CA1155325A

CA1155325A - Photosensitive photographic material including an iodide-containing silver halide emulsion of narrow grain size distribution

Info

Publication number: CA1155325A
Application number: CA000330481A
Authority: CA
Inventors: Otto Lapp; Lothar Endres; Harald Huckstadt; Franz Moll
Original assignee: Agfa Gevaert AG
Current assignee: Agfa Gevaert AG
Priority date: 1978-06-27
Filing date: 1979-06-25
Publication date: 1983-10-18
Also published as: JPS5536892A; JPS6330615B2; DE2960276D1; EP0006543B1; DE2828112A1; EP0006543A1

Abstract

A PHOTOSENSITIVE PHOTOGRAPHIC MATERIAL
Abstract Emulsions for photographic materials are obtained by a) treating a starting emulsion with a water-soluble halide to obtain at least partial conversion, and b) digesting this emulsion, further non-converted silver halide growing onto the converted grains.

Description

1 15532~

This invention relates to a photosensitive photographic material containing at least one silver halide emulsion layer, to a process for its production and to its use for the production of photographic images. More particularly, the invention relates to a photographic material containing an emulsion of narrow grain size distribution.
It is known that emulsions of narrow grain size distribution, particularly so-called monodisperse emulsions, can be produced and used for example for direct-positive photographic materials, but al~o ~or other photographic materials.
Emulsions such as these having a narrow grain size distribution are generally produced by the so-called "double jet process". In this process, the silver halide grains are produced by simultaneously running an aqueous solution oi a water-soluble silver salt~ for example silver nitrate~ and a water-soluble halide, ~or example an alkali metal halide, such as potassium bromide, into a vigorously stirred, aqueous solution of a silver halide peptising agent, preferably gelatin, a gelatin derivative or any other protein-based peptising agent. Suitable processes of this type are described in British Patent No. 1,027,146 and in an Article by E. Moisar and S. Wagner in "Berichte der Bunsengesellschaft fur physikalische Chemie", 67 (1963), pages 356 to 359.
- A characteristic of the double jet process is that large excesses of halide have to be avoided to prevent so-called Ostwald ripening which would result in a hetero-disperse grain size distribution~ For the same reason, other silver halide solvents can be added in only limited quantities.
One of the problems of the double jet process for the production of emulsions of narrow grain size .

distribution is that both the pH-value and also the pAg-value have to be kept strictly constant in order to prevent, on the one hand, undesirable Ostwald ripening and, on the other hand, the formation of nuclei which would again result in a hetero-disperse grain size distribution. For this reason, extreme care has to be taken to ensure that the silver salt and the halide, which are introduced simultaneously, are run in at the same volumetric rate and in the same concentration. Above all, care has to be taken to ensure that no local over-concentrations occur at the points of entry. Thus, the double jet process imposes stringent requirements in terms of process engineering which are not always easy to satisfy, particularly in the case of relatively large batches. In particular, it is extremely difficult to produce by this process silver halide emul~ions having a narrow grain size distributlon for relatively high iodide contents.
If excessive concentrations of iodide are introduced, new nuclei are generally formed and the emulsion generally becomes heterodisperse.
Although it is known from German Offenlegungs-schrift No. 2,043,392 and US-Patent No. 4,026,668 that the precipitation conditions prevailing in the double jet process, particularly the concentrations, and the pH and pAg-values can be controlled in the required manner, one disadvantage common to these methods and apparatus is that they are complicated and expensive.

