Note: Descriptions are shown in the official language in which they were submitted.
1 2 ~ ~ ~ 2 0 ~ 45443 C~N 4A
POST-PROCESSING STABILIZATION
OF PHOTOTHERMOGRAPHIC EMULSIONS
_eld of the Invention
This invention relates to photothermographic
materials and in particular to post-processing stabiliza-
tion of dry silver systems.
Bactcground of the Art
Silver halide photothermographic imagingmaterials, especially "dry silver" compositions, processed
lS with heat and without liquid development have been known
in the art for many years. Such materials are a mixture
of light insensitive silver salt of an organic acid ~e.g.,
silver behenate), a minor amount of catalytic light
sensitive silver halide, and a reducing agent for the
silver source.
The light sensitive silver halide is in
catalytic proximity to the light insensitive silver salt
such that the latent image formed by the irradiation of
the silver halide serves as a catalyst nucleus for the
oxidation-reduction reaction of the organic silver salt
with the reducing agent when heated above 80C. Such
media are described in U.S. Pat. Nos. 3,457,075;
3,839,049; and 4,260,677. Toning agents can be incor-
porated to improve the color of the silver image of
photothermographic emulsions as described in U.S. Pat.
Nos. 3,846,136; 3,994,732 and 4,021,249. Various methods
to produce dye images and multicolor images with photo-
graphic color couplers and leuco dyes are well known in
the art as represented by U.S. Pat. Nos. 4,022,617;
3,531,2B6; 3,180,731; 3,761,270; 4,460,681; 4,883,747 and
Research Disclosure 29963.
20~92Q3
A common problem that exists with these
photothermographic systems is the instability of the image
following processing. The photoactive silver halide still
present in the developed image may continue to catalyze
print-out of metallic silver even during room light
handling. Thus, there exists a need for stabilization of
the unreacted silver halide with the addition of separate
post-processing image stabilizers or stabilizer precursors
to provide the desired post-processing stability. Most
often these are sulfur containing compounds such as
mercaptans, thiones, thioethers as described in Research
disclosure 17029. U.S. Pat. No. 4,245,033 describes
sulfur compounds of the mercapto-type that are development
restrainers of photothermographic systems as do U.S. Pat.
Nos. 4,837,141 and 4,451,561. ~esoionic
1,2,4-triazolium-3-thiolates as fixing agents and silver
halide stabilizers are described in U.S. Pat. No.
4,378,424. Substituted 5-mercapto-1,2,4-triazoles such as
3-amino-5-benzothio-1,2,4-triazole as post-processing
stabilizers are described in U.S. Pat. No. 4,128,55~;
4,137,079; 4,138,265, and Research Disclosure 16977 and
16979.
Some of the problems with these stabilizers
include thermal fogging during processing or losses in
photographic sensitivity maximum density or contrast at
stabilizer concentrations in which stabilization of the
post-processed image can occur.
Stabilizer precursors have blocking or modifying
groups that are usually cleaved during processing with
heat and/or alkali. This provides the remaining moiety or
primary active stabilizer to combine with the photoactive
silver halide in the unexposed and undeveloped areas of
the photographic material. For example, in the presence
of a silver halide precursor in which the sulfur atom is
blocked upon processing, the resulting silver mercaptide
will be more stable than the silver halide to light,
atmospheric and ambient conditions.
_3_ 2 ~ 92 ~3
Various blocking techniques have been utilized
in developing the stabilizer precursors. U.S. Patent No.
3,615,617 describes acyl blocked photographically useful
stabilizers. U.S. Patent Nos. 3,674,478 and 3,993,661
describe hydroxyarylmethyl blocking groups. Benzylthio
releasing groups are described in U.S. Patent No.
3,698,898. ~hiocarbonate blocking groups are described in
U.S. Patent No. 3,791,830, and thioether blocking groups
in U.S. Patent Nos. 4,335,200, 4,416,977, and 4,420,554.
Photographically useful stabilizers which are blocked as
urea or thiourea derivatives are described in U.S. Patent
No. 4,310,612. Blocked imidomethyl derivatives are
described in U.S. Patent No. 4,350,752, and imide or
thioimide derivatives are described in U.5. Patent No.
4,888,268. Removal of all of these aforementioned
blocking groups from the photographically useful
stabilizers is accomplished by an increase of pH during
alkaline processing conditions of the exposed imaging
material.
Other blocking groups which are thermally
sensitive have also been utilized. These blocking groups
are removed by heating the imaging material during
processing. Photographically useful stabilizers blocked
as thermally sensitive carbamate derivates are described
in U.S. Patent Nos. 3,844,797 and 4,144,072. These
carbamate derivatives presumably regenerate the photo-
graphic stabilizer through loss of an isocyanate.
Hydroxymethyl blocked photographic reagents which are
unblocked through loss of formaldehyde during heating are
described in U.S. Patent No. 4,510,236. Development
inhibitor releasing couplers releasing tetrazolylthio
moieties are described in U.S. Patent No. 3,700,457.
Substituted benzylthio releasing groups are described in
U.S. Patent No. 4,678,735; and U.S. Patent Nos. 4,351,896
and 4,404,390 utilize carboxybenzylthio blocking groups
for mesoionic 1,2,4-triazolium-3-thiolates stabilizers.
Photographic stabilizers which are blocked by a
2 ~ ~J
--4--
Michael-type addition to the carbon-carbon double bond of
either acr~lonitrile or alkyl acrylates are described in
U.S. Patent Nos. 4,009,029 and 4,511,644, respectively.
Heatinq of these blocked derivatives causes unblocking by
a retro-Michael reaction.
various disadvantages attend these different
blocking techniques. Highly basic solutions which are
necessary to cause deblocking of the alkali sensitive
blocked derivatives are corrosive and irritating to the
skin. with the photographic stabil}zers which are blocked
with a heat removable group, it is often found that the
liberated reagent or by-product, for example,
acrylonitrile, can react with other components of the
imaging construction and cause adverse effects.
Also, inadequate or premature release of the
stabilizing moiety within the desired time during
processing may occur.
Thus, there has been a continued need for
improved post-processing stabilizers that do not fog or
desensitize the photographic materials, and stabilizer
precursors that release the stabilizing moiety at the
appropriate time and do not have any detrimental effects
on the photosensitive material or user of said material.
Summary of the Invention
According to this invention, the incorporation
of novel azlactone-functional stabilizer precursor of
Formula I and/or 2-alkenyl azlactones of Formula II and/or
azlactones of Formula III into the photothermoqraphic
emulsion layer or a layer adjacent to the emulsion layer
stabilizes the photoactive silver halide for improved
post-processing stabilization without desensiting or
fogging the heat developable photographic material and
process. The general formulae I, II, and III describe
such compounds thereof:
2?~2~
--5--
¦ I ¦ 3 ~R6 f~R6
2 1o~n\R7 R2 \ ~\
O O
R~R5
lS Rg C
O ~ ~ R7
m
wherein
A represents a residue of a post-processing
stabilizing group AH in which a hydrogen atom of the
post-processing stabilizer has been replaced by the
remainder of the structure shown in Formula I;
R1, R2, and R3 are independently hydrogen or
methyl, with the proviso that R1 can also represent an
aryl group when R2 and R3 are hydrogen;
R4 and R5 independently represent an alkyl
group, a cyclo alkyl group, an aryl group or R~ and R5
taken together with the carbon atom to which they are
joined form a ring of 4 to 12 atoms;
R6 and R7 are independently hydrogen or lower
alkyl, preferably C-1 to C-4 alkyl;
R~ is any organic group such as alkyl groups
(e.g., of 1 to 20 carbon atoms, more preferably 1 to 12
carbon ato~s, and inclusive of cycloalkyl of 3 to 20
-
.
