Note: Descriptions are shown in the official language in which they were submitted.
~ ~756g2
--1--
DIRECT REVERSAL EMULSIONS AND PHOTOGRAPHIC
ELEMENTS USEFUL IN IMAGE TRANSFER FILM UNITS
This invention relates to novel direct
reversal emulsions and to photographic elements
incorporating these emulsions. Further, the lnven-
tion rel~tes to image transfer ilm uni~s incorporat-
ing these emulsions.
_ck&round of the I vention
The most commonly employed photographic ele-
ments are those containing one or more radiatlon sen~sitive silver halide emulsion layers. Their wide-
spread use is attributable to the excellent quality
images they are capable of producing and to their
high speed 9 allowing them ~o be employed in hand-held
cameras under a variety of lighting conditions.
Nevertheless, silver halide photographic
elements have historically exhibited two significant
limitations in terms of vlewing the photographic
imag~O Firs~, imagewise exposure of the silver
halide emulsion layer does not produce an immediately
viewable photographic image. Exposure produces an
invisible laten~ image in the silver halide emul
sion. Processing o the latent image is required to
produce a viewable image. Historically this has
meant removing the photographic element from the
camera and processing ln one or more queous solu-
tions to obtRin a viewable image. Second, in most
instances the first viewable image obtained is ~
negative image~ and a second exposure through the
negative lmage of an additional photographic element
and processing thereof i6 required to produce a view
able positive of the ima8e initially photographedO
The f~rst limitat~on can be overcome by employing
image transfer technlques, and the second limitation
can be overcome by employing direct-positive im~ging,
partlcularly direct reversal imaging.
a. D'~e~ e~
Photcgraphic elements which produce ima~es
having an optical density directly related to the
radiation received on exposure are said to be nega-
tive-working. A positive photographic image can be
formed by producing a negative photographic lmage and
then forming a second pho~ographic image which is a
negative o the first negative- that ls, a positive
image. A direct-positive image is understood in
photography to be a positive image that is formed
without first forming a negative image. Positive dye
images which are not direct-positive images are com-
monly produced in color photography by reversal pro-
cessing in which a negatlve silver image is formed
and a comple~entary posi~ive dye image is then formed
in the same photographic element. The term "direct
reversal" has been applied to direct-pos1tive photo-
graphic elements and processing which produces a
positive dye image withou~ forming a negative silver
image. Direct-positive photography in general and
direct reversal photography in particular are advan-
tageous in providing a more straight forward approach
to obtaining positive photographic images.
A conventional approach to forming direct-
positive images is to use photographic elementsemploying internal latent image-forming silver halide
grains. After imagewise exposure, the sllver halide
grains are developed with a surface developer--that
is, one whlch will leave the la~ent image sites with-
in the sllver halide grains substantially unreveal-
ed. Simultaneously, either by uniform light exposure
or by the use of a nucleating agent, the silver
halide grains are subjected ~o development conditions
that would cause fogging of a surface latent image-
forming photographic element. The internal latentimage-forming silver halide grains which received
actinic radiation during imagewise exposure develop
1756~2
--3--
under these conditions at a slow rate AS compared to
the internal latent imag2-forming silver halide
grains not lmagewise exposed. The result is a
direct-positive silver image. In color photography,
the oxidized developer that is produced during silver
development ls used ~o produce a correspondlng posi-
tive~ direct reversal dye image. Multicolor dlrect
reversal photographic images have been extensively
investigated in connection with image ~ransfer pho-
tography.
It has been found advan~ageous to employnucleating agents in preference to uniform l~ght
exposure in the process described above. The term
"nucleating agent" is employed herein in i~s art-
recognized usage to mean a fogging agent ~apable ofpermit~ing the selective development of internal
laten~ image-forming B ilver halide grains which have
not been imagewise exposed in preference to the
development of silver halide grains having an inter-
nal latent image formed by imagewise exposureO
While nucleating agents have been long knownto ~he photographic art, recent interest has focused
on identifying nucleating agents that are effective
in relatively low concentration levels and that can
be incorporated directly into silver halide emul-
sions. Exemplary of known incorporated nucleating
agents are those disclosed by Whitmore U.S. Patent
3~227,S52, Lincoln et al U.S. Patent 3,615,615, Kurtz
et al U.S. Patents 3,719,494 and 3,734,738, Lincoln
et al U.S. P~tent 3,759,901, Leone et al U.S. Patents
4,030,925, 4,080,207, and 4,276,364, Adachi et al
U.S. Patent 4,115,122, von Koni~ et al U.S. Patent
4,139,387, and U.K. Patents 2~011,391 and 2,012,443.
Nucleating agen~s particularly adapted for use in
direct reversal photographic elements intended to be
processed at lower pH levels are disclosed by Baralle
et al U.S. Patents 4,306,016, 4,306,017, and
~,315,986.
1 ~7~6~2
Dlrect reversal emulslons useful with
adsorbed nucleating agents ~nclude emulsions capable
of forming latent image centers primarlly in the
interior of the silver hal1de grains as opposed to
~heir surface--hereinaf~er also referred to as inter-
nal latent i~age-forming emulsions. Such emulsions
can ~ake the form of halide~conversion ~ype emul
sions, such as illustrated by Knot~ et al U.S. Patent
29456,953 and Davey et ~1 U.S. Patent 2,592,250, and
core-shell emulsions, such as illustrated by Porter
et al U.S. Patent 3 9 206,313, Evans U.S. Patents
3,761,276 and 3,923,513; and Atwell e~ al U.S. Patent
4,035,185-
Direct reversal emulsions exhlbit art-
recognized disadvantages as compared ~o negative-
working emulsions. Although Evans, cited above, has
been able to increase photographic speeds by prop~rly
balancing internal and surface sensitivities, direct
reversal emulsions have not achieved photographic
speeds equal to the faster surface latent image-form-
ing emulsions. Second, direct reversal emulsions are
limited in their permissible exposure latitude~ When
exposure is extended rereversal oc:curs. That is, in
areas receiving extended exposure a negative image is
produced. This is a sign~ficant limitation to
in-camera use of direct reversal photograph~c ele-
ments, since candid photography does not always per-
mlt control of exposure condi~ions. For example, a
very high contrast scene can lead to rereversal in
some lmage areas~
A schematic lllustratlon o rereversal is
provided in Figure 1, which plots density versus
exposure. A charac~eristic curve 1 (stylized to
exaggerate curve features for simplicity of discus-
sion~ is shown for a direct reversal ~muls~on. Whenthe emulsion i8 coated as a layer on a support9
exposed, and processed, a density is produced. The
6 9
-5 -
characteristic curve ls the result of plot~lng
varicus levels of exposure ver~us the corresponding
density produced on proce~ing. At exposures below
level A underexposure occurs and a m~ximum density is
obtained which does not vary as a function of expo-
sure. At exposure levels between A and B useful
direc~ reversal imaging can be nchieved, since
d nsity varies inversely with exposure. If exposure
occurs between the levels indicated ~y B and C, over-
exposure results. That is 9 density ceases to vary asa function of exposure in this range of exposures.
If a subject to be photographed varies locally over a
broad range of reflected light intensi~ies, a photo-
graphic element containing the direc~ reversal emul-
sion can be simultaneously exposed in diferen~ areasat levels less than A and greater than B. The result
may, however, still ~e aesthetically pleasing,
although highlight and shadow detail of the subject
are both lost. If it is attemptecl to increase expo-
sure for this subject, however, to pick up shadowdetail, ~he result can be to increase highlight expo-
sure to levels above C. When this occurs, rereversal
is encountered. That is, the area6 overexposed
beyond exposure level C appear as highly ob~ection-
able negative images, since densit:y is now increasingdirectly with exposure. Useful exposure lati~ude can
be increased by more widely separating exposure
levels A and B, but this is objectionable to the
extent that it reduces contrast below optimum levels
for most subjects. Therefore reduction in rereversal
is most profitably directed to increasing the separa-
tion be~ween expo~ure levels B and C so that over-
exposed areas are less likely to produce negative
images. (In actual practice the various segments of
the characteris~lc curve tend ~o merge more smoothly
than illustrated.)
:175~9
-6
b. ~ e transfer photog~aphy
Image transfer photography has made it
possible to reduce the delay between imagewise expo-
sure and obtaining a viewable image. Immediately
after imagewise exposing ~he radiation sensltive
silver halide emulsion layer or l~yers, a processing
solution can be brought into contact therewlth. As
silver halide develo?ment occurs, a black~and-white
~ransferred 6ilver image or A transferred dye image
can be formed in a receivlng layer for viewing. In
this way, visual access to the photographic image can
occur in minutes or even seconds.
Still, though measured in seconds, the delay
in providing visual access remains an lmportant limi-
tation ln silver halide image ~ransfer photography.
Sub~ect opportunlties can be fleeting, and the pho-
tographer needs as nearly an instantaneous visual
verification of an acceptable photographic image as
can be offerred.
Although image transfer has reduced the time
required for image access in silver halide photogra-
phy, this advantage has not been achieved withou~
other sacrifices. One significan~: long term concern
of image trsnsfer photography relates to consumption
of silver~ Multicolor silver hallde photographic
elements which are conventionally processed and dye
image transfer film un~ts both employ relatively high
silver coverages to obtain maximum photographic
speed. Typically about 1000 milligrams per square
meter of silver is required to form each of the blue,
green, and red exposure records. In conventionally
processed multicolor photographic elements the image
produced contains no silver and all of the eilver
present in the photographic element is, in theory,
recoverable~ On the other hand, in image transfer
photography silver is seldom recovered, and in inte-
gral format image transfer film uni~s all of the sil-
6 9 ~
--7--ver remains with the photographic film units forming
the viewable image.
Another disadvantage9 lnherent in image
transfer pho~ography, is the reduction ln image
sharpness attributable to diffusion. As the lmage
forming materials diffuse from the silver halide
emulsion layer or an adjacent dye releasing layer,
diffusion occurs both in the direction of the receiv-
ing layer and laterally, leading to image spreading
and loss of sharpness. Sharpneæs can be improved by
decreasing the length of the diffusion path to the
receiving layer. This is controlled by the number
alld thickness of the layers to be traversed. Unfor-
tunately, ~h~ minimum thickness of the silver halide
emulsion layers is limited by the size of the silver
halide grains and the weight ratio of gelatin to sil-
ver halide. Further, in multicolor lmage transfer
film units employing ~hree superimposed dye-providing
layer units, in~ervening dye-providlng layer units
2Q and separating interlayers must be penetrated by dlf-
fusing dyes migrating to the receiving layer.
Another consideratlon that arises in image
transfer photography is image density variance as a
function of temperature differences. S~nce subject
opportunities are presented under a variety of tem-
perature conditions and ~nce the primary advantage
of image transfer photography is ready image access,
i~ follows that the ability of image transfer photo-
graphic elements ~o produce acceptable images at a
variety of temperatures is also import~nt. Image
~ransfer pho~ography is much different than conven-
tional photography in this respect, since in the
latter processing ls rarely undertaken wl~hout con-
trol of temperature.
A number of imaging limitations are encoun-
tered in producing transferred images with dyes. For
example, both the high silver coverages noted above
17569
8-
and larger ~han stoichiome~rically predic~ed amounts
of dye-image-providing materials are required to
obtain transferred dye images of acceptable maximum
densities. To the extent ths~ the eficiency of dye
transfer declines from stoichiometrically predicted
levels, more dye-image-providing materials must be
incorporated in the photographic elemen~s and the
layer thicknesses must be increased to incorporate
added amounts of these materials. Further, the rate
of release of dyes for transfer can affect the time
required to produce a viewable image. When the
development reactlon product is relied upon to
preclude dye transfer, as in the case of many conven-
tional positive-working dye-image-forms, the rate of
silver halide development also limits the maximum
rate at which image dye can become available for
transfer, s;nce too rapid release of image dye in
relation to the rate of silver halide development can
result in the loss of image discrimination. Improve-
ments of any one or a combination of these character-
lstics can9 of course, significantly improve dye
image transfer.
Silver hallde image transfer film units are
generally well known in the art of photography and
require no detailed description. Broad discussions
of image transfer elements and processes (including
process solu~ions) can be found in Chapter 12 9 "One
StPp Photography", Neblette's Handbook of Photo~raphy
and Reprography Materials, Processes and Systems, 7th
Ed. (1977), in Chapter 16, "Diffusion Transfer and
Monobaths", T. H. James, The Theory of ~he Photo~ra-
phic Process, 4th Ed. (1977), and A. Rott and E.
Weyde Photo~raphic Silver Halide Diffusion Pro-
cesses, Focal Press, (1972).
c. Tabular silver halide ~,ralns
A great varie~y of regular and irregular
grain shapes h~ve been observed in silver halide
photographic emulsions intended for imaging applica
tions. Regular gralns are often cubic or octa-
hedral. Grain edges can exhibit rounding due to
ripening effects, and in the presence of strong
ripening agents~ such as ammonia, the grains may even
be spherical or near spherical thick platelets, as
described, for example by Land U.S. Patent 3,8~4~871
and ~elikman and Levi Makin~ and Coatin~ Photogra
Emulsions, Focal Press, 1964, page 223. Rods and
~abular grains in varied portions have been frequent-
ly observed mixed in among other grain shapes, par~
ticularly where the pAg (the negative logarithm of
silver ion concentra~ion) of the emulsions has been
varied during precipitation, as occurs, for example
in single-~et precipîtations.
Tabular grains (those areally extended in
two dimensions as compared to their thickness) have
been extensively studied, often ln macro-sizes having
no photographic utility. Tabular grains are herein
defined as those having two substantially parallel
crystal faces, each of which is substantially larger
than any other single crystal face of the grain. A
discussion of tabular bromoiodide grains appears in
Duffin, _otographio Emulsion Chemistry, Focal Press,
1966, pp. 66-72, and Trivelli and Smith, "The Effect
of Silver Iodide Upon the S~ructure of Silver
Bromo-Iodide Precipitation Series", The Photographic
Journal, Vol. LXXX, July 1940, pp. 285-288. Trivelli
and Smith observed a pronounced reduc~ion in both
grain size and aspect ratio with the introduction of
iodide. Tabular silver bromide emulsions are
discussed by de Cugnac and Cha~eau, "Evolution of the
Morphology o Silver Bromide Crystals During Physical
Ripening", Science et Industries Photo~raphi~ues,
Vol~ 33, No. 2 (1962), pp. 121-125. 5ulfur
sen~iti~-ed tabular grain silver bromide emulsions
having an average aspect ratio of from about 5 to 7:1
I ~ 7~9~
10 -
wherein the tabular grains account for greater than
50% of the projected area of the total grain
population were incorporated in a direct X~ray
radiographic product, No Screen X-Ray Code 5133 ~old
S by Eastman Kodak Company from 1937 until the 1950's.
Gutoff, "Nucleation and Growth R~tes During the
Precipitation of Silver Halide Photographic
Emulsions", Photographic Science and En~ineering,
Vol. 14, NQ. 4, July-August 1970, pp. 248~257,
reports preparing silver brom1de and silver
bromoiodide emulsions of the type prepared by
single-jet precipitations using a continuous
precipitation apparatus.
Bogg, Lewis, and Maternaghan have recently
published specific procedures for preparing emul~ions
in which a m~Jor proportion of the silver halide is
present in the form of tabulsr grains. Bogg U.S.
Patent 4,063,951 teaches forming silver halide
crystals of tabular habit bounded by {100} cubic
faces and having an aspect ratio (based on edge
length) of from 1.5 to 7:1. The tabular grains exhi-
bit square and rectangular major ~urfaces charac~er-
istic of ~100} crystal faces. Lewis U.S. Patent
4,067,739 teaches the preparation of silver halide
emulsions wherein most of the crystals are of the
twinned oc~ahedral type by forming seed crystals
causing ~he seed crystals to increase in size by
Ostwald ripening in the presence of a silver halide
solvent, and completing grain growth without renu-
cleation or Ostwald ripening while controlling pBr(~he negative logarithm of bromide ion eoncentra-
tion~. Maternaghan U.SO Patents 4,150,994 and
4,184~877~ teach the formation of silver halide
grains of fla~ twinned octahedral configuration by
employing seed crystals which are at least 90 mole
percent iodide. (Except as otherwise indicated9 all
references to halide percentages are based on silver
`` ~ 175692
present in ~he corresponding emulsion, grain, or
grain region being discussed; e.g., a grain consist-
ing of silver brom;odide containing 40 mole percent
iodide also con~ains 60 mole percent bromide.) Lewis
and Maternaghan report increased covering power.
Maternaghan states that the emulsions are useful in
camera films, both black-and-white and colorO Bogg
specifically reports an upper limit on aspect ratios
of 7:1, but, from the very low aspect ratios obtained
by the examples, the 7:1 aspect ratio appears unreal-
istically high. It appears from repeating examples
and viewing the photomicrographs published that the
aspect ratios realized by Lewis and Maternaghan were
also less than 7-1.
Ma~ernaghan U.S. Patent 4,184,878 (wi~h
which U.K. Pa~ent 1,570,581 and German OLS publica-
tions 2,905,655 and 2,921,077 are considered essen-
tially cumulativ~ teaches the formation of direct-
positive images by preparing a tabular grain e~ulsion
essentially similarly as described by Maternaghan
U.S. Patent 4,184,877, but with the incorporation of
an internal sensitizer and processing in a developer
containing a nucleating agent.
Wilgus and Haefner Can. Ser.No. 415,345 9
filed concurrently herewith and commonly assigned,
titled HIGH ASPECT RATIO SILVER BROMOIODIDE EMULSIONS
AND PROCESSES FOR THEIR PREPARATION, discloses high
aspect ratio ~ilver bromoiodide emulsions and a
process for their preparation.
Daubendiek and Strong Can. Ser.No. 415,364,
filed concurrently herewith and commonly assigned,
titled AN IMPROVED PROCESS FOR THE PREPARATION OF
HTGH ASPECT RATIO SILVER BROMOIODIDE EMULSIONS,
discloses an improvement on the processes of
Maternaghan whereby high aspect ratio tabular grain
silver bromoiodide emulsions can be prepared.
fi ~ 2
-12-
Solberg, Piggin, and Wilgus Can. Ser.No.
415,250, filed concurrently herewith and commonly
assigned, titled RADIATION-SENSITIVE SILVER
BROMOIODIDE EMULSIONS 9 PHOTOGRAPHIC ELEMENTS, AND
PROCESSES FOR THEIR USE, discloses high aspect ratio
tabular grain silver bromoiodide emulsions wherein a
higher concentration of iodide is present in an
annular region than in a central region of the
tabular grains.
Wey Can. Ser.No. 415,257, filed concurrently
herewith and commonly assigned, titled IMPROVED
DOUBLE-JET PRECIPITATION PROCESSES AND PRODUCTS
THEREOF, discloses a process of preparing tabular
silver chloride grains which are substantially
internally free of both silver bromide and silver
iodide. The emulsions have an average aspect ratio
of greater than 8:1.
Kofron et al Can. Ser.No. 415,363, filed
concurrently herewith and commonly assigned, titl~d
SENSITIZED HIGH ASPECT RATIO SILVER HALIDE EMULSIONS
AND PHOTOGRAPHIC ELEMENTS, discloses chemically and
spectrally sensltized high aspect ratio tabular grain
silver halide emulsions and phstographic elements
incorporating these emulsions.
Mignot Can. Ser.No. 415,263, filed concur-
rently ~erewith and commonly assigned, titled SILVER
BROMIDE EMULSIONS OF NARROW GRAIN SIZE DISTRIBUTION
AND PROCESSES FOR THEIR PREPAKATION, discloses high
aspect ratio tabular grain silver bromide emulsions
wherein the tabular grains are square or rectangular.
Dickerson Can. Ser.No. 415,336, filed
concurrently herewith and commonly assigned, titled
FOREHARDENED PHOTOGRAPHIC ELEMENTS AND PROCESSES FOR
THEIR USE, discloses producing silver images of high
covering power by employing photographic ele~ents
containing forehardened high aspect ra~io tabular
grain silver halide emulsions.
.~
7~2
-13-
Abbott and Jones Can. Ser.No. 415,366, filed
concurrently herewith and commonly assigned, titled
RADIOGRAPHIC ELEMENTS EXHIBITING REDUCED CROSSOVER,
discloses the use of high aspect ratio tabular grain
silver halide emulsions in radiographic elements
coated on both ma;or surfaces of a radiation trans-
mit~ing support to control crossover.
Jones and Hill C~n. Ser.No. 415,263, filed
concurrently herewith and commonly assigned, titled
PHOTOGRAPHIC IMAGE TRANSFER FILM UNIT, discloses
image transfer film units containing tabular grain
silver halide emulsions.
Hoyen Can. Ser.No. 415,367, filed concur-
ren~ly herewith and commonly assigned, ~itled
DIRECT-POSITIVE CORE-SHELL EMULSIONS AND PHOTOGRAPHIC
ELEMENTS AND PROCESSES FOR THEIR USE, discloses the
use of divalen~ or trivalent metal ion dopan~s in the
shell of core-shell emulsions to reduce rereversal.
Summary of the Invention
-
In one aspect this invention is directed to
a radiation~sensitive emulsion particularly adapted
to forming a direct-positive image comprised of a
dispersing medium, silver halide grains capable of
forming an internal laten~ image, and a nucleating
agent. At least 50 percent of t:he total projected
area of the silver halide grains is provided by
tabular grains which have an average thickness of
less than 0~5 micron and an average aspect ratio of
greater ~han 8:1.
In another aspect, this invention is
directed to a photographic element comprised of a
support and at least one radiation-sensitive emulsion
layer compris~d of a radiation-sensi~ive emulsioa as
described above.
In an additional aspect, this invention is
directed to a pho~ographic image tr~nsfer film unit
comprising a suppor~, at least one emulsion layer on
,~
6 9 ~
the support containing a dispersing med~um, radia
tion-sensitive silver halide grains capable of
formlng an lnternal latent ima~e; and a nucleatlng
agent adsorbed to the surface of said silver halide
grains. At least 50 percent of the total pro~ected
area of the silver halide grains is prov~ded by
tabular grain6 which have an average aspect ratio of
greater than 8:1.
It is an adv~ntage o the present invention
that direct-positive and, more specifically, direct
reversal images can be produced while realizing also
the advantages of tabular grain emulsions. The
emulsions of the present inven~ion exhibit improved
s~ability and less image dependence on temperature as
compared to nontabul~r direct reversal emulsions.
Further~ the emulsionæ of the present invention in
certain preferred embodiments permit wider exposure
latitude without encoun ering rereversal.
Kofron et al, cited above, discloses
slgnificant advantages in speed-granularity relation-
ship, sharpness 9 and blue and minus blue sensitivi~y
differences for chemically and spectrally sensitized
high aspect ratio tabular grain emulsion~. The high
aspect ratio tabular grain emulsions enhance sharp-
ness of underlying emulsion layers when they arepositioned to receive light that is free of signifi-
cant scattering. These emulsions are particularly
effective in this respect when they are loc~ted ln
the emulsion layers nearest the source of exposing
radiation. When spec~rally ~ensitized outside the
blue portion of the spectrum, the high ~spect ratlo
tabular grain silver bromide and bromoiodide emul-
sions exhibit a large separation in their æensitivity
in the blue region of the spectrum as compared to the
region of the spectrum to which they are spectrally
sensitized. Minus blue sensitized high aspect ratlo
tabular grain silver bromide and bromoiodide emul-
~ ~7~92
-15-
sions are much less sensitivP to blue light thPn to
minus blue light and do no~ require filter protect~on
to provide acceptable minus blue exposure records
when exposed in neutral light, such as daylight at
5500K. The high aspec~ ratio tabular graln silver
bromoiodide emulsions exhibit improved speed-granu-
larity relationshipæ as compared to previously known
tabular grain emulsions and as compared to the best
speed-granularity relationships heretofore achieved
with silver bromoiodide emulsions gener~lly. Very
large increases in blue speed of high aspect ratio
tabular grain silver bromide and bromoiodide emul-
sions have been realized as compared to their native
blue speed when blue spectral sensitizers are
employed. These advantages can also be realized by
the present inventlon.
Jones and Hill, cited above, teaches that
photographic image transfer film units containing one
or more high aspect ratio tabular graln emulsion
layers are capable of producing viewable images with
less time elapsed af~er the commencement of process-
ing. Further, the image transfer film units are
capable of producing images of improved sharpness.
They are partlcularly advantageous as applied to
multicolor dye image form~tlon, permitting reduction
in silver coverages, more efficient use of dye image
formers, more advantageous layer order arrangement~,
and elimination or reduction of yellow filter materi-
als. These advantages can also be realized by the
image transfer film units of this invention.
_ ~ee Ge--~Lly~on ~e hJ~Je~L~ ~
The invention can be better understood by
reference to the following detailed description of
preferred embodiments considered in con~unction with
the drawings, in which
Figure 1 is ~ stylized characteristic curve
of a direct reversal emulsion, and
13175B~2
-16-
Figure 2 is a schematic diagram illustra~ing
an arrangement for establishing angular scatter of
exposing radi~tion.
Description of Preferred Embodiments
This invention relates to high aspec~ ratio
tabular grain direct-positive silver halide emulsions
and to photographic elements which lncorporate one or
more of these emulsions. In one specific asp~c~ this
invention is d1rected to photographic image transfer
film units comprised of a photographic support, one
or more high aspect ratio tabular grain direct rever-
sal emulsions, and a receiving layer for providing a
viewable transferred image following lmagewise expo
sure and processing of the silver halide emulsion.
Although the invention is d~scribed below
employing topic héadings for convenience, it is
intended that the description be read and interpreted
as a whole to appreciate the invention fully.
Tabular Internal La~ent Ima~e-Formin~ Emu1sions
The emulsions employed in the practice of
this invention are high aspect ra~lo tabular grain
internal latent image-forming emulsions. The emul-
sions are comprised of a dispersing medlum, silver
halide grains capable of forming an internal latent
image, and a nucleating agent. As applied to the
emulsions of the present invention the term "high
~spect ratio'l is herein defined as requiring that the
silver halide grains of the emulslon have ~n average
aspect ratio of greater than 8:l and account for at
least 50 percent of the total projected area of the
silver halide grains.
As employed herein the term "aspect ratio"
refers to the ratio of the diameter of the grain to
its thickness. The "diameter" of the grain ~s ~n
turn defined as the diameter of a circle having an
area equal to the proJected area of the graln as
viewed in a photomicrograph of an emulsion sample.
~75~92
-17-
The internal latent image-forming tabular grains of
the presen~ invention have an average aspect ratlo of
grea~er ~han 8:1 and preEerably have an average
aspect ratio of greater than 10:1. Under optimum
condi~ions of preparation aspect ra~ios of 50:1 or
even 100:1 are contemplated. As will be apparent,
the thinner the gralns, the higher their aspect ratio
~or a given diameter. Typically grains of desirable
aspect ratios are those having an average thickness
of less than 0.5 micron, preferably less th~n 0.3
micron, and optimally less than 0.2 micron. Typical-
ly the tabular grains have an average thickness of at
least 0.03 micron9 although even thinner tabular
grains can in principle be employed--e.g. 9 as low as
0.01 micron, depending on halide content. In a
preferred form of the invention the tabular grains
account for at least 70 percent and optimally at
least 90 percent of the total pro~ec~ed area of the
silver halide grains.
Both the average aspect ratios of the
tabular grains snd the percentage of the total
projected area of the silver halide grains present
can be determined by procedures well known to those
skilled in the art. From shadowed elec~ron micro
graphs of emulsio~ samples it is possible to visually
identify the t~bular grains. These grains have
large, substantlally planar opposed ma~or surfaces.
The opposed major crystal faces of each tabular grain
are much larger than any remalning single crystal
face of the grain. By measuring the æhadow length
cast by each ~abular grain it i B pos~ible to deter-
mine its thickness. This can be compared to its
diameter to determine its aspect ratio. In practice
it ls usually simpler to ob~ain an average thickness
and an average diameter of the tabular grains and to
calculate the average aspeet ratio as the ratio of
these two averages. Whether the averaged individual
~5~2
-18-
aspect ratios or the averages of thickness and
diam ter are used to determine the average aspect
ratio9 within the tolerances of grain measurements
contemplated, the average aspect rfitios obtainPd do
S not sîgnificantly differ. The pro~ected areas of the
tabular sllver hallde grains can be summed, the
projected areas of the remaining silver halide grains
in the photomicrograph can be summed separately, and
from the two sums the percentage o the total
projected area of the silver halide grains provided
by the tabular grains can be calculated. The term
"projected area" is ueed in the same sense as he
terms "projection area" and "pro~ec~ive area"
commonly employed in ~he art; see, for example, James
and Higgins, Fundamentals of Photo~ra~hic Theory,
Morgan and Morgan, New York, p. 15.
The high aspect ratio tabular grain int~rnal
latent image-forming emulsions of thls inven~ion can
be prepared merely by modifying the processes for
preparing high aspect ratio tabular grain emulsions
such as those taught by Wilgus and Haefner,
Daub~ndiek and Strong, Solberg et al, Wey, and Wey
and Wilgus, ci~ed above, to favor the formation of
internal latent ~ma~e centers on exposure. This can
be accomplished by employing techniques similar to
those demonstrated in the examples of Porter e~ al
U.S. Patent 33206,313, Evans U.S. Patents 3,761,276
and 3,923,513, and Atwell et al U.S. P~tent
4,035,185, cited above to illustrate conventional
direct reversal emulsions. Typically internal lQtent
image-forming silver halide grains prepared by such
~echniques have an averege diameter of at least 0.6
micron, and the preferred tabular grains of this
invention also exhibit an ~verage diameter of at
least 0.6 micronO Since the tabulAr quality of high
aspect ratio grains i 5 degraded by high levels of
halide conversion, the use of halide conversion
1 175B9~
-19-
techniques, such as illustrated by Knott et al and
Davey e~ al, cited above, is not preferred in the
practice of thiæ invention. Specific preferred
techniques for modifying high a~pect ratio tabular
grain emulsions during their preparation ~o favor the
formation of internal laten~ image centers are
described below.
