Stable compositions of nano-particulate unmodified pigments and insoluble colorants in aqueous microemulsions, and principle of stability and methods of formation thereof
AssigneeHewlett-Packard Company
InventorMakarand P. Gore
Life of this patent
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Abstract
If the particle size of pigments in ink-jet inks is reduced below 500 nm, then the ink compositions achieved extraordinary stability; that is, there is no visible sediment formed after three weeks at ambient temperature and there is no sediment formed after heating to 70.degree. C. for 10 min followed by cooling to 0.degree. C. for 10 min. No dispersant is necessary, and the pigment particles having such a defined size may be incorporated into microemulsions, using a suitable oil (water-immiscible organic compound), at least one amphiphile, and water.
Claims22
A stable pigment-based ink-jet ink composition for ink-jet printing comprising:
- (a) at least one non-deagglomerated pigment having an average particle size less than 500 nm;
- (b) at least one water-insoluble organic compound;
- (c) at least one amphiphile;
- and
- (c) water.
A process for stabilizing at least one pigment in an ink-jet ink composition comprising:
- (a) providing particles of at least one non-deagglomerated pigment;
- and
- (b) in either order,
- (i) forming a microemulsion of said at least one non-deagglomerated pigment in a vehicle comprising at least one water-immiscible organic compound, at least one amphiphile, and water;
- and
- (ii) reducing the size of said particles to an average particle size below about 500 nm.
Dependencies are inferred from the claim text.