Method of processing comprising successive steps of redox and conventional development

Abstract: A process for the sequential development in the same processor of imagewise exposed low silver and conventional photographic recording materials comprises: (i) developing the low silver photographic recording material in a redox developer/amplifier solution containing: a colour developing agent an oxidizing agent a buffering agent and having a pH in the range from 10.0 to 12.5 and then removing the oxidizing agent and (ii) employing the solution to develop a conventional silver photographic recording material. The order of steps (i) and (ii) may be reversed in which case after the development of the conventional photographic recording material in step (ii), an oxidizing agent is added to the solution and the solution used as a redox developer/amplifier solution in step (i). The peroxide is conveniently removed by the addition of a reducing agent such as a sulphite.

Description: Field of the Invention This invention relates to a process for the sequential development of low silver and conventional photographic recording materials. Background of the Invention Redox amplification processes have been described, for example in British Specifications 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 treated with a redox amplifying solution (or a combined developer/amplifier) to form a dye image. The developer-amplifier solution contains a colour developing agent and an oxidising agent which will oxidise the colour developing agent in the presence of the silver image which acts as a catalyst. Oxidised colour developer reacts with a colour coupler to form the dye image. The amount of dye formed depends on the time of treatment or the availability of the colour coupler and is less dependent on the amount of silver in the image than is the case in conventional colour development processes. Examples of suitable oxidising agents include peroxy compounds including hydrogen peroxide and compounds which provide hydrogen peroxide, e.g. addition compounds of hydrogen peroxide such as perborates and addition compounds of hydrogen peroxide with urea. Other oxidizing agents include cobalt (III) complexes including cobalt hexammine complexes; and periodates. Mixtures of such compounds can also be used. EP-A-0600564 discloses a method of colour processing which comprises processing an imagewise exposed colour photographic silver halide material by treating it with a colour developer solution and then with a developer/amplifier solution containing a colour developing agent and hydrogen peroxide or a compound which provides hydrogen peroxide and in which said solutions are replenished and the overflow from the developer/amplifier solution is treated to remove hydrogen peroxide and used to form the sole replenisher for the colour developer solution. The level of hydrogen peroxide in the developer/amplifier solution is from 0.1 - 30, preferably from 1 - 5 ml/l (as 30% solution). EP-A-0654707 discloses an aqueous redox amplifier composition comprising a colour developing agent, hydrogen peroxide or a compound which provides hydrogen peroxide or a salt thereof wherein the concentration ranges are: hydrogen peroxide from 0.5 to 10 ml/l (as 30% w/w solution), hydroxylamine or a salt thereof from 0.25 to 5.5 g/l (as hydroxylamine sulphate), and wherein the pH is in the range from 10.5 to 12. Preferably, the composition is buffered by a phosphate. Problem to be solved by the invention. The redox process is designed for low silver colour paper for example about 200mg/sq.m or less of silver and cannot be used to process conventional paper which typically contains about 500 to 700 mg/sq.m because gross overamplification would occur. If it is necessary to process redox and conventional photographic recording materials in the same processing apparatus it is currently not possible to avoid the expense and inconvenience of having to empty and recharge the processor with the different processing solution. The present invention provides a solution to this problem and avoids the necessity of having to empty and recharge the processor by the provision of a solution which, with the addition or removal of oxidizing agent as appropriate, is suitable for both types of process. Summary of the Invention According to the present invention there is provided a process for the sequential development in the same processor of imagewise exposed low silver and conventional photographic recording materials which process comprises: (i) developing the low silver photographic recording material in a redox developer/amplifier solution containing: a colour developing agent an oxidizing agent a buffering agent and having a pH in the range from 10.0 to 12.5 and then removing the oxidizing agent and (ii) employing the solution to develop a conventional silver photographic recording material. The order of steps (i) and (ii) may be reversed, in which case after the development of the conventional photographic recording material in step (ii), an oxidizing agent is added to the solution and the solution used as a redox developer/amplifier solution in step (i). Advantageous Effect of the Invention The solutions of the present invention enable a processor to sequentially process low silver and conventional silver photographic materials without