Photographic element and process comprising a compound which comprises two timing groups in sequence

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to new photographic compounds which release photographically useful groups during photographic processing and to photographic materials and processes using such compounds.

2. Description of the State of the Art

Various ways are recognized in the photographic art for release of a photographically useful group (PUG) from a compound, such as a coupler, in photographic materials and processes. For example, U.S. Pat. No. 4,248,962, describes compounds that release a photographically useful group by means of an intramolecular nucleophilic displacement reaction in photographic materials. Other examples are described in U.S. Pat. No. 4,409,323, wherein couplers are described which release a photographically useful group by means of an electron transfer down a conjugated chain. These compounds capable of releasing a photographically useful group in a photographic material upon processing provide a degree of control over the timing and rate of release as well as the rate of diffusion and distance of diffusion of the photographically useful group in the photographic material.

A need has continued to exist for a higher degree of control over these parameters as well as a higher degree of freedom in the capability to design compounds having releasable photographically useful groups. Moreover, such needs have existed with the added parameter that such compounds must not require significantly modifying the photographically useful groups or the carrier compounds, such as the couplers, from which the photographically useful group are released, in a way which would be inconsistent with the ultimate use for which each is intended.

SUMMARY OF THE INVENTION

The present invention solves these problems by means of a photographic element comprising a support, at least one photographic emulsion layer and at least one compound A capable of releasing a photographically useful group (PUG), wherein the compound A comprises at least two differing timing groups in sequence capable, upon activation, of timing the release of the PUG and wherein at least two separate fragments are formed from the two differing timing groups upon processing the photographic element. A preferred compound (A) in a photographic element is a coupler having two differing timing groups, T.sub.1 and T.sub.2, in sequence. The timing groups are each capable upon activation of timing the release of the PUG. Also, two separate differing fragments are formed from the two differing timing groups. A highly preferred compound (A) has in sequence a timing group (T.sub.1) capable of an intramolecular nucleophilic displacement reaction to enable timed release and a timing group (T.sub.2) capable of electron transfer down a conjugated chain to enable timed release.

One embodiment of the invention is the photographic element comprising compound A as described. Another embodiment is a process of forming a photographic image by developing an exposed photographic element by means of a color developing agent in the presence of a compound A, particularly a coupler, as described. A further embodiment is a new coupler represented by the structure:

COUP--T.sub.1 --T.sub.2 --PUG

wherein:

COUP is a coupler moiety;

T.sub.1 is a first timing group capable of being released from COUP at the coupling position of COUP;

T.sub.2 is a second timing group, different from T.sub.1, capable of being released from T.sub.1 after T.sub.1 is released from COUP; and

PUG is a photographically useful group.

The compound A, preferably a coupler, contains two differing timing groups, in sequence capable upon activation of sequentially timing the release of a PUG. The reaction of compound A, preferably a coupler, with oxidized color developing agent cleaves the bond between the first timing group (T.sub.1) and the carrier portion of compound A, preferably the coupler moiety (COUP). Then the bond between the first timing group (T.sub.1) and the second timing group (T.sub.2) is cleaved. Finally, the bond between the second timing group (T.sub.2) and the PUG is cleaved enabling the PUG to perform its intended function. Bond cleavage between T.sub.1 and T.sub.2 or between T.sub.2 and PUG preferably does not involve the action of oxidized color developer. The sequential cleavage of the bond between the carrier portion of compound A and the first timing group, then the bond between the first timing group (T.sub.1) and the second timing group (T.sub.2), and finally the bond between the PUG and the second timing group (T.sub.2) enables the improved control over timing and rate of release of PUG. The sequential cleavage of these bonds is a characteristic feature of the invention.

One advantage of compounds of the invention is the greater variety of workable linking groups available for organic synthesis. Another advantage is that for the first time an extended timing period is available during which none of the PUG is released. For a given PUG, available single timing groups may provide a release rate too fast or too slow for the desired application, while two differing timing groups in sequence allows flexibility in attaining the desired release rate, typically with a half-life in the 0.1 to 60 second range, such as 15 seconds to 60 seconds. T.sub.1 and T.sub.2 are particularly useful when they have essentially matching timing of release.

