Light Sensitive, Color Photographic Silver Halide Compositions With DIR-couplers

This invention relates to a light sensitive, color photographic silver halide compositions which contain new DIR couplers in order to improve their color rendition and detail rendition.

It is known that one may add to light sensitive silver halide color photographic materials color couplers for the improvement of the quality of the image, which free development inhibitors during the color development proportional to the exposure. They are usually called DIR-couplers ("DIR" meaning "development inhibitor releasing") and are described in detail as to their structure, mechanism of coupling and photographic effect for instance by C. R. Barr, J. K. Thirtle and P. W. Vittum in Phot. Sci. Engn. 13, 274-79 (1969) and in U.S. Pat. No. 3,148,062. Photographic properties which can be improved with DIR-couplers are edge sharpness, color grain and color rendition.

These effects are based upon the diffusion of the freed inhibitor within that layer which contains the DIR-coupler (intra-image effect) and upon the diffusion into the adjacent layer (inter-image effect). The intra-image effect improves the rendition of detail and the inter-image effect may be used for color correction of undesired color layers of image coloring dyes. These effects based upon inhibiting effect and upon diffusion are described by, among others, W. T. Hanson and C. A. Horton in J. Optical Soc. America 42, 633-669 (1952); A. Thiele in Z. Wiss. Photogr., Photophys., Photochem. 47, 105-118 as well as 246-255 (1952) and in Federal Republic of Germany Offenlegungsschrift No. 2,509,722. Furthermore the DIR-couplers may be used according to U.S. Pat. No. 3,620,747 for control of gradation and, in connection with that, for the increase of the brightness of the coloring dyes and, also according to Federal Republic of Germany Offenlegungsschrift No. 2,533,176 for the reduction of development fog, particularly for work at elevated temperatures. The chemical structure of the known DIR-couplers embraces particularly acylacetanilide-, pyrazolone-(5)-, phenol-, or 1-naphthol-derivatives bonded to a usual diffusion-preventing ballast group and in coupling position to a splittable inhibitor group. Particularly effective DIR-couplers carry heterocyclic mercaptoazols, -azines, arylmercaptans or mercapto-carboxylic acids as splittable groups. The most typical diequivalent substituents are 2-nitro-, or 2-aminophenylthio-, benzthiazole-2-ylthio-, 1-phenyl-tetrazole-5-ylthio-, 5-phenyl-1,3,4-oxadiazole-2-ylthio- or benzoxazole-2-ylthio-groups. Syntheses of a multitude of DIR-couplers carrying the typical inhibitor groups are described in, among other places, U.S. Pat. Nos. 3,148,062, 3,227,551, 3,227,554 and in Federal Republic of Germany Offenlegungsschrift No. 2,247,496. The use of prior art DIR-couplers exhibits, though, certain disadvantages. Usually they cannot be used as the single coloring element because the strong inhibiting action of the splitting group retards the chromogenic development so strongly that even development at high temperature results in low saturated images. That necessitates the mixing in of coloring couplers which result in dyestuffs of the same absorption range at a higher yield. Examples of mixtures with two to seven different color couplers and DIR-compounds are shown in U.S. Pat. No. 3,703,375 or Federal Republic of Germany Offenlegungsschrift No. 2,530,645, and their influence upon improvements of definition, grain and color rendition are tabulated. Mixtures contain usually less than 10% of the above-described DIR-couplers. Mostly only incomplete decoupling of the DIR-coupler occurs due to this low concentration of coupler and also because the admixed color coupler exhibits in most cases a higher coupling speed. That leads to low concentrations of freed development inhibitor, in order to render possible particularly efficient inter-image effects by diffusion into adjacent layers. Therefore, special uses of known DIR-couplers are made, for example, in intermediate layers and auxiliary layers, which solely serve to correct color by the inter-image effect. They are, for example, described in U.S. Application No. 454,524, U.S. Pat. No. 3,006,759 and in Federal Republic of Germany Offenlegungsschrift Nos. 2,421,544 and 2,429,250 and are named also IIC-, ILC- or IIE-couplers. The use of higher concentrations of the known DIR-couplers is furthermore limited by the lowering of the sensitivity and gradation by the so-called "clearing effect." It always occurs when freeing of the inhibitor not proportional to illumination occurs before or during the chromogeneous development or when inappropriate purification methods do not succeed in bringing the residual inhibitor content of the DIR-couplers below 0.5%. Adequate purification is technically difficult and expensive and is sometimes very difficult, if not impossible, to achieve on a commercial scale. As an expedient serve complicated systems of layer construction, as claimed for example in U.S. Pat. Nos. 3,620,745, 3,620,747, Federal Republic of Germany Offenlegungsschrift Nos. 2,322,165, 2,421,544, 2,423,250 and 2,530,645. Here known DIR-couplers are introduced into the insensitive silver halide layers of variously constructed layer units of a color forming element in order to improve image definition and color rendition.

