GB2056103A - Silver Halide-containing Photothermographic Materials - Google Patents

Abstract

A hydrazone reducing agent contains a heterocyclic nucleus comprising a 5- or 6-membered heterocyclic ring and of which an oxidation product reacts with a dye- forming coupler to form an azo image dye can be used as a colour developing agent in a silver halide- containing sensitive photothermographic material. The material can be, for instance, a dry physical development material containing a light-insensitive organic silver salt or a dry chemical development material containing a base release agent. The material can be a multicolour material having silver halide layers sensitive to light of different spectral regions and containing couplers giving dyes of different colour on reaction with the hydrazone oxidation product. A dye image formed in the material by imagewise exposure and overall heating can be transferred by diffusion at an elevated temperature to an integral or separate receiving layer.

Description

SPECIFICATION Silver Halide-containing Photothermographic materials This invention relates to silver halide-containing photothermographic materials for producing dye images.

A sensitive photothermographic sheet material can be used for the production of a visible image by a process comprising imagewise exposure of the material to actinic radiation, to form a latent image in the sensitive coating, and overall heating, to develop the latent image to the desired visible image.

In the kind of material with which the present invention is concerned, a photographic silver halide is present in the sensitive coating and gives a latent image of silver specks, Two main classes of sensitive silver halide-containing photothermographic sheet material have become well known. With one class, the image silver is all provided by reduction of the silver halide by an incorporated developing agent, and such a material is conveniently termed a 'dry chemical development' photothermographic material (see 'The Theory of the Photographic Process' 4th Edr edited by T. H.James, The Macmillam Co. 1 977, pp 373-4). With the other class, much of the image silver is provided by a relatively light-insensitive organic silver salt, the latent image formed on exposing the silver halide serving to catalyze the reaction of this organic salt with an incorporated reducing agent. Such a sheet material is conveniently termed a 'dry physical development' photothermographic material (op. cuit).

A dry chemical development photothermographic material commonly contains a base release agent which, at the processing temperature, releases a base which activates the silver halide developing agent. The material may also contain a stabilizer (or a stabilizer precursor which releases a stabilizer at the processing temperature) to inhibit post-processing print-up. A dry physical development photothermographic material, also, may contain a stabilizer or stabilizer precursor but less usually contains a base release agent.

The present invention provides a sensitive photothermographic material which comprises a support coated on one side with at least one binder-containing layer and, incorporated in the said layer or layers a photographic silver halide, a dye-forming coupler and a hydrazone reducing agent which contains a heterocyclic nucleus comprising a 5- or 6-membered heterocylic ring and of which an oxidation product reacts with the coupler to form an image dye.

It should be remarked that in view of the different conditions (including pH) which may obtain during the processing of dry chemical development and dry physical development photothermographic materials, a constituent suitable for the one class of material is not necessarily suitable for the other.

The hydrazone reducing agents with which the present invention is concerned, however, have been found to be suitable for incorporation in silver-halide containing photothermographic materials in general and so may satisfactorily be incorporated in both dry chemical and dry physical development materials.

A photothermographic material of the invention may, if desired, be a diffusion transfer material, a dye image formed by imagewise exposure and overall heating of the material being transferred by diffusion to an adjacent receiving layer formed of, or containing, a mordant for the dye, and possibly carried by the same support.

Many hydrazone reducing agents comprising a 5- or 6-membered heterocylic ring can be used in photothermographic materials according to the invention. Those hydrazone compounds which do not, in their oxidized form, react with a dye-forming coupler to form a dye are not considered useful according to the invention. Selection of an optimum hydrazone reducing agent will depend upon such factors as the desired images, and the particular dye-forming coupler, photosensitive silver halide, coating formulation, and processing conditions chosen. A mixture of 5- or 6-membered heterocylic ring-containing hydrazone reducing agents can also be used.Preferred hydrazone reducing agents for the invention are represented by the formula:

wherein n is O or 1 R1 is hydrogen or an acyl group containing 1 to 20 carbon atoms, for example, 1 to 10 carbon atoms, including acetyl, butyryl or benzoyl; R2 is hydrogen or a substituent which can be split off during oxidative coupling and is an acyl or sulphonyl group containing 1 to 20 carbon atoms of the formula::

or-SO 2R4; R3 is alkyl, such as alkyl containing 1 to 20 carbon atoms, for example, methyl, ethyl, propyl, butyl, decyl, dodecyl and octadecyl, alkenyl containing 2 to 20 carbon atoms, such as ethenyl, propenyl, butenyl and hexenyl, alkynyl, cycloalkyl, such as cycloalkyl containing 5 to 8 carbon atoms, for example, cyclopentyl and cyclohexyl, aryl, such as aryl containing 6 to 12 carbon atoms, for example, phenyl, tolyl and xylyl, a heterocylic group, especially one containing a 5- or 6-membered heterocylic ring, such as an imidazolyl, thiazolyl, tetrazolyl or morpholinyl group, or an acyl or sulphonyl group containing 1 to 20 carbon atoms of formula -COR4 or -SO2R4;; R4 is hydroxyl, amino (-NH2), alkyl, such as alkyl containing 1 to 20 carbon atoms, for example, methyl, ethyl, propyl, butyl, decyl, dodecyl and octadecyl, or aryl, such as aryl containing 6 to 12 carbon atoms, for example, phenyl, tolyl or xylyl; and Z represents the non-metallic atoms necessary to complete a heterocyclic nucleus comprising a 5- or 6-membered heterocylic ring, such as a thiazole, oxazole, selenazole, benzoselenazole, naphthoselenazole, benzothiazole, or quinoline nucleus. The non-metallic atoms necessary to complete the 5- or 6-membered ring-containing heterocyclic nucleus include, for instance, carbon, sulphur, oxygen and nitrogen atoms.

Any hydrocarbon (e.g. alkyl, alkenyl, cycloalkyl or aryl) or heterocyclic portion of a substituent R1, R2, R3 or R4, or any heterocyclic nucleus completed by Z may carry substituent groups which do not adversely affect the sensitometric or other properties of the photothermographic material containing the hydrazone reducing agent concerned. Examples of substituents which may be present are nitro, alkoxy (e.g. ethoxy) and carbamate groups.

A hydrazone reducing agent used for the invention can be in the photothermographic material either as the free base or as a salt of hydrochloric, para-toluenesulphonic, phenylsulphonic or methylsuiphonic acid. Selection of the optimum form of the hydrazone reducing agent will depend upon such factors as the processing conditions, the particular reducible organic silver salt and the particular coupler.

Examples of hydrazone reducing agents useful for the invention are compounds represented by the formula:

wherein Z is as defined for Formula I, representing the non-metallic atoms necessary to complete a heterocyclic nucleus comprising a 5- or 6-membered heterocyclic ring such as a thiazole, oxazole.

selenazole, benzoselenazole, naphthoseienazole, benzothiazole or quinoline nucleus. Such hydrazone reducing agents include, for instance, the Hydrazones Nos. 1 to 7 specified below.

t=Ss N~NH2 fici CH3 2 1wN-NH2 HCt C113 C a CH3 4 #I S#N--NH2 -H C1 CHs Cl3 5 t j N~NH2 ; Cil3 sosi

6 t=-Nn2 CH3 s03d 7 ( NH2 (CH3) so4 COIL3 Hydrazone reducing agents particularly useful for dry physical development materials of the invention are represented by the formula:

wherein R is one of the following: Hydrazone No.

