Note: Descriptions are shown in the official language in which they were submitted.
1121644
Thls dlsclosure ls directed to a process Or
preparlng spectrally sensltlzed sllver hallde gralns and
to-products formed by the spectrally sensltlzed sllver
hallde gralns.
In spectrally sensltizing silver halide emulsions it
is conventional practice to adsorb the spectral sensitlzing
dyes to the surfaces of the silver halide gralns after
they have been completely formed. However, there are some
variant teachings in the art.
Hill U.S. Patent 2,735,766, issued February 21,
1956, discloses that photographlc spectral sensitlzing
dye wandering can be eliminated or reduced by introduclng
a merocyanine spectral sensitizing dye during silver halide
precipitation. H111 teaches to blend the spectral
sensitizing dye with either the silver salt or the halide
salt prior to bringlng these salts together to form silver
halide. Hill speciflcally states that the teachings do
not extend to other optical sensitizing dyes, such as
those of the carbocyanine class.
Philippaerts U.S. Patent 3,628,960, issued
December 21, 1971, in discussing methlne dye spectral
sensitization Or a blended emulsion states that the dyes
can be incorporated in a separate addition or can be
added as a mixture with one or more ingredlents used in
the formatlon of the dlfferent sllver halide grains,
during physlcal or chemical ripening or during another
step preceding the coating of the emulsion.
~P
. .
'-"` 112i64g
In one aspect, thls lnventlon ls dlrected to a
method of preparing a spectrally sensltlzed radlatlon-
sensitlve sllver hallde emulslon comprlsing lntroduclng
lnto a reactlon vessel an aqueous solutlon of a sllver
salt, an aqueous solutlon of a hallde salt, a peptlzer
and a methlne spectral sensltlzlng dye. The dye ls added
to the reactlon vessel durlng the course of lntroducing at
least one of the aqueous salt solutlons. In thls method
the lmprovement comprises delaylng addltlon of the spectral
sensltizing dye until sllver halide grain nuclei are present
wlthln the reactlon vessel.
In another aspect, the invention relates to the
products of the process descrlbed above.
Thls lnventlon offers one or more of the
following advantages: (1) improved photographic speeds,
partlcularly minus blue speeds; (2) better shelf life sta-
billty; (3) substantial eliminatlon of dye desorptlon and
staining; (4) altered dye absorptlon characterlstlcs, and/or
(5) control or modificatlon of the sllver hallde grain
crystal hablt.
Thls method ls generally appllcable to any con-
ventlonal method of forming radiatlon-sensltive sllver
hallde gralns in whlch an aqueous solution of a silver
112~6~4
salt and an aqueous solution of a hallde salt are brought
into association to form radiatlon-sensltlve sllver
halide grains as a reactlon product. Thls method ls
particularly appllcable to the spectral sensitlzatlon of
radiatlon-sensitlve sllver chlorlde, sllver lodlde,
silver bromlde, silver bromoiodide, sllver chlorobromlde,
sllver chlorolodlde and sllver chlorobromolodlde crystals.
It is generally preferred that the sllver halolodlde
crystals contaln less than about 10 mole percent lodide,
based on total hallde, although in specialized appllcations
high iodide sllver halolodldes can be advantageous.
The method of thls inventlon for preparing and
concurrently spectrally sensitizing silver halide emulsions
can be practiced by modifying, in the manner descrlbed below,
conventional procedures for slngle Jet and double ~et
preparation of silver halide emulsions. In single Jet
precipltatlons an aqueous solution of a silver salt, such
as sllver nltrate, is run into a reaction vessel containing
an aqueous solution of a halide salt, such as an alkali
e.g. sodium or potassium halide, and a peptizer. In
double Jet preclpltatlons the aqueous silver salt and the
aqueous halide salt are concurrently and separately
introduced into the reaction vessel. Typlcally at least
a portion of the peptizer is initially present in the
reaction vessel and additional peptizer is commonly
introduced into the reaction vessel during the run. An
illustrative conventional single Jet silver halide
precipitation technique is that disclosed by Trivelli and
--4--
-
:112~644
and Smlth, "The Photographlc Journal", No. LXXIX, May 1939,
pp. 330-338. Nletz and Russell U.S. Patent 2,222,264,
lssued November 19, 1940, ls lllustratlve of a double ~et
silver hallde emulslon preclpltatlon process. Single and
double ~et sllver hallde emulslon preclpitation methods
are also discussed in Chapters I and II of Mees and James,
The Theory of the Photographlc Process, Third Editlon, the
MacMillan Company, 1966.
Upon inltial introduction lnto the reactlon
vessel the dlssolved sllver salt reacts wlth dlssolved
hallde salt to form silver hallde crystals. This initial
phase of silver halide emulsion preparation in whlch new
silver hallde crystals are being formed is referred to as
nucleation. During subsequent addition of silver salt,
additional silver halide formed as a reaction product can be
precipitated onto these nuclei causing the mean size of the
silver halide grains to increase, ultimately resulting in
silver halide grains of the desired mean particle size.
Although nucleation and continued silver halide grain growth
most commonly occur in a single reaction vessel, it is
recognized that nucleation can be undertaken in one reaction
vessel, employing single or double ~et precipitation tech-
niques, and the resulting fine grained silver halide emul-
sion fed into a second reaction vessel along with or in
advance of additional amounts of halide and silver salts to
facilitate continued grain growth. Multiple stage or cascade
silver halide precipitation techniques of this type are
112i6~4
illustrated by Terwilliger et al, "Precipitation of Silver
Halide Emulsions in a Continuous Reaction", Item 14987,
Research Disclosure, September 1976, and Terwilliger et al
U.S. Patent 4,o46,576, issued September 6, 1977.
