GB2056104A - Dye Image Formation Process and Silver Halide Photographic Film Unit - Google Patents

Abstract

A process of forming a dye image, especially by dye image transfer, from a silver halide photographic recording material containing a ballasted electron-accepting nucleophilic displacement (BEND) compound wherein development takes place in the presence of a peroxide oxidising agent that is essentially inert to the image-forming oxidation-reduction reaction in the absence of silver catalyst. The preferred peroxide is hydrogen peroxide.

Description

SPECIFICATION Dye Image Formation Process and Silver IHalide Photographic Film Unit This invention is directed to processes of forming dye images and to photographic recording materials useful in such processes. More specifically this invention relates to peroxide amplification of photographic recording materials containing ballasted electron-accepting nucleophilic displacement compounds.

It is known in the art to use image dye providing materials in photographic elements such as image-transfer film units. Among the known image dye-providing materials are those which are initially immobile in a photographic element such as the initially immobile compounds which undergo a redox reaction followed by alkali cleavage to split off a diffusible dye moiety disclosed in U.S. Patent 4,076,529. These image dye-providing materials have come to be known in the art as redox-dye releasers, frequently referred to as RDRs. They have proven to be highly useful, but are generally limited in application by the fact that dye is released in direct proportion to imagewise odixation. Thus, a direct-positive silver halide emulsion, or some other reversing mechanism, is used if a positive transfer image is desired.

Positive-working immobile compounds, which can be used with negative-working silver halide emulsions to obtain positive images, are disclosed in U.S. Patents 4,139,379 and 4,139,389 (British Application Nos. 9043/78 and 9045/78). These are ballasted compounds that undergo intramolecular nucleophilic displacement to release a diffusible moiety. The compounds contain a precursor for a nucleophilic group which must accept at least one electron before the compound can undergo intramolecular nucleophilic displacement. These compounds are referred to as ballasted electron accepting nucleophilic displacement compounds and are frequently called BEND compounds. In a preferred embodiment described in U.S.Patent 4,139,379, the BEND compounds are processed in silver halide photographic elements with an electron transfer agent and an electron donor (i.e., reducing agent) which provides the necessary electrons to enable the compound to be reduced to a form which will undergo intramolecular nucleophilic displacement.

When used in such a photographic element or process, the BEND compound reacts with the electron donor to provide a nucleophilic group which in turn enters into an intramolecular nucelophilic displacement reaction to displace a diffusible group from the compound, such as a diffusible dye.

However, where there are no electrons transferred to the electron-accepting nucleophile precursor, it remains incapable of displacing the diffusible group. An imagewise distribution of electron donor is obtained in the photographic element by oxidizing the electron donor in an imagewise pattern before it has reacted with the BEND compound, leaving a distribution of unoxidized electron donor available to transfer electrons to the BEND compound. An imagewise distribution of oxidized electron donor is provided by reaction of the electron donor with an imagewise distribution of oxidized electron transfer agent, which in turn is obtained by reaction of a uniform distribution of electron transfer agent with an imagewise pattern of developable silver halide.Thus in processing an imagewise exposed photographic element containing a BEND compound the following reactions lead to an imagewise distribution of diffusible dye: In exposed areas, developable silver halide is developed by electron transfer agent thereby providing oxidized electron transfer agent which reacts with and oxidizes the electron donor thus preventing it from reacting with BEND compound. In unexposed areas, there is no developable silver halide and hence neither electron transfer agent nor electron donor are oxidized.

Thus, electron donor reacts with BEND compound to release diffusible dye.

In other embodiments an electron transfer agent is not employed. In these embodiments, the electron donor employed is a silver halide developing agent and an imagewise distribution of oxidized electron donor is obtained as a result of reaction of electron donor with the imagewise pattern or developable silver halide.

It is known in the art that oxidized electron transfer agent can be generated imagewise by reaction with a cobalt(lil) complex or a peroxide compound at a redox catalyst site. In one-form the catalyst site can be provided by developed silver. In this approach the amount of oxidized electron transfer agent is not stoichiometrically limited by the amount of silver which is or can be developed.

Imaging systems of this type are referred to in the art as dye image amplification systems, since the amount of dye formed is not limited by the amount of silver (or other redox catalyst) present. The use of redox dye-releasers in a dye image amplification system in which a cobalt(Ill) complex is employed as an oxidant is illustrated in U.S. Patents 3,862,842 and 3,862,855. The use of redox-dye-releasers in dye image amplification systems in which a peroxide compound is employed as an oxidant is illustrated in U.S. Patents 3,822,129 and 3,834,907 and in U.K. Patent Application 2,005,431 A published April 19,1979.

The specific disclosure of these specifications is restricted to the use of redox dye-releasers wherein dye is released by reaction with an oxidized colour developing agent or electron transfer agent.

Peroxide amplification is employed to generate additional oxidized material over and above that which would normally be obtained by silver halide development. In these reactions the point in time at which the oxidized material is generated is relatively noncritical, since the reactions can be allowed to proceed until the requisite amount of dye has been formed or released.

In contrast, in the present invention, dye is not formed or released by the oxidized material; rather, the oxidized material prevents release of dye. The oxidation of the electron donor, or the electron transfer agent and in turn the electron donor, renders the electron donor incapable of interacting with a BEND compound to release dye. Due to these differences in reaction mechanism, it was feared that peroxide amplification would cause the oxidation of electron donor or electron transfer agent in such a way as to inhibit dye release since, if electron donor or electron transfer agent are not oxidized sufficiently early in the reaction, subsequent oxidation would be too late to have any effect on image discrimination.

Nothing in the prior art suggests that peroxide amplification would occur early enough in the dyeforming reaction using BEND compounds to contribute to image discrimination. It is further noted that the preferred electron donors such as those which result from hydrolysis of benzisoxazolone precursors, are strong reducing agents. They are substantially stronger reducing agents than the conventional black-and-white and colour developing agents heretofore used with peroxide amplification. Peroxides, of course, are strong oxidizing agents and what might well have been expected under such circumstances is the indiscriminate reaction of the electron donor with peroxide.

This would not lead to amplification, but rather to the prevention of any dye release.

The present invention is based upon the unexpected observation that dye image amplification using a peroxide oxidizing agent that can be employed in the processing of photographic recording materials containing dye-providing BEND compounds to yield increases in photographic speed and to permit, if desired, the use of lower amounts of silver halide.