Besides the hereabove described DIR-couplers with thio-ether splittable groups of high inhibitor effect, U.S. Pat. No. 3,617,291 mentions, among others, DIR-couplers which have heterocyclic imino-compounds or precursors thereof which could serve as splittable groups. Typical couplers contain benztriazolyl- or nitrobenzimidazolyl- moieties or derivatives thereof. Compared to the aforementioned DIR-couplers having thioether structure, these compounds show too small DIR-effects and are less capable of color correction effects. It might be also disadvantageous that the known DIR-couplers are mostly hydrophobic compounds and that only rarely the usual inhibitor moieties are bound as splittable groups to hydrophilic compounds. They only can be used for photographic material when dispersed, which means an addition of high- or sometimes low-boiling solvents and emulsifiers, which is more expensive than the use of a simple solution.

It is an object of the invention to make possible by the use of new DIR-couplers the preparation of color photographic silver halide multilayer materials of good definition, grain and color rendition, avoiding the disadvantages of present technical solutions such as, for instance, too low intra- and inter-image effects due to a too small DIR-coupler percentage in mixtures with other couplers or the use of a complicated layer construction for a color photographic multilayer material or high costs of production caused by a complicated purification process for the DIR-couplers which are being used. Another aim of the invention is to lower the costs of the aforementioned silver halide materials by using new DIR-couplers which may be added to the color photographic silver halide layers as aqueous alkaline solutions.

According to the invention there are provided new DIR-couplers which may be added in high concentration in order to obtain efficient intra- and inter-image effects, which need little purification efforts when prepared, show high stability in the photographic layer and only negligible or no desensitizing effects and which may be added as well in dispersions as in aqueous alkaline solutions. According to the invention this task is fulfilled by using as DIR-couplers compounds of the general formula:

wherein

K is a color-forming group containing a diffusion preventing moiety, for reaction with an oxidation product of a color developer to yield purple, yellow, and blue-green dyes, simultaneously liberating a hydrophilically substituted development inhibitor, wherein the blue-green color coupler has a 1-naphthol- or phenol-structure, the purple color coupler has a 1-aryl-pyrazolone-5-structure and the yellow color coupler has an acylacetanilide-structure; and

Y is an aryl-substituted azole, azine or benzazole of the general formulae I or II: ##STR1## wherein Z represents atoms or atom groups completing the azole- or azine-ring,

X is O, S, or NR.sup.2,

R.sup.1 is OR.sup.3, COOR.sup.3, SO.sub.2 NHR.sup.3, SO.sub.3 R.sup.3,

R.sup.2 is H, or an alkyl moiety of one to five carbon atoms, and

R.sup.3 is H, an ammonium ion, or a metal ion.

FIG. 1 is an illustration of the results in Example 7; and

FIG. 2 is an illustration of the results in Example 8.

The yellow-, purple- and bluegreen-DIR-couplers according to the invention consist of a coupler moiety and a thio-ether or tautomer thio-imido splittable group. It is of decisive importance for the photochemical effect of the invention that the splittable group be a mercaptoazol or azine or a benzocondensed derivative thereof carrying a hydrophilic group R.sup.1 in the case of formula I.

The DIR-couplers according to the invention are very well suited for the improvement of the precision, color grain and color rendition of light-sensitive color photographic multilayer materials. They are distinguished by their remarkable range of dosage. They may be added in relatively high concentrations to individual silver halide layers in a proportion up to 50% relative to a colorcoupler for the same spectral range of the eventual image coloring material or in some cases even may be used as sole color forming element. The DIR-coupler may be added to silver halide dispersions in amounts between 1 and 100 g. per mole silver halide. When used in high concentrations up to its use as the sole color forming element, the amount is between 30 and 100 g. per mole silver halide.

The DIR-couplers of the invention may be used in addition to any other coupling compounds such as color couplers, masking couplers and colorless couplers in amounts from 1 to 30 g. per mole silver halide. The use at high concentrations guarantees good coupling, assuring color yields above 50% and simultaneously also the freeing of large amounts of development inhibitor causing effective intra- and inter-image effects.

