US3545976A - Photographic emulsions containing alkoxydihydromerocyanines - Google Patents

Description

United States Patent 3,545,976 PHOTOGRAPHIC EMULSIONS CONTAINING ALKOXYDIHYDROMEROCYANINES Frank G. Webster, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Nov. 30, 1967, Ser. No. 686,817 Int. Cl. G03c N36 US. Cl. 96-126 33 Claims ABSTRACT OF THE DISCLOSURE Photographic silver halide emulsions are provided which contain compounds having 2-arylindole joined by an alkoxymethylene linkage to isoxazoline or pyrazoline.

This invention relates to novel photographic materials, and more particularly to a new class of chemical compounds, and to novel photographic silver halide emulsions containing such compounds.

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 highlight areas of the images obtained with these materials are substantially free from fog. However, known mate rials of this type have not exhibited the high speed required for many applications of photography. Also, such known materials in many cases have not shown the desired selective sensitivity, especially to radiation in the blue 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 blue and longer wavelength radiations.

I have now found that certain alkoxydihyromerocyamines are highly useful electron acceptors for direct positive photographic silver halide emulsions. They also form valuable spectral sensitizer combinations with certain dyes which by themselves do not sensitize direct positive emulsions.

The novel compounds of the invention can be added to photographic silver halide reversal systems, such as fogged direct positive emulsions. Direct positive silver halide emulsions containing the compounds of this invention are characterized by both good speed and sensitivity to radiation primarily in the blue region of the spectrum. The images produced with these novel direct positive emulsions are clear and sharp, and of excellent contrast,

It is, accordingly, an object of this invention to provide a new class of compounds which function as highly useful electron acceptors for direct positive photographic silver halide emulsions. Another object of this invention is to provide novel light sensitive photographic silver halide emulsions containing one or more of the novel compounds of the invention. Another object of this invention is to provide photographic elements comprising a support having thereon at least one layer containing a novel direct positive emulsion of the invention. Other objects will become apparent from this disclosure and the appended claims.

The new class of chemical compounds of the invention comprise first and second 5- to 6-membered nitrogen containing heterocyclic nuclei joined by an alkoxymethylene (CH(OR)--) linkage; the first of said nuclei being a 2-arylindole nucleus joined at the Z-carbon atom thereof ice to said linkage; and the said second nucleus being a 3- isoxazolin-S-one nucleus or a 3-pyrazoline-5-one nucleus joined at the 4-carbon atoms thereof to said linkage, to complete said compound.

The preferred chemical compounds of the invention that are particularly useful as electron acceptors for direct positive photographic silver halide emulsions are represented by the following general formulas:

wherein R represents an alkyl group (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc., R and R each represents an alkyl group, including substituted alkyl (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopro pyl, 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., li-hydroxyethyl, w-hydroxybutyl, etc., and alkoxyalkyl group, e.g., fi-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., fl-sulfatoethyl, w-sulfatobutyl, etc., an acyloXyalkyl group, e.g., fl-acetoxyethyl, 'y-acetoxypropyl, w-butyryloxybutyl, etc., an alkoxycarbonylalkyl group, e.g., fl-methoxycarbonylethyl, w-ethoxycarbonylbutyl, etc., or an aralkyl group, e.g., benzyl, phenethyl, etc., and the like; an alkenyl group, e.g., allyl, l-propenyl, Z-butenyl, etc.; R represents an aryl group, e.g., phenyl, tolyl, naphthyl, methoxyphenyl, chlorophenyl, etc.; R and R each represents an alkyl group (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc., or an aryl group, e.g., phenyl, tolyl naphthyl, methoxyphenyl, chlorophenyl, etc.; R 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, hexyl, decyl, dodecyl, etc., or an aryl group, e.g., phenyl, tolyl, naphthyl, methoxyphenyl, chlorophenyl, etc.; and R and R each represents a hydrogen atom, a nitro group, an alkyl group (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, decyl, dodecyl, etc., an alkoxy group such as methoxy, ethoxy, etc., a halogen atom such as chlorine, and the like. The above-defined chemical sensitizer compounds of the invention are powerful electron acceptors for direct positive photographic silver halide emulsions. In addition, they are useful desensitizers in emulsions such as used in the process decribed in Stewart and Reeves, US. Pat. No. 3,250,618, issued May 10, 1966.

