Note: Descriptions are shown in the official language in which they were submitted.
sackground of the Invention
_eld of the Invention
This invention relates to toning agents in photo-
thermographic compositions and elements comprising certain
silver salts of certain heterocyclic thione compounds and to
photothermographic processes for preparing developed images
with them. In another aspect the invention relates to such
photothermographic elements, compositions and processes
comprising photographic silver halide in association with
the silver salt of certain heterocyclic thiones. A further
aspect of the invention relates to thermographic elements,
compositions and processes wherein the described toning agent
provides improved tone.
Description of the State of the Art
Photothermographic materials comprising a photo-
sensitive component such as photographic silver halide with a
silver salt of certain heterocyclic thione compounds are
described, for example, in U.S. Patent 3,785,830 issued
January 15, 1974. Such photothermographic elements comprise
~a) a photosensitive component consisting essentially of
photographic silver halide, such as photographic silver iodide,
~b) a reducing agent, and ~c) a silver salt of a thione
compound, such as a silver salt of a thiazoline-2-thione, benzo-
thiazoline-2-thione, imidazoline-2-thione or oxazoline-2-thione.
These photothermographic elements and compositions can provide
a developed image which is stable in the absence of a separate
stabilizing compound. The problem encountered with these
photothermographic elements and compositions is that the
developed image resulting from them does not have the desired
black tone. Also, the maximum density is often less than
desired.
None of the art describing various photothermographic
~.,''~
::. ... - , ' -
elements and compositions has provided a useful answer to this
tone problem. Typical photothermographic elements are described,
for example, in U.S. Patent 3,152,904 of Shepard et al, issued
October 13, 1964; U.S. Patent 3,392,020 of Yutzy et al, issued
July 9, 1968; U.S. Patent 3,457,075 of Morgan et al, issued
July 22, 1969 and U.S. Patent 3,672,904 of deMauriac, issued
June 27, 1972. Toning agents known in these photothermographic
materials and toning agents known in thermographic materials
have not, as a class, provided a satisfactory solution to the
described tone problem.
Heterocyclic mercapto compounds, as a class, do
not provide a useful solution to this problem. Heterocyclic
mercapto compounds have been used for various purposes in
photographic elements, such as photothermographic elements.
Such heterocyclic mercapto compounds in photographic and
photothermographic elements are described, for example, in
U.S. Patent 3,617,289 of Ohkubo et al, issued November 2,
1971; U.S. Patent 3,396,017 of Bacon et al, issued August
6, 1968; U.S. Patent 3,017,270 of Tregillus et al, issued
January 16, 1962; U.S. Patent 2,573,027 of Kendall et al; ;
issued October 30, 1951; U.S. Patent 2,590,775 of Kendall et
al, issued March 25, 1952; U.S. Patent 2,432,506 of Chilton et
al, issued December 16, 1947; Canadian Patent 905,191 issued
July 18, 1972 and Belgian Patent 768,071 issued July 30, 1971.
The fact that heterocyclic mercapto compounds as a class do
not provide the desired toning results is demonstrated in
comparative examples in following Table II.
There has been a need to provide photothermographic
elements, compositions and processes which produce improved
tone in a developed image wherein the photothermographic -
elements and
_
compositions comprise photographic silver halide in
as~ociation with a silver salt of certain heterocyclic thiones,
as described herein, and an organic reducing agent. There has
also been a need to provide thermographic elements, compositions
and processes which provide improved tone wherein the thermo-
graphic composition or element comprises the described silver
salt of certain thione compounds with an organic reducing agent.
There has also been a need to provide developed images in such
compositions and elements which are stable and do not
require a separate stabilizer or stabilizer precursor component.
Summary of the Invention
It has been found according to the invention that
the described improvement in tone is provided with no significant
adverse affect to sensitometric properties in a photothermo-
raphic element and composition comprising (a) photographic
sllver halide in association with (b) an image-forming
combination comprislng (i) a silver salt of a heterocyclic
thione wherein the heterocyclic thione is represented by the
formula:
,----C=S
R
"_,N-Z-COOH
whereln R represents atoms completing a 5-member heterocyclic
nucleus, Z is alkylene containing 1 to 30 carbon atoms, typically
1 to 10 carbon atoms, and (ii) an organic reducing agent, by a
toner which comprises certain mercapto heterocyclic compounds
which satisfies a test as described herein and is preferably
a compound selected from the group consisting of 3-mercapto-lH-l,
2,4-triazole, 3-imino-5-thiourazole, 4-methyl-dithiourazole, 4-
phenyldithiourazole, 4-t4-methoxyphenyl~-3,5-dithiourazole, 2,4-
dimercaptopyrimidine, 8-mercaptopurine and 2,6-dimercapto-
purine toners.
~ .
.
. , .
1(~3G~
Photothermographic elements according to this
invention comprise a support having thereon the described
components of the photothermographic material containing the
described toner in one or more layers. For example, all of the
components of the photothermographic composition or thermo-
graphic composition can be coated in a single layer or they
can be coated in two or more layers. For example, in a photo-
thermographic element according to the invention, one layer
can contain the photographic silver halide and one or more
other layers can contain the reducing agent and the silver
salt of the heterocyclic thione.
In a photothermographic material, as described, a
visible image can be prepared by imagewise exposing the photo-
ther~ographic material to suitable radiation, typically
actinic radiation or visible light, and then overall heating
the exposed element to a termperature and for a time which is
sufficient to develop a desired visible image.
It has also been found according to the invention
that a thermographic element or composition with improved tone
is provided by certain mercapto heterocyclic toners in a thermo-
graphic element or composition comprising a described silver
salt of a heterocyclic thione with an organic reducing agent.
An image is provided in such a thermographic element or
composition by imagewise heating the element or composition
to a temperature and for a time which provides a visible desired
image.
