EP0044813B1 - Process for the formation of negative 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 new process for producing negative color photographic images by the silver color bleaching process and the silver color bleaching material used in this process.

As is known, the silver color matching process is based on the fact that certain classes of dyes, especially azo dyes, are reductively bleached in the presence of finely divided silver by strongly acidic baths containing a silver complexing agent. This reaction can be accelerated by catalysts, especially diazine compounds.

The effect of finely divided silver on dyes can be used to convert photographically produced silver images into color images. Normally, the primary silver image is negative, i. H. opposed to submission. In the subsequent color bleaching process, a second image reversal takes place, so that the resulting dye image is positive, i. H. is in sync with the template. The silver color bleaching process is therefore primarily used to produce positive color copies based on slides.

• a) Umkehrentwicklung: das primär nach der Belichtung und ersten Entwicklung entstandene negative Silberbild wird oxidativ gebleicht, während das diffus belichtete oder chemisch verschleierte Silberhalogenid durch Zweitentwicklung zu einem Positivbild verarbeitet wird (z. B. DE-B-1 145487).
• b) Direktpositivemulsionen: sie arbeiten entweder nach dem Innenbild- oder Oberflächenschleierprinzip unter Mitwirkung von Desensibilisatoren und liefern direkt ein positives Silberbild.
• c) Silberkomplexdiffusion: man verwendet zur Entwicklung des negativen Silberbildes Entwickler, die Silberkomplexbildner enthalten. Die nichtentwickelten, unbelichteten Silberhalogenidbereiche lösen sich im Entwickler als Silberkomplexe und wandern bildweise in eine Empfangsschicht, die Entwicklungskeime enthält. An diesen Keimen wird durch physikalische Entwicklung aus der silberkomplexhaltigen Entwicklerlösung Silber abgeschieden, wodurch ein Positivbild entsteht (z. B. DE-A-1 572 206 oder GB-A-656 131).
• d) Bromid- oder Jodidionendiffusion: bei der Entwicklung von belichteten Silberbromid- oder Silberchloridemulsionen wird gleichzeitig mit der Entstehung von metallischem Silber das entsprechende Halogenidion freigesetzt, welches nun in der Emulsionsschicht frei diffundieren kann. Solche Ionen besitzen die Eigenschaft, die Entwicklung belichteter Kristalle von leichter löslichen Silberhalogeniden zu stören oder zu verhindern. So hemmen Bromidionen die Entwicklung von Silberchloridemulsionen, Jodidionen die Entwicklung von Silberchlorid- oder Silberbromidemulsionen. Dies gilt sowohl für die übliche chemische als auch für die physikalische Entwicklung von Silberhalogenidemulsionen.

So that the silver color bleaching process can also be used to generate negative color images, a positive silver image must be assumed. Several methods are known for producing positive silver images:

• a) Reverse development: the negative silver image, which primarily arises after exposure and the first development, is bleached oxidatively, while the diffusely exposed or chemically veiled silver halide is processed into a positive image by second development (e.g. DE-B-1 145487).
• b) Direct positive emulsions: they work either on the inside or surface veil principle with the participation of desensitizers and provide a positive silver image directly.
• c) Silver complex diffusion: developers containing silver complexing agents are used to develop the negative silver image. The undeveloped, unexposed silver halide areas dissolve in the developer as silver complexes and migrate imagewise into a receiving layer which contains development nuclei. Silver is deposited on these germs by physical development from the silver complex-containing developer solution, whereby a positive image is created (e.g. DE-A-1 572 206 or GB-A-656 131).
• d) Bromide or iodide ion diffusion: in the development of exposed silver bromide or silver chloride emulsions, the corresponding halide ion is released simultaneously with the formation of metallic silver, which can now diffuse freely in the emulsion layer. Such ions have the property of disrupting or preventing the development of exposed crystals of more soluble silver halides. Bromide ions inhibit the development of silver chloride emulsions, iodide ions inhibit the development of silver chloride or silver bromide emulsions. This applies to both the usual chemical and physical development of silver halide emulsions.

