Disclosed is an ink composition which comprises (1) water; (2) an anionic dye; and (3) a copolymer of vinyl pyrrolidinone and a vinyl imidazolium salt. Also disclosed are methods for using the aforementioned ink compositions in ink jet printing processes.

BACKGROUND OF THE INVENTION 
The present invention is directed to ink compositions and to processes for 
the preparation and use thereof. More specifically, the present invention 
is directed to compositions suitable for use in ink jet printing 
processes. One embodiment of the present invention is directed to an ink 
composition which comprises (1) water; (2) a dye; and (3) a copolymer of 
vinyl pyrrolidinone and a vinyl imidazolium salt. 
Ink jet printing systems generally are of two types: continuous stream and 
drop-on-demand. In continuous stream ink jet systems, ink is emitted in a 
continuous stream under pressure through at least one orifice or nozzle. 
The stream is perturbed, causing it to break up into droplets at a fixed 
distance from the orifice. At the break-up point, the droplets are charged 
in accordance with digital data signals and passed through an 
electrostatic field which adjusts the trajectory of each droplet in order 
to direct it to a gutter for recirculation or a specific location on a 
recording medium. In drop-on-demand systems, a droplet is expelled from an 
orifice directly to a position on a recording medium in accordance with 
digital data signals. A droplet is not formed or expelled unless it is to 
be placed on the recording medium. 
Since drop-on-demand systems require no ink recovery, charging, or 
deflection, the system is much simpler than the continuous stream type. 
There are two types of drop-on-demand ink jet systems. One type of 
drop-on-demand system has as its major components an ink filled channel or 
passageway having a nozzle on one end and a piezoelectric transducer near 
the other end to produce pressure pulses. The relatively large size of the 
transducer prevents close spacing of the nozzles, and physical limitations 
of the transducer result in low ink drop velocity. Low drop velocity 
seriously diminishes tolerances for drop velocity variation and 
directionality, thus impacting the system's ability to produce high 
quality copies. Drop-on-demand systems which use piezoelectric devices to 
expel the droplets also suffer the disadvantage of a slow printing speed. 
The other type of drop-on-demand system is known as thermal ink jet, or 
bubble jet, and produces high velocity droplets and allows very close 
spacing of nozzles. The major components of this type of drop-on-demand 
system are an ink filled channel having a nozzle on one end and a heat 
generating resistor near the nozzle. Printing signals representing digital 
information originate an electric current pulse in a resistive layer 
within each ink passageway near the orifice or nozzle, causing the ink in 
the immediate vicinity to evaporate almost instantaneously and create a 
bubble. The ink at the orifice is forced out as a propelled droplet as the 
bubble expands. When the hydrodynamic motion of the ink stops, the process 
is ready to start all over again. With the introduction of a droplet 
election system based upon thermally generated bubbles, commonly referred 
to as the "bubble jet" system, the drop-on-demand ink jet printers provide 
simpler, lower cost devices than their continuous stream counterparts, and 
yet have substantially the same high speed printing capability. 
The operating sequence of the bubble jet system begins with a current pulse 
through the resistive layer in the ink filled channel, the resistive layer 
being in close proximity to the orifice or nozzle for that channel. Heat 
is transferred from the resistor to the ink. The ink becomes superheated 
far above its normal boiling point, and for water based ink, finally 
reaches the critical temperature for bubble formation or nucleation of 
around 280.degree. C. Once nucleated, the bubble or water vapor thermally 
isolates the ink from the heater and no further heat can be applied to the 
ink. This bubble expands until all the heat stored in the ink in excess of 
the normal boiling point diffuses away or is used to convert liquid to 
vapor, which removes heat due to heat of vaporization. The expansion of 
the bubble forces a droplet of ink out of the nozzle, and once the excess 
heat is removed, the bubble collapses on the resistor. At this point, the 
resistor is no longer being heated because the current pulse has passed 
and, concurrently with the bubble collapse, the droplet is propelled at a 
high rate of speed in a direction towards a recording medium. The 
resistive layer encounters a severe cavitational force by the collapse of 
the bubble, which tends to erode it. Subsequently, the ink channel refills 
by capillary action. This entire bubble formation and collapse sequence 
occurs in about 10 microseconds. The channel can be refired after 100 to 
500 microseconds minimum dwell time to enable the channel to be refilled 
and to enable the dynamic refilling factors to become somewhat dampened. 
Thermal ink jet processes are well known and are described in, for 
example, U.S. Pat. No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 
4,410,899, U.S. Pat. No. 4,412,224, and U.S. Pat. No. 4,532,530, the 
disclosures of each of which are totally incorporated herein by reference. 