Excellent intra-image effects can be found within the layer, which are easily recognized by fine grain and good definition. Due to the high local concentration after the coupling reaction large amounts of development inhibitor can diffuse into adjacent layers. Thus the DIR-couplers according to the invention allow, for instance, an efficient correction of the incident color densities of the image dyestuffs in the adjacent layers due to the inter-image effect in a relatively simple layer construction of the color photographic material. These advantages of the couplers according to the invention are obviously caused by the fact that they contain as thio-ether splittable groups mercaptoazoles or mercapto-azines or respective benzocondensed derivatives therof which contain a hydrophilic group R.sup.1.

Kinetic measurements suggest that the efficient coupling together with high color yields compared to the heretofore known DIR-couplers is not caused by a higher speed of the color coupling process but by the specially advantageous inhibitor effects of the hydrophilic substituted thio-ether splittable groups contained by the DIR-couplers. These effects are largely independent of the type of the coupler K in the general formulas I and II of the DIR-coupler according to the invention. The execution of the kinetic investigation and the results of the measurements are shown in Table 2.

An additional advantage of the use of the DIR-couplers according to the invention is that small amounts of the respective unreacted hydrophilic substituted mercapto-heterocyclic compounds exhibit considerably lower losses of sensitivity than was the case with prior art DIR-couplers. Thus, there is less need for purification as compared with prior art DIR-couplers. The DIR-couplers according to the invention are furthermore excellently stable within a photographic layer and show no diminution of sensitivity due to splitting not proportional to illumination.

An added advantage of the invention is that the new couplers may be added to a photographic emulsion according to one of the usual dispersing methods, for instance as disclosed in Federal Republic of Germany Offenlegungsschrift No. 1,261,061, or as a solution. The solution is an alkaline medium containing a dipolar aprotic solvent, for instance DMF (see Addition Examples 1 to 5).

The DIR-couplers of the invention may be used along with other photochemical additives such as gelatine substitutes, hardeners, wetting agents, chemical and spectral sensitizers, stabilizers and clarifying agents, antioxidants, compounds for pH-regulation and so forth. Furthermore, the DIR-coupler of the invention may be used regardless of the constitution of the silver halide, its crystal structure and habitus, the base of the film, the constitution of the binder and the use of additional materials which aid in the preparation of silver halide multilayer materials. The DIR-couplers according to the invention may be used in photographic material in single layers or in multiple-layer constructions. The order of the layers in photographic materials which contain these DIR-couplers in single layers and in photographic materials which contain DIR-couplers in multiple layers is immaterial.

Some structures of the new compounds are shown in Table 1. These cited examples of DIR-couplers with hydrophilicly substituted inhibitor splittable groups in coupling position of prior art yellow-, purple- and blue-green color couplers do not limit the scope of the invention. They are produced according to the "Synthesis Examples" 1 to 6 or in an analogous manner. The principle of synthesis is to couple at 50.degree. to 150.degree. C. in a dipolar aprotic solvent the alkali salts of hydrophilic substituted mercapto-azoles to the respective color couplers which are halogen substituted in their coupling position. Synthesis of the mercapto-azoles may be performed in the case of hydrophilic substituted mercapto-azoles according to German Democratic Republic Patent No. 80,625. Table 1 shows the structures, their melting-points and the synthesis yields.

Kinetic investigations were performed on known DIR-couplers (compound Nos. 13, 14 and 21 in Table 2) which were synthesized analogously to the synthesis examples in U.S. Pat. No. 3,227,551 and which contain the known 1-phenyltetrazole-5-yl-thio- moiety as a splittable group, and were also performed on compounds 7, 10, 15, and 16 (Table 1) of the invention, which differ from compounds 13, 14, and 21 by the hydrophilic groups in the splittable groups. The reactions between these DIR-couplers and the oxidation product of N,N-diethyl-p-phenylenediamine were performed at 25.degree. C. in aqueous n-propanol. The dye formation follows the kinetic law of the second order and the rate of reaction is characterized by the rate constant K.sub.2, whose numerical values can be found in Table 2. The reaction rates of the compounds 13 and 10 or 14 and 7, or 21 and 15 and 16, belonging to the same type of couplers, respectively, differ only slightly and are in the same range. (see Table 2)

Synthesis Example 1: 4-[1-(3-carboxyphenyl)-tetrazole-5-yl]-mercapto-1-hydroxy-2-naphthoic acid-(2'-octadecyloxy)-anilide (Compound 1)