The generation of positive Siberian images by bromide ion diffusion is explained in DE-A-859711. An emulsion layer of the photographic material contains highly sensitive silver bromide, less sensitive, veiled silver chloride and colloidal silver, which supplies the development nuclei. During the development of the primary image formed in the silver bromide, bromide ions are formed which prevent the spontaneous development of neighboring silver chloride particles. Since the resulting positive image from the silver chloride has a much higher opacity than the negative image formed from the silver bromide at the same time, the result is a positive image. Similarly, positive silver images and the corresponding color images according to CH-A-564795 are produced by separating the pre-fogged layer rich in silver chloride, which contains a bleachable dye, from the sensitive layer rich in silver bromide.

Iodide ion diffusion is one method described in U.S.-A-3,695,881. There, in the adjacent layer to an emulsion containing silver iodide, an unveiled interior image emulsion is arranged, which is made difficult to fix by treatment with a heterocyclic nitrogen compound. The iodide ions migrating out of the silver iodide emulsion favor the dissolution of the interior image emulsions treated in this way in the fixing step. A positive image is thus again obtained in this emulsion, which can be used to produce a color image.

A disadvantage of the known silver dye bleaching materials is that one is normally forced to store light-absorbing dyes in emulsion layers which are sensitized in the main absorption area of the dye. This causes a great loss of sensitivity.

• Die Spontanentwicklung der oberflächenverschleierten Silberhalogenidemulsion setzt ein, bevor die Jodidionen aus der obersten Schicht eindiffundieren können. Damit entsteht kein oder nur ein sehr kontrastarmes, positives Silberbild.

Another disadvantage becomes apparent with regard to a special silver color bleaching process which uses iodide ion diffusion. Is z. B. a photographic material which contains on a support in a lowermost layer a bleachable dye and a relatively insensitive, surface-fogged silver hologenide emulsion and in an overlying layer a dye-free, highly sensitive, silver iodide-containing silver bromide emulsion, these two layers separated by a third layer containing only binders, exposed and developed and then subjected to the usual color bleaching process, the following processes take place:

• The surface veiled silver halide emulsion begins to develop spontaneously before the iodide ions can diffuse from the top layer. This creates no or only a very low-contrast, positive silver image.

The object of the present invention is therefore to provide a method for producing negative photographic color images using iodide ion diffusion, which largely overcomes these disadvantages.

It has now been found that an increase in the contrast of the positive silver image can be achieved if a core-shell emulsion is used in the layer containing a bleachable dye, the particles of which contain a veiled core which may have been treated with a development retarder. The onset of the spontaneous development of the core-shell emulsion can be influenced by the choice of a suitable shell thickness around the veiled core so that the spontaneous development coincides with the diffusion of the development-controlling iodide ions.

An additional development-retarding effect can be achieved by treating the cores with one of the customary development retarders before the silver halide shell is applied.

Furthermore, an improvement in sensitivity is achieved since the dye need not be present in the light-sensitive layer. This can also be strongly light-absorbing, e.g. B. black dyes are used, the use of which is normally excluded in a silver color bleaching material. This allows the production of a black and white negative material, the silver content of which is completely recoverable.

• a) eine erste Schicht, die eine hochempfindliche, gegebenenfalls spektral sensibilisierte Silberhalojodidemulsion enthält,
• b) eine weder Silberhalogenid noch Bildfarbstoff enthaltende Zwischenschicht und
• c) eine dritte Schicht enthält, die einen bleichbaren Biidfarbstoff und eine jodidfreie oder jodidarme Core-shell-Emulsion enthält, deren Partikel aus einem oberflächenverschleierten und gegebenenfalls mit einem Entwicklungsverzögerer behandelten Silberhalogenidkern und einer diesen umhüllenden Silberhalogenidschale bestehen, wobei sich diese Emulsion durch Einwirkung eines Entwicklers spontan bis zur Maximaldichte entwickeln läßt,

The invention thus relates to a process for producing negative color images by the silver color bleaching process, by exposure of a photographic material, silver development, color bleaching, silver bleaching and fixation, the silver bleaching optionally being combined with the color bleaching and / or fixation in a single treatment bath, the photographic material consists of a support with at least one layer package of three layers each, characterized in that each layer package, viewed from the side of the light,