In addition to providing improved developed image
tone, without the need for a separate stabilizer or stabilizer
precursor, the photothermographic elemen~s and compositions
and the thermographic elements and compositions of the invention -
have other advantageous properties. Although the photothermo-
graphic material or thermographic material, as coated on a
_5_
support, is initially opaque, upon heating to a temperature
at which development of an image takes place, it becomes trans-
parent in the non-image areas. This permits preparation of
transparencies when the compositions are coated on a trans-
parent support. It also permits the use of various colored
layers under the photothermographic or thermographic material
to provide a background of a desired color.
Additionally, the components of the photothermo-
graphic material and thermographic material according to the
invention are such that useful coatings can be prepared
without the need for a separate binder. This permits the
elimination of one of the components typically employed in a
photothermographic or thermographic material.
Detailed Description of the Invention
Certain toners can be used in the described photo-
thermographic and thermographic materials according to the
invention to provide improved tone. The toners of the
invention consist of certain mercapto heterocyclic compounds.
The choice of an optimum toner will depend upon such factors
as the particular photothermographic or ther graphic material,
the desired image, processing temperature, and the like.
Different tests can be used to determine operable mercapto
heterocyclic toners according to the invention. One test which
has been found useful for determining the mercapto heterocyclic
toners useful herein is one in which a mercapto heterocyclic
compound provides an average difference of less than 0.20
between (X) blue reflection density and (Y) visual reflection
density, as measured, at a density of 0.8, in the following
test:
(I) in an aqueous solvent (containing a water
miscible solvent such as CH30H, acetone, dimethylformamide, or
the like), is mixed:
--6--
~ : , - ~ . . . - .
'- ' ' :
~(~4~ 7
(1) 3-carboxymethyl-4-methyl-4-thiazoline-
2-thione silver salt,
(2) t-butyl hydroquinone,
(3) fine-grain photographic gelatino silver
iodide emulsion wherein said silver iodide
has an average grain size of about 0.01
micron to about 0.25 micron, and
(4) a coating aid consisting essentially of
nonylphenoxypolyglycidol;
(II) a proposed mercapto heterocyclic toner is
mixed into the resulting composition of step (I);
(III) the composition containing the mercapto
heterocyclic toner is then coated onto a polyethylene coated
paper support at the concentration which provides a coating
containing, per square meter of support 0.75 g. of total
silver of which 0.05 g. is contributed by the silver iodide,
1.88 g. of t-butyl hydroquinone, and 0.001 to 0.07 g. of the
mercapto heterocyclic toner, and subsequently the resulting
coating is dried to provide a photothermographic element (A);
(IV) the photothermographic element (A) i9
imagewise exposed to unfiltered tungsten light at least
sufficient to provide a latent image which can provide a ~ -
developed density of at least 0.8, then
(V) the latent image is developed by contacting -
the resulting exposed photothermographic element with a
heating means at about 140C. to about 170C. for about 2 to
about 8 seconds to provide a visible, developed image having
a developed density of at least 0.8, and
(VI) the difference between (X) blue reflection
density and (Y) visual reflection density is measured.
In this test the difference between (X) blue
reflection density and (Y) visual reflection density can be ~ -
.: :: : . - -..... . . . , , - .
1~3~1L7
described as a delta D range also described herein as a QD
range. In this test a mercapto heterocyclic compound which
provides, at the described density, a difference, i.e.,
delta D range, between (X) blue reflection density and (Y)
visual reflection density of less than 0.15 is considered
useful as a toner in a photothermographic material according
to the invention. Typically, however, the described difference
in the test between (X) blue reflection density and (Y)
visual reflection density is measured at a density of 1.0
rather than 0.8 because these developed images having a
maximum density of at least 1.0 are considered more useful for
many purposes. In the test, as described, blue reflection
density and visual reflection density are measured with
conventional density measuring techniques and apparatus known
in the photographic art. Values for blue reflection density
and visual reflection density can be measured with a conventional
densitometer employing the filters conventionally used for
determining the visual reflection range of a developed image.
Conventional filters can be used for measuring blue reflection
density. These filters filter radiation having a wavelength in
the portion of the spectrum other than the blue portion.
In the described test for a useful toner, if the
described photothermographic element in the test, upon
imagewise exposure and then heating, does not provide a
developed density of 0.8 or more, the photothermographic
element is not considered to provide a useful developed image.
In some cases, however, according to the invention, photo-
thermographic materials which provide a developed image
density of less than 0.8 can~be useful for some limited
purposes such as oscillograph recording.
One embodiment of the invention is: in a photo-
thermographic element comprising a support having thereon
.. . . ... . ..
~Q~3~7
(a) photographic silver halide in association with
(b) an image-forming combination comprising
(i) a silver salt of a heterocyclic thione,
said heterocyclic thione being represented
by the formula:
,~-C=S
~-N-Z-COOH
wherein R represents atoms completing a ~ :
5-member heterocyclic nucleus, Z is
alkylene containing 1 to 30 carbon atoms,
such as 1 to 10 carbon atoms,
(ii) an organic reducing agent, and
(c) a toner,
the improvement wherein said toner comprises a mercap~o
heterocyclic compound which is selected from the group
consisting of 3-mercapto-1,2,4-triazole,3-imino-5-thiourazole,
4-methyldithiourazole, 4-phenyldithiourazole, 4-methoxyphenyl-
dithiourazole, 2,4-dimercaptopyrimidine, 8-mercaptopurine ~ .
and 2,6-dimercaptopurine toners.
Useful toning agents in photothermographic and
thermographic materials according to the invention are, for
example,
3-mercapto-1,2,4-triazole,
3-imino-5-thiourazole,
4-methyldithiourazole,
4-phenyldithiourazole,
4-methoxyphenyldithiourazole,
2,4-dimercaptopyrimidine,
8'mercaptopurine, and
2,6-dimercaptopurine.