For compounds, such as couplers, involving release of a development inhibitor group in a photographic element, a coupler according to the invention enables more control over image sharpness, granularity, and balanced color reproduction without deleterious effects on desired properties, such as photographic speed and sensitometric curve shape. For compounds, such as couplers, involving release of a bleach accelerator group in a photographic material, this improved control of timed release enables processing steps, such as color development, prior to bleaching to proceed to completion without interference from prematurely released bleach accelerator. In photographic elements, particularly photographic elements involving diffusion of compounds and/or fragments of compounds between layers, the controlled delayed release according to the invention enables larger diffusion paths of a released fragment before release of a PUG and enables improved control of interlayer interimage effects.

A particularly useful coupler of the invention is represented by the formula: ##STR1## where COUP, T.sub.1 and PUG are the same as described while Z represents atoms necessary to complete a substituted or unsubstituted pyridine, pyrazole, benzene or naphthalene nucleus and R.sub.1 and R.sub.2 individually represent a hydrogen atom, alkyl or aryl, with the group ##STR2## being joined to the nucleus at the para or ortho position relative to the oxygen atom.

In chemical systems requiring timed release of a moiety the release mechanisms can be initiated by any means that initiates cleavage of the first timing group from the carrier moiety. Depending on the particular carrier compound, the particular timing groups, and the desired end use of the active moiety, the release mechanism can be initiated by, for example, reaction of the carrier compound with radiation, enzymes, moisture, acid or base, and/or oxidized reducing agent.

As used herein the terms "coupler" and "coupler compound" refer to the entire compound, including the coupler moiety, the timing groups and the PUG, while the term "coupler moiety" refers to that portion of the compound other than the timing groups and the PUG.

The particular timing groups employed, including the linkage by which they are attached to other portions of coupler and the nature of the substituents on them, can be varied to help control such parameters as rate and time of cleavage of the timing groups and of the PUG. Since these parameters can be controlled by modification of the timing groups, they need not be emphasized in selecting the particular coupler moiety and the particular PUG, thus providing greater freedom in selecting such moieties and groups for a particular end use.

If the PUG is joined to the coupler moiety only through the timing groups, then cleavage of the bond between the first timing groups and the coupler moiety releases the timing groups and the PUG as a unit. In this embodiment the particular timing groups employed, including the nature of the substituents on them, can additionally control the rate and distance of diffusion of the unit formed by the timing groups and the PUG after this unit is released from the coupler moiety but before the PUG is released from the second timing group. If the PUG is joined to the coupler moiety both directly and through the timing groups, the particular timing groups and the nature of the substituents on them can control the rates of cleavage of the timing groups and can control the rate at which the PUG is released. In this embodiment the direct linkage between the PUG and the coupler moiety helps prevent diffusion of the PUG.

The coupler moiety can be any moiety which will react with oxidized color developing agent to cleave the bond between the first timing group and the coupler moiety. It includes coupler moieties employed in conventional color-forming couplers which yield colorless products on reaction with oxidized color developing agents as well as coupler moieties which yield colored products on reaction with oxidized color developing agents. Both types of coupler moieties are well known to those skilled in the art.

The coupler moiety can be unballasted or ballasted with an oil-soluble or fat-tail group. It can be monomeric, or it can form part of a dimeric, oligomeric or polymeric coupler, in which case more than one COUP--T.sub.1 --T.sub.2 --PUG group can be contained in the coupler, or it can form part of a bis compound in which the T.sub.1, T.sub.2 and/or PUG groups form part of the link between two coupler moieties.

It will be appreciated that, depending upon the particular coupler moiety, the particular color developing agent and the type of processing, the reaction product of the coupler moiety and oxidized color developing agent can be: (1) colored and nondiffusible, in which case it will remain in the location where it is formed: (2) colored and diffusible, in which case it may be removed during processing from the location where it is formed or allowed to migrate to a different location; or (3) colorless and diffusible or nondiffusible, in which case it will not contribute to image density. In cases (2) and (3) the reaction product may be initially colored and/or nondiffusible but converted to colorless and/or diffusible products during the course of processing.

The --T.sub.1 --T.sub.2 --PUG group is joined to the coupler moiety at any of the positions from which groups released from couplers by reaction with oxidized color developing agent can be attached. Preferably, the --T.sub.1 --T.sub.2 --PUG group is attached at the coupling position of the coupler moiety so that upon reaction of the coupler with oxidized color developing agent the --T.sub.1 --T.sub.2 --PUG group will be displaced. However, the --T.sub.1 --T.sub.2 --PUG group can be in a non-coupling position of the coupler moiety from which position it will be displaced as a result of reaction of the coupler with oxidized color developing agent. In the case where the --T.sub.1 --T.sub.2 --PUG group is in a non-coupling position of the coupler moiety, other groups can be in the coupling position, including conventional coupling-off groups or the same or a different PUG from that contained in the --T.sub.1 --T.sub.2 --PUG group. Alternatively, the coupler moiety can have a --T.sub.1 --T.sub.2 --PUG group in each of the coupling position and a non-coupling position. Accordingly, couplers of this invention can release more than one mole of PUG per mole of coupler. The PUGs can be the same or different and can be released at the same or different times and rates.

