Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2002-09-06
2003-11-18
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S028000, C347S095000
Reexamination Certificate
active
06648464
ABSTRACT:
FIELD OF THE INVENTION
The present invention is drawn to the area of servicing ink-jet imaging pens. More specifically, the present invention is drawn to servicing ink-jet imaging pens such that two or more ink-jet pens containing ink-jet inks that are reactive with one another can share a common service station, or can utilize a common printhead.
BACKGROUND OF THE INVENTION
Computer printer technology has evolved to a point where very high resolution images can be transferred to various types of media, including paper. One particular type of printing involves the placement of small drops of a fluid ink onto a media surface in response to a digital signal. Typically, the fluid ink is placed or jetted onto the surface without physical contact between the printing device and the surface.
There are several reasons that ink-jet printing has become a popular way of recording images on various media surfaces, particularly paper. Some of these reasons include low printer noise, capability of high-speed recording, and multi-color recording. Additionally, these advantages can be obtained at a relatively low price to consumers. However, though there has been great improvement in ink-jet printing, accompanying this improvement are increased demands by consumers in this area, e.g., higher speeds, higher resolution, full color image formation, increased stability, etc.
In general, ink-jet inks are either dye- or pigment-based inks. Both are typically prepared in a liquid vehicle that contains the dye and/or the pigment. Dye-based ink-jet inks generally use a liquid colorant that is usually water-based to turn the media a specific color. Conversely, pigmented inks typically use a solid or dispersed colorant to achieve color.
Many properties that are desirable for ink-jet printing include good edge acuity and optical density of an image on a media substrate, good dry time of the ink on the substrate, adhesion to the substrate, lack of deviation of ink droplets when fired, presence of all dots, resistance of the ink after drying to water and other solvents, long-term storage stability, good dot size and dot gain, color-to-color bleed alleviation, acceptable coalescence, long term reliability without corrosion or nozzle clogging, good light fastness, good wet fastness, low humid hue shift, and other known properties. Many inks are known to possess some of the above described properties. However, few inks are known that possess all of these properties, since an improvement in one property often results in the degradation in another property. Accordingly, investigations continue into developing ink formulations that have improved properties and that do not improve one property at the significant detriment of another. However, many challenges still remain to further improve the image quality of ink-jet prints without sacrificing pen performance and reliability.
To illustrate advancement in the art that has evolved, there has been great interest in the area of reactive inks. These inks are designed such that a reaction occurs between two different ink colors at a border between the colors, e.g., an interaction such as precipitation occurs. This interaction can improve the edge acuity and/or color to color bleed between inks. For example, in order to have good black to color bleed and halo control, many ink-jet ink sets have been designed so that contact between the black and color inks promote destabilization of the black color causing it to agglomerate on the page. This can be accomplished by adding materials to the color inks that cause “crashing” of the black, usually acids or multivalent metal salts. Because of this reactivity, it has not been practical to put a reactive black and a multivalent salt- or acid-containing color ink set on the same printhead since agglomeration of the colorant may lead to clogging of the nozzles when the inks inevitably cross-contaminate. Because of this limitation, printhead configurations of reactive inks have often been limited to variations where reactive inks do not share a common printhead, e.g., three color pen and black pen are separate, or where each color has its own printhead.
In the prior art, care has been taken to avoid cross-contamination of printheads containing inks designed to be reactive with one another. One solution used to avoid cross-contamination, as mentioned, has been to provide separate service stations for inks intended to be reactive with one another. However, this is not always the most convenient arrangement. As alluded to, inkjet printers generally have one or more printhead service station(s) to which an ink-jet printhead is moved by a carriage. A cap that contacts or covers the printhead is also generally located at the service station. Further, at the service station, the printhead (or multiple heads if such are used) are occasionally cleaned and, if necessary, primed with ink. For use in this cleaning function, wipers can be present and located at the service station. The service station can also include a “sled” carrying these elements and others required to service the one or more printheads of the printer. This sled itself can be moved transversely to an axis of motion of the printhead carriage, for example in a vertical direction, so as to bring the caps or wipers into or out of contact with the printhead. Alternatively, a tumbler can be provided at the service station, and wipers, as well as caps, can be located on the tumbler. Rotation (and in some cases also vertical movement) of the tumbler effects wiping of the printhead, and/or alignment of one or more caps with one or more printheads positioned adjacent the tumbler at the service station. Though wiper and solvent systems are described in the prior art, the problems associated with cross-contamination of two reactive inks using a common service station or printhead has not been fully addressed.
SUMMARY OF THE INVENTION
It has been recognized that the use of certain components in ink-jet pen cleaning systems can provide acceptable printhead cleaning properties, even when two reactive inks are provided in multiple ink-jet pens sharing a common service station, a common printhead, or are in close proximity, thereby contributing to cross-contamination. Specifically, a method of printing two ink-jet inks reactive with one another from a printer having a common printhead while maintaining pen reliability can comprise the steps of jetting a first ink-jet ink from a common printhead and jetting a second ink-jet ink from the common printhead. The contacting of the inks from the common printhead results in the crashing of at least one of the inks thereby forming a crashed ink. The method further comprises dispensing a reactive cleaning fluid onto the printhead before or after crashing occurs, wherein the reactive cleaning fluid is chemically configured to react with the crashed ink, thereby minimizing or reverse crashing at the printhead.
In a further detailed aspect, a method of minimizing or reversing crashing of a first ink-jet ink that has reacted with a second ink-jet ink on a printhead can comprise the steps of (a) dispensing a reactive cleaning fluid that is chemically configured to react with the first ink-jet ink after crashing; and (b) cleaning a printhead having a crashed ink-jet ink thereon with the reactive cleaning fluid, thereby minimizing or reverse crashing at the printhead.
With respect to a related system, an ink-jet printing system can comprise a first ink-jet ink and a second ink-jet ink that is reactive with the first ink-jet ink such that when the first ink-jet ink contacts the second ink-jet ink, crashing of one of the first ink-jet ink and the second ink-jet ink occurs. The system can further comprise printing architecture configured for jetting the first ink-jet ink and the second ink-jet ink onto a substrate, wherein cross-contamination between the first ink-jet ink and the second ink-jet ink can occur on a printhead. A reactive cleaning fluid formulated to minimize or reverse crashing that occurs on the at least one printhead upon contact between the
Hewlett--Packard Development Company, L.P.
Meier Stephen D.
Shah Manish
LandOfFree
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