EP0044812B1 - 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

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 work practically 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 basic colors of cyan, 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 values occurring within the color space; 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 those of the yellow dye in red and green. As a result, the reproduction of pure blue and red tones 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 without disturbing secondary color densities could be found so far, 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, however, this method means that pure white tones (absence of any color density) can no longer be achieved, but in the best case neutral gray tones. The process 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. For example, according to U.S. Patents 2,387,754 and 2,193,931 masking techniques have been used.

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 imagewise by physical development by bromide ion diffusion from a silver bromide emulsion present in a neighboring layer. On a similar effect, namely the diffusion of iodide ions, a method for producing masked images based on the silver color bleaching method is based, as described in German Ausleeschschrift 2 547 720. According to this method, a material is used in which a layer with development nuclei is arranged 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, the first Dye is an iodide-containing, while the second dye is assigned an iodide-free or low-iodide silver halide emulsion. When developing this material, a small amount of a silver halide solvent, e.g. thiosulfate, must be added to the rope. From the second “color atolfo additive iodide-trolone emulsion, the unexposed and undevelopable silver halide formed a soluble complex that reduced to the silver layer on the interlayer to metallic silver. If the silver halide emulsion assigned to the first dye is now exposed, iodide ions form in the subsequent development at the image locations, which likewise migrate into the germ layer and at the relevant locations prevent silver accumulation from the complex. 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 possibly 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 nuclei, 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 eventually tend to separate out silver sludge. This contaminates the vessels, the rollers used in developing machines and ultimately the photographic material itself. Although it is possible to separate this sludge by adding so-called anti-sludge agents such. B. to prevent certain mercaptans or organic disulfides at least for a certain time, but this means an additional costly effort. It has also been found that the silver images formed when even small amounts of thiosulfate are present are more difficult 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 photographic materials are used for the silver dye 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, i. H. 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 which contains the latent image seed. 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, und
• 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 enthält, dadurch gekennzeichnet, daß das photographische Material
• 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 unverschleierten 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 and 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), and
• d) in the layer (s) c) and / or in a layer adjacent to this (these) an iodide-free dye (s) assigned to them or in comparison to the emuls mentioned under b) ions containing low-iodide silver halide emulsion, characterized in that the photographic material
• 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 under the action of a developer and optionally containing a development retardant,

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

The present invention also relates to the new photographic silver color bleaching material for carrying out the process according to the invention.

The production of core-shell emulsions has been described, inter alia, in German Offenlegungsschriften 1 597488, 2211 771 and 2801 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 a uniform growth of the shell, it is advantageous if the silver halide crystals are as large as possible. It is therefore primarily used monodisperse emulsions, as known by known methods, for. B. can be made in cubic or octahedral crystal costume. The production of monodisperse emulsions is e.g. B. described in German Offenlegungsschrift 1 904148.

The silver halide shell to be applied can consist of the same or a different silver halide as the core. The radius ratio of the core to the shell can also be varied within wide limits, particles which have a shell thickness that is relatively small in relation to the core diameter being primarily suitable for the present invention.

• a) das Auffällen von weiterem Silberha!ogenid durch gleichzeitige Zugabe von löslichem Silbersalz und einem löslichen Halogenid, wobei die Fällun_%Zjbedingungen (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. Halogenid- überschuß. 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 simultaneous addition of soluble silver salt and a soluble halide, the precipitation _% conditions (concentration, speed) being selected such that no new crystallization nuclei arise (e.g. 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 disappear by growing a shell made of the material of the added finely dispersed emulsion as in the Ostwald ripening around the coarser crystals of the silver halide emulsion (for example BUS patent specification 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 (for example, BUS Patent 3,917,485).

The core-shell technique makes it possible to carry out the usual surface-influencing photographic operations, such as, for example, on the silver halide crystals to be coated. B. ripening, obscuring, sensitization or the addition of other substances such as stabilizers, development accelerators and retarders to carry out, and then to move the surface thus treated by growing the shell inside the crystal [z. B. German Offenlegungsschrift 2 260 117 or E. Moisar and S. Wagner, Ber. Bunsen Society 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 correspondence can thus be achieved with the diffusion of the development-controlling iodide ions. Shell thicknesses between 5 and 100 nm, corresponding to approximately 7 to 140 silver halide lattice planes, preferably 10 to 25 nm, 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. B. benzotriazole, 2-mercaptobenzothiazole, N-methyl mercaptotriazole, phenyl mercaptotetrazole, triazolinedolizine and their derivatives. An important condition 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 which meet these conditions are suitable fulfill. 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. As such, z. B. 5-Merpaptotetrazole, in the 1-position with preferably multinuclear aryl groups, such as. B. naphthyl or diphenyl, optionally also with preferably higher alkyl groups (C ₃ -C ₁₈ ), or with aralkyl having at least 3, in particular 3 to 18 carbon atoms in the alkyl part. Phenyl and naphthyl are suitable as aryl groups in the aralkyl radical.

