Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-05-01
2003-07-01
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031430, C106S031750, C106S031860
Reexamination Certificate
active
06585817
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.
BACKGROUND OF THE INVENTION
The combination of low cost and high quality output have recently made ink-jet printers a popular alternative to other types of non-impact printers such as laser printers.
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 four-pen set including cyan, yellow, magenta and black inks is generally employed to achieve the necessary color combinations.
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. In piezoelectric ink-jet printing, ink droplets are ejected due to the vibrations of piezoelectric crystals stimulated by electrical signals generated by the microprocessor.
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 the 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.
In addition, interactions between the ink and both the surface and bulk of the print medium also play a key role in determining print quality. For example, a particular concern for color ink-jet printing, has been the mixing or “bleeding” that occurs both on the surface and within the print medium when inks of two different colors are printed side by side. Several methods, including reducing dry times and increasing penetration rates, have been proposed to reduce bleed of adjacent printing liquids. In addition, pH-sensitive dyes may also be employed to control bleed.
U.S. Pat. No. 5,181,045 (incorporated herein by reference) discloses a method of ink-jet printing wherein one ink (a pH sensitive ink, usually a black ink) contains a colorant that becomes insoluble under defined pH conditions, and a second ink (the target ink, usually a color ink) has a pH that renders the colorant contained in the first ink insoluble. In this context, organic acids and particularly carboxylic acids such as for example glycolic, malonic, malic, maleic, succinic, glutaric, fumaric, citric, tartaric, and lactic acids have recently become popular components of acidic target ink-jet ink compositions (see for example, U.S. Pat. Nos. 5,785,743 and 6,036,759 both incorporated herein by reference).
Although these organic acids improve bleed control they can also be detrimental to pen performance. As an example, succinic acid is known to be corrosive to ferrous metals. It has also recently been observed that inks containing carboxylic acids such as succinic and glycolic acid cause an adhesive of ink-jet printer pens to swell. For example an adhesive (typically an epoxy adhesive) is used to attach the print head to the pen body, and as such, acts as a seal that prevents ink contained in the print head from leaking into the pen body. However if the adhesive swells, it risks bringing ink from the print head into contact with some of the electronic circuitry contained in the pen body, thereby causing a short circuit, and ultimately pen failure.
Accordingly, a need exists in the art for a means to produce ink compositions for ink-jet printers that control bleed and yet exhibit favorable interactions with the components of the pen structure and in particular with the adhesives commonly used in ink-jet printer pens.
SUMMARY OF THE INVENTION
The invention is an ink-jet ink composition. The composition comprises at least one colorant and a vehicle. Preferably the ink composition causes negligible adhesive swell.
The vehicle includes at least one organo-phosphonic acid. 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 0.5 to about 20 wt %, for example from about 0.5 to about 10 wt %, from about 2 to about 10 wt %, or from about 5 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
Dangelewicz John
Lee Shirley
Hewlett--Packard Development Company, L.P.
Klemanski Helene
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