EP0023888B1 - Process for the production of masked positive colour images by the silver dye bleach process and the photographic silver dye bleach material for use therein - Google Patents

Description

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 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 teal, purple and yellow all have the desired absorption in addition 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: in yellow (main absorption in blue) in red and green, in purple (main absorption in green) in red and blue and in 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 the undesirable secondary color density of a dye in additional layers with opposite gradation 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 has the result 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.

The masking process has found widespread use in the field of chromogenic color photography (color development process). Various effects are used for masking. For example, the residual silver halide remaining after development can be used to form a mask image with the opposite gradation, as described in German Patent Specifications 743 535 and 898 709 or in Swiss Patent Specification 721 389. Other patents, such as German patent 950617 or British patents 665 657, 714 012 and 1 210893, describe the production of a mask image by chemical conversion of the color coupler which has remained unused during color development.

Another, e.g. The method described in German patents 1,643,980 and 2,185,220 or in Belgian patent specification 675,259 relates to the use of color couplers whose intrinsic color corresponds to the secondary color density to be compensated for in the dye developed therefrom (auto masking). Other processes are based on the bleaching of azo dyes by the image silver which is formed during the color development; such are e.g. in French Patent 1,414,803 or in GDR Patent 8,051. Counter-rotating color images can also be obtained in separate layers using direct positive emulsions, as described in French patent specification 904 964 or in GDR patent specification 8 051, or according to the silver color bleaching method according to US patent specification 2,336,380.

Further suggestions concern e.g. the bleaching of azo dyes by the oxidized color developer (German patent specification 1 150 275), the controlled diffusion of a bleaching bath (US patent specification 2 763 150) or the use of silver complex diffusion (German patent specification 1 008 117). Finally, masking effects can also be obtained by false sensitization of individual emulsions, as described in British Patent 685,610.

Masked color images used for the production of Color copies or color separations for the production of printing plates for reproduction can also be obtained by recording the compensating color images on separate supports and covering the latter, together with the original, before the copying process. Such methods are described, for example, in German patents 975 867, 976 138, 976 904, 965 615 and in German patent specification 1 142 757, as well as in British patent specification 903-050.

Masking processes have also become known in the production of subtractive positive images using the silver color bleaching process. For example, in US Pat. No. 2,387,754 the combination of layers with negative working emulsions with those containing a direct positive working emulsion is known. In this case, development and color bleaching produce opposing partial images of the desired color. US Pat. No. 2,193,931 describes the combination of positive silver color bleaching images with negative stain images produced from the image silver. The Swiss patent specification 209 656 describes the production of mask images using the silver color bleaching process, emulsions with a particularly flat gradation being used for the mask layer. Finally, a method has become known from British patent specification 523 179, in which a positive image is produced in the same layer by the silver color bleaching method and at the same time a negative image in a different color, e.g. the dye of the first image which gives the positive image during bleaching gives the negative image of the second color.

The methods described in these patent publications are for the production of color separations, e.g. suitable for reproductive purposes. However, because of the remaining color density at the image areas that should become white, they are not suitable for the direct production of positive images of a colored original. Only partial masking is permitted here, in which no light absorption takes place in the image areas that remain white. For such partial masking, the silver color bleaching process, in which all layers have a color gradation in the same pattern as the original, is surprisingly suitable if care is taken to ensure that a shift in sensitivity of the layers occurs during exposure in the individual partial areas in such a way that the desired masking effect occurs .

It has become 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 using bromide ion diffusion from a silver bromide emulsion present in a neighboring layer. A process for the production of masked images using the silver color bleaching process is based on a similar effect, namely the diffusion of iodide ions, as was 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 layer with a second dye whose main color density corresponds to the secondary color density of the first dye. wherein the first dye is associated with an iodide-containing, the second dye, on the other hand, an iodide-free or low-iodide silver halide emulsion. When developing this material, a small amount of a silver halide solvent, e.g. Thiosulfate. 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 was now exposed, iodide ions form at the image sites during the subsequent development, which likewise migrate into the seed layer and prevent silver accumulation from the complex at the relevant sites. 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 processes described in the latter two patent publications have proven to be very valuable for the production of masked images using the silver color bleaching process. However, they still have certain disadvantages associated with the formation of soluble silver complexes in the developer solution containing thiosulfate. It is known, for example, that developer solutions which, as is inevitable in complex diffusion processes, contain soluble silver complexes tend to separate silver sludge over time. As a result, the vessels and the rollers used in developing machines and ultimately the material itself become dirty. It is possible to remove this sludge by adding anti-sludge agents, e.g. To prevent certain mercaptans and organic disulfides at least for a certain time, but this means an expensive additional effort. It has also been shown that the silver images formed even in the presence of only small amounts of thiosulfate are more difficult to bleach and therefore require the use of special bleaching 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 color bleaching process, which instead of the seed layer (DE-OS 2547720, 2831 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 in the physical development of silver complexes on germs. The rate of spontaneous development can in this case by a simultaneously present in the layer development inhibitor on the diffusion rate of immigrant yo _'didi ons vote.

