US3505068A - Photographic element - Google Patents

Description

Unitecl States Patent 3,505,068 PHOTOGRAPHIC ELEMENT Clark Beckett and Henry D. Porter, Rochester, and Wilfred L. Wolf, Pittsford, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed June 23, 1967, Ser. No. 648,225 Int. Cl. G03c 1/76, 3/00 US. Cl. 96-68 17 Claims ABSTRACT OF THE DISCLOSURE Photographic elements are provided which have overlying silver halide emulsion layers of ditferent, overlapping speed sensitivities. The slower emulsion layer comprising grains having a shell composed of a silver halide substantially free from iodide, and a core which contains silver haloiodide; the faster emulsion layer comprises silver haloiodide grains. Lower contrast is obtained when such photographic elements are employed in photographic processes wherein a reversal dye image is formed. Preferably the slower emulsion layer is closest to the support.

This invention relates to photographic elements. In one important aspect it relates to photographic elements which are useful in photographic processes wherein reversal dye images are provided.

It is known that the latitude of photographic films may be increased by using double coated emulsion layers. For example, German Patent 1,121,470 suggests the use of double coated emulsion layers in at least one of the color producing layers of multilayer photographic color reversal films. The problem with such elements has been too high contrast, particularly in the toe or low density regions of the reversal sensitometric curve.

The problem of having too high contrast in photographic color films has been recognized. See, for example, US. Patent 3,183,087, issued May 11, 1965, where an additional processing step is suggested to lower contrast. Although that process may result in effective lowering of contrast, it does have the disadvantage of requiring an extra processing step. This extra processing step appeared essential to obtain lower contrast since, as noted in the US. patent referred to above, it had been felt that the contrast could only be slightly influenced by changes in the preparation of the emulsion.

One object of this invention is to provide novel photographic elements.

Another object of this invention is to provide novel photographic elements useful in producing color images.

Still another object of this invention is to provide photographic elements which exhibit reduced contrast when photographic reversal dye images are provided therewith.

Other objects of this invention will be apparent from the following disclosure and the appended claims.

In accordance with this invention, photographic elements adapted to produce reversal dye images include a support having coated thereon overlying silver halide emulsion layers having different, overlapping speed sensitivities, the faster of the emulsions comprising silver haloiodide grains, and the slower layer comprising grains which have a silver halide shell which is substantially free from silver iodide and a core which comprises a silver haloiodide. Photographic elements in accordance with this invention can be employed in any photographic processes wherein reversal dye images are formed. The improvement provided by such elements is a lower contrast in the reversal dye image, especially in the tow or low density regions of the reversal sensitometric curve.

"ice

In one embodiment of this invention, a photographic element is provided comprising a support having coated thereon first and second silver halide emulsion layers having different, overlapping speed sensitivities. The first of said emulsion layers is the faster of the two emulsions, and comprises silver haloiodide grains. The second of the emulsion layers is slower and comprises grains which have a shell composed of silver halide which is substantially free from iodide (either as silver iodide or silver haloiodide) and a core which comprises silver iodide (including silver haloiodide).

In another embodiment of this invention, photographic elements are provided which comprise a support having coated thereon a plurality of layer comprising three color forming units, one of the color-forming units comprising at least one silver halide emulsion layer which is spectrally sensitized to red radiation and adapted to provide a reversal cyan dye image; a second color-forming unit which comprises at least one silver halide emulsion layer which is spectrally sensitized to green radiation and adapted to provide a reversal magenta dye image and, a third color-forming unit comprising at least one silver halide emulsion layer sensitive to blue radiation and adapted to provide a reversal dye image; at least one of said color-forming units comprising at least two silver halide emulsion layers spectrally sensitized to the same wavelength radiation, one of said emulsion layers having a slower speed than the other and comprising grains which have a shell composed of a silver halide which is substantially free from iodide, and a core which is composed of a silver haloiodide; and, the second of said emulsion layers being the faster of the two emulsions, and comprising silver haloiodide grains. The color-forming units can be adapted to provide dye images in any convenient manner, such as by photographic color formers or bleachable dye incorporated in the element in association with the emulsion layers; introduction of photographic color former during development; or, by a diffusion transfer process such as the imagewise diffusion of dyes from the photographic element to a receiving sheet.