This invention provides a process of forming a dye image in an imagewise exposed photographic recording material which has a support bearing at least one light-sensitive silver halide emulsion layer containing a developable latent image therein and, associated with said emulsion layer, a nondiffusible ballasted electron-accepting nucleophilic displacement (BEND) compound which, on acceptance of an electron, is capable of undergoing an intramolecular nucleophilic displacement reaction to release a diffusible dye or other photographically useful moiety, there being at least one nondiffusible image dyeproviding compound associated with said emulsion layer, said BEND compound having the formula l::

wherein each of w, x, y, z, n and mis 1 or 2; (ENuP) is an electron-accepting, nucleophilic precursor group, which group, on acceptance (as herein defined) of an electron, becomes nucleophilic or (ENuP) is a hydrolysable precursor for said group; R1 is an acyclic or cyclic organic group to which (ENuP) and E are attached, optionally through R2 and R3 respectively; each of R2 and R3 is a bivalent organic group which contains from 1 to 3 atoms in the bivalent linkage and which may have substituents on the linkage atoms;; E and Q provide an electrophilic cleavage group wherein E is an electrophilic group and Q is a leaving group providing a monoatom linkage between E and X2 and which can be displaced from E by the nucleophilic group provided by (ENuP) on acceptance of an electron, and Q is an oxygen atom, a selenium atom or a sulphur atom, or a nitrogen atom in a group of formula -NR- wherein R is a substituent or together with X2 represents the atoms necessary to complete a 5- to 7-membered ring; X' is attached to at least one of R1, R2 and R3; and X1 or one of Qy~(X2)z is a ballast group and, respectively, one of Qy~(X2)z or X' is a dye or other photographically useful moiety and R', R2 and R3 are selected to provide such proximity of an (ENuP) to an E as to permit intramolecular release of a Q from an E; the process comprising the steps of a) developing the imagewise exposed photographic recording material with either 1) an electron donor which is a silver halide developing agent or 2) an electron transfer agent which is a silver halide developing agent in the presence of an electron donor to release diffusible dye or photographically useful moiety from the BEND compound as an inverse function of silver halide development, and b) transferring released diffusible dye to form a viewable dye image from at least one of the diffusible dye and the retained dye-providing compound, chåracterised in that development is effected in the presence of a peroxide oxidizing agent that is essentially inert to oxidation-reduction with the electron transfer agent and the electron donor in the absence of a silver catalyst.

The invention also provides a photographic image transfer film unit containing BEND compound as defined above characterised in that it contains a peroxide oxidizing agent as defined above.

The term "associated therewith" is a term of art in the photographic industry and in this specification and claims means that said immobile compound is in alkaline-permeabie relationship with said silver halide. The respective materials can be coated in the same layers or separate layers, as long as they are effectively accessible to each other during processing.

The term "nondiffusible" used herein has the meaning commonly applied to the term in photography. It denotes materials for all practical purposes do not migrate or wander through organic colloid layers, such as gelatin, in an alkaline medium, in the photographic elements of the invention when processed in a medium having a pH of 11 or greater. The same meaning is to be attached to the term "immobile". The term "diffusible" as applied to the materials of this invention has the converse meaning. It denotes materials having the property of diffusing effectively through the colloid layers of the photographic elements in an alkaline medium in the presence of "nondiffusible" materials.

"Mobile" has the same meaning.

By "acceptance" in the term "on acceptance of an electron" we mean that an atom in the precursor group increases its share of valency electrons.

The term "nucleophilic group" as used herein refers to an atom or group of atoms that have an electron pair capable of forming a cova!ent bond. Groups of this type are sometimes ionizable groups that react as anionic groups. The term "electron-accepting nucleophile precursor group" refers to that precursor group that, upon accepting at least one electron i.e., in a reduction reaction, provides a nucleophilic group. The electron-accepting nucleophile precursor groups are less nucleophilic in character than the reduced group or have a structure that adversely affects the proximity of the nucleophilic centre with respect to the electrophilic centre.

The nucleophilic group may contain one nucleophilic centre, such as the oxygen atom in a hydroxy group. The nucleophilic group may contain more than one atom which can be the nucleophilic centre such as in the case of an hydroxylamino group where either the nitrogen atom or the oxygen atom can be the nucleophilic centre. Where more than one nucleophilic centre is present in the nucleophilic group on the intramolecular nucleophilic displacement compounds of this invention, the nucleophilic attack and displacement will generally occur through the centre which is capable of forming the most favoured ring structure; i.e., if the oxygen atom of the hydroxylamino group would form a 7-membered ring and the nitrogen atom would form a 6-membered ring, the active nucleophilic centre would generally be the nitrogen atom.

The term "electrophilic group" refers to an atom or group of atoms that are capable of accepting an electron pair to form a covalent bond. Typical electrophilic groups are sulphonyl (~SO2~), carbonyl (-CO-) and thiocarbonyl (-CS-), where the carbon atom of the carbonyl group or the sulphur atom of the sulphonyl group forms the electrophilic centre of the group and can sustain a partial positive charge. The term "electrophilic cleavage group" is used herein to refer to a group (-E-Q-) wherein E is an electrophilic group and Q is a leaving group providing a mono atom linkage between E and X2 wherein said mono atom is a nonmetallic atom that has a negative valence of 2 or 3. The leaving group is capable of accepting a pair of electrons uDon being released from the electrophilic group.Where the nonmetallic atom is a trivalent atom, it can be monosubstituted by a group which can be a hydrogen atom, an alkyl group including substituted alkyl groups and cycloalkyl groups, an aryl group including substituted aryl groups, or the atoms necessary to form a 5 to 7 membered ring with X2 such as a pyridine or a piperidine group.

The term "intromolecular nucleophilic displacement" is understood to refer to a reaction in which a nucleophilic centre on a molecule reacts at another site in the same molecule, which is an electrophilic centre, to effect displacement of a group or atom attached to said electrophilic centre. The term "nucleophilic displacement" is intended to refer to a mechanism where a portion of the molecule is actually displaced rather than merely relocated on the molecule; i.e., the electrophilic centre must be capable of forming a ring structure with said nucleophilic group. The intramolecular nucleophilic displacement compounds of formula I have the nucleophilic group and the electrophilic group juxtaposed in the three-dimensional configuration of the molecule in close proximity whereby the intramolecular reaction can take place.

In general, the compounds of formula I are designed to undergo intramolecular nucleophilic displacement after accepting at least one electron to provide a nucleophile, and, thereby, to release a photographically useful moiety. This release means offers a new process advantage since it is controlled by reduction and has been found to be particularly attractive for photographic processes wherein organic reducing agents are used. The compounds used in the present invention may also be synthesised more efficiently and provide more latitude in the parameters of the imaging process than many other compounds proposed for image-transfer processes.

Compounds of formula I and methods of making them are described in U.K. Patent Application No. 9043/78.

The preferred embodiment of the present invention employs a dye-releasing BEND compound and where the description below refers only to this, it is to be understood that BEND compounds which release a photographically useful moiety may alternatively be employed.

In practicing the process of this invention an alkaline environment is provided in the photographic recording material containing developable silver halide and a dye-providing BEND compound.

