CA1140791A - Photographic emulsions including as nucleating agent a heterocyclic compound with arylamino vinylene or aryl oxy vinylene substituents - Google Patents

Abstract

Abstract of the Disclosure Silver halide emulsions are disclosed containing silver halide grains capable of forming an internal latent image. incorporated in the emulsions as a nucleating agent is a heterocyclic compound having an arylaminovinyl-ene or aryloxyvinylene substituent, thereby permitting a direct-positive image to be formed on imagewise exposure and photographic processing.

Description

P~OT~G~APHIC E~lULSIO~S AND ELEM~NTS CAPABLE OF
FOR~ING DIRECT-POSITIVE IMAGES
Field of the Invention The present invention is directed to silver halide emulsions and photographic elements useful in form-ing direct-positive images. More specifically, this in-vention is directed to internal latent image-forming sil-ver halide emulsions containing a nucleating agent and to photograpnic elements containing these emulsions. This invention is also directed to processes of forming direct-posicive im~ges.
Back~round of the Invention ~

Pnotograpnic elements which produce images having an opcical density directly related to tne radiation received on exposure are said to be negative-working. A
positive pnotographic image can De formed by producing a negative photographic image and then forming a second pho-tograpnic image WhiCh is a negative of the first negative, that is, a positive image. A direct-positive image is understood in pnotography to be a positive image that is formed without first forming a negative image. Positive dye images which are not direct-positive images are com-monly produced in color photography by reversal processing in which a negative silver image is formed and a com-plementary positive dye image is then formed in the samephotograpnic element. The term "direct reversal" has been applied to direct-positive photographic elements and pro-cessing which produces a positive dye image without form-ing a negative silver image. Direct-positive photography in general and direct reversal photography in particular are advantageous in providing a more straight-forward approach to obtaining positive pnotographic images.
One conventional approach ror obtainin~ direct-positive pnotographic images is to employ silver halide emulsions which are initially surface fogged. Surface fog is imagewise removed in exposed areas. ~hen a photon is acsor~ed by a silvec nalide grain, a nole (a positive charge) and an electron are released in tne silver nalide crystal. I~ligration of the hole to the grain surface 4~

resul~s in o~idation of a metallic silver atom (fog) ~o its ionic form, tnereby reducing the developability of the grain. The present invention is totally inapplicable ~o surface-fogged direct-positive emulsions, A second conventional approach to forming direct-positive images, to which the present invention rela~es, is to use photographic elements employing inter-nal latent image-forming silver nalide grains. After imagewise exposure, the siLver nalide grains are developed with a surface developer, that is, one which will leave the latent image sites within tne silver halide grains substantially unrevealed. Simultaneously, either by uni-form light e~posure or Dy tne use of a nucleating agent, the silver halide grains are subjected to development con-ditions that would cause fogging of a negative-working photographic element. The internal latent image-forming silver nalide grains WhiCh received actinic radia~ion dur-ing imagewise e.~posure develop under tnese conditions at a compara~ively slow rate, as compared to tne internal latent image-forming silver halide grains not imagewise e~posed. The result is a direc~-positive silver image.
In color pnotography, the oxidized developer that is pro-duced during silver development is used to produce a cor-responding positive, direct reversal dye image. ~ulti-color direct reversal pnotographic images have been e~ten-sively investigated in connection with image-transfer pho-tography.
It has been found advantageous to employ nucleat-ing agents in preference to uniform lignt e.~posure in che process described above. The term "nucleating agent" is employed nerein to mean a fogging agent capable of per-mitting tne selective development of internal latent image-forming silver halide grains wnich nave not been imagewise exposed in preference to the development of sil-ver nalide grains naving an internal latent image formed~y imagewise e~posure.
~ nile nUcLeating agents nave been long known to tne pnotographic art, recent interest has focused on iaen-.. .

~4~7~--3--tifying nucleating agents that are effective in relatively low concentration levels and that can be incorporated directly into silver nali~e emulsions. ~xemplary of known incorporated nucleating agents are those disclosed Dy ~hitmore U.~. Patent 3,2~7,55~, Lincoln et al U.~. Patent 3,~15,615, ~pence et al U.S. Patent 3,718,470, ~urtz et al U.~. Patents 3,719,494 and 3,734,7~8, Lincoln et al U.~.
Patent 3,759,901, Leone et al U.S. Patents 4,030,925 and 4,~80,~7, Adachi et al U.S. Patent 4,115,122, von Konig et al U.S. Patent 4,139,387, and U.K. Patents 2,011,391 and 2,012,443.
Spence et al U.S. Patent 3,718,470 discloses some o~ tne compounds employed in this invention as nucleating agents to be useful as intermediates in synthesizing spectral sensitizing dyes. Jones et al U.S. Patent ~,563,754, Vanassche et al U.S. Patent 4,059,450, and L~linara et al Defensive Putllication T967,002 disclose as sensitizers or desensitizers (but not nucleating agents) coinpoun~s containing a p-aminostyryl group attached to a neterocyclic nucleus of the type found in cyanine dyes.
~ummary of the Invention In one aspect this invention is directed to a silver nalide emulsion comprised of silver naliae grains capaDle of forming an internal latent image ana, adso~bed to Che surface of tne silver nalide grains, a nucleating agent. The nucleating agent is a compound of the formula (I) ~2 H
~ I I r~
zl ~_y2-c=c-c z2 Y m-l R An_ wherein Z~ represents the atoms completing an aromatic 3~ Carbocyclic nucleus of ~rom 6 to 10 carbon atoms;
yl and y2 are independently selected from among a divalent oxygen atom, a divalent sulEur atom, and ~2 represents the atoms completing a netero-cylclic nucleus of tne type found in cyanine dyes;

)7~1 A is an adsorp~ion promoting moiety;
m and n are l or 2; and ~ 2, and ~3 are in~ependently cnosen from ~n~ group consisting or hy~rogen, al~yl, aryl, alK-aryl, and aralkyl and Rl ana ~3 are adaitionally inde-pendently cnosen trom tne group consiscing of acyl, alKen-yl, and alkynyl, tne alipnatic moieties containing up to 5 CarDOn atoms and the aromatic moieties containing 6 to l0 carbon atoms.
In another aspect this invention is directed to a pnoto~raphic element comprised of a support and at least one layer of a silver halide emulsion as described above.
In still another aspect ~his invention is direct-ed to a pcocess of surface developing an imagewise exposed pnocographic element as described above to produce à vis-ible direct-positive image. The improvement comprises developing in tne presence of the nucleating agent ot formula I, identified above.
~escription of Prererred Embodiments ~eferring to formula I, above, the nucleating agents employed in the practice of this invention are cnaracterized Dy containing an aromatic carbocyclic nuc-leus of from 6 to 10 carbon atoms, sucn as a phenyl or naphtnyl nucleus. In a preferred form Gl re~resents the atoms completing a phenyl nucleus. Tne aromatic carbo-cyclic nucleus is linked through a divalent chalcogen, such as divalent o~ygen or sulfur atom, or a trivalent nitrogen atom to a vinylene group which is in turn bonded to a carbon atom of a neterocyclic nucleus of the type found in cyanine dyes. To facilitate description these nucleating agents are hereinafter referred to as vinylene nucleating agents.
Tne aromatic carbocyclic nucleus can be unsubsti-tuted (e.g., phenyl or naphthyl)~ in which case Rl is hydrogen and m is 1. The divalent vinylene group can also De unsubsticuted, in whicn case ~2 iS hydrogen. When y2 iS

31 14~79~

R3, wnicn satisfies tne tnird valence of the nitrogen atom, can be ny~rogen.
~t is also contemplated that the aromatic carbo-cyclic nucleus, tne trivalent ni~rogen atom, and the vinylene group can De subscituted, eacn independently of the otner. In preferred substituted forms, ~ 2, and ~3 can be selecced from among al~yl, aryl, alkaryl, ana aralKyl subscituents. ~or e~ample, Kl, ~2, and 0 1~3 can De independently selected from among al~yl groups, sucn as, metnyl, etnyl, n-propyl, i-p;opyl, _-bucyl, i-butyl~ t-butyl, n-pentyl, i-penty1, and neo-penLyl; aryl groups, such as, pneny1 and napnthyl;
alkaryl groups, sucn as, p-tolyl, o-tolyl, xylyl, ana

2,~,5-trimethylpnenyl; and aralkyl groups, such as, ~enzyl and pnenethyl. In further ~referred forms ~l and 1~3 can additionally be selected independently ~rom among acyl, alkenyl, and alkynyl substi~uents. Pre~erred acyl su~stituents are carboxyl substituents, such as, formyl, acetyl, propanoyl, butanoyl, and pentanoyL. E~emplary preferred alkenyl substituents are vinyl and allyL.
~emplary preferred alkynyl sUDStiCUen~s are propargy1 and ~-butynyl. In the foregoing preferred ~orms of ~', K2, and ~3, tne aliphatic moieties contain up to 5 car~on atoms and tne aryl moieties contain 6 to 10 carbon acoms. In a specifical1y preferred ~orm, ~1, when present as a substituent, is linked co t~e aromatic carbocyclic nucleus tnrough Y', whicn can be divalent cnalcogen, sucn as a divalent oxygen or sulfur atom, or -~-R3 Linked to the vinylene group in ~ormula I is a heterocyclic nucleus of the type found in cyanine dyes.
That is, Z~ completes a 5- or 6-membered heterocyclic ring containing at least one, typically one or two, non-metallic hetero atoms chosen from the group consisting o~c~alcogen, such as, oxygen, sulfur, and selenium, and nitrogen, the remaining ring atoms being carbon. In a preferred form a benzo group is fused to tne heterocyc1ic ring.
.

In a specifically preferred form the heterocyclic nucleus in the compound of ~ormula I can be (II) ____Z3 _____ An_ -C=(CH-CH)p l=N-R4 wherein A is an adsorption promoting moiety;
n and p are 1 or 2;
R4 represents a ring nitrogen substituent of 1~ the type found in cyanine dyes;
Z3 completes a heterocycle forming at least one 5- or 6-membered ring containing 1 or 2 hetero atoms in the ring chosen from the group consisting of oxygen, sulfur, selenium, and nitrogen, the remaining ring atoms being carbon; and X is an acid anion, i~ required to satisfy charge neutrality.
In preferred forms Z3 represents the non-metallic atoms required to complete a heterocyclic nucleus having from 5- to 6-atoms in a heterocyclic ring, which can contain a second hetero atom, e.g., a hetero oxygen, sulfur, or selenium atom, or a second nitrogen atom, such as, a thiazole nucleus (e.g., thiazole, 4-me~hyltbi-azole, 4-phenylthiazole, 5-methylthiazole, 4,5-dimethyl-thiazole, and 4,5-dip~enylthiazole), a benzothiazole nuc-leus (e.g., benzothiazole, 4-chlorobenzothiazole, 5-chlorobenzothiazole, 4-methylbenzothiazole, 6-methylbenzo-thiazole, 5-bromobenzothiazole, 5-methoxybenzothiazole, 6-iodobenzothiazole, and 5,6-dimethoxybenzothiazole), a naphthothiazole nucleus (e.g., a-naphthothiazole, ~-naphthothiazole, 5-methoxy-~-naphthotbiazole, 8-ethoxy-~-naphtbothiazole, and ~,~-naphthothiazole), a thia-naphtheno-7',6',4,5-thiazole nucleus (e.g., 4'-methoxy-thianaphtheno-7',6',4,5~thiazole), an oxazole nucleus (e.g., 4-methyloxazole, 5-methyloxazole, 4-phenyloxazole, 4,5-diphenyloxazole, 4-ethyloxazole, and 4,5-diethyl-oxazole), a benzoxazole nucleus (e.g., benzoxazole, 5-chlorobenzoxazole, 5-methylbenzoxazole, 5-phenylbenzox-azole, 6-methylbenzoxazole, 5,6-dimethylbenzoxazole, 4,6-79~L
--7--dimetnylbenzoxazole, 5-ethoxybenzo~azole, 5,6-dichloro-benzoxazole, and 5-hydro~ybenzoxazole), a naphthoxazole nucleus (e.g., ~-naphthoxazole, ~-naphthoxazole, and ~,~-naphthoxazole), a selenazole nucleus (e.g., 4-methylselenazole and 4-phenylselenazole), a benzoselen-azole nucleus (e.g., benzoselenazole, 5-chlorobenzoselen-azole, 6-methoxyDenzoselenazole, 5-hydroxybenzoselenazole, and a tetrahydrobenzoselenazole)~ a naphthoselenazole nucleus (e.g., ~-naphthoselenazole, ~-naphtho-selenazole, and ~,~-naphthoselenazole), a thiazoline nucleus (e.u., cniazoline and 4-metnylthiazoline), a 2-pyridine nucleus (e.g., 2-pyridine and 5-methyl-2-pyridine), a 4-pyridine nucleus (e.g., 4-pyridine and