• Aus der vorverschleierten Emulsion entstehen bei der Entwicklung Silberkeime, an denen sich unter physikalischer Entwicklung Silber anlagert. Die bildmässig einwandernden Jodidionen beeinflussen diese physikalische Entwicklung und erzeugen damit ein Maskenbild.

Pre-veiled emulsions for producing masking or intermediate image effects by utilizing an imagewise iodide ion diffusion from an adjacent layer are described, for example, in DE-OS 2 615 344. However, this is an effect that occurs in the presence of soluble silver complexes:

• During development, silver nuclei emerge from the pre-veiled emulsion, and silver accumulates during physical development. The immigrant iodide ions influence this physical development and thus create a mask image.

• (a) in mindestens einer Schicht mindestens einen ersten Bildfarbstoff, von welchem mindestens eine unerwünschte Nebenfarbdichte kompensiert werden soll,
• (b) in der (den) Schicht(en) (a) und/oder in einer zu dieser (diesen) Schicht(en) 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 zu kompensierenden Nebenfarbdichte des (der) ersten Farbstoff(e) entspricht, und
• (d) in der (den) Schicht(en) (c) und/oder in einer zu dieser (diesen) benachbarten Schicht(en) 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 mindestens einer Schicht (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 vorverschleierte, jodidfreie oder jodidarme, ohne Belichtung spontan zur Maximaldichte entwickelbare und einen Entwicklungsverzögerer enthaltende Silberhalogenidemulsion enthält, und die Entwicklung in einer Entwicklerlösung erfolgt, die keinen Silberkomplexbildner enthält.

The present invention thus relates to a process for producing masked positive color images by the silver color bleaching process, by exposure, silver development, color bleaching, silver bleaching and fixation, wherein the silver bleaching can optionally be carried out simultaneously with the color bleaching and / or the fixation in a combined processing bath, one photographic material which:

• (a) in at least one layer at least one first image 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 (s) (each) an iodide-containing silver halide emulsion assigned to this (these) dye (s),
• (c) at least one second dye in at least one further layer, the main color density of which corresponds to the secondary color density of the first dye (s) to be compensated for, and
• (d) in the layer (s) (c) and / or in a layer (s) adjacent to this one (s) an iodide-free dye (s) assigned to it or in comparison to the under (b) mentioned emulsions contains low-iodide silver halide emulsion, characterized in that the photographic material
• (e) in at least one layer (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, contains a pre-veiled, low-iodide or low-iodide silver halide emulsion which can be spontaneously developed to maximum density without exposure and which contains a development retarder, and the development takes place in a developer solution which does not contain any silver complexing agent.

A further embodiment of the method according to the invention relates to a photographic material which does not contain any pre-veiled, iodide-free or low-iodide silver halide emulsion in the layer (s) (c), but only has such an emulsion in at least one layer which is the layer (s) (en) (c) is adjacent and which is separated from one or more layers (a) by at least one intermediate layer.

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

A silver halide emulsion which is assigned to an image 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 (sensitive in the area of the complementary color of the image). A trichromatic material with which the entire visible dye 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 an image dye in a different spectral band, as is the case, for example, is common in infrared-sensitive false color films.

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.

According to the present invention, the developing solution contains no complexing agents; The iodide ions migrating from the neighboring layer directly influence the chemical development of the pre-veiled emulsion.

However, while this chemical development takes place at a relatively high speed, it takes a certain amount of time until the iodide ions migrating from the neighboring layer arrive at the place of their action. They only arise during the pictorial development of the neighboring layer and also have to cover the diffusion path. It is It is therefore important that the chemical development does not begin at least until the iodide ions controlling the masking effect have arrived in the layer. This goal is achieved by adding a development retarder to the layer containing the pre-fogged emulsion.

Suitable development delays are e.g. Benzotriazole, 2-mercaptobenzthiazole, N-methylmercaptotriazole, 2-mercaptobenzoxazole, phenylmercaptotetrazole, triazolindolizine and their derivatives. Information on the use of such development delays can be found e.g. in E. Birr, Mechanism of Stabilization of Photographic Emulsions, Journal for Scientific Photography 50, I, 107 (1955). 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 [cf. FROM. Cohen et al, in Photographic Sci. and eng. 9, 96, (1965)].