8 SO2Cti3 9 #=1 9 SO2# N02 10 ~502(CH2)3 CH3 11 -so243 12 -502-OCt2 H25 13 S02 (CH2)15 CH3 14 -S02 < o CNH b 0Cl4 H29n 15 N02 0 16 Preferred hydrazone reducing agents of Formula I are sulphonyl hydrazones. Also preferred are hydrazones of Formula I in which Z completes a benzothiazole nucleus.

A useful concentration of hydrazone reducing agent is normally within the range of 0.25 to 5 moles per mole of the photosensitive silver halide in the photothermographic material. In most cases at least 0.5 millimole of reducing agent per square metre of support is necessary in a dry physical development photothermographic material according to the invention to produce maximum useful reflection densities in a print format. The upper limit of concentration of the hydrazone reducing agent in a photothermographic material of the invention is influenced by the solubility of the agent in the coating formulation desired for producing a photosensitive layer containing the agent. An especially useful concentration is within the range of 0.5 to 1.5 moles of agent per mole of photosensitive silver halide sensitivity.Useful photosensitive silver halides include, for example, silver chloride, silver bromide, silver bromoiodide, silver chlorobromoiodide or mixtures thereof. A range of grain size of photosensitive silver halide from coarse-grain to fine-grain silver halide is useful.

The photosensitive silver halide is especially useful because it has a high degree of photosensitivity compared to other photosensitive components. A range of grain size of photosensitive silver halide is useful from very fine to coarse grain size.

A typical concentration of photosensitive silver halide in a photothermographic material according to the invention is within the range of 0.2 to 4 moles of photosensitive silver halide per mole of the described hydrazone reducing agent in the photothermographic material.

In a dry chemical development photothermographic material according to the invention the coverage of the photosensitive silver halide is preferably within the range of 10-4 to 5x10-2 mole of silver per square metre.

The most useful photosensitive silver halide for a dry chemical development material is in the form of an aqueous formulation, typically a gelatino silver halide emulsion. The aqueous formulation enables avoiding organic solvents which can be disadvantageous in some instances due to their flammability. The most useful hydrazone developing agents in such formulations are those which have a sufficient degree of water solubility to provide a desired aqueous coating formulation with the gelatino silver halide emulsion and other components of the photothermographic material.

The photosensitive silver halide for a dry physical development material can be prepared by any of the appropriate procedures known in the photographic art. Useful procedures are described in, for example, Research Disclosure, Volume 148, August 1976, Item 14879 of Rosenfeld: Research Disclosure, Volume 125, September 1974, Item 12537 of Ulbing, Hess and Terwilliger; and in U.S.

Patents 3,871,887 and 3,839,049 and British Patent 1,362,970.

Many dye-forming couplers may be used in the photothermographic materials according to the invention. The dye-forming coupler must be one which forms an azo dye with the oxidized form of the hydrazone reducing agent. That is, according to the invention the dye-forming coupler must form an azo dye with the oxidized form of the hydrazone reducing agent upon heating the material after exposure. The dye-forming coupler is preferably colourless in the photothermographic material prior to imagewise exposure and heat processing. The dye-forming coupler and other components should be stable to a sufficient degree to avoid any significant, adverse interaction prior to producing a desired image at processing temperatures. A simple test can be useful in some cases for selecting an optimum dye-forming coupler according to the invention.Such tests may be carried out using procedures as described in the following Examples 1 and 1 5, the dye-forming coupler to be tested being included in the photothermographic material instead of the dye-forming coupler described in the Example. If the dye image produced using the chosen procedure is at least as satisfactory as that of the Example on which the procedure is based then the compound containing the coupler moeity is considered to be useful. A compound that is a dye-forming coupler which produces a neutral (black) or nearly neutral appearing image is very useful in many instances for both dry chemical and dry physical development materials.

The dye-forming coupler can be a coupler which forms a yellow, magenta, cyan or other colour upon reaction with the oxidized form of the described hydrazone developing agent. The dye-forming coupler can be a monomeric or polymeric dye-forming coupler, the latter providing a non-diffusing image dye.

Suitable couplers include those that can withstand the chosen processing temperatures without adversely affecting the sensitometric properties of the photothermographic material. Useful compounds that are dye-forming couplers include those described in U.S. Patent 3,761,270 and resorcinolic couplers, such as are described in Research Disclosure, September 1978, Item No.17326.

Dye-forming couplers known in the photographic art to produce azomethine dyes by reaction with primary aromatic amine colour developing agents can be used in a photothermographic material according to the invention to produce azo dyes especially yellow azo dyes. Such yellow azo dyeforming couplers include, for example, those containing active methylene sites, such as pyrazolones, pyrazolotriazoles, indazoles and pyrazolobenzimidazoles containing such sites. In a like manner, naphtholic and phenolic compounds that are known in the photographic art to form indoaniline cyan dyes by reaction with primary aromatic amine colour developing agents can be useful according to the invention to produce magenta azo dyes. Useful dye-forming couplers can be selected from those described in, for example, "The Theory of the Photographic Process", edited by T. H. James, Fourth Edition, Chapter 12, 1977 and Research Disclosure, December 1978, Item No. 1 7643, Section VII.

Useful azo dye-forming couplers include two-equivalent and four-equivalent dye-forming couplers. Useful four-equivalent dye-forming couplers are described in, for example, U.S. 4,021 ,240.

Other useful dye-forming couplers include those containing what are known in the photographic art as coupling off substituents, such as development inhibitors. Useful developer inhibitor releasing couplers (also known as DIR couplers) are described in, for example, Research Disclosure, October 1972, Item No. 10226. Combinations of dye-forming couplers can be useful in a photothermographic material according to the invention.

Useful magenta dye-forming couplers include those described in following Table I in Example 1.

Other useful magenta dye-forming couplers include the following:

OH OH ûH OH Ol (4) Cl tCcoNH < oec(cH3) OH (6)/CONHZ OH (7) X OH (8) 's021(C12 H26-n)2 OH (9) 6 N(C2H5)2 Oil NHCOCH3 (lo) K003S S030K

COON ON CON (11) C2115 COON Oil C4N9 NHCOC3H7-n (12) t-#5ilj1 ffi;:;::{;Nil 7 I Oil fo2C16H37 (13) OQils F (i4) ) CONil# sO2NN(CH2)4O#C5ll11-t C5Hll -t 502 F Oil (is) CO Nil 0Cil3 0C16 H33- n ON CONilN (16) S Cl4il29 - n ON O (17) ~ so2##)) Cs H11-t Ct C4Hg - n

oil O 0 n-C12il2#ClCNil Cl O Ci YD\C4H9 -t OH (19) Cl OH /C4 Hg -t ClCONilNHCOCNO Oil C12 H25 Useful magenta dye-forming DIR couplers include::

g ON CONH(CH2)40 s -L N#N- C#ils I I N--N OH (21) +/CONHS (Q1) CONN# s ; oC6H5 N Oil CON N < 7 0C14N29 sy OH C0Nil# (23) CONH-0 Rz# X ,C2H5 N--N Yellow dye-forming couplers that are useful include::

COON (24) N N ((CH2)3oNHsogA COON CH3N iC0NHC18 H37 (25) -N- (Cil2) zoo N02 J > N' CH3 11 ilso3 Cil3 (26) N-N 0#'C17il35 (27) \N~N oM HNTh Cl Cl (28) GlCZNH-- Oil NilCOC(ilO# C12 c(Cil3)3 C6H5s (29) (29) NHCO Cl Ct (30) NNNNThcN Useful yellow dye-forming DIR couplers include::

