| 摘要 |
675,398. Producing photographs electrically. BATTELLE DEVELOPMENT CORPORATION. March 3, 1950, No. 5416/50. Class 98 (ii). [Also in Groups XVI and XXXV] Secured to an earthed electrically conductive drum 1 is a printing plate 9 (see Group XVI), comprising a flexible metal or other conductive backing and a non-conductive image layer, which is electrostatically charged by corona needles 30, 34. Powder triboelectricallyoppositely-charged flows from a hopper 11 to a receptacle 15 over part of the drum surface, and adheres to the image layer. The charge on the powder is increased by needles 34a of opposite polarity to needles 30, 34. A strip of transfer material such as paper is led from a roll 19 over part of the drum surface and thence over a shoot 23 to a take-up roll 24 driven in synchronism with the drum. The corona needles 30 produce a greater charge on the paper than on the image layer, and the powder is thus transferred to the paper, reproducing the image thereon, while the paper adheres to the drum by electrostatic attraction, and is removed therefrom by strippers 21. Needles 44 of opposite polarity may be used to loosen any powder left on the drum, which powder is removed by a cleaning device 38, which may be a wiping means, suction device, or air blast device. The needles 34 replenish the charge on the image layer, which was reduced by the needles 44. Fresh powder is then caused to adhere to the image layer as before. The powder image is fixed on the transfer strip by being fused into it by heating elements 37. The voltage of the supply for the needles is 5000-8000. and the needles may be 0.32 inch apart and <SP>7</SP>/ 16 inch from the image layer in the case of a negative charge, or 0.16 inch apart and # inch from the plate for a positive charge. Instead of the needles, an arrangement of spaced parallel wires axial to the drum, attached at their ends to insulating blocks, and mounted within a charging shield, the wires being about ¢ inch from the image layer and ¢ inch apart, may be used. The printing plate may comprise a backing of metal foil, and the design be traced on it with a non-conductive lacquer or paint, or the backing may be coated with a light-sensitive lacquer exposed to light through a negative, the unexposed portions being dissolved away and the image portion fixed by burning. A plate including a photo-conductive insulating layer may have a powder image produced thereon by electrostatic charging, exposure, and powder development, after which the image can be fused into the plate so as to become a permanent printing image.
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