Note: Descriptions are shown in the official language in which they were submitted.
`` 210156~
47471CAN3A
.
POST-PROCESSING STABILIZERS FOR
PHOTOT~ERMOGRAPHIC ARTICLES
FIELD OF THE INVENIION
This invention relates to photothermographic materials and in particular
to post-processing stabilization of photothermographic silver-containing
10 materials.
BACKGROI~ND OF THE ~VENI~ON
Silver halide containing photothermographic imaging materials processed
with heat, and without liquid development have been known in the art for many
15 years. These materials generally comprise a support having thereon a
photographic light-sensitive silver halide, a light-insensitive organic silver salt,
and a reducing agent for the organic silver salt.
The light-sensitive silver halide is in catalytic proximity to the
light-insensitive organic silver salt so that the latent image, forrned by
20 irradiaeion of the silver halide, ~erves as a caealyst nucleus for the
oxidation-reduction ~eaction of the organic silver salt with the reducing agent
when the emulsion is heated above about 80- C. Such media are described, for
example, in U.S. Pat. Nos. 3,457,075, 3,839,049, and 4,260,677. The silver
halide may also be generated in the media by a preheating step in which halide
25 ion is released to form silver halide.
A variety of ingredients may be added to these basic components to
enhance performance. For example, toning agents may be inco~porated to
improve the color of the silver image of the photothermographic emulsions, as
described in U.S. Pat. Nos. 3,846,136; 3,994,732 and 4,021,249. Various
30 n~ethods to produce dye images and multicolor images with photographic color
couplers and leuco dyes are hlown and described in U.S. Pat. Nos. 4,022,617;
. - -. .. , . . : . ~ : . . ....
21~1~6A
3,531,286; 3,180,731; 3,761,270; 4,460,681; 4,883,747 and Research
Disclosure, March 1989, item 29963.
A common problem that exists with phototherrnographic systems is
post-processing instability of the image. The photoactive silver halide still
5 present in the developed image may continue to catalyze print-out of metallic
silver during room light handling. Thus, there exists a need for stabilization of
the unreacted silver halide. The addition of separate post-processing image
stabilizers have been used to impart post-processing stability. Most often theseare sulfur containing compounds such as mercaptans, thiones, and thioethers as
10 described in Research Disclosure, June 1978, item 17029. U.S. Pat. Nos.
4,245,033; 4,837,141 and 4,451,561 describe sulfur compounds that are
development restrainers for photothermographic systems. Mesoionic
1,2,4-triazolium-3-thiolates as fixing agents and silver halide stabilizers are
described in U.S. Pat. No. 4,378,424. Substituted 5-mercapto-1,2,4-triazoles
15 such as 3-amino-5-benzothio-1,2,4-triazole as post-processing stabilizers aredescribed in U.S. Pat. Nos. 4,128,557; 4,137,079; 4,138,265, and Research
Disclosure, May 1978, items 16977 and 16979.
Problems ansing from the addition of stabilizers may include thermal
fogging during processing and losses irl photographic speed, maximum density
20 or contrast at effective stabilizer concentrations.
Stabilizer precursors have blocking or rnodifying groups that are usually
cleaved during processing with heat and/or alkali. This provides the primary
active stabilizer which can combine with the photoactive silver halide in the
unexposed and undeveloped areas of the photographic material. For example,
25 in the presence of a stabilizer precursor in which the sulfur atom is unblocked
upon processing, the resulting silver mercaptide will be more stable ~an the
silver halide to light, atmospheric, and ambient conditions.
Various blocking techniques have been utilized in developing the
stabilizer precursors. U.S. Pat. No. 3,61$1617 describes acyl blocked
30 photographically useful stabilizers. U.S. Pat. Nos. 3,674,478 and 3,993,661
describe hydroxyarylmethyl blocking groups. Benzylthio releasing groups are
-2-
., - . . ;, , ~ -
. :: . - .
.
21 ~6 J~
described in U.S. Pat. No. 3,698,898. Thiocarbonate blocking groups are
described in U.S. Pat. No. 3,791,830, and thioether blocking groups in U.S.
Pat. Nos. 4,335,200, 4,416,977, and 4,420,554. Photographically useful
stabilizers which are blocked as urea or thiourea derivatives are described in
S U.S. Pat. No. 4,310,612. Blocked imidomethyl derivatives are described in
U.S. Pat. No. 4,350,752, and imide or thioimide derivatives are described in
U.S. Pat. No. 4,888,268. Removal of all of these aforementioned blocking
groups from the photographically useful stabilizers is accomplished by an
increase of pH during alkaline processing conditions of the exposed imaging
10 material.
Thermally sensitive blocking groups have also been utilized. These
blocking groups are removed by heating the imaging material during
processing. Photographically useful stabilizers blocked as thermally sensitive
carbamate derivatives are described in U.S. Pat. Nos. 3,844,~97 and
15 4,144,072. These carbamate derivatives presumably regenerate the
photographic stabilizer through loss of an isocyanate. Hydroxymethyl blocked
photographic reagents which are unblocked through loss of formaldehyde duAng
heating are described in U.S. Pat. No. 4,510,236. Development inhibitor
releasing couplers releasing tetrazolythio moieties are descAbed in U.S. Pat.
20 No. 3,70û,457. Substituted benzylthio releasing group~ are described in U.S.
Pat. No. 4,678,735. U.S. Pat. Nos. 4,351,896 and 4,404,390 utilize
carboxybenzylthio blocking groups for mesoionic 1,2,4-triazolium-3-thiolate
stabilizers. Photogrdphic stabilizers that are blocked by a Michael-type addition
to the carbon-carbon double bond of either acrylonitAle or alkyl acrylates are
25 descAb d in U.S. Pat. Nos. 4,009,û29 and 4,511,644, ~espectively. Heating of
these blocked deAvatives causes unblocking by a retro-Michael reaction.
VaAous disadvantages attend these different blocking techniques.
Highly basic solutions, that are necessary to cause deblocking of the alkali
sensitive blocked deAvatives, are corrosive and irritating to the skin. With
30 photographic stabilizers that are blocked with a heat removable group, it is
ofte~ found that the liberated reagent or by-product can react with other
,
.
-- .
.. ...
2 ~
components of the imaging construction and cause adverse effects. Also,
inadequate or premature release of the stabilizing moiety during heat processingmay occur.
There has been a continued need for improved post-processing
5 stabi1izers or stabilizer precursors that do not fog or desensitize
phototherrnographic materials, and for stabilizer precursors that release the
stabilizing moiety at the appropriate time and do not have any detrimental
effects on the photosensitive material or user of said material.
Blocking groups which are removed by actinic radiation are discussed in
10 the context of organic synthesis utility in Amit et al., Israel J. Chem. 1~74, 12,
103; and V. N. R. Pillai, Synthesis, 1980, 1-26. The o-nitrobenzyl group has
been known as a photocleavable blocking group for some time (J. Barltrop et
al, J. Chem. Soc. Chem. Comm. 196C, 822-823.) Various substituted
analogues have been prepared in order to maximize the photochemical
15 efficiency and chemical yield, and to suppress colored products of the
photolysis. The o-nitrobenzyl group has been used to protect many different
functional groups, including carboxylic acids, amines, phenols, phosphates, and
thiols.
The o-nitrobenzyl moiety has been used in various imaging and
20 photoac~ive constructions. It has been used to block surfactants for
radiation-induced tape removal as described in U.S. Pat. Nos. 4,478,967;
4,599,273; and 4,740,600; and peel-apart imaging as described in U.S. Pat.
No. 4,554,238. Nitrobenzylated acids as sources of photogenerated acid for
photoresists have been extensively studied, in for example F. M. Houlihan et
25 al, Proc. SPIE-ln~. Soc. Op~. Eng. Vol. 920 (Advances in Resist Technology
and Processing V~ 1988, 67-74 and references therein. Otherphotoresist
applications are as follows. Nitrobenzyl groups incorporated into polyme~ic
structures are described in U.S. Pat. Nos. 4,108,839; 4,576,902; 4,465,760
and 4,456,679. Photoinhibitors for photopolymers are described in BAtish Pat.
30 No. 1,547,548; German Pat. No. 2,710,417, and U.S. Pat. No. 4,477,556.
- Nitrobenzyl compounds used as photoreductants and photoinhibitors for
4-
. .. . . - . . . :. - . ~
-: ~
- . .~ . . . .
.
: ~ , - ~ . :
-
-
210~
non-silver based photothermographic systems are described in U. S. Pat. Nos.
4,284,704; 4,273,860 and 3,880,659.
o-Nitrobenzylidene dyes have been used as photobleachable sensitizers
for nitrate ion based non-silver photothermographic systems as described in
5 co-pending cases U.S. Ser. Nos. 07/539,572 and 07/754,169, and U.S. Pat.
No. 5,077,178.
In U. S. Pat. Nos. 4,343,893 and 4,501,896 the ~nitrobenzyl
protecting group has been used in photographic applicationsalong with other
electron-poor benzyl protecting groups to mask development image modifier
10 compounds.
U.S. Pat. No. 4,416,981 descAbes substituted benzothiazolines as
photographic antifoggants but no special advantage is noted for the
~nitrobenzyl substitution.
