GB2137192A - Yellow Colour Couplers - Google Patents

Abstract

There is described a colour coupler of the general formula I:- <IMAGE> wherein A is a hydrogen atom or a C1-20 alkoxy group, B, C, D and E are each hydrogen or halogen atoms or optionally substituted alkyl, alkoxy, acyloxy, amido, ureido or disulphonyl groups, and R is an optionally substituted alkyl, alkaryl, aryl or C1-20 cycloalkyl, at least one of the substituents A, B, C, D, E or R comprising an alkyl group having at least 12 carbon atoms or an aryl group having at least two alkyl substituent groups as a ballasting group. The dyes formed from the colour coupling of the colour couplers of formula I have good absorption in the U.V. region of the spectrum.

Description

SPECIFICATION Yellow Colour Couplers This invention relates to novel yellow colour couplers.

Recently there has been introduced photographic film material in which a negative monochrome near-neutral dye image is produced after exposure and development. This monochrome image is used to print onto monochrome paper to yield a black and while print which exhibits a marked reduction in graininess compared with prints obtained from a negative silver image. The image-providing colour coupler used in such monochrome chromogenic film material is a yellow colour coupler or a mixture of yellow colour couplers. Most often cyan and magenta colour couplers are also present in the material but these couplers do not provide images which are used in the printing but help to provide the neutral image which helps to form the image during the printing process.

Both pivaloylacetanilide and benzoyl-acetanilide yellow colour couplers may be used in such monochrome chromogenic material, such couplers being used in normal subtractive colour photography as the yellow image forming component. However the absorbance of such yellow colour couplers does not replicate completely the absorbance of a silver image formed by development in a black and white film but a silver image absorbs more strongly in the near U-V region of the spectrum, that is to say in the region 350~400 nm, than do the conventional pivaloylacetanilide and benzoylacetanilide yellow colour couplers.Thus when such yellow colour couplers are used to provide the main light-absorbing image in a monochrome negative large speed losses are often experienced together with some unbalance in the print rendition when the printing light used is a tungsten filament lamp which comprises a large proportion of U-V light.

We have discovered a novel class of yellow colour coupler which in colour coupling with a primary aromatic amine colour developer yield a yellow dye which exhibits an absorbance in the 350400 nm region of the spectrum which is comparable with its absorbance in the 400-490 nm region of the spectrum.

According to the present invention there is provided a colour coupler of the general formula I:

wherein A is a hydrogen atom or an alkoxy group having from 1 to 20 carbon atoms, B, C, D and E are each hydrogen or halogen atoms or optionally substituted alkyl, alkoxy, acyloxy, amido, ureido or disulphonyl groups: and R is an optionally substituted alkyl, alkaryl, aryl or cycloalkyl group having from 1 to 20 carbon atoms, at least one of the substituents A, B, C, D, E or R comprising an alkyl group having at least 12 carbon atoms or an aryl group having at least two alkyl substituent group as a ballasting group.

The compounds of formula I comprise at least one ballasting group. That is to say the presence of the ballasting group renders the coupler substantive to the layer in which it is coated during the manufacture of photographic material which comprises the coupler. Furthermore long chain alkyl groups which comprise at least 12 carbon atoms or which comprise an alkyl substituted aryl group act as oil solubilising groups.

Most preferably the ballasting group is present as or in substituent A or R.

Compounds of formula I may be prepared by converting a benzoic acid of the general formula Il:

where A, B, C, D and E have the meanings assigned to them above to an acid chloride and reacting the acid chloride with an ester of the formula III;- CH3-C00-R III where R is as defined above in the presence of a base to yield a compound of the general formula IV:

where A, B, C, D and E have the meanings assigned to them above and then converting the compound of formula IV by reaction with chlorine or SO2CI2to a compound of formula I.

According to another aspect of the present invention there is provided colour photographic material which comprises on a photographic base at least one silver halide emulsion layer which comprises a colour coupler of formula I or which comprises in a layer in operative contact with the silver halide layer a compound of formula I. By layer in operative contact with a layer which contains a silver halide is meant a layer which is close enough to the layer which contains the silver halide for oxidised colour developer to diffuse imagewise to this layer to couple with the compound of formula I to form a dye image in conformity with the silver image in the silver halide layer.

