Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Patent
1985-12-16
1987-06-09
Goodrow, John L.
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
430 95, G03G 5082
Patent
active
046720154
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an electrophotographic member which contains amorphous silicon, and particularly to an improved structure of an electrophotographic member for a laser beam printer which makes use of a semiconductor laser.
BACKGROUND ART
Amorphous selenium, a composite material consisting of a CdS powder and an organic binder, and an organic photoconductive member have heretofore been used as electrophotographic members. In recent years, attention has been given to hydrogenated or halogenated amorphous silicon that works as a photoconductive material having a high resistance. Compared with the conventional photoconductive materials for electrophotography, this material exhibits a high photo response in the range of visible light, increased hardness and decreased toxicity, and is considered to be close to an ideal electrophotographic member. However, this material does not exhibit sharp photo response over a range of 780 to 800 nm where the wavelengths of light emitted by a semiconductor laser fall. Therefore, it has been desired to increase the sensitivity of this material for the light of wavelengths that lie over this region.
The art which uses amorphous silicon as the photosensitive film has been reported in Japanese Patent Laid-Open No. 78135/1979, and the structure which uses amorphous silicon as a photosensitive base film to exhibit a high sensitivity for the light of long wavelengths has been reported in Japanese Patent Laid-Open No. 146142/1981.
DISCLOSURE OF INVENTION
The object of the present invention is to provide structure of a photosensitive member which is highly sensitive and stable over a region of long wavelengths of light from a semiconductor laser.
In order to increase the sensitivity for the light of long wavelengths, the present invention deals with a composite structure consisting of two or more films that are sensitive to the light of long wavelengths, that form carriers, and that have different optical or electrical characteristics.
Concretely speaking, the present invention is concerned with an electrophotographic member having amorphous silicon layers, wherein at least two semiconductor films are laminated to form a region that produces carriers responsive to the light of long wavelengths, the two semiconductor films having at least different forbidden band gap widths or different electrical conductivities.
When a plurality of semiconductor films are used having different forbidden band gap widths, the forbidden band gap width should be narrowed toward the interface relative to the photosensitive base member. This helps decrease the difference in the potential and, whereby the photo carriers formed in the sensitizing layer can be easily taken out. Therefore, this is also effective to increase the sensitivity for the light of long wavelengths.
When the semiconductor layers having different electric conductivities are used, the electrons and positive holes are isolated well by the junction electric field of photo carriers formed in the sensitizing layer by the irradiation of light, and the sensitivity can be substantially increased.
It is allowable to use semiconductor layers of these two kinds in combination, as a matter of course.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a diagram showing in cross section the structure of a photosensitive member according to the present invention;
FIG. 2 is a diagram showing the band structure of the photosensitive member which is sensitive to the light of long wavelengths;
FIG. 3 is a diagram showing the band structures of sensitizing layers according to the present invention; and
FIG. 4(a) is a graph showing the spectral sensitivity of the electrophotographic member of the present invention in comparison with that of the conventional electrophotographic member, and
FIG. 4(b) is a graph showing the dark attenuation factor of voltage of the electrophotographic member of the present invention in comparison with that of the conventional electrophotographic member.
BEST MODE FOR CARRYING OUT THE INVENTION
REFERENCES:
patent: 4451549 (1984-05-01), Kato
patent: 4532198 (1985-07-01), Saitoh et al.
patent: 4555462 (1985-11-01), Yamazaki
Fujikura Makoto
Maruyama Eiichi
Matsubara Hirokazu
Shimada Toshikazu
Goodrow John L.
Hitachi , Ltd.
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