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AssigneeEastman Kodak Company
InventorsBernard A. Clark, Philip A. Allway, Tania Zuberi, Stephen P. Singer, Charles E. Heckler, Louis E. Friedrich
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The invention provides a color photographic element comprising at least one light-sensitive silver halide emulsion layer or a non silver-containing light-insensitive layer, in which at least one of these layers contains a colorless imidazole compound of formula (I) that undergoes less than 10% chemical or redox reaction with oxidized developer and which enables the photographic speed of the element to be increased by at least 0.05 stop without increasing granularity, compared to the same element without the compound, wherein the compound of formula (I) has the structure: wherein X is H or a substituent; Z represents the atoms necessary to complete an unsubstituted or substituted imidazole ring, which may form part of a fused unsubstituted or substituted ring system containing no further ring heteroatoms; wherein there is present at least one —NH group either in the imidazole ring or directly attached to the imidazole ring as part of X; provided that (a) when Z represents the atoms necessary to complete an unsubstituted or substituted benzimidazole ring, an —NH group is directly attached to the imidazole ring as part of X, and X is located between the imidazole nitrogen atoms; (b) when the —NH group is located in the ring adjacent to the carbon atom bearing X, and X is located between the imidazole nitrogen atoms, the imidazole ring is not fused to a phenanthrene ring. The compounds of formula (I) increase speed without a concomitant increase in size of the light-sensitive silver halide grains.
A colour photographic element comprising at least one light-sensitive silver halide emulsion layer or a non silver-containing light-insensitive layer, in which at least one of these layers contains a colourless imidazole compound of formula (I) that undergoes less than 10% chemical or redox reaction directly with oxidized developer and which enables the photographic speed of the element to be increased by at least 0.03 stop without increasing granularity, compared to the same element without the compound, wherein the compound of formula (I) has the structure:—
A colour photographic element as claimed in either of the preceding claims wherein the compound of formula (I) is contained in the most light-sensitive layer of two or more light-sensitive layers having the same spectral sensitivity.
A colour photographic element as claimed in any one of the preceding claims wherein the compound of formula (I) is located in the green record wherein the maximum spectral sensitivity to light is from 500 to 600 nm.
A colour photographic element as claimed in any one of the preceding claims wherein the silver halide comprises silver iodobromide.
A colour photographic element as claimed in any one of the preceding claims wherein the compound of formula (I) enables the photographic speed of the element to be increased by at least 0.10 stop without increasing granularity, compared to the same element without the compound.
A colour photographic element as claimed in any one of the preceding claims wherein the compound of formula (I) has one or more electron-withdrawing groups attached to the imidazole ring, a ring fused thereto or as part of substituent X.
A colour photographic element as claimed in any one of the preceding claims wherein when there is an —NH group as part of the imidazole ring X is selected from a cyano or an unsubstituted or substituted alkyl, aryl, alkyl- or aryl-sulfonyl, alkyl- or aryl-carbonyl, alkyl- or aryl-carbonyl, heterocyclyl or a group NRQR1, wherein R is hydrogen or an alkyl group, R1 is a substituent and Q is a carbonyl, sulfonyl or aryl group.
A colour photographic element as claimed in any one of the preceding claims wherein the compound has the formula (II)
A colour photographic element as claimed in any one of the preceding claims wherein the compound of formula (I) is selected from
A colour photographic element as claimed in any one of the preceding claims wherein when the compound is present in a sensitized layer the ratio of compound to silver is at least 0.1 mmol compound per mol silver halide.
A multi-colour photographic element comprising a support bearing yellow, magenta and cyan image-dye-forming units comprising at least one blue-, green- or red-sensitive silver halide emulsion layer having associated therewith at least one yellow, magenta or cyan dye-forming coupler respectively, wherein the element is as claimed in any one of the preceding claims.
Dependencies are inferred from the claim text.