?~ 2 ~1 ~
--6--
carbon atoms, preferably 5 to a carbon atoms), aryl groups
(e.g., up to 7 ring atoms) and heterocyclic groups
(preferably of C, S, N, o and Se atoms with up to 7 ring
atoms);
and n is 0 or 1.
In this application:
"alkenyl" and "alkenylene" mean the monovalent
and polyvalent residues remaining after removal of one and
at least two hydrogen atoms, respectively, from an alkene
containing 2 to 20 carbon atoms; functional groups which
may be present are one or more aryl, amide, thioamide,
ester, thioester, ketone ~to include oxo-carbons),
thioketone, nitrile, nitro, sulfide, sulfoxide, sulfone,
disulfide, tertiary amine, ether, urethane,
dithiocarbamate, quaternary ammonium and phosphonium,
halogen, silyl, silyloxy, and the like, wherein the
functional groups requiring substituents are substituted
with hydrogen, alkyl, or aryl groups where appropriate;
additionally, the alkenyl and alkenylene residues may
contain one or more catenary S, o, N, P, and si
heteroatoms;
"alkyl" and alkylene" mean the monovalent and
polyvalent residues remaining after removal of one and at
least two hydrogen atoms, respectively, from a linear or
branched chain hydrocarbon having 1 to 20 carbon atoms,
functional groups and catenary heteroatoms which may be
present are the same as those listed under the "alkenyl"
definition;
"aryl" and "arylene" me~n the monovalent and
polyvalent residues remaining after removal of one and at
least two hydrogen atoms, respectively, from an aromatic
compound (single ring and multi- and fused-cyclic) having
5 to 12 rinq atoms in which up to 5 ring atoms may be
selected from S, Si, O, N, and P heteroatoms, functional
groups which also may be present are the same as those
listed under the "alkenyl" definition;
.
-7-
"azlactone" means 2-oxazolin-5-one g~oups of
Formula VII and 2-oxa~in-6-one groups of Formula VIII
S
1 0 VII
Such compounds of Formula I are ~ichael reaction
products of selected Michael donors (A~) to 2-alkenyl
azlactone Michael acceptors (Formula II ) as illustrated by
a nitrogen nucleophile (IV) in the eguation below, to an
alkenyl azlactone Michael accepteor (V~ to form a Michael
adduct reaction product VI.
\ ¦ ~ \ N -
lV V VI
Detailed Description of the Invention
The addition of the novel azlactone-functional
stabilizer precursors of Formula I and/or the 2-al~enyl
azlactones of Formula II and/or the azlactones of Formula
III into the photothermographic emulsion layer or layer
adjacent to the emulsion layer provides the photoactive
silver halide emulsion with improved post-processing
stability without desensitizing or fogging said emulsion.
In general Formula I, A represents the residue
of the "primary" post-processing stabilizer, AH, in which
,
'
--8--
the hydrogen atom has been replaced by the azlactone
functional "secondary" stabilizer. The addition of the
alkenyl azlactone to AH blocks the activity of the primary
stabilizer AH, which left unblocked and added to the
emulsion at the same molar equivalent would desensitize
said emulsion. After processing, the azlactone functional
group releases the primary stabilizer providing improved
post-processing stabilization from both the primary
stabilizer and the secondary stabilizer, the azlactone
10 moiety.
The primary stabilizer AH represents any group
which links to the azlactone moiety by the loss of a
hydrogen atom from a sulfur or nitrogen atom from the
primary stabilizer.
AH has been defined as a post-processing
stabilizing group. This is a group, which when released
from the azlactone, stabilizes the image formed after
processing. The group could not have been originally
associated with the emulsion as the compound A-H because
that compound would have been too active and would have
actively suppressed image formation. The combination of
processing heat in the presence of the photothermographic
environment releases the group A from the azlactone at a
useful time. Also the presence of azlactone group itself
can give some post-processing stability. Post-processing
stabilizing groups usually have a sulfur or nitrogen atom
available for complexing silver ion. The compounds are
usually ring structures with the sulfur and/or nitrogen
within the ring or external to the ring. These compounds
are well known to the ordinary skilled photographic
chemist.
Suitable stabilizers are well known in the art
such as nitrogen-containing substituted or unsubstituted
heterocyclic rings; such as benzimidazole, benzotriazole;
triazoles; tetrazoles; imidazoles; various mercapto-
containing substituted or unsubstituted compounds; such as
mercapto triazoles, mercapto tetrazoles; thio-substituted
_9_
heterocycles; or any such compound that stabilizes the
said emulsion but at such concentrations desensitizes the
initial sensitometric response if left unblocked. Many of
such compounds are summarized in Research Disclosure 29963
from March, 19~9 entitled "Photothermographic Silver
Halide Systems~.
Specific examples of the novel azlactone-
functional stabilizer precursors of Formula I and
2-alkenyl azlactones or Formula II are shown by the
formulae below, which, however, does not limit the
compounds to be used in the present invention.
N,N~ N-N>~-- [~NNX~H
I-A I-B I-C
/~ N--X, whelein X, = CH2CH2--C/ ~C~
I-D
N N/ CH3 N CH3
1l )~ S wherein X2 = CH2-CH--C~ CH3
X2
I-E
.
.
~0~2~3
N CH3
~d H2C=CH - C 1 CH
0-~
S ~-A
Examples of suitable 2-alkenyl azlactones of
Formula II include: 2-vinyl-4,4-dimethyl-2-oxazolin-5-one
~II-A (VDM)), 2-isopropenyl-4,4-dimethyl-2-oxazolin-5-one,
2-vinyl-4-ethyl-4-methyl-2-oxazolin-5-one,
2-vinyl-4,4-dimethyl-1,3-oxazin-6-one and others disclosed
in U.S. Patent No. 4,304,705. The preferred 2-alkenyl
azlactones is VDM (available from SNPE, Inc., Princeton,
NJ).
Examples of suitable azlactones of Formula III
include: 2-methyl-4,4-dimethyl-2-oxazolin-5-one,
2-ethyl-4,4-dimethyl-2-oxazolin-5-one,
2-isopropyl-4-ethyl-4-methyl-2-oxazolin-5-one,
2-phenyl-4,4-dimethyl-2-oxazolin-5-one,
20 2-ethyl-4,4-dimethyl-1,3-oxazin-6-one, and others
described by Y. S. Rao and R. Filler in a review entitled
"Oxazolones" contained in "Heterocyclic Compounds, Vol.
