Note: Descriptions are shown in the official language in which they were submitted.
~045~378
Background of the Invention
.
Field of the Invention
This invention relates to certain stabilizer pre-
cursor combinations in photothermographic elements, com-
positions and processes to provide improved stable images.
In one of its aspec-ts it relates to a heat stabilizable
photothermographic element comprising photosensitive sil-
ver halide and a stabilizer precursor combination as des-
cribed. In another of its aspects it relates to a photo-
thermographic omposition comprising the described stab-
ilizer precusor combination. A further aspect relates
to a method of stabilizing an image in a photothermo-
graphic element comprising photosensitive silver halide
and a stabilizer precursor combination as described by
overall heating the exposed photothermographic element.
Description of the State of the Art
It is known to ~btain an image in a photosensitive
element by so-called dry processing with heat. The
photothermographic element empIoyedfor providing such an
image can contain a reducing agent, a light-insensitive
silver salt of an organic acid, such as silver behenate,
as an oxidizing agent and a low concentration of photo-
graphic silver halide. Such photothermographic elements
are described, for example, in U.S. Patent 3,457,075 of
Morgan et al, issued July 22, 1969; U.S. Patent 3,152,904
of Sorensen et al, issued October 13, 1964; British
Specification 1,161,777 published August 20, 1969; U.S.
Patent 3,707,377 of Tiers et al, issued December 26, 1972
and in Research Disclosure, January, 1973, pages 16-21.
In a photothermographic material one of the-;~main
difficulties involves post-processing stability. Because
heat developable photographic elements are suitable for
so-called
- 2 -
.
,
109~S878
dry processing with heat and are designed to eliminate
a fixing step which normally would remove undeveloped
silver, it is necessary that a means be provided for
post-processing stabilization to enable room-light
handling.
Several means have been proposed to answer the need
for post-processing stability of photothermographic
elements, such as (1) washing with water to remove undev-
eloped silver salts, (2) heating to release Bronstead or
Lewis acid such as HCl, fluoride or HF from incorporated
compounds such as m-nitrobenzenesulfonylchloride, para-
toluene sulfonic acid urea addition complex or ~-acetami-
dobenzenediazonium fluoroborate and (3)chelation of the
oxidizing agent with for example, salicylaldoxime or be~-
otriazole as described in U.S. Patent 3,152,904 of
Sorensen et al, issued October 13, 1964. Another method
proposed for solving the porblem of post-processing
instability is to provide a photothermographic combination
is on one sheet of material and the latent image formi~
photographic silver halide is on a separate sheet. The
sheets are separated after exposure such as described in
U.S. Patent 3,152,904. A futher means proposed for stab-
ilization involves swabbing a 1% solution of phenylmer-
captotetrazole onto the surface of the overall heated
photothermographic material or rubbing benzotriazole into
the surface of the coating. These proposed means for
stabilization are not useful for large volume handling
of heat developable photographic materials.
It has also been proposed to provide stabilized
images in heat developable materials by treating the dev- -
eloped image with a soluti~ containing certain thiol or
thione compound stabilizers. This is described, for
example, in U.S. Patent 3,617,289 of Ohkubo et al, issued ~ ~
NOvember 2, 1971. One of the compounds proposed for this `
solution stabilization is
. . . ' . ' ' - ' ', :- " ~ ' "' ',.,, ~. . '
,: : - , ` . : :: ... . :
- . : . . . .... . . .:: .
.
45878
l-phenyl-5-mercaptotetrazole. Unfortunately, the addition of
this compound to photographic silver compositions provides
undesired desensitization at concentrations which produce
stabilization and toning of a developed image.
Another means of stabilization of an image in a
photothermographic material is described in Belgian
Patent 768,071 published Julvv 30, 1971. Certain stabilizer
precursors which are azole thioethers or blocked azolinethiones
are employed in photothermographic materials according to ;~
the description in this patent. An example of a stabilizer
precursor proposed in photothermographic materials is
5-methoxycarbonylthio-1-phenyltetrazole. Unfortunately,
this compound does not always provide the desired increased
stability of a heat developed image.
Another means for post-processing stabili%ation of
certain photothermographic materials is described in U.S.
Patent 3,707,377 of Tiers et al, issued December 26, 1972.
Certain polyhalogenated organic oxidizing agents, such as
tetrabromobutane, are described in certain heat developable
photographic materials to provide post-processing stabilization.
As illustrated in the following comparative examples, certain
combinations of compounds can provide surprisingl~ improved
stabilization without the adverse sensitometric effects which
may be observed with certain polyhalogenated organic oxidizing
agents.
Halogenated organic compounds have been emplo~ed in
photographic materials for various purposes, such as antifoggants.
Monohalogenated organic antifoggants for photographic emulsions
10451~78
dre described, for example, in U.S. Patent 3,128,187 of
Sagal et al, issued April 7, 1964; U.S. Patent 3,232,762
of Ford et al, issued February 1, 1966; U.S. Patent
2,732,303 of Morgan et al, issued January 24,1956; U.S.
Patent 2,835,581 of Tinker et al, issued May 20, 1958
and U.S. Patent 3,271,154 o~ Dersch, issued September
6, 1966. None of these patents, however, indicate that
certain combinations of stabilizer:precursors can be em-
ployed in photothermographic materials to p~ovide im-
proved post-processing stability.
Also, while various 5-mercaptotetrazole compounds
are known in photographic materials for vario~spurpose
such as, known in photographic materials for various
purposes, such as descri'bed in British Patent 1,238,928
published July 14, 1971, and other of the described
patents, none of the art suggests a useful solution to
the continuing need for improved heat-developable, thicne(-
compound containing, photographic materials providing
improved post-processing stability.
Accordingly, there has been a continuing need for
heat-developable photographic materials, especially ph~o-
thermographic materials comprising an image-forming com-
bination containing a silver salt oxidizing agent, such
as silver behenate, with a reducing agent, and photo-
sensitive silver halide, which have improved post-pro-
cissing image stability, that is reduced background
density and more desired image tone, when employing
a combination of stabilizer precursors.
