Polymers derived from unsaturated surfactants for use in ink-jet inks

TECHNICAL FIELD

The present relates generally to ink-jet inks, and, more particularly, to additives, specifically, polymeric additives, for improving bleed control, water-fastness, and smear-fastness of ink-jet inks.

BACKGROUND ART

Thermal ink-jet printers offer a low cost, high quality, and comparatively noise-free option to other types of printers commonly used with computers. Such printers employ a resistor element in a chamber provided with an egress for ink to enter from a plenum. The plenum connects to a reservoir for storing the ink. A plurality of such resistor elements forms a pattern in a printhead. This pattern is called a primitive. Each of the resistor elements line up with a nozzle in a nozzle plate, through which ink is expelled toward a print medium. The entire assembly of printhead and reservoir comprises an ink-jet pen.

In operation, each resistor element connects through a conductive trace to a microprocessor, where current-carrying signals cause one or more selected elements to heat. The heating creates a bubble of ink in the chamber, which is expelled through the nozzle toward the print medium. Firing a plurality of such resistor elements, in a particular order, in a given primitive, forms alphanumeric characters, performs area-fills, and provides other print capabilities on the medium.

Ink-jet inks used in thermal ink-jet printing typically comprise a colorant and a vehicle, with the vehicle often containing water and other relatively low surface tension liquids. The colorant may comprise a water-miscible dye or a water-insoluble pigment that is dispersed in the ink with a dispersing agent.

The tight tolerances of the nozzles (typically 50 mm diameter) require that the ink not clog the nozzles. Furthermore, repeated firings of the resistor elements, which must withstand about 10 million firings over the life of the ink cartridge, can result in fouling of the resistor element. Kogation is the term used for this type of fouling. The ink composition must be capable of interacting with the print medium, especially paper, to penetrate it without undue spreading. The ink composition should be smear- and water-resistant on the paper. Finally, bleed between colors must be controlled, so that any invasion of a color by another color is reduced or even eliminated.

Many inks possess one or more of the foregoing properties. However, few ink compositions posses all of those properties, since an improvement in one property often results in the degradation of another property. Thus, inks used commercially represent a compromise in an attempt to achieve an ink evidencing at least an adequate performance in each of the aforementioned properties.

Accordingly, investigations continue into developing ink formulations that have improved properties such as reduced kogation and reduced crusting (i.e. improved decap). Further properties sought to be improved include high edge acuity, high optical density, fast drying times, good water-fastness, and good smear-fastness, all without sacrificing performance in other necessary properties.

Recent advances in ink-jet inks have incorporated pigments in place of the earlier water-miscible dyes. However, pigments by definition are not water-miscible, and require the presence of a dispersing agent. Further investigations into the use of pigments have determined that surface treatment of the pigment, to form either anionic or cationic functional groups on the surface, provides a macromolecular chromophore (MMC) that is water-soluble, thus eliminating the requirement for a dispersing agent.

Investigation continues into the use of pigments that have been treated to be water-miscible, but which possess most, if not all, of the foregoing desired properties. Further, there continues to be a need for inks that employ water-miscible dyes where it is desired to also improve the foregoing properties.

DISCLOSURE OF INVENTION

In accordance with the invention, the properties of ink-jet inks containing a colorant (pigment, macromolecular chromophore, or dye) are improved by adding thereto an additive, specifically, one or more polymers derived from unsaturated surfactants. The unsaturated surfactant(s) has at least one carbon-carbon double bond (C=C). The polymer may be simply an polymer of the unsaturated surfactant. Alternatively, the polymer may be co-polymerized with one or more vinyl monomers or one or more polymers based on the vinyl monomers may be mixed with the unsaturated surfactant polymer. As used herein, the term "copolymer" is used to include polymers derived from co-polymerizing two or more monomers as well as mixtures of polymers. The vinyl monomer(s) or polymer(s) is used to adjust or "tweak" the properties of the resultant polymer. For example, the more hydrophobic the polymer or the higher its molecular weight then the greater the water-fastness afforded the ink-jet ink.

The additive of the invention improves bleed control, water-fastness, and smear-fastness of ink-jet inks, particularly thermal ink-jet inks.

BEST MODES FOR CARRYING OUT THE INVENTION

The use of polymers derived from unsaturated surfactants unexpectedly improves several properties of ink-jet inks, whether the colorant is a water-insoluble pigment or a water-miscible dye. The unsaturated surfactants employed in the practice of the present invention have at least one carbon-carbon double bond (C=C) and are selected from the group consisting of (1) unsaturated zwitterionic surfactants, including unsaturated amines oxides, unsaturated betaines, and unsaturated betaine sulfonates, (2) unsaturated cationic surfactants, and (3) unsaturated fatty acids.