Acoustic ink jet printing processes are also known. As is known, an 
acoustic beam exerts a radiation pressure against objects upon which it 
impinges. Thus, when an acoustic beam impinges on a free surface (i.e., 
liquid/air interface) of a pool of liquid from beneath, the radiation 
pressure which it exerts against the surface of the pool may reach a 
sufficiently high level to release individual droplets of liquid from the 
pool, despite the restraining force of surface tension. Focusing the beam 
on or near the surface of the pool intensifies the radiation pressure it 
exerts for a given amount of input power. These principles have been 
applied to prior ink jet and acoustic printing proposals. For example, K. 
A. Krause, "Focusing Ink Jet Head," IBM Technical Disclosure Bulletin, Vol 
16, No. 4, September 1973, pp. 1168-1170, the disclosure of which is 
totally incorporated herein by reference, describes an ink jet in which an 
acoustic beam emanating from a concave surface and confined by a conical 
aperture was used to propel ink droplets out through a small ejection 
orifice. Acoustic ink printers typically comprise one or more acoustic 
radiators for illuminating the free surface of a pool of liquid ink with 
respective acoustic beams. Each of these beams usually is brought to focus 
at or near the surface of the reservoir (i.e., the liquid/air interface). 
Furthermore, printing conventionally is performed by independently 
modulating the excitation of the acoustic radiators in accordance with the 
input data samples for the image that is to be printed. This modulation 
enables the radiation pressure which each of the beams exerts against the 
free ink surface to make brief, controlled excursions to a sufficiently 
high pressure level for overcoming the restraining force of surface 
tension. That, in turn, causes individual droplets of ink to be ejected 
from the free ink surface on demand at an adequate velocity to cause them 
to deposit in an image configuration on a nearby recording medium. The 
acoustic beam may be intensity modulated or focused/defocused to control 
the ejection timing, or an external source may be used to extract droplets 
from the acoustically excited liquid on the surface of the pool on demand. 
Regardless of the timing mechanism employed, the size of the ejected 
droplets is determined by the waist diameter of the focused acoustic beam. 
Acoustic ink printing is attractive because it does not require the 
nozzles or the small ejection orifices which have caused many of the 
reliability and pixel placement accuracy problems that conventional drop 
on demand and continuous stream ink jet printers have suffered. The size 
of the ejection orifice is a critical design parameter of an ink jet 
because it determines the size of the droplets of ink that the jet ejects. 
As a result, the size of the ejection orifice cannot be increased, without 
sacrificing resolution. Acoustic printing has increased intrinsic 
reliability because there are no nozzles to clog. As will be appreciated, 
the elimination of the clogged nozzle failure mode is especially relevant 
to the reliability of large arrays of ink ejectors, such as page width 
arrays comprising several thousand separate ejectors. Furthermore, small 
ejection orifices are avoided, so acoustic printing can be performed with 
a greater variety of inks than conventional ink jet printing, including 
inks having higher viscosities and inks containing pigments and other 
particulate components. It has been found that acoustic ink printers 
embodying printheads comprising acoustically illuminated spherical 
focusing lenses can print precisely positioned pixels (i.e., picture 
elements) at resolutions which are sufficient for high quality printing of 
relatively complex images. It has also has been discovered that the size 
of the individual pixels printed by such a printer can be varied over a 
significant range during operation, thereby accommodating, for example, 
the printing of variably shaded images. Furthermore, the known droplet 
ejector technology can be adapted to a variety of printhead 
configurations, including (1) single ejector embodiments for raster scan 
printing, (2) matrix configured ejector arrays for matrix printing, and 
(3) several different types of pagewidth ejector arrays, ranging from 
single row, sparse arrays for hybrid forms of parallel/serial printing to 
multiple row staggered arrays with individual ejectors for each of the 
pixel positions or addresses within a pagewidth image field (i.e., single 
ejector/pixel/line) for ordinary line printing. Inks suitable for acoustic 
ink jet printing typically are liquid at ambient temperatures (i.e., about 
25.degree. C.), but in other embodiments the ink is in a solid state at 
ambient temperatures and provision is made for liquefying the ink by 
heating or any other suitable method prior to introduction of the ink into 
the printhead. Images of two or more colors can be generated by several 
methods, including by processes wherein a single printhead launches 
acoustic waves into pools of different colored inks. Further information 
regarding acoustic ink jet printing apparatus and processes is disclosed 
in, for example, U.S. Pat. No. 4,308,547, U.S. Pat. No. 4,697,195, U.S. 
Pat. No. 5,028,937, U.S. Pat. No. 5,041,849, U.S. Pat. No. 4,751,529, U.S. 
