Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2002-07-24
2004-06-22
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S567000
Reexamination Certificate
active
06753134
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to the preparation of radiation sensitive high bromide silver halide photographic emulsions, including emulsions useful in electronic printing methods wherein information is recorded in a pixel-by-pixel mode in a radiation sensitive silver halide emulsion layer. It particularly relates to the preparation of the exterior portions of silver halide emulsion grains after formation of a core.
DEFINITION OF TERMS
In referring to grains and emulsions containing two or more halides, the halides are named in order of ascending concentrations.
The term “high bromide” and “high chloride” in referring to silver halide grains and emulsions indicate greater than 50 mole percent bromide or chloride, respectively, based on total silver.
The term “equivalent circular diameter” or “ECD” indicates the diameter of a circle having an area equal to the projected area of a grain or particle.
The term “size” in referring to grains and particles, unless otherwise described, indicates ECD.
The term “regular grain” refers to a silver halide grain that is internally free of stacking faults, which include twin planes and screw dislocations.
The term “cubic grain” is employed to indicate a regular grain is that bounded by six {100} crystal faces. Typically the corners and edges of the grains show some rounding due to ripening, but no identifiable crystal faces other than the six {100} crystal faces. The six {100} crystal faces form three pairs of parallel {100} crystal faces that are equidistantly spaced.
The term “cubical grain” is employed to indicate grains that are at least in part bounded by {100} crystal faces satisfying the relative orientation and spacing of cubic grains. That is, three pairs of parallel {100} crystal faces are equidistantly spaced. Cubical grains include both cubic grains and grains that have one or more additional identifiable crystal faces. For example, tetradecahedral grains having six {100} and eight {111} crystal faces are a common form of cubical grains.
The term “roundness coefficient” (hereinafter assigned the symbol “n”) and the term “roundness index” (hereinafter assigned the symbol “Q”) are measures of the degree to which silver halide grain corners are rounded as defined by Mehta et al. in U.S. Pat. No. 6,048,683. “n” is chosen to satisfy the formula x
n
+y
n
=R
n
, where R is any vector extending from the center of a {100} crystal face of a grain to the projected peripheral edge of the grain viewed normal to the {100} crystal face, x is an X axis coordinate of R, y is a Y axis coordinate of R, and X and Y are mutually perpendicular axes in the plane of the {100} crystal face. For a circle, the roundness coefficient is 2, while for a square the roundness coefficient is increased to infinity. For convenience, roundness index Q is defined as being equal to 2
. Thus, the Q of a square is zero, while that for a circle is 1. The degree to which regular silver halide grains having {100} crystal faces exhibit corner rounding is determined by looking at the projected area of a grain in a photomicrograph viewed normal to a {100} crystal face. The value of n that most closely matches the peripheral boundery of the {100} grain face is the roundness coefficient of the grain. From measurement of a representative number of grains, an average roundness coefficient n and roundness index Q can be determined for an emulsion.
The term “central portion” or “core” in referring to silver halide grains refers to an interior portion of the grain structure that is first precipitated relative to a later precipitated portion.
The term “shell” in referring to silver halide grains refers to an exterior portion of the silver halide grain which is precipitated on a central portion.
The term “dopant” is employed to indicate any material within the rock salt face centered cubic crystal lattice structure of a silver halide grain other than silver ion or halide ion.
The term “dopant band” is employed to indicate the portion of the grain formed during the time that dopant was introduced to the grain during precipitation process.
The term “normalized shell molar addition rate”, hereinafter assigned the symbol R
s
, is a measure of the intensity of rate of addition of silver salt solution to a reaction vessel during formation of a shell. R
s
is defined by the formula:
R
s
=
M
s
M
t
t
s
2
where M
s
is the number of moles of silver halides added to the reaction vessel during the formation of the shell, t
s
is the run time, in minutes, of the silver salt solution for the formation of the shell, and M
t
is total moles of silver halides in the reaction vessel at the end of the precipitation.
The term “log E” is the logarithm of exposure in lux-seconds.
Photographic speed is reported in relative log units and therefore referred to as relative log speed. 1.0 relative log speed unit is equal to 0.01 log E.
The term “contrast” or “&ggr;” is employed to indicate the slope of a line drawn from stated density points on the characteristic curve.
The term “rapid access processing” and “rapid access processor” are employed to indicate the capability of providing dry-to-dry processing in 90 seconds or less. The term “dry-to-dry” is used to indicate the processing cycle that occurs between the time a dry, imagewise exposed element enters a processor to the time it emerges, developed, fixed and dry
Research Disclosure
is published by Kenneth Mason Publications, Ltd., Dudley House, 12 North St., Emsworth, Hampshire P010 7DQ, England.
BACKGROUND OF THE INVENTION
Double-jet precipitation is a common practice in the making of silver halide emulsions. Silver salt solution and halide salt solution are introduced simultaneously, but separately, into a precipitation reactor under mixing. In order to achieve desired crystal characteristics, typically, the silver ion activity or the halide ion activity is controlled during the precipitation by adjusting the feed rates of the salt solutions using either a silver ion sensor or a halide ion sensor.
Formation of silver halide emulsions typically involves a crystal nuclei-forming step wherein addition of silver ion results primarily in the precipitation of new crystal nuclei, and a subsequent double-jet growth step wherein the rate at which silver and halide are introduced is controlled to primarily grow the crystals already previously formed while avoiding the formation of new seed grains, i.e., renucleation. Addition rate control to avoid renucleation, and thereby generally provide for a more monodisperse grain size final grain population, is generally well known in the art, as illustrated by Wilgus German OLS No. 2,107,118; Irie U.S. Pat. No. 3,650,757; Kurz U.S. Pat. No. 3,672,900; Saito U.S. Pat. No. 4,242,445; Teitschied et al European Patent Application 80102242; “Growth Mechanism of AgBr Crystals in Gelatin Solution”, Photographic Science and Engineering, Vol. 21, No. 1, January/February 1977, p. 14, et seq. The term “critical crystal growth rate” is used in the art to describe the growth rate obtained at the maximum rate of silver ion and halide ion addition which does not produce renucleation. While maintaining silver and halide addition rates below that which form new grain populations is advantageous during grain growth in terms of controlling the emulsion grain population characteristics, it also can restrict obtainable emulsion concentrations (i.e., batch yields) and lengthen emulsion manufacturing times.
U.S. Pat. Nos. 5,549,879; 6,043,019; 6,048,683 and 6,265,145 disclose double jet techniques for preparing silver halide grains wherein silver and halide salt solutions are added at a “pulsed flow” rate designed to generate a second grain population (i.e., at a rate above that which would provide for the critical crystal growth rate), with multiple short “pulses” being separated by hold periods designed to allow the new grain population to be ripened out. U.S. Pat
Hasberg Dirk J.
Jones, Jr Ralph W.
Mehta Rajesh V.
Anderson Andrew J.
Le Hoa Van
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