EP0023668B1 - Photographic silverhalide emulsion with a stabilizer, process for its production and photographic recording material - Google Patents

Description

The invention relates to a silver halide emulsion which is stabilized against the formation of fog by the addition of at least one stabilizing agent. The invention further relates to a method for producing such an emulsion and photographic materials.

It is known that materials with light-sensitive silver halide emulsions, in particular chemically sensitized ones, tend to form fog caused by germs which can be developed without exposure. This formation of fog occurs particularly when stored for too long, especially at elevated temperature and humidity. ,

It is known to add so-called antifoggants or stabilizers to photographic silver halide emulsions to improve their stability. Stability of a photographic material means u. a. the lowest possible increase in fog during storage and the smallest possible density deviations of the stored material compared to the fresh state. In particular with silver bromide iodide emulsions, it is often observed that they increase in sensitivity when stored under elevated temperature conditions and, as a result, show increased fog values. This property is also given under the conditions of natural storage and causes a continuous change in density over the course of the storage time, which is particularly disadvantageous for materials for the needs of reprographic technology, where high demands are placed on the stability of the material. Have a stabilizing effect, for. B. heterocyclic mercapto compounds, e.g. B. those described in DE-B-1 183 371, DE-A-2 308 530 and DE-A-1 622 271.

However, these stabilizers have the disadvantage that they generally reduce the sensitivity of the stabilized emulsion in effective concentrations, thereby impairing their applicability. The gradation of the emulsion can also be adversely affected by these stabilizers.

• Der Erfindung lag u. a. die Aufgabe zugrunde, neue Stabilisierungsmittel aufzufinden.

Stabilizing agents, especially with regard to the interaction with other photographic additives and with regard to the diversity of photographic reproduction processes and the photographic materials used for this purpose, are subject to the most varied requirements which the known stabilizing agents do not meet:

• The invention was based on the object of finding new stabilizing agents.

worin bedeuten

• R¹ H; Alkyl-; Aryl-; Aralkyl-; Acylgruppe,
• R² Alkyl-; Aryl-; Aralkyl-; Acylgruppe,
• R3 H; Kation,
• R⁴ H; Alkyl-; Acylgruppe,
• n 0 oder eine ganze Zahl

und/oder

• R¹ zusammen mit R² Rest zur Vervollständigung eines vorzugsweise carbocyclischen Ringes, insbesondere eines Cyclopentyl oder Cyclohexylringes.

A photographic silver halide emulsion has now been found which contains at least one complex of cobalt with an aminocarboxylic acid of the following formula 1:

in what mean

• R ¹ H; Alkyl-; Aryl; Aralkyl-; Acyl group,
• R ² alkyl; Aryl; Aralkyl-; Acyl group,
• R3 H; Cation,
• R ⁴ H; Alkyl-; Acyl group,
• n 0 or an integer

and or

• R ¹ together with R ² radical to complete a preferably carbocyclic ring, in particular a cyclopentyl or cyclohexyl ring.

Such complexes can be prepared very simply by reacting a water-soluble cobalt salt with a compound of the formula I. The preparation of such complexes is also known from the literature. Complexes with a molar ratio of cobalt: amino acid such as 1: 1, 1: 2 and 1: 3 are preferred, in which the cobalt can be divalent or trivalent.

The invention further relates to a process for the preparation of photographic emulsions by precipitation in a protective colloid and addition of at least one compound to be used according to the invention to the emulsion. The invention further relates to a photographic material with a support, at least one silver halide emulsion layer and optionally further layers, wherein a compound to be used according to the invention is contained in at least one layer.

The compound to be used according to the invention is preferably in a silver halide emulsion sion layer included.

The alkyl, aryl and acyl groups mentioned can also be substituted with substituents which have no adverse effect in photographic materials.

Preferred alkyl radicals (R ¹ , R ² and R ⁴ ) have 1 -4 C atoms, for example methyl, butyl. Methyl and ethyl are particularly preferred.

Preferred aryl groups (R ¹ and R ² ) can be those with 6 to 12 carbon atoms, especially phenyl.

Preferred aralkyl groups (R 'and R ² ) have 1―2 C atoms in the aliphatic and 6―12 C atoms in the aromatic part, for example benzyl.

• R³ ist bevorzugt H, Ammonium und ein Alkali oder, insbesondere, Na oder K,
• n ist bevorzugt 0, oder 2, insbesondere 0.

