Note: Descriptions are shown in the official language in which they were submitted.
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PHOTOGRAE~IC SILV~ BRO~IODI~E EM~SION~
ELEME~TS A~D PRO~ E~
This invention relates to photographic
silver bromoiodide emulsions, photographic elementE
incorporating these emulsionQ, and proces~es for the
u~e of the photographic elemen~s.
Photographic emulsions useful in photography
typically comprise a dispersing medium, such as
gelatin, containing grains of photographic silver
halide. Emulsion other than silver bromoiodide have
found only limited use in camera speed photographic
elements. Silver bromoiodide emulsions and their
preparation are described in, for example, such
standard texts as Duffin, ~Photographic Emulsion
Chemistry", Focal Presæ, 1966 and Mees and James,
"~he Theory of the Photographic Process", MacMillan
Publishing Co., 4th Edition, 1977.
Photographic silver bromoiodide emul~ions
having variou~ grain sizes and ~hapes are also known
in photography. Illustrative emulsions containing
silver bromoiodide grains are described in, for
example, European Patent Application 330,508 and U.S.
Patents 4,433,048; 4,720,452; 3,505,068 and 4,704,351.
Photographic silver bromoiodide emulsions
that contain octahedral silver bromoiodide grains are
also known, such as de~cribed in U.S. Patents
4,150,994; 4,184,877 and 4,610,958 and published
~apanese Patent Application (~okai) 60-138538
publi~hed July 23, 1985.
Octahedral silver bromoiodide emulsions,
particularly monodispersed emulsions, are known to
have advantages, such as high sensitivity and
improved photographic properties. However, it has
been desirable to provide the following improvements:
(a) improved photographic speed and (b) decreased
granularity.
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It has been found that such requirements are
satisfied by a photographic silver bromoiodide
emulsion comprising a dispersing medium and silver
bromoiodide that (a) is octahedral silver
bromoiodide; (b) has a grain size within the range of
0.45 to 1.2 microns; (c) contains 1 to 12 mole
percent iodide; (d) has a core region (A), a surface
region (B) and a subsurface region (C) between core
region (A) and surface region (B); wherein (i)
subsurface region (C) contains an iodide
concentration higher than the iodide concentration of
core region (A); and, (e) the silver bromoiodide is
prepared by a process comprising, in sequence, (I) a
nucleation step comprising mixing bromide salts and
~ilver salts in a reaction medium; then, (II) a
crystal growth step under pBr conditions within the
range of 1.75 to 4.2 pBr, typically 2.0 to 2.8 pBr,
enabling formation of core region (A) comprising 50%
to 90% by weight of the silver bromoiodide; then,
(III) addition to the composition from step (II) of
iodide salt in which 25 to 100 mole percent of the
total iodide salt is added to the composition from
step (II) within a time period of 1 second to 20
minutes, such as, 1 second to 5 minutes; then, (IV)
holding the reaction mixture from step (III) for a
time period, such as 0.5 second to 20 minutes, that
aids in formation of subsurface (C); then, (V)
addition of silver salts and bromide to the reaction
mixture from step (IV) until reaction completion
forming surface region (B). The step (III) is
described herein as a "dump iodide step". The method
steps as described enable the formation of a higher
concentration of crystal defects in the silver
bromoiodide than would otherwise be expected. This
higher concentration of crystal defects is believed
to contribute to the unexpectedly higher photographic
2~2~7~
speed of the resulting octahedral silver bromoiodide
as described.
Another aepect of the invention is a
photographic element,`particularly a color
photographic element, comprised of a support bearing
at least one photographic silver bromoiodide emulsion
layer as described herein.
A further aspect of the invention i8 a
method of preparing the described silver bromoiodide
emulsion including the steps of the process
comprising, in sequence, (I) a nucleation step
comprising mixing bromide salts, particularly alkali
metal bromide salts, and silver salts, particularly
silver nitrate, in a reaction medium, such as an
aqueous gelatin reaction medium; then, (II) a crystal
growth step under pBr conditions within the range of
1.75 to 4.2 pBr, preferably within the range of Z.0
to 2.8 pBr, enabling formation of de~cribed core
region (A) comprising 50% to 90% by weight of the
silver bromoiodide; then, (III) addition to the
composition from step (II) of iodide salt in which 25
to 100 mole percent, preferably 50 to lO0 mole
percent, of the total iodide salt is added to the
composition from step (II) within a time period, such
as within a time period of 1 second to 20 minutes,
such as l second to 5 minutes, that enables formation
of subsurface region (C); then, (IV) holding the
reaction mixture from step (III) until the iodide
salt dissolves and reacts, ~uch as for a time period
within the range of 2 to 5 minutes; then, (V)
addition of silver salts, such as silv0r nitrate, to
the reaction mixture from step (IV) until reaction
completion forming surface region (B). The
octahedral silver bromoiodide grains that result from
the described process are preferably monodispersed
grains having a grain size within the range of 0.6 to
1 micron.
