IE54125B1 - Photographic image transfer film unit - Google Patents

Abstract

Photographic image transfer film units are disclosed employing high aspect ratio tabular grain silver halide emulsions comprising a support, at least one emulsion layer located on said support containing a dispersing medium and radiation- sensitive silver halide grains, and an image receiving layer. These units are characterized in that at least 50 percent of the total projected area of said radiation-sensitive silver halide grains of at least said one emulsion layer is provided by tabular silver halide grains having a thickness of less than 0.5 micrometer, a diameter of at least 0.6 micrometer, the diameter of a grain being defined as the diameter of a circle having an area equal to the projected area of said grain, and an average aspect ratio of greater than 8:1, which aspect ratio is defined as the ratio of grain diameter to thickness. The units allow the transferred image to be rapidly accessible for viewing, higher interim contrasts to be produced as a function of elapsed time of development, and improvements in photographic characteristics (such as sharpness), reduction in silver coverages, advantageous layer order arrangements, and reduction or elimination of various layers, such as yellow filter layers and scavenger interlayers.

Description

This invention relates to a photographic image transfer film unit comprising a support, at least one emulsion layer located on said support containing a dispersing medium and radiationsensitive silver halide grains, and an image receiving layer.

The most commonly employed photographic elements are those containing one or more radiation10 sensitive silver halide emulsion layers. Their widespread use is attributable to the excellent quality images they are capable of producing and to their high speed, allowing them to be employed in hand-held cameras under a variety of lighting condi15 tions.

Nevertheless, silver halide photographic elements exhibit a significant limitation in terms of viewing the photographic image. Imagewise exposure of the silver halide emulsion layer does not produce an immediately viewable photographic image. Exposure produces an invisible latent image in the silver halide emulsion. Processing of the latent image is required to produce a viewable image. Historically this has meant removing the photographic element from the camera, processing in aqueous solutions, and obtaining a viewable image. In most instances the first viewable image obtained is a negative image, and a second exposure through the negative image of an additional photographic element and processing thereof is required to produce a viewable positive of the image initially photographed. It is also possible with element or process modifications to produce a positive image directly in the photograohic element which Is imagewise exposed.

Image transfer photography has made it possible to reduce the delay between imagewise ΰ 4 χ - ·* -2exposure and obtaining a viewable image. Immediately after imagewise exposing the radiation-sensitive silver halide emulsion layer or layers, a processing solution can be brought into contact therewith. As silver halide development occurs, a black-and-white transferred silver image or a transferred dye image can be formed in a receiving layer for viewing. In this way, visual access to the photographic image can occur in minutes or even seconds.

Still, though measured in seconds, the delay in providing visual access remains an Important limitation in silver halide image transfer photography. Subject opportunities can be fleeting, and the photographer needs as nearly an instantaneous visual verification of an acceptable photographic image as can be offered.

Although image transfer has reduced the time required for image access in silver halide photography, this advantage has not been achieved without other sacrifices. One significant long term concern of image transfer photography relates to consumption of silver. Multicolor silver halide photographic elements which are conventionally processed and dye image transfer film units both employ relatively high silver coverages to obtain maximum photographic speed. Typically about 1000 milligrams of silver per square meter Is required to form each of the blue, green, and red exposure records. In conventionally processed multicolor photographic elements the image produced contains no silver and all of the silver present in the photographic element is, in theory, recoverable. On the other hand, in image transfer photography silver is seldom recovered, and in integral format image transfer film units all of the silver remains with the photographic film units forming the viewable image. . Λ I- Μ-3Another disadvantage, inherent in image transfer photography, is the reduction in image sharpness attributable to diffusion. As the image forming materials diffuse from the silver halide emulsion layer or an adjacent dye releasing layer, diffusion occurs hoth in the direction of the receiving layer and laterally, leading to image spreading and loss of sharpness. Sharpness can be improved by decreasing the length of the diffusion path to the receiving layer. This is controlled by the number and thickness of the layers to be traversed. Unfortunately, the minimum thickness of the silver halide emulsion layers is limited by the size of the silver halide grains and the weight ratio of gelatin to silver halide. Further, in multicolor image transfer film units employing three superimposed dye-providing layer units, intervening dye-providing layer units and separating interlayers must be penetrated by diffusing dyes migrating to the receiving layer.

Another consideration that arises in image transfer photography is image density variance as a function of temperature differences. Since subject opportunities are presented under a variety of temperature conditions and since the primary advantage of image transfer photography is ready image access, it follows that the ability of image transfer photographic elements to produce acceptable images at a variety of temperatures is also important. Image transfer photography Is much different from conventional photography in this respect, since in the latter processing Is rarely undertaken without control of temperature.

A number of imaging limitations are encoun35 tered in producing transferred images with dyes. For example, both the high silver coverages noted above -4and larger than stolchiometrlcally predicted amounts of dye-image-providing materials are required to obtain transferred dye Images of acceptable maximum densities. To the extent that the efficiency of dye transfer declines from stolchiometrlcally predicted levels, more dye-lmage-providlng materials must be Incorporated in the photographic elements and the layer thicknesses must be increased to Incorporate added amounts of these materials. Further, the rate of release of dyes for transfer can affect the time required to produce a viewable Image. Where the development reaction product is relied upon to preclude dye transfer, as in the case of many conventional positive-working dye-image-formere, the rate of silver halide development also llmlt6 the maximum rate at which image dye can become available for transfer, elnce too rapid release of image dye in relation to the rate of silver halide development can result in the loss of image discrimination. Improve20 ments of any one or a combination of these characteristics can, of course, significantly improve dye image transfer.

A great variety of regular and Irregular grain shapes have been observed in silver halide photographic emulsions intended for imaging applications. Regular grains are often cubic or octahedral. Grain edges can exhibit rounding due to ripening effects, and in the presence of strong ripening agents, such as ammonia, the grains may even be spherical or exist as thick platelets, which are nearly spherical, as described, for example by Land U.S. Patent 3,894,871 and Zelikman and Levi Making and Coating Photographic Emulsions, Focal Press, 1964, page 223. Rods and tabular grains in varied portions have been frequently observed mixed in among other grain shapes, particularly where the pAg (the <3 4*.—· -5negative logarithm of silver ion concentration) of the emulsions has been varied during precipitation, as occurs, for example in single-jet precipitations.

Tabular grains (those areally extended in 5 two dimensions as compared to their thickness) have been extensively studied, often in macro-sizes having no photographic utility. Tabular grains are herein defined as those having two parallel or substantially parallel crystal faces, each of which is substantially larger than any other single crystal face of the grain A discussion of tabular bromoiodide grains appears in Duffin, Photographic EmulBion Chemistry, Focal Press, 1966, pp. 66-72, and Trivelli and Smith, The Effect of Silver Iodide Upon the Structure of Silver Bromo-Iodide Precipitation Series, The Photographic Journal, Vol. LXXX, July 1940, pp. 285-288. Trivelli and Smith observed a pronounced reduction in both grain size and aspect ratio with the introduction of iodide. Tabular silver bromide emulsions ate discussed by de Cugnac and Chateau, Evolution of the Morphology of Silver Bromide Crystals During Physical Ripening, Science et Industries Photographiques, Vol. 33, No. 2 (1962), pp. 121-125.

Sulfur-sensitized tabular grain silver bromide emulsions having an average aspect ratio of from about 5 to 7:1 wherein the tabular grains account for greater than 507» of the projected area of the total grain population were incorporated in a direct x-ray radiographic product, No Screen X-Ray Code 5133 sold by Eastman Kodak Co. from 1937 until the 1950's. Gutoff, Nucleation and Growth Rates During the Precipitation of Silver Halide Photo- graphic Emulsions, Photographic Sciences and Engineering, Vol. 14, No. 4, July-August 1970, pp. 248-257, reports preparing silver bromide and silver bromoiodide emulsions of the type prepared by υ -., j .. j -6single-jet precipitations using a continuous precipitation apparatus.

Procedures have recently been published for preparing emulsions in which a major proportion of the silver halide is present in the form of tabular grains. U.S. Patent 4,063,951 teaches forming silver halide crystals of tabular habit bounded by {100} cubic faces and having an aspect ratio (based on edge length) of from 1.5 to 7:1. The tabular grains exhibit square and rectangular major surfaces characteristic of {l00} crystal faces. U.S. Patent 4,067,739 teaches the preparation of silver halide emulsions wherein most of the crystals are of the twinned octahedral type by forming seed crystals, by Ostwald ripening in the presence of a silver halide solvent, and completing grain growth without renucleation or Ostwald ripening while controlling pBr (the negative logarithm of bromide ion concentration).

U.S. Patents 4,150,994 and 4,184,877, U.K. Patent 1,570,581, and German OLS publications 2,905,655 and 2,921,077 teach the formation of silver halide grains of flat twinned octahedral configuration by employing seed crystals which are at least 90 mole percent iodide. (Except as otherwise indicated, all references to halide percentages are based on silver present in the corresponding emulsion, grain, or grain region being discussed; e.g., a grain consisting of silver bromoiodide containing 40 mole percent iodide also contains 60 mole percent bromide.) Several of the above references report increased covering power for the emulsions and state that they are useful in camera films, both black-and-white and color. U.S. Patent 4,063,951 specifically reports an upper limit on aspect ratios of 7:1, and, from the very low aspect ratios obtained by the examples (aspect ratio of 2:1), the 7:1 aspect ratio appears unrealistically high. It is clear from repeating -7examples and viewing the photomicrographs published that the aspect ratios realized in the other abovementioned references were also less than 7:1.

According to the present invention there is provided a photographic image transfer film unit comprising a support, at least one emulsion layer located on said support containing a dispersing medium and radiation-sensitive silver halide grains, and an image receiving layer characterized in that at least 50 percent of the total projected area of said radiation-sensitive silver halide grains of at least said one emulsion layer is provided by tabular silver halide grains having a thickness of less than 0.5 micrometer, a diameter of at least 0.6 micrometer, the diameter of a grain being defined as the diameter of a circle having an area equal to the projected area of said grain, and an average aspect ratio of greater than 8:1, which aspect ratio is defined as the ratio of grain diameter to thickness· It is an advantage of the present invention that the photographic image transfer film units are capable of producing viewable images with less time elapsed after the commencement of processing. The image transfer film units further produce higher interim contrasts as a function of elapsed time of development· The image transfer film units are capable of producing images of improved sharpness.

The present invention is particularly advantageous in permitting reduction in silver coverages without loss of photographic speed, more efficient use of dye image formers, more advantageous layer order arrangements, elimination or reduction of yellow filter materials, and less image dependence on temperature. Still other photographic advantages are realized with various specific forms of the image transfer film units described below. $412.? -8The use of chemically and spectrally sensitized high aspect ratio tabular grain emulsions in the image transfer film unite of the invention provides for additional significant advantages in speed5 granularity relationship, sharpness, and blue and minus blue sensitivity differences. The high aspect ratio tabular grain emulsions enhance sharpness of underlying emulsion layers when they are positioned to receive light that is free of significant scat10 tering. These emulsions are particularly effective in this respect when they are located in the emulsion layers nearest the source of exposing radiation.

When spectrally sensitized outside the blue portion of the spectrum, the high aspect ratio tabular grain silver bromide and bromolodlde emulsions exhibit a large separation in their sensitivity in the blue region of the spectrum as compared to the region of the spectrum to which they are spectrally sensitized. Minus blue sensitized high aspect ratio tabular grain silver bromide and bromolodlde emulsions are much less sensitive to blue light than to minus blue light and do not require filter protection to provide acceptable minus blue exposure records when exposed in neutral light, such as daylight at 5500°K. The high aspect ratio tabular grain emulsions exhibit improved speed-granularity relationships as compared to previously known tabular grain emulsions and as compared to the best speedgranularity relationships heretofore achieved with emulsions of the same halide content generally. Very large increases in blue speed of high aspect ratio tabular grain silver bromide and bromoiodide emulsions are realized as compared to their native blue speed when blue spectral sensitizers are employed.

The invention can be better appreciated by reference to the following detailed description considered in conjunction with the drawing, in which -9Figure 1 is a plot of silver coverage versus relative speed, where A is a control and B represents the invention.

Silver Halide Emulsions To obtain the advantages of the invention at least one emulsion layer of the image transfer film unit is a high aspect ratio tabular grain silver halide emulsion. As applied to the silver halide emulsions of the present invention the term high aspect ratio is herein defined as requiring that the silver halide grains having a thickness of less than 0.5 micrometer, preferably less than 0.3 micrometer, and a diameter of at least 0.6 micrometer have an average aspect ratio of greater than 8:1 and account for at least 50 percent of the total projected area of the silver halide grains.

The preferred high aspect ratio tabular grain silver halide emulsions of the Image transfer units of the present invention are those wherein the silver halide grains having a thickness of less than 0.5 micrometer (preferably less than 0.3 micrometer and optimally less than 0.2 micrometer) and a diameter of at least 0.6 micrometer have an average aspect ratio of at least 12:1 and optimally at least :1. These silver halide grains have an average diameter less than 30 micrometers (preferably less than 15 micrometers and optimally less than 10 micrometers) . In a preferred form of the invention these silver halide grains account for at least 70 percent and optimally at least 90 percent of the total projected area of the silver halide grains.

It is appreciated that the thinner the tabular grains accounting for a given percentage of the projected area, the higher the average aspect ratio of the emulsion.

Typically the tabular grains have an average thickness of at least 0.03 micrometer, although even thinner tabular grains can in principle be employed—e.g., as low as 0.01 -10micrometer.

The grain characteristics described above of the silver halide emulsions of this invention can be readily ascertained by procedures well known to those skilled in the art· As employed herein the term aspect ratio refers to the ratio of the diameter of the grain to its thickness. The diameter of the grain is in turn defined as the diameter of a circle having an area equal to the projected area of the grain as viewed in a photomicrograph or an electron micrograph of an emulsion sample. From shadowed electron micrographs of emulsion samples lt is possible to determine the thickness and diameter of each tabular grain and to identify those tabular grains having a thickness of less than 0.5 micrometer (or 0.3 micrometer) and a diameter of at least 0.6 micrometer. From this the aspect ratio of each such tabular grain can be calculated, and the aspect ratios of all the tabular grains in the sample meeting the thickness and diameter criteria can be averaged to obtain their average aspect ratio. By this definition the average aspect ratio is the average of individual tabular grain aspect ratios.

In practice it is usually simpler to obtain an average thickness and an average diameter of the tabular grains having a thickness of less than 0.5 or 0.3 micrometer and a diameter of at least 0.6 micrometer and to calculate the average aspect ratio as the ratio of these two averages. Whether the averaged individual aspect ratios or the averages of thickness and diameter are used to determine the average aspect ratio, within the tolerances of grain measurements possible, the average aspect ratios obtained do not significantly differ. The projected areas of the silver halide grains meeting the thickness and diameter criteria can be summed, the projected areas of the remaining silver halide grains in -lithe photomicrograph can be summed separately, and from the two sums the percentage of the total projected area of the silver halide grains provided by the tabular grains meeting the thickness and diameter critera can be calculated.

In the above determinations a reference tabular grain thickness of less than 0.5, preferably 0.3, micrometer was chosen to distinguish the uniquely thin tabular grains herein possible from thicker tabular grains which provide inferior emulsion properties. A reference grain diameter of 0.6 micrometer was chosen, since at lower diameters It is not always possible to distinguish tabular and nontabular grains in micrographs. The term projected area is used in the same sense as the terms projection area and projective area commonly employed in the art; see, for example, James and Higgins, Fundamentals of Photographic Theory, Morgan and Morgan, New York, p. 15.

The tabular grains can he of any silver halide crystal composition known to he useful in photography. In a preferred form offering a broad range of observed advantages the present invention employs high aspect ratio silver bromoiodide emulsions.