In a preferred embodiment of this invention, photographic elements of the type described above are provided which have in association with the blue, green and red sensitive emulsion layers, respectively, yellow, magenta and cyan photographic color former. The color former can be incorporated in the emulsion layers, or in layers contiguous thereto.

The slower of the silver halide emulsion layers featured in a dye forming unit of photographic elements in accordance with this invention comprise grains which have a shell composed essentially of a silver halide substantially free from iodide, and a core comprising silver haloiodide. Such grains can be referred to as buried iodide emulsion. The shell can be composed of, for example, silver bromide, silver chloride or silver chlorobromide. The shell should be free from iodide present either as silver iodide or silver haloiodide. Shells composed of silver bromide provide especially satisfactory results in the practice of the present invention. The thickness of the shell in these silver halide grains may be between a few (about 3) crystal lattice planes up to about ten times the diameter of the core of the emulsion grain. The core of these emulsions comprises, in accordance with the invention, silver iodide or a silver haloiodide, such as silver bromoiodide, silver chloroiodide or silver chlorobromoiodide. It is desirable that such grains contain a total of from .5 to 10 mole percent iodide, based on the total amount of halide in the grain (shell plus core). The remainder of the halide is bromide, chloride or bromide and chloride. Good results are obtained when the core is a silver bromoiodide core and the grains contain a total of about 1 to 8 mole percent iodide, with the remainder of the halide being bromide, chloride or bromochloride. Especially satisfactory results are achieved with grains which have a shell composed of silver bromide and a core composed of silver bromoiodide, which grains contain a total of from about 4 to 5 mole percent iodide, (the remainder of the halide being bromide). Advantageo-usly, these grains are relatively fine, preferably less than about .75 micron, and advantageously under .5 micron in diameter. It is generally desirable that the grains are at least .1 micron in diameter to obtain good exposure latitude. Grains of this type can be provided in any suitable manner, such as by the procedure described in British Patent 1,027,146 (complete specification published Apr. 27, 1966). A good way to prepare buried iodide emulsions is to form an iodide rich base during about the first percent of precipitation followed by the formation of an iodide-free silver halide phase thereover, and controlling the pAg at a constant level to obtain the desired grain size.

In some instances it may be desirable to reduce the speed of the slow emulsion layer, for example by adding suitable desensitizers which do not exhibit deleterious side effects, such as the production of fog or a high minimum density. Inorganic desensitizers, such as cupric nitrate, mercuric chloride, mercuric iodide, rhodium ammonium chloride or organic compounds such as phenazines can be utilized which meet the guidelines referred to above. The use of desensitizers is sometimes ad vantageous in order that grains can be used which are sufficiently thick (preferably at least .1 micron in thickness) to avoid being dissolved in any high solvent developer used, which would result in decreased latitude.

The faster emulsion employed in the units adapted to produce dye in accordance with the invention comprises regular silver haloiodide grains which contain about 2 to 10 mole percent iodide, and preferably from about 4 to 8 mole percent iodide. The term regular as used herein refers to grains which have approximately the same halide content throughout the grain, in order to distinguish the buried iodide grains used in the slow emulsion layer. The grains of the faster emulsion are generally somewhat coarser in grain size than the buried iodide silver halide grains employed in the slower emulsion layer. The faster grains generally have the diameter of at least 0.75 micron and preferably greater than 1 micron.

