Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Identified radiation sensitive composition with color...
Reexamination Certificate
2001-12-21
2003-04-29
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Identified radiation sensitive composition with color...
C430S567000, C430S570000, C430S551000
Reexamination Certificate
active
06555305
ABSTRACT:
FIELD OF INVENTION
This invention relates to silver halide photographic materials. More particularly, it relates to color photographic materials which contain spectrally sensitized tabular grain silver halide emulsions and dye-forming couplers in combination with non-imaging compounds which give rise to photographic images which have reduced levels of retained sensitizing dye after photographic processing.
BACKGROUND OF THE INVENTION
The conventional image-forming process of silver halide photography includes imagewise exposure of a photographic silver halide recording material to actinic radiation (such as visible light), and the eventual manifestation of a useable image by wet photochemical processing of that exposed material. A fundamental step of photochemical processing is the treatment of the material with one or more developing agents to reduce silver halide to silver metal. With black-and-white photographic materials, the metallic silver usually comprises the image. With color photographic materials, the useful image consists of one or more organic dye images produced from an oxidized color developing agent formed wherever silver halide is reduced to metallic silver. To obtain useful color images, it is usually necessary to remove all of the silver from the photographic element after color development. This is sometimes known as “desilvering”. Removal of silver is generally accomplished by oxidizing the metallic silver, and then dissolving it and undeveloped silver halide with a “solvent” or fixing agent in what is known as a fixing step. Oxidation is achieved using an oxidizing agent, commonly known as a bleaching agent. For some processing methods, these two steps can be performed in the same processing step in what is known as bleach-fixing. Common bleaching agents include ferric salts and ferric complexes of various polycarboxylic or polyaminopolycarboxylic chelating ligands. Common fixing agents include thiosulfate salts (both ammonium and sodium thio-sulfate salts) and thiocyanates.
Photographic silver halide materials often contain various spectral sensitizing dyes that extend the inherent photosensitivity of the photosensitive silver halide emulsions to electromagnetic radiation. One important class of such spectral sensitizing dyes includes carbocyanine sensitizing dyes that are commonly included in silver halide emulsion layers in photographic silver halide films. For example they are often present in color paper and color reversal photographic silver halide elements (photographic elements normally used to provide color positive images), as well as color negative photographic elements. Many photographic silver halide elements contain residual spectral sensitizing dyes after photoprocessing. In some cases, the level of retained spectral sensitizing dyes is inconsequential and thus, unobservable. In other instances, however, the high level of retained spectral sensitizing dye results in undesirably high dye stain (or unwanted color) in the elements. High levels of sensitizing dye can result in processed papers and reversal films which are visibly objectionable, and in negative films with inferior printing characteristics.
Tabular silver halide grains are generally regarded as silver halide grains having an aspect ratio of at least 2, where aspect ratio is defined as the equivalent circular diameter (ECD) of the major face of the grain divided by the grain thickness. A tabular grain emulsion is generally considered to be an emulsion for which greater than 50% of the total grain projected area of the emulsion is accounted for by tabular grains. Kofron, et al., U.S. Pat. No. 4,439,520 ushered in the current era of high performance silver halide photography. Kofron, et al., disclosed and demonstrated striking photographic advantages for chemically and spectrally sensitized tabular grain silver halide emulsions in which grains having a diameter of at least 0.6 &mgr;m and a thickness of less than 0.3 &mgr;m exhibit an average aspect ratio of greater than 8 and account for greater than 50 percent of total silver halide grain projected area. Kofron, et al., recognized that the chemically and spectrally sensitized emulsions disclosed in one or more of their various forms would be useful in color photography and in black-and-white photography (including indirect radiography). Spectral sensitizations in all portions of the visible spectrum and at longer wavelengths were addressed as well as orthochromatic and panchromatic spectral sensitizations for black-and-white imaging applications. Kofron, et al., employed combinations of one or more spectral sensitizing dyes along with middle chalcogen (e.g., sulfur) and/or noble metal (e.g., gold) chemical sensitizations, although still other conventional sensitizations, such as reduction sensitization were also disclosed.
When silver halide elements contain tabular grain silver halide emulsions, however, retained sensitizing dye stain problems may be aggravated due to the increased surface areas of the tabular grains requiring higher concentrations of spectral sensitizing dyes for optimal sensitization. Retained sensitizing dye stain is further aggravated for color elements which include dye-forming couplers due to interactions between the sensitizing dyes and couplers, or when the elements are designed for relatively short wet processing times such that less sensitizing dye is removed during shortened processing steps. Retained sensitizing dye can particularly be detrimental for color reversal elements, where the formed color image is intended for direct or projected viewing.
U.S. Pat. Nos. 5,188,926 and 5,192,646 teach the use of carbonamide and sulfoxide coupler solvents, respectively, to reduce sensitizing dye stain for certain applications. U.S. Pat. No. 5,352,572 disclose the use of bis urea, bis amide, and bis carbamate solvents in photographic elements, but no teaching is made to advantages for sensitizing dye stain, nor are any dipiperidine derivatives disclosed.
While various approaches have been proposed to minimize retained sensitizing dyes in photographic elements, it would be desirable to provide further improvements, particularly with respect to photographic elements employing spectrally sensitized tabular grain silver halide emulsions, more particularly for color photographic elements employing spectrally sensitized tabular grain silver halide emulsions, and especially for color reversal photographic elements employing spectrally sensitized tabular grain silver halide emulsions.
SUMMARY OF THE INVENTION
An objective of this invention is to provide photographic elements comprising spectrally sensitized tabular grain silver halide emulsions which exhibit reduced sensitizing dye stain after photographic processing. The present invention solves the problem by employing a substituted dipiperidine additive in the elements of the invention. In accordance with the invention, a photographic element is disclosed comprising a silver halide emulsion layer including a spectrally sensitized tabular grain emulsion and having associated therewith a compound of the following Formula I:
wherein n=0-6 and each R is independently hydrogen, an aromatic, cyclic, linear or branched chain hydrocarbon group, NR′R″, or OR′, where R′ is an aromatic, cyclic, linear or branched chain hydrocarbon group and R″ is hydrogen or an aromatic, cyclic, linear or branched chain hydrocarbon group.
We have found that the objective of the invention can be achieved with the use of dipiperidinediamide, dipiperidinedicarbamate or dipiperidinediurea compounds of Formula I as dye stain reducing addenda. In accordance with preferred embodiments of the invention, such compounds may be used in combination with dye-forming couplers. In addition to dye-stain reducing properties, compounds of Formula I have organic solvent properties, and accordingly may be advantageously used partly or totally in place of conventional high boiling permanent and/or auxiliary organic coupler solvents to disperse the dye-forming couplers. Photogra
Steele Margaret D.
Vargas J. Ramon
Anderson Andrew J.
Letscher Geraldine
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