CA1175692A - Emulsion containing high aspect ratio tabular silver halide grains and a nucleating agent - Google Patents

Abstract

Abstract of the Disclosure High aspect ratio tabular grain direct reversal silver halide emulsions are disclosed. The emulsions can be incorporated in photographic ele-ments, such as multicolor photographic elements.
Image transfer film units incorporating these direct reversal emulsions are specifically disclosed.

Description

~ ~756g2 DIRECT REVERSAL EMULSIONS AND PHOTOGRAPHIC
ELEMENTS USEFUL IN IMAGE TRANSFER FILM UNITS
This invention relates to novel direct reversal emulsions and to photographic elements incorporating these emulsions. Further, the lnven-tion rel~tes to image transfer ilm uni~s incorporat-ing these emulsions.
_ck&round of the I vention The most commonly employed photographic ele-ments are those containing one or more radiatlon sen~sitive silver halide emulsion layers. Their wide-spread use is attributable to the excellent quality images they are capable of producing and to their high speed 9 allowing them ~o be employed in hand-held cameras under a variety of lighting conditions.
Nevertheless, silver halide photographic elements have historically exhibited two significant limitations in terms of vlewing the photographic imag~O Firs~, imagewise exposure of the silver halide emulsion layer does not produce an immediately viewable photographic image. Exposure produces an invisible laten~ image in the silver halide emul sion. Processing o the latent image is required to produce a viewable image. Historically this has meant removing the photographic element from the camera and processing ln one or more queous solu-tions to obtRin a viewable image. Second, in most instances the first viewable image obtained is ~
negative image~ and a second exposure through the negative lmage of an additional photographic element and processing thereof i6 required to produce a view able positive of the ima8e initially photographedO
The f~rst limitat~on can be overcome by employing image transfer technlques, and the second limitation can be overcome by employing direct-positive im~ging, partlcularly direct reversal imaging.

a. D'~e~ e~
Photcgraphic elements which produce ima~es having an optical density directly related to the radiation received on exposure are said to be nega-tive-working. A positive photographic image can be formed by producing a negative photographic lmage and then forming a second pho~ographic image which is a negative o the first negative- that ls, a positive image. A direct-positive image is understood in photography to be a positive image that is formed without first forming a negative image. Positive dye images which are not direct-positive images are com-monly produced in color photography by reversal pro-cessing in which a negatlve silver image is formed and a comple~entary posi~ive dye image is then formed in the same photographic element. The term "direct reversal" has been applied to direct-pos1tive photo-graphic elements and processing which produces a positive dye image withou~ forming a negative silver image. Direct-positive photography in general and direct reversal photography in particular are advan-tageous in providing a more straight forward approach to obtaining positive photographic images.
A conventional approach to forming direct-positive images is to use photographic elementsemploying internal latent image-forming silver halide grains. After imagewise exposure, the sllver halide grains are developed with a surface developer--that is, one whlch will leave the la~ent image sites with-in the sllver halide grains substantially unreveal-ed. Simultaneously, either by uniform light exposure or by the use of a nucleating agent, the silver halide grains are subjected ~o development conditions that would cause fogging of a surface latent image-forming photographic element. The internal latentimage-forming silver halide grains which received actinic radiation during imagewise exposure develop 1756~2 under these conditions at a slow rate AS compared to the internal latent imag2-forming silver halide grains not lmagewise exposed. The result is a direct-positive silver image. In color photography, the oxidized developer that is produced during silver development ls used ~o produce a correspondlng posi-tive~ direct reversal dye image. Multicolor dlrect reversal photographic images have been extensively investigated in connection with image ~ransfer pho-tography.
It has been found advan~ageous to employnucleating agents in preference to uniform l~ght exposure in the process described above. The term "nucleating agent" is employed herein in i~s art-recognized usage to mean a fogging agent ~apable ofpermit~ing the selective development of internal laten~ image-forming B ilver halide grains which have not been imagewise exposed in preference to the development of silver halide grains having an inter-nal latent image formed by imagewise exposureO
While nucleating agents have been long knownto ~he photographic art, recent interest has focused on identifying nucleating agents that are effective in relatively low concentration levels and that can be incorporated directly into silver halide emul-sions. Exemplary of known incorporated nucleating agents are those disclosed by Whitmore U.S. Patent 3~227,S52, Lincoln et al U.S. Patent 3,615,615, Kurtz et al U.S. Patents 3,719,494 and 3,734,738, Lincoln et al U.S. P~tent 3,759,901, Leone et al U.S. Patents 4,030,925, 4,080,207, and 4,276,364, Adachi et al U.S. Patent 4,115,122, von Koni~ et al U.S. Patent 4,139,387, and U.K. Patents 2~011,391 and 2,012,443.
Nucleating agen~s particularly adapted for use in direct reversal photographic elements intended to be processed at lower pH levels are disclosed by Baralle et al U.S. Patents 4,306,016, 4,306,017, and ~,315,986.

1 ~7~6~2 Dlrect reversal emulslons useful with adsorbed nucleating agents ~nclude emulsions capable of forming latent image centers primarlly in the interior of the silver hal1de grains as opposed to ~heir surface--hereinaf~er also referred to as inter-nal latent i~age-forming emulsions. Such emulsions can ~ake the form of halide~conversion ~ype emul sions, such as illustrated by Knot~ et al U.S. Patent 29456,953 and Davey et ~1 U.S. Patent 2,592,250, and core-shell emulsions, such as illustrated by Porter et al U.S. Patent 3 9 206,313, Evans U.S. Patents 3,761,276 and 3,923,513; and Atwell e~ al U.S. Patent 4,035,185-Direct reversal emulsions exhlbit art-recognized disadvantages as compared ~o negative-working emulsions. Although Evans, cited above, has been able to increase photographic speeds by prop~rly balancing internal and surface sensitivities, direct reversal emulsions have not achieved photographic speeds equal to the faster surface latent image-form-ing emulsions. Second, direct reversal emulsions are limited in their permissible exposure latitude~ When exposure is extended rereversal oc:curs. That is, in areas receiving extended exposure a negative image is produced. This is a sign~ficant limitation to in-camera use of direct reversal photograph~c ele-ments, since candid photography does not always per-mlt control of exposure condi~ions. For example, a very high contrast scene can lead to rereversal in some lmage areas~
A schematic lllustratlon o rereversal is provided in Figure 1, which plots density versus exposure. A charac~eristic curve 1 (stylized to exaggerate curve features for simplicity of discus-sion~ is shown for a direct reversal ~muls~on. Whenthe emulsion i8 coated as a layer on a support9 exposed, and processed, a density is produced. The characteristic curve ls the result of plot~lng varicus levels of exposure ver~us the corresponding density produced on proce~ing. At exposures below level A underexposure occurs and a m~ximum density is obtained which does not vary as a function of expo-sure. At exposure levels between A and B useful direc~ reversal imaging can be nchieved, since d nsity varies inversely with exposure. If exposure occurs between the levels indicated ~y B and C, over-exposure results. That is 9 density ceases to vary asa function of exposure in this range of exposures.
If a subject to be photographed varies locally over a broad range of reflected light intensi~ies, a photo-graphic element containing the direc~ reversal emul-sion can be simultaneously exposed in diferen~ areasat levels less than A and greater than B. The result may, however, still ~e aesthetically pleasing, although highlight and shadow detail of the subject are both lost. If it is attemptecl to increase expo-sure for this subject, however, to pick up shadowdetail, ~he result can be to increase highlight expo-sure to levels above C. When this occurs, rereversal is encountered. That is, the area6 overexposed beyond exposure level C appear as highly ob~ection-able negative images, since densit:y is now increasingdirectly with exposure. Useful exposure lati~ude can be increased by more widely separating exposure levels A and B, but this is objectionable to the extent that it reduces contrast below optimum levels for most subjects. Therefore reduction in rereversal is most profitably directed to increasing the separa-tion be~ween expo~ure levels B and C so that over-exposed areas are less likely to produce negative images. (In actual practice the various segments of the characteris~lc curve tend ~o merge more smoothly than illustrated.) :175~9 b. ~ e transfer photog~aphy Image transfer photography has made it possible to reduce the delay between imagewise expo-sure and obtaining a viewable image. Immediately after imagewise exposing ~he radiation sensltive silver halide emulsion layer or l~yers, a processing solution can be brought into contact therewlth. As silver halide develo?ment occurs, a black~and-white ~ransferred 6ilver image or A transferred dye image can be formed in a receivlng 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 lmportant limi-tation ln silver halide image ~ransfer photography.
Sub~ect opportunlties can be fleeting, and the pho-tographer needs as nearly an instantaneous visual verification of an acceptable photographic image as can be offerred.
Although image transfer has reduced the time required for image access in silver halide photogra-phy, this advantage has not been achieved withou~
other sacrifices. One significan~: long term concern of image trsnsfer photography relates to consumption of silver~ Multicolor silver hallde photographic elements which are conventionally processed and dye image transfer film un~ts both employ relatively high silver coverages to obtain maximum photographic speed. Typically about 1000 milligrams per square meter of silver 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 eilver present in the photographic element is, in theory, recoverable~ On the other hand, in image transfer photography silver is seldom recovered, and in inte-gral format image transfer film uni~s all of the sil-6 9 ~
--7--ver remains with the photographic film units forming the viewable image.
Another disadvantage9 lnherent in image transfer pho~ography, is the reduction ln image sharpness attributable to diffusion. As the lmage forming materials diffuse from the silver halide emulsion layer or an adjacent dye releasing layer, diffusion occurs both in the direction of the receiv-ing layer and laterally, leading to image spreading and loss of sharpness. Sharpneæs can be improved by decreasing the length of the diffusion path to the receiving layer. This is controlled by the number alld thickness of the layers to be traversed. Unfor-tunately, ~h~ 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 sil-ver halide. Further, in multicolor lmage transfer film units employing ~hree superimposed dye-providing layer units, in~ervening dye-providlng layer units 2Q and separating interlayers must be penetrated by dlf-fusing dyes migrating to the receiving layer.
Another consideratlon that arises in image transfer photography is image density variance as a function of temperature differences. S~nce subject opportunities are presented under a variety of tem-perature conditions and ~nce the primary advantage of image transfer photography is ready image access, i~ follows that the ability of image transfer photo-graphic elements ~o produce acceptable images at a variety of temperatures is also import~nt. Image ~ransfer pho~ography is much different than conven-tional photography in this respect, since in the latter processing ls rarely undertaken wl~hout con-trol of temperature.
A number of imaging limitations are encoun-tered in producing transferred images with dyes. For example, both the high silver coverages noted above and larger ~han stoichiome~rically predic~ed amounts of dye-image-providing materials are required to obtain transferred dye images of acceptable maximum densities. To the extent ths~ the eficiency of dye transfer declines from stoichiometrically predicted levels, more dye-image-providing materials must be incorporated in the photographic elemen~s 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. When the development reactlon product is relied upon to preclude dye transfer, as in the case of many conven-tional positive-working dye-image-forms, the rate of silver halide development also limits the maximum rate at which image dye can become available for transfer, s;nce too rapid release of image dye in relation to the rate of silver halide development can result in the loss of image discrimination. Improve-ments of any one or a combination of these character-lstics can9 of course, significantly improve dye image transfer.
Silver hallde image transfer film units are generally well known in the art of photography and require no detailed description. Broad discussions of image transfer elements and processes (including process solu~ions) can be found in Chapter 12 9 "One StPp Photography", Neblette's Handbook of Photo~raphy and Reprography Materials, Processes and Systems, 7th Ed. (1977), in Chapter 16, "Diffusion Transfer and Monobaths", T. H. James, The Theory of ~he Photo~ra-phic Process, 4th Ed. (1977), and A. Rott and E.
Weyde Photo~raphic Silver Halide Diffusion Pro-cesses, Focal Press, (1972).
c. Tabular silver halide ~,ralns A great varie~y of regular and irregular grain shapes h~ve been observed in silver halide photographic emulsions intended for imaging applica tions. Regular gralns are often cubic or octa-hedral. 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 near spherical thick platelets, as described, for example by Land U.S. Patent 3,8~4~871 and ~elikman and Levi Makin~ and Coatin~ Photogra Emulsions, Focal Press, 1964, page 223. Rods and ~abular grains in varied portions have been frequent-ly observed mixed in among other grain shapes, par~
ticularly where the pAg (the negative logarithm of silver ion concentra~ion) of the emulsions has been varied during precipitation, as occurs, for example in single-~et precipîtations.
Tabular grains (those areally extended in two dimensions as compared to their thickness) have been extensively studied, often ln macro-sizes having no photographic utility. Tabular grains are herein defined as those having two 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, _otographio Emulsion Chemistry, Focal Press, 1966, pp. 66-72, and Trivelli and Smith, "The Effect of Silver Iodide Upon the S~ructure of Silver Bromo-Iodide Precipitation Series", The Photographic Journal, Vol. LXXX, July 1940, pp. 285-288. Trivelli and Smith observed a pronounced reduc~ion in both grain size and aspect ratio with the introduction of iodide. Tabular silver bromide emulsions are discussed by de Cugnac and Cha~eau, "Evolution of the Morphology o Silver Bromide Crystals During Physical Ripening", Science et Industries Photo~raphi~ues, Vol~ 33, No. 2 (1962), pp. 121-125. 5ulfur sen~iti~-ed tabular grain silver bromide emulsions having an average aspect ratio of from about 5 to 7:1 I ~ 7~9~

wherein the tabular grains account for greater than 50% of the projected area of the total grain population were incorporated in a direct X~ray radiographic product, No Screen X-Ray Code 5133 ~old S by Eastman Kodak Company from 1937 until the 1950's.
Gutoff, "Nucleation and Growth R~tes During the Precipitation of Silver Halide Photographic Emulsions", Photographic Science and En~ineering, Vol. 14, NQ. 4, July-August 1970, pp. 248~257, reports preparing silver brom1de and silver bromoiodide emulsions of the type prepared by single-jet precipitations using a continuous precipitation apparatus.
Bogg, Lewis, and Maternaghan have recently published specific procedures for preparing emul~ions in which a m~Jor proportion of the silver halide is present in the form of tabulsr grains. Bogg 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 exhi-bit square and rectangular major ~urfaces charac~er-istic of ~100} crystal faces. Lewis U.S. Patent 4,067,739 teaches the preparation of silver halide emulsions wherein most of the crystals are of the twinned oc~ahedral type by forming seed crystals causing ~he seed crystals to increase in size by Ostwald ripening in the presence of a silver halide solvent, and completing grain growth without renu-cleation or Ostwald ripening while controlling pBr(~he negative logarithm of bromide ion eoncentra-tion~. Maternaghan U.SO Patents 4,150,994 and 4,184~877~ teach the formation of silver halide grains of fla~ twinned octahedral configuration by employing seed crystals which are at least 90 mole percent iodide. (Except as otherwise indicated9 all references to halide percentages are based on silver `` ~ 175692 present in ~he corresponding emulsion, grain, or grain region being discussed; e.g., a grain consist-ing of silver brom;odide containing 40 mole percent iodide also con~ains 60 mole percent bromide.) Lewis and Maternaghan report increased covering power.
Maternaghan states that the emulsions are useful in camera films, both black-and-white and colorO Bogg specifically reports an upper limit on aspect ratios of 7:1, but, from the very low aspect ratios obtained by the examples, the 7:1 aspect ratio appears unreal-istically high. It appears from repeating examples and viewing the photomicrographs published that the aspect ratios realized by Lewis and Maternaghan were also less than 7-1.
Ma~ernaghan U.S. Patent 4,184,878 (wi~h which U.K. Pa~ent 1,570,581 and German OLS publica-tions 2,905,655 and 2,921,077 are considered essen-tially cumulativ~ teaches the formation of direct-positive images by preparing a tabular grain e~ulsion essentially similarly as described by Maternaghan U.S. Patent 4,184,877, but with the incorporation of an internal sensitizer and processing in a developer containing a nucleating agent.
Wilgus and Haefner Can. Ser.No. 415,345 9 filed concurrently herewith and commonly assigned, titled HIGH ASPECT RATIO SILVER BROMOIODIDE EMULSIONS
AND PROCESSES FOR THEIR PREPARATION, discloses high aspect ratio ~ilver bromoiodide emulsions and a process for their preparation.
Daubendiek and Strong Can. Ser.No. 415,364, filed concurrently herewith and commonly assigned, titled AN IMPROVED PROCESS FOR THE PREPARATION OF
HTGH ASPECT RATIO SILVER BROMOIODIDE EMULSIONS, discloses an improvement on the processes of Maternaghan whereby high aspect ratio tabular grain silver bromoiodide emulsions can be prepared.

fi ~ 2 Solberg, Piggin, and Wilgus Can. Ser.No.
415,250, filed concurrently herewith and commonly assigned, titled RADIATION-SENSITIVE SILVER
BROMOIODIDE EMULSIONS 9 PHOTOGRAPHIC ELEMENTS, AND
PROCESSES FOR THEIR USE, discloses high aspect ratio tabular grain silver bromoiodide emulsions wherein a higher concentration of iodide is present in an annular region than in a central region of the tabular grains.
Wey Can. Ser.No. 415,257, filed concurrently herewith and commonly assigned, titled IMPROVED
DOUBLE-JET PRECIPITATION PROCESSES AND PRODUCTS
THEREOF, discloses a process of preparing tabular silver chloride grains which are substantially internally free of both silver bromide and silver iodide. The emulsions have an average aspect ratio of greater than 8:1.
Kofron et al Can. Ser.No. 415,363, filed concurrently herewith and commonly assigned, titl~d SENSITIZED HIGH ASPECT RATIO SILVER HALIDE EMULSIONS
AND PHOTOGRAPHIC ELEMENTS, discloses chemically and spectrally sensltized high aspect ratio tabular grain silver halide emulsions and phstographic elements incorporating these emulsions.
Mignot Can. Ser.No. 415,263, filed concur-rently ~erewith and commonly assigned, titled SILVER
BROMIDE EMULSIONS OF NARROW GRAIN SIZE DISTRIBUTION
AND PROCESSES FOR THEIR PREPAKATION, discloses high aspect ratio tabular grain silver bromide emulsions wherein the tabular grains are square or rectangular.
Dickerson Can. Ser.No. 415,336, filed concurrently herewith and commonly assigned, titled FOREHARDENED PHOTOGRAPHIC ELEMENTS AND PROCESSES FOR
THEIR USE, discloses producing silver images of high covering power by employing photographic ele~ents containing forehardened high aspect ra~io tabular grain silver halide emulsions.
.~

7~2 Abbott and Jones Can. Ser.No. 415,366, filed concurrently herewith and commonly assigned, titled RADIOGRAPHIC ELEMENTS EXHIBITING REDUCED CROSSOVER, discloses the use of high aspect ratio tabular grain silver halide emulsions in radiographic elements coated on both ma;or surfaces of a radiation trans-mit~ing support to control crossover.
Jones and Hill C~n. Ser.No. 415,263, filed concurrently herewith and commonly assigned, titled PHOTOGRAPHIC IMAGE TRANSFER FILM UNIT, discloses image transfer film units containing tabular grain silver halide emulsions.
Hoyen Can. Ser.No. 415,367, filed concur-ren~ly herewith and commonly assigned, ~itled DIRECT-POSITIVE CORE-SHELL EMULSIONS AND PHOTOGRAPHIC
ELEMENTS AND PROCESSES FOR THEIR USE, discloses the use of divalen~ or trivalent metal ion dopan~s in the shell of core-shell emulsions to reduce rereversal.
Summary of the Invention -In one aspect this invention is directed to a radiation~sensitive emulsion particularly adapted to forming a direct-positive image comprised of a dispersing medium, silver halide grains capable of forming an internal laten~ image, and a nucleating agent. At least 50 percent of t:he total projected area of the silver halide grains is provided by tabular grains which have an average thickness of less than 0~5 micron and an average aspect ratio of greater ~han 8:1.
In another aspect, this invention is directed to a photographic element comprised of a support and at least one radiation-sensitive emulsion layer compris~d of a radiation-sensi~ive emulsioa as described above.
In an additional aspect, this invention is directed to a pho~ographic image tr~nsfer film unit comprising a suppor~, at least one emulsion layer on ,~

6 9 ~

the support containing a dispersing med~um, radia tion-sensitive silver halide grains capable of formlng an lnternal latent ima~e; and a nucleatlng agent adsorbed to the surface of said silver halide grains. At least 50 percent of the total pro~ected area of the silver halide grains is prov~ded by tabular grain6 which have an average aspect ratio of greater than 8:1.
It is an adv~ntage o the present invention that direct-positive and, more specifically, direct reversal images can be produced while realizing also the advantages of tabular grain emulsions. The emulsions of the present inven~ion exhibit improved s~ability and less image dependence on temperature as compared to nontabul~r direct reversal emulsions.
Further~ the emulsionæ of the present invention in certain preferred embodiments permit wider exposure latitude without encoun ering rereversal.
Kofron et al, cited above, discloses slgnificant advantages in speed-granularity relation-ship, sharpness 9 and blue and minus blue sensitivi~y differences for chemically and spectrally sensitized high aspect ratio tabular grain emulsion~. The high aspect ratio tabular grain emulsions enhance sharp-ness of underlying emulsion layers when they arepositioned to receive light that is free of signifi-cant scattering. These emulsions are particularly effective in this respect when they are loc~ted ln the emulsion layers nearest the source of exposing radiation. When spec~rally ~ensitized outside the blue portion of the spectrum, the high ~spect ratlo tabular grain silver bromide and bromoiodide emul-sions exhibit a large separation in their æensitivity 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 ratlo tabular grain silver bromide and bromoiodide emul-~ ~7~92 sions are much less sensitivP to blue light thPn to minus blue light and do no~ require filter protect~on to provide acceptable minus blue exposure records when exposed in neutral light, such as daylight at 5500K. The high aspec~ ratio tabular graln silver bromoiodide emulsions exhibit improved speed-granu-larity relationshipæ as compared to previously known tabular grain emulsions and as compared to the best speed-granularity relationships heretofore achieved with silver bromoiodide emulsions gener~lly. Very large increases in blue speed of high aspect ratio tabular grain silver bromide and bromoiodide emul-sions have been realized as compared to their native blue speed when blue spectral sensitizers are employed. These advantages can also be realized by the present inventlon.
Jones and Hill, cited above, teaches that photographic image transfer film units containing one or more high aspect ratio tabular graln emulsion layers are capable of producing viewable images with less time elapsed af~er the commencement of process-ing. Further, the image transfer film units are capable of producing images of improved sharpness.
They are partlcularly advantageous as applied to multicolor dye image form~tlon, permitting reduction in silver coverages, more efficient use of dye image formers, more advantageous layer order arrangement~, and elimination or reduction of yellow filter materi-als. These advantages can also be realized by the image transfer film units of this invention.
_ ~ee Ge--~Lly~on ~e hJ~Je~L~ ~
The invention can be better understood by reference to the following detailed description of preferred embodiments considered in con~unction with the drawings, in which Figure 1 is ~ stylized characteristic curve of a direct reversal emulsion, and 13175B~2 Figure 2 is a schematic diagram illustra~ing an arrangement for establishing angular scatter of exposing radi~tion.
Description of Preferred Embodiments This invention relates to high aspec~ ratio tabular grain direct-positive silver halide emulsions and to photographic elements which lncorporate one or more of these emulsions. In one specific asp~c~ this invention is d1rected to photographic image transfer film units comprised of a photographic support, one or more high aspect ratio tabular grain direct rever-sal emulsions, and a receiving layer for providing a viewable transferred image following lmagewise expo sure and processing of the silver halide emulsion.
Although the invention is d~scribed below employing topic héadings for convenience, it is intended that the description be read and interpreted as a whole to appreciate the invention fully.
Tabular Internal La~ent Ima~e-Formin~ Emu1sions The emulsions employed in the practice of this invention are high aspect ra~lo tabular grain internal latent image-forming emulsions. The emul-sions are comprised of a dispersing medlum, silver halide grains capable of forming an internal latent image, and a nucleating agent. As applied to the emulsions of the present invention the term "high ~spect ratio'l is herein defined as requiring that the silver halide grains of the emulslon have ~n average aspect ratio of greater than 8:l and account for at least 50 percent of the total projected area of the silver halide grains.
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 ~s ~n turn defined as the diameter of a circle having an area equal to the proJected area of the graln as viewed in a photomicrograph of an emulsion sample.

~75~92 The internal latent image-forming tabular grains of the presen~ invention have an average aspect ratlo of grea~er ~han 8:1 and preEerably have an average aspect ratio of greater than 10:1. Under optimum condi~ions of preparation aspect ra~ios of 50:1 or even 100:1 are contemplated. As will be apparent, the thinner the gralns, the higher their aspect ratio ~or a given diameter. Typically grains of desirable aspect ratios are those having an average thickness of less than 0.5 micron, preferably less th~n 0.3 micron, and optimally less than 0.2 micron. Typical-ly the tabular grains have an average thickness of at least 0.03 micron9 although even thinner tabular grains can in principle be employed--e.g. 9 as low as 0.01 micron, depending on halide content. In a preferred form of the invention the tabular grains account for at least 70 percent and optimally at least 90 percent of the total pro~ec~ed area of the silver halide grains.
Both the average aspect ratios of the tabular grains snd the percentage of the total projected area of the silver halide grains present can be determined by procedures well known to those skilled in the art. From shadowed elec~ron micro graphs of emulsio~ samples it is possible to visually identify the t~bular grains. These grains have large, substantlally planar opposed ma~or surfaces.
The opposed major crystal faces of each tabular grain are much larger than any remalning single crystal face of the grain. By measuring the æhadow length cast by each ~abular grain it i B pos~ible to deter-mine its thickness. This can be compared to its diameter to determine its aspect ratio. In practice it ls usually simpler to ob~ain an average thickness and an average diameter of the tabular grains and to calculate the average aspeet ratio as the ratio of these two averages. Whether the averaged individual ~5~2 aspect ratios or the averages of thickness and diam ter are used to determine the average aspect ratio9 within the tolerances of grain measurements contemplated, the average aspect rfitios obtainPd do S not sîgnificantly differ. The pro~ected areas of the tabular sllver hallde grains can be summed, the projected areas of the remaining silver halide grains in the photomicrograph can be summed separately, and from the two sums the percentage o the total projected area of the silver halide grains provided by the tabular grains can be calculated. The term "projected area" is ueed in the same sense as he terms "projection area" and "pro~ec~ive area"
commonly employed in ~he art; see, for example, James and Higgins, Fundamentals of Photo~ra~hic Theory, Morgan and Morgan, New York, p. 15.
The high aspect ratio tabular grain int~rnal latent image-forming emulsions of thls inven~ion can be prepared merely by modifying the processes for preparing high aspect ratio tabular grain emulsions such as those taught by Wilgus and Haefner, Daub~ndiek and Strong, Solberg et al, Wey, and Wey and Wilgus, ci~ed above, to favor the formation of internal latent ~ma~e centers on exposure. This can be accomplished by employing techniques similar to those demonstrated in the examples of Porter e~ al U.S. Patent 33206,313, Evans U.S. Patents 3,761,276 and 3,923,513, and Atwell et al U.S. P~tent 4,035,185, cited above to illustrate conventional direct reversal emulsions. Typically internal lQtent image-forming silver halide grains prepared by such ~echniques have an averege diameter of at least 0.6 micron, and the preferred tabular grains of this invention also exhibit an ~verage diameter of at least 0.6 micronO Since the tabulAr quality of high aspect ratio grains i 5 degraded by high levels of halide conversion, the use of halide conversion 1 175B9~

techniques, such as illustrated by Knott et al and Davey e~ al, cited above, is not preferred in the practice of thiæ invention. Specific preferred techniques for modifying high a~pect ratio tabular grain emulsions during their preparation ~o favor the formation of internal laten~ image centers are described below.
Perhaps the s~mplest manipulstive appro~ch to favoring internal latent image formation is to incorporate a metal dopant within the tabular grains as they are being formed. The metal dopant can be placed in the reaction vessel in which gra~n forma-tion occurs prior to the introduction of silver sal~. Alternately the metal dopant can be introduced during silver halide grain growth at any stage of precipitation, with or without interrupting silver and/or halide salt introduction.
Iridium is specifically contemplated as a metal dopan~ is preferably incorporated within the silver halide grains in concentrations of ~rom about 10- 8 to 10- 4 mole per mole of silver- The irldium can be conveniently incorporated into the reac~ion vessel as a water soluble salt, such as an alkali me~al salt of a halogen-iridium coordination complex, ~uch as sodlum or potassium hexachloroiri-date or hexabromoiridate. Specific examples of incorporating an iridium dopant are provided by Berriman U.S. Patent 3,~67,778.
Lead is also a specifically contemplated metal dopant fcr promoting the formation of internal lstent image centers. Lead is a common dopant ln direct print and printout emulsions and can be employed in the practice of this invention in s~milar concentration ranges. It is generally preferred that the lead dopant be present ln a eoncentration of at least 10- 4 mole per mole of silver. Concentrations up to about 5 X 10- 2, preferably 2 X 10- 2, mole ~75 per mole of silver are con~empl~ted. Lead dopan~s can be introduced similarly as iridium dopants in the form of water solllble salts, such as lead acetate, lead nitrate, and lead cyanide. Lead dopants are p~rticularly illustrated by McBride U.S. Patent 3,287,136 and Bacon U.S. Patent 3,531,291.
Another technlque for promoting the forma-tion of internal latent image centers is to stop silver halide grain precipitation after a grain nucleus or core has been produced and to sensitize chemically the surface of the core. Thereafter addi-tional precipitation of silver halide produces a shell surrounding the core. Particularly advanta-geous chemical sensitizers for this purpose are middle chalcogen sen~itizers--i.e., sulfur, selenium, and/or tellurium sensitizers. Middle chalcogen sen~
sitizers are preferably employed in concen~rations in the range of from about 0.05 to 15 mg per silver mole. Preferred concentrations are from about 0.1 to 10 mg per silver mole. Further aclvantages can be realized by employing a gold sensitizer in combina-tion. Gold sensitizers are preferably employed in concentrations ranging from 0.5 to 5 times that of the middle chalcogen sen~itizers. Preferred concen-25 trations of gold sensitizers typically range fromabout 0.01 ~o 40 mg per mole of silver, most prefer-ably from about 0.1 to 20 mg per mole of silver.
Controlling contrast by controlling the ratio of middle chalcogen to gold sensitizer is part~cularly 30 taught by Atwell et al U.S. Patent 4~035,185, cited above. Evans, cited above, provides specific examples of middle chalcogen internal sensitizations.
Although it is usually preferred to produce internal sensitization sites by the occlusion of 35 foreign (i.e., other than silver and halogen) materi-als within the tabular grains, this i~ not required~
Sensitization sites formed by the occlusion of 9 ~

