Note: Descriptions are shown in the official language in which they were submitted.
1 3 ~
TITLE PD-2375
PROCESS FOR PR~PARING A PHOTOGRAPHIC EMULSION
CONTAINING TABULAR GRAIN5 EXHIBITING HIGH SPEED
DESCRIPTI~N
5TECHNICAL FIELD
Thi6 inven~ian relates to a proce6~ for
preparing a photographic emulsion containing tabular
silver halide grainfi. More particula~ly thi6
invention relate~ ~o a pro~e~s ~or preparing a
photographic emul~ion wherein the tabular silver
; halide grain~ exhibi~ high Epeed upo~ 6ensitiza~ion.
BACKGROUND OF THR INVENTION
Tabular ~ilver halide grains, eheir
preparatio~ and use in photographic emul6ions, are
widely known. They have been exten~ively ~tudied in
the literature 6ince photographic emulsion6
containing these grains appeared to offer 60me
significant advantage~ over photographic emulsions
containing round or globular grain ~e.g., 6pla6h
prepared types). Generally, tabular g~ain6 are
large, flat ~ilver halide grains that are prepared by
employing lo~g ripening time~ or by balanced double
jet (BDJ) precipi~ation ~e~hod~. Commercial
~: emulsions u~ing tabular grains are conventionally
made ~y u6ing a BDJ proces~. The tabular grain~
usu211y have triangular parallel crystal face~ each
of which is u~ually Iar~ger than a~y other cry~tal
face o~ the grain and are conventionally defined by
their a~pect ratio (AR) which i~ the ratio of the
dia~ete~ of the grain to the thickne6s. Larger A~
grain~, e.g., at lea6t 8:1, have diame~ers of at
least 0.6 ~m a~d thickne~es oP less than 0.3 ~m.
~ These laLger ~abular grains have certain commercial
;~ adva~tage6 apparen~ to those of normal Ekill in the
~ 35 art. For example, they have a larger ~urfac~ area
13~l60~
and thus can accept more ~ensitizing dye. Since
the~e tabular g~ains u~ually are dye sen6itized, when
emul6ions u6ing ~uch tabular grains are present in
medical x-ray element~ an increase in sharpne66 can
result. In addi~ion, ~ince the tabular~grains
no~mally lie flat when coated from an emul~ion on a
support, the covering power i~ usually ~rèater and
thus the emulsion can be coated at ,a lower coaeing
weight and i6 therefore le~s costly. It i6 desired
to prepare photographic e~ul~ions containing ~abular
grains exhibiting high speed.
SUMMARY OP THE_INVENTION
In accordance with this invention there i~
provided a proce~6 for the prepa~ation of a photo-
graphic emulfiion containing tabular ~ilver halide
grains, which exhibit high speed upon sen~iti2ation,
having a thickne~s of about 0.05 to 0.5 ~m, average
grain volume oP about 0.05 to 1.0 ~m3, and a mean
a~pect ratio of greater than 2:1 comprising
A. adding silver nitrate to a
ves~el containing a dispersing
medium~bromide mixture wherein
the ini~ial bromide ion
concentration is 0.08 to 0.25
normal whereby tabular ~eed
grains are focmed:
B. adding an ammoniacal base
solution to achieve Q.002 to
Q.2 normal of the base after at
~o least 2% of the total silver
nitrate ha6 been added to the
ves6el: and
C. adding 6ilver ni~rate and
halide ta~en from the group
3s consi6ting of Br and BrI
by balanced double jet
-3- ~3~6~3~
procedure whereby tabular grains are formed.
DETAILED DE~SCRlPTION OF THE INVENTION
The process of this invention results in photog~raphic emulsions containing
tabular silver halide grains which are higher in speecl when compared to tabulargrains prepared according to known processes. The resultant high speed could nothave been predicted from the state of the art. It is also possible that the tabular silver
halide grains can be prepared having a narrow size distribution as taught in Nottorf,
Canadian Application Serial No. 548,682, filed October 6, 1987. The narrow size
distribution is achieved by using a silver halide solvent such as ammonia, ammonia
derivatives, etc., and by stopping the initial silver nitrate addition for a time period
of 1 to 60 minutes at a bromide ion concentration in the range of 0.005 to 0.05
normal (N).
