GB1215022A - Method of magnetic printing - Google Patents

Abstract

1,215,022. Printing processes. G. RITZERFELD. 14 Feb., 1968 [28 Feb., 1967; 2 March, 1967], No. 7303/68. Heading B6C. As an original image is made on one surface of a non-magnetizable sheet printing forme, e.g. by a type bar, by writing or by infra-red thermal transfer, a mirror image is produced on its other or printing side by transfer of magnetizable material from a sheet coated with it, then the transferred material is magnetized so that a magnetizable toner sticks to it and can be printed from it on to, for example, a sheet of paper. The toner may comprise iron powder, ferrite or iron oxide, ink and wax or plastics material. The printing forme 1, which may be a paper sheet, may be placed on cylinder 7 and the magnetizable material 4 of the mirror image, which may contain iron oxide or ferrite, with wax or plastics material, be magnetized by magnet 8 and have toner 11 applied to it by magnet 14, by a scoop band or by a statically chargeable conveyer belt. In the last case the toner is electrostatically chargeable as well as magnetizable, and is transferred magnetically from the belt to the mirror image. Paper sheets 17 are moistened at 21 with a fixing liquid such as alcohol, and are fed between cylinder 7 and roller 22 where the toner is transferred to the sheets 17, with assistance of electromagnets within roller 22, of a magnetic rubber coating on roller 22 or of a stationary eraser magnet within cylinder 7. Ink containing iron oxide or ferrite may be used to make the original image on the forme, and be magnetized together with the mirror image, and the surface of drum 7 may be magnetizable. The toner and the paper sheets 17 may be given static electrical charges of the same polarity before they meet, so as to assist transfer of toner to the surface of the sheets and the printing forme and toner may be given similar static electrical charges before the toner is applied to the mirror image to prevent toner from sticking to the forme as well as to the mirror image. The forme 1 may have on it a coating of tin, or of wax and tin, on the side where the original image is made, and be overlain prior to making of the original image by wax and paper layers. When the original image is made and the wax and paper layers are removed the tin goes with them from the area of the image, so that a negative image in tin remains on the side of the forme opposite the printing side, which carries the above-described mirror image in magnetizable material. The tin coating prevents a static electrical charge from being produced on the printing side of the forme at points where there is no magnetizable material and so prevents uncharged toner from sticking electrostatically to the surface of the printing forme.