EP0044812A2 - Process for the formation of masked positive colour images according to the silver dye-bleaching process, and the silver dye-bleaching material used in this process - Google Patents

Abstract

Preparation of masked positive color images by the silver color bleaching process by exposure of a photographic material for the silver color bleaching process, silver development, color bleaching, silver bleaching and fixation, whereby the silver bleaching can optionally be carried out simultaneously with the color equation and / or the fixation in a single processing bath. A photographic material is used which a) in at least one layer at least one first dye, of which at least one undesirable secondary color density is to be compensated, b) in layer (s) a) and / or in one of these layers Adjacent layer (each) of an iodide-containing silver halide emulsion assigned to this (these) dye (s), c) in at least one further layer at least one second dye, the main color density of which is to be compensated for the secondary color density (s) of the first Dye (s) corresponds to, d) in the layer (s) c) and / or in a layer adjacent to this (these) one iodide-free or assigned to this (these) dye (s) or in comparison to those under b) mentioned emulsions low-iodide silver halide emulsion, and e) in the layer (s) c) and / or in at least one further layer which is adjacent to the layer (s) c) and which of one or more layers a ) by mind at least one intermediate layer is separated, contains an iodide-free or low-iodide core-shell emulsion, the particles of which consist of a surface-veiled silver halide core and an unveiled silver halide shell enveloping it, this emulsion being able to develop spontaneously up to the maximum density through the action of a developer, and possibly a development retardant contains. The development speed of the core-shell emulsion and thus the masking effect can also be influenced by the shell thickness of the core-shell particles and by the sulfite content of the developer. Development takes place in a developer solution that contains no silver complexing agents.

Description

The present invention relates to a method for producing masked positive color images by the silver color bleaching method and the silver color bleaching material used in this method.

Photographic processes for producing colored images or for reproducing colored templates practically work exclusively on the subtractive principle. In general, three layers lying on top of one another are used on a transparent or opaque support, each of which contains a partial image in the subtractive colors teal, purple and yellow. It is thus possible to reproduce all color tones within the color space determined by the three primary colors. With a suitable choice of the image dyes, the colors occurring in nature or original can be satisfactorily reproduced with regard to tonal value and saturation. A prerequisite for this is a favorable mutual coordination within the triple dye and a high saturation of the individual primary colors.

Under practical conditions, however, there is a difficulty that cannot be easily overcome with simple photographic means: the dyes that are available for the reproduction of the three primary colors cyan, purple and yellow all show in addition to the desired absorption one of the three complementary main colors red, green or blue also has at least one further, albeit weaker absorption region in a spectral region assigned to the two other primary colors. This so-called secondary color density does not in itself prevent the reproduction of all color and brightness occurring within the color space values; however, it has the consequence that a change in the color density within a color layer, as can be achieved by known photographic processes with the aid of a correspondingly sensitized silver halide emulsion, affects both the main color density and the secondary color density. This results in undesirable color shifts and saturation losses, which significantly disturb the color fidelity when reproducing a template.

Secondary color densities are basically present in all three subtractive primary colors: yellow (main absorption in blue) in red and green, purple (main absorption in green) in red and blue and blue-green (main absorption in red) in green and blue. The secondary color densities of the purple dyes in blue and red, and also the secondary color density of the cyan dye in blue, are particularly strong and therefore disturbing. The secondary color density of the cyan dye in green is somewhat less disturbing, and to a lesser extent that of the yellow dye in red and green. As a result, the reproduction of pure blues and reds in photographic color materials is always associated with difficulties.

There has been no lack of attempts to remedy or to alleviate this fundamental error in the photographic color materials in various ways. Since no cyan, purple and yellow dyes could be found without disturbing secondary color densities, the goal had to be achieved in a roundabout way. One of the methods known as masking is based on compensating for the undesired secondary color density of a dye in additional layers with opposite gradation in such a way that, regardless of the respective main color density, the sum of the secondary color densities in the layer to be masked and the mask layer remains constant. Consistently applied to all six secondary color densities, this process means that pure white tones (absence of any color density) can no longer be achieved, but in the best case neutral gray tones. The method is therefore primarily suitable for the production of color negatives or color separations in reproduction processes, ie processes in which the disadvantage mentioned can in turn be compensated for in the subsequent copying or reproduction stage.

In the production of subtractive positive images using the silver color bleaching process, e.g. in accordance with U.S. Patent Nos. 2,387,754 and 2,193,931 masking techniques.

It is known from US Pat. No. 2,673,800 and German Auslegeschrift 1 181 055 that negative color images can be obtained by the silver color bleaching process with simultaneous use of silver complex diffusion. In these processes, the structure of the corresponding silver image is controlled by physical "image-wise development by bromide ion diffusion from a silver bromide emulsion present in a neighboring layer. A process for producing masked images based on the silver color bleaching process based on a similar effect, namely the diffusion of iodide ions, is based on a similar effect German publication 2 547 720. According to this method, a material is used in which there is one between a first layer with a dye whose undesired secondary color density is to be corrected and a second dye whose main color density corresponds to the secondary color density of the first dye A layer with development nuclei is arranged, the first dye being associated with an iodide-containing silver halide emulsion and the second dye with an iodide-free or low-iodide silver halide halide solvent, for example thiosulfate, may be present. The iodide-free emulsion assigned to the second dye forms a soluble complex from the unexposed and undevelopable silver halide, which is reduced to metallic silver at the germs of the intermediate layer. If the silver halide emulsion assigned to the first dye is now exposed, iodide ions form at the image points in the subsequent development, which also migrate into the seed layer and prevent silver accumulation from the complex at the relevant points. A silver image is formed in the seed layer, which is opposite to the silver image belonging to the first dye. This is used in the subsequent bleaching process to bleach the second dye, which creates the desired masking effect. A further development of this method is described in German Offenlegungsschrift 2,831,814. To reinforce the masking effect, a very insensitive emulsion and, if necessary, a stabilizer or development retardant are added to the germ layer. The reaction mechanism in the creation of the mask image remains the same; however, the insensitive silver halide emulsion in the seed layer acts as an additional silver supplier that also reacts to the immigrating iodide ions.