The fast and slow emulsion layers employed in accordance with the present invention are arranged in overlying relationship upon a support. The two layers can be separated, if desired, by an interlayer such as a hydrophilic colloid layer, e.g., gelatin. Preferably they are contiguous and the lower speed emulsion layer is coated closest to the support. While the two emulsion layers have different speeds as indicated heretofore, the speeds of the two layers should overlap to provide a continuous response over a Wide latitude of exposure. In other words, the fast and slow emulsion layers featured herein should have substantially juxtaposed speed sensitivities. Generally, highly useful results can be obtained when the fast emulsion layer is about twice as fast as the slow layer. Thus, the fast layer can have a relative speed of 100, and the slow emulsion layer can have a relative speed of about 50. The fast and slow emulsion layers featured in this invention are advantageously sensitive to approximately the same wavelength radiation.

The advantages of this invention, particularly the lowered reversal dye image contrast, is realized when photographic elements are provided for production of monochrome prints or in multilayer color films adapted to produce multicolor reversal dye images. For example, a typical multilayer color film may comprise three units, the first unit containing a silver halide emulsion layer sensitive to blue radiation and adapted to produce a yellow dye; a second unit comprising at least one silver halide emulsion layer sensitive to green radiation and adapted to produce magenta colored dye; and, a third unit comprising at least one silver halide emulsion layer sensitive to red radiation and adapted to produce cyan colored dye. Any one of such units, any two of such units, or all of such units can contain the special combination of slower and faster emulsion layers in accordance with this invention. The lower contrast is achieved whether the combination of emulsion layers provided by this invention is employed in a yellow, magneta, cyan or other colored dye producing color forming unit.

The featured fast and slow emulsion layers of this invention are useful in reducing the dye contrast in any photographic color process wherein reversal dye images are produced. For example, the featured emulsion layers of this invention are highly useful in complete photographic processes wherein a multilayer photographic element containing a plurality of differentially sensitized photographic silver halide emulsion layers is given a first exposure, followed by development in a photographic developer for producing a black-and-White silver negative image, and a second exposure followed by at least one additional development in a primary aromatic amino photographic developer for producing a color dye image. In color development, the color-former reacts with the reaction products of an oxidized primary aromatic amino color developer to form dye. In such systems, the dye image may be provided in one of two classical techniques. In one, color couplers are incorporated in the photographic element in association with (e.g., in, or in a colloid layer contiguous to) each of the photographic emulsions thereof prior to exposure. Generally, the color forming couplers in such processes are dispersed in a suitable medium, such as one of those described in U.S. Patents 2,322,027; 2,304,940; 2,801,171 or 2,852,382. Representative useful color formers which may be used in such processes are Well known in the literature, and are described for example in Fierke et al. U.S. Patent 2,801,171; Weissberger et al. U.S. Patent 2,474,293; Glass et al. U.S. Patent 2,521,908; and McCrossen et al. U.S. Patent 2,857,057; or, color-forming compounds of the fat-tail variety (see F.I.A.T. Final Report, No. 721, for examples thereof). Such elements can be developed by one of the processes described and referred to in Graham et al. U.S. Patent 3,046,129, columns 23 and 24. General classes of the most useful color formers include phenolic, 5-pyrazolone, heterocyclic and open-chain ketomethylene compounds.

The second of such color reversal photographic processes is characterized by the introduction into the photographic element of dye former contained in the developer. In such processes couplers of the type referred to above can be incorporated in a color developer solution. These processes are described in tthe literature, such as Mannes et al. U.S. Patent 2,252,718 issued Aug. 19, 1941.

The color forming developers which can be used in accordance with the two processes described above have been previously described in the art. The most useful of such color forming developers are the phenylene diamines and substituted derivatives thereof, such as those disclosed in Weissberger et al., U.S. Patent 2,548,574, issued Apr. 10, 1951; Weissberger et al., U.S. Patent 2,55 2,2402 issued May 8, 1951; and, Weissberger et al., U.S. Patent 2,566,271, issued Aug. 28, 1951. Other phenylene diamine color forming developers can be employed to advantage in the process of this invention.

The invention is useful in reducing reversal dye images contrast in other photographic processes for forming multicolor images, such as color diffusion transfer processes of the type described in Rogers U.S. Patent 2,983,- 606, issued May 9, 1961; Weyerts U.S. Patent 3,146,102, issued Aug. 25, 1964; Barr et al. U.S. 3,227,551, issued Jan. 4, 1966; Barr et al. U.S. Patent 3,227,554, issued Jan. 4, 1966; Barr U.S. Patent 3,243,294, issued Mar. 29, 1966; Whitmore et al., U.S. Patent 3,227,550, issued Jan.