:. :: :. ~:, - :: :, . : :,. , :,- . .. : . .. ... . . .: . .. : - .. .. - -
In the definition of Z, as well as zl, z2 and Z3,
as employed herein, alkylene includes straight chain alkylene
and branched chain alkylene, such as
21 ' -CH2CH2CH- , and -CH-
CH3 CH2CH3 CH2CH2CH3
The photosensitive component in photothermographic
materials according to the invention is photographic silver
halide. An advantage of the described photothermographic
materia~ is that the concentration of photographic silver
halide needed to provide a developable image can be low
compared to photographic materials which contain photographic
silver halide in the absence of other of the described components
of the photothermographic materials of the invention. For
example, the concentration of photographic silver halide use-
ful in photothermographic materials of the invention can be
about 0.0025 to about 0.3 mole of photographic silver halide
per mole of silver as the silver salt of the described
heterocyclic thiones. In a photothermographic element of
the invention, the concentration of photographic silver halide
is typically about 0.02 times 10 3 to about 0.12 times 10 3
mole of silver halide per 929 square centimeters of support.
Useful photographic silver halides include, for example,
silver chloride, silver bromide, silver iodide, silver bromo-
iodide, silver chlorobromoiodide, or mixtures thereof.
Photographic silver iodide is especially useful. The photo-
graphic silver halide can be coarse or fine-grain, very fine-
grain photographic silver halide being especially useful. The
photographic silver halide can be prepared by known procedures
in the photographic art. The silver halide can be prepared,
for example employing single-jet preparation techniques,
double-jet preparation techniques such as techniques employed
in preparing Lippmann emulsions and the like. Surface image
--10--
- .,, - - -
. . .
10~3~i~7silver halide can be used. If desired, mixtures of surface and
internal image silver halide can be used. Negative type silver
halide is typically employed. The silver halide can be regular
grain silver halide such as described in Klein and Moisar, -
Journal of Photographic Science, Volume 12, No. 5, September-
.
October (1964), pages 242-251.
The photographic silver halide can be chemically
sensitized employinq techniques known in the photographic art.
It is believed that the latent image of the
described photographic silver halide enables the reaction be-
tween the components of the photothermographic element according
to the invention to proceed more efficiently and at lower
temperatures than would be enabled in the ab~ence of the photo-
graphic silver halide.
The term "photographic silver halide in association
with~ a~ employed herein is intended to mean that the silver
halide is located within the photothermographic element or
compo~ition on or contiguous to the described image-forming
combination. The silver halide can be, for example, in the
~ame layer as the described image-forming combination or in a
separate layer which is in reactive association with the layer
containing the image-forming combination. This enables the
de~cribed improved lower processing temperature.
Various thione compounds are useful for preparing the -
silver salt of the described heterocyclic thiones. Selection
of an optimum heterocyclic thione silver salt will depend upon
such factors as the particular photothermographic material,
particular toning agent, processing temperature, desired image
and the like.
The heterocyclic thione silver salts comprise a
5-member heterocyclic nucleus as described. Examples of
suitable 5-member heterocyclic nuclei are those wherein R, as
--11--
.--
...... . . . . . . . . . .
described, completes a thiazoline-2-thione, benzothiazoline-2-
thione, imidazoline-2-thione, oxazoline-2-thione or similar
heterocyclic thione nucleus. The heterocyclic nucleus can be
substituted with groups which do not adversely affect the
photothermographic or thermographic properties of the composition,
such as alkyl containing 1 to 3 carbon atoms or phenyl.
Examples of useful thione compounds for preparing the
described silver salts are represented by the formula:
,R-~
~N - C=S
Z-COOH
wherein
z is alkylene containing 1 to 30 carbon atoms, such as
1 to 10 carbon atoms including, for example, methylene, ethylene,
propylene and butylene;
R represents atoms completing a 5-member heterocyclic
nucleus, such as a thiazoline-2-thione, benzothiazoline-2-thione,
imidazoline-2-thione or oxazoline-2-thione nucleus.
The atoms representing R can be substituted with
groups which do not adversely affect the photothermographic or
thermographic properties of the composition, such as alkyl
containing 1 to 3 carbon atoms or phenyl.
Thione compounds which are especially useful for
preparation of the described silver salts of heterocyclic
thiones are thiazoline-2-thiones represented by the formula:
~Rl S
2~C N, > -S
ZlCOOH
wherein
zl is alkylene containing 1 to 4 carbon atoms such
as methylene, ethylene, propylene and butylene;
Rl and R2 are each, independently, hydrogen, alkyl
-12-
1~43~7
containing 1 to 4 carbon atoms, such as methyl, ethyl, propyl
or butyl, or aryl containing 6 to 10 carbon atoms such as phenyl
or tolyl, or taken together are the atoms necessary to complete
a benzo group. The alkyl, aryl and benzo groups can be
substituted with groups which do not adversely affect the
sensitometric properties of the composition or element. For
example, the alkyl group can be substituted with hydroxy or
phenyl and the aryl or benzo groups can be substituted with
alkyl containing 1 to 4 carbon atoms.
Other thione compounds which are useful for preparing
the described silver salts of a heterocyclic thione are, for
. . .
example, imidazoline-2-thiones represented by the formula: ~
R3
~R41 N-
~RS > =S
Z2COOH
wherein
z2 i~ alkylene containing 1 to 4 carbon atom~ such
a~ methylene, ethylene, propylene and butylene; ;
R3 i~ alkyl, typically alkyl containing 1 to 3 carbon
atom~, such as methyl, ethyl or propyl or aryl containing 6
to 10 carbon atoms, such as phenyl or carboxyalkyl, ~uch as
carboxyethyl and carboxymethyl, ~
R4 and RS are the same as defined for Rl and R2. --
Further useful thione compounds for preparation of
the described silver salts of heterocyclic thiones are oxazo-
line~2-thione represented by the formula:
~ R ¦l > =S
Z3CoOH
wherein
Z3 is alkylene containing 1 to 4 carbon atoms such
-13-
. ' ,
as methylene, ethylene, propylenP and butylene;
R6 and R7 are the same as defined for Rl and R2.
