Concentrated solution for colour photographic development

Abstract: The present invention concerns a liquid photographic concentrate for a colour developer based on benzyl alcohol, water and organic solvents, a kit for a colour developer comprising this concentrate and a photographic processing method using this concentrate. The concentrate according to the invention comprises a quantity of benzyl alcohol of between 25 and 35%, a quantity of water between 3 and 8%, a quantity of ethylene glycol between 10 and 20% and a quantity of diethylene glycol between 35 and 60%. This concentrate dissolves rapidly in water.

Description: The present invention concerns a concentrated solution for preparing a colour developer comprising benzyl alcohol, water and organic solvents rapidly solubilizable in water. The invention also concerns a kit for a colour developer, that is to say a set of solutions comprising this concentrated solution and other solutions, to be mixed in order to obtain the ready-to-use developer, and a photographic processing method using this concentrated solution. In the field of photographic paper and film processing, colour developing solutions are used comprising, as the main constituents, a developing agent, benzyl alcohol as a permeability agent and alkaline bases. It is known that photographic processing solutions are packaged in the form of concentrated liquid solutions (hereinafter referred to as "concentrates"). For example, colour developers are often packaged in the form of several concentrates which are mixed at the time of preparation of the developer. These concentrates are particularly useful when there are stability problems with the various compounds constituting the ready-to-use processing solution. They also make it possible to solubilise each compound in the appropriate solvent. A clear homogenous ready-to-use developing solution must be obtained from these concentrates in a very short time without using complex handling. For example, US patent 3 574 619 describes a concentrated acidic solution comprising water, benzyl alcohol, a p-phenylene diamine, a sulphite and a liquid glycol present in the quantity necessary to obtain a uniform dispersion. According to this patent, a single glycol compound is used, chosen from amongst ethylene glycol, propylene glycol, diethylene glycol and triethylene glycol. Example 1 of the patent shows that it is possible to obtain a clear solution containing 67% benzyl alcohol, 10% water and 20% ethylene glycol. In all the other examples in the patent, the concentrate based on benzyl alcohol and glycol also contains the developer p-phenylene diamine. US patent 4 232 113 describes a concentrate in which a solution of 5 to 50 g of p-phenylenediamine developer in 100 ml of organic solvent is used to obtain a solution containing a quantity of water less than or equal to 5% of the total volume of the solution. The organic solvent is neutral and miscible in water in any proportion and can be chosen from amongst polyalcohols, polyoxyethylene glycols, or a mixture of these compounds. This concentrate can also contain benzyl alcohol. According to this patent, the developing composition is prepared by mixing this concentrate with at least a second concentrate consisting of an alkaline aqueous solution, and optionally with a third concentrate consisting of hydroxylamine, either in aqueous solution or in solution in an organic solvent. The known concentrated developing solutions do not give complete satisfaction because of (1) the difficulty of dissolving the concentrates in water, in particular concentrates comprising benzyl alcohol, and (2) the instability of these concentrates, in particular concentrates containing the developer, for example p-phenylenediamine. These problems of solubilisation and stability give rise to a waste of time and the formation of tars in the developer. In order to remedy the problems of solubilisation and stability mentioned above, commercially available colour developers are packaged in the form of three concentrates, such as for example the developer for Ektachrome-R3® photographic processing: a first concentrate which contains benzyl alcohol in aqueous solution, a second concentrate which contains the colour developer, and a third concentrate which contains one or more alkaline compounds in aqueous solution. Benzyl alcohol has a high chemical oxygen demand (COD), and this is why it is desirable to use it in as low quantity as possible. This reduction in the quantity of benzyl alcohol is all the more necessary as legislation is increasingly severe with regard to COD. When, in the benzyl alcohol-containing concentrate, attempts are made to reduce the quantity of this alcohol, it is also necessary to reduce the quantity of water in order to keep a concentrate which is stable and homogeneous and which is rapidly solubilizable in water. However, the reduction in the quantity of water contained in this concentrate gives rise to problems of solubilisation of the other photographically useful compounds present