Blended grain direct-positive emulsions and photographic elements and processes for their use

Claim 2

A radiation-sensitive emulsion particularly adapted to forming a direct-positive image comprised of a dispersing medium, a first, core-shell silver halide grain population having a coefficient of variation of less than 20%, and a second silver halide grain population capable of internally trapping photolytically generated electrons and substantially incapable of forming a surface latent image within the direct-positive exposure latitude of the first grain population, said second grain population having an average diameter less than 70% that of said first grain population, and said first and second silver halide grain populations being present in a weight ratio of from 5:1 to 1:5.

Claim 3

A radiation-sensitive emulsion according to claim 1 additionally including a nucleating agent incorporated therein.

Claim 4

A radiation-sensitive emulsion according to claim 2 wherein said nucleating agent is chosen from the class consisting of aromatic hydrazide nucleating agents, N-substituted cycloammonium quaternary salt nucleating agents, and mixtures thereof.

Claim 5

A radiation-sensitive emulsion according to claim 2 wherein said nucleating agent is a hydrazide of the formula ##STR25## wherein D is an acyl group; φ is a phenylene or a halo-, alkyl, or alkoxy-substituted phenylene group; and M is a moiety capable of restricting mobility.

Claim 6

A radiation-sensitive emulsion according to claim 1 wherein said first, core-shell grain population is sensitized with at least one of sulfur, selenium, and gold.

Claim 7

A radiation-sensitive emulsion according to claim 1 wherein said first, core-shell grain population contains a divalent or trivalent metal dopant capable of reducing rereversal.

Claim 8

A radiation-sensitive emulsion according to claim 1 wherein said second silver halide grain population is comprised of converted-halide silver halide grains.

Claim 9

A radiation-sensitive emulsion according to claim 1 wherein said second silver halide grain population is comprised of core-shell silver halide grains.

Claim 10

A radiation-sensitive emulsion according to claim 8 wherein said core-shell grains of said second grain population are substantially free of surface chemical sensitization.

Claim 11

A radiation-sensitive emulsion according to claim 8 wherein said core-shell grains of said second grain population are internally chemically sensitized.

Claim 12

A radiation-sensitive emulsion according to claim 1 wherein said second silver halide grain population is internally fogged.

Claim 13

A radiation-sensitive emulsion according to claim 1 wherein at least said core-shell grains of said first grain population are comprised of bromide.

Claim 14

A radiation-sensitive emulsion according to claim 12 wherein said bromide containing silver halide grains are additionally comprised of iodide.

Claim 15

A radiation-sensitive emulsion according to claim 1 wherein said second grain population has an average diameter less than 50% that of said first grain population.

Claim 16

A radiation-sensitive emulsion according to claim 14 wherein said second grain population has an average diameter less than 40% that of said first grain population.

Claim 17

A radiation-sensitive emulsion according to claim 1 wherein said first and second silver halide grain populations are present in a weight ratio of from 2:1 to 1:3.

Claim 18

A radiation-sensitive emulsion according to claim 1 wherein said first, core-shell grain population is comprised of tabular grains.

Claim 19

A radiation-sensitive emulsion according to claim 17 wherein said grains of said first grain population having a thickness of less than 0.5 micron and a diameter greater then 0.6 micron have an average aspect ratio greater than 8:1 and account for greater than 50% of the total projected surface area of said first grain population.

Claim 20

In a direct-positive photographic element comprised of a support and at least one radiation-sensitive emulsion layer, the improvement wherein said emulsion layer is comprised of an emulsion according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18.

Claim 21

Processing in a surface developer an imagewise exposed photographic element according to claim 19 (a) in the presence of a nucleating agent, or (b) with light flashing of the exposed photographic element during processing.

Claim 22

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, core-shell silver halide grains, and a nucleating agent, the improvement comprising, said core-shell silver halide grains in at least one of said emulsion layers being comprised of a first core-shell grain population having a coefficient of variation of less than 20% and chemically sensitized with at least one of sulfur, selenium, and gold, and a second core-shell grain population substantially free of surface chemical sensitization and substantially incapable of forming a surface latent image within the direct-positive exposure latitude of the first grain population, said second grain population having an average diameter less than 40% that of said first grain population, and said first and second grain populations being present in a weight ratio of from 2:1 to 1:3.

Claim 23

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, core-shell silver halide grains, and a nucleating agent, the improvement comprising, said core-shell silver halide grains in at least one of said emulsion layers being comprised of a first core-shell grain population having a coefficient of variation of less than 20% and chemically sensitized with at least one of sulfur, selenium, and gold, and a second core-shell grain population substantially free of surface chemical sensitization and substantially incapable of forming a surface latent image within the direct-positive exposure latitude of the first grain population, said second grain population having an average diameter less than 40% that of said first grain population, and said first and second grain populations being present in a weight ratio of from 2:1 to 1:3.

Claim 24

In a photographic element according to claim 21 the further improvement in which said core-shell grains are comprised of bromide.

