US3592653A - Silver halide emulsions containing pyrrole cyanine dyes - Google Patents

Silver halide emulsions containing pyrrole cyanine dyes Download PDF

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US3592653A
US3592653A US673001A US3592653DA US3592653A US 3592653 A US3592653 A US 3592653A US 673001 A US673001 A US 673001A US 3592653D A US3592653D A US 3592653DA US 3592653 A US3592653 A US 3592653A
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dye
silver halide
photographic
emulsion
silver
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Arthur Fumia Jr
Donald W Heseltine
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Eastman Kodak Co
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C1/00—Photosensitive materials
    • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
    • G03C1/485—Direct positive emulsions
    • G03C1/48515—Direct positive emulsions prefogged
    • G03C1/48523—Direct positive emulsions prefogged characterised by the desensitiser
    • G03C1/4853—Direct positive emulsions prefogged characterised by the desensitiser polymethine dyes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09B—ORGANIC DYES OR CLOSELY-RELATED COMPOUNDS FOR PRODUCING DYES, e.g. PIGMENTS; MORDANTS; LAKES
    • C09B23/00—Methine or polymethine dyes, e.g. cyanine dyes
    • C09B23/10—The polymethine chain containing an even number of >CH- groups
    • C09B23/105—The polymethine chain containing an even number of >CH- groups two >CH- groups

Definitions

  • This invention relates to novel photographic materials, and more particularly to a new class of cyanine dyes, to novel photographic silver halide emulsions containing these dyes, and to new photographic elements prepared with such emulsions.
  • Direct positive images are known to be obtained with certain types of photographic silver halide emulsions.
  • photographic emulsions have been proposed for this purpose comprising certain cyanine dyes which function as electron acceptors, and silver halide grains that have been fogged with a combination of a reducing agent and a compound of a metal more electropositive than silver.
  • One of the advantages of such direct positive emul sions is that the high-light areas of the images obtained with these materials are substantially free of fog.
  • known materials of tis type have not exhibited the high speed required for many applications of photography.
  • such known materials have not shown the desired selective sensitivity, especially to radiation in the green to red region of the spectrum. It is evident, therefore, that there is need in the art for improved direct positive photographic materials having both good speed and desirable sensitivity to longer wavelength radiations.
  • an object of this invention to provide a new class of cyanine dyes that avoid the above mentioned disadvantages of prior art desensitizing dyes. Another object is to provide novel and improved photographic silver halide emulsions, such as fogged direct positive emulsions containing one or more of the new cyanine dyes of this invention. Another object is to provide such novel emulsions containing a color former. Another object is to provide novel photographic elements comprising a support having thereon at least one layer containing a novel emulsion of this invention. Another object is to provide methods for the preparation of such novel dyes and photgraphic materials of this invention. Other objects will be apparent from this disclosure and the appended claims.
  • cyanine dyes derived from pyrroles containing a free 2-position carbon atom are outstanding electron acceptors and spectral sensitizers for direct positive type photographic silver halide emulsions. They provide superior reversal systems, especially with fogged silver halide emulsions that are characterized by both good speed and desired selective sensitivity to radia tion in the green to red region of the spectrum, with maximum sensitivity occurring in most cases in the region of about .540630 ITl/L.
  • the images produced with these new direct positive photographic emulsions are clear and sharp, and of excellent contrast.
  • the new class of cyanine dyes of this invention include those comprising first and second 5- to 6-membered nitrogen containing nuclei joined by a methine linkage; the first of said nuclei being a pyrrole nucleus joined at the 2-carbon atom thereof to said linkage; and said second nucleus 3,592,653 Patented July 13, 1971 being of the type used in the production of cyanine dyes including both sensitizing and desensitizing nuclei joined at a carbon atom thereof to said linkage, to complete said cyanine dye.
