EP0355568B1 - Preparation of a silver halide emulsion - Google Patents

Description

The invention relates to a process for the preparation of a light-sensitive silver halide emulsion by precipitation of the silver halide in the presence of gelatin, flocculation and washing of the silver halide precipitated in the presence of the gelatin and redispersion with the addition of further gelatin.

The oxidation of gelatins for inertization, i.e. to destroy photographically active substances, but also to remove bacterial contamination or to brighten the color of the gelatin, is known, using as the oxidizing agent hydrogen peroxide, peracids such as performic acid, peracetic acid, periodic acid, chloramine T (N-chloro-p-toluenesulfonic acid amide sodium) and the like .ä. be used.

From EP-A-0 227 444 and EP-A-0 228 256 it is known that the use of oxidized gelatin for the production of tabular silver halide emulsions, in particular if the emulsion contains a large proportion of chloride. However, it is disadvantageous that such gelatins lead to an intolerable increase in the haze.

The object of the invention was therefore to modify the production of a silver halide emulsion so that on the one hand an improved grain growth is achieved and on the other hand an undesirably high haze is avoided.

It has now been found that this object can be achieved in that in the process described at the outset the precipitation in the presence of a gelatin with a gold number of at most 10 μmol / g gelatin and a cysteine content of at most 6 ppm and the redispersion with a gelatin with a Gold number of at least 23 µmol / g gelatin is carried out and the weight ratio of the amount of gelatin used in the precipitation to the amount of gelatin added during the redispersion is 1: 1 to 1:10. The gelatin for redispersion preferably has cysteine contents of 6 to 16 ppm.

Gelatins with a gold value of at least 23 µmol / g are obtained with the usual alkaline or acidic liming. Gelatins with a gold value of at most 10 µmol / g and a cysteine content of at most 6 ppm are obtained from the usual gelatins by oxidation with the oxidizing agents specified above.

The gelatin-to-silver weight ratio (Ge-Si) of the finished emulsion is preferably 1: 1 to 1: 5, silver being used as the silver nitrate in the calculation.

The weight ratio of the amount of gelatin during the precipitation to the amount of gelatin that is added during the redispersion is preferably 1: 1 to 1: 5.

In a preferred embodiment of the invention, all light-sensitive silver halide emulsion layers contain silver halide emulsions produced according to the invention.

The oxidized gelatin can be acidic or alkaline. The raw material can be bone or skin. However, bone is preferred as the raw material, since this makes inert gelatins, i.e. Gelatins with low levels of photographically active contaminants, such as thiosulfate or sulfite, can be produced.

The gelatin can be oxidized at any time during the production of the gelatin. The oxidation can also take place in the gelatin solution before the beginning of the emulsion precipitation.

The pH during the oxidation can fluctuate within wide limits and is preferably between pH 2 and pH 8, higher and lower pH values are possible, but then the physical properties of the gelatin are deteriorated.

The oxidation of the gelatin can be checked by determining the gold value or the cysteine content and terminated according to the desired values.

To determine the gold number, the gelatin is titrated potentiometrically with tetrachloroauric acid at pH 2. Of the Gold consumption gives the gold number. According to this method, non-oxidized gelatins show gold numbers of ≧ 23 µmol / g. This corresponds approximately to a methionine content of ≧ 50 µmol / g.

The cysteine content of the gelatin is determined by a method described by H. Meichelbeck, AG Hack and Chr. Sentler in Z. Ges. Textilindustrie 70 , 242 (1968). Here, 1 g of gelatin with the addition of 1 ml of water and 1 ml of 30 wt .-% H₂SO₄ hydrolyzed for 60 minutes in a boiling water bath and after cooling with 3 m of tris (hydroxymethyl) aminomethane (TRIS) and a TRIS / HCl buffer adjusted to pH 7.4.

5,5′-dithiobis (2-nitrobenzoic acid) (DTNB) is used as the color reagent. The measurement is carried out at 412 nm. The same solution as the measurement solution, but without hydrolyzate, is used as the reference solution. However, since the gelatin hydrolyzates have different colors that absorb in this area, the hydrolyzate with all additives except DTNB must also be measured and subtracted from the absorbance of the measurement solution.