Examples of useful thione compounds for preparation
of the described silver salts of heterocyclic thiones within
the described formula include:
3-(2-carboxyethyl)-4-methyl-4-thiazoline-2-thione,
3-(2-carboxyethyl)benzothiazoline-2-thione,
3-(2-carboxyethyl)-5-phenyl-1,3,4-oxadiazoline-2-thione,
3-(2-carboxyethyl)-5-phenyl-1,3,4-thiadiazoline-2-thione,
3-carboxymethyl-4-methyl-4-thiazoline-2-thione,
3-(2-carboxyethyl)-1-phenyl-1,3,4-triazoline-2-thione,
1,3-bis(2-carboxyethyl)imidazoline-2-thione,
1,3-bis(2-carboxyethyl)benzimidazoline-2-thione,
3-(2-carboxyethyl)-1-methylimidazoline-2-thione,
3-(2-carboxyethyl)benzoxazoline-2-thione, and
3-(1-carboxyethyl)-4-methyl-4-thiazoline-2-thione.
The silver salt of the described heterocyclic thione
can be prepared directly in the photothermographic composition
or thermographic composition by combining a source of silver,
such as silver trifluoroacetate, with the described heterocyclic
thione in the composition, or the silver salts can be preformed
and isolated before addition to the photothermographic or
thermographic composition. The described thione compounds
can be prepared employing procedures known in the art. It is
desirable to avoid preparation of the silver salt of the
heterocyclic thione in the presence of compounds which could
cause undesired reduction.
Preparation of the heterocyclic thione compounds can
be carried out employing procedures described, for example, in
an article of R.W. Lamon and W.J. Humphlett, Journal of
Heterocyclic Chemistry, Volume 4, pages 605-609 (1967) or as
described in Belgian Patent 739,705. 4-Thiazoline-2-thiones
.
- . . ~
10~3~;~7
bearing a carboxyalkyl group on the nitrogen atom in the
thiazoline nucleus can, for example, be prepared by treating a
dithiocarbamic acid derived from an amino acid and carbon
disulfide with an ~-halogenated ketone. In this process the use
of methyl alcohol as a solvent can improve the solubility
of the reactants. .
The preparation of the silver salt of 3-carboxymethyl-
4-methyl-4-thiazoline-2-thione is typical. This silver complex
is prepared by mixing the described thiazoline-2-thione with
silver trifluoroacetate in water and thoroughly dispersing
the reactants. Concentrations of the reactants can be varied
to provide the desired ratio of silver to heterocyclic compound.
Typically, the ratio of the thione compound to silver ion is
about 2:1. For example, the described dispersion can contain
about 9.6 milligrams of silver/ml. dispersion. The resulting
silver salt can be purified and stored for later mixture with
other components of the described photothermographic or thermo-
graphic materials. The dispersing of the silver trifluoroacetate
with the heterocyclic compound is typically carried out at
about 38C. to about 71C.
Various reducing agents, also described herein as
developing agents, are useful in the photother graphic
and thermographic materials of the invention. These are
typically silver halide developing agents and include, for
example, polyhydroxybenzenes such as hydroquinones including,
for instance, hydroquinone, alkyl-substituted hydroquinone,
such as tertiary butyl hydroquinone, methyl hydroquinine, ethyl
hydroquinone, 2,5-dimethyl hydroquinone and 2,6-dimethyl
hydroquinone; catechols and pyrogallol; halo-substituted
hydroquinone such as chlorohydroquinone or dichlorohydroquinone;
alkoxy-substituted hydroquinones such as methoxy hydroquinone
or ethoxy hydroquinone and the like. Other reducing agents
-15-
....... : . - . ., :.. . : .. . . . .- , . . : .. . i . ~ ... ..
1(~36~7
which can be employed include reductones such as anhydro dihydro
piperidino hexose reductone; hydroxy tetronic acids and hydroxy
tetronic imides; 3-pyrazolidones such as 1-phenyl-3-pyrazolidone,
3',4,4-trimethyl-1-phenyl-3-pyrazolidone, 4-hydroxymethyl-2-
[N-(~-hydroxyphenyl)-N-methylamino-methyl~-4-methyl-1-phenyl-3-PY-
razolidinone 4-methyl-4-hydroxymethyl-1-phenyl-3-
pyrazolidone; hydroxylamines; ascorbic acid reducing agents,
such as ascorbic acid, ascorbic ketals and other ascorbic acid
derivatives; phenylenediamines; aminophenols; pyrimidine reduc-
ing agents, such as 2-isopropyl-4,5,6-trihydroxypyrimidine,
N-methyl-2-isopropyl-4,5,6-trihydroxypyrimidine and N-phenyl-2-
phenyl-4,5,6-trihydroxypyrimidine, and the like. Combinations
of reducing agents can be employed if desired. A useful
reducing agent or reducing agent combination is one in which the
photothermographic or thermographic materials of the invention
provide a developed image within about 90 seconds at a temper-
ature of about 100C. to about 250C.
A binder is useful, although not essential, in the
photothermographic and thermographic materials according to the
invention. Useful binders can be hydrophilic or hydrophobic,
transparent or translucent and include both naturally-occurring
substances such as proteins, for example, gelatin, gelatin
derivatives, cellulose derivatives, polysaccharides such as
dextran, gum arabic and the like; and synthetic polymeric
substances, such as acrylamide polymers.
The photothermographic element or thermographic element
of the invention can employ a wide variety of supports. Typical
supports include those that are resistant to distortion at the
processing temperatures employed for developing an image in the
elements of the invention. Typical supports include cellulose
nitrate film, cellulose ester film, poly(vinyl acetal) film,
polystyrene film, poly(ethylene terephthalate) film, poly(ethyl-
-16-
" ~ , . ,. .. , . . . . ~ . . . . ..