4.88 g (0.02 mol) Na-salt of 1-(3-carboxyphenyl)-5-mercapto-tetrazole and 12.2 g (0.02 mol) 4-bromo-1-hydroxy-2-naphthoic acid-(2'-octadecyloxy-)-anilide are heated eight hours under reflux in 200 ml. boiling acetone. The solvent is distilled off, the residue is taken up in 500 ml. boiling ethanol and separated from sodium bromide by filtration, while hot. After standing 6 to 10 hours at a temperature of 0.degree. to 10.degree. C., Compound 1 crystallizes. The supernatant liquid is sucked off, and the crystals are washed with ice cold ethanol and air-dried.

yield=4.9 g (1.times. ethanol)=32% of theoretical; melting point 134.degree. to 135.degree. C.

Synthesis Example 2: 3-stearoylamino-4-[(1-p-hydroxyphenyl)-tetrazole-5-yl]-1-phenylpyrazolone- (5) (Compound 4)

Analogously to Synthesis Example 1, 4.32 g. (0.02 mol) Na-salt of 1-p-hydroxyphenyl-5-mercaptotetrazole is reacted with 9.52 g (0.02 mol) 5-chloro-3-heptadecylcarbamoyl-1-phenylpyrazolone-(5).

yield=5.7 g (1.times. ethanol)=45% of theory; melting point 164.degree. to 166.degree. C.

The 5-chloropyrazolone needed is prepared as follows:

44.16 g (0.1 mol) 3-stearoylamino-1-phenyl-pyrazolone-(5) is stirred in 500 ml. absolute methylene chloride at 0.degree. to 10.degree. C. under exclusion of moisture. 9.5 ml (0.12 mol, sp. gr.=1.667 g/cm.sup.2) sulfurylchloride in 25 ml. absolute methylene chloride is added dropwise. After stirring for half an hour, the mixture is boiled 4 hours under reflux. The solvent is distilled off, the residue is recrystallized 1.times. from methanol and 1.times. from acetone.

yield=24.4 g.=51.3% of theoretical; melting point 52.degree. to 55.degree. C.

Synthesis Example 3: 2-(p-lauroylaminobenzoyl)-2-(1-p-hydroxy-phenyltetrazole-5-yl)-mercapto-(o -chloro)-acetanilide (Compound 2)

Analogously to Synthesis Example 1, 4.32 g. (0.02 mol) Na-salt of 1-(p-hydroxyphenyl)-5-mercaptotetrazole are reacted with 10.12 g (0.02 mol) 2-chloro-2-(p-lauroylamino)-benzoyl-(o-chloro)-acetanilide.

An an intermediate product the respective 2-chlorobenzoylacetanilide was prepared according to the method "chlorination with sulfurylchloride in methylene chloride" analogously to Synthesis Example 2.

yield=7.2 g. (1.times. ethanol)=76% of theoretical; melting point 142.degree. C.

Synthesis Example 4: 1-hydroxy-4-[-1-(4-hydroxyphenyl)-tetrazole-5-yl]-thio-2-naphthoic acid-[.gamma.-(di-tertiary-amylphenoxy)-butyl]-amide (Compound 15)

22.2 g (0.04 mol) 4-bromo-1-hydroxy-2-naphthoic acid-[.gamma.-(ditertiary-amylphenoxy)-butyl]-amide and 7.76 g (0.04 mol) 1-(p-hydroxy)-phenyl-5-mercaptotetrazole are suspended at room temperature in 100 ml ethanol. While the mixture is heated and stirred, 1.5 g (0.04 mol) NaOH are added and the mixture is slowly heated to a boil and boiled 8 hours under reflux. At the beginning the solids dissolve, and after a short while a small amount of NaBr precipitates.

The mixture is filtered while hot and kept 12 hours thereafter at 5.degree.-10.degree. C. in an icebox. The precipitate is sucked off on a Buechner funnel and is dried and spread at room temperature. The raw product weighs 21.5 g. It is recrystallized once from ethanol.

Yield: 17.0 g (1.times. recr.)=53.7% theor.; MP=223.degree. C.