the necessity of emptying and recharging the processor equipment. Detailed Description of the Invention The colour developing agent may be any of those known in the art, for example, the p-phenylene diamines eg 4-amino N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N,N-diethylaniline hydrochloride, 4-amino-3methyl-N-ethyl-N-(beta-(methanesulfonamido) ethyl)aniline sesquisulphate hydrate, 4-amino-3-methyl-N-ethyl-N-(beta hydroxyethyl)aniline sulphate, 4-amino-3-beta-(methanesulfonamido)ethyl-N,N-diethyl aniline hydrochloride and 4-amino-N-ethyl-N-(2-methoxyethyl)-m-toluidene di-p-toluene sulfonic acid. The oxidizing agent is preferably a peroxide or a compound that generates hydrogen peroxide and may be present in amounts from 0.5 to 30 ml/l preferably 5 to 20 ml/l (as 30% w/w aqueous solution). The developer can also include an antioxidant e.g. hydroxylamine or a salt thereof such as hydroxylamine chloride, phosphate or, preferably, sulphate. An N-substituted hydroxylamine which may be mono or disubstituted may be employed as well as hydroxylamine itself. Suitable substituents are monovalent organic groups containing not more than 12 carbon atoms. Suitable such groups are alkyl or aryl groups which may be substituted for example with sulphonate or carboxylate. Lower alkyl groups, for example containing from 1 to 6 carbon atoms are particularly suitable. The antioxidant may be present in an amount from 0.01 to 20g/l, preferably from 0.25 to 8 g/l. Preferred concentration ranges are from 0.1 to 10g/l of hydroxylamine sulphate and from 0.01 ml/l to 20ml/l (as 85% w/w aqueous solution) of the substituted hydroxylamine for example when diethylhydroxylamine is used. The pH is preferably buffered e.g. by a phosphate such as potassium hydrogen phosphate (K 2 HPO 4 ) or by another phosphate, or carbonate, silicate or mixture thereof. Conveniently the solution used in the present invention for redox development and conventional development has a pH in the range from 10.5 to 12.5 preferably 11.0 to 12.0, more preferably 11.0 to 11.7. After completing step (ii) the oxidizing agent such as peroxide or compound providing peroxide may be added to the solution and the solution used for the redox development of a low silver photographic recording material. The invention therefore provides a process comprising a plurality of steps carried out in the same processing equipment in which conventional and redox development follow each other eg redox development followed by conventional development followed by redox development followed by conventional development and so on and the change from one mode to the other is effected by the addition or removal (e.g. inactivation) of oxidizing agent as appropriate. In one embodiment of the invention, step (i) is carried out before step (ii), the oxidizing agent in the developer solution is removed in a suitable fashion , such as by adding a reducing agent (for example, a sulfite) to the developer solution. If step (ii) is carried out before step (i), the developer solution does not contain the oxidizing agent when used in step (ii), but it must be added to the developer solution prior to step (i). If a plurality of the series of steps (i) and (ii) are carried out, between each step (i) and (ii), there will be either removal or addition of the oxidizing agent to the developer solution depending on which step follows. The colour photographic material to be processed may be of any type for example it may contain low amounts of silver halide or conventional amounts of silver. Silver halide coverages may be in the range 6 to 700, in the case of low silver materials from 10 to 200 or 10 to 100 mg/m 2 (as silver). A particular application of redox amplification is in the processing of silver chloride colour paper, for example, paper comprising at least 85 mole % silver chloride, especially such paper with low silver levels for example levels below 200mg/m 2 , often below 100mg/m 2 . The photographic material may comprise the emulsions, sensitisers, couplers, supports, layers, additives, etc. described in Research Disclosure, December 1978, Item 17643, published by Kenneth Mason Publications Ltd, Dudley Annex, 12a North Street, Emsworth, Hants P010 7DQ, U.K. The photographic material to be processed may comprise a resin-coated paper support and the emulsion layers comprise more than 80%, preferably more than 90% silver chloride and may be composed of substantially pure silver chloride. The photographic materials (which can be low silver or conventional silver) can be single colour materials or multicolour materials. Multicolour materials 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 materials, including the layers of the image-forming units, can be arranged in various orders as known in the art. A typical multicolour photographic material comprises a support bearing a yellow dye image-forming unit comprised of at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler, and magenta and cyan dye image-forming units comprising at least one green- or red-sensitive silver halide emulsion layer having associated therewith at least one magenta or cyan dye-forming coupler respectively. The material can contain additional layers, such as filter layers. The process of the invention is particularly suitable for use in a tank of relatively small volume and in a