Dye-set for ink-jet printing inks

Abstract: A set of dyes is provided for use in vehicles employing high molecular weight saccharides. The dye-set comprises about 1 to 4% xanthene magenta, about 0.9 to 2% of a mixture of Acid Yellow 23 and Direct Yellow 86, and about 0.75 to 2.5 of Acid Blue 9 or a mixture of Acid Blue 9 and a copper phthalocyanine dye containing not more than about 25% copper phthalocyanine. The particular dye-set evidences the following properties: good crusting resistance, good stability, the proper viscosity, the proper surface tension, recognizable secondaries, high color saturation, little color-to-color bleed, rapid drytime, no negative reaction with the vehicle, be highly soluble in the vehicle, consumer-safe, and low strike-through.

Description: TECHNICAL FIELD The present invention relates to ink-jet printing, and, in particular, to a specific dye-set suitable for use with plain and coated papers and transparencies. BACKGROUND ART In the field of color printing, it is desirable to achieve as large of a color gamut as possible without sacrificing necessary ink performance parameters. It is also desirable to achieve secondary colors from the primaries which the consumer readily associates with a name such as blue or red. When the color ink is used in a digital printing device, that is, one in which a dot of color is either present or absent, the ability of the primaries to give recognizable secondaries is even more important. In printing processes such as lithography, dye transfer, and some types of thermal transfer, it is possible to vary spot size so that less is demanded of the primary colored inks when producing a good secondary. If such an ink is to be used in an ink-jet printing device, characteristics such as crusting, long term stability, and materials compatibility must also be addressed. If the ink is to be used in a thermal ink-jet printer, the further constraint of being thermally stable (kogation-resistant) is added. In general, a successful ink-set for color ink-jet printing must have the following properties: good crusting resistance, good stability, the proper viscosity, the proper surface tension, recognizable secondaries, high color saturation, little color-to-color bleed, rapid drytime, no negative reaction with the vehicle, be highly soluble in the vehicle, consumer-safe, and low strike-through. While formation of colors on plain papers is required, it is also necessary that the ink-set be useful on other print media as well, such as on transparency media. When placed into a thermal ink-jet system, the ink-set must also be kogation-resistant. Some of the conditions may be met by vehicle design; other conditions must be met by the proper selection and combination of the dyes. DE-A-3344648 describes aqueous ink-jet printer inks for color ink-jet printing. Suitable dyes used in the inks include: pyrazoline dyes, such as CI Acid Yellow 17 and CI Acid Yellow 23; phthalocyanine dyes, such as CI Direct Blue 87 and CI Acid Blue 249; xanthene dyes, such as CI Acid Red 52, 92, 94 or 289; and azo dyes, such as CI Acid Red 143, 254, 274 or 260. US-A-4818285 describes an ink-jet printer ink set for color ink-jet printing. The ink set includes: a first ink containing a water-soluble cyan dye, such as Direct Blue 86; a second ink containing a water-soluble magenta dye, such as Acid Red 52 or Reactive Red 40; and a third ink containing a water-soluble yellow dye, such as Direct Yellow 107. While it is fairly simple and obvious to make one ink which will satisfy the above conditions, it becomes very difficult to produce a set of inks to be used together to give three acceptable primaries and which will satisfy these conditions. The present invention provides an improved ink-jet dyeset for ink-jet printing comprising the following dyes: (a) a magenta dye comprising a xanthene magenta dye; (b) a yellow dye comprising a mixture of Acid Yellow 23 and Direct Yellow 86 yellow dyes; and (c) a cyan dye comprising a mixture of Acid Blue 9 and up to 25% of a copper phthalocyanine dye. The present invention also provides an ink-jet ink-set comprising magenta, yellow and cyan inks for use with ink-jet printers, each ink comprising a vehicle and at least one dye: (a) said vehicle containing at least one high molecular weight polysaccharide having a molecular weight of at least 10,000; (b) said magenta ink consisting essentially of 1 to 4% xanthene magenta dye and said vehicle; (c) said yellow ink consisting essentially of 0.9 to 2% of a mixture of Acid yellow 23 and Direct Yellow 86 dyes and said vehicle; and (d) said cyan ink consisting essentially of 0.75 to 2.5% of Acid Blue 9 dye or of a mixture of Acid Blue 9 dye and up to 25% of a copper phthalocyanine dye and said vehicle. The sole Figure, on coordinates of ΔE and dye concentration, is a plot of the effect