45" edited by I. J. Turchi, John Wiley and Sons, Inc., New
York, 1986, pp. 361-729 as well as multiazlactones such as
those described by J. K. Rasmussen, S. M. Heilmann and
L. R. Krepski in a review entitled "Polyazlactones"
contained in "Encyclopedia of Polymer Science and
Engineering, Vol. II," Second Edition, John Wiley and
Sons, Inc., New York, 1988, pp. 558-571.
3~ The general synthesis of the stabilizer
precursors in Formula I is described in the patent
application entitled "Azlactone Michael Adducts", File No.
45053USAlA. Specific synthesis examples of the compounds
according to the present invention are set forth below.
In all cases, structures of the compounds were
confirmed by spectral analysis, including IR, proton and
carbon NMR spectroscopy.
2 ~ t~
--11--
Synthesis Example 1
Synthesis of Compound I-A
A mixture of VDM ( 2-vinyl-4,4-dimethylazlactone)
(13.9 g, 0.10 mole) and 1-phenyl-lH-tetrazole-5-thiol
(17.8 g, 0.1 ~ole) was heated at 100C overnight to yield
the desired product.
Synthesis of Compound I-B
VDM (13.9 g, 0.10 mole) was cooled to 0~ and
mixed with l-phenyl-lH-tetrazole-5-thiol (17.8 g, 0.10
mole). The mixture was allowed to warm to room
temperature and kept at this temperature overnight to give
a quan~itive yield of the desired product as a white
solid. Structure of the product was confirmed by spectral
analyses.
Synthesis Example 2
Synthesis of Compound I-C
A mixture of VDM (13.9 g, 0.10 mole) and
benzimidazole (11.8 g, 0.10 mole) was heated at 100C
overnight to yield the desired product.
Synthesis Example 3
Synthesis of Compound I-D
A reaction flask equipped with a magnetic
stirrer was charged with 3-trifluoromethyl-4-methyl-5-
mercapto-1,2,4 triazole ( MFT) (36 g, 0.2 mole),
vinylazlactone (VDM) (55.6 g, 0.4 mole) and
30 1,8-diazabicyclol5.4Ølundec~7-ene (DBU) (1 ml). The
reaction mixture was then stirred at 65C for 15 hours.
The gummy material obtained was dissolved in toluene (220
ml) at room temperature and filtered. Addition of
n-hexane (200 ml) to the cold solution of the filtrate
(kept in an ice bath) yielded white crystals. m.p. 73C;
54g (88%).
2 ~'~t~2
-12-
Synthesis Example 4
Synthesis of Compound I-E
A mixture of IDM (2-isopropenyl-4,4-
dimethylazlactone) (7.65 g, 0.05 mole~, l-phenyl-1~-
tet~azole-5-thiol (8.9 g, ~.05 mole) and DBU (1,8-
diazabicyclo[5.4.0]undec-7-ene) ~0.38 9, 2.5 mmole) was
heated at 60C for 21 hours, then 100C for 3 hours to
give the desired product.
The amounts of the above described compounds
according to the present invention which are added can be
varied depending upon the particular compound used and
upon the photothermographic emulsion-type. Howeve~, they
are preferably added in an amount of 10- 3 to 50 mol, and
more preferably from 10-Z to 10 mol, per mol of silver
halide in the emulsion layer.
The photothermographic dry silver emulsions of
this invention may be constructed of one or more layers on
a substrate. Single layer constructions must contain the
silver source material, the silver halide, the developer
and binder as well as optional additional materials such
as toners, coating aids and other adjuvants. Two-layer
constructions must contain the silver source and silver
halide in one emulsion layer (usually the layer adjacent
the substrate) and some of the other ingredients in the
second layer or both layers. Multicolor photothermo-
geaphic dry silver constructions contain sets of these
bilayers for each color. Color forming layers are
maintained distinct from each other by the use of
functional or non-functional barrier layers between the
various photosensitive layers as described in U.S. Pat.
No. 4,460,681.
The silver source material, as mentioned above,
may be any material which contains a reducible source of
silver ions. Silver salts of organic acids, particularly
lon~ chain ~10 to 30, preferably 15 to 28 carbon atoms)
fatty carboxylic acids are preferred. Complexes of
20~ 2~3
-13-
organic or inorganic silver salts wherein the ligand has a
gross stability constant between 4.0 and 10.0 are also
desirable. The silver source material constitutes from
about 5 to 30 percent by weight of the imaging layer. The
second layer in a two-layer construction or in the bilayer
of a multi-color construction would not affect the
percentage of the silver source material desired in the
photosensitive single imaging layer.
The organic silver salt which can be used in the
present invention is a silver salt which is co~paratively
stable to light, but forms a silver image when heated to
80C or higher in the presence of an exposed photocatalyst
~such as silver halide) and a reducing agent.
Suitable organic silver salts include silver
salts of organic compounds having a carboxy group.
Preferred examples thereof include a silver salt of an
aliphatic carboxylic acid and a silver salt of an aromatic
carboxylic acid. Preferred examples of the silver salts
of aliphatic carboxylic acids include silver behenate,
silver stearate, silver oleate, silver laurate, silver
caprate, silver myristate, silver palmitate, silver
maleate, silver fumarate, silver tartarate, silver
furoate, silver linoleate, silver butyrate and silver
camphorate, mixtures thereof, etc. Silver salts which are
substituted with a halogen atom of a hydroxyl group can
also be effectively used. Preferred examples of the
silver salts of aromatic carboxylic acid and other
carboxyl group-containing compounds include silver
benzoate, a silver substituted benzoate such as silver
3,5-dihydroxybenzoate, silver o-methylbenzoate, silver
m-methylbenzoate, silver p-methylbenzoate, silver
2,4-dichlorobenzoate, ~ilver acetamidobenzoate, silver
p-phenyl benzoate, etc., silver gallate, silver tannate,
silver phthalate, silver terephthalate, silver salicylate,
silver phenylacetate, silver pyromellitate, a silver salt
of 3-carboxymethyl-4-methyl-4-thiazoline-2-thione or the
like as described in U.S. Pat. No. 3,785,830, and silver
,
~ ~2~.
-14-
salt of an aliphatic carboxylic acid containing a
thioether group as described in U.S. Pat. No. 3,330,663,
etc.
Silver salts of compounds containinq mercapto or
thione groups and derivatives thereof can be used.
Preferred examples of these compounds include a silver
salt of 3-mercapto-4-phenyl-1,2,4-triazole, a silver salt
of 2-mercaptobenzimidazole, a silver salt of 2-mercapto-5-
aminothiadiazole, a silver salt of 2-(S-ethylglycolamido)
benzothiazole, a silver salt of thioglycolic acid such as
a silver salt of a S-alkyl thioglycolic acid (wherein the
alkyl group has from 12 to 22 carbon atoms) as described
in Japanese patent application No. 28221/73, a silver salt
of a dithiocarboxylic acid such as a silver salt of
dithioacetic acid, a silver salt of thioamide, a silver
salt of 5-carboxylic-1-methyl-2-phenyl-4-thiopyridine, a
silver salt of mercaptotriazine, a silver salt of
2-mercaptobenzoxazole, a silver salt as described in U.S.
