EP0315833A2 - Colour-photographic material - Google Patents

Abstract

A colour-photographic material with at least one silver halide emulsion layer containing at least 60 mol % of AgCl, in which the layers applied to the base have together an iron content of </=50 ppm, relative to silver halide calculated as AgNO3, shows increased sensitivity and reduced fog.

Description

The invention relates to a color photographic material whose layers applied to the support have a low iron content.

To date, photographic materials have always contained a significant proportion of iron ions or compounds in the silver halide-containing layers, which have a number of unfavorable effects on the photographic properties of the materials. The causes of unwanted iron contamination in photographic materials are diverse. On the one hand, iron compounds can be introduced through the starting materials used to produce the emulsions, on the other hand through the technically used emulsion production and processing plants, which usually consist of stainless steels (O. Lapp in Ullmann's Encyklopadie der Technische Chemie, Verlag Chemie Weinheim (1979), Volume 18, page 428; VC Zelikman, SM Levi, Making and Coating Photographic Emulsions, Focal Press London / New York (1964), p. 19).

Silver halide emulsions, especially if, as is customary in the production of emulsions, an excess of soluble halide salt is present, also lead to the corrosion of high-quality austenitic stainless steels, especially if the silver halide consists entirely or partially of silver chloride.

The iron ions have a highly damaging effect on the emulsions because the silver ions or silver halide particles can be reduced to elemental silver and lead to photographic fog.

Iron ions have already been described by Borginon et al., J.Photogr. Sci. 28 , 111 (1980) as a likely system for many undesirable redox reactions in photographic emulsions, since iron ions easily change from the 2 to the 3-valent state and vice versa. This makes it possible for sensitivity nuclei and latent image nuclei to be oxidized. In the first case the sensitivity of the emulsion generally decreases, in the second case the latent image is completely or partially destroyed in the period between exposure and development of the photographic material.

There has been no shortage of attempts to produce photographic emulsions as iron-free as possible. An important possible source of iron ions is, for example, the gelatin used, L.Xuan-Ya, J.Photogr. Sci., Vol 30 , page 20 (1982), for example, determined iron contents between 10 and 80 ppm in various gelatins. W.Rong-qin et al., Phot-Gelatin Reports 1983, page 283, 4th IAG- Conference Friborg 1983, ed. By H. Ammann-Brass et Pouradier (1985) showed that strong desensitization of photographic emulsions can occur due to iron ions. As little as 5 ppm of iron ions can reduce the sensitivity by approx. 15%. There has therefore been no lack of attempts to at least largely remove iron ions from the gelatin. High quality gelatins for photographic purposes today contain less than 5 ppm iron.

Another possibility of retaining iron ions from the redox reactions in the emulsion are complexing agents for iron. However, such compounds are not specific for iron ions, but also complex other polyvalent ions such as e.g. Calcium ions. Some gelatins contain high amounts of calcium ions, up to 4,500 ppm, so that high amounts of complexing agents have to be added, which again has photographic disadvantages.

So far, however, it has not been possible to produce photographic materials whose layers applied to the support have a particularly low iron content, especially if the materials contain chloride emulsions.

The invention thus relates to a color photographic material with at least one silver halide emulsion layer with at least 60 mol% AgCl, the layers applied to the support together having an iron content of ≦ 50 ppm, preferably ≦ 20 ppm, in particular ≦ 10 ppm, based on silver halide, calculated as AgNO₃ have.

The iron content of the support is of no importance in this connection, in particular if the support is a polyethylene-coated paper, but of course the iron content of the entire material based on silver halide can also be within the specified limits.

The silver halide of the at least one silver halide emulsion layer preferably has a chloride content of at least 80 mol%. The silver halides of all silver halide emulsion layers preferably have a chloride content of at least 60 mol%, preferably at least 80 mol%. The material also contains 0 to 40 mol%, preferably 0 to 20 mol% bromide and 0 to 2 mol% iodide and is in particular iodide-free.

Photographic materials according to the invention are produced by using on the one hand starting materials, in particular gelatins, with the lowest iron content, and on the other hand using devices and systems which do not lead to iron contamination.

It has proven to be particularly advantageous for the production and processing of the emulsions according to the invention if all the devices with which the emulsion comes into contact have enamelled or plastic-coated surfaces or consist of metallic materials with a low iron content, for example alloys with nickel , Titanium or tantalum as the main component.

The light-sensitive layers of the material according to the invention contain a binder in addition to the silver halide.