Summary of the Invention
The described improvements are provided in a photo-
thermographic element or composition by~employing as astabilizer precursor, a $tabilizer PreCursor combination
of (a) a blocked thione stabilizer precursor with (b) a
halogen containing stabilizer precursor. This stabilizer
precursor combination is especially useful ln a photo-
~ ' .
.
1045878
thermographic material comprising phtosensitive silver
halide and an oxidation-reduction
.
~ .
~ ' ' ,.:
: ~ :
104587~3
image-forming combination comprising (i) a heavy metal
silver salt oxidizing agent, such as silver behenate -
and silver stearate, with (ii) a reducing agent.
The described improvements are provided, for
example, in a photothermographic element comprising
a support having thereon a layer comprising (A) photo-
sensitive silver halide in association with (B) an oxi-
dation-reduction image-forrning comb~nation comprising
(i) a silver aalt of a long-chain fatty acid, such as
a silver behenate and silver stearate with, (ii) an
organic reducing agent, such as a sulfonamidophenol
reducing agent, (C) a polymeric binder for the described
layer, such as poly(vinyl butyral) and(D) a stabilizer
precursor combination of (a) a blocked thione stabilizer -
precursor as described herein with (b) a halogen con-
taining stabilizer precursor, also as described herein.
Detailed Description of the Invention
A variety of blocked thione stabilizer precursors
can be emplyed in the practice of the invention to pro-
vide improved post-processi~g stability without adversely
affecting desired properties of the heat-developable
photographic material.
A blocked thione stabilizer precrusor as employed
herein is intended to mean a thione compound which con-
tains a group or moiety which blocks or prevents the
thione compound from reacting with silver ions in the
photothermographic material prior to heating the photo-
thermographic material. While the exact mechanism of
stabilization according to the invention is not fully
understood, it is believed that the blocked thione as-
described remains in a state which does not adversely
affect the photothermographic material containing the
blocked thione prior to heating. Upon heating, it is
believed that thione compound is changed from its bloc~ed
state tola state which enables reaction with silver -
ions in the unexposed areas of
:. . . . , . . . , i : . . . ................................... ...
.- . . . . . ~ . .. .
1045878
the photothermographic material to form a stable silver
mercaptide in the unexposed areas. This is believed to
prevent undesired decreased stability to room-light ex-
posure.
A test c~n be used to determine whether or not a
thione compound is a useful blocked thione image stabi-
lizer precursor as described. While different tests
can be employed to determine useful image stabilizer
percursors depending upon the particular photothermogra-
phic element and composition, desired image, processing
conditions and the like, one test which can be employed
for certain photothermographic elements is described in
following Example 4. The compound tested in the described
combination, after incorporation with the described
halogen containing compound in the photothermographic
element and after imagewise exposure and overall heating
of the element as described in Example 1, should pre-
vent the buildup of background density or minimum den-
sity above O.10 density unit more than the original
minmum density without undesired stain and without sig-
ni~icantly adversely affecting maximum density.
One class of especially useful blocked thione
stabilizer precursors is a 4-aryl-1-carbamoyl-2-tetrazo-
line-5~ thione represented by the formula:
N N - C ,- NH R
~ R I n
wherein R is aryl, sùch as aryl containing 6 to 12
carbon atoms, including phenyl and naphthyl; and nl i~
alkyl containing l to 12 carbon atoms, such as methyl,
propyl, butyl and hexyl, aryl, such as aryl containing
6 to 12 carbon
1~45878
atoms, includin~ phenyl and naphthyl, cycloalkyl containing
3 to 8 carbon atoms, such as cyclohexyl and cyclopropyl,
when n is 1, or alkylene containing 1 to 10 carbon atoms
when n is 2, such as alkylene containing 1 to 6 carbon atoms
including methylene and ethylene; and n is 1 or 2. These
blocked thione stabilizer precursors are described in
U.S. Patent 3,893,859 of D~ M. Burness et al, issued
July 8, 1975.
Useful blocked thione stabilizer precursors within
the described formula (I) include, for instance:
4-phenyl-1-phenylcarbamoyl-2-tetrazoline-5-thione,
l-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thione,
l-methylcarbamoyl-4-phenyl-2-tetrazoline-5-thione,
4-hexylcarbamoyl-1-phenyl-2-tetrazoline-5-thione,
N,N-hexamethylenebis(l-carbamoyl-4-phenyl-2-
tetrazoline-5-thione),
4-butylcarbamoyl-1-phenyl-2-tetrazoline-5-thione, and
di-2-(1-phenyl-5-thione-2-tetrazolin-4-ylcarbonylamino-
ethyl fumarate.
Other useful classes of blocked stabilizer precursors
are described, for example, in Belgian Patent 768,071
published July 30, 1971. Useful blocked thione and blocked ~:
thiol stabilizer precursors within these classes are:
5-Acetyl-2-benzoylthio-4-methylthiazole,
4-Benzoylmethyl-2-benzoylthiothiazole,
2-(2-~uroylthio)-4-hydroxymethylthiazole, ~ -
2-Benzoylthio-4-hydroxymethylthiazole,
2-Benzoylthio-4-tert.-butylthiazole,
5-Carbethoxy-4-methyl-2-(3-oxobutylthio)thiazole,
5-Acetyl-2-(2-benzoylethylthio)-4-methylthiazole,
,.
