CA1258396A - Direct positive photographic elements with incorporated maximum density enhancing antifoggants - Google Patents
Direct positive photographic elements with incorporated maximum density enhancing antifoggantsInfo
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- CA1258396A CA1258396A CA000471296A CA471296A CA1258396A CA 1258396 A CA1258396 A CA 1258396A CA 000471296 A CA000471296 A CA 000471296A CA 471296 A CA471296 A CA 471296A CA 1258396 A CA1258396 A CA 1258396A
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Abstract
DIRECT POSITIVE PHOTOGRAPHIC ELEMENTS
WITH INCORPORATED MAXIMUM DENSITY
ENHANCING ANTIFOGGANTS
Abstract of the Disclosure A black and white direct positive photo-graphic element intended for the formation of a viewable silver image is disclosed. One or more silver halide emulsion layers are present containing internal latent image forming silver halide grains.
A maximum density enhancing antifoggant is located in an undercoat between the emulsion layer or layers and the support to impart an increase in photographic speed, an extended overexposure margin before encoun-tering rereversal, a decrease in minimum density, and an increase in the covering power of developed silver.
WITH INCORPORATED MAXIMUM DENSITY
ENHANCING ANTIFOGGANTS
Abstract of the Disclosure A black and white direct positive photo-graphic element intended for the formation of a viewable silver image is disclosed. One or more silver halide emulsion layers are present containing internal latent image forming silver halide grains.
A maximum density enhancing antifoggant is located in an undercoat between the emulsion layer or layers and the support to impart an increase in photographic speed, an extended overexposure margin before encoun-tering rereversal, a decrease in minimum density, and an increase in the covering power of developed silver.
Description
DIRECT POSITIVE P~OTOGRAPHIC ELEMENTS
WITH INCORPORATED MAXIMUM DENSITY
ENHANCING ANTIFOGGAMTS
This invention relates to direct positive photographic elements intended to form silver images containing internal latent image forming silver halide grains and maximum density enhancing antifog-gants. The invention further relates to processes of obtaining direct positive images from such photo-graphic elements following imagewise exposure.Brief Description of the Drawings The invention can be better understood by reference to the following detailed description of preferred embodiments considered in conjunction with the drawings, in which Figure 1 is a stylized characteristic curve of a direct positive emulsion;
Figures 2, 6, and 7 present characteristic curves of example and coated emulsions; and Figures 3A, 3B, 4A, 4B, 5A, and 5~ are magnifications of imaged Control (A) and ~xample (~) elements.
Background of the Invention Photographic elements which produce images 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 image which is a negative of the first negative-that is, a positive image. A direct positive image is under-stood in photography to be a positive image that is formed without first forming a negative image.
Direct positive photography is advantageous in providing a more straightforward approach to obtain-ing positive photographic images.
While silver halide photography offers thehighest attainable photographic speeds for direct ,I,,~,a .~
WITH INCORPORATED MAXIMUM DENSITY
ENHANCING ANTIFOGGAMTS
This invention relates to direct positive photographic elements intended to form silver images containing internal latent image forming silver halide grains and maximum density enhancing antifog-gants. The invention further relates to processes of obtaining direct positive images from such photo-graphic elements following imagewise exposure.Brief Description of the Drawings The invention can be better understood by reference to the following detailed description of preferred embodiments considered in conjunction with the drawings, in which Figure 1 is a stylized characteristic curve of a direct positive emulsion;
Figures 2, 6, and 7 present characteristic curves of example and coated emulsions; and Figures 3A, 3B, 4A, 4B, 5A, and 5~ are magnifications of imaged Control (A) and ~xample (~) elements.
Background of the Invention Photographic elements which produce images 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 image which is a negative of the first negative-that is, a positive image. A direct positive image is under-stood in photography to be a positive image that is formed without first forming a negative image.
Direct positive photography is advantageous in providing a more straightforward approach to obtain-ing positive photographic images.
While silver halide photography offers thehighest attainable photographic speeds for direct ,I,,~,a .~
-2-positive imaging~ there are within the field of silver halide photography a surprising number of different approache~ for dixect positive imaging. A
number of these approaches are reviewed in James, Th Theory of the Photographic Pro~çss, 4th Ed., Macmillan 1977, Chapter 7, "Latent Image Effects Leading to Reversal and Desensitization".
Internal latent image desensitization type imaging is known to produce the highest attainable photographic speeds among the various direct positive silver halide imaging approaches. According to this approach a silver halide emulsion is employed containing internal latent image forming silver halide grains which are substantially free of surface fog. After imagewise exposure, the silver halide grains are developed with a surface developer-that is, one which will leave the latent image sites within the silver halide grains substantially unrevealed. Simultaneously, either by uniform light exposure or by the use of a nucleating agent, the silver halide grains are subjected to development conditions that would cause fogging of surface latent image forming silver halide grains. The internal latent image forming silver halide grains which received actinic radiation during imagewise exposure develop under these conditions at a slow rate as compared to the internal latent image forming silver halide grains remaining.
Stauffer U.S. Patent 2,497,917 recognized that certain antifoggants when employed in internal latent image desensitization direct positive imaging not only reduce fog in minimum density areas, but also increase maximum density. Subsequently it has become the accepted practice in the art to employ maximum density enhancing antifoggants in internal latent image desensitization direct positive imag-ing. This special class of antifoggants are known to
number of these approaches are reviewed in James, Th Theory of the Photographic Pro~çss, 4th Ed., Macmillan 1977, Chapter 7, "Latent Image Effects Leading to Reversal and Desensitization".
Internal latent image desensitization type imaging is known to produce the highest attainable photographic speeds among the various direct positive silver halide imaging approaches. According to this approach a silver halide emulsion is employed containing internal latent image forming silver halide grains which are substantially free of surface fog. After imagewise exposure, the silver halide grains are developed with a surface developer-that is, one which will leave the latent image sites within the silver halide grains substantially unrevealed. Simultaneously, either by uniform light exposure or by the use of a nucleating agent, the silver halide grains are subjected to development conditions that would cause fogging of surface latent image forming silver halide grains. The internal latent image forming silver halide grains which received actinic radiation during imagewise exposure develop under these conditions at a slow rate as compared to the internal latent image forming silver halide grains remaining.
Stauffer U.S. Patent 2,497,917 recognized that certain antifoggants when employed in internal latent image desensitization direct positive imaging not only reduce fog in minimum density areas, but also increase maximum density. Subsequently it has become the accepted practice in the art to employ maximum density enhancing antifoggants in internal latent image desensitization direct positive imag-ing. This special class of antifoggants are known to
-3- ~ 3f j be useful whether incorporated directly in the photographic element or incorporated in a processing solution, such as a developer. Applications of maximum density enhancing antifoggants to more modern forms of internal latent image desensitization direct positive imaging are illustrated by Evans U.S. Patent 3,761,276 and Research Disclosure, Vol. 151, November 1976, Item 15162. Research Disclosure and Product Licensin~ Index are published at Emsworth Studios, 535 West End Avenue, New York, New York 1002~.
Internal latent image desensitization direct positive imaging to produce silver images is specifically illus`trated by Hoyen and Silverman Can. Serial Nos.
415,280 and 415,290, each filed November 10, 1982, and both commonly assigned.
Direct positive silver halide emulsions exhibit art recognized disadvantages as compared to negative working silver halide emulsions. Although internal latent image desensitization imaging is the highest speed approach to direct positive imaging with silver halide emulsions, direct positive photo-graphic speeds are still not high as compared to those achieved routinely with negative working silver halide emulsions. Thus, there is a need in the art for improvements in the photographic speed of this imaging approach.
A second disadvantage of internal latent image desensitization direct positive imaging is that rereversal occurs on overexposure.
A schematic illustration of rereversal is provided in Figure 1, which plots density versus exposure. A characteristic curve (stylized to exaggerate curve features for simplicity of discus-sion) is shown for a direct positive emulsion. When the emulsion is coated as a layer on a support, exposed, and processed, a density is produced. The characteristic curve is the result of plotting various levels of exposure versus the corresponding density produced on processing. At exposures below level A underexposure occurs and a maximum density is obtained which does not vary as a function of expo-sure. At exposure levels between A and B usefuldirect positive imaging can be achieved, since density varies inversely with exposure. If exposure occurs between the levels indicated by B and C, overexposure results. That is, density ceases to vary as a function of exposure in this range of exposures. If a subject to be photographed varies locally over a broad range of reflected light inten-sities, a photographic element containing the direct positive emulsion can be simultaneously exposed in different areas at levels less than A and greater than B. The result may, however, still be aesthet-ically pleasing, although highlight and shadow detail of the subject are both lost. If it is attempted to increase exposure for this subject, however, to pick up shadow detail, the result can be to increase highlight exposure to levels above C. When this occurs, rereversal is encountered. That is, the areas overexposed beyond exposure level C appear as highly objectionable negative images, since density is now increasing directly with e~posure. Useful exposure latitude can be increased separating expo-sure 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 between exposure levels ~ and C so that overex-posed areas are less likely to produce negative images. (In actual practice the various segments of the characteristic curve tend to merge more smoothly than illustrated.) In silver halide photographic elements which produce dye images for viewing the form of the q~
developed silver is of little concern, since the silver produced on development i8 an unwanted by-product of dye formation and i~ generally bleached from the photographic element. ~owever, in blac~ and 5 white photography the usual practice is to rely on developed silver wholly or partially to produce the viewable image. The form of the silver produced on development can have important effectx on image quality and the amount of ~ilver required. One lO measure of the efficiency of ~ilver u~e in black and white imaging is covering power. Although expressed in various unit6 in the art, a~ herein employed covering power is defined as 100 times the ratio of maximum density to ~ilver, expre3sed in grams per square decimeter. From this definition it i8 appar-ent that achieving an increase in ~he maximum density of a ilver image without increasing xilver coverage i8 expre~sed more succinctly as increasing covering power.
Summary of the Invention In one aspect this invention is directed to a black and white direct positive photographic element intended for the foxmation of a viewable silver image and comprised of a ~upport~ one or more radiation sensitive emulsion layers containinginternal latent image forming silver halide grains, and a ma~imum density enhancing antifoggant. The pho~ographic element is further characterized by the improvement wherein the maximum density enhancing 30 antifoggant i8 located in an undercoat between the emul~ion layer 8 and the ~upport.
In anoth~r aspect this invention i8 directed to processing in a surface developer an imagewiæe exposed photographic element according to this invention a) in the presence of a nucleating agent or b) with light flashing of the photographic element during processing.
~ 3~i Several highly useful advantages have been observed in the viewable silver image forming direct positive photographic elements and processes of this invention. An increase in photographic speed has been observed. In some instances desirable increases in contrast have also be realized. An extended overexposure margin before encountering rereversal has been observed. Additionally, both desirable decreases in minimum density and increases in cover-ing power have been realized. Microscopic examina-tions of silver images produced have revealed an improvement in image quality due to the finer, more uniformly distributed silver filaments produced by processing.
Description of the Pref,erred Embodiments The present invention is generally applic-able to black and white direct positive photographic elements intended for use in forming a viewable retained silver image. The photographic elements have coated on a support one or more radiation sensi~,ive emulsion layers containing internal latent image forming silver halide grains. To achieve the advantages of this invention a maximum density enhancing antifoggant is located in an undercoat between the emulsion layer or layers and the support. For economy of expression this undercoat is hereinafter referred to as "the antifoggant undercoat"
Whereas the art has heretofore located maximum density enhancing antifoggant either in the silver halide emulsion layer of a black and white direct positive photographic element or in a process-ing solution therefor, the photographic elements of this invention position these maximum density enhanc-ing antifoggants between the silver halide emulsion layer or layers and the photographic support. Stated another way, the antifoggant undercoat lies nearer the support than any radiation sensitive silver halide emulsion imaging layer.
~ 3 In general ar.y of the maximum density enhancing antifoggants recognized ~o be useful in internal latent image desensitizatlon direct po6itive imaging can be employed in the practice of this 5 invention, singly or in combination. Useful maximum density enhancing antifoggants are azoles and azines. Such azoles and azines have an R
(I) I
-N-group in the azole or azine ring, wherein Rl represents hydrogen or an alkali hydrolyzable group.
Specific illustrations of such maximum density enhancing antifoggants are disclosed by Stauffer U.S.
15 Patent 2,497,917, Evans U.S. Patent 3,761,276, and Research Disclosure Item 15162, cited above.
Specifically preferred maximum density enhancing antifoggants are 1~2,3-triazoles, including those having a fused nromatic ring structure, such as 20 benzotriazoles. Illustrative of specifically prefer-red maximum density enhancing 1,2,3-triazole antifog-gants are those set for~h in Table I.
Table I
AF-l Benzotriazole 25 AF-2 5-Bromobenzotriazole AF-3 5-Methylbenzotriazole AF-4 4-Nitro-6~chlorobenzotriazole AF-5 i-Phenylcarbamoyl-5-methylbenzotriazole AF-6 1-Cyclohex~lcarbamoyl-5,6-dichlorobenzo-triazole AF-7 l-(~-Hexadecanesulfonamidobenzoyl)benzo-t~iazole AF-8 1,2,3-Triazole-4,5-dicarboxylic acid AF-9 5-Nitrobenzotriazole 35 AF-10 596-Dichlorobenzotriaæole The maximum density enhancing antifoggRnts can be employed in any effective amount. Generally concentrations of 0.1 mole per mole of silver or less are employed in the practice of this invention. The maximum density enhancing antifoggants, particularly the 1,2,3-triazole antifoggant6 described above, sre 5 preferably incorporated in the photographic element beneath the radiation sensitive silver halide emul-sion layer or layers in the antifoggant undercoat in a concentration of from 5 X 10-~ to 0.1 mole per mole of silver, preferably 10- 3 to 5 X 10- 2 mole 10 per mole of silver, when no other source of maximum density enhancing antifoggant is supplied. When another source of maximum density enhancing antifog-gant is supplied~ the concPntration of maximum density enhancing antifoggant in the antifoggant 15 undercoat can, but need not, be reduced. For example, it is conventional to incorporate maximum density enhancing antifoggants in processing solu-tions in concentrations ranging from about S X 10- 2 to 3 grams per liter. Even with these conventional 20 levels of maximum density enhancing antifoggants in the processing solutions employed, advantages can be achieved by the presence of maximum density enhancing antifoggant in the antifoggant undercoat.
In addition to the maximum density enhancing 25 antifoggant the antifoggant undercoat preferably includes a dispersing medium to fac~itate coating of the maximum density enhancing antifoggant at the desired coverage. The dispersing medium can be chosen from among those conventionally employed in 30 sllver halide emulsion and other processing solution permeable layers of photographic elements, more specifically described below.
In addition to the antifoggant undercoat the photographic elements of this invention additionally 35 include one or more radiation sensitive silver halide emulsion layers containing internal latent image forming silver halide grains.
_9_ As employed herein, the terms "internal latent image forming silver halide grains" and "silver halide grains capable of forming an ln~ernal latent image" are employed in the art-recognized 5 sense of designating silver halide grains whlch produce substantially higher optical densities when coated, imagewise exposed, and developed in an internal developer than when comparably coated, exposed and developed in a surface developer.
10 Preferred internal latent image forming silver halide grains ar~ those which, when examined according ~o normal photographic testing techniques, by coating a test portion on a photographic support (e.g., at a coverage of from 3 to 4 grams per square meter), 15 exposlng to a light intensity scale (e.g., with a 500-watt tungsten lamp at a distance of 61 cm) for a fixed time (e.g., between 1 X 10-2 and 1 second) and developing for S minutes at 25C in Kodak Developer DK-50 ~ (a surface developer), provide a 20 density of at least 0.5 less than when this testing procedure is repeated, substituting for the surface developer Kodak Developer DK-S0 ~ containing 0.5 gram per liter of potassium iodide (an internal developer). The internal latent image forming silver 25 halide grains most preferred for use in the practice of this invention are those which, when ~ested using an internal developer and a surface developer as indicated above, produce an optical density with the internal developer at least 5 times that produced by 30 the surface developer. It is additionally preferred that the internal latent image forming silver halide grains produce an optical density of less than 0.4 and, most preferably, less than 0.25 when coated, exposed and developed in surface developer as 35 indicated above, that is, the silver halide grain6 are preferably initially substantially unfogged and free of latent image on their surface.
r~ 3~
The surface developer referred to herein as Kodak Developer DK-50 ~ is described in the Handbook of Chemist~y and Physics, 30th edition, _ 1947, Chemical Rubber Publishing Company, Cleveland, 5 Ohlo, page 2558, and has the following composition:
Water, about 52C 500.0 cc N-methyl-~-aminophenol hemisulfate 2.5 g Sodium sulfite, desiccated 30.0 g Hydroquinone 2.5 g Sodium metaborate 10.0 g Potassium bromide 0-5 g Wa~er to make 1.0 liter.
Internal latent image forming silver halide grains which can be employed in the practice of this 15 invention are well known in the art. Paten~s teach-ing the use of internal la~ent image forming silver halide grains in photographic emulsions and elements include Davey et al U.S. Patent 2,592,250, Porter et al U.S. Patent 3,206,313, Milton U.S. Patent 20 3,761,266, Ridgway U.S. Patent 3,586,505, Gilman et al U.S. Patent 3,772,030, Gilman et al U.S. Patent 3,761,267, Evans U.S. Patent 3,761,276, and Atwell et al U.S. Patent 4,035,185.
Preferred internal latent image forming 25 silver halide emulsions are core-shell emulsions.
Such emulsions contain internal latent image forming silver halide grains which are internally sen6i-tized. The internal or core portion of the silver halide grain which is sensitized is covered wi~h an 30 additional portion of silver halide, referred to as a shell. The primary function of the shell is to prevent access of surface developer to latent image sites which are located internally by reason of the internal chemical sensitization. As employed herein 35 the term "core-shell" is intended to include any silver halide emulslon having these properties without regard to its method of manufacture.
~ 3~i Use~ul core-shell emulsions can be prepared by first forming a sensitized core emulsion. The core emulsion can be comprised of silver bromide, silver chloride, silver chlorobromide, silver chloro-5 iodide, silver bromoiodide, or 8 ilver chlorobromo-iodide grains. The grains can be coarse, medium, or fine and can be bounded by ~100}, {111}, {110} crystal planes or combinations thereof.
The coefficient of variation of the core grains 10 should be no higher than ~he desired coefficient of variation of the completed core-shell grains.
Perhaps the simplest manipulative approach to forming sensitized core grains is to incorporate a metal dopant within the core grains as they are being 15 formed. The metal dopant can be placed in the reaction vessel in which core grain formation occurs prior ~o the introduction of silver salt. Alter-nately the metal dopant can be introduced during silver halide grain growth at any stage of precipita-20 tion, with or without interrupting silver and/orhalide salt introduction.
Iridium is specifically contemplated as a metal dopant~ It is preferably incorporated within the silver halide grains in concentrations of from 25 about 10-8 to 10-4 mole per mole of silver. ~he iridium can be conveniently incorporated into the reaction vessel as a water soluble salt, such ~s an alkali metal salt of a halogen-iridium coordination complex, such as ~odium or potassium hexachloro-30 iridate or hexabromoiridate. Speciflc examples ofincorporating an lridium dopant are provided ~y Berriman U.S. Patent 3,367,778.
Léad is also a specifically contemplated metal dopant for core grain sensitization. Lead ifi a 35 common dopant in dlrect print and printout emulsions and can be employed in the practice of this invention in similar concentration ranges. It i~ generally -12~ 3~34~
preferred that the lead dopant be present in a concentration of at least 10- 4 mole per mole of silver. Concentrations up to about 5 X 10- 2, preferably 2 X 10- 2, mole per ~ole of silver are S contemplated. Lead dopants c~n be introduced 8 imi-larly as iridium dopants in the form of water soluble salts, such as lead acetate, lead nitrate, and lead cyanide. Lead dopants are particularly illustrated by McBride U.S. Patent 3,287,136 and Bacon U.~.
