CA1043615A - Low concentration sensitization and development acceleration - Google Patents

Abstract

LOW CONCENTRATION SENSITIZATION
AND DEVELOPMENT ACCELERATION

Abstract of the Disclosure A photographic element is disclosed comprised of a support having coated thereon a silver halide emulsion layer. In the emulsion layer or in a second layer adjacent to it, a development accelerating amount of a ruthenium cationic complex is included. The ruthenium complex includes a predominance of ammine and/or amine ligands.

Description

-3~5 This invention relates to photogr~phic materials, their preparation and use. In one aspect, this invention relates to photographic elements containing a ruthenium cationic complex having a predominance of ammine or amine ligands. In another aspect, this invention relates to photographic elements containing such complexes and further containing an azaindene.
In one aspect, this invention is comprised of a photographic element having coated thereon at least one layer comprising a photographic silver halide emulsion. In the emulsion layer, or in a second layer adjacent thereto, i9 incorporated a development accelerating amount of a ruthenium cationic complex having a predominance of coordination bonds formed by ligands chosen from the class con~isting of ammine and amine ligands. In one preferred form of this invention, the cationic ruthenium complex is present in a concentration of less than 100 mg per mole of silver. In another aspect, the pre`sent invention comprises the above-described photographic element further including in or adjacent the emulsion layer at least one azaindene.
Cadmium salts have long been employed in the photographic field for a variety of purposes. For example, it is stated in Glafkides, "Photographic Chemistry", Volume 1, 1958, page 151, that cadmium chloride can be used to increase the contrast in the silver halide emulsion.
U.S. Patent 3,488,709 issued January 6, 1970, to Sidebotham teaches that cadmium bromide stabilizes silver halide emul-sions precipitated in the presence of rhodium salts in that it reduces the loss of contrast and speed change upon storage and also that cadmium bromide acts to increase the contrast in a synergistic manner.
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Althou~h the concentrations of cadmium br~mide taught by ~iaebotham are reIatively small, i~e., 2Q to a~out 60 grams per mole of silver halide, the elimination or reduction of such cadmium salts appears to be ecologically advantageous since, during film processing, such cadmium salts are eventually washed out and may find their way into the environment.
~ n view of the now-recognized toxicity of cadmium and other trace metals, concern for the public health and the maintenance of a more normal ecological balance has led to a search for new means of achieving good prope~ties in photographic compositions by utilizing relatively non-toxic materials or, where necessary, substantially reduced amounts of toxic materials. One means of achieving this is des-criaed in Product ~icehsing Index, Vol. 100, August, 1972, publlcation 10014, wherein at least part of the cadmium salt i8 replaced by a water-soluble manganou~ salt. Despite the advantages of this development, however, a need still exists for improved photographic compositions which do not contaln cadmlum salts but which exhibit the increased photographic speed and the development acceleration obtainable with cadmium salts.
Smith and Trivel'li U.S. Patent 2,448,060 issued August 31, 1948, teach the use as sensitizers for Photo-graphlc emulslons of soluble compounds of the general formula:

wherein ~ represents a hydrogen atom, an alkali metal atom or an ammonium radical; M represents a metal atom ~elected from group VIII of the periodic arrangement of the elements having an atomic weight greater than 100, i.e., ruthenium, rhodium~ palladium, osmium, iridiu~. and platinum; and X ;
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, ` . ... . . -. . , . : . . - . ~ . i . .. ~ ... . . .

~ ~ 3~ 1 ~

represents a halogen atom, e.g., a chlorine or bromine atom. Smith and Trivelli recognize that these compounds will fog photographic emulsions and, therefore, suggest the use of concentrations below that which produces any substantial fog. Quantities of from o.8 to somewhat less than 39.4 mg of metal compound for each lO0 grams of silver in the emulsion are suggested. It is to be noted that ammonium radicals are Lewis acids, whereas ammonia and amine compounds are Lewis bases. Further, in the above Smith and Trivelli compounds, the metal atom is coordinated in a complex having an overall negative charge.
In my U.S. Patent 3,891,442, issued June 24, 1975, and having an effective filing date of December 4, 1972, I dis-closed trivalent cationlc complexes of trivalent metals such as Ru(III), Co(III) and Cr(III) with ammine or amine ligands to be useful addenda for lithographic silver chloride emul-clon~. These trlvalent cationic complexes when incorporated in concentrations of from 0.2 to 5.0 grams per mole of sllver are disclosed to promote increased photographic speed and development acceleration in a manner similar to the cadmlum salts previously employed for this purpose. However, the contrast obtained with photographic elements utilizing ruthenium(III) complexes was noted to be too low for use in lithographic elements. This is because ruthenium(III) complexes when employed in the concentration levels investi-gated produce an elevated level of emulsion fogging.
Based upon further investigations, I have dls-covered unique and surprising properties for ruthenium complexes containing a predominance of ruthenium coordination bonds formed by ammine or amine ligands. First, while cobalt(III) and chromium(III) complexes in emulsion con-centrations significantly below 200 mg per mole of silver ~1~
,: . ..... .
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~04~ 5 are su~st-ntially ineffective as sensitizers or development accelerators, I have found that much lower concentrations of ruthenium complexes having a predominance of ammine or amine ligand coordination bonds are surprisingly effective in pro-viding sensitization and development acceleration. Hence, I
have discovered these ruthenium complexes to be effective in a distinctly lower concen~ration range than that re~uried for cobalt (III~ and chromium(III) complexes.
Second, although cobalt complexes are effective only where the cobalt is in its trivalent oxidation state, it is surprising that the effectiveness of ruthenium is not dependent on its being in its trivalent oxidation state. Additionally, whereas cobalt(III) and chromium(III) complexes are sensitizers and development accelerators only for silver halide emulsions in which the halide consists of at least 50 mole percent chloride, the ruthenium complexes of m~ present invention are effective in sen~itizing and development of silver halide emulsions generally. Whereas cobalt~III) and chromium(III) complexes were disclosed in my earlier filed patent application only in high-contrast lith-type silver halide emulsions, I
have discovered that the ruthenium complexes as herein disclosed are useful in proper concentration ranges in improving both high and low contrast emulsions. Still further, the ruthenium complexes are distinctly superior to cobalt(III) and chromium-(III) complexes when employed in high contrast emulsions lacking alkylene oxide development restrainers. Additionally, the emulsions containing the ruthenium complexes of this invention are useful with a wider ranqe of developers than cobalt(III~ or chromiumCIII) complexes. It is, accordingly, apparent that the ruthenium complexes are considerably more versatile in providing sensitization and development ac-celeration than cobalt(III) and chromium(III) complexes.