• 5-Mercaptotetrazole, die in 1-Stellung mit einer der folgenden Gruppen substituiert sind: n-Propyl, i-Propyl, n-Butyl, i-Butyl, t-Butyl, i-Pentyl, i-Octyl, t-Octyl, Nonyl, Decyl, Lauryl, Myristyl, Palmityl, Stearyl, Ditert.-butyl-phenyl, Octylphenyl, Dodecylphenyl, Naphthyl, a- oder ß-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 geschehen. Unter dieser Bedingung können auch z.B. mit folgenden Gruppen in 1-Stellung substituierte 5-Mercaptotetrazole verwendet werden: Phenyl, mit Hydroxy, 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 2 bis 80 mMol, vorzugsweise von 20 bis 40 mMol pro Mol Silber in der vorverschleierten Emulsion eingesetzt.

In principle, all known development retarders that meet this condition 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 as such are, for example, 5-mercaptotetrazoles which are in the 1-position with aryl groups, preferably polynuclear aryl, such as naphthyl or diphenyl, optionally also with preferably longer alkyl- (C ₃ -C ₁₈ ) -substituted aryl groups, in particular phenyl, furthermore with aralkyl or are substituted with alkyl having preferably at least 3, in particular 3 to 18, carbon atoms. The following are particularly suitable as development retarders:

• 5-mercaptotetrazoles which are substituted in the 1-position with one of the following groups: n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, i-pentyl, i-octyl, t-octyl, nonyl , Decyl, Lauryl, Myristyl, Palmityl, Stearyl, Ditert.-butyl-phenyl, Octylphenyl, Dodecylphenyl, Naphthyl, a- or ß-Naphthyl or Diphenyl. Non-diffusion resistant mercaptotetrazoles without actual ballast groups can also be used. In this case, however, care must be taken to ensure that the development retardant does not diffuse in an undesirable direction into a neighboring layer and, for example, to delay the development of the emulsions which provide iodide ions. This can be done, 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 hydroxy, 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 significantly simplified. The development retarders are used in amounts of 2 to 80 mmol, preferably 20 to 40 mmol, per mol of silver in the pre-fogged emulsion.

Pre-veiled silver halide emulsions, which can be developed spontaneously without exposure, are prepared by methods known per se, e.g. by exposure to light or by chemical treatment with the usual fogging agents, such as thiourea dioxide, tin (2) chloride, hydrazine, boranes, formaldehyde sulfoxylates or gold salts (complex). Since the veiled emulsions must not develop too quickly, silver bromide emulsions are preferably used. Smaller proportions of up to about 20 mole percent silver chloride can be used; Emulsions with higher silver chloride contents can generally be developed too quickly. The proportion of silver iodide should be low, u. do not exceed about 1.0 mole percent, since otherwise the influencing of the development used in the process according to the invention by immigrating iodide ions would not be guaranteed.

• 1. Eine Gelatineschicht mit einem bleichbaren purpurfarbenen Azofarbstoff und grünsensibilisiertem Silberbromojodid.
• 2. Eine Gelatinezwischenschicht.
• 3. Eine vorverschleierte, spontan entwickelbare Silberbromidschicht, die einen Entwicklungsverzögerer enthält.
• 4. Eine Gelatineschicht mit einem bleichbaren gelben Azofarbstoff.

The processes taking place during exposure and subsequent processing are explained with the aid of the following experimental arrangement (see FIG. 1) using 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 silver bromide layer 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 and 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 pre-veiled emulsion spontaneously develops to maximum density; the green-sensitized emulsion remains unexposed and only develops up to the level of fog (A ₂ ). As a result, the yellow layer 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 is opaque to blue light, the green-sensitized emulsion layer associated with the purple layer is not exposed. The situation remains the same as in (A), ie the yellow layer is bleached to the maximum, while the purple layer remains intact (B ₃ ).

(C) Exposure to green or white light

The green-sensitive emulsion is gradually exposed according to the wedge. Development (C ₂ ) produces iodide ions proportional to the exposure, which migrate into the pre-veiled emulsion layer above and inhibit the spontaneous, exposure-independent development there. This creates a silver image that runs in the opposite direction to the image in the lower emulsion layer. After the color and silver Bleaching remains in the magenta layer with a dye image that runs in the same direction as the original, and in the yellow layer in an opposite direction.