It is also known to blend emulsions of different grain size in the presence of a silver halide sol-vent. One condition for such methods is that the silver halide crystals used have different solubili-ties. This can be effected by a different grain size and/or different halide composition. Such methods are known from US PS 2146938, 3206313,3317322, German Auslegeschrift 1207791 and the articles of D. Markocki and W. Romer in "Korpuskular Photographie IV, (1963) pages 149 seq and of Ondreichik in "Zhurnal Nauchnoi Prikladuei Fotografi Kinematografi 5, No. 2 (1960) pages 81-83.
The more soluble silver halide emulsions used in such processes are generally fine grain emulsions with an average grain size, which is smaller than the average grain size of the less soluble emulsion;
particularly useful are the so-called Lippmann emulsions which generally have an average grain size of less than 0.1~.
One advantage of thls method is that the formation of new silver halide nuclei is almost completely avoided. In addition, there is no need whatever to take any special precautions in terms of apparatus for avoiding overconcentrations or to use con-trol systems for the pH or pAg-value since the more soluble emulsion is in itself an optimally equimolar source of silver halide.
One disadvantage of the process described by Markocki and Romer is that the less soluble emulsions have to be produced by subjecting part of the Lippmann emulsion used, to Ostwald ripening with a high concentration of bromide ions in order in this way to obtain relatively large sllver halide grains. An emulsion having a heterodisperse grain size 1 1~5325 distribution is of course formed in this way. By contrast, for producing emulsions of narrow grain size d$stributlon, lt is of advantage for the prepared less soluble emulsion also to be present in a narrow grain size distribution, i.e. homodisperse. Another serious disadvantage of the process described by Markocki and Romer lies in the fact that it is virtually unuseable for relatively large emulsion batches. This is because Markocki and Romer's process is carried out by adding the Lippmann emulsion either continuously or batchwise to the core emulsion. Where the Lippmann emulsion is added continuously, the fine-grained component has to be added with extremely vigorous stirring to prevent the formation of heterodisperse emulsions. In the case of relatively large batches, this is virtually impossible. Where the Lippmann emulsion is added batchwise, the individual additions have to be separated by, ln some cases considerable, lntervals ln order to avoid the formation of heterodisperse systems. Accordingly, this variant is also unsuitable for practical application.
Furthermore, in the known blending processes only small amounts of iodide are used both in the more and the less soluble starting emulsion. Therefore, only emulsions with small amounts of iodide are obtained.
One object of the present invention is to provide an improved photographic material containing at least one photosensitive silver halide emulsion layer which is simple to produce in comparison with known methods and which may even have a relatively high iodide content. Another object of the invention is, in particular, to provide a simple process for producing silver halide emulsions of narrow grain size distribution.
A photosensitive photographic material which comprises a support bearing at least one silver halide emulsion layer with silver halide grains of narrow grain size distribution has now been found in which the silver halide emulsion is obtained by a) treating a starting silver halide emulsion of narrow grain size distribution with a water-soluble iodide, preferably an alkali or ammonium iodide, with at least partial conversion of the silver halide emulsion, and b) digesting the emulsion obtained with a silver halide solvent, optionally with addition of further silver halide emulsion which is more soluble than the converted starting emulsion the more soluble silver halide grains growing onto the converted silver halide grains.
Furthermore it has been found that this material is suitable for the production of photographic images.
In the context of the invention, an emulsion of narrow grain s$ze distribution is an emulsion in which at least 75% of the silver halide grains show a maximum deviation of 50% from the mean grain diameter.
In one preferred embodiment, the silver halide emulsions are monodisperse, monodisperse emulsions in the context of the invention being emulsions ln 1, which at least 95% of the silver halide grains show a maximum deviation of 40% from the mean grain diameter.
The emulsion to be treated with the water-soluble iodide may consist completely or predominantly of silver chloride and/or particularly of silver bromide; but this emulsion may also comprise silver iodide in optionally considerable amounts. The final emulsion obtained in accordance with the invention may contain any amount of silver iodide.
In one embodiment of the invention, a Lippmann emulsion of narrow grain size distribution consisting predominantly of silver bromide is added all at once or gradually to a solution of a protective colloid, particularly gelatin, and a certain quantity of iodide ions, for example ln the form of alkali iodide, a Llppmann emulslon belng understood to be an emulslon of which the silver halide grains have a maximum diameter of 0. 1 ~. This Lippmann emulsion may be produced by the usual processes and, in particularly, by the double jet process.
A silver halide solvent is then added. In this variant, the Lippmann emulsion serves as its own pre-precipitate. A corresponding proportion of the Lippmann emulsion is converted by the iodide ions initially introduced, the non converted grains growing onto the converted grains.
It is also possible additionally t~ add part of the silver halide solvent to the- initially introduced solution of the dispersant and the iodide ions. It is preferred to add at most 10 mole %
of t~e silver halide solvent, based on the quantity of silver halide used. This procedure is particularly 1 15~325 advisable in cases where it is intended to add relatively little iodide.
The mean grain diameter of the silver halide grains thus obtalned preferably lies between 0.4 and 1.5 ~ and is controlled by the choice of the dissolution/crystallisation conditions for the Lippmann emulsion and, in particular, by the temperature applied and by the quantity of silver halide solvent added.
In a second, preferred embodiment of the invention, a separate pre-precipitate is used. To this end, an emulsion of narrow grain size distribution, consisting of silver bromide or silver chloride or mixtures thereof, is initially prepared. Silver iodide may be present too.
Pre-precipitates such as these are obtained ln known manner ln a narrow grain size distribution, for example by the single or double jet process, optionally pAg-controlled.
According to the invention, this pre-precipitate is at least partly converted by the addition of iodide ions before or after physical ripening. The quantity of iodide added may be varied within wide limits without any undesirable hetero-dispersity occurring either in the pre-precipitate or in the emulsion ultimately obtained. The emulsion obtained is called the less soluble emulsion. This less soluble emulsion may comprise 10-100 mole %, preferably 15-75 mole %
of silver iodide.