The following compounds are typical of those described in the above formulas:

(l) 4 [Ethoxy (1-methyl-2-phenyl-3-indolyl)methyl]- 2-methyl-3-phenyl-3-isoxazolin-5-one (2) 4 [ethoxy (l-methyl--nitro-2-phenyl-3-indolyl)- methyl]-2-methyl-3-phenyl-3-isoxazolin-5-one (3) 4 [(1 butyl-5-chloro2-phenyl-3-indolyl)ethoxymethyl] -2-methyl-3 -phenyl-3 -isoxazolin-5-one (4) 4 [butoxy-(l ethyl-2-phenyl-3-indolyl)methyl-2- methyl-3-phenyl-3-isoxazolin-5-one (5) 4 [(1 allyl 2 phenyl-3-indolyl)ethoxymethyl]- 2,3-dimethyl-3-isoxazoline-5-one (6) 2 allyl-4-[(1 butyl-5-methoxy-2-phenyl-3-indolyl)- ethoxymethyl]-3-phenyl-3-isoxazolin-5-one (7) 2 methyl-4-[(1-methyl-2-phenyl-3-indolyl)-propoxymethyl]-3-phenyl-3-isoxazolin-5-one (8) 4 [ethoxy-(S-methoxy-l-methyl-2-phenyl-3-indolyl)- methyl]-1-ethyl-2-methyl-3-phenyl-3-pyrazolin-5-one (9) 4 [(S-chloro-1-methyl-2-phenyl-3-indolyl)-propoxymethyl]-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one (10) 4 [(l-allyl 2-phenyl-3-indolyl)-methoxymethyl]- 2,3-diethyl-1-phenyl-3-pyrazolin-5-one (11) 4 [ethoxy(5 ethyl-1-methyl-2-phenyl-3-indolyl)- methyl]2,3-dimethyl-1-phenyl-3-pyrazolin-5-one The novel compounds defined by Formulas I and II above are conveniently prepared, for example, by heating (1) a quaternated merocyanine dye selected from one of the following formulas:

wherein R R R R R R R and R are as previously defined, and X represents an acid anion, e.g., chloride, bromide, iodide, perchlorate, sulfamate, ptoulenesulfonate, methyl sulfate, fiuoborate, etc., with (2) an alkanol such as methanol, ethanol, propanol, butanol, decanol, dodecanol, etc., preferably in the proportions of from 1 to moles or more of (2) to each mole of (1), and preferably in the presence of a conventional basic condensing agent such as triethylamine. The product is then separated from the reaction mixture by evaporation or precipitation with ether and purified by one or more recrystallizations from an appropriate solvent such as ethanol. The reaction can be conducted at from about 20 C. up to reflux. Reaction at reflux ternperature is preferred.

The intermediate quaternated merocyanine dyes defined by Formulas III and IV above can be readily prepared by condensing (1) a heterocyclic compound of the formula:

by converting the purified dye thus obtained to a quaternated salt by conventional quaternization methods. For further details of this process, reference can be had to copending application of Brooker and Webster, Ser. No. 666,513, filed Sept. 8, 1967, and titled Novel Dyes and Direct Positive Emulsions.

Direct positive emulsions are provided herein which contain the combination of the novel compounds described above and a methine dye, preferably a cyanine dye, to obtain good speed as well as spectral sensitization. The methine dye employed in this combination is one which, by itself, does not spectrally sensitize direct positive emulsions but which does spectrally sensitize such emulsions when employed with a chemical sensitizer described above.

In accordance with the invention, novel direct positive photographic silver halide emulsions are prepared by incorporating one or more of the novel chemical compounds 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, irridium, 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 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 chemical compound can vary widely, e.g., from about to 2,000 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-aminophenol sulfate 2.5 Sodium sulfite (anhydrous) 30.0 Hydroquinone 2.5 Sodium metaborate 10.0 Potassium bromide 0.5

Water to make 1.0 l.