10 Patent 3,531,291.
Another technique for sensitizing the core grains is to stop silver halide grain precipitation after the core grain has been produced and to sensi-tize chemically the surface of the core. Thereafter 15 additional precipitation of silver halide produces a shell surrounding the core. Particularly advanta-geous chemical sensitizers for this purpose are middle chalcogen sensitizers--i.e., sulfur, selenium, and/or tellurium sensitizers. Middle chalcogen 20 sensitizers are preferably employed in concentrations 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 advantages can be realized by employing a gold sensitizer in combina-25 tion. Gold sensitizers are preferably employed inconcentrations ranging from 0.5 to 5 times that of the middle chalcogen sensitizers. Preferred coneen-trations of gold sensitizers ~ypically range from about 0.01 to 40 mg per mole of silver, most prefer-30 ably from about 0.1 to 20 mg per mole of silver.Controlling con~rast by controlling the ratio of middle chalcogen to gold sensitizer is particularly taught by Atwell et al U.S. Patent 4,035,185, cited above, specifically for this teaching. Evans U.S.
35 Patent 3,761,276, cited ~bove, provides 6pecific examples of middle chalcogen core grain sensitizations.
313~~
Although preferred, it is not essenti~l that the core grains be chemic~lly sensitized prior to shelling to form the completed core-shell grain6. It is merely necessary that the core-shell grains as 5 formed be capable of formlng internal latent image sites. Internal sensitization sites formed by shelling of sensitized core grains--that is, occlu-sion of foreign (i.e., other than silver and halogen) materials within the core-shell grains--are herein-10 after referred to as internal chemical sensitizationsites to distinguish them from internal physical sensitization sites. It is possible to incorporate internal physical sensitization sites by providing irregularities in the core-shell grain crystal 15 lattice. Such internal irregularities can be created by discontinuities in silver halide precipitation or by abrupt changes in the halide con~ent of the core-shell grains. For example, it has been observed that the precipitatlon of a silver bromide core 20 followed by shelling with silver bromoiodide of greater than 5 mole percent iodide requires no internal chemical sensitization ~o produce a direct positive image.
Although the sensitized core emulsion can be 25 shelled by the Os~wald ripening technique of Porter et al U.S. Patent 3,206,313, cited aboYe, it is preferred that the silver halide forming the shell portion of the grains be precipitated directly onto the sensitized core ~rains by the double jet additlon 30 technique. Double jet precipitation is well known in the art, as illustrated by Research Disclosure, Vol.
176, December 1978, Item 17643, Sectlon I. The halide content of the shell portlon of the grains can take any of the forms described above with reference 35 to the core emulsion. To improve developability it is preferred that the shell portion of the gra~ns contain at least 80 mole percent chloride, the -14- ~t)~ 3~;
remaining halide being bromide or bromide and up to 10 mole percent iodide. (Except a6 otherwise indi-cated, all re~erences to halide percentages are based on silver present in the corresponding emulsion, 5 grain, or grain region being discu6sed.) Improve-ments in low intensity reciprocity failure are also realized when the shell portion of the core-shell grains is comprised of at least 80 mole percent chloride, as described above. For each of these 10 advantages silver chloride is specifically prefer-red. On the other hand, the highest realized photo-graphic speeds are generally recognized to occur with predominantly bromide grains, as taught by Evans U.S.
Patent 3,761,276, cited above. Thus, the specific 15 choice of a preferred halide for the shell portion of ~he core-shell grains will depend upon the specific photographic application. When the same halides are chosen for forming both the core and shell portions of the core-shell grain structure, it is specifically 20 contemplated to employ double jet precipitation for producing both the core and shell portions of the grains without interrupting the introduction of silver and halide salts in the transition from core to shell formation.
The silver halide forming the shell portion of the core-shell grains must be suficient to restrict developer access to the sensitized core portion of the grains. This will vary as a function of the ability of the developer to dissolve the shell 30 portion of the grains durlng development. Although shell thicknesses as low as a few crystal lattice planes for developers having very low silver halide solvency are taught in the art, it is preferred that the shell portion of the core-shell grains be present 35 in a molar ratio with ~he core portlon of the grain~
of about 1:4 to 8:1, as taught by Porter et al U.S.
Patent 3,206,313 and Atwell et al ~.S. Patent
Internal latent image desensitization direct positive imaging to produce silver images is specifically illus`trated by Hoyen and Silverman Can. Serial Nos.
415,280 and 415,290, each filed November 10, 1982, and both commonly assigned.
Direct positive silver halide emulsions exhibit art recognized disadvantages as compared to negative working silver halide emulsions. Although internal latent image desensitization imaging is the highest speed approach to direct positive imaging with silver halide emulsions, direct positive photo-graphic speeds are still not high as compared to those achieved routinely with negative working silver halide emulsions. Thus, there is a need in the art for improvements in the photographic speed of this imaging approach.
A second disadvantage of internal latent image desensitization direct positive imaging is that rereversal occurs on overexposure.
A schematic illustration of rereversal is provided in Figure 1, which plots density versus exposure. A characteristic curve (stylized to exaggerate curve features for simplicity of discus-sion) is shown for a direct positive emulsion. When the emulsion is coated as a layer on a support, exposed, and processed, a density is produced. The characteristic curve is the result of plotting various levels of exposure versus the corresponding density produced on processing. At exposures below level A underexposure occurs and a maximum density is obtained which does not vary as a function of expo-sure. At exposure levels between A and B usefuldirect positive imaging can be achieved, since density varies inversely with exposure. If exposure occurs between the levels indicated by B and C, overexposure results. That is, density ceases to vary as a function of exposure in this range of exposures. If a subject to be photographed varies locally over a broad range of reflected light inten-sities, a photographic element containing the direct positive emulsion can be simultaneously exposed in different areas at levels less than A and greater than B. The result may, however, still be aesthet-ically pleasing, although highlight and shadow detail of the subject are both lost. If it is attempted to increase exposure for this subject, however, to pick up shadow detail, the result can be to increase highlight exposure to levels above C. When this occurs, rereversal is encountered. That is, the areas overexposed beyond exposure level C appear as highly objectionable negative images, since density is now increasing directly with e~posure. Useful exposure latitude can be increased separating expo-sure 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 between exposure levels ~ and C so that overex-posed areas are less likely to produce negative images. (In actual practice the various segments of the characteristic curve tend to merge more smoothly than illustrated.) In silver halide photographic elements which produce dye images for viewing the form of the q~
developed silver is of little concern, since the silver produced on development i8 an unwanted by-product of dye formation and i~ generally bleached from the photographic element. ~owever, in blac~ and 5 white photography the usual practice is to rely on developed silver wholly or partially to produce the viewable image. The form of the silver produced on development can have important effectx on image quality and the amount of ~ilver required. One lO measure of the efficiency of ~ilver u~e in black and white imaging is covering power. Although expressed in various unit6 in the art, a~ herein employed covering power is defined as 100 times the ratio of maximum density to ~ilver, expre3sed in grams per square decimeter. From this definition it i8 appar-ent that achieving an increase in ~he maximum density of a ilver image without increasing xilver coverage i8 expre~sed more succinctly as increasing covering power.
Summary of the Invention In one aspect this invention is directed to a black and white direct positive photographic element intended for the foxmation of a viewable silver image and comprised of a ~upport~ one or more radiation sensitive emulsion layers containinginternal latent image forming silver halide grains, and a ma~imum density enhancing antifoggant. The pho~ographic element is further characterized by the improvement wherein the maximum density enhancing 30 antifoggant i8 located in an undercoat between the emul~ion layer 8 and the ~upport.
In anoth~r aspect this invention i8 directed to processing in a surface developer an imagewiæe exposed photographic element according to this invention a) in the presence of a nucleating agent or b) with light flashing of the photographic element during processing.
~ 3~i Several highly useful advantages have been observed in the viewable silver image forming direct positive photographic elements and processes of this invention. An increase in photographic speed has been observed. In some instances desirable increases in contrast have also be realized. An extended overexposure margin before encountering rereversal has been observed. Additionally, both desirable decreases in minimum density and increases in cover-ing power have been realized. Microscopic examina-tions of silver images produced have revealed an improvement in image quality due to the finer, more uniformly distributed silver filaments produced by processing.
Description of the Pref,erred Embodiments The present invention is generally applic-able to black and white direct positive photographic elements intended for use in forming a viewable retained silver image. The photographic elements have coated on a support one or more radiation sensi~,ive emulsion layers containing internal latent image forming silver halide grains. To achieve the advantages of this invention a maximum density enhancing antifoggant is located in an undercoat between the emulsion layer or layers and the support. For economy of expression this undercoat is hereinafter referred to as "the antifoggant undercoat"
Whereas the art has heretofore located maximum density enhancing antifoggant either in the silver halide emulsion layer of a black and white direct positive photographic element or in a process-ing solution therefor, the photographic elements of this invention position these maximum density enhanc-ing antifoggants between the silver halide emulsion layer or layers and the photographic support. Stated another way, the antifoggant undercoat lies nearer the support than any radiation sensitive silver halide emulsion imaging layer.
~ 3 In general ar.y of the maximum density enhancing antifoggants recognized ~o be useful in internal latent image desensitizatlon direct po6itive imaging can be employed in the practice of this 5 invention, singly or in combination. Useful maximum density enhancing antifoggants are azoles and azines. Such azoles and azines have an R
(I) I
-N-group in the azole or azine ring, wherein Rl represents hydrogen or an alkali hydrolyzable group.
Specific illustrations of such maximum density enhancing antifoggants are disclosed by Stauffer U.S.
15 Patent 2,497,917, Evans U.S. Patent 3,761,276, and Research Disclosure Item 15162, cited above.
Specifically preferred maximum density enhancing antifoggants are 1~2,3-triazoles, including those having a fused nromatic ring structure, such as 20 benzotriazoles. Illustrative of specifically prefer-red maximum density enhancing 1,2,3-triazole antifog-gants are those set for~h in Table I.
Table I
AF-l Benzotriazole 25 AF-2 5-Bromobenzotriazole AF-3 5-Methylbenzotriazole AF-4 4-Nitro-6~chlorobenzotriazole AF-5 i-Phenylcarbamoyl-5-methylbenzotriazole AF-6 1-Cyclohex~lcarbamoyl-5,6-dichlorobenzo-triazole AF-7 l-(~-Hexadecanesulfonamidobenzoyl)benzo-t~iazole AF-8 1,2,3-Triazole-4,5-dicarboxylic acid AF-9 5-Nitrobenzotriazole 35 AF-10 596-Dichlorobenzotriaæole The maximum density enhancing antifoggRnts can be employed in any effective amount. Generally concentrations of 0.1 mole per mole of silver or less are employed in the practice of this invention. The maximum density enhancing antifoggants, particularly the 1,2,3-triazole antifoggant6 described above, sre 5 preferably incorporated in the photographic element beneath the radiation sensitive silver halide emul-sion layer or layers in the antifoggant undercoat in a concentration of from 5 X 10-~ to 0.1 mole per mole of silver, preferably 10- 3 to 5 X 10- 2 mole 10 per mole of silver, when no other source of maximum density enhancing antifoggant is supplied. When another source of maximum density enhancing antifog-gant is supplied~ the concPntration of maximum density enhancing antifoggant in the antifoggant 15 undercoat can, but need not, be reduced. For example, it is conventional to incorporate maximum density enhancing antifoggants in processing solu-tions in concentrations ranging from about S X 10- 2 to 3 grams per liter. Even with these conventional 20 levels of maximum density enhancing antifoggants in the processing solutions employed, advantages can be achieved by the presence of maximum density enhancing antifoggant in the antifoggant undercoat.
In addition to the maximum density enhancing 25 antifoggant the antifoggant undercoat preferably includes a dispersing medium to fac~itate coating of the maximum density enhancing antifoggant at the desired coverage. The dispersing medium can be chosen from among those conventionally employed in 30 sllver halide emulsion and other processing solution permeable layers of photographic elements, more specifically described below.
In addition to the antifoggant undercoat the photographic elements of this invention additionally 35 include one or more radiation sensitive silver halide emulsion layers containing internal latent image forming silver halide grains.
_9_ As employed herein, the terms "internal latent image forming silver halide grains" and "silver halide grains capable of forming an ln~ernal latent image" are employed in the art-recognized 5 sense of designating silver halide grains whlch produce substantially higher optical densities when coated, imagewise exposed, and developed in an internal developer than when comparably coated, exposed and developed in a surface developer.
10 Preferred internal latent image forming silver halide grains ar~ those which, when examined according ~o normal photographic testing techniques, by coating a test portion on a photographic support (e.g., at a coverage of from 3 to 4 grams per square meter), 15 exposlng to a light intensity scale (e.g., with a 500-watt tungsten lamp at a distance of 61 cm) for a fixed time (e.g., between 1 X 10-2 and 1 second) and developing for S minutes at 25C in Kodak Developer DK-50 ~ (a surface developer), provide a 20 density of at least 0.5 less than when this testing procedure is repeated, substituting for the surface developer Kodak Developer DK-S0 ~ containing 0.5 gram per liter of potassium iodide (an internal developer). The internal latent image forming silver 25 halide grains most preferred for use in the practice of this invention are those which, when ~ested using an internal developer and a surface developer as indicated above, produce an optical density with the internal developer at least 5 times that produced by 30 the surface developer. It is additionally preferred that the internal latent image forming silver halide grains produce an optical density of less than 0.4 and, most preferably, less than 0.25 when coated, exposed and developed in surface developer as 35 indicated above, that is, the silver halide grain6 are preferably initially substantially unfogged and free of latent image on their surface.
r~ 3~
The surface developer referred to herein as Kodak Developer DK-50 ~ is described in the Handbook of Chemist~y and Physics, 30th edition, _ 1947, Chemical Rubber Publishing Company, Cleveland, 5 Ohlo, page 2558, and has the following composition:
Water, about 52C 500.0 cc N-methyl-~-aminophenol hemisulfate 2.5 g Sodium sulfite, desiccated 30.0 g Hydroquinone 2.5 g Sodium metaborate 10.0 g Potassium bromide 0-5 g Wa~er to make 1.0 liter.
Internal latent image forming silver halide grains which can be employed in the practice of this 15 invention are well known in the art. Paten~s teach-ing the use of internal la~ent image forming silver halide grains in photographic emulsions and elements include Davey et al U.S. Patent 2,592,250, Porter et al U.S. Patent 3,206,313, Milton U.S. Patent 20 3,761,266, Ridgway U.S. Patent 3,586,505, Gilman et al U.S. Patent 3,772,030, Gilman et al U.S. Patent 3,761,267, Evans U.S. Patent 3,761,276, and Atwell et al U.S. Patent 4,035,185.
Preferred internal latent image forming 25 silver halide emulsions are core-shell emulsions.
Such emulsions contain internal latent image forming silver halide grains which are internally sen6i-tized. The internal or core portion of the silver halide grain which is sensitized is covered wi~h an 30 additional portion of silver halide, referred to as a shell. The primary function of the shell is to prevent access of surface developer to latent image sites which are located internally by reason of the internal chemical sensitization. As employed herein 35 the term "core-shell" is intended to include any silver halide emulslon having these properties without regard to its method of manufacture.
~ 3~i Use~ul core-shell emulsions can be prepared by first forming a sensitized core emulsion. The core emulsion can be comprised of silver bromide, silver chloride, silver chlorobromide, silver chloro-5 iodide, silver bromoiodide, or 8 ilver chlorobromo-iodide grains. The grains can be coarse, medium, or fine and can be bounded by ~100}, {111}, {110} crystal planes or combinations thereof.
The coefficient of variation of the core grains 10 should be no higher than ~he desired coefficient of variation of the completed core-shell grains.
Perhaps the simplest manipulative approach to forming sensitized core grains is to incorporate a metal dopant within the core grains as they are being 15 formed. The metal dopant can be placed in the reaction vessel in which core grain formation occurs prior ~o the introduction of silver salt. Alter-nately the metal dopant can be introduced during silver halide grain growth at any stage of precipita-20 tion, with or without interrupting silver and/orhalide salt introduction.
Iridium is specifically contemplated as a metal dopant~ It is preferably incorporated within the silver halide grains in concentrations of from 25 about 10-8 to 10-4 mole per mole of silver. ~he iridium can be conveniently incorporated into the reaction vessel as a water soluble salt, such ~s an alkali metal salt of a halogen-iridium coordination complex, such as ~odium or potassium hexachloro-30 iridate or hexabromoiridate. Speciflc examples ofincorporating an lridium dopant are provided ~y Berriman U.S. Patent 3,367,778.
Léad is also a specifically contemplated metal dopant for core grain sensitization. Lead ifi a 35 common dopant in dlrect print and printout emulsions and can be employed in the practice of this invention in similar concentration ranges. It i~ generally -12~ 3~34~
preferred that the lead dopant be present in a concentration of at least 10- 4 mole per mole of silver. Concentrations up to about 5 X 10- 2, preferably 2 X 10- 2, mole per ~ole of silver are S contemplated. Lead dopants c~n be introduced 8 imi-larly as iridium dopants in the form of water soluble salts, such as lead acetate, lead nitrate, and lead cyanide. Lead dopants are particularly illustrated by McBride U.S. Patent 3,287,136 and Bacon U.~.
10 Patent 3,531,291.
Another technique for sensitizing the core grains is to stop silver halide grain precipitation after the core grain has been produced and to sensi-tize chemically the surface of the core. Thereafter 15 additional precipitation of silver halide produces a shell surrounding the core. Particularly advanta-geous chemical sensitizers for this purpose are middle chalcogen sensitizers--i.e., sulfur, selenium, and/or tellurium sensitizers. Middle chalcogen 20 sensitizers are preferably employed in concentrations 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 advantages can be realized by employing a gold sensitizer in combina-25 tion. Gold sensitizers are preferably employed inconcentrations ranging from 0.5 to 5 times that of the middle chalcogen sensitizers. Preferred coneen-trations of gold sensitizers ~ypically range from about 0.01 to 40 mg per mole of silver, most prefer-30 ably from about 0.1 to 20 mg per mole of silver.Controlling con~rast by controlling the ratio of middle chalcogen to gold sensitizer is particularly taught by Atwell et al U.S. Patent 4,035,185, cited above, specifically for this teaching. Evans U.S.
35 Patent 3,761,276, cited ~bove, provides 6pecific examples of middle chalcogen core grain sensitizations.
313~~
Although preferred, it is not essenti~l that the core grains be chemic~lly sensitized prior to shelling to form the completed core-shell grain6. It is merely necessary that the core-shell grains as 5 formed be capable of formlng internal latent image sites. Internal sensitization sites formed by shelling of sensitized core grains--that is, occlu-sion of foreign (i.e., other than silver and halogen) materials within the core-shell grains--are herein-10 after referred to as internal chemical sensitizationsites to distinguish them from internal physical sensitization sites. It is possible to incorporate internal physical sensitization sites by providing irregularities in the core-shell grain crystal 15 lattice. Such internal irregularities can be created by discontinuities in silver halide precipitation or by abrupt changes in the halide con~ent of the core-shell grains. For example, it has been observed that the precipitatlon of a silver bromide core 20 followed by shelling with silver bromoiodide of greater than 5 mole percent iodide requires no internal chemical sensitization ~o produce a direct positive image.