3-metnyl-4-pyridine), a 2-quinoline nucleus (e.g., 2-quinoline, 3-methyl-2-quinoline, 5-ethyl-2-quinoline, 6-chloro-2-quinoline, 8-chloro-2-quinoline, 4-methoxy-2-quinoline and ~-hydroxy-2-quinoline, a 4-quinoline nucleus (e.g., 4-quinoline, 5-methyl-4-quinoline, 7-methyl-4-quinoline, and 8-chloro-4-quinoline), a l-isoquinoline nucleus (e.g., l-isoquinoline and 3,4-dihydro-1-isoquinoline), a 3-isoquinoline nucleus (e.g., 3-isoquinoline), a 3,3-dialkylindolenine nucleus (e.g., 3,3-dimethylindolenine, 3,3,5-trimethyl-indolenine, and 3,3,7-trimethylindolenine), an imidazole nucleus (e.g., imidazole, l-alkylimidazole, l-alkyl-~-phenylimidazole, and l-alkyl-4,5-dimethylimidazole), a Deinzimidazole nucleus (e.g., benzimidazole, l-alkylbenz-imidazole, l-arylbenzimidazole, and 5,6-dichlorobenzimid-azole), or a napnthimidazole nucleus (e.g., l-alkyl-~-napnthimadazole, l-aryl-~-naphthimidazole, and l-alkyl-5-methoxy-~-naphthimidazole).
R4 can be any ring nitrogen substituent ~ound in cyanine dyesO Such substituent is commonly an alkyl group having 1 to 18 carbon atoms, such as, methyl, ethyl, propyl, i-propyl, butyl, i_butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetra-decyl, pentadecyl, hexadecyl, heptadecyl~ and octadecyl.
R4 can alternatively be an aryl group (e.g., phenyl or 07~

naphthyl), an alkaryl group (e.g., tolyl, ethylphenyl, and xylyl), an arylkyl group (e.g., benzyl and phenethyl), or an alkenyl group (e.g., allyl, propenyl, l-butenyl, and 2-butenyl). The above hydrocarbon groups when present in cyanine dyes are frequently in turn substituted with halogen atoms or groups such as hydroxy, alkoxy, carboxy, sulfo, sulfato, alkanoyloxy, and alkoxycarbonyl groups.
It is generally preferred that the aliphatic moities of the R4 substituent contain 5 or fewer carbon atoms while 10 the aromatic moieties contain 6 to 10 carbon atoms. The aromatic moieties are most preferably phenyl groups.
It is well understood in the art that hetero-cyclic nuclei of cyanine dyes promote their adsorption to silver halide grain surfaces. Hence, the nucleating 15 agents of this invention, which contain a cyan;ne dye ~et~rocyclic nucleus, require no other adsorption promot-ing moiety to achieve effective association with silver halide grain surfaces. However, since higher degrees of adsorption to silver halide grain surfaces can reduce the 20 concentration of nucleating agent required to produce efficient nucleation, it is recognized that an additional adsorption promoting moiety can be usefully incorporated into the nucleating agent.
The adsorption promoting moiety can be chosen 25 from among those known to promote adsorption of photogra-phic addenda to silver halide grain surfaces. For exam-ple, a wide variety of such moieties are known and used in the photographic art to adsorb stabilizers, antifoggants 9 and sensitizing dyes to silver halide grain surfaces.
3 Typically such moieties contain a sulfur or nitrogen atom ~` capable of complexing with silver or otherwise exhibiting an affinity for the silver halide grain surface. The adsorption pro~oting sulfur atom can be present in the form of a thiacarbonyl or mercapto group. Particularly 35 useful mercapto groups are attached to a carbon atom of a carbocyclic or heterocyclic aromatic ring and may tautomerize ~o a thiacarbonyl form. Particularly ~seful thiacarbonyl groups can be present in acyclic moieties, . .

g sucn as thiourea moieties, or in heterocyclic nuclei (typically 5- or 6-membered heterocyclic rings) of the type found in stabilizers, antifo~gants and merocycanine spectral sensitizing dyes. Thio moieties, such as found in thiazole nuclei exhibit sufficient affinity for silver haLide grain surfaces to enhance adsorption. Nitrogen atom containing adsorption promoting moieties are typified by those containing a trivalent nitrogen atom with a displaceable hydrogen atom appended. Tne trivalent atom is usually a member of a 5- or 6-membered neterocyclic ring of the type found in stabilizers, antifoggants, and cyanine spectral sensitizing dyes.
The adsorption promoting moiety A can De any moiety which enhances the nucleating agent's capability of Deing adsorbed to tne silver halide grain surface. In structural terms, such moieties can include adsorption promoting groups selected from the following classes:
nitrogen-containing heterocyclic groups bearing an ionizable hydrogen atom, for example, triazole and benzotriazole radicals, and in particular 1,2,3-benzo-triazole-5-yl; tetrazole radicals, and in particular 5-tetrazolyl; benzimidazole radicals, particularly 1,3-benzimidazol-5-yl; imidazole, indazole, triazole, imidazotetrazole, and pyrazolotriazole radicals as well as hydroxytetraazindene and -pentaazaindene radicals, such as 4-hydroxy-6-methyl-1,3,3a,7-tetra-azaindene radicals;
heterocyclic groups having at least one ring nitrogen and at least one further ring atom which is o~ygen, sulfur, or selenium, for example, thiazole, benzothiazole, naphthothiazole, thiazoline, thiazoline thione, thiazolidine, thiadiazole, and rhodanine radi-cals as well as oxygen and selenium analogues thereof;
for example, benzoxazole and benzoselenazole radicals;
groups bearing mercapto ~roups or groups whicn can tautomerize to the thiol form; for example, radi-cals of alkyl thiols or derivatives such as cysteine;
or 179~L

heterocyclic rings bearing a mercapto group, such as, benzothiazole-2-thiols, benzoxazole-2~thiols, l-phen-yl-5-mercaptotetrazoles, and 1,2,3-benzotriazine-4-thiones; and groups containing the function S
/N-C- ;
for example, radicals of alkyl or aryl substituted thioamides (including thioureas), thiohy~antoins, thiobarbituric acids, and their derivatives; for example, thioacetamides or thioanilides, thiosemicarb-azides, and dithiocarbamates.
In addition to a group of the type identi~ied above capable of complexing with silver or otherwise pro-ducing an affinity for the silver halide grain surfaces, the adsorption promoting moiety can (but need no~) include a divalent linking group of any synthetically convenient form providing an attachment to the heterocyclic nucleus.
Among specifically contemplated linkages are amido, sul-fonamido, carbamoyl, sulfamoyl, and ester divalent linking groups, preferably in combination with divalent hydro-carbon or hydrocarbonoxy linking groups, such as, alkyl-ene, alkyleneoxy, and phenylene groups, wherein the alkyl-ene groups contain from 1 to 5 carbon atoms. Such dival-ent linking groups, when present, are artifacts of com-pound synthesis and exhibit only a secondary influence on : the activity of the compounds preparea. lt is therefore appar.ent that such divalent linking groups can be chosen from among a wide variety of known linking groups.
A preferred class of adsorption promoting groups are thioamides of the formula (III) S

I_Q_ wherein A2 is =N-R5, -S-, or -0-;

979~

Q represents the atoms necessary to complete a 5-membered heterocyclic nucleus; and Rs is chosen from among hydro~en, phenyl, alkyl, alkylphenyl, and phenylalkyl, the alkyl ~roups in each instance containing from 1 tc 5 carbon atoms.
The adsorption promotin~ groups have a 5-membered heterocyclic thioamide nucleus such as a 5-thiazoline-2-thione, thiazolidine-2-thione, 4-oxazoline-2-thione, ox-azolidine-2-thione, 2-pyrazoline-5-thione, pyrazolidine-5-thione, indoline-2-thione, or 4-imidazoline-2-thione. A
specifically preferred subclass of heterocyclic thioamide nuclei is formed when Q is as indicated in formula ~IV) (IV~ X
Il I

wherein X is S or O.
Specifically preferred illustrations of such values of Q
are 2-thiohydantoin, rhodanine, isorhodanine, and 2-thio-2,4-oxazolidinedione nuclei. It is believed that some 6-membered nuclei, such as thiobarbituric acid, may be equivalent to 5-membered nuclei embraced within formula (IV). These and more complex variant absorption promotin~
groups are disclosed in Leone et al U.S. Patent 4,080,207, the disclosure of which is here incorporated by reference.
The thioamide adsorption promotin~ groups useful in the practice of this invention need not form a hetero-cyclic ring in order to be effective. For example, the thioamide ~roup can take the form of a thiourea ~roup.
Preferred thiourea groups are those of the formula (V) R~ S
11 ~R6 -N - C-N
wherein R5, R7, and R8 can be independently selected from the group described above in connection with R2, provided at least one of R6, R7, and Ra is hydrogen and at least one of R6 and R7 is other than ~4~79~

hydro~en, and Rb and R7 can together form a hetero-cyclic nucleus having a 5- or 6-membered rin~, wherein the ring atoms are chosen from the class consisting of nitrogen, carbon, oxygen, sulfur, and selenium atoms. It is preferred tnat up to two of the ring atoms be hetero atoms and the remaining ring atoms be carbon atoms. The rin~ necessarily contains at least one nitrogen atom.
~xem~lary rings include morpholino, piperidino, pyrroli-dinyl, pyrrolinyl, thiomorpholino, tniazolidinyl, 4-thi-azolinyl, selenazolidinyl, 4-selenazolinyl, imidazoli-dinyl, imidazolinyl, oxazoliainyl, and 4-oxazolinyl rings. Speci~ically preterred rings are saturated or otnerwise constructed to avoid electron ~it~rawal from tne remaining nitro~en atom of cne tniourea moiety.
The a~sorption promotin~ group in another pre-ferred ~orm can be of the formula ~VI) 1I H .
-1 C~l2 In-C-N~ g ~;

wherein n is an integer of 1 to 4.
The preferred adsorption promoting groups can be of the type described in Leone et al U.~. Patents

4,030,9~5, 4,031,127, and 4,0~0,2~7, Leone Serial No.
105,317, filed December 1~ 7~, anà ~iahu et al _esearch ~isclosure, Vol. 17~, Decemtler 1978, Item 17~26, Illustrative specific vinylene nucleaCing agents usefu1 in tne practice of this invention are ~hose set forth Delo~ in Table I.
Table I NA-l 2-L~-anilinoviny~ -methylbenzothiazolium ~-toluenesulfonate NA-2 2-[~~N-methy1anilinovinyl~-3-methy1benzothiazolium ~-toluenesu1fonate NA-3 2-[~-(o-methy1thio-N-methylani1ino)viny1~-1-methylquinolinium p-toluenesulfonate "., ~

NA-4 2-[~-(N-propargylanilino)vinyl]-3-ethylbenzoxa-zolium bromide NA-5 2-[~-p-N-methylaminophenoxy)vinyl~-3-methylbenzo-thiazolium chloride NA-~ 2-[~-(o-methoxy-N-methylanilino)vinyl]-3-methyl-benzothiazolium ~-toluenesulfonate NA-7 2-[~-N-propar~ylanilinovinyl¦-3-ethylbenzoselena-zolium bromide NA-8 1-ethyl-~ -N-propar~ylanilinovinyl]-1,3-diethyl-

5,6-dichlorobenzimidazolium bromide NA-9 2-~ o-propargyl-thio-N-propar~yl-anilino)vinyl]-3-methyl-benzothiazolium bromide NA-10 2-[~-(o~methylthio-N-propargylanilino)vinyl]-3-methylbenzothiazolium ~-toluenesulfonate 5 NA-ll 2-~-methyl-~-(o-propargylthio-N-methylanilino)-vinyl]-3-methylbenzothiazolium bromide NA-12 2-~-N-propargylanilinovinyl]-3-methylbenzothi-azolium bromide NA-13 20~-N-methylanilinovinyl]-3-methyl-6-acetamido-benzothiazolium p-toluene sulfonate NA-14 2-[-~-(N-methylanilino)vinyl]-3-methyl-6-(N'-ethylthioureido)benzothiazolium bromide The vinylene nucleatin~ agents can be employed with any conventional photographic element capable of forming a direct-positive ima~e containing, coated on a photographic support, at least one silver halide emulsion layer containing a vehicle and silver halide grains cap-able of formin~ an internal latent image upon exposure to actinic radiation. As employed herein, the terms "inter-nal latent ima~e silver halide grains" and "silver halidegrains capable of forming an internal latent image" are employed in the art-recognized sense of designating silver halide grains which produce substantially higher vptical densities when coated, imagewise exposed and developed in an internal developer than when comparably coated, exposed and developed in a sur~ace developer. Pre~erred internal latent image silver halide grains are those which, when examined accordin~ to normal photographic testing tech niques, by coating a test portion on a photographic 9~

support (e.~., at a coverage of from 3 to 4 grams per square meter), exposing to a light intensity scale (e.g., with a 50~-watt tungsten lamp at a distance of 61 cm) for a fixed time (e.g., between l X l0 2 and l second) and developing for 5 minutes at 25C in Kodak Developer DK-50 (a surface developer), provide a density of at least 0.5 less than when this testing procedure is repeated, sub-stitutin~ ~or the surface developer Kodak Developer DK-50 containing 0.5 gram per liter of potassium iodide (an internal developer). The internal latent image silver halide grains most preferred for use in the practice of this invention are those which, when tested using an internal developer and a surface developer as indicated above, produce an optical density with the internal developer at least 5 times that produced Dy the surface aeveloper. It is additionally preferred that the internal latent image silver halide grains produce an optical density of less than 0.4 and, most preferably, less than 0.25 when coated, e~posed and developed in surface developer as indicated above, that is, the silver halide grains are preferably initially substantially unfogged and free of latent image on their surface.
The surface developer referred to herein as Kodak Developer DK-50 is described in the Handbook of Chemistry and Pnysics, 30th edition, 1947, Chemical ~ubber Publish-_ ing Company, Cleveland, Ohio, page 2558, and has the following composition:
Water, about 125F (52C) 500.0 cc N-methyl-p-aminophenol sulfate 2.5 g Sodium sulfite, desiccated30.0 g Hydroquinone 2.5 g Sodium metaborate l0.0 g Potassium bromide 0.5 g Water to make l.0 liter.
Internal latent ima~e silver halide grains which can ~e employed in tne practice of this invention are well known in t~e art. Patents teaching tne use of internal late~t ima~e silver halide ~rains in photographic emul-sions and elements include Davey et al U.S. Patent 2~592,250, Porter et al U.S. Patent 3,206,313, ~ilton U.S.
Patent 3,761,266, Rid~way U.S. Patent 3,586,505, Gilman et al U.S. Patent 3,772,030, Gilman et al U.S. Patent 3,761,267, and Evans U.S. Patent 3,761,276.