., .' :,
1~4S878
2-(3-Oxobutylthio)thiazole,
4,5-Dimethyl-2-(3-oxobutylthio)thiazole,
2-(3-Oxobutylthio)-4-phenylthiazole,
4-Carboxy-2-(3-oxobutylthio)thiazole,
4-Carboethoxy-2-(3-oxobutylthio)thiazole,
4-(4-Methoxyphenyl)-2-(3-oxobutylthio)thiazole,
4-(4-Methoxyphenyl)-2-(3-oxobutylthio)thiazole, ~ -
4-(4-Nitrophenyl)-2-(3-oxobutylthio)thiazole,
4-Tert.-butyl-2-(3-oxobutylthio) thiazole,
5-Acetyl-4-methyl-2-(3-oxobutylthio)thiazole,
5-Acetyl-2-furoylthio-4-methylthiazole,
4-Furoyl-3-(3-oxobutylthio)1,2,4-thiadiazoline-5-
thione,
3-Methylthio-4-benzoyl-1,2,4-thiadiazoline-5-thione, :
4-Acetyl-3-methylthio-1,2,4-thiadiazoline-5-thione, :~
4-Acetyl-3-furoylethylthio-1,2,4-thiadiazoline-5-
thione,
4-Furoyl-3-methylthio-1,2,4-thiadiazoline-5-thione, ~ ~:
5~(~enzoylethylthio)-]-phenyltetrazole,
5-(2-Acetylethylthio)-l-phenyltetrazole,
5-Methoxycarbonylthio-l-phenyltetrazole,
5-(4-Nitrobenzyloxycarbonylthio)phenyltetrazole,
5-(Ethoxycarbonylthio-l-phenyltetrazole
5-Benzoylthio-l-phenyltetrazole, ~. .
5-Acetyl-3-benzoyl-4-methylthiazoline-2-thione,
4-Benzoylmethyl-3-benzoylthiazoline-2-thione
3-Furoyl-4-hydroxymethylthiazoline-2-thione,
3-Benzoyl-4-hydroxymethylthiazoline-2-thione,
3-Benzoyl-4-tert.-butylthiazoline-2-thione, and
5-Carboethoxy-4-methyl-3-(3-oxobutyl)-thiazoline-
2-thione
The listed compounds have also in some cases been known
as azole thioethers and blocked azolinethiones. These
compounds can be prepared by methods known in the art
For example, they can be prepared by the Michael addition
of alpha,
_ 9 _ ' :,, .
.. : , : . :
- lO~S878
beta-uns~turated ketones such as methyl vinyl ketone to
4-thiazonline-2-thione. This is descrived in the Journal
of Heterocyclic Chemistry, 6, pages 397-401 (1969) by
Humphlett.
The blocked thione stabilizer precursors which are
tetrazoline-5-thione compounds can be prepared by reacting
l-phenyl-2-tetrazoline-5-thione in a suitable solvent in
the presence of a catalyst such as heptamethylisobigua-
nide, with a suitable isocyanate compound. The prepara-
tion of l-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-
thione is typical of a useful preparation. It is pre-
ferred that the resulting product be purified such as by
treatment with solvents and other typical purification
~ means.
- A variety of halogen containing stabilizer precur~r
can be employed accord~ng to the invention to prdvide im-
proved post-processing stability without adversely affect-
ing desired properties of the photothermographic material.
A test can be emplyed to determine useful halogen
containing compounds or materials such as described in
the following example 4. In this test, the halogen com-
pound, after incorporation with the described blocked
thione compound in the photothermographic element and
after imagewise exposure and overall heating of the ele
ment as described in Example 4, should prevent buildup
of background density or minimum density above 0.10
density unit more than the original minimum density
without undesired stain and without significantly advers-
ely affecting maximum density.
It is believed that the describ-ed halogen containing
stabilizer precursors are precursors to the moiety, com-
pound or material which, is formed upon heating and com-
bines with silver ions or atoms to prevent undesired in- - -
stability due to room-light exposure. However, the exact
' ~ - 10 - ,. . ..
,
. .: - . . , . . . .: .
~ 1045878
mechanism of stabilization is not fully understood.
The stabilizer precursors according to
~ ' ' ' ' ~ '
, .
.
' . . .. ...
';
~ ;'''.,'
- lOa -
1045878
the invention are compounds which do not prevent a redox reaction
upon imagewise exposure o~ the descri~ed photothermographic
materials. :-
One class of useful halogen containing stabilizer
precursors according to the invention comprises a compound repre-
sented by the formula:
: 3
R - C - X
: l4
R
: - 2 3 4
~herein X is chloro, bromo or iodo; R , R and R are individually
selected from the group consisting or hydrogen; alkyl, such as
alkyl containing 1 to 10 carbon atoms including methyl, ethyl,
propy~ or octyl; hydroxyalkyl, such as hydroxyalkyl containing 1
to 10 carbon atoms, including hydroxymethyl, hydroxyethyl and
hydroxyhexyl; acyloxyalkyl, such as acyloxyalkyl containing 2 to
10 carbon atoms; nitro; nitroalkyl, such as nitroalkyl contain~ng
1 to 10 carbon atoms; mm~uding nitromethyl, nitroethyl and
nitropropyl; aryl, such as aryl containing 6 to 12 carbon atoms,
including phenyl and naphthyl; acyl, such as acyl of the formula
R"-CO-wherein R" is alkyl containing 1 to 5 carbon atoms including
me~hyl, ethyl, propyl and butyl, or aryl containing 6 to 12
carbon atoms, such as phenyl and naphthyl; amido, such as amido
represènted by the formula .: :
R ~ O ~ :
~ N-C .~:
; R
7 8
wherein R and R individually selected from the group consis.tin~
of hydrogen, alkyl containing 1 to 5 carbon atoms, such as methyl, .
ethyl and propyl, phenyl and naphthyl; sulfonyl represented by .
9 9
the formula R - SO - wherein R is alkyl con.~aining 1 to 5 -
carbon atoms, such as methyl, ethyl and propyl or aryl, such as
aryl containing 6 to 12 carbon atoms, such as phenyl, .:
-
- 11 -
: . .