High aspect ratio tabular grain silver bromoiodide emulsions can be prepared by the following precipitation process: Into a conventional reaction vessel for silver halide precipitation equipped with an efficient stirring mechanism is introduced a dispersing medium. Typically the dispersing medium initially introduced into the reaction vessel is at least about 10 percent, prefer ably 20 to 80 percent, by weight, based on total weight, of the dispersing medium present in the silver bromoiodide emulsion at the conclusion of ·ι ι -12grain precipitation. Since dispersing medium can be removed from the reaction vessel by ultrafiltration during silver bromolodlde grain precipitation, as taught In Belgian Patent No. 886,645, corresponding to French Patent 2,471,620, it is appreciated that the volume of dispersing medium Initially present in the reaction vessel can equal or even exceed the volume of the silver bromoiodide emulsion present in the reaction vessel at the conclusion of grain precipitation. The dispersing medium initially introduced into the reaction vessel is preferably water or a dispersion of peptizer in water, optionally containing other ingredients, such as one or more silver halide ripening agents and/or metal dopants, more specifically described below. Where a peptizer is initially present, It is preferably employed in a concentration of at least 10 percent, most preferably at least 20 percent, of the total peptizer present at the completion of silver bromoiodide precipitation. Additional dispersing medium is added to the reaction vessel with the silver and halide ealts and can also be Introduced through a separate jet. It is common practice to adjust the proportion of dispersing medium, particularly to increase the proportion of peptizer, after the completion of the salt Introductions.

A minor portion, typically less than 10 percent, of the bromide salt employed in forming the silver bromolodlde grains is initially present in the reaction vessel to adjust the bromide ion concentration of the dispersing medium at the outset of silver bromolodlde precipitation. Also, the dispersing medium in the reaction vessel is initially substantially free of iodide ions, since the presence of iodide ions prior to concurrent introducton of silver and bromide salts favors the formation of thick and -1315 nontabular grains. As employed herein, the term substantially free of iodide ions as applied to the contents of the reaction vessel means that there are insufficient iodide ions present as compared to bromide ions to precipitate as a separate silver iodide phase. It is preferred to maintain the iodide concentration in the reaction vessel prior to silver salt introduction at less than 0.5 mole percent of the total halide ion concentration present. If the pBr of the dispersing medium is initially too high, the tabular silver bromoiodide grains produced will be comparatively thick and therefore of low aspect ratios. It is possible to maintain the pBr of the reaction vessel initially at or below 1.6, preferably below 1.5. On the other hand, if the pBr is too low, the formation of nontabular silver bromoiodide grains is favored. Therefore, it Is possible to maintain the pBr of the reaction vessel at or above 0.6, preferably above 1.1. As herein employed, pBr is defined as the negative logarithm of bromide ion concentration. Both pH and pAg are similarly defined for hydrogen and silver ion concentrations, respectively.

During precipitation silver, bromide, and iodide salts are added to the reaction vessel by techniques well known in the precipitation of silver bromoiodide grains. Typically an aqueous solution of a soluble silver salt, such as silver nitrate, is introduced into the reaction vessel concurrently with the introduction of the bromide and iodide salts.

The bromide and iodide salts are also typically introduced as aqueous salt solutions, such as aqueous solutions of one or more soluble ammonium, alkali metal (e.g., sodium or potassium), or alkaline earth metal (e.g., magnesium or calcium) halide salts. The silver salt is at least initially introduced into the 14reaction vessel separately from the iodide salt· The iodide and bromide salts can be added to the reaction vessel separately or as a mixture.

With the introduction of silver salt into the reaction vessel the nucleation stage of grain formation is initiated. A population of grain nuclei is formed which are capable of serving as precipitation sites for silver bromide and silver iodide as the introduction of silver, bromide, and iodide salts continues. The precipitation of silver bromide and silver iodide onto existing grain nuclei constitutes the growth stage of grain formation. The aspect ratios of the tabular grains formed according to this invention are less affected by iodide and bromide concentrations during' the growth stage than during the nucleation stage. It is therefore possible during the growth stage to increase the permissible latitude of pBr during concurrent introduction of silver, bromide, and iodide salts above 0.6, preferably in the range of from 0.6 to 2.2, most preferably from 0.8 to 1.6. It is, of course, possible and, in fact, preferred to maintain the pBr within the reaction vessel throughout silver and halide salt introduction within the initial limits, described above prior to silver salt introduction. This is particularly preferred where a substantial rate of grain nuclei formation continues throughout the introduction of silver, bromide, and iodide salts, such as in the preparation of highly polydispersed emulsions. Raising pBr values above 2.2 during tabular grain growth results in thickening of the grains, but can be tolerated in many instances while still realizing an average aspect ratio of greater than 8:1.

As an alternative to the introduction of silver, bromide, and iodide salts as aqueous soluΜ 1·*° -15tions, it is possible to introduce the silver, bromide, and iodide salts, initially or in the growth stage, in the form of fine silver halide grains suspended in dispersing medium. The grain size is such that they are readily Ostwald ripened onto larger grain nuclei, if any are present, once introj duced into the reaction vessel. The maximum useful I grain sizes will depend on the specific conditions t j. within the reaction vessel, such as temperature and the presence of solubilizing and ripening agents.

! Silver bromide, silver iodide, and/or silver bromoiodide grains can be introduced. (Since bromide and/or iodide are precipitated in preference to chloride, it is also possible to employ silver chlorobromide and silver chlorobromoiodide grains.) The silver halide grains are preferably very fine— e.g., less than 0.1 micrometer in mean diameter.

Subject to the pBr requirements set forth above, the concentrations and rates of silver, bromide, and iodide salt introductions can take any convenient conventional form. The Bilver and halide salts are preferably introduced in concentrations of from 0.1 to 5 moles per liter, although broader conventional concentration ranges, such as from 0.01 mole per liter to saturation, for example, are possible. Specifically preferred precipitation techniques are those which achieve shortened precipitation times by increasing the rate of silver and halide salt introduction during the run. The rate of silver and halide salt introduction can be increased either by increasing the rate at which the dispersing medium and the silver and halide salts are introduced or by increasing the concentrations of the silver and halide salts within the dispersing medium being introduced. It is specifically preferred to increase the rate of silver and halide salt introduction, but 541 25 -16to maintain the rate of introduction below the threshold level at which the formation of new grain nuclei is favored--!.e., to avoid renucleation, aa taught by U.S. Patents 3,650,757, 3,672,900, and 4,242,445, German OLS 2,107,118, European Patent Application 80102242, and Wey Growth Mechanism of AgBr Crystals in Gelatin Solution, Photographic Science and Engineering, Vol. 21, No. 1, January/ February 1977, p. 14, et. aeq. By avoiding the formation of additional grain nuclei after passing into the growth stage of precipitation, relatively monodispersed tabular silver bromoiodide grain populations can be obtained. Emulsions having coefficients of variation of less than about 30 percent can be prepared. As employed herein the coefficient of variation 1b defined as 100 times the standard deviation of the grain diameter divided by the average grain diameter. By intentionally favoring renucleation during the growth stage of preclpi20 tation, it is, of course, possible to produce polydispersed emusions of substantially higher coefficients of variation.

The concentration of iodide in the silver bromoiodide emulsions of the image transfer units of this invention can be controlled by the introduction of iodide salts. Any conventional iodide concentration can be employed· Even very small amounts of iodide—e.g., as low as 0.05 mole percent--are recognized in the art to be beneficial. In their preferred form the emulsions incorporate at least about 0.1 mole percent iodide. Silver iodide can be Incorporated into the tabular silver bromoiodide grains up to its solubility limit in silver bromide at the temperature of grain formation. Thus, silver iodide concentrations of up to about 40 mole percent in the tabular silver bromoiodide grains can be 17achleved at precipitation temperatures of 90°C. In practice precipitation temperatures can range down to near ambient room temperatures—e.g., about 30eC. It is generally preferred that precipitation be undertaken at temperatures in the range of from 40 to 80°C. For most photographic applications it is preferred to limit maximum iodide concentrations to about 20 mole percent, with optimum iodide concentrations being up to about 15 mole percent.

The relative proportion of iodide and bromide salts introduced into the reaction vessel during precipitation can be maintained in a fixed ratio to form a substantially uniform iodide profile in the tabular silver bromoiodide grains or varied to achieve differing photographic effects. Advantages in photographic speed and/or grain result from increasing the proportion of iodide in annular regions of high aspect ratio tabular grain silver bromoiodide emulsions as compared to central regions of the tabular grains. Iodide concentrations in the central regions of the tabular grains of from 0 to 5 mole percent, with at least one mole percent higher iodide concentrations in the laterally surrounding annular regions up to the solubility limit of silver iodide in silver bromide, preferably up to about 20 mole percent and optimally up to about 15 mole percent. In a variant form it is possible to terminate iodide or bromide and iodide salt addition to the reaction vessel prior to the termination of silver Balt addition so that excess bromide reacts with the silver salt. This results in a shell of silver bromide being formed on the tabular silver bromoiodide grains. Thus, it is apparent that the tabular silver bromoiodide grains of the image transfer units of the present Invention can exhibit substantially uniform or graded iodide concentration S 4 1 2 5 -18profiles and that the gradation can be controlled, && desired, to favor higher Iodide concentrations Internally or at or near the surfaces of the tabular silver bromoiodlde grains.

Although the preparation of the high aspect ratio tabular grain silver bromoiodlde emulsions has been described by reference to a process which produces neutral or nonammonlacal emulsions, the emulsions of the present invention and their utility are not limited by any particular process for their preparation. An alternate process Is an Improvement over U.S. Patent 4,150,994 and German OLS 2,985,655 and 2,921,077, wherein in a preferred form the silver iodide concentration in the reaction vessel is reduced below 0.05 mole per liter and the maximum size of the silver iodide grains Initially present in the reaction vessel is reduced below 0.05 micrometer.

High aspect ratio tabular grain silver bromide emulsions lacking iodide can be prepared by the process described in detail earlier modified to exclude iodide. High aspect ratio tabular grain silver bromide emulsions can alternatively be prepared following a procedure based on to that employed by Cugnac and Chateau, cited above. High aspect ratio silver bromide emulsions containing square and rectangular graine can be prepared by a process wherein cubic seed grains having an edge length of less than 0.15 micrometer are employed. While maintaining the pAg of the seed grain emulsion in the range of from 5.0 to 8.0, the emulsion is ripened in the substantial absence of nonhalide silver ion complexing agents to produce tabular silver bromide grains having an average aspect ratio of at least 8:1. Still other preparations of high aspect ratio tabular grain silver bromide emulsions lacking iodide are illustrated in the examples. 4 1 «ί b To illustrate other high aspect ratio tabular grain silver halide emulsions which can be employed in the practice of this invention, attention is directed to a process of preparing tabular silver chloride grains which are substantially internally free of both silver bromide and silver iodide. A double-jet precipitation process Is employed wherein chloride and silver salts are concurrently introduced into a reaction vessel containing dispersing medium in the presence of ammonia. During chloride ealt introduction the pAg within the dispersing medium is in the range of from 6.5 to 10 and the pH in the range of from 8 to 10. The presence of ammonia and high temperatures tends to cause thick grains to form. Therefore precipitation temperatures are limited to up to 60°C to produce high aspect ratio tabular grain silver chloride emulsions.

It is also possible to prepare tabular grains of at least 50 mole percent chloride having opposed crystal faces lying in {ill} crystal planes and, in one preferred form, at least one peripheral edge lying parallel to a <211> crystallographic vector in the plane of one of the major surfaces. Such tabular grain emulsions can be prepared by reacting aqueous silver and chloridecontaining halide salt solutions in the presence of a crystal habit modifying amount of an aminoazaindene and a peptizer having a thioether linkage.

Tabular grain emulsions can also be prepared wherein the silver halide grains contain chloride and bromide in at least annular grain regions and preferably throughout. The tabular grain regions containing silver chloride and bromide are formed by maintaining a molar ratio of chloride and bromide ions of from 1.6 to about 260:1 and the total concentration of halide ions in the reaction vessel in the range of 4 12 5 20from 0.10 to 0.90 normal during introduction of eilver, chloride, bromide, and, optionally, iodide salts into the reaction vessel. The molar ratio of silver chloride to silver bromide in the tabular grains can range from 1:99 to 2:3.

High aspect ratio tabular grain emulsions useful In the practice of this invention can have extremely high average aspect ratios. Tabular grain average aspect ratios can be Increased by increasing average grain diameters. This can produce sharpness advantages, but maximum average grain diameters are generally limited by granularity requirements for a specific photographic application. Tabular grain average aspect ratios can also or alternatively be Increased by decreasing average grain thicknesses. When silver coverages are held constant, decreasing the thickness of tabular grains generally Improves granularity as a direct function of Increasing aspect ratio. Hence the maximum average aspect ratios of the tabular grain emulsions of this invention are a function of the maximum average grain diameters acceptable for the specific photographic application and the minimum attainable tabular grain thicknesses which can be produced. Maximum average aspect ratios have been observed to vary, depending upon the precipitation technique employed and the tabular grain halide composition. The highest observed ' average aspect ratios, 500:1, for tabular grains with photographically useful average grain diameters, have been achieved by Ostwald ripening preparations of silver bromide grains, with aspect ratios of 100:1, 200:1, or even higher being obtainable by double-jet precipitation procedures. The presence of iodide generally decreases the maximum average aspect ratios realized, but the preparation of silver bromoiodide tabular grain emulsions having average aspect ratios -21of 100:1 or even 200:1 or more is feasible. Average aspect ratios as high as 50:1 or even 100:1 for silver chloride tabular grains, optionally containing bromide and/or iodide, can be prepared. The maximum average grain diameters of the high aspect ratio tabular grain emulsions are in all instances lees than 30 micrometers, preferably less than 15 micrometers, and optimally no greater than 10 micrometers.

Modifying compounds can be present during tabular grain precipitation. Such compounds can be initially in the reaction vessel or can be added along with one or more of the salts according to conventional procedures. Modifying compounds, such as compounds of copper, thallium, lead, bismuth, cadmium, zinc, middle chalcogens (i.e., sulfur, selenium, and tellurium), gold, and Group VIII noble metals, can be present during silver halide precipitation, as illustrated by U.S. Patents 1,195,432, 1,951,933, 2,448,060, 2,628,167, 2,950,972, 3,488,709, 3,737,313, 3,772,031, and 4,269,927, and Research Disclosure. Voi. 134, June 1975, Item 13452. Research Disclosure and its predecessor, Product Licensing Index, are publications of Industrial Opportunities Ltd.; Homewell, Havant; Hampshire, P09 1EF, United Kingdom. The tabular grain emulsions can be internally reduction sensi’ tized during precipitation, as illustrated by Moisar et al, Journal of Photographic Science, Voi. 25, 1977, pp. 19-27.

The individual silver and halide salts can he added to the reaction vessel through surface or subsurface delivery tubes by gravity feed or by delivery apparatus for maintaining control of the rate of delivery and the pH, pBr, and/or pAg of the reaction vessel contents, as illustrated by Culhane et al U.S. Patent 3,821,002, Oliver U.S. Patent 3,031,304 and Claes et al, Photographlsche Korrespondenz, Band 102, Number 10, 1967, p. 162. In order to obtain rapid distribution of the reactants within the reaction vessel, specially constructed mixing devices can be employed, as Illustrated by U.S. Patents 2,996,287, 3,342,605, 3,415,650, 3,785,777, 4,147,551, and 4,171,224, U.K. Patent Application 2,022,431A, German OLS 2,555,364 and 2,556,885, and Research Disclosure, Volume 166, February 1978, Item 16662.

In forming the tabular grain emulsions peptizer concentrations of from 0.2 to 10 percent by weight, based on the total weight of emulsion components in the reaction vessel, can be employed. It is common practice to maintain the concentration of the peptizer in the reaction vessel in the range of below about 6 percent, based on the total weight, prior to and during silver halide formation and to adjust the emulsion vehicle concentration upwardly for optimum coating characteristics by delayed, supplemental vehicle additions. It is possible that the emulsion as initially formed will contain from 5 to 50 grams of peptizer per mole of silver halide, preferably 10 to 30 grams of peptizer per mole of silver halide. Additional vehicle can be added later to bring the concentration up to as high as 1000 grams per mole of silver halide. Preferably the concentration of vehicle in the finished emulsion is above 50 grams per mole of silver halide. When coated and dried in forming a photographic element the vehicle preferably forms 30 to 70 percent by weight of the emulsion layer.