Perhaps the s~mplest manipulstive appro~ch
to favoring internal latent image formation is to
incorporate a metal dopant within the tabular grains
as they are being formed. The metal dopant can be
placed in the reaction vessel in which gra~n forma-
tion occurs prior to the introduction of silver
sal~. Alternately the metal dopant can be introduced
during silver halide grain growth at any stage of
precipitation, with or without interrupting silver
and/or halide salt introduction.
Iridium is specifically contemplated as a
metal dopan~ is preferably incorporated within
the silver halide grains in concentrations of ~rom
about 10- 8 to 10- 4 mole per mole of silver- The
irldium can be conveniently incorporated into the
reac~ion vessel as a water soluble salt, such as an
alkali me~al salt of a halogen-iridium coordination
complex, ~uch as sodlum or potassium hexachloroiri-
date or hexabromoiridate. Specific examples of
incorporating an iridium dopant are provided by
Berriman U.S. Patent 3,~67,778.
Lead is also a specifically contemplated
metal dopant fcr promoting the formation of internal
lstent image centers. Lead is a common dopant ln
direct print and printout emulsions and can be
employed in the practice of this invention in s~milar
concentration ranges. It is generally preferred that
the lead dopant be present ln a eoncentration of at
least 10- 4 mole per mole of silver. Concentrations
up to about 5 X 10- 2, preferably 2 X 10- 2, mole
~75
-20
per mole of silver are con~empl~ted. Lead dopan~s
can be introduced similarly as iridium dopants in the
form of water solllble salts, such as lead acetate,
lead nitrate, and lead cyanide. Lead dopants are
p~rticularly illustrated by McBride U.S. Patent
3,287,136 and Bacon U.S. Patent 3,531,291.
Another technlque for promoting the forma-
tion of internal latent image centers is to stop
silver halide grain precipitation after a grain
nucleus or core has been produced and to sensitize
chemically the surface of the core. Thereafter addi-
tional precipitation of silver halide produces a
shell surrounding the core. Particularly advanta-
geous chemical sensitizers for this purpose are
middle chalcogen sen~itizers--i.e., sulfur, selenium,
and/or tellurium sensitizers. Middle chalcogen sen~
sitizers are preferably employed in concen~rations in
the range of from about 0.05 to 15 mg per silver
mole. Preferred concentrations are from about 0.1 to
10 mg per silver mole. Further aclvantages can be
realized by employing a gold sensitizer in combina-
tion. Gold sensitizers are preferably employed in
concentrations ranging from 0.5 to 5 times that of
the middle chalcogen sen~itizers. Preferred concen-
25 trations of gold sensitizers typically range fromabout 0.01 ~o 40 mg per mole of silver, most prefer-
ably from about 0.1 to 20 mg per mole of silver.
Controlling contrast by controlling the ratio of
middle chalcogen to gold sensitizer is part~cularly
30 taught by Atwell et al U.S. Patent 4~035,185, cited
above. Evans, cited above, provides specific
examples of middle chalcogen internal sensitizations.
Although it is usually preferred to produce
internal sensitization sites by the occlusion of
35 foreign (i.e., other than silver and halogen) materi-
als within the tabular grains, this i~ not required~
Sensitization sites formed by the occlusion of
9 ~
-21-
foreign mater~als are hereinafter referred to as
internal chemical sensi~ization sites to distinguish
~hem from internal physical sensitizatlon 6itPS. I~
is possible to incorporate int~rnal physical senslti-
zation sites by providing irregularities in thecrystal lattice for capturing photolytically generat-
ed electrons. Such internal irregularities can be
created by discontinuities in silver halide grain
precipitatlon or by fibrupt changes in the halide
10 content of the tabular grains. For example, it has
been observed that the precipitation of a tabular
silver bromide core followed by shelling wi~h silver
bromoiodide of greater than 5 mole percent iodide
requires no internai chemical sensitizstion to pro-
15 duce a direct reversal image.
Silver halide surrounds the internal sen6itization sites within the tabular grains. The mini-
mum amount of overlying ~ilver halide is just that
required to prevent access of the developer employed
20 in processing to the in~ernal latent image. This
will ~ary as a function of the ability of the devel-
oper to dissolve the silver halide grains during
development. For developers having very low silver
halide solvency the la~ent image centers can be
25 located only a few crystal lattice planes below the
surface of the tabular sllver halicle grains. If the
internal latent image center forms at or near the
center of the grain, as where a metal dopant is
present in the reaction vessel at the start of silver
30 halide precipitation, then all or most of the silver
halide forming the grain will lie between the latent
image center and the grain surface. On the other
hand, if a tabular silver halide grain Is precipi-
tated to substantially its final slze and aspect
35 ratio before internal sensitization, the addition of
only a small amount of additional silver halide is
needed to protect the sensitizatlon sites from a
a~7~s~
22-
surface or sub-surface developer. The pl~cement of
internal sensitiza~ion ~ites in ~ilver halide grains
is particularly illustra~ed by Morgan U.S~ Patent
33917,485 and Research Disclosur~, Vol. 181, May
1979, Item 18155. Since grain nuslei formation is
critical to obtaining tabular grains of high aspect
ratio, it is generally preferred to delay internal
sensitization until at least the commencement of ~he
growth stage of tabular grain formation. When inter-
10 nal sensitizatiGn is delayed until the tabular grainshave substantially achieved their desired size and
aspect ra~io, then additional silver halide can be
precipi~ated onto the tabular graills by any conven-
tional silver halide precipitation ~echnique, includ-
15 ing Ostwald ripening of a ~lended shell emulsion aBtaught by Porter et al U.S. Patentæ 3,206 a 313 and
3,317,322.
The amount of overexposure which can be
tolerated withou~ encountering rereversal can be
20 increased by incorporating into the tabular silver
halide grains metal dopants for this purpose. Hoyen,
cited above, discloses the use of clivalent and
trivalent metal ions as dopants in the shell of
core-shell emulsions to reduce rereversal. Preferred
25 metal dopant~ for this purpose are cationic cadmium,
zinc, lead, and erbium. These dopants are generAlly
effective at concentration levels below about S X
10- 4 ~ preferably below 5 X 10-5, mole per mole of
sllver. Dopant concentrations of at least 10-~,
30 preferably at least 5 X 10-6, mole per silver mole,
should be present in the reaction vessel during
silver halide precipi~ation. The rereversal modify-
ing dopant is effective if in~roduced at any B~age of
~ilver halide precipitation. If the tabular silver
35 halide graiDs are viewed as being comprised sf ~ core
and a shell, the rereversal modifying dopant can be
incorporated in either or both of the core and
~ ~75~)92
-23 -
shell. It is preferred that the dopant be introduced
during the latter stag~s of precipi~ation (e.g.,
confined to the shell) for reasons previously noted.
The metal dopan~s can be introduced into the r~action
vessel as wa~er soluble metal salts, such as divalent
and trivalent metal halide salts. Zinc, lead, and
cadmium dopants for silver halide ln similar concen
trations, bu~ to achieve other modifying effects~ are
disclosed by McBride U.S. Paten~ 3,287,136, Mueller
10 et al V.S. Patent 2~950,972, Iwaosa et al U.S. Patent
3,901,711, and Atwell U.S. Patent 4,269,927. Other
techniques for improving rereversal characteristics
discussed below can be employed independently or in
combinatlon with the metal dopants described.
Preferred high aspect ratio lnternal latent
image-forming tabular grain emulsions according to
this invention are silver bromide and bromoiodide
emulsions. Subject to modifications to produce
internal sensitization sites and incorporate metal
20 dopants as described above, high aspect ratio tabular
grain silver bromoiodide emul6ions can be prepared by
a precipitation prooess which forms a part of the
Wilgus and Haefner invention. In~o a conventional
reaction vessel for silver halide precipitation
25 equipped with an efficient stirring mechanism is
introduced a disp~rsing medium. Typically the
dispersing medium initially introduced into the
reac~ion vessel is at least about 10 percent9 prefer-
ably 20 to 80 percent, by weight based on total
30 weight of ~he disperslng medium present ln the silver
bromoiodide emulsion at the conclusion of grain
precipitation~ Since disperæing medium can be
removed from the reaction vessel by ultrailtration
during silver bromoiodide gra~n precipitat~on, as
35 taugh~ by Mignot U.S. Patent 4,334,012, it is appre-
cia~ed that the volume of dispersing medium initially
present in the reaction vessel can equal or even
" ~ ~7S~9
-2~
exceed the volume of the silver bromoiodide emulsion
present in the reactlon vessel ~t the conclusion of
grain precipitation. The dispersing medium initially
introduced into the reaction vessel ~s preferably
water or a dispersion of peptizer in water~ option-
ally containing o~her ingredients, such as one or
more silver halide ripening agents and/or metal
dopants, more specifically described below. Where a
pep~izer is initially present, it is preferably
lO employed in a concentra~ion of at least 10 percent,
most preferably at least 20 percent, of the total
peptizer present at the completion of silver bromo-
iodide precipitation. Additional dispersing medium
is added to the reaction vessel with the silver and
15 halide salts and can also be introduced through a
separate je~. It is common practice to adjust the
proportion of dispersing medium, particularly to
increase the proportion of peptizer, after the
completion of the salt introductions.
In employing precipitation procedures as
taught by Wilgus and Haefner, citecl above, a m~nor
portion~ typically less than 10 percent, of the
bromide salt employed ln formlng the silver bromo-
iodide grains is initially present in the reaction
25 vessel to adjust the bromide ion concentration of the
dispersing medium ~t the outse~ of silver bromoiodide
precipitation. Also, the dispersing medium in the
reaction vessel is initially substantially free of
iodide ions, since the presence of iodide ions prior
30 to concurrent introducton of silver and bromide salts
favors the formation of thick and nontabular grains.
As employed herein, the term "substan~ially free of
iodide ions" as applied to the conten~s of the reac-
tlon vessel means that there are insufficient iodide
35 ions present as compared to bromide ions to precipi-
tate as a separate silver iodide phase. It is pre-
ferred to maintain the iodide concentration in the
1175692
-25-
reaction vessel prior to silver sal~ introduction at
less than 0.5 mole percent of the total halide ion
concentration present. If the pBr of the dispersing
medium is inltially too high, the tabular sil~er
bromoiodide grains produced will be comparatively
thick and ~herefore o low aspect ratios. It is
con~emplated to maintain the pBr of the reaction
vessel initially at or below 1.6, preferebly below
1.5. On the other hand, if the pBr is too low 3 the
forma~ion of nontabular silver bromoiodide grains is
favored~ TherPfore, it is contemplated to maintain
the pBr of the reaction vessel at or above 0.6. As
herein employed, pBr is defined as the negative
logarithm of bromide ion concentrationO pH, pI, and
pAg are similarly defined for hydrogen, iodide, and
silver ion concentrations, respectively.
During precipitation æilver, bromide, and
iodide salts are added ~o the reaction vessel by
techniques well known ln the precipitation of silver
bromoiodide grains. Typically an aqueous silver salt
solution of a soluble silver salt, ~uch as silver
nitrate, is introduced into ~he reaction vessel con-
currently with the introduction of the bromlde and
iodide salts. The bromide and lodide salts are ~lso
typically introduced as ~queous salt solutions, such
as aqueous solutions of one or more soluble ammonium,
~lkali metal (e.g.~ sodium or potassium), or alkaline
earth metal (e.g., magnesium or calcium) halide
salts. The silver salt is at least initially intro-
duced into the reaction vessel separately rom the
bromide and iodide salts. The iodide and bromide
salts are added to the reaction vessel separately or
as a mixture.
With the introduction of silver salt into
the reaction vessel the nucleation sta~e of grain
formation is initiated. A population of grain nuclei
are formed which are capable of serving as precipit~-
75~2
-z6 -
tion sltes for silver bromide and silver iodide as
the introduction of silver, bromlde, and lodide salts
con~inues. The precipitation of ilver bromide and
~ilver iodide onto existing grain nuclei constitutes
the growth stage of grain formation. The aspect
ratios of the tabular grains ormed according to this
invention are less affected by iodide and bromide
concentrations during the grow~h stage than during
the nucleation stage. It is therefore posslble to
10 increase the permissible la~itude of pBr during con-
current introduction of silver, bromide, and iodide
salts above 0.6, preferably in the range of from
about 0.6 to 2.2, most preferably from about 0.8 to
about 1.6. It is, o course, posslble and, in fact,
lS preferred to main~ain the pBr within the reaction
vessel throughout silver and halide salt introduction
within the initial limits, described above prior to
silver salt introduction. This is particularly
preferred where a substantial rate of grain nuclel
20 formation continues throughout the introduction oE
silver, bromide, and iodide salts, such as in the
preparation of highly polydispersed emulsions.
Raising pBr values above 2.2 during tabular grain
growth results in thickening of the grains, but can
25 be tolerated in many instances while still realizing
an average aspect ra~io of greater than 8:1.
As an ~lternative to the introduction of
silver, bromide, and iodide salts as aqueous solu-
tionsS it i B specifically contemplated to introduce
30 the silver~ bromide, and iodide salts, lnitially or
in the growth stage, in the form of ine silver
halide grains suspended in dispersing medium. The
grains are si7ed 60 that they are readily Ostwald
ripened onto larger grain nuclei, lf any are present,
35 once introduced into the reaction vesselO The
maximum useful grain sizes will depend on the specif-
ic conditions within the reaction vessel, such as
1756
-27 -
temperature and the presence of solubilizing and
ripening agents. Silver bromide, silver iodide,
and/or silver bromoiodide grains can be introduce~.
(Since bromide and/or ;odide are preclpitated in
preference to chloride, it is also possible to employ
silver chlorobromide and silver chlorobromoiodide
graîns.) The silver halide grains are preferably
very fine--e.g., less than 0.1 micron in mean
diameter.
Subject to the pBr requirements set forth
above, the concentrations and rates of silver,
bromide, and iodide salt introductions can take any
convenient conventional form. The æilver and halide
salts are preferably introduced in concentrations of
from 0.1 to 5 moles per liter, although broader
conventional concentration ranges, such as from 0.01
mole per liter to sa~uration, for example, are
contemplated. Specifically preferred precipitation
techniques are those which achieve shortened precipi-
tation times by increasing the rate of silver andhalide salt introduction during ~he run. The rate of
silver and halide salt introduction can be increased
either by increasing ~he rate at which the dispersing
medium and the silver and halide salts are introduced
or by increasing the concentrations of the silver and
halide salts within the dispersing medium being
introduced. It is specifically preferred to increase
the ra~e of silver and halide salt introduction, but
to maintain the rate of introduction below the
threshold level at which the formation of new grain
nuclei is favored--i.e., to avoid renucleation, as
taught by Irie U.S. Patent 3,650,757, Kurz U.S.
Patent 3,672,900, Saito U.S. Patent 4,242,445, Wilgus
German OLS 2,107,118, Teitscheid et al publi6hed
European Patent Application 80102242, and Wey "Growth
Mechanism of AgBr Crystals in Gelatin Solution",
Photographic Science and Engineering, Vol. 21, No. 1,
;~
- .,
1 175B~2
January/February 1977, p. 14~ et. seqO By avoiding
the formation of additional grain nuclei af~er pass-
ing into the growth stage of precipitation, relative-
ly monodispersed ~abular silver bromoiodide grain
populations can be obtained. Emulsions having
coefficients of variation of less than about 30
percent can be prepared. (As employed herein the
coefficient of varia~ion is defined 100 ~imes as the
standard deviation of the grain diameter divided by
10 the average grain diameter.) By intentionally favor
ing renucleation during the growth s~age of precipi-
tation, it i6, of course, possible to produce poly-
dispersed emusions of substantially higher coeffi-
cients of varlation.
The coneentration of iodide in the silver
bromoiodide e~ulsions of this invent~on can be con-
trolled by the introduction of lodide salts. Any
conventional iodide concentration can be employed.
Even very small amounts of iodide--e.g., as low as
20 0.05 mole percent--are recognized in the art to be
beneficial. In thelr preferred form the emulsions of
the present invention incorporate at least about 0.1
mole percent iodideO Silver iodid,e can be incor
porated into the tabular silver bromoiodide grains up
25 to its solubility limit in silver bromide at the
temperature of grain formation. Thus 7 silver iodide
concentrations of up to about 40 mole percent in the
tabular silver bromoiodlde grains can be achieved at
precipitation temper~tures of 90C. In practice
30 precipitation temperatures can range down to near
ambient room temperatures--e.g., about 30C. It is
generally preferred that precipitation be undertaken
at temperatures in the range of from 40 to 80C. For
most photographic applications it is preferred to
35 limit maximu~ iodide concentrations to about 20 mole
percent, with optimum iodide concentrations being up
to about 15 mole percent.
9 ~
-29-
The relative proportion of iodide and
bromide salts introduced in~o thP reactlon vessel
during precipitation can be maintained in a fixed
ratio to form a substantially uniform iodide profile
in the tabular silver bromoiodide grains or varied to
achieve di~fering photographic effec~s. Solberg e~
al, cited above, has r~cognized ~hat advantages in
pho~ographic speed and/or grain result from increas-
ing the proportion of iodide in annuler regions of
10 high aspect ratio tabular grain silver bromoiod;de
emulsions as compared to cen~ral regions of the
tabular grains. Solberg et al teaches iodide con-
centrations in the central regions of the tabular
grains of from 0 to 5 mole percent, with at least one
15 mole percent higher iodide concentrations in the
laterally surrounding annular regions up to the
solubility limi~ of silver iodide in silver bromide,
preferably up to about 20 mole percent and optimally
up ~o about 15 mole percent. In a variant form it is
20 specifically contemplated ~o terminate iodide or
bromide and iodide salt addition to the reaction
vessel prior to the termination of silver salt addi-
tion so that excess bromide reacts with the silver
salt. This results in a shell of silver bromide
25 being formed on the tabular silver bromoiodide
grains. Thus, it is apparent that the tabular silver
bromoiodide grains of the present invention can
exhibit substantially uniform or graded iodide con-
centration profiles and that the gradation can be
30 controlled, as desired, to favor higher iodide con-
centrations internAlly or at or near the surfaces of
the tabular silver bromoiodide grains.
It has been discovered quite unexpectedly
~hat increased exposure latitude prior to rereversal
35 can be achieved by employing higher iodide concentra-
tions in outer grain regions than ln central grain
regions. For example, if the grain is viewed as a
~75~9,~
-30
core surrounded by one or more shells, i~ has been
observed that incorporating at least two mole percent
more iodide in one or more shells than is present in
~he grain core increases the exposure lsvel required
to produce rereversal. It is preferred that ~t least
one shell have an iodide con~en~ that is at least 6
mole percent, optimally a~ least 10 mole percent,
gre~ter than the iodidP conten~ of the core. In a
specifically contemplated form the core can be sub-
10 stantially free of iodide. Preferably the iodidecontent of the core and shell are related similar as
the central and annular regions discussed above. It
is specifically contemplated to employ two~ three, or
even more shells, each increasing in iodide ~ontent
15 with respect to silver halide loca~ed internally
thereof.
Although ~he preparation of the high aspect
ratio tabulflr grain silver bromoiodide emulsions has
been described by reference to the process of Wilgus
20 and Haefner, which produces neutral or nonammoniacal
emulsions, the emulsions of the present invention and
their utility are no~ limited by any particular pro-
cess for their preparation. A process of preparing
high aspect ratio tabular grain silver bromoiodide
25 emulsions discovered subsequent to that of the
present invention is described by Daubendiek and
Strong, cited above. Daubendiek and S~rong teaches
an improvement over the processes of Maternaghan,
ci~ed above, wherein in a preferred form the 611ver
30 iodide concentrat;on in the reaction vessel is
reduced below 0.05 mole per liter and the maximum
size of the silver iodide grains ini~ially present in
the reaction vessel is reduced below 0.05 micron.
High aspect ratio tabular grain ~ilver
35 bromide emulsions lacking iodide can be prepared by
the process described by Wilgus and H&efner modlfied
to exclude iodide. High aspect ratio tabular gra~n
1 ~ 7~1~ 9 2
silver bromide emulsions can alternatively be
prepared following a procedure similar to that
employed by Cugnac and Chateau 3 cited above. High
espect ratio silver bromide emulsions con~ainlng
square and rec~angular grains can be prepared as
~aught by Mignot, titled SILV~R BROMIDE EMULSIONS OF
NARROW GRAIN SIZE DISTRIBUTION ~ND PROCESSES FOR
THEIR PREPARATION, clted above. In this process
cubic seed grains having an edge length of less than
10 0.15 micron are employed. While maintaining the pAg
of the seed grain emulsion in the range of from 5.0
to 8.0, the emulsion is rlpened in the substantial
absence of nonhalide silver ion complexlng agents to
produce tabular silver bromide grains having an
15 average aspect ratio of at least 8.5:1. Still other
preparations of high ~spect ratio tabular grain
silver bromide emulsions lacking iodide are illus-
trated in the examples.
To illustrate other high aspect ratio
20 tabular grain silver halide emulsions which can be
employed in the practlce of this invention, attention
is directed to Wey9 cited above, whlch discloses a
process of preparing tabular silver chloride grains
which are substantially internally free of both
25 silver bromide and silver iodide. Wey employs a
double-jet precipitation process wherein chloride and
silver salts are concurren~ly introduced into a
reaction vessel containing dispersing medium in the
presence of ammonia. During chloride salt introduc-
30 tion the pAg within the dispersing medium is in therange of from 6.5 to 10 and the pH in the range of
from 8 to 10. The presence of ammonia and hlgher
temperatures tends to cause thick grains to form,
therefore precipitation temperatures are limited to
35 up to 60C. The process can be optimized to produce
high aspect ratio tabular grain silver chloride
emulsions.
1 ~7~9~
-32-
Maskasky Can. Ser.No. 415~277, filed concur-
rently herewith and commonly assigned, titled SILVER
CHLORIDE EMULSIONS OF MODIFIE~ CRYSTAL H~BIT AND
PROCESSES FOR THEIR PREPARATION, discloses a process
of preparing tabular grains of at least 50 mole
percent chloride having opposed crystal faces lying
in tlll} crystal planes and, in one preferred
form, at least one peripheral edge lying parallel to
a <211> crystallographic vector in the plane of
one of the major surfaces. Such tabular grain
emulsions can be prepared by reacting aqueous silver
and chloride-containing halide salt solutions in the
presence oE a crystal habit modifying amount of an
aminoazaindene and a pep~izer having a thioether
linkage.
Wey and Wilgus, Can. Ser.No. 415,264, filed
concurrently herewith and commonly assigned, titled
NOVEL SILVER CHLO~OBROMIDE EMULSIONS AND PROCESSES
FOR THEIR PREPARATION, discloses tabular grain smul-
sions wherein the silver halide grains contain silverchloride and silver bromide in at least annular grain
regions and preferably throughout. The tabular grain
regions containing silver chloride and bromide are
formed by maintaining a molar ratio of chlorîde and
bromide ions of from 1.6 to about 260:1 and ~he total
concentration of halide ions in the reaction vessel
in the range of from 0.10 to 0.90 normal during
introduction of silver, chloride, bromide, and,
optionally, iodide salts into the reaction vessel.
The molar ratio of silver chloride to silver bromide
in the tabular grains can range from 1:99 to 2:3.
The individual silver and halide salts can
be added to the reaction vessel through surface or
subsurface delivery tubes by gravity feed or by
delivery apparatus for maintaining control of the
rate of delivery and the pH, pBr, and/or pAg of the
reacti.on vessel con~ents, as illustra~ed by Culhane
~7~
-33-
et al U.S, Patent 3,821,002, Oliver U.S. Patent
3,031,304 and Claes e~ al, Photographische Korrespon
denz, Band 102, Number 10, 1967, p. 162O In order to
obtain rapid distribution of the reactants within the
reaction vessel, specially contructed mixing devices
can be employed, as illustrated by Audran U.S. Patent
2,996,287, McCrossen et al U.S. Patent 3,342,605,
Frame et al U.S. Patent 3,415,650, Porter e~ al U.S.
Patent 3,7~5,777, Finnicum et al U.S. Patent
4~147~551, Verhille et al U.S. Patent 4,171,224,
Calamur published U.K. Patent Application 2~022,431A,
Saito et al German OLS 2~555,364 and 2,556,885, and
Research Disclosure, Volume 166, February 1978, Item
16662.
In forming the tabular grain emul6ions
peptizer concentrations of from 0.2 to abou-t 10 per-
cent by weight, based on the total weight of emulsion
components in the reaction vessel, can be employed~
It is common practice to maintain the concentration
of the peptizer in the reaction vessel in the range
of below about 6 percent, based on the total weight,
prior to and during silver halide formation and ~o
adjust the emulsion vehicle concentration upwardly
for optimum coating characteristics by delayed,
supplemental vehicle addi~ions. It is contemplated
that the emulsion as initially formed wlll contain
from about 5 to 50 grams of peptizer per mole of
silver halide, preferably about 10 to 30 grams of
peptizer per mole of silver halide. Additional vehi-
cle can be added later to bring the concen-tration up
to as high as 1000 grams per mole of silver halide.
Preferably the concentration oE vehicle in the
finished emulsion is above 50 grams per mole of sil-
ver halide~ When coated and dried in forming a
photographic element the vehicle preferably forms
~bout 30 to 70 percent by weight of the emulsion
layer~
6~2
-34-
Vehicles (which include both binders and
peptizers) c~n be chosen from among those conven-
tionally employed in silver halide emulsions. Pre~
ferred peptlzers are hydrophilic colloids, which can
be employed alone or in combination with hydrophobic
materials. Suitable hydrophilic materials include
both naturally occurrin~ substances such as proteins,
protein derivatives, cellulose derivatives--e.gO,
cellulose esters, gelatin--e.g., alkali treated gela-
10 tin (cattle bone or hide gelatin~ or acid-~reated
gelatin (pigskin gelatin), gelatin derivatives -e.g.,
acetylated gelatin, phthalated gelatin and the like,
polysaccharides such as dextran, gum arabic, zein,
casein, pectin, collagPn derivatives, sgar-agar,
15 arrowroot, albu~in and the like as described in Yu~zy
et al U.S. Patents 2,614,928 and '929, Lowe et al
U.S. Patents 2,691,582, 2,614,g30, '931, 2,327,808
and 2,448,5349 Gates et al U.S. Patents 2,787,545 and
2,956,880, Himmelmann e~ al U.S. Patent 3,061,436,
20 Farrell et al U.S. Patent 2,816 9 027, Ryan U~S.
Patents 3,132,945, 3,138,461 and 3,186,846, Dersch et
al U~K. Patent 1,167,159 and U.S. Patents 2,960,405
and 3,436,220, Geary U.S. Patent 3,486,896, Gazzard
U.K. Patent 793,549, Gates et al U.S. Patents
25 2,992,213, 3,157,5069 3,1849312 and 3,539,353, Miller
et al U.S. Patent 3,227,5717 Boyer et ~1 U.S. Patent
3,5329502, Malan U.S. Patent 3,551,151, Lohmer et al
U.S. Patent 4,018,609, Luciani et al U.K. Patent
1,186,790, Hori e~ al U.K. Patent 1,489,080 and
30 Belgian Patent 856,631, U.K. Patent 1,490,644, U.K.
Paten~ 1,483,551, Arase et al U.K. Patent 1,459,906,
Salo U.S. Patents 2,110,491 and 2,311,086, Fallesen
U.S. Patent 2,343,650, Yutzy U.S. Patent 2,322,085,
Lowe U.S. Patent 2,563,791~ Talbot et al U.S. Patent
35 2,725,293, Hilborn U.S. Patent 2,748,022, DePauw et
al U.S. Patent 2,956,8833 Ritchie V.K. Pa~ent 2,095,
DeStubner U.S. Patent 1,752,069, Sheppard et al U.S.
35-
Patent 2,127,573~ Lierg U.S~ Patent 2~256,720 9 Gaspar
U.S. Patent 2~361~936, Farmer U~Ko Pa~ent 15~727,
Steven~ U.K. Patent 1,062,116 and Yamamoto et ~1 U.S.
PatPnt 3~923,517.
Other m~erials commonly employed in com-
bina~ion with hydrophilic colloid pep~izers as vehi-
cles (including vehicle extenders--e.g., materials in
the form of latices~ include synthet~c polymer~c
peptizers, carriers and/or binder~ such as poly(vinyl
10 lactams), acrylamide polymers, polyvinyl alcohol and
its derivatives, polyvinyl acetals, polymer~ of alkyl
and sulfoalkyl acryla~es and methacrylates, hydroly~-
ed polyvinyl acetates~ polyamides, polyvinyl p~rl-
dine, acrylic acid polymers, maleic anhydride copoly-
15 mers, polyalkylene oxides, methacrylamide copolymers,polyvinyl oxazolidinones, maleic acid copolymers,
vinylamine copolymers, methacrylic acid copolymers 9
acryloyloxyalkylsulfonic acid copolymers, suloalkyl-
~crylamide copolymers, polyalkyleneimine copolymers,
20 polyamines, N,N-dialkylaminoalkyl acrylates, vinyl
imidazole copolymers, vinyl sulfide copolymers, hslo-
genated styrene polymers, amineacrylamide polymers,
polypep~id~s and the like as described in Holl~ster
et al U.S. Patents 3,679,425, 3,706,564 and
25 3,813,251, Lowe U.S. Patents 2,253,0785 2,276,322,
'323, 2,281,703, 2,311,058 and 2,414,207, Lowe et al
U.S. Pa~ents 2,484,456, 2,541,474 and 2,632,704,
Perry et al U.S~ Patent 3,425,836, Smith et al U.S.