The polymerization is conveniently performed by free radical polymerization in water, using an initiator. Specific examples are described below as to the monomer, the initiator, and its concentration.

1. Polymerization of OOAO and Other Amine Oxides

OOAO (N,N-dimethyl-N-(z-9-octadecenyl)-N-amine oxide) is an example of an unsaturated zwitterionic surfactant. This compound has previously been disclosed and claimed for its substantial effect in bleed control; see, e.g., U.S. Patent 5,116,409, issued on May 26, 1992, to John R. Moffatt and assigned to the same assignee as the present invention.

The inventors found that OOAO polymerizes in water with radical initiators, presumably by the following pathway: <chemistry id="chem0001" num="0001"><img file="EP1029902A1_D0001.tif" /></chemistry> where I· is an initiator.

For example, a 2% solution of OOAO in water showed a marked reduction of viscosity (about one order of magnitude) upon addition of 0.2 g of K₂S₂O₈ at temperature &gt;80°C with stirring for 5 minutes. In water, the monomeric amphiphiles form micelles at low concentrations, but at higher concentrations (and consequently higher viscosities), they probably form lamellar sheets.

Examples of initiators useful in the practice of the present invention include the sodium (Na⁺), potassium (K⁺), and ammonium (NH₄⁺) salts of persulfate (S₂O₈^-2). In addition, the following azo compounds may be used as initiators: <chemistry id="chem0002" num="0002"><img file="EP1029902A1_D0002.tif" /></chemistry> These compounds are also known as 1,1'-azobis(cyclohexanecarbonitrile) (A), 4,4'-azo(4-cyanovaleric acid) (B), and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (C), respectively. Examples of other initiators also useful in the practice of the present invention include 2,2'-azobisisobutyronitrile and 2,2'-azobis[2(2-imidazoline 2-yl) propane] dihydrochloride.

The amount of initiator is in the range of about 0.01 to 1.5 wt%, relative to the total monomer/water solution. The amount of monomer in solution is typically about 2 wt%, so that at the upper range of initiator concentration, the ratio of initiator to monomer is nearly 1:1.

Amine oxide surfactants are of interest in thermal ink-jet printing due to well-known properties of stability, water-fastness in macromolecular chromophores (MMCs), and bleed control. They are frequently mild toward pen materials, including the barrier layer. They can render carboxylated macromolecular complexes water-fast. It is anticipated that oligomers composed of their surfactants should behave equally well or superior to their monomeric counterparts.

The amine oxide surfactants employed in the practice of the present invention are represented by the general formula: <chemistry id="chem0003" num="0003"><img file="EP1029902A1_D0003.tif" /></chemistry> where R and R' are independently any alkyl chain having 1 to 20 carbon atoms and n is an integer from 1 to 20.

In addition to OOAO, examples of other amine oxides useful in the practice of the present invention include N,N-dimethyl-N-hexadecenyl-N-amine oxide, N,N-dimethyl-N-tetradecenyl-N-amine oxide, N,N-dimethyl-N-dodecenyl-N-amine oxide, and N,N-dimethyl-N-decenyl-N-amine oxide.

Included within the scope of the present invention are the structures predicted from molecular dynamics simulations of the dimer and trimer structures composed of OOAO monomer. These show that even these small oligomers have micelle mimic properties in that the hydrophobic groups are clustered in the interior and the water-soluble amine oxide N-O polar moiety is out towards the bulk water environment. It is possible to see that these types of molecules can very easily form shells around the pigment particles, such as Pigment Red 122 (Color Index No. 73915) or Pigment Yellow 74 (Color Index No. 11741) or macromolecular chromophores such as Cabo-Jet 300 and others. The above-referenced pigments are commercially available from, e.g., Sun Chemical (Cincinnati, OH). Macromolecular chromophores are disclosed and claimed, for example, in U.S. Patents 5,749,952; 5,571,311; and 5,630,868, in PCT published applications WO 96/18695, WO 96/18696, WO 97/48769, and in EP published application EP 688836A.

Treatment of OOAO at 2% by weight in water with 0.2% by weight Na₂S₂O₈ have particle sizes of 152 nm and viscosity of 0.93 cps, whereas OOAO treated under identical fashion except with 0.2% by weight Na₂SO₄, instead of Na₂S₂O₈, has particle size of 60 nm. This strongly suggests that OOAO polymerizes to small oligomers under these conditions.

