US3558320A

US3558320A - Direct positive silver halide emulsions containing 3 - nitrosoindole cyanine dyes

Info

Publication number: US3558320A
Application number: US660173A
Authority: US
Inventors: Leslie G S Brooker; John D Mee
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1967-08-14
Filing date: 1967-08-14
Publication date: 1971-01-26
Anticipated expiration: 1988-01-26
Also published as: GB1232093A; BE719182A; FR1584136A

Abstract

DIRECT POSITIVE EMULSIONS ARE SPECTRALLY SENSITIZED WITH CYANINE DYES DERIVED FROM 1,2-DISUBSTITUTED 3-NITROSOINDOLES.

Description

United States Patent Int. Cl. G03c N36 US. Cl. 96-101 26 Claims ABSTRACT OF THE DISCLOSURE Direct positive emulsions are spectrally sensitized with cyanine dyes derived from 1,2-disubstituted 3-nitrosoindoles.

This invention relates to novel photographic materials, and more particularly to new and improved direct positive photographic silver halide emulsions containing certain cyanine dyes, and to photographic elements prepared With such novel emulsions.

It is known that direct positive images can be obtained with certain types of photographic silver halide emulsions. For example, photographic emulsions have been proposed for this purpose comprising an electron acceptor 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 emulsions is that the high-light areas of the images obtained with these materials are substantially free from fog. However, known materials of this type have not exhibited the high speed required for many applications of photography. Also, such known materials have not shown the desired selective sensitivity, especially to radiation in the green to orange 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 selective sensitivity to longer than blue wavelength radiations.

It is, accordingly, an object of this invention to provide new and improved direct positive photographic silver halide emulsions, and more particularly fogged emulsions of this type containing one or more of the cyanine dyes of the invention. Another object of this invention is to provide novel light-sensitive photographic elements comprising a support material having thereon at least one layer of the novel direct positive photographic emulsions of this invention. Other objects will become apparent from the disclosure and the appended claims.

We have now found that cyanine dyes derived from certain 1,2 disubstituted 3 nitrosoindoles are excellent electron aceptors and spectral sensitizers in 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 sensitivity to radiation in the green to orange region of the spectrum, with maximum sensitivity occurring in the region of about 560 635 11111. The images produced with these new direct positive photographic emulsions are clear and sharp, and of excellent contrast.

Suitable cyanine dyes for preparing the novel and improved direct positive photographic silver halide emulsions, and more particularly fogged emulsions of this type, include carbocyanine dyes represented by the following general formula:

wherein Q represents the non-metallic atoms required to complete a 2-arylindole nucleus joined by the 3-carbon "ice atom thereof to the N atom in said formula; L represents a methine linkage; and D represents the non-metallic atoms required to complete a heterocylic aromatic nucleus containing a hetero nitrogen atom, joined by a carbon atom thereof to said methine linkage.

One highly useful class of carbocyanine dyes employed in the invention include the dyes having the formula:

wherein n represents a positive integer of from 1 to 2; L repersents a methine linkage, e.g., -CH=,

