METHOD OF TREATING PHOTOCONDUCTORS OF THE CADMIUM SERIES TO FORM ELECTROPHOTOSENSITIVE MATERIAL MANIFESTING PERSISTENT INTERNAL POLARIZATION

摘要

1,179,649. Electrophotographic material. KATSURAGAWA DENKI K.K. 14 Aug., 1968 [22 Aug., 1967], No. 38825/68. Heading H1K. Cadmium compounds exhibiting persistent internal polarization for use in electrophotography are made by diffusing impurities into the surface layer of the compound but not the body of the compound whereby deep trap levels are formed at the surface. CdS, CdSe, or ZnCdS 2 powder is fired with Cu or Ag bromide or chloride in an inert atmosphere or air. The powder is fired a second time in an atmosphere of sulphur. In an example, CdS, CdCl 2 , NH 4 Cl and CuCl 2 are fired in a quartz tube at 600‹ C., washed, dried, mixed with CuSO 4 and S and fired under N 2 at 600‹ C. The twicefired powder is mixed with polyvinyl acetate in an organic solvent and coated on a polyester film. Alternatively a support of metal foil or conductive glass may be used or an electrophotographic layer may be coated with a conductive paint. An insulating layer may be provided on top of the photo-conductive layer and also between the photo-conductive layer and the support.