Gelatin is preferably used as the binder. However, this can be replaced in whole or in part by other synthetic, semi-synthetic or naturally occurring polymers. Synthetic gelatin substitutes are, for example, polyvinyl alcohol, poly-N-vinylpyrolidone, polyacrylamides, polyacrylic acid and their derivatives, in particular their copolymers. Naturally occurring gelatin substitutes are, for example, other proteins such as albumin or casein, cellulose, sugar, starch or alginates. Semi-synthetic gelatin substitutes are usually modified natural products. Examples of these are cellulose derivatives such as hydroxyalkyl cellulose, carboxymethyl cellulose and phthalyl cellulose and gelatin derivatives which have been obtained by reaction with alkylating or acylating agents or by grafting on polymerizable monomers.

The binders should have a sufficient amount of functional groups so that enough resistant layers can be produced by reaction with suitable hardening agents. Such functional groups are in particular amino groups, but also carboxyl groups, hydroxyl groups and active methylene groups.

The gelatin which is preferably used can be obtained by acidic or alkaline digestion. The production of such gelatins is described, for example, in The Science and Technology of Gelatine, published by A.G. Ward and A. Courts, Academic Press 1977. page 295 ff. The gelatin used in each case should contain the lowest possible level of photographically active impurities (inert gelatin). High viscosity, low swelling gelatins are particularly advantageous. Oxidized gelatins are also suitable.

The silver halide present as a light-sensitive component in the photographic material can contain chloride, bromide or iodide or mixtures thereof as the halide. As already stated, chloride-rich emulsions are preferred. It can be overly compact crystals, e.g. are regular cubic or octahedral or can have transitional forms. However, platelet-shaped crystals may preferably also be present, the average ratio of diameter to thickness of which is preferably greater than 5: 1, the diameter of a grain being defined as the diameter of a circle with a circle content corresponding to the projected area of the grain.

The silver halide grains can also have a multi-layered grain structure, in the simplest case with an inner and an outer grain area (core / shell), the halide composition and / or other modifications such as doping of the individual grain areas being different. The average grain size of the emulsions is preferably between 0.2 μm and 2.0 μm, the grain size distribution can be both homo- and heterodisperse. Homodisperse grain size distribution means that 95% of the grains do not deviate from the mean grain size by more than ± 30%. In addition to the silver halide, the emulsions can also contain organic silver salts, for example silver benzotriazolate or silver behenate.

Two or more kinds of silver halide emulsions, which are prepared separately, can be used as a mixture.

The photographic emulsions can be prepared using various methods (e.g. P. Glafkides, Chimie et Physique Photographique, Paul Montel, Paris (1967), GF Duffin, Photographic Emulsion Chemistry, The Focal Press, London (1966), VL Zelikman et al, Making and Coating Photographic Emulsion, The Focal Press, London (1966) from soluble silver salts and soluble halides.

The halide silver is preferably precipitated in the presence of the binder, for example the gelatin, and can be carried out in the acidic, neutral or alkaline pH range, silver halide complexing agents preferably being additionally used. The latter include, for example, ammonia, thioether, imidazole, ammonium thiocyanate or excess halide. The water-soluble silver salts and the halides are combined either in succession by the single-jet process or simultaneously by the double-jet process or by any combination of the two processes. Dosing with increasing inflow rates is preferred, the "critical" feed rate, at which no new germs are being produced, should not be exceeded. The pAg range can vary within wide limits during the precipitation, preferably the so-called pAg-controlled method is used, in which a certain pAg value is kept constant or a defined pAg profile is traversed during the precipitation. In addition to the preferred precipitation with an excess of halide, so-called inverse precipitation with an excess of silver ions is also possible. In addition to precipitation, the silver halide crystals can also grow through physical ripening (Ostwald ripening), in the presence of excess halide and / or silver halide complexing agent. The growth of the emulsion grains can even take place predominantly by Ostwald ripening, preferably a fine-grained, so-called Lippmann emulsion, mixed with a less soluble emulsion and redissolved on the latter.

Salts or complexes of metals, such as Cd, Zn, Pb, Tl, Bi, Ir, Rh, may also be present during the precipitation and / or physical ripening of the silver halide grains.

The precipitation can also be carried out in the presence of sensitizing dyes. Complexing agents and / or dyes can be rendered ineffective at any time, e.g. by changing the pH or by an oxidative treatment.

