CA1116916A

CA1116916A - Photographic and thermographic material containing a resorcinol dye-forming coupler

Info

Publication number: CA1116916A
Application number: CA000305464A
Authority: CA
Inventors: Roland G. Willis; Phillip D. Knight; David A. Pupo
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1978-04-03
Filing date: 1978-06-14
Publication date: 1982-01-26
Also published as: GB2018453A

Abstract

Abstract of the Disclosure A heat developable photographic element for producing a dye enhanced silver image comprises, in reactive association, (a) photosensitive silver halide, (b) an image-forming combination comprising (i) an organic silver salt oxidizing agent, with (ii) an organic reducing agent, (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of the reducing agent and (d) a binder.
After imagewise exposure, a dye enhanced silver image can be produced in such a material by merely heating the material. The combination of the described organic silver salt oxidizing agent with the organic reducing agent and the resorcinol, dye-forming coupler can be useful in a thermographic material. Other addenda employed in heat developable photographic materials, such as sensitizing dyes, can be useful with the heat developable materials containing the resorcinol, dye-forming coupler.

Description

Background Or the Invention _ eld of the Invention This inventlon relates to heat developable photographic materials and processes for providing a dye enhanced silver image. In one cr its aspects it relates to a heat developable photographic element for producing a dye enhanced silver image comprising a support having thereon, in reactive association, a combination of photosensitive silver halide with a certain image-forming combination and a certain resorcinol, dye-forming coupler. In another of its aspects it relates to a process for providing such a dye enhanced silver image by merely heating the described heat developable photographic material after imagewise exposure. A further aspect of the invention relates to a thermographic material comprising the described image-forming combination with the resorcinol, dye-forming coupler.

Description of the State of the Art It is well known to provide a silver image in a heat developable photographic materlal. Heat developable photographic materials are also known as photothermographic materials. Heat developable photographic materials after imagewise exposure are heated to moderately elevated temperatures to provide a developed image in the absence of separate processing solutions or baths. The heat development can provide a developed silver image in the material.
The most common organic silver salts in heat developable photographic materials are silver salts of long-chain fatty acids, such as silver behenate, which generally require hydrophobic binders. These organic silver salts are useful with photosensitive silver halide in heat developable photographic materials. These heat developable photographic materials have encountered certain problems.
First, it is desirable to replace the silver salts long-chain fatty acids to enable more effective use of aqueous or hydrophilic compositions, such as aqueous silver halide emulsions. Use of silver behenate as a source of silver in heat developable photographic materials is not particularly compatible with aqueous formulations of photo-graphic silver halide.
Other organic silver salts have been proposed forheat developable photographic materials. These include, for example, silver salts of benzotriazole, silver salts of saccharin and related organic silver salts. These are described, for example, in heat developable photographic materials in ~.S. Patent 3,617,289 of Ohkubo et al, issued October 2, 1971. While many organic silver salts can provide an image in heat developable photographic silver halide, a problem is involved with them. These materials use undesirably high concentrations of total silver because any image formed results from silver compounds, No suitable answer to help solve this problem is apparent from the heat developable photographic silver art.
It is desirable in many cases to enable exposure of heat developable photographic materials to other than the blue region of the visible spectrum. Difficulty is often encountered in spectrally sensitizing photosensitive silver halide to enable exposure to a broader range of the visible spectrum in heat developable materials. It has been 3 desirable to produce a heat developable silver halide photo-graphic material that enables use of aqueous photographic silver halide technology, permitting use o~ a broader range of spectral sensitizing dyes while enabling the production of a dye enhanced silver image.
Heavy metal salts of certain heterocyclic compounds, such as heterocyclic azoles, are known in thermographic materials in which the visible image is formed by imagewise heating, not by a photographic process. The described thermographic materials are not photographic materials and do not involve problems encountered in dye enhancement of silver images.
Certain heat developable photographic materials are also known for producing a developed image in color as described, for example, in U.S. Patent 3,531,286 of Renfrew, issued September 29, 1970 and U.S. Patent 3,761,270 of deMauriac and Landholm, issued September 25, 1973. In these color-~orming materials a color-forming coupler is required to produce the color image. However, the heat developable materials are not designed to produce a dye enhanced silver irnage with a resorcinol coupler, partlcularly an image that has a neutral (black) or nearly neutral appearing color.
Thermographic materials are also known for producing an image in color. The image is produced by imagewise heating such materials. These materials are not useful for photographic processes requiring the photographic speed of photosensitive silver halide in which a latent image is produced by imagewise exposure to light. In addition, colored film materials are known which can be made clear or colorless in image areas when heated thermographically.

Such thermographic materials lack the desired photosensitivity of heat developable photographic materials. None of these materials involve the enhancement of a silver image with a ~ dye.
It has been proposed in certain photographic materials to use the oxidized form of certain compounds to react with other components of the material to change the color of the resulting image. For example, in a diffusion transfer photographic material, oxidized developer can be diffused to a contiguous layer. This, however, does not relate to heat developable photographic materials.
In photographic materials processed in processing solutions or baths, it has been known to produce a dye image which reinforces a silver image formed upon development.
This concept, however, has not been used in heat developable photographic materials which involve different problems due to the use of incorporated processing chemicals.
A heat developable photographic material which involves a dye enhanced silver image is described in Research Disclosure, Vol. 156, April 1977s Item 15676 of Willis. This heat developable material, however, does not involve a coupler which can form an image with oxidized developer. The heat developable photographic material in this publication involves providing a dye enhanced silver image by means of an element comprising (A) at least one heat developable photographic layer comprising (i) photosensitive silver halide, (ii) at least one active silver halide developing agent, (iii) an activating conccntration of a development activator precursor, and (iv) a polymeric binder and (B) at least one layer comprising an azoaniline dye that is bleached in the non-image areas of the described element upon development of a latent image in the layer (A) by uniformly heating. This involves a dye present at the time of imagewise exposure and does not involve a coupling mechanism.
There has been a continuing need to provide reduced concentrations of silver in heat developable silver halide photographic materials. There has also been a continuing need for such improved materials which have increased photosensitivity and enable more effective use of gelatino silver halide emulsion technology.

Summary of the Invention It has been found according to the invention that the described advantages are provided in a heat developable photo-graphic material for producing a dye enhanced silver image comprising, in reactive association, (a) photosensitive silver halide, with (b) an image-forming combination comprising (i) an organic silver salt oxidizlng agent, with (ii) an organlc reducing agent, and (c) a polymeric binder, by (d) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of the described reducing agent. After imagewise exposure, a dye enhanced silver image can be produced in the described photographic material by heating the material to a temperature within the range of about 100C to about 250C, such as about 135C to about 170C. ~referably, for many uses, the developed, dye enhanced silver image is neutral (black) or nearly neutral appearing.

The heat developable materials according to the invention can contain a wide range of grain size of photosensitive silver halide from very fine to coarse grain size. ~hen large-grain photosensitive silver halide is used in a heat developable material according to the invention, the dye enhancement produces relatively high photographic speeds by compensating for the low covering power of the silver obtained from the large-grain photosensitive silver halide. When fine-grain silver halide is used, lower concentrations of the fine-grain photosensitive silver halide can be used without significantly adversely affecting the desired image.
It has also been found that a thermographic material can provide a dye enhanced silver image by imagewise heating a material containing components (b), (c) and (d) in the absence of the photosensitive silver halide.

Detailed Description of the Invention . . . _ The term "material" as used herein, such as in photographic material and thermographic materlal, is intended to include elements and compositions. For lnstance, the use of "photographic material" is intended to refer to photographic element and photographic composition.
One embodiment of the invention, as described, is a heat developable, photographic element for producing a dye enhanced silver image comprising a support having thereon, in reactive association, described components (a), (b), (c) and (d). Another embodiment is a thermographic element for producing a dye enhanced silver image comprising a support having thereon, in reactive association, the described components (b), (c) and (d).

The heat developable photographic materials according to the invention comprise a photosensitive component which is photosensitive silver halide. The photosensitive silver halide is especially useful due to its high degree of photosensitivity compared to other photosensitive components.
A typical concentration of photosensitive silver halide in a heat developable photographic material according to the invention is within the range of about 0.01 to about 1.0 mole of photosensitive silver halide per mole of the described organic silver salt oxidizing agent in the heat developable photographic material. For example, a typical concentration of photosensitive silver halide in the heat developable photographic material is within the range of about 0.05 to about 0.35 mole of photosensitive silver halide per mole of silver salt of 1,2,4-mercaptotriazole derivative as described herein. Other photosensitive materials can be used in com-bination with the described photosensitive silver halide, if desired. Preferred photosensitive silver halides are silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide or mixtures thereof. A wide range of grain size of photosensitive silver halide from very coarse-grain to very fine-grain silver halide is useful. Selection o~ an optimum reducing agent and optimum resorcinol coupler will be influenced by the silver halide grain size and other properties of the particular silver halide grains.
The photosensitive silver halide can be prepared by any of the procedures known in the photographic art, especially those procedures which involve the preparation of photographic silver halide gelatino emulsions. Useful procedures and forms of photosensitive silver halide for purposes of the invention are described, for example, in the Product Licensing Index, Volume 92, December 1971, Publication 9232 on page 107, published by Industrial Opportunities 3 Ltd., Homewell, Havant Hampshire, P09 lEF, UK. The photographic silver halide, as described, can be washed or unwashed, can be chemically sensitized using chemical sensl~ization procedures and materials known in the art, can be protected against the production Or fog and stabilized against loss of sensitivity during keeping as described in the described Product Licensing Index publication.
A variety of organic silver salt oxidizing agents can be useful in the described photographic and thermograph~C
materials. Especially useful organic silver salt oxidizing agents are silver salts of 1,2,4-mercaptotriazole derivatives represented by the formula:

H
Z _~N~jLS-(CH2 )nY

wherein Y is aryl containing 6 to 12 carbon atoms, such as phenyl, naphthyl, and para-chlorophenyl; n is 0 to 2; and Z is hydrogen, hydroxyl or amine (-NH2). Especially useful organic silver salt oxidizing agents are those silver salts of the described 1,2,4-mercaptotrlazole derivatives wherein Y
is phenyl, naphthyl, or para-chlorophenyl and Z ls amine (-NH2) in the above formula (I). Such organic silver salt oxidizing agents are described, for example, in Research Disclosure, Vol. 158, June 1977, Item No. 15869 of Knight, deMauriac and Graham.
Another useful class Or organic silver salt oxidizlng agents is represented by the complexes of silver with a nitrogen acid, such as a nitrogen acid selected from the group consisting A
.~ . . .. . .... . .. . . . .. . . . . .

