US3813249A

US3813249A - Light sensitive photographic material

Info

Publication number: US3813249A
Application number: US00222663A
Authority: US
Inventors: A Ezekiel; M Wood; E Thurston; M Harper
Original assignee: Ilford Ltd
Current assignee: Ilford Imaging UK Ltd
Priority date: 1971-02-04
Filing date: 1972-02-01
Publication date: 1974-05-28
Anticipated expiration: 1991-05-28
Also published as: GB1322812A; FR2124446A1; BE778909A; DE2204057A1; FR2124446B1

Abstract

A PHOTOGRAPHIC MATERIAL COMPRISING IN AT LEAST ONE LAYER A WATER-SOLUBLE N-NITROSO-OXIME OF THE FORMULA

O=N-N(-A)-O-R

WHEREIN A REPRESENTS A PHENYL OR NAPHTH-1- OR -2-YL RADICAL OR A PHENYL OR NAPHTH-1- OR -2-YL RADICAL SUBSTITUTED BY ONE OR TWO MEMBERS SELECTED FROM HYDROGEN, ALKYL HAVING 1 TO 5 CARBON ATOMS, ALKOXY HAVING 1 TO 5 CARBON ATOMS, HYDROXYALKYL HAVING 1 TO 5 CARBON ATOMS, ARALKYL AND HYDROXY AND R IS A CATION AS MEANS FOR REDUCING SPOT FORMATION IS DESCRIBED.

Description

United States Patent 3,813,249 LIGHT SENSITIVE PHOTOGRAPHIC MATERIAL Aaron David Ezekiel, Elvin Frederick William Thurston, Michael Frederick Harper, and Malcom Barlow Wood, Ilford, England, assignors to Ilford Limited, Ilford, England No Drawing. Filed Feb. 1, 1972, Ser. No. 222,663 Claims priority, application Great Britain, Feb. 4, 1971, 3,957/71 Int. Cl. G03c 1/02, 1 76 U.S. Cl. 96-67 16 Claims ABSTRACT OF THE DISCLOSURE A photographic material comprising in at least one layer a Water-soluble N-nitroso-oxime of the formula A-NOR N=O (I) wherein A represents a phenyl or naphth-lor -2-yl radical or a phenyl or naphth-lor -2-yl radical substituted by one or two members selected from hydrogen, alkyl having 1 to 5 carbon atoms, alkoxy having 1 to 5 carbon atoms, hydroxyalkyl having 1 to 5 carbon atoms, aralkyl and hydroxy and R is a cation as means for reducing spot formation is described.

This invention relates to a light sensitive photographic material.

Normally photographic materials are manufactured under conditions wherein as little dust as possible is present in the atmosphere. However, despite every precaution it is not possible completely to prevent dust particles from being deposited on the photographic material in the course of its manufacture. Atmospheric dust has a very complex constitution but most atmospheric dust, especially that in the atmosphere of industrial areas, contains fine particles of metal, metal oxides and metal salts. Film base casting machines and film base coating machines comprise a large number of metal parts, for example copper or steel rollers, so that metal dust particles are continously produced by the working of such machines and these dust particles often settle on the film base or on the emulsion layer on the film base. Further, traces of metals or their compounds are often present in gelatin and other materials from which the various layers of the photographic material are made.

When photographic material containing metal particles and in particular particles of aluminium, chromium, iron, nickel and copper and the oxides and salts of these metals, is exposed and processed, these particles appear as spots visible to the naked eye. These spots are often many times bigger than the dust particles itself and are the results of the metal or its salts or oxidation products either desensitizing the photographic silver halide emulsion surrounding it or, in other cases, sensitizing the emulsion surrounding it. Furthermore, gross contamination by metal particles can result in spots being formed in non-emulsion layers of the photographic material which contain such particles.