i 1 15532~

g A more soluble, generally a fine grain emulsion, preferably a ~lppmann emulsion, is added to the less soluble emulsion. The more soluble emulsion generally consists of silver chloride or silver bromide or mixtures thereof and may comprise up to 10 mole %
preferahly up to 6 mole % silver iodide.
Furthermore, a silver halide solvent in a suitable amount is added. This amount depends inter alia on the type of the solvent used and the temperature of the blending process. Suitable amounts comprise 0.05-2 molar solutions.
The whole is then digested until the more soluble silver halide crystals have grown onto the converted, less soluble silver halide crystals to form an emulsion of narrow grain size distribution.
The molar ratio between the silver introduced with the more soluble emulslon and the silver added in the form of the converted emulsion is preferably between 0.3:1 and 30:1, preferably between 1:1 and 15:1.
Before blending the more and the less soluble emulsions, preferably at least one of these emulsions is freed from salt and/or concentrated, e.g. by flocculation. The emulsions can be mixed in coagulated form and redispersed together. Thus, very high silver halide concentrations are possible without the known impairing effects of high salt concentrations.
The silver halide concentrations may be between 0.2 and 2 mol of silver-halide per kg of emulsion.

AG 15~8 The more soluble silver halide may be added at different stages and more than once, but the addition can be made continuous-ly too.
In one preferred embodiment, the conversion and blending steps are made alternating more than once. Thus the position of iodide in the finished grains can be controlled. In this embodi-ment the more soluble emulsions used may have differing halide composition.
The blending procedure may be effected preferably between 40-60C, and at a pAg of 6,5 to 11,8. The time necessary for blending is generally between 5 and 90 minutes.
Particularly preferred silver halide solventsare:
halides, preferably alkali or ammonium halides, most preferably bromides or chlorides; ammonia, thiocyanates, preferably alkali and ammonium thiocyanates, sulphites, preferably alkali or ammonium sulphites; thiosulphate; organic amines; thioethers,imidazole and derivatives of imidazole. In a preferred embodiment of the inven-tion organic thioethers are used. Suitable thioethers are e.g., described in United States Patent Nos. 3,271,157, 3,507,657, 3,531,289 and 3,574,628. Particularly suitable thioethers are disclosed in the German Offenlgenungsschrift 2,624,862. Particu-larly suitable thioethers are:
HO~CH2)2-S-(cH2)2 S (CH2)2 HOOC-(CH2)3-S-(CH2 3-COOH

