US 2322027 A
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June 15, 1943. E. E. JELLEY EI'AL 2,322,027
COLOR PHOTOGRAPHY Filed Dec. 26, 1940 MATER/AL LOW-BOILING /6./
SOLVENT COUPLER LON-BOILING 50L VENT /0 2 H 2: -2 S/L VER HAL IDE I 3 Y EMULSION U L, l 5 'r fi i A;
COLLO/D M/LL STEAMBATH.
F/LM aAsE 23 BLUE SENSITIVE SILVER HAL/DE. 26 YELL ow COUPLER CRYSTALLO/DAL Z2 seas/v SENSITIVE SILVER HAL/DE 25 MAGENTA COUPLER+CRY$T4LLOIDAL V MATERIAL. 2/ RED SENSITIVE SILVER HAL/DE.
\ VAN COUPL ER? CRYSTAL LO/DAL MATERIAL.
f/JMNEJELLEY PAUL M V/Tn/M INVENTORS A TTORNE Y Patented June 15, 1943 COLOR PHOTOGRAPHY Edwin E. Jelley and Paul W. Vlttum, Rochester, N. Y., assignors to Eastman Kodak Company,
Rochester, N. Y., a corporation of New Jersey Application December 26, 1940, Serial No. 371,612 In Great Britain February 24, 1940 13 Claims.
This invention relates to color photography and particularly to a method for incorporating couplers'in silver halide emulsion layers.
The incorporation in silver halide emulsion layers of compounds which are capable of combining with the oxidation product of developin agents to produce dye images has been proposed many times. In 1913 Rudolf Fischer suggested a p ocess of three-color photography which involved the incorporation of couplers or color forming compounds in three differentially colorsensitized emulsion layers, each coupler capable of producing a color complementary to the sensitivity of the layer in which it was incorporated (Fischer U. S. Patent 1,055,155, March 4, 1913). The couplers suggested were compounds containing phenolic hydroxyl or acid methylene groups which were capable of reacting with the development product of aromatic amino developing agents on photographic development to form dyes of the indophenol, indoaniline and azomethine classes. While the Fischer process was theoretically feasible, it did not achieve successful results because, among other reasons, of the tendency of the couplers to wander from the emulsions in which they were incorporated either during coating or during processing. More recent patents have proposed the reaction of coupler molecules with high molecular or colloidal bodies so that the coupling properties of the coupler are not destroyed but the coupler is rendered nondiflusing in gelatin or other colloidal media, These proposals involve additional steps in the preparation of the emulsion and it is sometimes difficult to secure a product which has the desired coupling properties and which may be incorporated in the emulsion in a satisfactory manner.
A still different method of incorporating couplers in emulsion layers has been proposed in Martinez U. S. Patent 2,269,158, granted January 6, 1942, and in Mannes & Godowsky U. S. applications Serial Nos. 314,688 and 314,689, filed January 19, 1940. According to the methods of these applications, the coupler is mixed with a waterinsoluble colloid such as a natural or synthetic resin or a cellulose ester and the mixture of the coupler and the Water-insoluble colloid is dispersed in a gelatin emulsion. One of the advantages of these methods is that it is frequently unnecessary to increase the molecular weight of the coupler appreciably in order to prevent diffusion of the coupler in the emulsion. The existence of an interface between the materials in which the coupler is incorporated, that is, the water-insoluble cellulose esters or resins, and the gelatin of the emulsion, prevents wandering of the coupler. A further advantage of this method is that the couplers may be incorporated in their neutral form, that is, it is not necessary to form the sodium salt of the coupler as in the case of previous methods. The colloidal materials with which the couplers are mixed in these processes are usually solids at room temperature and, in order to incorporate the mixture in an emulsion, it is necessary to dissolve it in a volatile solvent for both the coupler and the colloidal material and to incorporate the solution in the emulsion after which the volatile solvent is removed, either in a separate step or in the natural process of drying the coated emulsion layer.
In processes of the latter type, difiiculties arise in some cases due to the solid nature of the final particles in which the couplers are incorporated. One of these difficulties is due to the limited solvent action which the solld colloid material has for the coupler and the dye derived from it, which increases the tendency for the coupler or dye, or both, to separate as a crystalline deposit on aging of the finished emulsion coatings. Furthermore, it is in some cases difllcult to find a colloid material having the necessary solvent action for the coupler which is also sufficiently permeable to the processing solutions.