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A further aspect of the invention is
directed to forming a visible photographic image,
particularly a color photographic image, by a process
comprising processing an exposed photographic
element, as described, herein in an aqueous alkaline
solution in the presence of a photographic developing
agent, particularly a color photographic silver
halide developing agent.
The described invention enables unique and
unexpected advantages. The described photographic
emulsion, element and process enable the improvement
of photographic speed and reduced granularity without
sacrificing the advantages of an octahedral silver
bromoiodide emulsion. The de~cribed emulsions are
particularly advantageous when chemically sensitized
and spectrally sensitized and in color photographic
materials designed to form dye images. The described
emulsions, elements and processes enable
significantly improved photographic speed for color
images, especially images that have particularly
useful sharpness and speed-grain relationship.
The term octahedral herein includes
octahedral and such grains that do not include sharp
edges, such as cubooctahedral grains.
The term core region (A) herein means the
central portion of the octahedral silver bromoiodide
grain according to the invention. This region (A)
can contain 0 to 9 mole percent iodide. It comprises
50% to 90%, typically 60% to 80% by weight of the
total silver bromoiodide grain.
The term surface region (B) herein means the
outer region of the octahedral silver bromoiodide
beyond sub8urface region (C). This region (B) can
contain 0 to 9 mole percent iodide. This typically
comprises 10% to 40% by weight of the total silver
bromoiodide grain.
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The term subsurface region (C) herein means
the region of the silver bromoiodide grain according
to the invention between the core region (A) and the
surface region (B) as described. The subsurface
region ~C> typically comprises 1% to 20% by weight of
the total silver bromoiodide grain. The interfaces
between the region~ (A), (B~ and (C) as described are
typically not sharply defined in the silver
bromoiodide grain according to the invention. Each
of the regions (A), (B~ and (C~ may, but typically do
not, comprise multiple regions within each of the
described regions, that is each region does not
typically comprise multiple shells.
In the process as described necessary
bromide can be added before or after the described
dump iodide step.
The step (IV~ can be essentially eliminated
or extended depending on the emulsion making
equipment capability. Preferably, the hold step (IV~
is present and is typically carried out within a
period of about 2 minutes to 10 minutes.
In the process of preparation of the silver
bromoiodide emulsion it is preferred to carry out a
finishing step as known in the photographic art.
This flnishing step is preferably carried out using
at least one spectral sensitizing dye as part of the
finishing step. Any spectral sensitizing dye known
to be useful in a finishing step can be used for this
purpose. In addition it is preferable to u~e a
finishing modifier known in the photographic art in
the finishing step, such as a benzothiazolium finish
modifier. Such a finishing step using at least one
spectral sensitizing dye and a finish modifier, such
as a benzothiazolium compound, enables the resulting
photographic silver bromoiodide emulsion of the
invention to have even higher photographic speed than
otherwise would be expected.
7 ~`
The term monodisper~ed herein means that at
least 95%, such as 95% to 99.9%, by weight of the
silver bromoiodide grains less than the mean grain
diameter and at least 95%, such as 95% to 99.9%, by
number of the silver bromoiodide grains larger than
than the mean grain diameter must be within 40% of
the mean grain diameter. The mean grain diameter
means the diameter of a circle equal in area to the
mean projected area of the ~ilver bromoiodide grains,
especially as viewed in a photomicrograph or an
electronmicrograph of an emulsion sample.
The octahedral silver bromoiodide grains as
described may have rounded corners and rounded edges.
The grain size and characteristics of the
silver bromoiodide grains as described can be readily
ascertained by procedures well known in the
photographic art. In some inst~nces a concentration
of silver halide grains that are not octahedral
silver bromoiodide grains can be present in the
emulsion and element of the invention without
adversely affecting the required properties of the
silver bromoiodide emulsion of the invention.
The silver bromoiodide emulsion of the
invention i8 prepared by controlling the introduction
of the iodide salts in the precipitation process.
The iodide is added in the process within a
reasonably short time and can be termed a ~dump
iodide process" because the iodide is not run into
the reaction mixture over the entire term of the
precipitation. The described step (III) is a ~dump
iodide step~.
In the process of preparing the ~ilver
bromoiodide emulsion as described typically a
dispersing medium, preferably an aqueous gelatin or
gelatin derivative composition, is introduced into a
conventional reaction vessel designed for silver
7 ~
halide precipitation equipped with an ef~icient
stirring mechanism. The volume of di8persing medium
initially present in the reaction vessel can equal or
exceed the volume of the silver bromoiodide emul~ion
present in the reaction at the conclusion of the
grain precipitation. The dispersing medium
introduced into the reaction vessel is preferably a
dispersion of peptizer in water, particularly gelatin
in water, optionally containing other ingredients,
suCh as silver halide ripening agents and/or metal
dopants. The peptizer, particularly gelatin or a
gelatin derivative, is typically initially present in
a concentration of at least 0.5%, preferably at least
1%, of the total peptizer present at the completion
of the silver bromoiodide precipitation. Additional
dispersing medium can optionally be added to the
reaction vessel with the silver salts and the alkali
metal bromide and iodide salts and also can be
introduced through a separate inlet means, such as a
separate jet. The proportion of dispersing medium
can be adjusted after the completion of the salt
introductions or after washing.
