Abstract Printing masters are formed by a photosensitization and selective conversion process. A surface material, preferably a ZnO resin binder system is provided which is normally hydrophobic/oleophilic in nature but which can be converted to hydrophilic/oleophobic in nature by chemical reaction. The surface material also is selected such that the rate of its conversion can be altered by exposure to radiation energy. Selected areas only are exposed to the radiation (heat may also be applied), to form a more reactive surface area where exposure has taken place. The entire surface is then contacted with a conversion reagent for a sufficient time to convert the exposed areas to a far greater extent than the non-exposed areas. The selectively convertible master then is used to perform the printing function.
A method of preparing a printing master comprising the steps of providing a master blank having an oleophilic/hydrophobic surface coating formed of a zinc oxide pigment in a binder resin consisting essentially of an acrylic ester resin exposing selected portions of the surface coating of said master blank to ultra violet radiation of 3800 angstroms and less thereby sensitizing said selected portions contacting said surface coating with a phosphate converting solution for a time sufficient to convert the sensitized portions of said coating to an ink repelling oleophobic/hydrophilic character while the unsensitized portions of said surface coating remain relatively oleophilic/hydrophobic and ink receptive.
Claim 2
Independent Claim
103 words
A method of preparing a printing master comprising the steps of providing a master blank having an oleophilic/hydrophobic surface coating formed of a zinc oxide pigment in a binder resin consisting essentially of an acrylic ester resin exposing selected portions of the surface coating of said master blank to ultra violet radiation of 3800 angstroms and less thereby sensitizing said selected portions contacting said surface coating with a phosphate converting solution for a time sufficient to convert the sensitized portions of said coating to an ink repelling oleophobic/hydrophilic character while the unsensitized portions of said surface coating remain relatively oleophilic/hydrophobic and ink receptive.
Claim 3
Dependent Claim
25 words
The method defined in claim 1 wherein said zinc oxide pigment and said acrylic ester resin are present in a ratio of about 16: 1.