Patents 3,415,653 and 3,615,6249 Smith U~S. Patent
30 3,488,708, Whiteley et al U.S. Paten~s 3,392,025 and
3,511,818, Fi~zgerald U.S. Pa~ents 3,681,079,
3,721,565, 3,852~073, 3,861,918 and 3,925,083,
Fitzgersld et al U.S. Patent 3~879,205, Nottorf U.S.
Pa~ent 3,142,568, Houck et al U.S. Patents 3,062 9 674
3S and 3,220,844, Dann et al U.S. Patent 2,882,161,
Schupp U.S. Pa~ent 2,5799016, Weaver U.S. Patent
2,829,053, Alles et al U.S. Paten~ 2 9 698,240, Priest
~7~9
-36-
et al U.S. Patent 3,003,8799 Merrill et al U.S.
Patent 3,419,397, Stonham U.S. Patent 3,284,207,
Lohmer et al UOS. Paten~ 3,167,430, Williams U.S.
Patent 2,957 7 767, Dawson et al U.SO Patent 2,893 9 867,
Smi~h e~ ~1 U.S. Patents 2,860,986 and 2,9043539,
Ponticello et al U.S. Pa~ents 3,929,4B2 and
3,860,428, Ponticello U.S. Patent 3,939,130, Dykstra
U.S. Patent 3,411,911 and Dykstra e~ al Canadi~n
Patent 774,054, Ream et al U.S. PatPnt 3,287,289,
10 Smith U.K. Patent 1,466,600, Stevens U.K. Patent
1,062,116, Fordyce U.S. Patent 2,2115 323, Martinez
U.S. Patent 2,284~877, Watkins U.S. Patent 2,420,455,
Jones U.S. Paten~ 2,533,166, Bolton V.S. Patent
2,495,918, Graves U.S. Patent 2,289,775, Yackel U.S.
15 Pa~ent 2,565,418, Unruh et al U~S. Patents 2,865,893
and 2,~75,059, Rees et al U.S. Patent 3,536,491,
Broadhead et al U.K. Patent 1,3489815, Taylor et al
U.S. Patent 3,4793186, Merrill et al U.S. Patent
3,520,857, Bacon et al U.S. Patent 3,690,888, Bowman
20 UOS. Pa~ent 3,748,143, Dickinson et al U.K. Patents
808,227 and '228~ Wood U.K. Patent 822,192 and Iguchi
et al U.K. P~ent 1,398,Q55. The~e addi~ion~l
materials need not be present in the react~on vessel
during silver halide prec~pitation, but rather are
25 conventionally added to the emulsion prior to coat-
ing. The vehicle materials, lncluding particularly
the hydroph~lic colloids, as well as the hydrophobic
materials useful in combination therewith can be
employed not only in the emulsion layers of the pho-
30 tographic elements of this invention, but also ino~her layers, such as overcoa~ layers, in~erlayer~
and layers positioned beneath the emulsion layers.
It is specifically contemplated that grain
rlpening can occur during the preparatlon of silver
35 halide emulsions according ~o the present invention,
and it is preferred that grain ripening occur within
the reaction vessel during at least silver bromo-
~756-37 -
iodide grain formation. Known silver halide solvents
are useful in promoting rlpening. For example, an
excess of bromide ions ~ when present in the reac~ion
vessel, is known to promote ripening. It is there-
fore apparent that the bromide salt solution run intothe reaction vessel can itself promo~e ripening.
Other ripening agents can also be employed and can be
entirely contained wi~hin the dispersing medium in
the reaction vessel before silver and halide salt
10 addition, or they can bP introduced into the reaction
vessel along with one or more of the halide sal~,
sllver salt, or peptizer. In still another variant
the ripening agent can be introduced independently
during halide and silver salt additions Although
15 ammonia is a known ripening agent, it is not ~ pre-
ferred ripening agent for the silver bromoiod~de
emulsions of this invention exhibiting the highest
realized speed-granulari~y relationships.
Among preferred ripening agents are those
20 containing sulfur. Thi~cyanate salts can be used,
such as alkali metal, mos~ commonly sodium and
potassium, and ammonium thiocyanate salts. While any
conventional quantity of the thiocyanate salts can be
introduced, preferred concentrations are generally
25 from about O.l to 20 grams of thiocyanate salt per
mole of silver halide. Illus~rative prior te~chings
of employin~ thiocyanate ripening agen~s are found in
Nietz et al, U.S. Patent 2,222,264, cited above; Lowe
et al U.S. Patent 2?448,534 and Illingsworth UOS.
30 Patent 3~320,069. Alternatively, conventional
thioether ripening agents, such as those dlsclosed in
McBrlde U.S. Patent 3,2717157, Jones U.S. Patent
3,574,628, and Rosecrant6 et al U.S. Patent
3,737,313, can be employed.
The high aspect ratio tabular grain emul-
slons are preferably washed to remove soluble salts~
The soluble salts can be removed by chill setting and
~75~92
-38 -
leaching, as illus~rated by Craft U.S. Patent
2,316,845 and McFall et al U.S. Paten~ 3,396,027; by
coagulation washing, as illustrated by Hewit60n et al
U.S. Paten~ 2,618,556 9 Yutzy et al U.S. Patent
2,6141928, Yackel U.S. Pa~ent 2,565,418, Hart et al
U.S. Patent 3,241,96~, Waller et al U.S. Patent
2,489,341, Klinger U.K. Patent 1,305,409 and Dersch
et al U.K. Patent 1,167,159; by centrifugatlon and
decantation of a coagulated emulsion, as illustrated
10 by Murray U.S. Patent 2,463,794, Ujihara et al U.S.
Patent 3,707p378, ~udran U.S. Patent 2,996,287 and
Timson U.S. Patent 3,498,454; by employing hydro-
cyclones alone or in combination wlth centrifuges, as
illustrated by U.K. Patent 1,336,692, Claes U~Ko
15 Patent ~,356,573 and Ushomirskii et al Soviet Chemi-
cal ~ y, Vol. 6, No. 3, 1974, pp. 181-185; by
diafiltration with a semipermeable membrane, as
illustrated by Research Disclosure~ Vol 102, October
1972, Item 10208, Hagemaier et al Re~earch Dis-
20 closure, Vol 131, March 1975, I~em 13122~ BonnetResearch Disclosure, Vol. 135, July 1975, Item 13577,
Berg et al German OLS 2,436,461, Bolton U.S. Patent
2,495,918, and Mignot U.S. Patent 4,334,012, cited
above, or by employing an ion exchange resin, as
25 illustrated by Maley U.S Patent 3,782,953 and Noble
U.S Paten~ 2,827,428. The emulsions~ with or
without sensitizers, can be drled and stored prior to
use as illustrated by Research Disclosure, Vol 101,
September 1972, Item 10152. In the present invention
30 washing is partlcularly advantageous in terminating
ripening of the tabular grains after the completion
of precipitation to avoid increasing their thickness
and reducing their aspect ratio.
Althou~h the procedures for preparing
35 tabular silver halide grains described above will
produce high aspect ratio tabular 8rain emulsions in
which ~he tabular grains account for at leas~ 50
~75
-39 -
percent of the total pro~ected area of the total
silver halide grain population, it is recogn~zed that
advantages can be realized by increasing the propor-
tion of such tabular grains present. Preferably at
least 70 percent ~optimally at least 90 percent) of
the total projected area i6 provided by tabular
silver halide grains. While minor amounts o nontab
ular grains are fully compatible with many photogra~
phic applications, to achieve the full advantages of
10 tabular grains the proportion of tabular grains can
be increased. Larger tabular silver halide grains
can be mechanically separated from smaller9 nontab-
ular grains in a mixed population of grains using
conventional separation techniques--e.g. 9 by using a
15 centrifuge or hydrocyclone. An lllustrative teaching
of hydrocyclone separation is provided by Audran et
al U.S. Patent 3,326,641.
The high a~pect ratio tabular grain internal
latent image-forming emulsions of ~he present inven-
20 ~ion are preferably intentionally surface chemicallysensitized to increase their photographic speed.
Useful surface chemical sensitizations are taught by
Evans U.S. Patent 3,761,276 and 3,923,513 and Atwell
et al U.SO Patent 4,035,185, each previously cited.
25 Any type of surface chemicsl ~ensitization known to
be useful with corresponding surface latent image-
forming silver halide emulsions can be employed, but
the degree of surface chemical sensitization is
limited to that whîch will increase the reversal
30 speed of the internal latent image-forming emulslon,
but which will not compete wi~h ~he in~ernal sensiti-
zation sites to the extent of caus~ng the location of
latent image centers formed on exposure to shift from
the interior to the surface of the tabular grains.
Thus, a balance be~ween internal and 6urface
sensltization is preferably maintained for maximum
speed, but wlth the internal sensi~ization predoml-
~ 1~569~
~o-
nating. Tolerable levels of surface chemical sensi-
tization can be readily determined by the following
test: A sample of the high aspect ratio tabular
grain internal latent image-forming silver halide
emulslon of the present invention is coated on a
tr~nsparent film support at a silver coverage of 4
grams per square meter. The coated s~mple is then
exposed to a 500 watt tungs~en lamp for times ranging
from 0.01 to 1 second at a distance of 0.6 meter.
The exposed coated sample is then developed for S
minutes a~ 20C in Developer Y below (an "internal
type" developer~ note the incorporation of iodlde to
provide access to the interior of the graln), fixed,
washed, and dried. The procedure described above i8
repeated with a second sample identically coated and
exposed. Processing is also identical, excep~ that
Developer X below ~a "surface type" developer) is
substituted for Developer Y. To satisfy the require-
ments of the present invention as being a useful
internal latent image-forming emulsion the sample
developed in the internal type developer, Developer
Y, must exhiblt a maximum denslty at least 5 times
greater than the sample developed in ~he surface type
developer, Developer X. This dif:Eerence in density
2S is a positive indication that the latent image
centers of the silver halide grains are forming pre-
dominantly in the interior of the grains and are for
the most part inacoessible to the surface type devel-
oper.
Developer X Grams
N-methyl~-aminophenol sulfate 2.5
Ascorbic acid 10.0
Potassium metabora~e 35.0
Potassium bromide 1.0
Wa~er to 1 liter.
~1
Developer Y Grams
N-methyl-~aminophenol sulfate 2.0
Sodium sulEite, desicc~ted 90.0
Hydroquinone ~-
Sodium carbon~te, monohydrate 52.5
Potassium bromlde i.O
Potassium iodide 0-5
Water to 1 liter.
The high aspect ra~io tabular grain internal
latent image-forming silver halide emulsions of the
presen~ inven~ion can be surface chemically sensi-
tized with active gelatin, as illustra~ed by T. H.
James, The Theory of the Photogr~hic Process, 4th
Ed., Macmillan, 1977, pp. 67-76, or with sulfur,
selenium, tellurium, gold, platinum, palladium,
iridium, osmium, rhodium, rhenium, or phosphorus
sensiti~ers or comblna~ions of the~e sensitizers,
such as at pAg levels of from 5 to 10, pH levels of
from 5 to 8 and temperatures of from 30 to 80C, as
illustrated by Research Disclosure, Vol. 120, April
1974, Item 12008, Research Disc}o~ure, Vol. 134, June
1975, Item 13452, Sheppard et al U.S. Patent
1,623,499, Matthies et al U.S. Patent 1,673,522,
Waller et al U.S. Patent 2,399,083, Damschroder et al
U.S. Patent 2,642,361, McVeigh U.S. Patent 3,2979447,
Dunn U.S. Patent 3,297,446, McBride U~Ko Patent
1,315,755, Berry et al U.S. Paten~ 3,772,031, Gilman
et al U.S. Patent 3,761,267, Ohi et al U.SO Patent
3,857,711, Klinger et al U.S. Patent 3,565,633,
Oftedshl U.S. Patents 3,901,714 and 3,904j415 and
Simons U.K. Patent 1~396,696; chemic~l sensitizati~n
being optionally conducted in the presence of thio-
cyanate compounds, as described in Damschroder U.S.
Paten~ 2,642,361, and sulfur containing compounds of
the type disclosed in Lowe et al U.S. Patent
2,521,926, Will~ams et al U.S. Patent 3,021,215, and
Bigelow U.S. Patent 4,054,457. It is specifically
~5~2,
42
con~emplated to sensi~ize chemically in the presence
of finish (chemical sensitiza~ion) modifiers--that
is, compounds known to suppresæ fog and increase
speed when pre~ent during chemical sensitization,
such as azaindenes, azapyridazines, azapyrimidines 9
benzothiazolium salts, and sensitlzers having one or
more heterocyclic nuclei. ~xemplary finish modifiers
are described in Brooker et al U.S. Patent 2,131,038,
Dostes U.S. Patent 3,411,914, Kuwabara et al U.S.
Patent 3,S54,757, Oguchi et al U.S. Pa~ent 3,565,631,
Oftedahl U.S. Patent 33901,714, Walworth Canadian
Patent 778,723, and Duffin Photographic Emulsion
Chemistry, Focal Press ~1966), New Ysrk, pp.
138-143. Additionally or alternatively, the emul-
sions can be reduction sensi~ized--e.g., wlth hydro-
gPn, as illustrated by Janusonis U.S. Patent
3,891,446 and Babcock et al U.S. Patent 3,984,249, by
low pAg (e.g., less than 5) and/or high pH (e.g.,
greater than 8) treatment or through the use of
reducing agents, such as stannous chlorids, thiourea
dioxide, polyamines and amineboranes, as illustrated
by Allen et al U.S. Patent 2,983,609, Oftedahl et al
Research Disclosure, Vol. 136, August 1975, Item
_
136549 Lowe et al U.S. Patents 2,518,698 and
2,739,060, Roberts et al U.S. Patents 2,743~182 and
'183, Chambers e~ al U.S. Patent 3,026,203 ~nd
Bigelow et al U.S. Patent 3,361,564. Surface chemi-
cal sensitization, including sub-surface sensi~iza-
tion, illustrated by Morgan UOS. Patent 39917,485 and
Becker UOS. Patent 3,966,476, is specifically
contemplated.
Although the high aspect ratio tabular grain
silver halide emulsions are generally responsive to
the techniques for chemical sensitization known in
the art in a quali~ative sense 9 in a quantitative
sense--that is, in terms of the actual speed
increases real~zed--the tabular graln emulsions
" ~ 17~2
-43 -
require careful investigation to identify the optimum
chemical sensitization for each individual emulsion,
certain preferred embodiments bein8 more speciflcally
discussed below.
The high aspect ratio tabular grain silver
halide emulsions can be spectrally sensitized. It is
specifically contemplsted to employ spectral sensi-
tizing dyes that exhibit absorption maxima in the
blue and minus blue--i.e., green and red, portions of
the visible spec~rum. In addition, for specialized
applications, spectral sensitizing dyes csn be
employed which improve spectral response beyond the
visible spectrum. For example, the use of infrared
absorbing sp~ctral sensitizers is specifically con-
templated.
The high aspect ratio tabular grain silverhalide emulsions can be spectrally sensitized with
dyes from a variety of classes, includ~ng the poly-
methine dye class, which includes the cyanines, mero-
cyanines, complex cyanines and merocyanines (i.e.,tri-, tetra- and poly-nuclear cyanines and mero-
cyanines), oxonols, hemioxonols, styryls, merostyryls
and streptocyanines.
The cyanine spectral sensitizing dyes
include, ~oined by a methine link~ge, two b~sic
heterocyclic nuclei, such as those derived from
quinolinium, pyridinium, isoquinolinium, 3H-indolium,
benz[e~indolium, oxazolium, oxazolinium, thiazolium,
thiazolinium, selenazolium, selenazolinium, imida-
zolium, imidazolinium, benzoxazolium, benzothia-
zolium, benzoselenazolium, benzimidazolium, naphth-
oxazolium, naphtho~hiazolium, naphthoselenazolium,
dihydronaph~hothiazolium, pyrylium, and imidazopyra-
z~nium quaternary salts.
The merocyanine spectral sensitizing dyes
include, ~oined by a methine linkage, a basic hetero-
cyclic nucleus of the cyanine dye type and an acidic
44 ~
nucleus, such as can be derived rom b~rbituric acid,
2-~hiobarbituric Acid~ rhodanine, hydan~oin, 2-thio-
hyd~ntoin, 4-thiohydantoin, 2-pyrazolin-5-one, 2-is-
oxazolin-S-one, indan-1,3-dione, cyclohexane-1,3-di-
one, 1,3-dioxane-4,6-dione, pyrezolin-3,5-dione, pen-
tane-2,4-dione, alkylsulfonylacetoni~rile 9 malono
nitrile, isoquinolin-4-one, and chroman-2,4-dione.
One or more spectral sensitizlng dyes may be
used. Dyes with sensitizing maxima at wavelengths
throughout the visible spectrum and with a great
variety of spectral sensitivity curve shapes are
known. The choice and relative proportions of dyes
depends upon the region of the spectrum to whlch
sensitivity is desired and upon the shape of the
spectral sensitivity curve desired. Dyes ~ith over-
lapping spectral sensitivity curves will often yield
in combination a curve in which the sensit~vity at
each wavelength in the area of overlap is approxi-
mately equal to the sum of the sensitivities of the
lndividual dyes. Thus, i~ is possible to use com-
binations of dyes with different max;ma to achieve a
spectral sensitivity curve with a maximum inter-
mediate to the sensitizing maxlma of the individual
dyes.
Combinations of spectral sensitizing dyes
can be used wh~ch result in supersensitizAtion--that
ls, spectral s~nsitization that is 8reater in some
spectral region than that from any concentration of
one of the dyes alone or that which would result from
~he additive effect of the dyes. Supersensitization
can be achieved with selec~ed combinations of spec-
tral sensitizing dyes and other ~ddenda3 such as
stabilizers and antifoggAnts, devPlopment acceler-
ators or inhibitors, coating aids, brighteners and
antistatic agents. Any one of several mechanisms as
well as compounds which can be responsible for super-
sensitization are discussed by Gilman, "Review of the
6 9 2
-4s -
Mechanisms of Supersensitization"~ e~
Science and ~ , Vol. 18, 1974, pp. 418-430.
Spec~ral sensitlzing dyes also affec~ the
emulsions in other ways~ Spectral sensltizing dyes
can also function as an~ifoggan~s or stabllizers,
development accelerators or inhibitors, and halogen
acceptors or electron accep~ors 9 as disclosed in
Brooker et al U.S. Patent 2,131,038 and Shiba et al
U.S. Patent 3,9305860.
Sensitizing action can be correlated to the
position of molecular energy levels of dye with
respect to ground state and conduction band energy
levels of the silver halide crystals. These energy
levels can in ~urn be correlated ~o polarographic
oxidation and reduction potentials 9 as discussed in
~ raphic Science and ~ Vol. 18, l.974,
pp. 49~53 (Sturmer et al)~ pp. 175-178 (Leubner) and
pp. 475-485 (Gilman). Oxidation and reductlon
potentials can be measured as described by R. F.
Large in Photo~raphic Sensitivityl Academic Press,
1973, Chapter 15.
The chemistry of cyanine and related dyes is
illustrated by Weissberger and Taylor, S~ecial Topics
of Heterocyclic Chemistr~, John Wiley and Sons~ New
York, 1977, Chapter VIII; Venkataraman, The Chemistry
of Synthetic ~X~ Academic Press, New York, 1971,
Chapter V; James, The Theory of the Pho~ Pro
cess, 4th Ed., Macmil-an, 1977, Chapter 8, and F. M.
Hamer, C~anine Dyes and Related Compounds, John Wiley
and Sons, 1964.
Although native blue sensitivity of silver
bromide or bromoiodide is usually relied upon in the
art in emulsion layers lntended to record exposure to
blue light, significant advantages can be obtained by
the use of spectral sensitizers 9 even where their
principal ab~orption is in the spectral region to
which the emulsions possess native sensitivity. For
~75&~
-4~ -
example, it is specifically recognized that advan-
tages can be realized from the use of blue spertral
sensitizing dyes. Even when ~he emulsions of the
~nvention are high aspect ratio tabular grain silver
bromide and silver bromoiodide emulsions, very l~rge
lncreases ln speed are realized by the use of blue
spectral s~nsitlzing dyes. Where it is lntended to
expose emulsions according to the present invention
in their region of native sensitivity7 advantages in
sensiti~ity ean be gained by increasing the average
thickness of the tabular grains up to 0.50 micron.
Useful blue spectral sensitizing dye~ for
high aspect ratio tabular grain silver bromide and
silver bromoiodide emulsions can be selected from any
of the dye classes known to yield spectral sensi-
tizers. Polymethine dyes, such as cyanines, mero-
cyanines~ hemicyaninesg hemioxonols, and merostyryls,
are preferred blue spectral ~ensitizers Generally
useful blue spectral sensitizers can be selected from
among these dye classes by their ab&orption charac-
teristics--i.e., hue. There are, however, general
structural correlations that can serve as a guide in
selecting useful blue sensitizers. Generally the
shorter the methine chain, the shorter the wsvelength
of the sensitizin~ maximum. Nuclei also influence
absorption. The addition of fused rings to nuclei
tends to favor longer wavelengths of absorption.
Substituents can also al~er absorption characteris-
tics.
Among useful spectral sensitizing dyes for
sensitizing silver halidP emulsions are those found
in U.K. Patent 742,112; Brooker U.S. Patents
1,846,300, '3019 '302, '3039 '304, 2,078,233 and
2~089,729, Brooker et al U.S. Patents 2,165,338,
2,213,238, 23231,65~, 2,493,747, '74~, 2,526,632,
2,739,964 (Reissue 24,292), 2,778,823, 2,917,516,
3,352,857, 3,411,916 ~nd 3,431,111, Wilmanns et al
~ ~75~2
-47-
U.S. Patent 2,295,276, Sprague U.S. Patents 2,481,698
and 2,503,776, Carroll et al U.S. Patents 2,688,545
and 2,704,714, Larive et al U~S. Patent 2,9219067,
Jones U~S. Paten~ 2,945,763 9 Nys et sl U.S. Patent
3,282,933, Schwan et al U.S. Paten~ 3 9 397,060,
Riester U.S. Patent 3,660,1029 Kampfer et al U.S.
Patent 3,660,103, Taber et al U.S. Pa~ents 3,335,010,
37352,680 and 3,384,486, Lincoln et al U.S. Patent
3,397,981, Fumia et al U.S. Patents 39482,978 and
3,623~881, Spence et al U.S. Pa~ent 3 3 718,470 and Mee
U~S. Patent 4,025,349. Examples of useful dye
combinations, including supersensitizing dye combina-
tions, are found in Motter U.S. Patent 3,506,443 and
Schwan et al U.S. Patent 3,6729898. As examples of
supersensitizing combinations of spectral senslti~.ing
dyes and nonligh~ absorbing addenda, it is specifi-
cally contemplated to employ thiocyanates during
spectral sensitization, as taught by Leermakers U.S.
Patent ~,221,805; bis-triazinylaminostilbenes, as
taught by McFall et al U.S. Patent 2,933,390; sulfo-
nated aromatic compounds, as taught by Jones et al
U.S. Patent 2,937,089; mercap~o-substltuted hetero-
cycles, as taught by Riester U.S. Patent 3,457,078;
iodide9 as taught by U.K. Patent 1,413,826; and still
other compounds, such as those disclosed by Gilman,
"Review of the Mechanisms of Supersensitization",
ci~ed above.
Conventio~al amounts of dyes c~n be employed
in spectrally sensitizing the emulsion layers
containing nontabular or low aspect ratio tabular
silver halide grains. To realize the $ull advantages
of this invention it is preferred to adsorb spectral
sensitizing dye to the grain surf&ceæ of the h~gh
~spect ratio tabular grain emulsions in a substan-
tially optimum amount--that is, in an amount suffl-
cient to reallze at least ~0 percent o the maximum
photographic speed attainable from the grains under
~ ~756g~
-48-
contemplated conditions of exposure. The quantl~y of
dye employed will vary wlth the specific dye or dye
oombination chosen as well as the size and aspect
ratio of the grains. It is known in the photographic
art ~hat optimum spectral sensitiza~ion iB obtained
with organic dyes at about 25 percen~ to 100 percent
or more of monolayer coverage of the total available
surface area of surface sensitive silver halide
grains, as disclosed, for example~ in West et al,
"The Adsorption of Sensitizing Dyes in Photographic
Emulsions", Journal of Phys. Chem., Vol 56, p. 1065,
1952, Spence et al, "Desensitization of Sensi~i~ing
Dyes", J rnal of Physieal and Colloid Chemi~t~
Vol. 56, No. 69 June 1948, pp. 1090-1103; and Gilman
et al U.S. Patent 3,979,213. Optimum dye concentra-
tion levels can be chosen by procedures taught by
Mees, Theory of the Photographic_Process 9 pp -
1067-1069.
Spectral sensitization can be undertaken at
any stage of emulsion preparation here~ofore known to
be useful. Most commonly spectral sensitization is
undertaken in thP art subsequent t:o the completion of
chemical sensitization. However9 lt is specifically
recognized that spectral æensitization can be under-
t~ken alternatively concurrently with chemical Rensi-
tization, can er.~lrely precede chemical sensitiza-
tion, and can even commence prior to the comple~ion
of silver halide grain precipitation, as taught by
Philippaerts et al U.S. Patent 3,628,960, and Locker
e~ al U.S. Patent 4,225~666. As taught by Locker et
al, it is specifically contemplated to distribute
introduction of the spec~ral sensitizing dye into the
emulslon so that a portion of the spectral sen~itiz-
ing dye is present prior to chemical sensitization
and a remaining portion is introduced after chemical
sensitization. Unlike Locker et al, it is specifi-
cally contemplated that the ~pectral sensitiæing dye
~Sfi92
-49 -
can be added to the emulsion after 80 percent of the
silver hallde has b~en precipitated. Sensit1zation
can be enhanced by pAg adjustment, including cycling,
during chemical and/or spectral sensitizatlon. A
specific exampl~ of pAg adjustment ls provided by
R earch Disclosure, VolO 181, May 1979, Item 18155.
It has been discovered quite unexpectedly by
Kofron et al, cited above, that high aspect ratio
tabular grain silver halide Pmulsions can exhibit
improved speed-granularity relationships when chemi-
cally and spectrally sensi~ized than have been here-
tofore realized using tabular grain ællver halide
emulsions and have been heretofore realized using
silver halide emulsions of the hlghest known speed-
granularity relationshipæ. Best results have beenachiev4d using minus blue (red and/or green) spectral
sensitizing dyes.
Although not required to re~lize all of
their advantages, the emulsions of the present inven-
tion are preferably, in accordance with prevailingmanufacturing practices, substantiLally optimally
chemically and spectrally ~ensitlzed. That is, they
preferably achleve speeds of at least 60 percent of
the maximum log speed attainable Erom the grains in
the spectral region of sensitizatLon under the con-
t4mplated conditions of use and processing. Lo~
speed is herein defined as lO0 (l-log E), where E is
measured in meter-candle-seconds at a density o Ool
below maximum density. Oncs the silver halide grains
of an emulsion have been char~cterized, it is
possible to estimate from further product analysls
and performance ev~luation whether an emulsion layer
of a product appears to be ~ubstantially optimally
chemically and spectrally sensiti ed ~n relation to
comparable commercial offerings of other
manufacturers.
~569
-50-
Nucleatin~ A~ents
The high aspect ratio tabular grain internal
la~en~ image-forming emulsions of this invention
incorporate a nucleating agent ~o promote the forma-
tion of a dlrect-positive image upon processing. The
nucleating agent can be incorporated in the emulsion
during processing, but ls preferably incorporated in
manufacture of the photographic element, usually
prior to coa~ing. This reduces the quantities of
nucl~ating agen~ requiredO The quantities of
nucleating agent requ~red can also be reduced by
res~ricting the mobility of the nuclea ing agent in
the photogr~phic element. Larg organic substituen~s
capable of performing at least to some extent a
ballasting function are commonly employed. Nucleat-
ing agents which include one or more groups to
promote adsGrption to the surf~ce of $he silver
halide grains have been found to be effec~ive in
extremely low concentrations.
A preferred general class of nucleatlng
agents for use in the practice of this invention are
aromatic hydrazides. Particularly preferred ~romatic
hydrazides are those in which the aromatic nucleus is
substituted with one or more group~ to restrict
mobility and, preferably, promote ad~orp~ion of thehydrazide to silver hallde gr~in suraces. More
specifically9 preferred hydrazides are those embraced
by formula (I) below:
(I)
H H
D-N-N-~-M
wherein
D is an acyl group;
~ is a phenylene or substituted (e.g., halo-,
alkyl-, or alkoxy-substituted~ phenylene group; and
M is a moiety capable of restricting mobility,
such as an adsorption promot~ng moiety.
~56
51
A particularly preferred class of phenyl-
hydrazides are acylhydrazinophenyl~hioureas repre~
sented by formula (II~ below.
