向极化.通过Arrhenius公式拟合计算了各极化过程的活化能,发现随着液晶含量的增大,转向极化的活化能从0.88 eV下降至0.83 eV,导致液晶分子转向的阈值场强和饱和场强降低.相比于交流电场,直流电场下热离子极化形成内建电场,导致阈值场强和饱和场强大幅增大,而极化弛豫时间的延长会导致响应时间的延长.此项研究对进一步分析和提升聚合物分散液晶薄膜的电光性能具有指导意义.The electro-optical properties of polymer dispersed liquid crystal film vary with liquid crystal content and externally applied electric field,but the analysis of the film morphology cannot directly reflect the mechanism of electro-optical properties.Therefore,the polymer dispersed liquid crystal film prepared by blending liquid crystal material E7 and photopolymer NOA65 is used.Herein,the dielectric polarization regulated electro-optical properties and their related mechanisms under different liquid crystal content and electric fields are revealed.The results show that in a frequency range of 10^(-1)-10^(6) Hz,the film exhibits three relaxation processes respectively at low frequency,medium frequency and high frequency,which are generated by thermionic polarization,interfacial polarization and orientation polarization.According to the Arrhenius equation,the activation energy values of such polarization processes are calculated.It is found that with the increase of liquid crystal content,the activation energy of orientation polarization decreases from 0.88 eV to 0.83 eV,leading the threshold field strength and the saturation field strength of the diversion of liquid crystal molecule to decrease.Thermionic polarization under DC electric field forms an internal electric field,which causes the threshold field strength and saturation field strength to increase greatly,as compared with the scenarios under AC electric field.Such a thermionic polarization also leads the polarization relaxation time to increase,resulting in the extension of response time.This study is of guiding significance in further analyzing and improving the electro-optical properties of polymer dispersed liquid crystal films.

关 键 词：介电松弛 电光性能 极化 弛豫时间 

分 类 号：TN29[电子电信—物理电子学] TB383.2[一般工业技术—材料科学与工程]