1~45878
napthyl or tolyl; bromo; chloro; and iodo; and wherein ~:
at least one of R , R , and R is hydroxyalkyl, acylox-
yalkyl, acyl, amido or sulfonyl as defined. Alkyl, aryl,
hydroxyalkyl, acyloxyalkyl, acyl, amido and sulfonyl as
employed herein include substituents on the defined grcups
which do not adversely affect stabilization or desired
properties of photothermographic materials according to
the invention. Suitable substituents include, for example, .
chloro, bromo, methoxy, phenyl, hydroxy, nitro and the
like.
Another class of useful stabilizer precursors accord-
ing to the--invention comprises a monohalogentaed organic
compound having at least one carbonyl or sulfonyl group
bonded to the carbon atom having the halogen substitu~nt,
such as an alpha-monohaloketone represented by the for-
mula: 5 6
R - CH - C - R
..
X O
wherein X is chloro, bromo or iodo; R is hydrogen, alkyl
containing 1 to 10 carbon atoms, such as methyl,ethyl,
propyl,butyl, ~pentyl or octyl, acyl containing 1 to 5
carbon atoms, such as acetyl and CH3CH2CO-, sulfamyl and
aryl containing 6 to 12 carbon atoms, such as phenyl and `
naphthyl; R is amino, alkyl containing 1 to 10 carbon
atoms, as described, and aryl containing 6 to 12 carbon
atoms, such as phenyl and naphthyl. The described sub-
stituent groups onthe alpha-monohaloketone compounds can
contain substituents which do not adversely affect the
stabilizing action of the alpha-monohaloketone, such as
methyl, ethyl and the like. ~::
Useful halogenated organic compound stabilizer pre ~ ~.
cursors within the described classes include the follow-
ing compounds: :
~-bromo-2,5-dimethoxyacetophenone
~-bromo-~- nitrol-~- phenylbutyrophenone
~2 ~:
. , . . ~. .
..
1~45878
2-bromo-2-~-tolylsulfonylacetamide
~-iodo-~~nitro-l)-phenylbutyrophenone
- 12a -
~ " '
-
lO~S878
a-bromo-_-nitrotoluene
2-bromo-4'-phenylacetophenone
2-chloro-4'-phenylacetophenone
Q-bromo-m-nitrotoluene
2-bromo-2-nitro-1,3-propanediol
1,3-dibenzoyloxy-2-bromo-2-nitropropane
2,2-dibromo-2-phenylsulfonylacetamide
2-bromo-2-~~tolylsulfonylacetamide
2-bromoacetophenone
~-chloro-~-nitrotoluene
2-bromo-2-phenylacetophenone
2-bromc-1,3-diphenyl-1,3-propanedione
tetrabromobutane
hexabromocyclohexane
hexabromoethane
2-tribromonethylsulfonylbenzothiazole
2-bromo-2-nitro-1,3-di-(4-nitrobenzoyloxy)propane --
2-bromo-1,3-di-(4-methoxybenzoyloxy)-2-nitropropane
The described halogen containing organic stabilizer
precursors can be prepared by methods known in the art.
For example, the parent organic compound can be halogen-
ated employing, for example, bromine or chlorine. The -~
resulting halogenated compounds can be purified empl~ing
purification procedures known in the art. Some organic ~:~
compound impurities can be present in the resulting com-
position. In some cases it is necessary to separate the
organic compound impurities before mixing the halogenated
organic stabilizer precursors with the described photo-
thermographic materials.
The useful concentration of the combination of stab-
ilizer precursors according to the invention will depend
upon different factors such as the particular photothermo-
graphic
- 13 -
.
.. .. .
1045878
element, processing temperatures, particular components
of the photographic element, desired image and the like.
A useful concentration of the combination of stab-
ilizer precursors according to the invention is (a) about
0.00~ to about 0.035 mole of the described blocked thione
stabilizer precursor per mole of total silver with (b)
about ô.OOl to about 1.0 mole of the described;,halogen
containing stabilizer precursor per mole of total silver
in the describ~ photothermographic material. The optimum
concentration useful can be determined based on the des
cribed factors.
The described halogen stabilizer precursors are also
observed to provide desired, incubation antifoggant acti-
vity in photothermographic materials according to the ~ -
invention at a concentration within the range of about
0.001 mole to about 0.025 mole of the described halogen
stabilizer precursor per mole of total silver in the
photothermographic material. The optimum concentration
of the halogen stabilizer precursor for incubation anti-
foggant activity will depend upon such factors as the
particular halogen compound, the particular photothermo-
graphic material, desired image and the like.
Typical photothermographic elements in which the
stabilizer precursor combination of the invention is use-
ful are described, for example, in U.S. Patent 3,457,075
of Morgan et al, issued July 22, 1969; U.S. Patent 3,152,
904 of Sorensen et al, issued October 13, 1964; U.S.
Patent 3,429,706 of Shepard et al, issued February 25,
1969; U.S. Patent 3,672,904 of deMauriac, issued June
27, 1972 and Research Disclosure, January, 1973, pages
16-21.
The stabilizer precursor combination of the inven-
tion is especially useful in photothermographic materials
comprising
- 14 -
, . , , . , , , , ~ , . . . . . . . . . .
- . , : : ,, , . .. . . :: : ~ - .... . ::: ..
1045878
photosensitive silver halide in association with an oxi-
dation-reduction irnage-forming combination comprising
(i) silver behenate, with (ii) a phenolic reducing agent,
such as a sulfonamidophenol reducing agent, a poly (viryl
butyral) binder, a spectral sensitizing dye, and a toning
agent (also known as an activator-toning agent) comprising
succinimide, N-hydroxynaphthalimide or phthalazinone.
Such a photothermographic material is described, for ex-
ample, in Research Disclosure, January, 1973, pages
16-21.