Development of silver halide to silver generates oxidized electron donor either directly or as a result of a reaction between oxidized electron transfer agent and electron donor. The developed silver serves as a catalytic site for a redox reaction between peroxide oxidizing agent and unoxidized electron donor or electron transfer agent thus generating additional oxidized electron donor. The electron donor which has been oxidized is rendered incapable of reacting with the BEND compound to release diffusible dye.

Thus, the process results in a pattern of diffusible dye or dye precursor which is inversely proportional to the amount of electron donor which has been oxidized. This diffusible dye can be transferred to a receiving element and employed as a transfer image. Alternatively, it can merely be removed from the element Whether the diffusible dye is employed to form a transfer image or not, the remaining BEND compound, from which dye has not been released, can be employed to form a retained image.

Alternatively, it can be contacted with an additional amount of unoxidized electron donor to release diffusible dye which in turn can be employed to form a transfer image.

This processing sequence has been described with respect to a simple photographic recording material which can comprise a support bearing a layer of the silver halide emulsion having associated therewith a dye providing BEND compound. Processing can be effected by contacting the recording material with an appropriate aqueous alkaline solution and effecting transfer by contacting the recording material during or subsequent to processing with a separate receiving element to effect transfer of the dye or by washing the recording material with an aqueous solution to remove dye.

However, this process can be employed with photographic recording materials which contains a receiver and some or all of the processing components. Such recording materials are well known in the art of color diffusion and are described, for example, in the representative patents referred to above in connection with the background discussion. Preferably, such a recording material would contain means from-which an alkaline composition, containing one or more of the processing components, can be discharged to effect development, release of dye, and transfer of dye to the receiver. The preferred recording material is so adapted, that the only manipulative steps required are discharge of the alkaline composition, and, with certain material, separation of the receiver from the remainder of the material.

Hence, in a preferred embodiment, the present photographic image transfer film unit further comprises an alkaline processing composition contained within means from which it can be discharged within said material.

The foregoing discussion has been directed largely to dye-providing BEND compounds. However, as indicated above and in the aforementioned U.S. Patents 4,139,379 and 4,139,389, there can be released from the BEND compound, rather than a dye, a photographically useful reagent, for example, an antifoggant, a development inhibitor, a development accelerator, a developing agent, a fixing agent, a silver halide solvent, a silver complexing agent, a hardener, a fogging agent, a sensitiser, a desensitiser, a fogging agent or a toner.With photographic elements containing such photographic reagent-providing BEND compounds, a dye image could be provided by a dye image-providing BEND compound, as described above, or it could be provided by a different type or dye providing material known to yield dye by perooxide amplification techniques, such as an RDR or a dye-forming coupler.

The peroxide oxidizing agents employed in the processes and elements of this invention can be chosen from among conventional peroxide oxidizing agents which require the presence of a catalyst to oxidize an electron donor or an electron transfer agent, that is, are essentially inert to oxidationreduction in the absence of catalyst. More specifically, in the absence of the catalyst the oxidant and the reductant can be described as being in a state where they are substantially kinetically stable; i.e., the kinetic reaction is so slow (or practically nonexistant) as to be not noticeable in the process.

Preferably, the peroxide oxidizing agent and the electron donor, or the electron donor and electron transfer agent, are so chosen that, when test samples thereof are each dissolved at a 0.01 molar concentration in an inert solvent at 200 C., essentially no redox reaction occurs for at least 10 minutes, and most preferably for several hours. Peroxide oxidizing agents of this type include water-insoluble compounds containing a peroxy group, such as inorganic peroxide compounds or salts of peracids.For example, perborates, percarbonates or persilicates and, particularly hydrogen peroxide, can be employed as peroxide oxidizing agents in the practice of this invention as well as organic peroxide compounds such as benzoyl peroxide, percarbamide and addition compounds of hydrogen peroxide and aliphatic acid amides. polyalcohols, amines, acylsubstituted hydrazines, etc. Hydrogen peroxide is preferred, since it is highly active in the presence of a silver catalyst and is easily handled in the form of aqueous solutions.

The silver halide emulsion layers can be of any convenient conventional type, such as disclosed, for example, in Research Disclosure, Item 1 7643, Section 1, December 1978. Research Disclosure is published by Industrial Opportunities Ltd., Homewell Havant Hampshire, P09 1 EF, United Kingdom.

The emulsions can be either negative-working or positive-working emulsions and can form either a surface or internal latent image upon exposure. With dye-providing BEND compounds, it is preferred that negative-working silver halide emulsions be employed. With photographic reagent-providing BEND compounds, the preferred silver halide emulsions will depend upon the type of dye-providing compound employed. For example with RDR's, positive-working silver-halide emulsions are preferred so that a positive image will be obtained. With such emulsions dye would be released from the RDR as a direct function of silver halide development and a photographic reagent, such as an antifoggant or development inhibitor, would be released from the BEND compound as an inverse function of silver halide development.

As described in the above referenced Research Disclosure Item 17643, the emulsions can be chemically sensitized (Section Lit), be spectrally sensitized or desensitized (Section IV), be hardened (Section X), include stabilizers and antifoggants (Section VI), and contain other conventional photographic addenda.

The electron donors, electron transfer agents and BEND compounds are extensively discussed in the above-referenced U.S. Patents 4,139,379 and 4,139,389 and reference is made thereto for amplification of the discussion which follows.

In one embodiment of this invention, the electron donor used in combination with the BEND compounds is capable of developing silver halide. Thus, the electron donor is oxidized by reaction with the imagewise pattern of developable silver halide. Generally, in this embodiment any electron donor can be used which has a faster reaction rate with the exposed silver halide than it does with the BEND compound. Typical useful electron donors in this embodiment include ascorbic acid, trihydroxypyrimidines such as 2-methyl-4,5,6-trihydroxypyrimidine and hydroxylamines such as diethylhydroxylamine.

In certain preferred embodiments, the electron donor is used in combination with an electrontransfer agent (herein referred to as ETA). Generally, the ETA is a compound which is a much better silver halide developing agent under the conditions of processing than the electron donor and, in those instances where the electron donor is incapable of or substantially ineffective in developing the silver halide, the ETA functions to develop the silver halide and provide a corresponding imagewise pattern of oxidized electron donor because the oxidized ETA readily accepts electrons from the electron donor.

Generally, the useful ETA's will at least provide a faster rate of silver halide development under the conditions of processing when the combination of the electron donor and the ETA is employed as compared with the development rate when the electron donor is used in the process without the ETA.

