EP0902321A1

EP0902321A1 - Photographic element comprising a mixture of sensitizing dyes

Info

Publication number: EP0902321A1
Application number: EP98203047A
Authority: EP
Inventors: Richard Lee Parton; John Derek Lewis; Thomas Robert Dobles; Karen J. Klingman; David Alan Stegman; Bruce E. Kahn; Teresa A. Smith
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1997-09-15
Filing date: 1998-09-11
Publication date: 1999-03-17
Also published as: JPH11143009A

Abstract

A photographic element comprising at least one silver halide emulsion layer in which the silver halide has been sensitized with a first blue sensitizing dye having a λ₁ less than or equal to about 475 nm and a second blue sensitizing dye having a λ₂, wherein λ₁ is longer than λ₂ and λ₁ and λ₂ are separated by an energy gap, ΔE, which does not exceed 0.12 eV, where ΔE is defined by the following relationship:

wherein λ₁ is the wavelength in nanometers (nm) of maximum absorption of a silver halide emulsion sensitized with the first dye and λ₂ is the wavelength of maximum absorption of a silver halide emulsion sensitized with the second dye, with the proviso that neither the first nor the second dye contains selenium. The silver halide emulsion of said layer is preferably chemically sensitized with a gold(I) compound and preferably with the combination of a gold compound and a disulfide compound.

Description

FIELD OF THE INVENTION

This invention relates to a photographic element, in particular to a photographic element comprising a silver halide emulsion layer containing at least two sensitizing dyes.

BACKGROUND OF THE INVENTION

It is well-known in the practice of spectral sensitization of silver halide emulsions for color photographic use that cyanine dyes used for this purpose typically J-aggregate upon adsorption to the silver halide crystal. (This is not to assert that J-aggregation is typical of cyanine dyes - only that it is a characteristic property of such cyanine dyes as are useful for photographic purposes.) A discussion of J-aggregation can be found in T.H. James, editor, The Theory of the Photographic Process, 4th Edition, Macmillan, New York, 1977. The discovery of two cyanine dyes which will, when applied to the emulsion simultaneously, form a so-called "mixed aggregate" has been a topic of great interest in the study of photographic science. See, for example, Y.Yonezawa, T. Miyama, and H Ishizawa, J. Imaging Sci. Technol., 39 331(1995); V. Bliznyuk and H. Mohwald, Thin Solid Films, 261 275 (1995); T. L. Penner and D. Mobius, Thin Solid Films, 132 185 (1985) and G. Scheibe, A. Mareis, H. Ecker, Naturwiss, 29 474(1937).
The phenomenon has much to offer in the practice of photographic science. For example, the practice of spectral sensitization would no longer be constrained by the position of single dyes; rather, mixtures of dyes could be used to manipulate the location of spectral sensitization with impunity. This would provide great value to photography, as often the light output of the image or scene to be photographed is not in harmony with the light-capturing location of the presently available sensitizing dyes. However, the literature reports only isolated examples of dyes which have been found to form a mixed aggregate, and the physical rules which govern this behavior are only qualitatively known, as is evidenced by the following statement from Bliznyuk and Mohwald: "However, little is known about the molecular properties that determine miscibility or immiscibility. This is unfortunate, because mixed aggregates are very promising for various reasons." The extent of the qualitative understanding is simply that dyes must be sufficiently similar sterically to be compatible in the mixed aggregate, and that their individual aggregates may not be too distant from one another energetically. For example, Yonezawa et al. state that "it is plausible" that "nearly equal" positions of the two individual aggregate positions "favor the formation of the HA aggregate" (HA is defined as "homogeneous aggregate").
Photographic elements typically contain a light sensitive silver halide emulsion layer sensitive to blue light. A sensitizing dye is generally used to provide the desired sensitivity to blue light. Dyes used for this purpose tend to be water insoluble and are added to a silver halide emulsion in a water/alcohol solution. A problem that arises with this procedure is crystallization of the dye. because of this, larger amounts of dye must be used to ensure the desired degree of sensitivity. Also crystallization of the dye poses difficulties in manufacture of photographic elements, e.g., plugging filters used to purify the emulsion prior to coating the emulsion on a support.
In the manufacture of photographic elements, the components used can result in undesirable results. For example, it is known to use certain gold compounds. However certain gold compounds react with gelatin which results in variability from batch to batch. Also, it is known to chemically sensitize silver halide using a gold compound that also contains sulfur. This limits the relative amounts of gold and sulfur to the stoichiometric amounts of the compound. It is desirable to vary the amount of gold versus sulfur to obtain the optimum sensitization for a particular photographic use.

PROBLEM TO BE SOLVED BY THE INVENTION

These vague guidelines discussed above are not useful to photographic scientists and engineers who seek to deliberately design and construct dyes which will form the so-called mixed aggregates, and further to place them at specific locations in the visible spectrum. The vagueness leaves no alternative but the trial-and-error technique exemplified by Edison a century ago, which may never allow the desired goal to be attained.
Photographic elements typically contain a light sensitive silver halide emulsion layer sensitive to blue light. A sensitizing dye is generally used to provide the desired sensitivity to blue light. Dyes used for this purpose tend to be water insoluble and are added to a silver halide emulsion in a water/alcohol solution. A problem that arises with this procedure is crystallization of the dye. because of this, larger amounts of dye must be used to ensure the desired degree of sensitivity. Also crystallization of the dye poses difficulties in manufacture of photographic elements, e.g., plugging filters used to purify the emulsion prior to coating the emulsion on a support.
In the manufacture of photographic elements, the components used can result in undesirable results. For example, it is known to use certain gold compounds. However certain gold compounds react with gelatin which results in variability from batch to batch. Also, it is known to chemically sensitize silver halide using a gold compound that also contains sulfur. This limits the relative amounts of gold and sulfur to the stoichiometric amounts of the compound. It is desirable to vary the amount of gold versus sulfur to obtain the optimum sensitization for a particular photographic use.
This invention also addresses the problems encountered in the manufacture of a photographic element, in particular, the problems of crystallization of the sensitizing dye, reaction of the gold compound with gelatin and optimizing the relative amounts of gold and sulfur used to chemically sensitize the silver halide.

SUMMARY OF THE INVENTION

We have discovered that the selection of appropriate sensitizing agents (both spectral and chemical sensitization) avoids the problems of the prior art.
One aspect of this invention comprises a photographic element comprising at least one silver halide emulsion layer in which:
a) the silver halide has been sensitized with a first blue sensitizing dye having a λ₁ less than or equal to about 475 nm and a second blue sensitizing dye having a λ₂, wherein wherein λ₁ is longer than λ₂ and λ₁ and λ₂ are separated by an energy gap, Δ E, which does not exceed 0.12 eV, where ΔE is defined by the following equation:
wherein λ₁ is the wavelength in nanometers (nm) of maximum absorption of a silver halide emulsion sensitized with the long dye and λ₂ is the wavelength of maximum absorption of a silver halide emulsion sensitized with the short dye,
with the proviso that neither the first nor the second dye contains selenium.
In preferred embodiments of the invention, the silver halide is chemically senstized with a gold(I) compound of formula (I) AuL2+X- or AuL(L1)+X- wherein
L is a mesoionic compound;
X is an anion; and
L¹ is a Lewis donor ligand.
It is also preferred that the silver halide emulsion layer further comprises a disulfide compound of formula (II):
wherein:
X' is independently -O-, -NH- or -NR-, where R is an alkyl group, a fluoroalkyl group, an aryl group or a sulfonyl group;
m and r are independently 0, 1 or 2, with the proviso that m and r are not both 0;
M is -H or a cationic species;
Ar is an aromatic group; and
L² is a linking group, where p is 1.

ADVANTAGEOUS EFFECT OF THE INVENTION

This invention: provides an adjustable sensitization envelope by the appropriate selection of the first and second dyes. Also, we have found much less speed loss when the first dye provides a maximum sensitization of 475 nm or less and the structural features of the dyes result in formation of a mixed aggregate.
In addition, this invention: (1) provides an adjustable sensitization envelope by the appropriate selection of the first and second dyes; (2) provides adjustable gold/sulfur chemical sensitization by use of appropriate amounts of a gold compound of formula (I) and a disulfide compound of formula (II) and (3) provides improved manufacturability.