Pat. No. 4,751,530, U.S. Pat. No. 4,751,534, U.S. Pat. No. 4,801,953, and 
U.S. Pat. No. 4,797,693, the disclosures of each of which are totally 
incorporated herein by reference. The use of focused acoustic beams to 
eject droplets of controlled diameter and velocity from a free-liquid 
surface is also described in J. Appl. Phys., vol. 65, no. 9 (May 1, 1989) 
and references therein, the disclosure of which is totally incorporated 
herein by reference. 
U.S. Pat. No. 5,250,107 (Bares), the disclosure of which is totally 
incorporated herein by reference, discloses a water-fast ink composition 
and method for making the same. A selected chemical dye having at least 
one functional group with an extractable hydrogen atom thereon (e.g. 
--COOH, --NH.sub.2, or --OH) is combined with an ammonium zirconium 
polymer salt (e.g. ammonium zirconium carbonate, ammonium zirconium 
acetate, ammonium zirconium sulfate, ammonium zirconium phosphate, and 
ammonium zirconium oxalate). The resulting mixture preferably contains 
about 0.01-5.0% by weight ammonium zirconium polymer salt and about 
0.5-5.0% by weight chemical dye. Upon dehydration of the mixture, the 
ammonium zirconium polymer salt and chemical dye form a cross-linked dye 
complex which is stable and water-fast. The mixture may be dispensed onto 
a variety of substrates (e.g. paper) using thermal ink jet or other 
printing systems. 
U.S. Pat. No. 4,267,088 (Kempf), the disclosure of which is totally 
incorporated herein by reference, discloses coatings particularly useful 
as marking inks in which an epichlorohydrin-modified polyethyleneimine and 
an ethylene oxide-modified polyethyleneimine cooperate in aqueous solution 
to form a composition capable of application to form deposits adherent to 
most materials and resistant to most organic solvents but readily 
removable by water. 
U.S. Pat. No. 4,197,135 (Bailey et al.), the disclosure of which is totally 
incorporated herein by reference, discloses an ink for use in ink jet 
printers containing a water soluble dye and a polyamine containing 7 or 
more nitrogen atoms per molecule, with the ink composition having a pH of 
8 or above, the upper pH limit being dye decomposition dependent. The ink 
has improved waterfastness over an equivalent ink formulation without the 
polyamine additive. 
U.S. Pat. No. 4,659,382 (Kang), the disclosure of which is totally 
incorporated herein by reference, discloses an ink jet ink composition 
comprising a major amount of water, a hydroxyethylated polyethyleneimine 
polymer, and a dye component, wherein the polymer has incorporated therein 
from about 65 to about 80 percent by weight of hydroxyethyl groups. 
Japanese Patent publication 57-198768, the disclosure of which is totally 
incorporated herein by reference, discloses a type of water-base ink made 
of acidic dye and/or direct dye, cationic water-soluble resin, 
water-soluble organic solvent, and water. 
Copending application U.S. Ser. No. (09/046,895), filed concurrently 
herewith, entitled "Ink Compositions and Multicolor Thermal Ink Jet 
Printing Process for the Production of High Quality Images," with the 
named inventor John Wei-Ping Lin, the disclosure of which is totally 
incorporated herein by reference, discloses a set of inks for printing 
multicolor images in an ink jet printer, said ink set comprising (A) a 
first ink having a first color and comprising water and a colorant 
selected from the group consisting of (1) anionic dyes, (2) dyes having 
physically or chemically associated therewith a stabilizing agent having 
anionic groups thereon, (3) pigment particles having anionic groups 
chemically attached thereto, (4) pigment particles having physically or 
chemically associated therewith a stabilizing agent having anionic groups 
thereon, and (5) mixtures thereof; and (B) a second ink comprising water, 
an optional colorant having a color other than the first color, and an 
ammonium salt having at least two cationic ammonium functional groups, 
wherein the colorant in the first ink is capable of being immobilized on a 
printing substrate by interaction with the ammonium salt having at least 
two cationic ammonium functional groups in the second ink. 
Copending application U.S. Ser. No. (09/047,097), filed concurrently 
herewith, entitled "Ink Compositions With Improved Waterfastness and Smear 
Resistance," with the named inventors Kurt B. Gundlach, Richard L. Colt, 
Luis A. Sanchez, Maura A. Sweeney, and Edward J. Radigan, Jr., the 
disclosure of which is totally incorporated herein by reference, discloses 
an ink composition which comprises water, an anionic dye, and a 
polyquaternary amine compound selected from the group consisting of 
polydiallyl dimethyl ammonium compounds, polyquaternized polyvinylamines, 
polyquaternized polyallylamines, and mixtures thereof. Also disclosed are 
methods for using the aforementioned ink composition in ink jet printing 
processes. 