Several types of additives have been proposed for the prevention of such spots. For example, British Patent Specification No. 623,488 describes the use of aldoximes which are added to the developer or the emulsion in order to decrease the activity of cupric ions which catalyse aerial fogging. US. Pat. No. 2,239,284 describes the use of alkali metaphosphates, alkali hexametaphosphates, alkali triphosphates and alkali pyrophosphates for iron, copper and aluminium ions. British Patent Specification No. 524,087 mentions the use of p-hydroxy phenylglycine in a gelatinosilver halide emulsion layer, and in British Patent Speci' fication No. 691,715 the use of ethylene diamine-tetraacetic acid in silver halide emulsions for inhibiting spots is described.

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However, it has been found that these compounds have limited effects in certain emulsions and their presence in emulsions often causes deleterious side effects such as deterioration of the latent image, fogging of the emulsion during storage, or deterioration in the mechanical properties of the photographic material, e.g. greater susceptibility to scratching.

Further, it is important in silver halide photographic materials that the latent image formed on exposure should be relatively stable over the period from exposure to development. The most common and serious form of latent image instability is the defect known as latent image regression. This manifests itself as an apparent decrease in the sensitivity of the photographic material. Usually the longer the period over which exposed material is kept before development the greater the apparent decrease in the sensitivity of the material. This apparent decrease in sensitivity is enhanced by storing the material at elevated temperatures. The exact cause of latent image regression is not at present known with any certainty but it is thought to be due in some instances at least to the presence in the emulsion of iron or copper. It is thought that these substances, when present in the exposed silver halide emulsion, oxidize some of the partially reduced silver which constitutes the latent image. In the case of color photographic material containing several silver halide emulsion layers the consequences of latent image regression are more serious because they are more obvious since it generally arises that the regression is not uniform for the several emulsion layers and there is consequently a shift in the color balance as well as an apparent loss of sensitivity. Generally latent image progression, another form of latent image instability, is not such a serious defect but when it occurs in color photographic material in one emulsion layer but not in another it can cause a shift in the color balance of the final color image.

It is the object of the present invention to provide a photographic material having additives therein which act to reduce the tendency of the photographic material to exhibit spot formation due to metal particle, metal oxide and metal salt contamination. Further it is the object of the present invention to provide silver halide emulsion photographic material which comprises an additive in operative contact with the silver halide emulsion serving to reduce the tendency of the emulsion to exhibit latent image instability. Further it is the object of the present invention to provide additives for photographic materials for the foregoing purposes which have a reduced tendency to produce undesirable side effects in the photographic material which contain them.

According to the present invention there is provided a photographic material which comprises a support base having coated thereon one or more layers, at least one of which is a photosensitive layer, there being present in at least one layer of the material a water-soluble N-nitroso oxime of the formula:

wherein A represents a phenyl or naphth-lor -2-yl radical or a phenyl or naphth-lor -2-yl radical substituted by one or two members selected from halogen, hydrogen, alkyl having 1 to 5 carbon atoms, alkoxy having 1 to 5 carbon atoms, hydroxyalkyl having 1 to 5 carbon atoms, aralkyl and hydroxy and R is a cation.

As a cation R, for example hydrogen, ammonium, lithium, sodium or potassium may be mentioned.

The N-nitroso oximes are known compounds and have found use in various industries and analytical techniques as metal chelating agents.

Preferred compounds for use in the present invention are those of formula (I) wherein A is a phenyl-, naphth- 1-yl-, 2,3- or 3,4-dimethyl-phen-l-yl-, 2- or 4 methylpheny-1-yl-, 4-chloro-phen-1-yl-, 2-chloro-5-methyl-phen- 1-yl-, 2- or 4-ethylphenyl-1-ylor 4 3 hydroxyethyl)- phen-l-yl-radical and R is the -NH.; group and which correspond to the formulae If-O-NHI N=O I III- NH| N= (III) If- 0 NH| 0 HI @0 H: If- 0 NH4 III- 0 NH| N=0 0131:

III-0 NH| N= (VII) III-O NH4 =0 (VIII) III-O NH| N=O I|-ION H4 N:

N-O-NHa 1 1:0 (XII) Compound II and compound III are the preferred ones.