3~7
ene 2,6-naphthylene dicarboxylate), polyesters of 1,1,3-trimethyl-
3-(p-carboxyphenyl)-5-carboxyindan and bisphenols, as described
in U.S. Patent 3,634,089 issued January 11, 1972, polycarbonate
film and related films or resinous materials, as well as glass,
paper, metal and the like. Typically, a flexible support is
employed, such as a paper support which can be partially
acetylated or coated with baryta or with an ~-olefin polymer
which is a polymer of an a-olefin containing 2 to 10 carbon atoms
such as polyethylene, polypropylene, ethylene-butene copolymers
and the like.
The photothermographic elements and compositions
according to the invention can contain addenda commonly employed
in photothermographic elements and compositions, such as
antistatic and/or conducting materials, plasticizers, lubricants,
surfactants, matting agents, brightening agents, light-absorbing
materials, filter dyes, antihalation dyes and absorbing dyes,
and the like.
Spectral sensitizing dyes can be useful to confer
additional sensitivity to the light sensitive silver halide in
the materials according to the invention. For instance,
additional sensitization can be obtained by treating the silver
halide with a solution of a sen~itizing dye in an organic sol-
vent or the dye can be added in the form of a dispersion.
Spectral sensitizers which can be useful include the cyanines,
merocyanines, complex(trinuclear or tetranuclear) merocyanines,
complex(trinuclear or tetranuclear) cyanines, holopolar
cyanines, styryls, hemicyanines, such as enamines, oxonols,
and hemioxonols.
The various components of the photothermographic mater-
ials or thermographic materials of the invention can be addedfrom water solutions or suitable organic solvents can be used to
-17-
3~7
aid in addition. The components can be mixed using various
procedures known in the photographic art.
The photothermographic and thermographic compositions
according to the invention can be coated on a support by various
coating procedures including dip coating, air knife coating,
curtain coating or extrusion coating using hoppers of the type
descrlbed in U.S. Patent 2,681,294 of Beguin, issued June 15, 1954.
If desired, two or more layers of the photothermographic element
or thermographic element according to the invention can be
coated simultaneously by procedures known in the photographic
art.
An especially useful embodiment of the invention is
a photothermographic element comprising a support having thereon,
in sequence, (I) a layer consisting of an acrylamide copolymer,
(II) a layer comprlsing (a) photographic silver iodide in
assoclatlon wlth (b) an image-formlng comblnatlon comprising
(i) a sllver salt of 3-carboxymethyl-4-methyl-4-thlazollne-
2-thlone, (il) a hydroqulnone sllver hallde developing agent,
(c) an acrylamlde copolymer binder, and (d) a toner comprising
3-mercapto-1,2,4-triazole, and (III) a layer consisting of
an acrylamide copolymer.
Acrylamide copolymers which are useful in the described
photothermographic element of the invention include, for eY~ample,
acrylamlde copolymers described in U.S. Patent 3,893,860 of
Sutton and Stapelfeldt.
Another embodiment of the invention is a photo-
thermographlc composition comprising (a) photographlc silver
halide in association with (b) an image-forming combination
comprising a silver salt of a heterocyclic thione as described,
with (ii) an organic reducing agent also as described and (c)
a mercapto heterocyclic toner which satisfies the described test,
- 18 -
" ,, : .. ~ . .... ,,:, .:.- , .., : , ...
,. : . - , . : .
: , .. - . . . . . . . .... . . . ...
3~7
preferably a 3-mercapto-1,2,4-triazole, 3-lmlno-5-thlourazole,
4-methyldithiourazole, 4-phenyldithiourazole, 4-methoxyphenyl-
dlthlourazole, 2,4-dlmercaptopyrlmidlne, 8-mercaptopurlne or
2,6-dimercaptopurlne toner.
A range of concentratlon of each component is useful
in the de~cribed photothermographic and thermographic materials
of the lnvention. Typically, a photothermographic element
according to the invention can comprlse a support having thereon
(a) about 0.02 tlmes 10 3 to about 0.12 times 10 3 mole of
photographlc sllver hallde, (b) about 0.125 times 10 3 to
about 1.0 tlmes 10 3 mole of reducing agent and (c) about
0.5 tlmes 10 3 to about 2 times 10 3 mole of sllver as the
described complex of silver with the heterocyclic thlone,
per 929 square centimeters of support. A preferred concentration
18 about 0.1 times 10 2 mole of the mercapto heterocyclic
toner per mole o~ total sllver ln the photothermographic or
thermographic materlal. The photothermographlc element typlcally
contains about 0.09 times 10 5 mole to about 5.5 times 10 5 mole
o~ described toning agent per 929 square centimeters of support.
me selectlon o~ an optimum concentration Or a tonlng agent will
depend upon such factors as the partlcular toning agent, the
partlcular components of the photothermographic materlal,
processlng condltions, deslred lmage and the like. T~pical
concentratlon ranges for varlous tonlng agents are as follows:
mercapto thiazoles: 0.01 _ 0.07 g/m2 of support
mercapto thiodiazoles: 0.003 _ 0 07 g/m2 of support
mercapto 1,2,4-triazoles: 0.002 _ 0.07 g/m2 of support
thlourazoles: 0.003 - 0.65 g/m2 of support
mercapto pyrimidines: 0.001 - 0.02 g/m2 of support
mercapto purines: 0.005 - 0.02 g/m2 of support
~ - 19 -
... . .. . . .. . .. . ..
Another embodiment of the invention accordingly is
a photothermographic composition comprising (a) photographic silver
halide in association with (b) about Z to about 35 moles a~ ~ilver of the
described silver salt of a heterocyclic thione per mole of said silver
halide, (c) about 2 to about 15 moles of the reducing agent per mole of
the silver halide, and (d) about 0. 05 to about 1. 0 mole of the described
toner per mole of the silver halide.
In this specification blue reflection density was
mea~ured using a Wratten 94 filter, and visual reflection density was
10 measured using a Wratten 106 filter. Both filters are st~ndards in
densitometers.