Typical useful ETA compounds include hydroquinone compounds such as hydroquinone, 2,5dichlorohydroquinone, 2-chlorohydroquinone and the like; aminophenol compounds such as 4aminophenol, N-methylaminophenol, 3-methyl-4-aminophenol, 3,5-dibromoaminophenol and the like; catechol compounds such as catechol, 4-cyclohexylcatechol, 3-methoxycatechol, 4-(N- octadecylamino)catechol and the like; phenylenediamine compounds such as N,N-diethyl-p phenylenediamine, 3-methyl-N,N-diethyl-p-phenylenediamine, 3-methoxy-N-ethyl-N-ethoxy-p- phenylenediamine, N,N,N',N'-tetramethyl-p-phenylenediamine and the like.In highly preferred embodiments, the ETA is a 3-pyrazolidone compound such as 1 -phenyl-3-pyrazolidone, 1 -phenyl-4,4- dimethyl-3-pyrazol idone, 4-hydroxymethyl-4-methyl- 1 -phenyl-3-pyrazolidone, 4-hydroxymethyl-4 methyl- 1 -(3,4-dimethylphenyl)-3-pyrazolidone, 1 -rn-tolyl-3-pyrazolidone, 1 -p-tolyl-3-pyrazolidone, 4- hydroxymethyl-4-methyl-1 -p-tolyl-3-pyrazolidone, 1 -phenyl-4-methyl-3-pyrazolidone, 1 -phenyl-5- methyl-3-pyrazolidone, 1 -phenyl-4,4-bis-(hydroxymethyl)-3-pyrazolidone, 1 ,4-dimethyl-3- pyrazolidone, 4-methyl-3-pyrazolidone, 4,4-dimethyl-3-pyrazolidone, 1 -(3-chlorophenyl)-4-methyl-3- pyrazolidone, 1 -(4-chlorophenyl)-4-methyl-3-pyrazolidone, 1 -(3-chlorophenyl)-3-pyrazolidone, 1 -(4- chlorophenyl)-3-pyrazolidone, 1 -(4-tolyl)-4-methyl-3-pyrazolidone, 1 -(2-tolyl)-4-methyl-3- pyrazolidone, 1 -(4-tolyl)-3-pyrazolidone, 1 -(3-tolyl)-3-pyrazolidone, 1 -(3-tolyl)-4,4-dimethyl-3- pyrazolidone, 1 -(2-trifluoroethyl)-4,4-dimethyl-3-pyrazolidone, 5-methyl-3-pyrazolidone and the like. A combination of different ETA's such as those disclosed in U.S. Patent 3,039,869 can also be employed.

The particular ETA selected will, of course, depend on the particular electron donor and BEND used in the process and the processing conditions for the particular photographic element.

In those embodiments where a very high degree of imagewise discrimination is desirable, such as in multicolour photographic elements, an alkali-labile electron-donor precursor is preferred. Generally, hydrolysis of the electron donor precursor will occur at a finite rate and, as the electron donor is produced, it will react readily with the oxidized ETA made available during the silver halide development reaction or with the developable silver halide. In preferred embodiments, the alkali-labile electron-donor precursor contains sufficient ballast groups to render it substantially immobile, especially when used in multicolor photographic elements.

In certain preferred embodiments, the alkali-labile electron-donor precursors have the following formula:

wherein A represents the atoms necessary to complete an aromatic ring containing from 5-6 atoms and preferably a carbocyclic aromatic ring; R' represents a hydrogen atom or one or more groups containing from 1-30 carbon atoms and preferably is of a size sufficient to render said compound immobile in the alkali-permeable layers of a photographic element, for example, groups containing from 8-30 carbon atoms, including N substituted carbamoyl groups such as N-alkylcarbamoyl, alkylthioether groups, N-substituted sulphamoyl groups such as N-alkylsuiphamoyl, aikoxycarbonyl groups, and R11 is a substituted or unsubstituted alkyl group containing from 1-30 carbon atoms or a substituted or unsubstituted aryl group containing from 6~30 carbon atoms and preferably is a methyl group. Typical useful compounds within this formula are:

In other embodiments, other hydrolyzable electron donors can be used, such as:

In still other embodiments, the electron donor can be present in the keto form, such as in a protohydroquinone, which enolizes in base to form an electron donor.A compound of this type is as follows:

In still other embodiments, electron-donors can be used which are not precursors, but are preferably at least semi-immobile in the layers of the photographic element Typical compounds of this type are as follows:

In the BEND compounds of formula I above, the electron-accepting nucleophilic group precursor represented by ENuP can be a precursor for a hydroxylamino group such as a nitroso group (NO), a stable nitroxyl free radical (N-0#), or, preferably, a nitro group (NO2), or it can be a precursor for a hydroxy group such as an oxo group (=0), or an imine group which is hydrolyzed to an oxo group in an alkaline environment.

The cyclic organic group represented by R' includes bridged-ring groups and other polycyclic groups which preferably have from 5-7 members in the ring to which ENuP and E are attached. R' is preferably an aromatic ring having 5-6 members in the ring and is a carbocyclic ring, e.g., benzenoid groups, or is a heterocyclic ring including nonaromatic rings where ENuP is part of the ring, (e.g., where ENUP is a nitroxyl group with the nitrogen atom in the ring). Generally, R' contains less than 50 atoms and preferably less than 1 5 atoms.

The bivalent organic groups containing from 1-3 atoms in the bivalent linkage represented by R2 and R3 can be alkylene, oxaalkylene, thiaalkylene, azaalkylene, alkyl- or aryl-substituted nitrogen including large groups in side chains on said linkage which can function as a ballast, e.g., groups containing at least 8 carbon atoms and which groups can be X1 when X is a ballast group. In certain embodiments R3 preferably contains a dialkyl-substituted methylene linkage such as a dimethylalkylene which is especially useful when Q is an oxygen atom and R1 and ENuP form a quinone.

In the electrophilic cleavage group provided by E and Q, E is preferably a carbonyl group, including carbonyl (-CO-) and thiocarbonyl (-CS-) or it can be a sulfonyl group. The mono atom linkage provided by Q is preferably a nitrogen atom which provides a bivalent amino group. The third valence of this nitrogen atom can be satisfied with a hydrogen atom, an alkyl group containing from 1-20 atoms and preferably 1~1 O carbon atoms, including substituted carbon atoms and carbocyclic groups, or an aryl group containing from 6-20 carbon atoms including substituted aryl groups and groups which are connected to X2 to form 5- to 7-atom cyclic groups.

The groups represented by R1, R2 and R3 are selected to provide substantial proximity of ENuP to E so as to permit intramolecular nucleophilic cleavage of Q from E and are preferably selected to provide 1 or 3 to 5 atoms between the atom which is the nucleophilic center of the nucleophilic group and the atom which is the electrophilic center, whereby said compound is capable of forming a 3- or 5to 7-membered ring and most preferably a 5- or 6-membered ring upon intramolecular nucleophilic displacement of the group Q-X2 from said electrophilic group.

