JPH05341432A - Thermooptical photographic element - Google Patents

Abstract

PURPOSE: To obtain an effective super sensitizer by spectrally sensitizing a silver halide to the irradiation of a specific wavelength and containing a heteroaromatic mercapto or disulfide compound in an emulsion. CONSTITUTION: In a phtothermal photographic emulsion containing a binder, a non-photosensitive silver salt, a reducing agent for silver and the silver halide, the silver halide is spectrally sensitized to the irradiation of light of 750-1300nm wavelength. The emulsion contains the super sensitizing quantity of a compound selected from a group composed of a heteroaromatic mercapto compound or the heteroaromatic disulfide compound. And the emulsion contains the super sensitizing compound expressed by one of formulas Ar-S-M and Ar-S-S-Ar. In the formulas, M represents hydrogen or an alkali metal and Ar represents a heteroaromatic ring group. And the super sensitizing compound can exit 10<(-3)-1> mol per 1mol silver in the emulsion and the silver halide can contain a cyanin dye, a carbocyanin dye or the like.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to materials which, when added to infrared sensitized photothermographic imaging elements, increase sensitivity to infrared radiation. These elements contain in a binder a light-sensitive silver halide, a silver salt oxidizing agent, an infrared sensitizing dye and a reducing agent for silver ions. The infrared supersensitizer of the present invention includes a mercapto-substituted heteroaromatic compound.

[0002]

BACKGROUND OF THE INVENTION Silver halide photographic imaging materials, often referred to as compositions called "dry silver" because they do not require a liquid developer to produce the final image, have been known in the art for many years. ing. Such imaging materials basically contain a non-photosensitive source of reducing silver, a photosensitive material that produces silver when irradiated, and a reducing agent for the silver source. In general, the photosensitive material should be in catalytic proximity to the non-photosensitive silver source. What is catalytic proximity?
The silver spec (s
pecks) or nuclei are said to have a close physical relationship between these two materials so that they can catalyze the reduction of the silver source by the reducing agent. It has been understood for many years that silver is a catalyst for the reduction of silver ions and that the photosensitive silver halide catalyst precursor that produces silver can be placed in catalytic proximity to the silver source in many different ways. It was For example, partial metathesis of a silver source using a halide-containing source (e.g., U.S. Pat.No. 3,457,075), coprecipitation of silver halide and silver source material (e.g., U.S. Pat.No. 3,839,049).
No.), and all other methods of closely relating the silver halide to the silver source.

Silver halide photothermographic imaging materials can be spectrally sensitized. This allows the silver halide grains to function by irradiation in the region of the electromagnetic spectrum where silver halide normally does not absorb. Dyes capable of assisting the photoreduction of silver ions to clusters of metallic silver by absorbing radiation and transferring energy to the grains have been used in the past for effective spectral sensitization. Infrared absorbing dyes are required to sensitize silver halide in the infrared region (750 to 1300 nm), and are described by Mees in "The Theory of Photography.
f the Photoqraphic Process ", 3rd edition (Macmillan (Ma
cMillan), 1966), pp. 198-201. 5 or more to sensitize infrared rays, generally 7
A problem arises because a conjugated methine chain of 4 carbon atoms is required, unlike visible dyes, which require a shorter methine chain.
The longer methine chains of IR dyes lead to poor sensitization efficiency and poor stability over time. Therefore, IR sensitization is very difficult unlike visible sensitization.

Supersensitization has been developed as a method to improve the efficiency and often stability of infrared sensitization. The supersensitizer is used in combination with the infrared sensitizing dye. The supersensitizer is added in an amount ranging from an equimolar ratio to a 100-fold molar excess with respect to the dye, and the spectral sensitization rate of the emulsion can be sensitized at a size exceeding the order. Some supersensitizers are dyes themselves. However, many others do not absorb a significant amount of radiation in the visible portion of the electromagnetic spectrum. Therefore, it cannot be said that the effect of the supersensitizer on the spectral sensitization clearly depends on the irradiation absorption ability in the visible or infrared part of the spectrum of the compound. Often, certain supersensitizers are more effective when used with the first sensitizing dye class rather than the second dye class. Supersensitizer-A wide selection of supersensitizers is desirable due to the specificity of the dye and the extreme sensitization provided by the supersensitizer.

So far, supersensitization has been used effectively in silver halide photographic systems to minimize the shortage of infrared sensitizing dyes. Such supersensitizers include diazenyl and triazenyl stilbenes such as those described in U.S. Pat. U.S. Pat. No. 4,607,006,
Thioureas as described in 3,458,318 and 3,954,481, thiatriazoles as described in U.S. Pat.Nos. 4,780,404 and 4,914,015, U.S. Pat.
Tetraazaindene and U.S. Patent No.
Included are certain heterocyclic salts as described in 4,596,767.

Mercaptoaromatics have also been used in silver halide photographic elements as infrared supersensitizers and include mercapto-substituted oxazines, oxazoles, thiazoles, thiadiazoles, as described in US Pat. No. 3,457,078. Included are imidazoles or tetrazoles and mercapto substituted triazoles as described in US Pat. No. 4,910,129.

Infrared supersensitization in photothermographic systems has already been demonstrated in US Pat. No. 4,873,184 with metal chelating agents and in J6 3,023,145A with pyridine, pyrimidine and triazine derivatives. However, due to the specificity of the dyes and the significant effects provided by supersensitization, more chemical classes of supersensitizers are desirable.