Copending application U.S. Ser. No. (09/046,852), filed concurrently 
herewith, entitled "Ink Compositions With Improved Shelf Stability", with 
the named inventors Kurt B. Gundlach, Luis A. Sanchez, Richard L. Colt, 
Maura A. Sweeney, and William M. Schwarz, the disclosure of which is 
totally incorporated herein by reference, discloses an ink composition 
which comprises (1) water; (2) a nonpolymeric salt comprising at least one 
cation and at least one anion; and (3) a colorant comprising an anionic 
dye complexed with a polyquaternary amine compound. Also disclosed is an 
ink composition which comprises (1) water; (2) a nonpolymeric salt 
comprising at least one cation and at least one anion; (3) an anionic dye; 
and (4) a polyquaternary amine compound. In one embodiment, the 
polyquaternary amine compound is selected from the group consisting of 
polydiallyl dimethyl ammonium compounds, polyquaternized polyvinylamines, 
polyquaternized polyallylamines, epichlorohydrin/amine copolymers, 
cationic amido amine copolymers, copolymers of vinyl pyrrolidinone and a 
vinyl imidazolium salt, and mixtures thereof. 
Copending application U.S. Ser. No. (09/046,849), filed concurrently 
herewith, entitled "Ink Compositions Containing Cationic Amido Amine 
Polymers", with the named inventor William M. Schwarz, the disclosure of 
which is totally incorporated herein by reference, discloses an ink 
composition which comprises (1) water; (2) a dye; and (3) a cationic amido 
amine copolymer. Also disclosed are methods for using the aforementioned 
ink composition in ink jet printing processes. 
While known compositions and processes are suitable for their intended 
purposes, a need remains for improved ink compositions suitable for ink 
jet printing processes. In addition, a need remains for ink compositions 
with improved waterfastness. Further, a need remains for ink compositions 
with improved wet smear resistance. Additionally, a need remains for ink 
compositions with reduced intercolor bleed when two or more colors are 
printed adjacent to each other. There is also a need for ink compositions 
for ink jet printing which contain acid dyes, which enable advantages such 
as bright colors, low cost, and high waterfastness when complexed with 
cationic polymers. In addition, there is a need for ink compositions with 
improved lightfastness. Further, there is a need for ink compositions 
suitable for use in ink jet printing processes and having relatively low 
viscosities. Additionally, there is a need for ink compositions which 
exhibit excellent smear resistance. A need also remains for ink 
compositions suitable for ink jet printing which exhibit reduced kogation 
in ink jet printer hardware. In addition, a need remains for ink 
compositions with desirable surface tension values for ink jet printing. 
Further, a need remains for ink compositions with good latency in ink jet 
printing processes. Additionally, a need remains for ink compositions 
which exhibit shelf and solution stability with respect to hydrolysis and 
oxidation. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide ink compositions with 
the above noted advantages. 
It is another object of the present invention to provide improved ink 
compositions suitable for ink jet printing processes. 
It is yet another object of the present invention to provide ink 
compositions with improved waterfastness. 
It is still another object of the present invention to provide ink 
compositions with improved wet smear resistance. 
Another object of the present invention is to provide ink compositions with 
reduced intercolor bleed when two or more colors are printed adjacent to 
each other. 
Yet another object of the present invention is to provide ink compositions 
for ink jet printing which contain acid dyes, which enable advantages such 
as bright colors, low cost, and high waterfastness when complexed with 
cationic polymers. 
Still another object of the present invention is to provide ink 
compositions with improved lightfastness. 
It is another object of the present invention to provide ink compositions 
suitable for use in ink jet printing processes and having relatively low 
viscosities. 
It is yet another object of the present invention to provide ink 
compositions which exhibit excellent smear resistance. 
It is still another object of the present invention to provide ink 
compositions suitable for ink jet printing which exhibit reduced kogation 
in ink jet printer hardware. 
Another object of the present invention is to provide ink compositions with 
desirable surface tension values for ink jet printing. 
Yet another object of the present invention is to provide ink compositions 
with good latency in ink jet printing processes. 
Still another object of the present invention is to provide ink 
compositions which exhibit shelf and solution stability with respect to 
hydrolysis and oxidation. 
These and other objects of the present invention (or specific embodiments 
thereof) can be achieved by providing an ink composition which comprises 
(1) water; (2) a dye; and (3) a copolymer of vinyl pyrrolidinone and a 
vinyl imidazolium salt. 
DETAILED DESCRIPTION OF THE INVENTION 
Inks of the present invention contain an aqueous liquid vehicle, a dye, and 
a copolymer of vinyl pyrrolidinone and a vinyl imidazolium salt. 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. 
