PYRAZOLONE COUPLERS AND COLOUR PHOTOGRAPHIC SILVER HALIDE RECORDING MATERIAL CONTAINING THEM

Abstract: Pyrazolone colour couplers of the formula wherein X is -O-, -S- or -Se-, R₁ is hydrogen, halogen, alkyl, alkoxy, alkylthio, phenyl, phenoxy, phenylthio or acyloxy; R₂ is -CO-alkyl, -CONH-alkyl, -SO₂-alkyl, phenyl, -CO-C₆H₅, -CONH-C₆H₅ or -SO₂-C₆H₅, R₃ is alkyl, -NH-alkyl, -NHCONH-alkyl, phenyl, -NH-C₆H₅, -NHCONH-C₆H₅ or -NHCO-C₆H₅, R₄ is hydrogen, alkyl or phenyl, are easy to prepare and have a good coupling activity. The dyes obtained by these couplers exhibit a good light-stability.

Description: Colour couplers This invention relates to pyrazolone colour couplers. Pyrazolone compounds have long been used as four-equivalent colour couplers in colour photographic materials. However, it has been found that these compounds are very susceptible to attack by formaldehyde and other aldehydes. Synthetic plastics materials have almost entirely replaced leather as camera cases and camera accessory bags. Unfortunately a number of these plastics materials are made by using formaldehyde or other aldehydes for example formaldehydemelamine resins and phenol-formaldehyde resins. Such plastics materials tend to produce a small but significant amount of formaldehyde vapour continuously. gen colour photographic material which comprises in a layer of the material a four-equivalent pyrazolone colour coupler is stored in a bag or case made from a plastics material which comprises formaldehyde or another aldehyde it has been found that the formaldehyde or other aldehydes have a deleterious effect on the pyrazolone colour coupler which is shown by a degradation in the dye produced by the coupling reaction when such photographic material has been exposed and colour processed. However, it has been found that 2-equivalent pyrazolone colour couplers are not affected in the same way by formaldehyde or other aldehydic vapours. But it has proved difficult to prepare on a commercial scale 2-equivalent pyrazolone colour couplers which exhibit sufficiently good coupling activity to be used in colour photographic material. We have found a novel class of 2-equivalent pyrazolone colour couplers which may be prepared on a commercial scale and which have a good coupling activity. Moreover, the dyes produced on the colour coupling of the pyrazolones have good light stability. According to the present invention there is provided a pyrazolone colour coupler of the formula EMI2.1 wherein X is -S-, -O- or -Se-, R1 is hydrogen, chlorine, bromine or iodine or optionally substituted alkyl, phenyl, alkoxy, phenoxy, acyloxy, alkylthio or phenylthio, R2 is -CO-alkyl, -CO-C6H5, -CONH-C6H5, -CONH-alkyl, -S02-alkyl or -S02-C6H5, wherein the alkyl and C H -radicals are optionally substituted, R3 is alkyl, phenyl, -NH-alkyl, -NH-C6H5, -NHCONH-alkyl, -NHCONH-C6H5, -NHCO-C H or -NHCO-alkyl, wherein the alkyl and C6H5 -radicals are optionally substituted, R4 is hydrogen or substituted alkyl or phenyl, at least in one of the alkyl or phenyl groups of R3 or R4 being present a ballasting group B. X in the compounds of the formula (1) denotes a hetero-atom such as -S-, -O- or -Se-. Preferably X is -S-. Substituent R1 is hydrogen or halogen such as chlorine, bromine or iodine. R1 further denotes alkyl, preferably having 1 to 6 carbon atoms such as methyl, ethyl, propyl, butyl, pentyl and hexyl as well as isomers thereof. The alkoxy and alkylthio radicals R1 are preferably those which can be derived from the alkyl radicals R1 just mentioned. Phenyl, phenoxy and phenylthio are further meanings of R1. R1 also denotes acyloxy, preferably carboxylic acid acyl of the formula EMI3.1 where A is aryl, preferably phenyl, or alkyl having preferably 1 to 6 carbon atoms. Substituent R1 is optionally further substituted by other phenyl groups or also by alkyl, alkoxy, EMI3.2 group, wherein the alkyl moieties preferably contain 1 to 4 carbon atoms. Further suitable substituents on R1 are halogen atoms such as chlorine and bromine. Substituent R2 represents an acyl or acylamino group preferably having the formulae -CO-alkyl, -SO2-alkyl, -CONH-alkyl, wherein