It is, therefore, an object of the present invention to provide a novel method for incorporating couplers in gelatin emulsions. A further object is to provide a method of improving the transmission characteristics of the image dyes produced by coupling. A still further object is to provide a method for rendering the particles containing the couplers more readily permeable by the photographic processing baths. Other objects will appear from the following description of our invention.
These objects are accomplished by forming a liquid solutionof the coupler and a high-boiling water-insoluble crystalloidal material and emulsilying or dispersing the mixture in a photographic emulsion.
In the accompanying drawing, Fig. 1 is a diagrammatic illustration of the steps in our process and Fig. 2 is an enlarged sectional view of a film made according to our invention.
According to the present invention, there is provided a sensitive photographic silver halide emulsion having a water-soluble binder such as material bein so chosen that the particles are liquid under the conditions of coating and processing the emulsion. We have found that couplers which are solids under ordinary conditions can be converted into liquids of oil consistency by the addition of certain high-boiling organic compounds which are insoluble or only very slightly soluble in water and in the liquid photographic emulsion. There is little or no tendency for crystallization to occur even when the coupler is present in a proportion amounting to 50% or more of the high-boiling crystalloidal material.
The invention, therefore, includes a sensitive photographic silver halide emulsion having a water-soluble binder such as gelatin in which are dispersed particles of oil-like consistency composed of coupler and a high-boiling waterinsoluble crystalloidal organic compound. In carrying out the invention, the coupler which has been mixed with the high-boiling organic compound to produce an oil-like mixture may be dispersed in water or gelatin solution or in any aqueous binder of colloidal character which is miscible with the silver halide emulsion. The dispersion may be afiected with the aid of homogenizer, colloid mill or the like and the dispersions may be stabilized by the addition of emulsifying agents such as those of the well known higher fatty alcohol sulfate type. The
dispersion may also be formed by dispersing a v solution of coupler, and crystalloidal material, in a solvent of low boiling point such as butyl acetate, with water or gelatin solution and subsequently removing the low boiling solvent by evaporation. Here also an emulsifying agent may be used.
In our process it is important that the mixture of coupler and crystalloidal material be a liquid at ordinary temperatures. This forms liquid particles when the mixture of coupler and crystalloidal material is emulsified in water and mixed with a gelatin emulsion, these particles retaining the coupler in solution, yet being readily penetrated by the photographic developing solution and other processing baths.
In ,our process we prefer to use the customary gelatino-silver halide emulsions although other water-soluble colloidal materials can be used for the photographic emulsion such as agar or watersoluble synthetic resins. The emulsions may be used in single layer or in multi-layer coatings and our invention is especially designed for the production of multi-layer coatings for natural color photography.
We have referred to the high-boiling crystalloidal materials with which the couplers are mixed. Since this constitutes a distinguishing feature of our invention, this material will now be fully described.
The high-boiling crystalloidal materials which .we contemplate using have been referred to as oil formers" because they have the property of producing an oily or liquid solution when mixed with the coupler even though the coupler is a solid. The compounds are generally liquid at ordinary temperatures or low melting solids (below 100 0.). that in general the most useful compounds contain one or more polar groups such as halogen, hydroxyl, carboxylic acid, amide, ketone, etc.. although this is not a limiting factor. They should have a high solvent action for the coupler and for the dye produced by coupling and should, of course be inert toward the silver halide emulsion in which they are incorporated. Th y It has been found also' should also be substantially colorless and stable toward light, heat and moisture, in addition to being inert to the various processing baths which may be encountered such as developers, oxidized developers, silver removal baths and fixing baths. They should be of low volatility and in general we have found that compounds suitable for this purpose have boiling points above or C. at atmospheric pressure. They should be permeable to photographic processing solutions since this affects the ease of dye formation and the removal of excess developer, the latter in turn affecting the formation of stain. They should have a sufiiciently low refractive index so that the solutions of couplers in them have approximately the same refractive index as gelatin. thereby minimizing the opacity or light scattering of the coating. Most couplers themselves have high refractive indices and for this reason it is desirable that the oil formers have low refractive indices. They should be easily dispersible in emulsions and should be chemically inert toward the couplers and dyes formed from them.
It is sometimes advantageous to employ a mixture of two or more individual crystalloidal materials or oil formers in the same dispersion in order to obtain the desired combination of properties. Thus one might use a mixture of one compound having exceptionally good solvent action, with another compound added in the correct proportions to give the final dispersion the desired refractive index.