Claim 25

In a photographic element according to claim 21 the further improvement in which said second core-shell grain population increases the minimum density of the photographic element to no more than 10% of its maximum density.

Claim 26

In a photographic element according to claim 21 the further improvement in which said first core-shell grain population contains a divalent or trivalent metal ion chosen from the group consisting of cadmium, lead, and erbium in an amount sufficient to reduce rereversal.

Claim 27

In a photographic image transfer film unit comprising a support, at least one emulsion layer located on said support containing a dispersing medium, core-shell silver halide grains, and a nucleating agent, a dye-image-providing material present in said emulsion layer or a layer adjacent thereto, and a receiving layer for providing a viewable transferred dye image following imagewise exposure and processing of said emulsion layer, the improvement comprising, said core-shell silver halide grains in at least one of said emulsion layers being comprised of a first core-shell grain population having a coefficient of variation of less than 20% and chemically sensitized with at least one of sulfur, selenium, and gold, and a second core-shell grain population substantially free of surface chemical sensitization and substantially incapable of forming a surface latent image within the direct-positive exposure latitude of the photographic element, said second grain population having an average diameter less than 40% that of said first grain population, and said first and second grain populations being present in a weight ratio of from 2:1 to 1:3.

Claim 28

In a photographic image transfer film unit comprising a support, at least one emulsion layer located on said support containing a dispersing medium, core-shell silver halide grains, and a nucleating agent, a dye-image-providing material present in said emulsion layer or a layer adjacent thereto, and a receiving layer for providing a viewable transferred dye image following imagewise exposure and processing of said emulsion layer, the improvement comprising, said core-shell silver halide grains in at least one of said emulsion layers being comprised of a first core-shell grain population having a coefficient of variation of less than 20% and chemically sensitized with at least one of sulfur, selenium, and gold, and a second core-shell grain population substantially free of surface chemical sensitization and substantially incapable of forming a surface latent image within the direct-positive exposure latitude of the photographic element, said second grain population having an average diameter less than 40% that of said first grain population, and said first and second grain populations being present in a weight ratio of from 2:1 to 1:3.

Claim 29

In a photographic element according to claim 25 the further improvement in which said core-shell grains are comprised of bromide.

Claim 30

In a photographic element according to claim 25 the further improvement in which said second core-shell grain population increases the minimum density of said emulsion layers to no more than 20% of their maximum density.

Claim 31

In a photographic element according to claim 25 the further improvement in which said first core-shell grain population contains a divalent or trivalent metal ion chosen from the group consisting of cadmium, lead, and erbium in an amount sufficient to reduce rereversal.

Claim 32

In a black-and-white photographic element capable of producing a direct-positive silver image and comprised of a support and, located thereon, at least one emulsion layer comprised of a dispersing medium, core-shell silver halide grains, and a nucleating agent, the improvement comprising, said core-shell silver halide grains in at least one emulsion layer being comprised of a first core-shell grain population having a coefficient of variation of less than 20% and chemically sensitized with at least one of sulfur, selenium, and gold, and a second core-shell grain population capable of internally trapping photolytically generated electrons and substantially incapable of forming a surface latent image within the direct-positive exposure latitude of the photographic element, said second grain population having an average diameter less than 40% that of said first grain population, and said first and second silver halide grain populations being present in a weight ratio of from 2:1 to 1:3.

Claim 33

In a black-and-white photographic element capable of producing a direct-positive silver image and comprised of a support and, located thereon, at least one emulsion layer comprised of a dispersing medium, core-shell silver halide grains, and a nucleating agent, the improvement comprising, said core-shell silver halide grains in at least one emulsion layer being comprised of a first core-shell grain population having a coefficient of variation of less than 20% and chemically sensitized with at least one of sulfur, selenium, and gold, and a second core-shell grain population capable of internally trapping photolytically generated electrons and substantially incapable of forming a surface latent image within the direct-positive exposure latitude of the photographic element, said second grain population having an average diameter less than 40% that of said first grain population, and said first and second silver halide grain populations being present in a weight ratio of from 2:1 to 1:3.

Claim 34

In a photographic element according to claim 29, the further improvement in which said photographic element is capable of producing an image contrast of greater than 8.

Claim 35

In a photographic element according to claim 29, the further improvement in which said first core-shell grain population exhibits a coefficient of variation of less than 10% and said photographic element is capable of producing a contrast of greater than 10.

Claim 36

In a photographic element according to claim 29, the further improvement in which said second core-shell grain population is substantially free of surface chemical sensitization.

Claim 37

In a photographic element according to claim 29, the further improvement in which said core-shell grains are comprised of bromide.

Claim 38

In a photographic element according to claim 29, the further improvement in which said second core-shell grain population increases the minimum density of the photographic element to no more than 5% of its maximum density.

Claim 39

In a photographic element according to claim 29, the further improvement in which said first core-shell grain population contains a divalent or trivalent metal ion chosen from the group consisting of cadmium, lead, and erbium in an amount sufficient to reduce rereversal.