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-veiled emulsion layer will be adjusted so that even in the maximum case, i.e. 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. have been described in German Offenlegungsschriften 2036918, 2132835 and 2132836. They primarily serve to influence the relatively steep gradation in silver color bleaching materials or to increase the sensitivity.

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 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 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). 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 non-water-soluble high-molecular substances. Is common. e.g. the use of dispersion polymers of a, β-unsaturated compounds such as acrylic acid esters, vinyl esters and vinyl ethers, vinyl chloride, vinylidene chloride and other mixtures and copolymers.

Intermediate layers (barrier or separating layers) generally contain only pure binder, e.g. B. gelatin and no dye or 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 other additives, such as substances that inhibit color bleaching, additional binders, such as contain water-soluble colloids or water-insoluble dispersion polymers, and also the additives customary 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 photosensitive layers are located on at least one side of this support, preferably in the known arrangement, i.e. 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 in the dry state should generally not exceed 20 tm.

Processing the exposed silver color bleach Materials are carried out in the usual way and include silver development, color bleaching, silver bleaching and fixation, and subsequent rinsing and, if necessary, also between the individual stages (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 containing hydroquinone as the developer, if desired additionally 1-phenyl-3-pyrazolidinone, but no 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. described 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 DE-A-2 448 443.

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) _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-A-2 258 076, 2 423 819).

The silver fixing bath can be composed in a known and customary manner. Is suitable as a fixative. 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.

In the examples below, parts and percentages are by weight unless otherwise stated.

example 1

• (a) Eine unsensibilisierte Silberjodobromidemulsion (94,1 Mol-Prozent AgBr, 5,9 Mol-Prozent AgJ), die 55 g Silber und 71 g Gelatine pro kg enthält, ferner pro kg 3,16 g des Purpurfarbstoffs der Formel
  

The following layers are cast in succession on a transparent polyester support:

• (a) An unsensitized silver iodobromide emulsion (94.1 mole percent AgBr, 5.9 mole percent AgJ) containing 55 g of silver and 71 g of gelatin per kg, further 3.16 g of the purple dye of the formula per kg
  

• (b) Eine Gelatineschicht mit einem Auftragsgewicht von 5,3 g pro m².
• (c) Eine vorbelichtete (vorverschleierte) Silberbromidemulsion, die pro kg 55 g Silber, 71 g Gelatine, 2 g 1-Phenyl-5-mercaptotetrazol (gelöst in 600 ml Äthylenglykol-monoäthyläther) und 2,48 g des gelben Farbstoffs der Formel
  

The layer thickness after drying is about 2 ILm, which corresponds to an application of 1.7 g of silver, 2.2 g of gelatin and 0.095 g of dye per m ² .

• (b) A gelatin layer with an application weight of 5.3 g per m ² .
• (c) A pre-exposed (pre-fogged) silver bromide emulsion containing 55 g of silver, 71 g of gelatin, 2 g of 1-phenyl-5-mercaptotetrazole (dissolved in 600 ml of ethylene glycol monoethyl ether) and 2.48 g of the yellow dye of the formula per kg
  

(dissolved in 248 ml of water). After drying, the layer thickness is 2 μm, which corresponds to an application of 1.7 g of silver, 2.2 g of gelatin and 0.075 g of dye per _M ² .

The samples of the potted and dried materials are exposed to white light from the carrier side using a step wedge and then processed as follows:

Watering is switched on between the individual processing stages and at the end.

During exposure, depending on the step wedge used, an opposing latent silver image is formed in layer (a); A fully developable latent image is consistently present in layer (c) due to the pre-exposure of the emulsion. During the development of the silver image in layer (a), iodide ions are released in proportion to the strength of the resulting negative step image, which migrate through the intermediate layer (b) to layer (c) and inhibit the development of the latent image there. This creates a counter-rotating silver image in this layer, i.e. where the greatest blackening occurs in layer (a), the silver image in layer (c) is weakest and vice versa. The 1-phenyl-5-mercaptotetrazole, which acts as a development retarder, is prevented by the intermediate layer (b) from diffusing into the layer (a) and therefore only influences the development rate in the layer (c).

In the subsequent combined color and silver bleaching, layers (a) and (c) each have a positive color image opposite to the silver image.

The finished copy obtained after fixation and washing is therefore showing a positive purple image that runs in the same direction as the exposure wedge and a yellow image that runs in the opposite direction.

Example 2

• (a) Eine unsensibiliserte Silberjodidemulsion (95,0 Mol-Prozent AgBr, 5,0 Mol-Prozent AgJ), die 55 g Silber und 71 g Gelatine pro kg enthält, ferner pro kg 3,16 g des Purpurfarbstoffs der Formel (101).