In the dye-providing BEND compounds, the dye-providing material provided by X' or Q-X2 is preferably a preformed dye or a shifted dye. Dyes of this type are well known in the art and includes dyes such as azo dyes including metallizable azo dyes and metailized azo dyes. Azomethine (imine) dyes, anthraquinone dyes, alizarin dyes, merocyanine dyes, quinoline dyes and cyanine dyes. The shifted dyes include those compounds wherein the light-absorption characteristics are shifted hypsochromically or bathochromically when subjected to a different environment such as a change in pH, reaction with a material to form a complex such as with a metal ion, removal of a group such as a hydrolyzable acyi group connected to an atom of the chromophore.In certain embodiments, the dyeproviding material is a chelating dye moiety that upon release can diffuse to an image-receiving layer containing metal ions to form a metal-complexed dye.

In certain preferred embodiments, the cleavable group is used as a substituent on a shiftable dye to control the resonance of the dye. Upon release of the dye, it will undergo a bathochromic or hypsochromic shift. In this embodiment, any dye can be used which contains an ionizable nitrogen atom, oxygen atom, sulphur atom or selenium atom which affects the resonance of the dye. The dye is attached to the compound so that the ionizable group is the leaving group in the electrophilic cleavage group.

In another embodiment, the dye providing material is an image-dye precursor. The term "imagedye precursor" is understood to refer to those compounds that undergo reactions encountered in a photographic imaging system to produce an image dye, such as colour couplers or oxichromic compounds.

In the photographically useful moiety-providing BEND compounds, the photographic reagent moiety represented by X1 or Q-X2, X' and Q-X2 may represent any moiety, which, after cleavage and in combination with a hydrogen atom, provides a photographic reagent. Where the photographic reagent is a development inhibitor or an antifoggant, Q is preferably an active nitrogen atom or an active sulphur atom, such as in a benzotriazole, benzimidazole or a mercaptotetrazole where the compound is blocked prior to release and becomes active upon release.

The nature of the ballasting groups in the above compounds is not critical as long as the portion of the compound on the ballast side of E is primarily responsible for the immobility; the other portion of the molecule on the other side of E generally contains sufficient solubilizing groups to render it mobile and diffusible in an alkaline medium after cleavage. Thus, X' could be a relatively small group as the remainder of R1, R2 and R3 confers sufficient insolubility to the compound to render it immobile.

However, when X' or --X2 serve as the ballast function, they generally comprise long-chain alkyl radicals, as well as aromatic radicals of the benzene and naphthalene series. Typical useful groups for the ballast function contain at least 8 carbon atoms and preferably at least 14 carbon atoms. Where Xa is a ballast, it can be one or more groups substituted on R', R2 or R3 which confer the desired immobility. Thus, for example, two small groups, such as groups containing from 5-12 carbon atoms, can be used to achieve the same immobility as one long ballast group containing from 8-20 carbon atoms.Where multiple ballast groups are used, it is sometimes convenient to have an electronwithdrawing group linkage between the major part of the ballast group and an aromatic ring to which it is attached, especially when the electron-accepting nucleophilic precursor is a nitro substituent on said ring.

In certain embodiments, the BEND compounds useful in accordance with the invention are ballasted compounds having the structure:

wherein ENuP is an electron-accepting precursor for a hydroxy nucleophilic group including imino groups and preferably oxo groups; G' is an imino group including alkylimino groups and sulphonimido groups, or, together with R4 or R6 is a cyclic group, or any of the groups specified for ENuP, and preferably G1 is para to the ENuP group; ; R7 is an alkylene group containing 31-3 carbon atoms in the linkage which may be substituted and preferably is an alkylene group containing 1 carbon atom in the linkage, e.g. a methylene linkage or a dialkyl- or diaryl-substituted methylene linkage and is selected to provide such proximity of said nucleophilic group to E as to permit intramolecular nucleophilic reaction with release of Q from E; nisi or2 R8 is an alkyl or substituted alkyl group containing from 1 aiO carbon atoms, a cycloalkyl group, an aryl or substituted aryl group containing from 6-40 carbon atoms, or it is the substituent X1; E is carbonyl or thiocarbonyl and is preferably carbonyl; Q is as defined above;; R9 is an aromatic group containing at least 5 atoms and preferably from 5-20 atoms including heterocyclic groups, for example, groups containing a nucleus such as pyridine, tetrazole, benzimidazole, benzotetrazole or isoquinoline, or a carbocyclic arylene group which preferably contains from 6-20 carbon atoms and which is preferably a phenylene group or a naphthylene group including substituted phenylene and naphthylene groups, or R9 is an aliphatic hydrocarbon group such as an alkylene group containing from 1-12 carbon atoms, including substituted alkylene groups;; X3 is a group which together with Q and R9 is a ballast group or said photographically useful moiety as defined for X1 below, provided one of X1 and -(-Q-R9-X3) is said ballast group and the other provides said photographically useful moiety; R6, R4 and R5 can each be hydrogen or halogen atoms or preferably polyatomic substituents which may be an alkyl containing from 1#0 carbon atoms, substituted alkyl, cycloalkyl, or alkoxy group containing 1-40 carbon atoms, an aryl or substituted aryl group containing from 6 40 carbon atoms, a carbonyl, a sulphamyl, or a sulphonamido group, or they can each be the substituent X' or R6 and R5 or R4 and R5, when they are on adjacent positions of the ring, may be taken together to form a 5to 7-membered ring, which- may be bridged, with the remainder of the molecule, the other of R4, R5 and R6 being as defined above, with the proviso that, when R9 is said aliphatic hydrocarbon group each of R6 and R4 must be polyatomic substituents, and preferably R5 is also a polyatomic substituent, and when G' is a substituent as defined for ENuP, an adjacent R4 or R6 may be the group:

wherein n, R7, R8, R9, E, Q and X3 are as defined above, to provide a compound which has multiple groups which can be released by nucleophilic displacement; X' is provided in at least one of the substituent positions and is a ballast group of sufficient size to render said compound nondiffusible, or is a dye or other photographically useful moiety, provided one of X' and -(-0-R9-X3) is a ballast group and the other is a photographically useful moiety.