o~ imidazole, p~razole, urazole, 1,2,4-triazole and lH-tetrazole nitrogen acids or combinations thereof. These silver salts of nitrogen acids are described in, for example, Research Disclosure, Vol. 150, October 1976, Item No. 15026 of deMauriac. Examples of ~seful silver salts of nitrogen acids are the silver salts of the following compounds: lH-tetrazole; ~-àodecyltetrazole; 5-n-butyl-lH-tetrazole; 1,2,~-triazole; urazole; pyrazole; imidazole; and benzimidazole.
The 3-amino derivative of 1,2,4-triazole does not provide useful results because the dye rormed is a ru~itive dye, that is the dye bleaches upon heating and does not provide the dye enhancement desired.
A furthe- class of useful organic silver salt oxidizing agents include silver salts Or certain heterocycllc thione compounds. Useful silver salts Or the described heterocyclic thione compounds include those represented by the formula:

`N - C=S
(Z')COOH

wherein Z' is alkylene containing 1 to 10 carbon atoms, such as methylene, ethylene and propylene, R represents the atoms necessary to complete a heterocyclic nucleus selected rrom carbon, oxygen, sulfur and nitrogen atoms, such as a thiazoline or imidazoline nucleus. Useful silver salts Or ~'~
., . , :

71;JI.fi~

the described thione compounds include, for example, the silver salts of the following compounds:
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.
Selection of an optimum organic silver salt oxidizing agent or silver salt oxidizing agent combination will depend upon such factors as the desired image, particular silver halide, particular resorcinol, dye-forming coupler, processing conditions and the like.
Preparation of the described organic silver salt oxidizing agent is typically not carried out in situ, that is not in combination with other components of the heat developable photographic materials described. Rather, the preparation of the oxidizing agent is typically carried out ex situ, that is separate from other components of the heat developable photographic materials. In most instances, the preparation of the silver salt oxidizing agent, as described, will be separate from the other components based on the ease of control of preparation and storage capability.
The terms "salt" and "complex" as used herein are intended to include any type of bonding or complexing mechanism which enables the resulting material to provide desired imaging properties in the described heat developable photographic materials and thermographic materials. In some instances the exact bonding of the described silver salt with the organic compound is not fully understood. Accordingly, the terms "salt" and "complex" are lntended to include various complexes and other forms of bonding which enable the desired image-forming combination to provide the desired image.
The terms "salt" and "complex" are intended to include neutral complexes and non-neutral complexes.
The described heat developable materials and thermographic materials can contain a variety of organic reducing agents. The organic reducing agent is typically an organic silver halide developing agent. Combinations of organic reducing agents, particularly combinations of organic silver halide developing agents, can be especially useful.
It is important that the organic reducing agent provide an oxidized form which ct~n react at processing temperature with the resorcinol dye-forming coupler to provide a dye~ preferably a neutral or nearly neutral appearing dye. Especially useful reducing agents are primary aromatic amines including, for instance, para-phenylenediamines. Examples of useful primary aromatic amines include 4-amino-N,N-dimethylaniline;

4-amino-N,N-diethylaniline; 4-amino-3-methyl-N,N-diethylaniline (also known as N,N-diethyl-3-methyl-para-phenylenediamine;
4-amino-N-ethyl-N-~-hydroxyethylaniline; 4-amino-3-methyl-N-ethyl-N-~-hydroxyethylaniline; 4-amino-3-methoxy-N-ethyl-N-~-hydroxyethylaniline; 4-amino-N-butyl-N-gamma-sulfobutylaniline;

4-amino-3-methyl-N-ethyl-N-B-sulfoethylaniline; 4-amino-3-~-(methanesulfonamido)ethyl-N,N-diethylaniline; 4-amino-3-methyl-N-ethyl-N-~-(methanesulfonamido)ethylaniline, 4-amino-3-methyl-N-ethyl-N-~-methoxyethylaniline and the like. Salt forms of the described reducing agents can be useful; however, in many cases the haloacid salts are preferably avoided to reduce undesired formation of silver halide. Selection of an optimum reducing agent or combination of reducing agents will depend upon such factors as the desired image, the particular photosensitive silver halide, the particular resorcinol, dye-forming coupler, the particular organic silver salt oxidizing agent, processing conditions and the like.
The term "silver halide developing agent" herein is intended to include compounds which are developing agents and developing agent precursors in the described heat developable photographic materials and thermographic materials. That is, those compounds are intended to be included which are not developing agents in the heat developable photographic material until a condition occurs such as heating of the photographic material.
An especlally useful reducing agent is one that consists essentially of a para-phenylenediamine silver halide developing agent that exhibits an E 1/2 value in aqueous solution at pH 10 within the range of -25 to ~175 millivolts versus SCE. The term "E 1/2 value" herein means half wave potential. The term "SCE" herein means saturated calomel electrode.
These values are determined using analytical procedures known in the photograpnic art and described, for instance, in the text "The Theory of the Photographic Process," 4th Edition, Mees and James, 1977.

A useful concentration of the described reducing agent in a heat developable photographic material according to the invention is typically within the range of about 0.25 mole to about 2.0 moles of the reducing agent per mole of the described silver salt oxidizing agent. An especially useful concentration of reducing agent is within the range of about 0.25 to about 1.0 moles of reducing agent per mole of the described silver salt oxidizing agent. The optimum concentration of reducing agent can be determined based upon such factors as the desired image, the particular organic silver salt oxidizing agent, processing conditions, other components of the heat developable photographic material and the like.
A variety of resorcinol, dye-forming couplers is useful in the heat developable photographic materials and thermographic materials of the invention. The resorcinol, dye-forming coupler is preferably one that forms a neutral (black) or nearly neutral appearing dye with the oxidized form of the described reducing agent. The mono-substituted resorcinol couplers wlth a substituent in the two position are particularly useful as described. The resorcinol, dye-forming coupler and other components in the materials of the invention should be stable to a sufficient degree that avoids any significant, adverse interaction in the photographic material and thermographic material prior to producing a desired image at processing temperatures. For instance, optimum results are obtained when the resorcinol, dye-forming coupler does not adversely interact with other components ln the photographic material and thermo-graphic material until the oxidized form of the described reducing agent is produced at processing temperature, as described. It is also necessary that the resorcinol dye-forming coupler be in a location with respect to the oxidized form of the described reducing agent upon processing to enable the formation of the desired dye to enhance the silver image formed upon heating of the photographic material.
Certain resorcinol couplers which are useful according to the invention can be represented by the structural formula:
COUP - LINK - Y' wherein COUP is a 2,6-dihydroxyphenyl moiety, a 2,4-dihydroxy-phenyl moiety or a 3,5-dihydroxyphenyl moiety, LINK is a divalent linking group which serves to join the COUP moiety - 14a -to the Y' moiety and Y' ls a moiety of such size and configuration that does not adversely affect the desired coupling or the desired sensitometric properties in the described heat developable photographic materials of the invention. The COUP moiety is preferably unsubstituted in its remaining ring positions, although it can contain substituents in one or more of the remaining positions on the benzene ring as long as the substituents do not adversely affect the desired coupling or other desired properties of the photographic or thermographic material of the invention.
Typical of such optional substituents are lower alkyl groups containing 1 to 4 carbon atoms, such as methyl, ethyl, propyl and butyl, and halogen substituents, such as chloro and bromo. The LINK group can be any divalent group which serves to connect the COUP moiety with the Y' moiety.
The particular structure of the coupler will affect the hue of the resulting dye image. Especially useful LINK groups include the following: -NHC0-, -CONH, -NHCONH-, -NHS02-, and -NH-. Numerous moieties are known for use in connection with couplers intended for incorporation in photographic elements and can be employed as Y' in the described resorcinol couplers according to the invention. Selection of an optimum COUP, LINK and Y' moiety will depend upon such factors as the particular components in the heat developable photographic material, desired image, processing conditions and the like.
A useful embodiment of the invention is one wherein the described coupler is a resorcinol compound represented by the formula:

~i$ :1-;

HO ~ OH

R ~ R2 - wherein O O O

Rl is hydrogen, COH, NHCR5, CR6, or NHSo2R7;
O O O
R2 is hydrogen, COH, CNHCH2CH20H, or CNH~C6H5~0C5Hlln;
O O
R3 is hydrogen, NHCR5, or CR6;
O O
R is hydrogen, COH, CNHCH2CH20H or o CNH~C6H5~0C5Hlln;

R5 is haloalkyl containing 1 to 3 carbon atoms, such as CC13 CF3, and C3H4Br3, CH20CH3, CH2SR , C2H4COOH, CH=CH2, NHC2H4Cl, alkyl containing 1 to 20 carbon atoms, such as 1 to 10 carbon atoms, including methyl, ethyl, propyl, and decyl, or phenyl;
R6 is OH, NH2, NHCH2CH20H, or NH~C6H5~0C5Hlln;

R7 is alkyl containing 1 to 5 carbon atoms, such as methyl, ethyl, propyl or pentyl, or phenyl; and R8 is hydrogen, haloalkyl containing 1 to 3 carbon atoms, such as CC13, CF3 and C3H4Br3, CH20CH3~ or C2H4COOH .
Alkyl and phenyl, as described, are intended to include alkyl and phenyl that are unsubstituted alkyl and phenyl as well as alkyl and phenyl that contain substituent groups that do not adversely effect the desired image. An example of a suitable substituent group is alkyl containing 1 to 3 carbon atoms, such as methyl or ethyl.

Representative use~ul resorcinol couplers include the following compounds:
/OH
- RC-l ./ \
NH
OH
~01 RC-2 ~ NHCO-~
OH

OH

RC-3 ~ H !~

/OH
RC-4 ~ -NHCO--~ /o OH C~

/OH
RC-5 ~ -NHCO--\ ~--CI
OH
- /OH
RC-6 ~ ~--NHCO~
OH Br /OH
RC-7 ~ -NHCO-~
\OH

/OH
10 RC-8 ~ ~--NHCO-~ -C-N
OH

/OH
RC-9 ~ -NHCO-~ -NH2 OH

~OH ~NH
RC-10 ~ NHCO-~
OH NH
~0 R C - l l ~-NHCO~
OH N~

~OH
RC-12 ~NHCO--~ ~t-NO
OH

~OH
RC -13 ~-NHCO-~
OH \N2 ~OH
RC- 14 ~ -NHCO-~
OH \CF3 ~OH ~CH
RC-15 ~ -NHCO ~-o = ~

~OH
R C -1 6 ~ -NHCO-~

HO~
RC-17 ~-NHCO--~ ~4-C H -t H~
~OH
RC-18 ~ ~--NHCO--~ ~--C H~-t \OH

*~

OH
RC-l9HO--~ /7-NHCO--~ ~--C H~-t /OH
RC-20 ~ -NHC-O-~ -C5H~l-n \OH
/OH
RC-21 ~ C 6 13 RC-22~ ~ -NHCO--\ /--c7Hl 5 n /OH
RC-23HO \ _ /- NHCO--\ /~-C8H -n /OH
RC-24~ _ ~ NHCO--\ /~-CeH~7-n (C-3) OH
HQ
RC-25~ _ ~ NHCO ~\ /'-C8H -n RC-26 \ _ ~ - NHCO-~ -CeH -n H C\ /OH
RC-27~ _ ~ NHCO--\ /~-C H -n /OH
10- RC-28~ _ ~ NHCO ~ -Cl~H -n - OH

s~

H~
RC-30 ~\ /b-NHCO~
H6 ~Hs /OH
RC-31 ~ -NHCO~ 5 OH ~Hs /OH
RC-32 ~ ~-NHCO~
OH O~H OCH

/OH
RC-33 ~ - NHCO--~ /-OH 0~ H -n H~
RC-34 \ _ /~ NHCO--\ /--OC H -n H~

/OH
RC-35 \ _ / N CO \ _ / OCsHl1 n /OH
\ _ /--NHcO~ -OC H -n /OH
RC-37 \ _ / NHC0 ~ -OCloH -n OH
. .- 20 -/OH
RC-38 ~ NHCO~
OH OC H -n 1 o zl OH
RC-39 _ / 9 \ /--OC H -n /OH
RC-40 ~ ~-- NHCO~ -OC H -n OH

RC-41 \ _ / NHCO-~\ /o-oc H -n H~
H~ .
RC-42 ~ -NHCO-~
H~ O~ H -n /OH
RC-43 ~ /'-NHCO-'~ ~' \OH O~ H -n 1 ~3 37 /OH
RC-44 ~ ~t-NHCO-~ -SCH3 OH
/OH
RC-45 ~ NHCO--~ ~-OH lo 2 ~ n /OH H~
RC-46 ~ ~-NHCO-~ -CONH-~
OH H~
. /OH
10- RC-47 ~ NHCO-~ -NHCOCH=CH
- . OH

.. ,OH
RC-48 ~ NHCO~ NHCOCF
OH
/OH
RC-49 ~ - NHCO-~ -NHCO
OH .