(II)
0 R2 S
Il H H l ll
R~C-N-N-Rl-N--C-~
R4
wherein
R is hydrogen or an alkyl, cycloalkyl, halo-
alkyl, alkoxyalkyl, or phenylalkyl substituen~ or aphenyl nucleus having a Hammett sigma-value-derived
electron-withdrawing characteristic more positive
than -0.30;
Rl is a phenylene or alkyl, halo , or
alkoxy-substituted phenylene group;
R2 is hydrogen, benzyl, alkoxybenzyl,
halobenzyl~ or alkylbenzyl;
R3 is a alkyl, haloalkyl, alkoxyalkyl, or
phenylalkyl subætituent hav~ng from 1 to 18 carbon
atoms, a cycloalkyl substituent~ a phenyl nucleus
having a Hammett sigma value deriYed electron-with-
drawiag char cteristic less positive than +0.50, or
naphthyl,
R4 is hydrogen or independently selected
from among the same substituents as R3; or
R3 and R4 together form a heterocyclic
nucleus forming a 5- or 6-membered ringy wherein the
ring atoms are chosen from the class consistlng of
nitrogen, carbon~ oxygen, sulfur~ and selenium atoms;
with the proviso tha~ at least one of R2
and R4 must be hydrogen and the alkyl moieties,
except as otherwise noted, ln each instance include
from 1 to 6 carbon atoms and the cycloalkyl moieties
have from 3 to 10 carbon atoms.
As indlcated by R in formula ~II), preferred
acylhydrazinophenylthioureas employed in the practice
of this inventlon contain an acyl ~roup which is the
-52- ~g~
residue of a carboxylic acid 9 such as one of the
acyclic carboxylic acids~ including formic ~cid,
acetic acid, propionic acid, bu~yric acid, higher
~omologues of these acids having up ~o about 7 oarbon
atoms, and halogen, alkoxy, phenyl and equivalent
substituted derivatives thereof. In a preferred
form, the acyl group is formed by an unsubstituted
acyclic aliphatic carboxyl~c acid having from 1 to 5
carbon atoms. Specifically preerred acyl groups are
formyl and acetyl. As between compounds which differ
solely in terms of having a formyl or an acetyl
group, the compound containing the formyl group
exhibits higher nuclea~ing agent activity. The alkyl
moieties ln the substituen~s to the carboxylic acids
are contemplated to have from 1 ~o 6 carbon atoms,
preferably from 1 to 4 carbon atoms.
In addition to the acyclic aliphatic car-
boxylic acids, it is recognized that the carboxylic
acid can be chosen so that R is a cyclic aliphatic
group havlng from about 3 to 10 carbon atoms, such
asg cyclopropyl, cyclobutyl, cyclopen~yl, cyclohexyl,
methylcyclohexyl, cyclooctyl, cyclodecyl, and bridged
ring variations9 such as, bornyl and isobornyl
groups. Cyclohexyl iæ a specifically preferred
cycloalkyl substituent. The use of alkoxy, cyano,
halogen, and equivalent substituted cycloalkyl
substituents is contemplated.
As indicated by Rl in formula (II), pre-
ferred acylhydrazinophenylthioureas employed in the
practice of this invention contaln a phenylene or
subs~ituted phenylene group. Specifically preferred
phenylene groups &re m- and p-phenylene groups.
Exemplary of preerred phenylene substituents are
alkoxy substituents having from 1 to 6 carbon atoms,
alkyl substituents having from 1 to 6 carbon atoms,
1uoro-, chloro-, bromo-, and lodo-substituents.
Unsubsti~uted p-phenylene groups are specifically
~5~9
~ 3
preferred. Specifically preferred alkyl moieties are
those which have from 1 ~o 4 carbon atoms. While
phenylene and substituted phenylene groups are pre
ferred linking ~roups, other functionally equlvalent
divalent aryl groups, such as naphthalene groups, can
be employed.
In one form R2 represents an unsubs~i~u~ed
benzyl group or substituted equivalents thereof, such
as alkyl, halo , or alkoxy-substituted benzyl
groups. In the preferred form no more than 6 and,
most preferably, no more than 4 carbon atoms are
contributed by substltuents to the benzyl group.
Substituents to the benzyl group are preferably
para-substituents. Speciically preferred benzyl
substi~uents are formed by unsubstituted, 47halo-sub-
stituted, 4-methoxy-substituted, and 4-methyl-substi-
tuted benzyl groups. In another specifically pre-
ferred form R2 represents hydrogen.
Referring again to formula (II) 3 it is
apparent that R3 and R4 can independently take a
variety of forms. One specifically contemplated form
can be an alkyl group or a substituted alkyl group,
such as P haloalkyl group, alkoxyalkyl group, phenyl- -
alkyl group~ or equivalent group, having a total of
up to 189 preferably up to 12~ carbon atoms. Speci-
fically R3 and/or R4 can take the orm of P
methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,
octyl, nonyl; decyl or higher homologue group having
up to 18 total carbon atoms; a fluoro-, chloro-,
bromo-, or iodo subætituted der~vative thereof; a
methoxy 3 ethoxy, propoxy, butoxy or higher homologue
alkoxy-substituted derivative thereof, wherein the
total number of carbon atoms are necessarily at least
2 up to 18; and a phenyl-substituted derivative
thereof, wherein the total number of carbon atoms is
necessarily at least 7, as ln the case nf benzyl,up
to about 18. In a specific preferred form R3
1 17~g2
and/or R4 can take the form of an alkyl or phenyl~
alkyl substituent, wherein the alkyl moieties are in
each instance from 1 ~o 6 carbon atoms.
In addition to the acyclic aliphatic and
aromatic forms discu~sed above, it i8 al60 contem-
plated that R3 and/or R4 can ~ake the form of a
cyclic aliphatic substituent, such as a cycloalkyl
~ubs~ituent having from 3 to 10 carbon atoms. The
use of cyclopropyl 9 cyclobutyl ? cyclopentyl, cyclo-
hPxyl, methylcyclohexyl, cyclooctyl, cyclodecyl andbridged rlng variations, such as, bornyl and iso-
bornyl groups, is contemplated. Cyclohexyl is a pre-
ferled cycloalkyl substituent. The use of alkoxy~
cyano ? halogen and equivalent substituted cycloalkyl
substituents is contemplated.
R3 and/or R4 can also be an aromatic
substituent, such as, phenyl or naphthyl (i.e~,
l-naphthyl or 2-naphthyl) or an equivalent aromatic
group, e.g., 1-, 2-, or 9-anthryl, etc. As indicated
in formula (II) R3 and/or R4 can take the form of
a phenyl nucl~us which ls either electron-donating or
electron-withdrawing, however phenyl nuclei which are
highly electron~withdrawing may produce inferior
nucleating agents.
The electron-withdrawing or electron-donat-
ing characteristic of a specific phenyl nucl~us can
be ~ssessed by reference to H~mmett sigma values.
The phenyl nucleus can be a6signed a Hammett sigma
value-derived electron-withdrawing characteristic
which is the algebraic sum of the Hammett s~gm~
values of its substituents (i.e. 7 those of the ~ub-
st~tuents, if any, to the phenyl group). For
example, the Hammet~ sigma values of any substituents
to the phenyl rlng of the phenyl nucleus can be
determined algebraically simply by determining from
the literature the known Hammett sigma values for
each substituent and obtaining the algebraic sum
55-
thereof. Electron-withdrawing subs~ituents ere
assigned positlve sigma values, while electron-donat-
ing substi~uents are assigned negative sigma values.
Exemplary meta- and ~ sigma values and
procedures for ~heir determination are set orth by
J. Hine in Phy~ L~ Ghemistry, second edi
tion, page 87, published in 19629 H. VanBekkum, P. E.
Verkade and B. M. Wepster in Rec. Trav. ChimO, Volume
78, page 815, published in 1959, P. R. Wells ln Chem.
Revs., Volume 63, page 171, published in 1963, by H.
H. Jaffe in Chem. Revs., Volume 53, page 191, pub-
lished in 1953, by M. J. S. Dewar and P. J. Grisdale
in J. Amer. Ci~em. Soc., Volume 84, page 354g9 pub
lished in 1962, and by Barlin and Perrin in Quart.
lS Revs., Volume 20, page 75 et ~, published in 1966.
For ~he purposes of this invention, ortho-substi-
tuents to the phenyl ring can be assigned to the pub-
lished para~sigma values.
It is preferred that R2 and/or R3 be a
phenyl nucleus having a Hammett sigma vslue-derived
electron-withdrawing characteristic less positive
than ~0.50. It is speclfically contemplated that
R2 and/or R3 be chosen rom among phenyl nuclei
having cyano, ~luoro-, chloro- 3 bromo-, iodo-, alkyl
groups h~ving from 1 to 6 carbon stoms, and alkoxy
groups having from l to 6 carbon atoms, ~s phenyl
ring substituents. Phenyl ring fiubstituents are pre-
ferred in the ~ - or 4-ring position.
Rather than being independen~ly chosen R3
and R3 can together form, along w~th the 3-position
nitrogen atom of the thlourea, a he~erocyclic nucleus
forming a 5- or 6~membered rin~. The ring atoms can
be chosen from ~mong nitrogen, carbon, oxygen, sulfur
and selenium atoms. The ring necessarily contains at
least one nitrogen atom. Exemplary rings include
morpholino, piperidino, pyrrolidinyl, pyrrolinyl~
thiomorpholino, thiazolidinyl, 4-thiazolinyl~ selen-
~ 56-
azolidinyl, 4-selenazolinyl, imidazolidinyl, imid-
azolinyl, ~xazolidinyl and 4-oxazolinyl rings.
Specifically preferred rings are saturated or other-
wise constructed to avoid electron withdrawal from
the 3-position nitrogen atom.
Acylhydrazinophenyl~hiourea nucleating
agents and their synthesis are more specifically dis~
closed in Leone U~S. Patents 4,030,925 and
4,276,364. Variants of ~he acylhydrazinophenyl-
thiourea nucleating agents described above aredisclosed in von Konig U.S. Patent 4,139,387 and
Adachi et al published U.K. Patent Application
2,012,443A.
Another preferred class of phenylhydrazide
nucleating agents are N (acylhydrazinophenyl~thio-
amide nucleat1ng agents, such as those indicated by
formula (III~ below:
(III)
O S
ll H H ll
R-C-N N-Rl-N---G---A
wherein
R and Rl are as defined in formula ~II);
A is =N-R2, -S- or -0-;
Ql represents the atoms necessary to com-
plete a five-membered heterocyclic nucleus;
R2 is independently chosen from hydrogen,
phenyl, alkyl, alkylphenyl, and phenylalkyl; and ~he
alkyl moieties in each instance include from 1 to 6
carbon atoms.
These compounds embrace those having a
five-membered heterocyclic thioamide nucleus, such as
a 4-thiazoline-2-thione, thiazolidine-2-thione,
4-oxazoline-2-thione~ oxa~olidine-2-thione,
2-pyrazoline-5-thione~ pyrazolidine-5-thione, indo-
line-2-thione, 4-imidazoline-2-thione, etc. A speci-
fically preferred subclass of heterocyclic thioamide
~ ~.756~
-57-
nuclei is formed when ~ is as indicated in formula
(IV~
(IV)
X
11 1
-C-CH2
wherein
X is =S or zO.
Specifically preferred illustrations of such values
of Q~ are 2-thiohydAntoin, rhodanine, isorhod~nine,
and 2-thio-2,4-oxazolidinedione nuclei. It is
believed th~t some six membered nuclei 9 such as thio-
barbituric acid, may be equivalent to five-membered
nuclei embraced within formula (III3.
Another specifically preferred subclass of
heterocyclic thioamide nuclei is formed when ~1 is
as indicated in formula (V~
(V)
X
11 1
-C-c~L L~n_lT
wherein
L ls a methine group;
Z~
l l o= <R4
T is -C-~CH=CH-~d lN-R3 or ~CH-~
R3 is an alkyl substituent 7
,R5
R4 is hydrogeni an alkyl, -N\R69 or an
alkoxy substituent;
Z represents the nonmetallic atoms necessary
to complete a baslc heterocyclic nucleus of the type
found ln cyanine dyes;
n ~nd d are independently chosen from the
integers 1 and 2;
~75
-58-
Rs and R6 are ~ndependently chosen from
hydrogen, phenyl, alkyl 9 alkylphenyl, and phenyl-
alkyl; and
the alkyl moie~ies in each ins~ance include
from 1 to 6 carbon atoms.
The formula (V) values for Ql provide a
heterocyclic thioamide nucleus oorresponding to a
methine substitu~ed form of the nuclei presen~ above
in formula (IV) values for Ql. In a specifically
preferred form the heterocyclic thioamid2 nucleus is
preferably a methine substitu~ed 2-thiohydantoîn 9
rhodanine, isorhodanine, or 2-thlo 2,4-oxazolidinedi
one nucleus. The heterocycllc thioamide nucleus of
formula (V) is directly, or through an intermediate
methine linkage, substituted with a basic het~ro~
cyclic nucleus of the type employed in cyanine dyes
or a eubstltuted benzylidene nuclues. Z preferably
represents the ~onmetallic Rtom~ necessary to com-
plete a basic 5- or 6-membered heterocycl~c nucleus
of ~he type found in cyanine dyes having ring-forming
atoms chosen from the class consi6ting of carbon,
nitrogen9 oxygen, sulfur, and selenium.
N-(acylhydrazinophenyl~thioamide nucleat~ng
agents and their synthesis are more specifi~ally dis-
closed in Leone et al U.S. Patent 4,080,207.
Still another preferred class of phenyl-
hydrazide nucleating agents are triazole-substituted
phenylhydrazide nucleating agents. More ~pecifi-
cally, preferr~d triazole-substi~uted phenylhydrazide
nucleating agents are those represented by formula VI
below:
(VI)
o
Il H H
R-C-N-N-RI-A~-A2-A 3
wherein
R and Rl are as defined in formula
~7
~59-
A' is alkylene or oxalkylene;
O O
Il ~ 11
A2 is -C-N- or S-N-; and
O
A3 is a triazolyl or benæotriazolyl
nucleus;
the alkyl and alkylene moieties in each
instance including from l to 6 carbon atoms.
Still more specifically preferred triazole-
substituted phenylhydrazide nucleating agents are
those represented by formula (VII) below:
(VII)
I l H H 11 H / \ /N~
R-C-N-N Rl-C~ i N
\ / \N/
H
wherein
R is hydrogen or methyl;
/~
Rl is ~ [CH2]n- or ~ OE
[CH2]n~
n is an integer of 1 to 4; and
E is alkyl of from 1 to 4 carbon atoms.
Triazole-substituted phenylhydrazide nuc-
leating agents and their synthesis are disclosed by
Sidhu et al U.S. Patent 4,278,748. Comparable
nucleating agents having a somewhat broader range of
adsorption promotlng groups are disclosed in corre-
sponding published UoK~ Patent Application 2,011,391A.
The aromatic hydrazides represented by
formulas (II), ~III), and (VI) each contain adsorp-
tion promoting substituents. In many ins~ances it is
preferred to employ in combination with these ~ro-
matic hyrazides additional hydrazides or hydrazones
which do not contain substituents specifically
.
~ ~7~9~
-60-
intended to promo~e adsorption to silver halide grain
surfaces. Such hyraæides or hydrazones, however,
often contain substituents to reduce ~heir mobility
when incorporated in photographic elements. These
hydrazide or hydrazones can be employed as the sole
nucleating agent, if desired.
Such hydrazides and hydrazones include those
represented by formula (VIII) and (IX) below:
(VIII)
H H
T-N-N-T' and
(IX)
H
T-N-N-T 2
wherein T is an aryl radical~ including a substituted
aryl radical, Tl is an acyl radical, and T~ is an
slkylidene radical and including substituted alkyli-
dene radicals. Typical aryl radicals for the sub-
stitu~ent T have the formula M-T3 T ~ wherein T3 is
an aryl radical (such as, phenyl, l-naphthyl,
2-naphthyl, etc.) and M can be such substituen~s as
hydrogen, hydroxy, amino, alkyl, alkylamino, aryl
amino, heterocyclidc amino (amino containing a
heterocyclic moiety), alkoxy9 aryloxy, acyloxy, aryl-
carbonamido, alkylcarbonamido, heterocyclic carbon-
amido (carbonamido contalning a heterocyclic moiety) 9
arylsulfonamido, alkylsulfonamido 9 and heterocyclic
sulfonamido (sulfonamido containlng a heterocyclic
molety). Typical acyl radicals for the substituent
Tl have the formula
O O
Il 11
~S-Y or -C-G
o
wherein Y can be such substituents as alkyl, aryl,
and heterocyclic radicals, G can represent a hydrogen
atom or the same substituent as Y as well as radicals
~ ~756~
-61-
having the formula
o
Il
- C -0 -~
to form oxalyl radicals wherein A is an alkyl~ aryl,
or a heterocyclic radical. Typical alkylidene radi-
cals for the substi~uent T2 have the formula GCH-D
wherein D can be a hydrogen atom or such radicals as
alkyl 7 aryl, and he~erocyclic radicals. Typical aryl
substituen~s for the above-described hydrazides ~nd
hydrazones include phenyl, naph~hyl 9 diphenyl, and
the like. Typical heterocyclic substituents for thP
above-described hydrazides and hydrazones include
azoles, azines, furan, thiophene~ quinoline, pyra-
zole, and the like. Typical alkyl (or alkylidene)substituents for the above-described hydrazides an~
hydrazones have 1 to 22 carbon atoms including
methyl, ethyl, isopropyl, n-propyl, isobutyl,
n-butyl, t butyl, amyl, n-octyl, n-decyl 9 n-dodecyl,
n-octadecyl, n-eicosyl, and n-docosyl.
The hydrazides and hydrazones represented by
formulas ~VIII) and (IX) as well as their synthesis
are disclosed by Whitmore U.S. Patent 3~227,552.
A secondary preferred general class of nuc-
leating agents for use in the practice of this lnven-
tion are N-substituted cycloammonium quaternary
salts. A particularly preferred species of such
nucleating agents is represented by formula (X) below:
(X)
1; - Z
N ~CH-CH)~ l=C-E
X- (CH2~a
E2
wherein
Zl repre6ents the atoms necessary to com-
plete a heterocyclic nucleus containing a hetero-
~756~2
-62 -
cyclic ring of 5 to 6 atoms including the qua~er~l~ry
nitrogen atoms, with the additional atom~ of ~aid
heterocyclic ring bein~ selected from carbon, nitro-
gen, oxygen, sulfur, and selenium;
j represents a positlve integer of rom l to
2;
a represen~s a positive integer of from 2 to
6,
X~ represen~s an acid anlon;
E2 represen~s a member selected from (a~ a
formyl radic~l (b) a radical having the formula
L
-C~
L2
wherein each of Ll and L2, when taken alone,
represen~6 a member selected from an alkoxy radical
~nd an alkylthio radlcal, and Ll and L2, when
taken together~ represent the atoms necessary to com-
plete a cyclic radical selected from cyclic oxy-
a~etals and cyclic thioacetals havlng from 5 to 6atoms in the heterocyclic acetal ring, and (c) a
l-hydrazonoalky radical; and
El represents either a hydrogen atom, an
alkyl radical, an aralkyl radical~ an alkylthio radi-
cal, or an ~ryl radical such as phenyl and naphthyl,and including substituted aryl rad~cals.
The N-substituted cycloammo~ium quaternary
salt nucleating agents of formula (X) and their
synthesis are disclosed by Lincoln and Heseltine U.S.
Patents 3,615,615 and 3,759,901. In a variant form
Ei can be a divalent ~lkylene group of from 2 to 4
carbon atoms joining two substituted heterocyclic
nuclei AS shown in formula (X). Such nurleating
agents ~nd their synthesis are dlsclosed by Kurtz and
Harbison U.S. Patent 3,734,738~
The substituent to the quaternized nitrogen
atom o the heterocyclic ring can, in another variant
-63-
form, itself form a fused ring wi~h the heterocyclic
ring. Such nucleating agents are illustrated by
dihydroaromatic quanternary salts comprlsing a
1,2-dihydroaromatic he~erocyclic nucleus including a
quaternary ni~rogen atom. Particularly advantageous
1,2-dihydroaromatic nuclei include such nuclei as a
1,2-dihydropyridinium nucleus. EspeciAlly preferred
dihydroaromatic quaternary salt nucleating agents
include those represented by formula (XI) below:
(XI)
I x~
¦ ~ R2 ¦ n
wherein
Z represents the nonmetall~c atoms necessary
to complete a heterocyclic nucleus containing a
heterocyclic ring of from 5 to 6 atoms includ~ng the
quaternary nitrogen atom, with the additional atoms
of said heterocyolic ring being selected from either
carbon, nitrogen, oxygen, sulfur, or selenium;
n represents a positive ~nteger having e
value of from 1 to 2;
when n is l, R represents a member selected
from the group consisting of a hydrogen atom, an
alkyl radic~l, an alkoxy radical, an aryl radical, an
aryloxy radical, and a carbamido radical and,
when n is 2, R represents an alkylene radi-
cal having from l to 4 carbon atoms,
each of Rl and R2 represents a member
selected from the group consisting of a hydrogen
atom, an alkyl radical, and an aryl radical; and
X~ represents an anion.
Dihydroaromatic quaternary sal~ nucleating
agents and their synthesis are disclosed by Kurtz and
Heseltine U.S. Patents 3,719,494.
~5
~4-
A specifically preferred class of N-substi-
tu~ed cycloammonium qua~ernary salt nucleating agents
are those whlch include one or more alkynyl 6ubs~i~u-
ents. Such nucleatlng agents include compounds with-
in ~he generic struc~ural definition set forth informula ~XII) below:
(XII)
, z~
1 0
wherein Z represents an atomic group necessary for
forming a 5- or 6-membered heterocyclic nucleus,
represents an aliphatic group 9 R2 repr~sents a
hydrogen atom or an aliphatic group, R3 and R4,
which may be ~he same or differen~, each represen~s a
hydrogen atom, e halogen atom, an aliphatic group, an
~lkoxy group, a hydroxy group, or an aromatic group,
at least one of Rl, R2, R3 and R4 being a
propargyl group, a butynyl group, or a substituent
containing a propargyl or butynyl group, X~ repre-
~ents an anion, n is 1 or 2, with n being 1 when the
compound forms an inner salt.
Such alkynyl-substituted cycloammonium
quaternary salt nucleating agents and their synthe~i 6
are illustrated by Adachi et al U.S. Patent 4,115,122.
The specific choice of nuclea~ing agents can
be influenced by a variety of faetors. The nucleat~
ing agents of Leone cited above are particularly pre-
ferred for many applications, since they are effec-
tive At very low concentrations. Minimum concentra-
~ions as low as 0.1 mg of nucleating agent per mole
of silver, preferably at least 0.5 mg per silver
mole, and optimally at least 1 mg per silver mole are
disclosed by Leone. The nuclea~ing agents of Leone
are par~icularly advantageou6 in reducing speed loss
~7$692
-65 -
and in some instances permit~ing speed galn with
increasing processlng temperatures. When the nuc-
leating agents of Leone are employed in combina~ion
with those of Whitmore spe d varia~ions as a function
of tempera~ure of processing can be mlnimized.
The aromatic hydrazide nucle~ting agents are
generally preferred for use ln photographic elements
intended to be processed at compara~ively high levels
of pH, typically above 13. ~he alkynyl~substituted
cycloammonium quaternary salt nucleating agerlts are
par~icul~rly useful for processing at a pH of 13 or
less. Adachi et al teaches these nucleating agents
to be useful ln processing within the pH range of
from 10 to 13, pr~ferably 11 to 12.5.
In addition to the nucleating agents des-
cribed above additional nucleating agen~s have been
identified which are useful in processing at pH
levels in the range of from about 10 to 13. An
N-substituted cycloammonium quaternary salt nucleat-
ing agent which can conta~n one or more alkynyl sub
stituents is illustrative of one class of nucleating
agents useful in processing below pH 13. Such nuc-
leating agents are illustrated by formula (XIII)
below:
(XIII)
R2 H
I I ~
C-Y2-C= C-C z2
~ lm_l~R An-l
wherein
zl represents the atoms completing an
aromatic carbocyclic nucleus of from 6 to 10 carbon
atoms;
yl ~nd y2 are independently selected
from among a divalent oxygen atom, a divalent sulfur
atom, and -N-R3
~ ~.566_
Z2 represents the atoms completing a
heterocylclic nucleus of the type found ~n cyanine
dyes;
A is an adsorption promoting moiety;
m and n are 1 or 2; &nd
Rl 9 R2, and R3 are independently
chosen from the group consisting of hydrogen, alkyl,
aryl, alkaryl, and aralkyl and Rl and R3 are
additionally independently chosen from the group con-
sisting of acyl, alkenyl, and alkynyl, the al~phatlc
moietie~ containing up to 5 carbon atoms and the
aromatic moieties containing 6 to 10 carbon atoms. A
preferred processing pH when these nucleating agen~s
are employed is in the ran~e of from 10.2 to 12Ø
Nucleating agents of the ~ype repreæented by
formula (XIII) and their synthesis are disclosed by
Baralle et al U.S. Patent 4,3069016, cited above.
Another class of nuclea~ing ag~nts effective
in the pH range of from lO to 13, preferably 10.2 to
12, are dihydrospiropyran bis-condensation products
of salicylic aldehyde and at leas~ one heterocyclic
ammonium salt. In a preferred form such nucleating
ag~nts are represen~ed by formula (XIV) below:
(XIV)
H /Y~~
H /f \N-~
R s
R7 T ;.\R4
wherein
X and Y each independently represent a sul-
fur atom, a selenlum atom or a -C(RIR2)- radical,
Rl and R2 independently represent lower
alkyl of from 1 to 5 carbon atoms or together repre
sent an alkylene radical of 4 or 5 carbon atoms,
~7
-67-
R3, R4, Rs, and R5 each represent
hydrogen, a hydroxy radical or a lower alkyl or
alkoxy radical of from 1 to 5 carbon atoms,
zl and Z2 each represents the nonmetal-
lic atoms completing a nitrogen-containing hetero-
cyclic nucleus of the type found in cyanine dyes and
R7 and R3 each represent a ring nitrogen
substituent of the type found in cyanine dyesO
Z~ and Z2 in a preferred form each com-
pletes a 5- or 6-membered ring, preferably fused with
at least one benzene ring, containing ~n the ring
structure carbon atoms, a single nitrogen atom and,
optionally, a sulfur or selenium atom.
Nuclea~ing agents of the type represented by
formula (XIV) and their synthesis are disclosed by
Baralle et al U.S. Patent 4,306,017, clted above.
Still another class of nucleating agents
effective in th~ pH range of from 10 to 13, prefer-
ably 10.2 to 12, are diphenylmethane nucleating
agents. Such nucleating agents are illus~rated by
formula (XV) b~low:
(XV)
~R3
`~ C\C /C_,
Rl/ \R2
wherein
zl and Z2 represent the atoms completing
a phenyl nucleus;
Rl represents hydrogen or alkyl of from 1
to 6 carbon atoms; and
R2, R3, and R4 are independently
selected from among hydrogen, halogen~ alkyl,
hydroxy, alkoxy, aryl, alkaryl, and aralkyl or R 3
and R4 together form a covalent bond, a divalent
",
-6~-
chalcogen linkage, or
/ \
Rl R2
wherein each alkyl moiety contains from 1 to 6 carbon
atoms and each ~ryl moiety contains 6 to lO c~rbon
atoms.
Nucleating agents of the ~ype represPn~ed by
formula (XV) and their synthesis are disclosed by
Baralle et al U.S. Patent 4,315,g86, cited above.
Silver Ima~in~
Once high ~spect ratio tabular grain inter-
nal latent image-forming emulsions have b~en gene-
rated by precipitation procedures, washed, and
sensitized, as described above, their preparation can
be completed by the incorporation of nucleat~ng
agents, described above, and conventional photo-
graphic addenda, and they can be usefully applied to
photographic applications requiring a silver image to
be produced- e.g., conventional black-and-white
photography.
Dickerson, cited above, discloses that
hardening photographic elements accordlng to the
present invention intended to form silver imAgeS to
an extent sufficient to obviate the necessity of
incorporating additional hardener during processing
permits increased silver covering power to be
realized as compared to photographic elements ~imi-
l~rly hardened ~nd processed, but employing nontabu-
lar or less than high ssp~ct ratio tabular grain
emulsions. Specifically, it is taught to harden the
high aspect ratio tabular grain emulslon layers and
other hydrophilic colloid layer~ of black-and-white
photographic elements in an amoun~ sufficient to
reduce swelling of ~he layers to less than 200
percent, percent 6welling bein~ determined by (~)
incubating the photographie element at 38C for 3
days at 50 percent relative humidity, (b) measuring
~7
-69
layer thickness, (c) immersing the photographic
element in distilled water at 21~C for 3 minu~es, and
(d) measuring change in layer thlckness. Although it
is specific~lly preferr d to harden the photograph1c
elements intended ~o form silver lmages ~o such an
extent that hardeners need not be lncorporated in
processing solutlons, ~t is recognlzed that the
emulsions of the present invention can be hardened to
any conventional level. It is fur~her specifically
contemplated to incorporate hardener~ ln processing
solutions, as illustrated, for example, by Research
Disclosure, Vol. 184, Augu6t 1979, Item 18431,
Paragraph K, relating particularly ~o the processing
of radiographic materials.
Typical useful incorporated hardeners (fore-
hardeners) include formaldehyde and free dialdehyde~,
such as succinaldehyde and glutaraldehyde, as illus~
trated by Allen et al U.S. Patent 3,232,764; blocked
dialdehydes, as illustrated by Ka~zuba U.S. Patent
2,586,168, Jeffreys U.S. Patent 2,870,013, and
Yamamoto et al U.S. Patent 3,819,608; ~-diketones,
as illustrated by Allen et al U.S. Patent 2,725,305;
active esters of the type described by Burness et al
U.S. Patent 3,542,55~; sulfonate esters, as illus-
trated by Allen et al U.S. Paten~s 2,725,305 ~nd2,726,162; aGtive halogen compounds, as illustrated
by Burness U.S. Patent 3,106l468, Silverman et al
U.S. Patent 3,839,042, Ballantine et al U.S. Patent
3,951,940 and Himmelmann et al U.S. Patent 3,174,861;
s triazines and di~zines, as illustrated by Yamamoto
et al U.S. Patent 3,3255287, Anderau et al U.S.
