EP0286593A2 - Process for producing colour-positive masked images according to the silver dye-bleaching process - Google Patents

Abstract

Verfahren zur Herstellung maskierter positiver Farbbilder nach dem Silberfarbbleichverfahren unter Verwendung einer Entwicklerlösung, die 0,3 bis 1,0 Mol/l eines Bromids enthält.

Description

The present invention relates to a method for producing masked positive color images by the silver color bleaching method.

Such a method is already known from DE-A-25 47 720. This method is based on assigning a iodide-free or low-iodide silver halide emulsion in a silver color bleaching material with several color layers absorbing in different spectral ranges, the main color density of which corresponds to a secondary absorption to be corrected in another layer, and a layer with colloidal in its immediate vicinity arranges nuclei suitable for physical silver development, while at the same time those iodide-containing silver halide emulsions are assigned to those color layers whose undesired secondary absorption is to be masked. If such a system is treated with a developer which contains a silver halide complexing agent after appropriate image-wise exposure, an accumulation of silver takes place in the germ-containing layer adjacent to the first-mentioned layer by physical development, which in the following processing step of color bleaching by the DE -A-2 036 918, 2 132 836 and 2 132 835 described remote bleaching effect in the adjacent color layer causes additional color bleaching. With simultaneous exposure of the iodide containing emulsions assigned to the other layers of color, iodide ions are split off and migrate during silver development. In a manner known per se, these inhibit the physical development in the seed layer and there form a mask image opposite to the negative images formed in the iodide-containing emulsion layers. DE-A-2 547 720 has described in detail how this mask image controlled by several layers can be used to produce a number of different masking effects, and how the method for producing images with improved color rendering can be used.

This method can be further improved according to the teaching given in DE-A-2 831 814 by adding a relatively insensitive, iodide-free silver halide emulsion and, if appropriate, a development inhibitor to the layer which contains the colloidal nuclei.

It has already been mentioned that the development stage in the processes mentioned requires the presence of silver complexing agents. Salts of rhodanhydric acid and especially thiosulfuric acid, in particular sodium thiosulfate, are described as examples of such complexing agents.

However, developer solutions containing such complexing agents have the disadvantage that the soluble silver complexes which accumulate therein during the development of the exposed materials are not stable under the prevailing reducing conditions. These silver complexes are gradually reduced to metallic silver, which is deposited in the form of an annoying silver sludge. This silver sludge can adhere to the photographic materials to be developed and produce stains therein or settle on parts of the processing system, which is a great disadvantage, particularly in the case of continuously operating systems.

The object of the present invention is therefore to modify the development step described in the processes according to DE-A-2 547 720 and 2 831 814 in such a way that the formation of the silver sludge in the developer solution does not occur.

This object is achieved according to the invention in that bromides are used in high concentration as silver complexing agents in the developer solution.

It is very surprising that high concentrations of bromide in developer solutions lead to good results. So far you had to e.g. according to P. Glafkides, Photographic Chemistry, Vol. 1, page 60, 1958, Fountain Press, assume that concentrations of over 2 g of potassium bromide per liter of developer solution can cause noticeable delays in development, while at the same time the sensitivity of the emulsion to be developed decreases and the Contrast increases. These changes, both in the developer solution and in the treated emulsion, are of course undesirable. After L.F.A. Mason, in Photographic Processing Chemistry, page 37, Focal Press, 1975, the usual amount of potassium bromide in a developer solution is between 1 and 15 g / l, i.e. in the order of about 0.01 to 0.1 mol / l, while in the processes according to DE-A-2 547 720 and 2 831 814 the development is carried out in the presence of only 2 g / l potassium bromide (0.016 mol) .

Completely unexpectedly, however, it has now been found that, contrary to the teachings given in this prior art, far higher concentrations of up to 1 mol / l bromide can be used in developer solutions. As a result, stable developer solutions are obtained in a surprisingly simple manner, in which practically no silver deposits form even after prolonged use.