• 5-Mercaptotetrazole, die in 1-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 ,8-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 verzögert. 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 Äthyl. Im allgemeinen ist jedoch die Verwendung diffusionsfester Entwicklungsverzögerer vorzuziehen, weil dadurch der Schichtaufbau, insbesondere von solchen Materialien mit einer Vielzahl von Farb- und Emulsionsschichten 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.

As development retarders such. B. Particularly suitable:

• 5-mercaptotetrazoles which are substituted in the 1-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, 8-naphthyl or diphenyl. Non-diffusion resistant mercaptotetrazoles without actual ballast groups can also be used. In this case, however, it must be ensured that the development retardant does not diffuse in an undesirable direction into a neighboring layer and z. B. delayed the development of the emulsions providing iodide ions. This can e.g. B. can be prevented by switching on an intermediate layer. Under this condition, z. B. with the following groups in the 1-position substituted 5-mercaptotetrazoles: phenyl, with hydroxyl, halogen (chlorine, bromine) or lower alkyl (C ₂ -C ₃ ) substituted phenyl, 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 significantly simplified. The development retarders are used in amounts of 1 to 80 mmol, preferably 3 to 40 mmol, per mol of silver in the pre-fogged emulsion.

The core of a core-shell particle is obscured by conventional methods, e.g. B. by diffuse exposure or with the usual chemical agents such. B. 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.

• 1. Eine Gelatineschicht mit einem bleichbaren purpurfarbenen Azofarbstoff und grünsensibilisiertem 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:

• 1. A gelatin layer 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.

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

(A) Unexposed areas (maximum density of the wedge)

The veiled emulsion (3) spontaneously develops to maximum density; the green-sensitized emulsion (1) remains unexposed and only develops up to the haze level (A _z ). As a result, the yellow layer (4) assigned to the pre-veiled emulsion is practically completely bleached out, the purple layer remains unaffected (A ₃ ).

(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 under (A), i. H. the yellow layer (4) is bleached to a maximum, while the purple layer (1) remains intact (Ba).

(C) Exposure to green or white light

The green-sensitive emulsion (1) is gradually exposed according to the wedge. Development (C ₂ ) produces iodide ions proportional to the exposure, which diffuse into the pre-veiled emulsion layer (3) above and inhibit 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, of course, the thickness and silver halide concentration of the pre-fogged emulsion layer will be adjusted so that even at maximum, i.e. H. in the case of a completely unexposed lower emulsion layer, only that part of the yellow layer which corresponds to the maximum secondary color density in blue of the unbleached purple layer is bleached away.

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. B. have been described in German CffenIlegungsschriften 2,036,918, 2,132,835 and 2,132,836. They are used primarily to influence the relatively steep gradation in silver color bleaching materials or to increase 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, the emulsion is spectrally sensitized so that its maximum sensitivity corresponds to the absorption maximum of the assigned image dye (is 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 the case, for example, in the B. is common in 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 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 preparation of dye-containing silver halide emulsions for the silver color bleaching material are described, for example, in US Pat. Nos. 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 consists of silver chloride and / or bromide (e.g. 0 to 99.9 mole percent silver chloride and 0 to 99.9 mole percent silver bromide). Contain iodide-free silver halide emulsions preferably 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 non-water-soluble high-molecular substances. Common is z. B. the use of dispersion polymers from aß-unsaturated compounds such as acrylic acid esters, vinyl esters and vinyl ethers, vinyl chloride, vinylidene chloride and from other mixtures and copolymers.

Intermediate layers (barrier or separating layers) generally contain only pure binder, e.g. B. gelatin and no dye that 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 also contain other additives, such as substances which inhibit color bleaching, additional binders, such as, for example. B. contain water-soluble colloids or water-soluble dispersion polymers, also the usual additives for the construction of the other photographic layers such as plasticizers, wetting agents, light stabilizers, filter dyes or curing 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 light-sensitive layers are located on at least one side of this support, preferably in the known arrangement, i. H. a red sensitized silver halide emulsion layer containing a blue-green azo dye, a green sensitized silver halide emulsion layer containing a purple azo dye and 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 when dry should not exceed 20 µm.

The exposed silver color bleaching materials are processed in the customary manner and include silver development, color bleaching, silver bleaching and fixation and subsequent rinsing or, if appropriate, also rinsing (see, for example, DE-OS 2 448 443). Color bleaching and silver bleaching, and possibly also fixation, can be combined in a single treatment step.