As in Example 1, the following layers are cast in succession on a transparent polyester support:

• (a) An unsensitized silver iodide emulsion (95.0 mole percent AgBr, 5.0 mole percent AgJ) containing 55 g of silver and 71 g of gelatin per kg, further 3.16 g of the purple dye of formula (101) per kg .

• (b) Eine Gelatineschicht mit einem Auftragsgewicht von 5,3 g pro m²,
• (c) Eine vorbelichtete (vorverschleierte) Silberbromidemulsion, die pro kg 35 g Silber, 45,5 g Gelatine, 1,2 g 1-Phenyl-5-mercaptotetrazol (gelöst in 385 ml Äthylenglykol-monoäthyläther) und 1,59 g des gelben Farbstoffs der Formel (102) . (gelöst in 158 ml Wasser) enthält. Die Schichtdicke beträgt nach der Trocknung 2 gm was einem Auftrag von 1,7 g Silber, 2,2 g Gelatine und 0,075 g Farbstoff pro m² entspricht.

After drying, the layer thickness is approximately 2 μm, which corresponds to an application of 1.7 g of silver, 2.2 g of gelatin and 0.095 g of dye per m ² .

• (b) a gelatin layer with an application weight of 5.3 g per m ² ,
• (c) A pre-exposed (pre-fogged) silver bromide emulsion containing 35 g of silver, 45.5 g of gelatin, 1.2 g of 1-phenyl-5-mercaptotetrazole (dissolved in 385 ml of ethylene glycol monoethyl ether) and 1.59 g of the yellow per kg Dye of formula (102). (dissolved in 158 ml of water). The layer thickness after drying is 2 gm, which corresponds to an application of 1.7 g of silver, 2.2 g of gelatin and 0.075 g of dye per m ² .

Samples of the potted and dried material are exposed to white light from the carrier side using a step wedge and then processed as in Example 1.

As described in Example 1, the combined color and silver bleaching produces in layers (a) and (c) a positive color image opposite to the silver image.

The finished copy obtained after fixation and washing is therefore showing a positive purple image that runs in the same direction as the exposure wedge and a yellow image that runs in the opposite direction.

Example 3

verwendet wird.The experiment described in Example 2 is repeated, except that in layer (c) a blue-green dye of the formula instead of the yellow dye

is used.

After the step exposure and subsequent processing, an image is obtained, each with a positive purple image and a negative cyan image in opposite direction.

Example 4

In this experiment, a material is used in which the yellow dye and the associated veiled emulsion are completely distributed, and the purple layer and the associated iodide-containing emulsion are partially distributed over two adjacent layers. At the same time, a diffusion-resistant development retardant is used, so that there is no need to arrange a separating layer between the two emulsion layers.

Four layers are applied to a transparent polyester carrier in the following order:

(a) Purple dye layer with emulsion containing iodide

The silver iodobromide emulsion used in Example 2 for layer (a) is sensitized green in the usual way. 5.5 g of the purple dye given in Example 1 in the form of a 1% strength aqueous solution are added to 100 g of this emulsion. The layer application after drying is 2 g of gelatin, 0.135 g of silver and 0.135 g of dye per _m ² _.

(b) Iodide-containing emulsion layer without dye

The green-sensitized emulsion used in layer (a) above is poured with the addition of further gelatin, but without the addition of colorants, to form a layer with the following composition: gelatin 1.5 g, silver 0.315 g (dry weight).

(c) Veiled, iodide-free emulsion layer

To 1 kg of a silver chloride bromide emulsion (10 mol percent silver chloride, 90 mol percent silver bromide), which contains 71 g silver and 73 g gelatin per kg, 10 g 1-stearyl-5-mercaptotetrazole, dissolved in 1500 ml 0, 02 normal aqueous sodium hydroxide solution added. The mixture is kept at 40 ° C. for 2 hours until the mercaptotetrazole is completely adsorbed and then pre-exposed to diffused daylight while stirring. From this veiled emulsion, a layer is produced with additional gelatin, which contains approximately 1.5 g gelatin and 0.3 g silver per m ² .

(d) To 100 g of a 10% aqueous gelatin solution, 75 g of a 1% solution of the yellow dye used in layer (c) of Example 1 are added. A layer with an application weight of 2 g gelatin and 0.15 g dye per m ^{2 is} cast from the mixture.

A sample of the dried four-layer cast is exposed to green light under a step wedge. The exposed wedge is processed in the same way as described in Example 1.