Compounds IV to XII have been synthesized by condensing the respective hydroxylamine with n-butylnitrite in the presence of ammonia. The structures of these compounds IV to XII has been established unequivocally from the evidence obtained from elementary analysis, infrared and proton magnetic resonance spectrocopy.

It is to be understood that the N-nitroso-oxime compound of formula I, may be present in any layer of the photographic material, for example a photosensitive layer, in any inter layer of the material, in a subbing layer, in a supercoat layer or in a layer distal to the photosensitive layer, for example in an anti-halation layer. When the photographic material comprises a silver halide emulsion layer and the compound of formula I is present in this emulsion layer or in a layer in operative contact with this layer, the presence of the compound of formula I reduces the tendency of any metallic contamination of the photographic material to produce spots in any of the layers of the material, reduces the tendency of any metallic contamination to react with the silver halide emulsion layer and produce desensitized or sensitized spot marks and reduces the tendency of the photographic material to exhibit latent image instability.

When the photographic material does not comprise a silver halide emulsion layer or the compound of formula I is not in the silver halide emulsion layer nor in a layer in operative contact therewith, then the presence of the compound of formula I in the photographic material acts only to reduce the tendency of any metallic contamination of the photographic material to produce spots in the layer in which it is present or in any layer in operative contact therewith.

Therefore, according to a preferred embodiment of the invention, there is provided photographic material which comprises a support base carrying a silver halide emulsion layer, there being present in the silver halide emulsion layer or in a layer in operative contact therewith a compound of formula I.

By layer in operative contact with a silver halide emulsion layer is meant a layer in contact with the emulsion layer so that during coating of the layers some at least of the water-soluble N-nitroso-oxime of formula I is able to migrate from the layer in which it is coated into the emulsion layer.

Preferably when the photographic material contains a silver halide emulsion the N-nitroso-oxime compound of formula I is added to the silver halide emulsion layer in an amount between 0.01 to 10 g. per mole of silver halide in the emulsion. Preferably the compound is added as an aqueous or alcoholic solution to the emulsion just prior to coating of the emulsion. It is to be understood that the preferred amount of the nitroso-oxime compound of formula I to be present in the material depends on the amount of metallic contamination present. Thus if coatings on a specific coating machine exhibit particularly high metallic contamination then more of the nitrosooxime compound will be required in photographic materials coated thereon than in material coated on machines wherein the coatings made thereon are not so severely contaminated with metallic particles.

It has been found that the N-nitroso-oxime compounds of formula I when present in photographic material do not occasion any deleterious eifects in the photographic material. In particular they do not cause fogging of the emulsion. Moreover, of course, they do not cause serious deterioration of the latent image. Further they do not cause any deterioration in the mechanical properties of the emulsion.

It has been found that the N-nitroso-oxime compounds of formula I act more efiiciently in preventing latent image instability and spot marks when there is present in the layer of the photographic material which contains the N-nitroso-oxime compound, or in a layer in operative contact therewith, a dispersion of a water-insoluble organic solvent-soluble high-boiling point liquid, a so-called oil former.

Preferably the oil-former employed should be chemically and photographically inert towards the layer of the photographic material in which it is incorporated and towards photographic processing baths. In general, oil-formers having boiling points above 150 C. are preferred.

It is, further, most advantageous that the oil-former should have a refractive index close to that of the binder, usually gelatin, of the layer in which it is dispersed.

Examples of suitable oil-formers which can be used are octadecanol, high boiling petroleum fractions, dibutyl phthalate, 1,2-dimethoxybenzene, diphenyl, diphenylether, NzN-dibutyl-lauramide, 2,4 di-n-amylphenyl, tricresyl phosphate, benzophenone, and ethyl oleate; some of these oil-formers and others suitable for the purpose are set out in British Patent Specification Nos. 541,589, 633,812 and 820,329.