foreign mater~als are hereinafter referred to as internal chemical sensi~ization sites to distinguish ~hem from internal physical sensitizatlon 6itPS. I~
is possible to incorporate int~rnal physical senslti-zation sites by providing irregularities in thecrystal lattice for capturing photolytically generat-ed electrons. Such internal irregularities can be created by discontinuities in silver halide grain precipitatlon or by fibrupt changes in the halide 10 content of the tabular grains. For example, it has been observed that the precipitation of a tabular silver bromide core followed by shelling wi~h silver bromoiodide of greater than 5 mole percent iodide requires no internai chemical sensitizstion to pro-15 duce a direct reversal image.
Silver halide surrounds the internal sen6itization sites within the tabular grains. The mini-mum amount of overlying ~ilver halide is just that required to prevent access of the developer employed 20 in processing to the in~ernal latent image. This will ~ary as a function of the ability of the devel-oper to dissolve the silver halide grains during development. For developers having very low silver halide solvency the la~ent image centers can be 25 located only a few crystal lattice planes below the surface of the tabular sllver halicle grains. If the internal latent image center forms at or near the center of the grain, as where a metal dopant is present in the reaction vessel at the start of silver 30 halide precipitation, then all or most of the silver halide forming the grain will lie between the latent image center and the grain surface. On the other hand, if a tabular silver halide grain Is precipi-tated to substantially its final slze and aspect 35 ratio before internal sensitization, the addition of only a small amount of additional silver halide is needed to protect the sensitizatlon sites from a a~7~s~

surface or sub-surface developer. The pl~cement of internal sensitiza~ion ~ites in ~ilver halide grains is particularly illustra~ed by Morgan U.S~ Patent 33917,485 and Research Disclosur~, Vol. 181, May 1979, Item 18155. Since grain nuslei formation is critical to obtaining tabular grains of high aspect ratio, it is generally preferred to delay internal sensitization until at least the commencement of ~he growth stage of tabular grain formation. When inter-10 nal sensitizatiGn is delayed until the tabular grainshave substantially achieved their desired size and aspect ra~io, then additional silver halide can be precipi~ated onto the tabular graills by any conven-tional silver halide precipitation ~echnique, includ-15 ing Ostwald ripening of a ~lended shell emulsion aBtaught by Porter et al U.S. Patentæ 3,206 a 313 and 3,317,322.
The amount of overexposure which can be tolerated withou~ encountering rereversal can be 20 increased by incorporating into the tabular silver halide grains metal dopants for this purpose. Hoyen, cited above, discloses the use of clivalent and trivalent metal ions as dopants in the shell of core-shell emulsions to reduce rereversal. Preferred 25 metal dopant~ for this purpose are cationic cadmium, zinc, lead, and erbium. These dopants are generAlly effective at concentration levels below about S X
10- 4 ~ preferably below 5 X 10-5, mole per mole of sllver. Dopant concentrations of at least 10-~, 30 preferably at least 5 X 10-6, mole per silver mole, should be present in the reaction vessel during silver halide precipi~ation. The rereversal modify-ing dopant is effective if in~roduced at any B~age of ~ilver halide precipitation. If the tabular silver 35 halide graiDs are viewed as being comprised sf ~ core and a shell, the rereversal modifying dopant can be incorporated in either or both of the core and ~ ~75~)92 shell. It is preferred that the dopant be introduced during the latter stag~s of precipi~ation (e.g., confined to the shell) for reasons previously noted.
The metal dopan~s can be introduced into the r~action vessel as wa~er soluble metal salts, such as divalent and trivalent metal halide salts. Zinc, lead, and cadmium dopants for silver halide ln similar concen trations, bu~ to achieve other modifying effects~ are disclosed by McBride U.S. Paten~ 3,287,136, Mueller 10 et al V.S. Patent 2~950,972, Iwaosa et al U.S. Patent 3,901,711, and Atwell U.S. Patent 4,269,927. Other techniques for improving rereversal characteristics discussed below can be employed independently or in combinatlon with the metal dopants described.
Preferred high aspect ratio lnternal latent image-forming tabular grain emulsions according to this invention are silver bromide and bromoiodide emulsions. Subject to modifications to produce internal sensitization sites and incorporate metal 20 dopants as described above, high aspect ratio tabular grain silver bromoiodide emul6ions can be prepared by a precipitation prooess which forms a part of the Wilgus and Haefner invention. In~o a conventional reaction vessel for silver halide precipitation 25 equipped with an efficient stirring mechanism is introduced a disp~rsing medium. Typically the dispersing medium initially introduced into the reac~ion vessel is at least about 10 percent9 prefer-ably 20 to 80 percent, by weight based on total 30 weight of ~he disperslng medium present ln the silver bromoiodide emulsion at the conclusion of grain precipitation~ Since disperæing medium can be removed from the reaction vessel by ultrailtration during silver bromoiodide gra~n precipitat~on, as 35 taugh~ by Mignot U.S. Patent 4,334,012, it is appre-cia~ed that the volume of dispersing medium initially present in the reaction vessel can equal or even " ~ ~7S~9

-2~
exceed the volume of the silver bromoiodide emulsion present in the reactlon vessel ~t the conclusion of grain precipitation. The dispersing medium initially introduced into the reaction vessel ~s preferably water or a dispersion of peptizer in water~ option-ally containing o~her ingredients, such as one or more silver halide ripening agents and/or metal dopants, more specifically described below. Where a pep~izer is initially present, it is preferably lO employed in a concentra~ion of at least 10 percent, most preferably at least 20 percent, of the total peptizer present at the completion of silver bromo-iodide precipitation. Additional dispersing medium is added to the reaction vessel with the silver and 15 halide salts and can also be introduced through a separate je~. 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.
In employing precipitation procedures as taught by Wilgus and Haefner, citecl above, a m~nor portion~ typically less than 10 percent, of the bromide salt employed ln formlng the silver bromo-iodide grains is initially present in the reaction 25 vessel to adjust the bromide ion concentration of the dispersing medium ~t the outse~ of silver bromoiodide precipitation. Also, the dispersing medium in the reaction vessel is initially substantially free of iodide ions, since the presence of iodide ions prior 30 to concurrent introducton of silver and bromide salts favors the formation of thick and nontabular grains.
As employed herein, the term "substan~ially free of iodide ions" as applied to the conten~s of the reac-tlon vessel means that there are insufficient iodide 35 ions present as compared to bromide ions to precipi-tate as a separate silver iodide phase. It is pre-ferred to maintain the iodide concentration in the reaction vessel prior to silver sal~ introduction at less than 0.5 mole percent of the total halide ion concentration present. If the pBr of the dispersing medium is inltially too high, the tabular sil~er bromoiodide grains produced will be comparatively thick and ~herefore o low aspect ratios. It is con~emplated to maintain the pBr of the reaction vessel initially at or below 1.6, preferebly below 1.5. On the other hand, if the pBr is too low 3 the forma~ion of nontabular silver bromoiodide grains is favored~ TherPfore, it is contemplated to maintain the pBr of the reaction vessel at or above 0.6. As herein employed, pBr is defined as the negative logarithm of bromide ion concentrationO pH, pI, and pAg are similarly defined for hydrogen, iodide, and silver ion concentrations, respectively.
During precipitation æilver, bromide, and iodide salts are added ~o the reaction vessel by techniques well known ln the precipitation of silver bromoiodide grains. Typically an aqueous silver salt solution of a soluble silver salt, ~uch as silver nitrate, is introduced into ~he reaction vessel con-currently with the introduction of the bromlde and iodide salts. The bromide and lodide salts are ~lso typically introduced as ~queous salt solutions, such as aqueous solutions of one or more soluble ammonium, ~lkali metal (e.g.~ sodium or potassium), or alkaline earth metal (e.g., magnesium or calcium) halide salts. The silver salt is at least initially intro-duced into the reaction vessel separately rom the bromide and iodide salts. The iodide and bromide salts are added to the reaction vessel separately or as a mixture.
With the introduction of silver salt into the reaction vessel the nucleation sta~e of grain formation is initiated. A population of grain nuclei are formed which are capable of serving as precipit~-75~2 -z6 -tion sltes for silver bromide and silver iodide as the introduction of silver, bromlde, and lodide salts con~inues. The precipitation of ilver bromide and ~ilver iodide onto existing grain nuclei constitutes the growth stage of grain formation. The aspect ratios of the tabular grains ormed according to this invention are less affected by iodide and bromide concentrations during the grow~h stage than during the nucleation stage. It is therefore posslble to 10 increase the permissible la~itude of pBr during con-current introduction of silver, bromide, and iodide salts above 0.6, preferably in the range of from about 0.6 to 2.2, most preferably from about 0.8 to about 1.6. It is, o course, posslble and, in fact, lS preferred to main~ain 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 nuclel 20 formation continues throughout the introduction oE
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 25 be tolerated in many instances while still realizing an average aspect ra~io of greater than 8:1.
As an ~lternative to the introduction of silver, bromide, and iodide salts as aqueous solu-tionsS it i B specifically contemplated to introduce 30 the silver~ bromide, and iodide salts, lnitially or in the growth stage, in the form of ine silver halide grains suspended in dispersing medium. The grains are si7ed 60 that they are readily Ostwald ripened onto larger grain nuclei, lf any are present, 35 once introduced into the reaction vesselO The maximum useful grain sizes will depend on the specif-ic conditions 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 introduce~.
(Since bromide and/or ;odide are preclpitated in preference to chloride, it is also possible to employ silver chlorobromide and silver chlorobromoiodide graîns.) The silver halide grains are preferably very fine--e.g., less than 0.1 micron 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 æilver 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 sa~uration, for example, are contemplated. Specifically preferred precipitation techniques are those which achieve shortened precipi-tation times by increasing the rate of silver andhalide salt introduction during ~he run. The rate of silver and halide salt introduction can be increased either by increasing ~he 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 ra~e of silver and halide salt introduction, but to maintain the rate of introduction below the threshold level at which the formation of new grain nuclei is favored--i.e., to avoid renucleation, as taught by Irie U.S. Patent 3,650,757, Kurz U.S.
Patent 3,672,900, Saito U.S. Patent 4,242,445, Wilgus German OLS 2,107,118, Teitscheid et al publi6hed European Patent Application 80102242, and Wey "Growth Mechanism of AgBr Crystals in Gelatin Solution", Photographic Science and Engineering, Vol. 21, No. 1, ;~
- ., 1 175B~2 January/February 1977, p. 14~ et. seqO By avoiding the formation of additional grain nuclei af~er pass-ing into the growth stage of precipitation, relative-ly monodispersed ~abular 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 varia~ion is defined 100 ~imes as the standard deviation of the grain diameter divided by 10 the average grain diameter.) By intentionally favor ing renucleation during the growth s~age of precipi-tation, it i6, of course, possible to produce poly-dispersed emusions of substantially higher coeffi-cients of varlation.
The coneentration of iodide in the silver bromoiodide e~ulsions of this invent~on can be con-trolled by the introduction of lodide salts. Any conventional iodide concentration can be employed.
Even very small amounts of iodide--e.g., as low as 20 0.05 mole percent--are recognized in the art to be beneficial. In thelr preferred form the emulsions of the present invention incorporate at least about 0.1 mole percent iodideO Silver iodid,e can be incor porated into the tabular silver bromoiodide grains up 25 to its solubility limit in silver bromide at the temperature of grain formation. Thus 7 silver iodide concentrations of up to about 40 mole percent in the tabular silver bromoiodlde grains can be achieved at precipitation temper~tures of 90C. In practice 30 precipitation temperatures can range down to near ambient room temperatures--e.g., about 30C. It is generally preferred that precipitation be undertaken at temperatures in the range of from 40 to 80C. For most photographic applications it is preferred to 35 limit maximu~ iodide concentrations to about 20 mole percent, with optimum iodide concentrations being up to about 15 mole percent.

9 ~

The relative proportion of iodide and bromide salts introduced in~o thP reactlon 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 di~fering photographic effec~s. Solberg e~
al, cited above, has r~cognized ~hat advantages in pho~ographic speed and/or grain result from increas-ing the proportion of iodide in annuler regions of 10 high aspect ratio tabular grain silver bromoiod;de emulsions as compared to cen~ral regions of the tabular grains. Solberg et al teaches iodide con-centrations in the central regions of the tabular grains of from 0 to 5 mole percent, with at least one 15 mole percent higher iodide concentrations in the laterally surrounding annular regions up to the solubility limi~ of silver iodide in silver bromide, preferably up to about 20 mole percent and optimally up ~o about 15 mole percent. In a variant form it is 20 specifically contemplated ~o terminate iodide or bromide and iodide salt addition to the reaction vessel prior to the termination of silver salt addi-tion so that excess bromide reacts with the silver salt. This results in a shell of silver bromide 25 being formed on the tabular silver bromoiodide grains. Thus, it is apparent that the tabular silver bromoiodide grains of the present invention can exhibit substantially uniform or graded iodide con-centration profiles and that the gradation can be 30 controlled, as desired, to favor higher iodide con-centrations internAlly or at or near the surfaces of the tabular silver bromoiodide grains.
It has been discovered quite unexpectedly ~hat increased exposure latitude prior to rereversal 35 can be achieved by employing higher iodide concentra-tions in outer grain regions than ln central grain regions. For example, if the grain is viewed as a ~75~9,~

core surrounded by one or more shells, i~ has been observed that incorporating at least two mole percent more iodide in one or more shells than is present in ~he grain core increases the exposure lsvel required to produce rereversal. It is preferred that ~t least one shell have an iodide con~en~ that is at least 6 mole percent, optimally a~ least 10 mole percent, gre~ter than the iodidP conten~ of the core. In a specifically contemplated form the core can be sub-10 stantially free of iodide. Preferably the iodidecontent of the core and shell are related similar as the central and annular regions discussed above. It is specifically contemplated to employ two~ three, or even more shells, each increasing in iodide ~ontent 15 with respect to silver halide loca~ed internally thereof.
Although ~he preparation of the high aspect ratio tabulflr grain silver bromoiodide emulsions has been described by reference to the process of Wilgus 20 and Haefner, which produces neutral or nonammoniacal emulsions, the emulsions of the present invention and their utility are no~ limited by any particular pro-cess for their preparation. A process of preparing high aspect ratio tabular grain silver bromoiodide 25 emulsions discovered subsequent to that of the present invention is described by Daubendiek and Strong, cited above. Daubendiek and S~rong teaches an improvement over the processes of Maternaghan, ci~ed above, wherein in a preferred form the 611ver 30 iodide concentrat;on in the reaction vessel is reduced below 0.05 mole per liter and the maximum size of the silver iodide grains ini~ially present in the reaction vessel is reduced below 0.05 micron.
High aspect ratio tabular grain ~ilver 35 bromide emulsions lacking iodide can be prepared by the process described by Wilgus and H&efner modlfied to exclude iodide. High aspect ratio tabular gra~n 1 ~ 7~1~ 9 2 silver bromide emulsions can alternatively be prepared following a procedure similar to that employed by Cugnac and Chateau 3 cited above. High espect ratio silver bromide emulsions con~ainlng square and rec~angular grains can be prepared as ~aught by Mignot, titled SILV~R BROMIDE EMULSIONS OF
NARROW GRAIN SIZE DISTRIBUTION ~ND PROCESSES FOR
THEIR PREPARATION, clted above. In this process cubic seed grains having an edge length of less than 10 0.15 micron are employed. While maintaining the pAg of the seed grain emulsion in the range of from 5.0 to 8.0, the emulsion is rlpened in the substantial absence of nonhalide silver ion complexlng agents to produce tabular silver bromide grains having an 15 average aspect ratio of at least 8.5:1. Still other preparations of high ~spect ratio tabular grain silver bromide emulsions lacking iodide are illus-trated in the examples.
To illustrate other high aspect ratio 20 tabular grain silver halide emulsions which can be employed in the practlce of this invention, attention is directed to Wey9 cited above, whlch discloses a process of preparing tabular silver chloride grains which are substantially internally free of both 25 silver bromide and silver iodide. Wey employs a double-jet precipitation process wherein chloride and silver salts are concurren~ly introduced into a reaction vessel containing dispersing medium in the presence of ammonia. During chloride salt introduc-30 tion the pAg within the dispersing medium is in therange of from 6.5 to 10 and the pH in the range of from 8 to 10. The presence of ammonia and hlgher temperatures tends to cause thick grains to form, therefore precipitation temperatures are limited to 35 up to 60C. The process can be optimized to produce high aspect ratio tabular grain silver chloride emulsions.

1 ~7~9~

Maskasky Can. Ser.No. 415~277, filed concur-rently herewith and commonly assigned, titled SILVER
CHLORIDE EMULSIONS OF MODIFIE~ CRYSTAL H~BIT AND
PROCESSES FOR THEIR PREPARATION, discloses a process of preparing tabular grains of at least 50 mole percent chloride having opposed crystal faces lying in tlll} 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 chloride-containing halide salt solutions in the presence oE a crystal habit modifying amount of an aminoazaindene and a pep~izer having a thioether linkage.
Wey and Wilgus, Can. Ser.No. 415,264, filed concurrently herewith and commonly assigned, titled NOVEL SILVER CHLO~OBROMIDE EMULSIONS AND PROCESSES
FOR THEIR PREPARATION, discloses tabular grain smul-sions wherein the silver halide grains contain silverchloride and silver 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 chlorîde and bromide ions of from 1.6 to about 260:1 and ~he total concentration of halide ions in the reaction vessel in the range of from 0.10 to 0.90 normal during introduction of silver, 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.
The individual silver and halide salts can be 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 reacti.on vessel con~ents, as illustra~ed by Culhane ~7~

et al U.S, Patent 3,821,002, Oliver U.S. Patent

3,031,304 and Claes e~ al, Photographische Korrespon denz, Band 102, Number 10, 1967, p. 162O In order to obtain rapid distribution of the reactants within the reaction vessel, specially contructed mixing devices can be employed, as illustrated by Audran U.S. Patent 2,996,287, McCrossen et al U.S. Patent 3,342,605, Frame et al U.S. Patent 3,415,650, Porter e~ al U.S.
Patent 3,7~5,777, Finnicum et al U.S. Patent

4~147~551, Verhille et al U.S. Patent 4,171,224, Calamur published U.K. Patent Application 2~022,431A, Saito et al German OLS 2~555,364 and 2,556,885, and Research Disclosure, Volume 166, February 1978, Item 16662.
In forming the tabular grain emul6ions peptizer concentrations of from 0.2 to abou-t 10 per-cent 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 ~o adjust the emulsion vehicle concentration upwardly for optimum coating characteristics by delayed, supplemental vehicle addi~ions. It is contemplated that the emulsion as initially formed wlll contain from about 5 to 50 grams of peptizer per mole of silver halide, preferably about 10 to 30 grams of peptizer per mole of silver halide. Additional vehi-cle can be added later to bring the concen-tration up to as high as 1000 grams per mole of silver halide.
Preferably the concentration oE vehicle in the finished emulsion is above 50 grams per mole of sil-ver halide~ When coated and dried in forming a photographic element the vehicle preferably forms ~bout 30 to 70 percent by weight of the emulsion layer~

6~2 Vehicles (which include both binders and peptizers) c~n be chosen from among those conven-tionally employed in silver halide emulsions. Pre~
ferred peptlzers are hydrophilic colloids, which can be employed alone or in combination with hydrophobic materials. Suitable hydrophilic materials include both naturally occurrin~ substances such as proteins, protein derivatives, cellulose derivatives--e.gO, cellulose esters, gelatin--e.g., alkali treated gela-10 tin (cattle bone or hide gelatin~ or acid-~reated gelatin (pigskin gelatin), gelatin derivatives -e.g., acetylated gelatin, phthalated gelatin and the like, polysaccharides such as dextran, gum arabic, zein, casein, pectin, collagPn derivatives, sgar-agar, 15 arrowroot, albu~in and the like as described in Yu~zy et al U.S. Patents 2,614,928 and '929, Lowe et al U.S. Patents 2,691,582, 2,614,g30, '931, 2,327,808 and 2,448,5349 Gates et al U.S. Patents 2,787,545 and 2,956,880, Himmelmann e~ al U.S. Patent 3,061,436, 20 Farrell et al U.S. Patent 2,816 9 027, Ryan U~S.
Patents 3,132,945, 3,138,461 and 3,186,846, Dersch et al U~K. Patent 1,167,159 and U.S. Patents 2,960,405 and 3,436,220, Geary U.S. Patent 3,486,896, Gazzard U.K. Patent 793,549, Gates et al U.S. Patents 25 2,992,213, 3,157,5069 3,1849312 and 3,539,353, Miller et al U.S. Patent 3,227,5717 Boyer et ~1 U.S. Patent 3,5329502, Malan U.S. Patent 3,551,151, Lohmer et al U.S. Patent 4,018,609, Luciani et al U.K. Patent 1,186,790, Hori e~ al U.K. Patent 1,489,080 and 30 Belgian Patent 856,631, U.K. Patent 1,490,644, U.K.
Paten~ 1,483,551, Arase et al U.K. Patent 1,459,906, Salo U.S. Patents 2,110,491 and 2,311,086, Fallesen U.S. Patent 2,343,650, Yutzy U.S. Patent 2,322,085, Lowe U.S. Patent 2,563,791~ Talbot et al U.S. Patent 35 2,725,293, Hilborn U.S. Patent 2,748,022, DePauw et al U.S. Patent 2,956,8833 Ritchie V.K. Pa~ent 2,095, DeStubner U.S. Patent 1,752,069, Sheppard et al U.S.

Patent 2,127,573~ Lierg U.S~ Patent 2~256,720 9 Gaspar U.S. Patent 2~361~936, Farmer U~Ko Pa~ent 15~727, Steven~ U.K. Patent 1,062,116 and Yamamoto et ~1 U.S.
PatPnt 3~923,517.
Other m~erials commonly employed in com-bina~ion with hydrophilic colloid pep~izers as vehi-cles (including vehicle extenders--e.g., materials in the form of latices~ include synthet~c polymer~c peptizers, carriers and/or binder~ such as poly(vinyl 10 lactams), acrylamide polymers, polyvinyl alcohol and its derivatives, polyvinyl acetals, polymer~ of alkyl and sulfoalkyl acryla~es and methacrylates, hydroly~-ed polyvinyl acetates~ polyamides, polyvinyl p~rl-dine, acrylic acid polymers, maleic anhydride copoly-15 mers, polyalkylene oxides, methacrylamide copolymers,polyvinyl oxazolidinones, maleic acid copolymers, vinylamine copolymers, methacrylic acid copolymers 9 acryloyloxyalkylsulfonic acid copolymers, suloalkyl-~crylamide copolymers, polyalkyleneimine copolymers, 20 polyamines, N,N-dialkylaminoalkyl acrylates, vinyl imidazole copolymers, vinyl sulfide copolymers, hslo-genated styrene polymers, amineacrylamide polymers, polypep~id~s and the like as described in Holl~ster et al U.S. Patents 3,679,425, 3,706,564 and 25 3,813,251, Lowe U.S. Patents 2,253,0785 2,276,322, '323, 2,281,703, 2,311,058 and 2,414,207, Lowe et al U.S. Pa~ents 2,484,456, 2,541,474 and 2,632,704, Perry et al U.S~ Patent 3,425,836, Smith et al U.S.
Patents 3,415,653 and 3,615,6249 Smith U~S. Patent 30 3,488,708, Whiteley et al U.S. Paten~s 3,392,025 and 3,511,818, Fi~zgerald U.S. Pa~ents 3,681,079, 3,721,565, 3,852~073, 3,861,918 and 3,925,083, Fitzgersld et al U.S. Patent 3~879,205, Nottorf U.S.
Pa~ent 3,142,568, Houck et al U.S. Patents 3,062 9 674 3S and 3,220,844, Dann et al U.S. Patent 2,882,161, Schupp U.S. Pa~ent 2,5799016, Weaver U.S. Patent 2,829,053, Alles et al U.S. Paten~ 2 9 698,240, Priest ~7~9 et al U.S. Patent 3,003,8799 Merrill et al U.S.
Patent 3,419,397, Stonham U.S. Patent 3,284,207, Lohmer et al UOS. Paten~ 3,167,430, Williams U.S.
Patent 2,957 7 767, Dawson et al U.SO Patent 2,893 9 867, Smi~h e~ ~1 U.S. Patents 2,860,986 and 2,9043539, Ponticello et al U.S. Pa~ents 3,929,4B2 and 3,860,428, Ponticello U.S. Patent 3,939,130, Dykstra U.S. Patent 3,411,911 and Dykstra e~ al Canadi~n Patent 774,054, Ream et al U.S. PatPnt 3,287,289, 10 Smith U.K. Patent 1,466,600, Stevens U.K. Patent 1,062,116, Fordyce U.S. Patent 2,2115 323, Martinez U.S. Patent 2,284~877, Watkins U.S. Patent 2,420,455, Jones U.S. Paten~ 2,533,166, Bolton V.S. Patent 2,495,918, Graves U.S. Patent 2,289,775, Yackel U.S.
15 Pa~ent 2,565,418, Unruh et al U~S. Patents 2,865,893 and 2,~75,059, Rees et al U.S. Patent 3,536,491, Broadhead et al U.K. Patent 1,3489815, Taylor et al U.S. Patent 3,4793186, Merrill et al U.S. Patent 3,520,857, Bacon et al U.S. Patent 3,690,888, Bowman 20 UOS. Pa~ent 3,748,143, Dickinson et al U.K. Patents 808,227 and '228~ Wood U.K. Patent 822,192 and Iguchi et al U.K. P~ent 1,398,Q55. The~e addi~ion~l materials need not be present in the react~on vessel during silver halide prec~pitation, but rather are 25 conventionally added to the emulsion prior to coat-ing. The vehicle materials, lncluding particularly the hydroph~lic colloids, as well as the hydrophobic materials useful in combination therewith can be employed not only in the emulsion layers of the pho-30 tographic elements of this invention, but also ino~her layers, such as overcoa~ layers, in~erlayer~
and layers positioned beneath the emulsion layers.
It is specifically contemplated that grain rlpening can occur during the preparatlon of silver 35 halide emulsions according ~o the present invention, and it is preferred that grain ripening occur within the reaction vessel during at least silver bromo-~756-37 -iodide grain formation. Known silver halide solvents are useful in promoting rlpening. For example, an excess of bromide ions ~ when present in the reac~ion vessel, is known to promote ripening. It is there-fore apparent that the bromide salt solution run intothe reaction vessel can itself promo~e ripening.
Other ripening agents can also be employed and can be entirely contained wi~hin the dispersing medium in the reaction vessel before silver and halide salt 10 addition, or they can bP introduced into the reaction vessel along with one or more of the halide sal~, sllver salt, or peptizer. In still another variant the ripening agent can be introduced independently during halide and silver salt additions Although 15 ammonia is a known ripening agent, it is not ~ pre-ferred ripening agent for the silver bromoiod~de emulsions of this invention exhibiting the highest realized speed-granulari~y relationships.
Among preferred ripening agents are those 20 containing sulfur. Thi~cyanate salts can be used, such as alkali metal, mos~ commonly sodium and potassium, and ammonium thiocyanate salts. While any conventional quantity of the thiocyanate salts can be introduced, preferred concentrations are generally 25 from about O.l to 20 grams of thiocyanate salt per mole of silver halide. Illus~rative prior te~chings of employin~ thiocyanate ripening agen~s are found in Nietz et al, U.S. Patent 2,222,264, cited above; Lowe et al U.S. Patent 2?448,534 and Illingsworth UOS.
30 Patent 3~320,069. Alternatively, conventional thioether ripening agents, such as those dlsclosed in McBrlde U.S. Patent 3,2717157, Jones U.S. Patent 3,574,628, and Rosecrant6 et al U.S. Patent 3,737,313, can be employed.
The high aspect ratio tabular grain emul-slons are preferably washed to remove soluble salts~
The soluble salts can be removed by chill setting and ~75~92 leaching, as illus~rated by Craft U.S. Patent 2,316,845 and McFall et al U.S. Paten~ 3,396,027; by coagulation washing, as illustrated by Hewit60n et al U.S. Paten~ 2,618,556 9 Yutzy et al U.S. Patent 2,6141928, Yackel U.S. Pa~ent 2,565,418, Hart et al U.S. Patent 3,241,96~, Waller et al U.S. Patent 2,489,341, Klinger U.K. Patent 1,305,409 and Dersch et al U.K. Patent 1,167,159; by centrifugatlon and decantation of a coagulated emulsion, as illustrated 10 by Murray U.S. Patent 2,463,794, Ujihara et al U.S.
Patent 3,707p378, ~udran U.S. Patent 2,996,287 and Timson U.S. Patent 3,498,454; by employing hydro-cyclones alone or in combination wlth centrifuges, as illustrated by U.K. Patent 1,336,692, Claes U~Ko 15 Patent ~,356,573 and Ushomirskii et al Soviet Chemi-cal ~ y, Vol. 6, No. 3, 1974, pp. 181-185; by diafiltration with a semipermeable membrane, as illustrated by Research Disclosure~ Vol 102, October 1972, Item 10208, Hagemaier et al Re~earch Dis-20 closure, Vol 131, March 1975, I~em 13122~ BonnetResearch Disclosure, Vol. 135, July 1975, Item 13577, Berg et al German OLS 2,436,461, Bolton U.S. Patent 2,495,918, and Mignot U.S. Patent 4,334,012, cited above, or by employing an ion exchange resin, as 25 illustrated by Maley U.S Patent 3,782,953 and Noble U.S Paten~ 2,827,428. The emulsions~ with or without sensitizers, can be drled and stored prior to use as illustrated by Research Disclosure, Vol 101, September 1972, Item 10152. In the present invention 30 washing is partlcularly advantageous in terminating ripening of the tabular grains after the completion of precipitation to avoid increasing their thickness and reducing their aspect ratio.
Althou~h the procedures for preparing 35 tabular silver halide grains described above will produce high aspect ratio tabular 8rain emulsions in which ~he tabular grains account for at leas~ 50 ~75 percent of the total pro~ected area of the total silver halide grain population, it is recogn~zed that advantages can be realized by increasing the propor-tion of such tabular grains present. Preferably at least 70 percent ~optimally at least 90 percent) of the total projected area i6 provided by tabular silver halide grains. While minor amounts o nontab ular grains are fully compatible with many photogra~
phic applications, to achieve the full advantages of 10 tabular grains the proportion of tabular grains can be increased. Larger tabular silver halide grains can be mechanically separated from smaller9 nontab-ular grains in a mixed population of grains using conventional separation techniques--e.g. 9 by using a 15 centrifuge or hydrocyclone. An lllustrative teaching of hydrocyclone separation is provided by Audran et al U.S. Patent 3,326,641.
The high a~pect ratio tabular grain internal latent image-forming emulsions of ~he present inven-20 ~ion are preferably intentionally surface chemicallysensitized to increase their photographic speed.
Useful surface chemical sensitizations are taught by Evans U.S. Patent 3,761,276 and 3,923,513 and Atwell et al U.SO Patent 4,035,185, each previously cited.
25 Any type of surface chemicsl ~ensitization known to be useful with corresponding surface latent image-forming silver halide emulsions can be employed, but the degree of surface chemical sensitization is limited to that whîch will increase the reversal 30 speed of the internal latent image-forming emulslon, but which will not compete wi~h ~he in~ernal sensiti-zation sites to the extent of caus~ng the location of latent image centers formed on exposure to shift from the interior to the surface of the tabular grains.
Thus, a balance be~ween internal and 6urface sensltization is preferably maintained for maximum speed, but wlth the internal sensi~ization predoml-~ 1~569~
~o-nating. Tolerable levels of surface chemical sensi-tization can be readily determined by the following test: A sample of the high aspect ratio tabular grain internal latent image-forming silver halide emulslon of the present invention is coated on a tr~nsparent film support at a silver coverage of 4 grams per square meter. The coated s~mple is then exposed to a 500 watt tungs~en lamp for times ranging from 0.01 to 1 second at a distance of 0.6 meter.
The exposed coated sample is then developed for S
minutes a~ 20C in Developer Y below (an "internal type" developer~ note the incorporation of iodlde to provide access to the interior of the graln), fixed, washed, and dried. The procedure described above i8 repeated with a second sample identically coated and exposed. Processing is also identical, excep~ that Developer X below ~a "surface type" developer) is substituted for Developer Y. To satisfy the require-ments of the present invention as being a useful internal latent image-forming emulsion the sample developed in the internal type developer, Developer Y, must exhiblt a maximum denslty at least 5 times greater than the sample developed in ~he surface type developer, Developer X. This dif:Eerence in density 2S is a positive indication that the latent image centers of the silver halide grains are forming pre-dominantly in the interior of the grains and are for the most part inacoessible to the surface type devel-oper.
Developer X Grams N-methyl~-aminophenol sulfate 2.5 Ascorbic acid 10.0 Potassium metabora~e 35.0 Potassium bromide 1.0 Wa~er to 1 liter.

