Photographic Material and Process (B)

This invention relates to new photographic compounds that release photographically useful groups by means of intramolecular nucloophilic displacement during photographic processing and to photographic materials and processes using such compounds.

Various ways are recognized in the photographic art for release of a photographically useful group (PUG) from a compound, such as a coupler, in a photographic material and process. For example, U.S. Pat. No. 4,248,962, describes compounds that release photographically useful groups by means of an intramolecular nucleophilic displacement reaction in photographic materials. These compounds, particularly couplers, 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 photogaphic material.

A need has existed for a compound, preferably a coupler, that not only provides the described release of a photographically useful group, but also provides increased resistance to hydrolysis during storage. A need has also existed for increased acutance of an image formed in a photographic material containing such a compound during processing. Moreover, such needs have existed with the added parameter that such a compound must not require significantly modifying the photographically useful groups or the carrier compounds, such as the couplers, in a way that would adversely affect the ultimate end use for which each is intended.

The present invention solves these problems by means of a photographic element comprising a support, at least one photographic silver halide emulsion layer and at least one compound (A) of the formula CAR-LINK-PUG where CAR is a carrier moiety capable of releasing LINK-PUG during photographic processing upon reaction with oxidized developing agent; LINK-PUG is in turn capable of releasing a photographically useful group (PUG) by an intramolecular molecular nucleophilic displacement reaction; and LINK-PUG is represented by the formula: ##STR2## wherein Q is N or CR.sub.z ;

R.sub.q is alkyl, cycloalkyl, heterocyclyl or aryl, or R.sub.q together with R.sub.1, R.sub.2 or R.sub.z can represent the atoms necessary to complete a non-aromatic ring;

R.sub.z, R.sub.1 and R.sub.2 are independently alkyl, cycloalkyl, heterocyclyl, aryl or hydrogen;

R.sub.3 is alkyl, cycloalkyl, heterocyclyl or aryl;

n is 0 or 1; and the LINK moiety enables increased resistance to hydrolysis.

Since similar LINK moieties in which Q-R.sub.q is methylene do not provide the required resistance to hydrolysis, as shown in the comparative data in the examples, it is thought that the presence of a bulky Q-R.sub.q group adjacent to the carboxy group in the LINK moiety may aid this improvement. Examples of such LINK-PUG groups are represented by the following: ##STR3## wherein PUG is as defined above.

A preferred compound (A) is a dye-forming coupler of the form COUP-LINK-PUG in which COUP is a coupler moiety and LINK-PUG is a coupling-off group.

A process of forming an image having the described advantages comprises developing an exposed photographic element by means of a color developing agent in the presence of described compound (A), particularly a coupler as described.

The compound (A), preferably a coupler, contains a coupling-off group -LINK-PUG that enables increased resistance to hydrolysis during storage. It also enables increased acutance of an image formed upon processing a photographic silver halide element containing the compound (A) when PUG is a development inhibitor moiety.

Illustrative preferred -LINK-PUG groups are represented by the formulas: ##STR4## wherein R.sub.4 is alkyl, such as alkyl containing 1 to 5 carbon atoms, or an electron density controlling group, that is an electron withdrawing group or an electron donating group as known in the organic compound synthesis art. These improvements for compounds of the invention are demonstrated by the data in the photographic examples when compared to couplers of the type described in U.S. Pat. No. 4,248,962.

The reaction of compound (A), preferably a development inhibitor releasing (DIR) coupler, with oxidized color developing agent cleaves the bond between the coupling-off group and the carrier portion of the compound (A), preferably the coupler moiety (COUP). Then the bond between the photographically useful group and the remainder of the coupling-off group is cleaved. Bond cleavage between the PUG and the remainder of the coupling-off group preferably does not involve the action of oxidized color developing agent. The cleavage of the bond between the PUG and the remainder of the coupling-off group is enabled by an intramolecular nucleophilic displacement reaction. Tailoring the structure of the LINK moiety to the requirements of a given PUG allows control over timing and rate of release of the PUG. The sequential cleavage of the bond between the coupling-off group and the carrier portion of the compound A and the bond between the PUG and the remainder of the coupling-off group is a characteristic feature of the compounds as described.

Particularly useful compounds as described are couplers represented by the formula: ##STR5## wherein R.sub.4 is an electron density controlling group and

PUG is a photographically useful group.

Examples of useful electron withdrawing groups as described for R.sub.4 include: ##STR6##

Examples of useful electron donating groups as described for R.sub.4 include: ##STR7##

When PUG is a development inhibitor, for instance, useful release times are generally achieved using electron withdrawing groups in R.sub.4 if PUG is a mercaptotetrazole derivative.

As used herein the terms "coupler" and "coupler compound" refer to the entire compound, including the coupler moiety and the coupling-off group including the PUG. The term "coupler moiety" refers to that portion of the compond other than the coupling-off group.

The coupler moiety (COUP) can be any moiety that will react with oxidized color developing agent to cleave the bond between the carboxy portion of the coupling-off group and the coupler moiety. The coupler moiety herein includes coupler moieties employed in conventional color-forming couplers that yield colorless products on reaction with oxidized color developing agents as well as coupler moieties that yield colored products on reaction with oxidized color developing agents. Both types of coupler moieties are well known to those skilled in the photographic art.

The coupler moiety can be ballasted or unballasted. In can be monomeric, or it can be part of a dimeric, oligomeric or polymeric coupler, in which case more than one group containing PUG can be contained in the coupler, or it can form part of a bis compound in which the PUG forms part of a 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 the oxidized color developing agent can be: (1) colored and nondiffusible, in which case it will remain in the location in which 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 non-diffusible in which case it will not contribute to image density.

The coupling-off group is joined to the coupler moiety at the coupling position of the coupler moiety. The coupling-off group is released from the coupling position by oxidative coupling reactions known in the photographic art.

As used herein, the term "intramolecular nucleophilic displacement reaction" means a reaction in which a nucleophilic center of a compound reacts directly, or indirectly through an intervening molecule, at another site on the compound, that 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 spacially related by the configuration of the molecule to promote reactive proximity. The electrophilic group and the nucleophilic group are located in the coupling-off group as described 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 is referred to as the electrophilic center.

The PUG can be any group that is typically made available in a photographic element in an imagewise fashion. The PUG can be a photographic reagent of a photographic dye. A photographic reagent herein is a moiety that upon release further reacts with components in the photographic element, such as a development inhibitor, a development accelerator, a bleach inhibitor, a bleach accelerator, a coupler (for example, a competing coupler, a dye-forming coupler, or a development inhibitor releasing coupler (DIR coupler), a dye precursor, a dye, a developing agent (for example, a competing developing agent, a dye-formng developing agent, or a silver halide developing agent), a silver complexng 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.

The PUG can be present in the coupling-off group as a preformed species or it can be present in a blocked form or as a precursor. The PUG can be for example a preformed development inhibitor or the development inhibiting function can be blocked by being the point of attachment to the carbonyl group bonded to PUG in the coupling-off group. Other examples are a preformed dye, a dye that is blocked to shift its absorption, and a leuco dye.

Preferred compound (A) is a photographic coupler containing a coupler moiety and a PUG containing a hetero atom from Group VA or VIA of the Periodic Table having a negative valence of 2 or 3 bonded to the carbon group of the coupling-off group.

There follows a listing of patents and publications which describe representative COUP groups useful in the invention. Also listed are structures of preferred COUP 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 as described. In the case of couplers according to the invention, Y represents ##STR8## as defined above.

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; 4,333,999 and "Farbkuppler-eine Literaturubersicht," published in Agfa Mitteilungen, Band III, pp. 156-175 (1961).

Preferably such couplers are phenols and naphthols which form cyan dyes on reaction with oxidized color developing agent. Structures of preferred such couplers are: ##STR9## where R.sub.6 represents a ballast group, and R.sub.7 represents one or more halogen such as chloro or fluoro; alkyl such as methyl, ethyl, butyl; or, alkoxy, such as 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 "Farbkuppler-eine Literaturubersicht," published in Agfa Mitteilungen, Band III, pp. 126-156 (1961).

Preferably, such couplers are pyrazolones and pyrazolotriazoles which form magenta dyes upon reaction which oxidized color developing agents and have the Y attached to the coupling position.

Structures of preferred such coupler moieties are: ##STR10## where R.sub.6 and R.sub.7 are chosen independently to be a ballast group, unsubstituted or 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 Literaturubersicht," published in Agfa Mitteilungen, Band III, pp. 112-126 (1961).

Preferably such yellow-dye forming couplers are acylacetamides, such as benzoylacetanilides and pivaloylacetanilides, and have the Y group attached to the coupling position, that is the active methylene carbon atom.

Structures of preferred such coupler moieties are: ##STR11## where R.sub.6 is as defined above and R.sub.7 and R.sub.8 are hydrogen or more or more halogen, lower alkyl, such as methyl and ethyl, lower alkoxy, such as methoxy and butoxy, 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. Pat. 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 Y group attached to the carbon atom in the .alpha.-position with respect to the carbonyl group.

Structures of preferred such coupler moieties are: ##STR12## where R.sub.6 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 Y group para to a hydroxy group.

Structures of preferred such coupler moieties are: ##STR13## where R.sub.9 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 R.sub.10 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.

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, oxadiazoles, benzotriazoles and benzodiazoles. Structures of preferred development inhibitor moieties are: ##STR14## where W.sub.1 is unsubstituted or substituted alkyl, such as butyl, 1-ethylpentyl, and 2-ethoxyethyl, or alkylthio, such as butylthio and octylthio; R.sub.11 and R.sub.12 are individually hydrogen, alkyl of 1 to 8 carbon atoms such as methyl, ethyl, or butyl, phenyl or substituted phenyl; and R.sub.13 and R.sub.14 are individually hydrogen or one or more halogen such as chloro, fluoro or bromo; 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, ##STR15## or nitro groups.

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

Suitable dyes and dye precursors include azo, azomethine, azopyrazolone, indoaniline, indophenol, 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: ##STR16##

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: ##STR17## where R.sub.17 is hydrogen or alkylcarbonyl, such as acetyl, and R.sub.18 and R.sub.19 are individually hydrogen or a solubilizing group, such as sulfo, aminosulfonyl, and carboxy ##STR18## where R.sub.19 is as defined above and R.sub.20 is halogen, aryloxy, arylthio, or a development inhibitor, such as a mercaptotetrazole, such as phenylmercaptotetrazole or ethyl mercaptotetrazole.

D. PUG's which form developing agents:

Developing agents released can be color developing agents, black-and-white developing agents or cross-oxidizing developing agents. They include aminophenols, phenylene diamines, hydroquinones and pyrazolidones. Representative patents are: U.S. Pat. Nos. 2,193,015; 2,108,243; 2,592,364; 3,656,950; 3,658,525; 2,751,297; 2,289,367; 2,772,282; 2,743,279; 2,753,256 and 2,304,953.

Structures of preferred developing agents are: ##STR19## where R.sub.21 is hydrogen or alkyl of 1 to 4 carbon atoms and R.sub.22 is hydrogen or one or more halogen such as chloro or bromo; or alkyl of 1 to 4 carbon atoms such as methyl, ethyl or butyl groups. ##STR20## where R.sub.22 is as defined above. ##STR21## where R.sub.23 is hydrogen or alkyl of 1 to 4 carbon atoms and R.sub.24, R.sub.25, R.sub.26, R.sub.27 and R.sub.28 are individually hydrogen, alkyl of 1 to 4 carbon atoms such as methyl or ethyl; hydroxyalkyl of 1 to 4 carbon atoms such as hydroxymethyl or hydroxyethyl or sulfoalkyl containing 1 to 4 carbon atoms.

E. PUG's which are bleach inhibitors:

Representative patents are U.S. Pat. Nos. 3,705,801; 3,715,208; and German OLS No. 2,405,279. Structures of preferred bleach inhibitors are: ##STR22## where R.sub.29 is an alkyl group of 6 to 20 carbon atoms.

F. PUG's which are bleach accelerators: ##STR23## wherein W.sub.1 is hydrogen, alkyl, such as ethyl and butyl, alkoxy, such as ethoxy and butoxy, or alkylthio, such as ethylthio and butylthio, for example containing 1 to 6 carbon atoms, and which may be unsubstituted or substituted; W.sub.2 is hydrogen, alkyl or aryl, such as phenyl; W.sub.3 and W.sub.4 are individually alkyl, such as alkyl containing 1 to 6 carbon atoms, for example ethyl and butyl; z is 1 to 6.

The Y and particularly the PUG are selected and prepared to adjust to the activity of the adjoining carrier moiety, particularly a coupler moiety and the other groups of the coupler in order to optimize release of the PUG for its intended purpose. Accordingly, PUG groups of differing structural types are useful which enable timing groups having a range of activities. Various properties, such as pKa, are also usefully considered in optimizing the selection of optimum groups for a particular purpose. An example of such a selection could involve, for instance, a benzotriazole moiety as a PUG. Such a benzotriazole moiety can be released too quickly from a timing group which involves an intramolecular nucleophilic displacement mechanism; however, the benzotriazole moiety can be modified from ##STR24## in order to modify the rate at which the benzotriazole moiety is cleaved from the Y. Another illustration of modifying the PUG involves changing, for example, a mercaptotetrazole moiety from ##STR25## at elevated pH, such as above about pH 10, wherein the --CH.sub.2 O-- portion of the group hydrolyzes rapidly leaving the remainder of the PUG free for its intended purpose.

The photographic couplers of this invention can be incorporated in photographic elements and/or in photographic processing solutions, such as developer solutions, so that upon development of an exposed photographic element they will be in reactive association with oxidized color developing agent. Coupler compounds incorporated in photographic processing solutions should be of such molecular size and configuration that they will diffuse through photographic layers with the processing solution. When incorporated in a photographic element, as a general rule, the coupler compounds should be nondiffusible, that is they should be of such molecular size and configuration that they will not significantly diffuse or wander from the layer in which they are coated.

Photographic elements of this invention can be processed by conventional techniques in which color forming couplers and color developing agents are incorporated in separate processing solutions or compositions or in the element.

Photographic elements in which the compounds of this invention are incorporated can be a simple element comprising a support and a single silver halide emulsion layer or they can be multilayer, multicolor elements. The compounds of this invention can be incorporated in at least one of the silver halide emulsion layers and/or in at least one other layer, such as an adjacent layer, where they will come into reactive association with oxidized color developing agent which has developed silver halide in the emulsion layer. The silver halide emulsion layer can contain or have associated with it, other photographic coupler compounds, such as dye-forming couplers, colored masking couplers, and/or competing couplers. These other photographic couplers can form dyes of the same or different color and hue as the photographic couplers of this invention. Additionally, the silver halide emulsion layers and other layers of the photographic element can contain addenda conventionally contained in such layers.

A typical multilayer, multicolor photographic element can comprise a support having thereon a red-sensitive 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 image-providing 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 associated therewith a photographic coupler of the invention. Each silver halide emulsion unit can be composed of one or more layer and the various units and layers can be arranged in different locations with respect to one another.

The couplers of this invention can be incorporated in or associated with one or more layers or units of the photographic element. For example, a layer or unit affected by PUG can be controlled by incorporating in appropriate locations in the element a scavenger layer which will confine the action of PUG to the desired layer or unit. At least one of the layers of the photographic element can be, for example, a mordant layer or a barrier layer.

The light sensitive silver halide emulsions can include coarse, regular or fine grain silver halide crystals or mixtures thereof and can be comprised of such silver halides as silver chloride, silver bromide, silver bromoiodide, silver chlorobromide, silver chloroiodide, silver chlorobromoiodide and mixtures thereof. The emulsions can be negative-working or direct-positive emulsions. They can form latent images predominantly on the surface of the silver halide grains or predominantly on the interior of the silver halide grains. They can be chemically and spectrally sensitized. The emulsions typically will be gelatin emulsions although other hydrophilic colloids are useful. Tabular grain light sensitive silver halides are particularly useful such as described in Research Disclosure, January 1983, Item No. 22534 and U.S. Pat. No. 4,434,226.

The support can be any support used with photographic elements. Typical supports include cellulose nitrate film, cellulose acetate film, polyvinylacetal film, polyethylene terephthalate film, polycarbonate film and related films or resinous materials as well as glass, paper, metal and the like. Typically, a flexible support is employed, such as a polymeric film or paper support. Paper supports can be acetylated or coated with baryta and/or an .alpha.-olefin polymer, particularly a polymer of an .alpha.-olefin containing 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylene-butene copolymers and the like.

The compound (A), particularly photographic couplers as described, can be used in photographic elements in the same way as photographic couplers which release PUGs have previously been used in photographic elements. However, because of the improved ability to control the release of the PUG, the couplers permit enhanced effects or more selective effects. In addition, the couplers can be employed in applications where conventional coupler have previously been employed and a separate component was employed to provide a PUG.

Depending upon the nature of the particular PUG, the couplers can be incorporated in a photographic element for different purposes and in different locations.

When the PUG released from the coupler is a development inhibitor, the coupler can be employed in a photographic element like couplers which release development inhibitors have been used in the photographic art. Couplers of this invention which release a development inhibitor can be contained in, or in reactive association with, one or more of the silver halide emulsion units in a color photographic element. If the silver halide emulsion unit is composed of more than one layer, one or more of such layers can contain the coupler of this invention. The layers can contain other photographic couplers conventionally used in the art. The coupling reaction using couplers of this invention can form dyes of the same color as the color forming coupler(s) in the layer or unit, it can form a dye of a different color, or it can result in a colorless or neutral reaction product. The range of operation between layers of the development inhibitor released from the coupler of this invention can be controlled by the use of scavenger layers, such as a layer of fine grain silver halide emulsion. Scavenger layers can be in various locations in an element containing couplers of this invention. They can be located between layers, between the layers and the support, or over all of the layers.

Couplers of this invention which release development inhibitors can enhance the effects heretofore obtained with DIR couplers since they can release a development inhibitor at a distance from the point at which oxidized color developing agent reacted with the coupler, in which case they can provide, for example, enhanced interlayer interimage effects.

Photographic couplers as described which release bleach inhibitors or bleach accelerators can be employed in the ways described in the photographic art to inhibit the bleaching of silver or accelerated bleaching in areas of a photographic element.

Photographic couplers as described which release a dye or dye precursor can be used in processes where the dye is allowed to diffuse to an integral or separate receiving layer to form a desired image. Alternatively, the dye can be retained in the location where it is released to augment the density of the dye formed from the coupler from which it is released or to modify or correct the hue of that dye or another dye. In another embodiment, the dye can be completely removed from the element and the dye which was not released from the coupler can be retained in the element as a color correcting mask.

Couplers as described can be employed to release another coupler and the PUG. If the released coupler is a dye-forming coupler it can react with oxidized developing agent in the same or an adjacent layer to form a dye of the same or a different color or hue as that obtained from the primary coupler. If the released coupler is a competing coupler it can react with oxidized color developing agent in the same or an adjacent layer to reduce dye density.

Photographic couplers as described in which the PUG is a developing agent can be used to release a developing agent which will compete with the color forming developing agent, and thus reduce dye density. Alternatively, the couplers can provide, in an imagewise manner, a developing agent which because of such considerations as activity would not desirably be introduced into the element in a uniform fashion.

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

In the following discussion of suitable materials for use in the emulsions and elements of this invention, reference will be made to Research Disclosure, December 1978, Item 17643, published by Industrial Opportunities Ltd., Homewell Havant, Hampshire, PO9 1EF, U.K., the disclosures of which are incorporated herein by reference. This publication will be identified hereafter by the term "Research Disclosure".

The photographic elements can be coated on a variety of supports as described in Research Disclosure Section XVII and the references described therein.

Photographic elements can be exposed to actinic radiation, typically in the visible region of the spectrum, to form a latent image as described in Research Disclosure Section XVIII and then processed to form a visible dye image as described in Research Disclosure Section XIX. Processing to form a visible dye image includes the step of contacting the element with a color developing agent to reduce developable silver halide and oxidize the color developing agent. Oxidized color developing agent to turn reacts with the coupler to yield a dye.

Preferred color developing agents useful in the invention are p-phenylene diamines. Especially preferred are 4-amino-N,N-diethylaniline hydrochloride; 4-amino-3-methyl-N,N-diethylaniline hydrochloride; 4-amino-3-methyl-N-ethyl-N-.beta.-(methanesulfonamido)ethylaniline sulfate hydrate; 4-amino-3-methyl-N-ethyl-N-.beta.-hydroxyethylaniline sulfate; 4-amino-3-.beta.-(methanesulfonamido)ethyl-N,N-diethylaniline hydrochloride; and 4-amino-N-ethyl-N-(2-methoxyethyl)-m-toluidine di-p-toluenesulfonic acid.

With negative working silver halide. The processing step described above gives a negative image. To obtain a positive (or reversal) image, this step can be preceded by development with a non-chromogenic developing agent to develop exposed silver halide, but not form a dye, and then uniformly fogging the element to render unexposed silver halide developable. Alternatively, a direct positive emulsion can be employed to obtain a positive image.

Development is followed by the conventional steps of bleaching, fixing, or bleach-fixing, to remove silver and silver halide, washing and drying.

Compounds as described can be prepared by reactions and methods known in the organic compound synthesis art. Typically, the couplers as described are prepared in Scheme A by first attaching the LINK group to the coupling position of the coupler moiety (COUP) without the PUG being present. Then the product is reacted with an appropriate derivative of the PUG to form the desired coupler. Alternatively, PUG may be attached first to the LINK group as in Scheme B, and then the LINK-PUG group attached to COUP. The following description illustrates these syntheses in which ##STR26##

A nitrogen-blocking group B is first attached to amino acid S-1 by treatment with S-2 and the resulting S-3 is allowed to react with the hydroxyl-coupler compound to produce S-4. The blocking group B (typically COOCH.sub.2 Ph or CH.sub.2 Ph) is then removed by hydrogenolysis to give the COUP-LINK moiety S-5. S-5 can also be made directly from S-1 by reaction with the hydroxyl-coupler compound, but yields and purity may suffer. Treatment of S-5 with phosgene converts it to the corresponding carbonyl chloride, which can further react with a given PUG to provide the desired COUP-LINK-PUG compound S-7. Alternatively, reaction of a PUG carbonyl chloride with S-5 can give S-7 directly. ##STR27##

A given PUG group can be attached to a hydrazine compound S-8 by reaction with S-9. The resultant S-10 is then treated with phosgene to give the carbonyl chloride derivative S-11, which can further react with the hydroxyl-coupler compound to give the desired COUP-LINK-PUG compound S-12.

The following examples illustrate syntheses of particular compounds (A), especially couplers, as described:

Synthesis of Compound 2: ##STR28## PMT herein means phenylmercaptotetrazole.

L-Alanine (44.6 g, 0.5 mole)) was taken up in 250 mL 2N-NaOH to which was added benzaldehyde (50 mL, 0.5 mole). The resulting suspension was stirred at room temperature for approximately 20 minutes. After this period a pale yellow solution resulted. This solution was cooled in an ice/acetone bath and sodium borohydride (5.7 g, 0.15 mole) added in 1.0 g portions while keeping the temperature below 15.degree. C. A large flask is necessary as a good deal of foaming takes place during the course of the reaction. The above process was repeated with the same quantities of benzaldehyde and sodium borohydride. However, this time after the addition of the sodium borohydride, the resulting solution was stirred for about 11/2 hours at room temperature and then washed with either (100 mL, .times.2). The ether extracts were discarded and the aqueous phase acidified with 6N-HCl to pH 6-7. The product precipitated out of the solution. The resulting mixture was left overnight in the refrigerator and filtered the following morning. The product was washed with a little cold water and air dried. Yield 67 g (75%).

The N-benzylalanine (1), (67 g, 0.374 mole) was taken up in formic acid (41 mL, 88%) and formaldehyde (37 mL, 38%) added. The resulting solution was heated on a steam bath for 11/2 hours. After this period the clear solution was cooled and as much of the solvent as possible removed under reduced pressure. Removal of the water was aided by co-evaporation with methanol. To the residual oil was added methanol (200 mL) and the solution diluted with ether yielding the product as a fine white powder, 63.7 g (88%).

The 1.4-dihydroxynaphthalene (10.0 g, 20.34 mmol) was taken up in THF (150 mL) and ethyl acetate (200 mL). DCC (4.2 g, 20.34 mmol) and N-benzyl-N-methylalanine (2), (4.32 g, 22.37 mmol) added followed by the N,N-dimethylaminopyridine catalyst (300 mg). The reaction was left to stir at room temperature overnight. The following morning a thin layer chromatography analysis (silica gel, 15% ethyl acetate in hexane) showed the reaction to be complete. The dicyclohexylurea was filtered off and the filtrate taken to an oil under reduced pressure. This oil was taken up in 15% ethyl acetate in hexane, filtered and chromatographed over silica gel eluting with the same solvent. The first major band was collected to give the product which crystallized from hexane. Yield 6.5 g (48%).

The N-benzyl-N-methylalanate (3), (2.0 g, 3.0 mmol) was taken up in acetic acid (50 mL), to which was added the catalyst, 10%-Pd-on-C (300 mg), and the solution hydrogenated for 2 hours at 45 psi. After this period a thin layer chromatography analysis (silica gel, 15% ethyl acetate in hexane, and also ethyl acetate alone) showed no starting material. The catalyst was filtered off and the acetic acid solution poured into water (200 mL) and extracted with methylene chloride (3.times.50 mL). The organic extracts were washed with sodium bicarbonate (1.times.50 mL) and dried (MgSO.sub.4). The solvent was removed to given an oil which crystallized from hexane. Yield 1.4 g (82%).

The N-methylalanate (9.7 g, 16.82 mmol) was taken up in dry THF (100 mL) to which was added the phosgene (100 mL of a 12% solution in toluene). The base, N,N-diethylaniline (DEA), (2.7 mL, 16.82 mmol) was then added and the reaction stirred at room temperature for about 20 minutes. At the end of this period, the solvent was removed under vacuum to give an oil which was used as such in the next step.

The N-methylalanate carbonyl chloride (S-19), (17.34 mmol, prepared as described above) was taken up in pyridine (100 mL), to which was added the phenylmercaptotetrazole (3.1 g, 17.34 mmol) and the reaction stirred at room temperature for several hours. A thin layer chromatography analysis (silica gel, 30% ethyl acetate in hexane) showed no starting material but just one new major spot which was more polar than the starting material. The pyridine was removed under reduced pressure, the oil taken up in ethyl acetate (100 mL), washed with 2N-HCl (2.times.100 mL), dried (MgSO.sub.4) and then the solvent removed under vacuum to yield an oil. This oil was taken up in 30% ethyl acetate in hexane eluting with the same solvent and the first major band collected. Yield 9.0 g (66%).

Calculated for C.sub.43 H.sub.52 N.sub.6 O.sub.6 S: %C=66.1, %H=6.7, %N=10.8, %S=4.1; Found: %C=66.0, %H=6.6, %N=10.6, %S=4.4

Synthesis of Compound 3: ##STR29##

Dimethylhydrazine dihydrochloride (10.0 g, 75.17 mmol), together with potassium carbonate (11.5 g, 82.64 mmol) were taken up in water (mL), and stirred at room temperature. To this solution was then added the bis-PMT-CO (2.4 g, 7.52 mmol) in ethyl acetate (100 mL) dropwise, over about a one-hour period. The reaction was stirred at room temperature overnight. Following morning the aqueous layer was run off and the organic layer washed with 10% sodium carbonate (2.times.50 mL). A thin layer chromatography analysis (silica gel, ethyl acetate) showed only one new spot. The solution was dried (MgSO.sub.4) and concentrated. The product crystallized out on addition of heptane, it was filtered off, air dried to give 1.25 g of the hydrazide (1), 63%.

The hydrazide (1.2 g, 4.54 mmol) was taken up in methylene chloride (20 mL) and the base, N,N-diisopropylethylamine (0.8 mL, 4.54 mmol), was added followed by the phosgene (19 mL of a 12% solution of phosgene in toluene, 22.70 mmol). The reaction was stirred for about 30 minutes at room teperature, after which a thin layer chromatography analysis (silica gel, ethyl acetate) showed no starting material. The solvent was removed under reduced pressure and the crude carbonyl chloride (2) used as such in the next step.

The above carbonyl chloride (about 4.54 mmol) together with the 1,4-dihydroxynaphthalene (3), (2.23 g, 4.54 mmol) were taken up in methylene chloride, (50 mL). To this solution was then added the base, N,N-diisopropylethylamine (0.8 mL, 4.54 mmol), followed by a catalytic amount of N,N-dimethylaminopyridine (about 10 mg). The reaction was stirred at room temperature for about one hour. At the end of this period a thin layer chromatography analysis (silica gel, 30% ethyl acetate in hexane) showed a new material present. The reaction was washed with 2N-HCl (xl, 50 mL), dried magnesium sulfate) and the solvent removed under vacuum. The residual oil was chromatographed over silica gel eluting 30% ethyl acetate in hexane containing a few percent of methylene chloride to aid dissolution. The main band was collected, concentrated and recrystallized from ethyl acetate/hexane. Yield 780 mg, 22%.

Calculated for C.sub.42 H.sub.51 N.sub.7 O.sub.6 S: %C=64.5, %H=6.6, %N=12.5, %S=4.1; Found: %C=64.6, %H=6.4, %N=12.4, %S=4.4

The following examples further illustrate the invention.

The half-life for release of the development inhibitor PUG from each DIR compound was determined in solution as a means for predicting the relative release rates when incorporated in film coatings. All reactions were carried out at a measured pH of 10.0+/-0.2 in aqueous 3% Triton X-100 (Triton X-100 is a trademark), ionic strength 0.375. Concentrations were chosen so that dye formation from COUP and LINK-PUG liberation would be complete in a fraction of a second. The rate of the coupling reaction and the limitations of hand pipetting imposed a one second lower limit on the range of half-lives which could be determined by this method.

To a scintillation via with magnetic stirbar were added coupler stock (1.0 mL of 2 mMolar solution in aqueous 12% Triton X-100), pH 10 phosphate buffer (1.0 mL, ionic strength 1.5), and aqueous CD-2 developer compound (1.0 mL of 2 mMolar solution). At time zero, aqueous ferricyanide (1.0 mL of 4 mMolar solution) was added to the rapidly stirred mixture, allowed to react for variable time periods, and then quenched with aqueous HCl (1.0 mL of 1.0 mMolar solution). The amount of released development inhibitor was determined by high pressure liquid chromatography and a first order rate constant k for inhibitor release was calculated from the inhibitor concentration vs. reaction time data. The half-life of release reported in Table I was then calculated using the formula t.sub.1/2 =ln (2)/k.

An acetonitrile solution of coupler (2 mL, 1.times.10.sup.-3 M) was mixed with aqueous potassium hydroxide (2 mL, 0.100N) and the time noted. The resulting solution was rapidly transferred to a quartz UV cell and the decrease in absorption due to coupler anion was monitored as a function of time. The mixture pH was measured before and after spectroscopic measurements. A first order rate constant for reaction of coupler anion k.sub.decomp, was calculated from absorbance vs. time data. In cases where an insignificant change in the absorbance spectrum occurred after .gtoreq.15 h, the mixture was analyzed by HPLC to verify and quantify the presence of unreacted coupler. Half-lives for coupler hydrolytic decomposition were calculated with the expression t.sub.1/2, hydr.=ln (2)/k.sub.decomp. The results are reported in Table I. ##STR30##

The data in Table I show that LINK groups, as described, which contain a bulky Q-R.sub.q group adjacent to the -O-CO-group, provide for improved resistance to hydrolysis when compared to linking groups containing a methylene Q-R.sub.q group of the type described in column 12 of U.S. Pat. No. 4,248,962. The larger the t.sub.1/2 of hydrolysis, the greater will be the stability of the link during preprocessing storage of photographic elements containing compounds of the type CAR-LINK-PUG. For example, multilayer coatings containing Compound C-2 or an equimolar amount of Compound 4 were kept for two weeks at 49.degree. C. and 50% relative humidity, then extracted to determine the amounts of coupler compound remaining intact. It was found that about 20% of Comparison Compound C-2 was lost while Compound 4 of the invention was stable to these conditions and was retained. This in-film test confirms the trends predicted by the solution hydrolysis relative rates shown in Table I.

Data in the last column of Table I indicates that increasing the bulk of the Q-R.sub.q group generally provides for a desirably faster PUG release, although full control of PUG release timing also depends on the choice of other groups in the LINK structure.

Photographic elements were prepared by coating the following layers on a cellulose ester film support (amounts of each component are indicated in mg/m.sup.2):

Structures of the image couplers are as follows: ##STR31##

Strips of each element were exposed to green light through a graduated density steptablet, or through a 35% modulation fringe chart for sharpness measurements, and then developed 3.25 minutes at 38.degree. C. in the following color developer, stopped, washed, bleached, fixed, washed and dried.

Processed images were read with red light to determine the contrast and AMT acutance. From plots of AMT acutance vs. the logarithm of the contrast for variations in the coated level of each DIR compound, the acutance was determined at a contrast of 0.8. The acutance value for comparison compound C-1 was subtracted from each AMT value to provide the relative sharpness value reported as AMT in Table I. AMT calculations employed the following formula in which the cascaded area under the system modulation transfer curve is shown in equation (21.104) on p. 629 of the "Theory of the Photographic Process", 4th Edition, 1977, edited by T. H. James:

where the magnification factor M=3.8 for the 35 mm system AMT. The use of CMT acutance is described by R. G. Gendron in "An Improved Objective Method for Rating Picture Sharpness: CMT Acutance" in the Journal of the SMPTE, Vol. 82, pp. 1009-12 (1973). AMT is a further modification of CMT useful for evaluating systems which include the viewing of a positive print made from a negative.

It can be seen from the AMT acutance values in Table II that the use in photographic elements of compounds of the invention, which contain a bulky Q-R.sub.q group in the LINK moiety, leads to improved sharpness from the combination of groups over that attained by using closely related groups in comparison DIR compounds which release the same development inhibitor PUG moieties. ##STR32##

The benefits to be gained from this invention are clearly demonstrated by the data in Table III. They show that comparison Compound C-12, of the type described in column 12 of U.S. Pat. No. 4,248,962, hydrolyzes rapidly under development conditions to produce a strong fogging agent, while incorporating Compound 8 of the invention, even at a much higher level, results in an image with less fog than the no-DIR control.

The release of a useful compound from a carrier compound (A) can also be useful in other applications wherein controlled release is desired. Initiation of such release may be triggered by hydrolysis or redox reactions, for example. For example, the described -LINK-PUG group can release, for example, pharmaceutically useful moieties, including drugs, dyes, analytical agents, agricultural chemicals, and other useful moieties.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.