After crystal formation has been completed or at an earlier point in time, the soluble salts are removed from the emulsion, e.g. by pasta and washing, by flakes and washing, by ultrafiltration or by ion exchangers.

The silver halide emulsion is generally subjected to chemical sensitization under defined conditions - pH, pAg, temperature, gelatin, silver halide and sensitizer concentration - until the optimum sensitivity and fog are reached. The procedure is e.g. described by H. Frieser "The basics of photographic processes with silver halides" page 675-734, Akademische Verlagsgesellschaft (1968).

The chemical sensitization can take place with the addition of compounds of sulfur, selenium, tellurium and / or compounds of gold, platinum, palladium, iridium or rhodium, furthermore thiocyanate compounds, surface-active compounds such as thioethers, heterocyclic nitrogen compounds (e.g. imidazoles, azaindenes) or also spectral sensitizers (described, for example, by F. Hamer "The Cyanine Dyes and Related Compounds ", 1964, or Ullmanns Encyclopedia of Technical Chemistry, 4th Edition, Vol. 18, pp. 431 ff. And Research Disclosure No. 17643, Section III). Alternatively or additionally, a reduction sensitization with the addition of reducing agents can be added (Tin-II salts, amines, hydrazine derivatives, aminoboranes, silanes, formamidinesulfinic acid) can be carried out by hydrogen, by low pAg (eg less than 5) and / or high pH (eg above 8).

The photographic emulsions may contain compounds to prevent fogging or to stabilize the photographic function during production, storage or photographic processing.

Azaindenes are particularly suitable, preferably tetra- and penta-azaindenes, in particular those which are substituted by hydroxyl or amino groups. Such connections are for example from Birr, Z. Wiss. Phot. 47 (1952), pp. 2-58. Salts of metals such as mercury or cadmium, aromatic sulfonic or sulfinic acids such as benzenesulfinic acid, or nitrogen-containing heterocycles such as nitrobenzimidazole, nitroindazole, (subst.) Benzotriazoles or benzothiazolium salts can also be used as antifoggants. Heterocycles containing mercapto groups, for example mercaptobenzthiazoles, mercaptobenzimidazoles, mercaptotetrazoles, mercaptothiadiazoles, mercapto, are particularly suitable pyrimidines, these mercaptoazoles also containing a water-solubilizing group, for example a carboxyl group or sulfo group. Other suitable compounds are published in Research Disclosure No. 17643 (1978), Section VI.

The stabilizers can be added to the silver halide emulsions before, during or after their ripening. Of course, the compounds can also be added to other photographic layers which are assigned to a halogen silver layer.

Mixtures of two or more of the compounds mentioned can also be used.

The photographic emulsion layers or other hydrophilic colloid layers of the light-sensitive material produced according to the invention can contain surface-active agents for various purposes, such as coating aids, to prevent electrical charging, to improve the sliding properties, to emulsify the dispersion, to prevent adhesion and to improve the photographic characteristics ( eg acceleration of development, high contrast, sensitization etc.).

The photographic emulsions can be spectrally sensitized using methine dyes or other dyes. Particularly suitable dyes are cyanine dyes, merocyanine dyes and complex merocyanine dyes.

Sensitizers can be dispensed with if the intrinsic sensitivity of the silver halide is sufficient for a certain spectral range, for example the blue sensitivity of silver bromide.

Color photographic materials usually contain at least one red-sensitive, green-sensitive and blue-sensitive emulsion layer. These emulsion layers are assigned non-diffusing monomeric or polymeric color couplers, which can be located in the same layer or in a layer adjacent to it. Usually cyan couplers are assigned to the red-sensitive layers, purple couplers to the green-sensitive layers and yellow couplers to the blue-sensitive layers.

Color couplers for producing the blue-green partial color image are usually couplers of the phenol or α-naphthol type; suitable examples of this are known in the literature.

Color couplers for producing the yellow partial color field are usually couplers with an open-chain catomethylene grouping, in particular couplers of the α-acylacetamide type; Suitable examples of this are α-benzoylacetanilide couplers and α-pivaloylacetanilide couplers, which are also known from the literature.

Color coupler for generating the purple partial color image are usually 5-pyrazolone, indazolone or pyrazoloazole type couplers; Suitable examples of this are described in large numbers in the literature.