During precipitation silver salts,
preferably silver nitrate, bromide salts, preferably
alkali metal bromide salts, and iodide salts,
preferably alkali metal bromide salts, are added to
the reaction vessel by techniques known in the
photographic emulsion making art. Typically an
aqueous silver salt solution, preferably an aqueous
silver nitrate solution, is introduced into the
reaction vessel concurrently with the introduction of
bromide alone or bromide and iodide salts. The
bromide and iodide salts are typically introduced as
aqueous solutions, preferably as aqueous solutions of
one or more alkali metal, such as potassium or sodium
salts. Alkaline earth metal salts can also be
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useful, such as calcium and magnesium salts. The
silver salt is introduced into the reaction vessel
separately from the halide salt. The iodide and
bromide salts can be added to the reaction vessel
separately or as a mixture.
With the introduction of the silver salts
into the reaction vessel the nucleation step of the
grain formation is initiated. A population of grain
nuclei are formed that are capable of serving as
precipitation sites for silver bromide and silver
iodide as the introduction of silver, bromide and
iodide salts continues. The precipitation of the
silver bromide and silver iodide onto the exi~ting
grain nuclei constitutes the crystal growth step of
grain formation. The permis~ible latitude of pBr
during the growth stage of the precipitation is
within the range of 1.75 to 4.2 pBr, preferably
within the range of 2.0 to 2.~ pBr. The pBr can be
measured and regulated during the precipitation by
methods and apparatus known in the photographic art.
The pBr is as defined in U.S. Patent 4,434,226 and is
the negative logarithm of bromide ion concentration.
Subject to requirements of the process as
described the concentrations and rates of silver
8alt, bromide 8alt and lodide salt introductions can
take any convenient and conventional form useful for
forming octahedral silver bromoiodide emulsions. The
silver and halide salts are preferably introduced in
concentrations within the range of 0.1 to 5 moles per
liter. The rate of silver and halide salt
introduction can be constant or optionally increased
either by increasing the rate at which the silver and
halide salt are introduced or by increasing the
concentrations of the silver and halide salts being
introduced. It i8 preferred to increase the rate of
silver and halide salt introduction, but to maintain
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the rate of introduction below that at which the
formation of new grain nuclel i8 favored to avoid
renucleation. The concentration of iodide in each
step i8 important to enable the higher concentration
of iodide in subsurface region ~C) as described.
The process can be carried out within
controlled pAg conditions using methods and apparatus
known in the photographic art. U~ing measuring
techniques, electrodes and conditions known in the
photographic art the vAg is, for example, controlled
within the range of +5 to +160 mV, preferably within
the range of +20 to +80 mV.
The process of preparing the described
silver bromoiodide is preferably carried out at a
temperature within the range of 25C to 80C, such as
45C.
Modifying compounds can be present during
the silver bromoiodide precipitation. Such compounds
can be initially in the reaction vessel or can be
added with one or more of the salts according to
conventional emulsion making procedures. Modifying
compounds, such as compounds of copper, lridium,
thallium, lead, bismuth, cadmium, zinc, middle
chalcogens, such as sulfur, selenium and tellurium,
gold, Group VIII noble metals, can be present during
the precipitation, a~ described in, for example, U.S.
Patent 4,433,048 and the art described therein.
The individual silver and halide salts or a
silver halide source, such as silver iodide seed~,
can be added to the reaction vessel through surface
or subsurface delivery tubes, by gravity feed or
delivery apparatus for maintaining control of the
rate of delivery and the p~, pBr, and/or pAg or the
reaction vessel contents as is used in the art of
photographic emulsion making.
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In forming the silver bromoiodide emulsions,
a dispersing medium preferably comprises in the
reaction vessel initially an aqueous peptizer
suspension. The peptizer concentration is typically
within the range of 0.2% to 10% by weight, based on
the total weight of the emulsion components in the
reaction vessel. Typically the concentration of
peptizer in the reaction vessel is maintained below
about 6%, based on the total weight, prior to and
during silver halide formation. The emulsion vehicle
concentration is typically adjusted upwardly for
optimum coating characteristics by delayed,
supplemental vehicle additions. Additional vehicle
can be added later to bring the concentration up to
as high as 1000 grams per mole of silver halide.
Preferably the concentration of vehicle in the
finished emulsion is above 50 grams per mole of
silver halide. When coated and dried on a support
forming a photographic element, the vehicle
preferably comprises about 30% to about 70% by weight
of the emulsion layer.
Vehicles, including both binders and
peptizers, can be selected from those conventionally
employed in photographic silver halide emulsions.
Preferred peptizers are hydrophilic colloids, that
can be used alone or in combination with hydrophobic
materials. Useful hydrophilic materials include both
naturally occurring substances, such as proteins,
protein derivatives, cellulose derivatives, such as
cellulose esters, gelatin, such as alkali treated
gelatin or acid treated gelatin, gelatin derivatives,
such as acetylated gelatin and phthalated gelatin,
polysaccharides, such as dextran, gum arabic, zein,
casein, pectin, collagen derivatives, agar-agar,
arrowroot and albumin and other vehicles and binders
known in the photographic art. Gelatin is highly
preferred.