Vehicles (which Include both binders and peptizers) can be chosen from among those conven-23tionally employed in silver halide emulsions.

Preferred peptizers are hydrophilic colloids, which can be employed alone or in combination with hydrophobic materials. Suitable hydrophilic vehicles include substances Buch as proteins, protein derivatives, cellulose derivatives—e.g., cellulose esters, gelatin—e.g., alkali-treated gelatin (cattle bone or hide gelatin) or acid-treated gelatin (pigskin gelatin), gelatin derivatives—e.g., acetylated gelatin and phthalated gelatin. These and other vehicles are disclosed In Research Disclosure. Vol. 176, December 1978, Item 17643, Section IX. The vehicle materials, including particularly the hydrophilic colloids, as well as the hydrophobic materials useful in combination therewith can be employed not only in the emulsion layers of the photographic elements of this invention, but also in other layers, such as overcoat layers, interlayers and layers positioned beneath the emulsion layers.

Grain ripening can occur during the preparation of silver halide emulsions according to the present invention, and it is preferred that grain ripening occur within the reaction vessel during at least silver bromoiodide grain formation. Known silver halide solvents are useful in promoting ripening. For example, an excess of bromide ions, when present in the reaction vessel, is known to promote ripening. It is therefore apparent that the bromide salt solution run into the reaction vessel can itself promote ripening. Other ripening agents can also be employed and can be entirely contained within the dispersing medium in the reaction vessel before silver and halide salt addition, or they can be introduced into the reaction vessel along with one or more of the halide salt, silver salt, or peptizer. In still another variant the ripening agent 4 1 2 5 -24can be Introduced Independently during halide and silver salt additions. Although ammonia is a known ripening agent, it is not a preferred ripening agent for the silver bromoiodide emulelons of this inven° tion exhibiting the highest realized speedgranularity relationships. The preferred emulsions for use In the present Invention are non-ammoniacal or neutral emulsions.

Among preferred ripening agents are those containing sulfur. Thiocyanate salts can be used, such as the alkali metal salts, most commonly sodium and potassium thiocyanate, and ammonium thiocyanate salts. While any conventional quantity of the thiocyanate salts can be Introduced, preferred concentrations are generally from about 0.1 to 20 grams of thiocyanate salt per mole of silver halide. Illustrative prior teachings of employing thiocyanate ripening agents are found in U.S. Patents 2,222,264, 2,448,534 and 3,320,069. Alternatively, conventional thioether ripening agents, such as those disclosed in U.S. Patents 3,271,157, 3,574,628, and 3,737,313, can be employed.

The high aspect ratio tabular grain emulsions are preferably washed to remove soluble salts.

The soluble salts can be removed by well known techniques, such as by decantation, filtration, and/or chill setting and leaching, as illustrated by Research Disclosure, Vol. 176, December 1978, Item 17643, Section II. The emulsions, with or without sensitizers, can be dried and stored prior to use.

In the present invention washing is particularly advantageous in terminating ripening of the tabular grains after the completion of precipitation to avoid increasing their thickness, reducing their aspect ratio and/or excessively increasing their diameter. ·, - 5412s Although the procedures for preparing tabular silver halide grains described above will produce high aspect ratio tabular grain emulsions in which the tabular grains satisfying the thickness and diameter criteria for aspect ratio account for at least 50 percent of the total projected area of the total silver halide grain population, it is recognized that further advantages can be realized by increasing the proportion of such tabular grains present. Preferably at least 70 percent (optimally at least 90 percent) of the total projected area is provided by tabular silver halide grains meeting the thickness and diameter criteria. While minor amounts of nontabular grains are fully compatible with many photographic applications, to achieve the full advantages of tabular grains the proportion of tabular grains can be increased. Larger tabular silver halide grains can be mechanically separated from smaller, nontabular grains in a mixed population of grains using conventional separation techniques-e.g., sy using a centrifuge or hydrocyclone. An illustrative teaching of hydrocyclone separation is provided by U.S. Patent 3,326,641.

In accordance with established practices within the art it is possible to blend the high , aspect ratio tabular grain emulsions with each other or with conventional emulsions to satisfy specific emulsion requirements. For example, it is known to blend emulsions to adjust the characteristic curve of a photographic element to satisfy a predetermined aim. Blending can be employed to increase or decrease maximum densities realized on exposure and processing, to decrease or increase minimum density, and to adjust characteristic curve shape between its toe and shoulder. Conventional silver halide emulsions suitable for use in blending are illustrated by -26Research Disclosure. Vol. 176, December 1978, Item 17643, Paragraph I.

The present high aspect ratio tabular grain silver halide emulsions are preferably chemically sensitized. They can be chemically sensitized with active gelatin, as illustrated by Τ. H. James, The Theory of the Photographic Process, 4th Ed., Macmillan, 1977, pp. 67-76, or with sulfur, selenium, tellurium, gold, platinum, palladium, Iridium, osmium, rhodium, rhenium, or phosphorus sensitizers or combinations of these sensitizers, such as at pAg levels of from 5 to 10, pH levels of from 5 to 8 and temperatures of from 30 to 80°C, as Illustrated by Research Disclosure, Vol. 120, April 1974, Item 12008, Research Disclosure, Vol. 134, June 1975, Item 13452, U.S. Patents 1,623,499, 1,673,522, 2,399,083, 2,642,361, 3,297,447, and 3,297,446, U.K. Patent 1,315,755, U.S. Patents 3,772,031,3,761,267, 3,857,711, 3,565,633, 3,901,714 and 3,904,415 and U.K. Patent 1,396,696; chemical sensitization being optionally conducted ln the presence of thiocyanate compounds in concentrations of up to 2 mole percent, based on silver, as described in U.S. Patent 2,642,361; sulfur containing compounds of the type disclosed in U.S. Patents 2,521,926, 3,021,215, and 4,054,457. It is possible to sensitize chemically in the presence of finish (chemical sensitization) modifiers—that is, compounds known to suppress fog and increase speed when present during chemical sensitization, such as azaindenes, azapyridazines, azapyrimidines, benzothiazolium salts, and sensitizers having one or more heterocyclic nuclei. Exemplary finish modifiers are described in U.S. Patents 2,131,038, 3,411,914, 3,554,757, 3,565,631, 3,901,714, Canadian Patent 778,723, and Duffin Photographic Emulsion Chemistry. Focal Press (1966) , 27New York, pp. 138-143. Additionally or alternatively, the emulsions can be reduction sensitized— e.g., with hydrogen, as illustrated by U.S. Patents 3,891,446 and 3,984,249, by low pAg (e.g., less than ) and/or high pH (e.g., greater than 8) treatment or through the use of reducing agents, such as stannous chloride, thiourea dioxide, polyamines and amineboranes, as illustrated by U.S. Patent 2,983,609, Oftedahl et al Research Disclosure, Vol. 136, August 1975, Item 13654, U.S. Patents 2,518,698, 2,739,060, 2,743,182, 2,743,183, 3,026,203 and 3,361,564.

Surface chemical sensitization, including sub-surface sensitization, illustrated by U.S. Patents 3,917,485 and 3,966,476, is possible.

The high aspect ratio tabular grain silver halide emulsions can he spectrally sensitized. It is possible to employ spectral sensitizing dyes that exhibit absorption maxima in the blue and minus blue—i.e., green and red, portions of the visible spectrum. In addition, for specialized applications, spectral sensitizing dyes can he employed which improve spectral response beyond the visible spectrum. For example, the use of infrared absorbing spectral sensitizers is possible.

The high aspect ratio tabular grain silver halide emulsions can be spectrally sensitized with dyes from a variety of classes, including the polyroethine dye class, which includes the cyanines, merocyanlnes, complex cyanines and merocyanlnes (1·®·» tri-, tetra- and poly-nuclear cyanines and merocyanlnes), oxonols, hemloxonols, styryls, merostyryls and streptocyanines.

The cyanine spectral sensitizing dyes include, joined by a methine linkage, two basic heterocyclic nuclei, such as those derived from quinolinium, pyridinium, isoquinolinium, 3H-indolium, 412 b benz[e]lndollum, oxazolium, oxazolinium, thiazolium, thiazolinium, selenazolium, selenazolinium, imidazolium, imidazolinium, benzoxazolium, benzothiazolium0 benzoselenazollum, benzimidazolium, naphthoxazolium, naphthothiazolium, naphthoselenazolium, dihydronaphthothiazolium, pyrylium and lmidazopyrazlnlum quaternary salts.

The merocyanine spectral sensitizing dyes inelistej joined by a double bond or methine linkage, a basic hetere^ cyclic nucleus o£ the cyanine dye type and an acidic nucleus, such as can be derived from barbituric acid, 2-thiobarbituric acid, rhodanine, hydantoin, 2-thiohydantoin, 4-thiohydantoin, 2-pyrazolin-5-one, 2-isoxazolln-5-one, indan-1,3-dione, cyclohexane-1,315 dione, l,3-dioxane-4,6-dione, pyrazolin-3,5-dione, pentane-2,4-dione, alkylsulfonylacetonitrile, malononitrile, isoquinolin-4-one, and chroman-2,4dione.

One or more spectral sensitizing dyes may be used. Dyes with sensitizing maxima at wavelengths throughout the visible spectrum and with a great variety of spectral sensitivity curve shapes are known. The choice and relative proportions of dyes depends upon the region of the spectrum for which sensitivity is desired and upon the shape of the spectral sensitivity curve desired. Dyes with overlapping spectral sensitivity curves will often ' yield in combination a curve in which the sensitivity at each wavelength in the area of overlap is approx!30 mately equal to the sum of the sensitivities of the Individual dyes. Thus, it is possible to use combinations of dyes with different maxima to achieve a spectral sensitivity curve with a maximum between the sensitizing maxima of the individual dyes.

Combinations of spectral sensitizing dyes can be used which result in supersensitization—that -29is, spectral sensitization that is greater in eome spectral region than that from any concentration of one of the dyes alone or that which would result from the additive effect of the dyes. Supersensitization can be achieved with selected combinations of spectral sensitizing dyes and other addenda, Buch as stabilizers and antifoggants, development accelerators or inhibitors, coating aids, brighteners and antistatic agents. Any one of several mechanisms as well as compounds which can be responsible for supersensitization are discussed by Gilman, Review of the Mechanisms of Supersensitization, Photographic Science and Engineering, Vol. 18, 1974, pp. 418-430.

Spectral sensitizing dyes also affect the emulsions in other ways. Spectral sensitizing dyes can also function as antifoggants or stabilizers, development accelerators or inhibitors, and halogen acceptors or electron acceptors, as disclosed in U.S.

Patents 2,131,038 and 3,930,860.

Although native blue sensitivity of silver bromide or bromoiodide is usually relied upon in the art in emulsion layers intended to record exposure to blue light, significant advantages can be obtained by the use of spectral sensitizers, even where their principal absorption is in the spectral region to which the emulsions possess native sensitivity. For ’ example, it is specifically recognized that advantages can be realized from the use of blue spectral sensitizing dyes. Even when the emulsions of the invention are high aspect ratio tabular grain silver bromide and silver bromoiodide emulsions, very large increases in speed are realized by the use of blue spectral sensitizing dyes. Where it is intended to expose emulsions according to the present invention in their region of native sensitivity, advantages in -30sensltivity can be gained by Increasing the thickness of the tabular grains.

Useful blue spectral sensitizing dyes for high aspect ratio tabular grain silver bromide and silver bromoiodide emulsions can be selected from any of the dye classes known to yield spectral sensitizers. Polymethlne dyes, such as cyanines, merocyanines, hemlcyanlnes, hemloxonols, and merostyryls, are preferred blue spectral eensltizers. Generally useful blue spectral sensitizers can be selected from among these dye classes by their absorption characteristics--!.e. , hue. There are, however, general structural correlations that can serve as a guide in selecting useful blue sensitizers. Generally the shorter the methine chain, the shorter the wavelength of the sensitizing maximum. Nuclei also influence absorption. The addition of fused rings to nuclei tends to favor longer wavelengths of absorption. Substituents can also alter absorption charac20 teristics.

Among useful spectral sensitizing dyes for sensitizing silver halide emulsions are those referred to in Research Disclosure. Voi. 176, December 1978, Item 17643, Section III.

Conventional amounts of dyes can be employed in spectrally sensitizing the emulsion layers containing nontabular silver halide grains. To ' realize the full advantages of this invention it is preferred to adsorb spectral sensitizing dye to the tabular grain surfaces in an optimum amount—that is, in an amount sufficient to realize at least 60 percent of the maximum photographic speed attainable from the grains under possible conditions of exposure. The quantity of dye employed will vary with the specific dye or dye combination chosen as well as the size and aspect ratio of the grains. It is known 4 1 -31in the photographic art that optimum spectral sensitization is obtained with organic dyes at 25 to 100 percent or more of monolayer coverage of the total available surface area of surface sensitive silver halide grains, as disclosed, for example, in West et al, The Adsorption of Sensitizing Dyes in Photographic Emulsions, Journal of Phys. Chem., Vol 56, p. 1065, 1952; Spence et al, Desensitization of Sensitizing Dyes, Journal of Physical and Colloid Chemistry, Vol. 56, No. 6, June 1948, pp. 1090-1103; and Oilman et al U.S. Patent 3,979,213. Optimum dye concentration levels can be chosen by procedures taught by Mees, Theory of the Photographic Process, 1942, Macmillan, pp. 1067-1069.

Spectral sensitization can be undertaken at any stage of emulsion preparation heretofore known to be useful. Most commonly spectral sensitization is undertaken in the art subsequent to the completion of chemical sensitization. However, it is specifically recognized that spectral sensitization can be undertaken alternatively concurrent with chemical sensitization, can entirely precede chemical sensitization, and can even commence prior to the completion of silver halide grain precipitation, as taught by U.S. Patents 3,628,960 and 4,225,666. As taught by U.S. Patent 4,225,666, it is possible to distribute introduction of the spectral sensitizing dye into the emulsion so that a portion of the spectral sensitizing dye is present prior to chemical sensitization and a remaining portion is introduced after chemical sensitization. Unlike U.S. Patent 4,225,666, it is possible that the spectral sensitizing dye can be added to the emulsion after 80 percent of the silver halide has been precipitated. Sensitization can be enhanced by pAg adjustment, including cycling, during chemical and/or spectral sensitization. A specific 125 -32example of pAg adjustment Is provided by Research Disclosure, Vol. 181, May 1979, Item 18155.

It has been discovered quite unexpectedly that high aspect ratio tabular grain eilver halide emulsions can exhibit higher speed-granularity relationships when chemically and spectrally sensitized than have been heretofore realized using tabular grain silver halide emulsions and have been heretofore realized using silver halide emulsions of the highest known speed-granularity relationships. Best results have been achieved using minus blue (red and/or green) spectral sensitizing dyes.

In one preferred form, spectral sensitizers can be incorporated in the present emulsions prior to chemical sensitization. Similar results have also been achieved in some Instances by introducing other adsorbable materials, such as finish modifiers, into the emulsions prior to chemical sensitization.

In another approach, which can be practiced in combination with the above approaches or separately thereof, it is preferred to adjust the concentration of silver and/or halide salts present immediately prior to or during chemical sensitization. Soluble silver salts, such as silver acetate, silver trifluoroacetate, and silver nitrate, can be introduced as well as silver salts capable of precipitating onto the grain surfaces, such as silver thiocyanate, silver phosphate, silver carbonate, and the like. Fine silver halide (i.e., silver bromide, 3Q iodide, and/or chloride) grains capable of Ostwald ripening onto the tabular grain surfaces can be introduced. For example, a Llppmann emulsion can be Introduced during chemical sensitization. Chemical sensitization of spectrally sensitized high aspect ratio tabular grain emulsions can be effected at one or more ordered discrete sites of the tabular 4 12 3 -33grains. It is believed that the preferential adsorption of spectral sensitizing dye on the crystallographic surfaces forming the major faces of the tabular grains allows chemical sensitization to occur selectively at unlike crystallographic surfaces of the tabular grains.

