Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-07-28
2001-08-28
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031470
Reexamination Certificate
active
06280512
ABSTRACT:
TECHNICAL FIELD
The present invention relates to aqueous liquid inks which are waterfast when applied and, more particularly, to enhancement in waterfastness of non-black ink jet inks by adding ammonium salts to an ink jet ink composition.
BACKGROUND ART
In the ink jet printing art, water soluble dyes are desirable for runnability. However, waterfast inks are highly desirable for producing permanent images. Waterfast non-black inks are highly desirable in ink-jet printing to produce water-resistant prints. Decreasing the solubility of the dye increases the waterfastness, and vice versa. Achieving improvement in waterfastness of ink jet inks remains a top priority. A waterfast ink is highly desired for publishing and documentation, including in the lottery industry, to prevent alteration of information on such documents.
One means for improving waterfastness is to use polymers and resins in inks to enhance adhesion of the dye to substrates. However, presence of resins in inks adversely affects machine runnability due to formation of deposits on orifice plates and charge plate buildup.
In commonly assigned U.S. Pat. No. 5,425,805, totally incorporated herein by reference, a waterfast ink comprising a liquid vehicle, a dye, EPI and NMP is disclosed. The use of ethoxylated polyethylene imine (EPI) and the like in the ink showed significant improvement in waterfastness from a range of 40-60% to a range of 70-95%, depending on the substrate and the dye in the ink. Unfortunately, non-black color dyes achieve only a modest improvement in water resistance with EPI, partially as a result of their extreme solubility. Therefore, it is a challenge in the ink jet printing industry to achieve waterfastness in an aqueous, non-black dye-based ink.
It is seen then that there is a need for improved waterfast color ink for use in ink jet recording equipment.
SUMMARY OF THE INVENTION
This need is met by the waterfast color ink composition according to the present invention, wherein enhancement in waterfastness of color ink jet inks was achieved by adding specific ammonium salts to the ink composition.
In accordance with one embodiment of the present invention, an ink composition comprises a liquid vehicle, a dye, a polymer, at least one water soluble organic solvent, and at least one ammonium salt for enhancement of waterfastness. The ink preferably comprises 1-10% of 18% stock ethoxylated polyethyleneimine to which is added 1-8% N-methyl-pyrrolidone, to increase the waterfastness of the ink to a level greater than 70%. The ammonium salts are preferably selected from the group comprising ammonium salts of mineral acids.
Other objects and advantages of the invention will be apparent from the following description and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
The ink jet ink composition of the present invention comprises a liquid vehicle, a dye, a polymer, a water soluble organic solvent, and at least one ammonium salt, in an amount up to approximately 1%.
Although ethoxylated polyethylene imine is very water soluble, a small portion of it tends to interact with the anionic dye prematurely to form insoluble residue. This is confirmed by an approximately 5% drop in absorbance after 2% of the polymer is added to the dye solution. When only 1% of the polymer is added, the drop in absorbance is insignificant. However, the waterfastness of the ink correspondingly drops by about 20%. The ink with 1% polymer has excellent runnability in the ink jet printer. The addition of 1-8% N-methyl-pyrrolidone (NMP) to the ink composition increases the waterfastness to a level greater than 90%, as compared to the same ink composition without NMP.
However, non-black color dyes achieve only a modest improvement in water resistance, even with both EPI and NMP added to the ink composition. Therefore, in accordance with the present invention, an ammonium salt is also added to ink compositions which contain color dyes, such as cyan, magenta, and yellow. The ammonium salt considerably improves water resistance of the ink, resulting in waterfast color inks for ink jet printing.
In a preferred embodiment of the present invention, the ink composition comprises 1-10% of 18% stock ethoxylated polyethyleneimine and 1-8% N-methyl-pyrrolidone, to which is added up to 1% of an ammonium salt, to increase the waterfastness of the ink to levels greater than 70%.
The liquid vehicle in the ink jet ink composition of the present invention comprises an amine, preferably alkyl- and alkanol-substituted amines such as dimethylethanolamine, triethanolamine, diethylethanolamine and the like. Other additives that are optionally included in the vehicle of the invention include a corrosion inhibitor in an amount from 0 to 0.2 wt. % such as an alkanolamine; and a wetting agent of from 0 to 1 wt. %, such as an ethoxylated glycol ether; and a lower aliphatic alcohol having one hydroxy group and up to five carbon atoms in a straight or branched chain in an amount of 0 to 10 wt. %; and a biocide from 0 to 0.5 wt. % such as dehydroacetic acid. The ink may also include an optional defoamer such as phosphate esters, silicone or non-silicone defoamer or acetylenic diol.
The dye in the ink jet ink composition of the present invention is water soluble color dye. In general, the concentration of the dye should be between about 2% and 4% by weight, in the powder form.
In accordance with the present invention, a multitude of suitable color dyes which are commercially available may be used to prepare the dye concentrate which can be used to formulate the waterfast color ink of the present invention. Examples of commercially available color dyes include TRICON COLORS, LLC Direct Blue 199 Na Solution, Direct Yellow 132 Na Solution, Acid Blue 9, Acid Yellow 23, Acid Red 52, Acid Yellow 17, Direct Red 227, Direct Yellow 86, Direct Yellow 132, Reactive Red 180; CROMPTON & KNOWLES COLORS INCORPORATED Intrajet Liquid Yellow DG, Intrajet Liquid Magenta KRP, Intrajet Liquid Blue JE, Intrajet Liquid Magenta VER, Intrabond Liquid Yellow G, Intralite Turquoise GLL-IJ, Intrabond Liquid Brilliant Pink BR 200%, Intracron Brilliant Yellow VS-GL; ZENECA SPECIALIST COLOURS Projet Cyan 1, Projet Cyan 2, Projet Magenta 1, Projet Magenta 2, Projet Yellow 1, Projet Yellow 2, Projet Magenta 3B-0A Liquid, Reactive Orange NBG 1531/24/3, Reactive Turquoise NBG 1531/24/8, Reactive Blue NBG 1531/24/6, Reactive Red NBG 1531/24/5, Reactive Red NBG 1531/24/4, Reactive Yellow NBG 1531/24/2, Reactive Yellow NBG 1531/24/1, and Projet Red H-8 BA Liquid; and various other dyes and combinations of dyes.
In accordance with the present invention, when an ammonium salt is added to ink comprising a dye, EPI, and NMP, the waterfastness of the ink is considerably enhanced. The following examples list various ammonium salts added to ink compositions and the effect of those ammonium salts on waterfastness of the ink.
REFERENCES:
patent: 5364462 (1994-11-01), Crystal et al.
patent: 5730789 (1998-03-01), Botros
patent: 5888285 (1999-03-01), Gundlach et al.
patent: 5973025 (1999-10-01), Nigam et al.
Faison Veronica F.
Haushalter Barbar Joan
Klemanski Helene
Scitex Digital Printing, Inc.
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