/OH /OCOCHS
- RC-50 ~ -NHCO-~
OH OCOCHS
. ~OH
RC-51 ~ -NHCO-~
\OH SOzCI
/ Oi~
RC-52 ~ -NHCOCH=CH-~
OH

RC-53 - ~ 112 5 n ~C4 H -t OH
~01 -RC-55 ~ ~-NHCO-CHzCH~CH~C
OH
/OH
RC-56 ~-NHCO-C H -n OH
/OH
RC-57 \ - /--NHco-cl7Hs~-n OH

RC-58 ~ NHC0 OH

~C-59 ~ ~ -NHCO~

/OH
RC-60 ~ _ , CONH~ -OC H -n OH

/OH
RC-61 ~ _ , , _ , 5 , 7 n - RC-62 HN--~ ~--CH=CH-~ -NH
C=O
C~O
n HO OH / ~
HO OH

, ~OH /CH
RC-63 ~ ~-NHCONH-~
OH C~3 0~ ' RC-64 ~ /--NHCONH-7~ ~--NH

~OH
RC-65 ~ NHSO C H -n OH

~OH

Other resorcinol couplers are described in the following examples.

A pre~erred resorcinol dye-rorming coupler ls represented by the rormula:
NHCoR5 H ~ OH

wherein R5 is as described. Within this formula resorcinol, dye-forming couplers areJ ~or instance, 2,6-dihydroxyacetanllide, 2',6'-dihydroxytri~luoroacetanilide, and a compound represented by the formula:

HO C ~

Due to differences ln solubility and other properties, it can be use~ul, in some cases to coat a coupler, as described, in the rorm of a latex dispersion or other suitable form than a solution in a suitable solvent. Those couplers that are soluble in water can be userully coated rrom an aqueous formulation.
Resorcinol couplers as descrlbed can be prepared ~rom amino resorcinols or dihydroxybenzoic acids. ~or some o~
the described resorcinol couplers, an appropriate amino resorclnol can be condensed with an appropriate acid chloride in the presence o~ a suitable base, such as pyridine, quinolin, 20 N,N-dimethylaniline and the like, as an acid acceptor to yield the desired resorcinol coupler. Other resorclnol couplers, as described, can be prepared by condensation Or an appropriate dihydroxybenzylic acid with an appropriate amine in the presence Or a phosphorous trifluoride catalyst and an amine acid acceptor. These resorcinol couplers can be prepared by ~irst converting the dihydroxybenzoic acid to the acid chloride (while blocking the hydroxyl groups to prevent the acid chloride :
'~

from reacting with itself) and then condensing the resultant acid chloride with an appropriate amine, followed by hydrolysis to deblock the hydroxy groups. Still other of the described resorcinol couplers can be prepared by converting an appropriate dihydroxybenzoic acid to its methyl ester and then conducting a transesterification reaction with an appropriate alcohol in the presence of a base catalyst, such as tetraisopropylortho-titanate. These same resorcinol couplers can be prepared by reacting the potassium salt of an appropriate dihydroxybenzoic acid with an appropriate bromide in the presence of a suitable catalyst, such as a suitable ether catalyst.
The concentration of resorcinol coupler incorporated in the photographic material is sufficient for each mole of total silver in the material to provide the desired dye. Less than the stoichiometric equivalent of coupler can be useful, particularly if the dye densities obtained with the photographic material are too high for the use intended for the material. Alternatively, a concentr-ation that is greater than the stoichiometric amount of coupler can be useful, if desired. Typically, the photographic material contains about 0.1 to about 1.0 mole cf the described resorcinol coupler per mole of total silver in the photographic material.
A preferred concentration of the resorcinol coupler is within the range of about 0.25 to about 0.75 mole of coupler per mole of total silver in the photographic material. A heat developable photographic material or thermographic material also typically comprises about 0.1 to about 1.0 mole of the described coupler per mole of the described organic silver salt oxidizing agent.
The tone of the combined silver and dye images produced 3 according to the invention will vary depending upon such factors as the silver morphology of the developed silver image, the covering power of the silver materials, the particular coupler, the particular developing agent, processing conditions, and the like. In heat developable materials that provide a brown silver image, the dye produced must be complimentary in hue in order to obtain a desired hue for the combined silver and dye image.
The term "neutral" as employed herein is intended to include hues which occasionally are referred to in the photographic art as blue-black, gray, purple-black, black and the like.
Whether or not a given developed image is "neutral" can be readily determined by visual inspection. A more precise procedure for determining whether or not an image is "neutral"
would be to formulate a photographic element according to the invention and then expose and develop it as described to provide a developed maximum density of between 0.3 and 2Ø This developed density would then be employed to generate a spectral photometric curve of wavelength versus diffuse reflection density or diffuse transmition density (depending on whether the support is opaque or transparent), uslng commonly available equipment used in the photographic art.
If the spectral photometric plot of density versus wavelength does not contain any 10 nanometer interval in the range of 420 to 650 nm which departs by more than 10% from the mean density over that range, then the image obtained would be considered to have a "neutral" hue for purposes of the invention.
It has been found that in some photographic materials, according to the invention, increased dye density can be provided by addition of a polymeric latex to the photographic material. Other advantageous affects can be provided by the addition of a latex with the described reducing agent. These advantages obtained when a latex is used with an incorporated silver halide developing agent are described, for example, in Research Disclosure, August 1976, Item No. 1~850, pages 77-99, published by Industrial Opportunities Ltd., Homewell, Havant Hampshire, PO9 lEF, UK. Accordingly, in some instances it is desirable to incorporate a latex into the photographic compositions in preparation of the photographic elements according to the invention. The latex is typically added to either or both of the resorcinol coupler and the described reducing agent prior to their being mixed and incorporated into the composition for coating on the described support.
The heat developable photographic elements and thermographic elements according to the invention can comprise a variety of supports which can tolerate the processing temperatures employed according to the invention. Typical supports include cellulose ester film, poly(vinyl acetal) film, poly(ethylene terephthalate) film, polycarbonate film and polyester film supports. Related film and resinous support materials, as well as paper, glass, metal and the llke supports which can withstand the processing temperatures descrlbed are also useful. Typically, a flexible support is most useful.
The heat developable photographic compositions and the thermographic compositlons according to the invention can be coated on a suitable support by various coating procedures known in the photographic art including dip coating, airknife coatlng, curtain coating or extrusion coating using hoppers.
If desired, two or more layers can be coated simultaneously.
It is often advantageous to include a heat sensitive base-release agent or base precursor in the heat developable 3 photographic materials and thermographic materials according to the invention to provide improved and more effective image development. A base-release agent or base precursor, as . ~..~11 employed herein, is intended to include compounds which upon heating in the heat developable photographic material and - thermographic material provide a more effective reaction between the described photosensitive silver halide, and the image-forming combination in addition to improved reaction between the oxidized form of the reducing agent and the resorcinol dye-forming coupler. Examples of useful heat sensitive base-release agents or base precursors are aminimide base-release agents as described in Research Disclosure, Vol. 157, May 1977, Items 15733, 15732, 15776 and 15734; guanidinium compounds, such as guanidinium trichloroacetate; and, other compounds which are known to release a base moiety but do not adversely affect photographic silver halide materials.
A range of concentration of the heat sensitive base-release agent or base precursor is useful in the described heat developable photographic materlals and thermographic materials. The optimum concentration of heat sensitive base-release agent or base precursor will depend upon such factors as the desired image, particular coupler, particular reducing agent, other components of the lmaging materlal, processlng conditions and the like. A useful concentratlon Or described base-release agent is typically within the range of about ~.25 to 2.5 mole of base-release agent or base precursor per mole of silver ln the heat developable photographic material and thermographic material according to the invention.
The heat developable photographic materials and thermographic materials according to the invention can contain an image toner if desired. The optimum toning agent will depend upon such factors as the particular heat developable 3 photographic material, the desired image tone, particular processing conditions, particular silver halide and the like.

- , ~, In some cases, certain image-toning agents can provide better results with certain organic silver salt oxidizing agents, such as certain 1,2,4-mercaptotriazole derivatives, than with other organic silver salts. A simple screening test can be useful to select an optimum image-toning agent, if desired. One such test comprises that described in following Example 1.
In this test the most useful toning agent is typically that toning agent that provides the most "neutral" image. Some toning agents are also found to have other desired effects in the heat developable photographic material and thermographic material. For instance, some toning agents provide added development acceleration in the described heat developable photographic materials. Combinations of toning agents can be useful if desired. In most instances, an added toning agent is not necessary to provide a desired "neutral" image tone in a heat developable photographic material and thermographic material according to the invention.
If a toning agent is used, a range of concentration of toning agent can be employed. A typically useful concen-tration of toning agent ls within the range of about 0.005 toabout 0.05 mole of toning agent per mole of silver in the heat developable photographic material and thermographic material.
The optimum concentration of toning agent will depend upon such factors as the particular photographic material, processing conditions, desired image, the nature of the toning agent, and the like.
A "melt-forming compound" can be useful in some of the photographic materials and thermographic materials in order to provide an improved developed image. A melt-forming compound can be especially useful with photographic materials containing silver salts of nitrogen acids. The term "melt-forming compound" as employed herein, is intended to .. ~, ... . .. . . . . . . .
.. .. . . . .