in the concentrate. It would therefore be particularly desirable to obtain a concentrate with a reduced benzyl alcohol content having improved stability and being rapidly solubilizable in water in order to obtain rapid preparation of the ready-to-use developer. The problem is resolved by the present invention, which concerns a stable concentrated solution for colour photographic development comprising benzyl alcohol which, when it is added to water, rapidly forms a homogeneous clear solution to be mixed with the other concentrates in order to obtain the ready-to-use developer. Another object of the invention concerns a kit for a colour developer comprising this concentrated solution, and a photographic processing method using the developer obtained from this kit. According to the present invention, it is now possible to obtain a concentrated solution for colour photographic development having reduced water and benzyl alcohol contents and a particular mixture of solvents while maintaining the photographic activity of the developer. This concentrate has a reduced COD and a reduced solubilising time in water. The time required for solubilising in water this concentrate is also referred to in the art as the "miscibility time". The concentrated solution for colour development according to the invention comprises a quantity of benzyl alcohol from 25 to 35%, a quantity of water from 3 to 8%, a quantity of ethylene glycol from 10 to 20% and a quantity of diethylene glycol from 35 and 60%. The concentrated solution containing benzyl alcohol, water and the co-solvents ethylene glycol and/or diethylene glycol is referred to in the remainder of the description as "concentrate (A)". The percentages are, unless otherwise indicated, based on the total weight of the concentrate and the sum of the percentages does not exceed 100%. According to a preferred embodiment, in the concentrate (A) according to the invention, the quantity of benzyl alcohol is between 25 and 35%, the quantity of water is approximately 5 ± 1%, the quantity of ethylene glycol is between 13 and 17% and the quantity of diethylene glycol is between 43 and 55%. Benzyl alcohol is commonly used in photographic solutions as a permeability agent, that is to say it assists in particular the reaction between the oxidation product of the developer in aqueous phase and the coupler in non-aqueous phase. Ethylene glycol and diethylene glycol form part of many organic co-solvents known to aid solubilisation of organic compounds in water. According to the present invention, the choice of the particular organic co-solvents in specific proportions and the reduction in the quantity of water in concentrate (A) make it possible to reduce substantially the miscibility time of concentrate (A) in the quantity of water required to obtain the ready-to-use developer. Concentrate (A) of the invention may contain other compounds habitually used in photographic processing baths. For example, this concentrate may contain organic antioxidants such as amines (propylamine, propylenediamine, hydroxylamine and their derivatives, etc). It may also contain a solvent for silver halides such as DTOD (2,2-ethylene dithioethanol. A preferred concentrate (A) contains benzyl alcohol, ethylene glycol, diethylene glycol, at least one antioxidant, preferably hydroxylamine chlorhydrate, and at least one solvent for silver halides, preferable DTOD. The colour developer according to the invention is in the form of a kit consisting of three concentrated solutions in three separate containers: concentrate (A) as described above, which contains benzyl alcohol ; a concentrate (B) which contains the developer in aqueous solution, and a concentrate (C) which contains the alkaline compound or compounds in aqueous solution. These concentrates are mixed at the time of use either to prepare the developer or to prepare a renewal solution replenisher solution designed to maintain the efficacy of the developer during use. In the following description and the claims accompanying it, the term "developer" designates either the developer solution or the replenisher. The developing agents used in concentrate (B) are in general p-phenylenediamines, for example 2-amino-5-diethylaminotoluene (known as CD2), 4-amino-N-ethyl-N-(β-methanesulphoamidoethyl)-m-toluidine (CD3), 4-amino-3-methyl-N-ethyl-N-(β-hydroxyethyl)-aniline (CD4). CD2 is generally used in colour developers for colour positive films, CD3 is generally used in colour developers for colour reversible films and papers, and CD4 is generally used in developers for colour negative films. Concentrate (B) containing the p-phenylene diamine developing agent may contain other compounds such as, for example, antioxidants or surfactants. Within the framework of the invention, concentrate (B) is in the form of an aqueous solution. The antioxidants which may be used in concentrate (B) are for example sulphites, metabisulphites and bisulphites of alkali metals, sulphurated compounds capable of generating sulphite ions in aqueous solutions, ascorbic