Baths of conventional composition can be used for silver development, e.g. B. those that contain hydroquinone as the developer, if desired additionally 1-phenyl-3-pyrazolidone, but no silver complexing agent. It may also 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 bleaching catalysts are primarily diazine compounds, e.g. B. derivatives of pyrazine, quinoxaline or phenazine. You are e.g. B. in German patent application 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 it can. As 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, such as. B. p-nitrosodimethylaniline, nitro compounds such as. B. aromatic nitro compounds and preferably aromatic mono- or dinitrobenzenesulfonic acids, e.g. B. 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) _m , 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, for. B. 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. B. contain hardening agents, wetting agents, optical brighteners or UV protection agents.

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

example 1

• a) eine grünsensibilisierte Silberjodidbromidgelatineemulsionsschicht (97,5 Mol-% AgBr, 2,5 Mol-% AgJ) mit einem Silbergehalt von 0,2 g/m², welche 0,13 g/m² 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
  

The following layers are poured onto a white opaque support:

• a) a green-sensitized silver iodide bromide gelatin emulsion layer (97.5 mol% AgBr, 2.5 mol% AgJ) with a silver content of 0.2 g / m ² , which contains 0.13 g / m ^{2 of} the purple-colored 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 contains 0.15 g / m ^{2 of} a yellow bleachable azo dye of the formula
  

• Eine kubisch-monodisperse Silberbromidemulsion (Kantenlänge der Kristalle 0,55 µm) wird während einer Stunde bei 60°C mit einer Lösung von 0,01% Natriumformaldehydsulfoxylat (HOCH2S02Na 2 H₂0) und 0,001% Goldchlorwasserstoffsäure (HAuC1₄) 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 0,02 µm Dicke aufgefüllt. Anstelle des 1-Phenyl-5-mercaptotetrazols 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 µm) is chemically veiled for one hour at 60 ° C with a solution of 0.01% sodium formaldehyde sulfoxylate (HOCH2S02Na 2 H ₂ 0) and 0.001% gold hydrochloric acid (HAuC1 ₄ ). The emulsion so veiled is inhibited by adding 3 mg of 1-phenyl-5-mercaptotetrazole per g of silver in the form of a 1% solution. Then a silver bromide shell 0.02 µm thick is filled onto the silver bromide crystals treated in this way. Instead of 1-phenyl-5-mercaptotetrazole 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 Stufon wedge and processed as follows:

At the end there is watering.

The processed copy then shows a positive purple image, which runs in the same direction as the exposure wedge, and on top of which is superimposed a decreasing yellow image. The measured analytical color densities are shown in Table 1 below. They show how the material according to the invention works.

Example 2

• a) Eine grünsensibilisierte Gelatine-Silberjodobromid-Emulsionsschicht (95 Mol-% Silberbromid, 5 Mol-% Silberjodid) mit einem Silbergehalt von 0,2 g/m², welche 0,13 g/m² des Purpurfarbstoffs der Formel (101) enthält,
• b) eine Gelatinezwischenschicht mit einem Auftragsgewicht von 5 g/m²,
• c) eine chemisch verschleierte und mit einem Entwickiungsverzögerer 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.

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 ² , which contains 0.13 g / m ^{2 of} the purple dye of the formula (101) ,
• 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 µm. Two variants are selected for the production of the crystal shells: A) shell thickness 0.01 µm and B) shell thickness 0.02 µm.

• a) Entwicklung 3 Minuten bei 30°C
  Das Entwicklungsbad bleicht 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 developing bath bleaches that in Example 1, but additionally contains 40 g of sodium sulfite per liter
• b) Combined color and silver bleaching for 3 minutes at 30 ° C
  The composition is the same as in Example 1
• c) fixing bath at 30 ° C for 3 minutes
  The 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 greatly 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 washing, 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.

The analysis yields the following sensitometric data in analytical densities:

Example 4

This example illustrates the development kinetics in the core-shell emulsion depending on 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 μm and an AgBr shell thickness of 0.015 μm. 6 mg of 1-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:

As Table 4 below shows, the counter gradation 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 the maximum density of the purple image increases somewhat as the sulfite concentration increases, while at the same time the gradation of the opposite yellow image is significantly flattened.

Example 5

• 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/m² 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 µm 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 µm 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.