The chemical compounds of this invention are also advantageously incorporated in direct positive emulsions of the type in which a silver halide grain has a Waterinsoluble silver salt center and an outer shell composed of a fogged water-insoluble silver salt that develops to silver Without exposure.

The chemical compounds 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 sutficient 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 sufficiently 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 Potasium 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 Sauvenier in Science et Industries Photographiques, vol. XXVIII, January 1957, pp. 1 to 23 and January 1957, pp. 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 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 chemical compounds 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. 619,936, filed Mar. 2, 1967, now Pat. No. 3,501,307, and titled Photographic Reversal Materials. 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-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 six minutes at about 68 F. in Kodak DK-SO developer after being bleached for about minutes at about 68 F. in a bleach composition of:

Potassium cyanide-50 mg. Acetic acid glacial)3 .47 cc. Sodium acetate11.49 g. Potassium bromide119 mg. 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 silve 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. As already indicated, the maximum density of the unbleached coating will be at least 30% greater, generally at least 60% greater, then 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 chlorobromoiodide, and the like. Silver halide grains having an average grain size less than about one micron, preferably less than about 0.5 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. 619,909 filed Mar. 2, 1967, now Pat. No. 3,501,306 and titled Direct Positive Photographic Emulsions. Such grains advantageously have a rather uniform diameter frequency distribution, as described and claimed in Illingsworth US. patent application Ser. No. 619,948, filed Mar. 2, 1967, now Pat. No. 3,501,305, and titled Photographic Reversal Emulsions. 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. LXXIX, 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 chemical compounds of the invention and mentioned combinations 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 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. Useful combinations can include any amount of the dye compound for increasing the spectral sensitivity, but preferably from about to 95 parts by weight thereof to from 95 to 5 parts by weight of a chemical compound of the invention, to make a total of 100%.

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 U.S. 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. The novel chemical compounds 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 4- [ethoxy-( 1mcthyl-2-phenyl-3-indolyl methyl] -2- methyl-3-phenyl-3-isoxazolin-5-one A mixture of l-methyl-3-[(2-methyl-5-oxo-3-phenyl-3- isoxazolin 4 yl)methylene]-2 phenyl 3H indolium iodide and ethanol are heated at the refluxing temperature until little or no color is left. The solution is then concentrated to about one-fifth the volume and chilled. The precipitate is collected and then recrystallized from ethanol. The tan crystals have a melting point of 157- 158 C., with decomposition.

The novel compound prepared in Example 1 is then photographically tested for its usefulness as an electron acceptor and spectral sensitizer for fogged direct posi tive 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, shredded and washed by leaching with cold water in the conventional manner. The emulsion is reduction-gold fog 'cd 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 compound of the above example, 4-l ethoxyl-methyl-2-phenyl-3-indolyl)methyl] -2-methyl-3-phenyl 3-isoxazolin-5-one, is then added to the above fogged emulsion in amount sufficient to give a concentration of about from 0.5 to 0.8 grams 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 Eastman lb sensitometer using a tungsten light source and processed for 6 minutes at room temperature in Kodak Dl9 developer which has the following composition:

N-methyl-p-aminophenol sulfate 2.0 Sodium sulfite (anhydrous) 90.0 Hydroquinone 8.0 Sodium carbonate (monohydrate) 52.0 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 compound of this example has a maximum density in the unexposed areas of 1.86 and a minimum density in exposed areas of 0.03, and a relative speed of 347. These results indicate that the compound of the above example qualifies as a powerful electron acceptor for direct positive photographic silver halide emulsions. Further reference to Table I indicates clearly that combination thereof with an equal amount of a dye (which does not by itself sensitize direct positive emulsions) such as 5-chloro-3- ethyl 2-(2-phenyliminopropylidene)benzothiazoline produces a spectrally sensitized foggcd direct positive photographic emulsion. The photographic test on the above combination gives densities of 1.86 and 0.03 for the unexposed and exposed areas, respectively, and a relative speed of 302. These values are practically the same as recorded for the compound of Example 1 alone. However, a maximum sensitivity at 465 nm. is obtained with the combination. Accordingly, the compound of the above example is not only a powerful electron acceptor, but in combination with certain dyes such as above mentioned improves the blue sensitivity of. direct positive emulsions. Excellent magenta images are obtained when the color former, 1- (2,4,6 trichlorophenyl) 3 {3 [(2,4 di tert pentylphenoxy)acetamido]benzimido}-2 pyrazolin-S-one, is incorporated in the emulsions of this example, the emulsions are coated on a support, exposed to a tungsten source through Wratten filters No. 61 and No. 16, and reversal processed as described in Graham et al. US. Pat. No. 3,046,129, issued July 24, 1962, in Example (a) C01. 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.