The ink also contains a copolymer of a vinyl imidazolium salt and vinyl 
pyrrolidinone. In one embodiment, the copolymer is of a vinyl imidazolium 
salt of the formula 
##STR1## 
wherein X is an anion and R is a hydrogen atom or an alkyl group, 
typically with from 1 to about 8 carbon atoms and preferably with from 1 
to about 3 carbon atoms, and vinyl pyrrolidinone, of the formula 
##STR2## 
wherein the copolymer is of the general formula 
##STR3## 
wherein X is any suitable or desired anion, such as Cl--, Br--, I--, 
HSO.sub.4 --, HSO.sub.3 --, SO.sub.4.sup.2-, SO.sub.3.sup.2-, CH.sub.2 
SO.sub.3 --, CH.sub.3 SO.sub.3 --, CH.sub.3 C.sub.6 H.sub.4 SO.sub.3 --, 
NO.sub.3 --, HCOO--, CH.sub.3 COO--, HCO.sub.3 --, CO.sub.3.sup.2-, 
H.sub.2 PO.sub.4 --, HPO.sub.4.sup.2-, PO.sub.4.sup.3-, SCN--, BF.sub.4 
--, ClO.sub.4 --, SSO.sub.3 --, or the like, R is a hydrogen atom or an 
alkyl group, typically with from 1 to about 8 carbon atoms and preferably 
with from 1 to about 3 carbon atoms, m is a integer representing the 
number of repeat vinyl imidazolium units, and n is an integer representing 
the number of repeat vinyl pyrrolidinone units. When R is a hydrogen atom, 
the pH of the ink can be adjusted to provide optimal ink-paper 
interaction; for example, the hydrogen atom can be extracted upon contact 
with the paper, or the cationic character of the polymer can be adjusted 
with ink pH. Random copolymers of the above formula generally are 
preferred, although alternating and block copolymers are also suitable. 
The weight average molecular weight of the polymer typically is from about 
1,000 to about 1,000,000, preferably from about 1,000 to about 100,000, 
and more preferably from about 2,000 to about 5,000, although the value 
can be outside of these ranges. The ratio of vinyl imidazolium monomers to 
vinyl pyrrolidinone monomers typically is from about 99:1 to about 5:95, 
preferably from about 95:5 to about 20:80, more preferably from about 95:5 
to about 30:70, and even more preferably from about 95:5 to about 50:50, 
although the value can be outside of these ranges. Vinyl 
pyrrolidinone/vinyl imidazolium salt copolymers are commercially 
available; for example, BASF, Parsippany, N.J., provides vinyl imidazolium 
chloride/vinyl pyrrolidinone copolymers (of the above formula wherein R is 
CH.sub.3) with a molecular weight of about 100,000 in three monomer 
ratios: LUVIQUAT.RTM. FC905 has a vinyl imidazolium chloride:vinyl 
pyrrolidinone ratio of 95:5 with 6.7 milliequivalents per gram of cationic 
groups, LUVIQUAT.RTM. FC550 has a vinyl imidazolium chloride:vinyl 
pyrrolidinone ratio of 50:50 with 3.0 milliequivalents per gram of 
cationic groups, and LUVIQUAT.RTM. FC370 has a vinyl imidazolium 
chloride:vinyl pyrrolidinone ratio of 30:70 with 1.8 milliequivalents per 
gram of cationic groups. Also available from BASF is LUVIQUAT.RTM. HM552, 
with a molecular weight of about 800,000 and a vinyl imidazolium 
chloride:vinyl pyrrolidinone ratio of 50:50. The vinyl pyrrolidinone/vinyl 
imidazolium salt copolymer is present in the ink in any desired or 
effective amount, typically from about 0.1 to about 30 percent by weight 
of the ink, preferably from about 0.2 to about 20 percent by weight of the 
ink, more preferably from about 0.5 to about 10 percent by weight of the 
ink, and even more preferably from about 1 to about 5 percent by weight of 
the ink, although the amount can be outside of these ranges. 
The dye can be any suitable or desired dye, including cationic dyes, 
anionic dyes, and the like, with anionic dyes being preferred. Examples of 
suitable dyes include Food dyes such as Food Black No. 1, Food Black No. 