In comparison to the color images produced by the processes according to DE-A-2 547 720 and 2 831 814, those produced by the process according to the invention show no quality differences whatsoever. The masking effect is equally good in all cases.

• (a) dem Farbstoff, dessen unerwünschte Nebenfarbdichte kompensiert werden soll, eine mindestens teilweise aus Silberjodid be­stehende Silberhalogenidemulsionsschicht zugeordnet ist,
• (b) in einer weiteren Schicht, mindestens ein zweiter Farbstoff, dessen Hauptfarbdichte einer zu kompensierenden Nebenfarbdichte des ersten Farbstoffes entspricht, und eine von Jodidionen freie Silberhalogenidemulsion vorhanden sind,
• (c) eine weitere Schicht, welche der Schicht (b) benachbart ist, kolloidale Keime, die befähigt sind, aus löslichen Silber­komplexen metallisches Silber abzuscheiden, gegebenenfalls eine unempfindliche, nicht spektral sensibilisierte jodidfreie Silberhalogenidemulsion und gegebenenfalls einen Entwicklungs­inhibitor aufweist, und
• (d) zwischen den Schichten (a) und (c) sich eine Trennschicht befindet,

und wobei die Entwicklerlösung, mit der das Material behandelt wird, einen Komplexbildner enthält, welcher wasserlösliche und diffusions­fähige Silberkomplexe zu erzeugen vermag, dadurch gekennzeichnet, dass die Entwicklerlösung als Komplexbildner 0,3 bis 1,0 Mol/l eines Bromids enthält.The present invention thus relates to a process for the production of masked positive color images by the silver color bleaching process by exposure, development, color bleaching, silver bleaching and fixing and using a photographic material which contains at least two layers of an imagewise bleachable dye, the absorption maximum of which is one of each corresponds to three main colors red, green and blue, each dye being assigned a silver halide emulsion layer sensitive in a specific spectral region, and in this material

• (a) the dye, the undesired secondary color density of which is to be compensated, is assigned a silver halide emulsion layer which consists at least partially of silver iodide,
• (b) in a further layer, at least one second dye, the main color density of which corresponds to a secondary color density of the first dye to be compensated, and a silver halide emulsion free of iodide ions are present,
• (c) a further layer which is adjacent to layer (b), colloidal nuclei which are capable of depositing metallic silver from soluble silver complexes, optionally having an insensitive, non-spectrally sensitized iodide-free silver halide emulsion and optionally a development inhibitor, and
• (d) there is a separating layer between layers (a) and (c),

and wherein the developer solution with which the material is treated contains a complexing agent which is capable of producing water-soluble and diffusible silver complexes, characterized in that the developer solution contains 0.3 to 1.0 mol / l of a bromide as complexing agent.

The present invention furthermore relates to the developer solution which can be used in the process according to the invention and contains 0.3 to 1.0 mol / l of a bromide.

A substance which is assigned to another is understood here to mean those which belong to the same layer or two adjacent layers of a photographic silver color bleaching material and can interact with one another.

A number of different masking effects can be achieved using the described method. Depending on the arrangement of the layers in the entire layer package, it is possible that one or two secondary color densities are compensated for by an image dye or that one secondary color density is compensated for each of two image dyes.

In addition, e.g. layer arrangements are possible in which two iodide-free and one iodide-containing emulsion layer are combined with only one seed layer in such a way that only one secondary color density is compensated for from each color layer.

The spectral sensitivity of the silver halide emulsions preferably coincides with the main absorption maximum of the image dye to which they are assigned.

The general case is that in which the dye and the associated emulsion sensitized to the complementary color of the base color are in the same layer. However, these related components can also be at least partially in a layer adjacent to the dye layer.