In certain preferred embodiments, the compounds of this invention are BEND compounds which have the formula:

where: ENuP is an electron-accepting precursor for a hydroxylamino group, e.g., nitroso (NO), stable nitroxyl radicals and preferably nitro groups (NO2); A represents the atoms necessary to form a 5- or 6-membered aromatic ring which may have other rings fused thereto, the aromatic rings being carbocyclic or heterocyclic rings which may include onium groups in the ring, A preferably representing the atoms necessary to form a carbocyclic ring system such as a benzene or naphthalene ring; W is an electron-withdrawing group having a positive Hammett sigma value;; R12 is a hydrogen atom, a substituted or unsubstituted alkyl group containing from 1-30 carbon atoms, or a substituted or unsubstituted aryl group containing from 6-30 carbon atoms; R3 is a bivalent organic group containing from 1-3 atoms in the bivalent linkage which rhay have substituents on the linkage atoms, for example, alkylene groups, oxaalkylene, thiaalkylene, iminoalkylene or alkyl or aryl-substituted nitrogen and is preferably an alkylene linkage containing at least one dialkyl- or diaryl-substituted methylene in said linkage; m and q are 1 or 2;; p and r are 1 or greater and preferably p is 3~4, with [ (R12) Wj q-1 being a substituent on any portion of the aromatic-ring structure of A; E and Q provide an electrophilic cleavage group wherein E is an electrophilic group and is preferably a carbonyl or thiocarbonyl group or it can be a sulphonyl group and 0 is as defined above e.g., an oxygen, sulphur or selenium atom or a nitrogen atom which provides an amino group and preferably 0 is an amino group with an alkyl group substituent containing from 1-20 atoms, including substituted alkyl groups or groups which are connected to x2 to form cyclic groups such as piperidine groups n is 1,2 or 3 and is preferably 1;; X2, together with Q is a diffusible image dye or image-dye precursor moiety or a photographically useful moiety; X' and/or R12 is present in the compound and is a ballasting group and preferably is a substituted or unsubstituted alkyl group containing from 8-30 carbon atoms, a substituted or unsubstituted aryl group containing from 8-30 carbon atoms including the necessary linking groups to the aromatic ring.

It is to be understood that, when multiple groups are present in the compound as designated in the above formula, they may be identical or different; i.e., when p is 3, each (R12-W-) may be selected from different substituents as specified.

The electron-withdrawing groups referred to which have a positive Hammett sigma value and preferably a sigma value more positive than 0.2 or a combined effect of more than 0.5 as substituents of the aromatic ring. The Hammett sigma values are calculated in accordance with the procedures in Steric Effects in Organic Chemistry, John Wiley and Sons, Inc.,1956, pp. 570-574, and Progress in Physical Organic Chemistry, Vol. 2, Interscience Publishers, 1964, pp. 333-339.

Typical useful electron-withdrawing groups having positive Hammett sigma values include cyano, nitro, fluoro, bromo, iodo, trifluoromethyl, trialkylammonium, carbonyl, N-substituted carbamoyl, su Iphoxide, sulphonyl and N-substituted sulphamyl esters.

In another preferred embodiment of this invention, the BEND compounds have the formula:

where: E, O, X' and X2 are as defined above.

Typical useful dye-providing BEND compounds are as follows:

Typical useful photographically useful moiety providing BEND compounds are as follows:

The photographic recording material processed in accordance with this invention can be a simple element comprising a support bearing a silver halide emulsion layer having a BEND compound associated therewith.

A typical multilayer multicolor photographic element comprises a support having thereon a redsensitive silver halide emulsion unit having associated therewith a cyan-dye-image-providing material, a green-sensitive silver halide emulsion unit having associated therewith a magenta-dye-imageproviding material and a blue-sensitive silver halide emulsion unit having associated therewith a yellow-dye-image-providing material, at least one of the silver halide emulsion units having a BEND compound associated therewith.

Each silver halide emulsion unit can be composed of one or more layers and the various units and layers can be arranged in different relationships with respect to one another in accordance with configurations known in the art. The emulsion layers can be of high silver halide coverage or low silver halide coverage. High silver halide coverage means that each emulsion layer contains at least 5.0 mg/dm2 of silver halide, based on the weight of silver. Such elements typically contain from 5.0 to 25 mg/dm2 of silver halide, based on the weight of silver. By contrast photographic elements having a low silver halide coverage typically contain from 0.001 to 5.0 mg/dm2 of silver halide, based on the weight of silver, in each emulsion layer.

The photographic recording materials can contain additional layers conventional in photographic elements, such as spacer layers, filter layers, antihalation layers or scavenger layers. The support can be any suitable support used with photographic elements. Typical supports include polymeric films, paper (including polymer-coated paper) and glass.

The BEND compounds can be incorporated in a silver halide layer, or in another layer where it will be in association with the silver halide emulsion layer. The BEND compound can be incorporated in these layers in the way photographic couplers are incorporated in such layers. Depending upon the physical properties of the BEND compound and its physical compatibility with the emulsion or vehicle, it can be dispersed directly therein, or it can be mixed with organic or aqueous solvents and then dispersed in the emulsion or vehicle. To obtain a visible image record with dye-providing BEND compounds they normally will be used in a concentration of at least 1 x 10-5 moles/m2 and preferably from about 1 x10-4 to 2x 10-3 moles/m2.With photographic-reagent-providing BEND compounds the concentration employed will depend upon the particular reagent, the magnitude of the effect desired from it and the nature of other components in the photographic recording material.

The electron donor is preferably incorporated in the same layer as the BEND compound, particularly when it is of the alkali-labile semi-immobile type discussed above, although it can be incorporated in an adjacent layer or in the processing composition. When incorporated in a layer, the electron donor is employed in a ratio of 1:2 to 2:1, and preferably 1:1 to 2:1, moles electron donor per mole BEND compound.

The electron transfer agent, if employed, is preferably incorporated in the processing composition, although it can be in a layer in a blocked or precursor form. When incorporated in the processing composition, the electron transfer agent is preferably present in a concentration of 0.5 to 20 gram/litre and most preferably 0.5 to 10 gram/litre. When incorporated into a layer, the electron transfer agent precursor is preferably present at a concentration of from about 0.2 to 1.8 millimoles per square metre, and most preferably 0.5 to 1.5 millimoles per square metre.

The peroxide is preferably present in the processing composition and is preferably employed in a concentration of 0.001 to 1.0 mole per litre. When incorporated in a layer it is preferably employed at a concentration of 2 to 8 grams per square metre.

When electron donor, electron transfer agent or peroxide is incorporated in the photographic recording material, rather than in the processing composition, the processing composition serves to activate the component and/or provide a medium in which it can contact the silver halide or the BEND compound, or both.

The processing composition is an aqueous alkaline solution of a base, such as an alkali metal hydroxide or carbonate (e.g. sodium hydroxide or sodium carbonate) or an amine) e.g. diethylamine).

Preferably the alkaline composition has a pH in excess of 11. Suitable materials for use in such compositions are disclosed in Research Disclosure, pages 79-80, November 1976.

Preferably, the alkaline processing composition is introduced into reactive association with other components of the photographic recording material from a rupturable container which is adapted to be positioned during processing so that a compressive force applied to the container by pressure-applying members will rupture the container and effect a discharge of the containers contents within the recording material. However, other methods of introducing the alkaline processing composition can be employed.

Preferred rupturable containers are described in U.S. Patents 2,543,181; 2,643,886; 2,653,732; 2,723,051; 3,056,492; 3,056,491 and 3,152,515. In general, such containers comprise a rectangular sheet of fluid- and air-impervious material folded longitudinally upon itself to form two walls which are sealed to one another along their longitudinal and end margins to form a cavity in which processing solution is contained.