It might be of advantage also to use oil formers which could be removed from the coated emulsion layer or layers at any desired stage of the process. This could be accomplished, for example. with some of the acidic oil formers which would be removed from the coating in an alkaline bath. An oil former might also be chosen which was incapable of difi'using through gelatin but which could be changed chemically before, during or after the processing steps into a substance or substances which would be removable.
The following high boiling crystalloidal materials or oil formers have been found suitable for use in our invention, this list being illustrative only.
Acids p-Sec. amylbenzoic acid fi-Phenylpropionic acid Dibenzyl acetic acid Phenyl ethyl acetic acid Mono-n-amylphthalate (acid ester) Undecylenic acid Benzyl hydrogen succinate (acid ester) Alcohols n-Hexylphenylcarbinol p-(p-Tert. butyl phenoxy) -ethyl alcohol Amides Acetyl n-butyl aniline Acetyl methyl p-toluidine Benzoyl piperidine Amide derivatives Carbamates Ethyl N,N-di-n-butyl carbamate Ethyl N-phenyl carbamate Esters Ketone derivatives Benzophenone 2,4-dichlorobenzophenone a-Methoxy acetophenone Acetophenone 2,4-dihydroxy valerophenone p-Sec.-amylbenzophenone Phenol ethers Veratrole (1,2-dimethoxybenzene) Eugenol methyl ether Hydroquinone dimethyl ether Phosphate esters Triphenyl phosphate Tricresyl phosphate Diphenyl mono-p-tert. butyl phenyl phosphate Monophenyl di-p-tert. butyl phenyl phosphate Diphenyl mono-o-chlorophenyl phosphate Monophenyl di-o-chlorophenyl phosphate Tri-p-tert. butyl phenyl phosphate Tri-o-phenylphenyl phosphate Di-p-tert. butyl phenyl mono (-tert. butyl-2- phenylphenyl) phosphate Sulfonamides p-Toluenesulfonyl methyl o-toluidine p-Toluenesulfonyl dimethylamide Sulfonamides derivatives p,p'-Di-n-amylbenzenesulfonanilide p-Toluenesulfonyl di-n-butyl amide Sulfones n-Butyl sulfone Iso-amyl sulfone Ureas N ,N'-diethyl-N,N'-diphenyl urea N,N-di-n-butyl urea In addition to these compounds there are other compounds suitable with respect to physical properties but unsuitable for other reasons. In some cases these compounds can be used in admixture with other compounds. For example, it has been found that nitrobenzene, o-nitrotoluene, 2-nitro-p-eymene and o-nitro-diphenyletherwhich are good oil formers,'unfortunately have a desensitizing action but by mixing the nitro compound with another material, for example, by mixing o-nitrodiphenylether with trio-eresylphosphate in amounts up to 25% there is no serious desensitization of the emulsion. Similarly, crystallization of an otherwise suitable combination of oil formers and couplers may often be prevented by using a mixture of closely related but non-isomorphous couplers.
We have referred to dissolving the coupler and the high boiling solvent in low boiling solvent and dispersing the mixture in an aqueous solution after which the lower boiling solvent is removed. Although this is not necessary in our process, in many cases it is desirable to proceed in this Way using a solvent which can be removed before coating the emulsion. Low boiling solvents suitable for our purposes include nitromethane, nitroethane, methyl, ethyl, propyl and butyl acetates and ethyl and butyl formate.
In dispersing the mixture of coupler and high boiling solvent in the aqueous solvent, it is desirable to use an emulsifying agent such as Gardinol a higher fatty alcohol sulfate) or Arctic Syntex T (U. S. Patent 1,932,180). Gelatin may also be used as an emulsifying agent or the mixture of coupler and high boiling solvent may be dispersed directly in the photographic emulsions. The coupler suitable for incorporation in emulsions according to our invention will be understood to be the customary type containing phenolic hydroxyl or reactive methylene groups. The following may be used.