Acyl radicals (R ¹ and R ² ) are understood in particular to be those which are derived from aliphatic or aromatic carboxylic or sulfonic acids, including carbonic acid monoesters, carbamic acids or sulfamic acids. Examples of such acyl radicals are formyl, benzoyl, phenylcarbamoyl, ethoxycarbonyl. Acetyl is particularly preferred.

• R ³ is preferably H, ammonium and an alkali or, in particular, Na or K,
• n is preferably 0, or 2, in particular 0.

Compounds in which n = 0 and R ⁴ = H are particularly preferred.

Examples of compounds still free of cobalt are contained in Table 1 below; the production is known from the literature.

Compound 1.1 (penicillamine) is known in DE-A-2 335 093 as an additive to photographic silver halide emulsions in amounts of 10-5000 mg per mole of AgX for stabilizing the latent image.

The preparation of cobalt complexes of penicillamine is described below as an example of the preparation of the compounds to be used according to the invention.

Variant 2.1

0.5 g penicillamine are dissolved in 100 ml H ₂ 0 and added to 100 ml of a 1% solution of CO (NO ₃ ) ₂ .6 H ₂ 0.

Variant 2.2

1.0 g penicillamine is dissolved in 100 ml H ₂ 0 and 100 ml of a 1% solution of CO (NO ₃ ) ₂ . 6 H ₂ 0 added.

Variant 2.3

2.0 g penicillamine are dissolved in 100 ml H ₂ 0 and added to 100 ml of a 1% solution of CO (N0 ₃ ) ₂ - 6 H ₂ 0.

The stabilizing agents which can be used according to the invention can be introduced into at least one layer or intermediate layer of a photographic material which is water-permeable in relation to the emulsion layer to be stabilized. You can especially the photosensitive silver halide emulsions such. B. added to the finished casting solution but can also be applied together with the last protective layer on the photographic material. The amount of stabilizing agent used can vary within wide limits. It depends on the type of emulsion and the desired effect. In general, the desired effects are achieved with amounts of 0.05 mg to 100 mg, in particular from 0.05 mg to 2 mg, per mole of silver halide.

This generally leads to a reduction in fog and a stabilization of density with constant sensitivity, in particular in the range from 0.1-2 mg of the cobalt chelate compound per mole of silver halide. Higher amounts of the cobalt chelate compound desensitize and stabilize photographic halosilver emulsions and are used in particular when an emulsion is to be rendered insensitive to bright darkroom light. Depending on the desired effect, amounts in excess of 2 mg per mole of silver halide of the cobalt chelate compound are to be used, in general amounts of 2 mg to 100 mg per mole of silver halide are sufficient.

For processing with darkroom lighting as bright as possible, it is practical to strongly desensitize the photographic material, which is possible by adding the compounds to be used according to the invention in larger amounts. So you get z. B. with an amount of about 30 mg of the cobalt chelate compound of penicillamine a reduction in sensitivity of about 1.3 log lt and can then process the material with significantly brighter darkroom lighting. This application is of interest for photographic materials for copying processes in which correspondingly strong light sources are available and it is not possible to convert to fine-grained, insensitive emulsions, since these do not bring the desired flat gradation. The optimal amount for each emulsion or each photographic material can be determined in a simple manner by the usual test experiments.

In principle, the stabilizing agents which can be used according to the invention can be added to light-sensitive silver halide emulsions at any time during the preparation or further processing of the emulsion. In a preferred embodiment, the stabilizing agents used are added to the silver halide emulsion during chemical ripening. In another preferred embodiment, they are only added to the finished casting solution after chemical ripening.

In a preferred embodiment, the compounds to be used according to the invention are used together with free compounds of the formula I, which are therefore not in the form of a complex.

This can increase both sensitivity and stability when the fog is reduced. The simultaneous use of the cobalt complex of penicillamine with free penicillamine is particularly suitable.

The stabilizers to be used according to the invention can be used in the usual light-sensitive photographic materials which are suitable for the production of black and white images, e.g. B. black and white recording or copying materials or reversal materials. Furthermore, color couplers can be contained in the material without affecting the stabilization.

The usual silver halide emulsions, which can consist of pure silver halides or mixtures thereof, are suitable for the present invention. For example, the silver halide grains can consist of silver chloride, silver bromide, silver iodide, silver chloride bromide, silver chloride iodide, silver bromide iodide and silver chloride bromide iodide. In particular, the present invention is suitable for silver bromide iodide emulsion with an iodide content of up to 8 mol%.