CH3 S (CH2)2 2 C2H5-S-(CH2)2 -S-(CH2)2-NH-CO)CH2)2COOH
C2H5-S- (CH2) 2-S- (CH2) 2-NH-CO-NH2 .- -- 10 --The emulsions obtained in accordance with the invention preferably may have any silver iodide con-tent, but preferably from 3 to 15 mole %.
For removing the water soluble salts, the silver halide emulsions produced in accordance with the invention may either be chilled, converted into noodle form and rinsed with water in known manner or may even be coagulated with a coagulating agent and subsequently washed, as known for example from German Offenlegungsschrift No. 2,614,862.
Suitable protective colloids and binders for the silver halide emulsion layer are the usual hydrophilic film-forming materials, for example proteins, particularly gelatin, alginic acid or derivatives thereof, such as esters, amides or salts, cellulose derivatives, such as carboxy methyl cellulose and cellulose sulphates, starch or derlvatives thereof or hydrophilic synthetic binders, such as polyvinyl alcohol, partially hydrolysed polyvinylacetate, polyvinyl pyrrolidone and others.
The layers may also contain in admixture with the hydrophilic binders 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, also vinyl polymers, such as vinyl esters or.vinyl ethers.
The emulsions according to the invention may be applied to the usual support.layers, for example to substrates of cellulose esters, such as cellulose acetate or cellulose acetobutyrate, also polyesters, p~rticularly polyethylene terephthalate, or polycarbonates, particularly based on bis-phenylol propane. Other suitable substrates are paper substrates which may contain water-impermeable polyoleiin layers, ior example oi polyethylene or polypropylene, and glass or metal substrates.
The emulsions may also be chemically sensitised, ~or example by the addition during chemical ripening oi sulphur-containing compounds, ~or example allyl 10 isothiocyanate, allyl thiourea and sodium thiosulphate.
Other suitable chemical sensitisers are reducing agents, ior example the tin compounds described in Belgian Patents Nos. 493,464 or $68,687, also polyamines, such as diethylene triamine or aminomethyl 15 sulphinic acid derivatives , ~or e~ample according to ~elgian Patent No. 547,32;.
Other suitable chemical sensitisers are noble metals and noble metal compound~, suah as gold, platinum~ palladium~ iridium, ruthenium or rhodium.
20 This method o~ chemical sensitisation is described in the article by R. ~oslowsky in Z. Wiss. Phot.
46, 65 - 72 (1951).
It is also possible to sensitise the emulsions with polyalkylene oxide derivatives, for example wit~
25 polyethylene o~ide having a molecular weight oi irom 1000 to 20,000, with condensation products o~ alkylene oxides and aliphatic alcohols, glycols, cyclic dehydration products o~ he~itols, with alkyl-substituted phenols, aliphatic carbo~ylic acids, aliphatic amines, 30 aliphatic diamines and amides. ~he condensation products have a molecular weight oi at least 700 and ) preferably o~ more than 1000. To obtain special effects, these sensitisers may o~ course be used in combination with one another, as described in Belgian Patent No. 537,278 and British Patent No. 727,982.
The emulsions may also be optically sensitised, for example with the usual polymethine dyes, such as neutrocyanines, basic or acid carbocyanines, rhoda-cyanines, hemicyanines, styryl dyes, o~onols and the like. Sensitisers such as these are described in F.M. Hamer's work entitled "The Cyanine Dyes and Related Compounds", l964, Interscience Publishers, John Wiley and Sons.
The emulsions may contain the usual stabilisers such as, for example, homopolar or salt-like compounds o~ mercury with aromatic or heterocyclic rings, such as mercapto triazoles, simple mercury salts, sulphoniummercury double salts and other mercury compounds. Other suitable stabilisers are azaindenes, preierably tetra- or penta-azaindenes, particularly those substituted by hydroxyl or amino groups.
Compounds such as these are described in the article by Birr in Z.Wiss.Phot. 47 (1952), 2 - 58. Other suitable stabilisers are inter alia heterocyclic mercapto compounds, ~or example phenyl mercapto tetrazole, quaternary benzthiazole derivati~es and benzotriazole.
The emulsions may be hardened in the usual way, for example with formaldehyde or halogen-substituted aldehydes containing a carboxyl group, such as mucobromic acid, diketones, methane sulphonic acid esters and dialdehydesO
The photographic layers may also be hardened with hardeners of the epoxy, heterocyclic ethylene imine or acryloyl type. Example~ of hardeners such as these are described ~or example in German 1 15S32~