preferred embodiment the ratio of the tank volume to maximum area of material accommodatable therein (i.e. maximum path length times width of material) is less than 11 dm 3 /m 2 , preferably less than 3dm 3 /m 2 . The process may be carried out in what is known in the art as a minilab for example the tank volume may be below 5 litres and sometimes below 3.0 litres conveniently in the range 1.5 to 2.5 litres and may be about 1 litre. The material to be processed is conveniently passed through the tank and preferably the developer solution is recirculated through the tank at a rate of 0.1 to 10 tank volumes per minute. The preferred recirculation rate is from 0.5 to 8 especially from 1 to 5 and particularly from 2 to 4 tank volumes per minute. The recirculation with or without replenishment may be carried out continuously or intermittently. In one method of working both can be carried out continuously while processing is in progress but not at all or intermittently when the tank is idle. Replenishment may be carried out by introducing the required amount of replenisher into the recirculation system either inside or outside the processing tank. 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 of less then llmm, preferably less than 5mm and especially about 2mm. The shape of the tank is not critical but it may conveniently 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 as or only just wider than the width of the material being processed. The total volume of the processing solution within the processing channel and recirculation system is relatively smaller as compared with prior art processes. 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% of the total volume of the processing solution in the entire system. Preferably the volume of the processing channel is at least about 50% 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 where 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; 5,179,404; 5,270,762; EP559,025; 559,026; 559,027; WO92/10790; WO92/17819; WO93/04404; WO92/17370; WO91/19226; WO91/12567; WO9207302; WO93/00612 and WO92/07301. According to another aspect of the invention there is provided a low volume thin tank system containing a solution which, by the addition or removal of oxidizing agent as appropriate, is suitable for use as a developer/amplifier for low silver photographic materials and as a developer solution for conventional silver photographic materials. When the oxidizing agent is a peroxide it may conveniently be removed by the addition of a reducing agent such as a sulphite. The invention is illustrated by the following Examples. Example 1. A developer for conventional high silver paper had the composition shown in Table 1 below. Component composition Sequestrant 0.8ml/l K 2 CO 3 25.0g/l KBr 0.02g/l KC1 2.8g/l Antioxidant 5.0ml/l K 2 SO 3 (45%w/w) 0/5ml/l TEA (100%) 5.5ml/l Versa TL-73 0.25ml/l Phorwite REU 1.0g/l Li 2 SO 4 2.0g/l Colour developing agent 4.35g/l pH 10.10 time 45 seconds Temperature 37.8°C Antioxidant is diethylhydroxylamine as 85% w/w aqueous solution Sequestrant used in all the examples is a 60% w/w aqueous solution of 1-hydroxyethylidene-1,1-diphosphonic acid. TEA is triethanolamine Versa TL is a commercially available surfactant Colour developing agent used in all the examples is N-(2-(4-amino-N-m-toluidino) ethyl)-methanesulphonamide sesquisulphate hydrate. Phorwite REU is an optical brightener. A developer/amplifier solution for processing low silver paper includes hydrogen peroxide but also needs to be further modified from that shown in Table 1 in order to improve the stability of the developer/amplifier solution. The changes are shown in Table 2. RX developer/amplifier Component composition Sequestrant 0.6ml/l DTPA 0.81g/l K 2 HPO 4 3H 2 O 40g/l KBr 1mg/l KCl 0.5g/l HAS 1.0g/l Colour developing agent 4.5g/l pH 11.40 time 45 seconds Temperature 35 o C HAS is hydroxylamine sulphate. In order to be able to process both types of paper in the same basic solution a hybrid solution is needed which satisfies as much as possible the needs of both systems. In order to retain the best stability of the RX developer/amplifier the changes shown in Table 3 are necessary. These include making the changes shown in Table 2 i.e. the antioxidant is changed to hydroxylamine, the buffer to phosphate and the pH to 11.4 and in addition including some components which are desirable for the proper performance of conventional or high silver paper. One of these components is a stain reducing agent (Phorwite REU) which is not necessary for the low silver case but is also not detrimental. Other components such as bromide and chloride season into the developer solution from the high silver paper and are thus unavoidable thus increasing the levels of potassium chloride and bromide. The solution whose composition is shown in Table 3 was used to process low silver paper in the presence of peroxide; after which the peroxide was removed by adding an equimolar amount of potassium sulphite. The resulting developer was then used to process conventional or high silver paper. RX and Conventional Developer(a). Component Composition Sequestrant 0.6ml/l DTPA 0.81g/l K 2 HPO 4 3H 2 O 40g/l KBr 20mg/l KCl 2.8g/l HAS 1.0g/l Colour developing agent 4.5g/l Phorwite REU 1.0g/l pH 11.40 H 2 O 2 (30%) 12.0ml/l for RX; 0 for conventional Time 45 seconds