Patent 3~288,775 and Stauner e~ al U.S. Paten~
3,9g2,366; epoxides, as illus~rated by Allen et al
U.S. Pa~en~ 3,047,394, Burness U.S. Paten~ 3,139~459
and Birr et al German Patent 1,085,663; aziridines,
as illu6tra~ed by Allen et al U.S. Patent 2,950,197,
Burness et al U.S. Patent 3,271,175 and Sato et al
~" 11~6~2
-70
U.S. Patent 3,575,705; active oleins having two or
more active vinyl group~ ~e.g. vinylsulfonyl groups) 9
as illustrated by Burness et al UOS Patent6
3,490,911, 3,539,644 ~nd 3,841,872 (Reissue 29J305)~
Cohen U.S. Patent 3~640,720, Kleis~ et ~1 German
Patent 872,153 and Allen U.S. Patent 2,992,109;
blocked active olefins, as illustra~ed by Burness et
al U.S. Patent 3,360,372 and Wilson U.S. Patent
3,345,177; carbodiimide~, as illustrated by Blout et
10 al German Patent 1,148,446; isoxazol~um salts
unsubstituted in the 3~posit;on, as illustrated by
Burness e~ Al U.S. Patent 3,321,313; esters of
2-alkoxy-N-carboxydihydroquinoline, as illustrated by
Bergthaller et al U.S. Paten~ 4,013,4689 N-carbamoyl
and N-carbamoyloxypyridinium ~alts, as illustrated by
Himmel~ann U.S. Patent 3,880,665; hardeners of mixed
function~ such as halogen-~ubstituted ~ldehyde acids
(e.g., mucochloric and mucobromic acids), as illus-
trated by White U.S. Patent 2,080,019~ 'onium substi-
tuted acroleins, as illustrated by Tschopp et 81 U . S -
Patent 3,792,021, and vinyl sulfones contalning other
h~rdening functional groups, as illustrated by Sera
et al U.S. Patent 4,028,320; and polymeric hardeners~
such as dialdehyde starches, as illustrated by
Jeffreys et al U.S. Patent 3,057,723, and copoly-
(acrolein-methacrylic acid), as illustr~ted by
Himmelmann e~ al U.S. Pstent 3,396,029.
The use of forehardeners in combination is
illustrated by Sieg et al U.S. Patent 3,497,358,
Dallon et al U.S. Patent 3,832,1Bl and 3,840,370 and
Yamamoto et al U.S. Patent 3,898,089. Hardening
accelerators can be used, as illustrated by Sheppard
et al U.S. Patent 2,165,421, Kleiæt German Patent
881,444, Rlebel et al U.S. Patent 3,628,961 and Ugi
et al U.S. P~tent 3,901,708.
Instabillty which decreases maximum density
in direct-posltive emulsion coatings can be protected
~ ~5~92
-71-
against by incorporation of fitabilizers, antiog-
gants, antikinking agents, l~ten~ imag ~tabilizers
~nd similar addenda in the emulsion and contiguous
layers prior to coating. A variety of such addend~
are disclosed in Research Disclosure, Vol. 176,
December 197B, Item 17643, P&ragraph VI. Many of the
antifoggants which are effective in emulsions can
also be used in developeræ ~nd can be classified
under a few general headings, as illustrated by
C.E.K. Mees, The Theor~ of the Photographic Process,
2nd Ed., Macmillan, 1954, pp. 677-680.
In eome applications improved results can be
obtained when the direct-positive emulsions are pro-
cessed in the presence of certain antifoggants, ~s
disclosed in Stauffer U~S. P~tent 2,497,917. Typical
useful antifoggants of thi6 type include benzotria-
zoles, such as benzotriazole, 5-methylbenzotriazole,
and 5-ethylbenzotriazole; benzimidazoles ~uch AS
5-nitrobenzimidazole; benzothiazoles such as 5-nitro-
benzothiazole and 5-methylbenzothiazole; heterocyclic
thiones such as l-methyl-2-tetrazoline-5-thione;
triazines such as 2,4-dimethylamino~6-chloro 5-tria-
zine; benzoxazoles such as ethylbenzoxazole; and
pyrroles such as 2,5-dimethylpyrrole.
In certain embodiments, good results are
obtained when the elements are processed in the
presence of high levels of ~he antifoggants mentioned
above. When antifoggants such as benzotriazoles are
used, good results c~n be obta~ned when the process
ing solution contains up to 5 grams per liter and
pref~rably l ~o 3 grams per liter; when they are
incorporsted in the photographic element 9 concentra-
tions of up to 1,000 mg per mole of æilver and pre-
ferably concentrations of 100 to 500 mg per mole of
silver are employed.
In addition to sensi~izer6, hardeners, Qnd
antifoggants ~nd stabilizer6, a variety of other
~756~
-72-
conventional photographic addenda can be present.
The specific choice of addenda depends upon the exact
nature of the photographic application and is well
within the capability of the art. A variety of use-
ful addenda are disclosed in Research Disclosure,Yol~ 176, December 1978, Item 17643. Op~ical
brighteners can be introduced, as disclosed by Item
17643 at Paragraph V. Absorbing and scattering
materials can be employed in the emulsions o the
invention and in separate layers of the photographic
elemen~s, as described in Paragraph VIII. Coating
aids, as described in Paragraph XI, and plasticizers
and lubricants, as described in Paragraph XII, can be
present. Antistatic layers, as described in Para-
lS graph XIII, can be prPsent. Methods of addition oaddenda are described in Paragraph XIV. Matting
agents can be incorporated, as dPscribed in Paragraph
XVI. Developing agents and development modifiers
can, if desired, be incorpora~ed, as descrîbed in
Paragraphs XX and XXIo When the photographic
elements of the invention are intended to serve
radiogr~phic applica~ions, emulsion and other layers
of ~he radiogr~phic element can take any of the forms
specifically described in Research Disclosure, Item
18431, cited aboveO The emulsions of ~he invention,
as well as other, conventional silver halide emulsion
l~yers~ interlayers, overcoats, and subbing layers,
if any, present in the photographic element8 can be
coated and dried as described in Item 17643, Para-
gr~ph XV~
It is specifically contempla~ed to blend thehigh aspect ratio tabular grain internal latent
imags-orming emulsions of the present invention w~th
each other or with conventional emulsions to satisfy
specific emulsion layer requirsments. For example,
~wo or more Pmulsions according to the present inven-
tion, but differing in average grain diameter can be
69
-73-
blended. It is specifically contemplated to employ
in blending internal latent image-forming grains of
similar grain size distribution to minimize migration
of addenda between different grain popula~ions. When
separate emulsions of similar grain size distribution
are employed in combination, their performance can be
differentiated by differences in surface sensitiza-
tion levels, differPnces relating to adsorbed nuc-
leating agents, or differences in proportions of
internal sensitizeres (taught by Atwell et al U.5.
Patent 4,035,185). Silverman et al Can. Ser.No.
415,280, filed concurrently herewith, enti~led
BLENDED DIRECT-POSITIVE EMULSIONS, PHOTOGRAPHIC
ELEMENTS, AND PROCESSES OF USE, commonly assigned,
discloses tha~ the blending of core-shell emulsions
in a weight rat~o of from 1:5 to 5:1, wherein a first
emulsion exhibits a coefficient of variation of less
than 20% and a second emulsion has an average grain
diameter less than 65% that of the first emulsion,
can result in unexpected increase in silver covering
power. A speed increase can also be realized, even
at reduced coating levels. The ratio of the first
emulsion to the second emulsion is preferably 1:3 to
2:1, based on weight of silver, and the average
diameter of the grains of the second emulsion is
preferably less than 50%, optimally less than 40% the
average diameter of the grains of the first emul-
sion. The second emulsion can be any conventional
internal latent image-forming emulsion, bu~ is
preferably substantially free of surace chemical
sensitization.
In their simplest form photographic elements
according to the present invention employ a slngle
silver halide emulsion layer containing a high aspect
ratio tabular grain emulsion according to the present
invention and a photographic support. It is, of
course, recognized that more than one silver halide
J~ ~-J
-74-
emulsion layer as well as overcoat, subbing, and
interlayers can be usefully included. Instead of
blending emulsions as described above the same effect
can frequently be achieved by coating the emulsions
to be blended as separate layers. Coating of sepa-
ra~e emulsion layers ~o achieve exposure latitude is
well known in the ar~, as illustrated by Zelikman and
Levi, Making and Coating Photographic Emulsions,
Focal Press, 1964, pp. 234-238; Wyckoff U.S. Patent
3,663,228; and U.K. Patent 923,045. It is further
well known in the art that increased photographic
speed can be real;zed when faster and slower silver
halide emulsions are coated in separate layers as
opposed to blending. Typically the faster emulsion
layer is coa~ed to lie nearer the exposing radl~tion
source than the slower emulsion layer. This approach
can be extended to three or more s~perimposed emul-
sion layers. Such layer arrangements are specifical-
ly contemplated in the practice of this invention.
The layers of the photographic elements can
be coated on a variety of supports. Typical photo-
graphic supports include polymeric film, wood
fiber--e.g., paper, metallic sheet and foil, glass
and ceramic supporting elements provided with one or
more subbing layers to enhance the adhesive, anti-
static, dimensional, abrasive, hardness, frictional,
antihalation and/or other properties of ~he support
surface.
Typical of useful polymeric film supports
are films of cellulose nitrate and cellulose esters
such as cellulose triacetate and diacetate, poly-
styrene, polyamides, homo- and co-polymers of vinyl
chloride, poly(vinyl acetal), polycarbonate, homo
and co-polymers of olefins, such as polyethylene and
polypropylene, and polyesters of dibasic aromatic
carboxylic acids with divalent alcohols, such as
poly(ethylene terephthalate).
1 175B9
~75-
Typical of useful paper supports are ~hose
which are partlally acetylatsd or coated with bary~a
and/or a polyolefin, particularly a polymer of an
~-olefin containing 2 to 10 carbon atoms 9 such as
polyethylene, polypropylene, copolymers of ethylene
and propylene and the like.
Polyolefins~ such as polyethylene, poly-
propylene and polyallomers--e.g., copolymers of
ethylene with propylene, as illustrated by Hagemey~r
et al U.S. Patent 39478,128, are preferably employed
as resin coatings over paper, as illustrated by
Crawford et al U.S. Patent 3,411,908 and Joseph et al
U.S. Patent 3,630,740, over polystyrene and polyester
film supports, as illustrated by Crawford e~ ~1 U.S.
P~tent 3,630,742, or can be employed as unitary
flexible reflection supports, as illustrated by Venor
et al U.S. Patent 3,973,963.
Preferred cellulose ester supportæ are
cellulose trlaceta~e supports, as illustrated by
Fordyce et al U.S. Patents 2,4929~77, '978 and
2,739,069, as well as mixed cellulose ester supports9
suoh as cellulose acetate propionate ~nd cellulose
acetate butyrate, as illustrated by Fordyce et al
U.S. Patent 2~739~070O
Preferred polyester film supports are com-
prised of linear polyester, such as illustra~ed by
Alles et al U.S. Patent 2,627,088, Wellman U.S.
Patent 2,720,503, Alles U.S. Patellt 2,779,684 and
Kibler et al U.S. Patent 2,901,466. Polyester films
can be formed by varied techniques, as illustra~ed by
Alles, cited above, Czerkas et al U.S. Paten~
3,663,683 ~nd Williams et al U.S~ Patent 3,504,075,
and modified for use as pho~ographic film support6,
as lllustrated by Van Stappen U.S. Patent 3,227,576 9
Nadeau et al U.S. Patent 3,501,301, Reedy et al U.S.
Patent 3,589,905, Babbitt et al U.S. Paten~
3,850,640, Bailey et al U.S. P~tent 3,888 9 678, Hunter
S 8 9 1~J
-76 -
U.S. Paten~ 3 9 904,420 and Mallinson et al U.S. Patent
3792~,697.
The phGtographic elements CRn employ sup-
ports which are reslstant to dimensional change at
elevated ~emperatures. Such supports can be com-
prised of linear condensa~ion polymers which have
glass ~ransi~ion temperatures above about 190C,
preferably 220~C, such as polycarbonates~ polycarb
oxylic esters, polyamides, polysulfonamides, poly-
ethers, polyimides, polyæulfonates and copolymervariants, as illustrated by Hamb U.S. Patents
3~634,089 and 3,772~405; Hamb et al U.S. Patents
3,725~070 and 3,793,24g; Wilson Research Disclosure,
Vol. 118, February 1974, Item 11833, and Vol. 120 9
April 1974, Item 12046; Conklin et al Research Dis-
closure, Vol. 120, April 1974, Item 1~012; Product
Licensing Index, Vol. 92, December 1971, Items 9205
and 9207; Research Disclosure 9 Vol. 101, September
1972, Items 10119 and 10148; Research Disclosure,
Vol. 106, February 1973, Item 10613; Research Disclo-
sure 9 Vol. 117, January 1974, Item 11709, and Re-
search Disclosure, Vol. 134, June 1975, Item 13455.
The photographic elements of the present
invention can be imagewise exposed in any conven-
tional manner. Attention is directed to ResearchDisclosure Item 17643~ cited above, Paragraph XVIII.
The present invention is particularly advantageous
when imagewise exposure is undertaken with electro-
magnetic radiation within the region of the spectrum
in which the spectral sensitizers present exhibit
absorption maxima. When the photographic elements
are intended to record blue, greenl red, or infrsred
exposures, spectral sensitizer absorblng in the blue,
green, red, or inrared portion of the spectrum is
present. For black-and-white imaging appllcations it
i6 preferred that the photographic elements be
orthochromatically or panchromatically sensitized to
~75
-77-
permit ligh~ to extend 6ensitivity within the visible
spectrum. Radiant energy employed for exposure can
be either noncoherent (random phase) or coheren~ (in
phase~, produced by lasers. Imagewise exposures at
ambient, elevated or reduced temperatures andtor
pressures, including high or low intensity exposures,
continuous or intermitten~ exposures, exposure tlmes
ranging from minutes ~o relatively short durations ln
the millisecond to microsecond range 9 can be employed
wi~hin the useful response ranges determined by
conventional sensitometric techniques, as illustrated
by T. H. James~ The Theory of the Photo~raphic
~rocess, 4th Ed., Macmillan, 1977, Chapters 4, 6, 17,
r ~ ~
18, and 23.
The ligh~-sensitive silver halide conta~ned
in the photographic elements can be processed follow-
ing exposure to form a visible image by associating
the silver halide with an aqueou~ alkaline med~um in
the presence of a developing agent contained in the
medium or the element. Processing formulations and
techniques are described in L. F. Mason, Photo~raphic
Processin~ Chemistry, Focal Press, London, 1966; Pro-
cessing Chemicals and Formulas, Publication J-l,
Eastman Kodak Company, 1973; Photo-Lab Index, Morgan
~nd Morgan, Inc., Dobbs Ferry, New York~ 1977, and
Neblette's Handbook of ~ and ~E~ e~-
Materials 9 Processes and ~y~ , YanNostrand
Reinhold Company, 7th Ed., 1977.
Included among the processing methods are
web processing, ~s illustrated by Tr~gillus et ~1
U.S. Patent 3,179,517; stabilization process$ng, as
illustrated by Herz et ai U.S. Pa~Pnt 3,220,839, Cole
U.S. Patent 3,615,511, Shipton et al U.K. Patent
1,258,906 and Haist et al U.S. Patent 3,647,453;
monobath processlng as described ln Haiæt, Monobath
Manual, Morgan and Morgan, Inc., 19667 Schuler U.S.
Patent 3,240,603, Haist et al U.S. Patents 3,615 9 513
~7~9
-7~-
and 3,628~955 and Price U.S. Patent 3,723~126; lnfec~
tious development 7 as illustrated by Milton U.S.
Patents 3,294,5377 3,600,174, 3,615,519 and
3,615,524, Whiteley U.S. Pa~ent 3,516,830, Drago U.S.
S Patent 3~615,488, Salesin et al U.S. Pa~ent
3 9 625,689, Illingsworth U S. Patent 3,632~340,
Salesin U.K. Patent 1,273,030 and U.S. Patent
3,708,303; hardening development, ~6 illustrated by
Allen et al U.S. Pa~ent 3,232,761j roller tr~nsport
processing, as illustra~ed by Russell et al U.S.
Patents 3,025,779 and 3,515,556, Masseth V.S. Patent
3,573,914, Taber e~ al U~S. Patent 3,647,459 and Rees
et al UoK~ Patent 1,269,268; alkaline vapor process-
lng, as illustrated by Product Lleensing Index, Vol.
97, May 1972, Item 9711, Goffe et al U.S. Patent
3,816,136 and King U.S~ Patent 3,9~5,564; metal ion
development as illustrated by Price, Photo~raphic
Science a Engineering, Vol. 19~ Number 5, 1975, pp.
283-287 and Vought Research Disclosure, Vol. 150,
October 1976, Item 15034; and surface application
processing, as illustrated by Kitze U.S. Patent
3,418,132.
The silver halide developers employed in
processing are surface developers. It is understood
that the term "surface developer" encompasses those
developers which will reveal the æurface latent image
centers on a silver halide grain, but will not reveal
substantial internal latent image centers in an
internal latent image-forming emulsion under the con
ditions generally used to develop a surface-sensitive
silver h~lide emulsion. The surface developers cen
generally utiliæe any of the sllver halide developing
agents or reducing agents, but the developing bath or
composition is generally substantially free of a
silver halide solvent (8uch as water-soluble thio-
cyanates, water-soluble thioethers, thiosulfates, and
ammonia) which will disrupt or dissolve the grAin to
6 9 2
-79
reveal substan~ial internal image. Low ~mountæ of
excess halide are sometimes desirable in the devel-
oper or lncorporated in the emulsion as halid0-
releasing compounds, but high amounts of iodide or
iodide releasing compounds are generally avoided to
prevent substantial disruption of the grain.
Typical silver halide developing agents
which can be used in the developing compositions of
this invention include hydroquinones 7 catechols,
aminophenols, 3-pyrazolidinones, ascorbic acid and
its derivatives, reductones, phenylenediamines, or
combinations thereof. The developing agents can be
incorporated in the photographic elements wherein
they are brought into contact with the silver halide
lS af~er imagewise exposure; however, in certain embodi-
ments they are preferably employed in the developing
bath.
Once a silver image has been formed in the
photographic element, it is conventional practice to
fix the undeveloped silver halide. The high aspect
ratio tabular grain emulsions of the present inven-
tion are par~icularly sdvantageous in allowing fixing
to be accomplished in a shorter time period. This
allows processing to be accelerated.
Dye Imagin~
The photographic elements and the techni~ues
described above for producing silver images can be
readily adapted to provide a colored image through
the use of dyes. In perhaps the slmplest approach to
obtaining a projectable color image a conventional
dye can be incorporated in the support of the photo-
graphic element, and silver image formation under-
taken as described above. In areas where a silver
image is ormed the ~lement is rendered substantîally
incapable of transmit~ing light therethrough, and in
the remaining areas light is transmitted corre~pond-
ing in color to the color of the support. In this
-~o -
way a colored image can be readily formed~ The same
effect c~n also be ~chieved by using a separa~e dye
filter layer or element with ~ transparent support
element.
The silver halide photographic element6 can
be used to form dye images therein through the selec-
tive destruction or formation of dyesO The photo-
graphic elements described above for orming silver
images can be used to iEorm dye images by employing
10 developers containing dye image formers, such as
color couplers 9 as lllustrated by U.K. Patent
478,984~ Yager et al U.S. Patent 3,113,8649 Vittum et
al U.S. Patents 3,002,836, ~ 3 271, 238 and 2, 362,5Y8,
Schwan e~ al U.S. Patent 29950,970, Carroll et al
U.S. Patent 2 ~ 592,243, Por~er et el U.S. Patents
2 9 343, 703, 2, 376,380 and 2,369,489, Spath U.K. Patent
886 9 723 and U.S. Patent 2 9 899,306, Tuite U.S. Patent
3,152 ,896 and Mannes et al U.S. P~ten~cs 2,115,394,
2,252,718 and 2,108,602, and Pilato U.S. Patent
3 ~ 547,650. In this form the developer contains a
color-dev~loping agent (e.g., a primary aromatic
amine) which in its oxidized form i6 capable of
reacting with ~he coupler (coupling) to form the
image dye.
The dye-formin~ couplers can be incorporated
in the photographic elements, as iLllustrated by
Schneider et al, Die Chemie, Vol. 57, 1944, p. 113,
Mannes et ~1 U.S. Patent 2,304,940, Martinez U.S.
I?atent 2,269,158, Jelley et al U.S. Patent 2,322,027,
30 Frolich et al U.S. Patent 2,376,679, Fierke et al
Il.S. Paten~ 2~801,171, Smith U.S. Patent 3,748,141,
Tong U.S. Patent 2,772,163, Thirtle et al U.5. Patent
2,835,579, Sawdey et al U.S. Patent 2,533,514,
Peterson U.S. Patent 2,353,754, Seidel U.S. Patent
35 3,409,435 and Chen Research Disclosure, Vol. 159,
July 1977, Item 15930. The dye-forming coupler6 can
be incorpora~ed in different amounts to achieve dif-
-81-
fering photographic e~fects. For example, U.K.
Patent 923,045 and Kumai et al U.S. Patent 3,843,369
teach limi~ing the concentration of coupler in rela-
~ion to ~he silver coverage to less than normally
employed amounts in faster and intermediat~ speed
emulsion layers.
The dye forming couplers are commonly chosen
to form subtractive primary (i.e., yellow, magenta
and cyan) image dyes and are nondiffusible, colorless
couplers, such as two and four equivalent couplers of
the open chain ketomethylene, pyrazolone, pyrazolo-
triazole, pyrazolobenzimidazole, phenol and naphthol
type hydrophobically ballasted for lncorporation in
high-boil~ng organic (coupler3 solven~s. Such coup-
lers are illustrated by Salminen et al U.S. Patents2,423,730, 2,772,i62, 2,89~,826, 2,710,803,
2,407,207, 3,737,316 and 2,367,531, Loria et al U.S.
Patents 2,772,161, 2,600,788, 3,006,759, 3,214,437
and 3,253,924, MeCrossen et al U.S. Patent 2,875,057,
Bush et al U.S. Patent 2,908,573, Gledhill et al U.S.
Patent 3,034,892, Weissberger et al U.S. Patents
2,474,293, 2,407,21G, 3,062,653, 3,265,506 and
3,384,657, Porter et al U.S. Patent 2,343,703,
Greenhalgh et al U.S. Patent 3,127,259, Feniak et al
U.S. Patents 2,865,748, 2,933,391 and 2,865,751,
Bailey et al U.S. Patent 3,725,067, Beavers et al
U.S. Patent 3,758,308, LAU U.S. Patent 3,779,763,
Fernandez U.S. Patent 3,785,829, U.K. Patent 969,921,
U.K. Patent 1,241,069, U.K. Patent 1~011,940, Vanden
Eynde et al U.S, Pa~ent 3,762,921, Beavers U.S~
Patent 2,983,608, Loria U.S. Patents 3,311,476,
3,408,194, 3,458,315, 3~447,928, 3,476,563, Cressman
et al U.S. Patent 3,419 9 390, Young U.S. Patent
3,419,391, Les~ina U.S. Pat~nt 3,519,429, U.K. Patent
975,928, U.K. Patent 1,111,554, Jaeken U.S. Patent
3,222,176 and Canadian Patent 726,651, Schulte et al
U.K. Patent 1,248,924 ~nd Whitmore et al U.S. Patent
1 ~ 7~6'~
-~2 -
3,227,550. Dye-forming couplers of differing reac-
~ion rates in single or separate layers can be
employ~d to achleve desired e~ects for specific
photographic applications.
The dye~forming couplers upon coupling can
release photographically useful fragments, ~uch as
development inhibitors or acceler~tors, bleach accel-
erators, developing agents, silver halide solvents,
toneræ, hardeners, fogging ~gents, antifoggants, com-
peting couplers, chemical or spectral sensitizers and
desensitizers. Development inhibitor-releasing (DIR)
couplers are illustrated by Whitmore et al U.S.
Patent 3,148,062, Barr et al U.S. Pa~en~ 3~227,554,
Barr U.S. Paten~ 3,733,201, Sawdey U.S. Patent
3~617,291, ~roet et al U.S. Patent 3~703,375, Abbott
et al U.S. P~tent 3,615,506, Weissberger et al U.S.
Patent 3,265,506, Seymour U.S. P~tent 3,620,745, Marx
et al U.S. Patent 3,632,345, Mader et al U.S. Patent
3,869,291, U.K. Patent 1j201,110, Oishi et al U.S.
Patent 3,fi42,485~ Verbrugghe U.K. Patent 1,236,767~
Fujiwhara et al U.S. Patent 3,770,436 and Matsuo et
al U~S. Patent 3,80~,945. Dye-forming couplers and
nondye-forming compounds which upon coupling release
a variety of photographically useful groups are des-
cribed by Lau U.S. Patent 4,248,962. DIR compoundswhich do no~ form dye upon reaction with oxidized
color-developing agent~ can be employed, as illus-
trated by Fu;iwhara et al German OLS 2,529,350 and
U.S. Patents 3,92~,041, 3,958,993 and 3,961,959,
Odenwalder et al German OLS 2,448,063; Tanaka et al
German OLS 2,610,546, Kikuchi et al U.S. Patent
4,049,455 and Credner et al U.S. Pa~ent 4,052,213.
DIR compounds which oxidatively cleave can be employ-
ed, as illustrated by Porter et al U.S. Patent
3,379,529, Green et al U.S. Patent 3,043,690, Barr
U.S. Patent 3,364,022, Duennebier et al U~S. Patent
3,297,445 and Rees et al U.S. Patent 3,287,129. Sil-
~ 3-
ver halide emulslons which are relatively light in-
sensitive, such as Lippmann emulsion6 9 have been
utilized as interlayers and overcoat layers to pre-
vent or control the migration of development inhibi-
tor fragments as described in Shiba et al U.S. Patent3,8929572.
The photographic elements can incorporate
colored dye-forming couplers, such as those employed
to form integral masks for nega~ive color imageæ~ as
illustrated by Hanson U.S. Patent 2,449,966, Glass et
al U.S. Patent 23521,908, Gl~dhill e~ al U.S. Patent
3,334/892, Loria U.S. Patent 39476,563, Lestina U.S.
Patent 3,519,429, Friedman U.S. Paten~ 2,543,691,
Puschel et al U.5. Patent 3,028,238, Menzel et al
U.S. Patent 3~061,432 and Greenhalgh U.K. Patent
19035,959, and/or competing couplers, as illustrated
by Murin et al U.S. Patent 3,876,428, Sakamoto et al
U.S. Patent 3,580,722, Puschel U.S. Patent 2,998,314,
Whitmore U.S. Patent 2,808,329, S~lminen U.S. Patent
2,742,832 and Weller et ~1 U.S. Patent 2,689,793.
The pho~ographic elements can include image
dye stabilizers. Such image dye stabilizers are
illustrated by U.K. Paten~ 1,326,889, Lestina et al
U.S. P~tents 3,432,300 and 39698,909, Stern et al
U.S. P~tent 3,574,627, ~rannock et al U.S. Patent
3,5733050, Arai et ~1 U.S. Patent 3,764,337 and Smlth
et al U.S. Patent 4,042,394.
Dye images can be formsd or amplified by
processes which employ in combination with a dye
image-generating reduclng ~gent an inert transition
metal ion complex oxldizing agent, as illustrated by
Bissonette U.S. Patents 3,748,138, 3,826,6S2,
3,862,842 and 3,989,526 and Travis U.S. PRtent
3,765,891, and/or a peroxide oxidizing agent, as
illustrated by Matejec U.S. Patent 3,674,490,
Rese~rch Disclosure, Vol. 116, December 1973, Item
11660, and Bissonette Research Disclosure, Vol. 148,
-
-84
August 1976, Items 14836, 14846 and 14847O The
photographic elemen~s can be particul~rly adapted to
form dye images by such processes~ as illustrated by
Dunn et al U.S. Paten~ 3,822,129, Bissonet~e U.SO
S Patents 3,834,907 and 3,902,905, Blssonet~e et al
U.S. Pa~ent 3,847,619 and Mowrey U.S. Patent
3,904,413.
The photographic elements can produce dye
images through the selective destruction of dyes or
dye precursors, such as silver-dye-bleach processes,
as illustrated by A. Meyer, The Journal of Photo-
~raphic Science, Vol. 13 9 1965, pp. 90-97. Bleach-
able azo, azoxy, xanthene, aæine, phenylmethan ,
nitroso complex, indigo, quinone, nitro-substituted,
phthalocyanine and formazan dyes, as illustrated by
S~auner et al U.S. Patent 3,754 9 923, Piller et al
U.S. Patent 3,749,576, Yoshida e~ al U.S~ Patent
3,738,839, Froelich et al U.S. Pa~ent 3,716,368,
Piller U.S. Pa~ent 3,655,388, Williams et al U.S.
Pa~ent 3,642,482, Gilman U. S . Patent 3,567,448,
Loeffel U.S. Paten~ 3,443,953, Anderau U.S. Patents
3,443,952 and 3,211,556, Mory et al U.S. Patents
3,202,511 and 3,178,291 and Anderau et al U.S.
