Method of processing a colour photographic silver halide material

Abstract: A method is provided for processing an imagewise exposed photographic silver halide colour material comprising two or more silver halide layers sensitised to different regions of the visible spectrum having associated therewith appropriate dye image forming couplers. The method comprises a colour development step followed by treatment in a combined amplifier/bleach/fix step comprising: (a) a redox oxidant which is capable of bleaching a silver image, and (b) a fixing agent which does not poison the catalytic properties of the silver image and which does not react with the redox oxidant.

Description: Field of the Invention This invention relates to a method of processing a colour photographic silver halide material and, in particular, a process in which dye image is formed by a redox amplification process. Background of the Invention Redox amplification processes have been described, for example in British Specification Nos. 1,268,126, 1,399,481, 1,403,418 and 1,560,572. In such processes colour materials are developed to produce a silver image (which may contain only small amounts of silver) and then treated with a redox amplifying solution (or a combined developer-amplifier) to form a dye image. Such a redox amplification process is known as an "RX" process for short. The image amplification takes place in the presence of the silver image which acts as a catalyst. Oxidised colour developer reacts with a colour coupler to form the image dye. The amount of dye formed depends on the time of treatment or the availability of colour coupler and is less dependent on the amount of silver in the image as is the case in conventional colour development processes. Examples of suitable redox oxidants include peroxy compounds including hydrogen peroxide and compounds which provide hydrogen peroxide, eg addition compounds of hydrogen peroxide; cobalt (III) complexes including cobalt hexammine complexes; and periodates. Mixtures of such compounds can also be used. When the silver coverage of the photographic material is very low, it is possible to avoid bleaching and/or fixing steps. However when the silver level is not quite so low, the developed silver image is just noticeable and is better removed together with any undeveloped silver halide. As with conventional processes this requires a bleach and fix or a combined bleach-fix processing step. WO-A-92/01972 discloses a method of processing an imagewise exposed photographic silver halide material which includes a redox amplification dye image-forming step and a bleach step using an aqueous solution of hydrogen peroxide or a compound capable of releasing hydrogen peroxide. Problem to be Solved by the Invention When it is desired to bleach and fix the photographic material after RX dye image formation it is necessary to have one or two extra processing steps. It is the object of the present invention to provide an RX process with a reduced number of processing baths. Summary of the Invention According to the present invention there is provided a method of processing an imagewise exposed photographic silver halide colour material comprising two or more silver halide layers sensitised to different regions of the visible spectrum having associated therewith appropriate dye image forming couplers which method comprises a colour development step followed by treatment in a combined amplifier/bleach/fix step comprising: (a) a redox oxidant which is capable of bleaching a silver image, and (b) a fixing agent which does not poison the catalytic properties of the silver image and which does not react with the redox oxidant. Advantageous Effect of the Invention An RX process may be performed including bleach and fix steps with the minimum number of processing baths. Detailed Description of the Invention The colour developer solution may contain any of the following colour developing agents: 4-amino-3-methyl-N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N-ethyl-N-b-(methanesulphonamido)-ethylaniline sulphate hydrate, 4-amino-3-methyl-N-ethyl-N-b-hydroxyethylaniline sulphate, 4-amino-3-b-(methanesulphonamido)ethyl-N,N-diethylaniline hydrochloride, 4-amino-N-ethyl-N-(2-methoxy-ethyl)-m-toluidine di-p-toluene sulphonate, and, especially, 4-N-ethyl-N-(b-methanesulphonamidoethyl)- o -toluidine sesquisulphate (CD3). The colour developer solution may also contain compounds which increase its stability, for example hydroxylamine, diethylhydroxylamine and/or a long chain compound which can adsorb to silver, eg dodecylamine. Such long chain compounds