This example relates to masking the blue secondary color density of a magenta dye in photographic (tripack) material. The following layers are poured onto 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 which contains 1.68 g / m ^{2 of} gelatin, 0.04 g / m ^{2 of} colloidal silver, 0.05 g / m ^{2 of} the yellow dye of the formula (102) and 0.72 g / m ^{2 of} the hydroquinone derivative Contains formula (104)
• 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 µm is mixed for 1 hour at 60 ° C. a solution of 0.01% formamidine sulfinic acid and 0.01% carbon tetrachloride and then covered with a silver bromide shell 0.025 µm 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 manganese dye - curve A (polychromatic exposure) deviates from curve B (blue exposure), i. H. over 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 (11)

1. A process for the production of a masked positive colour image by the silver dye bleach process, which comprises exposing a photographic material for the silver dye bleach process, silver developing, dye bleaching, silver bleaching and fixing, the silver bleaching being optionally carried out simultaneously with the dye bleaching and/or the fixing, in a single processing bath, and in which photographic material there is present

a) in at least one layer, at least one first dye from which at least one undesired secondary colour density is to be compensated,

b) in each layer or layers a) and/or in a layer adjacent to this layer, an iodide-containing silver halide emulsion associated with said dye or dyes,

c) in at least one other layer, per layer at least one second dye, the main colour density of which corresponds to the secondary colour density or densities to be compensated of the first dye or dyes, and

d) in the layer or layers c) and/or in a layer adjacent thereto, an iodide-free silver halide emulsion associated with said dye or dyes, or, in comparison with the emulsions mentioned under b), a silver halide emulsion of low iodide content, in which process the photographic material contains

e) in the layer or layers c) and/or in at least one other ₃yer which is adjacent to the layer or layers c) and which is separated from one or more layers a) by at least one intermediate layer, a core-shell emulsion which is free of iodide or has a low iodide content, the particles of which emulsion consist of a surface-fogged silver halide core and of an unfogged silver halide shell enclosing the latter, and which emulsion can be developed spontaneously up to the maximum density by the action of a developer, and optionally a developing retarder,

and in which process the developing is carried out in a developer solution which is free of silver-complexing agents.

2. A process according to claim 1, wherein 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 which core is fogged, before the shell is applied, by prior exposure or by chemical treatment.

3. A process according to either of claims 1 and 2, wherein the shell of a core-fogged core-shell particle consists of an unfogged silver halide, has a thickness of between 5 and 100 nm, and consists of the same silver halide as the core or of a different silver halide.

4. A process according to any one of claims 1 to 3, wherein after the fogging, but before the application of the shell, the silver halide crystal is treated, optionally with a developing retarder.

5. A process according to claim 1, wherein at least one intermediate layer which contains neither image dye nor silver halide is arranged in the photographic material between the layer e), which contains the pre-fogged core-shell emulsion, and the layer b), which contains an iodide-containing silver halide emulsion.

6. A process according to claim 1, wherein the silver halide emulsions associated with the image dyes show spectral sensitivities in the respective complementary colour of the image dye.

7. A process according to claim 1, wherein the photographic material has additional layers in which at least one of the two components consisting of image dye and silver halide is at least partially absent.

8. A process according to any one of claims 1 to 7, wherein the sensitised silver halide emulsions associated with the individual image dyes are located in the same layer as the corresponding image dyes or partially in a layer adjacent to the dye layer.

9. A process according to any one of claims 1 to 8, wherein the silver iodide-containing emulsions contain 0 to 99.9 mol-% of silver chloride, 0 to 99.9 mol-% of silver bromide and 0.1 to 10, preferably 1 to 5, mol-% of silver iodide.

10. A process according to any one of claims 1 to 9, wherein 2 to 100 g of an alkali metal sulfite or ammonium sulfite per litre of developer solution are used in the developer in order to control the developing kinetics.

11. A photographic silver dye bleach material for the production of a masked positive colour image, wherein there is present

a) in at least one layer, at least one first dye from which at least one undesired secondary colour density is to be compensated,

b) in each layer or layers a) and/or in a layer adjacent to this layer, an iodide-containing silver halide emulsion associated with said dye or dyes,

c) in at least one other layer, per layer at least one second dye, the main colour density of which corresponds to the secondary colour density or densities to be compensated of the first dye or dyes, and

d) in the layer or layers c) and/or in a layer adjacent thereto, an iodide-free silver halide emulsion associated with said dye or dyes, or, in comparison with the emulsions mentioned under b), a silver halide emulsion of low iodide content, said photographic material containing

e) in the layer or layers c) and/or in at least one other layer wich is adjacent to the layer or layers c) and which is separated from one or more layers a) by at least one intermediate layer, a core-shell emulsion which is free of iodide or has a low iodide content, the particles of which emulsion consist of a surface-fogged silver halide core and of an unfogged silver halide shell enclosing the latter, and which emulsion can be developed spontaneously up to the maximum density by the action of a developer, and optionally a developing retarder.

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