Couplers producing cyan images rmmylphenoxyhon'wnenulfnnnmlno) -l maphthol -(N-benzyl-N-nnphihalem-sulfonamino) -1-naphlhol -(n-benzyl-N-n-vulorylamino) -i mlphthol ma nroylnm nwl nn ph thol -ctlilolro-5-(N-n-valeryl-Nplsopropylbenzylaminn) l-nnnh Couplers producing magenta images nmylsullani- Couplers producing yellow images In order more clearly to explain our invention, reference will now be had to the accompanying drawing. As shown in Fig. 1, which is a diagrammatic illustration of our process, a mixing vessel I is used to produce an intimate mixture of the coupler and the high boiling crystalloidal material added to it. A suitable stirring device 2 may be attached to the tank and a low boiling solvent may be added through the pipe 3. After admixture of these materials in the tank I, water containing an emulsifying agent may be added through the pipe 4 and the mixing continued. The mixture is then passed through pipe 5 to the colloid mill or homogenizer 6 in which a dispersion of the coupler; high boiling crystalloidal material and low boiling solvent in water is produced. After homogenization, the dispersion is passed through pipe 1 to steam bath 8 which is heated by suitable means not shown and where the low boiling solvent is removed. Some of the water may also be removed at this stage leaving a dispersion of the coupler and high boiling material in an aqueous solution. This dispersion is passed through pipe 9 into container 80 where a gelatino silver halide emulsion is added through pipe II. The dispersion of coupler and high boiling material in water is mixed with the silver halide emulsion by means of any suitable device such as the stirrer l2 and the resulting emulsion is passed through pipe l3 to the coating hopper M where it is coated as a layer IS on the film base 16 passing beneath the coating outlet of the hopper l4.
Successive emulsion layers may be coated on the support in a similar manner after the first coated emulsion layer is dried or partially dried in the well known manner. The resulting film in sectional view is shown in Fig. 2-in which I1 is a support of suitable material such as cellulose ester, synthetic resin, metal or paper, coated with emulsion layers l8, l9 and 20 containing, respectively, red-sensitive silver halide grains 2!, green-sensitive silver halide grains 22 andbluesensitive silver halide grains 23. Emulsion layer l8 contains particles 24 of cyan coupler and crystalloidal material, emulsion layer I9 contains particles 25 of magenta coupler and crystalloidal material and emulsion layer 20 contains particles 26 of yellow coupler and crystalloidal material. The film also contains the usual yellow filter layer 21 between the green-sensitive emulsion layer 19 and the blue-sensitive emulsion layer 20. It is to be understood that by cyan coupler, magenta coupler and yellow coupler we mean that the dyes produced by these couplers on development are cyan, magenta and yellow and not that the couplers are these colors prior to development.
The following examples, which are illustrative only, indicate methods of forming dispersions of coupler and crystalloidal materials according to our invention:
Example 1 A solution of 7.5 grams of 2-lauryl-4-chlorophenol in grams of veratrole (1,2-dlmethoxybenzene) was added to 200 cc. of water contain 2.0 grams of the wetting agent, Gardinol WA. The whole mixture was stirred to effect preliminary emulsification, then passed through a colloid mill several times while the temperature of the solution and the mill was maintained at about C. In this way, a very stable and very fine emulsion was obtained which was added to 1000 cc. of a. melted silver halide gelatin emulsion.
The emulsion containing the added coupler dispersion was coated on a suitable support, set and dried in the usual manner. On development of this emulsion with a developing solution employing 2-amino fi-diethylaminotoluene as the developing agent and subsequent removal of silver, a cyan dye image was obtained.
Example 2 Five grams of the cyan coupler. 5-(N-benzyl- N-naphthalene-sulfonamino)-1-naphthol, were dissolved in a mixture of 15 grams ethyl acetate and 15 grams of ethyl N,N-di-n-butyl carbamate. To this solution was added a solution of 2 grams tri-isopropyl-naphthalene sulfonate and 0.2 gram glyceryl monostearate in 250 cc. of water. Emulsification was effected in the same manner as in Example 1, and the resulting emulsion added to 1000 cc. of melted silver halide gelatin emulsion. On development as described in Example 1, a cyan dye image was obtained.
Example 3 A solution was prepared by gentle warming of 5 grams of 1-p-phenoxyphenyl-3-amyl-fi-pyrazolone, 12.5 grams dimethylphthalate, and 20 cc. n-butylacetate. This solution was heated to F. and then added to 750 cc. of a melted silver halide gelatin emulsion, also at 95F. Preliminary emulsification was efiected by vigorous stirring, then the whole mixture passed through a colloid mill, the grinding chamber of which was maintained at 95 F. by means of water at this temperature circulated through the jacket. The emulsion containing the dispersed coupler and solvent was then coated, set and dried. On development as previously described, a magenta dye image resulted.