An especially useful embodiment of the invention
is a photothermographic element comprising a support
having thereon a layer comprising (a) photosensitive sil-
ver halide in association with (b) an oxidation-reduction
image-forming combination comprising (i) silver behene-
nate, with (ii) a phenolic reducing agent, such as a
sulfonamidophenol reducing agent, (c) a poly (vinyl but-
yral)binder, (d) a spectral sensitizing dye, (e) a toning ~ :
agent, such as succinimide or N-hydroxy-1,8-naphthalimide,
and a stabilizer precursor combination comprising (f)
l-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-5-thione
with (g) a halogen containing stabilizer precursor sel-
ected from tetrabromobutane,~ -bromo-gamma-nitro-~
phenylbutyrophenone, 2-bromo-2-~-tolylsulfonylacetamide, ~,
2-tribromomethylsulfonyl-benzothiazole, 2,2-dibromo-2-
phenylsulfonylacetamide, 1,3-dibenzoyloxy-2-bromo-2-
nitropropane, 2-bromo-2-nitro-1,3-propanediol and combin-
ations thereof.
The described photographic materials according to
the invention comprise a photosensitive component which
comprises photosensitive silver halide. In the photo-
thermographic materials comprising the described oxida-
tion-reduction image-forming combination, it is believed
that the photosensitive silver halide or a component re
sulting--from the photosensitive silver halide acts as a
catalyst for the described oxidation-reduction image-
- 15 -
.''~
: - , ;~, : :,:: .
- . - : : ~. :,~ : .
: . . . .
1045878
forming combination. A typical concentration range of
photosensitive silver halide is from about 0.01 mole
to about 20.0 moles of photosensitive silver halide per
mole of heavy metal salt oxidizing agent, for example,
per mole of silver salt oxidizing agent. Other photo~
sensitive components can be useful in combination with
photosensitive silver halide. Useful photosensitive sil-
ver salts include silver-dye complexes and other photo-
sensitive silver salts. Preferred photosensitive silver
halides are silver chloride, silver bromide, silver "~
bromoiodide, silver chlorobromoiodide or mixtures there-
of. Very fine-grain photosensitive silver halide is
especially useful although coarse or fine-grain photo-
sensitive silver halide can be employed if desired.iThe
photosensitive silver halide can be prepared by any of
the proàedures known in the photographic art. Such
procedures and forms of photosensitive silver halide
are described, for example, in the Product Licensing
Index, Volume 92~,~ December, 1971, publication 9232 at
page 107, paragraph I. The photosensitive silver halide
according to the invention can be unwashed or washed,
can be chemically sensitized, can be protected a~ainst
the production of fog and and stabilized again$t loss of
sensitivi~ty during keeping, as described in the Product
Licensing Index, Voiume 92, December, 1971, publication
9232, pages 107-110.
The photothermographic elements and compositions
according to the invention typically comprise an oxida-
tion-reduction image-forming combination which contains
an oxidizing agent, preferably a heavy metal salt oxidi-
zing agent. The heavy heavy metal salt oxidizing agent
can be a heavy metal salt of an organic acid such as a
fatty acid which is resistant to darkening upon illumin-
ation. An especially useful class of heavy metal salts
of organic acids is represented by the water insolub~e -
silver salts of long-chain fatty acids which are
- 16 -
: . - : . . :
-- 104S878
stable to light. Compounds which are suitable silver ;
slat oxidizing agent include: silver behenate, silver
stearate, silver oleate, silver laurate, silver hydroxy-
stearate, silver caparate, silver myristate and silver
palmitate. Silver salts can be employed as the heavy
metal salt oxidizing agent which are not silver salts of
long-chain fatty acids. Such silver salt oxidizing
agents which are useful include, for example, silver
benzoate, silver benzotriazole, silver terephthalate,
silver phthalate and the like.
The described photothermographic elements a~d com-
positions can comprise various reducing agents. Suitable
reducing agents which can be employed with the described
stabilizer precursors include substituted phenols and
naphthole, for example, bis-beta-napthols. Suitable bis-
beta-naphthols include, for exampl~e,2,2'-dihydroxy-1,1'
binaphthyl,6,6'-dibromo-2,2'-dihydroxy-1,1'-binaphthyl,
6,6'-dinitro-2,2'-dihydroxy-1,1'-binaphthyl and bis-
(2-hydroxy-1-maphthyl)methane. Other reducing agents
which can be employed in photothermographic elements,
according to the invention, include polyhydroxybenzenes
such as hydroquinone, alkyl-substituted hydroquinones
such as tertiary butylhydroquinone, methyl-hydroquinone,
2,5-dimethylhydroquinone and 2,6-dimethylhydro-quinone;
catechols and pyrogallols, chloro-substituted hydro-
quinones such as chlorohydroquinone or dichlorohydroqui-
none;alkoxy-substituted hydroquinone such as methoxyhy-
droquinone or ethoxyhydroquinone; aminophenol devel~ping
agents, such as 2,4-diaminophenols and methylaminophenols;
ascorbic acid developing agents such as ascorbic acid,
ascorbic acid ketals and ascorbic acid derivatives; hy-
droxylamine developing agents; 3-pyrazolidone developing
agents such as l-phenyl-3pyrazolidone and 4-methyl-4-
hydroxymethyl-l-phenyl-3-pyrazolidone and the like. Com-
binations of reducing agents can be employed if desired.
- 17 -
:
- ~ - ' , ' , . ' ~ :.,:
lQ~5878
Especially useful reducing agents which can be
employed in the photothermographic materials according to the
invention are sulfonamidophenol reducing agents as described
in Research Disclosure~ January, 1973, pages 16-21. One
especially useful class of sulfonamidophenol reducing agents
is represented by the formula:
OH
8 ~ R7
NHSO2-R
wherein R is phenyl, naphthyl, methylphenyl, thienyl,
quinolinyl, thiazyl, or alkyl containing 1 to 4 carbon atoms,
such as methyl, ethyl, propyl or butyl; R7 is hydrogen,
R SO2NH-, alkoxy containing 1 to 4 carbon atoms, such as
methoxy, ethoxy, propoxy and butoxy, bromo or chloro;
R is hydrogen, bromo, chloro, alkyl containing 1 to 4 carbon
atoms, as described, or alkoxy containing 1 to 4 carbon atoms~
such as methoxy~ ethoxy and propoxy. R7, R8 and/or R9 can
contain substituent groups which do not adversely affect the
reducing properties of the described sulfonamidophenol reducing
agents or the desired sensitometric properties of the photo-
thermographic elements and materials of the lnvention. Examples
of substituent groups which can be present are alkyl containing
1 to 3 carbon atoms such as methyl, ethyl and propyl, chloro,
bromo and phenyl. In some cases, it is desirable to avoid an
amino group as a substituent. The amino group, in some cases,
provides an overly active reducing agent. 5ulfonamidophenol
reducing agents, as described, include sulfonamidonaphthols.
