DETAILED DESCRIPTION OF THE INVENTION The invention relates to aqueous ink jet ink compositions which are particularly suited for use in ink jet printers in general, and thermal ink jet printers in particular.
The aqueous ink jet ink compositions encompasses both pigment-based inks and dye-based inks.
The ink compositions are particularly advantageous when the colorant is a pigment dispersion.
However, the cosolvents can also be used in aqueous dye-based ink to impart rapid drying and good image definition to these inks.
The pigment-based inks comprise an aqueous carrier medium, a selected sulfoxide or sulfone penetrant and a pigment dispersion.
The dye-based inks comprise an aqueous carrier medium, a dye and a selected sulfoxide or sulfone penetrant.
The inks of this invention may be adapted to the requirements of a particular ink jet printer to provide a balance of light stability, smear resistance, viscosity, surface tension, high optical density, and crust resistance.
Another advantage is the freedom of the sulfoxide or sulfone penetrants from hydrolysis in aqueous inks.
Aqueous Carrier Medium The aqueous carrier medium comprises water (preferably deionized water) or a mixture of water and at least one water soluble organic solvent other than the selected sulfoxide or sulfone penetrant.
The aqueous carrier medium is present in a major amount of the ink composition, i.
e.
, in the range of approximately 65 to 99.
89%, preferably approximately 85 to 98.
5%, based on total weight of the ink.
Representative examples of water-soluble organic solvents are disclosed in U.
S.
Pat.
No.
5,085,698, the disclosure of which is incorporated herein by reference.
Selection of a suitable mixture of water and water soluble organic solvent depends upon the requirements of the specific application, such as desired surface tension and viscosity, the selected colorant, drying time of the ink, and the type of substrate onto which the ink will be printed.
A mixture of a water soluble organic solvent having at least two hydroxyl groups (diethylene glycol, triethylene glycol, etc
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