Patents 3,17~,285 and 3,178,290, as well as their
hydrazo, diazonium and tetrazolium precursors and
leuco and shifted derivatives, as illustrated by U.K.
Patents 923,265, 999,996 and 1,042,300, Pelz et al
U.S. Patent 3,684,513, Watanabe et al U.S. P~tent
3,615,493, Wilson et al U.S. Paten~ 3,503~741, Boes
et al U.S. Patent 3,340,0599 Gompf et al U.S. Patent
3,493~372 and Puschel et al U.S. Patent 3,561,970,
can be employed.
It is common practice in forming dye images
in silver halide photo~raphic elements to remove the
silver which is developed by bleaching. Such removal
can be enhanced by incorporatlon of a bleach accel-
erator or a precursor thereof in a processing solu-
~ 5-
tion or in a layer of the element. In some instances
the amount o silver formed by development is small
in relation to the amount of dye produced, partlcu-
larly in dye image amplification, as described aboYe~
and silver bleaching is omitted without substantial
visual effect. In still other application6 the sil-
ver image is retained and the dye image ls intended
to enhance or supplement the density provided by the
image silver. In the case o dye enhanced silver
imaging i~ is usually preferred to form a neutral dye
or a combina~ion of dyes which together produce a
neutral image. Neutral dye-forming couplers useful
for ~his purpose are disclosed by Pupo et al Research
Disclosure, Vol. 162 7 October 1977, Item 16226. The
enhancement of silver images with dyes in photo-
graphic elements intended for thermal processing is
disclosed in Research Disclosure, Vol. 173, September
1973, Item 17326, and Houle U.S. Patent 4,137,079.
It is also possible to form monochromatlc or neutral
dye images using only dyes, silver being entirely
removed from the lmage-bearing photographic elements
by bleaching and fixing, as illustrated by Marchant
et al UOS. Patent 3,620,747.
Multicolor Photogra~
The present invention can be employed to
produce multicolor photographic images. Gener~lly
any conventional multicolor imaging direct reversal
photographic element containing at least one internal
latent lmage-forming silver halide emulsion layer can
be improved merely by adding or substituting a high
a~pect ratio tabular grain internal latent image-
forming emulsion according ~o the present invention.
Significant advantages can be realized by
the application of this inven~ion to multicolor
photographic elements which produce multicolor images
from combinations of sub~ractive primary imaging
dyes. Such photographic elements are comprised of a
~7~2
-86
support and typically at least a ~riad of super-
i~posed silver halide emulæion layers for 6ep~rately
recording blue, green, a~d red light exposures a~
yellow, magenta, and cyan dye images, respectively~
Although the present invention gener~lly embrsces any
mul~icolor photographic element of this type includ-
ing at least one high aspec~ ratio tabular grain
internal latent image-forming emulsion, additional
advantages can be realized when high aspect ratio
tabular grain internal latent image-forming silver
bromide and bromoiodide emulsions are employed.
Consequsntly, the following description is dirPcted
to certain preferred embodiments incorporating sllver
bromide and bromoiodide emulsions, but high aspect
ratio tabular grain internal latent image-forming
emulsions of any halide composition can be substi-
tuted, if desired. Except as specifically otherwl~e
described, the multicolor photographic elements can
incorporate the features of the photographic elements
described previously~
In a specific preferred form of the inven-
tion a minus blue sensitized high aspect ratio tab-
ular grain internal latent image-i-ormlng silver
bromide or bromoiodide enulsion according to the
invention having an average tabular grain thickness
of less ~han 0.3 micron forms at least one of the
emulsion layPrs intended to record green or red light
in a triad of blue, green, and red recording emulsion
layers of a multicolor photographic element and is
positioned to receive during exposure of the photo-
graphic element to neutral light at 5500K blue light
in additlon to the light the emulsion i6 intended to
recordO The relAtionship of the blue and minus blue
light the layer receives can be expressed in terms of5 ~ log E, where
a 1 Og E - log ET ~ log
~7~9
-87-
log ET being the log of exposure to green
or red light the tabular grain emulsion is intended
to record and
log E~ being the log of concurrent expo
sure to hlue light the tabular grain emulsion a1BO
receives. ~In each vccurrence exposure, E, is in
me~er-candle-seconds 9 unless otherwise indicated.
In the practice of the pre~en~ invention
log E can be less than 0.7 (preferably less than 0.3
while still obtaining acceptable color replication.
This iæ surprising in view of the high proportion of
grains present in the emulsions of the present inven-
tion having an average diameter of greater than 0.7
micron. If a comparable nontabular or lower aspect
ratio tabular grain emulsion of like halide composi-
tion and average grain diameter is subs~ituted for a
high aspect ratio ~abular grain eilver bromide or
bromoiodide emulsion of ~he present in~en~ion a
higher and usually unacceptable level of color falsi-
fication will result. It is known in the art thatcolor falsification by green or red sensitized silver
bromide and bromoiodide emulsions ran be reduced by
reduction of average grain diameters, but this
results in limiting maximum achievable photographic
speeds as well.
The present invention achieves not only
advantageous separation in blue and minus blue
speeds, but is able to Achieve this advantage without
any llmitatlon on maximum realizable minus blue
photographic speeds. In & specific preferred form of
the invention at least the minus blue recording emul
sion layers of the triad of blue, green, and red
recording emulsion layers are silver bromide or
bromoiodide emulslons according to the present inven-
tion. It is specifically contemplated that the bluerecording emulsion layer of the triad can advan-
tageously also be a high aspect ratio tabular grain
~756
-88-
emulsion according to ~he present invention. In a
specific preferred form of the invention the tabular
gralns present in each of the emul~ion layers of the
trlad have an average grain diameter of a~ ~east 1~0
micron~ preferably at least 2O0 mlcrons, and the
emulsion has an average aspect r&tio of at 1 ast
10:1. In a still further preferred form of the
invention the multicolor photographic elements can be
assigned an IS0 speed index of at least 180~
The multicolor pho~ographic elements of the
invention need contain no yellow filter layer posi-
tioned between the exposure source and the high
aspect ratio tabular grain green And/or red emulsion
layers to protect these layers from blue light expo-
sure, or the yellow filter layer9 if present9 can bereduced in density to less than any yellow filter
layer density heretofore employed ~o protect from
blue light exposure red or green recording emulsion
layers of photographic elements intended to be
exposed in daylight. In one specifically preferred
form of the invention no blue recording emulsion
layer is interposed between the green and/or red
recording emulsion layers of the triad and the source
of exposing radia~ion. Therefore the photographic
element is substantially free of blue Absorbing
material between ~he green and/or red emulsion layers
and incident expoæing radiation. If, in this
instance, a yellow filter layer is interposed between
the green and/or red recording emulsion layers and
lncident exposing radiation, lt accounts for all of
the interposed blue density.
Al~hough only one green or red recording
high aspect ratio tabular grain silver bromide or
bromoiodide emulsion as described above is required,
the multicolor photographic element contains at least
three separate emulslons for recording blue, green,
and red light, respectively. The emuls~ons other
1 :~756~2
-89-
than the required high aspect ratio tabular grain
green or red recording emulsion can be internal
latent image-forming emulsions of any convenient
conventional form. Evans U.S. Patents 3j761,276 and
3,923,513 and Atwell et al U.S. Patent 4,0353185,
cited above, illustrate preferred nont~bular internal
latent image-forming emulsions useful in combination
with the emulsions of thls invention. In a preferred
form of the invention all of the emulsion layers
contain silver bromide or bromoiodide gralns. In a
particularly preferred form of the invention at least
one green recording emulsion layer and at leas~ one
rPd recording emulslon layer is comprised of a high
aspect ratio tabular grain internal latent image-
forming emulsion accordlng to this invention. Ifmore than one emul6ion l~yer is provided to record in
the green and/or red portion of the spectrumS it is
preferred that at least the faster emulsion layer
contain high aspect ratio t~bular grain emulsion as
described above. It is, of course, recognized that
all of the blue, green, and red recording emulsion
layers of the photographic element can advantageously
be tabular as described above 9 if desired, although
this is not required for the practice of this inven-
tion.
The present invention is fully applicable tomulticolor photographic elements as described above
in which the speed and contrast of the blue, green,
and red recording emulsion layer~ vary widely. The
relative blue insensitivity of green or red spectral-
ly sensitlzed high aspect ratio tabular grain silver
bromide or silver bromoiodide emulsion layers employ
ed in this invention allow green and/or red recording
emulsion layers to be positioned at any location
within a multicolor photographic element independent-
ly of the remaining emulsion layers and without tak-
ing any conventional precautions to prev~nt their
exposure by blue light.
9 2
-so -
The present invention is part cularly appli-
cable to mul~icolor photographic elements intended to
replicate colors accurately when exposed in day-
light. Photographic elements of this $ype are char-
acteriæed by producing blue, green, and red exposurerecords of substantially matched con~rast and limited
speed variation when exposed to a 5500K (dayllght)
source. The term l'substantially matched con~rast" as
employed herein means that the blue, green, and red
records differ in contrast by less ~han 20 ~prefer-
ably less than 10) percent, based on the contras~ of
the blue record. The limited speed variation of the
blue, green, and r~d records can be expressed as a
speed variation (~ log E) of less ~han 0.3 log E,
where the speed variation is the larger of the dif-
ferences between the speed of the green and red
records and the speed of the blue record.
The multicolor photographic elements of this
invention c~pable of replicating accurately colors
when exposed in daylight offer significant advantages
over conventional photographic elements exhlbiting
these characteristics. In the photographic elements
of the invention the limited blue sensitivity of the
preferred green and red spectrally sensitlzed tabular
silver bromlde or bromoiodide emulsion layers can be
relied upon ~o separate the blue speed of the blue
recording emulsion layer and the blue speed of the
minus blue recording emulsion layers. Depending upon
~he specific application, the use of tabular grains
in the green and red re~ording emulsion layers can in
and of itself provide a desirably large separation in
the blue response of the blue and minus blue record-
ing emulsion layers.
In some applica~ions it may be desirable to
~ncrease further blue speed separations of blue and
minus blue recording emulsion layers by employing
conventional bluP speed separation techniques to
I :~ 7~9~
-91-
supplement the blue speed separations obtained by the
presence of the high aspect ratio tabular ~r~ins.
For example, if a multicolor photographic el2ment
places the fas~es~ green recording emulsion layer
nearest the exposing radiation source and the fastest
blue recording emulsion layer farthest from the
exposing radia~ion ~ource, the separation of the blue
speeds of the blue and green rPcording emulsion
layers, though a full order of magnitude ~1.0 log E)
different when the emulsions are separ~tely co~ted
and exposed, may be effectively reduced by the layer
order arrangement, since the green recording emulsion
layer receives all of the blue light during exposure~
but the green recording emulsion layer and other
lS overlying layers may absorb or reflect some of the
blue light before it re~ches the blue recording emul-
sion layer. In such circumstance employing a higher
proportion of iodide in the blue recording emulsion
layer can be relied upon to supplement the tabular
grains in i~creasing the blue speed separation of the
blue and minus blue recording emulsion layers. When
a blue recording emulsion layer is nearer the expos-
ing radiation source ~han the minus blue recording
emulsion layer, a limited density yellow filter
material coated between ~he blue and minus blue
recording emulsion layers can be employed to increase
blue and minus blue separstion. In no instance, how~
ever, is it necessary to make use of any of these
conventional ~peed ~eparation techniques to the
3~ extent that they in themselves provide an order of
magnitude difference in the blue speed sep~ration or
an ~pproximation thereof, as has heretofore been
required in the art talthough this is not precluded
if exceptionally large blue and minus blue speed
separation i~ desired for a specific applieation).
Thus, the prssent invention achieves the objectives
for multicolor photographic elements intended ~o
~56
-92-
replica~P image colors accurately when exposed under
balanced lighting conditions while permlt~ing a much
wider choice in element constructlon than has here-
tofore been possible.
Multicolor photographlc elements are often
described in terms of color-forming layer units.
~ost commonly multicolor photographic elements con-
tain three superimposed color-forming layer units
each containing at least one silver halide emulsion
layer capable of recording exposure to a dlfferent
third of ~he spectrum and capable of producing a
complementary subtractive primary dye image. Thus,
blue, green, and red recording color-orming layer
units are used to produce yellow, magenta, and cyan
dye images, respec~ively. Dye imaging materials need
not be present in any color-forming layer unit, but
can be entirely supplied from processing solutions.
When dye imaging materials are incorporated in the
photographic element, they can be located in an emul-
sion layer or in a layer located to receive oxidizeddeveloping or electron transfer agent from an adja-
cent emulsion layer of the same color-forming layer
unit.
To prevent migration of oxldized developing
or electron transfer ~gents between color-formin~
layer units with resultan~ color degradatlon, it is
common practice to employ scavengers. The scavengers
can be locsted in the emulsion layers themselves, as
taugh~ by Yutzy et al U.S. Patent 2,937~086 and/or ln
interlayers between adjacent color-forming layer
units, as illustrated by Weissberger et al U.S.
Patent 2,336~327.
Although each color-forming layer unit can
contain a single emulsion layer, two, three, or more
emulsion layers differing in photographic speed are
often incorporated in a ~lngle color-forming layer
unit. Where the desired layer order arrangement does
~7~9
-93-
no~ permit multiple emulsion l~yers differing in
speed to occur in a single color-forming layer unit,
it i5 common practice to provlde multiple (usually
two or three~ blue, green, and/or red recording
color-forming layer units 1n a single photographic
element.
It is a unique fea~ure of this invention
that ~t least one green or red recordin~ emulsion
layer containing ~abular silver bromide or bromo-
iodide grains as described above is located in themul~icolor photographic element to receive an
increased proportion of blue light during imagewise
exposure of the photographic elementO The increased
proportion of blue light reaching the high aspect
ratio t~bular grain emulsion layer can result from
reduced blue light absorption by an overlying yellow
filter layer orS preferably5 ellmination of overlying
yellow filter layers entirely. The increased propor-
tion of blue light reaching the high aspect ratio
tabular emulsion layer can result also from reposi-
tioning the color-forming layer unit in which it is
contained nearer to the source of exposing radia-
tion. For example, green and red recording color-
forming layer units containing green and red record-
ing high aspect ratio tabulAr emulsions, respectlve-
lyg cnn be positioned nearer to the source of expos-
ing radiation than ~ blue recording color-forming
layer unlt.
The mul~icolor photographic elements of this
lnven~ion can take any convenient form consi~tent
with the requirements indicated above. Any of the
six possible layer arrangements of Table 27a, p~ 211,
disclosed by Gorokhovskii, ~pectral Studies of the
Photographic Process, Focal Press, New York, can be
employed. To provide a Bimple 7 specific illustr~-
tion 9 it is possible to add to a conventional multi-
color silver halide photographic element during its
I ~ ~569
-94
preparation one or more high aspect ratio tabular
grain emulsion layers sensitized to the minus blue
portion of ~he spec~rum and positioned to receive
exposing radiation prior to the rema~ning emulsion
layers. However, in most instances~ it is preferred
to substitute one or more minus blue recording high
aspect ratio tabular grain emulsion layers or
conven~ional minus blue recording emulsion layers,
optionally in combination with layer order Rrrange-
ment modifica~ions. The invention can be betterappreciated by reference to the following preferred
illustrative forms.
Layer Order Arran~ement I
Exposure
_ ~ _ _ _
IL _
T5 _ _
IL _
TR _ _
Layer Order Arrangement II
Exposure
_
TFB
IL
TFG
IL
TFR _ _ _
_ IL
IL _
_ SG
IL
SR
:
- ~75~2
-95-
Layer Order Arran~emen~ III
Exposure
TG
IL
. . ~
TR
IL
= B ~ _ _
Layer Order Arr~n~ement IV
Exposure
TFG
_ IL
IL
TSG
IL
=
_ TSR
IL
B
_
Layer Order Arrangement V
Exposure
~ _
_ __ _ _ TFG _
IL
T~R
IL
TFB
IL
_
TSG
IL
TSR
IL T '
SB
7~69
-96 -
Exposure
,
TFR
....
IL ___
TB _ _
IL
_ _ TFG
IL
_
_ TFR
IL
S&
IL
.
SR
Layer Order Arran~ement VII
Exposure
_ .
TFR
IL
IL
TB
__ _ _ _
IL
_ TFG
IL
T5G
IL
_ _ _
IL _
TSR
where
B, G~ and R designate blue, green, ~nd red
recording color-forming layer unit~, respectively, of
any conven~ional type;
-97-
T appearing before the color-formlng layer
unit B, G, or R indica~es ~hat the emulsion layer or
layers contaln a high aspect ratio tabular gr~in
silver bromide or bromoiodide emulsion6 3 as more
specifically described above,
F appearing before the color-forming layer
unit B, G, or R indicates that the color-forming
layer unit is faster in photographic speed than at
least one other color forming layer unit which
records light exposure in the same third of the
spectrum in the same Layer Order Arrangement;
S appearing before the color-forming layer
unit B, G, or R indicates that the color-forming
layer unit is slower in photographic speed ~han at
least one other color-forming layer unit which
records light exposure in the same ~hird of the
spectrum in the same Layer Order Arr~ngement; and
IL designates an interlayer containlng a
scavenger, but substanti211y free of yellow filter
material. Each faster or slower color-forming layer
unit can differ in photographic speed from another
color-forming layer uni~ whieh records light exposure
in ~he same third of the spectrum as a result of its
position in the Layer Order Arran,gement, i~s inherent
speed properties, or a combination of both.
In Layer Order Arrangements I through VII,
the location of the support is not shown. Following
customary practice, the support will in most
instances be positioned farthest from the source of
exposing radiation--that isj beneath the layers as
shown. If the support is ~olorless and specularly
transmis~ive--i.e., transparent, it can be located
between the exposure source and the indicated
layers. Stated more generally, the support can be
located between the exposure source and any color-
forming layer unit intended to record light to which
the support is transparent.
~75
-98-
Turning first to Layer Order Arrangement I,
it can be seen tha~ ~he photographic element ls sub-
stantial1y free of yellow filter materialO However,
following conventional practice for elements contain-
ing yellow fllter material, the blue recordingcolor-forming layer unit lies nearest the ~ource of
exposing radiation. In a simple form each eolor-
forming layer unit is comprised of a single silver
halide emulsion layer. In another form each color
forming layer unit can contain two, three, or more
differen~ silver halide emulsion layers. When a
~riad of emulsion layers, one of highest speed from
each of the color-forming layer units, are compared,
they are preferably substantially matched in contrast
and the photographic speed of the green and red
recording emulsion layers differ from the speed of
the blue recording emulsion layer by less than 0.3
log E. When ~here are two~ three, or more different
emulsion layers differing in speed in each color-
forming layer unit, there are preferably two, three,or more triads of emulsion layers in Layer Order
Arrangement I having the stated c:ontrast and speed
relationship. The absence of yellow fil~er material
beneath the blue recording color forming unit
increases the photographic speed of this layerO
It is not necessary that the interlayers be
substantially free of yellow filter materi~l in Layer
Order Arrangement I. Less than conventional amounts
of yellow filter material can be located between the
blue and ~reen recording color-forming units without
departing from the teachings of this invention. Fur-
ther, the inte-layer separating the green and red
color-forming layer units can contain up to conven-
tional amounts of yellow filter material without
departing from the invention. Where conventional
amounts of yellow filter material are employed 9 the
red recording color-forming unit is not restricted to
~ ~7~692
99
the use of tabular silver bromide or bromoiodide
grains, as descri~ed above, but can take any conven-
tional form, subjec~ to the ~ontrast ~nd 6peed con-
siderations indicated.
To avoid repetitlon, only features that
distinguish Layer Order Arrangement6 II through V
from Layer Order Arrangement I are specifically
discussed. In Layer Order Arrangement II, rather
than incorporate faster and slower blue 9 red, or
green recording emulsion layers in the same color-
forming layer unit, two separa~e blue, green~ and red
recording color-forming layer units are provided.
Only the emul~ion layer or layers of thP faster
color-forming units need cont~in tabular silver
bromide or bromoiodide grains, as descrlbed above.
The slower green and red recording color-forming
layer units because of their slower speeds as well as
the overlying faster blue recording color-forming
layer unit, are adequately protected from blue light
exposure without employing a yellow filter material.
The use of high aspect ratio tabular 8rain silver
bromide or bromoiodide emulsions in the emulsion
layer or layers of the slower green and/or red
recording color-forming layer unit6 is, of course,
not precluded. In placing the faster red recording
color-forming layer un~t above the slower green
recording color-forming layer unit, increased speed
can be realized, as taught by Eeles et al U.S. Patent
4,184,876 D Ranz et al German OLS 2,704,797, and
Lohman et al German OLS 2,622,923, 2,622,924, and
2,704,~26.
Layer Ord~r Arrangement III differs from
Layer Order Arrangement I in placing the blue record-
ing color-orming layer unit farthest from the expo-
sure source. This then place6 the green recordingcolor-forming layer unit nearest and the red record-
ing color-forming layer uni~ ne~rer the exposure
9 ~
- 100-
source. This arrangemen~ is highly advantageous in
producing sharp 7 high quality multicolor images. The
green recording color-forming layer un~t, which makes
the most important visual contribu~ion to mul~icolor
imaging, as a resul~ of being located nearest the
exposure source is capable of producing a very sharp
image, since there are no overlying layers to scQtter
light. The red recording eolor-forming layer unit,
which makes the next most important visual contribu-
tion to the multicolor image, receives light that haspassed through only the green recording color-forming
layer unit and has therefore not been scattered in a
blue recording color-forming layer unit. Though the
blue recording color-forming layer unlt suffers in
comparison to Layer Order Arrangement I, the loss of
sharpness does not offset the advantages realized in
the ~reen and red recording color-forming layer
units, ~ince ~he blue recording color-orming layer
unit makes by far the least significant visual
contribution to the multicolor image produced.
Layer Order Arrangement IV expands Layer
Order Arrangemen~ III to include separate faster and
slower high aspect ratio tabular grain emulsion
cont~ining green and red recording color-forming
layer units. Layer Order Arrangement V differs from
LAyer Order Arrangement IV in providing an additional
blue recording color-forming lay~r unit above the
slower green, red9 and ~lue recordlng color-forming
layer units. The faster blue recording color-forming
layer unit employs high aspect ratio tabul2r grain
silver bromi.de or bromoiodide emulsion, as described
above. The fas~er blue recording color-forming layer
unit in this instance acts to absorb blue light and
therefore reduces ~he proportion of blue light
reaching the slower green and red recording color-
forming layer units. In a variant form, the slower
green and red recording color-forming layer units
~ ~7~692
-101 -
need not employ high aspect ratio tabular graln
emulsions.
Layer Order Arrangemen~ VI differs from
Layer Order Arrangment IV in locating a tabular grain
blue recording color-forming layer unit between the
green and red recording color-forming layer uni~æ and
~he source of exposing radiation. As is pointed out
above, the tabular grain blue recording color forming
layer unit can be comprised of one or more tabular
grain blue recording emulsion layers and, where
multiple blue recording emulsion layers are present,
they can differ in speed. To compensate for the less
favored position the red recording color~forming
layer units would otherwise occupy, Layer Order
Arrangement VI also dlffers from Layer Order Arrange-
ment IV in providing a se~ond fast red record~ng
color-orming layer unit, which is positioned between
the tabular grain blue recording color-forming layer
unit and the source of exposing radiation. Because
of the favored location which the second tabular
grain fast red recording color-forming layer unit
occupies i~ is faster ~han the first fast red record~
ing layer un~ if the two fast red-recording layer
units incorporate identical emulsions. It is, of
course, recognized that the firsl: and second fast
tabular grain red recording color-forming layer units
can, if desired, be formed of the same or different
emulsions and that their relative speeds can be
adjusted by techniques well known to those skilled in
the art. Instead of employing two fas~ red recording
layer units, as shown, the second fast red recording
layer unit cAn, if desired, be repl~ced with a second
fast green recording color-forming layer unit. Layer
Order Arrangemen~ VII can be ldent~cal ~o Layer Order
Arrangemen~ VI, but differs in provlding both a
second fast tabular grain red recording color~forming
layer unit and a second fast tabular grain green
~7
-102-
recording color-forming layer unit interposed between
the exposing radiation source and the tabular grain
blue recording color~forming layer unit.
There are~ of course, m~ny other advan
tageous layer order arrangements possible, Layer
Order Arrangemen~s I ~hrough VII being merely illus-
trative. In each of thP various Layer Order Arrange~
ments corresponding green and red recording color-
forming layer units can be interchanged- i.e., the
faster red and green recording color-forming layer
units can be interchanged in position in the various
layer order arrangements and additionally or alterna-
tively the slower green and red recording color-form-
ing layer units can be interchanged in position.
Although photographic emulsions intended to
form multicolor images comprised of combinations of
subtractive primary dyes normally take the form of a
plurality of superimposed layers containing incor-
porated dye-forming materials, such as dye-forming
couplers, this is by no means required. Three
color-forming componen~s, normally referred to as
packets, each containing a sil~er halide emulsion for
recording light in one third of the vislble spectrum
and a coupler capable of forming a complementary
subtractive primary dye, can be placed together in a
single layer of a photographlc element to produce
multicolor images. Exemplary mixed packet multicolor
photographic elements are disclosed by Godowsky U.S.
Patents 2,698,794 and 2,8439489. Although discussion
is directed to the more common arrangement in which a
single color-forming layer unit produces a single
subtractive primary dye, relevance to mixed packet
multicolor photographic elements will be readily
epparent.
It is the relatively large separation in the
blue and minus blue sensitivities of ~he green and
red recording color-forming layer units containing
~ 5~92
-103-
tabular grain silver bromide or bromoiodide emulfiions
that permits reduction or elimination of yellow
filter materials and/or the employment of novel layer
order arrangements. One technique that can be
employed for providing a quantitative measure of the
relative response of green and red recording color~
forming layer units to blue light in mul~icolor
photographlc elements is to expose through ~ step
tablet a sample of a mul~icolor photographic element
according to this invention employing first a neutral
exposure source -i.e., light at 5500K--and there-
after to process the sample. A second sample is then
identically exposed, except for the intPrposition of
a Wratten 98 filter, which transmits only light
be~ween 400 and 490 nm, and thereafter identically
processed. Using blue, green, and red transmission
d~nsities determined according to American Standard
PH2.1-1952, ~s described above, three dye character-
istic curves can be plotted for each sample. The
difference in blue speed of the blue recording
color-forming layer unit(s~ and the blue speed of the
green or red recording color-formlng layer unit(s)
can be determined from the relationship:
(A) (BW98 - GW9~) - (BN - GN) or
(B) (Bwg8 - RW98) (~N N)
where
Bw9~ is the blue speed of the blue record-
ing color-forming layer unit(s) exposed through the
Wratten 98 filter;
~ 98 is the blue speed of the green
recording color-forming layer unit(s) exposed through
the Wra~ten 98 filter;
~98 is the blue speed of the red record-
ing color-forming layer unit(s) exposed through the
Wratten 98 filter,
BN is the blue speed of the blue recording
color-forming layer unit(s) exposed to neutral
(5500K) light;
,:
~ ~7~692
-104~
GN is the green speed of the green record-
ing color-orming layer unit (6) exposed to neutral
(5500K) light; and
RN is the red speed of the red recording
color-forming layer unit(s) exposed to neutr~l
(5500K) light.
(The above descrip~icn imputes blue, green, and red
densities to the blue~ green, and red recording
color-forming layer units, respectively, ignoring
unwanted spectral absorption by the yellow, magenta,
and cyan dyes. Such unwanted spectral absorption is
rarely of suff;clent magnitude to affect materially
the results obtained for the purposes they are here
employed.) The preferred multicolor photographic
elements of the present invention ln the absence of
any yellow filter material exhibit a blue speed by
the blue recording color forming layer uni~s which is
at least 6 times, preferably at leas~ 8 times, and
optimally at least lO times the blue speed of green
and/or red recording color-forming layer units
containing high aspect ratio tabular grain emulsions,
as described above.
Another measure of the large separation in
the blue ~nd minus blue sensitivities of the multi-
color photographic elements of the present inventionis to compare the green speed of R green recording
color-forming layer unit or the red speed of a red
recording color-forming layer unit to its blue
speed. The same exposure and processing techniques
described above are employed, except that the neutral
light exposure is changed to ~ minus blue exposure by
interposing a Wratten 9 filter, which transmits only
light beyond 490 nm. The quantitative difference
being determined is
(C) ~ 9 - ~98 or
(D) ~ g ~ RW98
where
-
~S~92
-1~5-
Gw9~ and ~ 9~ are defin4d above;
Gw~ is the green speed of the green
recording color-forming layer un~t(s) exposed through
the Wrat~en 9 filter; and
~ 9 is the rPd speed of the red recording
color-forming layer uni~(s) exposed through the
Wra~en 9 filter. (Again unwanted spectral absorp-
tion by the dyes is rarely material and is ignored.
Red and green recording color-orming layer units
conteining tabular silver bromide or bromoiodide
emulsions, as described above, can exhibit a differ-
ence between their speed in the blue region of the
spectrum and their speed in the portion of the spec-
trum to which they are spectr~lly sensitized (i.e., a
difference in thelr blue and minus blue speeds3 of at
least 10 times (1'.0 log E), when the tabular grains
have an average thickness of less than 0.3 micron.
