| 摘要 |
1,119,793. Electrostatic screen-printing. CONTINENTAL CAN CO. Inc. 21 July, 1965 [27 July, 1964], No. 30920/65. Heading B6C. An article 10 of electrically non-conductive material e.g. acetate plastic, is printed by first providing the article with a distributed electrostatic charge, then locating the charged article in spaced relationship to an electrically conductive screen stencil 20 to establish an electric field between the article and the screen, and finally forcing electrically charged toner particles 34 through the stencil, so that under the action of the electric field the particles are deposited on the article in the required pattern and are subsequently bonded to the article by heating, or by exposure to the vapour of a toner solvent. The screen 20 may be earthed to increase the strength of the field. The charge on the article 10 is formed by placing the article between two corona electrodes connected to avan der Graff generator so that negative ions 15 are deposited on one face and positive ions 16 are deposited on the other face. The charging of the screen 20 under the action of the electric field may serve to charge the non-conductive toner particles, but the particles may be mixed with much. larger conductive particles of iron filings or other magnetic material whereby the particles are charged triboelectrically. The mesh of the screen is such that only the toner particles can pass therethrough. A brush may be used for forcing the particles through the screen, but in the case where the mixture including iron filings is employed, a bar magnet 31 may be dipped into some of the mixture to pick up a quantity 32 thereof and supply it to the screen. The article may be a flat sheet or a thin walled plastic bottle, and an electrode 47, Fig. 5 (not shown) connected to the screen 45 may be disposed within the bottle to increase the electric field. |