While introducing the aqueous silver salt into the
reaction vessel containing the silver halide nuclei a
conventional methine spectral sensitizing dye is introduced
into the reaction vessel. Where the spectral sensitizing
dye is itself soluble, it can be introduced as an aqueous
solution without any additional or auxiliary solvent being
present. In most instances it is convenient to dissolve
the spectral sensitizing dye in an organic water-miscible
solvent, such as acetone or an alcohol of from 1 to 3
carbon atoms. Surfactants and/or peptizers can also be
present in the spectral sensitizing dye solutions. The
spectral sensitizing dye solution can be introduced into
the reaction vessel in a separate jet or can be introduced
by mixing with the aqueous silver salt and/or the aqueous
halide salt being run into the reaction vessel. The
spectral sensitizing dye can be introduced into the
reaction vessel continuously or can be introduced into
the reaction vessel in discrete increments. For example,
the introduction of the silver salt and/or the halide
salt can be periodically interrupted while the spectral
sensitizing dye is introduced. Except as specifically
discussed below, techniques similar to those employed by
Hill U.S. Patent 2,735,766, cited above, can be employed
-
il2~ 4
as well as conventional techniques ~or introducing spectral
sens-Ltizing dyes into preformed silver halide emulsions,
such as those disclosed in Paragraph XVII., Product
Licensing Index, Vol. 92, December 1971, publication 9232.
By delaying introduction of the spectral sensitiz-
ing dye until silver halide nuclei are present in the
reaction vessel interference with nucleation is avoided.
Preferably introduction of the spectral sensitizing dye
is delayed until the mean diameter of the silver halide
nuclei is at least about 0.01 (most preferably 0.05) of
the mean diameter of the silver halide grains in the
finished emulsion. In the most common instance, that is,
where the reaction vessel is initially free of silver
halide nuclei at the beginning of the silver salt run,
adequate nucleation in the absence of dye is achieved
by delaying dye introduction until at least about 1 per-
cent of the silver salt has been run into the reaction
vessel, preferably about 2 percent, optimally at least
about 5 percent. (Although spectral sensitizing dye
addition is referenced to silver salt addition, it can
alternatively be referred to halide salt addition and the
same numerical lirnits applied.) Where silver halide
nuclei are separately formed and introduced into the
reaction vessel, spectral sensitizing dye introduction
into the reaction vessel can be commenced concurrently
with or even slightly in advance of silver and/or halide
salt introduction.
~3
11216~4
The lntroductlon of the spectral sensltlzln~ dye
ls preferably regulated so that a substantlal portion of the
sllver hallde graln, at least about 10 percent of the sur-
Pace area, remalns substantially free of adsorbed dye before
precipltation of sllver hallde onto the graln surfaces has
been completed. Where the dye ls added ln lncrements durlng
lnterruptlons ln the lntroductlon of one or both of the
aqueous salts separately contalning sllver and hallde ions,
lt is preferred that dye concentrations be limlted to less
than about ~0 percent, preferably less than about 10 per-
cent, of that requlred to provlde a monolayer coverage of the
sllver halide grains. Based on the surface area of the
flnal sllver hallde gralns, lt is preferred that the total
dye lntroductlon durlng sllver halide precipitatlon--that
ls, before completlon of the sllver salt run--be maintalned
wlthln about 20 to 80 percent, optlmally between about 30 to
40 percent, of the dye concentration necessary to provlde
monolayer coverage. Silver hallde graln coverages can be
approxlmately calculated knowlng the graln-slze dlstributlon
(i.e., the proportion of gralns falllng lnto differing graln
slze classes) of the emulslon and assuming a monomolecular
coverage of the adsorbed dye. In actuality, lt has been
observed that dye adsorptlon varies as a function of the
crystallographlc plane of the sllver halide graln surface,
thereby selectively leavlng those planes less favored for
adsorption substantially free of dye when the proportlon of
the spectral sensltizlng dye ls llmlted.
llZ1644
Introduction Or the spectral sensltlzing dye lnto
the reactlon vessel after silver hallde nuclel are present
can contlnue throughout sllver hallde preclpltation and can
extend beyond sllver hallde precipitatlon. The spectral
sensitlzing dye is introduced into the reaction vessel in a
spectral sensitizlng amount before at least about 85 percent
of the silver salt has been run into the reactlon vessel,
preferably before 80 percent of the silver salt has been
introduced and most preferably before 75 percent of the
silver salt has been introduced. Where no silver halide
nuclel are present ln the reaction vessel at the commence-
ment of the silver salt run, introduction of the spectral
sensitizing dye is advantageous when from 1 to 85 percent,
preferably 2 to 80, and most preferably 5 to 75 percent of
the silver salt has been introduced.
For best results, after an approprlate delay to
permit nucleation (quantltatlvely referenced to the sllver
halide nuclei diameters or the 1, 2 and 5 percent silver
salt introduction levels, identified above), the spectral
sensitizing dye is incrementally or continuously added
to the reaction vessel over the course of silver salt
lntroductlon thereto and is preferably completed before
silver salt introduction to the reaction vessel is completed
(quantltatively referenced to the 85, 80 and 75 percent
sllver salt lntroductlon levels identified above). The
rate of contlnuous dye introduction can be maintained
constant or can be accelerated to reflect the increasing
.
surface area of the silver halide grains being formed.