Qils (31) #O CilCONil N N C5 N3 OoC2Ns 3 /CsHg ss N C2Hs (32) t- C5N11# OCICO Csilll#tNNfL 0 s N1 N N C2ilS (33) t 0C1ilCONil# C# Nj1 -t N-C2Hg N-N Useful cyan dye-forming couplers include: (a) Substituted pyrazolines having the structure::

wherein R5 is substituted or unsubstituted alkyl, such as alkyl containing 1 to 20 carbon atoms, acyl, such as acyl containing 2 to 20 carbon atoms, or aryl, such as phenyl and R6 and R7 are alkyl, such as alkyl containing 1 to 20 carbon atoms, alkoxy, such as alkoxy containing 1 to 20 carbon atoms, acyl, such as acyl containing 2 to 20 carbon atoms, nitro, sulfamyl, halogen, especially chlorine or bromine, or hydrogen.Typical examples include:

(b) Substituted amidrazones can also be used such as:

(40) CH30 eCH=N~7 4 CH3 (41) Cm30 cN=N-N- CH2# CH3 (42) OCH-~N~g < CH3 (43) HO-CH=N--NN OC2H5 CH3 (44) HO CH3 (4s) Br# Cil=N-N CH3 (46) N~~CeCR=N~Nlt Cil3 Especially useful dye-forming couplers include:

oH #U) f::"' NHCOC3F7-n t - Cs H1l90CHCO H and #-C5Nj1# C5il11-t Cl (48) c#-ClN NilCOCl2O CgHII-t CiONilCO CgHII-t Examples of polymeric dye-forming couplers of value in dry chemical development materials of the invention are: poly [ 2-acryla mido-2-methylpropa ne- 1 -su Iphonic acid, sodium salt-co-1-(4,6-dichloro-2-methylphenyl)-3-acrylamido-2-pyrazolone-5-one-co-N-(2- aceto-acetoxyethyl) acrylamide ] and poly{2-acrylamido-2-methylpropane-1 -sulphonic acid, sodium salt-co-2'- [ 2-( 1 -hydroxy-2- naphthoyla mino)-ethyl] acrylanilide-co-N-(2-acetoacetoxyethyl)-acrylamide i.

The concentration of dye-forming coupler is preferably within the range of 0.1 to 10 moles of dye-forming coupler per mole of reducing agent in the photothermographic material. When a combination of dye-forming couplers is used, the total concentration of the combination is preferably within the described range. An especially useful concentration of dye-forming coupler is within the range of 0.25 mole to 2.0 moles of the dye-forming coupler per mole of the reducing agent.

Many reducible organic silver salts can be used in dry physical development materials according to the invention. One class of useful organic silver salts is constituted by silver salts of long-chain fatty acids, which salts are resistant to darkening upon exposure to light. Examples of such salts are silver behenate, silver stearate, silver oleate, silver borate, silver hydroxy stearate, silver caprate, silver myristate and silver palmitate. The term "long-chain fatty acid" is used herein to refer to fatty acids which contain 10 to 30 carbon atoms in the hydrocarbon portion. Another useful class of reducible organic silver salts comprises the complexes of silver with nitrogen acids, such as imidazole, pyrazole, urazole, 1 ,2,4-triazole and 1 H-tetrazole nitrogen acids and mixtures thereof.These silver salts of nitrogen acids are described in, for example, Research Disclosure, Volume 1 50, October 1976, Item 1 5026 of deMauriac.

The term "salt" and "complex" are used herein to refer to compounds including any type of bonding which enables those compounds to produce images in the described photothermographic materials.

A reducible organic silver salt may be used in a range of concentrations. A useful concentration is often within the range of 0.1 mole to 10 moles of the organic silver salt per mole of silver halide. An especially useful concentration is within the range of 0.5 mole to 2 moles of organic silver salt per mole of silver halide.

A photothermographic material according to the invention can contain a variety of binders alone or in combination in the layer or layers present. Useful binders include both hydrophilic and hydrophobic materials. They are transparent or translucent and include naturally-occurring substances or their derivatives, such as proteins (for example gelatin), gelatin derivatives, cellulose derivatives and polysaccharides, such as dextran. They also include synthetic polymeric materials such as hydrophilic polyvinyl compounds like poly(vinyl pyrrolidone) and acrylamide polymers. Other synthetic polymeric materials that can be useful include dispersed vinyl compounds such as in latex form and particularly those that increase the dimensional stability of the photothermographic materials.It is desirable to choose a polymer which is compatible with the described imaging components of the photothermographic materials according to the invention.

A dry physical development material containing a silver fatty acid salt commonly contains a hydrophobic binder such as poly(vinyl butyral), cellulose acetate butyrate, polymethylmethacrylate, ethyl cellulose, poly(vinyl chloride), chlorinated rubber, polyisobutylene, a butadiene-styrene copolymer, a vinyl chloride-vinyl acetate copolymer, a copolymer of vinyl acetate, vinyl choride and maleic acid.

A dry chemical development material usually contains a hydrophilic binder. Useful synthetic polymeric compounds include water insoluble polymers of alkyl-acrylates and methacrylates, acrylic acid, sulphoalkyl acrylates or methacrylates and those which have crosslinking sites which facilitate hardening or curing. An especially useful binder is gelatin or a gelatin derivative. Binders which are compatible with aqueous formulations are especially useful.

The tone of a developed silver and dye image produced with a material according to the invention will vary depending upon such factors as the silver morphology of the developed silver image, the particular coupler, the particular hydrazone reducing agent, and processing conditions. The coupler and reducing agent can be selected to produce a dye which is complementary in hue to the developed silver image in order to obtain a more neutral image colour.

The photothermographic material according to the invention can comprise a variety of supports, a support being chosen which can tolerate the intended processing temperatures. Typical supports include cellulose ester, poly(vinyl acetal), poly(ethylene terephthalate), polycarbonate and polyester film supports.

A photothermographic material according to the invention can be prepared by coating the necessary composition or compositions on the chosen support by various coating procedures known in the photographic art including dip coating, airknife coating, curtain coating or extrusion coating using hoppers.

A photothermographic material according to the invention may comprise an overcoat layer which may contain one or more of the described vehicles and binders. The overcoat layer helps avoid undesired abrasion and other markings as well as protecting the photosensitive layer.

A "melt-forming compound" can be useful in some photothermographic materials according to the invention to produce an improved developed image. A melt-forming compound can be especially useful with a dry physical development material containing a silver salt of a nitrogen acid. A "meltforming compound" produces at the processing temperature a reaction medium, typically a molten medium, wherein the image-forming reactions can more readily take place. Examples of useful meltforming compounds include beeswax, 1 ,6-hexanediol, methyl anisate sulphamide, acetamide and succinimide.

A "toning agent" such as 1 -(2H)-phthalazinone may be used in some materials of the invention.

A melt-forming compound may be used at a coverage within the range of 0.1 to 5.0 grams per square metre in the photothermographic material.

The reducible organic silver salt in a dry physical development material of the invention can contain a range of ratios of (1) the organic moiety, such as the nitrogen acid moiety or the long-chain fatty moiety, to (2) the silver ion. The optimum value of this ratio will depend upon such factors as the particular organic moiety, hydrazone reducing agent, processing conditions, and particular dye-forming coupler. The molar ratio of the organic moiety to silver as silver ion in the organic silver salt is preferably within the range of 10:1 to 1 :1. An especially preferred range for this molar ratio is from 2:1 to 1:1.

