銀塩写真の感光理論とその電子写真的意義

抄録

The present author expressed his opinion on the sensitivity of silver halide emulsion in 1950²⁾ maintaining that its change by light is rather more physical contrary to Mott's theory 1938. He defines¹⁾ also the photography of silver halide as a sort of Electrophotography in the sense that the light change of photosensitive material is physical.
This report is written in order to make clear the above mentioned maintenance.
The result is as follows.
Silver halide crystals are made as p type semiconductor at the first ripening. The crystals are desired to be of moderate size and complete. Those with defects are not good. The second ripening process is to adhere to the surfaces of those p type crystals the active gelatine or the active addition agents, which have semiconductive and photoconductive property, and also are desirable to be n type.
Thus, we obtain the emulsion crystals which have p n contact as semiconductor. This p n contact in emulsion crystals is the true form and essence of the socalled sensitivity speck.
But, this p n contact is electronically not in thermal equilibrium before exposure, namely the Fermi levels on both sides of p n junction are not equivalent. By exposure, charge carriers are transferred from the one side to the other in p n contact, and space charges emerge like Fig. 1(b) or (c) at the p n contact in proportion to the numbers of absorbed light quantums by moderate light intensity, so that Fermi levels on both sides move toward the equilibrium. The emergency of space charge at the p n contact by light or other effects is the latent image or the cause of fog. This charged part of p n contact also becomes the development centre.