  • the preferred cyanine dyes of the invention that are especially useful as electron acceptors and spectral sensitizers for direct positive photographic silver halide emulsions are represented by the following general formula:
  • n represents a positive integer of from 1 to 2;
  • R represents an alkyl group, including substituted alkyl, (preferably a lower alkyl containin gfrom 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, heXyl, cyclohexyl, decyl, dodecyl, etc., and substituted alkyl groups (preferably a substituted lower alkyl containing from 1 to 4 carbon atoms), such as a hydroxyalkyl group, e.g., fi-hydroxyethyl, w-hydroxybutyl, etc., an alkoxyalkyl group, e.g., ,B-methoxyethyl, wbutoxybutyl, etc., a carboxyalkyl group, e.g
  • R R R and R each represents a hydrogen atom, an alkyl group (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, decyl, dodecyl, etc., or an aryl group, e.g., phenyl, tolyl, naphthyl, methoxyphenyl, chlorophenyl, etc.;
  • X represents an acid anion, e.g., chloride
  • a thiazole nucleus e.g., thiazole, 4-methylthiazole, 4- phenylthiazole, S-methylthiazole, S-phenylthiazole, 4,5- dimethylthiazole, 4,5 diphenylthiazole, 4-(2-thienyl) thiazole, benzothiazole, 4-chlorobenzothiazole, 4- or 5- nitrobenzothiazole, 5-chlorobenzothiazole, 6-chlorobenzothiazole, 7-chlorobenzothiazole, 4-methylbenzothiazole, S-methylbenzothiazole, 6-methylbenzothiazole, 6-nitrobenzothiazole, S-bromobenzothiazole, 6-bromobenzothiazole, 5chloro-6-nitrobenzothiazole, 4-phenylbenzothiazole, 4-methoxybenzothiazole, S-methoxybenzothiazole, 6-methoxybenzothiazole, S-iodo
  • an oxazole nucleus e.g., 4-methyloxazole, 4-nitro-oxazole, S-methyloxazole, 4-phenyloxazole, 4,5-diphenyloxazole,
  • a selenazole nucleus e.g., 4-methylselenazole, 4-nitroselenazole, 4-phenylselenazole, benzoselenazole, 5-chlorobenzoselenazole, 5-methoxybenzoselenazole, 5-hydroxybenzoselenazole, 5- or 6-nitrobenzoselenazole, 5- chloro 6-nitrobenzoselenazole, tetrahydrobenzoselenazole, a-naphthoselenazole, B-naphthoselenazole, nitro group substituted naphthoselenazoles, etc.;
  • thiazoline nucleus e.g., thiazoline, 4-methylthiazoline
  • a pyridine nucleus e.g., Z-pyridine, S-methyl-Z-pyridine, 4-pyridine, 3-methyl-4-pyridine, nitro group substituted pyridines, etc.;
  • a quinoline nucleus e.g., Z-quinoline, B-methyl-Z-quinoline, S-ethyI-Z-quinoline, 6-chloro-2-quinoline, 6-nitro- 2-quinoline, 8-chloro-2-quinoline, 6-methoxy-2-quinoline, 8-ethoxy-2-quinoline, 8-hydroxy-2-quinoline, 4- quinoline, 6-methoxy-4-quinoline, 6-nitro-4-quinoline, 7-methyl-4-quinoline, 8-chloro-4-quinoline, l-isoquinoline, 3-isoquinoline, etc.;
  • a 3,3-dialkylindolenine nucleus preferably having a nitro or cyano substitutent, e.g., 3,3-dimethyl-5- or 6-nitroindolenine, 3,3-dimethyl-5- or 6-cyanoindolenine, etc.; and,
  • imidazole nucleus e.g., imidazole, l-alkylimidazole, 1-
  • alkyl-4-phenylimidazole 1-alkyl-4,S-dimethylimidazole, benzimidazole, l-alkylbenzimidazole, l-alkyl-S-nitrobenzimidazole, 1-aryl-5,6-dichlorobenzimidazole, 1- alkyl-a-naphthimidazole, 1-aryl-fl-naphthimidaz0le, 1- alkyl-S-methOXy-a-naphthimidazole, or,
  • an imidazo[4,5-b]quinoxaline nucleus e.g, 1,3-dialkylimidazo[4,5-b]quinoxaline such as 1,3-diethylimidazo- [4,5-b1quinoxaline, 6-chloro-1,3-diethylimidazo[4,5-b] quinoxaline, etc., 1,3-dialkenylimidazo[4,5-b]quinoxaline such as 1,3-diallylimidazo[4,5-b]quinoxaline, 6- chloro-1,3-diallylimidazo[4,5-b]quinoxaline, etc., 1,3- diarylimidazo[4,5-b]quinoxaline such as 1,3-diphenylimidazo[4,5-b1quinoxaline, 6-chloro 1,3-diphenylimidazo[4,5-b]quinoxaline, etc.;
  • a 3,3-dialkyl-3H-pyrrolo[2,3-b1pyridine nucleus e.g., 3,3- dimethyl-3H-pyrrolo[2,3-b]pyridine, 3,3 diethyl-3H- pyrrolo[2,3-b]pyridine, etc.;
  • Nuclei wherein Z completes an imidazo[4,5-b]quinoxaline nucleus, or a nitro group substituted thiazole, oxazole, selenazole, thiazoline, pyridine, quinoline, indole, or imidazole nucleus are desensitizing nuclei.
  • Dyes of the invention produced with these densensitizing nuclei are particularly efficacious, and in the instances wherein the pyrrole nucleus contains phenyl group substituents at the 1- and 5-positions of the pyrrole ring, they are outstanding electron acceptors and spectral sensitizers, and are the preferred dyes species of the invention.
  • novel cyanine dyes of the invention defined above are powerful electron acceptors and spectral sensitizers for direct positive photographic silver halide emulsions.
  • they are also useful desensitizers in emulsions used in the process described in Steward and Reeves, U.S. Pat. No. 3,250,618, issued May 10, 1966.
  • desensitizing nucleus refers to those nuclei which, when converted to a symmetrical carbocyanine dye and added to gelatin silver chlorobromide emulsion containing 40 mole percent chloride and 60 mole percent bromide, at a concentration of from 0.01 to 0.2 gram dye per mole of silver, cause by electron trapping at least about an percent loss in the blue speed of the emulsion when sensitometrically exposed and developed three minutes in Kodak developer D-19 at room temperature.
