05/249260

10/01/1974

05/01/1972

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Eastman Kodak Company (Rochester, NY)

430/352

430/370, 430/965, 430/619, 430/955, 430/611

G03C1/498; G03C5/26; B41M5/00; G03C1/02; G03C5/38; G03C1/34

96/114.1,48HD,5R,61R,109,66T 117/36.8

3679422		July 1972	DE Mauriac et al.
3700457		October 1972	Youngquist
3708304	USE OF DIVALENT METAL SALT IMAGE AMPLIFIERS IN PHOTOSENSITIVE AND THERMOSENSITIVE ELEMENTS	January 1973	Hiller
3751249	PHOTOTHERMIC SILVER HALIDE ELEMENT CONTAINING A BIS-BETA-NAPHTHOL REDUCING AGENT AND A 1, 3-DIHYDROXY-BENZENE REDUCING AGENT	August 1973	Hiller
3761279		September 1973	DE Mauriac et al.

Klein, David

Schilling, Richard L.

Knapp, Mr. R. E.

This is a continuation-in-part application of U.S. Application Ser. No. 43,171 of Hiller, filed June 3, 1970, now abandoned.

1. A photothermographic element comprising a support having thereon a layer comprising:

2. A photothermographic composition comprising:

3. A method of developing and stabilizing an image in a photothermographic element comprising a support having thereon a layer comprising:

4. A method as in claim 3 comprising heating said element for about 0.5 to

5. A phtothermographic element comprising a support having thereon photosensitive silver halide in association with an oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent with (ii) a reducing agent, a binder, and a stabilizer precursor which is a compound of the formula: ##SPC28##

6. A photothermographic element comprising a support having thereon photosensitive silver halide in association with an oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent with (ii) a reducing agent, a binder, and a stabilizer precursor which is a compound of the formula: ##SPC29##

7. A photothermographic element comprising a support having thereon photosensitive silver halide in association with an oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent with (ii) a reducing agent, a binder, and a stabilizer precursor which is a compound of the formula: ##SPC30## wherein R³ is acetyl, propionyl, butyryl, pentanoyl, carboxy, cyano, aroyl containing up to 13 carbon atoms or furyl; R⁶ is alkyl containing one to five carbon atoms, aryl containing six to 12 carbon

8. A photothermographic element comprising a support having thereon photosensitive silver halide in association with an oxidation-reduction image-forming combination comprising (i) silver behenate with (ii) a phenolic reducing agent, a binder, and a stabilizer precursor which is selected from the group consisting of

9. -acetyl-4-methyl-2-(3-oxobutylethio) thiazole,

10. -phenyl-4-thiazoline-2-thione,

11. -acetyl-4-methyl-4-thiazoline-2-thione,

12. A photothermographic element comprising a support having thereon photosensitive silver halide in association with an oxidation-reduction image-forming combination comprising (i) silver behenate with (ii) a bis-beta-napthol reducing agent, a binder and a stabilizer precursor which

13. A photothermographic composition comprising photosensitive silver halide in association with an oxidationreduction image-forming combination comprising (i) a heavy metal salt oxidizing agent with (ii) a reducing agent, a binder, and a stabilizer precursor which is a compound of the formula: ##SPC31##

14. A photothermographic composition comprising photosensitive silver halide in association with an oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent with (ii) a reducing agent, a binder, and a stabilizer precursor which is a compound of the formula: ##SPC32##

15. A photothermographic composition comprising photosensitive silver halide in association with an oxidationreduction image-forming combination comprising (i) a heavy metal salt oxidizing agent with (ii) a reducing agent, a binder, and a stabilizer precursor which is a compound of the formula: ##SPC33##

16. A photothermographic composition comprising photosensitive silver halide in association with an oxidation-reduction image-forming combination comprising (i) silver behenate with (ii) a phenolic reducing agent, a binder, and a stabilizer precursor which is a compound selected from the group consisting of

17. -acetyl-4-methyl-2-(3-oxobutylthio) thiazole,

18. -phenyl-4-thiazoline-2-thione,

19. -acetyl-4-methyl-4-thiazoline-2-thione,

20. A photothermographic composition comprising:

21. -acetyl-4-methyl-2-(3-oxobutylthio) thiazole,

22. -phenyl-4-thiazoline-2-thione,

23. -acetyl-4-methyl-4-thiazoline-2-thione,

24. A method of developing and stabilizing an image in an exposed photothermographic element as defined in claim 5 comprising heating said

25. A method of developing and stabilizing an image in an exposed photothermographic element as defined in claim 6 comprising heating said

26. A method of developing and stabilizing an image in an exposed photothermographic element as defined in claim 7 comprising heating said

27. A method of developing and stabilizing an image in an exposed photothermographic element as defined in claim 8 comprising heating said element to about 80°C. to about 250°C. for about 0.5 to about 60 seconds.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to photosensitive elements, compositions and processes for developing a latent image using so-called drying processing with heat. In one of its aspects, it relates to photosensitive elements, suitable for processing with heat, containing an azole thioether or a blocked azolinethione image stabilizing precursor, especially one containing a thiazole thioether, a thiadiazole thioether, a tetrazole thioether or a blocked thiazolinethione image stabilizing compound. In another of its aspects, it relates to a photosensitive composition suitable for processing with heat containing an image stabilizing compound as described. A further aspect relates to a dry process of developing and stabilizing the background density areas in a photosensitive and thermosensitive element containing an image stabilizing azole thioether or blocked azolinethione precursor, as described.

2. Description of Prior Art

It is known to obtain an image in a photosensitive element suitable for so-called dry processing with heat. The photosensitive element can contain a reducing agent, a light insensitive silver salt of an organic acid as an oxidizing agent and a low concentration of photographic silver halide as described in U.S. Pat. No. 3,152,904 of Sonenson et al issued Oct. 13, 1964. Methods of this type are also described, for example, in French Patent No. 1,441,619 and Belgian Pat. No. 705,872.

In a photosensitive and thermosensitive element suitable for so-called dry processing with heat one of the main difficulties involves post-processing print-out. Since these photosensitive elements are suitable for dry processing with heat and are designed to eliminate a fixing step which would normally remove undeveloped silver, it is imperative that a means be provided for preventing post-processing print-out due to room-light handling.

Several procedures have been proposed, e.g., washing with water to remove undeveloped silver salts, heating to release Bronstead or Lewis acids such as HCl, BF ₃ or HF from compounds such as m-nitrobenzenesulfonyl chloride, p-toluenesulfonic acid urea addition complex or p-acetamidobenzenediazonium fluoroborate and finally chelation of the oxidizing agent with, e.g., salicylaldoxime or benzotriazole as described in U.S. Pat. No. 3,152,903 of Shepard et al issued Oct. 13, 1964 and U.S. Pat. No. 3,152,904 of Sonenson et al issued Oct. 13, 1964. Another method of avoiding the problem of post-processing print-out is to coat the oxidation-reduction image-forming combination on one sheet of material and the latent image-forming photographic silver halide on a separate sheet. The sheets are separated after exposure to light as described in U.S. Pat. No. 3,152,903 and U.S. Pat. No. 3,152,904. A further example involves swabbing a 1 percent solution of phenylmercaptotetrazole solution onto the surface of the coating and rubbing benzotriazole into the surface of the coating. These alternatives are not suitable for large volume handling of photosensitive and thermosensitive elements.

A more recent development utilizes an aqueous composition containing an excess of silver ions and a silver salt or an aryl thiol which apparently decomposes upon heating at 175°C. to give a brownish-black image with a pale yellow background and renders the unexposed regions almost insensitive to further exposure by room light as described in British Patent No. 1,178,800 of Hellings et al issued Jan. 21, 1970.

In addition, it is known that heterocyclic compounds of the general formula: ##SPC1## can be employed as stabilizers and antifogging agents for light-sensitive gelatino silver halide emulsions without causing appreciable desensitization of the emulsions, wherein Z represents the atoms necessary to form a heterocyclic ring or a substituted heterocyclic ring, A is a --COR group or a --SO ₂ R group and R is alkyl, substituted alkyl, aryl and substituted aryl as described in Gevaert British Patent No. 1,053,587 published Jan. 4, 1967.

Unfortunately, in some cases these elements suffer from having poor spectral sensitivity and the resulting images after processing are of low maximum density, warm tone and poor image stability, i.e., they still lack protection against post-processing print-out due to room light exposure or have a stained background area.

Accordingly, there has been a continuing need for a photosensitive element suitable for so-called dry processing with heat, especially such an element which has an oxidationreduction image forming combination, which has improved postprocessing image stability, i.e., less background density and stain due to print-out and more neutral image tone (jet black).

SUMMARY OF THE INVENTION

The described improvements are provided in photosensitive and thermosensitive elements, compositions and processes employing such elements and compositions, by certain stabilizers precursors which are azole thioethers or blocked azolinethiones.

The described improvements are provided, for example, in a photosensitive and thermosensitive element, such as a photothermographic element, comprising a support having thereon an oxidation-reduction image-forming combination comprising

i. a heavy metal salt oxidizing agent with

ii. a reducing agent, a binder and an azole thioether or a blocked azolinethione stabilizer precursor.

DESCRIPTION OF PREFERRED EMBODIMENTS

A range of azole thioether or blocked azolinethione stabilizer precursors can be employed in the practice of the invention to reduce the amount of postprocessing print-out due to room-light exposure and to reduce the background stain.

Within this class a test can be used to determine whether or not a compound of material is an image stabilizer precursor as described. If the compound, after incorporation in the photothermographic element and after exposure and processing of the element as in following Example 2, prevents the buildup of background density or minimum density above 0.10 density unit above minimum density without undue stain as in Example 2 in comparison to a coating as in Example 1 where the stabilizer precursor has been omitted, then the compound is considered to be acting as a stabilizer precursor.

It is believed that the above azole thioether and blocked azolinethiones are the precursors of the actual moiety, compound or material which, upon combination with undeveloped silver ions or radicals prevents "print-out" due to room-light exposure and alleviates background stain. However, the exact mechanism of stabilization is not fully understood.

A suitable stabilizer precursor is a heterocyclic stabilizer precursor which includes compounds within the formulas: ##SPC2##

wherein Z represents atoms completing a 5 or 6 member heterocyclic nucleus, such as thiazole, thiadiazole, thiazoline and tetrazole, R ¹ is alkyl containing one to 10 carbon atoms, e.g., methyl, ethyl, propyl, butyl and pentyl, --(CH ₂ ) _n --R ³ , or a heterocyclic group, e.g., furyl; W represents atoms completing a thiazoline, thiadiazoline, tetrazoline, 3-- alkylthiothiadiazoline or 3-acylalkylthiothiadiazoline nucleus, R ² is --(CH ₂ ) _n --R ³ ; n is 0 or 2; R ³ is acetyl, propionyl, butyryl, pentanoyl, carboxy, cyano or aroyl, e.g., containing up to 13 carbon atoms, or furyl. The described groups can contain substituents which do not adversely affect the stabilizing activity of the described compounds.

Suitable azole thioether stabilizer precursors which can be employed in the described combination include, for example, thiazole thioethers of the formula: ##SPC3##

wherein R ³ is acetyl, propionyl, butyryl, pentanoyl, carboxy, cyano or aroyl containing up to 13 carbon atoms, such as benzoyl, including aroyl containing substituents which do not adversely affect stabilizing action, such as nitrobenzoyl, methoxybenzoyl and ethoxybenzoyl; or furyl; R ⁴ is hydrogen, alkyl containing one to five carbon atoms, alkyl containing substituents which do not adversely affect stabilizing activity, such as oxoalkyl, carboxy and carboxyalkyl; R ⁵ is hydrogen, alkyl containing one to five carbon atoms such as methyl, ethyl, propyl, butyl, tert.-butyl and pentyl including alkyl containing substituents which do not adversely affect stabilizing action as described, such as hydroxymethyl, carboxy and carboxyalkyl; aryl including aryl containing substituent groups which do not adversely affect stabilizing activity, e.g., nitrophenyl, methoxyphenyl, and benzoyl; n is 0 or 2. Alkyl and aryl as employed herein include alkyl and aryl containing substituent groups which do not adversely affect the desired stabilizing activity of the described compounds. The alkyl group can be, for example, carboxyalkyl or dicarboxyalkyl.

Other suitable azole thioether stabilizer precursors which can be employed in the described combination include thiazole thioethers of the formula: ##SPC4##

wherein R ⁶ is alkyl, e.g., straight- or branched-chain alkyl, containing one to 10 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, t-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and the like, including cycloalkyl, such as cycloalkyl containing five to seven carbon atoms, including cyclopentyl and cyclohexyl; aralkyl such as benzyl, p-nitrobenzyl, phenethyl, p-ethoxyphenethyl, 1-naphthylmethyl, and the like; an aryl group containing up to 20 carbon atoms, such as phenyl, naphthyl or 9-anthryl; R ⁷ is hydrogen, alkyl, e.g., alkyl containing one to 10 carbon atoms, such as a straight- or branched-chain alkyl, as described, an ester group represented by the formula: R ⁹ COO- wherein R ⁹ is alkyl, aralkyl or aryl, each as described regarding R ⁶ , or an acyl group containing one to 10 carbon atoms, preferably acetyl; R ⁸ is alkoxy containing one to 10 carbon atoms, such as methoxy, ethoxy or propoxy, aryl, alkyl, each as described regarding R ⁶ , preferably methyl, carboxy or a carboxyester, such as methoxycarbonyl, ethoxycarbonyl, butoxycarbonyl and phenoxycarbonyl. Alkyl and/or aryl, as described, can contain substituent groups which do not adversely affect the stabilizing action of the azole thioether stabilizer precursors, such as hydroxy or carboxy. Especially useful compounds are those wherein R ⁷ is acetyl and R ⁸ is methyl. Compounds within this class can be prepared by reacting a 2-- thionothiazoline, such as 5-acetyl-4-methyl-4-thiazoline-2-thione, with a chloroformate, represented by the formula: ##SPC5##

wherein R ⁶ is as described.

An especially suitable thiazole thioether is 5-- acetyl-4-methyl-2-(3-oxobutylthio)thiazole of the formula: ##SPC6##

Examples of suitable thiazole thioether stabilizer precursors which can be employed in the practice of the invention include:

5-Acetyl-2-benzoylthio-4-methylthiazole,

4-Benzoylmethyl-2-benzoylthiothiazole,

2-(2-Furoylthio)-4-hydroxymethylthiazole,

2-Benzoylthio-4-hydroxymethylthiazole,

2-Benzoylthio-4-tert.-butylthiazole,

5-Carbethoxy-4-methyl-2-(3-oxobutylthio)thiazole,

5-Acetyl-2-(2-benzoylethylthio)-4-methylthiazole,

2-(3-Oxobutylthio)thiazole,

4,5-Dimethyl-2-(3-oxobutylthio)thiazole,

2-(3-Oxobutylthio)-4-phenylthiazole,

4-Carboxy-2-(3-oxobutylthio)thiazole,

4-Carboxyethoxy-2-(3-oxobutylthio)thiazole,

4-(4-Methoxyphenyl)-2-(3-oxobutylthio)thiazole,

4-(4-Nitrophenyl)-2-(3-oxobutylthio)thiazole,

4-Tert.-butyl-2-(3-oxobutylthio)thiazole,

5-Acetyl-4-methyl-2-(3-oxobutylthio)thiazole,

5-Acetyl-2-furoylthio-4-methylthiazole, and compounds of the formula: ##SPC7##

wherein R ⁶ is --CH ₂ C ₆ H ₅ ; CH ₃ ; C ₂ H ₅ ; n-butyl; CH ₂ CH(CH ₃ ) ₂ ; ##SPC8##

Another suitable azole thioether which can be employed in the desired combination includes, for example, thiadiazole thioethers of the formula: ##SPC9##

wherein R ⁸ is the same as R ³ as described previously; R ⁹ is alkyl containing one to five carbon atoms, aryl containing six to 12 carbon atoms, or furyl; n is 0 or 2. Alkyl and aryl are as previously described.

An especially suitable thiadiazole thioether is 4-furoyl-3-methylthio-1,2,4-thiadiazoline-5-thione of the formula: ##SPC10## Other examples of suitable thiadiazole thioether stabilizer precursors which can be employed in the practice of the invention include:

4-Furoyl-3-(3-oxobutylthio)1,2,4-thiadiazoline-5-thione,

3-Methylthio-4-benzoyl-1,2,4-thiadiazoline-5-thione,

4-Acetyl-3-methylthio-1,2,4-thiadiazoline-5-thione, or

4-Acetyl-3-funoylethylthio-1,2,4-thiadiazoline-5-thione.

Still another suitable azole thioether stabilizer precursor which can be employed in the desired combination include, for example, tetrazole thioethers of the formula: ##SPC11##

wherein R ⁷ is phenyl, substituted phenyl such as 3,5-di-t-butyl--4-hydroxyphenyl, alkyl or ##SPC12##

wherein R ³ and n are as described previously, such as:

--OCH(CH ₃ ) ₂ , --O(CH ₂ ) ₂ CH ₃ , --OCH ₂ CCl ₃ , --OC ₆ H ₅ , ##SPC13##

or --OCH ₂ CH ₃ ; R ⁸ is alkyl, especially alkyl containing one to three carbon atoms, such as methyl, ethyl and propyl and aryl, such as phenyl.

An especially suitable tetrazole thioether is 3,5--di-tert-butyl-4-(1-hydroxyphenyl-5-tetrazolyl)thiopheno l of the formula: ##SPC14##

Other examples of suitable tetrazole thioether stabilizer precursors which can be employed in the practice of the invention include:

5-(2-Benzoylethylthio)-1-phenyltetrazole,

5-(2-Acetylethylthio)-1-phenyltetrazole,

5-Methoxycarbonylthio-1-phenyltetrazole,

5-(4-Nitrobenzyloxycarbonylthio)phenyltetrazole,

5-(Ethoxycarbonylthio)-1-phenyltetrazole and

5-Benzoylthio-1-phenyltetrazole.

Suitable blocked azolinethiones which can be employed in the desired combination include, for example, a thiazolinethione of the formula: ##SPC15##

wherein R ³ , R ⁴ , R ⁵ and n are as described previously. An especially suitable blocked azolinethione is 5-acetyl-4-methyl--3-(3-oxobutyl)thiazoline-2-thione of the formula: ##SPC16##

Other examples of suitable blocked thiazolinethione stabilizer precursors which can be employed in the practice of the invention include:

5-Acetyl-3-benzoyl-4-methylthiazoline-2-thione,

4-Benzoylmethyl-3-benzoylthiazoline-2-thione,

3-Furoyl-4-hydroxymethylthiazoline-2-thione,

3-Benzoyl-4-hydroxymethylthiazoline-2-thione

3-Benzoyl-4-tert.-butylthiazoline-2-thione, and

5-Carboethoxy-4-methyl-3-(3-oxobutyl)-thiazoline-2-thion e.

The described stabilizer precursors are suitable in a range of concentration; however, they are especially suitable at a concentration from about 0.002 to about 0.10 mole of stabilizer precursor per mole of oxidizing agent, e.g, silver behenate, according to the invention in an element as described.

The azole thioethers and blocked azolinethiones can be prepared by the Michael addition of α,β-unsaturated ketones such as methyl vinyl ketone to 4-thiazoline-2-thione. By carefully controlling the reaction conditions, either azole thioethers or blocked azolinethiones can be prepared almost exclusively of one another as described in J. Heterocyclic chem., 6,397-401 (1969) of Humphlett. The thermal reversibility of some of the azole thioethers formed via the Michael addition to 4-thiazoline-2-thiones is reported in Canadian J. Chem. 44, 2315-2321 (1966) of Allen et al. It is also known that the azole thiazoles can be rearranged under the proper conditions to the thiazolinethiones and it is believed that the 3-substituted thiazolinethiones are unlikely to revert back to the azole thiazoles and are thus called blocked azolinethiones.

Photosensitive and thermosensitive elements which are suitable for dry processing with heat can provide a developed image by physical development, such as described in U.S. Pat. No. 3,457,075 of Morgan et al. issued July 22, 1969. Other elements of this type are described, for example, in U.S. Pat. No. 3,429,706 of Shepard et al. issued Feb 25, 1969 and U.S. Pat. No. 3,152,904 of Sorenson et al. issued Oct. 13, 1964.

Suitable organic reducing agents which can be employed in the described combination include, for example, substituted phenols and naphthols. The bis-naphthol which is preferred is a bis-β-naphthol of the formula: ##SPC17##

wherein R ¹ and/or R ² is hydrogen, alkyl containing one to three carbon atoms, alkoxy, e.t., alkoxy containing one to two carbon atoms, such as methoxy or ethoxy; halogen, nitro, amino or a diazonium halide salt and n is 0 or 1. Suitable bis-β-naphthols which can be employed in the practice of the invention include: 2,2'-Dihydroxy-1,1-binaphthyl; 6,6'-Dibromo-2,2'-dihydroxy--1,1'-binaphthyl; 6,6'-Dinitro-2,2'-dihydroxy-1,1'-binaphthyl; and/or Bis-(-2-hydroxy-1-naphthyl)methane. The described reducing agent are suitable in a range of concentration; however, they are especially suitable, at a concentration from about 0.10 to about 0.50 moles of reducing agent per mole of oxidizing agent, e.g., per mole of silver behenate.

Reducing agents, which are typically silver halide developing agents, can be used in conjunction with the above bis-naphthol reducing agents. Suitable silver halide developing agents include, for example, polyhydroxybenzenes such as hydroquinone developing agents, e.g., hydroquinone alkylsubstituted hydroquinones as exemplified by tertiary butylhydroquinone, methylhydroquinone, 2,5-dimethylhydroquinone and 2,6-dimethylhydroquinone, catechols and pyrogallol; halo-substituted hydroquinones such as chlorohydroquinone or dichlorohydroquinone; alkoxy-substituted hydroquinones such as methoxyhydroquinone or ethoxyhydroquinone; methylhydroxynaphthalene; phenylenediamine developing agents; methylgallate; aminophenol developing agents, such as 2,4-diaminophenols and methylaminophenols; ascorbic acid developing agents such as ascorbic acid, ascorbic acid ketals and ascorbic acid derivatives such as those described in U.S. Pat. No. 3,337,342 of Green issued Aug. 22, 1967; hydroxylamine developing agents such as N,N'-di(2-ethoxyethyl)hydroxylamine; 3-pyrazolidone developing agents such as 1-phenyl-3-pyrazolidone and 4-methyl--4-hydroxymethyl-1-phenyl-3-pyrazolidone including those described in British Pat. No. 930,572 published July 3, 1963; hydroxytetronic acid, and hydroxytetronimide developing agents; reductone developing agents such as anhydrodihydropyrrolidino hexose reductone; and the like.

It is desirable to employ an activator-toning agent in the elements, compositions and processes of the invention to obtain a desired image, particularly when phenolic reducing agents are used. A suitable activator-toning agent is a heterocyclic activator-toning agent containing at least one nitrogen atom of the formula: ##SPC18## wherein R can be hydrogen, hydroxyl or a metal ion such as potassium, sodium, lithium, silver, gold or mercury; Z can be atoms completing a heterocyclic nucleus, especially a five or six member heterocyclic nucleus. The atoms completing the heterocyclic nucleus can be, for example, ##SPC19## or

an alkylene group containing three or four carbon atoms. The atoms completing the heterocyclic nucleus can contain various substituent groups, such as amino, alkyl amino, e.g. methylamino or ethylamino, hydroxyl, carbamyl and the like. An especially suitable activator-toning agent is a heterocyclic activatortoning agent containing at least one nitrogen atom which is preferably a cyclic-imide of the formula: ##SPC20##

wherein R can be hydrogen, hydroxyl, or a metal ion such as potassium, sodium, lithium, silver, gold or mercury; y represents carbon atoms of a series completing a cyclic-imide nucleus, typically consisting of from five to six carbon atoms, e.g., a phthalimide or succinimide nucleus. The atoms of the cyclic-imide nucleus can contain various substituent groups, especially amino, alkyl, such as alkyl containing one to five carbon atoms, such as methyl, ethyl, propyl, butyl or pentyl or anyl, such as aryl containing six to 20 carbons atoms, such as phenyl, tolyl and xylyl. Suitable activation-toning agents which can be employed in the practice of the invention include, for example: Phthalimide, N-Hydroxyphthalimide, N-Potassium phthalimide, N-silver phthalimide, N-Mercury phthalimide, Succinimide, and/or N-Hydroxysuccinimide. The described activator-toning agents are suitable in a range of concentration; however, they are especially suitable at a concentration from about 0.10 mole to about 1.05 moles of activator-toning agent per mole of oxidizing agent, e.g. per mole of silver behenate.

Other so-called activator toning agents can be employed in combination with other components of the described photosensitive and thermosensitive element in the practice of the invention. These have been described as toners or toning agents in other references. Typically a heterocyclic organic toning agent containing at least two hetero atoms in the heterocyclic ring of which at least one is a nitrogen atom is employed. These are described, for example, in U.S. Pat. No. 3,080,254 of Grant issued March 5, 1963. Suitable toners include, for example, phthalazinone, phthalic anhydride, 2-acetylphthalazinone and 2-phthalylphthalazinone. Other suitable toners are described, for example, in U.S. Pat. No. 3,446,648 of Workman issued May 27, 1969.

A non-aqueous, polar, organic solvent, such as a compound containing a ##SPC21##

or --SO ₂ -- moiety, in a photosensitive and thermosensitive element suitable for dry processing with heat, as described, can provide improved maximum image densities. Such compounds include, for example, tetrahydrothiophene-1,1-dioxide, 4-hydroxybutanoic acid lactone and methylsulfinylmethane.

The described elements contain an oxidizing agent especially a silver salt of an organic acid. The silver salt of the organic acid should be resistant to darkening under illumination to prevent undesired deterioration of a developed image. An especially suitable class of silver salts of organic acids is represented by the water insoluble silver salts of long-chain fatty acids which are stable to light. Compounds which are suitable silver salts include silver behenate, silver stearate, silver oleate, silver laurate, silver hydroxystearate, silver caprate, silver myristate, and silver palmitate. Other suitable oxidizing agents are silver benzoate, silver phthalazinone, silver benzotriazole, silver saccharin, silver 4'-n-octadecyloxydiphenyl-4-carboxylic acid, silver ortho-aminobenzoate, silver acetamidobenzoate, silver furoate, silver camphorate, silver p-phenylbenzoate, silver phenyl acetate, silver salicylate, silver butyrate, silver terephthalate, silver phthalate, silver acetate, and silver acid phthalate. Oxidizing agents which are not silver salts can be employed if desired, such as zinc oxide, gold stearate, mercury behenate, gold behenate and the like, but silver salts are preferred.

The described element can contain a photosensitive salt, especially a photosensitive silver salt. A typical concentration range of photosensitive silver salt is from about 0.005 to about 0.50 mole of silver salt per mole of silver salt of organic acid, e.g. per mole of silver behenate. preferred silver salts are photosensitive silver halides, e.g. silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide, or mixtures thereof. The photosensitive silver halide can be coarse or fine-grain, very finegrain emulsions being especially useful. The emulsion containing the photosensitive silver halide can be prepared by any of the well-known procedures in the photographic art, such single-jet emulsions, double-jet emulsions, such as Lippmann emulsions, ammoniacal emulsions, thiocyanate or thioether ripened emulsions, such as those described in U.S. Pat. No. 2,222,264 of Nietz et al. issued Nov. 14, 1940; U.S. Pat. No. 3,320,069 of Illingsworth issued May 15, 1967 and U.S. Pat. No. 3,271,157 of McBride issued Sept. 6, 1966. Surface image halide emulsions can be used. If desired, mixtures of surface and internal image silver halide emulsions can be used as described in U.S. Pat. No. 2,996,382 of Luckey et al. issued Apr. 15, 1961. Negative type emulsions can be used. The silver halide emulsion can be a regular grain emulsion such as described in Klein and Moisar, Journal of Photographic Science, Volume 12, No. 5, September-October (1964) pages 242-251.

The silver halide emulsions employed in the practice of the invention can be unwashed or washed to remove soluble salts. In the latter case the soluble salts can be removed by chill setting and leaching or the emulsion can be coagulation washed.

The silver halide employed in the practice of the invention can be sensitized with chemical sensitizers, such as with reducing agents; sulfur, selenium, or tellurium compounds; gold, platinum, or palladium compounds; or combinations of these. Suitable procedures are described, for example, in U.S. Pat. No. 1,623,499 of Shepard issued Apr. 5, 1927; U.S. Pat. No. 2,399,083 of Waller et al. issued Apr. 23, 1946; U.S. Pat. No. 3,297,447 of McVeigh issued Jan. 10, 1967; and U.S. Pat. No. 3,297,446 of Dunn issued Jan. 10, 1967.

Photosensitive silver halide emulsions employed in the practice of the invention can be protected against the production of fog and can be stabilized against loss of sensitivity during keeping. Suitable antifoggants and stabilizers, e.g. used alone or in combination include, for example, thiazolium salts; azaindenes; mercury salts as described, for example, in U.S. Pat. No. 2,728,663 of Allen et al. issued Dec. 27, 1955; urazoles; sulfocatechols; oximes described, for example, in British Patent No. 623,448; nitron, nitroindazoles; polyvalent metal salts described, for example, in U.S. Pat. No. 2,839,405 of Jones issued June 17, 1958; platinum, palladium and gold salts described, for example, in U.S. Pat. No. 2,566,263 of Trivelli et al. issued Aug. 28, 1951 and U.S. Pat. No. 2,597,915 of Yutzy et al. issued May 27, 1952.

A photosensitive and thermosensitive element and emulsions described and used in the practice of the invention can contain various colloids alone or in combination as vehicles, binding agents and in various layers. Suitable materials are typically hydrophobic but hydrophilic materials can also be employed. They are transparent or translucent and include both naturally-occurring substances such as proteins, for example, gelatin, gelatin derivatives, cellulose derivatives, polysaccharides such as dextran, gum arabic and the like; and synthetic polymeric substances such as watersoluble polyvinyl compounds like poly(vinyl pyrrolidone), acrylamide polymers and the like. Other synthetic polymeric compounds which can be employed include dispersed vinyl compounds such as in latex form and particularly those which increase dimensional stability of photographic materials. Suitable synthetic polymers include those described in U.S. Pat. No. 3,142,586 of Nottorf issued July 28, 1964; U.S. Pat. No. 3,193,386 of White issued July 6, 1955; U.S. Pat. No. 3,062,674 of Houck et al. issued Nov. 6, 1962; U.S. Pat. No. 3,220,844 of Houck et al. issued Nov. 30, 1965; U.S. Pat. No. 3,287,289 of Ream et al. issued Nov. 22, 1966; and U.S. Pat. No. 3,411,911 of Dykstra issued Nov. 19, 1968. Effective polymers include water insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates, and those which have cross-linking sites which facilitate hardening or curing as well as those having recurring sulfobetaine units as described in Canadian Patent 774,054. Preferred high molecular weight materials and resins include polyvinyl butyral, cellulose acetate butyrate, polymethyl methacrylate, poly(vinyl pyrrolidone), ethyl cellulose, polystyrene, polyvinyl chloride, chlorinated rubber, polyisobutylene, butadiene-styrene copolymers, vinyl chloride-vinyl acetate copolymers, copolymers of vinyl acetate, vinyl chloride and maleic acid, polyvinyl alcohol, and high molecular weight ethylene oxide polymers.

The photosensitive and thermosensitive layers and other layers of an element employed in the practice of the invention and described herein can be coated on a wide variety of supports. Typical supports include cellulose nitrate film, cellulose ester film, poly(vinyl-acetal) film, polystyrene film, poly(ethylene terephthalate) film, polycarbonate film and related films or resinous materials, as well as glass, paper, metal, and the like. Typically a flexible support is employed, especially a paper support which can be partially acetylated or coated with baryta and/or an alpha olefin polymer, particularly, a polymer of an alpha olefin containing two to 10 carbon atoms such as polyethylene, polypropylene, ethylenebutene copolymers and the like.

The photosensitive and thermosensitive and other hardenable layers of an element used in the practice of this invention can be hardened by various organic or inorganic hardeners, alone or in combination, such as aldehydes, and blocked aldehydes, ketones, carboxylic and carbonic acid derivatives, sulfonate esters, sulfonyl halides and vinyl sulfonyl ethers, active halogen compounds, epoxy compounds, aziridines, active olefins, isocyanates, carbodiimides, mixedfunction hardeners and polymeric hardeners such as oxidized polysaccharides like dialdehyde starch and oxyguargum and the like.

The photosensitive and thermosensitive elements used in the practice of the invention can contain antistatic or conducting layers. Such layers can comprise soluble salts such as chlorides, nitrates and the like, evaporated metal layers, ionic polymers such as those described in U.S. Pat. No. 2,861,056 of Minsk issued Nov. 18, 1958 and U.S. Pat. No. 3,206,312 of Sterman et al. issued Sept. 14, 1965 or insoluble inorganic salts such as those described in U.S. Pat. No. 3,428,451 of Trevoy issued Feb. 18, 1969. The photosensitive and thermosensitive elements can also contain antihalation materials and antihalation dyes.

The photosensitive and thermosensitive layers or other layers employed in the practice of the invention can contain plasticizers and lubricants. Suitable plasticizers and lubricants include, for example, polyalcohols such as glycerin and diols described, for example, in U.S. Pat. No. 2,960,404 of Milton et al. issued Nov. 1, 1966; fatty acids or esters such as those in U.S. Pat. No. 2,588,765 of Robijns issued March 11, 1952; U.S. Pat. No. 3,121,060 of Duane issued Feb. 11, 1964; and silicone resins such as those described in British 955,061.

The photosensitive and thermosensitive layers or other layers employed in the practice of the invention can contain surfactants such as saponin; anionic compounds such as alkylarylsulfonates described, for example, in U.S. Pat. No. 2,600,831 of Baldsiefen issued June 17, 1962; amphoteric compounds such as those described in U.S. Pat. No. 3,133,816 of Ben-Ezra issued May 19, 1964; and adducts of glycidol and an alkylphenol such as those described in British Patent No. 1,022,878.

If desired, the photosensitive and thermosensitive elements employed in the practice of the invention can contain matting agents such as starch, titanium dioxide, zinc oxide, silica, polymeric beads including beads described, for example, in U.S. Pat. No. 2,922,101 of Jelley et al. issued July 11, 1961 and U.S. Pat. No. 2,701,245 of Lynn issued Feb. 1, 1955.

The photosensitive and thermosensitive elements employed in the practice of the invention can contain brightening agents including stilbenes, triazines, oxazoles, and coumarin brightening agents. Water-soluble brightening agents can be used such as those described in German Patent No. 972,067 and U.S. Pat. No. 2,933,390 of McFall et al. issued Apr. 19, 1960 or dispersions of brighteners can be used such as those described in German Patent No. 1,150,274; U.S. Pat. No. 3,406,070 of Oetiker et al. issued Oct. 15, 1968 and French Patent No. 1,530,244.

The various layers including the photosensitive and thermosensitive layers of an element employed in the practice of the invention can contain light-absorbing materials, filter dyes, antihalation dyes and absorbing dyes such as those described in U.S. Pat. No. 3,253,921 of Sawdey issued May 31, 1966; U.S. Pat. No. 2,274,782 of Gaspar issued March 3, 1942; U.S. Pat. No. 2,527,583 of Silberstein et al. issued Oct. 31, 1950; and U.S. Pat. No. 2,956,879 of VanCampen issued Oct. 18, 1960. If desired, the dyes can be mordanted, for example, as described in U.S. Pat. No. 3,282,699 of Jones et al. issued Nov. 1, 1966.

The photosensitive and thermosensitive layers used in the practice of the invention can be coated by various coating procedures including dip coating; airknife coating, curtain coating or extrusion coating using hoppers such as described in U.S. Pat. No. 2,681,294 of Beguin issued June 15, 1954. If desired, two or more layers can be coated simultaneously such as by the procedures described in U.S. Pat. No. 2,761,791 of Russell issued Sept. 4, 1956 and British Patent No. 837,095.

If desired, the photosensitive silver halide can be prepared in situ in the photosensitive and thermosensitive coatings of an element employed in the practice of the invention. Such a method is described, for example, in U.S. Pat. No. 3,457,075 of Morgan et al. issued July 22, 1969. For example, a dilute solution of a halogen acid such as hydrochloric acid can be applied to the surface of a thin coating containing an organic silver salt, such as silver behenate, on a suitable substrate followed by removal of the solvent if desired. Silver halide is thus formed in situ throughout the surface of the coating of the organic silver salt.

The photosensitive silver halide can be prepared on the oxidizing agent such as silver behenate or silver stearate or other organic silver salt prior to application of the silver halide on the support employed. This is also described in U.S. Pat. No. 3,457,075 of Morgan et al. issued July 22, 1969, for example, a halogen acid such as hydrochloric acid or hydrobromic acid can be mixed with an organic silver salt in a suitable reaction medium. A halide salt more soluble than the organic silver salt can be added to a suspension of the organic silver salt to form the silver halide. A suitable reaction medium includes water or other solvents which do not interfere with the reaction.

Stability to print out from light exposure is increased by employing highly purified materials; for example, freedom from halides and sulfides increases stability to light exposure. The use of highly purified silver behenate can, for example, reduce propensity to print out in background areas of an element prepared according to the invention.

Spectral sensitizing dyes can be used conveniently to confer additional sensitivity to the light-sensitive silver halide employed in the practice of the invention. For instance, additional spectral sensitization can be obtained by treating the silver halide with a solution of a sensitizing dye in an organic solvent or the dye can be added in the form of a dispersion as described in British Patent No. 1,154,781. For optimum results the dye can either be added to the emulsion as a final step or at some earlier stage.

Sensitizing dyes useful in sensitizing silver halide emulsions are described, for example, in U.S. Patent No. 2,526,632 of Brooker et al. issued Oct. 24, 1950; U.S. Pat. No. 2,503,776 of Sprague issued Aprl. 11, 1950; U.S. Pat. No. 2,493,748 of Brooker et al. issued Jan. 10, 1950 and U.S. Pat. No. 3,384,486 of Taber et al. issued May 21, 1968. Spectral sensitizers which can be used include the cyanines, merocyanines, complex (trinuclear or tetranuclear) merocylanines, complex (trinuclear or tetranuclear) cyanines, holopolar cyanines, styryls, hemicyanines such as enamine, hemicyanines, oxonols and hemioxonols. Dyes of the cyanine classes can contain such basic nuclei as the thiazolines, oxazolines, pyrollines, pyridines, oxazoles, thiazoles, selenazoles, and imidazoles. Such nuclei can contain alkyl, alkylene, hydroxyalkyl, sulfoalkyl, carboxyalkyl, aminoalkyl, and enamine groups that can be fused to carbocyclic or heterocyclic ring systems either unsubstituted or substituted with halogen, phenyl, alkyl, haloalkyl, cyano, or alkoxy groups. The dyes can be symmetrical or unsymmetrical and can contain alkyl, phenyl, enamine or heterocyclic substituents on the methine or polymethine chain.

The merocyanine dyes can contain the basic nuclei described as well as acid nuclei such as thiohydantoins, rhodanines, oxazolidenediones, thiazolidenediones, barbituric acids , thiazolineones, and malononitrile. These acid nuclei can be substituted with alkyl, alkylene, phenyl, carboxyalkyl, sulfoalkyl, hydroxyalkyl, alkoxyalkyl, alkylamino groups, or heterocyclic nuclei. Combinations of these dyes can be used, if desired. In addition supersensitizing addenda which do not absorb visible light may be included such as, for instance, ascorbic acid derivatives, azaindenes, cadmium salts, and organic sulfonic acid as described in U.S. Pat. No. 2,933,390 of McFall et al. issued Apr. 19, 1960 and U.S. Pat. No. 2,937,089 of Jones et al. issued May 17, 1960.

The sensitizing dyes and other addenda used in the practice of the invention can be added from water solutions or suitable organic solvent solutions can be used. The compounds can be added using various procedures including, for example, those described in U.S. Pat. No. 2,912,343 of Collins et al. issued Nov. 10, 1959; U.S. Pat. No. 3,342,605 of McCrossen et al. issued Sept. 19, 1967; U.S. Pat. No. 2,996,287 of Audran issued Aug. 15, 1961; and U.S. Pat. No. 3,425,835 of Johnson et al. issued Feb 4, 1969.

A range of concentration of dye can be employed in the practice of the invention. the desired concentration will be influenced by the desired spectral sensitivity, other components in the system, the desired image, processing conditions and the like. typically a concentration of the described sensitizing dye is about 0.05 to about 1 milligram per square foot of the described photographic and thermosensitive element, usually about 0.1 milligram per square foot of dye being employed. In elements, as described, typically a support is provided with a light-stable organic silver salt oxidizing agent, an organic reducing agent, and photosensitive silver salt, especially silver haldide, which provides a photosensitive and thermosensitive element. A visible image on the photosensitive and thermosensitive element can be produced within a few seconds after exposure by heating the element to moderately elevated temperatures, e.g. about 80° to about 250°C.

Accordingly, one embodiment of the invention is a photosensitive and thermosensitive element comprising a support, an oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent with (ii) a reducing agent, and a binder; the improvement comprising a stabilizer precursor which is an azole thioether or a blocked azolinethione.

For example, the photosensitive and thermosensitive element, as described, can comprise:

a. poly(vinyl butyral) binder,

b. silver behenate,

c. 2,2'-dihydroxy-1,1'-binaphthyl,

d. photosensitive silver halide,

e. a sensitizing dye,

f. phthalimide activator-toner and

g. an image stabilizer precursor comprising 5-acetyl-4-methyl--2-(3-oxobutylthio)thiazole.

Another embodiment of the invention is a photosensitive and thermosensitive composition comprising an oxidation-reduction image-forming combination comprising

i. a heavy metal salt oxidizing agent with

ii. a reducing agent and a stabilizer precursor which is an azole thioether or a blocked azolinethione, as described.

Various concentrations of the described components can be employed. For example, the photosensitive and thermosensitive composition can comprise:

a. about 0.002 to about 0.10 mole of stabilizer precursor per mole of silver behenate oxidizing agent,

b. about 0.10 to about 0.50 mole of 2,2'-dihydroxy-1,1'-binaphthyl per mole of silver behenate oxidizing agent and

c. about 0.005 to about 0.05 mole of photosensitive silver halide per mole of silver behenate oxidizing agent.

After exposure of the described photosensitive and thermosensitive element, the resulting latent image is developed merely by heating the element. Accordingly, another embodiment of the invention is: in a method of developing and stabilizing an image in an exposed photosensitive and thermosensitive element comprising a support, an oxidation-reduction image-forming combination comprising (i) a heavy metal salt oxidizing agent with (ii) a reducing agent, a binder and a stabilizer precursor which is an azole thioether or a blocked azolinethione, comprising heating the described element to about 80°C. to about 250°C.

While a temperature range of about 80°C. to about 250°C. can be employed, a temperature range of about 125°C. to about 180°C. is usuallly suitable for developing and stabilizing a desired image. By increasing or decreasing the length of time of heating a higher or lower temperature within the described range can be employed. A developed image is typically produced within a few seconds such as about 0.5 second to about 60 seconds.

The photographic process can comprise, for example, exposing to actinic radiation a photosensitive and thermosensitive element comprising a support:

a. an oxidation-reduction image-forming combination comprising a 2,2'-dihydroxy-1,1'-binaphthyl reducing agent and silver behenate,

b. phthalimide activator-toning agent,

c. polyvinyl butyral,

d. photographic silver halide,

e. 5-acetyl-4-methyl- 2-(3-oxobutylthio)thiazole, and heating the described element to about 80°C. to about 250°C. for about 0.5 to about 60 seconds.

Processing is usually 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 preferred.

In some cases, if desired, an element can be prepared wherein the described silver halide can be in one layer and other components in other layers. For example, an element according to the invention can comprise a support, a layer containing photographic silver halide, and a layer comprising a so-called processing composition comprising:

a. a silver salt of an organic acid,

b. a reducing agent, as described,

c. an activator-toning agent, and

d. a stabilizer precursor, as described.

A processing composition of this type is a photographic processing composition comprising:

a. silver behenate,

b. 2,2'-dihydroxyl-1,1'-binaphthyl,

c. phthalimide or N-hydroxyphthalimide and

d. 5-acetyl-4-methyl2-(3-oxobutylthio)thiazole. Typically, a poly(vinyl butyral) binder is employed with this processing composition.

As another example, it is sometimes advantageous to incorporate the bis-β-napthol reducing agent and/or the 5--acetyl-4-methyl-2-(3-oxobutylthio)thiazole in a poly(vinyl butyral) or cellulose ester binder and coat the resulting composition as an anti-abrasion overcoat on the element as described previously.

Various methods can be employed in providing the necessary heating of the described photosensitive and thermosensitive elements. The heating means can be a simple hot plate, iron and the like.

Other addenda known to be useful in photosensitive and thermosensitive elements of this type, such as described in British Pat. No. 1,161,777 published Aug. 20, 1969 and U.S. Pat. No. 3,152,904 of Sorenson et al issued Oct. 13, 1964, can be employed in the practice of the invention.

The following examples are included for a further understanding of the invention.

Example 1:

This is a comparative example.

A photographic element is prepared as follows:

A coating composition is prepared by mixing the following components:

following components: silver behenate 42.0 g. behenic acid 32.0 g. poly(vinyl butyral) 30.0 g. phthalimide 8.5 g. NaBr (reacts with silver behenate to form silver bromide in situ) 2.4 g. acetone 250 ml. toluene 250 ml.

After ball-mixing for 18 hours, 141 milliliters of the above dispersion is combined with the following solutions:

acetone containing 6.4% by weight 50.0 ml. 2,2'-dihydroxy-1,1'-binaphthyl, acetone containing 0.08% by weight 8.8 ml. 3-carboxymethyl-5-[(3-methyl-2-(3)-thiazolinylidene)isopropy lidene]rhodani ne.

The composition is mixed and then coated on a water-resistant paper support and dried. A sample of this coating is exposed for one second to tungsten light and heat processed on a curved hot metal block for 10 seconds at a temperature of 140°C. The resulting image is subjected to an image-fading test which involves a fifteen minute exposure to ultraviolet light at about 22°C. and from about 40percent to about 50 percent relative humidity. The developed image is neutral with a pinkish-brown background and has a maximum density of 1.26 with a minimum density of 0.18.

Example 2:

The procedure set out in Example 1 is repeated with the exception that 50 milliliters of an acetone solution containing 0.8 percent by weight of 5-acetyl-4-methyl-2-(3-oxobutylthio) thiazole is added to the dispersion prior to coating. The element is exposed, heat processed and subjected to the image stabilization test as described in Example 1. The resulting image is neutral (jet-black) with an ivory-white background and has a maximum density of 1.24 and a minimum density of 0.09. The minimum density due to "print-out" is reduced by 50% over the control in Example 1.

Example 3:

This is a comparative example.

The procedure set out in Example 1 is repeated with the exception that an equimolar concentration of an acetone solution of benzotriazole is added to the dispersion prior to being coated. The element is exposed, processed and subjected to the image stabilization test as described in Example 1. The final image is grainy with a definite pinkish-brown background. No reduction in minimum density is observed.

Example 4:

This is a comparative example.

The procedure set out in Example 1 is repeated with the exception that an equal amount of the sensitizing dye, 3-ethyl-5-(3-ethyl-2(3H)-benzothialzylidene-isopropylidene)- -2-thio-2,4(3, 5)-oxazolidenedione is substituted for 3-carboxymethyl-5-[(3-methyl-2(3)thiazolinylidene)isopropyli dene]rhodanine in the final dispersion. The element is exposed, heat processed and subjected to the image stabilization test as described in Example 1. The resulting image is neutral (jet--black) with a pinkish-brown background and has a maximum density of 1.42 with a minimum density of 0.16.

Example 5:

This illustrates the invention.

The procedure set out in Example 4 is repeated with the exception that 52.1 ml. of an acetone solution containing 0.38% by weight of 4-(2-furoyl)-3-methylthio-1,2,4-thiadiazoline--5-thione is added to the dispersion prior to being coated. The element is exposed, heat processed and subjected to an image stabilization test as described in Example 1. The final image is neutral (jet-black) with an ivory-white back-ground and has a maximum density of 1.49 with a minimum density of 0.08. Once again, the minimum density or "print-out" is reduced by 50 percent.

Example 6:

This is a comparative example.

Example 4 is repeated with the exception that 1.5 milliliters of an acetone solution containing 5 percent by weight of 2,6-di-tert-butyl-4-(1-phenyl-5-tetrazolyl)thiophenol is added to the dispersion prior to being coated. The element is exposed, heat processed and subjected to the image stabilization test as described in Example 1. The final image is brownish-black with a white background; the minimum density is 36% less than a similar coating not containing the image stabilizing compound.

Example 7:

Similar results are obtained as in Example 2 also employing 5-acetyl-4-methyl-3-(3-oxobutyl)thiazoline-2-thione, as an image stabilizing precursor, in the described element.

Examples 8-20:

A silver bromide-silver behenate dispersion is prepared by mixing the following components and ball-milling them for several hours:

silver behenate 84.0 g. behenic acid 64.0 g. poly(vinyl butyral) 30.0 g. phthalimide 17.0 g. acetone-toluene (1:1 parts by volume) 1000.0 ml.

When the ball-milling procedure is completed, 150 ml. of a solution (1.0 percent by weight in acetone) of lithium bromide is added to the above dispersion and is stirred for several hours.

Several photothermographic elements are prepared by coating the following composition on a paper support at a wet thickness of 0.004 inch:

silver bromide-silver behenate dispersion 2.0 ml. (preparation as described above) 3-carboxymethyl-5-[(3-methyl-2(3H)-thia- 0.5 ml. zolinylidene)isopropylidene]rhodanine (0.01% by weight in acetone) 2,2'-dihydroxy-1,1'-binaphthyl (3% by 2.0 ml. weight in acetone) 2,4-dihydroxybenzophenone (1.0% by weight 0.5 ml. in acetone) stabilizer as described in Table 2 (0.5% 0.5 ml. in methanol) acetone-tolune (1:1 parts by volume) to a total volume of 9.0 ml.

The photothermographic elements are sensitometrically exposed to tungsten light in a contact printer for about 1.0 second and heat-processed for about 8-10 seconds by contacting the side of the photothermographic element opposite the photosensitive layer with a curved hot metal block at a temperature of about 135°C.

The exposed and heat-processed elements are subjected to a fade test comprising exposure of the samples to an 80-footcandle light source for 1 day in an 80 percent relative humidity atmosphere. The stabilizer precursors used are listed in following Table 1 and the results obtained are listed in Table 2. ##SPC22##

Table 2 ______________________________________ Example No. Dmin Dmax Visible Steps ______________________________________ control 0.15 1.20 8 8 0.08 1.10 9 9 0.09 1.40 10 10 0.07 1.30 10 11 0.11 1.30 10 12 0.08 1.20 11 13 0.11 1.20 10 14 0.08 1.40 9 15 0.08 1.10 10 16 0.10 1.20 10 17 0.09 1.10 9 18 0.09 1.20 10 19 0.06 1.20 10 20 0.09 1.00 10 ______________________________________

Surprisingly good results are obtained with the compound of Example 9 because it provides a combination of reduced minimum density, increased maximum density and wider exposure latitude as indicated by the number of visible steps developed.

Examples 21-31:

A photothermographic element is prepared as follows:

A silver behenate-benhenic acid dispersion is prepared by mixing the following components:

silver behenate 168 g. behenic acid 128 g. -poly(vinyl butyral) 60 g.-phthalimide 34 g. acetone-toluene (1:1 parts by volume) 1600 ml.

After ball milling for 64 hours, the following solutions are combined with 800 ml. of the above dispersion with stirring:

acetone-toluene (1:1 parts by volume) 100 ml. acetone containing 1% by weight lithium 150 ml. bromide

After stirring overnight, 71 ml. of the above mixture is combined with the following solutions:

acetone containing 6.3% by weight 2,2'- 26.0 ml. dihydroxy-1,1'-binaphthyl acetone containing 0.01% by weight 3- 2.0 ml. carboxymethyl-5-[(3-methyl-2-(3H)-thia- zolinylidene)isopropylidene]rhodanine acetone-tolune (1:1 parts by volume) 26.0 ml.

The final composition is mixed thoroughly, coated at 6.0 g. composition/ft. ² on a polyethylene-coated paper support, thereby providing a photothermographic element containing approximately 60 mg. Ag/ft. ² of support.

The photothermographic element is exposed sensitometrically through a graduated density step wedge (0.30 log E) to tungsten light for one-half second. The resulting latent image is developed by holding the side of the element opposite the photosensitive layer in contact with a curved heating block for 8 seconds at 140°C. The exposed and processed coating is then held for 5 days at 22.2°C. at 80 percent relative humidty at 80 ft./candles. The final image is neutral (jet black) with an orange background. The developed image has a background density of 0.33. This is designated as procedure A and comparative Example 21.

The procedure as set out in Example 21 is repeated with the exception that the solvent mixture, acetone-toluene (1:1 parts by volume), added to the final composition is reduced from 26 ml. to 18 ml. Also, 8 ml. of an organic solvent solution containing 1 percent by weight of each image stabilizer is added to the final composition. Each composition is coated as described in Example 21 and the dried elements are also exposed, processed and subjected to room-light exposure as described in Example 21. The compounds used are listed in following Table 3. The sensitometric results are listed in following Table 4. ##SPC23##

Table 4 ______________________________________ Organic Background Density Example Solvent (Dmin) ______________________________________ 21 (comparative example) 0.33 22 MeOH 0.17 23 acetone 0.20 24 MeOH 0.22 25 MeOH 0.22 26 EtOH 0.24 27 (comparative example) MeOH 0.25 28 (comparative example) MeOH 0.31 29 (comparative example) MeOH 0.32 30 (comparative example) MeOH 0.35 31 (comparative example) MeOH 0.37 ______________________________________

The following compounds provide stabilizing action similar to that provided by the stabilizer precursors of Examples 23-26.

Example 32: ##SPC24##

Example 33: ##SPC25##

Example 34: ##SPC26##

Example 35: ##SPC27##

The invention has been described in detail with particular refernece to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.