The excess ammoniacal base present upon completion of the final addition of
silver nitrate and halide can be neutraliæd with acid. Optionally the neutral;zed
emulsion containing the final tabular grains may be ripened further by the addition
of a thiocyanate salt ripening agent, e.g., alkali metal thiocyanate, for a period of
about 1 to 20 minutes. The speed advantage of the emulsion is achieved after it has
been chemically and spectrally sensitized by procedures known to those skillcd in the
art. The thinner grains exhibit higher speed.
The tabular silver halide grains which upon sensitization exhibit high speed are of the
silver bromide or silver bromoiodide types. The grains have
,~
t~
~ 3 ~ 3 ~
an average thicknes~ of about 0.05 to 0.5 ~m,
preferably O.OS ~o 0.2 ~m and more preferably 0.1
~m or below; an average grain volumle of 0.05 to 1.0
~m3, ereferably 0.1 to 0.3 ~m3 and a mean
a6pec~ ratio of greater than 2:1, preferably greater
than 5:1, and more preferably greater than 8:1.
The grain charactsristic~ de6~ribed above of
the ~ilver halide emul~ions o~ this invention can be
readily a~cectained by procedurefi well known to tho~e
skilled in the art. As employed herein the te~m
"aspect ratio" refers to the ratio of ~he diameter of
the ~rain to it~ thicknes6. The "diameter" of the
grai~ is in turn defined as the diameter of a circle
having an area equal to the projected area of the
grain a~ viewed in a photomicrograph or an electron
micrograeh o~ an emulsion ~ample. From ~hadowed
electron micrograph6 of emul~ion 6ampl2s it i8
pos6ible to determine the thickness and diameter of
~ each grain. From this ~he aspect ratio of each
; 20 tabular grain can be calculated, and the aspect
ra~ios of all the tabular grain6 in the ~ample can be
averaged to obtai~ their mean aspect ratio. By this
~ definition the ~ea~ a~pect ratio i6 the average of
: individual tabular grai~ aspect ratios. In practice
it is u~ually ~impler to obtain an average thicknees
and an avecage diameter of the tabular grain6 having
a thickne~ of les6 than 0.5 ~m and to calculate
the mean a~eect ratio as the ratio of the e two
average~. Whether the averaged individual aspect
ratios or the averages of thickness and diameter are
u~ed to determine the mean aspec~ ratio, within the
tolerance6 of grain mea~urements contemplated, the
mean afipect ratios obtained do not significantly
dif~er. The average qrain volume of a tabular grain
35 i8 de~ermined a~ taught by Holland et al. PS and E,
5 131~
volume 17, NoO 3 ~1973~, page 295 et ~eq. Normally
the6e determinations are ~ade u~ing ~abular grain6
which are in the gLain diameter range of 0.5 to Z.5
~m and appear tabular at 2,500 timeE; magnifica~ion.
In the preparation of the 1:abular grains
described above the ~ollowing proceclure i6 used.
Into a conven~ional reaction ve6~el for 6ilver halide
precipiSation equipped wi~h a stirri.ng mechanism i8
introduced a disper~ing medium/bromide mixture
wherein the initial bro~ide ion concentration i~ 0.08
to 0.25 N, which i~ the known range to produce
tabula~ grain~. Preferably the bromide ivn
concentration i~ 0.1 to 0.2 N. The bromide salt
~re6ent i~ typ;cally in the for~ of an aqueou6 ~alt
60lution, e.g., one or more ~oluble ammonium, alkali
metal, e.g., ~odium, potas6ium: alkaline earth metal.
e.g., magne6ium or calcium. Suitable disper~ing
media initially pre~ent in the reaction vessel
include water and a peptizer, e.g., gelatin,
including alkali-treated gelatin (cattle bon~ or hide
:~ gelatinS, acid-treated gelatin (pig6kin gelatin),
gelatin derivatives, e.gO, ace~ylated gelatin,
phShalated gelatin, etc.; protein6, protein
i deri~a~ives, c011U108e derivatives, e.g., cellulo~e
e6ters; p~ly6accharides, e.g., dextran, gum arabi~,
: zei~, ca~ein, pectin, collagen derivative~,
agar-agar, ar~owroot, albu~in, etc. Mixtures of
peptizer6 may be u~ed. A preferred peptizer i&
gela~in or a~gelatin deriva~ive.