An emulsion layer containing a dispersion of the oilformer may be obtained in a variety of ways. The oilformer may be dispersed in water or gelatin solution or in any aqueous solution of a water-soluble binder which ismiscible with and compatible with the layer e.g. the silver halide emulsion layer, and the dispersion so obtained added to the layer. Alternatively, the oil-former may be dissolved in a low boiling or water-miscible solvent prior to being dispersed. If a low-boiling solvent has been used this is removed by evaporation. If a watermiscible solvent has been used in a gelatin layer this solvent may be removed by washing the gelled and shredded dispersion. If desired a solvent dispersion, for example in gelatin, may be dried and reconstituted in water as required. The oil-former may also be dissolved in a watermisible solvent such as acetone, methanol or methyl acetate, a dispersing agent added and the whole added to an aqueous gelatin solution or gelatin silver halide emulsion when a fine dispersion of the oil-former is obtained.

Dispersing agents which may be used to aid and stabilise the dispersions include the sodium salt of dioctyl and sulphosuccinate, sodium lauryl sulphate and triisopropylnaphthalene sulphonate.

The dispersion may be elfected with the aid of a ho mogenizer, colloid mill or the like.

:A proportion of 0.5 to 5% by weight of a said oilformer layer, based on the formulated silver halide emulsion has been found to be suitable.

The preferred oil-former for use in the present invention is dibutyl phthalate. 7

It is not known with certainty why the presence of a dispersion of an oil-former in the layer containing the nitroso-oxime compound, or in a layer in operative contact therewith, enhances the effect of the N-nitroso-oxime compound. However it is thought that the complex formed between the metallic contaminants of the photographic material and the N-nitroso-oxime is extracted from the silver halide emulsion layer into the oil-former dispersion. It is possible that the complex formed between N-nitroso-oximes and metal contaminants has some effect on latent image stability and in the production of spot marks, but a much reduced effect compared with the metal contaminants per se, so that when this complex is completely removed from the silver halide phase an even greater improvement in latent image stability and reduction in spot marks is obtained. Complexes formed between the N-nitroso-oximes of formula I and copper or iron are more soluble in the oil-formers than in the gelatin or other binder phase of the emulsion and thus the complex is preferentially extracted from the silver halide phase into the oil-former phase of the layers.

The presence of iron and coper contamination has been stressed because most photographic silver halide emul' sions contain in the region of parts per million of iron and in the region of 20 parts per million of copper.

The presence of an oil-former in the photographic material which is able to extract the N-nitroso-oxime-metal complexes from the aqueous phase of the layers of the photographic material is advantageous even when the N nitroso-oxime is added to the material for the purpose of lessening the spot formation due to gross metallic contamination. This is illustrated in Example 5 which follows.

Therefore, according to another embodiment of the present invention there is provided photographic material which comprises a support base having coated thereon one or more layers, at least one of which is a photographic layer, there being present in at least one layer of the material a dispersion of an oil-former and there being present in the same layer or in a layer in operative contact therewith a N-nitroso-oxime of formula I.

In a preferred embodiment of this aspect of the present invention there is provided photographic material which comprises a support base carrying thereon a silver halide emulsion layer having dispersed therein a water-insoluble organic-solvent-soluble high boiling point oil-former, there being present in the silver halide emulsion layer or in a layer in operative contact therewith a N-nitrosooxime compound of formula I.

Preferably in this aspect of the invention the N-nitrosooxime is present in the silver halide emulsion layer, the preferred oil-former is dibutyl phthalate and the preferred N-nitroso-oxime is the compound of formula II.

It has been found that the N-nitroso-oxime compounds of formula I act more eiiiciently in preventing spot marks due to copper contamination when there is present in the layer of the photographic material which contains the N- nitroso-oxime compound, or in a layer in operative contact therewith, salicylaldoxime. Some increased effect is apparent also in the prevention of spots due to iron contamination.

Therefore, according to yet another embodiment of the present invention there is provided photographic material 'which comprises a support base having coated thereon one or more layers, at least one of which is a photographic layer, there being present in at least one layer of the material salicylaldoxime and there being present in the same layer or in a layer in operative contact therewith a N-nitroso-oxime of formula I.

