聚酰亚胺液晶垂直取向膜的制备与性质

Preparation and Properties of a Novel Polyimide Liquid Crystal Vertical Alignment Layer

虽然传统的平行取向技术已广泛应用于液晶显示器的生产,但其存在窄视角、低对比度和慢响应时间等问题,因此液晶分子的垂直取向技术在国外已经被广泛研究。在实验中,一种含有液晶结构侧链的聚酰亚胺通过均苯四羧酸二酐(PMDA),4,4′-二胺基二苯甲烷(MDA)和4-己氧基联苯酚-3′,5′-二胺基苯甲酸酯(C6BBDA,实验室自制)共聚被制备,并且被用作液晶取向膜,研究其取向性能。试验发现,该种聚酰亚胺作为取向膜可以诱导液晶分子垂直取向,即使在摩擦之后依然可以获得大于89°的预倾角;使用正交偏光显微镜观察所制得液晶盒中的液晶取向效果,发现垂直取向均匀良好;为了测试该垂直取向的热稳定性,将制备的液晶盒在120℃下烘烤12h后,偏光显微镜下观察发现垂直取向仍然良好均匀,表明该取向膜具有良好的热稳定性。

A polyimide （PI） prepared by copolymerization of pyromellitic dianhydride, 4,4＇-methylenedianiline and 4-butoxy-biphenol-3＇,5＇-diaminobenzoate in N-methyl-2-pyrrolodone was used as liquid crystal （LC） vertical alignment layer. The chemical structure of the PI was confirmed by Fourier Transform Infrared Spectroscopy. Subsequently, LC cells were fabricated using prepared PI as the alignment layer and the alignment properties were investigated. Without rubbing, the PI showed the vertical alignment. When the rubbing is performed, the pretilt angles induced by the PI were hardly changed. The polarizing microscopy validated that the vertical alignment was uniform. Although these LC cells using the PI as the alignment layer were baked at 120℃ for 12 h, the vertical alignment of LCs was still uniform and stable, and the pretilt angles closely to 90° were still kept.