After processing, a positive purple step wedge is obtained, similar to that in Example 1, on which a negative yellow wedge in the opposite direction is superimposed.

The analysis yields the following sensitometric values in analytical densities:

Example 5

• Auf einen weissopaken Träger werden nacheinander -folgende Schichten aufgetragen:
  • ein rotempfindliches Schichtenpaar, bestehend aus
    • a_i) einer rotempfindlichen Gelatine-Silberbromidjodid-emulsionsschicht mit einem Silbergehalt von 0,149 g/m² und 0,145 g/m² des bleichbaren blaugrünen Azofarbstoffes der Formel (103) und
    • a₂) einer von Bildfarbstoff freien Schicht aus einer rotempfindlichen Gelatine-Silberbromidjodid-Emulsion mit einem Silbergehalt von 0,300 g/m²,
    • b) eineGelatine-ZwischenschichtmiteinemAuftragsgewicht von 4,08 g/m²,
• ein grünempfindliches Schichtenpaar, bestehend aus
  • c₁) einer grünempfindlichen Gelatine-Silberbromidjodid (95 Mol-Prozent AgBr, 5 Mol-Prozent AgJ)-Schicht mit einem Silbergehalt von 0,138 g/m² und 0,174 g/m² des bleichbaren purpurfarbenen Azofarbstoffes der Formel (101) und
  • c₂) einer von Bildfarbstoff freien Schicht aus einer grünempfindlichen Gelatine-Silberbromidjodid-Emulsion (95 Mol-Prozent AgBr, 5 Mol-Prozent AgJ) mit einem Silbergehalt vn 0,375 g/m²,
  • d) eine von Bildfarbstoff freie Schicht mit einer spontanentwickelbaren, mit 1-Stearyl-5-mercapto--tetrazol inhibierten Silberschloridbromid-Emulsion (10 Mol-Prozent AgCI, 90 Mol-Prozent AgBr) mit einem Silbergehalt von 0,400 g/m² (Herstellung dieser Emulsion siehe Beispiel 4c),
• ein blauempfindliches Schichtenpaar, bestehend aus
  • e₁) einer blauempfindlichen jodidfreien Gelatine-Silberbromid-Schicht mit einem Silbergehalt von 0,400 g/m² und 0,149 g/m² des gelben bleichbaren Azofarbstoffes der Formel (102), und
  • e2) einer farbstofffreien blauempfindlichen Gelatine-Silberbromid-Schicht mit einem Silbergehalt von 0,360 g/m²; und
  • f) eine Gelatine-Schutzschicht.

A material suitable for the production of positive supervisory copies for the silver color bleaching process is produced in the following way:

• The following layers are applied in succession to a white opaque support:
  • a pair of layers sensitive to red, consisting of
    • a _i ) a red-sensitive gelatin-silver bromide iodide emulsion layer with a silver content of 0.149 g / m ² and 0.145 g / m ^{2 of} the bleachable blue-green azo dye of the formula (103) and
    • a ₂ ) an image dye-free layer of a red-sensitive gelatin-silver bromide iodide emulsion with a silver content of 0.300 g / m ² ,
    • b) an intermediate gelatin layer with an application weight of 4.08 g / m ² ,
• a pair of layers sensitive to green, consisting of
  • c ₁ ) a green-sensitive gelatin-silver bromide iodide (95 mol percent AgBr, 5 mol percent AgJ) layer with a silver content of 0.138 g / m ² and 0.174 g / m ^{2 of} the bleachable purple-colored azo dye of the formula (101) and
  • c ₂ ) an image dye-free layer of a green-sensitive gelatin-silver bromide iodide emulsion (95 mol percent AgBr, 5 mol percent AgJ) with a silver content of 0.375 g / m ² ,
  • d) an image dye-free layer with a spontaneously developable, with 1-stearyl-5-mercapto-tetrazole inhibited silver chloride bromide emulsion (10 mol percent AgCl, 90 mol percent AgBr) with a silver content of 0.400 g / m ² (production of this emulsion see example 4c),
• a blue-sensitive layer pair consisting of
  • e ₁ ) a blue-sensitive iodide-free gelatin-silver bromide layer with a silver content of 0.400 g / m ² and 0.149 g / m ^{2 of} the yellow bleachable azo dye of the formula (102), and
  • e2) a dye-free blue-sensitive gelatin-silver bromide layer with a silver content of 0.360 g / m ² ; and
  • f) a protective gelatin layer.