In a preferred embodiment of this aspect of the present invention there is provided photographic material which comprises a support base carrying thereon a silver halide emulsion layer which comprises salicylaldoxime, there being present in the silver halide emulsion layer or in a layer in operative contact therewith a N-nitrosooxime compound of formula I.

Preferably the amount of salicylaldoxime present in the silver halide emulsion is from 0.01-10 g. per mole of silver halide in the emulsion.

The N-nitroso-oxime compounds of formula I may be added to photographic emulsions at any stage in the emulsion making process provided they remain present in the finished emulsion.

The silver halide emulsion to which the N-nitrosooxime compounds of formula I may be added may comprise any of the normal silver halides, for example, silver chloride, silver bromide or silver iodobromide. The emulsion binder is preferably gelatin but may comprise other polymeric substances for example polyvinyl alcohol, polyvinyl pyrrolidone, ethyl cellulose or an alginate, either alone or in admixture with the gelatin.

The silver halide emulsion to which the N-nitrosooxime compounds of formula I may be added may contain any of the usual sulphur sensitizers for example thiourea or thiosulphate and may in addition be sensitized with a nobel metal, for example gold. Furthermore it may comprise polyethylene oxide sensitizers and the usual tetraazindene stabilizers and may contain further stabilizers, for example cadmium or mercury salts. The emulsion may also contain development anti-foggants.

The presence of color couplers in the silver halide emulsion does not appear to interfere in any way with the action of the N-nitroso-oxime compounds of formula I in reducing the tendency of the photographic material to exhibit latent image instability and the formation of spot marks.

The following Examples will serve to illustrate the invention.

EXAMPLE 1 A slow fine grain iodobromide emulsion was prepared, in gelatin solution, having 3.2 mole percent of silver iodide, the pH of the emulsion being adjusted to 6.0 and the pAg of the emulsion being adjusted to 8.4. This emulsion was digested at an elevated temperature in the presence of sodium thiosulphate and a gold salt to maximum sensitivity. The emulsion was then stabilized by the addition of a tetraazaindene compound and cooled. A wetting agent was then added to the emulsion, which was reheated and coated onto film strips. This was the control emulsion A.

Similar emulsions B and C were prepared and coated except that in the case of B, 5 mols of a 1% aqueous solution of the ammonium salt of N-nitroso-N-phenylhydroxylamine (the compound of formula II) was added per mole of silver halide in the emulsion to the emulsion immediately prior to coating the emulsion. In the case of emulsion C, 7 g. of a gelatin dispersion of dibutyl phthalate per mole of silver halide was added to the emulsion after digestion and then 5 moles of a 1% aqueous solution of the ammonium salt of N-nitroso-N- phenylhydroxylamine per mole of silver halide in the emulsion was added to the emulsion immediately prior to coating the emulsion.

The gelatin dispersion of dibutyl phthalate was made by adding 5% of dibutyl phthalate to 129 g. of gelatin dissolved to form a concentrated aqueous solution, ml. of Perminal BX, a naphthalene sulphonate based dispersing agent marketed by Imperial Chemical Industries Limited, was then added to the mixture and the mixture was mechanically stirred in order to disperse the dibutyl phthalate in the gelatin solution.

In each test one strip of the control emulsion and the strips of the test emulsions were all exposed to flash through a stepwedge and then incubated for 7 days at 69% RH. at 43 C. such conditions being chosen to accelerate any tendency to latent image regression.

All the strips were then processed for 8 minutes at C. in a metol/hydroquinone-based developers (ID-2 marketed by Ilford Limited). The relative log speed measured at a density of 0.1 above fog of all the strips was then determined and compared with the relative log speed at 0.1 above fog of identical strips of emulsions A, B and C which after coating were stored for seven days at room temperature, exposed through a stepwedge and then at once processed as above.

In the case of emulsion A there was a speed loss of 0.25 log E units in the sample which had been incubated for seven days after exposure compared with the sample which had been developed at once after exposure.

In the case of emulsion B there was a speed loss of 0.18 log E units in the sample which had been incubated for seven days after exposure compared with the sample which had been developed at once after exposure.

