US2742832A - Controlling grain and contrast in color photography - Google Patents

Description

April 24, 1956 l. SALMINEN 2,742,832

CONTROLLING GRAIN AND CONTRAST IN COLOR PHOTOGRAPHY Filed Feb. 17, 1955 DE/VS/TY RELATIVE L06 EXPOSURE /L MARI SALM/NE/V IN V EN TOR.

ATTOR/VE 8 AGENT United States Patent-IO CONTROLLING GRAIN AND CONTRAST IN COLOR PHOTOGRAPHY Ilmari Salminen, Rochesteig N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application February 17, 1955, Serial N 0. 488,957

18 Claims. (Cl. 95-6) halide developing agent in the presence of coupler com- 7 pounds which react with the oxidized developing agent to form dyes. In such a process of dye'image formation, commonly called color development, the dyes which are formed generally have relatively high covering power. Thus in a color developed image, consisting of a dye image and a silver image, the dye image exhibits a much higher density to light in the wavelength region corresponding to its absorption hand than does its accompanying silver image. For this reason a conventional emulsion layer, which on normal black-and-white processing yields a normal contrast silver image, produces a dye image on color development which has such excessive contrast that it is not usable in a color photographic process. 1

In order to overcome this intensification effect of color development, it is usually necessary to use, in color'photographic materials,much less silver halide in the emulsion layers than the amounts normally used in conventional black-and-white sensitive'materials. Serious and undesirable consequences of such a reduction in silver halide content of the emulsion layers are that the emulsion speed is reduced, the color-developed dye images have a coarsegrained structure, and a loss in image sharpness and definition occurs.

It would appear that this difficulty might be circumvented by using silver halide emulsions which are inherently finer grained so that the emulsion layers would have the same total silver halide content distributed among a larger number of grains. Unfortunately, this simple solution cannot be realized in those cases where emulsion speed is of importance, because the speed of a silver halide emulsion is, in generaL'directly related to the grainsize. Accordingly, for those color photographic materials where high emulsion speed is a necessary property, the relatively coarserrgrained silver halide emulsions must be employed and alternative solutions to the problems of g'raininess, and sharpness anddefinitionof the dye images must be sought. I

I have 'now discovered that a solution to this problem is attained when the silver halide emulsion layers containing relatively large amounts of silver halide or color developed in the presence of an agent which is capable of reacting with the oxidized developing agent, with the result that a portion of the total oxidized developer formed during development is rendered unavailable fordye image diflusible into the silver halide emulsion layers.

Patented Apr. 251, 6

'2 formation. In effect, the added agent competes with the coupler for the oxidized developer and thereby permits the formation during color development of an amount of oxidized developer in excess of that required to produce dye images of normal contrast. 7 This, in turn, permits the use of larger amounts of silver halide in the emulsion layers, and. as the end result one obtains dye images of the desired normal contrast which do not have the exaggerated graininess and low sharpness and definition which characterizethe images produced by conven tional color development procedures.

One object of my invention, therefore, is to'provide a process for obtaining dye images with improved graininess and sharpness characteristics. A further object is to provide a method for obtaining dye images of normal contrast by color development of silver halide emulsion layers which contain amounts of silver halide in excess of that required for the production of dye images by conventional color development procedures. Another object of the invention resides in repressing theinterimage effects which result from the wandering of oxidized developer, for example, from one layer to another in multilayer color film.

That is, the competing coupler reacts with such wandering oxidized developing agent is prevented from forming an insoluble dye image in the wrong region of the film. Other objects will become apparent from the following more detailed description .of my invention.

