量子化学計算によるポリイミドフィルムのヘテロ電荷蓄積の水分効果の検討

概要

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A lot of hetero charge was accumulated in Polyimide (PI) film containing water under high electrical stress. The positive charge was observed near cathode and the negative charge was near anode. The dynamic behavior of hetero charge complicated characteristics in space and time. A small amount of hetero charge was observed at an initial period, however the accumulated hetero charge disappeared soon. A few minutes later, a lot of hetero charge was observed again and a breakdown occurred finally. In order to analyze the complicated hetero charge behavior, the energy band structure of Polyimide (3 molecular size) which was subjected to water (some H2O) was obtained by using the Quantum Chemical Calculation. The hole-electron pair generation probability and the hole and electron hopping probability were evaluated from the values of energy gap and effective trap level respectively, which were obtained from the Quantum Chemical Calculation. It was found that water uptake narrowed the energy gap in PI, and the generation probability of hole-electron pair was increased with decreasing energy gap. In addition, the hopping probability of hole carrier also increased with decreasing the energy gap.