Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-08-31
2001-02-06
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031270, C106S031500, C106S031580
Reexamination Certificate
active
06183548
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to inks for ink jet printing that provide images with good lightfastness and improved color gamut.
BACKGROUND OF THE INVENTION
Ink jet printing is a non-impact method for producing images by the deposition of ink droplets in a pixel-by-pixel manner to an image-recording element in response to digital signals. There are various methods which may be utilized to control the deposition of ink droplets on the image-recording element to yield the desired image. In one process, known as continuous ink jet, a continuous stream of droplets is charged and deflected in an imagewise manner onto the surface of the image-recording element, while unimaged droplets are caught and returned to an ink sump. In another process, known as drop-on-demand ink jet, individual ink droplets are projected as needed onto the image-recording element to form the desired image. Common methods of controlling the projection of ink droplets in drop-on-demand printing include piezoelectric transducers and thermal bubble formation. Ink jet printers have found broad applications across markets ranging from industrial labeling to short run printing to desktop document and pictorial imaging.
The inks used in the various ink jet printers can be classified as either dye-based or pigment-based. A dye is a colorant, which is dissolved in the carrier medium. A pigment is a colorant that is insoluble in the carrier medium, but is dispersed or suspended in the form of small particles, often stabilized against flocculation and settling by the use of dispersing agents. The carrier medium can be a liquid or a solid at room temperature in both cases. Commonly used carrier media include water, mixtures of water and organic co-solvents and high boiling organic solvents, such as hydrocarbons, esters, ketones, etc. For aqueous dye-based inks, the dyes needs to be sufficiently soluble in water to prepare a solution that is capable of producing adequate density on the receiving element and stable for extended periods of storage without precipitation. High quality ink jet printing with dye-based inks requires dyes which will provide both bright hue and good light fastness.
To generate full color prints via ink jet printing, ink sets comprising at least cyan, magenta and yellow inks are normally utilized. In addition a black ink is often added to enhance the printing of text and darker colors. The range of colors that can be produced with a given set of inks defines the color gamut of that ink set. For the production of high quality photorealistic images via ink jet printing, ink sets with a large color gamut are preferred. In addition, it is important that the ink sets produce images with good fastness, especially to light.
The choice of the colorants in ink jet systems is critical for both light fastness and color gamut. The color gamut of an ink set is controlled primarily by the spectral absorption characteristics of the component dyes. The primary dyes (e.g. cyan, magenta and yellow) should only absorb light of the required wavelengths (i.e. have relatively narrow absorption bands) and not overlap excessively with the dyes in the complementary inks. While there are many dyes with bright hues that are useful in ink jet printing, many have poor light fastness. Conversely many light stable dyes suitable for ink jet printing have broad absorption bands and give dull colors and limited color gamut.
U.S. Pat. No. 5,851,273 relates to a set of inks comprising Direct Yellow 132, Magenta 377, Direct Blue 199 and optionally Reactive Black 31 offering good light fastness and color. However there is a problem with this ink set in that the color gamut is not as large as one would like.
It is an object of this invention to provide a set of inks capable of producing images via ink jet printing which have both good lightfastness and better color gamut than the ink sets of the prior art.
SUMMARY OF THE INVENTION
This and other objects are achieved in accordance with the present invention comprising a color ink jet ink set for color printing comprising:
(a) a yellow ink comprising a carrier and Direct Yellow 107, Direct Yellow 132 or Direct Yellow 86;
(b) a magenta ink comprising a carrier and a water soluble, transition metal complex of an 8-heterocyclylazo-5-hydroxyquinoline dye; and
(c) a cyan ink comprising a carrier and a sulfonated copper phthalocyanine dye.
Another embodiment of the invention relates to an ink jet printing method for printing color images, comprising the steps of:
providing an ink jet printer that is responsive to digital data signals;
loading the printer with ink receptive substrates;
loading the printer with an color ink jet ink set as described above; and printing on the ink receptive substrates in response to the digital data signals.
DETAILED DESCRIPTION OF THE INVENTION
Dyes referred to by dye numbers are numbers assigned by The Color Index. In a preferred embodiment of the invention, Reactive Black 31, Direct Black 19, Direct Black 168 or Solubilized Sulfur Black 1 (Duasyn ® Black SU-SF) can be added to further increase the available color gamut of this ink set.
For the purpose of this invention, color gamut is specified in the CIELAB metric. Color gamut is defined as the sum of the a*-b* areas of 9 L* slices (L*=10, 20, 30, 40, 50, 60, 70, 80 and 90) obtained when a given ink set is used. Color gamut may be obtained through measurement and estimation from a large sample of color patches which is very tedious and time-consuming, or calculated from the measured absorption characteristics of the individual dyes using the techniques described in J. Photographic Science, 38, 163 (1990).
The absorption characteristics of a given image dye will vary to some extent with a change in ink laydown or printed density. This is due to factors such as measurement flare, dye-dye interactions, dye-receiver interactions, dye concentration effects, and the presence of colored impurities in the media. However, by using characteristic vector analysis, sometimes referred to as principal component analysis or eigenvector analysis, one can determine a characteristic absorption curve that is representative of the absorption characteristics of the dye over the complete wavelength and density ranges of interest. The characteristic vector for each dye is thus a two-dimensional array of optical density and wavelength. This technique is described by Albert J. Sant in Photographic Science and Engineering, 5(3), May-June 1961 and by J.L.Simonds in the Journal of the Optical Society of America, 53(8), 968-974 (1963). Characteristic vectors thus derived can be used to calculate the color gamuts of ink sets described below as described in the above reference.
The following commercially available cyan, yellow and black dyes were used to formulate the inks employed in this invention:
A. Direct Blue 199, available as Duasyn Turquoise Blue FRL-SF® from Clariant Corp. as an approximately 10% solution in water.
B. ProJet Cyan 1®, available from Zeneca Specialties as an approximately 10% solution in water.
C. Direct Blue 86, available as Intrajet Blue DES® from Crompton and Knowles as an approximately 10% solution in water.
D. Direct Yellow 107, available as Intrajet Yellow DG® from Crompton and Knowles as an approximately 10% solution in water.
E. Direct Yellow 132, available as ProJet Yellow 1G® from Zeneca Specialties as an approximately 10% solution in water.
F. Direct Yellow 86, available as Aizen DY86® from Hodogaya Chemical Co.
G. Reactive Black 31, available as Duasyn Black KRL-SF® from Clariant Corp. as an approximately 10% solution in water.
H. Direct Black 168, available as Duasyn Black HEF-SF® from Clariant Corp. as an approximately 10% solution in water.
I. Solubilized Sulfur Black 1, available as Duasyn Black SU-SF® from Clariant Corp. as an approximately 10% solution in water.
J. Direct Black 19, available as Keyamine Black G Pure Liquid® from Keystone Corp. as an approximately 10% solution in water.
The magenta inks employed in the invention may by formulated with one or more water soluble
Erdtmann David
Evans Steven
Weber Helmut
Cole Harold E.
Eastman Kodak Company
Klemanski Helene
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