alkyl contains preferably 1 to 6 carbon atoms (suitable alkyl groups are mentioned above in the definitions of R1), or phenyl, -COC6H5, -SO2C6H5 or -CONH-C6H5. The alkyl and phenyl moieties present in R2 are optionally substituted by further alkyl or hydroxyalkyl radicals, EMI3.3 the alkyl moieties in these groups preferably containing 1 to 4 carbon atoms, or halogen such as chlorine or bromine. Substituent R3 denotes alkyl, -NH-alkyl, -NHCONH-alkyl or -NHCO-alkyl, the alkyl radicals having preferably 1 to 6 carbon atoms (suitable alkyl radicals are mentioned above), further phenyl, -NH-C6H5, -NHCONH-C6H5 or -NHCO-C6H5. The alkyl and phenyl moieties present in R3 are optionally further substituted by electronegative groups such as halogen, preferably chlorine or bromine, or cyano, or hydroxyalkyl, EMI4.1 -CONH-alkyl or -NHCO-alkyl, the alkyl radicals comprising preferably 1 to 6 carbon atoms. Substituent R4 is hydrogen or substituted alkyl or, preferably, substituted phenyl. Suitable substituents on phenyl and the alkyl radicals are halogen such as chlorine or bromine, alkyl, hydroxyalkyl or EMI4.2 alkyl, further -SO2NHR5, -NHCOR5 or -NHSO2R5, where R5 is alkyl or phenyl which is optionally further substituted by alkoxy such as methoxy or ethoxy, or halogen. All the alkyl moieties mentioned contain as a rule 1 to 6, preferably 1 to 4 carbon atoms. At least one of the alkyl or phenyl groups of R3 or R4 represent a ballasting group B. Preferably B comprises long chain alkyl groups having more than 10 carbon atoms, preferably up to 30 carbon atoms, such as decyl, dodecyl, hexadecyl, heptadecyl, octadecyl, eicosyl, tetracosyl or triacontyl, or more preferably B represents an aryloxy group substituted by tertiary alkyl radicals having 4 to 8 carbon atoms, for example, di-tertiary pentyl substituted phenoxy. In a preferred class of the couplers of the formula (1), R1 is hydrogen, chlorine, bromine or iodine or alkyl, alkoxy or alkylthio, wherein the alkyl moiety contains 1 to 6 carbon atoms, or phenyl, phenoxy, phenylthio or carboxylic acid acyl, R2 is -CO-alkyl, -CONHalkyl or -SO2-alkyl, wherein the alkyl moiety contains 1 to 6 carbon atoms, or -C6H5, -CO-C6H5, -CONH-C6H5 or -S02-C6H5, and wherein the alkyl and phenyl moieties are unsubstituted or substituted by alkyl or hydroxyalkyl, carbalkoxy, -NHCO-alkyl or halogen, the alkyl radicals containing 1 to 4 carbon atoms, R3 is alkyl, -NH-alkyl or -NHCONH-alkyl, the alkyl moieties containing 1 to 6 carbon atoms, or phenyl, -NH-C6H5, -NHCONH-C6H5 or -NHCOC6H5, wherein phenyl and the alkyl moieties are unsubstituted or substituted by halogen, cyano, hydroxyalkyl, carbalkoxy, -CONH-alkyl or -NHCO-alkyl, the alkyl rad icals containing 1 to 6 carbon atoms, R4 is hydrogen, alkyl having 1 to 6 carbon atoms or phenyl, where the alkyl moieties and phenyl are substituted by halogen, alkyl, hydroxyalkyl or carbalkoxy, the alkyl moiety containing 1 to 4 carbon atoms, or -SO2NHR5, -NHCOR5 or -NHSO2R5, wherein R5 is alkyl having 1 to 6 carbon atoms or phenyl, which radicals are unsubstituted or substituted by methoxy, ethoxy or halogen, at least one of the alkyl or phenyl groups of R3 or R4 being a ballasting group B, and X is as defined above. More preferably in the couplers of the formula (1), X is -O- or -S-, R1 is alkyl or alkoxy, wherein the alkyl moiety contains 1 to 6 carbon atoms, or phenyl or phenoxy, R2 is -CO-alkyl or -S02-phenyl, wherein phenyl and the alkyl moieties are unsubstituted or substituted by alkyl or hydroxyalkyl each having 1 to 4 carbon atoms, or halogen, R3 is alkyl, phenyl, -NH-C6H5, -NHCONH-C6H5 or -NHCO-C6H5, wherein phenyl and the alkyl moieties are unsubstituted or substituted by halogen, cyano, hydroxyalkyl, carbalkoxy, -CONH-alkyl or -NHCO-alkyl, the alkyl radicals containing 1 to 6 carbon atoms, R4 is phenyl substituted by halogen, -S02NHR5, -NHCOR5 or -NHSO2R5, where in R5 is alkyl having 1 to 6 carbon atoms, at least one of the alkyl or phenyl groups of R3 or R4 being a ballasting group B. It is to be understood that the compounds of the formula (1) may also be present as tautomers having