EP0023670B1 - Photographic emulsion, production process and photographic materials - Google Patents

Description

The invention relates to a photographic emulsion which is stabilized by the addition of certain amino carboxylic acids and whose sensitivity is improved. The invention further relates to a process for the preparation of photographic emulsions and photographic materials.

It is known that materials with light-sensitive silver halide emulsions tend to form fog caused by germs that can be developed without exposure. The 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 rise 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 show increased fog values associated therewith. 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.

Stabilizing agents have various requirements, particularly 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, which the known stabilizing agents do not meet.

It is also known to chemically sensitize photographic silver halide emulsions using sodium thiosulfate, polythionates, thiosinamine or other sulfur compounds, and also using gold or palladium compounds. It is also possible to increase sensitivity through reducing substances. This is generally associated with an increase in fog and a deterioration in stability.

Substances which increase the sensitivity usually show in the best case the property that when the stability of the photographic material is tested at an elevated temperature the fog is also increased somewhat in accordance with the increase in sensitivity.

The invention was u. a. based on the task of finding substances which improve the stability in the sense described and at the same time unchanged or increased sensitivity.

worin bedeuten

• R¹ H; Alkyl-; Aryl-; Aralkyl-; Acylgruppe,
• R² Alkyl-; Aryl-; Aralkyl-; Acylgruppe,
• _R ³ H; Kation,
• _R ⁴ H; Alkyl-; Acylgruppe,
• n 0 oder eine ganze Zahl,

und/oder

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

A photographic silver halide emulsion with at least one compound of the formula has now been found:

in what mean

• R ¹ H; Alkyl-; Aryl; Aralkyl-; Acyl group,
• R ² alkyl; Aryl; Aralkyl-; Acyl group,
• _R ³ 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 CyαIopentyI or cyclohexyl ring.

Compound I can optionally be present in the emulsion as a disulfide. It can also be present as a salt, and both the carboxyl and the amino group can be included in the salt formation.

The invention further relates to a process for the preparation of photographic emulsions by precipitation in the presence of a protective colloid and addition of the compounds to be used according to the invention to the emulsion. The invention furthermore relates to a photographic material with a support, at least one silver halide emulsion layer and optionally further layers, at least one layer containing a compound to be used according to the invention. The compound to be used according to the invention is preferably contained in a silver halide emulsion layer. However, it can optionally also be contained in another colloid layer which does not contain silver halide, but is in a water-permeable relationship to at least one silver halide emulsion layer.

The compounds to be used according to the invention are generally added to the emulsion in amounts of not more than 9 mg per mole of silver halide. In general, the emulsions thus contain no more than 9 mg of the compound to be used according to the invention per mole of silver halide.

A preferred amount range is from 0.1-8 mg per mole of silver halide, in particular from 0.2-4 mg per mole of silver halide.

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 ⁴ and R ² ) 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 6-12 C atoms, especially phenyl.

Preferred aralkyl groups (R ¹ 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 Alkalion, insbesondere Na oder K,
• n ist bevorzugt 0, 1 oder 2, insbesondere 0.

Acyl radicals (R ¹ , R ² and R ') are understood in particular to be those which are derived from aliphatic or aromatic carbon 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 ion, in particular Na or K,
• n is preferably 0, 1 or 2, in particular 0.

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

Examples of compounds which can be used according to the invention are contained in Table 1 below; the production is known from the literature:

Of the compounds to be used according to the invention, compound 1.1 (penicillamine) is particularly preferred. Penicmamm is described in DE-A-2335093 as an additive to photographic silver halide emulsions in an amount of 10 -5000 mg per mole of AgX to stabilize the latent image. It is therefore surprising that this compound in the amount range of <9 mg per mole of AgX added to the emulsion has a fog-reducing and density-stabilizing effect with significantly increased sensitivity.

The compounds which can be used according to the invention can be introduced into at least one layer or intermediate layer of a photographic material. For example, they can be added to the light-sensitive silver halide emulsion or the finished casting solution, or they can be applied to the photographic material together with the last protective layer.

In principle, the compounds 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 which can be used according to the invention are added after chemical ripening, preferably to the finished casting solution.

The compounds 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 emulsions 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, e.g. 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.