Pat. No. 4,123,274, for example, a silver salt of
1,2,4-mercaptothiazole derivative such as a silver salt of
3-amino-5-benzylthio-1,2,4-thiazole, a silver salt of
thione compound such as a silver salt of
3-(2-carboxyethyl)-4-methyl-4-thiazoline-2-thione as
disclosed in U.S. Pat. No. 3,301,678.
Furthermore, a silver salt of a compound
containing an imino group can be used. Preferred examples
of these compounds include a silver salt of benzothiazole
and a derivative thereof as described in Japanese patent
publications Nos. 30270/69 and 18146/70, for 0xample, a
silver salt of benzothiazole such as silver salt of
methylbenzotriazole, etc., a silver salt of a halogen
substituted benzotriazole, such as a silver salt of
5-chlorobenzotriazole, etc., a silver salt of
carboimidobenzotriazole, etc., a silver salt of
1,2,4-triazole, of l-H-tetrazole as described in U.S. Pat.
No. 4,220,709, a silver salt of imidazole and an imidazole
derivative, and the like.
.,,
2 ~
-15-
It is also found convenient to use silver
halfsoaps, of which an equimolar blend of silver behenate
and behenic acid, prepared by precipitation from aqueous
solution of the sodium salt of commercial behenic acid and
analyzing about 14.5 percent silver, represents a
preferred example. Transparent sheet materials made on
transparent film backing require a transparent coating and
for this purpose the silver behenate full soap, containing
not more than about four or 5 percent of free behenic acid
and analyzing about 25.2 percent silver may be used.
The method used for making silver soap
dispersions is well known in the art and is disclosed in
Research Disclosure April l9B3 (22812) ibid October 1983
(23419) and U.S. Pat. No. 3,985,565.
The light sensitive silver halide used in the
present invention can be employed in a range of 0~0005 mol
to 5 mol and, preferably, from 0.00~ mol to 1.0 mol per
mol of organic silver salt.
The silver halide may be any photosensitive
silver halide such as silver bromide, silver iodide,
silver chloride, silver bromoiodide, silver
chlorobromoiodide, silver chlorobromide, etc.
The silver halide used in the present invention
may be employed without modification. How0ver, it may be
chemically sensitized with a chemical sensitizing agent
such as a compound containing sulphur, selenium or
tellurium etc., or a compound containing gold, platinum,
palladium, rhodium or iridium, etc., a reducing agent such
as a tin halide, etc., or a combination thereof. The
details of these procedures are described in T.H. James
"The Theory of the Photographic Process", Fourth Edition,
Chapter 5, pages 149 to 169.
The silver halide may be added to the emulsion
layer in any fashion which places it in catalytic
proximity to the silver source.
The silver halide and the organic silver salt
which are separately formed in a binder can be mixed prior
.,,,, , . ~ . . .
2 ~ '~; C~
-16-
to use to prepare a coating solution, but it is also
effective to blend both of them in a ball mill for a long
period of time. Further, it is effective to use a process
which comprises adding a halogen-containing compound in
the organic silver salt prepared to partially convert the
silver of the organic silver salt to silver halide.
Methods of preparing these silver halide and
organic silver salts and manners of blending them are
described in Research Disclosures, No. 170-29, Japanese
Patent Applications Nos. 32928/75 and 42529/76, U.S. Pat.
No. 3,700,458, and Japanese Patent Applications Nos.
13224/74 and 17216/75.
The use of preformed silver halide emulsions of
this invention can be unwashed or washed to remove soluble
salts. In the latter case the soluble salts can be
removed by chill-setting and leaching or the emulsion can
be coagulation washed, e.g., by the procedures described
¦ in Hewitson, et al., U.S. Pat. No. 2,618,556; Yutzy et
al., U.S. Pat. No. 2,614,928; Yackel, U.S. Pat. No.
20 2,565,418;; Hart et al., U.S. Pat. NO. 3,241,969; and
Waller et al., U.S. Pat. No. 2,489,341. The silver halide
grains may have any crystalline habit including, but not
limited to cubic, tetrahedral, orthorhombic, tabular,
laminar, platelet, etc.
Photothermographic emulsions containing
preformed silver halide in accordance with this invention
can be sensitized with chemical sensitizers, such as with
reducing agents; sulfur, selenium or tellurium compounds;
gold, platinum or palladium compounds, or combinations of
these. Suitable chemical sensitization procedures are
described in Shepard, U.S. Pat. No. 1,623,499; Waller,
U.S. Pat. No. 2,399,083; McVeigh, U.S. Pat. No. 3,297,447;
and Dunn, U.S. Pat. No. 3,297,446.
The light-sensitive silver halides can be
spectrally sensitized with various known dyes including
cyanine, styryl, hemicyanine, oxonol, hemioxonol and
xanthene dyes. Useful cyanine dyes include those having a
-17- ~ 2~
basic nucleus, such as a thiazoline nucleus, an oxazoline
nucleus, a pyrroline nucleus, a pyridine nucleus, an
oxazole nucleus, a thiazole nucleus, a selenazole nucleus
and an imidazole nucleus. Useful merocyanine dyes which
are preferred include those having not only the above
described basic nuclei but also acid nuclei, such as a
thiohydantoin nucleus, a rhodanine nucleus, an
oxazolidinedione nucleus, a thiazolidinedione nucleus, a
barbituric acid nucleus, a thiazolinone nucleus, a
malonitrile nucleus and a pyrazolone nucleus. In the
above described cyanine and merocyanine dyes, those having
imino groups or carboxyl groups are particularly
effective. Practically, the sensitizing dye to be used in
the present invention is properly selected from known dyes
as described in ~.S. Pat. No. 3,761,279, 3,719,495 and
3,877,943, sritish Pat Nos. 1,466,201, 1,469,117 and
1,422,057, Japanese Patent Application (OPI) Nos. 27924/76
and 156424/75, and so on, and can be located in the
vicinity of the photocatalyst according to known methods
used in the above-described examples. These spectral
sensitizing dyes are used in amounts of about 10-4 mol to
about 1 mol per 1 mol of photocatalyst.
The reducing aqent for silver ion may be any
material, preferably organic material, which will reduce
silver ~on to metallic silver. Conventional photographic
developers such as phenidone, hydroquinones, and catechol
are useful but hindered phenol reducing agents are
preferred. The reducing agent should be present as 1 to
10 percent by weight of the imaging layer. In a two-layer
construction, if the reducing agent is in the second
layer, slightly high proportions, of from about 2 to 15
percent tend to be more desirable.
A wide range of reducing agents have been
disclosed in dry silver systems including amidoximes such
as phenylamidoxime, 2-thienylamidoxime and p-phenoxy-
phenylamidoxime, azine, e.g., 4-hydroxy-3,5-
dimethoxybenzaldehyde azine; a combination of aliphatic
,~:
.