  • the densitizing nuclei are those which, when converted to a symmetrical carbocyanine dye and tested as just described, essentially completely densensitize the test emulsion to blue radiation (i.e., cause more than about to loss of speed to blue radiation).
  • cyanine dyes defined by Formula I above are conveniently prepared, for example, by reacting at from 15 C. to refluxing temperatures a mixture of (1) a heterocyclic compound of the formula:
  • R X and Z are previously defined, and R represents methyl, ethyl, benzyl, etc., and (2) a pyrrole compound of the formula:
  • R R R and R are as previously defined, in approximately equimolar proportions, in the presence or absence, as desired, of a condensing agent such as a trialkylamine, e.g., triethylamine, etc., piperidine N-methylpiperidine, etc., in an inert solvent medium such as an alkanol, e.g., ethanol, or acetic anhydride.
  • a condensing agent such as a trialkylamine, e.g., triethylamine, etc., piperidine N-methylpiperidine, etc.
  • an inert solvent medium such as an alkanol, e.g., ethanol, or acetic anhydride.
  • Chain-substituted dyes are prepared when R represents ethyl, benzyl etc., The crude dyes are then separated from the reaction mixtures and purified by one or more recrystallizations from appropriate solvents such as methanol, mixtures of dimethyl
  • the intermediate compounds of Formula III above are conveniently prepared, for example, by reacting a mixture of approximately equimolar amounts of (1) a compound of the formula:
  • R R R and R are as previously defined, and (2) an N,N-dimethylformamide/phosph0ryl chloride complex, in an inert solvent medium such as dichloroethane.
  • an inert solvent medium such as dichloroethane.
  • (2) is agitated with the dichloroethane and the pyrrole compound (1) is slowly added thereto in the form of a solution thereof in dichloroethane at the temperature of an ice bath.
  • the mixture is then heated to reflux for a short period, cooled and an aqueous solution of sodium acetate is then added.
  • the crude product is separated by appropriate decantation and extraction methods and recrystallized from a suitable solvent such as ligroin.
  • novel and improved direct positive photographic silver halide emulsions are prepared by incorporating one or more of the cyanine dyes of the invention into a suitable fogged silver halide emulsion.
  • the emulsion can be fogged in any suitable manner, such as by light or with chemical fogging agents, e.g., stannous chloride, formaldehyde, thiourea dioxide, and the like.
  • the emulsion may be fogged by the addition thereto of a reducing agent, such as thiourea dioxide, and a compound of a metal more electropositive than silver, such as a gold salt, for example, potassium chloroaurate, as described in British Pat. 723,019 (1955).
  • Typical reducing agents that are useful in providing such emulsions include stannous salts, e.g., stannous chloride, hydrazine, sulfur compounds such as thiourea dioxide, phosphonium salts such as tetra(hydroxymethyl) phosphonium chloride, and the like.
  • Typical useful metal compounds that are more electropositive than silver include gold, rhodium, platinum, palladium, iridium, etc., preferably in the form of soluble salts thereof, e.g., potassium chloroaurate, auric chloride, (NH PdCl and the like.
  • reducing agent and metal compound e.g., metal salt
  • concentrations of reducing agent and metal compound can be varied over a considerable range.
  • good results are obtained using about .05 to 40 mg. reducing agent per mole of silver halide and 0.5 to 15.0 mg. metal compound per mole of silver halide. Best results are obtained at lower concentration levels of both reducing agent and metal compound.
  • the concentration of added dye can vary widely, e.g., from about 50 to 2000 mg. and preferably from about 400 to 800 mg. per mole of silver halide in the direct positive emulsions.
  • fogged refers to emulsions containing silver halide grains which produce a density of at least 0.5 when developed, with out exposure, for 5 minutes at 68 F. in developer Kodak DK-50 having the composition set forth below, when the emulsion is coated at a silver coverage of 50 mg. to 500 mg. per square foot.
  • the dyes of this invention are also advantageously incorporated in direct positive emulsions of the type in which a silver halide grain has a water-insoluble silver salt center and an outer shell composed of a fogged water-insoluble silver salt that develops to silver without exposure.
  • the dyes of the invention are incorporated, preferably, in the outer shell of such emulsions.
  • These emulsions can be prepared in various ways, such as those described in Berriman U.S. patent application Ser. No. 448,467, filed Apr. 15, 1965, now U.S. Pat. 3,367,778 issued Feb. 6, 1968.
  • the shell of the grains in such emulsions may be prepared by precipitating over the core grains a light-sensitive water-insoluble silver salt that can be fogged and which fog is removable by bleaching.
  • the shell is of sufficient thickness to prevent access of the developer used in processing the emulsions of the invention to the core.
  • the silver salt shell is surface fogged to make it developable to metallic silver with conventional surface image developing compositions.
  • the silver salt of the shell is sufiiciently fogged to produce a density of at least about 0.5 when developed for 6 minutes at 68 F. in Developer A below when the emulsion is coated at a silver coverage of 100 mg. per square foot.
