Fang Zikeng, Wan Jiaqi, Li Chenghang, Li Henan, Yan Ying
State Key Laboratory of High-Performance Precision Manufacturing, Dalian University of Technology, Dalian 116024, China.
College of Transportation, Ludong University, Yantai 264025, China.
Polymers (Basel). 2025 May 22;17(11):1436. doi: 10.3390/polym17111436.
LED polymer multilayer films offer clear advantages over single-layer coatings, such as minimized particle settling, finer control over particle distribution, and more precise spectral tuning. However, the standard "coat-dry-coat" process for these multilayer systems often traps air bubbles, degrading film quality and uniformity. This study investigates the air entrainment mechanism in multilayer film formation. Bubbles form when the cured bottom layer exhibits a low contact angle, which destabilizes the advancing liquid front. High-speed microscopy captured these interfacial dynamics, and contact-angle measurements quantified the wetting behavior. Numerical simulations further demonstrated that reduced wettability and vortex formation drive air entrainment. To mitigate air entrainment, a semi-cured slot die coating approach was proposed to modify the surface wettability and suppress the flow instabilities. Incorporating temperature-dependent viscosity into the simulation model improved its predictive accuracy, cutting the error in predicted coating-gap limits from 11.49% to 4.99%. This combined strategy delivers reliable, bubble-free multilayer films and paves the way for more consistent, high-quality LED polymer applications.
与单层涂层相比，LED聚合物多层膜具有明显优势，如颗粒沉降最小化、对颗粒分布的控制更精细以及光谱调谐更精确。然而，这些多层系统的标准“涂覆-干燥-涂覆”工艺常常会困住气泡，降低薄膜质量和均匀性。本研究调查了多层膜形成过程中的空气夹带机制。当固化的底层呈现低接触角时会形成气泡，这会使前进的液面前沿不稳定。高速显微镜捕捉到了这些界面动力学，接触角测量对润湿行为进行了量化。数值模拟进一步表明，润湿性降低和涡流形成会导致空气夹带。为了减轻空气夹带，提出了一种半固化狭缝式模头涂覆方法来改变表面润湿性并抑制流动不稳定性。将温度依赖性粘度纳入模拟模型提高了其预测准确性，将预测的涂层间隙极限误差从11.49%降低到了4.99%。这种综合策略可提供可靠的、无气泡的多层膜，并为更一致、高质量的LED聚合物应用铺平了道路。