The first timing group (T.sub.1) can be any organic group which will serve to connect COUP to the second timing group (T.sub.2) and which, after cleavage from COUP will cleave from the second timing group (T.sub.2), preferably by an intramolecular nucleophilic displacement reaction of the type described in, for example, U.S. Pat. No. 4,248,962.

As used herein, the term "intramolecular nucleophilic displacement reaction" refers to a reaction in which a nucleophilic center of a compound reacts directly, or indirectly through an intervening molecule, at another site on the compound, which is an electrophilic center, to effect displacement of a group or atom attached to the electrophilic center. Such compounds have a nucleophilic group and electrophilic group spatially related by the configuration of the molecule to promote reactive proximity. Preferably the nucleophilic group and the electrophilic group are located in the compound so that a cyclic organic ring, or a transient cyclic organic ring, can be easily formed by an intramolecular reaction involving the nucleophilic center and the electrophilic center.

A nucleophilic group is understood to be a grouping of atoms one of which is electron rich. This atom is referred to as the nucleophilic center. An electrophilic group is understood to be a grouping of atoms one of which is electron deficient. This atom is referred to as the electrophilic center.

Thus, in photographic couplers of this invention, the first timing group perferably contains a nucleophilic group and an electrophilic group which are spatially related with respect to one another so that upon release from the coupler moiety the nucleophilic center and the electrophilic center will react to effect displacement of the second timing group and PUG from the first timing group. In order to assure that the second timing group and the PUG are not released prior to release of the first timing group from the coupler moiety, the nucleophilic center should be prevented from reacting with the electrophilic center until such release and the electrophilic center should be resistant to external attack, e.g. hydrolysis. Premature reaction can be prevented by attaching the coupler moiety to the first timing group at the nucleophilic center or an atom in conjunction with a nucleophilic center, so that cleavage of the timing group and PUG from the coupler moiety unblocks the nucleophilic center and permits it to react with the electrophilic center, or by positioning the nucleophilic group and the electrophilic group so that they are prevented from coming into reactive proximity until release. Similarly, the second timing group will be attached at a position on the first timing group from which it will be displaced upon reaction of the nucleophilic center and the electrophilic center.

The second timing group (T.sub.2) can be any organic group different from the first timing group (T.sub.1), which will serve to connect the first timing group (T.sub.1) to the PUG, and which, after cleavage from the first timing group (T.sub.1), will cleave from the PUG. The cleavage of the second timing group (T.sub.2) from the PUG is preferably by means of an electron transfer down a conjugated chain.

As used herein the term "electron transfer down a conjugated chain" is understood to refer to transfer of an electron along a chain of atoms in which alternate single bonds and double bonds occur. A conjugated chain is understood to have the same meaning as commonly used in organic chemistry. Electron transfer down a conjugated chain is as described in, for example, U.S. Pat. No. 4,409,323.

The timing groups (T.sub.1 and/or T.sub.2) can contain moieties and substituents which will permit control of (i) one or more of the rates of reaction of COUP with oxidized color developing agent, (ii) the rate of diffusion of --T.sub.1 --T.sub.2 --PUG and/or --T.sub.2 --PUG and (iii) the rate of release of PUG. The timing groups can contain additional substituents, such as additional PUGs, or precursors thereof, which may remain attached to the timing groups or be released.

The PUG can be any group that is desirably made available in a photographic element in an imagewise fashion. The PUG can be a photograhic dye or a photographic reagent. A photographic reagent herein is a moiety which upon release further reacts with components in the element, such as a development inhibitor, a development accelerator, a bleach inhibitor, a bleach accelerator, a coupler (e.g. a competing coupler, a color-forming coupler, a DIR coupler), a dye precursor, a dye, a developing agent (e.g. a competing developing agent, a dye-forming developing agent or a silver halide developing agent), a silver complexing agent, a fixing agent, an image toner, a stabilizer, a hardener, a tanning agent, a fogging agent, an ultraviolet radiation absorber, an antifoggant, a nucleator, a chemical or spectral sensitizer or a desensitizer. Such dyes and photographic reagents generally contain a hetero atom having a negative valence of 2 or 3 from Group VA or VIA of the Periodic Table, such as oxygen, sulfur, selenium and nitrogen (e.g., nitrogen in a heterocyclic ring). Such an atom can conveniently serve as the point on the dye or photographic reagent at which the second timing group (T.sub.2) is joined.

