Ink jet ink

Abstract

The present invention pertains to an aqueous inkjet ink made from certain aqueous titanium dioxide slurries, and an associated inkjet ink set for inkjet printing. The invention also pertains to a method of inkjet printing with the ink and ink set. The use of the specific titanium dioxide slurries described herein result in inkjet inks having improved stability and better anti-settling performance with less pigment agglomeration and flocculation over time.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention pertains to an aqueous inkjet ink made from certain titanium dioxide slurries and an associated inkjet ink set for inkjet printing. The invention also pertains to a method of inkjet printing with the ink and ink set. The use of the specific titanium dioxide slurries described herein result in inkjet inks having improved stability and better anti-settling performance with less pigment agglomeration and flocculation over time. [0003] 2. Description of the Related Art [0004] Inkjet printing is a non-impact printing process in which droplets of ink are deposited on print media, such as paper or polymeric substrates, to form the desired image. The droplets are ejected from a printhead in response to electrical signals generated by a microprocessor. [0005] Colored inkjet inks comprise one or more colorants that are dissolved (e.g., dyes) and / or dispersed (e.g., pigments and dispersed dyes) in the ink...

AI Technical Summary

Benefits of technology

[0038] Advantageously, by use of the graft copolymer dispersant in combination with the block copolymer dispersant as listed above, an aqueous inkjet ink can be formulated in which settling of titanium dioxide particles is reduced. A further advantageous reduction in settling of particles is achieved using a blend of the graft copolymer dispersant, the block copolymer dispersant, and the phosphated acrylic copolymer as listed above. Moreover, even when settling does occur, the settling is “soft” settling, meaning the titanium dioxide pigment can be readily re-dispersed and rejuvenated by low shear mixing so as not to result in plugging of inkjet printhead nozzles. Low shear mixing includes, for example, simple shaking (e.g., by hand or movement of the inkjet printhead) or stirring with an impeller or mixing blades at speeds of less than about 500 rpm wherein no grinding occurs. In contrast, “hard” settling occurs with many titanium dioxide slurries of the prior art.

Problems solved by technology

There are many applications, though, where aqueous ink is typically unsuitable and non-aqueous ink must be used.

Generally, pigments that can be dispersed well in water do not disperse well in non-aqueous solvent, and vice versa.

Thus, pigments that may be “well dispersed” for other applications are often still inadequately dispersed for inkjet applications.

Current white ink formulations are not acceptable for numerous applications, such as commercial inkjet applications, primarily because of poor stability resulting in pigment settling and agglomeration.

Poor stability may result in “nozzle outs” or plugging of the ink jet nozzles.

Poor stability also results in poor hiding, non-uniform coverage and poor clarity in the printed surface.

White ink formulations based on inorganic white pigments, such as titanium dioxide (TiO2), may fail because of poor stabilization of the TiO2 pigment.

Pigment agglomeration and flocculation are often at fault in poor performance of white inks, particularly white inkjet inks, due to settling and nozzle plugging problems.