~1 Developer Y Grams N-methyl-~aminophenol sulfate 2.0 Sodium sulEite, desicc~ted 90.0 Hydroquinone ~-Sodium carbon~te, monohydrate 52.5 Potassium bromlde i.O
Potassium iodide 0-5 Water to 1 liter.
The high aspect ra~io tabular grain internal latent image-forming silver halide emulsions of the presen~ inven~ion can be surface chemically sensi-tized with active gelatin, as illustra~ed by T. H.
James, The Theory of the Photogr~hic Process, 4th Ed., Macmillan, 1977, pp. 67-76, or with sulfur, selenium, tellurium, gold, platinum, palladium, iridium, osmium, rhodium, rhenium, or phosphorus sensiti~ers or comblna~ions of the~e sensitizers, such as at pAg levels of from 5 to 10, pH levels of from 5 to 8 and temperatures of from 30 to 80C, as illustrated by Research Disclosure, Vol. 120, April 1974, Item 12008, Research Disc}o~ure, Vol. 134, June 1975, Item 13452, Sheppard et al U.S. Patent 1,623,499, Matthies et al U.S. Patent 1,673,522, Waller et al U.S. Patent 2,399,083, Damschroder et al U.S. Patent 2,642,361, McVeigh U.S. Patent 3,2979447, Dunn U.S. Patent 3,297,446, McBride U~Ko Patent 1,315,755, Berry et al U.S. Paten~ 3,772,031, Gilman et al U.S. Patent 3,761,267, Ohi et al U.SO Patent 3,857,711, Klinger et al U.S. Patent 3,565,633, Oftedshl U.S. Patents 3,901,714 and 3,904j415 and Simons U.K. Patent 1~396,696; chemic~l sensitizati~n being optionally conducted in the presence of thio-cyanate compounds, as described in Damschroder U.S.
Paten~ 2,642,361, and sulfur containing compounds of the type disclosed in Lowe et al U.S. Patent 2,521,926, Will~ams et al U.S. Patent 3,021,215, and Bigelow U.S. Patent 4,054,457. It is specifically ~5~2, con~emplated to sensi~ize chemically in the presence of finish (chemical sensitiza~ion) modifiers--that is, compounds known to suppresæ fog and increase speed when pre~ent during chemical sensitization, such as azaindenes, azapyridazines, azapyrimidines 9 benzothiazolium salts, and sensitlzers having one or more heterocyclic nuclei. ~xemplary finish modifiers are described in Brooker et al U.S. Patent 2,131,038, Dostes U.S. Patent 3,411,914, Kuwabara et al U.S.
Patent 3,S54,757, Oguchi et al U.S. Pa~ent 3,565,631, Oftedahl U.S. Patent 33901,714, Walworth Canadian Patent 778,723, and Duffin Photographic Emulsion Chemistry, Focal Press ~1966), New Ysrk, pp.
138-143. Additionally or alternatively, the emul-sions can be reduction sensi~ized--e.g., wlth hydro-gPn, as illustrated by Janusonis U.S. Patent 3,891,446 and Babcock et al U.S. Patent 3,984,249, by low pAg (e.g., less than 5) and/or high pH (e.g., greater than 8) treatment or through the use of reducing agents, such as stannous chlorids, thiourea dioxide, polyamines and amineboranes, as illustrated by Allen et al U.S. Patent 2,983,609, Oftedahl et al Research Disclosure, Vol. 136, August 1975, Item _ 136549 Lowe et al U.S. Patents 2,518,698 and 2,739,060, Roberts et al U.S. Patents 2,743~182 and '183, Chambers e~ al U.S. Patent 3,026,203 ~nd Bigelow et al U.S. Patent 3,361,564. Surface chemi-cal sensitization, including sub-surface sensi~iza-tion, illustrated by Morgan UOS. Patent 39917,485 and Becker UOS. Patent 3,966,476, is specifically contemplated.
Although the high aspect ratio tabular grain silver halide emulsions are generally responsive to the techniques for chemical sensitization known in the art in a quali~ative sense 9 in a quantitative sense--that is, in terms of the actual speed increases real~zed--the tabular graln emulsions " ~ 17~2 require careful investigation to identify the optimum chemical sensitization for each individual emulsion, certain preferred embodiments bein8 more speciflcally discussed below.
The high aspect ratio tabular grain silver halide emulsions can be spectrally sensitized. It is specifically contemplsted to employ spectral sensi-tizing dyes that exhibit absorption maxima in the blue and minus blue--i.e., green and red, portions of the visible spec~rum. In addition, for specialized applications, spectral sensitizing dyes csn be employed which improve spectral response beyond the visible spectrum. For example, the use of infrared absorbing sp~ctral sensitizers is specifically con-templated.
The high aspect ratio tabular grain silverhalide emulsions can be spectrally sensitized with dyes from a variety of classes, includ~ng the poly-methine dye class, which includes the cyanines, mero-cyanines, complex cyanines and merocyanines (i.e.,tri-, tetra- and poly-nuclear cyanines and mero-cyanines), oxonols, hemioxonols, styryls, merostyryls and streptocyanines.
The cyanine spectral sensitizing dyes include, ~oined by a methine link~ge, two b~sic heterocyclic nuclei, such as those derived from quinolinium, pyridinium, isoquinolinium, 3H-indolium, benz[e~indolium, oxazolium, oxazolinium, thiazolium, thiazolinium, selenazolium, selenazolinium, imida-zolium, imidazolinium, benzoxazolium, benzothia-zolium, benzoselenazolium, benzimidazolium, naphth-oxazolium, naphtho~hiazolium, naphthoselenazolium, dihydronaph~hothiazolium, pyrylium, and imidazopyra-z~nium quaternary salts.
The merocyanine spectral sensitizing dyes include, ~oined by a methine linkage, a basic hetero-cyclic nucleus of the cyanine dye type and an acidic 44 ~
nucleus, such as can be derived rom b~rbituric acid, 2-~hiobarbituric Acid~ rhodanine, hydan~oin, 2-thio-hyd~ntoin, 4-thiohydantoin, 2-pyrazolin-5-one, 2-is-oxazolin-S-one, indan-1,3-dione, cyclohexane-1,3-di-one, 1,3-dioxane-4,6-dione, pyrezolin-3,5-dione, pen-tane-2,4-dione, alkylsulfonylacetoni~rile 9 malono nitrile, isoquinolin-4-one, and chroman-2,4-dione.
One or more spectral sensitizlng 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 to whlch sensitivity is desired and upon the shape of the spectral sensitivity curve desired. Dyes ~ith over-lapping spectral sensitivity curves will often yield in combination a curve in which the sensit~vity at each wavelength in the area of overlap is approxi-mately equal to the sum of the sensitivities of the lndividual dyes. Thus, i~ is possible to use com-binations of dyes with different max;ma to achieve a spectral sensitivity curve with a maximum inter-mediate to the sensitizing maxlma of the individual dyes.
Combinations of spectral sensitizing dyes can be used wh~ch result in supersensitizAtion--that ls, spectral s~nsitization that is 8reater in some spectral region than that from any concentration of one of the dyes alone or that which would result from ~he additive effect of the dyes. Supersensitization can be achieved with selec~ed combinations of spec-tral sensitizing dyes and other ~ddenda3 such as stabilizers and antifoggAnts, devPlopment acceler-ators or inhibitors, coating aids, brighteners and antistatic agents. Any one of several mechanisms as well as compounds which can be responsible for super-sensitization are discussed by Gilman, "Review of the -4s -Mechanisms of Supersensitization"~ e~
Science and ~ , Vol. 18, 1974, pp. 418-430.
Spec~ral sensitlzing dyes also affec~ the emulsions in other ways~ Spectral sensltizing dyes can also function as an~ifoggan~s or stabllizers, development accelerators or inhibitors, and halogen acceptors or electron accep~ors 9 as disclosed in Brooker et al U.S. Patent 2,131,038 and Shiba et al U.S. Patent 3,9305860.
Sensitizing action can be correlated to the position of molecular energy levels of dye with respect to ground state and conduction band energy levels of the silver halide crystals. These energy levels can in ~urn be correlated ~o polarographic oxidation and reduction potentials 9 as discussed in ~ raphic Science and ~ Vol. 18, l.974, pp. 49~53 (Sturmer et al)~ pp. 175-178 (Leubner) and pp. 475-485 (Gilman). Oxidation and reductlon potentials can be measured as described by R. F.
Large in Photo~raphic Sensitivityl Academic Press, 1973, Chapter 15.
The chemistry of cyanine and related dyes is illustrated by Weissberger and Taylor, S~ecial Topics of Heterocyclic Chemistr~, John Wiley and Sons~ New York, 1977, Chapter VIII; Venkataraman, The Chemistry of Synthetic ~X~ Academic Press, New York, 1971, Chapter V; James, The Theory of the Pho~ Pro cess, 4th Ed., Macmil-an, 1977, Chapter 8, and F. M.
Hamer, C~anine Dyes and Related Compounds, John Wiley and Sons, 1964.
Although native blue sensitivity of silver bromide or bromoiodide is usually relied upon in the art in emulsion layers lntended to record exposure to blue light, significant advantages can be obtained by the use of spectral sensitizers 9 even where their principal ab~orption is in the spectral region to which the emulsions possess native sensitivity. For ~75&~
-4~ -example, it is specifically recognized that advan-tages can be realized from the use of blue spertral sensitizing dyes. Even when ~he emulsions of the ~nvention are high aspect ratio tabular grain silver bromide and silver bromoiodide emulsions, very l~rge lncreases ln speed are realized by the use of blue spectral s~nsitlzing dyes. Where it is lntended to expose emulsions according to the present invention in their region of native sensitivity7 advantages in sensiti~ity ean be gained by increasing the average thickness of the tabular grains up to 0.50 micron.
Useful blue spectral sensitizing dye~ 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 sensi-tizers. Polymethine dyes, such as cyanines, mero-cyanines~ hemicyaninesg hemioxonols, and merostyryls, are preferred blue spectral ~ensitizers Generally useful blue spectral sensitizers can be selected from among these dye classes by their ab&orption charac-teristics--i.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 wsvelength of the sensitizin~ maximum. Nuclei also influence absorption. The addition of fused rings to nuclei tends to favor longer wavelengths of absorption.
Substituents can also al~er absorption characteris-tics.
Among useful spectral sensitizing dyes for sensitizing silver halidP emulsions are those found in U.K. Patent 742,112; Brooker U.S. Patents 1,846,300, '3019 '302, '3039 '304, 2,078,233 and 2~089,729, Brooker et al U.S. Patents 2,165,338, 2,213,238, 23231,65~, 2,493,747, '74~, 2,526,632, 2,739,964 (Reissue 24,292), 2,778,823, 2,917,516, 3,352,857, 3,411,916 ~nd 3,431,111, Wilmanns et al ~ ~75~2 U.S. Patent 2,295,276, Sprague U.S. Patents 2,481,698 and 2,503,776, Carroll et al U.S. Patents 2,688,545 and 2,704,714, Larive et al U~S. Patent 2,9219067, Jones U~S. Paten~ 2,945,763 9 Nys et sl U.S. Patent 3,282,933, Schwan et al U.S. Paten~ 3 9 397,060, Riester U.S. Patent 3,660,1029 Kampfer et al U.S.
Patent 3,660,103, Taber et al U.S. Pa~ents 3,335,010, 37352,680 and 3,384,486, Lincoln et al U.S. Patent 3,397,981, Fumia et al U.S. Patents 39482,978 and 3,623~881, Spence et al U.S. Pa~ent 3 3 718,470 and Mee U~S. Patent 4,025,349. Examples of useful dye combinations, including supersensitizing dye combina-tions, are found in Motter U.S. Patent 3,506,443 and Schwan et al U.S. Patent 3,6729898. As examples of supersensitizing combinations of spectral senslti~.ing dyes and nonligh~ absorbing addenda, it is specifi-cally contemplated to employ thiocyanates during spectral sensitization, as taught by Leermakers U.S.
Patent ~,221,805; bis-triazinylaminostilbenes, as taught by McFall et al U.S. Patent 2,933,390; sulfo-nated aromatic compounds, as taught by Jones et al U.S. Patent 2,937,089; mercap~o-substltuted hetero-cycles, as taught by Riester U.S. Patent 3,457,078;
iodide9 as taught by U.K. Patent 1,413,826; and still other compounds, such as those disclosed by Gilman, "Review of the Mechanisms of Supersensitization", ci~ed above.
Conventio~al amounts of dyes c~n be employed in spectrally sensitizing the emulsion layers containing nontabular or low aspect ratio tabular silver halide grains. To realize the $ull advantages of this invention it is preferred to adsorb spectral sensitizing dye to the grain surf&ceæ of the h~gh ~spect ratio tabular grain emulsions in a substan-tially optimum amount--that is, in an amount suffl-cient to reallze at least ~0 percent o the maximum photographic speed attainable from the grains under ~ ~756g~

contemplated conditions of exposure. The quantl~y of dye employed will vary wlth the specific dye or dye oombination chosen as well as the size and aspect ratio of the grains. It is known in the photographic art ~hat optimum spectral sensitiza~ion iB obtained with organic dyes at about 25 percen~ 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 Sensi~i~ing Dyes", J rnal of Physieal and Colloid Chemi~t~
Vol. 56, No. 69 June 1948, pp. 1090-1103; and Gilman et al U.S. Patent 3,979,213. Optimum dye concentra-tion levels can be chosen by procedures taught by Mees, Theory of the Photographic_Process 9 pp -1067-1069.
Spectral sensitization can be undertaken at any stage of emulsion preparation here~ofore known to be useful. Most commonly spectral sensitization is undertaken in thP art subsequent t:o the completion of chemical sensitization. However9 lt is specifically recognized that spectral æensitization can be under-t~ken alternatively concurrently with chemical Rensi-tization, can er.~lrely precede chemical sensitiza-tion, and can even commence prior to the comple~ion of silver halide grain precipitation, as taught by Philippaerts et al U.S. Patent 3,628,960, and Locker e~ al U.S. Patent 4,225~666. As taught by Locker et al, it is specifically contemplated to distribute introduction of the spec~ral sensitizing dye into the emulslon so that a portion of the spectral sen~itiz-ing dye is present prior to chemical sensitization and a remaining portion is introduced after chemical sensitization. Unlike Locker et al, it is specifi-cally contemplated that the ~pectral sensitiæing dye ~Sfi92 can be added to the emulsion after 80 percent of the silver hallde has b~en precipitated. Sensit1zation can be enhanced by pAg adjustment, including cycling, during chemical and/or spectral sensitizatlon. A
specific exampl~ of pAg adjustment ls provided by R earch Disclosure, VolO 181, May 1979, Item 18155.
It has been discovered quite unexpectedly by Kofron et al, cited above, that high aspect ratio tabular grain silver halide Pmulsions can exhibit improved speed-granularity relationships when chemi-cally and spectrally sensi~ized than have been here-tofore realized using tabular grain ællver halide emulsions and have been heretofore realized using silver halide emulsions of the hlghest known speed-granularity relationshipæ. Best results have beenachiev4d using minus blue (red and/or green) spectral sensitizing dyes.
Although not required to re~lize all of their advantages, the emulsions of the present inven-tion are preferably, in accordance with prevailingmanufacturing practices, substantiLally optimally chemically and spectrally ~ensitlzed. That is, they preferably achleve speeds of at least 60 percent of the maximum log speed attainable Erom the grains in the spectral region of sensitizatLon under the con-t4mplated conditions of use and processing. Lo~
speed is herein defined as lO0 (l-log E), where E is measured in meter-candle-seconds at a density o Ool below maximum density. Oncs the silver halide grains of an emulsion have been char~cterized, it is possible to estimate from further product analysls and performance ev~luation whether an emulsion layer of a product appears to be ~ubstantially optimally chemically and spectrally sensiti ed ~n relation to comparable commercial offerings of other manufacturers.

~569 Nucleatin~ A~ents The high aspect ratio tabular grain internal la~en~ image-forming emulsions of this invention incorporate a nucleating agent ~o promote the forma-tion of a dlrect-positive image upon processing. The nucleating agent can be incorporated in the emulsion during processing, but ls preferably incorporated in manufacture of the photographic element, usually prior to coa~ing. This reduces the quantities of nucl~ating agen~ requiredO The quantities of nucleating agent requ~red can also be reduced by res~ricting the mobility of the nuclea ing agent in the photogr~phic element. Larg organic substituen~s capable of performing at least to some extent a ballasting function are commonly employed. Nucleat-ing agents which include one or more groups to promote adsGrption to the surf~ce of $he silver halide grains have been found to be effec~ive in extremely low concentrations.
A preferred general class of nucleatlng agents for use in the practice of this invention are aromatic hydrazides. Particularly preferred ~romatic hydrazides are those in which the aromatic nucleus is substituted with one or more group~ to restrict mobility and, preferably, promote ad~orp~ion of thehydrazide to silver hallde gr~in suraces. More specifically9 preferred hydrazides are those embraced by formula (I) below:
(I) H H
D-N-N-~-M
wherein D is an acyl group;
~ is a phenylene or substituted (e.g., halo-, alkyl-, or alkoxy-substituted~ phenylene group; and M is a moiety capable of restricting mobility, such as an adsorption promot~ng moiety.

~56 A particularly preferred class of phenyl-hydrazides are acylhydrazinophenyl~hioureas repre~
sented by formula (II~ below.
(II) Il H H l ll R~C-N-N-Rl-N--C-~

wherein R is hydrogen or an alkyl, cycloalkyl, halo-alkyl, alkoxyalkyl, or phenylalkyl substituen~ or aphenyl nucleus having a Hammett sigma-value-derived electron-withdrawing characteristic more positive than -0.30;
Rl is a phenylene or alkyl, halo , or alkoxy-substituted phenylene group;
R2 is hydrogen, benzyl, alkoxybenzyl, halobenzyl~ or alkylbenzyl;
R3 is a alkyl, haloalkyl, alkoxyalkyl, or phenylalkyl subætituent hav~ng from 1 to 18 carbon atoms, a cycloalkyl substituent~ a phenyl nucleus having a Hammett sigma value deriYed electron-with-drawiag char cteristic less positive than +0.50, or naphthyl, R4 is hydrogen or independently selected from among the same substituents as R3; or R3 and R4 together form a heterocyclic nucleus forming a 5- or 6-membered ringy wherein the ring atoms are chosen from the class consistlng of nitrogen, carbon~ oxygen, sulfur~ and selenium atoms;
with the proviso tha~ at least one of R2 and R4 must be hydrogen and the alkyl moieties, except as otherwise noted, ln each instance include from 1 to 6 carbon atoms and the cycloalkyl moieties have from 3 to 10 carbon atoms.
As indlcated by R in formula ~II), preferred acylhydrazinophenylthioureas employed in the practice of this inventlon contain an acyl ~roup which is the -52- ~g~
residue of a carboxylic acid 9 such as one of the acyclic carboxylic acids~ including formic ~cid, acetic acid, propionic acid, bu~yric acid, higher ~omologues of these acids having up ~o about 7 oarbon atoms, and halogen, alkoxy, phenyl and equivalent substituted derivatives thereof. In a preferred form, the acyl group is formed by an unsubstituted acyclic aliphatic carboxyl~c acid having from 1 to 5 carbon atoms. Specifically preerred acyl groups are formyl and acetyl. As between compounds which differ solely in terms of having a formyl or an acetyl group, the compound containing the formyl group exhibits higher nuclea~ing agent activity. The alkyl moieties ln the substituen~s to the carboxylic acids are contemplated to have from 1 ~o 6 carbon atoms, preferably from 1 to 4 carbon atoms.
In addition to the acyclic aliphatic car-boxylic acids, it is recognized that the carboxylic acid can be chosen so that R is a cyclic aliphatic group havlng from about 3 to 10 carbon atoms, such asg cyclopropyl, cyclobutyl, cyclopen~yl, cyclohexyl, methylcyclohexyl, cyclooctyl, cyclodecyl, and bridged ring variations9 such as, bornyl and isobornyl groups. Cyclohexyl iæ a specifically preferred cycloalkyl substituent. The use of alkoxy, cyano, halogen, and equivalent substituted cycloalkyl substituents is contemplated.
As indicated by Rl in formula (II), pre-ferred acylhydrazinophenylthioureas employed in the practice of this invention contaln a phenylene or subs~ituted phenylene group. Specifically preferred phenylene groups &re m- and p-phenylene groups.
Exemplary of preerred phenylene substituents are alkoxy substituents having from 1 to 6 carbon atoms, alkyl substituents having from 1 to 6 carbon atoms, 1uoro-, chloro-, bromo-, and lodo-substituents.
Unsubsti~uted p-phenylene groups are specifically ~5~9 ~ 3 preferred. Specifically preferred alkyl moieties are those which have from 1 ~o 4 carbon atoms. While phenylene and substituted phenylene groups are pre ferred linking ~roups, other functionally equlvalent divalent aryl groups, such as naphthalene groups, can be employed.
In one form R2 represents an unsubs~i~u~ed benzyl group or substituted equivalents thereof, such as alkyl, halo , or alkoxy-substituted benzyl groups. In the preferred form no more than 6 and, most preferably, no more than 4 carbon atoms are contributed by substltuents to the benzyl group.
Substituents to the benzyl group are preferably para-substituents. Speciically preferred benzyl substi~uents are formed by unsubstituted, 47halo-sub-stituted, 4-methoxy-substituted, and 4-methyl-substi-tuted benzyl groups. In another specifically pre-ferred form R2 represents hydrogen.
Referring again to formula (II) 3 it is apparent that R3 and R4 can independently take a variety of forms. One specifically contemplated form can be an alkyl group or a substituted alkyl group, such as P haloalkyl group, alkoxyalkyl group, phenyl- -alkyl group~ or equivalent group, having a total of up to 189 preferably up to 12~ carbon atoms. Speci-fically R3 and/or R4 can take the orm of P
methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl; decyl or higher homologue group having up to 18 total carbon atoms; a fluoro-, chloro-, bromo-, or iodo subætituted der~vative thereof; a methoxy 3 ethoxy, propoxy, butoxy or higher homologue alkoxy-substituted derivative thereof, wherein the total number of carbon atoms are necessarily at least 2 up to 18; and a phenyl-substituted derivative thereof, wherein the total number of carbon atoms is necessarily at least 7, as ln the case nf benzyl,up to about 18. In a specific preferred form R3 1 17~g2 and/or R4 can take the form of an alkyl or phenyl~
alkyl substituent, wherein the alkyl moieties are in each instance from 1 ~o 6 carbon atoms.
In addition to the acyclic aliphatic and aromatic forms discu~sed above, it i8 al60 contem-plated that R3 and/or R4 can ~ake the form of a cyclic aliphatic substituent, such as a cycloalkyl ~ubs~ituent having from 3 to 10 carbon atoms. The use of cyclopropyl 9 cyclobutyl ? cyclopentyl, cyclo-hPxyl, methylcyclohexyl, cyclooctyl, cyclodecyl andbridged rlng variations, such as, bornyl and iso-bornyl groups, is contemplated. Cyclohexyl is a pre-ferled cycloalkyl substituent. The use of alkoxy~
cyano ? halogen and equivalent substituted cycloalkyl substituents is contemplated.
R3 and/or R4 can also be an aromatic substituent, such as, phenyl or naphthyl (i.e~, l-naphthyl or 2-naphthyl) or an equivalent aromatic group, e.g., 1-, 2-, or 9-anthryl, etc. As indicated in formula (II) R3 and/or R4 can take the form of a phenyl nucl~us which ls either electron-donating or electron-withdrawing, however phenyl nuclei which are highly electron~withdrawing may produce inferior nucleating agents.
The electron-withdrawing or electron-donat-ing characteristic of a specific phenyl nucl~us can be ~ssessed by reference to H~mmett sigma values.
The phenyl nucleus can be a6signed a Hammett sigma value-derived electron-withdrawing characteristic which is the algebraic sum of the Hammett s~gm~
values of its substituents (i.e. 7 those of the ~ub-st~tuents, if any, to the phenyl group). For example, the Hammet~ sigma values of any substituents to the phenyl rlng of the phenyl nucleus can be determined algebraically simply by determining from the literature the known Hammett sigma values for each substituent and obtaining the algebraic sum thereof. Electron-withdrawing subs~ituents ere assigned positlve sigma values, while electron-donat-ing substi~uents are assigned negative sigma values.
Exemplary meta- and ~ sigma values and procedures for ~heir determination are set orth by J. Hine in Phy~ L~ Ghemistry, second edi tion, page 87, published in 19629 H. VanBekkum, P. E.
Verkade and B. M. Wepster in Rec. Trav. ChimO, Volume 78, page 815, published in 1959, P. R. Wells ln Chem.
Revs., Volume 63, page 171, published in 1963, by H.
H. Jaffe in Chem. Revs., Volume 53, page 191, pub-lished in 1953, by M. J. S. Dewar and P. J. Grisdale in J. Amer. Ci~em. Soc., Volume 84, page 354g9 pub lished in 1962, and by Barlin and Perrin in Quart.
lS Revs., Volume 20, page 75 et ~, published in 1966.
For ~he purposes of this invention, ortho-substi-tuents to the phenyl ring can be assigned to the pub-lished para~sigma values.
It is preferred that R2 and/or R3 be a phenyl nucleus having a Hammett sigma vslue-derived electron-withdrawing characteristic less positive than ~0.50. It is speclfically contemplated that R2 and/or R3 be chosen rom among phenyl nuclei having cyano, ~luoro-, chloro- 3 bromo-, iodo-, alkyl groups h~ving from 1 to 6 carbon stoms, and alkoxy groups having from l to 6 carbon atoms, ~s phenyl ring substituents. Phenyl ring fiubstituents are pre-ferred in the ~ - or 4-ring position.
Rather than being independen~ly chosen R3 and R3 can together form, along w~th the 3-position nitrogen atom of the thlourea, a he~erocyclic nucleus forming a 5- or 6~membered rin~. The ring atoms can be chosen from ~mong nitrogen, carbon, oxygen, sulfur and selenium atoms. The ring necessarily contains at least one nitrogen atom. Exemplary rings include morpholino, piperidino, pyrrolidinyl, pyrrolinyl~
thiomorpholino, thiazolidinyl, 4-thiazolinyl~ selen-~ 56-azolidinyl, 4-selenazolinyl, imidazolidinyl, imid-azolinyl, ~xazolidinyl and 4-oxazolinyl rings.
Specifically preferred rings are saturated or other-wise constructed to avoid electron withdrawal from the 3-position nitrogen atom.
Acylhydrazinophenyl~hiourea nucleating agents and their synthesis are more specifically dis~
closed in Leone U~S. Patents 4,030,925 and 4,276,364. Variants of ~he acylhydrazinophenyl-thiourea nucleating agents described above aredisclosed in von Konig U.S. Patent 4,139,387 and Adachi et al published U.K. Patent Application 2,012,443A.
Another preferred class of phenylhydrazide nucleating agents are N (acylhydrazinophenyl~thio-amide nucleat1ng agents, such as those indicated by formula (III~ below:
(III) O S
ll H H ll R-C-N N-Rl-N---G---A

wherein R and Rl are as defined in formula ~II);
A is =N-R2, -S- or -0-;
Ql represents the atoms necessary to com-plete a five-membered heterocyclic nucleus;
R2 is independently chosen from hydrogen, phenyl, alkyl, alkylphenyl, and phenylalkyl; and ~he alkyl moieties in each instance include from 1 to 6 carbon atoms.
These compounds embrace those having a five-membered heterocyclic thioamide nucleus, such as a 4-thiazoline-2-thione, thiazolidine-2-thione, 4-oxazoline-2-thione~ oxa~olidine-2-thione, 2-pyrazoline-5-thione~ pyrazolidine-5-thione, indo-line-2-thione, 4-imidazoline-2-thione, etc. A speci-fically preferred subclass of heterocyclic thioamide ~ ~.756~

nuclei is formed when ~ is as indicated in formula (IV~
(IV) X

wherein X is =S or zO.
Specifically preferred illustrations of such values of Q~ are 2-thiohydAntoin, rhodanine, isorhod~nine, and 2-thio-2,4-oxazolidinedione nuclei. It is believed th~t some six membered nuclei 9 such as thio-barbituric acid, may be equivalent to five-membered nuclei embraced within formula (III3.
Another specifically preferred subclass of heterocyclic thioamide nuclei is formed when ~1 is as indicated in formula (V~
(V) X