acid and its derivatives, etc. Concentrate (C) containing the alkaline compound or compounds is obtained from alkaline compounds such as sodium or potassium carbonate, borax, sodium or potassium hydroxide, or sodium metaborate in aqueous solution. This concentrate (C) generally contains sequestering agents and anti-liming agents such as aminopolycarboxylic acids, for example ethylenediaminetetracetic acid (EDTA), diethylenetriaminepentacetic acid (DTPA), isopropanoldiaminetetracetic acid (DPTA), aminopolyphosphonic acids, for example amino-N,N, dimethylenephosphonic acids, hexametaphosphate, Dequest® (2000, 2006, 2010, etc,) or Versenex 80®. Antiseptic compounds, anti-fogging agents, heat stabilisers, development activators such as thioether or oxothioether compounds and benzylamine may be added to these three concentrates. The colour developer of the present invention is obtained by mixing first of all concentrate (A) in water. When this mixture is homogeneous, concentrate (B) is introduced, and then concentrate (C), stirring after the introduction of each concentrate in order to obtain a homogeneous clear liquid. The pH of this developer is advantageously between 10.5 and 11.5. According to one embodiment, the colour developer is intended for the processing of reversible photographic products. This processing comprises a latent image silver development step (black and white development), a reversal step which consists of making the non-exposed residual silver halide grains developable by means of a fogging exposure or a chemical fogging, a fogged grain colour development step, a washing step, and a bleaching step followed by a fixing step. The silver development is effected in the presence of a reducing compound which enables the exposed silver halide grains to be transformed into metal silver. These compounds are described in paragraph XIX A of Research Disclosure of September 1994, Article 36544, hereinafter referred to as " Research Disclosure ", and may be chosen from amongst dihydroxybenzenes such as hydroquinone, 3-pyrazolidones, aminophenols, ascorbic acid, etc and mixtures of these. The reversal step may be effected by exposure to light, chemical step, for example by passing through a fogging bath containing a reducer, or by the introduction of the fogging agent into the colour developer. Fogging substances are for example stannous chloride, hydrazine and semi-carbazide salts, ethylenediamine, sodium borohydride, dimethylborane or thiourea dioxide. The colour development step makes it possible to obtain a colour image using a colour developer, such as the ones described in paragraph XIX A of Research Disclosure . During this step, reduction of the silver halide grains fogged during the reversal step is effected for example by means of p-phenylenediamine. The oxidised p-phenylenediamine then reacts with a dye-forming coupler present in the photographic emulsion layer in order to form a colour image. Bleaching of the photographic product is obtained by means of an oxidising compound which transforms the metallic silver into silver ions, such as the ones described in paragraph XX A of Research Disclosure . The oxidising compound can be chosen from amongst the alkali metal salts of a ferric complex of an aminocarboxylic acid, or persulphate compounds. The bleaching compounds habitually used are ferric complexes of nitrolotriacetic acid, ethylene diamine tetracetic acid, 1,3-propylenediamine tetraacetic acid, triethylenetriamine pentacetic acid, ortho-diaminocyclohexane tetracetic acid and ethyliminodiacetic acid. The fixing bath enables the silver halides to be totally transformed into water-soluble silver complexes, which are then eliminated from the layers of the photographic product by washing. The compounds used for fixing are described in paragraph XX B of Research Disclosure , for example thiosulphates such as ammonium thiosulphate or thiosulphates of alkali metals. The bleaching step and the fixing step may be replaced by a single bleaching/fixing step as described in paragraph XX C of Research Disclosure . The present invention is illustrated by the following examples. EXAMPLE 1 (Reference) : Ektachrome R-3® colour developer sold by Kodak. 50 ml of a concentrate (A) is prepared, containing the benzyl alcohol required for the preparation of a litre of a replenisher for a ready-to-use colour developer, by mixing the following compounds: CONCENTRATE A Benzyl alcohol 19.25 g 35% Diethylene glycol 15.0 g 27.3% Ethylene glycol - AgX solvent DTOD 0.3 g 0.54% HACl 5.6 g 10.2% Water 14.8 g 26.9% This concentrate (A) does not contain any ethylene glycol. To prepare a litre of replenisher for a ready-to-use colour developer, concentrate (A) is mixed with 3/4 of the quantity of water required to obtain 1 litre of the replenisher for a developer. The temperature of the water is between 30 and 35°C. This mixture is stirred until a clear solution is obtained (which determines the miscibility time). Concentrate (B) is then added, and then concentrate (C) of the