of Direct Blue 86 dye addition to a cyan dye on ΔE due to lightfade. The ink-set of the invention comprises a set of dyes in a vehicle containing polysaccharides having a molecular weight of at least 10,000. The following dyes are employed: (1) 1 to 4 wt% xanthene magenta, preferably Acid Red 52 or Acid Red 289; (2) 0.9 to 2 wt% of a mixture of Acid Yellow 23 and Direct Yellow 86, preferably in a range from 40:60 to 60:40 and most preferably about 50:50 at 1 to 1.5 wt%; and (3) 0.75 to 2.5 wt% Acid Blue 9 or a mixture of Acid Blue 9 and up to 25% of a copper phthalocyanine dye, preferably Direct Blue 86 or Direct Blue 199. All concentrations herein are in weight percent, unless otherwise indicated. The purity of all components is that employed in normal commercial practice for ink-jet inks. The inks may also include one or more biocides, fungicides, and/or slimicides, as is commonly practiced in the art. Microbial reagents include, but are not limited to, NUOSEPT (Nuodex, Inc., a division of Huls Americal), UCARCIDE (Union Carbide), VANCIDE (RT Vanderbilt Co.), and PROXEL (ICI Americas). Further, the inks may include one or more anti-kogating agents for use in thermal ink-jet printers. Anti-kogating agents are well-known and form no part of this invention. The xanthene dyes tend to have a very high chroma on paper; they also produce brilliant blue secondaries, so they make highly desirable primaries. For example, if Direct Red 227 or Reactive Red 180 or Acid Red 27 are substituted for the Acid Red 52 in an ink-set, the hue of the blue secondary suffers markedly. Acid Red 52 and Acid Red 289 are soluble in the vehicles discussed herein and have fewer toxicological concerns than other xanthene dyes. Acid Yellow 23 by itself is a very high chroma yellow. The parameters of an ink made with this dye are quite satisfactory. However, when Acid Yellow 23 is combined with Acid Red 52 on the paper to produce red, a chemical reaction takes place which increases the amount of photofade experienced. The fade observed is more rapid for the combination of Acid Yellow 23 and Acid Red 52 than for either dye individually. This surprising result makes the use of pure Acid Yellow 23 with pure Acid Red 52 undesirable. On the other hand, a yellow dye such as Direct Yellow 86, which has acceptable hue, chroma, and photofade characteristics when mixed with Acid Red 52, has insufficient solubility in the vehicle to achieve good saturation; that is, it is not possible to achieve acceptable hues in the secondaries, due to low dye concentrations. By mixing these two dyes together in the range of 40:60 to 60:40 AY23:DY86, however, an acceptably performing ink can be made. Such an ink is sufficiently soluble in the vehicle to produce good saturation and crusting performance, has high chroma, and good hue. The secondaries produced also do not show the photofade increase seen with pure Acid Yellow 23. Without subscribing to any particular theory, this result is probably due to the overall decreased concentration of Acid Yellow 23 (there is less to fade) and to the masking action of the other yellow dye (Direct Yellow 86) molecules present. Acid Blue 9 has been found to be a good cyan dye having high chroma and good hue. Its use alone is adequate for the cyan dye in the dye-set of the invention. The blue secondaries produced when Acid Blue 9 is mixed with Acid Red 52 also experience a slightly increased rate of fade, however. This rate can be reduced by the addition of up to 25% of a copper phthalocyanine dye. Without subscribing to any particular theory, the increase in fade resistance seen in this mixture is probably due to the presence of copper in the ink and the masking effect of the phthalocyanine molecules. Above about 25%, considerable pen start-up problems are experienced, which limit the useful composition range. These dyes include counter-ions for charge balance. In the as-received form, these dyes have sodium counter-ions. However, in some instances, it may be desirable to replace some or all of the counter-ions on the dye with another counter-ion, such as tetramethylammonium (as described in U.S. Patent 4,761,180), lithium (as described in U.S. Patent 4,994,110), or another appropriate ion. In the case of the present invention, the sodium (Na) forms of Acid Blue 9 and Acid Red 52 may be employed. For Acid Yellow 23 and Direct Yellow 86, tetramethyl ammonium (TMA) counter-ion is preferably used, in order to reduce crusting. For the copper phthalocyanine dyes, lithium counter-ion may be employed to improve crusting performance. In setting the concentrations of the dyes in the various inks, it is desired that the inks provide the following results: Dye nm max Abs (±0.005) AY23-TMA 428 0.026 DY86-TMA 380 0.025 AB9-Na 630 0.248 AR52-Na 566 0.209 The vehicle of the ink preferably contains the following