The internal latent ima~e silver halide grains preferably contain bromide as the predominant halide. The silver bromide grains can consist essentially of silver bromide or can contain silver bromoiodide, silver chloro-bromide, silver chlorobromoiodide crystals and mixtures thereof. Internal latent ima~e-formin~ sites can be incorporated into the grains by either physical or chemi-cal internal sensitization. Davey et al, cited above, forexample, teaches the physical formation of internal latent image-forming sites by the halide conversion technique.
Chemical formation of internal latent ima~e-formin~ sites can be produced through the use of sulfur, gold, selenium, tellurium and/or reduction sensitizers of the type des-cribed, for example, in Sheppard et al U.S. Patent 1,623,499, Waller et al U.S. Patent 2, 399,083, McVei~h U.S. Patent 3,297,447, and Dunn U.S. Patent 3,297,446, as tau~ht in the patents cited in the precedin~ para~raph.
Internal latent image sites can also be formed throu~h the incorporation of metal dopants, particularly Group VIII
noble metals, such as, ruthenium, rhodium, palladium, iri-dium, osmium and platinum, as tsu~ht by Berriman U.S.
Patent 3,367J778. The preferred foreign metal ions are polyvalent metal ions which include the above-noted Group VIII dopants, as well as polyvalent metal ions such as lead, antimony, bismuth, and arsenic, In other preferred embodiments9 the .silver halide grains may be formed in the presence of bismuth, lead or iridium ions. In a preferred approach, the internal latent image sites can be formed within the silver halide grains durin~ precipitation of silver halide. In an alternate approach, a core grain can be formed which is treated to form the internal image , ~
,, U79~

sites and then a shell deposited over the core grains, as taught by Porter et al, cited above.
The silver halide grains employed in the practice of this invention are preferably mono~ispersea, ana in some embodi~ents are preferably large-grain emulsions made according to Wilgus German ~LS 2,107,118.
The monodispersed emulsions are those which comprise silver halide grains having a substantially uniform diameter. Generally, in such emul-sions, no more than about 5 percent by number of the sil-ver halide grains smaller than the mean grain size and/or no more than about 5 percent by number of the silver halide grains larger than the mean grain size vary in diameter from the mean grain diameter by more than about 4~ percent. Preferred photographic emulsions of this invention comprise silver halide grains, at least ~5 per-cent by weight of said grains having a diameter which is witnln 4~ percent and pre~erably within about ~ percent of tne mean grain diameter. Mean grain diameter, i.e., average ~rain size, can be determined using conventional methods, e.g., such as projective area, as shown in an article by l`rivelli and ~mith entitled "~mpirical Kela-tions ~etween Sensitometric ana ~ize-~re~uency Character-istics in Photographic ~mulsion ~eries" in The _noto-graphic Journal, Volume LXXIX, 1939, pages 330 through3~. The aforementioned uniform size aistribution of sil-ver halide grains is a characteristic of the grains in monodispersed photographic silver haliae emulsions. Sil-ver halide grains having a narrow`size distribution can be 3 obtained by controlling the conditions at which the silver halide grains are prepared using a double run procedure.
In such a procedure, the silver halide grains are prepared ~y simultaneously running an aqueous solution of a silver salt, such as silver nitrate, and an aqueous solution of a water-soluble halide, for example, an alkali metal halide such as potassium bromide, into a rapidly agitated aqueous solution of a silver halide peptizer, preferably gelatin, a gelatin derivative or some other protein peptlzer.

:~14~

Suitable methods for preparing photographic silver halide emulsions having the required uniform particle size are disclosed in an article entitled "Ia: Properties of Pho-tographic Emulsion Grains", by Klein and Moisar, The Jour-nal of _ otographic Science, Volume 12, 1~6~, pages ~4~through 251; an article entitled "The Spectral Sensitiza-tion of ~ilver Bromide Emulsions on ~ifferent ~rystal-lographic Faces", by Markocki, The Journal of Photographic Science, Volume 13, 1965, pages 85 through 8~; an article entitled "Studies on Silver Bromide Sols, Part I. The For-mation and Aging of Monodispersed Silver Bromide ~ols", by Ottewill and Woodbridge, The Journal of Photographic Science, Volume 13, 1465, pages ~8 through 103; and an article entitled "Studies on Silver Bromide Sols, Part lI.
The Effect of Additives on the Sol Particles", by Ottewill and Woodbridge, The Journal of Photo~raphic Science, Vol-ume 13, 1965, pages 104 through 107.
Where internal latent image sites have been formed through internal chemical sensitization or the use of metal dopants, the surface of the silver halide grains can be sensitized to a level below that which will produce substantial density in a surface developer, that is, less than 0.4 (preferably less than 0.2i) when coate~, exposed and surface developed as described above. The silver halide grains are preferably predominantly silver bromiae grains chemically surface sensitized to a level which would provide a maximum density of at least 0.5 using undoped silver halide grains of the same size and halide composition when coated, exposed and developed as des-cribed above.
Surface chemical sensitization can be undertakenusing techniques such as those disclosed by Sheppard, Waller et al, McVeigh or Dunn, cited above. The silver halide grains can also be surface sensitized with salts of the noble metals, such as, ruthenium, palladium and platinum. Representative compounds are ammonium chloro-paliadate, potassium chloroplatinate and sodium chloro-palladite, which are used for sensitizing in amounts below 7g~

that which produces any substantial fog inhibition, as described in Smith et al U.S. Patent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli et al U.S. Patents 2,566,245 and 2,566,263. The silver halide grains can also be chemically sensitized with reducing agents, such as stannous salts (Carroll U.S.
Patent ~,487,850, polyamines, such as diethylene triamine (Lowe et al U.S. Patent 2,518,~98), polyamines, such as spermine (Lowe et al U.S. Patent 2,5~1,925), or bis-(~-aminoethyl)sulfide and its water-soluble salts (Lowe et al U.S. Patent 2,521,926).
The photographic silver halide emulsion layers and other layers of the photographic elements can contain various colloids alone or in combination as vehicles.
Suitable hydrophilic materials inclu~e both naturally occurring substances such as proteins, protein deriva-tives, cellulose derivatives, e.g., cellulose esters, gel-atin, e.g., alkali-treated gelatin (cattle bone or hide gelatin) or acid-treated gelatin (pigskin gelatin), gel-atin derivatives, e.g., acetylated gelatin, phthalatedgelatin, polysaccharides such as dextran, gum arabic, zein, casein, pectin, collagen derivatives, collodion, agar-agar, arrowroot, albumin, as ~escribed in Yutzy U.S.
Patents 2,614,928 and '929, Lowe et al U.S. Patents 2,691,582, 2,614,930 ana '931, 2,327,80~, and 2,448,5~4, Gates et al U.S. Patents 2,787,545 and 2,956,880, ~immelmann et al U.S. Patent 3,061,436, Farrell et al U.S.
Patent 2,816,027, Ryan U.S. Patents 3,132,945, 3,138,461, and 3,186,846, Dersch et al U.K. Patent 1,1~7,159 and U.S.
Patents 2,960,405 and 3,436,220, Geary U.S. Patent 3,486,896, Gazzard U.K. Patent 793,549, Gates et al U.S.
Patents 2,992,213, 3,157,506, 3,184,312, and 3,539,3S3, Miller et al U.S. Patent 3,227,571, Boyer et al U.S.
Patent 3,532502, Malan U.S. Patent 3,551,151, Lohmer et al U.S. Patent 4,018,604, Luciani et al U.K. Patent 1,186,790, Hori et al U.K. Patent 1,489,080 and Belgi3n Patent 856,~31, U.K. Patent 1,440,644, U.K. Patent 1,483,551, Arase et al U.K. Patent 1,459,906, Salo U.S.

79~

Patents 2,110,491 and 2,311,086, Fallesen U.S. Patent ~,34~,650, Yutzy U.S. Patent 2,322,085, Lowe U.S. Patent 2,563,791, Talbot et al U.S. Patent 2,725,293, ~ilborn U.S. Patent 2,748,022, DePauw et al U.S. Patent 2,956,883, Kitchie U.K. Patent 2,095, DeStubner U.S. Patent 1,752,069, S~eppard et al U.S. Patent 2,127,573, Lierg U.S. Patent 2,256,72~, Gaspar U.S. Patent 2,3~ 3~, Farmer U.K. Patent 15,727, Stevens U.K. Patent 1,06~,116, and Yamamoto et al U.S. Patent 3,923,517.
~0 Photographic emulsion layers, and other layers of photographic elements, such as, overcoat layers, inter-layers, and subbing layers, as well as receiving layers in image-transfer elements, can also contain alone or in com-bination with hydrophilic water-permeable colloids as vehicles or vehicle extenders (e.g., in the form of latices), synthetic polymeric peptizers, carriers and/or binders such as poly(vinyl lactams), acrylamide polymers, polyvinyl alcohol, and its derivatives, polyvinyl acetals, polymers of alkyl, and sulfoalkyl acrylates, and methac-rylates, hydrolyzed polyvinyl acetates, polyamides, poly-vinyl pyridine, acrylic acid polymers, maleic anhydride copolymers, polyalkylene oxides, methacrylamide copoly-mers, polyvinyl oxazolidinones, maleic acid copolymers, vinylamine copolymers, methacrylic acid copolymers, acryl-oyloxyalkylsulfonic acid copolymers, sulfoalkylacrylamidecopolymers, polyalkyleneimine c~polymers, polyamines, N,N-dialkylaminoalkyl acrylates, vinyl imidazole copoly-mers, vinyl sulfide copolymers, halogenated styrene poly-mers, amineacrylamide polymers, and polypeptides, as described in Hollister et al U.S. Patents 3,67,425, ~,706,564, and 3,813,251, ~owe U.S. Patents 2,253,07~, 2,276,322 and '323, 2,281,703, 2,311,058, and 2,414,207, Lowe et al U.S. Patents 2,484,456, 2,541,474, and 2,632,704, Perry et al U.S. Patent 3,425,836, Smith et al U.S. Patents 3,415,653 and 3,615,624, Smith U.S. Patent 3,488,708, Whiteley et al U.S. Patents 3,392,025 and 3,511,818, Fitzgerald U.S. Patents 3,681,079, 3,721,565, 3,852,073, 3,861,918, and 3,g25,083, Fitzgerald et al U.S.