A dry physical development photothermographic material of the invention can also contain a range of pAg. The pAg of a dispersion to be coated containing the necessary imaging constituents can be measured using conventional calomel and silver-silver chloride electrodes, connected to a commercial digital pH meter. The typical pAg in the dispersion is within the range of 2 to 9.5, with an especially useful pAg being within the range of 4.5 to 6. The pH of the dispersion is preferably within the range of 1.5 to 8.5. An especially useful pH is within the range of 4.5 to 7 with the most preferred range being 4.5 to 5.5.

Spectral sensitizing dyes can be useful in the photothermographic materials of the invention to confer additional sensitivity. Useful spectral sensitizing dyes can be selected from those described in, for example, Product Licensing Index, December 1 971, Item 9232 and Research Disclosure, June 1978, Item 17029.

The described components of a photothermographic material according to the invention can be in any locations which allow production of the desired image. For example, one or more of the components can be in one or more layers of the material. It can be desirable in some cases to include certain percentages of, for instance, the hydrazone reducing agent, in a protective, overcoat, layer. In other words it is necessary for the photosensitive silver halide and other components of the photothermographic materials to be in what is sometimes termed "reactive association" with each other.

Many 'base-release agents' are useful in dry chemical development photothermographic materials according to the invention. Base-release agents are also known as activators or activator precursors. The base-release agent chosen should be a compound which at the intended processing temperature releases a base which activates the developing agent concerned to develop a latent image formed in the photosensitive silver halide. Examples of useful base-release agents are described in Belgian Patent 709,967. These examples include guanidinium salts, such as guanidinium trichloroacetate, diguanidinium glutarate, succinate, and malinate. Other useful base-release agents include amino acids such as 6-amino carprilic acid and glycine as well as aminimides. Useful aminimides are described in, for example, Research Disclosure, June 1978, Item No.T 7029. An example of a useful aminimide is:

Base-release agents are appropriately used at a concentration within the range of 0.2 to 4.0 moles per mole of total silver in the photothermographic material. An especially useful concentration is within the range of 0.5 to 2.0 moles of base-release agent per mole of total silver.

A photothermographic material according to the invention can be a multilayer material which enables the production of more than one dye image. For example, the material can contain a layer which forms a cyan dye image with a separate layer which produces a magenta dye image. The photothermographic material accoringly can produce a multicolour dye image or a single dye image.

A photothermographic material of the invention can be a diffusion transfer material, a dye image formed on heating the imagewise exposed material being transferred by diffusion, at an elevated temperature, to a receiving layer. This layer may be integral with the material and may, for some image dyes, be constituted by the support. Alternatively, the receiving layer may be carried by a separate support and held in face to face contact with the photothermographic material during transfer.

Diffusion transfer may be aided by the presence of a solvent, such as methanol, ethanol or acetone, or a substance such as methyl anisate which is molten at the processing temperature. A receiving layer usually comprises a mordant for the dye image.

After transfer of a dye image to a receiving layer, that layer may in some instance be separated, for example by stripping, from the photothermographic layer, or layers, in which the image was produced. Another method of separation which is possible when the photothermographic layer is coated over the receiving layer comprises removing the photothermographic layer with a suitable solvent.

If desired, an "opacifying layer" can be included in the diffusion transfer photothermographic material to provide a background against which a dye image in the image-receiving layer can be seen.

The "opacifying layer" can contain a variety of agents, such as titanium dioxide, which produce the desired reflection.

A separation layer is often useful between layers of a photothermographic material according to the invention. A separation layer can be used for timing the diffusion of components between layers and to improve the adhesion between layers. A typical separation layer may comprise any of the binders as described.

If desired, the silver remaining in an exposed and processed photothermographic material according to the invention can be bleached with a suitable bleaching agent. Bleaching of the silver present in the photothermographic material can produce a residual negative dye image.

A variety of imagewise exposure means may be used with the photothermographic materials according to the invention. These materials are sensitive to ultraviolet and blue regions of the electromagnetic spectrum and, if spectrally sensitized, to longer wavelengths also.

A visible image can be developed in an imagewise exposed photothermographic material of the invention, within a short time, such as within several seconds, merely by uniformly heating the photothermographic material to a moderately elevated temperature. For example, the imagewise exposed photothermographic material can be heated to a temperature within the range of 800C to 200 C, preferably to a temperature within the range of 1 200C to 1 500C, until the desired image is produced. Heating is usually for a time of from 1 to 90, and preferably for from 5 to 30 seconds.

An especially useful embodiment of the invention is a dry physical development photothermographic material comprising a support having thereon, in binder (for instance poly(vinyl butyral)), (a) photosensitive silver halide in reactive association with (b) at least one dye-forming coupler, such as 1-hydroxy-2-naphthanilide, and (c) an oxidation-reduction image-forming combination comprising (i) a reducible organic silver salt, such as silver behenate, with (ii) a hydrazone reducing agent represented by the formula:

the nitro group preferably being in the meta or para position with respect to the sulphonyl group.

Another preferred embodiment of the invention is an image transfer, dry physical development photothermographic material comprising a support having thereon, in sequence, at least one layer (I) comprising, in binder (e.g. poly(vinyl butyral)) (a) photosensitive silver halide in reactive association with (b) at least one dye-forming coupler, such as 1 -hydroxy-2-naphthanilide, (c) an oxidationreduction image-forming combination comprising (i) a reducible organic silver salt, such as silver behenate, and (ii) a hydrazone reducing agent, for example of the formula (V) above, and at least one image-receiving layer (II) comprising a mordant for the dye produced upon imagewise exposure and heat processing of the material.

A further preferred embodiment of the invention is a dry chemical development photothermographic material for producing a dye image comprising a support having thereon, in a gelatino binder, (a) photosensitive silver halide in reactive association with (b) the dye-forming coupler poly [ 2-acrylamido-2-methylpropane-1 -sulphonic acid, sodium salt-co-i -(4,6-dichloro-2- methylphenyl)-3-acrylam ido-2-pyrazolone-5-one-co-N-2-acetoacetoxyethyl)acrylamide ] and (c) the hydrazone No. 1 specified above and (d) an activating concentration of the base-release agent trimethylamine cinnamide.

Another preferred embodiment of the invention is a photothermographic material comprising a support having thereon, in a gelatino binder, (a) photosensitive silver halide in reactive association with (b) the dye-forming coupler poly(2-acrylamido-2-methylpropane-1-sulphonic acid, sodium salt-co-2t- [ 2-(1 -hydroxy-2-naphthoylamino)ethyl ] acrylanilide-co-N-(2-acetoacetoxyethyl)acrylamidej and (c) the hydrazone No. 1 specified above.

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

Example 1: Use of Dye-forming Couplers This example illustrates the invention.

A series of photothermographic materials according to the invention containing the hydrazone reducing agent No. 1 5 and a variety of dye-forming couplers were prepared according to the following procedure: A dispersion was prepared by ball milling together the following components for 72 hours: silver behenate (oxidizing agent) 33.6 g behenic acid (antifoggant) 25.4g poly-(vinyl butyral) (binder) (BUTVAR B-76, trade mark, commercially available from Monsanto Co., U.S.A.) 12.0 g acetone-toluene (solvent) (1 :1 parts by volume) 400 ml The resulting dispersion was designated as dispersion A. Three milliliters of this dispersion were added to a solution containing 0.3 millimole (105.5 milligrams) of the hydrazone reducing agent No.