Where the dye is added in discrete increments, the in-
crements of dye addltion are preferably selected to
approximate continuous dye introduction over the selected
interval of silver salk introduction. Where introduction
of the spectral sensitizing dye is delayed until after
larger proportions of the silver salt have been intro-
duced into the reaction vessel, larger than about 75
percent of the silver salt, the spectral sensitization
achieved begins to approach more closely that observed
when the spectral sensitizing dye is run into the reaction
vessel after silver precipitation is completed according
to conventional techniques.
Where spectral sensitizing dye is run into the
reaction vessel during silver salt addition as required
above and is additionally run into the reaction vessel
during the latter stages of silver salt addition--that is,
after at least about 75 percent of the silver salt has
been introduced--and/or added to the silver halide emulsion
by conventional techniques after silver halide precipita-
tion is complete, a further unexpected improvement in
spectral sensitization can be obtained. Thus, further
spectral sensitization by conventional techniques and/or
toward the end of the silver salt run in combination
with spectral sensitization according to the preferred
embodiments of this method as described above is specifi-
cally contemplated and recognized to be advantageous.
Any conventional spectral sensitizing dye which will
alone improve the spectral response of the emulsion can
be employed in combination
--10--
llZ164~
wlth the methine spectral sensltizlng dyes lntroduced lnto
the reaction vessel accordlng to the method descrlbed above.
It ls speciflcally contemplated to use the same methine dyes
to spectrally sensitize the emulsions during silver halide
precipitation as described above and during the latter
stages of silver halide precipitation or after completion
of silver halide precipitation.
One or more conventional methine spectral sensitiz-
ing dyes can be introduced into the reaction vessel during
silver halide precipitation as described. Such dyes are
described, for example, in Brooker et al U.S. Patent 2,526,632
issued October 24, 1950; Sprague U.S. Patent 2,503,776
issued April 11, 1950; Brooker et al U.S. Patent 2,493,748
issued January 10, 1950; and Taber et al U.S. Patent 3,384,486
issued May 21, 1968. Spectral sensitizers which can be used
include the cyanines, merocyanines, complex (tri- or tetra-
nuclear) cyanines, holopolar cyanines, styryls, hemicyanines
(e.g. enamine hemicyanines), oxonols and hemioxonols.
Dyes of the cyanine classes suitable for sensi-
20 tizing silver halide can contain such basic nuclei as thethiazolines, oxazolines, pyrrolines, pyridines, oxazoles,
thiazoles, selenazoles and imidazoles. Such nuclei can
contain alkyl, alkylene, hydroxyalkyl, sulfoalkyl,
carboxyalkyl, aminoalkyl and enamine groups and can be
fused to carbocyclic or heterocyclic ring systems either
unsubstituted or substituted with halogen, phenyl, alkyl,
haloalkyl, cyano, or alkoxy groups. The dyes can be
symmetrical or unsymmetrical and can contain alkyl, phenyl,
--11--
llZ164~
enamine or heterocycllc substltuents on the methine or
polymethine chaln.
` The merocyanlne dyes can contain the basic nuclel
mentioned above as well as acid nuclei such as thiohydantoins,
rhodanines, oxazolldenedlones, thlazolidenediones, barbituric
acids, thiazolineones, and malononitrlle. These acid nuclel
can be appropriately substltuted with alkyl, alkylene, phenyl,
carboxyalkyl, sulfoalkyl, hydroxyalkyl, alkoxyalkyl,
alkylamino groups, or heterocyclic nuclei. Combinations of
these dyes can be used, if desired. In addition, super-
sensltizlng addenda which do not absorb visible light can
be lncluded, for lnstance, ascorbic acid derivatives,
azaindenes, cadmium salts, and organic sulfonic acids as
described ln McFall et al U.S. Patent 2,933,390 issued
April 19, 1960; and Jones et al U.S. Patent 2,937,089
issued May 17~ 1960.
The methine dyes employed in the practice of this
invention are in one preferred form imidazole, oxazole and
thiazole methine spectral sensitizing dyes. That is, they
are conventional methine spectral sensitizing dyes con-
taining at least one lmidazole, oxazole or thiazole nucleus.