The buffer is prepared as follows: 121 g of TRIS are dissolved in 500 ml of water and the pH is adjusted to 7.4 with HCl. The solution is then made up to 1000 ml.

Reagent solution: 10 ml of TRIS / HCl buffer are diluted to about 50 ml with water, containing 25 mg of reagent (DTNB) and 20 mg EDTA salt dissolved. The pH is adjusted to 4 with HCl. The solution is made up to 100 ml.

3 m TRIS is also required to adjust the pH of the gelatin hydrolyzate.

In order to obtain exact values, a double determination is essential. The fluctuation range of the measurements must not be greater than ± 1 ppm.

The cysteine content results from the measured value by means of a previously established calibration curve. As with H. Meichelbeck et al, loc. cit. specified, the cysteine content can also be obtained arithmetically from the measured value without a calibration curve.

Both the gold number determination and cysteine analysis are extremely reproducible.

The gelatins can be desalinated or not. Inert gelatins are preferred which are characterized in that they contain only a few photographically active compounds. Non-desalted inert gelatins often have a high content of Ca ions.

The silver halide present as a light-sensitive component in the photographic emulsion can contain chloride, bromide or iodide or mixtures thereof as the halide. For example, the halide content at least one layer consists of 0 to 15 mol% of iodide, 0 to 100 mol% of chloride and 0 to 100 mol% of bromide. In the case of color negative and color reversal films, silver bromide iodide emulsions are usually used; in the case of color negative and color reversal paper, silver chloride bromide emulsions are usually used. It can be predominantly compact crystals, which are, for example, regularly cubic or octahedral or can have transitional forms. However, platelet-shaped crystals can preferably also be present, the average ratio of diameter to thickness of which is preferably at least 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. However, the layers can also have tabular silver halide crystals in which the ratio of diameter to thickness is substantially greater than 5: 1, for example 12: 1 to 30: 1.

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 .mu.m and 5.0 .mu.m, particularly preferably 0.2 .mu.m and 2.0 .mu.m the grain size distribution can be both homo- and heterodisperse. Homodisperse grain size distribution means that 95% of the grains do not exceed ± 30% of deviate from the average grain size. 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 silver halide can be precipitated 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 just yet no new germs arise, 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 by 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, Fe 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, for example 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 by flocculation and washing.

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).

Chemical sensitization can be carried out with the addition of compounds of sulfur, selenium, tellurium and / or noble metal compounds (e.g. gold, platinum, palladium, iridium), 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 Industrial Chemistry, 4th edition, vol. 18, pp. 431 ff. and Research Disclosure No. 17643, section III) are added. As an alternative or in addition, a reduction sensitization can be carried out with the addition of reducing agents (tin-II salts, amines, hydrazine derivatives, aminoboranes, silanes, formamidine sulfinic acid) using hydrogen, by means of 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. Furthermore, 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, optionally substituted benzotriazoles or benzothiazolium salts can be used as antifoggants. Heterocycles containing mercapto groups, for example mercaptobenzthiazoles, mercaptobenzimidazoles, mercaptotetrazoles, mercaptothiadiazoles, mercaptopyrimidines, are particularly suitable, these mercaptoazoles also being able to contain 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.). In addition to natural surface-active compounds, e.g. Saponin, mainly synthetic surface-active compounds (surfactants) are used: non-ionic surfactants, e.g. Alkylene oxide compounds, glycerin compounds or glycidol compounds, cationic surfactants, e.g. higher alkyl amines, quaternary ammonium salts, pyridine compounds and other heterocyclic compounds, sulfonium compounds or phosphonium compounds, anionic surfactants containing an acid group, e.g. Carboxylic acid, sulfonic acid, a phosphoric acid, sulfuric acid ester or phosphoric acid ester group, ampholytic surfactants, e.g. Amino acid and aminosulfonic acid compounds as well as sulfuric or phosphoric acid esters of an amino alcohol.

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.

Research Disclosure 17643/1978 in Department IV contains an overview of the polymethine dyes suitable as spectral sensitizers, their suitable combinations and combinations with a super-sensitizing effect.