U. S. Pat. No. 4,187,110 also describes a development inhibitor releaser
15 (DIR) coupler for conventional silver halide emulsions containing the
~nitrobenzyl functionality. In those applications as well, a photographically
useful group is released from the blocking group by ~he action of processing,
specifically electron transfer.
Photolytically active stabilizer precursors for photothermographic silver
20 imaging compositions which apparently release bromine atoms are descAbed in
U.S. Pat. No. 4,459,350 and references cited therein.
Stabilizer precursors of the present invention are deblocked to release a
stabilizer by the action of actinic radiation. Additionally, stabilizer precursors
of this type can be added to photothermographic formulations without the
25 necessi~y of rebalancing the formulation to compensate for effects on
sensitometry, as is often the case with other stabilizers in the art.
SVMMARY OF THE INVENIION
In one aspect this invention relates to phototherrnographic articles
30 comprising a photothermographic composition coated on a substrate wherein thephotothermographic composition comprises a photographic silver salt, an
- - . - - ~ , , - . : .,
. ~ .
.
- . ~ . . .. . :
,
21~15'6g
organic silver salt, and a reducing agent for the organic silver salt, and a
stabilizer having a central nucleus of the formula:
H ,.,
S A--(L)n )~3
02N
The dashed line (---) on the bridging methine group is defined as indicating that
10 the valence of the ~arbon atom of the methine group is satisfied by any
conveniently selected chemical group covalently bonded to that carbon.
or a central nucleus of the formula:
~,Y
A--(L)n
02N
or a compound havirg the formula:
H~ ,y Rl
A--(L)n ~/R2
2~ 3
~4
~ .
-. ~ . - - - . - . - . . - - .
,
. .
21~15~ ~
wherein:
A represents any monovalent group for which the corresponding
compound AH functions as a post-processing stabilizer having from 1 to 50
carbon atoms, and
S Y, R', R2, R3, and R4 independently represent a group selected from
hydrogen, alkyl, alkoxycarbonyl, alkenyl, aryl, hydroxy, mercapto, amino,
amido, thioamido, carbamoyl, thiocarbamoyl, cyano, nitro, sulfo, carboxyl,
fluoro, forrnyl, sulfoxyl, sulfonyl, hydrodithio, ammonio, phosphonio, silyl,
and silyloxy groups having up to 18 carbon atoms, and wherein any two of R',
o R2, R3, and R4 may together form a fused ring structure with the central
benzene ring, and
L is a -CO2- or -CH20- group wherein A is bonded to the carbon atom
of L, and wherein L is lost during or after the deblocking step, and
nisOor 1.
The stabilizer precursors of the present invention may also be described
as having the general formula
A-T-M-Z
wherein:
A is as previously defined, and
T represents a covalent bond, or a -CO2- or -CH20- group, (wherein A
is bonded to the carbon atom of this group), and
M represents a carbon atom having at least one hydrogen atom, and
bonded thereto
Z represents an aromatic group having at least one nitro group
25 substituent in the position ortho- to the substituent A-T-M-.
Preferred stabilizer precursors are o-nitrobenzyl blocked derivatives of
heterocyclic compounds that stabilize silver images. They typically comprise
from about 0.01 wt% to 10 wt% of the dry photothermographi composition.
They may be incorporated directly into the silver cont~ining layer or into an
30 adJacent layer. The stabilizer precursors of the inven~on are especially useful in
-7-
.
`:
- . :
:
.
~10156`~
articles and compositions for the preparation of photothermographic color and
black and white images.
Photothermographic articles of the present invention are useful for color
and black and white imaging applications.
S o-Nitrobenzyl blocked stabilizers of the present invention stabiliæ silver
halide and/or minimize untimely leuco oxidation for improved post-processing
stabilization without desensitization or fogging during heat processing.
As used herein, the term ~nitrobenzyl refers to a 2-nitrobenzyl moiety
having at least one hydrogen on the benzylic carbon and one other substituent
10 which may be hydrogen, and optionally having substituents on the aromatic
ring, including ring fusions, or having the benzene ring replaced by a
substituted or unsubstituted polycyclic aromatic moiety.
Where the term group is used in describing substituents, substitution is
anticipated on the substituent for example, alkyl group includes ether groups
15 (e.g., CH3-CH2-CH2-O-CH2-), haloalkyls, nitroalkyls, carboxyalkyls,
hydroxyallyls, sulfoalkyls, etc. while the terrn alkyl includes only
hydrocarbons. Substituents which react with active ingredients, such as very
strongly electrophilic or oxidizing substituents, would of course be excluded asnot being inert or harmless.
As used he.ein the symbol "~" means phenyl.
The stabilizer precursors of this invention are deblocked to release the
parent stabilizer by the action of actinic radiation and therefore offer the
advantage over unprotected stabilizers and heat-releasable stabilizers of being
inert and inactive during the processing step, and resistant to thermal release
25 during shelf aging. They are only released when they are needed. They are
useful in a wide range of photothermographic media and processing conditions,
since they do not appear to have specific requirements for release that attend
most other masking groups in the art such as heating, acids or bases, or
coupling with a reduction step.
-8-
- .. .. .
- - ', ' ~ . ' ': .' : -
- ~ . -
-
. . . .
" 2101~6~
DETAILED DESCRIPrION OF THE INVENTION
Photothermographic articles of the present invention comprise aphotothermographic composition coated on a substrate wherein the
photothermographic construction comprises a photographic silver salt, an
S organic silver salt, a reducing agent for the organic silver salt, and a stabilizer
having the formula:
H~ ,Y
A--(L)n ~3
02N
or a compound of the formula:
~, y Rl
A--(L)n '~/R2
02N~`~3
R4
~0 wherein:
A represents any monovalent group for which the corresponding
compound AH functions as a post-processing stabilizer having from I to 50
carbon atoms.
Y, R1, R2, R3, and R4 independently represent a group selected from
25 hydrogen, alkyl, alkoxycarbonyl, alkenyl, aryl, hydroxy, mercapto, arnino,
amido, thioamido, carbamoyl, thiocarbamoyl, cyano, nitro, sulfo, carboxyl,
fluoro, chloro, bromo, formyl, sulfoxyl, sulfonyl, hydrvdithio, ammonio,
phosphonio, silyl, and silyloxy groups having up to 18 carbon atoms, and
wherein any two of R', R2, R3, and R~ may together form a fused ring
30 structure with the ~entral benzene ring. Preferably, Rl, R~7 R3, and R4 are
2101~
hydrogen. Y is preferably selected from hydrogen, alkyl, and alkoxycarbonyl.
More preferably Y is hydrogen.
L is a -CO2- or -CH2O- group wherein A is bonded to the carbon atom
of L, and wherein L is lost during or after the deblocking step.
n is 0 or 1. Preferably n is 0.
The stabilizer precursors of the present invention may also be described
as having the general for nula
A-T-M-Z
wherein:
A is as previously defined, and
T represents a covalent bond, or a -CO2- or -CH20- group, (with A
bonded to a carbon atom of this group) and
M represents a carbon atom having at least one hydrogen atom, and
bonded thereto
Z represents an aromatic group having at least one nitro group
substituent in the position ortho- to the substituent A-T-M-.
In photothermographic articles of the present invention the layer(s) that
contain the photographic silver salt are referred to herein as emulsion layer(s).
According to the present invention the o-nitrobenzyl blocked stabilizer is added20 either to one or more emulsion layers or to a layer or layers ad3acent to one o~
more emulsion layers. Layers that are adjacent to emulsion layers may be for
example, primer layers, image-receiving layers, interlayers, opacifying layers,
antihalation layer, banier layer, auxiliary layers, etc.
The o-nitrobenzyl group acts as a blocking group to block the activity of
25 the primary stabilizer AH. If AH is left unblocked and added to the
photothermographic emulsion at the same molar equivalent concentration as the
blocked compound, AH desensitizes or fogs the emulsion. Unblocking to
release the active stabili7er occurs after exposure and development, during
exposure to ambient light or to light in an accelerated aging device. Thus, the
30 blocked stabilizers of the present invention overcome the problems of
10-
. . .. .
- . . - : - - : - , . - ,
. .. : .. , . -, , - . , ~ ,
-- .- :. . : -. . . . : -
- - . -
- , ,. .. ': ~
2 ~
desensitization and fogging that occur when the stabilizers are use in their
unblocked form.
The substituents Y, R', R2, R3, and R4 are chosen so that the
compound or a model compound in which A is replaced by H passes the
S following test for photoreactivity and low background stain.
To a solution of 3 g of 7.5 weight percent polyvinyl butyral in
ethanol is added a solution of 8.5 millimoles of the compound in
question in 0.5 mL of ethanol or tetrahydrofuran. The resulting
solution is knife-coated 3 mil thick wet on unprimed opaque
polyethylene terephthalate film and dried in a 70 C convection
oven for 3 minutes. Samples of the coated film are exposed to
1200 foot-candle intensity fluorescent lights in a constant
temperature 26C and constant humidity (65% relative humidity~
chamber for zero, one, and six hours. The polyvinylbutyral
films are peeled from the polyester. If the infrared spectra of the
films show greater than ten percent loss of intensity of the nitro
band at about 1520 to 1540 cm~' after light exposure for one to
six hours the compound is suitable for use in the present
invention.0
Preferably o-nitrobenzyl moieties that are used in the present invention
show little or no color formation in the abovementioned film after light
exposure for several hours.