7~

Patent 3,879,205, Nottorf U.S. Patent 3,142,568, Houck et al U.S. Patents 3,06~,~74 and 3,220,~44, Dann et al U.S.
Patent 2,882,161, Schupp U.S. Patent 2,579,016, Weaver U.S. Patent 2,829,053, Alles et al U.S. Patent ~,69~,~40, Priest et al U.S. Patent 3,003,879, Merrill et al U:S.
Patent 3,~19,347, Stonham U.S. Patent 3,~84,~07, Lohmer et al U.S. Patent 3,167,430, Williams U.S. Patent 2,~57,767, Dawson et al~U.S. Patent ~,893,867, ~mith et al U.S.
Patents ~,860,986 and 2,904,539, Ponticello et al U.S.
Patents 3,~,482 and 3,8~0,4~, Ponticello IJ.S. Patent 3,~39,130, Dykstra U.S. Patent 3,411,911, Dykstra et al Canadian Patent 774,054, Ream et al U.S. Patent ~ 7,~8~, Smith U.K. ~atent 1,466,600, Stevens U.K. Patent 1,0~2,11~, ~`ordyce U.S. Patent ~,21~,32~, ~lartinez U.S.
Patent 2,284,877, Watkins U.S. Patent 2,420,455, Jones U.S. Patent 2,5~3,166, Bolton U.S. Patent ~,495,41~, Graves U.S. Patent 2,289,775, Yackel U.S. Patent 2,565,418, Unruh et al U.S. Patents 2,865,893 and 2,875,059, Rees et al U.S. Patent 3,536,491, Broadhead et al U.K. Patent 1,348,815, Taylor et al U.S. Patent ~,479,186, Merrill et al U.S. Patent 3,520,857, Bacon et al U.S. Patent 3,690,888, Bo~man U.S. Patent 3,748,143, Dickinson et al U.K. Patents 808,227 and '228, Wood U.K.
Patent 822,192, and Iguchi et al U.K. Patent 1,39~,055.
The layers of the photographic elements can be coated on a variety of supports. Typical photographic supports include polymeric film, wood fiber, e.g., paper, metallic sheet and foil, glass and ceramic supporting ele-ments provided with one or more subbing layers to enhance the adhesive, antistatic, dimensional, abrasive, hardness, frictional, antihalation, and/or other properties of the support surface.
Typical of useful polymeric film supports are films of cellulose nitrate and cellulose esters, such as, cellulose triacetate and diacetate, polystyrene, poly-amides, homo-polymers and co-polymers of vinyl chloride, poly(vinyl acetal), polycarbonate, homo-polymers and co-polymers of olefins, such as, polyethylene and poly-propylene, and polyesters of dibasic aromatic carboxylic acids with divalent alcohols, such as poly(ethylene tere-phthalate).
Typical of useful paper supports are those which are partially acetylated or coated with baryta and/or a polyolefin, particularly a polymer of an ~-olefin containing 2 to 10 carbon atoms, such as, polyethylene, polypropylene, copolymers of ethylene and propylene.
Polyolefins, such as, polyethylene, polypropylene and polyallomers, e.g., copolymers of ethylene with pro-pylene, as illustrated by Hagemeyer et al U.S. ~atent 3,478,1~8, are preferably employed as resin coatings over paper, as illustrated by ~rawford et al U.S. Patent 3,411,908 and Joseph et al U.S. Patent 3,630,740, over polystyrene and polyester film supports, as il:Lustrated by Crawford et al U.S. Patent 3,630,742, or car. be employed as unitary flexible reflection supports, as illustrated by Venor et al U.S. Patent 3,973,963.
Preferred cellulose ester supports are cellulose triacetate supports, as illustrated by Fordyce et al U.S.
Patents ~,492,977, '978, and 2,739,069, as well as mixed cellulose ester supports, such as, cellulose acetate pro-pionate and cellulose acetate butyrate, as illustrated by Fordyce et al U.S. Patent 2,739,070.
Preferred polyester film supports are comprised of linear polyester, such as illustrated by Alles et al U.S. Patent 2,627,088, Wellman U.S. Patent 2,720,503, Alles U.S. Patent ~,774,684, and Kibler et al U.S. Patent 2,901,466. Polyester films can be formed by varied tech-niques, as illustrated by Alles, cited above, Czerkas et al U.S. Patent 3,663,683, and Williams et al U.S. Patent 3,504~075, and modified for use as photographic film supports, as illustrated by Van Stappen U.S. Patent 3,227,576, Nadeau et al U.S. Patent 3,501,301, Reedy et al U.S. Patent 3,5&9,905, Babbitt et al U.S. Patent 3,850,640, Bailey et al U.S. Patent 3,888,678, Hunter U.S.
Patent 3,904,420, and Mallinson et al U.S. Patent 3,928,697.

79~

The photographic elements can employ supports which are resistant to dimensional change at elevated tem-peratures. Such supports can be comprised of linear con-densation polymers which have glass transition tempera-tures above about 190C, preferably 220C, such as, poly-carbonates, polycarboxylic esters, polyamides, polysulfon-amides, polyethers, polyimides, polysulfonates and copoly-mer variants, as illustrated by Hamb U.S. Patents 3,634,08~ and 3,772,405, ~amb et al U.S. Patents 3,7~5,070 and 3,793,24~, Wilson Research Disclosure, Volume 118, February 1974, Item 11833, and Volume 120, April 1474, ltem 1~04~, Conklin et al ~esearch Disclosure, Volume 1~0, April 1974, Item 1~012, Product Licensin~ lndex, Volume ~2, December 1971, Items ~205 and 4207, ~.esearch Dis-closure, Volume 101, ~eptember 1~7~, ltems 1~119 and 10148, Research Disclosure, Volume 106, February 1~73, Item 1~613, Research Disclosure, Volume 117, January 1974, ltem 11709, and Research Disclosure, Volume 134, June 1975, Item 13455. Both Research Disclosure and ~roduct Licensin~ Index are published by Industrial Opportunities, Ltd., Homewell, ~avant, Hampshire, PO9 lEF, United Kingdom The vinylene nucleating agents of this invention can be employed in any desired concentration that ~ill permit a degree of selectivity in developing imagewise silver halide grains capable of forming an internal latent image, which grains have not been imagewise exposed, as compared to silver halide grains containing an internal latent image formed by imagewise exposure.
It is preferred to incorporate the vinylene nuc-leating agents into the silver halide emulsions in concen-trations of from 10 5 to about 10-2 mole per mole of silver halide. Where an efficient adsorption promoting moiety is incorporated in the vinylene nucleating agent, such as a thioamide (particularly a thiourea) or a tri-azole, as described above, it is generally ~nnecessary toprovide nucleating concentrations in excess of about 10-3 mole per mole of silver halide. On the other hand, where such adsorption promoting nuicleating agents are U79~;

absent and tne heterocyclic nucleus is being relied upon co promote adsorption to ~he silver nalide grains, it is generally preferred that tne nucleating agents be incor-porated in a concentration of at least 10-4 mole per mole of silver halide. ~here the vinylene nucleating agent is to be adsor~ed to the surface of the silver halide grains, it can be adsorbed using tne procedures well known to those skilled in the art for adsorbing sensitizing dyes, such as, cyanine and merocyanine dyes, to the surface of silver halide grains.
A simple e~posure and development process can be used to for~ a direct-positive image. In one embodiment, a photographic element comprising at least one layer of a silver halide emulsion as described above can be imagewise exposed to light and then developed in a silver halide surface developer.
It is understood that the term "surface devel-oper" encompasses those developers which will reveal the surface latent ima~e on a silver nalide grain, but will not reveal substantial internal latent image in an inter-nal image-forming emulsion, and under the conditions gen-erally used develop a surface-sensitive silver halide emulsion. The surface developers can generally utilize any of the silver halide developing agents or reducing agents, but the developing bath or composition is gen-erally substantially free of a silver halide solvent (sucn as water-soluble thiocyanates, water-soluble thioethers, thiosulfates, and ammonia) which will disrupt or dissolve the grain to reveal substantial internal image. Low amounts of excess halide are sometimes desira~le in the developer or incorporated in the emulsion as halide-releasing compounds, but ~igh amounts of iodide or iodide-releasing compounds are generally avoided to prevent sub-stantial disruption of the grain. Typical silver halide developing agents which can be used in the developing compositions of this invention include hydroquinones, catechols~ aminophenols, 3-pyrazolidones, ascorbic acid and its derivatives, reductones and color developing )7~ .

agents, that is, primary aromatic amine developing agents, such as, aminophenols and para-phenylenediamines. The color ~eveloping agents are preferably employed in com-bination with blsck-and-white developing agents capable of acting as electron transfer agents. lllustrative of use-ful surface developers are those disclosed in lves U.S.
Patent 2,5~3,785, Evans U.S. Patent 3,761,27b, Knott et al U.S. Patent 2,456,953, and Juoy U.S. Patent 3,511,662.
Where the developing agents are initially entire-ly incorporated in the photographic elements, the remain-ing components (e.g., water, activators to adjust ph, pre-servatives, etc.) ~ormally present in surface developers constitute what is commonly referred to as an activator solution. Except for the omission of the developing agent, activator solutions are identical ~o developer solutions in composition and are employed identically with incorporated developing agent photographic elements. SUD_ sequent references to developing compositions are inclu-sive of both developer and activator solutions.
The surface developers are alkaline. Conven-tional activators, preferably in combination with buffer such as, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, trisodium phosphate or sodium metaphospha~e, can be employed to adjust p~ to a desired alkaline level. lhe amounts of these materials present are selected so as to adjust the developer to a p~
in the range of from 10 to 13, preferably from about lU.2 to 1~Ø
The developing compositions used in the process 30 of this invention can contain certain antifog~ants and development restrainers, or, optionally, they can be incorporated in layers of the photographic element. For example, in some applications, improved results can be obtained when the direct-positive emulsions are processed in the presence of certain antifoggants, as disclosed in Stauffer U.S. ~atent 2,4~7,~17, - I`ypical useful antifoggants inclu~e benzotria-zoles, such as, benzotriazole, 5-methylbenzotriazole, and 5-ethylbenzotriazole, benzimidazoles, such as, ~-nitro-benzimi~azole, benzothiazoles, such as, 5-nitrobenzo-thiazole and 5-methylbenzothiazole, heterocyclic thiones, such as; l-methyl-2-tetrazoline-5-thione, triazines, such as, ~,4-dimethylamino-6-chloro-5-triazine, benzoxazoles, such as, ethylbenzoxazole, and pyrroles, such as, 2,5-dimethylpyrrole ana the like.
Improved results are obtained when the element is processed in the presence of the antifoggants mentioned above. The antifoggants can be present in the processing solution during development or incorporated in the photo-graphic element. lt is preferred to incorporate the anti-foggant in the processing solution. Concentrations oi from about 1 mg to 1 gram per liter are contemplated, with concentrations of from about 5 to 5~U mg per liter being preferred. Optimum antifoggant concentrations are a func-tion of the specific antifoggant, element, and processing solution employed.
The essential features of the vinylene nucleating agents of this invention and the silver halide emulsions and photographic elements in which they are incorporated, as well as procedures for their use and processing, are described above. It is appreciated that, in preferred photographic applications, the emulsions and eLements can contain additional features which are in themselves well known to those familiar with the photographic arts.
Further, these applications can entail conventional modifications in the procedures described above. A
variety of such features are disclosed in Kesearch Dis-closure, Volume 17~, December 1978, ltem 1764~, particularly Paragraph II, Emulsion washing; Paragraph IV, Spectral sensitization and Desensitization; Paragraph V, Brighteners; Paragraph Vl, Antifoggants and stabilizers;
Paragraph Vlll, Absorbing and scattering materials;
Paragraph X~ ~ardeners; Paragraph Xl, ~oating aids;

~l~4~791 -~6-aragraph XlI, Plasticizers and lubricants; Paragraph XlII, ~ntistatic layers; Paragraph XIV7 Methods of addi-tion; Paragraph XV, Coating and drying Procedures; Para-graph XVI, Matting agents; Para~raph XVlII, Exposure;
Paragraph XIX, Processing (as applied to post-development processing and paragraphs G, H, I, and J, relating to amplification); Paragraph XX, ~eveloping agents; and Para-graph XXI, Development modifiers.
It is specifically contemplated that the vinylene nucleating agents of the present invention can be employed in combination with conventional nucleating agents of the quaternary ammonium salt, hydrazine, hydrazide, and hydra-zone type, such as those cited above to illustrate known nucleating agents. The conventional nucleating agents can be incorporated in the photographic element in previously taught concentrations, typically up to 2 grams per mole of silver. The conventional nucleating agents can also be present in the developer in previously taught concentra-tions, typically up to about 5 grams per liter. Since the use of conventional nucleating agents is not essential to the practice of this invention, no minimum concentration is required; however, when employed, conventional nucleat-ing agents are pre~erably present in a concentration range of from about 10 to 500 mg per mole of silver when present in the emulsion and from about 0.1 to 1 gram per liter when present in the developer.
~ he silver halide emulsions can be spectrally sensitized with cyanine, merocyanine, and other poly-methine dyes and supersensitizing combinations thereof well known in the art. Spectral sensitizers in conven-tional surface-sensitive emulsions are comparably effec-tive in the emulsions of this invention. In general, they enhance nucleation. Nonionic, zwitterionic and anionic spectral sensitizers are preferred. Particularly effec-tive are carboxy-substi~uted merocyanine dyes of the thio-hydantoin type described by Stauffer et al U.S. Patent 2,490,758.