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~ Ihe ruthenium complexes hereln disclosed also exhi~itunique and surprising properties as regards the ligands associated therewith. In working with cobalt(III) and chromium-(III) complexes, I have observed that the inclusion of ligands other than ammine or amine lig~nds, such as halogen, water, etc., render these complexes ineffective as sensitizers and development accelerators. While I have found ruthenium com-plexes comtaining only ammine or amine ligands to be distinctly superior, I have further observed that ruthenium complexes containing one or two ruthenium coordination bonds formed by ligands other than ammine or amine ligands afford substantial sensitizatiOn and development acceleration improvement and are superior to corresponding cobalt(III) and chromium(III) complexes, even when differences in effective concentrations are ignored.
The ruthenium complexes herein employed not only act as sensitizers and development accelerators, but they also act to reduce the development time dependence of the charac-teristic H and D curves of the photographic elements in which they are incorporated. As is well appreciated by those skilled in the art, H & D characteristic curves are translated along the log E axis as a function of development time. Shorter development times show the photographic elements to be of slower speed while longer development periods show the same photo-graphic elements to be faster. Since some variation in dev-elopment times occurs as a practical matter in photographic element processing, it is desirable to manufacture photographic elements which can tolerate a substantial latitude in processing times. If a pair of identical photographic elements lacking the ruthenium complexes of this invention are processed at 3n differing development times, they will exhibit a substantial difference in their log E values at a reference density. If an additional pair of photographic elements, including the -- . . . -. .. .. . . , ~ - . ~...... . . .. ~ j ` 1(~4~6~LS

ruthenium comple~es empl~yed in the practice of this invention, but otherwise i~entical, are processed similarly, I have dis-covered that a dramatically lower difference in their log E
Values at the reference density will be observed. Thus, the spacing between the H and D curves for the ruthenium complex containing photographic elements is compressed. This performance improvement for the photographic elements is typically referred to in the art as H & D curve compression or simply curve compre~sion.
The cationic ruthenium complexes employed in the practice of this invention include a predominance of ammine or amine ligand coordination bonds. The amine ligands include primary, secondary and tertiary amine ligands as well as diamine ligands. The amine ligands are preferably aliphatic amines and are most preferably comprised of alkyl, alkylene and alkanol aliphatic moieties. Each aliphatic moiety preferably includes 6 or fewer carbon atoms. Dialkanol amines have been found particularly useful in forming bidentate ligands as have alkylene diamines. Bidentate ligands which form with the ruthenium atom 5 to 8 membered rings have been found to produce particularly stable complexes. Exemplary preferred ammine and amine ligand-forming compounds include ammonia, ethylene diamine, trimethylene diamine, diethanol amine, dipropanol amine, di-ethylene triamine, alkyltetramines, etc.
A minor proportion of the coordination bonds making up the cationic ruthenium complex can be provided by ligand~
other than ammine or amine ligands. A ruthenium(II) and ~III) complex can contain 1 or 2 mondentate ligands, such as water, halogen, thiocyanate, etc., or a single bidentate ligand. I
These and other unique and advantageous features of 1--my inVentiOn will ~ecome further apparent in the following --description of certain preferred embodiments: ¦
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Th~ cat~on~c ruthenium complexes employed in the practice of t~s-~nvention comprise a ruthenium ion surrounded by ~ertain other molecules which are re~erred to as ligands.
The ruthenium ion is a Lewis acid; the ligands are Lewis bases.
Werner complexes are well-known examples of these complexes. As is wellunderstood by those skilled in the art, ruthenium can exhibit a variety of valences. Because of their availability, ruthenium complexes incorporating ruthenium(II) and ruthenium-(III) are preferred, although the effectiveness of the cationic ruthenium complexes has not been observed to depend on the oxidation state of the ruthenium. While it is possible to form ruthenium complexes that are neutral (i.e., carry no net charge) or are negatively charged, such as the ruthenium complexes disclosed by Smith and Trivelli, only ruthenium complexes exhib-iting a net positive charge, i.e., cationic complexes, are employed in the practice of this invention.
Exemplary cationic ruthenium complexes useful in the practice of my invention are set forth below:
TABLE I
E emplary Cationic Ruthenium Complexes RU-l hexammine ruthenium(III) RU-2 tris~ethylenediamine) ruthenium(III) RU-3 bis~diethanolamine) ruthenium(lII) RU-4 bis(dipropanolamine) ruthenium(III) RU-S tris(trimethylenediamine) ruthenium(III) RU-6 ethylenediaminebis(trimethylenediamine) ruthenium (III) RV-7 bis(ethylenediamine trimethylenediamine) ; ruthenium(III) RU-8 monochlor~pentammine ~ruthenium(III) RU~9 monoaquopentammine ruthenium(III) RU-10 bromopentammine ruthenium(III) RU-ll aquochlorotetrammine ruthenium(III) RU-12 bis(ethylenediamine) ruthenium(II) RU-13 bisCtrimethylenediamine) ruthenium(II) - . ., , . - : , .
. . . , - - .:

r~, There will, of course, be anions associated with the foregoing complex cations. Any anion which does not exert un-desirable effects upon the finished photographic element may be employed. Among those anions which will be found useful may be listed chloride, bromide, sulfite, sulfate, perchlorate, nitrite, nitrate, zinc bromide, tetrafluoroborate, hexafluorophosphate, thiocyanate, dithionate, methyl sulfonate, tolyl sulfonate, and the like.
The ruthenium complexes e~p~Dyed in the practice of this invention are incorporated within a sllver halide emulsion or in a layer adjacent to a silver halide emulsion layer. The silver halide emulsions can comprise, for example, silver chloride, silver bromide, silver bromoiodide, silver chlorobromide, silver chloroiodide, silver chlorobromoiodide crystals or mixtures thereof. The emulsions can be coarse or fine grain emulsions and can be prepared by a variety of techniques, e.g., single jet emulsions such as those described in Trivelli and Smith, The Photographic Journal, Vol. LXXIX, May, 1939 ~pages 330-338), double ~et emulsion8, sUch as Lippmann emulsions, ammoniacal emulsions, ¦ thiocyanate or thioether ripened emulsions, such as those des-cribed in Nietz et al U.S. Patent 2,222,264 issued November 19, 1940; Illingsworth U.S. Patent 3,320,069 issued May 16, 1967 and McBride U.S. Patent 3,271,157 issued September 6, 1966. Silver halide emulsions can form latent images predominantly on the sur-face of the silver halide grains, or predominant1y on the interior of the silver halide grains, such as those described in Davey et ; al U.S. Patent 2,592,250 issued May 8, 1952; Porter et al U.S.
Patent 3,206,313 issued September 14, 1965; Berriman U.S. Patent 3,367,778 issued February 6, 1968 and Bacon et al U.S. Patent 3,447,927 issued June 3, 1969. If desired, mixture of such sur-face and internal image-forming emulsions can be made, such being described in Luckey et al U.S. Patent 2,996,382 issued August 15, 1961. Silver halide _ 9 _ emulsions can be regular grain emulsions, such as the type des-cribed in Klein and Moisar, J. Phot. Sci., Vol. 12, No. 5, Sept/
Oct, 1964, pages 242-251, and German Patent 2,107,118. Negative type emulsions can be made, as well as direct positive emulsions as described in Leermakers U.S. Patent 2,184,013 issued December 19, 1939; Kendall et al U.S. Patent 2,541,472 issued February 13, 1951; Schouwenaars British Patent 723,019 issued February 2, 1955; Illingsworth et al French Patent 1,520,821 issued March

4, 1968; Illingsworth U.S. Patent 3,501,307 issued March 17, 1970; Ives U.S.

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Patent 2, 563,785 issued August 7, 1951; Knott et al U.S.
Patent 2,456,g53 issued December 21, 1948, and Land U.S.
Patent 2,861,885 issued November 25, 1958.
The ruthenium complexes employed in the practice of this invention will produce sensitization and develop-ment acceleration when incorporated in a photographic element in one or more silver halide emulsion layers or in a layer immediately ad~acent thereto in a concentration of as much as 5.0 grams per mole of silver, as indicated in my above-noted U.S. Patent 3,891,442.
However, since fogging increases dramatically at higher concentration levels, concentrations of the ruthenium complexes below 1.0 gram per mole silver are presently contemplated.
I have made the surprising discovery that the ruthenium complexes remain hlghly effective as sensitizers and development accelerators in concentratlon ranges of from 100 to 0.1 mg of ruthenium complex per mole of sllver while their emulsion fogging characteristic ls dramatically reduced. Accordingly, at concentrations below 100 mg per mole of silver, the ruthenium complexes can be employed ~-in silver halide emulsions generally, including particularly those requiring hlgh contrast. For most applications, I
prefer to incorporate from 50 to 0.5 milligrams ruthenium complex per mole of silver. Generally, concentrations of from about 20 to 1 milligram per mole silver have been observed to be optimum concentration ranges in photographic elements.
In one preferred form, the photographic silver ;
halide emulsions employed in the practice of this invention are lithographic silver halide emulsions in which the halide --11-- . .

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-- ~0436~5 generally comprlses at least about 50 mole percent chloride, up to about 10 mole percent iodide and any re~aining halide being bromide. Fcr convenience, these emulsions are referred to herein as lithographic silver halide emulsions. These hi8h contrast emulsions preferably contain at least 60 mole percent chloride, less than 40 mole percent bromide and less than 5 mole percent iodide.
If desired, the silver halides employed in the practice of this invention can be precipitated in the presence of a rhodium salt, as disclosed in Sidebotham U.S. Patent 3,488,709, cited above and British Patent 775,197. Typical useful rhodium salts are, for example, rhodium chloride, rhodium trichloride, rhodium ammonium chloride, etc. The rhodlum salts can be employed in any concentratlon whlch ls effectlve for the lntended purpose.
~speclally good results are obtalned when the concentration ls from sbout 0.01 to about 0.35 milligram per mole of silver hslide.
It is preferret that the photographic elements of thl~ lnvention further comprise at lesst one szaindene, locatet either in the photographic silver halide emulslon layer or ln a layer lmmedlately ad~acent thereto. The azalndene can be lncorporated for the purpose of reduclng fog formstion ~lthln the photographic element attributable to the presence of the catlonic ruthenium complex. The azalndene also has a sensltlzlng effect. ' The azalndene wlll generally be present ln a concentratlon of from about 0.2 to about 5.0 grams per mole of silver, preferably from about 0.3 to about 3.0 grams per mole of silver and, most preferably, from about 0.5 to about 1.0 gram per mole of sllver. Among these azaindenes which may be employed in the practlce of thls inventlon can be llsted, for example, 4-hydroxy,6~alkyl-1,3,3a,7-tetrazaindenes, such as, -12_ 3~

,, , 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene, 5-carboxy-4-hydroxy-1,3,3a,7-tetrazaindene, 6-methyl-1,3,3a,7-tetraza-indene-4-thiol, 5,7-dimethyl-4, 6-dioxo-4, 5,6,7-tetrahydro-1,2,3,5,7-pentazaindene, 6-phenyl-1,3,3a,7-tetrazaindene-4-thiol, 5-bromo-4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene-4-thiol, 2,6-dimethyl-1,3,3a,7-tetrazaindene-4-thiol, 6-methyl-2-methylthio-1,3,3a,7-tetrazaindene-4-thiol,

5-ethyl 6-methyl-1,3,3a,7-tetrazaindene-4-thiol, 5-iso-butyl-6-methyl-1,3,3a,7-tetrazaindene-4-thiol, S-phenyl-1,2,3a, 4-tetrazaindene-7-thiol, 6-ethyl-5-methyl-1,2,3a,4-tetrazaindene-7-thiol, 5-methyl-1,2,3a,4-tetrazaindene-7-thiol, 1,2-bis(4-hydroxy-6-methyl-1,3,3a,7-tetrazainden-2-yl)-1,2-dihydroxyethane, 1,6-bis(4-hydroxy-6-methyl-1,3,3a,7-tetrazainden-2-yl)-2,5-dioxahexane, 1,2-bis(4-hydroxy-6-methyl-1,3,3a,7-tetrazainden-2-yl)ethane, 1,4-bis(4-hydroxy-

6-methyl-1,3,3a,7-tetrazainden-2-yl)butane, 1,2,3,4-tetraki~4-hydroxy-6-methyl-1,3,3a,7-tetrazainden-2-yl)-butane, S-amino-7-hydroxy-2-phenyl-1,2,3,4,6-pentazaindene,

