Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-09-20
2004-03-30
Shosho, Callie (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S548000, C524S556000, C524S601000, C524S606000, C528S272000, C528S335000, C528S421000
Reexamination Certificate
active
06713530
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an inkjet ink composition comprising a dye and a hyperbranched polymer.
BACKGROUND OF THE INVENTION
Ink jet printing is a non-impact method for producing images by the deposition of ink droplets in a pixel-by-pixel manner to an image-recording element in response to digital signals. There are various methods which may be utilized to control the deposition of ink droplets on the image-recording element to yield the desired image. In one process, known as continuous ink jet, a continuous stream of droplets is charged and deflected in an imagewise manner onto the surface of the image-recording element, while unimaged droplets are caught and returned to an ink sump. In another process, known as drop-on-demand ink jet, individual ink droplets are projected as needed onto the image-recording element to form the desired image. Common methods of controlling the projection of ink droplets in drop-on-demand printing include piezoelectric transducers and thermal bubble formation. Inkjet printers have found broad applications across markets ranging from industrial labeling to short run printing to desktop document and pictorial imaging.
The inks used in the various ink jet printers can be classified as either dye-based or pigment-based. A dye is a colorant which is dissolved or dispersed in the carrier medium. A pigment is a colorant that is insoluble in the carrier medium, but is dispersed or suspended in the form of small particles, often stabilized against flocculation and settling by the use of dispersing agents. The carrier medium can be a liquid or a solid at room temperature in both cases. Commonly used carrier media include water, mixtures of water and organic co-solvents and high boiling organic solvents, such as hydrocarbons, esters, ketones, etc.
In traditional dye-based inks, no particles are observable under the microscope. Although there have been many recent advances in the art of dye-based ink jet inks, such inks still suffer from deficiencies such as low optical densities on plain paper and poor light-fastness. When water is used as the carrier, such inks also generally suffer from poor water fastness and poor smear resistance. These problems can be minimized by replacing the dyes used in ink formulations with insoluble pigments. In general, pigments are superior to dyes with respect to waterfastness, lightfastness, and stability towards pollutants in the air. However, the pigment inks tend to be unstable and settle out from the liquid vehicle over a long storage time. Pigment inks also have a tendency to clog the orifices of the printhead resulting in deterioration of print quality.
Accordingly, there is a need for inks having advantages of both dye-based inks and pigment based inks that have good lightfastness, stability towards pollutants, waterfastness and reliability in the printhead.
U.S. patent application Ser. No. 09/742,961, filed Dec. 20, 2000, discloses an inkjet printing method using an ink jet ink comprising a water soluble dye and a water dispersible polymer latex. However, there is a problem with this ink composition in that its viscosity is high, resulting in poor firability from a thermal ink jet printhead.
WO 00/37542 discloses a pigment-based ink jet ink using dendritic polymers as a dispersant. However, there is a problem with this ink in that the ink tends to be unstable and settles out from the liquid vehicle over a long storage time, and has a tendency to clog the orifices of the printhead.
Wang et. al. in pending U.S. patent application Ser. No. 09/918,584 filed Jul. 30, 2001 describes an ink jet ink composition comprising a hyperbranched polymeric dye to give improved dye stability and firability. However, there is still a need to improve the stability and firability without having to link the dye covalently through polymer synthesis.
It is an object of this invention to provide an inkjet ink composition that, when printed, provides an image which has improved waterfastness, lightfastness, and stability towards pollutants such as ozone. It is another object of this invention to provide an ink jet ink composition that has improved firability through an ink jet printhead.
SUMMARY OF THE INVENTION
These and other objects are achieved in accordance with this invention which relates to an inkjet ink composition comprising water, a humectant, a dye, and a hyperbranched polymer.
It has been found that this ink jet ink composition, when printed, provides an image which has improved waterfastness, lightfastness, and stability towards pollutants such as ozone and has improved firability through an ink jet printhead.
DETAILED DESCRIPTION OF THE INVENTION
Any hyperbranched polymer that is soluble or dispersible in an ink jet ink may be used in the invention. A dispersible hyperbranched polymer is one that can form a colloid in an inkjet ink with a particle size being less than 10 &mgr;m, preferably less than 500 nm, more preferably less than 200 nm.
Any hyperbranched polymer with various topologies and compositions may be used in the invention, e.g., homo-hyperbranched, random hyperbranched, block hyperbranched, graft hyperbranched, star hyperbranched, etc.
A hyperbranched polymer is defined as a polymer formed by polymerization of one or more branching monomers with or without no-branching monomers as described in J. Am. Chem. Soc., 74, p2718 (1952), the disclosure of which is hereby incorporated by reference. The terms “hyperbranched” used herein with respect to branched polymers are intended to designate polymers having a relatively high percentage of propagated branching sites per number of polymerized monomer units, e.g., at least one branching site per every ten monomer units, preferably at least one branching site per every five monomer units, and more preferably, at least one branching site per every two monomer units.
In general, hyperbranched polymers used in the present invention can be made through a chain polymerization or condensation polymerization processes, as described in J. Polym. Sci., Part A: Polym. Chem. 36, 1685-1698 (1998) and U.S. Pat. No. 4,857,630, the disclosures of which are hereby incorporated by reference. Specifically, the hyperbranched polymer used in the present invention can be made through the polymerization of A
n
-R
1
-B
m
monomers, wherein n and m are integers of at least 1 and R
1
represents a linking group between A and B or co-polymerization of A
s
+B
t
co-monomer pairs wherein s and t are integers of at least 2 and of at least 3, respectively, as described in U.S. Pat. No. 4,857,630, and co-pending Wang et al U.S. patent applications Ser. Nos. 09/697,205; 09/919,096; 09/919,390; and 09/919,097, filed Jul. 30, 2001, the disclosures of each of which are hereby incorporated by reference.
In a preferred embodiment, the hyperbranched polymer used in the invention is a polyamnide, polyester, polyether, vinylic polymer, polyimine, polysiloxane, polyurethane, polythioether, polyarylalkylene, polysilane, or polyesteramide.
In another preferred embodiment of the invention, the hyperbranched polymer is prepared by a chain polymerization of a monomer of the formula M
1
n
-R
1
-M
2
m
wherein (i) R
1
is a substituted or non-substituted straight, cyclic or branched alkyl, alkenyl, or aryl moiety and hetero atom containing substituted or non-substituted straight, cyclic or branched alkyl, alkenyl, or aryl moiety; (ii), M
1
and M
2
are reactive groups that react independently of each other in which M
1
is a polymerization group and M
2
is a precursor of a moiety M
2
* which initiates the polymerization of M
1
as a result of being activated by any source; and (iii), n and m are integers of at least 1, more preferably n is 1 and m is 1 or 2, most preferably n is 1 and m is 1.
In another preferred embodiment of the invention, the hyperbranched polymer is prepared by a condensation or addition polymerization of a monomer of the formula M
3
g
-R
1
-M
4
t
wherein (i) R
1
is defined above; (ii), M
3
and M
4
are groups that undergo a condensation or addition reaction with o
Chen Huijuan
Wang Jin-Shan
Eastman Kodak Company
Manne Kathleen Neuner
Shosho Callie
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