According to a third aspect of the present invention there is provided a process for the production of a coloured photographic image which comprises imagewise exposing the colour photographic material as just defined and developing the material in a colour developing solution which comprises a primary aromatic amine colour developing agent.

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, 4amino-3-methyl-N,N-diethylaniline hydrochloride and p-aminophenol compounds for example a paminophenol itself and 2,6-dichloro-4-aminophenol.

The oxidised colour developing agent couples at the

position in formula I forming a yellow which absorbs strongly in the U-V region of 350 to 400 nm as well as in the blue region of the spectrum 400 Zl90 nm.

The main utility of the colour couplers of the present invention is in a monochrome chromogenic process as described for example in European patent application 25775.

Examples of particularly useful dyes of formula I are:~

A suitable amount of the compound of formula I to be present in negative film material in which no silver image is left is 50-100 mg/dm2.

Any of the silver halides used in photographic materials can be used in the photographic material of the present invention, for example silver chlorobromide, silver chloride, silver iodobromide, silver bromide and silver iodobromochloride.

The silver halide crystals may be chemically sensitised by any of the well-known means, for example by use of sulphur, selenium and noble metals. Examples of suitable sensitising compounds are sodium thiosulphate and mercury, gold, palladium and platinum salts.

The emulsions used in the photographic material used in the present invention may be optically sensitised by the addition of optical sensitisers, for example carbocyanine and merocyanine dyes, to the emulsions.

These emulsions may contain any of the additives commonly used in photographic emulsion, for example wetting agents, stabilision agents, polyethylene oxides, metal sequestering agents and growth or crystal habit modifying agents commonly used for silver halide such as adenine.

Preferably the dispersing medium is gelatin or a mixture of gelatin and a water-soluble polymer, for example a latex vinyl acrylate-containing polymer. Most preferably if such a latex is present in the final emulsion it is added after all the crystal growth has occured. However other water-soluble colloids, for example casein, polyvinylpyrrolidine or polyvinyl alcohol, may be used alone or together with gelatin.

The support base used in the photographic material used in the present invention may be any one of the bases commonly used for photographic materials, for example baryta coated paper base, polyethylene laminated paper base, cellulose triacetate, cellulose acetate butyrate and subbed and biaxially oriented polyethylene terephthalate but mostly it will be a transparent film base and not a paper base.

The accompanying Examples will serve to illustrate the invention.

Example 1 Preparation of Colour Coupler 1.

Methyl (2-tetradecyloxybenzyl)acetate (precursor to coupler 7 in B.Patent 1 351 ,395). (1 5.6 g; 4x 102 ml) was dissolved in sodium-dried toluene (90 ml), Dean-Starked to remove moisture, cooled and treated with sulphuryl over 1 hr, so that the temperature remained below 250C. The mixture was left over-night, treated with anhydrous potassium carbonate (5.67 g) and stirred for 10 min. The mixture was filtered and the filtrate evaporated to yield the crude product (17.5 g) as an oil. This was crystallised by dissolving in 40/60 petrol (75 ml) and cooling swiftly to OOC. When crystallisation was complete, the paste was diluted with further petrol (75 ml) and the product obtained by filtration. It was dried in vacuum over phosphorus pentoxide. Yield was 11.9 g (70%) m. 36#9c.

Example 2 Use Example Formulation of compound 1 as prepared in Example 1 as an oil dispersion.

A. 0.05 of Compound 1 is dissolved in 0.2 g isopropylated phenyl phosphate and 0.2 g ethyl acetate mixture, by heating under reflux; cool to 500 C.

B. 0.2 ml 10% (v/v in water) sulphonated PEO wetting agent and 0.6 ml distilled water are added to 1.60 g 10% (w/s in water), pH 6.5) deionised gelatin at about 500 C.