2 ~ ?s)~
Other materials commonly used in combination
with hydrophilic colloid peptizers as vehicles,
including, for example, vehicle extenders such as
materials in the form of latices, are al~o useful in
the emulsions of the invention, such as polymeric
peptizers, carriers and/or binders, such as
poly(vinyl lactams), acrylamide polymers, poly(vinyl
alcohol) and its derivatives, poly(vinyl acetals),
polymers of alkyl and sulfoalkyl acrylates and
methacrylates, hydrolyzed poly(vinyl acetate~),
polyamides, poly(vinyl pyridine), acrylic acid
polymers, maleic acid copolymers, vinyl amine
copolymers, methacrylic acid copolymers,
acryloyloxyalkylsulfonic acid copolymers,
sulfoacrylamide copolymers, polyalkyleneimine
copolymers, polyamines, N,N-dialkylaminoalkyl
acrylates, vinyl imidazole polymers and copol~mers,
vinyl sulfide copolymers, halogenated styrene
polymers, amineacrylamide polymers, polypeptides and
other vehicles and binders known to be useful in the
photographic art, such as described in U.S. Patent
4,433,048.
These added materials need not be present in
the reaction vessel during the silver halide
precipitation, but rather can typically be added to
the emulsion prior to coating on the support. The
vehicles and binders, including the hydrophilic
colloids, as well as the hydrophobic materials, can
be employed alone or in combination, not only in the
emulsion layers of the photographic element, but also
can be used alone or in combination in other layers,
such as overcoat layers, interlayers, and layers
positioned between emulsion layers and the support.
Grain ripening can be carried out in
preparation of an emulsion according to the
invention. Grain ripening agents known to be useful
J ~3~ r~
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in the photographic art can be useful in the
photographic emulsions of the invention. For
example, a thioether ripening agent can be added to
the photographic silver bromoiodide emulsion. Useful
thioether ripening agents include, for example, those
described in U.S. Patents 3,271,157; 3,574,628; and
3,737,313.
The silver bromoiodide emulsions are
preferably washed to remove soluble salts. Any of
the proce~se3 and compositions known in the
photographic art for this purpose can useful for
washing the photographic silver bromoiodide emulsions
of the invention. The soluble æalts can be removed
by decantation, filtration, and/or chill setting and
leaching, coagulation washing, by centrifugation, and
by other methods and means known in the photographic
art.
If desired, the silver bromoiodide emulsion
of the invention can be blended or otherwise combined
with other photographic silver halide emulsions. The
photographic silver bromoiodide emulsions of the
invention can be, for example, optionally combined
with a tabular grain silver halide emulsion, such as
one described in U.S. Patent 4,433,048, or optionally
combined with a cubic grain silver halide emulsion,
such as one described in European Patent Application
No. 353,628.
The photographic silver bromoiodide can be
chemically sensitized by procedures and by compounds
known in the photographic art to be useful for this
purpose. For example, the silver bromoiodide can be
chemically sensitized with active gelatin, or with
sulfur, selenium, tellurium, gold, platinum,
palladium, iridium, osmium, rhodium, rhenium, or
phosphorous sensitizers or combinations of these
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sensitizers, such as at pAg levels within the range
of 90 to 120 mV and pH levels within the range of 5
to 8 at temperatures within the range of 300 to
800C. The silver bromoiodide can be chemically
sensitized in the presence of finish, al~o ~nown as
chemical sensitization, modifiers, such as compounds
known to suppress fog and increase speed during
chemical sensitization, such as azaindenes,
azapyridazines, azapyrimidines, benzothiazolium
salts, and sensitizers having more than one
heterocyclic nuclei. Optionally the silver
bromoiodide can be reduction sensitized, such as with
hydrogen, or through the use of reducing agents, such
as stannous chloride, thiourea dioxide, polyamines or
amineboranes.
The photographic silver bromoiodide emulsion
can be spectrally sensitized by methods and compounds
known in the photographic art. The silver halide
emulsion can be sensitized in the presence of
sensitizing dyes. The photographic silver
bromoiodide emulsion can be spectrally sensitized by,
for example, dyes of a variety of classes, including
the polymethine sensitizing dye class, including
cyanines, merocyanines, complex cyanines and
merocyanines, oxonols, hemioxonols, styryls,
merostyryls and streptocyanines. Combinations of
spectral sensitizers are also useful.
The photographic silver bromoiodide
emulsions of the invention can be used in ways, in
photographic element formats and for purposes that
silver bromoiodide emulsions have been used in the
photographic art.
Photographic silver halide elements
comprising a photographic silver bromoiodide emulsion
as described can be either single color or multicolor
element~. In a multicolor element, a cyan
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dye-forming coupler is typically associated with a
red-sensitive emulsion, a magenta dye-forming coupler
is typically associated with a green-sensitive
emulsion and a yellow dye-forming coupler i8
associated with a blue-sensitive emulsion.
