TRANSFERRING MAGNETIC TONER PARTICLES

• Main Author: GIAIMO E
• Format: Patent
• Language: English
• Published: 27.12.1972
• Subjects: CINEMATOGRAPHY; ELECTROGRAPHY; ELECTROPHOTOGRAPHY; HOLOGRAPHY; MAGNETOGRAPHY; PHOTOGRAPHY; PHYSICS

1343567 Electrostatic printing RCA CORPORATION 14 April 1972 [16 April 1971] 17452/72 Heading B6C [Also in Division G2] Developed electrostatic images, consisting of magnetic toner particles 32, electrostatically adhered to an element 10 or 58, are transferred to a receiving member 22 or 84 by magnetic attraction after their adhesion to the element 10 or 58 has been reduced. Preferably the toner particles consist of magnetic cores of, e.g., nickel, cobalt or soft iron in thermoplastic adhesive coats, and the element 10 or 58 is a photoconductive layer 28 or 56 on a translucent substrate 26 or 60, such as paper or plastics material with a conductive coating which may contain zinc oxide, polyviny. carbazole, leucobase of malachite green or titanium dioxide. The element 10 or 58 is electrostatically charged in darkness, e.g. by corona devices 68, 70, exposed imagewise to light, as at 72, from a film 74 and developed with toner. Then the image-bearing element 10 or 58 and the receiving member 22 or 84 are passed together between asymmetrically positioned magnetic poles 90, 92 and the photoconductive layer is exposed to light or other, suitable, electromagnetic radiation through its substrate as it passes a slit 20 or series of slits 100, 102, 104, so that the electrostatic image on it is discharged. The receiving member may then be heated, e.g. by passage over a heated non- magnetic guide member 116, and the toner particles thereby be fixed by fusion of their thermoplastic coats. Preferably the magnetic poles 90, 92 are parts of a controllable electromagnet, and the light which emerges from the slits 100, 102, 104, reaches them through a light pipe 94 which acts as a guide for the element 58. The element may contact the receiving member 84, instead of being spaced from it, and the receiving member may be unheated, and surfaced with a tacky adhesive material to fix the toner. Selective control of the transfer of images may be brought about by manual or computerdirected operation of switches controlling the electromagnet on one hand and of lamps 236, 238 which illuminate the light pipe on the other.