In this specification a typical molar ratio of thione
to ~ilver ion is 1.4:1 to 2:1, and a preferred ratio is 1. 6:1.
-19a_
.. . .-
~O~ L7
Various imagewise exposure means are useful with
photothermographic and thermographic elements according to the
invention. Photothermographic materials according to the ~ -
invention are typically sensitive to the ultraviolet and blue
regions of the spectrum and exposure means which provide this
radiation are preferred. Typically, a photothermographic
element according to the invention is exposed imagewise with a
visible light source such as a tungsten lamp.
The exposure means useful for a thermographic element
according to the invention will depend upon such factors as the
particular components of the thermographic element, desired image,
particular toning agent and the like. Typically, imagewise
heating of a thermographic element is provided with an infrared
lamp or other heating means such as a heated drum or heated platen.
A visible image can be developed in a photothermo-
graphic element as described, after imagewise exposure, within a
short time, by overall heating the photothermographic element.
For example, the photothermographic element can be overall heated
for about 1 to about 90 seconds at a temperature of about 100C.
to about 250C., preferably about 140C. to about 170C. Usually
the time of heating is less than about 20 seconds, such as
about 1 to about 4 seconds at a temperature of about 150C. to
about 170C. Increasing or decreasing the length of time of
heating can enable use of a higher or lower temperature within
the described range.
Any suitable means can be used for providing the
deslred processing temperature range. The heating means can be,
for example, a simple hot plate, iron or roller; or hot air
convection heating means; or dielectric heating means.
An especially useful photothermographic composition
according to the invention comprises (a) photographic silver
halide in association with (b) an image-forming combination
-20-
. . , . . . . ~ . ....................... .
:: . . : - ....
~(~43~L7
comprising (i) a silver salt of 3-carboxymethyl-4-methyl-4-
thiazoline-2-thione in association with (ii) an organic
reducing agent, preferably a hydroquinone silver halide
developing agent, and (c) a toner which is 3-mercapto-1,2,4-
triazole, 3-imino-5-thiourazole, 4-methyldithiourazole, 4-
phenyldithiourazole, 4-methoxyphenyldithiourazole, 2,4-dimercapto-
pyrimidine, 8-mercaptopurine or 2,6-dimercaptopurine.
Another embodiment of the invention is a toner-silver
salt composition comprising a silver salt of a heterocyclic
thione as described, with a toner, also as described.
The toner-silver salt composition can also comprise
a reducing agent for the silver salt of the heterocyclic thione.
Useful reducing agents are as described.
The toner-silver salt composition can also comprise
a polymeric binder, as described.
A typical toner-silver salt composition comprises
(1) a silver salt of 3-carboxymethyl-4-methyl-4-thiazoline-2-
thione in association with (2) a hydroquinone reducing agent,
such as tertiary butyl hydroquinone, and (3) 3-mercapto-1,2,4-
triazole.
A further embodiment of the invention is a thermographicelement comprising a support having thereon (a) a silver salt
of a heterocyclic thione as described, in association with (b)
an organic reducing agent for the silver salt of the heterocyclic
thione, and (c) a toner which is a 3-mercapto-1,2,4-triazole,
3-imino-5-thiourazole, 4-methyldithiourazole, 4-phenyldithiourazole,
4-methoxyphenyldithiourazole, 2,4-dimercaptopyrimidine, 8-
mercaptopurine or 2,6-dimercaptopurine toner.
An image in such a thermographic element can be
developed by imagewise heating the thermographic element to a
temperature of about 100C. to about 250C., about 140C. to
about 180C.
-21-
. -- .. -.~. - . ...... , , -. ... ,.. -.. - . .. . .
1(~4~7
The following examples are included for a further
understanding of the invention.
Examples 1-10 -
A silver salt dispersion was prepared by reacting
3-carboxymethyl-4-methyl-4-thiazoline-2-thione with silver
trifluoroacetate in water and mixing the reactants thoroughly.
The concentrations of reactants were selected to provide and
maintain a solution ratio of thione compound to silver ion of
about 1.6:1. This concentration usually provides 9.6 milligrams
of silver in each milliliter of the developing dispersion.
This silver salt dispersion was designated as Dispersion A.
A photothermographic element was prepared by coating
on a resin coated paper support a developing dispersion containing
the following:
silver salt Dispersion A 7.0 ml
reducing agent (10% by weight solution
in methanol) 1.0 ml
silver iodide gelatino emulsion ~21.2
milligrams of silver in each ml. of
emulsion) 0.4 ml
Surfactant lOG (0.5% by weight solution
in alcohol; the surfactant is nonylphenoxy-
polyglycidol available from Rohm and Haas Co., -~
U.S.A.) 0.4 ml
toning agent (concentration is given in
following Table I)
In order to aid mixing of the toning agents with
other components of the described composition, the toning
agent was dissolved in methanol with the reducing agent when
incorporated with the other components of the coating formulation.
The coating mixture was coated on the paper support
at 6.9 times 10 4 moles of total silver per 929 square centi-
meters of support. No separate binding agent was employed in
30the photothermographic composition.
-- lQ~3~7
The resulting photothermographic element was imagewise
exposed to tung~ten light to provide a developable image. The exposed
photothermographic element was then uniformly heated by contacting it
with a metal block at 150 C. for 4 seconds.
The particular toning agent, concentration of toning agent
in the coating mixture, particular reducing agent, Dmax, Dmin and
developed image tone are given in the following Table I.
Example~ la, 2a, 3a, 4a, Sa, 6a, 7a, 8a, 9a and lOa
The procedure described in Examples 1 to 10 was repeated,
wherein the developing dispersion coating composition additionally contained
1. 0 ml of polyvinyl alcohol ~10% by wt. solution in water). When the
elements ~ere exposed and processed the results were as shown in Table I
for Examplc~ I to 10.
.,
:,
.. ' ,
.,
.