The photothermographic infrared supersensitizer of the present invention is an aromatic heterocyclic mercapto or disulfide compound. Such compounds have been used extensively in photothermographic elements. The mercapto heterocycles are described in U.S. Pat.
4,639,408; 4,451,561; 3,961,963; 4,678,735 and 4,837,141 as antifoggants and development inhibitors, U.S. Pat.Nos. 3,617,289 and 3,997,346, U.S. Pat.No. 4,138,265. The same number 4,
As post-print stabilizers in the preparation of silver soaps such as 728,600 and 4,859,580, U.S. Pat.
No. 2 as a toner, and U.S. Pat. No. 3,359,105 describes rate enhancers for N-vinylcarbazole and organohalogen dye-forming thermal imaging systems.

US Pat. No. 4,968,597 describes the use of mercapto substituted heteroaromatic compounds in the blue light sensitive silver halide layers of color heat developable materials.
Supersensitization similar to the present invention, spectrally sensitized to blue, green or red, is not observed in this system. Supersensitization was observed only in the infrared sensitized system.

US Pat. No. 4,245,033 describes the use of many classes of sulfur compounds in heat developable photosensitive compositions. This system differs from the present invention in that thioethers and non-aromatic thiols act similarly to aromatic thiols.

US Pat. No. 4,105,451 describes the use of mercapto aromatic compounds in combination with silver salts of heterocyclic thiones in photothermographic materials containing very high levels of silver iodide. Infrared sensitization charges are not shown.

[0012]

SUMMARY OF THE INVENTION Photothermographic emulsions spectrally sensitized in the infrared and near infrared regions of the electromagnetic spectrum are supersensitized by the addition of mercapto-substituted heteroaromatic compounds.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Silver halide crystals have intrinsic photosensitivity only in the ultraviolet and blue regions of the electromagnetic spectrum. Dyes are used to provide the crystal with sensitivity to other parts of the electromagnetic spectrum. These dyes that extend the range of sensitivity of silver halide are commonly referred to as spectral sensitizing dyes. As mentioned above, supersensitizers increase the efficiency of such spectral sensitizing dyes.

Conventionally, emulsions spectrally sensitized to the infrared region of the spectrum have been insufficiently sensitized. The relative sensitivity of emulsions sensitized to the infrared in the spectrum tended to be lower than the relative sensitivity of emulsions spectrally sensitized to the visible. Therefore, it is generally considered that the demand for the supersensitizer in the infrared region is very important.

In the present invention, the heteroaromatic mercapto compound (I) or the heteroaromatic disulfide compound (II) is 7
Wavelengths longer than 50 nm (e.g. 750-1300 nm, preferably 75
It is an effective supersensitizer for photothermographic emulsions spectrally sensitized from 0 to 950 nm).

Ar-SM (I) Ar-SS-Ar (II) In the formula, M is a hydrogen atom or an alkali metal atom, and Ar is
Is an aromatic ring or fused aromatic ring having one or more nitrogen, sulfur, oxygen, selenium or tellurium atoms.
Preferably, the heteroaromatic ring is benzimidazole, naphthuimidazole, benzothiazole, naphthothiazole,
Benzoxazole, naphthoxazole, benzoselenazole, benzoterrazole, imidazole, oxazole, pyrazole, triazole, thiadiazole,
Tetrazole, triazine, pyrimidine, pyridazine,
Pyrazine, pyridine, purine, quinoline or quinazolinone. However, other heteroaromatic rings are within the scope of the invention.

The heteroaromatic ring is, for example, halogen (eg Br and Cl), hydroxy, amino, carboxy, alkyl (eg having one or more carbon atoms, preferably 1 to 4 carbon atoms). And alkoxy
It may have preferred substituents selected from the class consisting of (eg having one or more carbon atoms, preferably those having 1 to 4 carbon atoms).

The mercapto-substituted heteroaromatic compounds are listed below. However, the present invention is not limited to these.

M-1 2-mercaptobenzimidazole M-2 2-mercaptobenzoxazole M-3 2-mercaptobenzothiazole M-4 2-mercapto-5-methylbenzimidazole M-5 6-ethoxy-2-mercaptobenzo Thiazole M-6 2,2'-dithiobis- (benzothiazole) M-7 3-mercapto-1,2,4-triazole M-8 4,5-diphenyl-2-imidazolethiol M-9 2-mercaptoimidazole M -10 1-Ethyl-2-mercaptobenzimidazole M-11 2-Mercaptoquinoline M-12 8-Mercaptopurine M-13 2-Mercapto-4 (3H) -quinazolinone M-14 7-Trifluoromethyl-4-quinoline Thiol M-15 2,3,5,6-Tetrachloro-4-pyridine Thiol M-16 4-Amino-6-hydroxy-2-mercaptopyrimidine monohydrate M-17 2-Amino-5-mercapto-1, 3,4-thiadiazole M-18 3-amino-5-mercapto-1,2,4-tria M-19 4-Hydrocylo-2-mercaptopyrimidine M-20 2-Mercaptopyrimidine M-21 4,6-Diamino-2-mercaptopyrimidine M-22 2-Mercapto-4-methylpyrimidine hydrochloride M-23 3 -Mercapto-5-phenyl-1,2,4-triazole M-24 2-Mercapto-4-phenyloxazole

The supersensitizer is generally used in the emulsion layer in an amount of at least 0.001 mole per mole of silver. Usually, it is used in an amount of 0.001 to 1.0 mol per mol of silver, preferably 0.01 to 0.3 mol per mol of silver.

