EP0154921B1 - Emulsion with a high silver chloride content, photographic registration material and process for obtaining a photographic registration - Google Patents

Description

The invention relates to an emulsion rich in silver chloride, a photographic recording material and a method for producing photographic recordings.

Numerous types of silver halide emulsions are known which contain chloride, bromide, iodide or mixtures thereof as the halide. Silver bromide and silver bromide iodide emulsions are generally used for more sensitive recording materials. A disadvantage of the last-mentioned emulsions is that they have an intrinsic sensitivity in the blue spectral range. Therefore, in color recording materials, green and red sensitive layers are generally placed behind a filter that absorbs blue light. Furthermore, such emulsions are not as quickly developable as silver chloride emulsions.

Proposals for the use of silver chloride emulsions are known from various publications. Since silver chloride has almost no inherent sensitivity in the visible spectrum, filter layers for absorbing the blue light (yellow filter) can be dispensed with when using chloride-rich silver halide emulsions in a color photographic recording material. A disadvantage of silver chloride emulsions is their low sensitivity. According to EP-A 0017 148, an improvement in sensitivity is to be achieved by metal doping. Chloride-rich silver halide emulsions also have poor storage stability and therefore tend to obscure. According to EPA 0 072 695, the use of silver halide solvents is intended to reduce the veil during chemical ripening.

Chloride-containing silver halide emulsions are also known, the grains of which have a layered structure. Such grains have a core and at least one layer which surrounds the core and whose properties differ from the core (core / shell emulsions). It is known from DE-AS 1 169290 and GB 1027146 to coat a silver chloride shell on a silver bromide core. DE-OS 2308239 and US 3,935,014 relate to emulsions for producing directly positive images with silver halide grains which have a localized phase with a high silver chloride content.

From EP-A 0080905 silver halide emulsions with silver chloride-rich grains are known which have a layer consisting essentially of silver bromide on their surface.

However, the known chloride-rich silver halide emulsions are still in need of improvement, particularly with regard to their sensitivity and tendency to fog.

It was therefore an object of the present invention to provide chloride-rich silver halide emulsions which have improved sensitometric properties. In particular, it was a task to increase the sensitivity and reduce the tendency to fog.

• 1. mindestens 60 Mol-% des Halogenids Chlorid ist,
• 2. der Bromidanteil in der Zone Z_Br wenigstens 50 Mol-% beträgt und
• 3. keine bromidreiche Zone Z_Br an der Obefläche der Silberhalogenidkörner liegt.

A photographic silver halide emulsion was found which essentially contains chloride as the halide and whose grains have at least one zone Z _Br with a high bromide content. The grains are characterized in that

• 1. at least 60 mol% of the halide is chloride,
• 2. the bromide content in zone Z _{Br is} at least 50 mol% and
• 3. there is no bromide-rich zone Z _Br on the surface of the silver halide grains.

The zone Z _Br rich in silver bromide can be present as a core or as a layer within the silver halide grain. Preferably 20% by volume of the silver halide of the grain is further from the crystal center than the silver bromide-rich zone Z _Br .

In principle, the silver halide grains in the bromide-rich zone Z _Br and in the areas other than halide can have chloride, bromide, iodide or mixtures thereof. The transition from the bromide-rich zone Z _Br to an adjacent zone of a different composition can be sharp or continuous.

In a preferred embodiment, the chloride content of the total halide content is at least 85, in particular at least 90 mol%. In a further preferred embodiment, the zone Z _Br rich in silver bromide consists essentially, for example at least 90%, or exclusively of silver bromide.

The silver halide emulsions according to the invention can be prepared by means of the customary procedures (for example single entry, double entry, with constant or accelerated material flow). It is particularly preferred to use the double-inlet process under control of the pAg value. Reference is made to Research Disclosure No. 17643 of December 1978, Sections I and II, published by Industrial Opportunities Ltd., Homewell Havant, Hampshire, P091 1 EF in the United Kingdom. The precipitation of the silver halide can be carried out in the presence of conventional dopants, e.g. B. in the presence of Ir compounds.

