Ink compositions and processes

Details Ink compositions and processes Ink compositions and processes

1999-08-30

2003-04-15

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...

C524S609000, C526S287000

Reexamination Certificate

active

06548571

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is generally directed to ink compositions, and processes thereof, and more specifically, the present invention is directed to processes for the preparation of colored aqueous ink compositions, that is inks preferably containing a vehicle like water particularly suitable for use in ink jet printing processes, and especially thermal ink jet processes, and other similar processes, and wherein there is permitted minimal or no kogation, inks with suitable particle sizes, minimal intercolor bleed for the images developed, substantially stable latexes, and wherein paper curl is minimized and image smearing is minimal, or avoided. The inks in embodiments of the present invention are comprised of an ink vehicle, colorant, and additives, and wherein the inks can be prepared by blending and optionally heating an ionic sulfonate polymer latex and preferably a copolymer of unsaturated ionic sulfonate monomer or monomers and ethylenically unsaturated monomers, wherein the ethylenically unsaturated monomers are ethylenically unsaturated esters, styrene functional monomers or olefinic acids, and a colorant dispersion, and wherein the latex can be prepared by emulsion polymerization with at least two surfactants of, for example, an anionic surfactant and a nonionic surfactant, and wherein the inks exhibit substantially no kogation or heater deposits. Prevention of heater deposits/kogation enables for example, superior ink jetting performance and enhanced life in the printhead. The ionic sulfonate resin incorporated in the ink also enables, for example, excellent ink thermal stability, then the shelf life of the ink is prolonged, for example the ink does not decompose or settle for extended time periods of up to about one year.
PRIOR ART
Ink jet printing can be considered a non-impact method that produces droplets of ink that are deposited on a substrate, such as paper or transparent film, in response to an electronic digital signal. Thermal or bubble jet drop-on-demand ink jet printers are useful as outputs for personal computers in the office and in the home.
In existing thermal ink jet printing, the printhead typically comprises one or more ink jet ejectors, such as disclosed in U.S. Pat. No. 4,463,359, the disclosure of which is totally incorporated herein by reference, each ejector including a channel communicating with an ink supply chamber, or manifold, at one end and having an opening at the opposite end, referred to as a nozzle. A thermal energy generator, usually a resistor, is located in each of the channels a predetermined distance from the nozzles. The resistors are individually addressed with a current pulse to momentarily vaporize the ink and form a bubble which expels an ink droplet. As the bubble grows, the ink rapidly bulges from the nozzle and is momentarily contained by the surface tension of the ink as a meniscus. As the bubble begins to collapse, the ink remaining in the channel between the nozzle and bubble starts to move toward the collapsing bubble causing a volumetric contraction of the ink at the nozzle and resulting in the separation from the nozzle of the bulging ink as a droplet. The feed of additional ink provides the momentum and velocity for propelling the droplet towards a print sheet, such as a piece of paper. Since the droplet of ink is emitted only when the resistor is actuated, this type of thermal ink jet printing is known as “drop-on-demand” printing. Other types of ink jet printing, such as continuous-stream or acoustic, are also known.
Ink jet inks, and processes hereof are illustrated, for example, in U.S. Pat. Nos. 4,840,674; 5,021,802; 5,041,161; 4,853,036; 5,124,718; 5,065,167 and 5,043,084, the disclosures of which are totally incorporated herein by reference.
In a single-color ink jet printing apparatus, the printhead typically comprises a linear array of ejectors, and the printhead is moved relative to the surface of the print sheet, either by moving the print sheet relative to a stationary printhead, or vice-versa, or both. In some systems, a relatively small printhead moves across a print sheet numerous times in swathes, much like a typewriter. Alternatively, a printhead, which consists of an array of ejectors and extends the full width of the print sheet, may be passed once down the print sheet to give full-page images in what is known as a “full-width array” (FWA) printer. When the printhead and the print sheet are moved relative to each other, imagewise digital data is used to selectively activate the thermal energy generators in the printhead to permit the desired image to be created on the print sheet.
With the demand for higher resolution printers, the nozzles in ink jet printers, are decreasing in size. Nozzle openings are typically about 50 to 80 micrometers in width or diameter for 300 spi printers. With the advent of 600 spi printers, these nozzle openings are typically about 10 to about 40 micrometers in width or diameter These small dimensions require inks that do not plug the small openings.
Therefore, an important requirement for ink jet ink is the ability of the ink to be stable with minimal or no settling, the ability of the ink to remain in a fluid condition in a printhead opening on exposure to air, and moreover wherein when the inks are selected for ink jet printing there is minimized paper curl, or wherein paper curl can be controlled.
Another important measured property for an ink jet ink is the latency or decap time, which is the length of time over which an ink remains fluid in a printhead opening or nozzle when exposed to air and, therefore, is capable of firing a drop of ink at its intended target. Latency is the maximum idling times allowed for ink to be jetted by a printer with a speed equal to or greater than 5 m/s (equivalent to an ink traveling a distance of 0.5 millimeters in less than 100 &mgr;s) without a failure. This measurement can be accomplished with the printhead or nozzles uncovered or decapped and generally at a relative humidity of about 15 percent. The time interval, for example, is the longest length of time that the printhead, uncovered, will still fire or eject a specified drop without drop displacement or loss of density. The longer the latency time rating, the more desirable the ink. The inks of the present invention possess many of these characteristics in embodiments thereof.
Moreover, an important requirement for ink jet inks, especially for pigment, such as carbon black, based inks, is for the pigment dispersion to remain stable throughout the life of the ink jet cartridge. Dye-based ink jet inks suffer from deficiencies in shelf life, waterfastness and lightfastness after being printed on various substrates. Pigments provide an image on a wide variety of substrates, having high optical density with high waterfastness and lightfastness. Therefore, pigments are a preferred alternative to dyes, provided the pigment dispersions can be rendered stable to prevent flocculation and/or aggregation and settling. Some cosolvents that can be selected as clogging inhibitors cause destabilization of pigment dispersions and, therefore, are not usually effective in pigmented inks.
There is thus a need for aqueous ink compositions and processes thereof that can be utilized in high resolution ink jet printers. Additionally, there is a need for colored, especially pigmented inks that provide high latency and also remain stable throughout the life of the ink jet cartridge. There is also a need for colored inks that provide high optical density in a single pass. More importantly, there is a need for ink jet inks wherein paper curl, and/or image smearing can be eliminated or minimized when such inks are selected for ink jet printing processes, and wherein the images possess minimal, or acceptable intercolor bleed, that is for example, wherein color overlap, or diffusing of one color into another is minimal, or avoided; and wherein excellent waterfast and lightfast images can be generated. These and other needs and advantages can be achievable with the present inve

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