Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2000-10-17
2002-07-30
Letscher, Geraldine (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S615000, C430S505000, C430S507000, C430S510000, C430S955000
Reexamination Certificate
active
06426180
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Co-filed herewith is an application Ser. No. 09/690,310 directed to a light sensitive color photographic element containing a speed improving nitrogen heterocycle with at least 3 heteroatoms and a reflector layer and an application Ser. No. 09/690,230 directed to a an element containing a certain reflector layer.
FIELD OF THE INVENTION
This invention relates to a light sensitive color photographic element containing a speed improving nitrogen heterocycle with at least 3 heteroatoms and an electron transfer agent releasing compound (ETARC).
BACKGROUND OF THE INVENTION
It is a long-standing objective of color photographic origination materials to maximize the overall response to light while maintaining the lowest possible granularity. Increased photographic sensitivity to light (commonly referred to as photographic speed) allows for improved images captured under low light conditions or improved details in the shadowed regions of the image. Sensitivity is much more important with origination materials than with print materials, the latter depending entirely on operator supplied light. In general, the overall light sensitivity provided by the light sensitive silver halide emulsions is a function of the size of the emulsion grains. Larger emulsion grains capture more light. Upon development, the captured light is ultimately converted into dye deposits that constitute the reproduced image. Undesirably, the granularity exhibited by these dye deposits is directly proportional to the grain size of the silver halide emulsion. Thus, larger silver halide emulsion grains have higher sensitivity to light but also lead to higher granularity in the reproduced image. Therefore, it is a fundamental problem in photography to improve the light sensitivity of a silver halide element without a corresponding decrease in another property such as granularity. In this description, it will be understood that the demonstrated increase in sensitivity is accomplished without a significant sacrifice in granularity. Stated from another perspective, it has been a long-standing problem to provide materials which maximize the response to light of a silver halide emulsion for any given grain size. It is highly desirable to provide non-imaging materials that lead to increased photographic speed without having to increase the size of the light-sensitive silver halide grains.
European application EP 1016902 describes the use of certain compounds, including heterocycles with a C log P of 6.2 or greater, in a light sensitive silver halide emulsion layer or in an adjacent non-light sensitive layer to increase the overall light sensitivity of a photographic element.
U.S. Pat. No. 3,989,527 discloses a method of increasing photographic speed whereby a light insensitive reflecting emulsion having a particle size from 0.40-0.60 &mgr;m is blended within a sensitized emulsion. U.S. Pat. Nos. 5,994,042, 5,994,043, 5,998,113, 5,998,114, 6,001,548 and 5,998,115 all describe the use of non-light sensitive light scattering or reflecting emulsions, or a combination thereof, to increase photographic speed.
Electron Transfer Agent Releasing Compounds (ETARCs) are taught in U.S. Pat. Nos. 4,859,578 and 4,912,025 and their use with Soluble Mercaptan Releasing Couplers (SMRCs) is taught in copending U.S. Ser. No. 09/224,230. ETARCs can improve the developability of silver halide emulsions which in some cases, offers improvements in light sensitivity.
Thus it is known to incorporate various materials such as those that cause light reflecting, and certain heterocyclic compounds or ETARCs to improve the light sensitivity of photographic elements. A problem to be solved is to provide color photographic elements that exhibit still further improved photographic speed.
SUMMARY OF THE INVENTION
The invention provides a color silver halide photographic element comprising a support bearing:
(1) a light sensitive silver halide emulsion layer;
(2) a nitrogen heterocycle with a minimum of three heteroatoms that does not react with oxidized developer, does not contain free thiol substituents, and has a C log P sufficient to increase the photographic speed of said element compared to the same element without the compound, said heterocycle compound located either in said light sensitive layer or in a layer adjacent to it; and
(3) an ETARC, in or adjacent to said light sensitive silver halide emulsion layer, that releases, upon reaction with oxidized developer, an electron transfer agent having a C log P of at least 2.40. The invention also provides an imaging process.
The invention provides color photographic elements that exhibit a desirable increase in photographic speed.
DETAILED DESCRIPTION OF THE INVENTION
The invention is generally as described above. Typically, the color photographic element useful in the present invention contains at least one red sensitive silver halide emulsion layer with at least one non-diffusing cyan coupler, at least one green sensitive silver halide emulsion layer with at least one non-diffusing magenta coupler and at least one blue sensitive silver halide emulsion layer with at least one non-diffusing yellow coupler. The inventive elements are characterized in that there is associated with at least one of the light sensitive layers a nitrogen heterocycle with a minimum of three heteroatoms that does not react with oxidized developer, does not contain free thiol substituents, and has a C log P sufficient to increase the photographic speed of the element compared to the same element without the compound. The heterocycle compound is located either in the light sensitive layer or in a layer adjacent to it. The light reflecting material is located in either said light sensitive layer or in a layer proximate to it, meaning sufficiently close so as to effect a super-additive speed improvement compared to the speed improvement that would be realized from the separate addition of the two materials. The addition of the nitrogen heterocycle compound to a location as described imparts improved speed to the light sensitive layer with which it is associated.
The term “proximate” is used herein to describe the degree of proximity between the location of the heterocycle and reflecting material that enables the desired super-additive speed effect. Typically, the average distance between the nearest edges of the two layers is not more than 10 &mgr;m. as measured in a dry film.
The term “heteroatom” as used herein encompasses any atom other than carbon or hydrogen and includes, for example, nitrogen, sulfur, phosphorous and oxygen. The term “heteroatom” refers only to those ring-member atoms which form an integral part of the ring system and not to those atoms that are located externally to the ring system or separated from it by at least one single, unconjugated bond or are part of an additional substituent of the ring system.
In various aspects of the invention, the heterocycle compound is a particular kind of nitrogen heterocycle with a minimum of three heteroatoms and includes examples such as a tetraazaindene, a benzotriazole, a triazole, a tetrazole, a thiadiazole and an oxadiazole.
The heterocyclic compounds useful in the invention, or “speed compounds”, are similar to compounds known to cause inhibition of silver development, but, because of their increased hydrophobicity (as measured by a higher C log P), they do not cause inhibition of silver development per se. Among the classes of compounds that contain a minimum of three heteroatoms and are known to cause inhibition of silver development that can be included in the invention when appropriately substituted to increase hydrophobicity are: triazoles, oxadiazoles, thiadiazoles, oxathiazoles, thiatriazoles, benzotriazoles, tetrazoles, benzisodiazoles and purines and other polyazaindenes. Formulations useful for the purpose of the invention, namely an increase in photographic speed, have the desired overall hydrophobicity (as measured by C log P), do not contain a free thiol substituent. The minimum C log P for speed improvement may vary
Bringley Joseph F.
Friday James A.
Singer Stephen P.
Vitale Marcello
Eastman Kodak Company
Kluegel Arthur E.
Letscher Geraldine
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