2~ 1~2~3
-18-
carboxylic acid aryl hydrazides and ascorbic acid, such as
2,2-bis~hydroxymethyI)propionyl-beta-phenyl hydrazide in
combination with ascorbic acid; a combination of
polyhydroxybenzene and hydroxylamine, a reductone and/or a
hydrazine, e.q., a combination of hydroquinone and
bistethoxyethyl)hydroxylamine, piperidinohexose reductone
or formyl-4-methylphenyl hydrazine, hydroxamic acids such
as phenylhydroxamic acid, p-hydroxyphenyl hydroxamic acid,
and beta-alanine hydroxamic acid; a combination of azines
and sulphonamidophenols, e.g., phenothiazine and 2,6-
dichloro-4-benzenesulphonamidophenol; alpha-
cyanophenylacetic acid derivatives such as ethyl-alpha-
cyano-2-methylphenylacetate, ethyl alpha-
cyanophenylacetate; bis-beta-naphthols as illustrated by
2,2'-dihydroxy-1,1'-binaphthyl, 6,6'-dibromo-2,2'-
dihydroxy-1,1'-binaphthyl, and bis(2-hydroxy-1-
naphthyl)methane; a combination of bis-beta-naphthol and a
1,3-dihydroxybenzene derivative, e.g., 2,4-dihydroxy-
benzophenone or 2'4'-dihydroxyacetophenone; 5-pyrazolones
such as 3-methyl-1-phenyl-5-pyrazolone; reductones as
illustrated by dimethylamino hexose reductone, anhydro
dihydro amino hexose reductone, and anhydro dihydro
piperidone hexose reductone; sulphonamido-phenol reducing
agents such as 2,6-dichloro-4-benzensulphonamidophenol,
and p-benzenesulphonamidophenol; 2-phenylindane-1,3-dione
and the like; chromans such as 2,2-dimethyl-7-t-butyl-6-
hydroxychroman; 1,4-dihydro-pyridines such as 2,6-
dimethoxy-3,5-dicarbetoxy-1,4-dihydropyridine; bisphenols
e.g., bis(2-hydroxy-3-t-butyl-5-methylphenyl)methane,
2,2-bis(4-hydroxy-3-methylphenyl)propane, 4,4-ethylidene-
bis(2-tert-butyl-6-methylphenol), and 2,2-bis(3,5-
dimethyl-4-hydroxyphenyl)propane; ascorbic acid
derivatives, e.g., 1-ascorbylpalmitate, ascorbylstearate
and unsaturated aldehydes and ketones, such as benzyl and
diacetyl; 3-pyrazolidones and certain indane-1,3-diones.
The literature discloses additives, "toners",
which improve the image.
2Q~?~3
--19--
Toner materials may be present, for example, in
amounts from 0.1 to 10 percent by weight of all silver
bearing components. Toners are well known materials in
the photothermographic art as shown in U.S. Pat. Nos.
3,080,254; 3,847,612 and q,123,282.
Examples of toners include phthalimide and
N-hydroxyphthalimide; cyclic imides such as succinimide,
pyrazoline-5-ones, and a quinazolinone, 3-phenyl-2-
pyrazoline-5-one, l-phenylurazole, quinazoline, and 2,4-
thiazolidinedione; naphthalimides, e.g., N-hydroxy-1,8-
naphthalimide; cobalt complexes, e.g., cobaltic hexamine
trifluoroacetate; mercaptans as illustrated by 3-mercapto-
1,2,4-triazole, 2,4-dimercaptopyrimidine, 3-mercapto-4,5-
diphenyl-1,2,4-triazole and 2,5-dimercapto-1,3,4-
thiadiazole; N-(aminomethyl)aryl dicarboximides, e.g.
(N-dimethylaminomethyl)phthalimide, and
N-(dimethylaminomethyl)naphthalene-2,3-dicarboximide; and
a combination of blocked pyrazoles, isothiuronium
derivatives and certain photobleach agents, e.g., a
combination of N,N'-hexamethylene bis(1-carbamoyl-3,5-
dimethylpyrazole), 1,8-(3,6-diazaoctane)bis(isothiuronium
trifluoroacetate) and 2-(tribromomethylsulphonyl)-
benzothiazole); and merocyanine dyes such as
3-ethyl-5l(3-ethyl-2-benzothiazolinylidene)-1-
methylethylidene]-2-thio-2,4-oxazolidinedione;
phthalazinone, phthalazinone derivatives or metal salts or
these derivatives such as 4-(1-naphthyl)phthalazinone,
6-chlorophthalazinone, 5,7-dimethoxyphthalazinone, and
2,3-dihydro-1,4-phthalazinedione; a combination of
phthalazinone plus sulphinic acid derivatives, e.g.,
phthalic acid, 4-methylphthalic acid, 4-nitrophthalic
acid, and tetrachlorophthalic anhydride;
quinazolinediones, benzoxazine or naphthoxazine
derivatives; rhodium complexes functioning not only as
tone modifiers but also as sources of halide ion for
silver halide formation in situ, such as ammonium
hexachlororhodate (I$I), rhodium bromide, rhodium nitrate
~ 2~ 3
-20-
and potassium hexachlororhodate (III); inorganic peroxides
and persulphates, e.g., ammonium peroxydisulphate and
hydrogen peroxide; benzoxazine-2,4-diones such as
1,3-benzoxazine-2,4-dione, 8-methyl-1,3-benzoxazine-2,4-
dione, and 6-nitro-1,3-benzoxazine-2,4-dione; pyrimidines
and asym-triazines, e.g., 2,4-dihydroxypyrimidine,
2-hydroxy-4-aminopyrimidine, and azauracil, and
tetrazapentalene derivatives, e.g, 3,6-dimercapto-1,4-
diphenyl-lH,4H-2,3a,5,6a-tetrazapentalene, and
1,4-di~o-chloro-phenyl)3,6-dimercapto-lH,4H-2,3a,5,6a-
tetrazapentalene.
A number of methods have been proposed for
obtaining color images with dry silver systems. Such
methods include incorporated coupler materials, e.g., a
combination of silver benzotriazole, well known magenta,
yellow and cyan dye-forming couplers, aminophenol
developing agents, a base release agent such as
guanidinium trichloroacetate and silver bromide in
poly(vinyl butyral); a combination of silver bromoiodide,
sulphonamidophenol reducing agent, silver behenate,
poly(vinyl butyral), an amine such as n-octadecylamine and
2-equivalent or 4-equivalent cyan, magenta or yellow dye-
forming couplers; incorporating leuco dye bases which
oxidize to form a dye image, e.g., Malachite Green,
Crystal Violet and pararosaniline; a combination of in
situ silver halide, silver behenate, 3-methyl-1-
phenylpyrazolone and N,N'-dimethyl-p-phenylenediamine
hydrochloride; incorporating phenolic leuco dye reducing
agents such as 2-~3,5-di-tert-butyl-4-hydroxyphenyl)-4,5-
diphenylimidazole, and bis(3,S-di-tert-butyl-4-
hydroxyphenyl)phenylmethane, incorporating azomethine dyes
or azo dye reducing agents; silver dye bleach process,
e.g., an element comprising silver behenate, behenic acid,
pGly~vinyl butyral), poly~vinyl-butyral)peptized silver
3S bromoiodide emulsion, 2,6-dichloro-4-
benzenesulphonamidophenol, 1,8-~3,6-diazaoctane)bis-
isothiuronium-p-toluene sulphonate and an azo dye was
` -21- 2~
exposed and heat processed to obtain a negative silver
image with a uniform distribution of dye which was
laminated to an acid activator sheet comprisinq
polyacrylic acid, thiourea and p-toluene sulphonic acid
and heated to obtain well defined positive dye images; and
incorporating amines such as aminoacetanilide ~yellow
dye-forming~, 3,3'-dimethoxybenzidine (blue dye-forming)
or sulphanilanilide (magenta dye forming) which react with
the oxidized form of incorporated reducinq agents such as
2,6-dichloro-4-benzene-sulphonamido-phenol to form dye
images. Neutral dye images can be obtained by the
addition of amines such as behenylamine and p-anisidine.