the formula EMI5.1 wherein R1, R2, R3, R4 and X have the meanings assigned to them above. These compounds may be synthesised by reaction of a chloro or bromo pyrazolone of the formula EMI6.1 wherein R3 and R4 have the meanings assigned to them above, and Y is chlorine or bromine, with an oxa, thia- or selenadiazole compound of the formula EMI6.2 wherein R1 and R2 have the meanings assigned to them above, in the presence of a basic catalyst such as sodium or potassium hydroxide, carbonate or alkoxide, or an amine base, such as an excess of the compound of formula (4), either in the melt or in solution or su8- pension in a solvent, for example acetonitrile. Alternatively, and this is preferable, compounds of the formula (1) may be prepared from the reaction of an acyclic precursor already containing the oxa, thia- or selenadiazole ring of the formula EMI6.3 wherein H6 and R7 are each hydrogen, alkyl or phenyl, and R1, R2, R3 and X are groups as defined above, or groups which may be transformed into such s group, with a substituted hydrazine of the formula (6) H2N-NHR4 wherein R4 has the meaning assigned to it above, or is a group which may be transformed into such a group either in a melt, or in a suitable solvent, either in the presence of an acidic catalyst such as acetic acid, or of a basic catalyst such as pyridine or sodium ethoxide, or without catalyst at all, at room temperature or a higher temperature. Preferably the above reaction is carried out in the presence of an acid catalyst and most preferably this is in acetic acid. Preferably the above reaction is carried out in a solvent and most preferably this solvent is an (alkyl or substituted alkyl) alcohol. Suitable alcohols are ethanol, propanol and ethoxy-ethanol. Preferably the above reaction is carried out in an alcoholic solvent and the reaction temperature is at the boiling point of the solvent. An example of a group which can be transformed to a group as defined in the compounds of the formula (1) is the transformation of -NO2 to NH2 followed by conversion of -NH2 to -NHCOB, where B is as defined above, by reaction with an acid chloride. Another example of a transformable group is the protection of an hydroxy group in form of an ester group. The ester group can then be removed after the main reaction has taken place. Thus, for preparing a pyrazolone where R3 is -NH-C6H5, a suitable compound of the formula (5) is the compound of the formula EMI8.1 wherein R1, R2, R6 and X have the meanings assigned to them above, and R8 is phenyl, which may be substituted for example by chlorine, bromine, cyano, alkoxy, alkyl, amido or an ester group, or by a ballast group as defined above It is to be understood that compounds of the formula (7) may exist in the tautomeric form of the formula EMI8.2 wherein R1, R2, R6, R8 and X have the meanings assigned to them above. Compounds of the formula (7) or (8) may be prepared by reaction of an oxa-, thia- or selenadiazole of the formula (4) with a bromo or chloro compound of the formula EMI8.3 wherein R6 and R8 have the meaning assigned to them above, in the presence of a basic catalyst such as sodium or potassium hydroxide, carbonate or alkoxide, or an amine base such as an excess of the compound of the formula (4). Compounds of the formula (9) may be prepared as described in GB 1,325,828; GB 1,129,133; GB 1,129,334 or GB 1,455,967. Compounds of the formula (4) may be prepared as described in GB 1,566,618. Similarly, when the group R3 is alkyl, a suitable precursor of the formula (5) is the compound of the formula EMI9.1 wherein R1, R2, R6 and X have the meanings assigned to them above, and Rg is alkyl or cycloalkyl, which radicals may be substituted. Again, it is to be understood that the compounds of the formula (10) may exist in the tautomeric form of the formula EMI9.2 wherein R1, R2, R6, Rg and X have the meanings assigned to them above. Compounds of the formula (10) or (11) may be prepared by reaction of a chloro or bromo ester of the formula EMI9.3 wherein R6 and R9 have the meanings assigned to them above, and Y is chlorine or bromine with an oxa- thia- or selenadiazole