DESCRIPTION

This invention relates to a method of processing photographic silver halide colour material and in particular to the replenishment of a developer solution system for colour paper.

In the replenishment systems of the prior art liquid replenisher is added to the developer solution and spent developer is removed by allowing overflow. A stable condition in which chemicals used up during processing are replenished to maintain a working concentration may thus be maintained. However, replenishment systems which involve overflow are environmentally undesirable and the objective of the present invention is to provide a replenishment system without overflow.

A system for replenishing a colour paper processing system is described in European Specification No. 0,173,203. Using a concentrated source of

replenishment can result in zero-overflow from the developer tank and a build-up of seasoning products which is not significantly detrimental to sensitometry. This could involve rebalancing the sensitized coating to match aim sensitometry in the presence of higher levels of seasoning products. This is a major operation and is best avoided if a simpler option as is described in our invention is available. Another special case is where even though seasoning products do build-up with use, they do not affect sensitometry because the developer used already contains a more powerful inhibitor. For example, if a sensitized material containing a high silver chloride content is processed in a developer containing soluble sodium bromide (0.7 g/1), then the increase in chloride level during use would only have a small effect on sensitometry. This is similar to the method employed in EP-A-0,173,203 for a colour paper developer. To some extent this is an artificial case because high silver chloride coatings are best processed with much lower levels of bromide (about 20 mg/1) to allow for rapid processing (e.g. the RA-4 process). If seasoning products such as chloride are allowed to build up in the RA-4 process, then sensitometry and processing rapidity are detrimentally affected.

Whilst it is known to remove seasoning products from developers using ion-exchange resin, such resins have never been used in a system having such low replenishment rates as are achieved by the present invention. For example, in "Developer Recycling - A New Generation" Meckl, Journal of Imaging Technology, 13, (1987), 3, 85-89 there is described a system in which the overflow from the colour developer tank is passed to a holding tank and then through ion-exchange resin to remove bromide ions. The so treated solution is then passed to a mixing tank where replenisher components are added and the newly formed solution is then passed to the replenisher tank ready for use. The replenishment rate for a paper process is said to be 325 ml/m ² .

Japanese Application 62/019842 describes a method of reducing the bromide ion concentration of colour developer for silver bromide colour paper by coating an ion-exchange resin on the back of the colour paper. This then takes up bromide ions as it passes through the developer solution. Clearly this process is undesirable because a special and more costly photographic paper has to be used thus rendering the paper more expensive and the process non-universal.

The process wastes otherwise regeneratable ion- exchange resin.

In accordance with the present invention there is pro- vided a method of processing a photographic silver halide colour paper including the steps of replenish¬ ing the colour developer solution with a sufficiently small volume of replenishment components such that substantially no overflow is produced and removing by an in-line ion exchange resin system components which build up to an excessive concentration.

'In-line' (or on-line) means that the ion exchange system is contained in an integrated facility connected or connectable with the tank in which the processing takes place.

The overall volume of replenishment added is approximately equal to the volume loss caused by take-off by the paper and evaporation. The build-up in the liquid system of halides, principally chlorides, and to some extent sulphates is controlled by an on-line ion exchange system which is operated from time to time to remove these undesirable ions and

return the processed solution back to the vessel in which the liquid system is contained.

A replenishment system for a colour paper development solution system essentially comprises two components:

The colour developing agent,e.g.β methane sulphonamide- ethyl ethyl aminotoluidine sesquisulphate hydrate known as CD3, and an activator/replenisher for the other elements of the system as will subsequently be ex¬ plained.

Preferably the CD3 component can be added in solid form or as a liquid concentrate. The salt is essentially acid so is readily dissolved in the basic development solution with no substantial increase in volume. The activator/replenisher is added as a liquid.

The ion-exchange resin may comprise anionic (for the exchange of anions) or amphoteric types or mixtures thereof. A preferred type of anionic resin is based on a polystyrene matrix cross-linked, for example, with 3% to 5% of divinylbenzene. Its strongly basic

character is derived from quaternary ammonium groups. Examples of suitable anionic exchange resins are:

IRA 400 Rohm and Haas Dorvex 1-X8 Dow Chemical, and

Duolite A113 Diamond Shamrock

The in-line ion-exchange resin is preferably located in a cartridge through which the contents of the colour developer tank are pumped either continuously or when required. When it has been exhausted it may be discarded or regenerated as will be well understood.

The invention will be described by way of Example and with reference to the accompanying drawings wherein:-

Figure 1 is a diagram of the development tank and in-line ion-exchange; and

Figure 2 is a control plot.

The example given is for colour paper having substantially pure silver chloride emulsions however

the principle is valid for chlorobromide emulsions or any other silver halide or mixed silver halide emulsions used with the appropriate processing solutions.

Alternatively three liquid concentrates can be used as follows:-

PART A Triethanolamine 85% solution 292 g/1

N,N-Diethyl hydroxylamine 85% solution 144 g/1

Phorwite REU 60 g/1

Lithium Salt of Sulfonated Polystyrene 6.6 g/1

PART B

Potassium Sulphite 45% solution

CD3

Catechol Trisulphonate 11% solution

PART C

Potassium Hydroxide 45% solution 65 g/1

Potassium Carbonate 47% solution 1064 g/1

Disodium EDTA 60 g/1

The approximate replenishment rates for the above 3 part replenisher would be:

Part A 3 ml/m ²

Part C 1.6 ml/m ²

A replenishment assembly comprises: (a) Solid CD3 addition in an amount calculated at 5.76 mg/dm ² of pho- tographic colour paper having substantially pure chloride emulsions. This solid additive may be in the form of an acidic pellet which dissolves readily with the evolution of carbon dioxide in the basic developer solution. As alternatives the solid additive may be on a coated tape or in some kind of perforated container. However, the simple pellet method has been found to work quite effectively, (b) A solution of replenisher/activator which is added at 3.06 mis per sq.ft. (0.33 mg/dm ² ) and comprises:

Component Concentration g/1 or ml/1

Lithium Salt of Sulfonated Polystyrene as a Dispersant 0.25 ml

An antioxidant diethyl hydroxylamine 11.50 ml

Triethanolamine as a solvent 12.50 ml

Phorwite REU - an optical brightener 5.8 g

^K 2 ^C0 3 ^{" as a buf fer 26 , 5}

EDTA (water softener) 3.0 g Catechol Trisulphonate Solution 11% (water softener) 5.6 ml The pH of the solution is 11.30

This activator/replenishment solution was preferably kept in, and dispensed from a collapsible container. If the volume drops due to carry out on the developed paper the level is topped up with water.

With the above system an in-line, recirculatory ion exchange system is incorporated as shown in Figure 1. This system uses IRA400 resin and the developer

solution is pumped through the resin intermittently at a rate of about 3.7 ml per sq.ft. (0.40 mg/dm ² ) of processed paper and then returned directly to the tank. This procedure essentially removes all the chloride and sulphate from the volume of developer that passes through and the above rate is calculated so that the total chloride and sulphate removal is equivalent to the build up rate. The control plot in Figure 2 of the accompanying drawings shows that the CD3 level was maintained within the defined limits through the course of a run of 5 months.

Reference is made to the International Application of even date claiming priority from G.B. Application No. 8925311.6.