The silver halide grains can be designed, for example, as cubes, octahedra or tetradecahedra. The grain size is preferably between 0.1 and 2.5 μm, in particular between 0.2 and 1.0 μm.

In one embodiment of the invention, the emulsion has a narrow grain size distribution. In particular, at least 95% by weight of the grains have a diameter which does not deviate from the mean grain diameter by more than 40%. However, the emulsions can also have a wide grain size distribution. Here, at least 10%, preferably 20%, of Silver halide grains have a diameter that deviates at least 40% from the mean grain diameter.

The present invention further relates to a photographic recording material which contains at least one silver halide emulsion layer according to the invention on a support. The invention further relates to a method for producing photographic recordings by developing an exposed recording material according to the invention.

The emulsions according to the invention are preferably chemically sensitized on the grain surface to a high surface sensitivity. They can be chemically sensitized using known methods, e.g. B. with active gelatin or with compounds of sulfur, selenium, tellurium, gold, palladium, platinum, iridium, the pAg values between 4 and 10, the pH values between 3.5 and 9 and the temperatures between 30 ° C. and can fluctuate 90 ° C; chemical sensitization can be carried out in the presence of heterocyclic nitrogen compounds such as imidazoles, azaindenes, azapyridazines and azapyrimidines and thiocyanate derivatives, thioethers and other silver halide solvents. Alternatively or additionally, the emulsions according to the invention can be subjected to a reduction sensitization, e.g. by hydrogen, by low pAg (e.g. less than 5) and / or high pH (e.g. above 8), by reducing agents such as tin (11) chloride, thiourea dioxide and aminoborane. The surface ripening nuclei can also be present as troglodyte nuclei (sub-surface nuclei) according to DE-OS 2306447 and US Pat. No. 3,966,476. Other methods are described in the above. Research Disclosure No. 17643 in Section 111.

The emulsions can be optically sensitized in a manner known per se, e.g. with the usual polymethine dyes, such as neutrocyanines, basic or acidic carbocyanines, rhodacyanines, hemicyanines, styryl dyes, oxonols and the like. Such sensitizers are from F.M. Hamer in "The Cyanine Dyes and related Compounds", (1964). In this regard, reference is made to EP-A 0082649 and in particular to Ullmann's Encyclopedia of Industrial Chemistry, 4th edition, volume 18, pages 431 ff and to Research Disclosure No. 17643, section IV given above. The spectral sensitization can be carried out at any time Emulsion preparation takes place, d. H. during or after silver halide precipitation and before, during or after chemical sensitization.

The commonly used antifoggants and stabilizers can be used.

Particularly suitable stabilizers are azaindenes, preferably tetra- or penta-azaindenes, in particular those which are substituted by hydroxyl or amino groups. Such connections are e.g. B. in the article by Birr, Z. Wiss. Phot. 47, (1952), pp. 2-58. Other suitable stabilizers and antifoggants are given in Research Disclosure No. 17643 above in Section IV.

The recording material according to the invention is preferably a color photographic recording material. In a preferred embodiment, the color image is generated using color couplers. It is possible to let the color coupler diffuse into the recording material only during development.

In a preferred embodiment, however, the photographic material itself contains the usual color couplers, which can react with the oxidation product of developers, generally p-phenylenediamines, to form dyes. The red-sensitive layer can contain, for example, a non-diffusing color coupler for producing the blue-green partial color image, usually a coupler of the phenol or a-naphthol type. The green-sensitive layer can contain, for example, at least one non-diffusing color coupler for producing the purple partial color image, color couplers of the 5-pyrazolone type usually being used. The blue-sensitive layer can contain, for example, a non-diffusing color coupler for generating the yellow partial color image, usually a color coupler with an open-chain ketomethylene grouping. In the color couplers it can be, for. B. are 6-, 4- and 2-equivalent couplers, including the so-called white couplers, which do not give any dye when reacted with color developer oxidation products. Suitable couplers are known, for example, from the publications “Color Coupler” by W. Pelz in “Messages from the Research Laboratories of Agfa, Leverkusen / Munich”, Volume 111, page 111 (1961), K. Venkataraman in “The Chemistry of Synthetic Dyes”, Vol. 4, 341 to 387, Academic Press (1971) and TH James, "The Theory of the Photographic Process", 4th Ed., Pp. 353-362, and from Research Disclosure No. 17643, Section VII.