The PUG can be present in the coupler as a preformed species or it can be present in a blocked form or as a precursor. For example, a preformed development inhibitor may be attached to the second timing group or the devlopment inhibiting function may be blocked by being the point of attachment to the second timing group. Other examples are (i) a preformed dye attached to the second timing group, (ii) a dye which is blocked so as to shift its spectral absorption attached to the second timing group, or (iii) a leuco dye attached to the second timing group.

Preferred compounds according to this invention are photographic couplers containing a coupler moiety, a PUG containing a hetero atom from Group VA or VIA of the Periodic Table having a negative valence of 2 or 3, and timing groups (T.sub.1 and T.sub.2) joining the coupler moiety and the PUG. The first timing group (T.sub.1) perferably comprises a nucleophilic group attached to the coupler moiety at a position from which it is capable of being displaced as a result of reaction of the coupler moiety with oxidized color developing agent. The first timing group (T.sub.1) also preferably comprises an electrophilic group attached to the second timing group (T.sub.2) and capable of being displaced therefrom by the nucleophilic group after the nucleophilic group is displaced from the coupler moiety. The coupler also comprises a linking group spatially relating the nucleophilic group and the electrophilic group to enable an intramolecular nucleophilic displacement reaction which cleaves the bond between the second timing group (T.sub.2) and the first timing group (T.sub.1).

It will be appreciated that in the first timing group, for an intramolecular reaction to occur between the nucleophilic group and the electrophilic group, the groups should be spatially related after cleavage from the coupler, so that they can react with one another. Preferably, the nucleophilic group and the electrophilic group are spatially related within the first timing group so that the intramolecular nucleophilic displacement reaction involves the formation of a 3- to 7-membered ring, most preferably a 5- or 6-membered ring.

It will be further appreciated that for an intramolecular reaction to occur in the aqueous alkaline environment encountered during photograhic processing, displacing the second timing group from the first timing group, the thermodynamics should be such and the groups be so selected that the free energy of ring closure plus the bond energy of the bond formed between the nucleophilic group and the electrophilic group is greater than the bond energy between the electrophilic group and the second timing group. Not all possible combinations of nucleophilic group, linking group, electrophilic group and the atoms in the second timing group to which the electrophilic group is attached will yield a thermodynamic relationship favorable to breaking of the bond between the electrophilic group and the second timing group. However, it is within the skill of the art to select appropriate combinations taking the above energy relationships into account.

A preferred class of timing group (T.sub.1) is represented by the structure:

--Nu--X--E--

wherein:

Nu is a nucleophilic group attached to a position of COUP from which it will be displaced upon reaction of COUP with oxidized color developing agent;

E is an electrophilic group attached to an atom in the second timing group (T.sub.2) and is displacable therefrom by Nu after Nu is displaced from COUP; and

X is a linking group for spatially relating Nu and E, upon displacement of Nu from COUP, to undergo an intramolecular nucleophilic displacement reaction with the formation of a 3- to 7-membered ring and thereby release --T.sub.2 --PUG.

Representative Nu groups contain electron rich oxygen, sulfur and nitrogen atoms. Representative E groups contain electron deficient carbonyl, thiocarbonyl, phosphonyl and thiophosphonyl moieties. Other useful Nu and E groups will be apparent to those skilled in the art.

In the following listings of representative Nu and E groups, the groups are oriented so that the lefthand bond of Nu is joined to COUP and the righthand bond of Nu is joined to X, while the lefthand bond of E is joined to X and the righthand bond of E is joined to --T.sub.2 --PUG.