The intermediate image effect (compensation of the blue secondary color density of the purple layer) can be quantitatively recorded in a simple manner by exposing the green-sensitized layers through a step wedge: In this case, the optical density of the yellow layer in the blue spectral range is parallel to the exposure of the green-sensitive layers (and thus for the subsequent bleaching of the purple layer). The optimal intermediate image effect is achieved when the increase in density of the yellow layer corresponds to the blue secondary color density of the unbleached purple layer when the purple layer is fully exposed.

• 1. Entwicklungsbad 2¹/₂ Minuten/20⁰C Zusammensetzung wie in Beispiel 1, ausser dass die Benzotriazolkonzentration 1 g/1 beträgt
• 2. Zwischenwässerung 1 Minute
• 3. Kombiniertes Farb- und Silberbleichbad 3 Minuten/30°C Zusammensetzung wie in Beispiel 1
• 4. Zwischenwässerung 1 Minute
• 5. Fixierbad 3 Minuten/20°C Zusammensetzung wie in Beispiel 1
• 6. Schlusswässerung

The material described here is exposed through a step wedge with a green color filter and processed as follows:

• 1. developing bath 2 ¹ / is ₂ minutes / 20 ⁰ C composition as in Example 1 except that the Benzotriazolkonzentration 1 g / 1
• 2. Soak 1 minute
• 3. Combined color and silver bleach bath 3 minutes / 30 ° C. Composition as in Example 1
• 4. Soak 1 minute
• 5. Fixing bath 3 minutes / 20 ° C composition as in Example 1
• 6. Final watering

For comparison, a further material which has the same structure but does not contain any veiled emulsion in the layer (d) is exposed in green by the same step wedge and then further treated in the same manner as described above.

Table 2 below shows the resulting densities in the green (X = 570 nm) and in the blue spectral range (λ = 420 nm) for the different steps of the wedge (original density). Column a) relates to the material according to Example 4, column b) the comparative example without a coated emulsion in layer d).

TABLE 2

• a) erfindungsgemässes Material mit verschleierter Emulsion
• b) entsprechendes Material ohne verschleierte Emulsion
  

Optical density after green exposure (analytical density)

• a) Material according to the invention with a veiled emulsion
• b) appropriate material without veiled emulsion
  

It is readily apparent from Table 2 that material a) according to the present example shows the desired interlayer effect, while material b) does not have the effect.

If the material a) is exposed through a colored slide and then processed as described above, a positive copy of excellent color reproduction is obtained. Both the yellow, the blue and the red tones are equal in terms of hue and saturation of the original.

Example 6

For comparison with the processing method according to US Pat. No. 4,046,566, a strip of the material described in Example 5 is exposed and developed and then subjected to a bleaching treatment of 2, 3 or 4 minutes in the bleaching bath described in Example 4.

For comparison, three samples of the same material are developed according to the method described in US Pat. No. 4,046,566 in a bath to which 1.4 g of crystalline sodium thiosulfate are added per liter.

In both cases, the samples are fixed immediately after the bleaching treatment and the residual silver content is determined in the fixed samples.

TABLE 3

• a) gemäss vorliegender Erfindung: Entwickler ohne Thiosulfat
• b) gemäss US-Patentschrift 4 046 566: Entwickler mit Thiosulfat
  

Residual silver levels mg / m ² in the fixed material

• a) according to the present invention: developer without thiosulfate
• b) according to US Pat. No. 4,046,566: developer with thiosulfate
  

The table shows that the process according to the invention, without the addition of thiosulfate to the developer, can significantly reduce the residual silver content in the fixed image compared to the process described in US Pat. No. 4,046,566. The intermediate image effect achieved remains practically the same in both processes.

Example 7

In this example, the shelf life of a developer solution according to the invention is compared with that of a developer solution according to US Pat. No. 4,046,566, which contains sodium thiosulfate in order to achieve the intermediate image effect.

Half of a sheet of the material described in Example 5 is exposed to white light and then developed in a drum under the conditions given in Example 5. The used developer is collected in a beaker and observed for a long time. The solution remains clear and does not change color even after standing for several days.

The experiment is then repeated under the same conditions, except that 1.4 g of sodium thiosulfate (Na _z S ₂ 0 _3. 5 H _z O) per liter are added to the developer be set. The used developer turns brown after 10 minutes and is clearly cloudy after 20 minutes. After a few hours the wall of the beaker is brown.