7-amino-5-mercapto-2-p-sulfophenyl-1,2,3,4,6-pentazaindene 5-~mino-2 p-carboxyphenyl-7-hydroxy-1,2,3,4,6-pentazaindene, ;
5, 7-diamino-2-phenyl-1,2,3,4,6-pentazaindene, 7-amino-5-dimethylamino-2-phenyl-1,2,3,4,6-pentazaindene, 5-dimethyl-amino-7-hydroxy-2-phenyl-1,2,3,4,6-pentazaindene, 2-p-aminophenyl-5-amino-7-hydroxy-1,2,3,4,6-pentazaindene, 5-amino-7-hydroxy-2-p-methoxyphenyl-1,2,3,4,6-pentazaindene, 5-amino-2-p-chlorophenyl-7-hydroxy-1,2,3,4,6-pentazaindene, j 5-amino-2-hydro-7-hydroxy-1,2,3,4,6-pentazaindene, 5,7-dihydroxy-1,2,3,4,6-pentazaindene, 7-hydroxy-5-methyl- .
1,2,3,4,6-Pentazaindene, 7-hydroxy-1,2,3,4,6-pentazaindene, 7-hydroxy-5-mercapto-1,2,3,4,6-pentazaindene, 7-amino-5-carboxy-methylmercapto-1,2,3,4,6-pentazaindene, 7-mercapto "~ .

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1,2,3,4,6-pentazaindene, 5,7-dimercapto-1,2,3,4,6-pentazaindene, 5-ethylmercapto-7-hydroxy-1,2,3,4,6-pentazaindene, 5-hydroxy-1,2,3,4,6-pentazaindene, 5-hydroxy-7-mercapto-1,2,3,4,6-pentazaindene, 5-hydroxy-7-methyl-1,2,3,4,6-pentazaindene, 2,4-dihydroxy-6-methyl-1,3a,7-triazaindene, 4-hydroxy-5-chloro-1,3,3a,7-tetraza-indene, 4-hydroxy-5-iodo-1,3,3a,7-tetrazaindene, 2-methyl-4-hydroxy-6-methyl-3,3a,7_triazaindene and the like.
These azaindenes, as well as others which can be employed in ~he practice of this inventlon, are known in the art and have been described, for example, in ~eimbach et al U.S.
Patent 2,444,605 issued July 6, 1948; Allen et al U.S.
Patent 2~713,541 issued July 19, 1955; Carroll et al U.S.
Patent 2,716,062 issued August 23, 1955; Allen et al U.S, Patent 2,735,769 lssued February 21, 1956; Allen et al U.S. Patent 2,743,181 issued April 24, 1956; Tinker et al U.S. Patent 2,835~581 issued May 20, 1958~ Reynolds U.S.
Patent 2,756,147 issued July 24, 1956~ Tlnker U.S. Patent 2~852,375 lssued September 16, 1958; Carroll et al U.S.
Patent 2,743,180 issued April 24~ 1956~ Knott U.S. Patent 2,933~388 is~ued April 19, 1960; Carroll et al U.S. Patent 2,944,900 issued July 12, 1960; &leck et al U.S. Patent 3~432,304 issued March 11~ 1969; Ishikawa et al U.S. Patent 3~526~507 issued September 1, 1970; Baldock et al U.S.
Patent 3~573,056 lssued March 30, 1971; British Specifica-tlon 1,270,734 to Konishlroku Photo Industry Company, Llmltet, publlshet April.12, 1972 ant Zeitschrift Fur Wiss.
Phot. 47, 2-28 (1952) ant Piper U.S. Patent 2,886,437 issudd May 12, 1959.
The silver halide emulsion can contain a~y of the hydrophllic water-permeable binding materials known in the art to be suitable for this purpose. Suitable . .

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43~5 .
materials include gelatin, colloidal albumin, polyvinyl com-pounds, cellulose derivatives, acrylamide polymers, etc.
Mixtures of these binding agents can also be used. The binding agents for the emulsion layer of the photographic element can also contain dispersed polymerized vinyl compounds.
Typical synthetic polymers include those described in Nottorf --U.S. Patent 3,142,568 issued July 28, 1964; White U.S. Patent 3,193,386 issued July 6, 1965; Houck et al U.S. Patent 3,062,674 issued November 6, 1962; Houck et al U.S. Paten~
3,220,844 issued November 30, 1965; Ream et al U.S. Patent 3,287,289 issued November 22, 1966; and Dykstra U.S. Patent 3,411,911 issued November 19, 1968. Other vehicle materials include those water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates,;
those which have crosslinking sites which facilitate hardening or curing as described in Smith U.S. Patent 3,488,708 issued ~anuary 6, 1970, and those having recurring sulfobetaine units as described in Dykstra Canadian Patent 774,054. The vinyl polymers are generally employed in concentrations in the range of about 20 to about 80 percent, most often concentrations at least 50 percent, by weight, based on the weight of the binding agent. Silver halide emulsions wherein the binding agent -contains dispersed polymerized vinyl compound provide part-icularly good results in eliminating drag streaks and dot distortions in lithographic materials.
The silver halide emulsions can be sensitized using any of the well-known techniques in emulsion making, for example, by digesting with naturally active gelatin or various suI$ur, selenium, tellurium compounds and/or gold compounds.
; 30 The emulsions can be sensitized with salts of noble metals of Group VIII o$ the Periodic Table which have an atomic weight --~ - 15 -:. :.