Example 4 A solution was prepared containing 15 grams of methyl o-methoxy benzoate, 65 grams butyl acetate, 35 grams of ethyl acetate, and 5 grams of the magenta coupler 2-cyanoacetylcoumarone 5- (N-n-amyl-p-tert. amylsulfanilide) This solution was emulsified by passage through a homogenizer with 450 cc. of water containing 2.5 grams of Gardinol WA. The resulting dispersion was heated to C. on a steam bath with constant stirring and with a stream of air blowing over the surface of the solution until all of the ethyl and butyl acetates had been evaporated from the mixture. At this stage, the volume of the solution was about 200 cc. This was added to 1000 cc. of silver halide emulsion and further treated as described above. The material yields a magenta image.
Example 5 Ten grams of the yellow coupler, n-propyl-pbenzoylacetamino-benzenesulfonate, was dissolved in 25 grams of methyl-p-toluenesulfonate. This solution was shaken with cc. of a 2 per cent solution of gelatin at a temperature of 50 F. The whole was passed through a'colloid mill, and the resultant dispersion added to 1000 cc. of a melted silver halide gelatin emulsion. After coating, drying, and developing as described above, a yellow imagewas obtained.
Example 6 A solution was prepared from 25 grams ethyl benzylmalonate, 45 cc. ethylacetate, and 8 grams of the yellow coupler, N-(4-benzoylacetaminobenzenesulfonyl) -N-benzyl-m-toluidine. This was emulsified with 200 cc. oi water containing 2 grams of Gardinol WA, exactly as described in Example 1. A yellow image is obtained.
Example 7 A dispersion consisting of 1 gram of l-hydroxy- 2-(N-isoamyl N-phenyl) -naphthamide dissolved in 3 grams of tri-o-cresylphosphate in a total volume of 50 cc. of water was added to 95 cc. of a polyvinyl alcohol silver halide emulsion prepared as described in Lowe U. S. Patent 2,286,215, granted June 16, 1942. After running through a colloidal mill the emulsion containing tri-ocresylphosphate and its dissolved coupler was coated. This coating produces a cyan dye upon photographic development.
A similar coating was made containing a dispersion oi 0.5 gram of 1-p-laurylphenyl-3- methyl-5-pyrazolone dissolved in 2.5 grams of tri-o-cresylphosphate dispersed in 50 cc. of water. The dispersion of tri-o-cresyl phosphate containing the coupler was added to 80 cc. of a polyvinyl alcohol emulsion similar to that described above and, after homogenizing in a colloid mill, the emulsion containing the coupler dispersed in tri-o-cresyl phosphate was coated. The coupler produced a magenta dye upon exposure and development. Plates from the two preparations after drying were exposed to white light and de veloped in the following solution:
2-amino-5-diethylamino toluene HCl grams-.. 2 Sodium sulfite do 2 Sodium carbonate do 20 Potassium bromide do 2 Water to cc 1000 Cyan and magenta dyes were obtained in the portions of the plates which were exposed to light, the corresponding dye being produced in its respective coating.
In addition to the advantages which will be apparent from the foregoing description of our invention, we have also discovered the surprising fact that a number of the high-boiling crystalloidal materials possess the valuable property of causing a shift in the absorption of the dyes formed during color development. For example the dye from a magenta coupler of the cyanoacetylcoumarone type dispersed in tri-o-cresyl phosphate has its maximum absorption at 540 millimiorons. The same dye in a-naphtholacetate has its maximum absorption between 547 and 548 millimiorons. Similar shift in absorption is obtained with other couplers such as yellow and magenta couplers of the cyanoacetylnaphthalene and pyrazolone series. Crystalloidal materials exhibiting this behavior include acetyl-N-butylaniline, acetylmethyl-p-toluidine, methylphthalate, butyl-o-methoxybenzoate, 1,2- dimethoxyben'zene, N,N'-diethyl-N,N'-diphenyl urea and ethyl-N,N-di-n-butylcarbamate. In addition, many of the dyes produced in this way have better absorption characteristics than similar dyes dispersed in gelatin without the oil formers.
It is to be understood that the modifications and examples included in the present specification are illustrative only and that our invention is to be taken as limited only by the scope of the appended claims.
1. The method of incorporating a color-former in a water-soluble sensitive photographic colloid which comprises mixing a color-forming compound capable of reacting with a primary aromatic amino coupling developing agent on photographic development, with'a substantially waterinsoluble, low molecular weight, organic, crystalloidal material having a boiling point above about 175 C., said organic material having a high solvent action for thecolor-forming compound and for the dyes formed therefrom, and being permeableto photographic processing solutions, the nature and proportions of the colorforming compound and crystalloidal material being so chosen that particles thereof are liquid under conditions of coating and processing the sensitive photographic colloid, said mixture being a liquid solution of said color forming compound and said crystalloidal material, and dispersing said solution in the sensitive photographic colloid to form liquid, particles 01 the color-forming compound and crystalloidal material in dispersed form in the photographic colloid.
