Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-11-09
2003-03-25
Jagannathan, Vasu (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S594000, C524S595000, C525S508000, C525S505000, C347S100000
Reexamination Certificate
active
06538048
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an ink jet printing method using a dispersant for a pigment-based ink jet ink.
BACKGROUND OF THE INVENTION
Ink jet printing is a non-impact method for producing images by the deposition of ink droplets on a substrate (paper, transparent film, fabric, etc.) in response to digital signals. Ink jet 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 ink jet printers are generally classified as either dye-based or pigment-based.
A dye is a colorant which is molecularly dispersed or solvated by a carrier. The carrier can be a liquid or a solid at room temperature. A commonly used carrier is water or a mixture of water and organic co-solvents. Molecules of the carrier surround each individual dye molecule. In 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 lightfastness. When water is used as the carrier, such inks also generally suffer from poor water fastness.
In pigment-based inks, the colorant exists as discrete particles. These pigment particles are usually treated with addenda known as dispersants or stabilizers which serve to keep the pigment particles from agglomerating and settling out of the carrier. Water-based pigment-based inks are prepared by incorporating the pigment in the continuous water phase by a milling and dispersing process. Pigment-based inks require a water-soluble dispersant in the pigment slurry during the milling process. Such a dispersant is necessary to produce a stable colloidal mixture and an ink that can be “jetted” reliably without clogging the print head nozzles.
Dispersing agents in an ink jet ink have the dual function of helping to break down pigments to sub-micron size during the milling process and of keeping the colloidal dispersion stable and free from flocculation for a long period of time. In general, dispersions suffer from poor colloidal stability due to particle agglomeration and/or sedimentation, thus limiting the usefulness of the dispersions in inks.
Many dispersing agents are very selective in their ability to disperse these pigments to sub-micron size. This is probably one of the many reasons for the wide variety of known dispersing agents. In many instances, each class of pigments may require a specific dispersing agent. Another problem encountered with some dispersing agents is that the resulting inks suffer from unacceptable image quality properties. This can include unacceptable coalescence, banding, bleeding, densities, or other defects seen on the final printed image. Yet another problem with many commercially available dispersants is that they yield dispersions with very low surface tensions. Thus, there is a continuing need for improved dispersing agents for pigment-based inks.
DESCRIPTION OF RELATED ART
German patent application DE 19850152 discloses the use of ethoxylated alkyl-phenol surfactants for use in the preparation of pigment-based inks for ink-jet printing. However, there is a problem with these dispersants in that pigment dispersions using them have an unacceptably large particle size and are unstable at high temperatures, as will be shown hereinafter.
German patent application DE 19801759 discloses the use of sulfonated aromatic derivatives as dispersants for a wide range of pigment preparations including those in ink-jet printing. However, these dispersants differ significantly in structure to the materials employed in the invention.
It is an object of this invention to provide an ink jet printing method using a dispersant for a pigment-based ink jet ink which will enable the particle size of the dispersed pigment to be lower than that obtained using prior art dispersants disclosed for such use. It is another object of this invention to provide an ink jet printing method using a dispersant for a pigment-based ink wherein the particle size for the pigment is maintained when the dispersion is held at high temperatures. It is another object of this invention to provide an ink jet printing method using a dispersant for pigment-based ink-jet inks which will produce images which have a high D-max and which are free of defects.
SUMMARY OF THE INVENTION
These and other objects are achieved in accordance with this invention which relates to an ink jet printing method, comprising the steps of:
A) providing an ink jet printer that is responsive to digital data signals;
B) loading the printer with ink jet recording elements;
C) loading the printer with an ink jet ink composition comprising from about 0.5% to about 30% by weight of a pigment, a carrier and a dispersant, the dispersant comprising an anionic derivative of an ethoxylated alkylphenol-formaldehyde resin, the ratio of dispersant:pigment being from about 0.1:1 to about 5:1; and
D) printing on the ink jet recording element using the ink jet ink in response to the digital data signals.
Use of the dispersants in accordance with the invention will produce pigment dispersions on the order of 0.1 &mgr;m or less in size during the milling process. These dispersions are also characterized by excellent colloidal stability and lack of flocculation and/or sedimentation on keeping at high temperatures. In addition, these dispersing agents are useful with a wide variety of pigments.
DETAILED DESCRIPTION OF THE INVENTION
Any anionic derivative of an ethoxylated alkylphenol-formaldehyde resin dispersant may be used in the invention provided it produces the desired results. In a preferred embodiment of the invention, the dispersant has the formula:
wherein:
each R independently represents a linear or branched alkyl, alkenyl, or arylalkyl group having from about 4 to about 30 carbon atoms;
x is an integer from 0 to 20;
y is an integer from 1 to 20; with the proviso that x+y is from 2 to 20;
z is an integer from 4 to 20;
A is an anionic group, such as sulfate, sulfonate, phosphate, phosphonate or carboxylate; and
M is a cationic group, such as an alkali metal, alkaline earth metal, ammonium or substituted ammonium.
In a preferred embodiment of the invention, each R independently represents a linear or branched alkyl, alkenyl, or arylalkyl group having from about 6 to 15 carbon atoms, preferably from about 8 to about 12 carbon atoms. In another preferred embodiment, x+y is from 4 to 12, preferably 6 to 8. In still another preferred embodiment, z is an integer from 6 to 14, preferably from 8 to 12.
The ethoxylated alkylphenol-formaldehyde resin dispersant used in the invention is a comb-like material which possesses multiple hydrophobic blocks and multiple hydrophilic blocks.
In the present invention, any of the known pigments can be used. Pigments can be selected from those disclosed, for example, in U.S. Pat. Nos. 5,026,427; 5,085,698; 5,141,556; 5,160,370 and 5,169,436, the disclosures of which are hereby incorporated by reference. The exact choice of pigment will depend upon the specific color reproduction and image stability requirements of the printer and application. For four-color printers, a combination of cyan, magenta, yellow, and black (CMYK) pigments should be used. An exemplary four color set is copper phthalocyanine (pigment blue 15), quinacridone magenta (pigment red 122), pigment yellow 74 or pigment yellow 155 and carbon black (pigment black 7). Another exemplary four color set is bis(phthalocyanyl-alumino)tetra-phenyldisiloxane cyan pigment, quinacridone magenta (pigment red 122), pigment yellow 74 or pigment yellow 155 and carbon black (pigment black 7). In a preferred embodiment of the invention, the pigment has a particle size of from about 10 nanometers to about 1000 nanometers.
As noted above, the ink jet ink composition employed in the invention comprises from about 0.5% to about 30% by weight of a pigment. In a preferred embodiment of the invention, the ink composition comprises from about
Erdtmann David
Newington Ian M.
Pitt Alan R.
Cole Harold E.
Eastman Kodak Company
Jagannathan Vasu
Shosho Callie E
LandOfFree
Ink jet printing method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink jet printing method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink jet printing method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3063523