Supersensitization of infrared sensitized photothermographic elements with mercapto-substituted heteroaromatic compounds has been shown to be effective with a wide range of infrared sensitizing dyes. Preferred infrared dyes are the tricarbocyanine dyes described in US Pat. No. 4,536,473 and the fixed tricarbocyanine dyes described in US Pat. Nos. 4,515,888 and 4,959,294. Another useful class of infrared dyes are the 4-quinoline pentamethine dyes, merocyanine infrared dyes and trinuclear dyes described in US Pat. No. 4,536,473.

The infrared sensitizing dye used in the present invention is 1 × 10 ^-5 mol to 1 × 10 ^-2 mol, preferably 5 × 10 ^{-5 to} 5 × 10 ^-3 per mol of total silver in the silver photothermographic layer. It is contained at a molar content.

Specific examples of infrared sensitizing dyes preferable for use in the present invention are listed below. However, the present invention is not limited to these.

[0024]

[Chemical 1]

[0025]

[Chemical 2]

Conventional silver halide photographic chemistry is used as photothermographic chemistry in the system of this invention. Such chemistry is described in US Pat. No. 3,457,075;
No. 3,839,049; No. 3,985,565; No. 4,022,617 and No. 4,460,681. These can be black and white or color chemistry. In Sights
(In situ) Halogenation (eg, 3,457,075) or a preformed silver halide source (eg, 3,839,049) can be used. Any of a variety of photothermographic media such as complete soaps, partial soaps, complete salts and the like can be used in the photothermal chemistry.

Conventional photothermographic chemistry consists of a photosensitive silver halide catalyst, an essentially non-photosensitive silver compound capable of forming a metallic silver image by reduction (eg, both inorganic or organic silver salts, usually silver salts). Contains a photosensitive silver material, a silver complex), a developer for silver ions (a mild reducing agent for silver ions), and a binder. In addition, color photothermographic systems have a leuco dye or a dye-forming developer (alone or in combination with a developer for silver ions), or a color coupler that requires a color photographic developer used as a developer for silver ions. .. Therefore, it can be used for both negative and positive systems.

In particular, Japanese Patent Publication No. 50 dated February 25, 1982
The dyes listed in 0352/82 are preferred. Generally, naphthol and arylmethyl-1-naphthol are preferred.

Conventional photothermographic chemistry is usually constructed as one or two layers on a support. Single layer constructions should contain silver source materials, silver halide, developers and binders and additional materials such as toners, coating aids and other auxiliaries. A two-layer construction should contain the silver source and silver halide in one emulsion layer (usually the layer adjacent to the substrate) and the other ingredients in the second layer or both layers. In the present invention, it is preferable to use a two-layer chemistry.

As mentioned above, the silver source material is usually any material that contains a reducing source of silver ions. In the practice of the present invention silver salts or organic acids, especially long chain (10-30
Fatty acids having one, preferably 15 to 28 carbon atoms) are preferred. Complexes of organic or inorganic silver salts in which the ligand has a gross stability constant between 4.0 and 10.0 are also useful in the present invention. The silver source material comprises about 20-70% by weight of the imaging layer. Preferably it is present at 30-55% by weight.

Useful organic silver salts include silver salts of organic compounds having a carboxy group. Preferred examples thereof include silver salts of fatty acid carboxylic acids and silver salts of aromatic carboxylic acids. Preferred examples of the silver salt of fatty acid carboxylic acid include silver behenate, silver stearate, silver oleate, silver laurate, silver caprate, silver myristate, silver palmitate, silver malate, silver fumarate, silver tartarate,
Included are silver furoate, silver linoleate, silver butyrate and silver camphorate, mixtures thereof and the like. A silver salt substituted with a halogen atom of a hydroxyl group can also be effectively used. Preferred examples of silver salts of aromatic carboxylic acids and other carboxyl group-containing compounds include silver benzoate, silver 3,5-dihydroxybenzoate, silver o-methylbenzoate, silver m-methylbenzoate, silver p-methylbenzoate, silver Silver-substituted benzoates such as 2,4-dichlorobenzoate, silver acetamidobenzoate, silver p-phenylbenzoate, etc., silver gallates, silver tannates, silver phthalates, silver terephthalates, silver salicylates, silver phenylacetates, silver pyromellitates, U.S. Patents 3-carboxymethyl-4-as described in No. 3,785,830
Examples thereof include a silver salt of methyl-4-thiazoline-2-thione, and a silver salt of an aliphatic carboxylic acid containing a thioether group as described in US Pat. No. 3,330,633.

Silver salts of compounds containing mercapto or thione groups and their derivatives can be used. Preferred examples of these compounds include 3-mercapto-4-phenyl-1,2,
Silver salt of 4-triazole, silver salt of 2-mercaptobenzimidazole, silver salt of 2-mercapto-5-aminothiadiazole, silver salt of 2- (S-ethylglycolamide) benzothiazole, Japanese Patent Application No. 28221 / S-alkyl thioglycolic acid as described in No. 73 (wherein the alkyl group is 12-22
It has 4 carbon atoms. ) Silver salt of thioglycolic acid, silver salt of dithiocarboxylic acid such as silver salt of dithioacetic acid, silver salt of thioamide, 5-carboxylic-1-
Methyl-2-phenyl-4-thiopyridine silver salt, mercaptotriazine silver salt, 2-mercaptobenzoxazole silver salt, silver salts as described in U.S. Pat.No. 4,123,274, for example, 3-amino-5-benzylthio. A silver salt of a 1,2,4-mercaptothiazole derivative, such as a silver salt of -1,2,4-thiazole,
Silver salts of thione compounds such as the silver salt of 3- (2-carboxyethyl) -4-methyl-4-thiazoline-2-thione as described in US Pat. No. 3,301,678.