A sulfonamidonaphthol which is useful is represented by the
formula:
OH
NNSO~
-18-
104S878
The sulfonamido group in the described sulfonamidonaphthols can
be in the two, three, or four position. The sulfonamidonaphthols
and sulfonamidophenols which contain two sulfonamido groups
are more active compounds within the sulfonamido reducing agent
class. The sulfonamidophenols containing two or more sulfon-
amido groups are employed for shorter developing times or with
heavy metal salt oxidizing agents which are less active than
silver behenate. In some cases, image~:discrimination provided
by photothermographic materials containing the sulfonamido-
naphthols and trifunctional suIfonamidophenols is less than
that provided by other of the described sulfonamidophenols.
It is desirable, in some cases, to employ a so-called -
toning agent, also known as an accelerator-toning agent or
activator-toning agent, in the photothermographic materials
of the invention. Useful toning agents are described, for
example, in Belgian Patent 766,590 issued June 15, 1971 and
in Research Disclosure~ January~ 1973, pages 16-21. Combinations
of toning agents can be employed in the photothermographic
materials according to the invention if desired. Typical
toning agents include, for example, phthalimide, 2,3-
naphthalimide, N-hydroxyphthalimide, N-potassium phthalimide, -
succinimide, N-hydroxy-1,8-naphthalimide and/or N-hydroxy-
succinimide. In some cases~ other toning agents can be
employed such as 1-(2H)-phthalazinone and 2-acetylphthalazinone
and the like.
A photothermographic element or composition as
described according to the invention can contain various -
colloids alone or ln combination as vehicles~ binding agents
and in various layers. Suitable materials can be hydrophobic
or hydrophilic. They are transparent or translucent and
include both naturally-occurring substances such as proteins,
for example, gelatin, gelatin derivatives, cellulose derivatives,
1 9
.. , . . ~ . ..
lV45878
polysaccharides such as dextran, gum arabic and the like; and
synthetic polymeric substances such as water soluble polyvinyl
compounds like poly(vinylpyrrolidone), acrylamide polymers
and the like. Other synthetic polymeric compounds which can be
employed include dispersed vinyl compounds such as in latex
form and particularly those which increase dimensional stability
of photographic materials. Effective polymers include water-
insoluble polymers of alkyl acrylates and methacrylates,
acrylic acid, sulfoalkyl acrylates, methacrylates and those
which have crosslinking sites which facilitate hardening or
curing as well as those have recurring sulfobetaine units
as described in Canadian Patent 774,054. Especially useful
high molecular weight materials and resins include poly(vinyl
butyral), cellulose acetate butyrate, poly(methyl methacrylate~,
poly(vinylpyrrolidone), ethylcellulose, polystyrene, poly(vinyl
chloride), chlorinated rubber, polyisobutyleDe, butadiene-
styrene copolymers vinyl chloride-vinyl acetate copolymers,
copolymers of vinyl acetate, vinyl chloride and maleic acid
and poly(vinyl alcbhol).
The useful concentration of reducing agent according
to the invention will vary depending upon the particular ~-
photographic element, desired image, processing conditions,
particular stabilizer precursor combination employed and the like.
A suseful concentration of reducing agent is typically from
about 0,2 mole to about 2.0 moles of reducing agent per mole
of photosensitive silver halide. A suseful concentration
of reducing agent in relationship to oxidizing agent, such as
silver behenate or silver stearate, is typically from about
0.01 mole to about 20 moles of reducing agent per mole of
oxidizing agent such as per mole of silver behenate in the
photothermographic material. Combinations of reducing agents can
be employed if desired. When combinations are employed, the
total concentration of reducing agent is typically within the
' ' '
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. : :
. . .. .
1045878
described concentration range.
Pho~othenmographic materials according to the invention
can contain development modifiers that function as speed-
increasing compounds, hardeners, antistatic layers, plasticizers
and lubricants, coating aids, brighteners, spectral sensitizing
dyec, absorbing and filter dyes, also as described in the
Product Licensin~ Index, Volume 92, December, 1971J publication
9232, pages 107-110.
The photothermographic elements according to the
invention can comprise a wide variety of supports. Typical
supports include cellulose nitrate film, cellulose ester film,
poly(vinyl acetal) film, polystyrene film, poly(ethylene -
terephthalate) film, polycarbonate film and related films or
resinous materials, as well as glass " paper, metal and the like.
The support chosen should withstand the processing temperatures
employed according to the invention. Typically, a flexible
support is employed.
The photothermographic compositions and other
compositions according to the invention can be coated on a
suitable support by various coating procedures including dip
coating, air knife coating, curtain coating or extrusion
coating using hoppers such as described in U.S. Patent 2,681,294
of Beguin, issued June 15, 1954. If desired, two or more
layers can be coated simultaneously such as described in
U.S. Patent 2,761,791 of Russell, issued September 4, 1956 and
British Patent 837,095.
Spectral sensitizing dyes can be used in the described
photothermographic elements and compositions of the invention
to con~er additional sensitivity to the elements and compositions
of the invention. Useful sensitizing dyes are described, for
example, in the Product Licensing Index, Volume 92, December,
1971, publication 9232, paragraph XV.