r^

greater than 100. The emulsions can also contain addenda which increase speed and/or contrast such as quaternary ammonium salts, thioether sensitizers or combinations thereof.
The silver halide emulsions of this invention can conveniently be ortho-sensitized or pan-sensitized with spectral sensitizing dyes. Sensitizing dyes useful in sensiti~ing these silver halide emulsions are described, for example, in Brooker et al U.S. Patent 2,526,632 issued October 24, 1950;
Sprague U.S. Patent 2,503,776 issued April 11, 1950; Brooker et al U.S. Patent 2,493,748 issued January 10, 1950; and Taber et al U.S. Patent 3,384,486 issued May 21, 1968. Spectral sensitizers which can be used include the cyanines, merocyanines, complex (tri- or tetranuclear) cyanines, holopolar cyanines, styryls, hemicyanines (e.g., enamine cyanines), oxonols and hemioxonols.
In one preferred form, the silver halide emulsion can contain de~elopment ~odifiers that function as restrainers in silver halide emulsions requiring high contrast, such as lithographic silver halide emulsions. It is preferred to employ alkylene oxides in the emulsion for this purpose.
Typical useful alkylene oxides include polyethylene glycol, polyethylene glycol oleyl ether, polyethylene glycol cetyl ether, polyethylene oxide derivatives, block copolymers, such as those comprising blocks of polyoxypropylene, polyoxyethylene and the like, water-soluble organosilicone polyalkylenoxide polymers and the like. The alkylene oxide polymer can be used in any concentration effective for the intended purpose. When the alkylene oxide polymer is present in the photographic element, good results are obtained when the concentration is less than about 2 grams ~ 36 ~ ~

per mole of silver in the silver halide emulsion. A
preferred concentration range for the polymer in this embodiment is from about lO to about 800 mg per mole of s silver in the silver halide emulsion.
Where it is desired to incorporate the cationic ruthenium complex in a lithographic silver halide emulsion, it is, of course, recognized that one or more cobalt(III) or chromium(III) cationic complexes can additionally be incorporated into the emulsion to supplement the action 10 of the cationic ruthenium complex in sensitizing or accelerating development. These cobalt(III) and chromium-(III) cationic complexes are fully described in my U.S. Patent 3,891,442, noted above. The cobalt(III) and chromium(III) complexes are octahedral complexes formed by the metal atom acting as a Lewis acid with other associaJced molecule~ or ligands acting aR Lewis bases. These complexeR have coordination numbers of 6.
The cobalt(III) and chromium(III) cationic complexes useful in the practice of this invention in combination with cationic ruthenium complexes are formed entirely of ammine or amlne ligands, which can be identical to those previously described as useful in the ruthenium complexes. The cobalt(III) and chromium(III) cationic complexes are useful in concentration ranges of from 0.2 to 5 0 grams per mole of silver, preferably from about 0.3 to about 3 0 grams per mole of silver, and most preferably from about 0.5 to about l.0 gram per mole silver The cobalt(III) and chromium(III) complexes can be located directly within an emulsion layer or layers or in one or more layers 3 immediately ad~acent thereto, similarly as the ruthenium complexes. ;

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1(~43~5 The silver halide emulsions of this invention can also c~ntain conventional addenda such as gelatin plasticizers, coating aids, antifoggants and hardeners as described in Product Licensing Index, Vol. 92, December, 1971, publication 9232, pages 107-110.
As is well understood by those skilled in the art, the photographic emulsions above described can be coated onto a photographic support to form one or more silver halide emulsion la~ers. One or more nonimaging layers can also be coated onto the support along with the silver halide emulsion layer or layers. The nonimaging layers can take the form of subbing layers interlayers and/or overlayers of conventional character. Where the.cationic ruthenium complex is to be incorporated in a non-imaging layer adjacent to a silver halide emulsion layer, it i~ pxeferred that the nonimaging layer be comprised of a .hydrophilic, water-permeable binding material similar to those aescribed in connection with the silver halide emulsions.
The layers coated onto the photographic supports can be coated by various coating procedures including dip coating, air knife coating, curtain coating, or extrusion coating using hoppers of the type described in Beguin U.S. Patent 2,681,294 issued June 15, 1954. If desired, two or more layers can be coated simultaneously by the procedures described in Russell U.S. Patent 2,761,791 issued September 4, 1956; Hughes U.S.
Patent 3,508,947 i88ued April 28, 1970;. Wynn British Patent 837,095 published June 9, 1960; and Herzhof et al British Patent 1,208,809 published October 14, 1970. Also, silver halide layers can be coated by vacuum evaporation as described in British Patent 968,453 published September 2, 1964, and LuValle et al U.S. Patent 3,219,451 issued November 23, 1965.
The photographic layers, including silver halide ~ -emulsion layers and other layers of-.the Dhotographic element -1(~43~5 can be coated on a wide variety of supports. Typical supports include cellulose nitrate film oe llulose acetate film, poly-(vinyl acetal) film, polystyrene film, poly(ethylene terephthalate film, polycarbonate film and related films or resinous materials, as well as glass, paper, metal and the like. Typically, a flex-ible support is empolyed, especially a paper support, which can be partially acetylated or coated with baryta and/or an alpha-olefin polymer, particularly a polymer of an-alpha-olefin con-taining 2 to lO carbon atoms~ such as polyethylene, polypropylene, stnylenebutene copolymers and the like.
The ruthenium complexes, azaindenes and other addenda employed in the practice of this invention can be incorporated into the compositions forming the layer prior to coating or can be incorporated in a suitable solvent and added to the photo-graphic element after coating. In most instances, water is the preferred ~olvent. The addenda can be added using various pro-cedure~, including those de~cribed in Collin~ et al V.S. Patent 2,912,343 is~ued November 10, 1959; McCros~en et al U.S. Patent 3,342,605 issued September 19, 1967; Audran U.S. Patent 2,996,287 issued Augu~t lS, 1961, and Johnson et al U.S. Patent 3,425,83S
issued February 4, 1969.
In addition to photograph~c imaging, including forming images of high contrast of the type used for exposing lithographic printing plates, the silver halide photographic elements of this invention can be used for making lithographic printing plates such a8 by the colloid transfer of undeveloped and unhardened area~ ;
of an exposed and developed emulsion to a suitable support as described in Clark et al U.S. Patent 2,763,SS3 issued September 18, 1956; to provide a relief image as described in Woodward U.S.
Patent 3,402,045 issued September 17, 1968, or Spencer U.S. Patent 3,053,658 issued September 11, 1962; to prepare a relief printing plate as described in Baxter et al U.S. Patent 3,271,150 issued September 6, 1966; to prepare a silver salt diffusion transfer plate as de~cribed in Hepher et al British Patent 934,691 issued 43~