In the case of emulsion C there was a speed loss of 0.12 log E units in the sample which had been incubated for seven days after exposure compared with the sample which had been developed at once after exposure.

This test shows that the presence of the compound of formula II in the emulsion reduces the latent image regression of the emulsion after exposure. Also when the compound of formula II and a dispersion of dibutyl phthalate are present simultaneously in the emulsion the latent image regression of the emulsion after exposure is further reduced.

EXAMPLE 2 Three samples A, B and C of a fast coarse-grained iodobromide emulsion were prepared as in Example 1. Samples of these emulsions were exposed, incubated and processed as in Example 1.

Three sets of test were carried out. In tests 1, 2 and 3 the three emulsion samples A, B and C which had been incubated for seven days after exposure were compared for speed loss with the three same emulsion samples which had been exposed and processed at one. In test 1 the speed loss of the emulsion at 0.1 above fog was determined. In test 2 the speed loss or gain at 1.5 above fog was determined. In test 3 the development time of the emulsions was lowered to 3 minutes and the speed loss or gain at 0.1 above fog was determined. In test 4 the development time of the emulsions was also 3 minutes and the speed loss or gain at 1.5 above fog was determined.

Table 1 below shows the results obtained.

TABLE 1 Test (log E units) Emulsion 1 2 3 4 EXAMPLE 3 A slow fine grain iodobromide emulsion was prepared and coated exactly as in Example 1. This was the control emulsion A.

Similar emulsions D and B were prepared and coated except that in the case of D, 10 mols of a 1% aqueous solution of the compound of formula II was added per mole of silver halide. In the case of emulsion E 7 g. of a dibutyl phthalate dispersion (prepared as in Example 1) was added to the emulsion after digestion and then 10 mols of a 1% aqueous solution of the compound of formula III was added per mole of silver halide.

Strips of these three emulsions were tested as set forth in Example 1.

In the case of emulsion A there was a speed loss of 0.20 log E units in the sample which had been incubated for seven days after exposure compared with the sample which had been developed at once after exposure.

In the case of emulsion D there was a speed loss of 0.16 log E units in the sample which had been incubated for seven days after exposure compared with the sample which had been developed at once after exposure.

In the case of emulsion B there was a speed loss of 0.14 log E units in the sample which had been incubated for seven days after exposure compared with the sample which had been developed at once after exposure.

Comparably with Example 1 this test shows that the presence of the compound of formula -III in the emulsion reduces the latent image regression of the emulsion after exposure. Also when the compound of formula III and a dispersion of dibutyl phthalate are present simultaneously in the emulsion the latent image regression of the emulsion after exposure is further reduced.

9 EXAMPLE 4 A slow fine grain iodobromide emulsion was prepared and coated as in Example 1. This was the control emulsion A.

Similar emulsions F and G were prepared and coated except that in the case of emulsion F 160 mols of 1% aqueous solution of the compound of formula IV was added per mole of silver halide. In the case of emulsion G 7 g. of a dibutyl phthalate dispersion (prepared as in Example 1) was added to the emulsion after digestion and then 160 mols of a 1% aqueous solution of the compound of formula IV was added per mole of silver halide.

Strips of these three emulsions were tested as set forth in Example 1 In the case of emulsion A there was a speed loss of 0.36 log E units in the sample which had been incubated for seven days after exposure compared with the sample which had been developed at once after exposure.

In the case of emulsion F there was a speed loss of 0.30 log E units in the sample which had been incubated for seven days after exposure compared with the sample which had been developed at once after exposure.

In the case of emulsion G there was a speed loss of 0.24 log E units in the sample which had been incubated for seven days after exposure compared with the sample which had been developed at once after exposure. comparably with Examples 1 and 2 this test shows that the presence of the compound of formula IV in the emulsion reduces the latent image regression of the emulsion after exposure. Also when a compound of formula IV and a dispersion of dibutyl phthalate are present simultaneously in the emulsion the latent image regression of the emulsion after exposure is further reduced.