Although the sensitized core emulsion can be 25 shelled by the Os~wald ripening technique of Porter et al U.S. Patent 3,206,313, cited aboYe, it is preferred that the silver halide forming the shell portion of the grains be precipitated directly onto the sensitized core ~rains by the double jet additlon 30 technique. Double jet precipitation is well known in the art, as illustrated by Research Disclosure, Vol.
176, December 1978, Item 17643, Sectlon I. The halide content of the shell portlon of the grains can take any of the forms described above with reference 35 to the core emulsion. To improve developability it is preferred that the shell portion of the gra~ns contain at least 80 mole percent chloride, the -14- ~t)~ 3~;
remaining halide being bromide or bromide and up to 10 mole percent iodide. (Except a6 otherwise indi-cated, all re~erences to halide percentages are based on silver present in the corresponding emulsion, 5 grain, or grain region being discu6sed.) Improve-ments in low intensity reciprocity failure are also realized when the shell portion of the core-shell grains is comprised of at least 80 mole percent chloride, as described above. For each of these 10 advantages silver chloride is specifically prefer-red. On the other hand, the highest realized photo-graphic speeds are generally recognized to occur with predominantly bromide grains, as taught by Evans U.S.
Patent 3,761,276, cited above. Thus, the specific 15 choice of a preferred halide for the shell portion of ~he core-shell grains will depend upon the specific photographic application. When the same halides are chosen for forming both the core and shell portions of the core-shell grain structure, it is specifically 20 contemplated to employ double jet precipitation for producing both the core and shell portions of the grains without interrupting the introduction of silver and halide salts in the transition from core to shell formation.
The silver halide forming the shell portion of the core-shell grains must be suficient to restrict developer access to the sensitized core portion of the grains. This will vary as a function of the ability of the developer to dissolve the shell 30 portion of the grains durlng development. Although shell thicknesses as low as a few crystal lattice planes for developers having very low silver halide solvency are taught in the art, it is preferred that the shell portion of the core-shell grains be present 35 in a molar ratio with ~he core portlon of the grain~
of about 1:4 to 8:1, as taught by Porter et al U.S.
Patent 3,206,313 and Atwell et al ~.S. Patent
4,035,185, cited above.
~ ;3 The amount of overexposure which can be tolerated by the emulsions of this invention without encountering rereversal can be increased by incorpo-rating into the core-shell grains mPtal dopan~s for
~ ;3 The amount of overexposure which can be tolerated by the emulsions of this invention without encountering rereversal can be increased by incorpo-rating into the core-shell grains mPtal dopan~s for
5 this purpose. As employed herein the term "rere-versal" refers to the negative working characteristic exhibited by an overexposed direct positive emul-sion. (Rereversal is the converse of solarization, a positive working characteristic exhibited by an 10 overexposed negative working emulsion.) Hoyen U.S.
Patent 4,395,478 discloses the use of polyvalent metal ions as dopants in the shell of core~shell emulsions to reduce rereversal. Preferred metal dopants for this purpose are di~alent and trivalent 15 cationic metal dopants, such as cadmium, zinc, lead, and erbium. These dopants are generally effective at concentration levels below about 5 X 10- 4, prefer-ably below 5 X 10-5, mole per mole of silver.
Dopant concentrations of at least 10- 6, preferably 20 at least 5 X 10- 6, mole per silver mole, should be present in the reaction vessel during silver hallde precipitation. The rere~ersal modifying dopant is effective if introduced at any stage of silver halide precipitation. The rereversal modifying dopant can 25 be incorporated ln either or both of the core and shell. It is preferred that the dopant be introduced during th~ latter stages of precipitation (e.g., confined to the shell) when the core-shell grains are high aspect ratio tabular grains. The metal dopan~s 30 can be introduced into the reaction vessel as water soluble metal s~lts, such as divalent and trivalent metal halide salts. Zinc, lead, and cadmium dopants for silver halide in similar concentrations, but to achie~e other modifying effects, are disclosed by 35 McBride U.S. Patent 3,287,136, Mueller et al U.S.
Patent 2,950,972, Iwaosa et al U.S. Patent 3,901,711, and Atwell U.S. Patent 4,269,927. Other technlques ~ ~ S~ 3 for improving rereversal characteri6~ics discussed below can be employed independently or in combination with the metal dopant~ described.
After precipitation of a shell portion onto 5 the sensitized core grains to complete formation of the core-shell grains, the emulsions can be washed, if desired, to remove soluble salts. Conventional washing ~echniques can be employed, such as those disclosed by Research Disclosure, Item 17643, cited 10 above, Section II.
Since the core-shell emulsions are intended to form internal latent images, intentional sensiti-zation of the surfaces of the core-shell grains is not essential. However, to achieve the highest 15 attainable reversal speeds, it is preferred that ~he core-shell grains be surface chemically sensitized, as taught by Evans U.S. Patent 3,761,276 and Atwell et al U.S. Patent 4,035,185, cited above. Any type of surface chemical sensitization known to be useful 20 with corresponding surface latent image forming silver halide emulsions can be employed, such a6 disclosed by Research Disclosure, Item 17643, cited above, Section III. Middle chalcogen and/or noble metal sensitizations, as described by Atwell et al 25 U.S. Patent 4,035,185, cited above, are preferred.
Sulfur, selenium, and gold are specificslly preferred surface sensitizers.
The degree of surface chemical fiensitization is limited to that which will increase the reversal 30 speed of the in~ernal latent image forming emulsion, but which will ~ot compete with the internal sensiti-zation sités to the extent of causlng the location of latent image centers formed on expo6ure to shift from the interior to the surface of the tabular grains.
35 Thus, a balance between internal and surface senslti-zation is preferably maintained for maximum speed, but with the internal sensitization predominating.
Tolerable levels of surface chemical sensitizMtion can be readily determined by relating surface development to internal development as previously described.
In one specifically preferred form the core-shell emulsions employed in the practice of this invention are high aspect ratio tabular grain core-shell emulsions, as disclosed by Resea ch Disclosure, Vol. ~5, January, 1983, Item 22534, and Evans et al lO Can. Serial No. 415,270, filed November 10, 1982, commonly assigned. As applied to the emulsions the term "high aspect ra~io" is herein defined as requiring that the core-shell grains having a thickness of less than ~.5 micron (preferably 0.3 15 micron) and a diameter of at least 0.6 micron have an average aspect ratio of greater than 8:1 and account for at least 50 percent of the total projected area of the core-shell silver halide grains.
As employed herein the term "aspect ratio"
20 refers to the ratio of the diameter of the grain to its thickness. The "diameter" of the grain is in turn defined as the diameter of a circle having an area equal to the projected area of the grain as viewed in a photomicrograph of an emulsion sample.
25 The core-shell tabular grains of Evans et al have an average aspect ra~io of greater than 8:1 and prefer-ably have;an &verage aspect ratio of greater than 10:1. Uader optimum conditions of preparation aspect ratios of 50:1 or even 100:1 are contemplat d. As 30 will be apparent, the thinner the grains, the higher their aspect ratio for a given diameter. Typically grains of aesirable aspect ratios are those having an average thickness of less than 0.5 micron, preferably les 6 than 0.3 micron, and optimally less than 0.2 35 micron. Typically the tabular gra~n~ have an average thickness of at least 0.05 micron, although even thinner tabular grains can in principle be employed.
In a preferred form of the invention the tabular grains account for a~ least 70 percent and optimally at least 90 percent of the total projected surface area of ~he core-shell silver halide grains. Tabular 5 grain average diame~ers are in all instance6 less than 30 microns, preferably less than 15 microns, and optimally less than 10 microns.
It is specifically contempla~ed to blend the internal latent image forming emulsions to satisfy 10 specific emulsion layer requirements. For example, two or more emulsions differing in average grain diameter can be blended. It is specifically contem-plated to employ in blending internal latent image forming grains of similar grain size distribution to 15 minimize migration of addenda between different grain populations. When separate emulsionæ of similar grain size distribution are employed in combination, their performance can be differentiated by differ-ences in surface sensitization levels, differences 20 relating to adsorbed nucleating agents, or differ-ences in proportions of internal sensitizers, the latter being taught by Atwell et al U.S. Patent 4,035,185. Hoyen et al Can. Serial Nos. 415,290, titled PHOTOGRAPHIC ELEMENTS CONTAINING DIRECT
25 POSITIVE EMULSIONS AND PROCESSES FOR THEIR USE, and 415,280, titled BLENDED DIRECT-POSITIVE EMULSIONS, PHOTOGRAPHIC ELEMENTS, AND PROCESSES OF USE, both filed November lO, 1982, commonly assigned, disclose that the blending or double coating of a first, 30 core-shell emulsion and a 6econd, internal lAtent image forming or internally fogged emulsion in a weight rativ 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 ~verage grain 35 diameter less than 70% that of the first emulsion, can result in an increase in silver covering power.
A speed increase can also be realized, even at -19- ~ 3;~`3~i reduced coating levelsO 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 emul~ion i8 5 preferably less than 50%, optimally less than 40% the average diameter of the grains of the first emulsion.
In a speciically preerred form of the invention the grains of the second emulsion are also core-shell grains. They can be identical to the 10 core-shell grains of the first emulsion, subject to the considerations noted above. In general, when the second core-shell grain population satisfies the relative size requirements of the two grain popula-tions the other considerations will also be satisfled 15 when ~he firs~ and second grain population~ are of the same silver halide composition and similarly internally sensitized. Maintaining the second grain population substantially free of intentional surface chemical sensit;zation is also advantageous both in 20 reducing the surface latent image forming capability of the second grain population within the direct positive exposure latitude of the blended emulsion and in increasing the reversal speed of the blended emulsion. It is specifically preferrPd to blend 25 core-shell emulsions having surface chemical sensiti-zation of the type disclosed by Evans U.S. Paten~
3,761,176 and Atwell et al U.S. Patent 4,035,185, cited above, to form the first grain population with similar core-shell grainæ of smaller average graln 30 size and free of or exhibiting reduced surface chemical sensitization forming the ~econd grain population.
The internal latent image forming emulsions can, if desired, be spectrally sensitiz~d. For black 35 and white imaging applica~ions spectral sensitization is not required, although orthochromatic or pan-chromatic sensitization is usually preferred.
~ ~ 3~
Generally, any spectral sensitizing dye or dye combination known to be useful with a negatlve working silver halide emulslon can be employed with the internal latent image forming emulsions. Illus-5 trative spectral sensitizing dyes are those disclosedin Research Disclosure, Item 17643, cited above, Section IV. Particularly preferred spectral sensi-tizing dyes are those disclosed in Research Disclo-sure, Item 15162, cited above. Although the emul-10 sions can be spectrally sensitized with dyes from avariety of classes, preferred spectral sensitizing dyes are polymethine dyes, which include cyanine, merocyanine, complex cyanine and merocyanine (i.e., tri-~ tetra, and poly-nuclear cyanine and mero-15 cyanine), oxonol, hemioxonol, styryl, merostyryl, andstreptocyanine dyes. Cyanine and merocyanine dyes are specifically preferred. Spectral sensitizing dyes which sensitize surface fogged direct posltive emulsions generally desensitize both negative working 20 emulsions and the surface development of internal latent image forming emulsions and therefore are not normally contemplated for use in the practice of this invention. Spectral sensitization can be undertaken at any stage of emulsion preparation heretofore known 25 to be useful. Most commonly spectral sensitization is undertaken in the art subsequent to the completion of chemical sensitization. However, it is æpecif-ically recognized that spectr&l sensitization can be undertaken alternatively concurrently with chemical 30 sensitization or can entirely precede surface chemi~
cal sensitization. Sensi~ization can be enhanced by pAg adjust~ent, including cycling, during chemical and/or spectral sensitization.
It has been found advantageous to employ 35 nucleating agents in preference to uniform light exposure in processing. The term "nucleating agent"
(or "nucleator") is employed herein in its art-recog-~ 21-nized usage to mean a fogging agent capable of permitting the selective development of internal latent image forming silver halide grains which have not been ~magewise exposed in preference to the 5 development of silver halide grains having an intern-al latent image formed by imagewise exposure.
The internal latPnt image forming emulsions preferably incorpora~e a nucleating agent to promote the formation of a direct positive image upon 10 processing. The nucleating agent can be incorporated in the emulsion during processing, but it is prefer-ably incorporated in manufacture of the photographic element, usually prior to coating. This reduces ~he quantities of nucleating agent required. The quanti-15 ties of nucleating agent required can also be reducedby restricting t~e mobility of the nucleating agent in the photographic element. Large organic subs~it-uents capable of performing at least to some ex~ent a ballasting function ~re commonly employed. Nucleat-20 ing agents which include one or more groups topromote adsorption to the surface of the silver halide grains have been found to be effective in extremely low concentrations.
A preferred general class of nucleatlng 25 agents for use in the practice of this invention are aromatic hydrazides. Particularly preferred aromatic hydrazides are those in which the aromatic nucleus is substituted with one or more groups to restrict mobility and~ preferably, promote adsorption of the 30 hydrazide to silver halide grain surfaces. More specifically, pre~erred hydr~zides are those embraced by formula (II) below:
(II) J J
D-N-N-~-M
wherein D is an acyl group;
J is in one occurrence hydrogen and in the other occurrence hydrogen or a sulfinic acid radical;
~ is a phenylene or 6ub~tituted (e.g., 5 halo-, alkyl-, or slkoxy-sub6tituted) phenylene group; and M is a moiety capable of restricting mobil-ity, such as a ballasting or an adsorption promoting moiety.
The incorporation of a sulfinic acid radical substi~uent in an aroma~ic hydrazide nucleating agent is specifically taught by Hess et al U.S. Patent 4,478,928. The sulfinic acid radical substituent has an activating effect permi~ting increased levels of 15 nucleating agent activity to be realized. Reduced rereversal can also be achieved. The sulfinic acid radical substituent is preferably in the B positlon relative to the acyl group~
The term "sulfinic acid radical" is herein 2~ defined as the radical produced by the removal of the acid hydrogen ion from a sulfinic acid. Thus, the sulfinic acid radical can be produced from any conventional sulfinic acid. The sulfonyl group of the sulfinic acid can be bonded directly to either an 25 aliphatic or ~romatic residue. The aliphatic residue can, for example, be an alkyl substituent. A simple alkyl 6ubsitutent can take the orm of alkyl of from 1 to 8 carbon atoms~ most typic~lly 1 to 3 c~rbon atoms. In a preferred form the sulfinic acid radical 30 includes an aromatic residue. A preferred substit-uent can be rep~e&ented by the following:
(III) I
O=S~O
Ar' wherein Ar' is an aryl group. In a specifically pre~erred form of the invention Arl is a carbo-cyclic aromatic ring containing from 6 to 10 carbon atoms (e.g., phenyl or naphthyl) which can optlonally be substituted. While either electron withdr~wing or electron donating substituents can be employed, 5 highly electron donating substituents are not prefer-red. Substituents discussed below, typically contain up to 8 carbon atoms.
A particularly preferred class of phenyl-hydrazides are acylhydrazinophenylthioureas repre-10 sented by formula (IY) below.(IV) Il I I I 11 ,R
R-C-N-N-Rl-N--C-N
15 wherein J iB as defined above;
R is hydrogen or an alkyl, cycloalkyl, haloalkyl, alkoxyalkyl, or phenylalkyl sub6tituent or a phenyl nucleus having a Hammett sigma-value-derived 20 electron-withdrawing characteristic more positive than -0.30;
Rl is a phenylene or alkyl, halo-~ or alkoxy-substituted phenylene group;
R 2 iS hydrogen, benzyl, alkoxybenzyl, halo-25 benzyl, or alkylbenzyl, R 3 iS a alkyl, haloalkyl, alkoxyalkyl, orphenylalkyl 3ubstituent havlng from 1 to 18 carbon atoms, a cycloalkyl substituent, a phenyl nucleus having a Hammett R igma value-derived electron-with-30 drawing ch~ractèristic lesæ positive than +0.50, ornaphthyl~
R 4 iS hydrogen or independently selected from among the same substituents as R 3; or R 3 and R 4 together form a heterocyclic 35 nucleus forming a ~- or 6-membered ring, whereln the ring atoms are chosen from the class consisting of nitrogen, carbon, oxygen, sulfur~ and selenlum atoms;
with the proviso th~t at least one of R 2 and R 4 must be hydrogen and the alkyl moieties, except as otherwise noted, in each instance include from 1 to 6 carbon atoms and the cycloalkyl moieties have 5 from 3 to 10 carbon atoms.
As indicated by R in formula (IV), preferred acylhydrazinophenyl~hioureas employed in the practice of this invention contain an acyl group which is the residue of a carboxylic acid, such as one of the 10 acyclic carboxylic acids, including formic acid, acetic acid, propionic acid, butyric acid, higher homologues of these acids having up to about 7 carbon atoms, and halogen, alkoxy, phenyl and equivalent-substituted derivatives thereof. In a preferred 15 form, the acyl group is formed by an unsubstituted acyclic aliphatic carboxylic acid having from 1 to 5 carbon atoms. Specifically preferred acyl groups are formyl and acetyl. As between compounds which differ solely in terms of having a formyl or an acetyl 20 group, the compound containing the formyl group exhibits higher nucleating agent ac~ivity. The alkyl moieties in the substituents to the carboxylic acids are contemplated ~o have from l to 6 carbon atoms, preferably from 1 to 4 carbon atoms.
In addition to the acyclic aliphatic carboxylic acids, it is recognized that the carboxylic acid can be chosen so that R is a cyclic aliphatic group having from about 3 to 10 carbon atoms, such as, cy~lopropyl, cyclobutyl, cyclopentyl, 30 cyclohexyl, methylcyclohexyl, cyclooctyl, cyclodecyl, and bridged ring variations, such as, bornyl and isobornyl groups. Cyclohexyl i6 a specifically preferred cycloalkyl sub~tituent. The use of alkoxy, cyano, halogen, and equivalent substi~uted cycloalkyl 35 substituents is contemplated.
As indicated by Rl in formula (IV), preferred acylhydrazinophenylthioureas employed in ~ ~t~f~ 3 the practice of this invention contain a phenylene or substituted phenylene group~ Specifically preferred phenylene groups are m- and ~-phenylene groups.
Exemplary of preferred phenylene substi~uents are 5 alkoxy substituents having from 1 to 6 carbon a~oms, alkyl substituen~s having from 1 to 6 carbon atoms, fluoro-, chloro-, bromo , and iodo-substituents.
Unsubstituted ~-phenylene groups are specifically preferred. Specifically preferred alkyl moieties are 10 those which have from 1 to 4 carbon atoms~ While phenylene and substituted phenylene groups are preferred linking groups, other functionally equiva-lent divalent aryl groups, such as naphthalene groups, can be employed.
In one form R 2 represents an unsubs~ituted benzyl group or substituted equivalents thereof, such as alkyl, halo-, or alkoxy-~ubstituted benzyl groups. In the preferred form no more than 6 and, most preferably, no more than 4 carbon atoms are 20 contributed by subs~ituents to the benzyl group.
Substituents to the benzyl group are preferably para-substituents. Specifically preferred benzyl substituents are formed by unsubsti~uted~ 4-halo-sub-stituted, 4-methoxy-subs~ituted, and 4-methyl-sub-25 stituted benzyl groups. In another ~pecificallypreferred form R 2 represent6 hydrogen.