OtheE material~ commonly employed in
combination with hydrophilic colloid peptizer~ a
~: vehicle~ (including vehicle e~tender~, e.g.,
materials in the ~orm of latices) include 6ynthetic
:~ polymeri~ pep~izers, carrier~ and/o~ binders 6uch as
35 poly(vinyl lactams~, acrylamide polyme~, polyvinyl
alcohol and its derivative~, poly~inyl acetals,
' S
131~3~
~olymer~ o~ alkyl and ~ulfoalkyl acrylates and
methacrylates, hyd~olyzed polyvinyl acetates,
polyamide6, polyvinyl pyridine, a~rylic acid
eolymers, maleic anhydride copolymer6, polyalkylene
oxide~, methacrylamide copolymer6, maleic acid
copolymers~ vinylamine copolymer6, ~lethacrylic acid
copolymer~, ~ulfoalkylacrylamide copolymer6,
polyalkyleneimine copolymer~, polyamines,
N,N-dialkylaminoalkyl acrylates, vinyl imidazoIe
copolymer~, vinyl ~ulfide ~opolymer~, halogenated
~tyrene poly~ers, a~inea~rylamide polymer6,
polypeptide~ etc. The~e additional material6 need
;~ not be present in the reaction ve66el during sil~er
halide precipitation, but can be added to the
15 emul6ion prior to coating on a 6upport. The
tempeeature of the contents in the reaction ve6sel is
preferably in the range of 40 to 80C. Silver
nitrate i~ then added at a 6teady rate into the
~eac~ion ve~sel containing the disper~ing
20 medium/bromide mixture whereby ~abular 6eed grains
begi~ to form.
After approximately at lea6e 2 percen~ o~
the total ~ilver nitrate has been added to ensure
; proper size tabular 6eed grains have been permanently
25 ~ormed, an ammoniacal ba~e 601ut~ion i8 added to ~he
reaction ves6el to achîe~e about 0.002 to 0.2 N,
preferably 0.002 to 0.1 N, of the ba6e in the ve6~el.
Upon achieving a de6ired bromide io~
concentration in the ~eaction ve~6el, silver nitrate
30 i8 continually added into the ve~6el together with a
halide compound which introduce6 additional bromide
ions or bromoiodide ions by a balanced double jet
(BDJ) ~roceaure known to tho6e ~killed in the art
thereby maintaining the desired bromide ion
; 35 con~entration. It i~ i~n thi~ 6tep ~ha~ the ~abular
7 ~ 3 ~
grains achieve the desired propertie~ including mean
a~pect ratio. In ~he event that bromoiodide ion~ are
added during the B W procedure, the! a~ount o~ iodide
prefient in the emulsion i~ in the range of about 0.01
to 10.0 mol percent, preferably O.Cl to 2.0 mol
percent basQd o~ total silver.
A~ stated above and in order to ~pe~ifically
control the grai.n ~ize di~tribution, when the de ired
bromide ion concentration in the range of 0.005 to
0.05 N i~ achieved, and in the pre~ence of a silver
halide solvent, e.g., ammonia, ammonia derivativ~,
: etc., the initial silver nitrate addition optionally
may be stopped for a period of time in the range of 1
to 60 ~inute~.
After completion of the total ~ilver nitrat2
and halide addition by the BDJ procedure, any excess
ba6ic 601ution present in the emulsion optionally can
~ be neutralized ~ith a~id, e.g., acetic acid, ~ulfuric
:~ acid, ni~ric acid, hydrochloric acid, etç. The p~
achieved i~ in the range of abou~ 5.0 ~o 7.0,
preferably ~bout 6Ø Ae thi6 st~ge, the tabular
grains ~ay be further Lipened for a time period of l
: to 20 minute~ by the addition o~ a ~hiocyana~e salt
to the emulsion. UseFul ~hiocyanate ~alt6 include
alkali metal thiocyanates and ammonium thiocyanate,
e.g.. in an amount of 0.1 to 20 g 6alt/mole 6ilver
~ halide. Other ri~ening agents include thioether,
; etc., a~ well a~ o~hers known to those ~killed in the
art.
