Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-09-15
2002-12-17
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031490, C106S031500, C106S031580
Reexamination Certificate
active
06494942
ABSTRACT:
FIELD OF THE INVENTION
The present invention is drawn to dye-based ink jet ink compositions having improved stability and light fastness.
BACKGROUND OF THE INVENTION
In recent years, 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. Within this general technique, the specific method that the ink jet ink is deposited onto the printing surface varies from system to system, and can include continuous ink deposit and drop-on-demand ink deposit.
With regard to continuous printing systems, inks used are typically based on solvents such as methyl ethyl ketone and ethanol. Essentially, continuous printing systems function as a stream of ink droplets ejected and directed by a printer nozzle. The ink droplets are directed additionally with the assistance of an electrostatic charging device in close proximity to the nozzle. If the ink is not used on the desired printing surface, the ink is recycled for later use. With regard to drop-on-demand printing systems, the ink jet inks are typically based upon water and glycols. Essentially, with these systems, ink droplets are propelled from a nozzle by heat or by a pressure wave such that all of the ink droplets ejected are used to form the printed image.
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. As new ink jet inks are developed, there have been several traditional characteristics to consider when evaluating the ink in conjunction with a printing surface or substrate. Such characteristics include edge acuity and optical density of the image on the surface, dry time of the ink on the substrate, adhesion to the substrate, lack of deviation of ink droplets, presence of all dots, resistance of the ink after drying to water and other solvents, long term storage stability, and long term reliability without corrosion or nozzle clogging. Though the above list of characteristics provides a worthy goal to achieve, there are difficulties associated with satisfying all of the above characteristics. Often, the inclusion of an ink component meant to satisfy one of the above characteristics can prevent another characteristic from being met. Thus, most commercial inks for use in ink jet printers represent a compromise in an attempt to achieve at least an adequate response in meeting all of the above listed requirements.
In general, ink jet inks are either dye- or pigment-based inks. Dye-based ink jet inks generally use a liquid colorant that is usually water-based to turn the media a specific color. Because of their makeup, dye-based inks are usually not waterproof and tend to be more affected by UV light. This results in the color changing over time, or fading. For optimum performance, this type of ink has often required that the proper media be selected in accordance with the application, thus, reducing the choice of media for printing. Conversely, pigmented inks typically use a solid colorant to achieve color. In many cases, the line quality and accuracy of plots produced by pigment-based inks are usually superior to that of dye-based inks. With pigmented inks, solid particles adhere to the surface of the substrate. Once the water in the solution has evaporated, the particles will generally not go back into solution, and are therefore more waterproof. In addition, pigmented inks are much more UV resistant than dye-based inks, meaning that it takes much longer for noticeable fading to occur. Though pigmented inks, in some areas, exhibit superior characteristics, dyes tend to run cleaner, provide better yield, offer better particle size, and are easier to filter. Thus, dye-based inks have been more often used for common applications and have tended to be more chromatic and provide more highly saturated colors.
In order for ink jet prints to effectively compete with silver halide photography, one important improvement that must occur is that ink jet inks must improve their ability to remain stable to light exposure for longer periods of time. At this point in time, photographs typically will last much longer under prolonged light exposure, i.e., about 14-18 years under fluorescent light exposure. Conversely, some of the best ink jet printers will produce prints that last for only about 6-8 years under similar conditions. Particularly, with respect to dye-based ink jet ink, the phenomenon of discoloration occurs even more readily than is typical for pigment-based ink jet inks. However, as described above, dye-based inks are sometimes preferred because they are very convenient to use and have good distinction of color.
In the photographic industry, technologies have been developed which have been reported to last much longer than the typical 14-18 years, and even up to 60 years. Such long lasting ink stability has been attributed to a very stable magenta dye which is, in part, the subject of U.S. Pat. No. 5,242,785. That patent reports many new dyes and additives that have very good light fastness (2% dye loss after 16.5 years of simulated light exposure). However, though these dyes are very stable under prolonged light exposure, these dyes are not water-soluble and contain long chain organic groups necessary for anchoring dyes in photographic media. Such structures are not useable in aqueous-based ink jet systems.
Thus, it would be useful to provide aqueous ink jet inks for printing on media such that the inks are more stable under prolonged light exposure and/or exhibit good light fastness. This can be accomplished by providing dyes and/or additives for aqueous ink jet inks that improve these and other important properties.
SUMMARY OF THE INVENTION
An aqueous ink jet ink is disclosed which comprises an effective amount of an azomethine dye having at least one water solubilizing functional group covalently attached thereto wherein the water solubilizing functional group is directly attached to the azomethine dye or is attached to the azomethine dye through an electrophilic coupling moiety. If an organic spacer group is used to separate the water solubilizing functional group from azomethine dye or the electrophilic coupling moiety, then straight and branched chained alkyl linkers or spacers having from about 1 to 10 carbon atoms are preferred. Preferred azomethine dyes can be pyrazolone azomethines, pyrazolotriazole azomethines, and combinations thereof. Additionally, an aqueous ink jet ink is disclosed comprising an effective amount of a dye-based colorant and an essentially water soluble spiroindane additive for improving light fastness and stability of various dye-based colorants.
DETAILED DESCRIPTION OF THE INVENTION
Before the present invention is disclosed and described, it is to be understood that this invention is not limited to the particular process steps and materials disclosed herein because such process steps and materials may vary somewhat. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only. The terms are not intended to be limiting because the scope of the present invention is intended to be limited only by the appended claims and equivalents thereof.
It must be noted that, as used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plu
Deardurff Larrie A
Lincoln Christopher
White James David
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