The methods described in the latter two patent publications are therefore based on the formation of an opposing silver image by physical development on existing germs, a soluble silver complex providing the silver necessary for the construction of the image. Both methods have proven to be valuable for producing masked images using the silver color bleaching process. However, they still have certain disadvantages associated with the formation and accumulation of soluble silver complexes in the thiosulfate-containing developer solution. For example, it has long been known from the practice of complex diffusion processes that such developer solutions become cloudy over time and ultimately tend to separate out silver sludge. This will contaminate the vessels, the rollers used in developing machines, and ultimately the photographic material itself. It is possible to prevent this sludge separation by adding so-called anti-sludge-forming agents such as certain mercaptans or organic disulfides at least for a certain time, but this means an additional costly effort. It has also been shown that the presence of only small amounts of thiosulfate occurs in the presence Silver images are harder to bleach and therefore require the use of special bleach accelerators.

It is an object of the present invention to provide a new process for producing masked positive color images using the silver color bleaching process, which largely overcomes these disadvantages which still exist.

It has been found that a masking effect, without the need for silver complex diffusion and the presence of the disruptive thiosulfate in the developer solution, can be achieved if _m of photographic materials are used for the silver color bleaching process, which instead of the seed layer (DE-OS 2 547 720, 2 831 814) contain a layer with a pre-veiled silver halide emulsion which develops spontaneously to practically maximum density during development. The spontaneous development of such an emulsion, provided that it is itself iodide-free or low in iodide, can be influenced by immigrating iodide ions in a manner similar to that known from the physical development of silver complexes on silver nuclei. In contrast to the known methods, this is not a physical, but a normal chemical development, ie the silver attached to the development seed does not come from the developer solution or the silver complex dissolved therein, but directly from the crystal that contains the latent image seed contains. In order to be able to control the development by immigrating iodide ions in this case as well, it is necessary to adapt the beginning and the speed of the development to the diffusion rate of the iodide ions. This can be achieved either by a preferably substantive development inhibitor present in the layer, by a diffusion-inhibiting shell surrounding the veiled silver halide crystal or by a combination of both measures.

Silver halide emulsions, the veiled silver halide crystals of which are surrounded by a diffusion-inhibiting shell, can be produced in a particularly simple manner using the known core-shell technique.

Such emulsions are particularly suitable for use in a masking layer of a photographic material for the silver color bleaching process.

• a) in mindestens einer Schicht mindestens einen ersten Farbstoff, von welchem mindestens eine unerwünschte Nebenfarbdichte kompensiert werden soll,
• b) in der (den) Schicht(en) a) und/oder in einer zu dieser Schicht benachbarten Schicht (je) eine diesem (diesen) Farbstoff(en) zugeordnete jodidhaltige Silberhalogenidemulsion,
• c) in mindestens einer weiteren Schicht mindestens (je) einen zweiten Farbstoff, dessen Hauptfarbdichte der (den) zu kompensierenden Nebenfarbdichte(n) des (der) ersten Farbstoff(e) entspricht,
• d) in der (den) Schicht(en) c) und/oder in einer zu dieser (diesen) benachbarten Schicht eine diesem (diesen) Farbstoff(en) zugeordnete jodidfreie oder im Vergleich zu den unter b) erwähnten Emulsionen jodidarme Silberhalogenidemulsion, und
• e) in der (den) Schicht(en) c) und/oder in mindestens einer weiteren Schicht, welche der (den) Schicht(en) c) benachbart ist, und welche von einer oder mehreren Schichten a) durch mindestens eine Zwischenschicht getrennt ist, eine jodidfreie oder jodidarme Core-shell-Emulsion, deren Partikel aus einem oberflächenverschleierten Silberhalogenidkern und einer diesen umhüllenden un-verschleierten Silberhalogenidschale bestehen, wobei sich diese Emulsion durch Einwirkung eines Entwicklers spontan bis zur Maximaldichte entwickeln lässt, und gegebenenfalls einen Entwicklungsverzögerer enthält,

und dass die Entwicklung in einer von Silberkomplexbildnern freien Entwicklerlösung erfolgt.The present invention thus relates to a process for producing masked positive color images by the silver color bleaching process by exposure of a photographic material for the silver color bleaching process, silver development, color bleaching, silver bleaching and fixing, the silver bleaching optionally together with the color bleaching and / or the fixation in a single processing bath can be carried out simultaneously, characterized in that the photographic material

• a) in at least one layer at least one first dye, of which at least one undesired secondary color density is to be compensated,
• b) in the layer (s) a) and / or in a layer adjacent to this layer (each) an iodide-containing silver halide emulsion assigned to this (these) dye (s),
• c) in at least one further layer at least one second dye, the main color density of which corresponds to the secondary color density (s) to be compensated for, of the first dye (s),
• d) in the layer (s) c) and / or in a layer adjacent to this (these) a dye (s) associated with this iodide-free or low-iodide silver halide emulsion compared to the emulsions mentioned under b), and
• e) in the layer (s) c) and / or in at least one further layer which is adjacent to the layer (s) c) and which is separated from one or more layers a) by at least one intermediate layer is a iodide-free or low-iodide core-shell emulsion, the particles of which consist of a surface-veiled silver halide core and an enveloped, un-veiled silver halide shell, this emulsion being able to develop spontaneously up to the maximum density under the action of a developer and possibly containing a development retardant,

and that the development takes place in a developer solution free of silver complexing agents.

The present invention further relates to the new photographic silver color bleaching material for carrying out the process according to the invention, the use of the material for producing positive color images and the positive color images produced.