Temperature 32 o C where HAS is hydroxylamine sulphate. The process cycle used was as follows: develop or develop/amplify 45 seconds Kodak RA-4 Bleach-fix 45 seconds wash 2 minutes dry Processing was carried out with two different types of paper, where C is conventional high silver paper with about 650mg/sq.m of silver and RX is low silver paper with about 120mg/sq.m of silver. The results are shown in Table 4. It can be seen that the RX process results in a higher Dmin density than the conventional process and this is known to be due to iron catalysed oxidation of colour developing agent by peroxide in the bleach-fix. This Dmin can be prevented if the process cycle is changed to include a stop bath after the developer bath as follows: develop or develop/amplify 45 seconds stop 30 seconds Kodak RA-4 bleach-fix 45 seconds wash 2 minutes dry where stop is a solution of 20g/l of sodium metabisulphite The D min of the RX process is now the same as the conventional process. Example 2 In this Example the composition of the developer solution was changed slightly by lowering the HAS level to 0.6g/l. This has the effect of raising the activity for both types of paper. The composition of this developer solution is shown in Table 6. RX and conventional developer(b) Component composition Sequestrant 0.6ml/l DTPA 0.81g/l K 2 HPO 4 3H 2 O 40g/l KBr 20mg/l KCl 2.8g/l (2.5g/l added as 0.3g/l is from REU) HAS 0.6 g/l Colour developing agent 4.5g/l Phorwite REU 1.0g/l pH 11.40 H 2 O 2 (30%) 9.0ml/l for RX; 0 for conventional Time 45 seconds Temperature 32 o C A comparison between two RX processed samples of low silver paper shows RX3 which goes into RA-bleach-fix plus 50g/l sodium sulphite and RX4 where 100g/l of sodium sulphite was added to RA-4 bleach-fix. The results are shown in Table 7. Where the process is as follows: develop or develop/amplify 45 seconds Kodak RA-4 bleach-fix +sulphite 45 seconds wash 2 minutes dry C3 was high silver paper/no peroxide/RA-4 bleach-fix +50g/l sodium sulphite. C4 was high silver paper/no peroxide/RA-4 bleach-fix + 100 g/l sodium sulphite RX3 was low silver paper/peroxide/RA-4 bleach-fix + 50g/l sodium sulphite RX4 was low silver paper/peroxide/RA-4 bleach-fix + 100g/l sodium sulphite. It can be seen that the performance of the two paper types is similar. In particular the addition of sodium sulphite (100g/l) to RA-4 bleach fix lowers the Dmin of the RX processed paper to an acceptable level. If the process is repeated with a stop-bath and with a standard RA-4 bleach-fix as outlined in Example 1 so that the process cycle is as follows: develop or develop/amplify 45 seconds stop 30 seconds RA-4 bleach fix 45 seconds wash 2 minutes dry The results are shown in Table 8. Here it can be seen that the Dmin for the RX process and the conventional process are almost the same. Thus by this means both types of developer can be run in the same basic process except that the hydrogen peroxide in the developer bath is added for the RX process or removed with sulphite for the conventional process.

Claims: A process for the sequential development in the same processor of imagewise exposed low silver and conventional photographic recording materials which process comprises: (i) developing the low silver photographic recording material in a developer solution containing: a colour developing agent, and a buffering agent, and having a pH in the range from 10.0 to 12.5, and (ii) developing the conventional silver photographic recording material with said developer solution, provided that when step (i) is carried out, said developer solution further comprises an oxidizing agent which is a peroxide or a compound that provides peroxide to make the developer solution a redox developer/amplifier solution, and further provided that when step (i) is carried out first, said developer solution is treated to remove said oxidizing agent, and when step (ii) is carried out first, said oxidizing agent is added to said developer solution prior to step (i). A process as claimed in claim 1 wherein the developer solution further comprises hydroxylamine. A process as claimed in claim 1 or claim 2 wherein the peroxide is present in an amount of from 0.5 to 30 ml/l, preferably 0.5 to 20 ml/l (as 30% w/w aqueous solution) and the hydroxylamine is present in an amount from 0.1 to 10.0 g/l preferably from 0.25 to 8g/l (as hydroxylamine sulphate). A process as claimed in any one of the preceding claims wherein the buffering agent is a phosphate. A process as claimed in any one of the preceding claims wherein the peroxide is removed by the addition of a reducing agent. A process as claimed in claim 6 wherein the reducing agent is a sulphite. A process as claimed in any one of the preceding claims wherein there is present in the solution employed in both steps (i) and (ii), a stain reducing agent. A process as claimed in any one of the preceding claims wherein the process is carried out in a low volume developer tank, preferably a low volume thin tank. A process as claimed in any one of the preceding claims wherein the photographic recording materials are passed to a stop bath after the development.

Inventors: EVANS GARETH BRYN, TWIST PETER JEFFEREY, EVANS, GARETH BRYN, TWIST, PETER JEFFEREY
Applicants: EASTMAN KODAK CO, EASTMAN KODAK COMPANY
Application year: 1997
Main classification: G03C7
IPC codes: G03C7