The recording material can also contain DIR compounds. DIR compounds are understood to mean those compounds which, when reacted with color developer oxidation products, release diffusing organic compounds which inhibit the development of silver halide. The inhibitors can be eliminated directly or via non-inhibiting intermediates. Reference is made to GB 953454, US 3632345, US 4 248 962 and B 2 072 363.

The color couplers and DIR compounds can be incorporated into the materials according to the invention by customary, known methods. If the compounds are soluble in water or alkali, they can be in the form of aqueous solutions, optionally with the addition of water-miscible organic ones Solvents such as ethanol, acetone or dimethylformamide can be added. If the color couplers and DIR compounds are insoluble in water or alkali, they can be incorporated into the recording materials in dispersed form in a manner known per se. For example, a solution of these compounds in a low-boiling organic solvent can be mixed directly with the silver halide emulsion or initially with an aqueous gelatin solution and then the organic solvent can be removed. The dispersion of the respective compound obtained in this way can then be mixed with the silver halide emulsion. If necessary, so-called oil formers, generally higher-boiling organic compounds, are also used, which include the color couplers and DIR compounds to be dispersed in the form of oily droplets. In this connection, reference is made, for example, to US Pat. Nos. 2322027, 2533514, 3689271, 3764336 and 3765897.

The recording materials according to the invention preferably contain at least one silver halide emulsion layer unit for recording blue, green and red light.

The red-sensitive silver halide emulsion layer unit can be arranged closer to the support than the green-sensitive silver halide emulsion layer unit and this in turn can be arranged closer than the blue-sensitive one. In the case of copying materials in particular, however, the position of the blue and red sensitive layers can also be interchanged. The recording material may optionally contain a yellow filter layer; However, this can be dispensed with in particular if at least the red- and green-sensitive layers contain an emulsion according to the invention.

In a preferred embodiment, at least one of the units for recording green, red and blue light consists of at least two sub-layers. It is possible to combine sub-layers of different spectral sensitization according to their sensitivity.

The usual layer supports can be used for the materials according to the invention, e.g. B. carriers made of cellulose esters, for. B. cellulose acetate and polyester. Also suitable are paper supports, which can optionally be coated, e.g. with polyolefins, especially with polyethylene or polypropylene. In this regard, reference is made to Research Disclosure No. 17643, Section XVII.

The usual hydrophilic film-forming agents are suitable as protective colloid or binder for the layers of the recording material, e.g. B. proteins, especially gelatin, alginic acid or their derivatives such as esters, amides or salts, cellulose derivatives such as carboxymethyl cellulose and cellulose sulfates, starch or their derivatives or hydrophilic synthetic binders such as polyvinyl alcohol, partially saponified polyvinyl acetate, polyvinyl pyrrolidone and others. In a mixture with the hydrophilic binders, the layers can also contain other synthetic binders in dissolved or dispersed form, such as homopolymers or copolymers of acrylic or methacrylic acid or their derivatives, such as esters, amides or nitriles, and also vinyl polymers, such as vinyl esters or vinyl ethers. Reference is also made to the binders specified in Research Disclosure 17643 above in Section IX.

The layers of the photographic material can be hardened in the usual manner, for example with hardeners of the epoxy type, the heterocyclic ethylene imine and the acryloyl type. Furthermore, it is also possible to harden the layers in accordance with the process of German laid-open specification 2218009 in order to obtain color 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 or with hardeners of the vinyl sulfone type. Further suitable hardening agents are known from German laid-open documents 2439551, 2225230, 2317672 and from Research Disclosure 17643, section XI given above.