:

79~

E~fective red sensitizers are the carbocy~nines of formula (VII) (VIl) C=CH- C=CH-CrJ ( X^ ) n -G
Rl R2 wherein each of Z' and Z~ represents the atoms nec-essary to form a benzothiazole, benzoselenazole, naphtho-thiazole, or naphthoselenazole, the benzothiazole and benzoselenazole being preferably 5- and/or 6-substituted with groups such as lower alkyl, lower alkoxy, chloro, bromo, fluoro, hydroxy, acylamino, cyano, and trifluoro-methyl, G represents hydrogen and lower alkyl, preferably ethyl or methyl, each of Rl and R2 represents lower alkyl or hydroxy-(lower)alkyl, at least one of R' and R2 being preferably acid-substituted(lower)alkyl, such as, carboxy-ethyl, sulfopropyl, and sulfatoethyl, X represents an acid anion, and n is 1 or 2.
Particularly effective are certain supersensitiz-ing combinations of the above dyes with each other and with dyes or other adsorbed organic compounds having polarographic oxidation potentials (Eox) of about 0.3 to 0.~ volt. Many such combinations are described in Mees U.S. Patent 2,075,048, Carroll et al U.S. Patents 2,313,922, 2,533,426, 2,688,545, and ~,704,714, Jones U.S.
Patent 2,704,717, and Schwan 3,672,898, and include, as well, the acid-substituted analogues thereof well known in the art.
Effective green sensitizers are carbocyanines and cyanines of formulas (VIII) and ~IX) 79~

-2~-(VIIl) z1~ r~2 C CH-C=C~-C~ +~) (X~)n-I G
Rl R2 (IX) z3~ ~z~
C=CH-C~ ~ (X)n-wherein each of Zl and Z2 represents the atoms necessary to form benzoxazole and benzimidazole nuclei, benzimidazole being substituted in the 3-position by lower alkyl or aryl, and preferably in the 5- and/or ~-positions with groups selected from fluoro, chloro, bromo~ lower alkyl, cyano, acylamino and trifluoromethyl, and the benz-oxazole ring preferably substituted in the 5- or 6-posi-tions with lower alkyl, lower alkoxy, phenyl, fluoro, chloro, and bromo, Z3 represents the atoms necessary to form benz-othiazole, benzoselenazole, naphthothiazole, naphthoselen-azole, or 2-quinoline, Z4 represents the atoms necessary to form 2-quinoline, G represents lower alkyl and, if at least one of Zl and Z2 forms benzimidazole, hydrogen, each of Rl, R2, R3 and R4 represents lower alkyl or hydroxy(lower)alkyl, at least one of and R2 and of R3 and R4 being preferably acid-substituted(lower)alkyl such as carboxyethyl, sulfo-propyl, and sulfatoethyl, X represents an acid anion, and is 1 o~ 2.
Particularly effective are certain supersensitiz-ing combinations of the ~bove dyes, ~uch as tho~e de~-cribed in U.S. Patents Carroll et al U.S. Patents ~,688,545 and 2,701,198 and Nys et al 2~973~264J and their acid-substituted analogues well known ln the art.

:~14~

Effective blue sensitizers are simple cyanines and merocyanines of formulas (X) and (XII) (X) ~ /C=C~-C~ +) (X~) Rl ~2 (XI) I____z3____ 1 1I Ql Q?

wherein each of Zl and Z2 represents the atoms neces-sary to form benzothiazolel benzoselenazole, naphthothia-zole and naphthoselenazole nuclei which may be substituted with groups such as chloro, methyl or methoxy, chloro, bromo, lower alkyl, or lower alkoxy, Z3 represents benzothiazole, benzoselenazole which may be substituted as in Zl and Z2, and a pyri-dine nucleus, Q' and Q2 together represent the atoms neces-sary to complete a rhodanine, 2-thio-2,4-oxazolidinedione or 2-thiohydantoin ring, the latter having a second nitro-gen atom witn a substituent R5, m represents 0 or l, each of Rl, R2 and R3 represents lower alkyl or hydroxy(lower)alkyl~ at least one of Rl and R2 being preferably acid-substituted(lower)alkyl such as carboxyethyl, sulfopropyl, and sulfatoethyl, R4 and R5 represent lower alkyl and hydroxy-(lower)alkyl, and R4 additionally can represent carboxy-alkyl and sulfoalkyl, X is an acid anion, and n is l or 2.
(Lower alkyl in each occurrence of Formulas VII to XI
3 includes from l to 5 carbon atoms.) 9~

'lhe photographic elements are preferably color photographic elements which form dye images through the selective destruction, formation or physical removal of dyes.
The photographic elements can produce dye images through the selective destruction of dyes or dye precur-sors, such as silver-dye-bleach processes, as illustrated by A. Meyer, The Journal of Photographic Science, Volume 13, 1965, pages 90 through 97. Bleachable azo, azoxy, xanthene, azine, phenylmethane, nitroso complex, indigo, quinone, nitro-substituted, phthalocyanine and formazan dyes, as illustrated by Stauner et al U.S. Patent 3,754,923, Piller et al U.S. Patent 3,749,576, Yoshida et al U.S. Patent 3,738,839, Froelich et al U.S. Patent 3,716,3~, Piller U.S. Patent 3,655,388, Williams et al U.S. Patent 3,642,482, Gilman U.S. Patent 3,5~/,44~, Loeffel U.S. Patent 3,443,953, Anderau U.S. Patents 3,443,952 and 3,211,556, Mory et al U.S. Patents 3,202,511 and 3,178,291, and Anderau et al U.S. Patents 3,178,285 and 3,178,290 as well as their hydrazo, diazonium, and tetrazolium precursors and leuco and shifted derivatives, as illustrated by U.K. Patents 923,265, 9~9,9~6, and 1,042,300, Pelz et al U.S. Patent 3,684,513, Watanabe et al U.S. Patent 3,615,4~3, Wilson et al U.S. Patent 3,503,741, Boes et al U.S. Patent 3,340,059, Gompf et al U.S. Patent 3,493,372, and Puschel et al U.~. Patent 3,561,970 can be employed.
The photographic elements can produce dye images through the selective formation of dyes, such as by react-ing (coupling) a color-developing agent (e.g., a primary aromatic amine) in its oxidized form with a dye-forming coupler. The dye-forming couplers can be incorporated in the photographic elements, as illustrated by Schneider et al, Die ~hemie) Volume 57, 1944, page 113, ~annes et al U.S. Patent 2,304,940, Martinez U.S. Patent 2,2~4,158, Jelley et al U.S. Patent 2,322,027, Frolich et al U.S.
Patent 2,376,679, Fierke et al U.S. Patent 2,801,171, Smith U.S. Patent 3,748,141, Tong U.S. Patent 2,772,163, Thirtle et al U.S. Patent 2,835,57~, Sawdey et al U.S.
Patent 2,533,514, Peterson U.S. Patent ~,353,754, Seidel U.S. Patent 3,409,435, and Chen ~esearch Disclosure, Vol-ume 159, July 1977, Item 15930.
In one form, the dye-forming couplers are chosen to form subtractive primary (i.e., yellow, magenta, and cyan) image dyes and are nondiffusible, colorless coup-lers, such as, two- and four-equivalent couplers of the open chain ketomethylene, pyrazolone, pyrazolotriazole, pyrazolobenzimidazole, phenol, and naphthol type hydro-phobically ballasted for incorporation in high-boiling organic (coupler) solvents. Such couplers are illustrated by Salminen et al U.S. Patents 2,4~3,730, ~,77~,16~, 2,895,826, 2,710,803, ~,407,207, 3,737,316, and ~,367,531, Loria et al U.S. Patents 2,772,161, ~,600,7~&, 3,U~,759, 3,214,437, and 3,253,924, McCrossen et al U.S. Patent 2,875,057, Bush et al U.S. Patent 2,908,57~, ~ledhill et al U.S. Patent 3,034,892, Weissberger et al U.S. Patents 2,474,293~ 2,407,21~, 3,0~2,653, 3,2~5,50~, and ~,3~4,b57, Porter et al U.S. Patent 2,343,703, Greenhalgh et al U.S.
Patent 3,127,269, Feniak et al U.S. Patents 2,865,748, 2,933,391, and 2,865,751, Bailey et al U.S. Patent 3,725,067, Beavers et al U.S. Patent 3,758,308, Lau U.S.
Patent 3,779,763, Fernandez U.S. Patent 3,785,829, U~Ko Patent 969,~21, U.K. Patent 1,241,06~, U~K~ Patent 1,011,940, Vanden ~ynde et al U.S. Patent 3,762,921, Beavers U.S. Patent 2,983,608, Loria U.S. Patents 3,311,47~, 3,408,194, 3,458,315, 3,447,928, and 3,476,563, Cressman et al U.S. Patent 3,419,350, Young U.S. Patent 3,419,391, Lestina U.S. Patent 3,519,429, U.K. Patent 975,928, U.K. Patent 1,111,554, Jaeken UOS. Patent 3,222,176 and Canadian Patent 726,651, Schulte et al U.K.
Patent 1,~48,924, and Whitmore et al U.S. Patent 3,2~7,55~.
The photographic elements can incorporate alkali-soluble ballasted couplers, as illustrated by Froelich et al and Tong, cited above. I'he photographic elements can be adapted to form nondiffusible image dyes using aye-forming couplers in developers, as illustrated by U.K.

V~7~1 ~,~
Patent 478,984, Yager et al U.S. Patent 3,113,~64, Vittum et al U.S. Patents 3t00~,836, 2,'i7l~23~ and 2,362,59~, Schwan et al U.S. Patent 2,950,~70, Carroll et al U.S.
Patent 2,592,243, Porter et al U.S. Patents 2,343,703, 2,376,380, and 2,369,489, Spath U.K. Patent 886,723 and U.S. Patent 2,899,306, Tuite U.S. Patent 3,152,~96, and Mannes et al U.S. Patents 2,115,394, 2,252,718, and 2,108,602.
The dye-forming couplers upon coupling can release photographically useful fragments, such as, devel-opment inhibitors or accelerators, bleach accelerators, developing agents, silver halide solvents, toners, harden-ers, fogging agents, antifoggants, competing couplers, chemical or spectral sensitizers, and desensitizers.
1~ Development inhibitor-releasing (DIR) couplers are illus-trated by Whitmore et al U.S. Patent 3,148,06~, Barr et al U.S. Patent 3,2~7,554, Barr U.S. Patent ~,733,201, Sawdey U.S. Patent 3,617,291, ~roet et al U.S. Patent ~,7U3,375, Abbott et al U.S. Patent ~,615,506, Weissberger et al U.S.
Patent 3,265,506, Seymour U.S. Patent 3,620,745, ~arx et al U.S. Patent 3,632,345, Mader et al U.S. Patent 3,869,291, U.K. Patent 1,201,110, Oishi et al U.~. Patent 3,642,485, Verbrugghe U.K. Patent 1,236,767, Fujiwhara et al U.S. Patent 3,770,436, and Matsuo et al U.S. Patent 3,808,945. DIR compounds which do not form dye upon reaction with oxidized color-developing agents can be employed, as illustrated by Fujiwhara et al German OLS
2,529,350 and U.S. Patents 3,928,041, 3,958~993, and 3,961,459, Odenwalder et al German OLS ~,448,063, Tanaka et al German OLS 2,610,546, Kikuchi et al U.S. Patent 4,049,455, and Credner et al U.S. Patent 4,052,213. DIR
compounds which oxidatively cleave can be employed, as illustrated by Porter et al U.S. Patent 3,379,529, ~reen et al U.S. Patent 3,043,690, ~arr U.S. Patent ~364,022, Duennebier et al U,S. Patent 3,297,445, and ~ees et al U.S. Patent 3,~87,129.
The photographic elements can incorporate colored dye-forming couplers, such as those employed to Eorm inte-gral masks for negative color images, as illustrated by ~anson U.S. Patent 2,449,966, Glass et al U.S. Patent 2,5~1,90~, Gledhill et al U.S. Patent 3,0~4,8~2, Loria U.S. Patent 3,476,563, Lestina U.S. Patent 3,519,429, Friedman U.S. Patent 2,543,641, Puschel et al U.S. Patent 3,028,238, Menzel et al U.S. Patent 3,061,432, and Greenhalgh U.K. Patent 1,035,~59, and/or competing coup-lers, as illustrated by Murin et al U.S. Patent 3,876,428, Sakamoto et al U.S. Patent 3,580,722, Puschel U.S. Patent 2,998,314, Whitmore U.S. Patent 2,808,329, Salminen U.S.
Patent 2,742,832, and Weller et al U.S. Pater.t 2,689,793.
The photographic elements can produce dye images through the selective removal of dyes. Negative or posi-tive dye images can be produced by the immobilization of incorporated color-providing substances as a function of exposure and development, as illustrated by U.K. Patents 1,456,413, 1,479,734, 1,475,265, and 1,471,7~'~, Friedman U.S. Patent 2,543,691, Whitmore U.S. Patent 3,227,552, ~loom et al U.S. Patent 3,4$3,~4~, Morse U.S. Patent 3,549,364, Cook U.S. Patent 3,620,730, Danhauser U.S.
Patent 3,730,718, Staples U.S. Patent 3,923,510, Oishi et al U.S. Patent 4,052,214, and ~leckenstein et al U.S.
Patent 4,076,52~.
The photographic elements can contain antistain agents (i.e., oxidized developing agent scavengers) to prevent developing agents oxidized in one dye image layer unit from migrating to an adjacent dye image layer unit.
Such antistain agents include ballasted or otherwise non-diffusing antioxidants, as illustrated by Weissberger et 3 al U.S. Patent 2,336,327, Loria et al U.S. Patent 2,728,659, Vittum et al U.S. Patent 2,360,290, Jelley et al U.S. Patent 2,403,721, and Thirtle et al U.S. Patent 2,701,1~7. To avoid autooxidation the antistain agents can be employed in combination with other antioxidants, as illustrated by Knechel et al U.S. Patent 3,700,453.
The photographic elements can include image dye stabilizers. Such image dye stabilizers are illustrated by U.K. Patent 1,326,889, Lestina et al U.S. Patents 4~ 9 3,432,300 and 3,698,909, Stern et al U.S. Pa~ent 3,574,~27, Brannock et al U.S. Patent 3,573,050, Arai et al U.S. Patent 3,764,337, and Smith et al ~ atent 4,042,394.
This invention is particularly useful with photo-graphic elements used in image transfer processes or in image transfer film units.
Image transfer systems include colloid transfer systems, as illustrated by Yutzy et al U.S. Patents 2,596,756 and 2,716,059, silver salt diffusion transfer systems, as illustrated by Rott U.S. Patent 2,352,014, Land U.S. Patent 2,543,181, Yackel et al U.S. Patent 3,020,155, and Land U.S. Patent 2,861,885, imblbition transfer systems, as illustrated by Minsk U.S. Patent 2,882,15~, and color image transfer systems, as illustrat-ed by Research Disclosure, Volume 151, November 1976, ltem 151~2, and Volume 123, July 1974, Item 1~331.
Color image transfer systems (including emulsion layers, receiving layers, timing layers, acia layers, pro-cessing compositions, supports, and cover sheets) and the images they produce can be varied by choosing among a variety of features, combinations of which can be used together as desired.
Film units can be chosen which are either inte-grally laminated or separated during exposure, processingand/or viewing, as illustrated by Rogers U.S. Patent 2,983,606, Beavers et al U.S. Patent 3,445,228, Whitmore, Canadian Patent 674,082, Friedman et al U.S. Patent 3,309,201, Land U.S. Patents 2,543,181, 3,053,~5g, 3 3,415,644, 3,415,645, and 3,415,646, and Barr et al U.K.
Patent 1,330,524.
A variety of approaches are known in the art for obtaining transferred dye images. The approaches can be generally categorized in terms of the initial mobility of dye or dye precursor. (lnitial mobility refers to the mobility o~ the dye or dye precursor when it is contacted by the processing solution. Initially mobile dyes and dye precursors as coated do not migrate prior to contact with processing solution.) Dye image-providing compounds are classified as either positive-working or negative-working. Positive-working dye image-providing compounds are those which produce a positive transferred dye image when employed in combination with a conventional, negative-working silver halide emulsion. ~egative-working dye ima~e-providing compounds are those which produce a negative transferred dye image when employed in combination with conventional, ne~ative-working silver halide emulsions. (The foregoing techniques, such as those referred to in Research Dis-closure, Vol. 17~, December 197~, ltem 17~43, paragraph XXIIl-E.) When, as in the present invention, the silver halide emulsions are direct-positive emulsions, positive-working dye image-providing compounds produce negative transferred dye images and negative-working dye image-providing compounds produce positive transferred dye images.
lmage transfer systems, which include both the dye image-providing compounas and the silver halide emulsions, are positive-working when the transferred dye image is positive and negative-working when the transferred dye image is negative. When a retained dye image is formed, it is opposite in sense to the trans-ferred dye image.
A variety of dye image transfer systems have been developed and can be employed in the practice of t~is invention. One approach is to employ ballasted dye-3 forming (chromogenic~ or nondye-forming (nonchromogenic) couplers having a mobile dye attached at a coupling-off si~e. Upon coupling with an oxidized color developing agent, such as a para phenylenediamine, the mobile dye is displaced so that it can transfer to a receiver. This 35 negative-working image transfer approach is illustrated ~y Whitmore et al U.S. Patent 3,2~7,550, Whitmore U.S. Patent 3,2~7,552, and Fujihara et al U.K. Patent 1,445,7~7, 7~