• 1. als Rotsensibilisatoren
     9-Ethylcarbocyanine mit Benzthiazol, Benzselenazol oder Naphthothiazol als basische Endgruppen, die in 5- und/oder 6-Stellung durch Halogen, Methyl, Methoxy, Carbalkoxy, Aryl substituiert sein können sowie 9-Ethyl-naphthoxathia- bzw. -selencarbocyanine und 9-Ethyl-naphthothiaoxa- bzw. -benzimidazocarbocyanine, vorausgesetzt, daß die Farbstoffe mindestens eine Sulfoalkylgruppe am heterocyclischen Stickstoff tragen.
• 2. als Grünsensibilisatoren
     9-Ethylcarbocyanine mit Benzoxazol, Naphthoxazol oder einem Benzoxazol und einem Benzthiazol als basische Endgruppen sowie Benzimidazocarbocyanine, die ebenfalls weiter substituiert sein können und ebenfalls mindestens eine Sulfoalkylgruppe am heterocyclischen Stickstoff enthalten müssen.
• 3. als Blausensibilisatoren
     symmetrische oder asymmetrische Benzimidazo-, Oxa-, Thia- oder Selenacyanine mit mindestens einer Sulfoalkylgruppe am heterocyclischen Stickstoff und gegebenenfalls weiteren Substituenten am aromatischen Kern, sowie Apomerocyanine mit einer Rhodaningruppe.

The following dyes, sorted by spectral range, are particularly suitable:

• 1. as red sensitizers
  9-ethyl carbocyanines with benzthiazole, benzselenazole or naphthothiazole as basic end groups, which can be substituted in the 5- and / or 6-position by halogen, methyl, methoxy, carbalkoxy, aryl and 9-ethyl-naphthoxathia or -selencarbocyanines and 9- Ethyl naphthothiaoxa or benzimidazocarbocyanines, provided that the dyes carry at least one sulfoalkyl group on the heterocyclic nitrogen.
• 2. as green sensitizers
  9-ethylcarbocyanines with benzoxazole, naphthoxazole or a benzoxazole and a benzthiazole as basic end groups, and also benzimidazocarbocyanines, which may also be further substituted and must also contain at least one sulfoalkyl group on the heterocyclic nitrogen.
• 3. as blue sensitizers
  symmetrical or asymmetrical benzimidazo, oxa, thia or selenacyanines with at least one sulfoalkyl group on the heterocyclic nitrogen and optionally further substituents on the aromatic nucleus, and apomerocyanines with a rhodanine group.

In addition to the gelatins according to the invention, the emulsions can contain additional binders, such as synthetic or natural layer-forming polymers.

The emulsions according to the invention are suitable for all types of photographic materials, such as X-ray films, black and white film, black and white paper, but in particular for color photographic materials.

Examples of color photographic materials are color negative films, color reversal films, color positive films, color photographic paper, color reversal photographic paper, color sensitive materials for the color diffusion transfer process or the silver color bleaching process.

Suitable supports for the production of color photographic materials are, for example, films and foils of semi-synthetic and synthetic polymers, such as cellulose nitrate, Cellulose acetate, cellulose butyrate, polystyrene, polyvinyl chloride, polyethylene terephthalate and polycarbonate and paper laminated with a baryta layer or α-olefin polymer layer (eg polyethylene). These carriers can be colored with dyes and pigments, for example titanium dioxide. They can also be colored black for the purpose of shielding light. The surface of the support is generally subjected to a treatment in order to improve the adhesion of the photographic emulsion layer, for example a corona discharge with subsequent application of a substrate layer.

The color photographic materials usually contain at least one red-sensitive, green-sensitive and blue-sensitive silver halide emulsion layer and, if appropriate, intermediate layers and protective layers.

In addition to binders and silver halide grains, the color couplers are essential components of the photographic emulsion layers.

The differently sensitized 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.

Color couplers for generating the purple partial color image are usually couplers of the 5-pyrazolone, indazolone or pyrazoloazole type.

Color couplers for producing the yellow partial color image are generally couplers with an open-chain ketomethylene group, in particular couplers of the α-acylacetamide type; suitable examples are α-benzoylacetanilide couplers and α-pivaloylacetanilide couplers.

