| 摘要 |
1,067,919. Printing processes. RANK XEROX Ltd. Nov. 17, 1964 [Nov. 29, 1963], No. 46844/64. Heading B6C. [Also in Division G2] A surface coating of contaminant is deposited or removed imagewise on or from a frostable surface so that, on development by softening the surface and applying a uniform electric field, only the contaminated parts of the surface produce a frost image. The contaminant may reduce the threshold voltage of the thermally softened frostable material so that, on applying a weaker electric field than is normally used for development, the uncontaminated parts of the surface remain unchanged. The contaminant may be applied by spray or roller through a stencil (Fig. 1, not shown), by evaporative transfer from a uniform layer applied to the differentially absorptive surface of an original subjected to infra-red radiation (Fig. 3, not shown) or by direct contact with an original carrying an image-wise coating of contaminant, such as natural oils in the human skin (Fig. 4, finger printing, not shown). Alternatively, a uniform coating of contaminant may undergo image-wise removal by evaporation at the light struck areas of an intense, optically-projected image (Fig. 5, not shown). In this form, a continuously moving web (25) receives contaminant from an applicator roller (38) and is carried past an exposure station, a charging device (41) and a heater (42). The contaminant used is a fluorocarbon. The frost image is erased, for re-use of the material, by heating to a temperature higher than that used for development. In a xerographic application, Fig. 6, the contaminant is applied to the frostable surface by transfer from a photoconductive surface 50, on which it has been deposited by mist development, at 53, of an electrostatic latent image. The transfer to paper strip 58 carrying a frostable layer is assisted electrode 63. Charging electrodes 65 and heater 66 develop the frost image. One example of a frostable layer is a two micron thick coating of glyceryl ester of abietic acid on a conductive substrate or on a transparent insulating substrate having a conductive layer. A 50% reduction in the threshold voltage of this substance may be obtained by using dimethyl siloxane as contaminant. Other frostable materials include coumarone, styrene and indene resins and polyvinyl chloride. |