~ 6~

mean a compound which upon heating to the described processing temperature provides an improved reaction medium, typically a molten medium wherein the described image-forming combination can provide a better image upon development. The exact nature of the reaction medium at processing temperatures described is not fully understood; however, it is believed that at the reaction temperatures a melt occurs which permits the reaction components to better interact. If desired, a melt-forming compound can be included with other components of the heat developable photographic material and thermographic material.
The optimum concentration of the various components of the photographic material and thermographic material, according to the invention, will depend upon a variety of factors as described An especially useful heat developable photographic material according to the invention comprises, for each mole of photosensitive silver halide, 3.0 to 20.0 moles of the described organic silver salt oxidizing agent, and 1.0 to 5.0 mole of the described reducing agent with 1.0 to

5.oO mole of the resorcinol, dye-forming coupler.
The organic silver salt oxidlzing agent can contain a range of ratios of (1) the organic moiety, such as the 1,2,4-mercaptotriazole moiety, to (2) the silver ion. The optimum ratio of the organic moiety to silver ion in the organic silver salt oxidizing agent will depend upon the particular organic moiety, such as the particular 1,2,4-mercaptotriazole derivative, the particular heat developable photographic material or thermographic material, processing conditions, particular resorcinol coupler and the like. However, 3 the molar ratio of the organic moiety to silver as silver ion ln the salt is usefully within the range of about 0.5:1.0 to about 3.0:1Ø An especially useful ratio of the described organic moiety to silver as silver ion is wlthin the range of 1.0:1 to 2.0:1Ø
~ The heat developable photographic materials of the invention can also contain a range of pAg. The pAg can be measured using conventional calomel and silver-silver chloride electrodes, connected to a commercial digital pH meter.
The typical pAg in a dispersion containing the described imaging components according to the invention is within the range of about 2.5 to about 7.5, with a preferred range of pAg being 3.5 to 6.5. The optimum pAg will depend upon the described factors, such as the particular heat developable photographic material, desired image, processing conditions, and the like.
A dispersion containing the described components according to the invention typically has a pH which is within the range of about 1.5 to 7Ø An especially useful pH for a dispersion, as described, is within the range of about 2.0 to 6.o with the preferred range being about 2.5 to 5Ø
Spectral sensitizing dyes can be useful in the described materials of the invention to confer additional sensitivity to the materials. Useful spectral sensitizing dyes are described, for example, in the Product Licensing Index, Volume 92, December 1971, Publication 9232, pages 107-110, paragraph XV, published by Industrial Opportunities Ltd., Homewell, Havant Hampshire, PO9 lEF, UK. An advantage of certain heat developable photographic materials according to the invention, i.e. those that enable use of conventional silver halide emulsions, especially silver halide gelatino emulsions, is that a range of spectral sensitiæing dyes is useful in such materials. In many heat developable photographic materials the range of useful spectral sensitizing dyes is often undesirably limited. This advantage of these certain heat developable photographic materials of the invention is due p~

in part to the fact that these heat developable photographicmaterials can use conventional silver halide emulsions, especially silver halide gelatino emulsions. Selection of - an optimum spectral sensitizing dye or dye combination depends upon such factors as the particular silver halide used, the desired spectral sensitivity, and the like. A
preferred heat developable photographic material, according to the invention, contains a spectral sensitizing dye selected from the group consisting of cyanines and merocyanines and combinations of these dyes. Especially useful spectral sensitizing dyes include thiocarbocyanine dyes, merocyanine dyes containing a rhodanine moiety, solubilized oxacarbocyanine dyes, oxacarbocyanine dyes, and merocyanine dyes containing a 2-thio-2,4-oxazolidinedione moiety.
A range of concentration of spectral sensitizing dye or dye combination is useful in the described heat developable photographic materials. Typically, the spectral sensitizing dye or dye combination concentration is within the range of about 0.5 to about 2.0 grams of dye or dye combination per mole of silver halide in the heat developable photographic material.
It is desirable in certain cases depending upon the desired image to add a separate post-processing image stabilizer or stabilizer precursor to the described heat developable photo-graphic materials according to the lnvention. Such stabilizers or stabilizer precursors include sulfur compounds which do not adversely affect the desired sensitometric properties of the heat developable photographic material, but which upon heating of the photographic material form a stable mercaptide in the non-image areas of the photographic material. In certain cases photolytically activated polyhalogenated compounds can be useful, but these compounds have been found in some cases to be less desirable than other stabilizers or stabilizer precursors.

The heat developahle photographic materials accordingto the invention can contain other addenda such as development modifiers that function as speed-increasing compounds, hardeners, plasticizers and lubricants, coating aids, brighteners, absorbing and filter dyes, matting agents, antihalation dyes and antihalation layers, antistatic materials or layers, and the like. These are described, for example, in the Product Licensing Index, Volume q2, December 1971, Publication 9232, pages 107-110.
The described components of the photographic materials and thermographic materials according to the invention can be in any suitable location in the photographic material and thermographic material which provides the desired image.
For example, if desired, one or more of the components of the photographic element and thermographic element described can be in one or more layers of the element. In some cases it can be desirable to include certain percentages of the described reducing agent, organic silver salt oxidizing agent, and/or other addenda in a protective layer or overcoat layer over the photographic layer of the element as described. The components, however, must be in a location which enables their desired interaction upon processing.
It is necessary that the photosensitive silver halide, as described, and other components of the imaging combination be in "reactive association" with each other in order to provide the desired image. The term "in reactive association", as employed herein, is intended to mean that the photosensitive silver halide and the image-forming combination and described coupler are in a location with respect to each other which enables the desired processing and provides a useful dye enhanced silver image. It is believed that the latent image formed upon imagewise exposure of the photosensitive silver halide acts as a catalyst for the image-forming combination containing the organic silver salt oxidizing agent. In turn, the oxidized form of the reducing agent resulting upon processing reacts, it is believed, with the described resorcinol, dye-forming coupler to provide the desired dye in the image areas of the element.
If desired, other heat developable photographic materials or thermographic materials can be useful in combination with the photographic materials and thermographic materials according to the invention. The other heat developable photographic materials and thermographic materials must be compatible with and not adversely affect the image formation in a photographic material and thermographic material according to the invention.
An especially useful embodiment of the invention is a heat developabie photographic element for providing a dye enhanced silver image comprising a support having thereon, in reactive association, (a) a photographic silver hallde, especially a photographic silver halide gelatino emulsion, (b) an image-forming combination comprising (i) a silver salt of 3-amino-5-benzylthio-1,2,4-triazole, with (ii) an organic reducing agent consisting essentially of 4-amino-2-methoxy-N,~,5-trimethylanilinesulfate, (c) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide, and (d) a polymeric binder, such as a gelatino binder.
Another useful embodiment of the invention is a heat developable photographic element for providing a dye J~

enhanced silver image comprising a support having thereon, in reactive association, (a) photosensitive silver halide, (b) an image-forming combination comprising (i) a complex of ~ silver with 5-dodecyltetrazole, with (ii) an organic reducing agent consisting essentially of 4-amino-3-methyl-N-ethyl-N-~-hydroxyethylaniline hydrogen sulfate, (c) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide, (d) a polymeric binder, especially a gelatino binder and (e) a melt former, as described.
A further useful embodiment of the invention is a heat developable photographic element for providing a dye enhanced silver image, as described above, wherein the complex of silver with dodecyltetrazole is replaced with a silver salt of 3-carboxymethyl-4-methyl-4-thiazoline-2-thione. This embodiment of the invention can have improved post-processing image stability when the photosensitive silver halide is silver iodide.
Another embodiment of the invention is a heat developable photographic composition for providing a dye enhanced silver image comprising (a) photosensltive silver halide, (b) an image-forming combination comprising (i) an organic silver salt oxidizing agent, as described with (ii) an organic reducing agent, also as described, (c) a resorcinol, dye-forming coupler that forms a neutral or nearly neutral appearing dye with the oxidized form of the reducing agent and (d) a polymeric binder.
The heat developable photographic materials of the invention can be useful for thermographic imaging in the absence of the described photosensitive silver halide.
Accordingly, another embodiment of the invention is a thermographic element comprising a support having thereon, in reactive association, (a) an oxidation-reduction image-forming p~

combination comprising (i) an organic silver salt oxidizing agent,as described, with (ii) an organic reducing agent, also as described, (b) a resorcinol, dye-forming coupler that forms a neutral or nearly neutral appearing dye with the oxidized form of the reducing agent, and (c) a binder. An especially useful thermographic element comprises a support having thereon, in reactive association, (a) an oxidation-reduction image-forming combination comprising (i) a silver salt of 3-amino-5-benzothio-1,2,4-triazole, with (ii) an organic reducing agent consisting essentially of 4-amino-2-methoxy-N,N,5-trimethylanilinesulfate, and (b) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide, and (c) a polymeric binder, especially a gelatino binder.
A variety of imagewise exposure means are useful with the heat developable photographic materials according to the invention. The imaging 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, however, lf P spectral sensitizing dye is employed ln the heat developable photographlc materials, exposure means using other ranges of the spectrum are applicable. Typically, a heat developable photographic element according to the invention is exposed imagewise with a visible light source, such as a tungsten lamp, although other sources of radiation are useful. Such other sources of radiation include, for instance, lasers, electron beams, X-ray sources and the like. The heat developable photographic materials are typically exposed imagewise to provide a developable latent image.

::
. .:
,: :

A visible image can be developed in the photographic material according to the invention within a short time, such as within several seconds, merely by uniformly heating the heat developable photographic material to moderately elevated temperatures. For example, the exposed photographic material can be heated to a temperature within the range of about 100C to about 250C, such as a temperature within the range of about 135C to 170C. Heating is carried out until a desired image is developed, typically within about 1 to about 60 seconds, such as within about 1 to about 30 seconds.
At the lower processing temperatures, such as ternperatures of about 125C, development of an image may require a longer processing time. However, at the lower processing temperatures, such as below about 140C, post-processing stabilization may be somewhat less than desired in most instances.
Another embodiment of the invention is a process of developing a latent image in an exposed photographic elemert according to the inventlon comprising heating the element to a temperature withln the range of about 100C
to about 250C, such as a temperature within the range of about 135C to about 170C, until a neutral or near neutral appearing dye enhanced silver image is developed~
Although it is often undesirable, due to the lack of control in preparation, the described photosensitive silver halide can be prepared in situ in the described material according to the invention. Such a method of preparation of photosensitive silver halide in a photographic material is described, for example, in U.S. Patent 3,457,075 of Morgan et al, issued July 22, 1969.

A variety of means can be employed to provide the necessary heating of the described photograph~c material and thermographic material to provide a developed image. The heating means can be a simple hot plate, iron, roller, infrared . .
heating means, or the like.
Processing according to the invention is typically carried out under ambient conditions of pressure and humidity.
Pressures and humidity outside normal atmospheric conditions can be employed if desired; however, normal atmospheric conditions are pre~erred.
The following examples are included for a further understanding of the invention.