C(C H etc.; R represents an alkyl group, including substituted alkyl, (preferably a lower alkyl containing from 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., ,B-hydroxyethyl, w-hydroxybutyl, etc., an alkoxyalkyl group, e.g., B-methoxyethyl, w-butoxybutyl, etc., a carboxyalkyl group e.g., B-carboxyethyl, w-carboxybutyl, etc., a sulfoalkyl group, e.g., B- sulfoethyl, w-sulfobutyl, etc., a sulfatoalkyl group, e.g., fi-sulfatoethyl, w-sulfatobutyl, etc., an acyloxyalkyl group, e.g., ,B-acetoxyethyl, 'y-acetoxypropyl, w-butyryloxybutyl, etc., an alkoxycarbonylalkyl group, e.g., 5- methoxycarbonylethyl, w-ethoxycarbonylbutyl, etc., or an aralkyl group, e.g., benzyl, phenethyl, etc., and the like; an alkenyl group, e.g., allyl, l-propenyl, 2-butenyl, etc., or an aryl group, e.g., phenyl, tolyl, naphthyl, methoxyphenyl, chlorophenyl, etc. R represents an alkyl group (preferably a lower alkyl containing from 1 t0 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc., or an aryl group, e.g., phenyl tolyl, naphthyl, methoxyphenyl, cholorophenyl, nitrophenyl, etc.; R repersents an aryl group, e.g., phenyl, toyly, naphthyl, methoxyphenyl, nitrophenyl, chlorophenyl, etc.; A represents the non-metallic atoms required to complete an aryl ring e.g., phenyl, tolyl, naphthyl, methoxyphenyl, chlorophenyl, nitrophenyl, etc. ring; X represents and acid anion e.g., chloride, bromide, iodide, thiocyanate, sulfamate, perchlorate, p-toluenesulofonate, methyl sulfate, ethyl sulfate, etc.; and Z represents the non-metallic atoms required to complete a sensitizing or a desensitizing heterocyclic nucleus containing from 5 to 6 atoms in the heterocyclic ring including those known to give useful cyanine dyes, which nucleus may contain a second hetero atom such as oxygen, sulfur, selenium or nitrogen, such as the following nuclei: 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, 5 bromobenzothiazole, 6 bromobenzothiazole, 5 chloro 6 nitrobenzothiazole, 4 phenylbenzothiazole, 5 phenylbenzothiazole, 4 methoxybenzothiazole, 5 methoxybenzothiazole, 6 methoxybenzothiazole, 5 iodobenzothiazole, 6 iodobenzothiazole, 4 ethoxybenzothiazole, 5 ethoxybenzothiazole, tetrahydrobenzothiazole, 5,6 dimethoxybenzothiazole, 5, 6 dioxymethylenebenzothiazole, 5 hydroxybenzothiazole, 6 hydroxybenzothiazole, a naphthothiazole, p naphthothiazole, 5,5 naphthothiazole, 5 methoxy [3,6 naphthothiazole, ethoxy 3 naphthothiazole, 8 methoxy a naphthothiazole, 7 methoxy a naphthothiazole, 4 methoxythianaphtheno 7,6',4,5 thiazole, nitro group substituted naphthothiazoles, etc.; an oxazole nucleus, e.g., 4 methyloxazole, 4-nitro-oxazole, 5 methyloxazole, 4-phenyloxazole, 4,5-diphenyloxazole, 4 ethyloxazole, 4,5 dimethyloxazole, 5 phenyloxazole, benzoxazole, 5 chlorobenzoxazole, 5 methylbenzoxazole, 5 phenylbenzoxazole, 5- or 6-nitrobenzoxazole, 5 chloro 6-nitrobenzenoxazole, 6-methylbenzoxazole, 5,6 dimethylbenzoxazole, 4,6 dimethylbenzoxazole, 5 methoxybenzoxazole, 5 ethoxybenzoxazole, 5- chlorobenzoxazole, 6 methoxybenzoxazole, 5 hydroxybenzoxazole, 6 hydroxybenzoxazole, u naphthoxazole, 13 naphthoxazole, nitro group substituted naphthoxazoles, etc.; 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, or naphthoselenazole, 8 naphthoselenazole, nitro group substituted naphthoselenazoles, etc.; a thiazoline nucleus, e.g., thiazoline, 4 methylthiazoline, 4-nitrothiazoline, etc.; a pyridine nucleus, e.g., 2 pyridine, 5 methyl 2 pyridine, 4 pyridine, 3 methyl 4 pyridine, nitro group substituted pyridines, etc.; a quinoline nucleus, e.g., 2 quinoline, 3 methyl 2 quinoline, 5 ethyl 2 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, 1 isoquinoline, 6 nitro 1 isoquinoline, 3,4 dihydro 1 isoquinoline, 3 isoquinoline, etc.; a 3,3 dialkylindolenine nucleus, preferably having a nitro or cyano substituent, e.g., 3,3 dimethyl 5 or 6 nitroindolenine, 3,3- dimethyl 5- or 6 cyanoindolenine, etc.; and, an imidazole nucleus e.g., imidazole, 1 alkylirnidazole, l alkyl- 4 phenylimidazole, l alkyl 4,5 dimethylimidazole, benzimidazole, l alkylbenzimidazole, l aryl 5,6- dichlorobenzimidazole, l alkyl a naphthimidazole, 1 aryl 3 naphthimidazole, 1 alkyl 5 methoxy-anaphthimidazole, etc., an imidazo[4,5-b]quinoxaline nucleus, e.g., 1,3 dialkylimidazo[4,5-b]quinoxaline such as 1,3 diethylimidazo[4,5-b]quinoxaline, 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-b1quinoxaline, etc., 1,3 diarylimidazo[4,5-b]quinoxaline such as 1,3 phenylimidazo[4,5-b]quinoxaline, 6 chloro 1,3 diphenylimidazo[4,5-b]quinoxaline, etc.; a 3,3 dialkyl 3H pyrrolo[2,3-b] pyridine nucleus, e.g., 3,3 dimethyl 3H pyrrolo[2,3-b]pyridine, 3,3-diethyl- 3H pyrrolo[2,3-b] pyridine, etc.; a thiazolo[4,5-b]quinoline nucleus, and the like. Nuclei wherein Z completes an imidazo [4,5-b]quinoxaline nucleus, or a nitro group substituted thiazole, oxazole, selenazole, thiazoline, pyridine, quinoline or imidazole nucleus are termed desensitizing nuclei; dyes containing such nuclei give especially useful direct positive emulsions and are the preferred dyes of the invention.