  • Such fogging can be effected by chemically sensitizing to fog with the sensitizing agents described for chemically sensitizing the core emulsion, high intensity light and the like fogging means well known to those skilled in the art. While the core need not be sensitized to fog, the shell is fogged. Fogging by means of a reduction sensitizer, a noble metal salt such as gold salt plus a reduction sensitizer, a sulfur sensitizer, high pH and low pAg silver halide precipitating conditions, and the like can be suitably utilized. The shell portion of the subject grains can also be coated prior to fogging.
  • the core emulsion is first chemically or physically treated by methods previously described in the prior art to produce centers which promote the deposition of photolytic silver, i.e., latent image nucleating centers.
  • centers can be obtained by various techniques as described herein. Chemical sensitization techniques of the type described by Antoine Hautot and Henri Sauvenier in Science et Industries Photographiques, vol. XXVIII, January 1957, pages 1 to 23 and January 1957, pages 57 to 65 are particularly useful.
  • Such chemical sensitization includes three major classes, namely, gold or noble metal sensitization, sulfur sensitization, such as by a labile sulfur compound, and reduction sensitizati on, e.g., treatment of the silver halide with a strong reducing agent which introduces small specks of metallic silver into the silver salt crystal or grain.
  • the dyes of this invention are highly useful electron acceptors in high speed direct positive emulsions comprising fogged silver halide grains and a compound which accepts electrons, as described and claimed in Illingsworth U.S. patent application Ser. No. 619,936, filed Mar. 2, 1967, now U.S. Pat. 3,501,307, issued Mar. 17, 1970, and titled Photographic Reversal Materials Case C.
  • the fogged silver halide grains of such emulsions are such that a test portion thereof, when coated as a photographic silver halide emulsion on a support to give a maximum density of at least about one upon processing for six minutes at about 68 F.
  • the grains of such emulsions will lose at least about 25% and generally at least about 40% of their fog when bleached for ten minutes at 68 F. in a potassium cyanide bleach composition as described herein.
  • This fog loss can be illustrated by coating the silver halide grains as a photographic silver halide emulsion on a support to give a maximum density of at least 1.0 upon processing for six minutes at about 68 F. in Kodak DK-50 developer and comparing the density of such a coating with an identical coating which is processed for six minutes at 68 F. in Kodak DK-50 developer after being bleached for about 10 minutes at 68 F. in the potassium cyanide bleach composition.
  • the maximum density of the unbleached coating will be at least 30% greater, generally at least 60% greater, than the maximum density of the bleached coating.
  • the silver halides employed in the preparation of the photographic emulsions useful herein include any of the photographic silver halides as eX-amplified by silver bromide, silver iodide, silver chloride, silver chlorobromide, silver bromoiodide, silver chlorobromoiodide, and the like.
  • the silver halide gains can be regular and can be any suitable shape such as cubic or octahedral, as described and claimed in Illingsworth U.S. Patent application Ser. No. 619,909, filed Mar. 2, 1967, now U.S. Patent 3,501,306, issued Mar.
  • Such grains advantageously have a rather uniform diameter frequency distribution, as described and claimed in Illingsworth US. Pat. application Ser. No. 619,948, filed Mar. 2, 1967, now US. Pat. 3,501,305 issued Mar. 17, 1970, and titled Photographic Reversal Emulsions Case B.
  • at least 95%, by weight, of the photographic silver halide grains can have a diameter which is within about 40%, preferably within about 30% of the mean grain diameter.
  • Mean grain diameter i.e., average grain size
  • the fogged silver halide grains in these direct-positive photographic emulsions of this invention produce a density of at least 0.5 when developed without exposure for five minutes at 68 F. in Kodak DK50 developer when such an emulsion is coated at a coverage of 50 to about 500 mg. of silver per square foot of support.
  • the preferred photographic silver halide emulsions comprise at least 50 mole percent bromide, the most preferred emulsions being silver bromoiodide emulsions, particularly those containing less than about ten mole percent iodide.
  • the photographic silver halides can be coated at silver coverages in the range of about 50 to about 500 milligrams of silver per square foot of support.
  • the dyes of the invention are advantageously incorporated in the washed, finished silver halide emulsion and should, of course, be uniformly distributed throughout the emulsion.
  • the methods of incorporating dyes and other addenda in emulsions are relatively simple and well known to those skilled in the art of emulsion making. For example, it is convenient to add them from solutions in appropriate solvents, in which case the solvent selected should be completely free from any deleterious effect on the ultimate light-sensitive materials. Methanol, isopropanol, pyridine, water, etc., alone or in admixtures, have proven satisfactory as solvents for this purpose.
  • the type of silver halide emulsions that can be sensitized with the new dyes include any of those prepared with hydrophilic colloids that are known to be satisfactory for dispersing silver halides, for example, emulsions comprising natural materials such gelatin, albumin, agar-agar, gum arabic, alginic acid, etc. and hydrophilic synthetic resins such as polyvinyl alcohol, polyvinyl pyrrolidone, cellulose ethers partially hydrolyzed cellulose acetate, and the like.