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 point, 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), and the white couplers that react with color developer oxidation products yield essentially colorless products. The 2-equivalent couplers are also those couplers which contain a detachable radical in the coupling point, which in reaction with color developer oxidation products Freedom is set, either directly or after one or more other groups have been split off from the primarily split off remainder (e.g. DE-A-27 03-145, DE-A-28 55 697, DE-A-31 05 026, DE -A-33 19 428), develops a certain desired photographic effectiveness, 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.

DIR couplers which release development inhibitors of the azole type, for example triazoles and benzotriazoles, are described in DE-A-24 14 006, 26 10 546, 26 59 417, 27 54 281, 27 26 180, 36 26 219, 36 30 564, 36 36 824, 36 44 416 and 28 42 063. Further advantages for color reproduction, ie, color separation and color purity, and for detail reproduction, ie, sharpness and granularity, can be achieved with those DIR couplers which, for example, do not split off the development inhibitor directly as a result of the coupling with an oxidized color developer, but only after a further follow-up reaction, which is achieved, for example, with a timing group. Examples of these are in DE-A-28 55 697, 32 99 671, 38 18 231, 35 18 797, in EP-A-157 146 and 204 175, in US-A-4 146 396 and 4 438 393 and in GB -A-2 072 363.

DIR couplers which release a development inhibitor which is decomposed into essentially photographically ineffective products in the developer bath are described, for example, in DE-A-32 09 486 and in EP-A-167 168 and 219 713. This measure ensures trouble-free development and processing consistency.

When using DIR couplers, in particular those which release an easily diffusible development inhibitor, improvements in color rendering, e.g. achieve a more differentiated color rendering, as described, for example, in EP-A-115 304, 167 173, GB-A-2 165 058, DE-A-37 00 419 and US-A-4 707 436.

The DIR couplers can be added to a wide variety of layers in a multilayer photographic material, for example also light-insensitive or intermediate layers. However, they are preferably added to the light-sensitive silver halide emulsion layers, the characteristic properties of the silver halide emulsion, for example its iodide content, the structure of the silver halide grains or their grain size distribution having an influence on the photographic properties achieved. The influence of the inhibitors released can be limited, for example, by incorporating an inhibitor scavenger layer in accordance with DE-A-24 31 223. For reasons of reactivity or stability, it may be advantageous to use a DIR coupler which forms in the respective layer in which it is introduced a color which is different from the color to be produced in this layer in the coupling.

To increase the sensitivity, the contrast and the maximum density, DAR or FAR couplers can be used, which release a development accelerator or an fogger. Compounds of this type are, for example, in DE-A-25 34 466, 32 09 110, 33 33 355, 34 10 616, 34 29 545, 34 41 823, in EP-A-89 834, 110 511, 118 087, 147 765 and described in US-A-4,618,572 and 4,656,123.

As an example of the use of BAR couplers (Bleach Accelerator Releasing Coupler), reference is made to EP-A-193 389.

It can be advantageous to modify the effect of a photographically active group which is split off from a coupler in that an intermolecular reaction of this group occurs after its release with another group according to DE-A-35 06 805.

Since with DIR, DAR or FAR couplers mainly the effectiveness of the residue released during coupling is 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-15 47 640).

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).

The material may further contain compounds other than couplers, which can liberate, for example, a development inhibitor, a development accelerator, a bleaching accelerator, a developer, a silver halide solvent, a fogging agent or an antifoggant, for example so-called DIR hydroquinones and other compounds as described, for example, in US Pat US-A-4 636 546, 4 345 024, 4 684 604 and in DE-A-31 45 640, 25 15 213, 24 47 079 and in EP-A-198 438. These compounds perform the same function as the DIR, DAR or FAR couplers, except that they do not form coupling products.

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 40 376, 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. The selection of the suitable solvent or dispersing agent depends 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-26 09 741 and DE-A-26 09 742.

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-2 322 027, US-A-2 801 170, US-A-2 801 171 and EP-A-0 043 037.

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-25 41 230, DE-A-25 41 274, DE-A-28 35 856, EP-A-0 014 921, EP-A-0 069 671, EP-A-0 130 115, U.S.-A-4,291,113.

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

Suitable oil formers are e.g. Alkyl phthalates, phosphonic acid esters, phosphoric acid esters, citric acid esters, benzoic acid esters, amides, fatty acid esters, trimesic acid esters, alcohols, phenols, aniline derivatives and hydrocarbons.