As used herein 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 80 percent loss in blue speed of the emulsion when sensitometrically exposed and developed three minutes in Kodak developer D-19 at room temperature. Advantageously, the desensitizing nuclei are those which, when converted to a symmetrical carbocyanine dye and tested as just described, essentiall completely desensitize the test emulsion to blue radiation 4 (Le, cause more than about 90 to 95% loss of speed to blue radiation).

The cyanine dyes defined by Formula I above are conveniently prepared, for example, by heating a mixture of (1) a heterocyclic compound of the formula:

The intermediate compounds of Formula III above are conveniently prepared, for example, by reacting a mixture comprising approximately 2 moles of sodium nitrate with 1 mole of a compound for the formula:

wherein R R and A are as previously defined.

In accordance with the invention, 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, rholium, platinum, palladium, iridium, etc., preferably in the form of soluble salts thereof, e.g., potassium chloroaurate, auric chloride, (NH PdCl and the like.

Useful concentrations of reducing agent and metal compound (e.g., metal salt) can be varied over a considerable range. As a general guideline, good results are obtained using about .05 to 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 to 2000 mg. and preferably from about 400 to 800 mg. per mole of silver halide in the direct positive emulsions.

As used herein, and in the appended claims, fogged refers to emulsions containing silver halide grains which produce a density of at least 0.5 when developed, without 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.

DEVELOPER G. N-methyl-p-aminopheuol sulfate 2.5 Sodium sulfite (anhydrous) 30.0 Hydroquinone 2.5 Sodium metaborate 10.0 Potassium bromide 0.5

Water to mac 1.0 l.

The dyes of this invention are also advantageously incorpoarted 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 waterinsoluble 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 US. patent application Ser. No. 448,467, filed Apr. 15, 1965, now US. Pat. 3,367,778 issued Feb. 6, 1968. For example, 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 sufliciently 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.

DEVELOPER A G N-methyl-p-aminophenol sulfate 2.5 Ascorbic acid 10.0 Potassium metaborate 35.0 Potassium bromide 1.0

Water to 1 liter. pH of 9.6.

Before the shell of water-insoluble silver salt is added to the silver salt core, 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. Such centers can be obtained by various techniques as described herein. Chemical sensitization techniques of the type described by Antoine Hautot and Henri Saubenier in Science et Industries Photographiques, vol. XXVIH, January 1957, pp. 1-23 and January 1957, pp. 57-65 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 sensitization, 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 US. patent application Ser. No. 609,794, filed Jan. 17,

1967, and titled Photographic Reversal Materials 111, now abandoned, and continuation-in-part application Ser. No. 619,936 filed Mar. 2, 1967, now US. Pat. 3,501,307 issued Mar. 17, 1970. 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. 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 six minutes at about 68 F. in Kodak DK50 developer after being bleached for about 10 minutes at about 68 F. in a bleach composition of:

Potassium cyanide mg 50 Acetic acid (glacial) cc 3.47 Sodium acetate g 11.49 Potassium bromide mg 119 Water to 1 liter.

