Lee In-Hye, Shin Dong-Myung
J Nanosci Nanotechnol. 2018 Oct 1;18(10):7207-7210. doi: 10.1166/jnn.2018.15476.
Photo-activator is a kind of additive that can improve the anchoring energy by attacking some of the bonds of polyimide (PI). Photo-activators were synthesized from the reaction of cyclohexanone oxime with three different anhydrides, respectively. Each activator generates different active radicals when irradiated. These fragmented and activated radicals are responsible for the liquid crystal (LC) alignment of PI film. The reactivity was confirmed through UV-Visible spectroscopy. All the three photo-activators had characteristic bimodal-shaped absorption peaks at 270∼280 nm. The photofragmentation reactions were completed within 1 min of UV irradiation, which implies that the activators are highly reactive to UV light. The short reaction time is very useful for liquid crystal display (LCD) factory applications. The photo-activator using crotonic anhydride (CAP) showed the highest surface anchoring energy, of 6.92 × 10-5 J/m2, compared to that of the other activators and that obtained by rubbing methods; (1.11 × 10-5 J/m2). This result was obtained due to resonance stabilization from the allyl radicals of CAP. The photo-activator using acetic anhydride (AAP) reached its maximum anchoring energy in less than 3 min of irradiation, which is the shortest optimum irradiation time. Considering the fact that this process does not require additional procedure and time, the photo-activators can be considered an innovate additive.
光活化剂是一种添加剂，它可以通过破坏聚酰亚胺（PI）的一些化学键来提高锚固能。光活化剂分别由环己酮肟与三种不同的酸酐反应合成。每种活化剂在光照时会产生不同的活性自由基。这些断裂和活化的自由基负责PI膜的液晶（LC）取向。通过紫外可见光谱法证实了其反应活性。所有这三种光活化剂在270∼280nm处都有特征性的双峰形吸收峰。光碎片化反应在紫外线照射1分钟内完成，这意味着活化剂对紫外线具有高反应活性。短反应时间对于液晶显示器（LCD）工厂应用非常有用。与其他活化剂以及通过摩擦方法获得的活化剂（1.11×10 -5 J/m2）相比，使用巴豆酸酐（CAP）的光活化剂显示出最高的表面锚固能，为6.92×10 -5 J/m2。由于CAP的烯丙基自由基的共振稳定作用，得到了这一结果。使用乙酸酐（AAP）的光活化剂在照射不到3分钟的时间内达到其最大锚固能，这是最短的最佳照射时间。考虑到该过程不需要额外的步骤和时间，光活化剂可被视为一种创新的添加剂。