Multicolor elements typically contain dye-forming
units sensitive to each of the three primary regions
of the spectrum. Each unit can comprise a single
emulsion layer or multiple emulsion layers. The
layers of the element and the image-forming units can
be arranged in various orders as known in the
photographic art.
The photographic element can contain added
layers, such as filter layers, interlayers, overcoat
layer8, 8ubbing layers and other layers known in the
photographic art.
The $ollowing discussion of illustrative
materials that are useful in elements of the
invention reference will be made to Research
Disclosure, December 1978, Item No. 17643, published
by Kenneth Mason Publications Ltd., Dudley Annex, 21a
North Street, Emsworth, ~ampshire P010 7DQ, England.
The publication will be identified hereafter by the
term "Research Disclosure~'.
Silver hallde emulsions that can be employed
in combination with the silver bromoiodide emulsion
of the invention can be comprised of silver bromide,
silver chloride, silver iodide, silver chloroiodide,
silver chlorobromide or mixtures thereof. These
silver halide emulsions can include silver halide
grains of any conventional shape or size.
Specifically the emulsions can be coarse, medium or
fine grain. Tabular grain silver halide emulsions
are particularly useful in a photographic element as
described. The silver halide emulsions that are
7 ~
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useful with the silver bromoiodide emulsions of the
invention can be polydisperse or monodisperse as
precipitated. The grain size distribution of these
emulsions can be controlled by silver halide grain
separation techniques or by blending silver halide
emulsions of differing grain sizes. For example,
silver bromoiodide or silver bromides of different
sizes of the same type and shape can be blended.
Any coupler known in the photographic art
can be used with the silver bromoiodide emulsions as
described. Examples of useful couplers are de~cribed
in, for example, Research Disclosure Section VII,
paragraphs D, E, F, and G and in U.S. Patent
4,433,048 and the publications cited therein, as well
as in U.S. Patents 4,333,999; 4,443,536; 4,420,55~;
4,401,752; 4,777,121; 4,728,598; 4,753,871;
4,782,012; 4,477,563; 4,248,962; 4,409,323 and
European Patent Applications 284,239; 271,323;
271,324; 285,274; 193,389; 255,085 and 284,240.
Polymeric couplers are also useful with the described
silver bromoiodide e~ulsions, as described in, for
example, U.S. Patents 4,804,620; 4,540,654; and
4,576,910. The couplers can be incorporated as
described in Research Disclosure Section VII and the
publications cited therein.
The photographic emulsions and elements can
contain addenda known to be useful in the
photographic art. The photographic emul~ions and
elements can contain brighteners (Research Disclosure
Section V), antifoggants and stabilizers (Research
Disclosure Section VI), antistain agents and image
dye stabilizers (Research Disclosure Section VII,
paragraphs I and J), light absorbing and scattering
materials (Research Disclosure Section VIII),
hardeners (Research Disclosure Section XI),
plasticizers and lubricants (Research Disclosure
,
~ ~ ) J ~ ?7 D~
-16-
Section XII), antistatic agents (Research Disclosure
Section XIII), matting agents (Research Disclosure
Section XVI) and development modifiers (Research
Disclosure Section XXI).
The photographic emulsions can be coated on
a variety of supports as described in, for example,
Research Disclosure Section XVII and the references
cited therein.
The photographic elements as described can
be exposed to actinic radiation, typically in the
visible region of the spectrum, to form a latent
image a~ described in Research Disclosure Section
XVII and then processed to form a visible image using
proce~ses and compositions known in the photographic
art, such as described in Research Disclosure Section
XIX and U.S. Patent 4,433,048 and the references
described therein.
Processing of a color photographic element
as described to form a visible dye image includes the
step of contacting the element with a color
photographic silver halide developing agent to reduce
developable silver halide and oxidize the color
developing agent. Oxidized color developing agent in
turn reacts with at least one coupler to yield a dye.
Preferred color developing agents are
p-phenylenediamines. ~specially preferred are
4-amino-3-methyl-N,N-diethylaniline hydrochloride;
4-amino-3-methyl-N-ethyl-N-~-(methanesulfonamido)-
ethylaniline sulfate hydrate; 4 amino-3-methyl-N-
ethyl-N-~-hydroxyethylaniline sulfate;
4-amino-3-~-(methanesulfonamido)ethyl-N,N-diethyl-
aniline hydrochloride and 4-amino-N-ethyl-N-
(2-methoxyethyl)-m-toluidine di-p-toluene sulfonic
acid.
2 Q ~
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With the negative working silver bromoiodide
emulsion of the invention this processing step leads
to a negative image. To obtain a positive image (or
reversal image), this step can be preceded by
development with a non-chromogenic developing agent
to develop exposed silver halide, but not form dye,
and then uniform fogging of the element to render
unexposed silver halide developable.
Development is followed by conventional
steps of bleaching, fixing, or bleach-fixing, to
remove silver and silver halide, washing and drying.