~, ,
_23 _
. ~ ~
1 3 3
G .~ 1 0 0
o
H ~1 ~ G~ G h ~ G ~-I G G ~ .
G O 00CO O O a~ Ocr.IJ~
~ -1 0 0 .~ O .-1 0 ~I~`I ~1~1
O O O O O O O O OO O O
X I`t~ oo1` o ao
F~ O ~In ~)N ~) ~ ~ 1~~ O O
G G G G G G G G~ G
O O O O O O O OO O
G ~ G G G G G GG G
a) o o o o o o o oo a) o
o ~ ~ ~o~ ~ ~ ~ ~a~ o
G ~ 1~ G
t1- ~1 S S S S S S S S,C ~rl .C
0 ~ O ~ ~~ O
~ G ~ ~ S S S S S S SS S
~ ~ S
O
~' ~
HO ~ ~ ~t~
~~ ~ ~ e ~ e ~~ e
~nl ~ o o ~ o o o oIn oo I I
~~c
n~ ~ ~ l ~ ~ o ~
~c ~ ~ ~
g
~ G ~1~1
O O ' I
N N ~ ) X X
n~
~ 3 o ~ol
u o o '1o
G ~ S~1
a~ ~ ~ o E~ n~
tl~ ~1 ~ I O N I _I U _I UO U B~
nl ~ O ~ O
0 0~I N Q~ h I Na) Nal Q~a) 0 0
n~:1 o td ~3 n~ ~ n~l3 U
P~ G 1-1 U O G~ rl ~ rlU ~rl -- _
u ~s o a)s
o ~ e ~ ~ D G G
E~ O OI S I~rl I S '~ S 'I ' O O
a) , c m
~l
X h h
~ '~ ~ O ~ ~
O O
U
--24--
1o~ 7
Example 11
This is a comparative example.
The procedure descrlbed in Example 1 was repeated
with 6 milligrams of 1-phenyl-5-mercaptotetrazole added in
place of the described toning agent. The developed image tone
was brown. mis tone was the same as the comparative examples
in which no toning agent was employed as described in Table I.
Exam~le 12
A silver salt of 3-carboxymethyl-4-methyl-4-thiazoline-
2-thlone was prepared as described in Example 1 to provide a
silver salt Disperslon A.
A coating composition was prepared by mixing the
followlng ln an aqueous solvent (contalning a water misclble
solvent such as methanol, acetone, dlmethylformamlde or the
llke):
sllver salt Disperslon A 7.0 ml
tertlary butyl hydroquinone (18.8% 1.0 ml
by welght solutlon ln methanol)
flne-graln photographlc gelatlno 0.4 ml
sllver lodlde emulslon (each
mllllllter of emulslon contalned
21.2 milllgrams of sllver; the
silver lodlde had an average
graln slze of about 0.06 microns)
Surfactant lOG (nonylphenoxypoly- 0.4 ml
glycldol avai~able from Rohm and
Haas Co., U.S.A.)
mercapto heterocycllc toner as
indlcated in following Table II
The resultlng composition containing the mercapto
heterocyclic toner was then coated onto a polyethylene coated
paper support at the concentration which provided a coating
containing per square meter of support, 0.75 gram of total
silver of which o.o8 gram was contributed by the silver iodide.
The coatlng contained 1.88 grams of tertiary butyl hydroquinone
and 0.001 to 0.07 gram of the described mercapto heterocyclic
toner. The coating contained no separate binder. me
resulting coating was dried to provide a photothermographic element.
~ .
1(~4;~6~
The photothermographic element was imagewise exposed
to unfiltered tungsten light sufficient to provide a latent image
which was developable. The exposed photothermographic element
was then overall heated by contacting it with a metal block
at about 160C. for about 2 to about 8 seconds to provide
a visible developed image having a developed density of at least
1Ø
The blue reflection density of the developed image ,
was then measured employing a conven~ional densitometer with a
, 10 tungsten light source which was filtered to permit only the
I blue wavelengths to be reflected. Also, the visual reflection
density was measured employing a densitometer with a filter
which permitted the visual wavelengths of the spectrum to
¦ be reflected. The difference between the blue reflection
density (X) of the image and the visual reflection density (Y)
i of the developed image was assigned the designation of
delta D, also described as ~D. The difference between the
blue reflection density (X) and the visual reflection density (Y)
of the developed image was measured at 1.0 density of the
developed image.
An arbitrary toner activity rating was assigned to
each compound. Those compounds that provided a difference
between blue reflection density (X) and visual reflection
density (Y) of 0.00 to 0.15 were considered to be preferred
toners in the described photothermographic material. In
some cases compounds which provided a difference between
; blue reflection density (X) and visual reflection density (Y) of
greater than 0.20 provided other undesired effects such as
. undesired fogging, restraining of development and the like.
The results are given in following Table II. Those
examples in Table II which provided a delta D range of 0.20 or
greater are comparitive examples.
-26-
~ ~ ,
~ .. . .. .. .. .. .. .
