NOVEL ELECTROCHEMICAL METHOD FOR COPYING WITH XEROGRAPHY OR MASTER-BASED PRINTING SYSTEMS
Original Publication Date: 1976-Dec-31
Included in the Prior Art Database: 2004-Mar-27
Xerox Disclosure Journal
There is described a technique in which imagewise electro- chemical reduction of metal oxides embedded in a matrix to clean metal particles is exploited to produce copies or to prepare printing masters for conventional or waterless lithographic printing. It is known that certain metal oxides, for example, zinc oxide, lead oxide, cadmium oxide and indium oxide, when embedded in a polymer matrix can be converted into a uniform dispersion of small, clean metal particles by low voltage, low current electrochemical reduction, In addition the metal-polymer composite may be metallized by electroplating with zinc or copper or by deposition of copper from electroless plating solutions, This electrochemical reduction of metal oxides can be used to create a metal imaged master suitable for conventional lithography and also one for waterless lithography which prints from the metal areas and releases from the polymer areas, The typical preferred particle size for the metal oxides used in preparing the coatings is one micron or less. By dispersing an appropriate metal oxide in a hydrophilic polymer binder on a suitable substrate and converting the metal oxide to metal in an imagewise fashion, the resulting member can be overcoated with additional metal from an electroless plating solution thus creating a metal imaged master suitable for conventional lithography. To provide a master for a waterless litho- graphic method, the metal oxide is dispersed in a specific ink-releasing polymer binder converted to a metal image and overplated thus resulting in a master which prints from the metal areas and releases from the polymer areas. Instead of overplating the original metal image, an ink- accepting magnetic toner can be attracted to and fused on the surface of the member when an imagewise magnetic metal pattern is created from a non-magnetic or weakly magnetic metal oxide.