It is expected that hydrophobic character, ease of polymerization and self-solubilization of OOAO and other amine oxides will be useful in polymers of ink-jet inks. For example, other monomers may be incorporated into the amine oxide polymerization process to enhance the performance of the resulting polymer. Such other monomers are vinyl monomers, including acrylate, methacrylate, and vinyl ethers. Specific examples of such monomers include: <chemistry id="chem0004" num="0004"><img file="EP1029902A1_D0004.tif" /></chemistry><chemistry id="chem0005" num="0005"><img file="EP1029902A1_D0005.tif" /></chemistry>

The names of the foregoing compounds are as follows: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="2" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="78.75mm" /><colspec colnum="2" colname="col2" colwidth="78.75mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">NUMBER</entry><entry namest="col2" nameend="col2" align="left">NAME</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="center">1</entry><entry namest="col2" nameend="col2" align="left">alkyl vinyl ether</entry></row><row><entry namest="col1" nameend="col1" align="center">2</entry><entry namest="col2" nameend="col2" align="left">dimethyl diallyl ammonium chloride</entry></row><row><entry namest="col1" nameend="col1" align="center">3</entry><entry namest="col2" nameend="col2" align="left">bis-(N-allyl)hydroxy malonamide</entry></row><row><entry namest="col1" nameend="col1" align="center">4</entry><entry namest="col2" nameend="col2" align="left">diallyl amine</entry></row><row><entry namest="col1" nameend="col1" align="center">5</entry><entry namest="col2" nameend="col2" align="left">2,2-diallyl ethanoic acid acetal</entry></row><row><entry namest="col1" nameend="col1" align="center">6</entry><entry namest="col2" nameend="col2" align="left">diallyl ether</entry></row><row><entry namest="col1" nameend="col1" align="center">7</entry><entry namest="col2" nameend="col2" align="left">ethyl allyl ether</entry></row><row><entry namest="col1" nameend="col1" align="center">8</entry><entry namest="col2" nameend="col2" align="left">allyl glycidyl ether</entry></row><row><entry namest="col1" nameend="col1" align="center">9</entry><entry namest="col2" nameend="col2" align="left">N-vinylformamide</entry></row><row><entry namest="col1" nameend="col1" align="center">10</entry><entry namest="col2" nameend="col2" align="left">allyl-(1,1,2,3,3,3-hexafluoropropyl)ether</entry></row><row><entry namest="col1" nameend="col1" align="center">11</entry><entry namest="col2" nameend="col2" align="left">N-allyl-N-2-hydroxyethyl thiourea</entry></row><row><entry namest="col1" nameend="col1" align="center">12</entry><entry namest="col2" nameend="col2" align="left">3-imidazole propene</entry></row><row><entry namest="col1" nameend="col1" align="center">13</entry><entry namest="col2" nameend="col2" align="left">allyl methacrylate</entry></row><row><entry namest="col1" nameend="col1" align="center">14</entry><entry namest="col2" nameend="col2" align="left">allyl phenylamine</entry></row><row><entry namest="col1" nameend="col1" align="center">15</entry><entry namest="col2" nameend="col2" align="left">2-sulfoethyl acrylate</entry></row><row><entry namest="col1" nameend="col1" align="center">16</entry><entry namest="col2" nameend="col2" align="left">3-sulfopropylacrylate</entry></row><row><entry namest="col1" nameend="col1" align="center">17</entry><entry namest="col2" nameend="col2" align="left">3-sulfopropene</entry></row><row><entry namest="col1" nameend="col1" align="center">18</entry><entry namest="col2" nameend="col2" align="left">styrene sulfonate</entry></row><row><entry namest="col1" nameend="col1" align="center">19</entry><entry namest="col2" nameend="col2" align="left">styrene</entry></row><row><entry namest="col1" nameend="col1" align="center">20</entry><entry namest="col2" nameend="col2" align="left">methacrylate</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">21</entry><entry namest="col2" nameend="col2" align="left">N-(3,3-dimethyl-3-sulfopropyl)-N-(3-propyl ammonium hydrochloride) methacrylate</entry></row></tbody></tgroup></table></tables>

The polymer additive(s) may be polymerized without or with one or more of the vinyl monomers. The amount of vinyl monomer in the polymeric additive is in the range of 0 to about 99 wt% of the total polymer.