The preferred chemical sensitizers for the highest attained speed-granularity relationships are gold and sulfur sensitizers, gold and selenium sensitizers, and gold, sulfur, and selenium sensitizers. Thus, in a preferred form, the high aspect ratio tabular grain silver bromoiodlde emulsions as defined herein contain a middle chalcogen, such as sulfur and/or selenium, which may not be detectable, and gold, which is detectable. The emulsions can also contain detectable levels of thiocyanate, although the concentration of the thiocyanate in the final emulsions can be greatly reduced by known emulsion washing techniques. In various of the preferred forms indicated above the tabular silver bromoiodlde grains can have another silver salt at their surface, such as silver thiocyanate, silver chloride, or silver bromide, although the other silver salt may be present below detectable levels.

Although not required to realize all of their advantages, the present emulsions are preferably, in accordance with prevailing manufacturing practices, optimally chemically and spectrally sensitized. That is, they preferably achieve speeds of at least 60 percent of the maximum log speed attainable from the grains in the spectral region of sensitization under the possible conditions of use and processing. Log speed is herein defined as 100 (1-log E), where E is measured in meter-candle35 seconds at a density of 0.1 above fog. Once the silver halide grains of an emulsion have been charac5 4 12 5 eeri&ed, Sc is possible to estimate from further product analysis and performance evaluation whether an emulsion layer of a product appears to be optimally chemically and spectrally sensitized in rela5 tion to comparable commercial offerings of other manufacturers.

Silver Image Transfer In perhaps the simplest application of the Invention, a high aspect ratio tabular grain silver halide emulsion as described above is substituted for the silver halide emulsion layer in a conventional silver image transfer photographic film unit. In addition to a conventional photographic support on which the tabular silver halide emulsion layer is located, the silver image transfer film unit preferably includes a silver receiving layer comprised of silver halide physical developing nuclei or other silver precipitating agents. To produce a transferred silver image the silver receiving and emulsion layers are juxtaposed, and a processing solution containing a silver halide solvent is released to contact the emulsion and receiving layers after imagewise exposure of the tabular grain emulsion layer.

A wide variety of nuclei or silver precipitating agents can be utilized in the receiving layers used in silver image transfer processes. Such nuclei are Incorporated into conventional photographic organic hydrophilic colloid layers such as gelatin and polyvinyl alcohol layers and include such physical nuclei or chemical precipitants as (a) heavy metals, especially in colloidal form and salts of these metals, (b) salts, the anions of which form silver salts less soluble than the silver halide of the photographic emulsion to be processed, and (c) nondlffusible polymeric materials with functional -35groups capable of combining with and insolubilizing silver ions.

Typical useful Bilver precipitating agents include sulfides, selenides, polysulfides, polyselen5 ides, thiourea and its derivatives, mercaptnns, stannous halides, silver, gold, platinum, palladium, mercury, colloidal silver, aminoguanidine sulfate, aminoguanidine carbonate, arsenous oxide, sodium stannite, substituted hydrazines, xanthates, and the like. Poly(vinyl mercaptoacetate) is an example of a suitable nondiffusing polymeric silver precipitant. Heavy metal sulfides such as lead, silver, zinc, aluminum, cadmium and bismuth sulfides are useful, particularly the sulfides of lead and zinc alone or in an admixture or complex salts of these with thioacetamide, dithiooxamide, or dithiohiuret. The heavy metals and the noble metals particularly in colloidal form are especially effective. Other silver precipitating agents will occur to those skilled in the present art.

The processing solution can take the form of any conventional silver halide developer containing a silver halide solvent. Illustrative of silver halide solvent containing processing solutions useful in providing transferred silver image in combination with these photographic image transfer film units are those disclosed hy U.S. Patents 2,352,014, 2,543,181, ' 2,861,885, 3,020,155, and 3,769,014.

In silver image transfer film units the emulsion and receiving layers can be related in any convenient conventional manner. The emulsion layer or layers and the receiving layer can be located on the same support or different supports. When the receiving layer is coated on a separate support, the layer and the support, together with any additional layers present, are collectively termed a receiver.

E> 41 S 3 36In a common preferred peel-apart format the emulsion layer bearing support is opaque and the receiver support ls reflective (e.g., white) or is provided with a reflective layer beneath the receiving layer.

Exposure occurs before juxtaposing the receiver and emulelon layer for processing. In a common Integral format both the receiver support and the emulsion layer support are transparent and a reflective (e.g.o white) background for viewing the silver image is provided by overcoating the receiving layer with a reflective pigment layer or incorporating the pigment in the processing solution. A preferred receiver also commonly includes a neutralizing layer (also referred to as a pH lowering or acid layer) for terminating development and at least one timing layer (also sometimes referred to as a spacer or inert spacer layer.) Neutralizing and timing layers can alternatively be located on the emulsion bearing support. The receiver and emulsion bearing supports are preferably integral—that ls, joined during exposure, processing, and viewing, but ln various formats they can be separate during exposure, viewing, and/or a portion of processing. Exemplary materials for use ln the neutralizing and timing layers are described in Research Disclosure, Vol. 123, July 1974, Item 13331, and Vol. 135, Item 13525, July 1975. Details of reflective layers and support materials, including incorporated ultraviolet absorbers and optical brighteners, are disclosed ln Research Disclosure, Vol. 151, November 1976, Item 15162. Specifically preferred transparent eupport materials are poly(ethylene terephthalate) and cellulose esters. Preferred reflective supports are resin-coated paper supports.

In a preferred embodiment, the film units of this Invention contain an alkaline processing compo-37sition and means for its containment and discharge within the film unit. A preferred means is a rupturable container (e.g., pod) which is adapted to be positioned during processing of the film unit so that a compressive force applied to the container by pressure-applying members, such as found in a camera designed for in-camera processing, will effect a discharge of the container's contents within the film unit. However, other methods of introducing the alkaline processing composition can be employed. Processing alternatives are further illustrated by Research Disclosure, Item 17643, cited above, Paragraphs XXIII, C and G.

Dye Image Transfer The photographic image transfer film units of the invention can alternatively provide a transferred dye image. Except as noted, the features of dye image transfer film units can be identical to those of the silver image transfer film units discussed above and are not redescribed in detail* A silver image transfer film unit can be converted to a dye image transfer film unit merely by replacing the silver receiving layer with a dye receiving layer and incorporating a dye-image25 providing material in the silver halide emulsion layer or in an adjacent layer. Since silver halide is not normally transferred to the receiving layer of ' a dye image transfer film unit, silver halide solvent is not an essential component of the alkaline processing solution of a dye image transfer film unit. It is possible to construct a dye image transfer film unit according to the present invention capable of producing a monochromatic transferred dye image by locating on a support a Bingle dye-providing layer unit comprised of a tabular silver halide emulsion layer as described above and at least one 54135 -38dye-image-providlng material in the emulsion layer Itself or in an adjacent layer of the layer unit. In addition, the dye image transfer film unit Is comprised of a dye receiving layer capable of mordanting or otherwise immobilizing dye migrating to it. To produce a transferred dye image the tabular emulsion layer is Imagewise exposed and an alkaline processing solution is brought into contact with the emulsion layer with the dye receiving and emulsion layers juxtaposed. In a particularly advantageous application for monochromatic transferred dye Images a combination of dye-image-providing materials is employed to provide a neutral transferred dye image. This image can be used to supplement the transferred silver image or to replace it entirely in providing & viewable black-and-white image. Of course, monochromatic transferred dye Images of any hue can be produced, if desired.

Multicolor dye image transfer film units of this invention employ three dye-providing layer units: (1) a cyan-dye-providing layer unit comprised of a red-sensitive silver halide emulsion having associated therewith a cyan-dye-image-providing material, (2) a magenta-dye-providing layer unit comprised of a green-sensitive silver halide emulsion having associated therewith a magenta-dye-imageproviding material, and (3) a yellow-dye-providing ' layer unit comprised of a blue-sensitive silver halide emulsion having associated therewith a yellow30 dye-image-providing material. Each of the dyeproviding layer units can contain one, two, three, or more separate silver halide emulsion layers as well as the dye-image-providing material, located in the emulsion layers or in one or more separate layers forming part of the dye-providing layer unit. Any one or combination of the emulsion layers can be high 4 ί 2 5 -39aspect ratio tabular grain silver halide emulsion layers as described above. In a preferred form of the invention at least the fastest emulsion layers in the cyan and magenta-dye-providing layer units are high aspect ratio tabular grain silver halide emulsions as described above. At least the fastest emulsion layer in the yellow-dye-image-providing layer unit is also preferably comprised of a high aspect ratio tabular grain silver halide emulsion as described above, but the use of other, conventional silver halide emulsions in the yellow-dye-providing layer unit together with high aspect ratio tabular grain silver halide emulsions in the cyan and magenta-dye-providing layer units is also possible.

Depending upon the dye-image-providing material employed, it can be incorporated in the silver halide emulsion layer or in a separate layer associated with the emulsion layer. The dye-imageproviding material can be any of a number known in the art, such as dye-forming couplers, dye developers, and redox dye-releasers, and the particular one employed will depend on the nature of the element or film unit and the type of image desired. Materials useful in diffusion transfer film units contain a dye moiety and a monitoring moiety. The monitoring moiety, in the presence of the alkaline processing solution and as a function of silver halide development, is responsible for a change in mobility of the dye moiety. These dye-image-providing materials can be initially mobile and rendered immobile as a function of silver halide development, as described in U.S. Patent 2,983,606. Alternatively, they can be initially immobile and rendered mobile, in the presence of an alkaline processing solution, as a function of silver halide development. This latter class of materials include redox dye-releasing 54135 compounds. In such compounds, the monitoring group is a carrier from which the dye ls released as a direct function of silver halide development or as an inverse function of silver halide development.

Compounds which release dye as a direct function of silver halide development are referred to as negative-working release compound, while compounds which release dye as an Inverse function of silver halide development are referred to as positive10 working release compounds.

A preferred class of positive-working release compounds are the nitrobenzene and quinone compounds described in U.S. Patent 4,139,379. In these compounds the dye moiety is attached to an electrophilic cleavage group, such as a carbamate group, ortho to the nitro group or the quinone oxygen, and is released upon reduction of the compound by an electron donor compound contained in the element or the processing composition. In areas where the electron donor compound is consumed by developing silver halide, no dye moiety is released.

Other useful positive-working release compounds ere the hydroquinones described in U.S. Patent 3,980,479 and the benzisoxazolone compounds described in U.S. Patent 4,199,354.

A preferred class of negative-working release compounds are the ortho or para eulfonamido' phenols and naphthols described in U.S. Patents 4,054,312, 4,055,428, and 4,076,529. In these compounds the dye moiety ls attached to a sulfonamido group which is ortho or para to the phenolic hydroxy group and is released by hydrolysis after oxidation of the sulfonamido compound during development.

Another preferred class of negative-working release compounds are ballasted dye-forming (chromogenic) or nondye-forming (nonchromogenic) couplers 4 -41having a mobile dye attached to a coupling-off site. Upon coupling with an oxidized color developing agent, such as a para-phenvlenediamine. the mobile dye is displaced so that it can transfer to a receiver. The use of such negative-working dye image providing compounds is illustrated by U.S. Patents 3,227,550 and 3,227,552, and U.K. Patent 1,445,797.

Since the silver halide emulsions employed in the image transfer film units of the present invention are negative-working, the use of negativeworking release compounds will produce negative transferred dye images. In order to obtain a positive transferred dye image using negative-working release compounds, known image reversing film unit and processing variations can be employed, such as illustrated by U.S. Patents 3,998,637 and 4,258,117.

Any material can be employed as the dye receiving layer in the film units of this invention as long as It will mordant or otherwise immobilise the dye which diffuses to it. The optimum material chosen will, of course, depend upon the specific dye or dyes to be mordanted. The dye receiving layer can also contain ultraviolet absorbers to protect the dye image from fading due to ultraviolet light, brighteners, and similar materials to protect or enhance the dye image. A polyvalent metal, preferably immobilized by association with a polymer, can be placed in or adjacent the receiving layer to chelate the transferred image dye, as taught by U.S.

Patents 4,239,849 and 4,241,163. Useful dye receiving layers and materials for their fabrication are disclosed In Research Disclosure Item 15162 and U.S. Patent 4,258,117.

The alkaline processing composition employed in the dye image transfer film units can be an aqueous solution of an alkaline material, such as an 4254125 alkali metal hydroxide or carbonate (e.g., sodium hydroxide or sodium carbonate) or an amine (e.g., diethylamine). Preferably the alkaline composition has a pH in excess of 11. Suitable materials for use in such compositions are disclosed in Research Disclosure, Item 15162, cited above.

A developing agent is preferably contained in the alkaline processing composition, although it can be contained in a separate solution or process sheet, or it can be incorporated in any processing solution penetrable layer of the film unit. When the developing agent is separate from the alkaline processing composition, the alkaline composition serves to activate the developing agent and provide a medium in which the developing agent can contact and develop silver halide.

A variety of silver halide developing agents can be used in processing the film units of this Invention. The choice of an optimum developing agent will depend on the type of film unit with which it is used and the particular dye image-providing material employed. Suitable developing agents can be selected from such compounds as hydroquinone, aminophenols (e.g., N-methylaminophenol), l-phenyl-3-pyrazoli25 dinone, l-phenyl-4,4-dimethyl-3-pyrazolidinone, l-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidinone, and Ν,Ν,Ν’,N’-tetramethyl-£-phenylenediamine. The nonchromogenic developers in this list are preferred for use in dye transfer film units, Since they have a reduced propensity to stain dye image-receiving layers. All of these same developing agents are also useful in the silver transfer film units.

Tabular Grain Influence on Processing Rates One of the surprising advantages of the present invention is the rapidity with which the transferred image becomes viewable. The rapid 412 5 -43accessibility of the viewable transferred image is directly attributable to the presence of one or more high aspect ratio tabular grain silver halide emulsions as defined herein. Without being bound by any particular theory, it is believed that the geometrical configuration of the tabular eilver halide grains accounts for rapid access to the transferred images. Tabular grain geometry provides a very high surface area to the silver halide grains as compared to their volume, and this in turn is believed to Influence their rate of development. In image transfer processes it is the imagewise variation in development of the silver halide grains as a function of their imagewise exposure which modulates the trans15 ferred image. In some systems, such as those employing negative-working release compounds, described above, silver halide development is directly related to transferred imaging materials.

The faster the silver halide develops, the faster the imaging materials are made available for viewing. In other systems, such as the silver image transfer and dye image transfer systems employing positive-working release Compounds, described above, silver halide development is or controls a competing reaction that retards transfer of image materials and accounts for minimum density in the viewed image. When silver halide development is accelerated, the mechanisms accounting for transferred imaging materials with which silver halide development is competing and thereby modulating can also be accelerated.

The use of tabular grains to reduce the time elapsed between the commencement of processing and obtaining a viewable transferred image—i.e., access time—in no way precludes the use of conventional image transfer film unit features which are known to reduce access time. When the present invention is -44employed in combination with conventional features for reducing access time at least additive results ean be normally expected* In addition, there are still other features unique to the image transfer film units of this invention which can contribute to reduced access time.