DETAILED DESCRIPTION OF THE INVENTION

In our invention a silver halide emulsion is spectrally sensitized to blue light using a combination of two blue dyes. Preferred dyes are of the following classes:

wherein Z₁, Z₂ and Z" are independently a hydrogen or halogen atom or a substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aromatic, substituted or unsubstituted alkoxycarbonyl or substituted or unsubstituted heterocyclic group; and R₁ and R₂, are independently substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl or substituted or unsubstituted aryl. In preferred embodiments of the invention, at least one of R₁ and R₂, contains a water solubilizing group, such as sulfoalkyl, carboxyalkyl, sulfoaryl and the like. The dyes may also contain one or more substituents in other positions of the benzo ring.
The approximate peak wavelength for each of the parent chromophores, when optimally substituted to enable aggregation, is shown. In general, we designate the pair of dyes which comprise the mixed aggregate as comprising a "long dye" and a "short dye" (i.e. dyes corresponding to the first and second dyes, respectively). Proceeding from top to bottom of Table A, adjacent pairs of long and short dyes will, when optimally substituted, form mixed aggregates. That is, a dye with a maximum peak wavelength of about 470 nm will form a mixed aggregate with a dye with a maximum peak wavelength of about 450 nm or greater, a dye with a maximum peak wavelength of about 450 nm will form a mixed aggregate with a dye with a peak wavelength of about 440 nm or greater, and so on down to a dye with a maximum peak wavelength of about 420 nm will form a mixed aggregate with a dye with a maximum peak wavelength of about 410 nm or greater. In the blue region of the spectrum the differences in wavelengths between the short and long dyes determined by a ΔE that does not exceed 0.12 eV will range from about 15nm to about 25nm. Dyes need not be of different classes. For example, it has been found that a dye at the high end of the wavelength range for dyes of that class can be advantageously used with a dye at the low end of the wavelength range. For example a dye of class F having a peak wavelength of about 470 nm can be paired with a dye of class F having a peak wavelength of about 465 nm or less (not exceeding 0.12eV.)

The following Table A' provides a correlation between of the peak absorption wavelength of the long dye and the peak absorption wavelength of the the short dye such that the peak absorption wavelength between the two dyes does not exceed 0.12 eV.

Long dye wavelength in nm	Short dye wavelength in nm
400	385.2
401	386.1
402	387.1
403	388.0
404	388.9
405	389.8
406	390.8
407	391.7
408	392.6
409	393.5
410	394.5
411	395.4
412	396.3
413	397.2
414	398.2
415	399.1
416	400.0
417	400.9
418	401.9
419	402.8
420	403.7
421	404.6
422	405.6
423	406.5
424	407.4
425	408.3
426	409.3
427	410.2
428	411.1
429	412.0
430	413.0
431	413.9
432	414.8
433	415.7
434	416.6
435	417.6
436	418.5
437	419.4
438	420.3
439	421.2
440	422.2
441	423.1
442	424.0
443	424.9
444	425.8
445	426.8
446	427.7
447	428.6
448	429.5
449	430.4
450	431.4
451	432.3
452	433.2
453	434.1
454	435.0
455	436.0
456	436.9
457	437.8
458	438.7
459	439.6
460	440.5
461	441.5
462	442.4
463	443.3
464	444.2
465	445.1
466	446.0
467	447.0
468	447.9
469	448.8
470	449.7
471	450.6
472	451.5
473	452.5
474	453.4
475	454.3
476	455.2
477	456.1
478	457.0
479	457.9
480	458.9
481	459.8
482	460.7
483	461.6
484	462.5
485	463.4
486	464.3
487	465.2
488	466.2
489	467.1
490	468.0
491	468.9
492	469.8
493	470.7
494	471.6
495	472.5
496	473.5
497	474.4
498	475.3
499	476.2
500	477.1

As mentioned above, the dyes should be J-aggregating dyes which form a mixed aggregate when used in combination. As is well-known in the art, a very wide variety of substituents may be used to effect J-aggregation on predominantly AgBr emulsions. When the dye is an oxacyanine, thiacyanine, oxacarbocyanine, or thiacarbocyanine, there are abundant literature examples of aggregating cyanine dyes which contain lower alkyl, halo, lower alkoxy, aromatic and heterocyclic substituents.
When reference in this application is made to a particular moiety as a "group", this means that the moiety may itself be unsubstituted or substituted with one or more substituents. For example, "alkyl group" refers to a substituted or unsubstituted alkyl, alkoxy refers to a substituted or unsubstituted alkoxy group, "aromatic substituent" refers to a substituted or unsubstituted aromatic group and "heterocyclic substituent" refers to a substituted or unsubstituted heterocyclic group. Generally, unless otherwise specifically stated, substituent groups usable on molecules herein include any groups, whether substituted or unsubstituted, which do not destroy properties necessary for the photographic utility. Examples of substituents on any of the mentioned groups can include known substituents, such as: halogen, for example, chloro, fluoro, bromo, iodo; alkoxy, particularly those "lower alkyl" (that is, with 1 to 6 carbon atoms, for example, methoxy, ethoxy; substituted or unsubstituted alkyl, particularly lower alkyl (for example, methyl, trifluoromethyl); thioalkyl (for example, methylthio or ethylthio), particularly either of those with 1 to 6 carbon atoms; substituted and unsubstituted aryl, particularly those having from 6 to 20 carbon atoms (for example, phenyl); and substituted or unsubstituted heteroaryl, particularly those having a 5 or 6-membered ring containing 1 to 3 heteroatoms selected from N, O, or S (for example, pyridyl, thienyl, furyl, pyrrolyl); acid or acid salt groups such as any of those described below; and others known in the art. Alkyl substituents may specifically include "lower alkyl" (that is, having 1-6 carbon atoms), for example, methyl, ethyl, and the like. Further, with regard to any alkyl group or alkylene group, it will be understood that these can be branched or unbranched and include ring structures.
In embodiments of the invention in which the emulsion to be used is predominantly AgCI, the invention can be achieved with dyes that: (a) for the two dyes with one allowed 5-position substituent, it must be aromatic in character; and (b) for the dyes with two allowed 5-position substituents, at least one of them must be aromatic in character.

Examples of inventive and comparative dyes are shown in the following Table B. Note that the adjective "comparative" applies for these dyes only in reference to the AgCI emulsion; these dyes fail to aggregate or sustain the invention on this substrate. The predominant feature of this invention is that it applies to pairs of dyes rather than to single dyes.

Illustrative Inventive and Comparative Dyes
Chromophore Class	Inventive (I) or Comparative (C)	5-position substituent	5'-position substituent	Dye Identifier
F	I	chloro	phenyl	F1
	I	chloro	1-pyrrolyl	F2
	I (AgBr) or C (AgCI)	chloro	chloro	F3
	I	phenyl	phenyl	F4
	I	phenylcarbamoyl	phenyl	F5
	I	phenylcarboxamido	phenyl	F6
	I	phenyl	CO₂Me	F7
	I	fluorophenylcarboxamido	chloro	F8
	C (AgCI)	1-pyrrolyl	CF₃	F9
	C (AgCI)	phenyl	CF₃	F10
E	I	phenyl	n.a.	E1
	I	2-thienyl	n.a.	E2
	I	1-pyrrolyl	n.a.	E3
	I	2-furyl	n.a.	E6
	I (AgBr) or C (AgCI)	chloro	n.a.	E4
	I (AgBr) or C (AgCI)	methoxy	n.a.	E5
	I	n.a.	1-pyrrolyl	E'1
	I	n.a.	phenyl	E'2
D	I	chloro	phenyl	D1
C	I	n.a.	n.a.	C1
B	I	n.a.	phenyl	B1
A	I	phenyl	phenyl	A1

This invention describes the use of the combination of at least two blue sensitizing dyes having specifically different structures in combination with a silver halide emulsion so as to adjust the sensitization maximum of the element. This can afford improved color reproduction while maintaining high photographic sensitivity.
Preferred combinations of dyes include, for example:
A. the first dye is of the structure:
and the second dye is of the structure:
B. the first dye is of the structure:
and the second dye is of the structure:
C. the first dye is of the structure:
and the second dye is of the structure:
D. the first dye is of the structure:
and the second dye is of the structure:
E. the first dye is of the structure:
and the second dye is of the structure:
F. the first dye is of the structure:
and the second dye is of the structure:
G. the first dye is of the structure:
and the second dye is of the structure:
H. the first dye is of the structure:
and the second dye is of the structure:
wherein Z₁, Z₂ and Z"are independently a hydrogen or halogen atom or a substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aromatic, substituted or unsubstituted alkoxycarbonyl and substituted or unsubstituted heterocyclic group; and R₁ and R₂, are independently substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl or substituted or unsubstituted aryl.
Particularly preferred blue dyes for use in this invention are of structures I and II defined below.
wherein:
Z₁ is phenyl, pyrrolyl, furanyl, thienyl, alkoxycarbonyl or a fused benzene ring;
Z₂ is phenyl, pyrrolyl, furanyl, thienyl, alkoxycarbonyl or halogen, R₁ and R₂ are acid substituted alkyl groups; and
A⁺ is a counterion,

X is O or S,
Y₁ is pyrrolyl, furanyl, thienyl, alkoxycarbonyl or phenyl;
Y₂ is a 4,5-benzo substituent when X is O and a phenylcarbamoyl or a phenylcarboxamido substituent when X is S;
R₃ and R₄ are acid substituted alkyl groups; and
B⁺ is a counterion.