The emulsions can be chemically sensitized, e.g. B. by adding sulfur-containing compounds during chemical ripening, for example allyl isothiocyanate, allyl thiourea, sodium thiosulfate and the like. Reducing agents such as chemical sensitizers can also be used. B. the tin compounds described in Belgian patents 493 464 and 568 687, also polyamines such as diethylenetriamine or aminomethylsulfinic acid derivatives, e.g. B. according to Belgian patent 547 323 used.

Precious metal or noble metal compounds such as gold, platinum, palladium, iridium, ruthenium or rhodium are also suitable as chemical sensitizers. This method of chemical sensitization is described in the article by R. KOSLOWSKY, Z. Wiss. Phot. 46 (1951), pages 65-72.

It is also possible to sensitize the emulsions with polyalkylene oxide derivatives, e.g. B. with polyethylene oxide having a molecular weight between 1000 and 20,000, further with condensation products of alkylene oxides and aliphatic alcohols, glycols, cyclic dehydration products of hexitols, with alkyl-substituted phenols, aliphatic carboxylic acids, aliphatic amines, aliphatic diamines and amides. The condensation products have a molecular weight of at least 700, preferably more than 1000. To achieve special effects, these sensitizers can of course be used in combination, as described in Belgian patent 537 278 and British patent 727 982.

The emulsions are preferably not optically sensitized or orthosensitized with the usual dyes.

The emulsions can be hardened in the customary manner, for example with formaldehyde or halogen-substituted aldehydes which contain a carboxyl group, such as mucobromic acid, diketones, methanesulfonic acid esters and dialdehydes. Furthermore, the photographic layers can be hardened with hardeners of the epoxy type, the heterocyclic ethylene imine or the acryloyl type. Examples of such hardeners are e.g. B. described in German Offenlegungsschrift 2,263,602 or British Patent 1,266,655.

Furthermore, it is also possible to harden the layers in accordance with the process of German laid-open specification 2218009 in order to obtain photographic materials which are suitable for high-temperature processing.

It is also possible to harden the photographic layers or the color photographic multilayer materials with hardeners of the diazine, triazine or 1,2-dihydroquinoline series, as in British Patents 1 193 290, 1 251 091, 1 306 544, 1 266655, French Patent 7 102 716 or German Laid-Open Specification 2 332 317. Examples of such hardeners are alkyl or arylsulfonyl group-containing diazine derivatives, derivatives of hydrogenated diazines or triazines such as. B. 1,3,5-hexahydrotriazine, fluorine-substituted diazine derivatives such as. B. fluoropyrimidine, esters of 2-substituted 1,2-dihydroquinoline or 1,2-dihydroisoquinoline-N-carboxylic acids. Also useful are vinyl sulfonic acid hardeners, carbodiimide or carbamoyl hardeners such as. B. described in German Offenlegungsschriften 2 263 602, 2 225 230 and 1 808 685, French patent 1491807, German patent 872153 and GDR patent 7218. Other useful hardeners are described, for example, in British Patent 1,268,550.

The present invention can be applied to both black and white and color photographic images. Colored photographic images can e.g. B. according to the known principle of chromogenic development in the presence of color couplers, which react with the oxidation product of coloring p-phenylenediamine developers to form dyes. The color couplers can contain at least one layer of the photographic material, e.g. B. at least one silver halide layer itself. Examples of color couplers that can be used are the publication “Color Couplers” by W. PELZ in “Messages from the Research Laboratories of Agfa, Leverkusen / Munich”, Volume III (1961) by K. VENKA-TARAMAN in “The Chemistry of Synthetic Dyes”, Vol 4, pages 341-387, Academic Press (1971).

The emulsions can be applied to the usual substrates, e.g. B. on supports of cellulose esters such as cellulose acetate or cellulose acetobutyrate, further polyester, especially polyethylene terephthalate or polycarbonates, especially based on bis-phenylolpropane. Also suitable are paper supports, which are optionally impermeable polyolefin layers, e.g. Polyethylene or polypropylene, and glass or metal supports.

For a black / white development, the usual known black / white developer compounds are suitable, such as. B. hydroxybenzenes and 3-pyrazolidones.

The usual color developer substances can be used to generate color images.

example 1

A silver bromide emulsion sensitized with gold and thiosulfate with an iodide content of 2.5 mol% and a medium sensitivity is added after the final ripening to 1.2 g triazaindolizine per mole of silver halide. This emulsion, which was adjusted to a silver content of 170 g AgNO ₃ per liter and a gelatin content of 15%, was mixed with 0, 2, 4 and 8 ml of the 1: 100 diluted solution of the co-chelate compound according to variants 2.1, per mole of silver halide. 2.2 and 2.3 added. The mixture was then stirred at 40 ° C. for 10 minutes, then 20 ml of a 5% saponin solution were added. For hardening, 35 ml of a 2% formalin solution per mole of silver halide were added to the emulsion shortly before pouring.