of the formula (4), in the presence of a base such as sodium or potassium hydroxide, carbonate or alkoxide, in a suitable solvent such as acetonitrile. The chloro- or bromo- compounds of the formula (12) may be prepared from the corresponding ketoesters by chlorination or bromination by methods well known in the literature. Particularly useful pyrazolone compounds of the formula (1) are the compounds of the formulae EMI10.1 EMI11.1 EMI12.1 EMI13.1 According to another aspect of the present invention, there is provided colour photographic silver halide material which comprises in at least one silver halide layer a pyrazolone colour coupler of the formula (1). The compounds of the formula (1) wherein R is a -NH- substituent 3 group wherein the substituent group comprises a ballasting group B and R4 is a substituent phenyl group yield on coupling pure magenta dyes. The compounds of the formula (1) where the ballasting group B is present in R4 yield on coupling dyes which are reddish. These com pounds find use as colour couplers in chromogenic monochrome film material wherein the dyes form a monochrome image from which a black and white print is obtained. Photographic material which comprises in a layer thereof a compound of the formula (1) is processed after exposure by a colour development process using a primary aromatic amine colour developing agent of known type. As usual in colour development processes the primary aromatic amine develops the latent silver image to form a silver image and becomes oxidised, and the oxidised colour developer couples which the pyrazolone colour coupler of the formula (1) to form a magenta or reddish dye image. After the colour development reaction to form the dye image the unexposed silver halide in the photographic material is removed using a silver halide solvent and the silver image is removed using a silver bleach bath. The silver halide and the silver may be removed by use of a simple bleach-fix (blix) bath. Suitable primary aromatic amine colour developing agents are p-phenylenediamine compounds, for example 4-amino-N,N-dimethylaniline hydrochloride, 4-amino-N,N-diethylaniline hydrochloride, 4-amino-3methyl- N,N-diethylaniline hydrochloride and p-aminophenol compounds for example a p-aminophenol itself and 2,6-dichloro-4-aminophenol. The following Example will serve to illustrate the invention. Example 1: Synthesis of the compound of the formula (15): 2-p-Toluenesulfonylimino-5-isopropyl-l,3,4-thiadiazole (14.55 g) and solid potassium hydroxide (3.23 g) in toluene (150 ml) are heated under a Dean-Stark trap for 7 hours and then cooled. Acetonitrile (100 ml) and ethyl-2-chloro acetoacetate (10 ml) are added, and the reaction heated to reflux for 5 hours during which time a solid appears. Water (250 ml) is added, the organic layer separated and washed with water, and the aqueous layers extracted with ether. The combined organic layers are dried and evaporated, and the resulting oil is added to petrol (bp 80-100 C) (200 ml) with ethyl acetate (10 ml) and heated to boiling with charcoal. After filtration, 12.8 g of the product crystallise out on cooling (melting point 102-105 C). NMR analysis shows it to have the enol structure of the formula EMI15.1 The above compound (2.13 g) and 4-nitro phenyl hydrazine (0.77 g) in acetic acid (10 ml) and ethanol (5 ml) is heated to reflux for 3 hours and cooled. 2.68 g of the solid are filtered off (melting point 211-2l60C). NMR analysis shows it to have the following structure EMI15.2 A sample of this compound (2.63 g) is hydrogenated at room temperature in ethanol (100 ml) over a hydrogenation catalyst (10% palladium on charcoal) for 3 days. The catalyst is filtered off, and the solvent evaporated to give an oil, which is dissolved in tetrahydrofuran and pyridine, and reacted with the acid chloride from di-t-amylphenoxyacetic acid (1.49 g) for 3 hours. The product is added to hydrochloric acid, and extracted with ether. This ether phase is dried and evaporated, and 1.04 g of the compound of the formula (15) crystallise on triturating with methanol (melting point 168-174 C). Example 2: Synthesis of the compound of the formula (16): A sample of the nitro compound of the formula (24) is hydrogenated as described in Example 1. The amino compound produced (4.72 g) is dissolved in tetrahydrofuran (20 ml) and pyridine (10 ml), and 2,4-di tert.amylphenoxybutyryl chloride (3.12 g) is added. The solution obtained stands overnight at room temperature. Water (100 ml) is added, and the product extracted with ether, dried, and evaporated. 