Further, a silver salt of a compound containing an imino group can be used. Preferred examples of these compounds include silver salts of benzotriazole and their derivatives as described in Japanese Patent Publication Nos. 30270/69 and 18146/70, for example, 5-chlorobenzotriazole. Of halogen-substituted benzotriazoles such as silver salts of methylbenzotriazoles, silver salts of carboimidobenzotriazoles, 1,2,4-triazoles of US Pat. Such 1-H-tetrazole silver salts, imidazole and imidazole derivative silver salts, and the like are included.

The photosensitive silver halide used in the present invention is in the range of 0.0005 to 5 mol, preferably 0.005 mol per mol of the organic silver salt.
It is used in the range of 005 to 1.0 mol.

The silver halide can be any light sensitive silver halide such as silver bromide, silver iodide, silver chloride, silver bromoiodide, silver chlorobromoiodide, silver chlorobromide and the like. ..

The silver halide can be added to the emulsion layer in all ways such that it is in catalytic proximity to the silver source.

The coating solution may be prepared by mixing the separately formed silver halide and the organic silver salt in a binder before use. However, it is also effective to blend the both in a ball mill for a long time. Further, it is effective to use a method including a step of partially converting silver in the organic silver salt into silver halide by adding a halogen-containing compound into the prepared organic silver salt.

Methods for preparing such silver halides and organic silver salts and methods for mixing them are described in Research Disclosure No. 170-29, Japanese Patent Application Nos. 32928/75 and 42529/76, US Pat. No. 3,700,458 and Japanese Patent Application Nos. 13224/74 and 17216/75.

The use of the preformed silver halide emulsions of this invention can be unwashed or washed to remove soluble salts. In the latter case, soluble salts may be removed by cold coagulation and leaching, or the emulsion may be coagulated and washed. For example, such manipulations are described in Hewitson et al., U.S. Patent No. 2,618,556; Yutzy et al., U.S. Patent No. 2,614,928; Yacke.
l), U.S. Pat.No. 2,565,418; Hart et al., U.S. Pat.No. 3,241,969; and Waller et al., U.S. Pat.
89,341. The silver halide grains may be of any crystalline form and include, but are not limited to, cubic, tetrahedral, orthorhombic, tabular, layered, tabular and the like.

Photothermographic emulsions containing preformed silver halide according to the present invention include reducing agents; sulfur,
It can be sensitized with chemical sensitizers such as selenium or tellurium compounds; gold, platinum or palladium compounds or combinations thereof. Preferred chemical sensitization procedures are Shepard, U.S. Patent No. 1,623,499; Waller, U.S. Patent No. 2,399,083; McVe (McVe
igh), U.S. Pat. No. 3,297,447; and Dunn, U.S. Pat. No. 3,297,446.

The reducing agent for silver ions can be any material, preferably an organic material, that reduces silver ions to metallic silver. Conventional photographic developers such as phenidone, hydroquinone and catechol are useful, with sterically hindered phenol reducing agents being preferred. The reducing agent should be present as 1 to 20% by weight of the imaging layer. In a two-layer construction, a slightly higher percentage, about 2-20%, is more desirable when the reducing agent is in the second layer.

A wide range of reducing agents have been disclosed in dry silver systems, which include amido oximes such as phenylamido oxime, 2-thienylamido oxime and p-phenoxyphenylamido oxime, azines such as 4- Hydroxy-3,5-dimethoxybenzaldehyde azine; a combination of aliphatic carboxylic acid aryl hydrazide and ascorbic acid such as a combination of 2,2'-bis (hydroxymethyl) propionyl-β-phenylhydrazine and ascorbic acid; polyhydroxy A combination of benzene and hydroxylamine, reductone and / or hydrazine, for example, a combination of hydroquinone and bis (ethoxyethyl) hydroxylamine, piperidinohexose reductone or formyl-4-methylphenylhydrazine, fe Ruhidorokisamu acid, p- hydroxyphenyl hydroxamic acid, and β-
Hydroxamic acids such as alanine hydroxamic acid; combinations of azine and sulfonamide phenols, such as phenothiazine and 2,6-dichloro-4-benzenesulfonamide phenol; ethyl-α-cyano-2-methylphenylacetate, ethyl-α- Α-Cyanophenylacetic acid derivatives such as cyanophenylacetate; 2,2'-dihydroxy-1,1'-binaphthyl, 6,6'-dibromo-2,2'-dihydroxy-1,1'-binaphthyl, and bis (2-hydroxy-
1-naphthyl) methane-like bis-β-naphthol; bis-
A combination of β-naphthol and 1,3-dihydroxybenzene derivatives, eg 2,4-dihydroxy-benzophenone or 2 ', 4'-dihydroxyacetophenone; 5-pyrazolone such as 3-methyl-1-phenyl-5-pyrazolone Dimethylaminohexose reductone, anhydrodihydroaminohexose reductone and anhydrodihydropiperidone hexose reductone; reductones; 2,6-dichloro-4-benzenesulfonamidephenol and p-benzenesulfonamidephenol Sulfonamide phenol reducing agents such as; 2-phenylindane-1,3-dione, etc .; 2,2-dimethyl-7-t-butyl-6
-Chroman like hydroxychroman; like 2,6-dimethoxy-3,5-dicarbetoxy-1,4-dihydropyridine
1,4-dihydropyridine; bisphenols such as bis
(2-hydroxy-3-t-butyl-5-methylphenyl) methane,
2,2-bis (4-hydroxy-3-methylphenyl) propane,
4,4-Ethylidene-bis (2-t-butyl-6-methylphenol)
And 2,2-bis (3,5-dimethyl-4-hydroxyphenyl)
Propane; ascorbic acid derivatives such as 1-ascorbyl palmitate, ascorbyl stearate, and unsaturated aldehydes and ketones such as benzyl and diacetyl; pyrazolidone and certain indane-1,3
-Zeon is one of them.

