| 摘要 |
1,027,354. Electrophotographic apparatus. RANK XEROX Ltd. Sept. 20,1963 [Oct. 1,1962], No.37066/63. Heading G2H. [Also in Division H1] In an automatic electrophotographic copying machine, adapted for reproducing continuous tone originals, utilizing an electrophotographic plate with a substrate containing an optical screen provided with a pattern of small, alternating, discrete transparent and opaqueareos (see Division H1), the plate is in the form of a transparent drum 21 supporting an optical screen 22 and a photoconductive insulating layer 23. An earthed conductive contact is made to the inside face of the photoconductive layer 23 either by making the screen 22 or conductive material or by interposing a thin transparent conductive layer between the screen 22 and the layer 23. The plate is charged by a corona discharge apparatus 26 and exposed to an image produced by projector 28. The inside of the drum is simultaneously illuminated by source 24. The optical screen 22 allows small "islands" of photoconductive layer 23 to be discharged thus breaking up the areas of charge to produce better reproduction of large areas of tone due to the strong fringing fields obtained. The plate is developed by cascading a mixture 32 of carrier beads and toner particles over the plate. A copy web 36 is pressed against the drum by idlers 37 and a unit 38 transfers the toner particles to web 36 by corona discharge. Alternatively, web 36 may be adhesive to the toner particles. The image on the web is fixed by heating unit 39 and the plate is cleaned by brush 42. With screen patterns coarser than about 80 lines per inch the pattern is visible after development but with finer screens this effect becomes negligible. The light source 24 is switched off when reproducing line copies since superimposition of the screening pattern breaks up the strong fringing fields present and reduces the quality of the copies. |