-C-c~L L~n_lT
wherein L ls a methine group;
Z~
l l o= <R4 T is -C-~CH=CH-~d lN-R3 or ~CH-~
R3 is an alkyl substituent 7 ,R5 R4 is hydrogeni an alkyl, -N\R69 or an alkoxy substituent;
Z represents the nonmetallic atoms necessary to complete a baslc heterocyclic nucleus of the type found ln cyanine dyes;
n ~nd d are independently chosen from the integers 1 and 2;

~75 Rs and R6 are ~ndependently chosen from hydrogen, phenyl, alkyl 9 alkylphenyl, and phenyl-alkyl; and the alkyl moie~ies in each ins~ance include from 1 to 6 carbon atoms.
The formula (V) values for Ql provide a heterocyclic thioamide nucleus oorresponding to a methine substitu~ed form of the nuclei presen~ above in formula (IV) values for Ql. In a specifically preferred form the heterocyclic thioamid2 nucleus is preferably a methine substitu~ed 2-thiohydantoîn 9 rhodanine, isorhodanine, or 2-thlo 2,4-oxazolidinedi one nucleus. The heterocycllc thioamide nucleus of formula (V) is directly, or through an intermediate methine linkage, substituted with a basic het~ro~
cyclic nucleus of the type employed in cyanine dyes or a eubstltuted benzylidene nuclues. Z preferably represents the ~onmetallic Rtom~ necessary to com-plete a basic 5- or 6-membered heterocycl~c nucleus of ~he type found in cyanine dyes having ring-forming atoms chosen from the class consi6ting of carbon, nitrogen9 oxygen, sulfur, and selenium.
N-(acylhydrazinophenyl~thioamide nucleat~ng agents and their synthesis are more specifi~ally dis-closed in Leone et al U.S. Patent 4,080,207.
Still another preferred class of phenyl-hydrazide nucleating agents are triazole-substituted phenylhydrazide nucleating agents. More ~pecifi-cally, preferr~d triazole-substi~uted phenylhydrazide nucleating agents are those represented by formula VI
below:
(VI) o Il H H
R-C-N-N-RI-A~-A2-A 3 wherein R and Rl are as defined in formula ~7 ~59-A' is alkylene or oxalkylene;
O O
Il ~ 11 A2 is -C-N- or S-N-; and O
A3 is a triazolyl or benæotriazolyl nucleus;
the alkyl and alkylene moieties in each instance including from l to 6 carbon atoms.
Still more specifically preferred triazole-substituted phenylhydrazide nucleating agents are those represented by formula (VII) below:
(VII) I l H H 11 H / \ /N~
R-C-N-N Rl-C~ i N
\ / \N/
H

wherein R is hydrogen or methyl;
/~
Rl is ~ [CH2]n- or ~ OE
[CH2]n~
n is an integer of 1 to 4; and E is alkyl of from 1 to 4 carbon atoms.
Triazole-substituted phenylhydrazide nuc-leating agents and their synthesis are disclosed by Sidhu et al U.S. Patent 4,278,748. Comparable nucleating agents having a somewhat broader range of adsorption promotlng groups are disclosed in corre-sponding published UoK~ Patent Application 2,011,391A.
The aromatic hydrazides represented by formulas (II), ~III), and (VI) each contain adsorp-tion promoting substituents. In many ins~ances it is preferred to employ in combination with these ~ro-matic hyrazides additional hydrazides or hydrazones which do not contain substituents specifically .

~ ~7~9~

intended to promo~e adsorption to silver halide grain surfaces. Such hyraæides or hydrazones, however, often contain substituents to reduce ~heir mobility when incorporated in photographic elements. These hydrazide or hydrazones can be employed as the sole nucleating agent, if desired.
Such hydrazides and hydrazones include those represented by formula (VIII) and (IX) below:
(VIII) H H
T-N-N-T' and (IX) H

wherein T is an aryl radical~ including a substituted aryl radical, Tl is an acyl radical, and T~ is an slkylidene radical and including substituted alkyli-dene radicals. Typical aryl radicals for the sub-stitu~ent T have the formula M-T3 T ~ wherein T3 is an aryl radical (such as, phenyl, l-naphthyl, 2-naphthyl, etc.) and M can be such substituen~s as hydrogen, hydroxy, amino, alkyl, alkylamino, aryl amino, heterocyclidc amino (amino containing a heterocyclic moiety), alkoxy9 aryloxy, acyloxy, aryl-carbonamido, alkylcarbonamido, heterocyclic carbon-amido (carbonamido contalning a heterocyclic moiety) 9 arylsulfonamido, alkylsulfonamido 9 and heterocyclic sulfonamido (sulfonamido containlng a heterocyclic molety). Typical acyl radicals for the substituent Tl have the formula O O
Il 11 ~S-Y or -C-G
o wherein Y can be such substituents as alkyl, aryl, and heterocyclic radicals, G can represent a hydrogen atom or the same substituent as Y as well as radicals ~ ~756~

having the formula o Il - C -0 -~
to form oxalyl radicals wherein A is an alkyl~ aryl, or a heterocyclic radical. Typical alkylidene radi-cals for the substi~uent T2 have the formula GCH-D
wherein D can be a hydrogen atom or such radicals as alkyl 7 aryl, and he~erocyclic radicals. Typical aryl substituen~s for the above-described hydrazides ~nd hydrazones include phenyl, naph~hyl 9 diphenyl, and the like. Typical heterocyclic substituents for thP
above-described hydrazides and hydrazones include azoles, azines, furan, thiophene~ quinoline, pyra-zole, and the like. Typical alkyl (or alkylidene)substituents for the above-described hydrazides an~
hydrazones have 1 to 22 carbon atoms including methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl, t butyl, amyl, n-octyl, n-decyl 9 n-dodecyl, n-octadecyl, n-eicosyl, and n-docosyl.
The hydrazides and hydrazones represented by formulas ~VIII) and (IX) as well as their synthesis are disclosed by Whitmore U.S. Patent 3~227,552.
A secondary preferred general class of nuc-leating agents for use in the practice of this lnven-tion are N-substituted cycloammonium quaternary salts. A particularly preferred species of such nucleating agents is represented by formula (X) below:
(X) 1; - Z
N ~CH-CH)~ l=C-E
X- (CH2~a wherein Zl repre6ents the atoms necessary to com-plete a heterocyclic nucleus containing a hetero-~756~2 cyclic ring of 5 to 6 atoms including the qua~er~l~ry nitrogen atoms, with the additional atom~ of ~aid heterocyclic ring bein~ selected from carbon, nitro-gen, oxygen, sulfur, and selenium;
j represents a positlve integer of rom l to 2;
a represen~s a positive integer of from 2 to 6, X~ represen~s an acid anlon;
E2 represen~s a member selected from (a~ a formyl radic~l (b) a radical having the formula L

-C~

wherein each of Ll and L2, when taken alone, represen~6 a member selected from an alkoxy radical ~nd an alkylthio radlcal, and Ll and L2, when taken together~ represent the atoms necessary to com-plete a cyclic radical selected from cyclic oxy-a~etals and cyclic thioacetals havlng from 5 to 6atoms in the heterocyclic acetal ring, and (c) a l-hydrazonoalky radical; and El represents either a hydrogen atom, an alkyl radical, an aralkyl radical~ an alkylthio radi-cal, or an ~ryl radical such as phenyl and naphthyl,and including substituted aryl rad~cals.
The N-substituted cycloammo~ium quaternary salt nucleating agents of formula (X) and their synthesis are disclosed by Lincoln and Heseltine U.S.
Patents 3,615,615 and 3,759,901. In a variant form Ei can be a divalent ~lkylene group of from 2 to 4 carbon atoms joining two substituted heterocyclic nuclei AS shown in formula (X). Such nurleating agents ~nd their synthesis are dlsclosed by Kurtz and Harbison U.S. Patent 3,734,738~
The substituent to the quaternized nitrogen atom o the heterocyclic ring can, in another variant form, itself form a fused ring wi~h the heterocyclic ring. Such nucleating agents are illustrated by dihydroaromatic quanternary salts comprlsing a 1,2-dihydroaromatic he~erocyclic nucleus including a quaternary ni~rogen atom. Particularly advantageous 1,2-dihydroaromatic nuclei include such nuclei as a 1,2-dihydropyridinium nucleus. EspeciAlly preferred dihydroaromatic quaternary salt nucleating agents include those represented by formula (XI) below:
(XI) I x~
¦ ~ R2 ¦ n wherein Z represents the nonmetall~c atoms necessary to complete a heterocyclic nucleus containing a heterocyclic ring of from 5 to 6 atoms includ~ng the quaternary nitrogen atom, with the additional atoms of said heterocyolic ring being selected from either carbon, nitrogen, oxygen, sulfur, or selenium;
n represents a positive ~nteger having e value of from 1 to 2;
when n is l, R represents a member selected from the group consisting of a hydrogen atom, an alkyl radic~l, an alkoxy radical, an aryl radical, an aryloxy radical, and a carbamido radical and, when n is 2, R represents an alkylene radi-cal having from l to 4 carbon atoms, each of Rl and R2 represents a member selected from the group consisting of a hydrogen atom, an alkyl radical, and an aryl radical; and X~ represents an anion.
Dihydroaromatic quaternary sal~ nucleating agents and their synthesis are disclosed by Kurtz and Heseltine U.S. Patents 3,719,494.

~5 ~4-A specifically preferred class of N-substi-tu~ed cycloammonium qua~ernary salt nucleating agents are those whlch include one or more alkynyl 6ubs~i~u-ents. Such nucleatlng agents include compounds with-in ~he generic struc~ural definition set forth informula ~XII) below:
(XII) , z~

wherein Z represents an atomic group necessary for forming a 5- or 6-membered heterocyclic nucleus, represents an aliphatic group 9 R2 repr~sents a hydrogen atom or an aliphatic group, R3 and R4, which may be ~he same or differen~, each represen~s a hydrogen atom, e halogen atom, an aliphatic group, an ~lkoxy group, a hydroxy group, or an aromatic group, at least one of Rl, R2, R3 and R4 being a propargyl group, a butynyl group, or a substituent containing a propargyl or butynyl group, X~ repre-~ents an anion, n is 1 or 2, with n being 1 when the compound forms an inner salt.
Such alkynyl-substituted cycloammonium quaternary salt nucleating agents and their synthe~i 6 are illustrated by Adachi et al U.S. Patent 4,115,122.
The specific choice of nuclea~ing agents can be influenced by a variety of faetors. The nucleat~
ing agents of Leone cited above are particularly pre-ferred for many applications, since they are effec-tive At very low concentrations. Minimum concentra-~ions as low as 0.1 mg of nucleating agent per mole of silver, preferably at least 0.5 mg per silver mole, and optimally at least 1 mg per silver mole are disclosed by Leone. The nuclea~ing agents of Leone are par~icularly advantageou6 in reducing speed loss ~7$692 and in some instances permit~ing speed galn with increasing processlng temperatures. When the nuc-leating agents of Leone are employed in combina~ion with those of Whitmore spe d varia~ions as a function of tempera~ure of processing can be mlnimized.
The aromatic hydrazide nucle~ting agents are generally preferred for use ln photographic elements intended to be processed at compara~ively high levels of pH, typically above 13. ~he alkynyl~substituted cycloammonium quaternary salt nucleating agerlts are par~icul~rly useful for processing at a pH of 13 or less. Adachi et al teaches these nucleating agents to be useful ln processing within the pH range of from 10 to 13, pr~ferably 11 to 12.5.
In addition to the nucleating agents des-cribed above additional nucleating agen~s have been identified which are useful in processing at pH
levels in the range of from about 10 to 13. An N-substituted cycloammonium quaternary salt nucleat-ing agent which can conta~n one or more alkynyl sub stituents is illustrative of one class of nucleating agents useful in processing below pH 13. Such nuc-leating agents are illustrated by formula (XIII) below:
(XIII) I I ~
C-Y2-C= C-C z2 ~ lm_l~R An-l wherein zl represents the atoms completing an aromatic carbocyclic nucleus of from 6 to 10 carbon atoms;
yl ~nd y2 are independently selected from among a divalent oxygen atom, a divalent sulfur atom, and -N-R3 ~ ~.566_ Z2 represents the atoms completing a heterocylclic nucleus of the type found ~n cyanine dyes;
A is an adsorption promoting moiety;
m and n are 1 or 2; &nd Rl 9 R2, and R3 are independently chosen from the group consisting of hydrogen, alkyl, aryl, alkaryl, and aralkyl and Rl and R3 are additionally independently chosen from the group con-sisting of acyl, alkenyl, and alkynyl, the al~phatlc moietie~ containing up to 5 carbon atoms and the aromatic moieties containing 6 to 10 carbon atoms. A
preferred processing pH when these nucleating agen~s are employed is in the ran~e of from 10.2 to 12Ø
Nucleating agents of the ~ype repreæented by formula (XIII) and their synthesis are disclosed by Baralle et al U.S. Patent 4,3069016, cited above.
Another class of nuclea~ing ag~nts effective in the pH range of from lO to 13, preferably 10.2 to 12, are dihydrospiropyran bis-condensation products of salicylic aldehyde and at leas~ one heterocyclic ammonium salt. In a preferred form such nucleating ag~nts are represen~ed by formula (XIV) below:
(XIV) H /Y~~
H /f \N-~

R s R7 T ;.\R4 wherein X and Y each independently represent a sul-fur atom, a selenlum atom or a -C(RIR2)- radical, Rl and R2 independently represent lower alkyl of from 1 to 5 carbon atoms or together repre sent an alkylene radical of 4 or 5 carbon atoms, ~7 R3, R4, Rs, and R5 each represent hydrogen, a hydroxy radical or a lower alkyl or alkoxy radical of from 1 to 5 carbon atoms, zl and Z2 each represents the nonmetal-lic atoms completing a nitrogen-containing hetero-cyclic nucleus of the type found in cyanine dyes and R7 and R3 each represent a ring nitrogen substituent of the type found in cyanine dyesO
Z~ and Z2 in a preferred form each com-pletes a 5- or 6-membered ring, preferably fused with at least one benzene ring, containing ~n the ring structure carbon atoms, a single nitrogen atom and, optionally, a sulfur or selenium atom.
Nuclea~ing agents of the type represented by formula (XIV) and their synthesis are disclosed by Baralle et al U.S. Patent 4,306,017, clted above.
Still another class of nucleating agents effective in th~ pH range of from 10 to 13, prefer-ably 10.2 to 12, are diphenylmethane nucleating agents. Such nucleating agents are illus~rated by formula (XV) b~low:
(XV) ~R3 `~ C\C /C_, Rl/ \R2 wherein zl and Z2 represent the atoms completing a phenyl nucleus;
Rl represents hydrogen or alkyl of from 1 to 6 carbon atoms; and R2, R3, and R4 are independently selected from among hydrogen, halogen~ alkyl, hydroxy, alkoxy, aryl, alkaryl, and aralkyl or R 3 and R4 together form a covalent bond, a divalent ", -6~-chalcogen linkage, or / \
Rl R2 wherein each alkyl moiety contains from 1 to 6 carbon atoms and each ~ryl moiety contains 6 to lO c~rbon atoms.
Nucleating agents of the ~ype represPn~ed by formula (XV) and their synthesis are disclosed by Baralle et al U.S. Patent 4,315,g86, cited above.
Silver Ima~in~
Once high ~spect ratio tabular grain inter-nal latent image-forming emulsions have b~en gene-rated by precipitation procedures, washed, and sensitized, as described above, their preparation can be completed by the incorporation of nucleat~ng agents, described above, and conventional photo-graphic addenda, and they can be usefully applied to photographic applications requiring a silver image to be produced- e.g., conventional black-and-white photography.
Dickerson, cited above, discloses that hardening photographic elements accordlng to the present invention intended to form silver imAgeS to an extent sufficient to obviate the necessity of incorporating additional hardener during processing permits increased silver covering power to be realized as compared to photographic elements ~imi-l~rly hardened ~nd processed, but employing nontabu-lar or less than high ssp~ct ratio tabular grain emulsions. Specifically, it is taught to harden the high aspect ratio tabular grain emulslon layers and other hydrophilic colloid layer~ of black-and-white photographic elements in an amoun~ sufficient to reduce swelling of ~he layers to less than 200 percent, percent 6welling bein~ determined by (~) incubating the photographie element at 38C for 3 days at 50 percent relative humidity, (b) measuring ~7 layer thickness, (c) immersing the photographic element in distilled water at 21~C for 3 minu~es, and (d) measuring change in layer thlckness. Although it is specific~lly preferr d to harden the photograph1c elements intended ~o form silver lmages ~o such an extent that hardeners need not be lncorporated in processing solutlons, ~t is recognlzed that the emulsions of the present invention can be hardened to any conventional level. It is fur~her specifically contemplated to incorporate hardener~ ln processing solutions, as illustrated, for example, by Research Disclosure, Vol. 184, Augu6t 1979, Item 18431, Paragraph K, relating particularly ~o the processing of radiographic materials.
Typical useful incorporated hardeners (fore-hardeners) include formaldehyde and free dialdehyde~, such as succinaldehyde and glutaraldehyde, as illus~
trated by Allen et al U.S. Patent 3,232,764; blocked dialdehydes, as illustrated by Ka~zuba U.S. Patent 2,586,168, Jeffreys U.S. Patent 2,870,013, and Yamamoto et al U.S. Patent 3,819,608; ~-diketones, as illustrated by Allen et al U.S. Patent 2,725,305;
active esters of the type described by Burness et al U.S. Patent 3,542,55~; sulfonate esters, as illus-trated by Allen et al U.S. Paten~s 2,725,305 ~nd2,726,162; aGtive halogen compounds, as illustrated by Burness U.S. Patent 3,106l468, Silverman et al U.S. Patent 3,839,042, Ballantine et al U.S. Patent 3,951,940 and Himmelmann et al U.S. Patent 3,174,861;
s triazines and di~zines, as illustrated by Yamamoto et al U.S. Patent 3,3255287, Anderau et al U.S.
Patent 3~288,775 and Stauner e~ al U.S. Paten~
3,9g2,366; epoxides, as illus~rated by Allen et al U.S. Pa~en~ 3,047,394, Burness U.S. Paten~ 3,139~459 and Birr et al German Patent 1,085,663; aziridines, as illu6tra~ed by Allen et al U.S. Patent 2,950,197, Burness et al U.S. Patent 3,271,175 and Sato et al ~" 11~6~2 U.S. Patent 3,575,705; active oleins having two or more active vinyl group~ ~e.g. vinylsulfonyl groups) 9 as illustrated by Burness et al UOS Patent6 3,490,911, 3,539,644 ~nd 3,841,872 (Reissue 29J305)~
Cohen U.S. Patent 3~640,720, Kleis~ et ~1 German Patent 872,153 and Allen U.S. Patent 2,992,109;
blocked active olefins, as illustra~ed by Burness et al U.S. Patent 3,360,372 and Wilson U.S. Patent 3,345,177; carbodiimide~, as illustrated by Blout et 10 al German Patent 1,148,446; isoxazol~um salts unsubstituted in the 3~posit;on, as illustrated by Burness e~ Al U.S. Patent 3,321,313; esters of 2-alkoxy-N-carboxydihydroquinoline, as illustrated by Bergthaller et al U.S. Paten~ 4,013,4689 N-carbamoyl and N-carbamoyloxypyridinium ~alts, as illustrated by Himmel~ann U.S. Patent 3,880,665; hardeners of mixed function~ such as halogen-~ubstituted ~ldehyde acids (e.g., mucochloric and mucobromic acids), as illus-trated by White U.S. Patent 2,080,019~ 'onium substi-tuted acroleins, as illustrated by Tschopp et 81 U . S -Patent 3,792,021, and vinyl sulfones contalning other h~rdening functional groups, as illustrated by Sera et al U.S. Patent 4,028,320; and polymeric hardeners~
such as dialdehyde starches, as illustrated by Jeffreys et al U.S. Patent 3,057,723, and copoly-(acrolein-methacrylic acid), as illustr~ted by Himmelmann e~ al U.S. Pstent 3,396,029.
The use of forehardeners in combination is illustrated by Sieg et al U.S. Patent 3,497,358, Dallon et al U.S. Patent 3,832,1Bl and 3,840,370 and Yamamoto et al U.S. Patent 3,898,089. Hardening accelerators can be used, as illustrated by Sheppard et al U.S. Patent 2,165,421, Kleiæt German Patent 881,444, Rlebel et al U.S. Patent 3,628,961 and Ugi et al U.S. P~tent 3,901,708.
Instabillty which decreases maximum density in direct-posltive emulsion coatings can be protected ~ ~5~92 against by incorporation of fitabilizers, antiog-gants, antikinking agents, l~ten~ imag ~tabilizers ~nd similar addenda in the emulsion and contiguous layers prior to coating. A variety of such addend~
are disclosed in Research Disclosure, Vol. 176, December 197B, Item 17643, P&ragraph VI. Many of the antifoggants which are effective in emulsions can also be used in developeræ ~nd can be classified under a few general headings, as illustrated by C.E.K. Mees, The Theor~ of the Photographic Process, 2nd Ed., Macmillan, 1954, pp. 677-680.
In eome applications improved results can be obtained when the direct-positive emulsions are pro-cessed in the presence of certain antifoggants, ~s disclosed in Stauffer U~S. P~tent 2,497,917. Typical useful antifoggants of thi6 type include benzotria-zoles, such as benzotriazole, 5-methylbenzotriazole, and 5-ethylbenzotriazole; benzimidazoles ~uch AS

5-nitrobenzimidazole; benzothiazoles such as 5-nitro-benzothiazole and 5-methylbenzothiazole; heterocyclic thiones such as l-methyl-2-tetrazoline-5-thione;
triazines such as 2,4-dimethylamino~6-chloro 5-tria-zine; benzoxazoles such as ethylbenzoxazole; and pyrroles such as 2,5-dimethylpyrrole.
In certain embodiments, good results are obtained when the elements are processed in the presence of high levels of ~he antifoggants mentioned above. When antifoggants such as benzotriazoles are used, good results c~n be obta~ned when the process ing solution contains up to 5 grams per liter and pref~rably l ~o 3 grams per liter; when they are incorporsted in the photographic element 9 concentra-tions of up to 1,000 mg per mole of æilver and pre-ferably concentrations of 100 to 500 mg per mole of silver are employed.
In addition to sensi~izer6, hardeners, Qnd antifoggants ~nd stabilizer6, a variety of other ~756~

conventional photographic addenda can be present.
The specific choice of addenda depends upon the exact nature of the photographic application and is well within the capability of the art. A variety of use-ful addenda are disclosed in Research Disclosure,Yol~ 176, December 1978, Item 17643. Op~ical brighteners can be introduced, as disclosed by Item 17643 at Paragraph V. Absorbing and scattering materials can be employed in the emulsions o the invention and in separate layers of the photographic elemen~s, as described in Paragraph VIII. Coating aids, as described in Paragraph XI, and plasticizers and lubricants, as described in Paragraph XII, can be present. Antistatic layers, as described in Para-lS graph XIII, can be prPsent. Methods of addition oaddenda are described in Paragraph XIV. Matting agents can be incorporated, as dPscribed in Paragraph XVI. Developing agents and development modifiers can, if desired, be incorpora~ed, as descrîbed in Paragraphs XX and XXIo When the photographic elements of the invention are intended to serve radiogr~phic applica~ions, emulsion and other layers of ~he radiogr~phic element can take any of the forms specifically described in Research Disclosure, Item 18431, cited aboveO The emulsions of ~he invention, as well as other, conventional silver halide emulsion l~yers~ interlayers, overcoats, and subbing layers, if any, present in the photographic element8 can be coated and dried as described in Item 17643, Para-gr~ph XV~
It is specifically contempla~ed to blend thehigh aspect ratio tabular grain internal latent imags-orming emulsions of the present invention w~th each other or with conventional emulsions to satisfy specific emulsion layer requirsments. For example, ~wo or more Pmulsions according to the present inven-tion, but differing in average grain diameter can be blended. It is specifically contemplated to employ in blending internal latent image-forming grains of similar grain size distribution to minimize migration of addenda between different grain popula~ions. When separate emulsions of similar grain size distribution are employed in combination, their performance can be differentiated by differences in surface sensitiza-tion levels, differPnces relating to adsorbed nuc-leating agents, or differences in proportions of internal sensitizeres (taught by Atwell et al U.5.
Patent 4,035,185). Silverman et al Can. Ser.No.
415,280, filed concurrently herewith, enti~led BLENDED DIRECT-POSITIVE EMULSIONS, PHOTOGRAPHIC
ELEMENTS, AND PROCESSES OF USE, commonly assigned, discloses tha~ the blending of core-shell emulsions in a weight rat~o of from 1:5 to 5:1, wherein a first emulsion exhibits a coefficient of variation of less than 20% and a second emulsion has an average grain diameter less than 65% that of the first emulsion, can result in unexpected increase in silver covering power. A speed increase can also be realized, even at reduced coating levels. The ratio of the first emulsion to the second emulsion is preferably 1:3 to 2:1, based on weight of silver, and the average diameter of the grains of the second emulsion is preferably less than 50%, optimally less than 40% the average diameter of the grains of the first emul-sion. The second emulsion can be any conventional internal latent image-forming emulsion, bu~ is preferably substantially free of surace chemical sensitization.
In their simplest form photographic elements according to the present invention employ a slngle silver halide emulsion layer containing a high aspect ratio tabular grain emulsion according to the present invention and a photographic support. It is, of course, recognized that more than one silver halide J~ ~-J

emulsion layer as well as overcoat, subbing, and interlayers can be usefully included. Instead of blending emulsions as described above the same effect can frequently be achieved by coating the emulsions to be blended as separate layers. Coating of sepa-ra~e emulsion layers ~o achieve exposure latitude is well known in the ar~, as illustrated by Zelikman and Levi, Making and Coating Photographic Emulsions, Focal Press, 1964, pp. 234-238; Wyckoff U.S. Patent 3,663,228; and U.K. Patent 923,045. It is further well known in the art that increased photographic speed can be real;zed when faster and slower silver halide emulsions are coated in separate layers as opposed to blending. Typically the faster emulsion layer is coa~ed to lie nearer the exposing radl~tion source than the slower emulsion layer. This approach can be extended to three or more s~perimposed emul-sion layers. Such layer arrangements are specifical-ly contemplated in the practice of this invention.
The layers of the photographic elements can be coated on a variety of supports. Typical photo-graphic supports include polymeric film, wood fiber--e.g., paper, metallic sheet and foil, glass and ceramic supporting elements provided with one or more subbing layers to enhance the adhesive, anti-static, dimensional, abrasive, hardness, frictional, antihalation and/or other properties of ~he support surface.
Typical of useful polymeric film supports are films of cellulose nitrate and cellulose esters such as cellulose triacetate and diacetate, poly-styrene, polyamides, homo- and co-polymers of vinyl chloride, poly(vinyl acetal), polycarbonate, homo and co-polymers of olefins, such as polyethylene and polypropylene, and polyesters of dibasic aromatic carboxylic acids with divalent alcohols, such as poly(ethylene terephthalate).