A second advantage attainable with the image eransfer film units of the present invention containing at least one high aspect ratio tabular grain silver halo19 iodide (preferably silver bromoiodide) emulsion layer is the reduced variance of the transferred image as a function of temperature. This reduced variance in the transferred image is a direct result of employing one or more tabulargrain emulsion layers, as described above, wherein the „5 tabular grains contain at least about 2 mole percent iodide. Without being bound by any particular theory, it is believed that the tabular silver haloiodide grains show less variation in their development rates as a function of temperature. In image transfer systems in which silver haloiodide development is directly related to transferred imaging materials this reduced temperature dependence of tabular silver haloiodide grains results directly in reduced variance in the viewed image. In systems relying also upon competing mechanisms for generation of the viewable image, reduced silver haloiodide development variance as a function of temperature can reduce variance in the transferred image to the extent it is attributable to silver halide development variance and to the extent it complements temperature variances in the competing mechanisms employed in imaging.

Tabular Grain Influence on Silver Coverages It has been surprisingly observed that the dye image transfer film units of the present inven35 tion exhibit substantially higher photographic speeds at lower silver coverages than comparable conventional dye image transfer film units. It is well -45known to those skilled in the art that silver coverages below a threshold level result in reduction of observed photographic speed as determined from a transferred dye image. While speed decreases when 3 the silver coverages of silver halide emulsions are reduced, the speed reduction is much more gradual when high aspect ratio tabular grain emulsions are employed, thereby allowing lower silver coverages.

Acceptable photographic speeds in conven10 tional multicolor image transfer film units are commonly obtained by employing silver halide in each of the yellow, magenta, and cyan-dye-providing layer units at silver coverages of about 1000 mg/m2 or higher. It is possible to employ substantially lovrer 15 silver coverages in the practice of this invention. When the silver halide graine of the emulsion in the yellow, magenta, or cyan-dye-providing layer unit of the dye image transfer film unit of this invention are tabular as described above, the emulsions can be 20 efficiently employed at silver coverages of from 150 to 750 mg/m2, preferably from 200 to 700 mg/m2, and optimally from 300 to 650 mg/m2. At higher and lower silver coverages higher and lower photographic speeds, respectively, will be 25 realized, the stated ranges reflecting an efficient balance of photographic performance and silver coverages for most imaging applications. When the image transfer film unit contains a single dyeproviding layer unit containing tabular silver halide 30 grains, then these coverages are applicable to that of a single dye-providing layer unit. When all three dye-providing layer units contain tabular silver halide emulsions, at least additive silver savings can be realized.

Layer Order Arrangements The image transfer film units of this invention can employ any layer order arrangement -46heretofore known to be useful in conventional image transfer film units having one or more radiationsensitive silver halide emulsion layers. In addition, the distinctive properties of tabular silver halide emulsions make possible highly advantageous layer order arrangements not heretofore known to the art. The following specific layer order arrangements are merely illustrative, many other arrangements being possible, too: To avoid unnecessary repetition, discussion of each successive layer order arrangement is directed to features which are distinctive as compared to prior layer order arrangements. Stated another way, features and advantages shared by the layer order arrangements are fully discussed only in connection with the first layer order arrangement in which they appear. If a feature or advantage is not shared by a subsequently described layer order arrangement, this is specifically pointed out.

Layer Order Arrangement I A Laminate and Peel-Apart Silver Image Transfer Film Unit of the Invention _Reflective Support _Silver Receiving Layer Imagewise Exposure _+_ Tabular Silver Halide Emulsion Layer _Support_ Layer Order Arrangement I is illustrative of a conventional laminate and peel-apart silver image transfer film unit. Upon imagewise exposure, the negative-working tabular silver halide emulsion layer produces a developable latent image. The silver receiving layer containing precipitation nuclei is laminated and an alkaline processing composition, not shown, is released between the silver receiving layer 541‘ -47and emulsion layer following exposure. Development of the tabular silver halide grains bearing latent image sites occurs upon contact with the alkaline proces- sing composition. Silver halide solvent contained in the processing composition dissolves the silver halide grains which are not developed. The dissolved silver halide migrates to the silver receiving layer where physical development occurs. A positive transferred silver image is produced in the silver receiving layer. Processing is terminated by peeling the reflective support having the silver receiving layer coated thereon from the remainder of the image transfer film unit.

While the layer order arrangement is conven15 tional and employs conventional materials except for the tabular silver halide emulsion layer, significantly superior results are obtainable. The access time required to produce a viewable silver image in the receiving layer is substantially reduced. It is believed that this can be attributed to distinct advantages offered by tabular silver halide grains. First, tabular silver halide grains as defined herein develop at a faster rate than comparable nontabular silver halide grains. At least of equal importance is that tabular silver halide grains according to this Invention can be dissolved at a substantially higher rate than comparable nontabular grains.

Although the two processing mechanisms of development and solubilization can entirely account for the more rapid image access in Layer Order Arrangement 1, a third characteristic of tabular grain emulsions can also be used to further reduce image access times. While high aspect ratio tabular grain emulsion layers can be coated in the same layer thicknesses as conventional emulsions without departing from the teachings of this invention, it is 4854125 preferred to thin the high aspect ratio tabular grain silver halide emulsion layers as compared to corresponding conventional silver halide emulsion layers.

In conventional silver halide emulsions employed in image transfer the emulsion layer thickness ls substantially greater than the average grain diameter calculated from the grain projected areas. Further, the thickness of the layer is large enough to accommodate not just the average grains, but the largest grains present. Thus, if the largest nontabular silver halide grains in a silver halide emulsion layer of an image transfer film unit exhibit an average diameter of from 1 to 2 micrometers, the emulsion layer will be at least 1 to 2 micrometers in thickness and will usually be substantially greater in thickness. On the other hand, it is possible to employ tabular silver halide grains as defined herein having diameters based on average projected areas of 1 to 2 micrometers and often still larger while the thickness of the tabular grains is less than 0.5 or even 0.3 micrometer. Thus, in an exemplary emulsion in which the tabular grains have an average thickness of 0.1 micrometer with an average diameter of 1 to 2 micrometers, the silver halide emulsion layer thick25 ness can easily be reduced substantially below 1 micrometer. The present high aspect ratio tabular grain emulsion layers are preferably less than 4 times the average thickness of the tabular grains and are optimally less than twice the average thickness of the tabular grains. Significant reductions in the thickness of the high aspect ratio tabular grain silver halide emulsion layers can contribute to reduction in image access times by reducing the lengths of diffusion paths. Further, reduction of the lengths of diffusion paths can also contribute to improvements in sharpness. 4125 -49Layer Order Arrangement II An Integral Silver Image Transfer Film Unit of the Invention View + _Transparent Support_ _Neutralizing Layer_ _Timing Layer_ Silver Receiving Layer_ Reflective Layer _Opaque Layer_ Tabular Silver Halide Emulsion Layer Alkaline Processing Compost15 _tion 4- Opacifler_Transparent Support + Imagewise Exposure Layer Order Arrangement II is a conventional integral format silver image transfer film unit, differing from the art solely by the incorporation of the tabular silver halide emulsion layer. Layer Order Arrangement II combines all of the advantages provided by the tabular silver halide emulsion layer, discussed above in connection with Layer Order Arrangement I and additionally provides the art recognized advantages of an integral format. Because ' of the presence of an opacifler in the alkaline processing solution, it is necessary to place the alkaline processing solution in the location indicated after imagewise exposure. Once in place the opacifler prevents further exposure of the emulsion layer, as can occur, for example, when the image transfer film unit is removed from a camera. Proces35 sing is terminated by the timing and neutralizing layers. 54135 -50Laver Order Arrangement III An Integral Monochromatic Dye Image Transfer Film Unit of the Invention View + _Transparent Support_ _Dye Receiving Layer_ _Reflective Layer_ __Opaque Layer Tabular Silver Halide Emulsion Layer With Dye-Image Providing Material Alkaline Processing Composl_tion + Opacifier_ Timing Layer_ _Neutralizing Layer Transparent Support + Imagewise Exposure Initially the alkaline processing composition containing opacifier is not present in the location shown. Therefore, upon imagewise exposure light strikes the tabular silver halide emulsion layer. This produces a latent image corresponding to light-struck areas of the emulsion layer. To initiate processing the alkaline processing composition is placed in the position shown. Usually, but ' not necessarily, the image transfer film unit is removed from the camera in which lt is exposed Immediately following placement of the alkaline processing composition and opacifier. The opacifier and opaque layer together prevent further exposure of the emulsion layer. Upon development, a mobile dye or dye precursor is released from the emulsion layer. When the dye-image-providing material is a positive-working release compound, it is released in -51initially unexposed areas of the emulsion layer; when the dye-image-providing material is a negativeworking release compound, the converse is true. The mobile dye or dye precursor penetrates the opaque layer and the reflective layer and ls mordanted or otherwise immobilized in the dye receiving layer to permit viewing through the uppermost transparent support. Processing Ib terminated by the timing and neutralizing layers.

It is possible to convert Layer Order Arrangements I and 11 to monochromatic dye image transfer film units by including a dye-imageproviding material in the high aspect ratio tabular grain silver halide emulsion layers, substituting a dye receiving layer for the silver receiving layer, and employing an alkaline processing composition appropriate for dye image transfer. Thus, in terms of possible layer sequences, monochromatic transferred dye images could be readily obtained by modifying Layer Order Arrangements I and II. If these modifications were undertaken, Layer Order Arrangement III would still differ from Layer Order Arrangement II in the location of the timing and neutralizing layers. The positions of the timing and neutralizing layers in Layer Order Arrangements 11 and III are interchangeable. Although not specifically illustrated, lt is possible to combine both silver and dye image transfer in a single image transfer film unit, since the two are compatible. A useful application of such a combined image transfer film unit arises where the silver density is being supplemented by dye, allowing low silver coverages to be realized. Except for combined silver and dye imaging, dissolving of undeveloped silver halide is not normally undertaken in Layer Order Arrangement III and is not needed to obtain reduced transferred S4125 Image access times* The presence of dye-imageproviding material in the high aspect ratio tabular grain silver halide emulsion layer can significantly increase the thickness of this layer. As has been previously discussed, it is recognized that silver halide coverages can be significantly reduced in the high aspect ratio tabular grain silver halide emulsion layer while retaining acceptable photographic speed levels in dye image transfer film units. Layer Order Arrangement 111 is capable of providing this advantage. -53Layer Order Arrangement IV An Integral Multicolor Dye Image Transfer Film Unit of the Invention Imagewise Exposure + _Transparent Support_ _Neutralizing Layer_ _Timing Layer_ Alkaline Processing Composi_tion 4- Opacifier_ Transparent Overcoat Blue-sensitive Tabular Silver Halide Emulsion Layer Yellow Pye-Image-Providing Material Layer Interlayer With Scavenger Green-sensitive Tabular Silver Halide Emulsion Layer Magenta Dye-Image-Provldlng Material Layer Interlayer With Scavenger Red-sensitive Tabular Silver Halide Emulsion Layer Cyan Dye-Image-Providing Material Layer _Opaque Layer_ _Reflective Layer_ __Dye Receiving Layer_ Transparent Support ♦ View Layer Order Arrangement IV is essentially similar to Layer Order Arrangement III, but is modified to contain three separate dye-providing layer units, each comprised of one high aspect ratio tabular grain silver halide emulsion layer and one dye-image-providing material layer, instead of the single dye-image-providing material containing high 5413S aspect ratio tabular grain silver halide emulsion layer of Layer Order Arrangement III. Whether or not the dye-image-providing material ia placed in the emulsion layer itself or in an adjacent layer in Layer Order Arrangements III and IV is a matter of choice, either arrangement being feasible* To prevent color contamination of adjacent dye-providing layer units, an interlayer containing a scavenger is positioned between dye-providing layer units. The use of scavengers in interlayers is taught by U.S. Patent 2,336,327 and in the dyeproviding layer units themselves by U.S. Patent 2,937,086. The use of scavengers in either or both locations is possible.

In a modification of Layer Order Arrangement IV it is possible to eliminate the interlayers.

Since the high aspect ratio tabular grain silver halide emulsion layers can be quite thin in comparison to conventional silver halide emulsion layers typically employed in multicolor dye image transfer film units, each high aspect ratio tabular grain silver halide emulsion layer can be coated between two magenta dye-image-providing material layers. The two magenta-dye-image providing material layers preferably do not contain scavenger, but can contain scavenger, if desired, depending upon the sensitivity of the imaging application to color contamination and the specific choice of dye-image-providing materials. Providing dye-image-providing layers adjacent both sides of each high aspect ratio tabular grain silver halide emulsion layer provides a close association between the dye-image-providing materials and the silver halide. This arrangement is most advantageous where the dye-image-providing materials of each dye-providing layer unit is initially colorless or at least shifted in hue so that the dye-imageί) J. 2 3 -55providing material is not adsorbing in the spectral region to which the Bilver halide is intended to respond.

Where the yellow dye-image-providing material is initially yellow, it acte, together with the blue-sensitive high aspect ratio tabular grain silver halide emulsion layer, to intercept blue light that would otherwise reach the green and red-sensitive θ high aspect ratio tabular grain silver halide emulsion layers. Where the green and red-sensitive silver halide emulsion layers employ silver bromide or silver bromoiodide grains in a conventional multicolor dye image transfer film unit, it is L5 necessary to intercept blue light to avoid color contamination of the green and red-sensitive emulsion layers. However, where the green and red-sensitive emulsions are of high aspect ratio tabular grains as defined herein, it is unnecessary to filter blue light so that it is attenuated before reaching these emulsion layers. Thus, where the yellow dye-imageproviding material is initially colorless or at least nonabsorbing in the blue region of the spectrum, it is still possible for accurate color reproduction to occur in the magenta and cyan dye-providing layer units without any necessity of interposing a yellow filter layer. Further, as is more fully described below, the dye-providing color-forming layer units can be located in any desired order. 4 i. 3 5 -56Layer Order Arrangement V An Integral Multicolor Dye Image Transfer Film Unit of the Invention _Opaque Support_ Yellow Dye-Image-Provldlng Material Laver Blue-sensitive Tabular Silver Halide Emulsion Layer _Interlayer With Scavenger_ Cyan Dye-Image-Provldlng Material Layer Red-sensitive Tabular Silver _Halide Emulsion Layer_ _Interlayer With Scavenger_ Magenta Dye-Image-Providing Material Layer Green-sensitive Tabular Silver Halide Emulsion Layer _Transparent Overcoat_ Alkaline Processing Composition With Reflective Material and Indicator Dye _Dye Receiving Layer_ _Timing Layer_ _Neutralizing Layer_ Transparent Support + View and Imagewise Exposure In Layer Order Arrangement V during imagewise exposure the alkaline processing composition containing the reflective material and indicator dye is not in the position shown, but is released to the position shown after exposure to permit processing. The indicator dye exhibits a high density at the elevated levels of pH under which processing occurs. It thereby protects the silver halide emulsion layers from further exposure if the film unit is removed from a camera during processing. Once the neutralizing layer reduces the pH within the film unit to - 5 4.25 -5710 terminate processing, the indicator dye reverts to an essentially colorless form. The alkaline processing composition also contains a reflective material, which provides a background for viewing the transferred dye image after processing.

Layer Order Arrangement V is illustrative of the application of the invention to an integral multicolor dye image transfer film unit format in which imagewise exposure and viewing occur through the same support. Layer Order Arrangement V differs from the prior teachings of the art not only in the use of high aspect ratio tabular grain silver halide emulsions, but also in the order in which the dyeproviding layer units are arranged. The greensensitive high aspect ratio tabular grain silver halide emulsion layer is nearest to the exposing radiation source while the blue-sensitive high aspect ratio tabular grain silver halide emulsion layer is farthest removed. This arrangement is possible without color contamination because of the relatively large separations in blue and minus blue response attainable with minus blue spectrally sensitized high aspect ratio tabular grain silver halide emulsions.

By placing the magenta-dye-providing layer unit nearest the source of exposing radiation and nearest the dye receiving layer, the sharpness of the magenta dye image is improved and its accese time is reduced. The magenta dye image is, of course, the visually most important component of the multicolor dye image. The cyan Image is the visually second most important, and its location is also nearer the exposing radiation source and the dye receiving layer than in a corresponding conventional dye image transfer film unit. Thus, significant advantages in terms of reduced image access time and increased image sharpness are attainable with Layer Order 58Arrangement V in addition to those improvements attributable to high aspect ratio tabular grain silver halide grains previously discussed above in connection with other layer order arrangements.