In a preferred image transfer system accordin~ to this invention employin~ negative-workin~ dye image-providing compounds, a cross-oxidizin~ developing agent (electron transfer agent) develops silver halide and then cross-oxidizes with a compound containing a dye linked through an oxidizable sulfonamido group, such as a sulfon-amidophenol, sulfonamidoaniline, sulfonamidoanilide, sul-fonamidopyrazolobenzimidazole, sulfonamidoindole or sul-fonamidopyrazole. Followin~ cross-oxidation, hydrolytic deamidation cleaves the mobile dye with the sulfonamido ~roup attached. Such systems are illustrated by Fleckenstein U.S. Patents 3,928,312 and 4,053,312, Fleckenstein et al U.S. Patent 4,076,529, Melzer et al U~K. Patent 1,4B9,694, De~uchi, German OLS 2,729,820, Koyama et al, German OLS 2,613,005, Vetter et al German OLS 2,505,248, and Kestner et al Research Disclosure, Volume 151, November 1976, Item 15157. Also specifically contemplated are otherwise similar systems which employ an immobile, dye-releasing (a) hydroquinone, as illustrated by Gompf et al U.S. Patent 3,698,897 and Anderson et al U.S. Patent 3,725,062, (b) para-phenylenediamine, as illustrated by Whitmore et al Canadian Patent 602,607, or (c) quaternary ammonium compound, as illustrated by Becker et al U.S. Patent 3,728,113.
Another specifically contemplated dye image transfer system which is negative-workin~ reacts an oxi-dized electron transfer a~ent or, specifically, in certain forms, an oxidized para-phenylenediamine with a ballasted phenolic coupler havin~ a dye attached through a sulfon-amido linkage. Ring closure to form a phenazine releases mobile dye. Such an ima~ing approach is illustrated by Bloom et al U.S. Patents 3,443,939 and 3,443,940.
In still another negative-working syste~, ballasted sulfonylamidrazones, sulfonylhydrazones or sul-fonylcarbonylhydrazides can be reacted with oxidized para-phenylenediamine to release a mobile dye to be trans-ferred, as illustrated by Puschel et al U.S. Patents 3,628,952 and 3,844,785. In an additional negative-working system, a hydrazide can be reacted with silver 7~1:

halide havin~ a developable latent ima~e site and thereafter decompose to release a mobile, transferable dye, as ill~strated by Ro~ers U.S. Patent 3,245,789, Kohara et al, Bulletin Chemical Society of Japan, Volume 43, pages 2433 throu~h 2437, and Lestina et al Research Disclosure, Volume 28, December 1974, Item 12832.
Image transfer systems employing ne~ative-working ima~e dye-providing compounds are also known in which dyes are not initially present, but are formed by reactions occurrin~ in the photographic element or receiver follow-in~ exposure. For example, a ballasted coupler can react with color developin~ a~ent to form a mobile dye, as illustrated by Whitmore et al U.S. Patent 3,227,550, Whitmore U.S. Patent 3,227,552, Bush et al U.S. Patent 3,791,827, and Viro et al U.S. Patent 4,036,643. ~n im-mobile compound containin~ a coupler can react with oxi-dized ~ -phenylenediamine to release a mobile coupler which can react with additional oxidized para-phenylene-diamine before, during or after release to form a mobile dye, as illustrated by Figueras et al U.S~ Patent 3,734,726 and Janssens et al German OLS 2,317,134. In another form, a ballasted amidrazone reacts with an elec-tron transfer agent as a function of silver halide devel-opment to release a mobile amidrazone which reacts with a coupler to form a dye at the receiver, as illustrated by Ohyama et al U.S. Patent 3,933,493.
An image to be viewed can be transferred from the image-forming layers. A retained ima~e can be formed for viewing as a concurrently formed complement of the trans-ferred image. Positive transferred ima~es and useful ne~-ative retained images can be formed with the direct posi-tive silver halide emulsions of this invention when imag-ing chemistry is ne~ative working. Ima~es retained in and transferred from the ima~e-formin~ layers are illustra'.ed by U.K. Pa~ent 1,456,413, Friedman U.S. Patent 2,543,691, Bloom et al U.S. Patent 3,443,940, Staples U.S. Patent 3,923,510, and Fleckenstein et al U.5. Patent 4,076,529.

9~L
-3~-Where mobile dyes are transferred to the receiver a mordant is commonly present in a image dye-providing layer. ~lordants and mordant containing layers are des-cribed in the following references which are incorporated by reference: Sprague et al U.S. Patent 2,548,564, Weyerts U.~. Patent 2,548,575, Carroll et al U.S. Patent 2,675,316, Yutzy et al U.S. Patent 2,713,305, Saunders et al U.S. Patent 2,756,149, Reynolds et al U.S. Patent 2,768,078, Gray et al U.S. Patent 2,839,401, ~insk U.S.
Patents 2~882~15b and ~,945,00~, Whitmore et al U.S.
Patent 2,940,844, Condax U.S. Patent 2,952,566, ~ader et al U.S. Patent 3,016,3~, Minsk et al U.~,. Patents ~,048,487 and ~,184,309, Bush U.S. Patent 3,271,147, Whitmore U.S. Patent 3,~71,14$, Jones et al U.S. Patent 3,~82,699, Wolf et al U.S. Patent 3~408,193, Co~en et al U.S. Patents 3,488,706, 3,557,066, 3,625,694, 3,709,~90, 3,758,445, 3,788,855, 3,898,088, and 3,944,424, Cohen U.S.
Patent 3,639,357, Taylor U.S. Patent 3,770,439, Campbell et al U.S. Patents 3,958,995 and 4,193,795; and Ponticello et al Research ~isclosure, Vol. 120, April 1974, Item 12045.
One-step processing can be employed, as illus-trated by U.K. Patent 1,471,752, Land U.S. Patent 2,543,181, Rogers U.S. Patent 2,983,606 (pod processing), Land U.S. Patent 3,485,628 (soak image-former and laminate to receiver) and Land U.S. Patent 3,907,563 (soak receiver and laminate to image-forming element) or multi-step pro-cessing can be employed, as illustrated by Yutzy U.S.
Patent 2,756,142, Whitmore et al U.S. Patent 3,227,550, and Faul et al U.S. Patent 3,998,637.
Preformed reflective layers can be employed, as illustrated by Whitmore Canadian Patent 674,082, Beavers U.S. Patent 3,445,228, Land U.S. Patents 2,543,1~1, 3,415,644, '645 and '646, and Barr et al U.K. Patent 1,330,524 or processing-formed reflective layers can be employed, as illustrated by Land U.S. Patents 2,607,685 and 3,647,437, Rogers U.S. Patent 2,983,606, and Buckler U.S. Patent 3,661,585.

-3~-Generally, the image transfer film units in - accordance with this invention comprise:
(1) a photographic element comprising a support having thereon at least one silver halide emulsion layer containing radiation-sensitive internal latent image sil-ver halide grains and a vinylene nucleating agent, the emulsion layer preferably having in contact therewith an image dye-providing material, (~) an image-receiving layer, which can be located on a separate support and superposed or adapated to be superposed on the photographic element or, prefer-ably, can be coated as a layer in the photographic element, (3) an alkaline processing composition, (~l) means containing and adapted to release the alkaline processing composition inLo contact with the emulsion layer, and (5j a silver halide developing agent located in at least one of the photographic element and alkaline pro-cessing composition so that the processing composition and developing agent, when brought together, form a silver halide surface developer.
In highly preferred embodiments, the fllm units of this invention contain a support having thereon a layer containing a blue-sensitive emulsion and in contact there-with a yellow image dye-providing material, a red-sensi-tive silver halide emulsion and in contact therewith a cyan image dye-providing material, and a green-sensitive emulsion and in contact therewith a magenta image dye-pro-viding material, and preferably all of said image dye-pro-3 viding materials are initially immobile image dye-provid-ing materials.
The terms "diffusible" (or "mobilel') and "immobile" (or "nondiffusible"), as used herein, refer to compounds which are incorporated in the photographic ele-35 ment and, upon contact with an alkaline processing solu-tion, are substantially diffusible or substantially immo-bile, respectively, in the hydrophilic colloid layers of a photographic element.