The objects of my invention are preferably accomplished by using, for the formation of colored photographic images, silver halide emulsion layers containing amounts of silver halide in excess of those required'to produce images of normal contrast when conventional color development is carried out, and conductingthe color development of such emulsion layer in the presence of a compound, referred to hereinafter as a competing coupler, which competes with'another coupler present for the oxidized developer. The competing couplers appear to react with the oxidized developing agent to produce a Color development processes utilizing color ,development as the means of dye image formation are conven- 'iently divided into two classifications, which difier in the method of introducing the couplers into the system. The first type of such processes makes use of couplers which are soluble in the color developer solution and which are Here the dye-forming reactions occur between two components of the color developer solution to producea dye which is nondiffusible. 'In the second type of'color processes, non-ditfusing image-forming couplers are incorporated in the silver halide emulsion layers and the coupling reactions occur between these incorporated couplers and the primary aromatic amino developing agent supplied from the color developer solution as shown in Mannes et al. U. S. Patent 2,304,940 and Jelley and Vittum U. S. Patent 2,322,027. My invention is applicable to both types of color processes. In the first type of process which employs soluble diifusible couplers, the color developer solution contains ,the color developing agent,,the dye-image-forming coupler, and'the competing coupler. With the color process employing incorporated nondififusing image-forming couplers, the developer solution contains the color developing agent and the competing cou- 3 pler, or alternatively, the competing coupler can also be incorporated in the silver Halide emulsion layers.

As used herein, by competing coupler is meant one which can be incorporated in the developer or emulsion layer and which forms a soluble dye which quickly diffuses out of the emulsion layer, and by image-forming coupler is meant one which can be incorporated in the developer or emulsion layer, but forms a comparatively permanent, non-ditfusing dye.

The accompanying drawings show by means of graphical representation the effect upon contrast ct utilizing one of the competing couplers in the color development of a multilayer color film containing non-difiusing imageforming coupler compounds in the emulsion layers.

Weller and Groet U. S. Patent No. 2,689,793, granted September 21, 1954 discloses the use of certain compounds as competing couplers. However, the competing couplers of my invention are generally more useful than the sulfonated naphthol and pyrazolone couplers illustrating the Weller et al. invention, partly because those sulfonated compounds are somewhat more reactive as competing couplers than is desired and only a small concentration of those couplers is used in the developer solution to give the desired reduction in dye contrast. Because of this low concentration, the developing solution in the emulsion becomes locally exhausted with respect to the sulfonated coupler compound in areas of considerable development. This may cause, for example, in the red sensitive emulsion of a color film, a much greater contrast reduction in areas of red exposure as compared with areas where the red-sensitive emulsion has received the same exposure in the form of an exposure to white light. This situation leads to undesirable interimage effects in multi-layer films. On the other hand, because the competing coupler compounds of the present inventibn have a lower reactivity than the mentioned sulfonated coupler compounds, they can be used in higher concentrations in the developer solution and consequently the local exhaustion efiects are minimized. However, the reactivity of the competing coupler compounds of my invention is sutficiently high that excessively large concentrations are not required to give the desired degree of contrast reduction. Color development has previously been carried out in the presence of a mixture of couplers in emulsion layers as disclosed in Schneider et al. U. S. Patent 2,186,736, granted January 9, 1950, to obtain a colored image and in Vittum and Arnold U. S. Patent 2,428,054, granted September 30, 1947. However, these patents contemplate the use only of mixtures of image-forming couplers and do not contemplate the use of mixtures of image-forming couplers and competing couplers as in the present invention. Similarly, my invention is separate and distinct from any known use of a mixture of couplers in color developing solutions that form images of nonditfusing dyes.

The competing couplers which areemployed in my invention in conjunction with image-forming couplers are 3,5-dihydroxybenzoic acid, 2,6-dihydroxyisonicotinic acid, and derivatives of these compounds having the general formula:

Rio- (5-012,

wherein R represents a member of the class consisting "of hydroxyl, alkoxyl groups, e. g. methoxyl, ethoxyl,

sisting of a hydrogen atom and an acyl group of an organicacid, e. g. acetyland lauroyl, Xand Y represent the carbon atoms necessary to complete a 6-membered ring, and Z represents a member of the class consisting of a nitrogen atom and the group CH=.

The competing couplers having this formula have a nuclear position capable of coupling with the oxidation product of a primary aromatic amino silver halide developing agent produced in color development processes.

Representative compounds useful in my invention as competing couplers and having the above general formula are the following 1. 2,6-dihydroxyisonicotinic acid C O OH HO OH 2. 3,5-dihydroxybcnzoic acid (|JOOH Example I The use 'of 2,6-dihydroxyisonicotinic acid as a compet- .ing coupler in the processing by the reversal process of a multilayer color film is now given in particular reference to the "accompanying drawing.