• a) a first layer which contains a highly sensitive, optionally spectrally sensitized, silver haloiodide emulsion,
• b) an intermediate layer containing neither silver halide nor image dye and
• c) contains a third layer which contains a bleachable biidye and a iodide-free or low-iodide core-shell emulsion, the particles of which consist of a surface-fogged silver halide core, optionally treated with a development retarder, and a silver halide shell enveloping it, this emulsion being formed by the action of a developer spontaneously develop up to the maximum density,

that the photographic material, if it consists of more than one layer package, optionally contains intermediate layers d) between the layer packages, and that the development takes place in a developer solution free of silver complexing agents.

In layer a), silver haloiodide emulsion means a silver chloro or silver bromoiodide emulsion.

Another object of the invention relates to the silver color bleaching material suitable for the method according to the invention.

• Die in oberster Position befindliche hochempfindliche, jodidhaltige Silberbromidemulsionsschicht a) wird bildmäßig belichtet. Da diese Schicht keinen Farbstoff enthält, erreicht man eine sehr hohe photographische Empfindlichkeit. Die verschleierte Core-shell-Emulsion in der untersten Schicht c) wird wegen ihrer geringen Empfindlichkeit höchstens schwach anbelichtet, doch spielt dies wegen ihrer spontanen Entwickelbarkeit keine Rolle.

If the photographic material according to the invention described above is exposed and developed and then subjected to the usual color bleaching process, the following processes are shown in FIG. 1:

• The highly sensitive, iodide-containing silver bromide emulsion layer a) located in the top position is exposed imagewise. Since this layer contains no dye, very high photographic sensitivity is achieved. The veiled core-shell emulsion in the bottom layer c) is at most weakly exposed due to its low sensitivity, but this does not matter because of its spontaneous developability.

In the subsequent development, iodide ions are formed in the top layer a), which diffuse through the intermediate layer b) to the bottom layer c) and there inhibit the spontaneous development of the veiled core-shell emulsion. This creates a positive silver image in this layer. After bleaching the dye and removing all remaining silver compounds, the desired negative color image is finally obtained in the bottom layer.

If three of the layer packages described above, each containing a blue-green, a purple and a yellow image dye in layers c), are combined to form a trichromatic silver color bleaching material, intermediate layers d) may also be arranged between the individual layer packages.

The highly sensitive silver haloiodide emulsion of layer a) can have its maximum sensitivity both inside and outside the spectral range of the complementary color of the image dye in layer c).

The trichromatic material described is characterized by particularly high sensitivity.

Silver halide crystals with a diffusion-inhibiting silver halide shell can be produced in a simple manner using the known core-shell technique. Monodisperse emulsions are preferably used, the crystals of which are all within a relatively limited size range. Such an emulsion is veiled on the grain surface by customary methods, e.g. B. by exposure or by means known per se, such as u. a. in DE-A-1 597 488, 2 801 127, U.S.-A-3 761 266 and in Research Disclosure 16 345 (1977).

If desired, the veiled crystals can also be treated with a development inhibitor which adheres to their surface by adsorption before being provided with a thin shell covering the development centers by further precipitation of silver halide.

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 crystals to be coated 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 DE-A-1 904 148.

The shell to be applied can consist of another silver halide or the same silver halide (s) 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 Silberhalogenid durch gleichzeitige Zugabe von löslichem Silbersalz und löslichem Halogenid, wobei die Fällungsbedingungen (Konzentration, Zulaufgeschwindigkeit) so gewählt werden, daß keine neuen Kristallisationskeime entstehen (z. B. DE-A-2 015 070).
• b) Zugabe einer feindispersen Silberhalogendemulsion, deren Kristalle wesentlich kleiner sind als die zu umhüllenden Kristalle. Die feindispersen Kristalle verschwinden, indem sich wie bei der Ostwaldreifung um die größeren Kristalle eine Schale aus dem Material der zugefügten feindispersen Emulsion bildet (z. B. U.S.-A-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.-A-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 soluble halide, the precipitation conditions (concentration, feed rate) being chosen so that no new crystallization nuclei are formed (e.g. DE-A-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 forming a shell from the material of the finely dispersed emulsion added (for example BUS-A-3 206 313) as in the Ostwald ripening around the larger crystals.
• 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-A-3 917 485).