1 5 and 0.3 millimole of a coupler as listed in following Table 1 dissolved in 7 millilitres of a 2.0% by weight poly(vinyl butyral) solution in equal parts by volume acetone and toluene. To the resulting stirred mixture was added 0.8 millilitre of a silver bromiodide emulsion (6% iodide) (peptized in poly(vinyl butyral)) (0.3 millimole of silver ion) in acetone. The resulting composition contained 40 grams of poly(vinyl butyral) per mole of silver ion.

The resulting photothermographic composition was coated on a 0.1 mm thick, poly(ethylene terephthalate) film suppport at a 0.15 mm wet coating thickness at 380C. The resulting photothermographic material was permitted to dry. The dry photothermographic material was imagewise exposed to light (using a General Electric Company floodlamp, 32000 K) for 3 seconds at a distance of 38 centimetres. This produced a developable latent image. The material was then uniformly heated for a given time and temperature as indicated in Table 1 by contacting the support side thereof with a curved heating block.

The following Table 1 indicates the specific coupler and processing exposure-development time and temperature and the resulting image dye hue.

Table 1 Processing (exposurex development timex Result Coupler and Structure temperature) (Dye Hue) (12) (see above) 3"x15"x850C Magenta OH (49) C2HsXCsHll-t 3"x C5il11-t 31,x151,x850C Magenta CN3 F.HO il11-t Cl OH (50) CONH(CH2)40 < CsHX-t 3"x 1 5"x85"C Magenta OH CONH JzCONHCH2CH29 3"x15"x850C Magenta NHCOCH3 (52) CONH X 3"x 31,x15'1x850C Magenta (#3) ( 311x311x1250C Magenta OH (54) 0 #Non 3"x30"x1250C Magenta OH

Table 1 (continued) Processing exposure development timex Result Coupler and Structure temperature) (Dye Hue) (55) tis i̇$ 3"x20"x850C Yellow 0 < CH3 (cit2)3 (56) NN-N #NO2or 1000C Yellow C v H 3Nx20"x1250C Yellow (57) N Cil3 311x51,x1350C Yellow (48) (see above) 3"x25nx125 C Yellow (58) ClOt N-N N N --N 3"x15"x1100C Yellow Cl < Cl Cl 3"x3011x 1 000C (20) (see above) or 3"x30"x125 C Magenta (31) (see above) 3"x30"x 1250C Yellow (59) CNCH2CN 3"x 15"x1000C Yellow (60) C2H5 t-1i11C5 #OC1N-CONN C5Htit > CACTI2 CONH- 3"x15"x125 C Yellow CH (61) s noNH 3"x15"x1250C Blue (62) > N(C3H7)2 n 3"x15"x135 C Blue (63) > 3"x15"x1250C Blue

Table 1 (continued) Processing (exposurex development timex Result Coupler and Structure temperature) (Dye Hue) He on (64) 3Nx30"x1250C Orange 0 (65) HN~C~CH=CH 3"x30"x1250C Orange H Iq /OH (66) ss 3"x30"x1350C Cyan "CH2 ĭl3)2 311x607,x850C Purple NHSO;!C15 H31 -n 3Nx60"x850Cor 31,x30"x1 100C or [ 3"x30"x 125 C (36) (see above) 3"x30"x1100C Cyan Example 2 Use of Different Hydrazone Reducing Agents Photothermographic materials were prepared according to the procedure described in Example 1 except that the hydrazine No. 1 5 was replaced with equal molar amounts of the hydrazones 8 to 14 specified above the Hydrazones 17 to 20 of the formulae::

(17) NH--NHI CH3 cu3so4@ CH3 Qs)N--NHH-CO < N~NHs024 CHJ CH3 (20) N Nil SO CH1O) < XN~NHs024 The incorporated coupler in the photothermographic material was:

A sample of each photothermographic material was imagewise exposed as described in Example 1 for 3 seconds to provide a developable latent image, and heat processed as described in Example 1 at 11 00C for 15 seconds. In each instance a silver and magenta dye image was produced.

Example 3 Use of Toners Photothermographic materials were prepared as described in Example 1 which contained 0.3 millimole of described hydrazone No. 1 5 as the hydrazone reducing agent and 0.3 millimoles of the dye-forming coupler described in Example 2. Each photothermographic material also contained one or other of the toners phthalimide and 1 -(2H)-phthalazinone.

Samples of the resulting photothermographic materials were imagewise exposed as described in Example 1, to produce a developable latent image, and were heated at 11 ;:) C and 1 250C. A further photothermographic material containing no toner was similarly prepared and processed. The fog and image densities were measured as a function of processing time by infrared reflection densitometry.

Each of the samples produced a dye and silver image regardless of whether a toner was present.

However, each toner changed the rate of development and the final silver densities which were obtained in both the image and non-image areas. The image-fog discrimination was generally improved with the use of the described toners.

Example 4 Use of Developer Inhibitor Releasing Dye Forming Coupler This example illustrates use of a developer inhibitor releasing dye-forming coupler with a hydrazone reducing agent in a photothermographic material according to the invention.

Photothermographic materials were prepared according to the procedure of Example 2 with the exception that the photothermographic material contained 0.3 millimole of the following reducing agents and dye-forming couplers: Table 2 Element Reducing Agent Coupler 4A Hydrazone No. 1 5 No. 50 4B Hydrazone No. 1 5 No. 20 4C 2,6-dichloro-4-benzene- No. 50 (comparative sulphonamidophenol example) 4D 2,6-dichloro-4-benzene No. 20 (comparative sulphonamidophenol example Samples of each photothermographic material were identically imagewise exposed for 3 seconds as described in Example 1 to provide a developable latent image. Each photothermographic material after exposure was then intentionally over-processed by heating for 30 seconds at 10000, 12500 and 1 500C respectively.

Silver images and magenta dye images were produced in the photothermographic materials designated as 4A and 4B. However, when processed at 1 5000, only the sample of material 4B (containing the developer inhibitor releasing dye-forming coupler) produced a discernible image above fog.

Silver images, but no dye images, were produced in the samples of materials 4C and 4D. The silver development was the same regardless of the dye-forming coupler and at 1 500C silver development occurred overall with no image being apparent.

Example 5 A multilayer material was made as follows: To 3.0 millilitres of a 2.0% by weight solution of poly(vinyl butyral) (Butvar, a trade mark, commercially available from Monsanto Co., U.S.A.) were added 3.0 millilitres of the dispersion described in Example 2, 0.8 millilitre of silver bromoiodide emulsion (6% iodide), 0.5 millilitre of a green sensitizing dye solution containing 0.2 milligram per millilitre of a sensitizing dye 0.5 millilitre of acetone, 3.0 millilitres of a dispersion of 1 56 milligrams of hydrazone No. 1 5, as described, in 2% by weight poly(vinyl butyral) (Butvar) in toluene, and 195 milligrams of the dye forming coupler No. 47. The solution was coated at a 0.15 mm wet coating thickness on a 0.1 mm thick poly(ethylene terephthalate) film support.

The resulting photothermographic material was overcoated with a 5% by weight poly(vinyl alcohol) solution at a 0.15 m wet coating thickness.

After the overcoat of poly(vinyl alcohol) was dry the third layer was coated on the poly(vinyl alcohol) layer at a O. 1 5 mm wet coating thickness. The third layer consisted of 6.2 millilitres of 2% poly(vinyl butyral) ('Butvar' B-76), 3.0 millilitres of the silver behenate-behenic acid dispersion described in Example 1, 0.8 millilitre of a silver bromoiodide emulsion (6% iodide), 10 millilitres of acetone, 200 milligrams of the dye-forming coupler No. 48 and 140 milligrams of the hydrazone reducing agent No.16.