-21-
1045878
After imagewise exposure of the photographic element
according to the invention, typically to visible light, the
resulting latent image can be developed merely by overall
heating the~element to moderately elevated temperatures.
This overall heating merely involves heating the described
element overall in the range from about 80C. to about 250 C. such
as for about 0.5 to about 60 seconds. By increasing or
decreasing the length of time of heating, a higher or lower
temperature within the described range can be employed
depending upon the desired image, particular stabilizer
precursor, particular reducing agent, and the like. Typically,
a lower processing temperature is desired. A preferred
processing temperature range is from about 115C. to
about 175C. A developed and stabilized image is typically
produced within several seconds, such as from about 0.5
seconds to about 60 seconds.
Any suitable means can be used for providing the
desired processing temperature range. The heating means can be
a simple hot plate, iron, roller or the like. ;
Processing is usually carried out under ambient
conditions of pressure and humidity. Conditions outside
normal atmospheric pressure and humidity can be employed if
desired.
The described stabilizer precursors according to the
invention can be in any suitable location in the photographic
material ~according to the invention which provides the desired
stabilized image. If desired, one or more of the components
of the photothermographic element according to the invention
can be in one or more layers of the element. For example,
in some cases~ it can be desirable to~?include certain percentages
of the reducing agent, toner, image stabilizer precursors
and/or other addenda in a proteceive layer over the photothermo-
: : : . , . . .: . . ' .
.
.. , .. - . ' : :
1(;~45878
graphic element. This in some cases can reduce migration
of certain addenda in the layers of the photothermographic
element.
Another embodiment of the invention comprises a
photothermographic composition or element comprising (a) photo-
sensitive silver halide in association with (b) a photo-
sensitive silver halide developing agent, as described,
(c) a stabilizer precursor combination, also as described,
(d) a base-release agent, and (e) a polymeric binder for the
composition or element.
A further embodiment of the invention comprises
a photographic silver halide image stabilizer precursor
composition comprising (a) a polymeric binder for said-
composition with (b) a blocked thione, silver halide image
stabilizer precursor and (c) a halogen containing stabilizer
precursor as described.
A variety of base-release agents can be employed
in the photographic materials according to the invention
depending upon the particular photographic cQmponent, the
0 particular stabilizer precursor~ the desired image, processing
temperature range, and the like. A base-release agent as
employed herein is intended to mean a compound which releases
base upon heating to a desired temperature to/ provide activation
of st least one of the components of the photographic material,
such as activation of the reducing agent. Typical base-release
agents include those described, for example, iD U.s. Patent
3,531,285 of Haist et al, issued September 29, 1970. Useful
- base-release agents include~ for example, guanidinium salts,
such as guanidinium trichloroacetate, quaternary ammonium
malonates~ ce~tain amino acids, heat cleavable hydrzides, ~ -
and oxazolidones, as described in U.S. Patent 3,531,285.
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:, :' ~ ' ' '' " ''. . -
1~587&~
When a base-release agent is employed in a
photographic material according to the invention, a range of
concentration can be employed as described. A useful
concentration is typically about 0.25 mole to about 10 moles
of the base-release agent per mole of the photosensitive
silver salt in the photographic material. A photothermographic
composition or element according to the invention can accordingly
comprise (a) photosensitive silver halide in association
with (b) about 1 to about 4 moles of a silver halide developing
agent per mole of such silver halide, (c) a blocked thione
stabilizer precursor, as described, (d) a halogen containing
stabilizer precursor, also as described, (e) about 0.25 to
about 10 moles of a base-release agent per mole of such
silver halide, and (f) a pol~meric binder for the composition
or element.
If desired, the described stabilizer precursors,
according to the invention, can be used in combination with
other stabilizers or stabilizer precursors, such as with
S-carbamoyl stabilizer precursors in photographic elements and
compositions such as photothermographic materials. Useful
S-carbamoyl stabilizer precursors are described in U.S.
Patent 3,824,103 of Z. R. Pierce et al, issued Jul~ 16, 1974.
The following examples are included for a further
understanding of the invention.
~: :
Example 1
mis is a comparative example.
A silver behenate-behenic acid dispersion (I) is
prepared by ball-milling the following components for 64 hours:
silver behenate 168 g
behenic acid 64 g
lithium stearate 16.8 g
poly(vinylbut~ral) 120 g
acetone-toluene (1:1 by volume)2 liters
A~ - 24 _
. ...
1045878
The following addenda are combined with 71 ml of the
above-identified dlspersion (I), mixed thoroughly and then
coated on a suitable paper support at 0.86 g Ag/m2 and 2.5 g
poly(vinylbutyral)/m2.
Poly(vinylbutyral)-silverbro~oiodide11 ml
emulsion (3 l./mole Ag, 100 g
polymer/mole Ag, 6 mole % iodide)
Acetone-methanol solution (33:1 by 6 ml
volume) containing 0.01% by weight
3-carboxy~methyl-5-C(3-methyl-2-
thiazolinylidene)-l-methylethylidene~-
rhodanine and 0.03% ~y volume triethylamine
Acetone solution containing 10% by12 ml
weight 2,6-dichloro-4-benzenesulfon-
amidophenol
Acetone-toluene-methanol solution 11 ml
(1:1:1 by volume) containing 0.5%
by weight N-hydroxy-1,8-naphthalimide
Acetone 12 ml
The material is also overcoated with the following
composition at 0.95 g cellulose acetate/m2.
cellu~lose acetate 20.0 g
acetone-dichloromethane (1:1 by volume) 800 ml
The dried element is exposed imagewise to tungsten
light for 4 seconds and then heat-processed by contacting the
element with a metal block heated to 140C. for 2 seconds.
After a sensitometric curve is obtained of the
freshly processed sample, the coating is sub~ected to roomlight
(about 50-60 ft.-candles from a white fluorescent bulb) for
1~ 2~ ~ 24~ 48~ and 120 hours, respectively. After each time
interval, a new sensitometric curve is plotted from the
processed sample. The ~min a~d Dmax values are lis~ed in
following Table I.