Improvements in sharpness can be obtained
with a photographic silver bromoiodide emulsion and
element as described, a photographic silver halide
development inhibitor releasing compound or coupler
(DIR compound or DIAR compound). Any development
inhibitor releasing compound or coupler known in the
photographic art is useful with the photographic
silver bromoiodide emulsion and element of the
invention. Particularly useful development inhibitor
releasing compounds or couplers are represented by
the formula: CAR-TIME-INH wherein CAR is a carrier
moiety, preferably a coupler moiety; TIME is at least
one timing group; and IMH is a development inhibitor
moiety.
The ~IR compounds that satisfy the formula
CAR-TIME-INH are known in the art and are described
in, for example, U.S. Patents 4,248,962; 4,409,323;
4,684,604; 4,737,451; 4,546,073; 4,564,587;
4,618,571; 4,698,297; 4,782,012; and U.K Patent
2,099,167 and European Published Patent Applications
167,168 and 255,085 and German OLS 3,307,506.
The carrier moiety (CAR) can be any moiety
that, as a result of reaction with oxidized color
2~2~7 .~J
-18-
developing agent, will release the timing group
(TIME). Preferably the carrier i8 a coupler, but it
can be another group, such as a hydrazide, a
hydrazine or hydroquinone. Coupler moieties can be
colored or colorless, diffu~ible or nondiffusible,
reaction product with oxidized color developing agent.
When the carrier moiety i~ a coupler moiety,
the DIR compounds are DIR couplers represented by the
formula: COUP-TIME-INH wherein COUP iB a coupler
moiety.
Preferred timing groups are described in
U.S. Patents 4,248,962; 4,409,323; 4,7~2,012 and
European Patent Application 255,085.
The development inhibitor that is released
from the DIR compound or coupler during processin~ of
the element can be any of the development inhibitors
known in the photographic art. Illu~trative INH
moieties are mercaptotetrazoles, selenotetrazoles,
mercaptobenzolthiazoles, selenobenzothiazoles,
selenobenzimidazoleæ, mercaptobenzimidazoles,
mercaptobenzoxazoles, selenobenzoxazoles,
benzotriazoles, and benzodiazoles. Particularly
preferred are those described in U.S. Patents
4,477,563 and 4,782,012.
The following examples further illustrate
the invention.
~xample 1:
A series of 4 monodisperse silver
bromoiodide octahedral grain emulsions all containing
a total of 3 mole percent iodide were prepared. The
emulsions differed in the placement and method of
introduction of the iodide. Emulsions A and B are
comparison emulsions and emulsions C and D are
examples of the invention.
-
?J ~
-19-
E~amp.le.s.:
Emulsion A - (Iodide introduced uniformly throughout
the precipitation)
A monodisperse, octahedral grain, silver
bromoiodide (3Mr/o I) emulsion having a grain size of
0.8 micron was prepared in the following manner:
Eight ~olutions were prepared as follows:
Solution lA: (Placed in the reaction ve~sel)
Deionized Gelatin 36 g
Distilled Water 4000 ml
Dissolved at 800C
Solution 2A:
Sodium Bromide 14.8 g
Potassium Iodide 0.4 g
Distilled Water to 280 ml
Dissolved at room temperature
Solution 3A:
Sodium Bromide 898.2 g
Potassium Iodide 44.8 g
Distilled Water to4500 ml
Dissolved at room temperature
Solution 4A:
Silver Nitrate (5M solution) 37.8 g
Distilled Water to 225 ml
2 ~
-20-
Solution 5A:
Silver Nitrate (5M solution) 2138 g
DiQtilled Water to 3181 ml
Solution 6A:
Silver Nitrate (5M solution) 537.6 g
Distilled Water to 800 ml
Solution 7A:
Gelatin 150 g
Distilled Water 800 ml
Dissolved at 80OC
Solution 8A:
Gelatin 294 g
Distilled Water 1600 ml
Dissol~ed at 40C
To Solution lA, at 80C, were added 0.018 g
of l,10-dithio-4,7,13,16-tetraoxacyclooctadecane
dissolved in 36 ml of methanol and distilled water
(1:1~. The pH of the contents of the reaction vessel
was determined to be 5.22, and the pBr was adjusted
to 2.8 using a lM sodium bromide solution. Solutions
2A and 4A were then simultaneously run into Solution
3~ lA, with continuous agitation, for 5 minutes using a
balanced double jet technique at a flow rate of 15 ml
per minute, while maintaining the pBr at 2.8 and the
temperature at 80C. At this point Solution 7A was
added and the resulting composition was held for 5
minutes. At 2 l/2 minutes into the hold the pBr was
adjusted to 2.2 with Solution 3A. After the
9 r3 ~ ~1
completion of the hold, the precipitation was
continued by simultaneously adding Solutions 3A and
SA using an accelerated flow balanced double jet
technique according to the following profile: 15
minutes at 25 ml per minute, 10 minutes at 35 ml per
minute, 10 minutes at 65 ml per minute, 10 minutés at
105 ml per minute, then 155 ml per minute, until
Solution 5A was exhausted, while maintaining the pBr
at 2.2 and temperature at 80C. At this point the
pump supplying Solution 5A was switched to Solution
6A and the pump supplying Solution 3A was switched
off until the pBr was adjusted to 2.5. At this point
the salt 8upply pump was switched on and Solutions 3A
and 6A were simultaneously added at a rate of 35 ml
per minute until Solution 6A was exhausted. The
resulting emul~ion waæ then cooled to 40C and washed
using by diafiltration, with a semipermeable membrane
to a pBr of 3.4. Solution 8A was then added and the
p~ and pBr were adjusted to 5.6 and 3.4 respectively.