The production of core-shell emulsions has been described, inter alia, in German Offenlegungsschriften 1 597 488, 2 211 771 and 2 801 127, and in Research Disclosure 16 345 (1977). All customary silver halides can be used as silver halide crystals to be coated, that is to say silver chloride, silver bromide and silver iodide or mixed crystals of two or all three components. In order to ensure uniform growth of the shell, it is advantageous if the silver halide crystals are as large as possible. Therefore, primarily monodisperse emulsions are used, as are known methods, e.g. can be made in cubic or octahedral crystal costume. The production of monodisperse emulsions is e.g. in German Offenlegungsschrift 1 904 148.

The silver halide shell to be applied can consist of the same or a different silver halide as the core. That too Radius ratio of the core to the shell can be varied within wide limits, with the present invention primarily considering particles whose shell thickness is relatively small in relation to the core diameter.

• a) das Auffällen von weiterem Silberhalogenid durch gleichzeitige Zugabe von löslichem Silbersalz und einem löslichen Halogenid, wobei die Fällungsbedingungen (Konzentration, Geschwindigkeit) so gewählt werden, dass keine neuen Kristallisationskeime entstehen (z.B. deutsche Offenlegungsschrift 2 015 070).
• b) Zugabe einer feindispersen Silberhalogenidemulsion, deren Kristalle wesentlich kleiner sind als die zu umhüllenden Kristalle. Die feindispersen Kristalle verschwinden, indem wie bei der Ostwaldreifung um die gröberen Kristalle der Silberhalogenidemulsion eine Schale aus dem Material der zugefügten feindispersen Emulsion aufwächst (z.B. U.S. Patentschrift 3 206 313).
• c) durch Fällung während periodischem Wechsel des pAg-Wertes zwischen Silber- bzw. Halogenidüberschuss. Auf diese Art können Partikel mit mehrschichtigem-Aufbau erzeugt werden (z.B. U.S. Patentschrift 3 917 485).

There are three main methods of applying the shell to the core:

• a) the precipitation of further silver halide by the simultaneous addition of soluble silver salt and a soluble halide, the precipitation conditions (concentration, speed) being selected such that no new crystallization nuclei are formed (for example German Offenlegungsschrift 2,015,070).
• b) adding a finely dispersed silver halide emulsion, the crystals of which are significantly smaller than the crystals to be coated. The finely dispersed crystals vanish by, as in Ostwald ripening, growing around the coarser crystals of the silver halide emulsion a shell made from the material of the finely dispersed emulsion added (for example US Pat. No. 3,206,313).
• c) by precipitation during periodic change of the pAg value between excess silver or halide. In this way, particles with a multilayer structure can be produced (eg US Pat. No. 3,917,485).

The core-shell technique makes it possible to carry out the usual surface-influencing photographic operations on the silver halide crystals to be coated, e.g. Ripening, obscuring, sensitization or the addition of other substances such as stabilizers, development accelerators and retarders, and then to move the surface treated in this way by growing the shell inside the crystal [e.g. German Offenlegungsschrift 2 260 117 or E. Moisar and S. Wagner, Ber. Bunsengesellschaft 67, 356 (1963)].

It has been found that the selection of a suitable shell thickness around the veiled core of a core-shell particle is an excellent means of delaying the start of spontaneous development. A temporal coincidence can thus be achieved with the diffusion of the development-controlling iodide ions. Shell thicknesses between 50 and 100C Å, corresponding to about 7 to 140 silver halide lattice planes, preferably 100 to 250 Å, form a suitable range for the process according to the invention.

Another way of influencing the start of development of the core-veiled core-shell emulsions is to choose different concentrations of an ammonium or alkali metal sulfite in the developer solution. The kinetics of spontaneous development can be controlled within wide limits by means of the sulfite concentration (2 to 100 g per liter of developer solution).

The start and speed of the development process can also be influenced by the use of development-retarding substances. Such substances can be adsorbed on the veiled surface of the core before the shell grows.

Suitable development inhibitors and retarders are e.g. Benzotriazole, 2-mercaptobenzthiazole, N-methylmercaptotriazole, phenylmercaptotetrazole, triazolindolizine and their derivatives. An important condition here is that the solubility product of the silver salt formed from the development retarder is between that of the silver chloride and that of the silver iodide (see A.B. Cohen et al. In Photographic Sci. And Eng. 9, 96, (1965)).

In principle, all known development retarders that meet these conditions are suitable. However, preference is given to those compounds which can be embedded in the photographic layers in a diffusion-resistant manner. These are primarily compounds which are sparingly or practically insoluble in water and contain ballast groups. Suitable ones are, for example, 5-mercaptotetrazoles which are in the 1-position with preferably multinuclear aryl groups, such as naphthyl or diphenyl, optionally also with preferably higher alkyl groups (C ₃ -C ₁₈ ), or with aralkyl with at least 3, in particular 3 to 18 Carbon atoms in the alkyl part are substituted. Phenyl and naphthyl are suitable as aryl groups in the aralkyl radical.

