Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Two or more radiation-sensitive layers containing other than...
Reexamination Certificate
1999-12-28
2001-01-30
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Two or more radiation-sensitive layers containing other than...
Reexamination Certificate
active
06180328
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an improved silver halide photographic element for silver halide imaging systems. More specifically, it relates to such an element comprising at least five separately sensitized light-sensitive silver halide emulsion layers containing, in addition to the three conventional cyan, magenta, and yellow dye-forming layers, a fourth image dye-forming layer comprising a coupler wherein the dye formed by that coupler has a CIELAB h
ab
hue angle in the range of from not less than 355° to not more than 75°, and a fifth image dye-forming layer comprising a coupler wherein the dye formed by that coupler has a hue angle in the range of from not less than 225° to not more than 310°, which increases the gamut of colors possible.
BACKGROUND OF THE INVENTION
Color gamut is an important feature of color printing and imaging systems. It is a measure of the range of colors that can be produced using a given combination of colorants. It is desirable for the color gamut to be as large as possible. The color gamut of the imaging system is controlled primarily by the absorption characteristics of the set of colorants used to produce the image. Silver halide imaging systems typically employ three colorants, typically including cyan, magenta, and yellow in the conventional subtractive imaging system.
The ability to produce an image containing any particular color is limited by the color gamut of the system and materials used to produce the image. Thus, the range of colors available for image reproduction is limited by the color gamut that the system and materials can produce.
Color gamut is often thought to be maximized by the use of so-called “block dyes”. In
The Reproduction of Colour
4th ed., R. W. G. Hunt, pp 135-144, it has been suggested that the optimum gamut could be obtained with a subtractive three-color system using three theoretical block dyes where the blocks are separated at approximately 490 nm and 580 nm. This proposal is interesting but cannot be implemented for various reasons. In particular, there are no real organic based couplers which produce dyes corresponding to the proposed block dyes.
Variations in the block dye concept are advanced by Clarkson, M., E., and Vickerstaff, T., in “Brightness and Hue of Present-Day Dyes in Relation to Colour Photography,” Photo. J. 88b, 26 (1948). Three example spectral shapes are given by Clarkson and Vickerstaff: Block, Trapezoidal, and Triangular. The authors conclude, contrary to the teachings of Hunt, that trapezoidal absorption spectra may be preferred to a vertical sided block dye. Again, dyes having these trapezoidal spectra shapes are theoretical and are not available in practice.
Both commercially available dyes and theoretical dyes were investigated in “The Color Gamut Obtainable by the Combination of Subtractive Color Dyes. Optimum Absorption Bands as Defined by Nonlinear Optimization Technique,” J. Imaging Science, 30, 9-12. The author, N. Ohta, deals with the subject of real colorants and notes that the existing curve for a typical cyan dye, as shown in the publication, is the optimum absorption curve for cyan dyes from a gamut standpoint.
McInerney, et al, in U.S. Pat. Nos. 5,679,139; 5,679,140; 5,679,141; and 5,679,142 teach the shape of preferred subtractive dye absorption shapes for use in four color, C,M,Y,K based ink-jet prints.
McInerney, et al, in EP 0825,488 teaches the shape of preferred subtractive cyan dye absorption shape for use in silver halide based color prints.
Kitchin, et al, in U.S. Pat. No. 4,705,745, teach the preparation of a photographic element for preparing half-tone color proofs comprising four separate imaging layers capable of producing cyan, magenta, yellow and black images.
Powers, et al, in U.S. Pat. No. 4,816,378, teach an imaging process for the preparation of color half-tone images that contain cyan, magenta, yellow and, black images. The use of the black dye does little to improve the gamut of color reproduction.
Haraga, et al, in EP 0915374A1, teach a method for improving image clarity by mixing ‘invisible’ information in the original scene with a color print and reproducing it as an infrared dye, magenta dye or as a mixture of cyan magenta and yellow dyes to achieve improved color tone and realism. The addition of the resulting infrared, magenta, or black dye does little to improve the gamut.
In spite of the foregoing teachings relative to color gamut, the coupler sets which have been employed in silver halide color imaging have not provided the range of gamut desired for modern digital imaging; especially for so-called ‘spot colors’, or ‘HiFi colors’.
It is therefore a problem to be solved by providing a coupler set which provides an increase in color gamut compared to coupler sets comprised of cyan, magenta and yellow dye forming couplers by further incorporating red dye and blue dye forming couplers.
SUMMARY OF THE INVENTION
The invention provides a color photographic element comprising at least five imaging layers including:
a first light sensitive silver halide imaging layer having associated therewith a cyan image dye-forming coupler;
a second light sensitive silver halide imaging layer having associated therewith a magenta image dye-forming coupler;
a third light sensitive silver halide imaging layer having associated therewith a yellow image dye-forming coupler; and
a fourth light sensitive silver halide imaging layer having associated therewith a fourth image dye-forming coupler for which the normalized spectral transmission density distribution curve of the dye formed by the fourth image dye-forming coupler upon reaction with color developer has a CIELAB hue angle, h
ab
, from 225 to 310°; and
a fifth light sensitive silver halide imaging layer having associated therewith a fifth image dye-forming coupler for which the normalized spectral transmission density distribution curve of the dye formed by the fifth image dye-forming coupler upon reaction with color developer has a CIELAB hue angle, h
ab
, from not less than 355 to not more than 75°.
The invention also includes a process for forming an image in an element of the invention. Such an element provides an increase in the color gamut available for silver halide digital imaging.
DETAILED DESCRIPTION OF THE INVENTION
The invention is summarized in the preceding section. The photographic element of the invention employs subtractive color imaging. In such imaging, a viewable digital print color image is formed by generating a combination of cyan, magenta, yellow, red and blue colorants in proportion to the amounts of exposure of 5 different digitally controlled light sources respectively. The object is to provide a reproduction that is pleasing to the observer but also has the improved capability to specifically reproduce the so-called ‘spot colors’, Pantone® colors or Hi-Fi colors. Color in the reproduced image is composed of one or a combination of the cyan, magenta and yellow, red, and blue image colorants. The relationship of the original color to the reproduced color is a combination of many factors. It is, however, limited by the color gamut achievable by the multitude of combinations of cyan, magenta, yellow, red and blue colorants used to generate the final image.
In addition to the individual colorant characteristics, it is necessary to have cyan, magenta and yellow, red and blue colorants that have preferred absorption maxima relative to one another and that have absorption band shapes which function together to provide an optimum overall color gamut.
The CIELAB metrics, a*, b*, and L*, when specified in combination, describe the color of an object, whether it be red and blue, green, red and blue (under fixed viewing conditions, etc. The measurement of a*, b*, and L* are well documented and now represent an international standard of color measurement. (The well-known CIE system of color measurement was established by the International Commission on Illumination in 1931 and was further revised in 1971. For a more complete description of color measurement refer to “Principles o
Begley William J.
Edwards James L.
Eastman Kodak Company
Kluegel Arthur E.
Le Hoa Van
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