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 iden tical coating which is processed for six minutes at 68 F. in Kodak DK50 developer after being bleached for about 10 minutes at 68 F. in the potassium cyanide bleach composition. As already indicated, 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 exemplified by silver bromide, silver iodide, silver chloride, silver chlorobromide, silver bromoiodide, silver chlorobromide, and the like. Silver halide grains having an average grain size less than about one micron, preferably less than about 0.15 micron, give particularly good results. The silver halide grains can be regular and can be any suitable shape such as cubic or octahedral, as described and claimed in Illingsworth US. patent application Ser. No. 609,778, filed Jan. 17, 1967, and titled Direct Positive Photographic Emulsions 'I, now abandoned, and continuation-in-part application Ser. No. 619,909 filed Mar. 2, 1967, now US. Pat. 3,501,306 issued Mar. 17, 1970. Such grains advantageously have a rather uniform diameter frequency distribution, as described and claimed in Illingsworth US. patent application Ser. No. 609,790, filed Ian. 17, 1967, and titled Photographic Reversal Emulsions II, now abandoned, and continuation-impart application Ser. No. 619,948 filed Mar. 2, 1967, now US. Pat. 3,501,305 issued Mar. 17, 1970. For example, at least 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, can be determined using conventional methods, e.g., as shown in an article by Trivelli and Smith entitled Empirical Relations Between Sensitometric and Size-Frequency Characteristics in Photographic Emulsion Series in The Photographic Journal, vol. LXXlX, 1949, pp. 330-338. 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 DK-50 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.

In the preparation of the above photographic emulsions, the dyes of the invention are advantageously incorporated in the washed, finished silver halide emulsions 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 eflect 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 as 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 element can also contain dispersed polymerized vinyl compounds. Such compounds are disclosed, for example, in US. Pats. 3,142,568; 3,193,386; 3,062,674 and 3,220,844- and include the water insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

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.

The 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(ethylene 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 invention is further illustrated by the following examples.

EXAMPLE 1 3 '-ethyll-methyl-2-pheny1-8-aza-3 -indolothiacarbo cyanine iodide CzHs 1 1-methyl-3-nitroso-2-phenylindole (1.0 g., 1 mol.) and 3-ethyl-2-methy1benzothiazolium iodide (1.22 g., 0.95 mol.) in ethanol (20 ml.) are heated at reflux for 3 /2 hours. The mixture is chilled and the solid collected and washed with ether. After two recrystallizations from ethanol, the yield of purified dye is 0.76 g. (36%), M.P. 226227 C., dec.

The above dye containing the sensitizing benzothiazoliurn 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 35 minutes. The emulsion is chill-set, shreaded 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 60 minutes at 65 C. and then adding 4.0 mg. of potassium chloroaurate per mole of silver and heating for 60 minutes at 65 C. The dye of the above example is then added to the above fogged emulsion in amount sufiicient to give a concentration of 0.08 gram of the dye per mole of silver. The resulting emulsion is coated on a cellulose acetate film support at a coverage of 100 mg. of silver and 400 mg. of gelatin per square foot of support.

A sample of the coated support is then exposed on an Eastman Ib sensitometer using a tungsten light source and processed for 6 minutes at room temperature in Kodak D-19 developer which has the following composition:

N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite (anhydrous) 90.0 Hydroquinone 8.0 Sodium carbonate (monohydrate) 52.5 Potassium bromide 5.0

Water to make 1.0 liter.

then fixed, washed and dried. The results are listed in Table I hereinafter. Referring thereto, it will be seen that the dye of this example has a maximum density in the unexposed areas of 1.70 and a minimum density in exposed areas of 0.23, a maximum sensitivity of 570 nm, and a relative speed of 276. These results indicate that the dye compound of the above example is a moderately good electron acceptor and spectral sensitizer. It thus provides good quantity direct positive photographic silver halide emulsions. Excellent magenta images are obtained when the color former 1-(2,4,6-trichlorophenyl)-3,3'-(2",4-dit-amylphenoxyacetamido)benzimidazo-S-pyrazolone is incorporated in the emulsion of this example, the emulsion is coated on a support, exposed to a tungsten source through Wratten filter No. 61 and No. 16, and reversal processed as described in Graham et al. US. Pat. 3,046,- 129, issued July 24, 1962, in Example (a), col. 27, lines 27 et seq. except that black-and-white (MQ) development is omitted, the color development is reduced to one minute and is conducted in total darkness until after fixing.

EXAMPLE 2 3-ethyl-1-methyl-2-phenyl-8-aza-3-indo1oselenacarbocyanine iodide Q CHaN )-N=CH i 69/ C0115 III 1 l-methyl-3-nitroso-2-phenylindole (1.0 g., 1 mol.) and 3-ethyl-2-methylbenzoselenazoliumiodide (1.5 g., 1 mol.) in ethanol (30 ml.) are heated at reflux for 5 hours. The mixture is chilled and the solid collected and washed with ether. After two recrystallizations from methanol, the yield of purified dye is 0.57 g. (23%), MP. 231232 C., dec.