Offenlegungsschrift No. 2,263,602 or in British Patent No. 1,266,655. It is also possible to harden the layers by the process described in German Of~enlegungsschrift No. 2,218,009 in order to obtain colour photographic materials which are suitable for processing at high temperatures.
It is also possible to harden the photographic layers or the colour photographic multilayer materials with diazine, triazine or 1,2-dihydroquinoline hardeners, as described in British Patents Nos.
1,193,290; 1,251,091; 1,306,544 and 1,266,655;
French Patent No. 71 02 716 and German Offenlegung-sschrift No. 2,332,317. Examples of hardeners such as these are diazine derivatives containing alkyl or aryl sulphonyl groups, derivatives of hydrogenated diazines or triazines, such as for example 1,3,5-hexahydrotriazine, fluorine-substituted diazine derivatives such as, for example, fluoropyrimidine, esters of 2-substituted 1,2-dihydroquinoline or 1,2-dihydroi~oquinoline-N-carboxylic acids. Other suitable hardeners are vinyl sulphonic acid hardeners, carbodiimide or carbamoyl hardeners, as described ~or example in German Offenlegungsschrifts Nos. 2,263,602; 2,225,230 and 1,808,685; French Patent No. 1,491,807; German Patent No. 872,153 and East German Patent No. 7218. Other ~uitable hardeners are described, for example, in British Patent No. 1,268,550.
The present invention may be used for the production oi both black-and-white photographic images and colour photographic imagesO Colour photographic images may be obtained for example on the known principle of chromogenic development in the presence of colour couplers which react with the oxidation product of dye-giving ~-phenylene diamine developer~ to form dyes ~ he colour couplers may be added ior example to the colour developer on the principle of the so-called ~eveloping-in ~rocess. In a preierred embodiment, the photographic material itself contains the usual colour couplers which are generally incorporated into the silver halide layers. Thus, the red-sensitive layer may contain for example a non-difiusing colour coupler for producing the cyan component colour image, generally a phenol or a-naphthol couplerO The green-sensitive layer may contain for example at least one non-diffusing colour coupler for producing the magenta component colour image, 5-pyrazolone or imidazolone colour couplers normally being used.
The blue-sensitive layer may contain for e~ample a non-diffusing colour coupler for producing the yellow component colour image, generally a colour coupler containing an open-chain ketomethylene group.
Colour couplers of this type are known in large numbers and are desoribed in a large number of Patent Specifioations. In this connection, reference is made for example to the article entitled "Farbkuppler (Colour Couplers)" by W. Pelz in "Mitteilungen aus den Forschungslaboratorien der Agfa, Leverkusen/Munchen"
Vol. III (1961) and to Eo Venkataraman in "The Chemistry of Synthetic Dyes", Vol 4, 341-387, Aoademic Press, 1971.
Other suitable non-diffusing colour couplers are 2-equivalent couplers. 2-Equivalent couplers contain a removable substituent in the coupling position, so that, in contrast to the usual 4-equivalent couplers, they only require two equivalents of silver halide for dye formation.
Suitable 2-equivalent couplers include for example the known DIR-couplers, in which the removable radical is liberated as a diffusing development ~ 1598 inhibitor after reaction with colour developer oxidation products.
In addition, the so-called white couplers may be used for improving the properties of the photographic material.
The non-diffusing colour cou~lers and dye-giving oamFounds are added to the photosensitive silver halide emulsions or other casting solutions by standard methods. In the case of water-soluble or aLkali-soluble con~xnuxls, they may be added to the emulsions in the form of aqueous solutions, to which water-miscible organic solvents, such as ethanol, acetone or dimethyl formamide may be added. ~here the non-diffusing colour couplers and dye-giving compounds are water-insoluble or alkali-insoluble compounds, they may be emulsified in known manner, for example by directly mixing a solution of these compounds in a lcw-boiling organic solvent with the silver halide emulsion or initially with an aqueous gelatin solution, after which the organic solvent is removed in the usual way. m e resulting gelatin emulsion of the particular co~Found is then mixed with the silver halide emLlsion.
So-called coupler solvents or oil formers may additionally be used for emLlsifying hydrophobic compounds of the type in question. Coupler solvents or oil formers are gener~7ly relatively high boiling organic compounds which include the non-diffusing colour couplers and development-inhibitor-releasing ccnçx~Dnds to be emulsified in the silver halide emulsions in the form of oily droplets. In this connection, reference is made for example to US Patents No. 2,322,027;

2,533,514; 3,689,271; 3,764,336 and 3,765,897.
Photographic material according to the invention may be developed with the usual colour developer substances, for example N,N-dimethyl-E~phenylene diamine, 4-amino-3-methyl-N-ethyl-N-methoxyethyl aniline, 2-amino-5-diethylamino toluene, N-butyl-N-G~sulphobutyl-E~phenylene diamine, 2-amino-5-(N-ethyl-N-B-methane sulphonamidoethyl-amino)-toluene.
N-ethyl-N-~-hydroxyethyl-P-phenylene diamine, N,N-bis-(B-hydroxyethyl)-E~phenylene diamine, I
2-amino-5-(N-ethyl-N-B-hydroxyethylamino)-toluene.
Other suitable colour developers are described for example in J.Amer.Chem.Soc. 73, 3100 (1951).

The emulsions produced in acoordance with the invention may be used in a variety of ways. They may be used for thie production of photographic negative materials and also for the prcduction of photo-~raphic material with unfogged, dlrect-positive silver halide emul-sions, l.e. those which have a realtlvely high inner grain sensitivity without surface fogging and which are developed under fogging oondltions.
The emulsions according to the invention maybe used in known manner for instant colour picture processes and dye transfer processes. In these proce99e9, the dyes for the component colour images diffuse into an image receiving layer, where they are firmly anchored, or the colour couplers diffuse into the image-receiving layer where, after dye giving development in the usual way, they are reacted 15 to form the image dye. Dge transfer processes and couplers used in them are also described in US
Patents Nos. 2,983,606; 3,087,817; 3,185,567;