4, 1966; and, Whitmore U.S. Patent 3,227,552, issued Aug, 27, 1964.

The invention can also be employed to advantage in photographic elements which are useful in providing dye images of reduced contrast in the photographic silver dye bleach process. In such processes, which are described in the literature, bleachable dye is incroporated in or contiguous to a given silver halide layer, a silver image is produced after exposure, and the dye is bleached imagewise in proportion to the silver image developed to provide contrasting dye images.

As is known, one highly useful arrangement of light sensitive silver halide layers for the provision of multicolor photographic records comprises a support having coated thereon, respectively, superposed light sensitive silver halide colloid layers which are sensitive, respectively, to red, green and blue radiation. Silver images can be developed in such layers, and dyes formed imagewise in proportion to the developed silver image. Advantageously, cyan, magenta and yellow dyes are formed in proportion to the red, green and blue layers respectively. Such dyes can be formed in any convenient manner, such as in the color processes referred to above. Advantageously, a dye image is formed having a complementary relationship to the region of the spectrum to which the silver halide emulsion is sensitized.

The emulsions of our invention may employ various binders therefor. Among such materials are natural and/ or synthetic binding materials, for example, gelatin, colloidal albumin, water-soluble vinyl polymers, cellulose derivatives, proteins, water-soluble polyacrylamides, polyvinyl pyrrolidone and the like. These binders may be utilized alone or mixtures thereof may be utilized. In addition to the hydrophilic colloids, the binders may contain dispersed polymerized vinyl compounds, e.g. synthetic polymers of alkyl acrylates and methacrylates and acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

The various layers of the photographic elements of our invention can be hardened with any suitable hardener, including, for example, aldehyde hardeners, aziridine hardeners, hardeners which are derivatives of dioxane, oxypolysaccharides such as oxystarch, oxyplant gums and the like.

The photographic layers described herein can be coated on a wide variety of supports. Typical supports include those generally employed for photographic elements such as cellulose nitrate, cellulose acetate, polyvinyl acetal, polystyrene, polycarbonate, polyethylene terephthalate and related films or resinous materials,

The photographic emulsions and elements or our invention can also contain additional addenda such as stabilizers or antifoggants, speed-increasing materials, such as polyalkylene oxides, onium salts and thioethers, plasticizers, coating aids such as anionic, non-ionic and amphoteric surface active compounds and the like. The photographic silver halide emulsions disclosed herein can also be chemically sensitized with compounds of the sulfur group such as sulfur, selenium and tellurium sensitizers, noble metal salts such as gold, or reduction sensitized with reducing agents. Combinations of the above addenda, antifoggants, sensitizers, etc., may be utilized.

This invention will be further illustrated by the follow ing examples. Example 1 shows a photographic element in accordance with the invention. In that element, a fast red sensitive silver haloiodide emulsion is used in combination with a slow buried iodide red sensitive silver halide emulsion having a shell free from iodide and a core comprising silver haloiodide.

EXAMPLE 1 A photographic element of the type employed in this invention is prepared by coating a transparent cellulose acetate film support with the following hydrophilic colloid layers, in the order in which they are given starting from the support.

Layer ISl0w cyan-producing layer A gelatin silver bromoiodide emulsion containing a dispersion of a mixture of cyan-forming coupler, e.g., couplers Nos. 1 through 6 of Fierke et al. U.S. Patent 2,801,171 (colume 2) in conventional coupler solvent such as tri-o-cresyl phosphate is coated at the rate of milligrams per square foot gelatin, 65 milligrams per square foot silver and 50 milligrams per square foot cyan coupler mixture. It is spectrally sensitized to red radiation (600-700 nm.). The emulsion has a relative speed of 50. The grains of the emulsion are buried iodide grains which have an iodide-free shell composed of silver bromide and a core of silver bromoiodide such that the total halide in the grains is 95.4 mole percent bromide and 4.6 mole percent iodide, and are between .1 and .5 micron in size.

