White inkjet ink improved for dispersion stability
View Patent ↗An inkjet printing method includes the steps of a) providing a white inkjet ink and at least one color inkjet ink to an inkjet printer; and b) jetting the white inkjet ink at a higher temperature than the color inkjet ink onto an ink-receiver. The difference in jetting temperature between the white inkjet ink and the color inkjet ink is at least 5° C. Inkjet ink sets and inkjet printers are also disclosed.
1. A color inkjet ink set comprising:
a radiation curable white inkjet ink containing a pigment with a refractive index greater than 1.60; and
at least one color inkjet ink; wherein
a viscosity of the radiation curable white inkjet ink is at least 4 mPa·s greater than a viscosity of the at least one color inkjet ink, the viscosity being measured at 40° C. with a Brookfield DV-II+Pro at 12 rotations per minute; and
the radiation curable white inkjet ink includes a Norrish type I initiator or a Norrish type II initiator as a photo-initiator.
2. The color inkjet ink set according to claim 1 , wherein the pigment with a refractive index greater than 1.60 is titanium dioxide.
3. The color inkjet ink set according to claim 2 , wherein the viscosity of the radiation curable white inkjet ink is at least 8 mPa·s greater than the viscosity of the color inkjet ink.
4. The color inkjet ink set according to claim 2 , wherein the Norrish type I initiator is selected from the group consisting of acylphosphine oxides.
5. The color inkjet ink set according to claim 2 , wherein the titanium dioxide is rutile.
6. The color inkjet ink set according to claim 1 , wherein the radiation curable white inkjet ink includes at least 26 wt % of a white pigment based upon a total weight of the radiation curable white inkjet ink.
7. The color inkjet ink set according to claim 1 , wherein the at least one color inkjet ink is curable by radiation or electron beam.
8. The color inkjet ink set according to claim 1 , wherein the at least one color inkjet ink is curable by radiation or electron beam.
9. The color inkjet ink set according to claim 1 , wherein the viscosity of the radiation curable white inkjet ink is less than 15 mPa·s at a shear rate of 100 s −1 and a jetting temperature between 10° C. and 70° C.
10. The color inkjet ink set according to claim 1 , wherein the radiation curable white inkjet ink includes a polymerizable compound selected from the group consisting of isobornylacrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, and N-vinylcaprolactam.
11. The color inkjet ink set according to claim 10 , wherein the viscosity of the radiation curable white inkjet ink is at least 8 mPa·s greater than the viscosity of the color inkjet ink.
12. The color inkjet ink set according to claim 10 , wherein the Norrish type I initiator is selected from the group consisting of acylphosphine oxides.
13. The color inkjet ink set according to claim 10 , wherein the radiation curable white inkjet ink includes 2-(2-vinyloxyethoxy)ethyl (meth)acrylate.
14. The color inkjet ink set according to claim 1 , wherein the viscosity of the radiation curable white inkjet ink is less than 15 mPa·s at a shear rate of 100 s −1 and a jetting temperature between 10° C. and 70° C.
15. The color inkjet ink set according to claim 14 , wherein the viscosity of the radiation curable white inkjet ink is at least 8 mPa·s greater than the viscosity of the color inkjet ink.
16. The color inkjet ink set according to claim 14 , wherein the Norrish type I initiator is selected from the group consisting of acylphosphine oxides.
17. The color inkjet ink set according to claim 1 , wherein the radiation curable white inkjet ink includes a polymerizable compound selected from the group consisting of isobornylacrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate,2-(2-vinyloxyethoxy)ethyl (meth)acrylate, and N-vinylcaprolactam.
18. The color inkjet ink set according to claim 17 , wherein the radiation curable white inkjet ink includes 2-(2-vinyloxyethoxy)ethyl (meth)acrylate.
19. The color inkjet ink set according to claim 1 , wherein the viscosity of the radiation curable white inkjet ink is at least 8 mPa·s greater than the viscosity of the color inkjet ink.
20. The color inkjet ink set according to claim 1 , wherein the Norrish type I initiator is selected from the group consisting of acylphosphine oxides.