A multilayer color film is provided having coated on a film base a red-sensitized silver halide emulsion layer having dispersed therein the cyan-forming coupler compound, 2-(diamylphenoxyacetamido) 4,6 dichloro 5- methylphenol. Over this emulsion layer is coated a thin gelatin layer, and then a green-sensitized emulsion layer containing a dispersion of the magenta-forming coupler compound, 1-(2',4',6'trichloropheny1)-3-[3"(2,4"'-diamylphenoxyacetamido)benzanfidol-S-pyrazolone. Next 'is coated a yellow filter layer containing colloidal silver as the "colorant, and over this is coated a blue-sensitive silver halide emulsion layer containing the yellow-forming coupler compound, N-(4-benzoylacetaminobenzenc- 'sulfonyl) #N- ('y-phenyl-propyl) -p-toluidine. All of the coupler compounds in this multilayer coating are dispersed by the method of the Ielley and Vittum patent named above. Each of the emulsion layers contains from l50- 200mg. of silver (as silver halide), an amount considerably higher than would be used in a reversal film designed for normal processing. 'lf'wo strips of the multilayer coating were given an equal exposure behind a step-tablet silver scale and then simultaneously put through the following processing steps (allbathsat75F.):' 1

Reversal exposure:

sec. at 1 foot from a No. 2 flood lamp Wash 3 Each of the strips was then placed in a color developer solution containing N-ethyl-N-(,S-methanesulfonttmidO- ethyl)-3-methyl-4-aminoaniline sulfate as the color developing agent, one of the .color developer solutions cout-aining no competing coupler and the other containing 5 grams per liter, of 2,6-dihydroxyi sonicotinic acid as the competing coupler. The time ofcolor development was 12-minutes for both strips. Following the color development, the two stripswere put'through the remainder of the processing cycle together, as follows:

. Min. Wash 5 Clearing and fixing bath- 5 Rinse 1 Ferricyanide bleach bath 8 Rinse 1 Fixing bath 3 Wash 3 Dry The densities of the resulting neutral step-tablet images were then read through red, green, and blue filters to obtain the sensitometric curves of the cyan, magenta, and yellow dye images shown in the drawing.

In the accompanying drawing, curves (3, M and Y show the contrast of the cyan, magenta and yellow dye images developed as described in the absence of the competing coupler compound, and in general such contrasts are higher than desired. Curves Ca, Ma and Ya show the lower contrasts of the cyan, magenta and yellow dye images obtained through development in the presence of the competing coupler compound. Itis apparent therefrom that the employment of the competing coupler compound in the development of the emulsion layers rich in silver halide has lowered the contrast of the dye images to the desired contrast of the process.

Aswill be apparent, the competing couplers of the invention may also be incorporated into one or more of Exa mple II The use of a competing coupler compound in a mixed grain or packet emulsion system of color photography is illustrated as follows:

A single-layer, two-color mixed packet coating capable of development to produce cyan and magenta images, was prepared on film base, using the method described in U. S. Patent 2,698,794, granted January 4, 1955.

Two strips of the coating were given equal exposure through a step tablet and then simultaneously put through the following processing steps (all baths at 70 B):

Each of the strips was placed in a color developer solution containing 2-methyl-4-diethylamino aniline as the color developing agent, one of the color developer solutions containing no competing coupler and the other containing 10grams per liter of 2,6-dihydroxyisonicotinic acid as the competing coupler. The time of color developmentwas 10' minutes for both strips.- Following the color development, the two strips were put through the remainder of the processing cycle together, as follows:

. Min.

Wash 1 Acid stop bath 10 Wash 20 Ferricyanide bleach bath 10 Wash 5 Fixing bath 10 Wash 20 Visual or'microscopic examination of the two processed strips showed much less color contamination in the strip 7 which had been color developed in the presence of the competing coupler.