August 21, 1963, and AGfa British Patent 883,846 issued December 6, 1961; to provide an element which does not require washing or etching as described in Yackel et al U.S. Patent 3,146,104, reissue 25,885.
Although not critical to the present invention, it will be very convenient, and thus preferred, if a continuous method is employed for processing the exposed high contrast photographic elements. In such a method, the element is processed in one continuous motion by transporting it into and out of at least one processing solution in the manner sho~n, for example, by U.S. Patents 3,025,779 of Russell and Kunz issued March 20, 1962; 3,078,024 of Sardeson issued February 19, 1963; 3,122,086 of Fitch issued February 25, 1964; 3,149,551 of Cramer issued February 22, 1964; 3,156,173 of Meyer issued November 10, 1964;
and 3,224,356 of Fleisher and Hixon issued February 21, 1965.
It is preferred, where the photographic elements are intended to produce high contrast images upon expo~ure, that they be developed ln developers containing one or more amines and/or amine derivatives. A particularly desirable developer composition is described in Masseth U.S. Patent 3,573,914 which comprises a developing agent, a carbonyl bisulfite-amine con-densation product, and at least about 0.075 mole of free amine per liter of developer composition.
The developing agents which can be employed in these developer compositions can be any of those suitable for the in-tended purpose. Suitable silver halide developing agents, for example, include the dihydroxybenzenes, such as hydroquinone, chlorohydroquinone, bromohydroquinone, isopropylhydroquinone, toluhydroquinone, methylhydroquinone, 2,3-dichlorohydroquinone, 2,5-dimethylhydroquinone, 2,3-dibromohydroquinone, 1,4-dihydroxy -2-acetophenone-2,5-dimethylhydroguinone,2,5-diethylhydroquinone, 2,5-di-p-phenethylhydroquinone, 2,5-dibenzoylaminohydroquinone, 1(~43~

2,5-diacetaminohydroquinone, etc. Esters of such compounds, e.g., formates and acetates, can also be employed. These dev-eloping agents can be used alone or in any combination and can be employed in any concentration which is effective for develop- -ment. A suitable concentration for the developing agent is from -about 0 05 to about 0.50 mole per liter of deveIoper composition and is preferably from about 0.10 to about 0.30 mole per liter of developer composition.
The carbonyl bisulfite-amine condensation products lQ which can be used in this developer composition are preferably formaldehyde bisulfite-amine condensation products, such as sodium-2-hydroxyethylaminomethane sulfonate, sodium-2-hydroxy-propylaminomethane sulfonate, sodium-l,l-dimethyl-2-hydroxyl-aminomethane sulfonate, sodium-},l-bis (hydroxymethyl~ ethyl-aminomethane sulfonate, sodium-tris (hydroxymethyl) methyl-~mlnomethane sulfonate, sodium-3-hydroxypropylaminomethane 8ul-fonate, ~odium bis (2-hydroxyethyl) aminomethane sulfonate, sodium-N,N-bi~ (2-~1-hydroxylpropyl) amlnomethane sulfonate, sodium-N-i~opropyl-N-(2-hydroxyethyl) aminomethane sulfonate, sodium-N-ethyl-N-(2-hydroxyethyl) aminomethane sulfonate,~nd sodium-N-methyl-N-(2hp~droxyethyl) aminomethane sulfonate. The carbonyl bisulfite-amine condensation products can be used alone or in any combinations and can be employed in any concentration which is effective to provlde a low level of sulfite ion for the developer composition. A ~uitable concentration for the carbonyl bisu}U~ff~am~ine condensation product is from about 0.1 to about 1.0 mole per liter of liquid developer composition and is ,~ , .
preferably from about 0.25 to about 0.50 mole per liter of liquid developer composition.
The~carbonyl bisulfite-amine condensation product can be added to the developer composition as a separate compound or formed in situ. Methods for preparing these compounds are dis-10~ 5 closed, for example, in U.S. Patent 2,388,816 of Bean issued November 13, 1945.
The free or uncombined amine compounds which can be employed in these developer compositions include primary and secondary amines such as 2-aminoethanol, 1-amino-2-propanol, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol, 2-amino-2(hydroxymethyl)-1, 3-propanediol, 3-amino-1-propanol, 2-2'-iminodiethanol, di-iso-propanolamine, 2-isopropylaminoethanol, 2-ethylaminoethanol, 2-methylaminoethanol, etc. These amines can be used alone or in any combination and should be employed in a concentration of at least about 0.075 mole per liter of developer composition. A suitable range of concentrations for the amine compound is from about 0.075 to about 3.0 moles per liter of developer composi~ion and is preferably from about 0.20 to about 0.90 mole per ~o436~5 liter of developer composition. The free amine present in the developer compo~ition can be the same amine used :
to prepare the carbonyl bis~lfite-amine condensation product or it can be a different amine.
In addition to employing developers of the type disclosed in the above-citet Masseth patent, it is recognized that the photographic elements of thls inven~
tion can be developed with conventional photographlc developers exhibltlng a pH ln the range of from about 9 to 13. These developers are typically rentered basic by inorganlc ~olute~, such as alkali metal hytroxides, carbonates, pho~phates, slllcate~, etc. The developer also preferably contains at least a 0.001 molar concentra-tion of a stabillzer, such as an alkall metal or amlne blsulflte. me develop~ng agent can talce the form of`
~corblc acld or a polyhydroxybenzene, such a~ pyrogallol or any of the hydroqulnones noted above ln the Masseth dovoloporz. De~eloplng agent concentrations of fro~
0.01 to 0.5 mole of developing agent per liter of d-voloper r- typlcally preferred. Other conventlonal developer addenda canj of course, also be incorporated, if de~ired.
My lnventlon is further lllu~trated by the following examples.

i . .. ,..... .. ; .. -. ., , . . ~ ... : " ............... .

Examples 1 through 6 A fine grain silver chlorobromoiodide gelatin emulsion containing 90 mole percent chloride, 9 mols percent bromide and 1 mole percent iodide is chemically sensitized with sulfur and gold compounds. After the emulsion is heated to obtain optimum sensitlvity, the e~ulsion ls divided into equal portions~ and Ru(NH3)6C13 is added in various concen-tration levels, herein expressed in grams of ruthenium complex per mole of silver ln the photographic element.
The emulsion samples are then coated on a fllm support at a coverage of 50.5 mg silver/dm2 and 50.5 mg of gelatlnldm2.
The coated samples are then ldentically exposed and processed in a Kotak developer, D-85. Table II summarizes the observed results.
Table II

Example CompountDevelopment ~resh Re 5U lts Nô. (~/m)Time (Sec.) SPeet Fo~
Control none 60 32.5 .04 Control none 90 129 .04 Control none 120 289 .04 1 0.5 (A) 5 95 .09 2 0.5 ~A) 10 182 .14 3 0.5 (A) 20 234 .23 4 0.1 (A) 10 331 .13 ~ 0.1 (A) 15 389 .13 6 0.1 (A) 30 603 .35 Compount A - Ru(NH3)6C13 ~U~3~

From Table II it is apparent that the ruthenium complex greatly increa~es the speed of the emulsion and decreases the required time of development. It is extremely surprising that the use of 100 mg per mole of silver of ruthenium complex provides even higher speeds than using 500 mg per mole of silver.