Synthesis Example 5: 3-ethoxy-1[(2,4-ditert.-amylphenoxy)-acetamido]-phenyl-4-(1-p-hydroxypheny l-tetrazole-5-yl)-thio-pyrazolone-(5) (Compound 17)

21.3 g (0.11 mol) 1-(p-hydroxy)-phenyl-5-mercaptotetrazole are dissolved in 250 ml absolute dimethylglycol. 250 ml 7% Cl.sub.2 solution in CCl.sub.4 are added to the solution (.about.0.025 mol). The mixture is left standing 30 minutes at room temperature, the 250 ml solvents are distilled off quickly thereafter, and the residue is then poured at room temperature under stirring into a solution of 49.4 g (0.01 mol) 3-ethoxy-1-[(2,4-ditert.-amylphenoxy)acetamido]-phenylpyrazolone-(5) in 250 ml dimethylglycol, followed by two hours of boiling under reflux. Thereafter, the solvent is distilled off in a water jet vacuum and the residue is dissolved in 1000 ml CH.sub.3 OH. The methanolic solution is filtered and very slowly poured into 2000 ml ice cooled water, while constantly stirring and scratching. The precipitate is sucked off and washed thoroughly with aqua dest. While still moist, the raw product is dissolved in 100 ml CH.sub.3 OH and 50 ml 2 n NaOH, and diluted with 350 ml water. 10 g activated charcoal are added and the mixture is filtered. The clear solution is neutralized with glacial acetic acid and cooled for 4 hours. The precipitate is sucked off, washed thoroughly with aqua dest. and dried in air for 7 days at room temperature.

Yield: 30.5 g=44.5% theor. melting range: 145.degree.-160.degree. C.

Synthesis Example 6: 2-pivaloyl-2-(1-p-hydroxyphenyltetrazole-5-yl)thioacetic acid[5-chloro-3-[(ditert.-amylphenoxy)-.gamma.-butyryl]-anilide (Compound 20)

19.4 g (0.1 mol) 1-p-hydroxyphenyl-5-mercaptotetrazole and 4.0 (0.1 mol) caustic soda are dissolved in 100 ml water. The solution is filtered and kept under a water jet vacuum until dry. The residue is dissolved under heating to 50.degree. C. in 250 ml ethanol and 60.6 g (0.1 mol) 2 pivaloyl-acetic acid[5-chloro-3-[(ditert.-amylphenoxy)-.gamma.-butyryl]-amido]-anilide, and stirred roughly 8 hours at this temperature. The solution is slowly poured into 1000 ml ice cooled water while constantly stirring ad scratching. The raw product is sucked off after crystallization, washed several times with aqua dest. and dried in air for 7 days at room temperature.

Yield: 69.2 g=90.5% theor. MP=163.degree. to 165.degree. C.

The following "Addition Examples" show that, for example, the DIR-coupler compound 7 may be used in a form allowing the addition to a photographic emulsion. It may be used in an alkaline solution or in a dispersion.

Addition Example 1

5.3 g. (0.01 mol) of Compound 13 are dissolved in 17.5 ml ethyl acetate and 2.5 ml. dibutylphthalate at elevated temperature. The dispersing beaker contains at 40.degree. to 60.degree. C. 53 ml. 10% aqueous gelatine solution and 10 ml. 5% dodecylsulfonate aqueous solution. The coupler solution is poured hot into the beaker and stirred 3 minutes.

Subsequently, ethyl acetate is distilled off under vacuum and the residue is stabilized by the addition of 4 ml. aqueous phenol solution. The dispersion is congealed, chopped and kept in the refrigerator.

Addition Example 2

7.87 g. (0.01 mol) Compound 7 is dissolved in a warm mixture of 5 ml. dimethylsulfoxide, 10 ml. methylene chloride, 5 ml. dibutyl phthalate and 10 ml. ethyl acetate and added to a mixture of 79 ml. of 10% aqueous solution of gelatine and 15 ml. 5% aqueous dodecyl sulphonate. Further processing is according to Addition Example 1.

Addition Example 3

7.87 g. (0.01 mol) DIR-coupler Compound 7 is dissolved at 50.degree. C. in 6 ml. dimethylformamide. 11 ml. (0.022 mol) 2 N NaOH is added while stirring, the solution is filtered if impurities precipitate and water is added up to the desired volume.

Addition Example 4

0.25 g (0.0011 gram atoms) sodium are dissolved in 67 ml methanol and thereafter 3.7 g (0.0054 mol) of compound 17 is dissolved while skaking. The solution is ready to be poured after filling up to 100 ml and filtering.

The couplers 15 to 20 may be mixed in photographic silver halide emulsions as alkaline solutions by following the analogous dissolution procedure of purple-DIR-coupler 17.