~u18 ion B - (All of the iodide was introduced
uniformly throughout the first 80% of
the precipitation, followed by only
bromide for the last 20%)
Nine solutions were prepared as follows:
Solution lB: (Placed in the reaction vessel)
Deionized Gelatin 36 g
Distilled Water 4000 ml
Dissolved at 80C
2~7~
-22-
Solution 2B:
Sodium Bromide 14.8 g
Potassium Iodide 0.4 g
Distilled Water to 280 ml
Dissolved at room temperature
Solution 3B:
Sodium Bromide 672.3 g
Potassium Iodide 42.3 g
Distilled Water to3394 ml
Dissolved at room temperature
Solution 4B:
Sodium Bromide 257.3 g
Distilled Water to1250 ml
Dissolved at room temperature
Solution 5B:
Silver Nitrate (5M solution) 12.6 g
Distilled Water to 75 ml
Solution 6B:
Silver Nitrate (5M solution) 2138 g
Distilled Water to3181 ml
Solution 7B:
Silver Nitrate (5M solution) 537.6 g
Distilled Water to 800 ml
,~a~.s~
-23-
Solutlon 8B:
Gelatin 150 g
Di~tilled Water 800 ml
Dissolved at 80C
Solution 9B:
Gelatin 294 g
Distilled Water 1600 ml
Dissolved at 400C
To Solution lB, at 800C, were added 0.018 g
of l,10-dithio-4,7,13,16-tetraoxacyclooctadecane
dissolved in 36 ml of methanol and distilled water
(1:1). The pH of the contents of the reaction vessel
was determined to be 5.17, and the pBr was adjusted
to 2.8 using a lM solution of sodium bromide.
Solutions 2B and 5B were then simultaneously run into
Solution lB, with continuous agitation, for 5 minutes
using a balanced double jet technique at a flow rate
of 15 ml per minute, while maintaining the pBr at 2.8
and the temperature at 80C. At this point Solution
8B was added and the resulting composition was held
for 5 minutes. At 2 1/2 minutes into the hold the
pBr was adjusted to 2.2 with Solution 3B. Solutions
3B and 6B were then simultaneously run into the
reaction vessel using the same flow profile de~cribed
above in Emulsion A while maintaining the pBr at 2.2
until Solution 6B was exhausted. Solution 7B was
then added until the pBr reached 2.5. Solutions 4B
and 7B were then simultaneously introduced over a
period of 85.4 minutes using the same flow profile
described in Emulsion A above while maintaining a
pBr of 2.5. The resulting emulsion was then cooled
to 40C and washed by diafiltration, with a
semipermeable membrane, to a pBr of 3.5. Solution 9B
was then added and the pH and pBr were adjusted to
~ i3 ~
--24--
5.6 and 3.4, respectively. The resulting emulsion
had a grain 9ize of 0.7 micron.
~mulsion C - (All of the iodide was introduced at
one finite time during the
precipitation)
Ten solutions were prepared as follows:
Solution lC: (Placed in the reaction vessel~
Deionized Gelatin 40 g
Distilled Water 4000 ml
Dissolved at 800C
Solution 2C:
Sodium Bromide 51 g
Distilled Water to2000 ml
Dissolved at room temperature
Solution 3C:
Sodium Bromide 611.8 g
Distilled Water to2400 ml
Dissolved at 40C
Solution 4C:
Sodium Bromide 191.2 g
Potassium Iodide 3.3 g
Distilled Water to 500 ml
Dissolved at 40C
3S
2~ '3 7~,?
Solution 5C:
Silver Nitrate (5M solution) 145.2 g
Distilled Water to 17.28 ml
Dissolved at room temperature
Solution 6C:
Silver Nitrate (5M solution) 1868 g
Distilled Water to 2224 ml
Dissolved at room temperature
Solution 7C:
Silver Nitrate (5M solution) 941 g
Distilled Water to 1120 ml
Di~solved at room temperature
Solution 8C:
Preformed Silver Iodide492 g (0.22 mole)
emulsion grains having a
grain size of 0.05 micron
Dissolved at 40C
Solution 9C:
Gelatin 200 g
Distilled Water 800 ml
Dissolved at 800C
Solution lOC:
Gelatin 240 g
Distilled Water 1600 ml
Dissolved at 40C
-26-
The p~ of the reaction vessel was determined
to be 5.82, and the pBr was adjusted to 2.8 using a
lM solution of sodium bromide. Solutions 2C and 5C
were then simultaneously run into Solution lA in the
reaction vessel, with constant agitation. The
addition was performed over a 5-minute period, using
a balanced double jet technique at a flow rate of
24 ml per minute while maintainin~ the pBr at 2.8 and
the temperature at 800C. The precipitation was then
stopped and Solution 9C was added and the reaction
vessel and the resulting composition was held for 5
minutes. At 2 1/2 minutes into the hold the pBr was
adjusted to 2.2 with Solution 2C. After completion
of the hold, the precipitation was continued by
simultaneously Solutions 2C and 5C using an
accelerated flow balanced double jet technique at
flow rates of 24 ml per minute for 1 minute and
690 ml per minute until Solution 5C wa~ exhausted.
