Electrophotographic and structural studies on novel photoconductive polyimide films

Novel photoconductive polyimides have been developed, whose monomer units are composed of a series of thiophenylene moieties, -C6H4S-, and imide groups. The most photosensitive polyimide shows an excellent photosensitivity of less than 1.0 μJ/cm2 in the visible light region, 400–570 nm. These photosensitive polyimide films are prepared by polymerizing the cast prepolymer films and annealing at the melting points of the polyimides. In this process their photosensitivities remarkably increase with the increase of crystallinity. From the structural studies by ultraviolet visible absorption, x-ray diffraction, infrared absorption, and x-ray photoelectron spectroscopy measurements, it is proposed that the coplanary conformation takes place in the crystallizing. The overlapped π orbitals, perpendicular to the polymer chains, lead to the more expanded conjugate system.