Addition Example 5

4 g DIR-coupler 18 are dissolved in 2 ml dibutyl phthalate and 18 ml ethyl acetate. At 50.degree. C. this solution is mixed into 50 ml 10% aqueous gelatine solution containing 10 ml of a 5% dodecyl sulphonate solution. The mixture is dispersed for 5 minutes, then diluted with 20 ml water. The acetate is distilled off in a water jet vacuum and the dispersion is stabilized by the addition of 15 ml 1% aqueous phenol solution. The dispersion is allowed to solidify, is cut into strips, and is stored in cool surroundings.

The following examples demonstrate the advantages when using the DIR-couplers according to the invention. As a comparison for the present state of the art Compound 13 (U.S. Pat. No. 3,227,551) is being used in the first four examples.

A high sensitivity gold ripened silver bromideiodide high temperature emulsion, containing 25 g. silver per kg. emulsion, 6 mol% iodine and having an average grain size of 0.5 micrometer is sensitized by the addition of 7.10.sup.-4 mol 3-ethyl-3'-sulfoethyl-5,5'-dimethyl-9-ethylbenzthiotrimethine-cyaninebetai ne per mol silver and divided in four parts.

Part A contains 0.15 mol 1-hydroxy-naphthoic acid-(2)-[2-(n-octadecyl-methyl-amino)-5-sulpho]-anilide per mol silver and is designated "Typ."

Part B contains 0.15 mol Compound 13 per mol silver and represents the state of the prior art.

Part C contains 0.15 mol Compound 12 per mol silver according to the invention.

Part D contains 0.15 mol Compound 8 per mol silver according to the invention.

After the addition of the conventional additives, the emulsion samples are poured onto a support at a rate of 1 g. silver per m.sup.2.

Subsequently the samples are exposed under a gray wedge (factor 2) with red light and are processed as follows:

For bleach and fixing bath see specification 1.

The photographic results of filmstrips A to D are shown in Table 3 below. The data show that use of the Compounds 8 and 12 of the invention lead to considerably higher yields of dyestuff in comparison to Compound 13 according to the prior art.

Compound 12 in comparison to Compound 13 exhibits in both specifications a slight diminution of sensitivity.

A color photographic multilayer material I contains the following layers:

1. As a base coat, the formulation described in Example 1, part A is used and poured onto a carrier which is provided on its emulsion side with a reflection antihalation layer.

2. A gelatine interlayer.

3. For the intermediate layer the same emulsion as for the base coat is to be used, but spectrally sensitized by adding 2.5.10.sup.-4 mol 3,3'-bis-[.beta.-sulphatoethyl]-5,5'-diphenyl-9-ethyl-benzoxotrimethinecya ninebetaine per mol silver.

Besides the conventional coating additives 0.12 mol 1-phenyl-3-stearoylpyrazolone-5 is added per mol silver as purple coupler.

4. A yellow filter layer consisting of gelatine and colloidal silver.

5. As a top layer a high sensitivity silver bromide iodide emulsion is used having an average grain size of 0.7 micrometer, an iodine content of 5 mol% and a silver content of 27 g. per kg. of emulsion. As a yellow coupler are used 0.16 mol 4-stearoylamino-benzoylacet-[2-3',5'-carboxyphenoxy)-5-carboxy]-anilide.

6. A gelatine coating.

A second photographic multilayer material II is prepared like I but contains in its base coat instead of the aforementioned bluegreen couplers 0.15 mol Compound 12 per mol silver. Silver is applied at a rate of 2 g./m.sup.2. Both materials are exposed to light of a color temperature of 3200.degree. K. under a gray wedge (factor 2) and worked up according to Specification 2. Table 4 below shows the photographic results. The inter-image effects were calculated using the method described in Federal Republic of Germany Offenlegungschrift No. 2,509,722. ##EQU1## IIE is evaluated from base coat to middle coat. Its value is: Multilayer material I=2%

Multilayer material II=17%

In order to evaluate graininess the multilayer materials I and II were exposed up to density 1 and developed. Graininess was evaluated visually at 10.times. magnification. It was found here that material II is finer grained than material I, both exhibiting the same densitometric data (see Table 4)

A third photographic multilayer material III is prepared like I but contains in its base coat per mol silver 0.15 mol 1-hydroxy-naphthoic acid-(2)-[2-(n-octadecyl-methylamino-5-sulpho]-anilide and 0.04 mol of Compound 12 with 2 g. silver per m.sup.2. The materials I and III were exposed (3200.degree. K.) and worked up according to Specification 1. Material III exhibits, in comparison to material I, a desired lowering of gradation in the middle layer (see Table 5 below) and an obviously improved IIE of 35%, while material I shows only an improvement of 2%. Copies of material III show improved color rendition compared to material I.

