WO1992012463A1

WO1992012463A1 - Carryover reduction in photographic processing

Info

Publication number: WO1992012463A1
Application number: PCT/EP1992/000008
Authority: WO
Inventors: Alan Geoffrey Eeles; David Neil Rogers; John Martin Higgins; Peter Jeffery Twist; Nigel Richard Wildman; John Richard Fyson
Original assignee: Eastman Kodak Company; Kodak Limited
Priority date: 1991-01-10
Filing date: 1992-01-03
Publication date: 1992-07-23
Also published as: GB9100498D0

Abstract

The invention provides a method for reducing carryover reagents in the wet processing of a gelatin-based photographic material which method comprises causing the swellability of the gelatin layer in a first treatment bath to be reduced and maintaining said reduced swellability in the subsequent treatment baths thereby to reduce reagent carryover between baths. The process may be effected by reducing gel laydown of the photographic material or by adding a hardener in the first treatment bath. Not only is carryover reduced but also commensurately replenisher values and effluent are reduced.

Description

CARRYOVER REDUCTION IN PHOTOGRAPHIC PROCESSING

DESCRIPTION

The present invention relates to carryover reduction in photographic processing.

The wet processing of photographic materials relies on the diffusion of the reactive solutions into the swollen photographic material; essentially the gelatin base. However, the carryover of solution from one processing solution to the next is usually deleterious, because it dilutes and contaminates the next solution.

The need exists therefore to provide a method whereby the processing solution from one bath is not carried over into the next bath, or at least the carryover is reduced to a minimum. The invention is predicated on the observation that the amount of carryover is reduced by designing a photographic product such that it has low swell so that it is capable of absorbing enough reagent for photographic development purposes, for example, but has a limited a capacity for unwanted carryover to a succeeding treatment bath.

In US-A-3,467,519 there is disclosed a method for reversibly hardening developed gelatin layers in a photographic product whereby the swelling capacity of the layer is reduced. This is effected by adding to the final treatment bath an organic sulfonic acid or sulfate. Hardening agents such as these are now well known in the art and are revealed in the said US

Patent Specification as being utilized in the final stages of processing to reduce the water content of a developed photographic product so as to commensurately reduce drying t.i_me.

It has not been realised in this disclosure however that the application of hardners earlier in the processing cycle, most preferably at its initiation, give rise to the beneficial results of a reduction in carryover of reagents and hence lower contamination and commensurately lower replenishment levels, as well as a reduced drying time.

According therefore to the present invention there is provided a method for reducing carryover of reagents in the wet processing of a gelatin-based photographic material, which method comprises causing the swellability of the gelatin layer in a first treatment bath to be reduced, and maintaining said reduced swellability in a subsequent treatment bath(s) thereby to reduce reagent carryover between said bath(s) .

In the foregoing description the term "first treatment bath is utilized" . It will be understood that the f.irst treatment bath may be any bath utilized during the wet processing of a gelatin based photographic material so long as it is not the last bath. Thus although generally it is preferred that the f.irst bath in the wet processing of the photographic material is utilized for the present invention, this first bath can be a subsequent bath if desired. The reduction in swellability is most preferably caused by reducing the laydown values of the gelatin layer. However equally, or additionally, the reduction in swellability can be caused by adding a hardener or a water ejctracting agent to the first treatment bath.

This is preferred to reduce the reduction in carryover by a figure of up to 40% over that generally utilized. This can be achieved in one alternative by reducing the gelatin laydown by between 40 and 70% of standard values and preferably by about 60% to produce an equivalent percentage of carryover reduction.

When the standard gelatin laydown is of the order of

₂

15g/m is preferred that the modified gelatin laydown in accordance with this invention should be 7 to

11 g/m 2 and more preferably about 9g/m2.

The invention will now be described, by way of illustration only, with reference to the following Examples. EXAMPLE 1

Two multilayer films were coated, with a standard coating sJLmilar to Kodak 400 Gold, with a coated gel 2 laydown of 15.2g/m and another similar coating but

2 with the gel laydown reduced to 9.3g/m constituting a

61.18% reduction.

The amount of hardener used was adjusted when coating such that the gel/hardener ratio was kept constant. The degree of swell of the respective coatings were determined using a swellmeter and found to be 58 and 40 microns respectively. The carryover of developer was determined by dipping a weighed known length of the coatings into a C-41 developer at 38°C withdrawing them, waiting 10 seconds as a drain time, and then weighing the coating lengths again.

From the results the solution carryover of the C-41 developer into the subsequent (bleach) tank was

2 determined and found to be 63g/m for the st-andard 2 coating and 43g/m for the coating with a gel laydown; a 68% reduction.

EXAMP.LE 2

In no.rmal photographic developing processing a bleach bath follows the developer tank. In a conventional Bleach II ML process the replenisher rate is set at 1.2mls/ft to maintain a concentration of iron in the bleach at 0.27molar with the standard film passing through it. The new e.xperimental film requires the replenishment rate to be set a l.lmls/ft to maintain the same concentration of iron.

In an alternative to the foregoing Bleach bath a more active bleach is utilized which can work at a concentration of 0..1molar iron. It has been found that this can be replenished at a rate of 0.32ml/ft with a suitable replenisher with the standard film coating. This replenishment rate can be reduced to

0.2.1ml/ft with the film of reduced gel laydown, as set forth above constituting a reduction of 34% of the replenisher required and therefore a reduction of 34% in overflow volume effluent. There is of course a commensurate reduction in iron carried over into the next(fix) bath.

In accordance with the present invention the following advantages acrue.

The contam.ina ion of processing tanks by solutions from previous tanks is reduced, as is the dilution of processing tanks by solution from previous tanks. Thus the replenishment rate can be reduced for each tank thus reducing the reagent costs. Because the replenishment concentration can be reduced the effluent volume is commensurately reduced. Finally the potential for continued coupling in a bleach following a developer tank which is an ongoing problem is also reduced.

Claims

CLAIMS:

1. A method for reducing carryover of reagents in the wet processing of a gelatin-based photographic material which method comprises causing the swellability of the gelatin layer in a first treatment bath to be reduced, and maintaining said reduced swellability in the subsequent treatment baths thereby to reduce reagent carryover between baths.

2. A method according to cla 1 wherein the reduction in swellability is caused by reducing the laydown of gelatin.

3. A method according to claim 1 wherein the reduction in swellability is caused by adding a hardener or a water e^tracting agent to the f.irst treatment bath.

4. A method according to any preceding cla wherein the reduction in carryover when compared to a standard photographic material is up to 40%.

5. A method according to either of claims 1 or 2 wherein the gel laydown is reduced by 40 - 70% with a generally equivalent percentage reduction of carryover.

6. A method according to either of claims 1 or 2 wherein when the standard gelatin laydown is about

2 15g/m , the modified gel laydown is in the range of 7

2 to 11 g/m .