Layer II-Fast cyan-producing layer This layer has the same composition as layer I except that the relative speed of the emulsion is 100. and the grains are regular silver bromoiodide containing 6.4 mole percent iodide (the shell and core of the grains being silver bromoiodide), and are over 1 micron in size.

Layer III-Slow magenta-producing layer A silver bromoiodide (6 mole percent iodide) gelatin emulsion spectrally sensitized to green radiation (500- 600 nm.) and containing a dispersion in tri-o-cresyl phosphate of a pyrazolone coupler, e.g., couplers number 7 etc. of Fierke et al. U.S. Patent 2,801,171 (column 2) together with a phenylazopyrazolone coupler, e.g., coupler number 8 of U.S. Patent 2,801,171 is coated at the rate of 165 milligrams per square foot gelatin, 95 milligrams per square foot silver and 65 milligrams per square foot coupler mixture. The relative speed of the emulsion is 50.

Layer IVFast magenta-producing layer This layer is the same as layer III except that the relative speed of the emulsion is 100.

Layer VYellow filter layer A gelatin layer containing Carey-Lea colloidal silver is coated at the rate of 90 milligrams per square foot gelatin, and 10 milligrams per square foot silver.

Layer VISlow yellow-producing layer A gelatin silver bromoiodide emulsion (blue-sensitive) containing a yellow image-forming coupler, e.g., coupler Nos. I to V of McCrossen et al., U.S. Patent 2,875,057, issued Feb. 24, 1959, dispersed in dibutyl phthalate is coatedtt a concentration of milligrams per square foot gelatin, 70 milligrams per square foot silver and 50 milligrams per square foot color coupler. This layer has a relative speed of 50.

Layer VIIFast yellow producing layer This layer is the same as Layer VI except that the emulsion has a relative speed of 100.

The element thus prepared is exposed on an intensity scale sensitometer, and is processed in the color negative process, such as that described in Graham et al., U.S. 3,046,129 issued July 24, 1962, Col. 23 line 34 through Col. 24, line 22. The relative cyan lower scale contrast, as noted in Table I below, is 1.15. This is much lower than that of the cyan contrast of the related elements shown in comparison Examples 2, 3 and 4 below.

Examples 2, 3 and 4 show the undesirably high relative cyan lower scale contrast obtained with elements which do not contain red sensitive emulsion layers in accordance with the invention.

EXAMPLE 2 A photographic element is prepared as described in Example l, except that the grains of emulsion layer I are regular silver bromoiodide grains (no iodide-free shell) containing 4.6 mole percent iodide, and the grains of emulsion layer II are regular silver bromoiodide grains (no iodide-free shell) containing 1 mole percent iodide. The element is exposed and processed exactly as described in Example 1, with the results shown in Table I.

EXAMPLE 3 A photographic element is prepared as described in Example 2 except that the grains of emulsion layer II are regular silver 'bromoiodide grains (no iodide-free shell) containing 6.4 mole percent iodide. The element is ex posed and processed exactly as described in Example 1, with the results shown in Table I.

EXAMPLE 4 A photographic element is prepared as described in Example 2 except that emulsion layer I contains buried iodide grains which have a silver bromide shell (free from iodide) and a core of silver bromoiodide such that the grains have a total halide content of 95.4 mole percent bromide and 4.6 mole percent iodide. The element is exposed and processed exactly as described in Example 1, with the results shown in Table I.

TABLE 1 Relative Cyan Mole Percent Iodide in- Lower Scale Contrast (high- Eleruent Layer I Layer 11 light Contrast) Example 1 4.6% buried I 6.4% I- 1.15 Example 2.-- I- 1.0 a 1. 43 Example 3 4.6% I- 6.4% I 1. 31 Example 4 4.6% buried I- 1. 0% I- 1. 32

EXAMPLE 5 A photographic element prepared as in Example 1 but containing green-sensitized silver halide grains in emulsion layers III and IV which are the same as the silver halide grains in layers I and II, respectively, results in reduction in magenta lower scale contrast similar to the reduction in cyan contrast obtained in Example 1.