In the above formulae, A⁺ and B⁺ are counterions required to balance the net charge of the dye. Any positively charged counterion can be utilized. Common counterions that can be used include sodium, potassium, triethylammonium (TEA⁺), tetramethylguanidinium (TMG⁺), diisopropylammonium (DIPA⁺), and tetrabutylammonium (TBA⁺).
These dyes used in accordance with this invention can be synthesized by those skilled in the art according to the procedures described herein or IN F. M. Hamer, The Cyanine Dyes and Related Compounds (Interscience Publishers, New York, 1964).
Illustrative preferred dyes are given in Table C
The photographic element of the invention comprises a blue sensitive emulsion layer which has been chemically sensitized with a gold(I) compound of formula (Ia) or (Ib): AuL₂ ⁺X^- or AuL(L¹)⁺X^- wherein
L is a mesoionic compound;
X is an anion; and
L¹ is a Lewis donor ligand.
The compounds may be soluble in any of a variety of solvents, including water or organic solvents such as acetone or methanol, but the most preferred compounds are water soluble. The term water soluble herein means that the gold(I) compound dissolves in water at the concentration of at least 10^-5 mole per liter of water at a temperature of 20° C at normal pressure.
The mesoionic compound L herein is any such compound that can be coordinated with gold(I) ions to form a gold(I) compound that is water soluble and enables the described chemical sensitization of a photographic silver halide composition. The mesoionic compound is preferably represented by the formula:
wherein the circle with the + sign on the heterocyclic ring symbolizes six delocalized π electrons associated with a partial positive charge on the heterocyclic ring. The a, b, c, d, and e represent the unsubstituted or substituted atoms necessary to complete the mesoionic compound, for example the carbon and nitrogen atoms necessary to complete mesoionic triazolium or tetrazolium 5-member heterocyclic ring. The members of the heterocyclic ring (a, b, c, d, and e) may be CR₅ or NR₅' groups or chalcogen atoms. The minus sign indicates two additional electrons on the exocyclic group f which are conjugated with the six π electrons on the heterocyclic ring. It is understood that there is extensive delocalization and that the charges indicated are only partial charges. The exocyclic group f may be S, Se, or NR₅". The groups R₅, R₅' and R₅" may be hydrogen atoms, substituted or unsubstituted alkyl, aryl, or heterocyclic groups, or R₅, R₅' and R₅" may link together by bonding to form another ring. (Note: Structural representations for mesoionic compounds L which are different from that given above appear elsewhere in the literature, but here the conventions followed are those described by Ollis and Ramsden in Advances in Heterocyclic Chemistry, Vol. 19, Academic Press, London (1976). It is through the exocyclic group f that the mesoionic compound coordinates to gold(I) in the compounds used in the present invention. The exocyclic group f should not be ○ for the present invention since oxygen ligands are not known to form stable compounds with gold(I).

Examples of the gold(I) compounds of the invention are given in the table below. In the structural representations of the gold(I) compounds, the partial charges on the mesoionic ligands are dropped to avoid confusion with the overall charge of the complex ion. The rings symbolizing six delocalized π electrons on the heterocyclic moieties are retained, but will be understood not to imply aromaticity.

wherein R₆, R₇, and R₈ are independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an amino group, a substituted or unsubstituted aryl group, and X^- is a halogen or BF₄ ^- anion. Preferred compounds are listed in the following table:

Compound No.	R₆	R₇	R₈	X^-
1	CH₃	CH₃	CH₃	BF₄ ^-
2	CH₃	CH₃	CH₃	I^-
3	CH₃	CH₃	CH₃	Br^-
4	CH₃	CH₃	CH₃	Cl^-
5	CH₃	CH₂CH=CH₂	CH₃	BF₄ ^-
6	CH₃	CH₂CHOCH₃	CH₃	BF₄ ^-
7	CH₃	NH₂	CH₃	BF₄ ^-
8	CH₃	C₄H₉	CH₃	BF₄ ^-
9	CH₃	C₆H₁₁	CH₃	BF₄ ^-
10	CH₃	C₆H₅	CH₃	BF₄ ^-

Wherein R6, R7 and X^- are as defined above. Preferred compounds are given in the following table:

Compound No.	R₆	R₇	X^-
11	C₆H₅	C₆H₅	BF₄ ^-

wherein R₆, R₇, R₈, and R₉ are independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an amino group, a substituted or unsubstituted aryl group, and X^- is a halogen or BF₄ ^- anion. Preferred compounds are listed in the following table:

Compound No.	R₆	R₇	R₈	R₉	X^-
12	CH₃	CH₃	CH₃	CH₃	Cl-
13	CH₃	CH₃	CH₃	CH₃	BF₄ ^-
14	CH₃	CH₂CH=CH₂	CH₃	CH₃	BF₄ ^-

These gold(I) compounds are advantageous over certain other gold compounds containing sulfur known in the art such as trisodium aurous dithiosulfate because the compounds do not contain any labile S atoms, thus allowing independent choice and amount of S sensitizer, which is not possible with trisodium aurous dithiosulfate. The flexibility in choice and amount of sulfur sensitizer to be used in photographic emulsion is necessary in some cases to achieve proper gradation, reduced sensitivity to red light, and other sensitometric properties. The compounds of the present invention also are advantageous over other soluble gold(I) compounds which do not contain labile S atoms because the compounds have a lower dissociation constant and consequently have better solution stability. Alkyl or aryl thiolates, for example, have a propensity to form polymeric gold(I) compounds with a 1:1 thiolate to gold formula. The compounds of this invention contain discrete gold(I) complexes possessing two ligands. Consequently, the compounds have solubility properties which are convenient for dispersion in the emulsion without requiring that a sulfonic acid or other solubilizing group be attached to the ligand. The compounds of the present invention also are advantageous over prior art gold(I) compounds is very convenient and does not involve potentially explosive material.
The mesoionic compounds L used as starting materials to form the compounds with gold(I) may be made by methods described by Altland, Dedio and McSweeney, U.S. Pat. No. 4,378,424 (1983) or by methods described in the review article by Ollis and Ramsden cited above and references given therein. Synthesis of the gold(I) compounds can be effected by various techniques known to the art. One convenient method comprises reacting a gold(I) precursor compound with an appropriate amount of the mesoionic compound. In the ensuing reaction, which generally takes place with a few minutes at room temperature (about 20° C) or slightly above, the ligands of the gold(I) precursor compound are displaced by the mesoionic compounds, which have a higher affinity for gold(I). The product may then be isolated and purified by crystallization techniques.
The various substituent groups on the mesoionic compound modify the solubility of the final product gold(I) compound. The most desired gold(I) compounds are those which are soluble in water and which may be made in water. Those which are soluble in organic solvents such as acetone can still be used to sensitize aqueous emulsions, and can be used to sensitize emulsions in non-aqueous media. The gold compounds are described in more detail in U.S. Patent No. 5,049,485, the entire disclosure of which is incorporated herein by reference.
Disulfide compound used in the photographic element of this invention is preferably a compound represented by formula (II):
wherein:
X' is independently -O-, -NH- or -NR-, where R is an alkyl group, a fluoroalkyl group, an aryl group or a sulfonyl group;
m and r are independently 0, 1 or 2, with the proviso that m and r are not both 0;
M is -H or a cationic species;
Ar is an aromatic group;
p is 0 or 1; and
L² is a linking group, where p is 1.
Ar is an aromatic group either of a single ring or a condensed ring, preferably having 6 to 10 carbon atoms and more preferably having 6 carbon atoms. Examples of suitable aromatic groups include naphthyl and phenyl. Ar may be further substituted or may be unsubstituted, more preferably Ar is unsubstituted. Examples of suitable substituents include alkyl groups (for example, methyl, ethyl, hexyl), fluoroalkyl groups (for example, trifluoromethyl), alkoxy groups (for example, methoxy, ethoxy, octyloxy), aryl groups (for example, phenyl, naphthyl, tolyl), hydroxyl groups, halogen atoms, aryloxy groups (for example, phenoxyl), alkylthio groups (for example, methylthio, butylthio), arylthio groups (for example, phenylthio), acyl groups (for example, acetyl, propionyl, butyryl, valeryl), sulfonyl groups (for example, methylsulfonyl, phenylsulfonyl), acylamino groups, sulfonylamino groups, acyloxy groups (for example, acetoxy, benzoxy), carboxyl groups, cyano groups, sulfo groups, and amino groups. Preferred are simple alkyl groups and acylamino groups.
X' is independently an -O-, -NH- or -NR-. Most preferably X is -NH-. If X is -NR-, R is a substituent which does not interfere with the intended function of the disulfide compound in the photographic emulsion and which maintains the water soluability of the compound. Examples of suitable substituents include alkyl groups (for example, methyl, ethyl, hexyl), fluoroalkyl groups (for example, trifluoromethyl), aryl groups (for example, phenyl, naphthyl, tolyl), sulfonyl groups (for example, methylsulfonyl, phenylsulfonyl). Preferred are simple alkyl groups and simple fluoroalkyl groups.
r and m are independently 0, 1 or 2. Therefore, included are those compounds in which only one of the aromatic groups is substituted. Preferably m and r are both 1. X' is independently in any position in the aromatic nucleus relative to the sulfur. More preferably, the molecule is symmetrical and preferably X' is either in the para or ortho position.
L² is a linking group. p is 0 or 1. Preferably L² is a unsubstituted alkylene group and is usually -(CH₂)_n- where n ranges from zero to 11 and is preferably 1 to 3. Other examples of L' are given below,
M is either a hydrogen atom or a cationic species if the carboxyl group is in its ionized form. The cationic species may be a metal ion or an organic ion. Examples of organic cations include ammonium ions (for example, ammonium, tetramethylammonium, tetrabutylammonium), phosphonium ions (for example, tetraphenylphosphonium), and guanidyl groups. Preferably M is hydrogen or an alkali metal cation, with a sodium or potassium ion being most preferred.
Examples of the disulfide compounds of this invention are shown below. Compounds I-A through I-H are preferred with Compounds I-D and I-E being most preferred.
The solubilized disulfides of this invention are easily prepared using readily available starting materials. Most of the solubilized disulfides can be obtained by reacting aminophenyl disulfide or hydroxyphenyl disulfide with the appropriate cyclic anhydride followed by conversion of the free diacid to its anionic form using materials such as sodium bicarbonate. Other solubilized disulfides could be obtained by reacting aminophenyl disulfide or hydroxyphenyl disulfide with the mono chloride of a dicarboxylic acid mono ester, followed by hydrolysis of the ester to the carboxylic acid. A discussion of these disulfide compounds can be found in U.S. Patent No. 5,418,127, the entire disclosure of which is incorporated herein by reference.
The emulsion layer of the photographic element of the invention can comprise any one or more of the light sensitive layers of the photographic element. The photographic elements made in accordance with the present invention can be black and white elements, single color elements or multicolor elements. Multicolor elements contain dye image-forming units sensitive to each of the three primary regions of the spectrum. Each unit can be comprised of a single emulsion layer or of multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as known in the art. In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer.
A typical multicolor photographic element comprises a support bearing a cyan dye image-forming unit comprised of at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, and a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler. The element can contain additional layers, such as filter layers, interlayers, overcoat layers, subbing layers, antihalation layers and the like. All of these can be coated on a support which can be transparent or reflective (for example, a paper support).
Photographic elements of the present invention may also usefully include a magnetic recording material as described in Research Disclosure, Item 34390, November 1992, or a transparent magnetic recording layer such as a layer containing magnetic particles on the underside of a transparent support as in US 4,279,945 and US 4,302,523. The element typically will have a total thickness (excluding the support) of from 5 to 30 microns. While the order of the color sensitive layers can be varied, they will normally be red-sensitive, green-sensitive and blue-sensitive, in that order on a transparent support, (that is, blue sensitive furthest from the support) and the reverse order on a reflective support being typical.
The present invention also contemplates the use of photographic elements of the present invention in what are often referred to as single use cameras (or "film with lens" units). These cameras are sold with film preloaded in them and the entire camera is returned to a processor with the exposed film remaining inside the camera. Such cameras may have glass or plastic lenses through which the photographic element is exposed.
In the following discussion of suitable materials for use in elements of this invention, reference will be made to Research Disclosure, September 1996, Number 389, Item 38957, which will be identified hereafter by the term "Research Disclosure I." The Sections hereafter referred to are Sections of the Research Disclosure I unless otherwise indicated. All Research Disclosures referenced are published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire P010 7DQ, ENGLAND. The foregoing references and all other references cited in this application, are incorporated herein by reference.
The silver halide emulsions employed in the photographic elements of the present invention may be negative-working, such as surface-sensitive emulsions or unfogged internal latent image forming emulsions, or positive working emulsions of the internal latent image forming type (that are fogged during processing). Suitable emulsions and their preparation as well as methods of chemical and spectral sensitization are described in Sections I through V. Color materials and development modifiers are described in Sections V through XX. Vehicles which can be used in the photographic elements are described in Section II, and various additives such as brighteners, antifoggants, stabilizers, light absorbing and scattering materials, hardeners, coating aids, plasticizers, lubricants and matting agents are described, for example, in Sections VI through XIII. Manufacturing methods are described in all of the sections, layer arrangements particularly in Section XI, exposure alternatives in Section XVI, and processing methods and agents in Sections XIX and XX.
With negative working silver halide a negative image can be formed. Optionally a positive (or reversal) image can be formed although a negative image is typically first formed.
The photographic elements of the present invention may also use colored couplers (e.g. to adjust levels of interlayer correction) and masking couplers such as those described in EP 213 490; Japanese Published Application 58-172,647; U.S. Patent 2,983,608; German Application DE 2,706,117C; U.K. Patent 1,530,272; Japanese Application A-113935; U.S. Patent 4,070,191 and German Application DE 2,643,965. The masking couplers may be shifted or blocked.
The photographic elements may also contain materials that accelerate or otherwise modify the processing steps of bleaching or fixing to improve the quality of the image. Bleach accelerators described in EP 193 389; EP 301 477; U.S. 4,163,669; U.S. 4,865,956; and U.S. 4,923,784 are particularly useful. Also contemplated is the use of nucleating agents, development accelerators or their precursors (UK Patent 2,097,140; U.K. Patent 2,131,188); development inhibitors and their precursors (U.S. Patent No. 5,460,932; U.S. Patent No. 5,478,711); electron transfer agents (U.S. 4,859,578; U.S. 4,912,025); antifogging and anti color-mixing agents such as derivatives of hydroquinones, aminophenols, amines, gallic acid; catechol; ascorbic acid; hydrazides; sulfonamidophenols; and non color-forming couplers.
The elements may also contain filter dye layers comprising colloidal silver sol or yellow and/or magenta filter dyes and/or antihalation dyes (particularly in an undercoat beneath all light sensitive layers or in the side of the support opposite that on which all light sensitive layers are located) either as oil-in-water dispersions, latex dispersions or as solid particle dispersions. Additionally, they may be used with "smearing" couplers (e.g. as described in U.S. 4,366,237; EP 096 570; U.S. 4,420,556; and U.S. 4,543,323.) Also, the couplers may be blocked or coated in protected form as described, for example, in Japanese Application 61/258,249 or U.S. 5,019,492.
The photographic elements may further contain other image-modifying compounds such as "Development Inhibitor-Releasing" compounds (DIR's). Useful additional DIR's for elements of the present invention, are known in the art and examples are described in U.S. Patent Nos. 3,137,578; 3,148,022; 3,148,062; 3,227,554; 3,384,657; 3,379,529; 3,615,506; 3,617,291; 3,620,746; 3,701,783; 3,733,201; 4,049,455; 4,095,984; 4,126,459; 4,149,886; 4,150,228; 4,211,562; 4,248,962; 4,259,437; 4,362,878; 4,409,323; 4,477,563; 4,782,012; 4,962,018; 4,500,634; 4,579,816; 4,607,004; 4,618,571; 4,678,739; 4,746,600; 4,746,601; 4,791,049; 4,857,447; 4,865,959; 4,880,342; 4,886,736; 4,937,179; 4,946,767; 4,948,716; 4,952,485; 4,956,269; 4,959,299; 4,966,835; 4,985,336 as well as in patent publications GB 1,560,240; GB 2,007,662; GB 2,032,914; GB 2,099,167; DE 2,842,063, DE 2,937,127; DE 3,636,824; DE 3,644,416 as well as the following European Patent Publications: 272,573; 335,319; 336,411; 346,899; 362,870; 365,252; 365,346; 373,382; 376,212; 377,463; 378,236; 384,670; 396,486; 401,612; 401,613.
DIR compounds are also disclosed in "Developer-Inhibitor-Releasing (DIR) Couplers for Color Photography," C.R. Barr, J.R. Thirtle and P.W. Vittum in Photographic Science and Engineering, Vol. 13, p. 174 (1969), incorporated herein by reference.