The tabular grain emul~ion6 are pre~erably
washed to remove ~oluble ~alt~. Wa6hing technique6
are known to tho~e skilled in the art. The wa~hing
i6 advantageou6 in terminating ripening o~ ~he
~abular grai~6 after completion of precipitation ~o
avoid increa~ing their thickneEs and reducing their -
13~3~
aspect ratio. Hhile 6ub~tantially all ~he grains aretabular in form the emul~ion i6 not affected by the
pre~ence of a minor amount of nontabular grainæ.
Tabular grains of any aspect ratio can be made
according to the described proces~; for exa~ple.
large, thin tabular grain6 or, al~ernatively,
thicker, smaller tabular grain& can be prepared.
The emulsion containing tabular grain6
prepared according to this invention is generally
fully dispersed and bulked up with gelatin or other
disper~ion of peptizer de~cribed above and ~ubjected
to any of the known ~ethodc for achieving optimum
sen~iCivity whereby the high speed of the tabular
~ilver halide grain~ i6 achieved. Preferably optimum
chemical ~en~itization i8 achieved by the additior~ o~
sultur and gold. Other sensitizer6 include:
~elenium, tellurium, platinum, palladium, iridium,
osmium, rhodium, rhenium or phosehorous ~ensitizers
or combination6 thereof at 10 8 to 10 10 N silver
20 (pAg 8 to 10), pH of 6.0 to 7.0 and temperatu~es of
from 50 to 60C. Chemical ~en~itization can oecur in
::
the pre~ence of ~odifier6, e.g., compound~ known to
supyre~ fog and increace speed when pre6ent during
chemicai sensitization, such a~ azaindene6,
azapyridazines, azapyrimidine~, benzothiazolium
~alt6, and ~en6i~izerR having one or more
heterocyclic nuclei. The tabular grain silver halide
emulsion~ are also spectrally sen~itized. U~eful
sensitizing dyes are those dyes that exhibit
~; 30 ab60rption ~axima in the blue and minu~ blue ~i.e.,
green and red~ portion~ of the visible ~pectrum. In
addition for ~pecialized appli~ation6, spectral
en~itizinq dyes can~be employed which have improved
spectral re~pon~e beyond the vi~ible 6pectrum, e.g.
infrared absorbing spectral sensitizer6. Example~ of
:
11 3 ~
dye~ include ~ho~e di6closed in U.S. Paten~ No.
.42S.~26, col. 16, line 52 to col. 19, line 42,
The tabular grai~ e~ulsion6 are u~eful in
photoqraphic film element~. An emul6ion c-an ~e
coa~ed in the nocmal manner on any o~ the
conventional ~uppo~t~, e.g~. preferably polyethylene
teeephthalate ~ubbed in a eonventional ~anner. Any
of the other ~uppor~s known to the a~t can al~o be
used. Coating, wetti~g aides, aneifoggant6,
antistatic agent~0 etc., common t9 mo~t 6ilver halide
elements, can also be u6ed in the preparation of the
film element~.
Since element6 prepared from the emul~ion3
made u6ing the process of thi~ invention are
eminently ~uitable for u6e in x-ray elements, usually
the elements are coated on both sides of the support
which usually i~ tinted with a blue dye as i6 known
to tho~e 6killed in the x-ray art. The support may,
and preferably doe~ have the conventional reain-type
~ub a~plied to the ~uppo~t and the sublayer i8 the~
u~ually overcoated with a thi~ ~ub6tra~um of gelatin
~ over which the e~ul~ion i~ ~hen applied. ~he
:~ emulsion may be applied at coating weights of le6s
tha~ 5 g Agi~2, preferably les6 than 4 g Aq/m2,
for example, and then an abra6ion layer of ha~dened
gelatin applied thereto to provide protection for the
silver ~ontaining layer This element i8
conventionally expo6ed in a typical ~a~ette with a
: 30 paic of x-ray inten~ifying ~creens as i5 well known.
Of cour6e, this i8 only a preferre~ element e~ploying
emul~ions o~ thi~ inYention. The emulsion can be
u6ed conveniently in any of the well-known
photosen~itive ~ystem~ a~ noted below. A pre~erred
mod~ of the invention:i~ de~cribed in Exa-ple 5.