In a specifically preferred form~ the spectral sensitizing
dyes are cyanine dyes in which at least two nuclei of the
dye are chosen from imidazole, oxazole and thiazole
nuclei. Specifically preferred are cyanlne dyes in which
both of the nuclei are lmldazole, oxazole or thlazole
nuclei, such as those represented by the formula:
-12-
`` llZiL6~4
-- Z _ __ z
' ~
Rl-N~L=L~d-~C=L~L=L~m--C~L-L~n-~N-Rz
wherein
d and n each represents a posltive lnteger Or
from 1 to 2,
m represents a positive integer of from 1 to 3,
L represents a methlne group (e.g., -CH= and
( 3) ),
Rl and R2 each represents an alkyl group, prefer-
ably a lower alkyl contalning from one to four carbon atoms,
(e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl,
decyl or dodecyl)~ a substituted alkyl group, preferably a
substituted lower alkyl group containing one to four carbon
atoms, such as a hydroxyalkyl group (e.g., ~-hydroxyethyl,
y-hydroxypropyl or ~-hydroxybutyl), an alkoxyalkyl group (e.g.,
~-methoxyethyl or ~-butoxybutyl), a carboxyalkyl group (e.g.,
~-carboxyethyl or ~-carboxybutyl), a sulfoalkyl group (e.g.,
~-sulfatoethyl or ~-sulfatobutyl), an acyloxyalkyl group
(e.g., ~-acetoxyethyl or ~-propionyloxybutyl), an alkoxy-
carbonylalkyl group (e.g., ~-methoxycarbonylethyl or ~-
ethoxycarbonylbutyl), an allyl group, an aralkyl group (e.g.,
benzyl or phenethyl) or an aryl group (e.g., phenyl, tolyl,
chlorophenyl, sulfophenyl or carboxyphenyl), and
Z and Zl each represents an imidazole nucleus
(e.g., lmidazole, alkyl imldazoles, l-aryl lmldazoles,
benzlmldazole, l-alkyl benzlmldazoles, l-aryl benzlmlda-
zoles, 5-chloro-1-alkyl benzimldazoles, 5-chloro-1-aryl
llZ1644
benzimidazoles, 5,6-dichloro-1-alkyl benzlmidazoles, 5,6-
dichloro-1-aryl benzimidazoles, 5-methoxy-1-alkyl benzimida-
zoles, 5-methoxy-1-aryl benzimidazoles, 5-cyano-1-alkyl
benzimidazoles, 5-cyano-1-aryl benzimidazoles, naphth[l,2-
d]lmidazole, l-alkylnaphth[1,2-d]imidazoles or l-arylnaphth-
[1,2-d]imidazoles), an oxazole nucleus (e.g., oxazole, 4-
alkyl oxazoles, 4,5-dialkyl oxazoles, 4-aryl oxazoles, 4,5-
diaryl oxazoles, 4-nitrooxazole, benzoxazole, 5-chlorobenzOX-
azole, 5- or 6-nitrobenzoxazole, 5-arylbenzooxazole, 5- or
6-alkoxy benzoxazole, 5- or 6-hydroxy benzooxazole, naphtho-
[1,2-d]oxazole or nitro-substltuted naphth[1,2-d]oxazoles)
or a thiazole nucleus (e.g., thiazole, 4-alkyl thiazoles, 2-
thienyl thiazoles, 4-aryl thiazoles, 4,5-diaryl thiazoles,
benzothiazole, 5- or 6-chloro or bromobenzothiazoles, 4-
alkyl benzothiazoles, 5- or 6-alkoxy benzothiazoles or
4-aryl benzothiazoles).
It will be noted that in some instances, the acid
anion, represented by X in the above formula, is included in
the substituent represented by R2, such as in dyes containing
the betaine type structure. In the nuclei substituents
referred to above the alkyl moieties preferably contain
from 1 to 4 carbon atoms and the aryl substituents contain
from 6 to 10 carbon atoms, e.g., phenyl and naphthyl.
Imidazole, oxazole and thiazole cyanine spectral sensitizing
dyes are well known in the art and are disclosed, for example,
by A. H. Herz, Photographic Science and Engineering, Vol. 18,
No. 2, March-April 1974, pages 207 through 215; VanLare,
U.S. Patent 3,482,981, issued December 9, 1962; and in
numerous other patents and publications.
-14-
l~Zi6~4
Illustratlve o~ preferred merocyanlne spectral
sensltizlng dyes are those dlsclosed by Hlll U.S. Patent
2,735,766.
By employlng a slngle Jet or double ~et preclplta-
tion technlque as descrlbed above modlfled by the lntroduc-
tlon of a methlne spectral sensltlzlng dye lnto the reactlon
vessel after sllver hallde nucleatlon has commenced and
before completion of the sllver salt run, a silver hallde
emulslon can be prepared having unlque propertles. Such an
emulslon when coated onto a conventlonal photographlc fllm
or paper support to form a photographlc element exhlblts a
unlque spectral response whlch dlstlngulshes lt from other-
wlse ldentlcally formed photographlc elements ln which the
spectral sensitizing dye ls added to the emulsion after
completlon of the sllver hallde precipitation. Additional
preferred and unexpected characteristics can be imparted to
the photographic sllver halide emulslons and elements by
employlng ln comblnatlon materials and procedures more
specifically discussed below.
Although additional silver hallde graln formatlon
(additional nucleation~ can occur after lntroductlon of
spectral sensltizing dye into the reaction vessel, it is
preferred that nucleation of silver halide grains (forma-
tion of new grains) be substantially complete before
spectral sensitizing dye is run into the reaction vessel.
One technique which has been found particularly suitable
for insuring that additional silver halide precipitates
onto existing silver halide grain nuclei is either
stepwise or gradually to lncrease the rates of halide
and silver salt additions. Such techniques are
6~4
well known ln the art and are dlsclosed, for example, by
Kurz U.S~ Patent 3~672~900~ issued June 27~ 1972~ Kurz
teaches increasing the rates of silver and halide salt
introductions accordlng to the formula:
at 2 + bt + c
whereln t equals tlme of preclpitation and a, b and c are
constants dependent on factors such as, for example, temper-
ature, concentration, metal ion concentratlon and the llke,
and wherein the constants can be derived theoretlcally or
preferably are derived empirically for the particular condi-
tions of operation. The constants are preferably determined
for a value wherein new nuclei will not form after initial
precipitation whereby all grains will generally grow at the
same rate to produce a substantially monodispersed emulsion.
~ he reaction vessels as well as the apparatus and
techniques for associating the aqueous silver and halide
salt solutions and handling the silver halide emulsion which
is formed as a reaction product can be of any convenient
conventional type. Such apparatus and techniques are
illustrated by Hill, Philippaerts, and Product Licensing
Index publication 9232~ paragraph XVII, each cited above.
Such techniques and apparatus are further illustrated by
Culhane et al U.S. Patent 3~821~002; Brltlsh Patent
1~302~405; Irie et al U.S. Patent 3~650~757; Audran U.S.
