Ink jet ink

Abstract

Disclosed is a non-aqueous inkjet ink containing certain titanium dioxide slurries, an associated inkjet ink set for inkjet printing, and a method of inkjet printing with the inkjet ink or ink set. The solvent and mixtures of solvents used for the dispersed titanium dioxide have a hydrogen bonding solubility parameter of greater than about 9. The inks have improved anti-settling properties with less pigment agglomeration and flocculation over time such that they can be utilized to prepare a stable inkjet ink. Also described is the use of this ink to print on colored or transparent surfaces.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority under 35 U.S.C. §119 from U.S. Provisional Application Ser. No. 60 / 549,607 (filed Mar. 2, 2004), the disclosure of which is incorporated by reference herein for all purposes as if fully set forth.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This present invention pertains to a non-aqueous inkjet ink made from titanium dioxide 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 inks utilized herein have improved anti-settling performance with less pigment agglomeration and flocculation over time such that they can be utilized as a stable inkjet ink. The white ink based on the titanium dioxide provides new means to digitally print white ink by itself, but also with other colors. [0004] 2. Description of the Related Art [0005] Inkjet printing is a non-impact printing process in which droplets of...

AI Technical Summary

Benefits of technology

[0032] Unexpectedly, by use of the dispersant in combination with the non-aqueous solvent mixture with a Hansen solubility parameter of greater than 9, settling of titanium dioxide particles is significantly reduced. 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. For most of the dispersant / solvent combinations, negligible soft settling is observed.

Problems solved by technology

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.

U.S. Pat. No. 4,630,076 describes a color ink jet system with an additional white ink that is printed on top of the previously printed color dots, but does not provide a means to produce a stable useful white ink.

Current white ink formulations are not acceptable for numerous applications, such as commercial drop-on-demand 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.