  • the binding agents for the emulsion layer of the photographic elcment can also contain dispersed polymerized vinyl compounds. Such compounds are disclosed, for example, in US. Patents 3,142,568; 3,193,386; 3,062,674
  • the dyes, reducing agents and metal compounds of the invention can be used with emulsions prepared, as indicated above, with any of the light-sensitive silver halide salts including silver chloride, silver bromide, silver chlorobromide, silver bromoiodide, silver chlorobromoiodide, etc.
  • Particularly useful are direct positive fogged emulsions in which the silver salt is a silver bromohalide comprising more than 50 mole percent bromide.
  • Certain dyes of this invention are also useful in emulsions which contain color formers.
  • novel emulsions of this invention may be coated on any suitable photographic support, such as glass, film base such as cellulose acetate, cellulose acetate butyrate, polyesters such as poly(etl1ylene terephthalate), paper baryta coated paper, polyolefin coated paper, e.g., polyethylene or polypropylene coated paper, which may be electron bombarded to promote emulsion adhesion, to produce the novel photographic elements of the invention.
  • film base such as cellulose acetate, cellulose acetate butyrate
  • polyesters such as poly(etl1ylene terephthalate), paper baryta coated paper, polyolefin coated paper, e.g., polyethylene or polypropylene coated paper, which may be electron bombarded to promote emulsion adhesion, to produce the novel photographic elements of the invention.
  • the above prepared dye containing the desensitizing 3-ethyl-6-nitrobenzothiazole nucleus is photographically tested for its usefulness as an electron acceptor and spectral sensitizer for fogged direct positive photographic silver halide emulsions by the following procedure.
  • a gelatin silver bromoiodide emulsion (2.5 mole percent of the halide being iodide) and having an average grain size of about 0.2 micron is prepared by adding an aqueous solution of potassium bromide and potassium iodide, and an aqueous solution of silver nitrate, simultaneously to a rapidly agitated aqueous gelatin solution at a temperature of 70 C., over a period of about minutes.
  • the emulsion is chill-set, shredded and washed by leaching with cold water in the conventional manner.
  • the emulsion is reduction-gold fogged by first adding 0.2 mg. of thiourea dioxide per mole of silver and heating for minutes at C. and then adding 4.0 mg.
  • the dye of the above example 3-ethyl-6-nitro-2- [2 (2 pyrrolyl)-vinyl]benzothiazolium p-toluenesulfonate, is then added to the above fogged emulsion in amount sulficient to give the concentration recorded in Table I hereinafter of the dye per mole of silver.
  • the resulting emulsion is coated on a cellulose acetate film support at a coverage of mg. of silver and 400 mg. of gelatin per square foot of support.
  • a sample of the coated support is then exposed on an Easman lb sensitometer using a tungsten light source and processed for 6 minutes at room temperature in Kodak D-19 developer which has the folowing composition:
  • the dye of this example has a maximum density in the unexposed areas of 1.90 and a minimum density in exposed areas of 0.66, a maximum sensitivity of 585 nm. and a relative speed of 479.
  • the control containing no dye shows a speed of less than 1, and exhibits no reversal.
  • This dye containing the desensitizing 1,3,3-trimethyl- 5-nitro-3H-indole nucleus is photographically tested by the exact procedure described in above Example 1. The results are recorded in Table 1 hereinafter. Referring to the table, it will be noted that the densities are 1.74 and 0.12 for the unexposed and exposed areas, respectively, with a maximum sensitivity at 570 nm. and a relative speed of 832. Accordingly, this dye is a good quality electron acceptor and spectral sensitizer for fogged direct positive silver halide emulsions.
  • This dye containing the desensitizing 3-ethyl-6-nitro benzothiazole nucleus is tested by the exact procedure of above Example 1 and found, as shown in Table l hereinafter, to be an excellent electron acceptor and spectral sensitizer for fogged direct positive photographic emulsions.
  • the densities are shown to be 1.46 and 0.05 for the unexposed and exposed areas, respectively, with a maximum sensitivity at 585 nm. and a relative speed of 912.
  • the above prepared dye containing the desensitizing 1, 3,3-trimethyl-5-nitro-3H-indole nucleus is tested by the exact procedure described in above Example 1.
  • the results in Table 1 hereinafter show densities of 1.47 and 0.08 in the unexposed and exposed areas, respectively, with maximum sensitivity at 570 nm. and a relative speed of 692, thereby indicating the dye of the above example is an excellent electron acceptor and spectral sensitizer for fogged direct positive photographic emulsions.
  • the mixture is then heated at reflux for 5 minutes. After chilling, the crude dye is collected on a filter, rinsed with ethanol and dried. The crude yield is 3.6 g. (74%) and, after one recrystallization from methanol, the yield of purified dye is 2.4 g. (49%), M.P. 277-278" C., d.
  • the crude yield is 4.6 g. (96%) and, after one recrystallization from N,N-dimethylacetamide/ methanol, the yield of purified dye is 2.1 g. (44%), M.P. 2s1-2s2 (3., d.
  • This dye containing the desensitizing 1,3-diethylimidazo]4,5-b]quinoxaline nucleus is tested by the exact procedure of above Example 1 and found, as shown in Table 1 hereinafter, to be an exceptionally useful electron acceptor and spectral sensitizer for fogged direct positive photographic emulsions.