Thus, as in the case of the multilayer color films, when the competing coupler compound is employed in the matrix of a mixed packet emulsion, or in the particle containing silver halide and image-forming coupler compound, it tends to prevent wandering of oxidized developing agent through the matrix from packet to packet and thus diminishes interimage effects. V p

The more soluble competing coupler compounds of the invention such as compoundsNos. 1 to 4, 9, 10, 13 to 15 and 19 are preferably incorporated intoemulsions such as illustrated in Examples Land I]. above as their alkali metal salts. All of the coupler compounds may however be dispersed in such emulsion layers by means of oily coupler solvents by means ot the methods of the above patents. The esterified competing couplers illustrated above when used in emulsions can be expected to hydrolyze during the development process. to yield eventually the soluble dyes capable of being Washed out- 'i A comparison of the activity. of representatives competing couplers of the invention was carried out in the following manner. A fast bromo-iodide film was provided by the methods of the above patents having dis-- persed in the emulsion layer the cyan forming coupler compound Z-(diamylphenoxyacetamido)-4,6 dichloro-S- methyl phenol. A sample of the film was exposed under an image having graduated density and developed in a conventional color developer free of coupler compounds such as shown in the-above patents, followed by removal of the silver image and fixation. The density values of the silver image obtained as well as the density values of the dye image were noted.

Other samples of the single layer color film above containing the coupler compound in the emulsion layer were processed in the same manner except the developing solution contained the selected competing coupler. The silver density and the dye density values, of the developed samples of film were then noted. In the following table are tabulatedthe increase in silver density and decrease in dye density efiected by use of the various competing couplers in the developing solution:

Silver Deu- Dye Den- I Competing Coupler No. sity Inslty Decrease crease in reacting with excess oxidized color developer and thus.

7 diminishing its retarding effects upon silver halide-development.

The above tabulated values of decrease indye density are obtained by subtraction of the dye densities obtained by development of each sample of coupler-containing emulsion in the presence of the respective competing couplers, from the dye'density values of the check sample. Accordingly, these dye density decrease values reflect the competition between the competing coupler and the'imageforming coupler compound in the emulsion, for the oxidized developing agent produced in the development process, and further illustrate the etfectiven ess of the diffusing competing couplers of the invention in lowering contrast of dye images obtained from the image-forming coupler compound. Similar results are obtained when the couplers of the invention are employed in color developing compositions also containing image-forming couplers or when employed in emulsion layers also containing imageforming coupler compounds, as well as when the emulsions contain the competing coupler compounds of the invention and the image-forming coupler compounds are present in the color developing solution.

The following compounds are representative of related coupler compounds which show little activity as competing couplers:

2,4-dihydroxybenzoic acid 2,3-dihydroxybenzoic acid 4-(o-carboxybenzoyl)-resorcinol Salicylic acid m-Hydroxybenzoic acid 4-n-propyl-2,6-pyridinediol Z-carboxy-S-ethoxy phenol 2-amino-6-hydroxy pyridine sulfate S-acetamido-Z-carboxy phenol The more soluble diffusing couplers of the invention such as couplers Nos. 1 to 4, 9, 10, 13 to 15 and 19 can be used in color developing solutions in a manner similar to the above examples, the esterified coupler compounds, of course, hydrolyzing to some extent in the alkaline color developing solution. The quantity of competing coupler in the developing solutions, as in the case when the competing couplers are in the emulsion layers, depends in part upon the desired reduction in dye contrast and the coupling activity of the image-forming coupler employed in the process.

My process is primarily designed for, although not limited to use in systems of color photography employing superposed emulsion layers sensitized to the primary regions of the visible spectrum and containing in the respective emulsion layers nonditfusing image-forming coupler compounds yielding differently colored dye images. When my invention is employed as described with these superimposed emulsion layers and development is carried out in a color-forming developer composition containing a competing coupler yielding a diffusible dye, the contrast and grain characteristics of the dye images in all emulsion layers are improved substantially. The contrast reduction is illustrated in the drawings. Such films may be utilized in the well-known negative-positive and reversal color development processes in the manner described in the above examples.

The silver halide concentration per unit areas of the emulsion layers employed in my invention is that necessary to reduce the contrast and grain to the desired value and can be varied within rather wide limits depending upon the result desired and the particular process which is under consideration. Substantial improvements in grain characteristics are obtained by using at least about 50 milligrams per square foot of emulsion and preferably about 2 to 25 times the usual silver halide concentration of incorporated coupler'proccsses, or from about 50 to 750 milligrams of' silver halide (calculated as silver) per square foot of emulsion. As'is apparent, if the emulsions '8 contain substantially more than about 50 milligrams of silver per square foot, normal color development in absence of diffusible coupler compounds yields greater con trast than usually desired in color processes.