Referring again to formula (IV), it is apparent that R 3 and R 4 can independently take a variety of forms. One specifically contemplated form 30 can be an alkyl group or a substituted alkyl group, such as a haloalkyl group, alkoxyalkyl group, phenyl-alkyl group~ or equivalent group, havlng a total of up to 18, preferably up ~o 12, car~on atoms. Specif-ically R 3 and/or R 4 can take the form of a 35 methyl, ethyl, propyl~ butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl or higher homologue group having up ~o 18 total carbon atoms; a fluoro-, chloro-, ~ 3~i bromo-, or iodo-substituted derivative thereof; a methoxy 9 ethoxy, propoxy, butoxy or higher homologue alkoxy-substituted derivatiYe thereof, wherein the total number of carbon atoms are necessarily at lea~t 5 2 up to 18; and a phenyl-6ubs~ituted derivatlYe thereof, wherein the total number of carbon a~oms is necessarily at least 7, as in the case of benzyl,up to about 18. In a specific preferred form R 3 and/or R 4 can take the form of an alkyl or phenyl-lO alkyl substituent, wherein the alkyl moie~ies are ineach instance from l to ~ carbon atoms.
In addition to the acyclic alipha~ic and aromatic forms discussed above, it is also contem-plated that R 3 and/or R 4 can take the form of a 15 cyclic aliphatic substituent, such as a cycloalkyl substituent having from 3 to lO c~rbon atoms. The use of cyclopropyl, cyclobutyl a cyclopentyl, cyclo-hexyl, methylcyclohexyl, cyclooctyl, cyclodecyl, and bridged ring variations, such as, bornyl and 20 isobornyl groups, is contemplated. Cyclohexyl is a preferred cycloalkyl substituent. The use of alkoxy, cyano, halogen, and equivalent substi~uted cycloalkyl substituents is contemplated.
R 3 and/or R 4 can also be an aromatic 25 substituent, such as, phenyl or naphthyl (i.e., l-naphthyl or 2-naphthyl) or an equivalent aromatic group, e.~ , 2-, or 9-anthryl, etc. Aæ indicated in formula (IV) R 3 and/or R 4 can take the form of a phenyl nucleus which is either electron-donating or 30 electron-withdrawing, however phenyl nuclei which are highly electron-withdrawin~ may produce inferior nucleating agents.
The electron-withdrawing or electron-donat-ing characteristic of a specific phenyl nucleus can 35 be assessed by reference to HRmmett sigma values.
The phenyl nucleus can be assigned a Hamme~t sigma value-derived electron withdr~wing characteristic s j which is the algebraic sum of the Hammett sigma values of its subs~ituents (i.e., those of the substituents, if any, to the phenyl group). For example, the Hammett sigma values of any substituents 5 to the phenyl ring 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 6um thereof. Electron-withdrawing substituents are 10 assigned positive sigma values~ while electron-donat-ing substituents are assigned negative sigma values-Exemplary meta- and para-sigma values and procedures for their determination are set forth by J. Hine in Physical Or~anic Chemistry, ~econd 15 edition, page 87, published in 1962, H. VanBekkum, P.
E. Verkade and B. M. Wepster in Rec. Trav. Chim., _ .
Volume 78, page 815, published in 1959, P. R. Wells in Chem. Revs., Volume 63, page 171, published in 1963, by H. H. Jaffe in Chem. Revs., Volume 53, page 20 lgl, published in 1953, by M. J. S. Dewar and P. J.
Grisdale in J. Amer. Chem. Soc., Volume 84, page 3548, published in 1962, and by Barlin and Perrin in Quart. Revs., Volume 20, page 75 et seq, published in 1966. For the purposes of this invention, ortho-sub-25 stituents to the phenyl ring can be assigned to the published para-sigma values.
It is preferred that R2 and/or R3 be a phenyl nucleus having a Hammett sigma value-derived electron-withdrawing characteristic less positive 30 than ~0.50. It is specifically contemplated that R 2 and/or R 3 be chosen from among phenyl nuclei having cyano, fluoro-, chloro- 3 bromo-, iodo-, alkyl groups having from l to 6 carbon atoms, and alkoxy groups having from 1 to 6 carbon atoms, as phenyl 35 ring substituents. Phenyl ring substituents are preferred in the ~ - or 4 ring position.
1 ~J~ 4j Rather ~han being independently chosen R 2 and R 3 can together form, along with ~he 3-position nitrogen atom of the thiourea, a heterocyclic nucleus forming a 5- or 6-membered ring. The ring atoms can be chosen from among nitrogen, carbon, oxygen, sulfur and selenium ~toms. The ring neceæsarily contains at least one nitrogen atom. Exemplary rings include morpholino, piperidino, pyrrolidinyl, pyrrolinyl, thiomorpholino, thiazolidinyl, 4-thiazolinyl, selena-l~ zolidinyl, 4-selenazolinyl, imidazolidinyl, lmida-zolinyl, oxazolidinyl, and 4-oxazolinyl rings.
Specifically preferred rings are saturated or other-wise constructed to avoid electron withdrawal from the 3-position nitrogen atom.
Acylhydrazinophenylthiourea nucleating agents and their synthesis are more specifically disclosed in Leone U.S. Patents 4,Q30,925 and 4,276,364. Variants of the acylhydrazinophenylthiourea nuclea~ing agents 20 described above are disclosed in von Konig U.S.
Patent 4,139,387 and Adachi et al U.K. Patent Appli-cation 2,012,443A.
Another preferred class of phenylhydrazide nucleating agents are N-(acylhydrazinophenyl)thio-25 amide nucleating agents, such as those indicated byformula (V) below:
(V) Il I I H
R-C-N-N-Rl~N---C -wherein R, Rl, and J are as defined in formula (IV);
A is =N-R2, -S- or -0-;
Ql represents the atoms necessary to complete a five-membered heterocyclic nucleus;
R 2 iS independen~ly chosen from hydrogen, phenyl, alkyl, alkylphenyl, and phenylalkyl; and the 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-~hione, 4-oxazoline-2-thione, oxazolidine-2-thione, 2-pyra-zoline-5-thione, pyrazolidine-5-thione, indoline-2-10 thione, and 4-imidazoline-2-thione, etc. A specif-ically preferred subclas6 of heterocyclic thioamide nuclei is formed when Q' is as indicated in formula (VI) (VI) X
Il . I
wherein X is =S or =0.
20 Specifically preferred illustrations of such values of Ql are 2-thiohydantoin, rhodanine, isorhodanine, and 2-thio-2,4-oxazolidinedione nuclei. I~ i6 believed that some six-membered nuclei 3 such as thiobarbi~uric acid, may be equivalent to five-mem-25 bered nuclei embraced within formula (V).
Another specifically preferred subcla6s ofheterocyclic thioamide nuclei is formed when Ql is as indicated in formula (VII) (VII) X
Il I .
-c-c~-L~n _lT
wherein L is a methine group;
1 Z -I ~4 T is =C-~CH=CH-td lN-R3 or =CH--~ /~u R3 is an alkyl substituent, ~Rs R 4 iS hydrogen; ~n alkyl, -N ~ 6 ~ or 5 an alkoxy sub6tituent;
Z represents the nonmet~llic atoms nece6sary to complete a basic heterocyclic nucleu6 of the ~ype found in cyenine dyes;
n and d are independently chosen from the lnte-10 gers 1 and 2;
R 5 and R 6 are independently chosen fromhydrogen, phenyl, alkyl, alkylphenyl, and phenyl-alkyl; and the alkyl moieties in each instance include rom 15 1 to 6 carbon atoms.
The formula (VII) values for Q' provide a heterocyclic thioamide nucleus corresponding to a methine substituted form of the nuclei present above in formula (VI) values for ~'. In a specifically 20 preferred form the heterocyclic thioamide nucleus is preferably a methine substituted 2-thiohydantoin, rhodanine, isorhodanine, or 2-thio-2,4-oxazolidine-dione nucleus. The heterocyclic thioamide nucleus of formula (VII) is directly, or through an intermediate 25 methine linkage, substituted with a basic hetero-cyclic nucleus of the type employed in cyanine dyes or a substituted benzylidene nuclues. Z preferably represents the nonmetallic ~toms necessary to complete a basic 5- or 6-membered heterocyclic 30 nucleus of the type found in cyanine dyes having ring-forming atom~ chosen from the class consisting of carbon, nitrogen, oxygen, sulfur, and ~elenium.
N-(acylhydrazinophenyl)thioamide nucleating agents and their synthesis are more specifically 35 disclosed in Leone et al U.S. Patent 4,080,207.
Still another preferred class of phenyl-hydrazide nucleating agents are tri~zole-substituted ~ 3 phenylhydrazide nucleating agents. More specif-ically, preferred triazole-substituted phenylhydra-zide nucleating agents are those represented by formula (VIII) below:
5 (VIII) O J J
Il I I
R-c-N-N-Rl-A~ 2-A3 wherein R, Rl, and J are as defined in formul~
(II);
Al is alkylene or oxalkylene;
O O
Il H 11 A2 is -C-N- or -S-N-; and A3 is a triazolyl or benzotriazolyl nucleus;
the alkyl and alkylene moieties in each instance including from 1 to 6 carbon atoms.
Still more specifically preferred triazole-substituted phenylhydrazide nucleating agents are those represented by formula (IX) below:
(IX) O J J O
R-C-N-N-R'-C-N t \-/ \N
H
wherein J is as defined above;
R is hydrogen or methyl;
Rl is ~ ~--[CH23n- vr -o~ ~--OE
CCH2~n-n is an integer of 1 to 4; and E is alkyl of from 1 to 4 carbon atoms.
~32-Triazole-su'bstituted phenylhydrazide nucleating 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 5 adsorption promot- ing groups are dlsclosed in corresponding U.K. Patent Application 2,011,391A.
The aromatic hydrazides represented by formulas (IV), (V), and (VII) each contain adsorption promoting substituents. In many ins~ances it is 10 preferred to employ in combination with these aromatic hyrazides addi~ional hydrazides or hydra-zones which do not contain substituents specifically intended to promote adsorption to silver halide grain surfaces. Such hyrazides or hydrazones, however, 15 often contain substituents to reduce their 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 20 represented by formula (X) and (XI) below:
(X) H H
T-N-N~Tl and ~XI) H
T-N-N=T2 wherein T,is an aryl radical, including a substituted aryl radical, Tl is an acyl radical, and T2 is an alkylidene radical'and including substituted alkyli-30 dene radicals. Typical aryl radicals for the substitutent T have the formula M-T3-, wherein T3 is an aryl' radical (such as, phenyl, l-naphthyl, 2-naphthyl, etc.) and M can be such ~ubstituents as hydrogen, hydroxy, amino, alkyl, alkylamino, aryl-35 amino, heterocyclic amino (amino containing a hetero-cyclic moiety), alkoxy, aryloxy, acyloxy, arylcarbon-amido, alkylcarbonamido, heterocyclic cnrbonamido (carbonamido containing a heterocycllc moiety), arylsulfonamido, alkylsulfonamido~ and heterocyclic sulfonamido (sulfonamido containing a heterocyclic moiety). Typical acyl radicals for the substituent 5 Tl have the formula O O
Il 11 -S-Y or -C-G
o 10 wherein Y can be such substltuents as alkyl, aryl, and heterocyclic radicals, G can represen~ a hydrogen atom or the same substituent as Y as well as radicals having the formula o -C-~-A
to form oxalyl radicals wherein A is an alkyl, aryl~
or a heterocyclic radical. Typical slkylidene radicals for the substituent T 2 have the formula 20 =CH-D wherein D can be a hydrogen atom or such radicals as alkyl, aryl, and heteroeyclic radicals.
Typical aryl substituents for the above-described hydrazides and hydrazones include phenyl, naphthyl, diphenyl, and the like. Typical heterocyclic 25 substituents for the above-described hydrazides and hydrazones include azoles, azines, furan, thiophene, quinoline? pyrazole, and the like. Typical alkyl (or alkylidene) substituents for the sbove-described hydrazides and hydrazones have 1 to 22 carbon atoms 30 including methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl, t-butyl, amyl, _-octyl, _-decyl, n-dodecyl, n-octadecyl 9 n-eicosyl, and n-doco6yl.
The hydrazldes and hydr~zones represented by formulas (X) and (XI) as well as their synthesis are 35 disclosed by Whitmore U.S. Patent 3,227,552.
Still other useful hydrazine and hydrazide nucleating sgents are disclo6ed in Rese~rch Disclo-sure, Vol. 235, November, 1983~ Item 23510.
-34~
A secondary preferred general class of nucleating agents for use in the practice of this invention are N-substituted cycloammonium quaternary salts. A particularly preferred species of such 5 nucleating agents is represented by formula ~XII) below:
(XII) 1- - - Z'- - -I
N~=~CH-CH~j l=C-E
X-(CH 2) a wherein Zl represents the atoms necessary ~o complete a 15 heterocyclic nucleus containing a heterocyclic ring of 5 to 6 atoms including the quaternary nitrogen atoms, with the additional atoms of said heterocyclic ring being selected from carbon, nitrogen, oxygen, sulfur, and selenium;
j represents a positive integer of from 1 to 2;
a represents a positive integer of from 2 to 6, X~ represents an acid anion;
E 2 represents a member selected from (e) a formyl radical, (b) a radical having the formula -CH
;
wherein éach of Ll and L 2~ when ~aken alone, represents a member selected from an alkoxy radical 30 and an alkylthio radical, and El and L 2~ when taken together, represent the atoms necessary to complete a cyclic radical selected from cyclic oxyacetals and cyclic thioacetals having from 5 to 6 atoms in the heterocyclic acetal ring, and ~c) a 35 l-hydrazonoalky radical; and E' represents either a hydrogen atom, an alkyl radical, an aralkyl radical, an alkylthio radical, or -35- ~ ri~
an aryl radical such as phenyl and naphthyl, and including substituted aryl radicals.
The N substituted cycloammonium quaternary salt nucleating agents of formula (XII) and their 5 synthesis are disclo~ed by Lincoln and Heseltine U.S.
Pa~ents 3,615,615 and 3,759,901. In a variant form E' can be a divalent alkylene group of from 2 ~o 4 carbon atoms joining two substituted heterocyclic nuclei as shown in formula (XII). Such nucleating 10 agents and their synthesis are disclosed by Kurtz and Harbison U.S. Patent 3,734,738.
The substituent to the quaternized nitrogen atom of the heterocyclic ring can, in another variant form, itself form a fused ring with the heterocycllc 15 ring. Such nucleating agents are illustrated by dihydroaromatic quaternary salts comprising a 1,2 di hydroaromatic heterocyclic nucleus including a quaternary nitrogen atom. Particularly advantageous 1,2-dihydroaromatic nuclei include such nuclei as a 20 1,2-dihydropyridinium nucleus. Especi~lly preferred dihydroaromatic qua~ernary salt nucleating agents include those represented by formula (XIII) below:
(XIII) __ z ~ __ : H iH~ I R I n 30 wherein Z representS the nonmetallic atoms necessary to complete a heterocyclic nucleus containing a hetero-cyclic ring of from 5 to 6 atoms including the quaternary nitrogen atom, w1th the additional atoms 35 of said heterocyclic ring being selected from either carbon, nitrogen, oxygen, sulfur, or selenium;
n represents a positive integer having ~ value of from 1 to 2;
~ ~v~ t~
when n is 1, R represents a member selec~ed from the group consis~ing of a hydrogen atom, an alkyl radieal, an alkoxy radical, an aryl radical, an aryloxy radical, and a carbamido radical and, when n is 2, R represents an alkylene r~dical having from 1 to 4 carbon atoms;
each of Rl and R 2 represent6 a member select-ed from the group consisting of a hydrogen atom, an alkyl radical, and an aryl radical; and X~ represents an anion.
Dihydroaromatic quaternary salt nucleating agents and their synthesis are disclosed by Kurtz and Heseltine U.S. Patent 3,719,494.
A specifically preferred class of N-subEti-15 tuted cycloammonium quaternary salt nucleating agents are those which include one or more alkynyl substit-uents. Such nucleating agents include compounds within the generic structural definition set forth in formula ~XIV) below:
20 (XIV) "Z~
R4 ~ N
Rl wherein Z represents an atomic group necessary for forming a 5- or 6-membered heterocyclic nucleus, R
represents an aliphatic group, R 2 represents a hydrogen atom or an aliphatic group, R 3 and R4, 30 which may be the seme or different, each represents a hydrogen atom, a halogen atom, an allphatic group~ an alkoxy group, a hydroxy group, or an aromatic group, at least one of Rl, R29 R3 and R4 being a propargyl group, a butynyl group, or a sub6tituent 35 containing a propargyl or butynyl group, X~ repre-sents an anion, n is 1 or 2, with n being 1 when the compound formæ an inner salt.
_37~ s3~
Such alkynyl-substituted cycloammonium quaternary salt nucleating agents and their synthesis are illustrated by Adachi et al U.~. Patent 4,115,122. BallPsted nucleatlng agents of the type 5 shown in formula (XIV) are disclosed in Research Disclosure, Vol. 232, August 1983, Item 23213, and nucleating agents of the type shown in formula (XIV) containing an adsorption promoting group are disclosed by Parton et al U.S. Patent 4,471,044.
The specific choice of nucleating agents can be influenced by a variety of factors. The nucleat-ing agents of Leone U.S. Patents 4,030,925 and 4,276,364, cited above are par~icularly preferred for many applications, since ~hey are effective at very 15 low concentrations. Minimum concentrations a~ 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 di6clos-ed. These nucleating agents are particularly advan-20 tageous in reducing speed loss and in some instancespermitting speed gain with increasing processing temperatures.
The aromatic hydrazide nucleating agents are generally preferred for use in photographic elemen~s 25 intended to be processed at comparatively high levels of pH, typically ~bove 13. The alkynyl-sùbstituted cycloammonium quaternary salt nucleating agents are particularly useful for processing at a pH of 13 or less. Adachi et al U.S. Patent 4,115,122 teaches 30 these nucleat~ng agents to be useful in processing within the pH range of from 10 to 13, preferably 11 to 12.5. In addition to the nuclea~ing agents described above addltional nucleating ~gents have been identified which are useful in processing at pH
35 levels in the range of from about 10 to 13, such as N-substituted cycloammonium quaternary salt nucleat-ing agents of the type disclosed by Baralle et al U.S. Patent 4,306,016; dihydrospiropyran bis-condensa~ion products of salicylic aldehyde and at least one heterocyclic ammonium salt of the type disclosed by Baralle et al U.S. Patent 4,306,017; and 5 diphenylmethan~ nucleating agents of the type disclosed by Baralle et al U.S. Patent 4~315,986.
Instead of being incorporated in the photo-graphic element during manufacture, nucleating agents can alternatively or additionally be lncorporated in 10 the developer solution. Hydrazine ~H2N-NH 2) is an effective nucleating agent which ~an be incor-porated in the developing solution. As ~n alterna-tive to the use of hydrazine, any of a wide variety of water-soluble hydrazine derivatives can be added lS to the developing solution. Preferred hydrazine derivatives for use in developing solutions include organic hydrazine compounds of the formula:
(XV) I 3 2~ - N ~ 4 where Rl is an organic radical and each of R 2, R3 and R 4 iS a hydrogen atom or an organic radical. Organic radicals represented by Rl, R2, 25 R3 and R 4 include hydrocarbyl groups such as an alkyl group~ an aryl group, an aralkyl group, an alkaryl group, and an alicyclic group, as well as hydrocarbyl groups substituted with substituents such as alkoxy groups, carboxy groups, sulfonamido groups, 30 and halogen atoms.
Particularly preferred hydrazine derivative 8 for incorporation in developing solutions include alkylsulfonamidoarylhydrazines, such BS p- (methyl-sulfonamido)phenylhydrazine, and alkylsulfonamido-35 alkylaryl hydrazines, such ~s p-~methylsulfonamido~
methyl)phenylhydrazine.
The hydrazine and hydrazide derivatives described above are disclosed in Smith et al U.S.