It is also contemplated that the concepts of the present invention may be employed to obtain reflection color prints as described in Research Disclosure, November 1979, Item 18716, available from Kenneth Mason Publications, Ltd, Dudley Annex, 12a North Street, Emsworth, Hampshire P0101 7DQ, England, incorporated herein by reference. The emulsions and materials to form elements of the present invention, may be coated on pH adjusted support as described in U.S. 4,917,994; with epoxy solvents (EP 0 164 961); with additional stabilizers (as described, for example, in U.S. 4,346,165; U.S. 4,540,653 and U.S. 4,906,559); with ballasted chelating agents such as those in U.S. 4,994,359 to reduce sensitivity to polyvalent cations such as calcium; and with stain reducing compounds such as described in U.S. 5,068,171 and U.S. 5,096,805. Other compounds which may be useful in the elements of the invention are disclosed in Japanese Published Applications 83-09,959; 83-62,586; 90-072,629; 90-072,630; 90-072,632; 90-072,633; 90-072,634; 90-077,822; 90-078,229; 90-078,230; 90-079,336; 90-079,338; 90-079,690; 90-079,691; 90-080,487; 90-080,489; 90-080,490; 90-080,491; 90-080,492; 90-080,494; 90-085,928; 90-086,669; 90-086,670; 90-087,361; 90-087,362; 90-087,363; 90-087,364; 90-088,096; 90-088,097; 90-093,662; 90-093,663; 90-093,664; 90-093,665; 90-093,666; 90-093,668; 90-094,055; 90-094,056; 90-101,937; 90-103,409; 90-151,577.
The silver halide used in the photographic elements may be silver iodobromide, silver bromide, silver chloride, silver chlorobromide, silver chloroiodobromide, and the like.
The type of silver halide grains preferably include polymorphic, cubic, and octahedral. The grain size of the silver halide may have any distribution known to be useful in photographic compositions, and may be either polydipersed or monodispersed.
Tabular grain silver halide emulsions may also be used. Tabular grains are those with two parallel major faces each clearly larger than any remaining grain face and tabular grain emulsions are those in which the tabular grains account for at least 30 percent, more typically at least 50 percent, preferably >70 percent and optimally >90 percent of total grain projected area. The tabular grains can account for substantially all (>97 percent) of total grain projected area. The tabular grain emulsions can be high aspect ratio tabular grain emulsions--i.e., ECD/t >8, where ECD is the diameter of a circle having an area equal to grain projected area and t is tabular grain thickness; intermediate aspect ratio tabular grain emulsions--i.e., ECD/t = 5 to 8; or low aspect ratio tabular grain emulsions--i.e., ECD/t = 2 to 5. The emulsions typically exhibit high tabularity (T), where T (i.e., ECD/t²) > 25 and ECD and t are both measured in micrometers (µm). The tabular grains can be of any thickness compatible with achieving an aim average aspect ratio and/or average tabularity of the tabular grain emulsion. Preferably the tabular grains satisfying projected area requirements are those having thicknesses of <0.3 µm, thin (<0.2 µm) tabular grains being specifically preferred and ultrathin (<0.07 µm) tabular grains being contemplated for maximum tabular grain performance enhancements. When the native blue absorption of iodohalide tabular grains is relied upon for blue speed, thicker tabular grains, typically up to 0.5 µm in thickness, are contemplated.
High iodide tabular grain emulsions are illustrated by House U.S. Patent 4,490,458, Maskasky U.S. Patent 4,459,353 and Yagi et al EPO 0 410 410.
Tabular grains formed of silver halide(s) that form a face centered cubic (rock salt type) crystal lattice structure can have either {100} or {111} major faces. Emulsions containing {111} major face tabular grains, including those with controlled grain dispersities, halide distributions, twin plane spacing, edge structures and grain dislocations as well as adsorbed {111} grain face stabilizers, are illustrated in those references cited in Research Disclosure I, Section I.B.(3) (page 503).
The silver halide grains to be used in the invention may be prepared according to methods known in the art, such as those described in Research Disclosure I and James, The Theory of the Photographic Process. These include methods such as ammoniacal emulsion making, neutral or acidic emulsion making, and others known in the art. These methods generally involve mixing a water soluble silver salt with a water soluble halide salt in the presence of a protective colloid, and controlling the temperature, pAg, pH values, etc, at suitable values during formation of the silver halide by precipitation.
In the course of grain precipitation one or more dopants (grain occlusions other than silver and halide) can be introduced to modify grain properties. For example, any of the various conventional dopants disclosed in Research Disclosure, Item 38957, Section I. Emulsion grains and their preparation, sub-section G. Grain modifying conditions and adjustments, paragraphs (3), (4) and (5), can be present in the emulsions of the invention. In addition it is specifically contemplated to dope the grains with transition metal hexacoordination complexes containing one or more organic ligands, as taught by Olm et al U.S. Patent 5,360,712, the disclosure of which is here incorporated by reference.
It is specifically contemplated to incorporate in the face centered cubic crystal lattice of the grains a dopant capable of increasing imaging speed by forming a shallow electron trap (hereinafter also referred to as a SET) as discussed in Research Discolosure Item 36736 published November 1994, here incorporated by reference.
The SET dopants are effective at any location within the grains. Generally better results are obtained when the SET dopant is incorporated in the exterior 50 percent of the grain, based on silver. An optimum grain region for SET incorporation is that formed by silver ranging from 50 to 85 percent of total silver forming the grains. The SET can be introduced all at once or run into the reaction vessel over a period of time while grain precipitation is continuing. Generally SET forming dopants are contemplated to be incorporated in concentrations of at least 1 X 10^-7 mole per silver mole up to their solubility limit, typically up to about 5 X 10^-4 mole per silver mole.
SET dopants are known to be effective to reduce reciprocity failure. In particular the use of iridium hexacoordination complexes or Ir⁺⁴ complexes as SET dopants is advantageous.
Iridium dopants that are ineffective to provide shallow electron traps (non-SET dopants) can also be incorporated into the grains of the silver halide grain emulsions to reduce reciprocity failure. To be effective for reciprocity improvement the Ir can be present at any location within the grain structure. A preferred location within the grain structure for Ir dopants to produce reciprocity improvement is in the region of the grains formed after the first 60 percent and before the final 1 percent (most preferably before the final 3 percent) of total silver forming the grains has been precipitated. The dopant can be introduced all at once or run into the reaction vessel over a period of time while grain precipitation is continuing. Generally reciprocity improving non-SET Ir dopants are contemplated to be incorporated at their lowest effective concentrations.
The contrast of the photographic element can be further increased by doping the grains with a hexacoordination complex containing a nitrosyl or thionitrosyl ligand (NZ dopants) as disclosed in McDugle et al U.S. Patent 4,933,272, the disclosure of which is here incorporated by reference.
The contrast increasing dopants can be incorporated in the grain structure at any convenient location. However, if the NZ dopant is present at the surface of the grain, it can reduce the sensitivity of the grains. It is therefore preferred that the NZ dopants be located in the grain so that they are separated from the grain surface by at least 1 percent (most preferably at least 3 percent) of the total silver precipitated in forming the silver iodochloride grains. Preferred contrast enhancing concentrations of the NZ dopants range from 1 X 10^-11 to 4 X 10^-8 mole per silver mole, with specifically preferred concentrations being in the range from 10^-10 to 10^-8 mole per silver mole.
Although generally preferred concentration ranges for the various SET, non-SET Ir and NZ dopants have been set out above, it is recognized that specific optimum concentration ranges within these general ranges can be identified for specific applications by routine testing. It is specifically contemplated to employ the SET, non-SET Ir and NZ dopants singly or in combination. For example, grains containing a combination of an SET dopant and a non-SET Ir dopant are specifically contemplated. Similarly SET and NZ dopants can be employed in combination. Also NZ and Ir dopants that are not SET dopants can be employed in combination. Finally, the combination of a non-SET Ir dopant with a SET dopant and an NZ dopant. For this latter three-way combination of dopants it is generally most convenient in terms of precipitation to incorporate the NZ dopant first, followed by the SET dopant, with the non-SET Ir dopant incorporated last.
The photographic elements of the present invention, as is typical, provide the silver halide in the form of an emulsion. Photographic emulsions generally include a vehicle for coating the emulsion as a layer of a photographic element. Useful vehicles include both naturally occurring substances such as proteins, protein derivatives, cellulose derivatives (e.g., cellulose esters), gelatin (e.g., alkali-treated gelatin such as cattle bone or hide gelatin, or acid treated gelatin such as pigskin gelatin), deionized gelatin, gelatin derivatives (e.g., acetylated gelatin, phthalated gelatin, and the like), and others as described in Research Disclosure I. Also useful as vehicles or vehicle extenders are hydrophilic water-permeable colloids. These include synthetic polymeric peptizers, carriers, and/or binders such as poly(vinyl alcohol), poly(vinyl lactams), acrylamide polymers, polyvinyl acetals, polymers of alkyl and sulfoalkyl acrylates and methacrylates, hydrolyzed polyvinyl acetates, polyamides, polyvinyl pyridine, methacrylamide copolymers, and the like, as described in Research Disclosure I. The vehicle can be present in the emulsion in any amount useful in photographic emulsions. The emulsion can also include any of the addenda known to be useful in photographic emulsions.
The silver halide to be used in the invention may be advantageously subjected to chemical sensitization. Compounds and techniques useful for chemical sensitization of silver halide are known in the art and described in Research Disclosure I and the references cited therein. Compounds useful as chemical sensitizers, include, for example, active gelatin, sulfur, selenium, tellurium, gold, platinum, palladium, iridium, osmium, rhenium, phosphorous, or combinations thereof. Chemical sensitization is generally carried out at pAg levels of from 5 to 10, pH levels of from 2 to 8, and temperatures of from 30 to 80°C, as described in Research Disclosure I, Section IV (pages 510-511) and the references cited therein.
The silver halide may be sensitized by sensitizing dyes by any method known in the art, such as described in Research Disclosure I. The dye may be added to an emulsion of the silver halide grains and a hydrophilic colloid at any time prior to (e.g., during or after chemical sensitization) or simultaneous with the coating of the emulsion on a photographic element. The dyes may, for example, be added as a solution in water or an alcohol. The dye/silver halide emulsion may be mixed with a dispersion of color image-forming coupler immediately before coating or in advance of coating (for example, 2 hours).
Photographic elements of the present invention are preferably imagewise exposed using any of the known techniques, including those described in Research Disclosure I, section XVI. This typically involves exposure to light in the visible region of the spectrum, and typically such exposure is of a live image through a lens, although exposure can also be exposure to a stored image (such as a computer stored image) by means of light emitting devices (such as light emitting diodes, CRT and the like).
Photographic elements comprising the composition of the invention can be processed in any of a number of well-known photographic processes utilizing any of a number of well-known processing compositions, described, for example, in Research Disclosure I, or in T.H. James, editor, The Theory of the Photographic Process, 4th Edition, Macmillan, New York, 1977. In the case of processing a negative working element, the element is treated with a color developer (that is one which will form the colored image dyes with the color couplers), and then with a oxidizer and a solvent to remove silver and silver halide. In the case of processing a reversal color element, the element is first treated with a black and white developer (that is, a developer which does not form colored dyes with the coupler compounds) followed by a treatment to fog silver halide (usually chemical fogging or light fogging), followed by treatment with a color developer. Preferred color developing agents are p-phenylenediamines. Especially preferred are:
4-amino N,N-diethylaniline hydrochloride,
4-amino-3-methyl-N,N-diethylaniline hydrochloride,
4-amino-3-methyl-N-ethyl-N-(β-(methanesulfonamido) ethylaniline sesquisulfate hydrate,
4-amino-3-methyl-N-ethyl-N-(β-hydroxyethyl)aniline sulfate,
4-amino-3-β-(methanesulfonamido)ethyl-N,N-diethylaniline hydrochloride and
4-amino-N-ethyl-N-(2-methoxyethyl)-m-toluidine di-p-toluene sulfonic acid.
Dye images can be formed or amplified by processes which employ in combination with a dye-image-generating reducing agent an inert transition metal-ion complex oxidizing agent, as illustrated by Bissonette U.S. Patents 3,748,138, 3,826,652, 3,862,842 and 3,989,526 and Travis U.S. Patent 3,765,891, and/or a peroxide oxidizing agent as illustrated by Matejec U.S. Patent 3,674,490, Research Disclosure, Vol. 116, December, 1973, Item 11660, and Bissonette Research Disclosure, Vol. 148, August, 1976, Items 14836, 14846 and 14847. The photographic elements can be particularly adapted to form dye images by such processes as illustrated by Dunn et al U.S. Patent 3,822,129, Bissonette U.S. Patents 3,834,907 and 3,902,905, Bissonette et al U.S. Patent 3,847,619, Mowrey U.S. Patent 3,904,413, Hirai et al U.S. Patent 4,880,725, Iwano U.S. Patent 4,954,425, Marsden et al U.S. Patent 4,983,504, Evans et al U.S. Patent 5,246,822, Twist U.S. Patent No. 5,324,624, Fyson EPO 0 487 616, Tannahill et al WO 90/13059, Marsden et al WO 90/13061, Grimsey et al WO 91/16666, Fyson WO 91/17479, Marsden et al WO 92/01972. Tannahill WO 92/05471, Henson WO 92/07299, Twist WO 93/01524 and WO 93/11460 and Wingender et al German OLS 4,211,460.
Development is followed by bleach-fixing, to remove silver or silver halide, washing and drying.
The folloing examples illustrate the use of the dye combinations of the invention.