Samples of the resulting photothermographic material were imagewise exposed to light to provide a developable latent image and thermally processed as described in Example I at 11 00C for 15 seconds. The processed samples revealed a silver image and a magenta dye image in areas imagewise exposed to green light. No image was observed in areas exposed to red light because neither photosensitive layer was red sensitive. A silver image plus red dye image was observed in areas of white light exposure.

Example 6 Dyeing of Polyester Film Support The azo dyes resulting from the imagewise oxidation coupling of the hydrazone developer can be useful to dye polyester materials, such as a polyester film. This may occur directly by sublimation if the temperature exceeds both the sublimation temperature of the dye and the glass transition temperature of the polyester receiver. If, on the other hand, what is described as a dye carrier is added to the photothermographic material, the dye produced can enter the polyester dye receiver at a much lower temperature. A "dye carrier' as employed herein means a compound capable of causing the image dye to move through the film matrix at processing temperature, possibly due to solubilization of the dye in the melted carrier, and into the polyester material.It is believed that the carrier acts as a plasticizer for the polyester material, such as for the polyester film support.

A sample of the photothermographic material prepared as described in Example 1 and which contained the hydrazone No. 1 5 as the hydrazone reducing agent and the dye-forming coupler No. 52 (see Table 1 of Example 1) was imagewise exposed to provide a developable latent image. The imagewise exposed photothermographic material was then thermally processed as described in Example 1. The processed sample was then heated for 120 seconds at 900C while in contact with a second material containing 500 milligrams per 929 cm2 of methyl anisate. The methyl anisate acted as a dye carrier. Two hundred milligrams of poly(vinyl butyral) per 292 cm2 was also present in the material containing the methyl anisate to act as a binder.After heating, the materials were separated and the layer which contained the hydrazone reducing agent was physically removed from the film support. A well-defined magenta dye image was revealed in the poly(ethylene terephthalate) film support of the photothermographic material.

Other dyes can be produced according to the procedure described in Example 6. However, the temperature which is most useful for transfer of the dye and the efficiency of the transfer of the dye to the dye receiving element depends upon such factors as the dye structure, the particular dye carrier, processing conditions and the like.

Example 7 Use of a Silver Salt of 3-amino-l .2.4-triazole A photothermographic material containing a silver salt of 3-amino-1 ,2,4-triazole was prepared as follows: A dispersion was prepared by adding 10.0 millilitres of 1 molar silver nitrate solution during a three-minute period to a solution containing 10.0 millilitres of distilled water, 50 millilitres of a 20% aqueous solution of gelatin and 0.84 gram 1 -H-3-amino-1 ,2,4-triazole. The solution was mixed continually during the addition step by efficient dispersing means. One millilitre of the resulting dispersion contained 143 milligrams of gelatin and 1 5.4 milligrams of the silver salt of 1 -H-3-amino1,2,4-triazole.

A dispersion containing the dye-forming coupler No. 48 was prepared by mixing a solution containing 48 millilitres of a 10% aqueous solution of a surfactant (called Alkanol XC, a trade mark, and commercially available from E.l. duPont Co., U.S.A.); with a second solution containing 5.0 millilitres ethylacetate, 4.5 millilitres of 2,4-di-n-amylphenol (coupler solvent) and 6.1 5 grams of the dyeforming coupler, and dispersing the resulting mixture in a colloid mill.

A photothermographic material was prepared by dissolving 70 milligrams of the hydrazone No. 1 in a mixture of 5.0 millilitres of the dispersion containing the silver salt of 3-amino-1 ,2,4-triazole, 4.0 millilitres of the described dye-forming coupler dispersion, 1.0 millilitre of a 1.0% by weight surfactant solution (Surfactant 1 OG, a polyglycidol ether, available from the Olin Corp., U.S.A.) and 0.5 millilitre of a silver bromoiodide emulsion (3 mole per cent iodide). The resulting composition was coated at a 0.1 5 mm wet coating thickness on a poly(ethylene terephthalate) film support.

The photothermographic material was permitted to dry and then was imagewise exposed to light to produce a developable latent image. The imagewise exposed material was uniformly heated for 30 seconds at 1 500C. A yellowish brown, silver and dye image was produced. The photothermographic material was then treated for 5 minutes in a bleach-fix bath containing the following components and then washed with water and dried: acetic acid 20.0 ml (NH4)2S2O3(60% aqueous solution) 150.0 ml Na2SO3 15.0 grams Co(NH3)6C13 3.0 grams 2-hydroxytrimethylenedinitrolo tetraacetic acid 3.0 grams water to 1.0 litre The pH of the bleach-fix solution was 4.5.

An intense yellow dye image was revealed after removing the silver and silver halide from the photothermographic material in the bleach-fix solution.

An unexposed sample of the photothermographic material was treated in the described bleach-fix bath for 15 minutes. Substantially no dye was formed in the photothermographic material. This demonstrated that the bleach-fix solution did not directly oxidize the hydrazone reducing agent.

Example 8 Use of Dye-forming Couplers Color photothermographic materials were prepared, imagewise exposed, and processed according to the procedure described in Example 7 with the exception that the dye-forming couplers given in following Table 3 were in the photothermographic material instead of the described dyeforming coupler of Example 7. In each instance negative dye images were produced upon processing with an image hue as listed in following Table 3.

Table 3 Dye-forming Coupler Image Hue (47). Magenta (49) ' Magenta Magenta (28) Yellow

Yellow (36) Cyan (5) Magenta Example 9 Use of Other Organic Silver Salts Colour photothermographic materials similar to those described in Examples 7 and 8 were prepared except that the gelatin dispersion containing a silver salt of 3-amino-1 ,2,4-triazole was replaced with gelatin dispersions containing equivalent amounts (based on silver ion) of either silver amino tetrazole or silver methylimidazole-2-thiol salts.

After imagewise exposure and processing as described in Examples 7 and 8, negative dye images similar to those produced in Examples 7 and 8 were produced with the above organic silver salts.

Example 10 Use of Thermal Solvents A variety of water soluble compounds which are solid in a photothermographic material at room temperature but which melt during thermal processing of the photothermographic material were added to the photothermographic materials of the invention. These compounds are described herein as thermal solvents and were observed to enhance the mobility of the compounds in the photothermographic material at processing temperatures.

Photothermographic materials as described in Examples 7 and 8 were prepared except that they also contained 40, 60, 100 and 200 milligrams of one of the following thermal solvents per square foot (929 square centimetres) of support:sulphamide, acetamide, succinimide, I -(2H)-phthalazinone and N-hydroxynaphthalimide.

Samples of the resulting photothermographic materials were imagewise exposed as described in Example 7 to produce a developable latent image. The exposed materials were thermally processed as described in Example 7. The results of each sample produced more developed silver before bleaching and a substantial increase in maximum dye densities as compared to similar samples which did not contain the described thermal solvents.

Example 11 Multilayer Material A 2-colour photothermographic material was prepared in the following manner: A blue-and-green sensitive magenta-forming photosensitive layer was coated on a poly(ethylene terephthalate) film support in the following manner: A photothermographic composition was prepared containing the following components: 5.0 ml of the 3-amino-i ,2,4-triazolegelatin dispersion described in Example 7 4.0 ml of the coupler dispersion similar to that described in Example 7 except containing the dye forming coupler 49 of Example 1 dissolved in di-n-butyl phthalate 1.0 ml of a surfactant solution (Surfactant 1 OG) 70 mg of hydrazone reducing agent 200 mg of sulphamide 0.6 ml of a blue-and-green sensitive silver bromoiodide (3.0 mole % iodide) emulsion.