Patent 2,410,690, Stauffer et al UOS. Patent 2,419,975, and Hunsberger U.S. Patent 2,892,715. The 5 preferred hydrazines for incorporation in developers are described in Nothnagle U.S. Patent 4,269,929.
Another preferred class of nucleating agentR that can be incorporated in the developer correspond to formula (I) above, but with the moiety M capable of 10 restricting mobility absent. Nucleating agents of this type are disclosed in Okutsu et al U.S. Patent 4,221,857 and Takada et al U.S. Patent 4,224,401.
Once internal latent image forming emulsions have been generated by precipitation procedures, 15 washed, and sensitized, as described abov~, their preparation can be completed by the optional incor-poration of nucleating agents, described above, and conventional photographlc addenda, and they can be usefully applied to photographic applications requir-20 ing a silver image to be produced--e.g., conventional black and white photography.
The internal latent i~a8e forming emulsion is comprised of a dispersing medium in which the grains are dispersed. The dispersing medium of the 25 emulsion layers and other layers of the photographic elements, including the antifoggant undercoat, can contain various colloids alone or in combination as vehicles (which include both binders and peptizers3.
Preferred peptizers are hydrophilic colloids, which 30 can be employed alone or in combination with hydro-phobic materials. Preferred peptizers are gelatin--e.g., alkali-treated gelatin (cattle bone or hide gelatin) and acid-treated gelatin (pigskin gelatin) and gelatin derivatives--e.g., ace~ylated gelatin, 35 phthalated gelatin, and the like. Useful vehicles are illustrated by those disclosed in Research Disclosure, Item 1765~3, cited above, Section IX.
The layers of the photographic elements containing crosslinkable colloids, particularly ~he gelatin~con-taining layers, can be hardened by various organic and inorganic hardeners, as illustrated by Research 5 Disclosure, Item 17643, cited above, Sectlon X-In addition to the maximum density enhancingantifoggants in the undercoat described above, other antifoggants and stabilizers known to be useful in combination with internal latent desensitization 10 direct positive imaging can be incorporated in the photographic elements of this invention at any useful location. A variety of such addenda are disclosed in Research Disclosure, Item 17643, cited above, Section VI. Many of the antifoggants which are 15 effective in emulsions can also be used in developers and can be classïfied under a few general headings, as illustrated by C.E.K. Mees, The Theory of the Photographic Process, 2nd Ed., Macmillan, 1954, pp.
677-680.
In addition to sensitizers, hardeners, and antifoggants and stabilizers, a variety of other conventional photographic addenda can be present~
The specific choice of addenda depends upon the exact nature of the photographic application and is well 25 within the capability of the art. A variety of useful addenda are disclosed in Research Disclosure, Item 17643, cited above. Optical brightener6 can be introduced, as disclosed by Item 17643 at Section V.
Absorbing and scattering materials can be employed in 30 the emulsions of the invention and in separate layers of the photographlc elements, as described in Section VIII. Coating aids, as described in Section XI, and plasticizers and lubricants, as described in Section XII, can be present. Antistatic layers, a8 described 35 in Section XIII, can be present. Methods of addition of addenda are described in Section XIV. Matting agents can be incorporated, as described in Section ~ ~3~.3 XVI. Developing agents and development modifiers can, if desired9 be incorporated, as described in Sections XX and XXIo The sil~er halide emulsion layer or layers, antifoggant undercoat, as well as 5 optional interlayers, overcoa~s, and subbing layers, if any9 present in the photogrRphic elements can be coated and dried as described in Item 17643, Section XV .
The layers of the photographic elements can lO be coated on a variety of 6upports. Typical photo-graphic supports include polymeric film, wood fiber--e.g., paper, metalllc sheet and foil, gla~6, and ceramic supporting elPments provided with one or more subbing layers to enhance the adhesive, ~nti-15 static, dimensional, abrasive, hardness~ fri~tional, antihal~tion and/or other properties of the support surface. Suitable photographic supports are illus-trated by Research Disclosure, Item 17643, cited above, Section XVII.
Although the Pmulsion layer or layer~ are typically coated as continuous layers on supports having opposed planar major surfaces, this need not be the case. The emulsion layers can be coated as laterally displaced layer segments on a planar 25 support surface. When the emulsion layer or layers are segmented, it is preferred to employ a microcell-ular support. Useful microcellular supports are disclosed by Whitmore U.S. Patent 4,387,146.
Microcells can range from l to 200 microns in width 30 and up to 1000 micron6 in depth. It is generally preferred that the microc~ be &t least 4 microns in width and less than 200 micron6 in depth, with optimum dimensions being about 10 to 100 microns in width and depth for ordinary black and white imaging 35 applications- p~r~icularly where the photographic image is intended ~o be enlarged.
The photographic elements of the present inven~ion can be imagewise exposed in any convention-al manner. Attention i6 directed ~o Research Di~clo-.. .. . . .. .. ~__ sure Item 17643, cited above, Section XYIII. The 5 present invention is par~icularly advantageous whenimagewise exposure is undertaken with electromagnetic radiation within the region of the ~pectrum in which the spectral sensitizers present exhibit absorption maxima. When the photographic elements are intended 10 to record blue 3 green, red, or infrared exposures, spectral sensi- tizer absorbing in the blue, green~
red, or infrared portion of the spectrum i6 present.
As noted above, for black and white imaging applications it is preferred that the photographic 15 elements be ortho- chromatically or panchromatically sensitized to permit light to extend sensitivity within the visible spectrum. Radiant energy employed for exposure can be either noncoherent (random phase) or coherent (in phase), produced by lasers.
20 Imagewise exposures at ambient, eleva~ed, or reduced temperatures and/or pressures, including high or low intensity exposures, continuous or intermittent exposures, exposure times ranging from minutes to relatively short durations in the millisecond to 25 microsecond range, can be employed withln the useful response ranges determined by conven~ional sensitometric techniques, as illustra~ed by T. H.
James, The Theory of the Photographic Process~ 4th Ed., Macmillan, 197~ 9 Chapters 4, 6, 17, 18, and 23.
The light-sensitive silver halide contained in the photographic elements can be proce6sed follow~
ing exposure to form a visible image by associating the silver halide with an aqueous alkaline medium in the presence of a developing agent contained in the 35 medium or the element. Processing formulations and techniques are described in L. F. Mason, Photo&raphic Processing Chemistry, Focal Press, London, 1966;
Processin~ Chemicals and Formulas, Publication J-l, Eastman Kodak Company, 1973; Photo-Lab Index, ~lorgan and Morgan, Inc., Dobbs Ferry, New York, 1977, and Neblette~s Handbook of PhotograPhy and Repro ~aphy 5 Materials, rocesses and Systems, VanNostrand Reinhold Company, 7th Ed., 1977.
Included among the processing methods are web processing, as illustrated by Tregillus et al U.S. Patent 3,179,517; stabilization processing, as 10 illustrated by Herz et al U.S. Patent 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 processing as described in Haist, Monobath Manual, Morgan and Morgan, Inc., 1966, Schuler V.S.
15 Patent 3,240 9 603, Haist et al U.S. Pa~ents 3,615,513 and 3,628,955 and Price U.S. Patent 3,723,126;
infectious development, as illustrated by Milton V.S.
Patents 3,294,537, 3,600,174, 3,615,519 and 3,615,524, Whiteley U.S. Patent 3,516,830, Drago U.S.
20 Patent 3,615,488, Salesin e~ al U.S~ Patent 3,625,689, Illingsworth U.S. Patent 3,632,340, Salesin U.K. Patent 1,273,030 and U.S. Patent 3,708,303; hardening development, as illustrated by Allen et al U.S~ Patent 3,23~,761; roller transport 25 processing, as lllustra~ed by Russell et al U.S.
Patents 3,025,779 and 3,515,556, Masseth U.S. Patent 3,573,914, Taber et al U.S. Patent 3,647,459 and Rees et al U.K. Patent 1,269,268; alkaline vapor process-ing, as illustrated by Product Licensin~ Index~ Vol.
30 97, May 1972, Item 9711, Goffe et al U.S. Patent 3,816,136 and King U.S. Patent 3,985,564; metal ion developmen~ as illustrated by Price, Photo~raphic Science and Engineering, Vol. 19 3 Number 5, 1975, pp.
283-287 and Vought Research Disclosure, Vol. 150, 35 October 1976, Item 15034; and surface applicatlon processing, as illustrated by Kitze U.S. Patent 3,418~132.
Although development i6 preferably under-taken in the pr~sence of a nucleating ag~nt, as described above, giving the photographic elements an over-all light exposure either immediately prior to 5 or, preferably, during development can be undertaken as an alternative. When an over-all flash exposure is used, it can be of high intensity and short duration or of lower intensity for a longer duration.
The silver halide developers employed in 10 processing are surface developers. It is understood that the term l'surface developer" encompasses those developers which will reveal the surface latent image centers on a silver halide grain, but will not reveal substantial lnternal latent image centers in an 15 internal latent im~ge forming emul~ion under the conditions generally used to develop a surface sensitive silver halide emulsion. The surface developers can generally utilize any of the 6ilver halide developing agents or reducing agents, but the 20 developing bath or composition is generally substan-tially free of a silver halide solvent (such as water soluble thiocyanates, water soluble thioethers, thiosulfateE, and ammonia) which will disrupt or dissolve the grain to reveal substantial internal 25 image. Low amounts of excess halide are sometimes desirable in the developer or in~orporated in the emulsion ~s halide releasing compounds, but high amounts of iodide or iodide releasing compounds are generally avoided to prevent sub~tantial di6ruption 30 of the grain.
Typical silver halide developing agents which can be used in the developing compositionfi of this invention include hydroquinones, cntechols, aminophenols, 3-pyra~olidinones, ascorbic acid and 35 its derivatives, reductones, phenylenedi~mines, or combinations thereof. The developing agents can be incorporated in the photographic elements wherein they are brought into contact wi~h the silver halide after imagewise exposure; howeverS in cer~ain embodi-ments they are preferably employed in the developing bath.
Once a silver image h~s been formed in the photographic element, i~ is conventional practice to fix the undeveloped silver halide. The high aspect ratio tabular grain emulsions are particularly advantageous in allowing fixing to be accomplished in 10 a shorter time p~riod. This allows processing to be accelerated.
Except as otherwise stated, ~he remaining features of the black and white direct po6i~ive photographic elements of this inventioD and the 15 production of direct positive images by processing these photographic elements after imagewise exposure should be understood to contain features recognized in the art for such photographic applications.
Examples The invention can be better appreciated by reference to the following specific examples:
Example 1 _ Coa ings A. Control Coating A O.8 ~m octahedral core~shell AgBr emulsion was prepared by a double jet precipitation technique. The core grains consi6ted of a 0.55 ~m octahedr~l AgBr chemically sensitized with 0.78 mg Na2S 20 3-5H20/mole hg and l.lB mg KAuCl4/mole Ag 30 for 30 minutes at 85C. The core-shell emulsion was chemically sensitized with 1.0 mg Na2S203-5H ~/mole Ag for 30 ~inutes at 74C. The emulsion was coated on a polyester film support ~t 7.02 g/m 2 silver and 4.86 g/m2 gelatin. The emulsion layer also 35 contained the spectral sensitizing dyes anhydro-5,5'-dimethoxy-3,3'-bis(3-sulfopropyl~selenacyanine hydroxide, sodium salt (Dye A) and anhydro-5,5'-di-chloro-3,9~diethyl-3'-(3-sulfopropyl)oxacarbocyanine hydroxide (Dye B) each at 200 mg/mole Ag and the nucleating agent 6-ethylthiocarbamato-2-methyl-1-propar~ylquinaldinium trifluoromethanesulfonate at 30 5 mg/mole Ag. The element was overcoated with gelatin at 1.08 g/m2 containing 1.7% bis(vinylsulfonyl-methyl) ether by weight based on total gel content.
B. Example Coating The control coating was again prepared~ but 10 with 1.8 X 10-2 mole of AF-5 per silver mole and gelatin (1~29 g/m 2) in an antifoggant undercoat between ~he emulsion layer and ~he support.
II. Processin~
A. Control Coatin~: An exposed portion of 15 the control coating w~s processed for 75 seconds at 38C in Developer I, ~he developer additionally containing 0.10 gram of AF-5 and 0.16 gram of l-phenyl-5-mercaptotetrazole (hereinafter PMT) per liter.
B. Example Coating: An exposed portion of the example coating was processed for 75 seconds at 38C in Developer I, the developer additionally containing 0.15 gram of AF-5 and 0.11 gram of PMT per liter.
25 III- Sensitometry Sensitometric results are shown in Figure 2 and Table II.
Table II
Sensitometric Results Relative Developed Coatin& CR S eed* Contrast D-max ~2 D-min Control (C-l) 236 6.3 4.4 7.02 0.11 Example (E-l) 273 8.9 6.2 6.89 0.06 * Speed taken at 0.2 density ~ D-min for an expo-sure of 10-5 second through a 0-3~0 den~ity step tablet (0.15 density steps) plu6 & 0.86 neutral densi~y filter And with a filter to ~ '3~3~j simulate a phosphor emitting a~ a waYelength maximum of 465 nm.
As the results show, the effec~ of AF 5 in the undercoat was to increase speed, con~raæ~, and 5 D-max and to decrease D-min over the control. Since higher D-max was obtained at lower developed Ag, the covering power of the silver developed was 8reater for the invention. Also the example coating shows a greater exposure separa~ion between the positive 10 image and the rereversal negative image than in the control coating, as can be seen in Figure 2.
IV. Ima~e Qual ty Portions of the coatings were exposed similarly to those above, but through a microimage 15 target in place of the step tablet, and an estimation of the im ge qual-ity waæ deduced. Figure 3A shows the results of exposing the control ~oating at an exposure equivalent to s~ep #7 (see Figure 2) and the invention coating at step #9 (the photomicrographs 20 are at lOOX magnification). Corresponding photo-micrographs at 400X are shown in Figures 4A and 4B.
From these results, the invention coating show6 improved image ~uality over the control as well as more finely dispersed filamentary silver.
Electron microscopic cross ~ection6 of exposed and processed coatings taken from a step at density of ~0.4 are æhown for the control and invention coatings at magnifications of 22,000X.
Figures 5A and 5B, respectively.
These results show a more even distribution of the developed silver (2a and 2b) throughout the emulsion layer as well as more finely dispersed filamentary-type silver in the invention coating compared to the control coating, which showed a 35 concentration of developed silYer near the support (la and lb) surface.
Developer I
Component ~
Water, tap 850O0 Ethylenediaminotetraacetic acid 1.0 5 KOH, 45% 22.0 5-Methylbenzotriazole adjusted l-Phenyl-5-mercaptotetrazole { as needed Na 2S 3, anhydrous 75-0 4,4~-Dimethyl-l-phenyl-3-pyrazolidinone 0.4 10 NaBr 8.0 2-Ethylaminoethanol 58.6 3.3'-Diaminodipropylamine 4-0 Hydroquinone 40.0 KOH, 45% (adjusted pH to 10.7 at 27C) 7.0 15 Water, tap to 1 li~er Example 2 I. Coatings: Control and Example coatings were prepared essentially similar to those of Example 1, except that 1 percent by weight formaldehyde was used 20 to harden the overcoat rather than bis(vinylsulfonyl~
methyl) ether hardener and for the nucleating agent the following nucleating agents were substituted 1-[4-(2-formylhdrazino)phenyl~-3-hexylurea (276 mg/Ag mole) and l-~ormyl-2-~4 ~2-(2,4-di-tert-pentyl-25 phenoxy)butyramido]phenyl}hydrazine ~78 mg/Ag mole).II. Processin~:
Both control and example coatings were exposed and processed for 104 sec (38C) ln Developer II plus 0.05 g AF-5/Q + 0.08 g PMT/~.
30 III. Sensitometry The sensitometric results ~re shown in Figure 6, and Table III
-49~
Table III
Sensitometric Results .
Relative Coatin~CR Speed* Contrast D-max D-min . _ . .
5 Control (C-2)257 9 9 3.24 0.09 Example (E-2)286 6.7 3.35 0.04 * Speed as described in ExamplP 1.
As the results in Table III and Figure 6 show3 the effect of AF-5 in the undercoat wa~ to 10 increase speed and D-max, decrease D-min, and to increase the speed separation between the positive and negative responses compared to the control.
IV. Image Quality Photomicrographs, taken in a similar manner 15 to that of Example 1, showed similar improvement in the image qualitj of the example over the control.
Developer II
Component ~
Water, tap 850.0 20 Ethylenediaminotetraacetic acid1.0 KOH, 45% 22.0 5-Methylbenzotriazole adjusted l-Phenyl-5-mercaptotetrazole{ as needed Na 2S0 3, anhydrous 60.0 25 4,4'-Dimethyl-l-phenyl 3-pyrazolidinone 0.6 NaBr 3.0 2-Ethylsminoethanol 58.6 3.3'-Diaminodipropylamine 4.0 Hydroquinone 40.0 30 KOH, 45% (adjusted pH to 10.9 at 27C) 7.0 Water, tap to 1 llter Example 3 I. Coatin~s A. Control ~ (C-2): The control coating of 35 Example 2 was again prepared.
B. Control Coating (C-3): Th~ 8 control coating was simil~r to control coating C-2, but contained -50~ 3~
0.69 gram of silver per square meter and additlonally contained in the silver halide emulsion layer 1776 X
0 - 7 mole of AF-5 per silver mole.
C. Example Coatin~ (E-3) Ihis coating was 5 similar to the Example 2 coa~ing E-2, bu~ contained 0.67 gram of silYer per square meter and contained in the undercoat 1.85 X 10- 2 mole of AF-5 per sllver mole. The silver coverages and AF-5 concentrations in coatings C-3 and E-3 were substantially matched, lO the only material diff~rence between ~hese coatings being the presence of AF-5 in the undercoat of coating E-3 as opposed ~o the silver halide emulsion layer in coating C-3.
II. Processing All coatings exposed and processed for 75 seconds (38C) in Developer IXI.
III. Sensitometry Sensitometric reæults are shown in Figure 7 and Table IV.
Table IV
Sensitometric Reæults Reversal (Positi.ve Image CoatingCR Speed* Contrast D-max D-min Control (C-2)257 3.8 4.1 0.06 25 Control (C-3) 247 2.54.5 0.10 Example (E-3)282 5.0 4.0 0.03 * Speed;as described in Example 1.
The results in Table IV and Figure 7 show that the example coating E-3 with AF~5 in the under-30 coat yielded higher speed, higher contrast, lowerminimum density (D-min), ~nd increased exposure separation of the rereversal image compared to control coating C-2, which did not contain AF-5, and control coating C 3, which cont~ined AF-5 in the 35 silver halide emulsion layer~ The location of the maximum density enhancing antifoggant in the under-coat produced these d~fferences in performance.
Deve_oper III
Component ~
Water~ tap 850.0 E~hylenediaminotetraacetic acid 1.0 5 KOH, 45% 22.0 l-Phenyl-5-mercaptotetrazole 0.08 Na 2S0 3~ anhydrous 60~0 4,4~-Dimethyl-l-phenyl-3 pyrazolidinone 0.6 10 NaBr 3.0 2-Ethylaminoethanol 58.6 3.3'-Diaminodipropylamine 4.0 Hydroquinone 40.0 KOH, 45% (adjusted pH ~o 10.9 at 27C) 7.0 15 Water, tap to 1 liter The invention has been described with particular reference to preferred embodiments there-of, but it will be understood that variations and modifications can be effected within the spirit and 20 scope of the invention.
