The photosensitive materials are always polymer, when the photochemical reaction carries out, the backbone of polymer probably can obstruct the photosensitive group, which make the reactivity ratio of the film to be low.

• 这主要是由于人们多采用光敏高分子作为成膜材料,光敏基团在空间位置上受到高分子主链的阻隔,定向光化学反应程度低。