Blended grain direct-positive emulsions and photographic elements and processes for their use
AssigneeEastman Kodak Company
InventorsRobert A. Silverman, Harry A. Hoyen
Life of this patent
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Abstract
Blended emulsions for use in forming a direct-positive image are disclosed. The emulsions are comprised of a first, radiation-sensitive core-shell grain population having a relatively low coefficient of variation and a second, substantially smaller size grain population capable of internally trapping photolytically generated electrons. Photographic elements incorporating the blended emulsions exhibit improved covering power and can exhibit enhanced speed.
Claims35
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.
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.
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.
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.
Dependencies are inferred from the claim text.