Xerox Corporation (Norwalk, CT) earned U.S. Patent 7,649,026 for a variety of radiation curable compositions including UV curable ink compositions containing a polymeric dispersant, a curable material, and nanoscale pigments.
The pigment particle composition includes an organic monoazo laked pigment with at least one functional moiety, and a sterically bulky stabilizer compound that has at least one functional group. The functional moiety of the pigment associates non-covalently with the functional group of the stabilizer; and the presence of the associated stabilizer limits the extent of particle growth and aggregation, to afford nanoscale-sized pigment particles, according to inventors C. Geoffrey Allen Rina Carlini and Sandra J. Gardner.
Organic monoazo "laked" pigments are the insoluble metal salt colorants of monoazo colorants which can include monoazo dyes or pigments, and in certain geographic regions these pigments have been referred to as either "toners" or "lakes". The process of ion complexation with a metal salt, or "laking" process, provides decreased solubility of the non-ionic monoazo pigment, which can enhance the migration resistance and thermal stability properties of a monoazo pigment, and thereby enable the applications of such pigments for robust performance, such as colorizing plastics and heat-stable paints for outdoor use as well as in the inks of inkjet printers.