It has been found that the choice of a suitable shell thickness around the veiled core of a core-shell particle is an excellent means of delaying the onset of spontaneous development so that the spontaneous development coincides with the diffusion of the development-controlling iodide ions. Shell thicknesses between 5 and 100 mm, corresponding to approximately 7 to 140 silver halide lattice planes, preferably 10 to 25 mm, 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 the sulfite concentration (2 to 100 g per liter of developing solution).

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

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 the additional growth of the shell inside the crystal [z. B. DE-A-2 260 117 and E. Moisar, S. Wagner, Ber. Bunsen Society 67, 356 (1963)].

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 [cf. A. B. Cohen et al, Potographic Sci. and eng. 9.96, (1965)].

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 difficult or insoluble in water and contain ballast groups. As such, z. B. 5-mercaptotetrazoles, which in 1-position with acrylic groups, preferably polynuclear aryl, such as naphthyl or diphenyl, optionally also with preferably longer alkyl (C ₁₃ -C ₁₈ ) substituted aryl groups, in particular phenyl, furthermore with aralkyl or with alkyl with preferably at least 3, in particular 3 to 18 Carbon atoms are substituted.

• 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, a- oderd-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 Hydroxyl, Halogen (Chlor, Brom) oder Niederalkyl (C₂-C₃) substituiertes Phenyl, Benzoesäure-methyl- oder -äthylester, Methyl oder Aethyl. Im allgemeinen ist jedoch die Verwendung diffusionsfester Entwicklungsverzögerer vorzuziehen, weil dadurch der Schichtaufbau, insbesondere von solchen Materialien mit einer Vielzahl von Farb- und Emulsionsschichten wesentlich vereinfacht werden kann. Die Entwicklungsverzögerer werden in Mengen von 1 bis 80 mMol, vorzugsweise von 3 bis 40 mMol pro Mol Silber in 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, a- or d-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. done 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 veiling of the silver halide crystals, which then form the core of a core-shell particle, is carried out using customary 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 or silver chlorobromide emulsions are preferably used for their production. Smaller proportions of up to about 20 mole percent silver chloride can be used; Emulsions with higher silver chloride contents are generally too quick to develop. 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 immigrant iodide ions, which is important for the process according to the invention, would not be guaranteed.

The silver halide shell to be applied can consist of a different silver halide (s), of the same silver halides but in different halide proportions or preferably of the same silver halide or the same silver halides in the same halide proportions as the core.

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

In principle, all dyes which are generally used for the silver color bleaching process are suitable as bleachable dyes for the process according to the invention. If trichromatic negative images are to be produced, one of the subtractive basic dyes cyan, purple and yellow will be used in a layer package. To avoid bleach coupling, an additional separating layer d) must be arranged between two layer packets in this case. However, the method is also suitable for producing monochromatic negative images, an important application relating to the production of negative black / white images, as can be obtained by using a bleachable black dye.

Another use of monochromatic negative images is in the production of positive black and white images. The dye of the negative images according to the invention takes on the role of the light-absorbing silver halide of normal photographic materials. Bleachable dyes which are suitable for the process according to the invention are described, for example, in US Pat. Nos. 3,454,402, 3,443,933, 3,804,630, 3,716,368, 3,877,949, 3,623,874, 3,931,142 and 4,051,123 described.

The intermediate layers d) (barrier and separating layers) generally contain only pure binder, e.g. B. gelatin, but no dye and no silver halide. If it is favorable for the overall layer sequence, an already existing emulsion layer or a filter layer can optionally also serve as a separating layer. In addition to gelatin, the separating layer can contain further additives, such as substances which inhibit color bleaching, additional binders, such as, for example B. contain water-soluble colloids or water-insoluble dispersion polymers, also the usual additives for the construction of the other photographic layers such as plasticizers, wetting agents, light stabilizers, filter dyes, optical brighteners, UV absorbers or curing agents.