One of the two components, image dye and sensitized silver halide emulsion, is then nonexistent or only partially present in these layers. Such layer arrangements are e.g. in DE-A-2 036 918, 2 132 835 and 2 132 836. They primarily serve to influence the relatively steep gradation in silver color bleaching materials or to increase the sensitivity. However, there is a restriction for the layer that contains the dye whose main color density corresponds to a secondary color density to be masked, as can already be seen from the description of the material above: The iodide-free silver halide emulsion belonging to this dye must be in the layer itself, i.e. as close as possible to the associated dye. However, it is possible to assign an additional emulsion layer to this latter dye in an adjacent layer, which in this case must be on the side of the dye layer opposite the germ-containing layer.

This additional emulsion layer is preferably also iodide-free or, if desired, can also contain a small amount of iodide ions, as a result of which the strength of the desired masking effect can be controlled. It is also possible to select spectral sensitivities other than those in the respective complementary color for the emulsions assigned to the individual dye layers. Such variants, suitable for the construction of so-called false color films, are e.g. in DE-A-2 132 835.

Silver color bleaching materials for reproducing colored originals are generally trichromatic and contain three layers of color, one each in the subtractive basic colors yellow, purple and teal. To achieve special effects, materials with other colors or with only two layers of color can also be used. in the Otherwise, the yellow, purple and cyan dyes known per se for this purpose can be used as image dyes in combination with the appropriate spectral sensitizers.

As light-sensitive silver halide emulsions, those are normally used which contain silver chloride, bromide or iodide or mixtures of these halides. Silver halide emulsions containing iodide normally contain between 0.1 and 10 mole percent silver iodide, the rest being silver chloride and / or bromide (e.g. 0 to 99.9 mole percent silver chloride and 0 to 99.9 mole percent silver bromide). Iodide-free silver halide emulsions preferably contain silver chloride, silver bromide or a silver chloride-silver bromide mixture. The iodide-free silver halide emulsions of the seed layer are not sensitized.

Gelatin is usually used as a protective colloid to prepare these emulsions; however, other water-soluble protective colloids such as polyvinyl alcohol or polyvinyl pyrrolidone, etc. can also be used; furthermore, part of the gelatin can be replaced by dispersions of non-water-soluble high-molecular substances. Common is e.g. the use of dispersion polymers of α, β-unsaturated compounds such as acrylic esters, vinyl esters and ethers, vinyl chloride, vinylidene chloride and other mixtures and copolymers.

Suitable colloidal nuclei for the deposition of metallic silver from silver complex compounds are, for example, colloidal hydrosols made of noble metals such as gold, silver or palladium, and also metal sulfides such as nickel or silver sulfide. Since these germs only have to be introduced in very small amounts, for example 1 mg to 200 mg per m², there is generally no risk of interference due to light absorption or scattering. However, those germs are preferably introduced into the layer which can be removed later, for example during the processing process. A hydrosol made of colloidal silver is particularly suitable for this, which can be effortlessly removed from the material again in the silver bleaching process can. The yellow silver hydrosol, which can be installed directly below the yellow dye layer in a yellow filter layer intended to absorb the blue radiation, is particularly suitable.

If metallic silver is deposited on the nuclei during development in the presence of a silver complexing agent, care must be taken that this metallic silver only acts in the desired direction during the subsequent color bleaching, i.e. on the color layer in which the dye is located together with the preferably iodide-free silver halide emulsion. It is therefore necessary to arrange a barrier or separating layer with respect to the other color layers whose secondary color density is to be masked and to which a silver halide emulsion containing iodide is assigned. Such a release layer generally consists of pure binder, e.g. Gelatin, and contains neither dye nor silver halide emulsion. If it is favorable for the overall layer structure, it can also e.g. an existing emulsion layer or a filter layer serve as a separation layer. In addition to the gelatin, the separating layer can contain other additives, such as substances that inhibit color bleaching, additional binders, such as contain water-soluble colloids or water-insoluble dispersion polymers, furthermore the additives customary for the construction of photographic layers, such as plasticizers, wetting agents, light stabilizers, filter dyes or curing agents.

