Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-07-27
2003-07-15
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031430, C106S031750, C106S031860
Reexamination Certificate
active
06592657
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to ink compositions for ink-jet printing, and more particularly, to ink compositions that comprise organo-phosphonic acids and their salts.
BACKGROUND OF THE INVENTION
The ink-jet printing process involves the ejection of fine droplets of ink onto a print medium such as paper in response to electrical signals generated by a microprocessor. Typically, an ink-jet printer utilizes a pen set mounted on a carriage that is moved relative to the surface of a print medium. In commercially available ink-jet color printers, such as the DESKJET™ printer available from Hewlett-Packard Company. A typical pen includes print heads with orifice plates that have very small nozzles (10-50 &mgr;m diameter) through which the ink droplets are ejected. Adjacent to these nozzles are ink chambers where ink is stored prior to ejection. Ink drop ejection is currently achieved either thermally or piezoelectrically. In thermal ink-jet printing, each nozzle is associated with a resistor element. Each resistor element is in turn connected to a microprocessor, whose signals direct one or more resistor elements to heat up rapidly. This causes a rapid expansion of ink vapor that forces a drop of ink through the associated nozzle onto the print medium. A variety of complex interactions between the ink and pen structure (e.g. the resistor element, nozzle etc.) are known to affect both the short and long term reliability of pen performance and hence of print quality. Examples of these interactions include corrosion due to presence of metal ion impurities or other reactive components in the ink composition; kogation, defined as the build up of residue on the surface of resistor elements; puddling, defined as the formation of ink puddles on the orifice plates of the print head; and crusting, defined as the formation of insoluble crusts on the orifice plates of the print head.
High dot gain inks are desirable for ink jet printing because they give a large dot size for a given drop volume. The major advantage is that lower drop volumes can be used for a given printing application, resulting in lower cost per copy, reduced plain paper cockle and reduced amount of ink on transparency film. Most high dot gain inks have low surface tension, which causes the ink to spread across the orifice plates of the print head, to form so-called “puddling.” The ink drops must fire through the puddles, which results in misdirected drops and streaking of images, and lowers print head reliability and results in poor print quality.
Several methods of addressing the puddling are known in the art, for example, use of surfactants to adjust the ink property (U.S. Pat. No. 5,656,655), improved orifice plate designs (U.S. Pat. Nos. 5,595,785 and 5,434,606), improved designs of ink channel geometry (U.S. Pat. Nos. 5,755,032 and 5,274,400), and lastly, a more effective wiping system (U.S. Pat. No. 5,786,830) to clean the puddles. In some instances, adding surfactants is not an option because of adverse effect of the surfactants on the print quality. Mechanical wiping and design changes are often inefficient and add considerable expense to the cost of the printer.
Accordingly, a need exists in the art for a means to produce ink compositions for ink-jet printers that control puddling and yet exhibit favorable interactions with the components of the pen structure and in particular with the intented print media (e.g. paper) to maintain large dot size and high image quality.
SUMMARY OF THE INVENTION
The invention is an ink-jet ink composition. The composition comprises at least one colorant and a vehicle. The vehicle includes at least one organo-phosphonic acid or sodium or potassium salt of the said acid (In the following text, when organo-phosphonic acid is cited, the acid and it salt are implied). The vehicle may contain mixtures of two or more organo-phosphonic acids. The organo-phosphonic acid may be monofunctional or polyfunctional. Preferably the organo-phosphonic acid is polyfunctional. The concentration of organo-phosphonic acid may be from about 0.05 to about 10 wt %. The organo-phosphonic acids may be of general formula
wherein R
1
and R
2
are phosphonic acid groups, and R
3
and R
4
can each, independently of each other, be hydrogen, a hydroxyl group, a phosphonic acid group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. Preferably R
2
is a phosphonic acid group. More preferably R
2
is a phosphonic acid group, R
3
is a methyl group, R
4
is a hydroxyl group and the organo-phosphonic acid is hydroxyethylene di(phosphonic acid) (HEDP).
The organo-phosphonic acids may be of general formula
wherein R
1
is a methylene phosphonic acid group, and R
2
and R
3
can each, independently of each other, be hydrogen, a hydroxyl group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. Preferably R
2
is a methylene phosphonic acid group. More preferably R
2
and R
3
are methylene phosphonic acid groups and the organo-phosphonic acid is amino tri(methylene phosphonic acid) (ATMP).
The organo-phosphonic acids may be of general formula
wherein n is an integer between 1 and 6, R
1
is a methylene phosphonic acid group, and R
2
, R
3
and R
4
can each, independently of each other, be hydrogen, a hydroxyl group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. Preferably R
2
, R
3
and R
4
are methylene phosphonic acid groups. Preferably n=2 and the organo-phosphonic acid is ethylene diamine tetra(methylene phosphonic acid) (EDTMP), or n=6 and the organo-phosphonic acid is hexamethylene diamine tetra(methylene phosphonic acid) (HDTMP).
The organo-phosphonic acids may be of general formula
wherein n is an integer between 1 and 6, R
1
is a methylene phosphonic acid group, and R
2
, R
3
, R
4
and R
5
can each, independently of each other, be hydrogen, a hydroxyl group, an alkyl group, an aryl group, or a substituted alkyl or aryl group having substituents selected from the group of alkyl groups, aryl groups, hydroxyl groups, phosphonic acid groups, ether groups, ester groups, and mixtures thereof. Preferably R
2
, R
3
, R
4
and R
5
are methylene phosphonic acid groups. Preferably n=2, and the organo-phosphonic acid is diethylene triamine penta(methylene phosphonic acid) (DTPMP).
The vehicle may further include from about 0 to about 10 wt % surfactants, and from about 0.1 to about 40 wt % organic cosolvents. The pH of the ink composition may be from about 2 to about 10.
DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS
The invention will now be described with particular reference to certain preferred embodiments of the ink-jet ink compositions of the invention.
Exemplary embodiments of the ink compositions comprise, by weight (all percentages are by weight unless otherwise indicated) from 0.1 to 40%, preferably from 5 to 25% organic cosolvent; from 0 to 10%, preferably from 0.1 to 5% surfactant; from 0.5 to 10%, preferably from 0.5 to 5% colorant; and from 0.05 to 20%, preferably from 0.1 to 10%, organo-phosphonic acid. The remainder of the ink compositions are mostly water; however, other components including biocides that inhibit growth of microorganisms such as the preservative PROXEL™ GXL (available from Avecia Incorporated); chelating agents such as EDTA that eliminate deleterious effects of heavy metal impurities; buffers; and viscosity modifiers, may be added to improve various properties of the ink composition.
Organic Cosolvents
One or more organic cosolvents may be used to prepare the ink compositions of the present inve
Bauer Stephen W.
Lee Shirley
Prasad Keshava A.
Tanner Christopher S.
Webb Steven L.
Hewlett--Packard Development Company, L.P.
Klemanski Helene
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