In place of the intermediate quaternated merocyanine dye in the above example, there can be substituted any other of those defined by Formula III above to give the corresponding chemical sensitizers of the invention coming under Formula I above, including for example, the compound 4-[ethoxy-( 1,1-methyl 5 nitro-2 phenyl 3- indolyl)methyl]-2-methyl-3-phcnyl-3-isoxazolin-5-one, the compound 4-[(1-butyl-5-chloro-2-phenyl-3-indolyl)ethoxy-methyl]-2-methy1-3-phenyl-3-isoxazolin-5-one, the compound 4-[butoxy-(1-ethyl-2-phenyl-3-indolyl)methyl] 2- methyl 3 phenyl 3 isoxazolin 5 one, the compound 4 [1 allyl 2 phenyl 3 indolyl)ethoxymethyl] 2,3- dimethyl-3-isoxazolin-5-one, the compound 2-allyl-4[(lbuty 5 methoxy 2 phenyl 3 indolyl)[ethoxymcthyl]-3phenyl-3-isoxazolin-5-one, etc. These compounds likewise function as effective electron acceptors for direct positive photographic emulsions, and also to form advantageous combinations with dyes such as men-- tioned previously characterized by having both excellent electron acceptor and spectral sensitizer properties in direct positive emulsions.

the exact test procedure described in above Example 1. These illustrative results are listed in the following table.

* 5-chloro-3-cthyl-2-(Z-phenyliminopropylidcne)benzothiazoline.

EXAMPLE 2 2-methyl-4 1-methyl-2-phenyl-3-indolyl -propoxymethyl] -3-phenyl-3-isoxazolin-5 -one i Q CH3-N )on o OCHaCHzCHa CNCH3 out.

our.

A mixture of 5.1 g. (1 mol.) of 1-methyl-3-[(2-methyl- 5 oxo 3 phenyl 3 isoxazolin 4 yl)methylene] 2- pheny1-3H-indolium iodide, 2 ml. of triethylarnine and ml. of propanol is heated at steam-bath temperature until little or no color is left to the solution. The reaction mixture is cooled and ether is added, the precipitate is collected and washed with ether. After one crystallization from ethanol the yield of buff crystals is 9%, melting point of 145147 C., with decomposition.

This compound is photographically tested for reversal and sensitizing properties by the procedure described in above Example 1. The results are recorded in Table I hereinafter. Referring thereto, it will be noted that the densities are 1.90 and 0.08 for the unexposed and exposed areas, respectively, and the relative speed is 501. The above results clearly indicate that the compound of this example is an excellent electron acceptor for fogged direct positive photographic emulsions. It also forms advantageous combinations With dyes which are not themselves sensitizers for direct positive emulsions, such as with 5-chloro-3-ethyl-2-(2 phenyliminopropylidene)benzothiazoline, characterized by having both excellent electron acceptor and spectral sensitizing properties for direct positive photographic emulsions.

From the foregoing, it will be apparent that the corresponding novel chemical compounds containing the pyrazolin-5-one nucleus as defined in Formula 11 above can be readily prepared in accordance with the procedures of above Examples 1 and 2, and that these compounds also are characterized by excellent electron acceptor properties, and good spectral sensitizing properties when in combination with non-desensitizing sensitizers, for direct positive photographic emulsions. Such novel compounds include the compound 4-[ethoxy-(5-methoxy-1-methyl-2- phenyl-3-indolyl)methyl]-1-ethyl 2 methyl-3-phenyl-3- pyrazolin-S-one, the compound 4-[(5-chloro-1-methyl-2- phenyl-3-indolyl) propoxymethyl]-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one; the compound 4-[ (1-allyl-2-phenyl-3- indolyl) methoxymethyl] 2,3-diethyl-1-phenyl3-pyrazolin-5-one, and the compound 4-[(ethoxy-S-ethyl-l-methyl 2-phenyl-3-indolyl)-methyl] 2,3-dimethyl-1-phenyl-3- pyrazolin-S-one.