Example 1 This illustrates the invention.
A dispersion of a silver salt of 3-amino-5-benzylthio-1,2,4-triazole (referred to herein as ABT) was prepared having a silver salt dispersion weight of 5.753 kilograms per silver mole, approximately 1% gelatin at a ligand to silver ion molar ratio of 1.5 with pH adjusted to 2.5 with nitric acid. The resulting dispersion was mixed with other components to provide a heat developable photographic material as follows:

ABT silver salt dispersion 86.9 g (as above) 2',6'-dihydroxytrifluoro- 14.4 g acetanilide (resorcinol coupler) (C-l) (30~ by weight in water) distilled water 21.6 g surfactant (Surfactant lOG 0.7 g which is a trade name and a polyglycidol ether available from the Olin Corporation, U.S.A.) (10% by weight in water) 3~

3-methyl-5-mercapto-1,2,4- 2.25 g triazole (2.2~ by weight in ethanol) (antifoggant) gelatin (binder) (20~ by weight12.9 g in water, pH adjusted to 2.5 with nitric acid) 4-amino-2-methoxy-N,N~5~tri- 11.3 g methylanilinesulfate (reducing agent) (14.2% by weight in water) (D-l) silver bromoiodide (2.5% iodide, 2.16 g 0.24 ~m cubic grain, 0.754 kilograms per silver mole) The resulting composition was coated at 9.0 grams per square foot (equivalent to 96.9 grams per square meter) on a gelatin subcoated poly(ethylene terephthalate) film support.
The resulting heat developable photographic element was imagewise exposed to light to provide a developable latent image. The image was developed by heating the element to a temperature of 155C for 30 seconds. A dye enhanced silver image was produced having a maximum visual diffuse density of 1.63 and a minimum density of 0.20.

Examples 2-14 - Reducing Agents The procedure described in Example 1 was repeated with the exception that the reducing agents listed in following Table I were used in place of the described analinesulfate reducing agent of Example 1. The processing conditions including time and temperature range and the particular reducing agent are listed in Table I. In each instance a dye enhanced silver image was produced.

Table I

Proc e s s Example time/temp .
No. ~ (sec./C~

2 N (CH3) 230"/135-165 ~- NDS
COOH

(D-24) 3 H5c2-N-c2H4oH 30"/125-145 (D-26) 4 ~2Hs)2 30"/125-135 10~ , .
3 ~ S03K

t~-28, N (CH3) 230"/145-185 CI~Cl (D-7)

6 N (C2H5) 25 /135-155 (D-3)

7 N(CH3)2 30"/155-185 (D-29) Table I (continued ) Process Example time/temp.
No . Developer ( sec . / C )

8 30/135-155 ~ 1/2 H2S04 (D-2)

9 ~CH3)2 3o"/l45-l85 ~SO2,0 .`

(D-30) N (CH3 )2 30"/145-175 3~ 2PTS
NH
(D_4)2 11 HN-C2H5 5"/135-145 ~1 . H2S04 (D-31) 12 NH2 30"/175-200 [~S02CH3 (D-32) Table I (continued) Process Example time/temp.
No. Developer (sec./C) . .

13 N02 5"/125-145 PTS
`C~3 (D-33) 14 5C2 ~ 2H4N(CH3)3Cl 5"/155-175 ~O,,~ NDS

(D-34) PTS is p-toluenesulfonic acid3 ~ S03H .

SO H
NDS is 1,5-naphthalenedisulfonic acid 1 3 ~. ' 0is ~

If a free base developer is used~ then a suitable solvent~ sUch as methanol~ is useful to provide a desired composition.

~ 43 -Examples 15-21 - Couplers The procedure described in Exampie 1 was repeated with the exception that the couplers listed in following Table II were used in place of the designated coupler of Example 1. In each instance a dye enhanced silver image was produced with the exception that 2% gel was used rather than the 1% in Example 1 and also 30~ ethanol was used rather than 2% ethanol in Example 1.

Table II
Example No.

H O~,OH
' ~zJ
( C-l ) NHCOCH
16 ~f 3 (C-2 ) 17 H~[~f)H

(C-50 ) 18 HO ~,OH

(C-23 ) NHCOCH2CH2Cl 19 F~O ~[~ OH

(C-22 ) HO ~,OH
W

(C-51) COOH
21 H`[~3'OH

(C-40) ~,.1~

Example 22 A dispersion of a silver salt of 3-amino-5-benzylthio-1,2,4-triazole (ABT) was prepared similar to that described in Example 1. The resulting dispersion was mixed with the following components to provide a heat developable photographic material:

dispersion of silver salt of8.o ml ABT

silver bromoiodide gelatino emulsion 1.0 ml (2.5 mole percent iodide, cubic grain, 0.21 ~ grain) (10 mg of silver per ml) 4-amino-2-methoxy-N,N,5- 75 mg trimethylanilinesulfate (reducing agent) (D-l) 2,6-dihydroxyacetanilide 150 mg (resorcinol coupler) (C-2) solvent (95% ethanol, 5% 1.0 ml methanol) distilled water 1.0 ml surfactant (Surfactant lOG 0.2 ml which is a trade name and a polyglycidol ether available from the Olin Corporation, U.S.A.) The resulting photographic composltion was coated at a 5 mil wet coating thickness on a gelatin subcoated poly(ethylene terephthalate) film support. The heat developable photographic element was then imagewise exposed to light to provide a developable latent image in the element.
The latent image was developed by uniformly heating the element by contacting it with a heated metal block at 155C
for 30 seconds. A dye enhanced silver image was developed having a visual diffuse transmission density of 1.32 and a .. . . .

.

minimum density of 0.32.

Examples 23-?7 These are comparative examples.
The procedure described in Example 22 was repeated with the exception that the described resorcinol coupler was omitted and each of the following reducing agents was used individually in place of the described aniline developing agent.
In each instance a silver image was developed in the absence of dye and the maximum density was significantly less than that provided by the dye enhanced silver image of Example 22.

Table III

Example No. Reducing Agent Dmax/Dmin , 23 t-butylhydroquinone 0.16/0.10 24 ascorbic acid o.76/0.48 4-methyl-4-hydroxy- 0.54/0.30 methyl-l phenyl-3-pyrazolidone 26 dihydro anhydro- 0.70/0.40 piperldino hexose reductone 27 4-arnino-2-methoxy-N, 0.66/0.20 N,5-trimethylanlline-sulfate Example 28 - Use of silver salt of dodecyltetrazole to _epare a neutral (black~~image ~~
(A) - Prepara ion of dodecyltetrazole silver salt To a warm (30C) solution of 9.52 g (0.04 moles) of 5-dodecyltetrazole in 530 ml of acetonitrile was rapidly added a warm solution of 6.8 g (0.04 moles) of silver nitrate in 130 ml of acetonitrile. The mixture is diluted with 750 ml of cool distilled water and the white precipitate filtered and thoroughly washed with distilled water. The silver salt was dried overnight (16 hours) at 43~C.

~, . . ~ . .. .

(B) - Preparation of dispersion of silver dodecyltetrazole 3.45 g (0.01 mole) of silver dodecyltetrazole prepared as above was slurried with 25 ml ethanol. Total weight was taken to 100 g with distilled water and 4.0 g dry deionized gelatin added. It was heated with stirring until the gelatin dissolved. It was then cooled to 20C and mixed thoroughly using a sonification mixing apparatus with the sample in an ice-water bath. The resulting dispersion had a pH of 5.9 and a pAg of 6.4.
(C) - Coating preparation A coating melt was prepared by mixing the following components:
silver salt dispersion prepared as above 48.o ml silver bromoiodide gelatino emulsion 9.0 ml (2.5 mole ~ I, 20 mg Ag/ml) 1,3-dimethyl urea (40% in H20) 2.4 ml (melt former) 4-amino-N-ethyl-3-methyl-N-(~- 6.o ml hydroxyethyl)aniline sulfate (7% in H20) (developing agent) 2',6'-dihydroxytrifluoroacetanilide 3.6 ml (30% in H20) (coupler) (C-l) 5-amino-1,3,4-thiadiazole-2-thiol 2.4 ml (0.25% in ethanol) (toner) Surfactant lOG (10% in H20) (surfactant) o.6 ml 72.0 ml The resulting composition was coated at 12.0 ml/ft2 on gel-subbed pol~ester film support and dried at 43C.
After imagewise exposure through a step tablet with an Xenon flash and processing face up for 30 seconds on a hot shoe at 155C, a blue-black image having a visual transmission _ 48 -. ., . .

D-max/D-min of 1.52/0.21 was obtained. The image produced the D-max readings of 1.48, 1.53, and 1.48 obtained through blue, green, and red filters respectively.
tD) - Comparative example A coating was prepared as in (C) without the coupler.
After exposure and processing as above, a low density image having a visual transmission D-max/D-min of 0.52/0.23 was obtained. Maximum densities as read through blue, green, and red filters was 0.75, o.60, and 0.46. Thus, in the absence of dye enhancement images were obtained that had lower maximum density and were not neutral (black).

Example 2g - Magenta image with silver salt of ABT
A heat developable photographic element was prepared similar to that described in Example 28 and containing the developing agent designated herein as D-l, the resorcinol coupler designated herein as C-l, and the silver salt of the compound designated as ABT which is 3-amino-5-benzylthio-1,2,4-triazole. Upon imagewise exposure to light to provide a developable latent image followed by uniformly heating the element to optimum processing temperature, an image was developed in the element which was magenta in hue. me maximum density of the developed image (sllver plus dye) when read through appropriate filters was, respectively, in the blue, green and red regions of the spectrum: 1.74, 1.58, and l.lg.

Example 30 - Near neutral appearing image with silver salt of ABT
A heat developable photographic element was prepared similar to that described in Example 28 but containing the developing agent designated herein as D-2A, the resorcinol coupler designated herein as C-l, and the silver salt of ABT.
Upon imagewise exposure to light to provide a developable latent image followed by uniformly heating the element to optimum processing temperature, an image was developed in the element which was near neutral in appearance. The maximum density of the developed image (silver plus dye) when read through appropriate filters was, respectively, in the blue, green and red regions of the spectrum: 1.39, 1.22, and 1.24.
D-2A herein refers to the compound represented by ;
the formula:
~ 3 CN ~ NH2- H2S04 Example 31 - Neutral (black) image with silver salt of ABT
A heat developable photographic element was prepared similar to that described in Example 28 but containing the developing agent designated herein as D-2A, a coupler which was resorcinol, and the silver salt of ABT. Upon imagewise exposure to light to provide a developable latent image followed by uniformly heating the element to optimum processing temperature, an image was developed (silver plus dye) which was neutral (black) in appearance. The maximum density of the developed image (silver plus dye) when read through ~;
appropriate filters was, respectively, in the blue, green and red regions of the spectrum: 1.46, 1.39, and 1.41. ~ ;.
Examples 28-31 illustrate, among other things, that with proper selection of developing agent, coupler, silver halide, silver organic salt, and processing conditions, a neutral (black) image can be produced, as described.