The color couplers can be 4-equivalent couplers, but also 2-equivalent couplers. The latter are derived from the 4-equivalent couplers in that they contain a substituent in the coupling site which is split off during the coupling. The 2-equivalent couplers include those that are colorless, as well as those that have an intense intrinsic color that disappears when the color is coupled or is replaced by the color of the image dye produced (mask coupler), the white couplers that react with Color developer oxidation products result in essentially colorless products. The 2-equivalent couplers also include those couplers that contain a cleavable residue in the coupling point, which is released upon reaction with color developer oxidation products and thereby either directly or after one or more further groups have been cleaved from the primarily cleaved residue ( eg DE-A-27 03-145, DE-A-28 55 697, DE-A-31 05 026, DE-A-33 19 428), a certain desired photographic activity unfolds, for example as a development inhibitor or accelerator. Examples of such 2-equivalent couplers are the known DIR couplers as well as DAR or. FAR coupler.

Since with DIR, DAR or FAR couplers the effectiveness of the residue released during coupling is mainly desired and the color-forming properties of these couplers are less important, such DIR, DAR or FAR couplers are also suitable, which give essentially colorless products on coupling (DE-A-1 547 640).

The cleavable residue can also be a ballast residue, so that upon reaction with color developer oxidation products coupling products are obtained which are diffusible or at least have a weak or restricted mobility (US Pat. No. 4,420,556).

High molecular weight color couplers are described, for example, in DE-C-1 297 417, DE-A-24 07 569, DE-A-31 48 125, DE-A-32 17 200, DE-A-33 20 079, DE-A-33 24 932, DE-A-33 31 743, DE-A-33 400 376, EP-A-27 284, US-A-4 080 211. The high molecular weight color couplers are usually produced by polymerizing ethylenically unsaturated monomeric color couplers. However, they can also be obtained by polyaddition or polycondensation.

The couplers or other compounds can be incorporated into silver halide emulsion layers by first preparing a solution, a dispersion or an emulsion of the compound in question and then adding it to the casting solution for the layer in question. Choosing the right one Solvents or dispersants depend on the solubility of the compound.

Methods for introducing compounds which are essentially insoluble in water by grinding processes are described, for example, in DE-A-2 609 741 and DE-A-2 609 742.

Hydrophobic compounds can also be introduced into the casting solution using high-boiling solvents, so-called oil formers. Corresponding methods are described for example in US-A-2 332 027, US-A-2 801 170, US-A-2 801 171 and EP-A-O 043 037.

Instead of the high-boiling solvents, oligomers or polymers, so-called polymeric oil formers, can be used.

The compounds can also be introduced into the casting solution in the form of loaded latices. Reference is made, for example, to DE-A-2 541 230, DE-A-2 541 274, DE-A-2 835 856, EP-AO 014 921, EP-AO 069 671, EP-A-O 130 115, US Pat. A-4 291 113.

The diffusion-resistant incorporation of anionic water-soluble compounds (eg dyes) can also be carried out with the aid of cationic polymers, so-called pickling polymers.

Suitable oil formers are e.g. Alkyl phthalates, phosphoric acid esters, citric acid esters, benzoic acid esters, alkylamides, fatty acid esters and trimesic acid esters.

Color photographic material typically comprises at least one red-sensitive emulsion layer, at least one green-sensitive emulsion layer and at least one blue-sensitive emulsion layer on a support. The order of these layers can be varied as desired. Couplers which form blue-green, purple and yellow dyes are usually incorporated into the red, green or blue-sensitive emulsion layers. However, different combinations can also be used.

Each of the light-sensitive layers can consist of a single layer or can also comprise two or more silver halide emulsion partial layers (DE-C-1 121 470). Red-sensitive silver halide emulsion layers are often arranged closer to the support than green-sensitive silver halide emulsion layers and these are in turn closer than blue-sensitive layers, with a non-light-sensitive yellow filter layer generally being located between green-sensitive layers and blue-sensitive layers.

With a suitably low intrinsic sensitivity of the green or red-sensitive layers, other layer arrangements can be chosen without the yellow filter layer, in which, for example, the blue-sensitive, then the red-sensitive and finally the green-sensitive layers follow on the support.

The non-light-sensitive intermediate layers, which are generally arranged between layers of different spectral sensitivity, can contain agents which prevent undesired diffusion of developer oxidation products from one light-sensitive layer into another light-sensitive layer with different spectral sensitization.