Examples of suitable oil formers are dibutylphthalate, dicyclohexylphthalate, di-2-ethylhexylphthalate, decylphthalate, triphenylphosphate, tricresylphosphate, 2-ethylhexyldiphenylphosphate, tricyclohexylphosphate, tri-2-ethylhexylphosphate, tridecoxyphosphate, 2-ethylhexylphosphate, tridecoxyphosphate, 2-ethylhexylphosphate, , 2-ethylhexyl p-hydroxybenzoate, diethyldodecanamide, N-tetradecylpyrrolidone, isostearyl alcohol, 2,4-di-tert.-amylphenol, dioctylacelate, glycerol tributyrate, isostearyl lactate, trioctyl citrate, N, N-doxy-5-butyl-2-butyl -octylaniline, paraffin, dodecylbenzene and diisopropylnaphthalene.

Each of the differently sensitized, 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 Layer supports are often arranged closer than green-sensitive silver halide emulsion layers and these in turn are closer than blue-sensitive layers, 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 can be selected without the yellow filter layer, other layer arrangements in which e.g. the blue-sensitive, then the red-sensitive and finally the green-sensitive layers follow.

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.

Suitable agents, which are also called scavengers or EOP-catchers, are described in Research Disclosure 17 643 (Dec. 1978), Chapter VII, 17 842/1979, pages 94-97 and 18.716 / 1979, page 650 and in EP-A- 69,070, 98,072, 124,877, 125,522 and in US-A-463,226.

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 away 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-19 58 709, DE-A-25 30 645, DE-A-26 22 922).

The photographic material can also contain UV light-absorbing compounds, whiteners, spacers, filter dyes, formalin scavengers, light stabilizers, antioxidants, D _min dyes, additives to improve dye, coupler and white stabilization and to reduce the color fog, plasticizers (latices), Contain biocides 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. Usually for the two tasks Connections of different structures are used. 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, styryl 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 e.g. in Research Disclosure 17,643 (Dec. 1978), Chapter V, in US-A-2,632,701, 3,269,840 and in GB-A-852,075 and 1,319,763.

Certain layers of binder, in particular the layer furthest from the support, but also occasionally intermediate layers, especially if they represent the most distant layer from the support during production, can contain photographically inert particles of inorganic or organic nature, for example as matting agents or as spacers (DE-A-33 31 542, DE-A-34 24 893, Research Disclosure 17 643, Dec. 1978, 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.

Additives to improve dye, coupler and whiteness stability and to reduce the color fog (Research Disclosure 17 643/1978, Chapter VII) can belong to the following chemical substance classes: hydroquinones, 6-hydroxychromanes, 5-hydroxycoumarans, spirochromans, spiroindanes, p- Alkoxyphenols, sterically hindered phenols, gallic acid derivatives, methylenedioxybenzenes, aminophenols, sterically hindered amines, derivatives with esterified or etherified phenolic hydroxyl groups, metal complexes.

Compounds that have both a hindered amine partial structure and a hindered one Phenol partial structure in a molecule (US-A-4 268 593), are particularly effective for preventing the deterioration (deterioration or degradation) of yellow color images as a result of the development of heat, moisture and light. In order to prevent the deterioration (deterioration or degradation) of crimson color images, in particular their impairment (deterioration or degradation) as a result of exposure to light, Spiroindane (JP-A-159 644/81) and chromanes are caused by Hydroquinone diethers or monoethers are particularly effective (JP-A-89 835/80).