• 5-Mercaptotetrazole, die in I-Stellung mit einer der folgenden Gruppen substituiert sind:
• n-Propyl, i-Propyl, n-Butyl, i-Butyl, t-Butyl, i-Amyl, i-Octyl, t-Octyl, Nonyl, Decyl, Lauryl, Myristyl, Palmityl, Stearyl, Ditert.- butyl-phenyl, Octylphenyl, Dodecylphenyl, Naphthyl, α oder β-Naphthyl oder Diphenyl. Nicht-diffusionsfeste Mercaptotetrazole ohne eigentliche Ballastgruppen können ebenfalls verwendet werden. Es muss aber in diesem Fall dafür gesorgt werden, dass der Entwicklungsverzögerer nicht in unerwünschter Richtung in eine Nachbarschicht diffundiert und z.B. die Entwicklung der Jodidionen liefernden Emulsionen ver- _zögert. Dies kann z.B. durch Einschaltung einer Zwischenschicht verhindert werden. Unter dieser Bedingung können auch z.B. mit folgenden Gruppen in 1-Stellung substituierte 5-Mercaptotetrazole verwendet werden: Phenyl, mit Hydroxyl, Halogen (Chlor, Brom) oder Niederalkyl (C₂-C₃) substituiertes Phenyl, Benzoesäure-methyl- oder äthylester, Methyl oder Aethyl. Im allgemeinen ist jedoch die Verwendung diffusionsfester Entwicklungsverzögerer vorzuziehen, weil dadurch der Schichtaufbau, insbesondere von solchen Materialien mit einer Vielzahl von Farb- und Em-ulsionsschiehten wesentlich vereinfacht werden kann. Die Entwicklungsverzögerer werden in Mengen von 1 bis 80 mMol, vorzugsweise von 3: bis 40 mMol pro Mol Silber der vorverschleierten Emulsion eingesetzt.

The following are particularly suitable as development retarders:

• 5-mercaptotetrazoles which are substituted in the I-position by one of the following groups:
• n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, i-amyl, i-octyl, t-octyl, nonyl, decyl, lauryl, myristyl, palmityl, stearyl, ditert.-butyl-phenyl , Octylphenyl, dodecylphenyl, naphthyl, α or β-naphthyl or diphenyl. Non-diffusion resistant mercaptotetrazoles without actual ballast groups can also be used. But it must be ensured in this case that the development retarder does not diffuse in an undesirable direction in an adjacent layer and as the development of iodide ions forming emulsions _such comparable ögert. This can be prevented, for example, by switching on an intermediate layer. Under this condition, 5-mercaptotetrazoles substituted with the following groups in the 1-position can also be used: phenyl, phenyl substituted with hydroxyl, halogen (chlorine, bromine) or lower alkyl (C ₂ -C ₃ ), methyl or ethyl benzoate, Methyl or ethyl. In general, however, the use of diffusion-resistant development retarders is preferred because the layer structure, in particular of such materials with a large number of color and emulsion layers, can be simplified considerably. The development retarders are used in amounts of 1 to 80 mmol, preferably 3: to 40 mmol, per mole of silver in the pre-fogged emulsion.

The core of a core-shell particle is masked using customary methods, e.g. by diffuse exposure or with the usual chemical means such as Thiourea dioxide, tin (2) chloride, hydrazine, boranes, formaldehyde sulfoxylates or gold salts (complexes). Since the veiled cores should not develop too quickly, silver bromide is preferably used for their production. Smaller proportions of up to about 20 mole percent silver chloride can be used; higher proportions of silver chloride can generally be developed too quickly. The proportion of silver iodide should only be small and should not exceed about 1.0 mol percent, since otherwise the influencing of development by immigrating iodide ions used in the process according to the invention would not be guaranteed.

If the surface of the core is still treated with a development retarder, this is advantageously done after the covering, but before the shell has grown.

• _l. Eine Gelatineschicht mit einem bleichbaren purpurfarbenen Azofarbstoff und grünsensiblisiertem Silberbromojodid.
• 2. Eine Gelatinezwischenschicht.
• 3. Eine vorverschleierte, spontan entwickelbare Core-shell-Emulsion, die einen Entwicklungsverzögerer enthält.
• 4. Eine Gelatineschicht mit einem bleichbaren gelben Azofarbstoff.

The processes taking place during the exposure and subsequent processing of the photographic material are explained with the aid of the following experimental arrangement (see FIG. 1) with two image dyes. A material is used for this, which is coated on a transparent support in the order from bottom to top as follows:.

• _l . A layer of gelatin with a bleachable purple azo dye and green-sensitized silver bromoiodide.
• 2. An intermediate layer of gelatin.
• 3. A pre-veiled, spontaneously developable core-shell emulsion that contains a development retardant.
• 4. A layer of gelatin with a bleachable yellow azo dye.

• (A) Unbelichtete Stellen (maximale Dichte des Kopierkeils) Die verschleierte Emulsion (3) entwickelt spontan zur Maximaldichte; die grünsensibilisierte Emulsion (1) bleibt unbelichtet und entwickelt nur bis zum Schleierniveau (A₂). Die der vorverschleierten Emulsion zugeordnete Gelbschicht (4) wird infolgedessen praktisch vollständig ausgebleicht, die Purpurschicht bleibt unangegriffen (A3).

If such a material is now exposed behind a gray wedge, subsequently developed and as usual (color and silver bleaching and fixation) processed with known treatment baths, the following processes take place (FIG. 1):

• (A) Unexposed areas (maximum density of the copy wedge) The veiled emulsion (3) spontaneously develops to the maximum density; the green-sensitized emulsion (1) remains unexposed and only develops up to the level of fog (A ₂ ). As a result, the yellow layer (4) assigned to the pre-veiled emulsion is practically completely bleached out, the purple layer remains unaffected (A3).

(B) Exposure to blue light

Since the yellow dye layer (4) is opaque to blue light, the green-sensitized emulsion layer (1) assigned to the purple layer is not exposed. The situation remains the same as in (A), ie the yellow layer (4) is bleached to the maximum, while the purple layer (1) remains intact (B ₃ ).

(C) Exposure to green or white light

The green-sensitive emulsion (1) is gradually exposed according to the wedge. During development (C2), iodide ions are produced in proportion to the exposure that diffuses into the pre-veiled emulsion layer (3) above and inhibit the spontaneous, exposure-independent development there. This creates a silver image in the opposite direction to the image in the lower emulsion layer (3). After the color and silver bleaching, a dye image remaining in the magenta layer (1) is in the same direction as the original, and in the yellow layer (4) an opposite image (C ₃ ).