~75-Typical of useful paper supports are ~hose which are partlally acetylatsd or coated with bary~a and/or a polyolefin, particularly a polymer of an ~-olefin containing 2 to 10 carbon atoms 9 such as polyethylene, polypropylene, copolymers of ethylene and propylene and the like.
Polyolefins~ such as polyethylene, poly-propylene and polyallomers--e.g., copolymers of ethylene with propylene, as illustrated by Hagemey~r et al U.S. Patent 39478,128, are preferably employed as resin coatings over paper, as illustrated by Crawford et al U.S. Patent 3,411,908 and Joseph et al U.S. Patent 3,630,740, over polystyrene and polyester film supports, as illustrated by Crawford e~ ~1 U.S.
P~tent 3,630,742, or can be employed as unitary flexible reflection supports, as illustrated by Venor et al U.S. Patent 3,973,963.
Preferred cellulose ester supportæ are cellulose trlaceta~e supports, as illustrated by Fordyce et al U.S. Patents 2,4929~77, '978 and 2,739,069, as well as mixed cellulose ester supports9 suoh as cellulose acetate propionate ~nd cellulose acetate butyrate, as illustrated by Fordyce et al U.S. Patent 2~739~070O
Preferred polyester film supports are com-prised of linear polyester, such as illustra~ed by Alles et al U.S. Patent 2,627,088, Wellman U.S.
Patent 2,720,503, Alles U.S. Patellt 2,779,684 and Kibler et al U.S. Patent 2,901,466. Polyester films can be formed by varied techniques, as illustra~ed by Alles, cited above, Czerkas et al U.S. Paten~
3,663,683 ~nd Williams et al U.S~ Patent 3,504,075, and modified for use as pho~ographic film support6, as lllustrated by Van Stappen U.S. Patent 3,227,576 9 Nadeau et al U.S. Patent 3,501,301, Reedy et al U.S.
Patent 3,589,905, Babbitt et al U.S. Paten~
3,850,640, Bailey et al U.S. P~tent 3,888 9 678, Hunter S 8 9 1~J

U.S. Paten~ 3 9 904,420 and Mallinson et al U.S. Patent 3792~,697.
The phGtographic elements CRn employ sup-ports which are reslstant to dimensional change at elevated ~emperatures. Such supports can be com-prised of linear condensa~ion polymers which have glass ~ransi~ion temperatures above about 190C, preferably 220~C, such as polycarbonates~ polycarb oxylic esters, polyamides, polysulfonamides, poly-ethers, polyimides, polyæulfonates and copolymervariants, as illustrated by Hamb U.S. Patents 3~634,089 and 3,772~405; Hamb et al U.S. Patents 3,725~070 and 3,793,24g; Wilson Research Disclosure, Vol. 118, February 1974, Item 11833, and Vol. 120 9 April 1974, Item 12046; Conklin et al Research Dis-closure, Vol. 120, April 1974, Item 1~012; Product Licensing Index, Vol. 92, December 1971, Items 9205 and 9207; Research Disclosure 9 Vol. 101, September 1972, Items 10119 and 10148; Research Disclosure, Vol. 106, February 1973, Item 10613; Research Disclo-sure 9 Vol. 117, January 1974, Item 11709, and Re-search Disclosure, Vol. 134, June 1975, Item 13455.
The photographic elements of the present invention can be imagewise exposed in any conven-tional manner. Attention is directed to ResearchDisclosure Item 17643~ cited above, Paragraph XVIII.
The present invention is particularly advantageous when imagewise exposure is undertaken with electro-magnetic radiation within the region of the spectrum in which the spectral sensitizers present exhibit absorption maxima. When the photographic elements are intended to record blue, greenl red, or infrsred exposures, spectral sensitizer absorblng in the blue, green, red, or inrared portion of the spectrum is present. For black-and-white imaging appllcations it i6 preferred that the photographic elements be orthochromatically or panchromatically sensitized to ~75 permit ligh~ to extend 6ensitivity within the visible spectrum. Radiant energy employed for exposure can be either noncoherent (random phase) or coheren~ (in phase~, produced by lasers. Imagewise exposures at ambient, elevated or reduced temperatures andtor pressures, including high or low intensity exposures, continuous or intermitten~ exposures, exposure tlmes ranging from minutes ~o relatively short durations ln the millisecond to microsecond range 9 can be employed wi~hin the useful response ranges determined by conventional sensitometric techniques, as illustrated by T. H. James~ The Theory of the Photo~raphic ~rocess, 4th Ed., Macmillan, 1977, Chapters 4, 6, 17, r ~ ~
18, and 23.
The ligh~-sensitive silver halide conta~ned in the photographic elements can be processed follow-ing exposure to form a visible image by associating the silver halide with an aqueou~ alkaline med~um in the presence of a developing agent contained in the medium or the element. Processing formulations and techniques are described in L. F. Mason, Photo~raphic Processin~ Chemistry, Focal Press, London, 1966; Pro-cessing Chemicals and Formulas, Publication J-l, Eastman Kodak Company, 1973; Photo-Lab Index, Morgan ~nd Morgan, Inc., Dobbs Ferry, New York~ 1977, and Neblette's Handbook of ~ and ~E~ e~-Materials 9 Processes and ~y~ , YanNostrand Reinhold Company, 7th Ed., 1977.
Included among the processing methods are web processing, ~s illustrated by Tr~gillus et ~1 U.S. Patent 3,179,517; stabilization process$ng, as illustrated by Herz et ai U.S. Pa~Pnt 3,220,839, Cole U.S. Patent 3,615,511, Shipton et al U.K. Patent 1,258,906 and Haist et al U.S. Patent 3,647,453;
monobath processlng as described ln Haiæt, Monobath Manual, Morgan and Morgan, Inc., 19667 Schuler U.S.
Patent 3,240,603, Haist et al U.S. Patents 3,615 9 513 ~7~9 -7~-and 3,628~955 and Price U.S. Patent 3,723~126; lnfec~
tious development 7 as illustrated by Milton U.S.
Patents 3,294,5377 3,600,174, 3,615,519 and 3,615,524, Whiteley U.S. Pa~ent 3,516,830, Drago U.S.
S Patent 3~615,488, Salesin et al U.S. Pa~ent 3 9 625,689, Illingsworth U S. Patent 3,632~340, Salesin U.K. Patent 1,273,030 and U.S. Patent 3,708,303; hardening development, ~6 illustrated by Allen et al U.S. Pa~ent 3,232,761j roller tr~nsport processing, as illustra~ed by Russell et al U.S.
Patents 3,025,779 and 3,515,556, Masseth V.S. Patent 3,573,914, Taber e~ al U~S. Patent 3,647,459 and Rees et al UoK~ Patent 1,269,268; alkaline vapor process-lng, as illustrated by Product Lleensing Index, Vol.
97, May 1972, Item 9711, Goffe et al U.S. Patent 3,816,136 and King U.S~ Patent 3,9~5,564; metal ion development as illustrated by Price, Photo~raphic Science a Engineering, Vol. 19~ Number 5, 1975, pp.
283-287 and Vought Research Disclosure, Vol. 150, October 1976, Item 15034; and surface application processing, as illustrated by Kitze U.S. Patent 3,418,132.
The silver halide developers employed in processing are surface developers. It is understood that the term "surface developer" encompasses those developers which will reveal the æurface latent image centers on a silver halide grain, but will not reveal substantial internal latent image centers in an internal latent image-forming emulsion under the con ditions generally used to develop a surface-sensitive silver h~lide emulsion. The surface developers cen generally utiliæe any of the sllver halide developing agents or reducing agents, but the developing bath or composition is generally substantially free of a silver halide solvent (8uch as water-soluble thio-cyanates, water-soluble thioethers, thiosulfates, and ammonia) which will disrupt or dissolve the grAin to

6 9 2 reveal substan~ial internal image. Low ~mountæ of excess halide are sometimes desirable in the devel-oper or lncorporated in the emulsion as halid0-releasing compounds, but high amounts of iodide or iodide releasing compounds are generally avoided to prevent substantial disruption of the grain.
Typical silver halide developing agents which can be used in the developing compositions of this invention include hydroquinones 7 catechols, aminophenols, 3-pyrazolidinones, ascorbic acid and its derivatives, reductones, phenylenediamines, or combinations thereof. The developing agents can be incorporated in the photographic elements wherein they are brought into contact with the silver halide lS af~er imagewise exposure; however, in certain embodi-ments they are preferably employed in the developing bath.
Once a silver image has been formed in the photographic element, it is conventional practice to fix the undeveloped silver halide. The high aspect ratio tabular grain emulsions of the present inven-tion are par~icularly sdvantageous in allowing fixing to be accomplished in a shorter time period. This allows processing to be accelerated.
Dye Imagin~
The photographic elements and the techni~ues described above for producing silver images can be readily adapted to provide a colored image through the use of dyes. In perhaps the slmplest approach to obtaining a projectable color image a conventional dye can be incorporated in the support of the photo-graphic element, and silver image formation under-taken as described above. In areas where a silver image is ormed the ~lement is rendered substantîally incapable of transmit~ing light therethrough, and in the remaining areas light is transmitted corre~pond-ing in color to the color of the support. In this -~o -way a colored image can be readily formed~ The same effect c~n also be ~chieved by using a separa~e dye filter layer or element with ~ transparent support element.
The silver halide photographic element6 can be used to form dye images therein through the selec-tive destruction or formation of dyesO The photo-graphic elements described above for orming silver images can be used to iEorm dye images by employing 10 developers containing dye image formers, such as color couplers 9 as lllustrated by U.K. Patent 478,984~ Yager et al U.S. Patent 3,113,8649 Vittum et al U.S. Patents 3,002,836, ~ 3 271, 238 and 2, 362,5Y8, Schwan e~ al U.S. Patent 29950,970, Carroll et al U.S. Patent 2 ~ 592,243, Por~er et el U.S. Patents 2 9 343, 703, 2, 376,380 and 2,369,489, Spath U.K. Patent 886 9 723 and U.S. Patent 2 9 899,306, Tuite U.S. Patent 3,152 ,896 and Mannes et al U.S. P~ten~cs 2,115,394, 2,252,718 and 2,108,602, and Pilato U.S. Patent 3 ~ 547,650. In this form the developer contains a color-dev~loping agent (e.g., a primary aromatic amine) which in its oxidized form i6 capable of reacting with ~he coupler (coupling) to form the image dye.
The dye-formin~ couplers can be incorporated in the photographic elements, as iLllustrated by Schneider et al, Die Chemie, Vol. 57, 1944, p. 113, Mannes et ~1 U.S. Patent 2,304,940, Martinez U.S.
I?atent 2,269,158, Jelley et al U.S. Patent 2,322,027, 30 Frolich et al U.S. Patent 2,376,679, Fierke et al Il.S. Paten~ 2~801,171, Smith U.S. Patent 3,748,141, Tong U.S. Patent 2,772,163, Thirtle et al U.5. Patent 2,835,579, Sawdey et al U.S. Patent 2,533,514, Peterson U.S. Patent 2,353,754, Seidel U.S. Patent 35 3,409,435 and Chen Research Disclosure, Vol. 159, July 1977, Item 15930. The dye-forming coupler6 can be incorpora~ed in different amounts to achieve dif-fering photographic e~fects. For example, U.K.
Patent 923,045 and Kumai et al U.S. Patent 3,843,369 teach limi~ing the concentration of coupler in rela-~ion to ~he silver coverage to less than normally employed amounts in faster and intermediat~ speed emulsion layers.
The dye forming couplers are commonly chosen to form subtractive primary (i.e., yellow, magenta and cyan) image dyes and are nondiffusible, colorless couplers, such as two and four equivalent couplers of the open chain ketomethylene, pyrazolone, pyrazolo-triazole, pyrazolobenzimidazole, phenol and naphthol type hydrophobically ballasted for lncorporation in high-boil~ng organic (coupler3 solven~s. Such coup-lers are illustrated by Salminen et al U.S. Patents2,423,730, 2,772,i62, 2,89~,826, 2,710,803, 2,407,207, 3,737,316 and 2,367,531, Loria et al U.S.
Patents 2,772,161, 2,600,788, 3,006,759, 3,214,437 and 3,253,924, MeCrossen et al U.S. Patent 2,875,057, Bush et al U.S. Patent 2,908,573, Gledhill et al U.S.
Patent 3,034,892, Weissberger et al U.S. Patents 2,474,293, 2,407,21G, 3,062,653, 3,265,506 and 3,384,657, Porter et al U.S. Patent 2,343,703, Greenhalgh et al U.S. Patent 3,127,259, Feniak et al U.S. Patents 2,865,748, 2,933,391 and 2,865,751, Bailey et al U.S. Patent 3,725,067, Beavers et al U.S. Patent 3,758,308, LAU U.S. Patent 3,779,763, Fernandez U.S. Patent 3,785,829, U.K. Patent 969,921, U.K. Patent 1,241,069, U.K. Patent 1~011,940, Vanden Eynde et al U.S, Pa~ent 3,762,921, Beavers U.S~
Patent 2,983,608, Loria U.S. Patents 3,311,476, 3,408,194, 3,458,315, 3~447,928, 3,476,563, Cressman et al U.S. Patent 3,419 9 390, Young U.S. Patent 3,419,391, Les~ina U.S. Pat~nt 3,519,429, U.K. Patent 975,928, U.K. Patent 1,111,554, Jaeken U.S. Patent 3,222,176 and Canadian Patent 726,651, Schulte et al U.K. Patent 1,248,924 ~nd Whitmore et al U.S. Patent 1 ~ 7~6'~
-~2 -3,227,550. Dye-forming couplers of differing reac-~ion rates in single or separate layers can be employ~d to achleve desired e~ects for specific photographic applications.
The dye~forming couplers upon coupling can release photographically useful fragments, ~uch as development inhibitors or acceler~tors, bleach accel-erators, developing agents, silver halide solvents, toneræ, hardeners, fogging ~gents, antifoggants, com-peting couplers, chemical or spectral sensitizers and desensitizers. Development inhibitor-releasing (DIR) couplers are illustrated by Whitmore et al U.S.
Patent 3,148,062, Barr et al U.S. Pa~en~ 3~227,554, Barr U.S. Paten~ 3,733,201, Sawdey U.S. Patent 3~617,291, ~roet et al U.S. Patent 3~703,375, Abbott et al U.S. P~tent 3,615,506, Weissberger et al U.S.
Patent 3,265,506, Seymour U.S. P~tent 3,620,745, Marx et al U.S. Patent 3,632,345, Mader et al U.S. Patent 3,869,291, U.K. Patent 1j201,110, Oishi et al U.S.
Patent 3,fi42,485~ Verbrugghe U.K. Patent 1,236,767~
Fujiwhara et al U.S. Patent 3,770,436 and Matsuo et al U~S. Patent 3,80~,945. Dye-forming couplers and nondye-forming compounds which upon coupling release a variety of photographically useful groups are des-cribed by Lau U.S. Patent 4,248,962. DIR compoundswhich do no~ form dye upon reaction with oxidized color-developing agent~ can be employed, as illus-trated by Fu;iwhara et al German OLS 2,529,350 and U.S. Patents 3,92~,041, 3,958,993 and 3,961,959, Odenwalder et al German OLS 2,448,063; Tanaka et al German OLS 2,610,546, Kikuchi et al U.S. Patent 4,049,455 and Credner et al U.S. Pa~ent 4,052,213.
DIR compounds which oxidatively cleave can be employ-ed, as illustrated by Porter et al U.S. Patent 3,379,529, Green et al U.S. Patent 3,043,690, Barr U.S. Patent 3,364,022, Duennebier et al U~S. Patent 3,297,445 and Rees et al U.S. Patent 3,287,129. Sil-~ 3-ver halide emulslons which are relatively light in-sensitive, such as Lippmann emulsion6 9 have been utilized as interlayers and overcoat layers to pre-vent or control the migration of development inhibi-tor fragments as described in Shiba et al U.S. Patent3,8929572.
The photographic elements can incorporate colored dye-forming couplers, such as those employed to form integral masks for nega~ive color imageæ~ as illustrated by Hanson U.S. Patent 2,449,966, Glass et al U.S. Patent 23521,908, Gl~dhill e~ al U.S. Patent 3,334/892, Loria U.S. Patent 39476,563, Lestina U.S.
Patent 3,519,429, Friedman U.S. Paten~ 2,543,691, Puschel et al U.5. Patent 3,028,238, Menzel et al U.S. Patent 3~061,432 and Greenhalgh U.K. Patent 19035,959, and/or competing couplers, as illustrated by Murin et al U.S. Patent 3,876,428, Sakamoto et al U.S. Patent 3,580,722, Puschel U.S. Patent 2,998,314, Whitmore U.S. Patent 2,808,329, S~lminen U.S. Patent 2,742,832 and Weller et ~1 U.S. Patent 2,689,793.
The pho~ographic elements can include image dye stabilizers. Such image dye stabilizers are illustrated by U.K. Paten~ 1,326,889, Lestina et al U.S. P~tents 3,432,300 and 39698,909, Stern et al U.S. P~tent 3,574,627, ~rannock et al U.S. Patent 3,5733050, Arai et ~1 U.S. Patent 3,764,337 and Smlth et al U.S. Patent 4,042,394.
Dye images can be formsd or amplified by processes which employ in combination with a dye image-generating reduclng ~gent an inert transition metal ion complex oxldizing agent, as illustrated by Bissonette U.S. Patents 3,748,138, 3,826,6S2, 3,862,842 and 3,989,526 and Travis U.S. PRtent 3,765,891, and/or a peroxide oxidizing agent, as illustrated by Matejec U.S. Patent 3,674,490, Rese~rch Disclosure, Vol. 116, December 1973, Item 11660, and Bissonette Research Disclosure, Vol. 148, -August 1976, Items 14836, 14846 and 14847O The photographic elemen~s can be particul~rly adapted to form dye images by such processes~ as illustrated by Dunn et al U.S. Paten~ 3,822,129, Bissonet~e U.SO
S Patents 3,834,907 and 3,902,905, Blssonet~e et al U.S. Pa~ent 3,847,619 and Mowrey U.S. Patent 3,904,413.
The photographic elements can produce dye images through the selective destruction of dyes or dye precursors, such as silver-dye-bleach processes, as illustrated by A. Meyer, The Journal of Photo-~raphic Science, Vol. 13 9 1965, pp. 90-97. Bleach-able azo, azoxy, xanthene, aæine, phenylmethan , nitroso complex, indigo, quinone, nitro-substituted, phthalocyanine and formazan dyes, as illustrated by S~auner et al U.S. Patent 3,754 9 923, Piller et al U.S. Patent 3,749,576, Yoshida e~ al U.S~ Patent 3,738,839, Froelich et al U.S. Pa~ent 3,716,368, Piller U.S. Pa~ent 3,655,388, Williams et al U.S.
Pa~ent 3,642,482, Gilman U. S . Patent 3,567,448, Loeffel U.S. Paten~ 3,443,953, Anderau U.S. Patents 3,443,952 and 3,211,556, Mory et al U.S. Patents 3,202,511 and 3,178,291 and Anderau et al U.S.
Patents 3,17~,285 and 3,178,290, as well as their hydrazo, diazonium and tetrazolium precursors and leuco and shifted derivatives, as illustrated by U.K.
Patents 923,265, 999,996 and 1,042,300, Pelz et al U.S. Patent 3,684,513, Watanabe et al U.S. P~tent 3,615,493, Wilson et al U.S. Paten~ 3,503~741, Boes et al U.S. Patent 3,340,0599 Gompf et al U.S. Patent 3,493~372 and Puschel et al U.S. Patent 3,561,970, can be employed.
It is common practice in forming dye images in silver halide photo~raphic elements to remove the silver which is developed by bleaching. Such removal can be enhanced by incorporatlon of a bleach accel-erator or a precursor thereof in a processing solu-~ 5-tion or in a layer of the element. In some instances the amount o silver formed by development is small in relation to the amount of dye produced, partlcu-larly in dye image amplification, as described aboYe~
and silver bleaching is omitted without substantial visual effect. In still other application6 the sil-ver image is retained and the dye image ls intended to enhance or supplement the density provided by the image silver. In the case o dye enhanced silver imaging i~ is usually preferred to form a neutral dye or a combina~ion of dyes which together produce a neutral image. Neutral dye-forming couplers useful for ~his purpose are disclosed by Pupo et al Research Disclosure, Vol. 162 7 October 1977, Item 16226. The enhancement of silver images with dyes in photo-graphic elements intended for thermal processing is disclosed in Research Disclosure, Vol. 173, September 1973, Item 17326, and Houle U.S. Patent 4,137,079.
It is also possible to form monochromatlc or neutral dye images using only dyes, silver being entirely removed from the lmage-bearing photographic elements by bleaching and fixing, as illustrated by Marchant et al UOS. Patent 3,620,747.
Multicolor Photogra~
The present invention can be employed to produce multicolor photographic images. Gener~lly any conventional multicolor imaging direct reversal photographic element containing at least one internal latent lmage-forming silver halide emulsion layer can be improved merely by adding or substituting a high a~pect ratio tabular grain internal latent image-forming emulsion according ~o the present invention.
Significant advantages can be realized by the application of this inven~ion to multicolor photographic elements which produce multicolor images from combinations of sub~ractive primary imaging dyes. Such photographic elements are comprised of a ~7~2 support and typically at least a ~riad of super-i~posed silver halide emulæion layers for 6ep~rately recording blue, green, a~d red light exposures a~
yellow, magenta, and cyan dye images, respectively~
Although the present invention gener~lly embrsces any mul~icolor photographic element of this type includ-ing at least one high aspec~ ratio tabular grain internal latent image-forming emulsion, additional advantages can be realized when high aspect ratio tabular grain internal latent image-forming silver bromide and bromoiodide emulsions are employed.
Consequsntly, the following description is dirPcted to certain preferred embodiments incorporating sllver bromide and bromoiodide emulsions, but high aspect ratio tabular grain internal latent image-forming emulsions of any halide composition can be substi-tuted, if desired. Except as specifically otherwl~e described, the multicolor photographic elements can incorporate the features of the photographic elements described previously~
In a specific preferred form of the inven-tion a minus blue sensitized high aspect ratio tab-ular grain internal latent image-i-ormlng silver bromide or bromoiodide enulsion according to the invention having an average tabular grain thickness of less ~han 0.3 micron forms at least one of the emulsion layPrs intended to record green or red light in a triad of blue, green, and red recording emulsion layers of a multicolor photographic element and is positioned to receive during exposure of the photo-graphic element to neutral light at 5500K blue light in additlon to the light the emulsion i6 intended to recordO The relAtionship of the blue and minus blue light the layer receives can be expressed in terms of 5 ~ log E, where a 1 Og E - log ET ~ log ~7~9 log ET being the log of exposure to green or red light the tabular grain emulsion is intended to record and log E~ being the log of concurrent expo sure to hlue light the tabular grain emulsion a1BO
receives. ~In each vccurrence exposure, E, is in me~er-candle-seconds 9 unless otherwise indicated.
In the practice of the pre~en~ invention log E can be less than 0.7 (preferably less than 0.3 while still obtaining acceptable color replication.
This iæ surprising in view of the high proportion of grains present in the emulsions of the present inven-tion having an average diameter of greater than 0.7 micron. If a comparable nontabular or lower aspect ratio tabular grain emulsion of like halide composi-tion and average grain diameter is subs~ituted for a high aspect ratio ~abular grain eilver bromide or bromoiodide emulsion of ~he present in~en~ion a higher and usually unacceptable level of color falsi-fication will result. It is known in the art thatcolor falsification by green or red sensitized silver bromide and bromoiodide emulsions ran be reduced by reduction of average grain diameters, but this results in limiting maximum achievable photographic speeds as well.
The present invention achieves not only advantageous separation in blue and minus blue speeds, but is able to Achieve this advantage without any llmitatlon on maximum realizable minus blue photographic speeds. In & specific preferred form of the invention at least the minus blue recording emul sion layers of the triad of blue, green, and red recording emulsion layers are silver bromide or bromoiodide emulslons according to the present inven-tion. It is specifically contemplated that the bluerecording emulsion layer of the triad can advan-tageously also be a high aspect ratio tabular grain ~756 emulsion according to ~he present invention. In a specific preferred form of the invention the tabular gralns present in each of the emul~ion layers of the trlad have an average grain diameter of a~ ~east 1~0 micron~ preferably at least 2O0 mlcrons, and the emulsion has an average aspect r&tio of at 1 ast 10:1. In a still further preferred form of the invention the multicolor photographic elements can be assigned an IS0 speed index of at least 180~
The multicolor pho~ographic elements of the invention need contain no yellow filter layer posi-tioned between the exposure source and the high aspect ratio tabular grain green And/or red emulsion layers to protect these layers from blue light expo-sure, or the yellow filter layer9 if present9 can bereduced in density to less than any yellow filter layer density heretofore employed ~o protect from blue light exposure red or green recording emulsion layers of photographic elements intended to be exposed in daylight. In one specifically preferred form of the invention no blue recording emulsion layer is interposed between the green and/or red recording emulsion layers of the triad and the source of exposing radia~ion. Therefore the photographic element is substantially free of blue Absorbing material between ~he green and/or red emulsion layers and incident expoæing radiation. If, in this instance, a yellow filter layer is interposed between the green and/or red recording emulsion layers and lncident exposing radiation, lt accounts for all of the interposed blue density.
Al~hough only one green or red recording high aspect ratio tabular grain silver bromide or bromoiodide emulsion as described above is required, the multicolor photographic element contains at least three separate emulslons for recording blue, green, and red light, respectively. The emuls~ons other 1 :~756~2 than the required high aspect ratio tabular grain green or red recording emulsion can be internal latent image-forming emulsions of any convenient conventional form. Evans U.S. Patents 3j761,276 and 3,923,513 and Atwell et al U.S. Patent 4,0353185, cited above, illustrate preferred nont~bular internal latent image-forming emulsions useful in combination with the emulsions of thls invention. In a preferred form of the invention all of the emulsion layers contain silver bromide or bromoiodide gralns. In a particularly preferred form of the invention at least one green recording emulsion layer and at leas~ one rPd recording emulslon layer is comprised of a high aspect ratio tabular grain internal latent image-forming emulsion accordlng to this invention. Ifmore than one emul6ion l~yer is provided to record in the green and/or red portion of the spectrumS it is preferred that at least the faster emulsion layer contain high aspect ratio t~bular grain emulsion as described above. It is, of course, recognized that all of the blue, green, and red recording emulsion layers of the photographic element can advantageously be tabular as described above 9 if desired, although this is not required for the practice of this inven-tion.
The present invention is fully applicable tomulticolor photographic elements as described above in which the speed and contrast of the blue, green, and red recording emulsion layer~ vary widely. The relative blue insensitivity of green or red spectral-ly sensitlzed high aspect ratio tabular grain silver bromide or silver bromoiodide emulsion layers employ ed in this invention allow green and/or red recording emulsion layers to be positioned at any location within a multicolor photographic element independent-ly of the remaining emulsion layers and without tak-ing any conventional precautions to prev~nt their exposure by blue light.

