Ahn Jong-Soo, Park Su Hong, Kwon Na Yeon, Cho Min Ju, Paek Sang-Hyon, Choi Dong Hoon
Department of Chemistry, Research Institute for Natural Science, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Korea.
Department of Chemical Engineering, Kyung Hee University, 1732, Deogyeong-daero, Giheung-gu, Yongin-si 17104, Korea.
Polymers (Basel). 2021 Nov 11;13(22):3903. doi: 10.3390/polym13223903.
This study demonstrated the use of a thermally crosslinked polyimide (PI) for the liquid crystal (LC) alignment layer of an LC display (LCD) cell. Polyamic acid was prepared using 4,4'-oxydianiline (ODA) and 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA). The 6FDA-ODA-based polyimide (PI) prepared by the thermal cyclic dehydration of the polyamic acid (PAA) was soluble in various polar solvents. After forming a thin film by mixing trifunctional epoxide [4-(oxiran-2-ylmethoxy)-N,N-bis(oxiran-2-ylmethyl)aniline] with the 6FDA-ODA-based PAA, it was confirmed that thermal curing at -110 °C caused an epoxy ring opening reaction, which could result in the formation of a networked polyimide not soluble in tetrahydrofuran. The crosslinked PI film showed a higher rigidity than the neat PI films, as measured by the elastic modulus. Furthermore, based on a dynamic mechanical analysis of the neat PI and crosslinked PI films, the glass transition temperatures (Ts) were 217 and 339 °C, respectively, which provided further evidence of the formation of crosslinking by the addition of the epoxy reagent. After mechanical rubbing using these two PI films, an LC cell was fabricated using an anisotropic PI film as an LC alignment film. LC cells with crosslinked PI layers showed a high voltage holding ratio and low residual direct current voltage. This suggests that the crosslinked PI has good potential for use as an LC alignment layer material in advanced LCD technologies that require high performance and reliability.
本研究展示了一种热交联聚酰亚胺（PI）在液晶（LC）显示（LCD）单元的液晶取向层中的应用。聚酰胺酸是使用4,4'-二氨基二苯醚（ODA）和4,4'-（六氟异丙基）二邻苯二甲酸酐（6FDA）制备的。通过聚酰胺酸（PAA）的热循环脱水制备的基于6FDA-ODA的聚酰亚胺（PI）可溶于各种极性溶剂。在将三官能环氧化合物[4-（环氧乙烷-2-基甲氧基）-N,N-双（环氧乙烷-2-基甲基）苯胺]与基于6FDA-ODA的PAA混合形成薄膜后，证实-110°C的热固化会引起环氧开环反应，这可能导致形成不溶于四氢呋喃的网状聚酰亚胺。通过弹性模量测量，交联的PI膜比纯PI膜表现出更高的刚性。此外，基于对纯PI膜和交联PI膜的动态力学分析，玻璃化转变温度（Ts）分别为217和339°C，这进一步证明了通过添加环氧试剂形成了交联。使用这两种PI膜进行机械摩擦后，使用各向异性PI膜作为LC取向膜制造了一个LC单元。具有交联PI层的LC单元显示出高的电压保持率和低的残余直流电压。这表明交联PI在需要高性能和可靠性的先进LCD技术中作为LC取向层材料具有良好的应用潜力。