Patent 4,395,478 discloses the use of polyvalent metal ions as dopants in the shell of core~shell emulsions to reduce rereversal. Preferred metal dopants for this purpose are di~alent and trivalent 15 cationic metal dopants, such as cadmium, zinc, lead, and erbium. These dopants are generally effective at concentration levels below about 5 X 10- 4, prefer-ably below 5 X 10-5, mole per mole of silver.
Dopant concentrations of at least 10- 6, preferably 20 at least 5 X 10- 6, mole per silver mole, should be present in the reaction vessel during silver hallde precipitation. The rere~ersal modifying dopant is effective if introduced at any stage of silver halide precipitation. The rereversal modifying dopant can 25 be incorporated ln either or both of the core and shell. It is preferred that the dopant be introduced during th~ latter stages of precipitation (e.g., confined to the shell) when the core-shell grains are high aspect ratio tabular grains. The metal dopan~s 30 can be introduced into the reaction vessel as water soluble metal s~lts, such as divalent and trivalent metal halide salts. Zinc, lead, and cadmium dopants for silver halide in similar concentrations, but to achie~e other modifying effects, are disclosed by 35 McBride U.S. Patent 3,287,136, Mueller et al U.S.
Patent 2,950,972, Iwaosa et al U.S. Patent 3,901,711, and Atwell U.S. Patent 4,269,927. Other technlques ~ ~ S~ 3 for improving rereversal characteri6~ics discussed below can be employed independently or in combination with the metal dopant~ described.
After precipitation of a shell portion onto 5 the sensitized core grains to complete formation of the core-shell grains, the emulsions can be washed, if desired, to remove soluble salts. Conventional washing ~echniques can be employed, such as those disclosed by Research Disclosure, Item 17643, cited 10 above, Section II.
Since the core-shell emulsions are intended to form internal latent images, intentional sensiti-zation of the surfaces of the core-shell grains is not essential. However, to achieve the highest 15 attainable reversal speeds, it is preferred that ~he core-shell grains be surface chemically sensitized, as taught by Evans U.S. Patent 3,761,276 and Atwell et al U.S. Patent 4,035,185, cited above. Any type of surface chemical sensitization known to be useful 20 with corresponding surface latent image forming silver halide emulsions can be employed, such a6 disclosed by Research Disclosure, Item 17643, cited above, Section III. Middle chalcogen and/or noble metal sensitizations, as described by Atwell et al 25 U.S. Patent 4,035,185, cited above, are preferred.
Sulfur, selenium, and gold are specificslly preferred surface sensitizers.
The degree of surface chemical fiensitization is limited to that which will increase the reversal 30 speed of the in~ernal latent image forming emulsion, but which will ~ot compete with the internal sensiti-zation sités to the extent of causlng the location of latent image centers formed on expo6ure to shift from the interior to the surface of the tabular grains.
35 Thus, a balance between internal and surface senslti-zation is preferably maintained for maximum speed, but with the internal sensitization predominating.
Tolerable levels of surface chemical sensitizMtion can be readily determined by relating surface development to internal development as previously described.
In one specifically preferred form the core-shell emulsions employed in the practice of this invention are high aspect ratio tabular grain core-shell emulsions, as disclosed by Resea ch Disclosure, Vol. ~5, January, 1983, Item 22534, and Evans et al lO Can. Serial No. 415,270, filed November 10, 1982, commonly assigned. As applied to the emulsions the term "high aspect ra~io" is herein defined as requiring that the core-shell grains having a thickness of less than ~.5 micron (preferably 0.3 15 micron) and a diameter of at least 0.6 micron have an average aspect ratio of greater than 8:1 and account for at least 50 percent of the total projected area of the core-shell silver halide grains.
As employed herein the term "aspect ratio"
20 refers to the ratio of the diameter of the grain to its thickness. The "diameter" of the grain is in turn defined as the diameter of a circle having an area equal to the projected area of the grain as viewed in a photomicrograph of an emulsion sample.
25 The core-shell tabular grains of Evans et al have an average aspect ra~io of greater than 8:1 and prefer-ably have;an &verage aspect ratio of greater than 10:1. Uader optimum conditions of preparation aspect ratios of 50:1 or even 100:1 are contemplat d. As 30 will be apparent, the thinner the grains, the higher their aspect ratio for a given diameter. Typically grains of aesirable aspect ratios are those having an average thickness of less than 0.5 micron, preferably les 6 than 0.3 micron, and optimally less than 0.2 35 micron. Typically the tabular gra~n~ have an average thickness of at least 0.05 micron, although even thinner tabular grains can in principle be employed.
In a preferred form of the invention the tabular grains account for a~ least 70 percent and optimally at least 90 percent of the total projected surface area of ~he core-shell silver halide grains. Tabular 5 grain average diame~ers are in all instance6 less than 30 microns, preferably less than 15 microns, and optimally less than 10 microns.
It is specifically contempla~ed to blend the internal latent image forming emulsions to satisfy 10 specific emulsion layer requirements. For example, two or more emulsions differing in average grain diameter can be blended. It is specifically contem-plated to employ in blending internal latent image forming grains of similar grain size distribution to 15 minimize migration of addenda between different grain populations. When separate emulsionæ of similar grain size distribution are employed in combination, their performance can be differentiated by differ-ences in surface sensitization levels, differences 20 relating to adsorbed nucleating agents, or differ-ences in proportions of internal sensitizers, the latter being taught by Atwell et al U.S. Patent 4,035,185. Hoyen et al Can. Serial Nos. 415,290, titled PHOTOGRAPHIC ELEMENTS CONTAINING DIRECT
25 POSITIVE EMULSIONS AND PROCESSES FOR THEIR USE, and 415,280, titled BLENDED DIRECT-POSITIVE EMULSIONS, PHOTOGRAPHIC ELEMENTS, AND PROCESSES OF USE, both filed November lO, 1982, commonly assigned, disclose that the blending or double coating of a first, 30 core-shell emulsion and a 6econd, internal lAtent image forming or internally fogged emulsion in a weight rativ 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 ~verage grain 35 diameter less than 70% that of the first emulsion, can result in an increase in silver covering power.
A speed increase can also be realized, even at -19- ~ 3;~`3~i reduced coating levelsO 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 emul~ion i8 5 preferably less than 50%, optimally less than 40% the average diameter of the grains of the first emulsion.
In a speciically preerred form of the invention the grains of the second emulsion are also core-shell grains. They can be identical to the 10 core-shell grains of the first emulsion, subject to the considerations noted above. In general, when the second core-shell grain population satisfies the relative size requirements of the two grain popula-tions the other considerations will also be satisfled 15 when ~he firs~ and second grain population~ are of the same silver halide composition and similarly internally sensitized. Maintaining the second grain population substantially free of intentional surface chemical sensit;zation is also advantageous both in 20 reducing the surface latent image forming capability of the second grain population within the direct positive exposure latitude of the blended emulsion and in increasing the reversal speed of the blended emulsion. It is specifically preferrPd to blend 25 core-shell emulsions having surface chemical sensiti-zation of the type disclosed by Evans U.S. Paten~
3,761,176 and Atwell et al U.S. Patent 4,035,185, cited above, to form the first grain population with similar core-shell grainæ of smaller average graln 30 size and free of or exhibiting reduced surface chemical sensitization forming the ~econd grain population.
The internal latent image forming emulsions can, if desired, be spectrally sensitiz~d. For black 35 and white imaging applica~ions spectral sensitization is not required, although orthochromatic or pan-chromatic sensitization is usually preferred.
~ ~ 3~
Generally, any spectral sensitizing dye or dye combination known to be useful with a negatlve working silver halide emulslon can be employed with the internal latent image forming emulsions. Illus-5 trative spectral sensitizing dyes are those disclosedin Research Disclosure, Item 17643, cited above, Section IV. Particularly preferred spectral sensi-tizing dyes are those disclosed in Research Disclo-sure, Item 15162, cited above. Although the emul-10 sions can be spectrally sensitized with dyes from avariety of classes, preferred spectral sensitizing dyes are polymethine dyes, which include cyanine, merocyanine, complex cyanine and merocyanine (i.e., tri-~ tetra, and poly-nuclear cyanine and mero-15 cyanine), oxonol, hemioxonol, styryl, merostyryl, andstreptocyanine dyes. Cyanine and merocyanine dyes are specifically preferred. Spectral sensitizing dyes which sensitize surface fogged direct posltive emulsions generally desensitize both negative working 20 emulsions and the surface development of internal latent image forming emulsions and therefore are not normally contemplated for use in the practice of this invention. Spectral sensitization can be undertaken at any stage of emulsion preparation heretofore known 25 to be useful. Most commonly spectral sensitization is undertaken in the art subsequent to the completion of chemical sensitization. However, it is æpecif-ically recognized that spectr&l sensitization can be undertaken alternatively concurrently with chemical 30 sensitization or can entirely precede surface chemi~
cal sensitization. Sensi~ization can be enhanced by pAg adjust~ent, including cycling, during chemical and/or spectral sensitization.
It has been found advantageous to employ 35 nucleating agents in preference to uniform light exposure in processing. The term "nucleating agent"
(or "nucleator") is employed herein in its art-recog-~ 21-nized usage to mean a fogging agent capable of permitting the selective development of internal latent image forming silver halide grains which have not been ~magewise exposed in preference to the 5 development of silver halide grains having an intern-al latent image formed by imagewise exposure.
The internal latPnt image forming emulsions preferably incorpora~e a nucleating agent to promote the formation of a direct positive image upon 10 processing. The nucleating agent can be incorporated in the emulsion during processing, but it is prefer-ably incorporated in manufacture of the photographic element, usually prior to coating. This reduces ~he quantities of nucleating agent required. The quanti-15 ties of nucleating agent required can also be reducedby restricting t~e mobility of the nucleating agent in the photographic element. Large organic subs~it-uents capable of performing at least to some ex~ent a ballasting function ~re commonly employed. Nucleat-20 ing agents which include one or more groups topromote adsorption to the surface of the silver halide grains have been found to be effective in extremely low concentrations.
A preferred general class of nucleatlng 25 agents for use in the practice of this invention are aromatic hydrazides. Particularly preferred aromatic hydrazides are those in which the aromatic nucleus is substituted with one or more groups to restrict mobility and~ preferably, promote adsorption of the 30 hydrazide to silver halide grain surfaces. More specifically, pre~erred hydr~zides are those embraced by formula (II) below:
(II) J J
D-N-N-~-M
wherein D is an acyl group;
J is in one occurrence hydrogen and in the other occurrence hydrogen or a sulfinic acid radical;
~ is a phenylene or 6ub~tituted (e.g., 5 halo-, alkyl-, or slkoxy-sub6tituted) phenylene group; and M is a moiety capable of restricting mobil-ity, such as a ballasting or an adsorption promoting moiety.
The incorporation of a sulfinic acid radical substi~uent in an aroma~ic hydrazide nucleating agent is specifically taught by Hess et al U.S. Patent 4,478,928. The sulfinic acid radical substituent has an activating effect permi~ting increased levels of 15 nucleating agent activity to be realized. Reduced rereversal can also be achieved. The sulfinic acid radical substituent is preferably in the B positlon relative to the acyl group~
The term "sulfinic acid radical" is herein 2~ defined as the radical produced by the removal of the acid hydrogen ion from a sulfinic acid. Thus, the sulfinic acid radical can be produced from any conventional sulfinic acid. The sulfonyl group of the sulfinic acid can be bonded directly to either an 25 aliphatic or ~romatic residue. The aliphatic residue can, for example, be an alkyl substituent. A simple alkyl 6ubsitutent can take the orm of alkyl of from 1 to 8 carbon atoms~ most typic~lly 1 to 3 c~rbon atoms. In a preferred form the sulfinic acid radical 30 includes an aromatic residue. A preferred substit-uent can be rep~e&ented by the following:
(III) I
O=S~O
Ar' wherein Ar' is an aryl group. In a specifically pre~erred form of the invention Arl is a carbo-cyclic aromatic ring containing from 6 to 10 carbon atoms (e.g., phenyl or naphthyl) which can optlonally be substituted. While either electron withdr~wing or electron donating substituents can be employed, 5 highly electron donating substituents are not prefer-red. Substituents discussed below, typically contain up to 8 carbon atoms.
A particularly preferred class of phenyl-hydrazides are acylhydrazinophenylthioureas repre-10 sented by formula (IY) below.(IV) Il I I I 11 ,R
R-C-N-N-Rl-N--C-N
15 wherein J iB as defined above;
R is hydrogen or an alkyl, cycloalkyl, haloalkyl, alkoxyalkyl, or phenylalkyl sub6tituent or a phenyl nucleus having a Hammett sigma-value-derived 20 electron-withdrawing characteristic more positive than -0.30;
Rl is a phenylene or alkyl, halo-~ or alkoxy-substituted phenylene group;
R 2 iS hydrogen, benzyl, alkoxybenzyl, halo-25 benzyl, or alkylbenzyl, R 3 iS a alkyl, haloalkyl, alkoxyalkyl, orphenylalkyl 3ubstituent havlng from 1 to 18 carbon atoms, a cycloalkyl substituent, a phenyl nucleus having a Hammett R igma value-derived electron-with-30 drawing ch~ractèristic lesæ positive than +0.50, ornaphthyl~
R 4 iS hydrogen or independently selected from among the same substituents as R 3; or R 3 and R 4 together form a heterocyclic 35 nucleus forming a ~- or 6-membered ring, whereln the ring atoms are chosen from the class consisting of nitrogen, carbon, oxygen, sulfur~ and selenlum atoms;
with the proviso th~t at least one of R 2 and R 4 must be hydrogen and the alkyl moieties, except as otherwise noted, in each instance include from 1 to 6 carbon atoms and the cycloalkyl moieties have 5 from 3 to 10 carbon atoms.
As indicated by R in formula (IV), preferred acylhydrazinophenyl~hioureas employed in the practice of this invention contain an acyl group which is the residue of a carboxylic acid, such as one of the 10 acyclic carboxylic acids, including formic acid, acetic acid, propionic acid, butyric acid, higher homologues of these acids having up to about 7 carbon atoms, and halogen, alkoxy, phenyl and equivalent-substituted derivatives thereof. In a preferred 15 form, the acyl group is formed by an unsubstituted acyclic aliphatic carboxylic acid having from 1 to 5 carbon atoms. Specifically preferred acyl groups are formyl and acetyl. As between compounds which differ solely in terms of having a formyl or an acetyl 20 group, the compound containing the formyl group exhibits higher nucleating agent ac~ivity. The alkyl moieties in the substituents to the carboxylic acids are contemplated ~o have from l to 6 carbon atoms, preferably from 1 to 4 carbon atoms.
In addition to the acyclic aliphatic carboxylic acids, it is recognized that the carboxylic acid can be chosen so that R is a cyclic aliphatic group having from about 3 to 10 carbon atoms, such as, cy~lopropyl, cyclobutyl, cyclopentyl, 30 cyclohexyl, methylcyclohexyl, cyclooctyl, cyclodecyl, and bridged ring variations, such as, bornyl and isobornyl groups. Cyclohexyl i6 a specifically preferred cycloalkyl sub~tituent. The use of alkoxy, cyano, halogen, and equivalent substi~uted cycloalkyl 35 substituents is contemplated.
As indicated by Rl in formula (IV), preferred acylhydrazinophenylthioureas employed in ~ ~t~f~ 3 the practice of this invention contain a phenylene or substituted phenylene group~ Specifically preferred phenylene groups are m- and ~-phenylene groups.
Exemplary of preferred phenylene substi~uents are 5 alkoxy substituents having from 1 to 6 carbon a~oms, alkyl substituen~s having from 1 to 6 carbon atoms, fluoro-, chloro-, bromo , and iodo-substituents.
Unsubstituted ~-phenylene groups are specifically preferred. Specifically preferred alkyl moieties are 10 those which have from 1 to 4 carbon atoms~ While phenylene and substituted phenylene groups are preferred linking groups, other functionally equiva-lent divalent aryl groups, such as naphthalene groups, can be employed.
In one form R 2 represents an unsubs~ituted benzyl group or substituted equivalents thereof, such as alkyl, halo-, or alkoxy-~ubstituted benzyl groups. In the preferred form no more than 6 and, most preferably, no more than 4 carbon atoms are 20 contributed by subs~ituents to the benzyl group.
Substituents to the benzyl group are preferably para-substituents. Specifically preferred benzyl substituents are formed by unsubsti~uted~ 4-halo-sub-stituted, 4-methoxy-subs~ituted, and 4-methyl-sub-25 stituted benzyl groups. In another ~pecificallypreferred form R 2 represent6 hydrogen.
Referring again to formula (IV), it is apparent that R 3 and R 4 can independently take a variety of forms. One specifically contemplated form 30 can be an alkyl group or a substituted alkyl group, such as a haloalkyl group, alkoxyalkyl group, phenyl-alkyl group~ or equivalent group, havlng a total of up to 18, preferably up ~o 12, car~on atoms. Specif-ically R 3 and/or R 4 can take the form of a 35 methyl, ethyl, propyl~ butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl or higher homologue group having up ~o 18 total carbon atoms; a fluoro-, chloro-, ~ 3~i bromo-, or iodo-substituted derivative thereof; a methoxy 9 ethoxy, propoxy, butoxy or higher homologue alkoxy-substituted derivatiYe thereof, wherein the total number of carbon atoms are necessarily at lea~t 5 2 up to 18; and a phenyl-6ubs~ituted derivatlYe thereof, wherein the total number of carbon a~oms is necessarily at least 7, as in the case of benzyl,up to about 18. In a specific preferred form R 3 and/or R 4 can take the form of an alkyl or phenyl-lO alkyl substituent, wherein the alkyl moie~ies are ineach instance from l to ~ carbon atoms.
In addition to the acyclic alipha~ic and aromatic forms discussed above, it is also contem-plated that R 3 and/or R 4 can take the form of a 15 cyclic aliphatic substituent, such as a cycloalkyl substituent having from 3 to lO c~rbon atoms. The use of cyclopropyl, cyclobutyl a cyclopentyl, cyclo-hexyl, methylcyclohexyl, cyclooctyl, cyclodecyl, and bridged ring variations, such as, bornyl and 20 isobornyl groups, is contemplated. Cyclohexyl is a preferred cycloalkyl substituent. The use of alkoxy, cyano, halogen, and equivalent substi~uted cycloalkyl substituents is contemplated.
R 3 and/or R 4 can also be an aromatic 25 substituent, such as, phenyl or naphthyl (i.e., l-naphthyl or 2-naphthyl) or an equivalent aromatic group, e.~ , 2-, or 9-anthryl, etc. Aæ indicated in formula (IV) R 3 and/or R 4 can take the form of a phenyl nucleus which is either electron-donating or 30 electron-withdrawing, however phenyl nuclei which are highly electron-withdrawin~ may produce inferior nucleating agents.
The electron-withdrawing or electron-donat-ing characteristic of a specific phenyl nucleus can 35 be assessed by reference to HRmmett sigma values.
The phenyl nucleus can be assigned a Hamme~t sigma value-derived electron withdr~wing characteristic s j which is the algebraic sum of the Hammett sigma values of its subs~ituents (i.e., those of the substituents, if any, to the phenyl group). For example, the Hammett sigma values of any substituents 5 to the phenyl ring 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 6um thereof. Electron-withdrawing substituents are 10 assigned positive sigma values~ while electron-donat-ing substituents are assigned negative sigma values-Exemplary meta- and para-sigma values and procedures for their determination are set forth by J. Hine in Physical Or~anic Chemistry, ~econd 15 edition, page 87, published in 1962, H. VanBekkum, P.