EXAMPLE 6 A photographic element prepared as in Example 1 but containing blue-sensitive silver halide grains in emulsion layers VI and VII which are the same as the silver halide grains in layers I and II, respectively, result in'reduction in yellow low scale contrast similar to the reduction in cyan contrast obtained in Example 1.

The invention has been described in detail with particular reference to preferred embodiments thereof, but, it will be understood that variations and modifications can be effected within the spirit and scope of the invention described hereinabove and in the appended claims.

We claim:

1. A photographic element comprising a support having thereon first and second photographic silver halide emulsion layers having different, overlapping speed sensitivities, the first of said emulsions comprising regular silver haloiodide grains; and, said second emulsions comprising silver halide grains having a shell composed of silver halide substantially free from iodide, and a core comprising silver iodide.

2. A photographic element comprising a support having thereon first and second photographic silver halide emulsion layers having different, overlapping speed sensitivities, the first of said emulsions comprising regular silver haloiodide grains in which the total halide content is from 2 to 10 mole percent iodide; and, said second emulsion comprising silver halide grains having a shell composed of silver halide substantially free from iodide, and a core comprising silver iodide, the grains of said second emulsion layer having a total halide content of from about .5 to 10 mole percent iodide, the remainder of the halide in said grains being selected from bromide and chloride.

3. A photographic element as defined in claim 2 wherein the said first emulsion is about twice as fast as the second emulsion.

4. A photographic element comprising a support having thereon first and second photographic silver halide emulsion layers having different, overlapping speed sensitivities, the first of said emulsion layers being about twice as fast as said second emulsion layer; said first emulsion layer comprising silver haloiodide grains wherein 6 to 7 mole percent of the total halide content is iodide; and, said second emulsion comprising silver halide grains having a shell composed of silver halide substantially free from iodide, and a core comprising silver iodide, about 1 to 8 mole percent of the total halide content of said second emulsion being iodide, and the remainder of the halide in said grains being selected from bromide and chloride.

5. A photographic element comprising a support having thereon overlying first and second light sensitive photographic silver halide emulsion layers, said first emulsion being coated furthest from the support and comprising silver brornoiodide in which about 6 to 7 mole percent of the total halide is iodide; said second emulsion comprises a silver bromide shell substantially free from any iodide, and a core composed of silver bromoiodide, the total halide of said grains containing from about 4 to 5 mole percent iodide; and, said first and second emulsion layers having overlapping speed sensitivities.

6. A photographic element as defined in claim 5 wherein said first and second emulsion layers are contiguous and are sensitized to essentially the same spectral range, each of said emulsion layers having incorporated therein a color former.

7. A photographic element as defined in claim 6 wherein said emulsions are spectrally sensitized to red radiation; and, said color-former is one which forms a cyan colored dye with the reaction products of an oxidized primary aromatic amino color developing agent.

8. A photographic element comprising a support having thereon first, second and third light sensitive units each of which comprise at least one silver halide emulsion layer, the emulsion layer in said units being spectrally sensitized, respectively, to blue, green and red radiation; at least one of said units comprising first and second silver halide emulsion layers spectrally sensitive to radiation of the same Wavelength, said two emulsion layers in said unit having overlapping speed sensitivities, the silver halide grains of said first emulsion layer comprising regular. light sensitive silver haloiodide grains, and said second emulsion layer comprising grains having a shell of silver halide which is substantially free from iodide, and having a core which comprises silver iodide.

9. A photographic element as defined in claim 8 wherein the halide of said first silver haloiodide emulsion layer is from about 2 to 10 mole percent iodide, the remainder of said halide being selected from bromide and chloride; and, the halide of said second emulsion layer is from about .5 to 10 mole percent iodide, the remainder of said halide being selected from the group consisting of bromide and chloride.