The experiment described above serves to demonstrate the operation of the arrangement. In practice, the thickness and silver halide concentration of the pre-veiled emulsion layer will of course be set so that even in the maximum case, that is to say only when the lower emulsion layer is completely unexposed Part of the yellow layer is bleached away, which corresponds to the maximum secondary color density in blue of the unbleached purple layer.

In particular, use is also made of those photographic silver color bleaching materials in which the optical density of at least one image dye layer whose main color density corresponds to the secondary color density to be compensated for by another layer is increased by an amount which compensates for the loss of density after processing in the unexposed or blue-exposed state.

It is easy to see that a number of different masking effects can be achieved using the method described. Depending on the arrangement of the layers in the entire layer package, it is possible to mask one or two secondary color densities of one dye or one secondary color density of two dyes. The table (Fig. 2) shows the possible layer arrangements and combinations that lead to the different masking effects.

The scheme of the layer arrangement shows only the general case in which the dye and the associated emulsion sensitized in the complementary color of the basic color are in the same layer. Of course, these assembled components can also be distributed over two or even three different, adjacent layers. Such layer arrangements are e.g. in German Offenlegungsschriften 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.

A silver halide emulsion which is assigned to a dye layer is to be understood as an emulsion which, after exposure and development, provides a silver image which, in the subsequent color bleaching process, produces a counter-rotating dye image in a known manner in the assigned dye layer. Usually is the emulsion is spectrally sensitized in such a way that its maximum sensitivity corresponds to the absorption maximum of the assigned image dye (sensitive in the area of the complementary color of the image dye). A trichromatic material with which the entire visible color spectrum can be reproduced can then be produced in a known manner from three such dye-emulsion pairs. However, it is also possible to sensitize an emulsion assigned to a dye in another spectral range, as is customary, for example, in the infrared-sensitive false color films.

The sensitized silver halide emulsions assigned to the individual image dyes can be in the same layer as the associated image dyes or partially in a layer adjacent to the dye layer.

Adjacent layers are to be understood as layers which, due to their mutual position, promote the exchange of chemical species - molecules or ions. The term therefore also encompasses those layers which are not immediately adjacent but are optionally separated from one another by one or more thin layers which do not hinder diffusion.

Silver color bleaching materials for reproducing colored originals are generally trichromatic and contain three layers of color, one each in the subtractive primary colors yellow, purple and teal. To achieve special effects, materials with other colors or with only two layers of color can also be used. 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.

Bleachable dyes which are suitable for the production of dye-containing silver halide emulsions for the silver color bleaching material are described, for example, in the US Pat 3 454 402, 3 443 953, 3 804 630, 3 716 368, 3 877 949, 3 623 874, 3 931 142 and 4 051 123.

The material can also have additional layers in which at least one of the two components image dyes and silver halide is at least partially missing.

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, preferably 1 to 5 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:

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 water-insoluble, high molecular weight substances. the use of dispersion polymers made from α, β-unsaturated compounds such as acrylic esters, vinyl esters and ethers, vinyl chloride, vinylidene chloride and from other mixtures and copolymers.

Intermediate layers (barrier or separating layers) generally contain only pure solvent, for example gelatin and no dye which contributes to the formation of a color image, or no silver halide. If it is favorable for the overall layer structure, an existing emulsion layer or a filter layer can optionally also serve as a separation layer. In addition to the gelatin, the separating layer can contain further additives, such as substances that inhibit color bleaching, additional binders, such as, for example Contain water-soluble colloids or water-soluble dispersion polymers, as well as those customary for the construction of the other photographic layers: additives such as plasticizers, wetting agents, light stabilizers, filter dyes or hardening agents.

The emulsions can be applied to conventional supports for photographic recording material. Optionally, a mixture of several colloids can be used to disperse the silver halides.

The carrier can consist, for example, of pigmented cellulose triacetate or polyester. If it is made of paper felt, it must be coated on both sides or coated with polyethylene. The photosensitive layers are located on at least one side of this support, preferably in the known arrangement, i.e. at the bottom a red sensitized silver halide emulsion layer containing a blue-green azo dye, above that a green sensitized silver halide emulsion layer containing a purple azo dye and at the top a blue sensitive silver halide emulsion layer containing a yellow azo dye. The material can also contain sub-layers, intermediate layers, filter layers and protective layers. The total thickness of the layers in the dry state should generally not exceed 20 u.

The exposed silver color bleaching materials are processed in the usual way and include silver development, color bleaching, silver bleaching and fixation and subsequent washing or, if necessary, also between the individual steps (see e.g. DE-OS 2 448 443). Color bleaching and silver bleaching, and possibly also fixation, can be combined in a single treatment step.

Baths of customary composition can be used for silver development, for example those which use hydroquinone as developer substance, if desired additionally: l-phenyl-3-pyrazolidone, but not containing a silver complexing agent. In addition, it can be advantageous if the silver developing bath, as described in Swiss Patent 405 929, additionally contains a color bleaching catalyst.

Color bleaching baths - provided that the color bleaching is carried out as a separate treatment step - are advantageously those which, in addition to a strong acid, a water-soluble iodide and an antioxidant for the iodide, contain a color bleaching catalyst. Combined color and silver color bleaching baths usually contain a water-soluble oxidizing agent in addition to the specified components. Suitable color bleach catalysts are primarily diazine compounds, e.g. Derivatives of pyrazine, quinoxaline or phenazine. They are e.g. in German patent specifications 2 010 280, 2 144, 298 and 2 144.297, in French patent specification 1 489 460, in US patent specification 2: 270 118 and in DT-OS 2 448 442.

Strong acids are to be understood here as those which give the color bleach bath or the combined color and silver bleach bath a pH value of at most 2. So e.g. Hydrochloric acid, phosphoric acid and especially sulfuric acid or sulfamic acid can be used.