3,227,550; 3,227,551; 3,227,552; 3,227,554;
3,253,915; 3,415,644; 3,415,645 and 3,415,646.
The emulsions ac¢ording to the invention may also be used for dye transier processes in which the particular layer contains a non-difiusing compound which is a dye or a dye precursor and which, during development in the presence Or the alkali processing 25 masg~ giveg Oir dyes preferably containing acid groups which dirruse under the action of photographic developer oxidation products formed in imagewise distribution.
A variety o$ chemical compounds is available 30 for thi~ purpose~ Non-diffusing dye providing compounds according to US Patent No. 3,628,952 for e~ample are particularly suitable~ These compounds prov~de diffusing dyes on reaction with oxidation products of black and white or colour developers. Another suitable class of compounds is described in ~erman Patent No. 1,095,115. The compound~ in question, on 1 15532~

reaction with oxidised colour developer, give difiusing dyes which are generally azomethine dyes Another suitable dye provlding syst3m is described in US Patents Nos. 3,443,939 and 3,443,940. In this system, difiusing dyes are provided by a ring closing reaction under the action of oxidised developer substances.
Accordingly, the photographic materials according to the invention are particularly suitable ior the production oi photographic images by imagewise exposure, development and iurther processing in the usual way.
The materials according to the invention are distinguished by the iact that they contain at least one silver halide emulsion oi narrow grain size distribution for any iodide content and, in particular, ior relatively high iodide contents. In one preierred embodiment~ the emulsions produced in a¢cordance with the invention show high inhibitability and are thereiore particularly suitable ior producing high inter-image eiie¢tsO The inter-image eiiect is normally used ior improving the sensitometric properties oi photographic materials and is described ior example in the corresponding article by C.R. Barr in "Photographic Science and Engineering" 13 (1969), Pages 74 et seq.

A Lippmann emulsion was initially prepared by W. Markocki's process (Korpuluskar Photographie, IV
(1963), page 165), except that no cadmium nitrate was used. The grains oi the Lippmann emulsion had a mean grain diameter oi 0007 lu. 1500g oi the resulting Lippmann emulsion, together with silver halide in a quantity corresponding to 340 g oi silver nitrate, were added over a period oi 10 minutes at 45C to a solution oi 22.5 g oi potassium iodide and 120 g oi a 1 ~55325 gelatin containing inhibitors and ripeners in 5 litres of distilled water. After the Lippmann emulsion had been converted by the iodide ions initially introduced, 375 ml of a 14.7 molar ammonia solution were added. After digestion for 30 minutes at 45C, the emulsion was cooled in known manner and adjusted with dilute sulphuric acid to pH 5Ø The emulsion was then coagulated in known manner, washed and finally redispersed in known manner at pH 6.5 by the addition of water and gelatin of the above-mentioned type. The emulsion was then chemically sensitised in the usual way with a gold thiocyanate complex ~alt.
For after-ripening, the emulsion was digested at a temperature of 53C, after which phenol was added as preservative in the usual way.
The emulsion obtained had a narrow grain size distribution, its mean grain diameter amounting to 0,58 ,u. Figure 1 shows the so-¢alled cumulative size distri-bution curve of these emulsions. Each point on the ordinate of this cur~e indicates how many % of the crystals are larger than the associated abscissa value.
For determining the sensitometric properties, a sample of the emulsion was poured onto a suitable support, 20 ml (per kg of the emulsion samples) of a 1 % aqueous solution of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene, 35 ml/kg of a 7.5 % aqueous solution of saponin and 35 ml of a 2 % aqueous solution of mucochloric acid being added to the emulsion sample before casting. The photographic material obtained was egposed imagewise through a grey wedge in the usual way and developed ~or 7 minutes at 20C in the following developer:

1 15532~

Developer ethylene diamine tetraacetic acid 1.5 g sodium hexamethaphosphate 1 g sodium sulphite, sicc. 60 g S borax 15 g potassium bromide 3 g hydroquinone 6 g l-phenyl-3-pyrazolidone 0.7 g made up with water to 1 litre.
The ~alues set out in Table 1 were obtained.

The emulsion was produced in the same way as described in Example 1, except that only 750 g of the Lippmann emulsion were added to the solution o~
15 potassium iodide and gelatin in 5 litres o~ distilled water. The emulsion obtained was ~urther processed in the same way as described in Example 1. Figure 2 shows the cumulative size distribution curve of the emulsion obtained which had a mean grain diameter o~ o.65 y.
20 The sensitometric values a~ter exposure and processing in accordanoe with Ex~mple 1 are shown in Table 1.