Any material can be employed as the image-receiving layer in the recording materials of this invention as long as it will mordant, or otherwise fix, the dyes which diffuse to it. The particular material chosen will, of course, depend upon the dyes to be mordanted. The image-receiving layer can contain ultraviolet absorbers to protect the dye images from fading due to ultraviolet light, brighteners and similar materials used to protect or enhance photographic dye images.

Additional layers can be incorporated in the recording materials of this invention. These include pH lowering layers (sometimes referred to as acid layers or neutralizing layers), timing or spacing layers, opaque light-reflecting layers, opaque light-absorbing layers, scavenger layers, and the like.

Various formats for diffusion transfer recording materials are known in the art. The layer arrangement employed with them can be used in this invention. In one useful format the dye imagereceiving layer is located on a separate support adapted to be superposed on the photographic element after exposure thereof. Such image-receiving layers are generally disclosed, for example, in U.S. Patent 3,362,819.

In another useful format the dye image-receiving layer is located integral with the photographic element and is positioned between the support and the lowermost silver halide emulsion layer. One such format is disclosed in Belgian Patent 757,960. In such a format, the support for the photographic element is transparent and bears, in order, an image-receiving layer, a substantially opaque lightreflective layer, and then the photosensitive layer or layers. After imagewise exposure, a rupturable container containing the alkaline processing composition and an opaque process sheet are brought into superposed position. Pressure-applying members in the camera rupture the container and spread processing composition over the photographic element as the photographic recording material is withdrawn from the camera.The processing composition develops each exposed silver halide emulsion layer and dye images, formed as a function of development, diffuse to the image-receiving layer to provide a right-reading image which is viewed through the transparent support on the opaque reflecting layer backgrounds. For other details concerning the format of this particular integral recording material, reference is made to the above-mentioned Belgian Patent 757,960.

Another format is disclosed in Belgian Patent 757,959. In this embodiment, the support for the photographic element is transparent and bears, in order, the image-receiving layer, a substantially opaque, light-reflective layer and the photosensitive layer or layers. A rupturable container, containing an alkaline processing composition and an opacifier, is positioned between the uppermost emulsion layer and a transparent top sheet which has thereof a neutralizing layer and a timing layer. The recording material is placed in a camera exposed through the transparent top sheet and then passed through a pair of pressure-applying members in the camera as it is being removed therefrom.The pressure-applying members rupture the container and spread processing composition and opacifier over the photographic layers to commence development and protect the photosensitive layers from further light exposure. The processing composition develops each silver halide layer and dye images, formed as a result of development, diffuse to the image-receiving layer to provide a right-reading image which is viewed through the transparent support on the opaque reflecting layer background. For further details concerning the format of this particular integral recording material, reference is made to the above-mentioned Belgian Patent 757,959.

Still other useful formats in which this invention can be employed are described in U.S. Patents 3,415,644; 3,415,645; 3,415,646; 3,647,437; 3,635,707; and 3,993,486.

The following Examples further illustrate this invention. Certain results are shown in Figures 1 of the accompanying drawings.

Example 1 Two colour photographic elements identified by the following schematic structure were prepared.

Numerical values denoting quantity in g/m2 are given in parenthesis.

0.2#AgBr emulsion/BEND compound (0.49)/Electron donor (1.11)/ 2,4-di-n-amylphenol (0.79)/ Gelatin (3.24) / / / Poly(ethylene terephthalate) Film / / / / / / / / / / Support / / / / / / / / / / The amount of silver halide (as silver) in each element was as follows: Element g/m2Ag A and B 1.08 C and D 0.108 The BEND compound has the structure:

The Electron Donor had the structure:

Each element was exposed for 2 seconds through a 0-6 neutral graduated-density test object on a 1 B sensitometer.

Elements A and C were then processed by rupturing a pod containing 80 grams potassium hydroxide,10 g ethylenediamine tetraacetic acid, 1 g 4-methyl-4-hydroxymethyl-1 -phenyl-3 pyrazolidone, 0.1 g 5-methylbenzotriazole, and 51 g carboxymethyl cellulose per litre of water between the element and a receiving element schematically shown below.

Gelatin~(1.24) Gelatin-(2.64)/Titanium dioxide~(16.2) Gelatin-(2.29)/Mordant (2.29) Poly(ethylene terephthalate) Film Support Elements B and D were processed in the same way, except that the processing composition in the pod contained, in addition to the other ingredients, 20 ml per litre of 30% hydrogen peroxide.

After 10 minutes, the photosensitive elements and the receiving elements were separated and sensitometric curves corresponding to the cyan dye released from the BEND compound and transferred to the receiving elements were generated. These are shown in Figures 1 and 2.

It was observed that at the higher silver level (Figure 1), Element B, which was processing with hydrogen peroxide gave approximately a 0.6 log E speed increase compared with Element A. At the lower silver level (Figure 2), Element D, which was processed with hydrogen peroxide gave approximately the same speed and image discrimination as Element B, whereas Element C gave little or no image discrimination.

Example 2 Two colour photographic elements identified by the following schematic structure were prepared.

Numerical values denoting quantity in gIm2 are given in parenthesis.

0.75,uAgBr emulsion/BEND compound (0.27)/ Electron Donor (0.54)/2,4-di-n-amylphenol (0.39)/Gelatin (3.24) Poly(ethylene terephthalate) Film Support The amount of silver halide (as silver) in each element was as follows: Element g/m2Ag E and F 1.08 G and H 0.108 The BEND compound was the same as in Example 1.

The Electron Donor had the structure:

Each element was exposed and processed as described in Example 1 except that Element F was processed with a composition containing 5 ml per litre of 30% hydrogen peroxide and Element H was processed with a composition containing 15 ml per litre of 30% hydrogen peroxide. Sensitometric curves corresponding to the cyan dye images in the receiving elements were plotted and are shown in Figures 3 and 4. Again a significant speed increase was observed in the elements processed in the presence of hydrogen peroxide.