Representative Nu groups include: ##STR3## where each Ra is independently hydrogen, alkyl, such as alkyl of 1 to 20 carbon atoms including substituted alkyl such as methyl, ethyl, propyl, hexyl, decyl, pentadecyl, octadecyl, carboxyethyl, hydroxypropyl, sulfonamidobutyl and the like, or aryl, such as aryl of 6 to 20 carbon atoms including substituted aryl such as phenyl, naphthyl, benzyl, tolyl, t-butylphenyl, carboxyphenyl, chlorophenyl, hydroxyphenyl and the like, and n is an integer from 0 to 4 such that the ring formed by Nu, X and E upon nucleophilic attack of Nu upon the electrophilic center in E contains 3 to 7 ring atoms. Preferably Ra is hydrogen, lower alkyl of 1 to 4 carbon atoms or aryl of 6 to 10 carbon atoms.

Representative E groups include: ##STR4## where Ra and n are as defined above.

E is preferably an electrophilic group selected from the group consisting of ##STR5## wherein each Rb is independently hydrogen, alkyl, such as alkyl containing 1 to 20 carbon atoms, preferably alkyl containing 1 to 4 carbon atoms, or aryl, such as aryl containing 6 to 20 carbon atoms, preferably aryl containing 6 to 10 carbon atoms; and n is 0 to 4, such that the ring formed upon reaction of the nucleophilic center in Nu with the electrophilic center in E contains 5- or 6-members.

The linking group represented by X can be an acyclic group such as alkylene, such as methylene, ethylene or propylene, or a cyclic group such as an aromatic group, such as phenylene or naphthylene, or a heterocyclic group, such as furan, thiophene, pyridine, quinoline or benzoxazine. Preferably X is alkylene or arylene. The groups Nu and E are attached to X to provide, upon release of Nu from COUP, favorable spatial relationship for nucleophilic attack of the nucleophilic center in Nu on the electrophilic center in E. When X is a cyclic group, Nu and E can be attached to the same or adjacent rings. Aromatic groups in which Nu and E are attached to adjacent ring positions are particularly preferred X groups.

X can be unsubstituted or substituted. The substituents can be those which will modify the rate of reaction, diffusion, or displacement, such as halogen, including fluoro, chloro, bromo, or iodo, nitro, alkyl of 1 to 20 carbon atoms, acyl, such as carboxy, carboxyalkyl, alkoxycarbonyl, alkoxycarbonamido, sulfoalkyl, alkylsulfonamido, and alkylsulfonyl, solubilizing groups, ballast groups and the like, or they can be substituents which are separately useful in the photographic element such as a stabilizer, an antifoggant, a dye (e.g., a filter dye, a solubilized masking dye) and the like. For example, solubilizing groups will increase the rate of diffusion; ballast groups will decrease the rate of diffusion; electron withdrawing groups will decrease the rate of displacement of the second timing group and PUGs which remain attached to X can serve functions such as stabilization, masking and the like.

There follows a listing of patents and publications which described representative COUP groups useful in the invention. Also listed are structures of preferred COUP, T.sub.1, T.sub.2, and PUG groups. In these structures Y represents, in the case of a dye forming coupler that is useful with couplers according to the invention, a hydrogen atom or a coupling-off group known in the photographic art. In the case of couplers according to the invention, Y represents --T.sub.1 --T.sub.2 --PUG wherein T.sub.1, T.sub.2 and PUG are as defined above.

I. COUP's

A. Couplers which form cyan dyes upon reaction with oxidized color developing agents are described in such representative patents and publications as: U.S. Pat. Nos. 2,772,162, 2,895,826, 3,002,836, 3,034,892, 2,474,293, 2,423,730, 2,367,531, 3,041,236 and "Farbkuppler-eine Literatureubersicht," published in Agfa Mitteilungen, Band II, pp. 156-175 (1961).

Preferably such couplers are phenols and naphthols which form cyan dyes on reaction with oxidized color developing agent and have the --T.sub.1 --T.sub.2 --PUG group attached to the coupling position, i.e. the carbon atom in the 4-position. Structures of preferred such coupler moieties are: ##STR6## where Rc represents a ballast group, and Rd represents one or more halogen (e.g. chloro, fluoro), lower alkyl (e.g. methyl, ethyl, butyl) or lower alkoxy (e.g. methoxy, ethoxy, butoxy) groups.

B. Couplers which form magenta dyes upon reaction with oxidized color developing agent are described in such representative patents and publications as: U.S. Pat. Nos. 2,600,788, 2,369,489, 2,343,703, 2,311,082, 3,152,896, 3,519,429, 3,062,653, 2,908,573 and "Fabkupper-eine Literatureurubersicht," published in Agfa Mitteilungen, Band III, pp. 126-156 (1961).