If there are several sub-layers of the same spectral sensitization, these can differ with regard to their composition, in particular with regard to the type and amount of the silver halide grains. In general, the sublayer with higher sensitivity will be located further from the support than the sublayer with lower sensitivity. Partial layers of the same spectral sensitization can be adjacent to one another or through other layers, e.g. separated by layers of other spectral sensitization. For example, all highly sensitive and all low-sensitive layers can be combined to form a layer package (DE-A 1 958 709, DE-A 2 530 645, DE-A 2 622 922).

The photographic material may further contain compounds absorbing UV light, whiteners, spacers, filter dyes, formalin scavengers and others.

Compounds that absorb UV light are intended on the one hand to protect the image dyes from fading by UV-rich daylight and, on the other hand, as filter dyes to absorb the UV light in daylight upon exposure and thus improve the color rendering of a film. Connections of different structures are usually used for the two tasks. Examples are aryl substituted benzotriazole compounds (US-A 3 533 794), 4-thiazolidone compounds (US-A 3 314 794 and 3 352 681), benzophenone compounds (JP-A 2784/71), cinnamic acid ester compounds (US-A 3 705 805 and 3 707) 375), butadiene compounds (US-A 4 045 229) or benzoxazole compounds (US-A 3 700 455).

Ultraviolet absorbing couplers (such as α-naphthol type cyan couplers) and ultraviolet absorbing polymers can also be used. These ultraviolet absorbents can be fixed in a special layer by pickling.

Filter dyes suitable for visible light include oxonol dyes, hemioxonol dyes, styrene dyes, merocyanine dyes, cyanine dyes and azo dyes. Of these dyes, oxonol dyes, hemioxonol dyes and merocyanine dyes are used particularly advantageously.

Suitable whiteners are described, for example, in Research Disclosure December 1978, page 22 ff, Unit 17 643, Chapter V.

Certain binder layers, in particular the most distant layer from the support, but also occasionally intermediate layers, especially if they are the most distant layer from the support during manufacture, may contain photographically inert particles of inorganic or organic nature, e.g. as a matting agent or as a spacer (DE-A 3 331 542, DE-A 3 424 893, Research Disclosure December 1978, page 22 ff, Unit 17 643, Chapter XVI).

The average particle diameter of the spacers is in particular in the range from 0.2 to 10 μm. The spacers are water-insoluble and can be alkali-insoluble or alkali-soluble, the alkali-soluble ones generally being removed from the photographic material in the alkaline development bath. Examples of suitable polymers are polymethyl methacrylate, copolymers of acrylic acid and methyl methacrylate and hydroxypropyl methyl cellulose hexahydrophthalate.

The binders of the material according to the invention, in particular if gelatin is used as the binder, are hardened with suitable hardeners, for example with hardeners of the epoxy type, the ethyleneimine type, the acryloyl type or the vinylsulfone type. Diazine, triazine or 1,2-dihydroquinoline series hardeners are also suitable.

The binders of the material according to the invention are preferably hardened with instant hardeners.

Immediate hardeners are understood to mean compounds which crosslink suitable binders in such a way that the hardening is completed to such an extent immediately after casting, at the latest after 24 hours, preferably at the latest after 8 hours, that no further change in the sensitometry caused by the crosslinking reaction and the swelling of the layer structure occurs . Swelling is understood to mean the difference between the wet film thickness and the dry film thickness during the aqueous processing of the film (Photogr. Sci. Eng. 8 (1964), 275; Photogr. Sci. Eng. (1972), 449).

These hardening agents that react very quickly with gelatin are e.g. to carbamoylpyridinium salts, which are able to react with free carboxyl groups of the gelatin, so that the latter react with free amino groups of the gelatin to form peptide bonds and crosslink the gelatin.

• (a)
  
  worin
  R₁ Alkyl, Aryl oder Aralkyl bedeutet,
  R₂ die gleiche Bedeutung wir R₁ hat oder Alkylen, Arylen, Aralkylen oder Alkaralkylen bedeutet, wobei die zweite Bindung mit einer Gruppe der Formel
  
  verknüpft ist, oder
  R₁ und R₂ zusammen die zur Vervollständigung eines gegebenenfalls substituierten heterocyclischen Ringes, beispielsweise eines Piperidin-, Pipe­razin- oder Morpholinringes erforderlichen Atome bedeuten, wobei der Ring z.B. durch C₁-­C₃-Alkyl oder Halogen substituiert sein kann,
  R₃ für Wasserstoff, Alkyl, Aryl, Alkoxy, -NR₄-COR₅, -(CH₂)_m-NR₈R₉, -(CH₂)_n-CONR₁₃R₁₄ oder
  
