偶氮苯磺酸薄膜的光致取向可重复性  

Photoalignment repeatability of azobenzene sulfonic films

作　　者：杨小东 彭增辉[1] 穆全全[1] 刘怀宇 YANG Xiaodong;PENG Zenghui;MU Quanquan;LIU Huaiyu(Changchun Institute of Optics,Fine Mechanics and Physics,Chinese Academy of Sciences,Changchun 130033,China)

机构地区：[1]中国科学院长春光学精密机械与物理研究所,吉林长春130033

出　　处：《液晶与显示》2024年第5期553-560,共8页Chinese Journal of Liquid Crystals and Displays

基　　金：国家重点研发计划(No.2021YFB3600300);国家自然科学基金(No.61975202,No.U2030101)。

摘　　要：偶氮苯磺酸SD1作为一种液晶光致取向材料,具有强锚定、可再次重新取向等优点。本文研究了偶氮苯磺酸光取向材料SD1薄膜在405 nm线偏振光辐照下的光致取向重复写入性能。研究发现,在线偏振光重复擦写曝光SD1膜的过程中,随擦写次数增加,膜饱和有序度持续下降。经过200次重复擦写后(累计能量密度1200 J/cm^(2)),饱和有序度(S)从0.78下降到0.3,取向速度从0.39 s^(-1)下降到0.08 s^(-1)。对重复取向过程中SD1膜的紫外可见(UV-Vis)吸收光谱进行了实时监测,发现在单次取向过程中SD1膜的UV-Vis吸收光谱峰值吸光度先快速下降再缓慢回升后达到饱和,并整体呈现吸收下降的趋势。经历200次重取向后,吸光度从0.10下降到0.03。这表明重取向过程中面内反式SD1的分子数量逐渐减少导致取向能力减弱,因而重写次数受限。在关闭辐照光一段时间后,面内分子数量有一定程度的回升。总之,SD1薄膜在线偏振光重复擦写过程中出现面内分子数量持续下降的现象,由于SD1薄膜面内分子数量直接影响着其取向能力,这种部分可逆的面内分子数量变化导致SD1可重复取向能力有限。As a liquid crystal photooriented material,azobenzene sulfonic SD1 has the advantages of noncontact,strong anchoring and reorientation,etc.In this paper,the photooriented writing performance of SD1 thin film of azobenzene sulfonic acid was studied under 405 nm linearly polarized light.It is found that the saturation degree of SD1 film decreases continuously with the increase of the number of repeated erasings.After 200 times of repeated erasings(Cumulative energy 1200 J/cm^(2)),the saturation degree(S)decreases from 0.78 to 0.3,and the orientation velocity decreases from 0.39 s^(-1)to 0.08 s^(-1).Furthermore,the UV-Vis absorption spectrum of SD1 film during the repeated orientation process was monitored in real time.It is found that the peak absorbance of UV-Vis absorption spectrum of SD1 film decreases rapidly,then slowly rises and reaches saturation during single orientation,and the overall absorption shows a trend of decreasing.After 200 reorientations,the absorption of SD1 film was gradually reduced,and the absorbance decreased from 0.10 to 0.03.This indicates that the number of trans SD1 molecules in the plane decreases during reorientation,resulting in a decrease in orientation ability,and thus a limited number of overwrites.After turning off the light source for a period of time,the number of molecules in the surface increased to a certain extent.To sum up,the number of in-plane molecules in SD1 films continues to decline during the process of repeated erase by online polarized light.Since the number of in-plane molecules in SD1 films directly affects its orientation ability,this partially reversible change in in-plane molecule number leads to limited SD1 repeatable orientation ability.

关 键 词：偶氮苯磺酸 SD1 光致取向 

分 类 号：O753.2[理学—晶体学]