Example 1

This example demonstrates the use of dye combinations of this invention with a cubic AgCI emulsion.
In this experiment, a pure AgCI emulsion of predominantly cubic morphology was used. The median grain size was 0.39 micron cubic edge length (CEL). The emulsion was chemically sensitized (finished) by melting the emulsion at 40 degrees C, then adding colloidal aurous sulfide at 0.0177 g per mole of AgCI, and heating the emulsion to 65 degrees C for 55 minutes prior to chilling the emulsion.
The sensitizing dyes were added by re-melting the emulsion at 40 degrees C, and adding the dyes from methanolic solutions at a concentration of 0.000471 moles per liter to produce a dye-to-silver ratio of 3.8 x 10^-4 moles of dye per silver mole. The emulsion was held with stirring for 20 minutes, then chilled with stirring.
The two dyes comprising a particular combination were tested by adding each of them individually to the emulsion, and also by adding them to the emulsion simultaneously from pre-mixed co-solutions in the percentages 75% Dye 1, 25% Dye 2; 50% Dye 1,50% Dye 2; 25% Dye 1,75% Dye 2.
The dyed emulsions were coated onto an ESTAR™ support using a coating machine equipped with an extrusion device to deliver the melted emulsion onto the support.
The melt as coated consisted of emulsion, gelatin, water, dye solutions as described above, the surfactant saponin (which is a naturally occurring glycoside), and the hardener 1,1'-(oxybis-(methylenesulfonyl)bis-)ethene (BVSME).
The total "wet" laydown was 157.2 g/m² (14.6 mg/ft²⁾. After chilling and drying, the resulting single-layer coatings contained 3229 mg/m² of silver, 7319 mg/m² of gelatin, 122.6 mg/m² of BVSME, and 144.8 mg/m² of saponin.
A spectrum was obtained of the coated material using a scanning spectrophotometer equipped with an integrating sphere. The coated materials were exposed with a sensitometer equipped with a tungsten light source which is filtered with a collection of Wratten filters designed to approximate exposure through a color film negative. A step tablet was used to provide a D logE curve from which photographic speed at 0.8 density units above Dmin was determined, as is familiar to those skilled in the art.
The exposed strips were developed in the following process at 20 degrees C.
1. KODAK DK-50™ developer for 6 minutes, 0 seconds.
2. KODAK INDICATOR STOP™ stop bath for 15 seconds.
3. KODAK F5™ fix for 5 minutes 0 seconds.
4. Distilled water wash for 10 minutes 0 seconds.

The data from this experiment for a variety of inventive and comparative dye pairs is shown in Table I.

Data Obtained for Pairs of Dyes on AgCI Cubic Emulsion. I=inventive. C=comparative.
Type	Long Dye	Short Dye	ΔE (eV)	Ratio (% long dye	Aggregate Wavelength (nm)	Aggregate Peak Height (%A)	Speed**
C	F1	D1	0.15	100	465	60.5	144
				75	462	56.1	139
				50	459	53.0	135
				25	440	48.3	124
				0	440	58.0	101
C	D1	C1	-	100	439.2	55.2	n.a.***
				75	438.7	51.4	n.a.
				50	438.5	43.0	n.a.
				25	437.7	29.5	n.a.
				O	no peak;	does not	aggregate
C	C1	B1	-	100	no peak;	does not	aggregate
				75	no peak;	does not	aggregate
				50	424.1	36.4	n.a.
				25	423.1	45.3	n.a.
				0	421.0	49.0	n.a.
I	B1	A1	0.09	100	421.0	49.0	n.a.
				75	418.0	47.9	n.a.
				50	412.0	48.1	n.a.
				25	409.3	51.4	n.a.
				0	408.3	53.8	n.a.
I	F2	E1	0.11	100	470	60.9	145
				75	467	58.0	143
				50	462	55.8	138
				25	455	56.4	131
				0	451	59.5	116
I	F2	E2	0.08	100	470.4	56.3	150
				75	467.8	55.1	147
				50	464.7	51.1	133
				25	460.9	55.9	136
				0	456.9	56.4	122
I	F2	E6	0.07	100	470.4	56.3	150
				75	467.9	56.0	139
				50	464.9	54.9	129
				25	461.2	52.8	113
				0	457.9	54.4	97
I	F2	E3	0.09	100	470.0	52.3	137
				75	465.5	52.3	136
				50	461.1	52.5	132
				25	457.1	55.4	126
				0	454.3	59.7	118
I	F1	E1	0.08	100	464.7	60.3	136
				75	462.4	59.5	133
				50	459.2	56.8	128
				25	454.8	56.4	121
				0	451.2	60.3	109
I	F1	E4	0.09	100	465.1	55.2	143
				75	463.7	53.3	139
				50	461.6	48.3	129
				25	457.7	41.6	118
				0	450.2	32.7	88
I	F3	E1	0.09	100	465.8	50.1	106
				75	460.5	54.3	116
				50	457.2	57.5	117
				25	454.1	58.7	114
				0	450.9	58.6	108
I	F4	E1	0.08	100	464.1	54.2	138
				75	461.9	54.5	136
				50	458.0	53.6	130
				25	453.4	54.4	123
				0	450.9	58.6	108

This emulsion is predominantly AgCI, so that the structural requirement for the practice of the invention is much more stringent than when the substrate is predominantly AgBr. In particular, (a) where dyes may bear two 5 position substituents, at least one of them must be aromatic, and (b) the symmetrical dinapthoxazole chromophore is excluded from the invention because it does not aggregate on the AgCI emulsion.
It is readily apparent that the above data indicates that the inventive pairs of dyes maintain the height of the combined aggregate peak, that they result in a steady progression of peak wavelength between the long and the short dye, and that they preserve photographic speed, and that all three of these features are accomplished to a much greater extent than for the comparative pairs of dyes.