.
. .
11 3~3~
INDUSTRIAL APPLICABILITY
Pho~og~aphic ~ilver halide film elemen~s
having at iea~ one layer of an emulsion ~ontaining
the high ~peed tabular 6ilver halide grain~ prepa~ed
according to ~he pcoees6 of thi~ invention are u6eful
in conventional areas of photograph~y. The
photographic element~ are particularly useful a~
x-ray film6, e.g., ~upport ~oated on each ~ide, in
cooperation with x-ray inten~ifying 6creen6.
Sensitization can be in the green or blue portion of
the spectrum. Other u~e6 include: graphic arts
film~ color photographic fil~, etc~
E~AMPLE S
The following example~ illu6trate but do not
limit the invention. In the Control and Example6 the
percentage~ are by weight. N mean6 normal.
CONTROL 1
To 450 liters of a well-Rtirred aqueous
olution, which Gontained 1.6 percent photog~aphic
gelati~ and 9.1 kilogram6 of potafi6iu~ bromide and
which wa6 ~aintained at 60C, wa6 added a 1 N AgN03
solution at con~tant flow until the bromide io~
concentration was lswerea to 0.075 N. Double-jet
addition of a 3 N Ag~03 601u~ion and a 3 N K~r
~lution was ~hen initiated, with the AgN03 flow
increasing 200 ~lf~in/min for 20 minute6 and the KBr
flow increa~ing to maintain a growth bromide ion
concen~ration of 0.075 N. The KBr 601ution wa~
halted and the AgN03 ~olution continued at a
con6tant flow until ~he bromide ion concentration was
lowered to 0.025 N, which wa~ then maintained by
double-jet addition of K~r and AgN03 at con~tant
flow until 540 molefi of AgN03 wa~ di~pen~ed.
~ollowing precipitation, 675 gram~ of sodium
: 35 thiocyanate were added and the emul~ion ripened at
~ 31S~
11
60C for 15 minutes. The smlllsion was then cooled to
40C and washed by a coagulatio~ process three ~imes.
~ The re~ultan~ tabular grain AgBr e~ul6ion
: had an average grain volume o~ 0.1~5 ~m , an
S average grain thicknes6 o 0.10 ~m and an average
AR of 1~
E~AMPLE 1
To 550 liter~ o~ a well-s~i-red aqueou~
~olution. which contained 1.6 percent ehotographic
gelatin and 11.1 kilogra~s of pota~sium bromide and
which was maintained at 60C, wa~ added a 3 N AgN03
solution at constaRt flow. When the bromide ion
concen~ra~ion wa~ lowered to 0.058 N, 1210 gra~s of a
23 parcen~ ammonia 601utio~ were added. The AgN03
flow continued until the bro~ide ion concentration
was lowered to 0.020 N, at which time the AgN03
~olution wa6 halted. After 3 minutes double-jet
addition of a 3 N AgN03 solution and a 3 ~ XBr
solution wa~ initiated, with the AgNO3 flow
increasing 3 7 ml~in/min for 15 ~inutes and the ~Br
flow increasing eo maintain a growth bromide ion
concentration of 0.020 N. Double-jet addition
continued at constant flow until 660 moles of AgN03
were dispen6ed. Following precipitation, 925 grams
of glacial acetic acid were fiest added to neutralize
all remaining ammonia and then 625 grams of sodiu~
thiocyanate were added and the emulsion ripened at
60C for 15 minute6. The e~ulsion wa6 then cooled to
40C and wa~hed by a coagulation prnces6 three time6.
: 30 The resultant tabular grain AgBr emulsion
had an average grain volume of 0.09 ~m3, an
average grain thickne66 of 0.15 ~m and an a~erage
M of 6:1.