  oder ein Brückenglied oder eine direkte Bindung an eine Polymerkette steht, wobei
  R₄, R₆, R₇, R₉, R₁₄, R₁₅, R₁₇, R₁₈, und R₁₉ Wasserstoff oder C₁-C₄-Alkyl,
  R₅ Wasserstoff, C₁-C₄-Alkyl oder NR₆R₇,
  R₈ -COR₁₀
  R₁₀ NR₁₁R₁₂
  R₁₁ C₁-C₄-Alkyl oder Aryl, insbesondere Phenyl,
  R₁₂ Wasserstoff, C₁-C₄-Alkyl oder Aryl, insbeson­dere Phenyl,
  R₁₃ Wasserstoff, C₁-C₄-Alkyl oder Aryl, insbeson­dere Phenyl,
  R₁₆ Wasserstoff, C₁-C₄-Alkyl, COR₁₈ oder CONHR₁₉,
  m eine Zahl 1 bis 3
  n eine Zahl 0 bis 3
  p eine Zahl 2 bis 3 und
  Y O oder NR₁₇ bedeuten oder
  R₁₃ und R₁₄ gemeinsam die zur Vervollständigung eines gegebenenfalls substituierten hetero­cyclischen Ringes, beispielsweise eines Piperidin-, Piperazin- oder Morpholinringes erforderlichen Atome darstellen, wobei der Ring z.B. durch C₁-C₃-Alkyl oder Halogen substituiert sein kann,
  Z die zur Vervollständigung eines 5- oder 6-­gliedrigen aromatischen heterocyclischen Ringes, gegebenenfalls mit anelliertem Ben­zolring, erforderlichen C-Atome und
  X^⊖ ein Anion bedeuten, das entfällt, wenn bereits eine anionische Gruppe mit dem übrigen Molekül verknüpft ist;
• (b)
  
  worin
  R₁, R₂, R₃ und X^⊖ die für Formel (a) angegebene Bedeutung besitzen.

Suitable examples of instant hardeners are, for example, compounds of the general formulas

• (a)
  
  wherein
  R₁ denotes alkyl, aryl or aralkyl,
  R₂ has the same meaning as R₁ or means alkylene, arylene, aralkylene or alkaralkylene, the second bond having a group of the formula
  
  is linked, or
  R₁ and R₂ together represent the atoms required to complete an optionally substituted heterocyclic ring, for example a piperidine, piperazine or morpholine ring, which ring can be substituted, for example, by C₁-C₃alkyl or halogen,
  R₃ for hydrogen, alkyl, aryl, alkoxy, -NR₄-COR₅, - (CH₂) _m -NR₈R₉, - (CH₂) _n -CONR₁₃R₁₄ or
  
  or a bridge link or a direct bond to a polymer chain, wherein
  R₄, R₆, R₇, R₉, R₁₄, R₁₅, R₁₇, R₁₈, and R₁₉ are hydrogen or C₁-C₄-alkyl,
  R₅ is hydrogen, C₁-C₄-alkyl or NR₆R₇,
  R₈ -COR₁₀
  R₁₀ NR₁₁R₁₂
  R₁₁ C₁-C₄ alkyl or aryl, especially phenyl,
  R₁₂ is hydrogen, C₁-C₄ alkyl or aryl, especially phenyl,
  R₁₃ is hydrogen, C₁-C₄ alkyl or aryl, especially phenyl,
  R₁₆ is hydrogen, C₁-C₄-alkyl, COR₁₈ or CONHR₁₉,
  m is a number 1 to 3
  n is a number 0 to 3
  p is a number 2 to 3 and
  YO or NR₁₇ mean or
  R₁₃ and R₁₄ together represent the atoms required to complete an optionally substituted heterocyclic ring, for example a piperidine, piperazine or morpholine ring, which ring can be substituted, for example, by C₁-C₃alkyl or halogen,
  Z the C atoms and required to complete a 5- or 6-membered aromatic heterocyclic ring, optionally with a fused benzene ring
  X ^{⊖ is} an anion which is omitted if an anionic group is already linked to the rest of the molecule;
• (b)
  
  wherein
  R₁, R₂, R₃ and X ^{⊖ have} the meaning given for formula (a).

Of course, it must be ensured that all components of the photographic material are iron-free or sufficiently low in iron. This applies in particular to the binders.

The materials according to the invention, be it color negative, color direct positive or color reversal materials, are processed in the usual manner according to the processes recommended for this.