Suitable development inhibitors are the sulfur-containing compounds known as antifoggants from one of the following classes: aliphatic sulfur compounds, mercaptothiazolium salts, mercaptotriazolium salts, mercaptotetraazaindenes, mercaptotetrazoles and optionally other compounds whose silver salts have a solubility between that of silver bromide and silver sulfide. These development inhibitors are bound to the particles of the unsensitized, iodide-free silver halide emulsion of layer (c) by diffusion-resistant adsorption.

The following compounds are particularly suitable as stabilizing agents: cysteine, 2-mercaptobenzothiazole, N-methylmercaptotriazole, phenylmercaptotetrazole, the latter being preferred.

A fine-grained emulsion consisting of silver chloride, silver bromide or silver chlorobromide can be used as the insensitive emulsion, which is generally not spectrally sensitized and is so insensitive that upon exposure, under which the light-sensitive emulsions of the other layers exposed to saturation, there are no developable grains that could interfere with image formation.

If a silver chlorobromide emulsion is used, the proportion of silver chloride is about 10-90 mol%, preferably 30-70 mol%, and the emulsion should preferably also be iodide-free.

The average grain diameter is generally approximately 0.05 μm to 1.2 μm, preferably 0.4 μm to 0.8 μm.

As already mentioned, the exposed silver halide layers are developed in the presence of bromide as a silver complexing agent, i.e. of an anion which is capable of forming water-soluble, diffusible complexes with silver ions. One liter of developer solution should contain between 0.3 and 1.0 mole of a bromide, preferably an inorganic bromide such as e.g. Contain sodium, potassium and ammonium bromide, the optimum amount depending on the nature of the material, the temperature of the developing bath and the desired exposure time can vary within the specified limits.

A particularly favorable concentration range is between 0.50 and 0.75 mol / l. Potassium bromide is preferably used.

The following examples illustrate the invention without restricting it.

Example 1:

A silver dye bleaching material suitable for making positive overlay copies of a positive original is made in the following manner:

• 1. eine Cyanschicht, die 0,155 g/m² des Cyanfarbstoffs der Formel
  
  1,9 g/m² Gelatine und 0,140 g Silber als rotempfindliche Silber­bromojodidemulsion mit 5,2 Mol-% Jodid enthält;
• 2. eine Emulsionsschicht, die 1,8 g/m² Gelatine und 0,275 g/m² Silber als rotempfindliche Silberbromojodidemulsion mit 5,2 Mol-% Jodid enthält;
• 3. eine Zwischenschicht aus 4,0 g/m² Gelatine;
• 4. eine Magentaschicht, die 0,183 g/m² des Magentafarbstoffs der Formel
  
  2,3 g/m² Gelatine und 0,175 g/m² Silber als grünempfindliche Silberbromojodidemulsion mit 5,2 Mol-% Jodid enthält;
• 5. eine Emulsionsschicht, die 2,0 g/m² Gelatine und 0,30 g/m² Silber als grünempfindliche Silberbromojodidemulsion mit 5,2 Mol-% Jodid enthält;
• 6. eine Maskierschicht, die 3,75 g/m² Gelatine und 2 mg/m² Kolloid­silber enthält;
• 7. eine Gelbschicht, die 0,150 g/m² des Gelbfarbstoffs der Formel
  
  3,0 g/m² Gelatine und 0,42 g Silber als blauempfindliche Silber­bromidemulsion enthält;
• 8. eine Emulsionsschicht, die 1,86 g/m² Gelatine und 0,39 g/m² Silber als blauempfindliche Silberbromidemulsion enthält; und
• 9. eine Schutzschicht aus 1,65 g/m² Gelatine.

