To provide an optical density-changing element which has excellent properties that it can be brought into a colored state by applying only a low voltage and that it shows a rapid response speed and becomes completely colorless when restored to a bleached state from the colored state, and which can undergo a change in optical density in response to an applied voltage, to provide an optical element obtained by combining the optical density-changing element with an electromagnetic-wave electromotive force-generating element, and to provide a photographic unit using the optical element.
The optical density-changing element includes, on each of an anode and a cathode, at least one material selected from a material capable of donating and accepting an electron and, as a result of donating and accepting the electron, undergoing a change in absorption spectrum in a visible region and a material undergoing substantially no change in absorption spectrum in the visible region, wherein oxidation potential of the material and flatband potential of an anode semiconductor material satisfy a specific relation, and reduction potential of the material and flatband potential of a cathode semiconductor material satisfy a specific relation. The optical element comprises the optical density-changing element and an electromotive force-generating element which generates electromotive force in response to electromagnetic waves. The photographic unit includes the optical element.
KANEIWA HIDEKI
MATSUNAGA ATSUSHI
MORIMOTO KIYOSHI
Hironori Honda
Toshimitsu Ichikawa
Takeshi Takamatsu
Yuriko Hamada