The resulting photothermographic composition was coated at 600C at a 6 mil wet coating thickness on a poly(ethylene terephthalate) film support and permitted to dry.

A blue-sensitive, yellow dye-forming layer was coated on top of the green-sensitive photothermographic layer. The composition for the second layer was the same as the first layer except that the coupler dispersion was replaced by 4.0 millilitres of the dye-forming coupler No. 48 and the blue-and-green sensitive silver halide emulsion was replaced by an equivalent amount of a bluesensitive silver halide emulsion. The resulting photothermographic composition was coated directly on the dried blue-and-green sensitive layer at an 0.2 mm wet coating thickness.

The multilayer photothermographic material was permitted to dry and was then imagewise exposed with filtered light comprising separate blue, green and red imagewise exposures. The imagewise exposed photothermographic material was then uniformly heated for 1 5 seconds at 1 400C. The processed photothermographic material was then immersed in a bleach-fix solution, as described in Example 7, for 5 minutes, washed for 5 minutes in water and permitted to dry. A red dye image appeared in blue light exposed regions of the photothermographic material. Magenta dye images appeared in the green light exposed areas of the material. No dye image appeared in the red light exposed regions of the photothermographic material.

Example 12 Use of a Bleach4ix Layer A sample of the color photothermographic material described in Example 8 which contained dyeforming coupler No. 49 was imagewise exposed to light, to produce a developable latent image, and then uniformly heated for 30 seconds at 1 500 C. A negative silver plus dye image was obtained. The processed photothermographic material was then heated for 30 seconds at 1 200C while in contact with a bleach-fix layer on a poly(ethylene terephthalate) film support.The bleach-fix layer contained the following components per 929 square centimeters of support: 1,6-hexanediol (thermal solvent) 500 mg thiourea (complexing agent) 125 mg 1,1 '-dithiodiformamidine dihydrochloride (oxidizing agent) 125 mg poly(vinyl pyrrolidone) (binder) 500 mg para-toluene sulphonic acid (acid) 250 mg The silver image and undeveloped silver halide were bleach-fixed to colourless and transparent products revealing the negative magenta-dye image.

Example 13 This illustrates formation of a neutral appearing image by oxidative coupling of a sulphonylhydrazone reducing agent with a benzenesulphonamidophenol as a coupler in a dry physical development photothermographic material.

Three millilitres of silver behenate Dispersion A, as described in Example 1, were added to solutions containing varying amounts of hydrazone No. 1 5 and 2,6-dichloro-4-benzenesulphonamidophenol, as given in following Table 14A, dissolved in 3.2 millilitres of a 2.0% by weight poly(vinyl butyral) solution in acetone and 1.0 millilitre of additional acetone. The resulting mixture was stirred.

To the stirred mixture was added 0.8 millilitre (0.3 millimole silver ion) of a silver bromoiodide emulsion (6 mole % iodide) in acetone and peptized in poly(vinyl butyral).

The resulting photothermographic composition was coated at 380C onto an unsubbed poly(ethylene terephthalate) film support at a 0.15 mm wet coating thickness.

The resulting photothermographic material was permitted to dry. Samples of the material were imagewise exposed to light, to produce a developable latent image, and then uniformly heated by contacting the support side with a heated metal block at the temperature and for a time designated in following Table 4. The photothermographic layer side of the material was then pressed against a separate reflective image receiving sheet moistened with methanol. The resulting sandwich was then heated at 1 500C for 60 seconds. The image receiving sheet was then separated from the described material. A neutral (black appearing) or blue image was observed in the image receiver sheet. The results indicate that neutral dyes were formed when the described hydrazone compound was present in an amount greater than that equivalent to the amount of coupler in the photothermographic layer.

When the coupler was present in excess, the dye formed was blue.

A comparatiye example was also carried out. In this example the sulphonamidophenol coupler was replaced with an equivalent amount of N,N-dimethyl-4-benzenesulphonamidoaniline. In each instance no detectable dye or transferrable dye was observed upon imagewise exposure and thermal processing as described.

Table 4 Coating Coupler Hydrazone Process Result No. (mlllimoles) No. 15 (time/temperature) (transferred image) A A 0.05 0.30 60"/850C A 0.05 0.30 30"/1 1 00C A 0.05 0.30 30"/125 C B 0.10 0.30 60"/85 C B B 0.10 0.30 30'1/1100C B 0.10 0.30 30"111250C C 0.30 0.30 60"/850C C 0.30 0.30 30"/1 100C C 0.30 0.30 301,/1250C D 0.30 0.10 60fl/85CC D 0.30 0.10 30"/1100C D 0.30 0.10 3011/1250C E E 0.30 0.05 60R850C E 0.30 0.05 30"/110 C E 0.30 0.05 30'7/1250C

Neutral images, density increases with higher process temperature.

Neutral images, densities higher than those produced with Coating A.

Neutral images with slight bluish tinge.

Blue image Grey images Blue image Grey images with high bluish Admin.

Example 14 This is a comparative example.

A mixture of 2.95 grams of the naphtholic coupler:

and 25 ml of dimethylformamide (referred to herein as DMF) were added to 2.9 grams of compound 7A:

and 25 ml of DMF contained in a three-neck round bottom flask equipped with a stirrer, condenser and dropping funnel. Twenty millilitres of 2N sodium hydroxide and 50 ml of DMF were added with stirring to dissolve the mixture. A solution of 6.6 grams (0.02 mole) of K3Fe(CN)6 in 35 ml of water was then added dropwise. During the addition a gas was evolved and the solution turned a dark green. After stirring for 4 hours, the mixture was filtered and a tan solid was collected. Analysis by thin-layer chromatography revealed no dye nor quinoline compound was present. A sample of the collected material was further analyzed by mass spectrometry to confirm that no azo dye was formed.

The described procedure was repeated with the exception that hydrazone No. 9 was substituted for described compound 7A. A magenta azo dye was produced. This was confirmed by analysis by mass spectrometry.

Example 15 This illustrates the invention.

An aqueous photothermographic composition was prepared by mixing the following components with 2.9 ml of water: deionized gelatin (12.5 weight % aqueous solution) (binder) 3.76 ml surfactant (TX-100, which is a trade name of Rohm s Haas Inc., U.S.A.

and identified as octylphenoxy polyethoxyethanol) (10% aqueous solution) 0.8 ml hydrazone developing agent (0.48 millimole) 110 mg polymeric dye-forming coupler (0.48 millimole) 6.7 g bis-methylsulphonylmethyl ether (2% aqueous solution) (hardener) 1.24 ml silver bromoiodide gelatino emulsion (3 mole % iodide) 0.8 ml The hydrazone silver halide developing agent was hydrazone No. 1.

The polymeric dye-forming coupler was poly [ 2-acrylamido-2-methylpropane-1 -suiphonic acid, sodium salt-co-1 -(4,6-dichloro-2-methylphenyl)-3-acryla mido-2-pyrazolone-5-one-co-N-(2acetoacetoxyethyl)acrylamide ] .

The resulting photothermographic composition was coated on a poly(ethylene terephthalate) film support containing a gelatin subbing layer. the photothermographic composition was coated on the support at a 6 mil wet coating thickness.