2. Polymerization of Other Monomers

In addition to the use of amine oxides as described above, the following monomers may be used either with the above-described amine oxides or in place thereof. These monomers include: <ul id="ul0001" list-style="none" compact="compact"><li>(1) unsaturated betaines: <chemistry id="chem0006" num="0006"><img file="EP1029902A1_D0006.tif" /></chemistry> where R, R', and n are as defined above and where m is an integer ranging from 1 to 20 and preferably about 3. Examples of unsaturated betaines useful in the practice of the present invention include N,N-dimethyl-N-(4-z-dodecenyl)-N-ammonioethane carboxylate, N,N-dimethyl-N-tetradecenyl-N-ammonioethane carboxylate, N,N-dimethyl-N-hexadecenyl-N-ammonioethane carboxylate, N,N-dimethyl-N-octadecenyl)-N-ammonioethane carboxylate, and N,N-dimethyl-N-decenyl-N-ammonioethane carboxylate.</li><li>(2) unsaturated betaine sulfonates: <chemistry id="chem0007" num="0007"><img file="EP1029902A1_D0007.tif" /></chemistry> where R, R', n, and m are as defined above. Examples of unsaturated betaine sulfonates useful in the practice of the present invention include N,N-dimethyl-N-(4-z-dodecenyl)-N-ammoniopropane sulfonate, N,N-dimethyl-N-tetradecenyl-N-ammoniopropane sulfonate, N,N-dimethyl-N-hexadecenyl-N-ammoniopropane sulfonate, N,N-dimethyl-N-octadecenyl)-N-ammoniopropane sulfonate, and N,N-dimethyl-N-decenyl-N-ammoniopropane sulfonate.</li><li>(3) unsaturated fatty acids:         R-(CH=CH)_n-R'-COO^- where R, R', and n are as defined above. Examples of unsaturated fatty acids useful in the practice of the present invention include palmiteolate, oleate, lineolate, linolenate, ricineladate, and ricinolenate.</li><li>(4) unsaturated cationic surfactants: <chemistry id="chem0008" num="0008"><img file="EP1029902A1_D0008.tif" /></chemistry> where R, R', and n are as defined above and X^- is a counterion, such as Cl^-, Br^-, I^-, tosylate, phosphate, sulfate, or mesylate. Examples of unsaturated cationic surfactants useful in the practice of the present invention include N,N,N-trimethyl-N-(z-octadecenyl)ammonium chloride, N,N,N-trimethyl-N-hexadecenyl ammonium chloride, N,N,N-trimethyl-N-tetradecenyl ammonium chloride, N,N,N-trimethyl-N-dodecenyl ammonium chloride, and N,N,N-trimethyl-N-decenyl ammonium chloride.</li></ul>

As with the amine oxides, the monomers are polymerized by a free radical polymerization in water, again, using the same initiators disclosed above. These monomers may also be copolymerized with one or more of the vinyl monomers listed above, in the same concentration range as given above.

The inventors have found that smear-fastness performance against alkaline and acid high-lighters is improved by addition of these small oligomers in CaboJet 300, which is a chemically-modified carbon black pigment available from Cabot Corp. For example, an ink composed of 4 wt% CaboJet 300, 8 wt% glycerol, 8 wt% 1,5-pentanediol and 1 wt% of OOAO oligomer improved smear by 33% as compared to an ink without the oligomer. The smear-fastness appeared after heating and pressing the print sample for 1 to 3 seconds at 190°C. 100% water-fastness was observed after 3 minutes of drying time.

Thus, it is expected that OOAO polymerization or other zwitterionic surfactants with alkene groups will enhance the smear-fastness, water-fastness, and bleed control, serviceability by themselves or when incorporated into other co-polymers composed of vinyl monomers, such as acrylates, methacrylates, and vinyl ethers, used in thermal ink-jet inks. Copolymerization of OOAO and other unsaturated surfactants with vinyl polymers will enable a fusing process analogous to that used in laser printing. In essence, fuser technology is a post-printing treatment wherein the printed page is heated above the polymer's glass transition temperature (T_g) for a short duration. Thereby, the matrix consists of the polymer, colorants, and the media, physically fused as one.

3. Inks Employing the Foregoing Polymeric Additives

As with other ink-jet inks, the inks of the present invention comprise a vehicle and a colorant. The polymeric additive described above is added to the ink to provide a water-fast and smear-fast ink in which bleed is controlled.