A fourth photographic multilayer material IV is prepared as follows:

1. A double layer unit is used as a base coat. It consists of a non-sensitive layer nearer to the carrier with the reflection antihalation layer with a gold-ripened silver bromide iodide high temperature emulsion of 0.4 micrometer average grain size, a silver content of 20 g. per kg. emulsion and an iodide content of 4 mol% and a superimposed layer with a more sensitive silver bromide iodide high-temperature emulsion of 0.6 micrometer average grain size, a silver content of 25 g. per kg. emulsion and an iodine content of 6 mol%. Both layers are sensitized by the addition of 7.10.sup.-4 mol per mol silver 3-ethyl-3-sulfoethyl-5,5'-dimethyl-9-ethyl-benzthio methinecyaninebetaine. The less and more sensitive layers contain per mol silver 0.15 mol and 0.04 mol, respectively, 1-hydroxy-naphthoic acid-(2)-[2-(n-octadecyl-methyl-amino)-5-sulpho]-anilide. Both layers are coated with silver at a rate of 0.7 g. per m.sup.2.

2. A gelatine intermediate layer.

3. The middle layer consists of a unit of two layers. The emulsions used relate to the layers in the base coat. Both of the middle layers are spectrally sensitized with 2.5.10.sup.-4 mol 3,3'-bis[-sulphatoethyl]-5,5-diphenyl-9-ethyl-benzoxotrimethinecyaninebeta ine. The less sensitive layer, which lies closer to the support, contains 0.08 mol 1-phenyl-3-stearyl-pyrazolone-(5) and 0.06 mol 1-(4'-phenoxy-3'-sulpho)-phenyl-3-stearoylamino-4-[(-4'"-methyl-phenylsulp honyl)-4"-aminophenylazo]-pyrazolone-(5). The more sensitive layer contains 0.04 mol 1-phenyl-3-stearyl-pyrazolone-(5) per mol of silver.

A photographic multilayer material V is prepared like IV but contains according to the invention in the leass non-sensitive layer of the base coat 0.04 mol of Compound 8 and in the less non-sensitive layer of the middle layer 0.03 mol of Compound 4, calculated per mol silver, the silver content of the respective layers being increased by 30%. The materials IV and V are processed according to Specification 1. The photographic results are shown in Table 6 below.

The inter-image effect II E is:

A high-speed, highly sensitive gold ripened silver bromide iodide emulsion according to Example 1 is divided into four parts and these parts E,F,G and H are poured after the addition of conventional additives so that a silver coating of of 1 g per m.sup.2 results. The film samples are consecutively exposed behind a gray wedge (factor 2) to red light and processed according to rule 1 in example 1.

Part E contains 0.15 mol 1-hydroxynaphthoic acid-(2)-[2-(n-octadecylmethyl-amino)-5-sulfo]-anilide (Compound 22) per mol silver and is marked Typ.

Part F contains 0.15 mol Compound 21 per mol silver and corresponds to the state of the art.

Part G contains according to the invention 0.15 mol Compound 15 per mol silver.

Part H contains according to the invention 0.15 mol Compound 16 per mol silver.

Results of the photographic examination may be found in Table 7:

Compared with DIR-coupler 21, which corresponds to the State of the art, the blue-green DIR-couplers 15 and 16 of the invention obtain considerably higher color yields.

The emulsion according to example 1 is used for this test, but it is now, in contrast to example 1, not red-sensitized, but is green-sensitized by the addition of 2.5.10.sup.-4 mol 3,3'-bis[.beta.-sulfato-ethyl]-5,5'-diphenyl-9-ethyl-benzoxotrimethine-cya nomethine betaine per mol silver.

The emulsion is divided in three parts, poured upon acetylcellulose, illuminated behind a gray wedge (factor 2) with white light (color temperature=3200.degree. K.) and processed according to rule 1 in example 1. The photographic yields are found in table 8

Part I contains 0.12 mol of the purple coupler 1-phenyl-3-stearoylamino-pyrazolone-(5) (Compound 23).

Park K contains 0.12 mol of purple-DIR-coupler 1-[.alpha.-(2,4-ditert.-amylphenoxy)-butyrylamido)-phenyl-3-pyrrolidino 4-(1-phenyltetrazole-5-yl)-thiopyrazolone-(5) (Compound 24) representing the state of the art.