Claims (14)

Claims

1. A process of forming a dye image in an imagewise exposed photographic recording material which has a support bearing at least one light-sensitive silver halide emulsion layer containing a developable latent image therein and, associated with said emulsion layer, a nondiffusible ballasted electron-accepting nucleophilic displacement (BEND) compound which, on acceptance of an electron, is capable of undergoing an intramolecular nucleophilic displacement reaction to release a diffusible dye or other photographically useful moiety, there being at least one nondiffusible image dye-providing compound associated with said emulsion layer, said BEND compound having the formula l::

wherein each of w, x, y, z, n and m is 1 or 2; (ENuP) is an electron-accepting, nucleophilic precursor group, which group, on acceptance (as herein defined) of an electron, becomes nucleophilic or (ENuP) is a hydrolysable precursor for said group; R1 is an acyclic or cyclic organic group to which (ENuP) and E are attached, optionally through R2 and R3 respectively; each of R2 and R3 is a bivalent organic group which contains from 1 to 3 atoms in the bivalent linkage and which may have substituents on the linkage atoms;; E and 0 provide an electrophilic cleavage group wherein E is an electrophilic group and Q is a leaving group providing a monoatom linkage between E and X2 and which can be displaced from E by the nucleophilic group provided by (ENuP) on acceptance of an electron, and Q is an oxygen atom, a selenium atom or a sulphur atom, or a nitrogen atom in a group of formula -NR- wherein R is a substituent or together with X2 represents the atoms necessary to complete a 5- to 7-membered ring; X' is attached to at least one of R', R2 and R3;; and X1 or one of Q-(X2)2 is a ballast group and, respectively, one of Qy~(X2)z or X' is a dye or other photographically useful moiety and R', R2 and R3 are selected to provide such proximity of an (ENuP) to an E as to permit intramolecular release of a Q from an E; the process comprising the steps of a) developing the imagewise exposed photographic recording material with either 1) an electron donor which is a silver halide developing agent or 2) an electron transfer agent which is a silver halide developing agent in the presence of an electron donor to release diffusible dye or photographically useful moiety from the BEND compound as an inverse function of silver halide development, and b) transferring released diffusible dye to form a viewable dye image from at least one of the diffusible dye and the retained dye-providing compound, characterised in that development is effected in the presence of a peroxide oxidizing agent that is essentially inert to oxidation-reduction with the electron transfer agent and the electron donor in the absence of a silver catalyst.

2. A process as claimed in claim 1 in which the released diffusible dye is allowed to diffuse to an image receiving layer where it forms a viewable image.

3. A process as claimed in claim 1 or 2 in which the electron donor is provided by an alkali labile electron donor precursor.

4. A process as claimed in claim 3 in which the alkali labile electron donor precursor has the formula:

wherein A represents the atoms necessary to complete an aromatic ring containing from 5~6 atoms; R' represents a hydrogen atom or one or more groups containing from 1-30 carbon atoms; and R11 is a substituted or unsubstituted alkyl group containing from 1-30 carbon atoms or a substituted or unsubstituted aryl group containing from 6-30 carbon atoms.

5. A process as claimed in any of claims 1-4 in which the BEND compound has the formula:

wherein ENuP is an electron-accepting precursor for a hydroxy nucleophilic group; G1 is an imino group or, together with R4 or R6 is a cyclic group, or any of the groups specified for ENuP; R7 is an alkylene group containing 1-3 carbon atoms in the linkage which may be substituted and is selected to provide such proximity of said nucleophilic group to E as to permit intramolecular nucleophilic reaction with release of Q from E;; n is 1 or2 Ra is an alkyl or substituted alkyl group containing from 1-40 carbon atoms, a cycloalkyl group, an aryl or substituted aryl group containing from 6-40 carbon atoms, or it is the substituent X1.

E is carbonyl or thiocarbonyl; O is as defined in claim 1; R9 is an aromatic group containing at least 5 atoms or an aliphatic hydrocarbon group containing from 1-12 carbon atoms which may be substituted; X3 is a group which together with Q and R9 is a ballast group or said dye or other photographically useful moiety as defined for X1 below, provided one of X' and -(-Q-R9.-X3) is said ballast group and the other provides said photographically useful moiety;; R6, R4 and R5 can each be hydrogen or halogen atoms or preferably polyatomic substituents which may be an alkyl containing from 1-40 carbon atoms, substituted alkyl, cycloalkyl, or alkoxy group containing 1 40 carbon atoms, an aryl or substituted aryl group containing from 6~40 carbon atoms, a carbonyl, a sulphamyl, or a sulphonamido group, or they can each be the substituent X' or R6 and R5 or R4 and R5, when they are on adjacent positions of the ring, may be taken together to form a 5to 7-membered ring, which may be bridged, with the remainder of the molecule, the other of R4, R5 and R6 being as defined above, with the proviso that, when R9 is said aliphatic hydrocarbon group each of R6 and R4 must be polyatomic substituents, and when G' is a substituent as defined for ENuP, an adjacent R4 or R6 may be the group:

wherein n, R7, Re, R9, E, 0 and X3 are as defined above; X1 is provided in at least one of the substituent positions and is a ballast group of sufficient size to render said compound nondiffusible, or is a dye or other photograpically useful moiety, provided one of X' and -(-0-R9-X3) is a ballast group and the other is a photographically useful moiety.

6. A process as claimed in any of claims 1-4 in which the BEND compound has the formula:

where: ENuP is an electron-accepting precursor for a hydroxylamino group; A represents the atoms necessary to form a 5- or 6-membered aromatic ring which may have other rings fused thereto, the aromatic rings being carbocyclic or heterocyclic rings which may include onium groups in the ring; W is an electron-withdrawing group having a positive Hammett sigma value; R12 is a hydrogen atom, a substituted or unsubstituted alkyl group containing from 1-30 carbon atoms, or a substituted or unsubstituted aryl group containing from 6-30 carbon atoms;; R3 is a bivalent organic group containing from 1-3 atoms in the bivalent linkage which may have substituents on the linkage atoms; m and q are 1 or 2, p and rare 1 or greater, with [ (Fl12) W ] q-1 being a substituent on any portion of the aromatic-ring structure of A; E and Q provide an electrophilic cleavage group wherein E is an electrophilic group and 0 is as defined above; n is 1,2or3; X2, together with Q, is a diffusible image dye or image-dye precursor moiety or a photographically useful moiety; and X1 and/or R12 is present in the compound and is a ballasting group.

7. A process as claimed in any of claims 1-6 in which the peroxide oxidizing agent is hydrogen peroxide.

8. A process as claimed in any of claims 1-7 in which the electron transfer agent is a 3pyrazolidone.

9. A process according to claim 1 substantially as described herein and with reference to the Examples.

10. A photographic image-transfer film unit comprising: (a) a photographic recording material comprising a support bearing at least one light-sensitive silver halide emulsion layer having associated therewith a BEND compound as defined in any of claims 1. 5or6, (b) an image-receiving layer, and (c) either i) an electron donor which is a silver halide developing agent or ii) an electron donor in combination with an electron transfer agent which is a silver halide developing agent; characterised in that the film unit contains a peroxide oxidizing agent that is essentially inert to oxidation-reduction with the electron transfer agent and the electron donor in the absence of a silver catalyst.

11. A film unit as claimed in claim 10 further comprising an alkaline processing composition contained within means from which it can be discharged within the film unit.

12. A film unit as claimed in claim 11 wherein the electron transfer agent is in the alkaline processing composition and the electron donor is in the same layer as the BEND compound.

13. A film unit as claimed in claim 11 or 12 wherein the peroxide oxidising agent is in the alkaline processing composition.

14. A film unit according to claim 10 substantially as described herein and with reference to the Examples.