Stable oil-in-water ink emulsions based upon water-reducible nigrosine dyes for ink-jet printers and felt-tip and roller-ball pens

摘要

A highly fluid water-based ink composition that comprises a stable oil- in-water emulsion of a water-reducible, water-insoluble nigrosine dye- containing solvent solution, preferably containing a high flash- point and high-boiling point solvent, homogeneously dispersed as small, finely divided dye-containing oil droplets in an aqueous carrier solution containing an emulsion stabilizer of a water-soluble resin. Water- insoluble nigrosine dyes are dissolved preferably in relatively low VOC and non-flammable solvent solutions containing non-ionic surfactants to form emulsifiable water-reducible true nigrosine dye- containing solutions. The water-reducible nigrosine dye-containing solutions are then stably emulsified as dye-containing oil droplets in aqueous solutions that contain water, optional solvent diluents, and water- soluble resins that serves as an emulsion stabilizer. The stable oil-in- water ink emulsion is suitable to be ejected through small ink- jet printer nozzles, or through dispensing tips of felt-tip or roller- ball pens, onto a porous substrate, such as paper, to construct a water- fast printed image on the substrate.