-so -The present invention is part cularly appli-cable to mul~icolor photographic elements intended to replicate colors accurately when exposed in day-light. Photographic elements of this $ype are char-acteriæed by producing blue, green, and red exposurerecords of substantially matched con~rast and limited speed variation when exposed to a 5500K (dayllght) source. The term l'substantially matched con~rast" as employed herein means that the blue, green, and red records differ in contrast by less ~han 20 ~prefer-ably less than 10) percent, based on the contras~ of the blue record. The limited speed variation of the blue, green, and r~d records can be expressed as a speed variation (~ log E) of less ~han 0.3 log E, where the speed variation is the larger of the dif-ferences between the speed of the green and red records and the speed of the blue record.
The multicolor photographic elements of this invention c~pable of replicating accurately colors when exposed in daylight offer significant advantages over conventional photographic elements exhlbiting these characteristics. In the photographic elements of the invention the limited blue sensitivity of the preferred green and red spectrally sensitlzed tabular silver bromlde or bromoiodide emulsion layers can be relied upon ~o separate the blue speed of the blue recording emulsion layer and the blue speed of the minus blue recording emulsion layers. Depending upon ~he specific application, the use of tabular grains in the green and red re~ording emulsion layers can in and of itself provide a desirably large separation in the blue response of the blue and minus blue record-ing emulsion layers.
In some applica~ions it may be desirable to ~ncrease further blue speed separations of blue and minus blue recording emulsion layers by employing conventional bluP speed separation techniques to I :~ 7~9~

supplement the blue speed separations obtained by the presence of the high aspect ratio tabular ~r~ins.
For example, if a multicolor photographic el2ment places the fas~es~ green recording emulsion layer nearest the exposing radiation source and the fastest blue recording emulsion layer farthest from the exposing radia~ion ~ource, the separation of the blue speeds of the blue and green rPcording emulsion layers, though a full order of magnitude ~1.0 log E) different when the emulsions are separ~tely co~ted and exposed, may be effectively reduced by the layer order arrangement, since the green recording emulsion layer receives all of the blue light during exposure~
but the green recording emulsion layer and other lS overlying layers may absorb or reflect some of the blue light before it re~ches the blue recording emul-sion layer. In such circumstance employing a higher proportion of iodide in the blue recording emulsion layer can be relied upon to supplement the tabular grains in i~creasing the blue speed separation of the blue and minus blue recording emulsion layers. When a blue recording emulsion layer is nearer the expos-ing radiation source ~han the minus blue recording emulsion layer, a limited density yellow filter material coated between ~he blue and minus blue recording emulsion layers can be employed to increase blue and minus blue separstion. In no instance, how~
ever, is it necessary to make use of any of these conventional ~peed ~eparation techniques to the 3~ extent that they in themselves provide an order of magnitude difference in the blue speed sep~ration or an ~pproximation thereof, as has heretofore been required in the art talthough this is not precluded if exceptionally large blue and minus blue speed separation i~ desired for a specific applieation).
Thus, the prssent invention achieves the objectives for multicolor photographic elements intended ~o ~56 replica~P image colors accurately when exposed under balanced lighting conditions while permlt~ing a much wider choice in element constructlon than has here-tofore been possible.
Multicolor photographlc elements are often described in terms of color-forming layer units.
~ost commonly multicolor photographic elements con-tain three superimposed color-forming layer units each containing at least one silver halide emulsion layer capable of recording exposure to a dlfferent third of ~he spectrum and capable of producing a complementary subtractive primary dye image. Thus, blue, green, and red recording color-orming layer units are used to produce yellow, magenta, and cyan dye images, respec~ively. Dye imaging materials need not be present in any color-forming layer unit, but can be entirely supplied from processing solutions.
When dye imaging materials are incorporated in the photographic element, they can be located in an emul-sion layer or in a layer located to receive oxidizeddeveloping or electron transfer agent from an adja-cent emulsion layer of the same color-forming layer unit.
To prevent migration of oxldized developing or electron transfer ~gents between color-formin~
layer units with resultan~ color degradatlon, it is common practice to employ scavengers. The scavengers can be locsted in the emulsion layers themselves, as taugh~ by Yutzy et al U.S. Patent 2,937~086 and/or ln interlayers between adjacent color-forming layer units, as illustrated by Weissberger et al U.S.
Patent 2,336~327.
Although each color-forming layer unit can contain a single emulsion layer, two, three, or more emulsion layers differing in photographic speed are often incorporated in a ~lngle color-forming layer unit. Where the desired layer order arrangement does ~7~9 no~ permit multiple emulsion l~yers differing in speed to occur in a single color-forming layer unit, it i5 common practice to provlde multiple (usually two or three~ blue, green, and/or red recording color-forming layer units 1n a single photographic element.
It is a unique fea~ure of this invention that ~t least one green or red recordin~ emulsion layer containing ~abular silver bromide or bromo-iodide grains as described above is located in themul~icolor photographic element to receive an increased proportion of blue light during imagewise exposure of the photographic elementO The increased proportion of blue light reaching the high aspect ratio t~bular grain emulsion layer can result from reduced blue light absorption by an overlying yellow filter layer orS preferably5 ellmination of overlying yellow filter layers entirely. The increased propor-tion of blue light reaching the high aspect ratio tabular emulsion layer can result also from reposi-tioning the color-forming layer unit in which it is contained nearer to the source of exposing radia-tion. For example, green and red recording color-forming layer units containing green and red record-ing high aspect ratio tabulAr emulsions, respectlve-lyg cnn be positioned nearer to the source of expos-ing radiation than ~ blue recording color-forming layer unlt.
The mul~icolor photographic elements of this lnven~ion can take any convenient form consi~tent with the requirements indicated above. Any of the six possible layer arrangements of Table 27a, p~ 211, disclosed by Gorokhovskii, ~pectral Studies of the Photographic Process, Focal Press, New York, can be employed. To provide a Bimple 7 specific illustr~-tion 9 it is possible to add to a conventional multi-color silver halide photographic element during its I ~ ~569 preparation one or more high aspect ratio tabular grain emulsion layers sensitized to the minus blue portion of ~he spec~rum and positioned to receive exposing radiation prior to the rema~ning emulsion layers. However, in most instances~ it is preferred to substitute one or more minus blue recording high aspect ratio tabular grain emulsion layers or conven~ional minus blue recording emulsion layers, optionally in combination with layer order Rrrange-ment modifica~ions. The invention can be betterappreciated by reference to the following preferred illustrative forms.
Layer Order Arran~ement I
Exposure _ ~ _ _ _ IL _ T5 _ _ IL _ TR _ _ Layer Order Arrangement II
Exposure _ TFB
IL
TFG
IL
TFR _ _ _ _ IL

IL _ _ SG
IL
SR

:

- ~75~2 Layer Order Arran~emen~ III
Exposure TG
IL
. . ~
TR
IL
= B ~ _ _ Layer Order Arr~n~ement IV
Exposure TFG
_ IL

IL
TSG
IL
=
_ TSR
IL
B
_ Layer Order Arrangement V
Exposure ~ _ _ __ _ _ TFG _ IL
T~R
IL
TFB
IL
_ TSG
IL
TSR
IL T ' SB

7~69 Exposure , TFR
....
IL ___ TB _ _ IL
_ _ TFG
IL
_ _ TFR
IL
S&
IL
.
SR
Layer Order Arran~ement VII
Exposure _ .
TFR
IL

IL
TB
__ _ _ _ IL
_ TFG
IL

IL
_ _ _ IL _ TSR

where B, G~ and R designate blue, green, ~nd red recording color-forming layer unit~, respectively, of any conven~ional type;

T appearing before the color-formlng layer unit B, G, or R indica~es ~hat the emulsion layer or layers contaln a high aspect ratio tabular gr~in silver bromide or bromoiodide emulsion6 3 as more specifically described above, F appearing before the color-forming layer unit B, G, or R indicates that the color-forming layer unit is faster in photographic speed than at least one other color forming layer unit which records light exposure in the same third of the spectrum in the same Layer Order Arrangement;
S appearing before the color-forming layer unit B, G, or R indicates that the color-forming layer unit is slower in photographic speed ~han at least one other color-forming layer unit which records light exposure in the same ~hird of the spectrum in the same Layer Order Arr~ngement; and IL designates an interlayer containlng a scavenger, but substanti211y free of yellow filter material. Each faster or slower color-forming layer unit can differ in photographic speed from another color-forming layer uni~ whieh records light exposure in ~he same third of the spectrum as a result of its position in the Layer Order Arran,gement, i~s inherent speed properties, or a combination of both.
In Layer Order Arrangements I through VII, the location of the support is not shown. Following customary practice, the support will in most instances be positioned farthest from the source of exposing radiation--that isj beneath the layers as shown. If the support is ~olorless and specularly transmis~ive--i.e., transparent, it can be located between the exposure source and the indicated layers. Stated more generally, the support can be located between the exposure source and any color-forming layer unit intended to record light to which the support is transparent.

~75 Turning first to Layer Order Arrangement I, it can be seen tha~ ~he photographic element ls sub-stantial1y free of yellow filter materialO However, following conventional practice for elements contain-ing yellow fllter material, the blue recordingcolor-forming layer unit lies nearest the ~ource of exposing radiation. In a simple form each eolor-forming layer unit is comprised of a single silver halide emulsion layer. In another form each color forming layer unit can contain two, three, or more differen~ silver halide emulsion layers. When a ~riad of emulsion layers, one of highest speed from each of the color-forming layer units, are compared, they are preferably substantially matched in contrast and the photographic speed of the green and red recording emulsion layers differ from the speed of the blue recording emulsion layer by less than 0.3 log E. When ~here are two~ three, or more different emulsion layers differing in speed in each color-forming layer unit, there are preferably two, three,or more triads of emulsion layers in Layer Order Arrangement I having the stated c:ontrast and speed relationship. The absence of yellow fil~er material beneath the blue recording color forming unit increases the photographic speed of this layerO
It is not necessary that the interlayers be substantially free of yellow filter materi~l in Layer Order Arrangement I. Less than conventional amounts of yellow filter material can be located between the blue and ~reen recording color-forming units without departing from the teachings of this invention. Fur-ther, the inte-layer separating the green and red color-forming layer units can contain up to conven-tional amounts of yellow filter material without departing from the invention. Where conventional amounts of yellow filter material are employed 9 the red recording color-forming unit is not restricted to ~ ~7~692 the use of tabular silver bromide or bromoiodide grains, as descri~ed above, but can take any conven-tional form, subjec~ to the ~ontrast ~nd 6peed con-siderations indicated.
To avoid repetitlon, only features that distinguish Layer Order Arrangement6 II through V
from Layer Order Arrangement I are specifically discussed. In Layer Order Arrangement II, rather than incorporate faster and slower blue 9 red, or green recording emulsion layers in the same color-forming layer unit, two separa~e blue, green~ and red recording color-forming layer units are provided.
Only the emul~ion layer or layers of thP faster color-forming units need cont~in tabular silver bromide or bromoiodide grains, as descrlbed above.
The slower green and red recording color-forming layer units because of their slower speeds as well as the overlying faster blue recording color-forming layer unit, are adequately protected from blue light exposure without employing a yellow filter material.
The use of high aspect ratio tabular 8rain silver bromide or bromoiodide emulsions in the emulsion layer or layers of the slower green and/or red recording color-forming layer unit6 is, of course, not precluded. In placing the faster red recording color-forming layer un~t above the slower green recording color-forming layer unit, increased speed can be realized, as taught by Eeles et al U.S. Patent 4,184,876 D Ranz et al German OLS 2,704,797, and Lohman et al German OLS 2,622,923, 2,622,924, and 2,704,~26.
Layer Ord~r Arrangement III differs from Layer Order Arrangement I in placing the blue record-ing color-orming layer unit farthest from the expo-sure source. This then place6 the green recordingcolor-forming layer unit nearest and the red record-ing color-forming layer uni~ ne~rer the exposure 9 ~

source. This arrangemen~ is highly advantageous in producing sharp 7 high quality multicolor images. The green recording color-forming layer un~t, which makes the most important visual contribu~ion to mul~icolor imaging, as a resul~ of being located nearest the exposure source is capable of producing a very sharp image, since there are no overlying layers to scQtter light. The red recording eolor-forming layer unit, which makes the next most important visual contribu-tion to the multicolor image, receives light that haspassed through only the green recording color-forming layer unit and has therefore not been scattered in a blue recording color-forming layer unit. Though the blue recording color-forming layer unlt suffers in comparison to Layer Order Arrangement I, the loss of sharpness does not offset the advantages realized in the ~reen and red recording color-forming layer units, ~ince ~he blue recording color-orming layer unit makes by far the least significant visual contribution to the multicolor image produced.
Layer Order Arrangement IV expands Layer Order Arrangemen~ III to include separate faster and slower high aspect ratio tabular grain emulsion cont~ining green and red recording color-forming layer units. Layer Order Arrangement V differs from LAyer Order Arrangement IV in providing an additional blue recording color-forming lay~r unit above the slower green, red9 and ~lue recordlng color-forming layer units. The faster blue recording color-forming layer unit employs high aspect ratio tabul2r grain silver bromi.de or bromoiodide emulsion, as described above. The fas~er blue recording color-forming layer unit in this instance acts to absorb blue light and therefore reduces ~he proportion of blue light reaching the slower green and red recording color-forming layer units. In a variant form, the slower green and red recording color-forming layer units ~ ~7~692 need not employ high aspect ratio tabular graln emulsions.
Layer Order Arrangemen~ VI differs from Layer Order Arrangment IV in locating a tabular grain blue recording color-forming layer unit between the green and red recording color-forming layer uni~æ and ~he source of exposing radiation. As is pointed out above, the tabular grain blue recording color forming layer unit can be comprised of one or more tabular grain blue recording emulsion layers and, where multiple blue recording emulsion layers are present, they can differ in speed. To compensate for the less favored position the red recording color~forming layer units would otherwise occupy, Layer Order Arrangement VI also dlffers from Layer Order Arrange-ment IV in providing a se~ond fast red record~ng color-orming layer unit, which is positioned between the tabular grain blue recording color-forming layer unit and the source of exposing radiation. Because of the favored location which the second tabular grain fast red recording color-forming layer unit occupies i~ is faster ~han the first fast red record~
ing layer un~ if the two fast red-recording layer units incorporate identical emulsions. It is, of course, recognized that the firsl: and second fast tabular grain red recording color-forming layer units can, if desired, be formed of the same or different emulsions and that their relative speeds can be adjusted by techniques well known to those skilled in the art. Instead of employing two fas~ red recording layer units, as shown, the second fast red recording layer unit cAn, if desired, be repl~ced with a second fast green recording color-forming layer unit. Layer Order Arrangemen~ VII can be ldent~cal ~o Layer Order Arrangemen~ VI, but differs in provlding both a second fast tabular grain red recording color~forming layer unit and a second fast tabular grain green ~7 recording color-forming layer unit interposed between the exposing radiation source and the tabular grain blue recording color~forming layer unit.
There are~ of course, m~ny other advan tageous layer order arrangements possible, Layer Order Arrangemen~s I ~hrough VII being merely illus-trative. In each of thP various Layer Order Arrange~
ments corresponding green and red recording color-forming layer units can be interchanged- i.e., the faster red and green recording color-forming layer units can be interchanged in position in the various layer order arrangements and additionally or alterna-tively the slower green and red recording color-form-ing layer units can be interchanged in position.
Although photographic emulsions intended to form multicolor images comprised of combinations of subtractive primary dyes normally take the form of a plurality of superimposed layers containing incor-porated dye-forming materials, such as dye-forming couplers, this is by no means required. Three color-forming componen~s, normally referred to as packets, each containing a sil~er halide emulsion for recording light in one third of the vislble spectrum and a coupler capable of forming a complementary subtractive primary dye, can be placed together in a single layer of a photographlc element to produce multicolor images. Exemplary mixed packet multicolor photographic elements are disclosed by Godowsky U.S.
Patents 2,698,794 and 2,8439489. Although discussion is directed to the more common arrangement in which a single color-forming layer unit produces a single subtractive primary dye, relevance to mixed packet multicolor photographic elements will be readily epparent.
It is the relatively large separation in the blue and minus blue sensitivities of ~he green and red recording color-forming layer units containing ~ 5~92 tabular grain silver bromide or bromoiodide emulfiions that permits reduction or elimination of yellow filter materials and/or the employment of novel layer order arrangements. One technique that can be employed for providing a quantitative measure of the relative response of green and red recording color~
forming layer units to blue light in mul~icolor photographlc elements is to expose through ~ step tablet a sample of a mul~icolor photographic element according to this invention employing first a neutral exposure source -i.e., light at 5500K--and there-after to process the sample. A second sample is then identically exposed, except for the intPrposition of a Wratten 98 filter, which transmits only light be~ween 400 and 490 nm, and thereafter identically processed. Using blue, green, and red transmission d~nsities determined according to American Standard PH2.1-1952, ~s described above, three dye character-istic curves can be plotted for each sample. The difference in blue speed of the blue recording color-forming layer unit(s~ and the blue speed of the green or red recording color-formlng layer unit(s) can be determined from the relationship:
(A) (BW98 - GW9~) - (BN - GN) or (B) (Bwg8 - RW98) (~N N) where Bw9~ is the blue speed of the blue record-ing color-forming layer unit(s) exposed through the Wratten 98 filter;
~ 98 is the blue speed of the green recording color-forming layer unit(s) exposed through the Wra~ten 98 filter;
~98 is the blue speed of the red record-ing color-forming layer unit(s) exposed through the Wratten 98 filter, BN is the blue speed of the blue recording color-forming layer unit(s) exposed to neutral (5500K) light;
,:

~ ~7~692 -104~
GN is the green speed of the green record-ing color-orming layer unit (6) exposed to neutral (5500K) light; and RN is the red speed of the red recording color-forming layer unit(s) exposed to neutr~l (5500K) light.
(The above descrip~icn imputes blue, green, and red densities to the blue~ green, and red recording color-forming layer units, respectively, ignoring unwanted spectral absorption by the yellow, magenta, and cyan dyes. Such unwanted spectral absorption is rarely of suff;clent magnitude to affect materially the results obtained for the purposes they are here employed.) The preferred multicolor photographic elements of the present invention ln the absence of any yellow filter material exhibit a blue speed by the blue recording color forming layer uni~s which is at least 6 times, preferably at leas~ 8 times, and optimally at least lO times the blue speed of green and/or red recording color-forming layer units containing high aspect ratio tabular grain emulsions, as described above.
Another measure of the large separation in the blue ~nd minus blue sensitivities of the multi-color photographic elements of the present inventionis to compare the green speed of R green recording color-forming layer unit or the red speed of a red recording color-forming layer unit to its blue speed. The same exposure and processing techniques described above are employed, except that the neutral light exposure is changed to ~ minus blue exposure by interposing a Wratten 9 filter, which transmits only light beyond 490 nm. The quantitative difference being determined is (C) ~ 9 - ~98 or (D) ~ g ~ RW98 where -~S~92 -1~5-Gw9~ and ~ 9~ are defin4d above;
Gw~ is the green speed of the green recording color-forming layer un~t(s) exposed through the Wrat~en 9 filter; and ~ 9 is the rPd speed of the red recording color-forming layer uni~(s) exposed through the Wra~en 9 filter. (Again unwanted spectral absorp-tion by the dyes is rarely material and is ignored.
Red and green recording color-orming layer units conteining tabular silver bromide or bromoiodide emulsions, as described above, can exhibit a differ-ence between their speed in the blue region of the spectrum and their speed in the portion of the spec-trum to which they are spectr~lly sensitized (i.e., a difference in thelr blue and minus blue speeds3 of at least 10 times (1'.0 log E), when the tabular grains have an average thickness of less than 0.3 micron.
In comparing ~he quantitative rela~lonships A to B and C to D for a single layer order arrange-ment, the results will not be iden~ical, even if thegreen and red recording color-forming layer units are identical (except for their wavelengths of spectral sensitization). The reason is th,at in most instances the red recording color-forming layer unit(s) w~ll be receiving light that has alre~dy passed through the corresponding green recording color forming layer unit(s). However, if a second layer order arrange-ment is prepared which is identical to the first, except that ~he corresponding green and red recording color-forming layer units have been interchanged in position, then the red recording color forming l~yer unit(s) o the second layer order arrangement should exhibit substantially identical values for relation-ships B and D that the green recording color-forming layer units of the first layer order arrangement exhibi~ for relationships A and C, respectively.
Stated more succinc~ly, the mere choice of green ~756 spectral sensitization as opposed to red spectral sensitization does not significantly ~nfluence the values ob~ained by ~he ~bove quantitative compari-sons. Therefore~ it is common practice not to dif ferentiate green and red speeds in comparision to blue speed, but ~o refer to green and red speeds generically as minus blue speeds.
Reduced Hi~h~ le Scattering The high aspect ratio tabular grain emul-sions of ~he present invention are advant~geousbecause of their reduced high angle light scattering as compared to nontabular and lower aspect ratio tabular grain emulsions.
This can be quantitatively demonstrated~
Referring to Figure 2, a sample of an emulsion 1 according to the present invention is coated on ~
transparent (specularly transmisslve) support 3 at a silver coverage of 1.08 g/m~. Although not shown, the emulsion and support are preferably immersed ln a liquid having a subs~antially matched refractive index to minimize Fresnel reflections at the surfaces of the suppor~ and the emulsion. The emulsion coat-ing is exposed perpendicular ~o the support plane by a collimated light source 5. Light from the source following a path indicated by the dashed line 7, which forms an optical axis, strikes the emulsion coa~ing at polnt A. Light which passes through the support and emulsion can be sensed at a constan~
distance from the emulsion ~t a hemispherical detec-tlon surface 9. At a point B, which lies at theintersectlon of the extenslon of the initial light path and the detection surface~ light of ~ maximum intensity level is detected.
An arbitrarily selected point C i5 shown in Figure 2 on the detection surface. The d~shed line between A and C forms an &ngle ~ with the emulsion coating. By moving point C on the de~ection surface ~7~

it is possible to vary ~ from 0 to 90. By measur-ing the intensity of the light sc2ttered as a func-~ion of the angle ~ it is possible (because of the rota~ional symmetry of light scattering about the optical axis 7) to determine the cumulative light distribution as a function of the angle ~. (For a background description of the cumulative light dis-tribution see DePalma and Gasper, "Determining the Optical Properties of Photographic Emulsions by the Monte Carlo Method", ~ raphic Science and ~&_n~ , Vol. 16, No. 3, May-June 1971, pp.
181-191.) After determining the cumula~ive light dis-tributîon as a function of ~he angle ~ at vslues from 0 to 90 for the emulsion 1 according to the present invention9 the same procedure is repeated, but with a conventional emulsion of the same average grain volume coated at the same silver coverage on another por~ion of support 3. In comparing the cumulative ligh~ distribution as a function of the angle ~ for the two emuls~ons, for values of ~ up to 70 (and in some instances up to 80 snd hlgher) the amount of scattered light is lower with the emul-sions according to the present invent~on. In Figure 2 the angle 9 is shown as the complement of the angle ~. The angle of scattering is herein dis~
cussed by refer~nce ~o the angle ~. Thus, the high aspect ratio tabular grain emulsions of this inven-~ion exhibit less high-angle scattering. Since it is high angle scattering of light that contributes dis-proportions~ely to reduction in image sharpness 9 it follows that the h~gh aspect ratio tabular grain emuls~ons of the present invention are in each instance capable of producing sharper images.
As herein defined the term "collection angle" is the value of the angle ~ at which h~lf of the light striking the detection surface lies wi~hin , ~:

') 6 9 2 an area subtended by a cone formed by rotation of line AC about ~he polar axiæ at the angle ~ while half of the light striking the detec~ion surfacP
strikes the detection surface within the remaining area.
While not wishing to be bound by any par-ticular theory to account for the reduced high angle scattering properties of high aspect ratio tabular grain emulsions according to the presen~ invention, it is believed that the large flat major crystal faces presen~ed by the high aspect ratio tabular grains as well as the orientation of the grains in the coating account for the improvements in sharpness observed. Specifically, it has bePn observed that the tabular grains present in a silver halide emul-sion coatlng are substantially aligned with the planar support surface on which they lie. Thus, light directed perpendicular to the photographic ele-ment striking the emulsion layer tends to strike the tabular grains substantially perpendlcular to one major crystal face. The th;nness of tabular grains as well as their orientation when coated permits the high aspect ratio tabular grain emulsion layers of ~his invention to be substantially thinner than con-ventional emulsion coatings, which can also contri-bute to sharpness. However, the emulsion layers of this lnvention exhiblt enhanced sharpness even when they are coated to the same thicknesses as conven-tional emulsion layers.
In a specific preferred form of the inven-tion th high aspec~ ratio tabular grain emulsion layers exhibit a mlnimum average grain diameter of at least 1.0 micron, most preferably at least 2 mi-crons. Bo~h improved speed and sharpness are attain-able as average grain diameters are increased. While maximum useful average grain diameters will vary with the graininess tha~ can be tolerated for a speciic imaging application, the maximum average grain diame-ters of high aspec~ ratio tabular grain emulsions according to the pre~ent invent~on are in all ins~ances less than 30 microns, preerably less than S lS microns 9 and optimally no gr~a~er than 10 microns.
Although it i5 possible to ob~ain reduced high angle scattering with single layer coatings of high aspec~ ratio tabular grain emulsions according to the present invention, it does not follow that reduced high angle scattering is necessarily realized in multicolor coatings. In certain multicolor coat-ing formats enhanced sharpness can be achieved with the high aspect ratio tabular grain emulsions of this invention 9 bu~ in other multicolor coating formats the high aspect ratio tabular grain emulsions of this invention can actually degrade the sharpness of underlying emulsion layers.
Referr;ng back to Layer Order Arrangement I, it can be seen ~hat the blue recording emulsion layer lies nearest to the exposing radiation source while the underlying green recording emulsion layer is a tabular emulsion according to this invention. The green recording emulsion layer in turn overlies the red recording emulsion layer. If the blue recording emulsion layer contains grains having an average diameter in the range of from 0.2 to 0.6 micron, as is typical of many nontabular emulsions, it will exhibit maximum scattering of light passing through i~ to reach the green and red recording emulslon layers. Unfortunately, if light has alreAdy been scattered before it reaches the high aspect ratio tabular grain emulsion forming the green recording emulsion layer, the tabular grains can scatter the llght passing through to the red recording emulsion layer to an even greater degree than a conventlonal emulsion. Thus, this particular choice of emul~ions and layer arrangement resultæ in the sharpnes6 of the red recording emulsion layer being ignificantly degraded to an extent greater than would be the case if no emulsions according ~o this invention were presen~ ln the layer order arrangement.
In order ~o re~lize fully the sharpne6s advantages of the present inventlon in an emulsion layer that underlies a high aspect ratio tabular grain emulsion layer according to the present inven-~ion it is preferred that the thP tabular grain emul-sion layer be positioned to receive light that is free of significRnt scattering (that is, positioned to receive substantially specularly transmitted light). Stated ano~her way9 in the photographic elemen~s of this invention improvements in sharpness 5 iLI emulsion layers underlying tabul~r grain emulsion layers are best realized only when the tabular gr~in emulsion layer does not itself underlie a turbid layer. For example, if ~ high aspect ratio tabular grain green recording emulsion layer overlies a red recording emulsion layer and underlies a Lippmann emulsion layer and/or a high aspect ratio tabular grain blue recording emulsion l~yer according to this invention, the sharpness of the red recording emul-sion layer will be improved by the presence of the overlying tabular grain emulsion layer or layers.
Stated in quantitative terms, if the collection angle of the layer or layers overlying the high aspect ratio t~bul~r grain green recording emulsion layer is less than ~bout 10, an improvement in the sharpness of the red recording emulsion layer can be realized.
It is~ of course, immaterial whether the red record-ing emulsion layer is itself a high aspect ratio t~bular grain emulsion layer according to th{s inven~ion insof~r as the effect of the overlylng layers on its sharpness is concerned.
In a multicolor photogrRphic element con-taining superimposed color-forming units it is pre-ferred ~hat at least the emulsion lsyer lying nearestthe source of exposing radiation be a high aspect ratio tabular grain eml~lsion in order ~o obtain the advantages of sharpness offerred by this inventlon.
In a specifically preferred form of the lnvention each emulslon layer which lies nearPr the exposing radiation source than another image recording emul-sion layer is a high aspect ratio tabular grain emul-sion layerr Layer Order Arrangements II, III, IV, Vs VI, and VII, described above, are illustrative of multicolor photographic element layer arrangements according to the inventlon which are capable of impar~ing significant increases in sharpneæs to underlying emulsion layers.
Although the advantageous contribution of high aspect ratio tabular grain emulsions to image sharpness in multicolor photographic elements has been specifically described by reference to multi-color photographic elements, sharpness advantages can also be realized in multilayer black-and-white photo graphic elements intended to produce silver images.
It is conventional practice to divide emulsions form-ing black~and-whi~e images into faster and slower layers. By employing nigh aspect ratio tabular grain emulsions according to this invention in layers near-est the exposing radiation souroe the sharpness of underlying emulsion layers will be improved.
Dye Ima~e Transfer I~ is possible to construct a dye image transfer film unit according to the presen~ invention capable of producing a monochromatic transferred dye image by locating on a support a single dye-providing layer unit comprised of a tabular silver halide emul-sion layer as described above and at least one dye-image-providing material in the ~mulsion layer itself or in an adjacent layer of ~he layer unit. In addi-tion, the dye image transfer film unit is comprised 6~2 of a dye receiving layer capable of mordanting or otherwise immobilizing dye migrating to it. To pro-duce a transferred dye image ~he tabular grain emul-sion is imagewise exposed and contacted wlth an alkaline processing composi~ion with ~he dye receiv-ing and emulsion layers jux~aposed. In a particular ly advantageous application for monochromatic trans-ferred dye images a combination of dye-image-provid-ing materials is employed to provide a neutral trans-ferred dye image. ~onochromatic transferred dyeimages 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 magen~a-dy~-providing layer unit com-prised of a green-sensitive si]ver halide emulsion having associated therewith a magenta-dye-image-pro-viding material, and (3) a yellow-dye-providing layer unit comprised of a blue-sensitive silver halide emulsion having associated therewith a yellow-dye-image-providing material. Each oiE the dye-providing layer uni~s can contain one, two, three~ or more separate silver halide emulsion layers as well as the dye image-providing materi~l, locatPd in ~he emulsion layers or in one or more separate layers forming part of the dye-providing layer unit. Any one or combina-tion o the emulsion layers can be hi&h aspect rAtio tabular grain silver halide emulsion layers as des-cribed above. In a preferred form of the invention at least the fastes~ emulsion layers in the cyan nd magenta-dye-providing layer units are hlgh aspect ratio tabular grain silver halide emulsions as des-cribed above. At least the fas~est emulsion layer inthe yellow-dye-lmage-providing layer unit is also preferably comprised of a high aspect rOEtio tabular 56~'~