Examples 7 through 10 The procedure of Examples 1 through 6 was repeated u~ing as an antifoggant an azaindene (Compound B).
The results are summarized in Table III.
Table III
Example CompoundDevelopment Fresh Results _No. (g/m)Time (Sec.) Speed Fog Control none 90 100 .05 7 0.05 ~A) 10 331 .04 1.00 ~B)

8 0.05 ~A) 20 891 ,13 1.00 ~B)

9 0.1 ~A) 10 513 .09 1.0 ~B) 0.1 (A) 20 661 .09 1.0 (B) Compound B - 4-hydroxy-6-methyl-1,3,3a,7-tetra zaindene The combination of a ruthenium complex and an azaindene is beneficial since an improvement is observed in the fog-speed relationship when compared to coatings in Table II containing only the ruthenium complex.

iO436~5 Examples 11 throu~h 13 Photographic elements were prepared by the same general procedures described in Examples 1 through 6, except that poly(ethylene oxide) as described in U.S.
Patent 2,944,900 was incorporated in the emulsion coatings in a concentration of 0.25 gram per mole of silver. The photographic elements were processed in a hydroquinone developer. Development times of 90 seconds were employed in each instance to determine speed and fog for~the emuldons. To determlne the compres~ion of the character-lstlcs curves additional development timés of 1.0 mlnute and 2.75 mlnutes were employed and the development pro-cedures employed were those descrlbed in Masseth U.S.
Patent 3,573,914, Example 1, using Developer A thereof.
The greater the curve compression, of course, the less the tlfference ln the log E values at the faster and slower tovolopment tlme8. The results are summsrlzed ln Table IV.

Tsble IV

Exanple Compound Pre~h Tests Corpresslon No, (~R/mole) SPeed FoR 1~ lo~ E
Control none 57 .03 > 1.3 log e 11 10 (A) 447 .06 0.32 log E
12 10 (C) 112 .04 0.80 log E
13 lO (D) 65 .05 0.80 log E

Compound C - [Ru~NH3)40HC13 C1~2H20 D - ~Ru(NH3)5scn ~CH3S0~ 2 S

To provide a comparison of curve' compression performance of cobalt(III~ and chromium(III) complexes, four photographic elements were prepared as described in E~amples 1 through 6, one containing hexammine cobalt~III) chloride, one containing hexammine chromium(III) perchlorate and two lacking any cobalt, chromium or ruthenium addenda. These latter were pr~pared for control purposes. The cobalt(III) and chromium(III) complexes were both present in concentrations of lOO mg of complex per mole of silver halide. Employing the development and curve compression examination procedures described above, the photographic element containing the cobalt(III) complex exhibited a curve compression of 1.06 log E, which was identical to that of the control photographic element processed with it. The chromium(III) complex similarly processed exhibited a curve compression of 1.36 log E as compared to a curve compression of ,.
1.26 log E for the control photogxaphic element processed along wlth it. This illustrated that neither the cobalt(III) nor chromium(III) complexes were capable of providing significant curve compression a~ the concentration level of 100 mg per mole of silver halide, whereas the ruthenium complexes surprisingly exhibited very significant curve compression capabilities at one tenth this concentration level.

Example 14 The procedure of Examples 11 through 13 was repeated, but curve compression comparision was not undertaken. The results are summarized below in Table V.

,. ,~, , . . . , , ~ . , , ............... . . .

10436~5 Table V

Example Compound Fresh Results No. (m~Lmole) Speed Fo~
Control none 44 NR*
14 10 (E) 57 .Oô
Compound E _LRU(II) (NH2CH2CH2NH2)3~ ZnBr4 *NR - No value recorded Examples 15 throu~h 18 Ruthenlum complexes were incorporated into a llthographic silver chloride emulsion containing 200 mg of oleic ether of polyethylene glycol (molecular weight 1540) per mole of silver halide, with and without azaindene being present. The excellent speed and acceleration obtained with these addenda are summarizet below in Table Vl ln Developer A (containlng a diethanol-a~ine ant bisulfite addltlon complex) and Developer B
(a typlcal llthographic developer) Kotak Developer D-85.

-28_ ~043615 o ~ ~ o o vJJ V Q~
~ ~~ ~ V 0 V
~ __ , V U U U U
~ 5,. 5 ~o ~o u u u u u .,X,~ oo ooooo ~~ ~o o ooo,C)o ooo oo ... .. ... ..
o o o o o o o oo o s ~1 ` ~ ` ~
~ ~ N

O ~ C~ ' O`D ~
R u~ ~ oO 0~~
~ 't + + -I ' ~ _ _~ , _ ~ ~J' __ __ _ _ ~ _ ~ _ -- --14 .t: .¢_ ~ ~ _ ~
e o~'' ~ ~~ -~ ~ ~10 ~ 00 $
~o V o o ~ o o 4~ V o o ~ o o U~ ~
-' o ~ o ~ ~ ~ 0~ 0 3 q ~
~ ~ o ., ~
~ _, ~ ~

1~ c o u ~ , oo C~ C
. o ~o C~

-29_ - . -,............ . - . .. . . .- ~ ... ...

1~;~f~15 Examples 19 and 20 A silver chlorobromoiodide (90:9:1 mole ratio) emulsion is prepared using the "double jet" technique. The potassium chloride, potassium bromide and potassium iodide solution contained 0.15 milligram of rhodium ammonium chloride per mole of silver halide. The emulsion was sulfur and gold sensitized and heat finished to optimum sensitivity. The emulsion was then divided into equal portions and Ru(NH3)6C13 was added to the photographic element in various concentration levels, herein expressed in milligrams of ruthenium complex per mole of silver. The emulsion samples were then coated on a film support at a coverage of 50.5mg of silver/dm2 and 50.5 mg of gelatin/dm2. The coated samples were then identically exposed and processed for 2 3/4 minutes at room temperature in Kodak Developer D-85. Table VII summarizes the observed results:
Table VII

Example Compound Fresh Results No.(mg/mole) Speed ~ Fog Controlnone trace 2.8 .04 image 19(A) 2 57 10.1 .03 20(A) 5 100 8.8 .04 From Table VII it is apparent that the ruthenium complex greatly increases speed and contrast in rhodium containing silver halide emulsions. When an azaindene (Compound F) is added to Example~ 19 and 20 a further increase in speed is observed.