This dye containing the sensitizing benzoselenazolium nucleus is tested by the exact procedure described in above Example 1 and found, as shown in Table 1 hereinafter, to be a moderately good electron acceptor and spectral sensitizer for fogged direct positive photographic emulsions. The densities are shown to be 1.74 and 0.12 for the unexposed and exposed areas, respectively, with a maximum sensitivity at 590 nm. and a relative speed of 174.

EXAMPLE 3 3-ethyl-1methyl-6-nitro-2-phenyl-8-aza-3-indolothiacarbocyanine p-toluenesulfonate osomn,

C2115 1-methyl-3-nitroso-2-phenylindole (1.18 g., 1 mol.) and 3-ethyl-2-methyl-6-nitrobenzothiazolium p toluenesulfonate (1.98 g., 1 mol.) in ethanol ml.) are heated at reflux on a steam-bath for /2 hour. The mixture is chilled and the solid collected. After two recrystallizations from methanol, the yield of purified dye is 0.70 g. (23%), M.P. 255 C., dec.

The above prepared dye containing the desensitizing 6-m'trobenzothiazolium nucleus is tested by the exact procedure described in above Example 1. The results are shown in Table 1 hereinafter. Referring thereto, it will be seen that the dye of this example has a maximum density in the unexposed areas of 1.34 and a minimum density in the exposed areas of 0.34, a maximum sensitivity of 625 and a relative speed of 1260. These results indicate that the above prepared dye is an excellent electron acceptor and spectral sensitizer for fogged direct positive emulsions.

EXAMPLE 4 5-chloro-1.3'-dimethyl-6-nitro-2-pheny1-8-aza-3-indolothiacarbocyanine p-toluenesulfonate This dye is prepared and purified in the manner described for Example 3, except that 5-chloro-2,3-dimethyl- 6-nitrobenzothiazolium p-toluenesulfonate (1 mol.) is used in place of 3-ethyl-Z-methyl-6-nitrobenzothiazolium ptoluenesulfonate. The yield of purified dye is 0.20 g. (17%), M.P. indistinct.

This dye containing the 5-chloro-6-nitrobenzothiazolium nucleus is tested by the exact procedure described in above Example 1. The results in Table I hereinafter show densities of 1.52 and 0.70 in the unexposed and exposed areas, respectively, with maximum sensitivity at 620 nm. and a relative speed of 550, thereby indicating that the above prepared dye is a good electron acceptor and spectral sensitizer for fogged direct positive emulsions.

EXAMPLE 5 1,3-diethyl-1'-methyl-2'-phenyl-1 l-azaimidazo [4,5 -l)] quinoxalino-3'-indolocarbocyanine iodide This dye is prepared in the manner described for Example 4, except that 1,3-diethyl-2-methylimidazo[4,5-b] quinoxalinium iodide (1 mol.) is used in place of 3-ethyl- 2-methyl 6 nitrobenzothiazolium p-toluenesulfonate. After one recrystallization from methanol, the yield of purified dye is 0.11 g. (4%), M.P. 250 C., dec.

The above prepared dye containing the imidazo[4,5-b] quinoxaliniurn nucleus is tested in accordance with the procedure described in above Example 1. The results are shown in Table I hereinafter. Referring thereto, it will be seen that the densities are 1.26 and 0.09 in the unexposed and exposed areas, respectively, the maximum sensitivity is at 585 nm. and the relative speed is 501. Accordingly, the dye of this example is a highly useful electron acceptor and spectral sensitizer for fogged direct positive emulsions.