2, Food Red No. 40, Food Blue No. 1, Food Yellow No. 7, and the like, FD & 
C dyes, Acid Black dyes (No. 1, 7, 9, 24, 26, 48, 52, 58, 60, 61, 63, 92, 
107, 109, 118, 119, 131, 140, 155, 156, 172, 194, and the like), Acid Red 
dyes (No. 1, 8, 32, 35, 37, 52, 57, 92, 115, 119, 154, 249, 254, 256, and 
the like), Acid Blue dyes (No.1, 7, 9, 25, 40, 45, 62, 78, 80, 92, 102, 
104, 113, 117, 127, 158, 175, 183, 193, 209, and the like), Acid Yellow 
dyes (No. 3, 7, 17, 19, 23, 25, 29, 38, 42, 49, 59, 61, 72, 73, 114, 128, 
151, and the like), Direct Black dyes (No. 4, 14, 17, 22, 27, 38, 51, 112, 
117, 154, 168, and the like), Direct Blue dyes (No. 1, 6, 8, 14, 15, 25, 
71, 76, 78, 80, 86, 90, 106, 108, 123, 163, 165, 199, 226, and the like), 
Direct Red dyes (No. 1, 2, 16, 23, 24, 28, 39, 62, 72, 236, and the like), 
Direct Yellow dyes (No. 4, 11, 12, 27, 28, 33, 34, 39, 50, 58, 86, 100, 
106, 107, 118, 127, 132, 142, 157, and the like), anthraquinone dyes, 
monoazo dyes, disazo dyes, phthalocyanine derivatives, including various 
phthalocyanine sulfonate salts, aza(18)annulenes, formazan copper 
complexes, triphenodioxazines, Bernacid Red 2BMN; Pontamine Brilliant Bond 
Blue A; Pontamine; Caro direct Turquoise FBL Supra Conc. (Direct Blue 
199), available from Carolina Color and Chemical; Special Fast Turquoise 
8GL Liquid (Direct Blue 86), available from Mobay Chemical; Intrabond 
Liquid Turquoise GLL (Direct Blue 86), available from Crompton and 
Knowles; Cibracron Brilliant Red 38-A (Reactive Red 4), available from 
Aldrich Chemical; Drimarene Brilliant Red X-2B (Reactive Red 56), 
available from Pylam, Inc.; Levafix Brilliant Red E-4B, available from 
Mobay Chemical; Levafix Brilliant Red E-6BA, available from Mobay 
Chemical; Procion Red H8B (Reactive Red 31), available from ICI America; 
Pylam Certified D&C Red #28 (Acid Red 92), available from Pylam; Direct 
Brilliant Pink B Ground Crude, available from Crompton & Knowles; Cartasol 
Yellow GTF Presscake, available from Sandoz, Inc.; Tartrazine Extra Conc. 
(FD&C Yellow #5, Acid Yellow 23), available from Sandoz; Carodirect Yellow 
RL (Direct Yellow 86), available from Carolina Color and Chemical; 
Cartasol Yellow GTF Liquid Special 110, available from Sandoz, Inc.; D&C 
Yellow #10 (Acid Yellow 3), available from Tricon; Yellow Shade 16948, 
available from Tricon, Basacid Black X34, available from BASF, Carta Black 
2GT, available from Sandoz, Inc.; Neozapon Red 492 (BASF); Savinyl Blue 
GLS (Sandoz); Luxol Blue MBSN (Morton-Thiokol); Basacid Blue 750 (BASF); 
Bernacid Red, available from Berncolors, Poughkeepsie, N.Y.; Pontamine 
Brilliant Bond Blue; Berncolor A.Y. 34; Telon Fast Yellow 4GL-175; BASF 
Basacid Black SE 0228; the Pro-Jet.RTM. series of dyes available from ICI, 
including Pro-Jet.RTM. Yellow I (Direct Yellow 86), Pro-Jet.RTM. Magenta I 
(Acid Red 249), Pro-Jet.RTM. Cyan I (Direct Blue 199), Pro-Jet.RTM. Black 
I (Direct Black 168), Pro-Jet.RTM. Yellow 1-G (Direct Yellow 132), Aminyl 
Brilliant Red F-B, available from Sumitomo Chemical Company (Japan), the 
Duasyn.RTM. line of "salt-free" dyes available from Hoechst, such as 
Duasyn.RTM. Direct Black HEF-SF (Direct Black 168), Duasyn.RTM. D Black 
RL-SF (Reactive Black 31), Duasyn.RTM. Direct Yellow 6G-SF VP216 (Direct 
Yellow 157), Duasyn.RTM. Brilliant Yellow GL-SF VP220 (Reactive Yellow 
37), Duasyn.RTM. Acid Yellow XX-SF LP413 (Acid Yellow 23), Duasyn.RTM. 
Brilliant Red F3B-SF VP218 (Reactive Red 180), Duasyn.RTM. Rhodamine B-SF 
VP353 (Acid Red 52), Duasyn.RTM. Direct Turquoise Blue FRL-SF VP368 
(Direct Blue 199), Duasyn.RTM. Acid Blue AE-SF VP344 (Acid Blue 9), 
various Reactive dyes, including Reactive Black dyes, Reactive Blue dyes, 
Reactive Red dyes, Reactive Yellow dyes, and the like, as well as mixtures 
thereof. The dye is present in the ink composition in any desired or 
effective amount, typically from about 0.05 to about 10 percent by weight 
of the ink, preferably from about 0.1 to about 7 percent by weight of the 
ink, and more preferably from about 1 to about 5 percent by weight of the 
ink, although the amount can be outside of these ranges. 