The effectiveness of the compounds of Examples 1 and 2 as electron acceptors, and in combination with nonsensitizing dyes to provide spectral sensitization for fogged direct positive photographic emulsions is determined by The following examples further illustrate the preparation of fogged, direct positive photographic emulsions and elements with the novel compounds of the invention.

EXAMPLE 3 To 9.0 pounds of a silver chloride gelatin emulsion containing an equivalent of grams of silver nitrate is added 0.017 gram of 4-[ethoxy-(1-methyl-2-phenyl-3- indolyl)-methyl]-2-methy1-3-phenyl-3-isoxazolin 5 one (Example 1). 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 fogg'ed material can be exposed to an image with light modulated by a Wratten No. 15 filter to give a direct positive image. Generally similar results are obtained when the compound of Example 2 is used in place of the above compound.

EXAMPLE 4 Seven pounds of a silver chloride gelatin emulsion containing the equivalents 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 methyl 4 [(1 methyl 2 phenyl 3 indolyl) propoxymethyl]-3-phenyl-3 -isoxazolin-5-one is added (Example 2). The emulsion is coated on a support, and provides good direct positive images. Similar results are obtained when the compound of Example 1 is substituted for the above compound.

By substituting other chemical compounds of the invention, as defined in Formulae I and II above, into the procedure of the above examples, 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 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. Furthermore, these emulsions can contain color forming couplers or can be devolopcd in solutions containing couplers or other color generating materials. Among the useful color formers are the monomeric and polymeric color formers, e.g., pyrazoline 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., US. Pat. 2,322,027, issued June 15, 1943, Fierke et al., US. Pat. 2,801,171, issued July 30, 1957, Fisher U.S. Pats. 1,055,155 and 1,102,028, issued Mar. 4, 1913 and June 30, 1914, respectively, and Wilmanns US. 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 with the spirit and scope of the invention as described hereinabove, and as defined in the appended claims.

I claim:

1. A direct positive photographic silver halide emulsion containing at least one compound selected from those comprising first and second S-membered nitrogen containing heterocyclic nuclei joined by alkoxymethylene linkage; the first of said nuclei being 2-arylindole joined at the B-carbon atom thereof to said linkage; and said second nucleus being selected from the group consisting of 3-isoxazolin-5-one joined at the 4-carbon atom thereof to said linkage, and 3-pyrazolin6-one joined at the 4-carbon atom thereof to said linkage.

2. A direct positive emulsion in accordance with claim 1 wherein said second nucleus is 3-isoxazolin-5-one.

3. A direct positive emulsion in accordance with claim 1 wherein said second nucleus is 3-pyrazolin-5-one.

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

7. A direct positive emulsion in accordance with claim 1 containing a dye, which does not by itself sensitize direct positive emulsions.

8. A direct positive emulsion in accordane with claim 1 containing the dye 5-chloro-3-ethyl-2-(2-phenylirninopropylidene)benzothiazoline.

9. A direct positive, photographic emulsion in accordance with claim 1 in which the said silver halide is present in the form of 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 a developer having the following composition:

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

Water to make 1.0 1.

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] said developer after being bleached for about 10 minutes at about 68 F. in a bleach composition of:

Potassium cyanide\50 mg.

Acetic acid (glacial)-3.47 cc.

Sodium acetate-1l.49 g.

Potassium bromide-l 19 mg. Water to-1 liter 10. A direct positive, photographic emulsion in accordance with claim 1 in which the said silver halide is present in the form of 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.

11. A direct positive photographic silver halide emulsion containing at least one compound selected from one of those having the following general formulas:

wherein R represents an alkyl group; R and R each represents a member selected from the group consisting of an alkyl group, and an alkenyl group; R represents an aryl group; R and R each represents a member selected from the group consisting of an alkyl group and an aryl group; R represents a member selected from the group consisting of a hydrogen atom, an alkyl group and an aryl group; and R and R each represents a member selected from the group consisting of a hydrogen atom, a halogen atom, an alkoxy group, a nitro group, and an alkyl group.