Preferably, such couplers are pyrazolones and pyrazolotriazoles which form magenta dyes upon reaction with oxidized color developing agents and have the Y, i.e. --T.sub.1 --T.sub.2 --PUG group, attached to the coupling position. Structures of preferred such coupler moieties are: ##STR7## where Rc and Rd are chosen independently to be a ballast group, alkyl, substituted alkyl, phenyl or substituted phenyl.

C. Couplers which form yellow dyes upon reaction with oxidized and color developing agent are described in such representative patents and publications as: U.S. Pat. Nos. 2,875,057, 2,407,210, 3,265,506, 2,298,443, 3,048,194, 3,447,928 and "Farbkuppler-eine Literatureubersicht," published in Agfa Mitteilungen, Band III, pp. 112-126 (1961).

Preferably such yellow-dye forming couplers are acylacetamides, such as benzoylacetanilides and pivalylacetanilides, and have the --T.sub.1 --T.sub.2 --PUG group attached to the coupling position, i.e. the active methylene carbon atom.

Structures of preferred such coupler moieties are: ##STR8## where Rc is as defined above and Rd and Re are hydrogen or one or more halogen, lower alkyl, such as methyl and ethyl, or ballast groups, such as alkoxy of 16 to 20 carbon atoms.

D. Couplers which form colorless products upon reaction with oxidized color developing agent are described in such representative patents as: U.K. Patent No. 861,138; U.S. Pat. Nos. 3,632,345, 3,928,041, 3,958,993 and 3,961,959. Preferably such couplers are cyclic carbonyl containing compounds which form colorless products on reaction with oxidized color developing agent and have the --T.sub.1 --T.sub.2 --PUG group attached to the carbon atom in the .alpha.-position with respect to the carbonyl group.

Structures of preferred such coupler moieties are: ##STR9## where Rc is as defined above and n is 1 or 2.

E. Couplers which form black dyes upon reaction with oxidized color developing agent are described in such representative patents as U.S. Pat. Nos. 1,939,231; 2,181,944; 2,333,106; and 4,126,461; German OLS No. 2,644,194 and German OLS No. 2,650,764.

Preferably such couplers are resorcinols or m-aminophenols which form black or neutral products on reaction with oxidized color developing agent and have the --T.sub.1 --T.sub.2 --PUG group para to a hydroxy group.

Structures of preferred such coupler moieties are: ##STR10## where Re is alkyl of 3 to 20 carbon atoms, phenyl or phenyl substituted with hydroxy, halo, amino, alkyl of 1 to 20 carbon atoms or alkoxy of 1 to 20 carbon atoms; each Rf is independently hydrogen, alkyl of 1 to 20 carbon atoms, alkenyl of 1 to 20 carbon atoms, or aryl of 6 to 20 carbon atoms; and Rg is one or more halogen, alkyl of 1 to 20 carbon atoms, alkoxy of 1 to 20 carbon atoms or other monovalent organic groups.

II. First Timing Groups (T.sub.1)

Examples of first timing groups (T.sub.1) are as follows:

A. Acyclic T.sub.1 groups: ##STR11## where n is 1-4, preferably 2 or 3, Z.sub.1 is ##STR12## and R.sub.3 is hydrogen, alkyl, such as alkyl of 1 to 20 carbon atoms, preferably lower alkyl of 1 to 4 carbon atoms, or aryl, such as aryl of 6 to 20 carbon atoms, preferably aryl of 6 to 10 carbon atoms.

B. Aromatic T.sub.1 groups: ##STR13## where n is 0 or 1; Z.sub.2 is ##STR14## R.sub.3 is as defined above; and X.sub.1 is hydrogen or one or more substituent groups independently selected from cyano, fluoro, chloro, bromo, iodo, nitro, alkyl, such as alkyl of 1 to 20 carbon atoms, a dye, --OR.sub.4, --COOR.sub.4, --CONHR.sub.4, --NHCOR.sub.4, NHSO.sub.2 R.sub.4, --SO.sub.2 NHR.sub.4 of SO.sub.2 R.sub.4, where R.sub.4 is hydrogen, alkyl, such as alkyl of 1 to 20 carbon atoms, preferably alkyl of 1 to 4 carbon atoms, or aryl, such as aryl of 6 to 20 carbon atoms, preferably aryl of 6 to 10 carbon atoms.