Alkali iodides such as potassium iodide or sodium iodide can be used as the water-soluble iodide.

Suitable oxidizing agents are nitroso compounds, e.g. p-nitrosodimethylaniline, nitro compounds such as e.g. aromatic nitro compounds and preferably aromatic mono- or dinitrobenzenesulfonic acids, e.g. m-nitrobenzenesulfonic acid.

Reductones or water-soluble mercapto compounds are advantageously used as antioxidants. Suitable reductones are in particular aci reductones with a 3-carbonyl-endiol (1,2) grouping such as reductin, triose reductone or preferably ascorbic acid.

Suitable mercapto compounds are those of the formula HSA (B), in which A is an aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic bridge member, B is a water-solubilizing radical and m is an integer of at most 4 (DE-OS 2 258 076, 2 423 819).

The silver fixing bath can be composed in a known and customary manner. Suitable as a fixative is e.g. Sodium thiosulfate or advantageously ammonium thiosulfate, if desired with additives such as sodium bisulfite, sodium metabisulfite and / or ammonium bisulfite and optionally complexing agents such as ethylenediaminetetraacetic acid.

All treatment baths can contain other common additives such as Contain hardening agents, wetting agents, optical brighteners or UV protection agents.

Unless otherwise stated, parts and percentages in the following examples relate to the weight.

• a) eine grünsensiblisierte Silberjodidbromidgelatineemulsionsschicht (97,5 Mol-% AgBr, 2,5 Mol-% AgJ) mit einem Silbergehalt von 0,2 g/m , welche 0,13 g/m des purpurfarbenen Azofarbstoffs der Formel
  
  enthält,
• b) eine Gelatinezwischenschicht mit einem Auftragsgewicht von 5 g/m² Gelatine,
• c) eine chemisch verschleierte und mit einem Entwicklungsverzögerer behandelte Core-shell-Emulsion mit einem Silbergehalt von 0,2 g/m². Der Schicht werden ausserdem 0,15 g/m² eines gelben bleichbaren Azofarbstoffes der Formel
  
  beigefügt.

Example 1: The following layers are cast in succession on a white-opaque support:

• a) a green-sensitive silver iodide bromide gelatin emulsion layer (97.5 mol% AgBr, 2.5 mol% AgJ) with a silver content of 0.2 g / m, which contains 0.13 g / m of the purple azo dye of the formula
  
  contains
• b) an intermediate gelatin layer with an application weight of 5 g / m ² gelatin,
• c) a chemically veiled core-shell emulsion treated with a development retarder with a silver content of 0.2 g / m ² . The layer also 0.15 g / m ^{2 of} a yellow bleachable azo dye of the formula
  
  attached.

• Eine kubisch-monodisperse Silberbromidemulsion (Kantenlänge der Kristalle 0,55 µ) wird während einer Stunde bei 60°C mit einer Lösung von 0,01% Natriumformaldehydsulfoxylat (HOCH₂SO₂Na·2H₂O) und 0,001% Goldchlorwasserstoffsäure (HAuCl₄) chemisch verschleiert. Durch Zugabe von 3 mg 1-Phenyl-5-mercaptotetrazol pro g Silber in Form einer 1 %-igen Lösung wird die so verschleierte Emulsion inhibiert. Danach wird auf die so behandelten Silberbromidkristalle eine Silberbromidschale von 0,02µ Dicke aufgefällt. Anstelle des l-Phenyl-5-mercapto- tetrazols können auch Entwicklungsverzögerer wie Benzotriazol, 2-Mercaptobenzthiazol oder Triazoindolizin verwendet werden.

The emulsion used in this layer is made as follows:

• A cubic monodisperse silver bromide emulsion (edge length of the crystals 0.55 µ) is mixed for one hour at 60 ° C with a solution of 0.01% sodium formaldehyde sulfoxylate (HOCH ₂ SO ₂ Na · 2H ₂ O) and 0.001% gold hydrochloric acid (HAuCl ₄ ) chemically veiled. The emulsion thus veiled is inhibited by adding 3 mg of 1-phenyl-5-mercaptotetrazole per g of silver in the form of a 1% solution. A silver bromide is then applied to the silver bromide crystals treated in this way shell of 0.02µ thickness is noticeable. Instead of l-phenyl-5-mercapto-tetrazole, development retarders such as benzotriazole, 2-mercaptobenzothiazole or triazoindolizine can also be used.

A sample of the material coated in this way is exposed to green light through a step wedge and processed as follows:

The processed copy then displays a gleichläufiges for exposure wedge positive magenta image, to which a counter decreasing _G is superimposed elbbild. The measured analytical color densities are shown in Table 1 below. They show the functioning of the material according to the invention.

Example 2: Similar to Example 1, a photographic material with three layers is produced on an opaque support:

a) A green-sensitized gelatin-silver iodobromide emulsion layer (95 mol% silver bromide, 5 mol% silver iodide) with a silver content of 0.2 g / m, which contains 0.13 g / m of the purple dye of the formula (101) ,

• b) eine Gelatinezwischenschicht mit einem Auftragsgewicht von 5 g/m²,
• c) eine chemisch verschleierte und mit einem Entwicklungsverzögerer behandelte Core-shell-Emulsion mit einem Silbergehalt von 0,2 g/m². Der Schicht werden ausserdem 0,15 g des bleichbaren gelben Azofarbstoffs der Formel (102) beigefügt.

2nd

• b) an intermediate gelatin layer with an application weight of 5 g / m ² ,
• c) a chemically veiled core-shell emulsion treated with a development retarder with a silver content of 0.2 g / m ² . 0.15 g of the bleachable yellow azo dye of the formula (102) is also added to the layer.

The core-shell emulsion is produced in the same way as in Example 1; the edge length of the cubic silver halide crystals is 0.9 µ; Two variants are selected for the production of the crystal bowls: A) shell thickness 0.01 µ, and B) shell thickness 0.02 µ.