Leuco dye oxidation in such silver halide
systems are disclosed in U.S. Pat. Nos. 4,021,240,
4,374,821, 4,460,6Bl and 4,883,747.
Silver halide emulsions containing the
stabilizers of this invention can be protected further
against the additional production of fog and can be
stabilized against loss of sensitivity during keeping.
Suitable anti-foggants and stabilizers which can be used
alone or in combination, include the thiazolium salts
described in Staud, U.S. Pat. No. 2,131,038 and Allen U.s.
Pat. No. 2,694,716; the azaindenes described in Piper,
U.S. Pat. No. 2,886,437 and Heimbach, U.S. Pat. No.
2,444,605; the mercury salts described in Allen, U.S. Pat.
No. 2,728,663; the urazoles described in Anderson, U.S.
Pat. No. 3,287,135; the sulfocatechols described in
Kennard, U.S. Pat. No. 3,235,652; the oximes described in
Carrol et. al., British Patent No. 623,448; nitron;
nitroindazoles; the polyvalent metal salts described in
Jones, U.S. Pat. No. 2,839,405; the thiuronium salts
described by Herz, U.S. Pat. No. 3,220,839; and palladium,
platinum and gold salts described in Trivelli, U.S. Pat.
No. 2,566,263 and Damschroder, U.S. Pat. No. 2,597,915.
Stabilized emulsions of the invention can
contain plasticizers and lubricants such as polyalcohols,
e.g., glycerin and diols of the type described in Milton,
2~ ~?J~3
-22-
U.S. Pat. No. 2,960,404; fatty acids or esters such as
those described in Robins, U.S. Pat. NO . 2,5B8,765 and
Duane, U.s. Pat. No. 3,121,060; and silicone resins such
as those described in DuPont British Patent No. 955,061.
The photothermographic elements can include
image dye stabilizers. Such image dye stabilizers are
illustrated by U.K. Patent No. 1,326,BB9; Lestina et al.
U.S. Pat. Nos. 3,432,300 and 3,698,909; Stern et al. U.S.
Pat. No. 3,574,627; Brannock et al. U.S. Pat. No.
3,573,050; Arai et al. U.S. Pat. ~o. 3,764,337 and Smith
et al. U.S. Pat. No. 4,042,394.
Photothermographic elements containing emulsion
layers stabilized according to the present invention can
be used in photographic elements which contain light
absorbing materials and filter dyes such as those
described in Sawdey, U.S. Pat. No. 3,253,921; Gaspar U.S.
Pat. No. 2,274,782; Carroll et al., U.S. Pat. No.
2,527,583 and Van Campen, U.S. Pat. No. 2,956,879. If
desired, the dyes can be mordanted, for example, as
described in Milton and Jones, U.S. Pat. No. 3,282,699.
Photothermographic elements containing emulsion
layers stabilized as de~cribed herein can contain matting
agents such as starch, titanium dioxide, zinc oxide,
silica, polymeric beads including beads of the type
described in Jelley et al., U.S. Pat. No. 2,992,101 and
Lynn, U.S. Pat. No. 2,701,245.
Emulsions stabilized in accordance with this
invention can be used in photothermographic elements which
contain antistatic or conducting layers, such as layers
that comprise soluble salts, e.g., chlorides, nitrates,
etc., evaporated metal layers, ionic polymers such as
those described in Minsk, U.S. Pat. Nos. 2,861,056, and
3,206,312 or insoluble inorganic salts such as those
described in Trevoy, U.S. Pat. No. 3,428,451.
The binder may be selected from any of the well-
known natural or synthetic resins such as gelatin,
polyvinyl acetals, polyvinyl chloride, polyvinyl acetate,
. -; .
.
&~J
-23-
cellulose acetate, polyolefins, polyesters, polystyrene,
polyacrylonitrile, polycarbonates, and the like.
Copolymers and terpolymers are of course included in these
definitions. The preferred photothermographic silver
containing polymer is polyvinyl butyral, butethyl
cellulose, methacrylate copolymers, maleic anhydride ester
copGlymers, polystyrene, and butadiene-styrene copolymers.
Optionally these polymers may be used in
combination of two or more thereof. Such a polymer is
used in an amount sufficient to carry the components
dispersed therein, that is, within the effective range of
the action as the binder. The effective range can be
appropriately determined by one skilled in the art. As a
guide in the case of carrying at least an organic silver
salt, it can be said that a preferable ratio of the binder
to the organic silver salt ranges from 15:1 to 1:2, and
particularly from 8:1 to 1:1.
Photothermographic emulsions containing the
stabilizer of the invention can be coated on a wide
variety of supports. Typical supports include polyester
film, subbed polyester film, poly(ethylene
terephthalate)film, cellulose nitrate film, cellulose
ester film, polytvinyl acetal) film, polycarbonate film
and related or resinous materials, as well as glass, paper
metal and the like. Typically, a flexible support is
employed, especially a paper support, which can be
partially acetylated or coated with baryta and/or an
alphaolefin polymer, particularly a polymer of an
alpha-olefin containing 2 to 10 carbon atoms such as
polyethylene, polypropylene, ethylenebutene copolymers and
the like.
The substrate with backside resistive heating
layer may also be used in color photothermographic imaging
systems such as shown in U.S. Pat. No. 4,460,681 and
4,374,921.
Photothermographic emulsions of this invention
can be coated by various coating procedures including dip
2 ~3 ~ J ~q ~!
-24-
coating, air knife coating, curtain coating, or extrusion
coating using hoppers of the type descirbed in Benguin,
U.S. Pat. No. 2,681,294. If desired, two or more layers
may be coated simultaneously by the procedures described
in Russell, U.S. Pat~ No. 2,761,791 and Wynn sritish
Patent No. 837,095.
The present invention will be illustrated in
detail in reference to the following examples, but the
embodiment of the present invention is not limited
10 thereto.