In comparing ~he quantitative rela~lonships
A to B and C to D for a single layer order arrange-
ment, the results will not be iden~ical, even if thegreen and red recording color-forming layer units are
identical (except for their wavelengths of spectral
sensitization). The reason is th,at in most instances
the red recording color-forming layer unit(s) w~ll be
receiving light that has alre~dy passed through the
corresponding green recording color forming layer
unit(s). However, if a second layer order arrange-
ment is prepared which is identical to the first,
except that ~he corresponding green and red recording
color-forming layer units have been interchanged in
position, then the red recording color forming l~yer
unit(s) o the second layer order arrangement should
exhibit substantially identical values for relation-
ships B and D that the green recording color-forming
layer units of the first layer order arrangement
exhibi~ for relationships A and C, respectively.
Stated more succinc~ly, the mere choice of green
~756
-106-
spectral sensitization as opposed to red spectral
sensitization does not significantly ~nfluence the
values ob~ained by ~he ~bove quantitative compari-
sons. Therefore~ it is common practice not to dif
ferentiate green and red speeds in comparision to
blue speed, but ~o refer to green and red speeds
generically as minus blue speeds.
Reduced Hi~h~ le Scattering
The high aspect ratio tabular grain emul-
sions of ~he present invention are advant~geousbecause of their reduced high angle light scattering
as compared to nontabular and lower aspect ratio
tabular grain emulsions.
This can be quantitatively demonstrated~
Referring to Figure 2, a sample of an emulsion 1
according to the present invention is coated on ~
transparent (specularly transmisslve) support 3 at a
silver coverage of 1.08 g/m~. Although not shown,
the emulsion and support are preferably immersed ln a
liquid having a subs~antially matched refractive
index to minimize Fresnel reflections at the surfaces
of the suppor~ and the emulsion. The emulsion coat-
ing is exposed perpendicular ~o the support plane by
a collimated light source 5. Light from the source
following a path indicated by the dashed line 7,
which forms an optical axis, strikes the emulsion
coa~ing at polnt A. Light which passes through the
support and emulsion can be sensed at a constan~
distance from the emulsion ~t a hemispherical detec-
tlon surface 9. At a point B, which lies at theintersectlon of the extenslon of the initial light
path and the detection surface~ light of ~ maximum
intensity level is detected.
An arbitrarily selected point C i5 shown in
Figure 2 on the detection surface. The d~shed line
between A and C forms an &ngle ~ with the emulsion
coating. By moving point C on the de~ection surface
~7~
W107 -
it is possible to vary ~ from 0 to 90. By measur-
ing the intensity of the light sc2ttered as a func-
~ion of the angle ~ it is possible (because of the
rota~ional symmetry of light scattering about the
optical axis 7) to determine the cumulative light
distribution as a function of the angle ~. (For a
background description of the cumulative light dis-
tribution see DePalma and Gasper, "Determining the
Optical Properties of Photographic Emulsions by the
Monte Carlo Method", ~ raphic Science and
~&_n~ , Vol. 16, No. 3, May-June 1971, pp.
181-191.)
After determining the cumula~ive light dis-
tributîon as a function of ~he angle ~ at vslues
from 0 to 90 for the emulsion 1 according to the
present invention9 the same procedure is repeated,
but with a conventional emulsion of the same average
grain volume coated at the same silver coverage on
another por~ion of support 3. In comparing the
cumulative ligh~ distribution as a function of the
angle ~ for the two emuls~ons, for values of ~ up
to 70 (and in some instances up to 80 snd hlgher)
the amount of scattered light is lower with the emul-
sions according to the present invent~on. In Figure
2 the angle 9 is shown as the complement of the
angle ~. The angle of scattering is herein dis~
cussed by refer~nce ~o the angle ~. Thus, the high
aspect ratio tabular grain emulsions of this inven-
~ion exhibit less high-angle scattering. Since it is
high angle scattering of light that contributes dis-
proportions~ely to reduction in image sharpness 9 it
follows that the h~gh aspect ratio tabular grain
emuls~ons of the present invention are in each
instance capable of producing sharper images.
As herein defined the term "collection
angle" is the value of the angle ~ at which h~lf of
the light striking the detection surface lies wi~hin
, ~:
') 6 9 2
08-
an area subtended by a cone formed by rotation of
line AC about ~he polar axiæ at the angle ~ while
half of the light striking the detec~ion surfacP
strikes the detection surface within the remaining
area.
While not wishing to be bound by any par-
ticular theory to account for the reduced high angle
scattering properties of high aspect ratio tabular
grain emulsions according to the presen~ invention,
it is believed that the large flat major crystal
faces presen~ed by the high aspect ratio tabular
grains as well as the orientation of the grains in
the coating account for the improvements in sharpness
observed. Specifically, it has bePn observed that
the tabular grains present in a silver halide emul-
sion coatlng are substantially aligned with the
planar support surface on which they lie. Thus,
light directed perpendicular to the photographic ele-
ment striking the emulsion layer tends to strike the
tabular grains substantially perpendlcular to one
major crystal face. The th;nness of tabular grains
as well as their orientation when coated permits the
high aspect ratio tabular grain emulsion layers of
~his invention to be substantially thinner than con-
ventional emulsion coatings, which can also contri-
bute to sharpness. However, the emulsion layers of
this lnvention exhiblt enhanced sharpness even when
they are coated to the same thicknesses as conven-
tional emulsion layers.
In a specific preferred form of the inven-
tion th high aspec~ ratio tabular grain emulsion
layers exhibit a mlnimum average grain diameter of at
least 1.0 micron, most preferably at least 2 mi-
crons. Bo~h improved speed and sharpness are attain-
able as average grain diameters are increased. While
maximum useful average grain diameters will vary with
the graininess tha~ can be tolerated for a speciic
-109-
imaging application, the maximum average grain diame-
ters of high aspec~ ratio tabular grain emulsions
according to the pre~ent invent~on are in all
ins~ances less than 30 microns, preerably less than
S lS microns 9 and optimally no gr~a~er than 10 microns.
Although it i5 possible to ob~ain reduced
high angle scattering with single layer coatings of
high aspec~ ratio tabular grain emulsions according
to the present invention, it does not follow that
reduced high angle scattering is necessarily realized
in multicolor coatings. In certain multicolor coat-
ing formats enhanced sharpness can be achieved with
the high aspect ratio tabular grain emulsions of this
invention 9 bu~ in other multicolor coating formats
the high aspect ratio tabular grain emulsions of this
invention can actually degrade the sharpness of
underlying emulsion layers.
Referr;ng back to Layer Order Arrangement I,
it can be seen ~hat the blue recording emulsion layer
lies nearest to the exposing radiation source while
the underlying green recording emulsion layer is a
tabular emulsion according to this invention. The
green recording emulsion layer in turn overlies the
red recording emulsion layer. If the blue recording
emulsion layer contains grains having an average
diameter in the range of from 0.2 to 0.6 micron, as
is typical of many nontabular emulsions, it will
exhibit maximum scattering of light passing through
i~ to reach the green and red recording emulslon
layers. Unfortunately, if light has alreAdy been
scattered before it reaches the high aspect ratio
tabular grain emulsion forming the green recording
emulsion layer, the tabular grains can scatter the
llght passing through to the red recording emulsion
layer to an even greater degree than a conventlonal
emulsion. Thus, this particular choice of emul~ions
and layer arrangement resultæ in the sharpnes6 of the
9 2
-110-
red recording emulsion layer being ignificantly
degraded to an extent greater than would be the case
if no emulsions according ~o this invention were
presen~ ln the layer order arrangement.
In order ~o re~lize fully the sharpne6s
advantages of the present inventlon in an emulsion
layer that underlies a high aspect ratio tabular
grain emulsion layer according to the present inven-
~ion it is preferred that the thP tabular grain emul-
sion layer be positioned to receive light that is
free of significRnt scattering (that is, positioned
to receive substantially specularly transmitted
light). Stated ano~her way9 in the photographic
elemen~s of this invention improvements in sharpness
5 iLI emulsion layers underlying tabul~r grain emulsion
layers are best realized only when the tabular gr~in
emulsion layer does not itself underlie a turbid
layer. For example, if ~ high aspect ratio tabular
grain green recording emulsion layer overlies a red
recording emulsion layer and underlies a Lippmann
emulsion layer and/or a high aspect ratio tabular
grain blue recording emulsion l~yer according to this
invention, the sharpness of the red recording emul-
sion layer will be improved by the presence of the
overlying tabular grain emulsion layer or layers.
Stated in quantitative terms, if the collection angle
of the layer or layers overlying the high aspect
ratio t~bul~r grain green recording emulsion layer is
less than ~bout 10, an improvement in the sharpness
of the red recording emulsion layer can be realized.
It is~ of course, immaterial whether the red record-
ing emulsion layer is itself a high aspect ratio
t~bular grain emulsion layer according to th{s
inven~ion insof~r as the effect of the overlylng
layers on its sharpness is concerned.
In a multicolor photogrRphic element con-
taining superimposed color-forming units it is pre-
9 2
ferred ~hat at least the emulsion lsyer lying nearestthe source of exposing radiation be a high aspect
ratio tabular grain eml~lsion in order ~o obtain the
advantages of sharpness offerred by this inventlon.
In a specifically preferred form of the lnvention
each emulslon layer which lies nearPr the exposing
radiation source than another image recording emul-
sion layer is a high aspect ratio tabular grain emul-
sion layerr Layer Order Arrangements II, III, IV, Vs
VI, and VII, described above, are illustrative of
multicolor photographic element layer arrangements
according to the inventlon which are capable of
impar~ing significant increases in sharpneæs to
underlying emulsion layers.
Although the advantageous contribution of
high aspect ratio tabular grain emulsions to image
sharpness in multicolor photographic elements has
been specifically described by reference to multi-
color photographic elements, sharpness advantages can
also be realized in multilayer black-and-white photo
graphic elements intended to produce silver images.
It is conventional practice to divide emulsions form-
ing black~and-whi~e images into faster and slower
layers. By employing nigh aspect ratio tabular grain
emulsions according to this invention in layers near-
est the exposing radiation souroe the sharpness of
underlying emulsion layers will be improved.
Dye Ima~e Transfer
I~ is possible to construct a dye image
transfer film unit according to the presen~ invention
capable of producing a monochromatic transferred dye
image by locating on a support a single dye-providing
layer unit comprised of a tabular silver halide emul-
sion layer as described above and at least one dye-
image-providing material in the ~mulsion layer itself
or in an adjacent layer of ~he layer unit. In addi-
tion, the dye image transfer film unit is comprised
6~2
-112-
of a dye receiving layer capable of mordanting or
otherwise immobilizing dye migrating to it. To pro-
duce a transferred dye image ~he tabular grain emul-
sion is imagewise exposed and contacted wlth an
alkaline processing composi~ion with ~he dye receiv-
ing and emulsion layers jux~aposed. In a particular
ly advantageous application for monochromatic trans-
ferred dye images a combination of dye-image-provid-
ing materials is employed to provide a neutral trans-
ferred dye image. ~onochromatic transferred dyeimages of any hue can be produced~ if desired~
Multicolor dye image transfer film units of
this invention employ three dye-providing layer
units: (1) a cyan-dye-providing layer unit comprised
of a red-sensitive silver halide emulsion having
associated therewith a cyan-dye-image-providing
material, (2) a magen~a-dy~-providing layer unit com-
prised of a green-sensitive si]ver halide emulsion
having associated therewith a magenta-dye-image-pro-
viding material, and (3) a yellow-dye-providing layer
unit comprised of a blue-sensitive silver halide
emulsion having associated therewith a yellow-dye-
image-providing material. Each oiE the dye-providing
layer uni~s can contain one, two, three~ or more
separate silver halide emulsion layers as well as the
dye image-providing materi~l, locatPd in ~he emulsion
layers or in one or more separate layers forming part
of the dye-providing layer unit. Any one or combina-
tion o the emulsion layers can be hi&h aspect rAtio
tabular grain silver halide emulsion layers as des-
cribed above. In a preferred form of the invention
at least the fastes~ emulsion layers in the cyan nd
magenta-dye-providing layer units are hlgh aspect
ratio tabular grain silver halide emulsions as des-
cribed above. At least the fas~est emulsion layer inthe yellow-dye-lmage-providing layer unit is also
preferably comprised of a high aspect rOEtio tabular
56~'~
113-
~rain silver halide emulsion as described above, but
the use of other, conventional silver halide emul-
sions in the yellow-dye-providing layer unit together
with high aspect ratio tabular grain silver halide
S emulsions in the cyan and m~genta-dye-providing layer
units is also specifically contemplated.
Depending upon the dye~image-providing
material employed, it can be incorporated in the 6il-
ver halide emulsion layer or in a separate layer
associated with the emulsion layer. The dye-image-
providing material can be any of a number known in
the art, Such as dye-forming couplers, dye devel-
opers, and redox dye-releasers, and the particular
one employed will depend on the nature of the element
or film unit and the type of imsge desired. Materi-
als useful in diffusion transfer film units contain a
dye moiety and a monitoring moiety. The monitoring
moiety, in the presence of the alkaline processing
composition and as a function of silver halide devel-
opment, is responsible for a change i~ mobility ofthe dye moiety. These dye-image-providing materi~ls
can ~e initially mobile and rendered immobile as a
function of silver halide development, as described
in ~ogers U.S. Patent 2,983,606. Alternatively, they
can be initially immobile and rendered mobile, in the
presence of an alkaline processing composltion, as a
function of silver halide development. This latter
class of materials include redox dye-releasing com-
pounds. In such compounds, the monitoring group is a
carrier from which the dye is released as a direct
function of silver halide development or as an
inverse function of silver halide dev~lopment. Com-
pounds which release dye as a direct func~ion of
silver halide development are referred ~o as nega-
tive-working release compounds, while compounds which
release dye as an lnverse function of silver halide
development are referred to as positive-working
~,r3692
4-
release compounds. Since the internal laten~ image
forming emulsions of this invention develop in unex-
posed areas in the presence of a nucleating agen~ and
a surface developer, positive transferred dye lmages
are produced using negative-working release com-
pounds 9 and the latter Mre therefore preferred for
use in ~he practice of this invention.
A preferred class of negative-working
release compounds are the ortho or para sulfonamido-
phenols and naphthols described in Fleckenstein U.S.Pat~nt 4,054,312, Koyama et al U.S. Patent 4,055~428,
and Fleckenstein et al U.S. Patent 4,0769529. In
these compounds the dye moiety is attached to a sul-
fo~amido ~roup which is ortho or para to the phenolic
hydroxy ~roup and is released by hydrolysis af~er
oxidation oE the sulfonamido compound during develop-
ment.
Another preferred class of negative-working
release compounds are ball~sted dye-forming (chromo-
genic) or nondye-forming (nonchromogenic) couplers
having a mobile dye attached to a coupling-off site.
Upon coupling with an oxidized color developing
agent, such as a ~ara-phenylenediamine, the mobile
dye is displaced so that it can transfer to a
receiver. The use of such negative-working dye image
providing compounds is illustrated by Whltmore et al
U.S. Patent 3,227,550, Whitmore U.S. Patent
3,227,5523 and Fujiwhara et al U.K. Pa~en~ 1,445,797.
Since the silver halide emulsions employed
in the image transfer film units of the present
invention are positive-work~ng, the use of posi~ive
working release compounds will produce negative
transferred dye images. Useful positive-working
release compounds are nitrobenzene and quinone com-
pounds described in Chasman e~ al U.S. Patent4,139,379, the hydroquinones described in Fields et
al U.S. Patent 3,9B0,479 and the benzisoxazolone com-
" ~l7~692
-115-
pounds described in Hinshaw e~ al U.S. Pa~ent
4,199,354.
Further details regarding ~he above release
compounds, ~he manner in which they function, and the
procedures by which they can be prepared are con-
tained in the patents reerred to above~ the disclo-
sures of which are incorporated herein by reference.
Any material can be employed as the dye
receiving layer in the film units of ~his invention
as long as i~ will mordant or otherwise immobilize
the dye which diffuses to it. The optimum material
chosen will, of course, depend upon the specific dye
or dyes to be mordanted. The dye receiving layer can
also contain ultraviolet absorbers to protect the dye
image from fading due to ultraviolet light, brighten-
ers, and similar materials to protect or enhance the
dye ima~e. A polyvalent metal, preferably immobi-
lized by association with a polymer, can be placed in
or ad~acent in the receiving layer to chelate the
2Q ~ransferred image dye, as taught by Archie et al U.S.
Patent 4,239,849 and Myers et al U.S. Patent
4,241,163. Useful dye receiving layers and materials
for their fabrication are disclosed in _search Dis-
closure, Vol, 151, November 1976, Item 15162, and
~organ et al U.S. Patent 4,258,117.
The alkaline processing compositlon ~mployed
in the dye image transfer film units can be an
aqueous solution of an alkaline material 9 such as an
alkali metal hydroxide or carbonate (e.g., sodium
hydroxide or sodium carbonate) or an amine (e.g.,
diethylamine). Preferably the alkaline composition
has a pH in excess of 11. Suitable materials for use
in such compoæitions are disclosed in esearch Dis-
closure, I~em 15162, c1ted above.
A developing agent is preferably contained
ln the alkaline processing composition, although it
can be contained in a separate solution or process
1 ~L75~9
6 -
sheet, or it can be incorporated in any processing
composition penetrable layer of the film unit. When
the developing agent is separate from the alkaline
processing composition, the alkaline composition
serves to activate the developing agent and provide a
medium in which the developing agent can contact and
develop silver halide.
A variety of silver halide developing agents
can be used in processing the film units of this
invention. The choice of an optimum developlng agent
will depend on the type or film unit with which it is
used and the particular dye image-providing material
employed. Suitable developing agents can be selected
from such co~pounds as hydroquinone, aminophenols
(e.g., N-methylaminophenol), l-phenyl-3-pyrazolidin-
one, l-phenyl-4,4-dimethyl-3-pyrazolidinone,
l-phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidinone,
and N,N,N',N~-tetramethyl-~-phenylenediamine. The
nonchromogenic developers in this list are preferred
for use in dye transfer film units, since they have a
reduced propensity to s~ain dye image-receiving
layersO
The image transfer film units exh~bit
advantages similar to those observed by Jones and
Hill, cited above$ (as well as additional, unexpected
advantages illustrated in connection with the
examples).
One of these advantages is the rapidity with
which the transferred image becomes viewable. The
rapid accessibility of the viewable transferred image
i8 directly attributable to the presence of one or
more high aspect ratio tabular ~rain silver halide
emulsions according to the present inYention.
Without being bound by any particular theory 9 it is
believed ~hat the geome~rical configuration of the
tabular silver halide grains accounts for rapid
access to the transferred images. Tabular grain
3 ~7s~sæ
-117-
geometry provides a very high surface ~rea to the
silver halide grains as compared to their volume, and
this in turn is believed to influence their rate of
dPvelopment. In imege transfer processes it is the
imagewise variation in development of the silver
halide grains as a func~ion of their imagewise
exposure which modulates the transferred image. In
some systems, such as those employing negative-work-
ing release compounds, described above, silver halide
development is directly related to transferred
imaging materials. The faster the silver halide
develops, the faster the imaging materials are made
available for viewing.
The use of tabular grains ~o reduce the time
elapsed betwe~n the commencement oE processing and
obtaining a viewable transferred image--i.e., access
time--in no way precludes the use of conventional
image transfer film unit features which are known to
reduce access time. When the present invention is
employed in combination with conventional features
for reducing access time at least additive results
can be normally expected. In addition, ~here are
still other features unique to the image transfer
film units of this inventlon which can contribute to
reduced access time. These additional features are
discussed below.
A second advantage attainable with the image
transfer film units of the present invention is the
reduced variance of ~he transferred image as a
func~ion of temperature~ This reduced variance in
the transferred image is a direct result of employing
one or more tabular silver halide emulsion layers, as
described above. Without being bound by any particu-
lar theory, it is believed th~t the tabular silver
halide grains show less varlation in their develop-
ment rste6 as a function of temperature. In image
transfer systems in which silver halide development
~17~69
-118-
is direc~ly related ~o transferred imaging ma~erials
this reduced temperature dependence of tabular silver
halide grains results directly in reduced variance in
the viewed image. In sys~ems relying also upon
compe~ing mechanisms for gener~lon of the viewable
image, reduced silver halide development variance as
a function of temperature can reduce variance in the
transferred image Lo the extent it is attributable to
silver halide development variance and to the extent
it complements temperature variances in the competing
mechanisms employed in imaging.
It has be n surprisingly observed that the
dye image transfer film units of the present inven-
tion exhibit substantially higher photographic speeds
at lower silver coverages than comparable conven-
tional dye image transfer film units. It is well
known to those skilled in the art that silver cover-
ages below a threshold level result in reduction of
observed photographic speed as determined from a
transferred dye image. While speed decreases when
the silver coverages of silver h~lLde emulsions are
reduced, the speed reduction is much more gradual
when high aspect ratio tabular grain emulsions are
employed, thereby allowing lower silver coverages.
Acceptable photographic speeds in conven-
tional multicolor image transfer fLlm units are com-
monly obtained by employing silver halide in each of
the yellow, magenta, and cyan-dye-providing layer
units at silver coverages of about 1000 mg/m2 or
higher. It iB specifically contemplated to employ
substantially lower silver coverages in the practice
of this invention. When the silver halide emulsion
in the yellow, magenta, or cyan-dye-providing layer
unit of the dye image transfer film unit of this
lnvention is tabular as described above, it can be
efficiently employed at silver coverages of from
about 150 to 750 mg/m2, preferably from about 200
~ 7~6~2
-119
to 700 mg/m2, and optimally from about 300 to 650
mg/m2. At higher and lower silver coverages higher
and lower photographic speeds, respec~ively, will be
realized, the stated ranges reflecting an efficien~
balance of photographic performance and 8ilv r cover-
ages for most imaging applications. When the image
transf~r film unit eontains a single dye-providing
layer unit eontaining ~abular silver halide grains~
then these coverages are applicable ~o that of a
single dye-providing ,layer unit. When all three
dye-providing layer units contain tabular silver
halide emulsions, at least additive silver savin~s
can be realized.
The image transfer ilm units of this inven-
tion can employ any layer order arrangement hereto
fore known to be useful in conventional image trans-
fer film units having one or more radiation-sensitive
silver halide emulsion layers. In addition, the
distinctive properties of tabular silver halide emul-
sions make possible highly advantageous layer order
arrangements not heretofore known to the art~ The
following specific layer order arrangements are
merely illustrative, many other arrangements being
additionally contempla~ed:
To avoid unnecessary repetition, discussion
of each successive layer order arrangement is direct-
ed to features which are distinctive as compared to
prior layer order arrangements. Stated another way,
features and advantages shared by the layer order
arrangements are fully di6cussed only in connection
with the fir~t layer order arrangement in which they
appear. If a fea~ure or advantage is not shared by a
subsequently described layer order arrangement, this
is specifically pointed out.
~ 6~v~2
-120-
_age Transfer Film Unit I
A haminate and Peel-Apart Dye Image Transfer Film Unit
_ . . . .. .
Re~
D~e Receivin~ Layer
_
Imagewise Exposure
Tabular Silver Halide Emulsion Layer
~ rlal
Support
Image Transfer Film Unit I is illustrative
of a conventional laminate and peel-apsr~ image
transfer fllm unit~ Upon imagewise exposure, the
positive-working tabular silver halide emulslon layer
produces a developable la~ent image at centers
located on the interior of exposed grains. The dye
receiving layer is laminated and an alkaline
processing composition, no~ shown, iB released
between the dye receiving layer and emulsion layer
following exposure. Upon contact with the alkaline
processing composition development of the tabular
silver halide grains bearing internal latent image
centers occurs much more slowly than the development
of silver halide ~rains which do not contain internal
latent image cen~ers. Using a negative-working
dye-ima~e-providing material dye is released in those
areas in which silver development occurs and migrates
to the dye receiving layer where it is held in place
by a mordant. A positive transferred dye image is
produced in the dye receiving layer. Processing is
terminated by peeling ~he reflective support having
the dye receiving layer coated thereon from the
remainder of the image transfer ilm unit.
While the layer order arrangement is conven~
tional and employs conventional materials other than
the tabular silver halide emulsion layer, signifi
cantly superior results are obtainable. The access
-121
time required to produce a viewable dye image in the
receiving layer is substantially reduced. It is
believed that this can be attributed to dis~inct
advantages offered by in~ernal latent image-forming
tabular silver halide grains. Internal latent
image-forming tabular silver halide grains according
to ~his invention develop at a faster rate than
comparable nontabular internal latent image~forming
silver halide grains.
Although development can entirely account
for ~he more rapid image access in Image Transfer
Film Unit I~ another characteristic of tabular grain
emulsions can also be used to further raduce image
access times. While high aspect ratio tabular grain
emulsion layers can be coated in the same layer
thicknesses as conventional emulsions without depart-
ing from the teachings of this invention, it is pre-
ferred to thin the high aspect ratio tabular grain
silver halide emulsion layers as compared to corres-
ponding conventional silver halide emulsion layers.In conventional silver halide emulsions employed in
image transfer the emulsion layer thickness is sub-
stantially greater than the average grain diame~er
calcula~ed from the grain projected areas. Further,
the ~hickness of the layer is large enough to accom-
modate not ~ust the average grains, but the largest
grains present. Thus~ if the largest nontabular
silver halide grains in a silver halide emulsion
layer of an image transfer film unit exhibit an
average diameter of from 1 to 2 microns, the emulsion
layer will be at least 1 ~o 2 microns in thickness
and will usually be substantially greater in thick-
ness. On the other hand, it 16 possible to employ
tabular silver halide grains accordlng to the present
invention having diameters based on average projected
areas of 1 to 2 microns and often s~ill larger while
the thickness of the tabular grains is less ~han 0.5
.,:
-122-
or even 0.3 micron. Thus, in an exemplary emulsion
in which the tabular grains have an average thickness
of 0.1 micron with an average diameter of l to 2
microns, the silver halide emulsion layer thickness
can easily be reduced substantially below 1 micron.
The high aspect ratio tabular graln emulslon layers
of ~his invention are preferably less than 4 times
the average thickness of the tabular grains and are
optimally less than tw~ce the average thickn~ss of
the tabular grains. Significant reductions in the
thickness of the high aspect ratio tabular grain
silver halide emulsion layers of the invention can
con~ribute to reduction in image access times by
reducing ~he lengths of diffusion paths. Further,
reduction of the lengths of diffusion paths can also
contribute to improv~ments in sharpness.
Image Transfer Film Unit II
An Integral Monochromatic Dye Image Transfer Film Unit
Yiew
Transparent Support
Dye Receiving Layer
_Reflective Laye~ _
__ O~a~ue Layer _ _
Tabular Silver Halide Emulslon Layer
Wi~h Dye-Ima~e Providing Material
Alkaline Processing Composl-
_tion + Opacifier
Timing Layer
Neutrallbl~ 5
Transparent Support
Imagewise Exposure
Initially the alkaline processing composi-
tion containing opacifier is not present in the loca-
tion shown. Therefore, upon imagewise exposure light
~ ~7~6~
-123-
strikes the tabular silver halide emulsion layer.
This produces a latent image eorresponding to light-
struck areas of the emulsion layer. To initiate pro-
cessing the alkaline processing composition ls placed
in the position shown. Usually, bu~ not necessarily,
~he image transfPr film unit is removed from the
camera in which it is expo ed i~mediately followin~
placement of the alkaline processing composition and
opacifier. The opacifier and opaque layer together
pr~vent further exposure of the emulsion layer. Upon
development, a mobile dye or dye precursor is releaso
ed from the emulsion layer. The mobile dye or dye
precursor penetrates the opaque layer and the reflec-
tive layer and is mordanted or otherwise im~obilized
ln the dye receiving layer to permit viewing through
the uppermost transparent support. Processing is
terminated by the timing and neutralizing layers.
, .
~ 17~69'2
-124-
I ~
An Integral Multicolor Dye Image Transfer Film Unit
Imagewise Exposure
.
Timin~ Layer
_.___ _
Alkaline Processlng Compssi-
_ Trans~a~7b~E~2~Dr~6~
Blue-sensitive Tabular Silver
Ha I i~e ~ n La vur
Y low Dye ~
15Interlayer With Scaven~er _ _
Green-sensitive Tabular Silver
Halide Emulsion Layer
~enta Dye-Ima~e-Provid ~ ~aterial Layer
~ e~l!L__---------venger
20Red-sensitive Tabular Silver
_ _clld- r~ulsion Layer
Cyan Dye-Ima e-Providin& Material Layer
Op~que Layer
Reflective L ~er
~ ~ yer
3~o:e __, ~_upport
View
Image Transfer Film Unit III is essentially
slmilar to Image Transfer Film Unit II, but is modi-
fied to contain three separate dye-providing lay0r
units, each comprised of one high aspPct ra~io tab-
ular grain silver halide emulsion layer and one
dye-image providing material layer, instead of the
single dye-image^providing material containing high
aspect ratio tabular grain silver halide emulsion
layer of Im~ge Transfer Film Uni~ II. (Whether or
1 ~5
- 1 z 5 -
not the dye-image-providing material is placed in the
emulsion layer itself or in an adjacent layer in
Image Transfer Film Units II And III is a matter of
choice, either arrangement being feaslble.)
To prevent color contamination of adjacent
dye-providing layer unit6, an interlayer containing a
scavenger is positioned be~ween dye-providing layer
units. The use of scavengers in interlayers and/or
in the dye~providlng layer units themselves is con-
templa~ed. In some instances reductions in minimum
edge densities ean also be realized by incorporating
a negative-working silver halide emulsion in the
interlayers.