The concentration of the polymeric additive of the invention is in the range of about 0.25 to 15 wt%, and preferably in the range of about 0.5 to 8 wt%, of the total ink composition.

In addition to the above-mentioned polymeric additive, various other additives are included in the ink; as is well-known in the art. Such additional additives are employed to optimize the properties of the ink for specific applications. For example, as is well-known to those skilled in the art, biocides may be used in the ink composition to inhibit growth of microorganisms, sequestering agents such as EDTA may be included to eliminate deleterious effects of heavy metal impurities, and buffer solutions may be used to control the pH of the ink. Other known additives such as viscosity modifiers and other acrylic or non-acrylic polymers may be added to improve various properties of the ink compositions as desired. Such additives typically comprise up to about 5 wt% of the ink. The purity of all components is that normally employed in conventional commercial practice of formulating ink-jet inks.

The colorant comprises either one or more pigments or one or more dyes. If pigments are employed, either a dispersant is used or the pigments are chemically modified. Dispersants used in conjunction with pigments are disclosed, for example, in U.S. Patent 5,085,698 to S.-H. Ma et al. Chemical modification of pigments is disclosed and claimed, for example, in application Serial No. 08/955,477, filed October 2, 1997, and application Serial No. 08/958,948, filed October 28, 1997 [PD-10970695-1].

If a pigment is employed as the colorant, one or more of the following pigments are useful in the practice of the invention; however, this listing is not intended to limit the invention. The following pigments are available from BASF: Paliogen® Orange, Heliogen® Blue L 6901F, Heliogen® Blue NBD 7010, Heliogen® Blue K 7090, Heliogen® Blue L 7101F, Paliogen® Blue L 6470, Heliogen® Green K 8683, and Heliogen® Green L 9140. The following pigments are available from Cabot: Monarch® 1400, Monarch® 1300, Monarch® 1100, Monarch® 1000, Monarch® 900, Monarch® 880, Monarch® 800, and Monarch® 700. The following pigments are available from Ciba-Geigy: Chromophtal® Yellow 3G, Chromophtal® Yellow GR, Chromophtal® Yellow 8G, Igrazin® Yellow 5GT, Igralite® Rubine 4BL, Monastral® Magenta, Monastral® Scarlet, Monastral® Violet R, Monastral® Red B, and Monastral® Violet Maroon B. The following pigments are available from Columbian: Raven 7000, Raven 5750, Raven 5250, Raven 5000, and Raven 3500. The following pigments are available from Degussa: Color Black FW 200, Color Black FW 2, Color Black FW 2V, Color Black FW 1, Color Black FW 18, Color Black S 160, Color Black S 170, Special Black 6, Special Black 5, Special Black 4A, Special Black 4, Printex U, Printex V, Printex 140U, and Printex 140V. The following pigment is available from DuPont: Tipure® R-101. The following pigments are available from Heubach: Dalamar® Yellow YT-858-D and Heucophthal® Blue G XBT-583D. The following pigments are available from Hoechst: Permanent Yellow GR, Permanent Yellow G, Permanent Yellow DHG, Permanent Yellow NCG-71, Permanent Yellow GG, Hansa Yellow RA, Hansa Brilliant Yellow 5GX-02, Hansa Yellow-X, Novoperm® Yellow HR, Novoperm® Yellow FGL, Hansa Brilliant Yellow 10GX, Permanent Yellow G3R-01, Hostaperm® Yellow H4G, Hostaperm® Yellow H3G, Hostaperm® Orange GR, Hostaperm® Scarlet GO, and Permanent Rubine F6B. The following pigments are available from Mobay: Quindo® Magenta, Indofast® Brilliant Scarlet, Quindo® Red R6700, Quindo® Red R6713, and Indofast® Violet. The following pigments are available from Sun Chemical: L74-1357 Yellow, L75-1331 Yellow, L75-2577 Yellow, YGD 9374 Yellow, YHD 9123 Yellow, YCD 9296 Yellow, YFD 1100 Yellow, QHD6040 Magenta, QFD1180 Magenta, RFD3217 Magenta, QFD1146 Magenta, RFD9364 Magenta, QFD 9334 Magenta, BCD6105 Cyan, BCD9448 Cyan, BCD6060 Cyan, BFD5002 Cyan, BFD1121 Cyan, and LHD9303 Black.