.. ; . ::.: , ,: , . ., :
N U) D O Ir~ ~ ~ N N ~ O ~r ~D O ~` ') O (` CO r-l ~ I` rl N O ~ N ~1
~1 ~) ~ ~) ~ N ') r~ N N N N N N N r-l ~ ~1 ~ N --1 N N N ~ N ') ')
1~
O 00000000000000000000000000000
Id
~U Ul
O ~4
~rl
u~ a) s
Q~ ~U I r l
O r l ~ Cl O ~ I
rl O O ~ N rlU~
al o N-rl-rl (d O
~\ N ~ N a)
Ul Id rl .IJ rl ~ la rl ~ r l
~ ~ rl ~ I r~l O ~ O ~rl O
1-1 E~ ~ o rl ~ N ~U r~ N r~l
) ~ r~l I N ,q O 1~1 rl O 11l 0
~ ~ r~l r~ rl ~ a N 1~
la U1 N ~ O I ~rl ~ r~rl td ~) r~l
~¢ O al ~1 r~l N aJ ~ r~l ~ O I ~rl ~ rl I O
E-l R1 ~1 ~ O w.C k O I NIt~ U~ N
~ R~ r N ~r-l Ql I N ~rId ~ I ~ W ~rl ~ I W
O E ~ h
~J _ ~ ~1 ~ ~ N ~ S ~----I ~
u~ ~1 o o o )~ o I o h ` O O O O--I--~ ` ~ ~1 0 0 ~
~1 ~) ~rl ~ ~rl ~ ~ O ~ ~ ~1 rl N N N O _I I tr~ O ~-rl N
~1 0 ~ ~C--I S ~ I ~ ~ P~ O I S ~ W W N ~ J W O
lu N W ~ O ~ --I ~r W Q~ W rl--I ~ h ~ ~ W ~
1~ W O O N ~U O ~ C) W t) .C ~ ;J ~ ~-1 C~ ~ I W S ~1 ~ Ql
rl ~ o 1 rl o w ~ U O ~ rl ~1) .,1 ~1 0 ~ ~ ~ U Q ~ ~1) W
13 N rl S N ~ S N ~ .C _I ~ S rl ~S ~ Il)
~l O ~1 I W O ~ W ~1 1 I k I I ~1 ~ a) ~ O ~ ~ S X ~ W e I a) 5:
.i ~ ~ N ~ ~ O ~ J O ~ I N N I 1~ I N ~rl ~--1 IJ O O t) I O E~
-- ~ ~ S tJ) I ~ I ~ I I ~r ~ ~1U') W ~ ~ ~rl S S~l Sl N ~-- I I
~,1 e td ~ ~ I o x I h--I ~1 ~ ~ ~ o I ~ I --I--
_I w ~ a w O ~ 1 ~ ~ O ~1 0 0 ~ I e o w m
O O S N ~ U N ~ S ~q ~ O .C ~ e ~
o ~ s ~ s s ~ o w e s ~ s ~ e ~ I ~ s
O I I I S I I S ~ I I I I I I 0 1 1 ~1 1 1 1 1 1 ~ I I ~ I I
., C,) N r-l N ~ N ~ h ,1 ~ ~ ul ,1 _I ~ ~ ~ ~ ~ ~r ~ ~r ~r ~ N 1~ N N _I r--1
.,
.
O ,~
3 ~t N ~ m ~D r` 00 ~ O ~I N ~ 0 ~ O ~I N ~ ~ 11~ ~D 1~ CO ~ O
X ~1 ~1 ~1 ~1 ~ I N N N N N N N ~ N N ~ ~ ~ ~ t~ 1~ ~ ~) ~ ~)
J ~
i ~ ~ - 2 7-
~, ,
~ (~4~G~''7
Concentration of Toning Agents:
Examples 12, 13, 14, 16, 17, 19, 21, 23, 24, 37, 39,
40, 47, 48, 49 50, 52, 53 and 54 is 6 mg, Examples 15, 18, 20,
; 29~ 30, 38, 42, 43, 44, 45, 46 and 51 is 1 mg, Examples 22, 27
and 36 is 4 mg, Example 25 is 2.5 mg, and Example 41 is o .5 mg.
Examples 26, 28 and 31 to 35 is 2 mg.
- 27a -
. . . . .
~ ~ , ., . , , - ' . '. , '
: :.. . . . ..
1(~4~3~1'7
O x ~
x ~,
--o ~ ~ ~ ~ ~ ~ ~ o~ X
_ ~ ~ O _ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~t ~
O O O G O O O O O O O O O O ~ ~ ~ O
U
~R~ E~
V
V
~, 5 ~ a d 5 0 '~
a ~ u ~ h
~`i ~ N 0 ~ N ~ ~ o7 ~ O E ~ e ~,
E a æ ~ ~
E~ ~ o ~
: z . ~ R . -
.: ~ ~ x ~ o ~
:. ' -
., . ' .
,
~ 7
Example 55
The procedure described in Example 1 was repeated
with the exception that L-(+) ascorbic acid was employed in
place of hydroquinone as the reducing agent. A developed image
resulted upon imagewise exposure ana overall heating of the
element to provide a developed image having a maximum density
of 1.64 and a minimum density of 0.08. i~
Example 56
The procedure described in Example 1 was repeated
with the exception that 2-isopropyl-4,5,6-trihydroxypyrimidine
was employed as a reducing agent in place of hydroquinone.
' Upon imagewise exposure and heating of the resulting element
as described in Example 1, a developed image was produced
having a maximum density of 1.62 and a minimum density of 0.09.
Example 57
The procedure described in Example 1 was repeated
with the exception that anhydro dihydro piperidino hexose
reductone was employed as the reducing agent in place of
hydroquinone. Upon imagewise exposure and heating of the
' 20 resulting photothermographic element, a developed image was
I, produced having a maximum density of 1.77 and a minimum density
of 0.16.
Example 58
The procedure described in Example 1 was repeated
w~th the exception that l-phenyl-3-pyrazolidone was employed
~ as a reducing agent in place of hydroquinone. Upon imagewise
., exposure and overall heating the resulting photothermographic
¦ element as described in Example 1, a developed image was
produced having a maximum density of 1.28 and a minimum density
' 30 of 0~37~
3 With most of the mercapto heterocyclic toning agents
~ of the invention it is desirable to avoid processing temperatures
;,
-29-
which are significantly above that which provides a developed
image. If processing temperatures above that required to
provide a developed image are used, decreases in desired image
tone can occur. For example, when using mercapto-1,2,4-triazole
as a toning agent, it is usually desirable to avoid processing
temperatures above 160C. Above 160C. this toning agent may
tend to produce less than a neutral black image.
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 opirit and scope of the invention.
' ,
~J
.~ ,.
'
'~ 20
,,~ .
.
l - ,
; ', ,'
'
:. ., , -,
,',' ':" ,
.
.~' .