The quantity of competing diffusible coupler which is used in the color developing compositions is dependent upon a number of factors. One of these is the relative coupling activity of the image-forming couplers compared to that of the competing couplers. In a given color system a suitable type and quantity of competing coupler can be readily ascertained. Another factor is the contrast desired in the particular color process under consideration. That is, in a color printing process a contrast of 2.5 may be desired, whereas in a negative color process, a contrast of only about 0.7 may be desired. More competing diffusible coupler can be employed in conjunction with the latter process to effect a greater reduction in contrast. We naturally use sufiicient competing couplers in the developer composition that after color development of the emulsion layers containing coupler compound followed by Washing out the diifusible dye image, there are obtained nonditfusible dye images having the contrast of the process under consideration, such as contrasts of the order of about 0.5 to 2.5.

In connection with multilayer color films for which our process is particularly adapted, these color films may contain in the respective emulsion layers nondiffusible imageforming couplers of different coupler activity. Therefore, the relative increase in the silver halide concentration required in the emulsion layers may differ depending upon the coupling characteristics of the couplers in each emulsion layer.

It will be apparent that my invention can be used in conjunction with many types of emulsion layers regardless of silver halide concentration to atfect contrast and grain favorably. While the faster and coarser grained emulsions of the concentration indicated are particularly adapted to use in our process, for some purposes the finer-grained emulsions can be used but the alteration in contrast and grain of the dye images contained therefrom is less pronounced.

The invention is particularly applicable to use in conjunction with multilayer color films containing colored color-forming coupler compounds such as disclosed in U. S. Patents 2,428,054 and 2,499,966. Likewise mixed grain photographic elements such as described in U. S. Patents 2,490,749 and 2,490,751 are adapted to use in my process for the mentioned purposes of utilizing couplercontaining mixed-grain emulsions having silver halide concentrations of the order indicated and developing such emulsions with color developer compositions containing competing coupler compounds such as illustrated.

As indicated, the soluble competing couplers forming diffusible dyes, such as mentioned, can be used in color developing compositions also containing soluble coupler compounds forming substantially nondifiusible dyes. The nondifiusible dyes then remain in the photographic layer forming the color photographic image whereas the diffusible dye images formed along with them in color development leach out of the photographic layers in washing. Such developer compositions are particularly useful for the development of dye images in emulsion layers devoid of coupler compounds; however, the etlect obtained may be somewhat difierent from the case when the competing coupler is in the developer and the image-forming coupler is in the emulsion.

A useful application of the process of my invention is in the production of monochrome fine-grain dye images in processes normally employing only black-and-white materials and processing. For example, in processes in which a'fine-grain silver image is usually employed it was found that my process could be used to obtain the requisite fine-grain image with a substantial increase in the efiective emulsion speed, or alternately a reduction in graininess without loss of effective emulsion speed. The process was carried out substantially as set forthin the above examples employing the image-forming coupler or mixture of different image-forming couplers in the emulsion and the competing coupler in the color-developing solution, the silver image being removed from the emulsion'following development leaving a fine-grained dye image. Alternately, both the image-forming coupler and the competing coupler can be used in the developer which permits the use of conventional black-and-white' sensitive materials.

What I claim is: i

l. A process for preparing colored photographic images which comprises developing an exposed silver halide emulsion layer with a color developing solution containing a primary aromatic amino silver halide developing agent, said development being carried out in the presence of both an image-forming coupler compound, and a competing coupler compound having the general formula:

wherein R represents a member of the class consisting of 2. A process for preparing colored photographic images which comprises exposing to a subject a light-sensitive silver halide emulsion layer containing an image-forming coupler compound, developing the exposed emulsion layer with a color-developing solution containing a primary aromatic amino silver halide developing agent, said development being carried out in the presence of a competing coupler compound having the general formula:

wherein R represents a member of the class consisting of hydroxyl, alkoxyl and amido groups, R1 and R2 each represent a member of the class consisting of a hydrogen atom and an acyl group, X and Y represent the carbon atoms necessary to complete a 6-membered ring, and Z represents a member of the class consisting of a nitrogen atom and the group CH=, to obtain in the exposed region of the developed emulsion layer both a ditfusible dye from the competing coupler compound and a nonditfusible dye image from the image-forming coupler compound, and washing the ditfusible dye from the emulsion layer.