A and B are then mixed with hand stirring and are dispersed on an ultrasonic mixer for about 30 seconds.

Formulation for Coating 0.45 g of the above coupler dispersion are added to 10% deionised gel solution and 0.28 of a 9.2% iodide silver iodobromide emulsion. The emulsion contains 162 g silver and 100 g gel in 1467 g total weight. Triazine hardener is added to the formulation at 20 mole/105 g gel. After adequate mixing, the coating formulation is spread by hand on to 2.4 dm2 polyester (5thou'thick) base, maintained at 400C during coating. Coating weight of 6 mg/dm2 coupler and silver coating weights of approximately 12 mg/dm2 with a gel coating weight of about 80 mg/dm2 was obtained. Coatings are dried and then incubated for about 12 hours at 450C, 65% R.H. The coatings were overall exposed to white light for 10 seconds and processed as follows at 380C.

Development 5 mins. 0,37 g K2CO3 1.5 ml K2SO3, 65% solution 1.05g KBr 6.0 ml DTPA (37% solution) 2 g Hydroxylamine sulphate 1 mlH2SO4(5N) 2.40gCD4 1.33 g Na2S2O5 0.94 ml Acetic acid (80% w/v) H20 to 1 litre pH 10.20 Bleach 63 mins Ammonium bromide 150 g Ferric ammonium EDTA 112 9 EDTA 2.5 g Sodium nitrate 35 g Acetic acid, glacial 10 ml Water to 1 litre pH 6.0+0.2 Fix 62 mins Ammonium thiosulphate 130 g Disodium EDTA 1.25 g Sodium metabisulphite 12 9 Sodium hydroxide 2 9 pH 6.5+0.2 Wash 3 mins, 380C CD4 is 4 N-ethyl-N-(2'hydroxyethyl)amino-2-methylaniline hydroxsulphate EDTA is Ethylenediamine tetra-acetic acid DTPA is Diethylenetriamine penta-acetic acid As comparison the following two known yellow couplers A and B were also formulated in coatings as above.

The following results were obtained.

Colour coupler A max (nm) A min (nm) ratio DmaxlDmin 1. 439 363 1.8:1 A 452 360 4.7:1 B 449 360 3:1 Spectra relating to coupler 1 + comparison A+B are attached hereto.

The greatly enhanced UV absorption in the dye coupler of the invention can be seen.

Claims (6)

1. A colour coupler of the general formula I:

wherein A is a hydrogen atom of an alkoxy group having from 1 to 20 carbon atoms, B, C, D and E are each hydrogen or halogen atoms or optionally substituted alkyl, alkoxy, acyloxy, amido, ureido or disulphonyl groups, and R is an optionally substituted alkyl, alkaryl, aryl or cycloalkyl group having from 1 to 20 carbon atoms, at least one of the substituents A, B, C, D, E or R comprising an alkyl group having at least 12 carbon atoms or an aryl group having at least two alkyl substituent groups as a ballasting group.

2. A colour coupler according to claim 1 wherein the ballasting group is present either in substituent A or B.

3. Any one of colour couplers 1 to 5 as hereinbefore set forth.

4. A process for the preparation of a colour coupler as claimed in claim 1 which comprises converting a benzoic acid of the general formula II:

where A, B, C, D and E have the meaning assigned to them in claim 1 to an acid chloride and reacting the acid chloride with an ester of the formula III:- CH3-CO0-R Ill where R is as defined in claim 1 in the presence of a base to yield a compound of the general formula IV:-

where A, B, C, D and E have the meaning assigned to them in claim 1 and then converting the compound of formula IVby reaction with chlorine or SO2CI2 to a compound of formula I.

5. Colour photographic material which comprises on a photographic base at least one silver halide emulsion layer which comprises a colour coupler of formula I or which comprises in a layer in operative contact with the silver halide layer a compound of formula I.

6. A process for production of a coloured photographic image which comprises imagewise exposing the colour photographic material as claimed in claim 5 and developing the material in a colour developing solution which comprises a primary aromatic amine colour developing agent.