The layers of the photographic material can be hardened with the usual hardening agents. Suitable curing agents include formaldehyde, glutaraldehyde and similar aldehyde compounds, diacetyl, cyclopentadione and similar ketone compounds, bis (2-chloroethylurea), 2-hydroxy-4,6-dichloro-1,3,5-triazine and other compounds, the reactive halogen contain (US-A-3 288 775, US-A-2 732 303, GB-A-974 723 and GB-A-1 167 207) divinyl sulfone compounds, 5-acetyl-1,3-diacryloylhexahydro-1,3,5 triazine and other compounds containing a reactive olefin bond (US-A-3 635 718, US-A-3 232 763 and GB-A-994 869); N-hydroxymethylphthalimide and other N-methylol compounds (US-A-2 732 316 and US-A-2 586 168); Isocyanates (US-A-3 103 437); Aziridine compounds (US-A-3 017 280 and US-A-2 983 611); Acid derivatives (US-A-2 725 294 and US-A-2 725 295); Carbodiimide type compounds (US-A-3 100 704); Carbamoylpyridinium salts (DE-A-22 25 230 and DE-A-24 39 551); Carbamoyloxypyridinium compounds (DE-A-24 08 814); Compounds with a phosphorus-halogen bond (JP-A-113 929/83); N-carbonyloximide compounds (JP-A-43353/81); N-sulfonyloximido compounds (US-A-4 111 926), dihydroquinoline compounds (US-A-4 013 468), 2-sulfonyloxypyridinium salts (JP-A-110 762/81), formamidinium salts (EP-A-0 162 308) , Compounds with two or more N-acyloximino groups (US-A-4 052 373), epoxy compounds (US-A-3 091 537), isoxazole-type compounds (US-A-3 321 313 and US-A-3 543 292); Halocarboxyaldehydes such as mucochloric acid; Dioxane derivatives such as dihydroxydioxane and di-chlorodioxane; and inorganic hardeners such as chrome alum and zirconium sulfate.

The hardening can be effected in a known manner by adding the hardening agent to the casting solution for the layer to be hardened, or by overlaying the layer to be hardened with a layer which contains a diffusible hardening agent.

There are slow-acting and fast-acting hardeners and so-called instant hardeners, which are particularly advantageous, in the classes listed. 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 crosslinking reactions result conditional change in the sensitometry 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.

There are diffusible curing agents that have the same curing effect on all layers within a layer structure. But there are also layer-limited, non-diffusing, low-molecular and high-molecular hardeners. With them, individual layers, e.g. crosslink the protective layer particularly strongly. This is important if the silver halide layer is hardened little because of the increase in silver opacity and the protective layer has to improve the mechanical properties (EP-A 0 114 699).

Color photographic negative materials are usually processed by developing, bleaching, fixing and washing or by developing, bleaching, fixing and stabilizing without subsequent washing, with bleaching and fixing can be combined into one processing step. All developer compounds which have the ability to react in the form of their oxidation product with color couplers to form azomethine or indophenol dyes can be used as the color developer compound. Suitable color developer compounds are aromatic compounds of the p-phenylenediamine type containing at least one primary amino group, for example N, N-dialkyl-p-phenylenediamines such as N, N-diethyl-p-phenylenediamine, 1- (N-ethyl-N-methanesulfonamidoethyl) -3 -methyl-p-phenylenediamine, 1- (N-ethyl-N-hydroxyethyl) -3-methyl-p-phenylenediamine and 1- (N-ethyl-N-methoxyethyl) -3-methyl-p-phenylenediamine. Other useful color developers are described, for example, in J. Amer. Chem. Soc. 73 , 3106 (1951) and G. Haist, Modern Photographic Processing, 1979, John Wiley and Sons, New York, page 545 ff.

After the color development, an acidic stop bath or watering can follow.

Usually the material is bleached and fixed immediately after color development. For example, Fe (III) salts and Fe (III) complex salts such as ferricyanides, dichromates, water-soluble cobalt complexes can be used as bleaching agents. Iron (III) complexes of aminopolycarboxylic acids, in particular, for example, ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, iminodiacetic acid, N-hydroxyethylethylenediaminetriacetic acid, are particularly preferred, Alkyliminodicarboxylic acids and corresponding phosphonic acids. Persulphates and peroxides, for example hydrogen peroxide, are also suitable as bleaching agents.

The bleach-fixing bath or fixing bath is usually followed by washing, which is designed as countercurrent washing or consists of several tanks with their own water supply.

Favorable results can be obtained using a subsequent final bath which contains little or no formaldehyde.

However, the washing can be completely replaced by a stabilizing bath, which is usually carried out in countercurrent. When formaldehyde is added, this stabilizing bath also acts as a final bath.

In the case of color reversal materials, development is first carried out using a black and white developer whose oxidation product is not capable of reacting with the color couplers. This is followed by a diffuse second exposure and then development with a color developer, bleaching and fixing.