9 ~' The term "ima~e dye-providing material", as used herein, is understood to refer to those compounds which are employed to form dye images in photographic elements.
Tnese compounds include aye developers, shifted dyes, color couplers, oxicnromic compounds, dye redox releasers, etc, as described above in connection with positive-work-ing and negative-working image transfer systems.
In one preferred embodiment, the receiver layer is coated on tne same support with the photosensitive sil-ver ~alide emulsion layers, the support is preferably a transparent support, an opaque layer is preferably posi-tioned between the image-receiving layer and t~e photo-sensitive silver halide layer, and the alkaline processing composition preferably contains an opacifying su~stance, such as carbon or a pH-indicator dye which is discharged into the film unit between a dimensionally stable support or cover sheet and the photosensitive element.
In certain embodiments, the cover sheet can be superposed or is adapted to be superposed on tne photo-sensitive element. The image-receiving layer can De located on the cover sheet so that it becomes an image-receiving element. In certain preferred embodiments where the image-receiving layer is located in the photosensitive element, a neutralizing layer is located on the cover s~eet.
Increases in maximum density can ~e obtained in color image transfer film units containing internally sulfur and gold-sensitized emulsions of the type described by Evans U.S. Patent 3,761,276, and sulfonamidonaphthol 3 redox dye-releasing compounds of the type described by Fleckenstein British Patent 1,405,662, by incorporation into the emulsion layers of a variety of chemical addenda generally recognized in the art as antifoggants or devel-opment inhibitors, as well as hydrolyzable precursors thereof. Many of ~hese compounds also provide improved stabilization of sensitometric properties of liquid emul-sion and of the storage life of the coated emulsion. The effects, shown in film units of the type described in E~amples 40 through 42 of British Patent 1,~05,662, are in 7 9 ~' addition to the effect of 5-methylbenzotriazole in the processin~ composition even when tne latter is present in quantities as high as 4 grams per liter. Effeccive com-pounds in general are selected from ~he group consisting of (a) 1,2,3-triazoles, tetrazoles and benzotriazoles having an N-RI group in ~he neterocyclic ring, wherein ~1 represents hydrogen or an al~ali-hydrolyzable group, or (b) neterocyclic mercaptans or tniones and p~ecursors tnereoI, mostly naving one of the formulas (XII) or (XIII):
(XII) ~ 1~ or (XIII) Z N~
1 1 '~ I
C ~2 C=~
- w~erein ~ comprises the atoms necessary to complete an azole ring, and R2 represents, in addition to the groups speci-fied above for ~1, a metal ion.
rne compounds are generally employed at concen-trations less than about 300 mg per mole of silver, each compound naving an optimum concentration above which development and/or nucleation are inhibited and ~max decreases witn increasing concencration. Specifical1y preferred antlfog~ants and stabilizers, as well as other preferred color image transfer ~ilm unit and system features, are more specifically disclosed in Kesearch ~is-closure, Vo1ume 151, Novem~er 1976, Item 1516~
-A more detailed descrip~ion of useful image transfer film units and systems is contained in the patents relating to image transfer cited above~

specific preferred image-transfer film unit and image transfer system is that disclosed by ~eone et al U.S.
Patent 4,030,925, cited above, In a specific preferred form the photographic elements of this invention are intended to produce multi-7~1 color images which can be viewed in the elements or ln a receiver when the elements form a part of à multicolor image transfer system. For multicolor imaging at least three superimposed color-forming layer units are coated on a support. Each of the layer units is comprised of at least one silver halide emulsion layer. At least one of the silver halide emulsion layers, preferably at least one of the silver halide emulsion layers in each color-forming layer unit and most preferably each of the silver halide emulsion layers, contain an emulsion according to this invention substantially as described above. The emulsion layers of one of the layer units are primarily responsive to the blue region of the spectrum, the emulsion layers of a second of the layer units are primarily responsive to the green region of the spectrum, and the emulsion layers of a third of the layer units are primarily responsive to the red region of the spectrum. The layer units can be coated in any conventional order. In a preferred layer arrangement the red responsive layer unit is coated 2~ nearest the support and is overcoated by the green responsive layer unit, a yellow filter layer and a blue responsive layer unit. The layer units each contain in the emulsion layers or in adjacent hydrophilic colloid layers at least one image dye-providing compound. Such compounds can be selected from among those described above. Incorporated dye-forming couplers and redox dye-releasers constitute exemplary preferred image dye provid-ing compounds. The blue, green and cyan responsive layer units preferably contain yellow, magenta and red image dye providing compounds, respectively.
The preparation of compounds useful as nucleating agents in the practice of this invention is generally known. An exhaustive description of the methods used for the synthesis of such compounds is given for example in F.
35 M. Hamer's book, The Cyanine Dyes and ~elated ~ompounds, Interscience Publishers, John Wiler ~ Sons, New York, 1964 ~pp 447 et seq.). These methods can be used to prepare the nucleating agents of the invention.

91' A few examples of preparation of compounds useful as nucleatin~ a~ents are ~iven hereafter.
Compound NA-l 2-[~-anilinovinyl]-3-methylbenzothiazolium p-toluenesulfonate 112 g of 2,3-dimethyl-benzothiazolium p-toluene-sulfonate were introduced into 200 ml of xylene. The mixture was heated to 70-80C and a previously prepared mixture of 75 g of ethyl o-formiate, 93 g of aniline and 50 ml of xylene and 1 ml of sulfuric acid as a reaction catalyst was added with ~ood stirrin~. An orange colored product was obtained (Yield: 80%, m.p. 244C).
Analysis: C23H22N203 S2 Percent: C H N S
Calculated: 63.01 5.02 6.39 14.61 Found: 62.18 4.83 6.23 16.01 Compound NA-2 2-[~-(N-methylanilino)vinyll-3-methyl-benzothiazolium ~-toluenesulfonate To 100 ml of acetone were added 13.3 g of 3-methyl-2-~-anilinoethylidene benzothiazoline, The mixture was stirred, then 10 g of methyl p-toluene-sulfonate were added. The reagents were left in contact for 72 hours. A solid was formed, collected and drained, then recrystallized from a mixture of ethanol and ether (m.p. 138C).
25Analysis: C24~24N2O3S2 (mol. weight: 452) Percent: C H N
Calculated: 63.71 5.38 6.19 Found: 60.66 5.45 5.92 Compound NA-3 2-[~-(-o-methylthio-N-methylanilino~-vinyl~-l-methylquinolinium p-toluene-sulfonate 15.2 ~ of 1-methyl-2 (3-methyl-2-benzothiazolin-ylidene)quinolinium ~-toluenesulfonate were dissol~ed in 120 ml of toluene. 10 g of methyl p-toluenesulfonate were added. The precipitate formed was drained and recrystal-lized from methanol.

9~

Analysis:C27H2~N203S2 tmol. weight: 492) Percent: C ~ N S
Calculated: 65.85 5.69 5.69 13.00 Found: 62.73 5.70 5.37 13.07 Compound NA-4 2-[~-(N-propargylanilino)vinyl]-3-ethyl-benzoxazolium bromide 13.2 g of ~-anilinoethylidene ethyl-3-benzoxa-zoline were dissolved in 250 ml of acetone; 6 ml of pro-pargyl bromide were added at room temperature. Crystals were formed after 2 hours of contact. Stirring was con-tinued for 24 hours. The product was filtered off and recrystallized from a methanol/ether mixture (m.p. 198~C).
Analysis: C2 o Hl 9 BrN20 (mol. weight: 383) Percent: C H N
Calculated: 62.66 4.96 7.30 Found: 61.76 4.75 7.20 Compound NA-5 2-[~-(p-N-methylaminophenoxy)vinyl-3-methylbenzothiazolium chloride To 200 ml of ethanol were added 34.4 g of ~-hydroxymethylaminobenzene sulfate and 11.2 g of potassiumhydroxide. This mixture was stirred for 30 minutes, its temperature being maintained between 5-lODC. 40.6 g of 2-(N-benzoylanilinovinyl)-3-methylbenzothiazolium chloride were added. A solubilization occurred first, then a precipitation while a strong red color was formed. The product was drained, washed with acetone and recrystal-lized from a methanol/ether mixture (m.p. of the purified product 262C).
Analysis: Cl 7 Hl 7 ClN20S (mol. weight: 332.5) 30Percent: C H N Cl S
Calculated: 61.35 5.11 8.42 10.67 9~67 Found: 59.15 5.12 8.36 10.77 9.52 Compound NA-6 2-[~-(o-metboxy-N-methylanilino)vinyl]-3-methylbenzothiazolium ~-tcluenesulfonate To 250 ml of ethanol were added 46.8 g o~ 2~
(o-methoxyanilino)vinyl]-3-methylbenzothiazolium ~-tol-uenesulfonate; 10 g of pelleted potassium hydroxide were 1~1379'1:

added and the mixture was stirred for ~0 minutes at room temperature. A gummy material was obtained.
5~0 ml of water were aaded; the half-gummy, hal~-crystalline material formed was filtered and dissolved in 500 ml of toluene; it was dried on potassium hydroxide, filtered and 18.6 g of methyl p-toluene-sulfonate (0.09 mole) were added to the toluene solution. l`he mixture was allowed to rest for 24 hours; a precipitate was formed and filtered, then recrystallized from a methanol/ether mix-ture (m.p. of the purified product: 188~C).
Analysis: C2sH26N204S~ (mol. weight: 488) Percent: C H N S
Calculated: ~2.24 5.39 5.80 13.2 Found: 61.85 5.20 5.79 14.4 5 Compound NA-7 2-[~-(N-propargylanilino)vinylj-3-ethyl-benzoselenazolium bromide In 200 ml of ethanol were dissolved 5.03 g of ethyl-3,2-anilinovinylbenzoselenazolium p-toluene-sulfonate. 1 g of pelleted potassium hydroxide was added at room temperature and stirring was continued for 4 hours. The precipitate was drained and extracted with benzene. To the benzene solution were added ~ g of propargyl bromide which were lett in contact for 72 hours. The precipitate formed was drained and recrystal-lized from a methanol/ether mixture (m.p. of the product thus purified: 2~0C).
Analysis: C2 OHlgBrN2Se (mol. weight: 446) Percent: C H N
Calculated: 53.&1 4.26 6.27 3Found: 53.59 4.32 6.28 Compound NA-8 2-L~-(N-propargylanilino)vinyll-1,3-di-ethyl-5,6-dichloro benzimidazolium bromide 11.4 g of 1,3-diethyl-5,6-dichloro-2-anilino-vinyl-benzimidazolium p-toluenesul~onate were added to 25 ml of ethanol. 2 g of pelleted potassium hydroxide were added and the mixture (sparingly soluble at the beginning of the reaction) was stirred and slowly solubilized. Then the base froze. It was drained after two hours of contact '7 and extracted with toluene. 10 g of propargyl bromide were added to the toluene solution, then it was stirred for 72 hours at room temperature; the product was drained and recrystallized from a methanol/ether mixture (m.p. of the purified product: 144C).
Analysis: C22H22BrCl2N3-CH30~ (mol. weight: 511) Percent: C h N
Calculated: 54.11 5.09 8.21 Found: 53.02 5.14 8.29 0 ~ompound NA-9 2-L~-o-propargylthio-N-propargylanilino-vinyl~-3-methylbenzothiazolium bromide In 20 ml of acetone, were dissolved 2 g of 3-pro-pargyl-2-~(methyl-3'-benzothiazolinylidene~methyl~benzo-thiazoline. 2 ml of propargyl bromide were added. A
precipiate was rapidly formed. The mixture was stirred and cooled, then the precipitate was filtered out and washed with acetone. The material was recrystallized from a methanol/ether mixture.
Analysis: C22H1gBrN2S2 (mol. weight: 455) Percent: C H N
Calculated: 58.02 4.19 6.15 Found: 57.52 4.18 6.12 Compound NA-10 2-~-(o-methylthio-N-propargylanilino)-vinyl]-3-methyl-benzothiazolium ~-toluene-sulfonate The procedure described for the snythesis of Com-pound NA-9 was used, but methyl p-toluenesulfonate was substituted in place of propargyl bromide.
Analysis: C27H26N203S3 (mol. weight: 522 3 Percent: C H N
Calculated: 62.06 4.98 5.36 Found: 61.90 4.94 5.15 Compound NA-ll 2-[~-methyl-~-(o-propargylthio-N-methylanilino)vinyl]-3-methyl-benzothi-azolium bromide To 20 ml of benzene, were added 3.12 g of di-methyl-2,3-[(methyl-3'-benzothiazolinylidene)methyl]-2-benzothiazoline (1/100 mol.). The suspension was stirred ~.41~79~

at room temperature. 4 ml of propargyl bromide were added. A gum was formed. After 2 hours rest, benzene was decanted and the residue was washed with acetone.
The residue was dissolved in ethanol and filtered. The filtrate was poured into hexane and the product crystallized out; it was drained and washed with hexane (m.p. 170C).
Analysis: C21~2,BrN2S2 (mol. weight: 445) Percent: C H N
Calculated: 56.63 4.71 6.2 Found: 54.19 4.63 6.01 Compound NA-12 2-[~-(N-propargylanilino)vinyl~-3-methyl-benzothiazolium bromide 26.6 g of N-anilinoethylidene methyl-3-benzothiazoline were suspended in 250 ml of acetone. 13 g of propargyl bromide were added in one portion. The mixture was stirred for 72 hours at room temperature. The precipitate formed was filtered out and recrystallized from a methanol/acetone/ether mixture. The product was drained and washed with acetone.
Analysis: C~gHl7BrN2S (mol. weight: 385) Percent: C ~ N
Calculated: 59.22 4.41 7.27 Found: 58.61 4.31 7.25 Compound NA-13 ~ -(N-methylanilino)vinyl]-3-methyl-N-(N'-ethylthioureido)benzothiazolium bromide (a) Preparation of ~ -anilinovinyl)-3-methyl-6-acetamiao-benzothiazolium p-toluenesulfonate A solution of 6.05 g of ethyl o-formiate and 3.8 g of aniline in 50 ml of xylene containing a ~race of concentrated sulfuric acid was added to a suspension of 14 g o~ dimethyl-2,5-acetamido-6-benzothiazolium p-toluene-sulfonate. The mixture was heated for 4 hours at 80C; it was completely dissolved, then reprecipitated. The solid formed (13 g, yield: 73.5%) was filtered out, washed with acetone and recrystallized from methanol.