The photothermographic layer was permitted to dry and the resulting photothermographic material was imagewise exposed to light through a graduated density test object to produce a developable latent image. The exposed material was uniformly heated by contacting for 1 5 seconds with a curved metal block at a temperature of 1 800C. A yellowish-brown image comprising a developed silver image and a dye image was obtained.

The processed photothermographic material was then immersed in a commercial bleach-fix solution containing an iron complex of ethylenediamine tetaacetic acid, sodium sulphite and ammonium sulphite. The photothermographic element was permitted to remain in the bleach-fix solution for 4 minutes at 230C and then washed for 5 minutes with water and dried. A well-defined negative yellow dye image was obtained.

Example 16 This also illustrates the invention.

A photothermographic material was prepared and processed as described in Example 15 with the exception that the described dye-forming coupler was replaced with an equivalent amount of the dye :Forming coupler: polyj2-acrylamido-2-methylpropane-1 -sulphonic acid, sodium salt-co-2'- [ 2-(1 hydroxy-2-naphthoylamino)ethyljacrylanilide-co-N-(2-acetoacetoxyethyl)acrylam ide I.

A reddish magenta dye image was produced in the photothermographic material upon processing.

Example 17 This further illustrates the invention with a base-release agent in the photothermographic material.

A single layer photothermographic material was prepared by mixing the following components with 5.25 ml of water and 3.76 ml of 12.5% by weight gelatin aqueous solution and coating the resulting composition on a poly(ethylene terephthalate) film support containing a gelatin subbing layer at a wet coating thickness of 6 mils: surfactant (TX-100, as described) (10% by weight aqueous solution) 0.8 ml hydrazone silver halide developing agent No.1 110 mg dye-forming coupler (as described in Example 15) 4.35 g trimethylamine cinnimide (base-release agent) 400 mg silver bromoiodide gelatino emulsion (3 mole % iodide) 0.8 ml bis-methylvinylmethyl ether (2% aqueous solution) (hardener) 1.24 ml The resulting photothermographic material was permitted to dry and was then imagewise exposed to light through a graduated density test object to produce a developable latent image. This latent image was developed by contacting the material for 15 seconds with a curved metal block heated to 1 500C. A much denser silver image than that produced in Example 15 was produced according to this procedure. Dye image formation was also observed.The dye density was about equal to that dye density produced in Example 15.

Example 18 This illustrates sensitive materials of the invention containing water-soluble dye-forming couplers.

A variety of water soluble dye-forming couplers were tested in photothermographic materials as described in Example 15 (containing no base-release agent) and Example 17 (containing a baserelease agent). The dye-forming coupler in each formulation of the respective examples was replaced with 0.3 millimole of one of the water-soluble dye-forming couplers identified in following Table 5.

Samples of the photothermographic materials in each instance were imagewise exposed to light through a graduated density test object to produce a developable latent image. This latent image was developed by heating the material at a temperature of 1 300C to 1 600C for 15 to 30 seconds. A negative silver image and dye image were produced in each photothermographic material.

One of the processed photothermographic materials was immersed in a bleach-fix solution for 60 seconds as described, washed with water and then permitted to dry. In each instance a transparent negative dye image was observed after this bleach-fix treatment.

The dye images produced in a second set of processed photothermographic materials as described were transferred by diffusion away from the silver images in the photothermographic materials by contacting each sample for several seconds with a reflective receiving sheet which contained titanium dioxide and the dye receiving mordant poly(styrene-co-N,N,N-tri-n-hexyl-N vinylbenzylammonium chloride) and which had been moistened with methanol. The transferred images were of the colour indicated in table 5.

Table 5 Coupler Dye Hue 0 H3CCNH OH Magenta N035 503N HO iy Yellowish-brown 1 On ,S03K Orange Nay35 SOhNa ~2it20 S O Magenta H H

Claims (19)

Claims

1. A sensitive photothermographic material which comprises a support coated on one side with at least one binder-containing layer and, incorporated in the said layer or layers, a photographic silver halide, a dye-forming coupler, and a hydrazone reducing agent which contains a heterocyclic nucleus comprising a 5- or 6-membered heterocyclic ring and of which an oxidation product reacts with the coupler to form an image dye.

2. A material according to claim 1, wherein the hydrazone reducing agent is a compound, or salt of a compound, of the formula:

wherein n is O or 1, R1 is hydrogen or an acyl group containing 1 to 20 carbon atoms, R2 is hydrogen or a group of formula -COR4 or --SO,R4 wherein R4 is as defined below, R3 is an alkyl, alkenyl or alkynyl group having up to 20 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, an aryl group having 6 to 12 carbon atoms, a heterocyclic group comprising a 5- or 6-membered heterocylic ring or a group of formula -COR4 or --SO,R4, each R4 is a hydroxy or amino group, an alkyl group having up to 20 carbon atoms, or an aryl group having 6 to 12 carbon atoms and Z represents atoms which complete the heterocyclic nucleus comprising the 5- or 6-membered heterocyclic ring, any group R1, R2, R3 and R4 or the heterocyclic nucleus completed by Z possibly being a substituted group or nucleus.

3. A material according to claim 2 wherein the hydrazone reducing agent is a compound or salt of a compound of the formula I for the case where each of R1 and R2 is hydrogen, R3 is a methyl group and n is zero.

4. A material according to claim 1 wherein the hydrazone reducing agent is one of the Hydrazones 1 to 20 specified herein.

5. A material according to any of the preceding claims which comprises in the said layer or layers a melt-forming compound.

6. A material according to any of the preceding claims for producing a multicolour image, the material comprising photographic silver halide-containing layers having different spectral sensitivities and containing dye-forming couplers giving image dyes of different colour on reaction with an oxidation product of the hydrazone reducing agent.

7. A material according to any of the preceding claims which is a dry physical development material, there being incorporated in the said layer or layers an organic silver salt which provides, with the hydrazone reducing agent, an oxidation-reduction image-forming composition.

8. A material according to claim 7 wherein the organic silver salt is a salt of a long-chain fatty acid containing from 10 to 30 carbon atoms in the fatty acid portion.

9. A material according to claim 7 wherein the organic silver salt is a salt of a nitrogen acid.

10. A material according to any of claims 1 to 6 which is a dry chemical development material, there being incorporated in the said layer or layers a base release agent.

1 A material according to any of claims 1 to 6 and 10 wherein the dye-forming coupler is polymeric.

12. A material according to any of claims 1 to 10 which is a diffusion transfer material comprising an image receiving layer coated on the same side of the support as the said layer or layers.

13. A coating composition which comprises a binder, a photographic silver halide, a dye-forming coupler, and a hydrazone reducing agent which contains a heterocyclic nucleus comprising a 5- or 6membered heterocylic ring and of which an oxidation product reacts with the coupler to form an image dye.

14. A coating composition according to claim 1 3 wherein the hydrazone reducing agent is of the formula I of claim 2.

15. A coating composition according to claim 1 3 wherein the hydrazone reducing agent is one of the Hydrazones 1 to 20 specified herein.

16. A coating composition according to any of claims 13 to 15 which contains an organic silver salt which provides, with the hydrazone reducing agent, an oxidation-reduction-image forming composition.

17. A sensitive photothermographic material which comprises a support coated with a layer of a composition according to any of claims 13 to 16.

18. A method of forming a silver and dye image which comprises imagewise exposing a sensitive photographic thermographic material as specified in any of claims 1 to 12 and 17 to form a latent image and heating the material overall to develop the latent image to the desired image.

19. A method according to claim 18 wherein the photothermographic material is according to claim 12 and the material is heated during processing so that the dye image is transferred by diffusion to the receiving layer.