A is preferably attached through a nitrogen atom. Post-processing
25 stabilizing groups for stabilizing silver ion AH usually have a heteroatom such
as nitrogen available for complexing silver ion. The compounds are usually
ring structures with the heteroatom within the ring or external to the ring.
These compounds are well known to one ordinarily skilled in the photographic
art. Examples of AH include nitrogen-containing heterocycles, substituted or
30 unsubstituted, including but not limited to benzimidazole, benzotriazole,
t~iazoles, tetrazoles, phenylmercaptotetra~oles, imidazoles, pyr~olidinones or
-11-
.
- ,
.
.
2~ 01~
any such compound that stabilizes the emulsion layer, and particularly those
that have deleterious effects on the initial sensitometry or excessive fog if used
unblocked. Non-limiting examples of A~ include imidazoles such as
benzimidazole and benzimidazole derivatives; triazoles such as benzotriazole,
5 1 ,2,4-triazole, 3-amino-1 ,2,4-triazole, and 2-thioalkyl-5-phenyl-1 ,2,4-triazoles;
tetrazoles such as 5-amino tetrazole; triazines such as
mercaptotetrahydrotriazine; piperidones; tetraazaindans; 8-azaguanine; thymine;
thiazolines such as 2-amin~2-thiazoline, indazoles; hypoxanthines;
2H-pyridooxazin-3(4H)-one and other nitrogen containing heterocycles. Many
10 of such compounds are summarized in Research Disclosure, March 1989, item
29963. AH may also be a compound which stabiliæs a leuco dye, usually a
reducing agent which has an active hydrogen which can be masked by
replacement with the nitrobenzyl group. An example of a useful reducing agent
is l-phenyl-3-pyrazolidinone (described in U.S. Pat. No. 4,423,139 for
15 stabilizing leuco dyes). Masking of such reducing agents during the processing
step is usually necessary since they may act as developers or development
accelerators to cause unacceptable fogging.
In another preferred embodiment of the invention, Y represents a
hydrogen, alkyl, or an alkoxycarbonyl group; Rl-R4represent hydrogen, n is 0,
20 and AH is a post-processing stabilizer identified to be most advantageous for a
given photothermographic construction; for instance, l-phenyl-3-pyra~olidinone,
benzotriazole, or 3-(n-hexylthio)-5-phenyl-1,2,4-triazole.
Photothermographic articles of the invention may contain other
post-processing stabilizers or stabilizer precursors in combination with the
25 compounds of the invention, as well as other additives in combination with the
compound of the invention such as shelf-life stabilizers, toners, development
accelerators and other image modifying agents.
Non-limiting examples of o-nitrobenzyl protected stabilizer precursors
are:
- . - . . - .
.. . . . . , . . ~....... .. . ~ .
2101~
P~--N/~o Ph--N~o Ph--N/ ~ ~o
02N o2N~3~NO2 ~3
Pn--N~o Ph N/~o ~--N~o
H3C~ ~OCH3
02N 02N OCH3 02N ~3
N ~N ~--SC6H,3 N `N ~SC6HI3
H~c~3 o2N~3
,N ¢~ N~,N
~ o2N
The amounts of the above described ingredients that are added to the
emulsion layer according to the present invention may be varied depending
upon the particular compound used and upon the type of emulsion layer ~i.e.,
black and white or color). However, the ingredients are preferably added in an
S amount of 0.01 to 100 mol, and more preferably from 0.1 to 5û mol per mol of
silver halide in the emulsion layer.
-13-
~- '
.
- .....
:; ,,, -
- ~ :
2101~ ~
The photothermographic dry silver emulsions of this invention may be
constructed of one or more layers on a substrate. Single layer constructions
must contain the silver source material, ~he silver halide, the developer and
binder as well as optional additional materials such as toners, coating aids, and
5 other adjuvants. Two-layer constructions must contain the silver source and
silver halide in one emulsion layer (usually the layer adjacent to the substrate)
and some of the other ingredients in the second layer or both layers, although
t~vo layer constructions compAsing a single emulsion layer containing all the
ingredients and a protective topcoat are envisioned. Multicolor
10 photothermographic dry silver constructions may contain sets of these bilayers
for each color, or they may contain all ingredients within a single layer as
described in U.S. Pat. No. 4,708,928. In the case of multilayer multicolor
photothermographic articles the various emulsion layers are generally
maintained distinct from each other by the use of functional or non-functional
15 barrier layers between the various photosensitive layers as described in U.S. Pat. No. 4,460,681.
While not necessary for practice of the present invention, it may be
advantageous to add mercury aI) salts to the emulsion layer(s) as an
antifoggant. Preferred mercury (II) salts for this purpose are mercuric acetate
20 and mercuric bromide.
The light sensitive silver halide used in the present invention may
typically be employed in a range of 0.75 to 25 mol percent and, preferably,
from 2 to 20 mol percent of organic silver salt.
The silver halide may be any photosensitive silver halide such as silver - -
25 bromide, silver iodicle, silver chloride, silver bromoiodide, silver
chlorobromoiodide, silver chlorobromide, etc. The silver halide may be in any
form which is photosensitive including, but not limited to cubic, orthorhombic,
tabular, tetrahedral, etc., and may have epita~ial growth of crystals thereon.
The silver halide used in the present invention may be employed without
30 modification. However, it may be chemically sensitized with a chemical
sensitizing agent such as a compound containing sulfur, selenium or tellurium
-14-
..
. ~ -. ' ', '- : . , :
. ,. . - - ;. ~ . ~ ~. .
- : . . -
- - . . . - :
- ' ' ' ' , '' -, . '
. .. . . - .
2101~
etc., or a compound containing gold, platinum, palladium, rhodium or iridium,
etc., a reducing agent such as a tin halide, etc., or a combination thereof. Thedetails of these procedures are described in T.N. James "The Theory of the
Photographic Process", Fourth Edition, Chapter 5, pages 149 to 169.
S The silver halide may be added to the emulsion layer in any fashion
which places it in catalytic proximity to the silver source. Silver halide and
the organic silver salt which are separately formed or "prefonned" in a binder
can be mixed prior to use to prepare a coating solution, but it is also effective
to blend both of them in a ball mill for a long period of time. Further, it is
10 effective to use a process which comprises adding a halogen-containing
compound in the organic silver salt prepared to partially convert the silver of
the organic silver salt to silver halide.
Methods of preparing these silver halide and organic silver salts and
manners of blending them are known in the art and described in Research
Disclosure, June 1978, item 17029, and U.S. Pat. No. 3,700,458.
The use of preformed silver halide emulsions of this invention can be
unwashed or washed to remove soluble salts. In the latter case the soluble saltscan be removed by chill-setting and leaching or the emulsion can be coagulation
washed, e.g., by the procedures described in U.S. Pat. Nos. 2,618,5S6;
2,614,928; 2,565,418; 3~241,969; and 2,489,341. The silver halide grains
may have any crystalline habit including, but not limited to cubic, tetrahedral,orthorhombic, tabular, laminar, platelet, etc.
The organic silver salt may be any organic material which contains a
reducible source of silver ions. Silver salts of organic acids, particularly long
chain (10 to 30 preferably 15 to 28 carbon atoms) fatty carboxylic acids are
preferred. Complexes of organic or inorganic silver salts wherein the ligand
has a gross stability constant between 4.0 and 10.0 are also desirable. The
silver source material should preferably constitute from about 5 to 30 percent
by weight of the imaging layer.
The organic silver salt which can be used in the present invention is a
silver salt which is comparatively stable to light, but forms a silver image when
-15-
.
,
~ ' ,~ ' ' - ~ -
- :
.
21~1 5G i~
heated to 80 C or higher in the presence of an exposed photocatalyst (such as
photographic silver halide) and a reducing agent.
Preferred organic silver salts include silver salts of organic compounds
having a carboxy group. Non-limiting examples thereof include silver salts of
5 an aliphatic carboxylic acid and a silver salt of an aromatic carboxylic acid.Preferred examples of the silver salts of aliphatic carboxylic acids include silver
behenate, silver stearate, silver oleate, silver laurate, silver caproate, silver
myristate, silver palmitate, silver maleate, silver fumarate, silver tartrate,
silver linolea~e, silver butyrate and silver camphorate, mixtures thereof, etc.
10 Silver salts with a halogen atom or a hydroxyl on the aliphatic carboxylic acid
can also be effectively used. Preferred examples of the silver salts of aromaticcarboxylic acids and other carboxyl group-containing compounds include silver
benzoate, a silver substituted benzoate such as silver 3,5-dihydroxybenzoate,
silver o-methylbenzoate, silver m-methylbenzoate, silver p-methylbenzoate,
15 silver 2,4-dichlorobenzoate, silver acetamidobenzoate, silver p-phenyl benzoate,
etc., silver gallate, silver tannate, silver phthalate, silver ~erephthalate, silver
salicylate, silver phenylacetate, silver pyromellitate, a silver salt of
3-carboxymethyl~-methyl-4-thiazoline-2-thione or the like as described in U.S.
Pat. No. 3,785,830, and silver salt of an aliphatic carboxylic acid containing a20 thioether group as described in U.S. Pat. No. 3,330,663, etc.