It is also possible to sensitize the emulsions with polyalkylene oxide derivatives, e.g. B. with polyethylene oxide of 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 usual 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, 1 266 655, French Patent 7 102 716 or German Laid-Open Specification 2 232 317. 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. Vmylsulfonic acid hardeners, carbodiimide or carbmoyl hardeners such as e.g. B. in German laid-open publications 2 263 602, 2 225 230 and 1 808 685, French patent specification 1 491 807, German patent specification 872 153 and GDR patent specification 7 218 are described. 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) and K. Venkataraman in “The Chemistry of Synthetic Dyes”, Vol. 4 , Pp. 341-387, Academic Press (1971).

The emulsions can be applied to the usual substrates, e.g. B. on carriers 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. B. of polyethylene or polypropylene, can also contain supports made of glass or metal.

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 iodide emulsion sensitized with gold and thiosulfate with an iodide content of 2.5 mol% and an average sensitivity is added after the maturation has ended to 1.2 g of triazaindolizine per mole of silver halide. This emulsion, which was adjusted to a silver content of 170 g AgN0 ₃ per liter and a gelatin content of 15%, was 0, 0.25, 0.5, 1.0, 2.0 and 4.0 mg per mole of silver halide Penicillamine added and the emulsion stirred at 40 ° C for 10 minutes. Then 20 ml of a 5% saponin solution was added to the emulsion. 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. From the cast-ready emulsion a web with a silver coating of 9.5 g AgN0 _{3 /} m ² and a protective layer thickness of 1.8 ₁₁ m was poured onto a polyester base with anti-halo 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 1 sind die Schleierwerte, Empfindlichkeiten, Gradienten und die Empfindlichkeitsanstiege nach der Lagerung der frischen und der im Heizschrank gelagerten Proben zusammengestellt.The developer contained:

posed. The development time at 26 ° C was 2 minutes 30 seconds. Table 1 shows the haze values, sensitivities, gradients and increases in sensitivity after storing the fresh samples and the samples stored in the heating cabinet.

The test series shows that with an addition of 0.25 mg penicillamine per mole of silver halide, the haze and sensitivity increase after storage in the heating cabinet is already reduced. The optimal result is achieved with an amount of 2.0 mg penicillamine per mole of silver halide, with a sensitivity increase of 50% being observed.

Claims (6)

1. A photographic silver halide emulsion characterised in that it contains at the most 9 mg, per mol of silver halide, of at least one compound of the general formula I

wherein

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

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

R³ represents hydrogen or a cation,

R⁴ represents hydrogen or an alkyl or acyl group and

n represents 0 or a whole number,

and/or

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

and/or of the corresponding disulphide.

2. Process for the preparation of a photographic silver halide emulsion by precipitation of a silver halide in the presence of a protective colloid, characterised in that, per mol of silver halide, at least one compound of the formula

wherein

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

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

R³ represents hydrogen or a cation,

R⁴ represents hydrogen or an alkyl or acyl group and

n represents 0 or a whole number,

and/or

R^l and R² together represent the atoms required to complete a ring,

and/or the corresponding disulphide
is added to the emulsion in such a quantity that the finished silver halide emulsion contains at the most 9 mg of the compound per mol of silver halide.

3. A photographic material consisting of a support layer and at least one photosensitive silver halide emulsion layer and optionally further layers, characterised in that it contains at the most 9 mg, per mol of silver halide, of at least one compound of the general formula

wherein

R^I represents hydrogen or an alkyl, aryl, aralkyl or acyl group,

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

R³ represents hydrogen or a cation,

R⁴ represents hydrogen or an alkyl or acyl group and

n represents 0 or a whole number,

and/or

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

and/or of the corresponding disulphide.

4. A photographic material according to claim 3, characterised in that the compound is contained in a silver halide emulsion layer in a quantity of at the most 9 mg per mol of silver halide.

5. A material according to claim 3, characterised in that

R¹ represents hydrogen or alkyl with 1 to 4 carbon atoms,

R² represents alkyl with 1 to 4 carbon atoms,

R³ represents hydrogen or a cation,

R⁴ represents hydrogen and

n represents 0, 1 or 2.

6. A material according to claim 5, characterised in that

R¹ represents CH₃,

R² represents CH₃,

R³ represents hydrogen,

R⁴ represents hydrogen and

n represents 0.