The present invention provides a birefringent film that hardly generates cracks even when the film is exposed under a high-temperature and high-humidity environment for a long period of time. The birefringent film of the present invention is a film containing, as a major component, a lyotropic liquid crystalline polycyclic compound containing an acenaphtho[1,2-b]quinoxaline derivative unit in a molecular structure and having a molecular weight of 500 or higher. The birefringent film of the present invention preferably has a refractive index ellipsoid showing a relationship of nx≧nz>ny, and more preferably has an in-plane birefringence of 0.01 or higher at the wavelength of 590 nm.
本发明提供了一种双折射薄膜,即使在高温高湿环境下长时间暴露,也几乎不会产生裂纹。本发明的双折射薄膜是一种包含
亚胺并[1,2-b]
喹喔啉衍
生物单元的莱奥特罗匹液晶
多环化合物作为主要组分,并且具有分子量为500或更高的分子结构的薄膜。本发明的双折射薄膜最好具有折射率椭球体的关系nx≧nz>ny,并且最好在波长为590纳米时具有0.01或更高的面内双折射。