Solutions 3C and 6C were then introduced using flow
rates of 24 ml per minute for 10 minutes, 40 ml per
minute for 10 minutes, 65 ml per minute for 10
minutes, 105 ml per minute for 10 minutes and 155 ml
per minute until Solution 6C was exhausted while
maintaining a pBr of 2.2. Solution 4C was then
dumped into the reaction vessel and the resulting
composition was held for 2 minutes, at which time
Solution 8C was dumped into the reaction vessel and
the composition was again held for 2 minutes.
Solution 7C was then introduced at a flow rate of
77 ml per minute for 10 minutes, then 33 ml per
minute until a pBr of 2.5 was reached. The emulsion
was then cooled to 40C and washed U8 ing by
diafiltration, with a semipermeable membrane to a pBr
of 3.5. Solution lOC was then added and the p~ and
pBr were adjusted to 5.6 and 3.4 respectively. The
emulsion had a grain size of 0.7 micron.
2 ~ 7 9
-27-
~mulsion ~ - (The introduction of the iodide was
partly accompli8hed in a uniform manner
during the run phase of the
precipitation and partly during a
finite time in the precipitation)
The emulsion was prepared using the same
procedure described above for Emulsion C with the
following differences in composition of the solution~:
Solution 2D:
As Solution 2C plus 1.4 g Potassium Iodide
Solution 3D:
As Solution 3C plu8 16.5 g Potassium Iodide
Solution 8D:
As Solution 8C except only 0.12 moles of the
preformed silver iodide emulsion.
The emulsion had a grain size of 0.6 micron.
The series of monodisperse octahedral grain
silver bromoiodide emulsions described above were
spectrally sensitized to the red region of the
visible spectrum then optimally sulfur and gold
chemically sensitized in the presence of sodium
thiocyanate and the finish modifier N-~N-(methyl-
sulfonyl)carbamoylethyl]benzothiazoliumtetra-
fluoroborate. The emulsions were separately coated
in a single-layer cyan dye-forming format on a
cellulose triacetate film support. Each of the
coated elements comprised the respective emulsion at
2 ~
0.8 g Ag/m2, gelatin at 3.2 g/m2, a solvent
dispersion of the cyan dye image-forming coupler
(Coupler A) at .97 g/m2 and the DIR coupler
(Coupler B) at 0.03 g/m2. An overcoat layer
comprising gelatin at 4.3 g/m2 and the hardener
bi6(vinylsulfonylmethyl)ether at 1.75% based on the
total gelatin weight was applied.
The resulting photographic elements were
imagewise exposed at 1/100 of a second through a
0 - 4.0 density step tablet pluæ a Wratten No. 29
filter (Wratten i8 a trademark of Eastman Kodak Co.,
U.S.A.) to a 600W, 5500 K tungsten light source.
Processing was accomplished at 37.7C in a color
process of the type described in the British Journal
of Photography Annual 1979, pages 204 -206, at a
development time of 3 minutes 15 seconds. The
processed photographic elements were then evaluated
for speed and relative granularity po~ition. The
results are given in following Table I:
TABLE I
Element/
Emulsion a Log E Granularity Position
(Grain Size~ vs. Element I Relative tQ ~lement I
I-A (0.8 Micron)
25II-B (0.7 Micron) -.04 +2 grain units
III-C (0.7 Micron) +.25 -5 grain units
IV-D (0.6 Micron) +.08 -4 grain units
When radiation-sensitive silver halide
emulsions differing in mean grain size are optimally
sensitized, there is a predictable relationship
between photographic speed and granularity. It is
generally recognized that each doubling of
photographic speed results in an increase of 5 - 7
granularity units. When emulsions of differing speed
also differ in granularity by a predicted number of
. , .
.~
-29-
granularity units, the emulsions are said to exhibit
the same speed-granularity relationship. An emulsion
which shows increased speed without a proportional
increase in granularity units is not only a fa~ter
emulsion, but an emulsion exhibiting a superior
speed-granularity relationship. An emulsion which
exhibits reduced granularity without a proportionate
loss of speed also exhibits an improved
speed-granularity relationship.
It i8 clearly demonstrated in Table I that
emulsions C and D of the present invention exhibit an
improved speed granularity relationship relative to
comparative emulsions A and B.
The invention has been described in detail
with particular reference to preferred embodiments
thereof, but it will be understood that variations
and modifications can be effected within the spirit
and scope of the invention.