can also be present in the amplification/bleach/fix solution. The redox amplification/bleach/fix solution contains a redox oxidant, eg hydrogen peroxide or a compound that yields hydrogen peroxide. It may contain from 0.1 to 150, preferably 10 to 50 ml/l hydrogen peroxide 30% w/w solution. The pH of the amplifier/bleach/fix solution may be in the range 6 to 11. Preferably the pH is in the range 8 to 10. It may be buffered. The redox amplification/bleach/fix solution also contains a fixing agent which does not poison the catalytic properties of the silver image. Such compounds include polycarboxylic or polyphosphonic amino acids. The preferred fixing agents include compounds having at least one: N-[(CH 2 ) n -A] p moeity wherein A is -COOH or -PO 3 H 2 and n is 1-6 and p is 1-3 provided that the compound contains at least 2 A groups. Examples of such compounds include: ethylenediamine tetra acetic acid (EDTA), propylendiamine tetra acetic acid, 2-hydroxy-1,3-propylene diamine tetra acetic acid, diethylene triamine penta acetic acid, nitrilo triacetic acid, ethylene diamine tetra methylene phosphonic acid, diethylene triamine penta methylene phosphonic acid, cylcohexylene diamine tetra acetic acid, [(Ethylene dioxy)diethylene dinitrilo] tetra acetic acid, and ethylene dinitrilo-N,N'-bis(2-hydroxy benzyl)-N,N'-diacetic acid The amplifier/bleach/fix solution may also contain a fix accelerator. Such fix accelerators may be an alkanolamine or a dithioalkane diol. The fix accelerator should not inhibit redox image amplification or react with hydrogen peroxide. They may be chosen from among known fix accelerators by testing them to see if they inhibit the redox image amplification or react with hydrogen peroxide. compounds having at least one: N-[(CH 2 ) n -A] p moeity wherein A is -COOH or -PO 3 H 2 and n is 1-6 and p is 1-3 provided that the compound contains at least 2 A groups. Examples of fix accelerators are: primary, secondary, tertiary alkylamines, for example, ethylamine, propylamine, diethylamine, triethylamine or cyclohexylamine; alkyl diamines, for example, ethylene diamine, propylene diamine or cyclohexyl diamine; alkyl triamines, tetramines, pentamines, hexamines, for example, diethylene triamine, triethylene tetramine; cyclic polyamines, for example, hexamethylene tetramine; aryl amines, for example, benzyl amine; mono, di, tri-alkanolamines, for example, ethanolamine, propanolamine, diethanolamine, or dipropanolamine; thioethers, for example, dithiaoctane diol; thioamines; morpholine. The fixing agents may be present in amounts in the range from 0.5 to 150 g/l preferably from 10 to 100 and especially from 40 to 60 g/l. The effectiveness of fix accelerator varies considerably but typically they may be present in amounts in the range from 0.01 to 150 g/l preferably from 0.1 to 80 g/l. The amplification/bleach/fix step may be followed by a wash step. A particular application of this technology is in the processing of silver chloride colour paper, for example paper comprising at least 85 mole percent silver chloride, especially such paper with low silver levels, for example total silver levels below 130 mg/m 2 , eg from 25 to 120 mg/m 2 , preferably below 70 mg/m 2 and particularly in the range 20 to 70 mg/m 2 . Within these total ranges the blue sensitive emulsion layer unit may comprise 20 to 60 mg/m 2 , preferably 25 to 50 mg/m 2 with the remaining silver divided between the red and green-sensitive layer units, preferably more or less equally between the red and green-sensitive layer units. The photographic materials can be two 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 a 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 at 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, subbing layers, and the like. Suitable materials for use in the emulsions and elements processed by the method of this invention, are described in Research Disclosure Item 36544, September 1994, published by Kenneth Mason Publications, Emsworth, Hants, United Kingdom. The present processing method is preferably carried out by passing the material to be processed through a tank containing the processing solution which is recirculated through the tank at a rate of from 0.1 to 10 tank volumes per minute. Such a tank is often called a low volume thin tank or LVTT for short. The preferred recirculation rate is from 0.5 to 8, especially from 1 to 5 and particular from 2 to 4 tank volumes per minute. The recirculation, with or without replenishment, is carried out continuously or intermittently. In one method of working both could be carried out continuously