Example 1
A dispersion of silver behenate half soap was
made at 10% solids in toluene and acetone by
homogenization. To 127g of this silver half soap
dispersion was added 252g methyl ethyl ketone, 104g
isopropyl alcohol and 0.5g of polyvinylbutyral. After 15
minutes of mixing, 4 ml of mercuric bromide (.36/10 ml
methanol) were added. Then 8.0 ml of calcium bromide
(.236g/lOml methanol) was added 30 minutes later. After
two hours of mixing, 27.0 g of polyvinylpyrrolidone was
added, and 27.0 g of polyvinylbutyral was added one hour
later.
To 32.1 g of the prepared cilver premix
described above was added 2.0 ~ll of the sensitizing dye A
(0.045g/SOml of methanol) shown below.
o
~ S C--N--GH2COOH-N(C2H5
A ~ N S S
C2Hs
After 20 minutes, a yellow color-forming leuco dye
solution was added as shown below.
2 ~ 2 ~ ~
-25-
Component Amount
Leuco Dye B 0 . 275 g
Tribenzylamine 0.24 g
5 Phthalazinone 0.1~ g
Tetrahydrofuran 6.0 ml
The leuco dye is disclosed in U.S. Pat. No. 4,883,747 and
has the following formula:
o
HllC6 J~ ~C6Hll
N N
,~
HO CH2
N(CH3)2
After sensitization with the dye and the addition of the
leuco base dye solution, Compounds I-A and I-B were added
in the amounts of 0.2 ml or 1.0 ml at a concentration of
O.lg/5 ml of methanol to a 9.9 g aliquot of the yellow
coating solution. The resulting solutions were coated
along with a solution not containing any stabilizer
precursor at a wet thickness of 3 mils and dried at 82C
in an oven for 5 minutes onto a vesicular polyester base.
30 A topcoat solution was coated at a wet thickness of 3 mils
over the ~ilver halide layer and dried at 82C in an oven
for 5 minutes. The topcoat solution consisted of 7%
polyvinyl alcohol in an approximate 50:50 mixture of water
and methanol and 0.2% phthalazine.
The samples were exposed for 10- 3 seconds
through a 47B Wratten filter and a 0 to 3 continuous wedge
and developed by heating to approximately 138C for 6
2o~1~,a.~
-26-
seconds. The density of the dye was measured using a blue
filter of a computer ~ensitometer. Post-processing
stability was measured by exposing imaged samples to 1200
ft-candles of illumination for 6 hours at 65~ relative
humidity and 26.7C. The initial sensitometric data are
shown below:
Dmin Dmax Speed~ Contrast2
Control (O.Oml) 0.13 2.47 1.99 5.54
lO 0.2 ml I-A 0.14 2.34 1.94 6.13
1.0 ml I-A 0.14 1.68 1.96 4.41
0.2 ml I-B 0.13 2.39 1.93 6.2S
1.0 ml I-~ 0.13 1.73 2.01 4.43
1 Log exposure corresponding to density of 0.6 above Dmin.
2 Average contrast measured by the slope of the line
joining density points 0.3 and 0.9 above Dmin.
The post-processing print stability results are shown
below:
~Dmin ~Dmax
Control (O.Oml) +0.53 -0.10
25 0.2 ml I-A +0.33 -0.13
1.0 ml I-A +0.26 -0.11
0.2 ml I-B +0.36 -0.10
1.0 ml I-B +0.25 -0.10
At the 0.2 ml addition of compound I-A or I-B, a greater
than 32% Dmin post-processing improvement vs. unstabilized
control was observed without any effect on initial
sensitometric responses.
35Example lA (Comparison)
To 9.9 g of the yellow silver halide coating
solution as described in Example 1 was added 0.5 ml or
2 a ~ 2 ~ 3
-27-
1.0 ml of 1-phenyl-5-mercapto-tetrazole ( PMT) at a
concentration of 0.1 g/5 ml methanol. The silver
solutions and topcoats were coated, exposed and procesed
as described in Example 1. The initial sensitometric data
are shown below.
Dm_n Dmax S~ed~ Contrast~
Control (0.0 ml) 0.13 2.30 2.03 4.94
0.5 ml PMT 0.13 1.72 2.15 4.06
10 Control (0.0 ml) 0.13 2.47 1.99 5.54
1.0 ml PMT 0.13 0.81 2.64 --
1Log exposure corresponding to density of 0.6 above Dmin.
2Average contrast measured by the slope of the line
joining density points 0.3 and 0.9 above Dmin.
The post-processing print stability was measured
as described in Example 1 and the results are shown below.
~Dmin ~Dmax
Control ~0.0 ml) +0.46 -0.20
0.5 ml PMT ~0.29 -0.14
Control (0.0 ml) +0.53 -0.10
25 1.0 ml PMT +0.25 -0.07
At these concentrations of PMT, significant
desensitization of the silver halide emulsion has occured
for post-processing Dmin improvement greater than 40%. In
Example 1, PMT was significantly blocked by the azlactone
group to minimize any desensitization effects but still
allowed the release of PMT for the Dmin post-processing
improvements observed in Example l-A with the unblocked
PMT stabilizer.
2~92~3
-28-
Example 2
To 9 . 9 9 of the yellow silver halide coating
solution as described in Example 1 was added 1.0 of
compound II-A at a concentration of 0.1 g/5 ml in
methanol. The silver solutions and topcoats were coated,
exposed, and processed as described in Example l. The
initial sensitometric data are shown below.
Dmin Dmax Speed contrast2
Control (0.0 ml) 0.12 2.22 1.84 4.52
1.0 ml II-A 0.11 2.26 1.79 4.94
1Log exposure corresponding to density of 0.6 above Dmin.
2Average contrast measured by the slope of the line
joining density points 0.3 and 0.9 above Dmin.
The post processing print stability was measured
as described in Example 1 and the results are shown below.
~ Dmin ~Dmax
Control (0.0 ml) +0.47 ~0.20
1.0 ml II-A +0.43 +0.11
With no effect on the initial sensitometric responses,
compound II-A improves the Dmin post-processing stability
approximately 10%. Thus, the compound II-A functions as a
post-processing stabilizer and will contribute to the
overall postprocessing Dmin improvement as the blocking
moiety to post-processing stabilizer precursors.
Example 3
To 9.9 g of a yellow silver halide solution
similar to Example 1, was added 0.2 ml or 0.5 ml of
compound I-E at a concentration of 0.2 9/5 ml of methanol.
A similar topcoat was coated over the yellow silver layer
,
.
-
29 2~ ~92~3
as described in Example 1. The coatings were exposed andprocessed as de~cribed in Example 1 and the initial
sensitometric data are shown below.
Dmin Dmax Speedl Contrast2
Control tO.0 ml) 0.11 2.46 1.77 5.09
0.2 ml I-E 0.13 2.41 1.77 4.77
0.5 ml I-E 0.15 2.25 1.79 3.50
10 ~ Log exposure corresponding to density of 0.6 above Dmin.
2Average contrast measured by the slope of the line
joining density points 0.3 and 0.9 above Dmin.
The post-processing results are shown below.
~Dmin ~Pmax
Control (0.0 ml) +0.48 -0.02
0.2 ml I-E +0.37 -0.03
0.5 ml I-E +0.26 -0.04
A 23% post-processing Dmin improvement was observed at the
0.2 ml addition of compound I-E without significant
effects on the initial sensitometric responses.