- . : . . . . , - - . .
. .. ........ .. - . . .. .. :.. ~ .. : .

10~361~
Examples 21 and 22 A silver chlorobromoiodide (90:9:1 mole ratio) emulsion is sulfur and gold sensitized and heat finished to optimum sensitivity. To the emulsion is added 0.5 gm of 5-bromo-4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene/mole of silver halide. The emulsion is divided into e~ual portions and the addenda described in Table VIII is added. The emulsion samples are then coated on a film support, exposed and processed as described in Examples 1 through 6. The development time is 1 minute 45 seconds. Table VIII
summarizes the observed results.
Table VIII

Example Compound Compound Fresh Results No. (G) gm/mole (A) mg/mole Speed ~ Fog Control 1.0 -- 100 8.6 .02 -- 7.9 200 6.4 .05 21 0.6 3.2 214 7.5 .03 22 0.4 4.7 234 8.1 .04 Compound G - tris~ethylenediamine)cobalt~III)chloride From Table VIII it can be seen that a combination of a cobalt complex and a ruthenium complex provides higher speed than either complex employed alone.
Example 23 Ammonium hexachloropalladite and potassium tetrachloropalladite were tested in a similar manner as deQcribed in Examples 1-6. It was found that they did not increase speed or development acceleration.
The invention has been described in detail with par-ticular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

. . , ,: ~ . :... -. . , . . ~ .

Claims (25)

I CLAIM:

1. A photographic element comprising a support having coated thereon at least one layer comprising a photographic silver halide emulsion and in said layer or in a second layer adjacent thereto a development accelerating amount of a ruthenium cationic complex including a predominance of ligands chosen from the class consisting of ammine and amine ligands, said ruthenium cationic complex being present in a concentration of less than 1 gram per mole of silver.

2. A photographic element according to claim 1 in which said element contains from 100 to 0.1 mg of said ruthenium complex per mole of silver.

3. A photographic element according to claim 2 in which said element contains from 50 to 0.5 mg of said ruthenium complex per mole of silver.

4. A photographic element according to claim 3 in which said element contains from 20 to 1 mg of said ruthenium complex per mole of silver.

5. A photographic element according to claim 1 in which said silver halide emulsion layer or said second adjacent layer contains an azaindene antifoggant.

6. A photographic element according to claim 5 in which said azaindene is a tetraazaindene.

7. A photographic element according to claim 1 in which said element contains an alkylene oxide development restrainer.

8. A photographic element according to claim 1 in which said ruthenium complex is a hexacoordinated divalent or trivalent cationic complex.

9. A photographic element according to claim 8 in which said ruthenium complex includes at least four amine or ammine ligands.

10. A photographic element according to claim 9 in which said ruthenium complex includes at least five or six ammine or amine ligands.

11. A photographic element according to claim 10 in which said ammine and amine ligands are chosen from the class consisting of ammine ligands and aliphatic amine ligands con-taining six or fewer carbon atoms.

12. A photographic element according to claim 11 in which said amine ligands are chosen from the class consisting of ethylene diamine, trimethylene diamine, diethanol amine and dipropanol amine ligands.

13. A photographic element according to claim 1 in which said ligands other than said ammine and amine ligands are chosen from the class consisting of water, halogen and thiocyanate ligands.

14. A photographic element according to claim 1 in which said amine ligands are chosen from the class consisting of aliphatic amine ligands containing six or fewer carbon atoms.

15. A lith-type photographic element comprising a support having coated thereon a high contrast lithographic silver halide emulsion containing at least 50 mole percent silver chloride and in said emulsion layer or in a layer adjacent thereto from 100 to 0.1 mg per mole of silver of a hexacoordinated ruthenium cationic complex including at least four ligands chosen from the class consisting of ammine ligands and aliphatic amine ligands containing six or fewer carbon atoms, and an azaindene antifoggant.

16. A lith-type photographic element according to claim 15 in which said lithographic silver chloride emulsion is comprised of silver halide grains in which the halide consists of at least 50 mole percent chloride, up to about 10 mole per-cent iodide and any remaining halide being bromide.

17. A lith-type photographic element according to claim 15 in which said ruthenium complex is present in a concentration of from 50 to 0.5 mg per mole of silver.

18. A lith-type photographic element according to claim 17 in which said ruthenium complex is present in a concentration of from 20 to 1 mg per mole of silver.

19. A lith-type photographic element according to claim 15 in which said silver halide emulsion incorporates a rhodium salt.

20. A lith-type photographic element according to claim 15 in which said silver halide emulsion layer or said second adjacent layer contains a tetrazaindene antifoggant.

21. A lith-type photographic element according to claim 15 in which said silver halide emulsion layer or said second adjacent layer contains a cationic cobalt (III) complex having amine or amine ligands.

22. A lith-type photographic element comprising a support having coated thereon a high contrast litho-graphic silver halide emulsion containing at least 50 mole percent silver chloride and in said emulsion or in a layer adjacent thereto 100 to 0.1 mg per mole of silver of hexa-coordinated ruthenium cationic complex including at least four ligands chosen from the class consisting of amine ligands and aliphatic amine ligands containing six or fewer carbon atoms; and 0.2 to 5.0 grams per mole of silver of a hexaccordinated cobalt or chromium(III) cationic complex.

23. A lith-type photographic element according to claim 22 in which said silver halide emulsion or said adjacent layer contains a tetrazaindene.

24. A lith-type photographic element according to claim 23 in which said ruthenium complex and said cobalt(III) complex are both hexamine complexes.

25. A lith-type photographic element comprising a support having coated thereon a high contrast lithographic silver halide emulsion containing at least 50 mole percent silver chloride, up to 10 mole percent silver iodide and any remaining silver halide being a silver bromide and in said emulsion or in a layer adjacent thereto 20 to 1 mg per mole of silver of a hexammine ruthenium cationin complex;
0.3 to 3.0 grams per mole of silver of a hexammine cobalt (III) cationic complex; and 0.3 to 3.0 grams per mole of silver of 5-bromo-4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene.