FIELD OF THE INVENTION The present invention relates to a photographic silver halide element containing a novel coupler which is capable of releasing a development accelerator and to a method for processing such an element.

BACKGROUND OF THE INVENTION Couplers which release a development accelerator (DARCs) are known in the art. They are added to silver halide emulsions in order to achieve an increase in speed or contrast, brought about by the increased image development caused by the image- wise release of the development accelerator. Typically, these couplers release a hydrazide nucleator, which is activated by oxidized colour developing agent and hydroxyl ions.

EP-A-O 896 248 discloses a fogging photographic processing solution for a reversal process comprising a l-phenyl-3-pyrazolidinone derivative and a bi-nucleophilic agent. EP-A-O 896 249 discloses a DARC that releases a l-phenyl-3-pyrazolidinone derivative which, in the presence of a colour developing solution containing a bi-nucleophilic agent, is then converted into a development accelerator. US Patent No. 6,756,188 discloses the synergistic speed improvement when a DARC of the type that releases a hydrazide nucleator is used in combination with an electron transfer agent-releasing coupler (ETARC).

PROBLEM TO BE SOLVED BY THE INVENTION

The DARCs described in EP-A-O 896 249 only release the development accelerators at higher pH or development time than required in the standard colour development process, namely the C-41 ™ development process. It would therefore be desirable to provide a novel DARC of the general type described therein showing, however, good speed increase without the need for modification of the standard colour development process and secondly to extend the known range of DARCs. Furthermore it would be advantageous to

provide a novel DARC that would maintain the synergistic speed improvement as described in US Patent No. 6,756,188 when used in combination with an electron transfer agent-releasing coupler (ETARC) under standard processing conditions.

SUMMARY OF THE INVENTION

According to the present invention there is provided a photographic element comprising a support bearing at least one silver halide emulsion layer and associated therewith a coupler capable of releasing a development accelerator on colour development in the presence of a bi-nucleophilic agent, the coupler having the formula (I):-

(I) wherein

COUP is a coupler moiety; T is a timing group and n is 0, 1 or 2; X ₁ and X ₂ are independently selected from an unsubstituted or substituted alkyl, -CH ₂ OCOR- -CH ₂ COOR'-, -CH ₂ NHCOR- -CH ₂ NRCOR', aryl or heterocyclic group, wherein R and R' are each an unsubstituted or substituted alkyl, aryl or heterocyclic group and R' may also be hydrogen; or

X ₁ and X ₂ may combine to form an unsubstituted or substituted cycloalkyl ring which may include one or more heteroatoms selected from nitrogen, oxygen and sulfur;

X ₃ and X ₄ are independently selected from hydrogen or an unsubstituted or substituted alkyl, aryl or heterocyclic group; or

X ₁ to X ₄ may combine to form an unsubstituted or substituted cycloalkyl ring which may include one or more heteroatoms selected from nitrogen, oxygen and sulfur;

L is a linking group and r is 0, 1 or 2; and A is a group capable of being adsorbed to the silver halide surface.

In another embodiment of the invention there is provided a multicolour photographic element comprising a support bearing yellow, magenta and cyan image-dye-forming units comprising at least one blue-, green- or red- sensitive silver halide emulsion layer having associated therewith, at least one yellow, magenta or cyan dye-forming coupler respectively, wherein the element is as herein described.

In a further embodiment there is provided a method of processing an image-wise exposed photographic element containing a coupler capable of releasing a development accelerator as above defined wherein the element is processed in a colour developing solution containing a colour developer and a bi- nucleophilic agent.

ADVANTAGEOUS EFFECT OF THE INVENTION The elements comprising the novel DARCs of the present invention, in the presence of a bi-nucleophilic agent, allow a speed increase under standard processing conditions. In addition, they can provide synergistic speed improvement when used in combination with ETARCs.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention X ₁ and X ₂ are independently selected from an an unsubstituted or substituted alkyl, -CH ₂ OCOR-, -CH ₂ COOR'- -CH ₂ NHCOR- -CH ₂ NRCOR', aryl or heterocyclic group, wherein R and R' are each an unsubstituted or substituted alkyl, aryl or heterocyclic group and R' may also be hydrogen. Alternatively X ₁ and X ₂ may combine to form an unsubstituted or substituted cycloalkyl ring which may include one or more heteroatoms selected from nitrogen, oxygen and sulfur.

Preferably each alkyl group has from 1 to 12 carbon atoms, more preferably from 1 to 4 carbon atoms, and is more especially methyl or ethyl. When X ₁ and X ₂ combine to form a cycloalkyl ring, this is preferably to form a cyclopentyl or cyclohexyl ring. As substituents on the alkyl groups a large number of substituents may be contemplated. For example the substituent may be one or more cyano, fluoro, chloro, bromo, hydroxy or carboxy groups, or one or more unsubstituted or substituted alkyl, aryl, heterocyclyl, alkoxy, aryloxy, alkyl- or aryl-carbonyl, alkyl- or aryl-oxycarbonyl, acyloxy, carbonamido, alkyl- or aryl-carbonamido, alkyl- or aryl-oxycarbonylamino, alkyl- or aryl-sulfonyl, alkyl- or aryl- sulfonyloxy, alkyl- or aryl-oxysulfonyl, alkyl- or aryl-sulfoxide, alkyl- or aryl- sulfamoyl, alkyl- or aryl-sulfamoylamino, alkyl- or aryl-sulfonamido, alkyl- or aryl-thio, alkyl- or aryl- phosphonate, nitro, alkyl- or aryl-amino, alkyl- or aryl- ureido or alkyl- or aryl-carbamoyl groups, any of which may be further substituted, for example with one or more other such substituents such as, for example an alkyl group.

When X ₁ and/or X ₂ is an aryl group this is preferably a phenyl group optionally substituted, for example, with one or more cyano, chloro, fluoro, bromo, or one or more unsubstituted or substituted alkyl- or aryl-carbonyl, alkyl- or aryl-oxycarbonyl, acyloxy, carbonamido, alkyl- or aryl-carbonamido, alkyl- or aryl-oxycarbonylamino, alkyl- or aryl-sulfonyl, alkyl- or aryl-sulfonyloxy, alkyl- or aryl-oxysulfonyl, alkyl- or aryl-sulfoxide, alkyl- or aryl-sulfamoyl, alkyl- or aryl-sulfamoylamino, alkyl- or aryl-sulfonamido, aryl, alkyl, alkoxy, aryloxy, nitro, alkyl- or aryl-ureido or alkyl- or aryl-carbamoyl groups, any of which may be further substituted.

X ₃ and X ₄ are independently selected from hydrogen or an unsubstituted or substituted alkyl, aryl or heterocyclic group, although X ₁ to X ₄ may combine to form an unsubstituted or substituted cycloalkyl ring which may include one or more heteroatoms selected from nitrogen, oxygen and sulfur. When X ₁ to X ₄ combine to form a cycloalkyl ring, this is preferably to form a cyclopentyl or cyclohexyl ring.

As used herein and throughout the specification unless where specifically stated otherwise, the term "alkyl" refers to a saturated or unsaturated, straight or branched chain alkyl group including alkenyl and aralkyl, and includes cyclic groups, including cycloalkenyl, having 3-8 carbon atoms. The term "aryl" includes fused aryl.

The group A capable of being adsorbed to the silver halide surface defines a group well known in the photographic field For example, A can be selected from the class consisting of unsubstituted or substituted purines, triazoles, benzotriazoles, tetrazoles, indazoles, imidazoles, benzimidazoles, thioureas, mercaptotetrazoles, mercaptoimidazoles, mercaptothiazoles, mercaptooxazoles, mercaptotriazoles, thioethers, thiadiazoles, aminothiadiazoles, mercapto- thiadiazoles and mercaptopurines. Suitable substituents on A may be, for example a NHCOR group, such as when A is a mercaptothiadiazole, or for example a group SR, such as when A is an aminothiadiazole, wherein R is an unsubstituted or substituted alkyl, aryl or heterocyclyl group.

Preferred silver adsorbing groups A are selected from the following: -

N-N N-N

^\ _S -^SH ^g^NH

The linking group is selected from alkylene, -CO-, -CO-O-, -O-CO- -CONR'-, -NR' CO- -SO ₂ NR'- -NR ⁵ SO ₂ - -O- -0(CH ₂ ) _n - -NR'SO ₂ (CH ₂ ) _n - -NR'CO(CH ₂ ) _n - -NR ⁵ SO ₂ (C ₆ H ₄ )CONH- -NR' CO(CH ₂ ) _I iO-CO-, or a combination of these when r is 2, for example, -O(CH ₂ ) _n -O- ₅ and -0(CH ₂ ) _n -0-C0- wherein R' is hydrogen or an unsubstituted or substituted alkyl, aryl or heterocyclyl group and n is an integer from 1-5.

The timing group T can be any group which can be used to control the speed of release of a photographically useful group (PUG). Two timing groups may be used in circumstances where staged release is required. Exemplary timing groups include those shown below, wherein PUG is included to show the point of attachment: -

O

-0-CH ₂ -PUG X

—0 PUG

Unless otherwise specifically stated, substituent groups which may be substituted on molecules herein include any groups, whether substituted or unsubstituted, which do not destroy properties necessary for photographic utility. When the term "group" is applied to the identification of a substituent containing a substitutable hydrogen, it is intended to encompass not only the substituent's unsubstituted form, but also its form further substituted with any group or groups as herein mentioned. Suitably, the group may be halogen or may be bonded to the

remainder of the molecule by an atom of carbon, silicon, oxygen, nitrogen, phosphorous or sulfur. The substituent may be, for example, halogen, such as chlorine, bromine or fluorine; nitro; hydroxyl; cyano; carboxyl; or groups which may be further substituted, such as alkyl, including straight or branched chain. alkyl, such as methyl, trifluoromethyl, ethyl, t-butyl, 3-(2,4-di-t-pentylphenoxy) propyl and tetradecyl; alkenyl, such as ethylene, 2-butene; alkoxy, such as methoxy, ethoxy, propoxy, butoxy, 2-methoxyethoxy, see-butoxy, hexyloxy, 2-ethylhexyloxy, tetradecyloxy, 2-(2,4-di-t-pentylphenoxy)ethoxy and 2-dodecyl- oxyethoxy; aryl such as phenyl, 4-t-butyl-phenyl, 2,4,6-trimethylphenyl, naphthyl; aryloxy, such as phenoxy, 2-methylphenoxy, alpha- or beta-naphthyloxy and 4-tolyloxy; carbonamido, such as acetamido, benzamido, butyramido, tetradecanamido, alpha-(2,4-di-?-pentylphenoxy)acetamido, alpha-(2,4-di-z ^l -pentyl- phenoxy)butyramido, alpha-(3-pentadecylphenoxy)hexanamido, alpha- (4-hydroxy-3 -t-butylphenoxy)tetradecanamido, 2-oxopyrrolidin- 1 -yl, 2-oxo- 5-tetradecylpyrrolin-l-yl, N-methyltetradecanamido, N-succirώnido,

N-phthalimido, 2,5-dioxo-l-oxazolidinyl, 3-dodecyl-2,5-dioxo-l-imidazolyl and N-acetyl-N-dodecylamino, ethoxycarbonylamino, phenoxycarbonylamino, benzyloxycarbonylamino, hexadecyloxycarbonylamino, 2,4-di-t-butylphenoxy- carbonylamino, phenylcarbonylamino, 2,5-(di-/ ^t -pentylphenyl)carbonylamino, p-dodecylphenylcarbonylamino, p-toluylcarbonylamino, N-methylureido, N,N-dimethylureido, N-methyl-N-dodecyl-ureido, N-hexadecylureido, N,N-dioctadecylureido, N,N-dioctyl-N'-ethylureido, N-phenylureido, N,N-di- phenylureido, N-phenyl-N-p-toluylureido, N-(7n-hexa-decylphenyl)ureido, N,N-(2,5-di-t-pentylphenyl)-N'-ethylureido and t-butylcarbonamido; sulfonamido, such as methylsulfonamido, benzenesulfonamido, p-toluylsulfonamido,

/»-dodecylbenzenesulfonamido, N-methyltetradecylsulfonamido, N,N-dipropyl- sulfamoylamino and hexadecylsulfonamido; sulfamoyl, such as N-methyl- sulfamoyl, N-ethylsulfamoyl, N,N-dipropylsulfamoyl, N-hexadecylsulfamoyl, N,N-dimethylsulfamoyl; N-[3-(dodecyloxy)propyl]sulfamoyl, N-[4-(2,4-di- f-pentylphenoxy)butyl] sulfamoyl, N-methyl-N-tetradecylsulfamoyl and

N-dodecylsulfamoyl; carbamoyl, such as N-methylcarbamoyl, N,N-dibutyl- carbamoyl, N-octadecylcarbamoyl, N-[4-(2,4-di-t-pentylphenoxy)butyl]-

carbamoyl, N-methyl-N-tetradecylcarbamoyl and N,N-di-octylcarbamoyl; acyl, such as acetyl, (2,4-di-t-amylphenoxy)acetyl, phenoxycarbonyl, j^-dodecyloxy- phenoxycarbonyl, methoxycarbonyl, butoxycarbonyl, tetradecyloxycarbonyl, ethoxycarbonyl, benzyloxycarbonyl, 3-pentadecyloxycarbonyl and dodecyl- oxycarbonyl; sulfonyl, such as methoxysulfonyl, octyloxysulfonyl, tetradecyl- oxysulfonyl, 2-ethylhexyloxysulfonyl, phenoxysulfonyl, 2,4-di-t-pentyl- phenoxysulfonyl, methylsulfonyl, octylsulfonyl, 2-ethylhexylsulfonyl, dodecylsulfonyl, hexadecylsulfonyl, phenylsulfonyl, 4-nonylphenylsulfonyl and ^-toluylsulfonyl; sulfonyloxy, such as dodecylsulfonyloxy and hexadecyl- sulfonyloxy; sulfinyl, such as methylsulfinyl, octylsulfinyl, 2-ethylhexylsulfinyl, dodecylsulfinyl, hexadecylsulfmyl, phenylsulfinyl, 4-nonylphenylsulfmyl and j?-toluylsulfinyl; thio, such as ethylthio, octylthio, benzylthio, tetradecylthio, 2-(2,4-di-t-pentylphenoxy)-ethylthio, phenylthio, 2-butoxy-5-t-octylphenylthio and p-tolylthio; acyloxy, such as acetyloxy, benzoyloxy, octadecanoyloxy, p-dodecylamidobenzoyloxy, N-phenylcarbamoyloxy, N-ethylcarbamoyloxy and cyclohexylcarbonyloxy; amino, such as phenylanilino, 2-chloroanilino, diethylamino and dodecylamino; immo, such as 1 (N-phenylimido)ethyl, N-succinimido or 3-benzyl-hydantoinyl; phosphate, such as dimethylphosphate and ethylbutylphosphate; phosphite, such as diethyl and dihexylphosphite; a heterocyclic group, a heterocyclic oxy group or a heterocyclic thio group, each of which may be substituted and which contain a 3 to 7 membered heterocyclic ring composed of carbon atoms and at least one hetero atom selected from the group consisting of oxygen, nitrogen and sulfur, such as 2-furyl, 2-thienyl, 2-benzimidazolyloxy or 2-benzothiazolyl; quaternary ammonium, such as triethylarnmonium; and silyloxy, such as trimethylsilyloxy.

If desired, the substitαents may themselves be further substituted one or more times with the described substituent groups. The particular substituents used may be selected by those skilled in the art to attain the desired photographic properties for a specific application and can include, for example, hydrophobic groups, solubilizing groups, blocking groups, releasing or releasable groups. Generally, the above groups and substituents thereof may include those having up to 48 carbon atoms, typically 1 to 36 carbon atoms and usually less than

24 carbon atoms, but greater numbers are possible depending on the particular substituents selected.

Representative substituents on ballast groups include alkyl, aryl, alkoxy, aryloxy, alkylthio, hydroxy, halogen, alkoxycarbonyl, aryloxycarbonyl, carboxy, acyl, acyloxy, amino, anilino, carbonamido, carbamoyl, alkylsulfonyl, arylsulfonyl, sulfonamido and sulfamoyl groups wherein the substituents typically contain 1 to 42 carbon atoms. Such substituents can also be further substituted.

The coupler moiety COUP from which the developing accelerator moiety is released can be in the present invention any moiety of known couplers wherein COUP is bonded to the released moiety in the coupling-off position.

The coupler moieties capable by reaction with oxidised developing agent of releasing a photographically useful group are particularly well known in development accelerator technology. Typically, the coupler moiety (COUP) from which the development accelerator moiety is released includes a coupler moiety employed in conventional colour-forming photographic processes which yield coloured products based on reaction of couplers with oxidised colour developing agents. The coupler moiety can yield colourless products, or coloured products that can be washed out to remove any retained colour on reaction with oxidised colour developing agents. The COUP can be unballasted or ballasted with an oil-soluble or lipophilic group.

The coupler moiety can be a magenta, yellow, cyan or universal coupler.

Magenta couplers are described in such representative patents and publications as: US Patent Nos. 2,311,082, 2,343,703, 2,369,489, 2,600,788, 2,908,573, 3,062,653, 3,152,896, 3,519,429, and "Farbkuppler-eine Literaturubersicht," published in Agfa Mitteilungen, Band III, pp. 126-156 (1961). Preferably such couplers are pyrazolones, pyrazolotriazoles or pyrazolo- benzimidazoles. Cyan couplers are described in such representative patents and publications as: US Patent Nos. 2,367,531, 2,423,730, 2,474.293, 2,772,162, 2,895,826, 3,002,836, 3,034,892, 3,041,236, 4,333,999, 4,883,746 and

"Farbkuppler-eine Literaturubersicht," published in Agfa Mitteilungen, Band III, pp. 156-175 (1961). Preferably such couplers are phenols and naphthols.

Yellow couplers are described in such representative patents and publications as: US Patent Nos. 2,298,443, 2,407,210, 2,875,057, 3,048,194, 3,265,506, 3,447,928, 4,022,620, 4,443,536, and "Farbkuppler-eine

Literaturubersicht," published in Agfa Mitteilungen, Band III, pp. rl2-126 (1961). Such couplers are typically open chain ketomethylene compounds.

Couplers that form colourless products upon reaction with oxidised colour developing agent are described in such representative patents as: British PatentNo. 861,138; US Patent Nos. 3,632,345, 3,928,041, 3,958,993 and

3,961,959. Typically such couplers are cyclic carbonyl containing compounds that form colourless products on reaction with an oxidised colour developing agent.

According to the present invention, the DARC coupler gives a dye on reaction with oxidised colour developing agent at the coupling-off position, the thus released moiety forming in the presence of a bi-nucleophilic agent a development accelerator.

In the scope of the present invention, a bi-nucleophilic agent is an agent which comprises two active nucleophilic sites. A bi-nucleophilic agent is for example hydroxylamine, hydrogen peroxide, hydrazine or a substituted hydrazine or a derivative of any of these. According to a preferred embodiment, the bi-nucleophilic agent is hydroxylamine, particularly in the form of its sulfate. Indeed, hydroxylamine sulfate is generally already present in the developing solution in order to prevent oxidation of the solution. The bi-nucleophilic agent can be present either in the photographic material or in the developing solution. When present in the photographic material, the amount of the bi-nucleophilic agent is from 0.1 to 10 g/m ² , preferably from 0.5 to 5 g/m ² , more preferably from 1 to 3 g/m ² . The bi-nucleophilic agent can be present either in the same layer as the DARC compound or in a different layer. When the bi-nucleophilic agent is present in the developing solution, the useful amount is from 0.1 to 20 g/1, preferably from 1 to 4 g/1, most preferably from 1.5g/l to 2.5 g/1.

The coating weight of a DARC in the photographic material is from 0.0001 mmol/m ² to 0.5 mmol/ m ² , preferably 0.0003 mmol/ m ² to 0.1 mmol/ m ² , most preferably 0.0005 mmol/ m ² to 0.02 mmol/ m ² . When an ETARC is present this may generally be included in a ratio of 5% to 60% of total coupler (image coupler + ETARC) on a molar basis, preferably 10% to 50% of total coupler, most preferably 20% to 40 % of total coupler, (the amount of DARC being very small in comparison).

The photographic material of the present invention will normally also contain a conventional image-dye forming coupler in addition to the DARC.

The DARC compounds of the present invention and, when present, the conventional coupler compound can be incorporated in silver halide emulsions and the emulsions can be coated on a support to form a photographic recording material. Alternatively, one or more DARC compounds and conventional couplers can be incorporated in photographic layers adjacent to the silver halide emulsion where, during development, the DARC compounds and coupler(s) will be in reactive association with the oxidised colour developing agent and bi- nucleophilic agent.

The photographic elements can be single colour elements or multicolour elements. Multicolour elements contain dye image-forming units sensitive to each of the three primary regions of the spectrum. Each unit can be comprised of a single emulsion layer or of multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as known in the art. In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer.

A typical multicolour photographic element comprises a support bearing a cyan dye image-forming unit comprised of a least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye- forming coupler, a magenta dye image-forming unit comprising at least one green sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, and a yellow dye image-forming unit comprising at

least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler. The element can contain additional layers, such as filter layers, interlayers, overcoat layers and subbing layers.

In the following discussion of suitable materials for use in the emulsions and elements of this invention, reference will be made to Research Disclosure Item 36544, September 1994, published by Kenneth Mason Publications, Emsworth, Hants POlO 7DQ, United Kingdom which will be identified hereafter by the term "Research Disclosure".

The contents of the Research Disclosure, including the patents and publications referenced therein, are incorporated herein by reference, and the Sections hereafter referred to are Sections of the Research Disclosure.

The silver halide emulsions employed in the elements of this invention can be either negative- working or positive- working. Suitable emulsions and their preparation as well as methods of chemical and spectral sensitisation are described in Sections I through IY. Colour materials and development modifiers are described in Sections V and XXI. Vehicles are described in Section IX, and various additives such as brighteners, antifoggants, stabilisers, light absorbing and scattering materials, hardeners, coating aids, plasticisers, lubricants and matting agents are described, for example, in Sections V, VI, VIII, X, XI, XII, and XVI. Manufacturing methods are described in Sections XIV and XV, other layers and supports in Sections XIII and XVII, processing methods and agents in Sections XIX and XX, and exposure alternatives in Section XVIII.

Processing to form a visible dye image includes the step of contacting the element with a colour developing agent to reduce developable silver halide and oxidise the colour developing agent. Oxidised colour developing agent in turn reacts with the coupler to yield a dye.

Preferred colour developing agents are p-phenylenediamines. Especially preferred are 4-amino-3-methyl-N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N-ethyl-N-β-(metlianesulfonamido)ethylanil ine sulfate hydrate, 4-amino-3-methyl-N-ethyl-N-β-hydroxyethylanilme sulfate, 4-amino-

3-β- (methane-sulfonamido)ethyl-N,N-diethylaniline hydrochloride and 4-amino- N-ethyl-N-(2-methoxyethyl)-m-toluidine di-p-toluene sulfate.

With negative- working silver halide emulsions this processing step leads to 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 dye, and then uniform fogging of 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. Examples of suitable DARCS within the scope of formula (I) are as follows:-.

CYAN DARC COUPLERS

Cl

C6 C7

C8

15

ClO

CIl

C12 C13

10

15

C14 C15

C16 C17

C18 C19

C21 C22

C23

C24 C25

C26

C27

YELLOW DARC COUPLERS

Yl

Y2

Y3

Y4

Y7

Y8

Y9

YlO

YIl

Y12

Y13 Y14

Y15 Y16

Y17

Y18

Y19

Y20

Y21

Y22

Y23

MAGENTA DARC COUPLERS

Ml M2

M5 M6

M7 M8

M9 MlO

Mil M12

Ml 3

UNIVERSAL DARC COUPLERS

U5 U6

SELF-DESTRUCT COUPLERS

SDl

SD2

The invention is described herein with reference to the following examples which are not however to be construed as limiting the scope thereof.

EXAMPLE 1 Synthesis of Cyan PARC C7

Preparation of 1-1

To a solution of commercially avilable p-nitrophenyl hydrazine (50.37g, 0.33mol) in pyridine (500ml) at 5C under an atmosphere of nitrogen was added 3-chloro-pivaloyl chloride dropwise. The reaction mixture was stirred at room temperature for 1 h and then heated at 8OC for a further 18 h. After this

time it was cooled, poured into a mixture of concentrated HCl (500ml) and water (1.51) and the resulting solid collected by filtration. It was triturated with Et ₂ O followed by filtration give the product as an orange solid (55g, 71%). LCMS 100%.

Preparation of 1-2

A solution of 1-1 (40.5g, 0.17mol) in tetrahydrofuran)(THF) (450ml) was hydrogenated over 10% palladium-on-carbon (4g) at room temperature under a pressure of 30atm of hydrogen. After 24 h the catalyst was removed by filtration through a pad of Kieselguhr gel and washed with fresh THF. The resulting intense deep purple coloured filtrate was concentrated under reduced pressure to give the product as a dark green solid (100%), which was used immediately in the next step.

Preparation of 1-3

To a solution of 1-2 (20.7g, O.lQmol) in dry THF (300ml) at 5C under an atmosphere of nitrogen was added N,N-dimethylaniline (12.2g, O.lOmol) dropwise over 30 min. A solution of chloroacetyl chloride (11.3Ig ₅ O.lOmol) in dry THF (50ml) was then added dropwise at the same temperature over 30 min and the resulting dark blue-green solution stirred for a further 30 min at 5C. Tie after this time showed the absence of any starting material and the reaction was poured into a mixture of water (500ml) and concentrated HCl (10ml) with stirring. It was extracted with EtOAc (2x500ml), washed with water (2x500ml) and brine (2x300ml) and the organic phase was dried (MgSO ₄ ), filtered and concentrated under reduced pressure to give a brown solid which was triturated with diethyl ether (250ml). The solid was filtered, washed with ether and dried under vacuum to give the product as a brown solid (23.23g, 82%). LCMS 100%.

Preparation of 1-4

To an orange solution of 1-3 (2.Og, 7.1mmol) in dry THF (20ml) and dimethylacetamide (8ml) at 5C under an atmosphere of nitrogen was added di-isopropylethylamine (1.83g, 14.2mmol) dropwise. N,N-dimethylamino- pyridine (lOmg) was then added followed by the dropwise addition of a solution of p-nitrophenylchloroformate (1.43g, 7.1mmol) in dry THF (15ml) at the same temperature. The red-brown solution was allowed to reach ambient temperature and stirred overnight. Tie after this time showed the absence of any starting material and the reaction mixture was poured into a mixture OfICeZH ₂ O (200ml) and concentrated HCl (1 OmI), the organic phase was extracted with EtOAc

(2x50ml), washed with water (2x5 OmI), dried (MgSO ₄ ), filtered and concentrated under reduced pressure. The resulting sugary solid was triturated with Et ₂ O and filtered to give the product as a sandy solid (2.33g, 74%). LCMS 99%.

Preparation of 1-5

1-5 was prepared by combining phenyl l,4-dihydroxy-2-naphthoate with 2-methyl-5-dodecyloxyaniline in xylene at 150C for 5 h. The solvent was removed under reduced pressure and the residue recrystallised from 10% toluene in petrol (b.p. 60-80C) to give pure 1-5 in 70% yield.

Preparation of 1-6

To a dark orange solution of 1-4 (1Og, 22.4mmol) and 1-5, (10.7g, 22.4mmol), in dry THF (200ml) at 5C under an atmosphere of nitrogen was added l,8-diaza-bicyclo[5.4.0]undec-7-ene (3.4Ig ₉ 22.4mmol) dropwise. After stirring for 2 days, the reaction mixture was poured into a mixture of ice/H ₂ O (500ml) and concentrated HCl (50ml), the organic phase was extracted with EtOAc (2x250ml), washed with water (2x250ml), dried (MgSO ₄ ), filtered and concentrated under reduced pressure. The resulting residue was triturated twice with Et ₂ O and filtered to give the product as a sandy solid (8.55g, 48%). LCMS 100%.

Preparation of DARC C-7

To a pink suspension of 1-6 (690mg, 0.88mmol) in dry THF (10ml) at room temperature under an atmosphere of nitrogen was added a suspension of 2-mercaptopurine hydrate (150mg, 0.88mmol) in THF (10ml) followed by the addition of l,8-diazabicyclo[5.4.0]undec-7-ene (134mg, 0.88mmol) dropwise.

After heating the reaction at reflux for 3 h, it was poured into a mixture of ice/H ₂ θ (200ml) and concentrated HCl (10ml), the organic phase was extracted with EtOAc (2x100ml), washed with water (2x100ml), dried (MgSO ₄ ), filtered and concentrated under reduced pressure. The resulting residue was triturated twice with Et ₂ O and filtered to give the title product as a pale pink solid (690mg, 87%). LCMS 100%.

All other DARC compounds can be prepared analogously by reacting the appropriate coupler and coupling-off moiety as exemplified in the specification by methods known in the art.

EXAMPLE 2

Single Layer Film

Cyan development accelerator-releasing couplers (DARCs) of the present invention (and control compounds) were incorporated as solid particle dispersions in photographic coatings on a transparent cellulose acetate support (with Gel U-coat and removable carbon antihalation backing), according to the coating diagram shown in TABLE 1 below.

TABLE l

Structure of Photographic Element

Gel Supercoat Gelatin 1.000 g/m ²

Bis(vinylsulfonyl)methane (hardener) 0.166 g/m ²

Red-sensitised silver bromoiodide 0.807 g/m ²

(96.3% silver bromide, 3.7 % silver iodide)

Image Coupler IC-I X g/m ²

Emulsion Layer DARC Y g/m ²

ETARC Z g/m ² Gelatin 2.420 g/m ²

Support Cellulose acetate (with Gel U-coat and removable carbon antihalation backing)

The respective laydowns of the image coupler IC-I, DARC and ETARC (viz. X ₅ Y and Z g/m ² ) are shown for each individual coating in TABLES 2 and 3.

Solid particle dispersions of the DARCs were prepared by milling with zirconium beads (1.0-1.25 mm) in water with a blend of commercially available surfactants according to the following formulation: -

DARC 0.40Og

10% Dapral GE202 (Akzo Nobel Chemicals) 0.80Og

47% Dowfax 2Al (Dow Chemicals) 0.043g

10% Luviskol K30 (BASF) 0.40Og

Water 18.357g

After milling for 7 days, the milling media were removed using a suitably fine sieve and the resultant dispersion diluted 1:1 with water to give 40.Og of a 1% DARC ball-milled dispersion of average particle size < 250nm (Z-Average mean, Malvern ZetaSizer). Aqueous dispersions of the image coupler and ETARC were prepared by methods known in the art. The cyan dye-forming coupler dispersion contained 8% by wt. of gelatin, 6% by wt. of coupler IC-I and a 1 : 1 :2 weight ratio of coupler to di-n-butyl sebacate coupler solvent to ethyl acetate auxiliary solvent. The auxiliary solvent was included to aid in dispersion preparation and was removed by evaporation. The cyan ETARC dispersion contained 6% by wt of gelatin, 2% by wt of ETARC-I and a 1 :2:3 weight ratio of coupler to di-ethyl lauramide coupler solvent to 2-(2-butoxyethoxy)ethyl acetate auxiliary solvent. The auxiliary solvent was included to aid in dispersion preparation and was removed by washing the dispersion for 6 h at 4C and pH 6.0. The single layer photographic coatings prepared in this way were slit and chopped into 30cm x 35mm test strips. After hardening the strips were exposed (0.01 sec) through a 0-4.0 neutral density step wedge (0.2 ND step increments) and Daylight V and Wratten 9 and 1.0 ND filters and then processed through a standard KODAK FLEXICOLOR™ (C-41) process as described in the British Journal of Photography Annual (1988) 196 -198 using the following steps and process times:

Developer 2.5 min.

Bleach 4.0 min.

Wash 2.0 min. Fix 4.0 min.

Wash 2.0 min.

The processed images were read with red light to determine the ΔDj _nm (the minimum density minus the minimum density for the corresponding image coupler only coating (i.e. SL-I and SL-7 hi TABLES 2 and 3 respectively)) and ΔKIT speed (the exposure point minus the same point for the corresponding image coupler only coating (i.e. SL-I and SL-7 in TABLES 2 and 3 respectively)

as computed as follows: the exposure required to produce a specified film density (Ds) in the toe of a sensitometric DlogE curve of 0.2 x gradient (γ) at that density above D _m i _n (i.e. Ds = 0.2γ + D _m j _n )). Results for two separate experiments are shown in TABLES 2 and 3.

The image coupler IC-I, ETARC-I and comparative DARC-I are shown below: -

(IC-I)

(DARC-I) (Comparative)

(ETARC-I)

TABLE 2 - CYAN DARCS

TABLE 3 - CYAN DARCS

The results in TABLE 2 indicate that the cyan DARC C-7 for use in the invention, when coated at a laydown of 0.008 mmol/m ² with the image coupler IC-I (SL-4), gives a speed enhancement which is much greater than that observed with the comparative compound DARC-I (SL-3). When both the compound C-7 and the ETARC-I are coated with the image coupler IC-I (as in SL-6) the speed enhancement obtained is equal to the sum of the two individual speed increases seen when the compounds are coated alone with image coupler IC-I (as in SL-2 and SL-4), i.e. the effects are additive. Furthermore it will be seen that the ΔD _m i _n of the sample containing

ETARC-I and the compound for use in the invention C-7 (sample SL-6) is reduced in comparison with the sample containing the ETARC-I and comparative DARC-I (sample SL-5).

The results in TABLE 3 indicate that the cyan DARC C-7 for use in the invention, when coated at the lower laydown of 0.0016 mmol/m ² with the image coupler IC-I (SL-IO), gives a speed enhancement considerably greater than that observed with the comparative compound DARC-I (SL-9) and similar to that obtained when coated at the higher level of 0.008 mmol/m ² . When both the compound C-7 and ETARC-I are coated with the image coupler IC-I (as in SL- 12) the speed enhancement obtained is greater than the sum of the two individual speed increases seen when the compounds are coated alone with image coupler IC-I (as in SL-8 and SL-IO), i.e. a synergistic effect is obtained.

Moreover it will be seen that the ΔD _m i _n of the sample containing ETARC-I and the compound for use in the invention C-7 (sample SL- 12) is reduced in comparison with the sample containing the ETARC-I and comparative

DARC-I (sample SL-I l).

It would therefore appear that the compound C-7 for use in the invention can be used at low laydowns with the added benefits of reduced chemical cost per unit coated area and lower minimum density (D _m m)- Furthermore it is a particular advantage that C-7 can be used to provide the benefit of the invention under standard C-41™ processing conditions.

The patents and publications referred to herein are incorporated by reference in their entirety.

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