Example 1 (comparative example )

A silver chloride emulsion is produced in a vessel made of V4A stainless steel (DIN material number 1.4571, AISI standard 316 L) according to the following procedure:

In 4 l of a 9% by weight solution of a low-iron inert bone gelatin (≦ 5 ppm Fe), which contains 25 g NaCl and 0.5 g 1,8-dihydroxy-3,6-dithiaoctane, is stirred vigorously at 45 ° C each 10 l of a 2.5 N AgNO₃ and a 2.5 N NaCl solution run in by the double-jet process in 55 minutes, the run-in speed being 10 times as great at the end as at the beginning. The pCl is kept at 0.95 and the pH is kept at 4.0 with nitric acid. The emulsion obtained has an average grain size (diameter of the same-volume sphere) of 0.8 μm.

The emulsion is freed from excess salts by the coagulation process and adjusted to a silver content of 200 g (as AgNO 3) / kg at a gelatin concentration of 7.5% by weight with the addition of further low-iron inert bone gelatin.

The emulsion was chemically ripened optimally with thiosulfate and gold salts and cast on a substrate with an application of 5 g of silver (as AgNO₃). After exposure for 5 sec with a tungsten lamp of 200 W. through a step wedge and development with a developer of the composition N-methyl-p-aminophenol 1.0 g Sodium sulfite anhydrous 13.0 g Hydroquinone 3.0 g Sodium carbonate anhydrous 26.0 g Potassium bromide 1.0 g dissolved in 1 liter of water a relative sensitivity of 100 is obtained with a fog of 0.16.

At the same time, the iron content was measured by means of atomic absorption spectroscopy. An iron content of 150 ppm Fe, based on AgNO₃, was determined in the emulsion.

Example 2 (according to the invention

A silver chloride emulsion was prepared in the same way as in Example 1, but the container and all parts of the system, such as stirrers, etc., with which the emulsion comes into contact, were made from titanium (DIN material number 3.7025, AISI standard Ti Grade 2).

The emulsion was chemically ripened in the same way as that in Example 1 and checked photographically. A relative sensitivity of 125 was found with a fog of 0.11.

In the same way as in Example 1, an iron determination was carried out in the emulsion. The iron content found was 2 ppm, based on AgNO₃.

Example 3 (comparison)

• 1. Eine Substratschicht aus 200 mg Gelatine mit KNO₃- und Chromalaunzusatz.
• 2. Eine Haftschicht aus 320 mg Gelatine.
• 3. Eine blauempfindliche Silberbromidchloridemulsions­schicht (99 mol-% Chlorid) aus 600 mg AgNO₃ mit 1600 mg Gelatine, 1,0 mmol Gelbkuppler, 27,7 mg 2,5-Dioctylhydrochinon und 650 mg Trikresylphosphat.
  Die Emulsion wurde durch Doppeleinlauf mit einer Korngröße von 0,8 µm hergestellt, in der üblichen Weise geflockt, gewaschen und mit Gelatine redis­pergiert. Das Gewichtsverhältnis Gelatine-Silber (als AgNO₃) betrug 0,5. Die Emulsion wurde anschließend mit 60 µmol Thiosulfat pro mol Ag zur optimalen Empfindlichkeit gereift, für den blauen Spektralbereich sensibilisiert und stabilisiert.
• 4. Eine Zwischenschicht aus 1200 mg Gelatine, 80 mg 2,5-Dioctylhydrochinon und 100 mg Trikresylphos­phat.
• 5. Eine grünempfindliche Silberbromidchloridemulsions­schicht (99 mol-% Chlorid) aus 530 mg AgNO₃ mit 750 mg Gelatine, 0,625 mmol Purpurkuppler, 118 mg α-(3-t-Butyl-4-hydroxyphenoxy)-myristinsäureethyl­ester, 43 mg 2,5-Dioctylhydrochinon, 343 mg Dibu­tylphthalat und 43 mg Trikresylphosphat.
• 6. Eine Zwischenschicht aus 1550 mg Gelatine, 285 mg eines UV-Absorbers der Formel
  
  80 mg Dioctylhydrochinon und 650 mg Trikresylphos­phat.
• 7. Eine rotempfindliche Silberbromidchloridemulsions­schicht (99 mol-% Chlorid) aus 400 mg AgNO₃ mit 1470 mg Gelatine, 0,780 mmol Blaugrünkuppler, 285 mg Dibutylphthalat und 122 mg Trikresylphos­phat.
• 8. Eine Schutzschicht aus 1200 mg Gelatine, 134 mg eines UV-Absorbers gemäß 6. Schicht und 240 mg Tri­kresylphosphat.
• 9. Eine Härtungsschicht aus 400 mg Gelatine une 400 mg Härtungsmittel der Formel
  

A layer support made of paper coated on both sides with polyethylene was provided with the following layers. The quantities refer to 1 m².