12. A direct positive emulsion in accordance with claim 11 wherein said compound is represented by the following formula:

wherein R represents an alkyl group, R and R each represents a member selected from the group consisting of an alkyl group and an alkenyl group; R represents an aryl group; R represents a member selected from the group consisting of an alkyl group and an aryl group; and R and R each represents a member selected from the group consisting of a hydrogen atom, a halogen atom, an alkoxy group, a nitro group, and an alkyl group.

13. A direct positive emulsion in accordance with claim 12 wherein said compound is 4-[ethoxy-(1-methyl-2- phenyl 3-indolyl)methyl]-2-methyl-3-phenyl-3-isoxazolin-5-one.

14. A direct positive emulsion in accordance with claim 13 wherein said compound is 2-methyl-4-[(1-methyl-2- phenyl 3 indolyl)-propoxymethyl]-3-phenyl-3-isoxazolin-5-one.

15. A direct positive emulsion in accordance with claim 12 in which the said silver halide is present in the form of fogged silver halide grains.

16. A direct positive emulsion in accordance with claim 12 in which the said silver halide is present in the form of reduction and gold fogged silver halide grains.

17. A direct positive emulsion in accordance with claim 12 containing a color former.

18. A direct positive emulsion in accordance with claim 13 12 containing a dye which by itself does not sensitize direct positive emulsions.

19. A direct positive emulsion in accordance with claim 12 containing the sensitizer -chloro-3-ethyl-2-(2-phenyliminopropylidene)benzothiazoline.

20. A direct positive photographic emulsion in accordance with claim 11 in which the said silver halide is present in the form of 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 a developer having the following composition:

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

Water to make 1.01.

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 said developer after being bleached for about 10 minutes at about 68 F. in bleach composition of:

Potassium cyanide-50 mg. Acetic acid glacial)3 .47 c.c. Sodium acetate-J 1.49 g. Potassium bromide-119 mg. Water to1 liter 21. A direct positive photographic emulsion in accordance with claim 11 in which the said silver halide is present in the form of 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.

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

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 10.

25. A photographic element comprising a support hav ing thereon at least one layer containing a direct positive emulsion of claim 12.

26. A photographic element comprising a support having thereon at least one layer containing a direct positive emulsion of claim 19.

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

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

29. A light sensitive photographic silver halide emulsion containing at least one compound selected from those comprising first and second S-membered nitrogen containing heterocyclic nuclei joined by alkoxymethylene linkage; the first of said nuclei being Z-arylindole joined at the 3-carbon atom thereof to said linkage; and said second nucleus being selected from the group consisting of 3-isoxazolin-5-one joined at the 4-carbon atom thereof to said linkage; and 3-pyrazolin-5-one joined at the 4-carbon atom thereof to said linkage.

30. A light sensitive photographic silver halide emulsion in accordance with claim 29 wherein said second nucleus is 3-isoxazolin-5-one.

31. A light sensitive photographic silver halide emulsion in accordance with claim 29 wherein said second nucleus is 3-pyrazolin-5-one.

32. A light sensitive photographic silver halide emulsion in accordance with claim 29 wherein said compound is 4 [ethoxy (l-methyl-2-phenyl-3-indolyl)methyl]-2- methyl-3-phenyl-3-isoxazolin-5-one.

33. A light sensitive photographic silver halide emulsion in accordance with claim 29 wherein said compound is 2 methyl-4-[(1-methyl-2-phenyl-3-indolyl)-propoxymethyl]-3-phenyl-3-isoxazolin-5-one.

References Cited UNITED STATES PATENTS 3,287,136 11/1966 McBride 96-106 3,314,796 4/1967 GoetZe et a1. 96-101 FOREIGN PATENTS 1,048,888 11/1966 Great Britain.

WILLIAM D. MARTIN, Primary Examiner M. SOFOCLEOUS, Assistant Examiner U.S. Cl. X.R.