2. The method of incorporating a color-former in a gelatino-silver halide emulsion which comprises mixing a color-forming compound capable of reacting with a primary aromatic amino coupling developing agent on photographic development, with a substantially water-insoluble, low molecular weight, organic, crystalloidal material having a boiling point above about C., said organic material having a high solvent action for the color-forming compound and for the dyes formed therefrom, and being permeable to photographic processing solutions, the nature and proportions of the color-forming compound and crystalloidal material being so chosen that particles thereof are liquid under conditions of coating and processing the emulsion, said mixture being a liquid solution of said color-forming compound and said crystalloidal material, and dispersing said solution in the gelatino-silver halide emulsion to form liquid particles of the colorforming compound and crystalloidal material in dispersed form in the emulsion.
3. The method of incorporating a color former in a gelatino-silver halide emulsion which comprisesmixing a color-forming compound capable of reacting with a primary aromatic amino coupling developing agent on photographic development, with a low boiling water-insoluble organic solvent for the color-forming compound and a substantially water insoluble, low molecular weight, organic, crystalloidal material having a boiling point above about 175 C., said organic material having a high solventaction for the color-forming compound and for the dyes formed therefrom, and being permeable to photographic processing solutions, the nature and proportions of the color-forming compound and crystalloidal material being so chosen that particles thereof are liquid under conditions of coating and processing the emulsion, said mixture being a liquid solution of said color-forming compound and said crystalloidal material, dispersing the mixture in water, removing the low boiling solvent and dispersing said solution in the gelatino-silver halide emulsion to form liquid particles of the color-forming compound and crystalloidal material in dispersed form in the'emulsion.
4. The process of claim 3, in which the crystalloidal material is a triaryl ester of phosphoric acid.
5. The process of claim 3, in which the crystalloidal material is a triaryl ester of phosphoric acid and the low-boiling solvent is an ester of a lower fatty acid and a lower fatty alcohol.
6. The process of claim 3, in which the crystalloidal material in tricresyl phosphate and the low-boiling solvent is butyl acetate.
7. The process of claim 3, in which the crystalloldalmaterial is methyl phthalate and the low-boiling solvent is butyl acetate.
8. The process of claim 3 in which the crystalloidal material is dibutylphthalate and the low-boiling solvent is ethyl acetate.
9. A light-sensitive emulsion for producing a colored image comprising finely divided liquid particles of a mixture of color former and a substantially water-insoluble, low molecular weight, organic, crystalloidal material having a boiling point above about 175 C., said crystalloidal material having a high solvent action for the color former and for the dye formed therefrom, and being permeable to photographic processing solutions, the nature and proportions of the color former and crystalloidal material being so chosen that particles thereof are liquid under conditions of coating and processing the emulsion, said particles being dispersed in a gelatino-silver halide emulsion.
10. A multi-layer photographic element comprising at least one gelatino-silver halide emulsion containing finely divided liquid particles of a mixture of color former and a substantially water-insoluble, low molecular weight, organic, crystalloidal material having a boiling point above about 175 C. said crystalloidal material having a high solvent action for the color former and for the dye formed therefrom and being permeable to photographic processing solutions, the nature and proportions of the color former and crystalloidal material beingso chosen that particles thereof are liquid under conditions of coating and processing the emulsion, said particles being dispersed in the emulsion.
11. In the method of incorporating a coupler in a gelatlno-silver halide emulsion layer, the
steps which comprise forming a liquid mixture of the coupler and a crystalloidal material having a boiling point above about 175 C., the nature and proportions of the coupler and crystalloidal material being so chosen that particles thereof are liquid under conditions of coating and processing the emulsion, and dispersing said mixture as finely divided liquid particles permeable to photographic processing solutions in said emulsion.
12. In the method of incorporating a coupler in a gelatino silver halide emulsion layer, the steps which comprise forming a. liquid mixture of the coupler and a triaryl ester of phosphoric acid and dispersing said mixture as finely divided liquid particles in said emulsion.
13. In the method of incorporating a coupler in a gelatino-silver halide emulsion layer, the steps which comprise forming a liquid mixture of the coupler and tricresyl phosphate and dispersing said mixture as finely-divided liquid particles in said emulsion.
EDWIN E. JELLEY. PAUL W. VITTUM.