2.87 g of the compound of the formula (16) crystallise on triturating with petrol (80-1000C) (melting point 137-141 C). Example 3: A coating is prepared having the following coating weights: Compound of the formula (15) 6 mg/dm2 dissolved in tricresylphosphate 12 mg/dm2 with a conventional silver chlorobromide photographic emulsion giving a silver coating weigth af 12 mg/dm2 in gelatin 80 mg/dm2 This is compared with a similar coating containing instead of compound (15) the conventional 4-equivalent magenta coupler of the formula EMI16.1 The coatings are fogged with light and then developed at 380C in a developing solution containing: 4-amino-3-methyl-N-ethyl-N-2-hydroxyethyl aniline sulfate (3.2 g), hydroxylamine sulfate (3 g), sodium carbonate (30 g), potassium bromide (1.8 g), potassium hydrogen sulfate (7 g), sodium bicarbonate (8 g), sodium sulfite (2 g) and sodium tripolyphosphate (2 g) and water to make up to 1 litre. The coatings are bleached and fixed, and the densities measured: Compound of the formula (15) density 1.57; max. 532 nm Compound of the formula (25) (control) density 1.45; max. 555 nm. These coatings are then exposed in a Xenotest machine for 50 hours. The reduction of density is as follows: Compound of the formula (15) 9%, Control compound 16%. Different samples of the coatings are dipped in a 1% aqueous formaldehyde solution for 2 minutes and then processed as above. The reduction in density of the coating of compound (15) is about 3%, whereas with the control compound of the formula (25) practically no density remains. Example 4: 3 g of the nitro compound of the formula (24) are hydrogenated as described in Example 1. The product is added to the acid chloride from y-2,4-di-tert.amylphenoxy butyric acid (1.8 g) in tetrahydrofuran and the solution obtained stands at room temperature for 20 hours with pyridine. The resulting solution is extracted with ethylacetate and recrystallised from mixtures of petrol and ethylacetate, yielding 0.8 g of the product of the formula EMI18.1 Example 5: A sample of the nitro compound of the formula (25) is prepared as described in Example 1. This compound has a melting point of 191-194 C. EMI18.2 This compound (1.07 g) is hydrogenated in ethanol (50 ml) using palladium on charcoal as the catalyst. The solvent is then removed, and the residue dissolved in tetrahydrofuran (50 ml) and pyridine (0.5 ml) and di-tert.amylphenoxy acetic acid chloride (0.73 g) is added. The mixture stands at room temperature for 6 hours, and then diluted hydrochloric acid (50 ml) is added. The product is crystallised from a methanol/ethanol (2:1) mixture giving 1.01 g of the compound of the formula EMI19.1 (melting point 115-1190C).

Claims: CLAIMS: 1. A pyrazolone colour coupler of the formula EMI20.1 wherein X is -S-, -o- or -Se-, R1 is hydrogen, chlorine, bromine or iodine or optionally substituted alkyl, phenyl, alkoxy, phenoxy, acyloxy, alkylthio or phenylthio, H2 is -CO-alkyl, -CO-C6H5, -CONII-C6H5, -CONH-alkyl, -S02-alkyl or -S02-C6H5, wherein the alkyl and C6H5-radicals are optionally substituted, R3 is alkyl, phenyl, -NH-alkyl, -NH-C6H5, -NHCONH-alkyl, -NHCONH-C 6H5, -NHCO-C6H5 or -NHCO-alkyl, wherein tne alkyl and C H -radicals are optionally sub 65 stituted, R4 is hydrogen or substituted alkyl or phenyl, at least in one of the alkyl or phenyl groups of R3 or R4 being present a ballasting group B. 2. A pyrazolone colour coupler according to claim 1, wherein R1 is hydro- gen, chlorine, bromine or iodine or alkyl, alkoxy or alkylthio, wherein the alkyl moiety contains 1 to 6 carbon atoms, or phenyl, phenoxy. phenylthio or carboxylic acid acyl, R2 is -CO-alkyl, -CONHalkyl or -S02-alkyl, wherein