1 1~5325 Table l ,_ Example ~ E S D Ag-coating No. max (g of ~gN03/
m2 1.92 27.7 o.lo 3.75 7.2 2 1.65 31.3 o.o6 3.70 7.4 ~ = gradation E = sensitivity; an increase of 3.o units represents a doubling of sensitivity S = fogging DmaX = maximum densityO

A) An emulsion according to Example l was melted in known manner, followed by the addition of 180 g per mole oi silver halide of a sensitiser correspondlng to the formula e H5C~ c-c~ c~ ~ C2 5 4 The following components were also added:
1.) 50 g of a cyan colour coupler corresponding to the formula OH
~ CoNH-(cH2)4-o ~ C12~25 per mole of qilver expressed as silver nitrate 2.) 1,5 g oi 4-hydroxy-6-methyl-1,3,3a,7-tetra-azaindene per mole oi silver expressed as silver nitrate and a wetting agent.
The emulsion was cast onto a support of cellulose acetate (silver coating, expressed as silver nitrate : 3.7 g/m2).
Aiter drying and exposure behind a step wedge and a suitable iilter in a sensitometer, the material was developed ior 3,25 minutes at 38C in the following developer:
Developer i potassium sulphite 5 g potassium bromide 104 g potassium carbonate 35 g ethylene diamine tetraacetic acid 1~5 g disodium salt oi l-hydroxyethane-l,l-diphosphonic acid 2 g ~odlum metabisulphite 0.28 g sodium bicarbonate 1.55 g

4-amino-3-methyl-N-ethyl-N-(~-hydroxyethyl)-aniline 4,7 g hydroxylamine sulphate 2.4 g made up with water to l litre.
Aiter development, the material was further processed in the usual way.
B) An emulsion was melted and ~urther processed in the same way as in A). 4 g per mole of silver (e~pressed as silver nitrate) of a DIR-coupler corresponding to the formula were additionally added:

. ~q~

H3C-(CH2)15-0 ~ ~ ,N

Further treatment and development were carried out in the same way as described in A).
Figure 3 shows the density curves obtained. It can be seen that the emulsion had a pronounced reaction to the stabiliser released by the DIR-coupler.
~ he sensitometric data are shown in Table 2.
~able 2 Material E ~ S
10 A without DIR-coupler 34.0 1.70 0.14 B with DIR-coupler 28.9 0.84 0.14 ~ = gradation 1598.

1 1~5325 Example 4 A silver chlorobromide emulsion with 52 moles % of bromide with an average grain size of 0.35/u was prepared as described by Glafkides, Photographic Chemistry, Fountain Press, 1956, pp 341 seqq. An aqueous 10~ solution of Kl, equirnolar to 12 mole % of the silver halide, was added. After digestion the emulsion was cooled, flocculated and washed.
After redispersion the emulsion contained 1,1 moles of silver halide per kg; the ratio gelatine/silver nitrate was 0.3. To 1 kg of this emulsion were added: 500 ml of water, 35 g of NH4Br and 500 ml of a 7~ methione-solution. At 65C 1,1 moles of a AgBr-Lippmann emulsion were added.This mixture was maintained at a temperature of 65C for 15 minutes.
The emulsion was then cooled and freed from the soluble salts. After redisperslon the emulslon contained 6 moles ~ of AgJ. The emulslon was rlpened at 54C, then conventlonal adjurants were added, then the emulsion was coated on a suitable support and exposed and developed a~ described in Example 1. The sensitometric results showed that an emulsion of medium speed had been obtained.
Example 5 An ammouiacal silver bromiodide emulsion was prepared as described by Glafkides (cf.Example 4). An aqueous 10% solution of Kl, equimolar to 19 mole % of the emulsion, was added. The silver halide grains obtained had a narrow grain size distribution and an average grain size of 0.55 ~.
The emulsion was flocculated and washed. After redispersion the emulsion contained 1,1 moleS of silver halide per kg of emulsion.

The ratio gelatine/silver nitrate was 0,35.
To 1 kg of this emulslon were added: 500 ml water, 30 g of NH4Br and 350 ml of a 7% aqueous solution of imidazole. At 65 C 2,2 mole of a silver bromoicdide Lippmann-emulsion (Br:I=96:4) were added. Then 2,2 moles of a AgBr Lippmann-emulsion were added. The emulsion which was obtained contained 6 mole % of silver iodide.
The emulsion was then cooled and freed from the soluble salts. After redispersion the emulsion had a gelatine/silver nitrate ratio of 1,0. The emulsion was sulphur- and gold-sensitized as generally known. Then conventional adjuvants were added and the emulsion was coated on a suitable support and exposed and developed as described in Example 1. The sensitometric results showed that a high speed emulsion with a high contrast had been obtained.
Example 6 A silver bromoiodide emulsion of a narrow grain size distribution with 6 moles % o silver iodide and an average grain size of 0.18 ~ was produced by the double-jet process. An aqueous solution of KI, equimolar to 42 mole % of the silver halide, was added. After digestion the emulsion was flocculated, and washed. After re-dispersion the emulsion contained 1,4 moles o silver halide per kg. To 1 kg of the redispersed emulsion were added: 500 ml of water, 75 g of NH4BR and 1500 ml of a 7% methionine solution. Then 9,8 moles of a AgBr Lippmann-emulsion were added. The emulsion was digested 45 minutes at 65C, cooled, flocculated and redispersed.