Part L contains 0.12 mol of compound 17 per mol silver according to the invention.

The results are tabulated in table 8. Compared with DIR-coupler 24, the compound 17 of the invention leads to improved results.

The blue-green couplers 15, 16 and 21 are tested according to Example 5 in red-sensitized single layers. In contrast to Example 5 the DIR-couplers were tested together with the blue-green coupler 22.

Part E contains 0.15 mol of compound 22 (compare Example 5),

Part M contains a mixture of 0.15 mol of Compound 22 and 0.015 mole compound 21,

Part N contains a mixture of 0.15 mol of Compound 22 and 0.015 mol Compound 15, and

Part O contains a mixture of 0.15 mol of Compound 22 and 0.015 mol of Compound 16 per mol of silver.

The results of testing the materials E,M,N and O may be found in table 9:

An admixture of 10 mole % of the DIR-couplers 21, 15 and 16 results in an improvement of the .sup.D min values and in desired lowering of gradation. In contrast to the DIR-coupler which represents the state of the art, the addition of compounds 15 and 16 of the invention does not cause a disadvantageous reduction of maximal density.

The advantageous shape of the characteristic curve--an extended straightly linear part with great latitude of exposure--is well illustrated in FIG. 1 which contains the characteristic curves of materials E and O.

Furthermore, the graininess of materials M, N, and O is improved. For evaluation, the materials E, M, N and O were exposed to a density 1 and developed. A visual evaluation followed of 10.times. magnified copies. The scale of evaluation reached from 1 to 5. Lower values characterize better graininess (see table 9).

In order to test purple DIR-coupler 24 and the purple-DIR-coupler 17 of the invention as additives to purple coupler 23, the green-sensitized emulsion of Example 6 is divided in three parts as in Example 6, poured into single layers as in Example 6, exposed and worked up.

Part I contains 0.15 mol of Compound 23 (see Example 6).

Part P contains 0.15 mol of Compound 23 and 0.015 mol of DIR-coupler 24, and

Part Q contains 0.15 mole of Compound 23 and 0.015 mol of DIR-coupler 17 of the invention per mol silver.

Table 10 contain the results:

In comparison to purple DIR-coupler 24, the Compound 17 of the invention resulted in a better color yield. In comparison to sample I which contains only purple coupler 23, minimum density and graininess were improved and the desired reduction of gradation was obtained. The advantageous course of the characteristic curve with Compound 17 (curve Q) as compared with Compound 23 (curve I) may be found in FIG. 2.

In order to measure the intermediate layer effects of the blue-green DIR-couplers, a material was prepared showed the following layer sequence:

Material R:

1. a green-sensitized emulsion layer according to Example 6, containing 0.15 mol blue-green-coupler per mole silver, silver application=1 g/m.sup.2.

2. a micron gelatine interlayer.

3. a red-sensitized emulsion layer according to Example 1, containing 0.14 mol purple-coupler per mol silver and the same silver application as in layer 1.

Material S:

prepared as material R, except the first layer additionally contains 0.015 mol of the blue-green coupler 21.

Material T:

prepared as material R, except the first layer additionally contains 0.015 mole of the blue-green DIR-coupler 16 of the invention.

The intermediate layer effect (IIE) is calculated according to formula ##EQU2## (see Example 2). In order to be capable of measuring the gradation values of the third layer of Materials R, S, and T, the materials were at first exposed to red light and then to white light and developed each time according to rule 1 in Example 1. In the first case, only layer 3 was selectively exposed and in the second case, both layers were exposed. It is possible to read from the characteristic curves of the third layer the gradation values .gamma.s (red exposure) and .gamma.w (white exposure). Table 11 contains the results of the photographic tests.

The blue-green DIR-coupler 16 of the invention (see material T) causes a sufficiently large II-effect, which may be used to correct the vicinal color density of the blue-green dyestuff.

One thereby obtains the desired gradation values in the first and in the third layer and sensitometric data comparable to Typ(Material R). The blue-green DIR-coupler of the state of the art (Compound 21, Material S) obtains a larger II-effect, but in the first as well as in the third layer, this DIR-coupler causes too large a deficiency of maximum density, gradation and sensitivity. The results may be found in table 11.

The examples 5 to 9 serve to illustrate the DIR-effects of the DIR-couplers of the invention compared to known DIR-couplers. These examples are illustrative of the present invention and are not intended to limit its scope. All materials E to T were worked up according to rule 1 in example 1. Working according to rule 2 brings equally good results.