Patent 2~996~382; British Patent 846~190; Frame et al
U.S. Patent 3~415~650; Porter et al U.S. Patent 3~785~i77;
Porter et al U.S. Patent 3~782~954; West German OLS 2~555~364;
West German OLS 2~555~885; Posse et al U.S. Patent 3~790~386;
and Forster et al U.S. Patent 3~897~935
- 16 -
`` llZ~64~
Photographic compositions and elements lncluding
si~ver halide grains spectrally sensitized as described
above can include a number of compatible, conventional
features not specifically described. Such conventional
aspects of the composition and element types and processes
for their preparation and use are disclosed in Product
Licensing Index, Vol. 92, December 1971, publication
9232, pages 107-110. The silver halide emulsions can
be either unwashed or washed as disclosed by paragraph II.
Emulsion washing. The emulsions can be chemically sensitiz-
ed as disclosed by paragraph III. Chemical sensitizing.
The emulsions can contain development modifiers, anti-
foggants and stabilizers, developing agents and hardeners,
as disclosed in paragraphs IV through VII. Any of the
conventional vehicles for the emulsions disclosed in
paragraph VIII can be employed. The emulsions and other
element layers can be coated on photographic supports
as disclosed in paragraph X. Supports. Any conventional
spectral sensitizing dye can be incorporated into the
emulsion in addition to the spectral sensitizing dyes
added during silver halide precipitation. Typical
conventional dyes are disclosed in paragraph XV. Spectral
sensitization. These additional spectral sensitizing dyes
as well as other addenda can be introduced into the
emulsion compositions by the techniques disclosed, for
example, in paragraph XVII. Methods of addition. The
remaining paragraphs of the Product Licensing Index publi-
cation disclose still other photographic features and
methods of photographic
-17-
`' \ ' ,
11~1644
procesælng whlch can be employed ln comblnatlon with the
features of thls lnventlon speclflcally dlsclosed. Both
Product Llcensln~ Index and Research Dlsclosure are pub-
llshed by Industrlal Opportunltles Llmlted, Homewell, Havant
Hampshire, P09 lEF, Unlted Klngdom.
The lnvention ls further illustrated by the
followlng examples:
Example 1 - Illustratlng Spectral Sensltlzatlon of a Silver
Chloride with a Benzothiazole Merocyanine
The following solutions were employed:
Solutlon A
Phthalated gelatin 240 g
1,8-Dihydroxy-3,6-dithiaoctane2.1 g
21.9% by welght sodium chloride
in water 246 ml
Distilled water 8400 ml
Solution B
Sodlum chloride 520 g
Distilled water to total volume of 3460 ml
Solutlon C
Silver nltrate 1020 g
Dlstllled water to total volume of 3460 ml
`` ~lZ1644
Solutlon D
Dye I* o.78 g
1:1, volume ratio, acetone to water 500 ml
Distilled water 127 ml
Solution A was placed in a reaction vessel equipped
with a mechanical agitator and ad~usted to a pH of 5.6 and
pAg of 6.7 at 60C. Whlle agltatlng Solutlon A, Solutions
B and C were separately lntroduced lnto the reaction vessel
ln separate ~ets at a uniform rate over a period of 40
minutes while maintaining the pAg of the composition wlthin
the reaction vessel at 6.7. Two minutes after starting the
lntroductlon of Solutlons B and C, Solutlon D was introduced
into the reaction vessel in a separate Jet at a uniform rate,
and the addition of Solution D was halted two minutes prlor
to the end of the addltlon of Solutions B and C.
The emulslon produced was coagulated by lowering
the pH and the supernatant liquid was decanted. After
decantlng the supernatant liquid, the coagulum was redispersed
in water. This procedure was repeated twice. The final
coagulum was dispersed in water at 40C/pH 5.6/pAg 7.6.
*Dye I
5-(3-Ethyl-2-benzothiazolldinylldene)-3-~-sulfoethylrhodanine
C H
,, --l!?--
.~
`` ~lZ~644
Electron micrographs showed that the sllver halide grains
were predomlnantly octahedral.
The emulslon was chemically sensltlzed wlth gold
sulflde, comblned with a cyan dye-forming coupler, l-hydroxy-
2-~-(2,4-di-tert-amylphenoxy)-n-butyl]naphthamide, and
coated on a cellulose acetate fllm support at 1.62 g Ag/m2,
7.0 g gelatin/m2 and 1.78 g coupler/m2.
The drled coating was exposed for 1/25 second to
tungsten light which was filtered to provide a 470 nm exposure
and processed for 60 seconds/31C in the color developer
set forth in Table I.
Table I
Color Developer
4-amino-3-methyl-N-ethyl-N-~-
(methanesulfonamldo)ethylanlllne
sulfate hydrate 4.3 g
Potasslum bromide 0.15 g
Potassium chloride 1.0 g
Benzyl alcohol 11.0 g
Hydroxylamlne sulfate3.4 g
Potassium carbonate31.0 g
Potassium bicarbonate0.5 g
Potassium sulflte 2.0 g
Hydroxyethylcellulose
(Natrosol 250L trademark) 0. o6
Water to 1 liter
(P~:10.08)
-20-
112~ 4
The silver chloride emulsion exhibited a mean ~rain
diameter of 0.65 micron. The silver chloride grains were mono-
dispersed and of octahedral grain morphology. The contrast of
the emulsion was 2.0a, the minimum density 0.10 and the maximum
density 2.00. For purposes of comparison with the remaining
examples, a relative speed value of 100 was assigned to the
emulsion. Speed was measured at 0.30 above minimum density on
the characteristic curve.