The following alkaline ashed bone gelatins were used for the examples.

example 1

With gelatin 1, a silver bromide chloride emulsion with 10 mol% silver chloride was prepared by the double-jet method at 56 ° C. At the end of the silver halide precipitation, the GeSi was 0.15. The emulsion was flocculated by adding a flocculant and lowering the pH to 3.5 and then washing. The pH was then adjusted again to 4.5, further gelatin 1 was added, and the emulsion was redispersed with heating. After redispersion, the GeSi was 0.65. The emulsion was then matured with the addition of thiosulfate for optimal sensitivity (emulsion A).

Another emulsion with gelatin 2 was prepared by precipitation and redispersion using the same process (emulsion B).

Another emulsion with gelatin 2 during precipitation and gelatin 1 during redispersion was prepared in the same way (emulsion C).

The grain size distributions were determined with the Möller counter (G. Möller Int. Congr. Phot. Sci. Moscow 1970 , p.125).

The emulsions were provided per 100 g AgNO₃ 180 mg of a blue sensitizer and 120 g of a yellow coupler and poured onto a PE-coated paper base. One was placed over the emulsion layer Gelatin layer pulled with a hardener. After drying, the layers were exposed in a sensitometer and developed using the EP 2 process.

The latent image was determined 6 hours after the exposure, the exposed strip being stored at room temperature.

E Latentbild [log I.t].

The directly developed materials and those developed after 6 hours of storage were compared and found

E latent image [log it].

The grain distributions are shown in Fig. 1 (Emulsion A), Fig. 2 (B) and Fig. 3 (C).

The examples show that the use of oxidized gelatin in the batch has an improved grain distribution, i.e. very monodisperse emulsions. When using oxidized gelatin in post-ripening, however, there is a higher haze. In addition, the decline in the latent picture is noticeably stronger. If, on the other hand, the non-oxidized gelatin is used in the post-ripening, a better haze and a more stable latent image is obtained with a good grain distribution.

Example 2

Example 1 was repeated with gelatin 3 instead of gelatin 1 and gelatin 4 instead of gelatin 2. The silver chloride bromide emulsion contained 95 mol% of silver chloride, the ripening for optimum sensitivity was carried out with the addition of gold salts and thiosulfate. All other parameters remained unchanged. Emulsions D (gelatin 3 only), E (gelatin 4 only) and F (gelatin 4 during precipitation, gelatin 3 during redispersion) resulted.

As described in Example 1, the emulsions were provided with a blue sensitizer and a yellow coupler and then poured onto a PE coated paper backing. A layer of gelatin with a hardening agent is applied over the emulsion.

The emulsions were tested as in Example 1.

It is also shown that with this desalted, inert bone gelatin the oxidation does improve grain growth, but creates a higher haze. If the oxidized gelatin is used only when the unoxidized gelatin is precipitated and used after-ripening, good grain growth with good fog and good latent image stability is achieved.

Claims (5)

1. A process for the production of a photosensitive silver halide emulsion by precipitation of the silver halide in the presence of gelatine, flocculation and washing of the silver halide precipitated in the presence of the gelatine and redispersion with addition of more gelatine, the precipitation being carried out in the presence of a gelatine having a gold number of at most 10 µmol/g gelatine and a cysteine content of at most 6 ppm and redispersion being carried out with a gelatine having a gold number of at least 23 µmol/g gelatine, characterized in that the ratio by weight of the quantity of gelatine used during precipitation to the quantity of gelatine used during redispersion is from 1:1 to 1:10.
2. A process as claimed in claim 1, characterized in that the gelatine for redispersion has a cysteine content of 6 to 16 ppm.
3. A process as claimed in claim 1, characterized in that the ratio by weight of gelatine to silver in the final emulsion is from 1:1 to 1:5, silver being included in the calculation as silver nitrate.
4. A photographic silver halide recording material, characterized in that it contains at least one silver halide emulsion layer comprising a silver halide emulsion produced by the process claimed in claims 1 to 3.
5. A photographic silver halide recording material as claimed in claim 4, characterized in that all the photosensitive silver halide emulsion layers comprise silver halide emulsions produced by the process claimed in claims 1 to 3.

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