while processing was in progress but not at all or intermittently when the machine was idle. Replenishment may be carried out by introducing the required amount of replenisher into the recirculation stream either inside or outside the processing tank. It is advantageous to use a tank of relatively small volume. Hence in a preferred embodiment of the present invention the ratio of tank volume to maximum area of material accomodatable therein (ie maximum path length x width of material) is less than 11 dm 3 /m 2 , preferably less than 3 dm 3 /m 2 . The shape and dimensions of the processing tank are preferably such that it holds the minimum amount of processing solution while still obtaining the required results. The tank is preferably one with fixed sides, the material being advanced therethrough by drive rollers. Preferably the photographic material passes through a thickness of solution less than 11 mm, preferably less than 5 mm and especially about 2 mm. The shape of the tank is not critical but it could be in the shape of a shallow tray or, preferably U-shaped. It is preferred that the dimensions of the tank be chosen so that the width of the tank is the same or only just wider than the width of the material to be processed. The total volume of the processing solution within the processing channel and recirculation system is relatively smaller as compared to prior art processors. In particular, the total amount of processing solution in the entire processing system for a particular module is such that the total volume in the processing channel is at least 40 percent of the total volume of processing solution in the system. Preferably, the volume of the processing channel is at least about 50 percent of the total volume of the processing solution in the system. In order to provide efficient flow of the processing solution through the opening or nozzles into the processing channel, it is desirable that the nozzles/opening that deliver the processing solution to the processing channel have a configuration in accordance with the following relationship: 0.6 ≥ F/A ≤ 23 wherein: F is the flow rate of the solution through the nozzle in litres/minute; and A is the cross-sectional area of the nozzle provided in square centimetres. Providing a nozzle in accordance with the foregoing relationship assures appropriate discharge of the processing solution against the photosensitive material. Such Low Volume Thin Tank systems are described in more detail in the following patent specifications: US 5,294,956, US 5,179,404, US 5,270,762, EP 559,025, EP 559,026, EP 559,027, WO 92/10790, WO 92/17819, WO 93/04404, WO 92/17370, WO 91/19226, WO 91/12567, WO 92/07302, WO 93/00612, WO 92/07301, and WO 92/09932 The following Examples are included for a better understanding of the invention and to provide experimental evidence which demonstrates the phenomena involved. EXAMPLE 1 In this example experiments are carried out to establish a fixer formulation in which the fixing agent does not poison the catalytic properties of the silver image and which does not react with the redox oxidant A developer solution of the following composition was prepared. Developer Composition Component Concentration Dev(1) Dev(2) AC5 0.6g/l = DTPA 0.81g/l = K 2 HPO 4 .3H 2 O 40g/l = KBr 1mg/l = KCl 0.5g/l = KOH(50%) 10ml/l = DEH 1.0ml/l = CD3 4.5g/l 10g/l pH 11.4 = Temp 35 °C = Time 30 seconds = Where AC5 is a 60% solution of 1-hydroxyethylidene-1,1-diphosphonic acid, DTPA is diethylene triamine penta acetic acid, DEH is an 85% solution of diethyl hydroxylamine and CD3 is N-[2-(4-amino-N-ethyl-m-toluidino)ethyl]-methanesuiphonamide sesquisulphate hydrate. In order to determine if fixer compositions removed all the silver halide from a developed strip a diagnostic test in which a developer/amplifier was used after room light exposure as in the following process cycle. Develop 30 seconds Fix 2 minutes Wash 2 minutes Expose to room light Devamp 45 seconds Wash 2 minutes Dry The developer/amplifier(devamp) had the following composition. Developer/Amplifier Composition Component Concentration AC5 0.6g/l DTPA 0.81g/l K 2 HPO 4 .3H 2 O 40g/l KBr 1mg/l KCl 0.5g/l KOH(50%) 10ml HAS 1.0g/l CD3 4.5g/l pH 11.4 H 2 O 2 (30% w/w) 2.0ml/l Temp 35 °C Time 45 seconds Some fixer compositions and process cycle variations were carried-out in order to establish a composition that would fix and which was also likely to be compatible with hydrogen peroxide. The paper used was a multilayer containing emulsions which were substantially pure silver chloride with a total silver content of about 64 mg/m 2 . Fixer Effectiveness