While Layer Order Arrangement V is useful with all high aspect ratio tabular grain silver halides, it is particularly advantageous with high aspect ratio tabular grain silver bromide or bromoiodide. ύ ii X >« U -59Layer Order Arrangement VI An Integral Multicolor Dye Image Transfer Film Unit according to the Invention With Image Reversal Expose + _Transparent Support_ _Neutralizing Layer_ _Timing Layer_ Alkaline Processing Composition + Opacifier Green-sensitive Tabular Silver _Halide Emulsion Layer_ _Interlayer With Scavenger_ Magenta Dye-Image-Providing Material _and Nuclei_ Interlayer With Scavenger and Nuclei Red-sensitive Tabular Silver _Halide Emulsion Layer_ _Interlayer With Scavenger_ Cyan Dye-Image-Providing Material and Nuclei Interlayer With Scavenger and Nuclei Blue-sensitive Tabular Silver _Halide Emulsion Layer_ _Interlayer With Scavenger_ Yellow Dye-Image-Providing Material _and Nuclei_ _Opaque Layer_ _Reflective Layer_ Dye Receiving Layer Transparent Support + View -6010 During imagewise exposure of Layer Order Arrangement VI the alkaline processing composition containing the opacifier is not in the location shown. The alkaline processing composition is placed in the position shown to commence processing. Initially each of the high aspect ratio tabular grain silver halide emulelon layers develop in the areas which are light-struck during exposure. The emulsion layers each contain a scavenger to prevent any interaction of the oxidized developing agent produced by development of the light-struck silver halide and the dye-image-providing materials. A scavenger containing interlayer is also positioned between each high aspect ratio tabular grain silver halide emulsion layer and its corresponding dye-image-providing material layer for this purpose.

In the areas of the high aspect ratio tabular grain silver halide emulsion layers in which silver halide development does not occur, eilver halide is solubilized by silver halide solvent contained in the alkaline processing composition.

The solubilized silver halide migrates through the .adjacent interlayer containing scavenger and is converted to silver on the nuclei present in the layer containing the dye-image-providing material.

The nuclei can be those employed for physical development in silver image transfer. The oxidized developing agent produced as a result of physical development is free to react with the dye-imageproviding material to release a mobile dye or dye precursor. Color contamination between adjacent dye-providing layer units is prevented by interposing therebetween a layer containing a scavenger to prevent the migration of oxidized developing agent therethrough and nuclei to prevent the migration of solubilized silver halide therethrough. -6110 Layer Order Arrangement VI is illustrative of an integral multicolor dye image transfer film unit which produces a positive transferred dye image using negative-working silver halide emulsions and negative-working release compounds materials.

Although the basic approach has been previously disclosed in the art, as illustrated by U.K. Patent 904,364, there are unexpected advantages to employing high aspect ratio tabular grain silver halide emulsions as herein described. It is to be noted that both the development and solubilizing of silver halide is required to obtain a transferred dye image. Because of the increased rates of development and solubilizing possible with high aspect ratio tabular grain silver halide emulsions as defined herein, it is possible to reduce transferred image access times below those that have been previously obtained with ths type of image reversal arrangement. Layer Order Arrangement Vl also exhibits advantages attributable to a dye-providing layer unit arrangement similar to those already described in connection with Layer Order Arrangement V.

Although the invention has been particularly described with reference to certain preferred layer order arrangements, it is appreciated that the high aspect ratio tabular grain silver halide emulsions need not always be present as planar, uninterrupted layers. Rather than being continuous, the layers can be subdivided into discrete laterally displaced portions or segments· In multicolor image transfer film units the layers need not be superimposed, but can be present in the form of interlaid layer segments. It is possible to employ high aspect ratio tabular grain silver halide emulsions as herein disclosed in microcellular image transfer film unit arrangements, such as disclosed by Patent Cooperation 4 4 2 5 -62Treaty published application W080/01614, published August 7, 1980· The present invention is also fully applicable to microcellular image transfer film units containing microcells which are improvements on PCT published application W080/01614, such as U.K. Patent Application No. 2,091,433 and U.S. Patent 4,307,165.

Although all of the advantages attributable to high aspect ratio tabular grain silver halide emulsions can be realized in microcellular image transfer film units, the large minus blue and blue speed separations obtainable with spectrally sensitized high aspect ratio tabular grain silver halide emulsions, most notably silver bromide and bromoiodide emulsions, are particularly advantageous in microcellular image transfer film units intended to produce multicolor images. Since the microcell triads intended to respond to blue, green, and red light are positioned to receive the same incident light, yellow filters are interposed using conventional silver bromide and bromoiodide emulsions to improve minus blue and blue speed separation. This can involve an additional coating or cell filling step and reduce photographic speed. The high aspect ratio tabular grain silver halide emulsions as defined herein can be employed in multicolor microcellular image transfer film units without the use of yellow filters, thereby significantly simplifying construction and improving performance.

As will be readily apparent to those skilled in the art the image transfer film units can contain a variety of conventional addenda not specifically discussed above. For example, the image transfer film units can contain brightenere, antifoggants, stabilizers, scattering or absorbing materials, hardeners, coating aids, plasticizers, lubricants, and matting agents, as described in Research 4 X — ΰ -63Disclosure, Voi. 176, December 1978, Item 17643, Paragraphs V, VI, VIII, X, XI, XII, and XVI. Methods of addition and coating and drying procedures can be employed, as described in Paragraphs XIV and XV. 3 Conventional photographic supports can be employed, as described in Paragraph XVII. Other compatible conventional features, not specifically described, will be readily apparent to those skilled in the art.

Further applications filed concurrently with the present one describe in further detail subject matter which is referred to above. These applications are application Afos. hu/u, χτ-οο/sx, xvoi/sx, xyos/gx, xy-o^sx^ IT-of/il, Moijtz, and- i-e-fei'tnce· mxy afso be made. Ιό Bn'ti'sh Patent Spier# icstion M>s. 3,10^5^77, 2,.10% Ϊ72} χ,ιιο,Ι, οι, and ζζκο,^οίζ Examples The invention can be better appreciated by reference to the following illustrative examples.

In each of the examples the term percent means percent by weight, unless otherwise indicated, and the term M etands for molar concentration, unless otherwise indicated. All solutions, unless otherwise indicated, are aqueous solutions. Although some tabular grains of less than 0.6 micrometer in diameter were included in computing the tabular grain average diameters and percent projected area in the example emulsions, except where their exclusion is specifically noted, insufficient small diameter tabular grains were present to alter significantly the numbers reported. 3θ Example 1 Control Emulsion A-l A conventional low aspect ratio silver bromoiodide control emulsion having an average grain diameter of 1.1 micrometers and containing 9 mole percent iodide was prepared as described in U.S.

Patent 3,320,069. The emulsion was optimally sensitized with sulfur and gold in the presence of thio54125 -64cyanate and spectrally sensitized to green light using a supersensitizing combination of carbocyanine dyes.

Tabular Grain Emulsion B A high aspect ratio tabular grain silver bromide emulsion containing tabular silver bromide grains having an average grain diameter of 4 micrometers, an average grain thickness of 0.13 micrometer, and an average aspect ratio of approximately 30:1 was prepared. The tabular silver bromide grains accounted for approximately 90 percent of the total grain projected area. The emulsion was optimally sensitized chemically with sulfur and gold in the presence of thiocyanate and spectrally sensitized with the same supersensitizing dye combination employed in Control Emulsion A-l.

Dye Image Transfer Film Units Control Emulsion A-l was coated on a support having an antihalation layer in a decreasing silver coverage series (1.38, 0.69, 0.53, and 0.36 g/m2) along with the materials shown below: Coverage Redox Dye-Releaser 1 0.69 g/m2 Incorporated Reducing Agent 2 0.42 g/m2 Inhibitor 3 0.009 g/m2 4-Hydroxy-6-methy1-1,3,3a,7- tetraazaindene 1.2 g/mole Ag Gelatin 1.1 g/m2 In addition to the gelatin shown above, for each gram of silver coated, an equal weight of gelatin was also present in the coating.

Tabular Grain Emulsion B was coated on a clear cellulose acetate support in a decreasing silver coverage series (1.35, 0.67, and 0.40 g/m2) along with the materials shown below: 4 λ. 2 2L -65Coverage Redox Dye-Releaser 1 0.80 g/m2 Incorporated Reducing Agent 2 0.37 g/m1 Inhibitor 3 0.01 g/m1 4-Hydroxy-6-methyl-1,3,3a,7- tetraazaindene 3.6 g/mole Ag Gelatin 1.2 g/m2 In addition to the gelatin shown ahove, for each gram of silver coated, an equal weight of gelatin was also present in the coating.

Redox Dye-Releaser 1 (PRDR-l) CHj I Ri U 1' z V CHj I Ri -CH—/ >-C-CHj CHj CHj N=-NCi 2H2 5 j ι y ι Ra «-CHaN-COO-j^ \ ^•Z XSO2NH2I V\fi 6cON-CHj .A./ < 11 I CHj I CHaN-COCFj • «· NHSOa-ζ )*-CHj Dispersed, in diethyllauramide solid:solvent 1:1 -66Incorporated Reducing Agent 2 (IRA-2) OH /C0NH(CH»)*0-\ )*-CiHn-t U I 1 CHj I I NHCOCHCO-C-CHj I I HjCCOO CHj Dispersed in diethyllauramide Inhibitor 3 (INH-3) I CjHn-t solid:solvent 2:1 II CHj I zN-N n-CuHis. /·< ,CH2NC0S--r II ll fl >NΝΛ /\ /\ I ll >-SC0NCH2 λ CiiH2s-n 1 N-N . ~ ' I CHj / S I ,j Dispersed in diethyllauramide '/ S J. V solid:solvent 2:1 Dye Image Receiver The dye image receiver consisted of the following structure. Coverages are shown parenthetically in g/mJ. 6. Hydroxyethylcellulose layer (Natrosol 250L) (0.97) . Gelatin layer (1.1) 4. Opaque layer: Carbon (1.9), Gelatin (1.1) 3. Reflecting layer: Titanium dioxide (19), Gelatin (3.0) 2. Mordant layer: Poly(4-vinylpyridine) (2.2), Gelatin (2.2) 1. Metal-containing layer: Nickel sulfate hexahydrate (0.58), gelatin (1.1) Coated on clear polyester support in the order of numbering.

Exposure and Processing The dye image transfer film units described above were exposed for 1/100 second to a 600 watt 4 12 5 -672850°K tungsten light source through a step-chart, a 1*0 neutral density filter and a Wratten 16 filter.

The dye image transfer film units were processed by releasing processing fluid from a pod to the interface of the dye receiver and the emulsion layer by laminating between stainless steel rollers providing a 75 micrometer developer layer thickness. The processing composition for Control Emulsion A-l (Pod L) is shown below in Example 2. The composition of the pod for Tabular Emulsion B was identical to Pod L, except it contained 16 grams/liter of the 3-pyrazolidinone electron transfer agent rather than 8 grams/liter.

In both instances transfers were carried out for 10 minutes at room temperature. The receivers were separated and the Status A green density was read. Characteristic curves were plotted, and relative speeds were determined at 0.2 density units below maximum density.

The sensitometric results obtained are shown below. Of particular interest are the relative threshold speeds at decreasing silver coverages for the two emulsions. The tabular grain emulsion coating maintained significantly higher relative speeds as the silver coverage was reduced compared to the conventional three-dimensional emulsion coating. 68Rela- Coating/Ag CoveragePmaxDmln Contrast tive Speed* Control Emulsion A- 1 1.38 g/m2 1.74 0.16 1.7 100 0.69 g/m2 2.04 0.17 2.2 59 0.53 g/m2 2.11 0.13 2.4 51 0.36 g/m2 2.16 0.17 2.3 24 Tabular Grain Emulsion B 1.35 g/m2 1.04 0.12 1.2 100 0.67 g/m2 1.44 0.12 1.8 90 0.40 g/m2 1.77 0.10 2.1 88 * 30 - 0.3 log E. The effect is also shown graphically in Figure 1.

Example 2 Control Emulsion A-2 A conventional low aspect ratio polydisperse silver bromoiodide emulsion containing some large grains up to about 2 micrometers and containing 6.2 mole percent iodide was prepared as described in U.S. Patent 3,320,069. The emulsion was optimally chemically sensitized with sulfur and gold in the presence of thiocyanate and spectrally sensitized to green light using the same sensitizers employed with the tabular grain emulsion, Tabular Grain Emulsion C, described below.

Tabular Grain Emulsion C A high aspect ratio tabular silver bromoiodide emulsion containing tabular grains having an average grain diameter of 4.7 micrometers, an average grain thickness of 0.16 micrometer, and an average aspect ratio of 29:1 was prepared.

The tabular silver bromoiodide grains accounted for greater than 95 percent of the total projected grain area. The emulsion was optimally 69sensitized chemically with sulfur and gold ln the presence of thiocyanate and spectrally sensitized to green light using a supersensitizing combination of carbocyanine dyes· Dye Image Transfer Film Units Integral imaging receivers (IIR's) using the above emulsions of the following structure were prepared. Coverages are in (g/m2) unless otherwise specified. 7. Hydroxyethylcellulose (Natrosol 2501.) overcoat layer (0.54) 6. Magenta imaging layer: Green-sensitized negative silver halide Tabular Grain Emulsion C (0.74 Ag), Redox Dye-Releaser-1 (0.67), Reducing Agent-2 (0.36), Inhibitor-3 (0.009), 4-hydroxy-6methyl-l,3,3a,7-tetraazaindene (3.5 g/Ag mole), gelatin (1.7) . Gelatin interlayer (1.2) 4. Opaque layer: Carbon (1.9), gelatin (1.2) 3. Reflecting layer: Titanium dioxide (16.0), gelatin (2.6) 2. Mordant layer: Poly(4-vinylpyridine) (2.2), gelatin (2.2) 1. Metal-containing layer: Nickel sulfate hexahydrate (0.58), gelatin (1.1) Coated on clear polyester eupport in the order of numbering· A control was the same as the example coating described above, except Control Emulsion A-2 was used at 1.48 g Ag/m2. Both coatings were hardened with bis(vinylsulfonyl)methane at 1.1 percent of the gelatin weight.

Cover sheets of the following structure were prepared: 2. Timing layer: 1:1 physical mixture of the following two polymers coated at 4.8 g/m2: -70Poly(acrylonitrile-co-vinylidene chloride-coacrylic acid) at a 14:79:7 weight ratio The carboxy ester lactone formed by cyclization of a vinyl acetate-maleic anhydride copolymer in the presence of 1-butanol to produce a partial butyl ester of acid:ester of 15:85 1. Acid layer: Poly(n-butyl aerylate-co-acrylie acid) at a 30:70 weight ratio equivalent to 140 meq acid/m2 Coated on clear polyester support in the order numbered.

Processing pods of the following two compo- sitions were prepared: Pod L Pod M 15 Potassium hydroxide 60 g/1 60 g/1 4-Hydroxymethyl-4-methyl-l- pheny1-3-pyrazolidinone 8 g/1 6 g/1 Potassium bromide 5 g/1 10 g/1 Sodium sulfite 2 g/1 2 g/1 20 Carboxymethylcellulose 57 g/1 57 g/1 Exposure and Processing Each integral imaging receiver (HR) was exposed in a sensitometer to yield a full-scale Dmin^Dmax *°a8e after processing with a viscous processing composition in a pod. The processing composition was spread between the 1IR and the cover sheet using a pair of rollers which provide a 100 pm gap. Within 12 to 24 hours the Status A green density of the receiver side of the HR was read to obtain the sensitometric curves. The sensitometric parameters, Dmax, Dm£n» contrast, and relative speed (at D - 0.3 below D __) were read from the nsx curves· As the data below shows, the Tabular Grain Emulsion C, with either pod L, or the less active M pod, produced a relative speed that was 0.2 -71log E faster than the control emulsion processed with the same pod, despite the much lower sliver coverage (0.74 g Ag/m2 versus 1.48 g Ag/m2) of the tabular grain emulsion. The speed difference wae even greater, 0.4 log E, when comparing the two emulsions at more nearly equal maximum densities. At the direct viewing conditions (1:1 magnification) normally used for products of thie type, there was no difference in graininesB apparent upon visual inspection.