E~A~PLE 2~
To 550 liters of a well-6tirred aqueous
~olutio~, which ~ontained 1.6 per~en~ photographic
: ;
11
12 ~31~3~
gelatin and 11.1 kilogram6 of potas6ium bromide and
which wa~ ~aintained at 60C, wa~ added a 3 N AgN03
solution at constant flow. When thle bromide ion
concentration was lowered to O.OS~ N, 3226 grams of a
S 23 percen~ ammonia solution were added. The AgN03
flow continued until the bromide ion concentration
was lowered to 0.010 N, a which time ~he AgN03
~olution was halted. After 3 minu~e~ double-jet
addition of a 3 N AgN03 solution and a 3 N KBr
solution waQ initiated, with ehe AgN03 flow
increasing 413 ml~min/min for lS minute~ and the ~Br
; flow increasing to maintain a gLow~h bLo~ide ion
concentration of O o O10 N. Double~jet addition
continued at con~tant flow until 660 moles of AgN03
lS were di6pensed. Following preci~itation, 2440 grams
of glacial acetic acid were fi~st added to neutralize
all eemaining ammonia and then 825 qram6 of ~odium
thiocyanate were added and the emulsion ripened at
600C for 15 minutes. The emulsion ~a& then cooled to
40C and washed by a coagulati~n process three ~imes.
The resultant tabular qrain AgBr emulsion
had an average grain volume of 0.13 ~m3, an
averase grain ~hickne6s of 0.35 ~m and an average
AR of 2~
l'he emul~ions of Control 1 and E~amples 1
and 2 were che~ically 6en6itized with sulfur and gold
and spectrally senRitized to ~he green portion of the
spect~um with 1.3 g/Ag mole of anhydro-9-ethyl-5,5'-
dichloro-3,3'-bi6(4-sulfobutyl)oxacarbocyanine
hydroxide, triethylamine 8alt ~ensitizing dye and 0.2
g~Ag mols of ~otas6ium iodide. The ~en~itized
: emulsions were coated on both 6ide~ of a.polyethylene
terephthalate film support and given a SOkVp, lOOm~,
40 m6 exposur~ 40 inehe6 tlOl.6 cm) from a standard
tung~ten x-ray source through a continuou6 aluminum
13 ~3~3~
~epwedge and through a ~tandard green light emitting
6c~een such as Du Pont Quanta~V and proce~ed in a
conventional radiogra~hic element procee~or, Du Pon~
QC-I~T, u~ing a 6tandard developer solution, Du Pont
HSD.
The propertie~ of the resultant image~ are
6ummarized in Table 1 belo~.
Table 1
Cont.
1~ or Grain Grain
~x. Ba~ic Thick. Vol.Rel. PER
No. Geowth ~L_ (um3~AR SPeed SPeed
Cl No 0.10 0.16 14:1 225 100
El Yes 0.15 0.09 6:1 245 175
E2 Yes 0.35 0.13 2:1 260 140
1 Pro~ec~ed Equivolume Relative (PER) Speed i6
the average of the speed predicted by a~u~ing
speed i~ proportional to ~olume and ~hat
predicted by a~uming speed is proportional to
~olume to the 2/3.
EXAMPL~_3
To 4.375 liter6 of a well-stirred aqueous
601ution, which contained I.6 percent photographic
gel~ and 88.51 gra~ of poeassiu~ bromide and
; 25 which wae maintained at 60C, wa~ added a 3 N AgN03
601ution a~ constant 10w. When the broMide ion
concentration Wa8 10WeEed tO 0 . 058 N, 3 . B m1S Of a 23
;percent ammonia 601utio~n were added. The AgN03
flow cuntinued until the bromide ion concentration
~ 30 was lowered to 0.010 N, at which ~lme double-jet
:: addi~ion of a 3 N Ag~03 601ution and a 3 N KBr
eolution was initiated, with the AgN03 ~low
increa~ing 3.0 ml/min~min for 15 minute~ and ~he KBr
flow increa~ing to maintain a growth bromide io~
concentration of 0.010 N. Double-jet addition
. .
: ~ 13
14 ~3~3~
continued at constant flow until 5~25 moles of
AgN03 were dispensed. Following precipitation,
glacial acetic acid was fir6t added to neutralize all
remaining ammonia and then 6.5S grams of ~odium
thiocyanate were added and ~he emulsion ripened at
60C for 15 minutes. The emulsion was ~hen ~ooled to
40C and wa~hed by a coagulation proce6~ three time~.
The resultant tabular grairl AgBr emulsion
had an ave~age grain volume of 0.11 ~m3~ an
av~rage grain thickne~6 of 0.15 ~m and an average
AR of 6:1.