The following layers are applied to a white opaque substrate in the order given:

• 1. a cyan layer, the 0.155 g / m² of the cyan dye of the formula
  
  Contains 1.9 g / m² gelatin and 0.140 g silver as a red-sensitive silver bromoiodide emulsion with 5.2 mol% iodide;
• 2. an emulsion layer containing 1.8 g / m² gelatin and 0.275 g / m² silver as red-sensitive silver bromoiodide emulsion with 5.2 mol% iodide;
• 3. an intermediate layer of 4.0 g / m² gelatin;
• 4. a magenta layer containing 0.183 g / m² of the magenta dye of the formula
  
  Contains 2.3 g / m² gelatin and 0.175 g / m² silver as a green-sensitive silver bromoiodide emulsion with 5.2 mol% iodide;
• 5. an emulsion layer containing 2.0 g / m² gelatin and 0.30 g / m² silver as green-sensitive silver bromoiodide emulsion with 5.2 mol% iodide;
• 6. a masking layer containing 3.75 g / m² of gelatin and 2 mg / m² of colloidal silver;
• 7. a yellow layer containing 0.150 g / m² of the yellow dye of the formula
  
  Contains 3.0 g / m² gelatin and 0.42 g silver as a blue-sensitive silver bromide emulsion;
• 8. an emulsion layer containing 1.86 g / m² of gelatin and 0.39 g / m² of silver as a blue-sensitive silver bromide emulsion; and
• 9. a protective layer of 1.65 g / m² gelatin.

The material also contains 0.48 g / m² of the curing agent 2-amino-4-hydroxy-6- (4-methylmorpholinium) -1,3,5-triazine tetrafluoroborate.

The material is exposed behind a gray wedge individually with an additive color filter blue, green or red, and in one case with all three filters (blue + green + red). The exposure times are set so that in the superposition (blue + green + red) a gray wedge is created which is as neutral as possible after processing.

Subsequently, processing is carried out according to the following regulation:
Development 3 minutes
Soak 1 minute
Silver and color bleaching 3 minutes
Soak 1 minute
Fixation 3 minutes
Soak 3 minutes
Drying

The temperature of the processing baths is 30 ° C.

The developer bath contains the following components per liter of solution:
Ethylene diamine tetraacetic acid sodium salt 4.0 g
Potassium sulfite 19.9 g
Sodium sulfite 38.0 g
Lithium sulfite 0.6 g
Hydroquinone 8.0 g
Phenidon Z 0.5 g
Potassium carbonate 19.5 g
Potassium bicarbonate 13.3 g
Benzotriazole 1.0 g
Potassium bromide 40.0 g (0.33 m)

The bleaching bath has the following composition per liter of solution:
Sulfuric acid (100%) 41.8 g
m-Nitrobenzenesulfonic acid sodium salt 7.5 g
Potassium iodide 9.0 g
2,3,4-trimethylquinoxaline 1.1 g
Bis-cyanoethyl-sulfoethyl-phosphine, potassium salt 2.9 g

The fixer contains per liter of solution:
Ammonium thiosulfate 200.0 g
Ammonium bisulfite 6.9 g
Ammonium sulfite 17.9 g

The color densities of the four wedges obtained (blue, green, red and gray wedges) are measured with a densitometer and from this the analytical color densities of the three color channels cyan (C) magenta (M) and yellow (Y) calculated. The color density curves of the various wedges thus obtained are recorded in FIGS. 1A to 1D, the density of the exposed gray wedge on the abscissa and the color densities in "Unity neutral normalized analytical densities" (UNNAD) on the ordinate, cf. AJSant, Phot.Sci.Eng. 14.356 (1970).

The masking effect can be expressed as the difference between the sensitivity of the yellow layer when exposed to gray (blue + green + red) and the sensitivity of the yellow layer when exposed to blue alone. It is 0.13 log. Units at UNNAD 0.4.

If the same material is processed in a developer that does not contain potassium bromide, the curves in Figures 2A to 2D are obtained. There is no masking effect. The sensitivity of the yellow layer to blue exposure is even 0.09 log. Units less sensitive (for UNNAD 0.4) than the sensitivity for gray exposure.