3. The process of claim 1 wherein both the imageforming coupler compound and the designated competing coupler compound are present in the emulsion layer prior to the development step.

4. The process of claim 2 wherein the image-forming coupler compound is present in the emulsion layer prior ,to the development step and the designated competing coupler compound is present in the color developing solution. a 5. The process of claim 2 wherein both .the imageforming coupler compound andthe designated competing coupler compound are present; in the color developing solution.

6. The process of claim 2 wherein the competing coupler compoundv designated is present'inl the emulsion layer prior to the development step and the emulsion layer is a mixed grain emulsion layer. r 7. A process for preparing colored photographic images which comprises exposing to a subject a light-sensitive silver halide emulsion layer containing an image-forming coupler compound, developing the exposed emulsion layer with a color developing solution containing a primary aromatic amino silver halide developing agent, said development being carried out in the presence of 2,6-dihydroxyisonicotinic acid, to obtain in the exposed region of the developed emulsion layer both a difiusible dye from 2,6-dihydroxyisonicotinic acid and a nondifiusible dye image, from the image-forming coupler compound, and washing the difiusibledye from the emulsion layer.

' 8. A process for preparing colored photographic images which comprises exposing to a subject a light-sensitive silver halide emulsion layer containing an image-forming coupler compound, developing the exposed emulsion layer with a color' developing solution containing a primary aromatic amino silver halide developing agent, said development being carried out in the presence of 3,5-dihydroxybenzoic acid, to obtain in the exposed region. of the developed emulsion layer both a diffusible dye from 3,5-dihydroxybenzoic acid and a nonditfusible dye image from the image-forming coupler compound, and washing the diffusible dye from the emulsion layer.

9. The process of claim 7 wherein the 2,6-dihydroxyisonicotinic acid is present in the emulsion layer prior to the development step.

10. The process of claim 7 wherein the 2,6-dihydroxywherein R represents a member of the class consisting of hydroxyl, alkoxyl and amido groups, R1 and R2 each represent a member of the class consisting of a hydrogen atom and an acyl group, X and Y represent the carbon atoms necessary to complete a 6-membered ring, and Z represents a member of the class consisting of a nitrogen atom and the group CH=.

14. A light-sensitive photographic emulsion comprising silver halide, an image-forming coupler compound and a competing coupler compound having the general formula:

wherein R represents amember of'th'e class consisting of hydroxyl, alkoxyl and amido groups, R1 and R2 each represent a member-of the class consisting of a hydrogen atom and an acyl group, X and Y represent the carbon atoms necessary to complete a 6-membered ring, and Z represents a member of the class consisting of a nitrogen atom and the group -CH=.

15. A light-sensitive photographic emulsion comprising silver halide, an image-forming coupler compound and 2,6-dihydroxyisonicotinic acid.

16. A light-sensitivephotographic emulsion comprising silver-halide, an image-forming coupler compound and 3,5-dihydroxybenzoic acid. Y

17. A photographic color developing solution comprising an alkaline material, a primary aromatic amino silver halide developing agent, and 2,6-dihydroxyisonicotinic-acid.

18. A photographic color developing solution comprising an alkalinematerial, a primary aromatic amino silver halide developing agent, and 3,5-clihydroxybcnzoic acid.

No references cited.

Claims (1)

1. A PROCESS FOR PREPARING COLORED PHOTOGRAPHIC IMAGES WHICH COMPRISES DEVELOPING AN EXPOSED SILVER HALIDE EMULSION LAYER WITH A COLOR DEVELOPING SOLUTION CONTAINING A PRIMARY AROMATIC AMINO SILVER HALIDE DEVELOPING AGENT, SAID DEVELOPMENT BEING CARRIED OUT IN THE PRESENCE OF BOTH IMAGE-FORMING COUPLER COMPOUND, AND A COMPETING COUPLER COMPOUND HAVING THE GENERAL FORMULA:

Images