components: (a) 0.05 to 0.75 wt% of a high molecular weight polysaccharide having a molecular weight of at least 10,000; (b) 0.05 to 5 wt% of at least one member selected from the group consisting of zwitterionic surfactants and non-ionic amphiphiles; (c) 0.5 to 20 wt% of 1,5-pentanediol; and (d) the balance water. The large polysaccharides disclosed herein for use in ink-jet printing are effective at 0.05 to 0.75 wt% in alleviating bleed. At levels much higher than this, the viscosity of the ink is too high to jet from a pen. The polysaccharides used in the practice of the invention include polysaccharides derived from natural sources, such as salts of alginic acid, mannomuronic acid, carrageenan, guar and xanthan gums, dextran, chitin, and chitosan. Alginates are naturally occurring block copolymers of the salts of L-guluronic acid and D-mannuronic acid. Carrageenans are water-soluble, cell wall polysaccharides. Three usual forms exist: the kappa, iota, and lambda forms. All three polymers interact to form carrageenan. Typical molecular weight ranges of carrageenan are from about 300,000 to 500,000. Guar gums isolated from several sources give highly variable structures. Estimates of average molecular weight range from about 500,000 to 2,000,000. Xanthan gums have a structure comprising a cellulose backbone. A trisaccharide side chain on alternating sugar residues of the backbone distinguishes xanthan gums from cellulose. Several X-ray structures show that xanthan gums consist of several entwined polymer chains. The present invention preferably uses "sodium" alginate having a molecular weight of about 12,000 to 80,000 and a typical degree of polymerization range of about 60 to 400. This range provides the desired bleed control of the inks. Typical analysis gives 5.5% sodium, 2% calcium, and 9.5% potassium as the principal counter-ions, along with trace amounts of other mono- and di-valent cations. The alginates most preferably employed in the practice of the invention are characterized by relatively low viscosity: a 1% solution in water yields a viscosity of 60 centipoise (cp), while a 2% solution in water yields a viscosity of 500 cp. Such material is commercially available from Aldrich Chemical Company (Milwaukee, WI). The concentration of the polysaccharide, e.g., alginate, preferably from about 0.05 to 0.3 wt%, and is dependent on the particular type of amphoteric or non-ionic cosurfactant(s) employed. Such dependency is easily determined by means of print quality and ink rheology. The co-surfactant is used for bleed alleviation, as described and claimed in application Serial No. 07/686,731, filed April 17, 1991, by John R. Moffatt, entitled "Bleed Alleviation in Ink-Jet Inks", and assigned to the same assignee as the present application. Use of the polysaccharides described above in conjunction with the surfactants of that application further improves the text print quality and renders the line definition sharper between colors printing adjacent one another. The co-surfactant (typically, one or two may be employed) is a zwitterionic surfactant or a non-ionic amphiphile, such as an amine oxide. An example of bleed alleviating surfactant amphoteric molecules is an amine oxide, such as N,N-dimethyl-N-dodecyl amine oxide (NDAO): Also, in place of the C 12 H 25 - moiety, any R moiety may be used. The following moieties, their name and abbreviation are useful in the practice of the invention: N,N-dimethyl-N-tetradecyl amine oxide (NTAO); N,N-dimethyl-N-hexadecyl amine oxide (NHAO); N,N-dimethyl-N-octadecyl amine oxide (NOAO); N,N-dimethyl-N-(Z-9-octadecenyl)-N-amine oxide (OOAO). Another example is N-dodecyl-N,N-dimethyl glycinate: The SURFYNOLS are acetylenic polyethylene oxide surfactants, and are available from Air Products & Chemicals, Inc. They are useful in the practice of the invention and are represented as where n + m = 0 to 50. Preferably, the vehicle of the invention consists essentially of: about 0.05 to 0.3% polysaccharide, such as sodium alginate, about 0.05 to 1.1% N,N-dimethyl-N-(Z-9-octadecenyl)-N-amine oxide (OOAO), about 0.1 to 2.35% SURFYNOL 465 (an acetylenic polyethylene oxide surfactant), about 0.1 to 0.4% biocide, e.g., UCARCIDE 250, about 4 to 9.4% 1,5-pentanediol, and the balance water. Most preferably, the vehicle of the invention consists essentially of about 0.28% sodium alginate, about 1.01% OOAO, about 2.24% SURFYNOL 465, about 0.3% biocide (UCARCIDE 250), about 8.96% 1,5-pentanediol, and the balance water. This composition gives the best compromise between bleed alleviation and print quality. EXAMPLES The following are illustrative examples of individual red, yellow and cyan inks for use in the ink-jet ink-sets according to the present invention, together with suitable comparative examples to illustrate the advantages of the present