The literature discloses image improving additives or “toners”. For example, the toner material may be present in an amount of 0.1-10% by weight of all silver supporting compounds. Toners are well known materials as shown in U.S. Pat. Nos. 3,080,254, 3,847,612 and 4,123,282.

Examples of toners are phthalimide and N-hydroxyphthalimide; succinimide, pyrazoline-5-
Cyclic imides such as ones, and quinazolinones, 3-phenyl-2-pyrazolin-5-ones, 1-phenylurazoles, quinazolines and 2,4-thiazolidinediones; naphthalimides such as N-hydroxy-1,8- Naphthalimide; Cobalt complexes such as cobalt hexamine trifluoroacetate; 3-mercapto-1,2,4-triazole, 2,4-dimercaptopyrimidine, 3-mercapto-
Mercaptans exemplified by 4,5-diphenyl-1,2,4-triazole and 2,5-dimercapto-1,3,4-thiadiazole; N- (aminomethyl) aryldicarboximide, for example, (N-dimethyl Aminomethyl) phthalimide and N-
(Dimethylaminomethyl) naphthalene-2,3-dicarboximide; and blocked pyrazoles, isothiuronium derivatives and certain photobleaching agents, for example N, N ′.
-Hexamethylenebis (1-carbamoyl-3,5-dimethylpyrazole), 1,8- (3,6-diazaoctane) bis (isothiuronium trifluoroacetate) and 2-tribromomethylsulfonyl)-(benzothiazole) And 3-ethyl
-5 [(3-Ethyl-2-benzothiazolinylidene) -1-methylethylidene] -2-thio-2,4-oxazolidinedione; phthalazinone, phthalazinone derivative or metal salt or 4- (1-naphthyl) phthalazinone , Derivatives such as 6-chlorophthalazinone, 5,7-dimethoxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione; combinations of phthalazinone and sulfinic acid derivatives, for example phthalic acid, 4- Methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic anhydride; Quinazolinedione, benzoxazine or naphthoxazine derivatives; Ammonium hexachlororhodate (III), rhodium bromide, rhodium nitrate and potassium hexachlororhodate (III) tones Not only as a (tone) regulator but also as a source of halide ions for in-situ silver halide production. Rhodium complexes that work; inorganic peroxides and persulfates, such as ammonium peroxydisulfate and hydrogen peroxide; 1,3-benzoxazine-2,4-dione, 8-methyl-1,3-benzoxazine-2 , 4-dione and
Benzoxazine-2,4-diones such as 6-nitro-1,3-benzoxazine-2,4-dione; pyrimidines and asyn-triazines, for example 2,4-dihydroxypyrimidine, 2-hydroxy-4-amino Pyrimidine, and azouracil,
And tetraazapentalene derivatives, for example, 3,6-dimercapto-1,4-diphenyl-1H, 4H-2,3a, 5,6a-tetraazapentalene, and 1,4-di (o-chlorophenyl)- 3,6-dimercapto-1H, 4H-2,3a, 5,6a-tetraazapentalene.

Many methods have been proposed for obtaining color images using the dry ilver system. Such methods include coupler materials formulated in poly (vinyl butyral) such as silver benzotriazole combinations, the well known magenta, yellow and cyan dye forming couplers, aminophenol developers, guanidinium trichloroacetate and And silver bromide; combinations of silver bromoiodide, sulfonamide phenol reducing agents, silver behenate, poly (vinyl butyral), amines such as n-octadecylamine, divalent and tetravalent cyan, magenta or yellow dye forming couplers. A combination of a leuco dye base that forms a dye image upon oxidation, such as malachite green, crystal violet and pararose aniline; in situ silver halide, silver behenate, 3-methyl-1-phenylpyrazolone and N, N'-dimethyl-p-phenyle A combination of diamine dihydrochloride; 2- (3,5-di-t-butyl-4-hydroxyphenyl) -4,5-
Diphenylimidazole and bis (3,4-di-t-butyl-4)
-Hydroxyphenyl) compounding of a phenolic leuco dye reducing agent such as phenylmethane; compounding of an azomethine dye or an azo dye reducing agent; silver dye bleaching method, for example, silver behenate, behenic acid, poly (vinyl butyral), poly
(Vinyl butyral) digested silver bromoiodide emulsion, 2,
6-dichloro-4-benzenesulfonamide phenol, 1,8
An acid-activated sheet containing polyacrylic acid, thiourea and p-toluenesulfonic acid by exposing and heat-treating an element containing-(3,6-diazaoctane) bis-isothiuronium-p-toluenesulfonate and azo dye A method of obtaining a negative silver image having a uniform dispersion of the dye laminated to and obtaining a well-defined positive dye image by heating; and aminoacetanilide (yellow dye formation), 3,3′-dimethoxybenzidine ( Blue dye formation) or sulfanilanilide (magenta dye formation) and by reacting with a formulated reducing agent in an oxidized form such as 2,6-dichloro-4-benzenesulfonamidophenol. A method of forming a dye image can be mentioned. The neutral dye image is obtained by the addition of amines such as behenylamine and p-anisidine.