  • the densities are shown to be 1.50 and 0.04 for the unexposed and exposed areas, respectively, with a maximum sensitivity at 545 nm. and a relative speed of 1290.
  • EXAMPLE 9 l,3-diethyl-2-[2-(1-p-nitrophenyl-2-pyrrolyl)vinyl] imidazo[4,5-b] quinoxalinium iodide 1 (p-nitrophenyl) 2 pyrrolecarboxaldehyde (1.1 g., .005 mole) and 1,3 diethyl 2 methylimidazo[4,5-b] quinoxalinium p-toluenesulfonate (2.1 g., .005 mole) are dissolved in acetic anhydride (15 ml.) and heated at reflux, with stirring, for 1% minutes. After chilling, the solid is collected on a filter and rinsed with acetone.
  • acetic anhydride 15 ml.
  • the filtrate is terated with ether (300 ml.) and, after decanting, a sticky residue is obtained.
  • the solid and sticky residue are combined and disolved in warm ethanol.
  • the ethanol solution is treated with an aqueous solution of sodium iodide (1.0 g.) and, after chilling, the solid is collected on a filter. After one recrystallization from ethanol, the yield of purified dye is 0.3 g. (11%), MP. 236-237" C., d.
  • This dye containing the desensitizing 1,3-diethyl-imidazo[4,5-b]quinoxaline nucleus is tested by the exact procedure of above Example 1 and is indicated by the values in Table 1 hereinafter, it is an excellent electron acceptor and spectral sensitizer for fogged direct positive photographic emulsions.
  • the desities are shown to be 1.17 and 0.05 for the unexposed and exposed areas, respectively, with a maximum sensitivity at 550 nm. and a relative speed of 1260.
  • Examples 10, 11 and 12 illustrate the remarkable extension of spectral sensitivity and increase in relative speed when the pyrrole nucleus is substituted at both the 1-position and the 5-position of the pyrrole ring.
  • This dye containing the desensitizing 1,3,3-trimethyl- 5-nitro-3H-indole nucleus is tested by the procedure described in above Example 1. The results are recorded in Tabel 1 hereinafter. Referring thereto, the densities are 1.64 and 0.06 for the unexposed and exposed areas, respectively, with maximum sensitivity at 625 nm. and a relative speed of 2400. These results indicate that this dye is an outstanding electron acceptor and spectral sensitizer for fogged direct positive silver halide emulsions.
  • EXAMPLE 12 2- [2- 1,5-diphenyl-2-pyrrolyl vinyl] 1 ,3 -diethylimidazo [4,5 -b] -quinoxalinium perchlorate 1,5-diphenylpyrrole-2-carboxaldehyde (2.5 g., .01 mole) and 1,3-diethyl-2methylimidazo[4,5-b]quinoxalinium ptoluene sulfonate (4.1 g., .01 mole) are dissolved in acetic anhydride (15 ml.) and heated at reflux, with stirring, for 2 minutes. After cooling, 175 ml. are added with stirring.
  • the ether is then decanted, the residue dissolved in a minimum of boiling ethanol, and then a hot aqueous solution of sodium perchlorate (1.5 g./ 10 ml.) is added. After chilling, the solid is collected on a filter and recrystallized from N,N-dimethylacetamide/ methanol. The yield is 2.7 g. (47%), MP. 293-294 C., dec.
  • This dye containing the desensitizing 1,3-diethylimidazo [4,5-b1quinoxaline nucleus is tested by the exact procedure of above Example 1 and, as shown by the values in Table 1 hereinafter, it is an outstanding electron acceptor and spectral sensitizer for fogged direct positive photographic emulsions.
  • the densities are 1.72 and 0.05 for the unexposed and exposed areas, respectively, with a maximum sensitivity at 600 nm. and a relative speed of 1590.
  • cyanine dyes of this invention having generally similar electron acceptor and spectral sensitizing properties may be prepared by appropriate selection of intermediates defined by Formulas II and III above.
  • Typical other dye compounds wherein Z of Formula I above completes a desensitizing nucleus includes, for example, the dye 3- ethyl 2 [2-(1-methyl-2-pyrrolyl)vinyl]-6-nitrobenzoxazolium salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc.
  • the dye 3-ethyl-2-[2- (1 methyl 2 pyrrolyl)vinyl]-6-nitrobenzoselenazolium salt e.g., the chloride, bromide, iodide, perchlorate, ptoluenesulfonate, etc. salts
  • the dye 3-ethyl-6-nitro-2-[2- (l-phenyl-Z-pyrrolyl)vinyl]benzoxazolium salt e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc.
  • the dye 3-ethyl-6-nitro-2-[2-(l-phenyl-Z-pyrrolyl)vinyl]benzoselenazolium salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salt), 3 phenyl-6-nitro-2-[2-(l-phenyl-Z-pyrrolyl)vinyl]benzothiazolium salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc.
  • the dye 3-ethyl-6-nitro-2-[2-(l-phenyl-Z-pyrrolyl)vinyl]benzoselenazolium salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc.