~4~79 (b) Preparation of 2-(~-N-methylanilino-vinyl)-3-methyl-6-acetamido-benzothiazolium p-toluenesulfonate To a solution of 6.5 g of the preceding material in 65 ml of methanol were aaded 4 g of 3070 sodium methylate. The solution left for 5 hours at room temperature became green, the precipitate formed was filtered out, wasned with water and acetone and placed in a cartridge of a Kumagawa extractor. After extraction with ~00 ml of benzene (the insolu~le residue in the cartridge was eLminiated) and concentration of t~e benzene, 65 ml of acetone and 3 g of methyl p-toluenesulfonate were added. Tne solution was refluxed for ~ nours. rhe yellow product (4 g, yiela: ~Oh) wnich precipitated was filtered out and washed with ether.
(c) Preparation of 2-L~ -methylanillno)-vinyll-3-methyl-6-amino-benzothiazolium bromide A suspension of 2.475 g of Che preceding material in 6 ml of ~51~ nydrochloric acid was refluxed for 1 hour.
After solubilization, then reprecipitation, ~.6 g of potassium bromide were added and stirring was continued for l hour at room temperature. After neutralization with an aqueous solution of sodium nydroxiae, the preci~itate (1.6 g, yield: ~7.5~lO) was filtered out and dried.
(d) Preparation of 2-~-(N-methylanilino)-vinyl]-3-methyl-6-N-(N-methylthioureido)-~enzothiazolium 0.55 g of ethyl isothiocyanate were added to a 30 solution oE 1.47 g of tne preceding material in 15~ ml of ethanol. The solution was reflu~ed tor 1 hour 30 minutes under a nitrogen atmosphere. The precipitate formed was filtered out and washed with ether (1.1 g, yield 60~/o)~
The following examples illustrate the use of che 35 vinylene compounds as nucleating agents ~or internal latent image-forming direct-positive emulsions.

79~L

Examples 1 through 3 A gelatino-silver bromide emulsion capa~le of forming an internal latent image of the tvpe disclosed in Evans U.S. Patent 3,761,276 was employed. The emulsion was internallv sulfur and gold sensitized and surface sulfur and gold sensitized to a lesser extent to provide a high ratio of internal to surface chemical sensitization.
The emulsion contained cuhic silver bromide grains having an average diameter of 0.6 micron. (The average grain diameter is the diameter of a circle equal in area to the mean projected area of the silver halidé grains.) To various samples of the emulsion were added a nucleating agent, the nucleating agent and the amount ~eing identified in Table II. Each emulsion sample was separately coated on a poly(ethylene terephthalate) photographic film support at a coverage of 125 mg/dm of ~elatin and 50 mg/dm2 of silver.
The resulting photographic elements were then ~iven a sensitometric exposure with a li~ht source having a temperature of 2850K. A sample of each element was developed in Developer A below and another sample was developed in Developer B below. Both developers were surface developers; that is, they did not develop the internal latent image. Both developers produced direct-reversal images.
Developer A
Elon 1 g Ascorbic acid 10 g Sodium metaborate 40 g Water to make 1 liter p~ 10.2 Developer B
Elon 1 g Ascorbic acid 10 g Sodium metaborate 40 g Benzotriazole 0.1 g Water to make 1 liter pH adjusted to 12.3 with ~OH

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~ 37~1 Examples 4 and 5 An internal image silver bromide emulsion was prepared by the procedure of Example 1. ~o a first sample of this emulsion were added 400 mg per silver mole of Compound NA-2, and to a second sample were added L~O mg per silver mole of Compound NA-14. These two emulsion samples were coated on a polyolefin-coated photographic paper support at a coverage of 5 mg/dm2 of silver and 27.5 mg/dm2 of gelatin. This emulsion contained 6 mg/dm~
of a yellow dye-forming coupler having the following formula:
CH3 0 0 ~1 CH3-C - C-CH-C-N~ - 0 t\C5h 0 \NH-C-(C~I2)3-O--~ ~--t-Cs~
.~-\.

,. .
= - . = .
SO -~ ~ -O- CH2~
A gelatin layer was then coated over each emul-sion layer.
Each sample was exposed as in Example 1, then processed for 4 minutes at 38C in the surface developer - having the following composition:
Developer C
Benzyl alcohol 1~ ml N-ethyl-N-methyl-sulfon-amidoethyl-2-methyl-~-phenylenediamine sesqui-sulfate 6 g Piperidino hexose reductone 0.5 g Sodium sulfite 1.5 g Potassium carbonate 30 g Benzotrlazole 10 mg - Water to make 1 liter p~: 10.5 '7 Processing was finished as follows:
Stop bath 20 seconds ~leach-fixing 1 minute Washing 2 minutes.
In both cases a yellow positive image was obtained whose characteristics are given in Table Ill.
Table IlI
Nucleating Agent Amount mg/mole A~ Dmin max NA-2 400 0.14 1.90 NA-14 40 0.12 2.05 When the procedure described above was repeated with a third sample lacking vinylene compound incorporated as a nucleating agent, substantially no positive image was discernible at the end of 4 minutes, but after 12 minutes a positive image was visible. Thus, the nucleating agents of the present invention are capable oE significantly accelerating the formation of a positive image.
The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Claims (21)

WHAT IS CLAIMED IS

1. A silver halide emulsion comprised of silver halide grains capable of forming an internal latent image and, adsorbed to the surface of said silver halide grains, a nucleating amount of a compound of the formula wherein Z1 represents the atoms completing an aromatic carbocyclic nucleus of from 6 to 10 carbon atoms;
Yl and Y2 are independently selected from among a divalent oxygen atom, a divalent sulfur atom, and ;
Z2 represents the atoms completing a hetero-cyclic nucleus of the type found in cyanine dyes;
A is an adsorption promoting moiety;
m and n are 1 or 2; and R1, R2, and R3 are independently chosen from the group consisting of hydrogen, alkyl, aryl, alk-aryl, and aralkyl and R1 and R3 are additionally inde-pendently chosen from the group consisting of acyl, alken-yl, and alkynyl, the aliphatic moieties containing up to 5 carbon atoms and the aromatic moieties containing 6 to 10 carbon atoms.

2. A silver halide emulsion according to claim 1 wherein said silver halide grains are predominantly sil-ver bromide and contain metal dopants occluded therein, which grains when coated on a photographic support, exposed to a light intensity scale, and developed for 5 minutes at 25°C in test surface developer provide (a) a density of less than 0.4 and (b) a density of at least 0.5 less than when this testing procedure is repeated modify-ing the test surface developer by the inclusion of 0.5 gram per liter of potassium iodide, the test surface developer being of the following composition:

Water 500.0 cc N-metnyl-p-aminophenol sulfate 2.5 g Sodium sulfite, desiccated 30.0 g Hydroquinone 2.5 g Sodium metaborate 10.0 g Potassium bromide 0.5 g Water to make 1.0 liter.

3. A silver halide emulsion according to claim 2 wherein said compound is present in a concentration of from 10-5 to 10-2 mole per mole of silver halide.

4. A silver halide emulsion according to claim 2 wherein said compound is of the formula X-wherein m and p are 1 or 2;
y1 and y2 are independently selected from among a divalent oxygen atom, a divalent sulfur atom, and ;
Z3 completes a heterocycle forming at least one 5- or 6-membered ring containing 1 or 2 heteroatoms in the ring chosen from the group consisting of oxygen, sulfur, selenium, and nitrogen, the remaining ring atoms being carbon;
R1, R2, and R3 are independently chosen from the group consisting of hydrogen, alkyl, aryl, alkaryl, and aralkyl, R1 and R3 are additionally independently chosen from the group consisting of acyl, alkenyl, and alkynyl, and R4 is independently chosen from the group consisting of alkyl, aryl, alkaryl, alkenyl, and aralkyl, the aliphatic moieties containing up to 5 carbon aoms and aromatic moieties containing 6 to 10 carbon atoms; and X is an acid anionif required for charge neutrality.

5. A silver halide emulsion according to claim 4 wherein said compound is present in a concentration of from 10-4 to 10-2 mole per mole of silver halide.

6. A silver halide emulsion according to claim 5 wherein Y2 is oxygen.

7. A silver nalide emulsion according to claim 6 wherein said compound is an alkylaminophenoxyvinyl-3-alkylbenzothiazole salt.

8. A silver halide emulsion according to claim 5 wherein Y2 is -N-R3 .

9. A silver naiide emulsion according to claim 8 wherein said compound is an N-alkyl substituted benzo-tniazolium, quinolium, benzoxazolium, benzoselenazolium, or benzimidazolium salt wnich is .beta.-anilinovinyl sub-stituted.

10. A silver halide emulsion according to claim 2 wherein said compound is of the formula X-wherein m and p are 1 or 2;
Y1 and Y2 are independently selected from among a divalent oxygen atom, a divalent sulfur atom, and -N-R3;
Z3 completes a heterocycle forming at least one 5- or 6-membered ring containing 1 or 2 heteroatoms in the ring chosen from the group consisting of oxygen, sulfur, selenium, and nitrogen, the remining ring atoms being carbon;
A is an adsorption promoting moiety chosen from the class consisting of thioamide and triazole adsorption promoting groups;
R1, R2, and R3 are independently chosen from the group consisting of hydrogen, alkyl, aryl, alkaryl, and aralkyl, R1 and R3 are additionally independently chosen from the group consisting of acyl, alkenyl, and alkynyl, and R4 is independently chosen from the group consisting of alkyl, aryl, alkaryl, alkenyl, and aralkyl, the aliphatic moieties containing up to 5 carbon atoms and aromatic moieties containing 6 to 10 carbon atoms; and X is an acid anion, if required for charge neutrality.

11. A silver halide emulsion according to claim 10 wherein said compound is present in a concentration of from 10-5 to 10-3 mole per mole of silver halide.

12. A silver halide emulsion according to claim 11 wnerein said adsorption promoting group is a thioureido group.

13. A silver halide emulsion according to claim 12 wherein said compound is a thioureido substituted benzothiazolium salt which is N-substituted with an alkyl group and substituted in its 2-position with .beta.-anilino-vinyl group.

14. A photographic element comprising a support and a silver halide emulsion according to claim 1 forming a layer on said support.

15. A process comprising surface developing an imagewise exposed photographic element according to claim 14 to produce a visible direct-positive image.

16. A process according to claim 15 in which a surrface developer is employed having a pH in the range of from 10 to 13Ø

17. A process according to claim 16 in which surface development occurs in the presence of a benzo-triazole antifoggant.

18. In a photographic element capable of forming direct-reversal photographic images comprised of a support, a red responsive cyan dye image-forming layer unit, a green responsive magenta dye image-forming layer unit, and a blue responsive magenta dye image-forming layer, each of said layer units containing silver halide grains capable of forming an internal latent image and, adsorbed to the surface of the silver halide grains, a nucleating agent, the improvement comprising said nucleating agent being of the formula wherein Z1 represents the atoms completing an aromatic carbocyclic nucleus of from 6 to 10 carbon atoms;
Y1 and Y2 are independently selected from among a divalent oxygen atom, a divalent sulfur atom, and -N-R3 ;
Z2 represents the atoms completing a hetero-cylclic nucleus of the type found in cyanine dyes;
A is an adsorption promoting moiety;
m and n are 1 or 2; and R1, R2, and R3 are independently chosen from the group consisting of hydrogen, alkyl, aryl, alk-aryl, and aralkyl and R1 and R3 are additionally inde-pendently chosen from the group consisting of acyl, alken-yl, and alkynyl, the alipbatic moieties containing up to 5 carbon atoms and the aromatic moieties containing 6 to 10 carbon atoms.

19. In a photographic element according to claim 18 the further improvement wherein said silver halide grains are predominantly silver bromide and contain metal dopants occluded therein, which grains when coated on a photographic support, exposed to a light intensity scale, and developed for 5 minutes at 25°C in test surface developer provide (a) a density of less than 0.25 and (b) a density of at least 5 times greater when this testing procedure is repeated modifying the test surface developer by the inclusion of 0.5 gram per liter of potassium iodide, the test surface developer being of the following composition:

Water 500.0 cc N-methyl-?-aminophenol sulfate 2.5 g Sodium sulfite, desiccated 30.0 g Hydroquinone 2.5 g Sodium metaborate 10.0 g Potassium bromide 0.5 g Water to make 1.0 liter.

20. In a photographic element according to claim 19 the further improvement wherein said nucleating agent is of the formula X
wherein m, n, and p are 1 or 2;
Y1 and Y2 are independently selected from among a divalent oxygen atom, a divalent sulfur atom, and -N-R3 ;
Z3 completes a heterocycle forming at least one 5- or 6-membered ring containing 1 or 2 heteroatoms in the ring chosen from the group consisting of oxygen, sulfur, selenium, and nitrogen, the remining ring atoms being carbon;
A is a thioureido adsorption promoting group;
R1, R2, and R3 are independently chosen from the group consisting of hydrogen, alkyl, aryl, alkaryl, and aralkyl, R1 and R3 are additionally independently chosen from the group consisting of acyl, alkenyl, and alkynyl, and R4 is independently chosen from the group consisting of alkyl, aryl, alkaryl, alkenyl, and aralkyl, the aliphatic moieties containing up to 5 carbon aoms and aromatic moieties containing 6 to 10 carbon atoms; and X is an acid anion if required to satisfy charge neutrality.

21. In a process of developing an imagewise exposed internal latent image-forming photographic element containing three dye image-forming layer units in a sur-face developer to form a multicolor direct-reversal image, the improvement comprising developing a photogra-pnic element according to claim 18, 19, or 20 in a surface developer having a pH in the range of from 10.2 to 12.0 and containing from 5 to 500 mg per liter of a benzotri-azole antifoggant.