Claims (15)

1. - 1. A process for the production of masked positive colour images by the silver dye bleach process, by exposing, silver developing, dye-bleaching, silver-bleaching and fixing a photographic material, the step of silver-bleaching being optionally carried out in a combined treatment bath together with dye-bleaching and/or fixing, said photographic material containing

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

   (b) in the layer or layers (a) and/or in a layer adjacent to the said layer or layers (a), an iodide-containing silver halide emulsion for said dye or for each of said dyes,

   (c) in at least one further layer, at least a second dye, the main colour density of which corresponds to the secondary colour density of the first dye or dyes which is to be compensated, and

   (d) in the layer or layers (c) and/or in a layer or layers adjacent to the said layer or layers (c), a silver halide emulsion which is free from iodide, or which has a low iodide content compared with the emulsions mentioned under (b), for said dye or dyes, wherein said photographic material contains

   (e) in at least one layer (c) and/or in at least one further layer which is adjacent to the layer or layers (c) and which is separated from one or more layers (a) by at least one interlayer, a prefogged silver halide emulsion which is free from iodide or has a low iodide content, is spontaneously developable to maximum density without exposure and contains a development retarder,

   
   and developing is carried out in a developer solution which does not contain any silver complexing agents.
2. 2. A process according to claim 1, wherein the development retarder used is a 5-mercaptotetrazole substituted in the 1-position by an alkyl, aryl or aralkyl group.
3. 3. A process according to claim 1, wherein the layer or layers (c) do not contain a prefogged silver halide emulsion which does not contain iodide or which has a low content of iodide, and in the photographic material there is provided at least one interlayer which contains neither dye nor silver halide between the layer (e), which contains the prefogged silver halide emulsion, and the layer (b), which contains an iodide-containing silver halide emulsion.
4. 4. A process according to claim 1, wherein the silver halide emulsions for the image dyes have colour sensitivities in the respective complementary colour of the image dye, or have other colour sensitivities.
5. 5. A process according to claim 1, wherein the two corresponding components image dye and silver halide are distributed over two or three different adjacent layers.
6. 6. A process according to claims 1 to 5, wherein a trichromatic material is used which contains, in each individual layer, as image dye, a cyan dye, a magenta dye and a yellow dye.
7. 7. A process according to claim 1 to 6, wherein the sensitised silver halide emulsions for the individual image dyes are present in the same layer as the image dyes appertaining thereto.
8. 8. A process according to claims 1 to 7, wherein the sensitised silver halide emulsions allocated to the individual image dyes are present, at least partly, in a layer adjacent to the dye layer.
9. 9. A process according to claims 1 to 8, wherein one or two secondary colour densities of an image dye in a multi-layer material are compensated.
10. 10. A process according to claims 1 to 8, wherein one secondary colour density of each of two image dyes in a multi-layer material is compensated.
11. 11. A process according to claims 1 to 10, wherein the emulsion layers which are free from silver iodide and are allocated to a second dye contain silver chloride or silver bromide or a mixture of the two halides.
12. 12. A process according to claims 1 to 11, wherein the amulsions containing silver iodide contain 0 to 99.9 mole % of silver chloride, 0 to 99.9 mole % of silver bromide and 0.1 to 10 and preferably 1 to 5 mole % of silver iodide.
13. 13. A process according to claims 1 to 12, wherein the prefogged, spontaneously developable emulsion is a silver chlorobromide or silver bromide emulsion which contains not more than 20 mol% of silver chloride and not more than 1.0 mol% of silver iodide and has been fogged by pre-exposure or by chemical treatment.
14. 14. A photographic silver dye-bleach material for the production of masked positive colour images, which contains

    (a) in at least one layer, at least one image dye, which has at least one undesired secondary colour density which is to be compensated,

    (b) in the layer or layers (a) and/or in a layer adjacent to the said layer or layers (a), an iodide-containing silver halide emulsion for said dye or for each of said dyes,

    (c) in at least one further layer at least one second dye, the main colour density of which corresponds to the secondary colour density of the first dye or dyes which is to be compensated,

    (d) in the layer or layers (c) and/or in a layer or layers adjacent to the said layer or layers (c), a silver halide emulsion which is free from iodide or has a low iodide content compared with the emulsions mentioned under (b) and is allocated to the said dye or dyes, wherein said photographic material contains

    (e) in at least one layer (c) and/or in at least one further layer which is adjacent to the layer or layers (c) and which is separated from one or more layers (a) by at least one interlayer, a prefogged silver halide emulsion which is free from iodide or has a low iodide content, is spontaneously developable to maximum density without exposure and contains a development retarder.
15. 15. A silver dye-bleach material according to claim 14, wherein the optical density of at least one image dye layerthe main colour density of which corresponds to the secondary colour density to be compensated in another layer, is increased by an amount which compensates the loss in density after processing, when this other layer is not exposed.

Images