Relative Emulsion Pod Dg-max Dg-min Green Contrast Green Speed Control-A-2 L 1.3 0.13 1.4 100 Tabular Grain Emulsion C L 1.8 0.13 2.0 119 Control-A-2 M 1.6 0.13 1.6 77 Tabular Grain Emulsion C M 1.9 0.13 1.8 99 Example 3 A multicolor integral imaging receiver (HR) of the following structure was prepared: 11. Overcoat layer . Yellow imaging layer 9· Interlayer 8. Magenta imaging layer: Green-sensitized negative silver bromoiodide Tabular Grain Emulsion D (a remake of Tabular Grain Emulsion C) (0.65 Ag), Redox Dye Releaser-1 (0.63), Reducing Agent-2 (0.32), Inhibitor-3 (0.010), 4-hydroxy-6methyl- l,3,3a,7-tetraazaindene (3.6 g/mole Ag), gelatin (1.3) 7. Interlayer 6. Cyan imaging layer -725. Gelatin Interlayer 4 Opaque layer 3. Reflecting layer 2. Mordant layer: Poly(4-vinylpyridine) (2.2), gelatin (2.2) 1. Metal-containing layer: Nickel sulfate hexahydrate (0.58), gelatin (1.1) The layers were coated on clear polyester support In the order of numbering.

A control was similar to the example, but used a low-aspect ratio silver bromoiodlde emulsion, A-3, at 0.99 g Ag/m2 in layer 8, the magenta imaging layer.

Both the example and the control were hardened with bis(vinylsulfonyl)methane at 0.9 percent of the gelatin weight.

The cover sheet was the same as was used for Example 2.

Processing pods of the following composition were prepared: Pod N Potassium hydroxide 60.0 g/A 4-Hydroxymethy1-4-methyl-1- I>-tolyl-3-pyrazolidinone 12.0 g/* Potassium bromide 5.0 g/t Ethylenediaminetetraacetic acid, disodium salt 10.0 g/s. Carboxymethylcellulose 57.0 g/Jt The above elements were used as follows: The multicolor integral imaging receiver (1IR) was exposed in a sensitometer to give a neutral image at a Status A density of 1.0 after processing with a viscous processing composition in a pod. The pod contents were spread between the 11R and the cover sheet using a pair of rollers which provide a 100 urn gap. Within 12 to 24 hours the Status A 412 5 green density of the receiver side of the HR was read to obtain the sensitometric curve. The green density sensitometric parameters, Dmax» Dmin» contrast, and relative speed (at D » 0.2 below D ___) were read from the curve. n&x The data below shows that the Tabular Grain Emulsion D, had a relative speed that was almost 0.3 log E faster than the control, yet used only 2/3 the quantity of silver. Again, at the direct viewing conditions (1:1 magnification) used for products of this type, no significant difference in observed graininess was seen ae viewed through a green filter.

Relative Green Green Emulsion Pod Dg-maxD0nin Contrast Speed Control A-3 N 1.9 0.12 1.5 100 Tabular Grain Emulsion D N 2.0 0.23 1.4 127 Example 4 Tabular Grain Emulsion E A high aspect ratio tabular grain silver chloride emulsion containing tabular grains having an average grain diameter of 6.0 micrometeis, an average grain thickness of 0.28 micrometer and an average aspect ratio of 22:1 was prepared. The tabular silver chloride grains accounted for greater than 80 percent of the total projected area. The emulsion was optimally sensitized chemically with sulfur and gold in the presence of thiocyanate and spectrally sensitized to green light with an oxacarbocyanine dye in the presence of 3 mole percent bromide.

Dye Image Transfer Film Units Integral imaging receivers (HR's using Tabular Emulsion E were otherwise identical to those of Example 2. -74The cover sheet and the pods L and N are £fee same as those of Examples 2 and 3.

The above elements were used In the manner described In Example 2.

The above I1R using Emulsion E yielded a full-scale D-mln/D-max Image when exposed In an Eastman IB SensItometer at 1/100 sec through a graduated density test object. This Indicates that Emulsion E had sufficient photographic sensitivity to be considered suitable for camera-speed use with image transfer materials. Sensitometric parameters are tabulated below. Green Emuleion Pod Dg-max Dg-min Contrast E L 1.6 «0.3 1.1 E N 1.0 0.31 0.7 Example 5 Tabular Grain Emulsion F A high aspect ratio tabular silver bromo20 iodide host emulsion sensitized with silver chloride epitaxial deposition containing tabular grains with an average grain diameter of 3.0 micrometers, an average grain thickness of 0.09 micrometer and an average aspect ratio of 33:1 was prepared. The tabular grains accounted for greater than 85' percent of the total grain area.

An integral imaging receiver (1IR) was prepared similar to that of Example 2, except: in layer 6, Tabular Emulsion F was used (0.67 Ag), and layer 5 was omitted.

The cover sheet and pod N were the same as Examples 2 and 3. The above elements were used in the same manner as described in the referenced Example 2.

The above IIR using Emulsion F yielded a full-scale Dm£n/Dmax image when exposed in an Eastman ZB Sensitometer at 1/100 sec through a 541^ -75graduated density test object. This indicates that Emulsion F had sufficient photographic sensitivity to be considered suitable for camera-epeed use with image transfer materials. Sensitometric parameters are tabulated below.

Green Emulsion Pod DG‘fflaX ®G m^n Contrast F N 2.0 “0.15 2.1 Example 6 10 Emulsion G, a tabular grain AgBrI (97:3 molar ratio of Br to 1) emulsion, had an average tabular grain diameter of 1.6 pm, an average tabular grain thickness of 0.10 pm, and an average aspect ratio of 16:1, and greater than 801 of the total projected area of the grains was provided by the tabular grains.

This emulsion was optimally chemically sensitized with 100 mg sodium thiocyanate/Ag aole, 9.0 mg sodium thiosulfate pentahydrate/Ag aole, end 3.0 mg potassium tetrachloroaurate/Ag aole and optimally spectrally aensltlzed to tha green region with a green absorbing carbocyanine dye.

A control AgBrI (97:3) emulsion, designated as Control Emulsion C-6, of the type described in IllingBworth U.S. Patent 3,320,069, had an average grain diameter of 0.81 pm, an average grain thickness of approximately 0.55 pm, and an average aspect ratio of 1.5:1.

Control Emulsion C-6 was optimally cheml30 cally sensitized with 1.2 mg sodium thlosulfste pentahydrate/Ag mole and 0.4 mg potassium tatreehloroaurate/Ag mole and optimally spectrally sensitized to the green region of the spectrum with the same green absorbing csrbocyanlne dye employed above.

A single color Integral Imaging receiver, HR, of the following structure was prepared using -76the above-described Tabular Emulsion G, and Control Emulsion C-6. Coverages are In (g/m1). 7. Overcoat layer: BiB(vlnylsulfonyl)aeth«ne (0.071), gelatin (0.54) 6. Silver halide layer: Graen-sanaltlced silver bromoiodide (3X I) tabular grain eaulaion. Emulsion G, (0.81 Ag), PRDR-1 (0.67), IRA-2 (0.32), Inhibitor-3 (0.043), gelatin (1.6) . Gelatin layer (4.8) 4. Opaque layer: Carbon (1.9) gelatin 1.3) 3. Reflecting layer: Titanium dioxide (17), gelatin (2.6) 2. Mordant layer: Poly(4-vinylpyridine) (2.2), gelatin (2.2) 1. Metal-containing layer: Nickel sulfate hexahydrate (0.58), gelatin (1.1) Coated on clear polyester support in the order of numbering.

A alngle color control coating of tha same structure was prepared, except layer 6 had gxaansensltized silver bromoiodide (31 I) Control Emulsion C-6 (0.81 Ag).

Pods of the following composition were prepared.

Potassium hydroxide 55.0 g/l Electron transfer agent (ETA): 4-Hydroxymethyl-4-methyl- l-j>-tolyl-3-pyrazolidinone 15.0 g/l Potassium bromide 4.0 g/l Ethylenedlamlnetetraacetic acid 7.8 g/l Sodium sulfite 2.0 g/l Carhoxymethylcellulos e 56.0 g/l Carbon 165.0 g/l Anionic surfactant (Tamol SN)* 2.0 g/l Lead oxide 0.4 g/l * The sodium salt of a condensate of formaldehyde and naphthalene sulfonic acid. -77Tamol is a trade mark.

Cover sheets as described in Example 2 vere prepared.

The monochrome HR containing either Emulsion G or C-6 was exposed in a sensitometer through a graduated-density test object at 1/200 sec with neutral density filtration sufficient to produce a full-scale D . /D_. image after * oBx nm processing with a viscous processing composition in a pod. The pod contents vere spread at room temperature (23°) between the 1IR end cover sheet using a pair of 100 micrometer gap juxtaposed rollers. After a period of not less then 24 hours, the receiver side of the HR vas read to Status A density and a computer Integrated D log E reversal curve was . obtained. Sensitometric parameters from this reversal curve are tabulated below: Emulsion Contrast* Relative? Speed &mlnDmax (Example) » G 3.2 100 0.22 1.8 (Control) C-6 2.0 99 0.22 1.6 * The contrast is measured from 0.2 density above D-mln to 0.2 below D-max. t The relative speed 1b measured at Density “ 0.5, 30 >* 0.3 log E.

The data ahow that the example high-aspect ratio tabular grain emuleion had significantly higher contrast compared to an equivalent apeed three-dimensional emulsion. Db1q values vere the same; the experiment emulsion also had the additional benefit of· alightly higher Toe end shoulders vere equivalent. Higher contrast, at a given silver coverage, is a very desirable feature in camera-speed direct image vleving products of thiε type. 54125 -78Example 7 Two serlee of single color Integral Imaging receiver (IIR) elements of the same structure as Example 6 (but with modifications of layer 6) were prepared using the tabular grain Emulsion G and the Control Emulsion, C-6, optimally sensitised as described In Example 6.

Silver halide layer 6: Green-sensitised silver bromoiodide (3% I) tabular grain Emulsion G, or green-sensltlzed silver bromoiodide (31 I) control Emulsion C-6, dispersions of Imaging reagents are tabulated below; Example Emulsion Control Emulsion Emulsion G (g/m2) C-6 (g/m*) Silver Coverage (see Table below) 0.08-0.97 0.08-0.97 PRDR-l 0.67 0.67 IRA-2 0.11 0.15 Inhibitor 3 0.086 0.17 Gelatin 1.6 1.6 Pods were prepared as Example 6, except containing 20.0 g/1 of the ETA and 2.0 g/1 of potassium bromide. The same cover sheets were used as for Example 2. The same procedure was used as for Example 6, except the exposure time was 1/50 second. -795¾. A.· Relative Coating Ag Coverage - Green Dye Density Threshold Speed * ASpeed** D-max D-mln Tabular Grain Emulsion G 0.97 g/m2 1.55 0.16 198 0.65 g/m2 1.70 0.17 187 0.32 g/m2 1.87 0.18 163 48 0.16 g/m2 1.93 0.24 139 Control Emulsion C-6 0.97 g/m2 0.63 0.16 — 0.65 g/m2 1.63 0.16 180 0.32 g/m2 1.98 0.17 130 89 0.16 g/m2 2.03 0.41 91 * 30 unite - 0.3 log E, measured at approximately 0.3 density units below DMX ** Over range 0.16 to 0.65 g/m2 Emulsion fog is evidenced by lowered transferred dye D-max. High D-min reflects an Insufficient degree of oxidation of the IRA by developing silver halide to prevent the reduction of the PRDR by the IRA. At the 0.65 g/m2 silver halide coverage, both emulsions had nearly equivalent threshold speed. At the 0.97 g/m2, the control emulsion gave too much fog to have a meaningful speed value. As the levels of silver halide dropped through the range to 0.16 g/m2, both emulsions gave good image discrimination, but the control emulsion dropped 89 units in speed while the tabular emulsion lost only 48 units.

In these two comparisons the levels of IRA and inhibitor (which is released imagewise in the unexpoBed area, thereby suppressing fog) are notably different. Substantially lower levels of IRA and Inhibitor are required for the tabular emulsion to provide comparable results at any level of silver halide coverage. Therefore, less of the photographic reagents are neceseery. When the control 34125 -80emulsion was coated with the IRA-2 and Inhibitor-3 as the the three higher levels were (D-max = 0.17 to 0.22). same lower levels of tabular emulsion, completely fogged Appendix The following details relate to emulsion precipitation: Emulsion B To an aqueous bone gelatin, 0.17 molar 10 potassium bromide solution (1.5X gelatin, Solution A) at pBr 0.77 and 55eC were added by double-jet with stirring at a constant flow rate for 0.5 minutes (consuming 0.06X of total silver nitrate used), aqueous solutions of potassium bromide (1.51 molar, Solution B-l) and silver nitrate (1.0 molar, Solution C-l). (In all emuleion preparations the contents of the reaction vessel were vigorously stirred during silver salt addition.) Solutions B-l and C-l were halted; the emulsion was held for 5 minutes at pBr 0.77 and 55°C.

Solution C-l was added next at a constant flow rate until pBr 1.14 at 55°C was attained, consuming 3.49X of total silver nitrate used.

Solution C-l was halted.

Aqueous solutions of potassium bromide (4.52 molar, Solution B-2) and silver nitrate (2.0 molar, Solution C-2) were added next by double jet at an accelerated flow rate (6.5X from start to finish i.e. 6.5 times faster at the end than at the start) at pBr 1.14 and 55°C until Solution C-2 was exhausted (approximately 64 minutes; consuming 93.OX of the total silver nitrate used). Solution B-2 was halted. -81-. e: < Γί ο β. -t a- a An aqueous silver nitrate solution (2.0 molar, Solution C-3) was added next until pBr 1.51 at 55°C was attained, consuming 3.42% of the total silver nitrate used. 6.45 Moles of silver nitrate were used to prepare this emulsion.

Finally, the emulsion was cooled to 35°C and coagulation washed by the procedure of U.S.

Patent 2,614,929.

Emulsion C 7*0 liters of an aqueous bone gelatin, 0.17 molar sodium bromide solution (17.1% gelatin, Solution A) at pH 2.0 and 70°C was prepared. To Solution A, adjusted to pBr 0.77 at pH 2.0 and 70°C, were added by double-jet technique at constant flow rate for 4 minutes (0.67% of total silver nitrate consumed), aqueous solutions of sodium bromide (0.45 molar, Solution B-l) and silver nitrate (0.10 molar, Solution C-l). Solutions B-l and C-l were halted; the reaction vessel was held for 2 minutes at 70°C.

Solutions B-l and C-l were added next to Solution A, while maintaining pBr 0.77, at a constant flow rate while simultaneously adding at one-half the flow rate aqueous solutions of sodium bromide (3.78 molar, Solution B-2) and silver nitrate (2.72 molar, Solution C-2) to Solutions B-l and C-l, respectively. When Solutions B-l and B-2 were depleted (approximately 29 minutes; 81.8% of total silver nitrate consumed), the addition of Solution C-l was continued until pBr 1.15 vas attained. Solutions C-l and C-2 were halted.

An aqueous solution of sodium iodide (0.13 molar, Solution D) was added next at constant flow rate for approximately 2.5 minutes. After holding Solution A for 2 minutes at 70”C and pBr 1.02, Solutions C-l and C-2 were continued until depleted (17.6% of total silver nitrate consumed). Total run ο412ΰ -82time for Solution C was approximately 43 minutes.