Silver salts of compounds containing mercapto or thione groups and
derivatives thereof can also be used. Preferred examples of these compounds
include a silver salt of 3-mercapto-4-phenyl-1,2,4-triazole, a silver salt of
2-mercaptobenzimidazole, a silver salt of 2-mercapto-5-aminothiadiazole, a
25 silver salt of 2-1ethylglycolamido) benzothiazole, a silver salt of thioglycolic
acid such as a silver salt of an S-allyl thioglycolic acid (wherein the alkyl group
has from 12 to 22 carbon atoms), a silver salt of a dithiocarboxylic acid such as
a silver salt of dithioacetic acid, a silver salt of a thioamide, a silver salt of
5-carboxylic-1-methyl-2-phenyl-4-thiopyridine, a silver salt of mercaptotriazine,
30 a silver salt of 2-mercaptobenzoxazole, a silver salt as described in U.S. Pat.
No. 4,123,274, for example, a silver salt of 1,2, 4-mercaptothiazole derivative
-16-
- . , - . . . . .
2 1 ~
such as a silver salt of 3-amino-5-benzylthio-1,2,4-thiazole, a silver salt of
thione compound such as a silver salt of
3-(2-carboxyethyl)-4-methyl-4-thiazoline-2-thioneas disclosed in U!S. Pat. No.
3,301,678.
S Furthermore, a silver salt of a compound containing an imino group may
be used. Preferred examples of these compounds include silver salts of
benzothiazole and derivatives thereof, for example, silver salts of
benzothiazoles such as silver methylbenzotriazolate, etc., silver salt of
halogen-substituted benzotriazoles, such as silver S-chlorobenzotriazolate, etc.,
10 silver salts of carboimidobenzotriazole, etc., silver salt of 1,2,4-triazoles or
l-H-tetrazoles as described in U.S Pat. No. 4,220,709, silver salts of imidazoles
and imidazole derivatives, and the like. Various silver acetylide compounds
can also be used, for instance, as described in U.S. Pat. Nos. 4,761,361 and
4,775,613.
It is also found convenient to use silver half soaps, of which an
equimolar blend of silver behenate and behenic acid, prepared by precipitation
from aqueous solution of the sodium salt of commercial behenic acid and
analyzing about 14.5 percent silver, represents a prefelTed example.
Transparent sheet materials made on transparent film backing require a
20 transparent coating and for this purpose the silver behenate full soap, containing
not more than about four or five percent of free behenic acid and analyzing
about 25.2 percent silver may be used.
The method used for making silver soap dispersions is well known in the
art and is disclosed in Research Disclosure, April 1983, item 22812, Research
25 Disclos~lre, October 1983, item 23419 and U.S. Pat. No. 3,985,565.
The light-sensitive silver halides may be advantageously spechally
sensitized with various l~own dyes including cyanine, merocyanine, styryl,
hemicyanine, oxonol, hemioxonol and xanthene dyes. Useful cyanine dyes
include those having a basic nucleus, such as a thiazoline nucleus, an o~azoline30 nucleus, a pyrroline nucleus, a pyridine mlcleus, an oxazole nucleus, a thiazole
nucleus, a selenazole nucleus and an imidazole nucleus. Useful merocyanine
.- -- . . . .- ~
' ' . ' ' - ' : - - ' -
. .-.:
,
~- .
2 101 ~ ~
dyes which are preferred include those having not only the above described
basic nuclei but also acid nuclei, such as a thiohydantoin nucleus, a rhodanine
nucleus, an oxazolidinedione nucleus, a thiazolidinedione nucleus, a barbituric
acid nucleus, a thiazolinone nucleus, a malononitrile nucleus and a pyrazolone
5 nucleus. In the above described cyanine and merocyanine dyes, those having
imino groups or carboxyl groups are particularly effective. Practically, the
sensitizing dyes to be used in the present invention may be properly ælected
from known dyes such as those described in U.S. Pat. Nos. 3,761,279,
3,719,~95, and 3,877,943, British Pat Nos. 1,466,201, 1,469,117 and
10 1,422,057, and can be located in the vicinity of the photocatalyit according to
known methods. Spectral sensitizing dyes may be typically used in amounts of
about 10~ mol to about 1 mol per 1 mol of silver halide.
The reducing agent for the organic silver salt may be any material,
preferably organic material, that can reduce silver-ion to metallic silver.
15 Conventional photographic developers such as phenidone, hydroquinones, and
catechol are useful but hindered phenol reducing agents are preferred. The
reducing agent should be present as 1 to 10 percent by weight of the imaging
layer. In multilayer constructions, if the reducing a~ent is added to a layer
other than an emulsion layer, slightly higher proportions, of from about 2 to 1520 percent tend to be more desirable.
A wide range of reducing agents has been disclosed in dry silver
systems including amidoximes such as phenylamidoxime, 2-thienylamidoxime
and p-phenoxyphenylamidoxime, azines
(e.g., 4-hydroxy-3,5-dimethoxybenzaldehydeazine); a combination of aliphatic
25 carboxylic acid aryl hydrazides and ascorbic acid, such as
2,2'-bis(hydroxymethyl)propionyl-,B-phenylhydrazide in combination with
ascorbic acid; a combination of polyhydroxybenzene and hydroxylamine, a
reductone and/o~ a hydrazine (e.g., a combination of hydroquinone and
bis(ethoxyethyl)hydroxylarnine, piperidinohexose reductone or
30 fonnyl-4-methylphenylhydrazine); hydroxamic acids such as phenylhydroxamic
acid, p-hydroxyphenylhydroxamic acid, and ~B-alaninehydroxamic acid; a
-18-
: . . ... - . . . .. .
: .. , . - -, ,, ~ ' -
, . .-. - : -
., ~
- : . . - : - - . ~ .
. ~ . ' -'~ ~ " '
::, -- ' ' '" : ' - ' ' . '
' - .' ' ' . ' ' .' . . :
.
- 210~5~
combination of azines and sulfonamidophenols, (e.g., phenothiazine and
2,6-dichloro-4-benzenesulfonamidophenol); cY-cyanophenylacetic acid derivatives
such as ethyl-~-cyano-2-methylphenylacetate, ethyl a-cyanophenylacetate;
bis-,B-naphthols as illustrated by 2,2'-dihydroxyl-1-binaphthyl,
5 6,6'-dibromo-2,2'-dihydroxy-1,1'-binaphthyl, and
bis(2-hydroxy-1-naphthyl)methane; a combination of bis-,B-naphthol and a
1,3-dihydroxybenzene derivative, (e.g., 2,4-dihydroxybenzophenone or
2,4-dihydroxyacetophenone); 5-pyrazolones such as
3-methyl-1-phenyl-5-"razolone; reductones as illustrated by
10 dimethylaminohexose reductone, anhydrodihydroaminohexose reductone, and
anhydrodihydropiperidonehexose reductone; sulfonamido-phenol reducing agents
such as 2,6-dichloro-4-benzensulfonamidophenol, and
p-benzenesulfonamidophenol; 2-phenylindane-1,3-dione and the like; chromans
such as 2,2-dimethyl-7-t-butyl-6-hydroxychroman; 1,4-dihydropyridines such as
15 2,6-dimethoxy-3,5-dicarboethoxy-1,4-dihydrowridine; bisphenols (e.g.,
bis(2-hydroxy-3-t-butyl-5-methylphenyl)methane,
2,2-bis(4-hydroxy-3-methylphenyl)propane,
4,4-ethylidene-bis(2-t-butyl-6-methylphenol), and
2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane); ascorbic acid derivatives (e.g.,
20 1-ascorbyl palmitate, ascorbyl stearate); and unsaturated aldehydes and ketones,
such as benzil and biacetyl; 3-pyrazolidones and certain indane-1,3-diones.
In addition to the aformementioned ingredients it may be advantageous
to include additives known as "toners" that improve the image. Toner materials
may be present, for example, in amounts from 0.1 to 10 percent by weight of
25 all silver bearing components. Toners are well known materials in the
photothermographic art as shown in U.~. Pat. Nos. 3,080,254; 3,847,612 and
4,123,282.
Examples of toners include phthalimide and N-hydroxyphthalimide;
cyclic imides such as succinimide, pyrazoline-S-ones, and a quinazolinone,
30 3-phenyl-2- pyrazoline-S-one, 1-phenylurazole, quinazoline, and 2,4-
thiazolidinedione; naphthalimides (e.g., N-hydroxy-1,8-naphthalimide); cobalt
-19-
- ~ .