Strip Develop Fix Expose Dev/amp Densities (x100) Dmax Dmin R G B R G B 0 yes(1) none yes yes 269 264 255 268 262 255 1 yes(1) A yes yes 269 262 253 18 32 129 2 yes(1) A no yes 277 267 256 13 13 12 3 yes(1) B no yes 270 271 254 14 14 15 4 yes(1) B yes yes 277 263 256 11 12 13 10 yes(1) C yes yes 276 265 246 11 14 13 24 yes(1) D yes yes 259 265 255 13 17 32 25 yes(1) D no yes 274 271 262 13 17 29 30 yes(1) E yes yes 274 268 254 12 13 14 31 yes(1) F yes yes 284 269 253 14 16 20 Fixer Compositions Fixer Components Concentration A AC8 50ml/l B AC8 50ml/l DEA 50ml/l C AC8 50ml/l DEA 50ml/l pH 9.0 with acetic acid D AC8 50ml/l DTOD 1.0g/l E AC8 50ml/l DTOD 0.1g/l F NTA 10g/l DTOD 0.1g/l Where AC8 is a 40% solution of the penta sodium salt of diethylene triamine penta acetic acid, DEA is diethanolamine, DTOD is dithiaoctane diol, NTA is nitrilotriacetic acid. It can be seen that when there is no fixing the Dmin density is about the same as the Dmax density thus the method is a sensitive test for the effectiveness of the fixer bath. Strip 1 shows that fixer A fixes the top two layers quite well but only partially fixes the bottom or yellow layer.If the expose step is ommitted as in strip 2 then normal Dmin densities are obtained. Strip 3 shows the effect of adding a fixing accelerator, diethanolamine, to AC8 to make fixer B. Now it can be seen with strips 3 and 4 that normal Dmin densities are obtained with or without exposure before the devamp stage. This indicates complete fixing in 2 min in fixer B. Strip 10 shows that fixer C which is the same as fixer B except that the pH has been adjusted to 9.0 with acetic acid also fixes completley in 2 min. Strip 24 shows that another fixer accelerator DTOD gives almost complete fixing although the yellow Dmin is somewhat high. Strip 25 is a repeat of 24 but now without any expose step after fixing and yet the same slightly high yellow Dmin is obtained. This shows that the Dmin is not due to incomplete fixing but to some fogging action of DTOD. If the level of DTOD if lowered as in fixer E then this fogging is not present and fixing is complete. Fixer F shows that another amino carboxylic acid, NTA, also acts as a fixing agent in combination with DTOD. It appears for the purposes of making an amplifier-bleach-fixer that fixers B or C would be suitable and this is illustrated in example 2. EXAMPLE 2 In this example hydrogen peroxide is added to the fixer in order to convert it to a fixer which will also amplify and bleach. A process cycle was carried out as follows; Develop 30 sec Amplify/fix 1-2 min wash 2 min expose to room light devamp 45 sec fix 1 min wash 2 min where fix is a standard Kodak fixer. An amplifier-bleach-fixer(ABF) of the composition shown below was made up; Amplifier-Bleach-fix (G) AC8 50ml/l DEA 50ml/l H 2 O 2 (30% w/w) 50ml/l Acetic acid to pH 9.0 Strips were processed according to the above process cycle and the results are shown in Table 5 below. Amplifier-Bleach-Fixers Strip develop ABF expose devamp Densities (x100) Dmax Dmin R G B R G B 8 yes(1) none no no 67 74 78 10 10 8 8a yes(1) none no yes 275 258 251 1 13 12 11 yes(1) G(2') yes yes 159 145 134 12 14 15 12 yes(1) G(1') yes yes 144 140 133 12 15 15 13 yes(1) G(1') yes no 151 143 136 13 14 14 53 yes(2) G(1') no no 214 216 183 13 13 15 54 yes(2) G(1') yes yes 207 229 189 13 13 15 Where G(1') means 1 minute immersion in the amplifier-bleach-fix(G). These data show that all three operations have occurred in the amplifier-bleach-fixer. The increase in density of 11, 12 and 13 compared with 8 indicates amplification. Full Dmax is not achieved because the CD3 level in developer(1) needs to be higher for this to occur as shown with strip 53 which used developer (2) with 10g/l CD3. The low Dmax in the first part is intentional in this experiment because an intermediate Dmax density will be increased to show if bleaching has or has not occurred. This is because the devamp amplifies on the unbleached silver as shown by comparing the Dmax densities of strips 8 and 8a. The fact that strips 12 and 13 are almost the same Dmax density means that no amplification has occurred at the devamp stage with strip 12 and so there is no silver or silver halide in the Dmax areas and so bleaching (and fixing) must have occurred. This is confirmed by comparison with the strip 8a which was not bleached or fixed and the Dmax density is now much higher and about the same as the samples which were fixed but not bleached in table 3 in example 1. Finally there is no increase in the Dmin of 12 compared with 13 indicating that all the silver halide has been fixed.