115~325 After redisperslon the gelatine/silver nitEate ratio was 0,7. The emulsion was digested and further processed as described in Example 5. The sensitometric results showed that an emulsion of medium speed had been obtained with an average grain size of 0,45 ~.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the production of a photosensitive material containing at least one iodide-containing silver halide emulsion of narrow grain size distribution, which process comprises:
(a) treating a starting silver halide emulsion of narrow grain size distribution, which emulsion consists at least predominantly of silver chloride and/or silver bromide, with a water-soluble iodide so as to convert all or a portion of the silver halide of the starting emulsion to silver iodide, (b) (i) necessarily, when all of the silver halide of the starting emulsion has been converted to silver iodide in step (a), or (ii) optionally, when only a portion of the silver halide of the starting emulsion has been converted to silver iodide in step (a), adding further silver halide emulsion the grains of which are more soluble than silver iodide grains formed in step (a), and (c) digesting the converted emulsion thus obtained in step (a) or a blend obtained in step (b), in the presence of a silver halide solvent until silver halide grains which are more soluble than the silver iodide grains have grown onto the grains of silver iodide, the silver halide being derived from the starting emulsion which has not been converted to silver iodide by the addition of the water-soluble iodide in step (a) and/or being derived from the further silver halide emulsion added in step (b).

2. A process according to Claim 1 for the production of a photosensi-tive material, wherein only a portion of the silver halide of the starting emulsion is converted to silver iodide in step (a).

3. A process according to Claim 2, wherein no further silver halide emulsion is added in step (b).

4. A process according to claim 2, wherein further silver halide emulsion is added in step (b).

5. A process according to claim 2, wherein the starting silver halide emulsion of narrow grain size distribution includes silver halide grains having an average grain size of less than 0.1 µ.

6. A process according to Claim 4, wherein further silver emulsion added in step (b) includes silver halide grain having an average grain size of less than 0.1 µ.

7. A process according to Claim 2, 3 or 4, wherein as the silver halide solvent a member selected from the group consisting of ammonia, imidazole, imidazole derivatives and thioethers is employed.

8. A process according to Claim 1, wherein the starting emulsion contains at least 10 mole % of silver iodide.

9. A process according to claim 4, wherein at least one of the emul-sion obtained in step (a) and the emulsion to be added in step (b) is concen-trated and/or freed from salt before blending them.

10. A process according to Clim 1, wherein the converting and digesting steps are repeated in sequence more than once.

11. A process according to claim 1, 2 or 5, wherein the converted emul-sion obtained in step (a) contains 10 to 100 mol % of silver iodide.

12. A photosenitive material containing at least one iodide-containing silver halide emulsion of narrow grain size distribution with grains which is produced by a process comprising:
(a) treating a starting silver halide emulsion of narrow grain size distribution, which emulsion consists at least predominantly of silver chloride and/or silver bromide, with a water-soluble iodide so as to convert all or a portion of the silver halide of the starting emulsion to silver iodide, (b) i) necessarily, when all of the silver halide of the starting emulsion has been converted to silver iodide in step (a), or ii) optionally, when only a portion of the silver halide of the starting emulsion has been converted to silver iodide in step (a), adding further silver halide emulsion the grains of which are more soluble than silver iodide grains formed in step (a), and (c) digesting the converted emulsion thus obtained in step (a) or a blend obtained in step (b), in the presence of a silver halide solvent until silver halide grains which are more soluble than the silver iodide grains have grown onto the grains of silver iodide, the silver halide being derived from the starting emulsion which has not been converted to silver iodide by the addition of the water-soluble iodide in step (a) and/or being derived from the further silver halide emulsion added in step (b).

13. A material according to Claim 12, wherein at least 75% of the iodide-containing silver halide grains of the silver halide emulsion have a diameter which deviates from the mean diameter by no more than 50%.

14. A material according to Claim 12 or 13, wherein colour couplers are present.

15. A material according to Claim 12 or 13, which contains 3 to 15 mol % of silver iodide based on the total silver halide.