- - , -
- ~
21~15~
complexes (e.g., cobaltic hexammine trifluoroacetate); mercaptans as illustratedby 3-mercapto-1,2,4-triazole, 2,4-dimercaptopyrimidine,
3-mercapto-4,5-diphenyl-1,2,4-triazole and 2,5-dimercapto-1 ,3,4-thiadiazole;
N-(aminomethyl)aryldicarboximides, (e.g.,
5 (N,N-dimethylaminomethyl)phthalimide, and
N,N-(dimethylaminomethyl)naphthalene-2,3-dicarboximide); and a combination
of blocked pyrazoles, isothiuronium derivatives and certain photobleaching
agents (e.g., a combination of N,N'-hexarnethylene
bis(l-carbamoyl-3,5-dimethylpyrazole), 1,8-(3,~diazaoctane)bis(isothiuronium
10 trifluoroacetate) and 2-(tribromomethylsulfonyl)benzothiazole); and merocyanine
dyes such as
3-ethyl-5[(3-ethyl-2-benzothiazolinylidene)-l-methylethylidenq-2-thio-2~4-
oxazolidinedione; phthalazinone and phthalazinone derivatives or metal salts or
these derivatives such as 4-(1-naphthyl)phthalazinone, 6-chlorophthalazinone,
15 5,7-dimethoxyphthalazinone, and 2,3-dihydr~1,4-phthalazinedione; a
combination of phthalazinone plus sulfinic acid derivatives (e.g., phthalic acid,
4-methylphthalic acid, 4-nitrophthalic acid, and tetrachlorophthalic anhydride);quinazolinediones, benzoxazine or naphthoxazine derivatives; rhodium
complexes functioning not only as tone modifiers, but also as sources of halide
20 ion for silver halide formation in situ, such as ammonium hexachlororhodate
(III), rhodium bromide, rhodium nitrate and potassium hexachlororhodate (III);
inorganic peroxides and persulfates (e.g., ammonium peroxydisulfate and
hydrogen peroxide); benzoxazine-2,4-dîones such as 1,3-benzoxazine-2,4-dione,
8-methyl-1,3-benzoxazine-2,4-dione, and ~nitro-1,3-benzoxazine-2,4-dione;
25 pyrimidines and asymmetric triazines (e.g., 2,4-dihydroxypynmidine,
2-hydroxy-4-aminopyrimidine), azauracils, and tetrazapentalene derivatives
(e.g, 3,~dimercapt~1 ,4-diphenyl-lN,4H-2,3a,5,6a-tetraz~pentalene, and
1,4-di(o-chlorophenyl)-3,~dimercapto-lH,4H-2,3a,5,6a-tetrazapentalene).
A number of methods are known in the art for obtaining color images
30 with dry silver systems including: a combination of silver benzotriazole, well
known magenta, yellow and cyan dye-forming couplers, aminophenol
-20-
-
,
- . ' ' ' ':
2101~
developing agents, a base release agent such as guanidinium trichloroacetate andsilver bromide in poly(vinyl butyral) as described in U.S. Pat. Nos. 4,847,188
and 5,064,742; preformed dye release systems such as those described in U.S.
Pat. No. 4,678,739; a combination of silver bromoiodide, sul~onamidophenol
5 reducing agent, silver behenate, poly(vinyl butyral), an amine such as
n~octadecylamine and 2-equivalent or 4-equivalent cyan, magenta or yellow
dye-forming couplers; leuco dye bases which oxidize to form a dye image ~e.g.,
Malachite Green, Crystal Violet and para-rosaniline); a combination of in situ
silver halide, silver behenate, 3-methyl-1-phenylpyrazolone and
10 N,N'-dimethyl-p-phenylenediamine hydrochloride; incorporating phenolic leuco
dye reducing agents such as
2(3,5-di-(t-butyl)-4-hydroxyphenyl)-4,5-diphenylimidazole, and
bis(3,5-di-(t-butyl)-4- hydroxyphenyl)phenylmethanç, incorporating azomethine
dyes or azo dye reducing agents; silver dye bleach processes (for example, an
15 element comprising silver behenate, behenic acid, poly(vinyl butyral),
poly(vinyl-butyral)peptized silver bromoiodide emulsion,
2,~dichloro-4-benzçnesulfonamidophenol,
1,8-(3,~diazaoctane)bis(isothiuronium-p-toluenesulfonate) and an azo dye can be
exposed and heat processed to obtain a negative silver image with a uniform
20 distribution of dye, and then laminated to an acid activator sheet comprisingpolyacrylic acid, thiourea and p-toluenesulfonic acid and heated to obtain well
defined positive dye images); and amines such as aminoacetanilide (yellow
dye-forming), 3,3'-dimethoxybenzidine (blue dye-forming) or sulfanilide
(magenta dye forming) that react with the oxidized form of incorporated
25 reducing agents such as 2,6-dichloro-4-benænesulfonamidophenol to form dye
images. Neutral dye images can be obtained by the addition of amines such as
behenylamine and p-anisidine.
Leuco dye oxidation in such silver halide systems for color formation is
disclosed in U.S. Pat. Nos. 4,021,240, 4,374,821, 4,460,681 and 4,883,747.
Silver halide emulsions containing the stabilizers of this inventiori can be
protected further against the additional production of fog and can be stabilized
-21-
-~ , - -
.: ~ ', '- ', - ~ ' ' , ~
. - ~ .. . - . .
... : - -- - . . .-
: ,
2101.~
against loss of sensitivity during shelf storage. Suitable antifoggants, stabiliærs,
and stabilizer precursors which can be used alone or in combination, include
thiazolium salts as described in U.S. Pat. Nos. 2,131,038 and 2,694,716;
azaindenes as descAbed in U.S. Pat. Nos. 2,886,437and 2,444,605; mercury
S salts as described in U.S. Pat. No. 2,728,663; urazoles as described in U.S.
Pat. No. 3,287!135; sulfocatechols as descAbed in U.S. Pat. No. 3,235,652;
oximes as described in BAtish Pat. No. 623,448; nitrones; nitroindazoles;
polyvalent metal salts as descAbed in U.S. Pat. No. 2,839,405; thiouronium
salts as descAbed in U.S. Pat. No. 3,220,839; and palladium, platinum and
gold salts descAbed in U.S. Pat. Nos. 2,566,263 and 2,597,915;
halogen-substituted organic compounds as descAbed in U.S. Pat. Nos.
4,108,665 and 4,442,202; tAazines as descAbed in U.S. Pat. Nos. 4,128,557;
4,137,079; 4,138,265; and 4,459,350; and phosphorous compounds as
descrAbed in U.S. Pat. No. 4,411,985.
Stabilized emulsions of the invention can contain plasticizers and
lubricants such as polyalcohols (e.g., glyceAn and diols of the type described in
U.S. Pat. No. 2,960,404); fatty acids or esters SUC}I as those descAbed in U.S.
Pat. No. 2,588,765 and U.S. Pat. No. 3,121,060; and silicone resins such as
those descAbed in BAtish Pat. No. 955,061.
The photothermographic elements of the present invention may include
image dye stabiliærs. Such image dye stabilizers are illustrated by British Pat.No. 1,326,889; U.S. Pat. Nos. 3,432,300; 3,698,909; 3,574,627; 3,573,050;
3,764,337 and 4,042,394.
Photothermographic elements containing emulsion layers stabili~ed
25 according ~o the present invention can be used in photographic elements whichcontain light absorbing mateAals and filter dyes such as those descAbed in U.S.
Pat. Nos. 3,253,921; 2,274,782; 2,527,583 and 2,~56,879. If desired, the
dyes can be mordanted, for example, as described in U.S. Pat. No. 3,282,699.
Photothermographic elements containing emulsion layers stabilized as
30 descAbed herein can contain matting agents such as starch, titanium dioxide,
.
-22-
:, '
.:" ':
2 1 ~
zinc oxide, silica, polymeric beads including beads of the type described in
U.S. Pat. No. 2,992,101 and U.S. Pat. No. 2,701,245.
Emulsions stabilized in accordance with this invention can be used in
photothermographic elements which contain antistatic or conducting layers, such.5 as layers that comprise soluble salts (e.g., chlorides, nitrates, etc.), evaporated
metal layers, ionic polymers such as those described in U.S. Pat. Nos.
2,861,056 and 3,206,312 or insoluble inorganic salts such as those described in
U.S. Pat. No. 3,428,451.
The binder may be selected from any of the well-known natural or
10 synthetic resins such as gelatin, polyvinyl acetals, polyvinyl chloride, polyvinyl
acetate, cellulose acetate, polyolefins, polyesters, polystyrene, polyacrylonitrile,
polycarbonates, and the like. Copolymers and terpolymers are of course
included in these definitions. The preferred phototherrnographic silver
containing polymers are polyvinyl butyral, butyl ethyl cellulose, methacrylate
15 copolymers, maleic anhydride ester copolymers, polystyrene, and
butadiene-styrene copolymers.
Optionally, these polymers may be used in combinations of two or more
thereof. Such a polymer is used in an amount sufficient to carry the
components dispersed therein, that is, within the effective range of the action
20 as the binder. The effective range can be appropriately determined by one
skilled in the art. As a guide in the case of carrying at least an organic silver
salt, it can be said that a preferable ratio of the binder to the organic silver salt
ranges from 15:1 to 1:2, and particularly from 8:1 to 1:1.
Photothermographic emulsions containing a stabilizer according to the
25 present invention may be coated on a wide variety of supports. Typical
supports include polyester film, subbed polyester film, poly(ethylene
terephthalate)film, cellulose nitrate film, cellulose ester film, poiy(vinyl acetal)
film, polycarbonate film and related or resinous materials, as well as glass,
paper metal and the like. Typically, a flexible support is employed, especially
3Q a paper support, which may be partially acetylated or coated with baryta and/or
an a-olefin polymer, particularly a polymer of an a-olefin containing 2 to 10
-23-
:
2~0~6 ~
carbon atoms such as polyethylene, polypropylene, ethylene-butene copolymers
and the like. Substrates may be transparent or opaque.
