Silver bromide emulsions of narrow grain size distribution and processes for their preparation
AssigneeEastman Kodak Company
InventorAndre G. E. Mignot
Life of this patent
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Abstract
Radiation-sensitive emulsions are disclosed containing tabular silver bromide grains bounded by two substantially parallel square or rectangular crystal faces and having an average aspect ratio of at least 8.5:1. The tabular grains preferably exhibit a coefficient of variation of less than 30. The tabular grains are formed by providing cubic seed grains having an edge length of less than 0.15 micron and ripening the seed grains at a pAg in the range of from 5.0 to 8.0 in the substantial absence of non-halide silver ion complexing agents.
Claims20
A radiation-sensitive emulsion comprised of a dispersing medium and silver bromide grains, wherein tabular silver bromide grains bounded by two substantially parallel square or rectangular major crystal faces and having an average aspect ratio of at least 8.5:1 account for at least 50 percent of the total projected surface area of the silver bromide grains present in the emulsion.
A radiation-sensitive emulsion comprised of a dispersing medium and silver bromide grains, wherein tabular silver bromide grains having a thickness of less than 0.3 micron bounded by (100) crystallographic planes and having two substantially parallel square or rectangular major crystal faces have an average aspect ratio of greater than 10:1, account for at least 70 percent of the projected surface area of the silver bromide grains, and exhibit a coefficient of variation of less than 20.
A radiation-sensitive emulsion comprised of a dispersing medium and silver bromide grains, wherein tabular silver bromide grains having a thickness of less than 0.2 micron bounded by (100) crystallographic planes and having two substantially parallel square or rectangular major crystal faces have an average aspect ratio of greater than 10:1, account for at least 90 percent of the projected surface area of the silver bromide grains, and exhibit a coefficient of variation of less than 20.
In a process of producing a silver bromide emulsion containing tabular silver bromide grains bounded by two substantially parallel square or rectangular major crystal faces comprising
- providing a monodisperse silver bromide emulsion containing cubic seed grains having an edge length of less than 0.15 micron and
- ripening the seed grains to produce tabular grains,
- the improvement comprising
- while maintaining the pAg of the seed grain emulsion in the range of from 5.0 to 8.0, ripening the emulsion in the substantial absence of nonhalide silver ion complexing agents to produce tabular silver bromide grains having an average aspect ratio of at least 8.5:1.
In a process of producing a silver bromide emulsion comprised of a dispersing medium and tabular grains bounded by (100) crystal faces comprising
- providing a monodisperse emulsion containing cubic seed grains and
- ripening the seed grains to produce tabular grains
- the improvement comprising
- precipitating at a pAg of from 6.5 to 7.5, a pH of from 2.0 to 4.5, and a temperature of greater than 20.degree. C. a monodisperse silver bromide emulsion comprised of a dispersing medium and cubic seed grains having an average edge length of less than 0.08 micron, and
- while maintaining the seed grain emulsion at a pAg in the range of from 6.5 to 7.5, a pH in the range of 6.0 to 7.0, and a temperature of from 50.degree. to 70.degree. C., ripening the seed grain emulsion in the absence of silver ion complexing agents other than bromide to produce tabular silver bromide grains having an average aspect ratio of at least 10:1 and a coefficient of variation of less than 20.
Dependencies are inferred from the claim text.