Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2001-05-04
2003-04-01
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031270, C106S031490
Reexamination Certificate
active
06540821
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to ink-jet printing, and in particular, to a specific ink set suitable for use with an off-axis printer system.
BACKGROUND OF THE INVENTION
Ink-jet printing is a non-impact printing process in which droplets of ink are deposited on a print medium in a particular order to form alphanumeric characters, area-fills, and other patterns thereon. Low cost and high quality of the hardcopy output, combined with relatively noise-free operation, have made ink-jet printers a popular alternative to other types of printers used with computers. One particular type of ink-jet printer, known as an off-axis printer, includes a replaceable print cartridge A fluid interconnect on the print cartridge connects it to a separate ink supply located within the printer.
The non-impact printing process of ink-jet printing involves the ejection of fine droplets of ink onto a print medium such as paper, transparency film, or textiles in response to electrical signals generated by a microprocessor. There are two basic means currently available for achieving ink droplet ejection in ink-jet printing: thermally and piezoelectrically. In thermal ink-jet printing, the energy for drop ejection is generated by electrically heated resistor elements, which heat up rapidly in response to electrical signals from a microprocessor to create a vapor bubble, resulting in the expulsion of ink through nozzles associated with the resistor elements. In piezoelectric ink-jet printing, the ink droplets are ejected due to the vibrations of piezoelectric crystals, again, in response to electrical signals generated by the microprocessor.
Commercially-available off-axis ink-jet printers, such as a DeskJet® 2200 printer available from Hewlett-Packard Company, use inks of differing hues, namely, magenta, yellow, and cyan, and optionally black. The particular set of colorants, for example, dyes, used to make the inks is called a “primary dye set.” A spectrum of colors, e.g., secondary colors, can be generated using different combinations of the primary dye set.
Any given perceived color can be described using any one of the color spaces, as is well known in the art. For example, in the CIELAB color space, a color is defined using three terms L*, a*, and b*. L* defines the lightness of a color, and it ranges from zero (black) to 100 (white). The terms a* and b*, together, define the hue and chroma characteristics of a given color. The term a* ranges from a more negative number, green, to a more positive number, red. The term b* ranges from a more negative number, blue, to a more positive number, yellow.
To determine the concentration or amount of a given substance (e.g., a dye) in a solution, absorbance is commonly used by chemists. Many molecules and ions have the ability to absorb visible light. When these ions or molecules are present in solution, the amount of light absorbed is directly related to the number of molecules in solution. Each ion or molecule will have characteristic absorption spectra wherein the various wavelengths of light present in visible “white” light are differentially absorbed. It is desirable in most cases to measure the absorbance where the absorbance is strongest (lambda
max
) or most sensitive. Absorbance values can be calculated according to Beers Law:
Absorbance=Ebc where
a. E is equal to molar absorptivity which is an intrinsic property of the molecule
b. b is equal to the path length the light must travel
c. c is equal to the solution concentration
The resulting absorbance value can then be applied to determine the concentration of molecules. In the case of dyes, the absorbance is taken as the measure of concentration or amount of dye molecules present, just as weight would be used if dry material were used. In the manufacture of inks using dyes, it is desirable to use absorbance due to the expense associated in drying dyestuffs for the sole purpose of measuring the same by dry weight and redissolving them. There are health hazards associated with handling dried dye that require expensive safety procedures to be implemented and, often times, the raw dye from the manufacturer is not 100% pure, creating further problems. When working with a dyestuff that is not 100% pure, dry weight of dye is actually misleading as a given dry weight of dye could contain a variable number or concentration of dye molecules dependant on the purity, which are the functional element in the ink. By using absorbance as a measure of dye concentration the accurate reproducible manufacture of inks using dyes is assured.
In general, a successful ink set for color ink-jet printing must have the following properties: good crusting resistance, good stability, the proper viscosity, the proper surface tension, good color-to-color bleed alleviation, rapid dry time, consumer-safety, and low strike-through. When placed into a thermal ink-jet system, the ink set must also be kogation-resistant.
In addition, the ink set must be able to provide printed images having good color characteristics, such as correct hue and high chroma. While formation of colors on plain paper is required, it is also necessary that the ink set be useful on other print media, such as transparency film,coated paper, and photo paper. Another requirement for the ink set is to provide a hard copy output that is lightfast, thus preserving the integrity of the original color information.
While some of these conditions may be met by ink vehicle design, other conditions must be met by the proper selection and combination of the colorants. The selection of the colorants becomes especially important when additional limitations are placed on the choice of the colorants because of other system requirements, such as the color-to-color bleed control mechanism.
Regardless of whether an ink is dye-based or pigment-based, ink-jet inks commonly face the challenge of color-to-color or black-to-color bleed control. The term “bleed,” as used herein, is defined to be the invasion of one color into another, once the ink is deposited on the print medium, as evidenced by a ragged border of mixed color therebetween. Bleed occurs as colors mix both on the surface of the paper substrate as well as within the substrate itself. The occurrence of bleed is especially problematic between a black ink and an adjacently-printed color ink because it is all the more visible. Hence, to achieve good print quality, bleed must be substantially reduced or eliminated such that borders between colors are clean and free from the invasion of one color into the other.
Many proposals are made to obtain high quality ink compositions for ink-jet printing which attempt to meet the above-mentioned characteristics. Although various inks are known which possess one or more of the of the foregoing properties, few inks possess all of these properties, since an improvement in one property often results in the degradation of another property. For example, to obtain improved color reproduction performance, U.S. Pat. No. 5,143,547 discloses the combination of C.I. Acid Yellow 23, C.I. Direct Red 227, and C.I. Acid Blue 9; while U.S. Pat. No. 5,145,519 discloses the combination of C.I. Direct yellow 86, C.I. Acid Red 52, and C.I. Acid Blue 9. These sets of ink compositions, however, possess a number of shortcomings. For example, the C.I. Yellow 23 for use in the yellow ink composition disclosed in U.S. Pat. No. 5,143,547 has poor light resistance.
A different approach used for controlling bleed between the printed images, as disclosed in U.S. Pat. No. 5,428,383, is to provide a first ink composition comprising a first colorant, and a second ink composition comprising a second colorant and a precipitating agent (e.g., inorganic salts), which will react with the first colorant in the first ink composition so that upon contact of the first ink and the second ink on the printing medium a precipitate is formed, thus preventing color bleed between the first ink composition and the second ink composition.
Likewise, many inks used commercially represent a compromise
Adamic Raymond J
Austin Mary E
Lauw Hiang P
Parazak Dennis P
Rehman Zia
Hewlett--Packard Company
Klemanski Helene
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