E~AMPLE_4
To 4.375 liters of a well~stirred aqueou~
solution, which contained 1.6 percent photograehic
gelatin and 88.51 grams of pota~sium bromide and
which wa6 maintained at 60C, was added a 3 N AgN03
solution at constant flow. When the bromide ion
cQncentration was lowered to O.Q58 N, 9.4 mls of a 23
percent ammonia fiolution were added. The AgN03
flow continued until the bromide ion concen~ration
was lowered ~o 0.020 N. at which time the AgN03
solution was halted. After 3 ~inutes double-jet
:~ addition of a 3 N AgN0 ~olution and a 3 N KBr
solu~:ion was initiated, with the AgN03 flow
in~rea6ing 3.0 ml/min/min fo.r 15 minutes and the KBr
; flow increasing to maintain a growth bromide ion
concentratio~ of O.Q20 N. Double-jet addition
continued at constant flow until 5.25 moles of
~; : AgN03 were dispensed. Following precipitation,
: 30 glacial a~etic acid ~as first added to neutralize all
~emaining ammonia and th~en 6.55 grams of sodium
- thiocyanate were added and the e~ul~ion ripened at
69C for 15 minute~. The emulsion wa~ then cooled to
40CC and washed by a coa~ulation process three times.
:
14
~316~3~
The resultant tabular grain AgBr emulsion
had an average grain volume o~ O.:L5 ~m , an
average grain thickness of 0.15 ~Dn~ and an average
AR of 7:1.
EXAMPLE 5
To 4.375 liters of a well-stirred aqueou
~olution, which ~o~ained 1.6 percent photogsaphic
gelatin and 08.51 gram~ of pota~ium bromide and
which was maintained at 60C, wa~ added a 3 N AgN03
~olution at constant flow. When the bromide io~
concentration wa~ lowered ~o 0.058 N, 7.0 mls of a 23
percent ammonia 601ution were added. The AgN03
flow continued until the bromide ion concentra~ion
wa~ lowered to 0.090 N, at which time the AgN03
solution wa6 halted. After 3 minutes double-jet
addition of a 3 N AgN03 ~olution and a 3 N KBr
solution was initiated, with the AgN03 flo~
increasing 3.2 ml/min/min for 15 minutes and the KBr
flow increasing to maintain a growth bro~ide ion
concentration of 0.040 N. Double-jet addition
continued at constant flow for 14 minutes, at which
; time the KBr solutiQn was hal~ed and the AgN03
~olution continued a~ con6tant flow until ~he bromide
ion concent~ation was lowered ~o O.OlS N, which was
then maintained by double-jet addition of ~Br and
: AgN03 at con~tant flo~ until 5.25 ~ole6 of A~N0~
wa6 dispen~ed. ~ol}owing precipi~ation, glacial
acetic acid was fir~t added to neutralize all
remaining a~onîa and then 6.55 grams of &odium
thiocyanate were added and the emul~ion ripened at
60C for lS minu~es. The emul~ion wa~ then cooled to
40C and wa~hed by a coagulation process three time~.
The resultant tabular grain AgBr emulsion
had an average grai~ volum~ of 0.23 ~m3, an
average grain thickne~ of 0.10 ~m, and an average
AR of 17:1.
~3~L6~3~
1~
The emulsions of Examples 3 to S were
chemically sensitized, spectrally 6ensitized, coated
~ingle 6ide on a sueport, and expo6ed a6 de~cribed
prior to Table 1.
The properties of the resultant images are
summarized in Table 2 below.
Table ?
Halt Grain Grain
: E~. Ripen- Thick. Vol. Rel. PEa
No~ inq (um) (~m3) AR Speed Speed
E3 no 0.15 .116:1 250 100
E~ y~s 0.15 .157:1 335 105
E5 yes 0.10 .2317:1 600 130
1 Projected Equivolume Relative ~PER~ Speed is
the average of the speed predicted by as6uming
speed is proportional to volume and that
-predicted by assuming speed i6 proportional to
volume~to the 2/3.
~ 0
,:~
~ 25
.
;
. 30
~'~
: : 35
';
.
~ 16