Oxidation of leuco dyes in such silver halide systems is described in US Pat. Nos. 4,021,240; 4,374,821.
Nos. 4,460,681 and 4,883,747.

The silver halide emulsion containing the supersensitizer of the present invention is further protected against fog formation and stabilized against loss of sensitivity during storage. Suitable antifoggants which may be used alone or in combination include Staud, U.S. Pat.No. 2,131,038 and Allen (A
Llen), U.S. Pat.No. 2,694,716; thiazolium salts; Piper, U.S. Pat.No. 2,886,437 and Heimbach, U.S. Pat.No. 2,444,605; Azaindene; Allen, U.S. Pat. 2,728,663
Salt described in U.S. Pat. No. 3,287,135; Anderson;
d), sulfocatechols described in U.S. Pat.No. 3,235,652;
Carol et al., British Patent No. 623,448, oxime; nitrone; nitroindazole; Jones (J
ones), polyvalent metal salts described in U.S. Pat.No. 2,839,405; Herz, thiuronium salts described in U.S. Pat.No. 3,220,839; and Trivelli, U.S. Pat.
63 and Damschroder, U.S. Patent No.
Includes platinum and gold salts described in 2,597,915.

The supersensitized emulsions of the present invention are polyalcohols such as Milton, US Pat.
Glycerin and diols of the type described in 2,906,404; fatty acids or esters such as those described in Robins, U.S. Pat.No. 2,588,765 and Duane, U.S. Pat.No. 3,121,060; and DuPont.
May include plasticizers and lubricants such as silicone resins as described in British Patent No. 955,061.

The photothermographic element may contain an image dye stabilizer. Such image dye stabilizers are described in British Patent 1,326,
889; Lestina et al., U.S. Pat.No. 3,432,300
And U.S. Pat. No. 3,698,909; Stern et al., U.S. Patent No. 3,573,050; Arai et al., U.S. Patent No. 3,764,3.
37 and Smith et al., US Pat. No. 4,042,394.

Photothermographic elements having an emulsion layer supersensitized according to the present invention are described in Sawdey, US Pat. No. 3,253,921; Gaspar, US Pat.
2,274,782; Carroll et al., U.S. Pat.
583 and Van Campen, U.S. Patent No.
It contains light absorbing materials and filter dyes as described in 2,956,879. If desired, for example, Milton (M
ilton) and Jones, U.S. Pat.No. 3,282,699
The dyes may be mordanted as described in US Pat.

Photothermographic elements having a supersensitized emulsion layer as described herein include starch, titanium dioxide, zinc oxide, silica, Jelley et al., US Pat. No. 2,992,101 and Lynn, US Pat. 2,701,2
It may include polymeric beads such as the type described in No. 45.

Emulsions supersensitized according to the present invention include, for example, soluble salts such as chlorides, nitrates, evaporated metal layers, Minsk, US Pat. No. 2,861,0.
56 and 3,206,312 with an ionic polymer or Trevoy, U.S. Pat.
It can be used in photothermographic elements having antistatic or conductive layers such as layers containing insoluble inorganic salts as described in US Pat.

The binder is gelatin, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate,
It may be selected from well known natural or synthetic resins such as cellulose acetate, polyolefins, polyesters, polystyrenes, polyacrylonitriles, polycarbonates and the like. Of course, copolymers and terpolymers are included in this definition. The preferred photothermographic silver-containing polymer is polyvinyl butyral. However, ethyl cellulose, methacrylate copolymers, maleic anhydride ester copolymers, polystyrene and butadiene-styrene copolymers are also useful.

If desired, these polymers may be used in combination of two or more kinds. Such polymers are used in an amount sufficient to hold the components therein. That is, it is used in a range effective to function as a binder. The effective range can be easily determined by those skilled in the art. As an index for holding at least the organic silver salt, the ratio of the binder to the organic silver salt is 15: 1 to 1: 2, particularly 8: 1.
A range of up to 1: 1 is preferred.

Photothermographic emulsions containing the supersensitizers of this invention can be coated on a wide variety of supports. Typical supports include polyester films, subbed polyester films, poly (ethylene terephthalate) films, cellulose nitrate films, cellulose ester films, poly (vinyl acetal) films, polycarbonate films and related or resinous materials, and glass, Includes paper and metal. A flexible support is typically used. In particular, it is partially acetylated or coated with a baryta and / or an α-olefin polymer, especially a polymer of α-olefins having 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylene, butene copolymers and the like. Preferred paper supports are.

US Pat. Nos. 4,460,681 and 4,374,9
No. 21 backside resistive heating layer (backside resist
Ive heating layers) may also be used in photothermographic imaging systems.

The photothermographic emulsions of this invention can be dip coated, air knife coated, curtain coated or Bengin (B
Enguin), U.S. Pat. No. 2,681,294 and may be coated by a variety of coating operations including extrusion coating using a hopper of the type. If desired, Russell,
Two or more layers are coated simultaneously by the method described in U.S. Pat. No. 2,761,791 and Wynn, British Patent No. 837,095.

[0058]

The present invention is explained in more detail by the following examples. However, the embodiments of the present invention are not limited to these.

[0059]

Examples 1-13 Silver halide / silver behenate dry soaps were prepared by the procedure described in US Pat. No. 3,839,049. Silver halide accounted for 9% of total silver and silver behenate accounted for 91% of total silver. The silver halide was a 50/50 mixture of preformed silver halide grains. Both had compositions of 2% iodide and 98% bromide, which were monodispersed. The two silver bromoiodide emulsions are 0.
It had a grain size of 055 to 0.07 microns. 300g
525g of the above silver halide-silver behenate dry soap
A photothermographic emulsion was prepared by homogenizing with 1,75 g of toluene, 1675 g of 2-butanone and 50 g of poly (vinyl butyral) (B-76, Monsanto).