Example 2:

The material according to Example 1 is exposed and processed as described there, with the exception that the developer solution contains 60 g of potassium bromide per liter (0.50 m / l). The difference between the sensitivity of the yellow layer when exposed to gray and the sensitivity of the yellow layer when exposed to blue alone is 0.24 log. Units at UNNAD 0.4.

Example 3:

The material according to Example 1 is exposed and processed as described there, with the exception that the developer solution contains 80 g of potassium bromide per liter (0.67 m / l). The difference between the sensitivity of the yellow layer when exposed to gray and the sensitivity of the yellow layer when exposed to blue alone is 0.31 log. Units at UNNAD 0.4.

Example 4:

The material according to Example 1 is exposed and processed as described there, with the exception that the developer solution contains 100 g of potassium bromide per liter (0.84 m / l). The differences The limit between the sensitivity of the yellow layer when exposed to gray and the sensitivity of the yellow layer when exposed to blue alone is 0.25 log. Units at UNNAD 0.4.

Example 5:

If the material according to Example 1 is treated with the developer solutions described in DE-A-2 547 720 and 2 831 814 and additionally contain 2.0 g / l potassium bromide, the masking effect obtained is the same as in Example 3, but must accept all the disadvantages associated with the formation of silver sludge.

Claims (11)

1. Process for the production of masked positive color images by the silver color bleaching process by exposure, development, color bleaching, silver bleaching and fixing and using a photographic material which contains at least two layers of imagewise bleachable dye, the absorption maximum of which is one of the three main colors red, green and corresponds to blue, with each dye being assigned a silver halide emulsion layer sensitive in a specific spectral region, and in this material
a) the dye, the undesired secondary color density of which is to be compensated, is assigned a silver halide emulsion layer which consists at least partially of silver iodide,
b) in a further layer, at least one second dye, the main color density of which corresponds to a secondary color density of the first dye to be compensated, and a silver halide emulsion free of iodide ions,
c) a further layer, which is adjacent to layer (b), has colloidal nuclei which are capable of separating metallic silver from soluble silver complexes, optionally having an insensitive, non-spectrally sensitized iodide-free silver halide emulsion and optionally a development inhibitor, and
d) there is a separating layer between layers (a) and (c),
and wherein the developer solution with which the material is treated contains a complexing agent which is capable of producing water-soluble and diffusible silver complexes,
characterized in that the developer solution contains 0.3 to 1.0 mol / l of a bromide as complexing agent. 2. The method according to claim 1, characterized in that the spectral sensitivity of the silver halide emulsions coincides with the main absorption maximum of the image dye to which they are assigned. 3. The method according to claim 1, characterized in that a trichromatic material is used which contains a cyan, a purple and a yellow dye in each layer as the image dye. 4. The method according to claim 1, characterized in that the silver halide emulsions assigned to the individual image dyes are in the same layer as the associated image dyes or are at least partially in a layer adjacent to the dye layer. 5. The method according to claim 1, characterized in that one or two secondary color densities are compensated for by an image dye of a multilayer material. 6. The method according to claim 1, characterized in that a secondary color density is compensated by two image dyes of a multilayer material. 7. The method according to claim 1, characterized in that the silver iodide-containing emulsion layer contains 0.1 to 10 mol% of silver iodide. 8. The method according to claim 1, characterized in that the nuclei capable of separating metallic silver consist of colloidal silver. 9. The method according to claim 1, characterized in that between 0.3 and 1.0 mol / l potassium, sodium or ammonium bromide are used in the developer solution. 10. The method according to claim 8, characterized in that between 0.50 and 0.75 mol / l potassium, sodium or ammonium bromide are used in the developer solution. 11. Suitable developer solution for carrying out the process according to one of claims 1 to 9, which contains 0.3 to 1.0 mol / l of a bromide.

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