Resolution improvement was attempted with the following two items :- Adjustment in Boundary conditions of photosensitive layer and surfaceprotection layer of amorphous silicon drum.- Adjustment of doping amount of impurity in photosensitive layer.To achieve 600(dpi) high resolution, up till today, photosensitive layer thickness had to be reduced. But this time, high resolution was achieved without reducing photosensitive layer thickness. The minimum doping amount of impurity(B2H6) was identified, and by optimizing impurity doping amount, a kind of characteristics which has both charging capability and resolution capability was obtained. Here is the report to explain the details.