In a modification of Image Transfer Film
Unit III it is possible to eliminate the inter-
layers. Since the high aspect ratio tabular grain
silver halide emulsion layers can be qui~e thin in
comparison to conventional silver halide emulsion
layers typically employed in multicolor dye image
transfer film units, each high aspect ratio tabular
grain silver halide emulsion layer can be coated
be~ween two magenta dye-image-providing material
layers. The two magenta-dye-image providing material
layers preferably do not contain scavenger, but can
contain scavenger, if desired, depending upon the
sensitivity of the imaging application to color con-
tamination and the specific choice of dye-image-pro-
viding materials. Providing dye-image-providing
layers adjacent bo~h sides of each high aspect ratio
tabular grain silver halide emulsion layer provides a
close association between the dye-image-providing
materials and the silver halide. This arrangement is
most advantageous where the dye-image-providing
materials of each dye-providing layer unit is ini-
tially colorless or at leas~ shifted in hue so thatthe dye-lmage-providing material is not adsorbing in
the spectr~l region to which the silver halide is
intended to respond.
-126-
Where the yellow dye-image-providing
material is initially yellow9 it scts, together wlth
the blue-sensitive high aspect ratio tabular grain
silver halide emulsion layer, to intercept blue light
that would otherwise reach the 8reen and red sensi-
tive high aspect ra~io tabular grain silver halide
emulsion layers. Where the green and red-sensitive
silver halide emulsion layers employ silver bromide
or silver bromoiodide grains in a con~entional multi-
color dye image transfer film unit, it is necessaryto intercept blue light to avoid color contamination
of the green and red-sensitive emulsion layers. How-
ever, where the green and red-sensitive emulsions are
high aspect ratio tabular grain internal latent
image-forming emulsions according to this invention
as specifically described above, it is unnecessary to
filter blue light so that it is a~tenuated before
reaching these emulsion layers. Thus, where the
yellow dye-image-providing material is initially
colorless or at least nonabsorbing in the blue region
of the spectrum, it is still possible for accurate
color reproduction to occur in the magenta and cyan
dye-providing layer units without any necessity of
interposing a yellow filter layer. Further, as is
more fully described below, the dye-providing color-
forming layer units can be located in any desired
Grder .
9 ~
-~27
Image Transfer Film Unit IV
An Integral Multicolor Dye Image Transfer Film Unit
_ Opaque Su~port
Blue sensitive Tabular Silver
_Halide Emulsion Lay r
~ = =~_
Red-sensitive Tabular Silver
Ma~enta Dy
Green-sensitive Tabular Silver
T ansparent Overcoat
Alkaline Processing Composition With
Reflective Material and Indicator Dye
_Dye Receiving Layer
Timing Layer
er _ _
Trans~aren~ Support
View and Imagewise Exposure
In Image Transfer Film Unit IV during i~age-
wise exposure the alkaline processing composition
containing the reflect~ve materi~l and indicator dye
is not ln the position shown, but is released to the
posi~ion shown after exposure to permit processing.
The indicator dye exhibits a high density at the
elevated levels of pH under which processing occurs~
It thereby protects the silver halide emulsion layers
from further exposure i the film unit is removed
from a camera during process~ng. Once the neutraliz-
ing layer reduces the pH within the film unit toterminate processing 3 the indicator dye reverts to an
essentially colorless form. The alkaline processing
~ 9
-128-
composition also contains an opaque re1ective
material, which provides a white background for view-
ing the transferred dye image after processing and
prevents additional exposure.
Image Transfer Film Unit IV is illustrative
of the Application of the invention to an in~egral
multicolor dye image transfer film unit format in
which imagewise exposure and viewing occur through
the same support. Image Trhnsfer Film Unit IV dif-
fers from the prior teachings of the art not only ln
the use of high aspect ratio tabular grain silver
halide emulsions, but also in the order in which the
dye-proYiding layer units are arranged. The green-
sensitive high aspect ratio tabular grain silver
halide emulsion layer is nearest to the exposing
radia~ion source wh~le the blue-sensitlve high OEspect
ratio tabular grain silver halide emulsion layer is
farthest removed. This arrangement is possible with-
out color con~amination because of the relatively
large separa~ions in blue and minus blue response
attainable with minus blue speotrally sensitized high
aspec~ ratio tabular grain silver halide emulsions.
By placing the magenta-dye-providing layer unit
nearest the source of exposing radiation and nearest
~5 the dye receiving layer, the sharpness of the magenta
dye image is improved and lts access time is
reduced. The magenta dye image is, of course, the
visually most important component of the multicolor
dye image. The cyan image is the visually second
most important 9 and its location is also nearer the
exposing radiation source and the dye receiving layer
than in a corresponding conventional dye image trans-
fer film unit. Thus, significant advantages in terms
of reduced image ~ccess time and increased image
sharpness are attainable wi~h Im~ge Transfer Film
Uni~ IV in addition to those improvements attribut-
able to high aspect ratio tabular grain silver halide
` ~7St~
-1 29 -
grains previously discussed above in connec~ion with
other layer order arrangements. While Image Transfer
Film Unit IV is useful with all high aspect ratio
tabular grain silver halides, it is particularly
advantageous with high aspect ratio tabular grain
silver bromide or bromoiodide.
Although the invention has been par~icularly
described with reference tv certain preferred layer
order arrangements, it is appreciated that the high
aspect rati~ tabular grain silver hallde emulsions
need not always be present as planar, uninterrupted
layers. Rather than being continuous, the layers can
be subdivided into discrete laterally displaced
portions or segments. In multicolor image transfer
film units the layers need not be superimposed, but
can be present in the form o interlaid layer seg-
ments. It is specifically contemplated to employ
high aspect ratio tabular grain silver halide emul-
sions as herein disclosed in microcellular image
transfer film unit arrangements, such as disclosed by
Whitmore Patent Cooperation Treaty published applica-
tion W080/01614, published August 7, 1980. The
present invention is also fully applicable to micro-
cellular image transfer film units containing micro-
cells which are improvements on Whitmore, such asGilmour Can. Ser.No. 385,171, filed September 3,
1981, titled AN IMPROVEMENT IN THE FABRICATION OF
ARRAYS CONTAI~ING INTERLAID PATTERNS OF MICROC~LLS;
Blazey et al U~S. Patent 4,307,165; and Gilmour et al
Can. Ser.No. 385,363, filed September 8, 1981, titled
ELEMENTS CONTAINING ORDERED WALL ARRAYS AND PROCESS
FOR THEIR FABRICATION.
Although all of the advantages attributable
to high aspect ratio tabular grain silver halide
emulsions can be realized in microcellular image
transfer film units, the large minus blue and blue
speed sepqra~ions obtainable with spectrally sensi~
1 1751~2
30 -
tized high aspect ra~io tabular grain silver halide
emulsions, mos~ notably silver bromide and bromo-
iodide emulsions, are particularly advantageous in
microrellular image transfer film units intended to
produce multicolor images. Sinee the microcell
triads intended to respond to blue~ green, and red
light are poæitioned to receive the same incident
light, yellow fil~ers are usually in~erposed when
using conventional silver bromide and bromoiodlde
emulsions to improve minus blue and blue speed
separation. This can involve an additional coating
or cell filling step and reduce photographic speed.
The high aspec~ ratio tabular grain silver halide
emulsions of this invention can be employed in multi-
color micro~ellular image transfer film units withoutthe use of yellow filters, thereby significantly
simplifying construc~ion and improving performance.
_a~
The invention cen be better appreciated by
referenc~ to the following illustrative examples. In
each of the emulsion preparations the contents of the
reaction vessel were vigorously stirred during silver
salt addition; the term "percent" means percent by
weigh~, unless otherwise indicated; and the tem "M"
stands for molar concentrations, unless otherwise
indicated. All solutions, unless otherwi~e indi-
cated 3 are aqueous solutions.
_ulsio~ _on
The emulæions used in this invent~on were
prepared as follows:
Emulsion A Core Tabular AgBrI Emulsion
A AgI seed grain emulsion was prepared by a
double-jet precipitat~on technique at pI 2.85 and
35C. To prepare 0.125 moleæ of emulsion 5.0M silver
ni~r~te and 5.OM ~odium iodide solutions were added
over a period of 3.5 minutes to a reaction vessel
containing 60 grams of deionized bone gelatin
~ 92
-131-
dissolved in 2.5 li~ers of water. The resulting
silver iodide emulsion had a mean grain diameter of
0.027 ~m and the crystals were of hexagonal
bipyramidal structure.
Then 1.75 moles of silver bromide was preci-
pita~ed onto 2.4 x lO 3 mole of the Rilver iodide
seed grains by a double-jet technique. 4.0M silver
nitrate and 4.OM sodium bromide reagents were added
over a 15 minutes period at 80C using accelerated
flow (6.0X from start to finish). The pBr was main-
tained a~ 1.3 during the first 5 minutes, sdjusted to
a pBr of 2~2 over the next 3 minu~es, and main~ained
at 2.2 for the remainder of the precipitation.
The resulting tabular AgBrI crystals had a
mean grain diameter of l.O ~m, an a~erage thickness
of 0.08 ~m 9 and an average aspect ratio of 12.5:1
and account for greater than 90 percent of the total
projected area of the silver halicle grains.
Emulsion A was then chemically sensitized
with 1.9 mg/Ag mole sodium thiosulfate pentahydrate
and 2.9 mg/Ag mole potassium tetrachloroaurate for 30
minutes at 80C.
Emulsion B Core/Shell Tabular AgBrI Emulsion
The chemically sensitizecl Emulsion A (0.22
mole) was placed in a reaction vessel at pBr 1.7 at
80C. Then onto Emulsion A, 5.78 moles of silver
bromide were precipitated by ~ double-~et addition
technique. 4.~M silver nitrate and 4.0M sodium
bromide solutions were added in an accelerated flow
(4.0X from start to finish) over a period of 46.5
minutes whlle maintaining a pBr of 1.7. The result-
ing AgBrI crystals had a mean grain dlameter of 3.0
~m, an average thickness of 0.25 ~m, and average
aspect ratio of 12:1.
Emulsion B was chemically sensitized wi~h
1.0 mg/Ag mole sodlum thiosulfate pen~ahydrate for 40
minutes at 74C and red spectrally sensitized with
-132-
250 mg/Ag mole anhydro-5,5'-dichloro-9-ethyl~393'-
bis(3-~ulfobutyl)~hiacarbocyanine hydroxide.
Emulsion C Cadmium Doped Tabular AgBrI Internal
La~ent Image-Forming Emulsion
Emulsion C was prepared the same as Emulsion
B with the excep~ion that a~ 8 minutes into the
shelling stage of the core/shell precipitation
cadmium bromide was addPd at 0.05 mole percent (based
on the moles of sllver in the shell).
Emulsion D Control Emulsion
A 1.8 ~m monodispersed internal image
octahedral AgBr emulsion similar to that described in
Example 7 of Evans U.S. Patent 3,~23,513, was used as
a control for the above emulsion. The 1.25 ~m core
emulsion was chemically ~ensitized with 0.4 mg/Ag
mole sodium thiosulfate pentahydrate and 0.6 mgtAg
mole potassium tetrachloroaurate. The shelled emul-
sion was chemically sensitized wi~h 0.35 mg/Ag mole
sodium thiosulfate pentahydrate. The control emul-
sion was then sensitized wi~h 100 mg/Ag mole anhy-
dro-5,5'-di-chloro-9~ethyl-3,3'-bis(3-sulfobutyl)-
thiacarbocyanine hydroxide.
Emulsion E Tabular Graln AgBrI Internal Latent
Imag~-Forming Emulsion
A core emulsion was prepared similar to
Emulsion A above. The emulsion was chemically sensi-
tized with 2.5 mg/Ag mole ~odium thiosulfste penta
hydrate and 3.75 mg/Ag mole potasslum tetrachloro-
aurate for 10 minutes at 80C. Then 0.067 mole of
~he chemical~y sensitized emulsion wa6 further preci-
pltated with silver bromide by a double-jet addition
technique. 5.0 Molar AgN0 3 and 5.0 Molar NaBr
reagents were each added for 16.6 minutes at pBr 2.4
at 80C, precipitating an additional 0.133 mole of
silver bromide. The resultant tabular AgBrI (<0.10
mole percent I) crystals had a mean grain diameter of
1.5 ~m, an average thickness of 0.14 ~m, and an
~7569
-133-
average aspect ratio of 10.7:1, and account for
greater than 85 percent of the total pro~ected sur-
face area of the silver halide gralns~
Emulsion F Tabular Grain AgBrI In~ernal La~n~
Image-Forming Emulsion
A core emulsion was prepared and chemic~lly
sensitized as described for Emulsion E above.
Following chemical sensitization 0.067 mole of the
core emulsion was shelled with addltional silver
bromoiodide in the following manner: 5.0 Molar
silver and halide salt reagents were added at a
constant flow rate for ll.l minutes at pBr 2.4 at
80C. The halide salts conRisted of 90 mole percent
bromide and 10 mole percent iodide. A total of 0.045
mole of additional AgBrI was added. A second ~hell
was then precipitated identical to the first with the
exception that the halide salts consisted of 80 mole
percen~ bromide and 20 mole percent iodide. Similar-
ly a third shell was precipitated over the second
with the exception that the halide salts consisted of
70 mole percent bromide and 30 mole percent iodide.
The resultant tabular AgBrI (13.3 mole percent I)
crystals had a mean grain diameter of 1.5 ~m, an
average thickness of 0.14 ~m, and an average aspect
ratio of 10~7:1, and account for greater than 85 per-
cent of the total proJected area of the silver halide
grains.
Example lA
This example shows that a red-sensitized
~abular grain internal latent image-forming emulsion,
Emulsion B, provides an advantage in developability
over an extended temperature range compared to a
red-sensitized internal laten~ image-forming octa-
hedral grain emulsion, Emulsion D, as used in a
multicolor image transfer latent element us1ng
sulfonamidonaphthol redox dye-release (RDR) chPmistry.
~ 2
-134-
An integral imaging receiver (IIR~ of the
following layer order arrangement was prepar~d:
Coverages are in (g/m2~ or ~mg/Ag mole3. Chemlcal
structures are shown in the Appendix below. ~ : Overcoa~ layer: Scavenger VIII (0.11),
gelatin (0.89), Bis(~inylsulfonylmethyl)
ether hardener at l percent of the total
gelatin weight
Layer 15: Blue-sen~itive silver halide layer: The
emulsion is similar to the octahedral
grain control Fmulsion D except that it is
blue-sensitized. Silver halide (1.34 Ag),
nucleating agent V [13.0], nucleating
agent VI [0.41], scavenger VII t4000],
gelatin (1.34)
Interlayer: Titanium dioxide (0.27),
gelatin (0.65)
Layer 13: Yellow dye-releaser layer: RDR I (0.65),
gela~in (0.86)
La~er 12: Interlayer: Negative silver bromide emul-
sion (0.11 Ag), scavenger VIII (1.1),
gelatin (1.3)
Layer 11: Green-sensitive silver halide layer: The
emulsion is similar to the octahedral
grain con~rol ~mulsion D except that it is
green-sensitized. Silver h~lide (1.34
Ag), nucleating agen~ V [17.0J, nucleating
agent VI [0.87], scavenger VII ~4000],
gelatln (1.34)
~y_r 10: Interlayer: Ti~anium dioxide (0.32),
gelatin (0.65)
Layer 9- Magenta dye-releaser layer: RDR II
(0.43), gelatin (0.86)
~ Interlayer: Negative silver bromide emul-
~ion (0.05 Ag~, scavenger VIII (1.1),
gelatin (1.2)
-135-
La~er 7: Red-sensitive silver halide layer: Emul-
sion B (1.34 Ag)~ nucleatlng agent V
~2.0], scavenger VII ~4000], gelatin (1.34
~ Gel (0.43) interlayer ~y~ Interlayer: Titanium dioxide (0.81~,
gelatin (0.65)
Cyan dye-releaser layer: RDR III (0.43
gelatin (0.65)
Layer 3: Opaque layer: Carbon (1.9)9 KDR IV
(0.02), scavenger VII (0.03), gelatin (1.2)
r 2: Reflecting l~yer: Titanium dioxide
(22.0), gelatin (3~4)
Layer 1: ~eceiving layer: Mordant IX (4~8~ 9 gela-
tin (2 . 3)5 The layers were coated on a clear polyester support
in the order of numbering.
A control integral imaging receiver of the
same layer order arrangement was prepared as above
except Layer 7 had Emulsion D a~ 1.4 g Ag/m2.
The following processing pod composition was
employed in both units:
Potassium hydroxide 46.8 g/Q
4-Methyl-4-hydroxymethyl-1-~-
tolyl-3-pyrazolidone 15.0 g/Q
S-Methylbenzotriazole 5O0 g/Q
Carboxymethylcellulose 46.0 8/Q
Potassium fluoride 10.0 g/Q
Anionic dispersant ~Tamol SN~604 g/Q
Potassium sulfite (anhydrous~3.0 g/Q
1,4-Cyclohexanedimethanol3.0 g/Q
Carbon 191.0 g/Q
Two cover sheets of the following structure were
prepared:
Layer 2: Timing layer: 1:1 physical mixture of the
following two polymers coa~ed at 3.2
glm .
~ 6~2
-136-
Poly(acrylonitrile co-vinylidene
chloride-co-acrylic acid) at a weight
ratio of 14:79:7 (isolated as a latex,
dried and dispersed in an organic
solvent)O A carboxy ester lactone was
formed by cyclization of a vinyl
acetate-m~leic anhydride copolymer in the
presence of l-butanol to produce a p~rtial
butyl ester with a weight ra~io of acid to
butyl ester of 15:85 (See Abel U.S. Patent
4,229,516). This layer also contains
t-butylhydroquinone monoacetate at 0.22
g/m2 as a ~ompetor and 5-(2-cyanoethyl-
thio)-l-phenyltetrazole at 0.11 g/m2 as
a blocked inhibitor.
Layer 1: Acid layer: Poly(n-butyl acrylate~co-
acrylic acid) 30:70 weight ratio equi-
valent to 140 meq acid/m2.
The layers were coated on a clear polyester support0 in the order of numbering.
The above image transfer film units
including the processing composition and cover sheet
were used in the following manner:
Each multicolor photosensitive integral
imaging receiver was exposed for 1/100 second in a
sensitometer through a step tablet to 5000K illumi-
nation (daylight balance-neutral), then proce~sed at
a controlled temperature ~either 16C or 22C) using
a viscous processing composition contained in a pod.
The processing composi~ion was spread be~ween the IIR
and the transparent cover sheet using a pair of ~ux-
taposed rollers to provide a processing gap of about
6S ~m.
After a period of more than one hour the
red density of the stepped image was read. The red
minimum density (Dmin) and maximum density (Dm~X)
values were read from the above produc~d sensito-
metrlc curve.
27~2
~137-
The data obtained and tabulated below show
higher maximum red dye denslty at both 16C and 22~C
processing for the tabular grain emulsion. The dif-
ference in red DmaX at these two ~emperatures is
smaller with the tabular grain emulsion than the
octahedral grain check indicating improved processing
temperature lati~ude of the red layer. The speed of
the control and example emulsion were essentially
equivalent.
Red Densit
max/ minDmaxjDmin
_ulsion_Ty~ (22C) 16C ~Dmax_
Octahedral (D)1.73/0.22~.99/0.21 ~0.74
(Control) (-43%)
15 Tabular (B) 1~98/0.361.37/0.29 ~0.61
(Exampl~ 31%)
_ample lB
The same improved processing temperature
latitude and improved Dm~X at low temperature
development are shown in ~ single color coating with
equivalen~ emulsions.
Coatings similar to those of Example lA (but
Single Color~ were made but did not contain layers 15
to 8 (overcoat 16 was coated on top of the red-sensi-
tive silver halide layer, 7). The pod and coversheet are equivalent to those of Example lA except
the cover sheet had 0.043 g/m 2 each of inhibitor
and competor~
Red DensitY
Dmax/Dmin~maxt~min
~ Ye~ (22C) 16C ~Dmax
Octahedral (D)1.66/0.180.54/0.18 -1.12
(Control) t-68%)
Tabular (B) 1.80/0.241.14/0.21 -0.66
35 (Example) ( 37%)
~ 2
-138-
Example 2
This example shows tha~ a coat~ng containing
red-sensitized in~ernal la~ent image-forming ~abular
grain Emulsion B as used in Example lA has improved
room keeping compared to control octahedral grain
Emulsion D.
The example single color coating is the same
as the example coating of Example lB. Two control
coatings were employed similar to the con~rol of
Example lB except layer 7 contained 1.4 ~m and 1.8
~m octahedral emusions, respectively. The pod and
cover sheet were similar ~o those of Example lB.
The experimental procedure used was the same
as Example lA except processing was done only at room
temperature (~22C). To evaluate keeping stability
one set of coatings was exposed and processed resh,
while another set was exposed and processed after
being stored at room temper~ture for seven weeks.
The data below show that both control coat-
ings using the octahedral grain emulsions lose con-
siderably more DmaX after room temperature storage
for seven weeks than example Emulsion B. Dmin
changes (and speed changes) are not 6ignificantly
different.
Red Densi~y
Dmax/Dmin~max/Dmln
(After
Emulsion Type(Fresh)7 weeks) ~Dmax
Octahedral (D)1.62/0.211.17/0.16 -0.45
1.4 ~m (-28%)
Octahedral (D)1.50/0.201.07/0.17 -0.43
1.8 ~m (-28%)
Tabular (B) 1.70/0.281.50/0.21 -0.20
( -12/o)
~ 3i7569
-139
Example 3
This example shows that single color
red-sensitized coatings of tabular grain internal
latent image-forming emulsions have both improved
reversal speed and rereversal separation when cadmium
doped.
The control coating con~ains an emulsion
free of cadmium dopant, Emulsion B, the same a~ uset
in Example lB. The example coa~ing con~ains an equi-
valent cadmium doped Emulsion C, as ou~lined above.The coating structure consists of layers 16 7 and 7 to
1 as described for Example lB. The pod and cover
sheet are equivalent to Example lB. The experimental
procedure is the same as Example lA except processing
is done only at room temperature (~22C). Thresh-
old reversal speeds are read at 0.3 density below
DmaX~ the reversal/rere~ersal separation is read at
0.7 density. A difference of 30 relative speed units
equals 0.30 log E.
The data below show that the cadmium doped
emulsion i6 0.20 log E faster and has a net speed
reversal/rereversal separation of 0.37 log E more
~han does the corresponding emulsion free of cadmium
doping. It is highly desirable that the reversal
speed becomes faster and the rereversal speed slower.
Relative Relative
Reversal Rereversal
EmulsionS~eed (D = 0.7~ Speed (D = 0.7)
B (non CdII
doped) 272 77 195
C (CdII doped) 292 60 232
(Net gain 37)
Experimental results have also shown thatthe surface negative image can be significantly
reduced if the shell portion of the tabular grain
emulsion is doped with either lead (II) or erbium
(III).
~7
-140
Exa~le 4
This example demonstrates tha~ coatings of
tabular grain internal latent image-formlng emulsion
have increased reversal-surface negative image
separation when the shell portion of the tabular
emulsion contains iodide in increasing molar concen-
tration towards the crystal surface.
Emulsions E and F were each spectrally sen-
sitized with 125 mg/Ag mole anhydro-5~5',6,6'-tetra-
chloro-1,1'-diethyl-3,3'-di(3-sulfobutyl~benz~m-
idazolcarbocyanine hydroxide and 125 mgtAg mole
anhydro-5,5'-dichloro-3,9-diethyl-31-(3-sulfopropyl)-
oxacarbocyanine hydroxide. The emulsions were then
coated on polyester film support at 2.15 g/m2 sil-
ver and 4.52 g/m2 gelatin. The coatings were ex~posed for 10- 2 second to a Xenon flash through a
continuous density tablet on an Edgerton, ~ermes-
hausen, and Grier sensitometer and processed for 4
minutes in an ~-methylaminophenol sulfate (Elon¢)-
hydroquinone developer containing 4-(B-methane-
sulfonamidoethyl)phenylhydrazlne hydrochloride at 2.1
g/Q as the nucleating agent and 0.2 g/Q 5-methyl-
benzotriazole. Sensitometric results including the
undyed emulsion controls are given below.
~"
9 ~
- ~41-
~ ~ ~D
a *
A A
Cd ~ O
U)
l ,4 r~
V ~ ~ U~
0 ~ ~ 11
a~ ~ ~ ~ * ~
O h u~ C: ~ ~ ~o
Q~
O
_~
0 ~ ~ X
O 0
r~
~' ~ C~l
O P. C~
00 IJ
h C q-~
~ Cq
O
~C
U
o e ou
a ~ ~ ~ ~
U 0 U~
1 3 t`J
o o a~
~1
X E~ ~a ~ ,~
w o ~
x ~ ~ c~
0 o w ~
. ~ . . ~ .e
~ o ~ ~ ~ o ~
o ~
JJ
~ ~d
p~ ~ w ~
~ N 3 0 r`
~I ~
~n w r-l O
O ~O q~ ~ ~
O ~ æ ~ æ ~
SJ ~ t,
~ ~ Q~
C~ ~ ~ ~ ~
~ ~ o
IY
,i ~
~ o
~ W
-142-
As can be seen Emulsion F which contained
tabular ~rains of increased iodide content in the
shell portion, displayed significantly grea~er rever
~al/rereversal separation than Emulsion E which was
S 6helled with pure AgBr. The spectrally sensitized
Emulsion F had a reversal/rereversal separhtion of
greater than 3,26 lo~ E units at a density of 0.70
whereas the spec~rally sensitized control Emulsion E
had a separation of 1.22 log E units. It was also
noted thst the spectrally sensitized Emulsion F dis
played less blue speed desensitization than the spee-
trally æensitized control Emulsion E,
Example 5
A high aspect ratio tabular grain internal
latent image-forming silver bromide emulsion having
an average grain ~iameter of 5.5 microns, an sverage
~rain thickness of 0.12 micron, and an average aspeet
ratio of 46:1 with the tabular grain accoun~ing for
85 percent of the total grain projected area was
prepared as follows:
A core emulsion having a grain diameter of
2.8 microns and an average grain ~:hickness of 0.08
micron was precipitated by double jet addition at pBr
1.3 at 80C. The AgBr core emulsion was chemically
sensitized with 0.9 mg Na2S203~5H20/Ag mole and 0.6
mg KAuCl 4 /Ag mole for 20 minutes at 80C. Then
the emulsion was precipitated with additional silver
bromide at p8r 1.3 at 70C. The resultant core-shell
tabular grain emulsion was not surface sen~itized.
The emulsion was coated on a polyester film
support at 2.15 g/m2 silver and 10.4 g/m2 gel~-
tinO A second co~ting was prep~red that contained S0
mg/Ag mole 1-(2 propynyl)-2-methylquinolinium bro-
mide. A third coating was prepared that contained 25
mg/Ag mole 1-(2-propynyl)-2-methyl-6-ethoxyth~oform-
amidoquinolinium trifluoromethanesulfonate. The
coatings were exposed for 1/10 second to a 600W
~ 6
-143-
5500K tungsten light source and processed for 3
minutes at 20~C in R IMeto~(N-methy~ aminophenol
sulfate~-hydroquinone developer containing 0.25 g/l
5-methylbenzotriazole.
Sensitome~ric results revealed that the con-
trol coating displayed no reversal image. However,
the core-shell tabular grain emulsion coating that
contained 1-(2~propynyl~2 methylquinolinium bromide
resulted in a reversal image with a D of 0.69
max
and a Dmin of 0.18.
Similarly, the core-shell tabular grain
emulsion coating that contained l-(2-propynyl)-2-
methyl-6-ethoxythioformamidcquinolinium trifluoro-
methanesulfonate resulted in a reveræ~l image of good
discrimination with a DmaX of 0.95 and a Dmin of
0.30.
Appendix
The redox dye-releasers (~DR's) I to IV are
of the structures described in Research Dlsclosure,
2~ Vol. 182, July 1979, Item 18268, pages 329-31.
I. Yellow RDR
OH
CON(CIsH37)2
i!
~./ \o~
NH /OHSO2CH3
~o--~ X ~-N=N-~
\CN \Cl
(dispersed in di-n-butylphthalate)
s ~ ~
-144
II. Magenta RDR
0~
ON(ClsH37)2
t
NH
/
SO2_ ~ N=N NHSO2CH3
.~ \./ ~.
! !1
(CH 3 ) 3 CNHS02
OH
(dispersed in diethyllauramide~
III. Cyan RDR
OH
N(clsH37)2
NH
10 /=
2 ~ SO2CH3
SO2-NH N=~-~ NO2
.~-\./-~.
11
t S02N(is0-~3~7)2
OH
(dispersed in N-n-butylacetanilide)
IV. Cyan RDR
OH C2Hs
1 1 /.,.
CON-CH2CH-O~
\C l s H 3 I -n
~H
SO2--~ S02NH NsN~ NO2
t i
t
OH
~5
-145-
(dispersed in N n-butylace~anilid~
The nucleating agents V and VI, ~re of the
following structure:
V.
o ~ H2
CH3CO~NHNH~ NH-C-~
o
lo I~ t-CsHl 1
~.,
t~CsHI 1
VI.
15 o S
Il . .-., 11
H-C-NHNH~ - NH-C-NHCH3
The oxidized developer scavengers ~re the
following:
VII.
OH
~ C H -s
OH
VIII.
OH
Cl2H2s~s
S -C l 2H2s~i
OH
The mordant is as follows:
IX.
poly(styrPne-co-l-vinylimldazole-co-3-
35 benzyl-l-vinylimidazolium chloride) (weight
ratio approx. 50:40:10)
6 9 2
- 146 -
The invention has been described in detail
with particular reference to preferred embodiments
thereof, but it will be understood that variatlons
and modifications ean be effected within the spirit
and scope of the invention.
. .