E. Verkade and B. M. Wepster in Rec. Trav. Chim., _ .
Volume 78, page 815, published in 1959, P. R. Wells in Chem. Revs., Volume 63, page 171, published in 1963, by H. H. Jaffe in Chem. Revs., Volume 53, page 20 lgl, published in 1953, by M. J. S. Dewar and P. J.
Grisdale in J. Amer. Chem. Soc., Volume 84, page 3548, published in 1962, and by Barlin and Perrin in Quart. Revs., Volume 20, page 75 et seq, published in 1966. For the purposes of this invention, ortho-sub-25 stituents to the phenyl ring can be assigned to the published para-sigma values.
It is preferred that R2 and/or R3 be a phenyl nucleus having a Hammett sigma value-derived electron-withdrawing characteristic less positive 30 than ~0.50. It is specifically contemplated that R 2 and/or R 3 be chosen from among phenyl nuclei having cyano, fluoro-, chloro- 3 bromo-, iodo-, alkyl groups having from l to 6 carbon atoms, and alkoxy groups having from 1 to 6 carbon atoms, as phenyl 35 ring substituents. Phenyl ring substituents are preferred in the ~ - or 4 ring position.
1 ~J~ 4j Rather ~han being independently chosen R 2 and R 3 can together form, along with ~he 3-position nitrogen atom of the thiourea, a heterocyclic nucleus forming a 5- or 6-membered ring. The ring atoms can be chosen from among nitrogen, carbon, oxygen, sulfur and selenium ~toms. The ring neceæsarily contains at least one nitrogen atom. Exemplary rings include morpholino, piperidino, pyrrolidinyl, pyrrolinyl, thiomorpholino, thiazolidinyl, 4-thiazolinyl, selena-l~ zolidinyl, 4-selenazolinyl, imidazolidinyl, lmida-zolinyl, oxazolidinyl, and 4-oxazolinyl rings.
Specifically preferred rings are saturated or other-wise constructed to avoid electron withdrawal from the 3-position nitrogen atom.
Acylhydrazinophenylthiourea nucleating agents and their synthesis are more specifically disclosed in Leone U.S. Patents 4,Q30,925 and 4,276,364. Variants of the acylhydrazinophenylthiourea nuclea~ing agents 20 described above are disclosed in von Konig U.S.
Patent 4,139,387 and Adachi et al U.K. Patent Appli-cation 2,012,443A.
Another preferred class of phenylhydrazide nucleating agents are N-(acylhydrazinophenyl)thio-25 amide nucleating agents, such as those indicated byformula (V) below:
(V) Il I I H
R-C-N-N-Rl~N---C -wherein R, Rl, and J are as defined in formula (IV);
A is =N-R2, -S- or -0-;
Ql represents the atoms necessary to complete a five-membered heterocyclic nucleus;
R 2 iS independen~ly chosen from hydrogen, phenyl, alkyl, alkylphenyl, and phenylalkyl; and the 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-~hione, 4-oxazoline-2-thione, oxazolidine-2-thione, 2-pyra-zoline-5-thione, pyrazolidine-5-thione, indoline-2-10 thione, and 4-imidazoline-2-thione, etc. A specif-ically preferred subclas6 of heterocyclic thioamide nuclei is formed when Q' is as indicated in formula (VI) (VI) X
Il . I
wherein X is =S or =0.
20 Specifically preferred illustrations of such values of Ql are 2-thiohydantoin, rhodanine, isorhodanine, and 2-thio-2,4-oxazolidinedione nuclei. I~ i6 believed that some six-membered nuclei 3 such as thiobarbi~uric acid, may be equivalent to five-mem-25 bered nuclei embraced within formula (V).
Another specifically preferred subcla6s ofheterocyclic thioamide nuclei is formed when Ql is as indicated in formula (VII) (VII) X
Il I .
-c-c~-L~n _lT
wherein L is a methine group;
1 Z -I ~4 T is =C-~CH=CH-td lN-R3 or =CH--~ /~u R3 is an alkyl substituent, ~Rs R 4 iS hydrogen; ~n alkyl, -N ~ 6 ~ or 5 an alkoxy sub6tituent;
Z represents the nonmet~llic atoms nece6sary to complete a basic heterocyclic nucleu6 of the ~ype found in cyenine dyes;
n and d are independently chosen from the lnte-10 gers 1 and 2;
R 5 and R 6 are independently chosen fromhydrogen, phenyl, alkyl, alkylphenyl, and phenyl-alkyl; and the alkyl moieties in each instance include rom 15 1 to 6 carbon atoms.
The formula (VII) values for Q' provide a heterocyclic thioamide nucleus corresponding to a methine substituted form of the nuclei present above in formula (VI) values for ~'. In a specifically 20 preferred form the heterocyclic thioamide nucleus is preferably a methine substituted 2-thiohydantoin, rhodanine, isorhodanine, or 2-thio-2,4-oxazolidine-dione nucleus. The heterocyclic thioamide nucleus of formula (VII) is directly, or through an intermediate 25 methine linkage, substituted with a basic hetero-cyclic nucleus of the type employed in cyanine dyes or a substituted benzylidene nuclues. Z preferably represents the nonmetallic ~toms necessary to complete a basic 5- or 6-membered heterocyclic 30 nucleus of the type found in cyanine dyes having ring-forming atom~ chosen from the class consisting of carbon, nitrogen, oxygen, sulfur, and ~elenium.
N-(acylhydrazinophenyl)thioamide nucleating agents and their synthesis are more specifically 35 disclosed in Leone et al U.S. Patent 4,080,207.
Still another preferred class of phenyl-hydrazide nucleating agents are tri~zole-substituted ~ 3 phenylhydrazide nucleating agents. More specif-ically, preferred triazole-substituted phenylhydra-zide nucleating agents are those represented by formula (VIII) below:
5 (VIII) O J J
Il I I
R-c-N-N-Rl-A~ 2-A3 wherein R, Rl, and J are as defined in formul~
(II);
Al is alkylene or oxalkylene;
O O
Il H 11 A2 is -C-N- or -S-N-; and A3 is a triazolyl or benzotriazolyl nucleus;
the alkyl and alkylene moieties in each instance including from 1 to 6 carbon atoms.
Still more specifically preferred triazole-substituted phenylhydrazide nucleating agents are those represented by formula (IX) below:
(IX) O J J O
R-C-N-N-R'-C-N t \-/ \N
H
wherein J is as defined above;
R is hydrogen or methyl;
Rl is ~ ~--[CH23n- vr -o~ ~--OE
CCH2~n-n is an integer of 1 to 4; and E is alkyl of from 1 to 4 carbon atoms.
~32-Triazole-su'bstituted phenylhydrazide nucleating 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 5 adsorption promot- ing groups are dlsclosed in corresponding U.K. Patent Application 2,011,391A.
The aromatic hydrazides represented by formulas (IV), (V), and (VII) each contain adsorption promoting substituents. In many ins~ances it is 10 preferred to employ in combination with these aromatic hyrazides addi~ional hydrazides or hydra-zones which do not contain substituents specifically intended to promote adsorption to silver halide grain surfaces. Such hyrazides or hydrazones, however, 15 often contain substituents to reduce their 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 20 represented by formula (X) and (XI) below:
(X) H H
T-N-N~Tl and ~XI) H
T-N-N=T2 wherein T,is an aryl radical, including a substituted aryl radical, Tl is an acyl radical, and T2 is an alkylidene radical'and including substituted alkyli-30 dene radicals. Typical aryl radicals for the substitutent T have the formula M-T3-, wherein T3 is an aryl' radical (such as, phenyl, l-naphthyl, 2-naphthyl, etc.) and M can be such ~ubstituents as hydrogen, hydroxy, amino, alkyl, alkylamino, aryl-35 amino, heterocyclic amino (amino containing a hetero-cyclic moiety), alkoxy, aryloxy, acyloxy, arylcarbon-amido, alkylcarbonamido, heterocyclic cnrbonamido (carbonamido containing a heterocycllc moiety), arylsulfonamido, alkylsulfonamido~ and heterocyclic sulfonamido (sulfonamido containing a heterocyclic moiety). Typical acyl radicals for the substituent 5 Tl have the formula O O
Il 11 -S-Y or -C-G
o 10 wherein Y can be such substltuents as alkyl, aryl, and heterocyclic radicals, G can represen~ a hydrogen atom or the same substituent as Y as well as radicals having the formula o -C-~-A
to form oxalyl radicals wherein A is an alkyl, aryl~
or a heterocyclic radical. Typical slkylidene radicals for the substituent T 2 have the formula 20 =CH-D wherein D can be a hydrogen atom or such radicals as alkyl, aryl, and heteroeyclic radicals.
Typical aryl substituents for the above-described hydrazides and hydrazones include phenyl, naphthyl, diphenyl, and the like. Typical heterocyclic 25 substituents for the above-described hydrazides and hydrazones include azoles, azines, furan, thiophene, quinoline? pyrazole, and the like. Typical alkyl (or alkylidene) substituents for the sbove-described hydrazides and hydrazones have 1 to 22 carbon atoms 30 including methyl, ethyl, isopropyl, n-propyl, isobutyl, n-butyl, t-butyl, amyl, _-octyl, _-decyl, n-dodecyl, n-octadecyl 9 n-eicosyl, and n-doco6yl.
The hydrazldes and hydr~zones represented by formulas (X) and (XI) as well as their synthesis are 35 disclosed by Whitmore U.S. Patent 3,227,552.
Still other useful hydrazine and hydrazide nucleating sgents are disclo6ed in Rese~rch Disclo-sure, Vol. 235, November, 1983~ Item 23510.
-34~
A secondary preferred general class of nucleating agents for use in the practice of this invention are N-substituted cycloammonium quaternary salts. A particularly preferred species of such 5 nucleating agents is represented by formula ~XII) below:
(XII) 1- - - Z'- - -I
N~=~CH-CH~j l=C-E
X-(CH 2) a wherein Zl represents the atoms necessary ~o complete a 15 heterocyclic nucleus containing a heterocyclic ring of 5 to 6 atoms including the quaternary nitrogen atoms, with the additional atoms of said heterocyclic ring being selected from carbon, nitrogen, oxygen, sulfur, and selenium;
j represents a positive integer of from 1 to 2;
a represents a positive integer of from 2 to 6, X~ represents an acid anion;
E 2 represents a member selected from (e) a formyl radical, (b) a radical having the formula -CH
;
wherein éach of Ll and L 2~ when ~aken alone, represents a member selected from an alkoxy radical 30 and an alkylthio radical, and El and L 2~ when taken together, represent the atoms necessary to complete a cyclic radical selected from cyclic oxyacetals and cyclic thioacetals having from 5 to 6 atoms in the heterocyclic acetal ring, and ~c) a 35 l-hydrazonoalky radical; and E' represents either a hydrogen atom, an alkyl radical, an aralkyl radical, an alkylthio radical, or -35- ~ ri~
an aryl radical such as phenyl and naphthyl, and including substituted aryl radicals.
The N substituted cycloammonium quaternary salt nucleating agents of formula (XII) and their 5 synthesis are disclo~ed by Lincoln and Heseltine U.S.
Pa~ents 3,615,615 and 3,759,901. In a variant form E' can be a divalent alkylene group of from 2 ~o 4 carbon atoms joining two substituted heterocyclic nuclei as shown in formula (XII). Such nucleating 10 agents and their synthesis are disclosed by Kurtz and Harbison U.S. Patent 3,734,738.
The substituent to the quaternized nitrogen atom of the heterocyclic ring can, in another variant form, itself form a fused ring with the heterocycllc 15 ring. Such nucleating agents are illustrated by dihydroaromatic quaternary salts comprising a 1,2 di hydroaromatic heterocyclic nucleus including a quaternary nitrogen atom. Particularly advantageous 1,2-dihydroaromatic nuclei include such nuclei as a 20 1,2-dihydropyridinium nucleus. Especi~lly preferred dihydroaromatic qua~ernary salt nucleating agents include those represented by formula (XIII) below:
(XIII) __ z ~ __ : H iH~ I R I n 30 wherein Z representS the nonmetallic atoms necessary to complete a heterocyclic nucleus containing a hetero-cyclic ring of from 5 to 6 atoms including the quaternary nitrogen atom, w1th the additional atoms 35 of said heterocyclic ring being selected from either carbon, nitrogen, oxygen, sulfur, or selenium;
n represents a positive integer having ~ value of from 1 to 2;
~ ~v~ t~
when n is 1, R represents a member selec~ed from the group consis~ing of a hydrogen atom, an alkyl radieal, an alkoxy radical, an aryl radical, an aryloxy radical, and a carbamido radical and, when n is 2, R represents an alkylene r~dical having from 1 to 4 carbon atoms;
each of Rl and R 2 represent6 a member select-ed from the group consisting of a hydrogen atom, an alkyl radical, and an aryl radical; and X~ represents an anion.
Dihydroaromatic quaternary salt nucleating agents and their synthesis are disclosed by Kurtz and Heseltine U.S. Patent 3,719,494.
A specifically preferred class of N-subEti-15 tuted cycloammonium quaternary salt nucleating agents are those which include one or more alkynyl substit-uents. Such nucleating agents include compounds within the generic structural definition set forth in formula ~XIV) below:
20 (XIV) "Z~
R4 ~ N
Rl wherein Z represents an atomic group necessary for forming a 5- or 6-membered heterocyclic nucleus, R
represents an aliphatic group, R 2 represents a hydrogen atom or an aliphatic group, R 3 and R4, 30 which may be the seme or different, each represents a hydrogen atom, a halogen atom, an allphatic group~ an alkoxy group, a hydroxy group, or an aromatic group, at least one of Rl, R29 R3 and R4 being a propargyl group, a butynyl group, or a sub6tituent 35 containing a propargyl or butynyl group, X~ repre-sents an anion, n is 1 or 2, with n being 1 when the compound formæ an inner salt.
_37~ s3~
Such alkynyl-substituted cycloammonium quaternary salt nucleating agents and their synthesis are illustrated by Adachi et al U.~. Patent 4,115,122. BallPsted nucleatlng agents of the type 5 shown in formula (XIV) are disclosed in Research Disclosure, Vol. 232, August 1983, Item 23213, and nucleating agents of the type shown in formula (XIV) containing an adsorption promoting group are disclosed by Parton et al U.S. Patent 4,471,044.
The specific choice of nucleating agents can be influenced by a variety of factors. The nucleat-ing agents of Leone U.S. Patents 4,030,925 and 4,276,364, cited above are par~icularly preferred for many applications, since ~hey are effective at very 15 low concentrations. Minimum concentrations a~ 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 di6clos-ed. These nucleating agents are particularly advan-20 tageous in reducing speed loss and in some instancespermitting speed gain with increasing processing temperatures.
The aromatic hydrazide nucleating agents are generally preferred for use in photographic elemen~s 25 intended to be processed at comparatively high levels of pH, typically ~bove 13. The alkynyl-sùbstituted cycloammonium quaternary salt nucleating agents are particularly useful for processing at a pH of 13 or less. Adachi et al U.S. Patent 4,115,122 teaches 30 these nucleat~ng agents to be useful in processing within the pH range of from 10 to 13, preferably 11 to 12.5. In addition to the nuclea~ing agents described above addltional nucleating ~gents have been identified which are useful in processing at pH
35 levels in the range of from about 10 to 13, such as N-substituted cycloammonium quaternary salt nucleat-ing agents of the type disclosed by Baralle et al U.S. Patent 4,306,016; dihydrospiropyran bis-condensa~ion products of salicylic aldehyde and at least one heterocyclic ammonium salt of the type disclosed by Baralle et al U.S. Patent 4,306,017; and 5 diphenylmethan~ nucleating agents of the type disclosed by Baralle et al U.S. Patent 4~315,986.
Instead of being incorporated in the photo-graphic element during manufacture, nucleating agents can alternatively or additionally be lncorporated in 10 the developer solution. Hydrazine ~H2N-NH 2) is an effective nucleating agent which ~an be incor-porated in the developing solution. As ~n alterna-tive to the use of hydrazine, any of a wide variety of water-soluble hydrazine derivatives can be added lS to the developing solution. Preferred hydrazine derivatives for use in developing solutions include organic hydrazine compounds of the formula:
(XV) I 3 2~ - N ~ 4 where Rl is an organic radical and each of R 2, R3 and R 4 iS a hydrogen atom or an organic radical. Organic radicals represented by Rl, R2, 25 R3 and R 4 include hydrocarbyl groups such as an alkyl group~ an aryl group, an aralkyl group, an alkaryl group, and an alicyclic group, as well as hydrocarbyl groups substituted with substituents such as alkoxy groups, carboxy groups, sulfonamido groups, 30 and halogen atoms.
Particularly preferred hydrazine derivative 8 for incorporation in developing solutions include alkylsulfonamidoarylhydrazines, such BS p- (methyl-sulfonamido)phenylhydrazine, and alkylsulfonamido-35 alkylaryl hydrazines, such ~s p-~methylsulfonamido~
methyl)phenylhydrazine.
The hydrazine and hydrazide derivatives described above are disclosed in Smith et al U.S.
Patent 2,410,690, Stauffer et al UOS. Patent 2,419,975, and Hunsberger U.S. Patent 2,892,715. The 5 preferred hydrazines for incorporation in developers are described in Nothnagle U.S. Patent 4,269,929.
Another preferred class of nucleating agentR that can be incorporated in the developer correspond to formula (I) above, but with the moiety M capable of 10 restricting mobility absent. Nucleating agents of this type are disclosed in Okutsu et al U.S. Patent 4,221,857 and Takada et al U.S. Patent 4,224,401.
Once internal latent image forming emulsions have been generated by precipitation procedures, 15 washed, and sensitized, as described abov~, their preparation can be completed by the optional incor-poration of nucleating agents, described above, and conventional photographlc addenda, and they can be usefully applied to photographic applications requir-20 ing a silver image to be produced--e.g., conventional black and white photography.
The internal latent i~a8e forming emulsion is comprised of a dispersing medium in which the grains are dispersed. The dispersing medium of the 25 emulsion layers and other layers of the photographic elements, including the antifoggant undercoat, can contain various colloids alone or in combination as vehicles (which include both binders and peptizers3.
Preferred peptizers are hydrophilic colloids, which 30 can be employed alone or in combination with hydro-phobic materials. Preferred peptizers are gelatin--e.g., alkali-treated gelatin (cattle bone or hide gelatin) and acid-treated gelatin (pigskin gelatin) and gelatin derivatives--e.g., ace~ylated gelatin, 35 phthalated gelatin, and the like. Useful vehicles are illustrated by those disclosed in Research Disclosure, Item 1765~3, cited above, Section IX.
The layers of the photographic elements containing crosslinkable colloids, particularly ~he gelatin~con-taining layers, can be hardened by various organic and inorganic hardeners, as illustrated by Research 5 Disclosure, Item 17643, cited above, Sectlon X-In addition to the maximum density enhancingantifoggants in the undercoat described above, other antifoggants and stabilizers known to be useful in combination with internal latent desensitization 10 direct positive imaging can be incorporated in the photographic elements of this invention at any useful location. A variety of such addenda are disclosed in Research Disclosure, Item 17643, cited above, Section VI. Many of the antifoggants which are 15 effective in emulsions can also be used in developers and can be classïfied under a few general headings, as illustrated by C.E.K. Mees, The Theory of the Photographic Process, 2nd Ed., Macmillan, 1954, pp.
677-680.
In addition to sensitizers, hardeners, and antifoggants and stabilizers, a variety of other conventional photographic addenda can be present~
The specific choice of addenda depends upon the exact nature of the photographic application and is well 25 within the capability of the art. A variety of useful addenda are disclosed in Research Disclosure, Item 17643, cited above. Optical brightener6 can be introduced, as disclosed by Item 17643 at Section V.