Example 2

In this example a predominantly AgBr three-dimensional emulsion of cubic morphology was used.
The nominal halide composition was AgBr _97.4% I _2.6%. The median grain size was 0.20 µm equivalent spherical diameter (esd). The emulsion was chemically sensitized by melting the emulsion and applying the chemical sensitizers NaSCN at a level of 44 mg per mole of silver, Na₂S₂O₃.5H2O at a level of 33 mg per mole of silver, and KAuCl₄ at a level of 6.6 mg per silver mole.
The sensitizing dyes were added by re-melting the emulsion at 40 degrees C, and adding the dyes from methanolic solutions at a concentration of 0.00035 moles per liter to produce a dye-to-silver ratio of 8 x 10^-4 moles of dye per silver mole. The emulsion was held with stirring for 20 minutes, then chilled with stirring.
The two dyes comprising a particular combination were tested by adding each of them individually to the emulsion, and also by adding them to the emulsion simultaneously from pre-mixed co-solutions in the percentages 75% Dye 1, 25% Dye 2; 50% Dye 1,50% Dye 2; 25% Dye 1,75% Dye 2.
The cubic emulsion melts were coated on a machine equipped with an extrusion device to deliver the melted emulsion as a single layer to ESTAR™ support. The melts were coated at 10.8 mg/dm² silver and 77 mg/dm² gelatin, and hardened with 0.08% bis(vinylsulfonyl)methylether (BVSME).
A spectrum was obtained of the coated material using a scanning spectrophotometer equipped with an integrating sphere. The coated materials were exposed with a single-grating transmission sensitometer which produces a separate D log E curve at 10 nm intervals across the visible spectrum. The result is a "wedge spectrograph", which is well-known in the art. (See, for example, "Use of Spectral Sensitizing Dyes To Estimate Effective Energy Levels of Silver Halide Substrates", by P. B. Gilman, Jr., in Photographic Science and Engineering, Volume 18, Number 5, September/October 1974.) The exposed coatings were processed at 35 degrees C in an Eastman KODAK RP X-OMAT™ machine.

The data from this experiment for a variety of inventive and comparative dye pairs is shown in Table II.

Data Obtained for Pairs of Dyes on AgBr Cubic Emulsion. I=inventive. C=comparative.
Type	Long Dye	Short Dye	ΔE (eV)	Ratio (% long dye	Aggregate Wavelength (nm)	Aggregate Peak Height (%A)	Speed**
I	F1	E1	0.08	100	464.3	57.1	248
				75	461.6	55.2	245
				50	457.7	53.4	241
				25	453.7	54.9	245
				0	451.1	56.8	247
I	F3	E1	0.09	100	465.6	57.3	247
				75	461.6	54.8	237
				50	457.4	55.4	240
				25	454.1	56.1	n.a.
				0	451.1	56.8	244
I	D1	C1	0.05	100	441.0	62.0	224
				75	439.7	59.7	222
				50	436.9	57.9	221
				25	435.1	59.4	222
				0	433.6	54.2	218
I	C1	B1	0.06	100	433.7	54.0	218
				75	432.9	59.4	220
				50	430.2	60.1	222
				25	427.5	62.9	225
				0	425.0	65.6	229
I	B1	A1	0.08	100	425.1	65.9	229
				75	423.6	64.5	227
				50	419.1	63.1	222
				25	414.1	65.7	226
				0	413.4	68.8	239
C	F1	C1	0.21	100	467.4	59.2	250
				75	465.0	54.1	240
				50	462 & 433	45 & 48	227 & 215
				25	460 & 434	35 & 53.6	208 & 217
				0	433.6	54.2	218
C	F1	A1	0.35	100	467.4	59.3	250
				75	464.6	52.5	244
				50	460.8	44.7	233
				25	455 & 411	34 &62	220 & 226
				0	413.5	68.9	238

It is readily apparent that the above data indicates that the inventive pairs of dyes maintain the height of the combined aggregate peak, that they result in a steady progression of peak wavelength between the long and the short dye, and that they preserve photographic speed, and that all three of these features are accomplished to a much greater extent than for the comparative pairs of dyes.

Example 3

In this example a predominantly AgBr three-dimensional emulsion of octahedral morphology was used.
The nominal halide composition was AgBr _97.0% I _3.0% . The median grain size was 0.30 µm equivalent spherical diameter (esd). The emulsion was chemically sensitized by melting the emulsion and applying the chemical sensitizers NaSCN at a level of 150 mg per mole of silver, Na₂S₂O₃.5H₂O at a level of 8 mg per mole of silver, and KAuCl₄ at a level of 5 mg per silver mole.
The cubic emulsion melts were coated on a machine equipped with an extrusion device to deliver the melted emulsion as a single layer to ESTAR™ support. The melts were coated at 21.5 mg/dm² silver and 86 mg/dm² gelatin, and hardened with 0.08% bis(vinylsulfonyl)methylether (BVSME).
The sensitizing dyes were added by re-melting the emulsion at 40 degrees C, and adding the dyes from methanolic solutions at a concentration of 0.00032 moles per liter to produce a dye-to-silver ratio of 4.0 x 10^-4 moles of dye per silver mole. The emulsion was held with stirring for 20 minutes, then chilled with stirring.
The two dyes comprising a particular combination were tested by adding each of them individually to the emulsion, and also by adding them to the emulsion simultaneously from pre-mixed co-solutions in the percentages 75% Dye 1, 25% Dye 2; 50% Dye 1,50% Dye 2; 25% Dye 1,75% Dye 2.
A spectrum was obtained of the coated material using a scanning spectrophotometer equipped with an integrating sphere. The coated materials were exposed with a single-grating transmission sensitometer which produces a separate D log E curve at 10nm intervals across the visible spectrum. The result is a "wedge spectrograph", which is well-known in the art. (See, for example, "Use of Spectral Sensitizing Dyes To Estimate Effective Energy Levels of Silver Halide Substrates", by P. B. Gilman, Jr., in Photographic Science and Engineering, Volume 18, Number 5, September/October 1974.) The exposed coatings were processed at 35 degrees C in an Eastman KODAK RP X-OMAT™ machine.

The data from this experiment for a variety of inventive and comparative dye pairs is shown in Table III.

Data Obtained for Pairs of Dyes on AgBr Octahedral Emulsion. I=inventive. C=comparative.
Type	Long Dye	Short Dye	ΔE (eV)	Ratio (% long dye	Aggregate Wavelength (nm)	Aggregate Peak Height (%A)	Speed**
I	F1	E1	0.06	100	460.6	61.6	257
				75	458.2	60.6	253
				50	455.2	60.1	252
				25	452.3	60.9	253
				0	450.1	62.7	255
I	F3	E1	0.10	100	466.6	60.9	255
				75	458.5	60.2	253
				50	454.6	61.7	254
				25	452.1	62.0	255
				0	450.1	62.7	255
I	F1	E5	0.05	100	460.8	61.0	257
				75	458.9	59.7	255
				50	456.4	58.6	253
				25	454.0	59.9	256
				0	452.8	58.2	262
C	F1	D2	0.15	100	460.8	61.0	257
				75	457.6	58.2	255
				50	451 & 435	56 & 60	250
				25	435.2	60.2	244
				0	436.0	64.3	245

Example 4

In this example the emulsion used was a predominantly silver chloride, ruthenium doped, (1.0.0) tabular grain emulsion. The average grain diameter was 0.60 microns equivalent circular diameter (ecd). The average grain thickness was 0.17 microns. The precise halide ratio was 99.404% chloride and 0.596 % iodide. The emulsion was doped with 125 ppm ruthenium hexacyanide.
The emulsion was heated to 39°C and 50 mg/Ag mole of potassium bromide, 1.7 mg/Ag mole of potassium tetrachloroaurate, sensitizing dyes F2 and E1 (ΔE = 0.09 eV) in ratios shown in Table IV, and 3.4 mg/Ag mole of sodium thiosulfate was added. The emulsion was heated to 60°C, held for 25 min. and then cooled to 39°C. Then 100 mg/Ag mole of 1-(3-acetamidophenyl)-5-mercaptotetrazole was added. The emulsion was then coated on triacetate film with the yellow coupler of formula Y-C. The film was then dried.

The film was exposed to white light at 3000K for a time of 0.004 sec. It was then processed in the ECP-2™ process for 3 min. at 98°F. The spectral absorption of the coated film samples was measured on a spectrophotometer. Results were obtained for the different ratiosof sensitizing dyes. These results are given in Table IV.

Sample Number	F2 quantity (%)	E1 quantity (%)	Minimum density	Speed**	Aggregate Wavelength (nm)	Aggregate Peak Height (%A)
5-1	100	0	0.15	168	471	30.8
5-2	83.5	16.5	0.12	190	469	29.0
5-3	67.0	33.0	0.11	172	468	26.1
5-4	58.7	41.3	0.10	167	466	25.8
5-5	50.3	49.7	0.08	164	462	24.8
5-6	42.0	58.0	0.10	166	461	22.3
5-7	33.7	66.3	0.10	169	459	25.1
5-8	16.8	83.2	0.09	160	458	27.3
5-9	0	100	0.08	156	456	30.6

The dye quantities given are the percent ratios of the millimoles of dye per silver mole. As can be seen, the dye peak transitions smoothly from 471 nm to 456 nm as the ratio of dye changes.