Homogenized photothermographic emulsion (500 g)
And 100 g of 2-butanone were cooled to 55 ° F with stirring. Additional poly (vinyl butyral) (75.7g, B-76) was added and stirred for 20 minutes. Pyrinidium hydrobromide perbromide (0.45 g) was added, and the mixture was stirred for 2 hours. 3.25 ml calcium bromide solution (1 g CaBr ₂ and 10 ml methanol)
Was added and stirred for 30 minutes. Raise the temperature to 70 ° F and then increase the following ingredients in 15 minute increments
Was added with stirring. 2- (4-chlorobenzoyl) benzoic acid 3 g, IR dye solution (D-1 dye; 8.8 mg D-1 in 7.1 g DMF)
And 1,1-bis (2-hydroxy-3,5-dimethylphenyl)-
3,5,5-Trimethylhexane 16.6 g.

The photothermographic emulsion was divided into 40 g parts. The control was coated at this stage with no additives added. The remaining aliquot was treated with a three-step heteroaromatic mercapto compound added as a 1% solution in methanol (W / V). The best balance of low fog and high speed corresponding to the level of heteroaromatic mercapto compound listed as dry weight per 40 g aliquot is shown in Table 1.

The silver photothermographic emulsion was coated on a clear 3 mil (0.76 x 10 ^-4 m) polyester using a knife coater and dried at 175 ° F for 4 minutes. Dry coating weight is 23g / m ²
Met.

An active protective topcoat solution was prepared using the following ingredients. 256g Acetone 123g 2-Butanone 50g Methanol 20.2g Cellulose acetate 2.89g Phthalazine 2.02g 4-Methylphthalic acid 0.69g Tetrachlorophthalic acid 0.90g Tetrabromophthalic anhydride 1.50g Tetrachlorophthalic anhydride 0.45g 4-Tribromomethylpyrimidine Silver layer The topcoat solution was coated on top with a dry weight of 3.0 g / m ² . The layer was dried at 165 ° F for 4 minutes.

The coating material is then coated with a continuous wedge and EK.
Exposed for 30.2 seconds through a 780 nm narrow band filter using a -101 sensitometer. After exposure, the film pieces were processed at 260 ° F for 10 seconds. The images obtained were evaluated by a dentimeter. Sensitometric results include Dmin, velocity (measured at Spd: OD = 1.0), erg (power to reach optical density of 1.0), change in velocity from emulsion without heteroaromatic mercapto compound (dSpd). And the percentage of velocity change (dSpd) (% Spd). In all coatings, maximum densities in the range 3.2-3.5 were not recorded.

[0065]

[Table 1]

A series of experiments were performed to determine the field of view of the present invention. Table 2 shows sulfur compounds and silver halides,
Includes a list of infrared supersensitizers evaluated in the above formula described in Examples 1-13. The compounds were tested at the three levels described in Examples 1-13. The best levels are listed in Table 2. These results indicate that thioethers, thioureas and thiones do not supersensitize infrared photothermographic systems. Thiourea and benzotriazole and Leucophor BCF (Sandoz,
Sulfonated triazenyl stilbene) is widely used as a silver halide and infrared supersensitizer, but does not supersensitize photothermographic systems.

[0067]

[Table 2]

[0068]

Examples 14-26 5 of the preformed 0.055 and 0.07 micron silver bromoiodide grains used in Examples 1-13.
The same silver and topcoat formulations were used in these examples as in Examples 1-13 except that 0.05 micron of pure silver bromide grain was used instead of the 0/50 mixture.

These examples were also performed in 40 g aliquots with the control coated without the addition of the heteroaromatic mercapto compound. The heteroaromatic mercapto compounds used in Examples 14-17 were evaluated at 3 levels and Examples 18-26 were evaluated at 2 levels. The coated film strips were exposed using a laser sensitometer with a 780 nm laser diode. After exposure, the film pieces were treated at 26 ° F for 10 seconds. The results are shown in Table 3.

[0070]

[Table 3]

Experiments were conducted to confirm the need to have a heteroaromatic system as a mercapto supersensitizer. The silver and topcoat formulations were the same as in Examples 14-26.
The results are shown in Table 4. Here, the importance of having a heteroaromatic system linked to a mercapto group for supersensitizing infrared photothermographic films is shown.

[0072]

[Table 4]

[0073]

Examples 27-33 The supersensitizing effect of mercaptoheteroaromatic compounds on infrared sensitized photothermographic systems was evaluated for other infrared sensitizing dyes. The formulation was the same as in Examples 14-26. The infrared dye was evaluated with and without M-1 (2-mercaptobenzimidazole). The maximum sensitivity of infrared dyed photothermographic films was found by exposing with a series of narrow band filters and an EK101 sensitometer. The speed and supersensitization effect were evaluated using a laser sensitometer with a 780 nm laser diode. The Dmin value was not affected by adding M-1. The results are shown in Table 5. It has been clearly shown that mercapto heteroaromatic compounds supersensitize all infrared dye classes in photothermographic compositions.