• a) Entwicklung 3 Minuten bei 30°C Das Entwicklungsbad gleicht dem in Beispiel 1, enthält jedoch zusätzlich 40 g Natriumsulfit pro Liter
• b) Kombinierte Farb- und Silberbleichung 3 Minuten bei 30°C Zusammensetzung gleicht der in Beispiel 1
• c) Fixierbad 3 Minuten bei 30°C Zusammensetzung gleicht der in Beispiel 1

A sample of each variant is exposed to green light through a step wedge and processed as follows:

• a) Development for 3 minutes at 30 ° C. The development bath is similar to that in Example 1, but contains an additional 40 g of sodium sulfite per liter
• b) Combined color and silver bleaching for 3 minutes at 30 ° C. composition is the same as in Example 1
• c) Fixing bath for 3 minutes at 30 ° C composition is the same as in Example 1

As Table 2 below shows, the intermediate image effect, measured by the gradation of the opposite yellow image, can be strongly influenced by a suitable choice of the shell thickness of the veiled core-shell emulsion.

Example 3 This example relates to a photographic material according to the present invention in which hydroquinone is incorporated as a developer in a concentration of 1 g / m ² in the layers.

The material is produced in the manner described in Example 1, except that an emulsion of 95 mol% silver bromide and 5 mol% silver iodide is used for layer a).

After exposure through a step wedge with green light, an activation bath of the following composition is used instead of a developer:

Activation bath

The further processing, consisting of a combined color and silver bleaching, fixation and final rinsing, is carried out as in Example 1.

The processed material shows a purple image that runs in the same direction as the exposure wedge and an opposite increase in density of the yellow dye.

Beispiel 4: Dieses Beispiel illustriert die Entwicklungskinetik in der Core-shell-Emulsion in Abhängigkeit vom Sulfitgehalt des Entwicklers.The analysis yields the following sensitometric data in analytical densities:

Example 4: This example illustrates the development kinetics in the core-shell emulsion as a function of the sulfite content of the developer.

As in Example 2, a photographic material with three layers is produced on an opaque support, but using a core-shell emulsion whose cubic crystals have an edge length of 0.55 p and an AgBr shell thickness of 0.015 μ. 6 mg of l-phenyl-5-mercaptotetrazole per g of silver are used as development retardants.

4 samples of this material are exposed to green light through a step wedge and processed as follows:

b) Combined color and silver bleach bath for 3 minutes at 30 ° C composition is the same as in Example 1

c) Fixing bath for 3 minutes at 30 ° C composition is the same as in Example 1

As Table 4 below shows, the countergradation of the yellow image can be influenced by the sulfite content in the developer. The numerical values in the table mean analytical densities at the specified wavelength.

It can be seen from Table 4 that with increasing sulfite concentration the maximum density of the purple image increases somewhat, while at the same time the gradation of the opposite yellow image is significantly flattened.

• a) eine rotsensibilisierte Silberjodidbromidgelatineemulsionsschicht mit 97,4 Mol-% AgBr und 2,6 Mol-% AgJ und einem Silbergehalt von 0,17 g/m², welche 0,13 g/m² des Cyanfarbstoffs der Formel
  
  enthält,
• b) eine Gelatinezwischenschicht mit einem Auftragsgewicht von 1,52 g/m², welche 0,42 g/m² eines (blockierten) Hydrochinonderivates der Formel
  
  enthält,
• c) eine grünsensibilisierte Silberjodidbromidgelatineemulsionsschicht mit 95 Mol-% Silberbromid, 5 Mol-% Silberjodid und einem Silbergehalt von 0,22 g/m², welche 0,154 g/m² des Magentafarbstoffes der Formel (101) enthält,
• d) eine Gelbfilterschicht, welche 1,68 g/m² Gelatine, ₀,₀4 g_/m ² kolloidales Silber, 0,05 g/m² des Gelbfarbstoffes der Formel (102) und 0,72 g/m² des Hydrochinonderivats der Formel (104) enthält,
• e) eine chemisch verschleierte Core-shell-Emulsion mit einem Silbergehalt von 0,1 g/m² (die wie folgt hergestellt wird: eine kubisch-monodisperse Silberbromidemulsion(Kantenlänge der Kristalle 0,59 µ) wird während 1 Stunde bei 60°C mit einer Lösung von 0,01 % Formamidinsulfinsäure und 0,01 % Tetrachlorgoldsäure verschleiert und danach mit einer Silberbromidschale von 0,025 µ Dicke überzogen),
• f) eine blauempfindliche Silberbromidgelatineemulsionsschicht mit einem Silbergehalt von 0,36 g/m², welche 0,11 g/m² des Gelbfarbstoffes der Formel (102) enthält, und
• g) eine Gelatineschutzschicht mit einem Giessgewicht von 1,16 g/m².

Example 5: This example relates to the masking of the blue secondary color density of a magenta dye in photographic (tripack) material. The following layers are cast successively on a white opaque support:

• a) a red-sensitized silver iodide bromide gelatin emulsion layer with 97.4 mol% AgBr and 2.6 mol% AgJ and a silver content of 0.17 g / m ² , which 0.13 g / m ^{2 of} the cyan dye of the formula
  
  contains
• b) an intermediate gelatin layer with an application weight of 1.52 g / m ² , which is 0.42 g / m ^{2 of} a (blocked) hydroquinone derivative of the formula
  
  contains
• c) a green-sensitized silver iodide bromide gelatin emulsion layer with 95 mol% silver bromide, 5 mol% silver iodide and a silver content of 0.22 g / m ² , which contains 0.154 g / m ^{2 of} the magenta dye of the formula (101),
• d) a yellow filter layer containing 1.68 g / m ² of gelatin, _{0, 0} 4 g _{/ m} ² colloidal silver, 0.05 g / m ² of the yellow dye of formula (102) and 0.72 g / m ² of hydroquinone derivative of the formula (104) contains
• e) a chemically veiled core-shell emulsion with a silver content of 0.1 g / m ² (which is produced as follows: a cubic monodisperse silver bromide emulsion (edge length of the crystals 0.59 μ)) is stirred at 60 ° C. for 1 hour with a solution of 0.01% formamidine sulfinic acid and 0.01% tetrachloroauric acid and then coated with a silver bromide dish 0.025 µ thick),
• f) a blue-sensitive silver bromide gelatin emulsion layer with a silver content of 0.36 g / m ² , which contains 0.11 g / m ^{2 of} the yellow dye of the formula (102), and
• g) a protective gelatin layer with a casting weight of 1.16 g / m ² .

