Specific core-shell binders and additives for use in ink-jet
printing ink compositions are provided. One class of specific core / shell binders has the general formula [AmBnC'p]x, where A and B are hydrophobic components in which A exhibits a
glass transition temperature Tg between about -150° and +25° C. and B exhibits a
glass transition temperature greater than 25° C., C' is a component that forms a hydrophilic or water-soluble component in the
polymer chain, and has an ionic or non-ionic structure, m<30 wt %, n>40 wt %, and p<30 wt %, with the total of m+n+p=100 wt %, and x=1 to 100,000. The molecular weight (weight average) of the
polymer is between about 1,000 and 2,000,000. The polymers useful in the practice of the invention are prepared by emulsifying the monomers and then conducting a free-
radical polymerization in water. The foregoing binder
polymer is used in conjunction with additives comprising either (a) amine alcohols having the general formulawhere R1 and R2 are independently selected from the group consisting of
hydrogen,
alkyl, alkoxy,
aryl, and phenoxy, R is
alkyl, X is selected from the group consisting of
hydrogen,
alkyl,
aryl, -OH, -COOH, -CHO, and substituted groups or (b) organic acids (water-soluble or water-dispersive), including polymeric acids. Other additives include amines, polyalcohols, polyamines, and polyesters. In the ink compositions of the present invention, the ratio of binder (1) to colorant (
pigment) is greater than 1 to 10. The concentration of the additive is within the range of 0.005 to 50 wt %. The general ink formulation comprises: 5 to 50 wt % water-miscible
solvent; 0.5 to 10 wt % colorant; 0.005 to 50 wt % additive; and water.