Claims: A method of processing an imagewise exposed photographic silver halide colour material comprising two or more silver halide layers sensitised to different regions of the visible spectrum having associated therewith appropriate dye image forming couplers which method comprises a colour development step followed by treatment in a combined amplifier/bleach/fix step comprising: (a) a redox oxidant which is capable of bleaching a silver image, and (b) a fixing agent which does not poison the catalytic properties of the silver image and which does not react with the redox oxidant. A method as claimed in claim 1 in which the fixing agent is a polycarboxylic amino acid. A method as claimed in claim 1 or 2 in which the fixing agent is a compound having at least one: N-[(CH 2 ) n -A] p moeity wherein A is -COOH or -PO 3 H 2 , n is 1-6 and p is 1-3 provided that the compound contains at least 2 A groups. A method as claimed in any of claims 1-3 in which the fixing agent is: ethylenediamine tetra acetic acid (EDTA), Propylendiamine tetra acetic acid, 2-hydroxy-1,3-propylene diamine tetra acetic acid, diethylene triamine penta acetic acid, nitrilo triacetic acid, ethylene diamine tetra methylene phosphonic acid, diethylene triamine penta methylene phosphonic acid, cylcohexylene diamine tetra acetic acid, [(Ethylene dioxy)diethylene dinitrilo] tetra acetic acid, or ethylene dinitrilo-N,N'-bis(2-hydroxy benzyl)-N,N'-diacetic acid A method as claimed in any of claims 1-4 in which the redox oxidant is hydrogen peroxide or a compound that provides hydrogen peroxide. A method as claimed in claim 5 in which the hydrogen peroxide is present in an amount of from 0.5 to 150 ml/l as a 30% w/w solution. A method as claimed in any of claims 1-6 in which the amplifier/bleach/fix solution contains a fix accelerator. A method as claimed in claim 7 in which the fix accelerator is a primary, secondary, or tertiary alkylamine; an alkyl diamine, triamine, tetramine, pentamine or hexamine; a cyclic polyamine, an aryl amine; a mono, di, or tri-alkanolamine, a thioether, a thioamine; or morpholine. A method as claimed in any of claims 1-8 in the processing is carried out by passing the material to be processed through a tank containing the processing solution which is recirculated through the tank at a rate of from 0.1 to 10 tank volumes per minute. A method as claimed in claim 9 in which the ratio of tank volume to maximum area of photographic material accomodatable therein (ie maximum path length x width of material) is less than 11 dm 3 /m 2 .

Inventors: TWIST PETER JEFFREY, TWIST, PETER JEFFREY, TWIST, PETER JEFFREY, C/O KODAK LTD.
Applicants: EASTMAN KODAK CO, KODAK LTD, EASTMAN KODAK COMPANY, KODAK LIMITED
Application year: 1996
Main classification: G03C7
IPC codes: G03C7