A fully aromatic unfluorinated polyimide (PI) exhibiting high transparency in the visible region and small thermal expansion was designed and prepared. The formation ability of charge transfer (CT) interactions in PIs estimated using the density functional theory clarified that polychlorine-substituted benzidines should give transparent PIs due to their low electron-donating properties. A combination of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 2,2',6,6'-tetrachloro-4,4'-diaminobiphenyl (4ClBZ) gave a PI exhibiting good transparency (52% at 420 nm and 81% at 600 nm), a high Tg (368°C), a high refractive index (1.6473 at 1.31μm) and a low CTE (13 ppm/K). This material is suitable for thermally stable, transparent, and inexpensive substrates for flexible displays and organic thin film transistors.