C. Heterocyclic T.sub.1 groups: ##STR15## where n is 0 or 1, Z.sub.2, X.sub.1 and R.sub.3 are as defined above.

D. Bis T.sub.1 groups: ##STR16## where Y.sub.1 is a linking group, such as ##STR17## or --NHSO.sub.2 CH.sub.2 SO.sub.2 NH--; n is 0 or 1 and X.sub.1, Z.sub.2 and R.sub.3 are as defined above. ##STR18## where n is 0 or 1 and Z.sub.2, and R.sub.3 are as defined above.

Such timing groups are described in, for example, U.S. Pat. No. 4,248,962.

III. Second Timing Group (T.sub.2)

Examples of the second timing group (T.sub.2) are represented by the following formulas: ##STR19## wherein the righthand bond is joined to PUG; the lefthand bond is attached to the first timing group (T.sub.1), Z.sub.3 is 0, S or ##STR20## R.sub.3 R.sub.4, R.sub.5 and R.sub.6 are individually a hydrogen atom, alkyl or aryl group, and Q is a pyridylene, 1,2- or 1,4-phenylene or naphthylene group. The pyridylene, phenylene or naphthylene can be unsubstituted or substituted by halogen, alkyl, alkoxy, --CN, --NO.sub.2, --NHCOR or --COOR wherein R is alkyl.

Such timing groups are described in, for example, U.S Pat. No. 4,409,323 and Research Disclosure, December 1981, Item No. 21228.

IV. PUG's

A. PUG's which form development inhibitors upon release are described in such representative patents as U.S. Pat. Nos. 3,227,554; 3,384,657; 3,615,506; 3,617,291, 3,733,201 and U.K. Pat. No. 1,450,479. Preferred development inhibitors are iodide and heterocyclic compounds such as mercaptotetrazoles, selenotetrazoles, mercaptobenzothiazoles, selenobenzothiazoles, mercaptobenzoxazoles, selenobenzoxazoles, mercaptobenzimidazoles, selenobenzimidazoles, benzotriazoles and benzodiazoles. Structures of preferred development inhibitors moieties are: ##STR21## where R.sub.7 and R.sub.8 are individually hydrogen, alkyl of 1 to 8 carbon atoms (e.g. methyl, ethyl, butyl), phenyl or substituted phenyl and R.sub.9 and R.sub.10 are individually hydrogen or one or more halogen (e.g. chloro, fluoro, bromo), lower alkyl of 1 to 4 carbon atoms, carboxyl, carboxy esters, such as --COOCH.sub.3, --NHCOOCH.sub.3, --SO.sub.2 OCH.sub.3, --OCH.sub.2 CH.sub.2 SO.sub.2 CH.sub.3, ##STR22##

B. PUG's which are, or form, dyes upon release:

Suitable dyes and dye precursors include azo, azomethine, azopyrazolone, indoaniline, indophenyl, anthraquinone, triarylmethane, alizarin, nitro, quinoline, indigoid and phthalocyanine dyes or precursors of such dyes such as leuco dyes, tetrazolium salts or shifted dyes. These dyes can be metal complexed or metal complexable. Representative patents describing such dyes are U.S. Pat. Nos. 3,880,658; 3,931,144; 3,932,380; 3,932,381; and 3,942,987. Preferred dyes and dye precursors are azo, azomethine and indoaniline dyes and dye precursors. Structures of some preferred dyes and dye precursors are:

______________________________________ ##STR23## IIIB-1 ##STR24## IIIB-2 ##STR25## IIIB-3 ##STR26## IIIB-4 ______________________________________ R.sub.11 R.sub.12 ______________________________________ ##STR27## Cl ##STR28## Cl ##STR29## ______________________________________

C. PUG's which are couplers:

Couplers released can be nondiffusible color-forming couplers, non-color forming couplers or diffusible competing couplers. Representative patents and publications describing competing couplers are: "On the Chemistry of White Couplers," by W. Puschel, Agfa-Gevaert AG Mitteilungen and der Forschungs-Laboratorium der Agfa-Gevaert AG, Springer Verlag, 1954, pp. 352-367; U.S. Pat. Nos. 2,998,314, 2,808,329, 2,689,793; 2,742,832; German Pat. No. 1,168,769 and British Pat. No. 907,274. Structures of preferred competing couplers are: ##STR30## where R.sub.13 is hydrogen or alkylcarbonyl, such as acetyl, and R.sub.14 and R.sub.15 are individually hydrogen or a solubilizing group, such as