EXAMPLE 5 6.5. This material is referred to as sample M. A similar.

sample was prepared (referred to as N) except that there was added to 1 kg. of the silver halide emulsion just prior to coating 100 ml. of a 1% ethanolic solution of the compound of formula H. A third sample P was prepared; in this sample there was added to the silver halide emulsion prior to coating, in addition to the compound of formula II, 100 ml. of a gelatin dispersion containing 30% dibutyl phthalate.

A fourth sample Q was prepared as M except that there was added to 1 kg. of the silver halide emulsion just prior to coating 100 ml. of a 1% ethanolic solution of the compound of formula III. A fifth sample R was prepared and in this sample there was added to 1 kg. of the silver halide emulsion prior to coating in addition to the compound of formula HI, 100 ml. of a gelatin dispersion containing 30% dibutyl phthalate. A sixth sample S was prepared as sample M except that there was added to 1 kg. of the silver halide emulsion just prior to coating 100 ml. of a 1% ethanolic solution of the compound of formula VII. A seventh sample T was also prepared and in this sample there was added to 1 kg. of the silver halide emulsion just prior to coating 100 ml. of a gelatin dispersion containing 30% dibutyl phthalate in addition to the compound of formula VII.

Samples M, N, -P, Q, R, S and T were exposed to light and developed for 4 minutes in a Phenidone/hydroquinone based developer. On inspection, after drying, sample M was found to have numerous light patches centered on the copper particles. Samples N, Q and S were found to have some light patches centered on the copper particles, but

very much fewer than in sample M. However, in samples P, R and T there were almost no light patches centered on the copper particles.

EXAMPLE 6 This example illustrates the effect caused by iron and rust on the silver halide emulsion and illustrates the improvement obtained by the additives used in the present invention.

A silver iodobromide emulsion having a pH of 6.5 was applied to a gelatin layer which contained very fine iron powder and rust coated on a film support (sample VIII). A similar sample Y was prepared except that there was added to 1 kg. of the silver iodobromide emulsion just prior to coating 75 mols of a 1% aqueous solution of the compound of formula IH. Similar samples U, V, W and Z were prepared containing respectively 75 mols of a 1% solution of the compound of formulae III, IV, V and VIII. Samples X, Y, Z, U, V and NV were then light exposed and developed for 4 minutes in a l-phenyl-3- pyrazolidone/hydroquinone based developer. In sample VIII there were found to be a large number of sensitized black spots which were due to (metal ions from) the iron and rust coming into contact with the silver halide emulsion and causing sensitized marks. However, in samples Y, Z, U, V and W the number of sensitized black marks was considerably reduced compared with sample VHI.

EXAMPLE 7 A silver iodobromide emulsion having a pH of 6.5 was applied to a gelatin layer which contained very fine copper particles coated onto a film support (sample A). Similar samples were prepared except that there were added to the silver iodobromide emulsion 6 mols of a 20% ethanolic solution of salicylaldoxime per mole of silver halide (sample B) mols of a 2% aqueous solution of the ammonium salt of N-nitrosoN-phenylhydroxylamine (the compound of formula II) per mole of silver halide (sample C) and finally salicylaldoxime and the ammonium salt of N-nitroso-N-phenylhydroxylamine ta gether in the above quantities (sample D). Samples A, B, C and D were then light exposed and developed for 4 minutes in a 1-phenyl-3-pyrazolidone/hydroquinonebased developer. In sample A there were numerous desensitized (white) spots centered on the copper particles. In sample B, these desensitized spots were slightly reduced in size, while in sample C both their numbers and their intensities were greatly reduced. In sample D no desensitized areas were observed.

What we claim is:

1. A photographic material which comprises a support base having coated thereon one or more layers, at least one of which is a photosensitive silver halide emulsion layer, there being present in at least one layer of the material a water-soluble N-nitroso-oxime of the formula wherein A represents a phenyl or naphth-lor -2-yl radical or a phenyl or naphth-lor -2-yl radical substituted by one or two members selected from hydrogen, halogen, alkyl having 1 to 5 carbon atoms, alkoxy having 1 to 5 carbon atoms, hydroxyalkyl having 1 to 5 carbon atoms and aralkyl and R is a cation.