It will be apparent from the foregoing that the intermediates (Formula II above) employed in the above Examples 1 to 5 can be substituted by equivalent amounts of any other of those defined by Formula II above to give still other related cyanine dye salts of the invention having generally similar properties as electron acceptors and spectral sensitizers for direct positive, and more particularly fogged direct positive, photographic reversal emulsions, for example, the dye 3'-ethyl (or methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc.)-lmethyl 2 phenyl-8-aza-3-indolothiacarbocyanine salt (quaternary salt e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salt); the dye 3'-ethyl (or methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc.)-1-methyl 2 phenyl-8-aza-3-indoloselenacarbocyanine salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salt); the dye 3-ethyl (or methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc.)-1-methyl 2 phenyl 8 aZa-3-indolooxacarbocyanine salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salt); the dye 3-ethyl (or methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc.)-l-methyl 6' nitro-2-phenyl-8-aza-3-in dolothiacarbocyanine salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salt); the dye 3'-ethyl (or methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc.)-1-methyl 6' nitro-2-phenyl-8-aza- 3-indoloselenacarbocyanine salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salt); the dye 1,3-diethyl (or dimethyl, diethyl, dipropyl, diisopropyl, dibutyl, dihexyl, diallyl, diphenyl, etc.)-l'-methyl- 2-phenyl 11 aZaimidazo[4,5-b]quinoxalino-3-indolocarbocyanine salt (e.g., the chloride, bromide, iodide, perchlorate, p-toluenesulfonate, etc. salt); and the like.

It will also be apparent that the intermediates (Formula III above) employed in the above Examples 1 to 5 can be substituted by equivalent amounts of any other of those defined by Formula III above to give yet other related cyanine dye salts of the invention having generally similar properties as electron acceptors and spectral sen sitizers for direct positive photographic emulsions.

The following example illustrates the preparation of some of the 1,2-disubstituted-3-nitrosoindole intermediates defined by Formula III above.

EXAMPLE 6 1-methyl-3-nitros0-2-phenylindole A concentrated aqueous solution of sodium nitrite (1.38 g., 2 mols.) is added slowly, with stirring, to a solution of 1-methy-2-phenylindole (2.07 g., 1 mol.) in acetic acid ml.) at room temperature. After 2 hours, the mixture is slowly diluted with water (500 ml.), then stirred for /2 hour. The solid (1.08 g., 78%) was collected. After recrystallization from ethanol, the yield was 0.83 g., (40%) of emerald green plates, M.P. 143144 C dec.

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. Furthermore, these emulsions can contain color forming couplers or can be developed in solutions containing couplers or other color generating materials. Among the 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 TABLE I Density Dye coneentration Relative Maximum Minimum g./mole clear unexposed exposed Sensltmlng, Dye of example No. silver speed areas areas max. (nm.)

1 90 276 1. 70 23 570 2. 20 174 1. 74 12 690 3- 477 1, 260 1. 34 34 625 4. 284 550 1. 52 70 620 5 200 501 1. 26 09 585 Control 0. 00 1 1. 90 No reversal.

The following examples further illustrates the preparation of fogged, direct positive photographic emulsions and elements with the cyanine dyes of the invention.

EXAMPLE 7 To 9.0 pounds of silver chloride gelatin emulsion containing an equivalent of 100 grams of silver nitrate is added 0.017 gram of 3'-ethyl-1-methyl-6-nitro-2-phenyl- 8-aza-3-indolothiacarbocyanine iodide (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:

Grams N-methyl-p-aminophenol sulfate 3.1 Sodium sulfite, des. 45 Hydroquinone 12 Sodium carbonate, des 67.5 Potassium bromide 1.9

Water to 1 liter.

The light fogged material can be exposed to an image with light modulated by a Wratten No. 15 filter to give a good quality direct positive image. Generally similar results are obtained when the dye of Example 4 is used in place of the above dye.

EXAMPLE :8

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 the 1,B-diethyl-1'-methyl-2'-phenyl-l l-azaimidazo [4,5-b] quinoxalino-3'-indolocarbocyanine iodide is added (Example 5). The emulsion is coated on a support, and provides good quality direct positive images. Satisfactory results are obtained also when the dyes of Examples 1 and 2 are substituted in above Examples 7 and 8.

By substituting other dye compounds of the invention, as defined in Formula I above, into the procedure of the above examples, generally similar fogged, direct positive photographic silver halide emulsions and photographic elements may be prepared.

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 aldehydre 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 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. US. Pat. 2,322,027, issued June 15, 1943, Fierke et al. US. Pat. 2,801,171, issued July 30, 1957, Fisher US. Pat. 1,055,155 and 1,102,028, issued Mar. 4, 1913 and June 30, 1914, respectively, and Wilmanns U.S. Pat. 2,186,849 issued Jan. 9, 1940. They can also be developed using incorporated developers such as polyhydroxybenzenes, aminophenols, 3-pyrazolidones, and the like.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

We claim:

1. A fogged direct positive photographic silver halide emulsion containing at least one cyanine dye having the formula:

wherein Q represents the non-metallic atoms required to complete a 2-arylindole nucleus joined by the 3-carbon thereof to the N atom in said formula; L represents a methine linkage; and, D represents the non-metallic atoms required to complete a desensitizing heterocyclic aromatic nucleus containing a hetero nitrogen atom, joined by a carbon atom thereof to said methine linkage.

