Dielectric characterization of unpolymerized and photopolymerized NOA65 in a parallel-plate configuration

Hung-Chi Tseng¹, Hong-Kun Chen^1*, Gen-Wen Hsieh², Wei Lee³

¹Institute of Photonic System, College of Photonics, National Yang Ming Chiao Tung University, Tainan, Taiwan
²Institute of Lighting and Energy Photonics, College of Photonics, National Yang Ming Chiao Tung University, Tainan, Taiwan
³Institute of Imaging and Biomedical Photonics, College of Photonics, National Yang Ming Chiao Tung University, Tainan, Taiwan

* Presenter:Hong-Kun Chen, email:chenhonghkun@gmail.com

Recent decades have witnessed a notable advancement in liquid crystal (LC) research, underscoring the pivotal role of polymer materials in optimizing the performance of LC materials and devices. To illustrate, Norland UV-curable optical adhesive (NOA65) has exhibited promising results across a spectrum of industrial applications. This present study investigates the dielectric behavior of NOA65 in a parallel-plate company cell. Given the broad and asymmetric nature of the dielectric dispersion curve, the two-relaxation Havriliak-Negami model was employed in the study to analyze the complex dielectric spectra of NOA65 before and after photocured. The findings indicate that as temperature increased, the dielectric relaxation of NOA65 shifts to higher frequencies and became superimposed with pseudo-dielectric relaxation, resulting in augmented dielectric loss signals. Additionally, at elevated temperatures, the intrinsic dielectric loss signal of NOA65 becomes undetectable outside the frequency range of the pseudo-dielectric relaxation signal.

Keywords: Polymer, Optical Adhesive, Photopolymerization, Dielectric Spectroscopy, Pseudo-Dielectric Relaxation