~rain silver halide emulsion as described above, but the use of other, conventional silver halide emul-sions in the yellow-dye-providing layer unit together with high aspect ratio tabular grain silver halide S emulsions in the cyan and m~genta-dye-providing layer units is also specifically contemplated.
Depending upon the dye~image-providing material employed, it can be incorporated in the 6il-ver halide emulsion layer or in a separate layer associated with the emulsion layer. The dye-image-providing material can be any of a number known in the art, Such as dye-forming couplers, dye devel-opers, and redox dye-releasers, and the particular one employed will depend on the nature of the element or film unit and the type of imsge desired. Materi-als useful in diffusion transfer film units contain a dye moiety and a monitoring moiety. The monitoring moiety, in the presence of the alkaline processing composition and as a function of silver halide devel-opment, is responsible for a change i~ mobility ofthe dye moiety. These dye-image-providing materi~ls can ~e initially mobile and rendered immobile as a function of silver halide development, as described in ~ogers U.S. Patent 2,983,606. Alternatively, they can be initially immobile and rendered mobile, in the presence of an alkaline processing composltion, as a function of silver halide development. This latter class of materials include redox dye-releasing com-pounds. In such compounds, the monitoring group is a carrier from which the dye is released as a direct function of silver halide development or as an inverse function of silver halide dev~lopment. Com-pounds which release dye as a direct func~ion of silver halide development are referred ~o as nega-tive-working release compounds, while compounds which release dye as an lnverse function of silver halide development are referred to as positive-working ~,r3692 release compounds. Since the internal laten~ image forming emulsions of this invention develop in unex-posed areas in the presence of a nucleating agen~ and a surface developer, positive transferred dye lmages are produced using negative-working release com-pounds 9 and the latter Mre therefore preferred for use in ~he practice of this invention.
A preferred class of negative-working release compounds are the ortho or para sulfonamido-phenols and naphthols described in Fleckenstein U.S.Pat~nt 4,054,312, Koyama et al U.S. Patent 4,055~428, and Fleckenstein et al U.S. Patent 4,0769529. In these compounds the dye moiety is attached to a sul-fo~amido ~roup which is ortho or para to the phenolic hydroxy ~roup and is released by hydrolysis af~er oxidation oE the sulfonamido compound during develop-ment.
Another preferred class of negative-working release compounds are ball~sted dye-forming (chromo-genic) or nondye-forming (nonchromogenic) couplers having a mobile dye attached to a coupling-off site.
Upon coupling with an oxidized color developing agent, such as a ~ara-phenylenediamine, 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 Whltmore et al U.S. Patent 3,227,550, Whitmore U.S. Patent 3,227,5523 and Fujiwhara et al U.K. Pa~en~ 1,445,797.
Since the silver halide emulsions employed in the image transfer film units of the present invention are positive-work~ng, the use of posi~ive working release compounds will produce negative transferred dye images. Useful positive-working release compounds are nitrobenzene and quinone com-pounds described in Chasman e~ al U.S. Patent4,139,379, the hydroquinones described in Fields et al U.S. Patent 3,9B0,479 and the benzisoxazolone com-" ~l7~692 pounds described in Hinshaw e~ al U.S. Pa~ent 4,199,354.
Further details regarding ~he above release compounds, ~he manner in which they function, and the procedures by which they can be prepared are con-tained in the patents reerred to above~ the disclo-sures of which are incorporated herein by reference.
Any material can be employed as the dye receiving layer in the film units of ~his invention as long as i~ will mordant or otherwise immobilize 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, brighten-ers, and similar materials to protect or enhance the dye ima~e. A polyvalent metal, preferably immobi-lized by association with a polymer, can be placed in or ad~acent in the receiving layer to chelate the 2Q ~ransferred image dye, as taught by Archie et al U.S.
Patent 4,239,849 and Myers et al U.S. Patent 4,241,163. Useful dye receiving layers and materials for their fabrication are disclosed in _search Dis-closure, Vol, 151, November 1976, Item 15162, and ~organ et al U.S. Patent 4,258,117.
The alkaline processing compositlon ~mployed in the dye image transfer film units can be an aqueous solution of an alkaline material 9 such as an 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 compoæitions are disclosed in esearch Dis-closure, I~em 15162, c1ted above.
A developing agent is preferably contained ln the alkaline processing composition, although it can be contained in a separate solution or process 1 ~L75~9 sheet, or it can be incorporated in any processing composition 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 developlng agent will depend on the type or film unit with which it is used and the particular dye image-providing material employed. Suitable developing agents can be selected from such co~pounds as hydroquinone, aminophenols (e.g., N-methylaminophenol), l-phenyl-3-pyrazolidin-one, l-phenyl-4,4-dimethyl-3-pyrazolidinone, l-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidinone, and N,N,N',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 s~ain dye image-receiving layersO
The image transfer film units exh~bit advantages similar to those observed by Jones and Hill, cited above$ (as well as additional, unexpected advantages illustrated in connection with the examples).
One of these advantages is the rapidity with which the transferred image becomes viewable. The rapid accessibility of the viewable transferred image i8 directly attributable to the presence of one or more high aspect ratio tabular ~rain silver halide emulsions according to the present inYention.
Without being bound by any particular theory 9 it is believed ~hat the geome~rical configuration of the tabular silver halide grains accounts for rapid access to the transferred images. Tabular grain 3 ~7s~sæ

geometry provides a very high surface ~rea to the silver halide grains as compared to their volume, and this in turn is believed to influence their rate of dPvelopment. In imege transfer processes it is the imagewise variation in development of the silver halide grains as a func~ion of their imagewise exposure which modulates the transferred image. In some systems, such as those employing negative-work-ing 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.
The use of tabular grains ~o reduce the time elapsed betwe~n the commencement oE 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 employed in combination with conventional features for reducing access time at least additive results can be normally expected. In addition, ~here are still other features unique to the image transfer film units of this inventlon which can contribute to reduced access time. These additional features are discussed below.
A second advantage attainable with the image transfer film units of the present invention is the reduced variance of ~he transferred image as a func~ion of temperature~ This reduced variance in the transferred image is a direct result of employing one or more tabular silver halide emulsion layers, as described above. Without being bound by any particu-lar theory, it is believed th~t the tabular silver halide grains show less varlation in their develop-ment rste6 as a function of temperature. In image transfer systems in which silver halide development ~17~69 is direc~ly related ~o transferred imaging ma~erials this reduced temperature dependence of tabular silver halide grains results directly in reduced variance in the viewed image. In sys~ems relying also upon compe~ing mechanisms for gener~lon of the viewable image, reduced silver halide development variance as a function of temperature can reduce variance in the transferred image Lo 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.
It has be n surprisingly observed that the dye image transfer film units of the present inven-tion exhibit substantially higher photographic speeds at lower silver coverages than comparable conven-tional dye image transfer film units. It is well known to those skilled in the art that silver cover-ages below a threshold level result in reduction of observed photographic speed as determined from a transferred dye image. While speed decreases when the silver coverages of silver h~lLde 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 conven-tional multicolor image transfer fLlm units are com-monly 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 iB specifically contemplated to employ substantially lower silver coverages in the practice of this invention. When the silver halide emulsion in the yellow, magenta, or cyan-dye-providing layer unit of the dye image transfer film unit of this lnvention is tabular as described above, it can be efficiently employed at silver coverages of from about 150 to 750 mg/m2, preferably from about 200 ~ 7~6~2 to 700 mg/m2, and optimally from about 300 to 650 mg/m2. At higher and lower silver coverages higher and lower photographic speeds, respec~ively, will be realized, the stated ranges reflecting an efficien~
balance of photographic performance and 8ilv r cover-ages for most imaging applications. When the image transf~r film unit eontains a single dye-providing layer unit eontaining ~abular silver halide grains~
then these coverages are applicable ~o that of a single dye-providing ,layer unit. When all three dye-providing layer units contain tabular silver halide emulsions, at least additive silver savin~s can be realized.
The image transfer ilm units of this inven-tion can employ any layer order arrangement hereto fore known to be useful in conventional image trans-fer film units having one or more radiation-sensitive silver halide emulsion layers. In addition, the distinctive properties of tabular silver halide emul-sions 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 additionally contempla~ed:
To avoid unnecessary repetition, discussion of each successive layer order arrangement is direct-ed 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 di6cussed only in connection with the fir~t layer order arrangement in which they appear. If a fea~ure or advantage is not shared by a subsequently described layer order arrangement, this is specifically pointed out.

~ 6~v~2 _age Transfer Film Unit I
A haminate and Peel-Apart Dye Image Transfer Film Unit _ . . . .. .
Re~
D~e Receivin~ Layer _ Imagewise Exposure Tabular Silver Halide Emulsion Layer ~ rlal Support Image Transfer Film Unit I is illustrative of a conventional laminate and peel-apsr~ image transfer fllm unit~ Upon imagewise exposure, the positive-working tabular silver halide emulslon layer produces a developable la~ent image at centers located on the interior of exposed grains. The dye receiving layer is laminated and an alkaline processing composition, no~ shown, iB released between the dye receiving layer and emulsion layer following exposure. Upon contact with the alkaline processing composition development of the tabular silver halide grains bearing internal latent image centers occurs much more slowly than the development of silver halide ~rains which do not contain internal latent image cen~ers. Using a negative-working dye-ima~e-providing material dye is released in those areas in which silver development occurs and migrates to the dye receiving layer where it is held in place by a mordant. A positive transferred dye image is produced in the dye receiving layer. Processing is terminated by peeling ~he reflective support having the dye receiving layer coated thereon from the remainder of the image transfer ilm unit.
While the layer order arrangement is conven~
tional and employs conventional materials other than the tabular silver halide emulsion layer, signifi cantly superior results are obtainable. The access time required to produce a viewable dye image in the receiving layer is substantially reduced. It is believed that this can be attributed to dis~inct advantages offered by in~ernal latent image-forming tabular silver halide grains. Internal latent image-forming tabular silver halide grains according to ~his invention develop at a faster rate than comparable nontabular internal latent image~forming silver halide grains.
Although development can entirely account for ~he more rapid image access in Image Transfer Film Unit I~ another characteristic of tabular grain emulsions can also be used to further raduce image access times. While high aspect ratio tabular grain emulsion layers can be coated in the same layer thicknesses as conventional emulsions without depart-ing from the teachings of this invention, it is pre-ferred to thin the high aspect ratio tabular grain silver halide emulsion layers as compared to corres-ponding conventional silver halide emulsion layers.In conventional silver halide emulsions employed in image transfer the emulsion layer thickness is sub-stantially greater than the average grain diame~er calcula~ed from the grain projected areas. Further, the ~hickness of the layer is large enough to accom-modate not ~ust 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 microns, the emulsion layer will be at least 1 ~o 2 microns in thickness and will usually be substantially greater in thick-ness. On the other hand, it 16 possible to employ tabular silver halide grains accordlng to the present invention having diameters based on average projected areas of 1 to 2 microns and often s~ill larger while the thickness of the tabular grains is less ~han 0.5 .,:

or even 0.3 micron. Thus, in an exemplary emulsion in which the tabular grains have an average thickness of 0.1 micron with an average diameter of l to 2 microns, the silver halide emulsion layer thickness can easily be reduced substantially below 1 micron.
The high aspect ratio tabular graln emulslon layers of ~his invention are preferably less than 4 times the average thickness of the tabular grains and are optimally less than tw~ce the average thickn~ss of the tabular grains. Significant reductions in the thickness of the high aspect ratio tabular grain silver halide emulsion layers of the invention can con~ribute to reduction in image access times by reducing ~he lengths of diffusion paths. Further, reduction of the lengths of diffusion paths can also contribute to improv~ments in sharpness.
Image Transfer Film Unit II
An Integral Monochromatic Dye Image Transfer Film Unit Yiew Transparent Support Dye Receiving Layer _Reflective Laye~ _ __ O~a~ue Layer _ _ Tabular Silver Halide Emulslon Layer Wi~h Dye-Ima~e Providing Material Alkaline Processing Composl-_tion + Opacifier Timing Layer Neutrallbl~ 5 Transparent Support Imagewise Exposure Initially the alkaline processing composi-tion containing opacifier is not present in the loca-tion shown. Therefore, upon imagewise exposure light ~ ~7~6~

strikes the tabular silver halide emulsion layer.
This produces a latent image eorresponding to light-struck areas of the emulsion layer. To initiate pro-cessing the alkaline processing composition ls placed in the position shown. Usually, bu~ not necessarily, ~he image transfPr film unit is removed from the camera in which it is expo ed i~mediately followin~
placement of the alkaline processing composition and opacifier. The opacifier and opaque layer together pr~vent further exposure of the emulsion layer. Upon development, a mobile dye or dye precursor is releaso ed from the emulsion layer. The mobile dye or dye precursor penetrates the opaque layer and the reflec-tive layer and is mordanted or otherwise im~obilized ln the dye receiving layer to permit viewing through the uppermost transparent support. Processing is terminated by the timing and neutralizing layers.

, .

~ 17~69'2 I ~
An Integral Multicolor Dye Image Transfer Film Unit Imagewise Exposure .

Timin~ Layer _.___ _ Alkaline Processlng Compssi-_ Trans~a~7b~E~2~Dr~6~
Blue-sensitive Tabular Silver Ha I i~e ~ n La vur Y low Dye ~
15Interlayer With Scaven~er _ _ Green-sensitive Tabular Silver Halide Emulsion Layer ~enta Dye-Ima~e-Provid ~ ~aterial Layer ~ e~l!L__---------venger 20Red-sensitive Tabular Silver _ _clld- r~ulsion Layer Cyan Dye-Ima e-Providin& Material Layer Op~que Layer Reflective L ~er ~ ~ yer 3~o:e __, ~_upport View Image Transfer Film Unit III is essentially slmilar to Image Transfer Film Unit II, but is modi-fied to contain three separate dye-providing lay0r units, each comprised of one high aspPct ra~io tab-ular grain silver halide emulsion layer and one dye-image providing material layer, instead of the single dye-image^providing material containing high aspect ratio tabular grain silver halide emulsion layer of Im~ge Transfer Film Uni~ II. (Whether or 1 ~5 - 1 z 5 -not the dye-image-providing material is placed in the emulsion layer itself or in an adjacent layer in Image Transfer Film Units II And III is a matter of choice, either arrangement being feaslble.) To prevent color contamination of adjacent dye-providing layer unit6, an interlayer containing a scavenger is positioned be~ween dye-providing layer units. The use of scavengers in interlayers and/or in the dye~providlng layer units themselves is con-templa~ed. In some instances reductions in minimum edge densities ean also be realized by incorporating a negative-working silver halide emulsion in the interlayers.
In a modification of Image Transfer Film Unit III it is possible to eliminate the inter-layers. Since the high aspect ratio tabular grain silver halide emulsion layers can be qui~e 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 be~ween 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 con-tamination and the specific choice of dye-image-pro-viding materials. Providing dye-image-providing layers adjacent bo~h 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 ini-tially colorless or at leas~ shifted in hue so thatthe dye-lmage-providing material is not adsorbing in the spectr~l region to which the silver halide is intended to respond.

Where the yellow dye-image-providing material is initially yellow9 it scts, together wlth the blue-sensitive high aspect ratio tabular grain silver halide emulsion layer, to intercept blue light that would otherwise reach the 8reen and red sensi-tive high aspect ra~io 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 con~entional multi-color dye image transfer film unit, it is necessaryto intercept blue light to avoid color contamination of the green and red-sensitive emulsion layers. How-ever, where the green and red-sensitive emulsions are high aspect ratio tabular grain internal latent image-forming emulsions according to this invention as specifically described above, it is unnecessary to filter blue light so that it is a~tenuated before reaching these emulsion layers. Thus, where the yellow dye-image-providing 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 Grder .

9 ~
-~27 Image Transfer Film Unit IV
An Integral Multicolor Dye Image Transfer Film Unit _ Opaque Su~port Blue sensitive Tabular Silver _Halide Emulsion Lay r ~ = =~_ Red-sensitive Tabular Silver Ma~enta Dy Green-sensitive Tabular Silver T ansparent Overcoat Alkaline Processing Composition With Reflective Material and Indicator Dye _Dye Receiving Layer Timing Layer er _ _ Trans~aren~ Support View and Imagewise Exposure In Image Transfer Film Unit IV during i~age-wise exposure the alkaline processing composition containing the reflect~ve materi~l and indicator dye is not ln the position shown, but is released to the posi~ion 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 i the film unit is removed from a camera during process~ng. Once the neutraliz-ing layer reduces the pH within the film unit toterminate processing 3 the indicator dye reverts to an essentially colorless form. The alkaline processing ~ 9 composition also contains an opaque re1ective material, which provides a white background for view-ing the transferred dye image after processing and prevents additional exposure.
Image Transfer Film Unit IV is illustrative of the Application of the invention to an in~egral multicolor dye image transfer film unit format in which imagewise exposure and viewing occur through the same support. Image Trhnsfer Film Unit IV dif-fers from the prior teachings of the art not only ln the use of high aspect ratio tabular grain silver halide emulsions, but also in the order in which the dye-proYiding layer units are arranged. The green-sensitive high aspect ratio tabular grain silver halide emulsion layer is nearest to the exposing radia~ion source wh~le the blue-sensitlve high OEspect ratio tabular grain silver halide emulsion layer is farthest removed. This arrangement is possible with-out color con~amination because of the relatively large separa~ions in blue and minus blue response attainable with minus blue speotrally sensitized high aspec~ ratio tabular grain silver halide emulsions.
By placing the magenta-dye-providing layer unit nearest the source of exposing radiation and nearest ~5 the dye receiving layer, the sharpness of the magenta dye image is improved and lts access 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 9 and its location is also nearer the exposing radiation source and the dye receiving layer than in a corresponding conventional dye image trans-fer film unit. Thus, significant advantages in terms of reduced image ~ccess time and increased image sharpness are attainable wi~h Im~ge Transfer Film Uni~ IV in addition to those improvements attribut-able to high aspect ratio tabular grain silver halide ` ~7St~

grains previously discussed above in connec~ion with other layer order arrangements. While Image Transfer Film Unit IV 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.
Although the invention has been par~icularly described with reference tv certain preferred layer order arrangements, it is appreciated that the high aspect rati~ tabular grain silver hallde 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 o interlaid layer seg-ments. It is specifically contemplated to employ high aspect ratio tabular grain silver halide emul-sions as herein disclosed in microcellular image transfer film unit arrangements, such as disclosed by Whitmore Patent Cooperation Treaty published applica-tion W080/01614, published August 7, 1980. The present invention is also fully applicable to micro-cellular image transfer film units containing micro-cells which are improvements on Whitmore, such asGilmour Can. Ser.No. 385,171, filed September 3, 1981, titled AN IMPROVEMENT IN THE FABRICATION OF
ARRAYS CONTAI~ING INTERLAID PATTERNS OF MICROC~LLS;
Blazey et al U~S. Patent 4,307,165; and Gilmour et al Can. Ser.No. 385,363, filed September 8, 1981, titled ELEMENTS CONTAINING ORDERED WALL ARRAYS AND PROCESS
FOR THEIR FABRICATION.
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 sepqra~ions obtainable with spectrally sensi~

1 1751~2 tized high aspect ra~io tabular grain silver halide emulsions, mos~ notably silver bromide and bromo-iodide emulsions, are particularly advantageous in microrellular image transfer film units intended to produce multicolor images. Sinee the microcell triads intended to respond to blue~ green, and red light are poæitioned to receive the same incident light, yellow fil~ers are usually in~erposed when using conventional silver bromide and bromoiodlde 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 aspec~ ratio tabular grain silver halide emulsions of this invention can be employed in multi-color micro~ellular image transfer film units withoutthe use of yellow filters, thereby significantly simplifying construc~ion and improving performance.
_a~
The invention cen be better appreciated by referenc~ to the following illustrative examples. In each of the emulsion preparations the contents of the reaction vessel were vigorously stirred during silver salt addition; the term "percent" means percent by weigh~, unless otherwise indicated; and the tem "M"
stands for molar concentrations, unless otherwise indicated. All solutions, unless otherwi~e indi-cated 3 are aqueous solutions.
_ulsio~ _on The emulæions used in this invent~on were prepared as follows:
Emulsion A Core Tabular AgBrI Emulsion A AgI seed grain emulsion was prepared by a double-jet precipitat~on technique at pI 2.85 and 35C. To prepare 0.125 moleæ of emulsion 5.0M silver ni~r~te and 5.OM ~odium iodide solutions were added over a period of 3.5 minutes to a reaction vessel containing 60 grams of deionized bone gelatin ~ 92 dissolved in 2.5 li~ers of water. The resulting silver iodide emulsion had a mean grain diameter of 0.027 ~m and the crystals were of hexagonal bipyramidal structure.
Then 1.75 moles of silver bromide was preci-pita~ed onto 2.4 x lO 3 mole of the Rilver iodide seed grains by a double-jet technique. 4.0M silver nitrate and 4.OM sodium bromide reagents were added over a 15 minutes period at 80C using accelerated flow (6.0X from start to finish). The pBr was main-tained a~ 1.3 during the first 5 minutes, sdjusted to a pBr of 2~2 over the next 3 minu~es, and main~ained at 2.2 for the remainder of the precipitation.
The resulting tabular AgBrI crystals had a mean grain diameter of l.O ~m, an a~erage thickness of 0.08 ~m 9 and an average aspect ratio of 12.5:1 and account for greater than 90 percent of the total projected area of the silver halicle grains.
Emulsion A was then chemically sensitized with 1.9 mg/Ag mole sodium thiosulfate pentahydrate and 2.9 mg/Ag mole potassium tetrachloroaurate for 30 minutes at 80C.
Emulsion B Core/Shell Tabular AgBrI Emulsion The chemically sensitizecl Emulsion A (0.22 mole) was placed in a reaction vessel at pBr 1.7 at 80C. Then onto Emulsion A, 5.78 moles of silver bromide were precipitated by ~ double-~et addition technique. 4.~M silver nitrate and 4.0M sodium bromide solutions were added in an accelerated flow (4.0X from start to finish) over a period of 46.5 minutes whlle maintaining a pBr of 1.7. The result-ing AgBrI crystals had a mean grain dlameter of 3.0 ~m, an average thickness of 0.25 ~m, and average aspect ratio of 12:1.
Emulsion B was chemically sensitized wi~h 1.0 mg/Ag mole sodlum thiosulfate pen~ahydrate for 40 minutes at 74C and red spectrally sensitized with 250 mg/Ag mole anhydro-5,5'-dichloro-9-ethyl~393'-bis(3-~ulfobutyl)~hiacarbocyanine hydroxide.
Emulsion C Cadmium Doped Tabular AgBrI Internal La~ent Image-Forming Emulsion Emulsion C was prepared the same as Emulsion B with the excep~ion that a~ 8 minutes into the shelling stage of the core/shell precipitation cadmium bromide was addPd at 0.05 mole percent (based on the moles of sllver in the shell).
Emulsion D Control Emulsion A 1.8 ~m monodispersed internal image octahedral AgBr emulsion similar to that described in Example 7 of Evans U.S. Patent 3,~23,513, was used as a control for the above emulsion. The 1.25 ~m core emulsion was chemically ~ensitized with 0.4 mg/Ag mole sodium thiosulfate pentahydrate and 0.6 mgtAg mole potassium tetrachloroaurate. The shelled emul-sion was chemically sensitized wi~h 0.35 mg/Ag mole sodium thiosulfate pentahydrate. The control emul-sion was then sensitized wi~h 100 mg/Ag mole anhy-dro-5,5'-di-chloro-9~ethyl-3,3'-bis(3-sulfobutyl)-thiacarbocyanine hydroxide.
Emulsion E Tabular Graln AgBrI Internal Latent Imag~-Forming Emulsion A core emulsion was prepared similar to Emulsion A above. The emulsion was chemically sensi-tized with 2.5 mg/Ag mole ~odium thiosulfste penta hydrate and 3.75 mg/Ag mole potasslum tetrachloro-aurate for 10 minutes at 80C. Then 0.067 mole of ~he chemical~y sensitized emulsion wa6 further preci-pltated with silver bromide by a double-jet addition technique. 5.0 Molar AgN0 3 and 5.0 Molar NaBr reagents were each added for 16.6 minutes at pBr 2.4 at 80C, precipitating an additional 0.133 mole of silver bromide. The resultant tabular AgBrI (<0.10 mole percent I) crystals had a mean grain diameter of 1.5 ~m, an average thickness of 0.14 ~m, and an ~7569 average aspect ratio of 10.7:1, and account for greater than 85 percent of the total pro~ected sur-face area of the silver halide gralns~
Emulsion F Tabular Grain AgBrI In~ernal La~n~
Image-Forming Emulsion A core emulsion was prepared and chemic~lly sensitized as described for Emulsion E above.
Following chemical sensitization 0.067 mole of the core emulsion was shelled with addltional silver bromoiodide in the following manner: 5.0 Molar silver and halide salt reagents were added at a constant flow rate for ll.l minutes at pBr 2.4 at 80C. The halide salts conRisted of 90 mole percent bromide and 10 mole percent iodide. A total of 0.045 mole of additional AgBrI was added. A second ~hell was then precipitated identical to the first with the exception that the halide salts consisted of 80 mole percen~ bromide and 20 mole percent iodide. Similar-ly a third shell was precipitated over the second with the exception that the halide salts consisted of 70 mole percent bromide and 30 mole percent iodide.
The resultant tabular AgBrI (13.3 mole percent I) crystals had a mean grain diameter of 1.5 ~m, an average thickness of 0.14 ~m, and an average aspect ratio of 10~7:1, and account for greater than 85 per-cent of the total proJected area of the silver halide grains.
Example lA
This example shows that a red-sensitized ~abular grain internal latent image-forming emulsion, Emulsion B, provides an advantage in developability over an extended temperature range compared to a red-sensitized internal laten~ image-forming octa-hedral grain emulsion, Emulsion D, as used in a multicolor image transfer latent element us1ng sulfonamidonaphthol redox dye-release (RDR) chPmistry.

~ 2 An integral imaging receiver (IIR~ of the following layer order arrangement was prepar~d:
Coverages are in (g/m2~ or ~mg/Ag mole3. Chemlcal structures are shown in the Appendix below. ~ : Overcoa~ layer: Scavenger VIII (0.11), gelatin (0.89), Bis(~inylsulfonylmethyl) ether hardener at l percent of the total gelatin weight Layer 15: Blue-sen~itive silver halide layer: The emulsion is similar to the octahedral grain control Fmulsion D except that it is blue-sensitized. Silver halide (1.34 Ag), nucleating agent V [13.0], nucleating agent VI [0.41], scavenger VII t4000], gelatin (1.34) Interlayer: Titanium dioxide (0.27), gelatin (0.65) Layer 13: Yellow dye-releaser layer: RDR I (0.65), gela~in (0.86) La~er 12: Interlayer: Negative silver bromide emul-sion (0.11 Ag), scavenger VIII (1.1), gelatin (1.3) Layer 11: Green-sensitive silver halide layer: The emulsion is similar to the octahedral grain con~rol ~mulsion D except that it is green-sensitized. Silver h~lide (1.34 Ag), nucleating agen~ V [17.0J, nucleating agent VI [0.87], scavenger VII ~4000], gelatln (1.34) ~y_r 10: Interlayer: Ti~anium dioxide (0.32), gelatin (0.65) Layer 9- Magenta dye-releaser layer: RDR II
(0.43), gelatin (0.86) ~ Interlayer: Negative silver bromide emul-~ion (0.05 Ag~, scavenger VIII (1.1), gelatin (1.2) La~er 7: Red-sensitive silver halide layer: Emul-sion B (1.34 Ag)~ nucleatlng agent V
~2.0], scavenger VII ~4000], gelatin (1.34 ~ Gel (0.43) interlayer ~y~ Interlayer: Titanium dioxide (0.81~, gelatin (0.65) Cyan dye-releaser layer: RDR III (0.43 gelatin (0.65) Layer 3: Opaque layer: Carbon (1.9)9 KDR IV
(0.02), scavenger VII (0.03), gelatin (1.2) r 2: Reflecting l~yer: Titanium dioxide (22.0), gelatin (3~4) Layer 1: ~eceiving layer: Mordant IX (4~8~ 9 gela-tin (2 . 3) 5 The layers were coated on a clear polyester support in the order of numbering.
A control integral imaging receiver of the same layer order arrangement was prepared as above except Layer 7 had Emulsion D a~ 1.4 g Ag/m2.
The following processing pod composition was employed in both units:
Potassium hydroxide 46.8 g/Q
4-Methyl-4-hydroxymethyl-1-~-tolyl-3-pyrazolidone 15.0 g/Q
S-Methylbenzotriazole 5O0 g/Q
Carboxymethylcellulose 46.0 8/Q
Potassium fluoride 10.0 g/Q
Anionic dispersant ~Tamol SN~604 g/Q
Potassium sulfite (anhydrous~3.0 g/Q
1,4-Cyclohexanedimethanol3.0 g/Q
Carbon 191.0 g/Q
Two cover sheets of the following structure were prepared:
Layer 2: Timing layer: 1:1 physical mixture of the following two polymers coa~ed at 3.2 glm .