invention. Example 1: Inks having the following compositions were prepared in which the vehicle comprised the following composition: 0.28% sodium alginate 1.01% OOAO 2.24% SURFYNOL 465 0.3% UCARCIDE 250 8.96% 1,5-pentanediol balance water. The yellow inks contained Acid Yellow 23 (comparative examples), Direct Yellow 86 (comparative examples) and 50% Acid Yellow 23 and 50% Direct Yellow 86 dyes. The magenta inks contained Acid Red 52 or Direct Red. 227 dye (comparative example). The cyan inks contained Acid Blue 9 or 75% Acid Blue 9 and 25% Direct Blue 86 dyes. Print samples produced using inks employing the different dyes and dye blends were measured in the L*a*b* colorspace from print samples. For comparative purposes, ΔE* is obtained by taking the square root of the sum of the squares of the differences of two samples. The L*a*b* coordinates for the primary and secondary colors obtained using the various magentas are summarized in Table I below. The data were measured on a Minolta chromameter, D65 Illuminant, full density print samples on Gilbert bond paper. In considering hue changes, one looks primarily at the a* and b* coordinates; as a general rule, a shift of 2 units is easily visible. Example 2 : The purpose of this work done for this Example was to determine whether the addition of a copper phthalocyanine dye to a cyan ink containing the vehicle of Example 1 and Acid Blue 9 dye would increase the lightfastness of the primary and the secondaries. The functionality of such systems was also investigated. Five inks were made up using the vehicle set forth in Example 1, in which approximately 0%, 25%, 50%*, 75%*, and 100%* of the cyan dye used was Direct Blue 86 (copper phthalocyanine), the remainder being Acid Blue 9. These inks were tested for lightfade, short term crusting, and long term crusting. The inks containing the DB86 were significantly more fade resistant in both the primaries and the secondaries than the ink which contained just AB9. Adding up to about 50% DB86 did not appreciably change the hue of the primary or secondaries. Inks with more than 25% DB86 displayed considerable start-up problems. Specifically, both the long term and short term decap times were found to decrease until at 100% DB86, the pen was unable to fire. The results are tabulated in Table II below. Crusting of DB86/AB 9 Mixtures (24°C, 45% RH). %DB86 %AB9 Short Term (seconds) Long Term (spits) 0 100 28 107 25 75 42 6016 50 50 15 NR 75 25 15 NR 100 0 5 13250 The sole Figure shows the change in ΔE values versus the amount of DB9 present in the ink. The blue (AR52 + cyan) and green (AY23+DY86 + cyan) secondaries (Curves 10 and 12) are shown as well as the cyan primary (Curve 14). In all cases, there is a dramatic non-linear decrease in ΔE with the addition of 25% DB86. Higher levels of DB86 only result in linear gains in lightfastness. From these results, it may be concluded that the addition of a copper phthalocyanine dye to the ink containing AB9 is a promising solution to the cyan fade problem. Example 3 : The effect upon secondary red lightfastness by yellow was studied, using a Minolta chromameter, D65 Illuminant, full density print samples on transparency film. The results are tabulated in Table III, below. Effect upon Secondary Red Light- fastness by DY86 (Yellow). Dye L* a* b* AR52 + AY23 (secondary red)(comparative example) Unfaded 69.56 42.94 0.98 Faded 71.01 44.16 -20.06 ΔE* = 20.24 AR52 + (AY23:DY86) (50:50) (secondary red) Unfaded 71.34 41.31 9.44 Faded 71.34 42.66 - 1.79 ΔE* = 11.31 The greater the ΔE value, the greater the hue difference in the samples. Table III shows that a red produced using AR52 and a mixture of DY86 and AY23 fades about half as much as a red produced using just AY23 in combination with AR52, by comparing the respective ΔE values. Example 4 : The effect upon secondary blue lightfastness by Direct Blue 86 was studied, using a Minolta chromameter, D65 Illuminant, full density print samples on Gilbert bond. The results are tabulated in Table IV, below. Effect upon Secondary Blue Lightfastness by DB86 (Cyan). Dye L* a* b* AR52 + AB9 (secondary blue) Unfaded 34.83 35.84 -62.9 Faded 74.81 15.66 - 2.106 ΔE* = 75.51 AR52 + (AB9:DB86) (75:25) (secondary blue) Unfaded 33.64 32.61 -62.1 Faded 47.14 12.56 -27.7 ΔE* = 42.04 Table IV shows that the addition of DB86 to AB9 reduces fade considerably (nearly 50%). This is also shown in the sole Figure, discussed above. Finally, the preferred ink-set of the invention prints a good black color as compared to the various dye combinations that are possible from the foregoing dyes. Thus, there has been disclosed an ink-set for use in ink-jet printers. It will be readily apparent to those skilled in this art that various changes and modifications are considered to fall within the scope of this invention, as defined by the appended claims.