the alkyl moiety contains 1 to 6 carbon atoms, or -C6H5, -CO-C6H5, -CONH-C6H5 or -S02-C6H5, and wherein the alkyl and phenyl moieties are unsubstituted or substituted by alkyl or hydroxyalkyl, carbalkoxy, -NHCO-alkyl or halogen, the alkyl radicals containing 1 to 4 carbon atoms, R3 is alkyl, -NH-alkyl or -NHCONH-alkyl, the alkyl moieties containing 1 to 6 carbon atoms, or phenyl, -NH-C6H5, -NHCONH-C6H5 or -NHCO-C6H5, wherein phenyl and the alkyl moieties are unsubstituted or substituted by halogen, cyano, hydroxyalkyl, cnrbnlkoxy, -CONH-.ilkyl or -NHCO-alky1, tlie alkyl rld- icals containing 1 to 6 carbon atoms, R4 is hydrogen, alkyl having i to 6 carbon atoms or phenyl, where the alkyl moieties and phenyl are substituted by halogen, alkyl, hydroxyalkyl or carbalkoxy, the alkyl moiety containing 1 to 4 carbon atoms, or -S02NHR5, -NHCOR5 or -NHS02R5, wherein R5 is alkyl having 1 to 6 carbon atoms or phenyl, which radicals are unsubstituted or substituted by methoxy, ethoxy or halogen, at least one of the alkyl or phenyl groups of R3 or R4 being a ballasting group B, and X is as defined in claim 1. 3. A pyrazolone colour coupler according to claim 2, wherein X is -O- or -S-, H1 is alkyl or alkoxy, wherein the alkyl moiety contains 1 to 6 carbon atoms, or phenyl or phenoxy, R2 is -CO-alkyl or -S02-phenyl, wherein phenyl and the alkyl moieties are unsubstituted or substituted by alkyl or hydroxyalkyl each having 1 to 4 carbon atoms, or halogen, R3 is alkyl, phenyl, -NH-C6H5, -NISCONE-C6E.5 or -NHCO-C6H5, wherein phenyl and the alkyl moieties are unsubstituted or substituted by halogen, cyano, hydroxyalkyl, carbalkoxy, -CONH-alkyl or -NHCO-alkyl, the alkyl radicals containing 1 to 6 carbon atoms, R4 is phenyl substituted by halogen, -SO2NHR5, -NHCOR5 or -NHS02R5, wherein H5 is alkyl having 1 to 6 carbon atoms, at least one of the alkyl or phenyl groups of R3 or R4 being a ballasting group B. 4. A pyrazolone colour coupler according to claim 3, wherein B is alkyl having more than 10 carbon atoms or aryloxy substituted by tertiary alkyl groups having 4 to 8 carbon atoms. 5. A pyrazolone colour coupler according to claim 4, wherein B is alkyl having 10 to 30 carbon atoms or phenoxy substituted by tertiary pentyl groups. 6. A pyrazolone colour coupler according to claim 3 wherein X is -S-. 7. A process for the preparation of a pyrazolone colour coupler according to claim 1 which comprises reacting a pyrazolone of the formula EMI22.1 wherein R3 and R4 are as defined in claim 1 and Y is chlorine or bromine, with an oxa- thia- or selenadiazole of the formula EMI22.2 wherein R1 and R2 are as defined in claim 1, in the presence of a base either in a melt or in solution or suspension in a solvent. 8. A process for the preparation of a pyrazolone colour coupler according to claim 1 which comprises reacting a compound of the formula EMI22.3 wherein R6 and R7 are each hydrogen, alkyl or phenyl, and R1, R2, R3 and X are as defined in claim 1 or groups which may be transformed into such groups, with a hydrazine of the formula H2N-NHR4 wherein R4 has the meaning assigned to it in claim 1, or is a group which may be transformed into such a group either in a melt or in a solvent, optionally in the presence of an acidic catalyst or a basic catalyst, at ambient or higher temperature. 9. A process according to claim 8, wherein the reaction is carried out in the presence of an acidic catalyst. 10. A process according to claim 9, wherein the acidic catalyst is acetic acid. 11. A process according to claim 8, wherein the process is carried out in a solvent. 12. A process according to claim 11, wherein the solvent is an unsubstituted or substituted alcohol. 13. A process according to claim 12, wherein the process is carried out at the boiling point temperature of the alcohol used. 14. Colour photographic silver halide material which comprises in at least one silver halide layer a pyrazolone colour coupler according to claim 1.

Inventors: LONG, WILLIAM EDWARD, WEBB, TERENCE CHARLES
Applicants: CIBA-GEIGY AG
Application year: 1983
Main classification: G03C7
IPC codes: G03C7, C07D421, C07D413, C07D417