Examples of macromolecular chromophores include Cabojet 200 and Cabojet 300, which are available from Cabot Corporation (Billerica, MA), and Microjet Black CW, which is available from Orient Chemical (Osaka, Japan). Reference is also made to the above-listed patents regarding MMCs (U.S. Patents 5,749,952; 5,571,311; 5,630,868 and PCT published applications WO 96/18695, WO 96/18696, WO 97/48769, and in EP published application EP 688836A, listed above.

If a dye is employed, one or more of the following dyes are useful in the practice of the present invention; however, this listing is not intended to limit the invention: nitroso (CI Numbers 10000-10299), nitro (CI Numbers 10300-10999), monoazo (CI Numbers 11000-19999), disazo (CI Numbers 20000-29999), trisazo (CI Numbers 30000-34999), polyazo (CI Numbers 35000-36999), azoic (CI Numbers 37000-39999), stilbene (CI Numbers 40000-40799), carotenoid (CI Numbers 40800-40999), diphenylmethane (CI Numbers 41000-41999), triarylmethane (CI Numbers 42000-44999), xanthene (CI Numbers 45000-45999), acridine (CI Numbers 46000-46999), quinoline (CI Numbers 47000-47999), methine and polymethine (CI Numbers 48000-48999), thiazole (CI Numbers 49000-49399), indamine and indophenol (CI Numbers 49400-49999), azine (CI Numbers 50000-50999), oxazine (CI Numbers 51000-51999), thiazine (CI Numbers 52000-52999), sulfur (CI Numbers 53000-54999), lactone (CI Numbers 55000-55999), aminoketone (CI Numbers 56000-56999), hydroxyketone (CI Numbers 57000-57999), anthraquinone (CI Numbers 58000-72999), Indigoid (CI Numbers 73000-73999), phthalocyanine (CI Numbers 74000-74999), natural organic coloring matters (CI Numbers 75000-75999), oxidation bases (CI Numbers 76000-76999), and inorganic coloring matters (CI Numbers 77000-77999). The foregoing dyes are listed in the Color Index, Vol. 4, 3^rd Ed., published by the Society of Dyers and Colorists, Yorkshire, England (1971).

The concentration of the colorant is in the range of about 0.01 to 8 wt% of the ink, and preferably in the range of about 0.01 to 3 wt%, of the total ink composition.

The vehicle comprises one or more co-solvents and water. The co-solvents comprise one or more organic, water-miscible solvents commonly employed in ink-jet printing. Classes of co-solvents employed in the practice of this invention include, but are not limited to, aliphatic alcohols, aromatic alcohols, diols, glycol ethers, poly(glycol) ethers, caprolactams, formamides, acetamides, and long chain alcohols. Examples of compounds employed in the practice of this invention include, but are not limited to, primary aliphatic alcohols of 30 carbons or less, primary aromatic alcohols of 30 carbons or less, secondary aliphatic alcohols of 30 carbons or less, secondary aromatic alcohols of 30 carbons or less, 1,2-alcohols of 30 carbons or less, 1,3-alcohols of 30 carbons or less, 1,ω-alcohols of 30 carbons or less, ethylene glycol alkyl ethers, propylene glycol alkyl ethers, poly(ethylene glycol) alkyl ethers, higher homologs of poly(ethylene glycol) alkyl ethers, poly(propylene glycol) alkyl ethers, higher homologs of poly(propylene glycol) alkyl ethers, N-alkyl caprolactams, unsubstituted caprolactams, substituted formamides, unsubstituted formamides, substituted acetamides, and unsubstituted acetamides. Specific examples of co-solvents that are preferably employed in the practice of this invention include, but are not limited to, N-methyl pyrrolidone, 1,5-pentanediol, 2-pyrrolidone, diethylene glycol, 1,3-(2-methyl)-propanediol, 1,3,5-(2-methyl)-pentanetriol, tetramethylene sulfone, 3-methoxy-3-methylbutanol, glycerol, and 1,2-alkyldiols.

The concentration of the co-solvent is in the range of about 0.01 to 30 wt% of the ink, and preferably in the range of about 1 to 15 wt%, of the total ink composition.

The balance of the ink formulation comprises water.

INDUSTRIAL APPLICABILITY

The inks containing polymeric additives formed from unsaturated amine oxides, unsaturated fatty acids, betaine sulfonates, and unsaturated cationic surfactants are expected to find use in ink-jet inks for improving water-fastness, smear-fastness, and bleed control.

Thus, there has been disclosed an ink for ink-jet printing that includes specific polymeric additives. It will be readily apparent to those skilled in the art that various changes and modifications of an obvious nature may be made, and all such changes and modifications are considered to fall within the scope of the appended claims.