Example 2
This is a comparative example
This example is like Example 1 except that the
composition now contains 2.5 ml of an acetone solution containing
3% by weight of 1-cyclohexylcarbamoyl-4-phenyl-2-tetrazoline-
-25-
- , . : . ,
. ~, . . - ~ : : .
1~4S878
5-thione, designated Compound A, corresponding to 0.017
molelmole Ag. The thione compound is added to the described
photothermographic composition prior to coating on the paper
support. The sample is exposed, heat processed and subjected
to roomlight handling as described in Example 1. The results
are given in following Table I.
Example 3
This is a comparative example.
This example is like Example 1 except that the
composition now contains 20 ml of an acetonesolutlon~
containing 10~/o by weight of ~-bromo-2-nitro-~-phenyl-
butyrophenone, designated as Compound B, corresponding to
0.35 mole/mole Ag. The bromo compound is added to the
described photothermographic composition prior to coating
on the paper support. The samp~e is exposed, heat processed
and subjected to the roomlight handling as described in ;
Example 1. The results are given in~ollowing Table I.
Example 4
The procedure in Example 1 is repeated except that
the element contains the blocked thione and the ~haloketone -
of Examples 2 and 3 at the concentrations specified in Table I.
The photothermographic element is exposed, heat processed
and subjected to the roomlight handling as described in
Example 1. The results are given in following Table I.
.. . . . . . . . . . . . .
1045878
X ,~ ~ o
, . ~
~o
.c , o o o
o U) ~ ~ C~
o o o o
~ 0
~ ~ ~ 0 oo
U~ ~ ~ C~l .
~ ~ o o o o
a 0 .
e ~ ~ O
~ ~ O O O O
~ .
.. U~
~ ~ U~ O
~ P~ ~J O O O O
~
U~
O
~ 1 _ N CO O
,~; I ~r) ~r) U 1
-I o o o o
~ ' ~1~ ~ 0 ~
,C
O O O O O ' '
ro ,
O
~¢ O 1` 1~, .
C~ O ~
O O t~ O ' ~1
0 X '
_~ ~
XO p~
..,
. ~ ~
~ ,
.
- 2 7_ :
: .- - , . , ,. ,: - ., -, ., , ~ ,
1~)4S87~3
Examples_5-19
Similar results are obtained when the following
halogen containing stabilizer precursors are employed in the
photothermographic element according to Example 4 in place of
Compound B:
Example 5
Tetrabromobutane
Example 6
2-tribromomethylsulfonylbenzothiazole
Example 7
2,2-dibromo-2-phenylsulfonylacetamide
~~ S2 CBr2 CONH2
Example 8
2-bromoacetophenone
~ COCH2Br ,.
Example 9
~-chloro-p-nitrotoluene
. ' CH2Cl ~ .
.'
Example 10
2,4'-dibromoacetophenone
COC323r
Br
-28-
"'
109~587~
Example 11
2-bromo-2-phenylac~tophenone
~ CHBrCO
Exam~ e 12
2-bromo-1,3-diphenyl-1,3-propanedione
~ COCHBrCO
Example 13
~_bromo-2,5-dimethoxyacetophenone
H3CO~ ~ COCH2Br
OCH
Example 14
2-bromo-2-~-tolylsulfonylacetamide
CH3 ~ SO2CHBrCONH2
Example 15
~-iodo-r-nitro-~-phenylbutyrophenone
No2CH2-CHCHICOC6H5
6 5
Example 16
~-bromo-p-nitrotoluene
;; CH2Br
2 ~ :
-29-
'
- - - :: :
- . : : ' ' - . .:
1045878
Example 17
2-bromo-4'-phenylacetophenone
~)_ COCH2Br
Example 18
~-bromo~m-nitrotoluene
Br
~l ' .
2
Example 19
2-bromo-2-nitro-1,3-propanediol
N02
H0 H2 , 2
Br
Example l9-A
1,3-dibenzoyloxy-2-bromo-2-nitropropane
: 0 N0 0
C6H5C OCH2 - ,C - CH2 - - C - C6H5
Br
Another advantage which the described halogen
contain~ng stabilizer precursors provide in silver halide
- photothermographic materials is that they provide enhanced
shelf-life or incubation stability at elevated temperatures
o~ long-term keeping at ambient room conditions as described.
Examples 20-23
Similar results are obtained when the following blocked
thione stabilizer precursors are employed in the photothermographic
element according to Example 4 in place of Compound A:
.',:
: 30
16~145878
Example 20
l-methylcarbamoyl-4-phenyl-2-tetrazoline-5-thione
Example 21
4-hexylcarbamoyl-1-phenyl-2-tetrazoline-5-thione
Example 22
N,N'-hexamethylenebis(l-carbamoyl-4-phenyl-2-
tetrazoline-5-thione
Example 23
4-phenyl-1-phenylcarbamoyl-2-tetrazoline-5-thione
Example 24
The following example illustrates a photothermographic
material according to the invention comprising a base-release
agent as described: a composition is prepared by mixing
hydroquinone, 4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone,
guanidinium trichloroacetate, poly(vinyl alcohol) binder in
alcohol and water as described in Example 1 of U.S. Patent
3,531,285 of Haist et al, issued September 29, 1970.
l-Cyclohexylcarbamoyl-4-phenyl-tetrazoline-5-thione and
tetrabromobutane also are added to the composition. The
composition is coated on a photographic paper containing a
gelatino, silver bromide photographic layer. Upon imagewise
exposure to light followed by overall heating the element
to about 190C. for a few sedonds, a developed and stabilized
image results.
The invention has been described in detail with ~-
particular reference to preferred embodiments thereof, but
it will be understood that variations and modifications
can be effected within the spirit and scope of the invention.
~': ':.
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