Example 2 - Illustrating Varied Dye Additions
The procedure of Example 1 was repeated, except that
addition of Solutions B and C were halted 30 minutes after the
beginning of the precipitation step, and Solution D was then
added to the reaction vessel over a period of 5 minutes. After
Solution D's addition was complete, Solutions B and C were added
to the reaction vessel to complete precipitation of silver halide.
The silver halide emulsion produced was polydispersed
with mean grain diameters falling within the range of from 0.45
to 0.95 micron. The contrast of the emulsion was 2.16, the
minimum density 0.10 and the maximum density 2.00. The relative
speed, compared to Example 1, was 46.
I)
- 21 -
1121644
In a separate run, when the lntroductlon of Solutlon
D was delayed untll after Solutlons B and C had been run for
35 minutes, the resultlng emulslon exhlblted comparable
minlmum and maximum densltles, but a somewhat lower speed
and contrast.
(Comparatlve) Example 3 - Comparing a Conventlonal Post-
Precipitation Spectrally Sensitized Emulslon
To provlde a dlrect comparison with conventional
precipitation techniques, the procedure of Example 1 was
repeated, except that Dye I was not present during the
precipitation step. Dye I was added ~ust prior to coating
the emulsion on the support at a coverage of 130 mg/mole Ag.
The emulsion was monodispersed having a mean
grain diameter of 0.70 micron. The silver chloride grains were
cublc. The contrast was 2.20, the mlnimum denslty 0.10
and the maximum denslty 2.00. The relative speed, compared
to Example 1, was 25.
This example, compared with Examples 1 and 2,
demonstrates that the method herein dlsclosed ls capable
of producing silver halide emulsions of very signlflcantly
enhanced speeds and that dlfferent grain structure can be
obtalned as a result of lntroduclng the spectral sensltizlng
dye after nucleatlon and durlng sllver hallde preclpitation.
When Examples 1 and 3 were repeated, but with an
exposure of 365 nm being chosen to ascertain the lntrlnslc
speeds of the emulslons outside of the region of spectral
sensitlzatlon, lt was determined that the element produced
by Example 1 was 100 percent faster than that produced by
Example 3.
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.. , .. ... .. .. . . _ . . . . _ . .. ... . .. . .
." ' .
1~21644
When the elements produced by Examples 1 and 3
were separately immersed in an agitated 1:1 (weight ratio)
methanol-water solution, it was observed that spectral
sensitizing dye entered the solution from the element of
Example 3. No spectral sensitizing dye was removed from
the element of Example 1. This showed the dye in the
Example 1 element to be so tightly held as to be non-
wandering. It is not understood exactly how the spectral
sensitizing dye added during silver halide precipitation
is associated with the silver halide grains, but it appears
that the relationship of the dye to the grains produced
by this method is demonstratably different than that
produced by introducing the spectral sensitizing dye after
silver halide precipitation.
(Comparatlve) Example 4 - Illustrating Prenucleation Dye Additions
The concept of introducing the spectral sensitizing
dye lnto the reaction vessel along with one of the silver or
halide salts before silver halide nucleation is known in the
art, as illustrated by the teachings of Hill and Philippaerts,
cited above. When Example 1 was repeated with Dye I
.
llZ1644
incorporated ln the aqueous hallde salt golutlon, Solutlon B,
a markedly inferlor, polydlspersed sllver hallde emulslon
was obtalned. The relatlve speed of the emulslon, compared
wlth Example l, was only 1. When the procedure was performed
agaln, but wlth the spectral sensltlzlng dye combined wlth
the aqueous sllver salt solutlon, Solutlon C, the llquld ln
the reactlon chamber separated lnto two separate phases, and
the experiment was dlscontinued.
Example 5 - Illustratlng the Use o~ Cyanlne Spectral
Sensitlzing Dyes
Example l was repeated substituting in each instance
one of the dyes listed below for Dye I:
Dye II - Anhydro-5-chloro-9-ethyl-5'-phenyl-3'-(3-sulfo-
butyl)-3-(3-sulfopropyl)oxocarbocyanlne hydroxlde,
sodium salt
p /-=CH-CH-CH=CH--~
(CH2) 3 ( lc 2) 3 Na
503e CHSO3
CH3
Dye III - Anhydro-5,5',6,6'-tetrachloro-1,1',3-triethyl-
3'-(3-sulfobutyl)benzimidazolocarbocyanine
hydroxide
CH2CH3 CH2CH3
c I I p ; ,C=CH-CH=CH-C~ ~ p t Cl
CH CH
~ 2
CH3 ICH2
H-CH-SO3
CH3
; -24-
644
Dye IV - Anhydro-9-ethyl-5',6'-dlmethoxy-5-phenyl-3'-
(3-sulrobutyl)-3-(3-sul~opropyl)oxathiocarbocyanlne
hydroxlde, sodium salt
a \;~ =cH--C-CH-~ I 0 = pheny I
(CH2) ~S03e~a0 (CHZ) 2CHSOe
CH3
Dye V - Anhydro-3,3'-bis(3-sulfopropyl)-4,5,4',5'-dibenzo-
- thiocyanine hydroxide, sodium salt
~-=CH~
(CHZ) 3SOS
(( :H2) 3SO3 eNa0
Dye VI - Anhydro-5,5'-dimethoxy-3,3'-bis(3-sulfopropyl)
thiocyanine hydroxide, sodium salt
I lt \.=CH--~ n
CHZCHZCH2503
(CH2') 3SO3Na~
1121644
The results obtalned were qualltatlvely slmllar
to those of Example 1, although ln some lnstances an
alteratlon ln graln morphology was observed. Whereas Dye I
produced monodlspersed octahedral sllver hallde grains,
Dye II produced very pronounced cubic grain structures.