2. A direct positive emulsion in accordance with claim 1 wherein said cyanine dye contains a nitrosubstituted desensitizing nucleus.

3. A direct positive emulsion in accordance with claim 1 wherein said cyanine dye contains an imidazo[4,5-b] quinoxaline desensitizing nucleus.

4. A direct positive emulsion in accordance with claim 1 in which the said silver halide is present in the form of chemically fogged silver halide grains.

5. A direct positive emulsion in accordance with claim 1 in which the said silver halide is present in the form of reduction and gold fogged silver halide grains.

6. A direct positive emulsion in accordance with claim 1 containing a photographic color coupler dispersed in coupler solvent.

7. 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 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-SO developer after 13 being bleached for about minutes at about 68 F. in a bleach composition of:

wherein 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 represents a member selected from thegroup consisting of an alkyl group and an aryl group; R represents an aryl group; A represents the non-metallic atoms required to complete an aryl ring; X represents an acid anion; and, Z represents the nonmetallic atoms required to complete a desensitizing heterocyclic nucleus containing 5 to 6 atoms in the ring.

10. A direct positive emulsion in accordance with claim 9 wherein said Z represents the non-metallic atoms required to complete a nitrobenzothiazole nucleus.

11. A direct positive emulsion in accordance with claim 9 wherein said Z represents the non-metallic atoms required to complete a nitrobenzoxazole nucleus.

12. A direct positive emulsion in accordance with claim 9 wherein said Z represents the non-metallic atoms required to complete a nitrobenzoselenazole nucleus.

13. A direct positive emulsion in accordance with claim 9 wherein said Z represents the non-metallic atoms required to complete an imidazo[4,5-b1quinoxaline nucleus.

14. A direct positive emulsion in accordance with claim 9 in which the said silver halide is present in the form of chemically fogged silver halide grains.

15. A direct positive emulsion in accordance with claim 9 in which the said silver halide is present in the form of reduction and gold fogged silver halide grains.

16. A direct positive emulsion in accordance with claim 9 containing a photographic color coupler dispersed in coupler solvent.

17. 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-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:

18. 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 size which is within about 40% of the average grain size.

19. A fogged direct positive emulsion containing a cyanine dye selected from the group consisting of a 3'- ethyl 1-methyl-2-phenyl-8-aza-3-indolothiacarbocyanine salt, a 3'-ethyl-1-methyl-2-phenyl-8-aza-3-indoloselenacarbocyanine salt, a 3-ethyl-1-methyl-6'-nitro-2-phenyl-8- aza 3 indolothiacarbocyanine salt, a 5'-chloro-1,3-dimethyl 6'-nitro-2-phenyl-8-aza-3-indolothiacarbocyanine salt, and a 1,3-diethyl-1'-methyl-2'-phenyl-1l-azaimidazo- [4,5-b]quinoxalino-3'-indolocarbocyanine salt.

20. A photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 1.

21. A photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 7.

22. A photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 8.

23. A photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 9.

24. A photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 17 25. A photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 18.

26. A fogged direct positive photographic silver halide emulsion containing at least one cyanine dye selected from those represented by the following general formula:

wherein 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 represents a member selected from the group consisting of an alkyl group and an aryl group; R represents an aryl group; A represents the non-metallic atoms required to complete an aryl ring; X represents an acid anion; and, Z represents the nonmetallic atoms required to complete a nucleus selected from the group consisting of a nitro-substituted thiazole nucleus, a nitro-substituted oxazole nucleus, a nitro-substituted selenazole nucleus, a nitro-substituted thiazoline nucleus, a nitro-substituted pyridine nucleus, at nitro-substituted quinoline nucleus, a nitro-substituted imidazole nucleus and an imidazo [4,5-b]quinoxazoline nucleus.

References Cited Mann et al.: Chemical Society Journal, pp. 670-677 (1944).

J. TRAVIS BROWN, Primary Examiner U.S. Cl. X.R. 96-102; 260240