Substrates with a backside resistive heating layer may also be used in
color phototherrnographic imaging systems such as shown in U.S. Pat. Nos.
5 4,460,681 and 4,374,921.
Photothermographic emulsions of this invention can be coated by various
coating procedures including dip coating, air hlife coating, curtain coating, orextrusion coating using hoppers of the type described in U.S. Pat. No.
2,681,294. If desired, two or more layers may be coated simultaneously by the
10 procedures described in U.S. Pat. No. 2,761,791 and British Pat. No. 837,095.Additional layers may be incorporated into photothermographic articles
of the present invention such as dye receptive layers for receiving a mobile dyeimage, an opacifying layer when reflection prints are desired, a protective
topcoat layer and a primer layer as is known in the photothermographic art.
15 Additionally, it may be desirable in some instances to coat different emulsion
layers on both sides of a transparent substrate, especially when it is desirable to
isolate the imaging chemistries OI the different emulsion layers.
The present invention will be illustrated in detail in the following
examples, but the embodiment of the present invention is not limited thereto.
EXAMPLES
The first three examples are typical synthetic procedures for compounds
of the invention. E~amples 4 through 8 illustrate the utility of the invention in
photothermographic imaging constructions. The scope of the invention is not
25 limited to the examples herein.
TLC means "thin layer chromatographyn.
All materials used in the following examples were readildy available
from standard commercial sources such as Aldrich Chemical Co. (Milwaukee,
WI) unless otherwise noted.
-2~-
- ~ .. .
`' ` 1 ~ ' `
~: . . .
. : ' ': ~ ' . ' '
"
2 ~
Densitometry measurements were made on a custom built computer
scanned densitometer and are believed to be comparable to measuremnts
obtainable from commercially av~ilable densitometers.
The structure of compounds I-A and I-B; lI, IIA, and IIB; IIIA, IIIB,
5 and mc are shown below:
[~N [~--11
O N ~3
02N
I-A I-B
1~
:.:
.
. .: ~ ~ -
,
2101V~
HO~
Se~tizing Dye A
10 1~,o~
CH2 N
Leuco Dys B
N~Nl$C H N N~\SC6H~3 `NlSC6Hl3
02N f 3,No2
Il II-A II-B
-2
. . . , . ~ ~ . . . . . . .. . . . . .
:. . . , - . : . . .
- . . , ~ . . - - ~. :
-; . -
- : - - - - -:
2101~
'I) ~N ~o '1) ~ ~I) o/N~O
02N~ H3Co~;X3 CH3OC~,3
m-A m-s m-c
~tCH3)3
,,~,,OH
O~ C(cH )
CH3CH2~ HO2CH~C~S
H~ \~
D
.. .~ .- ~ ` . .
- . - : . . .: ,-
- , : : :
, ; . ~ : - :
2101~ ~
Example 1
This examp!e describes a preparation generally useful for this class of
compounds and particularly shown as the preparation of 1- and
2-(o-nitrobenzyl)benzotriazole (I-A and I-B, respectively)
S 2-Nitrobenzyl bromide (9.1 g) and 5 g benzotriazole were stirred
together with 4.24 g triethylamine in 25 mL dichloromethane . The reaction
mixture was allowed to stir for 5 hours, then extracted with dilute sodium
carbonate solution and dried with magnesium sulfate, filtered, and evaporated.
The crude product (8.1 g) was recrystaUized from methanol/ethyl acetate. TLC
10 (on silica) showed two components, I-A (minor) and I-B (major). The crude
product was used for examples that follow.
Example 2
This example demonstrates the preparation of compounds ~-A and II-B.
To a stirred solution of 5.00 g 3-(n-hexylthio)-5-phenyl-1,2,4-triazole
(Il), 4.13 g o-nitrobenzyl bromide, and 0.310 g tetra-n-butylammonium
bromide in 200 mL dichloromethane was added a solution of 4.57 g sf
potassium carbonate in water. After vigorous stirring for five days, the layers
were separated. The aqueous layer was washed with dichloromethane and the
20 combined organic layers washed with brine (3xlO0 mL) and dried with sodium
sulfate, filtered and concentrated in vacuo ~o give 7.4 g of a light yellow oil.Chromatography on a silica gel flash column (4.6 x 15 cm dry packed and
eluted with 50:50 dichloromethane-hexane) gave 4.45 g II-A and 1.22 g of a
mix~ure of II-A and I~-B containing ca. 18~6 II-A. As the isomers II-A and
25 II-B were equally effective, separation was not necessary.
Example 3
This example demonstrates ~e preparation of compound m-A.
To a suspension of 4.32 g 1-phenyl-3-pyrazolidinonè in 30 mL
30 anhydrous ethanol under nitrogen was added 19 mL of 1.07 M sodium ethoxide
in ethanol, and 3.08 g 2-nitrobenzyl bromide was added. After about 100
-28-
. ~; . ' . :
.... : .
2:101~g'~
minutes, TLC (in ether) showed the reaction complete. The solvent was
removed in vacuo overnight. The residue was taken up in ethyl acetate, washed
with aqueous sodium bicarbonate and water, and evaporated. A viscous oil
(5.74 g) was obtained. The crude product was flash chromatographed with
S silica gel in ether. After evaporation of solvent, 3.75 g III-A was obtained,
which crystallized on standing.
Exarnple 4
A silver premix was prepared as follows: a dispersion of silver behenate
10 half soap was made at 10% solids in toluene and acetone by homogenization.
To 223.3 g of the silver half soap dispersion was added 0.34 g of polyvinyl
butyral. After 15 minutes of mixing, 7.6 mL of a solution of 0.963 g
mercuric acetate in 19.0 g methanol, and 21.2 mL of a solution of l.0 g
calcium bromide in 49.0 g ethanol were added. Then 14.5 mL of a solution of
15 1.45 g calcium bromide in 48.5 g e~hanol was added 60 minutes later. After 60 minutes of mixing 41.2 g of polyvinylbuty~l was added.
To 29.3 g of the silver premi~ described above was added 1.47 mL of a
solution of 0.021 g sensitizing dye A in 50 mL methanol.
After 30 minutes a magenta color-forming leuco dye B solution was
20 added as shown below.
C~mponent Amount
LeucD Dye B 0.61 g
Phthalazinone 0.916 g
Tetrahydrofuran 22.4 g
Methyl Ethyl Ketone 33.6 g
VAGH~ (IJnion Carbide) 2.2 g
~a vinyl acetate/vinyl chloride copolymer)
P~lyvinylbutyral 9.8 g
.
3~
-29-
-, . . , - . . : :. , - . -
- . - -
-
,- : - .: - . - . - . . -
2101~
The leuco dye B is disclosed in U.S. Pat. No. 4,795,697.
A topcoat solution was prepared consisting of 23% by weight
polystyrene resin, and 3.1 wt % Acryloid B-66 (Monsanto) in approximately
50:50 mixture of toluene and methyl ethyl ketone.
To lO.Og of the magenta silver coating solution was added 0.4 mL or
0.9 mL of the mixture of I-A and I-B from Example 1, at a concentration of
0.25 g mixture in 5.0 mL of tetrahydrofuran, or 0.3 mL of benzotriazole ~BZT)
at a concentration of 0.34 g in 5 mL ethanol, or 0.4 mL or 0.9 mL of
o-nitrobenzyl alcohol (BA) at a concentration of 0.14 g in 5.0 mL ethanol.
The magenta silver layer and topcoat were each coated at a wet
thickness of 2 mils, and dried for 5 minutes at 82C. The samples were
exposed for 10-3 seconds th~ough a 58 Wratten filter and a 0 to 3 continuous
wedge and developed by heating to approximately 138C for 6 seconds.
The density of magenta color for each sample was measured using a
15 green filter of a computer densitometer.
The initial sensitometric data were:
Stabilizer D""" D",~,~ Speedl Cont~ast2
~ ~ ~
Control (0.0 mL) 0.10 1.68 2.19 1.25
0.3 mL BZT 0.10 0.11 ** **
0.4 mL BA 0.10 1.72 2.20 1.24
0.9 mL BA 0.10 1.78 2.22 1.31
0.4 mLI-A + I-B3 0.10 1.77 2.16 1.26
0.9 mLI-A + I-B 0.10 1.73 2.20 1.31
*~ In this and subsequent tables, means the value was not obtainable (i.e., no
image)
I Log exposure corresponding to densi~ of 0.6 above D"" ,.
~ Average contrast measured by the slope of the line joining density
points 0.3 and 0.9 above D,......
3 This iS an approximate molar equivalent of the BZT parent stabilizer.
-30-
.
- . ~ -. . - . .
.. . .. .
' ~
: ,' . . ' :
..
- .
21~1~6 -~
Post-processing stability was measured by exposing imaged sarnples to
1200 ft-candles of illumination (daylight fluorescent bulbs) for 6 and 24 hours
at 655'0 relative humidity and 26.7 C.