The highly sensitive silver haloiodide emulsions (first layer of a layer package viewed from the side of the light) are normally those which contain silver chloride and / or bromide and silver iodide. The iodide content is normally between 0.1 and 10, preferably 1 and 5 mol percent, the rest consists of silver chloride and / or bromide (e.g. 0 to 99.9 mol percent silver bromide).

Gelatin is usually used as a protective colloid to prepare these emulsions; It Kings _- but NEN other water-soluble protective colloids such as polyvinyl alcohol or polyvinyl etc. are 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 of a ,, 8-unsaturated compounds such as acrylic acid esters, vinyl esters and vinyl ethers, vinyl chloride, vinylidene chloride and other mixtures and copolymers.

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 exposed silver color bleaching materials are processed in the customary manner and include silver development, color bleaching, silver bleaching and fixing and subsequent rinsing and, if appropriate, also between the individual steps (see, for example, DE-A-2448443). Color bleaching and silver bleaching, and possibly also fixation, can be combined in a single treatment step. It is also possible to incorporate developer compounds or developer precursors into the emulsion layers. Suitable buffering ensures that these substances remain inactive in the dry layer during storage. In this case, all that is required to start development is an activator bath with a high pH, which can be free of developer substances.

Baths of conventional composition can be used for silver development, e.g. B. those that contain hydroquinone as developer or additionally 1-phenyl-3-pyrazolidinone, but do not contain silver complexing agents. It may also be advantageous if the silver developing bath, as described in Swiss Patent 405 929, additionally contains a color bleaching catalyst. Activator baths contain only strong alkalis and possibly other additives such as buffer substances, wetting agents etc. as active substances.

As color bleachers - if the color bleaching is carried out as a separate treatment step - those are advantageously used 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 generally contain a water-soluble oxidizing agent in addition to the specified components. Suitable color bleaching catalysts are primarily diazine compounds, e.g. B. in DE-B-2 010 280, 2 144 298 and 2 144 297, in FR-A-1 489 460, in US-A-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 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 used in particular as antioxidants. Suitable reductones are especially 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, cycloalphatic, 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, 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 preferably 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 retainers or UV protection agents.

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

example

• 1. Eine Schicht, die eine chemisch verschleierte und mit einem Entwicklungsverzögerer (Inhibitor) behandelte Core-shell-Emulsion mit einem Silbergehalt von 0,8 g/m², sowie 0,3 g/m² eines schwarzen bleichbaren Farbstoffs der Formel
  
  enthält. Die in dieser Schicht verwendete Core-shell-Emulsion wird wie folgt hergestellt: Eine kubisch-monodisperse Silberbromidemulsion (Kantenlänge 0,55 µm) wird während einer Stunde bei 60°C mit einer Lösung von 0,01% Natriumformaldehydsulfoxylat (HOCH₂SO₂Na · 2H₂0) 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 verschleierte Emulsion inhibiert: Auf die so vorbehandelten Silberbromidkristalle wird eine Silberbromidschale von 0,02 µm Dicke aufgefällt.
• 2. Eine Gelatine-Zwischenschicht mit einem Auftragsgewicht von 5 g/m² Gelatine.
• 3. Eine grün sensibilisierte Silberjodobromidgelatineemulsionsschicht (95 Mol-% AgBr, 5 Mol-% AgJ) mit einem Auftragsgewicht von 0,8 g Silber/m².