10. A photographic element as defined in claim 9 wherein each of said light sensitive units has a photographic color former incorporated therein in association with each of the silver halide emulsion layers.

11. A photographic element as defined in claim 10 wherein the unit sensitive to red radiation contains said first and second emulsion layers, and the color-former in association with said first and second emulsion layers is a cyan color former.

12. A photographic element as defined in claim 9 wherein the grains of said first silver haloiodide emulsion are silver bromoiodide grains containing from about 4 to 8 mole percent iodide; and, the grains of said second emulsion comprise a core of silver bromoiodide and a shell composed of silver bromide substantially free from any silver iodide, the total halide of the grains of said second emulsion being from 2 to 8 mole percent iodide, and the remainder of the halide being bromide.

13. A photographic element comprising a support having thereon a plurality of layers comprising three colorforming units:

(1) a first color-forming unit comprising first and second overlying silver halide emulsion layers having different, overlapping speed sensitivities, each of said emulsions being sensitive to red radiation and containing a color former which produces cyan dye on reaction with the oxidation products of primary aromatic amino color developing agent;

(2) a second color-forming unit comprising first and second overlying light sensitive silver halide emulsion layers having different, overlapping speed sensitivities, each of said emulsions being sensitive to green radiation and containing a color former which produces magenta dye on reaction with the oxidation products of primary aromatic amino color developing agent; and,

(3) a third colonforming unit comprising first and second overlying silver halide emulsion layers having different, overlapping speed sensitivities, each of said emulsions being sensitive to blue radiation and containing a color former which produces yellow dye upon reaction with the oxidation products of primary aromatic amino color developing agent; the first emulsion layer of at least one of said units comprising regular silver haloiodide grains having a total halide content of from 2 to mole percent iodide, the remainder of the halide being selected from bromide and chloride; and the second emulsion layer of said unit being slower than said first emulsion layer containing regular silver halide grains, said second emulsion layer comprising buried iodide silver halide grains which have a silver halide shell substantially free from iodide, and a core comprising silver iodide, the total halide in the grains of said second emulsion being from .5 to 10 mole percent iodide, the remainder of the halide being selected from bromide and chloride.

14. A photographic element as defined in claim 13 wherein the first color-forming unit comprises said first and second emulsion layers containing, respectively, said regular silver haloiodide grains and said buried iodide silver halide grains.

15. A photographic element as defined in claim 13 wherein said regular silver haloiodide grains are silver bromoiodide grains which contain from 4 to 8 mole percent iodide; and, said buried iodide silver halide grains have a core of silver bromoiodide and a shell of silver bromide, the total halide in said grains being from 1 to 8 mole percent iodide.

16. In a photographic element having thereon overlying silver halide emulsion layers having different, overlapping speed sensitivities, said silver halide emulsion layers be ing sensitized to the same spectral region and adapted to produce reversal dye image, the improvement whereby lower reversal dye image contrast is obtained which comprises employing in the faster of said silver halide emulsion layers silver haloiodide grains; and, in the slower emulsion layer, employing silver halide grains which comprise a shell composed of a silver halide essentially free from silver iodide and a core which comprises silver iodide.

17. A photographic element as defined in claim 16 wherein the silver haloiodide grains in said faster emulsion layer are silver bromoiodide grains having a total halide content of 2 to 10 mole percent iodide, the remainder of the halide being bromide; and, the grains in said slower emulsion layer have a silver bromoiodide core and a silver bromide shell, the total halide in the grains being from .5 to 10 mole percent iodide, the remainder of the halide being bromide.

References Cited UNITED STATES PATENTS 2,996,382 8/1961 Luckey et a1. 96-68 FOREIGN PATENTS 818,687 8/1959 Great Britain. 1,181,056 11/1964 Germany.

OTHER REFERENCES Chem. Absts., vol. 26, p. 5859.

NORMAN G. TORCHIN, Primary Examiner M. F. KELLEY, Assistant Examiner US. Cl. X.R. 96-69, 74