• 1. A substrate layer of 200 mg of gelatin with KNO₃- and Chromalaunzusatz.
• 2. An adhesive layer made of 320 mg of gelatin.
• 3. A blue-sensitive silver bromide chloride emulsion layer (99 mol% chloride) from 600 mg AgNO₃ with 1600 mg gelatin, 1.0 mmol yellow coupler, 27.7 mg 2,5-dioctylhydroquinone and 650 mg tricresyl phosphate.
  The emulsion was prepared by double inlet with a grain size of 0.8 μm, flocculated in the usual way, washed and redispersed with gelatin. The gelatin-silver weight ratio (as AgNO₃) was 0.5. The emulsion was then ripened with 60 μmol thiosulfate per mol Ag for optimal sensitivity, sensitized to the blue spectral range and stabilized.
• 4. An intermediate layer of 1200 mg gelatin, 80 mg 2,5-dioctylhydroquinone and 100 mg tricresyl phosphate.
• 5. A green-sensitive silver bromide chloride emulsion layer (99 mol% chloride) from 530 mg AgNO₃ with 750 mg gelatin, 0.625 mmol magenta coupler, 118 mg α- (3-t-butyl-4-hydroxyphenoxy) -myristinic acid ester, 43 mg 2,5-dioctylhydroquinone , 343 mg of dibutyl phthalate and 43 mg of tricresyl phosphate.
• 6. An intermediate layer of 1550 mg gelatin, 285 mg of a UV absorber of the formula
  
  80 mg dioctyl hydroquinone and 650 mg tricresyl phosphate.
• 7. A red-sensitive silver bromide chloride emulsion layer (99 mol% chloride) from 400 mg AgNO₃ with 1470 mg gelatin, 0.780 mmol cyan coupler, 285 mg dibutyl phthalate and 122 mg tricresyl phosphate.
• 8. A protective layer of 1200 mg of gelatin, 134 mg of a UV absorber according to the 6th layer and 240 mg of tricresyl phosphate.
• 9. A hardening layer of 400 mg gelatin and 400 mg hardening agent of the formula
  

The following connections were used as color couplers:

The gelatin used in Example 1 was used; the emulsions were prepared in steel kettles according to Example 1. The iron content of the layer package applied to the support was 85 ppm based on AgNO₃.

Example 4

A material was produced according to Example 3, but with the difference that the emulsions were produced in a device according to Example 2. The iron content of the layer package applied to the carrier was 12 ppm based on AgNO₃.

Example 5

The materials of Examples 3 and 4 were processed according to the standard process for color negative paper RA 4 / AP 94.

The following results were obtained for the individual color layers (E = relative sensitivity, S = fog) yellow purple Blue green E S E S E S Ex. 3 110 0.16 100 0.09 100 0.08 Ex. 4 114 0.10 106 0.08 108 0.07

Claims (7)

1. Color photographic material with at least one red-sensitive, containing at least one blue-green coupler, with at least one green-sensitive, containing at least one magenta coupler and with at least one blue-sensitive, containing at least one yellow coupler silver halide emulsion layer, at least one silver halide emulsion layer being a silver halide with at least 60 mol% AgCl contains, characterized in that the layers applied to the carrier together have an iron content of ≦ 50 ppm, based on silver halide, calculated as AgNO₃. 2. Photographic material according to claim 1, characterized in that the iron content is ≦ 20 ppm. 3. Photographic material according to claim 1, characterized in that the iron content is ≦ 10 ppm. 4. Photographic material according to claim 1, characterized in that the silver halide of the at least one silver halide emulsion layer consist of at least 80 mol% of silver chloride. 5. Photographic material according to claim 1, characterized in that the silver halides of all Silver halide emulsion layers consist of at least 60 mol% of silver chloride. 6. Photographic material according to claim 5, characterized in that the silver halides of all silver halide emulsion layers consist of at least 80 mol% of silver chloride. 7. Photographic material according to claim 1, characterized in that the carrier is polyethylene-coated paper.