Example 4
A magenta color-forming silver halide dispersion
was prepared by using 502 g of the silver half soap
dispersion of Example 1 and adding 0.4 g of
polyvinylbutyral. After 15 minutes of mixing, a 0.5
g/9.75 g mercuric acetate in methanol solution and a
0.55g/18.4 g calcium bromide in methanol solution wee
added. Then an additional 0.55 g/18.4 g calcium bromide
in methanol solution was added 30 minutes later. After 45
minutes of mixing, 49.8 g of polyvinylbutyral was added.
_30_ 2~2~3
To 35.8 g of the prepared silver premix
described above was added 1.4 ml of the sensitizing dye C
(0.021 g/100 ml of methanol) shown below.
IH2 1 1CH3
CH2 C = CH - C C - S
C N
C2H4CO2H ~ ~ N
C2H~
After 30 minutes, a magenta color-forming leuco dye
solution was added as shown below.
Component Amount
Leuco Dye D 0.593 g
Phthalazinone 0.901 g
20 Tetrahydrofuran 47.6 g
VAGH (Union Carbide) 2.2 g
Polyvinylbutyral 10.2 g
The leuco dye i8 disclosed in U.S. Pat. No. 4,795,697 and
has the following formula.
~CO ~
~ ~ C2
CK~H3
A topcoat solution wa prepared consisting of 24.0%
polystyrene resin in approximately 52% tetrahydrofuran,
17% toluene, 2% acetone and 5% methanol.
- .
2 ~
--31--
To 10.0 9 of the magenta silver coatinq solution
was added 0.2 ml or 1.0 ml of compound I-C at a
concentration of 0.2 g/5 ml of methanol. The magenta
silver layer and topcoat are coated simultaneously at a
wet thickness of 2 mils, respectively and dried for 5
minutes at 82C.
The samples were exposed for 10 3 seconds
through a 58 Wratten filter and a 0 to 3 continuous wedge
and developed by heating to approximately 138C for 6
10 Seconds.
The density of the dye for each sample was
measured using a green filter of a computer densitometer.
Post-processing stability was measured by exposing imaged
samples to 1200 ft-candles of illumination for 7 hours at
15 65% relative humidity and 26.7C. The initial
sensitometric data are shown below.
Dmin Dmax Speed Contrast2
Control (0.0 ml) 0.11 1.76 2.032.12
20 0-2 ml I-C 0.11 1.74 2.04 2.16
1.0 ml I-C 0.12 1.12 2.83 1.38
1Log exposure corresponding to density of 0.6 above Dmin.
2Average contrast measured by the slope of the line
joining density points 0.3 and 0.9 above Dmin.
The post-processing print stability was measured and the
results are shown below.
~Dmin ~Dmax
Control (0.0 ml) ~0.19 -0.14
0.2 ml I-C +0.15 -0.12
1.0 ml I-C +0.08 -0.32
2 ~ ~ ~ 2 ~ ~
--32--
At a 0.2 ml addition of I-C, 21% Dmin post-processing
improvement was observed before the initial sensitometric
response was affected.
Example 4-A (Comparison)
To 10.0 g of the magenta silver halide coating
solution as described in Example 4, was added 0.35 ml or
1.0 ml of benzimidazole tsI) at a concentration of 0.1 g/5
ml of methanol. The silver solutions and topcoat were
coated, exposed, and processed as described in Example 4.
The initial sensitometric data are shown below.
Dmin Dmax Speed~ Contrast2
Control (0.0 ml) 0.09 1.71 1.96 1.87
0.35 ml BI 0.09 1.60 2.29 1.77
1.0 ml ~I 0.08 1.25 2.72 1.44
lLog exposure corresponding to density of 0.6 above Dmin.
2Average contrast measured by the slope of the line
joining density points 0.3 and 0.9 above Dmin.
The post-processing print stability was measured as
described in Example 4 and the results are shown below.
~Dmin ~Dmax
Control ~0.0 ml) +0.16 -0.22
0.35 ml BI +0.14 -0.27
1.0 ml BI +0.10 -0.31
At these concentrations of BI, significant
desensitization of the silver halide emulsion has occured
for the post-processing Dmin improvement of 12%. In
Example 4, BI was significantly blocked (0.2 ml) by the
azlactone group to minimize any desensitization effects
_33- 2~ 3
but still allowed the release of ~I for the Dmin
post-processing improvements observed in Example 4~A with
the unblocked LI stabilizer.
Example 5
A two color formulation was studied with
compound I-D. To 10.0 g of a yellow silver solution
similar to Example 1, was added 0.45 ml or 0.6 ml of
compound I-D at a concentration of 0.4 g/5 ml of ethanol.
A similar topcoat was coated over the yellow silver layer
as described in Example 1. In addition to the yellow
silver halide and topcoat layers, a magenta color-forming
silver halide layer and topcoat as described in Example 4
were coated simultaneously over the yellow topcoat. The
samples were exposed and processed as described in Example
1. The initial sensitometric data are shown below.
Dmin Dmax Speed~ Contrast2
Control (0.0 ml) 0.16 1.65 1.84 4.83
0.45 ml I-D 0.16 1.62 1.78 5.03
0.6 ml I-D 0.16 1.63 1.82 4.33
1Log exposure corresponding to density of 0.6 above Dmin.
2Average contrast measured by the slope of the line
joining density points 0.3 and 0.9 above Dmin.
The post-processing print stability was measured and the
results are shown below.
~Dmin ~Dmax
Control (0.0 ml) +0.53 +0.02
0.45 ml I-D +0.28 0
0.6 ml I-D +0.27 -0.02
-34-
At these concentrations, approximately a 50
Dmin post-processing improvement was observed with no
effect on the initial sensitometric responses.
Example 5-A ~Comparison~
To 10.0 g of the yellow silver halide coating
solution described in Example 5, ws added 1.0 ml of
3-trifluoromethyl-4-methyl-5-mercapto-1,2,4-triazole (MFT)
at a concentration of 0.2 g/4 ml of ethanol. The topcoat,
magenta silver and topcoat solutions were coated over the
yellow silver halide layer as described in Example 5. The
samples were exposed and processed as described in Example
1. The initial sensitometric data are shown below.
Dmin Dmax Speed Contrast2
Control (0.0 ml) 0.13 1.73 1.95 3.63
1.0 ml MFT 0.15 .63 -- --
~Log exposure corresponding to density of 0.6 above Dmin.
2Average contrast measured by the slope of the line
joining density points 0.3 and 0.9 above Dmin.
The post-processing print stability was measured and the
results are shown below.
~Dmin~Dmax
Control (0.0 ml) l0.51-0.02
1.0 ml MFT l0.24 --
At this concentration of MFT, significant
desensitization of the silver halide emulsion has occured
for the Dmin post-processing improvement of 53%. In
Example 5, MFT was blocked by the azlactone group to
minimize any desensitization effects but still allowed the
release of MFT for the Dmin post-processing improvements
observed in Example 5-A with the unblocked MFT stabilizer.
.............. ..