Examples 32-~7 - Use of silver salt of 1-methYl-4-imidazoline-2-thione (MITl .
Silver salt dispersion preparation of l-methyl-4 imidazoline-2-thione, designated herein as MIT. 5.7 grams, (0.05 mole) of MIT was dissolved in 75 ml of isopropanol and 125 ml of water in a mechanical blender fitted with a 21C water Jacket. While blending the resulting composition at a low speed, silver nitrate (6.07 grams, 0.0357 mole) in 50 ml of water was added quickly and the blending speed was increased and then continued for 15 minutes until a stable dispersion resulted. A small concentration of 3-mercapto-1,2,4-triazole (toner) was also added to the resulting dispersion. One ml of the dispersion (A) contained

10 mg of silver.

A heat developable, photographic silver halide composition was prepared by mixing the following components:

1.4/1 Dispersion (A) of a silver salt 100 ml of l-methyl-4-imidazoline-2-thione (as described) silver bromoiodide gelatino photographic 10 ml emulsion (1 ml contains 13 mg of silver) water 10 ml 15% resorcinol coupler, designated herein 20 ml as C-2, in methanol) 5~ surfactant in water (Surfactant lOG, 2 ml a polyglycidol ether available from Olin Chemical Co., U.S.A.) Seven ml of the resulting mixture was then mixed with two ml of 5% by weight aqueous photographic gelatin in which 0.25 mmoles of the developing agent had been dissolved and coated on gel subbed poly(ethylene terephthalate) film support at about 50C at a wet coating thickness of 4 mil. The resulting coating was dried at 150F (65C). After drying, this photographic element was imagewise exposed to light in a commercial sensitometer to provide a developable latent image.
The diffuse visual, developed densities as a function of developing agent are given in the following Table 32A for processing times resulting in equal fog levels of about 0.2 density units.

-' ~ ' , ' ' .- : ' ' ;

a h ~
H h o s~ s~ O ~ I
a~ bD
h ~ ~ ,D
rl v ~n ~r) ~1 C\i N N
O ~ O
X \ ~ ~ ~ ~ ~ h o ~ ~~i,~ ~ ~

~ N C\J r~l ¦ ~--o~ L~ O15~ h bD u~ L~
P~ ~
3 ~ ~ ~ ~ ~ ~ ~ ~ h ~ CQ ~--a) c~ V K
E~ C) a~ ~ ~ o L~ ~ ~ s~
0 13 ~ V ~ N N p~
o v ~ ~ ~ h E3 o o ~
C) O--`
O q~ ~ ~ _ _ _ .,1 ~ ~ ~
~0 ,~ p~ P; P
O X
-a, ~1 ~ ~ ~ L~
~ ~ ~ ~ ~ ~ ft~

X

Examples 38-56 - Use of silver salt of 3-carbox, methy1-4-meth-y1-4-thiazoline-2-~thlone A heat developable photographic composition was prepared by mixing the following components and coating the resulting material on a support at the noted levels:

dispersion of silver salt of 3-carboxymethyl-4-methyl-4-thiazoline-2-thione (designated herein as CMMTT) (dispersion silver - 64 mg/ft2) (CMMTT - 167 mg/ft2) 3-mercapto-1,2,4-triazole (toner) 0.93 mg/ft2 2,4-dimercaptopyrimidine (toner) 0.23 mg/ft2 silver iodide 7.0 Agrng/ft2 poly(vinyl alcohol) (binder) 40.0 mg/ft2 The resulting coating contained a CMMTT to silver ion molar ratio of 1.5 to 1. The coating was overcoated with a solution of the developing agent designated in the following table (0.1 mmoles) in 2% by weight aqueous poly(vinyl alcohol) (9.2 ml) containing a surfactant (Surfactant lOG, o.o6 ml of a 10~ by 20 weight aqueous solution) and resorcinol (90 mg) at a wet coating thickness of 4 mil at about 90F (32C). l~e resulting coating was dried at 155F (68C). The heat developable, photographic element was imagewise exposed to light in a commercial sensitometer to provide a developable latent image. The image was developed by uniformly heating the element. Each element was heated for five seconds. The elements of Examples 38-52 were uniformly heated at 135C. The element of Examples 53 and 54 were uniformly heated at 165C.
The element of Example 55 was heated at 185C. The elements 30 containing less active developing agents require higher processing times and temperatures to produce better images.

~ N ~ N
d o o o ~1 o o ~ ~ ~i C
o~
a) E~ . ~ ~
o U~
~; C~
E~
1~ P~ N N ~:
a~ c~

C ~ N ~

æ ~ ~ N ~ N ~--t~) ~

~1 ~i o~

, ~, ~

.. : ' . . ~ .:

o ~ ~
~ o ,D ~:) H

l O O

Ll~
X ~ CO
~ ~ O

C

¢

C ~ N C\~l a 5 bD +~
bD ~ ~o ~ .
C ~ ~ ~ _~
O u~ ~ ~ C~l ~ _~ N

~1 X ~ N

~1 C~ Y~ 3 ~, H

C¦ N N
Ql O O o Xo~
0~
l O O
_~ p ~1 C

0~

C . N C~l ~ æ,~ @~, ~1 :~;

h O

C>
I ~ C~
a) (~
bC
æ
~ s~
H bD

~ N CO
rl N N ~1 l O O O

3 0~ ct~ , ~ O O ~
_~ ~ O
~5 a o .
¢

C~

~ c ~ æ ~

~ ~1 ~ t"
¢ ~
bD ~ ~:C N
~ ~ /--\ ~ N ^ ~) O
R u~ ~ O \~
~1~ ~J ~ P~ N 0~:) o _ ~) ,~ N ~I C ) , N ~1 N~

~1 x ~

g1~3~;

V o~ ~ ~

C ~ N
O O O

~1 o ~D.
~ ,i ,i 0 C

1:
c ~
N (r ~ ~ N
O /~ /--~ N O~ ~ N O Pi~l /

P v 1~ N

8) ~Z J O

o E ~ c E ¦ . '~ cu ~, ~1 ~ o ~
~1 0 ~5 C) ~" o C
Cl ~ C ' ~
C ¦ I~ N

I O

c , .. . . . . . _ .... . . . . . .
:

Example 57 - Use of water insoluble resorcinol cou~ler .
A heat developable photographic composition was prepared by mixing the following components:
Surfactant lOG (10~ by weight in water) 0.5 ml bis(vinylsulfonylmethyl) ether (2% by 1.0 ml weight in water) (referred to herein as BVSME) coupler C-3 (6% by weight latex using 4.0 ml copoly(n-butyl acrylate 2-acrylamido-2-methylpropane sulfonic acid) (90:10) 3~ by weight gelatin) (30 mg of coupler per ml) D-l developing agent o.o80 g silver ABT salt (200 g/M gelatin) 8.o ml (30% ethanol) silver bromoiodide gelatino emulsion 0.7 ml (o,843 Kg/Ag mole) (diluted 9:1 with water) (0.14~ , 2.5 mole % iodide) The composition was coated at 139.8 mg of silver/ft2 on a poly(ethylene terephthalate) film support at a wet coating thickness of 5 mils. The coating was dried at 120F (49C).
The resulting heat developable photographic element was imagewise exposed to light in a commercial sensitometer to provide a developable latent image using a 1.5 neutral density filter. The image was developed by unlformly heatlng the exposed element on a heated metal block at 160C for 15 seconds. The resulting visible im.age (silver plus dye) had a diffuse visual maximum density of 1.60 and a minimum density of 0.28~

0 Exam~le 58 - Use of water insoluble resorcinol coupler and coupler solven_ A heat developable photographic composition was prepared by mixing the following components:

water 3.5 ml surfactant (Surfactant lOG, lQ~ by 0.5 ml weight in water) developing agent D-l o.o80 g resorcinol coupler C-4 (0.260 g in 8.o ml 0.5 ml diethyllauramide and 0.25 ml ethyl acetate in 16 ml of silver salt of ABT dispersion, as described, and milled through a colloid mill) 4-carboxy-4-thiazoline-2-thione 0.004 g silver bromoiodide gelatino emulsion 0.7 ml (diluted 9:1 with water) (0.14~, 2.5 mole ~ iodide) The composition was coated at a 5 mil wet coating thickness on a polycarbonate film support and dried at 130F (54C).
The resulting heat developable, photographic element was imagewise exposed to light in a commercial sensitometer to produce a developable latent image in the element. The exposed element was then uniformly heated on a heated metal block at 160C for 30 seconds. The resulting visible image had a diffuse maximum density as follows using appropriate filters: red, 1.44; green, 1.57, and blue, 1.61.
C-4 as referred to herein is O
~ ~ 4Hg-t ~ .
Examples 59-110 A heat developable photographic composition was pre~ared b~ mixing the following components:

water 1.5 ml surfactant (Surfactant lOG, 10~ by 0.5 ml weight in water) BVSME (2~ by weight in water) 1.0 ml (hardener) 5-methyl-3-mercapto-1,2,~-triazole 1.0 ml (antifoggant) (3 mg/ml of water) ethyl acetate 0.5 ml resorcinol coupler (as designated in ~.6 m mole following Table 59A) developîng agent (as designated in o.o80 g the following Table 59~) (0.3 m mole) silver salt of ABT (dispersion, as 8.o ml described, 200 g/M gelatin, 30 ethanol) silver bromoiodide gelatino emulsion 0.7 ml (10 mg Ag) The composition was coated at a 5 mil wet coating thickness on a subbed poly(ethylene terephthalate) film support at 120F
(49C). The resulting heat developable, photographic element was imagewise exposed to light in a commercial sensitometer to produce a developable latent image. The element was then uniformly heated on a metal block at 160C for 20 seconds.
The results obtained are given in the followlng table.

, *Used wlth couplers which ~ere sparingly soluble in water.

a _ ~ q m m X ~ ~ ~ N O 5-~
~ h m m m ~ ~ ~
H ~1 j Li F:l j O E~

W ~ F~ u N ~D

¢ ~ ~ C O-V ~
~1~ ~ O - V ~ 0 >
~ S~ ~ o>J
V

~0 S~ ~
~1 ~ C\J ~ ,~ ~D
V V
V U~

O c~ O ~I N
~1 ~
X

E~ ~ ~ C p.

C
oC l l C ~ o C~ o Xo ~_o ~_,,, o- ~ C~l ~> ~ PC~:o ~

O
a~ ~
~1 ~ ~ ~1 ~;
a) ~ ~
O

`' ~ o ~ o~
m ,, ~ ~ rl O ~ ~d~ N
x ~ ~m ~ ,i ~
a~ ~ ~ X
~ ~ m ~3 ~ m ~
F ~ ~ ~ ~ ~
H 1--l ~ ~ ~ ~ ~ ~1 U~ h P; H ~ ~:
_ m m~

bD

~ C

~oc C~

~~ k, --~

s~
~1 ~B ~ O
bD

~i ~C

~ ~ ~ r u K r ~ ~ ~

~5 o a ~ ¢ a ~ a a a~
a s~
~ ~ ~: ~
~ '~0) o ~ ~ F

o ~1 ~ ~ ~ U~
V C~ V
a ~; ~
C~

X C) c^
Q~ O a~ o ~ o a o ~ h ES~ E3 h ~
~4 h ~ ~ ~ Si ~ O ~ ~0 ~ O ,~
a) t~
~ a) 3 ~ ~3 ~ 3 ~ a~
E ~ ~ ~ ~
H ~ O ~ O ~ O ~, bD

~, ¢

r X ~ X

O
~@ v v V v ~, ~

~ ~_ S~

~1~

s~ ~ O a " ~

H H m ~ h Q~I o U~

3~
QC~ ~

4 b o h _I
,~
~ N N N N
0~ V
~ , ':'~

~ CO

~ .

. .

~ :" ~ m H O
m _ ~ ~:

bD
~bD ~

~ , a ~ ~ 0-- + 1 ~
O

Ll~
~1 ~ N
O ~
C~ ~q ~ N
E 00 ~ ~ 1 X

` .. -............... .

c~ - ~ ~
- ~ ~ ~ ~
~r~ E E

E ~ 3 ~" m ~ m H .--1 C~ ~

b~
,~1 l l l -G) ~ r ~" ' ' ~ ' ~ ~

c a~
o~ V V V V
a) ~ C) ~ x o~ x ~ ~

~o o 3 ~ o 3 ~ ~ ~ ~ O
bD h bD h ~ h ~ ~ D ~ 3: ~ &~
H ~1 ~ ~ 3 U~

b5 ~ ~ .

a) C

~1 N ~ ~ I`f) C.) U~

~Z;

x E ~ ~ ~ o X

Cl~ C ~c ~

H ~ N ~ ~

~ C
o a bf 1~1 ~:. ¢

a) C C C

~-- V ~= ~ ~ O
~ ~0=~ ~.0 ~1=o E~

~_1 ~D ~ 0 ~bD V
O
~q . C) Zi ~ .
a~ ~ "~

K O K

11~3 C) a o ~
o a) s~

C ~ C O
~ ~ h ~ ~ O ~ o s: o + ~ ~ m e~ a) X~ ,I s~
bD ~ ~ m ~, ~c td ~ ~ ~
E ~ ~ ~ ~Y; ~ ~ a) ~

o a) I l l l .
~I bD 1 ¢

S~ ~1 .
a ~ ~ ~ S

tc ~ ~ tq E~ V

Co O
O ~

~i 8 o X

``.

~1 ~
m ,i ~ P

bD ~ m ~ N
H ~1 I C ~ ¦ O

bD . :- ~

~plb I Q

a~

C j ~ O- ~ ~

P~ .

`,, O
æ cd a) ~ ~ : .
~1 I O ~ O
X
C~

. - . . - , . . .

9~:~

,~ m ~_ ~ 3 ~ ,, ~
m m ~ ' .

C~l ~

'~

~o _I

~ O ~ ~1 ~

1-3 , ~1 ~
~ .
_ m *
X
bD~ H h ~3 ~ a~
H 1--l ~:5 ~ cq ~
rl a) .c~ E3 u~ ~ ,1a) ~
a) X O
b~ ~q O a~ I ~1 ~ ¢ ~ O
a a)~
q~ tB
h 5-~
~0 ~ ~ ~ C
<~V~

~ O
~ t~
C ~B
~0 ~I cd ~ C~ ~

C~

x ~ o Example 111 A heat developable, photographic element prepared as described herein with the silver salt of ABT, developing agentD-l, and the resorcinol coupler, designated C-l was imagewise exposed to light in a commercial sensitometer.
The resulting latent image was developed by uniformly heating the element at 165C for 15 seconds. The following Dmax/Dmin values (diffuse, transmission) were obtained, respectively, for the image for the blue, green and red areas of the spectrum with appropriate filters:
2.21/0.22, 1.98/0.17, and 1.47/0.14.
A comparative element was prepared, exposed, and processed in the same manner, but without the C-l coupler. The following Dmax/Dmin values (diffuse, transmission) were obtained, respectively, for the image for the blue, green and red areas of the spectrum with the appropriate filters:
1.33/0.18; 0.83/0.13, and 0.66/0.10.
mis illustrates that the heat developable material containing developing agent D-l and coupler C-l provided enhanced maximum density and a more neutral lmage hue.

Example 11?
A heat developable photographic element prepared as described herein with the silver salt of ABT, resorcinol as the coupler, and the developing agent designated D-2A was imagewise exposed to light in a commercial sensitometer. The resulting latent image was developed by uniformly heating the element at 155C for 30 seconds. me following Dmax values (diffuse, transmission) were obtained, respectively, for the image for the blue, green and red areas of the spectrum with the appropriate filters: 1.70, 1.54, and 1.45.
A comparative element was prepared, exposed, and processed in the same manner, but without the resorcinol coupler. The following Dmax values were obtained, respectively, for the image for the blue, green and red areas of the spectrum with the appropriate filters: 1.09, 0.72, and 0.53.
This illustrates that the described element containing the resorcinol coupler produced enhanced maximum image density and a more neutral tone image than the element without the resorcinol coupler.
The optimum image will be influenced in many heat developable materials, as described, by selection of the most suitable silver halide grain size.
The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

~ .

:

Claims

WHAT IS CLAIMED IS:

1. In a heat developable photographic element for producing a dye enhanced silver image, comprising a support having thereon, in reactive association, in binder:
(a) photosensitive silver halide, (b) an image-forming combination comprising (i) an organic, silver salt oxidizing agent, with (ii) an organic reducing agent for said silver salt oxidizing agent, the improvement wherein said element comprises (c) a resorcinol, dye-forming coupler that forms a dye imagewise with the oxidized form of said reducing agent, and wherein said element forms a neutral or nearly neutral appearing image upon imagewise exposure and thermal processing.

2. A heat developable photographic element as in Claim 1 wherein said binder consists essentially of a gelatino binder.

3. A heat developable photographic element as in Claim 1 comprising about 0.1 to about 1.0 mole of said coupler per mole of said silver salt oxidizing agent.

4. A heat developable photographic element as in Claim 1 wherein said coupler consists essentially of a resorcinol compound represented by the formula:

wherein R1 is hydrogen, , , , or ;

R2 is hydrogen, , , or ;
R3 is hydrogen, , or ;
R4 is hydrogen, , or ;

R5 is haloalkyl containing 1 to 3 carbon atoms, CH2OCH3, CH2SR7, NHR8, C2H4COOH, CH-CH2, NHC2H4Cl, alkyl containing 1 to 20 carbon atoms, or phenyl;
R6 is OH, NH2, NHCH2CH2OH, or NH?C6H5?OC5H11n;
R7 is alkyl containing 1 to 5 carbon atoms, or phenyl;
and, R8 is hydrogen, haloalkyl containing 1 to 3 carbon atoms, CH2OCH3, or C2H4COOH.

5. A heat developable photographic element as in Claim 1 wherein said coupler consists essentially of a compound represented by the formula wherein R5 is haloalkyl containing 1 to 3 carbon atoms, CH2OCH3, CH2SR7, NHR8, C2H4COOH, CH=CH2, NHC2H4Cl, alkyl containing 1 to 10 carbon atoms or phenyl; R7 is alkyl containing 1 to 5 carbon atoms or phenyl; and, R8 is hydrogen, haloalkyl containing 1 to 3 carbon atoms, CH2OCH3 or C2H4COOH.

6. A heat developable photographic element as in Claim 1 wherein said coupler consists essentially of 2,6-dihydroxyacetanilide.

7. A heat developable photographic element as in Claim 1 wherein said coupler consists essentially of 2',6'-dihydroxytrifluoroacetanilide.

8. A heat developable photographic element as in Claim 1 wherein said coupler consists essentially of an acetanilide represented by the formula:

9. A heat developable photographic element as in Claim 1 wherein said silver halide consists essentially of a photographic silver halide gelatino emulsion.

10. A heat developable photographic element as in Claim 1 wherein said reducing agent consists essentially of a p-phenylenediamine silver halide developing agent that exhibits a half wave potential value in aqueous solution at pH 10 within the range of minus 25 to plus 175 millivolts versus a saturated calomel electrode.

11. A heat developable photographic element as in Claim 1 also comprising a heat sensitive base-release agent.

12. A heat developable photographic element as in Claim 1 also comprising a heat sensitive base-release agent comprising an aminimide base-release agent.

13. A heat developable photographic element as in Claim 1 wherein said oxidizing agent consists essentially of a silver salt of a 1,2,4-mercaptotriazole derivative repre-sented by the formula:

wherein Y is aryl containing 6 to 12 carbon atoms; n is an integer from 0 to 2; and Z is hydrogen, hydroxyl or amine.

14. A heat developable photographic element as in Claim 1 wherein said oxidizing agent is a silver salt of 3-amino-5-benzylthio-1,2,4-triazole.

15. A heat developable photographic element for producing a dye enhanced silver image comprising a support having thereon, in reactive association, in a gelatino binder:
(a) a photographic silver halide gelatino emulsion, (b) an image-forming combination comprising (i) a silver salt of a 1,2,4-mercaptotriazole derivative represented by the formula:

wherein Y is aryl containing 6 to 12 carbon atoms; n is an integer from 0 to 2; and Z is hydrogen, hydroxyl, or amine, and (ii) an organic reducing agent for said silver salt in (b)(i);

(c) a resorcinol, dye-forming coupler that forms a dye imagewise with the oxidized form of said reducing agent.

16. A heat developable photographic element for providing a dye enhanced, silver image comprising a support having thereon, in reactive association, in a polymeric binder:
(a) a photographic silver halide gelatino emulsion, (b) an image-forming combination comprising (i) a silver salt of 3-amino-5-benzylthio-1,2,4-triazole, with (ii) an organic reducing agent consisting essentially of 4-amino-2-methoxy-N,N,5-trimethylaniline sulfate which is a reducing agent for said silver salt in (b)(i), and (c) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide.

17. A heat developable photographic element for providing a dye enhanced, silver image comprising a support having thereon, in reactive association, in a polymeric binder:
(a) photosensitive silver halide, (b) an image-forming combination comprising (i) a complex of silver with a nitrogen acid, with (ii) an organic reducing agent for said complex of silver with a nitrogen acid, and (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent.

18. A heat developable photographic element for producing a dye enhanced silver image comprising a support having thereon, in reactive association, in a gelatino binder:
(a) a photosensitive silver halide gelatino emulsion, (b) an image-forming combination comprising (i) a complex of silver with a nitrogen acid which is a compound selected from the group consisting of imidazole, pyrazole, urazole, 1,2,4-triazole and 1H-tetrazole nitrogen acids and combinations thereof, and (ii) an organic reducing agent for said complex of silver in (b)(i), said reducing agent consisting essentially of a p-phenylene-diamine silver halide developing agent that exhibits an E value in aqueous solu-tion at pH 10 within the range of minus 25 to plus 175 millivolts versus a saturated calomel electrode, and (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent and consists essentially of a compound represented by the formula:

wherein R5 is haloalkyl containing 1 to 3 carbon atoms, CH2OCH3, CH2SR7, NHR8, C2H4COOH, CH=CH2, NHC2H4Cl, alkyl containing 1 to 10 carbon atoms or phenyl; R7 is alkyl containing 1 to 5 carbon atoms or phenyl; and, R8 is hydrogen, haloalkyl containing 1 to 3 carbon atoms, CH2OCH3 or C2H4COOH.

19. A heat developable photographic element for providing a dye enhanced, silver image comprising a support having thereon, in reactive association, in a polymeric binder:
(a) a photosensitive silver halide gelatino emulsion, (b) an image-forming combination comprising (i) a complex of silver with imidazole, with (ii) an organic reducing agent for said complex of silver with imidazole, and (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent.

20. A heat developable photographic element for producing a dye enhanced silver image comprising a support having thereon, in reactive association, in a gelatino binder:
(a) photosensitive silver halide gelatino emulsion, (b) an image-forming combination comprising (i) a complex of silver with dodecyltetrazole, with, (ii) an organic reducing agent consisting essentially of 2-methyl-4-(N-ethyl-N-hydroxyethyl)-aminoaniline hydrogen sulfate which is a reducing agent for said complex of silver in (b)(i), (c) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide, and (d) a melt-forming compound.

21. A heat developable photographic element for providing a dye enhanced silver image comprising a support having thereon, in reactive association, in a polymeric binder:
(a) photosensitive silver halide, (b) an image-forming combination comprising (i) a silver salt of a heterocyclic thione represented by the formula:

wherein Z' is alkylene containing 1 to 1 carbon atoms; R represents the atoms necessary to complete a heterocyclic nucleus selected from carbon, oxygen, sulfur and nitrogen atoms, with (ii) an organic reducing agent for said silver salt of a heterocyclic thione, and (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent.

22. A heat developable photographic element for providing a dye enhanced silver image comprising a support having thereon, in reactive association, in a polymeric binder:
(a) photosensitive silver halide, (b) an image-forming combination comprising (i) a silver salt of 3-carboxymethyl-4-methyl-4-thiazoline-2-thione, with (ii) an organic reducing agent consisting essentially of 4-amino-2-methoxy-N,N,5-trimethylaniline sulfate which is a reducing agent for said silver salt in (b)(i), and (c) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide.

23. In a heat developable photographic composition for providing a dye enhanced silver image comprising, in a polymeric binder:
(a) photosensitive silver halide, (b) an image-forming combination comprising (i) an organic silver salt oxidizing agent, with (ii) an organic reducing agent for said silver salt oxidizing agent, the improvement wherein said composition comprises (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent, and wherein said composition forms a neutral or nearly neutral appearing image upon imagewise exposure and thermal proces-sing.

24. A heat developable photographic composition as in Claim 23 wherein said binder consists essentially of a gelatino binder.

25. A heat developable photographic composition as in Claim 23 comprising about 0.1 to about 1.0 mole of said coupler per mole of said silver salt oxidizing agent.

26. A heat developable photographic composition as in Claim 23 wherein said coupler consists essentially of a compound represented by the formula:

wherein R5 is haloalkyl containing 1 to 3 carbon atoms, CH2OCH3, CH2SR7, NHR8, C2H4COOH, CH=CH2, NHC2H4Cl, alkyl containing 1 to 10 carbon atoms or phenyl; R7 is alkyl containing 1 to 5 carbon atoms or phenyl; and, R8 is hydrogen, haloalkyl containing 1 to 3 carbon atoms, CH2OCH3 or C2H4COOH.

27. A heat developable photographic composition as in Claim 23 wherein said coupler consists essentially of 2,6-dihydroxyacetanilide.

28. A heat developable photographic composition as in Claim 23 wherein said coupler consists essentially of 2',6'-dihydroxytrifluoroacetanilide.

29. A heat developable photographic composition as in Claim 23 wherein said coupler consists essentially of a compound represented by the formula:

30. A heat developable photographic composition as in Claim 23 wherein said (a) consists essentially of a photographic silver halide gelatino emulsion.

31. A heat developable photographic composition as in Claim 23 wherein said reducing agent is a p-phenylene-diamine silver halide developing agent that exhibits an E
value in aqueous solution at pH 10 within the range of minus 25 to plus 175 millivolts versus a saturated calomel elec-trode.

32. A heat developable photographic composition as in Claim 23 also comprising a heat sensitive base-release agent.

33. A heat developable photographic composition as in Claim 23 also comprising a heat sensitive base-release agent comprising an aminimide base-release agent.

34. A heat developable photographic composition as in Claim 23 wherein the organic silver salt oxidizing agent consists essentially of a silver salt of a 1,2,4-mercaptotriazole derivative represented by the formula:

wherein Y is aryl containing 6 to 12 carbon atoms; n is an integer from 0 to 2;
and Z is hydrogen, hydroxyl or amine.

35. A heat developable photographic composition as in Claim 23 wherein the organic silver salt oxidizing agent consists essentially of a silver salt of 3-amino-5-benzylthio-1,2,4-triazole.

36. A heat developable photographic composition for providing a dye enhanced silver image comprising, in a polymeric binder:
(a) a photographic silver halide gelatino emulsion, (b) an image-forming combination comprising (i) a silver salt of 3-amino-5-benzylthio-1,2,4-triazole, with (ii) an organic reducing agent consisting essentially of 4-amino-2-methoxy-N,N,5-trimethylaniline sulfate which is a reducing agent for said silver salt in (b)(i), and (c) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide.

37. A heat developable photographic composition comprising, in a polymeric binder:
(a) photosensitive silver halide, (b) an image-forming combination comprising (i) a complex of silver with a nitrogen acid, with (ii) an organic reducing agent for said com-plex of silver with a nitrogen acid, and (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent.

38. A heat developable photographic composition comprising, in a polymeric binder:
(a) a photosensitive silver halide gelatino emulsion, (b) an image-forming combination comprising (i) a complex of silver with imidazole, with (ii) an organic reducing agent for said complex of silver with imidazole, and (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent.

39. A heat developable photographic composition for providing a dye enhanced silver image comprising, in a polymeric binder:
(a) photosensitive silver halide gelatino emulsion, (b) an image-forming combination comprising (i) a complex of silver with dodecyltetra-zole, with (ii) an organic reducing agent consisting essentially of 2-methyl-4-(N-ethyl-N-hydroxyethyl)-aminoaniline hydrogen sulfate which is a reducing agent for said complex of silver in (b)(i), (c) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide, and (d) a melt-forming compound.

40. A heat developable photographic composition for providing a dye enhanced silver image comprising, in a polymeric binder:
(a) photosensitive silver halide, (b) an image-forming combination comprising (i) a silver salt of a heterocyclic thione represented by the formula:

wherein Z' is alkylene containing 1 to 10 carbon atoms; R represents the atoms necessary to complete a heterocyclic nucleus selected from carbon, oxygen, sulfur and nitrogen atoms, with (ii) an organic reducing agent for said silver salt of a heterocyclic thione, and (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent.

41. A heat developable photographic composition for providing a dye enhanced silver image comprising, in a polymeric binder:
(a) photosensitive silver halide, (b) an image-forming combination comprising (i) a silver salt of 3-carboxymethyl-4 methyl-4-thiazoline-2-thione, with (ii) an organic reducing agent consisting essentially of 4-amino-2-methoxy-N,N,5-trimethylaniline sulfate which is a reducing agent for said silver salt in (b)(i), and (c) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide.

42. In a thermographic element comprising a support having thereon, in reactive association, in a polymeric binder:
(a) an oxidation-reduction image-forming combina-tion comprising (i) an organic silver salt oxidizing agent, with (ii) an organic reducing agent for said organic silver salt oxidizing agent, the improvement comprising (b) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent.

43. A thermographic element as in Claim 42 wherein said coupler consists essentially of a compound represented wherein R5 is haloalkyl containing 1 to 3 carbon atoms, CH2OCH3, CH2SR7, NHR8, C2H4COOH, CH=CH2, NHC2H4Cl, alkyl containing 1 to 10 carbon atoms or phenyl; R7 is alkyl containing 1 to 5 carbon atoms or phenyl; and, R8 is hydrogen, haloalkyl containing 1 to 3 carbon atoms, CH2OCH3 or C2H4COOH.

44. A thermographic element comprising a support having thereon, in reactive association, in a polymeric binder:
(a) an oxidation-reduction image-forming combina-tion comprising (i) a silver salt of 3-amino-5-benzylthio-1,2,4-tetrazole, with (ii) an organic reducing agent consisting essentially of 4-amino-2-methoxy-N,N,5-trimethylaniline sulfate which is a reducing agent for said silver salt in (b)(i), and (b) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide.

45. A thermographic element comprising a support having thereon, in reactive association, in a polymeric binder:
(a) an oxidation-reduction image-forming combina-tion comprising (i) a complex of silver with imidazole, with (ii) an organic reducing agent for said com-plex of silver with imidazole, and (b) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent.

46. In a thermographic composition comprising (a) an oxidation-reduction image-forming combina-tion comprising (i) an organic silver salt oxidizing agent, with (ii) an organic reducing agent for said organic silver salt oxidizing agent, and (b) a polymeric binder, the improvement wherein said composition comprises (c) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent.

47. A thermographic composition as in Claim 46 wherein said coupler consists essentially of a compound represented by the formula:

wherein R5 is haloalkyl containing 1 to 3 carbon atoms, CH2OCH3, CH2SR7, NHR8, C2H4COOH, CH=CH2, NHC2H4Cl, alkyl containing 1 to 10 carbon atoms or phenyl; R7 is alkyl containing 1 to 5 carbon atoms or phenyl; and, R8 is hydrogen, haloalkyl containing 1 to 3 carbon atoms, CH2OCH3 or C2H4COOH.

48. A thermographic composition comprising (a) an oxidation-reduction image-forming combina-tion comprising (i) a silver salt of 3-amino-5-benzylthio-1,2,4-triazole, with (ii) an organic reducing agent consisting essentially of 4-amino-2-methoxy-N,N,5-trimethylaniline sulfate which is a reducing agent for said silver salt in (b)(i), and (b) a coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide, and (c) a polymeric binder.

49. A thermographic composition comprising (a) an oxidation-reduction image-forming combina-tion comprising (i) a complex of silver with imidazole, with (ii) an organic reducing agent for said com-plex of silver wlth imidazole, (b) a resorcinol, dye-forming coupler that forms a dye with the oxidized form of said reducing agent, and (c) a polymeric binder.

50. A process of developing a latent image in an exposed photographic element as defined in Claim 1 comprising heating said element to a temperature within the range of about 100°C to about 250°C until a dye enhanced silver image is developed.

51. A process of developing a latent image in an exposed photographic element as defined in Claim 15 comprising heating said element to a temperature within the range of about 100°C to about 250°C until a dye enhanced silver image is developed.

52. A process of developing a latent image in an exposed photographic element as defined in Claim 17 comprising heating said element to a temperature within the range of about 100°C to about 250°C until a dye enhanced silver image is developed.

53. A process of developing a latent image in an exposed photographic element as defined in Claim 21 comprising heating said element to a temperature within the range of about 100°C to about 250°C until a dye enhanced silver image is developed.