| 摘要 |
1,221,347. Electro-photographic development. EASTMAN KODAK CO. March 11, 1968 [March 13, 1967], No. 11762/68. Heading G2H. A method of forming an electro-photographic image comprises imagewise exposing a photoconductive layer carried by an electrically conducting layer, electro-phoretically depositing toner particles on the image areas, and treating the photo-conductive layer in a manner which inhibits deposition of toner in non-image areas. In one embodiment, shown in Fig. 1, an image of a transparency 26 is projected on to the photoconductive layer 22 carried on a conductive layer 21, which is placed in and insulated from a metal developing cassette 10, and a field applied between layer 22 and a transparent development electrode 19 causes negatively charged toner particles 13, in an insulating organic liquid 12, to be deposited on the image areas. Toner deposition in non-image areas is inhibited by pre-charging layer 22, e.g. with a corona charger, or by a first development step using charged toner particles of low colour density, followed by development with toner particles of high colour density. In a second embodiment Fig.2 (not shown), the photo-conductive layer is exposed through a transparent conductive backing, and positively charged toner particles are used. In a contact printing embodiment Fig.3 (not shown) a pre-charged photo-conductive belt (37) is exposed to a source (34), the image electrophoretically developed by contacting the surface of a developer (11) and the developed image transferred to a paper web (43). The photo-conductive layer 22 may be organic, e. g. a triphenylamine compound or inorganic e.g. selenium, the conductive backing layer 21 may be aluminium or transparent, conducting cellulose acetate, and the development electrode may be of Nesa glass. Many examples are given of toner preparation and composition. |