Other optional additives to the inks include biocides such as Dowicil 150, 
200, and 75, benzoate salts, sorbate salts, and the like, present in an 
amount of from about 0.0001 to about 4 percent by weight of the ink, and 
preferably from about 0.01 to about 2.0 percent by weight of the ink, pH 
controlling agents such as acids or, bases, phosphate salts, carboxylates 
salts, sulfite salts, amine salts, and the like, present in an amount of 
from 0 to about 1 percent by weight of the ink and preferably from about 
0.01 to about 1 percent by weight of the ink, or the like. 
One example of an additive to the inks is a polymeric additive consisting 
of two polyalkylene oxide chains bound to a central bisphenol-A-type 
moiety. This additive is of the formula 
##STR4## 
wherein R.sup.1 and R.sup.2 are independently selected from the group 
consisting of hydrogen, alkyl groups with from 1 to about 8 carbon atoms, 
such as methyl, ethyl, propyl, and the like, and alkoxy groups with from 1 
to about 8 carbon atoms, such as methoxy, ethoxy, butoxy, and the like, 
R.sup.3 and R.sup.4 are independently selected from the group consisting 
of alkyl groups with from 1 to about 4 carbon atoms, and x and y are each 
independently a number of from about 100 to about 400, and preferably from 
about 100 to about 200. Generally, the molecular weight of the 
polyalkylene oxide polymer is from about 14,000 to about 22,000, and 
preferably from about 15,000 to about 20,000, although the molecular 
weight can be outside this range. Materials of this formula are 
commercially available; for example, Carbowax M20, a polyethylene 
oxide/bisphenol-A polymer of the above formula with a molecular weight of 
about 18,000, available from Union Carbide Corporation, Danbury, Conn., is 
a suitable polymeric additive for the inks of the present invention. In 
addition, compounds of the above formula can be prepared by the methods 
disclosed in Polyethers, N. G. Gaylord, John Wiley & Sons, New York (1963) 
and "Laboratory Synthesis of Polyethylene Glycol Derivatives," J. M. 
Harris, J. Molecular Science--Rev. Macromol. Chem. Phys., C25(3), 325-373 
(1985), the disclosures of each of which are totally incorporated herein 
by reference. The polyalkylene oxide additive is generally present in the 
ink in an amount of at least about 1 part per million by weight of the 
ink. Typically, the polyalkylene oxide additive is present in amounts of 
up to 1 percent by weight of the ink, and preferably in amounts of up to 
0.5 percent by weight of the ink; larger amounts of the additive may 
increase the viscosity of the ink beyond the desired level, but larger 
amounts can be used in applications wherein increased ink viscosity is not 
a problem. Inks containing these additives are disclosed in U.S. Pat. No. 
5,207,825, the disclosure of which is totally incorporated herein by 
reference. 
The ink compositions are generally of a viscosity suitable for use in 
thermal ink jet printing processes. At room temperature (i.e., about 
25.degree. C.), typically, the ink viscosity is no more than about 10 
centipoise, and preferably is from about 1 to about 5 centipoise, more 
preferably from about 1 to about 4 centipoise, although the viscosity can 
be outside this range. 
Ink compositions of the present invention can be of any suitable or desired 
pH. For some embodiments, such as thermal ink jet printing processes, 
typical pH values are from about 3 to about 11, preferably from about 5 to 
about 10, and more preferably from about 7 to about 8, although the pH can 
be outside of these ranges. 
Ink compositions suitable for ink jet printing can be prepared by any 
suitable process. Typically, the inks are prepared by simple mixing of the 
ingredients. One process entails mixing all of the ink ingredients 
together and filtering the mixture to obtain an ink. Inks can be prepared 
by preparing a conventional ink composition according to any desired 
process, such as by mixing the ingredients, heating if desired, and 
filtering, followed by adding any desired additional additives to the 
mixture and mixing at room temperature with moderate shaking until a 
homogeneous mixture is obtained, typically from about 5 to about 10 
minutes. Alternatively, the optional ink additives can be mixed with the 
other ink ingredients during the ink preparation process, which takes 
place according to any desired procedure, such as by mixing all the 
ingredients, heating if desired, and filtering. In a preferred embodiment, 
the ink ingredients are mixed in the following order: (1) water; (2) any 
salts present in the ink; (3) any cosolvents or humectants present in the 
ink; (4) polyquaternary compound; (5) dye. If the polyquaternary compound 
and the dye are added to water prior to addition of salts and/or 
cosolvents and/or humectants, a precipitated complex may form, which 
generally will tend to dissolve slowly to homogeneity subsequent to 
addition of the other ink ingredients. 