6 hours 24 hours
Stabilizer D~ ""' t~D,~ D"""' ~D""~'
Con~ol (0.0 mL) +.17 -.19 +.24 -.54
0.3 mL BZT +.11 ** +.11 **
0.4 mL BA +.13 -.25 +.22 -.66
0.9 mL BA +.11 -.23 +.21 -.78
0.4mLI-A + I-B +.11 -.23 +.11 -.66
0.9 mL I-A + I-B +.09 -.21 +.08 -.77
- -
I ~D = DF;~ - D~,;". D values represent reflectance optical density
through a green filter.
At this concentration of the primary stabilizer benwtriazole, D",~,
20 post-processing improvements were obs~rved, but significan~ desensitization of
the silver halide emulsion had occurred. With the use of the masked
benzotriazoles I-A ~t I-B, ~e benzotria~ole activity was adequately blocked to
minimize any initial desensitization effects and yet release of BZT occurred at
the appropriate time for D""" post processing improvements similar to the
25 unblocked BZT stabilizer. 2-Nitrobenzyl alcohol alone (BA) also contributes
some post processing stabilization at 6 hours, but the effect is minimal after
prolonged exposure to 24 hours illumination.
- - . - .. . . . . . - .
- ~
~ . . .
., -. . . - , . , . - . .: . .. . . . .
.. . .
- - - . -
2101~
Example 5
To lO.Og of a magenta silver halide coating solution similar in
component composition as described in Example 4, was added 0.8 mL of an
isomer mixture, compounds II-A and II-B at a concentration of 0.3 g in 5.0
5 mL ethanol, or 0.8 mL of the primary stabilizer
3-(n-hexylthio)-5-phenyl-1,2,4-triazole (Il) at a concentration of 0.2 g in 5.0
mL ethanol. The silver solutions and topcoats were coated, exposed, and
processed as described in Exarnple 4. The density of magenta color for each
sample was measured using a green filter of a computer densitometer. The
10 initial sensitometric data are shown below.
Stabilizer D"", D""" Speedl Contrast2 Contrast3
Control (0.0 mL) .08 1.73 1.85 1.60 1.80
15 0.8 mLIIA + IIB .08 1.54 1.86 1.63 1.43
0.8 mL II .08 1.09 2.72 1.11 ~**
' Log e~posure corresponding to density of 0.6 above D~"",. -
2 Average contrast me~sured by the slope of the line joining density
points 0.3 and 0.9 ~bove D,
3 Average contrast measured by the slope of the liDe joining density
points 0.6 and 1.20 above D . .
The post-processing print stabili~ was measured as described in
25 Example 4, and the results are shown below.
6 hours 24 hours
~D""~, AD",," D",~, aD"",~
Control (O.O mL) +.16 -.14 +.21 -.50
0.8 mL II-A + II-B +.12 -.11 +.13 -.48
0.8 mL II +.13 -.19 +.14 -.48
At this ~ncentra~on of the primary stabilizer II, D""" post-processing
improvements were observed wi~ significant desensitization of the silvor halide
-32-
: .
- - . , - - ~ ~ . . .
2101.~
emulsion. With the addition of an equivalent molar amount of II-A + II-B,
the parent compound was adequately blocked to minimize most desensitization
and yet release of the primary stabilizer II occurred at the appropriate time
after processing for D~ post-processing stabilization similar to the unblocked
5 II stabilizer.
Example 6
A silver premix was prepared as follows: a dispersion of silver behenate
half soap was made at 10% solids in toluene and ethanol by homogenization
10 and contained 1.5% by weight polyvinyl butyral. To 71g of this silver half
soap dispersion was added 200g of ethanol. After lS minutes of mixing, 2.6
mL of a mercuric bromide solution (0. l9g in 10 mL methanol) was added.
Then an additional 2.6 mL of mercuric bromide solution(0.19g in lQ rnL
methanol) was added lS minutes later. After 60 minutes of mixing 25g of
15 polyvinyl butyral was added.
To 82.7g of the prepared silver premix described above was added a
cyan color-forming leuco dye solution as shown below.
Component Amount
Leuco Dye C 0. 82g
Toluene 11.7g
Ethyl methacrylate copolymer 2.3g
(Acryloid~ B72, Rohm and Haas)
FC-431~ (a fluorocarbon surfactant, 3M) 0.2 ~
Ethanol 1.21 g
Preparation of leuco dye C is disclosed in U.S. Pat. No. 4,782,010.
After the addition of ~e leuco dye premix solution, 1.2 rnL of the
sensitizing dye D (0.016g / 13 mL methanol + 37 mL toluene), shown above,
3Q was- added and aliQwed to sensitize for 30 minu~s.
-33-
- - - . - .. ~: .. -
. .
. . : -, ,
.: .' , . , .' : , '' , ~ ': .
2101~
A topcoat solution was prepared containing approximately 17% Scripset
640~ (Monsanto, styrene/maleic anhydride copolymer), 1.1% Syloid 244~
(Monsanto, colloidal silica), 1.37% phthalic acid, 0.14% benzotriazole, and
0.44% of a fluorocarbon surfactant in an approximate 50:50 mixture of
5 methanol and ethanol.
To 15.0 g aliquots of the topcoat solution described above was added
0.182% or 0.455% by weight compound m-A, or 0.1% or 0.25% by weight
l-phenyl-3-pyrazolidinone (P).
The cyan silver layer and topcoat were each coated at a wet thickness of
10 2 mils and 1.5 mils, respectively and dried for 3 minutes at 82 C. The
samples were exposed for 10-3 seconds through a 25 Wratten filter and a 0 to 3
continuous wedge and developed by heating to approximately 138- C for 6
seconds.
The density of the cyan color for each sample was measured using a red
15 filter of a computer densitometer. Post-processing stability was measured by
exposing imaged samples to 1200 ft. candles of illumination for 6 and 24 hours
at 65% relative humidity and 26.7 C. The initial sensitometric data are shown
below.
-34-
., . . - . .
. .
`~ '
'
210~ L~
D" ", Dmax Speed' Contrast2 ContrasP
Control (0.0) .17 2.08 1.57 1.44 1.37
S 0.1% P .77 ** ** ** **
0.25% P 1.14 ** ~* ** **
0.182% m-A .18 1.93 1.58 1.43 1.42
0.455% m-A .19 2.10 1.47 1.62 1.69
' Log e~posure co~TespondiDg to density of 0.6 above D,
2Ave~age contrast measured by the slope of the line joiniDg density points
0.3 and 0.9 above D
3 Ave~uge contrast measured by the slope of the line joining densi~ points
0.6 and 1.20 above D . .
The post-processing print stability results are shown below.
6 hours 24 hours~D~ D""" ~D""~
Control (0.0) +.32 -.05 + .76 -.02
0.182% m-A +.30 +.04 +.69 +.08
0.455% m-~ +.30 +.04 +.67 +.03
-
The addition of l-phenyl-3-pyrazolidinone increased the initial D,.....
significantly, but the addition of the blocked l-phenyl-3-pyrazolidinone m-A,
at a molar amoun~ e:quivalent to the parent compound g~ve negligible effects on
initial sensitometry . Small D~ o post-processing improvements were observed
30 with m-A, though l-phenyl-3-pyrazolidinone alone did not significan~y
stabilize the post-processed irnage.
,
-35-
. . . : ., , :
.- - . :. . . -. . ~ .. ~ -
- . . - , - -- .
- . . - ~ : . ~: -
, . . - :
- - , .: . -
- . . . - - . . :
,
- . ~ . - -
. . . . . . . .
2101~
Example 7
To l5.0g aliquots of the topcoat solution described in Example 6 was
added 0.192% or 0.67% by weight compound m-B, which has the structure
shown above.
S The silver solutions and topcoats were coated, exposed, and processed as
described in Example 6. The initial sensitometric data are shown below.
Stabilizer D""~, D,~ Speedl Contrast2
Control (0.0) .15 1.81 1.90 1.43
0.192% m-B .15 1.92 1.78 1.69
0.67% m-B .15 1.90 1.74 1.90
' Log e~posure co~espond~ng to a density of 0.6 above D
2 Average contrast messured by the slope of the l~ne joiniDg density poi~ts 0.3 and
0.9 ~bove D,.~..
The post-processing print stability was measured at 100 ft. candles of
illumination for 7 and 14 days at 73% relative humidi~y and 70 C. These
results are shown below.
7 days ` 14 days
~D""" ~D"",~ ~D""" ~D,
_ ~
Control (0.0) +.43 +.12 +.64 +.16
0.192% m-B +.36 +.07 +.50 +.07
0.67% m-B +.35 +.Og +.50 +.06
As described in Example 6 the parent compound
l~henyl-3-py~azolidinor~e greatly increased initial D~""" but an equivalent molar
- 35 amount of the blocked 1-phenyl-3-pyrazolidinone m-B adequately blocked the
., ~ ..
-
.
.: ~ - - -. :. . . .
. ~- .. - . - , .
~ . . . .
2 1 0 ~
activity of the l-phenyl-3-pyrazolidinone to minimize initial sensitometry
effects. Modest post-processing D""" improvements were observed.
.
Example 8
To a 15.0 g aliquot of topcoat solution described in Example 6 was
added 0.77% by weight compound m-c.
The silver solutions and topcoats were coated, exposed and pr~cessed as
described in Example 6. The initial sensitometric data are shown below.