~ 6~2 Poly(acrylonitrile co-vinylidene chloride-co-acrylic acid) at a weight ratio of 14:79:7 (isolated as a latex, dried and dispersed in an organic solvent)O A carboxy ester lactone was formed by cyclization of a vinyl acetate-m~leic anhydride copolymer in the presence of l-butanol to produce a p~rtial butyl ester with a weight ra~io of acid to butyl ester of 15:85 (See Abel U.S. Patent 4,229,516). This layer also contains t-butylhydroquinone monoacetate at 0.22 g/m2 as a ~ompetor and 5-(2-cyanoethyl-thio)-l-phenyltetrazole at 0.11 g/m2 as a blocked inhibitor.
Layer 1: Acid layer: Poly(n-butyl acrylate~co-acrylic acid) 30:70 weight ratio equi-valent to 140 meq acid/m2.
The layers were coated on a clear polyester support 0 in the order of numbering.
The above image transfer film units including the processing composition and cover sheet were used in the following manner:
Each multicolor photosensitive integral imaging receiver was exposed for 1/100 second in a sensitometer through a step tablet to 5000K illumi-nation (daylight balance-neutral), then proce~sed at a controlled temperature ~either 16C or 22C) using a viscous processing composition contained in a pod.
The processing composi~ion was spread be~ween the IIR
and the transparent cover sheet using a pair of ~ux-taposed rollers to provide a processing gap of about 6S ~m.
After a period of more than one hour the red density of the stepped image was read. The red minimum density (Dmin) and maximum density (Dm~X) values were read from the above produc~d sensito-metrlc curve.

27~2 ~137-The data obtained and tabulated below show higher maximum red dye denslty at both 16C and 22~C
processing for the tabular grain emulsion. The dif-ference in red DmaX at these two ~emperatures is smaller with the tabular grain emulsion than the octahedral grain check indicating improved processing temperature lati~ude of the red layer. The speed of the control and example emulsion were essentially equivalent.
Red Densit max/ minDmaxjDmin _ulsion_Ty~ (22C) 16C ~Dmax_ Octahedral (D)1.73/0.22~.99/0.21 ~0.74 (Control) (-43%) 15 Tabular (B) 1~98/0.361.37/0.29 ~0.61 (Exampl~ 31%) _ample lB
The same improved processing temperature latitude and improved Dm~X at low temperature development are shown in ~ single color coating with equivalen~ emulsions.
Coatings similar to those of Example lA (but Single Color~ were made but did not contain layers 15 to 8 (overcoat 16 was coated on top of the red-sensi-tive silver halide layer, 7). The pod and coversheet are equivalent to those of Example lA except the cover sheet had 0.043 g/m 2 each of inhibitor and competor~
Red DensitY
Dmax/Dmin~maxt~min ~ Ye~ (22C) 16C ~Dmax Octahedral (D)1.66/0.180.54/0.18 -1.12 (Control) t-68%) Tabular (B) 1.80/0.241.14/0.21 -0.66 35 (Example) ( 37%) ~ 2 Example 2 This example shows tha~ a coat~ng containing red-sensitized in~ernal la~ent image-forming ~abular grain Emulsion B as used in Example lA has improved room keeping compared to control octahedral grain Emulsion D.
The example single color coating is the same as the example coating of Example lB. Two control coatings were employed similar to the con~rol of Example lB except layer 7 contained 1.4 ~m and 1.8 ~m octahedral emusions, respectively. The pod and cover sheet were similar ~o those of Example lB.
The experimental procedure used was the same as Example lA except processing was done only at room temperature (~22C). To evaluate keeping stability one set of coatings was exposed and processed resh, while another set was exposed and processed after being stored at room temper~ture for seven weeks.
The data below show that both control coat-ings using the octahedral grain emulsions lose con-siderably more DmaX after room temperature storage for seven weeks than example Emulsion B. Dmin changes (and speed changes) are not 6ignificantly different.
Red Densi~y Dmax/Dmin~max/Dmln (After Emulsion Type(Fresh)7 weeks) ~Dmax Octahedral (D)1.62/0.211.17/0.16 -0.45 1.4 ~m (-28%) Octahedral (D)1.50/0.201.07/0.17 -0.43 1.8 ~m (-28%) Tabular (B) 1.70/0.281.50/0.21 -0.20 ( -12/o) ~ 3i7569 Example 3 This example shows that single color red-sensitized coatings of tabular grain internal latent image-forming emulsions have both improved reversal speed and rereversal separation when cadmium doped.
The control coating con~ains an emulsion free of cadmium dopant, Emulsion B, the same a~ uset in Example lB. The example coa~ing con~ains an equi-valent cadmium doped Emulsion C, as ou~lined above.The coating structure consists of layers 16 7 and 7 to 1 as described for Example lB. The pod and cover sheet are equivalent to Example lB. The experimental procedure is the same as Example lA except processing is done only at room temperature (~22C). Thresh-old reversal speeds are read at 0.3 density below DmaX~ the reversal/rere~ersal separation is read at 0.7 density. A difference of 30 relative speed units equals 0.30 log E.
The data below show that the cadmium doped emulsion i6 0.20 log E faster and has a net speed reversal/rereversal separation of 0.37 log E more ~han does the corresponding emulsion free of cadmium doping. It is highly desirable that the reversal speed becomes faster and the rereversal speed slower.
Relative Relative Reversal Rereversal EmulsionS~eed (D = 0.7~ Speed (D = 0.7) B (non CdII
doped) 272 77 195 C (CdII doped) 292 60 232 (Net gain 37) Experimental results have also shown thatthe surface negative image can be significantly reduced if the shell portion of the tabular grain emulsion is doped with either lead (II) or erbium (III).

~7 Exa~le 4 This example demonstrates tha~ coatings of tabular grain internal latent image-formlng emulsion have increased reversal-surface negative image separation when the shell portion of the tabular emulsion contains iodide in increasing molar concen-tration towards the crystal surface.
Emulsions E and F were each spectrally sen-sitized with 125 mg/Ag mole anhydro-5~5',6,6'-tetra-chloro-1,1'-diethyl-3,3'-di(3-sulfobutyl~benz~m-idazolcarbocyanine hydroxide and 125 mgtAg mole anhydro-5,5'-dichloro-3,9-diethyl-31-(3-sulfopropyl)-oxacarbocyanine hydroxide. The emulsions were then coated on polyester film support at 2.15 g/m2 sil-ver and 4.52 g/m2 gelatin. The coatings were ex~posed for 10- 2 second to a Xenon flash through a continuous density tablet on an Edgerton, ~ermes-hausen, and Grier sensitometer and processed for 4 minutes in an ~-methylaminophenol sulfate (Elon¢)-hydroquinone developer containing 4-(B-methane-sulfonamidoethyl)phenylhydrazlne hydrochloride at 2.1 g/Q as the nucleating agent and 0.2 g/Q 5-methyl-benzotriazole. Sensitometric results including the undyed emulsion controls are given below.

~"
9 ~
- ~41-~ ~ ~D
a *
A A

Cd ~ O
U) l ,4 r~
V ~ ~ U~
0 ~ ~ 11 a~ ~ ~ ~ * ~
O h u~ C: ~ ~ ~o Q~
O
_~
0 ~ ~ X

r~
~' ~ C~l O P. C~

h C q-~
~ Cq O
~C
U
o e ou a ~ ~ ~ ~
U 0 U~
1 3 t`J
o o a~
~1 X E~ ~a ~ ,~

w o ~
x ~ ~ c~
0 o w ~
. ~ . . ~ .e ~ o ~ ~ ~ o ~
o ~
JJ
~ ~d p~ ~ w ~
~ N 3 0 r`
~I ~
~n w r-l O
O ~O q~ ~ ~
O ~ æ ~ æ ~
SJ ~ t, ~ ~ Q~
C~ ~ ~ ~ ~
~ ~ o IY
,i ~
~ o ~ W

As can be seen Emulsion F which contained tabular ~rains of increased iodide content in the shell portion, displayed significantly grea~er rever ~al/rereversal separation than Emulsion E which was S 6helled with pure AgBr. The spectrally sensitized Emulsion F had a reversal/rereversal separhtion of greater than 3,26 lo~ E units at a density of 0.70 whereas the spec~rally sensitized control Emulsion E
had a separation of 1.22 log E units. It was also noted thst the spectrally sensitized Emulsion F dis played less blue speed desensitization than the spee-trally æensitized control Emulsion E, Example 5 A high aspect ratio tabular grain internal latent image-forming silver bromide emulsion having an average grain ~iameter of 5.5 microns, an sverage ~rain thickness of 0.12 micron, and an average aspeet ratio of 46:1 with the tabular grain accoun~ing for 85 percent of the total grain projected area was prepared as follows:
A core emulsion having a grain diameter of 2.8 microns and an average grain ~:hickness of 0.08 micron was precipitated by double jet addition at pBr 1.3 at 80C. The AgBr core emulsion was chemically sensitized with 0.9 mg Na2S203~5H20/Ag mole and 0.6 mg KAuCl 4 /Ag mole for 20 minutes at 80C. Then the emulsion was precipitated with additional silver bromide at p8r 1.3 at 70C. The resultant core-shell tabular grain emulsion was not surface sen~itized.
The emulsion was coated on a polyester film support at 2.15 g/m2 silver and 10.4 g/m2 gel~-tinO A second co~ting was prep~red that contained S0 mg/Ag mole 1-(2 propynyl)-2-methylquinolinium bro-mide. A third coating was prepared that contained 25 mg/Ag mole 1-(2-propynyl)-2-methyl-6-ethoxyth~oform-amidoquinolinium trifluoromethanesulfonate. The coatings were exposed for 1/10 second to a 600W

~ 6 5500K tungsten light source and processed for 3 minutes at 20~C in R IMeto~(N-methy~ aminophenol sulfate~-hydroquinone developer containing 0.25 g/l 5-methylbenzotriazole.
Sensitome~ric results revealed that the con-trol coating displayed no reversal image. However, the core-shell tabular grain emulsion coating that contained 1-(2~propynyl~2 methylquinolinium bromide resulted in a reversal image with a D of 0.69 max and a Dmin of 0.18.
Similarly, the core-shell tabular grain emulsion coating that contained l-(2-propynyl)-2-methyl-6-ethoxythioformamidcquinolinium trifluoro-methanesulfonate resulted in a reveræ~l image of good discrimination with a DmaX of 0.95 and a Dmin of 0.30.
Appendix The redox dye-releasers (~DR's) I to IV are of the structures described in Research Dlsclosure, 2~ Vol. 182, July 1979, Item 18268, pages 329-31.
I. Yellow RDR
OH
CON(CIsH37)2 i!

~./ \o~

~o--~ X ~-N=N-~
\CN \Cl (dispersed in di-n-butylphthalate) s ~ ~

II. Magenta RDR
0~
ON(ClsH37)2 t NH
/
SO2_ ~ N=N NHSO2CH3 .~ \./ ~.
! !1 (CH 3 ) 3 CNHS02 OH
(dispersed in diethyllauramide~
III. Cyan RDR
OH
N(clsH37)2 NH
10 /=
2 ~ SO2CH3 SO2-NH N=~-~ NO2 .~-\./-~.

t S02N(is0-~3~7)2 OH
(dispersed in N-n-butylacetanilide) IV. Cyan RDR
OH C2Hs 1 1 /.,.
CON-CH2CH-O~
\C l s H 3 I -n ~H
SO2--~ S02NH NsN~ NO2 t i t OH

~5 (dispersed in N n-butylace~anilid~
The nucleating agents V and VI, ~re of the following structure:
V.
o ~ H2 CH3CO~NHNH~ NH-C-~
o lo I~ t-CsHl 1 ~., t~CsHI 1 VI.
15 o S
Il . .-., 11 H-C-NHNH~ - NH-C-NHCH3 The oxidized developer scavengers ~re the following:
VII.
OH
~ C H -s OH
VIII.
OH
Cl2H2s~s S -C l 2H2s~i OH
The mordant is as follows:
IX.
poly(styrPne-co-l-vinylimldazole-co-3-35 benzyl-l-vinylimidazolium chloride) (weight ratio approx. 50:40:10) The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variatlons and modifications ean be effected within the spirit and scope of the invention.

. .

Claims (86)

WHAT IS CLAIMED IS

1. A radiation-sensitive emulsion capable of forming a direct-positive image comprised of a dispersing medium, silver halide grains capable of forming an internal latent image, and a nucleating agent, at least 50 percent of the total projected area of said silver halide grains being provided by tabular grains which have an average thickness of less than 0.5 micron and an average aspect ratio of greater than 8:1.

2. A tabular grain silver halide emulsion according to claim 1 wherein said silver halide grains are comprised of bromide.

3. A tabular grain silver halide emulsion according to claim 2 wherein said silver halide grains are additionally comprised of iodide.

4. A tabular grain silver halide emulsion according to claim 1 wherein said dispersing medium is comprised of a peptizer.

5. A tabular grain silver halide emulsion according to claim 4 wherein said peptizer is gelatin or a gelatin derivative.

6. A tabular grain silver halide emulsion according to claim 1 wherein said tabular silver halide grains have an average aspect ratio of at least 10:1.

7. A tabular grain silver halide emulsion according to claim 1 wherein said tabular silver halide grains account for at least 70 percent of the total projected area of said silver halide grains.

8. A tabular grain silver halide emulsion according to claim 1 wherein said tabular silver halide grains account for at least 90 percent of the total projected area of said silver halide grains.

9. A radiation-sensitive emulsion accord-ing to claim 1 wherein said emulsion when coated on a transparent film support at a silver coverage of 4 grams per square meter, exposed to a 500 watt tungsten lamp for times ranging from 0.01 to 1 second at a distance of 0.6 meter, developed for 5 minutes at 20°C in Developer Y below, fixed, washed, and dried, has a maximum density at least five times the maximum density of an identical test portion which has been exposed in the same way and developed for minutes at 20°C in Developer X below, fixed, washed, and dried:

10. A radiation-sensitive emulsion accord-ing to claim 1 wherein said tabular silver halide grains contain internal physical sensitization sites.

11. A radiation-sensitive emulsion accord-ing to claim 1 wherein said tabular silver halide grains contain internal chemical sensitization sites.

12. A radiation-sensitive emulsion accord-ing to claim 11 wherein said internal chemical sensi-tization sites are produced by at least one of iridium and lead dopants.

13. A radiation-sensitive emulsion accord-ing to claim 11 wherein said internal chemical sensi-tization sites are produced by a middle chalcogen incorporated within said tabular grains.

14. A radiation-sensitive emulsion accord-ing to claim 13 wherein said tabular grains addition-ally include gold incorporated therein.

15. A radiation-sensitive emulsion accord-ing to claim 1 wherein said tabular grains contain at least one of lead, cadmium, zinc, and erbium in an amount sufficient to reduce rereversal.

16. A radiation-sensitive emulsion accord-ing to claim 1 wherein said tabular grains are silver bromoiodide grains and at least one blue spectral sensitizer is present in said emulsion chosen from the class consisting of cyanine, merocyanine, hemi-cyanine, hemioxonol, and merostyryl sensitizing dyes.

17. A radiation-sensitive emulsion accord-ing to claim 1 wherein said nucleating agent is chosen from the class consisting of aromatic hydra-zide nucleating agents, N-substituted cycloammonium quaternary salt nucleating agents, and mixtures thereof.

18. A radiation-sensitive emulsion accord-ing to claim 1 wherein said nucleating agent is a hydrazide of the formula wherein D is an acyl group;
? is a phenylene or a halo-, alkyl-, or alkoxy-substituted phenylene group; and M is a moiety capable of restricting mobility.

9. A radiation-sensitive emulsion accord-ing to claim 1 wherein said nucleating agent is a phenylhydrazide of the formula wherein R is hydrogen or an alkyl, cycloalkyl, halo-alkyl, alkoxyalkyl, or phenylalkyl substituent or a phenyl nucleus having a Hammett sigma-value-derived electron-withdrawing characteristic more positive than -0.30;
R1 is a phenylene or alkyl, halo-, or alkoxy-substituted phenylene group;
R2 is hydrogen, benzyl, alkoxybenzyl, halobenzyl, or alkylbenzyl;
R3 is a alkyl, haloalkyl, alkoxyalkyl, or phenylalkyl substituent having from 1 to 18 carbon atoms, a cycloalkyl substituent, a phenyl nucleus having a Hammett sigma value-derived electron-with-drawing characteristic less positive than +0.50, or naphthyl, and R4 is hydrogen or independently selected from among the same substituents as R3, or R3 and R4 together form a heterocyclic nucleus forming a 5- or 6-membered ring, wherein the ring atoms are chosen from the class consisting of nitrogen, carbon, oxygen, sulfur, and selenium atoms;
the alkyl moieties, except as otherwise noted, in each instance include from 1 to 6 carbon atoms and the cycloalkyl moieties have from 3 to 10 carbon atoms and at least one of R2 and R3 must be hydrogen.

20. A radiation-sensitive emulsion according to claim 1 wherein said nucleating agent is a hydrazide or hydrazone of the formula or wherein T is a phenyl or naphthyl substituent;

T1 is an acyl radical; and T2 is an alkylidene substituent having from 1 to 22 carbon atoms.

21. A radiation-sensitive emulsion capable of forming a direct-positive reversal dye image comprised of gelatin or a gelatin-derived peptizer, surface chemically sensitized silver bromide or bromoiodide grains capable of forming an internal latent image, a dye image former, and a nucleating agent, at least 70 percent of the total projected area of said grains being provided by tabular grains which have an average diameter of at least 1.0 micron, an average thickness of less than 0.3 micron, and an average aspect ratio of at least 10:1, and said emulsion when coated on a transparent film support at a silver coverage of 4 grams per square meter, exposed to e 500 watt tungsten lamp for times ranging from 0.01 to 1 second at a distance of 0.6 meter, developed for 5 minutes at 20°C in Devel-oper Y below, fixed, washed, and dried, having a maximum silver density at least five times the maximum density of an identical test portion which has been exposed in the same way and developed for 6 minutes at 20°C in Developer X below, fixed, washed, and dried:

22. A radiation-sensitive emulsion accord-ing to claim 21 wherein said tabular grains contain iridium as an internal dopant in a concentration of from about 10-8 to 10-4 mole per silver mole.

23. A radiation-sensitive emulsion accord-ing to claim 21 wherein said tabular grains contain lead as an internal dopant in a concentration of from about 10-4 to 5 X 10-2 mole per silver mole.

24. A radiation-sensitive emulsion accord ing to claim 21 wherein said tabular grains are internally sensitized with sulfur optionally in com-bination with gold.

25. A radiation-sensitive emulsion accord-ing to claim 21 wherein said tabular grains are com-prised of a core and at least one shell containing cadmium, lead, or mixtures thereof in a concentration below about 5 X 10- 4 mole per mole of silver.

26. A radiation-sensitive emulsion accord-ing to claim 21 wherein said tabular grains are com-prised of silver bromoiodide.

27. A radiation-sensitive emulsion accord-ing to claim 26 wherein an outer region contains at least 2 mole percent more iodide than a central region of said tabular grains.

28. A radiation-sensitive emulsion accord-ing to claim 27 wherein said tabular grains contain a core and at least one shell and iodide is present in said shell in a concentration of at least 6 mole per-cent more than present in said core.

29. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 1.

30. In a multicolor direct reversal photo-graphic element comprised of a support and, located thereon, emulsion layers for separately recording blue, green, and red light each comprised of a dispersing medium, internal latent image-forming silver halide grains, and a nucleating agent, said green and red recording emulsion layers con-taining green and red spectral sensitizing dyes, respectively, the improvement comprising in at least one of said green and red recording emulsion layers at least 50 percent of the total projected area of said silver halide grains being provided by internal latent image-forming tabular silver halide grains having an average thickness of less than 0.3 micron, an average diameter of at least 0.6 micron, and average aspect ratio of greater than 8:1.

31. An improved multicolor photographic element according to claim 30 wherein one of said emulsion layers containing said tabular silver halide grains is positioned to receive exposing radiation prior to remaining emulsion layers of said multicolor photographic element.

32. An improved multicolor photographic element according to claim 30 wherein one of said emulsion layers containing said tabular silver halide grains is positioned to receive specularly trans-mitted light and overlies at least one other emulsion layer of said multicolor photographic element.

33. An improved multicolor photographic element according to claim 32 wherein said tabular silver halide grains of said one emulsion layer have an average diameter of at least 2 microns.

34. An improved multicolor photographic element according to claim 30 wherein said blue recording emulsion layer is comprised of internal latent image forming tabular silver halide grains having an average thickness of less than 0.5 micron and an average diameter of at least 0.6 micron, accounting for at least 50 percent of the total projected area of said silver halide grains present in the same emulsion layer.

35. An improved multicolor photographic element according to claim 30 wherein at least one of said green and red recording emulsion layers contain-ing tabular grains is comprised of silver bromide or bromoiodide.

36. In a multicolor direct reversal photo-graphic element comprised of a film support and, located thereon, color-forming layer units for separately record-ing blue, green, and red light containing yellow, magenta, and cyan dye-forming couplers, respectively, said color-forming layer units being chosen so that when said photographic element is exposed at a color temperature of 5500°K through a spectrally nonselective step wedge and processed said photogra-phic element exhibits, in relation to blue contrast and speed, green and red contrast variations of less than 20 percent and green and red speed variations of less than 0.3 log E, each of said color-forming layer units including at least one emulsion layer comprised of a dispersing medium, silver halide grains, and a nucleating agent, said silver halide grains of at least a triad of said emulsion layers for separately recording blue, green a and red light being positioned to receive exposing radiation prior to any remaining emulsion layers and having an average diameter of at least 2.0 microns, the improvement wherein at least 70 percent of the total projected area of internal latent image-forming tabular silver bromide or bromoiodide grains in at least one of said green and red record-ing emulsion layers have an average thickness of less than 0.2 micron, an average diameter of at lest 0.6 micron, and an average aspect ratio of at least 10:1, said internal latent image-forming tabular grains in said green and red recording emulsion layers being both internally and surface chemically sensitized.

37. A multicolor photographic element according to claim 36 in which said element is substantially free of yellow filter material inter-posed between exposing radiation incident upon said element and at least one of said tabular grain containing emulsion layers.

38. A multicolor photographic element according to claim 36 in which at least one of said layers containing tabular grains is positioned to receive exposing radiation prior to said blue record-ing emulsion layer.

39. A multicolor photographic element according to claim 36 in which at least one of said layers containing said tabular grains is positioned to receive exposing radiation prior to all other sil-ver halide emulsion layers of said photographic ele-ment.

40. A multicolor photographic element according to claim 36 in which said tabular grains are present in said green recording emulsion layer.

41. A multicolor photographic element according to claim 36 in which said tabular grains are present in said red recording emulsion layer.

42. A multicolor photographic element according to claim 36 in which said tabular grains are present in each of said green and red recording emulsion layers.

43. In a photographic image transfer film unit comprising a support, at least one emulsion layer located on said support containing a dispersing medium, radiation-sensitive internal latent image-forming silver halide grains, and a nucleating agent, a dye-image-providing material present in said emulsion layer or a layer adjacent thereto, and a receiving layer for providing a viewable trans-ferred dye image following imagewise exposure and processing of said emulsion layer, the improvement wherein internal latent image-forming tabular silver halide grains in at least said one emulsion layer having an average thickness of less than 0.5 micron, an average diameter of at least 0.6 micron, and an average aspect ratio of greater than 8:1 account for at least 50 percent of the total projected area of said radiation-sensitive silver halide grains present in said emulsion layer.

44. A photographic image transfer film unit according to claim 43 in which said receiving layer is positioned adjacent a second support.

45. A photographic image transfer film unit according to claim 44 in which said second support is a reflective support.

46. A photographic image transfer film unit according to claim 44 in which said second support is transparent.

47. A photographic image transfer film unit according to claim 43 wherein said receiving layer is positioned between said support and said emulsion layers.

48. A photographic image transfer film unit according to claim 43 in which said tabular silver halide grains account for at least 70 percent of the total projected area of said radiation-sensitive grains present in the same emulsion layer.

49. A photographic image transfer film unit according to claim 43 in which the halide of said silver halide grains consists essentially of bromide optionally an combination with iodide.

50. A photographic image transfer film unit according to claim 43 in which said tabular silver halide grains have an average aspect ratio of at least 10:1.

51. In a dye image transfer film unit com-prising a transparent support, at least one emulsion layer located on said support containing a dispersing medium, radiation-sensitive internal latent image-forming silver halide grains, and a nucleating agent, a dye-image-providing material located in said emulsion layer or in a layer adjacent thereto, a transparent cover sheet, a dye receiving layer located on said cover sheet a an alkaline processing solution, and means for releasing said alkaline processing solution into contact with said emulsion layers, the improvement wherein at least 70 percent of the total projected area of said radiation-sensi-tive silver halite grains is provided by internal latent image-forming tabular silver halide grains having an average thickness of less than 0.5 micron, an average diameter of at least 0.6 micron, and an average aspect ratio of at least 10:1 .

52. A dye image transfer film unit accord-ing to claim 51 additionally including means for terminating silver halide development positioned adjacent one of said support and said cover sheet.

53. A dye image transfer film unit accord-ing to claim 51 additionally including a reflective layer positioned adjacent said receiving layer and between said receiving layer and said one emulsion layer.

54. A dye image transfer film unit accord-ing to claim 51 in which said tabular silver halide grains have an average thickness of less than 0.3 micron.

55. In a multicolor dye image transfer film unit 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, radiation-sensitive internal latent image forming silver halide grains, and a nucleating agent, said dye-providing layer units including a dye-providing layer unit containing a red-sensitive emulsion and a cyan-dye-image-provid-ing material, a dye-providing layer unit containing a green-sensitive emulsion and a magenta-dye-image-pro-viding material, and a dye-providing layer unit con-taining a blue-sensitive emulsion and a yellow-dye-image-providing material, and a receiving layer for providing a viewable trans-ferred multicolor dye image following imagewise expo-sure and processing, the improvement wherein at least 70 percent of the total projected area of said radiation-sensi-tive grains in at least one of said emulsions is provided by internal latent image-forming tabular silver halide grains having an average thickness of less than 0.5 micron, an average diameter of at least 1.0 micron, and an average aspect ratio of at least 10:1.

56. A multicolor dye image transfer film unit according to claim 55 in which said tabular silver halide grains account for at least 90 percent of the total grain area of at least said one emulsion.

57. A multicolor dye image transfer film unit according to claim 55 in which said emulsion containing said tabular grains is a red-sensitive or green-sensitive 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.

58. A multicolor dye image transfer film unit according to claim 55 wherein said dye-image-providing materials are negative-working redox dye-releasers.

59. A multicolor dye image transfer film unit according to claim 55 wherein said tabular grains contain at least one of lead, cadmium, zinc, and erbium in an amount sufficient to reduce rereversal.

60. A multicolor dye image transfer film unit according to claim 55 wherein said nucleating agent is a hydrazide of the formula wherein D is an acyl group;
? is a phenylene or halo-, alkyl-, or a alkoxy-substituted phenylene group; and M is a moiety capable of restricting mobility.

61. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 2.

62. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 3.

63. In a photographic element comprised of 8 support and at least one radiation sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 4.

64. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 5.

65. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 6.

66. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 7.

67. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 8.

68. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of An emulsion according to claim 9.

69. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 10.

70. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 11.

71. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 12.

72. In a photographic element comprised of a support and at least one radiation sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 13.

73. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 14.

74. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 15.

75. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 16.

76. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 17.

77. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer 3 the improvement wherein said emulsion layer is comprised of an emulsion according to claim 18.

78. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 19.

79. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 20.

80. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 21.

81. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 22.

82. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 23.

83. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 24.

84. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 26.

85. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprlsed of an emulsion according to claim 27.

86. In a photographic element comprised of a support and at least one radiation-sensitive emul-sion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 28.