The protective layer contained 5% of a suitable protective layer gelatin as well as 40 ml of a 5% saponin solution and 40 ml of a 5% sucrose monolaurate solution per liter of protective layer solution. One web of each cast-ready emulsion was cast with a silver coating of 9.5 g AgNO ₃ / m ² and a protective layer thickness of 1.8 μm onto a polyester base with anti-halo backing and dried. The total layer thickness of this film was 12 µm.

Sensitometer strips of the fresh film and of the film stored at 60 ° C. for 72 hours were then exposed on a short-term sensitometer at 1/1000 seconds and processed as usual.

gestellt. Die Entwicklungszeit bei 26°C betrug 2 Minuten 30 Sekunden. In der Tabelle 2 sind die sensitometrischen Werte der Proben zusammengestellt.

The developer contained:

posed. The development time at 26 ° C was 2 minutes 30 seconds. Table 2 shows the sensitometric values of the samples.

The results show that the haze when storing the heating cabinet is significantly reduced everywhere in the chelate compounds to be used according to the invention and the different amounts used.

The higher the molar ratio of cobalt to penicillamine, the lower the sensitivity increase after storage in the heating cabinet.

Example 2

After adding the triazaindolizine, 2 mg of penicillamine as a 0.1% aqueous solution and after a stirring time of 10 minutes at 40 ° C., 2, 4, 8.16 ml of the cobalt chelate compound 2.2 (1: 100 diluted) are added to a silver halide emulsion according to Example 1. added. As a comparison, the emulsion without the addition of the penicillamine and the cobalt chelate compound is used. The further processing of the emulsion is carried out in accordance with Example 1. The results of the sensitometric test are summarized in Table 3.

The results show that with the combination of penicillamine and the cobalt chelate compound of penicillamine, an additional increase in sensitivity can be achieved with a considerable reduction in the haze values and the increase in sensitivity after storage in the heating cabinet.

Claims (7)

1. A photographic silver halide emulsion, characterised in that the emulsion contains a complex of cobalt with a compound of the following formula I:

in which

R¹ denotes hydrogen or an alkyl, aryl, aralkyl or acyl group,

R² denotes an alkyl, aryl, aralkyl or acyl group,

R³ denotes hydrogen or a cation,

R⁴ denotes hydrogen or an alkyl or acyl group,

n = 0 or an integer,

and/or

R¹ and R² together represent the atoms required to complete a ring.

2. An emulsion according to Claim 1, characterised in that it contains from 0.05 mg to 100 mg of cobalt complex per mole of silver halide.

3. A process for the preparation of a silver halide emulsion by precipitating the silver halide in the presence of a protective colloid, characterised in that a complex of cobalt with a compound of the following formula I:

in which

R¹ denotes hydrogen or an alkyl, aryl, aralkyl or acyl group,

R² denotes an alkyl, aryl, aralkyl or acyl group,

R³ denotes hydrogen or a cation,

R⁴ denotes hydrogen or an alkyl or acyl group,

n = 0 or an integer,

and/or

R¹ and R² together represent the atoms required to complete a ring;

is added to the emulsion.

4. A photographic material comprising a substrate and, applied thereto, at least one photosensitive silver halide emulsion layer, and optionally comprising other layers, characterised in that at least one layer contains a complex of cobalt with a compound of the following formula I:

in which

R¹ denotes hydrogen or an alkyl, aryl, aralkyl or acyl group,

R² denotes an alkyl, aryl, aralkyl or acyl group,

R³ denotes hydrogen or a cation,

R⁴ denotes hydrogen or an alkyl or acyl group,

n = 0 or an integer,

and/or

R^I and R² together represent the atoms required to complete a ring.

5. A photographic material according to Claim 4, characterised in that the cobalt complex is contained in a silver halide emulsion layer.

6. A material according to Claim 4, characterised in that

R¹ denotes hydrogen or alkyl with 1 -4 C atoms,

R² denotes alkyl with 1 -4 C atoms,

R³ denotes hydrogen or a cation,

R⁴ denotes hydrogen,

and

n 0, or2.

7. A material according to Claim 6, characterised in that

R¹ denotes CH₃,

R2 denotes CH₃,

R³ denotes hydrogen,

R⁴ denotes hydrogen,

and

n =0.