Ektachrome-R3® photographic process sold by KODAK. The mixture is stirred after adding concentrate (B) and after adding concentrate (C). The quantity of water required to obtain 1 litre of replenisher for a developer is then added to this mixture. Concentrate (B) is an aqueous concentrate which contains the developer CD3, sodium metabisulphite as an antioxidant and a non-ionic surfactant. Concentrate (C) is an aqueous concentrate which contains potassium carbonate, potassium hydroxide, sodium sulphite, an anti-liming agent and a sequestering agent. The pH of the ready-to-use replenisher is adjusted to 10.45 by adding NaOH/KOH. For one litre of the replenisher the contribution of concentrate (A) to the COD is equal to 65 g for a total COD of approximately 75 g and the miscibility time of concentrate (A) in water is 110 seconds. In all the examples the times indicated are those measured for a volume of 2 litres under stirring obtained with a magnetic bar. EXAMPLE 2 (comparative) 35 ml of a concentrate (A) is prepared, containing the benzyl alcohol required for the preparation of a litre of replenisher for a ready-to-use colour developer, by mixing the following compounds: CONCENTRATE A Benzyl alcohol 13.5 g 34.8% Diethylene glycol 10.5 g 27.1% Ethylene glycol - AgX solvent DTOD 0.3 g 0.77% HACl 5.6 g 14.4% Water 8.9 g 22.9% Using this concentrate (A), a ready-to-use developer is prepared in accordance with the operating method described above. In this example, the developer has a lower COD than in the previous example since the quantity of concentrate (A), in particular the quantity of benzyl alcohol and diethylene glycol, is 30% less than that in the previous example. For 1 litre of replenisher, the contribution of concentrate (A) to the COD is 50 g for a total COD of approximately 60 g and the miscibility time of concentrate (A) in water is 110 seconds. These results show that, when the quantity of diethylene glycol and benzyl alcohol is reduced, the COD is reduced but without modifying the miscibility time of concentrate (A) in water. EXAMPLE 3 (Comparative) 50 ml of a concentrate (A) is prepared, containing the benzyl alcohol required for the preparation of a litre of ready-to-use colour developer, by mixing the following compounds: CONCENTRATE A Benzyl alcohol 13.5 g 23.9% Diethylene glycol 27.7 g 49.2% Ethylene glycol 6.7 g 11.9% AgX solvent DTOD 0.3 g 0.53% HACl 5.6 g 9.95% Water 2.5 g 4.4% Using this concentrate (A), a ready-to-use developer is prepared in accordance with the operating method described above, except that the pH is adjusted to 11.0 in order to preserve the photographic activity. For 1 litre of replenisher, the contribution of concentrate (A) to the COD is increased to 75 g for a total COD of approximately 85 g but the miscibility time of concentrate (A) in water is greatly reduced (20 seconds). These results show that the miscibility time of concentrate (A) in water is greatly reduced when a reduction in the quantity benzyl alcohol is combined with the use of a ternary diethylene glycol/ethylene glycol/water mixture in which the quantity of water is reduced and replaced with the two co-solvents. EXAMPLE 4 (Invention) 45 ml of a concentrate (A) is prepared, containing the benzyl alcohol required for the preparation of a litre of ready-to-use colour developer, by mixing the following compounds: Benzyl alcohol 13.5 g 26.5% Diethylene glycol 23.8 g 46.7% Ethylene glycol 5.4 g 10.6% AgX solvent DTOD 0.3 g 0.58% HACl 5.6 g 11.0% Water 2.3 g 4.5 Using this concentrate (A), a ready-to-use developer is prepared in accordance with the operating method of Example 3. For 1 litre of replenisher, the contribution of concentrate (A) to the COD is 70 g for a total COD of approximately 80 g, but the miscibility time of concentrate (A) in water is 30 seconds. These results show that, by reducing the quantities of ethylene glycol and diethylene glycol, provided that the quantity of water remains low compared with the quantities of ethylene glycol and diethylene glycol, it is possible to reduce the COD whilst preserving a reduced miscibility time compared with the concentrates (A) which contain similar quantities of water and diethylene glycol but not ethylene glycol. EXAMPLE 5 (Invention) 40 ml of a concentrate (A) is prepared, containing the benzyl alcohol required for the preparation of a litre of ready-to-use colour developer, by mixing the following compounds: CONCENTRATE A Benzyl alcohol 13.5 g 29.9% Diethylene glycol 17.0 g 37.7% Ethylene glycol 6.7 g 14.8% AgX solvent DTOD 0.3 g 0.67% HACl 5.6 g 12.1% Water 2.0 g 4.3% Using this concentrate (A), a ready-to-use developer according to the operating method of Example 3 is prepared. For 1 litre of replenisher, the contribution of concentrate (A) to the COD is 60 g and the miscibility time of concentrate (A) in water is reduced to 50 seconds. These results show that it is possible to obtain a COD as low as that of reference Example 1 whilst reducing the miscibility time. When a quantity of ethylene glycol below 13% is added, the