| 摘要 |
In a method of printing on a printing medium (S) a variable thickness ink dot pattern representing an original image in response to an incoming digital data stream, a printing member, e.g. a cylinder (72), is formed which defines a multiplicity of discrete, independently electrically chargable capacitor microcells (94) adjacent to a printing surface of that member. Selected ones of the microcells (94) are activated in accordance with the incoming data stream so that the activated microcells are geometrically related to the dots in the pattern to be printed. Then, electrical charges are deposited on the microcells (94) selected for activation at controlled variable coulombic charge levels to create at the printing surface localized electrical fields of various strengths that are proportional to the print densities desired for the related dots in the pattern to be printed. Following this, the printing surface is contacted by a two-component, voltage sensitive, thermoplastic whereby the ink, under the influence of the fields, is deposited on the printing surface only at the locations of the microcells selected for activation, with the thickness of each ink deposit being proportional to the strength of the field at that microcell, thereby to form a variable-thickness ink pattern on the printing surface. That ink pattern is then transferred completely to the printing medium to provide a faithful hardcopy reproduction of the original image. Apparatus for practicing the method are also disclosed. |