This suggests that Dye I adsorbs preferentially on
111 crystal surfaces, thereby promotlng octahedral graln
growth, whereas Dye II adsorbs best on 100 crystal surfaces,
thereby enhanclng the probabllity of cubic crystal
formation occurring.
Example 6 - Illustrating the Effect of Comblning Spectral
Sensitization Durlng the Silver Salt Run with
Post-Precipitatlon Spectral Sensltization
Substitutlng Dye II for Dye I, Example 3 was
repeated uslng two different dye concentrations set out
below in Table II, and Example 1 was repeated using 250 mg
of Dye II per mole of silver, as set out in Table II. In a
fourth run Example 1 was repeated using 200 mg of Dye II ~;
per mole of silver and Dye II was also added to the emulsion
~ust prior to coating to bring the total Dye II concentration
to 450 mg per mole of silver. The relative speeds are set
out in Table II.
-26-
llZ~644
~ I
h ~ ~
C~ ~ t) o
o u, o P~ a~
~d O ~ o
~n ~ ~ ~ C J~
O ~ O ~ O J~ O O
E a) N o N o N c) ~ N
o h
0
O Q) O ~ O ~ O F~ a~
O ~
~ ~ ~ o a~
H C~
q:~
a~
j~; N N =1- :~
OH
E~ H
a~
~ ~1 ~
,1 ~ E ~ ~D
E ~ x a~
X ~
E .Y E ~d
--27 -
.
llZ16~4
The relatlve speeds show a dlstinct advantage for post-
nucleatlon spectral sensltizatlon as compared to post-
preclpltation spectral sensltization. Additionally, where
post-nucleation and post-preclpltatlon spectral sensltlzatlon
are comblned, the improvement ln relatlve speeds ls
unexpectedly enhanced.
Example 7 - Illustrating Spectral Sensltization of Silver
Bromolodlde
The following solutions were employed:
-28-
llZ:~6~4
Solution A
Phthalated gelatin 116 g
KBr 609 g
XI 4.4 g
Distilled water 4943 ml
So lut l on B
KI 46.6 g
Distilled H 0 to
total volume2 2070 ml
Solution C
AgN03 822 g
HgC12 .13 mg
Distilled H 0 t~>
total volume 9300 ml
Solution D
Dye VI 1.1 g
Distilled H 0 to
total volume 63 9 ml
--29--
.
.
.
112~644
Step 1: Solution A was placed ln a reactlon vessel
and ad~usted to a temperature of 80C.
Step 2: Solutlon B and C were run lnto Solution A
(with agitation) such that the B solution was completely
added ln 20 minutes and the C solution was completely added
in 40 minutes. Two minutes after starting the flow of
Solutions B and C, Solution D was added to A. The addition
of D was completed in 35 minutes.
Step 3: One minute after the completion of the addition
of Solution C, temperature of the solution was lowered to
50C, 60 grams of sodlum thiocyanate were added to the solution,
and the resulting mixture was stirred for 25 minutes.
Step 4: The emulsion was coagulated by lowering the
pH and the supernatant liquid was decanted. The coagulum was
then redispersed in water. To the redispersed solution,
5.6 grams of KBr were added and the solution was stirred for
3 minutes at 30C. The coagulation procedure was then repeated
two more times. The final coagulum was dispersed in water at
40C/pH 6.5/pAg 8.o.
Photomicrographs of this emulsion showed that the
emulsion grains ranged in size from less than 0.2 ~m in
diameter to greater than 3.0 ~m ln diameter.
For purposes of comparison a control emulsion was
prepared as described above, except that the dye was added
to the emulsion ~ust prior to coating. Photomicrographs
indicated that this emulsion was in the size range of 0.3
to 3.5 microns in mean grain diameter with most of the grains
being in the range of 0.5 to 0.7 micron. This latter size
-30-
llZi644
class contributed markedly to llght scatter and was not
nearly a~ prevalent in the emulslon formed above by dye
addltion after nucleation.
Both of the above emulslons were gold and sulfur
sensltlzed and coated ln a color photographic format on a
cellulose acetate fllm support at 1.62 g Ag/m2 and 7.0 g
gelatln/m2. These elements were exposed to a tungsten light
source for 1/25 second, color processed in a color developer
containing ~-phenylenediamine as a developing agent at 80~C
and a pH of 10, and compared sensitometrically. It was
found that the post-precipitatlon spectrally sensitized
control element had a higher contrast than the post-nuclea-
tion spectrally sensitized element prepared according to
this process, but that both elements had identical threshold
sensitivities. Turbidlty of the control emulsion was higher
than for the emulsion according to this process. This
result lndicated an lmproved speed/ sharpness characteristic
for the element prepared according to this method.
Example 8 - Illustrating Spectral Sensitization of Silver
Chlorobromide
-31-
' ' . ' ~ `'' '
llZ~44
Solutlon A
Phthalated gelatln 240 g
21.9% solution of NaCl/H20 260 ml
4.4% solutlon of KBr/H2O 147 ml
Dlstllled water 8400 ml
Solutlon B
NaCl 489 g
NaBr 51-7 g
Distllled water to
total volume 3380 ml
Temperature 50C
Solution C
AgN03 1020 g
Distilled water to
total volume 3380 ml
Temperature 50C
Solutlon D
Dye I 0.78 g
1:1 methanol H2O 500 ml
Distllled water 127 ml
Temperature 50C
~ . . .