10 Stabilizer D,~", D"",~ Speedl Contrast2
~ . ... _ _
Control (0.0) .16 2.33 1.91 3.23
0.77~0 m-c .17 2.21 1.84 3.25
' Log e~posure corre~ponding to density of 0.6 above D,.....
2 Average contrast malsured by the dope of the line joining 0.3 and 0.9 above D~o ".
-37-
- -- .
.- . - - - ~ -
2 1 ~
The post-processing stability was measured as described in Example 7
and the results are shown below.
.
Stabiliær /~D"", ~D,
1200 foot-candles
6 hours 24 hours
Control (0.0) +.29 +.70
0.77%m-C +.27 +.67
100 foot-candles
7 days 14 days
Control (0.0) +.45 +.67
0.77% m-c +.37 +.51
--- _
As described in Example 6 the parent compound
1-phenyl-3-pyrazolidinone greatly increased initial D",~" but an equivalent molar
amount of the blocked l-phenyl-3-py~azolidinone, III-C, adequately blocked the
acti~ity of the parent compound to give minimal effects on the initial
20 sensitometry. Modest post-processing D""" improvements were observed at
both intensities of illumination.
Example 9
This example illustrates the effectiveness of a nitrobenzyl-protected
25 stabilizer in a mercury-free formulation.
To 200 g of a silver half soap dispersion containing preformed silver
bromide crystals at 55 C was added 32 g of polyvinyl butyral. Aher 30
minutes of mixing, three portions of 55 mg of pyridinium hydrobromide
perbromide in 2 mL ethanol each were added at 60 minute intervals. Finally,
30 1.3 mL 10 wt % calcium bromide in ethanol was added 30 minutes later. The
mixture was incubated overnight, then 17 mL of a solution of 21 mg of
sensiti~ing dye A in 100 mL metllanol was added and stinred for 30 minutes.
-38-
.. . . . , . :. . . .
. . . .
. - -. -.,. . : - . - ~ .
~ .. .. , ~ . . . .
. . ~ -,: ~ . - . ~ -
. . ~ . - ,. .
. ., : - ~
.- - ~. ~: - :
21015~
To 7.0 g of the above silver dispersion was added 12.5 g of the below
described magenta color-forming leuco dye B.
Com~onent Amount
Leuco Dye B O.9g
Phthalazir~one 1.8g
Tetrahydrofuran 80.0g
VAGH (Union Carbide) 2.7g
(vinyl acetate/vinyl chloride copolymer~
Polyvinylbutyral 7.6g
A topcoat solution was prepared consisting of lS g of 4.6% by weight
cellulose acetate resin in approximately 11214 mixture of methanol, methyl ethylketone, and acetone, with 25 mg of 2,5-bis(tribromomethyl)-l-thia-3,4-diazole.
lS To 19.5g of the magenta silver coating solution was added 20 to S0 mg
of the mixture of compounds I-A and I-B, as a methanol solution.
The magenta silver layer and topcoat were each coated at a wet
thickness of 2 mils, and dried for 4 minutes at 77 C. The samples were
exposed for 10-3 seconds through a 58 Wratten filter and a 0 to 3 continuous
20 wedge and develope~ by heating to ap~r~ximately 136 C for 14 seconds.
The density of magenta color for each sample was measured using a
green filter of a cornputer densitometer. Post-processing stability was measuredby exposing imaged samples to 1200 ft-candles of illumination (daylight
fluorescent bulbs) for 6 and 24 hours at 65% relative humidity and 26.7 C.
25 The initial sensitometric data a~e shown below.
-39-
, . :
- . .. . . .
.. - .,, .- . . .- - - : i . . - - ' ' :
. . , . . , . : . .
.~ . . . . . . . . .
. . . . . . - .
.. . .
2101~ ~
Do~n D"""~ S~eed' Contrast2
.
Control (0.0 mL) .. 11 2.19 1.23 3.90
520 mg I-A+I-B .12 2.20 1.22 3.89
30 mg I-A+I-B .11 2.20 1.20 3.76
40 mg I-A+I-B .13 2.22 1.22 4.01
50 mg I-A+I-B .12 2.21 1.22 3.84
~ Log e~tposure corresponding to derlsity of 0.6 above D,......
2 Average contrast measured by the slope of the line joining density points 0.3 alld
0.9 above Dm
3 This iS Ul appro~ te molar equivalent of the BZT parent stAbilizer.
The post processing print stabili~ of these constructions was measured
at 1200 ft candles and the results are shown below.
Stabilizer 6 hours 24 hours
~D"",1 %Fade /~D~,,,,,I %Fade
; ~ . ~ . _.
Control (0.0 mL) ~.16 11% +.26 40%
20 mg I-A+I-B +.10 13% +.14 44%
2S 30 mg I-A+][-B +.09 14% +.15 44%
40 mg I-A+]l-B +.07 12% +.11 46%
50 mg I-A+I-B +.08 15% +.11 46%
~ Final D",b, - ~iti~l D",b,. Refers to refleclance optical density throu~h a gree~ filter.
Substantial improvements in red and blue filter ~\D""" were also seen
with I-A + I-B. Note that addition of this stabilizer gives no adverse effects
on sensitometry.
~0-
. :. .
, . ' . ':
2 1 0 1 ~ ~ ~
Examples 10-13
A silver halide-silver behenate dry soap was prepared by the procedures
described in U.S. Pat. No. 3,839,049. The silver halide totalled 9~ of the
total silver while silver behenate comprised 9% of the total silver. The silver
5 halide was a O.OSS micron silver bromoiodide emulsion with 2% iodide.
A photothermographic emulsion was prepared by homogenizing 300 g of
the silver halide-silver behenate dry soap described above with 525 g toluene,
1675 g 2-butanone and S0 g poly(vinylbutyral) (13-76, Monsanto).
The homogenized photothermographic emulsion (500 g) and 100 g
10 2-butanone were cooled to 55F with stirring. Additional poly(vinylbutyral)
75.7 g ~76) was added and stirred for 20 minutes. Pyridinum hydrobromide
perbromide (PHP, 0.45 g) was added and stirred for 2 hours. The addition of
3.25 ml of a calcium bromide solution (1 g of CaBr2 and 10 ml of methanol)
was followed by 30 minutes of stirring. The temperature was raised to 70F
15 and the following were added in 15 minute increments with stirnng:
3.0 g (2-(4-chlorobenzoyl)benzoic acid, IR dye solution (D-l dye; 10.5 mg D-l
in 6g dimethylformamide), 185 mg of 2-mercaptobenzimidazole in 5g methanol,
16.4 g of developer 1,1-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-
trimethylhexane, and 1.7 g 2-(tribromomethylsulfone)benzotlliazole.
(CH2)2COO- (cH2)
D-1
The photothermographic emulsion wæ divided into 40g portions. The
control was coated at this stage without any additions (cont~ol) as were
Examples 12 and 13. Examples 10 and 11 contained equal molar levels of the
30 parent compound (BZI~ and the blocked denvative (I-A + I-B) respectively.
. ~ , . ...
- - - .
: . : .. . .
~ ~ :
- - : ' ~ ~
21 ~15~ -~
The photothermographic emulsions were coated on 3 mil (0.76 x lO~m)
polyester base by means of a knife coater and dried at 175F for four minutes.
The dry coating weight was 23 g/m2.
An active, protective topcoat solution-was prepared with the following
5 ingredients:
256.0 g acetone
123.0 g 2-butanone
50.0 g methanol
20.2 g cellulose acetate
2.89 g phthalazine
1.55 g 4-methylphthalic acid
1.01 g tetrachlorophthalic acid
1.50 g tetrachlorophthalic anhydride
The bulk topcoat was split into 20 g portions. Equal molar levels of BZT and
15 I-A + I-B were added to the topcoat solutions for examples 12 and 13. The
topcoat solutions were coated over the silver layer at a dry weight of 3.0 g/m2.The layer was dried at 175F for four minutes.
The coated materials were then exposed with a laser sensitometer
incorporating a 780 nm diode. After exposure, the film strips were processed
20 at 260F for ten seconds. The images obtained were evaluated by a
densitometer. Sensitometric results include Dmin, Dmax, Spd (relative speed at
a density of 1.0 above Dmin versus a control wtih no added test compound set
at 100) and average contrast (cont measured frorn a density of 0.25 to 2.0
above Dmin). The processed film strips were tested for print stability by
25 taping the strips to a view box (type employed by radiologists). The film strips
were placed on the view box with the raw polyester side next to the view box
and the silver and topcoat side out. The view box remained on during the four
day test period. The Dmin values were read after the four day print stability
test and are reportesl in Table 1.
-42-
- ~ . . . ~
.
: ....... ; . - . : - , . . ~ . ,., . . -
- ~ . . . - -- .
2 1 ~
The results compiled in Table 1 show that both the parent compound
BZT and the blocked version I-A + I-B greatly improve the print stability.
The blocked benzotriazole, I-A + I-B, would be preferred due to the smaller
reduction in intial sensitivity.
-43-
. ::, , .
;, ~ ,;
.. . .
.~ . ,
21 01 5 ~ L~
c~ O. 2 =0 =0 O
_ _ _
~ ~ e _ O O O O
;~ 8 ~o o ~ 8
~,
--o _ O o o
~ ~ ~ --æ ~ O O
~ .
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