Preparation of permanent color inks from water-soluble colorants using specific phosphonium salts
First Claim
1. A water-fast, dye-based, aqueous ink-jet which contains at least one anionic dye, said ink-jet further containing an amount of at least one water-fast phosphonium salt, the amount effective to improve color permanence of the ink, the at least one water-fast phosphonium salt having a chain of at least 5 carbon atoms, and wherein said ink further contains at least one additional cationic salt selected from the group consisting of )a) non-water-fast phosponium salts, (b) cationic salts, (c) catonic polymers, and (d) polyfunctional cationic salts, said at least one cationic salt partially replacing said at least one water-fast phosphonium salt to thereby improve aqueous dispersion stability and printability.
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Abstract
Water-fastness in aqueous ink-jet inks containing water-soluble dyes is achieved by using a specific ionic species having a charge opposite to that on the dye molecule. Anionic dyes typically contain sulfonate (or carboxylate) anionic groups. Using at least one specific ionic species of opposite charge, specifically, phosphonium salts, causes the colorant components to “crash” or precipitate out of the water-based ink onto the print medium due to the formation of a suitable charge complex between the ionic parts of the dye and the opposite charge of the counter-ion species. Other positively charged salts, such as quaternary ammonium salts, carbonium salts, iodonium salts, sulfonium salts, and pyrillium salts may be used to improve aqueous dispersion stability and thus printability. Such additional cationic salt partially replaces the phosphonium salt(s). Alternatively, certain surfactants, such as aromatic ethoxylates, polyethylene oxide ethers, or polypropylene oxide ethers may be used to improve print quality.
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Citations
10 Claims
- 1. A water-fast, dye-based, aqueous ink-jet which contains at least one anionic dye, said ink-jet further containing an amount of at least one water-fast phosphonium salt, the amount effective to improve color permanence of the ink, the at least one water-fast phosphonium salt having a chain of at least 5 carbon atoms, and wherein said ink further contains at least one additional cationic salt selected from the group consisting of )a) non-water-fast phosponium salts, (b) cationic salts, (c) catonic polymers, and (d) polyfunctional cationic salts, said at least one cationic salt partially replacing said at least one water-fast phosphonium salt to thereby improve aqueous dispersion stability and printability.
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10. A method for forming a water-fast, dye-based, aqueous ink-jet ink which contains at least one anionic dye, said method comprising:
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(1) forming a dye-based, aqueous ink-jet ink; and
(2) adding to said dye-based, aqueous ink-jet ink an amount of at least one water-fast phosphonium salt, the amount effective to improve color permanence of the ink, the at least one water-fast phosphonium salt having a chain of at least 5 carbon atoms wherein said at least one water-fast phosphonium salt has a formula selected from the group consisting of
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Specification