DETAILED DESCRIPTION OF THE INVENTION The first and second inks of the present invention contain an aqueous liquid vehicle.
The liquid vehicle can consist solely of water, or it can comprise a mixture of water and a water soluble or water miscible organic component, such as ethylene glycol, propylene glycol, diethylene glycols, glycerine, dipropylene glycols, polyethylene glycols, polypropylene glycols, amides, ethers, urea, substituted ureas, ethers, carboxylic acids and their salts, esters, alcohols, organosulfides, organosulfoxides, sulfones (such as sulfolane), alcohol derivatives, carbitol, butyl carbitol, cellusolve, tripropylene glycol monomethyl ether, ether derivatives, amino alcohols, ketones, N-methylpyrrolidinone, 2-pyrrolidinone, cyclohexylpyrrolidone, hydroxyethers, amides, sulfoxides, lactones, polyelectrolytes, methyl sulfonylethanol, imidazole, betaine, and other water soluble or water miscible materials, as well as mixtures thereof.
When mixtures of water and water soluble or miscible organic liquids are selected as the liquid vehicle, the water to organic ratio typically ranges from about 100:0 to about 30:70, and preferably from about 97:3 to about 40:60.
The non-water component of the liquid vehicle generally serves as a humectant or cosolvent which has a boiling point higher than that of water (100.
degree.
C.
).
In the ink compositions of the present invention, the liquid vehicle is typically present in an amount of from about 80 to about 99.
9 percent by weight of the ink, and preferably from about 90 to about 99 percent by weight of the ink, although the amount can be outside these ranges.
In one preferred embodiment, the first ink contains a polar cosolvent in a relatively high concentration, typically from about 10 to about 60 percent by weight of the ink, preferably from about 10 to about 40 percent by weight of the ink, and more preferably from about 10 to about 35 percent by weight of the ink, although the amount can be outside of these ranges.
Preferred polar solvents typically have dipole moments of from about 2 to about 5 debyes, and preferably from about 2
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