[0074]

[Table 5]

[0075]

Example 34 Using a mercapto heteroaromatic compound,
An in-situ halided photothermographic system was tested for infrared supersensitization. 206 g of silver behenate total soap dispersion (2
A photothermographic emulsion was prepared by mixing 6 silver wt%) and the following components in this order: 40 g 2-butanone 0.54 g N-methylpyrrolidone 5.4 ml ZnBr ₂ solution (10 g ZnBr ₂ and 100 ml methanol) This mixture was kept for 4 hours, after which the following components were added. 3.6 g Poly (vinyl butyral) B-76 2.6 ml Pyridine solution (pyridine 3.6 g and 2-butanone 71 g) 27.5 g Poly (vinyl butyral) B-76 4.6 ml NBS solution (N-bromosuccinimide 0.67 g and 2-butanone 40 g ) This mixture was kept overnight after which the following ingredients were added. 6.3g 2,2'-Methylenebis (4-ethyl-6-t-butylphenol) IR dye solution (6mg D-1 and 4.0g DMF)

The resulting composition was divided into 40 g portions. The control was coated without additional additives. However, the second aliquot contains M-1 (2-mercaptobenzimidazole).
Was added. The results are shown in Table 6. Clear silver photothermographic emulsion using knife coater 3 mil (0.76 × 10 ^-4 m)
Coated on polyester and dried at 185 ° F for 3 minutes.
The dry coating weight was 17 g / m ² .

An active protective topcoat solution was prepared using the following ingredients. 224g 2-butanone 33.3g acetone 13.8g methanol 20.7g cellulose acetate 2.64g phthalazine 1.86g 4-methylphthalic acid 1.23g tetrachlorophthalic anhydride 0.57g tetrachlorophthalic acid 1.80g 2- (tribromomethylsulfone) benzothiazole silver coating Topcoat solution at 2.7 g / m ² on top of 185
Dry for 3 minutes at ° F. The coated material was exposed using a laser sensitometer with a 780 nm laser diode and treated at 260 ° F for 10 seconds. The results are shown in Table 6. The mercapto heteroaromatic compounds have been shown to supersensitize infrared sensitized in-situ halided photothermographic systems.

[0078]

[Table 6]

[0079]

Examples 35-40 The following coatings show that the combination of mercaptoheteroaromatic compounds can provide improved results as an infrared supersensitizer for photothermographic systems.
Identical silver and topcoat formulations as provided in Examples 14-26 except using higher infrared dye levels (> 50% IR dye, D-1) and changing tribromofogging agent. Was used in these examples. Example 14
~ 26 has 0.45 g of 4-tribromomethylpyrimidine in the topcoat solution and Examples 35-40 have 2.25 g of 2- (tribromomethylsulfone) benzothiazole in the same amount of topcoat solution. Contained.

This example was performed again as a 40 g aliquot. The coated film strip was exposed with a laser sensitometer with a 780 nm laser diode.
After exposure, the film pieces were processed at 260 ° F for 10 seconds. The results are shown in Table 7.

In Example 35, from the viewpoint of speed or sensitivity,
The level for M-1 (2-mercaptobenzimidazole) was optimized. In Examples 36 to 38, although slightly slower than M-1 in speed, contrast (cont = 0.25 on fog
The optimum level of M-3 (2-mercaptobenzothiazole) is shown to be higher in contrast measured from a density of 2.0). The combination of the two mercaptoheteroaromatic compounds in Examples 39 and 40 provided higher speed and contrast than when tested separately. The difference between Examples 39 and 40 is that in Example 30, first, M-
In Example 40, M-3 was added first, and 15 minutes later M-1 was added, although 1 was added and 15 minutes later M-3 was added. Table 7 shows that the mercaptoheteroaromatic compounds provide higher speed and high contrast and are useful in photographic applications.

[0082]

[Table 7]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Gary Lee Featherstone 3M Center, Saint Paul, Minnesota, USA 55144-1000 3M Center (No address)

Claims (10)

[Claims] 1. A photothermographic emulsion containing a binder, a non-photosensitive silver salt, a reducing agent for silver ions, and silver halide, the silver halide being spectrally sensitized to radiation of 750 to 1300 nm. The photothermographic emulsion comprises a superaromatic amount of a compound selected from the group consisting of a heteroaromatic mercapto compound and a heteroaromatic disulfide compound. 2. Ar-SM and Ar-SS-Ar, wherein M is hydrogen or an alkali metal and Ar is a heteroaromatic ring group. ] The emulsion of Claim 1 containing the supersensitizing compound shown by any one of. 3. The emulsion according to claim 2, wherein the supersensitizing compound is present in an amount of 10 ⁻³ to 1 mol per 1 mol of silver in the emulsion. 4. The emulsion according to claim 2, wherein the spectrally sensitized silver halide contains a silver halide and a cyanine dye, a carbocyanine dye or a tricarbocyanine dye. 5. Ar is benzimidazole, naphthuimidazole, benzothiazole, naphthothiazole, benzoxazole, naphthoxazole, benzoselenazole, imidazole, oxazole, pyrazole, triazole, thiadiazole, tetrazole, triazine, pyrimidine, pyridazine, pyrazine, An emulsion according to claim 4 selected from the group consisting of pyridine, purine, quinoline and quinazolinone. 6. The emulsion according to claim 2, wherein the non-photosensitive silver halide contains a silver salt of an organic acid. 7. The emulsion according to claim 6, wherein the organic acid is a fatty carboxylic acid. 8. Emulsion according to claim 2 or 3, containing at least two different compounds of the supersensitizing compound. 9. Emulsion according to claim 4, containing at least two different compounds of the supersensitizing compound. 10. The emulsion according to claim 7, which contains at least two different compounds of the supersensitizing compound.