A sample of this material is exposed through a step wedge (A) polychromatic, (B) with blue and (C) with green light and processed as follows:

e) final watering

The analytical densities of the color wedges obtained are appropriate. The results are shown in Fig. 3 in the form of D / log E curves.

In the case of an advantageous intermediate image effect - for masking the blue secondary color density of the magenta dye - curve A (polychromatic exposure) deviates from curve B (blue exposure), i.e. With a larger original density range, a higher yellow density is obtained with polychromatic exposure than with blue exposure.

This intermediate image effect is also present with green exposure (curve C). The copy then shows a decrease in the magenta density parallel to the exposure wedge and an increasing yellow density in the opposite direction.

Claims (13)

_1st Process for the production of masked positive color images by the silver color bleaching process by exposure of a photographic material for the silver color bleaching process, silver development, color bleaching, silver bleaching and fixing, the silver bleaching optionally being able to be carried out simultaneously with the color bleaching and / or the fixing in a single processing bath, characterized in that that the photographic material a) in at least one layer at least one first dye, of which at least one undesired secondary color density is to be compensated, b) in the layer (s) a) and / or in a layer adjacent to this layer (each) an iodide-containing silver halide emulsion assigned to this (these) dye (s), c) in at least one further layer at least one second dye, the main color density of which corresponds to the secondary color density (s) to be compensated for, of the first dye (s), d) in the layer (s) c) and / or in a layer adjacent to this (these) a dye (s) associated with this iodide-free or low-iodide silver halide emulsion compared to the emulsions mentioned under b), and e) in the layer (s) c) and / or in at least one further layer which is adjacent to the layer (s) c and which is separated from one or more layers a) by at least one intermediate layer , a iodide-free or low-iodide core-shell emulsion, the particles of which consist of a surface-veiled silver halide core and an enveloped, unveiled silver halide shell, this emulsion spontaneously developing through the action of a developer Has maximum density developed, and possibly contains a development retardant, and that the development takes place in a developer solution free of silver complexing agents. 2. The method according to claim 1, characterized in that the core of a core-shell particle consists of silver bromide or silver chlorobromide with a content of at most 20 mol% of silver chloride and at most 1.0 mol% of silver iodide and before application of the shell by pre-exposure or by chemical treatment is disguised. 3. The method according to claims 1 and 2, characterized in that the shell of a core-veiled core-shell particle consists of an unveiled silver halide, its strength is between 50 and 1000 Å and it consists of the same or a different silver halide as the core. 4. The method according to claims 1 to 3, characterized in that after the fogging, but before applying the shell, the silver halide crystal is optionally treated with a development retarder. 5. The method according to claim 1, characterized in that in the photographic material between layer e), which contains the pre-veiled core-shell emulsion and layer i) containing an iodide-containing silver halide emulsion, at least one intermediate layer, which contains neither image dye nor silver halide , arranges. 6. The method according to claim 1, characterized in that the silver halide emulsions assigned to the image dyes have spectral sensitivities in the respective complementary color of the image dye. ₇ . A method according to claim 1, characterized in that the photographic material has additional layers in which at least one of the two components image dye and silver halide is at least partially missing. 8. The method according to claims 1 to 7, characterized in that the sensitized silver halide emulsions assigned to the individual image dyes are in the same layer as the associated image dyes or partially in a layer adjacent to the dye layer. 9. The method according to claims 1 to 8, characterized in that the silver iodide-containing emulsions 0 to 99.9 mol-Z silver chloride, 0 to 99.9 mol-Z silver bromide and 0.1 to 10, preferably 1 to 5 mol% Silver iodide included. 10. The method according to claims 1 to 9, characterized in that 2 to 100 g of an alkali metal or ammonium sulfite per liter of developer solution are used to control the development kinetics in the developer. ll. Photographic silver color bleaching material for producing masked positive color images, characterized in that it a) in at least one layer at least one first dye, of which at least one undesired secondary color density is to be compensated, b) in the layer (s) a) and / or in a layer adjacent to this layer (each) an iodide-containing silver halide emulsion assigned to this (these) dye (s), c) in at least one further layer at least one second dye, the main color density of which corresponds to the secondary color density (s) to be compensated for, of the first dye (s), d) in the layer (s) c) and / or in a layer adjacent to this (these) a dye (s) associated with this (this) iodide-free or low-iodide silver halide emulsion compared to the emulsion mentioned under b) and e) in the layer (s) c) and / or in at least one further layer which is adjacent to the layer (s) c) and which is separated from one or more layers a) by at least one intermediate layer is a iodide-free or low-iodide core-shell emulsion, the particles of which consist of a surface-veiled silver halide core and an enveloped, unveiled silver halide shell, this emulsion being able to develop spontaneously up to the maximum density by the action of a developer, and, if necessary, for further control of the development kinetics, contains a development retardant. 12. Use of the silver color photographic bleaching material according to claim 11 for the production of masked color photographic images. 13. The masked positive color images produced by the method according to one of claims 1 to 10.

Images