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

• 1. A layer containing a chemically veiled and treated with a development retardant (inhibitor) core-shell emulsion with a silver content of 0.8 g / m ² , and 0.3 g / m ^{2 of} a black bleachable dye of the formula
  
  contains. The core-shell emulsion used in this layer is produced as follows: A cubic monodisperse silver bromide emulsion (edge length 0.55 µm) is mixed with a solution of 0.01% sodium formaldehyde sulfoxylate (HOCH ₂ SO ₂ Na · 2H ₂ 0) and 0.001% gold hydrochloric acid (HAuC1 ₄ ) chemically veiled. The veiled emulsion is inhibited by adding 3 mg of 1-phenyl-5-mercaptotetrazole per g of silver, in the form of a 1% solution: a silver bromide shell of 0.02 μm thick is struck on the silver bromide crystals pretreated in this way.
• 2. A gelatin intermediate layer with an application weight of 5 g / m ² gelatin.
• 3. A green sensitized silver iodobromide gelatin emulsion layer (95 mol% AgBr, 5 mol% AgJ) with an application weight of 0.8 g silver / m ² .

Man erhält nach beendeter Verarbeitung ein negatives, d. h. zur Vorlage gegenläufiges SchwarzWeiß-Bild von sehr hohem Kontrast (y ≈ 5).A sample of the material coated in this way is exposed to green light under a gradient wedge and processed as follows:

After processing has been completed, a negative, ie counter-rotating, black and white image of very high contrast (y ≈ 5) is obtained.

The measured transmission densities are shown in Table 1 below:

Claims (11)

1. A process for the production of a negative colour image by the silver dye bleach process, by exposing a photographic silver dye bleach material, 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 treatment bath, said photographic silver dye bleach material consisting of a support with at least one layer assembly of three layers each, characterised in that each layer assembly contains, as viewed from the side of incident light:

a) a first layer which contains a highly sensitive and optionally spectrally sensitised silver halogenoiodide emulsion,

b) an intermediate layer containing neither silver halide nor image dye, and

c) a third layer which contains a bleachable image dye and 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 optionally treated with a developing retarder, and of a silver halide shell enclosing said core, and which emulsion can be developed spontaneously up to the maximum density by the action of a developer, and

that the photographic material, where it consists of more than one layer assembly, optionally contains intermediate layers d) between the layer assemblies, and
that the developing is carried out in a developer solution which is free of silver-complexing agent.

2. A process according to claim 1, wherein the core and shell of a core-shell particle consist 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.

3. A process according to either claim 1 or claim 2, wherein the core of a core-shell particle is fogged by prior exposure or by chemical treatment and optionally treated with a developing retarder, before the shell is applied.

4. A process according to any one of claims 1 to 3, wherein the fogged core of a core-shell particle is enclosed by an unfogged silver halide shell with a thickness in the range from 5 to 100 nm, preferably from 10 to 25 nm.

5. A process according to any one of claims 1 to 4, which comprises the use of a trichromatic material which consists of three layer assemblies each consisting of three layers and each having a cyan image dye, a magenta image dye and a yellow image dye in the layers c), with intermediate layers d) optionally arranged between the layer assemblies.

6. A process according to any one of claims 1 to 5, wherein the silver halogenoiodide 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.

7. A process according to any one of claims 1 to 6, wherein at least one of the intermediate layers b) within the layer assemblies, and/or of the intermediate layers d) between the layer assemblies, contains, apart from the binder, further substance such as bleach inhibitors, filter dyes, light stabilisers, fluorescent whitening agents, plasticisers, UV-absorbers or wetting agents.

8. A process according to any one of claims 1 to 7, wherein a developer substance or a developer precursor is incorporated in at least one the layers of the photographic material, and, in this case, a strongly alkaline activating bath is used for the developing instead of a developing bath.

9. A process according to any one of claims 1 to 8, which comprises the use of a developer solution which contains 2 to 100 g/litre of an alkali metal sulfide or ammonium sulfide for the purpose of controlling the kinetics of spontaneous developing.

10. A photographic silver dye bleach material for the production of a negative colour image, said material consisting of a support with at least one layer assembly of three layers each, each said layer assembly containing, as viewed from the side of incident light:

a) a first layer which contains a highly sensitive and optionally spectrally sensitised silver halogenoiodide emulsion,

b) an intermediate layer containing neither silver halide nor image dye, and

c) a third layer which contains a bleachable image dye and 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 optionally treated with a developing retarder, and of a silver halide shell enclosing said core, and said material, where it contains more than one layer assembly, optionally containing intermediate layers d) between the layer assemblies.

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