Research on surface charges of polyimide films by the Kelvin Force Microscope

To investigate the effect of inorganic nanoparticles on the surface charge properties of polyimide (PI) at the micro/nano scale, the measurement on surface charge was carried out with both the original PI film and nano-Al₂O₃ filled corona-resisting PI film by Kelvin Force Microscope (KFM). Experimental results show that: the surface charge accumulation on corona-resisting PI film under the same constraints reduced to 50% of that on original PI film, and charge dissipate quickly for the corona-resisting PI film. Time constant of exponential decay on original PI is four to five times to the corona-resisting PI. It could be deduced from above results that due to doping of Al₂O₃ made the injection barrier increases and the resistivity decreases for corona-resisting PI film than original PI fill. These factors lead to reduce the surface charge accumulation and avoid distortion of local electric field. Hence, the corona resistant performance is enhanced.