Method of inkjet printing green images
View Patent ↗Aqueous green inkjet ink compositions are prepared from aqueous organic pigment dispersions for use in various inkjet printing methods. In particular, these methods provide a green image or expanded color gamut for other inkjet printed colors. The aqueous organic pigment dispersion contains a green copper phthalocyanine pigment and an azo-coupled β-ketoamide pigment and an organic pigment dispersant. The weight ratio of the green copper phthalocyanine pigment to the azo-coupled β-ketoamide pigment is from 1:1 to 10:1. The median particle diameter of each of the green copper phthalocyanine pigment and the azo-coupled β-ketoamide pigment is less than 85 nm. At least 95% of the total particles of each of the green copper phthalocyanine pigment and the azo-coupled β-ketoamide pigment have a particle diameter of less than 150 nm.
1. A method of inkjet printing, comprising:
providing a substrate,
ink jetting an aqueous green inkjet ink composition as spaced green drops to provide a green color image on the substrate,
wherein the aqueous green inkjet ink composition comprises:
(a) an aqueous organic pigment dispersion comprising:
a green copper phthalocyanine pigment,
an azo-coupled β-ketoamide pigment, and
at least one organic pigment dispersant in an amount of at least 40 weight % and up to and including 100 weight %, based on the sum of the weights of the green copper phthalocyanine pigment and the azo-coupled β-ketoamide pigment,
the weight ratio of the green copper phthalocyanine pigment to the azo-coupled β-ketoamide pigment is from 1:1 to and including 10:1, and
the median particle diameter of each of the green copper phthalocyanine pigment and the azo-coupled β-ketoamide pigment is less than 85 nm and at least 95% of the total particles of each of the green copper phthalocyanine pigment and the azo-coupled β-ketoamide pigment have a particle diameter of less than 150 nm when measured in intensity mode using a laser light scattering particle size analyzer, and
(b) at least one humectant,
the aqueous green inkjet ink composition having a viscosity of less than 3 centipoise (0.003 N-sec) at 25° C.
2. The method of claim 1 , comprising:
ink jetting the aqueous green inkjet ink composition from a main fluid supply as a continuous stream that is broken into both the spaced green drops and non-printing green drops; and
collecting and returning the non-printing green drops to the main fluid supply.
3. The method of claim 1 , wherein the aqueous green inkjet ink composition is provided as spaced green drops and non-printing green drops using a continuous inkjet printing apparatus.
4. The method of claim 3 , comprising:
delivering an aqueous green inkjet ink composition to a first drop generator mechanism,
ejecting the aqueous green inkjet ink composition from the first drop generator mechanism as spaced green drops in a controlled manner to provide a green color image on the substrate;
delivering an additional aqueous color inkjet ink composition to a second drop generator mechanism, which additional aqueous color inkjet ink composition comprises a colorant that is not a green colorant, and
ejecting the additional aqueous color inkjet ink composition from the second drop generator mechanism as spaced additional color drops in a controlled manner to provide an additional color image on the substrate.
5. The method of claim 4 , comprising:
delivering the additional aqueous color inkjet ink composition from an additional main fluid supply as a continuous stream that is broken into both the spaced additional color drops and additional non-printing color drops;
collecting and returning the additional non-printing color drops to the additional main fluid supply.
6. The method of claim 1 , comprising ink jetting the aqueous green color inkjet ink composition at a frequency of at least 350 kHz with a near nozzle velocity of at least 15 m/sec.
7. The method of claim 1 , wherein the aqueous green color inkjet ink composition has a viscosity of less than or equal to 2 centipoise (0.002 N-sec) at 25° C.
8. The method of claim 1 , wherein the aqueous green inkjet ink composition further comprising an anionic polyurethane having an acid number of at least 50 or an anionic acrylic or anionic styrene-acrylic polymer, or both the anionic polyether polyurethane and the anionic acrylic or anionic styrene-acrylic polymer.
9. The method of claim 1 , wherein the weight ratio of the green copper phthalocyanine pigment to the azo-coupled β-ketoamide pigment in the aqueous green inkjet ink composition is from 3:1 to and including 6:1.
10. The method of claim 1 , wherein the aqueous green inkjet ink composition exhibits CIELAB color characteristics of a* of at least −80 and up to and including −20, b* of at least 20 and up to and including 80, and L* of at least 20 and up to and including 90.
11. The method of claim 1 , wherein the azo-coupled β-ketoamide pigment is a yellow mono-azo-coupled β-ketoamide pigment.
12. The method of claim 1 , wherein the green copper phthalocyanine pigment is a halogenated green copper phthalocyanine pigment.
13. The method of claim 1 , wherein the green copper phthalocyanine pigment is C.I. Pigment Green 7 and the azo-coupled β-ketoamide pigment is Pigment Yellow 74.
14. The method of claim 1 , wherein the green copper phthalocyanine pigment is present in the aqueous green inkjet ink composition in an amount of at least 1 weight % and up to and including 5 weight %, based on the total weight of the aqueous green inkjet ink composition.