Claims: An ink-jet dye-set for ink-jet printing comprising the following dyes: (a) a magenta dye comprising a xanthene magenta dye; (b) a yellow dye comprising a mixture of Acid Yellow 23 and Direct Yellow 86 yellow dyes; and (c) a cyan dye comprising a mixture of Acid Blue 9 and up to 25% wt of a copper phthalocyanine dye. An ink-jet ink-set comprising magenta, yellow and cyan inks for use with ink-jet printers, each ink comprising a vehicle and at least one dye: (a) said vehicle containing at least one high molecular weight polysaccharide having a molecular weight of at lest 10,000; (b) said magenta ink consisting essentially of 1 to 4% wt. xanthene magenta dye and said vehicle; (c) said yellow ink consisting essentially of 0.9 to 2% wt of a mixture of Acid Yellow 23 and Direct Yellow 86 dyes and said vehicle; and (d) said cyan ink consisting essentially of 0.75 to 2.5% wt of Acid Blue 9 dye or of a mixture of Acid Blue 9 dye and up to 25% wt of a copper phthalocyanine dye and said vehicle. The ink-set of claim 2 wherein said xanthene magenta dye is selected from the group consisting of Acid Red 52 and Acid Red 289 dyes. The ink-set of Claim 2 wherein said mixture of Acid Yellow 23 and Direct Yellow 86 dyes ranges in ratio from 40:60 to 60:40 of AY23:DY86. The ink-set of Claim 4 wherein said ratio is about 50:50 and said mixture is present in said ink in an amount ranging from 1 to 1.5% wt. The ink-set of Claim 2, wherein both Acid Yellow and Direct Yellow 86 dyes include tetramethylammonium counter-ion. The ink-set of Claim 2 wherein said copper phthalocyanine dye is selected from the group consisting of Direct Blue 86 and Direct Blue 199 dyes. The ink-set of Claim 7, wherein said copper phthalocyanine dye includes lithium counter-ion. The ink-set of Claim 2 wherein said vehicle comprises: (a) 0.05 to 0.75 wt% of a high molecular weight polysaccharide having a molecular weight of at least 10,000; (b) 0.05 to 5 wt% of at least one member selected from the group consisting of zwitterionic surfactants and non-ionic amphiphiles; (c) 0.5 to 20 wt% of 1,5-pentanediol; and (d) the balance water. The ink-set of Claim 9 wherein said high molecular weight polysaccharide is selected from the group consisting of alginic acid, mannomuronic acid, carrageenan, guar and xanthan gums, dextran, chitin, and chitosan and wherein said amphoteric surfactants are pH-sensitive surfactants selected from the group consisting of N,N-dimethyl-N-dodecyl amine oxide, N,N-dimethyl-N-tetradecyl amine oxide, N,N-dimethyl-N-hex-adecyl amine oxide, N,N-dimethyl-N-octadecyl amine oxide, N,N-dimethyl-N -(Z-9-octadecenyl)-N-amine oxide, N-dodecyl-N,N-dimethyl glycine, and an acetylenic polyethylene oxide surfactant.

Inventors: JOHNSON LOREN E, MOFFATT JOHN R, JOHNSON, LOREN E., MOFFATT, JOHN R.
Applicants: HEWLETT PACKARD CO, HEWLETT-PACKARD COMPANY
Application year: 1992
Main classification: C09D11
IPC codes: C09D11, B41J2, B41M5