  • the dye 1,3-diallyl 2- 2- l-phenyl-Z-pyrrolyl vinyl] imidazo [4,5 -b quinoxazolium salt e.g., the chloride, bromide, iodide, perchlorate, p-toluenesul'fonate, etc. salts
  • the dye 1,3-diphenyl 2 [2-(1-phenyl-2-pyrrolyl)vinyl]imidazo[4,5-b] quinoxazolium salt e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc.
  • the dye 2-[2- (1,5 diphenyl 2-pyrrolyl)'vinyl]-1,3-diallylimidazo[4,5- b]quinoxazolium salt e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salts
  • the dye 2-[2- (1,5 diphenyl 2 pyrrolyl)vinyl]-1,3-diphenylimidazo [4,5-b]quinoxazolium salt e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salts
  • the like dyes e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salts
  • "Still other highly useful cyanine dyes of the invention wherein Z of Formula I above completes a sensitizing nucleus includes, for example, the dye 3-ethyl-2-[2-(lmethyl-2-pyrrolyl)vinyl]benzothiazolium salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salts), the dye 3-ethyl-2-[2-(1-methyl-2-pyrrolyl) vinyl]benzoxazolium salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc.
  • the dye 3-ethyl-2-[2-(1-methyl-2-pyrrolyl) vinyl]benzoxazolium salt e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulf
  • the dye 3-ethyl-2- [2- l-methyI-Z-pyrrolyl vinyl] benzoselenazolium salt e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salts
  • the like dyes e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salts
  • EXAMPLE l4 5-methylpyrrole-2carboxaldehyde In a 500 ml. 3-neck flask equipped with a reflux condenser, thermometer, stirring device, and a dropping funnel is placed N,N-dimethylformamide (19.0 g., 0.26 mole). After cooling to C., POCl (40 g., 0.26 mole) is added, with stirring, over the course of minutes with the temperature kept between 1020 C. The mixture is then allowed to stir at room temperature for 15 minutes and then dichloroethane (60 ml.) is added.
  • N,N-dimethylformamide (19.0 g., 0.26 mole).
  • POCl 40 g., 0.26 mole
  • the mixture is then allowed to stir at room temperature for 15 minutes and then dichloroethane (60 ml.) is added.
  • This compound is prepared in the manner described by Treibs and Dena, Ann., 589, 176.
  • EXAMPLE 20 To 9.0 pounds of a silver chloride gelatin emulsion containing an equivalent of grams of silver nitrate is added 0.017 gram of 3-ethy1-2-[2-(l-methyl-Z-pyrrolyl) vinyl] 6 nitrobenzothiazolium p toluenesulfonate (Example 3). The emulsion is coated on a non-glossy paper support, and is flashed with white light to give a density of 1.2 when developed in the following developer, diluted 1 part to 2 parts of water:
  • the light fogged material can be exposed to an image with light modulated by a Wratten No. 15 filter to give a direct positive image.
  • a Wratten No. 15 filter to give a direct positive image.
  • the dyes of Examples 6, 7, 8 and 9 are used in place of the above dye.
  • EXAMPLE 21 Seven pounds of a silver chloride gelatin emulsion containing the equivalent of 100 g. of silver nitrate is heated to 40 C. and the pH is adjusted to 7.8. Eight cc. of full strength (40%) formalin solution is added and the emulsion is held at 40 C. for 10 minutes. At the end of the holding period, the pH is adjusted to 6.0 and 0.125 g. of 2-[2-(1,S-diphenyl-Z-pyrrolyl)vinyl] 3 ethyl 6 nitrobenzothiazolium perchlorate is added (Example 10). The emulsion is coated on a support, and provides good direct positive images. Similar results are obtained when the dyes of Examples 11 and 12 are substituted for the above dye.
  • the photographic silver halide emulsion and other layers present in the photographic elements made according to the invention can be hardened with any suitable hardener, including aldehyde hardeners such as formaldehyde, and mucochloric acid, aziridine hardeners, hardeners which are derivatives of dioxane, oxypolysaccharides such as oxy starch or oxy plant gums, and the like.
  • the emulsion layers can also contain additional additives, particularly those known to be beneficial in photographic emulsions, including, for example, lubricating materials, stabilizers, speed increasing materials, absorbing dyes, plasticizers, and the like. These photographic emulsions can also contain in some cases additional spectral sensitizing dyes.
  • these emulsions can contain color forming couplers or can be developed in solutions containing couplers or other color generating materials.
  • useful color formers are the monomeric and polymeric color formers, e.g., pyrazolone color formers, as well as phenolic, heterocyclic and open chain couplers having a reactive methylene group.
  • the color forming couplers can be incorporated into the direct positive photographic silver halide emulsion using any suitable technique, e.g., techniques of the type shown in Jelley et al. U.S. Pat. 2,322,027, issued June 15, 1943, Fierke et a].
  • a direct positive emulsion in accordance with claim 1 containing a photographic color former 6.