The photographic materials according to the invention may also contain other substances, in particular plasticizers, wetting agents, screen dyes, light scattering agents, light reflecting agents, lubricants, antistatic agents, matting agents, etc. Reference is made to Research Disclosure 17643 and "Product Licensing Index" from December 1971, pages 107 -110.

Suitable color developer substances for the material according to the invention are in particular those of the p-phenylenediamine type, e.g. B. 4-amino-N, N-diethyl-aniline hydrochloride; 4-amino-3-methyl-N-ethyl-N-ß- (methanesulfonamido) ethylianilinsulfate hydrate; 4-amino-3-methyl-N-ethyl-N-β-hydroxyethylaniline sulfate; 4-amino-N-ethyl-N- (2-methoxyethyl) -m-toluidine-di-p-toluenesulfonic acid and N-ethyl-N-ß-hydroxyethyl-p-phenylenediamine. Other useful color developers are described, for example, in J. Amer. Chem. Soc. 73, 3100 (1951) and in G. Haist, Modern Photographic Processing, 1979, John Wiley and Sons, New York, pages 545ff. The color developers may contain the usual remaining ingredients, e.g. B. lime and antioxidants and agents for changing fog, such as. B. bromide or stabilizers known per se.

After color development, the material is usually bleached and fixed. Bleaching and fixing can be carried out separately or together. The usual compounds can be used as bleaching agents, e.g. B. Fe ^{3 +} salts and Fe ^{3 +} complex salts such as ferricyanides, dichromates, water-soluble cobalt complexes, etc. Especially iron III complexes of aminopolycarboxylic acids are preferred, especially z. B. ethylenediaminetetraacetic acid, nitrilotriacetic acid, iminodiacetic acid, N-hydroxyethylethylenediaminetriacetic acid, alkyliminodicarboxylic acids and corresponding phosphonic acids. Persulphates are also suitable as bleaching agents.

example 1

Emulsion A according to the invention

A silver chloride emulsion is produced within 18 minutes by simultaneous pAg-controlled introduction of a 0.3 N NaCl and a 0.3 N AgNO ₃ solution into a 2.4% gelatin solution brought to a temperature of 60 ° C. The average particle size is 0.16 µm and the emulsion has a monodisperse distribution. The crystals of this starting emulsion are enlarged to 13.4 times the volume by further addition of 2 n NaCl and 2 n AgNO ₃ solutions. The pAg value is kept constant at 6.8. An AgBr shell is struck on the AgCI emulsion thus produced by double entry of 2 n KBr and 2 n AgNO ₃ solutions. The precipitation is then continued by pAg-controlled double entry of 2n NaCl and 2n AgN0 ₃ solutions, an AgCl shell being applied to the previously precipitated AgBr layer. The emulsion produced in this way has an average particle diameter of 0.58 μm and a monodisperse distribution. The total content of AgBr is 6 mol%.

Comparative Emulsion B

For comparison purposes, a silver halide emulsion such as emulsion A is produced by pAg-controlled double enema, but a mixture of NaCl / KBr is used as the alkali halide solution in all precipitation stages. This mixed halide solution contains 94 mol% NaCl and 6 mol% KBr; the solutions are used in the concentrations indicated for emulsion A. The silver halide emulsion produced in this way has an average particle diameter of 0.60 μm and has a monodisperse grain size distribution; the total AgBr content is 6 mol% and is homogeneously distributed throughout the crystal.

Emulsions A and B are freed from the soluble salts by flocculation and washing in the usual way and then adjusted to a pAg of 7.6. Then both emulsions are chemically sensitized by adding sodium thiosulfate for 120 minutes at 55 ° C. For the sensitometric test, the ripened emulsions are mixed with a sensi dye that absorbs in the green spectral range and a usual purple coupler emulsate and applied to a layer support.

Aus der Tabelle 1 ist zu ersehen, dass die erfindungsgemässe Emulsion A bei geringerem Schleier eine deutlich höhere Empfindlichkeit aufweist.After exposure behind a step wedge and processing in the color development process known from British Journal of Photography, (1974) p.597, the sensitometric data given in Table 1 are obtained.