hydroxylamine chloride no longer dissolves in concentrate (A). If the quantity of benzyl alcohol is below 25%, the photographic activity of the developer becomes too low. EXAMPLE 6 (comparative) 40 ml of a concentrate (A) is prepared, containing the benzyl alcohol required for the preparation of a litre of ready-to-use colour developer, by mixing the following compounds: CONCENTRATE A Benzyl alcohol 13.5 g 29.0% Diethylene glycol 25.0 g 53.9% Ethylene glycol - AgX solvent DTOD 0.3 g 0.6% HACl 5.6 g 12.0% Water 2.0 g 4.3% With such a concentrate (A), it is impossible to solubilise the hydroxylamine chloride in the concentrate. It would be possible to solubilise the hydroxylamine chloride in the concentrate (A) described above by replacing some of the diethylene glycol with water, but with a prolonging of the miscibility time (110 seconds). EXAMPLE 7 7.1: a Kodak EKTACHROME Radiance® reversible photographic product was exposed and developed in accordance with the standard operating method of the Ektachrome R3® process in which the developer was obtained from the concentrate (A) of reference Example 1. 7.2: a Kodak EKTACHROME Radiance® reversible photographic product was exposed and developed in accordance with the standard operating method of the Ektachrome R3® process in which the developer was obtained from the concentrate (A) of Example 5 according to the invention. The baths used in Examples 7.1 and 7.2 are seasoned baths in a processing machine (at least 3 replacements of the volume of the machine tank in accordance with the principle of replenishment processes. The sensitometric results are set out in Table 2. For each sample the following were measured: the sensitivity expressed by the value ER 80, which is defined by the equation ER = 100(1-Log H) and measured at a density of 0.80. In this equation (H) represents the exposure required for obtaining a density of 0.80, the densities in the toe region of curve TD80 and TD04 measured respectively at 0.8 and 0.4 Log H of point (ER80), the density in the shoulder of curve SD05 measured at 0.5 Log H of point (ER80), the minimum (Dmin) and maximum (Dmax) densities. The characteristics were measured in the red, green and blue regions. These results show that the efficacy of the developer of the present invention compared with the existing bath is preserved.

Claims: Concentrated solution for a colour photographic developer, comprising benzyl alcohol, water, ethylene glycol and diethylene glycol, characterised in that the quantity of benzyl alcohol is between 25 and 35%, the quantity of water is between 3 and 8%, the quantity of ethylene glycol is between 10 and 20% and the quantity of diethylene glycol is between 35 and 60% ; the percentages being based on the total weight of the concentrated solution and the sum of the percentages not exceeding 100%. Concentrated solution according to Claim 1, in which the quantity of benzyl alcohol is between 25 and 35%, the quantity of water is equal to 5 ± 1% by weight, the quantity of ethylene glycol is between 13 and 17% and the quantity of diethylene glycol is between 43 and 55%. Concentrated solution according to Claim 1, which also contains an antioxidant and a solvent for silver halides. Concentrated solution according to Claim 3, in which the antioxidant is hydroxylamine chlorhydrate and the solvent for silver halides is 2,2-ethylene dithioethanol (DTOD). Kit for a colour developer comprising a first concentrated solution containing benzyl alcohol as defined according to one of Claims 1 to 4, a second concentrated solution containing a developing agent in aqueous phase, and a third concentrated solution containing an alkaline solution. Kit according to Claim 5, in which the developing agent is a p-phenylenediamine. Colour developer comprising, in a mixture in water, a first concentrated solution containing benzyl alcohol, a second concentrated solution containing a developing agent in aqueous phase, a third concentrated solution containing an alkaline solution, the concentrated solution containing the benzyl alcohol being as defined according to any one of Claims 1 to 4. Colour developer according to Claim 7, in which the pH of the developer is adjusted to a value between 10.5 and 11.5. Development method with reversal step, which consists of processing an exposed silver halide photographic product with the following steps: (1) a step consisting of the silver development of the latent image, (2) a reversal step which consists of making the non-exposed residual silver halide grains developable by exposure to light or by chemical fogging, (3) a step consisting of the colour development of the fogged grains, (4) a bleaching step followed (5) by a fixing step, characterised in that the colour development step (3) is used with the developer as defined according to either one of Claims 7 or 8.

Inventors: MASSON JEAN-PIERRE RAYMOND MAR, MASSON, JEAN-PIERRE RAYMOND MARCEL
Applicants: EASTMAN KODAK CO, EASTMAN KODAK COMPANY
Application year: 1996
Main classification: G03C5
IPC codes: G03C7, G03C5