  • a direct positive, photographic emulsion in accordance with claim 1 which comprises fogged silver halide grains, said grains being such that a test portion thereof, when coated as a photographic silver emulsion on a support to give a miximum density of at least about 1 upon processing for 6 minutes at about 68 F. in Kodak DK-SO developer, has a maximum density which is at least about 30% greater than the maximum density of an identical coated test portion which is processed for 6 minutes at about 68 F. in Kodak DK-SO developer after being bleached for about 10 minutes at about 68 F. in a bleach composition of:
  • a direct positive, photographic emulsion in accordance with claim 1 which comprises fogged silver halide grains, at least 95%, by weight, of said grains having a diameter which is Within about 40% of the mean grain diameter.
  • n represents a positive integer of from 1 to 2;
  • L represents a methine linkage;
  • R represents a member selected from the group consisting of an alkyl group, an alkenyl group and an aryl group;
  • R R R and R each represents a member selected from the group consisting of a hydrogen atom, an alkyl group, and an aryl group;
  • X represents an acid anion;
  • Z represents the non-metallic atoms required to complete a 5- to 6-membered nitrogen containing desensitizing nucleus.
  • a direct positive photographic emulsion in accordance with claim 9 which comprises fogged silver halide grains, said grains being such that a test portion thereof, when coated as a photographic silver halide emulsion on a support to give a maximum density of at least about 1 upon processing for 6 minutes at about 68 F. in Kodak DK-50 developer, has a maximum density which is at least about 30% greater than the maximum density of an identical coated test portion which is processed for 6 minutes at about 68 F. in Kodak DK-50 developer after being bleached for about 10 minutes at about 68 F. in a bleach composition of:
  • a direct positive photographic emulsion in accordance with claim 9 which comprises fogged silver halide grains, at least by weight, of said grains having a diameter which is within about 40% of the mean grain diameter.
  • a photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 7.
  • a photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 8.
  • a photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 9.
  • a photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 18.
  • a photographic element comprising a support having at least one layer containing a direct positive emulsion of claim 19.

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3816138A (en) * 1971-07-02 1974-06-11 Agfa Gevaert Ag Spectrally sensitized direct positive silver halide emulsion layers
US4006137A (en) * 1975-08-21 1977-02-01 E. R. Squibb & Sons, Inc. 2-Ethenyl imidazolium derivatives
US4839271A (en) * 1987-06-26 1989-06-13 E. I. Du Pont De Nemours And Company Direct positive dimethine cyanine dyes containing 1-aryl-2-heteroaryl indole nucleus
US4927933A (en) * 1987-06-26 1990-05-22 E. I. Du Pont De Nemours And Company Direct positive dimethine cyanine dyes containing 1-aryl-2-heteroaryl indole nucleus
US5004812A (en) * 1987-06-26 1991-04-02 E. I. Du Pont De Nemours And Company Direct positive dimethine cyanine dyes containing 1-aryl-2-heteroaryl indole nucleus
US5008401A (en) * 1990-04-17 1991-04-16 Asahi Chemical Co., Ltd. Cyanine compounds
US5087704A (en) * 1988-09-09 1992-02-11 Asahi Chemical Co., Ltd. Cyanine compounds
US5418126A (en) * 1992-11-19 1995-05-23 Eastman Kodak Company Furan or pyrrole substituted dye compounds and silver halide photographic elements containing such dyes
USRE35044E (en) * 1987-08-07 1995-09-26 Asahi Chemical Co., Ltd. Cyanine compounds
US6066443A (en) * 1994-05-18 2000-05-23 Eastman Kodak Company Blue sensitizing dyes with heterocyclic substituents

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3816138A (en) * 1971-07-02 1974-06-11 Agfa Gevaert Ag Spectrally sensitized direct positive silver halide emulsion layers
US4006137A (en) * 1975-08-21 1977-02-01 E. R. Squibb & Sons, Inc. 2-Ethenyl imidazolium derivatives
US4839271A (en) * 1987-06-26 1989-06-13 E. I. Du Pont De Nemours And Company Direct positive dimethine cyanine dyes containing 1-aryl-2-heteroaryl indole nucleus
US4927933A (en) * 1987-06-26 1990-05-22 E. I. Du Pont De Nemours And Company Direct positive dimethine cyanine dyes containing 1-aryl-2-heteroaryl indole nucleus
US5004812A (en) * 1987-06-26 1991-04-02 E. I. Du Pont De Nemours And Company Direct positive dimethine cyanine dyes containing 1-aryl-2-heteroaryl indole nucleus
USRE35044E (en) * 1987-08-07 1995-09-26 Asahi Chemical Co., Ltd. Cyanine compounds
US5087704A (en) * 1988-09-09 1992-02-11 Asahi Chemical Co., Ltd. Cyanine compounds
US5008401A (en) * 1990-04-17 1991-04-16 Asahi Chemical Co., Ltd. Cyanine compounds
US5418126A (en) * 1992-11-19 1995-05-23 Eastman Kodak Company Furan or pyrrole substituted dye compounds and silver halide photographic elements containing such dyes
US6066443A (en) * 1994-05-18 2000-05-23 Eastman Kodak Company Blue sensitizing dyes with heterocyclic substituents

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