It can be seen from Table 1 that the emulsion A according to the invention has a significantly higher sensitivity with a lower haze.

Example 2

An emulsion C according to the invention is produced similarly to that described in Example 1. Like the emulsion A described there, the emulsion contains an AgBr layer, the AgBr content, based on the total halide, being 5 mol%. This emulsion C has a monodisperse grain size distribution and an average particle diameter of 0.56 _I Lm.

For comparison purposes, an emulsion is produced by pAg-controlled double entry of aqueous silver nitrate and halide solutions, as described in EP-A 080 905 in Example 1 under Em-4. So that this comparison emulsion D can be compared sensitometrically with the emulsion C according to the invention, the AgCI core is enlarged before the AgBr shell is precipitated so that the final grain size of this emulsion is 0.57 μm. This emulsion also has a narrow (monodisperse) grain size distribution; the total AgBr content is 5 mol% and is found exclusively in one layer on the crystal surface.

Emulsions C and D are freed from the soluble salts by flocculation and washing in the usual way and then adjusted to a pAg value of 7.6. After the addition of sodium thiosulfate pentahydrate, both emulsions are chemically sensitized for 120 minutes at 55 ° C. The emulsions which have matured in this way are then mixed with a dye which absorbs in the green spectral range and a customary purple coupler emulsate for sensitometric testing and applied to a layer support.

Aus der Tabelle 2 ist zu ersehen, dass die Empfindlichkeit der erfindungsgemässen Emulsion C bei sonst vergleichbaren sensitometrischen Werten erheblich höher ist als bei der Vergleichsemulsion D.After processing according to Example 1, the sensitometric values given in Table 2 are obtained. The sensitivity specification is based on the comparison emulsion D.

It can be seen from Table 2 that the sensitivity of the emulsion C according to the invention is considerably higher at sensitometric values that are otherwise comparable than with the comparison emulsion D.

Example 3

For a further sensitometric comparison, the emulsions C and D given in Example 2 are mixed after the chemical ripening with a sensitizing dye which absorbs in the blue spectral range and a yellow coupler emulsate and are poured onto a layer support.

Der Emulsionsvergleich in Tabelle 3 zeigt, dass die erfindungsgemässe Emulsion C eine höhere Empfindlichkeit bei erheblich geringerem Schleier aufweist.After processing according to Example 1, the sensitometric data listed in Table 3 below are obtained.

The emulsion comparison in Table 3 shows that the emulsion C according to the invention has a higher sensitivity with a significantly lower fog.

Claims (9)

1. Photographic silver halide emulsion in which the halide content consists substantially of chloride and the grains have at least one zone Z_Br having a high bromide content, characterised in that

(1.) at least 60 mol % of the halide is chloride;

(2.) the bromide content in a zone Z_Br amounts to at least 50 mol %; and

(3.) no bromide-rich zone Z_Br is present on the surface of the silver halide grains.

2. Photographic silver halide emulsion according to claim 1, characterised in that at least 85 mol % of the total halide present is chloride.

3. Photographic silver halide emulsion according to claim 1, characterised in that the halide in the bromide-rich zone Z_Br consists substantially or exclusively of silver bromide.

4. Photographic silver halide emulsion according to claim 1, characterised in that the average grain size is from 0.1 to 2.5 gm.

5. Photographic silver halide emulsion according to claim 1, characterised in that it has a narrow grain size distribution.

6. Photographic silver halide emulsion according to claim 1, characterised in that the emulsion has a wide grain size distribution.

7. Photographic silver halide emulsion according to claim 1, characterised in that it is chemically and spectrally sensitized on the surface.

8. Photographic recording material comprising a support and at least one silver halide emulsion layer applied thereto, characterised in that the material has at least one emulsion according to claim 1.

9. Process for the production of photographic recording by the development of an exposed recording material, characterised in that a recording material according to claim 8 is used.