Absorbing and scattering materials can be employed in 30 the emulsions of the invention and in separate layers of the photographlc elements, as described in Section VIII. Coating aids, as described in Section XI, and plasticizers and lubricants, as described in Section XII, can be present. Antistatic layers, a8 described 35 in Section XIII, can be present. Methods of addition of addenda are described in Section XIV. Matting agents can be incorporated, as described in Section ~ ~3~.3 XVI. Developing agents and development modifiers can, if desired9 be incorporated, as described in Sections XX and XXIo The sil~er halide emulsion layer or layers, antifoggant undercoat, as well as 5 optional interlayers, overcoa~s, and subbing layers, if any9 present in the photogrRphic elements can be coated and dried as described in Item 17643, Section XV .
The layers of the photographic elements can lO be coated on a variety of 6upports. Typical photo-graphic supports include polymeric film, wood fiber--e.g., paper, metalllc sheet and foil, gla~6, and ceramic supporting elPments provided with one or more subbing layers to enhance the adhesive, ~nti-15 static, dimensional, abrasive, hardness~ fri~tional, antihal~tion and/or other properties of the support surface. Suitable photographic supports are illus-trated by Research Disclosure, Item 17643, cited above, Section XVII.
Although the Pmulsion layer or layer~ are typically coated as continuous layers on supports having opposed planar major surfaces, this need not be the case. The emulsion layers can be coated as laterally displaced layer segments on a planar 25 support surface. When the emulsion layer or layers are segmented, it is preferred to employ a microcell-ular support. Useful microcellular supports are disclosed by Whitmore U.S. Patent 4,387,146.
Microcells can range from l to 200 microns in width 30 and up to 1000 micron6 in depth. It is generally preferred that the microc~ be &t least 4 microns in width and less than 200 micron6 in depth, with optimum dimensions being about 10 to 100 microns in width and depth for ordinary black and white imaging 35 applications- p~r~icularly where the photographic image is intended ~o be enlarged.
The photographic elements of the present inven~ion can be imagewise exposed in any convention-al manner. Attention i6 directed ~o Research Di~clo-.. .. . . .. .. ~__ sure Item 17643, cited above, Section XYIII. The 5 present invention is par~icularly advantageous whenimagewise exposure is undertaken with electromagnetic radiation within the region of the ~pectrum in which the spectral sensitizers present exhibit absorption maxima. When the photographic elements are intended 10 to record blue 3 green, red, or infrared exposures, spectral sensi- tizer absorbing in the blue, green~
red, or infrared portion of the spectrum i6 present.
As noted above, for black and white imaging applications it is preferred that the photographic 15 elements be ortho- chromatically or panchromatically sensitized to permit light to extend sensitivity within the visible spectrum. Radiant energy employed for exposure can be either noncoherent (random phase) or coherent (in phase), produced by lasers.
20 Imagewise exposures at ambient, eleva~ed, or reduced temperatures and/or pressures, including high or low intensity exposures, continuous or intermittent exposures, exposure times ranging from minutes to relatively short durations in the millisecond to 25 microsecond range, can be employed withln the useful response ranges determined by conven~ional sensitometric techniques, as illustra~ed by T. H.
James, The Theory of the Photographic Process~ 4th Ed., Macmillan, 197~ 9 Chapters 4, 6, 17, 18, and 23.
The light-sensitive silver halide contained in the photographic elements can be proce6sed follow~
ing exposure to form a visible image by associating the silver halide with an aqueous alkaline medium in the presence of a developing agent contained in the 35 medium or the element. Processing formulations and techniques are described in L. F. Mason, Photo&raphic Processing Chemistry, Focal Press, London, 1966;
Processin~ Chemicals and Formulas, Publication J-l, Eastman Kodak Company, 1973; Photo-Lab Index, ~lorgan and Morgan, Inc., Dobbs Ferry, New York, 1977, and Neblette~s Handbook of PhotograPhy and Repro ~aphy 5 Materials, rocesses and Systems, VanNostrand Reinhold Company, 7th Ed., 1977.
Included among the processing methods are web processing, as illustrated by Tregillus et al U.S. Patent 3,179,517; stabilization processing, as 10 illustrated by Herz et al U.S. Patent 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 processing as described in Haist, Monobath Manual, Morgan and Morgan, Inc., 1966, Schuler V.S.
15 Patent 3,240 9 603, Haist et al U.S. Pa~ents 3,615,513 and 3,628,955 and Price U.S. Patent 3,723,126;
infectious development, as illustrated by Milton V.S.
Patents 3,294,537, 3,600,174, 3,615,519 and 3,615,524, Whiteley U.S. Patent 3,516,830, Drago U.S.
20 Patent 3,615,488, Salesin e~ al U.S~ Patent 3,625,689, Illingsworth U.S. Patent 3,632,340, Salesin U.K. Patent 1,273,030 and U.S. Patent 3,708,303; hardening development, as illustrated by Allen et al U.S~ Patent 3,23~,761; roller transport 25 processing, as lllustra~ed by Russell et al U.S.
Patents 3,025,779 and 3,515,556, Masseth U.S. Patent 3,573,914, Taber et al U.S. Patent 3,647,459 and Rees et al U.K. Patent 1,269,268; alkaline vapor process-ing, as illustrated by Product Licensin~ Index~ Vol.
30 97, May 1972, Item 9711, Goffe et al U.S. Patent 3,816,136 and King U.S. Patent 3,985,564; metal ion developmen~ as illustrated by Price, Photo~raphic Science and Engineering, Vol. 19 3 Number 5, 1975, pp.
283-287 and Vought Research Disclosure, Vol. 150, 35 October 1976, Item 15034; and surface applicatlon processing, as illustrated by Kitze U.S. Patent 3,418~132.
Although development i6 preferably under-taken in the pr~sence of a nucleating ag~nt, as described above, giving the photographic elements an over-all light exposure either immediately prior to 5 or, preferably, during development can be undertaken as an alternative. When an over-all flash exposure is used, it can be of high intensity and short duration or of lower intensity for a longer duration.
The silver halide developers employed in 10 processing are surface developers. It is understood that the term l'surface developer" encompasses those developers which will reveal the surface latent image centers on a silver halide grain, but will not reveal substantial lnternal latent image centers in an 15 internal latent im~ge forming emul~ion under the conditions generally used to develop a surface sensitive silver halide emulsion. The surface developers can generally utilize any of the 6ilver halide developing agents or reducing agents, but the 20 developing bath or composition is generally substan-tially free of a silver halide solvent (such as water soluble thiocyanates, water soluble thioethers, thiosulfateE, and ammonia) which will disrupt or dissolve the grain to reveal substantial internal 25 image. Low amounts of excess halide are sometimes desirable in the developer or in~orporated in the emulsion ~s halide releasing compounds, but high amounts of iodide or iodide releasing compounds are generally avoided to prevent sub~tantial di6ruption 30 of the grain.
Typical silver halide developing agents which can be used in the developing compositionfi of this invention include hydroquinones, cntechols, aminophenols, 3-pyra~olidinones, ascorbic acid and 35 its derivatives, reductones, phenylenedi~mines, or combinations thereof. The developing agents can be incorporated in the photographic elements wherein they are brought into contact wi~h the silver halide after imagewise exposure; howeverS in cer~ain embodi-ments they are preferably employed in the developing bath.
Once a silver image h~s been formed in the photographic element, i~ is conventional practice to fix the undeveloped silver halide. The high aspect ratio tabular grain emulsions are particularly advantageous in allowing fixing to be accomplished in 10 a shorter time p~riod. This allows processing to be accelerated.
Except as otherwise stated, ~he remaining features of the black and white direct po6i~ive photographic elements of this inventioD and the 15 production of direct positive images by processing these photographic elements after imagewise exposure should be understood to contain features recognized in the art for such photographic applications.
Examples The invention can be better appreciated by reference to the following specific examples:
Example 1 _ Coa ings A. Control Coating A O.8 ~m octahedral core~shell AgBr emulsion was prepared by a double jet precipitation technique. The core grains consi6ted of a 0.55 ~m octahedr~l AgBr chemically sensitized with 0.78 mg Na2S 20 3-5H20/mole hg and l.lB mg KAuCl4/mole Ag 30 for 30 minutes at 85C. The core-shell emulsion was chemically sensitized with 1.0 mg Na2S203-5H ~/mole Ag for 30 ~inutes at 74C. The emulsion was coated on a polyester film support ~t 7.02 g/m 2 silver and 4.86 g/m2 gelatin. The emulsion layer also 35 contained the spectral sensitizing dyes anhydro-5,5'-dimethoxy-3,3'-bis(3-sulfopropyl~selenacyanine hydroxide, sodium salt (Dye A) and anhydro-5,5'-di-chloro-3,9~diethyl-3'-(3-sulfopropyl)oxacarbocyanine hydroxide (Dye B) each at 200 mg/mole Ag and the nucleating agent 6-ethylthiocarbamato-2-methyl-1-propar~ylquinaldinium trifluoromethanesulfonate at 30 5 mg/mole Ag. The element was overcoated with gelatin at 1.08 g/m2 containing 1.7% bis(vinylsulfonyl-methyl) ether by weight based on total gel content.
B. Example Coating The control coating was again prepared~ but 10 with 1.8 X 10-2 mole of AF-5 per silver mole and gelatin (1~29 g/m 2) in an antifoggant undercoat between ~he emulsion layer and ~he support.
II. Processin~
A. Control Coatin~: An exposed portion of 15 the control coating w~s processed for 75 seconds at 38C in Developer I, ~he developer additionally containing 0.10 gram of AF-5 and 0.16 gram of l-phenyl-5-mercaptotetrazole (hereinafter PMT) per liter.
B. Example Coating: An exposed portion of the example coating was processed for 75 seconds at 38C in Developer I, the developer additionally containing 0.15 gram of AF-5 and 0.11 gram of PMT per liter.
25 III- Sensitometry Sensitometric results are shown in Figure 2 and Table II.
Table II
Sensitometric Results Relative Developed Coatin& CR S eed* Contrast D-max ~2 D-min Control (C-l) 236 6.3 4.4 7.02 0.11 Example (E-l) 273 8.9 6.2 6.89 0.06 * Speed taken at 0.2 density ~ D-min for an expo-sure of 10-5 second through a 0-3~0 den~ity step tablet (0.15 density steps) plu6 & 0.86 neutral densi~y filter And with a filter to ~ '3~3~j simulate a phosphor emitting a~ a waYelength maximum of 465 nm.
As the results show, the effec~ of AF 5 in the undercoat was to increase speed, con~raæ~, and 5 D-max and to decrease D-min over the control. Since higher D-max was obtained at lower developed Ag, the covering power of the silver developed was 8reater for the invention. Also the example coating shows a greater exposure separa~ion between the positive 10 image and the rereversal negative image than in the control coating, as can be seen in Figure 2.
IV. Ima~e Qual ty Portions of the coatings were exposed similarly to those above, but through a microimage 15 target in place of the step tablet, and an estimation of the im ge qual-ity waæ deduced. Figure 3A shows the results of exposing the control ~oating at an exposure equivalent to s~ep #7 (see Figure 2) and the invention coating at step #9 (the photomicrographs 20 are at lOOX magnification). Corresponding photo-micrographs at 400X are shown in Figures 4A and 4B.
From these results, the invention coating show6 improved image ~uality over the control as well as more finely dispersed filamentary silver.
Electron microscopic cross ~ection6 of exposed and processed coatings taken from a step at density of ~0.4 are æhown for the control and invention coatings at magnifications of 22,000X.
Figures 5A and 5B, respectively.
These results show a more even distribution of the developed silver (2a and 2b) throughout the emulsion layer as well as more finely dispersed filamentary-type silver in the invention coating compared to the control coating, which showed a 35 concentration of developed silYer near the support (la and lb) surface.
Developer I
Component ~
Water, tap 850O0 Ethylenediaminotetraacetic acid 1.0 5 KOH, 45% 22.0 5-Methylbenzotriazole adjusted l-Phenyl-5-mercaptotetrazole { as needed Na 2S 3, anhydrous 75-0 4,4~-Dimethyl-l-phenyl-3-pyrazolidinone 0.4 10 NaBr 8.0 2-Ethylaminoethanol 58.6 3.3'-Diaminodipropylamine 4-0 Hydroquinone 40.0 KOH, 45% (adjusted pH to 10.7 at 27C) 7.0 15 Water, tap to 1 li~er Example 2 I. Coatings: Control and Example coatings were prepared essentially similar to those of Example 1, except that 1 percent by weight formaldehyde was used 20 to harden the overcoat rather than bis(vinylsulfonyl~
methyl) ether hardener and for the nucleating agent the following nucleating agents were substituted 1-[4-(2-formylhdrazino)phenyl~-3-hexylurea (276 mg/Ag mole) and l-~ormyl-2-~4 ~2-(2,4-di-tert-pentyl-25 phenoxy)butyramido]phenyl}hydrazine ~78 mg/Ag mole).II. Processin~:
Both control and example coatings were exposed and processed for 104 sec (38C) ln Developer II plus 0.05 g AF-5/Q + 0.08 g PMT/~.
30 III. Sensitometry The sensitometric results ~re shown in Figure 6, and Table III
-49~
Table III
Sensitometric Results .
Relative Coatin~CR Speed* Contrast D-max D-min . _ . .
5 Control (C-2)257 9 9 3.24 0.09 Example (E-2)286 6.7 3.35 0.04 * Speed as described in ExamplP 1.
As the results in Table III and Figure 6 show3 the effect of AF-5 in the undercoat wa~ to 10 increase speed and D-max, decrease D-min, and to increase the speed separation between the positive and negative responses compared to the control.
IV. Image Quality Photomicrographs, taken in a similar manner 15 to that of Example 1, showed similar improvement in the image qualitj of the example over the control.
Developer II
Component ~
Water, tap 850.0 20 Ethylenediaminotetraacetic acid1.0 KOH, 45% 22.0 5-Methylbenzotriazole adjusted l-Phenyl-5-mercaptotetrazole{ as needed Na 2S0 3, anhydrous 60.0 25 4,4'-Dimethyl-l-phenyl 3-pyrazolidinone 0.6 NaBr 3.0 2-Ethylsminoethanol 58.6 3.3'-Diaminodipropylamine 4.0 Hydroquinone 40.0 30 KOH, 45% (adjusted pH to 10.9 at 27C) 7.0 Water, tap to 1 llter Example 3 I. Coatin~s A. Control ~ (C-2): The control coating of 35 Example 2 was again prepared.
B. Control Coating (C-3): Th~ 8 control coating was simil~r to control coating C-2, but contained -50~ 3~
0.69 gram of silver per square meter and additlonally contained in the silver halide emulsion layer 1776 X
0 - 7 mole of AF-5 per silver mole.
C. Example Coatin~ (E-3) Ihis coating was 5 similar to the Example 2 coa~ing E-2, bu~ contained 0.67 gram of silYer per square meter and contained in the undercoat 1.85 X 10- 2 mole of AF-5 per sllver mole. The silver coverages and AF-5 concentrations in coatings C-3 and E-3 were substantially matched, lO the only material diff~rence between ~hese coatings being the presence of AF-5 in the undercoat of coating E-3 as opposed ~o the silver halide emulsion layer in coating C-3.
II. Processing All coatings exposed and processed for 75 seconds (38C) in Developer IXI.
III. Sensitometry Sensitometric reæults are shown in Figure 7 and Table IV.
Table IV
Sensitometric Reæults Reversal (Positi.ve Image CoatingCR Speed* Contrast D-max D-min Control (C-2)257 3.8 4.1 0.06 25 Control (C-3) 247 2.54.5 0.10 Example (E-3)282 5.0 4.0 0.03 * Speed;as described in Example 1.
The results in Table IV and Figure 7 show that the example coating E-3 with AF~5 in the under-30 coat yielded higher speed, higher contrast, lowerminimum density (D-min), ~nd increased exposure separation of the rereversal image compared to control coating C-2, which did not contain AF-5, and control coating C 3, which cont~ined AF-5 in the 35 silver halide emulsion layer~ The location of the maximum density enhancing antifoggant in the under-coat produced these d~fferences in performance.
Deve_oper III
Component ~
Water~ tap 850.0 E~hylenediaminotetraacetic acid 1.0 5 KOH, 45% 22.0 l-Phenyl-5-mercaptotetrazole 0.08 Na 2S0 3~ anhydrous 60~0 4,4~-Dimethyl-l-phenyl-3 pyrazolidinone 0.6 10 NaBr 3.0 2-Ethylaminoethanol 58.6 3.3'-Diaminodipropylamine 4.0 Hydroquinone 40.0 KOH, 45% (adjusted pH ~o 10.9 at 27C) 7.0 15 Water, tap to 1 liter The invention has been described with particular reference to preferred embodiments there-of, but it will be understood that variations and modifications can be effected within the spirit and 20 scope of the invention.
Claims (8)
1. In a black and white direct positive photographic element intended for the formation of a viewable silver image and comprised of a support, one or more radiation sensitive emulsion layers containing internal latent image forming silver halide grains, and a maximum density enhancing 1,2,3-triazole antifoggant, the improvement wherein said maximum density enhancing 1,2,3-triazole antifoggant is located in an undercoat between said emulsion layers and said support.
2. A black and white direct positive photographic element according to claim 1 additional-ly including a nucleating agent.
3. A black and white direct positive photographic element according to claim 2 wherein said nucleating agent is chosen from the class consisting of aromatic hydrazide nucleating agents, N-substituted cycloammonium quaternary salt nucleat-ing agents, and mixtures thereof.
4. A black and white direct positive photographic element according to claim 2 wherein said nucleating agent is a hydrazide of the formula wherein J is in one occurrence hydrogen and in the other occurrence hydrogen or a sulfinic acid radical derived substituent;
.PHI. is a phenylene group; and M is a moiety capable of restricting mobility.
.PHI. is a phenylene group; and M is a moiety capable of restricting mobility.
5. A black and white direct positive photographic element according to claim 1 wherein said silver halide grains are core-shell silver halide grains.
6 A black and white direct positive photographic element according to claim 1 wherein said 1,2,3-triazole antifoggant is present in concentration of from 5 X 10-4 to 0.1 mole per silver mole.
7. A black and white direct positive photographic element according to claim 6 wherein said 1,2,3-triazole includes a fused aromatic ring.
8. Processing in a surface developer an imagewise exposed photographic element according to claim 1 a) in the presence of a nucleating agent or b) with light flashing of the exposed photo-graphic element during processing.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US61251184A | 1984-05-21 | 1984-05-21 | |
US612,511 | 1984-05-21 |
Publications (1)
Publication Number | Publication Date |
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CA1258396A true CA1258396A (en) | 1989-08-15 |
Family
ID=24453470
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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CA000471296A Expired CA1258396A (en) | 1984-05-21 | 1985-01-02 | Direct positive photographic elements with incorporated maximum density enhancing antifoggants |
Country Status (2)
Country | Link |
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JP (1) | JPS60260039A (en) |
CA (1) | CA1258396A (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH0690437B2 (en) | 1987-12-02 | 1994-11-14 | 富士写真フイルム株式会社 | Direct positive photographic material |
ATE539919T1 (en) | 2004-11-15 | 2012-01-15 | Harman Becker Automotive Sys | MOTOR VEHICLE NAVIGATION DEVICE AND STORAGE UNIT MOUNTING DEVICE |
-
1985
- 1985-01-02 CA CA000471296A patent/CA1258396A/en not_active Expired
- 1985-05-21 JP JP10707385A patent/JPS60260039A/en active Granted
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JPH0320742B2 (en) | 1991-03-20 |
JPS60260039A (en) | 1985-12-23 |
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