The final pBr in the reaction vessel was about 1.83. 6.0 Molee of silver nitrate were used to prepare this emulsion.

The emulsion was cooled to 40°C and coagulation washed as described for Emulsion B.

Emulsion D Prepared similarly as Emulelon C.

Emulsion E 2.0 liters of an aqueous poly(3-thiapentyl methvacrylate-co-acrylic acid-co-2-methacryloyloxyethyl-l-sulfonic acid, eodium salt) (1:2:7 molar ratio) solution (0.63% polymer, Solution A) containing calcium chloride dihydrate (0.50 molar), adenine (0.35%) and sodium bromide (0.013 molar) at pH 2.6 and 55°C was prepared. To Solution A, maintained at the original chloride ion concentration throughout the entire procedure, were added by double-jet at constant flow rate for 1 minute (0.7% of total silver nitrate consumed), aqueous solutions of calcium chloride (2.0 molar, Solution B) and silver nitrate (2.0 molar, Solution C).

After the initial minute at constant flow rate, Solutions B and C were added by double-jet at an accelerated flow rate (2.3X from start to finish) for 15 minutes (18.8% of total silver nitrate consumed).

After the 15 minute accelerated flow rate period, Solutions B and C were added by double-jet at a constant flow rate for approximately 46 minutes (80.5% of total silver nitrate consumed).

An aqueous solution of sodium hydroxide (0.2 molar, Solution D) was used to maintain pH 2.6 at 55°C. 4.0 Moles of silver nitrate were used to precipitate this emulsion. -8354125 Emulslon F To 6.0 liters of a 1.51 gelatin, 0.12 molar potassium bromide solution at 55°C were added with stirring and by double-jet, a 2.0 molar KBr solution containing 0.12 molar Kl and a 2.0 molar AgNOj solution over an eight minute period, while maintaining the pBr of 0.92 (consuming 5.3X of the total silver nitrate used). The bromide and silver nitrate solutions were then run concurrently maintaining pBr 0.92 in an accelerated flow (6.OX from start to finish) over 41 minutes (consuming 94.71 of the total silver nitrate used). A total of approximately 3.0 moles of silver nitrate was used. The emulsion was cooled to 35°C, washed by the coagulation method of U.S. Patent 2,614,929, and stored at pAg 7.6, measured at 40°C. In the resultant tabular grain AgBrl (6 mole X iodide) emulsion those grains having an average grain size of 3.0 pm, an average thickness of 0.09 pm, an aspect ratio of 33:1, accounted for 85X of the projected area of the grains in the emulsion. 120 g of the AgBrl emulsion (0.12 mole) prepared above were adjusted to pAg 7.2 at 40° C by the simultaneous addition of 0.1 molar AgNOj and 0.006 molar Kl solutions. Then 3.0 ml of a 0.74 molar NaCl solution were added. The emulsion was spectrally sensitized with 1.5 millimole of anhydro5-chloro-9-ethy1-5’-phenyl-3,3'-di-(3-sulfopropyl)oxacarbocyanine hydroxide, triethylamine salt/mole Ag and held for 30 minutes at 40°C. Then the spectrally sensitized emulsion was centrifuged and resuspended in a 1.85 x 10*2 molar NaCl solution two times.

Into 40.0 g of the emulsion (0.04 mole) were precipitated 1.25 mole X AgCl by double-jet addition for 2.1 minutes of 0.55 molar NaCl and 0.5 molar AgNOj solutions while maintaining the pAg at 7.5 at 40°C. 412 5 -84Fifteen seconds after the start of the AgCl precipitation 0.5 mg Na2S2Oj’5HzO and 0.5 mg KAuClt/mole Ag were added to the precipitation vessel.

In the preparation of each of the emulsions the contents of the reaction vessel was vigorously stirred during introduction of silver and halide salts.

Claims (19)

1. A photographic inage transfer film unit comprising a support, 5 at least one emulsion layer located on said support containing a dispersing medium and radiationsensitive silver halide grains, and an image receiving layer, characterized in that at least 50 percent of 10 the total projected area of said radiation-sensitive silver halide grains of at least said one emulsion layer is provided by tabular silver halide grains having a thickness of less than 0.5 micrometer, a diameter of at least 0.6 micrometer, the diameter of 15 a grain being defined as the diameter of a circle having an area equal to the projected area of said grain, and an average aspect ratio of greater than 8:1, which aspect ratio is defined as the ratio of grain diameter to thickness. 20

2. A photographic image transfer film unit according to claim 1, characterized in that Bald receiving layer is positioned adjacent a second support.

3. A photographic image transfer film unit 25 according to claim 2, characterized in that said second support is a reflective support.

4. A photographic image transfer film unit according to claim 2, characterized in that said second support is transparent. 30 5. A photographic image transfer film unit according to any one of claims 2 to 4, characterized in that said film unit additionally includes an alkaline processing composition and means for releasing said composition between said supports. 35 6. A photographic image transfer film unit according to claim 5, characterized in that said -86alkallne processing composition Includes a silver halide solvent and said receiving layer includes physical development nuclei for promoting the physical development of solubilized silver halide.

5. 7* A photographic image transfer film unit according to any one of claims 1 to 6, characterized in that a dye-image-providing material is present in said emulsion layer or layers or a layer adjacent thereto. 10 8. A photographic image transfer film unit according to any one of claims 1 to 7, characterized . in that said tabular silver halide grains account for at least 70 percent of the total projected area of said radiation-sensitive grains present in said 15 emulsion layer or layers.

6. 9. A photographic image transfer film unit according to any one of claims 1 to 8, characterized in that said silver halide grains are silver bromide or silver bromoiodlde grains. 20 10. A photographic image transfer film unit according to any one of claims 1 to 9, characterized in that said tabular silver halide grains have an average aspect ratio of at least 12:1. 11. A silver image transfer film unit 25 according to any one of claims 1 to 10, comprising a transparent support, at least one emulsion layer located on said support containing a dispersing medium and chemically and spectrally sensitized radiation-sensitive silver 30 halide grains, a transparent cover sheet, and a silver receiving layer located on said cover sheet for receiving silver transferred from said emulsion layer through an alkaline processing compo35 sition containing a silver halide solvent located between said receiving and emulsion layers, -8734125 characterized in that at least 70 percent of the total projected area of said radiation-sensitive silver halide grains is provided by tabular silver halide grains having a thickness of less than 0.5 5 micrometer, a diameter of at least 0.6 micrometer, and an average aspect ratio of at least 12:1. 12. A silver image transfer film unit according to claim 11, characterized in that it additionally includes means for initially confining

7. 10 and, following imagewise exposure, releasing the alkaline processing composition between said emulsion and receiving layers and means for terminating silver halide development positioned adjacent one of said support and said cover sheet.

8. 15 13. A silver image transfer film unit according to claims 11 or 12, characterized in that it additionally includes a reflective layer positioned adjacent said receiving layer and between said receiving layer and said emulsion layer or layers. 20 14. A silver image transfer film unit according to any one of claims 11 to 13, characterized in that said tabular silver halide grains bave an average aspect ratio of at least 20:1. 15. A dye image transfer film unit accord25 ing to any one of claims 1 to 10, comprising a transparent support, at least one emuleion layer located on said support containing a dispersing medium and chemically and spectrally sensitized radiation-sensitive silver 30 halide grains, a dye-image-providing material located in said emulsion layer or layers or in a layer adjacent thereto, a transparent cover sheet, a dye image receiving layer located on said cover sheet to receive image dye transferred through an -8854135 alkaline processing composition located between eaid receiving and emulsion layers, characterized in that at least 70 percent of the total projected area of said radiation-sensitive 5 silver halide grains is provided by tabular silver halide grains having a thickness of less than 0.5 micrometer, a diameter of at least 0.6 micrometer, and an average aspect ratio of at least 12:1.

9. 16. A dye image transfer film unit accord10 ing to claim 15, characterized in that it additionally includes means for initially confining and, following imagewise exposure, releasing the alkaline processing composition between said emulsion and receiving layers and means for terminating silver 15 halide development positioned adjacent one of said support and said cover sheet.

10. 17. A dye image transfer film unit according to claims 15 or 16, characterized in that it additionally includes a reflective layer positioned 20 adjacent said receiving layer and between said receiving layer and said emulsion layer or layers.

11. 18. A dye image transfer film unit according to any one of claims 15 to 17, characterized in that said tabular silver halide grains have an 25 average aspect ratio of at least 20:1.

12. 19. A dye image transfer film unit according to any one of claims 15 to 18, characterized in that said emulsion layer provides a silver coverage of less than 750 mg/m 4 . 30 20. A multicolor dye image transfer film unit according to any one of claims 1 to 10, comprising a support, dye-providing layer units located on said support each comprised of at least one dye-image-providing 35 material and at least one silver halide emulsion containing a dispersing medium and radiation-89sensitive silver halide grains, said dye-providing layer units including a dye-providing layer unit containing a red-sensitive emulsion and a cyan-dyeimage-providing material, a dye-providing layer unit containing a green-sensitive emuleion and a magentadye-image-providing material, and a dye-providing layer unit containing a blue-sensitive emuleion and a yellow-dye-image-providing material, and a multicolor dye image receiving layer, characterized in that at least 70 percent of the total projected area of Bald radiation-sensitive silver halide grains in at least one of said emulsions is provided by tabular silver halide grains having a thickness of less than 0.5 micrometer, a diameter of at least 0.6 micrometer, and an average aspect ratio of at least 12:1. 21. A multicolor dye image transfer film unit according to claim 20 characterized in that said tabular silver halide grains account for at least 90 percent of the total projected area of the grains of at least said one emulsion layer. 22. A multicolor dye image transfer film unit according to claims 20 or 21, characterized in that said at least one emulsion ls coated to provide a silver coverage in the range of from 150 to 750 mg/m 2 . 23. A multicolor dye image transfer film unit according to claims 20 or 22, characterized in that at least 70 percent of the total projected area of said radiation-sensitive silver halide grains in each of said green- and red-sensitive emulsions is provided by tabular grains having a thickness of less than 0.3 micrometer, a diameter of at least 0.6 micrometer, and an average aspect ratio of at legst 20:1. -9024. A multicolor dye image transfer film unit according to any one of claims 20 to 23, characterized in that eaid at least one emulsion containing said tabular grains is a red-sensitive or greensensitive silver bromide emulsion optionally containing silver iodide and is positioned to receive exposing radiation prior to the remaining silver halide emulsions of said film unit. 25. A multicolor dye image transfer film unit according to claim 1, comprising a support, dye-providing layer units located on said support each comprised of at least one dye-image-providing material and at least one silver halide emulsion containing a dispersing medium and radiationsensitive silver halide grains, said dye-providing layer units including a dye-providing layer unit containing a red-sensitive emulsion and a cyan-dyeimage-providing material, a dye-providing layer unit containing a green-sensitive emulsion and a magentadye -image -providing material, and a dye-providing layer unit containing a blue-sensitive emulsion and a yellow-dye-image-providing material, and a transparent cover sheet, a dye receiving layer located on said support or said cover sheet, an alkaline processing composition, means for releasing said processing composition into contact with said dye-providing layer units, and means for terminating silver halide development positioned adjacent said support or said cover sheet, characterized in that at least 70 percent of the total projected area of said radiation-sensitive silver halide grains present in at least said one said emulsion is provided by tabular silver halide grains having a thickness of less than 0.5 micro5 412 5 -91meter, a diameter of at least 0.6 micrometer, and an average aspect ratio of at least 12:1, said Bilver halide grains in at least said one emulsion being coated at a silver coverage of from 150 to 750 5 mg/m 2 . 26. A multicolor dye image transfer film unit according to claim 1, comprising a support, dye-providing layer units located on said support 10 each comprised of one positive-working redox dye releaser and at least one negative-working emulsion containing a dispersing medium and radiationsensitive silver bromide or bromoiodide grains, said dye-providing layer units including a dye-providing 15 layer unit containing a red-sensitive emulsion and a cyan redox dye-releaser material, a dye-providing layer unit containing a green-sensitive emulsion and a magenta redox dye-releaser material, and a dyeproviding layer unit containing a blue-sensitive

13. 20 emulsion and a yellow redox dye-releaser material, and a transparent cover sheet, a dye receiving layer located on said support or said cover sheet, an alkaline processing composition,

14. 25 means for releasing said processing composition into contact with said dye-providing layer units, and means for terminating silver halide development positioned adjacent said support or said cover sheet, characterized in that at least 70 percent of 30 the total projected area of said radiation-sensitive silver halide grains present in said emulsion is provided by tabular silver bromide or bromoiodide grains having a thickness of less than 0.3 micrometer, a diameter of at least 0.6 micrometer, and an 35 average aspect ratio of at least 12:1, said grains of 54135 -92each of said emulsions being coated at a silver coverage of from 200 to 700 mg/m^.

15. 27* A multicolor dye image transfer film unit according to claim 26 characterized in that each 5 of said emulsions is coated at a silver coverage of from 300 to 650 mg/»2.

16. 28· A multicolor dye image transfer film unit according to claim 1, comprising a support, 10 a yellow-dye-providing layer unit located on said support comprised of a yellow-dye-image-providing material and a blue-sensitive negative-working emulsion, a scavenger-containing transparent first inter15 layer, a cyan-dye-providing layer unit located on said first interlayer comprised of a cyan-dye-imageproviding material and a red-sensitive negativeworking emulsion, 20 a scavenger-containing transparent second interlayer, a magenta-dye-providing layer unit located on said second interlayer comprised of a magenta-dyeimage -providing material and a green-sensitive 25 negative-working emulsion, each of said emulsions containing a dispersing medium and radiation-sensitive silver bromide or bromoiodide grains, and a receiving layer for providing a viewable 50 transferred multicolor dye image following imagewise exposure and processing of said emulsions, characterized in that at least 70 percent of the total projected area of said radiation-sensitive silver halide grains present in at least said 35 green- and red-sensitive emulsions is provided by tabular eilver bromide or bromoiodide 5 412 δ -93grains having a thickness of less than 0.3 micrometer and a diameter of at least 0.6 micrometer having an average aspect ratio of at least 12:1, said grains of each of said green and red5 sensitive emulsions being coated at a silver coverage of from 200 to 700 mg/m2, and said receiving layer being located nearer said cyan-dye-providing or said magenta-dye-providing layer unit than said remaining dye-providing layer units during processing. 10

17. 29* A multicolor image transfer film unit according to claim 28 characterized in that said dye-image-providing materials are dye developers.

18. 30. A multicolor dye image transfer film unit according to claim 1, comprising 15 an opaque support, a yellow-dye-providing layer unit located on said support comprised of a positive-working yellow redox dye-releaser material and a blue-sensitive negativeworking emulsion, 20 a scavenger-containing transparent first interlayer, a cyan-dye-providing layer unit located on said first interlayer comprised of a positive-working cyan redox dye-releaser material and a red-sensitive 25 negative-working emulsion, a scavenger-containing transparent second interlayer, a magenta-dye-providing layer unit located on said second interlayer comprised of a positive30 working magenta redox dye-releaser material and a green-sensitive negative-working emulsion, each of said emulsions containing a dispersing medium and radiation-sensitive silver bromide or bromoiodide grains, and 35 a transparent cover sheet, a dye receiving layer located on said cover sheet, -94an alkaline processing composition containing reflective material and an indicator dye which is colored at an alkaline pH and substantially colorless at an acid pH, 5 means for releasing said processing composition between said receiving layer and eaid dye-providing layer units, and means for terminating silver halide development positioned adjacent said support or said cover sheet, 10 characterized in that at least 70 percent of the total projected area of said radiation-sensitive grains present in said green- and red-sensitive emulsions are provided by tabular grains having a thickness of less than 0.3 micrometer, a diameter of 15 at leaet 0.6 micrometer, and an average aspect ratio of at least 12:1, said grains of said green and red-sensitive emulsions each being coated at a silver coverage of from 300 to 650 mg/m^.

19. 31. A photographic image transfer film unit according to any of the preceding claims, substantially as described herein by way of Example.