The present invention is also directed to a process which entails 
incorporating an ink composition of the present invention into an ink jet 
printing apparatus and causing droplets of the ink composition to be 
ejected in an imagewise pattern onto a substrate. In a particularly 
preferred embodiment, the printing apparatus employs a thermal ink jet 
process wherein the ink in the nozzles is selectively heated in an 
imagewise pattern, thereby causing droplets of the ink to be ejected in 
imagewise pattern. Any suitable substrate can be employed, including plain 
papers such as Xerox.RTM. 4024 papers, Xerox.RTM. Image Series papers, 
Courtland 4024 DP paper, ruled notebook paper, bond paper, silica coated 
papers such as Sharp Company silica coated paper, JuJo paper, and the 
like, transparency materials, fabrics, textile products, plastics, 
polymeric films, inorganic substrates such as metals and wood, and the 
like. In a preferred embodiment, the process entails printing onto a 
porous or ink absorbent substrate, such as plain paper. 
Specific embodiments of the invention will now be described in detail. 
These examples are intended to be illustrative, and the invention is not 
limited to the materials, conditions, or process parameters set forth in 
these embodiments. All parts and percentages are by weight unless 
otherwise indicated.

EXAMPLE I 
An ink composition was prepared by simple mixing of the following 
ingredients: 
______________________________________ 
Amount 
Ingredient Supplier (wt. %) 
______________________________________ 
deionized water -- 38 
2-pyrrolidinone Aldrich Chemical Co. 
20 
sulfolane* Phillips Petroleum Co. 
20 
imidazolium chloride 
Aldrich Chemical Co. 
5 
butyl carbitol Van Waters & Rogers 
10 
LUVIQUAT FC 905 copolymer 
BASF 2 
Acid Yellow 23 dye 
Warner & Jenkinson 
5 
______________________________________ 
*containing 95 wt. % sulfolane and 5 wt. % water 
The ink composition thus prepared was hand coated onto Xerox.RTM. 4024 DP 
20# paper with a #7 Meier rod. The image dried in 2 seconds and exhibited 
an optical density of 1.02. The image was subsequently washed in water for 
20 seconds, after which the optical density was 0.87. Wet smear was barely 
detectable. 
EXAMPLE II 
An ink composition was prepared by simple mixing of the following 
ingredients: 
______________________________________ 
Amount 
Ingredient Supplier (wt. %) 
______________________________________ 
deionized water -- 60 
2-pyrrolidinone Aldrich Chemical Co. 
20 
imidazole Aldrich Chemical Co. 
5 
imidazolium chloride 
Aldrich Chemical Co. 
5 
LUVIQUAT FC 905 copolymer 
BASF 5 
Acid Yellow 23 dye 
Warner & Jenkinson 
5 
______________________________________ 
The ink composition thus prepared was hand coated onto Hammermill Tidal DP 
paper with a #7 Meier rod. The image dried in 2 seconds and exhibited an 
optical density of 1.11. The image was subsequently washed in water for 20 
seconds, after which the optical density was 0.93. Wet smear was barely 
detectable. 
The process was repeated with Xerox.RTM. Image Series LX paper. The image 
dried in 10 seconds and exhibited an optical density of 1.16. The image 
was subsequently washed in water for 20 seconds, after which the optical 
density was 0.95. 
EXAMPLE III 
An ink composition was prepared by simple mixing of the following 
ingredients: 
______________________________________ 
Amount 
Ingredient Supplier (wt. %) 
______________________________________ 
deionized water -- 48 
2-pyrrolidinone Aldrich Chemical Co. 
20 
sulfolane* Phillips Petroleum Co. 
20 
imidazolium chloride 
Aldrich Chemical Co. 
5 
LUVIQUAT FC 905 copolymer 
BASF 2 
Acid Yellow 23 dye 
Warner & Jenkinson 
5 
______________________________________ 
*containing 95 wt. % sulfolane and 5 wt. % water 
The ink composition thus prepared was hand coated onto Xerox.RTM. 4024 DP 
paper with a #7 Meier rod. The image dried in 37 seconds and exhibited an 
optical density of 1.23. The image was subsequently washed in water for 20 
seconds, after which the optical density was 0.95. 
Other embodiments and modifications of the present invention may occur to 
those of ordinary skill in the art subsequent to a review of the 
information presented herein; these embodiments and modifications, as well 
as equivalents thereof, are also included within the scope of this 
invention.