Direct-positive core-shell emulsions and photographic elements and processes for their use

A radiation-sensitive emulsion particularly adapted to forming a direct-positive image comprised of

• a nucleating agent,
• gelatin or a gelatin-derived peptizer,
• silver halide grains sensitized with at least one of sulfur, selenium, and gold, and capable of forming an internal latent image,
• said silver halide grains being comprised of a core and a shell, and
• said shell incorporating a divalent or trivalent metal cationic dopant in a concentration of from about 10.sup.-3 to 10.sup.-7 mole per mole of silver chosen from the group consisting of manganese, copper, zinc, cadmium, lead, bismuth, and lanthanides, said emulsion when coated on a transparent film support at a silver coverage of 4 grams per square meter, exposed to a 500 watt tungsten lamp for times ranging from 0.01 to 1 second at a distance of 0.6 meter, developed for 5 minutes at 20.degree. C. in Developer Y below, fixed, washed, and dried, having a maximum density at least five times the maximum density of an identical test portion which has been exposed in the same way and developed for 6 minutes at 20.degree. C. in Developer X below, fixed, washed, and dried:
• ______________________________________ Grams ______________________________________ Developer X N--methyl-p-aminophenol sulfate 2.5 Ascorbic acid 10.0 Potassium metaborate 35.0 Potassium bromide 1.0 Water to 1 liter Developer Y N--methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5 Potassium bromide 5.0 Potassium iodide 0.5 Water to 1 liter. ______________________________________

A radiation-sensitive emulsion particularly adapted to forming a direct-positive dye image comprised of

• a dye image former,
• a nucleating agent,
• silver halide grains sensitized with at least one of sulfur, selenium, and gold capable of forming an internal latent image,
• said silver halide grains being comprised of a core and a shell, and
• said shell incorporating divalent cadmium in a concentration of from about 5.times.10.sup.-4 to 10.sup.-6 mole per mole of silver, said emulsion when coated on a transparent film support at a siver coverage of 4 grams per square meter, exposed to a 500 watt tungsten lamp for times ranging from 0.01 to 1 second at a distance of 0.6 meter, developed for 5 minutes at 20.degree. C. in Developer Y below, fixed, washed, and dried, having a maximum density at least five times the maximum density of an identical test portion which has been exposed in the same way and developed for 6 minutes at 20.degree. C. in Developer X below, fixed, washed, and dried:
• ______________________________________ Grams ______________________________________ Developer X N--methyl-p-aminophenol sulfate 2.5 Ascorbic acid 10.0 Potassium metaborate 35.0 Potassium bromide 1.0 Water to 1 liter Developer Y N--methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5 Potassium bromide 5.0 Potassium iodide 0.5 Water to 1 liter. ______________________________________

In a multicolor direct-positive photographic element comprised of a support and, located thereon,

• emulsion layers for separately recording blue, green, and red light each comprised of a dispersing medium, internal latent image-forming core-shell silver halide grains, and a nucleating agent, said emulsion when coated on a transparent film support at a siver coverage of 4 grams per square meter, exposed to a 500 watt tungsten lamp for times ranging from 0.01 to 1 second at a distance of 0.6 meter, developed for 5 minutes at 20.degree. C. in Developer Y below, fixed, washed, and dried, having a maximum density at least five times the maximum density of an identical test portion which has been exposed in the same way and developed for 6 minutes at 20.degree. C. in Developer X below, fixed, washed, and dried:
• ______________________________________ Grams ______________________________________ Developer X N--methyl-p-aminophenol sulfate 2.5 Ascorbic acid 10.0 Potassium metaborate 35.0 Potassium bromide 1.0 Water to 1 liter Developer Y N--methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5 Potassium bromide 5.0 Potassium iodide 0.5 Water to 1 liter. ______________________________________
• the improvement comprising said core-shell silver halide grains in at least one of said emulsion layers being sensitized with at least one of sulfur, selenium, and gold and containing a shell portion incorporating in an amount sufficient to reduce rereversal one or more polyvalent metal ions chosen from the group consisting of manganese, copper, zinc, cadmium, lead, bismuth, and lanthanides.

In a photographic image transfer film unit comprising

• a support,
• at least one emulsion layer located on said support containing a dispersing medium, radiation-sensitive core-shell internal latent image-forming silver halide grains, and a nucleating agent, said emulsion when coated on a transparent film support at a siver coverage of 4 grams per square meter, exposed to a 500 watt tungsten lamp for times ranging from 0.01 to 1 second at a distance of 0.6 meter, developed for 5 minutes at 20.degree. C. in Developer Y below, fixed, washed, and dried, having a maximum density at least five times the maximum density of an identical test portion which has been exposed in the same way and developed for 6 minutes at 20.degree. C. in Developer X below, fixed, washed, and dried:
• ______________________________________ Grams ______________________________________ Developer X N--methyl-p-aminophenol sulfate 2.5 Ascorbic acid 10.0 Potassium metaborate 35.0 Potassium bromide 1.0 Water to 1 liter Developer Y N--methyl-p-aminophenol sulfate 2.0 Sodium sulfite, desiccated 90.0 Hydroquinone 8.0 Sodium carbonate, monohydrate 52.5 Potassium bromide 5.0 Potassium iodide 0.5 Water to 1 liter. ______________________________________
• a dye-image-providing material present in said emulsion layer or a layer adjacent thereto, and
• a receiving layer for providing a viewable transferred dye image following imagewise exposure and processing of said emulsion layer,
• the improvement comprising, said core-shell silver halide grains present in at least one emulsion layer being sensitized with at least one of sulfur, selenium, and gold and containing a shell portion incorporating in an amount sufficient to reduce rereversal one or more polyvalent metal ions chosen from the group consisting of manganese, copper, zinc, cadmium, lead, bismuth, and lanthanides.