2. A photographic material according to claim 1 which comprises a compound of formula I defined in claim 1 wherein A is a phenyl-, naphth-l-yl-, 2,3- or 3,4-dimethylphen-1-yl-, 2- or 4-methyl-pheny-l-yl-, 4-chlorophen-l-yl-, Z-chloro-S-methyl-phen-l-yl-, 2- or 4-ethylpheny-l-ylor 4-(fl-hydroxyethyl)-phen-l-yl-radical and R is the NH.; group as the water-soluble N-nitroso-oxime.

3. A photographic material according to claim 1 which comprises a compound of formula I defined in claim 1 wherein A is phenyl and R is the NH., group as the water-soluble N-nitroso-oxime.

4. A photographic material according to claim 1 which comprises a compound of formula I defined in claim 1 wherein A is naphth-l-yl and R is the NH.; group as the water-soluble N-nitroso-oxime.

5. A photographic material according to claim 1 which comprises at least one layer containing dispersed therein a water-insoluble organic-solvent-soluble high 'boiling point oil-former, selected from the group consisting of a high boiling petroleum fraction, dibutyl phthalate, 1,2- di-methoxybenzene, verotrole, diphenyl, diphenylether, N,N-dibutyllauramide, 2,4 di-n-amylphenyl, tricresylphosphate, benzophenone and ethyloleate and a watersoluble N-nitroso-oxime of the formula I A-N-O-R N L .0

wherein A and R have the meanings given in claim 1 which oxime is contained in the same layer or in a layer adjacent to the layer containing the oil-former.

6. A photographic material according to claim 5 which comprises a compound of the formula I defined in claim 5 wherein A is phenyl and R is the -NH.; group as the water-soluble N-nitroso-oxime.

7. A photographic material according to claim 5 which comprises a compound of the formula I defined in claim 5 wherein A is naphth-l-yl and R is the -NH.; group as the water-soluble N-nitroso-oxime.

8. A photographic material according to claim 1 wherein salicylaldoxime is contained in the same layer as the water-soluble N-nitroso-oxime or in a layer adjacent to the said layer.

9. A photographic material according to claim 1 which comprises a silver halide emulsion layer as the photosensitive layer and a water-soluble N-nitroso-oxime of formula I wherein A and R have the meanings given in claim 1 which oxime is contained in said silver halide emulsion layer or in a layer adjacent to said layer.

10. A photographic material according to claim 9 which comprises a compound of formula I defined in claim 9 wherein A is phenyl and R is the ---NH.; group.

'11. A photographic material according to claim 9 which comprises a compound of formula I defined in claim 9 wherein A is naphth-l-yl and R is the NH; group.

12. A photographic material according to claim 9 wherein the water-soluble N-nitroso-oxime is present in an amount of from 0.01 to 10 g. per mole of silver halide in the silver halide emulsion layer or in a layer adjacent to said layer.

13. A photographic material, according to claim 5 wherein the oil-former is dibutyl phthalate.

14. A photographic material according to claim 9 wherein 'both the water-soluble N-nitroso-oxime of the formula I AN0R wherein A and R have the meaning given in claim 9 and salicylaldoxime are present in a silver halide emulsion layer.

15. A photographic material according to claim 14 wherein the salicylaldoxime is present in an amount of from 0.01 to 10 g. per mole of silver halide, in the silver halide emulsion layer.

16. A photographic material according to claim 15 which comprises a compound of formula I wherein A is phenyl and R is the -NH group as water-soluble N- nitroso-oxime.

References Cited UNITED STATES PATENTS 2,675,314 4/1954 Vittum 96109 3,148,066 9/1964 I-Iolstead 96-109 3,189,454 6/1965 Luckey 9661 R 3,393,072 7/1968 Ohi 96109 3,271,143 9/1966 Sorensen 96--1'1.7

NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant Examiner US. Cl. X.R.