1~216~4
Step 1: Solution A was ad~usted to 80C/pH 5.55/vAg
89 mv.
Step 2: Solutions B and C were added simultaneouslY
to Solution A with agitation over a period of 90 minutes.
Ten minutes after Solutlons B and C were started, Solutlon C
was added to Solution A over a period of 34 minutes.
Step 3: The emulsion was cooled to 33C and coagulated
by lowering the pH to 3.90. The supernatant was decanted
and the coagulum was redispersed in water at pH 6.o/40C.
This procedure was repeated and the emulsion was redispersed
at pH 5.6/pAg 7.6 after adding a solution of distilled
water t600 ml) and bone gelatin (120 g).
Electron micrographs shows a polydispersed, 0.75 ~m -
1.25 ~m, cubo-octahedral emulsion. The emulsion was
chemically sensitized, combined with a coupler, coated
exposed and processed as described for Example 1. This
emulsion had a relative speed of 25 in comparisor. to Example 1.
Example 9 - Illustrating Incremental Dye Additlon During
Silver Iodide Precipitation
The following solutions were prepared:
Solution A
Gelatin 17.5 g
Water 1.5 1
Temperature 35C
pH 6.o
-33-
llZ~;'14
Solutlon B
200 ml of a 2.5 molar aqueous solution
of Sodium lodlde
Solution C
200 ml of a 2. 5 molar solutlon of silver
nitrate
Solution D*
170 ml contalning 606 mg Dye-VII anhydro-
5,5~ ,6,6l ,-tetrachloro-1,1'-diethyl-3,3'-
di(3-thiosulfatopropyl)benzimidazolocarbocyanine
hydroxide, tetramethylguanidinium salt.
Solution A was placed in a reaction vessel and
ad~usted to a pAg of 6.45 with Solution B. Solutions B and
C were then added simultaneously at an accelerated flow
rate (1 ml/minute initial flow rate, 9 ml/min final flow
rate) to the reaction vessel containlng Solution A over a
period of 50 minutes. At the time intervals lndicated
below the introduction of Solutions B and C were interrupted
and the indicated amounts of Solution D were added:
Time (min) 5 11 18 22.2
ml Solution D 3.9 7.25 11.1 15.6
Time tmin) 28.2 34.2 39.2 44.3
ml Solution D 21.15 27. 3 32.6 37.5
After each dye addition, the emulsion was ad~usted to pH 7.5,
held for 2 minutes, read~usted to pH 6.o and then precipita-
tion was resumed by introducing Solutions B and C once again.
~Dye VII was dissolved in phenoxyethanol (trademark Dowanol),
acidified and then diluted to 170 ml total volume with methanol.
- 34 -
llZ1~4q~
At the completion Or the run the pAg of the emulslon was
ad~usted wlth an additlonal quantlty of Solutlon C. At the
completion of the run the emulsion contalned 1.1 grams of
Dye VII per mole of sllver. The excess soluble salts were
removed from the emulsion wlth an lon exchange resln by the
procedure described ln Maley U.S. Patent 3,782,953. The
emulslon was ad~usted to 4.5 kg/mole sllver, pH of 3.0 and a
pAg of 2Ø
Generally slmilar emulslon making procedures were
employed to prepare emulsions each containing one of the
following dyes:
Dye VIII anhydro-9-methyl-3,3'-di(3-sulfobutyl)benzo-
thiazolocarbocyanine triethylamine, sodium salt
Dye IX 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenz-
imidazolocarbocyanine _-toluene sulfonate
Dye X 3,3'-diethyl-5,5'-diphenylbenzoxazolocarbocyanine
iodide.
The emulsions were coated on transparent photo-
graphic film supports at coverages of 8.07 mg sllver per
square declmeter and 97.9 mg gelatln per square decimeter.
Coating melts contained saponln and 2-methyl-2,4-pentanediol
as a spreading agent and humectant, respectively. The
emulsion was ad~usted to a pH of 4 and a pAg of 6 at 35C
prior to coating. Samples of the photographic elements were
exposed using wedge spectrographs and developed for 10
mlnutes at room temperature ln Kodak D-l9 developer con-
talnlng 1 gram of poly(ethylene oxlde) and flxed uslng Kodak
F5 fix solutlon. Correspondlng controls were prepared,
exposed and processed whlch ln each instance varled only in
that the dye was added to the emulslon after sllver halide
precipitation was completed ln accordance with conventional
practlce.
-35-
. ... ... . .
.
16~
The photographlc elements prepared accordlng to
the method of this invention using Dye VII showed a stronger
absorptlon band at 545 nm at a coatlng pAg of 6.5 and a
red-shlft J-band was observed when the element was coated
at a pAg of 10.5. Dye VIII showed a bathochromic adsorptlon
shift as compared to the control and J-bandlng whlch was
absent from the control. With Dye IX a large enhancement in
maxlmum densities were obtained throughout the visible
spectrum as well as an enhancement in J-bandlng. With Dye X
an enhancement of blue sensitivity was obtained. Although
variations ln response attrlbutable to runnlng the dye lnto
the reaction vessel during silver halide precipitation
appeard to be a functlon of the particular dye chosen, in
each lnstance lt was apparent that the emulsion prepared
accordlng to the process of this invention differed in its
properties from the control emulsion.
The invention has been described with reference to
particular preferred embodiments thereof but it will be
understood that variations and modifications can be effected
within the spirit and scope of the invention.
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