Example 5

Dye combinations (Table V) were made from two dyes (Table B) which were blended in the following ratios 75/25, 50/50 and 25/75. Dyes and dye combination at a level of 3.8 x 10^-4 moles/Ag mole, were added to an aurous sulfide sensitized 0.39 µm(cubic edge length) silver chloride cubic emulsions which had 1.0% bromide present. The emulsions were coated on a polyester support in a Black and White format. The coatings were given a 1/10 second exposure on a wedge spectrographic instrument covering a wavelength range from 350 to 750 nm. The instrument contains a tungsten light source and a step tablet ranging in density from 0 to 3 density steps. Correction for the instrument's variation in spectral irradiance with wavelength is done via computer. Results are reported in Table V. Delta is the speed of a coating at a Dye 1/Dye 2 ratio of 25/75 minus the speed at a Dye 1/Dye 2 ratio of 75/25 . The λmax at each dye ratio was determined from spectrophotometric measurements of the coatings.

Processing

Temperature 68°F (20°C)

Chemical	Process time
DK-50 developer	6 minutes 0 seconds
Stop bath	15 seconds
Fix	5 minutes 0 seconds
Wash	10 minutes 0 seconds

As can be seen from Table V, the invention dye combinations allow the sensitization maximum to be adjusted by varying the ratio of the two dyes. The invention dye combinations give less speed loss than the comparison dye combination.

Example 6

Invention

The emulsion (invention) is precipitated by bringing together NaCI and AgNO₃, in the presence of gelatin, antifoamant, dithio-3,6-octane-1,8-diol, and glutaryldiaminophenyldisulfide to form grains of cubic edge length 0.5 µm - 0.8 µm, with an aspect ratio of 1.2 or less. After desalting, the emulsion is then chemically and spectrally sensitized by the addition of orthosuccinamidophenyldisulfide, gold(I) bis(1,4,5-trimethyl- 1,2,4-triazolium-3-thiolate)gold(I) fluoroborate, Dye F2, Dye E1 and sodium thiosulfate followed by a heat cycle.
After the heat cycle, these three chemicals are added in any sequence: 1-(3-acetamidophenyl)-5-mercaptotetrazole at about 70 mg/Ag mol, and potassium bromide 0.005 mol bromide/mol Ag.

Check

The emulsion (check) is precipitated by bringing together NaCI and AgNO3, in the presence of gelatin antifoamant, dithio-3,6-octane-1,8-diol, nitric acid,and Hg to form gains of cubic edge length 0.0 µm - 0.8 µm. The smulsion is then finished by addition of iridium (K₂IrCl₆), sulfur gold(I)/sulfur compound (AuO₆S4.2H₂O 3Na, 1-(3-acetamidophenyl)-5-mercaptotetrazole, and thiourea, followed by a heat cycle, followed by addition of comparative dye COMP-1, 1-(3-acetamidophenyl)-5-mercaptotetrazole, KBr, and gelatin.
In the check emulsion, some of the dye COMP-1 crystallizes making it necessary to filter the emulsion before storage and/or use. Further excess dye is needed to compensate for the dye that crystallizes out of the emulsion.
In the inventive emulsion, the dye combination of dye F2 and dye E1 does not crystallize in solution, in the sensitized emulsion. Spectroscopic analysis of the emulsions have shown there to be no free dye. Therefore, no filtering is required of the emulsion prior to storage. Dyes F2 and E1 are fully incorporated into the emulsion.
To illustrate that the new emulsion provides the same sensitometric performance as the check emulsion, the new emulsion was evaluated in the multilayer format shown in Table V.

SC-1 = 1,4-isododecyl hydroquinone

Film samples were given white light exposures and processed in Kodak's ECP-2B process, which is well-known in the trade and is documented in Kodak's H-24 manual. The results are given in Table VI(a).

Emulsion performance characteristics
CHARACTERISTIC	CHECK EMULSION	INVENTION EMULSION
Wasted dye due to crystals	30%	none
Organic solvents	yes	none
speed	100	100
contrast	1.0	1.0
short-term LIK	<0.01 logE speed change per 1.0 log10(minutes)	<0.01 logE speed change per 1.0 log10(minutes)
raw stock keeping	no change 3months/13°C	no change 3months/13°C
lambda-max	461nm	466nm
High intensity reciprocity failure	no change 1/2000" - 1/100"	no change 1/2000" - 1/100"
sulfur:gold molar ratio	2:1 minimum	unrestricted

The invention has been described in detail with particular reference to preferred embodiments, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims

A photographic element comprising at least one silver halide emulsion layer in which the silver halide has been sensitized with a first blue sensitizing dye having a λ₁ less than or equal to about 475 nm and a second blue sensitizing dye having a λ₂, wherein λ₁ is longer than λ₂ and λ₁ and λ₂ are separated by an energy gap, ΔE, which does not exceed 0.12 eV, where ΔE is defined by the following relationship:
wherein λ₁ is the wavelength in nanometers (nm) of maximum absorption of a silver halide emulsion sensitized with the first dye and λ₂ is the wavelength of maximum absorption of a silver halide emulsion sensitized with the second dye, with the proviso that neither the first nor the second dye contains selenium.
A photographic element according to claim 1, wherein the dyes are selected from the group consisting of:

and
wherein Z₁, Z₂ and Z" are independently a hydrogen or halogen atom or a substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aromatic and substituted or unsubstituted heterocyclic group; and R₁ and R₂, are independently substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl or substituted or unsubstituted aryl.
A photographic element according to claim 2, wherein the first dye and second dye are selected from the following pairs of dyes:

A. the first dye is of the structure:
and the second dye is of the structure:

B. the first dye is of the structure:
and the second dye is of the structure:

C. the first dye is of the structure:
and the second dye is of the structure:

D. the first dye is of the structure:
and the second dye is of the structure:

E. the first dye is of the structure:
and the second dye is of the structure:

F. the first dye is of the structure:
and the second dye is of the structure:

G. the first dye is of the structure:
and the second dye is of the structure:

H. the first dye is of the structure:
and the second dye is of the structure:
wherein Z₁, Z₂ and Z"are independently a hydrogen or halogen atom or a substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aromatic, substituted or unsubstituted alkoxycarbonyl and substituted or unsubstituted heterocyclic group; and R₁ and R₂, are independently substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl or substituted or unsubstituted aryl.
A photographic element according to any one of claims 1, 2, 3 or 4 , wherein at least one of the dyes of structure I:
wherein:

Z₁ is phenyl, pyrrolyl, furanyl, thienyl, alkoxycarbonyl or a fused benzene ring;

Z₂ is phenyl, pyrrolyl, furanyl, thienyl, alkoxycarbonyl or halogen, R₁ and R₂ are acid substituted alkyl groups; and

A⁺ is a counterion,
A photographic element according to claim 1, wherein at least one of the dyes is of structure II:
wherein

X is O or S,

Y₁ is pyrrolyl, furanyl, thienyl, alkoxycarbonyl or phenyl;

Y₂ is a 4,5-benzo substituent when X is O and a phenylcarbamoyl or a phenylcarboxamido substituent when X is S;

R₃ and R₄ are acid substituted alkyl groups; and

B⁺ is a counterion.
A photographic element according to any preceding claim, wherein the silver halide has been chemically sensitized with a gold(I) compound of formula (Ia) or (Ib): AuL₂ ⁺X^- or AuL(L¹)⁺X^- wherein

L is a mesoionic compound;

X is an anion; and

L¹ is a Lewis donor ligand;
A photographic element according to claim 6, wherein L is a mesoionic compound represented by the formula:
wherein a, b, c, d, and e represent the unsubstituted or substituted atoms necessary to complete a heterocyclic ring, preferable a triazolium or tetrazolium 5-membered ring; the circle with the + sign on the heterocyclic ring symbolizes six delocalized π electrons associated with a partial positive charge on the heterocyclic ring.
A photographic element according to claim 6, wherein the gold (I) compound is of the formula:
wherein R₆, R7, and R₈ are independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an amino group, a substituted or unsubstituted aryl group, and X^- is a halogen or BF₄ ^- anion;
or of the formula
wherein R₆ and R₇ are independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an amino group, a substituted or unsubstituted aryl group, and X^- is a halogen or BF₄ ^- anion;
or of the formula:
wherein R₆, R₇, R₈, and R₉ are independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, an amino group, a substituted or unsubstituted aryl group, and X^- is a halogen or BF₄ ^- anion.
A photographic element according to any preceding claim, which further comprises a disulfide compound of formula (II):
wherein:

X' is independently -O-, -NH- or -NR-, where R is an alkyl group, a fluoroalkyl group, an aryl group or a sulfonyl group;

m and r are independently 0, 1 or 2, with the proviso that m and r are not both 0;

M is -H or a cationic species;

Ar is an aromatic group; and

L² is a linking group, where p is 1.
A photographic element according to claim 9, wherein the disulfide compound is represented by formula (II):
wherein:

X' is independently -O-, -NH- or -NR-, where R is an alkyl group, a fluoroalkyl group, an aryl group or a sulfonyl group;

m and r are independently 0, 1 or 2, with the proviso that m and r are not both 0;

M is -H or a cationic species;

Ar is an aromatic group;

p is 0 or 1; and

L² is a linking group, where p is 1.